1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
3 @c 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009,
4 @c 2010, 2011 Free Software Foundation, Inc.
7 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
8 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
26 @c readline appendices use @vindex, @findex and @ftable,
27 @c annotate.texi and gdbmi use @findex.
31 @c !!set GDB manual's edition---not the same as GDB version!
32 @c This is updated by GNU Press.
35 @c !!set GDB edit command default editor
38 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
40 @c This is a dir.info fragment to support semi-automated addition of
41 @c manuals to an info tree.
42 @dircategory Software development
44 * Gdb: (gdb). The GNU debugger.
48 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
49 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
50 Free Software Foundation, Inc.
52 Permission is granted to copy, distribute and/or modify this document
53 under the terms of the GNU Free Documentation License, Version 1.3 or
54 any later version published by the Free Software Foundation; with the
55 Invariant Sections being ``Free Software'' and ``Free Software Needs
56 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
57 and with the Back-Cover Texts as in (a) below.
59 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
60 this GNU Manual. Buying copies from GNU Press supports the FSF in
61 developing GNU and promoting software freedom.''
65 This file documents the @sc{gnu} debugger @value{GDBN}.
67 This is the @value{EDITION} Edition, of @cite{Debugging with
68 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
69 @ifset VERSION_PACKAGE
70 @value{VERSION_PACKAGE}
72 Version @value{GDBVN}.
78 @title Debugging with @value{GDBN}
79 @subtitle The @sc{gnu} Source-Level Debugger
81 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
82 @ifset VERSION_PACKAGE
84 @subtitle @value{VERSION_PACKAGE}
86 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
90 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
91 \hfill {\it Debugging with @value{GDBN}}\par
92 \hfill \TeX{}info \texinfoversion\par
96 @vskip 0pt plus 1filll
97 Published by the Free Software Foundation @*
98 51 Franklin Street, Fifth Floor,
99 Boston, MA 02110-1301, USA@*
100 ISBN 978-0-9831592-3-0 @*
107 @node Top, Summary, (dir), (dir)
109 @top Debugging with @value{GDBN}
111 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
113 This is the @value{EDITION} Edition, for @value{GDBN}
114 @ifset VERSION_PACKAGE
115 @value{VERSION_PACKAGE}
117 Version @value{GDBVN}.
119 Copyright (C) 1988-2010 Free Software Foundation, Inc.
121 This edition of the GDB manual is dedicated to the memory of Fred
122 Fish. Fred was a long-standing contributor to GDB and to Free
123 software in general. We will miss him.
126 * Summary:: Summary of @value{GDBN}
127 * Sample Session:: A sample @value{GDBN} session
129 * Invocation:: Getting in and out of @value{GDBN}
130 * Commands:: @value{GDBN} commands
131 * Running:: Running programs under @value{GDBN}
132 * Stopping:: Stopping and continuing
133 * Reverse Execution:: Running programs backward
134 * Process Record and Replay:: Recording inferior's execution and replaying it
135 * Stack:: Examining the stack
136 * Source:: Examining source files
137 * Data:: Examining data
138 * Optimized Code:: Debugging optimized code
139 * Macros:: Preprocessor Macros
140 * Tracepoints:: Debugging remote targets non-intrusively
141 * Overlays:: Debugging programs that use overlays
143 * Languages:: Using @value{GDBN} with different languages
145 * Symbols:: Examining the symbol table
146 * Altering:: Altering execution
147 * GDB Files:: @value{GDBN} files
148 * Targets:: Specifying a debugging target
149 * Remote Debugging:: Debugging remote programs
150 * Configurations:: Configuration-specific information
151 * Controlling GDB:: Controlling @value{GDBN}
152 * Extending GDB:: Extending @value{GDBN}
153 * Interpreters:: Command Interpreters
154 * TUI:: @value{GDBN} Text User Interface
155 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
156 * GDB/MI:: @value{GDBN}'s Machine Interface.
157 * Annotations:: @value{GDBN}'s annotation interface.
158 * JIT Interface:: Using the JIT debugging interface.
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
193 @unnumbered Summary of @value{GDBN}
195 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
196 going on ``inside'' another program while it executes---or what another
197 program was doing at the moment it crashed.
199 @value{GDBN} can do four main kinds of things (plus other things in support of
200 these) to help you catch bugs in the act:
204 Start your program, specifying anything that might affect its behavior.
207 Make your program stop on specified conditions.
210 Examine what has happened, when your program has stopped.
213 Change things in your program, so you can experiment with correcting the
214 effects of one bug and go on to learn about another.
217 You can use @value{GDBN} to debug programs written in C and C@t{++}.
218 For more information, see @ref{Supported Languages,,Supported Languages}.
219 For more information, see @ref{C,,C and C++}.
221 Support for D is partial. For information on D, see
225 Support for Modula-2 is partial. For information on Modula-2, see
226 @ref{Modula-2,,Modula-2}.
228 Support for OpenCL C is partial. For information on OpenCL C, see
229 @ref{OpenCL C,,OpenCL C}.
232 Debugging Pascal programs which use sets, subranges, file variables, or
233 nested functions does not currently work. @value{GDBN} does not support
234 entering expressions, printing values, or similar features using Pascal
238 @value{GDBN} can be used to debug programs written in Fortran, although
239 it may be necessary to refer to some variables with a trailing
242 @value{GDBN} can be used to debug programs written in Objective-C,
243 using either the Apple/NeXT or the GNU Objective-C runtime.
246 * Free Software:: Freely redistributable software
247 * Contributors:: Contributors to GDB
251 @unnumberedsec Free Software
253 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
254 General Public License
255 (GPL). The GPL gives you the freedom to copy or adapt a licensed
256 program---but every person getting a copy also gets with it the
257 freedom to modify that copy (which means that they must get access to
258 the source code), and the freedom to distribute further copies.
259 Typical software companies use copyrights to limit your freedoms; the
260 Free Software Foundation uses the GPL to preserve these freedoms.
262 Fundamentally, the General Public License is a license which says that
263 you have these freedoms and that you cannot take these freedoms away
266 @unnumberedsec Free Software Needs Free Documentation
268 The biggest deficiency in the free software community today is not in
269 the software---it is the lack of good free documentation that we can
270 include with the free software. Many of our most important
271 programs do not come with free reference manuals and free introductory
272 texts. Documentation is an essential part of any software package;
273 when an important free software package does not come with a free
274 manual and a free tutorial, that is a major gap. We have many such
277 Consider Perl, for instance. The tutorial manuals that people
278 normally use are non-free. How did this come about? Because the
279 authors of those manuals published them with restrictive terms---no
280 copying, no modification, source files not available---which exclude
281 them from the free software world.
283 That wasn't the first time this sort of thing happened, and it was far
284 from the last. Many times we have heard a GNU user eagerly describe a
285 manual that he is writing, his intended contribution to the community,
286 only to learn that he had ruined everything by signing a publication
287 contract to make it non-free.
289 Free documentation, like free software, is a matter of freedom, not
290 price. The problem with the non-free manual is not that publishers
291 charge a price for printed copies---that in itself is fine. (The Free
292 Software Foundation sells printed copies of manuals, too.) The
293 problem is the restrictions on the use of the manual. Free manuals
294 are available in source code form, and give you permission to copy and
295 modify. Non-free manuals do not allow this.
297 The criteria of freedom for a free manual are roughly the same as for
298 free software. Redistribution (including the normal kinds of
299 commercial redistribution) must be permitted, so that the manual can
300 accompany every copy of the program, both on-line and on paper.
302 Permission for modification of the technical content is crucial too.
303 When people modify the software, adding or changing features, if they
304 are conscientious they will change the manual too---so they can
305 provide accurate and clear documentation for the modified program. A
306 manual that leaves you no choice but to write a new manual to document
307 a changed version of the program is not really available to our
310 Some kinds of limits on the way modification is handled are
311 acceptable. For example, requirements to preserve the original
312 author's copyright notice, the distribution terms, or the list of
313 authors, are ok. It is also no problem to require modified versions
314 to include notice that they were modified. Even entire sections that
315 may not be deleted or changed are acceptable, as long as they deal
316 with nontechnical topics (like this one). These kinds of restrictions
317 are acceptable because they don't obstruct the community's normal use
320 However, it must be possible to modify all the @emph{technical}
321 content of the manual, and then distribute the result in all the usual
322 media, through all the usual channels. Otherwise, the restrictions
323 obstruct the use of the manual, it is not free, and we need another
324 manual to replace it.
326 Please spread the word about this issue. Our community continues to
327 lose manuals to proprietary publishing. If we spread the word that
328 free software needs free reference manuals and free tutorials, perhaps
329 the next person who wants to contribute by writing documentation will
330 realize, before it is too late, that only free manuals contribute to
331 the free software community.
333 If you are writing documentation, please insist on publishing it under
334 the GNU Free Documentation License or another free documentation
335 license. Remember that this decision requires your approval---you
336 don't have to let the publisher decide. Some commercial publishers
337 will use a free license if you insist, but they will not propose the
338 option; it is up to you to raise the issue and say firmly that this is
339 what you want. If the publisher you are dealing with refuses, please
340 try other publishers. If you're not sure whether a proposed license
341 is free, write to @email{licensing@@gnu.org}.
343 You can encourage commercial publishers to sell more free, copylefted
344 manuals and tutorials by buying them, and particularly by buying
345 copies from the publishers that paid for their writing or for major
346 improvements. Meanwhile, try to avoid buying non-free documentation
347 at all. Check the distribution terms of a manual before you buy it,
348 and insist that whoever seeks your business must respect your freedom.
349 Check the history of the book, and try to reward the publishers that
350 have paid or pay the authors to work on it.
352 The Free Software Foundation maintains a list of free documentation
353 published by other publishers, at
354 @url{http://www.fsf.org/doc/other-free-books.html}.
357 @unnumberedsec Contributors to @value{GDBN}
359 Richard Stallman was the original author of @value{GDBN}, and of many
360 other @sc{gnu} programs. Many others have contributed to its
361 development. This section attempts to credit major contributors. One
362 of the virtues of free software is that everyone is free to contribute
363 to it; with regret, we cannot actually acknowledge everyone here. The
364 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
365 blow-by-blow account.
367 Changes much prior to version 2.0 are lost in the mists of time.
370 @emph{Plea:} Additions to this section are particularly welcome. If you
371 or your friends (or enemies, to be evenhanded) have been unfairly
372 omitted from this list, we would like to add your names!
375 So that they may not regard their many labors as thankless, we
376 particularly thank those who shepherded @value{GDBN} through major
378 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
379 Jim Blandy (release 4.18);
380 Jason Molenda (release 4.17);
381 Stan Shebs (release 4.14);
382 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
383 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
384 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
385 Jim Kingdon (releases 3.5, 3.4, and 3.3);
386 and Randy Smith (releases 3.2, 3.1, and 3.0).
388 Richard Stallman, assisted at various times by Peter TerMaat, Chris
389 Hanson, and Richard Mlynarik, handled releases through 2.8.
391 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
392 in @value{GDBN}, with significant additional contributions from Per
393 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
394 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
395 much general update work leading to release 3.0).
397 @value{GDBN} uses the BFD subroutine library to examine multiple
398 object-file formats; BFD was a joint project of David V.
399 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
401 David Johnson wrote the original COFF support; Pace Willison did
402 the original support for encapsulated COFF.
404 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
406 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
407 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
409 Jean-Daniel Fekete contributed Sun 386i support.
410 Chris Hanson improved the HP9000 support.
411 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
412 David Johnson contributed Encore Umax support.
413 Jyrki Kuoppala contributed Altos 3068 support.
414 Jeff Law contributed HP PA and SOM support.
415 Keith Packard contributed NS32K support.
416 Doug Rabson contributed Acorn Risc Machine support.
417 Bob Rusk contributed Harris Nighthawk CX-UX support.
418 Chris Smith contributed Convex support (and Fortran debugging).
419 Jonathan Stone contributed Pyramid support.
420 Michael Tiemann contributed SPARC support.
421 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
422 Pace Willison contributed Intel 386 support.
423 Jay Vosburgh contributed Symmetry support.
424 Marko Mlinar contributed OpenRISC 1000 support.
426 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
428 Rich Schaefer and Peter Schauer helped with support of SunOS shared
431 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
432 about several machine instruction sets.
434 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
435 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
436 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
437 and RDI targets, respectively.
439 Brian Fox is the author of the readline libraries providing
440 command-line editing and command history.
442 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
443 Modula-2 support, and contributed the Languages chapter of this manual.
445 Fred Fish wrote most of the support for Unix System Vr4.
446 He also enhanced the command-completion support to cover C@t{++} overloaded
449 Hitachi America (now Renesas America), Ltd. sponsored the support for
450 H8/300, H8/500, and Super-H processors.
452 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
454 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
457 Toshiba sponsored the support for the TX39 Mips processor.
459 Matsushita sponsored the support for the MN10200 and MN10300 processors.
461 Fujitsu sponsored the support for SPARClite and FR30 processors.
463 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
466 Michael Snyder added support for tracepoints.
468 Stu Grossman wrote gdbserver.
470 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
471 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
473 The following people at the Hewlett-Packard Company contributed
474 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
475 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
476 compiler, and the Text User Interface (nee Terminal User Interface):
477 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
478 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
479 provided HP-specific information in this manual.
481 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
482 Robert Hoehne made significant contributions to the DJGPP port.
484 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
485 development since 1991. Cygnus engineers who have worked on @value{GDBN}
486 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
487 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
488 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
489 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
490 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
491 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
492 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
493 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
494 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
495 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
496 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
497 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
498 Zuhn have made contributions both large and small.
500 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
501 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
503 Jim Blandy added support for preprocessor macros, while working for Red
506 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
507 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
508 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
509 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
510 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
511 with the migration of old architectures to this new framework.
513 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
514 unwinder framework, this consisting of a fresh new design featuring
515 frame IDs, independent frame sniffers, and the sentinel frame. Mark
516 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
517 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
518 trad unwinders. The architecture-specific changes, each involving a
519 complete rewrite of the architecture's frame code, were carried out by
520 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
521 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
522 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
523 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
526 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
527 Tensilica, Inc.@: contributed support for Xtensa processors. Others
528 who have worked on the Xtensa port of @value{GDBN} in the past include
529 Steve Tjiang, John Newlin, and Scott Foehner.
531 Michael Eager and staff of Xilinx, Inc., contributed support for the
532 Xilinx MicroBlaze architecture.
535 @chapter A Sample @value{GDBN} Session
537 You can use this manual at your leisure to read all about @value{GDBN}.
538 However, a handful of commands are enough to get started using the
539 debugger. This chapter illustrates those commands.
542 In this sample session, we emphasize user input like this: @b{input},
543 to make it easier to pick out from the surrounding output.
546 @c FIXME: this example may not be appropriate for some configs, where
547 @c FIXME...primary interest is in remote use.
549 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
550 processor) exhibits the following bug: sometimes, when we change its
551 quote strings from the default, the commands used to capture one macro
552 definition within another stop working. In the following short @code{m4}
553 session, we define a macro @code{foo} which expands to @code{0000}; we
554 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
555 same thing. However, when we change the open quote string to
556 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
557 procedure fails to define a new synonym @code{baz}:
566 @b{define(bar,defn(`foo'))}
570 @b{changequote(<QUOTE>,<UNQUOTE>)}
572 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
575 m4: End of input: 0: fatal error: EOF in string
579 Let us use @value{GDBN} to try to see what is going on.
582 $ @b{@value{GDBP} m4}
583 @c FIXME: this falsifies the exact text played out, to permit smallbook
584 @c FIXME... format to come out better.
585 @value{GDBN} is free software and you are welcome to distribute copies
586 of it under certain conditions; type "show copying" to see
588 There is absolutely no warranty for @value{GDBN}; type "show warranty"
591 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
596 @value{GDBN} reads only enough symbol data to know where to find the
597 rest when needed; as a result, the first prompt comes up very quickly.
598 We now tell @value{GDBN} to use a narrower display width than usual, so
599 that examples fit in this manual.
602 (@value{GDBP}) @b{set width 70}
606 We need to see how the @code{m4} built-in @code{changequote} works.
607 Having looked at the source, we know the relevant subroutine is
608 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
609 @code{break} command.
612 (@value{GDBP}) @b{break m4_changequote}
613 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
617 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
618 control; as long as control does not reach the @code{m4_changequote}
619 subroutine, the program runs as usual:
622 (@value{GDBP}) @b{run}
623 Starting program: /work/Editorial/gdb/gnu/m4/m4
631 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
632 suspends execution of @code{m4}, displaying information about the
633 context where it stops.
636 @b{changequote(<QUOTE>,<UNQUOTE>)}
638 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
640 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
644 Now we use the command @code{n} (@code{next}) to advance execution to
645 the next line of the current function.
649 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
654 @code{set_quotes} looks like a promising subroutine. We can go into it
655 by using the command @code{s} (@code{step}) instead of @code{next}.
656 @code{step} goes to the next line to be executed in @emph{any}
657 subroutine, so it steps into @code{set_quotes}.
661 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
663 530 if (lquote != def_lquote)
667 The display that shows the subroutine where @code{m4} is now
668 suspended (and its arguments) is called a stack frame display. It
669 shows a summary of the stack. We can use the @code{backtrace}
670 command (which can also be spelled @code{bt}), to see where we are
671 in the stack as a whole: the @code{backtrace} command displays a
672 stack frame for each active subroutine.
675 (@value{GDBP}) @b{bt}
676 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
678 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
680 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
681 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
683 #4 0x79dc in expand_input () at macro.c:40
684 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
688 We step through a few more lines to see what happens. The first two
689 times, we can use @samp{s}; the next two times we use @code{n} to avoid
690 falling into the @code{xstrdup} subroutine.
694 0x3b5c 532 if (rquote != def_rquote)
696 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
697 def_lquote : xstrdup(lq);
699 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
702 538 len_lquote = strlen(rquote);
706 The last line displayed looks a little odd; we can examine the variables
707 @code{lquote} and @code{rquote} to see if they are in fact the new left
708 and right quotes we specified. We use the command @code{p}
709 (@code{print}) to see their values.
712 (@value{GDBP}) @b{p lquote}
713 $1 = 0x35d40 "<QUOTE>"
714 (@value{GDBP}) @b{p rquote}
715 $2 = 0x35d50 "<UNQUOTE>"
719 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
720 To look at some context, we can display ten lines of source
721 surrounding the current line with the @code{l} (@code{list}) command.
727 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
729 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
732 538 len_lquote = strlen(rquote);
733 539 len_rquote = strlen(lquote);
740 Let us step past the two lines that set @code{len_lquote} and
741 @code{len_rquote}, and then examine the values of those variables.
745 539 len_rquote = strlen(lquote);
748 (@value{GDBP}) @b{p len_lquote}
750 (@value{GDBP}) @b{p len_rquote}
755 That certainly looks wrong, assuming @code{len_lquote} and
756 @code{len_rquote} are meant to be the lengths of @code{lquote} and
757 @code{rquote} respectively. We can set them to better values using
758 the @code{p} command, since it can print the value of
759 any expression---and that expression can include subroutine calls and
763 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
765 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
770 Is that enough to fix the problem of using the new quotes with the
771 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
772 executing with the @code{c} (@code{continue}) command, and then try the
773 example that caused trouble initially:
779 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
786 Success! The new quotes now work just as well as the default ones. The
787 problem seems to have been just the two typos defining the wrong
788 lengths. We allow @code{m4} exit by giving it an EOF as input:
792 Program exited normally.
796 The message @samp{Program exited normally.} is from @value{GDBN}; it
797 indicates @code{m4} has finished executing. We can end our @value{GDBN}
798 session with the @value{GDBN} @code{quit} command.
801 (@value{GDBP}) @b{quit}
805 @chapter Getting In and Out of @value{GDBN}
807 This chapter discusses how to start @value{GDBN}, and how to get out of it.
811 type @samp{@value{GDBP}} to start @value{GDBN}.
813 type @kbd{quit} or @kbd{Ctrl-d} to exit.
817 * Invoking GDB:: How to start @value{GDBN}
818 * Quitting GDB:: How to quit @value{GDBN}
819 * Shell Commands:: How to use shell commands inside @value{GDBN}
820 * Logging Output:: How to log @value{GDBN}'s output to a file
824 @section Invoking @value{GDBN}
826 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
827 @value{GDBN} reads commands from the terminal until you tell it to exit.
829 You can also run @code{@value{GDBP}} with a variety of arguments and options,
830 to specify more of your debugging environment at the outset.
832 The command-line options described here are designed
833 to cover a variety of situations; in some environments, some of these
834 options may effectively be unavailable.
836 The most usual way to start @value{GDBN} is with one argument,
837 specifying an executable program:
840 @value{GDBP} @var{program}
844 You can also start with both an executable program and a core file
848 @value{GDBP} @var{program} @var{core}
851 You can, instead, specify a process ID as a second argument, if you want
852 to debug a running process:
855 @value{GDBP} @var{program} 1234
859 would attach @value{GDBN} to process @code{1234} (unless you also have a file
860 named @file{1234}; @value{GDBN} does check for a core file first).
862 Taking advantage of the second command-line argument requires a fairly
863 complete operating system; when you use @value{GDBN} as a remote
864 debugger attached to a bare board, there may not be any notion of
865 ``process'', and there is often no way to get a core dump. @value{GDBN}
866 will warn you if it is unable to attach or to read core dumps.
868 You can optionally have @code{@value{GDBP}} pass any arguments after the
869 executable file to the inferior using @code{--args}. This option stops
872 @value{GDBP} --args gcc -O2 -c foo.c
874 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
875 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
877 You can run @code{@value{GDBP}} without printing the front material, which describes
878 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
885 You can further control how @value{GDBN} starts up by using command-line
886 options. @value{GDBN} itself can remind you of the options available.
896 to display all available options and briefly describe their use
897 (@samp{@value{GDBP} -h} is a shorter equivalent).
899 All options and command line arguments you give are processed
900 in sequential order. The order makes a difference when the
901 @samp{-x} option is used.
905 * File Options:: Choosing files
906 * Mode Options:: Choosing modes
907 * Startup:: What @value{GDBN} does during startup
911 @subsection Choosing Files
913 When @value{GDBN} starts, it reads any arguments other than options as
914 specifying an executable file and core file (or process ID). This is
915 the same as if the arguments were specified by the @samp{-se} and
916 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
917 first argument that does not have an associated option flag as
918 equivalent to the @samp{-se} option followed by that argument; and the
919 second argument that does not have an associated option flag, if any, as
920 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
921 If the second argument begins with a decimal digit, @value{GDBN} will
922 first attempt to attach to it as a process, and if that fails, attempt
923 to open it as a corefile. If you have a corefile whose name begins with
924 a digit, you can prevent @value{GDBN} from treating it as a pid by
925 prefixing it with @file{./}, e.g.@: @file{./12345}.
927 If @value{GDBN} has not been configured to included core file support,
928 such as for most embedded targets, then it will complain about a second
929 argument and ignore it.
931 Many options have both long and short forms; both are shown in the
932 following list. @value{GDBN} also recognizes the long forms if you truncate
933 them, so long as enough of the option is present to be unambiguous.
934 (If you prefer, you can flag option arguments with @samp{--} rather
935 than @samp{-}, though we illustrate the more usual convention.)
937 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
938 @c way, both those who look for -foo and --foo in the index, will find
942 @item -symbols @var{file}
944 @cindex @code{--symbols}
946 Read symbol table from file @var{file}.
948 @item -exec @var{file}
950 @cindex @code{--exec}
952 Use file @var{file} as the executable file to execute when appropriate,
953 and for examining pure data in conjunction with a core dump.
957 Read symbol table from file @var{file} and use it as the executable
960 @item -core @var{file}
962 @cindex @code{--core}
964 Use file @var{file} as a core dump to examine.
966 @item -pid @var{number}
967 @itemx -p @var{number}
970 Connect to process ID @var{number}, as with the @code{attach} command.
972 @item -command @var{file}
974 @cindex @code{--command}
976 Execute commands from file @var{file}. The contents of this file is
977 evaluated exactly as the @code{source} command would.
978 @xref{Command Files,, Command files}.
980 @item -eval-command @var{command}
981 @itemx -ex @var{command}
982 @cindex @code{--eval-command}
984 Execute a single @value{GDBN} command.
986 This option may be used multiple times to call multiple commands. It may
987 also be interleaved with @samp{-command} as required.
990 @value{GDBP} -ex 'target sim' -ex 'load' \
991 -x setbreakpoints -ex 'run' a.out
994 @item -directory @var{directory}
995 @itemx -d @var{directory}
996 @cindex @code{--directory}
998 Add @var{directory} to the path to search for source and script files.
1002 @cindex @code{--readnow}
1004 Read each symbol file's entire symbol table immediately, rather than
1005 the default, which is to read it incrementally as it is needed.
1006 This makes startup slower, but makes future operations faster.
1011 @subsection Choosing Modes
1013 You can run @value{GDBN} in various alternative modes---for example, in
1014 batch mode or quiet mode.
1021 Do not execute commands found in any initialization files. Normally,
1022 @value{GDBN} executes the commands in these files after all the command
1023 options and arguments have been processed. @xref{Command Files,,Command
1029 @cindex @code{--quiet}
1030 @cindex @code{--silent}
1032 ``Quiet''. Do not print the introductory and copyright messages. These
1033 messages are also suppressed in batch mode.
1036 @cindex @code{--batch}
1037 Run in batch mode. Exit with status @code{0} after processing all the
1038 command files specified with @samp{-x} (and all commands from
1039 initialization files, if not inhibited with @samp{-n}). Exit with
1040 nonzero status if an error occurs in executing the @value{GDBN} commands
1041 in the command files. Batch mode also disables pagination, sets unlimited
1042 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1043 off} were in effect (@pxref{Messages/Warnings}).
1045 Batch mode may be useful for running @value{GDBN} as a filter, for
1046 example to download and run a program on another computer; in order to
1047 make this more useful, the message
1050 Program exited normally.
1054 (which is ordinarily issued whenever a program running under
1055 @value{GDBN} control terminates) is not issued when running in batch
1059 @cindex @code{--batch-silent}
1060 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1061 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1062 unaffected). This is much quieter than @samp{-silent} and would be useless
1063 for an interactive session.
1065 This is particularly useful when using targets that give @samp{Loading section}
1066 messages, for example.
1068 Note that targets that give their output via @value{GDBN}, as opposed to
1069 writing directly to @code{stdout}, will also be made silent.
1071 @item -return-child-result
1072 @cindex @code{--return-child-result}
1073 The return code from @value{GDBN} will be the return code from the child
1074 process (the process being debugged), with the following exceptions:
1078 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1079 internal error. In this case the exit code is the same as it would have been
1080 without @samp{-return-child-result}.
1082 The user quits with an explicit value. E.g., @samp{quit 1}.
1084 The child process never runs, or is not allowed to terminate, in which case
1085 the exit code will be -1.
1088 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1089 when @value{GDBN} is being used as a remote program loader or simulator
1094 @cindex @code{--nowindows}
1096 ``No windows''. If @value{GDBN} comes with a graphical user interface
1097 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1098 interface. If no GUI is available, this option has no effect.
1102 @cindex @code{--windows}
1104 If @value{GDBN} includes a GUI, then this option requires it to be
1107 @item -cd @var{directory}
1109 Run @value{GDBN} using @var{directory} as its working directory,
1110 instead of the current directory.
1112 @item -data-directory @var{directory}
1113 @cindex @code{--data-directory}
1114 Run @value{GDBN} using @var{directory} as its data directory.
1115 The data directory is where @value{GDBN} searches for its
1116 auxiliary files. @xref{Data Files}.
1120 @cindex @code{--fullname}
1122 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1123 subprocess. It tells @value{GDBN} to output the full file name and line
1124 number in a standard, recognizable fashion each time a stack frame is
1125 displayed (which includes each time your program stops). This
1126 recognizable format looks like two @samp{\032} characters, followed by
1127 the file name, line number and character position separated by colons,
1128 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1129 @samp{\032} characters as a signal to display the source code for the
1133 @cindex @code{--epoch}
1134 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1135 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1136 routines so as to allow Epoch to display values of expressions in a
1139 @item -annotate @var{level}
1140 @cindex @code{--annotate}
1141 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1142 effect is identical to using @samp{set annotate @var{level}}
1143 (@pxref{Annotations}). The annotation @var{level} controls how much
1144 information @value{GDBN} prints together with its prompt, values of
1145 expressions, source lines, and other types of output. Level 0 is the
1146 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1147 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1148 that control @value{GDBN}, and level 2 has been deprecated.
1150 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1154 @cindex @code{--args}
1155 Change interpretation of command line so that arguments following the
1156 executable file are passed as command line arguments to the inferior.
1157 This option stops option processing.
1159 @item -baud @var{bps}
1161 @cindex @code{--baud}
1163 Set the line speed (baud rate or bits per second) of any serial
1164 interface used by @value{GDBN} for remote debugging.
1166 @item -l @var{timeout}
1168 Set the timeout (in seconds) of any communication used by @value{GDBN}
1169 for remote debugging.
1171 @item -tty @var{device}
1172 @itemx -t @var{device}
1173 @cindex @code{--tty}
1175 Run using @var{device} for your program's standard input and output.
1176 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1178 @c resolve the situation of these eventually
1180 @cindex @code{--tui}
1181 Activate the @dfn{Text User Interface} when starting. The Text User
1182 Interface manages several text windows on the terminal, showing
1183 source, assembly, registers and @value{GDBN} command outputs
1184 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1185 Text User Interface can be enabled by invoking the program
1186 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1187 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1190 @c @cindex @code{--xdb}
1191 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1192 @c For information, see the file @file{xdb_trans.html}, which is usually
1193 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1196 @item -interpreter @var{interp}
1197 @cindex @code{--interpreter}
1198 Use the interpreter @var{interp} for interface with the controlling
1199 program or device. This option is meant to be set by programs which
1200 communicate with @value{GDBN} using it as a back end.
1201 @xref{Interpreters, , Command Interpreters}.
1203 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1204 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1205 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1206 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1207 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1208 @sc{gdb/mi} interfaces are no longer supported.
1211 @cindex @code{--write}
1212 Open the executable and core files for both reading and writing. This
1213 is equivalent to the @samp{set write on} command inside @value{GDBN}
1217 @cindex @code{--statistics}
1218 This option causes @value{GDBN} to print statistics about time and
1219 memory usage after it completes each command and returns to the prompt.
1222 @cindex @code{--version}
1223 This option causes @value{GDBN} to print its version number and
1224 no-warranty blurb, and exit.
1229 @subsection What @value{GDBN} Does During Startup
1230 @cindex @value{GDBN} startup
1232 Here's the description of what @value{GDBN} does during session startup:
1236 Sets up the command interpreter as specified by the command line
1237 (@pxref{Mode Options, interpreter}).
1241 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1242 used when building @value{GDBN}; @pxref{System-wide configuration,
1243 ,System-wide configuration and settings}) and executes all the commands in
1247 Reads the init file (if any) in your home directory@footnote{On
1248 DOS/Windows systems, the home directory is the one pointed to by the
1249 @code{HOME} environment variable.} and executes all the commands in
1253 Processes command line options and operands.
1256 Reads and executes the commands from init file (if any) in the current
1257 working directory. This is only done if the current directory is
1258 different from your home directory. Thus, you can have more than one
1259 init file, one generic in your home directory, and another, specific
1260 to the program you are debugging, in the directory where you invoke
1264 If the command line specified a program to debug, or a process to
1265 attach to, or a core file, @value{GDBN} loads any auto-loaded
1266 scripts provided for the program or for its loaded shared libraries.
1267 @xref{Auto-loading}.
1269 If you wish to disable the auto-loading during startup,
1270 you must do something like the following:
1273 $ gdb -ex "set auto-load-scripts off" -ex "file myprogram"
1276 The following does not work because the auto-loading is turned off too late:
1279 $ gdb -ex "set auto-load-scripts off" myprogram
1283 Reads command files specified by the @samp{-x} option. @xref{Command
1284 Files}, for more details about @value{GDBN} command files.
1287 Reads the command history recorded in the @dfn{history file}.
1288 @xref{Command History}, for more details about the command history and the
1289 files where @value{GDBN} records it.
1292 Init files use the same syntax as @dfn{command files} (@pxref{Command
1293 Files}) and are processed by @value{GDBN} in the same way. The init
1294 file in your home directory can set options (such as @samp{set
1295 complaints}) that affect subsequent processing of command line options
1296 and operands. Init files are not executed if you use the @samp{-nx}
1297 option (@pxref{Mode Options, ,Choosing Modes}).
1299 To display the list of init files loaded by gdb at startup, you
1300 can use @kbd{gdb --help}.
1302 @cindex init file name
1303 @cindex @file{.gdbinit}
1304 @cindex @file{gdb.ini}
1305 The @value{GDBN} init files are normally called @file{.gdbinit}.
1306 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1307 the limitations of file names imposed by DOS filesystems. The Windows
1308 ports of @value{GDBN} use the standard name, but if they find a
1309 @file{gdb.ini} file, they warn you about that and suggest to rename
1310 the file to the standard name.
1314 @section Quitting @value{GDBN}
1315 @cindex exiting @value{GDBN}
1316 @cindex leaving @value{GDBN}
1319 @kindex quit @r{[}@var{expression}@r{]}
1320 @kindex q @r{(@code{quit})}
1321 @item quit @r{[}@var{expression}@r{]}
1323 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1324 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1325 do not supply @var{expression}, @value{GDBN} will terminate normally;
1326 otherwise it will terminate using the result of @var{expression} as the
1331 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1332 terminates the action of any @value{GDBN} command that is in progress and
1333 returns to @value{GDBN} command level. It is safe to type the interrupt
1334 character at any time because @value{GDBN} does not allow it to take effect
1335 until a time when it is safe.
1337 If you have been using @value{GDBN} to control an attached process or
1338 device, you can release it with the @code{detach} command
1339 (@pxref{Attach, ,Debugging an Already-running Process}).
1341 @node Shell Commands
1342 @section Shell Commands
1344 If you need to execute occasional shell commands during your
1345 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1346 just use the @code{shell} command.
1350 @cindex shell escape
1351 @item shell @var{command string}
1352 Invoke a standard shell to execute @var{command string}.
1353 If it exists, the environment variable @code{SHELL} determines which
1354 shell to run. Otherwise @value{GDBN} uses the default shell
1355 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1358 The utility @code{make} is often needed in development environments.
1359 You do not have to use the @code{shell} command for this purpose in
1364 @cindex calling make
1365 @item make @var{make-args}
1366 Execute the @code{make} program with the specified
1367 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1370 @node Logging Output
1371 @section Logging Output
1372 @cindex logging @value{GDBN} output
1373 @cindex save @value{GDBN} output to a file
1375 You may want to save the output of @value{GDBN} commands to a file.
1376 There are several commands to control @value{GDBN}'s logging.
1380 @item set logging on
1382 @item set logging off
1384 @cindex logging file name
1385 @item set logging file @var{file}
1386 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1387 @item set logging overwrite [on|off]
1388 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1389 you want @code{set logging on} to overwrite the logfile instead.
1390 @item set logging redirect [on|off]
1391 By default, @value{GDBN} output will go to both the terminal and the logfile.
1392 Set @code{redirect} if you want output to go only to the log file.
1393 @kindex show logging
1395 Show the current values of the logging settings.
1399 @chapter @value{GDBN} Commands
1401 You can abbreviate a @value{GDBN} command to the first few letters of the command
1402 name, if that abbreviation is unambiguous; and you can repeat certain
1403 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1404 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1405 show you the alternatives available, if there is more than one possibility).
1408 * Command Syntax:: How to give commands to @value{GDBN}
1409 * Completion:: Command completion
1410 * Help:: How to ask @value{GDBN} for help
1413 @node Command Syntax
1414 @section Command Syntax
1416 A @value{GDBN} command is a single line of input. There is no limit on
1417 how long it can be. It starts with a command name, which is followed by
1418 arguments whose meaning depends on the command name. For example, the
1419 command @code{step} accepts an argument which is the number of times to
1420 step, as in @samp{step 5}. You can also use the @code{step} command
1421 with no arguments. Some commands do not allow any arguments.
1423 @cindex abbreviation
1424 @value{GDBN} command names may always be truncated if that abbreviation is
1425 unambiguous. Other possible command abbreviations are listed in the
1426 documentation for individual commands. In some cases, even ambiguous
1427 abbreviations are allowed; for example, @code{s} is specially defined as
1428 equivalent to @code{step} even though there are other commands whose
1429 names start with @code{s}. You can test abbreviations by using them as
1430 arguments to the @code{help} command.
1432 @cindex repeating commands
1433 @kindex RET @r{(repeat last command)}
1434 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1435 repeat the previous command. Certain commands (for example, @code{run})
1436 will not repeat this way; these are commands whose unintentional
1437 repetition might cause trouble and which you are unlikely to want to
1438 repeat. User-defined commands can disable this feature; see
1439 @ref{Define, dont-repeat}.
1441 The @code{list} and @code{x} commands, when you repeat them with
1442 @key{RET}, construct new arguments rather than repeating
1443 exactly as typed. This permits easy scanning of source or memory.
1445 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1446 output, in a way similar to the common utility @code{more}
1447 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1448 @key{RET} too many in this situation, @value{GDBN} disables command
1449 repetition after any command that generates this sort of display.
1451 @kindex # @r{(a comment)}
1453 Any text from a @kbd{#} to the end of the line is a comment; it does
1454 nothing. This is useful mainly in command files (@pxref{Command
1455 Files,,Command Files}).
1457 @cindex repeating command sequences
1458 @kindex Ctrl-o @r{(operate-and-get-next)}
1459 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1460 commands. This command accepts the current line, like @key{RET}, and
1461 then fetches the next line relative to the current line from the history
1465 @section Command Completion
1468 @cindex word completion
1469 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1470 only one possibility; it can also show you what the valid possibilities
1471 are for the next word in a command, at any time. This works for @value{GDBN}
1472 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1474 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1475 of a word. If there is only one possibility, @value{GDBN} fills in the
1476 word, and waits for you to finish the command (or press @key{RET} to
1477 enter it). For example, if you type
1479 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1480 @c complete accuracy in these examples; space introduced for clarity.
1481 @c If texinfo enhancements make it unnecessary, it would be nice to
1482 @c replace " @key" by "@key" in the following...
1484 (@value{GDBP}) info bre @key{TAB}
1488 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1489 the only @code{info} subcommand beginning with @samp{bre}:
1492 (@value{GDBP}) info breakpoints
1496 You can either press @key{RET} at this point, to run the @code{info
1497 breakpoints} command, or backspace and enter something else, if
1498 @samp{breakpoints} does not look like the command you expected. (If you
1499 were sure you wanted @code{info breakpoints} in the first place, you
1500 might as well just type @key{RET} immediately after @samp{info bre},
1501 to exploit command abbreviations rather than command completion).
1503 If there is more than one possibility for the next word when you press
1504 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1505 characters and try again, or just press @key{TAB} a second time;
1506 @value{GDBN} displays all the possible completions for that word. For
1507 example, you might want to set a breakpoint on a subroutine whose name
1508 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1509 just sounds the bell. Typing @key{TAB} again displays all the
1510 function names in your program that begin with those characters, for
1514 (@value{GDBP}) b make_ @key{TAB}
1515 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1516 make_a_section_from_file make_environ
1517 make_abs_section make_function_type
1518 make_blockvector make_pointer_type
1519 make_cleanup make_reference_type
1520 make_command make_symbol_completion_list
1521 (@value{GDBP}) b make_
1525 After displaying the available possibilities, @value{GDBN} copies your
1526 partial input (@samp{b make_} in the example) so you can finish the
1529 If you just want to see the list of alternatives in the first place, you
1530 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1531 means @kbd{@key{META} ?}. You can type this either by holding down a
1532 key designated as the @key{META} shift on your keyboard (if there is
1533 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1535 @cindex quotes in commands
1536 @cindex completion of quoted strings
1537 Sometimes the string you need, while logically a ``word'', may contain
1538 parentheses or other characters that @value{GDBN} normally excludes from
1539 its notion of a word. To permit word completion to work in this
1540 situation, you may enclose words in @code{'} (single quote marks) in
1541 @value{GDBN} commands.
1543 The most likely situation where you might need this is in typing the
1544 name of a C@t{++} function. This is because C@t{++} allows function
1545 overloading (multiple definitions of the same function, distinguished
1546 by argument type). For example, when you want to set a breakpoint you
1547 may need to distinguish whether you mean the version of @code{name}
1548 that takes an @code{int} parameter, @code{name(int)}, or the version
1549 that takes a @code{float} parameter, @code{name(float)}. To use the
1550 word-completion facilities in this situation, type a single quote
1551 @code{'} at the beginning of the function name. This alerts
1552 @value{GDBN} that it may need to consider more information than usual
1553 when you press @key{TAB} or @kbd{M-?} to request word completion:
1556 (@value{GDBP}) b 'bubble( @kbd{M-?}
1557 bubble(double,double) bubble(int,int)
1558 (@value{GDBP}) b 'bubble(
1561 In some cases, @value{GDBN} can tell that completing a name requires using
1562 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1563 completing as much as it can) if you do not type the quote in the first
1567 (@value{GDBP}) b bub @key{TAB}
1568 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1569 (@value{GDBP}) b 'bubble(
1573 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1574 you have not yet started typing the argument list when you ask for
1575 completion on an overloaded symbol.
1577 For more information about overloaded functions, see @ref{C Plus Plus
1578 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1579 overload-resolution off} to disable overload resolution;
1580 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1582 @cindex completion of structure field names
1583 @cindex structure field name completion
1584 @cindex completion of union field names
1585 @cindex union field name completion
1586 When completing in an expression which looks up a field in a
1587 structure, @value{GDBN} also tries@footnote{The completer can be
1588 confused by certain kinds of invalid expressions. Also, it only
1589 examines the static type of the expression, not the dynamic type.} to
1590 limit completions to the field names available in the type of the
1594 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1595 magic to_fputs to_rewind
1596 to_data to_isatty to_write
1597 to_delete to_put to_write_async_safe
1602 This is because the @code{gdb_stdout} is a variable of the type
1603 @code{struct ui_file} that is defined in @value{GDBN} sources as
1610 ui_file_flush_ftype *to_flush;
1611 ui_file_write_ftype *to_write;
1612 ui_file_write_async_safe_ftype *to_write_async_safe;
1613 ui_file_fputs_ftype *to_fputs;
1614 ui_file_read_ftype *to_read;
1615 ui_file_delete_ftype *to_delete;
1616 ui_file_isatty_ftype *to_isatty;
1617 ui_file_rewind_ftype *to_rewind;
1618 ui_file_put_ftype *to_put;
1625 @section Getting Help
1626 @cindex online documentation
1629 You can always ask @value{GDBN} itself for information on its commands,
1630 using the command @code{help}.
1633 @kindex h @r{(@code{help})}
1636 You can use @code{help} (abbreviated @code{h}) with no arguments to
1637 display a short list of named classes of commands:
1641 List of classes of commands:
1643 aliases -- Aliases of other commands
1644 breakpoints -- Making program stop at certain points
1645 data -- Examining data
1646 files -- Specifying and examining files
1647 internals -- Maintenance commands
1648 obscure -- Obscure features
1649 running -- Running the program
1650 stack -- Examining the stack
1651 status -- Status inquiries
1652 support -- Support facilities
1653 tracepoints -- Tracing of program execution without
1654 stopping the program
1655 user-defined -- User-defined commands
1657 Type "help" followed by a class name for a list of
1658 commands in that class.
1659 Type "help" followed by command name for full
1661 Command name abbreviations are allowed if unambiguous.
1664 @c the above line break eliminates huge line overfull...
1666 @item help @var{class}
1667 Using one of the general help classes as an argument, you can get a
1668 list of the individual commands in that class. For example, here is the
1669 help display for the class @code{status}:
1672 (@value{GDBP}) help status
1677 @c Line break in "show" line falsifies real output, but needed
1678 @c to fit in smallbook page size.
1679 info -- Generic command for showing things
1680 about the program being debugged
1681 show -- Generic command for showing things
1684 Type "help" followed by command name for full
1686 Command name abbreviations are allowed if unambiguous.
1690 @item help @var{command}
1691 With a command name as @code{help} argument, @value{GDBN} displays a
1692 short paragraph on how to use that command.
1695 @item apropos @var{args}
1696 The @code{apropos} command searches through all of the @value{GDBN}
1697 commands, and their documentation, for the regular expression specified in
1698 @var{args}. It prints out all matches found. For example:
1709 set symbol-reloading -- Set dynamic symbol table reloading
1710 multiple times in one run
1711 show symbol-reloading -- Show dynamic symbol table reloading
1712 multiple times in one run
1717 @item complete @var{args}
1718 The @code{complete @var{args}} command lists all the possible completions
1719 for the beginning of a command. Use @var{args} to specify the beginning of the
1720 command you want completed. For example:
1726 @noindent results in:
1737 @noindent This is intended for use by @sc{gnu} Emacs.
1740 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1741 and @code{show} to inquire about the state of your program, or the state
1742 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1743 manual introduces each of them in the appropriate context. The listings
1744 under @code{info} and under @code{show} in the Index point to
1745 all the sub-commands. @xref{Index}.
1750 @kindex i @r{(@code{info})}
1752 This command (abbreviated @code{i}) is for describing the state of your
1753 program. For example, you can show the arguments passed to a function
1754 with @code{info args}, list the registers currently in use with @code{info
1755 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1756 You can get a complete list of the @code{info} sub-commands with
1757 @w{@code{help info}}.
1761 You can assign the result of an expression to an environment variable with
1762 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1763 @code{set prompt $}.
1767 In contrast to @code{info}, @code{show} is for describing the state of
1768 @value{GDBN} itself.
1769 You can change most of the things you can @code{show}, by using the
1770 related command @code{set}; for example, you can control what number
1771 system is used for displays with @code{set radix}, or simply inquire
1772 which is currently in use with @code{show radix}.
1775 To display all the settable parameters and their current
1776 values, you can use @code{show} with no arguments; you may also use
1777 @code{info set}. Both commands produce the same display.
1778 @c FIXME: "info set" violates the rule that "info" is for state of
1779 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1780 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1784 Here are three miscellaneous @code{show} subcommands, all of which are
1785 exceptional in lacking corresponding @code{set} commands:
1788 @kindex show version
1789 @cindex @value{GDBN} version number
1791 Show what version of @value{GDBN} is running. You should include this
1792 information in @value{GDBN} bug-reports. If multiple versions of
1793 @value{GDBN} are in use at your site, you may need to determine which
1794 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1795 commands are introduced, and old ones may wither away. Also, many
1796 system vendors ship variant versions of @value{GDBN}, and there are
1797 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1798 The version number is the same as the one announced when you start
1801 @kindex show copying
1802 @kindex info copying
1803 @cindex display @value{GDBN} copyright
1806 Display information about permission for copying @value{GDBN}.
1808 @kindex show warranty
1809 @kindex info warranty
1811 @itemx info warranty
1812 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1813 if your version of @value{GDBN} comes with one.
1818 @chapter Running Programs Under @value{GDBN}
1820 When you run a program under @value{GDBN}, you must first generate
1821 debugging information when you compile it.
1823 You may start @value{GDBN} with its arguments, if any, in an environment
1824 of your choice. If you are doing native debugging, you may redirect
1825 your program's input and output, debug an already running process, or
1826 kill a child process.
1829 * Compilation:: Compiling for debugging
1830 * Starting:: Starting your program
1831 * Arguments:: Your program's arguments
1832 * Environment:: Your program's environment
1834 * Working Directory:: Your program's working directory
1835 * Input/Output:: Your program's input and output
1836 * Attach:: Debugging an already-running process
1837 * Kill Process:: Killing the child process
1839 * Inferiors and Programs:: Debugging multiple inferiors and programs
1840 * Threads:: Debugging programs with multiple threads
1841 * Forks:: Debugging forks
1842 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1846 @section Compiling for Debugging
1848 In order to debug a program effectively, you need to generate
1849 debugging information when you compile it. This debugging information
1850 is stored in the object file; it describes the data type of each
1851 variable or function and the correspondence between source line numbers
1852 and addresses in the executable code.
1854 To request debugging information, specify the @samp{-g} option when you run
1857 Programs that are to be shipped to your customers are compiled with
1858 optimizations, using the @samp{-O} compiler option. However, some
1859 compilers are unable to handle the @samp{-g} and @samp{-O} options
1860 together. Using those compilers, you cannot generate optimized
1861 executables containing debugging information.
1863 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1864 without @samp{-O}, making it possible to debug optimized code. We
1865 recommend that you @emph{always} use @samp{-g} whenever you compile a
1866 program. You may think your program is correct, but there is no sense
1867 in pushing your luck. For more information, see @ref{Optimized Code}.
1869 Older versions of the @sc{gnu} C compiler permitted a variant option
1870 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1871 format; if your @sc{gnu} C compiler has this option, do not use it.
1873 @value{GDBN} knows about preprocessor macros and can show you their
1874 expansion (@pxref{Macros}). Most compilers do not include information
1875 about preprocessor macros in the debugging information if you specify
1876 the @option{-g} flag alone, because this information is rather large.
1877 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1878 provides macro information if you specify the options
1879 @option{-gdwarf-2} and @option{-g3}; the former option requests
1880 debugging information in the Dwarf 2 format, and the latter requests
1881 ``extra information''. In the future, we hope to find more compact
1882 ways to represent macro information, so that it can be included with
1887 @section Starting your Program
1893 @kindex r @r{(@code{run})}
1896 Use the @code{run} command to start your program under @value{GDBN}.
1897 You must first specify the program name (except on VxWorks) with an
1898 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1899 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1900 (@pxref{Files, ,Commands to Specify Files}).
1904 If you are running your program in an execution environment that
1905 supports processes, @code{run} creates an inferior process and makes
1906 that process run your program. In some environments without processes,
1907 @code{run} jumps to the start of your program. Other targets,
1908 like @samp{remote}, are always running. If you get an error
1909 message like this one:
1912 The "remote" target does not support "run".
1913 Try "help target" or "continue".
1917 then use @code{continue} to run your program. You may need @code{load}
1918 first (@pxref{load}).
1920 The execution of a program is affected by certain information it
1921 receives from its superior. @value{GDBN} provides ways to specify this
1922 information, which you must do @emph{before} starting your program. (You
1923 can change it after starting your program, but such changes only affect
1924 your program the next time you start it.) This information may be
1925 divided into four categories:
1928 @item The @emph{arguments.}
1929 Specify the arguments to give your program as the arguments of the
1930 @code{run} command. If a shell is available on your target, the shell
1931 is used to pass the arguments, so that you may use normal conventions
1932 (such as wildcard expansion or variable substitution) in describing
1934 In Unix systems, you can control which shell is used with the
1935 @code{SHELL} environment variable.
1936 @xref{Arguments, ,Your Program's Arguments}.
1938 @item The @emph{environment.}
1939 Your program normally inherits its environment from @value{GDBN}, but you can
1940 use the @value{GDBN} commands @code{set environment} and @code{unset
1941 environment} to change parts of the environment that affect
1942 your program. @xref{Environment, ,Your Program's Environment}.
1944 @item The @emph{working directory.}
1945 Your program inherits its working directory from @value{GDBN}. You can set
1946 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1947 @xref{Working Directory, ,Your Program's Working Directory}.
1949 @item The @emph{standard input and output.}
1950 Your program normally uses the same device for standard input and
1951 standard output as @value{GDBN} is using. You can redirect input and output
1952 in the @code{run} command line, or you can use the @code{tty} command to
1953 set a different device for your program.
1954 @xref{Input/Output, ,Your Program's Input and Output}.
1957 @emph{Warning:} While input and output redirection work, you cannot use
1958 pipes to pass the output of the program you are debugging to another
1959 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1963 When you issue the @code{run} command, your program begins to execute
1964 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1965 of how to arrange for your program to stop. Once your program has
1966 stopped, you may call functions in your program, using the @code{print}
1967 or @code{call} commands. @xref{Data, ,Examining Data}.
1969 If the modification time of your symbol file has changed since the last
1970 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1971 table, and reads it again. When it does this, @value{GDBN} tries to retain
1972 your current breakpoints.
1977 @cindex run to main procedure
1978 The name of the main procedure can vary from language to language.
1979 With C or C@t{++}, the main procedure name is always @code{main}, but
1980 other languages such as Ada do not require a specific name for their
1981 main procedure. The debugger provides a convenient way to start the
1982 execution of the program and to stop at the beginning of the main
1983 procedure, depending on the language used.
1985 The @samp{start} command does the equivalent of setting a temporary
1986 breakpoint at the beginning of the main procedure and then invoking
1987 the @samp{run} command.
1989 @cindex elaboration phase
1990 Some programs contain an @dfn{elaboration} phase where some startup code is
1991 executed before the main procedure is called. This depends on the
1992 languages used to write your program. In C@t{++}, for instance,
1993 constructors for static and global objects are executed before
1994 @code{main} is called. It is therefore possible that the debugger stops
1995 before reaching the main procedure. However, the temporary breakpoint
1996 will remain to halt execution.
1998 Specify the arguments to give to your program as arguments to the
1999 @samp{start} command. These arguments will be given verbatim to the
2000 underlying @samp{run} command. Note that the same arguments will be
2001 reused if no argument is provided during subsequent calls to
2002 @samp{start} or @samp{run}.
2004 It is sometimes necessary to debug the program during elaboration. In
2005 these cases, using the @code{start} command would stop the execution of
2006 your program too late, as the program would have already completed the
2007 elaboration phase. Under these circumstances, insert breakpoints in your
2008 elaboration code before running your program.
2010 @kindex set exec-wrapper
2011 @item set exec-wrapper @var{wrapper}
2012 @itemx show exec-wrapper
2013 @itemx unset exec-wrapper
2014 When @samp{exec-wrapper} is set, the specified wrapper is used to
2015 launch programs for debugging. @value{GDBN} starts your program
2016 with a shell command of the form @kbd{exec @var{wrapper}
2017 @var{program}}. Quoting is added to @var{program} and its
2018 arguments, but not to @var{wrapper}, so you should add quotes if
2019 appropriate for your shell. The wrapper runs until it executes
2020 your program, and then @value{GDBN} takes control.
2022 You can use any program that eventually calls @code{execve} with
2023 its arguments as a wrapper. Several standard Unix utilities do
2024 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2025 with @code{exec "$@@"} will also work.
2027 For example, you can use @code{env} to pass an environment variable to
2028 the debugged program, without setting the variable in your shell's
2032 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2036 This command is available when debugging locally on most targets, excluding
2037 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2039 @kindex set disable-randomization
2040 @item set disable-randomization
2041 @itemx set disable-randomization on
2042 This option (enabled by default in @value{GDBN}) will turn off the native
2043 randomization of the virtual address space of the started program. This option
2044 is useful for multiple debugging sessions to make the execution better
2045 reproducible and memory addresses reusable across debugging sessions.
2047 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2048 On @sc{gnu}/Linux you can get the same behavior using
2051 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2054 @item set disable-randomization off
2055 Leave the behavior of the started executable unchanged. Some bugs rear their
2056 ugly heads only when the program is loaded at certain addresses. If your bug
2057 disappears when you run the program under @value{GDBN}, that might be because
2058 @value{GDBN} by default disables the address randomization on platforms, such
2059 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2060 disable-randomization off} to try to reproduce such elusive bugs.
2062 On targets where it is available, virtual address space randomization
2063 protects the programs against certain kinds of security attacks. In these
2064 cases the attacker needs to know the exact location of a concrete executable
2065 code. Randomizing its location makes it impossible to inject jumps misusing
2066 a code at its expected addresses.
2068 Prelinking shared libraries provides a startup performance advantage but it
2069 makes addresses in these libraries predictable for privileged processes by
2070 having just unprivileged access at the target system. Reading the shared
2071 library binary gives enough information for assembling the malicious code
2072 misusing it. Still even a prelinked shared library can get loaded at a new
2073 random address just requiring the regular relocation process during the
2074 startup. Shared libraries not already prelinked are always loaded at
2075 a randomly chosen address.
2077 Position independent executables (PIE) contain position independent code
2078 similar to the shared libraries and therefore such executables get loaded at
2079 a randomly chosen address upon startup. PIE executables always load even
2080 already prelinked shared libraries at a random address. You can build such
2081 executable using @command{gcc -fPIE -pie}.
2083 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2084 (as long as the randomization is enabled).
2086 @item show disable-randomization
2087 Show the current setting of the explicit disable of the native randomization of
2088 the virtual address space of the started program.
2093 @section Your Program's Arguments
2095 @cindex arguments (to your program)
2096 The arguments to your program can be specified by the arguments of the
2098 They are passed to a shell, which expands wildcard characters and
2099 performs redirection of I/O, and thence to your program. Your
2100 @code{SHELL} environment variable (if it exists) specifies what shell
2101 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2102 the default shell (@file{/bin/sh} on Unix).
2104 On non-Unix systems, the program is usually invoked directly by
2105 @value{GDBN}, which emulates I/O redirection via the appropriate system
2106 calls, and the wildcard characters are expanded by the startup code of
2107 the program, not by the shell.
2109 @code{run} with no arguments uses the same arguments used by the previous
2110 @code{run}, or those set by the @code{set args} command.
2115 Specify the arguments to be used the next time your program is run. If
2116 @code{set args} has no arguments, @code{run} executes your program
2117 with no arguments. Once you have run your program with arguments,
2118 using @code{set args} before the next @code{run} is the only way to run
2119 it again without arguments.
2123 Show the arguments to give your program when it is started.
2127 @section Your Program's Environment
2129 @cindex environment (of your program)
2130 The @dfn{environment} consists of a set of environment variables and
2131 their values. Environment variables conventionally record such things as
2132 your user name, your home directory, your terminal type, and your search
2133 path for programs to run. Usually you set up environment variables with
2134 the shell and they are inherited by all the other programs you run. When
2135 debugging, it can be useful to try running your program with a modified
2136 environment without having to start @value{GDBN} over again.
2140 @item path @var{directory}
2141 Add @var{directory} to the front of the @code{PATH} environment variable
2142 (the search path for executables) that will be passed to your program.
2143 The value of @code{PATH} used by @value{GDBN} does not change.
2144 You may specify several directory names, separated by whitespace or by a
2145 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2146 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2147 is moved to the front, so it is searched sooner.
2149 You can use the string @samp{$cwd} to refer to whatever is the current
2150 working directory at the time @value{GDBN} searches the path. If you
2151 use @samp{.} instead, it refers to the directory where you executed the
2152 @code{path} command. @value{GDBN} replaces @samp{.} in the
2153 @var{directory} argument (with the current path) before adding
2154 @var{directory} to the search path.
2155 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2156 @c document that, since repeating it would be a no-op.
2160 Display the list of search paths for executables (the @code{PATH}
2161 environment variable).
2163 @kindex show environment
2164 @item show environment @r{[}@var{varname}@r{]}
2165 Print the value of environment variable @var{varname} to be given to
2166 your program when it starts. If you do not supply @var{varname},
2167 print the names and values of all environment variables to be given to
2168 your program. You can abbreviate @code{environment} as @code{env}.
2170 @kindex set environment
2171 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2172 Set environment variable @var{varname} to @var{value}. The value
2173 changes for your program only, not for @value{GDBN} itself. @var{value} may
2174 be any string; the values of environment variables are just strings, and
2175 any interpretation is supplied by your program itself. The @var{value}
2176 parameter is optional; if it is eliminated, the variable is set to a
2178 @c "any string" here does not include leading, trailing
2179 @c blanks. Gnu asks: does anyone care?
2181 For example, this command:
2188 tells the debugged program, when subsequently run, that its user is named
2189 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2190 are not actually required.)
2192 @kindex unset environment
2193 @item unset environment @var{varname}
2194 Remove variable @var{varname} from the environment to be passed to your
2195 program. This is different from @samp{set env @var{varname} =};
2196 @code{unset environment} removes the variable from the environment,
2197 rather than assigning it an empty value.
2200 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2202 by your @code{SHELL} environment variable if it exists (or
2203 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2204 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2205 @file{.bashrc} for BASH---any variables you set in that file affect
2206 your program. You may wish to move setting of environment variables to
2207 files that are only run when you sign on, such as @file{.login} or
2210 @node Working Directory
2211 @section Your Program's Working Directory
2213 @cindex working directory (of your program)
2214 Each time you start your program with @code{run}, it inherits its
2215 working directory from the current working directory of @value{GDBN}.
2216 The @value{GDBN} working directory is initially whatever it inherited
2217 from its parent process (typically the shell), but you can specify a new
2218 working directory in @value{GDBN} with the @code{cd} command.
2220 The @value{GDBN} working directory also serves as a default for the commands
2221 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2226 @cindex change working directory
2227 @item cd @var{directory}
2228 Set the @value{GDBN} working directory to @var{directory}.
2232 Print the @value{GDBN} working directory.
2235 It is generally impossible to find the current working directory of
2236 the process being debugged (since a program can change its directory
2237 during its run). If you work on a system where @value{GDBN} is
2238 configured with the @file{/proc} support, you can use the @code{info
2239 proc} command (@pxref{SVR4 Process Information}) to find out the
2240 current working directory of the debuggee.
2243 @section Your Program's Input and Output
2248 By default, the program you run under @value{GDBN} does input and output to
2249 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2250 to its own terminal modes to interact with you, but it records the terminal
2251 modes your program was using and switches back to them when you continue
2252 running your program.
2255 @kindex info terminal
2257 Displays information recorded by @value{GDBN} about the terminal modes your
2261 You can redirect your program's input and/or output using shell
2262 redirection with the @code{run} command. For example,
2269 starts your program, diverting its output to the file @file{outfile}.
2272 @cindex controlling terminal
2273 Another way to specify where your program should do input and output is
2274 with the @code{tty} command. This command accepts a file name as
2275 argument, and causes this file to be the default for future @code{run}
2276 commands. It also resets the controlling terminal for the child
2277 process, for future @code{run} commands. For example,
2284 directs that processes started with subsequent @code{run} commands
2285 default to do input and output on the terminal @file{/dev/ttyb} and have
2286 that as their controlling terminal.
2288 An explicit redirection in @code{run} overrides the @code{tty} command's
2289 effect on the input/output device, but not its effect on the controlling
2292 When you use the @code{tty} command or redirect input in the @code{run}
2293 command, only the input @emph{for your program} is affected. The input
2294 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2295 for @code{set inferior-tty}.
2297 @cindex inferior tty
2298 @cindex set inferior controlling terminal
2299 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2300 display the name of the terminal that will be used for future runs of your
2304 @item set inferior-tty /dev/ttyb
2305 @kindex set inferior-tty
2306 Set the tty for the program being debugged to /dev/ttyb.
2308 @item show inferior-tty
2309 @kindex show inferior-tty
2310 Show the current tty for the program being debugged.
2314 @section Debugging an Already-running Process
2319 @item attach @var{process-id}
2320 This command attaches to a running process---one that was started
2321 outside @value{GDBN}. (@code{info files} shows your active
2322 targets.) The command takes as argument a process ID. The usual way to
2323 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2324 or with the @samp{jobs -l} shell command.
2326 @code{attach} does not repeat if you press @key{RET} a second time after
2327 executing the command.
2330 To use @code{attach}, your program must be running in an environment
2331 which supports processes; for example, @code{attach} does not work for
2332 programs on bare-board targets that lack an operating system. You must
2333 also have permission to send the process a signal.
2335 When you use @code{attach}, the debugger finds the program running in
2336 the process first by looking in the current working directory, then (if
2337 the program is not found) by using the source file search path
2338 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2339 the @code{file} command to load the program. @xref{Files, ,Commands to
2342 The first thing @value{GDBN} does after arranging to debug the specified
2343 process is to stop it. You can examine and modify an attached process
2344 with all the @value{GDBN} commands that are ordinarily available when
2345 you start processes with @code{run}. You can insert breakpoints; you
2346 can step and continue; you can modify storage. If you would rather the
2347 process continue running, you may use the @code{continue} command after
2348 attaching @value{GDBN} to the process.
2353 When you have finished debugging the attached process, you can use the
2354 @code{detach} command to release it from @value{GDBN} control. Detaching
2355 the process continues its execution. After the @code{detach} command,
2356 that process and @value{GDBN} become completely independent once more, and you
2357 are ready to @code{attach} another process or start one with @code{run}.
2358 @code{detach} does not repeat if you press @key{RET} again after
2359 executing the command.
2362 If you exit @value{GDBN} while you have an attached process, you detach
2363 that process. If you use the @code{run} command, you kill that process.
2364 By default, @value{GDBN} asks for confirmation if you try to do either of these
2365 things; you can control whether or not you need to confirm by using the
2366 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2370 @section Killing the Child Process
2375 Kill the child process in which your program is running under @value{GDBN}.
2378 This command is useful if you wish to debug a core dump instead of a
2379 running process. @value{GDBN} ignores any core dump file while your program
2382 On some operating systems, a program cannot be executed outside @value{GDBN}
2383 while you have breakpoints set on it inside @value{GDBN}. You can use the
2384 @code{kill} command in this situation to permit running your program
2385 outside the debugger.
2387 The @code{kill} command is also useful if you wish to recompile and
2388 relink your program, since on many systems it is impossible to modify an
2389 executable file while it is running in a process. In this case, when you
2390 next type @code{run}, @value{GDBN} notices that the file has changed, and
2391 reads the symbol table again (while trying to preserve your current
2392 breakpoint settings).
2394 @node Inferiors and Programs
2395 @section Debugging Multiple Inferiors and Programs
2397 @value{GDBN} lets you run and debug multiple programs in a single
2398 session. In addition, @value{GDBN} on some systems may let you run
2399 several programs simultaneously (otherwise you have to exit from one
2400 before starting another). In the most general case, you can have
2401 multiple threads of execution in each of multiple processes, launched
2402 from multiple executables.
2405 @value{GDBN} represents the state of each program execution with an
2406 object called an @dfn{inferior}. An inferior typically corresponds to
2407 a process, but is more general and applies also to targets that do not
2408 have processes. Inferiors may be created before a process runs, and
2409 may be retained after a process exits. Inferiors have unique
2410 identifiers that are different from process ids. Usually each
2411 inferior will also have its own distinct address space, although some
2412 embedded targets may have several inferiors running in different parts
2413 of a single address space. Each inferior may in turn have multiple
2414 threads running in it.
2416 To find out what inferiors exist at any moment, use @w{@code{info
2420 @kindex info inferiors
2421 @item info inferiors
2422 Print a list of all inferiors currently being managed by @value{GDBN}.
2424 @value{GDBN} displays for each inferior (in this order):
2428 the inferior number assigned by @value{GDBN}
2431 the target system's inferior identifier
2434 the name of the executable the inferior is running.
2439 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2440 indicates the current inferior.
2444 @c end table here to get a little more width for example
2447 (@value{GDBP}) info inferiors
2448 Num Description Executable
2449 2 process 2307 hello
2450 * 1 process 3401 goodbye
2453 To switch focus between inferiors, use the @code{inferior} command:
2456 @kindex inferior @var{infno}
2457 @item inferior @var{infno}
2458 Make inferior number @var{infno} the current inferior. The argument
2459 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2460 in the first field of the @samp{info inferiors} display.
2464 You can get multiple executables into a debugging session via the
2465 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2466 systems @value{GDBN} can add inferiors to the debug session
2467 automatically by following calls to @code{fork} and @code{exec}. To
2468 remove inferiors from the debugging session use the
2469 @w{@code{remove-inferiors}} command.
2472 @kindex add-inferior
2473 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2474 Adds @var{n} inferiors to be run using @var{executable} as the
2475 executable. @var{n} defaults to 1. If no executable is specified,
2476 the inferiors begins empty, with no program. You can still assign or
2477 change the program assigned to the inferior at any time by using the
2478 @code{file} command with the executable name as its argument.
2480 @kindex clone-inferior
2481 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2482 Adds @var{n} inferiors ready to execute the same program as inferior
2483 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2484 number of the current inferior. This is a convenient command when you
2485 want to run another instance of the inferior you are debugging.
2488 (@value{GDBP}) info inferiors
2489 Num Description Executable
2490 * 1 process 29964 helloworld
2491 (@value{GDBP}) clone-inferior
2494 (@value{GDBP}) info inferiors
2495 Num Description Executable
2497 * 1 process 29964 helloworld
2500 You can now simply switch focus to inferior 2 and run it.
2502 @kindex remove-inferiors
2503 @item remove-inferiors @var{infno}@dots{}
2504 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2505 possible to remove an inferior that is running with this command. For
2506 those, use the @code{kill} or @code{detach} command first.
2510 To quit debugging one of the running inferiors that is not the current
2511 inferior, you can either detach from it by using the @w{@code{detach
2512 inferior}} command (allowing it to run independently), or kill it
2513 using the @w{@code{kill inferiors}} command:
2516 @kindex detach inferiors @var{infno}@dots{}
2517 @item detach inferior @var{infno}@dots{}
2518 Detach from the inferior or inferiors identified by @value{GDBN}
2519 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2520 still stays on the list of inferiors shown by @code{info inferiors},
2521 but its Description will show @samp{<null>}.
2523 @kindex kill inferiors @var{infno}@dots{}
2524 @item kill inferiors @var{infno}@dots{}
2525 Kill the inferior or inferiors identified by @value{GDBN} inferior
2526 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2527 stays on the list of inferiors shown by @code{info inferiors}, but its
2528 Description will show @samp{<null>}.
2531 After the successful completion of a command such as @code{detach},
2532 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2533 a normal process exit, the inferior is still valid and listed with
2534 @code{info inferiors}, ready to be restarted.
2537 To be notified when inferiors are started or exit under @value{GDBN}'s
2538 control use @w{@code{set print inferior-events}}:
2541 @kindex set print inferior-events
2542 @cindex print messages on inferior start and exit
2543 @item set print inferior-events
2544 @itemx set print inferior-events on
2545 @itemx set print inferior-events off
2546 The @code{set print inferior-events} command allows you to enable or
2547 disable printing of messages when @value{GDBN} notices that new
2548 inferiors have started or that inferiors have exited or have been
2549 detached. By default, these messages will not be printed.
2551 @kindex show print inferior-events
2552 @item show print inferior-events
2553 Show whether messages will be printed when @value{GDBN} detects that
2554 inferiors have started, exited or have been detached.
2557 Many commands will work the same with multiple programs as with a
2558 single program: e.g., @code{print myglobal} will simply display the
2559 value of @code{myglobal} in the current inferior.
2562 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2563 get more info about the relationship of inferiors, programs, address
2564 spaces in a debug session. You can do that with the @w{@code{maint
2565 info program-spaces}} command.
2568 @kindex maint info program-spaces
2569 @item maint info program-spaces
2570 Print a list of all program spaces currently being managed by
2573 @value{GDBN} displays for each program space (in this order):
2577 the program space number assigned by @value{GDBN}
2580 the name of the executable loaded into the program space, with e.g.,
2581 the @code{file} command.
2586 An asterisk @samp{*} preceding the @value{GDBN} program space number
2587 indicates the current program space.
2589 In addition, below each program space line, @value{GDBN} prints extra
2590 information that isn't suitable to display in tabular form. For
2591 example, the list of inferiors bound to the program space.
2594 (@value{GDBP}) maint info program-spaces
2597 Bound inferiors: ID 1 (process 21561)
2601 Here we can see that no inferior is running the program @code{hello},
2602 while @code{process 21561} is running the program @code{goodbye}. On
2603 some targets, it is possible that multiple inferiors are bound to the
2604 same program space. The most common example is that of debugging both
2605 the parent and child processes of a @code{vfork} call. For example,
2608 (@value{GDBP}) maint info program-spaces
2611 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2614 Here, both inferior 2 and inferior 1 are running in the same program
2615 space as a result of inferior 1 having executed a @code{vfork} call.
2619 @section Debugging Programs with Multiple Threads
2621 @cindex threads of execution
2622 @cindex multiple threads
2623 @cindex switching threads
2624 In some operating systems, such as HP-UX and Solaris, a single program
2625 may have more than one @dfn{thread} of execution. The precise semantics
2626 of threads differ from one operating system to another, but in general
2627 the threads of a single program are akin to multiple processes---except
2628 that they share one address space (that is, they can all examine and
2629 modify the same variables). On the other hand, each thread has its own
2630 registers and execution stack, and perhaps private memory.
2632 @value{GDBN} provides these facilities for debugging multi-thread
2636 @item automatic notification of new threads
2637 @item @samp{thread @var{threadno}}, a command to switch among threads
2638 @item @samp{info threads}, a command to inquire about existing threads
2639 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2640 a command to apply a command to a list of threads
2641 @item thread-specific breakpoints
2642 @item @samp{set print thread-events}, which controls printing of
2643 messages on thread start and exit.
2644 @item @samp{set libthread-db-search-path @var{path}}, which lets
2645 the user specify which @code{libthread_db} to use if the default choice
2646 isn't compatible with the program.
2650 @emph{Warning:} These facilities are not yet available on every
2651 @value{GDBN} configuration where the operating system supports threads.
2652 If your @value{GDBN} does not support threads, these commands have no
2653 effect. For example, a system without thread support shows no output
2654 from @samp{info threads}, and always rejects the @code{thread} command,
2658 (@value{GDBP}) info threads
2659 (@value{GDBP}) thread 1
2660 Thread ID 1 not known. Use the "info threads" command to
2661 see the IDs of currently known threads.
2663 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2664 @c doesn't support threads"?
2667 @cindex focus of debugging
2668 @cindex current thread
2669 The @value{GDBN} thread debugging facility allows you to observe all
2670 threads while your program runs---but whenever @value{GDBN} takes
2671 control, one thread in particular is always the focus of debugging.
2672 This thread is called the @dfn{current thread}. Debugging commands show
2673 program information from the perspective of the current thread.
2675 @cindex @code{New} @var{systag} message
2676 @cindex thread identifier (system)
2677 @c FIXME-implementors!! It would be more helpful if the [New...] message
2678 @c included GDB's numeric thread handle, so you could just go to that
2679 @c thread without first checking `info threads'.
2680 Whenever @value{GDBN} detects a new thread in your program, it displays
2681 the target system's identification for the thread with a message in the
2682 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2683 whose form varies depending on the particular system. For example, on
2684 @sc{gnu}/Linux, you might see
2687 [New Thread 0x41e02940 (LWP 25582)]
2691 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2692 the @var{systag} is simply something like @samp{process 368}, with no
2695 @c FIXME!! (1) Does the [New...] message appear even for the very first
2696 @c thread of a program, or does it only appear for the
2697 @c second---i.e.@: when it becomes obvious we have a multithread
2699 @c (2) *Is* there necessarily a first thread always? Or do some
2700 @c multithread systems permit starting a program with multiple
2701 @c threads ab initio?
2703 @cindex thread number
2704 @cindex thread identifier (GDB)
2705 For debugging purposes, @value{GDBN} associates its own thread
2706 number---always a single integer---with each thread in your program.
2709 @kindex info threads
2710 @item info threads @r{[}@var{id}@dots{}@r{]}
2711 Display a summary of all threads currently in your program. Optional
2712 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2713 means to print information only about the specified thread or threads.
2714 @value{GDBN} displays for each thread (in this order):
2718 the thread number assigned by @value{GDBN}
2721 the target system's thread identifier (@var{systag})
2724 the thread's name, if one is known. A thread can either be named by
2725 the user (see @code{thread name}, below), or, in some cases, by the
2729 the current stack frame summary for that thread
2733 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2734 indicates the current thread.
2738 @c end table here to get a little more width for example
2741 (@value{GDBP}) info threads
2743 3 process 35 thread 27 0x34e5 in sigpause ()
2744 2 process 35 thread 23 0x34e5 in sigpause ()
2745 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2749 On Solaris, you can display more information about user threads with a
2750 Solaris-specific command:
2753 @item maint info sol-threads
2754 @kindex maint info sol-threads
2755 @cindex thread info (Solaris)
2756 Display info on Solaris user threads.
2760 @kindex thread @var{threadno}
2761 @item thread @var{threadno}
2762 Make thread number @var{threadno} the current thread. The command
2763 argument @var{threadno} is the internal @value{GDBN} thread number, as
2764 shown in the first field of the @samp{info threads} display.
2765 @value{GDBN} responds by displaying the system identifier of the thread
2766 you selected, and its current stack frame summary:
2769 (@value{GDBP}) thread 2
2770 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2771 #0 some_function (ignore=0x0) at example.c:8
2772 8 printf ("hello\n");
2776 As with the @samp{[New @dots{}]} message, the form of the text after
2777 @samp{Switching to} depends on your system's conventions for identifying
2780 @vindex $_thread@r{, convenience variable}
2781 The debugger convenience variable @samp{$_thread} contains the number
2782 of the current thread. You may find this useful in writing breakpoint
2783 conditional expressions, command scripts, and so forth. See
2784 @xref{Convenience Vars,, Convenience Variables}, for general
2785 information on convenience variables.
2787 @kindex thread apply
2788 @cindex apply command to several threads
2789 @item thread apply [@var{threadno} | all] @var{command}
2790 The @code{thread apply} command allows you to apply the named
2791 @var{command} to one or more threads. Specify the numbers of the
2792 threads that you want affected with the command argument
2793 @var{threadno}. It can be a single thread number, one of the numbers
2794 shown in the first field of the @samp{info threads} display; or it
2795 could be a range of thread numbers, as in @code{2-4}. To apply a
2796 command to all threads, type @kbd{thread apply all @var{command}}.
2799 @cindex name a thread
2800 @item thread name [@var{name}]
2801 This command assigns a name to the current thread. If no argument is
2802 given, any existing user-specified name is removed. The thread name
2803 appears in the @samp{info threads} display.
2805 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2806 determine the name of the thread as given by the OS. On these
2807 systems, a name specified with @samp{thread name} will override the
2808 system-give name, and removing the user-specified name will cause
2809 @value{GDBN} to once again display the system-specified name.
2812 @cindex search for a thread
2813 @item thread find [@var{regexp}]
2814 Search for and display thread ids whose name or @var{systag}
2815 matches the supplied regular expression.
2817 As well as being the complement to the @samp{thread name} command,
2818 this command also allows you to identify a thread by its target
2819 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2823 (@value{GDBN}) thread find 26688
2824 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2825 (@value{GDBN}) info thread 4
2827 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
2830 @kindex set print thread-events
2831 @cindex print messages on thread start and exit
2832 @item set print thread-events
2833 @itemx set print thread-events on
2834 @itemx set print thread-events off
2835 The @code{set print thread-events} command allows you to enable or
2836 disable printing of messages when @value{GDBN} notices that new threads have
2837 started or that threads have exited. By default, these messages will
2838 be printed if detection of these events is supported by the target.
2839 Note that these messages cannot be disabled on all targets.
2841 @kindex show print thread-events
2842 @item show print thread-events
2843 Show whether messages will be printed when @value{GDBN} detects that threads
2844 have started and exited.
2847 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2848 more information about how @value{GDBN} behaves when you stop and start
2849 programs with multiple threads.
2851 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2852 watchpoints in programs with multiple threads.
2855 @kindex set libthread-db-search-path
2856 @cindex search path for @code{libthread_db}
2857 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2858 If this variable is set, @var{path} is a colon-separated list of
2859 directories @value{GDBN} will use to search for @code{libthread_db}.
2860 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2861 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
2862 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
2865 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2866 @code{libthread_db} library to obtain information about threads in the
2867 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2868 to find @code{libthread_db}.
2870 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
2871 refers to the default system directories that are
2872 normally searched for loading shared libraries.
2874 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
2875 refers to the directory from which @code{libpthread}
2876 was loaded in the inferior process.
2878 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2879 @value{GDBN} attempts to initialize it with the current inferior process.
2880 If this initialization fails (which could happen because of a version
2881 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2882 will unload @code{libthread_db}, and continue with the next directory.
2883 If none of @code{libthread_db} libraries initialize successfully,
2884 @value{GDBN} will issue a warning and thread debugging will be disabled.
2886 Setting @code{libthread-db-search-path} is currently implemented
2887 only on some platforms.
2889 @kindex show libthread-db-search-path
2890 @item show libthread-db-search-path
2891 Display current libthread_db search path.
2893 @kindex set debug libthread-db
2894 @kindex show debug libthread-db
2895 @cindex debugging @code{libthread_db}
2896 @item set debug libthread-db
2897 @itemx show debug libthread-db
2898 Turns on or off display of @code{libthread_db}-related events.
2899 Use @code{1} to enable, @code{0} to disable.
2903 @section Debugging Forks
2905 @cindex fork, debugging programs which call
2906 @cindex multiple processes
2907 @cindex processes, multiple
2908 On most systems, @value{GDBN} has no special support for debugging
2909 programs which create additional processes using the @code{fork}
2910 function. When a program forks, @value{GDBN} will continue to debug the
2911 parent process and the child process will run unimpeded. If you have
2912 set a breakpoint in any code which the child then executes, the child
2913 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2914 will cause it to terminate.
2916 However, if you want to debug the child process there is a workaround
2917 which isn't too painful. Put a call to @code{sleep} in the code which
2918 the child process executes after the fork. It may be useful to sleep
2919 only if a certain environment variable is set, or a certain file exists,
2920 so that the delay need not occur when you don't want to run @value{GDBN}
2921 on the child. While the child is sleeping, use the @code{ps} program to
2922 get its process ID. Then tell @value{GDBN} (a new invocation of
2923 @value{GDBN} if you are also debugging the parent process) to attach to
2924 the child process (@pxref{Attach}). From that point on you can debug
2925 the child process just like any other process which you attached to.
2927 On some systems, @value{GDBN} provides support for debugging programs that
2928 create additional processes using the @code{fork} or @code{vfork} functions.
2929 Currently, the only platforms with this feature are HP-UX (11.x and later
2930 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2932 By default, when a program forks, @value{GDBN} will continue to debug
2933 the parent process and the child process will run unimpeded.
2935 If you want to follow the child process instead of the parent process,
2936 use the command @w{@code{set follow-fork-mode}}.
2939 @kindex set follow-fork-mode
2940 @item set follow-fork-mode @var{mode}
2941 Set the debugger response to a program call of @code{fork} or
2942 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2943 process. The @var{mode} argument can be:
2947 The original process is debugged after a fork. The child process runs
2948 unimpeded. This is the default.
2951 The new process is debugged after a fork. The parent process runs
2956 @kindex show follow-fork-mode
2957 @item show follow-fork-mode
2958 Display the current debugger response to a @code{fork} or @code{vfork} call.
2961 @cindex debugging multiple processes
2962 On Linux, if you want to debug both the parent and child processes, use the
2963 command @w{@code{set detach-on-fork}}.
2966 @kindex set detach-on-fork
2967 @item set detach-on-fork @var{mode}
2968 Tells gdb whether to detach one of the processes after a fork, or
2969 retain debugger control over them both.
2973 The child process (or parent process, depending on the value of
2974 @code{follow-fork-mode}) will be detached and allowed to run
2975 independently. This is the default.
2978 Both processes will be held under the control of @value{GDBN}.
2979 One process (child or parent, depending on the value of
2980 @code{follow-fork-mode}) is debugged as usual, while the other
2985 @kindex show detach-on-fork
2986 @item show detach-on-fork
2987 Show whether detach-on-fork mode is on/off.
2990 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
2991 will retain control of all forked processes (including nested forks).
2992 You can list the forked processes under the control of @value{GDBN} by
2993 using the @w{@code{info inferiors}} command, and switch from one fork
2994 to another by using the @code{inferior} command (@pxref{Inferiors and
2995 Programs, ,Debugging Multiple Inferiors and Programs}).
2997 To quit debugging one of the forked processes, you can either detach
2998 from it by using the @w{@code{detach inferiors}} command (allowing it
2999 to run independently), or kill it using the @w{@code{kill inferiors}}
3000 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3003 If you ask to debug a child process and a @code{vfork} is followed by an
3004 @code{exec}, @value{GDBN} executes the new target up to the first
3005 breakpoint in the new target. If you have a breakpoint set on
3006 @code{main} in your original program, the breakpoint will also be set on
3007 the child process's @code{main}.
3009 On some systems, when a child process is spawned by @code{vfork}, you
3010 cannot debug the child or parent until an @code{exec} call completes.
3012 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3013 call executes, the new target restarts. To restart the parent
3014 process, use the @code{file} command with the parent executable name
3015 as its argument. By default, after an @code{exec} call executes,
3016 @value{GDBN} discards the symbols of the previous executable image.
3017 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3021 @kindex set follow-exec-mode
3022 @item set follow-exec-mode @var{mode}
3024 Set debugger response to a program call of @code{exec}. An
3025 @code{exec} call replaces the program image of a process.
3027 @code{follow-exec-mode} can be:
3031 @value{GDBN} creates a new inferior and rebinds the process to this
3032 new inferior. The program the process was running before the
3033 @code{exec} call can be restarted afterwards by restarting the
3039 (@value{GDBP}) info inferiors
3041 Id Description Executable
3044 process 12020 is executing new program: prog2
3045 Program exited normally.
3046 (@value{GDBP}) info inferiors
3047 Id Description Executable
3053 @value{GDBN} keeps the process bound to the same inferior. The new
3054 executable image replaces the previous executable loaded in the
3055 inferior. Restarting the inferior after the @code{exec} call, with
3056 e.g., the @code{run} command, restarts the executable the process was
3057 running after the @code{exec} call. This is the default mode.
3062 (@value{GDBP}) info inferiors
3063 Id Description Executable
3066 process 12020 is executing new program: prog2
3067 Program exited normally.
3068 (@value{GDBP}) info inferiors
3069 Id Description Executable
3076 You can use the @code{catch} command to make @value{GDBN} stop whenever
3077 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3078 Catchpoints, ,Setting Catchpoints}.
3080 @node Checkpoint/Restart
3081 @section Setting a @emph{Bookmark} to Return to Later
3086 @cindex snapshot of a process
3087 @cindex rewind program state
3089 On certain operating systems@footnote{Currently, only
3090 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3091 program's state, called a @dfn{checkpoint}, and come back to it
3094 Returning to a checkpoint effectively undoes everything that has
3095 happened in the program since the @code{checkpoint} was saved. This
3096 includes changes in memory, registers, and even (within some limits)
3097 system state. Effectively, it is like going back in time to the
3098 moment when the checkpoint was saved.
3100 Thus, if you're stepping thru a program and you think you're
3101 getting close to the point where things go wrong, you can save
3102 a checkpoint. Then, if you accidentally go too far and miss
3103 the critical statement, instead of having to restart your program
3104 from the beginning, you can just go back to the checkpoint and
3105 start again from there.
3107 This can be especially useful if it takes a lot of time or
3108 steps to reach the point where you think the bug occurs.
3110 To use the @code{checkpoint}/@code{restart} method of debugging:
3115 Save a snapshot of the debugged program's current execution state.
3116 The @code{checkpoint} command takes no arguments, but each checkpoint
3117 is assigned a small integer id, similar to a breakpoint id.
3119 @kindex info checkpoints
3120 @item info checkpoints
3121 List the checkpoints that have been saved in the current debugging
3122 session. For each checkpoint, the following information will be
3129 @item Source line, or label
3132 @kindex restart @var{checkpoint-id}
3133 @item restart @var{checkpoint-id}
3134 Restore the program state that was saved as checkpoint number
3135 @var{checkpoint-id}. All program variables, registers, stack frames
3136 etc.@: will be returned to the values that they had when the checkpoint
3137 was saved. In essence, gdb will ``wind back the clock'' to the point
3138 in time when the checkpoint was saved.
3140 Note that breakpoints, @value{GDBN} variables, command history etc.
3141 are not affected by restoring a checkpoint. In general, a checkpoint
3142 only restores things that reside in the program being debugged, not in
3145 @kindex delete checkpoint @var{checkpoint-id}
3146 @item delete checkpoint @var{checkpoint-id}
3147 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3151 Returning to a previously saved checkpoint will restore the user state
3152 of the program being debugged, plus a significant subset of the system
3153 (OS) state, including file pointers. It won't ``un-write'' data from
3154 a file, but it will rewind the file pointer to the previous location,
3155 so that the previously written data can be overwritten. For files
3156 opened in read mode, the pointer will also be restored so that the
3157 previously read data can be read again.
3159 Of course, characters that have been sent to a printer (or other
3160 external device) cannot be ``snatched back'', and characters received
3161 from eg.@: a serial device can be removed from internal program buffers,
3162 but they cannot be ``pushed back'' into the serial pipeline, ready to
3163 be received again. Similarly, the actual contents of files that have
3164 been changed cannot be restored (at this time).
3166 However, within those constraints, you actually can ``rewind'' your
3167 program to a previously saved point in time, and begin debugging it
3168 again --- and you can change the course of events so as to debug a
3169 different execution path this time.
3171 @cindex checkpoints and process id
3172 Finally, there is one bit of internal program state that will be
3173 different when you return to a checkpoint --- the program's process
3174 id. Each checkpoint will have a unique process id (or @var{pid}),
3175 and each will be different from the program's original @var{pid}.
3176 If your program has saved a local copy of its process id, this could
3177 potentially pose a problem.
3179 @subsection A Non-obvious Benefit of Using Checkpoints
3181 On some systems such as @sc{gnu}/Linux, address space randomization
3182 is performed on new processes for security reasons. This makes it
3183 difficult or impossible to set a breakpoint, or watchpoint, on an
3184 absolute address if you have to restart the program, since the
3185 absolute location of a symbol will change from one execution to the
3188 A checkpoint, however, is an @emph{identical} copy of a process.
3189 Therefore if you create a checkpoint at (eg.@:) the start of main,
3190 and simply return to that checkpoint instead of restarting the
3191 process, you can avoid the effects of address randomization and
3192 your symbols will all stay in the same place.
3195 @chapter Stopping and Continuing
3197 The principal purposes of using a debugger are so that you can stop your
3198 program before it terminates; or so that, if your program runs into
3199 trouble, you can investigate and find out why.
3201 Inside @value{GDBN}, your program may stop for any of several reasons,
3202 such as a signal, a breakpoint, or reaching a new line after a
3203 @value{GDBN} command such as @code{step}. You may then examine and
3204 change variables, set new breakpoints or remove old ones, and then
3205 continue execution. Usually, the messages shown by @value{GDBN} provide
3206 ample explanation of the status of your program---but you can also
3207 explicitly request this information at any time.
3210 @kindex info program
3212 Display information about the status of your program: whether it is
3213 running or not, what process it is, and why it stopped.
3217 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3218 * Continuing and Stepping:: Resuming execution
3220 * Thread Stops:: Stopping and starting multi-thread programs
3224 @section Breakpoints, Watchpoints, and Catchpoints
3227 A @dfn{breakpoint} makes your program stop whenever a certain point in
3228 the program is reached. For each breakpoint, you can add conditions to
3229 control in finer detail whether your program stops. You can set
3230 breakpoints with the @code{break} command and its variants (@pxref{Set
3231 Breaks, ,Setting Breakpoints}), to specify the place where your program
3232 should stop by line number, function name or exact address in the
3235 On some systems, you can set breakpoints in shared libraries before
3236 the executable is run. There is a minor limitation on HP-UX systems:
3237 you must wait until the executable is run in order to set breakpoints
3238 in shared library routines that are not called directly by the program
3239 (for example, routines that are arguments in a @code{pthread_create}
3243 @cindex data breakpoints
3244 @cindex memory tracing
3245 @cindex breakpoint on memory address
3246 @cindex breakpoint on variable modification
3247 A @dfn{watchpoint} is a special breakpoint that stops your program
3248 when the value of an expression changes. The expression may be a value
3249 of a variable, or it could involve values of one or more variables
3250 combined by operators, such as @samp{a + b}. This is sometimes called
3251 @dfn{data breakpoints}. You must use a different command to set
3252 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3253 from that, you can manage a watchpoint like any other breakpoint: you
3254 enable, disable, and delete both breakpoints and watchpoints using the
3257 You can arrange to have values from your program displayed automatically
3258 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3262 @cindex breakpoint on events
3263 A @dfn{catchpoint} is another special breakpoint that stops your program
3264 when a certain kind of event occurs, such as the throwing of a C@t{++}
3265 exception or the loading of a library. As with watchpoints, you use a
3266 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3267 Catchpoints}), but aside from that, you can manage a catchpoint like any
3268 other breakpoint. (To stop when your program receives a signal, use the
3269 @code{handle} command; see @ref{Signals, ,Signals}.)
3271 @cindex breakpoint numbers
3272 @cindex numbers for breakpoints
3273 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3274 catchpoint when you create it; these numbers are successive integers
3275 starting with one. In many of the commands for controlling various
3276 features of breakpoints you use the breakpoint number to say which
3277 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3278 @dfn{disabled}; if disabled, it has no effect on your program until you
3281 @cindex breakpoint ranges
3282 @cindex ranges of breakpoints
3283 Some @value{GDBN} commands accept a range of breakpoints on which to
3284 operate. A breakpoint range is either a single breakpoint number, like
3285 @samp{5}, or two such numbers, in increasing order, separated by a
3286 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3287 all breakpoints in that range are operated on.
3290 * Set Breaks:: Setting breakpoints
3291 * Set Watchpoints:: Setting watchpoints
3292 * Set Catchpoints:: Setting catchpoints
3293 * Delete Breaks:: Deleting breakpoints
3294 * Disabling:: Disabling breakpoints
3295 * Conditions:: Break conditions
3296 * Break Commands:: Breakpoint command lists
3297 * Save Breakpoints:: How to save breakpoints in a file
3298 * Error in Breakpoints:: ``Cannot insert breakpoints''
3299 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3303 @subsection Setting Breakpoints
3305 @c FIXME LMB what does GDB do if no code on line of breakpt?
3306 @c consider in particular declaration with/without initialization.
3308 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3311 @kindex b @r{(@code{break})}
3312 @vindex $bpnum@r{, convenience variable}
3313 @cindex latest breakpoint
3314 Breakpoints are set with the @code{break} command (abbreviated
3315 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3316 number of the breakpoint you've set most recently; see @ref{Convenience
3317 Vars,, Convenience Variables}, for a discussion of what you can do with
3318 convenience variables.
3321 @item break @var{location}
3322 Set a breakpoint at the given @var{location}, which can specify a
3323 function name, a line number, or an address of an instruction.
3324 (@xref{Specify Location}, for a list of all the possible ways to
3325 specify a @var{location}.) The breakpoint will stop your program just
3326 before it executes any of the code in the specified @var{location}.
3328 When using source languages that permit overloading of symbols, such as
3329 C@t{++}, a function name may refer to more than one possible place to break.
3330 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3333 It is also possible to insert a breakpoint that will stop the program
3334 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3335 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3338 When called without any arguments, @code{break} sets a breakpoint at
3339 the next instruction to be executed in the selected stack frame
3340 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3341 innermost, this makes your program stop as soon as control
3342 returns to that frame. This is similar to the effect of a
3343 @code{finish} command in the frame inside the selected frame---except
3344 that @code{finish} does not leave an active breakpoint. If you use
3345 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3346 the next time it reaches the current location; this may be useful
3349 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3350 least one instruction has been executed. If it did not do this, you
3351 would be unable to proceed past a breakpoint without first disabling the
3352 breakpoint. This rule applies whether or not the breakpoint already
3353 existed when your program stopped.
3355 @item break @dots{} if @var{cond}
3356 Set a breakpoint with condition @var{cond}; evaluate the expression
3357 @var{cond} each time the breakpoint is reached, and stop only if the
3358 value is nonzero---that is, if @var{cond} evaluates as true.
3359 @samp{@dots{}} stands for one of the possible arguments described
3360 above (or no argument) specifying where to break. @xref{Conditions,
3361 ,Break Conditions}, for more information on breakpoint conditions.
3364 @item tbreak @var{args}
3365 Set a breakpoint enabled only for one stop. @var{args} are the
3366 same as for the @code{break} command, and the breakpoint is set in the same
3367 way, but the breakpoint is automatically deleted after the first time your
3368 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3371 @cindex hardware breakpoints
3372 @item hbreak @var{args}
3373 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3374 @code{break} command and the breakpoint is set in the same way, but the
3375 breakpoint requires hardware support and some target hardware may not
3376 have this support. The main purpose of this is EPROM/ROM code
3377 debugging, so you can set a breakpoint at an instruction without
3378 changing the instruction. This can be used with the new trap-generation
3379 provided by SPARClite DSU and most x86-based targets. These targets
3380 will generate traps when a program accesses some data or instruction
3381 address that is assigned to the debug registers. However the hardware
3382 breakpoint registers can take a limited number of breakpoints. For
3383 example, on the DSU, only two data breakpoints can be set at a time, and
3384 @value{GDBN} will reject this command if more than two are used. Delete
3385 or disable unused hardware breakpoints before setting new ones
3386 (@pxref{Disabling, ,Disabling Breakpoints}).
3387 @xref{Conditions, ,Break Conditions}.
3388 For remote targets, you can restrict the number of hardware
3389 breakpoints @value{GDBN} will use, see @ref{set remote
3390 hardware-breakpoint-limit}.
3393 @item thbreak @var{args}
3394 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3395 are the same as for the @code{hbreak} command and the breakpoint is set in
3396 the same way. However, like the @code{tbreak} command,
3397 the breakpoint is automatically deleted after the
3398 first time your program stops there. Also, like the @code{hbreak}
3399 command, the breakpoint requires hardware support and some target hardware
3400 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3401 See also @ref{Conditions, ,Break Conditions}.
3404 @cindex regular expression
3405 @cindex breakpoints at functions matching a regexp
3406 @cindex set breakpoints in many functions
3407 @item rbreak @var{regex}
3408 Set breakpoints on all functions matching the regular expression
3409 @var{regex}. This command sets an unconditional breakpoint on all
3410 matches, printing a list of all breakpoints it set. Once these
3411 breakpoints are set, they are treated just like the breakpoints set with
3412 the @code{break} command. You can delete them, disable them, or make
3413 them conditional the same way as any other breakpoint.
3415 The syntax of the regular expression is the standard one used with tools
3416 like @file{grep}. Note that this is different from the syntax used by
3417 shells, so for instance @code{foo*} matches all functions that include
3418 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3419 @code{.*} leading and trailing the regular expression you supply, so to
3420 match only functions that begin with @code{foo}, use @code{^foo}.
3422 @cindex non-member C@t{++} functions, set breakpoint in
3423 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3424 breakpoints on overloaded functions that are not members of any special
3427 @cindex set breakpoints on all functions
3428 The @code{rbreak} command can be used to set breakpoints in
3429 @strong{all} the functions in a program, like this:
3432 (@value{GDBP}) rbreak .
3435 @item rbreak @var{file}:@var{regex}
3436 If @code{rbreak} is called with a filename qualification, it limits
3437 the search for functions matching the given regular expression to the
3438 specified @var{file}. This can be used, for example, to set breakpoints on
3439 every function in a given file:
3442 (@value{GDBP}) rbreak file.c:.
3445 The colon separating the filename qualifier from the regex may
3446 optionally be surrounded by spaces.
3448 @kindex info breakpoints
3449 @cindex @code{$_} and @code{info breakpoints}
3450 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3451 @itemx info break @r{[}@var{n}@dots{}@r{]}
3452 Print a table of all breakpoints, watchpoints, and catchpoints set and
3453 not deleted. Optional argument @var{n} means print information only
3454 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3455 For each breakpoint, following columns are printed:
3458 @item Breakpoint Numbers
3460 Breakpoint, watchpoint, or catchpoint.
3462 Whether the breakpoint is marked to be disabled or deleted when hit.
3463 @item Enabled or Disabled
3464 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3465 that are not enabled.
3467 Where the breakpoint is in your program, as a memory address. For a
3468 pending breakpoint whose address is not yet known, this field will
3469 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3470 library that has the symbol or line referred by breakpoint is loaded.
3471 See below for details. A breakpoint with several locations will
3472 have @samp{<MULTIPLE>} in this field---see below for details.
3474 Where the breakpoint is in the source for your program, as a file and
3475 line number. For a pending breakpoint, the original string passed to
3476 the breakpoint command will be listed as it cannot be resolved until
3477 the appropriate shared library is loaded in the future.
3481 If a breakpoint is conditional, @code{info break} shows the condition on
3482 the line following the affected breakpoint; breakpoint commands, if any,
3483 are listed after that. A pending breakpoint is allowed to have a condition
3484 specified for it. The condition is not parsed for validity until a shared
3485 library is loaded that allows the pending breakpoint to resolve to a
3489 @code{info break} with a breakpoint
3490 number @var{n} as argument lists only that breakpoint. The
3491 convenience variable @code{$_} and the default examining-address for
3492 the @code{x} command are set to the address of the last breakpoint
3493 listed (@pxref{Memory, ,Examining Memory}).
3496 @code{info break} displays a count of the number of times the breakpoint
3497 has been hit. This is especially useful in conjunction with the
3498 @code{ignore} command. You can ignore a large number of breakpoint
3499 hits, look at the breakpoint info to see how many times the breakpoint
3500 was hit, and then run again, ignoring one less than that number. This
3501 will get you quickly to the last hit of that breakpoint.
3504 @value{GDBN} allows you to set any number of breakpoints at the same place in
3505 your program. There is nothing silly or meaningless about this. When
3506 the breakpoints are conditional, this is even useful
3507 (@pxref{Conditions, ,Break Conditions}).
3509 @cindex multiple locations, breakpoints
3510 @cindex breakpoints, multiple locations
3511 It is possible that a breakpoint corresponds to several locations
3512 in your program. Examples of this situation are:
3516 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3517 instances of the function body, used in different cases.
3520 For a C@t{++} template function, a given line in the function can
3521 correspond to any number of instantiations.
3524 For an inlined function, a given source line can correspond to
3525 several places where that function is inlined.
3528 In all those cases, @value{GDBN} will insert a breakpoint at all
3529 the relevant locations@footnote{
3530 As of this writing, multiple-location breakpoints work only if there's
3531 line number information for all the locations. This means that they
3532 will generally not work in system libraries, unless you have debug
3533 info with line numbers for them.}.
3535 A breakpoint with multiple locations is displayed in the breakpoint
3536 table using several rows---one header row, followed by one row for
3537 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3538 address column. The rows for individual locations contain the actual
3539 addresses for locations, and show the functions to which those
3540 locations belong. The number column for a location is of the form
3541 @var{breakpoint-number}.@var{location-number}.
3546 Num Type Disp Enb Address What
3547 1 breakpoint keep y <MULTIPLE>
3549 breakpoint already hit 1 time
3550 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3551 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3554 Each location can be individually enabled or disabled by passing
3555 @var{breakpoint-number}.@var{location-number} as argument to the
3556 @code{enable} and @code{disable} commands. Note that you cannot
3557 delete the individual locations from the list, you can only delete the
3558 entire list of locations that belong to their parent breakpoint (with
3559 the @kbd{delete @var{num}} command, where @var{num} is the number of
3560 the parent breakpoint, 1 in the above example). Disabling or enabling
3561 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3562 that belong to that breakpoint.
3564 @cindex pending breakpoints
3565 It's quite common to have a breakpoint inside a shared library.
3566 Shared libraries can be loaded and unloaded explicitly,
3567 and possibly repeatedly, as the program is executed. To support
3568 this use case, @value{GDBN} updates breakpoint locations whenever
3569 any shared library is loaded or unloaded. Typically, you would
3570 set a breakpoint in a shared library at the beginning of your
3571 debugging session, when the library is not loaded, and when the
3572 symbols from the library are not available. When you try to set
3573 breakpoint, @value{GDBN} will ask you if you want to set
3574 a so called @dfn{pending breakpoint}---breakpoint whose address
3575 is not yet resolved.
3577 After the program is run, whenever a new shared library is loaded,
3578 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3579 shared library contains the symbol or line referred to by some
3580 pending breakpoint, that breakpoint is resolved and becomes an
3581 ordinary breakpoint. When a library is unloaded, all breakpoints
3582 that refer to its symbols or source lines become pending again.
3584 This logic works for breakpoints with multiple locations, too. For
3585 example, if you have a breakpoint in a C@t{++} template function, and
3586 a newly loaded shared library has an instantiation of that template,
3587 a new location is added to the list of locations for the breakpoint.
3589 Except for having unresolved address, pending breakpoints do not
3590 differ from regular breakpoints. You can set conditions or commands,
3591 enable and disable them and perform other breakpoint operations.
3593 @value{GDBN} provides some additional commands for controlling what
3594 happens when the @samp{break} command cannot resolve breakpoint
3595 address specification to an address:
3597 @kindex set breakpoint pending
3598 @kindex show breakpoint pending
3600 @item set breakpoint pending auto
3601 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3602 location, it queries you whether a pending breakpoint should be created.
3604 @item set breakpoint pending on
3605 This indicates that an unrecognized breakpoint location should automatically
3606 result in a pending breakpoint being created.
3608 @item set breakpoint pending off
3609 This indicates that pending breakpoints are not to be created. Any
3610 unrecognized breakpoint location results in an error. This setting does
3611 not affect any pending breakpoints previously created.
3613 @item show breakpoint pending
3614 Show the current behavior setting for creating pending breakpoints.
3617 The settings above only affect the @code{break} command and its
3618 variants. Once breakpoint is set, it will be automatically updated
3619 as shared libraries are loaded and unloaded.
3621 @cindex automatic hardware breakpoints
3622 For some targets, @value{GDBN} can automatically decide if hardware or
3623 software breakpoints should be used, depending on whether the
3624 breakpoint address is read-only or read-write. This applies to
3625 breakpoints set with the @code{break} command as well as to internal
3626 breakpoints set by commands like @code{next} and @code{finish}. For
3627 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3630 You can control this automatic behaviour with the following commands::
3632 @kindex set breakpoint auto-hw
3633 @kindex show breakpoint auto-hw
3635 @item set breakpoint auto-hw on
3636 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3637 will try to use the target memory map to decide if software or hardware
3638 breakpoint must be used.
3640 @item set breakpoint auto-hw off
3641 This indicates @value{GDBN} should not automatically select breakpoint
3642 type. If the target provides a memory map, @value{GDBN} will warn when
3643 trying to set software breakpoint at a read-only address.
3646 @value{GDBN} normally implements breakpoints by replacing the program code
3647 at the breakpoint address with a special instruction, which, when
3648 executed, given control to the debugger. By default, the program
3649 code is so modified only when the program is resumed. As soon as
3650 the program stops, @value{GDBN} restores the original instructions. This
3651 behaviour guards against leaving breakpoints inserted in the
3652 target should gdb abrubptly disconnect. However, with slow remote
3653 targets, inserting and removing breakpoint can reduce the performance.
3654 This behavior can be controlled with the following commands::
3656 @kindex set breakpoint always-inserted
3657 @kindex show breakpoint always-inserted
3659 @item set breakpoint always-inserted off
3660 All breakpoints, including newly added by the user, are inserted in
3661 the target only when the target is resumed. All breakpoints are
3662 removed from the target when it stops.
3664 @item set breakpoint always-inserted on
3665 Causes all breakpoints to be inserted in the target at all times. If
3666 the user adds a new breakpoint, or changes an existing breakpoint, the
3667 breakpoints in the target are updated immediately. A breakpoint is
3668 removed from the target only when breakpoint itself is removed.
3670 @cindex non-stop mode, and @code{breakpoint always-inserted}
3671 @item set breakpoint always-inserted auto
3672 This is the default mode. If @value{GDBN} is controlling the inferior
3673 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3674 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3675 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3676 @code{breakpoint always-inserted} mode is off.
3679 @cindex negative breakpoint numbers
3680 @cindex internal @value{GDBN} breakpoints
3681 @value{GDBN} itself sometimes sets breakpoints in your program for
3682 special purposes, such as proper handling of @code{longjmp} (in C
3683 programs). These internal breakpoints are assigned negative numbers,
3684 starting with @code{-1}; @samp{info breakpoints} does not display them.
3685 You can see these breakpoints with the @value{GDBN} maintenance command
3686 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3689 @node Set Watchpoints
3690 @subsection Setting Watchpoints
3692 @cindex setting watchpoints
3693 You can use a watchpoint to stop execution whenever the value of an
3694 expression changes, without having to predict a particular place where
3695 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3696 The expression may be as simple as the value of a single variable, or
3697 as complex as many variables combined by operators. Examples include:
3701 A reference to the value of a single variable.
3704 An address cast to an appropriate data type. For example,
3705 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3706 address (assuming an @code{int} occupies 4 bytes).
3709 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3710 expression can use any operators valid in the program's native
3711 language (@pxref{Languages}).
3714 You can set a watchpoint on an expression even if the expression can
3715 not be evaluated yet. For instance, you can set a watchpoint on
3716 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3717 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3718 the expression produces a valid value. If the expression becomes
3719 valid in some other way than changing a variable (e.g.@: if the memory
3720 pointed to by @samp{*global_ptr} becomes readable as the result of a
3721 @code{malloc} call), @value{GDBN} may not stop until the next time
3722 the expression changes.
3724 @cindex software watchpoints
3725 @cindex hardware watchpoints
3726 Depending on your system, watchpoints may be implemented in software or
3727 hardware. @value{GDBN} does software watchpointing by single-stepping your
3728 program and testing the variable's value each time, which is hundreds of
3729 times slower than normal execution. (But this may still be worth it, to
3730 catch errors where you have no clue what part of your program is the
3733 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3734 x86-based targets, @value{GDBN} includes support for hardware
3735 watchpoints, which do not slow down the running of your program.
3739 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3740 Set a watchpoint for an expression. @value{GDBN} will break when the
3741 expression @var{expr} is written into by the program and its value
3742 changes. The simplest (and the most popular) use of this command is
3743 to watch the value of a single variable:
3746 (@value{GDBP}) watch foo
3749 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3750 argument, @value{GDBN} breaks only when the thread identified by
3751 @var{threadnum} changes the value of @var{expr}. If any other threads
3752 change the value of @var{expr}, @value{GDBN} will not break. Note
3753 that watchpoints restricted to a single thread in this way only work
3754 with Hardware Watchpoints.
3756 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3757 (see below). The @code{-location} argument tells @value{GDBN} to
3758 instead watch the memory referred to by @var{expr}. In this case,
3759 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3760 and watch the memory at that address. The type of the result is used
3761 to determine the size of the watched memory. If the expression's
3762 result does not have an address, then @value{GDBN} will print an
3765 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3766 of masked watchpoints, if the current architecture supports this
3767 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3768 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
3769 to an address to watch. The mask specifies that some bits of an address
3770 (the bits which are reset in the mask) should be ignored when matching
3771 the address accessed by the inferior against the watchpoint address.
3772 Thus, a masked watchpoint watches many addresses simultaneously---those
3773 addresses whose unmasked bits are identical to the unmasked bits in the
3774 watchpoint address. The @code{mask} argument implies @code{-location}.
3778 (@value{GDBP}) watch foo mask 0xffff00ff
3779 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
3783 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3784 Set a watchpoint that will break when the value of @var{expr} is read
3788 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3789 Set a watchpoint that will break when @var{expr} is either read from
3790 or written into by the program.
3792 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
3793 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
3794 This command prints a list of watchpoints, using the same format as
3795 @code{info break} (@pxref{Set Breaks}).
3798 If you watch for a change in a numerically entered address you need to
3799 dereference it, as the address itself is just a constant number which will
3800 never change. @value{GDBN} refuses to create a watchpoint that watches
3801 a never-changing value:
3804 (@value{GDBP}) watch 0x600850
3805 Cannot watch constant value 0x600850.
3806 (@value{GDBP}) watch *(int *) 0x600850
3807 Watchpoint 1: *(int *) 6293584
3810 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3811 watchpoints execute very quickly, and the debugger reports a change in
3812 value at the exact instruction where the change occurs. If @value{GDBN}
3813 cannot set a hardware watchpoint, it sets a software watchpoint, which
3814 executes more slowly and reports the change in value at the next
3815 @emph{statement}, not the instruction, after the change occurs.
3817 @cindex use only software watchpoints
3818 You can force @value{GDBN} to use only software watchpoints with the
3819 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3820 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3821 the underlying system supports them. (Note that hardware-assisted
3822 watchpoints that were set @emph{before} setting
3823 @code{can-use-hw-watchpoints} to zero will still use the hardware
3824 mechanism of watching expression values.)
3827 @item set can-use-hw-watchpoints
3828 @kindex set can-use-hw-watchpoints
3829 Set whether or not to use hardware watchpoints.
3831 @item show can-use-hw-watchpoints
3832 @kindex show can-use-hw-watchpoints
3833 Show the current mode of using hardware watchpoints.
3836 For remote targets, you can restrict the number of hardware
3837 watchpoints @value{GDBN} will use, see @ref{set remote
3838 hardware-breakpoint-limit}.
3840 When you issue the @code{watch} command, @value{GDBN} reports
3843 Hardware watchpoint @var{num}: @var{expr}
3847 if it was able to set a hardware watchpoint.
3849 Currently, the @code{awatch} and @code{rwatch} commands can only set
3850 hardware watchpoints, because accesses to data that don't change the
3851 value of the watched expression cannot be detected without examining
3852 every instruction as it is being executed, and @value{GDBN} does not do
3853 that currently. If @value{GDBN} finds that it is unable to set a
3854 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3855 will print a message like this:
3858 Expression cannot be implemented with read/access watchpoint.
3861 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3862 data type of the watched expression is wider than what a hardware
3863 watchpoint on the target machine can handle. For example, some systems
3864 can only watch regions that are up to 4 bytes wide; on such systems you
3865 cannot set hardware watchpoints for an expression that yields a
3866 double-precision floating-point number (which is typically 8 bytes
3867 wide). As a work-around, it might be possible to break the large region
3868 into a series of smaller ones and watch them with separate watchpoints.
3870 If you set too many hardware watchpoints, @value{GDBN} might be unable
3871 to insert all of them when you resume the execution of your program.
3872 Since the precise number of active watchpoints is unknown until such
3873 time as the program is about to be resumed, @value{GDBN} might not be
3874 able to warn you about this when you set the watchpoints, and the
3875 warning will be printed only when the program is resumed:
3878 Hardware watchpoint @var{num}: Could not insert watchpoint
3882 If this happens, delete or disable some of the watchpoints.
3884 Watching complex expressions that reference many variables can also
3885 exhaust the resources available for hardware-assisted watchpoints.
3886 That's because @value{GDBN} needs to watch every variable in the
3887 expression with separately allocated resources.
3889 If you call a function interactively using @code{print} or @code{call},
3890 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3891 kind of breakpoint or the call completes.
3893 @value{GDBN} automatically deletes watchpoints that watch local
3894 (automatic) variables, or expressions that involve such variables, when
3895 they go out of scope, that is, when the execution leaves the block in
3896 which these variables were defined. In particular, when the program
3897 being debugged terminates, @emph{all} local variables go out of scope,
3898 and so only watchpoints that watch global variables remain set. If you
3899 rerun the program, you will need to set all such watchpoints again. One
3900 way of doing that would be to set a code breakpoint at the entry to the
3901 @code{main} function and when it breaks, set all the watchpoints.
3903 @cindex watchpoints and threads
3904 @cindex threads and watchpoints
3905 In multi-threaded programs, watchpoints will detect changes to the
3906 watched expression from every thread.
3909 @emph{Warning:} In multi-threaded programs, software watchpoints
3910 have only limited usefulness. If @value{GDBN} creates a software
3911 watchpoint, it can only watch the value of an expression @emph{in a
3912 single thread}. If you are confident that the expression can only
3913 change due to the current thread's activity (and if you are also
3914 confident that no other thread can become current), then you can use
3915 software watchpoints as usual. However, @value{GDBN} may not notice
3916 when a non-current thread's activity changes the expression. (Hardware
3917 watchpoints, in contrast, watch an expression in all threads.)
3920 @xref{set remote hardware-watchpoint-limit}.
3922 @node Set Catchpoints
3923 @subsection Setting Catchpoints
3924 @cindex catchpoints, setting
3925 @cindex exception handlers
3926 @cindex event handling
3928 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3929 kinds of program events, such as C@t{++} exceptions or the loading of a
3930 shared library. Use the @code{catch} command to set a catchpoint.
3934 @item catch @var{event}
3935 Stop when @var{event} occurs. @var{event} can be any of the following:
3938 @cindex stop on C@t{++} exceptions
3939 The throwing of a C@t{++} exception.
3942 The catching of a C@t{++} exception.
3945 @cindex Ada exception catching
3946 @cindex catch Ada exceptions
3947 An Ada exception being raised. If an exception name is specified
3948 at the end of the command (eg @code{catch exception Program_Error}),
3949 the debugger will stop only when this specific exception is raised.
3950 Otherwise, the debugger stops execution when any Ada exception is raised.
3952 When inserting an exception catchpoint on a user-defined exception whose
3953 name is identical to one of the exceptions defined by the language, the
3954 fully qualified name must be used as the exception name. Otherwise,
3955 @value{GDBN} will assume that it should stop on the pre-defined exception
3956 rather than the user-defined one. For instance, assuming an exception
3957 called @code{Constraint_Error} is defined in package @code{Pck}, then
3958 the command to use to catch such exceptions is @kbd{catch exception
3959 Pck.Constraint_Error}.
3961 @item exception unhandled
3962 An exception that was raised but is not handled by the program.
3965 A failed Ada assertion.
3968 @cindex break on fork/exec
3969 A call to @code{exec}. This is currently only available for HP-UX
3973 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
3974 @cindex break on a system call.
3975 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
3976 syscall is a mechanism for application programs to request a service
3977 from the operating system (OS) or one of the OS system services.
3978 @value{GDBN} can catch some or all of the syscalls issued by the
3979 debuggee, and show the related information for each syscall. If no
3980 argument is specified, calls to and returns from all system calls
3983 @var{name} can be any system call name that is valid for the
3984 underlying OS. Just what syscalls are valid depends on the OS. On
3985 GNU and Unix systems, you can find the full list of valid syscall
3986 names on @file{/usr/include/asm/unistd.h}.
3988 @c For MS-Windows, the syscall names and the corresponding numbers
3989 @c can be found, e.g., on this URL:
3990 @c http://www.metasploit.com/users/opcode/syscalls.html
3991 @c but we don't support Windows syscalls yet.
3993 Normally, @value{GDBN} knows in advance which syscalls are valid for
3994 each OS, so you can use the @value{GDBN} command-line completion
3995 facilities (@pxref{Completion,, command completion}) to list the
3998 You may also specify the system call numerically. A syscall's
3999 number is the value passed to the OS's syscall dispatcher to
4000 identify the requested service. When you specify the syscall by its
4001 name, @value{GDBN} uses its database of syscalls to convert the name
4002 into the corresponding numeric code, but using the number directly
4003 may be useful if @value{GDBN}'s database does not have the complete
4004 list of syscalls on your system (e.g., because @value{GDBN} lags
4005 behind the OS upgrades).
4007 The example below illustrates how this command works if you don't provide
4011 (@value{GDBP}) catch syscall
4012 Catchpoint 1 (syscall)
4014 Starting program: /tmp/catch-syscall
4016 Catchpoint 1 (call to syscall 'close'), \
4017 0xffffe424 in __kernel_vsyscall ()
4021 Catchpoint 1 (returned from syscall 'close'), \
4022 0xffffe424 in __kernel_vsyscall ()
4026 Here is an example of catching a system call by name:
4029 (@value{GDBP}) catch syscall chroot
4030 Catchpoint 1 (syscall 'chroot' [61])
4032 Starting program: /tmp/catch-syscall
4034 Catchpoint 1 (call to syscall 'chroot'), \
4035 0xffffe424 in __kernel_vsyscall ()
4039 Catchpoint 1 (returned from syscall 'chroot'), \
4040 0xffffe424 in __kernel_vsyscall ()
4044 An example of specifying a system call numerically. In the case
4045 below, the syscall number has a corresponding entry in the XML
4046 file, so @value{GDBN} finds its name and prints it:
4049 (@value{GDBP}) catch syscall 252
4050 Catchpoint 1 (syscall(s) 'exit_group')
4052 Starting program: /tmp/catch-syscall
4054 Catchpoint 1 (call to syscall 'exit_group'), \
4055 0xffffe424 in __kernel_vsyscall ()
4059 Program exited normally.
4063 However, there can be situations when there is no corresponding name
4064 in XML file for that syscall number. In this case, @value{GDBN} prints
4065 a warning message saying that it was not able to find the syscall name,
4066 but the catchpoint will be set anyway. See the example below:
4069 (@value{GDBP}) catch syscall 764
4070 warning: The number '764' does not represent a known syscall.
4071 Catchpoint 2 (syscall 764)
4075 If you configure @value{GDBN} using the @samp{--without-expat} option,
4076 it will not be able to display syscall names. Also, if your
4077 architecture does not have an XML file describing its system calls,
4078 you will not be able to see the syscall names. It is important to
4079 notice that these two features are used for accessing the syscall
4080 name database. In either case, you will see a warning like this:
4083 (@value{GDBP}) catch syscall
4084 warning: Could not open "syscalls/i386-linux.xml"
4085 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4086 GDB will not be able to display syscall names.
4087 Catchpoint 1 (syscall)
4091 Of course, the file name will change depending on your architecture and system.
4093 Still using the example above, you can also try to catch a syscall by its
4094 number. In this case, you would see something like:
4097 (@value{GDBP}) catch syscall 252
4098 Catchpoint 1 (syscall(s) 252)
4101 Again, in this case @value{GDBN} would not be able to display syscall's names.
4104 A call to @code{fork}. This is currently only available for HP-UX
4108 A call to @code{vfork}. This is currently only available for HP-UX
4113 @item tcatch @var{event}
4114 Set a catchpoint that is enabled only for one stop. The catchpoint is
4115 automatically deleted after the first time the event is caught.
4119 Use the @code{info break} command to list the current catchpoints.
4121 There are currently some limitations to C@t{++} exception handling
4122 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4126 If you call a function interactively, @value{GDBN} normally returns
4127 control to you when the function has finished executing. If the call
4128 raises an exception, however, the call may bypass the mechanism that
4129 returns control to you and cause your program either to abort or to
4130 simply continue running until it hits a breakpoint, catches a signal
4131 that @value{GDBN} is listening for, or exits. This is the case even if
4132 you set a catchpoint for the exception; catchpoints on exceptions are
4133 disabled within interactive calls.
4136 You cannot raise an exception interactively.
4139 You cannot install an exception handler interactively.
4142 @cindex raise exceptions
4143 Sometimes @code{catch} is not the best way to debug exception handling:
4144 if you need to know exactly where an exception is raised, it is better to
4145 stop @emph{before} the exception handler is called, since that way you
4146 can see the stack before any unwinding takes place. If you set a
4147 breakpoint in an exception handler instead, it may not be easy to find
4148 out where the exception was raised.
4150 To stop just before an exception handler is called, you need some
4151 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4152 raised by calling a library function named @code{__raise_exception}
4153 which has the following ANSI C interface:
4156 /* @var{addr} is where the exception identifier is stored.
4157 @var{id} is the exception identifier. */
4158 void __raise_exception (void **addr, void *id);
4162 To make the debugger catch all exceptions before any stack
4163 unwinding takes place, set a breakpoint on @code{__raise_exception}
4164 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4166 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4167 that depends on the value of @var{id}, you can stop your program when
4168 a specific exception is raised. You can use multiple conditional
4169 breakpoints to stop your program when any of a number of exceptions are
4174 @subsection Deleting Breakpoints
4176 @cindex clearing breakpoints, watchpoints, catchpoints
4177 @cindex deleting breakpoints, watchpoints, catchpoints
4178 It is often necessary to eliminate a breakpoint, watchpoint, or
4179 catchpoint once it has done its job and you no longer want your program
4180 to stop there. This is called @dfn{deleting} the breakpoint. A
4181 breakpoint that has been deleted no longer exists; it is forgotten.
4183 With the @code{clear} command you can delete breakpoints according to
4184 where they are in your program. With the @code{delete} command you can
4185 delete individual breakpoints, watchpoints, or catchpoints by specifying
4186 their breakpoint numbers.
4188 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4189 automatically ignores breakpoints on the first instruction to be executed
4190 when you continue execution without changing the execution address.
4195 Delete any breakpoints at the next instruction to be executed in the
4196 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4197 the innermost frame is selected, this is a good way to delete a
4198 breakpoint where your program just stopped.
4200 @item clear @var{location}
4201 Delete any breakpoints set at the specified @var{location}.
4202 @xref{Specify Location}, for the various forms of @var{location}; the
4203 most useful ones are listed below:
4206 @item clear @var{function}
4207 @itemx clear @var{filename}:@var{function}
4208 Delete any breakpoints set at entry to the named @var{function}.
4210 @item clear @var{linenum}
4211 @itemx clear @var{filename}:@var{linenum}
4212 Delete any breakpoints set at or within the code of the specified
4213 @var{linenum} of the specified @var{filename}.
4216 @cindex delete breakpoints
4218 @kindex d @r{(@code{delete})}
4219 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4220 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4221 ranges specified as arguments. If no argument is specified, delete all
4222 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4223 confirm off}). You can abbreviate this command as @code{d}.
4227 @subsection Disabling Breakpoints
4229 @cindex enable/disable a breakpoint
4230 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4231 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4232 it had been deleted, but remembers the information on the breakpoint so
4233 that you can @dfn{enable} it again later.
4235 You disable and enable breakpoints, watchpoints, and catchpoints with
4236 the @code{enable} and @code{disable} commands, optionally specifying
4237 one or more breakpoint numbers as arguments. Use @code{info break} to
4238 print a list of all breakpoints, watchpoints, and catchpoints if you
4239 do not know which numbers to use.
4241 Disabling and enabling a breakpoint that has multiple locations
4242 affects all of its locations.
4244 A breakpoint, watchpoint, or catchpoint can have any of four different
4245 states of enablement:
4249 Enabled. The breakpoint stops your program. A breakpoint set
4250 with the @code{break} command starts out in this state.
4252 Disabled. The breakpoint has no effect on your program.
4254 Enabled once. The breakpoint stops your program, but then becomes
4257 Enabled for deletion. The breakpoint stops your program, but
4258 immediately after it does so it is deleted permanently. A breakpoint
4259 set with the @code{tbreak} command starts out in this state.
4262 You can use the following commands to enable or disable breakpoints,
4263 watchpoints, and catchpoints:
4267 @kindex dis @r{(@code{disable})}
4268 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4269 Disable the specified breakpoints---or all breakpoints, if none are
4270 listed. A disabled breakpoint has no effect but is not forgotten. All
4271 options such as ignore-counts, conditions and commands are remembered in
4272 case the breakpoint is enabled again later. You may abbreviate
4273 @code{disable} as @code{dis}.
4276 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4277 Enable the specified breakpoints (or all defined breakpoints). They
4278 become effective once again in stopping your program.
4280 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4281 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4282 of these breakpoints immediately after stopping your program.
4284 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4285 Enable the specified breakpoints to work once, then die. @value{GDBN}
4286 deletes any of these breakpoints as soon as your program stops there.
4287 Breakpoints set by the @code{tbreak} command start out in this state.
4290 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4291 @c confusing: tbreak is also initially enabled.
4292 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4293 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4294 subsequently, they become disabled or enabled only when you use one of
4295 the commands above. (The command @code{until} can set and delete a
4296 breakpoint of its own, but it does not change the state of your other
4297 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4301 @subsection Break Conditions
4302 @cindex conditional breakpoints
4303 @cindex breakpoint conditions
4305 @c FIXME what is scope of break condition expr? Context where wanted?
4306 @c in particular for a watchpoint?
4307 The simplest sort of breakpoint breaks every time your program reaches a
4308 specified place. You can also specify a @dfn{condition} for a
4309 breakpoint. A condition is just a Boolean expression in your
4310 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4311 a condition evaluates the expression each time your program reaches it,
4312 and your program stops only if the condition is @emph{true}.
4314 This is the converse of using assertions for program validation; in that
4315 situation, you want to stop when the assertion is violated---that is,
4316 when the condition is false. In C, if you want to test an assertion expressed
4317 by the condition @var{assert}, you should set the condition
4318 @samp{! @var{assert}} on the appropriate breakpoint.
4320 Conditions are also accepted for watchpoints; you may not need them,
4321 since a watchpoint is inspecting the value of an expression anyhow---but
4322 it might be simpler, say, to just set a watchpoint on a variable name,
4323 and specify a condition that tests whether the new value is an interesting
4326 Break conditions can have side effects, and may even call functions in
4327 your program. This can be useful, for example, to activate functions
4328 that log program progress, or to use your own print functions to
4329 format special data structures. The effects are completely predictable
4330 unless there is another enabled breakpoint at the same address. (In
4331 that case, @value{GDBN} might see the other breakpoint first and stop your
4332 program without checking the condition of this one.) Note that
4333 breakpoint commands are usually more convenient and flexible than break
4335 purpose of performing side effects when a breakpoint is reached
4336 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4338 Break conditions can be specified when a breakpoint is set, by using
4339 @samp{if} in the arguments to the @code{break} command. @xref{Set
4340 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4341 with the @code{condition} command.
4343 You can also use the @code{if} keyword with the @code{watch} command.
4344 The @code{catch} command does not recognize the @code{if} keyword;
4345 @code{condition} is the only way to impose a further condition on a
4350 @item condition @var{bnum} @var{expression}
4351 Specify @var{expression} as the break condition for breakpoint,
4352 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4353 breakpoint @var{bnum} stops your program only if the value of
4354 @var{expression} is true (nonzero, in C). When you use
4355 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4356 syntactic correctness, and to determine whether symbols in it have
4357 referents in the context of your breakpoint. If @var{expression} uses
4358 symbols not referenced in the context of the breakpoint, @value{GDBN}
4359 prints an error message:
4362 No symbol "foo" in current context.
4367 not actually evaluate @var{expression} at the time the @code{condition}
4368 command (or a command that sets a breakpoint with a condition, like
4369 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4371 @item condition @var{bnum}
4372 Remove the condition from breakpoint number @var{bnum}. It becomes
4373 an ordinary unconditional breakpoint.
4376 @cindex ignore count (of breakpoint)
4377 A special case of a breakpoint condition is to stop only when the
4378 breakpoint has been reached a certain number of times. This is so
4379 useful that there is a special way to do it, using the @dfn{ignore
4380 count} of the breakpoint. Every breakpoint has an ignore count, which
4381 is an integer. Most of the time, the ignore count is zero, and
4382 therefore has no effect. But if your program reaches a breakpoint whose
4383 ignore count is positive, then instead of stopping, it just decrements
4384 the ignore count by one and continues. As a result, if the ignore count
4385 value is @var{n}, the breakpoint does not stop the next @var{n} times
4386 your program reaches it.
4390 @item ignore @var{bnum} @var{count}
4391 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4392 The next @var{count} times the breakpoint is reached, your program's
4393 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4396 To make the breakpoint stop the next time it is reached, specify
4399 When you use @code{continue} to resume execution of your program from a
4400 breakpoint, you can specify an ignore count directly as an argument to
4401 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4402 Stepping,,Continuing and Stepping}.
4404 If a breakpoint has a positive ignore count and a condition, the
4405 condition is not checked. Once the ignore count reaches zero,
4406 @value{GDBN} resumes checking the condition.
4408 You could achieve the effect of the ignore count with a condition such
4409 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4410 is decremented each time. @xref{Convenience Vars, ,Convenience
4414 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4417 @node Break Commands
4418 @subsection Breakpoint Command Lists
4420 @cindex breakpoint commands
4421 You can give any breakpoint (or watchpoint or catchpoint) a series of
4422 commands to execute when your program stops due to that breakpoint. For
4423 example, you might want to print the values of certain expressions, or
4424 enable other breakpoints.
4428 @kindex end@r{ (breakpoint commands)}
4429 @item commands @r{[}@var{range}@dots{}@r{]}
4430 @itemx @dots{} @var{command-list} @dots{}
4432 Specify a list of commands for the given breakpoints. The commands
4433 themselves appear on the following lines. Type a line containing just
4434 @code{end} to terminate the commands.
4436 To remove all commands from a breakpoint, type @code{commands} and
4437 follow it immediately with @code{end}; that is, give no commands.
4439 With no argument, @code{commands} refers to the last breakpoint,
4440 watchpoint, or catchpoint set (not to the breakpoint most recently
4441 encountered). If the most recent breakpoints were set with a single
4442 command, then the @code{commands} will apply to all the breakpoints
4443 set by that command. This applies to breakpoints set by
4444 @code{rbreak}, and also applies when a single @code{break} command
4445 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4449 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4450 disabled within a @var{command-list}.
4452 You can use breakpoint commands to start your program up again. Simply
4453 use the @code{continue} command, or @code{step}, or any other command
4454 that resumes execution.
4456 Any other commands in the command list, after a command that resumes
4457 execution, are ignored. This is because any time you resume execution
4458 (even with a simple @code{next} or @code{step}), you may encounter
4459 another breakpoint---which could have its own command list, leading to
4460 ambiguities about which list to execute.
4463 If the first command you specify in a command list is @code{silent}, the
4464 usual message about stopping at a breakpoint is not printed. This may
4465 be desirable for breakpoints that are to print a specific message and
4466 then continue. If none of the remaining commands print anything, you
4467 see no sign that the breakpoint was reached. @code{silent} is
4468 meaningful only at the beginning of a breakpoint command list.
4470 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4471 print precisely controlled output, and are often useful in silent
4472 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4474 For example, here is how you could use breakpoint commands to print the
4475 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4481 printf "x is %d\n",x
4486 One application for breakpoint commands is to compensate for one bug so
4487 you can test for another. Put a breakpoint just after the erroneous line
4488 of code, give it a condition to detect the case in which something
4489 erroneous has been done, and give it commands to assign correct values
4490 to any variables that need them. End with the @code{continue} command
4491 so that your program does not stop, and start with the @code{silent}
4492 command so that no output is produced. Here is an example:
4503 @node Save Breakpoints
4504 @subsection How to save breakpoints to a file
4506 To save breakpoint definitions to a file use the @w{@code{save
4507 breakpoints}} command.
4510 @kindex save breakpoints
4511 @cindex save breakpoints to a file for future sessions
4512 @item save breakpoints [@var{filename}]
4513 This command saves all current breakpoint definitions together with
4514 their commands and ignore counts, into a file @file{@var{filename}}
4515 suitable for use in a later debugging session. This includes all
4516 types of breakpoints (breakpoints, watchpoints, catchpoints,
4517 tracepoints). To read the saved breakpoint definitions, use the
4518 @code{source} command (@pxref{Command Files}). Note that watchpoints
4519 with expressions involving local variables may fail to be recreated
4520 because it may not be possible to access the context where the
4521 watchpoint is valid anymore. Because the saved breakpoint definitions
4522 are simply a sequence of @value{GDBN} commands that recreate the
4523 breakpoints, you can edit the file in your favorite editing program,
4524 and remove the breakpoint definitions you're not interested in, or
4525 that can no longer be recreated.
4528 @c @ifclear BARETARGET
4529 @node Error in Breakpoints
4530 @subsection ``Cannot insert breakpoints''
4532 If you request too many active hardware-assisted breakpoints and
4533 watchpoints, you will see this error message:
4535 @c FIXME: the precise wording of this message may change; the relevant
4536 @c source change is not committed yet (Sep 3, 1999).
4538 Stopped; cannot insert breakpoints.
4539 You may have requested too many hardware breakpoints and watchpoints.
4543 This message is printed when you attempt to resume the program, since
4544 only then @value{GDBN} knows exactly how many hardware breakpoints and
4545 watchpoints it needs to insert.
4547 When this message is printed, you need to disable or remove some of the
4548 hardware-assisted breakpoints and watchpoints, and then continue.
4550 @node Breakpoint-related Warnings
4551 @subsection ``Breakpoint address adjusted...''
4552 @cindex breakpoint address adjusted
4554 Some processor architectures place constraints on the addresses at
4555 which breakpoints may be placed. For architectures thus constrained,
4556 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4557 with the constraints dictated by the architecture.
4559 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4560 a VLIW architecture in which a number of RISC-like instructions may be
4561 bundled together for parallel execution. The FR-V architecture
4562 constrains the location of a breakpoint instruction within such a
4563 bundle to the instruction with the lowest address. @value{GDBN}
4564 honors this constraint by adjusting a breakpoint's address to the
4565 first in the bundle.
4567 It is not uncommon for optimized code to have bundles which contain
4568 instructions from different source statements, thus it may happen that
4569 a breakpoint's address will be adjusted from one source statement to
4570 another. Since this adjustment may significantly alter @value{GDBN}'s
4571 breakpoint related behavior from what the user expects, a warning is
4572 printed when the breakpoint is first set and also when the breakpoint
4575 A warning like the one below is printed when setting a breakpoint
4576 that's been subject to address adjustment:
4579 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4582 Such warnings are printed both for user settable and @value{GDBN}'s
4583 internal breakpoints. If you see one of these warnings, you should
4584 verify that a breakpoint set at the adjusted address will have the
4585 desired affect. If not, the breakpoint in question may be removed and
4586 other breakpoints may be set which will have the desired behavior.
4587 E.g., it may be sufficient to place the breakpoint at a later
4588 instruction. A conditional breakpoint may also be useful in some
4589 cases to prevent the breakpoint from triggering too often.
4591 @value{GDBN} will also issue a warning when stopping at one of these
4592 adjusted breakpoints:
4595 warning: Breakpoint 1 address previously adjusted from 0x00010414
4599 When this warning is encountered, it may be too late to take remedial
4600 action except in cases where the breakpoint is hit earlier or more
4601 frequently than expected.
4603 @node Continuing and Stepping
4604 @section Continuing and Stepping
4608 @cindex resuming execution
4609 @dfn{Continuing} means resuming program execution until your program
4610 completes normally. In contrast, @dfn{stepping} means executing just
4611 one more ``step'' of your program, where ``step'' may mean either one
4612 line of source code, or one machine instruction (depending on what
4613 particular command you use). Either when continuing or when stepping,
4614 your program may stop even sooner, due to a breakpoint or a signal. (If
4615 it stops due to a signal, you may want to use @code{handle}, or use
4616 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4620 @kindex c @r{(@code{continue})}
4621 @kindex fg @r{(resume foreground execution)}
4622 @item continue @r{[}@var{ignore-count}@r{]}
4623 @itemx c @r{[}@var{ignore-count}@r{]}
4624 @itemx fg @r{[}@var{ignore-count}@r{]}
4625 Resume program execution, at the address where your program last stopped;
4626 any breakpoints set at that address are bypassed. The optional argument
4627 @var{ignore-count} allows you to specify a further number of times to
4628 ignore a breakpoint at this location; its effect is like that of
4629 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4631 The argument @var{ignore-count} is meaningful only when your program
4632 stopped due to a breakpoint. At other times, the argument to
4633 @code{continue} is ignored.
4635 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4636 debugged program is deemed to be the foreground program) are provided
4637 purely for convenience, and have exactly the same behavior as
4641 To resume execution at a different place, you can use @code{return}
4642 (@pxref{Returning, ,Returning from a Function}) to go back to the
4643 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4644 Different Address}) to go to an arbitrary location in your program.
4646 A typical technique for using stepping is to set a breakpoint
4647 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4648 beginning of the function or the section of your program where a problem
4649 is believed to lie, run your program until it stops at that breakpoint,
4650 and then step through the suspect area, examining the variables that are
4651 interesting, until you see the problem happen.
4655 @kindex s @r{(@code{step})}
4657 Continue running your program until control reaches a different source
4658 line, then stop it and return control to @value{GDBN}. This command is
4659 abbreviated @code{s}.
4662 @c "without debugging information" is imprecise; actually "without line
4663 @c numbers in the debugging information". (gcc -g1 has debugging info but
4664 @c not line numbers). But it seems complex to try to make that
4665 @c distinction here.
4666 @emph{Warning:} If you use the @code{step} command while control is
4667 within a function that was compiled without debugging information,
4668 execution proceeds until control reaches a function that does have
4669 debugging information. Likewise, it will not step into a function which
4670 is compiled without debugging information. To step through functions
4671 without debugging information, use the @code{stepi} command, described
4675 The @code{step} command only stops at the first instruction of a source
4676 line. This prevents the multiple stops that could otherwise occur in
4677 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4678 to stop if a function that has debugging information is called within
4679 the line. In other words, @code{step} @emph{steps inside} any functions
4680 called within the line.
4682 Also, the @code{step} command only enters a function if there is line
4683 number information for the function. Otherwise it acts like the
4684 @code{next} command. This avoids problems when using @code{cc -gl}
4685 on MIPS machines. Previously, @code{step} entered subroutines if there
4686 was any debugging information about the routine.
4688 @item step @var{count}
4689 Continue running as in @code{step}, but do so @var{count} times. If a
4690 breakpoint is reached, or a signal not related to stepping occurs before
4691 @var{count} steps, stepping stops right away.
4694 @kindex n @r{(@code{next})}
4695 @item next @r{[}@var{count}@r{]}
4696 Continue to the next source line in the current (innermost) stack frame.
4697 This is similar to @code{step}, but function calls that appear within
4698 the line of code are executed without stopping. Execution stops when
4699 control reaches a different line of code at the original stack level
4700 that was executing when you gave the @code{next} command. This command
4701 is abbreviated @code{n}.
4703 An argument @var{count} is a repeat count, as for @code{step}.
4706 @c FIX ME!! Do we delete this, or is there a way it fits in with
4707 @c the following paragraph? --- Vctoria
4709 @c @code{next} within a function that lacks debugging information acts like
4710 @c @code{step}, but any function calls appearing within the code of the
4711 @c function are executed without stopping.
4713 The @code{next} command only stops at the first instruction of a
4714 source line. This prevents multiple stops that could otherwise occur in
4715 @code{switch} statements, @code{for} loops, etc.
4717 @kindex set step-mode
4719 @cindex functions without line info, and stepping
4720 @cindex stepping into functions with no line info
4721 @itemx set step-mode on
4722 The @code{set step-mode on} command causes the @code{step} command to
4723 stop at the first instruction of a function which contains no debug line
4724 information rather than stepping over it.
4726 This is useful in cases where you may be interested in inspecting the
4727 machine instructions of a function which has no symbolic info and do not
4728 want @value{GDBN} to automatically skip over this function.
4730 @item set step-mode off
4731 Causes the @code{step} command to step over any functions which contains no
4732 debug information. This is the default.
4734 @item show step-mode
4735 Show whether @value{GDBN} will stop in or step over functions without
4736 source line debug information.
4739 @kindex fin @r{(@code{finish})}
4741 Continue running until just after function in the selected stack frame
4742 returns. Print the returned value (if any). This command can be
4743 abbreviated as @code{fin}.
4745 Contrast this with the @code{return} command (@pxref{Returning,
4746 ,Returning from a Function}).
4749 @kindex u @r{(@code{until})}
4750 @cindex run until specified location
4753 Continue running until a source line past the current line, in the
4754 current stack frame, is reached. This command is used to avoid single
4755 stepping through a loop more than once. It is like the @code{next}
4756 command, except that when @code{until} encounters a jump, it
4757 automatically continues execution until the program counter is greater
4758 than the address of the jump.
4760 This means that when you reach the end of a loop after single stepping
4761 though it, @code{until} makes your program continue execution until it
4762 exits the loop. In contrast, a @code{next} command at the end of a loop
4763 simply steps back to the beginning of the loop, which forces you to step
4764 through the next iteration.
4766 @code{until} always stops your program if it attempts to exit the current
4769 @code{until} may produce somewhat counterintuitive results if the order
4770 of machine code does not match the order of the source lines. For
4771 example, in the following excerpt from a debugging session, the @code{f}
4772 (@code{frame}) command shows that execution is stopped at line
4773 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4777 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4779 (@value{GDBP}) until
4780 195 for ( ; argc > 0; NEXTARG) @{
4783 This happened because, for execution efficiency, the compiler had
4784 generated code for the loop closure test at the end, rather than the
4785 start, of the loop---even though the test in a C @code{for}-loop is
4786 written before the body of the loop. The @code{until} command appeared
4787 to step back to the beginning of the loop when it advanced to this
4788 expression; however, it has not really gone to an earlier
4789 statement---not in terms of the actual machine code.
4791 @code{until} with no argument works by means of single
4792 instruction stepping, and hence is slower than @code{until} with an
4795 @item until @var{location}
4796 @itemx u @var{location}
4797 Continue running your program until either the specified location is
4798 reached, or the current stack frame returns. @var{location} is any of
4799 the forms described in @ref{Specify Location}.
4800 This form of the command uses temporary breakpoints, and
4801 hence is quicker than @code{until} without an argument. The specified
4802 location is actually reached only if it is in the current frame. This
4803 implies that @code{until} can be used to skip over recursive function
4804 invocations. For instance in the code below, if the current location is
4805 line @code{96}, issuing @code{until 99} will execute the program up to
4806 line @code{99} in the same invocation of factorial, i.e., after the inner
4807 invocations have returned.
4810 94 int factorial (int value)
4812 96 if (value > 1) @{
4813 97 value *= factorial (value - 1);
4820 @kindex advance @var{location}
4821 @itemx advance @var{location}
4822 Continue running the program up to the given @var{location}. An argument is
4823 required, which should be of one of the forms described in
4824 @ref{Specify Location}.
4825 Execution will also stop upon exit from the current stack
4826 frame. This command is similar to @code{until}, but @code{advance} will
4827 not skip over recursive function calls, and the target location doesn't
4828 have to be in the same frame as the current one.
4832 @kindex si @r{(@code{stepi})}
4834 @itemx stepi @var{arg}
4836 Execute one machine instruction, then stop and return to the debugger.
4838 It is often useful to do @samp{display/i $pc} when stepping by machine
4839 instructions. This makes @value{GDBN} automatically display the next
4840 instruction to be executed, each time your program stops. @xref{Auto
4841 Display,, Automatic Display}.
4843 An argument is a repeat count, as in @code{step}.
4847 @kindex ni @r{(@code{nexti})}
4849 @itemx nexti @var{arg}
4851 Execute one machine instruction, but if it is a function call,
4852 proceed until the function returns.
4854 An argument is a repeat count, as in @code{next}.
4861 A signal is an asynchronous event that can happen in a program. The
4862 operating system defines the possible kinds of signals, and gives each
4863 kind a name and a number. For example, in Unix @code{SIGINT} is the
4864 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4865 @code{SIGSEGV} is the signal a program gets from referencing a place in
4866 memory far away from all the areas in use; @code{SIGALRM} occurs when
4867 the alarm clock timer goes off (which happens only if your program has
4868 requested an alarm).
4870 @cindex fatal signals
4871 Some signals, including @code{SIGALRM}, are a normal part of the
4872 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4873 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4874 program has not specified in advance some other way to handle the signal.
4875 @code{SIGINT} does not indicate an error in your program, but it is normally
4876 fatal so it can carry out the purpose of the interrupt: to kill the program.
4878 @value{GDBN} has the ability to detect any occurrence of a signal in your
4879 program. You can tell @value{GDBN} in advance what to do for each kind of
4882 @cindex handling signals
4883 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4884 @code{SIGALRM} be silently passed to your program
4885 (so as not to interfere with their role in the program's functioning)
4886 but to stop your program immediately whenever an error signal happens.
4887 You can change these settings with the @code{handle} command.
4890 @kindex info signals
4894 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4895 handle each one. You can use this to see the signal numbers of all
4896 the defined types of signals.
4898 @item info signals @var{sig}
4899 Similar, but print information only about the specified signal number.
4901 @code{info handle} is an alias for @code{info signals}.
4904 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4905 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4906 can be the number of a signal or its name (with or without the
4907 @samp{SIG} at the beginning); a list of signal numbers of the form
4908 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4909 known signals. Optional arguments @var{keywords}, described below,
4910 say what change to make.
4914 The keywords allowed by the @code{handle} command can be abbreviated.
4915 Their full names are:
4919 @value{GDBN} should not stop your program when this signal happens. It may
4920 still print a message telling you that the signal has come in.
4923 @value{GDBN} should stop your program when this signal happens. This implies
4924 the @code{print} keyword as well.
4927 @value{GDBN} should print a message when this signal happens.
4930 @value{GDBN} should not mention the occurrence of the signal at all. This
4931 implies the @code{nostop} keyword as well.
4935 @value{GDBN} should allow your program to see this signal; your program
4936 can handle the signal, or else it may terminate if the signal is fatal
4937 and not handled. @code{pass} and @code{noignore} are synonyms.
4941 @value{GDBN} should not allow your program to see this signal.
4942 @code{nopass} and @code{ignore} are synonyms.
4946 When a signal stops your program, the signal is not visible to the
4948 continue. Your program sees the signal then, if @code{pass} is in
4949 effect for the signal in question @emph{at that time}. In other words,
4950 after @value{GDBN} reports a signal, you can use the @code{handle}
4951 command with @code{pass} or @code{nopass} to control whether your
4952 program sees that signal when you continue.
4954 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4955 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4956 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4959 You can also use the @code{signal} command to prevent your program from
4960 seeing a signal, or cause it to see a signal it normally would not see,
4961 or to give it any signal at any time. For example, if your program stopped
4962 due to some sort of memory reference error, you might store correct
4963 values into the erroneous variables and continue, hoping to see more
4964 execution; but your program would probably terminate immediately as
4965 a result of the fatal signal once it saw the signal. To prevent this,
4966 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4969 @cindex extra signal information
4970 @anchor{extra signal information}
4972 On some targets, @value{GDBN} can inspect extra signal information
4973 associated with the intercepted signal, before it is actually
4974 delivered to the program being debugged. This information is exported
4975 by the convenience variable @code{$_siginfo}, and consists of data
4976 that is passed by the kernel to the signal handler at the time of the
4977 receipt of a signal. The data type of the information itself is
4978 target dependent. You can see the data type using the @code{ptype
4979 $_siginfo} command. On Unix systems, it typically corresponds to the
4980 standard @code{siginfo_t} type, as defined in the @file{signal.h}
4983 Here's an example, on a @sc{gnu}/Linux system, printing the stray
4984 referenced address that raised a segmentation fault.
4988 (@value{GDBP}) continue
4989 Program received signal SIGSEGV, Segmentation fault.
4990 0x0000000000400766 in main ()
4992 (@value{GDBP}) ptype $_siginfo
4999 struct @{...@} _kill;
5000 struct @{...@} _timer;
5002 struct @{...@} _sigchld;
5003 struct @{...@} _sigfault;
5004 struct @{...@} _sigpoll;
5007 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5011 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5012 $1 = (void *) 0x7ffff7ff7000
5016 Depending on target support, @code{$_siginfo} may also be writable.
5019 @section Stopping and Starting Multi-thread Programs
5021 @cindex stopped threads
5022 @cindex threads, stopped
5024 @cindex continuing threads
5025 @cindex threads, continuing
5027 @value{GDBN} supports debugging programs with multiple threads
5028 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5029 are two modes of controlling execution of your program within the
5030 debugger. In the default mode, referred to as @dfn{all-stop mode},
5031 when any thread in your program stops (for example, at a breakpoint
5032 or while being stepped), all other threads in the program are also stopped by
5033 @value{GDBN}. On some targets, @value{GDBN} also supports
5034 @dfn{non-stop mode}, in which other threads can continue to run freely while
5035 you examine the stopped thread in the debugger.
5038 * All-Stop Mode:: All threads stop when GDB takes control
5039 * Non-Stop Mode:: Other threads continue to execute
5040 * Background Execution:: Running your program asynchronously
5041 * Thread-Specific Breakpoints:: Controlling breakpoints
5042 * Interrupted System Calls:: GDB may interfere with system calls
5043 * Observer Mode:: GDB does not alter program behavior
5047 @subsection All-Stop Mode
5049 @cindex all-stop mode
5051 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5052 @emph{all} threads of execution stop, not just the current thread. This
5053 allows you to examine the overall state of the program, including
5054 switching between threads, without worrying that things may change
5057 Conversely, whenever you restart the program, @emph{all} threads start
5058 executing. @emph{This is true even when single-stepping} with commands
5059 like @code{step} or @code{next}.
5061 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5062 Since thread scheduling is up to your debugging target's operating
5063 system (not controlled by @value{GDBN}), other threads may
5064 execute more than one statement while the current thread completes a
5065 single step. Moreover, in general other threads stop in the middle of a
5066 statement, rather than at a clean statement boundary, when the program
5069 You might even find your program stopped in another thread after
5070 continuing or even single-stepping. This happens whenever some other
5071 thread runs into a breakpoint, a signal, or an exception before the
5072 first thread completes whatever you requested.
5074 @cindex automatic thread selection
5075 @cindex switching threads automatically
5076 @cindex threads, automatic switching
5077 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5078 signal, it automatically selects the thread where that breakpoint or
5079 signal happened. @value{GDBN} alerts you to the context switch with a
5080 message such as @samp{[Switching to Thread @var{n}]} to identify the
5083 On some OSes, you can modify @value{GDBN}'s default behavior by
5084 locking the OS scheduler to allow only a single thread to run.
5087 @item set scheduler-locking @var{mode}
5088 @cindex scheduler locking mode
5089 @cindex lock scheduler
5090 Set the scheduler locking mode. If it is @code{off}, then there is no
5091 locking and any thread may run at any time. If @code{on}, then only the
5092 current thread may run when the inferior is resumed. The @code{step}
5093 mode optimizes for single-stepping; it prevents other threads
5094 from preempting the current thread while you are stepping, so that
5095 the focus of debugging does not change unexpectedly.
5096 Other threads only rarely (or never) get a chance to run
5097 when you step. They are more likely to run when you @samp{next} over a
5098 function call, and they are completely free to run when you use commands
5099 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5100 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5101 the current thread away from the thread that you are debugging.
5103 @item show scheduler-locking
5104 Display the current scheduler locking mode.
5107 @cindex resume threads of multiple processes simultaneously
5108 By default, when you issue one of the execution commands such as
5109 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5110 threads of the current inferior to run. For example, if @value{GDBN}
5111 is attached to two inferiors, each with two threads, the
5112 @code{continue} command resumes only the two threads of the current
5113 inferior. This is useful, for example, when you debug a program that
5114 forks and you want to hold the parent stopped (so that, for instance,
5115 it doesn't run to exit), while you debug the child. In other
5116 situations, you may not be interested in inspecting the current state
5117 of any of the processes @value{GDBN} is attached to, and you may want
5118 to resume them all until some breakpoint is hit. In the latter case,
5119 you can instruct @value{GDBN} to allow all threads of all the
5120 inferiors to run with the @w{@code{set schedule-multiple}} command.
5123 @kindex set schedule-multiple
5124 @item set schedule-multiple
5125 Set the mode for allowing threads of multiple processes to be resumed
5126 when an execution command is issued. When @code{on}, all threads of
5127 all processes are allowed to run. When @code{off}, only the threads
5128 of the current process are resumed. The default is @code{off}. The
5129 @code{scheduler-locking} mode takes precedence when set to @code{on},
5130 or while you are stepping and set to @code{step}.
5132 @item show schedule-multiple
5133 Display the current mode for resuming the execution of threads of
5138 @subsection Non-Stop Mode
5140 @cindex non-stop mode
5142 @c This section is really only a place-holder, and needs to be expanded
5143 @c with more details.
5145 For some multi-threaded targets, @value{GDBN} supports an optional
5146 mode of operation in which you can examine stopped program threads in
5147 the debugger while other threads continue to execute freely. This
5148 minimizes intrusion when debugging live systems, such as programs
5149 where some threads have real-time constraints or must continue to
5150 respond to external events. This is referred to as @dfn{non-stop} mode.
5152 In non-stop mode, when a thread stops to report a debugging event,
5153 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5154 threads as well, in contrast to the all-stop mode behavior. Additionally,
5155 execution commands such as @code{continue} and @code{step} apply by default
5156 only to the current thread in non-stop mode, rather than all threads as
5157 in all-stop mode. This allows you to control threads explicitly in
5158 ways that are not possible in all-stop mode --- for example, stepping
5159 one thread while allowing others to run freely, stepping
5160 one thread while holding all others stopped, or stepping several threads
5161 independently and simultaneously.
5163 To enter non-stop mode, use this sequence of commands before you run
5164 or attach to your program:
5167 # Enable the async interface.
5170 # If using the CLI, pagination breaks non-stop.
5173 # Finally, turn it on!
5177 You can use these commands to manipulate the non-stop mode setting:
5180 @kindex set non-stop
5181 @item set non-stop on
5182 Enable selection of non-stop mode.
5183 @item set non-stop off
5184 Disable selection of non-stop mode.
5185 @kindex show non-stop
5187 Show the current non-stop enablement setting.
5190 Note these commands only reflect whether non-stop mode is enabled,
5191 not whether the currently-executing program is being run in non-stop mode.
5192 In particular, the @code{set non-stop} preference is only consulted when
5193 @value{GDBN} starts or connects to the target program, and it is generally
5194 not possible to switch modes once debugging has started. Furthermore,
5195 since not all targets support non-stop mode, even when you have enabled
5196 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5199 In non-stop mode, all execution commands apply only to the current thread
5200 by default. That is, @code{continue} only continues one thread.
5201 To continue all threads, issue @code{continue -a} or @code{c -a}.
5203 You can use @value{GDBN}'s background execution commands
5204 (@pxref{Background Execution}) to run some threads in the background
5205 while you continue to examine or step others from @value{GDBN}.
5206 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5207 always executed asynchronously in non-stop mode.
5209 Suspending execution is done with the @code{interrupt} command when
5210 running in the background, or @kbd{Ctrl-c} during foreground execution.
5211 In all-stop mode, this stops the whole process;
5212 but in non-stop mode the interrupt applies only to the current thread.
5213 To stop the whole program, use @code{interrupt -a}.
5215 Other execution commands do not currently support the @code{-a} option.
5217 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5218 that thread current, as it does in all-stop mode. This is because the
5219 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5220 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5221 changed to a different thread just as you entered a command to operate on the
5222 previously current thread.
5224 @node Background Execution
5225 @subsection Background Execution
5227 @cindex foreground execution
5228 @cindex background execution
5229 @cindex asynchronous execution
5230 @cindex execution, foreground, background and asynchronous
5232 @value{GDBN}'s execution commands have two variants: the normal
5233 foreground (synchronous) behavior, and a background
5234 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5235 the program to report that some thread has stopped before prompting for
5236 another command. In background execution, @value{GDBN} immediately gives
5237 a command prompt so that you can issue other commands while your program runs.
5239 You need to explicitly enable asynchronous mode before you can use
5240 background execution commands. You can use these commands to
5241 manipulate the asynchronous mode setting:
5244 @kindex set target-async
5245 @item set target-async on
5246 Enable asynchronous mode.
5247 @item set target-async off
5248 Disable asynchronous mode.
5249 @kindex show target-async
5250 @item show target-async
5251 Show the current target-async setting.
5254 If the target doesn't support async mode, @value{GDBN} issues an error
5255 message if you attempt to use the background execution commands.
5257 To specify background execution, add a @code{&} to the command. For example,
5258 the background form of the @code{continue} command is @code{continue&}, or
5259 just @code{c&}. The execution commands that accept background execution
5265 @xref{Starting, , Starting your Program}.
5269 @xref{Attach, , Debugging an Already-running Process}.
5273 @xref{Continuing and Stepping, step}.
5277 @xref{Continuing and Stepping, stepi}.
5281 @xref{Continuing and Stepping, next}.
5285 @xref{Continuing and Stepping, nexti}.
5289 @xref{Continuing and Stepping, continue}.
5293 @xref{Continuing and Stepping, finish}.
5297 @xref{Continuing and Stepping, until}.
5301 Background execution is especially useful in conjunction with non-stop
5302 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5303 However, you can also use these commands in the normal all-stop mode with
5304 the restriction that you cannot issue another execution command until the
5305 previous one finishes. Examples of commands that are valid in all-stop
5306 mode while the program is running include @code{help} and @code{info break}.
5308 You can interrupt your program while it is running in the background by
5309 using the @code{interrupt} command.
5316 Suspend execution of the running program. In all-stop mode,
5317 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5318 only the current thread. To stop the whole program in non-stop mode,
5319 use @code{interrupt -a}.
5322 @node Thread-Specific Breakpoints
5323 @subsection Thread-Specific Breakpoints
5325 When your program has multiple threads (@pxref{Threads,, Debugging
5326 Programs with Multiple Threads}), you can choose whether to set
5327 breakpoints on all threads, or on a particular thread.
5330 @cindex breakpoints and threads
5331 @cindex thread breakpoints
5332 @kindex break @dots{} thread @var{threadno}
5333 @item break @var{linespec} thread @var{threadno}
5334 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5335 @var{linespec} specifies source lines; there are several ways of
5336 writing them (@pxref{Specify Location}), but the effect is always to
5337 specify some source line.
5339 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5340 to specify that you only want @value{GDBN} to stop the program when a
5341 particular thread reaches this breakpoint. @var{threadno} is one of the
5342 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5343 column of the @samp{info threads} display.
5345 If you do not specify @samp{thread @var{threadno}} when you set a
5346 breakpoint, the breakpoint applies to @emph{all} threads of your
5349 You can use the @code{thread} qualifier on conditional breakpoints as
5350 well; in this case, place @samp{thread @var{threadno}} before or
5351 after the breakpoint condition, like this:
5354 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5359 @node Interrupted System Calls
5360 @subsection Interrupted System Calls
5362 @cindex thread breakpoints and system calls
5363 @cindex system calls and thread breakpoints
5364 @cindex premature return from system calls
5365 There is an unfortunate side effect when using @value{GDBN} to debug
5366 multi-threaded programs. If one thread stops for a
5367 breakpoint, or for some other reason, and another thread is blocked in a
5368 system call, then the system call may return prematurely. This is a
5369 consequence of the interaction between multiple threads and the signals
5370 that @value{GDBN} uses to implement breakpoints and other events that
5373 To handle this problem, your program should check the return value of
5374 each system call and react appropriately. This is good programming
5377 For example, do not write code like this:
5383 The call to @code{sleep} will return early if a different thread stops
5384 at a breakpoint or for some other reason.
5386 Instead, write this:
5391 unslept = sleep (unslept);
5394 A system call is allowed to return early, so the system is still
5395 conforming to its specification. But @value{GDBN} does cause your
5396 multi-threaded program to behave differently than it would without
5399 Also, @value{GDBN} uses internal breakpoints in the thread library to
5400 monitor certain events such as thread creation and thread destruction.
5401 When such an event happens, a system call in another thread may return
5402 prematurely, even though your program does not appear to stop.
5405 @subsection Observer Mode
5407 If you want to build on non-stop mode and observe program behavior
5408 without any chance of disruption by @value{GDBN}, you can set
5409 variables to disable all of the debugger's attempts to modify state,
5410 whether by writing memory, inserting breakpoints, etc. These operate
5411 at a low level, intercepting operations from all commands.
5413 When all of these are set to @code{off}, then @value{GDBN} is said to
5414 be @dfn{observer mode}. As a convenience, the variable
5415 @code{observer} can be set to disable these, plus enable non-stop
5418 Note that @value{GDBN} will not prevent you from making nonsensical
5419 combinations of these settings. For instance, if you have enabled
5420 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5421 then breakpoints that work by writing trap instructions into the code
5422 stream will still not be able to be placed.
5427 @item set observer on
5428 @itemx set observer off
5429 When set to @code{on}, this disables all the permission variables
5430 below (except for @code{insert-fast-tracepoints}), plus enables
5431 non-stop debugging. Setting this to @code{off} switches back to
5432 normal debugging, though remaining in non-stop mode.
5435 Show whether observer mode is on or off.
5437 @kindex may-write-registers
5438 @item set may-write-registers on
5439 @itemx set may-write-registers off
5440 This controls whether @value{GDBN} will attempt to alter the values of
5441 registers, such as with assignment expressions in @code{print}, or the
5442 @code{jump} command. It defaults to @code{on}.
5444 @item show may-write-registers
5445 Show the current permission to write registers.
5447 @kindex may-write-memory
5448 @item set may-write-memory on
5449 @itemx set may-write-memory off
5450 This controls whether @value{GDBN} will attempt to alter the contents
5451 of memory, such as with assignment expressions in @code{print}. It
5452 defaults to @code{on}.
5454 @item show may-write-memory
5455 Show the current permission to write memory.
5457 @kindex may-insert-breakpoints
5458 @item set may-insert-breakpoints on
5459 @itemx set may-insert-breakpoints off
5460 This controls whether @value{GDBN} will attempt to insert breakpoints.
5461 This affects all breakpoints, including internal breakpoints defined
5462 by @value{GDBN}. It defaults to @code{on}.
5464 @item show may-insert-breakpoints
5465 Show the current permission to insert breakpoints.
5467 @kindex may-insert-tracepoints
5468 @item set may-insert-tracepoints on
5469 @itemx set may-insert-tracepoints off
5470 This controls whether @value{GDBN} will attempt to insert (regular)
5471 tracepoints at the beginning of a tracing experiment. It affects only
5472 non-fast tracepoints, fast tracepoints being under the control of
5473 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5475 @item show may-insert-tracepoints
5476 Show the current permission to insert tracepoints.
5478 @kindex may-insert-fast-tracepoints
5479 @item set may-insert-fast-tracepoints on
5480 @itemx set may-insert-fast-tracepoints off
5481 This controls whether @value{GDBN} will attempt to insert fast
5482 tracepoints at the beginning of a tracing experiment. It affects only
5483 fast tracepoints, regular (non-fast) tracepoints being under the
5484 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5486 @item show may-insert-fast-tracepoints
5487 Show the current permission to insert fast tracepoints.
5489 @kindex may-interrupt
5490 @item set may-interrupt on
5491 @itemx set may-interrupt off
5492 This controls whether @value{GDBN} will attempt to interrupt or stop
5493 program execution. When this variable is @code{off}, the
5494 @code{interrupt} command will have no effect, nor will
5495 @kbd{Ctrl-c}. It defaults to @code{on}.
5497 @item show may-interrupt
5498 Show the current permission to interrupt or stop the program.
5502 @node Reverse Execution
5503 @chapter Running programs backward
5504 @cindex reverse execution
5505 @cindex running programs backward
5507 When you are debugging a program, it is not unusual to realize that
5508 you have gone too far, and some event of interest has already happened.
5509 If the target environment supports it, @value{GDBN} can allow you to
5510 ``rewind'' the program by running it backward.
5512 A target environment that supports reverse execution should be able
5513 to ``undo'' the changes in machine state that have taken place as the
5514 program was executing normally. Variables, registers etc.@: should
5515 revert to their previous values. Obviously this requires a great
5516 deal of sophistication on the part of the target environment; not
5517 all target environments can support reverse execution.
5519 When a program is executed in reverse, the instructions that
5520 have most recently been executed are ``un-executed'', in reverse
5521 order. The program counter runs backward, following the previous
5522 thread of execution in reverse. As each instruction is ``un-executed'',
5523 the values of memory and/or registers that were changed by that
5524 instruction are reverted to their previous states. After executing
5525 a piece of source code in reverse, all side effects of that code
5526 should be ``undone'', and all variables should be returned to their
5527 prior values@footnote{
5528 Note that some side effects are easier to undo than others. For instance,
5529 memory and registers are relatively easy, but device I/O is hard. Some
5530 targets may be able undo things like device I/O, and some may not.
5532 The contract between @value{GDBN} and the reverse executing target
5533 requires only that the target do something reasonable when
5534 @value{GDBN} tells it to execute backwards, and then report the
5535 results back to @value{GDBN}. Whatever the target reports back to
5536 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5537 assumes that the memory and registers that the target reports are in a
5538 consistant state, but @value{GDBN} accepts whatever it is given.
5541 If you are debugging in a target environment that supports
5542 reverse execution, @value{GDBN} provides the following commands.
5545 @kindex reverse-continue
5546 @kindex rc @r{(@code{reverse-continue})}
5547 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5548 @itemx rc @r{[}@var{ignore-count}@r{]}
5549 Beginning at the point where your program last stopped, start executing
5550 in reverse. Reverse execution will stop for breakpoints and synchronous
5551 exceptions (signals), just like normal execution. Behavior of
5552 asynchronous signals depends on the target environment.
5554 @kindex reverse-step
5555 @kindex rs @r{(@code{step})}
5556 @item reverse-step @r{[}@var{count}@r{]}
5557 Run the program backward until control reaches the start of a
5558 different source line; then stop it, and return control to @value{GDBN}.
5560 Like the @code{step} command, @code{reverse-step} will only stop
5561 at the beginning of a source line. It ``un-executes'' the previously
5562 executed source line. If the previous source line included calls to
5563 debuggable functions, @code{reverse-step} will step (backward) into
5564 the called function, stopping at the beginning of the @emph{last}
5565 statement in the called function (typically a return statement).
5567 Also, as with the @code{step} command, if non-debuggable functions are
5568 called, @code{reverse-step} will run thru them backward without stopping.
5570 @kindex reverse-stepi
5571 @kindex rsi @r{(@code{reverse-stepi})}
5572 @item reverse-stepi @r{[}@var{count}@r{]}
5573 Reverse-execute one machine instruction. Note that the instruction
5574 to be reverse-executed is @emph{not} the one pointed to by the program
5575 counter, but the instruction executed prior to that one. For instance,
5576 if the last instruction was a jump, @code{reverse-stepi} will take you
5577 back from the destination of the jump to the jump instruction itself.
5579 @kindex reverse-next
5580 @kindex rn @r{(@code{reverse-next})}
5581 @item reverse-next @r{[}@var{count}@r{]}
5582 Run backward to the beginning of the previous line executed in
5583 the current (innermost) stack frame. If the line contains function
5584 calls, they will be ``un-executed'' without stopping. Starting from
5585 the first line of a function, @code{reverse-next} will take you back
5586 to the caller of that function, @emph{before} the function was called,
5587 just as the normal @code{next} command would take you from the last
5588 line of a function back to its return to its caller
5589 @footnote{Unless the code is too heavily optimized.}.
5591 @kindex reverse-nexti
5592 @kindex rni @r{(@code{reverse-nexti})}
5593 @item reverse-nexti @r{[}@var{count}@r{]}
5594 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5595 in reverse, except that called functions are ``un-executed'' atomically.
5596 That is, if the previously executed instruction was a return from
5597 another function, @code{reverse-nexti} will continue to execute
5598 in reverse until the call to that function (from the current stack
5601 @kindex reverse-finish
5602 @item reverse-finish
5603 Just as the @code{finish} command takes you to the point where the
5604 current function returns, @code{reverse-finish} takes you to the point
5605 where it was called. Instead of ending up at the end of the current
5606 function invocation, you end up at the beginning.
5608 @kindex set exec-direction
5609 @item set exec-direction
5610 Set the direction of target execution.
5611 @itemx set exec-direction reverse
5612 @cindex execute forward or backward in time
5613 @value{GDBN} will perform all execution commands in reverse, until the
5614 exec-direction mode is changed to ``forward''. Affected commands include
5615 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5616 command cannot be used in reverse mode.
5617 @item set exec-direction forward
5618 @value{GDBN} will perform all execution commands in the normal fashion.
5619 This is the default.
5623 @node Process Record and Replay
5624 @chapter Recording Inferior's Execution and Replaying It
5625 @cindex process record and replay
5626 @cindex recording inferior's execution and replaying it
5628 On some platforms, @value{GDBN} provides a special @dfn{process record
5629 and replay} target that can record a log of the process execution, and
5630 replay it later with both forward and reverse execution commands.
5633 When this target is in use, if the execution log includes the record
5634 for the next instruction, @value{GDBN} will debug in @dfn{replay
5635 mode}. In the replay mode, the inferior does not really execute code
5636 instructions. Instead, all the events that normally happen during
5637 code execution are taken from the execution log. While code is not
5638 really executed in replay mode, the values of registers (including the
5639 program counter register) and the memory of the inferior are still
5640 changed as they normally would. Their contents are taken from the
5644 If the record for the next instruction is not in the execution log,
5645 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5646 inferior executes normally, and @value{GDBN} records the execution log
5649 The process record and replay target supports reverse execution
5650 (@pxref{Reverse Execution}), even if the platform on which the
5651 inferior runs does not. However, the reverse execution is limited in
5652 this case by the range of the instructions recorded in the execution
5653 log. In other words, reverse execution on platforms that don't
5654 support it directly can only be done in the replay mode.
5656 When debugging in the reverse direction, @value{GDBN} will work in
5657 replay mode as long as the execution log includes the record for the
5658 previous instruction; otherwise, it will work in record mode, if the
5659 platform supports reverse execution, or stop if not.
5661 For architecture environments that support process record and replay,
5662 @value{GDBN} provides the following commands:
5665 @kindex target record
5669 This command starts the process record and replay target. The process
5670 record and replay target can only debug a process that is already
5671 running. Therefore, you need first to start the process with the
5672 @kbd{run} or @kbd{start} commands, and then start the recording with
5673 the @kbd{target record} command.
5675 Both @code{record} and @code{rec} are aliases of @code{target record}.
5677 @cindex displaced stepping, and process record and replay
5678 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5679 will be automatically disabled when process record and replay target
5680 is started. That's because the process record and replay target
5681 doesn't support displaced stepping.
5683 @cindex non-stop mode, and process record and replay
5684 @cindex asynchronous execution, and process record and replay
5685 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5686 the asynchronous execution mode (@pxref{Background Execution}), the
5687 process record and replay target cannot be started because it doesn't
5688 support these two modes.
5693 Stop the process record and replay target. When process record and
5694 replay target stops, the entire execution log will be deleted and the
5695 inferior will either be terminated, or will remain in its final state.
5697 When you stop the process record and replay target in record mode (at
5698 the end of the execution log), the inferior will be stopped at the
5699 next instruction that would have been recorded. In other words, if
5700 you record for a while and then stop recording, the inferior process
5701 will be left in the same state as if the recording never happened.
5703 On the other hand, if the process record and replay target is stopped
5704 while in replay mode (that is, not at the end of the execution log,
5705 but at some earlier point), the inferior process will become ``live''
5706 at that earlier state, and it will then be possible to continue the
5707 usual ``live'' debugging of the process from that state.
5709 When the inferior process exits, or @value{GDBN} detaches from it,
5710 process record and replay target will automatically stop itself.
5713 @item record save @var{filename}
5714 Save the execution log to a file @file{@var{filename}}.
5715 Default filename is @file{gdb_record.@var{process_id}}, where
5716 @var{process_id} is the process ID of the inferior.
5718 @kindex record restore
5719 @item record restore @var{filename}
5720 Restore the execution log from a file @file{@var{filename}}.
5721 File must have been created with @code{record save}.
5723 @kindex set record insn-number-max
5724 @item set record insn-number-max @var{limit}
5725 Set the limit of instructions to be recorded. Default value is 200000.
5727 If @var{limit} is a positive number, then @value{GDBN} will start
5728 deleting instructions from the log once the number of the record
5729 instructions becomes greater than @var{limit}. For every new recorded
5730 instruction, @value{GDBN} will delete the earliest recorded
5731 instruction to keep the number of recorded instructions at the limit.
5732 (Since deleting recorded instructions loses information, @value{GDBN}
5733 lets you control what happens when the limit is reached, by means of
5734 the @code{stop-at-limit} option, described below.)
5736 If @var{limit} is zero, @value{GDBN} will never delete recorded
5737 instructions from the execution log. The number of recorded
5738 instructions is unlimited in this case.
5740 @kindex show record insn-number-max
5741 @item show record insn-number-max
5742 Show the limit of instructions to be recorded.
5744 @kindex set record stop-at-limit
5745 @item set record stop-at-limit
5746 Control the behavior when the number of recorded instructions reaches
5747 the limit. If ON (the default), @value{GDBN} will stop when the limit
5748 is reached for the first time and ask you whether you want to stop the
5749 inferior or continue running it and recording the execution log. If
5750 you decide to continue recording, each new recorded instruction will
5751 cause the oldest one to be deleted.
5753 If this option is OFF, @value{GDBN} will automatically delete the
5754 oldest record to make room for each new one, without asking.
5756 @kindex show record stop-at-limit
5757 @item show record stop-at-limit
5758 Show the current setting of @code{stop-at-limit}.
5760 @kindex set record memory-query
5761 @item set record memory-query
5762 Control the behavior when @value{GDBN} is unable to record memory
5763 changes caused by an instruction. If ON, @value{GDBN} will query
5764 whether to stop the inferior in that case.
5766 If this option is OFF (the default), @value{GDBN} will automatically
5767 ignore the effect of such instructions on memory. Later, when
5768 @value{GDBN} replays this execution log, it will mark the log of this
5769 instruction as not accessible, and it will not affect the replay
5772 @kindex show record memory-query
5773 @item show record memory-query
5774 Show the current setting of @code{memory-query}.
5778 Show various statistics about the state of process record and its
5779 in-memory execution log buffer, including:
5783 Whether in record mode or replay mode.
5785 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
5787 Highest recorded instruction number.
5789 Current instruction about to be replayed (if in replay mode).
5791 Number of instructions contained in the execution log.
5793 Maximum number of instructions that may be contained in the execution log.
5796 @kindex record delete
5799 When record target runs in replay mode (``in the past''), delete the
5800 subsequent execution log and begin to record a new execution log starting
5801 from the current address. This means you will abandon the previously
5802 recorded ``future'' and begin recording a new ``future''.
5807 @chapter Examining the Stack
5809 When your program has stopped, the first thing you need to know is where it
5810 stopped and how it got there.
5813 Each time your program performs a function call, information about the call
5815 That information includes the location of the call in your program,
5816 the arguments of the call,
5817 and the local variables of the function being called.
5818 The information is saved in a block of data called a @dfn{stack frame}.
5819 The stack frames are allocated in a region of memory called the @dfn{call
5822 When your program stops, the @value{GDBN} commands for examining the
5823 stack allow you to see all of this information.
5825 @cindex selected frame
5826 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5827 @value{GDBN} commands refer implicitly to the selected frame. In
5828 particular, whenever you ask @value{GDBN} for the value of a variable in
5829 your program, the value is found in the selected frame. There are
5830 special @value{GDBN} commands to select whichever frame you are
5831 interested in. @xref{Selection, ,Selecting a Frame}.
5833 When your program stops, @value{GDBN} automatically selects the
5834 currently executing frame and describes it briefly, similar to the
5835 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5838 * Frames:: Stack frames
5839 * Backtrace:: Backtraces
5840 * Selection:: Selecting a frame
5841 * Frame Info:: Information on a frame
5846 @section Stack Frames
5848 @cindex frame, definition
5850 The call stack is divided up into contiguous pieces called @dfn{stack
5851 frames}, or @dfn{frames} for short; each frame is the data associated
5852 with one call to one function. The frame contains the arguments given
5853 to the function, the function's local variables, and the address at
5854 which the function is executing.
5856 @cindex initial frame
5857 @cindex outermost frame
5858 @cindex innermost frame
5859 When your program is started, the stack has only one frame, that of the
5860 function @code{main}. This is called the @dfn{initial} frame or the
5861 @dfn{outermost} frame. Each time a function is called, a new frame is
5862 made. Each time a function returns, the frame for that function invocation
5863 is eliminated. If a function is recursive, there can be many frames for
5864 the same function. The frame for the function in which execution is
5865 actually occurring is called the @dfn{innermost} frame. This is the most
5866 recently created of all the stack frames that still exist.
5868 @cindex frame pointer
5869 Inside your program, stack frames are identified by their addresses. A
5870 stack frame consists of many bytes, each of which has its own address; each
5871 kind of computer has a convention for choosing one byte whose
5872 address serves as the address of the frame. Usually this address is kept
5873 in a register called the @dfn{frame pointer register}
5874 (@pxref{Registers, $fp}) while execution is going on in that frame.
5876 @cindex frame number
5877 @value{GDBN} assigns numbers to all existing stack frames, starting with
5878 zero for the innermost frame, one for the frame that called it,
5879 and so on upward. These numbers do not really exist in your program;
5880 they are assigned by @value{GDBN} to give you a way of designating stack
5881 frames in @value{GDBN} commands.
5883 @c The -fomit-frame-pointer below perennially causes hbox overflow
5884 @c underflow problems.
5885 @cindex frameless execution
5886 Some compilers provide a way to compile functions so that they operate
5887 without stack frames. (For example, the @value{NGCC} option
5889 @samp{-fomit-frame-pointer}
5891 generates functions without a frame.)
5892 This is occasionally done with heavily used library functions to save
5893 the frame setup time. @value{GDBN} has limited facilities for dealing
5894 with these function invocations. If the innermost function invocation
5895 has no stack frame, @value{GDBN} nevertheless regards it as though
5896 it had a separate frame, which is numbered zero as usual, allowing
5897 correct tracing of the function call chain. However, @value{GDBN} has
5898 no provision for frameless functions elsewhere in the stack.
5901 @kindex frame@r{, command}
5902 @cindex current stack frame
5903 @item frame @var{args}
5904 The @code{frame} command allows you to move from one stack frame to another,
5905 and to print the stack frame you select. @var{args} may be either the
5906 address of the frame or the stack frame number. Without an argument,
5907 @code{frame} prints the current stack frame.
5909 @kindex select-frame
5910 @cindex selecting frame silently
5912 The @code{select-frame} command allows you to move from one stack frame
5913 to another without printing the frame. This is the silent version of
5921 @cindex call stack traces
5922 A backtrace is a summary of how your program got where it is. It shows one
5923 line per frame, for many frames, starting with the currently executing
5924 frame (frame zero), followed by its caller (frame one), and on up the
5929 @kindex bt @r{(@code{backtrace})}
5932 Print a backtrace of the entire stack: one line per frame for all
5933 frames in the stack.
5935 You can stop the backtrace at any time by typing the system interrupt
5936 character, normally @kbd{Ctrl-c}.
5938 @item backtrace @var{n}
5940 Similar, but print only the innermost @var{n} frames.
5942 @item backtrace -@var{n}
5944 Similar, but print only the outermost @var{n} frames.
5946 @item backtrace full
5948 @itemx bt full @var{n}
5949 @itemx bt full -@var{n}
5950 Print the values of the local variables also. @var{n} specifies the
5951 number of frames to print, as described above.
5956 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5957 are additional aliases for @code{backtrace}.
5959 @cindex multiple threads, backtrace
5960 In a multi-threaded program, @value{GDBN} by default shows the
5961 backtrace only for the current thread. To display the backtrace for
5962 several or all of the threads, use the command @code{thread apply}
5963 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5964 apply all backtrace}, @value{GDBN} will display the backtrace for all
5965 the threads; this is handy when you debug a core dump of a
5966 multi-threaded program.
5968 Each line in the backtrace shows the frame number and the function name.
5969 The program counter value is also shown---unless you use @code{set
5970 print address off}. The backtrace also shows the source file name and
5971 line number, as well as the arguments to the function. The program
5972 counter value is omitted if it is at the beginning of the code for that
5975 Here is an example of a backtrace. It was made with the command
5976 @samp{bt 3}, so it shows the innermost three frames.
5980 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5982 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
5983 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5985 (More stack frames follow...)
5990 The display for frame zero does not begin with a program counter
5991 value, indicating that your program has stopped at the beginning of the
5992 code for line @code{993} of @code{builtin.c}.
5995 The value of parameter @code{data} in frame 1 has been replaced by
5996 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
5997 only if it is a scalar (integer, pointer, enumeration, etc). See command
5998 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
5999 on how to configure the way function parameter values are printed.
6001 @cindex optimized out, in backtrace
6002 @cindex function call arguments, optimized out
6003 If your program was compiled with optimizations, some compilers will
6004 optimize away arguments passed to functions if those arguments are
6005 never used after the call. Such optimizations generate code that
6006 passes arguments through registers, but doesn't store those arguments
6007 in the stack frame. @value{GDBN} has no way of displaying such
6008 arguments in stack frames other than the innermost one. Here's what
6009 such a backtrace might look like:
6013 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6015 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6016 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6018 (More stack frames follow...)
6023 The values of arguments that were not saved in their stack frames are
6024 shown as @samp{<optimized out>}.
6026 If you need to display the values of such optimized-out arguments,
6027 either deduce that from other variables whose values depend on the one
6028 you are interested in, or recompile without optimizations.
6030 @cindex backtrace beyond @code{main} function
6031 @cindex program entry point
6032 @cindex startup code, and backtrace
6033 Most programs have a standard user entry point---a place where system
6034 libraries and startup code transition into user code. For C this is
6035 @code{main}@footnote{
6036 Note that embedded programs (the so-called ``free-standing''
6037 environment) are not required to have a @code{main} function as the
6038 entry point. They could even have multiple entry points.}.
6039 When @value{GDBN} finds the entry function in a backtrace
6040 it will terminate the backtrace, to avoid tracing into highly
6041 system-specific (and generally uninteresting) code.
6043 If you need to examine the startup code, or limit the number of levels
6044 in a backtrace, you can change this behavior:
6047 @item set backtrace past-main
6048 @itemx set backtrace past-main on
6049 @kindex set backtrace
6050 Backtraces will continue past the user entry point.
6052 @item set backtrace past-main off
6053 Backtraces will stop when they encounter the user entry point. This is the
6056 @item show backtrace past-main
6057 @kindex show backtrace
6058 Display the current user entry point backtrace policy.
6060 @item set backtrace past-entry
6061 @itemx set backtrace past-entry on
6062 Backtraces will continue past the internal entry point of an application.
6063 This entry point is encoded by the linker when the application is built,
6064 and is likely before the user entry point @code{main} (or equivalent) is called.
6066 @item set backtrace past-entry off
6067 Backtraces will stop when they encounter the internal entry point of an
6068 application. This is the default.
6070 @item show backtrace past-entry
6071 Display the current internal entry point backtrace policy.
6073 @item set backtrace limit @var{n}
6074 @itemx set backtrace limit 0
6075 @cindex backtrace limit
6076 Limit the backtrace to @var{n} levels. A value of zero means
6079 @item show backtrace limit
6080 Display the current limit on backtrace levels.
6084 @section Selecting a Frame
6086 Most commands for examining the stack and other data in your program work on
6087 whichever stack frame is selected at the moment. Here are the commands for
6088 selecting a stack frame; all of them finish by printing a brief description
6089 of the stack frame just selected.
6092 @kindex frame@r{, selecting}
6093 @kindex f @r{(@code{frame})}
6096 Select frame number @var{n}. Recall that frame zero is the innermost
6097 (currently executing) frame, frame one is the frame that called the
6098 innermost one, and so on. The highest-numbered frame is the one for
6101 @item frame @var{addr}
6103 Select the frame at address @var{addr}. This is useful mainly if the
6104 chaining of stack frames has been damaged by a bug, making it
6105 impossible for @value{GDBN} to assign numbers properly to all frames. In
6106 addition, this can be useful when your program has multiple stacks and
6107 switches between them.
6109 On the SPARC architecture, @code{frame} needs two addresses to
6110 select an arbitrary frame: a frame pointer and a stack pointer.
6112 On the MIPS and Alpha architecture, it needs two addresses: a stack
6113 pointer and a program counter.
6115 On the 29k architecture, it needs three addresses: a register stack
6116 pointer, a program counter, and a memory stack pointer.
6120 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6121 advances toward the outermost frame, to higher frame numbers, to frames
6122 that have existed longer. @var{n} defaults to one.
6125 @kindex do @r{(@code{down})}
6127 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6128 advances toward the innermost frame, to lower frame numbers, to frames
6129 that were created more recently. @var{n} defaults to one. You may
6130 abbreviate @code{down} as @code{do}.
6133 All of these commands end by printing two lines of output describing the
6134 frame. The first line shows the frame number, the function name, the
6135 arguments, and the source file and line number of execution in that
6136 frame. The second line shows the text of that source line.
6144 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6146 10 read_input_file (argv[i]);
6150 After such a printout, the @code{list} command with no arguments
6151 prints ten lines centered on the point of execution in the frame.
6152 You can also edit the program at the point of execution with your favorite
6153 editing program by typing @code{edit}.
6154 @xref{List, ,Printing Source Lines},
6158 @kindex down-silently
6160 @item up-silently @var{n}
6161 @itemx down-silently @var{n}
6162 These two commands are variants of @code{up} and @code{down},
6163 respectively; they differ in that they do their work silently, without
6164 causing display of the new frame. They are intended primarily for use
6165 in @value{GDBN} command scripts, where the output might be unnecessary and
6170 @section Information About a Frame
6172 There are several other commands to print information about the selected
6178 When used without any argument, this command does not change which
6179 frame is selected, but prints a brief description of the currently
6180 selected stack frame. It can be abbreviated @code{f}. With an
6181 argument, this command is used to select a stack frame.
6182 @xref{Selection, ,Selecting a Frame}.
6185 @kindex info f @r{(@code{info frame})}
6188 This command prints a verbose description of the selected stack frame,
6193 the address of the frame
6195 the address of the next frame down (called by this frame)
6197 the address of the next frame up (caller of this frame)
6199 the language in which the source code corresponding to this frame is written
6201 the address of the frame's arguments
6203 the address of the frame's local variables
6205 the program counter saved in it (the address of execution in the caller frame)
6207 which registers were saved in the frame
6210 @noindent The verbose description is useful when
6211 something has gone wrong that has made the stack format fail to fit
6212 the usual conventions.
6214 @item info frame @var{addr}
6215 @itemx info f @var{addr}
6216 Print a verbose description of the frame at address @var{addr}, without
6217 selecting that frame. The selected frame remains unchanged by this
6218 command. This requires the same kind of address (more than one for some
6219 architectures) that you specify in the @code{frame} command.
6220 @xref{Selection, ,Selecting a Frame}.
6224 Print the arguments of the selected frame, each on a separate line.
6228 Print the local variables of the selected frame, each on a separate
6229 line. These are all variables (declared either static or automatic)
6230 accessible at the point of execution of the selected frame.
6233 @cindex catch exceptions, list active handlers
6234 @cindex exception handlers, how to list
6236 Print a list of all the exception handlers that are active in the
6237 current stack frame at the current point of execution. To see other
6238 exception handlers, visit the associated frame (using the @code{up},
6239 @code{down}, or @code{frame} commands); then type @code{info catch}.
6240 @xref{Set Catchpoints, , Setting Catchpoints}.
6246 @chapter Examining Source Files
6248 @value{GDBN} can print parts of your program's source, since the debugging
6249 information recorded in the program tells @value{GDBN} what source files were
6250 used to build it. When your program stops, @value{GDBN} spontaneously prints
6251 the line where it stopped. Likewise, when you select a stack frame
6252 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6253 execution in that frame has stopped. You can print other portions of
6254 source files by explicit command.
6256 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6257 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6258 @value{GDBN} under @sc{gnu} Emacs}.
6261 * List:: Printing source lines
6262 * Specify Location:: How to specify code locations
6263 * Edit:: Editing source files
6264 * Search:: Searching source files
6265 * Source Path:: Specifying source directories
6266 * Machine Code:: Source and machine code
6270 @section Printing Source Lines
6273 @kindex l @r{(@code{list})}
6274 To print lines from a source file, use the @code{list} command
6275 (abbreviated @code{l}). By default, ten lines are printed.
6276 There are several ways to specify what part of the file you want to
6277 print; see @ref{Specify Location}, for the full list.
6279 Here are the forms of the @code{list} command most commonly used:
6282 @item list @var{linenum}
6283 Print lines centered around line number @var{linenum} in the
6284 current source file.
6286 @item list @var{function}
6287 Print lines centered around the beginning of function
6291 Print more lines. If the last lines printed were printed with a
6292 @code{list} command, this prints lines following the last lines
6293 printed; however, if the last line printed was a solitary line printed
6294 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6295 Stack}), this prints lines centered around that line.
6298 Print lines just before the lines last printed.
6301 @cindex @code{list}, how many lines to display
6302 By default, @value{GDBN} prints ten source lines with any of these forms of
6303 the @code{list} command. You can change this using @code{set listsize}:
6306 @kindex set listsize
6307 @item set listsize @var{count}
6308 Make the @code{list} command display @var{count} source lines (unless
6309 the @code{list} argument explicitly specifies some other number).
6311 @kindex show listsize
6313 Display the number of lines that @code{list} prints.
6316 Repeating a @code{list} command with @key{RET} discards the argument,
6317 so it is equivalent to typing just @code{list}. This is more useful
6318 than listing the same lines again. An exception is made for an
6319 argument of @samp{-}; that argument is preserved in repetition so that
6320 each repetition moves up in the source file.
6322 In general, the @code{list} command expects you to supply zero, one or two
6323 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6324 of writing them (@pxref{Specify Location}), but the effect is always
6325 to specify some source line.
6327 Here is a complete description of the possible arguments for @code{list}:
6330 @item list @var{linespec}
6331 Print lines centered around the line specified by @var{linespec}.
6333 @item list @var{first},@var{last}
6334 Print lines from @var{first} to @var{last}. Both arguments are
6335 linespecs. When a @code{list} command has two linespecs, and the
6336 source file of the second linespec is omitted, this refers to
6337 the same source file as the first linespec.
6339 @item list ,@var{last}
6340 Print lines ending with @var{last}.
6342 @item list @var{first},
6343 Print lines starting with @var{first}.
6346 Print lines just after the lines last printed.
6349 Print lines just before the lines last printed.
6352 As described in the preceding table.
6355 @node Specify Location
6356 @section Specifying a Location
6357 @cindex specifying location
6360 Several @value{GDBN} commands accept arguments that specify a location
6361 of your program's code. Since @value{GDBN} is a source-level
6362 debugger, a location usually specifies some line in the source code;
6363 for that reason, locations are also known as @dfn{linespecs}.
6365 Here are all the different ways of specifying a code location that
6366 @value{GDBN} understands:
6370 Specifies the line number @var{linenum} of the current source file.
6373 @itemx +@var{offset}
6374 Specifies the line @var{offset} lines before or after the @dfn{current
6375 line}. For the @code{list} command, the current line is the last one
6376 printed; for the breakpoint commands, this is the line at which
6377 execution stopped in the currently selected @dfn{stack frame}
6378 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6379 used as the second of the two linespecs in a @code{list} command,
6380 this specifies the line @var{offset} lines up or down from the first
6383 @item @var{filename}:@var{linenum}
6384 Specifies the line @var{linenum} in the source file @var{filename}.
6386 @item @var{function}
6387 Specifies the line that begins the body of the function @var{function}.
6388 For example, in C, this is the line with the open brace.
6390 @item @var{function}:@var{label}
6391 Specifies the line where @var{label} appears in @var{function}.
6393 @item @var{filename}:@var{function}
6394 Specifies the line that begins the body of the function @var{function}
6395 in the file @var{filename}. You only need the file name with a
6396 function name to avoid ambiguity when there are identically named
6397 functions in different source files.
6400 Specifies the line at which the label named @var{label} appears.
6401 @value{GDBN} searches for the label in the function corresponding to
6402 the currently selected stack frame. If there is no current selected
6403 stack frame (for instance, if the inferior is not running), then
6404 @value{GDBN} will not search for a label.
6406 @item *@var{address}
6407 Specifies the program address @var{address}. For line-oriented
6408 commands, such as @code{list} and @code{edit}, this specifies a source
6409 line that contains @var{address}. For @code{break} and other
6410 breakpoint oriented commands, this can be used to set breakpoints in
6411 parts of your program which do not have debugging information or
6414 Here @var{address} may be any expression valid in the current working
6415 language (@pxref{Languages, working language}) that specifies a code
6416 address. In addition, as a convenience, @value{GDBN} extends the
6417 semantics of expressions used in locations to cover the situations
6418 that frequently happen during debugging. Here are the various forms
6422 @item @var{expression}
6423 Any expression valid in the current working language.
6425 @item @var{funcaddr}
6426 An address of a function or procedure derived from its name. In C,
6427 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6428 simply the function's name @var{function} (and actually a special case
6429 of a valid expression). In Pascal and Modula-2, this is
6430 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6431 (although the Pascal form also works).
6433 This form specifies the address of the function's first instruction,
6434 before the stack frame and arguments have been set up.
6436 @item '@var{filename}'::@var{funcaddr}
6437 Like @var{funcaddr} above, but also specifies the name of the source
6438 file explicitly. This is useful if the name of the function does not
6439 specify the function unambiguously, e.g., if there are several
6440 functions with identical names in different source files.
6447 @section Editing Source Files
6448 @cindex editing source files
6451 @kindex e @r{(@code{edit})}
6452 To edit the lines in a source file, use the @code{edit} command.
6453 The editing program of your choice
6454 is invoked with the current line set to
6455 the active line in the program.
6456 Alternatively, there are several ways to specify what part of the file you
6457 want to print if you want to see other parts of the program:
6460 @item edit @var{location}
6461 Edit the source file specified by @code{location}. Editing starts at
6462 that @var{location}, e.g., at the specified source line of the
6463 specified file. @xref{Specify Location}, for all the possible forms
6464 of the @var{location} argument; here are the forms of the @code{edit}
6465 command most commonly used:
6468 @item edit @var{number}
6469 Edit the current source file with @var{number} as the active line number.
6471 @item edit @var{function}
6472 Edit the file containing @var{function} at the beginning of its definition.
6477 @subsection Choosing your Editor
6478 You can customize @value{GDBN} to use any editor you want
6480 The only restriction is that your editor (say @code{ex}), recognizes the
6481 following command-line syntax:
6483 ex +@var{number} file
6485 The optional numeric value +@var{number} specifies the number of the line in
6486 the file where to start editing.}.
6487 By default, it is @file{@value{EDITOR}}, but you can change this
6488 by setting the environment variable @code{EDITOR} before using
6489 @value{GDBN}. For example, to configure @value{GDBN} to use the
6490 @code{vi} editor, you could use these commands with the @code{sh} shell:
6496 or in the @code{csh} shell,
6498 setenv EDITOR /usr/bin/vi
6503 @section Searching Source Files
6504 @cindex searching source files
6506 There are two commands for searching through the current source file for a
6511 @kindex forward-search
6512 @item forward-search @var{regexp}
6513 @itemx search @var{regexp}
6514 The command @samp{forward-search @var{regexp}} checks each line,
6515 starting with the one following the last line listed, for a match for
6516 @var{regexp}. It lists the line that is found. You can use the
6517 synonym @samp{search @var{regexp}} or abbreviate the command name as
6520 @kindex reverse-search
6521 @item reverse-search @var{regexp}
6522 The command @samp{reverse-search @var{regexp}} checks each line, starting
6523 with the one before the last line listed and going backward, for a match
6524 for @var{regexp}. It lists the line that is found. You can abbreviate
6525 this command as @code{rev}.
6529 @section Specifying Source Directories
6532 @cindex directories for source files
6533 Executable programs sometimes do not record the directories of the source
6534 files from which they were compiled, just the names. Even when they do,
6535 the directories could be moved between the compilation and your debugging
6536 session. @value{GDBN} has a list of directories to search for source files;
6537 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6538 it tries all the directories in the list, in the order they are present
6539 in the list, until it finds a file with the desired name.
6541 For example, suppose an executable references the file
6542 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6543 @file{/mnt/cross}. The file is first looked up literally; if this
6544 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6545 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6546 message is printed. @value{GDBN} does not look up the parts of the
6547 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6548 Likewise, the subdirectories of the source path are not searched: if
6549 the source path is @file{/mnt/cross}, and the binary refers to
6550 @file{foo.c}, @value{GDBN} would not find it under
6551 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6553 Plain file names, relative file names with leading directories, file
6554 names containing dots, etc.@: are all treated as described above; for
6555 instance, if the source path is @file{/mnt/cross}, and the source file
6556 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6557 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6558 that---@file{/mnt/cross/foo.c}.
6560 Note that the executable search path is @emph{not} used to locate the
6563 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6564 any information it has cached about where source files are found and where
6565 each line is in the file.
6569 When you start @value{GDBN}, its source path includes only @samp{cdir}
6570 and @samp{cwd}, in that order.
6571 To add other directories, use the @code{directory} command.
6573 The search path is used to find both program source files and @value{GDBN}
6574 script files (read using the @samp{-command} option and @samp{source} command).
6576 In addition to the source path, @value{GDBN} provides a set of commands
6577 that manage a list of source path substitution rules. A @dfn{substitution
6578 rule} specifies how to rewrite source directories stored in the program's
6579 debug information in case the sources were moved to a different
6580 directory between compilation and debugging. A rule is made of
6581 two strings, the first specifying what needs to be rewritten in
6582 the path, and the second specifying how it should be rewritten.
6583 In @ref{set substitute-path}, we name these two parts @var{from} and
6584 @var{to} respectively. @value{GDBN} does a simple string replacement
6585 of @var{from} with @var{to} at the start of the directory part of the
6586 source file name, and uses that result instead of the original file
6587 name to look up the sources.
6589 Using the previous example, suppose the @file{foo-1.0} tree has been
6590 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6591 @value{GDBN} to replace @file{/usr/src} in all source path names with
6592 @file{/mnt/cross}. The first lookup will then be
6593 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6594 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6595 substitution rule, use the @code{set substitute-path} command
6596 (@pxref{set substitute-path}).
6598 To avoid unexpected substitution results, a rule is applied only if the
6599 @var{from} part of the directory name ends at a directory separator.
6600 For instance, a rule substituting @file{/usr/source} into
6601 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6602 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6603 is applied only at the beginning of the directory name, this rule will
6604 not be applied to @file{/root/usr/source/baz.c} either.
6606 In many cases, you can achieve the same result using the @code{directory}
6607 command. However, @code{set substitute-path} can be more efficient in
6608 the case where the sources are organized in a complex tree with multiple
6609 subdirectories. With the @code{directory} command, you need to add each
6610 subdirectory of your project. If you moved the entire tree while
6611 preserving its internal organization, then @code{set substitute-path}
6612 allows you to direct the debugger to all the sources with one single
6615 @code{set substitute-path} is also more than just a shortcut command.
6616 The source path is only used if the file at the original location no
6617 longer exists. On the other hand, @code{set substitute-path} modifies
6618 the debugger behavior to look at the rewritten location instead. So, if
6619 for any reason a source file that is not relevant to your executable is
6620 located at the original location, a substitution rule is the only
6621 method available to point @value{GDBN} at the new location.
6623 @cindex @samp{--with-relocated-sources}
6624 @cindex default source path substitution
6625 You can configure a default source path substitution rule by
6626 configuring @value{GDBN} with the
6627 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6628 should be the name of a directory under @value{GDBN}'s configured
6629 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6630 directory names in debug information under @var{dir} will be adjusted
6631 automatically if the installed @value{GDBN} is moved to a new
6632 location. This is useful if @value{GDBN}, libraries or executables
6633 with debug information and corresponding source code are being moved
6637 @item directory @var{dirname} @dots{}
6638 @item dir @var{dirname} @dots{}
6639 Add directory @var{dirname} to the front of the source path. Several
6640 directory names may be given to this command, separated by @samp{:}
6641 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6642 part of absolute file names) or
6643 whitespace. You may specify a directory that is already in the source
6644 path; this moves it forward, so @value{GDBN} searches it sooner.
6648 @vindex $cdir@r{, convenience variable}
6649 @vindex $cwd@r{, convenience variable}
6650 @cindex compilation directory
6651 @cindex current directory
6652 @cindex working directory
6653 @cindex directory, current
6654 @cindex directory, compilation
6655 You can use the string @samp{$cdir} to refer to the compilation
6656 directory (if one is recorded), and @samp{$cwd} to refer to the current
6657 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6658 tracks the current working directory as it changes during your @value{GDBN}
6659 session, while the latter is immediately expanded to the current
6660 directory at the time you add an entry to the source path.
6663 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6665 @c RET-repeat for @code{directory} is explicitly disabled, but since
6666 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6668 @item set directories @var{path-list}
6669 @kindex set directories
6670 Set the source path to @var{path-list}.
6671 @samp{$cdir:$cwd} are added if missing.
6673 @item show directories
6674 @kindex show directories
6675 Print the source path: show which directories it contains.
6677 @anchor{set substitute-path}
6678 @item set substitute-path @var{from} @var{to}
6679 @kindex set substitute-path
6680 Define a source path substitution rule, and add it at the end of the
6681 current list of existing substitution rules. If a rule with the same
6682 @var{from} was already defined, then the old rule is also deleted.
6684 For example, if the file @file{/foo/bar/baz.c} was moved to
6685 @file{/mnt/cross/baz.c}, then the command
6688 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6692 will tell @value{GDBN} to replace @samp{/usr/src} with
6693 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6694 @file{baz.c} even though it was moved.
6696 In the case when more than one substitution rule have been defined,
6697 the rules are evaluated one by one in the order where they have been
6698 defined. The first one matching, if any, is selected to perform
6701 For instance, if we had entered the following commands:
6704 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6705 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6709 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6710 @file{/mnt/include/defs.h} by using the first rule. However, it would
6711 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6712 @file{/mnt/src/lib/foo.c}.
6715 @item unset substitute-path [path]
6716 @kindex unset substitute-path
6717 If a path is specified, search the current list of substitution rules
6718 for a rule that would rewrite that path. Delete that rule if found.
6719 A warning is emitted by the debugger if no rule could be found.
6721 If no path is specified, then all substitution rules are deleted.
6723 @item show substitute-path [path]
6724 @kindex show substitute-path
6725 If a path is specified, then print the source path substitution rule
6726 which would rewrite that path, if any.
6728 If no path is specified, then print all existing source path substitution
6733 If your source path is cluttered with directories that are no longer of
6734 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6735 versions of source. You can correct the situation as follows:
6739 Use @code{directory} with no argument to reset the source path to its default value.
6742 Use @code{directory} with suitable arguments to reinstall the
6743 directories you want in the source path. You can add all the
6744 directories in one command.
6748 @section Source and Machine Code
6749 @cindex source line and its code address
6751 You can use the command @code{info line} to map source lines to program
6752 addresses (and vice versa), and the command @code{disassemble} to display
6753 a range of addresses as machine instructions. You can use the command
6754 @code{set disassemble-next-line} to set whether to disassemble next
6755 source line when execution stops. When run under @sc{gnu} Emacs
6756 mode, the @code{info line} command causes the arrow to point to the
6757 line specified. Also, @code{info line} prints addresses in symbolic form as
6762 @item info line @var{linespec}
6763 Print the starting and ending addresses of the compiled code for
6764 source line @var{linespec}. You can specify source lines in any of
6765 the ways documented in @ref{Specify Location}.
6768 For example, we can use @code{info line} to discover the location of
6769 the object code for the first line of function
6770 @code{m4_changequote}:
6772 @c FIXME: I think this example should also show the addresses in
6773 @c symbolic form, as they usually would be displayed.
6775 (@value{GDBP}) info line m4_changequote
6776 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6780 @cindex code address and its source line
6781 We can also inquire (using @code{*@var{addr}} as the form for
6782 @var{linespec}) what source line covers a particular address:
6784 (@value{GDBP}) info line *0x63ff
6785 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6788 @cindex @code{$_} and @code{info line}
6789 @cindex @code{x} command, default address
6790 @kindex x@r{(examine), and} info line
6791 After @code{info line}, the default address for the @code{x} command
6792 is changed to the starting address of the line, so that @samp{x/i} is
6793 sufficient to begin examining the machine code (@pxref{Memory,
6794 ,Examining Memory}). Also, this address is saved as the value of the
6795 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6800 @cindex assembly instructions
6801 @cindex instructions, assembly
6802 @cindex machine instructions
6803 @cindex listing machine instructions
6805 @itemx disassemble /m
6806 @itemx disassemble /r
6807 This specialized command dumps a range of memory as machine
6808 instructions. It can also print mixed source+disassembly by specifying
6809 the @code{/m} modifier and print the raw instructions in hex as well as
6810 in symbolic form by specifying the @code{/r}.
6811 The default memory range is the function surrounding the
6812 program counter of the selected frame. A single argument to this
6813 command is a program counter value; @value{GDBN} dumps the function
6814 surrounding this value. When two arguments are given, they should
6815 be separated by a comma, possibly surrounded by whitespace. The
6816 arguments specify a range of addresses to dump, in one of two forms:
6819 @item @var{start},@var{end}
6820 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
6821 @item @var{start},+@var{length}
6822 the addresses from @var{start} (inclusive) to
6823 @code{@var{start}+@var{length}} (exclusive).
6827 When 2 arguments are specified, the name of the function is also
6828 printed (since there could be several functions in the given range).
6830 The argument(s) can be any expression yielding a numeric value, such as
6831 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
6833 If the range of memory being disassembled contains current program counter,
6834 the instruction at that location is shown with a @code{=>} marker.
6837 The following example shows the disassembly of a range of addresses of
6838 HP PA-RISC 2.0 code:
6841 (@value{GDBP}) disas 0x32c4, 0x32e4
6842 Dump of assembler code from 0x32c4 to 0x32e4:
6843 0x32c4 <main+204>: addil 0,dp
6844 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6845 0x32cc <main+212>: ldil 0x3000,r31
6846 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6847 0x32d4 <main+220>: ldo 0(r31),rp
6848 0x32d8 <main+224>: addil -0x800,dp
6849 0x32dc <main+228>: ldo 0x588(r1),r26
6850 0x32e0 <main+232>: ldil 0x3000,r31
6851 End of assembler dump.
6854 Here is an example showing mixed source+assembly for Intel x86, when the
6855 program is stopped just after function prologue:
6858 (@value{GDBP}) disas /m main
6859 Dump of assembler code for function main:
6861 0x08048330 <+0>: push %ebp
6862 0x08048331 <+1>: mov %esp,%ebp
6863 0x08048333 <+3>: sub $0x8,%esp
6864 0x08048336 <+6>: and $0xfffffff0,%esp
6865 0x08048339 <+9>: sub $0x10,%esp
6867 6 printf ("Hello.\n");
6868 => 0x0804833c <+12>: movl $0x8048440,(%esp)
6869 0x08048343 <+19>: call 0x8048284 <puts@@plt>
6873 0x08048348 <+24>: mov $0x0,%eax
6874 0x0804834d <+29>: leave
6875 0x0804834e <+30>: ret
6877 End of assembler dump.
6880 Here is another example showing raw instructions in hex for AMD x86-64,
6883 (gdb) disas /r 0x400281,+10
6884 Dump of assembler code from 0x400281 to 0x40028b:
6885 0x0000000000400281: 38 36 cmp %dh,(%rsi)
6886 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
6887 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
6888 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
6889 End of assembler dump.
6892 Some architectures have more than one commonly-used set of instruction
6893 mnemonics or other syntax.
6895 For programs that were dynamically linked and use shared libraries,
6896 instructions that call functions or branch to locations in the shared
6897 libraries might show a seemingly bogus location---it's actually a
6898 location of the relocation table. On some architectures, @value{GDBN}
6899 might be able to resolve these to actual function names.
6902 @kindex set disassembly-flavor
6903 @cindex Intel disassembly flavor
6904 @cindex AT&T disassembly flavor
6905 @item set disassembly-flavor @var{instruction-set}
6906 Select the instruction set to use when disassembling the
6907 program via the @code{disassemble} or @code{x/i} commands.
6909 Currently this command is only defined for the Intel x86 family. You
6910 can set @var{instruction-set} to either @code{intel} or @code{att}.
6911 The default is @code{att}, the AT&T flavor used by default by Unix
6912 assemblers for x86-based targets.
6914 @kindex show disassembly-flavor
6915 @item show disassembly-flavor
6916 Show the current setting of the disassembly flavor.
6920 @kindex set disassemble-next-line
6921 @kindex show disassemble-next-line
6922 @item set disassemble-next-line
6923 @itemx show disassemble-next-line
6924 Control whether or not @value{GDBN} will disassemble the next source
6925 line or instruction when execution stops. If ON, @value{GDBN} will
6926 display disassembly of the next source line when execution of the
6927 program being debugged stops. This is @emph{in addition} to
6928 displaying the source line itself, which @value{GDBN} always does if
6929 possible. If the next source line cannot be displayed for some reason
6930 (e.g., if @value{GDBN} cannot find the source file, or there's no line
6931 info in the debug info), @value{GDBN} will display disassembly of the
6932 next @emph{instruction} instead of showing the next source line. If
6933 AUTO, @value{GDBN} will display disassembly of next instruction only
6934 if the source line cannot be displayed. This setting causes
6935 @value{GDBN} to display some feedback when you step through a function
6936 with no line info or whose source file is unavailable. The default is
6937 OFF, which means never display the disassembly of the next line or
6943 @chapter Examining Data
6945 @cindex printing data
6946 @cindex examining data
6949 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6950 @c document because it is nonstandard... Under Epoch it displays in a
6951 @c different window or something like that.
6952 The usual way to examine data in your program is with the @code{print}
6953 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6954 evaluates and prints the value of an expression of the language your
6955 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6956 Different Languages}). It may also print the expression using a
6957 Python-based pretty-printer (@pxref{Pretty Printing}).
6960 @item print @var{expr}
6961 @itemx print /@var{f} @var{expr}
6962 @var{expr} is an expression (in the source language). By default the
6963 value of @var{expr} is printed in a format appropriate to its data type;
6964 you can choose a different format by specifying @samp{/@var{f}}, where
6965 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6969 @itemx print /@var{f}
6970 @cindex reprint the last value
6971 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6972 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6973 conveniently inspect the same value in an alternative format.
6976 A more low-level way of examining data is with the @code{x} command.
6977 It examines data in memory at a specified address and prints it in a
6978 specified format. @xref{Memory, ,Examining Memory}.
6980 If you are interested in information about types, or about how the
6981 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6982 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6986 * Expressions:: Expressions
6987 * Ambiguous Expressions:: Ambiguous Expressions
6988 * Variables:: Program variables
6989 * Arrays:: Artificial arrays
6990 * Output Formats:: Output formats
6991 * Memory:: Examining memory
6992 * Auto Display:: Automatic display
6993 * Print Settings:: Print settings
6994 * Pretty Printing:: Python pretty printing
6995 * Value History:: Value history
6996 * Convenience Vars:: Convenience variables
6997 * Registers:: Registers
6998 * Floating Point Hardware:: Floating point hardware
6999 * Vector Unit:: Vector Unit
7000 * OS Information:: Auxiliary data provided by operating system
7001 * Memory Region Attributes:: Memory region attributes
7002 * Dump/Restore Files:: Copy between memory and a file
7003 * Core File Generation:: Cause a program dump its core
7004 * Character Sets:: Debugging programs that use a different
7005 character set than GDB does
7006 * Caching Remote Data:: Data caching for remote targets
7007 * Searching Memory:: Searching memory for a sequence of bytes
7011 @section Expressions
7014 @code{print} and many other @value{GDBN} commands accept an expression and
7015 compute its value. Any kind of constant, variable or operator defined
7016 by the programming language you are using is valid in an expression in
7017 @value{GDBN}. This includes conditional expressions, function calls,
7018 casts, and string constants. It also includes preprocessor macros, if
7019 you compiled your program to include this information; see
7022 @cindex arrays in expressions
7023 @value{GDBN} supports array constants in expressions input by
7024 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
7025 you can use the command @code{print @{1, 2, 3@}} to create an array
7026 of three integers. If you pass an array to a function or assign it
7027 to a program variable, @value{GDBN} copies the array to memory that
7028 is @code{malloc}ed in the target program.
7030 Because C is so widespread, most of the expressions shown in examples in
7031 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
7032 Languages}, for information on how to use expressions in other
7035 In this section, we discuss operators that you can use in @value{GDBN}
7036 expressions regardless of your programming language.
7038 @cindex casts, in expressions
7039 Casts are supported in all languages, not just in C, because it is so
7040 useful to cast a number into a pointer in order to examine a structure
7041 at that address in memory.
7042 @c FIXME: casts supported---Mod2 true?
7044 @value{GDBN} supports these operators, in addition to those common
7045 to programming languages:
7049 @samp{@@} is a binary operator for treating parts of memory as arrays.
7050 @xref{Arrays, ,Artificial Arrays}, for more information.
7053 @samp{::} allows you to specify a variable in terms of the file or
7054 function where it is defined. @xref{Variables, ,Program Variables}.
7056 @cindex @{@var{type}@}
7057 @cindex type casting memory
7058 @cindex memory, viewing as typed object
7059 @cindex casts, to view memory
7060 @item @{@var{type}@} @var{addr}
7061 Refers to an object of type @var{type} stored at address @var{addr} in
7062 memory. @var{addr} may be any expression whose value is an integer or
7063 pointer (but parentheses are required around binary operators, just as in
7064 a cast). This construct is allowed regardless of what kind of data is
7065 normally supposed to reside at @var{addr}.
7068 @node Ambiguous Expressions
7069 @section Ambiguous Expressions
7070 @cindex ambiguous expressions
7072 Expressions can sometimes contain some ambiguous elements. For instance,
7073 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7074 a single function name to be defined several times, for application in
7075 different contexts. This is called @dfn{overloading}. Another example
7076 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7077 templates and is typically instantiated several times, resulting in
7078 the same function name being defined in different contexts.
7080 In some cases and depending on the language, it is possible to adjust
7081 the expression to remove the ambiguity. For instance in C@t{++}, you
7082 can specify the signature of the function you want to break on, as in
7083 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7084 qualified name of your function often makes the expression unambiguous
7087 When an ambiguity that needs to be resolved is detected, the debugger
7088 has the capability to display a menu of numbered choices for each
7089 possibility, and then waits for the selection with the prompt @samp{>}.
7090 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7091 aborts the current command. If the command in which the expression was
7092 used allows more than one choice to be selected, the next option in the
7093 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7096 For example, the following session excerpt shows an attempt to set a
7097 breakpoint at the overloaded symbol @code{String::after}.
7098 We choose three particular definitions of that function name:
7100 @c FIXME! This is likely to change to show arg type lists, at least
7103 (@value{GDBP}) b String::after
7106 [2] file:String.cc; line number:867
7107 [3] file:String.cc; line number:860
7108 [4] file:String.cc; line number:875
7109 [5] file:String.cc; line number:853
7110 [6] file:String.cc; line number:846
7111 [7] file:String.cc; line number:735
7113 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7114 Breakpoint 2 at 0xb344: file String.cc, line 875.
7115 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7116 Multiple breakpoints were set.
7117 Use the "delete" command to delete unwanted
7124 @kindex set multiple-symbols
7125 @item set multiple-symbols @var{mode}
7126 @cindex multiple-symbols menu
7128 This option allows you to adjust the debugger behavior when an expression
7131 By default, @var{mode} is set to @code{all}. If the command with which
7132 the expression is used allows more than one choice, then @value{GDBN}
7133 automatically selects all possible choices. For instance, inserting
7134 a breakpoint on a function using an ambiguous name results in a breakpoint
7135 inserted on each possible match. However, if a unique choice must be made,
7136 then @value{GDBN} uses the menu to help you disambiguate the expression.
7137 For instance, printing the address of an overloaded function will result
7138 in the use of the menu.
7140 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7141 when an ambiguity is detected.
7143 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7144 an error due to the ambiguity and the command is aborted.
7146 @kindex show multiple-symbols
7147 @item show multiple-symbols
7148 Show the current value of the @code{multiple-symbols} setting.
7152 @section Program Variables
7154 The most common kind of expression to use is the name of a variable
7157 Variables in expressions are understood in the selected stack frame
7158 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7162 global (or file-static)
7169 visible according to the scope rules of the
7170 programming language from the point of execution in that frame
7173 @noindent This means that in the function
7188 you can examine and use the variable @code{a} whenever your program is
7189 executing within the function @code{foo}, but you can only use or
7190 examine the variable @code{b} while your program is executing inside
7191 the block where @code{b} is declared.
7193 @cindex variable name conflict
7194 There is an exception: you can refer to a variable or function whose
7195 scope is a single source file even if the current execution point is not
7196 in this file. But it is possible to have more than one such variable or
7197 function with the same name (in different source files). If that
7198 happens, referring to that name has unpredictable effects. If you wish,
7199 you can specify a static variable in a particular function or file,
7200 using the colon-colon (@code{::}) notation:
7202 @cindex colon-colon, context for variables/functions
7204 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7205 @cindex @code{::}, context for variables/functions
7208 @var{file}::@var{variable}
7209 @var{function}::@var{variable}
7213 Here @var{file} or @var{function} is the name of the context for the
7214 static @var{variable}. In the case of file names, you can use quotes to
7215 make sure @value{GDBN} parses the file name as a single word---for example,
7216 to print a global value of @code{x} defined in @file{f2.c}:
7219 (@value{GDBP}) p 'f2.c'::x
7222 @cindex C@t{++} scope resolution
7223 This use of @samp{::} is very rarely in conflict with the very similar
7224 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7225 scope resolution operator in @value{GDBN} expressions.
7226 @c FIXME: Um, so what happens in one of those rare cases where it's in
7229 @cindex wrong values
7230 @cindex variable values, wrong
7231 @cindex function entry/exit, wrong values of variables
7232 @cindex optimized code, wrong values of variables
7234 @emph{Warning:} Occasionally, a local variable may appear to have the
7235 wrong value at certain points in a function---just after entry to a new
7236 scope, and just before exit.
7238 You may see this problem when you are stepping by machine instructions.
7239 This is because, on most machines, it takes more than one instruction to
7240 set up a stack frame (including local variable definitions); if you are
7241 stepping by machine instructions, variables may appear to have the wrong
7242 values until the stack frame is completely built. On exit, it usually
7243 also takes more than one machine instruction to destroy a stack frame;
7244 after you begin stepping through that group of instructions, local
7245 variable definitions may be gone.
7247 This may also happen when the compiler does significant optimizations.
7248 To be sure of always seeing accurate values, turn off all optimization
7251 @cindex ``No symbol "foo" in current context''
7252 Another possible effect of compiler optimizations is to optimize
7253 unused variables out of existence, or assign variables to registers (as
7254 opposed to memory addresses). Depending on the support for such cases
7255 offered by the debug info format used by the compiler, @value{GDBN}
7256 might not be able to display values for such local variables. If that
7257 happens, @value{GDBN} will print a message like this:
7260 No symbol "foo" in current context.
7263 To solve such problems, either recompile without optimizations, or use a
7264 different debug info format, if the compiler supports several such
7265 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
7266 usually supports the @option{-gstabs+} option. @option{-gstabs+}
7267 produces debug info in a format that is superior to formats such as
7268 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
7269 an effective form for debug info. @xref{Debugging Options,,Options
7270 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
7271 Compiler Collection (GCC)}.
7272 @xref{C, ,C and C@t{++}}, for more information about debug info formats
7273 that are best suited to C@t{++} programs.
7275 If you ask to print an object whose contents are unknown to
7276 @value{GDBN}, e.g., because its data type is not completely specified
7277 by the debug information, @value{GDBN} will say @samp{<incomplete
7278 type>}. @xref{Symbols, incomplete type}, for more about this.
7280 Strings are identified as arrays of @code{char} values without specified
7281 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7282 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7283 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7284 defines literal string type @code{"char"} as @code{char} without a sign.
7289 signed char var1[] = "A";
7292 You get during debugging
7297 $2 = @{65 'A', 0 '\0'@}
7301 @section Artificial Arrays
7303 @cindex artificial array
7305 @kindex @@@r{, referencing memory as an array}
7306 It is often useful to print out several successive objects of the
7307 same type in memory; a section of an array, or an array of
7308 dynamically determined size for which only a pointer exists in the
7311 You can do this by referring to a contiguous span of memory as an
7312 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7313 operand of @samp{@@} should be the first element of the desired array
7314 and be an individual object. The right operand should be the desired length
7315 of the array. The result is an array value whose elements are all of
7316 the type of the left argument. The first element is actually the left
7317 argument; the second element comes from bytes of memory immediately
7318 following those that hold the first element, and so on. Here is an
7319 example. If a program says
7322 int *array = (int *) malloc (len * sizeof (int));
7326 you can print the contents of @code{array} with
7332 The left operand of @samp{@@} must reside in memory. Array values made
7333 with @samp{@@} in this way behave just like other arrays in terms of
7334 subscripting, and are coerced to pointers when used in expressions.
7335 Artificial arrays most often appear in expressions via the value history
7336 (@pxref{Value History, ,Value History}), after printing one out.
7338 Another way to create an artificial array is to use a cast.
7339 This re-interprets a value as if it were an array.
7340 The value need not be in memory:
7342 (@value{GDBP}) p/x (short[2])0x12345678
7343 $1 = @{0x1234, 0x5678@}
7346 As a convenience, if you leave the array length out (as in
7347 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7348 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7350 (@value{GDBP}) p/x (short[])0x12345678
7351 $2 = @{0x1234, 0x5678@}
7354 Sometimes the artificial array mechanism is not quite enough; in
7355 moderately complex data structures, the elements of interest may not
7356 actually be adjacent---for example, if you are interested in the values
7357 of pointers in an array. One useful work-around in this situation is
7358 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7359 Variables}) as a counter in an expression that prints the first
7360 interesting value, and then repeat that expression via @key{RET}. For
7361 instance, suppose you have an array @code{dtab} of pointers to
7362 structures, and you are interested in the values of a field @code{fv}
7363 in each structure. Here is an example of what you might type:
7373 @node Output Formats
7374 @section Output Formats
7376 @cindex formatted output
7377 @cindex output formats
7378 By default, @value{GDBN} prints a value according to its data type. Sometimes
7379 this is not what you want. For example, you might want to print a number
7380 in hex, or a pointer in decimal. Or you might want to view data in memory
7381 at a certain address as a character string or as an instruction. To do
7382 these things, specify an @dfn{output format} when you print a value.
7384 The simplest use of output formats is to say how to print a value
7385 already computed. This is done by starting the arguments of the
7386 @code{print} command with a slash and a format letter. The format
7387 letters supported are:
7391 Regard the bits of the value as an integer, and print the integer in
7395 Print as integer in signed decimal.
7398 Print as integer in unsigned decimal.
7401 Print as integer in octal.
7404 Print as integer in binary. The letter @samp{t} stands for ``two''.
7405 @footnote{@samp{b} cannot be used because these format letters are also
7406 used with the @code{x} command, where @samp{b} stands for ``byte'';
7407 see @ref{Memory,,Examining Memory}.}
7410 @cindex unknown address, locating
7411 @cindex locate address
7412 Print as an address, both absolute in hexadecimal and as an offset from
7413 the nearest preceding symbol. You can use this format used to discover
7414 where (in what function) an unknown address is located:
7417 (@value{GDBP}) p/a 0x54320
7418 $3 = 0x54320 <_initialize_vx+396>
7422 The command @code{info symbol 0x54320} yields similar results.
7423 @xref{Symbols, info symbol}.
7426 Regard as an integer and print it as a character constant. This
7427 prints both the numerical value and its character representation. The
7428 character representation is replaced with the octal escape @samp{\nnn}
7429 for characters outside the 7-bit @sc{ascii} range.
7431 Without this format, @value{GDBN} displays @code{char},
7432 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7433 constants. Single-byte members of vectors are displayed as integer
7437 Regard the bits of the value as a floating point number and print
7438 using typical floating point syntax.
7441 @cindex printing strings
7442 @cindex printing byte arrays
7443 Regard as a string, if possible. With this format, pointers to single-byte
7444 data are displayed as null-terminated strings and arrays of single-byte data
7445 are displayed as fixed-length strings. Other values are displayed in their
7448 Without this format, @value{GDBN} displays pointers to and arrays of
7449 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7450 strings. Single-byte members of a vector are displayed as an integer
7454 @cindex raw printing
7455 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7456 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7457 Printing}). This typically results in a higher-level display of the
7458 value's contents. The @samp{r} format bypasses any Python
7459 pretty-printer which might exist.
7462 For example, to print the program counter in hex (@pxref{Registers}), type
7469 Note that no space is required before the slash; this is because command
7470 names in @value{GDBN} cannot contain a slash.
7472 To reprint the last value in the value history with a different format,
7473 you can use the @code{print} command with just a format and no
7474 expression. For example, @samp{p/x} reprints the last value in hex.
7477 @section Examining Memory
7479 You can use the command @code{x} (for ``examine'') to examine memory in
7480 any of several formats, independently of your program's data types.
7482 @cindex examining memory
7484 @kindex x @r{(examine memory)}
7485 @item x/@var{nfu} @var{addr}
7488 Use the @code{x} command to examine memory.
7491 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7492 much memory to display and how to format it; @var{addr} is an
7493 expression giving the address where you want to start displaying memory.
7494 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7495 Several commands set convenient defaults for @var{addr}.
7498 @item @var{n}, the repeat count
7499 The repeat count is a decimal integer; the default is 1. It specifies
7500 how much memory (counting by units @var{u}) to display.
7501 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7504 @item @var{f}, the display format
7505 The display format is one of the formats used by @code{print}
7506 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7507 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7508 The default is @samp{x} (hexadecimal) initially. The default changes
7509 each time you use either @code{x} or @code{print}.
7511 @item @var{u}, the unit size
7512 The unit size is any of
7518 Halfwords (two bytes).
7520 Words (four bytes). This is the initial default.
7522 Giant words (eight bytes).
7525 Each time you specify a unit size with @code{x}, that size becomes the
7526 default unit the next time you use @code{x}. For the @samp{i} format,
7527 the unit size is ignored and is normally not written. For the @samp{s} format,
7528 the unit size defaults to @samp{b}, unless it is explicitly given.
7529 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
7530 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
7531 Note that the results depend on the programming language of the
7532 current compilation unit. If the language is C, the @samp{s}
7533 modifier will use the UTF-16 encoding while @samp{w} will use
7534 UTF-32. The encoding is set by the programming language and cannot
7537 @item @var{addr}, starting display address
7538 @var{addr} is the address where you want @value{GDBN} to begin displaying
7539 memory. The expression need not have a pointer value (though it may);
7540 it is always interpreted as an integer address of a byte of memory.
7541 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7542 @var{addr} is usually just after the last address examined---but several
7543 other commands also set the default address: @code{info breakpoints} (to
7544 the address of the last breakpoint listed), @code{info line} (to the
7545 starting address of a line), and @code{print} (if you use it to display
7546 a value from memory).
7549 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7550 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7551 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7552 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7553 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7555 Since the letters indicating unit sizes are all distinct from the
7556 letters specifying output formats, you do not have to remember whether
7557 unit size or format comes first; either order works. The output
7558 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7559 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7561 Even though the unit size @var{u} is ignored for the formats @samp{s}
7562 and @samp{i}, you might still want to use a count @var{n}; for example,
7563 @samp{3i} specifies that you want to see three machine instructions,
7564 including any operands. For convenience, especially when used with
7565 the @code{display} command, the @samp{i} format also prints branch delay
7566 slot instructions, if any, beyond the count specified, which immediately
7567 follow the last instruction that is within the count. The command
7568 @code{disassemble} gives an alternative way of inspecting machine
7569 instructions; see @ref{Machine Code,,Source and Machine Code}.
7571 All the defaults for the arguments to @code{x} are designed to make it
7572 easy to continue scanning memory with minimal specifications each time
7573 you use @code{x}. For example, after you have inspected three machine
7574 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7575 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7576 the repeat count @var{n} is used again; the other arguments default as
7577 for successive uses of @code{x}.
7579 When examining machine instructions, the instruction at current program
7580 counter is shown with a @code{=>} marker. For example:
7583 (@value{GDBP}) x/5i $pc-6
7584 0x804837f <main+11>: mov %esp,%ebp
7585 0x8048381 <main+13>: push %ecx
7586 0x8048382 <main+14>: sub $0x4,%esp
7587 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
7588 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
7591 @cindex @code{$_}, @code{$__}, and value history
7592 The addresses and contents printed by the @code{x} command are not saved
7593 in the value history because there is often too much of them and they
7594 would get in the way. Instead, @value{GDBN} makes these values available for
7595 subsequent use in expressions as values of the convenience variables
7596 @code{$_} and @code{$__}. After an @code{x} command, the last address
7597 examined is available for use in expressions in the convenience variable
7598 @code{$_}. The contents of that address, as examined, are available in
7599 the convenience variable @code{$__}.
7601 If the @code{x} command has a repeat count, the address and contents saved
7602 are from the last memory unit printed; this is not the same as the last
7603 address printed if several units were printed on the last line of output.
7605 @cindex remote memory comparison
7606 @cindex verify remote memory image
7607 When you are debugging a program running on a remote target machine
7608 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7609 remote machine's memory against the executable file you downloaded to
7610 the target. The @code{compare-sections} command is provided for such
7614 @kindex compare-sections
7615 @item compare-sections @r{[}@var{section-name}@r{]}
7616 Compare the data of a loadable section @var{section-name} in the
7617 executable file of the program being debugged with the same section in
7618 the remote machine's memory, and report any mismatches. With no
7619 arguments, compares all loadable sections. This command's
7620 availability depends on the target's support for the @code{"qCRC"}
7625 @section Automatic Display
7626 @cindex automatic display
7627 @cindex display of expressions
7629 If you find that you want to print the value of an expression frequently
7630 (to see how it changes), you might want to add it to the @dfn{automatic
7631 display list} so that @value{GDBN} prints its value each time your program stops.
7632 Each expression added to the list is given a number to identify it;
7633 to remove an expression from the list, you specify that number.
7634 The automatic display looks like this:
7638 3: bar[5] = (struct hack *) 0x3804
7642 This display shows item numbers, expressions and their current values. As with
7643 displays you request manually using @code{x} or @code{print}, you can
7644 specify the output format you prefer; in fact, @code{display} decides
7645 whether to use @code{print} or @code{x} depending your format
7646 specification---it uses @code{x} if you specify either the @samp{i}
7647 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7651 @item display @var{expr}
7652 Add the expression @var{expr} to the list of expressions to display
7653 each time your program stops. @xref{Expressions, ,Expressions}.
7655 @code{display} does not repeat if you press @key{RET} again after using it.
7657 @item display/@var{fmt} @var{expr}
7658 For @var{fmt} specifying only a display format and not a size or
7659 count, add the expression @var{expr} to the auto-display list but
7660 arrange to display it each time in the specified format @var{fmt}.
7661 @xref{Output Formats,,Output Formats}.
7663 @item display/@var{fmt} @var{addr}
7664 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7665 number of units, add the expression @var{addr} as a memory address to
7666 be examined each time your program stops. Examining means in effect
7667 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7670 For example, @samp{display/i $pc} can be helpful, to see the machine
7671 instruction about to be executed each time execution stops (@samp{$pc}
7672 is a common name for the program counter; @pxref{Registers, ,Registers}).
7675 @kindex delete display
7677 @item undisplay @var{dnums}@dots{}
7678 @itemx delete display @var{dnums}@dots{}
7679 Remove items from the list of expressions to display. Specify the
7680 numbers of the displays that you want affected with the command
7681 argument @var{dnums}. It can be a single display number, one of the
7682 numbers shown in the first field of the @samp{info display} display;
7683 or it could be a range of display numbers, as in @code{2-4}.
7685 @code{undisplay} does not repeat if you press @key{RET} after using it.
7686 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7688 @kindex disable display
7689 @item disable display @var{dnums}@dots{}
7690 Disable the display of item numbers @var{dnums}. A disabled display
7691 item is not printed automatically, but is not forgotten. It may be
7692 enabled again later. Specify the numbers of the displays that you
7693 want affected with the command argument @var{dnums}. It can be a
7694 single display number, one of the numbers shown in the first field of
7695 the @samp{info display} display; or it could be a range of display
7696 numbers, as in @code{2-4}.
7698 @kindex enable display
7699 @item enable display @var{dnums}@dots{}
7700 Enable display of item numbers @var{dnums}. It becomes effective once
7701 again in auto display of its expression, until you specify otherwise.
7702 Specify the numbers of the displays that you want affected with the
7703 command argument @var{dnums}. It can be a single display number, one
7704 of the numbers shown in the first field of the @samp{info display}
7705 display; or it could be a range of display numbers, as in @code{2-4}.
7708 Display the current values of the expressions on the list, just as is
7709 done when your program stops.
7711 @kindex info display
7713 Print the list of expressions previously set up to display
7714 automatically, each one with its item number, but without showing the
7715 values. This includes disabled expressions, which are marked as such.
7716 It also includes expressions which would not be displayed right now
7717 because they refer to automatic variables not currently available.
7720 @cindex display disabled out of scope
7721 If a display expression refers to local variables, then it does not make
7722 sense outside the lexical context for which it was set up. Such an
7723 expression is disabled when execution enters a context where one of its
7724 variables is not defined. For example, if you give the command
7725 @code{display last_char} while inside a function with an argument
7726 @code{last_char}, @value{GDBN} displays this argument while your program
7727 continues to stop inside that function. When it stops elsewhere---where
7728 there is no variable @code{last_char}---the display is disabled
7729 automatically. The next time your program stops where @code{last_char}
7730 is meaningful, you can enable the display expression once again.
7732 @node Print Settings
7733 @section Print Settings
7735 @cindex format options
7736 @cindex print settings
7737 @value{GDBN} provides the following ways to control how arrays, structures,
7738 and symbols are printed.
7741 These settings are useful for debugging programs in any language:
7745 @item set print address
7746 @itemx set print address on
7747 @cindex print/don't print memory addresses
7748 @value{GDBN} prints memory addresses showing the location of stack
7749 traces, structure values, pointer values, breakpoints, and so forth,
7750 even when it also displays the contents of those addresses. The default
7751 is @code{on}. For example, this is what a stack frame display looks like with
7752 @code{set print address on}:
7757 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7759 530 if (lquote != def_lquote)
7763 @item set print address off
7764 Do not print addresses when displaying their contents. For example,
7765 this is the same stack frame displayed with @code{set print address off}:
7769 (@value{GDBP}) set print addr off
7771 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7772 530 if (lquote != def_lquote)
7776 You can use @samp{set print address off} to eliminate all machine
7777 dependent displays from the @value{GDBN} interface. For example, with
7778 @code{print address off}, you should get the same text for backtraces on
7779 all machines---whether or not they involve pointer arguments.
7782 @item show print address
7783 Show whether or not addresses are to be printed.
7786 When @value{GDBN} prints a symbolic address, it normally prints the
7787 closest earlier symbol plus an offset. If that symbol does not uniquely
7788 identify the address (for example, it is a name whose scope is a single
7789 source file), you may need to clarify. One way to do this is with
7790 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7791 you can set @value{GDBN} to print the source file and line number when
7792 it prints a symbolic address:
7795 @item set print symbol-filename on
7796 @cindex source file and line of a symbol
7797 @cindex symbol, source file and line
7798 Tell @value{GDBN} to print the source file name and line number of a
7799 symbol in the symbolic form of an address.
7801 @item set print symbol-filename off
7802 Do not print source file name and line number of a symbol. This is the
7805 @item show print symbol-filename
7806 Show whether or not @value{GDBN} will print the source file name and
7807 line number of a symbol in the symbolic form of an address.
7810 Another situation where it is helpful to show symbol filenames and line
7811 numbers is when disassembling code; @value{GDBN} shows you the line
7812 number and source file that corresponds to each instruction.
7814 Also, you may wish to see the symbolic form only if the address being
7815 printed is reasonably close to the closest earlier symbol:
7818 @item set print max-symbolic-offset @var{max-offset}
7819 @cindex maximum value for offset of closest symbol
7820 Tell @value{GDBN} to only display the symbolic form of an address if the
7821 offset between the closest earlier symbol and the address is less than
7822 @var{max-offset}. The default is 0, which tells @value{GDBN}
7823 to always print the symbolic form of an address if any symbol precedes it.
7825 @item show print max-symbolic-offset
7826 Ask how large the maximum offset is that @value{GDBN} prints in a
7830 @cindex wild pointer, interpreting
7831 @cindex pointer, finding referent
7832 If you have a pointer and you are not sure where it points, try
7833 @samp{set print symbol-filename on}. Then you can determine the name
7834 and source file location of the variable where it points, using
7835 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7836 For example, here @value{GDBN} shows that a variable @code{ptt} points
7837 at another variable @code{t}, defined in @file{hi2.c}:
7840 (@value{GDBP}) set print symbol-filename on
7841 (@value{GDBP}) p/a ptt
7842 $4 = 0xe008 <t in hi2.c>
7846 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
7847 does not show the symbol name and filename of the referent, even with
7848 the appropriate @code{set print} options turned on.
7851 Other settings control how different kinds of objects are printed:
7854 @item set print array
7855 @itemx set print array on
7856 @cindex pretty print arrays
7857 Pretty print arrays. This format is more convenient to read,
7858 but uses more space. The default is off.
7860 @item set print array off
7861 Return to compressed format for arrays.
7863 @item show print array
7864 Show whether compressed or pretty format is selected for displaying
7867 @cindex print array indexes
7868 @item set print array-indexes
7869 @itemx set print array-indexes on
7870 Print the index of each element when displaying arrays. May be more
7871 convenient to locate a given element in the array or quickly find the
7872 index of a given element in that printed array. The default is off.
7874 @item set print array-indexes off
7875 Stop printing element indexes when displaying arrays.
7877 @item show print array-indexes
7878 Show whether the index of each element is printed when displaying
7881 @item set print elements @var{number-of-elements}
7882 @cindex number of array elements to print
7883 @cindex limit on number of printed array elements
7884 Set a limit on how many elements of an array @value{GDBN} will print.
7885 If @value{GDBN} is printing a large array, it stops printing after it has
7886 printed the number of elements set by the @code{set print elements} command.
7887 This limit also applies to the display of strings.
7888 When @value{GDBN} starts, this limit is set to 200.
7889 Setting @var{number-of-elements} to zero means that the printing is unlimited.
7891 @item show print elements
7892 Display the number of elements of a large array that @value{GDBN} will print.
7893 If the number is 0, then the printing is unlimited.
7895 @item set print frame-arguments @var{value}
7896 @kindex set print frame-arguments
7897 @cindex printing frame argument values
7898 @cindex print all frame argument values
7899 @cindex print frame argument values for scalars only
7900 @cindex do not print frame argument values
7901 This command allows to control how the values of arguments are printed
7902 when the debugger prints a frame (@pxref{Frames}). The possible
7907 The values of all arguments are printed.
7910 Print the value of an argument only if it is a scalar. The value of more
7911 complex arguments such as arrays, structures, unions, etc, is replaced
7912 by @code{@dots{}}. This is the default. Here is an example where
7913 only scalar arguments are shown:
7916 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
7921 None of the argument values are printed. Instead, the value of each argument
7922 is replaced by @code{@dots{}}. In this case, the example above now becomes:
7925 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
7930 By default, only scalar arguments are printed. This command can be used
7931 to configure the debugger to print the value of all arguments, regardless
7932 of their type. However, it is often advantageous to not print the value
7933 of more complex parameters. For instance, it reduces the amount of
7934 information printed in each frame, making the backtrace more readable.
7935 Also, it improves performance when displaying Ada frames, because
7936 the computation of large arguments can sometimes be CPU-intensive,
7937 especially in large applications. Setting @code{print frame-arguments}
7938 to @code{scalars} (the default) or @code{none} avoids this computation,
7939 thus speeding up the display of each Ada frame.
7941 @item show print frame-arguments
7942 Show how the value of arguments should be displayed when printing a frame.
7944 @item set print entry-values @var{value}
7945 @kindex set print entry-values
7946 Set printing of frame argument values at function entry. In some cases
7947 @value{GDBN} can determine the value of function argument which was passed by
7948 the function caller, even if the value was modified inside the called function
7949 and therefore is different. With optimized code, the current value could be
7950 unavailable, but the entry value may still be known.
7952 The default value is @code{default} (see below for its description). Older
7953 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
7954 this feature will behave in the @code{default} setting the same way as with the
7957 This functionality is currently supported only by DWARF 2 debugging format and
7958 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
7959 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
7962 The @var{value} parameter can be one of the following:
7966 Print only actual parameter values, never print values from function entry
7970 #0 different (val=6)
7971 #0 lost (val=<optimized out>)
7973 #0 invalid (val=<optimized out>)
7977 Print only parameter values from function entry point. The actual parameter
7978 values are never printed.
7980 #0 equal (val@@entry=5)
7981 #0 different (val@@entry=5)
7982 #0 lost (val@@entry=5)
7983 #0 born (val@@entry=<optimized out>)
7984 #0 invalid (val@@entry=<optimized out>)
7988 Print only parameter values from function entry point. If value from function
7989 entry point is not known while the actual value is known, print the actual
7990 value for such parameter.
7992 #0 equal (val@@entry=5)
7993 #0 different (val@@entry=5)
7994 #0 lost (val@@entry=5)
7996 #0 invalid (val@@entry=<optimized out>)
8000 Print actual parameter values. If actual parameter value is not known while
8001 value from function entry point is known, print the entry point value for such
8005 #0 different (val=6)
8006 #0 lost (val@@entry=5)
8008 #0 invalid (val=<optimized out>)
8012 Always print both the actual parameter value and its value from function entry
8013 point, even if values of one or both are not available due to compiler
8016 #0 equal (val=5, val@@entry=5)
8017 #0 different (val=6, val@@entry=5)
8018 #0 lost (val=<optimized out>, val@@entry=5)
8019 #0 born (val=10, val@@entry=<optimized out>)
8020 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
8024 Print the actual parameter value if it is known and also its value from
8025 function entry point if it is known. If neither is known, print for the actual
8026 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
8027 values are known and identical, print the shortened
8028 @code{param=param@@entry=VALUE} notation.
8030 #0 equal (val=val@@entry=5)
8031 #0 different (val=6, val@@entry=5)
8032 #0 lost (val@@entry=5)
8034 #0 invalid (val=<optimized out>)
8038 Always print the actual parameter value. Print also its value from function
8039 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
8040 if both values are known and identical, print the shortened
8041 @code{param=param@@entry=VALUE} notation.
8043 #0 equal (val=val@@entry=5)
8044 #0 different (val=6, val@@entry=5)
8045 #0 lost (val=<optimized out>, val@@entry=5)
8047 #0 invalid (val=<optimized out>)
8051 For analysis messages on possible failures of frame argument values at function
8052 entry resolution see @ref{set debug entry-values}.
8054 @item show print entry-values
8055 Show the method being used for printing of frame argument values at function
8058 @item set print repeats
8059 @cindex repeated array elements
8060 Set the threshold for suppressing display of repeated array
8061 elements. When the number of consecutive identical elements of an
8062 array exceeds the threshold, @value{GDBN} prints the string
8063 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
8064 identical repetitions, instead of displaying the identical elements
8065 themselves. Setting the threshold to zero will cause all elements to
8066 be individually printed. The default threshold is 10.
8068 @item show print repeats
8069 Display the current threshold for printing repeated identical
8072 @item set print null-stop
8073 @cindex @sc{null} elements in arrays
8074 Cause @value{GDBN} to stop printing the characters of an array when the first
8075 @sc{null} is encountered. This is useful when large arrays actually
8076 contain only short strings.
8079 @item show print null-stop
8080 Show whether @value{GDBN} stops printing an array on the first
8081 @sc{null} character.
8083 @item set print pretty on
8084 @cindex print structures in indented form
8085 @cindex indentation in structure display
8086 Cause @value{GDBN} to print structures in an indented format with one member
8087 per line, like this:
8102 @item set print pretty off
8103 Cause @value{GDBN} to print structures in a compact format, like this:
8107 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
8108 meat = 0x54 "Pork"@}
8113 This is the default format.
8115 @item show print pretty
8116 Show which format @value{GDBN} is using to print structures.
8118 @item set print sevenbit-strings on
8119 @cindex eight-bit characters in strings
8120 @cindex octal escapes in strings
8121 Print using only seven-bit characters; if this option is set,
8122 @value{GDBN} displays any eight-bit characters (in strings or
8123 character values) using the notation @code{\}@var{nnn}. This setting is
8124 best if you are working in English (@sc{ascii}) and you use the
8125 high-order bit of characters as a marker or ``meta'' bit.
8127 @item set print sevenbit-strings off
8128 Print full eight-bit characters. This allows the use of more
8129 international character sets, and is the default.
8131 @item show print sevenbit-strings
8132 Show whether or not @value{GDBN} is printing only seven-bit characters.
8134 @item set print union on
8135 @cindex unions in structures, printing
8136 Tell @value{GDBN} to print unions which are contained in structures
8137 and other unions. This is the default setting.
8139 @item set print union off
8140 Tell @value{GDBN} not to print unions which are contained in
8141 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
8144 @item show print union
8145 Ask @value{GDBN} whether or not it will print unions which are contained in
8146 structures and other unions.
8148 For example, given the declarations
8151 typedef enum @{Tree, Bug@} Species;
8152 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
8153 typedef enum @{Caterpillar, Cocoon, Butterfly@}
8164 struct thing foo = @{Tree, @{Acorn@}@};
8168 with @code{set print union on} in effect @samp{p foo} would print
8171 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
8175 and with @code{set print union off} in effect it would print
8178 $1 = @{it = Tree, form = @{...@}@}
8182 @code{set print union} affects programs written in C-like languages
8188 These settings are of interest when debugging C@t{++} programs:
8191 @cindex demangling C@t{++} names
8192 @item set print demangle
8193 @itemx set print demangle on
8194 Print C@t{++} names in their source form rather than in the encoded
8195 (``mangled'') form passed to the assembler and linker for type-safe
8196 linkage. The default is on.
8198 @item show print demangle
8199 Show whether C@t{++} names are printed in mangled or demangled form.
8201 @item set print asm-demangle
8202 @itemx set print asm-demangle on
8203 Print C@t{++} names in their source form rather than their mangled form, even
8204 in assembler code printouts such as instruction disassemblies.
8207 @item show print asm-demangle
8208 Show whether C@t{++} names in assembly listings are printed in mangled
8211 @cindex C@t{++} symbol decoding style
8212 @cindex symbol decoding style, C@t{++}
8213 @kindex set demangle-style
8214 @item set demangle-style @var{style}
8215 Choose among several encoding schemes used by different compilers to
8216 represent C@t{++} names. The choices for @var{style} are currently:
8220 Allow @value{GDBN} to choose a decoding style by inspecting your program.
8223 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
8224 This is the default.
8227 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
8230 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
8233 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
8234 @strong{Warning:} this setting alone is not sufficient to allow
8235 debugging @code{cfront}-generated executables. @value{GDBN} would
8236 require further enhancement to permit that.
8239 If you omit @var{style}, you will see a list of possible formats.
8241 @item show demangle-style
8242 Display the encoding style currently in use for decoding C@t{++} symbols.
8244 @item set print object
8245 @itemx set print object on
8246 @cindex derived type of an object, printing
8247 @cindex display derived types
8248 When displaying a pointer to an object, identify the @emph{actual}
8249 (derived) type of the object rather than the @emph{declared} type, using
8250 the virtual function table.
8252 @item set print object off
8253 Display only the declared type of objects, without reference to the
8254 virtual function table. This is the default setting.
8256 @item show print object
8257 Show whether actual, or declared, object types are displayed.
8259 @item set print static-members
8260 @itemx set print static-members on
8261 @cindex static members of C@t{++} objects
8262 Print static members when displaying a C@t{++} object. The default is on.
8264 @item set print static-members off
8265 Do not print static members when displaying a C@t{++} object.
8267 @item show print static-members
8268 Show whether C@t{++} static members are printed or not.
8270 @item set print pascal_static-members
8271 @itemx set print pascal_static-members on
8272 @cindex static members of Pascal objects
8273 @cindex Pascal objects, static members display
8274 Print static members when displaying a Pascal object. The default is on.
8276 @item set print pascal_static-members off
8277 Do not print static members when displaying a Pascal object.
8279 @item show print pascal_static-members
8280 Show whether Pascal static members are printed or not.
8282 @c These don't work with HP ANSI C++ yet.
8283 @item set print vtbl
8284 @itemx set print vtbl on
8285 @cindex pretty print C@t{++} virtual function tables
8286 @cindex virtual functions (C@t{++}) display
8287 @cindex VTBL display
8288 Pretty print C@t{++} virtual function tables. The default is off.
8289 (The @code{vtbl} commands do not work on programs compiled with the HP
8290 ANSI C@t{++} compiler (@code{aCC}).)
8292 @item set print vtbl off
8293 Do not pretty print C@t{++} virtual function tables.
8295 @item show print vtbl
8296 Show whether C@t{++} virtual function tables are pretty printed, or not.
8299 @node Pretty Printing
8300 @section Pretty Printing
8302 @value{GDBN} provides a mechanism to allow pretty-printing of values using
8303 Python code. It greatly simplifies the display of complex objects. This
8304 mechanism works for both MI and the CLI.
8307 * Pretty-Printer Introduction:: Introduction to pretty-printers
8308 * Pretty-Printer Example:: An example pretty-printer
8309 * Pretty-Printer Commands:: Pretty-printer commands
8312 @node Pretty-Printer Introduction
8313 @subsection Pretty-Printer Introduction
8315 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
8316 registered for the value. If there is then @value{GDBN} invokes the
8317 pretty-printer to print the value. Otherwise the value is printed normally.
8319 Pretty-printers are normally named. This makes them easy to manage.
8320 The @samp{info pretty-printer} command will list all the installed
8321 pretty-printers with their names.
8322 If a pretty-printer can handle multiple data types, then its
8323 @dfn{subprinters} are the printers for the individual data types.
8324 Each such subprinter has its own name.
8325 The format of the name is @var{printer-name};@var{subprinter-name}.
8327 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
8328 Typically they are automatically loaded and registered when the corresponding
8329 debug information is loaded, thus making them available without having to
8330 do anything special.
8332 There are three places where a pretty-printer can be registered.
8336 Pretty-printers registered globally are available when debugging
8340 Pretty-printers registered with a program space are available only
8341 when debugging that program.
8342 @xref{Progspaces In Python}, for more details on program spaces in Python.
8345 Pretty-printers registered with an objfile are loaded and unloaded
8346 with the corresponding objfile (e.g., shared library).
8347 @xref{Objfiles In Python}, for more details on objfiles in Python.
8350 @xref{Selecting Pretty-Printers}, for further information on how
8351 pretty-printers are selected,
8353 @xref{Writing a Pretty-Printer}, for implementing pretty printers
8356 @node Pretty-Printer Example
8357 @subsection Pretty-Printer Example
8359 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
8362 (@value{GDBP}) print s
8364 static npos = 4294967295,
8366 <std::allocator<char>> = @{
8367 <__gnu_cxx::new_allocator<char>> = @{
8368 <No data fields>@}, <No data fields>
8370 members of std::basic_string<char, std::char_traits<char>,
8371 std::allocator<char> >::_Alloc_hider:
8372 _M_p = 0x804a014 "abcd"
8377 With a pretty-printer for @code{std::string} only the contents are printed:
8380 (@value{GDBP}) print s
8384 @node Pretty-Printer Commands
8385 @subsection Pretty-Printer Commands
8386 @cindex pretty-printer commands
8389 @kindex info pretty-printer
8390 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8391 Print the list of installed pretty-printers.
8392 This includes disabled pretty-printers, which are marked as such.
8394 @var{object-regexp} is a regular expression matching the objects
8395 whose pretty-printers to list.
8396 Objects can be @code{global}, the program space's file
8397 (@pxref{Progspaces In Python}),
8398 and the object files within that program space (@pxref{Objfiles In Python}).
8399 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
8400 looks up a printer from these three objects.
8402 @var{name-regexp} is a regular expression matching the name of the printers
8405 @kindex disable pretty-printer
8406 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8407 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8408 A disabled pretty-printer is not forgotten, it may be enabled again later.
8410 @kindex enable pretty-printer
8411 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8412 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8417 Suppose we have three pretty-printers installed: one from library1.so
8418 named @code{foo} that prints objects of type @code{foo}, and
8419 another from library2.so named @code{bar} that prints two types of objects,
8420 @code{bar1} and @code{bar2}.
8423 (gdb) info pretty-printer
8430 (gdb) info pretty-printer library2
8435 (gdb) disable pretty-printer library1
8437 2 of 3 printers enabled
8438 (gdb) info pretty-printer
8445 (gdb) disable pretty-printer library2 bar:bar1
8447 1 of 3 printers enabled
8448 (gdb) info pretty-printer library2
8455 (gdb) disable pretty-printer library2 bar
8457 0 of 3 printers enabled
8458 (gdb) info pretty-printer library2
8467 Note that for @code{bar} the entire printer can be disabled,
8468 as can each individual subprinter.
8471 @section Value History
8473 @cindex value history
8474 @cindex history of values printed by @value{GDBN}
8475 Values printed by the @code{print} command are saved in the @value{GDBN}
8476 @dfn{value history}. This allows you to refer to them in other expressions.
8477 Values are kept until the symbol table is re-read or discarded
8478 (for example with the @code{file} or @code{symbol-file} commands).
8479 When the symbol table changes, the value history is discarded,
8480 since the values may contain pointers back to the types defined in the
8485 @cindex history number
8486 The values printed are given @dfn{history numbers} by which you can
8487 refer to them. These are successive integers starting with one.
8488 @code{print} shows you the history number assigned to a value by
8489 printing @samp{$@var{num} = } before the value; here @var{num} is the
8492 To refer to any previous value, use @samp{$} followed by the value's
8493 history number. The way @code{print} labels its output is designed to
8494 remind you of this. Just @code{$} refers to the most recent value in
8495 the history, and @code{$$} refers to the value before that.
8496 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
8497 is the value just prior to @code{$$}, @code{$$1} is equivalent to
8498 @code{$$}, and @code{$$0} is equivalent to @code{$}.
8500 For example, suppose you have just printed a pointer to a structure and
8501 want to see the contents of the structure. It suffices to type
8507 If you have a chain of structures where the component @code{next} points
8508 to the next one, you can print the contents of the next one with this:
8515 You can print successive links in the chain by repeating this
8516 command---which you can do by just typing @key{RET}.
8518 Note that the history records values, not expressions. If the value of
8519 @code{x} is 4 and you type these commands:
8527 then the value recorded in the value history by the @code{print} command
8528 remains 4 even though the value of @code{x} has changed.
8533 Print the last ten values in the value history, with their item numbers.
8534 This is like @samp{p@ $$9} repeated ten times, except that @code{show
8535 values} does not change the history.
8537 @item show values @var{n}
8538 Print ten history values centered on history item number @var{n}.
8541 Print ten history values just after the values last printed. If no more
8542 values are available, @code{show values +} produces no display.
8545 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
8546 same effect as @samp{show values +}.
8548 @node Convenience Vars
8549 @section Convenience Variables
8551 @cindex convenience variables
8552 @cindex user-defined variables
8553 @value{GDBN} provides @dfn{convenience variables} that you can use within
8554 @value{GDBN} to hold on to a value and refer to it later. These variables
8555 exist entirely within @value{GDBN}; they are not part of your program, and
8556 setting a convenience variable has no direct effect on further execution
8557 of your program. That is why you can use them freely.
8559 Convenience variables are prefixed with @samp{$}. Any name preceded by
8560 @samp{$} can be used for a convenience variable, unless it is one of
8561 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
8562 (Value history references, in contrast, are @emph{numbers} preceded
8563 by @samp{$}. @xref{Value History, ,Value History}.)
8565 You can save a value in a convenience variable with an assignment
8566 expression, just as you would set a variable in your program.
8570 set $foo = *object_ptr
8574 would save in @code{$foo} the value contained in the object pointed to by
8577 Using a convenience variable for the first time creates it, but its
8578 value is @code{void} until you assign a new value. You can alter the
8579 value with another assignment at any time.
8581 Convenience variables have no fixed types. You can assign a convenience
8582 variable any type of value, including structures and arrays, even if
8583 that variable already has a value of a different type. The convenience
8584 variable, when used as an expression, has the type of its current value.
8587 @kindex show convenience
8588 @cindex show all user variables
8589 @item show convenience
8590 Print a list of convenience variables used so far, and their values.
8591 Abbreviated @code{show conv}.
8593 @kindex init-if-undefined
8594 @cindex convenience variables, initializing
8595 @item init-if-undefined $@var{variable} = @var{expression}
8596 Set a convenience variable if it has not already been set. This is useful
8597 for user-defined commands that keep some state. It is similar, in concept,
8598 to using local static variables with initializers in C (except that
8599 convenience variables are global). It can also be used to allow users to
8600 override default values used in a command script.
8602 If the variable is already defined then the expression is not evaluated so
8603 any side-effects do not occur.
8606 One of the ways to use a convenience variable is as a counter to be
8607 incremented or a pointer to be advanced. For example, to print
8608 a field from successive elements of an array of structures:
8612 print bar[$i++]->contents
8616 Repeat that command by typing @key{RET}.
8618 Some convenience variables are created automatically by @value{GDBN} and given
8619 values likely to be useful.
8622 @vindex $_@r{, convenience variable}
8624 The variable @code{$_} is automatically set by the @code{x} command to
8625 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8626 commands which provide a default address for @code{x} to examine also
8627 set @code{$_} to that address; these commands include @code{info line}
8628 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8629 except when set by the @code{x} command, in which case it is a pointer
8630 to the type of @code{$__}.
8632 @vindex $__@r{, convenience variable}
8634 The variable @code{$__} is automatically set by the @code{x} command
8635 to the value found in the last address examined. Its type is chosen
8636 to match the format in which the data was printed.
8639 @vindex $_exitcode@r{, convenience variable}
8640 The variable @code{$_exitcode} is automatically set to the exit code when
8641 the program being debugged terminates.
8644 @vindex $_sdata@r{, inspect, convenience variable}
8645 The variable @code{$_sdata} contains extra collected static tracepoint
8646 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
8647 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
8648 if extra static tracepoint data has not been collected.
8651 @vindex $_siginfo@r{, convenience variable}
8652 The variable @code{$_siginfo} contains extra signal information
8653 (@pxref{extra signal information}). Note that @code{$_siginfo}
8654 could be empty, if the application has not yet received any signals.
8655 For example, it will be empty before you execute the @code{run} command.
8658 @vindex $_tlb@r{, convenience variable}
8659 The variable @code{$_tlb} is automatically set when debugging
8660 applications running on MS-Windows in native mode or connected to
8661 gdbserver that supports the @code{qGetTIBAddr} request.
8662 @xref{General Query Packets}.
8663 This variable contains the address of the thread information block.
8667 On HP-UX systems, if you refer to a function or variable name that
8668 begins with a dollar sign, @value{GDBN} searches for a user or system
8669 name first, before it searches for a convenience variable.
8671 @cindex convenience functions
8672 @value{GDBN} also supplies some @dfn{convenience functions}. These
8673 have a syntax similar to convenience variables. A convenience
8674 function can be used in an expression just like an ordinary function;
8675 however, a convenience function is implemented internally to
8680 @kindex help function
8681 @cindex show all convenience functions
8682 Print a list of all convenience functions.
8689 You can refer to machine register contents, in expressions, as variables
8690 with names starting with @samp{$}. The names of registers are different
8691 for each machine; use @code{info registers} to see the names used on
8695 @kindex info registers
8696 @item info registers
8697 Print the names and values of all registers except floating-point
8698 and vector registers (in the selected stack frame).
8700 @kindex info all-registers
8701 @cindex floating point registers
8702 @item info all-registers
8703 Print the names and values of all registers, including floating-point
8704 and vector registers (in the selected stack frame).
8706 @item info registers @var{regname} @dots{}
8707 Print the @dfn{relativized} value of each specified register @var{regname}.
8708 As discussed in detail below, register values are normally relative to
8709 the selected stack frame. @var{regname} may be any register name valid on
8710 the machine you are using, with or without the initial @samp{$}.
8713 @cindex stack pointer register
8714 @cindex program counter register
8715 @cindex process status register
8716 @cindex frame pointer register
8717 @cindex standard registers
8718 @value{GDBN} has four ``standard'' register names that are available (in
8719 expressions) on most machines---whenever they do not conflict with an
8720 architecture's canonical mnemonics for registers. The register names
8721 @code{$pc} and @code{$sp} are used for the program counter register and
8722 the stack pointer. @code{$fp} is used for a register that contains a
8723 pointer to the current stack frame, and @code{$ps} is used for a
8724 register that contains the processor status. For example,
8725 you could print the program counter in hex with
8732 or print the instruction to be executed next with
8739 or add four to the stack pointer@footnote{This is a way of removing
8740 one word from the stack, on machines where stacks grow downward in
8741 memory (most machines, nowadays). This assumes that the innermost
8742 stack frame is selected; setting @code{$sp} is not allowed when other
8743 stack frames are selected. To pop entire frames off the stack,
8744 regardless of machine architecture, use @code{return};
8745 see @ref{Returning, ,Returning from a Function}.} with
8751 Whenever possible, these four standard register names are available on
8752 your machine even though the machine has different canonical mnemonics,
8753 so long as there is no conflict. The @code{info registers} command
8754 shows the canonical names. For example, on the SPARC, @code{info
8755 registers} displays the processor status register as @code{$psr} but you
8756 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
8757 is an alias for the @sc{eflags} register.
8759 @value{GDBN} always considers the contents of an ordinary register as an
8760 integer when the register is examined in this way. Some machines have
8761 special registers which can hold nothing but floating point; these
8762 registers are considered to have floating point values. There is no way
8763 to refer to the contents of an ordinary register as floating point value
8764 (although you can @emph{print} it as a floating point value with
8765 @samp{print/f $@var{regname}}).
8767 Some registers have distinct ``raw'' and ``virtual'' data formats. This
8768 means that the data format in which the register contents are saved by
8769 the operating system is not the same one that your program normally
8770 sees. For example, the registers of the 68881 floating point
8771 coprocessor are always saved in ``extended'' (raw) format, but all C
8772 programs expect to work with ``double'' (virtual) format. In such
8773 cases, @value{GDBN} normally works with the virtual format only (the format
8774 that makes sense for your program), but the @code{info registers} command
8775 prints the data in both formats.
8777 @cindex SSE registers (x86)
8778 @cindex MMX registers (x86)
8779 Some machines have special registers whose contents can be interpreted
8780 in several different ways. For example, modern x86-based machines
8781 have SSE and MMX registers that can hold several values packed
8782 together in several different formats. @value{GDBN} refers to such
8783 registers in @code{struct} notation:
8786 (@value{GDBP}) print $xmm1
8788 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
8789 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
8790 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
8791 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
8792 v4_int32 = @{0, 20657912, 11, 13@},
8793 v2_int64 = @{88725056443645952, 55834574859@},
8794 uint128 = 0x0000000d0000000b013b36f800000000
8799 To set values of such registers, you need to tell @value{GDBN} which
8800 view of the register you wish to change, as if you were assigning
8801 value to a @code{struct} member:
8804 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
8807 Normally, register values are relative to the selected stack frame
8808 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
8809 value that the register would contain if all stack frames farther in
8810 were exited and their saved registers restored. In order to see the
8811 true contents of hardware registers, you must select the innermost
8812 frame (with @samp{frame 0}).
8814 However, @value{GDBN} must deduce where registers are saved, from the machine
8815 code generated by your compiler. If some registers are not saved, or if
8816 @value{GDBN} is unable to locate the saved registers, the selected stack
8817 frame makes no difference.
8819 @node Floating Point Hardware
8820 @section Floating Point Hardware
8821 @cindex floating point
8823 Depending on the configuration, @value{GDBN} may be able to give
8824 you more information about the status of the floating point hardware.
8829 Display hardware-dependent information about the floating
8830 point unit. The exact contents and layout vary depending on the
8831 floating point chip. Currently, @samp{info float} is supported on
8832 the ARM and x86 machines.
8836 @section Vector Unit
8839 Depending on the configuration, @value{GDBN} may be able to give you
8840 more information about the status of the vector unit.
8845 Display information about the vector unit. The exact contents and
8846 layout vary depending on the hardware.
8849 @node OS Information
8850 @section Operating System Auxiliary Information
8851 @cindex OS information
8853 @value{GDBN} provides interfaces to useful OS facilities that can help
8854 you debug your program.
8856 @cindex @code{ptrace} system call
8857 @cindex @code{struct user} contents
8858 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
8859 machines), it interfaces with the inferior via the @code{ptrace}
8860 system call. The operating system creates a special sata structure,
8861 called @code{struct user}, for this interface. You can use the
8862 command @code{info udot} to display the contents of this data
8868 Display the contents of the @code{struct user} maintained by the OS
8869 kernel for the program being debugged. @value{GDBN} displays the
8870 contents of @code{struct user} as a list of hex numbers, similar to
8871 the @code{examine} command.
8874 @cindex auxiliary vector
8875 @cindex vector, auxiliary
8876 Some operating systems supply an @dfn{auxiliary vector} to programs at
8877 startup. This is akin to the arguments and environment that you
8878 specify for a program, but contains a system-dependent variety of
8879 binary values that tell system libraries important details about the
8880 hardware, operating system, and process. Each value's purpose is
8881 identified by an integer tag; the meanings are well-known but system-specific.
8882 Depending on the configuration and operating system facilities,
8883 @value{GDBN} may be able to show you this information. For remote
8884 targets, this functionality may further depend on the remote stub's
8885 support of the @samp{qXfer:auxv:read} packet, see
8886 @ref{qXfer auxiliary vector read}.
8891 Display the auxiliary vector of the inferior, which can be either a
8892 live process or a core dump file. @value{GDBN} prints each tag value
8893 numerically, and also shows names and text descriptions for recognized
8894 tags. Some values in the vector are numbers, some bit masks, and some
8895 pointers to strings or other data. @value{GDBN} displays each value in the
8896 most appropriate form for a recognized tag, and in hexadecimal for
8897 an unrecognized tag.
8900 On some targets, @value{GDBN} can access operating-system-specific information
8901 and display it to user, without interpretation. For remote targets,
8902 this functionality depends on the remote stub's support of the
8903 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
8908 List the types of OS information available for the target. If the
8909 target does not return a list of possible types, this command will
8912 @kindex info os processes
8913 @item info os processes
8914 Display the list of processes on the target. For each process,
8915 @value{GDBN} prints the process identifier, the name of the user, and
8916 the command corresponding to the process.
8919 @node Memory Region Attributes
8920 @section Memory Region Attributes
8921 @cindex memory region attributes
8923 @dfn{Memory region attributes} allow you to describe special handling
8924 required by regions of your target's memory. @value{GDBN} uses
8925 attributes to determine whether to allow certain types of memory
8926 accesses; whether to use specific width accesses; and whether to cache
8927 target memory. By default the description of memory regions is
8928 fetched from the target (if the current target supports this), but the
8929 user can override the fetched regions.
8931 Defined memory regions can be individually enabled and disabled. When a
8932 memory region is disabled, @value{GDBN} uses the default attributes when
8933 accessing memory in that region. Similarly, if no memory regions have
8934 been defined, @value{GDBN} uses the default attributes when accessing
8937 When a memory region is defined, it is given a number to identify it;
8938 to enable, disable, or remove a memory region, you specify that number.
8942 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
8943 Define a memory region bounded by @var{lower} and @var{upper} with
8944 attributes @var{attributes}@dots{}, and add it to the list of regions
8945 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
8946 case: it is treated as the target's maximum memory address.
8947 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
8950 Discard any user changes to the memory regions and use target-supplied
8951 regions, if available, or no regions if the target does not support.
8954 @item delete mem @var{nums}@dots{}
8955 Remove memory regions @var{nums}@dots{} from the list of regions
8956 monitored by @value{GDBN}.
8959 @item disable mem @var{nums}@dots{}
8960 Disable monitoring of memory regions @var{nums}@dots{}.
8961 A disabled memory region is not forgotten.
8962 It may be enabled again later.
8965 @item enable mem @var{nums}@dots{}
8966 Enable monitoring of memory regions @var{nums}@dots{}.
8970 Print a table of all defined memory regions, with the following columns
8974 @item Memory Region Number
8975 @item Enabled or Disabled.
8976 Enabled memory regions are marked with @samp{y}.
8977 Disabled memory regions are marked with @samp{n}.
8980 The address defining the inclusive lower bound of the memory region.
8983 The address defining the exclusive upper bound of the memory region.
8986 The list of attributes set for this memory region.
8991 @subsection Attributes
8993 @subsubsection Memory Access Mode
8994 The access mode attributes set whether @value{GDBN} may make read or
8995 write accesses to a memory region.
8997 While these attributes prevent @value{GDBN} from performing invalid
8998 memory accesses, they do nothing to prevent the target system, I/O DMA,
8999 etc.@: from accessing memory.
9003 Memory is read only.
9005 Memory is write only.
9007 Memory is read/write. This is the default.
9010 @subsubsection Memory Access Size
9011 The access size attribute tells @value{GDBN} to use specific sized
9012 accesses in the memory region. Often memory mapped device registers
9013 require specific sized accesses. If no access size attribute is
9014 specified, @value{GDBN} may use accesses of any size.
9018 Use 8 bit memory accesses.
9020 Use 16 bit memory accesses.
9022 Use 32 bit memory accesses.
9024 Use 64 bit memory accesses.
9027 @c @subsubsection Hardware/Software Breakpoints
9028 @c The hardware/software breakpoint attributes set whether @value{GDBN}
9029 @c will use hardware or software breakpoints for the internal breakpoints
9030 @c used by the step, next, finish, until, etc. commands.
9034 @c Always use hardware breakpoints
9035 @c @item swbreak (default)
9038 @subsubsection Data Cache
9039 The data cache attributes set whether @value{GDBN} will cache target
9040 memory. While this generally improves performance by reducing debug
9041 protocol overhead, it can lead to incorrect results because @value{GDBN}
9042 does not know about volatile variables or memory mapped device
9047 Enable @value{GDBN} to cache target memory.
9049 Disable @value{GDBN} from caching target memory. This is the default.
9052 @subsection Memory Access Checking
9053 @value{GDBN} can be instructed to refuse accesses to memory that is
9054 not explicitly described. This can be useful if accessing such
9055 regions has undesired effects for a specific target, or to provide
9056 better error checking. The following commands control this behaviour.
9059 @kindex set mem inaccessible-by-default
9060 @item set mem inaccessible-by-default [on|off]
9061 If @code{on} is specified, make @value{GDBN} treat memory not
9062 explicitly described by the memory ranges as non-existent and refuse accesses
9063 to such memory. The checks are only performed if there's at least one
9064 memory range defined. If @code{off} is specified, make @value{GDBN}
9065 treat the memory not explicitly described by the memory ranges as RAM.
9066 The default value is @code{on}.
9067 @kindex show mem inaccessible-by-default
9068 @item show mem inaccessible-by-default
9069 Show the current handling of accesses to unknown memory.
9073 @c @subsubsection Memory Write Verification
9074 @c The memory write verification attributes set whether @value{GDBN}
9075 @c will re-reads data after each write to verify the write was successful.
9079 @c @item noverify (default)
9082 @node Dump/Restore Files
9083 @section Copy Between Memory and a File
9084 @cindex dump/restore files
9085 @cindex append data to a file
9086 @cindex dump data to a file
9087 @cindex restore data from a file
9089 You can use the commands @code{dump}, @code{append}, and
9090 @code{restore} to copy data between target memory and a file. The
9091 @code{dump} and @code{append} commands write data to a file, and the
9092 @code{restore} command reads data from a file back into the inferior's
9093 memory. Files may be in binary, Motorola S-record, Intel hex, or
9094 Tektronix Hex format; however, @value{GDBN} can only append to binary
9100 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9101 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
9102 Dump the contents of memory from @var{start_addr} to @var{end_addr},
9103 or the value of @var{expr}, to @var{filename} in the given format.
9105 The @var{format} parameter may be any one of:
9112 Motorola S-record format.
9114 Tektronix Hex format.
9117 @value{GDBN} uses the same definitions of these formats as the
9118 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
9119 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
9123 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9124 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
9125 Append the contents of memory from @var{start_addr} to @var{end_addr},
9126 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
9127 (@value{GDBN} can only append data to files in raw binary form.)
9130 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
9131 Restore the contents of file @var{filename} into memory. The
9132 @code{restore} command can automatically recognize any known @sc{bfd}
9133 file format, except for raw binary. To restore a raw binary file you
9134 must specify the optional keyword @code{binary} after the filename.
9136 If @var{bias} is non-zero, its value will be added to the addresses
9137 contained in the file. Binary files always start at address zero, so
9138 they will be restored at address @var{bias}. Other bfd files have
9139 a built-in location; they will be restored at offset @var{bias}
9142 If @var{start} and/or @var{end} are non-zero, then only data between
9143 file offset @var{start} and file offset @var{end} will be restored.
9144 These offsets are relative to the addresses in the file, before
9145 the @var{bias} argument is applied.
9149 @node Core File Generation
9150 @section How to Produce a Core File from Your Program
9151 @cindex dump core from inferior
9153 A @dfn{core file} or @dfn{core dump} is a file that records the memory
9154 image of a running process and its process status (register values
9155 etc.). Its primary use is post-mortem debugging of a program that
9156 crashed while it ran outside a debugger. A program that crashes
9157 automatically produces a core file, unless this feature is disabled by
9158 the user. @xref{Files}, for information on invoking @value{GDBN} in
9159 the post-mortem debugging mode.
9161 Occasionally, you may wish to produce a core file of the program you
9162 are debugging in order to preserve a snapshot of its state.
9163 @value{GDBN} has a special command for that.
9167 @kindex generate-core-file
9168 @item generate-core-file [@var{file}]
9169 @itemx gcore [@var{file}]
9170 Produce a core dump of the inferior process. The optional argument
9171 @var{file} specifies the file name where to put the core dump. If not
9172 specified, the file name defaults to @file{core.@var{pid}}, where
9173 @var{pid} is the inferior process ID.
9175 Note that this command is implemented only for some systems (as of
9176 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
9179 @node Character Sets
9180 @section Character Sets
9181 @cindex character sets
9183 @cindex translating between character sets
9184 @cindex host character set
9185 @cindex target character set
9187 If the program you are debugging uses a different character set to
9188 represent characters and strings than the one @value{GDBN} uses itself,
9189 @value{GDBN} can automatically translate between the character sets for
9190 you. The character set @value{GDBN} uses we call the @dfn{host
9191 character set}; the one the inferior program uses we call the
9192 @dfn{target character set}.
9194 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
9195 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
9196 remote protocol (@pxref{Remote Debugging}) to debug a program
9197 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
9198 then the host character set is Latin-1, and the target character set is
9199 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
9200 target-charset EBCDIC-US}, then @value{GDBN} translates between
9201 @sc{ebcdic} and Latin 1 as you print character or string values, or use
9202 character and string literals in expressions.
9204 @value{GDBN} has no way to automatically recognize which character set
9205 the inferior program uses; you must tell it, using the @code{set
9206 target-charset} command, described below.
9208 Here are the commands for controlling @value{GDBN}'s character set
9212 @item set target-charset @var{charset}
9213 @kindex set target-charset
9214 Set the current target character set to @var{charset}. To display the
9215 list of supported target character sets, type
9216 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
9218 @item set host-charset @var{charset}
9219 @kindex set host-charset
9220 Set the current host character set to @var{charset}.
9222 By default, @value{GDBN} uses a host character set appropriate to the
9223 system it is running on; you can override that default using the
9224 @code{set host-charset} command. On some systems, @value{GDBN} cannot
9225 automatically determine the appropriate host character set. In this
9226 case, @value{GDBN} uses @samp{UTF-8}.
9228 @value{GDBN} can only use certain character sets as its host character
9229 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
9230 @value{GDBN} will list the host character sets it supports.
9232 @item set charset @var{charset}
9234 Set the current host and target character sets to @var{charset}. As
9235 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
9236 @value{GDBN} will list the names of the character sets that can be used
9237 for both host and target.
9240 @kindex show charset
9241 Show the names of the current host and target character sets.
9243 @item show host-charset
9244 @kindex show host-charset
9245 Show the name of the current host character set.
9247 @item show target-charset
9248 @kindex show target-charset
9249 Show the name of the current target character set.
9251 @item set target-wide-charset @var{charset}
9252 @kindex set target-wide-charset
9253 Set the current target's wide character set to @var{charset}. This is
9254 the character set used by the target's @code{wchar_t} type. To
9255 display the list of supported wide character sets, type
9256 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
9258 @item show target-wide-charset
9259 @kindex show target-wide-charset
9260 Show the name of the current target's wide character set.
9263 Here is an example of @value{GDBN}'s character set support in action.
9264 Assume that the following source code has been placed in the file
9265 @file{charset-test.c}:
9271 = @{72, 101, 108, 108, 111, 44, 32, 119,
9272 111, 114, 108, 100, 33, 10, 0@};
9273 char ibm1047_hello[]
9274 = @{200, 133, 147, 147, 150, 107, 64, 166,
9275 150, 153, 147, 132, 90, 37, 0@};
9279 printf ("Hello, world!\n");
9283 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
9284 containing the string @samp{Hello, world!} followed by a newline,
9285 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
9287 We compile the program, and invoke the debugger on it:
9290 $ gcc -g charset-test.c -o charset-test
9291 $ gdb -nw charset-test
9292 GNU gdb 2001-12-19-cvs
9293 Copyright 2001 Free Software Foundation, Inc.
9298 We can use the @code{show charset} command to see what character sets
9299 @value{GDBN} is currently using to interpret and display characters and
9303 (@value{GDBP}) show charset
9304 The current host and target character set is `ISO-8859-1'.
9308 For the sake of printing this manual, let's use @sc{ascii} as our
9309 initial character set:
9311 (@value{GDBP}) set charset ASCII
9312 (@value{GDBP}) show charset
9313 The current host and target character set is `ASCII'.
9317 Let's assume that @sc{ascii} is indeed the correct character set for our
9318 host system --- in other words, let's assume that if @value{GDBN} prints
9319 characters using the @sc{ascii} character set, our terminal will display
9320 them properly. Since our current target character set is also
9321 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
9324 (@value{GDBP}) print ascii_hello
9325 $1 = 0x401698 "Hello, world!\n"
9326 (@value{GDBP}) print ascii_hello[0]
9331 @value{GDBN} uses the target character set for character and string
9332 literals you use in expressions:
9335 (@value{GDBP}) print '+'
9340 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
9343 @value{GDBN} relies on the user to tell it which character set the
9344 target program uses. If we print @code{ibm1047_hello} while our target
9345 character set is still @sc{ascii}, we get jibberish:
9348 (@value{GDBP}) print ibm1047_hello
9349 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
9350 (@value{GDBP}) print ibm1047_hello[0]
9355 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
9356 @value{GDBN} tells us the character sets it supports:
9359 (@value{GDBP}) set target-charset
9360 ASCII EBCDIC-US IBM1047 ISO-8859-1
9361 (@value{GDBP}) set target-charset
9364 We can select @sc{ibm1047} as our target character set, and examine the
9365 program's strings again. Now the @sc{ascii} string is wrong, but
9366 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
9367 target character set, @sc{ibm1047}, to the host character set,
9368 @sc{ascii}, and they display correctly:
9371 (@value{GDBP}) set target-charset IBM1047
9372 (@value{GDBP}) show charset
9373 The current host character set is `ASCII'.
9374 The current target character set is `IBM1047'.
9375 (@value{GDBP}) print ascii_hello
9376 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
9377 (@value{GDBP}) print ascii_hello[0]
9379 (@value{GDBP}) print ibm1047_hello
9380 $8 = 0x4016a8 "Hello, world!\n"
9381 (@value{GDBP}) print ibm1047_hello[0]
9386 As above, @value{GDBN} uses the target character set for character and
9387 string literals you use in expressions:
9390 (@value{GDBP}) print '+'
9395 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
9398 @node Caching Remote Data
9399 @section Caching Data of Remote Targets
9400 @cindex caching data of remote targets
9402 @value{GDBN} caches data exchanged between the debugger and a
9403 remote target (@pxref{Remote Debugging}). Such caching generally improves
9404 performance, because it reduces the overhead of the remote protocol by
9405 bundling memory reads and writes into large chunks. Unfortunately, simply
9406 caching everything would lead to incorrect results, since @value{GDBN}
9407 does not necessarily know anything about volatile values, memory-mapped I/O
9408 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
9409 memory can be changed @emph{while} a gdb command is executing.
9410 Therefore, by default, @value{GDBN} only caches data
9411 known to be on the stack@footnote{In non-stop mode, it is moderately
9412 rare for a running thread to modify the stack of a stopped thread
9413 in a way that would interfere with a backtrace, and caching of
9414 stack reads provides a significant speed up of remote backtraces.}.
9415 Other regions of memory can be explicitly marked as
9416 cacheable; see @pxref{Memory Region Attributes}.
9419 @kindex set remotecache
9420 @item set remotecache on
9421 @itemx set remotecache off
9422 This option no longer does anything; it exists for compatibility
9425 @kindex show remotecache
9426 @item show remotecache
9427 Show the current state of the obsolete remotecache flag.
9429 @kindex set stack-cache
9430 @item set stack-cache on
9431 @itemx set stack-cache off
9432 Enable or disable caching of stack accesses. When @code{ON}, use
9433 caching. By default, this option is @code{ON}.
9435 @kindex show stack-cache
9436 @item show stack-cache
9437 Show the current state of data caching for memory accesses.
9440 @item info dcache @r{[}line@r{]}
9441 Print the information about the data cache performance. The
9442 information displayed includes the dcache width and depth, and for
9443 each cache line, its number, address, and how many times it was
9444 referenced. This command is useful for debugging the data cache
9447 If a line number is specified, the contents of that line will be
9450 @item set dcache size @var{size}
9452 @kindex set dcache size
9453 Set maximum number of entries in dcache (dcache depth above).
9455 @item set dcache line-size @var{line-size}
9456 @cindex dcache line-size
9457 @kindex set dcache line-size
9458 Set number of bytes each dcache entry caches (dcache width above).
9459 Must be a power of 2.
9461 @item show dcache size
9462 @kindex show dcache size
9463 Show maximum number of dcache entries. See also @ref{Caching Remote Data, info dcache}.
9465 @item show dcache line-size
9466 @kindex show dcache line-size
9467 Show default size of dcache lines. See also @ref{Caching Remote Data, info dcache}.
9471 @node Searching Memory
9472 @section Search Memory
9473 @cindex searching memory
9475 Memory can be searched for a particular sequence of bytes with the
9476 @code{find} command.
9480 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9481 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9482 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
9483 etc. The search begins at address @var{start_addr} and continues for either
9484 @var{len} bytes or through to @var{end_addr} inclusive.
9487 @var{s} and @var{n} are optional parameters.
9488 They may be specified in either order, apart or together.
9491 @item @var{s}, search query size
9492 The size of each search query value.
9498 halfwords (two bytes)
9502 giant words (eight bytes)
9505 All values are interpreted in the current language.
9506 This means, for example, that if the current source language is C/C@t{++}
9507 then searching for the string ``hello'' includes the trailing '\0'.
9509 If the value size is not specified, it is taken from the
9510 value's type in the current language.
9511 This is useful when one wants to specify the search
9512 pattern as a mixture of types.
9513 Note that this means, for example, that in the case of C-like languages
9514 a search for an untyped 0x42 will search for @samp{(int) 0x42}
9515 which is typically four bytes.
9517 @item @var{n}, maximum number of finds
9518 The maximum number of matches to print. The default is to print all finds.
9521 You can use strings as search values. Quote them with double-quotes
9523 The string value is copied into the search pattern byte by byte,
9524 regardless of the endianness of the target and the size specification.
9526 The address of each match found is printed as well as a count of the
9527 number of matches found.
9529 The address of the last value found is stored in convenience variable
9531 A count of the number of matches is stored in @samp{$numfound}.
9533 For example, if stopped at the @code{printf} in this function:
9539 static char hello[] = "hello-hello";
9540 static struct @{ char c; short s; int i; @}
9541 __attribute__ ((packed)) mixed
9542 = @{ 'c', 0x1234, 0x87654321 @};
9543 printf ("%s\n", hello);
9548 you get during debugging:
9551 (gdb) find &hello[0], +sizeof(hello), "hello"
9552 0x804956d <hello.1620+6>
9554 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
9555 0x8049567 <hello.1620>
9556 0x804956d <hello.1620+6>
9558 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
9559 0x8049567 <hello.1620>
9561 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
9562 0x8049560 <mixed.1625>
9564 (gdb) print $numfound
9567 $2 = (void *) 0x8049560
9570 @node Optimized Code
9571 @chapter Debugging Optimized Code
9572 @cindex optimized code, debugging
9573 @cindex debugging optimized code
9575 Almost all compilers support optimization. With optimization
9576 disabled, the compiler generates assembly code that corresponds
9577 directly to your source code, in a simplistic way. As the compiler
9578 applies more powerful optimizations, the generated assembly code
9579 diverges from your original source code. With help from debugging
9580 information generated by the compiler, @value{GDBN} can map from
9581 the running program back to constructs from your original source.
9583 @value{GDBN} is more accurate with optimization disabled. If you
9584 can recompile without optimization, it is easier to follow the
9585 progress of your program during debugging. But, there are many cases
9586 where you may need to debug an optimized version.
9588 When you debug a program compiled with @samp{-g -O}, remember that the
9589 optimizer has rearranged your code; the debugger shows you what is
9590 really there. Do not be too surprised when the execution path does not
9591 exactly match your source file! An extreme example: if you define a
9592 variable, but never use it, @value{GDBN} never sees that
9593 variable---because the compiler optimizes it out of existence.
9595 Some things do not work as well with @samp{-g -O} as with just
9596 @samp{-g}, particularly on machines with instruction scheduling. If in
9597 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
9598 please report it to us as a bug (including a test case!).
9599 @xref{Variables}, for more information about debugging optimized code.
9602 * Inline Functions:: How @value{GDBN} presents inlining
9603 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
9606 @node Inline Functions
9607 @section Inline Functions
9608 @cindex inline functions, debugging
9610 @dfn{Inlining} is an optimization that inserts a copy of the function
9611 body directly at each call site, instead of jumping to a shared
9612 routine. @value{GDBN} displays inlined functions just like
9613 non-inlined functions. They appear in backtraces. You can view their
9614 arguments and local variables, step into them with @code{step}, skip
9615 them with @code{next}, and escape from them with @code{finish}.
9616 You can check whether a function was inlined by using the
9617 @code{info frame} command.
9619 For @value{GDBN} to support inlined functions, the compiler must
9620 record information about inlining in the debug information ---
9621 @value{NGCC} using the @sc{dwarf 2} format does this, and several
9622 other compilers do also. @value{GDBN} only supports inlined functions
9623 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
9624 do not emit two required attributes (@samp{DW_AT_call_file} and
9625 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
9626 function calls with earlier versions of @value{NGCC}. It instead
9627 displays the arguments and local variables of inlined functions as
9628 local variables in the caller.
9630 The body of an inlined function is directly included at its call site;
9631 unlike a non-inlined function, there are no instructions devoted to
9632 the call. @value{GDBN} still pretends that the call site and the
9633 start of the inlined function are different instructions. Stepping to
9634 the call site shows the call site, and then stepping again shows
9635 the first line of the inlined function, even though no additional
9636 instructions are executed.
9638 This makes source-level debugging much clearer; you can see both the
9639 context of the call and then the effect of the call. Only stepping by
9640 a single instruction using @code{stepi} or @code{nexti} does not do
9641 this; single instruction steps always show the inlined body.
9643 There are some ways that @value{GDBN} does not pretend that inlined
9644 function calls are the same as normal calls:
9648 You cannot set breakpoints on inlined functions. @value{GDBN}
9649 either reports that there is no symbol with that name, or else sets the
9650 breakpoint only on non-inlined copies of the function. This limitation
9651 will be removed in a future version of @value{GDBN}; until then,
9652 set a breakpoint by line number on the first line of the inlined
9656 Setting breakpoints at the call site of an inlined function may not
9657 work, because the call site does not contain any code. @value{GDBN}
9658 may incorrectly move the breakpoint to the next line of the enclosing
9659 function, after the call. This limitation will be removed in a future
9660 version of @value{GDBN}; until then, set a breakpoint on an earlier line
9661 or inside the inlined function instead.
9664 @value{GDBN} cannot locate the return value of inlined calls after
9665 using the @code{finish} command. This is a limitation of compiler-generated
9666 debugging information; after @code{finish}, you can step to the next line
9667 and print a variable where your program stored the return value.
9671 @node Tail Call Frames
9672 @section Tail Call Frames
9673 @cindex tail call frames, debugging
9675 Function @code{B} can call function @code{C} in its very last statement. In
9676 unoptimized compilation the call of @code{C} is immediately followed by return
9677 instruction at the end of @code{B} code. Optimizing compiler may replace the
9678 call and return in function @code{B} into one jump to function @code{C}
9679 instead. Such use of a jump instruction is called @dfn{tail call}.
9681 During execution of function @code{C}, there will be no indication in the
9682 function call stack frames that it was tail-called from @code{B}. If function
9683 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
9684 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
9685 some cases @value{GDBN} can determine that @code{C} was tail-called from
9686 @code{B}, and it will then create fictitious call frame for that, with the
9687 return address set up as if @code{B} called @code{C} normally.
9689 This functionality is currently supported only by DWARF 2 debugging format and
9690 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9691 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9694 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
9695 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
9699 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
9701 Stack level 1, frame at 0x7fffffffda30:
9702 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
9703 tail call frame, caller of frame at 0x7fffffffda30
9704 source language c++.
9705 Arglist at unknown address.
9706 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
9709 The detection of all the possible code path executions can find them ambiguous.
9710 There is no execution history stored (possible @ref{Reverse Execution} is never
9711 used for this purpose) and the last known caller could have reached the known
9712 callee by multiple different jump sequences. In such case @value{GDBN} still
9713 tries to show at least all the unambiguous top tail callers and all the
9714 unambiguous bottom tail calees, if any.
9717 @anchor{set debug entry-values}
9718 @item set debug entry-values
9719 @kindex set debug entry-values
9720 When set to on, enables printing of analysis messages for both frame argument
9721 values at function entry and tail calls. It will show all the possible valid
9722 tail calls code paths it has considered. It will also print the intersection
9723 of them with the final unambiguous (possibly partial or even empty) code path
9726 @item show debug entry-values
9727 @kindex show debug entry-values
9728 Show the current state of analysis messages printing for both frame argument
9729 values at function entry and tail calls.
9732 The analysis messages for tail calls can for example show why the virtual tail
9733 call frame for function @code{c} has not been recognized (due to the indirect
9734 reference by variable @code{x}):
9737 static void __attribute__((noinline, noclone)) c (void);
9738 void (*x) (void) = c;
9739 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
9740 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
9741 int main (void) @{ x (); return 0; @}
9743 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
9744 DW_TAG_GNU_call_site 0x40039a in main
9746 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
9749 #1 0x000000000040039a in main () at t.c:5
9752 Another possibility is an ambiguous virtual tail call frames resolution:
9756 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
9757 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
9758 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
9759 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
9760 static void __attribute__((noinline, noclone)) b (void)
9761 @{ if (i) c (); else e (); @}
9762 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
9763 int main (void) @{ a (); return 0; @}
9765 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
9766 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
9767 tailcall: reduced: 0x4004d2(a) |
9770 #1 0x00000000004004d2 in a () at t.c:8
9771 #2 0x0000000000400395 in main () at t.c:9
9774 Frames #0 and #2 are real, #1 is a virtual tail call frame. The code can have
9775 possible execution paths
9776 @code{main@arrow{}a@arrow{}b@arrow{}c@arrow{}d@arrow{}f} or
9777 @code{main@arrow{}a@arrow{}b@arrow{}e@arrow{}f}, @value{GDBN} cannot find which
9778 one from the inferior state.
9780 @code{initial:} state shows some random possible calling sequence @value{GDBN}
9781 has found. It then finds another possible calling sequcen - that one is
9782 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
9783 printed as the @code{reduced:} calling sequence. That one could have many
9784 futher @code{compare:} and @code{reduced:} statements as long as there remain
9785 any non-ambiguous sequence entries.
9787 For the frame of function @code{b} in both cases there are different possible
9788 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
9789 also ambigous. The only non-ambiguous frame is the one for function @code{a},
9790 therefore this one is displayed to the user while the ambiguous frames are
9793 There can be also reasons why printing of frame argument values at function
9798 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
9799 static void __attribute__((noinline, noclone)) a (int i);
9800 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
9801 static void __attribute__((noinline, noclone)) a (int i)
9802 @{ if (i) b (i - 1); else c (0); @}
9803 int main (void) @{ a (5); return 0; @}
9806 #0 c (i=i@@entry=0) at t.c:2
9807 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
9808 function "a" at 0x400420 can call itself via tail calls
9809 i=<optimized out>) at t.c:6
9810 #2 0x000000000040036e in main () at t.c:7
9813 @value{GDBN} cannot find out from the inferior state if and how many times did
9814 function @code{a} call itself (via function @code{b}) as these calls would be
9815 tail calls. Such tail calls would modify thue @code{i} variable, therefore
9816 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
9817 prints @code{<optimized out>} instead.
9820 @chapter C Preprocessor Macros
9822 Some languages, such as C and C@t{++}, provide a way to define and invoke
9823 ``preprocessor macros'' which expand into strings of tokens.
9824 @value{GDBN} can evaluate expressions containing macro invocations, show
9825 the result of macro expansion, and show a macro's definition, including
9826 where it was defined.
9828 You may need to compile your program specially to provide @value{GDBN}
9829 with information about preprocessor macros. Most compilers do not
9830 include macros in their debugging information, even when you compile
9831 with the @option{-g} flag. @xref{Compilation}.
9833 A program may define a macro at one point, remove that definition later,
9834 and then provide a different definition after that. Thus, at different
9835 points in the program, a macro may have different definitions, or have
9836 no definition at all. If there is a current stack frame, @value{GDBN}
9837 uses the macros in scope at that frame's source code line. Otherwise,
9838 @value{GDBN} uses the macros in scope at the current listing location;
9841 Whenever @value{GDBN} evaluates an expression, it always expands any
9842 macro invocations present in the expression. @value{GDBN} also provides
9843 the following commands for working with macros explicitly.
9847 @kindex macro expand
9848 @cindex macro expansion, showing the results of preprocessor
9849 @cindex preprocessor macro expansion, showing the results of
9850 @cindex expanding preprocessor macros
9851 @item macro expand @var{expression}
9852 @itemx macro exp @var{expression}
9853 Show the results of expanding all preprocessor macro invocations in
9854 @var{expression}. Since @value{GDBN} simply expands macros, but does
9855 not parse the result, @var{expression} need not be a valid expression;
9856 it can be any string of tokens.
9859 @item macro expand-once @var{expression}
9860 @itemx macro exp1 @var{expression}
9861 @cindex expand macro once
9862 @i{(This command is not yet implemented.)} Show the results of
9863 expanding those preprocessor macro invocations that appear explicitly in
9864 @var{expression}. Macro invocations appearing in that expansion are
9865 left unchanged. This command allows you to see the effect of a
9866 particular macro more clearly, without being confused by further
9867 expansions. Since @value{GDBN} simply expands macros, but does not
9868 parse the result, @var{expression} need not be a valid expression; it
9869 can be any string of tokens.
9872 @cindex macro definition, showing
9873 @cindex definition of a macro, showing
9874 @cindex macros, from debug info
9875 @item info macro @var{macro}
9876 Show the current definition of the named @var{macro}, and describe the
9877 source location or compiler command-line where that definition was established.
9880 @item info macros @var{linespec}
9881 Show all macro definitions that are in effect at the location specified
9882 by @var{linespec}, and describe the source location or compiler
9883 command-line where those definitions were established.
9885 @kindex info definitions
9886 @item info definitions @var{macro}
9887 Show all definitions of the named @var{macro} that are defined in the current
9888 compilation unit, and describe the source location or compiler command-line
9889 where those definitions were established.
9891 @kindex macro define
9892 @cindex user-defined macros
9893 @cindex defining macros interactively
9894 @cindex macros, user-defined
9895 @item macro define @var{macro} @var{replacement-list}
9896 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
9897 Introduce a definition for a preprocessor macro named @var{macro},
9898 invocations of which are replaced by the tokens given in
9899 @var{replacement-list}. The first form of this command defines an
9900 ``object-like'' macro, which takes no arguments; the second form
9901 defines a ``function-like'' macro, which takes the arguments given in
9904 A definition introduced by this command is in scope in every
9905 expression evaluated in @value{GDBN}, until it is removed with the
9906 @code{macro undef} command, described below. The definition overrides
9907 all definitions for @var{macro} present in the program being debugged,
9908 as well as any previous user-supplied definition.
9911 @item macro undef @var{macro}
9912 Remove any user-supplied definition for the macro named @var{macro}.
9913 This command only affects definitions provided with the @code{macro
9914 define} command, described above; it cannot remove definitions present
9915 in the program being debugged.
9919 List all the macros defined using the @code{macro define} command.
9922 @cindex macros, example of debugging with
9923 Here is a transcript showing the above commands in action. First, we
9924 show our source files:
9932 #define ADD(x) (M + x)
9937 printf ("Hello, world!\n");
9939 printf ("We're so creative.\n");
9941 printf ("Goodbye, world!\n");
9948 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
9949 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
9950 compiler includes information about preprocessor macros in the debugging
9954 $ gcc -gdwarf-2 -g3 sample.c -o sample
9958 Now, we start @value{GDBN} on our sample program:
9962 GNU gdb 2002-05-06-cvs
9963 Copyright 2002 Free Software Foundation, Inc.
9964 GDB is free software, @dots{}
9968 We can expand macros and examine their definitions, even when the
9969 program is not running. @value{GDBN} uses the current listing position
9970 to decide which macro definitions are in scope:
9973 (@value{GDBP}) list main
9976 5 #define ADD(x) (M + x)
9981 10 printf ("Hello, world!\n");
9983 12 printf ("We're so creative.\n");
9984 (@value{GDBP}) info macro ADD
9985 Defined at /home/jimb/gdb/macros/play/sample.c:5
9986 #define ADD(x) (M + x)
9987 (@value{GDBP}) info macro Q
9988 Defined at /home/jimb/gdb/macros/play/sample.h:1
9989 included at /home/jimb/gdb/macros/play/sample.c:2
9991 (@value{GDBP}) macro expand ADD(1)
9992 expands to: (42 + 1)
9993 (@value{GDBP}) macro expand-once ADD(1)
9994 expands to: once (M + 1)
9998 In the example above, note that @code{macro expand-once} expands only
9999 the macro invocation explicit in the original text --- the invocation of
10000 @code{ADD} --- but does not expand the invocation of the macro @code{M},
10001 which was introduced by @code{ADD}.
10003 Once the program is running, @value{GDBN} uses the macro definitions in
10004 force at the source line of the current stack frame:
10007 (@value{GDBP}) break main
10008 Breakpoint 1 at 0x8048370: file sample.c, line 10.
10010 Starting program: /home/jimb/gdb/macros/play/sample
10012 Breakpoint 1, main () at sample.c:10
10013 10 printf ("Hello, world!\n");
10017 At line 10, the definition of the macro @code{N} at line 9 is in force:
10020 (@value{GDBP}) info macro N
10021 Defined at /home/jimb/gdb/macros/play/sample.c:9
10023 (@value{GDBP}) macro expand N Q M
10024 expands to: 28 < 42
10025 (@value{GDBP}) print N Q M
10030 As we step over directives that remove @code{N}'s definition, and then
10031 give it a new definition, @value{GDBN} finds the definition (or lack
10032 thereof) in force at each point:
10035 (@value{GDBP}) next
10037 12 printf ("We're so creative.\n");
10038 (@value{GDBP}) info macro N
10039 The symbol `N' has no definition as a C/C++ preprocessor macro
10040 at /home/jimb/gdb/macros/play/sample.c:12
10041 (@value{GDBP}) next
10043 14 printf ("Goodbye, world!\n");
10044 (@value{GDBP}) info macro N
10045 Defined at /home/jimb/gdb/macros/play/sample.c:13
10047 (@value{GDBP}) macro expand N Q M
10048 expands to: 1729 < 42
10049 (@value{GDBP}) print N Q M
10054 In addition to source files, macros can be defined on the compilation command
10055 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
10056 such a way, @value{GDBN} displays the location of their definition as line zero
10057 of the source file submitted to the compiler.
10060 (@value{GDBP}) info macro __STDC__
10061 Defined at /home/jimb/gdb/macros/play/sample.c:0
10068 @chapter Tracepoints
10069 @c This chapter is based on the documentation written by Michael
10070 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
10072 @cindex tracepoints
10073 In some applications, it is not feasible for the debugger to interrupt
10074 the program's execution long enough for the developer to learn
10075 anything helpful about its behavior. If the program's correctness
10076 depends on its real-time behavior, delays introduced by a debugger
10077 might cause the program to change its behavior drastically, or perhaps
10078 fail, even when the code itself is correct. It is useful to be able
10079 to observe the program's behavior without interrupting it.
10081 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
10082 specify locations in the program, called @dfn{tracepoints}, and
10083 arbitrary expressions to evaluate when those tracepoints are reached.
10084 Later, using the @code{tfind} command, you can examine the values
10085 those expressions had when the program hit the tracepoints. The
10086 expressions may also denote objects in memory---structures or arrays,
10087 for example---whose values @value{GDBN} should record; while visiting
10088 a particular tracepoint, you may inspect those objects as if they were
10089 in memory at that moment. However, because @value{GDBN} records these
10090 values without interacting with you, it can do so quickly and
10091 unobtrusively, hopefully not disturbing the program's behavior.
10093 The tracepoint facility is currently available only for remote
10094 targets. @xref{Targets}. In addition, your remote target must know
10095 how to collect trace data. This functionality is implemented in the
10096 remote stub; however, none of the stubs distributed with @value{GDBN}
10097 support tracepoints as of this writing. The format of the remote
10098 packets used to implement tracepoints are described in @ref{Tracepoint
10101 It is also possible to get trace data from a file, in a manner reminiscent
10102 of corefiles; you specify the filename, and use @code{tfind} to search
10103 through the file. @xref{Trace Files}, for more details.
10105 This chapter describes the tracepoint commands and features.
10108 * Set Tracepoints::
10109 * Analyze Collected Data::
10110 * Tracepoint Variables::
10114 @node Set Tracepoints
10115 @section Commands to Set Tracepoints
10117 Before running such a @dfn{trace experiment}, an arbitrary number of
10118 tracepoints can be set. A tracepoint is actually a special type of
10119 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
10120 standard breakpoint commands. For instance, as with breakpoints,
10121 tracepoint numbers are successive integers starting from one, and many
10122 of the commands associated with tracepoints take the tracepoint number
10123 as their argument, to identify which tracepoint to work on.
10125 For each tracepoint, you can specify, in advance, some arbitrary set
10126 of data that you want the target to collect in the trace buffer when
10127 it hits that tracepoint. The collected data can include registers,
10128 local variables, or global data. Later, you can use @value{GDBN}
10129 commands to examine the values these data had at the time the
10130 tracepoint was hit.
10132 Tracepoints do not support every breakpoint feature. Ignore counts on
10133 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
10134 commands when they are hit. Tracepoints may not be thread-specific
10137 @cindex fast tracepoints
10138 Some targets may support @dfn{fast tracepoints}, which are inserted in
10139 a different way (such as with a jump instead of a trap), that is
10140 faster but possibly restricted in where they may be installed.
10142 @cindex static tracepoints
10143 @cindex markers, static tracepoints
10144 @cindex probing markers, static tracepoints
10145 Regular and fast tracepoints are dynamic tracing facilities, meaning
10146 that they can be used to insert tracepoints at (almost) any location
10147 in the target. Some targets may also support controlling @dfn{static
10148 tracepoints} from @value{GDBN}. With static tracing, a set of
10149 instrumentation points, also known as @dfn{markers}, are embedded in
10150 the target program, and can be activated or deactivated by name or
10151 address. These are usually placed at locations which facilitate
10152 investigating what the target is actually doing. @value{GDBN}'s
10153 support for static tracing includes being able to list instrumentation
10154 points, and attach them with @value{GDBN} defined high level
10155 tracepoints that expose the whole range of convenience of
10156 @value{GDBN}'s tracepoints support. Namely, support for collecting
10157 registers values and values of global or local (to the instrumentation
10158 point) variables; tracepoint conditions and trace state variables.
10159 The act of installing a @value{GDBN} static tracepoint on an
10160 instrumentation point, or marker, is referred to as @dfn{probing} a
10161 static tracepoint marker.
10163 @code{gdbserver} supports tracepoints on some target systems.
10164 @xref{Server,,Tracepoints support in @code{gdbserver}}.
10166 This section describes commands to set tracepoints and associated
10167 conditions and actions.
10170 * Create and Delete Tracepoints::
10171 * Enable and Disable Tracepoints::
10172 * Tracepoint Passcounts::
10173 * Tracepoint Conditions::
10174 * Trace State Variables::
10175 * Tracepoint Actions::
10176 * Listing Tracepoints::
10177 * Listing Static Tracepoint Markers::
10178 * Starting and Stopping Trace Experiments::
10179 * Tracepoint Restrictions::
10182 @node Create and Delete Tracepoints
10183 @subsection Create and Delete Tracepoints
10186 @cindex set tracepoint
10188 @item trace @var{location}
10189 The @code{trace} command is very similar to the @code{break} command.
10190 Its argument @var{location} can be a source line, a function name, or
10191 an address in the target program. @xref{Specify Location}. The
10192 @code{trace} command defines a tracepoint, which is a point in the
10193 target program where the debugger will briefly stop, collect some
10194 data, and then allow the program to continue. Setting a tracepoint or
10195 changing its actions doesn't take effect until the next @code{tstart}
10196 command, and once a trace experiment is running, further changes will
10197 not have any effect until the next trace experiment starts.
10199 Here are some examples of using the @code{trace} command:
10202 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
10204 (@value{GDBP}) @b{trace +2} // 2 lines forward
10206 (@value{GDBP}) @b{trace my_function} // first source line of function
10208 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
10210 (@value{GDBP}) @b{trace *0x2117c4} // an address
10214 You can abbreviate @code{trace} as @code{tr}.
10216 @item trace @var{location} if @var{cond}
10217 Set a tracepoint with condition @var{cond}; evaluate the expression
10218 @var{cond} each time the tracepoint is reached, and collect data only
10219 if the value is nonzero---that is, if @var{cond} evaluates as true.
10220 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
10221 information on tracepoint conditions.
10223 @item ftrace @var{location} [ if @var{cond} ]
10224 @cindex set fast tracepoint
10225 @cindex fast tracepoints, setting
10227 The @code{ftrace} command sets a fast tracepoint. For targets that
10228 support them, fast tracepoints will use a more efficient but possibly
10229 less general technique to trigger data collection, such as a jump
10230 instruction instead of a trap, or some sort of hardware support. It
10231 may not be possible to create a fast tracepoint at the desired
10232 location, in which case the command will exit with an explanatory
10235 @value{GDBN} handles arguments to @code{ftrace} exactly as for
10238 @item strace @var{location} [ if @var{cond} ]
10239 @cindex set static tracepoint
10240 @cindex static tracepoints, setting
10241 @cindex probe static tracepoint marker
10243 The @code{strace} command sets a static tracepoint. For targets that
10244 support it, setting a static tracepoint probes a static
10245 instrumentation point, or marker, found at @var{location}. It may not
10246 be possible to set a static tracepoint at the desired location, in
10247 which case the command will exit with an explanatory message.
10249 @value{GDBN} handles arguments to @code{strace} exactly as for
10250 @code{trace}, with the addition that the user can also specify
10251 @code{-m @var{marker}} as @var{location}. This probes the marker
10252 identified by the @var{marker} string identifier. This identifier
10253 depends on the static tracepoint backend library your program is
10254 using. You can find all the marker identifiers in the @samp{ID} field
10255 of the @code{info static-tracepoint-markers} command output.
10256 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
10257 Markers}. For example, in the following small program using the UST
10263 trace_mark(ust, bar33, "str %s", "FOOBAZ");
10268 the marker id is composed of joining the first two arguments to the
10269 @code{trace_mark} call with a slash, which translates to:
10272 (@value{GDBP}) info static-tracepoint-markers
10273 Cnt Enb ID Address What
10274 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
10280 so you may probe the marker above with:
10283 (@value{GDBP}) strace -m ust/bar33
10286 Static tracepoints accept an extra collect action --- @code{collect
10287 $_sdata}. This collects arbitrary user data passed in the probe point
10288 call to the tracing library. In the UST example above, you'll see
10289 that the third argument to @code{trace_mark} is a printf-like format
10290 string. The user data is then the result of running that formating
10291 string against the following arguments. Note that @code{info
10292 static-tracepoint-markers} command output lists that format string in
10293 the @samp{Data:} field.
10295 You can inspect this data when analyzing the trace buffer, by printing
10296 the $_sdata variable like any other variable available to
10297 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
10300 @cindex last tracepoint number
10301 @cindex recent tracepoint number
10302 @cindex tracepoint number
10303 The convenience variable @code{$tpnum} records the tracepoint number
10304 of the most recently set tracepoint.
10306 @kindex delete tracepoint
10307 @cindex tracepoint deletion
10308 @item delete tracepoint @r{[}@var{num}@r{]}
10309 Permanently delete one or more tracepoints. With no argument, the
10310 default is to delete all tracepoints. Note that the regular
10311 @code{delete} command can remove tracepoints also.
10316 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
10318 (@value{GDBP}) @b{delete trace} // remove all tracepoints
10322 You can abbreviate this command as @code{del tr}.
10325 @node Enable and Disable Tracepoints
10326 @subsection Enable and Disable Tracepoints
10328 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
10331 @kindex disable tracepoint
10332 @item disable tracepoint @r{[}@var{num}@r{]}
10333 Disable tracepoint @var{num}, or all tracepoints if no argument
10334 @var{num} is given. A disabled tracepoint will have no effect during
10335 a trace experiment, but it is not forgotten. You can re-enable
10336 a disabled tracepoint using the @code{enable tracepoint} command.
10337 If the command is issued during a trace experiment and the debug target
10338 has support for disabling tracepoints during a trace experiment, then the
10339 change will be effective immediately. Otherwise, it will be applied to the
10340 next trace experiment.
10342 @kindex enable tracepoint
10343 @item enable tracepoint @r{[}@var{num}@r{]}
10344 Enable tracepoint @var{num}, or all tracepoints. If this command is
10345 issued during a trace experiment and the debug target supports enabling
10346 tracepoints during a trace experiment, then the enabled tracepoints will
10347 become effective immediately. Otherwise, they will become effective the
10348 next time a trace experiment is run.
10351 @node Tracepoint Passcounts
10352 @subsection Tracepoint Passcounts
10356 @cindex tracepoint pass count
10357 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
10358 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
10359 automatically stop a trace experiment. If a tracepoint's passcount is
10360 @var{n}, then the trace experiment will be automatically stopped on
10361 the @var{n}'th time that tracepoint is hit. If the tracepoint number
10362 @var{num} is not specified, the @code{passcount} command sets the
10363 passcount of the most recently defined tracepoint. If no passcount is
10364 given, the trace experiment will run until stopped explicitly by the
10370 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
10371 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
10373 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
10374 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
10375 (@value{GDBP}) @b{trace foo}
10376 (@value{GDBP}) @b{pass 3}
10377 (@value{GDBP}) @b{trace bar}
10378 (@value{GDBP}) @b{pass 2}
10379 (@value{GDBP}) @b{trace baz}
10380 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
10381 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
10382 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
10383 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
10387 @node Tracepoint Conditions
10388 @subsection Tracepoint Conditions
10389 @cindex conditional tracepoints
10390 @cindex tracepoint conditions
10392 The simplest sort of tracepoint collects data every time your program
10393 reaches a specified place. You can also specify a @dfn{condition} for
10394 a tracepoint. A condition is just a Boolean expression in your
10395 programming language (@pxref{Expressions, ,Expressions}). A
10396 tracepoint with a condition evaluates the expression each time your
10397 program reaches it, and data collection happens only if the condition
10400 Tracepoint conditions can be specified when a tracepoint is set, by
10401 using @samp{if} in the arguments to the @code{trace} command.
10402 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
10403 also be set or changed at any time with the @code{condition} command,
10404 just as with breakpoints.
10406 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
10407 the conditional expression itself. Instead, @value{GDBN} encodes the
10408 expression into an agent expression (@pxref{Agent Expressions})
10409 suitable for execution on the target, independently of @value{GDBN}.
10410 Global variables become raw memory locations, locals become stack
10411 accesses, and so forth.
10413 For instance, suppose you have a function that is usually called
10414 frequently, but should not be called after an error has occurred. You
10415 could use the following tracepoint command to collect data about calls
10416 of that function that happen while the error code is propagating
10417 through the program; an unconditional tracepoint could end up
10418 collecting thousands of useless trace frames that you would have to
10422 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
10425 @node Trace State Variables
10426 @subsection Trace State Variables
10427 @cindex trace state variables
10429 A @dfn{trace state variable} is a special type of variable that is
10430 created and managed by target-side code. The syntax is the same as
10431 that for GDB's convenience variables (a string prefixed with ``$''),
10432 but they are stored on the target. They must be created explicitly,
10433 using a @code{tvariable} command. They are always 64-bit signed
10436 Trace state variables are remembered by @value{GDBN}, and downloaded
10437 to the target along with tracepoint information when the trace
10438 experiment starts. There are no intrinsic limits on the number of
10439 trace state variables, beyond memory limitations of the target.
10441 @cindex convenience variables, and trace state variables
10442 Although trace state variables are managed by the target, you can use
10443 them in print commands and expressions as if they were convenience
10444 variables; @value{GDBN} will get the current value from the target
10445 while the trace experiment is running. Trace state variables share
10446 the same namespace as other ``$'' variables, which means that you
10447 cannot have trace state variables with names like @code{$23} or
10448 @code{$pc}, nor can you have a trace state variable and a convenience
10449 variable with the same name.
10453 @item tvariable $@var{name} [ = @var{expression} ]
10455 The @code{tvariable} command creates a new trace state variable named
10456 @code{$@var{name}}, and optionally gives it an initial value of
10457 @var{expression}. @var{expression} is evaluated when this command is
10458 entered; the result will be converted to an integer if possible,
10459 otherwise @value{GDBN} will report an error. A subsequent
10460 @code{tvariable} command specifying the same name does not create a
10461 variable, but instead assigns the supplied initial value to the
10462 existing variable of that name, overwriting any previous initial
10463 value. The default initial value is 0.
10465 @item info tvariables
10466 @kindex info tvariables
10467 List all the trace state variables along with their initial values.
10468 Their current values may also be displayed, if the trace experiment is
10471 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
10472 @kindex delete tvariable
10473 Delete the given trace state variables, or all of them if no arguments
10478 @node Tracepoint Actions
10479 @subsection Tracepoint Action Lists
10483 @cindex tracepoint actions
10484 @item actions @r{[}@var{num}@r{]}
10485 This command will prompt for a list of actions to be taken when the
10486 tracepoint is hit. If the tracepoint number @var{num} is not
10487 specified, this command sets the actions for the one that was most
10488 recently defined (so that you can define a tracepoint and then say
10489 @code{actions} without bothering about its number). You specify the
10490 actions themselves on the following lines, one action at a time, and
10491 terminate the actions list with a line containing just @code{end}. So
10492 far, the only defined actions are @code{collect}, @code{teval}, and
10493 @code{while-stepping}.
10495 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
10496 Commands, ,Breakpoint Command Lists}), except that only the defined
10497 actions are allowed; any other @value{GDBN} command is rejected.
10499 @cindex remove actions from a tracepoint
10500 To remove all actions from a tracepoint, type @samp{actions @var{num}}
10501 and follow it immediately with @samp{end}.
10504 (@value{GDBP}) @b{collect @var{data}} // collect some data
10506 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
10508 (@value{GDBP}) @b{end} // signals the end of actions.
10511 In the following example, the action list begins with @code{collect}
10512 commands indicating the things to be collected when the tracepoint is
10513 hit. Then, in order to single-step and collect additional data
10514 following the tracepoint, a @code{while-stepping} command is used,
10515 followed by the list of things to be collected after each step in a
10516 sequence of single steps. The @code{while-stepping} command is
10517 terminated by its own separate @code{end} command. Lastly, the action
10518 list is terminated by an @code{end} command.
10521 (@value{GDBP}) @b{trace foo}
10522 (@value{GDBP}) @b{actions}
10523 Enter actions for tracepoint 1, one per line:
10526 > while-stepping 12
10527 > collect $pc, arr[i]
10532 @kindex collect @r{(tracepoints)}
10533 @item collect @var{expr1}, @var{expr2}, @dots{}
10534 Collect values of the given expressions when the tracepoint is hit.
10535 This command accepts a comma-separated list of any valid expressions.
10536 In addition to global, static, or local variables, the following
10537 special arguments are supported:
10541 Collect all registers.
10544 Collect all function arguments.
10547 Collect all local variables.
10550 Collect the return address. This is helpful if you want to see more
10554 @vindex $_sdata@r{, collect}
10555 Collect static tracepoint marker specific data. Only available for
10556 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
10557 Lists}. On the UST static tracepoints library backend, an
10558 instrumentation point resembles a @code{printf} function call. The
10559 tracing library is able to collect user specified data formatted to a
10560 character string using the format provided by the programmer that
10561 instrumented the program. Other backends have similar mechanisms.
10562 Here's an example of a UST marker call:
10565 const char master_name[] = "$your_name";
10566 trace_mark(channel1, marker1, "hello %s", master_name)
10569 In this case, collecting @code{$_sdata} collects the string
10570 @samp{hello $yourname}. When analyzing the trace buffer, you can
10571 inspect @samp{$_sdata} like any other variable available to
10575 You can give several consecutive @code{collect} commands, each one
10576 with a single argument, or one @code{collect} command with several
10577 arguments separated by commas; the effect is the same.
10579 The command @code{info scope} (@pxref{Symbols, info scope}) is
10580 particularly useful for figuring out what data to collect.
10582 @kindex teval @r{(tracepoints)}
10583 @item teval @var{expr1}, @var{expr2}, @dots{}
10584 Evaluate the given expressions when the tracepoint is hit. This
10585 command accepts a comma-separated list of expressions. The results
10586 are discarded, so this is mainly useful for assigning values to trace
10587 state variables (@pxref{Trace State Variables}) without adding those
10588 values to the trace buffer, as would be the case if the @code{collect}
10591 @kindex while-stepping @r{(tracepoints)}
10592 @item while-stepping @var{n}
10593 Perform @var{n} single-step instruction traces after the tracepoint,
10594 collecting new data after each step. The @code{while-stepping}
10595 command is followed by the list of what to collect while stepping
10596 (followed by its own @code{end} command):
10599 > while-stepping 12
10600 > collect $regs, myglobal
10606 Note that @code{$pc} is not automatically collected by
10607 @code{while-stepping}; you need to explicitly collect that register if
10608 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
10611 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
10612 @kindex set default-collect
10613 @cindex default collection action
10614 This variable is a list of expressions to collect at each tracepoint
10615 hit. It is effectively an additional @code{collect} action prepended
10616 to every tracepoint action list. The expressions are parsed
10617 individually for each tracepoint, so for instance a variable named
10618 @code{xyz} may be interpreted as a global for one tracepoint, and a
10619 local for another, as appropriate to the tracepoint's location.
10621 @item show default-collect
10622 @kindex show default-collect
10623 Show the list of expressions that are collected by default at each
10628 @node Listing Tracepoints
10629 @subsection Listing Tracepoints
10632 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
10633 @kindex info tp @r{[}@var{n}@dots{}@r{]}
10634 @cindex information about tracepoints
10635 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
10636 Display information about the tracepoint @var{num}. If you don't
10637 specify a tracepoint number, displays information about all the
10638 tracepoints defined so far. The format is similar to that used for
10639 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
10640 command, simply restricting itself to tracepoints.
10642 A tracepoint's listing may include additional information specific to
10647 its passcount as given by the @code{passcount @var{n}} command
10651 (@value{GDBP}) @b{info trace}
10652 Num Type Disp Enb Address What
10653 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
10655 collect globfoo, $regs
10664 This command can be abbreviated @code{info tp}.
10667 @node Listing Static Tracepoint Markers
10668 @subsection Listing Static Tracepoint Markers
10671 @kindex info static-tracepoint-markers
10672 @cindex information about static tracepoint markers
10673 @item info static-tracepoint-markers
10674 Display information about all static tracepoint markers defined in the
10677 For each marker, the following columns are printed:
10681 An incrementing counter, output to help readability. This is not a
10684 The marker ID, as reported by the target.
10685 @item Enabled or Disabled
10686 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
10687 that are not enabled.
10689 Where the marker is in your program, as a memory address.
10691 Where the marker is in the source for your program, as a file and line
10692 number. If the debug information included in the program does not
10693 allow @value{GDBN} to locate the source of the marker, this column
10694 will be left blank.
10698 In addition, the following information may be printed for each marker:
10702 User data passed to the tracing library by the marker call. In the
10703 UST backend, this is the format string passed as argument to the
10705 @item Static tracepoints probing the marker
10706 The list of static tracepoints attached to the marker.
10710 (@value{GDBP}) info static-tracepoint-markers
10711 Cnt ID Enb Address What
10712 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
10713 Data: number1 %d number2 %d
10714 Probed by static tracepoints: #2
10715 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
10721 @node Starting and Stopping Trace Experiments
10722 @subsection Starting and Stopping Trace Experiments
10726 @cindex start a new trace experiment
10727 @cindex collected data discarded
10729 This command takes no arguments. It starts the trace experiment, and
10730 begins collecting data. This has the side effect of discarding all
10731 the data collected in the trace buffer during the previous trace
10735 @cindex stop a running trace experiment
10737 This command takes no arguments. It ends the trace experiment, and
10738 stops collecting data.
10740 @strong{Note}: a trace experiment and data collection may stop
10741 automatically if any tracepoint's passcount is reached
10742 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
10745 @cindex status of trace data collection
10746 @cindex trace experiment, status of
10748 This command displays the status of the current trace data
10752 Here is an example of the commands we described so far:
10755 (@value{GDBP}) @b{trace gdb_c_test}
10756 (@value{GDBP}) @b{actions}
10757 Enter actions for tracepoint #1, one per line.
10758 > collect $regs,$locals,$args
10759 > while-stepping 11
10763 (@value{GDBP}) @b{tstart}
10764 [time passes @dots{}]
10765 (@value{GDBP}) @b{tstop}
10768 @anchor{disconnected tracing}
10769 @cindex disconnected tracing
10770 You can choose to continue running the trace experiment even if
10771 @value{GDBN} disconnects from the target, voluntarily or
10772 involuntarily. For commands such as @code{detach}, the debugger will
10773 ask what you want to do with the trace. But for unexpected
10774 terminations (@value{GDBN} crash, network outage), it would be
10775 unfortunate to lose hard-won trace data, so the variable
10776 @code{disconnected-tracing} lets you decide whether the trace should
10777 continue running without @value{GDBN}.
10780 @item set disconnected-tracing on
10781 @itemx set disconnected-tracing off
10782 @kindex set disconnected-tracing
10783 Choose whether a tracing run should continue to run if @value{GDBN}
10784 has disconnected from the target. Note that @code{detach} or
10785 @code{quit} will ask you directly what to do about a running trace no
10786 matter what this variable's setting, so the variable is mainly useful
10787 for handling unexpected situations, such as loss of the network.
10789 @item show disconnected-tracing
10790 @kindex show disconnected-tracing
10791 Show the current choice for disconnected tracing.
10795 When you reconnect to the target, the trace experiment may or may not
10796 still be running; it might have filled the trace buffer in the
10797 meantime, or stopped for one of the other reasons. If it is running,
10798 it will continue after reconnection.
10800 Upon reconnection, the target will upload information about the
10801 tracepoints in effect. @value{GDBN} will then compare that
10802 information to the set of tracepoints currently defined, and attempt
10803 to match them up, allowing for the possibility that the numbers may
10804 have changed due to creation and deletion in the meantime. If one of
10805 the target's tracepoints does not match any in @value{GDBN}, the
10806 debugger will create a new tracepoint, so that you have a number with
10807 which to specify that tracepoint. This matching-up process is
10808 necessarily heuristic, and it may result in useless tracepoints being
10809 created; you may simply delete them if they are of no use.
10811 @cindex circular trace buffer
10812 If your target agent supports a @dfn{circular trace buffer}, then you
10813 can run a trace experiment indefinitely without filling the trace
10814 buffer; when space runs out, the agent deletes already-collected trace
10815 frames, oldest first, until there is enough room to continue
10816 collecting. This is especially useful if your tracepoints are being
10817 hit too often, and your trace gets terminated prematurely because the
10818 buffer is full. To ask for a circular trace buffer, simply set
10819 @samp{circular-trace-buffer} to on. You can set this at any time,
10820 including during tracing; if the agent can do it, it will change
10821 buffer handling on the fly, otherwise it will not take effect until
10825 @item set circular-trace-buffer on
10826 @itemx set circular-trace-buffer off
10827 @kindex set circular-trace-buffer
10828 Choose whether a tracing run should use a linear or circular buffer
10829 for trace data. A linear buffer will not lose any trace data, but may
10830 fill up prematurely, while a circular buffer will discard old trace
10831 data, but it will have always room for the latest tracepoint hits.
10833 @item show circular-trace-buffer
10834 @kindex show circular-trace-buffer
10835 Show the current choice for the trace buffer. Note that this may not
10836 match the agent's current buffer handling, nor is it guaranteed to
10837 match the setting that might have been in effect during a past run,
10838 for instance if you are looking at frames from a trace file.
10842 @node Tracepoint Restrictions
10843 @subsection Tracepoint Restrictions
10845 @cindex tracepoint restrictions
10846 There are a number of restrictions on the use of tracepoints. As
10847 described above, tracepoint data gathering occurs on the target
10848 without interaction from @value{GDBN}. Thus the full capabilities of
10849 the debugger are not available during data gathering, and then at data
10850 examination time, you will be limited by only having what was
10851 collected. The following items describe some common problems, but it
10852 is not exhaustive, and you may run into additional difficulties not
10858 Tracepoint expressions are intended to gather objects (lvalues). Thus
10859 the full flexibility of GDB's expression evaluator is not available.
10860 You cannot call functions, cast objects to aggregate types, access
10861 convenience variables or modify values (except by assignment to trace
10862 state variables). Some language features may implicitly call
10863 functions (for instance Objective-C fields with accessors), and therefore
10864 cannot be collected either.
10867 Collection of local variables, either individually or in bulk with
10868 @code{$locals} or @code{$args}, during @code{while-stepping} may
10869 behave erratically. The stepping action may enter a new scope (for
10870 instance by stepping into a function), or the location of the variable
10871 may change (for instance it is loaded into a register). The
10872 tracepoint data recorded uses the location information for the
10873 variables that is correct for the tracepoint location. When the
10874 tracepoint is created, it is not possible, in general, to determine
10875 where the steps of a @code{while-stepping} sequence will advance the
10876 program---particularly if a conditional branch is stepped.
10879 Collection of an incompletely-initialized or partially-destroyed object
10880 may result in something that @value{GDBN} cannot display, or displays
10881 in a misleading way.
10884 When @value{GDBN} displays a pointer to character it automatically
10885 dereferences the pointer to also display characters of the string
10886 being pointed to. However, collecting the pointer during tracing does
10887 not automatically collect the string. You need to explicitly
10888 dereference the pointer and provide size information if you want to
10889 collect not only the pointer, but the memory pointed to. For example,
10890 @code{*ptr@@50} can be used to collect the 50 element array pointed to
10894 It is not possible to collect a complete stack backtrace at a
10895 tracepoint. Instead, you may collect the registers and a few hundred
10896 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
10897 (adjust to use the name of the actual stack pointer register on your
10898 target architecture, and the amount of stack you wish to capture).
10899 Then the @code{backtrace} command will show a partial backtrace when
10900 using a trace frame. The number of stack frames that can be examined
10901 depends on the sizes of the frames in the collected stack. Note that
10902 if you ask for a block so large that it goes past the bottom of the
10903 stack, the target agent may report an error trying to read from an
10907 If you do not collect registers at a tracepoint, @value{GDBN} can
10908 infer that the value of @code{$pc} must be the same as the address of
10909 the tracepoint and use that when you are looking at a trace frame
10910 for that tracepoint. However, this cannot work if the tracepoint has
10911 multiple locations (for instance if it was set in a function that was
10912 inlined), or if it has a @code{while-stepping} loop. In those cases
10913 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
10918 @node Analyze Collected Data
10919 @section Using the Collected Data
10921 After the tracepoint experiment ends, you use @value{GDBN} commands
10922 for examining the trace data. The basic idea is that each tracepoint
10923 collects a trace @dfn{snapshot} every time it is hit and another
10924 snapshot every time it single-steps. All these snapshots are
10925 consecutively numbered from zero and go into a buffer, and you can
10926 examine them later. The way you examine them is to @dfn{focus} on a
10927 specific trace snapshot. When the remote stub is focused on a trace
10928 snapshot, it will respond to all @value{GDBN} requests for memory and
10929 registers by reading from the buffer which belongs to that snapshot,
10930 rather than from @emph{real} memory or registers of the program being
10931 debugged. This means that @strong{all} @value{GDBN} commands
10932 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
10933 behave as if we were currently debugging the program state as it was
10934 when the tracepoint occurred. Any requests for data that are not in
10935 the buffer will fail.
10938 * tfind:: How to select a trace snapshot
10939 * tdump:: How to display all data for a snapshot
10940 * save tracepoints:: How to save tracepoints for a future run
10944 @subsection @code{tfind @var{n}}
10947 @cindex select trace snapshot
10948 @cindex find trace snapshot
10949 The basic command for selecting a trace snapshot from the buffer is
10950 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
10951 counting from zero. If no argument @var{n} is given, the next
10952 snapshot is selected.
10954 Here are the various forms of using the @code{tfind} command.
10958 Find the first snapshot in the buffer. This is a synonym for
10959 @code{tfind 0} (since 0 is the number of the first snapshot).
10962 Stop debugging trace snapshots, resume @emph{live} debugging.
10965 Same as @samp{tfind none}.
10968 No argument means find the next trace snapshot.
10971 Find the previous trace snapshot before the current one. This permits
10972 retracing earlier steps.
10974 @item tfind tracepoint @var{num}
10975 Find the next snapshot associated with tracepoint @var{num}. Search
10976 proceeds forward from the last examined trace snapshot. If no
10977 argument @var{num} is given, it means find the next snapshot collected
10978 for the same tracepoint as the current snapshot.
10980 @item tfind pc @var{addr}
10981 Find the next snapshot associated with the value @var{addr} of the
10982 program counter. Search proceeds forward from the last examined trace
10983 snapshot. If no argument @var{addr} is given, it means find the next
10984 snapshot with the same value of PC as the current snapshot.
10986 @item tfind outside @var{addr1}, @var{addr2}
10987 Find the next snapshot whose PC is outside the given range of
10988 addresses (exclusive).
10990 @item tfind range @var{addr1}, @var{addr2}
10991 Find the next snapshot whose PC is between @var{addr1} and
10992 @var{addr2} (inclusive).
10994 @item tfind line @r{[}@var{file}:@r{]}@var{n}
10995 Find the next snapshot associated with the source line @var{n}. If
10996 the optional argument @var{file} is given, refer to line @var{n} in
10997 that source file. Search proceeds forward from the last examined
10998 trace snapshot. If no argument @var{n} is given, it means find the
10999 next line other than the one currently being examined; thus saying
11000 @code{tfind line} repeatedly can appear to have the same effect as
11001 stepping from line to line in a @emph{live} debugging session.
11004 The default arguments for the @code{tfind} commands are specifically
11005 designed to make it easy to scan through the trace buffer. For
11006 instance, @code{tfind} with no argument selects the next trace
11007 snapshot, and @code{tfind -} with no argument selects the previous
11008 trace snapshot. So, by giving one @code{tfind} command, and then
11009 simply hitting @key{RET} repeatedly you can examine all the trace
11010 snapshots in order. Or, by saying @code{tfind -} and then hitting
11011 @key{RET} repeatedly you can examine the snapshots in reverse order.
11012 The @code{tfind line} command with no argument selects the snapshot
11013 for the next source line executed. The @code{tfind pc} command with
11014 no argument selects the next snapshot with the same program counter
11015 (PC) as the current frame. The @code{tfind tracepoint} command with
11016 no argument selects the next trace snapshot collected by the same
11017 tracepoint as the current one.
11019 In addition to letting you scan through the trace buffer manually,
11020 these commands make it easy to construct @value{GDBN} scripts that
11021 scan through the trace buffer and print out whatever collected data
11022 you are interested in. Thus, if we want to examine the PC, FP, and SP
11023 registers from each trace frame in the buffer, we can say this:
11026 (@value{GDBP}) @b{tfind start}
11027 (@value{GDBP}) @b{while ($trace_frame != -1)}
11028 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
11029 $trace_frame, $pc, $sp, $fp
11033 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
11034 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
11035 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
11036 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
11037 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
11038 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
11039 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
11040 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
11041 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
11042 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
11043 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
11046 Or, if we want to examine the variable @code{X} at each source line in
11050 (@value{GDBP}) @b{tfind start}
11051 (@value{GDBP}) @b{while ($trace_frame != -1)}
11052 > printf "Frame %d, X == %d\n", $trace_frame, X
11062 @subsection @code{tdump}
11064 @cindex dump all data collected at tracepoint
11065 @cindex tracepoint data, display
11067 This command takes no arguments. It prints all the data collected at
11068 the current trace snapshot.
11071 (@value{GDBP}) @b{trace 444}
11072 (@value{GDBP}) @b{actions}
11073 Enter actions for tracepoint #2, one per line:
11074 > collect $regs, $locals, $args, gdb_long_test
11077 (@value{GDBP}) @b{tstart}
11079 (@value{GDBP}) @b{tfind line 444}
11080 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
11082 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
11084 (@value{GDBP}) @b{tdump}
11085 Data collected at tracepoint 2, trace frame 1:
11086 d0 0xc4aa0085 -995491707
11090 d4 0x71aea3d 119204413
11093 d7 0x380035 3670069
11094 a0 0x19e24a 1696330
11095 a1 0x3000668 50333288
11097 a3 0x322000 3284992
11098 a4 0x3000698 50333336
11099 a5 0x1ad3cc 1758156
11100 fp 0x30bf3c 0x30bf3c
11101 sp 0x30bf34 0x30bf34
11103 pc 0x20b2c8 0x20b2c8
11107 p = 0x20e5b4 "gdb-test"
11114 gdb_long_test = 17 '\021'
11119 @code{tdump} works by scanning the tracepoint's current collection
11120 actions and printing the value of each expression listed. So
11121 @code{tdump} can fail, if after a run, you change the tracepoint's
11122 actions to mention variables that were not collected during the run.
11124 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
11125 uses the collected value of @code{$pc} to distinguish between trace
11126 frames that were collected at the tracepoint hit, and frames that were
11127 collected while stepping. This allows it to correctly choose whether
11128 to display the basic list of collections, or the collections from the
11129 body of the while-stepping loop. However, if @code{$pc} was not collected,
11130 then @code{tdump} will always attempt to dump using the basic collection
11131 list, and may fail if a while-stepping frame does not include all the
11132 same data that is collected at the tracepoint hit.
11133 @c This is getting pretty arcane, example would be good.
11135 @node save tracepoints
11136 @subsection @code{save tracepoints @var{filename}}
11137 @kindex save tracepoints
11138 @kindex save-tracepoints
11139 @cindex save tracepoints for future sessions
11141 This command saves all current tracepoint definitions together with
11142 their actions and passcounts, into a file @file{@var{filename}}
11143 suitable for use in a later debugging session. To read the saved
11144 tracepoint definitions, use the @code{source} command (@pxref{Command
11145 Files}). The @w{@code{save-tracepoints}} command is a deprecated
11146 alias for @w{@code{save tracepoints}}
11148 @node Tracepoint Variables
11149 @section Convenience Variables for Tracepoints
11150 @cindex tracepoint variables
11151 @cindex convenience variables for tracepoints
11154 @vindex $trace_frame
11155 @item (int) $trace_frame
11156 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
11157 snapshot is selected.
11159 @vindex $tracepoint
11160 @item (int) $tracepoint
11161 The tracepoint for the current trace snapshot.
11163 @vindex $trace_line
11164 @item (int) $trace_line
11165 The line number for the current trace snapshot.
11167 @vindex $trace_file
11168 @item (char []) $trace_file
11169 The source file for the current trace snapshot.
11171 @vindex $trace_func
11172 @item (char []) $trace_func
11173 The name of the function containing @code{$tracepoint}.
11176 Note: @code{$trace_file} is not suitable for use in @code{printf},
11177 use @code{output} instead.
11179 Here's a simple example of using these convenience variables for
11180 stepping through all the trace snapshots and printing some of their
11181 data. Note that these are not the same as trace state variables,
11182 which are managed by the target.
11185 (@value{GDBP}) @b{tfind start}
11187 (@value{GDBP}) @b{while $trace_frame != -1}
11188 > output $trace_file
11189 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
11195 @section Using Trace Files
11196 @cindex trace files
11198 In some situations, the target running a trace experiment may no
11199 longer be available; perhaps it crashed, or the hardware was needed
11200 for a different activity. To handle these cases, you can arrange to
11201 dump the trace data into a file, and later use that file as a source
11202 of trace data, via the @code{target tfile} command.
11207 @item tsave [ -r ] @var{filename}
11208 Save the trace data to @var{filename}. By default, this command
11209 assumes that @var{filename} refers to the host filesystem, so if
11210 necessary @value{GDBN} will copy raw trace data up from the target and
11211 then save it. If the target supports it, you can also supply the
11212 optional argument @code{-r} (``remote'') to direct the target to save
11213 the data directly into @var{filename} in its own filesystem, which may be
11214 more efficient if the trace buffer is very large. (Note, however, that
11215 @code{target tfile} can only read from files accessible to the host.)
11217 @kindex target tfile
11219 @item target tfile @var{filename}
11220 Use the file named @var{filename} as a source of trace data. Commands
11221 that examine data work as they do with a live target, but it is not
11222 possible to run any new trace experiments. @code{tstatus} will report
11223 the state of the trace run at the moment the data was saved, as well
11224 as the current trace frame you are examining. @var{filename} must be
11225 on a filesystem accessible to the host.
11230 @chapter Debugging Programs That Use Overlays
11233 If your program is too large to fit completely in your target system's
11234 memory, you can sometimes use @dfn{overlays} to work around this
11235 problem. @value{GDBN} provides some support for debugging programs that
11239 * How Overlays Work:: A general explanation of overlays.
11240 * Overlay Commands:: Managing overlays in @value{GDBN}.
11241 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
11242 mapped by asking the inferior.
11243 * Overlay Sample Program:: A sample program using overlays.
11246 @node How Overlays Work
11247 @section How Overlays Work
11248 @cindex mapped overlays
11249 @cindex unmapped overlays
11250 @cindex load address, overlay's
11251 @cindex mapped address
11252 @cindex overlay area
11254 Suppose you have a computer whose instruction address space is only 64
11255 kilobytes long, but which has much more memory which can be accessed by
11256 other means: special instructions, segment registers, or memory
11257 management hardware, for example. Suppose further that you want to
11258 adapt a program which is larger than 64 kilobytes to run on this system.
11260 One solution is to identify modules of your program which are relatively
11261 independent, and need not call each other directly; call these modules
11262 @dfn{overlays}. Separate the overlays from the main program, and place
11263 their machine code in the larger memory. Place your main program in
11264 instruction memory, but leave at least enough space there to hold the
11265 largest overlay as well.
11267 Now, to call a function located in an overlay, you must first copy that
11268 overlay's machine code from the large memory into the space set aside
11269 for it in the instruction memory, and then jump to its entry point
11272 @c NB: In the below the mapped area's size is greater or equal to the
11273 @c size of all overlays. This is intentional to remind the developer
11274 @c that overlays don't necessarily need to be the same size.
11278 Data Instruction Larger
11279 Address Space Address Space Address Space
11280 +-----------+ +-----------+ +-----------+
11282 +-----------+ +-----------+ +-----------+<-- overlay 1
11283 | program | | main | .----| overlay 1 | load address
11284 | variables | | program | | +-----------+
11285 | and heap | | | | | |
11286 +-----------+ | | | +-----------+<-- overlay 2
11287 | | +-----------+ | | | load address
11288 +-----------+ | | | .-| overlay 2 |
11290 mapped --->+-----------+ | | +-----------+
11291 address | | | | | |
11292 | overlay | <-' | | |
11293 | area | <---' +-----------+<-- overlay 3
11294 | | <---. | | load address
11295 +-----------+ `--| overlay 3 |
11302 @anchor{A code overlay}A code overlay
11306 The diagram (@pxref{A code overlay}) shows a system with separate data
11307 and instruction address spaces. To map an overlay, the program copies
11308 its code from the larger address space to the instruction address space.
11309 Since the overlays shown here all use the same mapped address, only one
11310 may be mapped at a time. For a system with a single address space for
11311 data and instructions, the diagram would be similar, except that the
11312 program variables and heap would share an address space with the main
11313 program and the overlay area.
11315 An overlay loaded into instruction memory and ready for use is called a
11316 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
11317 instruction memory. An overlay not present (or only partially present)
11318 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
11319 is its address in the larger memory. The mapped address is also called
11320 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
11321 called the @dfn{load memory address}, or @dfn{LMA}.
11323 Unfortunately, overlays are not a completely transparent way to adapt a
11324 program to limited instruction memory. They introduce a new set of
11325 global constraints you must keep in mind as you design your program:
11330 Before calling or returning to a function in an overlay, your program
11331 must make sure that overlay is actually mapped. Otherwise, the call or
11332 return will transfer control to the right address, but in the wrong
11333 overlay, and your program will probably crash.
11336 If the process of mapping an overlay is expensive on your system, you
11337 will need to choose your overlays carefully to minimize their effect on
11338 your program's performance.
11341 The executable file you load onto your system must contain each
11342 overlay's instructions, appearing at the overlay's load address, not its
11343 mapped address. However, each overlay's instructions must be relocated
11344 and its symbols defined as if the overlay were at its mapped address.
11345 You can use GNU linker scripts to specify different load and relocation
11346 addresses for pieces of your program; see @ref{Overlay Description,,,
11347 ld.info, Using ld: the GNU linker}.
11350 The procedure for loading executable files onto your system must be able
11351 to load their contents into the larger address space as well as the
11352 instruction and data spaces.
11356 The overlay system described above is rather simple, and could be
11357 improved in many ways:
11362 If your system has suitable bank switch registers or memory management
11363 hardware, you could use those facilities to make an overlay's load area
11364 contents simply appear at their mapped address in instruction space.
11365 This would probably be faster than copying the overlay to its mapped
11366 area in the usual way.
11369 If your overlays are small enough, you could set aside more than one
11370 overlay area, and have more than one overlay mapped at a time.
11373 You can use overlays to manage data, as well as instructions. In
11374 general, data overlays are even less transparent to your design than
11375 code overlays: whereas code overlays only require care when you call or
11376 return to functions, data overlays require care every time you access
11377 the data. Also, if you change the contents of a data overlay, you
11378 must copy its contents back out to its load address before you can copy a
11379 different data overlay into the same mapped area.
11384 @node Overlay Commands
11385 @section Overlay Commands
11387 To use @value{GDBN}'s overlay support, each overlay in your program must
11388 correspond to a separate section of the executable file. The section's
11389 virtual memory address and load memory address must be the overlay's
11390 mapped and load addresses. Identifying overlays with sections allows
11391 @value{GDBN} to determine the appropriate address of a function or
11392 variable, depending on whether the overlay is mapped or not.
11394 @value{GDBN}'s overlay commands all start with the word @code{overlay};
11395 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
11400 Disable @value{GDBN}'s overlay support. When overlay support is
11401 disabled, @value{GDBN} assumes that all functions and variables are
11402 always present at their mapped addresses. By default, @value{GDBN}'s
11403 overlay support is disabled.
11405 @item overlay manual
11406 @cindex manual overlay debugging
11407 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
11408 relies on you to tell it which overlays are mapped, and which are not,
11409 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
11410 commands described below.
11412 @item overlay map-overlay @var{overlay}
11413 @itemx overlay map @var{overlay}
11414 @cindex map an overlay
11415 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
11416 be the name of the object file section containing the overlay. When an
11417 overlay is mapped, @value{GDBN} assumes it can find the overlay's
11418 functions and variables at their mapped addresses. @value{GDBN} assumes
11419 that any other overlays whose mapped ranges overlap that of
11420 @var{overlay} are now unmapped.
11422 @item overlay unmap-overlay @var{overlay}
11423 @itemx overlay unmap @var{overlay}
11424 @cindex unmap an overlay
11425 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
11426 must be the name of the object file section containing the overlay.
11427 When an overlay is unmapped, @value{GDBN} assumes it can find the
11428 overlay's functions and variables at their load addresses.
11431 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
11432 consults a data structure the overlay manager maintains in the inferior
11433 to see which overlays are mapped. For details, see @ref{Automatic
11434 Overlay Debugging}.
11436 @item overlay load-target
11437 @itemx overlay load
11438 @cindex reloading the overlay table
11439 Re-read the overlay table from the inferior. Normally, @value{GDBN}
11440 re-reads the table @value{GDBN} automatically each time the inferior
11441 stops, so this command should only be necessary if you have changed the
11442 overlay mapping yourself using @value{GDBN}. This command is only
11443 useful when using automatic overlay debugging.
11445 @item overlay list-overlays
11446 @itemx overlay list
11447 @cindex listing mapped overlays
11448 Display a list of the overlays currently mapped, along with their mapped
11449 addresses, load addresses, and sizes.
11453 Normally, when @value{GDBN} prints a code address, it includes the name
11454 of the function the address falls in:
11457 (@value{GDBP}) print main
11458 $3 = @{int ()@} 0x11a0 <main>
11461 When overlay debugging is enabled, @value{GDBN} recognizes code in
11462 unmapped overlays, and prints the names of unmapped functions with
11463 asterisks around them. For example, if @code{foo} is a function in an
11464 unmapped overlay, @value{GDBN} prints it this way:
11467 (@value{GDBP}) overlay list
11468 No sections are mapped.
11469 (@value{GDBP}) print foo
11470 $5 = @{int (int)@} 0x100000 <*foo*>
11473 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
11477 (@value{GDBP}) overlay list
11478 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
11479 mapped at 0x1016 - 0x104a
11480 (@value{GDBP}) print foo
11481 $6 = @{int (int)@} 0x1016 <foo>
11484 When overlay debugging is enabled, @value{GDBN} can find the correct
11485 address for functions and variables in an overlay, whether or not the
11486 overlay is mapped. This allows most @value{GDBN} commands, like
11487 @code{break} and @code{disassemble}, to work normally, even on unmapped
11488 code. However, @value{GDBN}'s breakpoint support has some limitations:
11492 @cindex breakpoints in overlays
11493 @cindex overlays, setting breakpoints in
11494 You can set breakpoints in functions in unmapped overlays, as long as
11495 @value{GDBN} can write to the overlay at its load address.
11497 @value{GDBN} can not set hardware or simulator-based breakpoints in
11498 unmapped overlays. However, if you set a breakpoint at the end of your
11499 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
11500 you are using manual overlay management), @value{GDBN} will re-set its
11501 breakpoints properly.
11505 @node Automatic Overlay Debugging
11506 @section Automatic Overlay Debugging
11507 @cindex automatic overlay debugging
11509 @value{GDBN} can automatically track which overlays are mapped and which
11510 are not, given some simple co-operation from the overlay manager in the
11511 inferior. If you enable automatic overlay debugging with the
11512 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
11513 looks in the inferior's memory for certain variables describing the
11514 current state of the overlays.
11516 Here are the variables your overlay manager must define to support
11517 @value{GDBN}'s automatic overlay debugging:
11521 @item @code{_ovly_table}:
11522 This variable must be an array of the following structures:
11527 /* The overlay's mapped address. */
11530 /* The size of the overlay, in bytes. */
11531 unsigned long size;
11533 /* The overlay's load address. */
11536 /* Non-zero if the overlay is currently mapped;
11538 unsigned long mapped;
11542 @item @code{_novlys}:
11543 This variable must be a four-byte signed integer, holding the total
11544 number of elements in @code{_ovly_table}.
11548 To decide whether a particular overlay is mapped or not, @value{GDBN}
11549 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
11550 @code{lma} members equal the VMA and LMA of the overlay's section in the
11551 executable file. When @value{GDBN} finds a matching entry, it consults
11552 the entry's @code{mapped} member to determine whether the overlay is
11555 In addition, your overlay manager may define a function called
11556 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
11557 will silently set a breakpoint there. If the overlay manager then
11558 calls this function whenever it has changed the overlay table, this
11559 will enable @value{GDBN} to accurately keep track of which overlays
11560 are in program memory, and update any breakpoints that may be set
11561 in overlays. This will allow breakpoints to work even if the
11562 overlays are kept in ROM or other non-writable memory while they
11563 are not being executed.
11565 @node Overlay Sample Program
11566 @section Overlay Sample Program
11567 @cindex overlay example program
11569 When linking a program which uses overlays, you must place the overlays
11570 at their load addresses, while relocating them to run at their mapped
11571 addresses. To do this, you must write a linker script (@pxref{Overlay
11572 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
11573 since linker scripts are specific to a particular host system, target
11574 architecture, and target memory layout, this manual cannot provide
11575 portable sample code demonstrating @value{GDBN}'s overlay support.
11577 However, the @value{GDBN} source distribution does contain an overlaid
11578 program, with linker scripts for a few systems, as part of its test
11579 suite. The program consists of the following files from
11580 @file{gdb/testsuite/gdb.base}:
11584 The main program file.
11586 A simple overlay manager, used by @file{overlays.c}.
11591 Overlay modules, loaded and used by @file{overlays.c}.
11594 Linker scripts for linking the test program on the @code{d10v-elf}
11595 and @code{m32r-elf} targets.
11598 You can build the test program using the @code{d10v-elf} GCC
11599 cross-compiler like this:
11602 $ d10v-elf-gcc -g -c overlays.c
11603 $ d10v-elf-gcc -g -c ovlymgr.c
11604 $ d10v-elf-gcc -g -c foo.c
11605 $ d10v-elf-gcc -g -c bar.c
11606 $ d10v-elf-gcc -g -c baz.c
11607 $ d10v-elf-gcc -g -c grbx.c
11608 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
11609 baz.o grbx.o -Wl,-Td10v.ld -o overlays
11612 The build process is identical for any other architecture, except that
11613 you must substitute the appropriate compiler and linker script for the
11614 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
11618 @chapter Using @value{GDBN} with Different Languages
11621 Although programming languages generally have common aspects, they are
11622 rarely expressed in the same manner. For instance, in ANSI C,
11623 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
11624 Modula-2, it is accomplished by @code{p^}. Values can also be
11625 represented (and displayed) differently. Hex numbers in C appear as
11626 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
11628 @cindex working language
11629 Language-specific information is built into @value{GDBN} for some languages,
11630 allowing you to express operations like the above in your program's
11631 native language, and allowing @value{GDBN} to output values in a manner
11632 consistent with the syntax of your program's native language. The
11633 language you use to build expressions is called the @dfn{working
11637 * Setting:: Switching between source languages
11638 * Show:: Displaying the language
11639 * Checks:: Type and range checks
11640 * Supported Languages:: Supported languages
11641 * Unsupported Languages:: Unsupported languages
11645 @section Switching Between Source Languages
11647 There are two ways to control the working language---either have @value{GDBN}
11648 set it automatically, or select it manually yourself. You can use the
11649 @code{set language} command for either purpose. On startup, @value{GDBN}
11650 defaults to setting the language automatically. The working language is
11651 used to determine how expressions you type are interpreted, how values
11654 In addition to the working language, every source file that
11655 @value{GDBN} knows about has its own working language. For some object
11656 file formats, the compiler might indicate which language a particular
11657 source file is in. However, most of the time @value{GDBN} infers the
11658 language from the name of the file. The language of a source file
11659 controls whether C@t{++} names are demangled---this way @code{backtrace} can
11660 show each frame appropriately for its own language. There is no way to
11661 set the language of a source file from within @value{GDBN}, but you can
11662 set the language associated with a filename extension. @xref{Show, ,
11663 Displaying the Language}.
11665 This is most commonly a problem when you use a program, such
11666 as @code{cfront} or @code{f2c}, that generates C but is written in
11667 another language. In that case, make the
11668 program use @code{#line} directives in its C output; that way
11669 @value{GDBN} will know the correct language of the source code of the original
11670 program, and will display that source code, not the generated C code.
11673 * Filenames:: Filename extensions and languages.
11674 * Manually:: Setting the working language manually
11675 * Automatically:: Having @value{GDBN} infer the source language
11679 @subsection List of Filename Extensions and Languages
11681 If a source file name ends in one of the following extensions, then
11682 @value{GDBN} infers that its language is the one indicated.
11700 C@t{++} source file
11706 Objective-C source file
11710 Fortran source file
11713 Modula-2 source file
11717 Assembler source file. This actually behaves almost like C, but
11718 @value{GDBN} does not skip over function prologues when stepping.
11721 In addition, you may set the language associated with a filename
11722 extension. @xref{Show, , Displaying the Language}.
11725 @subsection Setting the Working Language
11727 If you allow @value{GDBN} to set the language automatically,
11728 expressions are interpreted the same way in your debugging session and
11731 @kindex set language
11732 If you wish, you may set the language manually. To do this, issue the
11733 command @samp{set language @var{lang}}, where @var{lang} is the name of
11734 a language, such as
11735 @code{c} or @code{modula-2}.
11736 For a list of the supported languages, type @samp{set language}.
11738 Setting the language manually prevents @value{GDBN} from updating the working
11739 language automatically. This can lead to confusion if you try
11740 to debug a program when the working language is not the same as the
11741 source language, when an expression is acceptable to both
11742 languages---but means different things. For instance, if the current
11743 source file were written in C, and @value{GDBN} was parsing Modula-2, a
11751 might not have the effect you intended. In C, this means to add
11752 @code{b} and @code{c} and place the result in @code{a}. The result
11753 printed would be the value of @code{a}. In Modula-2, this means to compare
11754 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
11756 @node Automatically
11757 @subsection Having @value{GDBN} Infer the Source Language
11759 To have @value{GDBN} set the working language automatically, use
11760 @samp{set language local} or @samp{set language auto}. @value{GDBN}
11761 then infers the working language. That is, when your program stops in a
11762 frame (usually by encountering a breakpoint), @value{GDBN} sets the
11763 working language to the language recorded for the function in that
11764 frame. If the language for a frame is unknown (that is, if the function
11765 or block corresponding to the frame was defined in a source file that
11766 does not have a recognized extension), the current working language is
11767 not changed, and @value{GDBN} issues a warning.
11769 This may not seem necessary for most programs, which are written
11770 entirely in one source language. However, program modules and libraries
11771 written in one source language can be used by a main program written in
11772 a different source language. Using @samp{set language auto} in this
11773 case frees you from having to set the working language manually.
11776 @section Displaying the Language
11778 The following commands help you find out which language is the
11779 working language, and also what language source files were written in.
11782 @item show language
11783 @kindex show language
11784 Display the current working language. This is the
11785 language you can use with commands such as @code{print} to
11786 build and compute expressions that may involve variables in your program.
11789 @kindex info frame@r{, show the source language}
11790 Display the source language for this frame. This language becomes the
11791 working language if you use an identifier from this frame.
11792 @xref{Frame Info, ,Information about a Frame}, to identify the other
11793 information listed here.
11796 @kindex info source@r{, show the source language}
11797 Display the source language of this source file.
11798 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
11799 information listed here.
11802 In unusual circumstances, you may have source files with extensions
11803 not in the standard list. You can then set the extension associated
11804 with a language explicitly:
11807 @item set extension-language @var{ext} @var{language}
11808 @kindex set extension-language
11809 Tell @value{GDBN} that source files with extension @var{ext} are to be
11810 assumed as written in the source language @var{language}.
11812 @item info extensions
11813 @kindex info extensions
11814 List all the filename extensions and the associated languages.
11818 @section Type and Range Checking
11821 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
11822 checking are included, but they do not yet have any effect. This
11823 section documents the intended facilities.
11825 @c FIXME remove warning when type/range code added
11827 Some languages are designed to guard you against making seemingly common
11828 errors through a series of compile- and run-time checks. These include
11829 checking the type of arguments to functions and operators, and making
11830 sure mathematical overflows are caught at run time. Checks such as
11831 these help to ensure a program's correctness once it has been compiled
11832 by eliminating type mismatches, and providing active checks for range
11833 errors when your program is running.
11835 @value{GDBN} can check for conditions like the above if you wish.
11836 Although @value{GDBN} does not check the statements in your program,
11837 it can check expressions entered directly into @value{GDBN} for
11838 evaluation via the @code{print} command, for example. As with the
11839 working language, @value{GDBN} can also decide whether or not to check
11840 automatically based on your program's source language.
11841 @xref{Supported Languages, ,Supported Languages}, for the default
11842 settings of supported languages.
11845 * Type Checking:: An overview of type checking
11846 * Range Checking:: An overview of range checking
11849 @cindex type checking
11850 @cindex checks, type
11851 @node Type Checking
11852 @subsection An Overview of Type Checking
11854 Some languages, such as Modula-2, are strongly typed, meaning that the
11855 arguments to operators and functions have to be of the correct type,
11856 otherwise an error occurs. These checks prevent type mismatch
11857 errors from ever causing any run-time problems. For example,
11865 The second example fails because the @code{CARDINAL} 1 is not
11866 type-compatible with the @code{REAL} 2.3.
11868 For the expressions you use in @value{GDBN} commands, you can tell the
11869 @value{GDBN} type checker to skip checking;
11870 to treat any mismatches as errors and abandon the expression;
11871 or to only issue warnings when type mismatches occur,
11872 but evaluate the expression anyway. When you choose the last of
11873 these, @value{GDBN} evaluates expressions like the second example above, but
11874 also issues a warning.
11876 Even if you turn type checking off, there may be other reasons
11877 related to type that prevent @value{GDBN} from evaluating an expression.
11878 For instance, @value{GDBN} does not know how to add an @code{int} and
11879 a @code{struct foo}. These particular type errors have nothing to do
11880 with the language in use, and usually arise from expressions, such as
11881 the one described above, which make little sense to evaluate anyway.
11883 Each language defines to what degree it is strict about type. For
11884 instance, both Modula-2 and C require the arguments to arithmetical
11885 operators to be numbers. In C, enumerated types and pointers can be
11886 represented as numbers, so that they are valid arguments to mathematical
11887 operators. @xref{Supported Languages, ,Supported Languages}, for further
11888 details on specific languages.
11890 @value{GDBN} provides some additional commands for controlling the type checker:
11892 @kindex set check type
11893 @kindex show check type
11895 @item set check type auto
11896 Set type checking on or off based on the current working language.
11897 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11900 @item set check type on
11901 @itemx set check type off
11902 Set type checking on or off, overriding the default setting for the
11903 current working language. Issue a warning if the setting does not
11904 match the language default. If any type mismatches occur in
11905 evaluating an expression while type checking is on, @value{GDBN} prints a
11906 message and aborts evaluation of the expression.
11908 @item set check type warn
11909 Cause the type checker to issue warnings, but to always attempt to
11910 evaluate the expression. Evaluating the expression may still
11911 be impossible for other reasons. For example, @value{GDBN} cannot add
11912 numbers and structures.
11915 Show the current setting of the type checker, and whether or not @value{GDBN}
11916 is setting it automatically.
11919 @cindex range checking
11920 @cindex checks, range
11921 @node Range Checking
11922 @subsection An Overview of Range Checking
11924 In some languages (such as Modula-2), it is an error to exceed the
11925 bounds of a type; this is enforced with run-time checks. Such range
11926 checking is meant to ensure program correctness by making sure
11927 computations do not overflow, or indices on an array element access do
11928 not exceed the bounds of the array.
11930 For expressions you use in @value{GDBN} commands, you can tell
11931 @value{GDBN} to treat range errors in one of three ways: ignore them,
11932 always treat them as errors and abandon the expression, or issue
11933 warnings but evaluate the expression anyway.
11935 A range error can result from numerical overflow, from exceeding an
11936 array index bound, or when you type a constant that is not a member
11937 of any type. Some languages, however, do not treat overflows as an
11938 error. In many implementations of C, mathematical overflow causes the
11939 result to ``wrap around'' to lower values---for example, if @var{m} is
11940 the largest integer value, and @var{s} is the smallest, then
11943 @var{m} + 1 @result{} @var{s}
11946 This, too, is specific to individual languages, and in some cases
11947 specific to individual compilers or machines. @xref{Supported Languages, ,
11948 Supported Languages}, for further details on specific languages.
11950 @value{GDBN} provides some additional commands for controlling the range checker:
11952 @kindex set check range
11953 @kindex show check range
11955 @item set check range auto
11956 Set range checking on or off based on the current working language.
11957 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11960 @item set check range on
11961 @itemx set check range off
11962 Set range checking on or off, overriding the default setting for the
11963 current working language. A warning is issued if the setting does not
11964 match the language default. If a range error occurs and range checking is on,
11965 then a message is printed and evaluation of the expression is aborted.
11967 @item set check range warn
11968 Output messages when the @value{GDBN} range checker detects a range error,
11969 but attempt to evaluate the expression anyway. Evaluating the
11970 expression may still be impossible for other reasons, such as accessing
11971 memory that the process does not own (a typical example from many Unix
11975 Show the current setting of the range checker, and whether or not it is
11976 being set automatically by @value{GDBN}.
11979 @node Supported Languages
11980 @section Supported Languages
11982 @value{GDBN} supports C, C@t{++}, D, Objective-C, Fortran, Java, OpenCL C, Pascal,
11983 assembly, Modula-2, and Ada.
11984 @c This is false ...
11985 Some @value{GDBN} features may be used in expressions regardless of the
11986 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
11987 and the @samp{@{type@}addr} construct (@pxref{Expressions,
11988 ,Expressions}) can be used with the constructs of any supported
11991 The following sections detail to what degree each source language is
11992 supported by @value{GDBN}. These sections are not meant to be language
11993 tutorials or references, but serve only as a reference guide to what the
11994 @value{GDBN} expression parser accepts, and what input and output
11995 formats should look like for different languages. There are many good
11996 books written on each of these languages; please look to these for a
11997 language reference or tutorial.
12000 * C:: C and C@t{++}
12002 * Objective-C:: Objective-C
12003 * OpenCL C:: OpenCL C
12004 * Fortran:: Fortran
12006 * Modula-2:: Modula-2
12011 @subsection C and C@t{++}
12013 @cindex C and C@t{++}
12014 @cindex expressions in C or C@t{++}
12016 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
12017 to both languages. Whenever this is the case, we discuss those languages
12021 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
12022 @cindex @sc{gnu} C@t{++}
12023 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
12024 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
12025 effectively, you must compile your C@t{++} programs with a supported
12026 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
12027 compiler (@code{aCC}).
12029 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
12030 format; if it doesn't work on your system, try the stabs+ debugging
12031 format. You can select those formats explicitly with the @code{g++}
12032 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
12033 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
12034 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
12037 * C Operators:: C and C@t{++} operators
12038 * C Constants:: C and C@t{++} constants
12039 * C Plus Plus Expressions:: C@t{++} expressions
12040 * C Defaults:: Default settings for C and C@t{++}
12041 * C Checks:: C and C@t{++} type and range checks
12042 * Debugging C:: @value{GDBN} and C
12043 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
12044 * Decimal Floating Point:: Numbers in Decimal Floating Point format
12048 @subsubsection C and C@t{++} Operators
12050 @cindex C and C@t{++} operators
12052 Operators must be defined on values of specific types. For instance,
12053 @code{+} is defined on numbers, but not on structures. Operators are
12054 often defined on groups of types.
12056 For the purposes of C and C@t{++}, the following definitions hold:
12061 @emph{Integral types} include @code{int} with any of its storage-class
12062 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
12065 @emph{Floating-point types} include @code{float}, @code{double}, and
12066 @code{long double} (if supported by the target platform).
12069 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
12072 @emph{Scalar types} include all of the above.
12077 The following operators are supported. They are listed here
12078 in order of increasing precedence:
12082 The comma or sequencing operator. Expressions in a comma-separated list
12083 are evaluated from left to right, with the result of the entire
12084 expression being the last expression evaluated.
12087 Assignment. The value of an assignment expression is the value
12088 assigned. Defined on scalar types.
12091 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
12092 and translated to @w{@code{@var{a} = @var{a op b}}}.
12093 @w{@code{@var{op}=}} and @code{=} have the same precedence.
12094 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
12095 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
12098 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
12099 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
12103 Logical @sc{or}. Defined on integral types.
12106 Logical @sc{and}. Defined on integral types.
12109 Bitwise @sc{or}. Defined on integral types.
12112 Bitwise exclusive-@sc{or}. Defined on integral types.
12115 Bitwise @sc{and}. Defined on integral types.
12118 Equality and inequality. Defined on scalar types. The value of these
12119 expressions is 0 for false and non-zero for true.
12121 @item <@r{, }>@r{, }<=@r{, }>=
12122 Less than, greater than, less than or equal, greater than or equal.
12123 Defined on scalar types. The value of these expressions is 0 for false
12124 and non-zero for true.
12127 left shift, and right shift. Defined on integral types.
12130 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12133 Addition and subtraction. Defined on integral types, floating-point types and
12136 @item *@r{, }/@r{, }%
12137 Multiplication, division, and modulus. Multiplication and division are
12138 defined on integral and floating-point types. Modulus is defined on
12142 Increment and decrement. When appearing before a variable, the
12143 operation is performed before the variable is used in an expression;
12144 when appearing after it, the variable's value is used before the
12145 operation takes place.
12148 Pointer dereferencing. Defined on pointer types. Same precedence as
12152 Address operator. Defined on variables. Same precedence as @code{++}.
12154 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
12155 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
12156 to examine the address
12157 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
12161 Negative. Defined on integral and floating-point types. Same
12162 precedence as @code{++}.
12165 Logical negation. Defined on integral types. Same precedence as
12169 Bitwise complement operator. Defined on integral types. Same precedence as
12174 Structure member, and pointer-to-structure member. For convenience,
12175 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
12176 pointer based on the stored type information.
12177 Defined on @code{struct} and @code{union} data.
12180 Dereferences of pointers to members.
12183 Array indexing. @code{@var{a}[@var{i}]} is defined as
12184 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
12187 Function parameter list. Same precedence as @code{->}.
12190 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
12191 and @code{class} types.
12194 Doubled colons also represent the @value{GDBN} scope operator
12195 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
12199 If an operator is redefined in the user code, @value{GDBN} usually
12200 attempts to invoke the redefined version instead of using the operator's
12201 predefined meaning.
12204 @subsubsection C and C@t{++} Constants
12206 @cindex C and C@t{++} constants
12208 @value{GDBN} allows you to express the constants of C and C@t{++} in the
12213 Integer constants are a sequence of digits. Octal constants are
12214 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
12215 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
12216 @samp{l}, specifying that the constant should be treated as a
12220 Floating point constants are a sequence of digits, followed by a decimal
12221 point, followed by a sequence of digits, and optionally followed by an
12222 exponent. An exponent is of the form:
12223 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
12224 sequence of digits. The @samp{+} is optional for positive exponents.
12225 A floating-point constant may also end with a letter @samp{f} or
12226 @samp{F}, specifying that the constant should be treated as being of
12227 the @code{float} (as opposed to the default @code{double}) type; or with
12228 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
12232 Enumerated constants consist of enumerated identifiers, or their
12233 integral equivalents.
12236 Character constants are a single character surrounded by single quotes
12237 (@code{'}), or a number---the ordinal value of the corresponding character
12238 (usually its @sc{ascii} value). Within quotes, the single character may
12239 be represented by a letter or by @dfn{escape sequences}, which are of
12240 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
12241 of the character's ordinal value; or of the form @samp{\@var{x}}, where
12242 @samp{@var{x}} is a predefined special character---for example,
12243 @samp{\n} for newline.
12246 String constants are a sequence of character constants surrounded by
12247 double quotes (@code{"}). Any valid character constant (as described
12248 above) may appear. Double quotes within the string must be preceded by
12249 a backslash, so for instance @samp{"a\"b'c"} is a string of five
12253 Pointer constants are an integral value. You can also write pointers
12254 to constants using the C operator @samp{&}.
12257 Array constants are comma-separated lists surrounded by braces @samp{@{}
12258 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
12259 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
12260 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
12263 @node C Plus Plus Expressions
12264 @subsubsection C@t{++} Expressions
12266 @cindex expressions in C@t{++}
12267 @value{GDBN} expression handling can interpret most C@t{++} expressions.
12269 @cindex debugging C@t{++} programs
12270 @cindex C@t{++} compilers
12271 @cindex debug formats and C@t{++}
12272 @cindex @value{NGCC} and C@t{++}
12274 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
12275 proper compiler and the proper debug format. Currently, @value{GDBN}
12276 works best when debugging C@t{++} code that is compiled with
12277 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
12278 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
12279 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
12280 stabs+ as their default debug format, so you usually don't need to
12281 specify a debug format explicitly. Other compilers and/or debug formats
12282 are likely to work badly or not at all when using @value{GDBN} to debug
12288 @cindex member functions
12290 Member function calls are allowed; you can use expressions like
12293 count = aml->GetOriginal(x, y)
12296 @vindex this@r{, inside C@t{++} member functions}
12297 @cindex namespace in C@t{++}
12299 While a member function is active (in the selected stack frame), your
12300 expressions have the same namespace available as the member function;
12301 that is, @value{GDBN} allows implicit references to the class instance
12302 pointer @code{this} following the same rules as C@t{++}.
12304 @cindex call overloaded functions
12305 @cindex overloaded functions, calling
12306 @cindex type conversions in C@t{++}
12308 You can call overloaded functions; @value{GDBN} resolves the function
12309 call to the right definition, with some restrictions. @value{GDBN} does not
12310 perform overload resolution involving user-defined type conversions,
12311 calls to constructors, or instantiations of templates that do not exist
12312 in the program. It also cannot handle ellipsis argument lists or
12315 It does perform integral conversions and promotions, floating-point
12316 promotions, arithmetic conversions, pointer conversions, conversions of
12317 class objects to base classes, and standard conversions such as those of
12318 functions or arrays to pointers; it requires an exact match on the
12319 number of function arguments.
12321 Overload resolution is always performed, unless you have specified
12322 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
12323 ,@value{GDBN} Features for C@t{++}}.
12325 You must specify @code{set overload-resolution off} in order to use an
12326 explicit function signature to call an overloaded function, as in
12328 p 'foo(char,int)'('x', 13)
12331 The @value{GDBN} command-completion facility can simplify this;
12332 see @ref{Completion, ,Command Completion}.
12334 @cindex reference declarations
12336 @value{GDBN} understands variables declared as C@t{++} references; you can use
12337 them in expressions just as you do in C@t{++} source---they are automatically
12340 In the parameter list shown when @value{GDBN} displays a frame, the values of
12341 reference variables are not displayed (unlike other variables); this
12342 avoids clutter, since references are often used for large structures.
12343 The @emph{address} of a reference variable is always shown, unless
12344 you have specified @samp{set print address off}.
12347 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
12348 expressions can use it just as expressions in your program do. Since
12349 one scope may be defined in another, you can use @code{::} repeatedly if
12350 necessary, for example in an expression like
12351 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
12352 resolving name scope by reference to source files, in both C and C@t{++}
12353 debugging (@pxref{Variables, ,Program Variables}).
12356 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
12357 calling virtual functions correctly, printing out virtual bases of
12358 objects, calling functions in a base subobject, casting objects, and
12359 invoking user-defined operators.
12362 @subsubsection C and C@t{++} Defaults
12364 @cindex C and C@t{++} defaults
12366 If you allow @value{GDBN} to set type and range checking automatically, they
12367 both default to @code{off} whenever the working language changes to
12368 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
12369 selects the working language.
12371 If you allow @value{GDBN} to set the language automatically, it
12372 recognizes source files whose names end with @file{.c}, @file{.C}, or
12373 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
12374 these files, it sets the working language to C or C@t{++}.
12375 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
12376 for further details.
12378 @c Type checking is (a) primarily motivated by Modula-2, and (b)
12379 @c unimplemented. If (b) changes, it might make sense to let this node
12380 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
12383 @subsubsection C and C@t{++} Type and Range Checks
12385 @cindex C and C@t{++} checks
12387 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
12388 is not used. However, if you turn type checking on, @value{GDBN}
12389 considers two variables type equivalent if:
12393 The two variables are structured and have the same structure, union, or
12397 The two variables have the same type name, or types that have been
12398 declared equivalent through @code{typedef}.
12401 @c leaving this out because neither J Gilmore nor R Pesch understand it.
12404 The two @code{struct}, @code{union}, or @code{enum} variables are
12405 declared in the same declaration. (Note: this may not be true for all C
12410 Range checking, if turned on, is done on mathematical operations. Array
12411 indices are not checked, since they are often used to index a pointer
12412 that is not itself an array.
12415 @subsubsection @value{GDBN} and C
12417 The @code{set print union} and @code{show print union} commands apply to
12418 the @code{union} type. When set to @samp{on}, any @code{union} that is
12419 inside a @code{struct} or @code{class} is also printed. Otherwise, it
12420 appears as @samp{@{...@}}.
12422 The @code{@@} operator aids in the debugging of dynamic arrays, formed
12423 with pointers and a memory allocation function. @xref{Expressions,
12426 @node Debugging C Plus Plus
12427 @subsubsection @value{GDBN} Features for C@t{++}
12429 @cindex commands for C@t{++}
12431 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
12432 designed specifically for use with C@t{++}. Here is a summary:
12435 @cindex break in overloaded functions
12436 @item @r{breakpoint menus}
12437 When you want a breakpoint in a function whose name is overloaded,
12438 @value{GDBN} has the capability to display a menu of possible breakpoint
12439 locations to help you specify which function definition you want.
12440 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
12442 @cindex overloading in C@t{++}
12443 @item rbreak @var{regex}
12444 Setting breakpoints using regular expressions is helpful for setting
12445 breakpoints on overloaded functions that are not members of any special
12447 @xref{Set Breaks, ,Setting Breakpoints}.
12449 @cindex C@t{++} exception handling
12452 Debug C@t{++} exception handling using these commands. @xref{Set
12453 Catchpoints, , Setting Catchpoints}.
12455 @cindex inheritance
12456 @item ptype @var{typename}
12457 Print inheritance relationships as well as other information for type
12459 @xref{Symbols, ,Examining the Symbol Table}.
12461 @cindex C@t{++} symbol display
12462 @item set print demangle
12463 @itemx show print demangle
12464 @itemx set print asm-demangle
12465 @itemx show print asm-demangle
12466 Control whether C@t{++} symbols display in their source form, both when
12467 displaying code as C@t{++} source and when displaying disassemblies.
12468 @xref{Print Settings, ,Print Settings}.
12470 @item set print object
12471 @itemx show print object
12472 Choose whether to print derived (actual) or declared types of objects.
12473 @xref{Print Settings, ,Print Settings}.
12475 @item set print vtbl
12476 @itemx show print vtbl
12477 Control the format for printing virtual function tables.
12478 @xref{Print Settings, ,Print Settings}.
12479 (The @code{vtbl} commands do not work on programs compiled with the HP
12480 ANSI C@t{++} compiler (@code{aCC}).)
12482 @kindex set overload-resolution
12483 @cindex overloaded functions, overload resolution
12484 @item set overload-resolution on
12485 Enable overload resolution for C@t{++} expression evaluation. The default
12486 is on. For overloaded functions, @value{GDBN} evaluates the arguments
12487 and searches for a function whose signature matches the argument types,
12488 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
12489 Expressions, ,C@t{++} Expressions}, for details).
12490 If it cannot find a match, it emits a message.
12492 @item set overload-resolution off
12493 Disable overload resolution for C@t{++} expression evaluation. For
12494 overloaded functions that are not class member functions, @value{GDBN}
12495 chooses the first function of the specified name that it finds in the
12496 symbol table, whether or not its arguments are of the correct type. For
12497 overloaded functions that are class member functions, @value{GDBN}
12498 searches for a function whose signature @emph{exactly} matches the
12501 @kindex show overload-resolution
12502 @item show overload-resolution
12503 Show the current setting of overload resolution.
12505 @item @r{Overloaded symbol names}
12506 You can specify a particular definition of an overloaded symbol, using
12507 the same notation that is used to declare such symbols in C@t{++}: type
12508 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
12509 also use the @value{GDBN} command-line word completion facilities to list the
12510 available choices, or to finish the type list for you.
12511 @xref{Completion,, Command Completion}, for details on how to do this.
12514 @node Decimal Floating Point
12515 @subsubsection Decimal Floating Point format
12516 @cindex decimal floating point format
12518 @value{GDBN} can examine, set and perform computations with numbers in
12519 decimal floating point format, which in the C language correspond to the
12520 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
12521 specified by the extension to support decimal floating-point arithmetic.
12523 There are two encodings in use, depending on the architecture: BID (Binary
12524 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
12525 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
12528 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
12529 to manipulate decimal floating point numbers, it is not possible to convert
12530 (using a cast, for example) integers wider than 32-bit to decimal float.
12532 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
12533 point computations, error checking in decimal float operations ignores
12534 underflow, overflow and divide by zero exceptions.
12536 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
12537 to inspect @code{_Decimal128} values stored in floating point registers.
12538 See @ref{PowerPC,,PowerPC} for more details.
12544 @value{GDBN} can be used to debug programs written in D and compiled with
12545 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
12546 specific feature --- dynamic arrays.
12549 @subsection Objective-C
12551 @cindex Objective-C
12552 This section provides information about some commands and command
12553 options that are useful for debugging Objective-C code. See also
12554 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
12555 few more commands specific to Objective-C support.
12558 * Method Names in Commands::
12559 * The Print Command with Objective-C::
12562 @node Method Names in Commands
12563 @subsubsection Method Names in Commands
12565 The following commands have been extended to accept Objective-C method
12566 names as line specifications:
12568 @kindex clear@r{, and Objective-C}
12569 @kindex break@r{, and Objective-C}
12570 @kindex info line@r{, and Objective-C}
12571 @kindex jump@r{, and Objective-C}
12572 @kindex list@r{, and Objective-C}
12576 @item @code{info line}
12581 A fully qualified Objective-C method name is specified as
12584 -[@var{Class} @var{methodName}]
12587 where the minus sign is used to indicate an instance method and a
12588 plus sign (not shown) is used to indicate a class method. The class
12589 name @var{Class} and method name @var{methodName} are enclosed in
12590 brackets, similar to the way messages are specified in Objective-C
12591 source code. For example, to set a breakpoint at the @code{create}
12592 instance method of class @code{Fruit} in the program currently being
12596 break -[Fruit create]
12599 To list ten program lines around the @code{initialize} class method,
12603 list +[NSText initialize]
12606 In the current version of @value{GDBN}, the plus or minus sign is
12607 required. In future versions of @value{GDBN}, the plus or minus
12608 sign will be optional, but you can use it to narrow the search. It
12609 is also possible to specify just a method name:
12615 You must specify the complete method name, including any colons. If
12616 your program's source files contain more than one @code{create} method,
12617 you'll be presented with a numbered list of classes that implement that
12618 method. Indicate your choice by number, or type @samp{0} to exit if
12621 As another example, to clear a breakpoint established at the
12622 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
12625 clear -[NSWindow makeKeyAndOrderFront:]
12628 @node The Print Command with Objective-C
12629 @subsubsection The Print Command With Objective-C
12630 @cindex Objective-C, print objects
12631 @kindex print-object
12632 @kindex po @r{(@code{print-object})}
12634 The print command has also been extended to accept methods. For example:
12637 print -[@var{object} hash]
12640 @cindex print an Objective-C object description
12641 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
12643 will tell @value{GDBN} to send the @code{hash} message to @var{object}
12644 and print the result. Also, an additional command has been added,
12645 @code{print-object} or @code{po} for short, which is meant to print
12646 the description of an object. However, this command may only work
12647 with certain Objective-C libraries that have a particular hook
12648 function, @code{_NSPrintForDebugger}, defined.
12651 @subsection OpenCL C
12654 This section provides information about @value{GDBN}s OpenCL C support.
12657 * OpenCL C Datatypes::
12658 * OpenCL C Expressions::
12659 * OpenCL C Operators::
12662 @node OpenCL C Datatypes
12663 @subsubsection OpenCL C Datatypes
12665 @cindex OpenCL C Datatypes
12666 @value{GDBN} supports the builtin scalar and vector datatypes specified
12667 by OpenCL 1.1. In addition the half- and double-precision floating point
12668 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
12669 extensions are also known to @value{GDBN}.
12671 @node OpenCL C Expressions
12672 @subsubsection OpenCL C Expressions
12674 @cindex OpenCL C Expressions
12675 @value{GDBN} supports accesses to vector components including the access as
12676 lvalue where possible. Since OpenCL C is based on C99 most C expressions
12677 supported by @value{GDBN} can be used as well.
12679 @node OpenCL C Operators
12680 @subsubsection OpenCL C Operators
12682 @cindex OpenCL C Operators
12683 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
12687 @subsection Fortran
12688 @cindex Fortran-specific support in @value{GDBN}
12690 @value{GDBN} can be used to debug programs written in Fortran, but it
12691 currently supports only the features of Fortran 77 language.
12693 @cindex trailing underscore, in Fortran symbols
12694 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
12695 among them) append an underscore to the names of variables and
12696 functions. When you debug programs compiled by those compilers, you
12697 will need to refer to variables and functions with a trailing
12701 * Fortran Operators:: Fortran operators and expressions
12702 * Fortran Defaults:: Default settings for Fortran
12703 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
12706 @node Fortran Operators
12707 @subsubsection Fortran Operators and Expressions
12709 @cindex Fortran operators and expressions
12711 Operators must be defined on values of specific types. For instance,
12712 @code{+} is defined on numbers, but not on characters or other non-
12713 arithmetic types. Operators are often defined on groups of types.
12717 The exponentiation operator. It raises the first operand to the power
12721 The range operator. Normally used in the form of array(low:high) to
12722 represent a section of array.
12725 The access component operator. Normally used to access elements in derived
12726 types. Also suitable for unions. As unions aren't part of regular Fortran,
12727 this can only happen when accessing a register that uses a gdbarch-defined
12731 @node Fortran Defaults
12732 @subsubsection Fortran Defaults
12734 @cindex Fortran Defaults
12736 Fortran symbols are usually case-insensitive, so @value{GDBN} by
12737 default uses case-insensitive matches for Fortran symbols. You can
12738 change that with the @samp{set case-insensitive} command, see
12739 @ref{Symbols}, for the details.
12741 @node Special Fortran Commands
12742 @subsubsection Special Fortran Commands
12744 @cindex Special Fortran commands
12746 @value{GDBN} has some commands to support Fortran-specific features,
12747 such as displaying common blocks.
12750 @cindex @code{COMMON} blocks, Fortran
12751 @kindex info common
12752 @item info common @r{[}@var{common-name}@r{]}
12753 This command prints the values contained in the Fortran @code{COMMON}
12754 block whose name is @var{common-name}. With no argument, the names of
12755 all @code{COMMON} blocks visible at the current program location are
12762 @cindex Pascal support in @value{GDBN}, limitations
12763 Debugging Pascal programs which use sets, subranges, file variables, or
12764 nested functions does not currently work. @value{GDBN} does not support
12765 entering expressions, printing values, or similar features using Pascal
12768 The Pascal-specific command @code{set print pascal_static-members}
12769 controls whether static members of Pascal objects are displayed.
12770 @xref{Print Settings, pascal_static-members}.
12773 @subsection Modula-2
12775 @cindex Modula-2, @value{GDBN} support
12777 The extensions made to @value{GDBN} to support Modula-2 only support
12778 output from the @sc{gnu} Modula-2 compiler (which is currently being
12779 developed). Other Modula-2 compilers are not currently supported, and
12780 attempting to debug executables produced by them is most likely
12781 to give an error as @value{GDBN} reads in the executable's symbol
12784 @cindex expressions in Modula-2
12786 * M2 Operators:: Built-in operators
12787 * Built-In Func/Proc:: Built-in functions and procedures
12788 * M2 Constants:: Modula-2 constants
12789 * M2 Types:: Modula-2 types
12790 * M2 Defaults:: Default settings for Modula-2
12791 * Deviations:: Deviations from standard Modula-2
12792 * M2 Checks:: Modula-2 type and range checks
12793 * M2 Scope:: The scope operators @code{::} and @code{.}
12794 * GDB/M2:: @value{GDBN} and Modula-2
12798 @subsubsection Operators
12799 @cindex Modula-2 operators
12801 Operators must be defined on values of specific types. For instance,
12802 @code{+} is defined on numbers, but not on structures. Operators are
12803 often defined on groups of types. For the purposes of Modula-2, the
12804 following definitions hold:
12809 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
12813 @emph{Character types} consist of @code{CHAR} and its subranges.
12816 @emph{Floating-point types} consist of @code{REAL}.
12819 @emph{Pointer types} consist of anything declared as @code{POINTER TO
12823 @emph{Scalar types} consist of all of the above.
12826 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
12829 @emph{Boolean types} consist of @code{BOOLEAN}.
12833 The following operators are supported, and appear in order of
12834 increasing precedence:
12838 Function argument or array index separator.
12841 Assignment. The value of @var{var} @code{:=} @var{value} is
12845 Less than, greater than on integral, floating-point, or enumerated
12849 Less than or equal to, greater than or equal to
12850 on integral, floating-point and enumerated types, or set inclusion on
12851 set types. Same precedence as @code{<}.
12853 @item =@r{, }<>@r{, }#
12854 Equality and two ways of expressing inequality, valid on scalar types.
12855 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
12856 available for inequality, since @code{#} conflicts with the script
12860 Set membership. Defined on set types and the types of their members.
12861 Same precedence as @code{<}.
12864 Boolean disjunction. Defined on boolean types.
12867 Boolean conjunction. Defined on boolean types.
12870 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12873 Addition and subtraction on integral and floating-point types, or union
12874 and difference on set types.
12877 Multiplication on integral and floating-point types, or set intersection
12881 Division on floating-point types, or symmetric set difference on set
12882 types. Same precedence as @code{*}.
12885 Integer division and remainder. Defined on integral types. Same
12886 precedence as @code{*}.
12889 Negative. Defined on @code{INTEGER} and @code{REAL} data.
12892 Pointer dereferencing. Defined on pointer types.
12895 Boolean negation. Defined on boolean types. Same precedence as
12899 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
12900 precedence as @code{^}.
12903 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
12906 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
12910 @value{GDBN} and Modula-2 scope operators.
12914 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
12915 treats the use of the operator @code{IN}, or the use of operators
12916 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
12917 @code{<=}, and @code{>=} on sets as an error.
12921 @node Built-In Func/Proc
12922 @subsubsection Built-in Functions and Procedures
12923 @cindex Modula-2 built-ins
12925 Modula-2 also makes available several built-in procedures and functions.
12926 In describing these, the following metavariables are used:
12931 represents an @code{ARRAY} variable.
12934 represents a @code{CHAR} constant or variable.
12937 represents a variable or constant of integral type.
12940 represents an identifier that belongs to a set. Generally used in the
12941 same function with the metavariable @var{s}. The type of @var{s} should
12942 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
12945 represents a variable or constant of integral or floating-point type.
12948 represents a variable or constant of floating-point type.
12954 represents a variable.
12957 represents a variable or constant of one of many types. See the
12958 explanation of the function for details.
12961 All Modula-2 built-in procedures also return a result, described below.
12965 Returns the absolute value of @var{n}.
12968 If @var{c} is a lower case letter, it returns its upper case
12969 equivalent, otherwise it returns its argument.
12972 Returns the character whose ordinal value is @var{i}.
12975 Decrements the value in the variable @var{v} by one. Returns the new value.
12977 @item DEC(@var{v},@var{i})
12978 Decrements the value in the variable @var{v} by @var{i}. Returns the
12981 @item EXCL(@var{m},@var{s})
12982 Removes the element @var{m} from the set @var{s}. Returns the new
12985 @item FLOAT(@var{i})
12986 Returns the floating point equivalent of the integer @var{i}.
12988 @item HIGH(@var{a})
12989 Returns the index of the last member of @var{a}.
12992 Increments the value in the variable @var{v} by one. Returns the new value.
12994 @item INC(@var{v},@var{i})
12995 Increments the value in the variable @var{v} by @var{i}. Returns the
12998 @item INCL(@var{m},@var{s})
12999 Adds the element @var{m} to the set @var{s} if it is not already
13000 there. Returns the new set.
13003 Returns the maximum value of the type @var{t}.
13006 Returns the minimum value of the type @var{t}.
13009 Returns boolean TRUE if @var{i} is an odd number.
13012 Returns the ordinal value of its argument. For example, the ordinal
13013 value of a character is its @sc{ascii} value (on machines supporting the
13014 @sc{ascii} character set). @var{x} must be of an ordered type, which include
13015 integral, character and enumerated types.
13017 @item SIZE(@var{x})
13018 Returns the size of its argument. @var{x} can be a variable or a type.
13020 @item TRUNC(@var{r})
13021 Returns the integral part of @var{r}.
13023 @item TSIZE(@var{x})
13024 Returns the size of its argument. @var{x} can be a variable or a type.
13026 @item VAL(@var{t},@var{i})
13027 Returns the member of the type @var{t} whose ordinal value is @var{i}.
13031 @emph{Warning:} Sets and their operations are not yet supported, so
13032 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
13036 @cindex Modula-2 constants
13038 @subsubsection Constants
13040 @value{GDBN} allows you to express the constants of Modula-2 in the following
13046 Integer constants are simply a sequence of digits. When used in an
13047 expression, a constant is interpreted to be type-compatible with the
13048 rest of the expression. Hexadecimal integers are specified by a
13049 trailing @samp{H}, and octal integers by a trailing @samp{B}.
13052 Floating point constants appear as a sequence of digits, followed by a
13053 decimal point and another sequence of digits. An optional exponent can
13054 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
13055 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
13056 digits of the floating point constant must be valid decimal (base 10)
13060 Character constants consist of a single character enclosed by a pair of
13061 like quotes, either single (@code{'}) or double (@code{"}). They may
13062 also be expressed by their ordinal value (their @sc{ascii} value, usually)
13063 followed by a @samp{C}.
13066 String constants consist of a sequence of characters enclosed by a
13067 pair of like quotes, either single (@code{'}) or double (@code{"}).
13068 Escape sequences in the style of C are also allowed. @xref{C
13069 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
13073 Enumerated constants consist of an enumerated identifier.
13076 Boolean constants consist of the identifiers @code{TRUE} and
13080 Pointer constants consist of integral values only.
13083 Set constants are not yet supported.
13087 @subsubsection Modula-2 Types
13088 @cindex Modula-2 types
13090 Currently @value{GDBN} can print the following data types in Modula-2
13091 syntax: array types, record types, set types, pointer types, procedure
13092 types, enumerated types, subrange types and base types. You can also
13093 print the contents of variables declared using these type.
13094 This section gives a number of simple source code examples together with
13095 sample @value{GDBN} sessions.
13097 The first example contains the following section of code:
13106 and you can request @value{GDBN} to interrogate the type and value of
13107 @code{r} and @code{s}.
13110 (@value{GDBP}) print s
13112 (@value{GDBP}) ptype s
13114 (@value{GDBP}) print r
13116 (@value{GDBP}) ptype r
13121 Likewise if your source code declares @code{s} as:
13125 s: SET ['A'..'Z'] ;
13129 then you may query the type of @code{s} by:
13132 (@value{GDBP}) ptype s
13133 type = SET ['A'..'Z']
13137 Note that at present you cannot interactively manipulate set
13138 expressions using the debugger.
13140 The following example shows how you might declare an array in Modula-2
13141 and how you can interact with @value{GDBN} to print its type and contents:
13145 s: ARRAY [-10..10] OF CHAR ;
13149 (@value{GDBP}) ptype s
13150 ARRAY [-10..10] OF CHAR
13153 Note that the array handling is not yet complete and although the type
13154 is printed correctly, expression handling still assumes that all
13155 arrays have a lower bound of zero and not @code{-10} as in the example
13158 Here are some more type related Modula-2 examples:
13162 colour = (blue, red, yellow, green) ;
13163 t = [blue..yellow] ;
13171 The @value{GDBN} interaction shows how you can query the data type
13172 and value of a variable.
13175 (@value{GDBP}) print s
13177 (@value{GDBP}) ptype t
13178 type = [blue..yellow]
13182 In this example a Modula-2 array is declared and its contents
13183 displayed. Observe that the contents are written in the same way as
13184 their @code{C} counterparts.
13188 s: ARRAY [1..5] OF CARDINAL ;
13194 (@value{GDBP}) print s
13195 $1 = @{1, 0, 0, 0, 0@}
13196 (@value{GDBP}) ptype s
13197 type = ARRAY [1..5] OF CARDINAL
13200 The Modula-2 language interface to @value{GDBN} also understands
13201 pointer types as shown in this example:
13205 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
13212 and you can request that @value{GDBN} describes the type of @code{s}.
13215 (@value{GDBP}) ptype s
13216 type = POINTER TO ARRAY [1..5] OF CARDINAL
13219 @value{GDBN} handles compound types as we can see in this example.
13220 Here we combine array types, record types, pointer types and subrange
13231 myarray = ARRAY myrange OF CARDINAL ;
13232 myrange = [-2..2] ;
13234 s: POINTER TO ARRAY myrange OF foo ;
13238 and you can ask @value{GDBN} to describe the type of @code{s} as shown
13242 (@value{GDBP}) ptype s
13243 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
13246 f3 : ARRAY [-2..2] OF CARDINAL;
13251 @subsubsection Modula-2 Defaults
13252 @cindex Modula-2 defaults
13254 If type and range checking are set automatically by @value{GDBN}, they
13255 both default to @code{on} whenever the working language changes to
13256 Modula-2. This happens regardless of whether you or @value{GDBN}
13257 selected the working language.
13259 If you allow @value{GDBN} to set the language automatically, then entering
13260 code compiled from a file whose name ends with @file{.mod} sets the
13261 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
13262 Infer the Source Language}, for further details.
13265 @subsubsection Deviations from Standard Modula-2
13266 @cindex Modula-2, deviations from
13268 A few changes have been made to make Modula-2 programs easier to debug.
13269 This is done primarily via loosening its type strictness:
13273 Unlike in standard Modula-2, pointer constants can be formed by
13274 integers. This allows you to modify pointer variables during
13275 debugging. (In standard Modula-2, the actual address contained in a
13276 pointer variable is hidden from you; it can only be modified
13277 through direct assignment to another pointer variable or expression that
13278 returned a pointer.)
13281 C escape sequences can be used in strings and characters to represent
13282 non-printable characters. @value{GDBN} prints out strings with these
13283 escape sequences embedded. Single non-printable characters are
13284 printed using the @samp{CHR(@var{nnn})} format.
13287 The assignment operator (@code{:=}) returns the value of its right-hand
13291 All built-in procedures both modify @emph{and} return their argument.
13295 @subsubsection Modula-2 Type and Range Checks
13296 @cindex Modula-2 checks
13299 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
13302 @c FIXME remove warning when type/range checks added
13304 @value{GDBN} considers two Modula-2 variables type equivalent if:
13308 They are of types that have been declared equivalent via a @code{TYPE
13309 @var{t1} = @var{t2}} statement
13312 They have been declared on the same line. (Note: This is true of the
13313 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
13316 As long as type checking is enabled, any attempt to combine variables
13317 whose types are not equivalent is an error.
13319 Range checking is done on all mathematical operations, assignment, array
13320 index bounds, and all built-in functions and procedures.
13323 @subsubsection The Scope Operators @code{::} and @code{.}
13325 @cindex @code{.}, Modula-2 scope operator
13326 @cindex colon, doubled as scope operator
13328 @vindex colon-colon@r{, in Modula-2}
13329 @c Info cannot handle :: but TeX can.
13332 @vindex ::@r{, in Modula-2}
13335 There are a few subtle differences between the Modula-2 scope operator
13336 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
13341 @var{module} . @var{id}
13342 @var{scope} :: @var{id}
13346 where @var{scope} is the name of a module or a procedure,
13347 @var{module} the name of a module, and @var{id} is any declared
13348 identifier within your program, except another module.
13350 Using the @code{::} operator makes @value{GDBN} search the scope
13351 specified by @var{scope} for the identifier @var{id}. If it is not
13352 found in the specified scope, then @value{GDBN} searches all scopes
13353 enclosing the one specified by @var{scope}.
13355 Using the @code{.} operator makes @value{GDBN} search the current scope for
13356 the identifier specified by @var{id} that was imported from the
13357 definition module specified by @var{module}. With this operator, it is
13358 an error if the identifier @var{id} was not imported from definition
13359 module @var{module}, or if @var{id} is not an identifier in
13363 @subsubsection @value{GDBN} and Modula-2
13365 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
13366 Five subcommands of @code{set print} and @code{show print} apply
13367 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
13368 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
13369 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
13370 analogue in Modula-2.
13372 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
13373 with any language, is not useful with Modula-2. Its
13374 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
13375 created in Modula-2 as they can in C or C@t{++}. However, because an
13376 address can be specified by an integral constant, the construct
13377 @samp{@{@var{type}@}@var{adrexp}} is still useful.
13379 @cindex @code{#} in Modula-2
13380 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
13381 interpreted as the beginning of a comment. Use @code{<>} instead.
13387 The extensions made to @value{GDBN} for Ada only support
13388 output from the @sc{gnu} Ada (GNAT) compiler.
13389 Other Ada compilers are not currently supported, and
13390 attempting to debug executables produced by them is most likely
13394 @cindex expressions in Ada
13396 * Ada Mode Intro:: General remarks on the Ada syntax
13397 and semantics supported by Ada mode
13399 * Omissions from Ada:: Restrictions on the Ada expression syntax.
13400 * Additions to Ada:: Extensions of the Ada expression syntax.
13401 * Stopping Before Main Program:: Debugging the program during elaboration.
13402 * Ada Tasks:: Listing and setting breakpoints in tasks.
13403 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
13404 * Ravenscar Profile:: Tasking Support when using the Ravenscar
13406 * Ada Glitches:: Known peculiarities of Ada mode.
13409 @node Ada Mode Intro
13410 @subsubsection Introduction
13411 @cindex Ada mode, general
13413 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
13414 syntax, with some extensions.
13415 The philosophy behind the design of this subset is
13419 That @value{GDBN} should provide basic literals and access to operations for
13420 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
13421 leaving more sophisticated computations to subprograms written into the
13422 program (which therefore may be called from @value{GDBN}).
13425 That type safety and strict adherence to Ada language restrictions
13426 are not particularly important to the @value{GDBN} user.
13429 That brevity is important to the @value{GDBN} user.
13432 Thus, for brevity, the debugger acts as if all names declared in
13433 user-written packages are directly visible, even if they are not visible
13434 according to Ada rules, thus making it unnecessary to fully qualify most
13435 names with their packages, regardless of context. Where this causes
13436 ambiguity, @value{GDBN} asks the user's intent.
13438 The debugger will start in Ada mode if it detects an Ada main program.
13439 As for other languages, it will enter Ada mode when stopped in a program that
13440 was translated from an Ada source file.
13442 While in Ada mode, you may use `@t{--}' for comments. This is useful
13443 mostly for documenting command files. The standard @value{GDBN} comment
13444 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
13445 middle (to allow based literals).
13447 The debugger supports limited overloading. Given a subprogram call in which
13448 the function symbol has multiple definitions, it will use the number of
13449 actual parameters and some information about their types to attempt to narrow
13450 the set of definitions. It also makes very limited use of context, preferring
13451 procedures to functions in the context of the @code{call} command, and
13452 functions to procedures elsewhere.
13454 @node Omissions from Ada
13455 @subsubsection Omissions from Ada
13456 @cindex Ada, omissions from
13458 Here are the notable omissions from the subset:
13462 Only a subset of the attributes are supported:
13466 @t{'First}, @t{'Last}, and @t{'Length}
13467 on array objects (not on types and subtypes).
13470 @t{'Min} and @t{'Max}.
13473 @t{'Pos} and @t{'Val}.
13479 @t{'Range} on array objects (not subtypes), but only as the right
13480 operand of the membership (@code{in}) operator.
13483 @t{'Access}, @t{'Unchecked_Access}, and
13484 @t{'Unrestricted_Access} (a GNAT extension).
13492 @code{Characters.Latin_1} are not available and
13493 concatenation is not implemented. Thus, escape characters in strings are
13494 not currently available.
13497 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
13498 equality of representations. They will generally work correctly
13499 for strings and arrays whose elements have integer or enumeration types.
13500 They may not work correctly for arrays whose element
13501 types have user-defined equality, for arrays of real values
13502 (in particular, IEEE-conformant floating point, because of negative
13503 zeroes and NaNs), and for arrays whose elements contain unused bits with
13504 indeterminate values.
13507 The other component-by-component array operations (@code{and}, @code{or},
13508 @code{xor}, @code{not}, and relational tests other than equality)
13509 are not implemented.
13512 @cindex array aggregates (Ada)
13513 @cindex record aggregates (Ada)
13514 @cindex aggregates (Ada)
13515 There is limited support for array and record aggregates. They are
13516 permitted only on the right sides of assignments, as in these examples:
13519 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
13520 (@value{GDBP}) set An_Array := (1, others => 0)
13521 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
13522 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
13523 (@value{GDBP}) set A_Record := (1, "Peter", True);
13524 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
13528 discriminant's value by assigning an aggregate has an
13529 undefined effect if that discriminant is used within the record.
13530 However, you can first modify discriminants by directly assigning to
13531 them (which normally would not be allowed in Ada), and then performing an
13532 aggregate assignment. For example, given a variable @code{A_Rec}
13533 declared to have a type such as:
13536 type Rec (Len : Small_Integer := 0) is record
13538 Vals : IntArray (1 .. Len);
13542 you can assign a value with a different size of @code{Vals} with two
13546 (@value{GDBP}) set A_Rec.Len := 4
13547 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
13550 As this example also illustrates, @value{GDBN} is very loose about the usual
13551 rules concerning aggregates. You may leave out some of the
13552 components of an array or record aggregate (such as the @code{Len}
13553 component in the assignment to @code{A_Rec} above); they will retain their
13554 original values upon assignment. You may freely use dynamic values as
13555 indices in component associations. You may even use overlapping or
13556 redundant component associations, although which component values are
13557 assigned in such cases is not defined.
13560 Calls to dispatching subprograms are not implemented.
13563 The overloading algorithm is much more limited (i.e., less selective)
13564 than that of real Ada. It makes only limited use of the context in
13565 which a subexpression appears to resolve its meaning, and it is much
13566 looser in its rules for allowing type matches. As a result, some
13567 function calls will be ambiguous, and the user will be asked to choose
13568 the proper resolution.
13571 The @code{new} operator is not implemented.
13574 Entry calls are not implemented.
13577 Aside from printing, arithmetic operations on the native VAX floating-point
13578 formats are not supported.
13581 It is not possible to slice a packed array.
13584 The names @code{True} and @code{False}, when not part of a qualified name,
13585 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
13587 Should your program
13588 redefine these names in a package or procedure (at best a dubious practice),
13589 you will have to use fully qualified names to access their new definitions.
13592 @node Additions to Ada
13593 @subsubsection Additions to Ada
13594 @cindex Ada, deviations from
13596 As it does for other languages, @value{GDBN} makes certain generic
13597 extensions to Ada (@pxref{Expressions}):
13601 If the expression @var{E} is a variable residing in memory (typically
13602 a local variable or array element) and @var{N} is a positive integer,
13603 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
13604 @var{N}-1 adjacent variables following it in memory as an array. In
13605 Ada, this operator is generally not necessary, since its prime use is
13606 in displaying parts of an array, and slicing will usually do this in
13607 Ada. However, there are occasional uses when debugging programs in
13608 which certain debugging information has been optimized away.
13611 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
13612 appears in function or file @var{B}.'' When @var{B} is a file name,
13613 you must typically surround it in single quotes.
13616 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
13617 @var{type} that appears at address @var{addr}.''
13620 A name starting with @samp{$} is a convenience variable
13621 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
13624 In addition, @value{GDBN} provides a few other shortcuts and outright
13625 additions specific to Ada:
13629 The assignment statement is allowed as an expression, returning
13630 its right-hand operand as its value. Thus, you may enter
13633 (@value{GDBP}) set x := y + 3
13634 (@value{GDBP}) print A(tmp := y + 1)
13638 The semicolon is allowed as an ``operator,'' returning as its value
13639 the value of its right-hand operand.
13640 This allows, for example,
13641 complex conditional breaks:
13644 (@value{GDBP}) break f
13645 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
13649 Rather than use catenation and symbolic character names to introduce special
13650 characters into strings, one may instead use a special bracket notation,
13651 which is also used to print strings. A sequence of characters of the form
13652 @samp{["@var{XX}"]} within a string or character literal denotes the
13653 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
13654 sequence of characters @samp{["""]} also denotes a single quotation mark
13655 in strings. For example,
13657 "One line.["0a"]Next line.["0a"]"
13660 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
13664 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
13665 @t{'Max} is optional (and is ignored in any case). For example, it is valid
13669 (@value{GDBP}) print 'max(x, y)
13673 When printing arrays, @value{GDBN} uses positional notation when the
13674 array has a lower bound of 1, and uses a modified named notation otherwise.
13675 For example, a one-dimensional array of three integers with a lower bound
13676 of 3 might print as
13683 That is, in contrast to valid Ada, only the first component has a @code{=>}
13687 You may abbreviate attributes in expressions with any unique,
13688 multi-character subsequence of
13689 their names (an exact match gets preference).
13690 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
13691 in place of @t{a'length}.
13694 @cindex quoting Ada internal identifiers
13695 Since Ada is case-insensitive, the debugger normally maps identifiers you type
13696 to lower case. The GNAT compiler uses upper-case characters for
13697 some of its internal identifiers, which are normally of no interest to users.
13698 For the rare occasions when you actually have to look at them,
13699 enclose them in angle brackets to avoid the lower-case mapping.
13702 (@value{GDBP}) print <JMPBUF_SAVE>[0]
13706 Printing an object of class-wide type or dereferencing an
13707 access-to-class-wide value will display all the components of the object's
13708 specific type (as indicated by its run-time tag). Likewise, component
13709 selection on such a value will operate on the specific type of the
13714 @node Stopping Before Main Program
13715 @subsubsection Stopping at the Very Beginning
13717 @cindex breakpointing Ada elaboration code
13718 It is sometimes necessary to debug the program during elaboration, and
13719 before reaching the main procedure.
13720 As defined in the Ada Reference
13721 Manual, the elaboration code is invoked from a procedure called
13722 @code{adainit}. To run your program up to the beginning of
13723 elaboration, simply use the following two commands:
13724 @code{tbreak adainit} and @code{run}.
13727 @subsubsection Extensions for Ada Tasks
13728 @cindex Ada, tasking
13730 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
13731 @value{GDBN} provides the following task-related commands:
13736 This command shows a list of current Ada tasks, as in the following example:
13743 (@value{GDBP}) info tasks
13744 ID TID P-ID Pri State Name
13745 1 8088000 0 15 Child Activation Wait main_task
13746 2 80a4000 1 15 Accept Statement b
13747 3 809a800 1 15 Child Activation Wait a
13748 * 4 80ae800 3 15 Runnable c
13753 In this listing, the asterisk before the last task indicates it to be the
13754 task currently being inspected.
13758 Represents @value{GDBN}'s internal task number.
13764 The parent's task ID (@value{GDBN}'s internal task number).
13767 The base priority of the task.
13770 Current state of the task.
13774 The task has been created but has not been activated. It cannot be
13778 The task is not blocked for any reason known to Ada. (It may be waiting
13779 for a mutex, though.) It is conceptually "executing" in normal mode.
13782 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
13783 that were waiting on terminate alternatives have been awakened and have
13784 terminated themselves.
13786 @item Child Activation Wait
13787 The task is waiting for created tasks to complete activation.
13789 @item Accept Statement
13790 The task is waiting on an accept or selective wait statement.
13792 @item Waiting on entry call
13793 The task is waiting on an entry call.
13795 @item Async Select Wait
13796 The task is waiting to start the abortable part of an asynchronous
13800 The task is waiting on a select statement with only a delay
13803 @item Child Termination Wait
13804 The task is sleeping having completed a master within itself, and is
13805 waiting for the tasks dependent on that master to become terminated or
13806 waiting on a terminate Phase.
13808 @item Wait Child in Term Alt
13809 The task is sleeping waiting for tasks on terminate alternatives to
13810 finish terminating.
13812 @item Accepting RV with @var{taskno}
13813 The task is accepting a rendez-vous with the task @var{taskno}.
13817 Name of the task in the program.
13821 @kindex info task @var{taskno}
13822 @item info task @var{taskno}
13823 This command shows detailled informations on the specified task, as in
13824 the following example:
13829 (@value{GDBP}) info tasks
13830 ID TID P-ID Pri State Name
13831 1 8077880 0 15 Child Activation Wait main_task
13832 * 2 807c468 1 15 Runnable task_1
13833 (@value{GDBP}) info task 2
13834 Ada Task: 0x807c468
13837 Parent: 1 (main_task)
13843 @kindex task@r{ (Ada)}
13844 @cindex current Ada task ID
13845 This command prints the ID of the current task.
13851 (@value{GDBP}) info tasks
13852 ID TID P-ID Pri State Name
13853 1 8077870 0 15 Child Activation Wait main_task
13854 * 2 807c458 1 15 Runnable t
13855 (@value{GDBP}) task
13856 [Current task is 2]
13859 @item task @var{taskno}
13860 @cindex Ada task switching
13861 This command is like the @code{thread @var{threadno}}
13862 command (@pxref{Threads}). It switches the context of debugging
13863 from the current task to the given task.
13869 (@value{GDBP}) info tasks
13870 ID TID P-ID Pri State Name
13871 1 8077870 0 15 Child Activation Wait main_task
13872 * 2 807c458 1 15 Runnable t
13873 (@value{GDBP}) task 1
13874 [Switching to task 1]
13875 #0 0x8067726 in pthread_cond_wait ()
13877 #0 0x8067726 in pthread_cond_wait ()
13878 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
13879 #2 0x805cb63 in system.task_primitives.operations.sleep ()
13880 #3 0x806153e in system.tasking.stages.activate_tasks ()
13881 #4 0x804aacc in un () at un.adb:5
13884 @item break @var{linespec} task @var{taskno}
13885 @itemx break @var{linespec} task @var{taskno} if @dots{}
13886 @cindex breakpoints and tasks, in Ada
13887 @cindex task breakpoints, in Ada
13888 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
13889 These commands are like the @code{break @dots{} thread @dots{}}
13890 command (@pxref{Thread Stops}).
13891 @var{linespec} specifies source lines, as described
13892 in @ref{Specify Location}.
13894 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
13895 to specify that you only want @value{GDBN} to stop the program when a
13896 particular Ada task reaches this breakpoint. @var{taskno} is one of the
13897 numeric task identifiers assigned by @value{GDBN}, shown in the first
13898 column of the @samp{info tasks} display.
13900 If you do not specify @samp{task @var{taskno}} when you set a
13901 breakpoint, the breakpoint applies to @emph{all} tasks of your
13904 You can use the @code{task} qualifier on conditional breakpoints as
13905 well; in this case, place @samp{task @var{taskno}} before the
13906 breakpoint condition (before the @code{if}).
13914 (@value{GDBP}) info tasks
13915 ID TID P-ID Pri State Name
13916 1 140022020 0 15 Child Activation Wait main_task
13917 2 140045060 1 15 Accept/Select Wait t2
13918 3 140044840 1 15 Runnable t1
13919 * 4 140056040 1 15 Runnable t3
13920 (@value{GDBP}) b 15 task 2
13921 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
13922 (@value{GDBP}) cont
13927 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
13929 (@value{GDBP}) info tasks
13930 ID TID P-ID Pri State Name
13931 1 140022020 0 15 Child Activation Wait main_task
13932 * 2 140045060 1 15 Runnable t2
13933 3 140044840 1 15 Runnable t1
13934 4 140056040 1 15 Delay Sleep t3
13938 @node Ada Tasks and Core Files
13939 @subsubsection Tasking Support when Debugging Core Files
13940 @cindex Ada tasking and core file debugging
13942 When inspecting a core file, as opposed to debugging a live program,
13943 tasking support may be limited or even unavailable, depending on
13944 the platform being used.
13945 For instance, on x86-linux, the list of tasks is available, but task
13946 switching is not supported. On Tru64, however, task switching will work
13949 On certain platforms, including Tru64, the debugger needs to perform some
13950 memory writes in order to provide Ada tasking support. When inspecting
13951 a core file, this means that the core file must be opened with read-write
13952 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
13953 Under these circumstances, you should make a backup copy of the core
13954 file before inspecting it with @value{GDBN}.
13956 @node Ravenscar Profile
13957 @subsubsection Tasking Support when using the Ravenscar Profile
13958 @cindex Ravenscar Profile
13960 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
13961 specifically designed for systems with safety-critical real-time
13965 @kindex set ravenscar task-switching on
13966 @cindex task switching with program using Ravenscar Profile
13967 @item set ravenscar task-switching on
13968 Allows task switching when debugging a program that uses the Ravenscar
13969 Profile. This is the default.
13971 @kindex set ravenscar task-switching off
13972 @item set ravenscar task-switching off
13973 Turn off task switching when debugging a program that uses the Ravenscar
13974 Profile. This is mostly intended to disable the code that adds support
13975 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
13976 the Ravenscar runtime is preventing @value{GDBN} from working properly.
13977 To be effective, this command should be run before the program is started.
13979 @kindex show ravenscar task-switching
13980 @item show ravenscar task-switching
13981 Show whether it is possible to switch from task to task in a program
13982 using the Ravenscar Profile.
13987 @subsubsection Known Peculiarities of Ada Mode
13988 @cindex Ada, problems
13990 Besides the omissions listed previously (@pxref{Omissions from Ada}),
13991 we know of several problems with and limitations of Ada mode in
13993 some of which will be fixed with planned future releases of the debugger
13994 and the GNU Ada compiler.
13998 Static constants that the compiler chooses not to materialize as objects in
13999 storage are invisible to the debugger.
14002 Named parameter associations in function argument lists are ignored (the
14003 argument lists are treated as positional).
14006 Many useful library packages are currently invisible to the debugger.
14009 Fixed-point arithmetic, conversions, input, and output is carried out using
14010 floating-point arithmetic, and may give results that only approximate those on
14014 The GNAT compiler never generates the prefix @code{Standard} for any of
14015 the standard symbols defined by the Ada language. @value{GDBN} knows about
14016 this: it will strip the prefix from names when you use it, and will never
14017 look for a name you have so qualified among local symbols, nor match against
14018 symbols in other packages or subprograms. If you have
14019 defined entities anywhere in your program other than parameters and
14020 local variables whose simple names match names in @code{Standard},
14021 GNAT's lack of qualification here can cause confusion. When this happens,
14022 you can usually resolve the confusion
14023 by qualifying the problematic names with package
14024 @code{Standard} explicitly.
14027 Older versions of the compiler sometimes generate erroneous debugging
14028 information, resulting in the debugger incorrectly printing the value
14029 of affected entities. In some cases, the debugger is able to work
14030 around an issue automatically. In other cases, the debugger is able
14031 to work around the issue, but the work-around has to be specifically
14034 @kindex set ada trust-PAD-over-XVS
14035 @kindex show ada trust-PAD-over-XVS
14038 @item set ada trust-PAD-over-XVS on
14039 Configure GDB to strictly follow the GNAT encoding when computing the
14040 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
14041 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
14042 a complete description of the encoding used by the GNAT compiler).
14043 This is the default.
14045 @item set ada trust-PAD-over-XVS off
14046 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
14047 sometimes prints the wrong value for certain entities, changing @code{ada
14048 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
14049 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
14050 @code{off}, but this incurs a slight performance penalty, so it is
14051 recommended to leave this setting to @code{on} unless necessary.
14055 @node Unsupported Languages
14056 @section Unsupported Languages
14058 @cindex unsupported languages
14059 @cindex minimal language
14060 In addition to the other fully-supported programming languages,
14061 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
14062 It does not represent a real programming language, but provides a set
14063 of capabilities close to what the C or assembly languages provide.
14064 This should allow most simple operations to be performed while debugging
14065 an application that uses a language currently not supported by @value{GDBN}.
14067 If the language is set to @code{auto}, @value{GDBN} will automatically
14068 select this language if the current frame corresponds to an unsupported
14072 @chapter Examining the Symbol Table
14074 The commands described in this chapter allow you to inquire about the
14075 symbols (names of variables, functions and types) defined in your
14076 program. This information is inherent in the text of your program and
14077 does not change as your program executes. @value{GDBN} finds it in your
14078 program's symbol table, in the file indicated when you started @value{GDBN}
14079 (@pxref{File Options, ,Choosing Files}), or by one of the
14080 file-management commands (@pxref{Files, ,Commands to Specify Files}).
14082 @cindex symbol names
14083 @cindex names of symbols
14084 @cindex quoting names
14085 Occasionally, you may need to refer to symbols that contain unusual
14086 characters, which @value{GDBN} ordinarily treats as word delimiters. The
14087 most frequent case is in referring to static variables in other
14088 source files (@pxref{Variables,,Program Variables}). File names
14089 are recorded in object files as debugging symbols, but @value{GDBN} would
14090 ordinarily parse a typical file name, like @file{foo.c}, as the three words
14091 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
14092 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
14099 looks up the value of @code{x} in the scope of the file @file{foo.c}.
14102 @cindex case-insensitive symbol names
14103 @cindex case sensitivity in symbol names
14104 @kindex set case-sensitive
14105 @item set case-sensitive on
14106 @itemx set case-sensitive off
14107 @itemx set case-sensitive auto
14108 Normally, when @value{GDBN} looks up symbols, it matches their names
14109 with case sensitivity determined by the current source language.
14110 Occasionally, you may wish to control that. The command @code{set
14111 case-sensitive} lets you do that by specifying @code{on} for
14112 case-sensitive matches or @code{off} for case-insensitive ones. If
14113 you specify @code{auto}, case sensitivity is reset to the default
14114 suitable for the source language. The default is case-sensitive
14115 matches for all languages except for Fortran, for which the default is
14116 case-insensitive matches.
14118 @kindex show case-sensitive
14119 @item show case-sensitive
14120 This command shows the current setting of case sensitivity for symbols
14123 @kindex info address
14124 @cindex address of a symbol
14125 @item info address @var{symbol}
14126 Describe where the data for @var{symbol} is stored. For a register
14127 variable, this says which register it is kept in. For a non-register
14128 local variable, this prints the stack-frame offset at which the variable
14131 Note the contrast with @samp{print &@var{symbol}}, which does not work
14132 at all for a register variable, and for a stack local variable prints
14133 the exact address of the current instantiation of the variable.
14135 @kindex info symbol
14136 @cindex symbol from address
14137 @cindex closest symbol and offset for an address
14138 @item info symbol @var{addr}
14139 Print the name of a symbol which is stored at the address @var{addr}.
14140 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
14141 nearest symbol and an offset from it:
14144 (@value{GDBP}) info symbol 0x54320
14145 _initialize_vx + 396 in section .text
14149 This is the opposite of the @code{info address} command. You can use
14150 it to find out the name of a variable or a function given its address.
14152 For dynamically linked executables, the name of executable or shared
14153 library containing the symbol is also printed:
14156 (@value{GDBP}) info symbol 0x400225
14157 _start + 5 in section .text of /tmp/a.out
14158 (@value{GDBP}) info symbol 0x2aaaac2811cf
14159 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
14163 @item whatis [@var{arg}]
14164 Print the data type of @var{arg}, which can be either an expression
14165 or a name of a data type. With no argument, print the data type of
14166 @code{$}, the last value in the value history.
14168 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
14169 is not actually evaluated, and any side-effecting operations (such as
14170 assignments or function calls) inside it do not take place.
14172 If @var{arg} is a variable or an expression, @code{whatis} prints its
14173 literal type as it is used in the source code. If the type was
14174 defined using a @code{typedef}, @code{whatis} will @emph{not} print
14175 the data type underlying the @code{typedef}. If the type of the
14176 variable or the expression is a compound data type, such as
14177 @code{struct} or @code{class}, @code{whatis} never prints their
14178 fields or methods. It just prints the @code{struct}/@code{class}
14179 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
14180 such a compound data type, use @code{ptype}.
14182 If @var{arg} is a type name that was defined using @code{typedef},
14183 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
14184 Unrolling means that @code{whatis} will show the underlying type used
14185 in the @code{typedef} declaration of @var{arg}. However, if that
14186 underlying type is also a @code{typedef}, @code{whatis} will not
14189 For C code, the type names may also have the form @samp{class
14190 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
14191 @var{union-tag}} or @samp{enum @var{enum-tag}}.
14194 @item ptype [@var{arg}]
14195 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
14196 detailed description of the type, instead of just the name of the type.
14197 @xref{Expressions, ,Expressions}.
14199 Contrary to @code{whatis}, @code{ptype} always unrolls any
14200 @code{typedef}s in its argument declaration, whether the argument is
14201 a variable, expression, or a data type. This means that @code{ptype}
14202 of a variable or an expression will not print literally its type as
14203 present in the source code---use @code{whatis} for that. @code{typedef}s at
14204 the pointer or reference targets are also unrolled. Only @code{typedef}s of
14205 fields, methods and inner @code{class typedef}s of @code{struct}s,
14206 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
14208 For example, for this variable declaration:
14211 typedef double real_t;
14212 struct complex @{ real_t real; double imag; @};
14213 typedef struct complex complex_t;
14215 real_t *real_pointer_var;
14219 the two commands give this output:
14223 (@value{GDBP}) whatis var
14225 (@value{GDBP}) ptype var
14226 type = struct complex @{
14230 (@value{GDBP}) whatis complex_t
14231 type = struct complex
14232 (@value{GDBP}) whatis struct complex
14233 type = struct complex
14234 (@value{GDBP}) ptype struct complex
14235 type = struct complex @{
14239 (@value{GDBP}) whatis real_pointer_var
14241 (@value{GDBP}) ptype real_pointer_var
14247 As with @code{whatis}, using @code{ptype} without an argument refers to
14248 the type of @code{$}, the last value in the value history.
14250 @cindex incomplete type
14251 Sometimes, programs use opaque data types or incomplete specifications
14252 of complex data structure. If the debug information included in the
14253 program does not allow @value{GDBN} to display a full declaration of
14254 the data type, it will say @samp{<incomplete type>}. For example,
14255 given these declarations:
14259 struct foo *fooptr;
14263 but no definition for @code{struct foo} itself, @value{GDBN} will say:
14266 (@value{GDBP}) ptype foo
14267 $1 = <incomplete type>
14271 ``Incomplete type'' is C terminology for data types that are not
14272 completely specified.
14275 @item info types @var{regexp}
14277 Print a brief description of all types whose names match the regular
14278 expression @var{regexp} (or all types in your program, if you supply
14279 no argument). Each complete typename is matched as though it were a
14280 complete line; thus, @samp{i type value} gives information on all
14281 types in your program whose names include the string @code{value}, but
14282 @samp{i type ^value$} gives information only on types whose complete
14283 name is @code{value}.
14285 This command differs from @code{ptype} in two ways: first, like
14286 @code{whatis}, it does not print a detailed description; second, it
14287 lists all source files where a type is defined.
14290 @cindex local variables
14291 @item info scope @var{location}
14292 List all the variables local to a particular scope. This command
14293 accepts a @var{location} argument---a function name, a source line, or
14294 an address preceded by a @samp{*}, and prints all the variables local
14295 to the scope defined by that location. (@xref{Specify Location}, for
14296 details about supported forms of @var{location}.) For example:
14299 (@value{GDBP}) @b{info scope command_line_handler}
14300 Scope for command_line_handler:
14301 Symbol rl is an argument at stack/frame offset 8, length 4.
14302 Symbol linebuffer is in static storage at address 0x150a18, length 4.
14303 Symbol linelength is in static storage at address 0x150a1c, length 4.
14304 Symbol p is a local variable in register $esi, length 4.
14305 Symbol p1 is a local variable in register $ebx, length 4.
14306 Symbol nline is a local variable in register $edx, length 4.
14307 Symbol repeat is a local variable at frame offset -8, length 4.
14311 This command is especially useful for determining what data to collect
14312 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
14315 @kindex info source
14317 Show information about the current source file---that is, the source file for
14318 the function containing the current point of execution:
14321 the name of the source file, and the directory containing it,
14323 the directory it was compiled in,
14325 its length, in lines,
14327 which programming language it is written in,
14329 whether the executable includes debugging information for that file, and
14330 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
14332 whether the debugging information includes information about
14333 preprocessor macros.
14337 @kindex info sources
14339 Print the names of all source files in your program for which there is
14340 debugging information, organized into two lists: files whose symbols
14341 have already been read, and files whose symbols will be read when needed.
14343 @kindex info functions
14344 @item info functions
14345 Print the names and data types of all defined functions.
14347 @item info functions @var{regexp}
14348 Print the names and data types of all defined functions
14349 whose names contain a match for regular expression @var{regexp}.
14350 Thus, @samp{info fun step} finds all functions whose names
14351 include @code{step}; @samp{info fun ^step} finds those whose names
14352 start with @code{step}. If a function name contains characters
14353 that conflict with the regular expression language (e.g.@:
14354 @samp{operator*()}), they may be quoted with a backslash.
14356 @kindex info variables
14357 @item info variables
14358 Print the names and data types of all variables that are defined
14359 outside of functions (i.e.@: excluding local variables).
14361 @item info variables @var{regexp}
14362 Print the names and data types of all variables (except for local
14363 variables) whose names contain a match for regular expression
14366 @kindex info classes
14367 @cindex Objective-C, classes and selectors
14369 @itemx info classes @var{regexp}
14370 Display all Objective-C classes in your program, or
14371 (with the @var{regexp} argument) all those matching a particular regular
14374 @kindex info selectors
14375 @item info selectors
14376 @itemx info selectors @var{regexp}
14377 Display all Objective-C selectors in your program, or
14378 (with the @var{regexp} argument) all those matching a particular regular
14382 This was never implemented.
14383 @kindex info methods
14385 @itemx info methods @var{regexp}
14386 The @code{info methods} command permits the user to examine all defined
14387 methods within C@t{++} program, or (with the @var{regexp} argument) a
14388 specific set of methods found in the various C@t{++} classes. Many
14389 C@t{++} classes provide a large number of methods. Thus, the output
14390 from the @code{ptype} command can be overwhelming and hard to use. The
14391 @code{info-methods} command filters the methods, printing only those
14392 which match the regular-expression @var{regexp}.
14395 @cindex reloading symbols
14396 Some systems allow individual object files that make up your program to
14397 be replaced without stopping and restarting your program. For example,
14398 in VxWorks you can simply recompile a defective object file and keep on
14399 running. If you are running on one of these systems, you can allow
14400 @value{GDBN} to reload the symbols for automatically relinked modules:
14403 @kindex set symbol-reloading
14404 @item set symbol-reloading on
14405 Replace symbol definitions for the corresponding source file when an
14406 object file with a particular name is seen again.
14408 @item set symbol-reloading off
14409 Do not replace symbol definitions when encountering object files of the
14410 same name more than once. This is the default state; if you are not
14411 running on a system that permits automatic relinking of modules, you
14412 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
14413 may discard symbols when linking large programs, that may contain
14414 several modules (from different directories or libraries) with the same
14417 @kindex show symbol-reloading
14418 @item show symbol-reloading
14419 Show the current @code{on} or @code{off} setting.
14422 @cindex opaque data types
14423 @kindex set opaque-type-resolution
14424 @item set opaque-type-resolution on
14425 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
14426 declared as a pointer to a @code{struct}, @code{class}, or
14427 @code{union}---for example, @code{struct MyType *}---that is used in one
14428 source file although the full declaration of @code{struct MyType} is in
14429 another source file. The default is on.
14431 A change in the setting of this subcommand will not take effect until
14432 the next time symbols for a file are loaded.
14434 @item set opaque-type-resolution off
14435 Tell @value{GDBN} not to resolve opaque types. In this case, the type
14436 is printed as follows:
14438 @{<no data fields>@}
14441 @kindex show opaque-type-resolution
14442 @item show opaque-type-resolution
14443 Show whether opaque types are resolved or not.
14445 @kindex maint print symbols
14446 @cindex symbol dump
14447 @kindex maint print psymbols
14448 @cindex partial symbol dump
14449 @item maint print symbols @var{filename}
14450 @itemx maint print psymbols @var{filename}
14451 @itemx maint print msymbols @var{filename}
14452 Write a dump of debugging symbol data into the file @var{filename}.
14453 These commands are used to debug the @value{GDBN} symbol-reading code. Only
14454 symbols with debugging data are included. If you use @samp{maint print
14455 symbols}, @value{GDBN} includes all the symbols for which it has already
14456 collected full details: that is, @var{filename} reflects symbols for
14457 only those files whose symbols @value{GDBN} has read. You can use the
14458 command @code{info sources} to find out which files these are. If you
14459 use @samp{maint print psymbols} instead, the dump shows information about
14460 symbols that @value{GDBN} only knows partially---that is, symbols defined in
14461 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
14462 @samp{maint print msymbols} dumps just the minimal symbol information
14463 required for each object file from which @value{GDBN} has read some symbols.
14464 @xref{Files, ,Commands to Specify Files}, for a discussion of how
14465 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
14467 @kindex maint info symtabs
14468 @kindex maint info psymtabs
14469 @cindex listing @value{GDBN}'s internal symbol tables
14470 @cindex symbol tables, listing @value{GDBN}'s internal
14471 @cindex full symbol tables, listing @value{GDBN}'s internal
14472 @cindex partial symbol tables, listing @value{GDBN}'s internal
14473 @item maint info symtabs @r{[} @var{regexp} @r{]}
14474 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
14476 List the @code{struct symtab} or @code{struct partial_symtab}
14477 structures whose names match @var{regexp}. If @var{regexp} is not
14478 given, list them all. The output includes expressions which you can
14479 copy into a @value{GDBN} debugging this one to examine a particular
14480 structure in more detail. For example:
14483 (@value{GDBP}) maint info psymtabs dwarf2read
14484 @{ objfile /home/gnu/build/gdb/gdb
14485 ((struct objfile *) 0x82e69d0)
14486 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
14487 ((struct partial_symtab *) 0x8474b10)
14490 text addresses 0x814d3c8 -- 0x8158074
14491 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
14492 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
14493 dependencies (none)
14496 (@value{GDBP}) maint info symtabs
14500 We see that there is one partial symbol table whose filename contains
14501 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
14502 and we see that @value{GDBN} has not read in any symtabs yet at all.
14503 If we set a breakpoint on a function, that will cause @value{GDBN} to
14504 read the symtab for the compilation unit containing that function:
14507 (@value{GDBP}) break dwarf2_psymtab_to_symtab
14508 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
14510 (@value{GDBP}) maint info symtabs
14511 @{ objfile /home/gnu/build/gdb/gdb
14512 ((struct objfile *) 0x82e69d0)
14513 @{ symtab /home/gnu/src/gdb/dwarf2read.c
14514 ((struct symtab *) 0x86c1f38)
14517 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
14518 linetable ((struct linetable *) 0x8370fa0)
14519 debugformat DWARF 2
14528 @chapter Altering Execution
14530 Once you think you have found an error in your program, you might want to
14531 find out for certain whether correcting the apparent error would lead to
14532 correct results in the rest of the run. You can find the answer by
14533 experiment, using the @value{GDBN} features for altering execution of the
14536 For example, you can store new values into variables or memory
14537 locations, give your program a signal, restart it at a different
14538 address, or even return prematurely from a function.
14541 * Assignment:: Assignment to variables
14542 * Jumping:: Continuing at a different address
14543 * Signaling:: Giving your program a signal
14544 * Returning:: Returning from a function
14545 * Calling:: Calling your program's functions
14546 * Patching:: Patching your program
14550 @section Assignment to Variables
14553 @cindex setting variables
14554 To alter the value of a variable, evaluate an assignment expression.
14555 @xref{Expressions, ,Expressions}. For example,
14562 stores the value 4 into the variable @code{x}, and then prints the
14563 value of the assignment expression (which is 4).
14564 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
14565 information on operators in supported languages.
14567 @kindex set variable
14568 @cindex variables, setting
14569 If you are not interested in seeing the value of the assignment, use the
14570 @code{set} command instead of the @code{print} command. @code{set} is
14571 really the same as @code{print} except that the expression's value is
14572 not printed and is not put in the value history (@pxref{Value History,
14573 ,Value History}). The expression is evaluated only for its effects.
14575 If the beginning of the argument string of the @code{set} command
14576 appears identical to a @code{set} subcommand, use the @code{set
14577 variable} command instead of just @code{set}. This command is identical
14578 to @code{set} except for its lack of subcommands. For example, if your
14579 program has a variable @code{width}, you get an error if you try to set
14580 a new value with just @samp{set width=13}, because @value{GDBN} has the
14581 command @code{set width}:
14584 (@value{GDBP}) whatis width
14586 (@value{GDBP}) p width
14588 (@value{GDBP}) set width=47
14589 Invalid syntax in expression.
14593 The invalid expression, of course, is @samp{=47}. In
14594 order to actually set the program's variable @code{width}, use
14597 (@value{GDBP}) set var width=47
14600 Because the @code{set} command has many subcommands that can conflict
14601 with the names of program variables, it is a good idea to use the
14602 @code{set variable} command instead of just @code{set}. For example, if
14603 your program has a variable @code{g}, you run into problems if you try
14604 to set a new value with just @samp{set g=4}, because @value{GDBN} has
14605 the command @code{set gnutarget}, abbreviated @code{set g}:
14609 (@value{GDBP}) whatis g
14613 (@value{GDBP}) set g=4
14617 The program being debugged has been started already.
14618 Start it from the beginning? (y or n) y
14619 Starting program: /home/smith/cc_progs/a.out
14620 "/home/smith/cc_progs/a.out": can't open to read symbols:
14621 Invalid bfd target.
14622 (@value{GDBP}) show g
14623 The current BFD target is "=4".
14628 The program variable @code{g} did not change, and you silently set the
14629 @code{gnutarget} to an invalid value. In order to set the variable
14633 (@value{GDBP}) set var g=4
14636 @value{GDBN} allows more implicit conversions in assignments than C; you can
14637 freely store an integer value into a pointer variable or vice versa,
14638 and you can convert any structure to any other structure that is the
14639 same length or shorter.
14640 @comment FIXME: how do structs align/pad in these conversions?
14641 @comment /doc@cygnus.com 18dec1990
14643 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
14644 construct to generate a value of specified type at a specified address
14645 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
14646 to memory location @code{0x83040} as an integer (which implies a certain size
14647 and representation in memory), and
14650 set @{int@}0x83040 = 4
14654 stores the value 4 into that memory location.
14657 @section Continuing at a Different Address
14659 Ordinarily, when you continue your program, you do so at the place where
14660 it stopped, with the @code{continue} command. You can instead continue at
14661 an address of your own choosing, with the following commands:
14665 @item jump @var{linespec}
14666 @itemx jump @var{location}
14667 Resume execution at line @var{linespec} or at address given by
14668 @var{location}. Execution stops again immediately if there is a
14669 breakpoint there. @xref{Specify Location}, for a description of the
14670 different forms of @var{linespec} and @var{location}. It is common
14671 practice to use the @code{tbreak} command in conjunction with
14672 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
14674 The @code{jump} command does not change the current stack frame, or
14675 the stack pointer, or the contents of any memory location or any
14676 register other than the program counter. If line @var{linespec} is in
14677 a different function from the one currently executing, the results may
14678 be bizarre if the two functions expect different patterns of arguments or
14679 of local variables. For this reason, the @code{jump} command requests
14680 confirmation if the specified line is not in the function currently
14681 executing. However, even bizarre results are predictable if you are
14682 well acquainted with the machine-language code of your program.
14685 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
14686 On many systems, you can get much the same effect as the @code{jump}
14687 command by storing a new value into the register @code{$pc}. The
14688 difference is that this does not start your program running; it only
14689 changes the address of where it @emph{will} run when you continue. For
14697 makes the next @code{continue} command or stepping command execute at
14698 address @code{0x485}, rather than at the address where your program stopped.
14699 @xref{Continuing and Stepping, ,Continuing and Stepping}.
14701 The most common occasion to use the @code{jump} command is to back
14702 up---perhaps with more breakpoints set---over a portion of a program
14703 that has already executed, in order to examine its execution in more
14708 @section Giving your Program a Signal
14709 @cindex deliver a signal to a program
14713 @item signal @var{signal}
14714 Resume execution where your program stopped, but immediately give it the
14715 signal @var{signal}. @var{signal} can be the name or the number of a
14716 signal. For example, on many systems @code{signal 2} and @code{signal
14717 SIGINT} are both ways of sending an interrupt signal.
14719 Alternatively, if @var{signal} is zero, continue execution without
14720 giving a signal. This is useful when your program stopped on account of
14721 a signal and would ordinary see the signal when resumed with the
14722 @code{continue} command; @samp{signal 0} causes it to resume without a
14725 @code{signal} does not repeat when you press @key{RET} a second time
14726 after executing the command.
14730 Invoking the @code{signal} command is not the same as invoking the
14731 @code{kill} utility from the shell. Sending a signal with @code{kill}
14732 causes @value{GDBN} to decide what to do with the signal depending on
14733 the signal handling tables (@pxref{Signals}). The @code{signal} command
14734 passes the signal directly to your program.
14738 @section Returning from a Function
14741 @cindex returning from a function
14744 @itemx return @var{expression}
14745 You can cancel execution of a function call with the @code{return}
14746 command. If you give an
14747 @var{expression} argument, its value is used as the function's return
14751 When you use @code{return}, @value{GDBN} discards the selected stack frame
14752 (and all frames within it). You can think of this as making the
14753 discarded frame return prematurely. If you wish to specify a value to
14754 be returned, give that value as the argument to @code{return}.
14756 This pops the selected stack frame (@pxref{Selection, ,Selecting a
14757 Frame}), and any other frames inside of it, leaving its caller as the
14758 innermost remaining frame. That frame becomes selected. The
14759 specified value is stored in the registers used for returning values
14762 The @code{return} command does not resume execution; it leaves the
14763 program stopped in the state that would exist if the function had just
14764 returned. In contrast, the @code{finish} command (@pxref{Continuing
14765 and Stepping, ,Continuing and Stepping}) resumes execution until the
14766 selected stack frame returns naturally.
14768 @value{GDBN} needs to know how the @var{expression} argument should be set for
14769 the inferior. The concrete registers assignment depends on the OS ABI and the
14770 type being returned by the selected stack frame. For example it is common for
14771 OS ABI to return floating point values in FPU registers while integer values in
14772 CPU registers. Still some ABIs return even floating point values in CPU
14773 registers. Larger integer widths (such as @code{long long int}) also have
14774 specific placement rules. @value{GDBN} already knows the OS ABI from its
14775 current target so it needs to find out also the type being returned to make the
14776 assignment into the right register(s).
14778 Normally, the selected stack frame has debug info. @value{GDBN} will always
14779 use the debug info instead of the implicit type of @var{expression} when the
14780 debug info is available. For example, if you type @kbd{return -1}, and the
14781 function in the current stack frame is declared to return a @code{long long
14782 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
14783 into a @code{long long int}:
14786 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
14788 (@value{GDBP}) return -1
14789 Make func return now? (y or n) y
14790 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
14791 43 printf ("result=%lld\n", func ());
14795 However, if the selected stack frame does not have a debug info, e.g., if the
14796 function was compiled without debug info, @value{GDBN} has to find out the type
14797 to return from user. Specifying a different type by mistake may set the value
14798 in different inferior registers than the caller code expects. For example,
14799 typing @kbd{return -1} with its implicit type @code{int} would set only a part
14800 of a @code{long long int} result for a debug info less function (on 32-bit
14801 architectures). Therefore the user is required to specify the return type by
14802 an appropriate cast explicitly:
14805 Breakpoint 2, 0x0040050b in func ()
14806 (@value{GDBP}) return -1
14807 Return value type not available for selected stack frame.
14808 Please use an explicit cast of the value to return.
14809 (@value{GDBP}) return (long long int) -1
14810 Make selected stack frame return now? (y or n) y
14811 #0 0x00400526 in main ()
14816 @section Calling Program Functions
14819 @cindex calling functions
14820 @cindex inferior functions, calling
14821 @item print @var{expr}
14822 Evaluate the expression @var{expr} and display the resulting value.
14823 @var{expr} may include calls to functions in the program being
14827 @item call @var{expr}
14828 Evaluate the expression @var{expr} without displaying @code{void}
14831 You can use this variant of the @code{print} command if you want to
14832 execute a function from your program that does not return anything
14833 (a.k.a.@: @dfn{a void function}), but without cluttering the output
14834 with @code{void} returned values that @value{GDBN} will otherwise
14835 print. If the result is not void, it is printed and saved in the
14839 It is possible for the function you call via the @code{print} or
14840 @code{call} command to generate a signal (e.g., if there's a bug in
14841 the function, or if you passed it incorrect arguments). What happens
14842 in that case is controlled by the @code{set unwindonsignal} command.
14844 Similarly, with a C@t{++} program it is possible for the function you
14845 call via the @code{print} or @code{call} command to generate an
14846 exception that is not handled due to the constraints of the dummy
14847 frame. In this case, any exception that is raised in the frame, but has
14848 an out-of-frame exception handler will not be found. GDB builds a
14849 dummy-frame for the inferior function call, and the unwinder cannot
14850 seek for exception handlers outside of this dummy-frame. What happens
14851 in that case is controlled by the
14852 @code{set unwind-on-terminating-exception} command.
14855 @item set unwindonsignal
14856 @kindex set unwindonsignal
14857 @cindex unwind stack in called functions
14858 @cindex call dummy stack unwinding
14859 Set unwinding of the stack if a signal is received while in a function
14860 that @value{GDBN} called in the program being debugged. If set to on,
14861 @value{GDBN} unwinds the stack it created for the call and restores
14862 the context to what it was before the call. If set to off (the
14863 default), @value{GDBN} stops in the frame where the signal was
14866 @item show unwindonsignal
14867 @kindex show unwindonsignal
14868 Show the current setting of stack unwinding in the functions called by
14871 @item set unwind-on-terminating-exception
14872 @kindex set unwind-on-terminating-exception
14873 @cindex unwind stack in called functions with unhandled exceptions
14874 @cindex call dummy stack unwinding on unhandled exception.
14875 Set unwinding of the stack if a C@t{++} exception is raised, but left
14876 unhandled while in a function that @value{GDBN} called in the program being
14877 debugged. If set to on (the default), @value{GDBN} unwinds the stack
14878 it created for the call and restores the context to what it was before
14879 the call. If set to off, @value{GDBN} the exception is delivered to
14880 the default C@t{++} exception handler and the inferior terminated.
14882 @item show unwind-on-terminating-exception
14883 @kindex show unwind-on-terminating-exception
14884 Show the current setting of stack unwinding in the functions called by
14889 @cindex weak alias functions
14890 Sometimes, a function you wish to call is actually a @dfn{weak alias}
14891 for another function. In such case, @value{GDBN} might not pick up
14892 the type information, including the types of the function arguments,
14893 which causes @value{GDBN} to call the inferior function incorrectly.
14894 As a result, the called function will function erroneously and may
14895 even crash. A solution to that is to use the name of the aliased
14899 @section Patching Programs
14901 @cindex patching binaries
14902 @cindex writing into executables
14903 @cindex writing into corefiles
14905 By default, @value{GDBN} opens the file containing your program's
14906 executable code (or the corefile) read-only. This prevents accidental
14907 alterations to machine code; but it also prevents you from intentionally
14908 patching your program's binary.
14910 If you'd like to be able to patch the binary, you can specify that
14911 explicitly with the @code{set write} command. For example, you might
14912 want to turn on internal debugging flags, or even to make emergency
14918 @itemx set write off
14919 If you specify @samp{set write on}, @value{GDBN} opens executable and
14920 core files for both reading and writing; if you specify @kbd{set write
14921 off} (the default), @value{GDBN} opens them read-only.
14923 If you have already loaded a file, you must load it again (using the
14924 @code{exec-file} or @code{core-file} command) after changing @code{set
14925 write}, for your new setting to take effect.
14929 Display whether executable files and core files are opened for writing
14930 as well as reading.
14934 @chapter @value{GDBN} Files
14936 @value{GDBN} needs to know the file name of the program to be debugged,
14937 both in order to read its symbol table and in order to start your
14938 program. To debug a core dump of a previous run, you must also tell
14939 @value{GDBN} the name of the core dump file.
14942 * Files:: Commands to specify files
14943 * Separate Debug Files:: Debugging information in separate files
14944 * Index Files:: Index files speed up GDB
14945 * Symbol Errors:: Errors reading symbol files
14946 * Data Files:: GDB data files
14950 @section Commands to Specify Files
14952 @cindex symbol table
14953 @cindex core dump file
14955 You may want to specify executable and core dump file names. The usual
14956 way to do this is at start-up time, using the arguments to
14957 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
14958 Out of @value{GDBN}}).
14960 Occasionally it is necessary to change to a different file during a
14961 @value{GDBN} session. Or you may run @value{GDBN} and forget to
14962 specify a file you want to use. Or you are debugging a remote target
14963 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
14964 Program}). In these situations the @value{GDBN} commands to specify
14965 new files are useful.
14968 @cindex executable file
14970 @item file @var{filename}
14971 Use @var{filename} as the program to be debugged. It is read for its
14972 symbols and for the contents of pure memory. It is also the program
14973 executed when you use the @code{run} command. If you do not specify a
14974 directory and the file is not found in the @value{GDBN} working directory,
14975 @value{GDBN} uses the environment variable @code{PATH} as a list of
14976 directories to search, just as the shell does when looking for a program
14977 to run. You can change the value of this variable, for both @value{GDBN}
14978 and your program, using the @code{path} command.
14980 @cindex unlinked object files
14981 @cindex patching object files
14982 You can load unlinked object @file{.o} files into @value{GDBN} using
14983 the @code{file} command. You will not be able to ``run'' an object
14984 file, but you can disassemble functions and inspect variables. Also,
14985 if the underlying BFD functionality supports it, you could use
14986 @kbd{gdb -write} to patch object files using this technique. Note
14987 that @value{GDBN} can neither interpret nor modify relocations in this
14988 case, so branches and some initialized variables will appear to go to
14989 the wrong place. But this feature is still handy from time to time.
14992 @code{file} with no argument makes @value{GDBN} discard any information it
14993 has on both executable file and the symbol table.
14996 @item exec-file @r{[} @var{filename} @r{]}
14997 Specify that the program to be run (but not the symbol table) is found
14998 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
14999 if necessary to locate your program. Omitting @var{filename} means to
15000 discard information on the executable file.
15002 @kindex symbol-file
15003 @item symbol-file @r{[} @var{filename} @r{]}
15004 Read symbol table information from file @var{filename}. @code{PATH} is
15005 searched when necessary. Use the @code{file} command to get both symbol
15006 table and program to run from the same file.
15008 @code{symbol-file} with no argument clears out @value{GDBN} information on your
15009 program's symbol table.
15011 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
15012 some breakpoints and auto-display expressions. This is because they may
15013 contain pointers to the internal data recording symbols and data types,
15014 which are part of the old symbol table data being discarded inside
15017 @code{symbol-file} does not repeat if you press @key{RET} again after
15020 When @value{GDBN} is configured for a particular environment, it
15021 understands debugging information in whatever format is the standard
15022 generated for that environment; you may use either a @sc{gnu} compiler, or
15023 other compilers that adhere to the local conventions.
15024 Best results are usually obtained from @sc{gnu} compilers; for example,
15025 using @code{@value{NGCC}} you can generate debugging information for
15028 For most kinds of object files, with the exception of old SVR3 systems
15029 using COFF, the @code{symbol-file} command does not normally read the
15030 symbol table in full right away. Instead, it scans the symbol table
15031 quickly to find which source files and which symbols are present. The
15032 details are read later, one source file at a time, as they are needed.
15034 The purpose of this two-stage reading strategy is to make @value{GDBN}
15035 start up faster. For the most part, it is invisible except for
15036 occasional pauses while the symbol table details for a particular source
15037 file are being read. (The @code{set verbose} command can turn these
15038 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
15039 Warnings and Messages}.)
15041 We have not implemented the two-stage strategy for COFF yet. When the
15042 symbol table is stored in COFF format, @code{symbol-file} reads the
15043 symbol table data in full right away. Note that ``stabs-in-COFF''
15044 still does the two-stage strategy, since the debug info is actually
15048 @cindex reading symbols immediately
15049 @cindex symbols, reading immediately
15050 @item symbol-file @r{[} -readnow @r{]} @var{filename}
15051 @itemx file @r{[} -readnow @r{]} @var{filename}
15052 You can override the @value{GDBN} two-stage strategy for reading symbol
15053 tables by using the @samp{-readnow} option with any of the commands that
15054 load symbol table information, if you want to be sure @value{GDBN} has the
15055 entire symbol table available.
15057 @c FIXME: for now no mention of directories, since this seems to be in
15058 @c flux. 13mar1992 status is that in theory GDB would look either in
15059 @c current dir or in same dir as myprog; but issues like competing
15060 @c GDB's, or clutter in system dirs, mean that in practice right now
15061 @c only current dir is used. FFish says maybe a special GDB hierarchy
15062 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
15066 @item core-file @r{[}@var{filename}@r{]}
15068 Specify the whereabouts of a core dump file to be used as the ``contents
15069 of memory''. Traditionally, core files contain only some parts of the
15070 address space of the process that generated them; @value{GDBN} can access the
15071 executable file itself for other parts.
15073 @code{core-file} with no argument specifies that no core file is
15076 Note that the core file is ignored when your program is actually running
15077 under @value{GDBN}. So, if you have been running your program and you
15078 wish to debug a core file instead, you must kill the subprocess in which
15079 the program is running. To do this, use the @code{kill} command
15080 (@pxref{Kill Process, ,Killing the Child Process}).
15082 @kindex add-symbol-file
15083 @cindex dynamic linking
15084 @item add-symbol-file @var{filename} @var{address}
15085 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
15086 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
15087 The @code{add-symbol-file} command reads additional symbol table
15088 information from the file @var{filename}. You would use this command
15089 when @var{filename} has been dynamically loaded (by some other means)
15090 into the program that is running. @var{address} should be the memory
15091 address at which the file has been loaded; @value{GDBN} cannot figure
15092 this out for itself. You can additionally specify an arbitrary number
15093 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
15094 section name and base address for that section. You can specify any
15095 @var{address} as an expression.
15097 The symbol table of the file @var{filename} is added to the symbol table
15098 originally read with the @code{symbol-file} command. You can use the
15099 @code{add-symbol-file} command any number of times; the new symbol data
15100 thus read keeps adding to the old. To discard all old symbol data
15101 instead, use the @code{symbol-file} command without any arguments.
15103 @cindex relocatable object files, reading symbols from
15104 @cindex object files, relocatable, reading symbols from
15105 @cindex reading symbols from relocatable object files
15106 @cindex symbols, reading from relocatable object files
15107 @cindex @file{.o} files, reading symbols from
15108 Although @var{filename} is typically a shared library file, an
15109 executable file, or some other object file which has been fully
15110 relocated for loading into a process, you can also load symbolic
15111 information from relocatable @file{.o} files, as long as:
15115 the file's symbolic information refers only to linker symbols defined in
15116 that file, not to symbols defined by other object files,
15118 every section the file's symbolic information refers to has actually
15119 been loaded into the inferior, as it appears in the file, and
15121 you can determine the address at which every section was loaded, and
15122 provide these to the @code{add-symbol-file} command.
15126 Some embedded operating systems, like Sun Chorus and VxWorks, can load
15127 relocatable files into an already running program; such systems
15128 typically make the requirements above easy to meet. However, it's
15129 important to recognize that many native systems use complex link
15130 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
15131 assembly, for example) that make the requirements difficult to meet. In
15132 general, one cannot assume that using @code{add-symbol-file} to read a
15133 relocatable object file's symbolic information will have the same effect
15134 as linking the relocatable object file into the program in the normal
15137 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
15139 @kindex add-symbol-file-from-memory
15140 @cindex @code{syscall DSO}
15141 @cindex load symbols from memory
15142 @item add-symbol-file-from-memory @var{address}
15143 Load symbols from the given @var{address} in a dynamically loaded
15144 object file whose image is mapped directly into the inferior's memory.
15145 For example, the Linux kernel maps a @code{syscall DSO} into each
15146 process's address space; this DSO provides kernel-specific code for
15147 some system calls. The argument can be any expression whose
15148 evaluation yields the address of the file's shared object file header.
15149 For this command to work, you must have used @code{symbol-file} or
15150 @code{exec-file} commands in advance.
15152 @kindex add-shared-symbol-files
15154 @item add-shared-symbol-files @var{library-file}
15155 @itemx assf @var{library-file}
15156 The @code{add-shared-symbol-files} command can currently be used only
15157 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
15158 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
15159 @value{GDBN} automatically looks for shared libraries, however if
15160 @value{GDBN} does not find yours, you can invoke
15161 @code{add-shared-symbol-files}. It takes one argument: the shared
15162 library's file name. @code{assf} is a shorthand alias for
15163 @code{add-shared-symbol-files}.
15166 @item section @var{section} @var{addr}
15167 The @code{section} command changes the base address of the named
15168 @var{section} of the exec file to @var{addr}. This can be used if the
15169 exec file does not contain section addresses, (such as in the
15170 @code{a.out} format), or when the addresses specified in the file
15171 itself are wrong. Each section must be changed separately. The
15172 @code{info files} command, described below, lists all the sections and
15176 @kindex info target
15179 @code{info files} and @code{info target} are synonymous; both print the
15180 current target (@pxref{Targets, ,Specifying a Debugging Target}),
15181 including the names of the executable and core dump files currently in
15182 use by @value{GDBN}, and the files from which symbols were loaded. The
15183 command @code{help target} lists all possible targets rather than
15186 @kindex maint info sections
15187 @item maint info sections
15188 Another command that can give you extra information about program sections
15189 is @code{maint info sections}. In addition to the section information
15190 displayed by @code{info files}, this command displays the flags and file
15191 offset of each section in the executable and core dump files. In addition,
15192 @code{maint info sections} provides the following command options (which
15193 may be arbitrarily combined):
15197 Display sections for all loaded object files, including shared libraries.
15198 @item @var{sections}
15199 Display info only for named @var{sections}.
15200 @item @var{section-flags}
15201 Display info only for sections for which @var{section-flags} are true.
15202 The section flags that @value{GDBN} currently knows about are:
15205 Section will have space allocated in the process when loaded.
15206 Set for all sections except those containing debug information.
15208 Section will be loaded from the file into the child process memory.
15209 Set for pre-initialized code and data, clear for @code{.bss} sections.
15211 Section needs to be relocated before loading.
15213 Section cannot be modified by the child process.
15215 Section contains executable code only.
15217 Section contains data only (no executable code).
15219 Section will reside in ROM.
15221 Section contains data for constructor/destructor lists.
15223 Section is not empty.
15225 An instruction to the linker to not output the section.
15226 @item COFF_SHARED_LIBRARY
15227 A notification to the linker that the section contains
15228 COFF shared library information.
15230 Section contains common symbols.
15233 @kindex set trust-readonly-sections
15234 @cindex read-only sections
15235 @item set trust-readonly-sections on
15236 Tell @value{GDBN} that readonly sections in your object file
15237 really are read-only (i.e.@: that their contents will not change).
15238 In that case, @value{GDBN} can fetch values from these sections
15239 out of the object file, rather than from the target program.
15240 For some targets (notably embedded ones), this can be a significant
15241 enhancement to debugging performance.
15243 The default is off.
15245 @item set trust-readonly-sections off
15246 Tell @value{GDBN} not to trust readonly sections. This means that
15247 the contents of the section might change while the program is running,
15248 and must therefore be fetched from the target when needed.
15250 @item show trust-readonly-sections
15251 Show the current setting of trusting readonly sections.
15254 All file-specifying commands allow both absolute and relative file names
15255 as arguments. @value{GDBN} always converts the file name to an absolute file
15256 name and remembers it that way.
15258 @cindex shared libraries
15259 @anchor{Shared Libraries}
15260 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
15261 and IBM RS/6000 AIX shared libraries.
15263 On MS-Windows @value{GDBN} must be linked with the Expat library to support
15264 shared libraries. @xref{Expat}.
15266 @value{GDBN} automatically loads symbol definitions from shared libraries
15267 when you use the @code{run} command, or when you examine a core file.
15268 (Before you issue the @code{run} command, @value{GDBN} does not understand
15269 references to a function in a shared library, however---unless you are
15270 debugging a core file).
15272 On HP-UX, if the program loads a library explicitly, @value{GDBN}
15273 automatically loads the symbols at the time of the @code{shl_load} call.
15275 @c FIXME: some @value{GDBN} release may permit some refs to undef
15276 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
15277 @c FIXME...lib; check this from time to time when updating manual
15279 There are times, however, when you may wish to not automatically load
15280 symbol definitions from shared libraries, such as when they are
15281 particularly large or there are many of them.
15283 To control the automatic loading of shared library symbols, use the
15287 @kindex set auto-solib-add
15288 @item set auto-solib-add @var{mode}
15289 If @var{mode} is @code{on}, symbols from all shared object libraries
15290 will be loaded automatically when the inferior begins execution, you
15291 attach to an independently started inferior, or when the dynamic linker
15292 informs @value{GDBN} that a new library has been loaded. If @var{mode}
15293 is @code{off}, symbols must be loaded manually, using the
15294 @code{sharedlibrary} command. The default value is @code{on}.
15296 @cindex memory used for symbol tables
15297 If your program uses lots of shared libraries with debug info that
15298 takes large amounts of memory, you can decrease the @value{GDBN}
15299 memory footprint by preventing it from automatically loading the
15300 symbols from shared libraries. To that end, type @kbd{set
15301 auto-solib-add off} before running the inferior, then load each
15302 library whose debug symbols you do need with @kbd{sharedlibrary
15303 @var{regexp}}, where @var{regexp} is a regular expression that matches
15304 the libraries whose symbols you want to be loaded.
15306 @kindex show auto-solib-add
15307 @item show auto-solib-add
15308 Display the current autoloading mode.
15311 @cindex load shared library
15312 To explicitly load shared library symbols, use the @code{sharedlibrary}
15316 @kindex info sharedlibrary
15318 @item info share @var{regex}
15319 @itemx info sharedlibrary @var{regex}
15320 Print the names of the shared libraries which are currently loaded
15321 that match @var{regex}. If @var{regex} is omitted then print
15322 all shared libraries that are loaded.
15324 @kindex sharedlibrary
15326 @item sharedlibrary @var{regex}
15327 @itemx share @var{regex}
15328 Load shared object library symbols for files matching a
15329 Unix regular expression.
15330 As with files loaded automatically, it only loads shared libraries
15331 required by your program for a core file or after typing @code{run}. If
15332 @var{regex} is omitted all shared libraries required by your program are
15335 @item nosharedlibrary
15336 @kindex nosharedlibrary
15337 @cindex unload symbols from shared libraries
15338 Unload all shared object library symbols. This discards all symbols
15339 that have been loaded from all shared libraries. Symbols from shared
15340 libraries that were loaded by explicit user requests are not
15344 Sometimes you may wish that @value{GDBN} stops and gives you control
15345 when any of shared library events happen. Use the @code{set
15346 stop-on-solib-events} command for this:
15349 @item set stop-on-solib-events
15350 @kindex set stop-on-solib-events
15351 This command controls whether @value{GDBN} should give you control
15352 when the dynamic linker notifies it about some shared library event.
15353 The most common event of interest is loading or unloading of a new
15356 @item show stop-on-solib-events
15357 @kindex show stop-on-solib-events
15358 Show whether @value{GDBN} stops and gives you control when shared
15359 library events happen.
15362 Shared libraries are also supported in many cross or remote debugging
15363 configurations. @value{GDBN} needs to have access to the target's libraries;
15364 this can be accomplished either by providing copies of the libraries
15365 on the host system, or by asking @value{GDBN} to automatically retrieve the
15366 libraries from the target. If copies of the target libraries are
15367 provided, they need to be the same as the target libraries, although the
15368 copies on the target can be stripped as long as the copies on the host are
15371 @cindex where to look for shared libraries
15372 For remote debugging, you need to tell @value{GDBN} where the target
15373 libraries are, so that it can load the correct copies---otherwise, it
15374 may try to load the host's libraries. @value{GDBN} has two variables
15375 to specify the search directories for target libraries.
15378 @cindex prefix for shared library file names
15379 @cindex system root, alternate
15380 @kindex set solib-absolute-prefix
15381 @kindex set sysroot
15382 @item set sysroot @var{path}
15383 Use @var{path} as the system root for the program being debugged. Any
15384 absolute shared library paths will be prefixed with @var{path}; many
15385 runtime loaders store the absolute paths to the shared library in the
15386 target program's memory. If you use @code{set sysroot} to find shared
15387 libraries, they need to be laid out in the same way that they are on
15388 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
15391 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
15392 retrieve the target libraries from the remote system. This is only
15393 supported when using a remote target that supports the @code{remote get}
15394 command (@pxref{File Transfer,,Sending files to a remote system}).
15395 The part of @var{path} following the initial @file{remote:}
15396 (if present) is used as system root prefix on the remote file system.
15397 @footnote{If you want to specify a local system root using a directory
15398 that happens to be named @file{remote:}, you need to use some equivalent
15399 variant of the name like @file{./remote:}.}
15401 For targets with an MS-DOS based filesystem, such as MS-Windows and
15402 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
15403 absolute file name with @var{path}. But first, on Unix hosts,
15404 @value{GDBN} converts all backslash directory separators into forward
15405 slashes, because the backslash is not a directory separator on Unix:
15408 c:\foo\bar.dll @result{} c:/foo/bar.dll
15411 Then, @value{GDBN} attempts prefixing the target file name with
15412 @var{path}, and looks for the resulting file name in the host file
15416 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
15419 If that does not find the shared library, @value{GDBN} tries removing
15420 the @samp{:} character from the drive spec, both for convenience, and,
15421 for the case of the host file system not supporting file names with
15425 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
15428 This makes it possible to have a system root that mirrors a target
15429 with more than one drive. E.g., you may want to setup your local
15430 copies of the target system shared libraries like so (note @samp{c} vs
15434 @file{/path/to/sysroot/c/sys/bin/foo.dll}
15435 @file{/path/to/sysroot/c/sys/bin/bar.dll}
15436 @file{/path/to/sysroot/z/sys/bin/bar.dll}
15440 and point the system root at @file{/path/to/sysroot}, so that
15441 @value{GDBN} can find the correct copies of both
15442 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
15444 If that still does not find the shared library, @value{GDBN} tries
15445 removing the whole drive spec from the target file name:
15448 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
15451 This last lookup makes it possible to not care about the drive name,
15452 if you don't want or need to.
15454 The @code{set solib-absolute-prefix} command is an alias for @code{set
15457 @cindex default system root
15458 @cindex @samp{--with-sysroot}
15459 You can set the default system root by using the configure-time
15460 @samp{--with-sysroot} option. If the system root is inside
15461 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15462 @samp{--exec-prefix}), then the default system root will be updated
15463 automatically if the installed @value{GDBN} is moved to a new
15466 @kindex show sysroot
15468 Display the current shared library prefix.
15470 @kindex set solib-search-path
15471 @item set solib-search-path @var{path}
15472 If this variable is set, @var{path} is a colon-separated list of
15473 directories to search for shared libraries. @samp{solib-search-path}
15474 is used after @samp{sysroot} fails to locate the library, or if the
15475 path to the library is relative instead of absolute. If you want to
15476 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
15477 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
15478 finding your host's libraries. @samp{sysroot} is preferred; setting
15479 it to a nonexistent directory may interfere with automatic loading
15480 of shared library symbols.
15482 @kindex show solib-search-path
15483 @item show solib-search-path
15484 Display the current shared library search path.
15486 @cindex DOS file-name semantics of file names.
15487 @kindex set target-file-system-kind (unix|dos-based|auto)
15488 @kindex show target-file-system-kind
15489 @item set target-file-system-kind @var{kind}
15490 Set assumed file system kind for target reported file names.
15492 Shared library file names as reported by the target system may not
15493 make sense as is on the system @value{GDBN} is running on. For
15494 example, when remote debugging a target that has MS-DOS based file
15495 system semantics, from a Unix host, the target may be reporting to
15496 @value{GDBN} a list of loaded shared libraries with file names such as
15497 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
15498 drive letters, so the @samp{c:\} prefix is not normally understood as
15499 indicating an absolute file name, and neither is the backslash
15500 normally considered a directory separator character. In that case,
15501 the native file system would interpret this whole absolute file name
15502 as a relative file name with no directory components. This would make
15503 it impossible to point @value{GDBN} at a copy of the remote target's
15504 shared libraries on the host using @code{set sysroot}, and impractical
15505 with @code{set solib-search-path}. Setting
15506 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
15507 to interpret such file names similarly to how the target would, and to
15508 map them to file names valid on @value{GDBN}'s native file system
15509 semantics. The value of @var{kind} can be @code{"auto"}, in addition
15510 to one of the supported file system kinds. In that case, @value{GDBN}
15511 tries to determine the appropriate file system variant based on the
15512 current target's operating system (@pxref{ABI, ,Configuring the
15513 Current ABI}). The supported file system settings are:
15517 Instruct @value{GDBN} to assume the target file system is of Unix
15518 kind. Only file names starting the forward slash (@samp{/}) character
15519 are considered absolute, and the directory separator character is also
15523 Instruct @value{GDBN} to assume the target file system is DOS based.
15524 File names starting with either a forward slash, or a drive letter
15525 followed by a colon (e.g., @samp{c:}), are considered absolute, and
15526 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
15527 considered directory separators.
15530 Instruct @value{GDBN} to use the file system kind associated with the
15531 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
15532 This is the default.
15537 @node Separate Debug Files
15538 @section Debugging Information in Separate Files
15539 @cindex separate debugging information files
15540 @cindex debugging information in separate files
15541 @cindex @file{.debug} subdirectories
15542 @cindex debugging information directory, global
15543 @cindex global debugging information directory
15544 @cindex build ID, and separate debugging files
15545 @cindex @file{.build-id} directory
15547 @value{GDBN} allows you to put a program's debugging information in a
15548 file separate from the executable itself, in a way that allows
15549 @value{GDBN} to find and load the debugging information automatically.
15550 Since debugging information can be very large---sometimes larger
15551 than the executable code itself---some systems distribute debugging
15552 information for their executables in separate files, which users can
15553 install only when they need to debug a problem.
15555 @value{GDBN} supports two ways of specifying the separate debug info
15560 The executable contains a @dfn{debug link} that specifies the name of
15561 the separate debug info file. The separate debug file's name is
15562 usually @file{@var{executable}.debug}, where @var{executable} is the
15563 name of the corresponding executable file without leading directories
15564 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
15565 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
15566 checksum for the debug file, which @value{GDBN} uses to validate that
15567 the executable and the debug file came from the same build.
15570 The executable contains a @dfn{build ID}, a unique bit string that is
15571 also present in the corresponding debug info file. (This is supported
15572 only on some operating systems, notably those which use the ELF format
15573 for binary files and the @sc{gnu} Binutils.) For more details about
15574 this feature, see the description of the @option{--build-id}
15575 command-line option in @ref{Options, , Command Line Options, ld.info,
15576 The GNU Linker}. The debug info file's name is not specified
15577 explicitly by the build ID, but can be computed from the build ID, see
15581 Depending on the way the debug info file is specified, @value{GDBN}
15582 uses two different methods of looking for the debug file:
15586 For the ``debug link'' method, @value{GDBN} looks up the named file in
15587 the directory of the executable file, then in a subdirectory of that
15588 directory named @file{.debug}, and finally under the global debug
15589 directory, in a subdirectory whose name is identical to the leading
15590 directories of the executable's absolute file name.
15593 For the ``build ID'' method, @value{GDBN} looks in the
15594 @file{.build-id} subdirectory of the global debug directory for a file
15595 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
15596 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
15597 are the rest of the bit string. (Real build ID strings are 32 or more
15598 hex characters, not 10.)
15601 So, for example, suppose you ask @value{GDBN} to debug
15602 @file{/usr/bin/ls}, which has a debug link that specifies the
15603 file @file{ls.debug}, and a build ID whose value in hex is
15604 @code{abcdef1234}. If the global debug directory is
15605 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
15606 debug information files, in the indicated order:
15610 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
15612 @file{/usr/bin/ls.debug}
15614 @file{/usr/bin/.debug/ls.debug}
15616 @file{/usr/lib/debug/usr/bin/ls.debug}.
15619 You can set the global debugging info directory's name, and view the
15620 name @value{GDBN} is currently using.
15624 @kindex set debug-file-directory
15625 @item set debug-file-directory @var{directories}
15626 Set the directories which @value{GDBN} searches for separate debugging
15627 information files to @var{directory}. Multiple directory components can be set
15628 concatenating them by a directory separator.
15630 @kindex show debug-file-directory
15631 @item show debug-file-directory
15632 Show the directories @value{GDBN} searches for separate debugging
15637 @cindex @code{.gnu_debuglink} sections
15638 @cindex debug link sections
15639 A debug link is a special section of the executable file named
15640 @code{.gnu_debuglink}. The section must contain:
15644 A filename, with any leading directory components removed, followed by
15647 zero to three bytes of padding, as needed to reach the next four-byte
15648 boundary within the section, and
15650 a four-byte CRC checksum, stored in the same endianness used for the
15651 executable file itself. The checksum is computed on the debugging
15652 information file's full contents by the function given below, passing
15653 zero as the @var{crc} argument.
15656 Any executable file format can carry a debug link, as long as it can
15657 contain a section named @code{.gnu_debuglink} with the contents
15660 @cindex @code{.note.gnu.build-id} sections
15661 @cindex build ID sections
15662 The build ID is a special section in the executable file (and in other
15663 ELF binary files that @value{GDBN} may consider). This section is
15664 often named @code{.note.gnu.build-id}, but that name is not mandatory.
15665 It contains unique identification for the built files---the ID remains
15666 the same across multiple builds of the same build tree. The default
15667 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
15668 content for the build ID string. The same section with an identical
15669 value is present in the original built binary with symbols, in its
15670 stripped variant, and in the separate debugging information file.
15672 The debugging information file itself should be an ordinary
15673 executable, containing a full set of linker symbols, sections, and
15674 debugging information. The sections of the debugging information file
15675 should have the same names, addresses, and sizes as the original file,
15676 but they need not contain any data---much like a @code{.bss} section
15677 in an ordinary executable.
15679 The @sc{gnu} binary utilities (Binutils) package includes the
15680 @samp{objcopy} utility that can produce
15681 the separated executable / debugging information file pairs using the
15682 following commands:
15685 @kbd{objcopy --only-keep-debug foo foo.debug}
15690 These commands remove the debugging
15691 information from the executable file @file{foo} and place it in the file
15692 @file{foo.debug}. You can use the first, second or both methods to link the
15697 The debug link method needs the following additional command to also leave
15698 behind a debug link in @file{foo}:
15701 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
15704 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
15705 a version of the @code{strip} command such that the command @kbd{strip foo -f
15706 foo.debug} has the same functionality as the two @code{objcopy} commands and
15707 the @code{ln -s} command above, together.
15710 Build ID gets embedded into the main executable using @code{ld --build-id} or
15711 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
15712 compatibility fixes for debug files separation are present in @sc{gnu} binary
15713 utilities (Binutils) package since version 2.18.
15718 @cindex CRC algorithm definition
15719 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
15720 IEEE 802.3 using the polynomial:
15722 @c TexInfo requires naked braces for multi-digit exponents for Tex
15723 @c output, but this causes HTML output to barf. HTML has to be set using
15724 @c raw commands. So we end up having to specify this equation in 2
15729 <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>
15730 + <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
15736 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
15737 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
15741 The function is computed byte at a time, taking the least
15742 significant bit of each byte first. The initial pattern
15743 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
15744 the final result is inverted to ensure trailing zeros also affect the
15747 @emph{Note:} This is the same CRC polynomial as used in handling the
15748 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
15749 , @value{GDBN} Remote Serial Protocol}). However in the
15750 case of the Remote Serial Protocol, the CRC is computed @emph{most}
15751 significant bit first, and the result is not inverted, so trailing
15752 zeros have no effect on the CRC value.
15754 To complete the description, we show below the code of the function
15755 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
15756 initially supplied @code{crc} argument means that an initial call to
15757 this function passing in zero will start computing the CRC using
15760 @kindex gnu_debuglink_crc32
15763 gnu_debuglink_crc32 (unsigned long crc,
15764 unsigned char *buf, size_t len)
15766 static const unsigned long crc32_table[256] =
15768 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
15769 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
15770 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
15771 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
15772 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
15773 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
15774 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
15775 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
15776 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
15777 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
15778 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
15779 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
15780 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
15781 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
15782 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
15783 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
15784 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
15785 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
15786 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
15787 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
15788 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
15789 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
15790 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
15791 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
15792 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
15793 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
15794 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
15795 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
15796 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
15797 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
15798 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
15799 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
15800 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
15801 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
15802 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
15803 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
15804 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
15805 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
15806 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
15807 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
15808 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
15809 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
15810 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
15811 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
15812 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
15813 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
15814 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
15815 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
15816 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
15817 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
15818 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
15821 unsigned char *end;
15823 crc = ~crc & 0xffffffff;
15824 for (end = buf + len; buf < end; ++buf)
15825 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
15826 return ~crc & 0xffffffff;
15831 This computation does not apply to the ``build ID'' method.
15835 @section Index Files Speed Up @value{GDBN}
15836 @cindex index files
15837 @cindex @samp{.gdb_index} section
15839 When @value{GDBN} finds a symbol file, it scans the symbols in the
15840 file in order to construct an internal symbol table. This lets most
15841 @value{GDBN} operations work quickly---at the cost of a delay early
15842 on. For large programs, this delay can be quite lengthy, so
15843 @value{GDBN} provides a way to build an index, which speeds up
15846 The index is stored as a section in the symbol file. @value{GDBN} can
15847 write the index to a file, then you can put it into the symbol file
15848 using @command{objcopy}.
15850 To create an index file, use the @code{save gdb-index} command:
15853 @item save gdb-index @var{directory}
15854 @kindex save gdb-index
15855 Create an index file for each symbol file currently known by
15856 @value{GDBN}. Each file is named after its corresponding symbol file,
15857 with @samp{.gdb-index} appended, and is written into the given
15861 Once you have created an index file you can merge it into your symbol
15862 file, here named @file{symfile}, using @command{objcopy}:
15865 $ objcopy --add-section .gdb_index=symfile.gdb-index \
15866 --set-section-flags .gdb_index=readonly symfile symfile
15869 There are currently some limitation on indices. They only work when
15870 for DWARF debugging information, not stabs. And, they do not
15871 currently work for programs using Ada.
15873 @node Symbol Errors
15874 @section Errors Reading Symbol Files
15876 While reading a symbol file, @value{GDBN} occasionally encounters problems,
15877 such as symbol types it does not recognize, or known bugs in compiler
15878 output. By default, @value{GDBN} does not notify you of such problems, since
15879 they are relatively common and primarily of interest to people
15880 debugging compilers. If you are interested in seeing information
15881 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
15882 only one message about each such type of problem, no matter how many
15883 times the problem occurs; or you can ask @value{GDBN} to print more messages,
15884 to see how many times the problems occur, with the @code{set
15885 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
15888 The messages currently printed, and their meanings, include:
15891 @item inner block not inside outer block in @var{symbol}
15893 The symbol information shows where symbol scopes begin and end
15894 (such as at the start of a function or a block of statements). This
15895 error indicates that an inner scope block is not fully contained
15896 in its outer scope blocks.
15898 @value{GDBN} circumvents the problem by treating the inner block as if it had
15899 the same scope as the outer block. In the error message, @var{symbol}
15900 may be shown as ``@code{(don't know)}'' if the outer block is not a
15903 @item block at @var{address} out of order
15905 The symbol information for symbol scope blocks should occur in
15906 order of increasing addresses. This error indicates that it does not
15909 @value{GDBN} does not circumvent this problem, and has trouble
15910 locating symbols in the source file whose symbols it is reading. (You
15911 can often determine what source file is affected by specifying
15912 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
15915 @item bad block start address patched
15917 The symbol information for a symbol scope block has a start address
15918 smaller than the address of the preceding source line. This is known
15919 to occur in the SunOS 4.1.1 (and earlier) C compiler.
15921 @value{GDBN} circumvents the problem by treating the symbol scope block as
15922 starting on the previous source line.
15924 @item bad string table offset in symbol @var{n}
15927 Symbol number @var{n} contains a pointer into the string table which is
15928 larger than the size of the string table.
15930 @value{GDBN} circumvents the problem by considering the symbol to have the
15931 name @code{foo}, which may cause other problems if many symbols end up
15934 @item unknown symbol type @code{0x@var{nn}}
15936 The symbol information contains new data types that @value{GDBN} does
15937 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
15938 uncomprehended information, in hexadecimal.
15940 @value{GDBN} circumvents the error by ignoring this symbol information.
15941 This usually allows you to debug your program, though certain symbols
15942 are not accessible. If you encounter such a problem and feel like
15943 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
15944 on @code{complain}, then go up to the function @code{read_dbx_symtab}
15945 and examine @code{*bufp} to see the symbol.
15947 @item stub type has NULL name
15949 @value{GDBN} could not find the full definition for a struct or class.
15951 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
15952 The symbol information for a C@t{++} member function is missing some
15953 information that recent versions of the compiler should have output for
15956 @item info mismatch between compiler and debugger
15958 @value{GDBN} could not parse a type specification output by the compiler.
15963 @section GDB Data Files
15965 @cindex prefix for data files
15966 @value{GDBN} will sometimes read an auxiliary data file. These files
15967 are kept in a directory known as the @dfn{data directory}.
15969 You can set the data directory's name, and view the name @value{GDBN}
15970 is currently using.
15973 @kindex set data-directory
15974 @item set data-directory @var{directory}
15975 Set the directory which @value{GDBN} searches for auxiliary data files
15976 to @var{directory}.
15978 @kindex show data-directory
15979 @item show data-directory
15980 Show the directory @value{GDBN} searches for auxiliary data files.
15983 @cindex default data directory
15984 @cindex @samp{--with-gdb-datadir}
15985 You can set the default data directory by using the configure-time
15986 @samp{--with-gdb-datadir} option. If the data directory is inside
15987 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15988 @samp{--exec-prefix}), then the default data directory will be updated
15989 automatically if the installed @value{GDBN} is moved to a new
15992 The data directory may also be specified with the
15993 @code{--data-directory} command line option.
15994 @xref{Mode Options}.
15997 @chapter Specifying a Debugging Target
15999 @cindex debugging target
16000 A @dfn{target} is the execution environment occupied by your program.
16002 Often, @value{GDBN} runs in the same host environment as your program;
16003 in that case, the debugging target is specified as a side effect when
16004 you use the @code{file} or @code{core} commands. When you need more
16005 flexibility---for example, running @value{GDBN} on a physically separate
16006 host, or controlling a standalone system over a serial port or a
16007 realtime system over a TCP/IP connection---you can use the @code{target}
16008 command to specify one of the target types configured for @value{GDBN}
16009 (@pxref{Target Commands, ,Commands for Managing Targets}).
16011 @cindex target architecture
16012 It is possible to build @value{GDBN} for several different @dfn{target
16013 architectures}. When @value{GDBN} is built like that, you can choose
16014 one of the available architectures with the @kbd{set architecture}
16018 @kindex set architecture
16019 @kindex show architecture
16020 @item set architecture @var{arch}
16021 This command sets the current target architecture to @var{arch}. The
16022 value of @var{arch} can be @code{"auto"}, in addition to one of the
16023 supported architectures.
16025 @item show architecture
16026 Show the current target architecture.
16028 @item set processor
16030 @kindex set processor
16031 @kindex show processor
16032 These are alias commands for, respectively, @code{set architecture}
16033 and @code{show architecture}.
16037 * Active Targets:: Active targets
16038 * Target Commands:: Commands for managing targets
16039 * Byte Order:: Choosing target byte order
16042 @node Active Targets
16043 @section Active Targets
16045 @cindex stacking targets
16046 @cindex active targets
16047 @cindex multiple targets
16049 There are multiple classes of targets such as: processes, executable files or
16050 recording sessions. Core files belong to the process class, making core file
16051 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
16052 on multiple active targets, one in each class. This allows you to (for
16053 example) start a process and inspect its activity, while still having access to
16054 the executable file after the process finishes. Or if you start process
16055 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
16056 presented a virtual layer of the recording target, while the process target
16057 remains stopped at the chronologically last point of the process execution.
16059 Use the @code{core-file} and @code{exec-file} commands to select a new core
16060 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
16061 specify as a target a process that is already running, use the @code{attach}
16062 command (@pxref{Attach, ,Debugging an Already-running Process}).
16064 @node Target Commands
16065 @section Commands for Managing Targets
16068 @item target @var{type} @var{parameters}
16069 Connects the @value{GDBN} host environment to a target machine or
16070 process. A target is typically a protocol for talking to debugging
16071 facilities. You use the argument @var{type} to specify the type or
16072 protocol of the target machine.
16074 Further @var{parameters} are interpreted by the target protocol, but
16075 typically include things like device names or host names to connect
16076 with, process numbers, and baud rates.
16078 The @code{target} command does not repeat if you press @key{RET} again
16079 after executing the command.
16081 @kindex help target
16083 Displays the names of all targets available. To display targets
16084 currently selected, use either @code{info target} or @code{info files}
16085 (@pxref{Files, ,Commands to Specify Files}).
16087 @item help target @var{name}
16088 Describe a particular target, including any parameters necessary to
16091 @kindex set gnutarget
16092 @item set gnutarget @var{args}
16093 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
16094 knows whether it is reading an @dfn{executable},
16095 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
16096 with the @code{set gnutarget} command. Unlike most @code{target} commands,
16097 with @code{gnutarget} the @code{target} refers to a program, not a machine.
16100 @emph{Warning:} To specify a file format with @code{set gnutarget},
16101 you must know the actual BFD name.
16105 @xref{Files, , Commands to Specify Files}.
16107 @kindex show gnutarget
16108 @item show gnutarget
16109 Use the @code{show gnutarget} command to display what file format
16110 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
16111 @value{GDBN} will determine the file format for each file automatically,
16112 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
16115 @cindex common targets
16116 Here are some common targets (available, or not, depending on the GDB
16121 @item target exec @var{program}
16122 @cindex executable file target
16123 An executable file. @samp{target exec @var{program}} is the same as
16124 @samp{exec-file @var{program}}.
16126 @item target core @var{filename}
16127 @cindex core dump file target
16128 A core dump file. @samp{target core @var{filename}} is the same as
16129 @samp{core-file @var{filename}}.
16131 @item target remote @var{medium}
16132 @cindex remote target
16133 A remote system connected to @value{GDBN} via a serial line or network
16134 connection. This command tells @value{GDBN} to use its own remote
16135 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
16137 For example, if you have a board connected to @file{/dev/ttya} on the
16138 machine running @value{GDBN}, you could say:
16141 target remote /dev/ttya
16144 @code{target remote} supports the @code{load} command. This is only
16145 useful if you have some other way of getting the stub to the target
16146 system, and you can put it somewhere in memory where it won't get
16147 clobbered by the download.
16149 @item target sim @r{[}@var{simargs}@r{]} @dots{}
16150 @cindex built-in simulator target
16151 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
16159 works; however, you cannot assume that a specific memory map, device
16160 drivers, or even basic I/O is available, although some simulators do
16161 provide these. For info about any processor-specific simulator details,
16162 see the appropriate section in @ref{Embedded Processors, ,Embedded
16167 Some configurations may include these targets as well:
16171 @item target nrom @var{dev}
16172 @cindex NetROM ROM emulator target
16173 NetROM ROM emulator. This target only supports downloading.
16177 Different targets are available on different configurations of @value{GDBN};
16178 your configuration may have more or fewer targets.
16180 Many remote targets require you to download the executable's code once
16181 you've successfully established a connection. You may wish to control
16182 various aspects of this process.
16187 @kindex set hash@r{, for remote monitors}
16188 @cindex hash mark while downloading
16189 This command controls whether a hash mark @samp{#} is displayed while
16190 downloading a file to the remote monitor. If on, a hash mark is
16191 displayed after each S-record is successfully downloaded to the
16195 @kindex show hash@r{, for remote monitors}
16196 Show the current status of displaying the hash mark.
16198 @item set debug monitor
16199 @kindex set debug monitor
16200 @cindex display remote monitor communications
16201 Enable or disable display of communications messages between
16202 @value{GDBN} and the remote monitor.
16204 @item show debug monitor
16205 @kindex show debug monitor
16206 Show the current status of displaying communications between
16207 @value{GDBN} and the remote monitor.
16212 @kindex load @var{filename}
16213 @item load @var{filename}
16215 Depending on what remote debugging facilities are configured into
16216 @value{GDBN}, the @code{load} command may be available. Where it exists, it
16217 is meant to make @var{filename} (an executable) available for debugging
16218 on the remote system---by downloading, or dynamic linking, for example.
16219 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
16220 the @code{add-symbol-file} command.
16222 If your @value{GDBN} does not have a @code{load} command, attempting to
16223 execute it gets the error message ``@code{You can't do that when your
16224 target is @dots{}}''
16226 The file is loaded at whatever address is specified in the executable.
16227 For some object file formats, you can specify the load address when you
16228 link the program; for other formats, like a.out, the object file format
16229 specifies a fixed address.
16230 @c FIXME! This would be a good place for an xref to the GNU linker doc.
16232 Depending on the remote side capabilities, @value{GDBN} may be able to
16233 load programs into flash memory.
16235 @code{load} does not repeat if you press @key{RET} again after using it.
16239 @section Choosing Target Byte Order
16241 @cindex choosing target byte order
16242 @cindex target byte order
16244 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
16245 offer the ability to run either big-endian or little-endian byte
16246 orders. Usually the executable or symbol will include a bit to
16247 designate the endian-ness, and you will not need to worry about
16248 which to use. However, you may still find it useful to adjust
16249 @value{GDBN}'s idea of processor endian-ness manually.
16253 @item set endian big
16254 Instruct @value{GDBN} to assume the target is big-endian.
16256 @item set endian little
16257 Instruct @value{GDBN} to assume the target is little-endian.
16259 @item set endian auto
16260 Instruct @value{GDBN} to use the byte order associated with the
16264 Display @value{GDBN}'s current idea of the target byte order.
16268 Note that these commands merely adjust interpretation of symbolic
16269 data on the host, and that they have absolutely no effect on the
16273 @node Remote Debugging
16274 @chapter Debugging Remote Programs
16275 @cindex remote debugging
16277 If you are trying to debug a program running on a machine that cannot run
16278 @value{GDBN} in the usual way, it is often useful to use remote debugging.
16279 For example, you might use remote debugging on an operating system kernel,
16280 or on a small system which does not have a general purpose operating system
16281 powerful enough to run a full-featured debugger.
16283 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
16284 to make this work with particular debugging targets. In addition,
16285 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
16286 but not specific to any particular target system) which you can use if you
16287 write the remote stubs---the code that runs on the remote system to
16288 communicate with @value{GDBN}.
16290 Other remote targets may be available in your
16291 configuration of @value{GDBN}; use @code{help target} to list them.
16294 * Connecting:: Connecting to a remote target
16295 * File Transfer:: Sending files to a remote system
16296 * Server:: Using the gdbserver program
16297 * Remote Configuration:: Remote configuration
16298 * Remote Stub:: Implementing a remote stub
16302 @section Connecting to a Remote Target
16304 On the @value{GDBN} host machine, you will need an unstripped copy of
16305 your program, since @value{GDBN} needs symbol and debugging information.
16306 Start up @value{GDBN} as usual, using the name of the local copy of your
16307 program as the first argument.
16309 @cindex @code{target remote}
16310 @value{GDBN} can communicate with the target over a serial line, or
16311 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
16312 each case, @value{GDBN} uses the same protocol for debugging your
16313 program; only the medium carrying the debugging packets varies. The
16314 @code{target remote} command establishes a connection to the target.
16315 Its arguments indicate which medium to use:
16319 @item target remote @var{serial-device}
16320 @cindex serial line, @code{target remote}
16321 Use @var{serial-device} to communicate with the target. For example,
16322 to use a serial line connected to the device named @file{/dev/ttyb}:
16325 target remote /dev/ttyb
16328 If you're using a serial line, you may want to give @value{GDBN} the
16329 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
16330 (@pxref{Remote Configuration, set remotebaud}) before the
16331 @code{target} command.
16333 @item target remote @code{@var{host}:@var{port}}
16334 @itemx target remote @code{tcp:@var{host}:@var{port}}
16335 @cindex @acronym{TCP} port, @code{target remote}
16336 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
16337 The @var{host} may be either a host name or a numeric @acronym{IP}
16338 address; @var{port} must be a decimal number. The @var{host} could be
16339 the target machine itself, if it is directly connected to the net, or
16340 it might be a terminal server which in turn has a serial line to the
16343 For example, to connect to port 2828 on a terminal server named
16347 target remote manyfarms:2828
16350 If your remote target is actually running on the same machine as your
16351 debugger session (e.g.@: a simulator for your target running on the
16352 same host), you can omit the hostname. For example, to connect to
16353 port 1234 on your local machine:
16356 target remote :1234
16360 Note that the colon is still required here.
16362 @item target remote @code{udp:@var{host}:@var{port}}
16363 @cindex @acronym{UDP} port, @code{target remote}
16364 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
16365 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
16368 target remote udp:manyfarms:2828
16371 When using a @acronym{UDP} connection for remote debugging, you should
16372 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
16373 can silently drop packets on busy or unreliable networks, which will
16374 cause havoc with your debugging session.
16376 @item target remote | @var{command}
16377 @cindex pipe, @code{target remote} to
16378 Run @var{command} in the background and communicate with it using a
16379 pipe. The @var{command} is a shell command, to be parsed and expanded
16380 by the system's command shell, @code{/bin/sh}; it should expect remote
16381 protocol packets on its standard input, and send replies on its
16382 standard output. You could use this to run a stand-alone simulator
16383 that speaks the remote debugging protocol, to make net connections
16384 using programs like @code{ssh}, or for other similar tricks.
16386 If @var{command} closes its standard output (perhaps by exiting),
16387 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
16388 program has already exited, this will have no effect.)
16392 Once the connection has been established, you can use all the usual
16393 commands to examine and change data. The remote program is already
16394 running; you can use @kbd{step} and @kbd{continue}, and you do not
16395 need to use @kbd{run}.
16397 @cindex interrupting remote programs
16398 @cindex remote programs, interrupting
16399 Whenever @value{GDBN} is waiting for the remote program, if you type the
16400 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
16401 program. This may or may not succeed, depending in part on the hardware
16402 and the serial drivers the remote system uses. If you type the
16403 interrupt character once again, @value{GDBN} displays this prompt:
16406 Interrupted while waiting for the program.
16407 Give up (and stop debugging it)? (y or n)
16410 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
16411 (If you decide you want to try again later, you can use @samp{target
16412 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
16413 goes back to waiting.
16416 @kindex detach (remote)
16418 When you have finished debugging the remote program, you can use the
16419 @code{detach} command to release it from @value{GDBN} control.
16420 Detaching from the target normally resumes its execution, but the results
16421 will depend on your particular remote stub. After the @code{detach}
16422 command, @value{GDBN} is free to connect to another target.
16426 The @code{disconnect} command behaves like @code{detach}, except that
16427 the target is generally not resumed. It will wait for @value{GDBN}
16428 (this instance or another one) to connect and continue debugging. After
16429 the @code{disconnect} command, @value{GDBN} is again free to connect to
16432 @cindex send command to remote monitor
16433 @cindex extend @value{GDBN} for remote targets
16434 @cindex add new commands for external monitor
16436 @item monitor @var{cmd}
16437 This command allows you to send arbitrary commands directly to the
16438 remote monitor. Since @value{GDBN} doesn't care about the commands it
16439 sends like this, this command is the way to extend @value{GDBN}---you
16440 can add new commands that only the external monitor will understand
16444 @node File Transfer
16445 @section Sending files to a remote system
16446 @cindex remote target, file transfer
16447 @cindex file transfer
16448 @cindex sending files to remote systems
16450 Some remote targets offer the ability to transfer files over the same
16451 connection used to communicate with @value{GDBN}. This is convenient
16452 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
16453 running @code{gdbserver} over a network interface. For other targets,
16454 e.g.@: embedded devices with only a single serial port, this may be
16455 the only way to upload or download files.
16457 Not all remote targets support these commands.
16461 @item remote put @var{hostfile} @var{targetfile}
16462 Copy file @var{hostfile} from the host system (the machine running
16463 @value{GDBN}) to @var{targetfile} on the target system.
16466 @item remote get @var{targetfile} @var{hostfile}
16467 Copy file @var{targetfile} from the target system to @var{hostfile}
16468 on the host system.
16470 @kindex remote delete
16471 @item remote delete @var{targetfile}
16472 Delete @var{targetfile} from the target system.
16477 @section Using the @code{gdbserver} Program
16480 @cindex remote connection without stubs
16481 @code{gdbserver} is a control program for Unix-like systems, which
16482 allows you to connect your program with a remote @value{GDBN} via
16483 @code{target remote}---but without linking in the usual debugging stub.
16485 @code{gdbserver} is not a complete replacement for the debugging stubs,
16486 because it requires essentially the same operating-system facilities
16487 that @value{GDBN} itself does. In fact, a system that can run
16488 @code{gdbserver} to connect to a remote @value{GDBN} could also run
16489 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
16490 because it is a much smaller program than @value{GDBN} itself. It is
16491 also easier to port than all of @value{GDBN}, so you may be able to get
16492 started more quickly on a new system by using @code{gdbserver}.
16493 Finally, if you develop code for real-time systems, you may find that
16494 the tradeoffs involved in real-time operation make it more convenient to
16495 do as much development work as possible on another system, for example
16496 by cross-compiling. You can use @code{gdbserver} to make a similar
16497 choice for debugging.
16499 @value{GDBN} and @code{gdbserver} communicate via either a serial line
16500 or a TCP connection, using the standard @value{GDBN} remote serial
16504 @emph{Warning:} @code{gdbserver} does not have any built-in security.
16505 Do not run @code{gdbserver} connected to any public network; a
16506 @value{GDBN} connection to @code{gdbserver} provides access to the
16507 target system with the same privileges as the user running
16511 @subsection Running @code{gdbserver}
16512 @cindex arguments, to @code{gdbserver}
16513 @cindex @code{gdbserver}, command-line arguments
16515 Run @code{gdbserver} on the target system. You need a copy of the
16516 program you want to debug, including any libraries it requires.
16517 @code{gdbserver} does not need your program's symbol table, so you can
16518 strip the program if necessary to save space. @value{GDBN} on the host
16519 system does all the symbol handling.
16521 To use the server, you must tell it how to communicate with @value{GDBN};
16522 the name of your program; and the arguments for your program. The usual
16526 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
16529 @var{comm} is either a device name (to use a serial line) or a TCP
16530 hostname and portnumber. For example, to debug Emacs with the argument
16531 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
16535 target> gdbserver /dev/com1 emacs foo.txt
16538 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
16541 To use a TCP connection instead of a serial line:
16544 target> gdbserver host:2345 emacs foo.txt
16547 The only difference from the previous example is the first argument,
16548 specifying that you are communicating with the host @value{GDBN} via
16549 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
16550 expect a TCP connection from machine @samp{host} to local TCP port 2345.
16551 (Currently, the @samp{host} part is ignored.) You can choose any number
16552 you want for the port number as long as it does not conflict with any
16553 TCP ports already in use on the target system (for example, @code{23} is
16554 reserved for @code{telnet}).@footnote{If you choose a port number that
16555 conflicts with another service, @code{gdbserver} prints an error message
16556 and exits.} You must use the same port number with the host @value{GDBN}
16557 @code{target remote} command.
16559 @subsubsection Attaching to a Running Program
16560 @cindex attach to a program, @code{gdbserver}
16561 @cindex @option{--attach}, @code{gdbserver} option
16563 On some targets, @code{gdbserver} can also attach to running programs.
16564 This is accomplished via the @code{--attach} argument. The syntax is:
16567 target> gdbserver --attach @var{comm} @var{pid}
16570 @var{pid} is the process ID of a currently running process. It isn't necessary
16571 to point @code{gdbserver} at a binary for the running process.
16574 You can debug processes by name instead of process ID if your target has the
16575 @code{pidof} utility:
16578 target> gdbserver --attach @var{comm} `pidof @var{program}`
16581 In case more than one copy of @var{program} is running, or @var{program}
16582 has multiple threads, most versions of @code{pidof} support the
16583 @code{-s} option to only return the first process ID.
16585 @subsubsection Multi-Process Mode for @code{gdbserver}
16586 @cindex @code{gdbserver}, multiple processes
16587 @cindex multiple processes with @code{gdbserver}
16589 When you connect to @code{gdbserver} using @code{target remote},
16590 @code{gdbserver} debugs the specified program only once. When the
16591 program exits, or you detach from it, @value{GDBN} closes the connection
16592 and @code{gdbserver} exits.
16594 If you connect using @kbd{target extended-remote}, @code{gdbserver}
16595 enters multi-process mode. When the debugged program exits, or you
16596 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
16597 though no program is running. The @code{run} and @code{attach}
16598 commands instruct @code{gdbserver} to run or attach to a new program.
16599 The @code{run} command uses @code{set remote exec-file} (@pxref{set
16600 remote exec-file}) to select the program to run. Command line
16601 arguments are supported, except for wildcard expansion and I/O
16602 redirection (@pxref{Arguments}).
16604 @cindex @option{--multi}, @code{gdbserver} option
16605 To start @code{gdbserver} without supplying an initial command to run
16606 or process ID to attach, use the @option{--multi} command line option.
16607 Then you can connect using @kbd{target extended-remote} and start
16608 the program you want to debug.
16610 In multi-process mode @code{gdbserver} does not automatically exit unless you
16611 use the option @option{--once}. You can terminate it by using
16612 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
16613 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
16614 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
16615 @option{--multi} option to @code{gdbserver} has no influence on that.
16617 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
16619 This section applies only when @code{gdbserver} is run to listen on a TCP port.
16621 @code{gdbserver} normally terminates after all of its debugged processes have
16622 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
16623 extended-remote}, @code{gdbserver} stays running even with no processes left.
16624 @value{GDBN} normally terminates the spawned debugged process on its exit,
16625 which normally also terminates @code{gdbserver} in the @kbd{target remote}
16626 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
16627 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
16628 stays running even in the @kbd{target remote} mode.
16630 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
16631 Such reconnecting is useful for features like @ref{disconnected tracing}. For
16632 completeness, at most one @value{GDBN} can be connected at a time.
16634 @cindex @option{--once}, @code{gdbserver} option
16635 By default, @code{gdbserver} keeps the listening TCP port open, so that
16636 additional connections are possible. However, if you start @code{gdbserver}
16637 with the @option{--once} option, it will stop listening for any further
16638 connection attempts after connecting to the first @value{GDBN} session. This
16639 means no further connections to @code{gdbserver} will be possible after the
16640 first one. It also means @code{gdbserver} will terminate after the first
16641 connection with remote @value{GDBN} has closed, even for unexpectedly closed
16642 connections and even in the @kbd{target extended-remote} mode. The
16643 @option{--once} option allows reusing the same port number for connecting to
16644 multiple instances of @code{gdbserver} running on the same host, since each
16645 instance closes its port after the first connection.
16647 @subsubsection Other Command-Line Arguments for @code{gdbserver}
16649 @cindex @option{--debug}, @code{gdbserver} option
16650 The @option{--debug} option tells @code{gdbserver} to display extra
16651 status information about the debugging process.
16652 @cindex @option{--remote-debug}, @code{gdbserver} option
16653 The @option{--remote-debug} option tells @code{gdbserver} to display
16654 remote protocol debug output. These options are intended for
16655 @code{gdbserver} development and for bug reports to the developers.
16657 @cindex @option{--wrapper}, @code{gdbserver} option
16658 The @option{--wrapper} option specifies a wrapper to launch programs
16659 for debugging. The option should be followed by the name of the
16660 wrapper, then any command-line arguments to pass to the wrapper, then
16661 @kbd{--} indicating the end of the wrapper arguments.
16663 @code{gdbserver} runs the specified wrapper program with a combined
16664 command line including the wrapper arguments, then the name of the
16665 program to debug, then any arguments to the program. The wrapper
16666 runs until it executes your program, and then @value{GDBN} gains control.
16668 You can use any program that eventually calls @code{execve} with
16669 its arguments as a wrapper. Several standard Unix utilities do
16670 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
16671 with @code{exec "$@@"} will also work.
16673 For example, you can use @code{env} to pass an environment variable to
16674 the debugged program, without setting the variable in @code{gdbserver}'s
16678 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
16681 @subsection Connecting to @code{gdbserver}
16683 Run @value{GDBN} on the host system.
16685 First make sure you have the necessary symbol files. Load symbols for
16686 your application using the @code{file} command before you connect. Use
16687 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
16688 was compiled with the correct sysroot using @code{--with-sysroot}).
16690 The symbol file and target libraries must exactly match the executable
16691 and libraries on the target, with one exception: the files on the host
16692 system should not be stripped, even if the files on the target system
16693 are. Mismatched or missing files will lead to confusing results
16694 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
16695 files may also prevent @code{gdbserver} from debugging multi-threaded
16698 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
16699 For TCP connections, you must start up @code{gdbserver} prior to using
16700 the @code{target remote} command. Otherwise you may get an error whose
16701 text depends on the host system, but which usually looks something like
16702 @samp{Connection refused}. Don't use the @code{load}
16703 command in @value{GDBN} when using @code{gdbserver}, since the program is
16704 already on the target.
16706 @subsection Monitor Commands for @code{gdbserver}
16707 @cindex monitor commands, for @code{gdbserver}
16708 @anchor{Monitor Commands for gdbserver}
16710 During a @value{GDBN} session using @code{gdbserver}, you can use the
16711 @code{monitor} command to send special requests to @code{gdbserver}.
16712 Here are the available commands.
16716 List the available monitor commands.
16718 @item monitor set debug 0
16719 @itemx monitor set debug 1
16720 Disable or enable general debugging messages.
16722 @item monitor set remote-debug 0
16723 @itemx monitor set remote-debug 1
16724 Disable or enable specific debugging messages associated with the remote
16725 protocol (@pxref{Remote Protocol}).
16727 @item monitor set libthread-db-search-path [PATH]
16728 @cindex gdbserver, search path for @code{libthread_db}
16729 When this command is issued, @var{path} is a colon-separated list of
16730 directories to search for @code{libthread_db} (@pxref{Threads,,set
16731 libthread-db-search-path}). If you omit @var{path},
16732 @samp{libthread-db-search-path} will be reset to its default value.
16734 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
16735 not supported in @code{gdbserver}.
16738 Tell gdbserver to exit immediately. This command should be followed by
16739 @code{disconnect} to close the debugging session. @code{gdbserver} will
16740 detach from any attached processes and kill any processes it created.
16741 Use @code{monitor exit} to terminate @code{gdbserver} at the end
16742 of a multi-process mode debug session.
16746 @subsection Tracepoints support in @code{gdbserver}
16747 @cindex tracepoints support in @code{gdbserver}
16749 On some targets, @code{gdbserver} supports tracepoints, fast
16750 tracepoints and static tracepoints.
16752 For fast or static tracepoints to work, a special library called the
16753 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
16754 This library is built and distributed as an integral part of
16755 @code{gdbserver}. In addition, support for static tracepoints
16756 requires building the in-process agent library with static tracepoints
16757 support. At present, the UST (LTTng Userspace Tracer,
16758 @url{http://lttng.org/ust}) tracing engine is supported. This support
16759 is automatically available if UST development headers are found in the
16760 standard include path when @code{gdbserver} is built, or if
16761 @code{gdbserver} was explicitly configured using @option{--with-ust}
16762 to point at such headers. You can explicitly disable the support
16763 using @option{--with-ust=no}.
16765 There are several ways to load the in-process agent in your program:
16768 @item Specifying it as dependency at link time
16770 You can link your program dynamically with the in-process agent
16771 library. On most systems, this is accomplished by adding
16772 @code{-linproctrace} to the link command.
16774 @item Using the system's preloading mechanisms
16776 You can force loading the in-process agent at startup time by using
16777 your system's support for preloading shared libraries. Many Unixes
16778 support the concept of preloading user defined libraries. In most
16779 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
16780 in the environment. See also the description of @code{gdbserver}'s
16781 @option{--wrapper} command line option.
16783 @item Using @value{GDBN} to force loading the agent at run time
16785 On some systems, you can force the inferior to load a shared library,
16786 by calling a dynamic loader function in the inferior that takes care
16787 of dynamically looking up and loading a shared library. On most Unix
16788 systems, the function is @code{dlopen}. You'll use the @code{call}
16789 command for that. For example:
16792 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
16795 Note that on most Unix systems, for the @code{dlopen} function to be
16796 available, the program needs to be linked with @code{-ldl}.
16799 On systems that have a userspace dynamic loader, like most Unix
16800 systems, when you connect to @code{gdbserver} using @code{target
16801 remote}, you'll find that the program is stopped at the dynamic
16802 loader's entry point, and no shared library has been loaded in the
16803 program's address space yet, including the in-process agent. In that
16804 case, before being able to use any of the fast or static tracepoints
16805 features, you need to let the loader run and load the shared
16806 libraries. The simplest way to do that is to run the program to the
16807 main procedure. E.g., if debugging a C or C@t{++} program, start
16808 @code{gdbserver} like so:
16811 $ gdbserver :9999 myprogram
16814 Start GDB and connect to @code{gdbserver} like so, and run to main:
16818 (@value{GDBP}) target remote myhost:9999
16819 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
16820 (@value{GDBP}) b main
16821 (@value{GDBP}) continue
16824 The in-process tracing agent library should now be loaded into the
16825 process; you can confirm it with the @code{info sharedlibrary}
16826 command, which will list @file{libinproctrace.so} as loaded in the
16827 process. You are now ready to install fast tracepoints, list static
16828 tracepoint markers, probe static tracepoints markers, and start
16831 @node Remote Configuration
16832 @section Remote Configuration
16835 @kindex show remote
16836 This section documents the configuration options available when
16837 debugging remote programs. For the options related to the File I/O
16838 extensions of the remote protocol, see @ref{system,
16839 system-call-allowed}.
16842 @item set remoteaddresssize @var{bits}
16843 @cindex address size for remote targets
16844 @cindex bits in remote address
16845 Set the maximum size of address in a memory packet to the specified
16846 number of bits. @value{GDBN} will mask off the address bits above
16847 that number, when it passes addresses to the remote target. The
16848 default value is the number of bits in the target's address.
16850 @item show remoteaddresssize
16851 Show the current value of remote address size in bits.
16853 @item set remotebaud @var{n}
16854 @cindex baud rate for remote targets
16855 Set the baud rate for the remote serial I/O to @var{n} baud. The
16856 value is used to set the speed of the serial port used for debugging
16859 @item show remotebaud
16860 Show the current speed of the remote connection.
16862 @item set remotebreak
16863 @cindex interrupt remote programs
16864 @cindex BREAK signal instead of Ctrl-C
16865 @anchor{set remotebreak}
16866 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
16867 when you type @kbd{Ctrl-c} to interrupt the program running
16868 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
16869 character instead. The default is off, since most remote systems
16870 expect to see @samp{Ctrl-C} as the interrupt signal.
16872 @item show remotebreak
16873 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
16874 interrupt the remote program.
16876 @item set remoteflow on
16877 @itemx set remoteflow off
16878 @kindex set remoteflow
16879 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
16880 on the serial port used to communicate to the remote target.
16882 @item show remoteflow
16883 @kindex show remoteflow
16884 Show the current setting of hardware flow control.
16886 @item set remotelogbase @var{base}
16887 Set the base (a.k.a.@: radix) of logging serial protocol
16888 communications to @var{base}. Supported values of @var{base} are:
16889 @code{ascii}, @code{octal}, and @code{hex}. The default is
16892 @item show remotelogbase
16893 Show the current setting of the radix for logging remote serial
16896 @item set remotelogfile @var{file}
16897 @cindex record serial communications on file
16898 Record remote serial communications on the named @var{file}. The
16899 default is not to record at all.
16901 @item show remotelogfile.
16902 Show the current setting of the file name on which to record the
16903 serial communications.
16905 @item set remotetimeout @var{num}
16906 @cindex timeout for serial communications
16907 @cindex remote timeout
16908 Set the timeout limit to wait for the remote target to respond to
16909 @var{num} seconds. The default is 2 seconds.
16911 @item show remotetimeout
16912 Show the current number of seconds to wait for the remote target
16915 @cindex limit hardware breakpoints and watchpoints
16916 @cindex remote target, limit break- and watchpoints
16917 @anchor{set remote hardware-watchpoint-limit}
16918 @anchor{set remote hardware-breakpoint-limit}
16919 @item set remote hardware-watchpoint-limit @var{limit}
16920 @itemx set remote hardware-breakpoint-limit @var{limit}
16921 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
16922 watchpoints. A limit of -1, the default, is treated as unlimited.
16924 @cindex limit hardware watchpoints length
16925 @cindex remote target, limit watchpoints length
16926 @anchor{set remote hardware-watchpoint-length-limit}
16927 @item set remote hardware-watchpoint-length-limit @var{limit}
16928 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
16929 a remote hardware watchpoint. A limit of -1, the default, is treated
16932 @item show remote hardware-watchpoint-length-limit
16933 Show the current limit (in bytes) of the maximum length of
16934 a remote hardware watchpoint.
16936 @item set remote exec-file @var{filename}
16937 @itemx show remote exec-file
16938 @anchor{set remote exec-file}
16939 @cindex executable file, for remote target
16940 Select the file used for @code{run} with @code{target
16941 extended-remote}. This should be set to a filename valid on the
16942 target system. If it is not set, the target will use a default
16943 filename (e.g.@: the last program run).
16945 @item set remote interrupt-sequence
16946 @cindex interrupt remote programs
16947 @cindex select Ctrl-C, BREAK or BREAK-g
16948 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
16949 @samp{BREAK-g} as the
16950 sequence to the remote target in order to interrupt the execution.
16951 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
16952 is high level of serial line for some certain time.
16953 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
16954 It is @code{BREAK} signal followed by character @code{g}.
16956 @item show interrupt-sequence
16957 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
16958 is sent by @value{GDBN} to interrupt the remote program.
16959 @code{BREAK-g} is BREAK signal followed by @code{g} and
16960 also known as Magic SysRq g.
16962 @item set remote interrupt-on-connect
16963 @cindex send interrupt-sequence on start
16964 Specify whether interrupt-sequence is sent to remote target when
16965 @value{GDBN} connects to it. This is mostly needed when you debug
16966 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
16967 which is known as Magic SysRq g in order to connect @value{GDBN}.
16969 @item show interrupt-on-connect
16970 Show whether interrupt-sequence is sent
16971 to remote target when @value{GDBN} connects to it.
16975 @item set tcp auto-retry on
16976 @cindex auto-retry, for remote TCP target
16977 Enable auto-retry for remote TCP connections. This is useful if the remote
16978 debugging agent is launched in parallel with @value{GDBN}; there is a race
16979 condition because the agent may not become ready to accept the connection
16980 before @value{GDBN} attempts to connect. When auto-retry is
16981 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
16982 to establish the connection using the timeout specified by
16983 @code{set tcp connect-timeout}.
16985 @item set tcp auto-retry off
16986 Do not auto-retry failed TCP connections.
16988 @item show tcp auto-retry
16989 Show the current auto-retry setting.
16991 @item set tcp connect-timeout @var{seconds}
16992 @cindex connection timeout, for remote TCP target
16993 @cindex timeout, for remote target connection
16994 Set the timeout for establishing a TCP connection to the remote target to
16995 @var{seconds}. The timeout affects both polling to retry failed connections
16996 (enabled by @code{set tcp auto-retry on}) and waiting for connections
16997 that are merely slow to complete, and represents an approximate cumulative
17000 @item show tcp connect-timeout
17001 Show the current connection timeout setting.
17004 @cindex remote packets, enabling and disabling
17005 The @value{GDBN} remote protocol autodetects the packets supported by
17006 your debugging stub. If you need to override the autodetection, you
17007 can use these commands to enable or disable individual packets. Each
17008 packet can be set to @samp{on} (the remote target supports this
17009 packet), @samp{off} (the remote target does not support this packet),
17010 or @samp{auto} (detect remote target support for this packet). They
17011 all default to @samp{auto}. For more information about each packet,
17012 see @ref{Remote Protocol}.
17014 During normal use, you should not have to use any of these commands.
17015 If you do, that may be a bug in your remote debugging stub, or a bug
17016 in @value{GDBN}. You may want to report the problem to the
17017 @value{GDBN} developers.
17019 For each packet @var{name}, the command to enable or disable the
17020 packet is @code{set remote @var{name}-packet}. The available settings
17023 @multitable @columnfractions 0.28 0.32 0.25
17026 @tab Related Features
17028 @item @code{fetch-register}
17030 @tab @code{info registers}
17032 @item @code{set-register}
17036 @item @code{binary-download}
17038 @tab @code{load}, @code{set}
17040 @item @code{read-aux-vector}
17041 @tab @code{qXfer:auxv:read}
17042 @tab @code{info auxv}
17044 @item @code{symbol-lookup}
17045 @tab @code{qSymbol}
17046 @tab Detecting multiple threads
17048 @item @code{attach}
17049 @tab @code{vAttach}
17052 @item @code{verbose-resume}
17054 @tab Stepping or resuming multiple threads
17060 @item @code{software-breakpoint}
17064 @item @code{hardware-breakpoint}
17068 @item @code{write-watchpoint}
17072 @item @code{read-watchpoint}
17076 @item @code{access-watchpoint}
17080 @item @code{target-features}
17081 @tab @code{qXfer:features:read}
17082 @tab @code{set architecture}
17084 @item @code{library-info}
17085 @tab @code{qXfer:libraries:read}
17086 @tab @code{info sharedlibrary}
17088 @item @code{memory-map}
17089 @tab @code{qXfer:memory-map:read}
17090 @tab @code{info mem}
17092 @item @code{read-sdata-object}
17093 @tab @code{qXfer:sdata:read}
17094 @tab @code{print $_sdata}
17096 @item @code{read-spu-object}
17097 @tab @code{qXfer:spu:read}
17098 @tab @code{info spu}
17100 @item @code{write-spu-object}
17101 @tab @code{qXfer:spu:write}
17102 @tab @code{info spu}
17104 @item @code{read-siginfo-object}
17105 @tab @code{qXfer:siginfo:read}
17106 @tab @code{print $_siginfo}
17108 @item @code{write-siginfo-object}
17109 @tab @code{qXfer:siginfo:write}
17110 @tab @code{set $_siginfo}
17112 @item @code{threads}
17113 @tab @code{qXfer:threads:read}
17114 @tab @code{info threads}
17116 @item @code{get-thread-local-@*storage-address}
17117 @tab @code{qGetTLSAddr}
17118 @tab Displaying @code{__thread} variables
17120 @item @code{get-thread-information-block-address}
17121 @tab @code{qGetTIBAddr}
17122 @tab Display MS-Windows Thread Information Block.
17124 @item @code{search-memory}
17125 @tab @code{qSearch:memory}
17128 @item @code{supported-packets}
17129 @tab @code{qSupported}
17130 @tab Remote communications parameters
17132 @item @code{pass-signals}
17133 @tab @code{QPassSignals}
17134 @tab @code{handle @var{signal}}
17136 @item @code{hostio-close-packet}
17137 @tab @code{vFile:close}
17138 @tab @code{remote get}, @code{remote put}
17140 @item @code{hostio-open-packet}
17141 @tab @code{vFile:open}
17142 @tab @code{remote get}, @code{remote put}
17144 @item @code{hostio-pread-packet}
17145 @tab @code{vFile:pread}
17146 @tab @code{remote get}, @code{remote put}
17148 @item @code{hostio-pwrite-packet}
17149 @tab @code{vFile:pwrite}
17150 @tab @code{remote get}, @code{remote put}
17152 @item @code{hostio-unlink-packet}
17153 @tab @code{vFile:unlink}
17154 @tab @code{remote delete}
17156 @item @code{noack-packet}
17157 @tab @code{QStartNoAckMode}
17158 @tab Packet acknowledgment
17160 @item @code{osdata}
17161 @tab @code{qXfer:osdata:read}
17162 @tab @code{info os}
17164 @item @code{query-attached}
17165 @tab @code{qAttached}
17166 @tab Querying remote process attach state.
17168 @item @code{traceframe-info}
17169 @tab @code{qXfer:traceframe-info:read}
17170 @tab Traceframe info
17172 @item @code{disable-randomization}
17173 @tab @code{QDisableRandomization}
17174 @tab @code{set disable-randomization}
17178 @section Implementing a Remote Stub
17180 @cindex debugging stub, example
17181 @cindex remote stub, example
17182 @cindex stub example, remote debugging
17183 The stub files provided with @value{GDBN} implement the target side of the
17184 communication protocol, and the @value{GDBN} side is implemented in the
17185 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
17186 these subroutines to communicate, and ignore the details. (If you're
17187 implementing your own stub file, you can still ignore the details: start
17188 with one of the existing stub files. @file{sparc-stub.c} is the best
17189 organized, and therefore the easiest to read.)
17191 @cindex remote serial debugging, overview
17192 To debug a program running on another machine (the debugging
17193 @dfn{target} machine), you must first arrange for all the usual
17194 prerequisites for the program to run by itself. For example, for a C
17199 A startup routine to set up the C runtime environment; these usually
17200 have a name like @file{crt0}. The startup routine may be supplied by
17201 your hardware supplier, or you may have to write your own.
17204 A C subroutine library to support your program's
17205 subroutine calls, notably managing input and output.
17208 A way of getting your program to the other machine---for example, a
17209 download program. These are often supplied by the hardware
17210 manufacturer, but you may have to write your own from hardware
17214 The next step is to arrange for your program to use a serial port to
17215 communicate with the machine where @value{GDBN} is running (the @dfn{host}
17216 machine). In general terms, the scheme looks like this:
17220 @value{GDBN} already understands how to use this protocol; when everything
17221 else is set up, you can simply use the @samp{target remote} command
17222 (@pxref{Targets,,Specifying a Debugging Target}).
17224 @item On the target,
17225 you must link with your program a few special-purpose subroutines that
17226 implement the @value{GDBN} remote serial protocol. The file containing these
17227 subroutines is called a @dfn{debugging stub}.
17229 On certain remote targets, you can use an auxiliary program
17230 @code{gdbserver} instead of linking a stub into your program.
17231 @xref{Server,,Using the @code{gdbserver} Program}, for details.
17234 The debugging stub is specific to the architecture of the remote
17235 machine; for example, use @file{sparc-stub.c} to debug programs on
17238 @cindex remote serial stub list
17239 These working remote stubs are distributed with @value{GDBN}:
17244 @cindex @file{i386-stub.c}
17247 For Intel 386 and compatible architectures.
17250 @cindex @file{m68k-stub.c}
17251 @cindex Motorola 680x0
17253 For Motorola 680x0 architectures.
17256 @cindex @file{sh-stub.c}
17259 For Renesas SH architectures.
17262 @cindex @file{sparc-stub.c}
17264 For @sc{sparc} architectures.
17266 @item sparcl-stub.c
17267 @cindex @file{sparcl-stub.c}
17270 For Fujitsu @sc{sparclite} architectures.
17274 The @file{README} file in the @value{GDBN} distribution may list other
17275 recently added stubs.
17278 * Stub Contents:: What the stub can do for you
17279 * Bootstrapping:: What you must do for the stub
17280 * Debug Session:: Putting it all together
17283 @node Stub Contents
17284 @subsection What the Stub Can Do for You
17286 @cindex remote serial stub
17287 The debugging stub for your architecture supplies these three
17291 @item set_debug_traps
17292 @findex set_debug_traps
17293 @cindex remote serial stub, initialization
17294 This routine arranges for @code{handle_exception} to run when your
17295 program stops. You must call this subroutine explicitly near the
17296 beginning of your program.
17298 @item handle_exception
17299 @findex handle_exception
17300 @cindex remote serial stub, main routine
17301 This is the central workhorse, but your program never calls it
17302 explicitly---the setup code arranges for @code{handle_exception} to
17303 run when a trap is triggered.
17305 @code{handle_exception} takes control when your program stops during
17306 execution (for example, on a breakpoint), and mediates communications
17307 with @value{GDBN} on the host machine. This is where the communications
17308 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
17309 representative on the target machine. It begins by sending summary
17310 information on the state of your program, then continues to execute,
17311 retrieving and transmitting any information @value{GDBN} needs, until you
17312 execute a @value{GDBN} command that makes your program resume; at that point,
17313 @code{handle_exception} returns control to your own code on the target
17317 @cindex @code{breakpoint} subroutine, remote
17318 Use this auxiliary subroutine to make your program contain a
17319 breakpoint. Depending on the particular situation, this may be the only
17320 way for @value{GDBN} to get control. For instance, if your target
17321 machine has some sort of interrupt button, you won't need to call this;
17322 pressing the interrupt button transfers control to
17323 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
17324 simply receiving characters on the serial port may also trigger a trap;
17325 again, in that situation, you don't need to call @code{breakpoint} from
17326 your own program---simply running @samp{target remote} from the host
17327 @value{GDBN} session gets control.
17329 Call @code{breakpoint} if none of these is true, or if you simply want
17330 to make certain your program stops at a predetermined point for the
17331 start of your debugging session.
17334 @node Bootstrapping
17335 @subsection What You Must Do for the Stub
17337 @cindex remote stub, support routines
17338 The debugging stubs that come with @value{GDBN} are set up for a particular
17339 chip architecture, but they have no information about the rest of your
17340 debugging target machine.
17342 First of all you need to tell the stub how to communicate with the
17346 @item int getDebugChar()
17347 @findex getDebugChar
17348 Write this subroutine to read a single character from the serial port.
17349 It may be identical to @code{getchar} for your target system; a
17350 different name is used to allow you to distinguish the two if you wish.
17352 @item void putDebugChar(int)
17353 @findex putDebugChar
17354 Write this subroutine to write a single character to the serial port.
17355 It may be identical to @code{putchar} for your target system; a
17356 different name is used to allow you to distinguish the two if you wish.
17359 @cindex control C, and remote debugging
17360 @cindex interrupting remote targets
17361 If you want @value{GDBN} to be able to stop your program while it is
17362 running, you need to use an interrupt-driven serial driver, and arrange
17363 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
17364 character). That is the character which @value{GDBN} uses to tell the
17365 remote system to stop.
17367 Getting the debugging target to return the proper status to @value{GDBN}
17368 probably requires changes to the standard stub; one quick and dirty way
17369 is to just execute a breakpoint instruction (the ``dirty'' part is that
17370 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
17372 Other routines you need to supply are:
17375 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
17376 @findex exceptionHandler
17377 Write this function to install @var{exception_address} in the exception
17378 handling tables. You need to do this because the stub does not have any
17379 way of knowing what the exception handling tables on your target system
17380 are like (for example, the processor's table might be in @sc{rom},
17381 containing entries which point to a table in @sc{ram}).
17382 @var{exception_number} is the exception number which should be changed;
17383 its meaning is architecture-dependent (for example, different numbers
17384 might represent divide by zero, misaligned access, etc). When this
17385 exception occurs, control should be transferred directly to
17386 @var{exception_address}, and the processor state (stack, registers,
17387 and so on) should be just as it is when a processor exception occurs. So if
17388 you want to use a jump instruction to reach @var{exception_address}, it
17389 should be a simple jump, not a jump to subroutine.
17391 For the 386, @var{exception_address} should be installed as an interrupt
17392 gate so that interrupts are masked while the handler runs. The gate
17393 should be at privilege level 0 (the most privileged level). The
17394 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
17395 help from @code{exceptionHandler}.
17397 @item void flush_i_cache()
17398 @findex flush_i_cache
17399 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
17400 instruction cache, if any, on your target machine. If there is no
17401 instruction cache, this subroutine may be a no-op.
17403 On target machines that have instruction caches, @value{GDBN} requires this
17404 function to make certain that the state of your program is stable.
17408 You must also make sure this library routine is available:
17411 @item void *memset(void *, int, int)
17413 This is the standard library function @code{memset} that sets an area of
17414 memory to a known value. If you have one of the free versions of
17415 @code{libc.a}, @code{memset} can be found there; otherwise, you must
17416 either obtain it from your hardware manufacturer, or write your own.
17419 If you do not use the GNU C compiler, you may need other standard
17420 library subroutines as well; this varies from one stub to another,
17421 but in general the stubs are likely to use any of the common library
17422 subroutines which @code{@value{NGCC}} generates as inline code.
17425 @node Debug Session
17426 @subsection Putting it All Together
17428 @cindex remote serial debugging summary
17429 In summary, when your program is ready to debug, you must follow these
17434 Make sure you have defined the supporting low-level routines
17435 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
17437 @code{getDebugChar}, @code{putDebugChar},
17438 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
17442 Insert these lines near the top of your program:
17450 For the 680x0 stub only, you need to provide a variable called
17451 @code{exceptionHook}. Normally you just use:
17454 void (*exceptionHook)() = 0;
17458 but if before calling @code{set_debug_traps}, you set it to point to a
17459 function in your program, that function is called when
17460 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
17461 error). The function indicated by @code{exceptionHook} is called with
17462 one parameter: an @code{int} which is the exception number.
17465 Compile and link together: your program, the @value{GDBN} debugging stub for
17466 your target architecture, and the supporting subroutines.
17469 Make sure you have a serial connection between your target machine and
17470 the @value{GDBN} host, and identify the serial port on the host.
17473 @c The "remote" target now provides a `load' command, so we should
17474 @c document that. FIXME.
17475 Download your program to your target machine (or get it there by
17476 whatever means the manufacturer provides), and start it.
17479 Start @value{GDBN} on the host, and connect to the target
17480 (@pxref{Connecting,,Connecting to a Remote Target}).
17484 @node Configurations
17485 @chapter Configuration-Specific Information
17487 While nearly all @value{GDBN} commands are available for all native and
17488 cross versions of the debugger, there are some exceptions. This chapter
17489 describes things that are only available in certain configurations.
17491 There are three major categories of configurations: native
17492 configurations, where the host and target are the same, embedded
17493 operating system configurations, which are usually the same for several
17494 different processor architectures, and bare embedded processors, which
17495 are quite different from each other.
17500 * Embedded Processors::
17507 This section describes details specific to particular native
17512 * BSD libkvm Interface:: Debugging BSD kernel memory images
17513 * SVR4 Process Information:: SVR4 process information
17514 * DJGPP Native:: Features specific to the DJGPP port
17515 * Cygwin Native:: Features specific to the Cygwin port
17516 * Hurd Native:: Features specific to @sc{gnu} Hurd
17517 * Neutrino:: Features specific to QNX Neutrino
17518 * Darwin:: Features specific to Darwin
17524 On HP-UX systems, if you refer to a function or variable name that
17525 begins with a dollar sign, @value{GDBN} searches for a user or system
17526 name first, before it searches for a convenience variable.
17529 @node BSD libkvm Interface
17530 @subsection BSD libkvm Interface
17533 @cindex kernel memory image
17534 @cindex kernel crash dump
17536 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
17537 interface that provides a uniform interface for accessing kernel virtual
17538 memory images, including live systems and crash dumps. @value{GDBN}
17539 uses this interface to allow you to debug live kernels and kernel crash
17540 dumps on many native BSD configurations. This is implemented as a
17541 special @code{kvm} debugging target. For debugging a live system, load
17542 the currently running kernel into @value{GDBN} and connect to the
17546 (@value{GDBP}) @b{target kvm}
17549 For debugging crash dumps, provide the file name of the crash dump as an
17553 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
17556 Once connected to the @code{kvm} target, the following commands are
17562 Set current context from the @dfn{Process Control Block} (PCB) address.
17565 Set current context from proc address. This command isn't available on
17566 modern FreeBSD systems.
17569 @node SVR4 Process Information
17570 @subsection SVR4 Process Information
17572 @cindex examine process image
17573 @cindex process info via @file{/proc}
17575 Many versions of SVR4 and compatible systems provide a facility called
17576 @samp{/proc} that can be used to examine the image of a running
17577 process using file-system subroutines. If @value{GDBN} is configured
17578 for an operating system with this facility, the command @code{info
17579 proc} is available to report information about the process running
17580 your program, or about any process running on your system. @code{info
17581 proc} works only on SVR4 systems that include the @code{procfs} code.
17582 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
17583 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
17589 @itemx info proc @var{process-id}
17590 Summarize available information about any running process. If a
17591 process ID is specified by @var{process-id}, display information about
17592 that process; otherwise display information about the program being
17593 debugged. The summary includes the debugged process ID, the command
17594 line used to invoke it, its current working directory, and its
17595 executable file's absolute file name.
17597 On some systems, @var{process-id} can be of the form
17598 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
17599 within a process. If the optional @var{pid} part is missing, it means
17600 a thread from the process being debugged (the leading @samp{/} still
17601 needs to be present, or else @value{GDBN} will interpret the number as
17602 a process ID rather than a thread ID).
17604 @item info proc mappings
17605 @cindex memory address space mappings
17606 Report the memory address space ranges accessible in the program, with
17607 information on whether the process has read, write, or execute access
17608 rights to each range. On @sc{gnu}/Linux systems, each memory range
17609 includes the object file which is mapped to that range, instead of the
17610 memory access rights to that range.
17612 @item info proc stat
17613 @itemx info proc status
17614 @cindex process detailed status information
17615 These subcommands are specific to @sc{gnu}/Linux systems. They show
17616 the process-related information, including the user ID and group ID;
17617 how many threads are there in the process; its virtual memory usage;
17618 the signals that are pending, blocked, and ignored; its TTY; its
17619 consumption of system and user time; its stack size; its @samp{nice}
17620 value; etc. For more information, see the @samp{proc} man page
17621 (type @kbd{man 5 proc} from your shell prompt).
17623 @item info proc all
17624 Show all the information about the process described under all of the
17625 above @code{info proc} subcommands.
17628 @comment These sub-options of 'info proc' were not included when
17629 @comment procfs.c was re-written. Keep their descriptions around
17630 @comment against the day when someone finds the time to put them back in.
17631 @kindex info proc times
17632 @item info proc times
17633 Starting time, user CPU time, and system CPU time for your program and
17636 @kindex info proc id
17638 Report on the process IDs related to your program: its own process ID,
17639 the ID of its parent, the process group ID, and the session ID.
17642 @item set procfs-trace
17643 @kindex set procfs-trace
17644 @cindex @code{procfs} API calls
17645 This command enables and disables tracing of @code{procfs} API calls.
17647 @item show procfs-trace
17648 @kindex show procfs-trace
17649 Show the current state of @code{procfs} API call tracing.
17651 @item set procfs-file @var{file}
17652 @kindex set procfs-file
17653 Tell @value{GDBN} to write @code{procfs} API trace to the named
17654 @var{file}. @value{GDBN} appends the trace info to the previous
17655 contents of the file. The default is to display the trace on the
17658 @item show procfs-file
17659 @kindex show procfs-file
17660 Show the file to which @code{procfs} API trace is written.
17662 @item proc-trace-entry
17663 @itemx proc-trace-exit
17664 @itemx proc-untrace-entry
17665 @itemx proc-untrace-exit
17666 @kindex proc-trace-entry
17667 @kindex proc-trace-exit
17668 @kindex proc-untrace-entry
17669 @kindex proc-untrace-exit
17670 These commands enable and disable tracing of entries into and exits
17671 from the @code{syscall} interface.
17674 @kindex info pidlist
17675 @cindex process list, QNX Neutrino
17676 For QNX Neutrino only, this command displays the list of all the
17677 processes and all the threads within each process.
17680 @kindex info meminfo
17681 @cindex mapinfo list, QNX Neutrino
17682 For QNX Neutrino only, this command displays the list of all mapinfos.
17686 @subsection Features for Debugging @sc{djgpp} Programs
17687 @cindex @sc{djgpp} debugging
17688 @cindex native @sc{djgpp} debugging
17689 @cindex MS-DOS-specific commands
17692 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
17693 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
17694 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
17695 top of real-mode DOS systems and their emulations.
17697 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
17698 defines a few commands specific to the @sc{djgpp} port. This
17699 subsection describes those commands.
17704 This is a prefix of @sc{djgpp}-specific commands which print
17705 information about the target system and important OS structures.
17708 @cindex MS-DOS system info
17709 @cindex free memory information (MS-DOS)
17710 @item info dos sysinfo
17711 This command displays assorted information about the underlying
17712 platform: the CPU type and features, the OS version and flavor, the
17713 DPMI version, and the available conventional and DPMI memory.
17718 @cindex segment descriptor tables
17719 @cindex descriptor tables display
17721 @itemx info dos ldt
17722 @itemx info dos idt
17723 These 3 commands display entries from, respectively, Global, Local,
17724 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
17725 tables are data structures which store a descriptor for each segment
17726 that is currently in use. The segment's selector is an index into a
17727 descriptor table; the table entry for that index holds the
17728 descriptor's base address and limit, and its attributes and access
17731 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
17732 segment (used for both data and the stack), and a DOS segment (which
17733 allows access to DOS/BIOS data structures and absolute addresses in
17734 conventional memory). However, the DPMI host will usually define
17735 additional segments in order to support the DPMI environment.
17737 @cindex garbled pointers
17738 These commands allow to display entries from the descriptor tables.
17739 Without an argument, all entries from the specified table are
17740 displayed. An argument, which should be an integer expression, means
17741 display a single entry whose index is given by the argument. For
17742 example, here's a convenient way to display information about the
17743 debugged program's data segment:
17746 @exdent @code{(@value{GDBP}) info dos ldt $ds}
17747 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
17751 This comes in handy when you want to see whether a pointer is outside
17752 the data segment's limit (i.e.@: @dfn{garbled}).
17754 @cindex page tables display (MS-DOS)
17756 @itemx info dos pte
17757 These two commands display entries from, respectively, the Page
17758 Directory and the Page Tables. Page Directories and Page Tables are
17759 data structures which control how virtual memory addresses are mapped
17760 into physical addresses. A Page Table includes an entry for every
17761 page of memory that is mapped into the program's address space; there
17762 may be several Page Tables, each one holding up to 4096 entries. A
17763 Page Directory has up to 4096 entries, one each for every Page Table
17764 that is currently in use.
17766 Without an argument, @kbd{info dos pde} displays the entire Page
17767 Directory, and @kbd{info dos pte} displays all the entries in all of
17768 the Page Tables. An argument, an integer expression, given to the
17769 @kbd{info dos pde} command means display only that entry from the Page
17770 Directory table. An argument given to the @kbd{info dos pte} command
17771 means display entries from a single Page Table, the one pointed to by
17772 the specified entry in the Page Directory.
17774 @cindex direct memory access (DMA) on MS-DOS
17775 These commands are useful when your program uses @dfn{DMA} (Direct
17776 Memory Access), which needs physical addresses to program the DMA
17779 These commands are supported only with some DPMI servers.
17781 @cindex physical address from linear address
17782 @item info dos address-pte @var{addr}
17783 This command displays the Page Table entry for a specified linear
17784 address. The argument @var{addr} is a linear address which should
17785 already have the appropriate segment's base address added to it,
17786 because this command accepts addresses which may belong to @emph{any}
17787 segment. For example, here's how to display the Page Table entry for
17788 the page where a variable @code{i} is stored:
17791 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
17792 @exdent @code{Page Table entry for address 0x11a00d30:}
17793 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
17797 This says that @code{i} is stored at offset @code{0xd30} from the page
17798 whose physical base address is @code{0x02698000}, and shows all the
17799 attributes of that page.
17801 Note that you must cast the addresses of variables to a @code{char *},
17802 since otherwise the value of @code{__djgpp_base_address}, the base
17803 address of all variables and functions in a @sc{djgpp} program, will
17804 be added using the rules of C pointer arithmetics: if @code{i} is
17805 declared an @code{int}, @value{GDBN} will add 4 times the value of
17806 @code{__djgpp_base_address} to the address of @code{i}.
17808 Here's another example, it displays the Page Table entry for the
17812 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
17813 @exdent @code{Page Table entry for address 0x29110:}
17814 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
17818 (The @code{+ 3} offset is because the transfer buffer's address is the
17819 3rd member of the @code{_go32_info_block} structure.) The output
17820 clearly shows that this DPMI server maps the addresses in conventional
17821 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
17822 linear (@code{0x29110}) addresses are identical.
17824 This command is supported only with some DPMI servers.
17827 @cindex DOS serial data link, remote debugging
17828 In addition to native debugging, the DJGPP port supports remote
17829 debugging via a serial data link. The following commands are specific
17830 to remote serial debugging in the DJGPP port of @value{GDBN}.
17833 @kindex set com1base
17834 @kindex set com1irq
17835 @kindex set com2base
17836 @kindex set com2irq
17837 @kindex set com3base
17838 @kindex set com3irq
17839 @kindex set com4base
17840 @kindex set com4irq
17841 @item set com1base @var{addr}
17842 This command sets the base I/O port address of the @file{COM1} serial
17845 @item set com1irq @var{irq}
17846 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
17847 for the @file{COM1} serial port.
17849 There are similar commands @samp{set com2base}, @samp{set com3irq},
17850 etc.@: for setting the port address and the @code{IRQ} lines for the
17853 @kindex show com1base
17854 @kindex show com1irq
17855 @kindex show com2base
17856 @kindex show com2irq
17857 @kindex show com3base
17858 @kindex show com3irq
17859 @kindex show com4base
17860 @kindex show com4irq
17861 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
17862 display the current settings of the base address and the @code{IRQ}
17863 lines used by the COM ports.
17866 @kindex info serial
17867 @cindex DOS serial port status
17868 This command prints the status of the 4 DOS serial ports. For each
17869 port, it prints whether it's active or not, its I/O base address and
17870 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
17871 counts of various errors encountered so far.
17875 @node Cygwin Native
17876 @subsection Features for Debugging MS Windows PE Executables
17877 @cindex MS Windows debugging
17878 @cindex native Cygwin debugging
17879 @cindex Cygwin-specific commands
17881 @value{GDBN} supports native debugging of MS Windows programs, including
17882 DLLs with and without symbolic debugging information.
17884 @cindex Ctrl-BREAK, MS-Windows
17885 @cindex interrupt debuggee on MS-Windows
17886 MS-Windows programs that call @code{SetConsoleMode} to switch off the
17887 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
17888 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
17889 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
17890 sequence, which can be used to interrupt the debuggee even if it
17893 There are various additional Cygwin-specific commands, described in
17894 this section. Working with DLLs that have no debugging symbols is
17895 described in @ref{Non-debug DLL Symbols}.
17900 This is a prefix of MS Windows-specific commands which print
17901 information about the target system and important OS structures.
17903 @item info w32 selector
17904 This command displays information returned by
17905 the Win32 API @code{GetThreadSelectorEntry} function.
17906 It takes an optional argument that is evaluated to
17907 a long value to give the information about this given selector.
17908 Without argument, this command displays information
17909 about the six segment registers.
17911 @item info w32 thread-information-block
17912 This command displays thread specific information stored in the
17913 Thread Information Block (readable on the X86 CPU family using @code{$fs}
17914 selector for 32-bit programs and @code{$gs} for 64-bit programs).
17918 This is a Cygwin-specific alias of @code{info shared}.
17920 @kindex dll-symbols
17922 This command loads symbols from a dll similarly to
17923 add-sym command but without the need to specify a base address.
17925 @kindex set cygwin-exceptions
17926 @cindex debugging the Cygwin DLL
17927 @cindex Cygwin DLL, debugging
17928 @item set cygwin-exceptions @var{mode}
17929 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
17930 happen inside the Cygwin DLL. If @var{mode} is @code{off},
17931 @value{GDBN} will delay recognition of exceptions, and may ignore some
17932 exceptions which seem to be caused by internal Cygwin DLL
17933 ``bookkeeping''. This option is meant primarily for debugging the
17934 Cygwin DLL itself; the default value is @code{off} to avoid annoying
17935 @value{GDBN} users with false @code{SIGSEGV} signals.
17937 @kindex show cygwin-exceptions
17938 @item show cygwin-exceptions
17939 Displays whether @value{GDBN} will break on exceptions that happen
17940 inside the Cygwin DLL itself.
17942 @kindex set new-console
17943 @item set new-console @var{mode}
17944 If @var{mode} is @code{on} the debuggee will
17945 be started in a new console on next start.
17946 If @var{mode} is @code{off}, the debuggee will
17947 be started in the same console as the debugger.
17949 @kindex show new-console
17950 @item show new-console
17951 Displays whether a new console is used
17952 when the debuggee is started.
17954 @kindex set new-group
17955 @item set new-group @var{mode}
17956 This boolean value controls whether the debuggee should
17957 start a new group or stay in the same group as the debugger.
17958 This affects the way the Windows OS handles
17961 @kindex show new-group
17962 @item show new-group
17963 Displays current value of new-group boolean.
17965 @kindex set debugevents
17966 @item set debugevents
17967 This boolean value adds debug output concerning kernel events related
17968 to the debuggee seen by the debugger. This includes events that
17969 signal thread and process creation and exit, DLL loading and
17970 unloading, console interrupts, and debugging messages produced by the
17971 Windows @code{OutputDebugString} API call.
17973 @kindex set debugexec
17974 @item set debugexec
17975 This boolean value adds debug output concerning execute events
17976 (such as resume thread) seen by the debugger.
17978 @kindex set debugexceptions
17979 @item set debugexceptions
17980 This boolean value adds debug output concerning exceptions in the
17981 debuggee seen by the debugger.
17983 @kindex set debugmemory
17984 @item set debugmemory
17985 This boolean value adds debug output concerning debuggee memory reads
17986 and writes by the debugger.
17990 This boolean values specifies whether the debuggee is called
17991 via a shell or directly (default value is on).
17995 Displays if the debuggee will be started with a shell.
18000 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
18003 @node Non-debug DLL Symbols
18004 @subsubsection Support for DLLs without Debugging Symbols
18005 @cindex DLLs with no debugging symbols
18006 @cindex Minimal symbols and DLLs
18008 Very often on windows, some of the DLLs that your program relies on do
18009 not include symbolic debugging information (for example,
18010 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
18011 symbols in a DLL, it relies on the minimal amount of symbolic
18012 information contained in the DLL's export table. This section
18013 describes working with such symbols, known internally to @value{GDBN} as
18014 ``minimal symbols''.
18016 Note that before the debugged program has started execution, no DLLs
18017 will have been loaded. The easiest way around this problem is simply to
18018 start the program --- either by setting a breakpoint or letting the
18019 program run once to completion. It is also possible to force
18020 @value{GDBN} to load a particular DLL before starting the executable ---
18021 see the shared library information in @ref{Files}, or the
18022 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
18023 explicitly loading symbols from a DLL with no debugging information will
18024 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
18025 which may adversely affect symbol lookup performance.
18027 @subsubsection DLL Name Prefixes
18029 In keeping with the naming conventions used by the Microsoft debugging
18030 tools, DLL export symbols are made available with a prefix based on the
18031 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
18032 also entered into the symbol table, so @code{CreateFileA} is often
18033 sufficient. In some cases there will be name clashes within a program
18034 (particularly if the executable itself includes full debugging symbols)
18035 necessitating the use of the fully qualified name when referring to the
18036 contents of the DLL. Use single-quotes around the name to avoid the
18037 exclamation mark (``!'') being interpreted as a language operator.
18039 Note that the internal name of the DLL may be all upper-case, even
18040 though the file name of the DLL is lower-case, or vice-versa. Since
18041 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
18042 some confusion. If in doubt, try the @code{info functions} and
18043 @code{info variables} commands or even @code{maint print msymbols}
18044 (@pxref{Symbols}). Here's an example:
18047 (@value{GDBP}) info function CreateFileA
18048 All functions matching regular expression "CreateFileA":
18050 Non-debugging symbols:
18051 0x77e885f4 CreateFileA
18052 0x77e885f4 KERNEL32!CreateFileA
18056 (@value{GDBP}) info function !
18057 All functions matching regular expression "!":
18059 Non-debugging symbols:
18060 0x6100114c cygwin1!__assert
18061 0x61004034 cygwin1!_dll_crt0@@0
18062 0x61004240 cygwin1!dll_crt0(per_process *)
18066 @subsubsection Working with Minimal Symbols
18068 Symbols extracted from a DLL's export table do not contain very much
18069 type information. All that @value{GDBN} can do is guess whether a symbol
18070 refers to a function or variable depending on the linker section that
18071 contains the symbol. Also note that the actual contents of the memory
18072 contained in a DLL are not available unless the program is running. This
18073 means that you cannot examine the contents of a variable or disassemble
18074 a function within a DLL without a running program.
18076 Variables are generally treated as pointers and dereferenced
18077 automatically. For this reason, it is often necessary to prefix a
18078 variable name with the address-of operator (``&'') and provide explicit
18079 type information in the command. Here's an example of the type of
18083 (@value{GDBP}) print 'cygwin1!__argv'
18088 (@value{GDBP}) x 'cygwin1!__argv'
18089 0x10021610: "\230y\""
18092 And two possible solutions:
18095 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
18096 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
18100 (@value{GDBP}) x/2x &'cygwin1!__argv'
18101 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
18102 (@value{GDBP}) x/x 0x10021608
18103 0x10021608: 0x0022fd98
18104 (@value{GDBP}) x/s 0x0022fd98
18105 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
18108 Setting a break point within a DLL is possible even before the program
18109 starts execution. However, under these circumstances, @value{GDBN} can't
18110 examine the initial instructions of the function in order to skip the
18111 function's frame set-up code. You can work around this by using ``*&''
18112 to set the breakpoint at a raw memory address:
18115 (@value{GDBP}) break *&'python22!PyOS_Readline'
18116 Breakpoint 1 at 0x1e04eff0
18119 The author of these extensions is not entirely convinced that setting a
18120 break point within a shared DLL like @file{kernel32.dll} is completely
18124 @subsection Commands Specific to @sc{gnu} Hurd Systems
18125 @cindex @sc{gnu} Hurd debugging
18127 This subsection describes @value{GDBN} commands specific to the
18128 @sc{gnu} Hurd native debugging.
18133 @kindex set signals@r{, Hurd command}
18134 @kindex set sigs@r{, Hurd command}
18135 This command toggles the state of inferior signal interception by
18136 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
18137 affected by this command. @code{sigs} is a shorthand alias for
18142 @kindex show signals@r{, Hurd command}
18143 @kindex show sigs@r{, Hurd command}
18144 Show the current state of intercepting inferior's signals.
18146 @item set signal-thread
18147 @itemx set sigthread
18148 @kindex set signal-thread
18149 @kindex set sigthread
18150 This command tells @value{GDBN} which thread is the @code{libc} signal
18151 thread. That thread is run when a signal is delivered to a running
18152 process. @code{set sigthread} is the shorthand alias of @code{set
18155 @item show signal-thread
18156 @itemx show sigthread
18157 @kindex show signal-thread
18158 @kindex show sigthread
18159 These two commands show which thread will run when the inferior is
18160 delivered a signal.
18163 @kindex set stopped@r{, Hurd command}
18164 This commands tells @value{GDBN} that the inferior process is stopped,
18165 as with the @code{SIGSTOP} signal. The stopped process can be
18166 continued by delivering a signal to it.
18169 @kindex show stopped@r{, Hurd command}
18170 This command shows whether @value{GDBN} thinks the debuggee is
18173 @item set exceptions
18174 @kindex set exceptions@r{, Hurd command}
18175 Use this command to turn off trapping of exceptions in the inferior.
18176 When exception trapping is off, neither breakpoints nor
18177 single-stepping will work. To restore the default, set exception
18180 @item show exceptions
18181 @kindex show exceptions@r{, Hurd command}
18182 Show the current state of trapping exceptions in the inferior.
18184 @item set task pause
18185 @kindex set task@r{, Hurd commands}
18186 @cindex task attributes (@sc{gnu} Hurd)
18187 @cindex pause current task (@sc{gnu} Hurd)
18188 This command toggles task suspension when @value{GDBN} has control.
18189 Setting it to on takes effect immediately, and the task is suspended
18190 whenever @value{GDBN} gets control. Setting it to off will take
18191 effect the next time the inferior is continued. If this option is set
18192 to off, you can use @code{set thread default pause on} or @code{set
18193 thread pause on} (see below) to pause individual threads.
18195 @item show task pause
18196 @kindex show task@r{, Hurd commands}
18197 Show the current state of task suspension.
18199 @item set task detach-suspend-count
18200 @cindex task suspend count
18201 @cindex detach from task, @sc{gnu} Hurd
18202 This command sets the suspend count the task will be left with when
18203 @value{GDBN} detaches from it.
18205 @item show task detach-suspend-count
18206 Show the suspend count the task will be left with when detaching.
18208 @item set task exception-port
18209 @itemx set task excp
18210 @cindex task exception port, @sc{gnu} Hurd
18211 This command sets the task exception port to which @value{GDBN} will
18212 forward exceptions. The argument should be the value of the @dfn{send
18213 rights} of the task. @code{set task excp} is a shorthand alias.
18215 @item set noninvasive
18216 @cindex noninvasive task options
18217 This command switches @value{GDBN} to a mode that is the least
18218 invasive as far as interfering with the inferior is concerned. This
18219 is the same as using @code{set task pause}, @code{set exceptions}, and
18220 @code{set signals} to values opposite to the defaults.
18222 @item info send-rights
18223 @itemx info receive-rights
18224 @itemx info port-rights
18225 @itemx info port-sets
18226 @itemx info dead-names
18229 @cindex send rights, @sc{gnu} Hurd
18230 @cindex receive rights, @sc{gnu} Hurd
18231 @cindex port rights, @sc{gnu} Hurd
18232 @cindex port sets, @sc{gnu} Hurd
18233 @cindex dead names, @sc{gnu} Hurd
18234 These commands display information about, respectively, send rights,
18235 receive rights, port rights, port sets, and dead names of a task.
18236 There are also shorthand aliases: @code{info ports} for @code{info
18237 port-rights} and @code{info psets} for @code{info port-sets}.
18239 @item set thread pause
18240 @kindex set thread@r{, Hurd command}
18241 @cindex thread properties, @sc{gnu} Hurd
18242 @cindex pause current thread (@sc{gnu} Hurd)
18243 This command toggles current thread suspension when @value{GDBN} has
18244 control. Setting it to on takes effect immediately, and the current
18245 thread is suspended whenever @value{GDBN} gets control. Setting it to
18246 off will take effect the next time the inferior is continued.
18247 Normally, this command has no effect, since when @value{GDBN} has
18248 control, the whole task is suspended. However, if you used @code{set
18249 task pause off} (see above), this command comes in handy to suspend
18250 only the current thread.
18252 @item show thread pause
18253 @kindex show thread@r{, Hurd command}
18254 This command shows the state of current thread suspension.
18256 @item set thread run
18257 This command sets whether the current thread is allowed to run.
18259 @item show thread run
18260 Show whether the current thread is allowed to run.
18262 @item set thread detach-suspend-count
18263 @cindex thread suspend count, @sc{gnu} Hurd
18264 @cindex detach from thread, @sc{gnu} Hurd
18265 This command sets the suspend count @value{GDBN} will leave on a
18266 thread when detaching. This number is relative to the suspend count
18267 found by @value{GDBN} when it notices the thread; use @code{set thread
18268 takeover-suspend-count} to force it to an absolute value.
18270 @item show thread detach-suspend-count
18271 Show the suspend count @value{GDBN} will leave on the thread when
18274 @item set thread exception-port
18275 @itemx set thread excp
18276 Set the thread exception port to which to forward exceptions. This
18277 overrides the port set by @code{set task exception-port} (see above).
18278 @code{set thread excp} is the shorthand alias.
18280 @item set thread takeover-suspend-count
18281 Normally, @value{GDBN}'s thread suspend counts are relative to the
18282 value @value{GDBN} finds when it notices each thread. This command
18283 changes the suspend counts to be absolute instead.
18285 @item set thread default
18286 @itemx show thread default
18287 @cindex thread default settings, @sc{gnu} Hurd
18288 Each of the above @code{set thread} commands has a @code{set thread
18289 default} counterpart (e.g., @code{set thread default pause}, @code{set
18290 thread default exception-port}, etc.). The @code{thread default}
18291 variety of commands sets the default thread properties for all
18292 threads; you can then change the properties of individual threads with
18293 the non-default commands.
18298 @subsection QNX Neutrino
18299 @cindex QNX Neutrino
18301 @value{GDBN} provides the following commands specific to the QNX
18305 @item set debug nto-debug
18306 @kindex set debug nto-debug
18307 When set to on, enables debugging messages specific to the QNX
18310 @item show debug nto-debug
18311 @kindex show debug nto-debug
18312 Show the current state of QNX Neutrino messages.
18319 @value{GDBN} provides the following commands specific to the Darwin target:
18322 @item set debug darwin @var{num}
18323 @kindex set debug darwin
18324 When set to a non zero value, enables debugging messages specific to
18325 the Darwin support. Higher values produce more verbose output.
18327 @item show debug darwin
18328 @kindex show debug darwin
18329 Show the current state of Darwin messages.
18331 @item set debug mach-o @var{num}
18332 @kindex set debug mach-o
18333 When set to a non zero value, enables debugging messages while
18334 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
18335 file format used on Darwin for object and executable files.) Higher
18336 values produce more verbose output. This is a command to diagnose
18337 problems internal to @value{GDBN} and should not be needed in normal
18340 @item show debug mach-o
18341 @kindex show debug mach-o
18342 Show the current state of Mach-O file messages.
18344 @item set mach-exceptions on
18345 @itemx set mach-exceptions off
18346 @kindex set mach-exceptions
18347 On Darwin, faults are first reported as a Mach exception and are then
18348 mapped to a Posix signal. Use this command to turn on trapping of
18349 Mach exceptions in the inferior. This might be sometimes useful to
18350 better understand the cause of a fault. The default is off.
18352 @item show mach-exceptions
18353 @kindex show mach-exceptions
18354 Show the current state of exceptions trapping.
18359 @section Embedded Operating Systems
18361 This section describes configurations involving the debugging of
18362 embedded operating systems that are available for several different
18366 * VxWorks:: Using @value{GDBN} with VxWorks
18369 @value{GDBN} includes the ability to debug programs running on
18370 various real-time operating systems.
18373 @subsection Using @value{GDBN} with VxWorks
18379 @kindex target vxworks
18380 @item target vxworks @var{machinename}
18381 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
18382 is the target system's machine name or IP address.
18386 On VxWorks, @code{load} links @var{filename} dynamically on the
18387 current target system as well as adding its symbols in @value{GDBN}.
18389 @value{GDBN} enables developers to spawn and debug tasks running on networked
18390 VxWorks targets from a Unix host. Already-running tasks spawned from
18391 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
18392 both the Unix host and on the VxWorks target. The program
18393 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
18394 installed with the name @code{vxgdb}, to distinguish it from a
18395 @value{GDBN} for debugging programs on the host itself.)
18398 @item VxWorks-timeout @var{args}
18399 @kindex vxworks-timeout
18400 All VxWorks-based targets now support the option @code{vxworks-timeout}.
18401 This option is set by the user, and @var{args} represents the number of
18402 seconds @value{GDBN} waits for responses to rpc's. You might use this if
18403 your VxWorks target is a slow software simulator or is on the far side
18404 of a thin network line.
18407 The following information on connecting to VxWorks was current when
18408 this manual was produced; newer releases of VxWorks may use revised
18411 @findex INCLUDE_RDB
18412 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
18413 to include the remote debugging interface routines in the VxWorks
18414 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
18415 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
18416 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
18417 source debugging task @code{tRdbTask} when VxWorks is booted. For more
18418 information on configuring and remaking VxWorks, see the manufacturer's
18420 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
18422 Once you have included @file{rdb.a} in your VxWorks system image and set
18423 your Unix execution search path to find @value{GDBN}, you are ready to
18424 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
18425 @code{vxgdb}, depending on your installation).
18427 @value{GDBN} comes up showing the prompt:
18434 * VxWorks Connection:: Connecting to VxWorks
18435 * VxWorks Download:: VxWorks download
18436 * VxWorks Attach:: Running tasks
18439 @node VxWorks Connection
18440 @subsubsection Connecting to VxWorks
18442 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
18443 network. To connect to a target whose host name is ``@code{tt}'', type:
18446 (vxgdb) target vxworks tt
18450 @value{GDBN} displays messages like these:
18453 Attaching remote machine across net...
18458 @value{GDBN} then attempts to read the symbol tables of any object modules
18459 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
18460 these files by searching the directories listed in the command search
18461 path (@pxref{Environment, ,Your Program's Environment}); if it fails
18462 to find an object file, it displays a message such as:
18465 prog.o: No such file or directory.
18468 When this happens, add the appropriate directory to the search path with
18469 the @value{GDBN} command @code{path}, and execute the @code{target}
18472 @node VxWorks Download
18473 @subsubsection VxWorks Download
18475 @cindex download to VxWorks
18476 If you have connected to the VxWorks target and you want to debug an
18477 object that has not yet been loaded, you can use the @value{GDBN}
18478 @code{load} command to download a file from Unix to VxWorks
18479 incrementally. The object file given as an argument to the @code{load}
18480 command is actually opened twice: first by the VxWorks target in order
18481 to download the code, then by @value{GDBN} in order to read the symbol
18482 table. This can lead to problems if the current working directories on
18483 the two systems differ. If both systems have NFS mounted the same
18484 filesystems, you can avoid these problems by using absolute paths.
18485 Otherwise, it is simplest to set the working directory on both systems
18486 to the directory in which the object file resides, and then to reference
18487 the file by its name, without any path. For instance, a program
18488 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
18489 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
18490 program, type this on VxWorks:
18493 -> cd "@var{vxpath}/vw/demo/rdb"
18497 Then, in @value{GDBN}, type:
18500 (vxgdb) cd @var{hostpath}/vw/demo/rdb
18501 (vxgdb) load prog.o
18504 @value{GDBN} displays a response similar to this:
18507 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
18510 You can also use the @code{load} command to reload an object module
18511 after editing and recompiling the corresponding source file. Note that
18512 this makes @value{GDBN} delete all currently-defined breakpoints,
18513 auto-displays, and convenience variables, and to clear the value
18514 history. (This is necessary in order to preserve the integrity of
18515 debugger's data structures that reference the target system's symbol
18518 @node VxWorks Attach
18519 @subsubsection Running Tasks
18521 @cindex running VxWorks tasks
18522 You can also attach to an existing task using the @code{attach} command as
18526 (vxgdb) attach @var{task}
18530 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
18531 or suspended when you attach to it. Running tasks are suspended at
18532 the time of attachment.
18534 @node Embedded Processors
18535 @section Embedded Processors
18537 This section goes into details specific to particular embedded
18540 @cindex send command to simulator
18541 Whenever a specific embedded processor has a simulator, @value{GDBN}
18542 allows to send an arbitrary command to the simulator.
18545 @item sim @var{command}
18546 @kindex sim@r{, a command}
18547 Send an arbitrary @var{command} string to the simulator. Consult the
18548 documentation for the specific simulator in use for information about
18549 acceptable commands.
18555 * M32R/D:: Renesas M32R/D
18556 * M68K:: Motorola M68K
18557 * MicroBlaze:: Xilinx MicroBlaze
18558 * MIPS Embedded:: MIPS Embedded
18559 * OpenRISC 1000:: OpenRisc 1000
18560 * PA:: HP PA Embedded
18561 * PowerPC Embedded:: PowerPC Embedded
18562 * Sparclet:: Tsqware Sparclet
18563 * Sparclite:: Fujitsu Sparclite
18564 * Z8000:: Zilog Z8000
18567 * Super-H:: Renesas Super-H
18576 @item target rdi @var{dev}
18577 ARM Angel monitor, via RDI library interface to ADP protocol. You may
18578 use this target to communicate with both boards running the Angel
18579 monitor, or with the EmbeddedICE JTAG debug device.
18582 @item target rdp @var{dev}
18587 @value{GDBN} provides the following ARM-specific commands:
18590 @item set arm disassembler
18592 This commands selects from a list of disassembly styles. The
18593 @code{"std"} style is the standard style.
18595 @item show arm disassembler
18597 Show the current disassembly style.
18599 @item set arm apcs32
18600 @cindex ARM 32-bit mode
18601 This command toggles ARM operation mode between 32-bit and 26-bit.
18603 @item show arm apcs32
18604 Display the current usage of the ARM 32-bit mode.
18606 @item set arm fpu @var{fputype}
18607 This command sets the ARM floating-point unit (FPU) type. The
18608 argument @var{fputype} can be one of these:
18612 Determine the FPU type by querying the OS ABI.
18614 Software FPU, with mixed-endian doubles on little-endian ARM
18617 GCC-compiled FPA co-processor.
18619 Software FPU with pure-endian doubles.
18625 Show the current type of the FPU.
18628 This command forces @value{GDBN} to use the specified ABI.
18631 Show the currently used ABI.
18633 @item set arm fallback-mode (arm|thumb|auto)
18634 @value{GDBN} uses the symbol table, when available, to determine
18635 whether instructions are ARM or Thumb. This command controls
18636 @value{GDBN}'s default behavior when the symbol table is not
18637 available. The default is @samp{auto}, which causes @value{GDBN} to
18638 use the current execution mode (from the @code{T} bit in the @code{CPSR}
18641 @item show arm fallback-mode
18642 Show the current fallback instruction mode.
18644 @item set arm force-mode (arm|thumb|auto)
18645 This command overrides use of the symbol table to determine whether
18646 instructions are ARM or Thumb. The default is @samp{auto}, which
18647 causes @value{GDBN} to use the symbol table and then the setting
18648 of @samp{set arm fallback-mode}.
18650 @item show arm force-mode
18651 Show the current forced instruction mode.
18653 @item set debug arm
18654 Toggle whether to display ARM-specific debugging messages from the ARM
18655 target support subsystem.
18657 @item show debug arm
18658 Show whether ARM-specific debugging messages are enabled.
18661 The following commands are available when an ARM target is debugged
18662 using the RDI interface:
18665 @item rdilogfile @r{[}@var{file}@r{]}
18667 @cindex ADP (Angel Debugger Protocol) logging
18668 Set the filename for the ADP (Angel Debugger Protocol) packet log.
18669 With an argument, sets the log file to the specified @var{file}. With
18670 no argument, show the current log file name. The default log file is
18673 @item rdilogenable @r{[}@var{arg}@r{]}
18674 @kindex rdilogenable
18675 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
18676 enables logging, with an argument 0 or @code{"no"} disables it. With
18677 no arguments displays the current setting. When logging is enabled,
18678 ADP packets exchanged between @value{GDBN} and the RDI target device
18679 are logged to a file.
18681 @item set rdiromatzero
18682 @kindex set rdiromatzero
18683 @cindex ROM at zero address, RDI
18684 Tell @value{GDBN} whether the target has ROM at address 0. If on,
18685 vector catching is disabled, so that zero address can be used. If off
18686 (the default), vector catching is enabled. For this command to take
18687 effect, it needs to be invoked prior to the @code{target rdi} command.
18689 @item show rdiromatzero
18690 @kindex show rdiromatzero
18691 Show the current setting of ROM at zero address.
18693 @item set rdiheartbeat
18694 @kindex set rdiheartbeat
18695 @cindex RDI heartbeat
18696 Enable or disable RDI heartbeat packets. It is not recommended to
18697 turn on this option, since it confuses ARM and EPI JTAG interface, as
18698 well as the Angel monitor.
18700 @item show rdiheartbeat
18701 @kindex show rdiheartbeat
18702 Show the setting of RDI heartbeat packets.
18706 @item target sim @r{[}@var{simargs}@r{]} @dots{}
18707 The @value{GDBN} ARM simulator accepts the following optional arguments.
18710 @item --swi-support=@var{type}
18711 Tell the simulator which SWI interfaces to support.
18712 @var{type} may be a comma separated list of the following values.
18713 The default value is @code{all}.
18726 @subsection Renesas M32R/D and M32R/SDI
18729 @kindex target m32r
18730 @item target m32r @var{dev}
18731 Renesas M32R/D ROM monitor.
18733 @kindex target m32rsdi
18734 @item target m32rsdi @var{dev}
18735 Renesas M32R SDI server, connected via parallel port to the board.
18738 The following @value{GDBN} commands are specific to the M32R monitor:
18741 @item set download-path @var{path}
18742 @kindex set download-path
18743 @cindex find downloadable @sc{srec} files (M32R)
18744 Set the default path for finding downloadable @sc{srec} files.
18746 @item show download-path
18747 @kindex show download-path
18748 Show the default path for downloadable @sc{srec} files.
18750 @item set board-address @var{addr}
18751 @kindex set board-address
18752 @cindex M32-EVA target board address
18753 Set the IP address for the M32R-EVA target board.
18755 @item show board-address
18756 @kindex show board-address
18757 Show the current IP address of the target board.
18759 @item set server-address @var{addr}
18760 @kindex set server-address
18761 @cindex download server address (M32R)
18762 Set the IP address for the download server, which is the @value{GDBN}'s
18765 @item show server-address
18766 @kindex show server-address
18767 Display the IP address of the download server.
18769 @item upload @r{[}@var{file}@r{]}
18770 @kindex upload@r{, M32R}
18771 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
18772 upload capability. If no @var{file} argument is given, the current
18773 executable file is uploaded.
18775 @item tload @r{[}@var{file}@r{]}
18776 @kindex tload@r{, M32R}
18777 Test the @code{upload} command.
18780 The following commands are available for M32R/SDI:
18785 @cindex reset SDI connection, M32R
18786 This command resets the SDI connection.
18790 This command shows the SDI connection status.
18793 @kindex debug_chaos
18794 @cindex M32R/Chaos debugging
18795 Instructs the remote that M32R/Chaos debugging is to be used.
18797 @item use_debug_dma
18798 @kindex use_debug_dma
18799 Instructs the remote to use the DEBUG_DMA method of accessing memory.
18802 @kindex use_mon_code
18803 Instructs the remote to use the MON_CODE method of accessing memory.
18806 @kindex use_ib_break
18807 Instructs the remote to set breakpoints by IB break.
18809 @item use_dbt_break
18810 @kindex use_dbt_break
18811 Instructs the remote to set breakpoints by DBT.
18817 The Motorola m68k configuration includes ColdFire support, and a
18818 target command for the following ROM monitor.
18822 @kindex target dbug
18823 @item target dbug @var{dev}
18824 dBUG ROM monitor for Motorola ColdFire.
18829 @subsection MicroBlaze
18830 @cindex Xilinx MicroBlaze
18831 @cindex XMD, Xilinx Microprocessor Debugger
18833 The MicroBlaze is a soft-core processor supported on various Xilinx
18834 FPGAs, such as Spartan or Virtex series. Boards with these processors
18835 usually have JTAG ports which connect to a host system running the Xilinx
18836 Embedded Development Kit (EDK) or Software Development Kit (SDK).
18837 This host system is used to download the configuration bitstream to
18838 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
18839 communicates with the target board using the JTAG interface and
18840 presents a @code{gdbserver} interface to the board. By default
18841 @code{xmd} uses port @code{1234}. (While it is possible to change
18842 this default port, it requires the use of undocumented @code{xmd}
18843 commands. Contact Xilinx support if you need to do this.)
18845 Use these GDB commands to connect to the MicroBlaze target processor.
18848 @item target remote :1234
18849 Use this command to connect to the target if you are running @value{GDBN}
18850 on the same system as @code{xmd}.
18852 @item target remote @var{xmd-host}:1234
18853 Use this command to connect to the target if it is connected to @code{xmd}
18854 running on a different system named @var{xmd-host}.
18857 Use this command to download a program to the MicroBlaze target.
18859 @item set debug microblaze @var{n}
18860 Enable MicroBlaze-specific debugging messages if non-zero.
18862 @item show debug microblaze @var{n}
18863 Show MicroBlaze-specific debugging level.
18866 @node MIPS Embedded
18867 @subsection MIPS Embedded
18869 @cindex MIPS boards
18870 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
18871 MIPS board attached to a serial line. This is available when
18872 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
18875 Use these @value{GDBN} commands to specify the connection to your target board:
18878 @item target mips @var{port}
18879 @kindex target mips @var{port}
18880 To run a program on the board, start up @code{@value{GDBP}} with the
18881 name of your program as the argument. To connect to the board, use the
18882 command @samp{target mips @var{port}}, where @var{port} is the name of
18883 the serial port connected to the board. If the program has not already
18884 been downloaded to the board, you may use the @code{load} command to
18885 download it. You can then use all the usual @value{GDBN} commands.
18887 For example, this sequence connects to the target board through a serial
18888 port, and loads and runs a program called @var{prog} through the
18892 host$ @value{GDBP} @var{prog}
18893 @value{GDBN} is free software and @dots{}
18894 (@value{GDBP}) target mips /dev/ttyb
18895 (@value{GDBP}) load @var{prog}
18899 @item target mips @var{hostname}:@var{portnumber}
18900 On some @value{GDBN} host configurations, you can specify a TCP
18901 connection (for instance, to a serial line managed by a terminal
18902 concentrator) instead of a serial port, using the syntax
18903 @samp{@var{hostname}:@var{portnumber}}.
18905 @item target pmon @var{port}
18906 @kindex target pmon @var{port}
18909 @item target ddb @var{port}
18910 @kindex target ddb @var{port}
18911 NEC's DDB variant of PMON for Vr4300.
18913 @item target lsi @var{port}
18914 @kindex target lsi @var{port}
18915 LSI variant of PMON.
18917 @kindex target r3900
18918 @item target r3900 @var{dev}
18919 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
18921 @kindex target array
18922 @item target array @var{dev}
18923 Array Tech LSI33K RAID controller board.
18929 @value{GDBN} also supports these special commands for MIPS targets:
18932 @item set mipsfpu double
18933 @itemx set mipsfpu single
18934 @itemx set mipsfpu none
18935 @itemx set mipsfpu auto
18936 @itemx show mipsfpu
18937 @kindex set mipsfpu
18938 @kindex show mipsfpu
18939 @cindex MIPS remote floating point
18940 @cindex floating point, MIPS remote
18941 If your target board does not support the MIPS floating point
18942 coprocessor, you should use the command @samp{set mipsfpu none} (if you
18943 need this, you may wish to put the command in your @value{GDBN} init
18944 file). This tells @value{GDBN} how to find the return value of
18945 functions which return floating point values. It also allows
18946 @value{GDBN} to avoid saving the floating point registers when calling
18947 functions on the board. If you are using a floating point coprocessor
18948 with only single precision floating point support, as on the @sc{r4650}
18949 processor, use the command @samp{set mipsfpu single}. The default
18950 double precision floating point coprocessor may be selected using
18951 @samp{set mipsfpu double}.
18953 In previous versions the only choices were double precision or no
18954 floating point, so @samp{set mipsfpu on} will select double precision
18955 and @samp{set mipsfpu off} will select no floating point.
18957 As usual, you can inquire about the @code{mipsfpu} variable with
18958 @samp{show mipsfpu}.
18960 @item set timeout @var{seconds}
18961 @itemx set retransmit-timeout @var{seconds}
18962 @itemx show timeout
18963 @itemx show retransmit-timeout
18964 @cindex @code{timeout}, MIPS protocol
18965 @cindex @code{retransmit-timeout}, MIPS protocol
18966 @kindex set timeout
18967 @kindex show timeout
18968 @kindex set retransmit-timeout
18969 @kindex show retransmit-timeout
18970 You can control the timeout used while waiting for a packet, in the MIPS
18971 remote protocol, with the @code{set timeout @var{seconds}} command. The
18972 default is 5 seconds. Similarly, you can control the timeout used while
18973 waiting for an acknowledgment of a packet with the @code{set
18974 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
18975 You can inspect both values with @code{show timeout} and @code{show
18976 retransmit-timeout}. (These commands are @emph{only} available when
18977 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
18979 The timeout set by @code{set timeout} does not apply when @value{GDBN}
18980 is waiting for your program to stop. In that case, @value{GDBN} waits
18981 forever because it has no way of knowing how long the program is going
18982 to run before stopping.
18984 @item set syn-garbage-limit @var{num}
18985 @kindex set syn-garbage-limit@r{, MIPS remote}
18986 @cindex synchronize with remote MIPS target
18987 Limit the maximum number of characters @value{GDBN} should ignore when
18988 it tries to synchronize with the remote target. The default is 10
18989 characters. Setting the limit to -1 means there's no limit.
18991 @item show syn-garbage-limit
18992 @kindex show syn-garbage-limit@r{, MIPS remote}
18993 Show the current limit on the number of characters to ignore when
18994 trying to synchronize with the remote system.
18996 @item set monitor-prompt @var{prompt}
18997 @kindex set monitor-prompt@r{, MIPS remote}
18998 @cindex remote monitor prompt
18999 Tell @value{GDBN} to expect the specified @var{prompt} string from the
19000 remote monitor. The default depends on the target:
19010 @item show monitor-prompt
19011 @kindex show monitor-prompt@r{, MIPS remote}
19012 Show the current strings @value{GDBN} expects as the prompt from the
19015 @item set monitor-warnings
19016 @kindex set monitor-warnings@r{, MIPS remote}
19017 Enable or disable monitor warnings about hardware breakpoints. This
19018 has effect only for the @code{lsi} target. When on, @value{GDBN} will
19019 display warning messages whose codes are returned by the @code{lsi}
19020 PMON monitor for breakpoint commands.
19022 @item show monitor-warnings
19023 @kindex show monitor-warnings@r{, MIPS remote}
19024 Show the current setting of printing monitor warnings.
19026 @item pmon @var{command}
19027 @kindex pmon@r{, MIPS remote}
19028 @cindex send PMON command
19029 This command allows sending an arbitrary @var{command} string to the
19030 monitor. The monitor must be in debug mode for this to work.
19033 @node OpenRISC 1000
19034 @subsection OpenRISC 1000
19035 @cindex OpenRISC 1000
19037 @cindex or1k boards
19038 See OR1k Architecture document (@uref{www.opencores.org}) for more information
19039 about platform and commands.
19043 @kindex target jtag
19044 @item target jtag jtag://@var{host}:@var{port}
19046 Connects to remote JTAG server.
19047 JTAG remote server can be either an or1ksim or JTAG server,
19048 connected via parallel port to the board.
19050 Example: @code{target jtag jtag://localhost:9999}
19053 @item or1ksim @var{command}
19054 If connected to @code{or1ksim} OpenRISC 1000 Architectural
19055 Simulator, proprietary commands can be executed.
19057 @kindex info or1k spr
19058 @item info or1k spr
19059 Displays spr groups.
19061 @item info or1k spr @var{group}
19062 @itemx info or1k spr @var{groupno}
19063 Displays register names in selected group.
19065 @item info or1k spr @var{group} @var{register}
19066 @itemx info or1k spr @var{register}
19067 @itemx info or1k spr @var{groupno} @var{registerno}
19068 @itemx info or1k spr @var{registerno}
19069 Shows information about specified spr register.
19072 @item spr @var{group} @var{register} @var{value}
19073 @itemx spr @var{register @var{value}}
19074 @itemx spr @var{groupno} @var{registerno @var{value}}
19075 @itemx spr @var{registerno @var{value}}
19076 Writes @var{value} to specified spr register.
19079 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
19080 It is very similar to @value{GDBN} trace, except it does not interfere with normal
19081 program execution and is thus much faster. Hardware breakpoints/watchpoint
19082 triggers can be set using:
19085 Load effective address/data
19087 Store effective address/data
19089 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
19094 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
19095 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
19097 @code{htrace} commands:
19098 @cindex OpenRISC 1000 htrace
19101 @item hwatch @var{conditional}
19102 Set hardware watchpoint on combination of Load/Store Effective Address(es)
19103 or Data. For example:
19105 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
19107 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
19111 Display information about current HW trace configuration.
19113 @item htrace trigger @var{conditional}
19114 Set starting criteria for HW trace.
19116 @item htrace qualifier @var{conditional}
19117 Set acquisition qualifier for HW trace.
19119 @item htrace stop @var{conditional}
19120 Set HW trace stopping criteria.
19122 @item htrace record [@var{data}]*
19123 Selects the data to be recorded, when qualifier is met and HW trace was
19126 @item htrace enable
19127 @itemx htrace disable
19128 Enables/disables the HW trace.
19130 @item htrace rewind [@var{filename}]
19131 Clears currently recorded trace data.
19133 If filename is specified, new trace file is made and any newly collected data
19134 will be written there.
19136 @item htrace print [@var{start} [@var{len}]]
19137 Prints trace buffer, using current record configuration.
19139 @item htrace mode continuous
19140 Set continuous trace mode.
19142 @item htrace mode suspend
19143 Set suspend trace mode.
19147 @node PowerPC Embedded
19148 @subsection PowerPC Embedded
19150 @cindex DVC register
19151 @value{GDBN} supports using the DVC (Data Value Compare) register to
19152 implement in hardware simple hardware watchpoint conditions of the form:
19155 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
19156 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
19159 The DVC register will be automatically used when @value{GDBN} detects
19160 such pattern in a condition expression, and the created watchpoint uses one
19161 debug register (either the @code{exact-watchpoints} option is on and the
19162 variable is scalar, or the variable has a length of one byte). This feature
19163 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
19166 When running on PowerPC embedded processors, @value{GDBN} automatically uses
19167 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
19168 in which case watchpoints using only one debug register are created when
19169 watching variables of scalar types.
19171 You can create an artificial array to watch an arbitrary memory
19172 region using one of the following commands (@pxref{Expressions}):
19175 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
19176 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
19179 PowerPC embedded processors support masked watchpoints. See the discussion
19180 about the @code{mask} argument in @ref{Set Watchpoints}.
19182 @cindex ranged breakpoint
19183 PowerPC embedded processors support hardware accelerated
19184 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
19185 the inferior whenever it executes an instruction at any address within
19186 the range it specifies. To set a ranged breakpoint in @value{GDBN},
19187 use the @code{break-range} command.
19189 @value{GDBN} provides the following PowerPC-specific commands:
19192 @kindex break-range
19193 @item break-range @var{start-location}, @var{end-location}
19194 Set a breakpoint for an address range.
19195 @var{start-location} and @var{end-location} can specify a function name,
19196 a line number, an offset of lines from the current line or from the start
19197 location, or an address of an instruction (see @ref{Specify Location},
19198 for a list of all the possible ways to specify a @var{location}.)
19199 The breakpoint will stop execution of the inferior whenever it
19200 executes an instruction at any address within the specified range,
19201 (including @var{start-location} and @var{end-location}.)
19203 @kindex set powerpc
19204 @item set powerpc soft-float
19205 @itemx show powerpc soft-float
19206 Force @value{GDBN} to use (or not use) a software floating point calling
19207 convention. By default, @value{GDBN} selects the calling convention based
19208 on the selected architecture and the provided executable file.
19210 @item set powerpc vector-abi
19211 @itemx show powerpc vector-abi
19212 Force @value{GDBN} to use the specified calling convention for vector
19213 arguments and return values. The valid options are @samp{auto};
19214 @samp{generic}, to avoid vector registers even if they are present;
19215 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
19216 registers. By default, @value{GDBN} selects the calling convention
19217 based on the selected architecture and the provided executable file.
19219 @item set powerpc exact-watchpoints
19220 @itemx show powerpc exact-watchpoints
19221 Allow @value{GDBN} to use only one debug register when watching a variable
19222 of scalar type, thus assuming that the variable is accessed through the
19223 address of its first byte.
19225 @kindex target dink32
19226 @item target dink32 @var{dev}
19227 DINK32 ROM monitor.
19229 @kindex target ppcbug
19230 @item target ppcbug @var{dev}
19231 @kindex target ppcbug1
19232 @item target ppcbug1 @var{dev}
19233 PPCBUG ROM monitor for PowerPC.
19236 @item target sds @var{dev}
19237 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
19240 @cindex SDS protocol
19241 The following commands specific to the SDS protocol are supported
19245 @item set sdstimeout @var{nsec}
19246 @kindex set sdstimeout
19247 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
19248 default is 2 seconds.
19250 @item show sdstimeout
19251 @kindex show sdstimeout
19252 Show the current value of the SDS timeout.
19254 @item sds @var{command}
19255 @kindex sds@r{, a command}
19256 Send the specified @var{command} string to the SDS monitor.
19261 @subsection HP PA Embedded
19265 @kindex target op50n
19266 @item target op50n @var{dev}
19267 OP50N monitor, running on an OKI HPPA board.
19269 @kindex target w89k
19270 @item target w89k @var{dev}
19271 W89K monitor, running on a Winbond HPPA board.
19276 @subsection Tsqware Sparclet
19280 @value{GDBN} enables developers to debug tasks running on
19281 Sparclet targets from a Unix host.
19282 @value{GDBN} uses code that runs on
19283 both the Unix host and on the Sparclet target. The program
19284 @code{@value{GDBP}} is installed and executed on the Unix host.
19287 @item remotetimeout @var{args}
19288 @kindex remotetimeout
19289 @value{GDBN} supports the option @code{remotetimeout}.
19290 This option is set by the user, and @var{args} represents the number of
19291 seconds @value{GDBN} waits for responses.
19294 @cindex compiling, on Sparclet
19295 When compiling for debugging, include the options @samp{-g} to get debug
19296 information and @samp{-Ttext} to relocate the program to where you wish to
19297 load it on the target. You may also want to add the options @samp{-n} or
19298 @samp{-N} in order to reduce the size of the sections. Example:
19301 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
19304 You can use @code{objdump} to verify that the addresses are what you intended:
19307 sparclet-aout-objdump --headers --syms prog
19310 @cindex running, on Sparclet
19312 your Unix execution search path to find @value{GDBN}, you are ready to
19313 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
19314 (or @code{sparclet-aout-gdb}, depending on your installation).
19316 @value{GDBN} comes up showing the prompt:
19323 * Sparclet File:: Setting the file to debug
19324 * Sparclet Connection:: Connecting to Sparclet
19325 * Sparclet Download:: Sparclet download
19326 * Sparclet Execution:: Running and debugging
19329 @node Sparclet File
19330 @subsubsection Setting File to Debug
19332 The @value{GDBN} command @code{file} lets you choose with program to debug.
19335 (gdbslet) file prog
19339 @value{GDBN} then attempts to read the symbol table of @file{prog}.
19340 @value{GDBN} locates
19341 the file by searching the directories listed in the command search
19343 If the file was compiled with debug information (option @samp{-g}), source
19344 files will be searched as well.
19345 @value{GDBN} locates
19346 the source files by searching the directories listed in the directory search
19347 path (@pxref{Environment, ,Your Program's Environment}).
19349 to find a file, it displays a message such as:
19352 prog: No such file or directory.
19355 When this happens, add the appropriate directories to the search paths with
19356 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
19357 @code{target} command again.
19359 @node Sparclet Connection
19360 @subsubsection Connecting to Sparclet
19362 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
19363 To connect to a target on serial port ``@code{ttya}'', type:
19366 (gdbslet) target sparclet /dev/ttya
19367 Remote target sparclet connected to /dev/ttya
19368 main () at ../prog.c:3
19372 @value{GDBN} displays messages like these:
19378 @node Sparclet Download
19379 @subsubsection Sparclet Download
19381 @cindex download to Sparclet
19382 Once connected to the Sparclet target,
19383 you can use the @value{GDBN}
19384 @code{load} command to download the file from the host to the target.
19385 The file name and load offset should be given as arguments to the @code{load}
19387 Since the file format is aout, the program must be loaded to the starting
19388 address. You can use @code{objdump} to find out what this value is. The load
19389 offset is an offset which is added to the VMA (virtual memory address)
19390 of each of the file's sections.
19391 For instance, if the program
19392 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
19393 and bss at 0x12010170, in @value{GDBN}, type:
19396 (gdbslet) load prog 0x12010000
19397 Loading section .text, size 0xdb0 vma 0x12010000
19400 If the code is loaded at a different address then what the program was linked
19401 to, you may need to use the @code{section} and @code{add-symbol-file} commands
19402 to tell @value{GDBN} where to map the symbol table.
19404 @node Sparclet Execution
19405 @subsubsection Running and Debugging
19407 @cindex running and debugging Sparclet programs
19408 You can now begin debugging the task using @value{GDBN}'s execution control
19409 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
19410 manual for the list of commands.
19414 Breakpoint 1 at 0x12010000: file prog.c, line 3.
19416 Starting program: prog
19417 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
19418 3 char *symarg = 0;
19420 4 char *execarg = "hello!";
19425 @subsection Fujitsu Sparclite
19429 @kindex target sparclite
19430 @item target sparclite @var{dev}
19431 Fujitsu sparclite boards, used only for the purpose of loading.
19432 You must use an additional command to debug the program.
19433 For example: target remote @var{dev} using @value{GDBN} standard
19439 @subsection Zilog Z8000
19442 @cindex simulator, Z8000
19443 @cindex Zilog Z8000 simulator
19445 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
19448 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
19449 unsegmented variant of the Z8000 architecture) or the Z8001 (the
19450 segmented variant). The simulator recognizes which architecture is
19451 appropriate by inspecting the object code.
19454 @item target sim @var{args}
19456 @kindex target sim@r{, with Z8000}
19457 Debug programs on a simulated CPU. If the simulator supports setup
19458 options, specify them via @var{args}.
19462 After specifying this target, you can debug programs for the simulated
19463 CPU in the same style as programs for your host computer; use the
19464 @code{file} command to load a new program image, the @code{run} command
19465 to run your program, and so on.
19467 As well as making available all the usual machine registers
19468 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
19469 additional items of information as specially named registers:
19474 Counts clock-ticks in the simulator.
19477 Counts instructions run in the simulator.
19480 Execution time in 60ths of a second.
19484 You can refer to these values in @value{GDBN} expressions with the usual
19485 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
19486 conditional breakpoint that suspends only after at least 5000
19487 simulated clock ticks.
19490 @subsection Atmel AVR
19493 When configured for debugging the Atmel AVR, @value{GDBN} supports the
19494 following AVR-specific commands:
19497 @item info io_registers
19498 @kindex info io_registers@r{, AVR}
19499 @cindex I/O registers (Atmel AVR)
19500 This command displays information about the AVR I/O registers. For
19501 each register, @value{GDBN} prints its number and value.
19508 When configured for debugging CRIS, @value{GDBN} provides the
19509 following CRIS-specific commands:
19512 @item set cris-version @var{ver}
19513 @cindex CRIS version
19514 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
19515 The CRIS version affects register names and sizes. This command is useful in
19516 case autodetection of the CRIS version fails.
19518 @item show cris-version
19519 Show the current CRIS version.
19521 @item set cris-dwarf2-cfi
19522 @cindex DWARF-2 CFI and CRIS
19523 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
19524 Change to @samp{off} when using @code{gcc-cris} whose version is below
19527 @item show cris-dwarf2-cfi
19528 Show the current state of using DWARF-2 CFI.
19530 @item set cris-mode @var{mode}
19532 Set the current CRIS mode to @var{mode}. It should only be changed when
19533 debugging in guru mode, in which case it should be set to
19534 @samp{guru} (the default is @samp{normal}).
19536 @item show cris-mode
19537 Show the current CRIS mode.
19541 @subsection Renesas Super-H
19544 For the Renesas Super-H processor, @value{GDBN} provides these
19549 @kindex regs@r{, Super-H}
19550 Show the values of all Super-H registers.
19552 @item set sh calling-convention @var{convention}
19553 @kindex set sh calling-convention
19554 Set the calling-convention used when calling functions from @value{GDBN}.
19555 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
19556 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
19557 convention. If the DWARF-2 information of the called function specifies
19558 that the function follows the Renesas calling convention, the function
19559 is called using the Renesas calling convention. If the calling convention
19560 is set to @samp{renesas}, the Renesas calling convention is always used,
19561 regardless of the DWARF-2 information. This can be used to override the
19562 default of @samp{gcc} if debug information is missing, or the compiler
19563 does not emit the DWARF-2 calling convention entry for a function.
19565 @item show sh calling-convention
19566 @kindex show sh calling-convention
19567 Show the current calling convention setting.
19572 @node Architectures
19573 @section Architectures
19575 This section describes characteristics of architectures that affect
19576 all uses of @value{GDBN} with the architecture, both native and cross.
19583 * HPPA:: HP PA architecture
19584 * SPU:: Cell Broadband Engine SPU architecture
19589 @subsection x86 Architecture-specific Issues
19592 @item set struct-convention @var{mode}
19593 @kindex set struct-convention
19594 @cindex struct return convention
19595 @cindex struct/union returned in registers
19596 Set the convention used by the inferior to return @code{struct}s and
19597 @code{union}s from functions to @var{mode}. Possible values of
19598 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
19599 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
19600 are returned on the stack, while @code{"reg"} means that a
19601 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
19602 be returned in a register.
19604 @item show struct-convention
19605 @kindex show struct-convention
19606 Show the current setting of the convention to return @code{struct}s
19615 @kindex set rstack_high_address
19616 @cindex AMD 29K register stack
19617 @cindex register stack, AMD29K
19618 @item set rstack_high_address @var{address}
19619 On AMD 29000 family processors, registers are saved in a separate
19620 @dfn{register stack}. There is no way for @value{GDBN} to determine the
19621 extent of this stack. Normally, @value{GDBN} just assumes that the
19622 stack is ``large enough''. This may result in @value{GDBN} referencing
19623 memory locations that do not exist. If necessary, you can get around
19624 this problem by specifying the ending address of the register stack with
19625 the @code{set rstack_high_address} command. The argument should be an
19626 address, which you probably want to precede with @samp{0x} to specify in
19629 @kindex show rstack_high_address
19630 @item show rstack_high_address
19631 Display the current limit of the register stack, on AMD 29000 family
19639 See the following section.
19644 @cindex stack on Alpha
19645 @cindex stack on MIPS
19646 @cindex Alpha stack
19648 Alpha- and MIPS-based computers use an unusual stack frame, which
19649 sometimes requires @value{GDBN} to search backward in the object code to
19650 find the beginning of a function.
19652 @cindex response time, MIPS debugging
19653 To improve response time (especially for embedded applications, where
19654 @value{GDBN} may be restricted to a slow serial line for this search)
19655 you may want to limit the size of this search, using one of these
19659 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
19660 @item set heuristic-fence-post @var{limit}
19661 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
19662 search for the beginning of a function. A value of @var{0} (the
19663 default) means there is no limit. However, except for @var{0}, the
19664 larger the limit the more bytes @code{heuristic-fence-post} must search
19665 and therefore the longer it takes to run. You should only need to use
19666 this command when debugging a stripped executable.
19668 @item show heuristic-fence-post
19669 Display the current limit.
19673 These commands are available @emph{only} when @value{GDBN} is configured
19674 for debugging programs on Alpha or MIPS processors.
19676 Several MIPS-specific commands are available when debugging MIPS
19680 @item set mips abi @var{arg}
19681 @kindex set mips abi
19682 @cindex set ABI for MIPS
19683 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
19684 values of @var{arg} are:
19688 The default ABI associated with the current binary (this is the
19699 @item show mips abi
19700 @kindex show mips abi
19701 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
19704 @itemx show mipsfpu
19705 @xref{MIPS Embedded, set mipsfpu}.
19707 @item set mips mask-address @var{arg}
19708 @kindex set mips mask-address
19709 @cindex MIPS addresses, masking
19710 This command determines whether the most-significant 32 bits of 64-bit
19711 MIPS addresses are masked off. The argument @var{arg} can be
19712 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
19713 setting, which lets @value{GDBN} determine the correct value.
19715 @item show mips mask-address
19716 @kindex show mips mask-address
19717 Show whether the upper 32 bits of MIPS addresses are masked off or
19720 @item set remote-mips64-transfers-32bit-regs
19721 @kindex set remote-mips64-transfers-32bit-regs
19722 This command controls compatibility with 64-bit MIPS targets that
19723 transfer data in 32-bit quantities. If you have an old MIPS 64 target
19724 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
19725 and 64 bits for other registers, set this option to @samp{on}.
19727 @item show remote-mips64-transfers-32bit-regs
19728 @kindex show remote-mips64-transfers-32bit-regs
19729 Show the current setting of compatibility with older MIPS 64 targets.
19731 @item set debug mips
19732 @kindex set debug mips
19733 This command turns on and off debugging messages for the MIPS-specific
19734 target code in @value{GDBN}.
19736 @item show debug mips
19737 @kindex show debug mips
19738 Show the current setting of MIPS debugging messages.
19744 @cindex HPPA support
19746 When @value{GDBN} is debugging the HP PA architecture, it provides the
19747 following special commands:
19750 @item set debug hppa
19751 @kindex set debug hppa
19752 This command determines whether HPPA architecture-specific debugging
19753 messages are to be displayed.
19755 @item show debug hppa
19756 Show whether HPPA debugging messages are displayed.
19758 @item maint print unwind @var{address}
19759 @kindex maint print unwind@r{, HPPA}
19760 This command displays the contents of the unwind table entry at the
19761 given @var{address}.
19767 @subsection Cell Broadband Engine SPU architecture
19768 @cindex Cell Broadband Engine
19771 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
19772 it provides the following special commands:
19775 @item info spu event
19777 Display SPU event facility status. Shows current event mask
19778 and pending event status.
19780 @item info spu signal
19781 Display SPU signal notification facility status. Shows pending
19782 signal-control word and signal notification mode of both signal
19783 notification channels.
19785 @item info spu mailbox
19786 Display SPU mailbox facility status. Shows all pending entries,
19787 in order of processing, in each of the SPU Write Outbound,
19788 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
19791 Display MFC DMA status. Shows all pending commands in the MFC
19792 DMA queue. For each entry, opcode, tag, class IDs, effective
19793 and local store addresses and transfer size are shown.
19795 @item info spu proxydma
19796 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
19797 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
19798 and local store addresses and transfer size are shown.
19802 When @value{GDBN} is debugging a combined PowerPC/SPU application
19803 on the Cell Broadband Engine, it provides in addition the following
19807 @item set spu stop-on-load @var{arg}
19809 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
19810 will give control to the user when a new SPE thread enters its @code{main}
19811 function. The default is @code{off}.
19813 @item show spu stop-on-load
19815 Show whether to stop for new SPE threads.
19817 @item set spu auto-flush-cache @var{arg}
19818 Set whether to automatically flush the software-managed cache. When set to
19819 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
19820 cache to be flushed whenever SPE execution stops. This provides a consistent
19821 view of PowerPC memory that is accessed via the cache. If an application
19822 does not use the software-managed cache, this option has no effect.
19824 @item show spu auto-flush-cache
19825 Show whether to automatically flush the software-managed cache.
19830 @subsection PowerPC
19831 @cindex PowerPC architecture
19833 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
19834 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
19835 numbers stored in the floating point registers. These values must be stored
19836 in two consecutive registers, always starting at an even register like
19837 @code{f0} or @code{f2}.
19839 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
19840 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
19841 @code{f2} and @code{f3} for @code{$dl1} and so on.
19843 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
19844 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
19847 @node Controlling GDB
19848 @chapter Controlling @value{GDBN}
19850 You can alter the way @value{GDBN} interacts with you by using the
19851 @code{set} command. For commands controlling how @value{GDBN} displays
19852 data, see @ref{Print Settings, ,Print Settings}. Other settings are
19857 * Editing:: Command editing
19858 * Command History:: Command history
19859 * Screen Size:: Screen size
19860 * Numbers:: Numbers
19861 * ABI:: Configuring the current ABI
19862 * Messages/Warnings:: Optional warnings and messages
19863 * Debugging Output:: Optional messages about internal happenings
19864 * Other Misc Settings:: Other Miscellaneous Settings
19872 @value{GDBN} indicates its readiness to read a command by printing a string
19873 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
19874 can change the prompt string with the @code{set prompt} command. For
19875 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
19876 the prompt in one of the @value{GDBN} sessions so that you can always tell
19877 which one you are talking to.
19879 @emph{Note:} @code{set prompt} does not add a space for you after the
19880 prompt you set. This allows you to set a prompt which ends in a space
19881 or a prompt that does not.
19885 @item set prompt @var{newprompt}
19886 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
19888 @kindex show prompt
19890 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
19893 Versions of @value{GDBN} that ship with Python scripting enabled have
19894 prompt extensions. The commands for interacting with these extensions
19898 @kindex set extended-prompt
19899 @item set extended-prompt @var{prompt}
19900 Set an extended prompt that allows for substitutions.
19901 @xref{gdb.prompt}, for a list of escape sequences that can be used for
19902 substitution. Any escape sequences specified as part of the prompt
19903 string are replaced with the corresponding strings each time the prompt
19909 set extended-prompt Current working directory: \w (gdb)
19912 Note that when an extended-prompt is set, it takes control of the
19913 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
19915 @kindex show extended-prompt
19916 @item show extended-prompt
19917 Prints the extended prompt. Any escape sequences specified as part of
19918 the prompt string with @code{set extended-prompt}, are replaced with the
19919 corresponding strings each time the prompt is displayed.
19923 @section Command Editing
19925 @cindex command line editing
19927 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
19928 @sc{gnu} library provides consistent behavior for programs which provide a
19929 command line interface to the user. Advantages are @sc{gnu} Emacs-style
19930 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
19931 substitution, and a storage and recall of command history across
19932 debugging sessions.
19934 You may control the behavior of command line editing in @value{GDBN} with the
19935 command @code{set}.
19938 @kindex set editing
19941 @itemx set editing on
19942 Enable command line editing (enabled by default).
19944 @item set editing off
19945 Disable command line editing.
19947 @kindex show editing
19949 Show whether command line editing is enabled.
19952 @ifset SYSTEM_READLINE
19953 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
19955 @ifclear SYSTEM_READLINE
19956 @xref{Command Line Editing},
19958 for more details about the Readline
19959 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
19960 encouraged to read that chapter.
19962 @node Command History
19963 @section Command History
19964 @cindex command history
19966 @value{GDBN} can keep track of the commands you type during your
19967 debugging sessions, so that you can be certain of precisely what
19968 happened. Use these commands to manage the @value{GDBN} command
19971 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
19972 package, to provide the history facility.
19973 @ifset SYSTEM_READLINE
19974 @xref{Using History Interactively, , , history, GNU History Library},
19976 @ifclear SYSTEM_READLINE
19977 @xref{Using History Interactively},
19979 for the detailed description of the History library.
19981 To issue a command to @value{GDBN} without affecting certain aspects of
19982 the state which is seen by users, prefix it with @samp{server }
19983 (@pxref{Server Prefix}). This
19984 means that this command will not affect the command history, nor will it
19985 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
19986 pressed on a line by itself.
19988 @cindex @code{server}, command prefix
19989 The server prefix does not affect the recording of values into the value
19990 history; to print a value without recording it into the value history,
19991 use the @code{output} command instead of the @code{print} command.
19993 Here is the description of @value{GDBN} commands related to command
19997 @cindex history substitution
19998 @cindex history file
19999 @kindex set history filename
20000 @cindex @env{GDBHISTFILE}, environment variable
20001 @item set history filename @var{fname}
20002 Set the name of the @value{GDBN} command history file to @var{fname}.
20003 This is the file where @value{GDBN} reads an initial command history
20004 list, and where it writes the command history from this session when it
20005 exits. You can access this list through history expansion or through
20006 the history command editing characters listed below. This file defaults
20007 to the value of the environment variable @code{GDBHISTFILE}, or to
20008 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
20011 @cindex save command history
20012 @kindex set history save
20013 @item set history save
20014 @itemx set history save on
20015 Record command history in a file, whose name may be specified with the
20016 @code{set history filename} command. By default, this option is disabled.
20018 @item set history save off
20019 Stop recording command history in a file.
20021 @cindex history size
20022 @kindex set history size
20023 @cindex @env{HISTSIZE}, environment variable
20024 @item set history size @var{size}
20025 Set the number of commands which @value{GDBN} keeps in its history list.
20026 This defaults to the value of the environment variable
20027 @code{HISTSIZE}, or to 256 if this variable is not set.
20030 History expansion assigns special meaning to the character @kbd{!}.
20031 @ifset SYSTEM_READLINE
20032 @xref{Event Designators, , , history, GNU History Library},
20034 @ifclear SYSTEM_READLINE
20035 @xref{Event Designators},
20039 @cindex history expansion, turn on/off
20040 Since @kbd{!} is also the logical not operator in C, history expansion
20041 is off by default. If you decide to enable history expansion with the
20042 @code{set history expansion on} command, you may sometimes need to
20043 follow @kbd{!} (when it is used as logical not, in an expression) with
20044 a space or a tab to prevent it from being expanded. The readline
20045 history facilities do not attempt substitution on the strings
20046 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
20048 The commands to control history expansion are:
20051 @item set history expansion on
20052 @itemx set history expansion
20053 @kindex set history expansion
20054 Enable history expansion. History expansion is off by default.
20056 @item set history expansion off
20057 Disable history expansion.
20060 @kindex show history
20062 @itemx show history filename
20063 @itemx show history save
20064 @itemx show history size
20065 @itemx show history expansion
20066 These commands display the state of the @value{GDBN} history parameters.
20067 @code{show history} by itself displays all four states.
20072 @kindex show commands
20073 @cindex show last commands
20074 @cindex display command history
20075 @item show commands
20076 Display the last ten commands in the command history.
20078 @item show commands @var{n}
20079 Print ten commands centered on command number @var{n}.
20081 @item show commands +
20082 Print ten commands just after the commands last printed.
20086 @section Screen Size
20087 @cindex size of screen
20088 @cindex pauses in output
20090 Certain commands to @value{GDBN} may produce large amounts of
20091 information output to the screen. To help you read all of it,
20092 @value{GDBN} pauses and asks you for input at the end of each page of
20093 output. Type @key{RET} when you want to continue the output, or @kbd{q}
20094 to discard the remaining output. Also, the screen width setting
20095 determines when to wrap lines of output. Depending on what is being
20096 printed, @value{GDBN} tries to break the line at a readable place,
20097 rather than simply letting it overflow onto the following line.
20099 Normally @value{GDBN} knows the size of the screen from the terminal
20100 driver software. For example, on Unix @value{GDBN} uses the termcap data base
20101 together with the value of the @code{TERM} environment variable and the
20102 @code{stty rows} and @code{stty cols} settings. If this is not correct,
20103 you can override it with the @code{set height} and @code{set
20110 @kindex show height
20111 @item set height @var{lpp}
20113 @itemx set width @var{cpl}
20115 These @code{set} commands specify a screen height of @var{lpp} lines and
20116 a screen width of @var{cpl} characters. The associated @code{show}
20117 commands display the current settings.
20119 If you specify a height of zero lines, @value{GDBN} does not pause during
20120 output no matter how long the output is. This is useful if output is to a
20121 file or to an editor buffer.
20123 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
20124 from wrapping its output.
20126 @item set pagination on
20127 @itemx set pagination off
20128 @kindex set pagination
20129 Turn the output pagination on or off; the default is on. Turning
20130 pagination off is the alternative to @code{set height 0}. Note that
20131 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
20132 Options, -batch}) also automatically disables pagination.
20134 @item show pagination
20135 @kindex show pagination
20136 Show the current pagination mode.
20141 @cindex number representation
20142 @cindex entering numbers
20144 You can always enter numbers in octal, decimal, or hexadecimal in
20145 @value{GDBN} by the usual conventions: octal numbers begin with
20146 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
20147 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
20148 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
20149 10; likewise, the default display for numbers---when no particular
20150 format is specified---is base 10. You can change the default base for
20151 both input and output with the commands described below.
20154 @kindex set input-radix
20155 @item set input-radix @var{base}
20156 Set the default base for numeric input. Supported choices
20157 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
20158 specified either unambiguously or using the current input radix; for
20162 set input-radix 012
20163 set input-radix 10.
20164 set input-radix 0xa
20168 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
20169 leaves the input radix unchanged, no matter what it was, since
20170 @samp{10}, being without any leading or trailing signs of its base, is
20171 interpreted in the current radix. Thus, if the current radix is 16,
20172 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
20175 @kindex set output-radix
20176 @item set output-radix @var{base}
20177 Set the default base for numeric display. Supported choices
20178 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
20179 specified either unambiguously or using the current input radix.
20181 @kindex show input-radix
20182 @item show input-radix
20183 Display the current default base for numeric input.
20185 @kindex show output-radix
20186 @item show output-radix
20187 Display the current default base for numeric display.
20189 @item set radix @r{[}@var{base}@r{]}
20193 These commands set and show the default base for both input and output
20194 of numbers. @code{set radix} sets the radix of input and output to
20195 the same base; without an argument, it resets the radix back to its
20196 default value of 10.
20201 @section Configuring the Current ABI
20203 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
20204 application automatically. However, sometimes you need to override its
20205 conclusions. Use these commands to manage @value{GDBN}'s view of the
20212 One @value{GDBN} configuration can debug binaries for multiple operating
20213 system targets, either via remote debugging or native emulation.
20214 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
20215 but you can override its conclusion using the @code{set osabi} command.
20216 One example where this is useful is in debugging of binaries which use
20217 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
20218 not have the same identifying marks that the standard C library for your
20223 Show the OS ABI currently in use.
20226 With no argument, show the list of registered available OS ABI's.
20228 @item set osabi @var{abi}
20229 Set the current OS ABI to @var{abi}.
20232 @cindex float promotion
20234 Generally, the way that an argument of type @code{float} is passed to a
20235 function depends on whether the function is prototyped. For a prototyped
20236 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
20237 according to the architecture's convention for @code{float}. For unprototyped
20238 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
20239 @code{double} and then passed.
20241 Unfortunately, some forms of debug information do not reliably indicate whether
20242 a function is prototyped. If @value{GDBN} calls a function that is not marked
20243 as prototyped, it consults @kbd{set coerce-float-to-double}.
20246 @kindex set coerce-float-to-double
20247 @item set coerce-float-to-double
20248 @itemx set coerce-float-to-double on
20249 Arguments of type @code{float} will be promoted to @code{double} when passed
20250 to an unprototyped function. This is the default setting.
20252 @item set coerce-float-to-double off
20253 Arguments of type @code{float} will be passed directly to unprototyped
20256 @kindex show coerce-float-to-double
20257 @item show coerce-float-to-double
20258 Show the current setting of promoting @code{float} to @code{double}.
20262 @kindex show cp-abi
20263 @value{GDBN} needs to know the ABI used for your program's C@t{++}
20264 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
20265 used to build your application. @value{GDBN} only fully supports
20266 programs with a single C@t{++} ABI; if your program contains code using
20267 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
20268 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
20269 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
20270 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
20271 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
20272 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
20277 Show the C@t{++} ABI currently in use.
20280 With no argument, show the list of supported C@t{++} ABI's.
20282 @item set cp-abi @var{abi}
20283 @itemx set cp-abi auto
20284 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
20287 @node Messages/Warnings
20288 @section Optional Warnings and Messages
20290 @cindex verbose operation
20291 @cindex optional warnings
20292 By default, @value{GDBN} is silent about its inner workings. If you are
20293 running on a slow machine, you may want to use the @code{set verbose}
20294 command. This makes @value{GDBN} tell you when it does a lengthy
20295 internal operation, so you will not think it has crashed.
20297 Currently, the messages controlled by @code{set verbose} are those
20298 which announce that the symbol table for a source file is being read;
20299 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
20302 @kindex set verbose
20303 @item set verbose on
20304 Enables @value{GDBN} output of certain informational messages.
20306 @item set verbose off
20307 Disables @value{GDBN} output of certain informational messages.
20309 @kindex show verbose
20311 Displays whether @code{set verbose} is on or off.
20314 By default, if @value{GDBN} encounters bugs in the symbol table of an
20315 object file, it is silent; but if you are debugging a compiler, you may
20316 find this information useful (@pxref{Symbol Errors, ,Errors Reading
20321 @kindex set complaints
20322 @item set complaints @var{limit}
20323 Permits @value{GDBN} to output @var{limit} complaints about each type of
20324 unusual symbols before becoming silent about the problem. Set
20325 @var{limit} to zero to suppress all complaints; set it to a large number
20326 to prevent complaints from being suppressed.
20328 @kindex show complaints
20329 @item show complaints
20330 Displays how many symbol complaints @value{GDBN} is permitted to produce.
20334 @anchor{confirmation requests}
20335 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
20336 lot of stupid questions to confirm certain commands. For example, if
20337 you try to run a program which is already running:
20341 The program being debugged has been started already.
20342 Start it from the beginning? (y or n)
20345 If you are willing to unflinchingly face the consequences of your own
20346 commands, you can disable this ``feature'':
20350 @kindex set confirm
20352 @cindex confirmation
20353 @cindex stupid questions
20354 @item set confirm off
20355 Disables confirmation requests. Note that running @value{GDBN} with
20356 the @option{--batch} option (@pxref{Mode Options, -batch}) also
20357 automatically disables confirmation requests.
20359 @item set confirm on
20360 Enables confirmation requests (the default).
20362 @kindex show confirm
20364 Displays state of confirmation requests.
20368 @cindex command tracing
20369 If you need to debug user-defined commands or sourced files you may find it
20370 useful to enable @dfn{command tracing}. In this mode each command will be
20371 printed as it is executed, prefixed with one or more @samp{+} symbols, the
20372 quantity denoting the call depth of each command.
20375 @kindex set trace-commands
20376 @cindex command scripts, debugging
20377 @item set trace-commands on
20378 Enable command tracing.
20379 @item set trace-commands off
20380 Disable command tracing.
20381 @item show trace-commands
20382 Display the current state of command tracing.
20385 @node Debugging Output
20386 @section Optional Messages about Internal Happenings
20387 @cindex optional debugging messages
20389 @value{GDBN} has commands that enable optional debugging messages from
20390 various @value{GDBN} subsystems; normally these commands are of
20391 interest to @value{GDBN} maintainers, or when reporting a bug. This
20392 section documents those commands.
20395 @kindex set exec-done-display
20396 @item set exec-done-display
20397 Turns on or off the notification of asynchronous commands'
20398 completion. When on, @value{GDBN} will print a message when an
20399 asynchronous command finishes its execution. The default is off.
20400 @kindex show exec-done-display
20401 @item show exec-done-display
20402 Displays the current setting of asynchronous command completion
20405 @cindex gdbarch debugging info
20406 @cindex architecture debugging info
20407 @item set debug arch
20408 Turns on or off display of gdbarch debugging info. The default is off
20410 @item show debug arch
20411 Displays the current state of displaying gdbarch debugging info.
20412 @item set debug aix-thread
20413 @cindex AIX threads
20414 Display debugging messages about inner workings of the AIX thread
20416 @item show debug aix-thread
20417 Show the current state of AIX thread debugging info display.
20418 @item set debug check-physname
20420 Check the results of the ``physname'' computation. When reading DWARF
20421 debugging information for C@t{++}, @value{GDBN} attempts to compute
20422 each entity's name. @value{GDBN} can do this computation in two
20423 different ways, depending on exactly what information is present.
20424 When enabled, this setting causes @value{GDBN} to compute the names
20425 both ways and display any discrepancies.
20426 @item show debug check-physname
20427 Show the current state of ``physname'' checking.
20428 @item set debug dwarf2-die
20429 @cindex DWARF2 DIEs
20430 Dump DWARF2 DIEs after they are read in.
20431 The value is the number of nesting levels to print.
20432 A value of zero turns off the display.
20433 @item show debug dwarf2-die
20434 Show the current state of DWARF2 DIE debugging.
20435 @item set debug displaced
20436 @cindex displaced stepping debugging info
20437 Turns on or off display of @value{GDBN} debugging info for the
20438 displaced stepping support. The default is off.
20439 @item show debug displaced
20440 Displays the current state of displaying @value{GDBN} debugging info
20441 related to displaced stepping.
20442 @item set debug event
20443 @cindex event debugging info
20444 Turns on or off display of @value{GDBN} event debugging info. The
20446 @item show debug event
20447 Displays the current state of displaying @value{GDBN} event debugging
20449 @item set debug expression
20450 @cindex expression debugging info
20451 Turns on or off display of debugging info about @value{GDBN}
20452 expression parsing. The default is off.
20453 @item show debug expression
20454 Displays the current state of displaying debugging info about
20455 @value{GDBN} expression parsing.
20456 @item set debug frame
20457 @cindex frame debugging info
20458 Turns on or off display of @value{GDBN} frame debugging info. The
20460 @item show debug frame
20461 Displays the current state of displaying @value{GDBN} frame debugging
20463 @item set debug gnu-nat
20464 @cindex @sc{gnu}/Hurd debug messages
20465 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
20466 @item show debug gnu-nat
20467 Show the current state of @sc{gnu}/Hurd debugging messages.
20468 @item set debug infrun
20469 @cindex inferior debugging info
20470 Turns on or off display of @value{GDBN} debugging info for running the inferior.
20471 The default is off. @file{infrun.c} contains GDB's runtime state machine used
20472 for implementing operations such as single-stepping the inferior.
20473 @item show debug infrun
20474 Displays the current state of @value{GDBN} inferior debugging.
20475 @item set debug jit
20476 @cindex just-in-time compilation, debugging messages
20477 Turns on or off debugging messages from JIT debug support.
20478 @item show debug jit
20479 Displays the current state of @value{GDBN} JIT debugging.
20480 @item set debug lin-lwp
20481 @cindex @sc{gnu}/Linux LWP debug messages
20482 @cindex Linux lightweight processes
20483 Turns on or off debugging messages from the Linux LWP debug support.
20484 @item show debug lin-lwp
20485 Show the current state of Linux LWP debugging messages.
20486 @item set debug observer
20487 @cindex observer debugging info
20488 Turns on or off display of @value{GDBN} observer debugging. This
20489 includes info such as the notification of observable events.
20490 @item show debug observer
20491 Displays the current state of observer debugging.
20492 @item set debug overload
20493 @cindex C@t{++} overload debugging info
20494 Turns on or off display of @value{GDBN} C@t{++} overload debugging
20495 info. This includes info such as ranking of functions, etc. The default
20497 @item show debug overload
20498 Displays the current state of displaying @value{GDBN} C@t{++} overload
20500 @cindex expression parser, debugging info
20501 @cindex debug expression parser
20502 @item set debug parser
20503 Turns on or off the display of expression parser debugging output.
20504 Internally, this sets the @code{yydebug} variable in the expression
20505 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
20506 details. The default is off.
20507 @item show debug parser
20508 Show the current state of expression parser debugging.
20509 @cindex packets, reporting on stdout
20510 @cindex serial connections, debugging
20511 @cindex debug remote protocol
20512 @cindex remote protocol debugging
20513 @cindex display remote packets
20514 @item set debug remote
20515 Turns on or off display of reports on all packets sent back and forth across
20516 the serial line to the remote machine. The info is printed on the
20517 @value{GDBN} standard output stream. The default is off.
20518 @item show debug remote
20519 Displays the state of display of remote packets.
20520 @item set debug serial
20521 Turns on or off display of @value{GDBN} serial debugging info. The
20523 @item show debug serial
20524 Displays the current state of displaying @value{GDBN} serial debugging
20526 @item set debug solib-frv
20527 @cindex FR-V shared-library debugging
20528 Turns on or off debugging messages for FR-V shared-library code.
20529 @item show debug solib-frv
20530 Display the current state of FR-V shared-library code debugging
20532 @item set debug target
20533 @cindex target debugging info
20534 Turns on or off display of @value{GDBN} target debugging info. This info
20535 includes what is going on at the target level of GDB, as it happens. The
20536 default is 0. Set it to 1 to track events, and to 2 to also track the
20537 value of large memory transfers. Changes to this flag do not take effect
20538 until the next time you connect to a target or use the @code{run} command.
20539 @item show debug target
20540 Displays the current state of displaying @value{GDBN} target debugging
20542 @item set debug timestamp
20543 @cindex timestampping debugging info
20544 Turns on or off display of timestamps with @value{GDBN} debugging info.
20545 When enabled, seconds and microseconds are displayed before each debugging
20547 @item show debug timestamp
20548 Displays the current state of displaying timestamps with @value{GDBN}
20550 @item set debugvarobj
20551 @cindex variable object debugging info
20552 Turns on or off display of @value{GDBN} variable object debugging
20553 info. The default is off.
20554 @item show debugvarobj
20555 Displays the current state of displaying @value{GDBN} variable object
20557 @item set debug xml
20558 @cindex XML parser debugging
20559 Turns on or off debugging messages for built-in XML parsers.
20560 @item show debug xml
20561 Displays the current state of XML debugging messages.
20564 @node Other Misc Settings
20565 @section Other Miscellaneous Settings
20566 @cindex miscellaneous settings
20569 @kindex set interactive-mode
20570 @item set interactive-mode
20571 If @code{on}, forces @value{GDBN} to assume that GDB was started
20572 in a terminal. In practice, this means that @value{GDBN} should wait
20573 for the user to answer queries generated by commands entered at
20574 the command prompt. If @code{off}, forces @value{GDBN} to operate
20575 in the opposite mode, and it uses the default answers to all queries.
20576 If @code{auto} (the default), @value{GDBN} tries to determine whether
20577 its standard input is a terminal, and works in interactive-mode if it
20578 is, non-interactively otherwise.
20580 In the vast majority of cases, the debugger should be able to guess
20581 correctly which mode should be used. But this setting can be useful
20582 in certain specific cases, such as running a MinGW @value{GDBN}
20583 inside a cygwin window.
20585 @kindex show interactive-mode
20586 @item show interactive-mode
20587 Displays whether the debugger is operating in interactive mode or not.
20590 @node Extending GDB
20591 @chapter Extending @value{GDBN}
20592 @cindex extending GDB
20594 @value{GDBN} provides two mechanisms for extension. The first is based
20595 on composition of @value{GDBN} commands, and the second is based on the
20596 Python scripting language.
20598 To facilitate the use of these extensions, @value{GDBN} is capable
20599 of evaluating the contents of a file. When doing so, @value{GDBN}
20600 can recognize which scripting language is being used by looking at
20601 the filename extension. Files with an unrecognized filename extension
20602 are always treated as a @value{GDBN} Command Files.
20603 @xref{Command Files,, Command files}.
20605 You can control how @value{GDBN} evaluates these files with the following
20609 @kindex set script-extension
20610 @kindex show script-extension
20611 @item set script-extension off
20612 All scripts are always evaluated as @value{GDBN} Command Files.
20614 @item set script-extension soft
20615 The debugger determines the scripting language based on filename
20616 extension. If this scripting language is supported, @value{GDBN}
20617 evaluates the script using that language. Otherwise, it evaluates
20618 the file as a @value{GDBN} Command File.
20620 @item set script-extension strict
20621 The debugger determines the scripting language based on filename
20622 extension, and evaluates the script using that language. If the
20623 language is not supported, then the evaluation fails.
20625 @item show script-extension
20626 Display the current value of the @code{script-extension} option.
20631 * Sequences:: Canned Sequences of Commands
20632 * Python:: Scripting @value{GDBN} using Python
20636 @section Canned Sequences of Commands
20638 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
20639 Command Lists}), @value{GDBN} provides two ways to store sequences of
20640 commands for execution as a unit: user-defined commands and command
20644 * Define:: How to define your own commands
20645 * Hooks:: Hooks for user-defined commands
20646 * Command Files:: How to write scripts of commands to be stored in a file
20647 * Output:: Commands for controlled output
20651 @subsection User-defined Commands
20653 @cindex user-defined command
20654 @cindex arguments, to user-defined commands
20655 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
20656 which you assign a new name as a command. This is done with the
20657 @code{define} command. User commands may accept up to 10 arguments
20658 separated by whitespace. Arguments are accessed within the user command
20659 via @code{$arg0@dots{}$arg9}. A trivial example:
20663 print $arg0 + $arg1 + $arg2
20668 To execute the command use:
20675 This defines the command @code{adder}, which prints the sum of
20676 its three arguments. Note the arguments are text substitutions, so they may
20677 reference variables, use complex expressions, or even perform inferior
20680 @cindex argument count in user-defined commands
20681 @cindex how many arguments (user-defined commands)
20682 In addition, @code{$argc} may be used to find out how many arguments have
20683 been passed. This expands to a number in the range 0@dots{}10.
20688 print $arg0 + $arg1
20691 print $arg0 + $arg1 + $arg2
20699 @item define @var{commandname}
20700 Define a command named @var{commandname}. If there is already a command
20701 by that name, you are asked to confirm that you want to redefine it.
20702 @var{commandname} may be a bare command name consisting of letters,
20703 numbers, dashes, and underscores. It may also start with any predefined
20704 prefix command. For example, @samp{define target my-target} creates
20705 a user-defined @samp{target my-target} command.
20707 The definition of the command is made up of other @value{GDBN} command lines,
20708 which are given following the @code{define} command. The end of these
20709 commands is marked by a line containing @code{end}.
20712 @kindex end@r{ (user-defined commands)}
20713 @item document @var{commandname}
20714 Document the user-defined command @var{commandname}, so that it can be
20715 accessed by @code{help}. The command @var{commandname} must already be
20716 defined. This command reads lines of documentation just as @code{define}
20717 reads the lines of the command definition, ending with @code{end}.
20718 After the @code{document} command is finished, @code{help} on command
20719 @var{commandname} displays the documentation you have written.
20721 You may use the @code{document} command again to change the
20722 documentation of a command. Redefining the command with @code{define}
20723 does not change the documentation.
20725 @kindex dont-repeat
20726 @cindex don't repeat command
20728 Used inside a user-defined command, this tells @value{GDBN} that this
20729 command should not be repeated when the user hits @key{RET}
20730 (@pxref{Command Syntax, repeat last command}).
20732 @kindex help user-defined
20733 @item help user-defined
20734 List all user-defined commands, with the first line of the documentation
20739 @itemx show user @var{commandname}
20740 Display the @value{GDBN} commands used to define @var{commandname} (but
20741 not its documentation). If no @var{commandname} is given, display the
20742 definitions for all user-defined commands.
20744 @cindex infinite recursion in user-defined commands
20745 @kindex show max-user-call-depth
20746 @kindex set max-user-call-depth
20747 @item show max-user-call-depth
20748 @itemx set max-user-call-depth
20749 The value of @code{max-user-call-depth} controls how many recursion
20750 levels are allowed in user-defined commands before @value{GDBN} suspects an
20751 infinite recursion and aborts the command.
20754 In addition to the above commands, user-defined commands frequently
20755 use control flow commands, described in @ref{Command Files}.
20757 When user-defined commands are executed, the
20758 commands of the definition are not printed. An error in any command
20759 stops execution of the user-defined command.
20761 If used interactively, commands that would ask for confirmation proceed
20762 without asking when used inside a user-defined command. Many @value{GDBN}
20763 commands that normally print messages to say what they are doing omit the
20764 messages when used in a user-defined command.
20767 @subsection User-defined Command Hooks
20768 @cindex command hooks
20769 @cindex hooks, for commands
20770 @cindex hooks, pre-command
20773 You may define @dfn{hooks}, which are a special kind of user-defined
20774 command. Whenever you run the command @samp{foo}, if the user-defined
20775 command @samp{hook-foo} exists, it is executed (with no arguments)
20776 before that command.
20778 @cindex hooks, post-command
20780 A hook may also be defined which is run after the command you executed.
20781 Whenever you run the command @samp{foo}, if the user-defined command
20782 @samp{hookpost-foo} exists, it is executed (with no arguments) after
20783 that command. Post-execution hooks may exist simultaneously with
20784 pre-execution hooks, for the same command.
20786 It is valid for a hook to call the command which it hooks. If this
20787 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
20789 @c It would be nice if hookpost could be passed a parameter indicating
20790 @c if the command it hooks executed properly or not. FIXME!
20792 @kindex stop@r{, a pseudo-command}
20793 In addition, a pseudo-command, @samp{stop} exists. Defining
20794 (@samp{hook-stop}) makes the associated commands execute every time
20795 execution stops in your program: before breakpoint commands are run,
20796 displays are printed, or the stack frame is printed.
20798 For example, to ignore @code{SIGALRM} signals while
20799 single-stepping, but treat them normally during normal execution,
20804 handle SIGALRM nopass
20808 handle SIGALRM pass
20811 define hook-continue
20812 handle SIGALRM pass
20816 As a further example, to hook at the beginning and end of the @code{echo}
20817 command, and to add extra text to the beginning and end of the message,
20825 define hookpost-echo
20829 (@value{GDBP}) echo Hello World
20830 <<<---Hello World--->>>
20835 You can define a hook for any single-word command in @value{GDBN}, but
20836 not for command aliases; you should define a hook for the basic command
20837 name, e.g.@: @code{backtrace} rather than @code{bt}.
20838 @c FIXME! So how does Joe User discover whether a command is an alias
20840 You can hook a multi-word command by adding @code{hook-} or
20841 @code{hookpost-} to the last word of the command, e.g.@:
20842 @samp{define target hook-remote} to add a hook to @samp{target remote}.
20844 If an error occurs during the execution of your hook, execution of
20845 @value{GDBN} commands stops and @value{GDBN} issues a prompt
20846 (before the command that you actually typed had a chance to run).
20848 If you try to define a hook which does not match any known command, you
20849 get a warning from the @code{define} command.
20851 @node Command Files
20852 @subsection Command Files
20854 @cindex command files
20855 @cindex scripting commands
20856 A command file for @value{GDBN} is a text file made of lines that are
20857 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
20858 also be included. An empty line in a command file does nothing; it
20859 does not mean to repeat the last command, as it would from the
20862 You can request the execution of a command file with the @code{source}
20863 command. Note that the @code{source} command is also used to evaluate
20864 scripts that are not Command Files. The exact behavior can be configured
20865 using the @code{script-extension} setting.
20866 @xref{Extending GDB,, Extending GDB}.
20870 @cindex execute commands from a file
20871 @item source [-s] [-v] @var{filename}
20872 Execute the command file @var{filename}.
20875 The lines in a command file are generally executed sequentially,
20876 unless the order of execution is changed by one of the
20877 @emph{flow-control commands} described below. The commands are not
20878 printed as they are executed. An error in any command terminates
20879 execution of the command file and control is returned to the console.
20881 @value{GDBN} first searches for @var{filename} in the current directory.
20882 If the file is not found there, and @var{filename} does not specify a
20883 directory, then @value{GDBN} also looks for the file on the source search path
20884 (specified with the @samp{directory} command);
20885 except that @file{$cdir} is not searched because the compilation directory
20886 is not relevant to scripts.
20888 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
20889 on the search path even if @var{filename} specifies a directory.
20890 The search is done by appending @var{filename} to each element of the
20891 search path. So, for example, if @var{filename} is @file{mylib/myscript}
20892 and the search path contains @file{/home/user} then @value{GDBN} will
20893 look for the script @file{/home/user/mylib/myscript}.
20894 The search is also done if @var{filename} is an absolute path.
20895 For example, if @var{filename} is @file{/tmp/myscript} and
20896 the search path contains @file{/home/user} then @value{GDBN} will
20897 look for the script @file{/home/user/tmp/myscript}.
20898 For DOS-like systems, if @var{filename} contains a drive specification,
20899 it is stripped before concatenation. For example, if @var{filename} is
20900 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
20901 will look for the script @file{c:/tmp/myscript}.
20903 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
20904 each command as it is executed. The option must be given before
20905 @var{filename}, and is interpreted as part of the filename anywhere else.
20907 Commands that would ask for confirmation if used interactively proceed
20908 without asking when used in a command file. Many @value{GDBN} commands that
20909 normally print messages to say what they are doing omit the messages
20910 when called from command files.
20912 @value{GDBN} also accepts command input from standard input. In this
20913 mode, normal output goes to standard output and error output goes to
20914 standard error. Errors in a command file supplied on standard input do
20915 not terminate execution of the command file---execution continues with
20919 gdb < cmds > log 2>&1
20922 (The syntax above will vary depending on the shell used.) This example
20923 will execute commands from the file @file{cmds}. All output and errors
20924 would be directed to @file{log}.
20926 Since commands stored on command files tend to be more general than
20927 commands typed interactively, they frequently need to deal with
20928 complicated situations, such as different or unexpected values of
20929 variables and symbols, changes in how the program being debugged is
20930 built, etc. @value{GDBN} provides a set of flow-control commands to
20931 deal with these complexities. Using these commands, you can write
20932 complex scripts that loop over data structures, execute commands
20933 conditionally, etc.
20940 This command allows to include in your script conditionally executed
20941 commands. The @code{if} command takes a single argument, which is an
20942 expression to evaluate. It is followed by a series of commands that
20943 are executed only if the expression is true (its value is nonzero).
20944 There can then optionally be an @code{else} line, followed by a series
20945 of commands that are only executed if the expression was false. The
20946 end of the list is marked by a line containing @code{end}.
20950 This command allows to write loops. Its syntax is similar to
20951 @code{if}: the command takes a single argument, which is an expression
20952 to evaluate, and must be followed by the commands to execute, one per
20953 line, terminated by an @code{end}. These commands are called the
20954 @dfn{body} of the loop. The commands in the body of @code{while} are
20955 executed repeatedly as long as the expression evaluates to true.
20959 This command exits the @code{while} loop in whose body it is included.
20960 Execution of the script continues after that @code{while}s @code{end}
20963 @kindex loop_continue
20964 @item loop_continue
20965 This command skips the execution of the rest of the body of commands
20966 in the @code{while} loop in whose body it is included. Execution
20967 branches to the beginning of the @code{while} loop, where it evaluates
20968 the controlling expression.
20970 @kindex end@r{ (if/else/while commands)}
20972 Terminate the block of commands that are the body of @code{if},
20973 @code{else}, or @code{while} flow-control commands.
20978 @subsection Commands for Controlled Output
20980 During the execution of a command file or a user-defined command, normal
20981 @value{GDBN} output is suppressed; the only output that appears is what is
20982 explicitly printed by the commands in the definition. This section
20983 describes three commands useful for generating exactly the output you
20988 @item echo @var{text}
20989 @c I do not consider backslash-space a standard C escape sequence
20990 @c because it is not in ANSI.
20991 Print @var{text}. Nonprinting characters can be included in
20992 @var{text} using C escape sequences, such as @samp{\n} to print a
20993 newline. @strong{No newline is printed unless you specify one.}
20994 In addition to the standard C escape sequences, a backslash followed
20995 by a space stands for a space. This is useful for displaying a
20996 string with spaces at the beginning or the end, since leading and
20997 trailing spaces are otherwise trimmed from all arguments.
20998 To print @samp{@w{ }and foo =@w{ }}, use the command
20999 @samp{echo \@w{ }and foo = \@w{ }}.
21001 A backslash at the end of @var{text} can be used, as in C, to continue
21002 the command onto subsequent lines. For example,
21005 echo This is some text\n\
21006 which is continued\n\
21007 onto several lines.\n
21010 produces the same output as
21013 echo This is some text\n
21014 echo which is continued\n
21015 echo onto several lines.\n
21019 @item output @var{expression}
21020 Print the value of @var{expression} and nothing but that value: no
21021 newlines, no @samp{$@var{nn} = }. The value is not entered in the
21022 value history either. @xref{Expressions, ,Expressions}, for more information
21025 @item output/@var{fmt} @var{expression}
21026 Print the value of @var{expression} in format @var{fmt}. You can use
21027 the same formats as for @code{print}. @xref{Output Formats,,Output
21028 Formats}, for more information.
21031 @item printf @var{template}, @var{expressions}@dots{}
21032 Print the values of one or more @var{expressions} under the control of
21033 the string @var{template}. To print several values, make
21034 @var{expressions} be a comma-separated list of individual expressions,
21035 which may be either numbers or pointers. Their values are printed as
21036 specified by @var{template}, exactly as a C program would do by
21037 executing the code below:
21040 printf (@var{template}, @var{expressions}@dots{});
21043 As in @code{C} @code{printf}, ordinary characters in @var{template}
21044 are printed verbatim, while @dfn{conversion specification} introduced
21045 by the @samp{%} character cause subsequent @var{expressions} to be
21046 evaluated, their values converted and formatted according to type and
21047 style information encoded in the conversion specifications, and then
21050 For example, you can print two values in hex like this:
21053 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
21056 @code{printf} supports all the standard @code{C} conversion
21057 specifications, including the flags and modifiers between the @samp{%}
21058 character and the conversion letter, with the following exceptions:
21062 The argument-ordering modifiers, such as @samp{2$}, are not supported.
21065 The modifier @samp{*} is not supported for specifying precision or
21069 The @samp{'} flag (for separation of digits into groups according to
21070 @code{LC_NUMERIC'}) is not supported.
21073 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
21077 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
21080 The conversion letters @samp{a} and @samp{A} are not supported.
21084 Note that the @samp{ll} type modifier is supported only if the
21085 underlying @code{C} implementation used to build @value{GDBN} supports
21086 the @code{long long int} type, and the @samp{L} type modifier is
21087 supported only if @code{long double} type is available.
21089 As in @code{C}, @code{printf} supports simple backslash-escape
21090 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
21091 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
21092 single character. Octal and hexadecimal escape sequences are not
21095 Additionally, @code{printf} supports conversion specifications for DFP
21096 (@dfn{Decimal Floating Point}) types using the following length modifiers
21097 together with a floating point specifier.
21102 @samp{H} for printing @code{Decimal32} types.
21105 @samp{D} for printing @code{Decimal64} types.
21108 @samp{DD} for printing @code{Decimal128} types.
21111 If the underlying @code{C} implementation used to build @value{GDBN} has
21112 support for the three length modifiers for DFP types, other modifiers
21113 such as width and precision will also be available for @value{GDBN} to use.
21115 In case there is no such @code{C} support, no additional modifiers will be
21116 available and the value will be printed in the standard way.
21118 Here's an example of printing DFP types using the above conversion letters:
21120 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
21124 @item eval @var{template}, @var{expressions}@dots{}
21125 Convert the values of one or more @var{expressions} under the control of
21126 the string @var{template} to a command line, and call it.
21131 @section Scripting @value{GDBN} using Python
21132 @cindex python scripting
21133 @cindex scripting with python
21135 You can script @value{GDBN} using the @uref{http://www.python.org/,
21136 Python programming language}. This feature is available only if
21137 @value{GDBN} was configured using @option{--with-python}.
21139 @cindex python directory
21140 Python scripts used by @value{GDBN} should be installed in
21141 @file{@var{data-directory}/python}, where @var{data-directory} is
21142 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
21143 This directory, known as the @dfn{python directory},
21144 is automatically added to the Python Search Path in order to allow
21145 the Python interpreter to locate all scripts installed at this location.
21147 Additionally, @value{GDBN} commands and convenience functions which
21148 are written in Python and are located in the
21149 @file{@var{data-directory}/python/gdb/command} or
21150 @file{@var{data-directory}/python/gdb/function} directories are
21151 automatically imported when @value{GDBN} starts.
21154 * Python Commands:: Accessing Python from @value{GDBN}.
21155 * Python API:: Accessing @value{GDBN} from Python.
21156 * Auto-loading:: Automatically loading Python code.
21157 * Python modules:: Python modules provided by @value{GDBN}.
21160 @node Python Commands
21161 @subsection Python Commands
21162 @cindex python commands
21163 @cindex commands to access python
21165 @value{GDBN} provides one command for accessing the Python interpreter,
21166 and one related setting:
21170 @item python @r{[}@var{code}@r{]}
21171 The @code{python} command can be used to evaluate Python code.
21173 If given an argument, the @code{python} command will evaluate the
21174 argument as a Python command. For example:
21177 (@value{GDBP}) python print 23
21181 If you do not provide an argument to @code{python}, it will act as a
21182 multi-line command, like @code{define}. In this case, the Python
21183 script is made up of subsequent command lines, given after the
21184 @code{python} command. This command list is terminated using a line
21185 containing @code{end}. For example:
21188 (@value{GDBP}) python
21190 End with a line saying just "end".
21196 @kindex maint set python print-stack
21197 @item maint set python print-stack
21198 This command is now deprecated. Instead use @code{set python
21201 @kindex set python print-stack
21202 @item set python print-stack
21203 By default, @value{GDBN} will not print a stack trace when an error
21204 occurs in a Python script. This can be controlled using @code{set
21205 python print-stack}: if @code{on}, then Python stack printing is
21206 enabled; if @code{off}, the default, then Python stack printing is
21210 It is also possible to execute a Python script from the @value{GDBN}
21214 @item source @file{script-name}
21215 The script name must end with @samp{.py} and @value{GDBN} must be configured
21216 to recognize the script language based on filename extension using
21217 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
21219 @item python execfile ("script-name")
21220 This method is based on the @code{execfile} Python built-in function,
21221 and thus is always available.
21225 @subsection Python API
21227 @cindex programming in python
21229 @cindex python stdout
21230 @cindex python pagination
21231 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
21232 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
21233 A Python program which outputs to one of these streams may have its
21234 output interrupted by the user (@pxref{Screen Size}). In this
21235 situation, a Python @code{KeyboardInterrupt} exception is thrown.
21238 * Basic Python:: Basic Python Functions.
21239 * Exception Handling:: How Python exceptions are translated.
21240 * Values From Inferior:: Python representation of values.
21241 * Types In Python:: Python representation of types.
21242 * Pretty Printing API:: Pretty-printing values.
21243 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
21244 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
21245 * Inferiors In Python:: Python representation of inferiors (processes)
21246 * Events In Python:: Listening for events from @value{GDBN}.
21247 * Threads In Python:: Accessing inferior threads from Python.
21248 * Commands In Python:: Implementing new commands in Python.
21249 * Parameters In Python:: Adding new @value{GDBN} parameters.
21250 * Functions In Python:: Writing new convenience functions.
21251 * Progspaces In Python:: Program spaces.
21252 * Objfiles In Python:: Object files.
21253 * Frames In Python:: Accessing inferior stack frames from Python.
21254 * Blocks In Python:: Accessing frame blocks from Python.
21255 * Symbols In Python:: Python representation of symbols.
21256 * Symbol Tables In Python:: Python representation of symbol tables.
21257 * Lazy Strings In Python:: Python representation of lazy strings.
21258 * Breakpoints In Python:: Manipulating breakpoints using Python.
21262 @subsubsection Basic Python
21264 @cindex python functions
21265 @cindex python module
21267 @value{GDBN} introduces a new Python module, named @code{gdb}. All
21268 methods and classes added by @value{GDBN} are placed in this module.
21269 @value{GDBN} automatically @code{import}s the @code{gdb} module for
21270 use in all scripts evaluated by the @code{python} command.
21272 @findex gdb.PYTHONDIR
21273 @defvar gdb.PYTHONDIR
21274 A string containing the python directory (@pxref{Python}).
21277 @findex gdb.execute
21278 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
21279 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
21280 If a GDB exception happens while @var{command} runs, it is
21281 translated as described in @ref{Exception Handling,,Exception Handling}.
21283 @var{from_tty} specifies whether @value{GDBN} ought to consider this
21284 command as having originated from the user invoking it interactively.
21285 It must be a boolean value. If omitted, it defaults to @code{False}.
21287 By default, any output produced by @var{command} is sent to
21288 @value{GDBN}'s standard output. If the @var{to_string} parameter is
21289 @code{True}, then output will be collected by @code{gdb.execute} and
21290 returned as a string. The default is @code{False}, in which case the
21291 return value is @code{None}. If @var{to_string} is @code{True}, the
21292 @value{GDBN} virtual terminal will be temporarily set to unlimited width
21293 and height, and its pagination will be disabled; @pxref{Screen Size}.
21296 @findex gdb.breakpoints
21297 @defun gdb.breakpoints ()
21298 Return a sequence holding all of @value{GDBN}'s breakpoints.
21299 @xref{Breakpoints In Python}, for more information.
21302 @findex gdb.parameter
21303 @defun gdb.parameter (parameter)
21304 Return the value of a @value{GDBN} parameter. @var{parameter} is a
21305 string naming the parameter to look up; @var{parameter} may contain
21306 spaces if the parameter has a multi-part name. For example,
21307 @samp{print object} is a valid parameter name.
21309 If the named parameter does not exist, this function throws a
21310 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
21311 parameter's value is converted to a Python value of the appropriate
21312 type, and returned.
21315 @findex gdb.history
21316 @defun gdb.history (number)
21317 Return a value from @value{GDBN}'s value history (@pxref{Value
21318 History}). @var{number} indicates which history element to return.
21319 If @var{number} is negative, then @value{GDBN} will take its absolute value
21320 and count backward from the last element (i.e., the most recent element) to
21321 find the value to return. If @var{number} is zero, then @value{GDBN} will
21322 return the most recent element. If the element specified by @var{number}
21323 doesn't exist in the value history, a @code{gdb.error} exception will be
21326 If no exception is raised, the return value is always an instance of
21327 @code{gdb.Value} (@pxref{Values From Inferior}).
21330 @findex gdb.parse_and_eval
21331 @defun gdb.parse_and_eval (expression)
21332 Parse @var{expression} as an expression in the current language,
21333 evaluate it, and return the result as a @code{gdb.Value}.
21334 @var{expression} must be a string.
21336 This function can be useful when implementing a new command
21337 (@pxref{Commands In Python}), as it provides a way to parse the
21338 command's argument as an expression. It is also useful simply to
21339 compute values, for example, it is the only way to get the value of a
21340 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
21343 @findex gdb.post_event
21344 @defun gdb.post_event (event)
21345 Put @var{event}, a callable object taking no arguments, into
21346 @value{GDBN}'s internal event queue. This callable will be invoked at
21347 some later point, during @value{GDBN}'s event processing. Events
21348 posted using @code{post_event} will be run in the order in which they
21349 were posted; however, there is no way to know when they will be
21350 processed relative to other events inside @value{GDBN}.
21352 @value{GDBN} is not thread-safe. If your Python program uses multiple
21353 threads, you must be careful to only call @value{GDBN}-specific
21354 functions in the main @value{GDBN} thread. @code{post_event} ensures
21358 (@value{GDBP}) python
21362 > def __init__(self, message):
21363 > self.message = message;
21364 > def __call__(self):
21365 > gdb.write(self.message)
21367 >class MyThread1 (threading.Thread):
21369 > gdb.post_event(Writer("Hello "))
21371 >class MyThread2 (threading.Thread):
21373 > gdb.post_event(Writer("World\n"))
21375 >MyThread1().start()
21376 >MyThread2().start()
21378 (@value{GDBP}) Hello World
21383 @defun gdb.write (string @r{[}, stream{]})
21384 Print a string to @value{GDBN}'s paginated output stream. The
21385 optional @var{stream} determines the stream to print to. The default
21386 stream is @value{GDBN}'s standard output stream. Possible stream
21393 @value{GDBN}'s standard output stream.
21398 @value{GDBN}'s standard error stream.
21403 @value{GDBN}'s log stream (@pxref{Logging Output}).
21406 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
21407 call this function and will automatically direct the output to the
21412 @defun gdb.flush ()
21413 Flush the buffer of a @value{GDBN} paginated stream so that the
21414 contents are displayed immediately. @value{GDBN} will flush the
21415 contents of a stream automatically when it encounters a newline in the
21416 buffer. The optional @var{stream} determines the stream to flush. The
21417 default stream is @value{GDBN}'s standard output stream. Possible
21424 @value{GDBN}'s standard output stream.
21429 @value{GDBN}'s standard error stream.
21434 @value{GDBN}'s log stream (@pxref{Logging Output}).
21438 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
21439 call this function for the relevant stream.
21442 @findex gdb.target_charset
21443 @defun gdb.target_charset ()
21444 Return the name of the current target character set (@pxref{Character
21445 Sets}). This differs from @code{gdb.parameter('target-charset')} in
21446 that @samp{auto} is never returned.
21449 @findex gdb.target_wide_charset
21450 @defun gdb.target_wide_charset ()
21451 Return the name of the current target wide character set
21452 (@pxref{Character Sets}). This differs from
21453 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
21457 @findex gdb.solib_name
21458 @defun gdb.solib_name (address)
21459 Return the name of the shared library holding the given @var{address}
21460 as a string, or @code{None}.
21463 @findex gdb.decode_line
21464 @defun gdb.decode_line @r{[}expression@r{]}
21465 Return locations of the line specified by @var{expression}, or of the
21466 current line if no argument was given. This function returns a Python
21467 tuple containing two elements. The first element contains a string
21468 holding any unparsed section of @var{expression} (or @code{None} if
21469 the expression has been fully parsed). The second element contains
21470 either @code{None} or another tuple that contains all the locations
21471 that match the expression represented as @code{gdb.Symtab_and_line}
21472 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
21473 provided, it is decoded the way that @value{GDBN}'s inbuilt
21474 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
21477 @defun gdb.prompt_hook (current_prompt)
21478 @anchor{prompt_hook}
21480 If @var{prompt_hook} is callable, @value{GDBN} will call the method
21481 assigned to this operation before a prompt is displayed by
21484 The parameter @code{current_prompt} contains the current @value{GDBN}
21485 prompt. This method must return a Python string, or @code{None}. If
21486 a string is returned, the @value{GDBN} prompt will be set to that
21487 string. If @code{None} is returned, @value{GDBN} will continue to use
21488 the current prompt.
21490 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
21491 such as those used by readline for command input, and annotation
21492 related prompts are prohibited from being changed.
21495 @node Exception Handling
21496 @subsubsection Exception Handling
21497 @cindex python exceptions
21498 @cindex exceptions, python
21500 When executing the @code{python} command, Python exceptions
21501 uncaught within the Python code are translated to calls to
21502 @value{GDBN} error-reporting mechanism. If the command that called
21503 @code{python} does not handle the error, @value{GDBN} will
21504 terminate it and print an error message containing the Python
21505 exception name, the associated value, and the Python call stack
21506 backtrace at the point where the exception was raised. Example:
21509 (@value{GDBP}) python print foo
21510 Traceback (most recent call last):
21511 File "<string>", line 1, in <module>
21512 NameError: name 'foo' is not defined
21515 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
21516 Python code are converted to Python exceptions. The type of the
21517 Python exception depends on the error.
21521 This is the base class for most exceptions generated by @value{GDBN}.
21522 It is derived from @code{RuntimeError}, for compatibility with earlier
21523 versions of @value{GDBN}.
21525 If an error occurring in @value{GDBN} does not fit into some more
21526 specific category, then the generated exception will have this type.
21528 @item gdb.MemoryError
21529 This is a subclass of @code{gdb.error} which is thrown when an
21530 operation tried to access invalid memory in the inferior.
21532 @item KeyboardInterrupt
21533 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
21534 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
21537 In all cases, your exception handler will see the @value{GDBN} error
21538 message as its value and the Python call stack backtrace at the Python
21539 statement closest to where the @value{GDBN} error occured as the
21542 @findex gdb.GdbError
21543 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
21544 it is useful to be able to throw an exception that doesn't cause a
21545 traceback to be printed. For example, the user may have invoked the
21546 command incorrectly. Use the @code{gdb.GdbError} exception
21547 to handle this case. Example:
21551 >class HelloWorld (gdb.Command):
21552 > """Greet the whole world."""
21553 > def __init__ (self):
21554 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
21555 > def invoke (self, args, from_tty):
21556 > argv = gdb.string_to_argv (args)
21557 > if len (argv) != 0:
21558 > raise gdb.GdbError ("hello-world takes no arguments")
21559 > print "Hello, World!"
21562 (gdb) hello-world 42
21563 hello-world takes no arguments
21566 @node Values From Inferior
21567 @subsubsection Values From Inferior
21568 @cindex values from inferior, with Python
21569 @cindex python, working with values from inferior
21571 @cindex @code{gdb.Value}
21572 @value{GDBN} provides values it obtains from the inferior program in
21573 an object of type @code{gdb.Value}. @value{GDBN} uses this object
21574 for its internal bookkeeping of the inferior's values, and for
21575 fetching values when necessary.
21577 Inferior values that are simple scalars can be used directly in
21578 Python expressions that are valid for the value's data type. Here's
21579 an example for an integer or floating-point value @code{some_val}:
21586 As result of this, @code{bar} will also be a @code{gdb.Value} object
21587 whose values are of the same type as those of @code{some_val}.
21589 Inferior values that are structures or instances of some class can
21590 be accessed using the Python @dfn{dictionary syntax}. For example, if
21591 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
21592 can access its @code{foo} element with:
21595 bar = some_val['foo']
21598 Again, @code{bar} will also be a @code{gdb.Value} object.
21600 A @code{gdb.Value} that represents a function can be executed via
21601 inferior function call. Any arguments provided to the call must match
21602 the function's prototype, and must be provided in the order specified
21605 For example, @code{some_val} is a @code{gdb.Value} instance
21606 representing a function that takes two integers as arguments. To
21607 execute this function, call it like so:
21610 result = some_val (10,20)
21613 Any values returned from a function call will be stored as a
21616 The following attributes are provided:
21619 @defvar Value.address
21620 If this object is addressable, this read-only attribute holds a
21621 @code{gdb.Value} object representing the address. Otherwise,
21622 this attribute holds @code{None}.
21625 @cindex optimized out value in Python
21626 @defvar Value.is_optimized_out
21627 This read-only boolean attribute is true if the compiler optimized out
21628 this value, thus it is not available for fetching from the inferior.
21632 The type of this @code{gdb.Value}. The value of this attribute is a
21633 @code{gdb.Type} object (@pxref{Types In Python}).
21636 @defvar Value.dynamic_type
21637 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
21638 type information (@acronym{RTTI}) to determine the dynamic type of the
21639 value. If this value is of class type, it will return the class in
21640 which the value is embedded, if any. If this value is of pointer or
21641 reference to a class type, it will compute the dynamic type of the
21642 referenced object, and return a pointer or reference to that type,
21643 respectively. In all other cases, it will return the value's static
21646 Note that this feature will only work when debugging a C@t{++} program
21647 that includes @acronym{RTTI} for the object in question. Otherwise,
21648 it will just return the static type of the value as in @kbd{ptype foo}
21649 (@pxref{Symbols, ptype}).
21653 The following methods are provided:
21656 @defun Value.__init__ (@var{val})
21657 Many Python values can be converted directly to a @code{gdb.Value} via
21658 this object initializer. Specifically:
21661 @item Python boolean
21662 A Python boolean is converted to the boolean type from the current
21665 @item Python integer
21666 A Python integer is converted to the C @code{long} type for the
21667 current architecture.
21670 A Python long is converted to the C @code{long long} type for the
21671 current architecture.
21674 A Python float is converted to the C @code{double} type for the
21675 current architecture.
21677 @item Python string
21678 A Python string is converted to a target string, using the current
21681 @item @code{gdb.Value}
21682 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
21684 @item @code{gdb.LazyString}
21685 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
21686 Python}), then the lazy string's @code{value} method is called, and
21687 its result is used.
21691 @defun Value.cast (type)
21692 Return a new instance of @code{gdb.Value} that is the result of
21693 casting this instance to the type described by @var{type}, which must
21694 be a @code{gdb.Type} object. If the cast cannot be performed for some
21695 reason, this method throws an exception.
21698 @defun Value.dereference ()
21699 For pointer data types, this method returns a new @code{gdb.Value} object
21700 whose contents is the object pointed to by the pointer. For example, if
21701 @code{foo} is a C pointer to an @code{int}, declared in your C program as
21708 then you can use the corresponding @code{gdb.Value} to access what
21709 @code{foo} points to like this:
21712 bar = foo.dereference ()
21715 The result @code{bar} will be a @code{gdb.Value} object holding the
21716 value pointed to by @code{foo}.
21719 @defun Value.dynamic_cast (type)
21720 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
21721 operator were used. Consult a C@t{++} reference for details.
21724 @defun Value.reinterpret_cast (type)
21725 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
21726 operator were used. Consult a C@t{++} reference for details.
21729 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
21730 If this @code{gdb.Value} represents a string, then this method
21731 converts the contents to a Python string. Otherwise, this method will
21732 throw an exception.
21734 Strings are recognized in a language-specific way; whether a given
21735 @code{gdb.Value} represents a string is determined by the current
21738 For C-like languages, a value is a string if it is a pointer to or an
21739 array of characters or ints. The string is assumed to be terminated
21740 by a zero of the appropriate width. However if the optional length
21741 argument is given, the string will be converted to that given length,
21742 ignoring any embedded zeros that the string may contain.
21744 If the optional @var{encoding} argument is given, it must be a string
21745 naming the encoding of the string in the @code{gdb.Value}, such as
21746 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
21747 the same encodings as the corresponding argument to Python's
21748 @code{string.decode} method, and the Python codec machinery will be used
21749 to convert the string. If @var{encoding} is not given, or if
21750 @var{encoding} is the empty string, then either the @code{target-charset}
21751 (@pxref{Character Sets}) will be used, or a language-specific encoding
21752 will be used, if the current language is able to supply one.
21754 The optional @var{errors} argument is the same as the corresponding
21755 argument to Python's @code{string.decode} method.
21757 If the optional @var{length} argument is given, the string will be
21758 fetched and converted to the given length.
21761 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
21762 If this @code{gdb.Value} represents a string, then this method
21763 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
21764 In Python}). Otherwise, this method will throw an exception.
21766 If the optional @var{encoding} argument is given, it must be a string
21767 naming the encoding of the @code{gdb.LazyString}. Some examples are:
21768 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
21769 @var{encoding} argument is an encoding that @value{GDBN} does
21770 recognize, @value{GDBN} will raise an error.
21772 When a lazy string is printed, the @value{GDBN} encoding machinery is
21773 used to convert the string during printing. If the optional
21774 @var{encoding} argument is not provided, or is an empty string,
21775 @value{GDBN} will automatically select the encoding most suitable for
21776 the string type. For further information on encoding in @value{GDBN}
21777 please see @ref{Character Sets}.
21779 If the optional @var{length} argument is given, the string will be
21780 fetched and encoded to the length of characters specified. If
21781 the @var{length} argument is not provided, the string will be fetched
21782 and encoded until a null of appropriate width is found.
21786 @node Types In Python
21787 @subsubsection Types In Python
21788 @cindex types in Python
21789 @cindex Python, working with types
21792 @value{GDBN} represents types from the inferior using the class
21795 The following type-related functions are available in the @code{gdb}
21798 @findex gdb.lookup_type
21799 @defun gdb.lookup_type (name @r{[}, block@r{]})
21800 This function looks up a type by name. @var{name} is the name of the
21801 type to look up. It must be a string.
21803 If @var{block} is given, then @var{name} is looked up in that scope.
21804 Otherwise, it is searched for globally.
21806 Ordinarily, this function will return an instance of @code{gdb.Type}.
21807 If the named type cannot be found, it will throw an exception.
21810 If the type is a structure or class type, or an enum type, the fields
21811 of that type can be accessed using the Python @dfn{dictionary syntax}.
21812 For example, if @code{some_type} is a @code{gdb.Type} instance holding
21813 a structure type, you can access its @code{foo} field with:
21816 bar = some_type['foo']
21819 @code{bar} will be a @code{gdb.Field} object; see below under the
21820 description of the @code{Type.fields} method for a description of the
21821 @code{gdb.Field} class.
21823 An instance of @code{Type} has the following attributes:
21827 The type code for this type. The type code will be one of the
21828 @code{TYPE_CODE_} constants defined below.
21831 @defvar Type.sizeof
21832 The size of this type, in target @code{char} units. Usually, a
21833 target's @code{char} type will be an 8-bit byte. However, on some
21834 unusual platforms, this type may have a different size.
21838 The tag name for this type. The tag name is the name after
21839 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
21840 languages have this concept. If this type has no tag name, then
21841 @code{None} is returned.
21845 The following methods are provided:
21848 @defun Type.fields ()
21849 For structure and union types, this method returns the fields. Range
21850 types have two fields, the minimum and maximum values. Enum types
21851 have one field per enum constant. Function and method types have one
21852 field per parameter. The base types of C@t{++} classes are also
21853 represented as fields. If the type has no fields, or does not fit
21854 into one of these categories, an empty sequence will be returned.
21856 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
21859 This attribute is not available for @code{static} fields (as in
21860 C@t{++} or Java). For non-@code{static} fields, the value is the bit
21861 position of the field. For @code{enum} fields, the value is the
21862 enumeration member's integer representation.
21865 The name of the field, or @code{None} for anonymous fields.
21868 This is @code{True} if the field is artificial, usually meaning that
21869 it was provided by the compiler and not the user. This attribute is
21870 always provided, and is @code{False} if the field is not artificial.
21872 @item is_base_class
21873 This is @code{True} if the field represents a base class of a C@t{++}
21874 structure. This attribute is always provided, and is @code{False}
21875 if the field is not a base class of the type that is the argument of
21876 @code{fields}, or if that type was not a C@t{++} class.
21879 If the field is packed, or is a bitfield, then this will have a
21880 non-zero value, which is the size of the field in bits. Otherwise,
21881 this will be zero; in this case the field's size is given by its type.
21884 The type of the field. This is usually an instance of @code{Type},
21885 but it can be @code{None} in some situations.
21889 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
21890 Return a new @code{gdb.Type} object which represents an array of this
21891 type. If one argument is given, it is the inclusive upper bound of
21892 the array; in this case the lower bound is zero. If two arguments are
21893 given, the first argument is the lower bound of the array, and the
21894 second argument is the upper bound of the array. An array's length
21895 must not be negative, but the bounds can be.
21898 @defun Type.const ()
21899 Return a new @code{gdb.Type} object which represents a
21900 @code{const}-qualified variant of this type.
21903 @defun Type.volatile ()
21904 Return a new @code{gdb.Type} object which represents a
21905 @code{volatile}-qualified variant of this type.
21908 @defun Type.unqualified ()
21909 Return a new @code{gdb.Type} object which represents an unqualified
21910 variant of this type. That is, the result is neither @code{const} nor
21914 @defun Type.range ()
21915 Return a Python @code{Tuple} object that contains two elements: the
21916 low bound of the argument type and the high bound of that type. If
21917 the type does not have a range, @value{GDBN} will raise a
21918 @code{gdb.error} exception (@pxref{Exception Handling}).
21921 @defun Type.reference ()
21922 Return a new @code{gdb.Type} object which represents a reference to this
21926 @defun Type.pointer ()
21927 Return a new @code{gdb.Type} object which represents a pointer to this
21931 @defun Type.strip_typedefs ()
21932 Return a new @code{gdb.Type} that represents the real type,
21933 after removing all layers of typedefs.
21936 @defun Type.target ()
21937 Return a new @code{gdb.Type} object which represents the target type
21940 For a pointer type, the target type is the type of the pointed-to
21941 object. For an array type (meaning C-like arrays), the target type is
21942 the type of the elements of the array. For a function or method type,
21943 the target type is the type of the return value. For a complex type,
21944 the target type is the type of the elements. For a typedef, the
21945 target type is the aliased type.
21947 If the type does not have a target, this method will throw an
21951 @defun Type.template_argument (n @r{[}, block@r{]})
21952 If this @code{gdb.Type} is an instantiation of a template, this will
21953 return a new @code{gdb.Type} which represents the type of the
21954 @var{n}th template argument.
21956 If this @code{gdb.Type} is not a template type, this will throw an
21957 exception. Ordinarily, only C@t{++} code will have template types.
21959 If @var{block} is given, then @var{name} is looked up in that scope.
21960 Otherwise, it is searched for globally.
21965 Each type has a code, which indicates what category this type falls
21966 into. The available type categories are represented by constants
21967 defined in the @code{gdb} module:
21970 @findex TYPE_CODE_PTR
21971 @findex gdb.TYPE_CODE_PTR
21972 @item gdb.TYPE_CODE_PTR
21973 The type is a pointer.
21975 @findex TYPE_CODE_ARRAY
21976 @findex gdb.TYPE_CODE_ARRAY
21977 @item gdb.TYPE_CODE_ARRAY
21978 The type is an array.
21980 @findex TYPE_CODE_STRUCT
21981 @findex gdb.TYPE_CODE_STRUCT
21982 @item gdb.TYPE_CODE_STRUCT
21983 The type is a structure.
21985 @findex TYPE_CODE_UNION
21986 @findex gdb.TYPE_CODE_UNION
21987 @item gdb.TYPE_CODE_UNION
21988 The type is a union.
21990 @findex TYPE_CODE_ENUM
21991 @findex gdb.TYPE_CODE_ENUM
21992 @item gdb.TYPE_CODE_ENUM
21993 The type is an enum.
21995 @findex TYPE_CODE_FLAGS
21996 @findex gdb.TYPE_CODE_FLAGS
21997 @item gdb.TYPE_CODE_FLAGS
21998 A bit flags type, used for things such as status registers.
22000 @findex TYPE_CODE_FUNC
22001 @findex gdb.TYPE_CODE_FUNC
22002 @item gdb.TYPE_CODE_FUNC
22003 The type is a function.
22005 @findex TYPE_CODE_INT
22006 @findex gdb.TYPE_CODE_INT
22007 @item gdb.TYPE_CODE_INT
22008 The type is an integer type.
22010 @findex TYPE_CODE_FLT
22011 @findex gdb.TYPE_CODE_FLT
22012 @item gdb.TYPE_CODE_FLT
22013 A floating point type.
22015 @findex TYPE_CODE_VOID
22016 @findex gdb.TYPE_CODE_VOID
22017 @item gdb.TYPE_CODE_VOID
22018 The special type @code{void}.
22020 @findex TYPE_CODE_SET
22021 @findex gdb.TYPE_CODE_SET
22022 @item gdb.TYPE_CODE_SET
22025 @findex TYPE_CODE_RANGE
22026 @findex gdb.TYPE_CODE_RANGE
22027 @item gdb.TYPE_CODE_RANGE
22028 A range type, that is, an integer type with bounds.
22030 @findex TYPE_CODE_STRING
22031 @findex gdb.TYPE_CODE_STRING
22032 @item gdb.TYPE_CODE_STRING
22033 A string type. Note that this is only used for certain languages with
22034 language-defined string types; C strings are not represented this way.
22036 @findex TYPE_CODE_BITSTRING
22037 @findex gdb.TYPE_CODE_BITSTRING
22038 @item gdb.TYPE_CODE_BITSTRING
22041 @findex TYPE_CODE_ERROR
22042 @findex gdb.TYPE_CODE_ERROR
22043 @item gdb.TYPE_CODE_ERROR
22044 An unknown or erroneous type.
22046 @findex TYPE_CODE_METHOD
22047 @findex gdb.TYPE_CODE_METHOD
22048 @item gdb.TYPE_CODE_METHOD
22049 A method type, as found in C@t{++} or Java.
22051 @findex TYPE_CODE_METHODPTR
22052 @findex gdb.TYPE_CODE_METHODPTR
22053 @item gdb.TYPE_CODE_METHODPTR
22054 A pointer-to-member-function.
22056 @findex TYPE_CODE_MEMBERPTR
22057 @findex gdb.TYPE_CODE_MEMBERPTR
22058 @item gdb.TYPE_CODE_MEMBERPTR
22059 A pointer-to-member.
22061 @findex TYPE_CODE_REF
22062 @findex gdb.TYPE_CODE_REF
22063 @item gdb.TYPE_CODE_REF
22066 @findex TYPE_CODE_CHAR
22067 @findex gdb.TYPE_CODE_CHAR
22068 @item gdb.TYPE_CODE_CHAR
22071 @findex TYPE_CODE_BOOL
22072 @findex gdb.TYPE_CODE_BOOL
22073 @item gdb.TYPE_CODE_BOOL
22076 @findex TYPE_CODE_COMPLEX
22077 @findex gdb.TYPE_CODE_COMPLEX
22078 @item gdb.TYPE_CODE_COMPLEX
22079 A complex float type.
22081 @findex TYPE_CODE_TYPEDEF
22082 @findex gdb.TYPE_CODE_TYPEDEF
22083 @item gdb.TYPE_CODE_TYPEDEF
22084 A typedef to some other type.
22086 @findex TYPE_CODE_NAMESPACE
22087 @findex gdb.TYPE_CODE_NAMESPACE
22088 @item gdb.TYPE_CODE_NAMESPACE
22089 A C@t{++} namespace.
22091 @findex TYPE_CODE_DECFLOAT
22092 @findex gdb.TYPE_CODE_DECFLOAT
22093 @item gdb.TYPE_CODE_DECFLOAT
22094 A decimal floating point type.
22096 @findex TYPE_CODE_INTERNAL_FUNCTION
22097 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
22098 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
22099 A function internal to @value{GDBN}. This is the type used to represent
22100 convenience functions.
22103 Further support for types is provided in the @code{gdb.types}
22104 Python module (@pxref{gdb.types}).
22106 @node Pretty Printing API
22107 @subsubsection Pretty Printing API
22109 An example output is provided (@pxref{Pretty Printing}).
22111 A pretty-printer is just an object that holds a value and implements a
22112 specific interface, defined here.
22114 @defun pretty_printer.children (self)
22115 @value{GDBN} will call this method on a pretty-printer to compute the
22116 children of the pretty-printer's value.
22118 This method must return an object conforming to the Python iterator
22119 protocol. Each item returned by the iterator must be a tuple holding
22120 two elements. The first element is the ``name'' of the child; the
22121 second element is the child's value. The value can be any Python
22122 object which is convertible to a @value{GDBN} value.
22124 This method is optional. If it does not exist, @value{GDBN} will act
22125 as though the value has no children.
22128 @defun pretty_printer.display_hint (self)
22129 The CLI may call this method and use its result to change the
22130 formatting of a value. The result will also be supplied to an MI
22131 consumer as a @samp{displayhint} attribute of the variable being
22134 This method is optional. If it does exist, this method must return a
22137 Some display hints are predefined by @value{GDBN}:
22141 Indicate that the object being printed is ``array-like''. The CLI
22142 uses this to respect parameters such as @code{set print elements} and
22143 @code{set print array}.
22146 Indicate that the object being printed is ``map-like'', and that the
22147 children of this value can be assumed to alternate between keys and
22151 Indicate that the object being printed is ``string-like''. If the
22152 printer's @code{to_string} method returns a Python string of some
22153 kind, then @value{GDBN} will call its internal language-specific
22154 string-printing function to format the string. For the CLI this means
22155 adding quotation marks, possibly escaping some characters, respecting
22156 @code{set print elements}, and the like.
22160 @defun pretty_printer.to_string (self)
22161 @value{GDBN} will call this method to display the string
22162 representation of the value passed to the object's constructor.
22164 When printing from the CLI, if the @code{to_string} method exists,
22165 then @value{GDBN} will prepend its result to the values returned by
22166 @code{children}. Exactly how this formatting is done is dependent on
22167 the display hint, and may change as more hints are added. Also,
22168 depending on the print settings (@pxref{Print Settings}), the CLI may
22169 print just the result of @code{to_string} in a stack trace, omitting
22170 the result of @code{children}.
22172 If this method returns a string, it is printed verbatim.
22174 Otherwise, if this method returns an instance of @code{gdb.Value},
22175 then @value{GDBN} prints this value. This may result in a call to
22176 another pretty-printer.
22178 If instead the method returns a Python value which is convertible to a
22179 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
22180 the resulting value. Again, this may result in a call to another
22181 pretty-printer. Python scalars (integers, floats, and booleans) and
22182 strings are convertible to @code{gdb.Value}; other types are not.
22184 Finally, if this method returns @code{None} then no further operations
22185 are peformed in this method and nothing is printed.
22187 If the result is not one of these types, an exception is raised.
22190 @value{GDBN} provides a function which can be used to look up the
22191 default pretty-printer for a @code{gdb.Value}:
22193 @findex gdb.default_visualizer
22194 @defun gdb.default_visualizer (value)
22195 This function takes a @code{gdb.Value} object as an argument. If a
22196 pretty-printer for this value exists, then it is returned. If no such
22197 printer exists, then this returns @code{None}.
22200 @node Selecting Pretty-Printers
22201 @subsubsection Selecting Pretty-Printers
22203 The Python list @code{gdb.pretty_printers} contains an array of
22204 functions or callable objects that have been registered via addition
22205 as a pretty-printer. Printers in this list are called @code{global}
22206 printers, they're available when debugging all inferiors.
22207 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
22208 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
22211 Each function on these lists is passed a single @code{gdb.Value}
22212 argument and should return a pretty-printer object conforming to the
22213 interface definition above (@pxref{Pretty Printing API}). If a function
22214 cannot create a pretty-printer for the value, it should return
22217 @value{GDBN} first checks the @code{pretty_printers} attribute of each
22218 @code{gdb.Objfile} in the current program space and iteratively calls
22219 each enabled lookup routine in the list for that @code{gdb.Objfile}
22220 until it receives a pretty-printer object.
22221 If no pretty-printer is found in the objfile lists, @value{GDBN} then
22222 searches the pretty-printer list of the current program space,
22223 calling each enabled function until an object is returned.
22224 After these lists have been exhausted, it tries the global
22225 @code{gdb.pretty_printers} list, again calling each enabled function until an
22226 object is returned.
22228 The order in which the objfiles are searched is not specified. For a
22229 given list, functions are always invoked from the head of the list,
22230 and iterated over sequentially until the end of the list, or a printer
22231 object is returned.
22233 For various reasons a pretty-printer may not work.
22234 For example, the underlying data structure may have changed and
22235 the pretty-printer is out of date.
22237 The consequences of a broken pretty-printer are severe enough that
22238 @value{GDBN} provides support for enabling and disabling individual
22239 printers. For example, if @code{print frame-arguments} is on,
22240 a backtrace can become highly illegible if any argument is printed
22241 with a broken printer.
22243 Pretty-printers are enabled and disabled by attaching an @code{enabled}
22244 attribute to the registered function or callable object. If this attribute
22245 is present and its value is @code{False}, the printer is disabled, otherwise
22246 the printer is enabled.
22248 @node Writing a Pretty-Printer
22249 @subsubsection Writing a Pretty-Printer
22250 @cindex writing a pretty-printer
22252 A pretty-printer consists of two parts: a lookup function to detect
22253 if the type is supported, and the printer itself.
22255 Here is an example showing how a @code{std::string} printer might be
22256 written. @xref{Pretty Printing API}, for details on the API this class
22260 class StdStringPrinter(object):
22261 "Print a std::string"
22263 def __init__(self, val):
22266 def to_string(self):
22267 return self.val['_M_dataplus']['_M_p']
22269 def display_hint(self):
22273 And here is an example showing how a lookup function for the printer
22274 example above might be written.
22277 def str_lookup_function(val):
22278 lookup_tag = val.type.tag
22279 if lookup_tag == None:
22281 regex = re.compile("^std::basic_string<char,.*>$")
22282 if regex.match(lookup_tag):
22283 return StdStringPrinter(val)
22287 The example lookup function extracts the value's type, and attempts to
22288 match it to a type that it can pretty-print. If it is a type the
22289 printer can pretty-print, it will return a printer object. If not, it
22290 returns @code{None}.
22292 We recommend that you put your core pretty-printers into a Python
22293 package. If your pretty-printers are for use with a library, we
22294 further recommend embedding a version number into the package name.
22295 This practice will enable @value{GDBN} to load multiple versions of
22296 your pretty-printers at the same time, because they will have
22299 You should write auto-loaded code (@pxref{Auto-loading}) such that it
22300 can be evaluated multiple times without changing its meaning. An
22301 ideal auto-load file will consist solely of @code{import}s of your
22302 printer modules, followed by a call to a register pretty-printers with
22303 the current objfile.
22305 Taken as a whole, this approach will scale nicely to multiple
22306 inferiors, each potentially using a different library version.
22307 Embedding a version number in the Python package name will ensure that
22308 @value{GDBN} is able to load both sets of printers simultaneously.
22309 Then, because the search for pretty-printers is done by objfile, and
22310 because your auto-loaded code took care to register your library's
22311 printers with a specific objfile, @value{GDBN} will find the correct
22312 printers for the specific version of the library used by each
22315 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
22316 this code might appear in @code{gdb.libstdcxx.v6}:
22319 def register_printers(objfile):
22320 objfile.pretty_printers.add(str_lookup_function)
22324 And then the corresponding contents of the auto-load file would be:
22327 import gdb.libstdcxx.v6
22328 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
22331 The previous example illustrates a basic pretty-printer.
22332 There are a few things that can be improved on.
22333 The printer doesn't have a name, making it hard to identify in a
22334 list of installed printers. The lookup function has a name, but
22335 lookup functions can have arbitrary, even identical, names.
22337 Second, the printer only handles one type, whereas a library typically has
22338 several types. One could install a lookup function for each desired type
22339 in the library, but one could also have a single lookup function recognize
22340 several types. The latter is the conventional way this is handled.
22341 If a pretty-printer can handle multiple data types, then its
22342 @dfn{subprinters} are the printers for the individual data types.
22344 The @code{gdb.printing} module provides a formal way of solving these
22345 problems (@pxref{gdb.printing}).
22346 Here is another example that handles multiple types.
22348 These are the types we are going to pretty-print:
22351 struct foo @{ int a, b; @};
22352 struct bar @{ struct foo x, y; @};
22355 Here are the printers:
22359 """Print a foo object."""
22361 def __init__(self, val):
22364 def to_string(self):
22365 return ("a=<" + str(self.val["a"]) +
22366 "> b=<" + str(self.val["b"]) + ">")
22369 """Print a bar object."""
22371 def __init__(self, val):
22374 def to_string(self):
22375 return ("x=<" + str(self.val["x"]) +
22376 "> y=<" + str(self.val["y"]) + ">")
22379 This example doesn't need a lookup function, that is handled by the
22380 @code{gdb.printing} module. Instead a function is provided to build up
22381 the object that handles the lookup.
22384 import gdb.printing
22386 def build_pretty_printer():
22387 pp = gdb.printing.RegexpCollectionPrettyPrinter(
22389 pp.add_printer('foo', '^foo$', fooPrinter)
22390 pp.add_printer('bar', '^bar$', barPrinter)
22394 And here is the autoload support:
22397 import gdb.printing
22399 gdb.printing.register_pretty_printer(
22400 gdb.current_objfile(),
22401 my_library.build_pretty_printer())
22404 Finally, when this printer is loaded into @value{GDBN}, here is the
22405 corresponding output of @samp{info pretty-printer}:
22408 (gdb) info pretty-printer
22415 @node Inferiors In Python
22416 @subsubsection Inferiors In Python
22417 @cindex inferiors in Python
22419 @findex gdb.Inferior
22420 Programs which are being run under @value{GDBN} are called inferiors
22421 (@pxref{Inferiors and Programs}). Python scripts can access
22422 information about and manipulate inferiors controlled by @value{GDBN}
22423 via objects of the @code{gdb.Inferior} class.
22425 The following inferior-related functions are available in the @code{gdb}
22428 @defun gdb.inferiors ()
22429 Return a tuple containing all inferior objects.
22432 @defun gdb.selected_inferior ()
22433 Return an object representing the current inferior.
22436 A @code{gdb.Inferior} object has the following attributes:
22439 @defvar Inferior.num
22440 ID of inferior, as assigned by GDB.
22443 @defvar Inferior.pid
22444 Process ID of the inferior, as assigned by the underlying operating
22448 @defvar Inferior.was_attached
22449 Boolean signaling whether the inferior was created using `attach', or
22450 started by @value{GDBN} itself.
22454 A @code{gdb.Inferior} object has the following methods:
22457 @defun Inferior.is_valid ()
22458 Returns @code{True} if the @code{gdb.Inferior} object is valid,
22459 @code{False} if not. A @code{gdb.Inferior} object will become invalid
22460 if the inferior no longer exists within @value{GDBN}. All other
22461 @code{gdb.Inferior} methods will throw an exception if it is invalid
22462 at the time the method is called.
22465 @defun Inferior.threads ()
22466 This method returns a tuple holding all the threads which are valid
22467 when it is called. If there are no valid threads, the method will
22468 return an empty tuple.
22471 @findex gdb.read_memory
22472 @defun Inferior.read_memory (address, length)
22473 Read @var{length} bytes of memory from the inferior, starting at
22474 @var{address}. Returns a buffer object, which behaves much like an array
22475 or a string. It can be modified and given to the @code{gdb.write_memory}
22479 @findex gdb.write_memory
22480 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
22481 Write the contents of @var{buffer} to the inferior, starting at
22482 @var{address}. The @var{buffer} parameter must be a Python object
22483 which supports the buffer protocol, i.e., a string, an array or the
22484 object returned from @code{gdb.read_memory}. If given, @var{length}
22485 determines the number of bytes from @var{buffer} to be written.
22488 @findex gdb.search_memory
22489 @defun Inferior.search_memory (address, length, pattern)
22490 Search a region of the inferior memory starting at @var{address} with
22491 the given @var{length} using the search pattern supplied in
22492 @var{pattern}. The @var{pattern} parameter must be a Python object
22493 which supports the buffer protocol, i.e., a string, an array or the
22494 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
22495 containing the address where the pattern was found, or @code{None} if
22496 the pattern could not be found.
22500 @node Events In Python
22501 @subsubsection Events In Python
22502 @cindex inferior events in Python
22504 @value{GDBN} provides a general event facility so that Python code can be
22505 notified of various state changes, particularly changes that occur in
22508 An @dfn{event} is just an object that describes some state change. The
22509 type of the object and its attributes will vary depending on the details
22510 of the change. All the existing events are described below.
22512 In order to be notified of an event, you must register an event handler
22513 with an @dfn{event registry}. An event registry is an object in the
22514 @code{gdb.events} module which dispatches particular events. A registry
22515 provides methods to register and unregister event handlers:
22518 @defun EventRegistry.connect (object)
22519 Add the given callable @var{object} to the registry. This object will be
22520 called when an event corresponding to this registry occurs.
22523 @defun EventRegistry.disconnect (object)
22524 Remove the given @var{object} from the registry. Once removed, the object
22525 will no longer receive notifications of events.
22529 Here is an example:
22532 def exit_handler (event):
22533 print "event type: exit"
22534 print "exit code: %d" % (event.exit_code)
22536 gdb.events.exited.connect (exit_handler)
22539 In the above example we connect our handler @code{exit_handler} to the
22540 registry @code{events.exited}. Once connected, @code{exit_handler} gets
22541 called when the inferior exits. The argument @dfn{event} in this example is
22542 of type @code{gdb.ExitedEvent}. As you can see in the example the
22543 @code{ExitedEvent} object has an attribute which indicates the exit code of
22546 The following is a listing of the event registries that are available and
22547 details of the events they emit:
22552 Emits @code{gdb.ThreadEvent}.
22554 Some events can be thread specific when @value{GDBN} is running in non-stop
22555 mode. When represented in Python, these events all extend
22556 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
22557 events which are emitted by this or other modules might extend this event.
22558 Examples of these events are @code{gdb.BreakpointEvent} and
22559 @code{gdb.ContinueEvent}.
22562 @defvar ThreadEvent.inferior_thread
22563 In non-stop mode this attribute will be set to the specific thread which was
22564 involved in the emitted event. Otherwise, it will be set to @code{None}.
22568 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
22570 This event indicates that the inferior has been continued after a stop. For
22571 inherited attribute refer to @code{gdb.ThreadEvent} above.
22573 @item events.exited
22574 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
22575 @code{events.ExitedEvent} has two attributes:
22577 @defvar ExitedEvent.exit_code
22578 An integer representing the exit code, if available, which the inferior
22579 has returned. (The exit code could be unavailable if, for example,
22580 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
22581 the attribute does not exist.
22583 @defvar ExitedEvent inferior
22584 A reference to the inferior which triggered the @code{exited} event.
22589 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
22591 Indicates that the inferior has stopped. All events emitted by this registry
22592 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
22593 will indicate the stopped thread when @value{GDBN} is running in non-stop
22594 mode. Refer to @code{gdb.ThreadEvent} above for more details.
22596 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
22598 This event indicates that the inferior or one of its threads has received as
22599 signal. @code{gdb.SignalEvent} has the following attributes:
22602 @defvar SignalEvent.stop_signal
22603 A string representing the signal received by the inferior. A list of possible
22604 signal values can be obtained by running the command @code{info signals} in
22605 the @value{GDBN} command prompt.
22609 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
22611 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
22612 been hit, and has the following attributes:
22615 @defvar BreakpointEvent.breakpoints
22616 A sequence containing references to all the breakpoints (type
22617 @code{gdb.Breakpoint}) that were hit.
22618 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
22620 @defvar BreakpointEvent.breakpoint
22621 A reference to the first breakpoint that was hit.
22622 This function is maintained for backward compatibility and is now deprecated
22623 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
22627 @item events.new_objfile
22628 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
22629 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
22632 @defvar NewObjFileEvent.new_objfile
22633 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
22634 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
22640 @node Threads In Python
22641 @subsubsection Threads In Python
22642 @cindex threads in python
22644 @findex gdb.InferiorThread
22645 Python scripts can access information about, and manipulate inferior threads
22646 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
22648 The following thread-related functions are available in the @code{gdb}
22651 @findex gdb.selected_thread
22652 @defun gdb.selected_thread ()
22653 This function returns the thread object for the selected thread. If there
22654 is no selected thread, this will return @code{None}.
22657 A @code{gdb.InferiorThread} object has the following attributes:
22660 @defvar InferiorThread.name
22661 The name of the thread. If the user specified a name using
22662 @code{thread name}, then this returns that name. Otherwise, if an
22663 OS-supplied name is available, then it is returned. Otherwise, this
22664 returns @code{None}.
22666 This attribute can be assigned to. The new value must be a string
22667 object, which sets the new name, or @code{None}, which removes any
22668 user-specified thread name.
22671 @defvar InferiorThread.num
22672 ID of the thread, as assigned by GDB.
22675 @defvar InferiorThread.ptid
22676 ID of the thread, as assigned by the operating system. This attribute is a
22677 tuple containing three integers. The first is the Process ID (PID); the second
22678 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
22679 Either the LWPID or TID may be 0, which indicates that the operating system
22680 does not use that identifier.
22684 A @code{gdb.InferiorThread} object has the following methods:
22687 @defun InferiorThread.is_valid ()
22688 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
22689 @code{False} if not. A @code{gdb.InferiorThread} object will become
22690 invalid if the thread exits, or the inferior that the thread belongs
22691 is deleted. All other @code{gdb.InferiorThread} methods will throw an
22692 exception if it is invalid at the time the method is called.
22695 @defun InferiorThread.switch ()
22696 This changes @value{GDBN}'s currently selected thread to the one represented
22700 @defun InferiorThread.is_stopped ()
22701 Return a Boolean indicating whether the thread is stopped.
22704 @defun InferiorThread.is_running ()
22705 Return a Boolean indicating whether the thread is running.
22708 @defun InferiorThread.is_exited ()
22709 Return a Boolean indicating whether the thread is exited.
22713 @node Commands In Python
22714 @subsubsection Commands In Python
22716 @cindex commands in python
22717 @cindex python commands
22718 You can implement new @value{GDBN} CLI commands in Python. A CLI
22719 command is implemented using an instance of the @code{gdb.Command}
22720 class, most commonly using a subclass.
22722 @defun Command.__init__ (name, @var{command_class} @r{[}, var{completer_class} @r{[}, var{prefix}@r{]]})
22723 The object initializer for @code{Command} registers the new command
22724 with @value{GDBN}. This initializer is normally invoked from the
22725 subclass' own @code{__init__} method.
22727 @var{name} is the name of the command. If @var{name} consists of
22728 multiple words, then the initial words are looked for as prefix
22729 commands. In this case, if one of the prefix commands does not exist,
22730 an exception is raised.
22732 There is no support for multi-line commands.
22734 @var{command_class} should be one of the @samp{COMMAND_} constants
22735 defined below. This argument tells @value{GDBN} how to categorize the
22736 new command in the help system.
22738 @var{completer_class} is an optional argument. If given, it should be
22739 one of the @samp{COMPLETE_} constants defined below. This argument
22740 tells @value{GDBN} how to perform completion for this command. If not
22741 given, @value{GDBN} will attempt to complete using the object's
22742 @code{complete} method (see below); if no such method is found, an
22743 error will occur when completion is attempted.
22745 @var{prefix} is an optional argument. If @code{True}, then the new
22746 command is a prefix command; sub-commands of this command may be
22749 The help text for the new command is taken from the Python
22750 documentation string for the command's class, if there is one. If no
22751 documentation string is provided, the default value ``This command is
22752 not documented.'' is used.
22755 @cindex don't repeat Python command
22756 @defun Command.dont_repeat ()
22757 By default, a @value{GDBN} command is repeated when the user enters a
22758 blank line at the command prompt. A command can suppress this
22759 behavior by invoking the @code{dont_repeat} method. This is similar
22760 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
22763 @defun Command.invoke (argument, from_tty)
22764 This method is called by @value{GDBN} when this command is invoked.
22766 @var{argument} is a string. It is the argument to the command, after
22767 leading and trailing whitespace has been stripped.
22769 @var{from_tty} is a boolean argument. When true, this means that the
22770 command was entered by the user at the terminal; when false it means
22771 that the command came from elsewhere.
22773 If this method throws an exception, it is turned into a @value{GDBN}
22774 @code{error} call. Otherwise, the return value is ignored.
22776 @findex gdb.string_to_argv
22777 To break @var{argument} up into an argv-like string use
22778 @code{gdb.string_to_argv}. This function behaves identically to
22779 @value{GDBN}'s internal argument lexer @code{buildargv}.
22780 It is recommended to use this for consistency.
22781 Arguments are separated by spaces and may be quoted.
22785 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
22786 ['1', '2 "3', '4 "5', "6 '7"]
22791 @cindex completion of Python commands
22792 @defun Command.complete (text, word)
22793 This method is called by @value{GDBN} when the user attempts
22794 completion on this command. All forms of completion are handled by
22795 this method, that is, the @key{TAB} and @key{M-?} key bindings
22796 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
22799 The arguments @var{text} and @var{word} are both strings. @var{text}
22800 holds the complete command line up to the cursor's location.
22801 @var{word} holds the last word of the command line; this is computed
22802 using a word-breaking heuristic.
22804 The @code{complete} method can return several values:
22807 If the return value is a sequence, the contents of the sequence are
22808 used as the completions. It is up to @code{complete} to ensure that the
22809 contents actually do complete the word. A zero-length sequence is
22810 allowed, it means that there were no completions available. Only
22811 string elements of the sequence are used; other elements in the
22812 sequence are ignored.
22815 If the return value is one of the @samp{COMPLETE_} constants defined
22816 below, then the corresponding @value{GDBN}-internal completion
22817 function is invoked, and its result is used.
22820 All other results are treated as though there were no available
22825 When a new command is registered, it must be declared as a member of
22826 some general class of commands. This is used to classify top-level
22827 commands in the on-line help system; note that prefix commands are not
22828 listed under their own category but rather that of their top-level
22829 command. The available classifications are represented by constants
22830 defined in the @code{gdb} module:
22833 @findex COMMAND_NONE
22834 @findex gdb.COMMAND_NONE
22835 @item gdb.COMMAND_NONE
22836 The command does not belong to any particular class. A command in
22837 this category will not be displayed in any of the help categories.
22839 @findex COMMAND_RUNNING
22840 @findex gdb.COMMAND_RUNNING
22841 @item gdb.COMMAND_RUNNING
22842 The command is related to running the inferior. For example,
22843 @code{start}, @code{step}, and @code{continue} are in this category.
22844 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
22845 commands in this category.
22847 @findex COMMAND_DATA
22848 @findex gdb.COMMAND_DATA
22849 @item gdb.COMMAND_DATA
22850 The command is related to data or variables. For example,
22851 @code{call}, @code{find}, and @code{print} are in this category. Type
22852 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
22855 @findex COMMAND_STACK
22856 @findex gdb.COMMAND_STACK
22857 @item gdb.COMMAND_STACK
22858 The command has to do with manipulation of the stack. For example,
22859 @code{backtrace}, @code{frame}, and @code{return} are in this
22860 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
22861 list of commands in this category.
22863 @findex COMMAND_FILES
22864 @findex gdb.COMMAND_FILES
22865 @item gdb.COMMAND_FILES
22866 This class is used for file-related commands. For example,
22867 @code{file}, @code{list} and @code{section} are in this category.
22868 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
22869 commands in this category.
22871 @findex COMMAND_SUPPORT
22872 @findex gdb.COMMAND_SUPPORT
22873 @item gdb.COMMAND_SUPPORT
22874 This should be used for ``support facilities'', generally meaning
22875 things that are useful to the user when interacting with @value{GDBN},
22876 but not related to the state of the inferior. For example,
22877 @code{help}, @code{make}, and @code{shell} are in this category. Type
22878 @kbd{help support} at the @value{GDBN} prompt to see a list of
22879 commands in this category.
22881 @findex COMMAND_STATUS
22882 @findex gdb.COMMAND_STATUS
22883 @item gdb.COMMAND_STATUS
22884 The command is an @samp{info}-related command, that is, related to the
22885 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
22886 and @code{show} are in this category. Type @kbd{help status} at the
22887 @value{GDBN} prompt to see a list of commands in this category.
22889 @findex COMMAND_BREAKPOINTS
22890 @findex gdb.COMMAND_BREAKPOINTS
22891 @item gdb.COMMAND_BREAKPOINTS
22892 The command has to do with breakpoints. For example, @code{break},
22893 @code{clear}, and @code{delete} are in this category. Type @kbd{help
22894 breakpoints} at the @value{GDBN} prompt to see a list of commands in
22897 @findex COMMAND_TRACEPOINTS
22898 @findex gdb.COMMAND_TRACEPOINTS
22899 @item gdb.COMMAND_TRACEPOINTS
22900 The command has to do with tracepoints. For example, @code{trace},
22901 @code{actions}, and @code{tfind} are in this category. Type
22902 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
22903 commands in this category.
22905 @findex COMMAND_OBSCURE
22906 @findex gdb.COMMAND_OBSCURE
22907 @item gdb.COMMAND_OBSCURE
22908 The command is only used in unusual circumstances, or is not of
22909 general interest to users. For example, @code{checkpoint},
22910 @code{fork}, and @code{stop} are in this category. Type @kbd{help
22911 obscure} at the @value{GDBN} prompt to see a list of commands in this
22914 @findex COMMAND_MAINTENANCE
22915 @findex gdb.COMMAND_MAINTENANCE
22916 @item gdb.COMMAND_MAINTENANCE
22917 The command is only useful to @value{GDBN} maintainers. The
22918 @code{maintenance} and @code{flushregs} commands are in this category.
22919 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
22920 commands in this category.
22923 A new command can use a predefined completion function, either by
22924 specifying it via an argument at initialization, or by returning it
22925 from the @code{complete} method. These predefined completion
22926 constants are all defined in the @code{gdb} module:
22929 @findex COMPLETE_NONE
22930 @findex gdb.COMPLETE_NONE
22931 @item gdb.COMPLETE_NONE
22932 This constant means that no completion should be done.
22934 @findex COMPLETE_FILENAME
22935 @findex gdb.COMPLETE_FILENAME
22936 @item gdb.COMPLETE_FILENAME
22937 This constant means that filename completion should be performed.
22939 @findex COMPLETE_LOCATION
22940 @findex gdb.COMPLETE_LOCATION
22941 @item gdb.COMPLETE_LOCATION
22942 This constant means that location completion should be done.
22943 @xref{Specify Location}.
22945 @findex COMPLETE_COMMAND
22946 @findex gdb.COMPLETE_COMMAND
22947 @item gdb.COMPLETE_COMMAND
22948 This constant means that completion should examine @value{GDBN}
22951 @findex COMPLETE_SYMBOL
22952 @findex gdb.COMPLETE_SYMBOL
22953 @item gdb.COMPLETE_SYMBOL
22954 This constant means that completion should be done using symbol names
22958 The following code snippet shows how a trivial CLI command can be
22959 implemented in Python:
22962 class HelloWorld (gdb.Command):
22963 """Greet the whole world."""
22965 def __init__ (self):
22966 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
22968 def invoke (self, arg, from_tty):
22969 print "Hello, World!"
22974 The last line instantiates the class, and is necessary to trigger the
22975 registration of the command with @value{GDBN}. Depending on how the
22976 Python code is read into @value{GDBN}, you may need to import the
22977 @code{gdb} module explicitly.
22979 @node Parameters In Python
22980 @subsubsection Parameters In Python
22982 @cindex parameters in python
22983 @cindex python parameters
22984 @tindex gdb.Parameter
22986 You can implement new @value{GDBN} parameters using Python. A new
22987 parameter is implemented as an instance of the @code{gdb.Parameter}
22990 Parameters are exposed to the user via the @code{set} and
22991 @code{show} commands. @xref{Help}.
22993 There are many parameters that already exist and can be set in
22994 @value{GDBN}. Two examples are: @code{set follow fork} and
22995 @code{set charset}. Setting these parameters influences certain
22996 behavior in @value{GDBN}. Similarly, you can define parameters that
22997 can be used to influence behavior in custom Python scripts and commands.
22999 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
23000 The object initializer for @code{Parameter} registers the new
23001 parameter with @value{GDBN}. This initializer is normally invoked
23002 from the subclass' own @code{__init__} method.
23004 @var{name} is the name of the new parameter. If @var{name} consists
23005 of multiple words, then the initial words are looked for as prefix
23006 parameters. An example of this can be illustrated with the
23007 @code{set print} set of parameters. If @var{name} is
23008 @code{print foo}, then @code{print} will be searched as the prefix
23009 parameter. In this case the parameter can subsequently be accessed in
23010 @value{GDBN} as @code{set print foo}.
23012 If @var{name} consists of multiple words, and no prefix parameter group
23013 can be found, an exception is raised.
23015 @var{command-class} should be one of the @samp{COMMAND_} constants
23016 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
23017 categorize the new parameter in the help system.
23019 @var{parameter-class} should be one of the @samp{PARAM_} constants
23020 defined below. This argument tells @value{GDBN} the type of the new
23021 parameter; this information is used for input validation and
23024 If @var{parameter-class} is @code{PARAM_ENUM}, then
23025 @var{enum-sequence} must be a sequence of strings. These strings
23026 represent the possible values for the parameter.
23028 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
23029 of a fourth argument will cause an exception to be thrown.
23031 The help text for the new parameter is taken from the Python
23032 documentation string for the parameter's class, if there is one. If
23033 there is no documentation string, a default value is used.
23036 @defvar Parameter.set_doc
23037 If this attribute exists, and is a string, then its value is used as
23038 the help text for this parameter's @code{set} command. The value is
23039 examined when @code{Parameter.__init__} is invoked; subsequent changes
23043 @defvar Parameter.show_doc
23044 If this attribute exists, and is a string, then its value is used as
23045 the help text for this parameter's @code{show} command. The value is
23046 examined when @code{Parameter.__init__} is invoked; subsequent changes
23050 @defvar Parameter.value
23051 The @code{value} attribute holds the underlying value of the
23052 parameter. It can be read and assigned to just as any other
23053 attribute. @value{GDBN} does validation when assignments are made.
23056 There are two methods that should be implemented in any
23057 @code{Parameter} class. These are:
23059 @defun Parameter.get_set_string (self)
23060 @value{GDBN} will call this method when a @var{parameter}'s value has
23061 been changed via the @code{set} API (for example, @kbd{set foo off}).
23062 The @code{value} attribute has already been populated with the new
23063 value and may be used in output. This method must return a string.
23066 @defun Parameter.get_show_string (self, svalue)
23067 @value{GDBN} will call this method when a @var{parameter}'s
23068 @code{show} API has been invoked (for example, @kbd{show foo}). The
23069 argument @code{svalue} receives the string representation of the
23070 current value. This method must return a string.
23073 When a new parameter is defined, its type must be specified. The
23074 available types are represented by constants defined in the @code{gdb}
23078 @findex PARAM_BOOLEAN
23079 @findex gdb.PARAM_BOOLEAN
23080 @item gdb.PARAM_BOOLEAN
23081 The value is a plain boolean. The Python boolean values, @code{True}
23082 and @code{False} are the only valid values.
23084 @findex PARAM_AUTO_BOOLEAN
23085 @findex gdb.PARAM_AUTO_BOOLEAN
23086 @item gdb.PARAM_AUTO_BOOLEAN
23087 The value has three possible states: true, false, and @samp{auto}. In
23088 Python, true and false are represented using boolean constants, and
23089 @samp{auto} is represented using @code{None}.
23091 @findex PARAM_UINTEGER
23092 @findex gdb.PARAM_UINTEGER
23093 @item gdb.PARAM_UINTEGER
23094 The value is an unsigned integer. The value of 0 should be
23095 interpreted to mean ``unlimited''.
23097 @findex PARAM_INTEGER
23098 @findex gdb.PARAM_INTEGER
23099 @item gdb.PARAM_INTEGER
23100 The value is a signed integer. The value of 0 should be interpreted
23101 to mean ``unlimited''.
23103 @findex PARAM_STRING
23104 @findex gdb.PARAM_STRING
23105 @item gdb.PARAM_STRING
23106 The value is a string. When the user modifies the string, any escape
23107 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
23108 translated into corresponding characters and encoded into the current
23111 @findex PARAM_STRING_NOESCAPE
23112 @findex gdb.PARAM_STRING_NOESCAPE
23113 @item gdb.PARAM_STRING_NOESCAPE
23114 The value is a string. When the user modifies the string, escapes are
23115 passed through untranslated.
23117 @findex PARAM_OPTIONAL_FILENAME
23118 @findex gdb.PARAM_OPTIONAL_FILENAME
23119 @item gdb.PARAM_OPTIONAL_FILENAME
23120 The value is a either a filename (a string), or @code{None}.
23122 @findex PARAM_FILENAME
23123 @findex gdb.PARAM_FILENAME
23124 @item gdb.PARAM_FILENAME
23125 The value is a filename. This is just like
23126 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
23128 @findex PARAM_ZINTEGER
23129 @findex gdb.PARAM_ZINTEGER
23130 @item gdb.PARAM_ZINTEGER
23131 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
23132 is interpreted as itself.
23135 @findex gdb.PARAM_ENUM
23136 @item gdb.PARAM_ENUM
23137 The value is a string, which must be one of a collection string
23138 constants provided when the parameter is created.
23141 @node Functions In Python
23142 @subsubsection Writing new convenience functions
23144 @cindex writing convenience functions
23145 @cindex convenience functions in python
23146 @cindex python convenience functions
23147 @tindex gdb.Function
23149 You can implement new convenience functions (@pxref{Convenience Vars})
23150 in Python. A convenience function is an instance of a subclass of the
23151 class @code{gdb.Function}.
23153 @defun Function.__init__ (name)
23154 The initializer for @code{Function} registers the new function with
23155 @value{GDBN}. The argument @var{name} is the name of the function,
23156 a string. The function will be visible to the user as a convenience
23157 variable of type @code{internal function}, whose name is the same as
23158 the given @var{name}.
23160 The documentation for the new function is taken from the documentation
23161 string for the new class.
23164 @defun Function.invoke (@var{*args})
23165 When a convenience function is evaluated, its arguments are converted
23166 to instances of @code{gdb.Value}, and then the function's
23167 @code{invoke} method is called. Note that @value{GDBN} does not
23168 predetermine the arity of convenience functions. Instead, all
23169 available arguments are passed to @code{invoke}, following the
23170 standard Python calling convention. In particular, a convenience
23171 function can have default values for parameters without ill effect.
23173 The return value of this method is used as its value in the enclosing
23174 expression. If an ordinary Python value is returned, it is converted
23175 to a @code{gdb.Value} following the usual rules.
23178 The following code snippet shows how a trivial convenience function can
23179 be implemented in Python:
23182 class Greet (gdb.Function):
23183 """Return string to greet someone.
23184 Takes a name as argument."""
23186 def __init__ (self):
23187 super (Greet, self).__init__ ("greet")
23189 def invoke (self, name):
23190 return "Hello, %s!" % name.string ()
23195 The last line instantiates the class, and is necessary to trigger the
23196 registration of the function with @value{GDBN}. Depending on how the
23197 Python code is read into @value{GDBN}, you may need to import the
23198 @code{gdb} module explicitly.
23200 @node Progspaces In Python
23201 @subsubsection Program Spaces In Python
23203 @cindex progspaces in python
23204 @tindex gdb.Progspace
23206 A program space, or @dfn{progspace}, represents a symbolic view
23207 of an address space.
23208 It consists of all of the objfiles of the program.
23209 @xref{Objfiles In Python}.
23210 @xref{Inferiors and Programs, program spaces}, for more details
23211 about program spaces.
23213 The following progspace-related functions are available in the
23216 @findex gdb.current_progspace
23217 @defun gdb.current_progspace ()
23218 This function returns the program space of the currently selected inferior.
23219 @xref{Inferiors and Programs}.
23222 @findex gdb.progspaces
23223 @defun gdb.progspaces ()
23224 Return a sequence of all the progspaces currently known to @value{GDBN}.
23227 Each progspace is represented by an instance of the @code{gdb.Progspace}
23230 @defvar Progspace.filename
23231 The file name of the progspace as a string.
23234 @defvar Progspace.pretty_printers
23235 The @code{pretty_printers} attribute is a list of functions. It is
23236 used to look up pretty-printers. A @code{Value} is passed to each
23237 function in order; if the function returns @code{None}, then the
23238 search continues. Otherwise, the return value should be an object
23239 which is used to format the value. @xref{Pretty Printing API}, for more
23243 @node Objfiles In Python
23244 @subsubsection Objfiles In Python
23246 @cindex objfiles in python
23247 @tindex gdb.Objfile
23249 @value{GDBN} loads symbols for an inferior from various
23250 symbol-containing files (@pxref{Files}). These include the primary
23251 executable file, any shared libraries used by the inferior, and any
23252 separate debug info files (@pxref{Separate Debug Files}).
23253 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
23255 The following objfile-related functions are available in the
23258 @findex gdb.current_objfile
23259 @defun gdb.current_objfile ()
23260 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
23261 sets the ``current objfile'' to the corresponding objfile. This
23262 function returns the current objfile. If there is no current objfile,
23263 this function returns @code{None}.
23266 @findex gdb.objfiles
23267 @defun gdb.objfiles ()
23268 Return a sequence of all the objfiles current known to @value{GDBN}.
23269 @xref{Objfiles In Python}.
23272 Each objfile is represented by an instance of the @code{gdb.Objfile}
23275 @defvar Objfile.filename
23276 The file name of the objfile as a string.
23279 @defvar Objfile.pretty_printers
23280 The @code{pretty_printers} attribute is a list of functions. It is
23281 used to look up pretty-printers. A @code{Value} is passed to each
23282 function in order; if the function returns @code{None}, then the
23283 search continues. Otherwise, the return value should be an object
23284 which is used to format the value. @xref{Pretty Printing API}, for more
23288 A @code{gdb.Objfile} object has the following methods:
23290 @defun Objfile.is_valid ()
23291 Returns @code{True} if the @code{gdb.Objfile} object is valid,
23292 @code{False} if not. A @code{gdb.Objfile} object can become invalid
23293 if the object file it refers to is not loaded in @value{GDBN} any
23294 longer. All other @code{gdb.Objfile} methods will throw an exception
23295 if it is invalid at the time the method is called.
23298 @node Frames In Python
23299 @subsubsection Accessing inferior stack frames from Python.
23301 @cindex frames in python
23302 When the debugged program stops, @value{GDBN} is able to analyze its call
23303 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
23304 represents a frame in the stack. A @code{gdb.Frame} object is only valid
23305 while its corresponding frame exists in the inferior's stack. If you try
23306 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
23307 exception (@pxref{Exception Handling}).
23309 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
23313 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
23317 The following frame-related functions are available in the @code{gdb} module:
23319 @findex gdb.selected_frame
23320 @defun gdb.selected_frame ()
23321 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
23324 @findex gdb.newest_frame
23325 @defun gdb.newest_frame ()
23326 Return the newest frame object for the selected thread.
23329 @defun gdb.frame_stop_reason_string (reason)
23330 Return a string explaining the reason why @value{GDBN} stopped unwinding
23331 frames, as expressed by the given @var{reason} code (an integer, see the
23332 @code{unwind_stop_reason} method further down in this section).
23335 A @code{gdb.Frame} object has the following methods:
23338 @defun Frame.is_valid ()
23339 Returns true if the @code{gdb.Frame} object is valid, false if not.
23340 A frame object can become invalid if the frame it refers to doesn't
23341 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
23342 an exception if it is invalid at the time the method is called.
23345 @defun Frame.name ()
23346 Returns the function name of the frame, or @code{None} if it can't be
23350 @defun Frame.type ()
23351 Returns the type of the frame. The value can be one of:
23353 @item gdb.NORMAL_FRAME
23354 An ordinary stack frame.
23356 @item gdb.DUMMY_FRAME
23357 A fake stack frame that was created by @value{GDBN} when performing an
23358 inferior function call.
23360 @item gdb.INLINE_FRAME
23361 A frame representing an inlined function. The function was inlined
23362 into a @code{gdb.NORMAL_FRAME} that is older than this one.
23364 @item gdb.TAILCALL_FRAME
23365 A frame representing a tail call. @xref{Tail Call Frames}.
23367 @item gdb.SIGTRAMP_FRAME
23368 A signal trampoline frame. This is the frame created by the OS when
23369 it calls into a signal handler.
23371 @item gdb.ARCH_FRAME
23372 A fake stack frame representing a cross-architecture call.
23374 @item gdb.SENTINEL_FRAME
23375 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
23380 @defun Frame.unwind_stop_reason ()
23381 Return an integer representing the reason why it's not possible to find
23382 more frames toward the outermost frame. Use
23383 @code{gdb.frame_stop_reason_string} to convert the value returned by this
23384 function to a string.
23388 Returns the frame's resume address.
23391 @defun Frame.block ()
23392 Return the frame's code block. @xref{Blocks In Python}.
23395 @defun Frame.function ()
23396 Return the symbol for the function corresponding to this frame.
23397 @xref{Symbols In Python}.
23400 @defun Frame.older ()
23401 Return the frame that called this frame.
23404 @defun Frame.newer ()
23405 Return the frame called by this frame.
23408 @defun Frame.find_sal ()
23409 Return the frame's symtab and line object.
23410 @xref{Symbol Tables In Python}.
23413 @defun Frame.read_var (variable @r{[}, block@r{]})
23414 Return the value of @var{variable} in this frame. If the optional
23415 argument @var{block} is provided, search for the variable from that
23416 block; otherwise start at the frame's current block (which is
23417 determined by the frame's current program counter). @var{variable}
23418 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
23419 @code{gdb.Block} object.
23422 @defun Frame.select ()
23423 Set this frame to be the selected frame. @xref{Stack, ,Examining the
23428 @node Blocks In Python
23429 @subsubsection Accessing frame blocks from Python.
23431 @cindex blocks in python
23434 Within each frame, @value{GDBN} maintains information on each block
23435 stored in that frame. These blocks are organized hierarchically, and
23436 are represented individually in Python as a @code{gdb.Block}.
23437 Please see @ref{Frames In Python}, for a more in-depth discussion on
23438 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
23439 detailed technical information on @value{GDBN}'s book-keeping of the
23442 The following block-related functions are available in the @code{gdb}
23445 @findex gdb.block_for_pc
23446 @defun gdb.block_for_pc (pc)
23447 Return the @code{gdb.Block} containing the given @var{pc} value. If the
23448 block cannot be found for the @var{pc} value specified, the function
23449 will return @code{None}.
23452 A @code{gdb.Block} object has the following methods:
23455 @defun Block.is_valid ()
23456 Returns @code{True} if the @code{gdb.Block} object is valid,
23457 @code{False} if not. A block object can become invalid if the block it
23458 refers to doesn't exist anymore in the inferior. All other
23459 @code{gdb.Block} methods will throw an exception if it is invalid at
23460 the time the method is called. This method is also made available to
23461 the Python iterator object that @code{gdb.Block} provides in an iteration
23462 context and via the Python @code{iter} built-in function.
23466 A @code{gdb.Block} object has the following attributes:
23469 @defvar Block.start
23470 The start address of the block. This attribute is not writable.
23474 The end address of the block. This attribute is not writable.
23477 @defvar Block.function
23478 The name of the block represented as a @code{gdb.Symbol}. If the
23479 block is not named, then this attribute holds @code{None}. This
23480 attribute is not writable.
23483 @defvar Block.superblock
23484 The block containing this block. If this parent block does not exist,
23485 this attribute holds @code{None}. This attribute is not writable.
23489 @node Symbols In Python
23490 @subsubsection Python representation of Symbols.
23492 @cindex symbols in python
23495 @value{GDBN} represents every variable, function and type as an
23496 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
23497 Similarly, Python represents these symbols in @value{GDBN} with the
23498 @code{gdb.Symbol} object.
23500 The following symbol-related functions are available in the @code{gdb}
23503 @findex gdb.lookup_symbol
23504 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
23505 This function searches for a symbol by name. The search scope can be
23506 restricted to the parameters defined in the optional domain and block
23509 @var{name} is the name of the symbol. It must be a string. The
23510 optional @var{block} argument restricts the search to symbols visible
23511 in that @var{block}. The @var{block} argument must be a
23512 @code{gdb.Block} object. If omitted, the block for the current frame
23513 is used. The optional @var{domain} argument restricts
23514 the search to the domain type. The @var{domain} argument must be a
23515 domain constant defined in the @code{gdb} module and described later
23518 The result is a tuple of two elements.
23519 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
23521 If the symbol is found, the second element is @code{True} if the symbol
23522 is a field of a method's object (e.g., @code{this} in C@t{++}),
23523 otherwise it is @code{False}.
23524 If the symbol is not found, the second element is @code{False}.
23527 @findex gdb.lookup_global_symbol
23528 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
23529 This function searches for a global symbol by name.
23530 The search scope can be restricted to by the domain argument.
23532 @var{name} is the name of the symbol. It must be a string.
23533 The optional @var{domain} argument restricts the search to the domain type.
23534 The @var{domain} argument must be a domain constant defined in the @code{gdb}
23535 module and described later in this chapter.
23537 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
23541 A @code{gdb.Symbol} object has the following attributes:
23544 @defvar Symbol.type
23545 The type of the symbol or @code{None} if no type is recorded.
23546 This attribute is represented as a @code{gdb.Type} object.
23547 @xref{Types In Python}. This attribute is not writable.
23550 @defvar Symbol.symtab
23551 The symbol table in which the symbol appears. This attribute is
23552 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
23553 Python}. This attribute is not writable.
23556 @defvar Symbol.name
23557 The name of the symbol as a string. This attribute is not writable.
23560 @defvar Symbol.linkage_name
23561 The name of the symbol, as used by the linker (i.e., may be mangled).
23562 This attribute is not writable.
23565 @defvar Symbol.print_name
23566 The name of the symbol in a form suitable for output. This is either
23567 @code{name} or @code{linkage_name}, depending on whether the user
23568 asked @value{GDBN} to display demangled or mangled names.
23571 @defvar Symbol.addr_class
23572 The address class of the symbol. This classifies how to find the value
23573 of a symbol. Each address class is a constant defined in the
23574 @code{gdb} module and described later in this chapter.
23577 @defvar Symbol.is_argument
23578 @code{True} if the symbol is an argument of a function.
23581 @defvar Symbol.is_constant
23582 @code{True} if the symbol is a constant.
23585 @defvar Symbol.is_function
23586 @code{True} if the symbol is a function or a method.
23589 @defvar Symbol.is_variable
23590 @code{True} if the symbol is a variable.
23594 A @code{gdb.Symbol} object has the following methods:
23597 @defun Symbol.is_valid ()
23598 Returns @code{True} if the @code{gdb.Symbol} object is valid,
23599 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
23600 the symbol it refers to does not exist in @value{GDBN} any longer.
23601 All other @code{gdb.Symbol} methods will throw an exception if it is
23602 invalid at the time the method is called.
23606 The available domain categories in @code{gdb.Symbol} are represented
23607 as constants in the @code{gdb} module:
23610 @findex SYMBOL_UNDEF_DOMAIN
23611 @findex gdb.SYMBOL_UNDEF_DOMAIN
23612 @item gdb.SYMBOL_UNDEF_DOMAIN
23613 This is used when a domain has not been discovered or none of the
23614 following domains apply. This usually indicates an error either
23615 in the symbol information or in @value{GDBN}'s handling of symbols.
23616 @findex SYMBOL_VAR_DOMAIN
23617 @findex gdb.SYMBOL_VAR_DOMAIN
23618 @item gdb.SYMBOL_VAR_DOMAIN
23619 This domain contains variables, function names, typedef names and enum
23621 @findex SYMBOL_STRUCT_DOMAIN
23622 @findex gdb.SYMBOL_STRUCT_DOMAIN
23623 @item gdb.SYMBOL_STRUCT_DOMAIN
23624 This domain holds struct, union and enum type names.
23625 @findex SYMBOL_LABEL_DOMAIN
23626 @findex gdb.SYMBOL_LABEL_DOMAIN
23627 @item gdb.SYMBOL_LABEL_DOMAIN
23628 This domain contains names of labels (for gotos).
23629 @findex SYMBOL_VARIABLES_DOMAIN
23630 @findex gdb.SYMBOL_VARIABLES_DOMAIN
23631 @item gdb.SYMBOL_VARIABLES_DOMAIN
23632 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
23633 contains everything minus functions and types.
23634 @findex SYMBOL_FUNCTIONS_DOMAIN
23635 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
23636 @item gdb.SYMBOL_FUNCTION_DOMAIN
23637 This domain contains all functions.
23638 @findex SYMBOL_TYPES_DOMAIN
23639 @findex gdb.SYMBOL_TYPES_DOMAIN
23640 @item gdb.SYMBOL_TYPES_DOMAIN
23641 This domain contains all types.
23644 The available address class categories in @code{gdb.Symbol} are represented
23645 as constants in the @code{gdb} module:
23648 @findex SYMBOL_LOC_UNDEF
23649 @findex gdb.SYMBOL_LOC_UNDEF
23650 @item gdb.SYMBOL_LOC_UNDEF
23651 If this is returned by address class, it indicates an error either in
23652 the symbol information or in @value{GDBN}'s handling of symbols.
23653 @findex SYMBOL_LOC_CONST
23654 @findex gdb.SYMBOL_LOC_CONST
23655 @item gdb.SYMBOL_LOC_CONST
23656 Value is constant int.
23657 @findex SYMBOL_LOC_STATIC
23658 @findex gdb.SYMBOL_LOC_STATIC
23659 @item gdb.SYMBOL_LOC_STATIC
23660 Value is at a fixed address.
23661 @findex SYMBOL_LOC_REGISTER
23662 @findex gdb.SYMBOL_LOC_REGISTER
23663 @item gdb.SYMBOL_LOC_REGISTER
23664 Value is in a register.
23665 @findex SYMBOL_LOC_ARG
23666 @findex gdb.SYMBOL_LOC_ARG
23667 @item gdb.SYMBOL_LOC_ARG
23668 Value is an argument. This value is at the offset stored within the
23669 symbol inside the frame's argument list.
23670 @findex SYMBOL_LOC_REF_ARG
23671 @findex gdb.SYMBOL_LOC_REF_ARG
23672 @item gdb.SYMBOL_LOC_REF_ARG
23673 Value address is stored in the frame's argument list. Just like
23674 @code{LOC_ARG} except that the value's address is stored at the
23675 offset, not the value itself.
23676 @findex SYMBOL_LOC_REGPARM_ADDR
23677 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
23678 @item gdb.SYMBOL_LOC_REGPARM_ADDR
23679 Value is a specified register. Just like @code{LOC_REGISTER} except
23680 the register holds the address of the argument instead of the argument
23682 @findex SYMBOL_LOC_LOCAL
23683 @findex gdb.SYMBOL_LOC_LOCAL
23684 @item gdb.SYMBOL_LOC_LOCAL
23685 Value is a local variable.
23686 @findex SYMBOL_LOC_TYPEDEF
23687 @findex gdb.SYMBOL_LOC_TYPEDEF
23688 @item gdb.SYMBOL_LOC_TYPEDEF
23689 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
23691 @findex SYMBOL_LOC_BLOCK
23692 @findex gdb.SYMBOL_LOC_BLOCK
23693 @item gdb.SYMBOL_LOC_BLOCK
23695 @findex SYMBOL_LOC_CONST_BYTES
23696 @findex gdb.SYMBOL_LOC_CONST_BYTES
23697 @item gdb.SYMBOL_LOC_CONST_BYTES
23698 Value is a byte-sequence.
23699 @findex SYMBOL_LOC_UNRESOLVED
23700 @findex gdb.SYMBOL_LOC_UNRESOLVED
23701 @item gdb.SYMBOL_LOC_UNRESOLVED
23702 Value is at a fixed address, but the address of the variable has to be
23703 determined from the minimal symbol table whenever the variable is
23705 @findex SYMBOL_LOC_OPTIMIZED_OUT
23706 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
23707 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
23708 The value does not actually exist in the program.
23709 @findex SYMBOL_LOC_COMPUTED
23710 @findex gdb.SYMBOL_LOC_COMPUTED
23711 @item gdb.SYMBOL_LOC_COMPUTED
23712 The value's address is a computed location.
23715 @node Symbol Tables In Python
23716 @subsubsection Symbol table representation in Python.
23718 @cindex symbol tables in python
23720 @tindex gdb.Symtab_and_line
23722 Access to symbol table data maintained by @value{GDBN} on the inferior
23723 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
23724 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
23725 from the @code{find_sal} method in @code{gdb.Frame} object.
23726 @xref{Frames In Python}.
23728 For more information on @value{GDBN}'s symbol table management, see
23729 @ref{Symbols, ,Examining the Symbol Table}, for more information.
23731 A @code{gdb.Symtab_and_line} object has the following attributes:
23734 @defvar Symtab_and_line.symtab
23735 The symbol table object (@code{gdb.Symtab}) for this frame.
23736 This attribute is not writable.
23739 @defvar Symtab_and_line.pc
23740 Indicates the current program counter address. This attribute is not
23744 @defvar Symtab_and_line.line
23745 Indicates the current line number for this object. This
23746 attribute is not writable.
23750 A @code{gdb.Symtab_and_line} object has the following methods:
23753 @defun Symtab_and_line.is_valid ()
23754 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
23755 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
23756 invalid if the Symbol table and line object it refers to does not
23757 exist in @value{GDBN} any longer. All other
23758 @code{gdb.Symtab_and_line} methods will throw an exception if it is
23759 invalid at the time the method is called.
23763 A @code{gdb.Symtab} object has the following attributes:
23766 @defvar Symtab.filename
23767 The symbol table's source filename. This attribute is not writable.
23770 @defvar Symtab.objfile
23771 The symbol table's backing object file. @xref{Objfiles In Python}.
23772 This attribute is not writable.
23776 A @code{gdb.Symtab} object has the following methods:
23779 @defun Symtab.is_valid ()
23780 Returns @code{True} if the @code{gdb.Symtab} object is valid,
23781 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
23782 the symbol table it refers to does not exist in @value{GDBN} any
23783 longer. All other @code{gdb.Symtab} methods will throw an exception
23784 if it is invalid at the time the method is called.
23787 @defun Symtab.fullname ()
23788 Return the symbol table's source absolute file name.
23792 @node Breakpoints In Python
23793 @subsubsection Manipulating breakpoints using Python
23795 @cindex breakpoints in python
23796 @tindex gdb.Breakpoint
23798 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
23801 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal@r{]]]})
23802 Create a new breakpoint. @var{spec} is a string naming the
23803 location of the breakpoint, or an expression that defines a
23804 watchpoint. The contents can be any location recognized by the
23805 @code{break} command, or in the case of a watchpoint, by the @code{watch}
23806 command. The optional @var{type} denotes the breakpoint to create
23807 from the types defined later in this chapter. This argument can be
23808 either: @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
23809 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal} argument
23810 allows the breakpoint to become invisible to the user. The breakpoint
23811 will neither be reported when created, nor will it be listed in the
23812 output from @code{info breakpoints} (but will be listed with the
23813 @code{maint info breakpoints} command). The optional @var{wp_class}
23814 argument defines the class of watchpoint to create, if @var{type} is
23815 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it is
23816 assumed to be a @code{gdb.WP_WRITE} class.
23819 @defun Breakpoint.stop (self)
23820 The @code{gdb.Breakpoint} class can be sub-classed and, in
23821 particular, you may choose to implement the @code{stop} method.
23822 If this method is defined as a sub-class of @code{gdb.Breakpoint},
23823 it will be called when the inferior reaches any location of a
23824 breakpoint which instantiates that sub-class. If the method returns
23825 @code{True}, the inferior will be stopped at the location of the
23826 breakpoint, otherwise the inferior will continue.
23828 If there are multiple breakpoints at the same location with a
23829 @code{stop} method, each one will be called regardless of the
23830 return status of the previous. This ensures that all @code{stop}
23831 methods have a chance to execute at that location. In this scenario
23832 if one of the methods returns @code{True} but the others return
23833 @code{False}, the inferior will still be stopped.
23835 You should not alter the execution state of the inferior (i.e.@:, step,
23836 next, etc.), alter the current frame context (i.e.@:, change the current
23837 active frame), or alter, add or delete any breakpoint. As a general
23838 rule, you should not alter any data within @value{GDBN} or the inferior
23841 Example @code{stop} implementation:
23844 class MyBreakpoint (gdb.Breakpoint):
23846 inf_val = gdb.parse_and_eval("foo")
23853 The available watchpoint types represented by constants are defined in the
23858 @findex gdb.WP_READ
23860 Read only watchpoint.
23863 @findex gdb.WP_WRITE
23865 Write only watchpoint.
23868 @findex gdb.WP_ACCESS
23869 @item gdb.WP_ACCESS
23870 Read/Write watchpoint.
23873 @defun Breakpoint.is_valid ()
23874 Return @code{True} if this @code{Breakpoint} object is valid,
23875 @code{False} otherwise. A @code{Breakpoint} object can become invalid
23876 if the user deletes the breakpoint. In this case, the object still
23877 exists, but the underlying breakpoint does not. In the cases of
23878 watchpoint scope, the watchpoint remains valid even if execution of the
23879 inferior leaves the scope of that watchpoint.
23882 @defun Breakpoint.delete
23883 Permanently deletes the @value{GDBN} breakpoint. This also
23884 invalidates the Python @code{Breakpoint} object. Any further access
23885 to this object's attributes or methods will raise an error.
23888 @defvar Breakpoint.enabled
23889 This attribute is @code{True} if the breakpoint is enabled, and
23890 @code{False} otherwise. This attribute is writable.
23893 @defvar Breakpoint.silent
23894 This attribute is @code{True} if the breakpoint is silent, and
23895 @code{False} otherwise. This attribute is writable.
23897 Note that a breakpoint can also be silent if it has commands and the
23898 first command is @code{silent}. This is not reported by the
23899 @code{silent} attribute.
23902 @defvar Breakpoint.thread
23903 If the breakpoint is thread-specific, this attribute holds the thread
23904 id. If the breakpoint is not thread-specific, this attribute is
23905 @code{None}. This attribute is writable.
23908 @defvar Breakpoint.task
23909 If the breakpoint is Ada task-specific, this attribute holds the Ada task
23910 id. If the breakpoint is not task-specific (or the underlying
23911 language is not Ada), this attribute is @code{None}. This attribute
23915 @defvar Breakpoint.ignore_count
23916 This attribute holds the ignore count for the breakpoint, an integer.
23917 This attribute is writable.
23920 @defvar Breakpoint.number
23921 This attribute holds the breakpoint's number --- the identifier used by
23922 the user to manipulate the breakpoint. This attribute is not writable.
23925 @defvar Breakpoint.type
23926 This attribute holds the breakpoint's type --- the identifier used to
23927 determine the actual breakpoint type or use-case. This attribute is not
23931 @defvar Breakpoint.visible
23932 This attribute tells whether the breakpoint is visible to the user
23933 when set, or when the @samp{info breakpoints} command is run. This
23934 attribute is not writable.
23937 The available types are represented by constants defined in the @code{gdb}
23941 @findex BP_BREAKPOINT
23942 @findex gdb.BP_BREAKPOINT
23943 @item gdb.BP_BREAKPOINT
23944 Normal code breakpoint.
23946 @findex BP_WATCHPOINT
23947 @findex gdb.BP_WATCHPOINT
23948 @item gdb.BP_WATCHPOINT
23949 Watchpoint breakpoint.
23951 @findex BP_HARDWARE_WATCHPOINT
23952 @findex gdb.BP_HARDWARE_WATCHPOINT
23953 @item gdb.BP_HARDWARE_WATCHPOINT
23954 Hardware assisted watchpoint.
23956 @findex BP_READ_WATCHPOINT
23957 @findex gdb.BP_READ_WATCHPOINT
23958 @item gdb.BP_READ_WATCHPOINT
23959 Hardware assisted read watchpoint.
23961 @findex BP_ACCESS_WATCHPOINT
23962 @findex gdb.BP_ACCESS_WATCHPOINT
23963 @item gdb.BP_ACCESS_WATCHPOINT
23964 Hardware assisted access watchpoint.
23967 @defvar Breakpoint.hit_count
23968 This attribute holds the hit count for the breakpoint, an integer.
23969 This attribute is writable, but currently it can only be set to zero.
23972 @defvar Breakpoint.location
23973 This attribute holds the location of the breakpoint, as specified by
23974 the user. It is a string. If the breakpoint does not have a location
23975 (that is, it is a watchpoint) the attribute's value is @code{None}. This
23976 attribute is not writable.
23979 @defvar Breakpoint.expression
23980 This attribute holds a breakpoint expression, as specified by
23981 the user. It is a string. If the breakpoint does not have an
23982 expression (the breakpoint is not a watchpoint) the attribute's value
23983 is @code{None}. This attribute is not writable.
23986 @defvar Breakpoint.condition
23987 This attribute holds the condition of the breakpoint, as specified by
23988 the user. It is a string. If there is no condition, this attribute's
23989 value is @code{None}. This attribute is writable.
23992 @defvar Breakpoint.commands
23993 This attribute holds the commands attached to the breakpoint. If
23994 there are commands, this attribute's value is a string holding all the
23995 commands, separated by newlines. If there are no commands, this
23996 attribute is @code{None}. This attribute is not writable.
23999 @node Lazy Strings In Python
24000 @subsubsection Python representation of lazy strings.
24002 @cindex lazy strings in python
24003 @tindex gdb.LazyString
24005 A @dfn{lazy string} is a string whose contents is not retrieved or
24006 encoded until it is needed.
24008 A @code{gdb.LazyString} is represented in @value{GDBN} as an
24009 @code{address} that points to a region of memory, an @code{encoding}
24010 that will be used to encode that region of memory, and a @code{length}
24011 to delimit the region of memory that represents the string. The
24012 difference between a @code{gdb.LazyString} and a string wrapped within
24013 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
24014 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
24015 retrieved and encoded during printing, while a @code{gdb.Value}
24016 wrapping a string is immediately retrieved and encoded on creation.
24018 A @code{gdb.LazyString} object has the following functions:
24020 @defun LazyString.value ()
24021 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
24022 will point to the string in memory, but will lose all the delayed
24023 retrieval, encoding and handling that @value{GDBN} applies to a
24024 @code{gdb.LazyString}.
24027 @defvar LazyString.address
24028 This attribute holds the address of the string. This attribute is not
24032 @defvar LazyString.length
24033 This attribute holds the length of the string in characters. If the
24034 length is -1, then the string will be fetched and encoded up to the
24035 first null of appropriate width. This attribute is not writable.
24038 @defvar LazyString.encoding
24039 This attribute holds the encoding that will be applied to the string
24040 when the string is printed by @value{GDBN}. If the encoding is not
24041 set, or contains an empty string, then @value{GDBN} will select the
24042 most appropriate encoding when the string is printed. This attribute
24046 @defvar LazyString.type
24047 This attribute holds the type that is represented by the lazy string's
24048 type. For a lazy string this will always be a pointer type. To
24049 resolve this to the lazy string's character type, use the type's
24050 @code{target} method. @xref{Types In Python}. This attribute is not
24055 @subsection Auto-loading
24056 @cindex auto-loading, Python
24058 When a new object file is read (for example, due to the @code{file}
24059 command, or because the inferior has loaded a shared library),
24060 @value{GDBN} will look for Python support scripts in several ways:
24061 @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section.
24064 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
24065 * .debug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
24066 * Which flavor to choose?::
24069 The auto-loading feature is useful for supplying application-specific
24070 debugging commands and scripts.
24072 Auto-loading can be enabled or disabled,
24073 and the list of auto-loaded scripts can be printed.
24076 @kindex set auto-load-scripts
24077 @item set auto-load-scripts [yes|no]
24078 Enable or disable the auto-loading of Python scripts.
24080 @kindex show auto-load-scripts
24081 @item show auto-load-scripts
24082 Show whether auto-loading of Python scripts is enabled or disabled.
24084 @kindex info auto-load-scripts
24085 @cindex print list of auto-loaded scripts
24086 @item info auto-load-scripts [@var{regexp}]
24087 Print the list of all scripts that @value{GDBN} auto-loaded.
24089 Also printed is the list of scripts that were mentioned in
24090 the @code{.debug_gdb_scripts} section and were not found
24091 (@pxref{.debug_gdb_scripts section}).
24092 This is useful because their names are not printed when @value{GDBN}
24093 tries to load them and fails. There may be many of them, and printing
24094 an error message for each one is problematic.
24096 If @var{regexp} is supplied only scripts with matching names are printed.
24101 (gdb) info auto-load-scripts
24103 Yes py-section-script.py
24104 full name: /tmp/py-section-script.py
24105 Missing my-foo-pretty-printers.py
24109 When reading an auto-loaded file, @value{GDBN} sets the
24110 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
24111 function (@pxref{Objfiles In Python}). This can be useful for
24112 registering objfile-specific pretty-printers.
24114 @node objfile-gdb.py file
24115 @subsubsection The @file{@var{objfile}-gdb.py} file
24116 @cindex @file{@var{objfile}-gdb.py}
24118 When a new object file is read, @value{GDBN} looks for
24119 a file named @file{@var{objfile}-gdb.py},
24120 where @var{objfile} is the object file's real name, formed by ensuring
24121 that the file name is absolute, following all symlinks, and resolving
24122 @code{.} and @code{..} components. If this file exists and is
24123 readable, @value{GDBN} will evaluate it as a Python script.
24125 If this file does not exist, and if the parameter
24126 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
24127 then @value{GDBN} will look for @var{real-name} in all of the
24128 directories mentioned in the value of @code{debug-file-directory}.
24130 Finally, if this file does not exist, then @value{GDBN} will look for
24131 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
24132 @var{data-directory} is @value{GDBN}'s data directory (available via
24133 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
24134 is the object file's real name, as described above.
24136 @value{GDBN} does not track which files it has already auto-loaded this way.
24137 @value{GDBN} will load the associated script every time the corresponding
24138 @var{objfile} is opened.
24139 So your @file{-gdb.py} file should be careful to avoid errors if it
24140 is evaluated more than once.
24142 @node .debug_gdb_scripts section
24143 @subsubsection The @code{.debug_gdb_scripts} section
24144 @cindex @code{.debug_gdb_scripts} section
24146 For systems using file formats like ELF and COFF,
24147 when @value{GDBN} loads a new object file
24148 it will look for a special section named @samp{.debug_gdb_scripts}.
24149 If this section exists, its contents is a list of names of scripts to load.
24151 @value{GDBN} will look for each specified script file first in the
24152 current directory and then along the source search path
24153 (@pxref{Source Path, ,Specifying Source Directories}),
24154 except that @file{$cdir} is not searched, since the compilation
24155 directory is not relevant to scripts.
24157 Entries can be placed in section @code{.debug_gdb_scripts} with,
24158 for example, this GCC macro:
24161 /* Note: The "MS" section flags are to remove duplicates. */
24162 #define DEFINE_GDB_SCRIPT(script_name) \
24164 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
24166 .asciz \"" script_name "\"\n\
24172 Then one can reference the macro in a header or source file like this:
24175 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
24178 The script name may include directories if desired.
24180 If the macro is put in a header, any application or library
24181 using this header will get a reference to the specified script.
24183 @node Which flavor to choose?
24184 @subsubsection Which flavor to choose?
24186 Given the multiple ways of auto-loading Python scripts, it might not always
24187 be clear which one to choose. This section provides some guidance.
24189 Benefits of the @file{-gdb.py} way:
24193 Can be used with file formats that don't support multiple sections.
24196 Ease of finding scripts for public libraries.
24198 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
24199 in the source search path.
24200 For publicly installed libraries, e.g., @file{libstdc++}, there typically
24201 isn't a source directory in which to find the script.
24204 Doesn't require source code additions.
24207 Benefits of the @code{.debug_gdb_scripts} way:
24211 Works with static linking.
24213 Scripts for libraries done the @file{-gdb.py} way require an objfile to
24214 trigger their loading. When an application is statically linked the only
24215 objfile available is the executable, and it is cumbersome to attach all the
24216 scripts from all the input libraries to the executable's @file{-gdb.py} script.
24219 Works with classes that are entirely inlined.
24221 Some classes can be entirely inlined, and thus there may not be an associated
24222 shared library to attach a @file{-gdb.py} script to.
24225 Scripts needn't be copied out of the source tree.
24227 In some circumstances, apps can be built out of large collections of internal
24228 libraries, and the build infrastructure necessary to install the
24229 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
24230 cumbersome. It may be easier to specify the scripts in the
24231 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
24232 top of the source tree to the source search path.
24235 @node Python modules
24236 @subsection Python modules
24237 @cindex python modules
24239 @value{GDBN} comes with several modules to assist writing Python code.
24242 * gdb.printing:: Building and registering pretty-printers.
24243 * gdb.types:: Utilities for working with types.
24244 * gdb.prompt:: Utilities for prompt value substitution.
24248 @subsubsection gdb.printing
24249 @cindex gdb.printing
24251 This module provides a collection of utilities for working with
24255 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
24256 This class specifies the API that makes @samp{info pretty-printer},
24257 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
24258 Pretty-printers should generally inherit from this class.
24260 @item SubPrettyPrinter (@var{name})
24261 For printers that handle multiple types, this class specifies the
24262 corresponding API for the subprinters.
24264 @item RegexpCollectionPrettyPrinter (@var{name})
24265 Utility class for handling multiple printers, all recognized via
24266 regular expressions.
24267 @xref{Writing a Pretty-Printer}, for an example.
24269 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
24270 Register @var{printer} with the pretty-printer list of @var{obj}.
24271 If @var{replace} is @code{True} then any existing copy of the printer
24272 is replaced. Otherwise a @code{RuntimeError} exception is raised
24273 if a printer with the same name already exists.
24277 @subsubsection gdb.types
24280 This module provides a collection of utilities for working with
24281 @code{gdb.Types} objects.
24284 @item get_basic_type (@var{type})
24285 Return @var{type} with const and volatile qualifiers stripped,
24286 and with typedefs and C@t{++} references converted to the underlying type.
24291 typedef const int const_int;
24293 const_int& foo_ref (foo);
24294 int main () @{ return 0; @}
24301 (gdb) python import gdb.types
24302 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
24303 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
24307 @item has_field (@var{type}, @var{field})
24308 Return @code{True} if @var{type}, assumed to be a type with fields
24309 (e.g., a structure or union), has field @var{field}.
24311 @item make_enum_dict (@var{enum_type})
24312 Return a Python @code{dictionary} type produced from @var{enum_type}.
24316 @subsubsection gdb.prompt
24319 This module provides a method for prompt value-substitution.
24322 @item substitute_prompt (@var{string})
24323 Return @var{string} with escape sequences substituted by values. Some
24324 escape sequences take arguments. You can specify arguments inside
24325 ``@{@}'' immediately following the escape sequence.
24327 The escape sequences you can pass to this function are:
24331 Substitute a backslash.
24333 Substitute an ESC character.
24335 Substitute the selected frame; an argument names a frame parameter.
24337 Substitute a newline.
24339 Substitute a parameter's value; the argument names the parameter.
24341 Substitute a carriage return.
24343 Substitute the selected thread; an argument names a thread parameter.
24345 Substitute the version of GDB.
24347 Substitute the current working directory.
24349 Begin a sequence of non-printing characters. These sequences are
24350 typically used with the ESC character, and are not counted in the string
24351 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
24352 blue-colored ``(gdb)'' prompt where the length is five.
24354 End a sequence of non-printing characters.
24360 substitute_prompt (``frame: \f,
24361 print arguments: \p@{print frame-arguments@}'')
24364 @exdent will return the string:
24367 "frame: main, print arguments: scalars"
24372 @chapter Command Interpreters
24373 @cindex command interpreters
24375 @value{GDBN} supports multiple command interpreters, and some command
24376 infrastructure to allow users or user interface writers to switch
24377 between interpreters or run commands in other interpreters.
24379 @value{GDBN} currently supports two command interpreters, the console
24380 interpreter (sometimes called the command-line interpreter or @sc{cli})
24381 and the machine interface interpreter (or @sc{gdb/mi}). This manual
24382 describes both of these interfaces in great detail.
24384 By default, @value{GDBN} will start with the console interpreter.
24385 However, the user may choose to start @value{GDBN} with another
24386 interpreter by specifying the @option{-i} or @option{--interpreter}
24387 startup options. Defined interpreters include:
24391 @cindex console interpreter
24392 The traditional console or command-line interpreter. This is the most often
24393 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
24394 @value{GDBN} will use this interpreter.
24397 @cindex mi interpreter
24398 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
24399 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
24400 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
24404 @cindex mi2 interpreter
24405 The current @sc{gdb/mi} interface.
24408 @cindex mi1 interpreter
24409 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
24413 @cindex invoke another interpreter
24414 The interpreter being used by @value{GDBN} may not be dynamically
24415 switched at runtime. Although possible, this could lead to a very
24416 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
24417 enters the command "interpreter-set console" in a console view,
24418 @value{GDBN} would switch to using the console interpreter, rendering
24419 the IDE inoperable!
24421 @kindex interpreter-exec
24422 Although you may only choose a single interpreter at startup, you may execute
24423 commands in any interpreter from the current interpreter using the appropriate
24424 command. If you are running the console interpreter, simply use the
24425 @code{interpreter-exec} command:
24428 interpreter-exec mi "-data-list-register-names"
24431 @sc{gdb/mi} has a similar command, although it is only available in versions of
24432 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
24435 @chapter @value{GDBN} Text User Interface
24437 @cindex Text User Interface
24440 * TUI Overview:: TUI overview
24441 * TUI Keys:: TUI key bindings
24442 * TUI Single Key Mode:: TUI single key mode
24443 * TUI Commands:: TUI-specific commands
24444 * TUI Configuration:: TUI configuration variables
24447 The @value{GDBN} Text User Interface (TUI) is a terminal
24448 interface which uses the @code{curses} library to show the source
24449 file, the assembly output, the program registers and @value{GDBN}
24450 commands in separate text windows. The TUI mode is supported only
24451 on platforms where a suitable version of the @code{curses} library
24454 @pindex @value{GDBTUI}
24455 The TUI mode is enabled by default when you invoke @value{GDBN} as
24456 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
24457 You can also switch in and out of TUI mode while @value{GDBN} runs by
24458 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
24459 @xref{TUI Keys, ,TUI Key Bindings}.
24462 @section TUI Overview
24464 In TUI mode, @value{GDBN} can display several text windows:
24468 This window is the @value{GDBN} command window with the @value{GDBN}
24469 prompt and the @value{GDBN} output. The @value{GDBN} input is still
24470 managed using readline.
24473 The source window shows the source file of the program. The current
24474 line and active breakpoints are displayed in this window.
24477 The assembly window shows the disassembly output of the program.
24480 This window shows the processor registers. Registers are highlighted
24481 when their values change.
24484 The source and assembly windows show the current program position
24485 by highlighting the current line and marking it with a @samp{>} marker.
24486 Breakpoints are indicated with two markers. The first marker
24487 indicates the breakpoint type:
24491 Breakpoint which was hit at least once.
24494 Breakpoint which was never hit.
24497 Hardware breakpoint which was hit at least once.
24500 Hardware breakpoint which was never hit.
24503 The second marker indicates whether the breakpoint is enabled or not:
24507 Breakpoint is enabled.
24510 Breakpoint is disabled.
24513 The source, assembly and register windows are updated when the current
24514 thread changes, when the frame changes, or when the program counter
24517 These windows are not all visible at the same time. The command
24518 window is always visible. The others can be arranged in several
24529 source and assembly,
24532 source and registers, or
24535 assembly and registers.
24538 A status line above the command window shows the following information:
24542 Indicates the current @value{GDBN} target.
24543 (@pxref{Targets, ,Specifying a Debugging Target}).
24546 Gives the current process or thread number.
24547 When no process is being debugged, this field is set to @code{No process}.
24550 Gives the current function name for the selected frame.
24551 The name is demangled if demangling is turned on (@pxref{Print Settings}).
24552 When there is no symbol corresponding to the current program counter,
24553 the string @code{??} is displayed.
24556 Indicates the current line number for the selected frame.
24557 When the current line number is not known, the string @code{??} is displayed.
24560 Indicates the current program counter address.
24564 @section TUI Key Bindings
24565 @cindex TUI key bindings
24567 The TUI installs several key bindings in the readline keymaps
24568 @ifset SYSTEM_READLINE
24569 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
24571 @ifclear SYSTEM_READLINE
24572 (@pxref{Command Line Editing}).
24574 The following key bindings are installed for both TUI mode and the
24575 @value{GDBN} standard mode.
24584 Enter or leave the TUI mode. When leaving the TUI mode,
24585 the curses window management stops and @value{GDBN} operates using
24586 its standard mode, writing on the terminal directly. When reentering
24587 the TUI mode, control is given back to the curses windows.
24588 The screen is then refreshed.
24592 Use a TUI layout with only one window. The layout will
24593 either be @samp{source} or @samp{assembly}. When the TUI mode
24594 is not active, it will switch to the TUI mode.
24596 Think of this key binding as the Emacs @kbd{C-x 1} binding.
24600 Use a TUI layout with at least two windows. When the current
24601 layout already has two windows, the next layout with two windows is used.
24602 When a new layout is chosen, one window will always be common to the
24603 previous layout and the new one.
24605 Think of it as the Emacs @kbd{C-x 2} binding.
24609 Change the active window. The TUI associates several key bindings
24610 (like scrolling and arrow keys) with the active window. This command
24611 gives the focus to the next TUI window.
24613 Think of it as the Emacs @kbd{C-x o} binding.
24617 Switch in and out of the TUI SingleKey mode that binds single
24618 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
24621 The following key bindings only work in the TUI mode:
24626 Scroll the active window one page up.
24630 Scroll the active window one page down.
24634 Scroll the active window one line up.
24638 Scroll the active window one line down.
24642 Scroll the active window one column left.
24646 Scroll the active window one column right.
24650 Refresh the screen.
24653 Because the arrow keys scroll the active window in the TUI mode, they
24654 are not available for their normal use by readline unless the command
24655 window has the focus. When another window is active, you must use
24656 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
24657 and @kbd{C-f} to control the command window.
24659 @node TUI Single Key Mode
24660 @section TUI Single Key Mode
24661 @cindex TUI single key mode
24663 The TUI also provides a @dfn{SingleKey} mode, which binds several
24664 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
24665 switch into this mode, where the following key bindings are used:
24668 @kindex c @r{(SingleKey TUI key)}
24672 @kindex d @r{(SingleKey TUI key)}
24676 @kindex f @r{(SingleKey TUI key)}
24680 @kindex n @r{(SingleKey TUI key)}
24684 @kindex q @r{(SingleKey TUI key)}
24686 exit the SingleKey mode.
24688 @kindex r @r{(SingleKey TUI key)}
24692 @kindex s @r{(SingleKey TUI key)}
24696 @kindex u @r{(SingleKey TUI key)}
24700 @kindex v @r{(SingleKey TUI key)}
24704 @kindex w @r{(SingleKey TUI key)}
24709 Other keys temporarily switch to the @value{GDBN} command prompt.
24710 The key that was pressed is inserted in the editing buffer so that
24711 it is possible to type most @value{GDBN} commands without interaction
24712 with the TUI SingleKey mode. Once the command is entered the TUI
24713 SingleKey mode is restored. The only way to permanently leave
24714 this mode is by typing @kbd{q} or @kbd{C-x s}.
24718 @section TUI-specific Commands
24719 @cindex TUI commands
24721 The TUI has specific commands to control the text windows.
24722 These commands are always available, even when @value{GDBN} is not in
24723 the TUI mode. When @value{GDBN} is in the standard mode, most
24724 of these commands will automatically switch to the TUI mode.
24726 Note that if @value{GDBN}'s @code{stdout} is not connected to a
24727 terminal, or @value{GDBN} has been started with the machine interface
24728 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
24729 these commands will fail with an error, because it would not be
24730 possible or desirable to enable curses window management.
24735 List and give the size of all displayed windows.
24739 Display the next layout.
24742 Display the previous layout.
24745 Display the source window only.
24748 Display the assembly window only.
24751 Display the source and assembly window.
24754 Display the register window together with the source or assembly window.
24758 Make the next window active for scrolling.
24761 Make the previous window active for scrolling.
24764 Make the source window active for scrolling.
24767 Make the assembly window active for scrolling.
24770 Make the register window active for scrolling.
24773 Make the command window active for scrolling.
24777 Refresh the screen. This is similar to typing @kbd{C-L}.
24779 @item tui reg float
24781 Show the floating point registers in the register window.
24783 @item tui reg general
24784 Show the general registers in the register window.
24787 Show the next register group. The list of register groups as well as
24788 their order is target specific. The predefined register groups are the
24789 following: @code{general}, @code{float}, @code{system}, @code{vector},
24790 @code{all}, @code{save}, @code{restore}.
24792 @item tui reg system
24793 Show the system registers in the register window.
24797 Update the source window and the current execution point.
24799 @item winheight @var{name} +@var{count}
24800 @itemx winheight @var{name} -@var{count}
24802 Change the height of the window @var{name} by @var{count}
24803 lines. Positive counts increase the height, while negative counts
24806 @item tabset @var{nchars}
24808 Set the width of tab stops to be @var{nchars} characters.
24811 @node TUI Configuration
24812 @section TUI Configuration Variables
24813 @cindex TUI configuration variables
24815 Several configuration variables control the appearance of TUI windows.
24818 @item set tui border-kind @var{kind}
24819 @kindex set tui border-kind
24820 Select the border appearance for the source, assembly and register windows.
24821 The possible values are the following:
24824 Use a space character to draw the border.
24827 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
24830 Use the Alternate Character Set to draw the border. The border is
24831 drawn using character line graphics if the terminal supports them.
24834 @item set tui border-mode @var{mode}
24835 @kindex set tui border-mode
24836 @itemx set tui active-border-mode @var{mode}
24837 @kindex set tui active-border-mode
24838 Select the display attributes for the borders of the inactive windows
24839 or the active window. The @var{mode} can be one of the following:
24842 Use normal attributes to display the border.
24848 Use reverse video mode.
24851 Use half bright mode.
24853 @item half-standout
24854 Use half bright and standout mode.
24857 Use extra bright or bold mode.
24859 @item bold-standout
24860 Use extra bright or bold and standout mode.
24865 @chapter Using @value{GDBN} under @sc{gnu} Emacs
24868 @cindex @sc{gnu} Emacs
24869 A special interface allows you to use @sc{gnu} Emacs to view (and
24870 edit) the source files for the program you are debugging with
24873 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
24874 executable file you want to debug as an argument. This command starts
24875 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
24876 created Emacs buffer.
24877 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
24879 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
24884 All ``terminal'' input and output goes through an Emacs buffer, called
24887 This applies both to @value{GDBN} commands and their output, and to the input
24888 and output done by the program you are debugging.
24890 This is useful because it means that you can copy the text of previous
24891 commands and input them again; you can even use parts of the output
24894 All the facilities of Emacs' Shell mode are available for interacting
24895 with your program. In particular, you can send signals the usual
24896 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
24900 @value{GDBN} displays source code through Emacs.
24902 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
24903 source file for that frame and puts an arrow (@samp{=>}) at the
24904 left margin of the current line. Emacs uses a separate buffer for
24905 source display, and splits the screen to show both your @value{GDBN} session
24908 Explicit @value{GDBN} @code{list} or search commands still produce output as
24909 usual, but you probably have no reason to use them from Emacs.
24912 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
24913 a graphical mode, enabled by default, which provides further buffers
24914 that can control the execution and describe the state of your program.
24915 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
24917 If you specify an absolute file name when prompted for the @kbd{M-x
24918 gdb} argument, then Emacs sets your current working directory to where
24919 your program resides. If you only specify the file name, then Emacs
24920 sets your current working directory to the directory associated
24921 with the previous buffer. In this case, @value{GDBN} may find your
24922 program by searching your environment's @code{PATH} variable, but on
24923 some operating systems it might not find the source. So, although the
24924 @value{GDBN} input and output session proceeds normally, the auxiliary
24925 buffer does not display the current source and line of execution.
24927 The initial working directory of @value{GDBN} is printed on the top
24928 line of the GUD buffer and this serves as a default for the commands
24929 that specify files for @value{GDBN} to operate on. @xref{Files,
24930 ,Commands to Specify Files}.
24932 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
24933 need to call @value{GDBN} by a different name (for example, if you
24934 keep several configurations around, with different names) you can
24935 customize the Emacs variable @code{gud-gdb-command-name} to run the
24938 In the GUD buffer, you can use these special Emacs commands in
24939 addition to the standard Shell mode commands:
24943 Describe the features of Emacs' GUD Mode.
24946 Execute to another source line, like the @value{GDBN} @code{step} command; also
24947 update the display window to show the current file and location.
24950 Execute to next source line in this function, skipping all function
24951 calls, like the @value{GDBN} @code{next} command. Then update the display window
24952 to show the current file and location.
24955 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
24956 display window accordingly.
24959 Execute until exit from the selected stack frame, like the @value{GDBN}
24960 @code{finish} command.
24963 Continue execution of your program, like the @value{GDBN} @code{continue}
24967 Go up the number of frames indicated by the numeric argument
24968 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
24969 like the @value{GDBN} @code{up} command.
24972 Go down the number of frames indicated by the numeric argument, like the
24973 @value{GDBN} @code{down} command.
24976 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
24977 tells @value{GDBN} to set a breakpoint on the source line point is on.
24979 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
24980 separate frame which shows a backtrace when the GUD buffer is current.
24981 Move point to any frame in the stack and type @key{RET} to make it
24982 become the current frame and display the associated source in the
24983 source buffer. Alternatively, click @kbd{Mouse-2} to make the
24984 selected frame become the current one. In graphical mode, the
24985 speedbar displays watch expressions.
24987 If you accidentally delete the source-display buffer, an easy way to get
24988 it back is to type the command @code{f} in the @value{GDBN} buffer, to
24989 request a frame display; when you run under Emacs, this recreates
24990 the source buffer if necessary to show you the context of the current
24993 The source files displayed in Emacs are in ordinary Emacs buffers
24994 which are visiting the source files in the usual way. You can edit
24995 the files with these buffers if you wish; but keep in mind that @value{GDBN}
24996 communicates with Emacs in terms of line numbers. If you add or
24997 delete lines from the text, the line numbers that @value{GDBN} knows cease
24998 to correspond properly with the code.
25000 A more detailed description of Emacs' interaction with @value{GDBN} is
25001 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
25004 @c The following dropped because Epoch is nonstandard. Reactivate
25005 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
25007 @kindex Emacs Epoch environment
25011 Version 18 of @sc{gnu} Emacs has a built-in window system
25012 called the @code{epoch}
25013 environment. Users of this environment can use a new command,
25014 @code{inspect} which performs identically to @code{print} except that
25015 each value is printed in its own window.
25020 @chapter The @sc{gdb/mi} Interface
25022 @unnumberedsec Function and Purpose
25024 @cindex @sc{gdb/mi}, its purpose
25025 @sc{gdb/mi} is a line based machine oriented text interface to
25026 @value{GDBN} and is activated by specifying using the
25027 @option{--interpreter} command line option (@pxref{Mode Options}). It
25028 is specifically intended to support the development of systems which
25029 use the debugger as just one small component of a larger system.
25031 This chapter is a specification of the @sc{gdb/mi} interface. It is written
25032 in the form of a reference manual.
25034 Note that @sc{gdb/mi} is still under construction, so some of the
25035 features described below are incomplete and subject to change
25036 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
25038 @unnumberedsec Notation and Terminology
25040 @cindex notational conventions, for @sc{gdb/mi}
25041 This chapter uses the following notation:
25045 @code{|} separates two alternatives.
25048 @code{[ @var{something} ]} indicates that @var{something} is optional:
25049 it may or may not be given.
25052 @code{( @var{group} )*} means that @var{group} inside the parentheses
25053 may repeat zero or more times.
25056 @code{( @var{group} )+} means that @var{group} inside the parentheses
25057 may repeat one or more times.
25060 @code{"@var{string}"} means a literal @var{string}.
25064 @heading Dependencies
25068 * GDB/MI General Design::
25069 * GDB/MI Command Syntax::
25070 * GDB/MI Compatibility with CLI::
25071 * GDB/MI Development and Front Ends::
25072 * GDB/MI Output Records::
25073 * GDB/MI Simple Examples::
25074 * GDB/MI Command Description Format::
25075 * GDB/MI Breakpoint Commands::
25076 * GDB/MI Program Context::
25077 * GDB/MI Thread Commands::
25078 * GDB/MI Ada Tasking Commands::
25079 * GDB/MI Program Execution::
25080 * GDB/MI Stack Manipulation::
25081 * GDB/MI Variable Objects::
25082 * GDB/MI Data Manipulation::
25083 * GDB/MI Tracepoint Commands::
25084 * GDB/MI Symbol Query::
25085 * GDB/MI File Commands::
25087 * GDB/MI Kod Commands::
25088 * GDB/MI Memory Overlay Commands::
25089 * GDB/MI Signal Handling Commands::
25091 * GDB/MI Target Manipulation::
25092 * GDB/MI File Transfer Commands::
25093 * GDB/MI Miscellaneous Commands::
25096 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25097 @node GDB/MI General Design
25098 @section @sc{gdb/mi} General Design
25099 @cindex GDB/MI General Design
25101 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
25102 parts---commands sent to @value{GDBN}, responses to those commands
25103 and notifications. Each command results in exactly one response,
25104 indicating either successful completion of the command, or an error.
25105 For the commands that do not resume the target, the response contains the
25106 requested information. For the commands that resume the target, the
25107 response only indicates whether the target was successfully resumed.
25108 Notifications is the mechanism for reporting changes in the state of the
25109 target, or in @value{GDBN} state, that cannot conveniently be associated with
25110 a command and reported as part of that command response.
25112 The important examples of notifications are:
25116 Exec notifications. These are used to report changes in
25117 target state---when a target is resumed, or stopped. It would not
25118 be feasible to include this information in response of resuming
25119 commands, because one resume commands can result in multiple events in
25120 different threads. Also, quite some time may pass before any event
25121 happens in the target, while a frontend needs to know whether the resuming
25122 command itself was successfully executed.
25125 Console output, and status notifications. Console output
25126 notifications are used to report output of CLI commands, as well as
25127 diagnostics for other commands. Status notifications are used to
25128 report the progress of a long-running operation. Naturally, including
25129 this information in command response would mean no output is produced
25130 until the command is finished, which is undesirable.
25133 General notifications. Commands may have various side effects on
25134 the @value{GDBN} or target state beyond their official purpose. For example,
25135 a command may change the selected thread. Although such changes can
25136 be included in command response, using notification allows for more
25137 orthogonal frontend design.
25141 There's no guarantee that whenever an MI command reports an error,
25142 @value{GDBN} or the target are in any specific state, and especially,
25143 the state is not reverted to the state before the MI command was
25144 processed. Therefore, whenever an MI command results in an error,
25145 we recommend that the frontend refreshes all the information shown in
25146 the user interface.
25150 * Context management::
25151 * Asynchronous and non-stop modes::
25155 @node Context management
25156 @subsection Context management
25158 In most cases when @value{GDBN} accesses the target, this access is
25159 done in context of a specific thread and frame (@pxref{Frames}).
25160 Often, even when accessing global data, the target requires that a thread
25161 be specified. The CLI interface maintains the selected thread and frame,
25162 and supplies them to target on each command. This is convenient,
25163 because a command line user would not want to specify that information
25164 explicitly on each command, and because user interacts with
25165 @value{GDBN} via a single terminal, so no confusion is possible as
25166 to what thread and frame are the current ones.
25168 In the case of MI, the concept of selected thread and frame is less
25169 useful. First, a frontend can easily remember this information
25170 itself. Second, a graphical frontend can have more than one window,
25171 each one used for debugging a different thread, and the frontend might
25172 want to access additional threads for internal purposes. This
25173 increases the risk that by relying on implicitly selected thread, the
25174 frontend may be operating on a wrong one. Therefore, each MI command
25175 should explicitly specify which thread and frame to operate on. To
25176 make it possible, each MI command accepts the @samp{--thread} and
25177 @samp{--frame} options, the value to each is @value{GDBN} identifier
25178 for thread and frame to operate on.
25180 Usually, each top-level window in a frontend allows the user to select
25181 a thread and a frame, and remembers the user selection for further
25182 operations. However, in some cases @value{GDBN} may suggest that the
25183 current thread be changed. For example, when stopping on a breakpoint
25184 it is reasonable to switch to the thread where breakpoint is hit. For
25185 another example, if the user issues the CLI @samp{thread} command via
25186 the frontend, it is desirable to change the frontend's selected thread to the
25187 one specified by user. @value{GDBN} communicates the suggestion to
25188 change current thread using the @samp{=thread-selected} notification.
25189 No such notification is available for the selected frame at the moment.
25191 Note that historically, MI shares the selected thread with CLI, so
25192 frontends used the @code{-thread-select} to execute commands in the
25193 right context. However, getting this to work right is cumbersome. The
25194 simplest way is for frontend to emit @code{-thread-select} command
25195 before every command. This doubles the number of commands that need
25196 to be sent. The alternative approach is to suppress @code{-thread-select}
25197 if the selected thread in @value{GDBN} is supposed to be identical to the
25198 thread the frontend wants to operate on. However, getting this
25199 optimization right can be tricky. In particular, if the frontend
25200 sends several commands to @value{GDBN}, and one of the commands changes the
25201 selected thread, then the behaviour of subsequent commands will
25202 change. So, a frontend should either wait for response from such
25203 problematic commands, or explicitly add @code{-thread-select} for
25204 all subsequent commands. No frontend is known to do this exactly
25205 right, so it is suggested to just always pass the @samp{--thread} and
25206 @samp{--frame} options.
25208 @node Asynchronous and non-stop modes
25209 @subsection Asynchronous command execution and non-stop mode
25211 On some targets, @value{GDBN} is capable of processing MI commands
25212 even while the target is running. This is called @dfn{asynchronous
25213 command execution} (@pxref{Background Execution}). The frontend may
25214 specify a preferrence for asynchronous execution using the
25215 @code{-gdb-set target-async 1} command, which should be emitted before
25216 either running the executable or attaching to the target. After the
25217 frontend has started the executable or attached to the target, it can
25218 find if asynchronous execution is enabled using the
25219 @code{-list-target-features} command.
25221 Even if @value{GDBN} can accept a command while target is running,
25222 many commands that access the target do not work when the target is
25223 running. Therefore, asynchronous command execution is most useful
25224 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
25225 it is possible to examine the state of one thread, while other threads
25228 When a given thread is running, MI commands that try to access the
25229 target in the context of that thread may not work, or may work only on
25230 some targets. In particular, commands that try to operate on thread's
25231 stack will not work, on any target. Commands that read memory, or
25232 modify breakpoints, may work or not work, depending on the target. Note
25233 that even commands that operate on global state, such as @code{print},
25234 @code{set}, and breakpoint commands, still access the target in the
25235 context of a specific thread, so frontend should try to find a
25236 stopped thread and perform the operation on that thread (using the
25237 @samp{--thread} option).
25239 Which commands will work in the context of a running thread is
25240 highly target dependent. However, the two commands
25241 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
25242 to find the state of a thread, will always work.
25244 @node Thread groups
25245 @subsection Thread groups
25246 @value{GDBN} may be used to debug several processes at the same time.
25247 On some platfroms, @value{GDBN} may support debugging of several
25248 hardware systems, each one having several cores with several different
25249 processes running on each core. This section describes the MI
25250 mechanism to support such debugging scenarios.
25252 The key observation is that regardless of the structure of the
25253 target, MI can have a global list of threads, because most commands that
25254 accept the @samp{--thread} option do not need to know what process that
25255 thread belongs to. Therefore, it is not necessary to introduce
25256 neither additional @samp{--process} option, nor an notion of the
25257 current process in the MI interface. The only strictly new feature
25258 that is required is the ability to find how the threads are grouped
25261 To allow the user to discover such grouping, and to support arbitrary
25262 hierarchy of machines/cores/processes, MI introduces the concept of a
25263 @dfn{thread group}. Thread group is a collection of threads and other
25264 thread groups. A thread group always has a string identifier, a type,
25265 and may have additional attributes specific to the type. A new
25266 command, @code{-list-thread-groups}, returns the list of top-level
25267 thread groups, which correspond to processes that @value{GDBN} is
25268 debugging at the moment. By passing an identifier of a thread group
25269 to the @code{-list-thread-groups} command, it is possible to obtain
25270 the members of specific thread group.
25272 To allow the user to easily discover processes, and other objects, he
25273 wishes to debug, a concept of @dfn{available thread group} is
25274 introduced. Available thread group is an thread group that
25275 @value{GDBN} is not debugging, but that can be attached to, using the
25276 @code{-target-attach} command. The list of available top-level thread
25277 groups can be obtained using @samp{-list-thread-groups --available}.
25278 In general, the content of a thread group may be only retrieved only
25279 after attaching to that thread group.
25281 Thread groups are related to inferiors (@pxref{Inferiors and
25282 Programs}). Each inferior corresponds to a thread group of a special
25283 type @samp{process}, and some additional operations are permitted on
25284 such thread groups.
25286 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25287 @node GDB/MI Command Syntax
25288 @section @sc{gdb/mi} Command Syntax
25291 * GDB/MI Input Syntax::
25292 * GDB/MI Output Syntax::
25295 @node GDB/MI Input Syntax
25296 @subsection @sc{gdb/mi} Input Syntax
25298 @cindex input syntax for @sc{gdb/mi}
25299 @cindex @sc{gdb/mi}, input syntax
25301 @item @var{command} @expansion{}
25302 @code{@var{cli-command} | @var{mi-command}}
25304 @item @var{cli-command} @expansion{}
25305 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
25306 @var{cli-command} is any existing @value{GDBN} CLI command.
25308 @item @var{mi-command} @expansion{}
25309 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
25310 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
25312 @item @var{token} @expansion{}
25313 "any sequence of digits"
25315 @item @var{option} @expansion{}
25316 @code{"-" @var{parameter} [ " " @var{parameter} ]}
25318 @item @var{parameter} @expansion{}
25319 @code{@var{non-blank-sequence} | @var{c-string}}
25321 @item @var{operation} @expansion{}
25322 @emph{any of the operations described in this chapter}
25324 @item @var{non-blank-sequence} @expansion{}
25325 @emph{anything, provided it doesn't contain special characters such as
25326 "-", @var{nl}, """ and of course " "}
25328 @item @var{c-string} @expansion{}
25329 @code{""" @var{seven-bit-iso-c-string-content} """}
25331 @item @var{nl} @expansion{}
25340 The CLI commands are still handled by the @sc{mi} interpreter; their
25341 output is described below.
25344 The @code{@var{token}}, when present, is passed back when the command
25348 Some @sc{mi} commands accept optional arguments as part of the parameter
25349 list. Each option is identified by a leading @samp{-} (dash) and may be
25350 followed by an optional argument parameter. Options occur first in the
25351 parameter list and can be delimited from normal parameters using
25352 @samp{--} (this is useful when some parameters begin with a dash).
25359 We want easy access to the existing CLI syntax (for debugging).
25362 We want it to be easy to spot a @sc{mi} operation.
25365 @node GDB/MI Output Syntax
25366 @subsection @sc{gdb/mi} Output Syntax
25368 @cindex output syntax of @sc{gdb/mi}
25369 @cindex @sc{gdb/mi}, output syntax
25370 The output from @sc{gdb/mi} consists of zero or more out-of-band records
25371 followed, optionally, by a single result record. This result record
25372 is for the most recent command. The sequence of output records is
25373 terminated by @samp{(gdb)}.
25375 If an input command was prefixed with a @code{@var{token}} then the
25376 corresponding output for that command will also be prefixed by that same
25380 @item @var{output} @expansion{}
25381 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
25383 @item @var{result-record} @expansion{}
25384 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
25386 @item @var{out-of-band-record} @expansion{}
25387 @code{@var{async-record} | @var{stream-record}}
25389 @item @var{async-record} @expansion{}
25390 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
25392 @item @var{exec-async-output} @expansion{}
25393 @code{[ @var{token} ] "*" @var{async-output}}
25395 @item @var{status-async-output} @expansion{}
25396 @code{[ @var{token} ] "+" @var{async-output}}
25398 @item @var{notify-async-output} @expansion{}
25399 @code{[ @var{token} ] "=" @var{async-output}}
25401 @item @var{async-output} @expansion{}
25402 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
25404 @item @var{result-class} @expansion{}
25405 @code{"done" | "running" | "connected" | "error" | "exit"}
25407 @item @var{async-class} @expansion{}
25408 @code{"stopped" | @var{others}} (where @var{others} will be added
25409 depending on the needs---this is still in development).
25411 @item @var{result} @expansion{}
25412 @code{ @var{variable} "=" @var{value}}
25414 @item @var{variable} @expansion{}
25415 @code{ @var{string} }
25417 @item @var{value} @expansion{}
25418 @code{ @var{const} | @var{tuple} | @var{list} }
25420 @item @var{const} @expansion{}
25421 @code{@var{c-string}}
25423 @item @var{tuple} @expansion{}
25424 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
25426 @item @var{list} @expansion{}
25427 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
25428 @var{result} ( "," @var{result} )* "]" }
25430 @item @var{stream-record} @expansion{}
25431 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
25433 @item @var{console-stream-output} @expansion{}
25434 @code{"~" @var{c-string}}
25436 @item @var{target-stream-output} @expansion{}
25437 @code{"@@" @var{c-string}}
25439 @item @var{log-stream-output} @expansion{}
25440 @code{"&" @var{c-string}}
25442 @item @var{nl} @expansion{}
25445 @item @var{token} @expansion{}
25446 @emph{any sequence of digits}.
25454 All output sequences end in a single line containing a period.
25457 The @code{@var{token}} is from the corresponding request. Note that
25458 for all async output, while the token is allowed by the grammar and
25459 may be output by future versions of @value{GDBN} for select async
25460 output messages, it is generally omitted. Frontends should treat
25461 all async output as reporting general changes in the state of the
25462 target and there should be no need to associate async output to any
25466 @cindex status output in @sc{gdb/mi}
25467 @var{status-async-output} contains on-going status information about the
25468 progress of a slow operation. It can be discarded. All status output is
25469 prefixed by @samp{+}.
25472 @cindex async output in @sc{gdb/mi}
25473 @var{exec-async-output} contains asynchronous state change on the target
25474 (stopped, started, disappeared). All async output is prefixed by
25478 @cindex notify output in @sc{gdb/mi}
25479 @var{notify-async-output} contains supplementary information that the
25480 client should handle (e.g., a new breakpoint information). All notify
25481 output is prefixed by @samp{=}.
25484 @cindex console output in @sc{gdb/mi}
25485 @var{console-stream-output} is output that should be displayed as is in the
25486 console. It is the textual response to a CLI command. All the console
25487 output is prefixed by @samp{~}.
25490 @cindex target output in @sc{gdb/mi}
25491 @var{target-stream-output} is the output produced by the target program.
25492 All the target output is prefixed by @samp{@@}.
25495 @cindex log output in @sc{gdb/mi}
25496 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
25497 instance messages that should be displayed as part of an error log. All
25498 the log output is prefixed by @samp{&}.
25501 @cindex list output in @sc{gdb/mi}
25502 New @sc{gdb/mi} commands should only output @var{lists} containing
25508 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
25509 details about the various output records.
25511 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25512 @node GDB/MI Compatibility with CLI
25513 @section @sc{gdb/mi} Compatibility with CLI
25515 @cindex compatibility, @sc{gdb/mi} and CLI
25516 @cindex @sc{gdb/mi}, compatibility with CLI
25518 For the developers convenience CLI commands can be entered directly,
25519 but there may be some unexpected behaviour. For example, commands
25520 that query the user will behave as if the user replied yes, breakpoint
25521 command lists are not executed and some CLI commands, such as
25522 @code{if}, @code{when} and @code{define}, prompt for further input with
25523 @samp{>}, which is not valid MI output.
25525 This feature may be removed at some stage in the future and it is
25526 recommended that front ends use the @code{-interpreter-exec} command
25527 (@pxref{-interpreter-exec}).
25529 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25530 @node GDB/MI Development and Front Ends
25531 @section @sc{gdb/mi} Development and Front Ends
25532 @cindex @sc{gdb/mi} development
25534 The application which takes the MI output and presents the state of the
25535 program being debugged to the user is called a @dfn{front end}.
25537 Although @sc{gdb/mi} is still incomplete, it is currently being used
25538 by a variety of front ends to @value{GDBN}. This makes it difficult
25539 to introduce new functionality without breaking existing usage. This
25540 section tries to minimize the problems by describing how the protocol
25543 Some changes in MI need not break a carefully designed front end, and
25544 for these the MI version will remain unchanged. The following is a
25545 list of changes that may occur within one level, so front ends should
25546 parse MI output in a way that can handle them:
25550 New MI commands may be added.
25553 New fields may be added to the output of any MI command.
25556 The range of values for fields with specified values, e.g.,
25557 @code{in_scope} (@pxref{-var-update}) may be extended.
25559 @c The format of field's content e.g type prefix, may change so parse it
25560 @c at your own risk. Yes, in general?
25562 @c The order of fields may change? Shouldn't really matter but it might
25563 @c resolve inconsistencies.
25566 If the changes are likely to break front ends, the MI version level
25567 will be increased by one. This will allow the front end to parse the
25568 output according to the MI version. Apart from mi0, new versions of
25569 @value{GDBN} will not support old versions of MI and it will be the
25570 responsibility of the front end to work with the new one.
25572 @c Starting with mi3, add a new command -mi-version that prints the MI
25575 The best way to avoid unexpected changes in MI that might break your front
25576 end is to make your project known to @value{GDBN} developers and
25577 follow development on @email{gdb@@sourceware.org} and
25578 @email{gdb-patches@@sourceware.org}.
25579 @cindex mailing lists
25581 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25582 @node GDB/MI Output Records
25583 @section @sc{gdb/mi} Output Records
25586 * GDB/MI Result Records::
25587 * GDB/MI Stream Records::
25588 * GDB/MI Async Records::
25589 * GDB/MI Frame Information::
25590 * GDB/MI Thread Information::
25591 * GDB/MI Ada Exception Information::
25594 @node GDB/MI Result Records
25595 @subsection @sc{gdb/mi} Result Records
25597 @cindex result records in @sc{gdb/mi}
25598 @cindex @sc{gdb/mi}, result records
25599 In addition to a number of out-of-band notifications, the response to a
25600 @sc{gdb/mi} command includes one of the following result indications:
25604 @item "^done" [ "," @var{results} ]
25605 The synchronous operation was successful, @code{@var{results}} are the return
25610 This result record is equivalent to @samp{^done}. Historically, it
25611 was output instead of @samp{^done} if the command has resumed the
25612 target. This behaviour is maintained for backward compatibility, but
25613 all frontends should treat @samp{^done} and @samp{^running}
25614 identically and rely on the @samp{*running} output record to determine
25615 which threads are resumed.
25619 @value{GDBN} has connected to a remote target.
25621 @item "^error" "," @var{c-string}
25623 The operation failed. The @code{@var{c-string}} contains the corresponding
25628 @value{GDBN} has terminated.
25632 @node GDB/MI Stream Records
25633 @subsection @sc{gdb/mi} Stream Records
25635 @cindex @sc{gdb/mi}, stream records
25636 @cindex stream records in @sc{gdb/mi}
25637 @value{GDBN} internally maintains a number of output streams: the console, the
25638 target, and the log. The output intended for each of these streams is
25639 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
25641 Each stream record begins with a unique @dfn{prefix character} which
25642 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
25643 Syntax}). In addition to the prefix, each stream record contains a
25644 @code{@var{string-output}}. This is either raw text (with an implicit new
25645 line) or a quoted C string (which does not contain an implicit newline).
25648 @item "~" @var{string-output}
25649 The console output stream contains text that should be displayed in the
25650 CLI console window. It contains the textual responses to CLI commands.
25652 @item "@@" @var{string-output}
25653 The target output stream contains any textual output from the running
25654 target. This is only present when GDB's event loop is truly
25655 asynchronous, which is currently only the case for remote targets.
25657 @item "&" @var{string-output}
25658 The log stream contains debugging messages being produced by @value{GDBN}'s
25662 @node GDB/MI Async Records
25663 @subsection @sc{gdb/mi} Async Records
25665 @cindex async records in @sc{gdb/mi}
25666 @cindex @sc{gdb/mi}, async records
25667 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
25668 additional changes that have occurred. Those changes can either be a
25669 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
25670 target activity (e.g., target stopped).
25672 The following is the list of possible async records:
25676 @item *running,thread-id="@var{thread}"
25677 The target is now running. The @var{thread} field tells which
25678 specific thread is now running, and can be @samp{all} if all threads
25679 are running. The frontend should assume that no interaction with a
25680 running thread is possible after this notification is produced.
25681 The frontend should not assume that this notification is output
25682 only once for any command. @value{GDBN} may emit this notification
25683 several times, either for different threads, because it cannot resume
25684 all threads together, or even for a single thread, if the thread must
25685 be stepped though some code before letting it run freely.
25687 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
25688 The target has stopped. The @var{reason} field can have one of the
25692 @item breakpoint-hit
25693 A breakpoint was reached.
25694 @item watchpoint-trigger
25695 A watchpoint was triggered.
25696 @item read-watchpoint-trigger
25697 A read watchpoint was triggered.
25698 @item access-watchpoint-trigger
25699 An access watchpoint was triggered.
25700 @item function-finished
25701 An -exec-finish or similar CLI command was accomplished.
25702 @item location-reached
25703 An -exec-until or similar CLI command was accomplished.
25704 @item watchpoint-scope
25705 A watchpoint has gone out of scope.
25706 @item end-stepping-range
25707 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
25708 similar CLI command was accomplished.
25709 @item exited-signalled
25710 The inferior exited because of a signal.
25712 The inferior exited.
25713 @item exited-normally
25714 The inferior exited normally.
25715 @item signal-received
25716 A signal was received by the inferior.
25719 The @var{id} field identifies the thread that directly caused the stop
25720 -- for example by hitting a breakpoint. Depending on whether all-stop
25721 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
25722 stop all threads, or only the thread that directly triggered the stop.
25723 If all threads are stopped, the @var{stopped} field will have the
25724 value of @code{"all"}. Otherwise, the value of the @var{stopped}
25725 field will be a list of thread identifiers. Presently, this list will
25726 always include a single thread, but frontend should be prepared to see
25727 several threads in the list. The @var{core} field reports the
25728 processor core on which the stop event has happened. This field may be absent
25729 if such information is not available.
25731 @item =thread-group-added,id="@var{id}"
25732 @itemx =thread-group-removed,id="@var{id}"
25733 A thread group was either added or removed. The @var{id} field
25734 contains the @value{GDBN} identifier of the thread group. When a thread
25735 group is added, it generally might not be associated with a running
25736 process. When a thread group is removed, its id becomes invalid and
25737 cannot be used in any way.
25739 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
25740 A thread group became associated with a running program,
25741 either because the program was just started or the thread group
25742 was attached to a program. The @var{id} field contains the
25743 @value{GDBN} identifier of the thread group. The @var{pid} field
25744 contains process identifier, specific to the operating system.
25746 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
25747 A thread group is no longer associated with a running program,
25748 either because the program has exited, or because it was detached
25749 from. The @var{id} field contains the @value{GDBN} identifier of the
25750 thread group. @var{code} is the exit code of the inferior; it exists
25751 only when the inferior exited with some code.
25753 @item =thread-created,id="@var{id}",group-id="@var{gid}"
25754 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
25755 A thread either was created, or has exited. The @var{id} field
25756 contains the @value{GDBN} identifier of the thread. The @var{gid}
25757 field identifies the thread group this thread belongs to.
25759 @item =thread-selected,id="@var{id}"
25760 Informs that the selected thread was changed as result of the last
25761 command. This notification is not emitted as result of @code{-thread-select}
25762 command but is emitted whenever an MI command that is not documented
25763 to change the selected thread actually changes it. In particular,
25764 invoking, directly or indirectly (via user-defined command), the CLI
25765 @code{thread} command, will generate this notification.
25767 We suggest that in response to this notification, front ends
25768 highlight the selected thread and cause subsequent commands to apply to
25771 @item =library-loaded,...
25772 Reports that a new library file was loaded by the program. This
25773 notification has 4 fields---@var{id}, @var{target-name},
25774 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
25775 opaque identifier of the library. For remote debugging case,
25776 @var{target-name} and @var{host-name} fields give the name of the
25777 library file on the target, and on the host respectively. For native
25778 debugging, both those fields have the same value. The
25779 @var{symbols-loaded} field is emitted only for backward compatibility
25780 and should not be relied on to convey any useful information. The
25781 @var{thread-group} field, if present, specifies the id of the thread
25782 group in whose context the library was loaded. If the field is
25783 absent, it means the library was loaded in the context of all present
25786 @item =library-unloaded,...
25787 Reports that a library was unloaded by the program. This notification
25788 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
25789 the same meaning as for the @code{=library-loaded} notification.
25790 The @var{thread-group} field, if present, specifies the id of the
25791 thread group in whose context the library was unloaded. If the field is
25792 absent, it means the library was unloaded in the context of all present
25795 @item =breakpoint-created,bkpt=@{...@}
25796 @itemx =breakpoint-modified,bkpt=@{...@}
25797 @itemx =breakpoint-deleted,bkpt=@{...@}
25798 Reports that a breakpoint was created, modified, or deleted,
25799 respectively. Only user-visible breakpoints are reported to the MI
25802 The @var{bkpt} argument is of the same form as returned by the various
25803 breakpoint commands; @xref{GDB/MI Breakpoint Commands}.
25805 Note that if a breakpoint is emitted in the result record of a
25806 command, then it will not also be emitted in an async record.
25810 @node GDB/MI Frame Information
25811 @subsection @sc{gdb/mi} Frame Information
25813 Response from many MI commands includes an information about stack
25814 frame. This information is a tuple that may have the following
25819 The level of the stack frame. The innermost frame has the level of
25820 zero. This field is always present.
25823 The name of the function corresponding to the frame. This field may
25824 be absent if @value{GDBN} is unable to determine the function name.
25827 The code address for the frame. This field is always present.
25830 The name of the source files that correspond to the frame's code
25831 address. This field may be absent.
25834 The source line corresponding to the frames' code address. This field
25838 The name of the binary file (either executable or shared library) the
25839 corresponds to the frame's code address. This field may be absent.
25843 @node GDB/MI Thread Information
25844 @subsection @sc{gdb/mi} Thread Information
25846 Whenever @value{GDBN} has to report an information about a thread, it
25847 uses a tuple with the following fields:
25851 The numeric id assigned to the thread by @value{GDBN}. This field is
25855 Target-specific string identifying the thread. This field is always present.
25858 Additional information about the thread provided by the target.
25859 It is supposed to be human-readable and not interpreted by the
25860 frontend. This field is optional.
25863 Either @samp{stopped} or @samp{running}, depending on whether the
25864 thread is presently running. This field is always present.
25867 The value of this field is an integer number of the processor core the
25868 thread was last seen on. This field is optional.
25871 @node GDB/MI Ada Exception Information
25872 @subsection @sc{gdb/mi} Ada Exception Information
25874 Whenever a @code{*stopped} record is emitted because the program
25875 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
25876 @value{GDBN} provides the name of the exception that was raised via
25877 the @code{exception-name} field.
25879 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25880 @node GDB/MI Simple Examples
25881 @section Simple Examples of @sc{gdb/mi} Interaction
25882 @cindex @sc{gdb/mi}, simple examples
25884 This subsection presents several simple examples of interaction using
25885 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
25886 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
25887 the output received from @sc{gdb/mi}.
25889 Note the line breaks shown in the examples are here only for
25890 readability, they don't appear in the real output.
25892 @subheading Setting a Breakpoint
25894 Setting a breakpoint generates synchronous output which contains detailed
25895 information of the breakpoint.
25898 -> -break-insert main
25899 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25900 enabled="y",addr="0x08048564",func="main",file="myprog.c",
25901 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
25905 @subheading Program Execution
25907 Program execution generates asynchronous records and MI gives the
25908 reason that execution stopped.
25914 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
25915 frame=@{addr="0x08048564",func="main",
25916 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
25917 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
25922 <- *stopped,reason="exited-normally"
25926 @subheading Quitting @value{GDBN}
25928 Quitting @value{GDBN} just prints the result class @samp{^exit}.
25936 Please note that @samp{^exit} is printed immediately, but it might
25937 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
25938 performs necessary cleanups, including killing programs being debugged
25939 or disconnecting from debug hardware, so the frontend should wait till
25940 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
25941 fails to exit in reasonable time.
25943 @subheading A Bad Command
25945 Here's what happens if you pass a non-existent command:
25949 <- ^error,msg="Undefined MI command: rubbish"
25954 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25955 @node GDB/MI Command Description Format
25956 @section @sc{gdb/mi} Command Description Format
25958 The remaining sections describe blocks of commands. Each block of
25959 commands is laid out in a fashion similar to this section.
25961 @subheading Motivation
25963 The motivation for this collection of commands.
25965 @subheading Introduction
25967 A brief introduction to this collection of commands as a whole.
25969 @subheading Commands
25971 For each command in the block, the following is described:
25973 @subsubheading Synopsis
25976 -command @var{args}@dots{}
25979 @subsubheading Result
25981 @subsubheading @value{GDBN} Command
25983 The corresponding @value{GDBN} CLI command(s), if any.
25985 @subsubheading Example
25987 Example(s) formatted for readability. Some of the described commands have
25988 not been implemented yet and these are labeled N.A.@: (not available).
25991 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25992 @node GDB/MI Breakpoint Commands
25993 @section @sc{gdb/mi} Breakpoint Commands
25995 @cindex breakpoint commands for @sc{gdb/mi}
25996 @cindex @sc{gdb/mi}, breakpoint commands
25997 This section documents @sc{gdb/mi} commands for manipulating
26000 @subheading The @code{-break-after} Command
26001 @findex -break-after
26003 @subsubheading Synopsis
26006 -break-after @var{number} @var{count}
26009 The breakpoint number @var{number} is not in effect until it has been
26010 hit @var{count} times. To see how this is reflected in the output of
26011 the @samp{-break-list} command, see the description of the
26012 @samp{-break-list} command below.
26014 @subsubheading @value{GDBN} Command
26016 The corresponding @value{GDBN} command is @samp{ignore}.
26018 @subsubheading Example
26023 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26024 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26025 fullname="/home/foo/hello.c",line="5",times="0"@}
26032 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26033 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26034 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26035 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26036 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26037 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26038 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26039 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26040 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26041 line="5",times="0",ignore="3"@}]@}
26046 @subheading The @code{-break-catch} Command
26047 @findex -break-catch
26050 @subheading The @code{-break-commands} Command
26051 @findex -break-commands
26053 @subsubheading Synopsis
26056 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
26059 Specifies the CLI commands that should be executed when breakpoint
26060 @var{number} is hit. The parameters @var{command1} to @var{commandN}
26061 are the commands. If no command is specified, any previously-set
26062 commands are cleared. @xref{Break Commands}. Typical use of this
26063 functionality is tracing a program, that is, printing of values of
26064 some variables whenever breakpoint is hit and then continuing.
26066 @subsubheading @value{GDBN} Command
26068 The corresponding @value{GDBN} command is @samp{commands}.
26070 @subsubheading Example
26075 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26076 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26077 fullname="/home/foo/hello.c",line="5",times="0"@}
26079 -break-commands 1 "print v" "continue"
26084 @subheading The @code{-break-condition} Command
26085 @findex -break-condition
26087 @subsubheading Synopsis
26090 -break-condition @var{number} @var{expr}
26093 Breakpoint @var{number} will stop the program only if the condition in
26094 @var{expr} is true. The condition becomes part of the
26095 @samp{-break-list} output (see the description of the @samp{-break-list}
26098 @subsubheading @value{GDBN} Command
26100 The corresponding @value{GDBN} command is @samp{condition}.
26102 @subsubheading Example
26106 -break-condition 1 1
26110 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26111 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26112 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26113 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26114 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26115 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26116 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26117 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26118 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26119 line="5",cond="1",times="0",ignore="3"@}]@}
26123 @subheading The @code{-break-delete} Command
26124 @findex -break-delete
26126 @subsubheading Synopsis
26129 -break-delete ( @var{breakpoint} )+
26132 Delete the breakpoint(s) whose number(s) are specified in the argument
26133 list. This is obviously reflected in the breakpoint list.
26135 @subsubheading @value{GDBN} Command
26137 The corresponding @value{GDBN} command is @samp{delete}.
26139 @subsubheading Example
26147 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26148 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26149 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26150 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26151 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26152 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26153 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26158 @subheading The @code{-break-disable} Command
26159 @findex -break-disable
26161 @subsubheading Synopsis
26164 -break-disable ( @var{breakpoint} )+
26167 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
26168 break list is now set to @samp{n} for the named @var{breakpoint}(s).
26170 @subsubheading @value{GDBN} Command
26172 The corresponding @value{GDBN} command is @samp{disable}.
26174 @subsubheading Example
26182 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26183 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26184 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26185 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26186 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26187 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26188 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26189 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
26190 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26191 line="5",times="0"@}]@}
26195 @subheading The @code{-break-enable} Command
26196 @findex -break-enable
26198 @subsubheading Synopsis
26201 -break-enable ( @var{breakpoint} )+
26204 Enable (previously disabled) @var{breakpoint}(s).
26206 @subsubheading @value{GDBN} Command
26208 The corresponding @value{GDBN} command is @samp{enable}.
26210 @subsubheading Example
26218 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26219 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26220 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26221 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26222 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26223 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26224 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26225 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26226 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26227 line="5",times="0"@}]@}
26231 @subheading The @code{-break-info} Command
26232 @findex -break-info
26234 @subsubheading Synopsis
26237 -break-info @var{breakpoint}
26241 Get information about a single breakpoint.
26243 @subsubheading @value{GDBN} Command
26245 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
26247 @subsubheading Example
26250 @subheading The @code{-break-insert} Command
26251 @findex -break-insert
26253 @subsubheading Synopsis
26256 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
26257 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26258 [ -p @var{thread} ] [ @var{location} ]
26262 If specified, @var{location}, can be one of:
26269 @item filename:linenum
26270 @item filename:function
26274 The possible optional parameters of this command are:
26278 Insert a temporary breakpoint.
26280 Insert a hardware breakpoint.
26281 @item -c @var{condition}
26282 Make the breakpoint conditional on @var{condition}.
26283 @item -i @var{ignore-count}
26284 Initialize the @var{ignore-count}.
26286 If @var{location} cannot be parsed (for example if it
26287 refers to unknown files or functions), create a pending
26288 breakpoint. Without this flag, @value{GDBN} will report
26289 an error, and won't create a breakpoint, if @var{location}
26292 Create a disabled breakpoint.
26294 Create a tracepoint. @xref{Tracepoints}. When this parameter
26295 is used together with @samp{-h}, a fast tracepoint is created.
26298 @subsubheading Result
26300 The result is in the form:
26303 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
26304 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
26305 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
26306 times="@var{times}"@}
26310 where @var{number} is the @value{GDBN} number for this breakpoint,
26311 @var{funcname} is the name of the function where the breakpoint was
26312 inserted, @var{filename} is the name of the source file which contains
26313 this function, @var{lineno} is the source line number within that file
26314 and @var{times} the number of times that the breakpoint has been hit
26315 (always 0 for -break-insert but may be greater for -break-info or -break-list
26316 which use the same output).
26318 Note: this format is open to change.
26319 @c An out-of-band breakpoint instead of part of the result?
26321 @subsubheading @value{GDBN} Command
26323 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
26324 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
26326 @subsubheading Example
26331 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
26332 fullname="/home/foo/recursive2.c,line="4",times="0"@}
26334 -break-insert -t foo
26335 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
26336 fullname="/home/foo/recursive2.c,line="11",times="0"@}
26339 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26340 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26341 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26342 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26343 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26344 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26345 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26346 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26347 addr="0x0001072c", func="main",file="recursive2.c",
26348 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
26349 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
26350 addr="0x00010774",func="foo",file="recursive2.c",
26351 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
26353 -break-insert -r foo.*
26354 ~int foo(int, int);
26355 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
26356 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
26360 @subheading The @code{-break-list} Command
26361 @findex -break-list
26363 @subsubheading Synopsis
26369 Displays the list of inserted breakpoints, showing the following fields:
26373 number of the breakpoint
26375 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
26377 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
26380 is the breakpoint enabled or no: @samp{y} or @samp{n}
26382 memory location at which the breakpoint is set
26384 logical location of the breakpoint, expressed by function name, file
26387 number of times the breakpoint has been hit
26390 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
26391 @code{body} field is an empty list.
26393 @subsubheading @value{GDBN} Command
26395 The corresponding @value{GDBN} command is @samp{info break}.
26397 @subsubheading Example
26402 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26403 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26404 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26405 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26406 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26407 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26408 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26409 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26410 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
26411 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26412 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
26413 line="13",times="0"@}]@}
26417 Here's an example of the result when there are no breakpoints:
26422 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26423 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26424 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26425 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26426 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26427 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26428 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26433 @subheading The @code{-break-passcount} Command
26434 @findex -break-passcount
26436 @subsubheading Synopsis
26439 -break-passcount @var{tracepoint-number} @var{passcount}
26442 Set the passcount for tracepoint @var{tracepoint-number} to
26443 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
26444 is not a tracepoint, error is emitted. This corresponds to CLI
26445 command @samp{passcount}.
26447 @subheading The @code{-break-watch} Command
26448 @findex -break-watch
26450 @subsubheading Synopsis
26453 -break-watch [ -a | -r ]
26456 Create a watchpoint. With the @samp{-a} option it will create an
26457 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
26458 read from or on a write to the memory location. With the @samp{-r}
26459 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
26460 trigger only when the memory location is accessed for reading. Without
26461 either of the options, the watchpoint created is a regular watchpoint,
26462 i.e., it will trigger when the memory location is accessed for writing.
26463 @xref{Set Watchpoints, , Setting Watchpoints}.
26465 Note that @samp{-break-list} will report a single list of watchpoints and
26466 breakpoints inserted.
26468 @subsubheading @value{GDBN} Command
26470 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
26473 @subsubheading Example
26475 Setting a watchpoint on a variable in the @code{main} function:
26480 ^done,wpt=@{number="2",exp="x"@}
26485 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
26486 value=@{old="-268439212",new="55"@},
26487 frame=@{func="main",args=[],file="recursive2.c",
26488 fullname="/home/foo/bar/recursive2.c",line="5"@}
26492 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
26493 the program execution twice: first for the variable changing value, then
26494 for the watchpoint going out of scope.
26499 ^done,wpt=@{number="5",exp="C"@}
26504 *stopped,reason="watchpoint-trigger",
26505 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
26506 frame=@{func="callee4",args=[],
26507 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26508 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
26513 *stopped,reason="watchpoint-scope",wpnum="5",
26514 frame=@{func="callee3",args=[@{name="strarg",
26515 value="0x11940 \"A string argument.\""@}],
26516 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26517 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26521 Listing breakpoints and watchpoints, at different points in the program
26522 execution. Note that once the watchpoint goes out of scope, it is
26528 ^done,wpt=@{number="2",exp="C"@}
26531 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26532 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26533 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26534 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26535 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26536 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26537 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26538 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26539 addr="0x00010734",func="callee4",
26540 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26541 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
26542 bkpt=@{number="2",type="watchpoint",disp="keep",
26543 enabled="y",addr="",what="C",times="0"@}]@}
26548 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
26549 value=@{old="-276895068",new="3"@},
26550 frame=@{func="callee4",args=[],
26551 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26552 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
26555 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26556 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26557 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26558 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26559 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26560 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26561 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26562 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26563 addr="0x00010734",func="callee4",
26564 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26565 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
26566 bkpt=@{number="2",type="watchpoint",disp="keep",
26567 enabled="y",addr="",what="C",times="-5"@}]@}
26571 ^done,reason="watchpoint-scope",wpnum="2",
26572 frame=@{func="callee3",args=[@{name="strarg",
26573 value="0x11940 \"A string argument.\""@}],
26574 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26575 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26578 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26579 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26580 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26581 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26582 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26583 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26584 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26585 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26586 addr="0x00010734",func="callee4",
26587 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26588 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
26593 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26594 @node GDB/MI Program Context
26595 @section @sc{gdb/mi} Program Context
26597 @subheading The @code{-exec-arguments} Command
26598 @findex -exec-arguments
26601 @subsubheading Synopsis
26604 -exec-arguments @var{args}
26607 Set the inferior program arguments, to be used in the next
26610 @subsubheading @value{GDBN} Command
26612 The corresponding @value{GDBN} command is @samp{set args}.
26614 @subsubheading Example
26618 -exec-arguments -v word
26625 @subheading The @code{-exec-show-arguments} Command
26626 @findex -exec-show-arguments
26628 @subsubheading Synopsis
26631 -exec-show-arguments
26634 Print the arguments of the program.
26636 @subsubheading @value{GDBN} Command
26638 The corresponding @value{GDBN} command is @samp{show args}.
26640 @subsubheading Example
26645 @subheading The @code{-environment-cd} Command
26646 @findex -environment-cd
26648 @subsubheading Synopsis
26651 -environment-cd @var{pathdir}
26654 Set @value{GDBN}'s working directory.
26656 @subsubheading @value{GDBN} Command
26658 The corresponding @value{GDBN} command is @samp{cd}.
26660 @subsubheading Example
26664 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
26670 @subheading The @code{-environment-directory} Command
26671 @findex -environment-directory
26673 @subsubheading Synopsis
26676 -environment-directory [ -r ] [ @var{pathdir} ]+
26679 Add directories @var{pathdir} to beginning of search path for source files.
26680 If the @samp{-r} option is used, the search path is reset to the default
26681 search path. If directories @var{pathdir} are supplied in addition to the
26682 @samp{-r} option, the search path is first reset and then addition
26684 Multiple directories may be specified, separated by blanks. Specifying
26685 multiple directories in a single command
26686 results in the directories added to the beginning of the
26687 search path in the same order they were presented in the command.
26688 If blanks are needed as
26689 part of a directory name, double-quotes should be used around
26690 the name. In the command output, the path will show up separated
26691 by the system directory-separator character. The directory-separator
26692 character must not be used
26693 in any directory name.
26694 If no directories are specified, the current search path is displayed.
26696 @subsubheading @value{GDBN} Command
26698 The corresponding @value{GDBN} command is @samp{dir}.
26700 @subsubheading Example
26704 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
26705 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
26707 -environment-directory ""
26708 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
26710 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
26711 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
26713 -environment-directory -r
26714 ^done,source-path="$cdir:$cwd"
26719 @subheading The @code{-environment-path} Command
26720 @findex -environment-path
26722 @subsubheading Synopsis
26725 -environment-path [ -r ] [ @var{pathdir} ]+
26728 Add directories @var{pathdir} to beginning of search path for object files.
26729 If the @samp{-r} option is used, the search path is reset to the original
26730 search path that existed at gdb start-up. If directories @var{pathdir} are
26731 supplied in addition to the
26732 @samp{-r} option, the search path is first reset and then addition
26734 Multiple directories may be specified, separated by blanks. Specifying
26735 multiple directories in a single command
26736 results in the directories added to the beginning of the
26737 search path in the same order they were presented in the command.
26738 If blanks are needed as
26739 part of a directory name, double-quotes should be used around
26740 the name. In the command output, the path will show up separated
26741 by the system directory-separator character. The directory-separator
26742 character must not be used
26743 in any directory name.
26744 If no directories are specified, the current path is displayed.
26747 @subsubheading @value{GDBN} Command
26749 The corresponding @value{GDBN} command is @samp{path}.
26751 @subsubheading Example
26756 ^done,path="/usr/bin"
26758 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
26759 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
26761 -environment-path -r /usr/local/bin
26762 ^done,path="/usr/local/bin:/usr/bin"
26767 @subheading The @code{-environment-pwd} Command
26768 @findex -environment-pwd
26770 @subsubheading Synopsis
26776 Show the current working directory.
26778 @subsubheading @value{GDBN} Command
26780 The corresponding @value{GDBN} command is @samp{pwd}.
26782 @subsubheading Example
26787 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
26791 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26792 @node GDB/MI Thread Commands
26793 @section @sc{gdb/mi} Thread Commands
26796 @subheading The @code{-thread-info} Command
26797 @findex -thread-info
26799 @subsubheading Synopsis
26802 -thread-info [ @var{thread-id} ]
26805 Reports information about either a specific thread, if
26806 the @var{thread-id} parameter is present, or about all
26807 threads. When printing information about all threads,
26808 also reports the current thread.
26810 @subsubheading @value{GDBN} Command
26812 The @samp{info thread} command prints the same information
26815 @subsubheading Result
26817 The result is a list of threads. The following attributes are
26818 defined for a given thread:
26822 This field exists only for the current thread. It has the value @samp{*}.
26825 The identifier that @value{GDBN} uses to refer to the thread.
26828 The identifier that the target uses to refer to the thread.
26831 Extra information about the thread, in a target-specific format. This
26835 The name of the thread. If the user specified a name using the
26836 @code{thread name} command, then this name is given. Otherwise, if
26837 @value{GDBN} can extract the thread name from the target, then that
26838 name is given. If @value{GDBN} cannot find the thread name, then this
26842 The stack frame currently executing in the thread.
26845 The thread's state. The @samp{state} field may have the following
26850 The thread is stopped. Frame information is available for stopped
26854 The thread is running. There's no frame information for running
26860 If @value{GDBN} can find the CPU core on which this thread is running,
26861 then this field is the core identifier. This field is optional.
26865 @subsubheading Example
26870 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
26871 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
26872 args=[]@},state="running"@},
26873 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
26874 frame=@{level="0",addr="0x0804891f",func="foo",
26875 args=[@{name="i",value="10"@}],
26876 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
26877 state="running"@}],
26878 current-thread-id="1"
26882 @subheading The @code{-thread-list-ids} Command
26883 @findex -thread-list-ids
26885 @subsubheading Synopsis
26891 Produces a list of the currently known @value{GDBN} thread ids. At the
26892 end of the list it also prints the total number of such threads.
26894 This command is retained for historical reasons, the
26895 @code{-thread-info} command should be used instead.
26897 @subsubheading @value{GDBN} Command
26899 Part of @samp{info threads} supplies the same information.
26901 @subsubheading Example
26906 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
26907 current-thread-id="1",number-of-threads="3"
26912 @subheading The @code{-thread-select} Command
26913 @findex -thread-select
26915 @subsubheading Synopsis
26918 -thread-select @var{threadnum}
26921 Make @var{threadnum} the current thread. It prints the number of the new
26922 current thread, and the topmost frame for that thread.
26924 This command is deprecated in favor of explicitly using the
26925 @samp{--thread} option to each command.
26927 @subsubheading @value{GDBN} Command
26929 The corresponding @value{GDBN} command is @samp{thread}.
26931 @subsubheading Example
26938 *stopped,reason="end-stepping-range",thread-id="2",line="187",
26939 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
26943 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
26944 number-of-threads="3"
26947 ^done,new-thread-id="3",
26948 frame=@{level="0",func="vprintf",
26949 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
26950 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
26954 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26955 @node GDB/MI Ada Tasking Commands
26956 @section @sc{gdb/mi} Ada Tasking Commands
26958 @subheading The @code{-ada-task-info} Command
26959 @findex -ada-task-info
26961 @subsubheading Synopsis
26964 -ada-task-info [ @var{task-id} ]
26967 Reports information about either a specific Ada task, if the
26968 @var{task-id} parameter is present, or about all Ada tasks.
26970 @subsubheading @value{GDBN} Command
26972 The @samp{info tasks} command prints the same information
26973 about all Ada tasks (@pxref{Ada Tasks}).
26975 @subsubheading Result
26977 The result is a table of Ada tasks. The following columns are
26978 defined for each Ada task:
26982 This field exists only for the current thread. It has the value @samp{*}.
26985 The identifier that @value{GDBN} uses to refer to the Ada task.
26988 The identifier that the target uses to refer to the Ada task.
26991 The identifier of the thread corresponding to the Ada task.
26993 This field should always exist, as Ada tasks are always implemented
26994 on top of a thread. But if @value{GDBN} cannot find this corresponding
26995 thread for any reason, the field is omitted.
26998 This field exists only when the task was created by another task.
26999 In this case, it provides the ID of the parent task.
27002 The base priority of the task.
27005 The current state of the task. For a detailed description of the
27006 possible states, see @ref{Ada Tasks}.
27009 The name of the task.
27013 @subsubheading Example
27017 ^done,tasks=@{nr_rows="3",nr_cols="8",
27018 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
27019 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
27020 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
27021 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
27022 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
27023 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
27024 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
27025 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
27026 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
27027 state="Child Termination Wait",name="main_task"@}]@}
27031 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27032 @node GDB/MI Program Execution
27033 @section @sc{gdb/mi} Program Execution
27035 These are the asynchronous commands which generate the out-of-band
27036 record @samp{*stopped}. Currently @value{GDBN} only really executes
27037 asynchronously with remote targets and this interaction is mimicked in
27040 @subheading The @code{-exec-continue} Command
27041 @findex -exec-continue
27043 @subsubheading Synopsis
27046 -exec-continue [--reverse] [--all|--thread-group N]
27049 Resumes the execution of the inferior program, which will continue
27050 to execute until it reaches a debugger stop event. If the
27051 @samp{--reverse} option is specified, execution resumes in reverse until
27052 it reaches a stop event. Stop events may include
27055 breakpoints or watchpoints
27057 signals or exceptions
27059 the end of the process (or its beginning under @samp{--reverse})
27061 the end or beginning of a replay log if one is being used.
27063 In all-stop mode (@pxref{All-Stop
27064 Mode}), may resume only one thread, or all threads, depending on the
27065 value of the @samp{scheduler-locking} variable. If @samp{--all} is
27066 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
27067 ignored in all-stop mode. If the @samp{--thread-group} options is
27068 specified, then all threads in that thread group are resumed.
27070 @subsubheading @value{GDBN} Command
27072 The corresponding @value{GDBN} corresponding is @samp{continue}.
27074 @subsubheading Example
27081 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
27082 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
27088 @subheading The @code{-exec-finish} Command
27089 @findex -exec-finish
27091 @subsubheading Synopsis
27094 -exec-finish [--reverse]
27097 Resumes the execution of the inferior program until the current
27098 function is exited. Displays the results returned by the function.
27099 If the @samp{--reverse} option is specified, resumes the reverse
27100 execution of the inferior program until the point where current
27101 function was called.
27103 @subsubheading @value{GDBN} Command
27105 The corresponding @value{GDBN} command is @samp{finish}.
27107 @subsubheading Example
27109 Function returning @code{void}.
27116 *stopped,reason="function-finished",frame=@{func="main",args=[],
27117 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
27121 Function returning other than @code{void}. The name of the internal
27122 @value{GDBN} variable storing the result is printed, together with the
27129 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
27130 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
27131 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27132 gdb-result-var="$1",return-value="0"
27137 @subheading The @code{-exec-interrupt} Command
27138 @findex -exec-interrupt
27140 @subsubheading Synopsis
27143 -exec-interrupt [--all|--thread-group N]
27146 Interrupts the background execution of the target. Note how the token
27147 associated with the stop message is the one for the execution command
27148 that has been interrupted. The token for the interrupt itself only
27149 appears in the @samp{^done} output. If the user is trying to
27150 interrupt a non-running program, an error message will be printed.
27152 Note that when asynchronous execution is enabled, this command is
27153 asynchronous just like other execution commands. That is, first the
27154 @samp{^done} response will be printed, and the target stop will be
27155 reported after that using the @samp{*stopped} notification.
27157 In non-stop mode, only the context thread is interrupted by default.
27158 All threads (in all inferiors) will be interrupted if the
27159 @samp{--all} option is specified. If the @samp{--thread-group}
27160 option is specified, all threads in that group will be interrupted.
27162 @subsubheading @value{GDBN} Command
27164 The corresponding @value{GDBN} command is @samp{interrupt}.
27166 @subsubheading Example
27177 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
27178 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
27179 fullname="/home/foo/bar/try.c",line="13"@}
27184 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
27188 @subheading The @code{-exec-jump} Command
27191 @subsubheading Synopsis
27194 -exec-jump @var{location}
27197 Resumes execution of the inferior program at the location specified by
27198 parameter. @xref{Specify Location}, for a description of the
27199 different forms of @var{location}.
27201 @subsubheading @value{GDBN} Command
27203 The corresponding @value{GDBN} command is @samp{jump}.
27205 @subsubheading Example
27208 -exec-jump foo.c:10
27209 *running,thread-id="all"
27214 @subheading The @code{-exec-next} Command
27217 @subsubheading Synopsis
27220 -exec-next [--reverse]
27223 Resumes execution of the inferior program, stopping when the beginning
27224 of the next source line is reached.
27226 If the @samp{--reverse} option is specified, resumes reverse execution
27227 of the inferior program, stopping at the beginning of the previous
27228 source line. If you issue this command on the first line of a
27229 function, it will take you back to the caller of that function, to the
27230 source line where the function was called.
27233 @subsubheading @value{GDBN} Command
27235 The corresponding @value{GDBN} command is @samp{next}.
27237 @subsubheading Example
27243 *stopped,reason="end-stepping-range",line="8",file="hello.c"
27248 @subheading The @code{-exec-next-instruction} Command
27249 @findex -exec-next-instruction
27251 @subsubheading Synopsis
27254 -exec-next-instruction [--reverse]
27257 Executes one machine instruction. If the instruction is a function
27258 call, continues until the function returns. If the program stops at an
27259 instruction in the middle of a source line, the address will be
27262 If the @samp{--reverse} option is specified, resumes reverse execution
27263 of the inferior program, stopping at the previous instruction. If the
27264 previously executed instruction was a return from another function,
27265 it will continue to execute in reverse until the call to that function
27266 (from the current stack frame) is reached.
27268 @subsubheading @value{GDBN} Command
27270 The corresponding @value{GDBN} command is @samp{nexti}.
27272 @subsubheading Example
27276 -exec-next-instruction
27280 *stopped,reason="end-stepping-range",
27281 addr="0x000100d4",line="5",file="hello.c"
27286 @subheading The @code{-exec-return} Command
27287 @findex -exec-return
27289 @subsubheading Synopsis
27295 Makes current function return immediately. Doesn't execute the inferior.
27296 Displays the new current frame.
27298 @subsubheading @value{GDBN} Command
27300 The corresponding @value{GDBN} command is @samp{return}.
27302 @subsubheading Example
27306 200-break-insert callee4
27307 200^done,bkpt=@{number="1",addr="0x00010734",
27308 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27313 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27314 frame=@{func="callee4",args=[],
27315 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27316 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27322 111^done,frame=@{level="0",func="callee3",
27323 args=[@{name="strarg",
27324 value="0x11940 \"A string argument.\""@}],
27325 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27326 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27331 @subheading The @code{-exec-run} Command
27334 @subsubheading Synopsis
27337 -exec-run [--all | --thread-group N]
27340 Starts execution of the inferior from the beginning. The inferior
27341 executes until either a breakpoint is encountered or the program
27342 exits. In the latter case the output will include an exit code, if
27343 the program has exited exceptionally.
27345 When no option is specified, the current inferior is started. If the
27346 @samp{--thread-group} option is specified, it should refer to a thread
27347 group of type @samp{process}, and that thread group will be started.
27348 If the @samp{--all} option is specified, then all inferiors will be started.
27350 @subsubheading @value{GDBN} Command
27352 The corresponding @value{GDBN} command is @samp{run}.
27354 @subsubheading Examples
27359 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
27364 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27365 frame=@{func="main",args=[],file="recursive2.c",
27366 fullname="/home/foo/bar/recursive2.c",line="4"@}
27371 Program exited normally:
27379 *stopped,reason="exited-normally"
27384 Program exited exceptionally:
27392 *stopped,reason="exited",exit-code="01"
27396 Another way the program can terminate is if it receives a signal such as
27397 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
27401 *stopped,reason="exited-signalled",signal-name="SIGINT",
27402 signal-meaning="Interrupt"
27406 @c @subheading -exec-signal
27409 @subheading The @code{-exec-step} Command
27412 @subsubheading Synopsis
27415 -exec-step [--reverse]
27418 Resumes execution of the inferior program, stopping when the beginning
27419 of the next source line is reached, if the next source line is not a
27420 function call. If it is, stop at the first instruction of the called
27421 function. If the @samp{--reverse} option is specified, resumes reverse
27422 execution of the inferior program, stopping at the beginning of the
27423 previously executed source line.
27425 @subsubheading @value{GDBN} Command
27427 The corresponding @value{GDBN} command is @samp{step}.
27429 @subsubheading Example
27431 Stepping into a function:
27437 *stopped,reason="end-stepping-range",
27438 frame=@{func="foo",args=[@{name="a",value="10"@},
27439 @{name="b",value="0"@}],file="recursive2.c",
27440 fullname="/home/foo/bar/recursive2.c",line="11"@}
27450 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
27455 @subheading The @code{-exec-step-instruction} Command
27456 @findex -exec-step-instruction
27458 @subsubheading Synopsis
27461 -exec-step-instruction [--reverse]
27464 Resumes the inferior which executes one machine instruction. If the
27465 @samp{--reverse} option is specified, resumes reverse execution of the
27466 inferior program, stopping at the previously executed instruction.
27467 The output, once @value{GDBN} has stopped, will vary depending on
27468 whether we have stopped in the middle of a source line or not. In the
27469 former case, the address at which the program stopped will be printed
27472 @subsubheading @value{GDBN} Command
27474 The corresponding @value{GDBN} command is @samp{stepi}.
27476 @subsubheading Example
27480 -exec-step-instruction
27484 *stopped,reason="end-stepping-range",
27485 frame=@{func="foo",args=[],file="try.c",
27486 fullname="/home/foo/bar/try.c",line="10"@}
27488 -exec-step-instruction
27492 *stopped,reason="end-stepping-range",
27493 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
27494 fullname="/home/foo/bar/try.c",line="10"@}
27499 @subheading The @code{-exec-until} Command
27500 @findex -exec-until
27502 @subsubheading Synopsis
27505 -exec-until [ @var{location} ]
27508 Executes the inferior until the @var{location} specified in the
27509 argument is reached. If there is no argument, the inferior executes
27510 until a source line greater than the current one is reached. The
27511 reason for stopping in this case will be @samp{location-reached}.
27513 @subsubheading @value{GDBN} Command
27515 The corresponding @value{GDBN} command is @samp{until}.
27517 @subsubheading Example
27521 -exec-until recursive2.c:6
27525 *stopped,reason="location-reached",frame=@{func="main",args=[],
27526 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
27531 @subheading -file-clear
27532 Is this going away????
27535 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27536 @node GDB/MI Stack Manipulation
27537 @section @sc{gdb/mi} Stack Manipulation Commands
27540 @subheading The @code{-stack-info-frame} Command
27541 @findex -stack-info-frame
27543 @subsubheading Synopsis
27549 Get info on the selected frame.
27551 @subsubheading @value{GDBN} Command
27553 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
27554 (without arguments).
27556 @subsubheading Example
27561 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
27562 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27563 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
27567 @subheading The @code{-stack-info-depth} Command
27568 @findex -stack-info-depth
27570 @subsubheading Synopsis
27573 -stack-info-depth [ @var{max-depth} ]
27576 Return the depth of the stack. If the integer argument @var{max-depth}
27577 is specified, do not count beyond @var{max-depth} frames.
27579 @subsubheading @value{GDBN} Command
27581 There's no equivalent @value{GDBN} command.
27583 @subsubheading Example
27585 For a stack with frame levels 0 through 11:
27592 -stack-info-depth 4
27595 -stack-info-depth 12
27598 -stack-info-depth 11
27601 -stack-info-depth 13
27606 @subheading The @code{-stack-list-arguments} Command
27607 @findex -stack-list-arguments
27609 @subsubheading Synopsis
27612 -stack-list-arguments @var{print-values}
27613 [ @var{low-frame} @var{high-frame} ]
27616 Display a list of the arguments for the frames between @var{low-frame}
27617 and @var{high-frame} (inclusive). If @var{low-frame} and
27618 @var{high-frame} are not provided, list the arguments for the whole
27619 call stack. If the two arguments are equal, show the single frame
27620 at the corresponding level. It is an error if @var{low-frame} is
27621 larger than the actual number of frames. On the other hand,
27622 @var{high-frame} may be larger than the actual number of frames, in
27623 which case only existing frames will be returned.
27625 If @var{print-values} is 0 or @code{--no-values}, print only the names of
27626 the variables; if it is 1 or @code{--all-values}, print also their
27627 values; and if it is 2 or @code{--simple-values}, print the name,
27628 type and value for simple data types, and the name and type for arrays,
27629 structures and unions.
27631 Use of this command to obtain arguments in a single frame is
27632 deprecated in favor of the @samp{-stack-list-variables} command.
27634 @subsubheading @value{GDBN} Command
27636 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
27637 @samp{gdb_get_args} command which partially overlaps with the
27638 functionality of @samp{-stack-list-arguments}.
27640 @subsubheading Example
27647 frame=@{level="0",addr="0x00010734",func="callee4",
27648 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27649 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
27650 frame=@{level="1",addr="0x0001076c",func="callee3",
27651 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27652 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
27653 frame=@{level="2",addr="0x0001078c",func="callee2",
27654 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27655 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
27656 frame=@{level="3",addr="0x000107b4",func="callee1",
27657 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27658 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
27659 frame=@{level="4",addr="0x000107e0",func="main",
27660 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27661 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
27663 -stack-list-arguments 0
27666 frame=@{level="0",args=[]@},
27667 frame=@{level="1",args=[name="strarg"]@},
27668 frame=@{level="2",args=[name="intarg",name="strarg"]@},
27669 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
27670 frame=@{level="4",args=[]@}]
27672 -stack-list-arguments 1
27675 frame=@{level="0",args=[]@},
27677 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
27678 frame=@{level="2",args=[
27679 @{name="intarg",value="2"@},
27680 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
27681 @{frame=@{level="3",args=[
27682 @{name="intarg",value="2"@},
27683 @{name="strarg",value="0x11940 \"A string argument.\""@},
27684 @{name="fltarg",value="3.5"@}]@},
27685 frame=@{level="4",args=[]@}]
27687 -stack-list-arguments 0 2 2
27688 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
27690 -stack-list-arguments 1 2 2
27691 ^done,stack-args=[frame=@{level="2",
27692 args=[@{name="intarg",value="2"@},
27693 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
27697 @c @subheading -stack-list-exception-handlers
27700 @subheading The @code{-stack-list-frames} Command
27701 @findex -stack-list-frames
27703 @subsubheading Synopsis
27706 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
27709 List the frames currently on the stack. For each frame it displays the
27714 The frame number, 0 being the topmost frame, i.e., the innermost function.
27716 The @code{$pc} value for that frame.
27720 File name of the source file where the function lives.
27721 @item @var{fullname}
27722 The full file name of the source file where the function lives.
27724 Line number corresponding to the @code{$pc}.
27726 The shared library where this function is defined. This is only given
27727 if the frame's function is not known.
27730 If invoked without arguments, this command prints a backtrace for the
27731 whole stack. If given two integer arguments, it shows the frames whose
27732 levels are between the two arguments (inclusive). If the two arguments
27733 are equal, it shows the single frame at the corresponding level. It is
27734 an error if @var{low-frame} is larger than the actual number of
27735 frames. On the other hand, @var{high-frame} may be larger than the
27736 actual number of frames, in which case only existing frames will be returned.
27738 @subsubheading @value{GDBN} Command
27740 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
27742 @subsubheading Example
27744 Full stack backtrace:
27750 [frame=@{level="0",addr="0x0001076c",func="foo",
27751 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
27752 frame=@{level="1",addr="0x000107a4",func="foo",
27753 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27754 frame=@{level="2",addr="0x000107a4",func="foo",
27755 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27756 frame=@{level="3",addr="0x000107a4",func="foo",
27757 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27758 frame=@{level="4",addr="0x000107a4",func="foo",
27759 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27760 frame=@{level="5",addr="0x000107a4",func="foo",
27761 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27762 frame=@{level="6",addr="0x000107a4",func="foo",
27763 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27764 frame=@{level="7",addr="0x000107a4",func="foo",
27765 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27766 frame=@{level="8",addr="0x000107a4",func="foo",
27767 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27768 frame=@{level="9",addr="0x000107a4",func="foo",
27769 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27770 frame=@{level="10",addr="0x000107a4",func="foo",
27771 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27772 frame=@{level="11",addr="0x00010738",func="main",
27773 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
27777 Show frames between @var{low_frame} and @var{high_frame}:
27781 -stack-list-frames 3 5
27783 [frame=@{level="3",addr="0x000107a4",func="foo",
27784 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27785 frame=@{level="4",addr="0x000107a4",func="foo",
27786 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27787 frame=@{level="5",addr="0x000107a4",func="foo",
27788 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
27792 Show a single frame:
27796 -stack-list-frames 3 3
27798 [frame=@{level="3",addr="0x000107a4",func="foo",
27799 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
27804 @subheading The @code{-stack-list-locals} Command
27805 @findex -stack-list-locals
27807 @subsubheading Synopsis
27810 -stack-list-locals @var{print-values}
27813 Display the local variable names for the selected frame. If
27814 @var{print-values} is 0 or @code{--no-values}, print only the names of
27815 the variables; if it is 1 or @code{--all-values}, print also their
27816 values; and if it is 2 or @code{--simple-values}, print the name,
27817 type and value for simple data types, and the name and type for arrays,
27818 structures and unions. In this last case, a frontend can immediately
27819 display the value of simple data types and create variable objects for
27820 other data types when the user wishes to explore their values in
27823 This command is deprecated in favor of the
27824 @samp{-stack-list-variables} command.
27826 @subsubheading @value{GDBN} Command
27828 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
27830 @subsubheading Example
27834 -stack-list-locals 0
27835 ^done,locals=[name="A",name="B",name="C"]
27837 -stack-list-locals --all-values
27838 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
27839 @{name="C",value="@{1, 2, 3@}"@}]
27840 -stack-list-locals --simple-values
27841 ^done,locals=[@{name="A",type="int",value="1"@},
27842 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
27846 @subheading The @code{-stack-list-variables} Command
27847 @findex -stack-list-variables
27849 @subsubheading Synopsis
27852 -stack-list-variables @var{print-values}
27855 Display the names of local variables and function arguments for the selected frame. If
27856 @var{print-values} is 0 or @code{--no-values}, print only the names of
27857 the variables; if it is 1 or @code{--all-values}, print also their
27858 values; and if it is 2 or @code{--simple-values}, print the name,
27859 type and value for simple data types, and the name and type for arrays,
27860 structures and unions.
27862 @subsubheading Example
27866 -stack-list-variables --thread 1 --frame 0 --all-values
27867 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
27872 @subheading The @code{-stack-select-frame} Command
27873 @findex -stack-select-frame
27875 @subsubheading Synopsis
27878 -stack-select-frame @var{framenum}
27881 Change the selected frame. Select a different frame @var{framenum} on
27884 This command in deprecated in favor of passing the @samp{--frame}
27885 option to every command.
27887 @subsubheading @value{GDBN} Command
27889 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
27890 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
27892 @subsubheading Example
27896 -stack-select-frame 2
27901 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27902 @node GDB/MI Variable Objects
27903 @section @sc{gdb/mi} Variable Objects
27907 @subheading Motivation for Variable Objects in @sc{gdb/mi}
27909 For the implementation of a variable debugger window (locals, watched
27910 expressions, etc.), we are proposing the adaptation of the existing code
27911 used by @code{Insight}.
27913 The two main reasons for that are:
27917 It has been proven in practice (it is already on its second generation).
27920 It will shorten development time (needless to say how important it is
27924 The original interface was designed to be used by Tcl code, so it was
27925 slightly changed so it could be used through @sc{gdb/mi}. This section
27926 describes the @sc{gdb/mi} operations that will be available and gives some
27927 hints about their use.
27929 @emph{Note}: In addition to the set of operations described here, we
27930 expect the @sc{gui} implementation of a variable window to require, at
27931 least, the following operations:
27934 @item @code{-gdb-show} @code{output-radix}
27935 @item @code{-stack-list-arguments}
27936 @item @code{-stack-list-locals}
27937 @item @code{-stack-select-frame}
27942 @subheading Introduction to Variable Objects
27944 @cindex variable objects in @sc{gdb/mi}
27946 Variable objects are "object-oriented" MI interface for examining and
27947 changing values of expressions. Unlike some other MI interfaces that
27948 work with expressions, variable objects are specifically designed for
27949 simple and efficient presentation in the frontend. A variable object
27950 is identified by string name. When a variable object is created, the
27951 frontend specifies the expression for that variable object. The
27952 expression can be a simple variable, or it can be an arbitrary complex
27953 expression, and can even involve CPU registers. After creating a
27954 variable object, the frontend can invoke other variable object
27955 operations---for example to obtain or change the value of a variable
27956 object, or to change display format.
27958 Variable objects have hierarchical tree structure. Any variable object
27959 that corresponds to a composite type, such as structure in C, has
27960 a number of child variable objects, for example corresponding to each
27961 element of a structure. A child variable object can itself have
27962 children, recursively. Recursion ends when we reach
27963 leaf variable objects, which always have built-in types. Child variable
27964 objects are created only by explicit request, so if a frontend
27965 is not interested in the children of a particular variable object, no
27966 child will be created.
27968 For a leaf variable object it is possible to obtain its value as a
27969 string, or set the value from a string. String value can be also
27970 obtained for a non-leaf variable object, but it's generally a string
27971 that only indicates the type of the object, and does not list its
27972 contents. Assignment to a non-leaf variable object is not allowed.
27974 A frontend does not need to read the values of all variable objects each time
27975 the program stops. Instead, MI provides an update command that lists all
27976 variable objects whose values has changed since the last update
27977 operation. This considerably reduces the amount of data that must
27978 be transferred to the frontend. As noted above, children variable
27979 objects are created on demand, and only leaf variable objects have a
27980 real value. As result, gdb will read target memory only for leaf
27981 variables that frontend has created.
27983 The automatic update is not always desirable. For example, a frontend
27984 might want to keep a value of some expression for future reference,
27985 and never update it. For another example, fetching memory is
27986 relatively slow for embedded targets, so a frontend might want
27987 to disable automatic update for the variables that are either not
27988 visible on the screen, or ``closed''. This is possible using so
27989 called ``frozen variable objects''. Such variable objects are never
27990 implicitly updated.
27992 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
27993 fixed variable object, the expression is parsed when the variable
27994 object is created, including associating identifiers to specific
27995 variables. The meaning of expression never changes. For a floating
27996 variable object the values of variables whose names appear in the
27997 expressions are re-evaluated every time in the context of the current
27998 frame. Consider this example:
28003 struct work_state state;
28010 If a fixed variable object for the @code{state} variable is created in
28011 this function, and we enter the recursive call, the variable
28012 object will report the value of @code{state} in the top-level
28013 @code{do_work} invocation. On the other hand, a floating variable
28014 object will report the value of @code{state} in the current frame.
28016 If an expression specified when creating a fixed variable object
28017 refers to a local variable, the variable object becomes bound to the
28018 thread and frame in which the variable object is created. When such
28019 variable object is updated, @value{GDBN} makes sure that the
28020 thread/frame combination the variable object is bound to still exists,
28021 and re-evaluates the variable object in context of that thread/frame.
28023 The following is the complete set of @sc{gdb/mi} operations defined to
28024 access this functionality:
28026 @multitable @columnfractions .4 .6
28027 @item @strong{Operation}
28028 @tab @strong{Description}
28030 @item @code{-enable-pretty-printing}
28031 @tab enable Python-based pretty-printing
28032 @item @code{-var-create}
28033 @tab create a variable object
28034 @item @code{-var-delete}
28035 @tab delete the variable object and/or its children
28036 @item @code{-var-set-format}
28037 @tab set the display format of this variable
28038 @item @code{-var-show-format}
28039 @tab show the display format of this variable
28040 @item @code{-var-info-num-children}
28041 @tab tells how many children this object has
28042 @item @code{-var-list-children}
28043 @tab return a list of the object's children
28044 @item @code{-var-info-type}
28045 @tab show the type of this variable object
28046 @item @code{-var-info-expression}
28047 @tab print parent-relative expression that this variable object represents
28048 @item @code{-var-info-path-expression}
28049 @tab print full expression that this variable object represents
28050 @item @code{-var-show-attributes}
28051 @tab is this variable editable? does it exist here?
28052 @item @code{-var-evaluate-expression}
28053 @tab get the value of this variable
28054 @item @code{-var-assign}
28055 @tab set the value of this variable
28056 @item @code{-var-update}
28057 @tab update the variable and its children
28058 @item @code{-var-set-frozen}
28059 @tab set frozeness attribute
28060 @item @code{-var-set-update-range}
28061 @tab set range of children to display on update
28064 In the next subsection we describe each operation in detail and suggest
28065 how it can be used.
28067 @subheading Description And Use of Operations on Variable Objects
28069 @subheading The @code{-enable-pretty-printing} Command
28070 @findex -enable-pretty-printing
28073 -enable-pretty-printing
28076 @value{GDBN} allows Python-based visualizers to affect the output of the
28077 MI variable object commands. However, because there was no way to
28078 implement this in a fully backward-compatible way, a front end must
28079 request that this functionality be enabled.
28081 Once enabled, this feature cannot be disabled.
28083 Note that if Python support has not been compiled into @value{GDBN},
28084 this command will still succeed (and do nothing).
28086 This feature is currently (as of @value{GDBN} 7.0) experimental, and
28087 may work differently in future versions of @value{GDBN}.
28089 @subheading The @code{-var-create} Command
28090 @findex -var-create
28092 @subsubheading Synopsis
28095 -var-create @{@var{name} | "-"@}
28096 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
28099 This operation creates a variable object, which allows the monitoring of
28100 a variable, the result of an expression, a memory cell or a CPU
28103 The @var{name} parameter is the string by which the object can be
28104 referenced. It must be unique. If @samp{-} is specified, the varobj
28105 system will generate a string ``varNNNNNN'' automatically. It will be
28106 unique provided that one does not specify @var{name} of that format.
28107 The command fails if a duplicate name is found.
28109 The frame under which the expression should be evaluated can be
28110 specified by @var{frame-addr}. A @samp{*} indicates that the current
28111 frame should be used. A @samp{@@} indicates that a floating variable
28112 object must be created.
28114 @var{expression} is any expression valid on the current language set (must not
28115 begin with a @samp{*}), or one of the following:
28119 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
28122 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
28125 @samp{$@var{regname}} --- a CPU register name
28128 @cindex dynamic varobj
28129 A varobj's contents may be provided by a Python-based pretty-printer. In this
28130 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
28131 have slightly different semantics in some cases. If the
28132 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
28133 will never create a dynamic varobj. This ensures backward
28134 compatibility for existing clients.
28136 @subsubheading Result
28138 This operation returns attributes of the newly-created varobj. These
28143 The name of the varobj.
28146 The number of children of the varobj. This number is not necessarily
28147 reliable for a dynamic varobj. Instead, you must examine the
28148 @samp{has_more} attribute.
28151 The varobj's scalar value. For a varobj whose type is some sort of
28152 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
28153 will not be interesting.
28156 The varobj's type. This is a string representation of the type, as
28157 would be printed by the @value{GDBN} CLI.
28160 If a variable object is bound to a specific thread, then this is the
28161 thread's identifier.
28164 For a dynamic varobj, this indicates whether there appear to be any
28165 children available. For a non-dynamic varobj, this will be 0.
28168 This attribute will be present and have the value @samp{1} if the
28169 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28170 then this attribute will not be present.
28173 A dynamic varobj can supply a display hint to the front end. The
28174 value comes directly from the Python pretty-printer object's
28175 @code{display_hint} method. @xref{Pretty Printing API}.
28178 Typical output will look like this:
28181 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
28182 has_more="@var{has_more}"
28186 @subheading The @code{-var-delete} Command
28187 @findex -var-delete
28189 @subsubheading Synopsis
28192 -var-delete [ -c ] @var{name}
28195 Deletes a previously created variable object and all of its children.
28196 With the @samp{-c} option, just deletes the children.
28198 Returns an error if the object @var{name} is not found.
28201 @subheading The @code{-var-set-format} Command
28202 @findex -var-set-format
28204 @subsubheading Synopsis
28207 -var-set-format @var{name} @var{format-spec}
28210 Sets the output format for the value of the object @var{name} to be
28213 @anchor{-var-set-format}
28214 The syntax for the @var{format-spec} is as follows:
28217 @var{format-spec} @expansion{}
28218 @{binary | decimal | hexadecimal | octal | natural@}
28221 The natural format is the default format choosen automatically
28222 based on the variable type (like decimal for an @code{int}, hex
28223 for pointers, etc.).
28225 For a variable with children, the format is set only on the
28226 variable itself, and the children are not affected.
28228 @subheading The @code{-var-show-format} Command
28229 @findex -var-show-format
28231 @subsubheading Synopsis
28234 -var-show-format @var{name}
28237 Returns the format used to display the value of the object @var{name}.
28240 @var{format} @expansion{}
28245 @subheading The @code{-var-info-num-children} Command
28246 @findex -var-info-num-children
28248 @subsubheading Synopsis
28251 -var-info-num-children @var{name}
28254 Returns the number of children of a variable object @var{name}:
28260 Note that this number is not completely reliable for a dynamic varobj.
28261 It will return the current number of children, but more children may
28265 @subheading The @code{-var-list-children} Command
28266 @findex -var-list-children
28268 @subsubheading Synopsis
28271 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
28273 @anchor{-var-list-children}
28275 Return a list of the children of the specified variable object and
28276 create variable objects for them, if they do not already exist. With
28277 a single argument or if @var{print-values} has a value of 0 or
28278 @code{--no-values}, print only the names of the variables; if
28279 @var{print-values} is 1 or @code{--all-values}, also print their
28280 values; and if it is 2 or @code{--simple-values} print the name and
28281 value for simple data types and just the name for arrays, structures
28284 @var{from} and @var{to}, if specified, indicate the range of children
28285 to report. If @var{from} or @var{to} is less than zero, the range is
28286 reset and all children will be reported. Otherwise, children starting
28287 at @var{from} (zero-based) and up to and excluding @var{to} will be
28290 If a child range is requested, it will only affect the current call to
28291 @code{-var-list-children}, but not future calls to @code{-var-update}.
28292 For this, you must instead use @code{-var-set-update-range}. The
28293 intent of this approach is to enable a front end to implement any
28294 update approach it likes; for example, scrolling a view may cause the
28295 front end to request more children with @code{-var-list-children}, and
28296 then the front end could call @code{-var-set-update-range} with a
28297 different range to ensure that future updates are restricted to just
28300 For each child the following results are returned:
28305 Name of the variable object created for this child.
28308 The expression to be shown to the user by the front end to designate this child.
28309 For example this may be the name of a structure member.
28311 For a dynamic varobj, this value cannot be used to form an
28312 expression. There is no way to do this at all with a dynamic varobj.
28314 For C/C@t{++} structures there are several pseudo children returned to
28315 designate access qualifiers. For these pseudo children @var{exp} is
28316 @samp{public}, @samp{private}, or @samp{protected}. In this case the
28317 type and value are not present.
28319 A dynamic varobj will not report the access qualifying
28320 pseudo-children, regardless of the language. This information is not
28321 available at all with a dynamic varobj.
28324 Number of children this child has. For a dynamic varobj, this will be
28328 The type of the child.
28331 If values were requested, this is the value.
28334 If this variable object is associated with a thread, this is the thread id.
28335 Otherwise this result is not present.
28338 If the variable object is frozen, this variable will be present with a value of 1.
28341 The result may have its own attributes:
28345 A dynamic varobj can supply a display hint to the front end. The
28346 value comes directly from the Python pretty-printer object's
28347 @code{display_hint} method. @xref{Pretty Printing API}.
28350 This is an integer attribute which is nonzero if there are children
28351 remaining after the end of the selected range.
28354 @subsubheading Example
28358 -var-list-children n
28359 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28360 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
28362 -var-list-children --all-values n
28363 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28364 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
28368 @subheading The @code{-var-info-type} Command
28369 @findex -var-info-type
28371 @subsubheading Synopsis
28374 -var-info-type @var{name}
28377 Returns the type of the specified variable @var{name}. The type is
28378 returned as a string in the same format as it is output by the
28382 type=@var{typename}
28386 @subheading The @code{-var-info-expression} Command
28387 @findex -var-info-expression
28389 @subsubheading Synopsis
28392 -var-info-expression @var{name}
28395 Returns a string that is suitable for presenting this
28396 variable object in user interface. The string is generally
28397 not valid expression in the current language, and cannot be evaluated.
28399 For example, if @code{a} is an array, and variable object
28400 @code{A} was created for @code{a}, then we'll get this output:
28403 (gdb) -var-info-expression A.1
28404 ^done,lang="C",exp="1"
28408 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
28410 Note that the output of the @code{-var-list-children} command also
28411 includes those expressions, so the @code{-var-info-expression} command
28414 @subheading The @code{-var-info-path-expression} Command
28415 @findex -var-info-path-expression
28417 @subsubheading Synopsis
28420 -var-info-path-expression @var{name}
28423 Returns an expression that can be evaluated in the current
28424 context and will yield the same value that a variable object has.
28425 Compare this with the @code{-var-info-expression} command, which
28426 result can be used only for UI presentation. Typical use of
28427 the @code{-var-info-path-expression} command is creating a
28428 watchpoint from a variable object.
28430 This command is currently not valid for children of a dynamic varobj,
28431 and will give an error when invoked on one.
28433 For example, suppose @code{C} is a C@t{++} class, derived from class
28434 @code{Base}, and that the @code{Base} class has a member called
28435 @code{m_size}. Assume a variable @code{c} is has the type of
28436 @code{C} and a variable object @code{C} was created for variable
28437 @code{c}. Then, we'll get this output:
28439 (gdb) -var-info-path-expression C.Base.public.m_size
28440 ^done,path_expr=((Base)c).m_size)
28443 @subheading The @code{-var-show-attributes} Command
28444 @findex -var-show-attributes
28446 @subsubheading Synopsis
28449 -var-show-attributes @var{name}
28452 List attributes of the specified variable object @var{name}:
28455 status=@var{attr} [ ( ,@var{attr} )* ]
28459 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
28461 @subheading The @code{-var-evaluate-expression} Command
28462 @findex -var-evaluate-expression
28464 @subsubheading Synopsis
28467 -var-evaluate-expression [-f @var{format-spec}] @var{name}
28470 Evaluates the expression that is represented by the specified variable
28471 object and returns its value as a string. The format of the string
28472 can be specified with the @samp{-f} option. The possible values of
28473 this option are the same as for @code{-var-set-format}
28474 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
28475 the current display format will be used. The current display format
28476 can be changed using the @code{-var-set-format} command.
28482 Note that one must invoke @code{-var-list-children} for a variable
28483 before the value of a child variable can be evaluated.
28485 @subheading The @code{-var-assign} Command
28486 @findex -var-assign
28488 @subsubheading Synopsis
28491 -var-assign @var{name} @var{expression}
28494 Assigns the value of @var{expression} to the variable object specified
28495 by @var{name}. The object must be @samp{editable}. If the variable's
28496 value is altered by the assign, the variable will show up in any
28497 subsequent @code{-var-update} list.
28499 @subsubheading Example
28507 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
28511 @subheading The @code{-var-update} Command
28512 @findex -var-update
28514 @subsubheading Synopsis
28517 -var-update [@var{print-values}] @{@var{name} | "*"@}
28520 Reevaluate the expressions corresponding to the variable object
28521 @var{name} and all its direct and indirect children, and return the
28522 list of variable objects whose values have changed; @var{name} must
28523 be a root variable object. Here, ``changed'' means that the result of
28524 @code{-var-evaluate-expression} before and after the
28525 @code{-var-update} is different. If @samp{*} is used as the variable
28526 object names, all existing variable objects are updated, except
28527 for frozen ones (@pxref{-var-set-frozen}). The option
28528 @var{print-values} determines whether both names and values, or just
28529 names are printed. The possible values of this option are the same
28530 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
28531 recommended to use the @samp{--all-values} option, to reduce the
28532 number of MI commands needed on each program stop.
28534 With the @samp{*} parameter, if a variable object is bound to a
28535 currently running thread, it will not be updated, without any
28538 If @code{-var-set-update-range} was previously used on a varobj, then
28539 only the selected range of children will be reported.
28541 @code{-var-update} reports all the changed varobjs in a tuple named
28544 Each item in the change list is itself a tuple holding:
28548 The name of the varobj.
28551 If values were requested for this update, then this field will be
28552 present and will hold the value of the varobj.
28555 @anchor{-var-update}
28556 This field is a string which may take one of three values:
28560 The variable object's current value is valid.
28563 The variable object does not currently hold a valid value but it may
28564 hold one in the future if its associated expression comes back into
28568 The variable object no longer holds a valid value.
28569 This can occur when the executable file being debugged has changed,
28570 either through recompilation or by using the @value{GDBN} @code{file}
28571 command. The front end should normally choose to delete these variable
28575 In the future new values may be added to this list so the front should
28576 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
28579 This is only present if the varobj is still valid. If the type
28580 changed, then this will be the string @samp{true}; otherwise it will
28584 If the varobj's type changed, then this field will be present and will
28587 @item new_num_children
28588 For a dynamic varobj, if the number of children changed, or if the
28589 type changed, this will be the new number of children.
28591 The @samp{numchild} field in other varobj responses is generally not
28592 valid for a dynamic varobj -- it will show the number of children that
28593 @value{GDBN} knows about, but because dynamic varobjs lazily
28594 instantiate their children, this will not reflect the number of
28595 children which may be available.
28597 The @samp{new_num_children} attribute only reports changes to the
28598 number of children known by @value{GDBN}. This is the only way to
28599 detect whether an update has removed children (which necessarily can
28600 only happen at the end of the update range).
28603 The display hint, if any.
28606 This is an integer value, which will be 1 if there are more children
28607 available outside the varobj's update range.
28610 This attribute will be present and have the value @samp{1} if the
28611 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28612 then this attribute will not be present.
28615 If new children were added to a dynamic varobj within the selected
28616 update range (as set by @code{-var-set-update-range}), then they will
28617 be listed in this attribute.
28620 @subsubheading Example
28627 -var-update --all-values var1
28628 ^done,changelist=[@{name="var1",value="3",in_scope="true",
28629 type_changed="false"@}]
28633 @subheading The @code{-var-set-frozen} Command
28634 @findex -var-set-frozen
28635 @anchor{-var-set-frozen}
28637 @subsubheading Synopsis
28640 -var-set-frozen @var{name} @var{flag}
28643 Set the frozenness flag on the variable object @var{name}. The
28644 @var{flag} parameter should be either @samp{1} to make the variable
28645 frozen or @samp{0} to make it unfrozen. If a variable object is
28646 frozen, then neither itself, nor any of its children, are
28647 implicitly updated by @code{-var-update} of
28648 a parent variable or by @code{-var-update *}. Only
28649 @code{-var-update} of the variable itself will update its value and
28650 values of its children. After a variable object is unfrozen, it is
28651 implicitly updated by all subsequent @code{-var-update} operations.
28652 Unfreezing a variable does not update it, only subsequent
28653 @code{-var-update} does.
28655 @subsubheading Example
28659 -var-set-frozen V 1
28664 @subheading The @code{-var-set-update-range} command
28665 @findex -var-set-update-range
28666 @anchor{-var-set-update-range}
28668 @subsubheading Synopsis
28671 -var-set-update-range @var{name} @var{from} @var{to}
28674 Set the range of children to be returned by future invocations of
28675 @code{-var-update}.
28677 @var{from} and @var{to} indicate the range of children to report. If
28678 @var{from} or @var{to} is less than zero, the range is reset and all
28679 children will be reported. Otherwise, children starting at @var{from}
28680 (zero-based) and up to and excluding @var{to} will be reported.
28682 @subsubheading Example
28686 -var-set-update-range V 1 2
28690 @subheading The @code{-var-set-visualizer} command
28691 @findex -var-set-visualizer
28692 @anchor{-var-set-visualizer}
28694 @subsubheading Synopsis
28697 -var-set-visualizer @var{name} @var{visualizer}
28700 Set a visualizer for the variable object @var{name}.
28702 @var{visualizer} is the visualizer to use. The special value
28703 @samp{None} means to disable any visualizer in use.
28705 If not @samp{None}, @var{visualizer} must be a Python expression.
28706 This expression must evaluate to a callable object which accepts a
28707 single argument. @value{GDBN} will call this object with the value of
28708 the varobj @var{name} as an argument (this is done so that the same
28709 Python pretty-printing code can be used for both the CLI and MI).
28710 When called, this object must return an object which conforms to the
28711 pretty-printing interface (@pxref{Pretty Printing API}).
28713 The pre-defined function @code{gdb.default_visualizer} may be used to
28714 select a visualizer by following the built-in process
28715 (@pxref{Selecting Pretty-Printers}). This is done automatically when
28716 a varobj is created, and so ordinarily is not needed.
28718 This feature is only available if Python support is enabled. The MI
28719 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
28720 can be used to check this.
28722 @subsubheading Example
28724 Resetting the visualizer:
28728 -var-set-visualizer V None
28732 Reselecting the default (type-based) visualizer:
28736 -var-set-visualizer V gdb.default_visualizer
28740 Suppose @code{SomeClass} is a visualizer class. A lambda expression
28741 can be used to instantiate this class for a varobj:
28745 -var-set-visualizer V "lambda val: SomeClass()"
28749 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28750 @node GDB/MI Data Manipulation
28751 @section @sc{gdb/mi} Data Manipulation
28753 @cindex data manipulation, in @sc{gdb/mi}
28754 @cindex @sc{gdb/mi}, data manipulation
28755 This section describes the @sc{gdb/mi} commands that manipulate data:
28756 examine memory and registers, evaluate expressions, etc.
28758 @c REMOVED FROM THE INTERFACE.
28759 @c @subheading -data-assign
28760 @c Change the value of a program variable. Plenty of side effects.
28761 @c @subsubheading GDB Command
28763 @c @subsubheading Example
28766 @subheading The @code{-data-disassemble} Command
28767 @findex -data-disassemble
28769 @subsubheading Synopsis
28773 [ -s @var{start-addr} -e @var{end-addr} ]
28774 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
28782 @item @var{start-addr}
28783 is the beginning address (or @code{$pc})
28784 @item @var{end-addr}
28786 @item @var{filename}
28787 is the name of the file to disassemble
28788 @item @var{linenum}
28789 is the line number to disassemble around
28791 is the number of disassembly lines to be produced. If it is -1,
28792 the whole function will be disassembled, in case no @var{end-addr} is
28793 specified. If @var{end-addr} is specified as a non-zero value, and
28794 @var{lines} is lower than the number of disassembly lines between
28795 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
28796 displayed; if @var{lines} is higher than the number of lines between
28797 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
28800 is either 0 (meaning only disassembly), 1 (meaning mixed source and
28801 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
28802 mixed source and disassembly with raw opcodes).
28805 @subsubheading Result
28807 The output for each instruction is composed of four fields:
28816 Note that whatever included in the instruction field, is not manipulated
28817 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
28819 @subsubheading @value{GDBN} Command
28821 There's no direct mapping from this command to the CLI.
28823 @subsubheading Example
28825 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
28829 -data-disassemble -s $pc -e "$pc + 20" -- 0
28832 @{address="0x000107c0",func-name="main",offset="4",
28833 inst="mov 2, %o0"@},
28834 @{address="0x000107c4",func-name="main",offset="8",
28835 inst="sethi %hi(0x11800), %o2"@},
28836 @{address="0x000107c8",func-name="main",offset="12",
28837 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
28838 @{address="0x000107cc",func-name="main",offset="16",
28839 inst="sethi %hi(0x11800), %o2"@},
28840 @{address="0x000107d0",func-name="main",offset="20",
28841 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
28845 Disassemble the whole @code{main} function. Line 32 is part of
28849 -data-disassemble -f basics.c -l 32 -- 0
28851 @{address="0x000107bc",func-name="main",offset="0",
28852 inst="save %sp, -112, %sp"@},
28853 @{address="0x000107c0",func-name="main",offset="4",
28854 inst="mov 2, %o0"@},
28855 @{address="0x000107c4",func-name="main",offset="8",
28856 inst="sethi %hi(0x11800), %o2"@},
28858 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
28859 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
28863 Disassemble 3 instructions from the start of @code{main}:
28867 -data-disassemble -f basics.c -l 32 -n 3 -- 0
28869 @{address="0x000107bc",func-name="main",offset="0",
28870 inst="save %sp, -112, %sp"@},
28871 @{address="0x000107c0",func-name="main",offset="4",
28872 inst="mov 2, %o0"@},
28873 @{address="0x000107c4",func-name="main",offset="8",
28874 inst="sethi %hi(0x11800), %o2"@}]
28878 Disassemble 3 instructions from the start of @code{main} in mixed mode:
28882 -data-disassemble -f basics.c -l 32 -n 3 -- 1
28884 src_and_asm_line=@{line="31",
28885 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
28886 testsuite/gdb.mi/basics.c",line_asm_insn=[
28887 @{address="0x000107bc",func-name="main",offset="0",
28888 inst="save %sp, -112, %sp"@}]@},
28889 src_and_asm_line=@{line="32",
28890 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
28891 testsuite/gdb.mi/basics.c",line_asm_insn=[
28892 @{address="0x000107c0",func-name="main",offset="4",
28893 inst="mov 2, %o0"@},
28894 @{address="0x000107c4",func-name="main",offset="8",
28895 inst="sethi %hi(0x11800), %o2"@}]@}]
28900 @subheading The @code{-data-evaluate-expression} Command
28901 @findex -data-evaluate-expression
28903 @subsubheading Synopsis
28906 -data-evaluate-expression @var{expr}
28909 Evaluate @var{expr} as an expression. The expression could contain an
28910 inferior function call. The function call will execute synchronously.
28911 If the expression contains spaces, it must be enclosed in double quotes.
28913 @subsubheading @value{GDBN} Command
28915 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
28916 @samp{call}. In @code{gdbtk} only, there's a corresponding
28917 @samp{gdb_eval} command.
28919 @subsubheading Example
28921 In the following example, the numbers that precede the commands are the
28922 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
28923 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
28927 211-data-evaluate-expression A
28930 311-data-evaluate-expression &A
28931 311^done,value="0xefffeb7c"
28933 411-data-evaluate-expression A+3
28936 511-data-evaluate-expression "A + 3"
28942 @subheading The @code{-data-list-changed-registers} Command
28943 @findex -data-list-changed-registers
28945 @subsubheading Synopsis
28948 -data-list-changed-registers
28951 Display a list of the registers that have changed.
28953 @subsubheading @value{GDBN} Command
28955 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
28956 has the corresponding command @samp{gdb_changed_register_list}.
28958 @subsubheading Example
28960 On a PPC MBX board:
28968 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
28969 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
28972 -data-list-changed-registers
28973 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
28974 "10","11","13","14","15","16","17","18","19","20","21","22","23",
28975 "24","25","26","27","28","30","31","64","65","66","67","69"]
28980 @subheading The @code{-data-list-register-names} Command
28981 @findex -data-list-register-names
28983 @subsubheading Synopsis
28986 -data-list-register-names [ ( @var{regno} )+ ]
28989 Show a list of register names for the current target. If no arguments
28990 are given, it shows a list of the names of all the registers. If
28991 integer numbers are given as arguments, it will print a list of the
28992 names of the registers corresponding to the arguments. To ensure
28993 consistency between a register name and its number, the output list may
28994 include empty register names.
28996 @subsubheading @value{GDBN} Command
28998 @value{GDBN} does not have a command which corresponds to
28999 @samp{-data-list-register-names}. In @code{gdbtk} there is a
29000 corresponding command @samp{gdb_regnames}.
29002 @subsubheading Example
29004 For the PPC MBX board:
29007 -data-list-register-names
29008 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
29009 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
29010 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
29011 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
29012 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
29013 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
29014 "", "pc","ps","cr","lr","ctr","xer"]
29016 -data-list-register-names 1 2 3
29017 ^done,register-names=["r1","r2","r3"]
29021 @subheading The @code{-data-list-register-values} Command
29022 @findex -data-list-register-values
29024 @subsubheading Synopsis
29027 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
29030 Display the registers' contents. @var{fmt} is the format according to
29031 which the registers' contents are to be returned, followed by an optional
29032 list of numbers specifying the registers to display. A missing list of
29033 numbers indicates that the contents of all the registers must be returned.
29035 Allowed formats for @var{fmt} are:
29052 @subsubheading @value{GDBN} Command
29054 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
29055 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
29057 @subsubheading Example
29059 For a PPC MBX board (note: line breaks are for readability only, they
29060 don't appear in the actual output):
29064 -data-list-register-values r 64 65
29065 ^done,register-values=[@{number="64",value="0xfe00a300"@},
29066 @{number="65",value="0x00029002"@}]
29068 -data-list-register-values x
29069 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
29070 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
29071 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
29072 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
29073 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
29074 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
29075 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
29076 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
29077 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
29078 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
29079 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
29080 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
29081 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
29082 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
29083 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
29084 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
29085 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
29086 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
29087 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
29088 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
29089 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
29090 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
29091 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
29092 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
29093 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
29094 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
29095 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
29096 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
29097 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
29098 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
29099 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
29100 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
29101 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
29102 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
29103 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
29104 @{number="69",value="0x20002b03"@}]
29109 @subheading The @code{-data-read-memory} Command
29110 @findex -data-read-memory
29112 This command is deprecated, use @code{-data-read-memory-bytes} instead.
29114 @subsubheading Synopsis
29117 -data-read-memory [ -o @var{byte-offset} ]
29118 @var{address} @var{word-format} @var{word-size}
29119 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
29126 @item @var{address}
29127 An expression specifying the address of the first memory word to be
29128 read. Complex expressions containing embedded white space should be
29129 quoted using the C convention.
29131 @item @var{word-format}
29132 The format to be used to print the memory words. The notation is the
29133 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
29136 @item @var{word-size}
29137 The size of each memory word in bytes.
29139 @item @var{nr-rows}
29140 The number of rows in the output table.
29142 @item @var{nr-cols}
29143 The number of columns in the output table.
29146 If present, indicates that each row should include an @sc{ascii} dump. The
29147 value of @var{aschar} is used as a padding character when a byte is not a
29148 member of the printable @sc{ascii} character set (printable @sc{ascii}
29149 characters are those whose code is between 32 and 126, inclusively).
29151 @item @var{byte-offset}
29152 An offset to add to the @var{address} before fetching memory.
29155 This command displays memory contents as a table of @var{nr-rows} by
29156 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
29157 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
29158 (returned as @samp{total-bytes}). Should less than the requested number
29159 of bytes be returned by the target, the missing words are identified
29160 using @samp{N/A}. The number of bytes read from the target is returned
29161 in @samp{nr-bytes} and the starting address used to read memory in
29164 The address of the next/previous row or page is available in
29165 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
29168 @subsubheading @value{GDBN} Command
29170 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
29171 @samp{gdb_get_mem} memory read command.
29173 @subsubheading Example
29175 Read six bytes of memory starting at @code{bytes+6} but then offset by
29176 @code{-6} bytes. Format as three rows of two columns. One byte per
29177 word. Display each word in hex.
29181 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
29182 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
29183 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
29184 prev-page="0x0000138a",memory=[
29185 @{addr="0x00001390",data=["0x00","0x01"]@},
29186 @{addr="0x00001392",data=["0x02","0x03"]@},
29187 @{addr="0x00001394",data=["0x04","0x05"]@}]
29191 Read two bytes of memory starting at address @code{shorts + 64} and
29192 display as a single word formatted in decimal.
29196 5-data-read-memory shorts+64 d 2 1 1
29197 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
29198 next-row="0x00001512",prev-row="0x0000150e",
29199 next-page="0x00001512",prev-page="0x0000150e",memory=[
29200 @{addr="0x00001510",data=["128"]@}]
29204 Read thirty two bytes of memory starting at @code{bytes+16} and format
29205 as eight rows of four columns. Include a string encoding with @samp{x}
29206 used as the non-printable character.
29210 4-data-read-memory bytes+16 x 1 8 4 x
29211 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
29212 next-row="0x000013c0",prev-row="0x0000139c",
29213 next-page="0x000013c0",prev-page="0x00001380",memory=[
29214 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
29215 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
29216 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
29217 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
29218 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
29219 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
29220 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
29221 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
29225 @subheading The @code{-data-read-memory-bytes} Command
29226 @findex -data-read-memory-bytes
29228 @subsubheading Synopsis
29231 -data-read-memory-bytes [ -o @var{byte-offset} ]
29232 @var{address} @var{count}
29239 @item @var{address}
29240 An expression specifying the address of the first memory word to be
29241 read. Complex expressions containing embedded white space should be
29242 quoted using the C convention.
29245 The number of bytes to read. This should be an integer literal.
29247 @item @var{byte-offset}
29248 The offsets in bytes relative to @var{address} at which to start
29249 reading. This should be an integer literal. This option is provided
29250 so that a frontend is not required to first evaluate address and then
29251 perform address arithmetics itself.
29255 This command attempts to read all accessible memory regions in the
29256 specified range. First, all regions marked as unreadable in the memory
29257 map (if one is defined) will be skipped. @xref{Memory Region
29258 Attributes}. Second, @value{GDBN} will attempt to read the remaining
29259 regions. For each one, if reading full region results in an errors,
29260 @value{GDBN} will try to read a subset of the region.
29262 In general, every single byte in the region may be readable or not,
29263 and the only way to read every readable byte is to try a read at
29264 every address, which is not practical. Therefore, @value{GDBN} will
29265 attempt to read all accessible bytes at either beginning or the end
29266 of the region, using a binary division scheme. This heuristic works
29267 well for reading accross a memory map boundary. Note that if a region
29268 has a readable range that is neither at the beginning or the end,
29269 @value{GDBN} will not read it.
29271 The result record (@pxref{GDB/MI Result Records}) that is output of
29272 the command includes a field named @samp{memory} whose content is a
29273 list of tuples. Each tuple represent a successfully read memory block
29274 and has the following fields:
29278 The start address of the memory block, as hexadecimal literal.
29281 The end address of the memory block, as hexadecimal literal.
29284 The offset of the memory block, as hexadecimal literal, relative to
29285 the start address passed to @code{-data-read-memory-bytes}.
29288 The contents of the memory block, in hex.
29294 @subsubheading @value{GDBN} Command
29296 The corresponding @value{GDBN} command is @samp{x}.
29298 @subsubheading Example
29302 -data-read-memory-bytes &a 10
29303 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
29305 contents="01000000020000000300"@}]
29310 @subheading The @code{-data-write-memory-bytes} Command
29311 @findex -data-write-memory-bytes
29313 @subsubheading Synopsis
29316 -data-write-memory-bytes @var{address} @var{contents}
29323 @item @var{address}
29324 An expression specifying the address of the first memory word to be
29325 read. Complex expressions containing embedded white space should be
29326 quoted using the C convention.
29328 @item @var{contents}
29329 The hex-encoded bytes to write.
29333 @subsubheading @value{GDBN} Command
29335 There's no corresponding @value{GDBN} command.
29337 @subsubheading Example
29341 -data-write-memory-bytes &a "aabbccdd"
29347 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29348 @node GDB/MI Tracepoint Commands
29349 @section @sc{gdb/mi} Tracepoint Commands
29351 The commands defined in this section implement MI support for
29352 tracepoints. For detailed introduction, see @ref{Tracepoints}.
29354 @subheading The @code{-trace-find} Command
29355 @findex -trace-find
29357 @subsubheading Synopsis
29360 -trace-find @var{mode} [@var{parameters}@dots{}]
29363 Find a trace frame using criteria defined by @var{mode} and
29364 @var{parameters}. The following table lists permissible
29365 modes and their parameters. For details of operation, see @ref{tfind}.
29370 No parameters are required. Stops examining trace frames.
29373 An integer is required as parameter. Selects tracepoint frame with
29376 @item tracepoint-number
29377 An integer is required as parameter. Finds next
29378 trace frame that corresponds to tracepoint with the specified number.
29381 An address is required as parameter. Finds
29382 next trace frame that corresponds to any tracepoint at the specified
29385 @item pc-inside-range
29386 Two addresses are required as parameters. Finds next trace
29387 frame that corresponds to a tracepoint at an address inside the
29388 specified range. Both bounds are considered to be inside the range.
29390 @item pc-outside-range
29391 Two addresses are required as parameters. Finds
29392 next trace frame that corresponds to a tracepoint at an address outside
29393 the specified range. Both bounds are considered to be inside the range.
29396 Line specification is required as parameter. @xref{Specify Location}.
29397 Finds next trace frame that corresponds to a tracepoint at
29398 the specified location.
29402 If @samp{none} was passed as @var{mode}, the response does not
29403 have fields. Otherwise, the response may have the following fields:
29407 This field has either @samp{0} or @samp{1} as the value, depending
29408 on whether a matching tracepoint was found.
29411 The index of the found traceframe. This field is present iff
29412 the @samp{found} field has value of @samp{1}.
29415 The index of the found tracepoint. This field is present iff
29416 the @samp{found} field has value of @samp{1}.
29419 The information about the frame corresponding to the found trace
29420 frame. This field is present only if a trace frame was found.
29421 @xref{GDB/MI Frame Information}, for description of this field.
29425 @subsubheading @value{GDBN} Command
29427 The corresponding @value{GDBN} command is @samp{tfind}.
29429 @subheading -trace-define-variable
29430 @findex -trace-define-variable
29432 @subsubheading Synopsis
29435 -trace-define-variable @var{name} [ @var{value} ]
29438 Create trace variable @var{name} if it does not exist. If
29439 @var{value} is specified, sets the initial value of the specified
29440 trace variable to that value. Note that the @var{name} should start
29441 with the @samp{$} character.
29443 @subsubheading @value{GDBN} Command
29445 The corresponding @value{GDBN} command is @samp{tvariable}.
29447 @subheading -trace-list-variables
29448 @findex -trace-list-variables
29450 @subsubheading Synopsis
29453 -trace-list-variables
29456 Return a table of all defined trace variables. Each element of the
29457 table has the following fields:
29461 The name of the trace variable. This field is always present.
29464 The initial value. This is a 64-bit signed integer. This
29465 field is always present.
29468 The value the trace variable has at the moment. This is a 64-bit
29469 signed integer. This field is absent iff current value is
29470 not defined, for example if the trace was never run, or is
29475 @subsubheading @value{GDBN} Command
29477 The corresponding @value{GDBN} command is @samp{tvariables}.
29479 @subsubheading Example
29483 -trace-list-variables
29484 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
29485 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
29486 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
29487 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
29488 body=[variable=@{name="$trace_timestamp",initial="0"@}
29489 variable=@{name="$foo",initial="10",current="15"@}]@}
29493 @subheading -trace-save
29494 @findex -trace-save
29496 @subsubheading Synopsis
29499 -trace-save [-r ] @var{filename}
29502 Saves the collected trace data to @var{filename}. Without the
29503 @samp{-r} option, the data is downloaded from the target and saved
29504 in a local file. With the @samp{-r} option the target is asked
29505 to perform the save.
29507 @subsubheading @value{GDBN} Command
29509 The corresponding @value{GDBN} command is @samp{tsave}.
29512 @subheading -trace-start
29513 @findex -trace-start
29515 @subsubheading Synopsis
29521 Starts a tracing experiments. The result of this command does not
29524 @subsubheading @value{GDBN} Command
29526 The corresponding @value{GDBN} command is @samp{tstart}.
29528 @subheading -trace-status
29529 @findex -trace-status
29531 @subsubheading Synopsis
29537 Obtains the status of a tracing experiment. The result may include
29538 the following fields:
29543 May have a value of either @samp{0}, when no tracing operations are
29544 supported, @samp{1}, when all tracing operations are supported, or
29545 @samp{file} when examining trace file. In the latter case, examining
29546 of trace frame is possible but new tracing experiement cannot be
29547 started. This field is always present.
29550 May have a value of either @samp{0} or @samp{1} depending on whether
29551 tracing experiement is in progress on target. This field is present
29552 if @samp{supported} field is not @samp{0}.
29555 Report the reason why the tracing was stopped last time. This field
29556 may be absent iff tracing was never stopped on target yet. The
29557 value of @samp{request} means the tracing was stopped as result of
29558 the @code{-trace-stop} command. The value of @samp{overflow} means
29559 the tracing buffer is full. The value of @samp{disconnection} means
29560 tracing was automatically stopped when @value{GDBN} has disconnected.
29561 The value of @samp{passcount} means tracing was stopped when a
29562 tracepoint was passed a maximal number of times for that tracepoint.
29563 This field is present if @samp{supported} field is not @samp{0}.
29565 @item stopping-tracepoint
29566 The number of tracepoint whose passcount as exceeded. This field is
29567 present iff the @samp{stop-reason} field has the value of
29571 @itemx frames-created
29572 The @samp{frames} field is a count of the total number of trace frames
29573 in the trace buffer, while @samp{frames-created} is the total created
29574 during the run, including ones that were discarded, such as when a
29575 circular trace buffer filled up. Both fields are optional.
29579 These fields tell the current size of the tracing buffer and the
29580 remaining space. These fields are optional.
29583 The value of the circular trace buffer flag. @code{1} means that the
29584 trace buffer is circular and old trace frames will be discarded if
29585 necessary to make room, @code{0} means that the trace buffer is linear
29589 The value of the disconnected tracing flag. @code{1} means that
29590 tracing will continue after @value{GDBN} disconnects, @code{0} means
29591 that the trace run will stop.
29595 @subsubheading @value{GDBN} Command
29597 The corresponding @value{GDBN} command is @samp{tstatus}.
29599 @subheading -trace-stop
29600 @findex -trace-stop
29602 @subsubheading Synopsis
29608 Stops a tracing experiment. The result of this command has the same
29609 fields as @code{-trace-status}, except that the @samp{supported} and
29610 @samp{running} fields are not output.
29612 @subsubheading @value{GDBN} Command
29614 The corresponding @value{GDBN} command is @samp{tstop}.
29617 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29618 @node GDB/MI Symbol Query
29619 @section @sc{gdb/mi} Symbol Query Commands
29623 @subheading The @code{-symbol-info-address} Command
29624 @findex -symbol-info-address
29626 @subsubheading Synopsis
29629 -symbol-info-address @var{symbol}
29632 Describe where @var{symbol} is stored.
29634 @subsubheading @value{GDBN} Command
29636 The corresponding @value{GDBN} command is @samp{info address}.
29638 @subsubheading Example
29642 @subheading The @code{-symbol-info-file} Command
29643 @findex -symbol-info-file
29645 @subsubheading Synopsis
29651 Show the file for the symbol.
29653 @subsubheading @value{GDBN} Command
29655 There's no equivalent @value{GDBN} command. @code{gdbtk} has
29656 @samp{gdb_find_file}.
29658 @subsubheading Example
29662 @subheading The @code{-symbol-info-function} Command
29663 @findex -symbol-info-function
29665 @subsubheading Synopsis
29668 -symbol-info-function
29671 Show which function the symbol lives in.
29673 @subsubheading @value{GDBN} Command
29675 @samp{gdb_get_function} in @code{gdbtk}.
29677 @subsubheading Example
29681 @subheading The @code{-symbol-info-line} Command
29682 @findex -symbol-info-line
29684 @subsubheading Synopsis
29690 Show the core addresses of the code for a source line.
29692 @subsubheading @value{GDBN} Command
29694 The corresponding @value{GDBN} command is @samp{info line}.
29695 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
29697 @subsubheading Example
29701 @subheading The @code{-symbol-info-symbol} Command
29702 @findex -symbol-info-symbol
29704 @subsubheading Synopsis
29707 -symbol-info-symbol @var{addr}
29710 Describe what symbol is at location @var{addr}.
29712 @subsubheading @value{GDBN} Command
29714 The corresponding @value{GDBN} command is @samp{info symbol}.
29716 @subsubheading Example
29720 @subheading The @code{-symbol-list-functions} Command
29721 @findex -symbol-list-functions
29723 @subsubheading Synopsis
29726 -symbol-list-functions
29729 List the functions in the executable.
29731 @subsubheading @value{GDBN} Command
29733 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
29734 @samp{gdb_search} in @code{gdbtk}.
29736 @subsubheading Example
29741 @subheading The @code{-symbol-list-lines} Command
29742 @findex -symbol-list-lines
29744 @subsubheading Synopsis
29747 -symbol-list-lines @var{filename}
29750 Print the list of lines that contain code and their associated program
29751 addresses for the given source filename. The entries are sorted in
29752 ascending PC order.
29754 @subsubheading @value{GDBN} Command
29756 There is no corresponding @value{GDBN} command.
29758 @subsubheading Example
29761 -symbol-list-lines basics.c
29762 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
29768 @subheading The @code{-symbol-list-types} Command
29769 @findex -symbol-list-types
29771 @subsubheading Synopsis
29777 List all the type names.
29779 @subsubheading @value{GDBN} Command
29781 The corresponding commands are @samp{info types} in @value{GDBN},
29782 @samp{gdb_search} in @code{gdbtk}.
29784 @subsubheading Example
29788 @subheading The @code{-symbol-list-variables} Command
29789 @findex -symbol-list-variables
29791 @subsubheading Synopsis
29794 -symbol-list-variables
29797 List all the global and static variable names.
29799 @subsubheading @value{GDBN} Command
29801 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
29803 @subsubheading Example
29807 @subheading The @code{-symbol-locate} Command
29808 @findex -symbol-locate
29810 @subsubheading Synopsis
29816 @subsubheading @value{GDBN} Command
29818 @samp{gdb_loc} in @code{gdbtk}.
29820 @subsubheading Example
29824 @subheading The @code{-symbol-type} Command
29825 @findex -symbol-type
29827 @subsubheading Synopsis
29830 -symbol-type @var{variable}
29833 Show type of @var{variable}.
29835 @subsubheading @value{GDBN} Command
29837 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
29838 @samp{gdb_obj_variable}.
29840 @subsubheading Example
29845 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29846 @node GDB/MI File Commands
29847 @section @sc{gdb/mi} File Commands
29849 This section describes the GDB/MI commands to specify executable file names
29850 and to read in and obtain symbol table information.
29852 @subheading The @code{-file-exec-and-symbols} Command
29853 @findex -file-exec-and-symbols
29855 @subsubheading Synopsis
29858 -file-exec-and-symbols @var{file}
29861 Specify the executable file to be debugged. This file is the one from
29862 which the symbol table is also read. If no file is specified, the
29863 command clears the executable and symbol information. If breakpoints
29864 are set when using this command with no arguments, @value{GDBN} will produce
29865 error messages. Otherwise, no output is produced, except a completion
29868 @subsubheading @value{GDBN} Command
29870 The corresponding @value{GDBN} command is @samp{file}.
29872 @subsubheading Example
29876 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
29882 @subheading The @code{-file-exec-file} Command
29883 @findex -file-exec-file
29885 @subsubheading Synopsis
29888 -file-exec-file @var{file}
29891 Specify the executable file to be debugged. Unlike
29892 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
29893 from this file. If used without argument, @value{GDBN} clears the information
29894 about the executable file. No output is produced, except a completion
29897 @subsubheading @value{GDBN} Command
29899 The corresponding @value{GDBN} command is @samp{exec-file}.
29901 @subsubheading Example
29905 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
29912 @subheading The @code{-file-list-exec-sections} Command
29913 @findex -file-list-exec-sections
29915 @subsubheading Synopsis
29918 -file-list-exec-sections
29921 List the sections of the current executable file.
29923 @subsubheading @value{GDBN} Command
29925 The @value{GDBN} command @samp{info file} shows, among the rest, the same
29926 information as this command. @code{gdbtk} has a corresponding command
29927 @samp{gdb_load_info}.
29929 @subsubheading Example
29934 @subheading The @code{-file-list-exec-source-file} Command
29935 @findex -file-list-exec-source-file
29937 @subsubheading Synopsis
29940 -file-list-exec-source-file
29943 List the line number, the current source file, and the absolute path
29944 to the current source file for the current executable. The macro
29945 information field has a value of @samp{1} or @samp{0} depending on
29946 whether or not the file includes preprocessor macro information.
29948 @subsubheading @value{GDBN} Command
29950 The @value{GDBN} equivalent is @samp{info source}
29952 @subsubheading Example
29956 123-file-list-exec-source-file
29957 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
29962 @subheading The @code{-file-list-exec-source-files} Command
29963 @findex -file-list-exec-source-files
29965 @subsubheading Synopsis
29968 -file-list-exec-source-files
29971 List the source files for the current executable.
29973 It will always output the filename, but only when @value{GDBN} can find
29974 the absolute file name of a source file, will it output the fullname.
29976 @subsubheading @value{GDBN} Command
29978 The @value{GDBN} equivalent is @samp{info sources}.
29979 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
29981 @subsubheading Example
29984 -file-list-exec-source-files
29986 @{file=foo.c,fullname=/home/foo.c@},
29987 @{file=/home/bar.c,fullname=/home/bar.c@},
29988 @{file=gdb_could_not_find_fullpath.c@}]
29993 @subheading The @code{-file-list-shared-libraries} Command
29994 @findex -file-list-shared-libraries
29996 @subsubheading Synopsis
29999 -file-list-shared-libraries
30002 List the shared libraries in the program.
30004 @subsubheading @value{GDBN} Command
30006 The corresponding @value{GDBN} command is @samp{info shared}.
30008 @subsubheading Example
30012 @subheading The @code{-file-list-symbol-files} Command
30013 @findex -file-list-symbol-files
30015 @subsubheading Synopsis
30018 -file-list-symbol-files
30023 @subsubheading @value{GDBN} Command
30025 The corresponding @value{GDBN} command is @samp{info file} (part of it).
30027 @subsubheading Example
30032 @subheading The @code{-file-symbol-file} Command
30033 @findex -file-symbol-file
30035 @subsubheading Synopsis
30038 -file-symbol-file @var{file}
30041 Read symbol table info from the specified @var{file} argument. When
30042 used without arguments, clears @value{GDBN}'s symbol table info. No output is
30043 produced, except for a completion notification.
30045 @subsubheading @value{GDBN} Command
30047 The corresponding @value{GDBN} command is @samp{symbol-file}.
30049 @subsubheading Example
30053 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30059 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30060 @node GDB/MI Memory Overlay Commands
30061 @section @sc{gdb/mi} Memory Overlay Commands
30063 The memory overlay commands are not implemented.
30065 @c @subheading -overlay-auto
30067 @c @subheading -overlay-list-mapping-state
30069 @c @subheading -overlay-list-overlays
30071 @c @subheading -overlay-map
30073 @c @subheading -overlay-off
30075 @c @subheading -overlay-on
30077 @c @subheading -overlay-unmap
30079 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30080 @node GDB/MI Signal Handling Commands
30081 @section @sc{gdb/mi} Signal Handling Commands
30083 Signal handling commands are not implemented.
30085 @c @subheading -signal-handle
30087 @c @subheading -signal-list-handle-actions
30089 @c @subheading -signal-list-signal-types
30093 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30094 @node GDB/MI Target Manipulation
30095 @section @sc{gdb/mi} Target Manipulation Commands
30098 @subheading The @code{-target-attach} Command
30099 @findex -target-attach
30101 @subsubheading Synopsis
30104 -target-attach @var{pid} | @var{gid} | @var{file}
30107 Attach to a process @var{pid} or a file @var{file} outside of
30108 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
30109 group, the id previously returned by
30110 @samp{-list-thread-groups --available} must be used.
30112 @subsubheading @value{GDBN} Command
30114 The corresponding @value{GDBN} command is @samp{attach}.
30116 @subsubheading Example
30120 =thread-created,id="1"
30121 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
30127 @subheading The @code{-target-compare-sections} Command
30128 @findex -target-compare-sections
30130 @subsubheading Synopsis
30133 -target-compare-sections [ @var{section} ]
30136 Compare data of section @var{section} on target to the exec file.
30137 Without the argument, all sections are compared.
30139 @subsubheading @value{GDBN} Command
30141 The @value{GDBN} equivalent is @samp{compare-sections}.
30143 @subsubheading Example
30148 @subheading The @code{-target-detach} Command
30149 @findex -target-detach
30151 @subsubheading Synopsis
30154 -target-detach [ @var{pid} | @var{gid} ]
30157 Detach from the remote target which normally resumes its execution.
30158 If either @var{pid} or @var{gid} is specified, detaches from either
30159 the specified process, or specified thread group. There's no output.
30161 @subsubheading @value{GDBN} Command
30163 The corresponding @value{GDBN} command is @samp{detach}.
30165 @subsubheading Example
30175 @subheading The @code{-target-disconnect} Command
30176 @findex -target-disconnect
30178 @subsubheading Synopsis
30184 Disconnect from the remote target. There's no output and the target is
30185 generally not resumed.
30187 @subsubheading @value{GDBN} Command
30189 The corresponding @value{GDBN} command is @samp{disconnect}.
30191 @subsubheading Example
30201 @subheading The @code{-target-download} Command
30202 @findex -target-download
30204 @subsubheading Synopsis
30210 Loads the executable onto the remote target.
30211 It prints out an update message every half second, which includes the fields:
30215 The name of the section.
30217 The size of what has been sent so far for that section.
30219 The size of the section.
30221 The total size of what was sent so far (the current and the previous sections).
30223 The size of the overall executable to download.
30227 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
30228 @sc{gdb/mi} Output Syntax}).
30230 In addition, it prints the name and size of the sections, as they are
30231 downloaded. These messages include the following fields:
30235 The name of the section.
30237 The size of the section.
30239 The size of the overall executable to download.
30243 At the end, a summary is printed.
30245 @subsubheading @value{GDBN} Command
30247 The corresponding @value{GDBN} command is @samp{load}.
30249 @subsubheading Example
30251 Note: each status message appears on a single line. Here the messages
30252 have been broken down so that they can fit onto a page.
30257 +download,@{section=".text",section-size="6668",total-size="9880"@}
30258 +download,@{section=".text",section-sent="512",section-size="6668",
30259 total-sent="512",total-size="9880"@}
30260 +download,@{section=".text",section-sent="1024",section-size="6668",
30261 total-sent="1024",total-size="9880"@}
30262 +download,@{section=".text",section-sent="1536",section-size="6668",
30263 total-sent="1536",total-size="9880"@}
30264 +download,@{section=".text",section-sent="2048",section-size="6668",
30265 total-sent="2048",total-size="9880"@}
30266 +download,@{section=".text",section-sent="2560",section-size="6668",
30267 total-sent="2560",total-size="9880"@}
30268 +download,@{section=".text",section-sent="3072",section-size="6668",
30269 total-sent="3072",total-size="9880"@}
30270 +download,@{section=".text",section-sent="3584",section-size="6668",
30271 total-sent="3584",total-size="9880"@}
30272 +download,@{section=".text",section-sent="4096",section-size="6668",
30273 total-sent="4096",total-size="9880"@}
30274 +download,@{section=".text",section-sent="4608",section-size="6668",
30275 total-sent="4608",total-size="9880"@}
30276 +download,@{section=".text",section-sent="5120",section-size="6668",
30277 total-sent="5120",total-size="9880"@}
30278 +download,@{section=".text",section-sent="5632",section-size="6668",
30279 total-sent="5632",total-size="9880"@}
30280 +download,@{section=".text",section-sent="6144",section-size="6668",
30281 total-sent="6144",total-size="9880"@}
30282 +download,@{section=".text",section-sent="6656",section-size="6668",
30283 total-sent="6656",total-size="9880"@}
30284 +download,@{section=".init",section-size="28",total-size="9880"@}
30285 +download,@{section=".fini",section-size="28",total-size="9880"@}
30286 +download,@{section=".data",section-size="3156",total-size="9880"@}
30287 +download,@{section=".data",section-sent="512",section-size="3156",
30288 total-sent="7236",total-size="9880"@}
30289 +download,@{section=".data",section-sent="1024",section-size="3156",
30290 total-sent="7748",total-size="9880"@}
30291 +download,@{section=".data",section-sent="1536",section-size="3156",
30292 total-sent="8260",total-size="9880"@}
30293 +download,@{section=".data",section-sent="2048",section-size="3156",
30294 total-sent="8772",total-size="9880"@}
30295 +download,@{section=".data",section-sent="2560",section-size="3156",
30296 total-sent="9284",total-size="9880"@}
30297 +download,@{section=".data",section-sent="3072",section-size="3156",
30298 total-sent="9796",total-size="9880"@}
30299 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
30306 @subheading The @code{-target-exec-status} Command
30307 @findex -target-exec-status
30309 @subsubheading Synopsis
30312 -target-exec-status
30315 Provide information on the state of the target (whether it is running or
30316 not, for instance).
30318 @subsubheading @value{GDBN} Command
30320 There's no equivalent @value{GDBN} command.
30322 @subsubheading Example
30326 @subheading The @code{-target-list-available-targets} Command
30327 @findex -target-list-available-targets
30329 @subsubheading Synopsis
30332 -target-list-available-targets
30335 List the possible targets to connect to.
30337 @subsubheading @value{GDBN} Command
30339 The corresponding @value{GDBN} command is @samp{help target}.
30341 @subsubheading Example
30345 @subheading The @code{-target-list-current-targets} Command
30346 @findex -target-list-current-targets
30348 @subsubheading Synopsis
30351 -target-list-current-targets
30354 Describe the current target.
30356 @subsubheading @value{GDBN} Command
30358 The corresponding information is printed by @samp{info file} (among
30361 @subsubheading Example
30365 @subheading The @code{-target-list-parameters} Command
30366 @findex -target-list-parameters
30368 @subsubheading Synopsis
30371 -target-list-parameters
30377 @subsubheading @value{GDBN} Command
30381 @subsubheading Example
30385 @subheading The @code{-target-select} Command
30386 @findex -target-select
30388 @subsubheading Synopsis
30391 -target-select @var{type} @var{parameters @dots{}}
30394 Connect @value{GDBN} to the remote target. This command takes two args:
30398 The type of target, for instance @samp{remote}, etc.
30399 @item @var{parameters}
30400 Device names, host names and the like. @xref{Target Commands, ,
30401 Commands for Managing Targets}, for more details.
30404 The output is a connection notification, followed by the address at
30405 which the target program is, in the following form:
30408 ^connected,addr="@var{address}",func="@var{function name}",
30409 args=[@var{arg list}]
30412 @subsubheading @value{GDBN} Command
30414 The corresponding @value{GDBN} command is @samp{target}.
30416 @subsubheading Example
30420 -target-select remote /dev/ttya
30421 ^connected,addr="0xfe00a300",func="??",args=[]
30425 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30426 @node GDB/MI File Transfer Commands
30427 @section @sc{gdb/mi} File Transfer Commands
30430 @subheading The @code{-target-file-put} Command
30431 @findex -target-file-put
30433 @subsubheading Synopsis
30436 -target-file-put @var{hostfile} @var{targetfile}
30439 Copy file @var{hostfile} from the host system (the machine running
30440 @value{GDBN}) to @var{targetfile} on the target system.
30442 @subsubheading @value{GDBN} Command
30444 The corresponding @value{GDBN} command is @samp{remote put}.
30446 @subsubheading Example
30450 -target-file-put localfile remotefile
30456 @subheading The @code{-target-file-get} Command
30457 @findex -target-file-get
30459 @subsubheading Synopsis
30462 -target-file-get @var{targetfile} @var{hostfile}
30465 Copy file @var{targetfile} from the target system to @var{hostfile}
30466 on the host system.
30468 @subsubheading @value{GDBN} Command
30470 The corresponding @value{GDBN} command is @samp{remote get}.
30472 @subsubheading Example
30476 -target-file-get remotefile localfile
30482 @subheading The @code{-target-file-delete} Command
30483 @findex -target-file-delete
30485 @subsubheading Synopsis
30488 -target-file-delete @var{targetfile}
30491 Delete @var{targetfile} from the target system.
30493 @subsubheading @value{GDBN} Command
30495 The corresponding @value{GDBN} command is @samp{remote delete}.
30497 @subsubheading Example
30501 -target-file-delete remotefile
30507 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30508 @node GDB/MI Miscellaneous Commands
30509 @section Miscellaneous @sc{gdb/mi} Commands
30511 @c @subheading -gdb-complete
30513 @subheading The @code{-gdb-exit} Command
30516 @subsubheading Synopsis
30522 Exit @value{GDBN} immediately.
30524 @subsubheading @value{GDBN} Command
30526 Approximately corresponds to @samp{quit}.
30528 @subsubheading Example
30538 @subheading The @code{-exec-abort} Command
30539 @findex -exec-abort
30541 @subsubheading Synopsis
30547 Kill the inferior running program.
30549 @subsubheading @value{GDBN} Command
30551 The corresponding @value{GDBN} command is @samp{kill}.
30553 @subsubheading Example
30558 @subheading The @code{-gdb-set} Command
30561 @subsubheading Synopsis
30567 Set an internal @value{GDBN} variable.
30568 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
30570 @subsubheading @value{GDBN} Command
30572 The corresponding @value{GDBN} command is @samp{set}.
30574 @subsubheading Example
30584 @subheading The @code{-gdb-show} Command
30587 @subsubheading Synopsis
30593 Show the current value of a @value{GDBN} variable.
30595 @subsubheading @value{GDBN} Command
30597 The corresponding @value{GDBN} command is @samp{show}.
30599 @subsubheading Example
30608 @c @subheading -gdb-source
30611 @subheading The @code{-gdb-version} Command
30612 @findex -gdb-version
30614 @subsubheading Synopsis
30620 Show version information for @value{GDBN}. Used mostly in testing.
30622 @subsubheading @value{GDBN} Command
30624 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
30625 default shows this information when you start an interactive session.
30627 @subsubheading Example
30629 @c This example modifies the actual output from GDB to avoid overfull
30635 ~Copyright 2000 Free Software Foundation, Inc.
30636 ~GDB is free software, covered by the GNU General Public License, and
30637 ~you are welcome to change it and/or distribute copies of it under
30638 ~ certain conditions.
30639 ~Type "show copying" to see the conditions.
30640 ~There is absolutely no warranty for GDB. Type "show warranty" for
30642 ~This GDB was configured as
30643 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
30648 @subheading The @code{-list-features} Command
30649 @findex -list-features
30651 Returns a list of particular features of the MI protocol that
30652 this version of gdb implements. A feature can be a command,
30653 or a new field in an output of some command, or even an
30654 important bugfix. While a frontend can sometimes detect presence
30655 of a feature at runtime, it is easier to perform detection at debugger
30658 The command returns a list of strings, with each string naming an
30659 available feature. Each returned string is just a name, it does not
30660 have any internal structure. The list of possible feature names
30666 (gdb) -list-features
30667 ^done,result=["feature1","feature2"]
30670 The current list of features is:
30673 @item frozen-varobjs
30674 Indicates support for the @code{-var-set-frozen} command, as well
30675 as possible presense of the @code{frozen} field in the output
30676 of @code{-varobj-create}.
30677 @item pending-breakpoints
30678 Indicates support for the @option{-f} option to the @code{-break-insert}
30681 Indicates Python scripting support, Python-based
30682 pretty-printing commands, and possible presence of the
30683 @samp{display_hint} field in the output of @code{-var-list-children}
30685 Indicates support for the @code{-thread-info} command.
30686 @item data-read-memory-bytes
30687 Indicates support for the @code{-data-read-memory-bytes} and the
30688 @code{-data-write-memory-bytes} commands.
30689 @item breakpoint-notifications
30690 Indicates that changes to breakpoints and breakpoints created via the
30691 CLI will be announced via async records.
30692 @item ada-task-info
30693 Indicates support for the @code{-ada-task-info} command.
30696 @subheading The @code{-list-target-features} Command
30697 @findex -list-target-features
30699 Returns a list of particular features that are supported by the
30700 target. Those features affect the permitted MI commands, but
30701 unlike the features reported by the @code{-list-features} command, the
30702 features depend on which target GDB is using at the moment. Whenever
30703 a target can change, due to commands such as @code{-target-select},
30704 @code{-target-attach} or @code{-exec-run}, the list of target features
30705 may change, and the frontend should obtain it again.
30709 (gdb) -list-features
30710 ^done,result=["async"]
30713 The current list of features is:
30717 Indicates that the target is capable of asynchronous command
30718 execution, which means that @value{GDBN} will accept further commands
30719 while the target is running.
30722 Indicates that the target is capable of reverse execution.
30723 @xref{Reverse Execution}, for more information.
30727 @subheading The @code{-list-thread-groups} Command
30728 @findex -list-thread-groups
30730 @subheading Synopsis
30733 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
30736 Lists thread groups (@pxref{Thread groups}). When a single thread
30737 group is passed as the argument, lists the children of that group.
30738 When several thread group are passed, lists information about those
30739 thread groups. Without any parameters, lists information about all
30740 top-level thread groups.
30742 Normally, thread groups that are being debugged are reported.
30743 With the @samp{--available} option, @value{GDBN} reports thread groups
30744 available on the target.
30746 The output of this command may have either a @samp{threads} result or
30747 a @samp{groups} result. The @samp{thread} result has a list of tuples
30748 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
30749 Information}). The @samp{groups} result has a list of tuples as value,
30750 each tuple describing a thread group. If top-level groups are
30751 requested (that is, no parameter is passed), or when several groups
30752 are passed, the output always has a @samp{groups} result. The format
30753 of the @samp{group} result is described below.
30755 To reduce the number of roundtrips it's possible to list thread groups
30756 together with their children, by passing the @samp{--recurse} option
30757 and the recursion depth. Presently, only recursion depth of 1 is
30758 permitted. If this option is present, then every reported thread group
30759 will also include its children, either as @samp{group} or
30760 @samp{threads} field.
30762 In general, any combination of option and parameters is permitted, with
30763 the following caveats:
30767 When a single thread group is passed, the output will typically
30768 be the @samp{threads} result. Because threads may not contain
30769 anything, the @samp{recurse} option will be ignored.
30772 When the @samp{--available} option is passed, limited information may
30773 be available. In particular, the list of threads of a process might
30774 be inaccessible. Further, specifying specific thread groups might
30775 not give any performance advantage over listing all thread groups.
30776 The frontend should assume that @samp{-list-thread-groups --available}
30777 is always an expensive operation and cache the results.
30781 The @samp{groups} result is a list of tuples, where each tuple may
30782 have the following fields:
30786 Identifier of the thread group. This field is always present.
30787 The identifier is an opaque string; frontends should not try to
30788 convert it to an integer, even though it might look like one.
30791 The type of the thread group. At present, only @samp{process} is a
30795 The target-specific process identifier. This field is only present
30796 for thread groups of type @samp{process} and only if the process exists.
30799 The number of children this thread group has. This field may be
30800 absent for an available thread group.
30803 This field has a list of tuples as value, each tuple describing a
30804 thread. It may be present if the @samp{--recurse} option is
30805 specified, and it's actually possible to obtain the threads.
30808 This field is a list of integers, each identifying a core that one
30809 thread of the group is running on. This field may be absent if
30810 such information is not available.
30813 The name of the executable file that corresponds to this thread group.
30814 The field is only present for thread groups of type @samp{process},
30815 and only if there is a corresponding executable file.
30819 @subheading Example
30823 -list-thread-groups
30824 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
30825 -list-thread-groups 17
30826 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
30827 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
30828 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
30829 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
30830 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
30831 -list-thread-groups --available
30832 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
30833 -list-thread-groups --available --recurse 1
30834 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
30835 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
30836 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
30837 -list-thread-groups --available --recurse 1 17 18
30838 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
30839 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
30840 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
30844 @subheading The @code{-add-inferior} Command
30845 @findex -add-inferior
30847 @subheading Synopsis
30853 Creates a new inferior (@pxref{Inferiors and Programs}). The created
30854 inferior is not associated with any executable. Such association may
30855 be established with the @samp{-file-exec-and-symbols} command
30856 (@pxref{GDB/MI File Commands}). The command response has a single
30857 field, @samp{thread-group}, whose value is the identifier of the
30858 thread group corresponding to the new inferior.
30860 @subheading Example
30865 ^done,thread-group="i3"
30868 @subheading The @code{-interpreter-exec} Command
30869 @findex -interpreter-exec
30871 @subheading Synopsis
30874 -interpreter-exec @var{interpreter} @var{command}
30876 @anchor{-interpreter-exec}
30878 Execute the specified @var{command} in the given @var{interpreter}.
30880 @subheading @value{GDBN} Command
30882 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
30884 @subheading Example
30888 -interpreter-exec console "break main"
30889 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
30890 &"During symbol reading, bad structure-type format.\n"
30891 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
30896 @subheading The @code{-inferior-tty-set} Command
30897 @findex -inferior-tty-set
30899 @subheading Synopsis
30902 -inferior-tty-set /dev/pts/1
30905 Set terminal for future runs of the program being debugged.
30907 @subheading @value{GDBN} Command
30909 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
30911 @subheading Example
30915 -inferior-tty-set /dev/pts/1
30920 @subheading The @code{-inferior-tty-show} Command
30921 @findex -inferior-tty-show
30923 @subheading Synopsis
30929 Show terminal for future runs of program being debugged.
30931 @subheading @value{GDBN} Command
30933 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
30935 @subheading Example
30939 -inferior-tty-set /dev/pts/1
30943 ^done,inferior_tty_terminal="/dev/pts/1"
30947 @subheading The @code{-enable-timings} Command
30948 @findex -enable-timings
30950 @subheading Synopsis
30953 -enable-timings [yes | no]
30956 Toggle the printing of the wallclock, user and system times for an MI
30957 command as a field in its output. This command is to help frontend
30958 developers optimize the performance of their code. No argument is
30959 equivalent to @samp{yes}.
30961 @subheading @value{GDBN} Command
30965 @subheading Example
30973 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30974 addr="0x080484ed",func="main",file="myprog.c",
30975 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
30976 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
30984 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
30985 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
30986 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
30987 fullname="/home/nickrob/myprog.c",line="73"@}
30992 @chapter @value{GDBN} Annotations
30994 This chapter describes annotations in @value{GDBN}. Annotations were
30995 designed to interface @value{GDBN} to graphical user interfaces or other
30996 similar programs which want to interact with @value{GDBN} at a
30997 relatively high level.
30999 The annotation mechanism has largely been superseded by @sc{gdb/mi}
31003 This is Edition @value{EDITION}, @value{DATE}.
31007 * Annotations Overview:: What annotations are; the general syntax.
31008 * Server Prefix:: Issuing a command without affecting user state.
31009 * Prompting:: Annotations marking @value{GDBN}'s need for input.
31010 * Errors:: Annotations for error messages.
31011 * Invalidation:: Some annotations describe things now invalid.
31012 * Annotations for Running::
31013 Whether the program is running, how it stopped, etc.
31014 * Source Annotations:: Annotations describing source code.
31017 @node Annotations Overview
31018 @section What is an Annotation?
31019 @cindex annotations
31021 Annotations start with a newline character, two @samp{control-z}
31022 characters, and the name of the annotation. If there is no additional
31023 information associated with this annotation, the name of the annotation
31024 is followed immediately by a newline. If there is additional
31025 information, the name of the annotation is followed by a space, the
31026 additional information, and a newline. The additional information
31027 cannot contain newline characters.
31029 Any output not beginning with a newline and two @samp{control-z}
31030 characters denotes literal output from @value{GDBN}. Currently there is
31031 no need for @value{GDBN} to output a newline followed by two
31032 @samp{control-z} characters, but if there was such a need, the
31033 annotations could be extended with an @samp{escape} annotation which
31034 means those three characters as output.
31036 The annotation @var{level}, which is specified using the
31037 @option{--annotate} command line option (@pxref{Mode Options}), controls
31038 how much information @value{GDBN} prints together with its prompt,
31039 values of expressions, source lines, and other types of output. Level 0
31040 is for no annotations, level 1 is for use when @value{GDBN} is run as a
31041 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
31042 for programs that control @value{GDBN}, and level 2 annotations have
31043 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
31044 Interface, annotate, GDB's Obsolete Annotations}).
31047 @kindex set annotate
31048 @item set annotate @var{level}
31049 The @value{GDBN} command @code{set annotate} sets the level of
31050 annotations to the specified @var{level}.
31052 @item show annotate
31053 @kindex show annotate
31054 Show the current annotation level.
31057 This chapter describes level 3 annotations.
31059 A simple example of starting up @value{GDBN} with annotations is:
31062 $ @kbd{gdb --annotate=3}
31064 Copyright 2003 Free Software Foundation, Inc.
31065 GDB is free software, covered by the GNU General Public License,
31066 and you are welcome to change it and/or distribute copies of it
31067 under certain conditions.
31068 Type "show copying" to see the conditions.
31069 There is absolutely no warranty for GDB. Type "show warranty"
31071 This GDB was configured as "i386-pc-linux-gnu"
31082 Here @samp{quit} is input to @value{GDBN}; the rest is output from
31083 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
31084 denotes a @samp{control-z} character) are annotations; the rest is
31085 output from @value{GDBN}.
31087 @node Server Prefix
31088 @section The Server Prefix
31089 @cindex server prefix
31091 If you prefix a command with @samp{server } then it will not affect
31092 the command history, nor will it affect @value{GDBN}'s notion of which
31093 command to repeat if @key{RET} is pressed on a line by itself. This
31094 means that commands can be run behind a user's back by a front-end in
31095 a transparent manner.
31097 The @code{server } prefix does not affect the recording of values into
31098 the value history; to print a value without recording it into the
31099 value history, use the @code{output} command instead of the
31100 @code{print} command.
31102 Using this prefix also disables confirmation requests
31103 (@pxref{confirmation requests}).
31106 @section Annotation for @value{GDBN} Input
31108 @cindex annotations for prompts
31109 When @value{GDBN} prompts for input, it annotates this fact so it is possible
31110 to know when to send output, when the output from a given command is
31113 Different kinds of input each have a different @dfn{input type}. Each
31114 input type has three annotations: a @code{pre-} annotation, which
31115 denotes the beginning of any prompt which is being output, a plain
31116 annotation, which denotes the end of the prompt, and then a @code{post-}
31117 annotation which denotes the end of any echo which may (or may not) be
31118 associated with the input. For example, the @code{prompt} input type
31119 features the following annotations:
31127 The input types are
31130 @findex pre-prompt annotation
31131 @findex prompt annotation
31132 @findex post-prompt annotation
31134 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
31136 @findex pre-commands annotation
31137 @findex commands annotation
31138 @findex post-commands annotation
31140 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
31141 command. The annotations are repeated for each command which is input.
31143 @findex pre-overload-choice annotation
31144 @findex overload-choice annotation
31145 @findex post-overload-choice annotation
31146 @item overload-choice
31147 When @value{GDBN} wants the user to select between various overloaded functions.
31149 @findex pre-query annotation
31150 @findex query annotation
31151 @findex post-query annotation
31153 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
31155 @findex pre-prompt-for-continue annotation
31156 @findex prompt-for-continue annotation
31157 @findex post-prompt-for-continue annotation
31158 @item prompt-for-continue
31159 When @value{GDBN} is asking the user to press return to continue. Note: Don't
31160 expect this to work well; instead use @code{set height 0} to disable
31161 prompting. This is because the counting of lines is buggy in the
31162 presence of annotations.
31167 @cindex annotations for errors, warnings and interrupts
31169 @findex quit annotation
31174 This annotation occurs right before @value{GDBN} responds to an interrupt.
31176 @findex error annotation
31181 This annotation occurs right before @value{GDBN} responds to an error.
31183 Quit and error annotations indicate that any annotations which @value{GDBN} was
31184 in the middle of may end abruptly. For example, if a
31185 @code{value-history-begin} annotation is followed by a @code{error}, one
31186 cannot expect to receive the matching @code{value-history-end}. One
31187 cannot expect not to receive it either, however; an error annotation
31188 does not necessarily mean that @value{GDBN} is immediately returning all the way
31191 @findex error-begin annotation
31192 A quit or error annotation may be preceded by
31198 Any output between that and the quit or error annotation is the error
31201 Warning messages are not yet annotated.
31202 @c If we want to change that, need to fix warning(), type_error(),
31203 @c range_error(), and possibly other places.
31206 @section Invalidation Notices
31208 @cindex annotations for invalidation messages
31209 The following annotations say that certain pieces of state may have
31213 @findex frames-invalid annotation
31214 @item ^Z^Zframes-invalid
31216 The frames (for example, output from the @code{backtrace} command) may
31219 @findex breakpoints-invalid annotation
31220 @item ^Z^Zbreakpoints-invalid
31222 The breakpoints may have changed. For example, the user just added or
31223 deleted a breakpoint.
31226 @node Annotations for Running
31227 @section Running the Program
31228 @cindex annotations for running programs
31230 @findex starting annotation
31231 @findex stopping annotation
31232 When the program starts executing due to a @value{GDBN} command such as
31233 @code{step} or @code{continue},
31239 is output. When the program stops,
31245 is output. Before the @code{stopped} annotation, a variety of
31246 annotations describe how the program stopped.
31249 @findex exited annotation
31250 @item ^Z^Zexited @var{exit-status}
31251 The program exited, and @var{exit-status} is the exit status (zero for
31252 successful exit, otherwise nonzero).
31254 @findex signalled annotation
31255 @findex signal-name annotation
31256 @findex signal-name-end annotation
31257 @findex signal-string annotation
31258 @findex signal-string-end annotation
31259 @item ^Z^Zsignalled
31260 The program exited with a signal. After the @code{^Z^Zsignalled}, the
31261 annotation continues:
31267 ^Z^Zsignal-name-end
31271 ^Z^Zsignal-string-end
31276 where @var{name} is the name of the signal, such as @code{SIGILL} or
31277 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
31278 as @code{Illegal Instruction} or @code{Segmentation fault}.
31279 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
31280 user's benefit and have no particular format.
31282 @findex signal annotation
31284 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
31285 just saying that the program received the signal, not that it was
31286 terminated with it.
31288 @findex breakpoint annotation
31289 @item ^Z^Zbreakpoint @var{number}
31290 The program hit breakpoint number @var{number}.
31292 @findex watchpoint annotation
31293 @item ^Z^Zwatchpoint @var{number}
31294 The program hit watchpoint number @var{number}.
31297 @node Source Annotations
31298 @section Displaying Source
31299 @cindex annotations for source display
31301 @findex source annotation
31302 The following annotation is used instead of displaying source code:
31305 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
31308 where @var{filename} is an absolute file name indicating which source
31309 file, @var{line} is the line number within that file (where 1 is the
31310 first line in the file), @var{character} is the character position
31311 within the file (where 0 is the first character in the file) (for most
31312 debug formats this will necessarily point to the beginning of a line),
31313 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
31314 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
31315 @var{addr} is the address in the target program associated with the
31316 source which is being displayed. @var{addr} is in the form @samp{0x}
31317 followed by one or more lowercase hex digits (note that this does not
31318 depend on the language).
31320 @node JIT Interface
31321 @chapter JIT Compilation Interface
31322 @cindex just-in-time compilation
31323 @cindex JIT compilation interface
31325 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
31326 interface. A JIT compiler is a program or library that generates native
31327 executable code at runtime and executes it, usually in order to achieve good
31328 performance while maintaining platform independence.
31330 Programs that use JIT compilation are normally difficult to debug because
31331 portions of their code are generated at runtime, instead of being loaded from
31332 object files, which is where @value{GDBN} normally finds the program's symbols
31333 and debug information. In order to debug programs that use JIT compilation,
31334 @value{GDBN} has an interface that allows the program to register in-memory
31335 symbol files with @value{GDBN} at runtime.
31337 If you are using @value{GDBN} to debug a program that uses this interface, then
31338 it should work transparently so long as you have not stripped the binary. If
31339 you are developing a JIT compiler, then the interface is documented in the rest
31340 of this chapter. At this time, the only known client of this interface is the
31343 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
31344 JIT compiler communicates with @value{GDBN} by writing data into a global
31345 variable and calling a fuction at a well-known symbol. When @value{GDBN}
31346 attaches, it reads a linked list of symbol files from the global variable to
31347 find existing code, and puts a breakpoint in the function so that it can find
31348 out about additional code.
31351 * Declarations:: Relevant C struct declarations
31352 * Registering Code:: Steps to register code
31353 * Unregistering Code:: Steps to unregister code
31357 @section JIT Declarations
31359 These are the relevant struct declarations that a C program should include to
31360 implement the interface:
31370 struct jit_code_entry
31372 struct jit_code_entry *next_entry;
31373 struct jit_code_entry *prev_entry;
31374 const char *symfile_addr;
31375 uint64_t symfile_size;
31378 struct jit_descriptor
31381 /* This type should be jit_actions_t, but we use uint32_t
31382 to be explicit about the bitwidth. */
31383 uint32_t action_flag;
31384 struct jit_code_entry *relevant_entry;
31385 struct jit_code_entry *first_entry;
31388 /* GDB puts a breakpoint in this function. */
31389 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
31391 /* Make sure to specify the version statically, because the
31392 debugger may check the version before we can set it. */
31393 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
31396 If the JIT is multi-threaded, then it is important that the JIT synchronize any
31397 modifications to this global data properly, which can easily be done by putting
31398 a global mutex around modifications to these structures.
31400 @node Registering Code
31401 @section Registering Code
31403 To register code with @value{GDBN}, the JIT should follow this protocol:
31407 Generate an object file in memory with symbols and other desired debug
31408 information. The file must include the virtual addresses of the sections.
31411 Create a code entry for the file, which gives the start and size of the symbol
31415 Add it to the linked list in the JIT descriptor.
31418 Point the relevant_entry field of the descriptor at the entry.
31421 Set @code{action_flag} to @code{JIT_REGISTER} and call
31422 @code{__jit_debug_register_code}.
31425 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
31426 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
31427 new code. However, the linked list must still be maintained in order to allow
31428 @value{GDBN} to attach to a running process and still find the symbol files.
31430 @node Unregistering Code
31431 @section Unregistering Code
31433 If code is freed, then the JIT should use the following protocol:
31437 Remove the code entry corresponding to the code from the linked list.
31440 Point the @code{relevant_entry} field of the descriptor at the code entry.
31443 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
31444 @code{__jit_debug_register_code}.
31447 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
31448 and the JIT will leak the memory used for the associated symbol files.
31451 @chapter Reporting Bugs in @value{GDBN}
31452 @cindex bugs in @value{GDBN}
31453 @cindex reporting bugs in @value{GDBN}
31455 Your bug reports play an essential role in making @value{GDBN} reliable.
31457 Reporting a bug may help you by bringing a solution to your problem, or it
31458 may not. But in any case the principal function of a bug report is to help
31459 the entire community by making the next version of @value{GDBN} work better. Bug
31460 reports are your contribution to the maintenance of @value{GDBN}.
31462 In order for a bug report to serve its purpose, you must include the
31463 information that enables us to fix the bug.
31466 * Bug Criteria:: Have you found a bug?
31467 * Bug Reporting:: How to report bugs
31471 @section Have You Found a Bug?
31472 @cindex bug criteria
31474 If you are not sure whether you have found a bug, here are some guidelines:
31477 @cindex fatal signal
31478 @cindex debugger crash
31479 @cindex crash of debugger
31481 If the debugger gets a fatal signal, for any input whatever, that is a
31482 @value{GDBN} bug. Reliable debuggers never crash.
31484 @cindex error on valid input
31486 If @value{GDBN} produces an error message for valid input, that is a
31487 bug. (Note that if you're cross debugging, the problem may also be
31488 somewhere in the connection to the target.)
31490 @cindex invalid input
31492 If @value{GDBN} does not produce an error message for invalid input,
31493 that is a bug. However, you should note that your idea of
31494 ``invalid input'' might be our idea of ``an extension'' or ``support
31495 for traditional practice''.
31498 If you are an experienced user of debugging tools, your suggestions
31499 for improvement of @value{GDBN} are welcome in any case.
31502 @node Bug Reporting
31503 @section How to Report Bugs
31504 @cindex bug reports
31505 @cindex @value{GDBN} bugs, reporting
31507 A number of companies and individuals offer support for @sc{gnu} products.
31508 If you obtained @value{GDBN} from a support organization, we recommend you
31509 contact that organization first.
31511 You can find contact information for many support companies and
31512 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
31514 @c should add a web page ref...
31517 @ifset BUGURL_DEFAULT
31518 In any event, we also recommend that you submit bug reports for
31519 @value{GDBN}. The preferred method is to submit them directly using
31520 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
31521 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
31524 @strong{Do not send bug reports to @samp{info-gdb}, or to
31525 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
31526 not want to receive bug reports. Those that do have arranged to receive
31529 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
31530 serves as a repeater. The mailing list and the newsgroup carry exactly
31531 the same messages. Often people think of posting bug reports to the
31532 newsgroup instead of mailing them. This appears to work, but it has one
31533 problem which can be crucial: a newsgroup posting often lacks a mail
31534 path back to the sender. Thus, if we need to ask for more information,
31535 we may be unable to reach you. For this reason, it is better to send
31536 bug reports to the mailing list.
31538 @ifclear BUGURL_DEFAULT
31539 In any event, we also recommend that you submit bug reports for
31540 @value{GDBN} to @value{BUGURL}.
31544 The fundamental principle of reporting bugs usefully is this:
31545 @strong{report all the facts}. If you are not sure whether to state a
31546 fact or leave it out, state it!
31548 Often people omit facts because they think they know what causes the
31549 problem and assume that some details do not matter. Thus, you might
31550 assume that the name of the variable you use in an example does not matter.
31551 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
31552 stray memory reference which happens to fetch from the location where that
31553 name is stored in memory; perhaps, if the name were different, the contents
31554 of that location would fool the debugger into doing the right thing despite
31555 the bug. Play it safe and give a specific, complete example. That is the
31556 easiest thing for you to do, and the most helpful.
31558 Keep in mind that the purpose of a bug report is to enable us to fix the
31559 bug. It may be that the bug has been reported previously, but neither
31560 you nor we can know that unless your bug report is complete and
31563 Sometimes people give a few sketchy facts and ask, ``Does this ring a
31564 bell?'' Those bug reports are useless, and we urge everyone to
31565 @emph{refuse to respond to them} except to chide the sender to report
31568 To enable us to fix the bug, you should include all these things:
31572 The version of @value{GDBN}. @value{GDBN} announces it if you start
31573 with no arguments; you can also print it at any time using @code{show
31576 Without this, we will not know whether there is any point in looking for
31577 the bug in the current version of @value{GDBN}.
31580 The type of machine you are using, and the operating system name and
31584 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
31585 ``@value{GCC}--2.8.1''.
31588 What compiler (and its version) was used to compile the program you are
31589 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
31590 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
31591 to get this information; for other compilers, see the documentation for
31595 The command arguments you gave the compiler to compile your example and
31596 observe the bug. For example, did you use @samp{-O}? To guarantee
31597 you will not omit something important, list them all. A copy of the
31598 Makefile (or the output from make) is sufficient.
31600 If we were to try to guess the arguments, we would probably guess wrong
31601 and then we might not encounter the bug.
31604 A complete input script, and all necessary source files, that will
31608 A description of what behavior you observe that you believe is
31609 incorrect. For example, ``It gets a fatal signal.''
31611 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
31612 will certainly notice it. But if the bug is incorrect output, we might
31613 not notice unless it is glaringly wrong. You might as well not give us
31614 a chance to make a mistake.
31616 Even if the problem you experience is a fatal signal, you should still
31617 say so explicitly. Suppose something strange is going on, such as, your
31618 copy of @value{GDBN} is out of synch, or you have encountered a bug in
31619 the C library on your system. (This has happened!) Your copy might
31620 crash and ours would not. If you told us to expect a crash, then when
31621 ours fails to crash, we would know that the bug was not happening for
31622 us. If you had not told us to expect a crash, then we would not be able
31623 to draw any conclusion from our observations.
31626 @cindex recording a session script
31627 To collect all this information, you can use a session recording program
31628 such as @command{script}, which is available on many Unix systems.
31629 Just run your @value{GDBN} session inside @command{script} and then
31630 include the @file{typescript} file with your bug report.
31632 Another way to record a @value{GDBN} session is to run @value{GDBN}
31633 inside Emacs and then save the entire buffer to a file.
31636 If you wish to suggest changes to the @value{GDBN} source, send us context
31637 diffs. If you even discuss something in the @value{GDBN} source, refer to
31638 it by context, not by line number.
31640 The line numbers in our development sources will not match those in your
31641 sources. Your line numbers would convey no useful information to us.
31645 Here are some things that are not necessary:
31649 A description of the envelope of the bug.
31651 Often people who encounter a bug spend a lot of time investigating
31652 which changes to the input file will make the bug go away and which
31653 changes will not affect it.
31655 This is often time consuming and not very useful, because the way we
31656 will find the bug is by running a single example under the debugger
31657 with breakpoints, not by pure deduction from a series of examples.
31658 We recommend that you save your time for something else.
31660 Of course, if you can find a simpler example to report @emph{instead}
31661 of the original one, that is a convenience for us. Errors in the
31662 output will be easier to spot, running under the debugger will take
31663 less time, and so on.
31665 However, simplification is not vital; if you do not want to do this,
31666 report the bug anyway and send us the entire test case you used.
31669 A patch for the bug.
31671 A patch for the bug does help us if it is a good one. But do not omit
31672 the necessary information, such as the test case, on the assumption that
31673 a patch is all we need. We might see problems with your patch and decide
31674 to fix the problem another way, or we might not understand it at all.
31676 Sometimes with a program as complicated as @value{GDBN} it is very hard to
31677 construct an example that will make the program follow a certain path
31678 through the code. If you do not send us the example, we will not be able
31679 to construct one, so we will not be able to verify that the bug is fixed.
31681 And if we cannot understand what bug you are trying to fix, or why your
31682 patch should be an improvement, we will not install it. A test case will
31683 help us to understand.
31686 A guess about what the bug is or what it depends on.
31688 Such guesses are usually wrong. Even we cannot guess right about such
31689 things without first using the debugger to find the facts.
31692 @c The readline documentation is distributed with the readline code
31693 @c and consists of the two following files:
31696 @c Use -I with makeinfo to point to the appropriate directory,
31697 @c environment var TEXINPUTS with TeX.
31698 @ifclear SYSTEM_READLINE
31699 @include rluser.texi
31700 @include hsuser.texi
31704 @appendix In Memoriam
31706 The @value{GDBN} project mourns the loss of the following long-time
31711 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
31712 to Free Software in general. Outside of @value{GDBN}, he was known in
31713 the Amiga world for his series of Fish Disks, and the GeekGadget project.
31715 @item Michael Snyder
31716 Michael was one of the Global Maintainers of the @value{GDBN} project,
31717 with contributions recorded as early as 1996, until 2011. In addition
31718 to his day to day participation, he was a large driving force behind
31719 adding Reverse Debugging to @value{GDBN}.
31722 Beyond their technical contributions to the project, they were also
31723 enjoyable members of the Free Software Community. We will miss them.
31725 @node Formatting Documentation
31726 @appendix Formatting Documentation
31728 @cindex @value{GDBN} reference card
31729 @cindex reference card
31730 The @value{GDBN} 4 release includes an already-formatted reference card, ready
31731 for printing with PostScript or Ghostscript, in the @file{gdb}
31732 subdirectory of the main source directory@footnote{In
31733 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
31734 release.}. If you can use PostScript or Ghostscript with your printer,
31735 you can print the reference card immediately with @file{refcard.ps}.
31737 The release also includes the source for the reference card. You
31738 can format it, using @TeX{}, by typing:
31744 The @value{GDBN} reference card is designed to print in @dfn{landscape}
31745 mode on US ``letter'' size paper;
31746 that is, on a sheet 11 inches wide by 8.5 inches
31747 high. You will need to specify this form of printing as an option to
31748 your @sc{dvi} output program.
31750 @cindex documentation
31752 All the documentation for @value{GDBN} comes as part of the machine-readable
31753 distribution. The documentation is written in Texinfo format, which is
31754 a documentation system that uses a single source file to produce both
31755 on-line information and a printed manual. You can use one of the Info
31756 formatting commands to create the on-line version of the documentation
31757 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
31759 @value{GDBN} includes an already formatted copy of the on-line Info
31760 version of this manual in the @file{gdb} subdirectory. The main Info
31761 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
31762 subordinate files matching @samp{gdb.info*} in the same directory. If
31763 necessary, you can print out these files, or read them with any editor;
31764 but they are easier to read using the @code{info} subsystem in @sc{gnu}
31765 Emacs or the standalone @code{info} program, available as part of the
31766 @sc{gnu} Texinfo distribution.
31768 If you want to format these Info files yourself, you need one of the
31769 Info formatting programs, such as @code{texinfo-format-buffer} or
31772 If you have @code{makeinfo} installed, and are in the top level
31773 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
31774 version @value{GDBVN}), you can make the Info file by typing:
31781 If you want to typeset and print copies of this manual, you need @TeX{},
31782 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
31783 Texinfo definitions file.
31785 @TeX{} is a typesetting program; it does not print files directly, but
31786 produces output files called @sc{dvi} files. To print a typeset
31787 document, you need a program to print @sc{dvi} files. If your system
31788 has @TeX{} installed, chances are it has such a program. The precise
31789 command to use depends on your system; @kbd{lpr -d} is common; another
31790 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
31791 require a file name without any extension or a @samp{.dvi} extension.
31793 @TeX{} also requires a macro definitions file called
31794 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
31795 written in Texinfo format. On its own, @TeX{} cannot either read or
31796 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
31797 and is located in the @file{gdb-@var{version-number}/texinfo}
31800 If you have @TeX{} and a @sc{dvi} printer program installed, you can
31801 typeset and print this manual. First switch to the @file{gdb}
31802 subdirectory of the main source directory (for example, to
31803 @file{gdb-@value{GDBVN}/gdb}) and type:
31809 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
31811 @node Installing GDB
31812 @appendix Installing @value{GDBN}
31813 @cindex installation
31816 * Requirements:: Requirements for building @value{GDBN}
31817 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
31818 * Separate Objdir:: Compiling @value{GDBN} in another directory
31819 * Config Names:: Specifying names for hosts and targets
31820 * Configure Options:: Summary of options for configure
31821 * System-wide configuration:: Having a system-wide init file
31825 @section Requirements for Building @value{GDBN}
31826 @cindex building @value{GDBN}, requirements for
31828 Building @value{GDBN} requires various tools and packages to be available.
31829 Other packages will be used only if they are found.
31831 @heading Tools/Packages Necessary for Building @value{GDBN}
31833 @item ISO C90 compiler
31834 @value{GDBN} is written in ISO C90. It should be buildable with any
31835 working C90 compiler, e.g.@: GCC.
31839 @heading Tools/Packages Optional for Building @value{GDBN}
31843 @value{GDBN} can use the Expat XML parsing library. This library may be
31844 included with your operating system distribution; if it is not, you
31845 can get the latest version from @url{http://expat.sourceforge.net}.
31846 The @file{configure} script will search for this library in several
31847 standard locations; if it is installed in an unusual path, you can
31848 use the @option{--with-libexpat-prefix} option to specify its location.
31854 Remote protocol memory maps (@pxref{Memory Map Format})
31856 Target descriptions (@pxref{Target Descriptions})
31858 Remote shared library lists (@pxref{Library List Format})
31860 MS-Windows shared libraries (@pxref{Shared Libraries})
31862 Traceframe info (@pxref{Traceframe Info Format})
31866 @cindex compressed debug sections
31867 @value{GDBN} will use the @samp{zlib} library, if available, to read
31868 compressed debug sections. Some linkers, such as GNU gold, are capable
31869 of producing binaries with compressed debug sections. If @value{GDBN}
31870 is compiled with @samp{zlib}, it will be able to read the debug
31871 information in such binaries.
31873 The @samp{zlib} library is likely included with your operating system
31874 distribution; if it is not, you can get the latest version from
31875 @url{http://zlib.net}.
31878 @value{GDBN}'s features related to character sets (@pxref{Character
31879 Sets}) require a functioning @code{iconv} implementation. If you are
31880 on a GNU system, then this is provided by the GNU C Library. Some
31881 other systems also provide a working @code{iconv}.
31883 If @value{GDBN} is using the @code{iconv} program which is installed
31884 in a non-standard place, you will need to tell @value{GDBN} where to find it.
31885 This is done with @option{--with-iconv-bin} which specifies the
31886 directory that contains the @code{iconv} program.
31888 On systems without @code{iconv}, you can install GNU Libiconv. If you
31889 have previously installed Libiconv, you can use the
31890 @option{--with-libiconv-prefix} option to configure.
31892 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
31893 arrange to build Libiconv if a directory named @file{libiconv} appears
31894 in the top-most source directory. If Libiconv is built this way, and
31895 if the operating system does not provide a suitable @code{iconv}
31896 implementation, then the just-built library will automatically be used
31897 by @value{GDBN}. One easy way to set this up is to download GNU
31898 Libiconv, unpack it, and then rename the directory holding the
31899 Libiconv source code to @samp{libiconv}.
31902 @node Running Configure
31903 @section Invoking the @value{GDBN} @file{configure} Script
31904 @cindex configuring @value{GDBN}
31905 @value{GDBN} comes with a @file{configure} script that automates the process
31906 of preparing @value{GDBN} for installation; you can then use @code{make} to
31907 build the @code{gdb} program.
31909 @c irrelevant in info file; it's as current as the code it lives with.
31910 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
31911 look at the @file{README} file in the sources; we may have improved the
31912 installation procedures since publishing this manual.}
31915 The @value{GDBN} distribution includes all the source code you need for
31916 @value{GDBN} in a single directory, whose name is usually composed by
31917 appending the version number to @samp{gdb}.
31919 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
31920 @file{gdb-@value{GDBVN}} directory. That directory contains:
31923 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
31924 script for configuring @value{GDBN} and all its supporting libraries
31926 @item gdb-@value{GDBVN}/gdb
31927 the source specific to @value{GDBN} itself
31929 @item gdb-@value{GDBVN}/bfd
31930 source for the Binary File Descriptor library
31932 @item gdb-@value{GDBVN}/include
31933 @sc{gnu} include files
31935 @item gdb-@value{GDBVN}/libiberty
31936 source for the @samp{-liberty} free software library
31938 @item gdb-@value{GDBVN}/opcodes
31939 source for the library of opcode tables and disassemblers
31941 @item gdb-@value{GDBVN}/readline
31942 source for the @sc{gnu} command-line interface
31944 @item gdb-@value{GDBVN}/glob
31945 source for the @sc{gnu} filename pattern-matching subroutine
31947 @item gdb-@value{GDBVN}/mmalloc
31948 source for the @sc{gnu} memory-mapped malloc package
31951 The simplest way to configure and build @value{GDBN} is to run @file{configure}
31952 from the @file{gdb-@var{version-number}} source directory, which in
31953 this example is the @file{gdb-@value{GDBVN}} directory.
31955 First switch to the @file{gdb-@var{version-number}} source directory
31956 if you are not already in it; then run @file{configure}. Pass the
31957 identifier for the platform on which @value{GDBN} will run as an
31963 cd gdb-@value{GDBVN}
31964 ./configure @var{host}
31969 where @var{host} is an identifier such as @samp{sun4} or
31970 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
31971 (You can often leave off @var{host}; @file{configure} tries to guess the
31972 correct value by examining your system.)
31974 Running @samp{configure @var{host}} and then running @code{make} builds the
31975 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
31976 libraries, then @code{gdb} itself. The configured source files, and the
31977 binaries, are left in the corresponding source directories.
31980 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
31981 system does not recognize this automatically when you run a different
31982 shell, you may need to run @code{sh} on it explicitly:
31985 sh configure @var{host}
31988 If you run @file{configure} from a directory that contains source
31989 directories for multiple libraries or programs, such as the
31990 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
31992 creates configuration files for every directory level underneath (unless
31993 you tell it not to, with the @samp{--norecursion} option).
31995 You should run the @file{configure} script from the top directory in the
31996 source tree, the @file{gdb-@var{version-number}} directory. If you run
31997 @file{configure} from one of the subdirectories, you will configure only
31998 that subdirectory. That is usually not what you want. In particular,
31999 if you run the first @file{configure} from the @file{gdb} subdirectory
32000 of the @file{gdb-@var{version-number}} directory, you will omit the
32001 configuration of @file{bfd}, @file{readline}, and other sibling
32002 directories of the @file{gdb} subdirectory. This leads to build errors
32003 about missing include files such as @file{bfd/bfd.h}.
32005 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
32006 However, you should make sure that the shell on your path (named by
32007 the @samp{SHELL} environment variable) is publicly readable. Remember
32008 that @value{GDBN} uses the shell to start your program---some systems refuse to
32009 let @value{GDBN} debug child processes whose programs are not readable.
32011 @node Separate Objdir
32012 @section Compiling @value{GDBN} in Another Directory
32014 If you want to run @value{GDBN} versions for several host or target machines,
32015 you need a different @code{gdb} compiled for each combination of
32016 host and target. @file{configure} is designed to make this easy by
32017 allowing you to generate each configuration in a separate subdirectory,
32018 rather than in the source directory. If your @code{make} program
32019 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
32020 @code{make} in each of these directories builds the @code{gdb}
32021 program specified there.
32023 To build @code{gdb} in a separate directory, run @file{configure}
32024 with the @samp{--srcdir} option to specify where to find the source.
32025 (You also need to specify a path to find @file{configure}
32026 itself from your working directory. If the path to @file{configure}
32027 would be the same as the argument to @samp{--srcdir}, you can leave out
32028 the @samp{--srcdir} option; it is assumed.)
32030 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
32031 separate directory for a Sun 4 like this:
32035 cd gdb-@value{GDBVN}
32038 ../gdb-@value{GDBVN}/configure sun4
32043 When @file{configure} builds a configuration using a remote source
32044 directory, it creates a tree for the binaries with the same structure
32045 (and using the same names) as the tree under the source directory. In
32046 the example, you'd find the Sun 4 library @file{libiberty.a} in the
32047 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
32048 @file{gdb-sun4/gdb}.
32050 Make sure that your path to the @file{configure} script has just one
32051 instance of @file{gdb} in it. If your path to @file{configure} looks
32052 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
32053 one subdirectory of @value{GDBN}, not the whole package. This leads to
32054 build errors about missing include files such as @file{bfd/bfd.h}.
32056 One popular reason to build several @value{GDBN} configurations in separate
32057 directories is to configure @value{GDBN} for cross-compiling (where
32058 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
32059 programs that run on another machine---the @dfn{target}).
32060 You specify a cross-debugging target by
32061 giving the @samp{--target=@var{target}} option to @file{configure}.
32063 When you run @code{make} to build a program or library, you must run
32064 it in a configured directory---whatever directory you were in when you
32065 called @file{configure} (or one of its subdirectories).
32067 The @code{Makefile} that @file{configure} generates in each source
32068 directory also runs recursively. If you type @code{make} in a source
32069 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
32070 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
32071 will build all the required libraries, and then build GDB.
32073 When you have multiple hosts or targets configured in separate
32074 directories, you can run @code{make} on them in parallel (for example,
32075 if they are NFS-mounted on each of the hosts); they will not interfere
32079 @section Specifying Names for Hosts and Targets
32081 The specifications used for hosts and targets in the @file{configure}
32082 script are based on a three-part naming scheme, but some short predefined
32083 aliases are also supported. The full naming scheme encodes three pieces
32084 of information in the following pattern:
32087 @var{architecture}-@var{vendor}-@var{os}
32090 For example, you can use the alias @code{sun4} as a @var{host} argument,
32091 or as the value for @var{target} in a @code{--target=@var{target}}
32092 option. The equivalent full name is @samp{sparc-sun-sunos4}.
32094 The @file{configure} script accompanying @value{GDBN} does not provide
32095 any query facility to list all supported host and target names or
32096 aliases. @file{configure} calls the Bourne shell script
32097 @code{config.sub} to map abbreviations to full names; you can read the
32098 script, if you wish, or you can use it to test your guesses on
32099 abbreviations---for example:
32102 % sh config.sub i386-linux
32104 % sh config.sub alpha-linux
32105 alpha-unknown-linux-gnu
32106 % sh config.sub hp9k700
32108 % sh config.sub sun4
32109 sparc-sun-sunos4.1.1
32110 % sh config.sub sun3
32111 m68k-sun-sunos4.1.1
32112 % sh config.sub i986v
32113 Invalid configuration `i986v': machine `i986v' not recognized
32117 @code{config.sub} is also distributed in the @value{GDBN} source
32118 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
32120 @node Configure Options
32121 @section @file{configure} Options
32123 Here is a summary of the @file{configure} options and arguments that
32124 are most often useful for building @value{GDBN}. @file{configure} also has
32125 several other options not listed here. @inforef{What Configure
32126 Does,,configure.info}, for a full explanation of @file{configure}.
32129 configure @r{[}--help@r{]}
32130 @r{[}--prefix=@var{dir}@r{]}
32131 @r{[}--exec-prefix=@var{dir}@r{]}
32132 @r{[}--srcdir=@var{dirname}@r{]}
32133 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
32134 @r{[}--target=@var{target}@r{]}
32139 You may introduce options with a single @samp{-} rather than
32140 @samp{--} if you prefer; but you may abbreviate option names if you use
32145 Display a quick summary of how to invoke @file{configure}.
32147 @item --prefix=@var{dir}
32148 Configure the source to install programs and files under directory
32151 @item --exec-prefix=@var{dir}
32152 Configure the source to install programs under directory
32155 @c avoid splitting the warning from the explanation:
32157 @item --srcdir=@var{dirname}
32158 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
32159 @code{make} that implements the @code{VPATH} feature.}@*
32160 Use this option to make configurations in directories separate from the
32161 @value{GDBN} source directories. Among other things, you can use this to
32162 build (or maintain) several configurations simultaneously, in separate
32163 directories. @file{configure} writes configuration-specific files in
32164 the current directory, but arranges for them to use the source in the
32165 directory @var{dirname}. @file{configure} creates directories under
32166 the working directory in parallel to the source directories below
32169 @item --norecursion
32170 Configure only the directory level where @file{configure} is executed; do not
32171 propagate configuration to subdirectories.
32173 @item --target=@var{target}
32174 Configure @value{GDBN} for cross-debugging programs running on the specified
32175 @var{target}. Without this option, @value{GDBN} is configured to debug
32176 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
32178 There is no convenient way to generate a list of all available targets.
32180 @item @var{host} @dots{}
32181 Configure @value{GDBN} to run on the specified @var{host}.
32183 There is no convenient way to generate a list of all available hosts.
32186 There are many other options available as well, but they are generally
32187 needed for special purposes only.
32189 @node System-wide configuration
32190 @section System-wide configuration and settings
32191 @cindex system-wide init file
32193 @value{GDBN} can be configured to have a system-wide init file;
32194 this file will be read and executed at startup (@pxref{Startup, , What
32195 @value{GDBN} does during startup}).
32197 Here is the corresponding configure option:
32200 @item --with-system-gdbinit=@var{file}
32201 Specify that the default location of the system-wide init file is
32205 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
32206 it may be subject to relocation. Two possible cases:
32210 If the default location of this init file contains @file{$prefix},
32211 it will be subject to relocation. Suppose that the configure options
32212 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
32213 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
32214 init file is looked for as @file{$install/etc/gdbinit} instead of
32215 @file{$prefix/etc/gdbinit}.
32218 By contrast, if the default location does not contain the prefix,
32219 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
32220 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
32221 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
32222 wherever @value{GDBN} is installed.
32225 @node Maintenance Commands
32226 @appendix Maintenance Commands
32227 @cindex maintenance commands
32228 @cindex internal commands
32230 In addition to commands intended for @value{GDBN} users, @value{GDBN}
32231 includes a number of commands intended for @value{GDBN} developers,
32232 that are not documented elsewhere in this manual. These commands are
32233 provided here for reference. (For commands that turn on debugging
32234 messages, see @ref{Debugging Output}.)
32237 @kindex maint agent
32238 @kindex maint agent-eval
32239 @item maint agent @var{expression}
32240 @itemx maint agent-eval @var{expression}
32241 Translate the given @var{expression} into remote agent bytecodes.
32242 This command is useful for debugging the Agent Expression mechanism
32243 (@pxref{Agent Expressions}). The @samp{agent} version produces an
32244 expression useful for data collection, such as by tracepoints, while
32245 @samp{maint agent-eval} produces an expression that evaluates directly
32246 to a result. For instance, a collection expression for @code{globa +
32247 globb} will include bytecodes to record four bytes of memory at each
32248 of the addresses of @code{globa} and @code{globb}, while discarding
32249 the result of the addition, while an evaluation expression will do the
32250 addition and return the sum.
32252 @kindex maint info breakpoints
32253 @item @anchor{maint info breakpoints}maint info breakpoints
32254 Using the same format as @samp{info breakpoints}, display both the
32255 breakpoints you've set explicitly, and those @value{GDBN} is using for
32256 internal purposes. Internal breakpoints are shown with negative
32257 breakpoint numbers. The type column identifies what kind of breakpoint
32262 Normal, explicitly set breakpoint.
32265 Normal, explicitly set watchpoint.
32268 Internal breakpoint, used to handle correctly stepping through
32269 @code{longjmp} calls.
32271 @item longjmp resume
32272 Internal breakpoint at the target of a @code{longjmp}.
32275 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
32278 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
32281 Shared library events.
32285 @kindex set displaced-stepping
32286 @kindex show displaced-stepping
32287 @cindex displaced stepping support
32288 @cindex out-of-line single-stepping
32289 @item set displaced-stepping
32290 @itemx show displaced-stepping
32291 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
32292 if the target supports it. Displaced stepping is a way to single-step
32293 over breakpoints without removing them from the inferior, by executing
32294 an out-of-line copy of the instruction that was originally at the
32295 breakpoint location. It is also known as out-of-line single-stepping.
32298 @item set displaced-stepping on
32299 If the target architecture supports it, @value{GDBN} will use
32300 displaced stepping to step over breakpoints.
32302 @item set displaced-stepping off
32303 @value{GDBN} will not use displaced stepping to step over breakpoints,
32304 even if such is supported by the target architecture.
32306 @cindex non-stop mode, and @samp{set displaced-stepping}
32307 @item set displaced-stepping auto
32308 This is the default mode. @value{GDBN} will use displaced stepping
32309 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
32310 architecture supports displaced stepping.
32313 @kindex maint check-symtabs
32314 @item maint check-symtabs
32315 Check the consistency of psymtabs and symtabs.
32317 @kindex maint cplus first_component
32318 @item maint cplus first_component @var{name}
32319 Print the first C@t{++} class/namespace component of @var{name}.
32321 @kindex maint cplus namespace
32322 @item maint cplus namespace
32323 Print the list of possible C@t{++} namespaces.
32325 @kindex maint demangle
32326 @item maint demangle @var{name}
32327 Demangle a C@t{++} or Objective-C mangled @var{name}.
32329 @kindex maint deprecate
32330 @kindex maint undeprecate
32331 @cindex deprecated commands
32332 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
32333 @itemx maint undeprecate @var{command}
32334 Deprecate or undeprecate the named @var{command}. Deprecated commands
32335 cause @value{GDBN} to issue a warning when you use them. The optional
32336 argument @var{replacement} says which newer command should be used in
32337 favor of the deprecated one; if it is given, @value{GDBN} will mention
32338 the replacement as part of the warning.
32340 @kindex maint dump-me
32341 @item maint dump-me
32342 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
32343 Cause a fatal signal in the debugger and force it to dump its core.
32344 This is supported only on systems which support aborting a program
32345 with the @code{SIGQUIT} signal.
32347 @kindex maint internal-error
32348 @kindex maint internal-warning
32349 @item maint internal-error @r{[}@var{message-text}@r{]}
32350 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
32351 Cause @value{GDBN} to call the internal function @code{internal_error}
32352 or @code{internal_warning} and hence behave as though an internal error
32353 or internal warning has been detected. In addition to reporting the
32354 internal problem, these functions give the user the opportunity to
32355 either quit @value{GDBN} or create a core file of the current
32356 @value{GDBN} session.
32358 These commands take an optional parameter @var{message-text} that is
32359 used as the text of the error or warning message.
32361 Here's an example of using @code{internal-error}:
32364 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
32365 @dots{}/maint.c:121: internal-error: testing, 1, 2
32366 A problem internal to GDB has been detected. Further
32367 debugging may prove unreliable.
32368 Quit this debugging session? (y or n) @kbd{n}
32369 Create a core file? (y or n) @kbd{n}
32373 @cindex @value{GDBN} internal error
32374 @cindex internal errors, control of @value{GDBN} behavior
32376 @kindex maint set internal-error
32377 @kindex maint show internal-error
32378 @kindex maint set internal-warning
32379 @kindex maint show internal-warning
32380 @item maint set internal-error @var{action} [ask|yes|no]
32381 @itemx maint show internal-error @var{action}
32382 @itemx maint set internal-warning @var{action} [ask|yes|no]
32383 @itemx maint show internal-warning @var{action}
32384 When @value{GDBN} reports an internal problem (error or warning) it
32385 gives the user the opportunity to both quit @value{GDBN} and create a
32386 core file of the current @value{GDBN} session. These commands let you
32387 override the default behaviour for each particular @var{action},
32388 described in the table below.
32392 You can specify that @value{GDBN} should always (yes) or never (no)
32393 quit. The default is to ask the user what to do.
32396 You can specify that @value{GDBN} should always (yes) or never (no)
32397 create a core file. The default is to ask the user what to do.
32400 @kindex maint packet
32401 @item maint packet @var{text}
32402 If @value{GDBN} is talking to an inferior via the serial protocol,
32403 then this command sends the string @var{text} to the inferior, and
32404 displays the response packet. @value{GDBN} supplies the initial
32405 @samp{$} character, the terminating @samp{#} character, and the
32408 @kindex maint print architecture
32409 @item maint print architecture @r{[}@var{file}@r{]}
32410 Print the entire architecture configuration. The optional argument
32411 @var{file} names the file where the output goes.
32413 @kindex maint print c-tdesc
32414 @item maint print c-tdesc
32415 Print the current target description (@pxref{Target Descriptions}) as
32416 a C source file. The created source file can be used in @value{GDBN}
32417 when an XML parser is not available to parse the description.
32419 @kindex maint print dummy-frames
32420 @item maint print dummy-frames
32421 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
32424 (@value{GDBP}) @kbd{b add}
32426 (@value{GDBP}) @kbd{print add(2,3)}
32427 Breakpoint 2, add (a=2, b=3) at @dots{}
32429 The program being debugged stopped while in a function called from GDB.
32431 (@value{GDBP}) @kbd{maint print dummy-frames}
32432 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
32433 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
32434 call_lo=0x01014000 call_hi=0x01014001
32438 Takes an optional file parameter.
32440 @kindex maint print registers
32441 @kindex maint print raw-registers
32442 @kindex maint print cooked-registers
32443 @kindex maint print register-groups
32444 @kindex maint print remote-registers
32445 @item maint print registers @r{[}@var{file}@r{]}
32446 @itemx maint print raw-registers @r{[}@var{file}@r{]}
32447 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
32448 @itemx maint print register-groups @r{[}@var{file}@r{]}
32449 @itemx maint print remote-registers @r{[}@var{file}@r{]}
32450 Print @value{GDBN}'s internal register data structures.
32452 The command @code{maint print raw-registers} includes the contents of
32453 the raw register cache; the command @code{maint print
32454 cooked-registers} includes the (cooked) value of all registers,
32455 including registers which aren't available on the target nor visible
32456 to user; the command @code{maint print register-groups} includes the
32457 groups that each register is a member of; and the command @code{maint
32458 print remote-registers} includes the remote target's register numbers
32459 and offsets in the `G' packets. @xref{Registers,, Registers, gdbint,
32460 @value{GDBN} Internals}.
32462 These commands take an optional parameter, a file name to which to
32463 write the information.
32465 @kindex maint print reggroups
32466 @item maint print reggroups @r{[}@var{file}@r{]}
32467 Print @value{GDBN}'s internal register group data structures. The
32468 optional argument @var{file} tells to what file to write the
32471 The register groups info looks like this:
32474 (@value{GDBP}) @kbd{maint print reggroups}
32487 This command forces @value{GDBN} to flush its internal register cache.
32489 @kindex maint print objfiles
32490 @cindex info for known object files
32491 @item maint print objfiles
32492 Print a dump of all known object files. For each object file, this
32493 command prints its name, address in memory, and all of its psymtabs
32496 @kindex maint print section-scripts
32497 @cindex info for known .debug_gdb_scripts-loaded scripts
32498 @item maint print section-scripts [@var{regexp}]
32499 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
32500 If @var{regexp} is specified, only print scripts loaded by object files
32501 matching @var{regexp}.
32502 For each script, this command prints its name as specified in the objfile,
32503 and the full path if known.
32504 @xref{.debug_gdb_scripts section}.
32506 @kindex maint print statistics
32507 @cindex bcache statistics
32508 @item maint print statistics
32509 This command prints, for each object file in the program, various data
32510 about that object file followed by the byte cache (@dfn{bcache})
32511 statistics for the object file. The objfile data includes the number
32512 of minimal, partial, full, and stabs symbols, the number of types
32513 defined by the objfile, the number of as yet unexpanded psym tables,
32514 the number of line tables and string tables, and the amount of memory
32515 used by the various tables. The bcache statistics include the counts,
32516 sizes, and counts of duplicates of all and unique objects, max,
32517 average, and median entry size, total memory used and its overhead and
32518 savings, and various measures of the hash table size and chain
32521 @kindex maint print target-stack
32522 @cindex target stack description
32523 @item maint print target-stack
32524 A @dfn{target} is an interface between the debugger and a particular
32525 kind of file or process. Targets can be stacked in @dfn{strata},
32526 so that more than one target can potentially respond to a request.
32527 In particular, memory accesses will walk down the stack of targets
32528 until they find a target that is interested in handling that particular
32531 This command prints a short description of each layer that was pushed on
32532 the @dfn{target stack}, starting from the top layer down to the bottom one.
32534 @kindex maint print type
32535 @cindex type chain of a data type
32536 @item maint print type @var{expr}
32537 Print the type chain for a type specified by @var{expr}. The argument
32538 can be either a type name or a symbol. If it is a symbol, the type of
32539 that symbol is described. The type chain produced by this command is
32540 a recursive definition of the data type as stored in @value{GDBN}'s
32541 data structures, including its flags and contained types.
32543 @kindex maint set dwarf2 always-disassemble
32544 @kindex maint show dwarf2 always-disassemble
32545 @item maint set dwarf2 always-disassemble
32546 @item maint show dwarf2 always-disassemble
32547 Control the behavior of @code{info address} when using DWARF debugging
32550 The default is @code{off}, which means that @value{GDBN} should try to
32551 describe a variable's location in an easily readable format. When
32552 @code{on}, @value{GDBN} will instead display the DWARF location
32553 expression in an assembly-like format. Note that some locations are
32554 too complex for @value{GDBN} to describe simply; in this case you will
32555 always see the disassembly form.
32557 Here is an example of the resulting disassembly:
32560 (gdb) info addr argc
32561 Symbol "argc" is a complex DWARF expression:
32565 For more information on these expressions, see
32566 @uref{http://www.dwarfstd.org/, the DWARF standard}.
32568 @kindex maint set dwarf2 max-cache-age
32569 @kindex maint show dwarf2 max-cache-age
32570 @item maint set dwarf2 max-cache-age
32571 @itemx maint show dwarf2 max-cache-age
32572 Control the DWARF 2 compilation unit cache.
32574 @cindex DWARF 2 compilation units cache
32575 In object files with inter-compilation-unit references, such as those
32576 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
32577 reader needs to frequently refer to previously read compilation units.
32578 This setting controls how long a compilation unit will remain in the
32579 cache if it is not referenced. A higher limit means that cached
32580 compilation units will be stored in memory longer, and more total
32581 memory will be used. Setting it to zero disables caching, which will
32582 slow down @value{GDBN} startup, but reduce memory consumption.
32584 @kindex maint set profile
32585 @kindex maint show profile
32586 @cindex profiling GDB
32587 @item maint set profile
32588 @itemx maint show profile
32589 Control profiling of @value{GDBN}.
32591 Profiling will be disabled until you use the @samp{maint set profile}
32592 command to enable it. When you enable profiling, the system will begin
32593 collecting timing and execution count data; when you disable profiling or
32594 exit @value{GDBN}, the results will be written to a log file. Remember that
32595 if you use profiling, @value{GDBN} will overwrite the profiling log file
32596 (often called @file{gmon.out}). If you have a record of important profiling
32597 data in a @file{gmon.out} file, be sure to move it to a safe location.
32599 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
32600 compiled with the @samp{-pg} compiler option.
32602 @kindex maint set show-debug-regs
32603 @kindex maint show show-debug-regs
32604 @cindex hardware debug registers
32605 @item maint set show-debug-regs
32606 @itemx maint show show-debug-regs
32607 Control whether to show variables that mirror the hardware debug
32608 registers. Use @code{ON} to enable, @code{OFF} to disable. If
32609 enabled, the debug registers values are shown when @value{GDBN} inserts or
32610 removes a hardware breakpoint or watchpoint, and when the inferior
32611 triggers a hardware-assisted breakpoint or watchpoint.
32613 @kindex maint set show-all-tib
32614 @kindex maint show show-all-tib
32615 @item maint set show-all-tib
32616 @itemx maint show show-all-tib
32617 Control whether to show all non zero areas within a 1k block starting
32618 at thread local base, when using the @samp{info w32 thread-information-block}
32621 @kindex maint space
32622 @cindex memory used by commands
32624 Control whether to display memory usage for each command. If set to a
32625 nonzero value, @value{GDBN} will display how much memory each command
32626 took, following the command's own output. This can also be requested
32627 by invoking @value{GDBN} with the @option{--statistics} command-line
32628 switch (@pxref{Mode Options}).
32631 @cindex time of command execution
32633 Control whether to display the execution time for each command. If
32634 set to a nonzero value, @value{GDBN} will display how much time it
32635 took to execute each command, following the command's own output.
32636 The time is not printed for the commands that run the target, since
32637 there's no mechanism currently to compute how much time was spend
32638 by @value{GDBN} and how much time was spend by the program been debugged.
32639 it's not possibly currently
32640 This can also be requested by invoking @value{GDBN} with the
32641 @option{--statistics} command-line switch (@pxref{Mode Options}).
32643 @kindex maint translate-address
32644 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
32645 Find the symbol stored at the location specified by the address
32646 @var{addr} and an optional section name @var{section}. If found,
32647 @value{GDBN} prints the name of the closest symbol and an offset from
32648 the symbol's location to the specified address. This is similar to
32649 the @code{info address} command (@pxref{Symbols}), except that this
32650 command also allows to find symbols in other sections.
32652 If section was not specified, the section in which the symbol was found
32653 is also printed. For dynamically linked executables, the name of
32654 executable or shared library containing the symbol is printed as well.
32658 The following command is useful for non-interactive invocations of
32659 @value{GDBN}, such as in the test suite.
32662 @item set watchdog @var{nsec}
32663 @kindex set watchdog
32664 @cindex watchdog timer
32665 @cindex timeout for commands
32666 Set the maximum number of seconds @value{GDBN} will wait for the
32667 target operation to finish. If this time expires, @value{GDBN}
32668 reports and error and the command is aborted.
32670 @item show watchdog
32671 Show the current setting of the target wait timeout.
32674 @node Remote Protocol
32675 @appendix @value{GDBN} Remote Serial Protocol
32680 * Stop Reply Packets::
32681 * General Query Packets::
32682 * Architecture-Specific Protocol Details::
32683 * Tracepoint Packets::
32684 * Host I/O Packets::
32686 * Notification Packets::
32687 * Remote Non-Stop::
32688 * Packet Acknowledgment::
32690 * File-I/O Remote Protocol Extension::
32691 * Library List Format::
32692 * Memory Map Format::
32693 * Thread List Format::
32694 * Traceframe Info Format::
32700 There may be occasions when you need to know something about the
32701 protocol---for example, if there is only one serial port to your target
32702 machine, you might want your program to do something special if it
32703 recognizes a packet meant for @value{GDBN}.
32705 In the examples below, @samp{->} and @samp{<-} are used to indicate
32706 transmitted and received data, respectively.
32708 @cindex protocol, @value{GDBN} remote serial
32709 @cindex serial protocol, @value{GDBN} remote
32710 @cindex remote serial protocol
32711 All @value{GDBN} commands and responses (other than acknowledgments
32712 and notifications, see @ref{Notification Packets}) are sent as a
32713 @var{packet}. A @var{packet} is introduced with the character
32714 @samp{$}, the actual @var{packet-data}, and the terminating character
32715 @samp{#} followed by a two-digit @var{checksum}:
32718 @code{$}@var{packet-data}@code{#}@var{checksum}
32722 @cindex checksum, for @value{GDBN} remote
32724 The two-digit @var{checksum} is computed as the modulo 256 sum of all
32725 characters between the leading @samp{$} and the trailing @samp{#} (an
32726 eight bit unsigned checksum).
32728 Implementors should note that prior to @value{GDBN} 5.0 the protocol
32729 specification also included an optional two-digit @var{sequence-id}:
32732 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
32735 @cindex sequence-id, for @value{GDBN} remote
32737 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
32738 has never output @var{sequence-id}s. Stubs that handle packets added
32739 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
32741 When either the host or the target machine receives a packet, the first
32742 response expected is an acknowledgment: either @samp{+} (to indicate
32743 the package was received correctly) or @samp{-} (to request
32747 -> @code{$}@var{packet-data}@code{#}@var{checksum}
32752 The @samp{+}/@samp{-} acknowledgments can be disabled
32753 once a connection is established.
32754 @xref{Packet Acknowledgment}, for details.
32756 The host (@value{GDBN}) sends @var{command}s, and the target (the
32757 debugging stub incorporated in your program) sends a @var{response}. In
32758 the case of step and continue @var{command}s, the response is only sent
32759 when the operation has completed, and the target has again stopped all
32760 threads in all attached processes. This is the default all-stop mode
32761 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
32762 execution mode; see @ref{Remote Non-Stop}, for details.
32764 @var{packet-data} consists of a sequence of characters with the
32765 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
32768 @cindex remote protocol, field separator
32769 Fields within the packet should be separated using @samp{,} @samp{;} or
32770 @samp{:}. Except where otherwise noted all numbers are represented in
32771 @sc{hex} with leading zeros suppressed.
32773 Implementors should note that prior to @value{GDBN} 5.0, the character
32774 @samp{:} could not appear as the third character in a packet (as it
32775 would potentially conflict with the @var{sequence-id}).
32777 @cindex remote protocol, binary data
32778 @anchor{Binary Data}
32779 Binary data in most packets is encoded either as two hexadecimal
32780 digits per byte of binary data. This allowed the traditional remote
32781 protocol to work over connections which were only seven-bit clean.
32782 Some packets designed more recently assume an eight-bit clean
32783 connection, and use a more efficient encoding to send and receive
32786 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
32787 as an escape character. Any escaped byte is transmitted as the escape
32788 character followed by the original character XORed with @code{0x20}.
32789 For example, the byte @code{0x7d} would be transmitted as the two
32790 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
32791 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
32792 @samp{@}}) must always be escaped. Responses sent by the stub
32793 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
32794 is not interpreted as the start of a run-length encoded sequence
32797 Response @var{data} can be run-length encoded to save space.
32798 Run-length encoding replaces runs of identical characters with one
32799 instance of the repeated character, followed by a @samp{*} and a
32800 repeat count. The repeat count is itself sent encoded, to avoid
32801 binary characters in @var{data}: a value of @var{n} is sent as
32802 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
32803 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
32804 code 32) for a repeat count of 3. (This is because run-length
32805 encoding starts to win for counts 3 or more.) Thus, for example,
32806 @samp{0* } is a run-length encoding of ``0000'': the space character
32807 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
32810 The printable characters @samp{#} and @samp{$} or with a numeric value
32811 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
32812 seven repeats (@samp{$}) can be expanded using a repeat count of only
32813 five (@samp{"}). For example, @samp{00000000} can be encoded as
32816 The error response returned for some packets includes a two character
32817 error number. That number is not well defined.
32819 @cindex empty response, for unsupported packets
32820 For any @var{command} not supported by the stub, an empty response
32821 (@samp{$#00}) should be returned. That way it is possible to extend the
32822 protocol. A newer @value{GDBN} can tell if a packet is supported based
32825 At a minimum, a stub is required to support the @samp{g} and @samp{G}
32826 commands for register access, and the @samp{m} and @samp{M} commands
32827 for memory access. Stubs that only control single-threaded targets
32828 can implement run control with the @samp{c} (continue), and @samp{s}
32829 (step) commands. Stubs that support multi-threading targets should
32830 support the @samp{vCont} command. All other commands are optional.
32835 The following table provides a complete list of all currently defined
32836 @var{command}s and their corresponding response @var{data}.
32837 @xref{File-I/O Remote Protocol Extension}, for details about the File
32838 I/O extension of the remote protocol.
32840 Each packet's description has a template showing the packet's overall
32841 syntax, followed by an explanation of the packet's meaning. We
32842 include spaces in some of the templates for clarity; these are not
32843 part of the packet's syntax. No @value{GDBN} packet uses spaces to
32844 separate its components. For example, a template like @samp{foo
32845 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
32846 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
32847 @var{baz}. @value{GDBN} does not transmit a space character between the
32848 @samp{foo} and the @var{bar}, or between the @var{bar} and the
32851 @cindex @var{thread-id}, in remote protocol
32852 @anchor{thread-id syntax}
32853 Several packets and replies include a @var{thread-id} field to identify
32854 a thread. Normally these are positive numbers with a target-specific
32855 interpretation, formatted as big-endian hex strings. A @var{thread-id}
32856 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
32859 In addition, the remote protocol supports a multiprocess feature in
32860 which the @var{thread-id} syntax is extended to optionally include both
32861 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
32862 The @var{pid} (process) and @var{tid} (thread) components each have the
32863 format described above: a positive number with target-specific
32864 interpretation formatted as a big-endian hex string, literal @samp{-1}
32865 to indicate all processes or threads (respectively), or @samp{0} to
32866 indicate an arbitrary process or thread. Specifying just a process, as
32867 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
32868 error to specify all processes but a specific thread, such as
32869 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
32870 for those packets and replies explicitly documented to include a process
32871 ID, rather than a @var{thread-id}.
32873 The multiprocess @var{thread-id} syntax extensions are only used if both
32874 @value{GDBN} and the stub report support for the @samp{multiprocess}
32875 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
32878 Note that all packet forms beginning with an upper- or lower-case
32879 letter, other than those described here, are reserved for future use.
32881 Here are the packet descriptions.
32886 @cindex @samp{!} packet
32887 @anchor{extended mode}
32888 Enable extended mode. In extended mode, the remote server is made
32889 persistent. The @samp{R} packet is used to restart the program being
32895 The remote target both supports and has enabled extended mode.
32899 @cindex @samp{?} packet
32900 Indicate the reason the target halted. The reply is the same as for
32901 step and continue. This packet has a special interpretation when the
32902 target is in non-stop mode; see @ref{Remote Non-Stop}.
32905 @xref{Stop Reply Packets}, for the reply specifications.
32907 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
32908 @cindex @samp{A} packet
32909 Initialized @code{argv[]} array passed into program. @var{arglen}
32910 specifies the number of bytes in the hex encoded byte stream
32911 @var{arg}. See @code{gdbserver} for more details.
32916 The arguments were set.
32922 @cindex @samp{b} packet
32923 (Don't use this packet; its behavior is not well-defined.)
32924 Change the serial line speed to @var{baud}.
32926 JTC: @emph{When does the transport layer state change? When it's
32927 received, or after the ACK is transmitted. In either case, there are
32928 problems if the command or the acknowledgment packet is dropped.}
32930 Stan: @emph{If people really wanted to add something like this, and get
32931 it working for the first time, they ought to modify ser-unix.c to send
32932 some kind of out-of-band message to a specially-setup stub and have the
32933 switch happen "in between" packets, so that from remote protocol's point
32934 of view, nothing actually happened.}
32936 @item B @var{addr},@var{mode}
32937 @cindex @samp{B} packet
32938 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
32939 breakpoint at @var{addr}.
32941 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
32942 (@pxref{insert breakpoint or watchpoint packet}).
32944 @cindex @samp{bc} packet
32947 Backward continue. Execute the target system in reverse. No parameter.
32948 @xref{Reverse Execution}, for more information.
32951 @xref{Stop Reply Packets}, for the reply specifications.
32953 @cindex @samp{bs} packet
32956 Backward single step. Execute one instruction in reverse. No parameter.
32957 @xref{Reverse Execution}, for more information.
32960 @xref{Stop Reply Packets}, for the reply specifications.
32962 @item c @r{[}@var{addr}@r{]}
32963 @cindex @samp{c} packet
32964 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
32965 resume at current address.
32967 This packet is deprecated for multi-threading support. @xref{vCont
32971 @xref{Stop Reply Packets}, for the reply specifications.
32973 @item C @var{sig}@r{[};@var{addr}@r{]}
32974 @cindex @samp{C} packet
32975 Continue with signal @var{sig} (hex signal number). If
32976 @samp{;@var{addr}} is omitted, resume at same address.
32978 This packet is deprecated for multi-threading support. @xref{vCont
32982 @xref{Stop Reply Packets}, for the reply specifications.
32985 @cindex @samp{d} packet
32988 Don't use this packet; instead, define a general set packet
32989 (@pxref{General Query Packets}).
32993 @cindex @samp{D} packet
32994 The first form of the packet is used to detach @value{GDBN} from the
32995 remote system. It is sent to the remote target
32996 before @value{GDBN} disconnects via the @code{detach} command.
32998 The second form, including a process ID, is used when multiprocess
32999 protocol extensions are enabled (@pxref{multiprocess extensions}), to
33000 detach only a specific process. The @var{pid} is specified as a
33001 big-endian hex string.
33011 @item F @var{RC},@var{EE},@var{CF};@var{XX}
33012 @cindex @samp{F} packet
33013 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
33014 This is part of the File-I/O protocol extension. @xref{File-I/O
33015 Remote Protocol Extension}, for the specification.
33018 @anchor{read registers packet}
33019 @cindex @samp{g} packet
33020 Read general registers.
33024 @item @var{XX@dots{}}
33025 Each byte of register data is described by two hex digits. The bytes
33026 with the register are transmitted in target byte order. The size of
33027 each register and their position within the @samp{g} packet are
33028 determined by the @value{GDBN} internal gdbarch functions
33029 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
33030 specification of several standard @samp{g} packets is specified below.
33032 When reading registers from a trace frame (@pxref{Analyze Collected
33033 Data,,Using the Collected Data}), the stub may also return a string of
33034 literal @samp{x}'s in place of the register data digits, to indicate
33035 that the corresponding register has not been collected, thus its value
33036 is unavailable. For example, for an architecture with 4 registers of
33037 4 bytes each, the following reply indicates to @value{GDBN} that
33038 registers 0 and 2 have not been collected, while registers 1 and 3
33039 have been collected, and both have zero value:
33043 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
33050 @item G @var{XX@dots{}}
33051 @cindex @samp{G} packet
33052 Write general registers. @xref{read registers packet}, for a
33053 description of the @var{XX@dots{}} data.
33063 @item H @var{op} @var{thread-id}
33064 @cindex @samp{H} packet
33065 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
33066 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
33067 it should be @samp{c} for step and continue operations (note that this
33068 is deprecated, supporting the @samp{vCont} command is a better
33069 option), @samp{g} for other operations. The thread designator
33070 @var{thread-id} has the format and interpretation described in
33071 @ref{thread-id syntax}.
33082 @c 'H': How restrictive (or permissive) is the thread model. If a
33083 @c thread is selected and stopped, are other threads allowed
33084 @c to continue to execute? As I mentioned above, I think the
33085 @c semantics of each command when a thread is selected must be
33086 @c described. For example:
33088 @c 'g': If the stub supports threads and a specific thread is
33089 @c selected, returns the register block from that thread;
33090 @c otherwise returns current registers.
33092 @c 'G' If the stub supports threads and a specific thread is
33093 @c selected, sets the registers of the register block of
33094 @c that thread; otherwise sets current registers.
33096 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
33097 @anchor{cycle step packet}
33098 @cindex @samp{i} packet
33099 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
33100 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
33101 step starting at that address.
33104 @cindex @samp{I} packet
33105 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
33109 @cindex @samp{k} packet
33112 FIXME: @emph{There is no description of how to operate when a specific
33113 thread context has been selected (i.e.@: does 'k' kill only that
33116 @item m @var{addr},@var{length}
33117 @cindex @samp{m} packet
33118 Read @var{length} bytes of memory starting at address @var{addr}.
33119 Note that @var{addr} may not be aligned to any particular boundary.
33121 The stub need not use any particular size or alignment when gathering
33122 data from memory for the response; even if @var{addr} is word-aligned
33123 and @var{length} is a multiple of the word size, the stub is free to
33124 use byte accesses, or not. For this reason, this packet may not be
33125 suitable for accessing memory-mapped I/O devices.
33126 @cindex alignment of remote memory accesses
33127 @cindex size of remote memory accesses
33128 @cindex memory, alignment and size of remote accesses
33132 @item @var{XX@dots{}}
33133 Memory contents; each byte is transmitted as a two-digit hexadecimal
33134 number. The reply may contain fewer bytes than requested if the
33135 server was able to read only part of the region of memory.
33140 @item M @var{addr},@var{length}:@var{XX@dots{}}
33141 @cindex @samp{M} packet
33142 Write @var{length} bytes of memory starting at address @var{addr}.
33143 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
33144 hexadecimal number.
33151 for an error (this includes the case where only part of the data was
33156 @cindex @samp{p} packet
33157 Read the value of register @var{n}; @var{n} is in hex.
33158 @xref{read registers packet}, for a description of how the returned
33159 register value is encoded.
33163 @item @var{XX@dots{}}
33164 the register's value
33168 Indicating an unrecognized @var{query}.
33171 @item P @var{n@dots{}}=@var{r@dots{}}
33172 @anchor{write register packet}
33173 @cindex @samp{P} packet
33174 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
33175 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
33176 digits for each byte in the register (target byte order).
33186 @item q @var{name} @var{params}@dots{}
33187 @itemx Q @var{name} @var{params}@dots{}
33188 @cindex @samp{q} packet
33189 @cindex @samp{Q} packet
33190 General query (@samp{q}) and set (@samp{Q}). These packets are
33191 described fully in @ref{General Query Packets}.
33194 @cindex @samp{r} packet
33195 Reset the entire system.
33197 Don't use this packet; use the @samp{R} packet instead.
33200 @cindex @samp{R} packet
33201 Restart the program being debugged. @var{XX}, while needed, is ignored.
33202 This packet is only available in extended mode (@pxref{extended mode}).
33204 The @samp{R} packet has no reply.
33206 @item s @r{[}@var{addr}@r{]}
33207 @cindex @samp{s} packet
33208 Single step. @var{addr} is the address at which to resume. If
33209 @var{addr} is omitted, resume at same address.
33211 This packet is deprecated for multi-threading support. @xref{vCont
33215 @xref{Stop Reply Packets}, for the reply specifications.
33217 @item S @var{sig}@r{[};@var{addr}@r{]}
33218 @anchor{step with signal packet}
33219 @cindex @samp{S} packet
33220 Step with signal. This is analogous to the @samp{C} packet, but
33221 requests a single-step, rather than a normal resumption of execution.
33223 This packet is deprecated for multi-threading support. @xref{vCont
33227 @xref{Stop Reply Packets}, for the reply specifications.
33229 @item t @var{addr}:@var{PP},@var{MM}
33230 @cindex @samp{t} packet
33231 Search backwards starting at address @var{addr} for a match with pattern
33232 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
33233 @var{addr} must be at least 3 digits.
33235 @item T @var{thread-id}
33236 @cindex @samp{T} packet
33237 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
33242 thread is still alive
33248 Packets starting with @samp{v} are identified by a multi-letter name,
33249 up to the first @samp{;} or @samp{?} (or the end of the packet).
33251 @item vAttach;@var{pid}
33252 @cindex @samp{vAttach} packet
33253 Attach to a new process with the specified process ID @var{pid}.
33254 The process ID is a
33255 hexadecimal integer identifying the process. In all-stop mode, all
33256 threads in the attached process are stopped; in non-stop mode, it may be
33257 attached without being stopped if that is supported by the target.
33259 @c In non-stop mode, on a successful vAttach, the stub should set the
33260 @c current thread to a thread of the newly-attached process. After
33261 @c attaching, GDB queries for the attached process's thread ID with qC.
33262 @c Also note that, from a user perspective, whether or not the
33263 @c target is stopped on attach in non-stop mode depends on whether you
33264 @c use the foreground or background version of the attach command, not
33265 @c on what vAttach does; GDB does the right thing with respect to either
33266 @c stopping or restarting threads.
33268 This packet is only available in extended mode (@pxref{extended mode}).
33274 @item @r{Any stop packet}
33275 for success in all-stop mode (@pxref{Stop Reply Packets})
33277 for success in non-stop mode (@pxref{Remote Non-Stop})
33280 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
33281 @cindex @samp{vCont} packet
33282 @anchor{vCont packet}
33283 Resume the inferior, specifying different actions for each thread.
33284 If an action is specified with no @var{thread-id}, then it is applied to any
33285 threads that don't have a specific action specified; if no default action is
33286 specified then other threads should remain stopped in all-stop mode and
33287 in their current state in non-stop mode.
33288 Specifying multiple
33289 default actions is an error; specifying no actions is also an error.
33290 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
33292 Currently supported actions are:
33298 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
33302 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
33307 The optional argument @var{addr} normally associated with the
33308 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
33309 not supported in @samp{vCont}.
33311 The @samp{t} action is only relevant in non-stop mode
33312 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
33313 A stop reply should be generated for any affected thread not already stopped.
33314 When a thread is stopped by means of a @samp{t} action,
33315 the corresponding stop reply should indicate that the thread has stopped with
33316 signal @samp{0}, regardless of whether the target uses some other signal
33317 as an implementation detail.
33320 @xref{Stop Reply Packets}, for the reply specifications.
33323 @cindex @samp{vCont?} packet
33324 Request a list of actions supported by the @samp{vCont} packet.
33328 @item vCont@r{[};@var{action}@dots{}@r{]}
33329 The @samp{vCont} packet is supported. Each @var{action} is a supported
33330 command in the @samp{vCont} packet.
33332 The @samp{vCont} packet is not supported.
33335 @item vFile:@var{operation}:@var{parameter}@dots{}
33336 @cindex @samp{vFile} packet
33337 Perform a file operation on the target system. For details,
33338 see @ref{Host I/O Packets}.
33340 @item vFlashErase:@var{addr},@var{length}
33341 @cindex @samp{vFlashErase} packet
33342 Direct the stub to erase @var{length} bytes of flash starting at
33343 @var{addr}. The region may enclose any number of flash blocks, but
33344 its start and end must fall on block boundaries, as indicated by the
33345 flash block size appearing in the memory map (@pxref{Memory Map
33346 Format}). @value{GDBN} groups flash memory programming operations
33347 together, and sends a @samp{vFlashDone} request after each group; the
33348 stub is allowed to delay erase operation until the @samp{vFlashDone}
33349 packet is received.
33351 The stub must support @samp{vCont} if it reports support for
33352 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
33353 this case @samp{vCont} actions can be specified to apply to all threads
33354 in a process by using the @samp{p@var{pid}.-1} form of the
33365 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
33366 @cindex @samp{vFlashWrite} packet
33367 Direct the stub to write data to flash address @var{addr}. The data
33368 is passed in binary form using the same encoding as for the @samp{X}
33369 packet (@pxref{Binary Data}). The memory ranges specified by
33370 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
33371 not overlap, and must appear in order of increasing addresses
33372 (although @samp{vFlashErase} packets for higher addresses may already
33373 have been received; the ordering is guaranteed only between
33374 @samp{vFlashWrite} packets). If a packet writes to an address that was
33375 neither erased by a preceding @samp{vFlashErase} packet nor by some other
33376 target-specific method, the results are unpredictable.
33384 for vFlashWrite addressing non-flash memory
33390 @cindex @samp{vFlashDone} packet
33391 Indicate to the stub that flash programming operation is finished.
33392 The stub is permitted to delay or batch the effects of a group of
33393 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
33394 @samp{vFlashDone} packet is received. The contents of the affected
33395 regions of flash memory are unpredictable until the @samp{vFlashDone}
33396 request is completed.
33398 @item vKill;@var{pid}
33399 @cindex @samp{vKill} packet
33400 Kill the process with the specified process ID. @var{pid} is a
33401 hexadecimal integer identifying the process. This packet is used in
33402 preference to @samp{k} when multiprocess protocol extensions are
33403 supported; see @ref{multiprocess extensions}.
33413 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
33414 @cindex @samp{vRun} packet
33415 Run the program @var{filename}, passing it each @var{argument} on its
33416 command line. The file and arguments are hex-encoded strings. If
33417 @var{filename} is an empty string, the stub may use a default program
33418 (e.g.@: the last program run). The program is created in the stopped
33421 @c FIXME: What about non-stop mode?
33423 This packet is only available in extended mode (@pxref{extended mode}).
33429 @item @r{Any stop packet}
33430 for success (@pxref{Stop Reply Packets})
33434 @anchor{vStopped packet}
33435 @cindex @samp{vStopped} packet
33437 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
33438 reply and prompt for the stub to report another one.
33442 @item @r{Any stop packet}
33443 if there is another unreported stop event (@pxref{Stop Reply Packets})
33445 if there are no unreported stop events
33448 @item X @var{addr},@var{length}:@var{XX@dots{}}
33450 @cindex @samp{X} packet
33451 Write data to memory, where the data is transmitted in binary.
33452 @var{addr} is address, @var{length} is number of bytes,
33453 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
33463 @item z @var{type},@var{addr},@var{kind}
33464 @itemx Z @var{type},@var{addr},@var{kind}
33465 @anchor{insert breakpoint or watchpoint packet}
33466 @cindex @samp{z} packet
33467 @cindex @samp{Z} packets
33468 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
33469 watchpoint starting at address @var{address} of kind @var{kind}.
33471 Each breakpoint and watchpoint packet @var{type} is documented
33474 @emph{Implementation notes: A remote target shall return an empty string
33475 for an unrecognized breakpoint or watchpoint packet @var{type}. A
33476 remote target shall support either both or neither of a given
33477 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
33478 avoid potential problems with duplicate packets, the operations should
33479 be implemented in an idempotent way.}
33481 @item z0,@var{addr},@var{kind}
33482 @itemx Z0,@var{addr},@var{kind}
33483 @cindex @samp{z0} packet
33484 @cindex @samp{Z0} packet
33485 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
33486 @var{addr} of type @var{kind}.
33488 A memory breakpoint is implemented by replacing the instruction at
33489 @var{addr} with a software breakpoint or trap instruction. The
33490 @var{kind} is target-specific and typically indicates the size of
33491 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
33492 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
33493 architectures have additional meanings for @var{kind};
33494 see @ref{Architecture-Specific Protocol Details}.
33496 @emph{Implementation note: It is possible for a target to copy or move
33497 code that contains memory breakpoints (e.g., when implementing
33498 overlays). The behavior of this packet, in the presence of such a
33499 target, is not defined.}
33511 @item z1,@var{addr},@var{kind}
33512 @itemx Z1,@var{addr},@var{kind}
33513 @cindex @samp{z1} packet
33514 @cindex @samp{Z1} packet
33515 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
33516 address @var{addr}.
33518 A hardware breakpoint is implemented using a mechanism that is not
33519 dependant on being able to modify the target's memory. @var{kind}
33520 has the same meaning as in @samp{Z0} packets.
33522 @emph{Implementation note: A hardware breakpoint is not affected by code
33535 @item z2,@var{addr},@var{kind}
33536 @itemx Z2,@var{addr},@var{kind}
33537 @cindex @samp{z2} packet
33538 @cindex @samp{Z2} packet
33539 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
33540 @var{kind} is interpreted as the number of bytes to watch.
33552 @item z3,@var{addr},@var{kind}
33553 @itemx Z3,@var{addr},@var{kind}
33554 @cindex @samp{z3} packet
33555 @cindex @samp{Z3} packet
33556 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
33557 @var{kind} is interpreted as the number of bytes to watch.
33569 @item z4,@var{addr},@var{kind}
33570 @itemx Z4,@var{addr},@var{kind}
33571 @cindex @samp{z4} packet
33572 @cindex @samp{Z4} packet
33573 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
33574 @var{kind} is interpreted as the number of bytes to watch.
33588 @node Stop Reply Packets
33589 @section Stop Reply Packets
33590 @cindex stop reply packets
33592 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
33593 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
33594 receive any of the below as a reply. Except for @samp{?}
33595 and @samp{vStopped}, that reply is only returned
33596 when the target halts. In the below the exact meaning of @dfn{signal
33597 number} is defined by the header @file{include/gdb/signals.h} in the
33598 @value{GDBN} source code.
33600 As in the description of request packets, we include spaces in the
33601 reply templates for clarity; these are not part of the reply packet's
33602 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
33608 The program received signal number @var{AA} (a two-digit hexadecimal
33609 number). This is equivalent to a @samp{T} response with no
33610 @var{n}:@var{r} pairs.
33612 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
33613 @cindex @samp{T} packet reply
33614 The program received signal number @var{AA} (a two-digit hexadecimal
33615 number). This is equivalent to an @samp{S} response, except that the
33616 @samp{@var{n}:@var{r}} pairs can carry values of important registers
33617 and other information directly in the stop reply packet, reducing
33618 round-trip latency. Single-step and breakpoint traps are reported
33619 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
33623 If @var{n} is a hexadecimal number, it is a register number, and the
33624 corresponding @var{r} gives that register's value. @var{r} is a
33625 series of bytes in target byte order, with each byte given by a
33626 two-digit hex number.
33629 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
33630 the stopped thread, as specified in @ref{thread-id syntax}.
33633 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
33634 the core on which the stop event was detected.
33637 If @var{n} is a recognized @dfn{stop reason}, it describes a more
33638 specific event that stopped the target. The currently defined stop
33639 reasons are listed below. @var{aa} should be @samp{05}, the trap
33640 signal. At most one stop reason should be present.
33643 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
33644 and go on to the next; this allows us to extend the protocol in the
33648 The currently defined stop reasons are:
33654 The packet indicates a watchpoint hit, and @var{r} is the data address, in
33657 @cindex shared library events, remote reply
33659 The packet indicates that the loaded libraries have changed.
33660 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
33661 list of loaded libraries. @var{r} is ignored.
33663 @cindex replay log events, remote reply
33665 The packet indicates that the target cannot continue replaying
33666 logged execution events, because it has reached the end (or the
33667 beginning when executing backward) of the log. The value of @var{r}
33668 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
33669 for more information.
33673 @itemx W @var{AA} ; process:@var{pid}
33674 The process exited, and @var{AA} is the exit status. This is only
33675 applicable to certain targets.
33677 The second form of the response, including the process ID of the exited
33678 process, can be used only when @value{GDBN} has reported support for
33679 multiprocess protocol extensions; see @ref{multiprocess extensions}.
33680 The @var{pid} is formatted as a big-endian hex string.
33683 @itemx X @var{AA} ; process:@var{pid}
33684 The process terminated with signal @var{AA}.
33686 The second form of the response, including the process ID of the
33687 terminated process, can be used only when @value{GDBN} has reported
33688 support for multiprocess protocol extensions; see @ref{multiprocess
33689 extensions}. The @var{pid} is formatted as a big-endian hex string.
33691 @item O @var{XX}@dots{}
33692 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
33693 written as the program's console output. This can happen at any time
33694 while the program is running and the debugger should continue to wait
33695 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
33697 @item F @var{call-id},@var{parameter}@dots{}
33698 @var{call-id} is the identifier which says which host system call should
33699 be called. This is just the name of the function. Translation into the
33700 correct system call is only applicable as it's defined in @value{GDBN}.
33701 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
33704 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
33705 this very system call.
33707 The target replies with this packet when it expects @value{GDBN} to
33708 call a host system call on behalf of the target. @value{GDBN} replies
33709 with an appropriate @samp{F} packet and keeps up waiting for the next
33710 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
33711 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
33712 Protocol Extension}, for more details.
33716 @node General Query Packets
33717 @section General Query Packets
33718 @cindex remote query requests
33720 Packets starting with @samp{q} are @dfn{general query packets};
33721 packets starting with @samp{Q} are @dfn{general set packets}. General
33722 query and set packets are a semi-unified form for retrieving and
33723 sending information to and from the stub.
33725 The initial letter of a query or set packet is followed by a name
33726 indicating what sort of thing the packet applies to. For example,
33727 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
33728 definitions with the stub. These packet names follow some
33733 The name must not contain commas, colons or semicolons.
33735 Most @value{GDBN} query and set packets have a leading upper case
33738 The names of custom vendor packets should use a company prefix, in
33739 lower case, followed by a period. For example, packets designed at
33740 the Acme Corporation might begin with @samp{qacme.foo} (for querying
33741 foos) or @samp{Qacme.bar} (for setting bars).
33744 The name of a query or set packet should be separated from any
33745 parameters by a @samp{:}; the parameters themselves should be
33746 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
33747 full packet name, and check for a separator or the end of the packet,
33748 in case two packet names share a common prefix. New packets should not begin
33749 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
33750 packets predate these conventions, and have arguments without any terminator
33751 for the packet name; we suspect they are in widespread use in places that
33752 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
33753 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
33756 Like the descriptions of the other packets, each description here
33757 has a template showing the packet's overall syntax, followed by an
33758 explanation of the packet's meaning. We include spaces in some of the
33759 templates for clarity; these are not part of the packet's syntax. No
33760 @value{GDBN} packet uses spaces to separate its components.
33762 Here are the currently defined query and set packets:
33766 @item QAllow:@var{op}:@var{val}@dots{}
33767 @cindex @samp{QAllow} packet
33768 Specify which operations @value{GDBN} expects to request of the
33769 target, as a semicolon-separated list of operation name and value
33770 pairs. Possible values for @var{op} include @samp{WriteReg},
33771 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
33772 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
33773 indicating that @value{GDBN} will not request the operation, or 1,
33774 indicating that it may. (The target can then use this to set up its
33775 own internals optimally, for instance if the debugger never expects to
33776 insert breakpoints, it may not need to install its own trap handler.)
33779 @cindex current thread, remote request
33780 @cindex @samp{qC} packet
33781 Return the current thread ID.
33785 @item QC @var{thread-id}
33786 Where @var{thread-id} is a thread ID as documented in
33787 @ref{thread-id syntax}.
33788 @item @r{(anything else)}
33789 Any other reply implies the old thread ID.
33792 @item qCRC:@var{addr},@var{length}
33793 @cindex CRC of memory block, remote request
33794 @cindex @samp{qCRC} packet
33795 Compute the CRC checksum of a block of memory using CRC-32 defined in
33796 IEEE 802.3. The CRC is computed byte at a time, taking the most
33797 significant bit of each byte first. The initial pattern code
33798 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
33800 @emph{Note:} This is the same CRC used in validating separate debug
33801 files (@pxref{Separate Debug Files, , Debugging Information in Separate
33802 Files}). However the algorithm is slightly different. When validating
33803 separate debug files, the CRC is computed taking the @emph{least}
33804 significant bit of each byte first, and the final result is inverted to
33805 detect trailing zeros.
33810 An error (such as memory fault)
33811 @item C @var{crc32}
33812 The specified memory region's checksum is @var{crc32}.
33815 @item QDisableRandomization:@var{value}
33816 @cindex disable address space randomization, remote request
33817 @cindex @samp{QDisableRandomization} packet
33818 Some target operating systems will randomize the virtual address space
33819 of the inferior process as a security feature, but provide a feature
33820 to disable such randomization, e.g.@: to allow for a more deterministic
33821 debugging experience. On such systems, this packet with a @var{value}
33822 of 1 directs the target to disable address space randomization for
33823 processes subsequently started via @samp{vRun} packets, while a packet
33824 with a @var{value} of 0 tells the target to enable address space
33827 This packet is only available in extended mode (@pxref{extended mode}).
33832 The request succeeded.
33835 An error occurred. @var{nn} are hex digits.
33838 An empty reply indicates that @samp{QDisableRandomization} is not supported
33842 This packet is not probed by default; the remote stub must request it,
33843 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33844 This should only be done on targets that actually support disabling
33845 address space randomization.
33848 @itemx qsThreadInfo
33849 @cindex list active threads, remote request
33850 @cindex @samp{qfThreadInfo} packet
33851 @cindex @samp{qsThreadInfo} packet
33852 Obtain a list of all active thread IDs from the target (OS). Since there
33853 may be too many active threads to fit into one reply packet, this query
33854 works iteratively: it may require more than one query/reply sequence to
33855 obtain the entire list of threads. The first query of the sequence will
33856 be the @samp{qfThreadInfo} query; subsequent queries in the
33857 sequence will be the @samp{qsThreadInfo} query.
33859 NOTE: This packet replaces the @samp{qL} query (see below).
33863 @item m @var{thread-id}
33865 @item m @var{thread-id},@var{thread-id}@dots{}
33866 a comma-separated list of thread IDs
33868 (lower case letter @samp{L}) denotes end of list.
33871 In response to each query, the target will reply with a list of one or
33872 more thread IDs, separated by commas.
33873 @value{GDBN} will respond to each reply with a request for more thread
33874 ids (using the @samp{qs} form of the query), until the target responds
33875 with @samp{l} (lower-case ell, for @dfn{last}).
33876 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
33879 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
33880 @cindex get thread-local storage address, remote request
33881 @cindex @samp{qGetTLSAddr} packet
33882 Fetch the address associated with thread local storage specified
33883 by @var{thread-id}, @var{offset}, and @var{lm}.
33885 @var{thread-id} is the thread ID associated with the
33886 thread for which to fetch the TLS address. @xref{thread-id syntax}.
33888 @var{offset} is the (big endian, hex encoded) offset associated with the
33889 thread local variable. (This offset is obtained from the debug
33890 information associated with the variable.)
33892 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
33893 load module associated with the thread local storage. For example,
33894 a @sc{gnu}/Linux system will pass the link map address of the shared
33895 object associated with the thread local storage under consideration.
33896 Other operating environments may choose to represent the load module
33897 differently, so the precise meaning of this parameter will vary.
33901 @item @var{XX}@dots{}
33902 Hex encoded (big endian) bytes representing the address of the thread
33903 local storage requested.
33906 An error occurred. @var{nn} are hex digits.
33909 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
33912 @item qGetTIBAddr:@var{thread-id}
33913 @cindex get thread information block address
33914 @cindex @samp{qGetTIBAddr} packet
33915 Fetch address of the Windows OS specific Thread Information Block.
33917 @var{thread-id} is the thread ID associated with the thread.
33921 @item @var{XX}@dots{}
33922 Hex encoded (big endian) bytes representing the linear address of the
33923 thread information block.
33926 An error occured. This means that either the thread was not found, or the
33927 address could not be retrieved.
33930 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
33933 @item qL @var{startflag} @var{threadcount} @var{nextthread}
33934 Obtain thread information from RTOS. Where: @var{startflag} (one hex
33935 digit) is one to indicate the first query and zero to indicate a
33936 subsequent query; @var{threadcount} (two hex digits) is the maximum
33937 number of threads the response packet can contain; and @var{nextthread}
33938 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
33939 returned in the response as @var{argthread}.
33941 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
33945 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
33946 Where: @var{count} (two hex digits) is the number of threads being
33947 returned; @var{done} (one hex digit) is zero to indicate more threads
33948 and one indicates no further threads; @var{argthreadid} (eight hex
33949 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
33950 is a sequence of thread IDs from the target. @var{threadid} (eight hex
33951 digits). See @code{remote.c:parse_threadlist_response()}.
33955 @cindex section offsets, remote request
33956 @cindex @samp{qOffsets} packet
33957 Get section offsets that the target used when relocating the downloaded
33962 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
33963 Relocate the @code{Text} section by @var{xxx} from its original address.
33964 Relocate the @code{Data} section by @var{yyy} from its original address.
33965 If the object file format provides segment information (e.g.@: @sc{elf}
33966 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
33967 segments by the supplied offsets.
33969 @emph{Note: while a @code{Bss} offset may be included in the response,
33970 @value{GDBN} ignores this and instead applies the @code{Data} offset
33971 to the @code{Bss} section.}
33973 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
33974 Relocate the first segment of the object file, which conventionally
33975 contains program code, to a starting address of @var{xxx}. If
33976 @samp{DataSeg} is specified, relocate the second segment, which
33977 conventionally contains modifiable data, to a starting address of
33978 @var{yyy}. @value{GDBN} will report an error if the object file
33979 does not contain segment information, or does not contain at least
33980 as many segments as mentioned in the reply. Extra segments are
33981 kept at fixed offsets relative to the last relocated segment.
33984 @item qP @var{mode} @var{thread-id}
33985 @cindex thread information, remote request
33986 @cindex @samp{qP} packet
33987 Returns information on @var{thread-id}. Where: @var{mode} is a hex
33988 encoded 32 bit mode; @var{thread-id} is a thread ID
33989 (@pxref{thread-id syntax}).
33991 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
33994 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
33998 @cindex non-stop mode, remote request
33999 @cindex @samp{QNonStop} packet
34001 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
34002 @xref{Remote Non-Stop}, for more information.
34007 The request succeeded.
34010 An error occurred. @var{nn} are hex digits.
34013 An empty reply indicates that @samp{QNonStop} is not supported by
34017 This packet is not probed by default; the remote stub must request it,
34018 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34019 Use of this packet is controlled by the @code{set non-stop} command;
34020 @pxref{Non-Stop Mode}.
34022 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
34023 @cindex pass signals to inferior, remote request
34024 @cindex @samp{QPassSignals} packet
34025 @anchor{QPassSignals}
34026 Each listed @var{signal} should be passed directly to the inferior process.
34027 Signals are numbered identically to continue packets and stop replies
34028 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
34029 strictly greater than the previous item. These signals do not need to stop
34030 the inferior, or be reported to @value{GDBN}. All other signals should be
34031 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
34032 combine; any earlier @samp{QPassSignals} list is completely replaced by the
34033 new list. This packet improves performance when using @samp{handle
34034 @var{signal} nostop noprint pass}.
34039 The request succeeded.
34042 An error occurred. @var{nn} are hex digits.
34045 An empty reply indicates that @samp{QPassSignals} is not supported by
34049 Use of this packet is controlled by the @code{set remote pass-signals}
34050 command (@pxref{Remote Configuration, set remote pass-signals}).
34051 This packet is not probed by default; the remote stub must request it,
34052 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34054 @item qRcmd,@var{command}
34055 @cindex execute remote command, remote request
34056 @cindex @samp{qRcmd} packet
34057 @var{command} (hex encoded) is passed to the local interpreter for
34058 execution. Invalid commands should be reported using the output
34059 string. Before the final result packet, the target may also respond
34060 with a number of intermediate @samp{O@var{output}} console output
34061 packets. @emph{Implementors should note that providing access to a
34062 stubs's interpreter may have security implications}.
34067 A command response with no output.
34069 A command response with the hex encoded output string @var{OUTPUT}.
34071 Indicate a badly formed request.
34073 An empty reply indicates that @samp{qRcmd} is not recognized.
34076 (Note that the @code{qRcmd} packet's name is separated from the
34077 command by a @samp{,}, not a @samp{:}, contrary to the naming
34078 conventions above. Please don't use this packet as a model for new
34081 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
34082 @cindex searching memory, in remote debugging
34083 @cindex @samp{qSearch:memory} packet
34084 @anchor{qSearch memory}
34085 Search @var{length} bytes at @var{address} for @var{search-pattern}.
34086 @var{address} and @var{length} are encoded in hex.
34087 @var{search-pattern} is a sequence of bytes, hex encoded.
34092 The pattern was not found.
34094 The pattern was found at @var{address}.
34096 A badly formed request or an error was encountered while searching memory.
34098 An empty reply indicates that @samp{qSearch:memory} is not recognized.
34101 @item QStartNoAckMode
34102 @cindex @samp{QStartNoAckMode} packet
34103 @anchor{QStartNoAckMode}
34104 Request that the remote stub disable the normal @samp{+}/@samp{-}
34105 protocol acknowledgments (@pxref{Packet Acknowledgment}).
34110 The stub has switched to no-acknowledgment mode.
34111 @value{GDBN} acknowledges this reponse,
34112 but neither the stub nor @value{GDBN} shall send or expect further
34113 @samp{+}/@samp{-} acknowledgments in the current connection.
34115 An empty reply indicates that the stub does not support no-acknowledgment mode.
34118 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
34119 @cindex supported packets, remote query
34120 @cindex features of the remote protocol
34121 @cindex @samp{qSupported} packet
34122 @anchor{qSupported}
34123 Tell the remote stub about features supported by @value{GDBN}, and
34124 query the stub for features it supports. This packet allows
34125 @value{GDBN} and the remote stub to take advantage of each others'
34126 features. @samp{qSupported} also consolidates multiple feature probes
34127 at startup, to improve @value{GDBN} performance---a single larger
34128 packet performs better than multiple smaller probe packets on
34129 high-latency links. Some features may enable behavior which must not
34130 be on by default, e.g.@: because it would confuse older clients or
34131 stubs. Other features may describe packets which could be
34132 automatically probed for, but are not. These features must be
34133 reported before @value{GDBN} will use them. This ``default
34134 unsupported'' behavior is not appropriate for all packets, but it
34135 helps to keep the initial connection time under control with new
34136 versions of @value{GDBN} which support increasing numbers of packets.
34140 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
34141 The stub supports or does not support each returned @var{stubfeature},
34142 depending on the form of each @var{stubfeature} (see below for the
34145 An empty reply indicates that @samp{qSupported} is not recognized,
34146 or that no features needed to be reported to @value{GDBN}.
34149 The allowed forms for each feature (either a @var{gdbfeature} in the
34150 @samp{qSupported} packet, or a @var{stubfeature} in the response)
34154 @item @var{name}=@var{value}
34155 The remote protocol feature @var{name} is supported, and associated
34156 with the specified @var{value}. The format of @var{value} depends
34157 on the feature, but it must not include a semicolon.
34159 The remote protocol feature @var{name} is supported, and does not
34160 need an associated value.
34162 The remote protocol feature @var{name} is not supported.
34164 The remote protocol feature @var{name} may be supported, and
34165 @value{GDBN} should auto-detect support in some other way when it is
34166 needed. This form will not be used for @var{gdbfeature} notifications,
34167 but may be used for @var{stubfeature} responses.
34170 Whenever the stub receives a @samp{qSupported} request, the
34171 supplied set of @value{GDBN} features should override any previous
34172 request. This allows @value{GDBN} to put the stub in a known
34173 state, even if the stub had previously been communicating with
34174 a different version of @value{GDBN}.
34176 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
34181 This feature indicates whether @value{GDBN} supports multiprocess
34182 extensions to the remote protocol. @value{GDBN} does not use such
34183 extensions unless the stub also reports that it supports them by
34184 including @samp{multiprocess+} in its @samp{qSupported} reply.
34185 @xref{multiprocess extensions}, for details.
34188 This feature indicates that @value{GDBN} supports the XML target
34189 description. If the stub sees @samp{xmlRegisters=} with target
34190 specific strings separated by a comma, it will report register
34194 This feature indicates whether @value{GDBN} supports the
34195 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
34196 instruction reply packet}).
34199 Stubs should ignore any unknown values for
34200 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
34201 packet supports receiving packets of unlimited length (earlier
34202 versions of @value{GDBN} may reject overly long responses). Additional values
34203 for @var{gdbfeature} may be defined in the future to let the stub take
34204 advantage of new features in @value{GDBN}, e.g.@: incompatible
34205 improvements in the remote protocol---the @samp{multiprocess} feature is
34206 an example of such a feature. The stub's reply should be independent
34207 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
34208 describes all the features it supports, and then the stub replies with
34209 all the features it supports.
34211 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
34212 responses, as long as each response uses one of the standard forms.
34214 Some features are flags. A stub which supports a flag feature
34215 should respond with a @samp{+} form response. Other features
34216 require values, and the stub should respond with an @samp{=}
34219 Each feature has a default value, which @value{GDBN} will use if
34220 @samp{qSupported} is not available or if the feature is not mentioned
34221 in the @samp{qSupported} response. The default values are fixed; a
34222 stub is free to omit any feature responses that match the defaults.
34224 Not all features can be probed, but for those which can, the probing
34225 mechanism is useful: in some cases, a stub's internal
34226 architecture may not allow the protocol layer to know some information
34227 about the underlying target in advance. This is especially common in
34228 stubs which may be configured for multiple targets.
34230 These are the currently defined stub features and their properties:
34232 @multitable @columnfractions 0.35 0.2 0.12 0.2
34233 @c NOTE: The first row should be @headitem, but we do not yet require
34234 @c a new enough version of Texinfo (4.7) to use @headitem.
34236 @tab Value Required
34240 @item @samp{PacketSize}
34245 @item @samp{qXfer:auxv:read}
34250 @item @samp{qXfer:features:read}
34255 @item @samp{qXfer:libraries:read}
34260 @item @samp{qXfer:memory-map:read}
34265 @item @samp{qXfer:sdata:read}
34270 @item @samp{qXfer:spu:read}
34275 @item @samp{qXfer:spu:write}
34280 @item @samp{qXfer:siginfo:read}
34285 @item @samp{qXfer:siginfo:write}
34290 @item @samp{qXfer:threads:read}
34295 @item @samp{qXfer:traceframe-info:read}
34300 @item @samp{qXfer:fdpic:read}
34305 @item @samp{QNonStop}
34310 @item @samp{QPassSignals}
34315 @item @samp{QStartNoAckMode}
34320 @item @samp{multiprocess}
34325 @item @samp{ConditionalTracepoints}
34330 @item @samp{ReverseContinue}
34335 @item @samp{ReverseStep}
34340 @item @samp{TracepointSource}
34345 @item @samp{QAllow}
34350 @item @samp{QDisableRandomization}
34355 @item @samp{EnableDisableTracepoints}
34362 These are the currently defined stub features, in more detail:
34365 @cindex packet size, remote protocol
34366 @item PacketSize=@var{bytes}
34367 The remote stub can accept packets up to at least @var{bytes} in
34368 length. @value{GDBN} will send packets up to this size for bulk
34369 transfers, and will never send larger packets. This is a limit on the
34370 data characters in the packet, including the frame and checksum.
34371 There is no trailing NUL byte in a remote protocol packet; if the stub
34372 stores packets in a NUL-terminated format, it should allow an extra
34373 byte in its buffer for the NUL. If this stub feature is not supported,
34374 @value{GDBN} guesses based on the size of the @samp{g} packet response.
34376 @item qXfer:auxv:read
34377 The remote stub understands the @samp{qXfer:auxv:read} packet
34378 (@pxref{qXfer auxiliary vector read}).
34380 @item qXfer:features:read
34381 The remote stub understands the @samp{qXfer:features:read} packet
34382 (@pxref{qXfer target description read}).
34384 @item qXfer:libraries:read
34385 The remote stub understands the @samp{qXfer:libraries:read} packet
34386 (@pxref{qXfer library list read}).
34388 @item qXfer:memory-map:read
34389 The remote stub understands the @samp{qXfer:memory-map:read} packet
34390 (@pxref{qXfer memory map read}).
34392 @item qXfer:sdata:read
34393 The remote stub understands the @samp{qXfer:sdata:read} packet
34394 (@pxref{qXfer sdata read}).
34396 @item qXfer:spu:read
34397 The remote stub understands the @samp{qXfer:spu:read} packet
34398 (@pxref{qXfer spu read}).
34400 @item qXfer:spu:write
34401 The remote stub understands the @samp{qXfer:spu:write} packet
34402 (@pxref{qXfer spu write}).
34404 @item qXfer:siginfo:read
34405 The remote stub understands the @samp{qXfer:siginfo:read} packet
34406 (@pxref{qXfer siginfo read}).
34408 @item qXfer:siginfo:write
34409 The remote stub understands the @samp{qXfer:siginfo:write} packet
34410 (@pxref{qXfer siginfo write}).
34412 @item qXfer:threads:read
34413 The remote stub understands the @samp{qXfer:threads:read} packet
34414 (@pxref{qXfer threads read}).
34416 @item qXfer:traceframe-info:read
34417 The remote stub understands the @samp{qXfer:traceframe-info:read}
34418 packet (@pxref{qXfer traceframe info read}).
34420 @item qXfer:fdpic:read
34421 The remote stub understands the @samp{qXfer:fdpic:read}
34422 packet (@pxref{qXfer fdpic loadmap read}).
34425 The remote stub understands the @samp{QNonStop} packet
34426 (@pxref{QNonStop}).
34429 The remote stub understands the @samp{QPassSignals} packet
34430 (@pxref{QPassSignals}).
34432 @item QStartNoAckMode
34433 The remote stub understands the @samp{QStartNoAckMode} packet and
34434 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
34437 @anchor{multiprocess extensions}
34438 @cindex multiprocess extensions, in remote protocol
34439 The remote stub understands the multiprocess extensions to the remote
34440 protocol syntax. The multiprocess extensions affect the syntax of
34441 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
34442 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
34443 replies. Note that reporting this feature indicates support for the
34444 syntactic extensions only, not that the stub necessarily supports
34445 debugging of more than one process at a time. The stub must not use
34446 multiprocess extensions in packet replies unless @value{GDBN} has also
34447 indicated it supports them in its @samp{qSupported} request.
34449 @item qXfer:osdata:read
34450 The remote stub understands the @samp{qXfer:osdata:read} packet
34451 ((@pxref{qXfer osdata read}).
34453 @item ConditionalTracepoints
34454 The remote stub accepts and implements conditional expressions defined
34455 for tracepoints (@pxref{Tracepoint Conditions}).
34457 @item ReverseContinue
34458 The remote stub accepts and implements the reverse continue packet
34462 The remote stub accepts and implements the reverse step packet
34465 @item TracepointSource
34466 The remote stub understands the @samp{QTDPsrc} packet that supplies
34467 the source form of tracepoint definitions.
34470 The remote stub understands the @samp{QAllow} packet.
34472 @item QDisableRandomization
34473 The remote stub understands the @samp{QDisableRandomization} packet.
34475 @item StaticTracepoint
34476 @cindex static tracepoints, in remote protocol
34477 The remote stub supports static tracepoints.
34479 @item EnableDisableTracepoints
34480 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
34481 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
34482 to be enabled and disabled while a trace experiment is running.
34487 @cindex symbol lookup, remote request
34488 @cindex @samp{qSymbol} packet
34489 Notify the target that @value{GDBN} is prepared to serve symbol lookup
34490 requests. Accept requests from the target for the values of symbols.
34495 The target does not need to look up any (more) symbols.
34496 @item qSymbol:@var{sym_name}
34497 The target requests the value of symbol @var{sym_name} (hex encoded).
34498 @value{GDBN} may provide the value by using the
34499 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
34503 @item qSymbol:@var{sym_value}:@var{sym_name}
34504 Set the value of @var{sym_name} to @var{sym_value}.
34506 @var{sym_name} (hex encoded) is the name of a symbol whose value the
34507 target has previously requested.
34509 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
34510 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
34516 The target does not need to look up any (more) symbols.
34517 @item qSymbol:@var{sym_name}
34518 The target requests the value of a new symbol @var{sym_name} (hex
34519 encoded). @value{GDBN} will continue to supply the values of symbols
34520 (if available), until the target ceases to request them.
34525 @item QTDisconnected
34532 @xref{Tracepoint Packets}.
34534 @item qThreadExtraInfo,@var{thread-id}
34535 @cindex thread attributes info, remote request
34536 @cindex @samp{qThreadExtraInfo} packet
34537 Obtain a printable string description of a thread's attributes from
34538 the target OS. @var{thread-id} is a thread ID;
34539 see @ref{thread-id syntax}. This
34540 string may contain anything that the target OS thinks is interesting
34541 for @value{GDBN} to tell the user about the thread. The string is
34542 displayed in @value{GDBN}'s @code{info threads} display. Some
34543 examples of possible thread extra info strings are @samp{Runnable}, or
34544 @samp{Blocked on Mutex}.
34548 @item @var{XX}@dots{}
34549 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
34550 comprising the printable string containing the extra information about
34551 the thread's attributes.
34554 (Note that the @code{qThreadExtraInfo} packet's name is separated from
34555 the command by a @samp{,}, not a @samp{:}, contrary to the naming
34556 conventions above. Please don't use this packet as a model for new
34573 @xref{Tracepoint Packets}.
34575 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
34576 @cindex read special object, remote request
34577 @cindex @samp{qXfer} packet
34578 @anchor{qXfer read}
34579 Read uninterpreted bytes from the target's special data area
34580 identified by the keyword @var{object}. Request @var{length} bytes
34581 starting at @var{offset} bytes into the data. The content and
34582 encoding of @var{annex} is specific to @var{object}; it can supply
34583 additional details about what data to access.
34585 Here are the specific requests of this form defined so far. All
34586 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
34587 formats, listed below.
34590 @item qXfer:auxv:read::@var{offset},@var{length}
34591 @anchor{qXfer auxiliary vector read}
34592 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
34593 auxiliary vector}. Note @var{annex} must be empty.
34595 This packet is not probed by default; the remote stub must request it,
34596 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34598 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
34599 @anchor{qXfer target description read}
34600 Access the @dfn{target description}. @xref{Target Descriptions}. The
34601 annex specifies which XML document to access. The main description is
34602 always loaded from the @samp{target.xml} annex.
34604 This packet is not probed by default; the remote stub must request it,
34605 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34607 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
34608 @anchor{qXfer library list read}
34609 Access the target's list of loaded libraries. @xref{Library List Format}.
34610 The annex part of the generic @samp{qXfer} packet must be empty
34611 (@pxref{qXfer read}).
34613 Targets which maintain a list of libraries in the program's memory do
34614 not need to implement this packet; it is designed for platforms where
34615 the operating system manages the list of loaded libraries.
34617 This packet is not probed by default; the remote stub must request it,
34618 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34620 @item qXfer:memory-map:read::@var{offset},@var{length}
34621 @anchor{qXfer memory map read}
34622 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
34623 annex part of the generic @samp{qXfer} packet must be empty
34624 (@pxref{qXfer read}).
34626 This packet is not probed by default; the remote stub must request it,
34627 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34629 @item qXfer:sdata:read::@var{offset},@var{length}
34630 @anchor{qXfer sdata read}
34632 Read contents of the extra collected static tracepoint marker
34633 information. The annex part of the generic @samp{qXfer} packet must
34634 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
34637 This packet is not probed by default; the remote stub must request it,
34638 by supplying an appropriate @samp{qSupported} response
34639 (@pxref{qSupported}).
34641 @item qXfer:siginfo:read::@var{offset},@var{length}
34642 @anchor{qXfer siginfo read}
34643 Read contents of the extra signal information on the target
34644 system. The annex part of the generic @samp{qXfer} packet must be
34645 empty (@pxref{qXfer read}).
34647 This packet is not probed by default; the remote stub must request it,
34648 by supplying an appropriate @samp{qSupported} response
34649 (@pxref{qSupported}).
34651 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
34652 @anchor{qXfer spu read}
34653 Read contents of an @code{spufs} file on the target system. The
34654 annex specifies which file to read; it must be of the form
34655 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
34656 in the target process, and @var{name} identifes the @code{spufs} file
34657 in that context to be accessed.
34659 This packet is not probed by default; the remote stub must request it,
34660 by supplying an appropriate @samp{qSupported} response
34661 (@pxref{qSupported}).
34663 @item qXfer:threads:read::@var{offset},@var{length}
34664 @anchor{qXfer threads read}
34665 Access the list of threads on target. @xref{Thread List Format}. The
34666 annex part of the generic @samp{qXfer} packet must be empty
34667 (@pxref{qXfer read}).
34669 This packet is not probed by default; the remote stub must request it,
34670 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34672 @item qXfer:traceframe-info:read::@var{offset},@var{length}
34673 @anchor{qXfer traceframe info read}
34675 Return a description of the current traceframe's contents.
34676 @xref{Traceframe Info Format}. The annex part of the generic
34677 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
34679 This packet is not probed by default; the remote stub must request it,
34680 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34682 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
34683 @anchor{qXfer fdpic loadmap read}
34684 Read contents of @code{loadmap}s on the target system. The
34685 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
34686 executable @code{loadmap} or interpreter @code{loadmap} to read.
34688 This packet is not probed by default; the remote stub must request it,
34689 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34691 @item qXfer:osdata:read::@var{offset},@var{length}
34692 @anchor{qXfer osdata read}
34693 Access the target's @dfn{operating system information}.
34694 @xref{Operating System Information}.
34701 Data @var{data} (@pxref{Binary Data}) has been read from the
34702 target. There may be more data at a higher address (although
34703 it is permitted to return @samp{m} even for the last valid
34704 block of data, as long as at least one byte of data was read).
34705 @var{data} may have fewer bytes than the @var{length} in the
34709 Data @var{data} (@pxref{Binary Data}) has been read from the target.
34710 There is no more data to be read. @var{data} may have fewer bytes
34711 than the @var{length} in the request.
34714 The @var{offset} in the request is at the end of the data.
34715 There is no more data to be read.
34718 The request was malformed, or @var{annex} was invalid.
34721 The offset was invalid, or there was an error encountered reading the data.
34722 @var{nn} is a hex-encoded @code{errno} value.
34725 An empty reply indicates the @var{object} string was not recognized by
34726 the stub, or that the object does not support reading.
34729 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
34730 @cindex write data into object, remote request
34731 @anchor{qXfer write}
34732 Write uninterpreted bytes into the target's special data area
34733 identified by the keyword @var{object}, starting at @var{offset} bytes
34734 into the data. @var{data}@dots{} is the binary-encoded data
34735 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
34736 is specific to @var{object}; it can supply additional details about what data
34739 Here are the specific requests of this form defined so far. All
34740 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
34741 formats, listed below.
34744 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
34745 @anchor{qXfer siginfo write}
34746 Write @var{data} to the extra signal information on the target system.
34747 The annex part of the generic @samp{qXfer} packet must be
34748 empty (@pxref{qXfer write}).
34750 This packet is not probed by default; the remote stub must request it,
34751 by supplying an appropriate @samp{qSupported} response
34752 (@pxref{qSupported}).
34754 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
34755 @anchor{qXfer spu write}
34756 Write @var{data} to an @code{spufs} file on the target system. The
34757 annex specifies which file to write; it must be of the form
34758 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
34759 in the target process, and @var{name} identifes the @code{spufs} file
34760 in that context to be accessed.
34762 This packet is not probed by default; the remote stub must request it,
34763 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34769 @var{nn} (hex encoded) is the number of bytes written.
34770 This may be fewer bytes than supplied in the request.
34773 The request was malformed, or @var{annex} was invalid.
34776 The offset was invalid, or there was an error encountered writing the data.
34777 @var{nn} is a hex-encoded @code{errno} value.
34780 An empty reply indicates the @var{object} string was not
34781 recognized by the stub, or that the object does not support writing.
34784 @item qXfer:@var{object}:@var{operation}:@dots{}
34785 Requests of this form may be added in the future. When a stub does
34786 not recognize the @var{object} keyword, or its support for
34787 @var{object} does not recognize the @var{operation} keyword, the stub
34788 must respond with an empty packet.
34790 @item qAttached:@var{pid}
34791 @cindex query attached, remote request
34792 @cindex @samp{qAttached} packet
34793 Return an indication of whether the remote server attached to an
34794 existing process or created a new process. When the multiprocess
34795 protocol extensions are supported (@pxref{multiprocess extensions}),
34796 @var{pid} is an integer in hexadecimal format identifying the target
34797 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
34798 the query packet will be simplified as @samp{qAttached}.
34800 This query is used, for example, to know whether the remote process
34801 should be detached or killed when a @value{GDBN} session is ended with
34802 the @code{quit} command.
34807 The remote server attached to an existing process.
34809 The remote server created a new process.
34811 A badly formed request or an error was encountered.
34816 @node Architecture-Specific Protocol Details
34817 @section Architecture-Specific Protocol Details
34819 This section describes how the remote protocol is applied to specific
34820 target architectures. Also see @ref{Standard Target Features}, for
34821 details of XML target descriptions for each architecture.
34825 @subsubsection Breakpoint Kinds
34827 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
34832 16-bit Thumb mode breakpoint.
34835 32-bit Thumb mode (Thumb-2) breakpoint.
34838 32-bit ARM mode breakpoint.
34844 @subsubsection Register Packet Format
34846 The following @code{g}/@code{G} packets have previously been defined.
34847 In the below, some thirty-two bit registers are transferred as
34848 sixty-four bits. Those registers should be zero/sign extended (which?)
34849 to fill the space allocated. Register bytes are transferred in target
34850 byte order. The two nibbles within a register byte are transferred
34851 most-significant - least-significant.
34857 All registers are transferred as thirty-two bit quantities in the order:
34858 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
34859 registers; fsr; fir; fp.
34863 All registers are transferred as sixty-four bit quantities (including
34864 thirty-two bit registers such as @code{sr}). The ordering is the same
34869 @node Tracepoint Packets
34870 @section Tracepoint Packets
34871 @cindex tracepoint packets
34872 @cindex packets, tracepoint
34874 Here we describe the packets @value{GDBN} uses to implement
34875 tracepoints (@pxref{Tracepoints}).
34879 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
34880 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
34881 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
34882 the tracepoint is disabled. @var{step} is the tracepoint's step
34883 count, and @var{pass} is its pass count. If an @samp{F} is present,
34884 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
34885 the number of bytes that the target should copy elsewhere to make room
34886 for the tracepoint. If an @samp{X} is present, it introduces a
34887 tracepoint condition, which consists of a hexadecimal length, followed
34888 by a comma and hex-encoded bytes, in a manner similar to action
34889 encodings as described below. If the trailing @samp{-} is present,
34890 further @samp{QTDP} packets will follow to specify this tracepoint's
34896 The packet was understood and carried out.
34898 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
34900 The packet was not recognized.
34903 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
34904 Define actions to be taken when a tracepoint is hit. @var{n} and
34905 @var{addr} must be the same as in the initial @samp{QTDP} packet for
34906 this tracepoint. This packet may only be sent immediately after
34907 another @samp{QTDP} packet that ended with a @samp{-}. If the
34908 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
34909 specifying more actions for this tracepoint.
34911 In the series of action packets for a given tracepoint, at most one
34912 can have an @samp{S} before its first @var{action}. If such a packet
34913 is sent, it and the following packets define ``while-stepping''
34914 actions. Any prior packets define ordinary actions --- that is, those
34915 taken when the tracepoint is first hit. If no action packet has an
34916 @samp{S}, then all the packets in the series specify ordinary
34917 tracepoint actions.
34919 The @samp{@var{action}@dots{}} portion of the packet is a series of
34920 actions, concatenated without separators. Each action has one of the
34926 Collect the registers whose bits are set in @var{mask}. @var{mask} is
34927 a hexadecimal number whose @var{i}'th bit is set if register number
34928 @var{i} should be collected. (The least significant bit is numbered
34929 zero.) Note that @var{mask} may be any number of digits long; it may
34930 not fit in a 32-bit word.
34932 @item M @var{basereg},@var{offset},@var{len}
34933 Collect @var{len} bytes of memory starting at the address in register
34934 number @var{basereg}, plus @var{offset}. If @var{basereg} is
34935 @samp{-1}, then the range has a fixed address: @var{offset} is the
34936 address of the lowest byte to collect. The @var{basereg},
34937 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
34938 values (the @samp{-1} value for @var{basereg} is a special case).
34940 @item X @var{len},@var{expr}
34941 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
34942 it directs. @var{expr} is an agent expression, as described in
34943 @ref{Agent Expressions}. Each byte of the expression is encoded as a
34944 two-digit hex number in the packet; @var{len} is the number of bytes
34945 in the expression (and thus one-half the number of hex digits in the
34950 Any number of actions may be packed together in a single @samp{QTDP}
34951 packet, as long as the packet does not exceed the maximum packet
34952 length (400 bytes, for many stubs). There may be only one @samp{R}
34953 action per tracepoint, and it must precede any @samp{M} or @samp{X}
34954 actions. Any registers referred to by @samp{M} and @samp{X} actions
34955 must be collected by a preceding @samp{R} action. (The
34956 ``while-stepping'' actions are treated as if they were attached to a
34957 separate tracepoint, as far as these restrictions are concerned.)
34962 The packet was understood and carried out.
34964 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
34966 The packet was not recognized.
34969 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
34970 @cindex @samp{QTDPsrc} packet
34971 Specify a source string of tracepoint @var{n} at address @var{addr}.
34972 This is useful to get accurate reproduction of the tracepoints
34973 originally downloaded at the beginning of the trace run. @var{type}
34974 is the name of the tracepoint part, such as @samp{cond} for the
34975 tracepoint's conditional expression (see below for a list of types), while
34976 @var{bytes} is the string, encoded in hexadecimal.
34978 @var{start} is the offset of the @var{bytes} within the overall source
34979 string, while @var{slen} is the total length of the source string.
34980 This is intended for handling source strings that are longer than will
34981 fit in a single packet.
34982 @c Add detailed example when this info is moved into a dedicated
34983 @c tracepoint descriptions section.
34985 The available string types are @samp{at} for the location,
34986 @samp{cond} for the conditional, and @samp{cmd} for an action command.
34987 @value{GDBN} sends a separate packet for each command in the action
34988 list, in the same order in which the commands are stored in the list.
34990 The target does not need to do anything with source strings except
34991 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
34994 Although this packet is optional, and @value{GDBN} will only send it
34995 if the target replies with @samp{TracepointSource} @xref{General
34996 Query Packets}, it makes both disconnected tracing and trace files
34997 much easier to use. Otherwise the user must be careful that the
34998 tracepoints in effect while looking at trace frames are identical to
34999 the ones in effect during the trace run; even a small discrepancy
35000 could cause @samp{tdump} not to work, or a particular trace frame not
35003 @item QTDV:@var{n}:@var{value}
35004 @cindex define trace state variable, remote request
35005 @cindex @samp{QTDV} packet
35006 Create a new trace state variable, number @var{n}, with an initial
35007 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
35008 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
35009 the option of not using this packet for initial values of zero; the
35010 target should simply create the trace state variables as they are
35011 mentioned in expressions.
35013 @item QTFrame:@var{n}
35014 Select the @var{n}'th tracepoint frame from the buffer, and use the
35015 register and memory contents recorded there to answer subsequent
35016 request packets from @value{GDBN}.
35018 A successful reply from the stub indicates that the stub has found the
35019 requested frame. The response is a series of parts, concatenated
35020 without separators, describing the frame we selected. Each part has
35021 one of the following forms:
35025 The selected frame is number @var{n} in the trace frame buffer;
35026 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
35027 was no frame matching the criteria in the request packet.
35030 The selected trace frame records a hit of tracepoint number @var{t};
35031 @var{t} is a hexadecimal number.
35035 @item QTFrame:pc:@var{addr}
35036 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
35037 currently selected frame whose PC is @var{addr};
35038 @var{addr} is a hexadecimal number.
35040 @item QTFrame:tdp:@var{t}
35041 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
35042 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
35043 is a hexadecimal number.
35045 @item QTFrame:range:@var{start}:@var{end}
35046 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
35047 currently selected frame whose PC is between @var{start} (inclusive)
35048 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
35051 @item QTFrame:outside:@var{start}:@var{end}
35052 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
35053 frame @emph{outside} the given range of addresses (exclusive).
35056 Begin the tracepoint experiment. Begin collecting data from
35057 tracepoint hits in the trace frame buffer. This packet supports the
35058 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
35059 instruction reply packet}).
35062 End the tracepoint experiment. Stop collecting trace frames.
35064 @item QTEnable:@var{n}:@var{addr}
35066 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
35067 experiment. If the tracepoint was previously disabled, then collection
35068 of data from it will resume.
35070 @item QTDisable:@var{n}:@var{addr}
35072 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
35073 experiment. No more data will be collected from the tracepoint unless
35074 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
35077 Clear the table of tracepoints, and empty the trace frame buffer.
35079 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
35080 Establish the given ranges of memory as ``transparent''. The stub
35081 will answer requests for these ranges from memory's current contents,
35082 if they were not collected as part of the tracepoint hit.
35084 @value{GDBN} uses this to mark read-only regions of memory, like those
35085 containing program code. Since these areas never change, they should
35086 still have the same contents they did when the tracepoint was hit, so
35087 there's no reason for the stub to refuse to provide their contents.
35089 @item QTDisconnected:@var{value}
35090 Set the choice to what to do with the tracing run when @value{GDBN}
35091 disconnects from the target. A @var{value} of 1 directs the target to
35092 continue the tracing run, while 0 tells the target to stop tracing if
35093 @value{GDBN} is no longer in the picture.
35096 Ask the stub if there is a trace experiment running right now.
35098 The reply has the form:
35102 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
35103 @var{running} is a single digit @code{1} if the trace is presently
35104 running, or @code{0} if not. It is followed by semicolon-separated
35105 optional fields that an agent may use to report additional status.
35109 If the trace is not running, the agent may report any of several
35110 explanations as one of the optional fields:
35115 No trace has been run yet.
35118 The trace was stopped by a user-originated stop command.
35121 The trace stopped because the trace buffer filled up.
35123 @item tdisconnected:0
35124 The trace stopped because @value{GDBN} disconnected from the target.
35126 @item tpasscount:@var{tpnum}
35127 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
35129 @item terror:@var{text}:@var{tpnum}
35130 The trace stopped because tracepoint @var{tpnum} had an error. The
35131 string @var{text} is available to describe the nature of the error
35132 (for instance, a divide by zero in the condition expression).
35133 @var{text} is hex encoded.
35136 The trace stopped for some other reason.
35140 Additional optional fields supply statistical and other information.
35141 Although not required, they are extremely useful for users monitoring
35142 the progress of a trace run. If a trace has stopped, and these
35143 numbers are reported, they must reflect the state of the just-stopped
35148 @item tframes:@var{n}
35149 The number of trace frames in the buffer.
35151 @item tcreated:@var{n}
35152 The total number of trace frames created during the run. This may
35153 be larger than the trace frame count, if the buffer is circular.
35155 @item tsize:@var{n}
35156 The total size of the trace buffer, in bytes.
35158 @item tfree:@var{n}
35159 The number of bytes still unused in the buffer.
35161 @item circular:@var{n}
35162 The value of the circular trace buffer flag. @code{1} means that the
35163 trace buffer is circular and old trace frames will be discarded if
35164 necessary to make room, @code{0} means that the trace buffer is linear
35167 @item disconn:@var{n}
35168 The value of the disconnected tracing flag. @code{1} means that
35169 tracing will continue after @value{GDBN} disconnects, @code{0} means
35170 that the trace run will stop.
35174 @item qTV:@var{var}
35175 @cindex trace state variable value, remote request
35176 @cindex @samp{qTV} packet
35177 Ask the stub for the value of the trace state variable number @var{var}.
35182 The value of the variable is @var{value}. This will be the current
35183 value of the variable if the user is examining a running target, or a
35184 saved value if the variable was collected in the trace frame that the
35185 user is looking at. Note that multiple requests may result in
35186 different reply values, such as when requesting values while the
35187 program is running.
35190 The value of the variable is unknown. This would occur, for example,
35191 if the user is examining a trace frame in which the requested variable
35197 These packets request data about tracepoints that are being used by
35198 the target. @value{GDBN} sends @code{qTfP} to get the first piece
35199 of data, and multiple @code{qTsP} to get additional pieces. Replies
35200 to these packets generally take the form of the @code{QTDP} packets
35201 that define tracepoints. (FIXME add detailed syntax)
35205 These packets request data about trace state variables that are on the
35206 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
35207 and multiple @code{qTsV} to get additional variables. Replies to
35208 these packets follow the syntax of the @code{QTDV} packets that define
35209 trace state variables.
35213 These packets request data about static tracepoint markers that exist
35214 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
35215 first piece of data, and multiple @code{qTsSTM} to get additional
35216 pieces. Replies to these packets take the following form:
35220 @item m @var{address}:@var{id}:@var{extra}
35222 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
35223 a comma-separated list of markers
35225 (lower case letter @samp{L}) denotes end of list.
35227 An error occurred. @var{nn} are hex digits.
35229 An empty reply indicates that the request is not supported by the
35233 @var{address} is encoded in hex.
35234 @var{id} and @var{extra} are strings encoded in hex.
35236 In response to each query, the target will reply with a list of one or
35237 more markers, separated by commas. @value{GDBN} will respond to each
35238 reply with a request for more markers (using the @samp{qs} form of the
35239 query), until the target responds with @samp{l} (lower-case ell, for
35242 @item qTSTMat:@var{address}
35243 This packets requests data about static tracepoint markers in the
35244 target program at @var{address}. Replies to this packet follow the
35245 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
35246 tracepoint markers.
35248 @item QTSave:@var{filename}
35249 This packet directs the target to save trace data to the file name
35250 @var{filename} in the target's filesystem. @var{filename} is encoded
35251 as a hex string; the interpretation of the file name (relative vs
35252 absolute, wild cards, etc) is up to the target.
35254 @item qTBuffer:@var{offset},@var{len}
35255 Return up to @var{len} bytes of the current contents of trace buffer,
35256 starting at @var{offset}. The trace buffer is treated as if it were
35257 a contiguous collection of traceframes, as per the trace file format.
35258 The reply consists as many hex-encoded bytes as the target can deliver
35259 in a packet; it is not an error to return fewer than were asked for.
35260 A reply consisting of just @code{l} indicates that no bytes are
35263 @item QTBuffer:circular:@var{value}
35264 This packet directs the target to use a circular trace buffer if
35265 @var{value} is 1, or a linear buffer if the value is 0.
35269 @subsection Relocate instruction reply packet
35270 When installing fast tracepoints in memory, the target may need to
35271 relocate the instruction currently at the tracepoint address to a
35272 different address in memory. For most instructions, a simple copy is
35273 enough, but, for example, call instructions that implicitly push the
35274 return address on the stack, and relative branches or other
35275 PC-relative instructions require offset adjustment, so that the effect
35276 of executing the instruction at a different address is the same as if
35277 it had executed in the original location.
35279 In response to several of the tracepoint packets, the target may also
35280 respond with a number of intermediate @samp{qRelocInsn} request
35281 packets before the final result packet, to have @value{GDBN} handle
35282 this relocation operation. If a packet supports this mechanism, its
35283 documentation will explicitly say so. See for example the above
35284 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
35285 format of the request is:
35288 @item qRelocInsn:@var{from};@var{to}
35290 This requests @value{GDBN} to copy instruction at address @var{from}
35291 to address @var{to}, possibly adjusted so that executing the
35292 instruction at @var{to} has the same effect as executing it at
35293 @var{from}. @value{GDBN} writes the adjusted instruction to target
35294 memory starting at @var{to}.
35299 @item qRelocInsn:@var{adjusted_size}
35300 Informs the stub the relocation is complete. @var{adjusted_size} is
35301 the length in bytes of resulting relocated instruction sequence.
35303 A badly formed request was detected, or an error was encountered while
35304 relocating the instruction.
35307 @node Host I/O Packets
35308 @section Host I/O Packets
35309 @cindex Host I/O, remote protocol
35310 @cindex file transfer, remote protocol
35312 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
35313 operations on the far side of a remote link. For example, Host I/O is
35314 used to upload and download files to a remote target with its own
35315 filesystem. Host I/O uses the same constant values and data structure
35316 layout as the target-initiated File-I/O protocol. However, the
35317 Host I/O packets are structured differently. The target-initiated
35318 protocol relies on target memory to store parameters and buffers.
35319 Host I/O requests are initiated by @value{GDBN}, and the
35320 target's memory is not involved. @xref{File-I/O Remote Protocol
35321 Extension}, for more details on the target-initiated protocol.
35323 The Host I/O request packets all encode a single operation along with
35324 its arguments. They have this format:
35328 @item vFile:@var{operation}: @var{parameter}@dots{}
35329 @var{operation} is the name of the particular request; the target
35330 should compare the entire packet name up to the second colon when checking
35331 for a supported operation. The format of @var{parameter} depends on
35332 the operation. Numbers are always passed in hexadecimal. Negative
35333 numbers have an explicit minus sign (i.e.@: two's complement is not
35334 used). Strings (e.g.@: filenames) are encoded as a series of
35335 hexadecimal bytes. The last argument to a system call may be a
35336 buffer of escaped binary data (@pxref{Binary Data}).
35340 The valid responses to Host I/O packets are:
35344 @item F @var{result} [, @var{errno}] [; @var{attachment}]
35345 @var{result} is the integer value returned by this operation, usually
35346 non-negative for success and -1 for errors. If an error has occured,
35347 @var{errno} will be included in the result. @var{errno} will have a
35348 value defined by the File-I/O protocol (@pxref{Errno Values}). For
35349 operations which return data, @var{attachment} supplies the data as a
35350 binary buffer. Binary buffers in response packets are escaped in the
35351 normal way (@pxref{Binary Data}). See the individual packet
35352 documentation for the interpretation of @var{result} and
35356 An empty response indicates that this operation is not recognized.
35360 These are the supported Host I/O operations:
35363 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
35364 Open a file at @var{pathname} and return a file descriptor for it, or
35365 return -1 if an error occurs. @var{pathname} is a string,
35366 @var{flags} is an integer indicating a mask of open flags
35367 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
35368 of mode bits to use if the file is created (@pxref{mode_t Values}).
35369 @xref{open}, for details of the open flags and mode values.
35371 @item vFile:close: @var{fd}
35372 Close the open file corresponding to @var{fd} and return 0, or
35373 -1 if an error occurs.
35375 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
35376 Read data from the open file corresponding to @var{fd}. Up to
35377 @var{count} bytes will be read from the file, starting at @var{offset}
35378 relative to the start of the file. The target may read fewer bytes;
35379 common reasons include packet size limits and an end-of-file
35380 condition. The number of bytes read is returned. Zero should only be
35381 returned for a successful read at the end of the file, or if
35382 @var{count} was zero.
35384 The data read should be returned as a binary attachment on success.
35385 If zero bytes were read, the response should include an empty binary
35386 attachment (i.e.@: a trailing semicolon). The return value is the
35387 number of target bytes read; the binary attachment may be longer if
35388 some characters were escaped.
35390 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
35391 Write @var{data} (a binary buffer) to the open file corresponding
35392 to @var{fd}. Start the write at @var{offset} from the start of the
35393 file. Unlike many @code{write} system calls, there is no
35394 separate @var{count} argument; the length of @var{data} in the
35395 packet is used. @samp{vFile:write} returns the number of bytes written,
35396 which may be shorter than the length of @var{data}, or -1 if an
35399 @item vFile:unlink: @var{pathname}
35400 Delete the file at @var{pathname} on the target. Return 0,
35401 or -1 if an error occurs. @var{pathname} is a string.
35406 @section Interrupts
35407 @cindex interrupts (remote protocol)
35409 When a program on the remote target is running, @value{GDBN} may
35410 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
35411 a @code{BREAK} followed by @code{g},
35412 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
35414 The precise meaning of @code{BREAK} is defined by the transport
35415 mechanism and may, in fact, be undefined. @value{GDBN} does not
35416 currently define a @code{BREAK} mechanism for any of the network
35417 interfaces except for TCP, in which case @value{GDBN} sends the
35418 @code{telnet} BREAK sequence.
35420 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
35421 transport mechanisms. It is represented by sending the single byte
35422 @code{0x03} without any of the usual packet overhead described in
35423 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
35424 transmitted as part of a packet, it is considered to be packet data
35425 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
35426 (@pxref{X packet}), used for binary downloads, may include an unescaped
35427 @code{0x03} as part of its packet.
35429 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
35430 When Linux kernel receives this sequence from serial port,
35431 it stops execution and connects to gdb.
35433 Stubs are not required to recognize these interrupt mechanisms and the
35434 precise meaning associated with receipt of the interrupt is
35435 implementation defined. If the target supports debugging of multiple
35436 threads and/or processes, it should attempt to interrupt all
35437 currently-executing threads and processes.
35438 If the stub is successful at interrupting the
35439 running program, it should send one of the stop
35440 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
35441 of successfully stopping the program in all-stop mode, and a stop reply
35442 for each stopped thread in non-stop mode.
35443 Interrupts received while the
35444 program is stopped are discarded.
35446 @node Notification Packets
35447 @section Notification Packets
35448 @cindex notification packets
35449 @cindex packets, notification
35451 The @value{GDBN} remote serial protocol includes @dfn{notifications},
35452 packets that require no acknowledgment. Both the GDB and the stub
35453 may send notifications (although the only notifications defined at
35454 present are sent by the stub). Notifications carry information
35455 without incurring the round-trip latency of an acknowledgment, and so
35456 are useful for low-impact communications where occasional packet loss
35459 A notification packet has the form @samp{% @var{data} #
35460 @var{checksum}}, where @var{data} is the content of the notification,
35461 and @var{checksum} is a checksum of @var{data}, computed and formatted
35462 as for ordinary @value{GDBN} packets. A notification's @var{data}
35463 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
35464 receiving a notification, the recipient sends no @samp{+} or @samp{-}
35465 to acknowledge the notification's receipt or to report its corruption.
35467 Every notification's @var{data} begins with a name, which contains no
35468 colon characters, followed by a colon character.
35470 Recipients should silently ignore corrupted notifications and
35471 notifications they do not understand. Recipients should restart
35472 timeout periods on receipt of a well-formed notification, whether or
35473 not they understand it.
35475 Senders should only send the notifications described here when this
35476 protocol description specifies that they are permitted. In the
35477 future, we may extend the protocol to permit existing notifications in
35478 new contexts; this rule helps older senders avoid confusing newer
35481 (Older versions of @value{GDBN} ignore bytes received until they see
35482 the @samp{$} byte that begins an ordinary packet, so new stubs may
35483 transmit notifications without fear of confusing older clients. There
35484 are no notifications defined for @value{GDBN} to send at the moment, but we
35485 assume that most older stubs would ignore them, as well.)
35487 The following notification packets from the stub to @value{GDBN} are
35491 @item Stop: @var{reply}
35492 Report an asynchronous stop event in non-stop mode.
35493 The @var{reply} has the form of a stop reply, as
35494 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
35495 for information on how these notifications are acknowledged by
35499 @node Remote Non-Stop
35500 @section Remote Protocol Support for Non-Stop Mode
35502 @value{GDBN}'s remote protocol supports non-stop debugging of
35503 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
35504 supports non-stop mode, it should report that to @value{GDBN} by including
35505 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
35507 @value{GDBN} typically sends a @samp{QNonStop} packet only when
35508 establishing a new connection with the stub. Entering non-stop mode
35509 does not alter the state of any currently-running threads, but targets
35510 must stop all threads in any already-attached processes when entering
35511 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
35512 probe the target state after a mode change.
35514 In non-stop mode, when an attached process encounters an event that
35515 would otherwise be reported with a stop reply, it uses the
35516 asynchronous notification mechanism (@pxref{Notification Packets}) to
35517 inform @value{GDBN}. In contrast to all-stop mode, where all threads
35518 in all processes are stopped when a stop reply is sent, in non-stop
35519 mode only the thread reporting the stop event is stopped. That is,
35520 when reporting a @samp{S} or @samp{T} response to indicate completion
35521 of a step operation, hitting a breakpoint, or a fault, only the
35522 affected thread is stopped; any other still-running threads continue
35523 to run. When reporting a @samp{W} or @samp{X} response, all running
35524 threads belonging to other attached processes continue to run.
35526 Only one stop reply notification at a time may be pending; if
35527 additional stop events occur before @value{GDBN} has acknowledged the
35528 previous notification, they must be queued by the stub for later
35529 synchronous transmission in response to @samp{vStopped} packets from
35530 @value{GDBN}. Because the notification mechanism is unreliable,
35531 the stub is permitted to resend a stop reply notification
35532 if it believes @value{GDBN} may not have received it. @value{GDBN}
35533 ignores additional stop reply notifications received before it has
35534 finished processing a previous notification and the stub has completed
35535 sending any queued stop events.
35537 Otherwise, @value{GDBN} must be prepared to receive a stop reply
35538 notification at any time. Specifically, they may appear when
35539 @value{GDBN} is not otherwise reading input from the stub, or when
35540 @value{GDBN} is expecting to read a normal synchronous response or a
35541 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
35542 Notification packets are distinct from any other communication from
35543 the stub so there is no ambiguity.
35545 After receiving a stop reply notification, @value{GDBN} shall
35546 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
35547 as a regular, synchronous request to the stub. Such acknowledgment
35548 is not required to happen immediately, as @value{GDBN} is permitted to
35549 send other, unrelated packets to the stub first, which the stub should
35552 Upon receiving a @samp{vStopped} packet, if the stub has other queued
35553 stop events to report to @value{GDBN}, it shall respond by sending a
35554 normal stop reply response. @value{GDBN} shall then send another
35555 @samp{vStopped} packet to solicit further responses; again, it is
35556 permitted to send other, unrelated packets as well which the stub
35557 should process normally.
35559 If the stub receives a @samp{vStopped} packet and there are no
35560 additional stop events to report, the stub shall return an @samp{OK}
35561 response. At this point, if further stop events occur, the stub shall
35562 send a new stop reply notification, @value{GDBN} shall accept the
35563 notification, and the process shall be repeated.
35565 In non-stop mode, the target shall respond to the @samp{?} packet as
35566 follows. First, any incomplete stop reply notification/@samp{vStopped}
35567 sequence in progress is abandoned. The target must begin a new
35568 sequence reporting stop events for all stopped threads, whether or not
35569 it has previously reported those events to @value{GDBN}. The first
35570 stop reply is sent as a synchronous reply to the @samp{?} packet, and
35571 subsequent stop replies are sent as responses to @samp{vStopped} packets
35572 using the mechanism described above. The target must not send
35573 asynchronous stop reply notifications until the sequence is complete.
35574 If all threads are running when the target receives the @samp{?} packet,
35575 or if the target is not attached to any process, it shall respond
35578 @node Packet Acknowledgment
35579 @section Packet Acknowledgment
35581 @cindex acknowledgment, for @value{GDBN} remote
35582 @cindex packet acknowledgment, for @value{GDBN} remote
35583 By default, when either the host or the target machine receives a packet,
35584 the first response expected is an acknowledgment: either @samp{+} (to indicate
35585 the package was received correctly) or @samp{-} (to request retransmission).
35586 This mechanism allows the @value{GDBN} remote protocol to operate over
35587 unreliable transport mechanisms, such as a serial line.
35589 In cases where the transport mechanism is itself reliable (such as a pipe or
35590 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
35591 It may be desirable to disable them in that case to reduce communication
35592 overhead, or for other reasons. This can be accomplished by means of the
35593 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
35595 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
35596 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
35597 and response format still includes the normal checksum, as described in
35598 @ref{Overview}, but the checksum may be ignored by the receiver.
35600 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
35601 no-acknowledgment mode, it should report that to @value{GDBN}
35602 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
35603 @pxref{qSupported}.
35604 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
35605 disabled via the @code{set remote noack-packet off} command
35606 (@pxref{Remote Configuration}),
35607 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
35608 Only then may the stub actually turn off packet acknowledgments.
35609 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
35610 response, which can be safely ignored by the stub.
35612 Note that @code{set remote noack-packet} command only affects negotiation
35613 between @value{GDBN} and the stub when subsequent connections are made;
35614 it does not affect the protocol acknowledgment state for any current
35616 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
35617 new connection is established,
35618 there is also no protocol request to re-enable the acknowledgments
35619 for the current connection, once disabled.
35624 Example sequence of a target being re-started. Notice how the restart
35625 does not get any direct output:
35630 @emph{target restarts}
35633 <- @code{T001:1234123412341234}
35637 Example sequence of a target being stepped by a single instruction:
35640 -> @code{G1445@dots{}}
35645 <- @code{T001:1234123412341234}
35649 <- @code{1455@dots{}}
35653 @node File-I/O Remote Protocol Extension
35654 @section File-I/O Remote Protocol Extension
35655 @cindex File-I/O remote protocol extension
35658 * File-I/O Overview::
35659 * Protocol Basics::
35660 * The F Request Packet::
35661 * The F Reply Packet::
35662 * The Ctrl-C Message::
35664 * List of Supported Calls::
35665 * Protocol-specific Representation of Datatypes::
35667 * File-I/O Examples::
35670 @node File-I/O Overview
35671 @subsection File-I/O Overview
35672 @cindex file-i/o overview
35674 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
35675 target to use the host's file system and console I/O to perform various
35676 system calls. System calls on the target system are translated into a
35677 remote protocol packet to the host system, which then performs the needed
35678 actions and returns a response packet to the target system.
35679 This simulates file system operations even on targets that lack file systems.
35681 The protocol is defined to be independent of both the host and target systems.
35682 It uses its own internal representation of datatypes and values. Both
35683 @value{GDBN} and the target's @value{GDBN} stub are responsible for
35684 translating the system-dependent value representations into the internal
35685 protocol representations when data is transmitted.
35687 The communication is synchronous. A system call is possible only when
35688 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
35689 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
35690 the target is stopped to allow deterministic access to the target's
35691 memory. Therefore File-I/O is not interruptible by target signals. On
35692 the other hand, it is possible to interrupt File-I/O by a user interrupt
35693 (@samp{Ctrl-C}) within @value{GDBN}.
35695 The target's request to perform a host system call does not finish
35696 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
35697 after finishing the system call, the target returns to continuing the
35698 previous activity (continue, step). No additional continue or step
35699 request from @value{GDBN} is required.
35702 (@value{GDBP}) continue
35703 <- target requests 'system call X'
35704 target is stopped, @value{GDBN} executes system call
35705 -> @value{GDBN} returns result
35706 ... target continues, @value{GDBN} returns to wait for the target
35707 <- target hits breakpoint and sends a Txx packet
35710 The protocol only supports I/O on the console and to regular files on
35711 the host file system. Character or block special devices, pipes,
35712 named pipes, sockets or any other communication method on the host
35713 system are not supported by this protocol.
35715 File I/O is not supported in non-stop mode.
35717 @node Protocol Basics
35718 @subsection Protocol Basics
35719 @cindex protocol basics, file-i/o
35721 The File-I/O protocol uses the @code{F} packet as the request as well
35722 as reply packet. Since a File-I/O system call can only occur when
35723 @value{GDBN} is waiting for a response from the continuing or stepping target,
35724 the File-I/O request is a reply that @value{GDBN} has to expect as a result
35725 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
35726 This @code{F} packet contains all information needed to allow @value{GDBN}
35727 to call the appropriate host system call:
35731 A unique identifier for the requested system call.
35734 All parameters to the system call. Pointers are given as addresses
35735 in the target memory address space. Pointers to strings are given as
35736 pointer/length pair. Numerical values are given as they are.
35737 Numerical control flags are given in a protocol-specific representation.
35741 At this point, @value{GDBN} has to perform the following actions.
35745 If the parameters include pointer values to data needed as input to a
35746 system call, @value{GDBN} requests this data from the target with a
35747 standard @code{m} packet request. This additional communication has to be
35748 expected by the target implementation and is handled as any other @code{m}
35752 @value{GDBN} translates all value from protocol representation to host
35753 representation as needed. Datatypes are coerced into the host types.
35756 @value{GDBN} calls the system call.
35759 It then coerces datatypes back to protocol representation.
35762 If the system call is expected to return data in buffer space specified
35763 by pointer parameters to the call, the data is transmitted to the
35764 target using a @code{M} or @code{X} packet. This packet has to be expected
35765 by the target implementation and is handled as any other @code{M} or @code{X}
35770 Eventually @value{GDBN} replies with another @code{F} packet which contains all
35771 necessary information for the target to continue. This at least contains
35778 @code{errno}, if has been changed by the system call.
35785 After having done the needed type and value coercion, the target continues
35786 the latest continue or step action.
35788 @node The F Request Packet
35789 @subsection The @code{F} Request Packet
35790 @cindex file-i/o request packet
35791 @cindex @code{F} request packet
35793 The @code{F} request packet has the following format:
35796 @item F@var{call-id},@var{parameter@dots{}}
35798 @var{call-id} is the identifier to indicate the host system call to be called.
35799 This is just the name of the function.
35801 @var{parameter@dots{}} are the parameters to the system call.
35802 Parameters are hexadecimal integer values, either the actual values in case
35803 of scalar datatypes, pointers to target buffer space in case of compound
35804 datatypes and unspecified memory areas, or pointer/length pairs in case
35805 of string parameters. These are appended to the @var{call-id} as a
35806 comma-delimited list. All values are transmitted in ASCII
35807 string representation, pointer/length pairs separated by a slash.
35813 @node The F Reply Packet
35814 @subsection The @code{F} Reply Packet
35815 @cindex file-i/o reply packet
35816 @cindex @code{F} reply packet
35818 The @code{F} reply packet has the following format:
35822 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
35824 @var{retcode} is the return code of the system call as hexadecimal value.
35826 @var{errno} is the @code{errno} set by the call, in protocol-specific
35828 This parameter can be omitted if the call was successful.
35830 @var{Ctrl-C flag} is only sent if the user requested a break. In this
35831 case, @var{errno} must be sent as well, even if the call was successful.
35832 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
35839 or, if the call was interrupted before the host call has been performed:
35846 assuming 4 is the protocol-specific representation of @code{EINTR}.
35851 @node The Ctrl-C Message
35852 @subsection The @samp{Ctrl-C} Message
35853 @cindex ctrl-c message, in file-i/o protocol
35855 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
35856 reply packet (@pxref{The F Reply Packet}),
35857 the target should behave as if it had
35858 gotten a break message. The meaning for the target is ``system call
35859 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
35860 (as with a break message) and return to @value{GDBN} with a @code{T02}
35863 It's important for the target to know in which
35864 state the system call was interrupted. There are two possible cases:
35868 The system call hasn't been performed on the host yet.
35871 The system call on the host has been finished.
35875 These two states can be distinguished by the target by the value of the
35876 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
35877 call hasn't been performed. This is equivalent to the @code{EINTR} handling
35878 on POSIX systems. In any other case, the target may presume that the
35879 system call has been finished --- successfully or not --- and should behave
35880 as if the break message arrived right after the system call.
35882 @value{GDBN} must behave reliably. If the system call has not been called
35883 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
35884 @code{errno} in the packet. If the system call on the host has been finished
35885 before the user requests a break, the full action must be finished by
35886 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
35887 The @code{F} packet may only be sent when either nothing has happened
35888 or the full action has been completed.
35891 @subsection Console I/O
35892 @cindex console i/o as part of file-i/o
35894 By default and if not explicitly closed by the target system, the file
35895 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
35896 on the @value{GDBN} console is handled as any other file output operation
35897 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
35898 by @value{GDBN} so that after the target read request from file descriptor
35899 0 all following typing is buffered until either one of the following
35904 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
35906 system call is treated as finished.
35909 The user presses @key{RET}. This is treated as end of input with a trailing
35913 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
35914 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
35918 If the user has typed more characters than fit in the buffer given to
35919 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
35920 either another @code{read(0, @dots{})} is requested by the target, or debugging
35921 is stopped at the user's request.
35924 @node List of Supported Calls
35925 @subsection List of Supported Calls
35926 @cindex list of supported file-i/o calls
35943 @unnumberedsubsubsec open
35944 @cindex open, file-i/o system call
35949 int open(const char *pathname, int flags);
35950 int open(const char *pathname, int flags, mode_t mode);
35954 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
35957 @var{flags} is the bitwise @code{OR} of the following values:
35961 If the file does not exist it will be created. The host
35962 rules apply as far as file ownership and time stamps
35966 When used with @code{O_CREAT}, if the file already exists it is
35967 an error and open() fails.
35970 If the file already exists and the open mode allows
35971 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
35972 truncated to zero length.
35975 The file is opened in append mode.
35978 The file is opened for reading only.
35981 The file is opened for writing only.
35984 The file is opened for reading and writing.
35988 Other bits are silently ignored.
35992 @var{mode} is the bitwise @code{OR} of the following values:
35996 User has read permission.
35999 User has write permission.
36002 Group has read permission.
36005 Group has write permission.
36008 Others have read permission.
36011 Others have write permission.
36015 Other bits are silently ignored.
36018 @item Return value:
36019 @code{open} returns the new file descriptor or -1 if an error
36026 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
36029 @var{pathname} refers to a directory.
36032 The requested access is not allowed.
36035 @var{pathname} was too long.
36038 A directory component in @var{pathname} does not exist.
36041 @var{pathname} refers to a device, pipe, named pipe or socket.
36044 @var{pathname} refers to a file on a read-only filesystem and
36045 write access was requested.
36048 @var{pathname} is an invalid pointer value.
36051 No space on device to create the file.
36054 The process already has the maximum number of files open.
36057 The limit on the total number of files open on the system
36061 The call was interrupted by the user.
36067 @unnumberedsubsubsec close
36068 @cindex close, file-i/o system call
36077 @samp{Fclose,@var{fd}}
36079 @item Return value:
36080 @code{close} returns zero on success, or -1 if an error occurred.
36086 @var{fd} isn't a valid open file descriptor.
36089 The call was interrupted by the user.
36095 @unnumberedsubsubsec read
36096 @cindex read, file-i/o system call
36101 int read(int fd, void *buf, unsigned int count);
36105 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
36107 @item Return value:
36108 On success, the number of bytes read is returned.
36109 Zero indicates end of file. If count is zero, read
36110 returns zero as well. On error, -1 is returned.
36116 @var{fd} is not a valid file descriptor or is not open for
36120 @var{bufptr} is an invalid pointer value.
36123 The call was interrupted by the user.
36129 @unnumberedsubsubsec write
36130 @cindex write, file-i/o system call
36135 int write(int fd, const void *buf, unsigned int count);
36139 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
36141 @item Return value:
36142 On success, the number of bytes written are returned.
36143 Zero indicates nothing was written. On error, -1
36150 @var{fd} is not a valid file descriptor or is not open for
36154 @var{bufptr} is an invalid pointer value.
36157 An attempt was made to write a file that exceeds the
36158 host-specific maximum file size allowed.
36161 No space on device to write the data.
36164 The call was interrupted by the user.
36170 @unnumberedsubsubsec lseek
36171 @cindex lseek, file-i/o system call
36176 long lseek (int fd, long offset, int flag);
36180 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
36182 @var{flag} is one of:
36186 The offset is set to @var{offset} bytes.
36189 The offset is set to its current location plus @var{offset}
36193 The offset is set to the size of the file plus @var{offset}
36197 @item Return value:
36198 On success, the resulting unsigned offset in bytes from
36199 the beginning of the file is returned. Otherwise, a
36200 value of -1 is returned.
36206 @var{fd} is not a valid open file descriptor.
36209 @var{fd} is associated with the @value{GDBN} console.
36212 @var{flag} is not a proper value.
36215 The call was interrupted by the user.
36221 @unnumberedsubsubsec rename
36222 @cindex rename, file-i/o system call
36227 int rename(const char *oldpath, const char *newpath);
36231 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
36233 @item Return value:
36234 On success, zero is returned. On error, -1 is returned.
36240 @var{newpath} is an existing directory, but @var{oldpath} is not a
36244 @var{newpath} is a non-empty directory.
36247 @var{oldpath} or @var{newpath} is a directory that is in use by some
36251 An attempt was made to make a directory a subdirectory
36255 A component used as a directory in @var{oldpath} or new
36256 path is not a directory. Or @var{oldpath} is a directory
36257 and @var{newpath} exists but is not a directory.
36260 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
36263 No access to the file or the path of the file.
36267 @var{oldpath} or @var{newpath} was too long.
36270 A directory component in @var{oldpath} or @var{newpath} does not exist.
36273 The file is on a read-only filesystem.
36276 The device containing the file has no room for the new
36280 The call was interrupted by the user.
36286 @unnumberedsubsubsec unlink
36287 @cindex unlink, file-i/o system call
36292 int unlink(const char *pathname);
36296 @samp{Funlink,@var{pathnameptr}/@var{len}}
36298 @item Return value:
36299 On success, zero is returned. On error, -1 is returned.
36305 No access to the file or the path of the file.
36308 The system does not allow unlinking of directories.
36311 The file @var{pathname} cannot be unlinked because it's
36312 being used by another process.
36315 @var{pathnameptr} is an invalid pointer value.
36318 @var{pathname} was too long.
36321 A directory component in @var{pathname} does not exist.
36324 A component of the path is not a directory.
36327 The file is on a read-only filesystem.
36330 The call was interrupted by the user.
36336 @unnumberedsubsubsec stat/fstat
36337 @cindex fstat, file-i/o system call
36338 @cindex stat, file-i/o system call
36343 int stat(const char *pathname, struct stat *buf);
36344 int fstat(int fd, struct stat *buf);
36348 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
36349 @samp{Ffstat,@var{fd},@var{bufptr}}
36351 @item Return value:
36352 On success, zero is returned. On error, -1 is returned.
36358 @var{fd} is not a valid open file.
36361 A directory component in @var{pathname} does not exist or the
36362 path is an empty string.
36365 A component of the path is not a directory.
36368 @var{pathnameptr} is an invalid pointer value.
36371 No access to the file or the path of the file.
36374 @var{pathname} was too long.
36377 The call was interrupted by the user.
36383 @unnumberedsubsubsec gettimeofday
36384 @cindex gettimeofday, file-i/o system call
36389 int gettimeofday(struct timeval *tv, void *tz);
36393 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
36395 @item Return value:
36396 On success, 0 is returned, -1 otherwise.
36402 @var{tz} is a non-NULL pointer.
36405 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
36411 @unnumberedsubsubsec isatty
36412 @cindex isatty, file-i/o system call
36417 int isatty(int fd);
36421 @samp{Fisatty,@var{fd}}
36423 @item Return value:
36424 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
36430 The call was interrupted by the user.
36435 Note that the @code{isatty} call is treated as a special case: it returns
36436 1 to the target if the file descriptor is attached
36437 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
36438 would require implementing @code{ioctl} and would be more complex than
36443 @unnumberedsubsubsec system
36444 @cindex system, file-i/o system call
36449 int system(const char *command);
36453 @samp{Fsystem,@var{commandptr}/@var{len}}
36455 @item Return value:
36456 If @var{len} is zero, the return value indicates whether a shell is
36457 available. A zero return value indicates a shell is not available.
36458 For non-zero @var{len}, the value returned is -1 on error and the
36459 return status of the command otherwise. Only the exit status of the
36460 command is returned, which is extracted from the host's @code{system}
36461 return value by calling @code{WEXITSTATUS(retval)}. In case
36462 @file{/bin/sh} could not be executed, 127 is returned.
36468 The call was interrupted by the user.
36473 @value{GDBN} takes over the full task of calling the necessary host calls
36474 to perform the @code{system} call. The return value of @code{system} on
36475 the host is simplified before it's returned
36476 to the target. Any termination signal information from the child process
36477 is discarded, and the return value consists
36478 entirely of the exit status of the called command.
36480 Due to security concerns, the @code{system} call is by default refused
36481 by @value{GDBN}. The user has to allow this call explicitly with the
36482 @code{set remote system-call-allowed 1} command.
36485 @item set remote system-call-allowed
36486 @kindex set remote system-call-allowed
36487 Control whether to allow the @code{system} calls in the File I/O
36488 protocol for the remote target. The default is zero (disabled).
36490 @item show remote system-call-allowed
36491 @kindex show remote system-call-allowed
36492 Show whether the @code{system} calls are allowed in the File I/O
36496 @node Protocol-specific Representation of Datatypes
36497 @subsection Protocol-specific Representation of Datatypes
36498 @cindex protocol-specific representation of datatypes, in file-i/o protocol
36501 * Integral Datatypes::
36503 * Memory Transfer::
36508 @node Integral Datatypes
36509 @unnumberedsubsubsec Integral Datatypes
36510 @cindex integral datatypes, in file-i/o protocol
36512 The integral datatypes used in the system calls are @code{int},
36513 @code{unsigned int}, @code{long}, @code{unsigned long},
36514 @code{mode_t}, and @code{time_t}.
36516 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
36517 implemented as 32 bit values in this protocol.
36519 @code{long} and @code{unsigned long} are implemented as 64 bit types.
36521 @xref{Limits}, for corresponding MIN and MAX values (similar to those
36522 in @file{limits.h}) to allow range checking on host and target.
36524 @code{time_t} datatypes are defined as seconds since the Epoch.
36526 All integral datatypes transferred as part of a memory read or write of a
36527 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
36530 @node Pointer Values
36531 @unnumberedsubsubsec Pointer Values
36532 @cindex pointer values, in file-i/o protocol
36534 Pointers to target data are transmitted as they are. An exception
36535 is made for pointers to buffers for which the length isn't
36536 transmitted as part of the function call, namely strings. Strings
36537 are transmitted as a pointer/length pair, both as hex values, e.g.@:
36544 which is a pointer to data of length 18 bytes at position 0x1aaf.
36545 The length is defined as the full string length in bytes, including
36546 the trailing null byte. For example, the string @code{"hello world"}
36547 at address 0x123456 is transmitted as
36553 @node Memory Transfer
36554 @unnumberedsubsubsec Memory Transfer
36555 @cindex memory transfer, in file-i/o protocol
36557 Structured data which is transferred using a memory read or write (for
36558 example, a @code{struct stat}) is expected to be in a protocol-specific format
36559 with all scalar multibyte datatypes being big endian. Translation to
36560 this representation needs to be done both by the target before the @code{F}
36561 packet is sent, and by @value{GDBN} before
36562 it transfers memory to the target. Transferred pointers to structured
36563 data should point to the already-coerced data at any time.
36567 @unnumberedsubsubsec struct stat
36568 @cindex struct stat, in file-i/o protocol
36570 The buffer of type @code{struct stat} used by the target and @value{GDBN}
36571 is defined as follows:
36575 unsigned int st_dev; /* device */
36576 unsigned int st_ino; /* inode */
36577 mode_t st_mode; /* protection */
36578 unsigned int st_nlink; /* number of hard links */
36579 unsigned int st_uid; /* user ID of owner */
36580 unsigned int st_gid; /* group ID of owner */
36581 unsigned int st_rdev; /* device type (if inode device) */
36582 unsigned long st_size; /* total size, in bytes */
36583 unsigned long st_blksize; /* blocksize for filesystem I/O */
36584 unsigned long st_blocks; /* number of blocks allocated */
36585 time_t st_atime; /* time of last access */
36586 time_t st_mtime; /* time of last modification */
36587 time_t st_ctime; /* time of last change */
36591 The integral datatypes conform to the definitions given in the
36592 appropriate section (see @ref{Integral Datatypes}, for details) so this
36593 structure is of size 64 bytes.
36595 The values of several fields have a restricted meaning and/or
36601 A value of 0 represents a file, 1 the console.
36604 No valid meaning for the target. Transmitted unchanged.
36607 Valid mode bits are described in @ref{Constants}. Any other
36608 bits have currently no meaning for the target.
36613 No valid meaning for the target. Transmitted unchanged.
36618 These values have a host and file system dependent
36619 accuracy. Especially on Windows hosts, the file system may not
36620 support exact timing values.
36623 The target gets a @code{struct stat} of the above representation and is
36624 responsible for coercing it to the target representation before
36627 Note that due to size differences between the host, target, and protocol
36628 representations of @code{struct stat} members, these members could eventually
36629 get truncated on the target.
36631 @node struct timeval
36632 @unnumberedsubsubsec struct timeval
36633 @cindex struct timeval, in file-i/o protocol
36635 The buffer of type @code{struct timeval} used by the File-I/O protocol
36636 is defined as follows:
36640 time_t tv_sec; /* second */
36641 long tv_usec; /* microsecond */
36645 The integral datatypes conform to the definitions given in the
36646 appropriate section (see @ref{Integral Datatypes}, for details) so this
36647 structure is of size 8 bytes.
36650 @subsection Constants
36651 @cindex constants, in file-i/o protocol
36653 The following values are used for the constants inside of the
36654 protocol. @value{GDBN} and target are responsible for translating these
36655 values before and after the call as needed.
36666 @unnumberedsubsubsec Open Flags
36667 @cindex open flags, in file-i/o protocol
36669 All values are given in hexadecimal representation.
36681 @node mode_t Values
36682 @unnumberedsubsubsec mode_t Values
36683 @cindex mode_t values, in file-i/o protocol
36685 All values are given in octal representation.
36702 @unnumberedsubsubsec Errno Values
36703 @cindex errno values, in file-i/o protocol
36705 All values are given in decimal representation.
36730 @code{EUNKNOWN} is used as a fallback error value if a host system returns
36731 any error value not in the list of supported error numbers.
36734 @unnumberedsubsubsec Lseek Flags
36735 @cindex lseek flags, in file-i/o protocol
36744 @unnumberedsubsubsec Limits
36745 @cindex limits, in file-i/o protocol
36747 All values are given in decimal representation.
36750 INT_MIN -2147483648
36752 UINT_MAX 4294967295
36753 LONG_MIN -9223372036854775808
36754 LONG_MAX 9223372036854775807
36755 ULONG_MAX 18446744073709551615
36758 @node File-I/O Examples
36759 @subsection File-I/O Examples
36760 @cindex file-i/o examples
36762 Example sequence of a write call, file descriptor 3, buffer is at target
36763 address 0x1234, 6 bytes should be written:
36766 <- @code{Fwrite,3,1234,6}
36767 @emph{request memory read from target}
36770 @emph{return "6 bytes written"}
36774 Example sequence of a read call, file descriptor 3, buffer is at target
36775 address 0x1234, 6 bytes should be read:
36778 <- @code{Fread,3,1234,6}
36779 @emph{request memory write to target}
36780 -> @code{X1234,6:XXXXXX}
36781 @emph{return "6 bytes read"}
36785 Example sequence of a read call, call fails on the host due to invalid
36786 file descriptor (@code{EBADF}):
36789 <- @code{Fread,3,1234,6}
36793 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
36797 <- @code{Fread,3,1234,6}
36802 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
36806 <- @code{Fread,3,1234,6}
36807 -> @code{X1234,6:XXXXXX}
36811 @node Library List Format
36812 @section Library List Format
36813 @cindex library list format, remote protocol
36815 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
36816 same process as your application to manage libraries. In this case,
36817 @value{GDBN} can use the loader's symbol table and normal memory
36818 operations to maintain a list of shared libraries. On other
36819 platforms, the operating system manages loaded libraries.
36820 @value{GDBN} can not retrieve the list of currently loaded libraries
36821 through memory operations, so it uses the @samp{qXfer:libraries:read}
36822 packet (@pxref{qXfer library list read}) instead. The remote stub
36823 queries the target's operating system and reports which libraries
36826 The @samp{qXfer:libraries:read} packet returns an XML document which
36827 lists loaded libraries and their offsets. Each library has an
36828 associated name and one or more segment or section base addresses,
36829 which report where the library was loaded in memory.
36831 For the common case of libraries that are fully linked binaries, the
36832 library should have a list of segments. If the target supports
36833 dynamic linking of a relocatable object file, its library XML element
36834 should instead include a list of allocated sections. The segment or
36835 section bases are start addresses, not relocation offsets; they do not
36836 depend on the library's link-time base addresses.
36838 @value{GDBN} must be linked with the Expat library to support XML
36839 library lists. @xref{Expat}.
36841 A simple memory map, with one loaded library relocated by a single
36842 offset, looks like this:
36846 <library name="/lib/libc.so.6">
36847 <segment address="0x10000000"/>
36852 Another simple memory map, with one loaded library with three
36853 allocated sections (.text, .data, .bss), looks like this:
36857 <library name="sharedlib.o">
36858 <section address="0x10000000"/>
36859 <section address="0x20000000"/>
36860 <section address="0x30000000"/>
36865 The format of a library list is described by this DTD:
36868 <!-- library-list: Root element with versioning -->
36869 <!ELEMENT library-list (library)*>
36870 <!ATTLIST library-list version CDATA #FIXED "1.0">
36871 <!ELEMENT library (segment*, section*)>
36872 <!ATTLIST library name CDATA #REQUIRED>
36873 <!ELEMENT segment EMPTY>
36874 <!ATTLIST segment address CDATA #REQUIRED>
36875 <!ELEMENT section EMPTY>
36876 <!ATTLIST section address CDATA #REQUIRED>
36879 In addition, segments and section descriptors cannot be mixed within a
36880 single library element, and you must supply at least one segment or
36881 section for each library.
36883 @node Memory Map Format
36884 @section Memory Map Format
36885 @cindex memory map format
36887 To be able to write into flash memory, @value{GDBN} needs to obtain a
36888 memory map from the target. This section describes the format of the
36891 The memory map is obtained using the @samp{qXfer:memory-map:read}
36892 (@pxref{qXfer memory map read}) packet and is an XML document that
36893 lists memory regions.
36895 @value{GDBN} must be linked with the Expat library to support XML
36896 memory maps. @xref{Expat}.
36898 The top-level structure of the document is shown below:
36901 <?xml version="1.0"?>
36902 <!DOCTYPE memory-map
36903 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
36904 "http://sourceware.org/gdb/gdb-memory-map.dtd">
36910 Each region can be either:
36915 A region of RAM starting at @var{addr} and extending for @var{length}
36919 <memory type="ram" start="@var{addr}" length="@var{length}"/>
36924 A region of read-only memory:
36927 <memory type="rom" start="@var{addr}" length="@var{length}"/>
36932 A region of flash memory, with erasure blocks @var{blocksize}
36936 <memory type="flash" start="@var{addr}" length="@var{length}">
36937 <property name="blocksize">@var{blocksize}</property>
36943 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
36944 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
36945 packets to write to addresses in such ranges.
36947 The formal DTD for memory map format is given below:
36950 <!-- ................................................... -->
36951 <!-- Memory Map XML DTD ................................ -->
36952 <!-- File: memory-map.dtd .............................. -->
36953 <!-- .................................... .............. -->
36954 <!-- memory-map.dtd -->
36955 <!-- memory-map: Root element with versioning -->
36956 <!ELEMENT memory-map (memory | property)>
36957 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
36958 <!ELEMENT memory (property)>
36959 <!-- memory: Specifies a memory region,
36960 and its type, or device. -->
36961 <!ATTLIST memory type CDATA #REQUIRED
36962 start CDATA #REQUIRED
36963 length CDATA #REQUIRED
36964 device CDATA #IMPLIED>
36965 <!-- property: Generic attribute tag -->
36966 <!ELEMENT property (#PCDATA | property)*>
36967 <!ATTLIST property name CDATA #REQUIRED>
36970 @node Thread List Format
36971 @section Thread List Format
36972 @cindex thread list format
36974 To efficiently update the list of threads and their attributes,
36975 @value{GDBN} issues the @samp{qXfer:threads:read} packet
36976 (@pxref{qXfer threads read}) and obtains the XML document with
36977 the following structure:
36980 <?xml version="1.0"?>
36982 <thread id="id" core="0">
36983 ... description ...
36988 Each @samp{thread} element must have the @samp{id} attribute that
36989 identifies the thread (@pxref{thread-id syntax}). The
36990 @samp{core} attribute, if present, specifies which processor core
36991 the thread was last executing on. The content of the of @samp{thread}
36992 element is interpreted as human-readable auxilliary information.
36994 @node Traceframe Info Format
36995 @section Traceframe Info Format
36996 @cindex traceframe info format
36998 To be able to know which objects in the inferior can be examined when
36999 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
37000 memory ranges, registers and trace state variables that have been
37001 collected in a traceframe.
37003 This list is obtained using the @samp{qXfer:traceframe-info:read}
37004 (@pxref{qXfer traceframe info read}) packet and is an XML document.
37006 @value{GDBN} must be linked with the Expat library to support XML
37007 traceframe info discovery. @xref{Expat}.
37009 The top-level structure of the document is shown below:
37012 <?xml version="1.0"?>
37013 <!DOCTYPE traceframe-info
37014 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
37015 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
37021 Each traceframe block can be either:
37026 A region of collected memory starting at @var{addr} and extending for
37027 @var{length} bytes from there:
37030 <memory start="@var{addr}" length="@var{length}"/>
37035 The formal DTD for the traceframe info format is given below:
37038 <!ELEMENT traceframe-info (memory)* >
37039 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
37041 <!ELEMENT memory EMPTY>
37042 <!ATTLIST memory start CDATA #REQUIRED
37043 length CDATA #REQUIRED>
37046 @include agentexpr.texi
37048 @node Target Descriptions
37049 @appendix Target Descriptions
37050 @cindex target descriptions
37052 One of the challenges of using @value{GDBN} to debug embedded systems
37053 is that there are so many minor variants of each processor
37054 architecture in use. It is common practice for vendors to start with
37055 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
37056 and then make changes to adapt it to a particular market niche. Some
37057 architectures have hundreds of variants, available from dozens of
37058 vendors. This leads to a number of problems:
37062 With so many different customized processors, it is difficult for
37063 the @value{GDBN} maintainers to keep up with the changes.
37065 Since individual variants may have short lifetimes or limited
37066 audiences, it may not be worthwhile to carry information about every
37067 variant in the @value{GDBN} source tree.
37069 When @value{GDBN} does support the architecture of the embedded system
37070 at hand, the task of finding the correct architecture name to give the
37071 @command{set architecture} command can be error-prone.
37074 To address these problems, the @value{GDBN} remote protocol allows a
37075 target system to not only identify itself to @value{GDBN}, but to
37076 actually describe its own features. This lets @value{GDBN} support
37077 processor variants it has never seen before --- to the extent that the
37078 descriptions are accurate, and that @value{GDBN} understands them.
37080 @value{GDBN} must be linked with the Expat library to support XML
37081 target descriptions. @xref{Expat}.
37084 * Retrieving Descriptions:: How descriptions are fetched from a target.
37085 * Target Description Format:: The contents of a target description.
37086 * Predefined Target Types:: Standard types available for target
37088 * Standard Target Features:: Features @value{GDBN} knows about.
37091 @node Retrieving Descriptions
37092 @section Retrieving Descriptions
37094 Target descriptions can be read from the target automatically, or
37095 specified by the user manually. The default behavior is to read the
37096 description from the target. @value{GDBN} retrieves it via the remote
37097 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
37098 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
37099 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
37100 XML document, of the form described in @ref{Target Description
37103 Alternatively, you can specify a file to read for the target description.
37104 If a file is set, the target will not be queried. The commands to
37105 specify a file are:
37108 @cindex set tdesc filename
37109 @item set tdesc filename @var{path}
37110 Read the target description from @var{path}.
37112 @cindex unset tdesc filename
37113 @item unset tdesc filename
37114 Do not read the XML target description from a file. @value{GDBN}
37115 will use the description supplied by the current target.
37117 @cindex show tdesc filename
37118 @item show tdesc filename
37119 Show the filename to read for a target description, if any.
37123 @node Target Description Format
37124 @section Target Description Format
37125 @cindex target descriptions, XML format
37127 A target description annex is an @uref{http://www.w3.org/XML/, XML}
37128 document which complies with the Document Type Definition provided in
37129 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
37130 means you can use generally available tools like @command{xmllint} to
37131 check that your feature descriptions are well-formed and valid.
37132 However, to help people unfamiliar with XML write descriptions for
37133 their targets, we also describe the grammar here.
37135 Target descriptions can identify the architecture of the remote target
37136 and (for some architectures) provide information about custom register
37137 sets. They can also identify the OS ABI of the remote target.
37138 @value{GDBN} can use this information to autoconfigure for your
37139 target, or to warn you if you connect to an unsupported target.
37141 Here is a simple target description:
37144 <target version="1.0">
37145 <architecture>i386:x86-64</architecture>
37150 This minimal description only says that the target uses
37151 the x86-64 architecture.
37153 A target description has the following overall form, with [ ] marking
37154 optional elements and @dots{} marking repeatable elements. The elements
37155 are explained further below.
37158 <?xml version="1.0"?>
37159 <!DOCTYPE target SYSTEM "gdb-target.dtd">
37160 <target version="1.0">
37161 @r{[}@var{architecture}@r{]}
37162 @r{[}@var{osabi}@r{]}
37163 @r{[}@var{compatible}@r{]}
37164 @r{[}@var{feature}@dots{}@r{]}
37169 The description is generally insensitive to whitespace and line
37170 breaks, under the usual common-sense rules. The XML version
37171 declaration and document type declaration can generally be omitted
37172 (@value{GDBN} does not require them), but specifying them may be
37173 useful for XML validation tools. The @samp{version} attribute for
37174 @samp{<target>} may also be omitted, but we recommend
37175 including it; if future versions of @value{GDBN} use an incompatible
37176 revision of @file{gdb-target.dtd}, they will detect and report
37177 the version mismatch.
37179 @subsection Inclusion
37180 @cindex target descriptions, inclusion
37183 @cindex <xi:include>
37186 It can sometimes be valuable to split a target description up into
37187 several different annexes, either for organizational purposes, or to
37188 share files between different possible target descriptions. You can
37189 divide a description into multiple files by replacing any element of
37190 the target description with an inclusion directive of the form:
37193 <xi:include href="@var{document}"/>
37197 When @value{GDBN} encounters an element of this form, it will retrieve
37198 the named XML @var{document}, and replace the inclusion directive with
37199 the contents of that document. If the current description was read
37200 using @samp{qXfer}, then so will be the included document;
37201 @var{document} will be interpreted as the name of an annex. If the
37202 current description was read from a file, @value{GDBN} will look for
37203 @var{document} as a file in the same directory where it found the
37204 original description.
37206 @subsection Architecture
37207 @cindex <architecture>
37209 An @samp{<architecture>} element has this form:
37212 <architecture>@var{arch}</architecture>
37215 @var{arch} is one of the architectures from the set accepted by
37216 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
37219 @cindex @code{<osabi>}
37221 This optional field was introduced in @value{GDBN} version 7.0.
37222 Previous versions of @value{GDBN} ignore it.
37224 An @samp{<osabi>} element has this form:
37227 <osabi>@var{abi-name}</osabi>
37230 @var{abi-name} is an OS ABI name from the same selection accepted by
37231 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
37233 @subsection Compatible Architecture
37234 @cindex @code{<compatible>}
37236 This optional field was introduced in @value{GDBN} version 7.0.
37237 Previous versions of @value{GDBN} ignore it.
37239 A @samp{<compatible>} element has this form:
37242 <compatible>@var{arch}</compatible>
37245 @var{arch} is one of the architectures from the set accepted by
37246 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
37248 A @samp{<compatible>} element is used to specify that the target
37249 is able to run binaries in some other than the main target architecture
37250 given by the @samp{<architecture>} element. For example, on the
37251 Cell Broadband Engine, the main architecture is @code{powerpc:common}
37252 or @code{powerpc:common64}, but the system is able to run binaries
37253 in the @code{spu} architecture as well. The way to describe this
37254 capability with @samp{<compatible>} is as follows:
37257 <architecture>powerpc:common</architecture>
37258 <compatible>spu</compatible>
37261 @subsection Features
37264 Each @samp{<feature>} describes some logical portion of the target
37265 system. Features are currently used to describe available CPU
37266 registers and the types of their contents. A @samp{<feature>} element
37270 <feature name="@var{name}">
37271 @r{[}@var{type}@dots{}@r{]}
37277 Each feature's name should be unique within the description. The name
37278 of a feature does not matter unless @value{GDBN} has some special
37279 knowledge of the contents of that feature; if it does, the feature
37280 should have its standard name. @xref{Standard Target Features}.
37284 Any register's value is a collection of bits which @value{GDBN} must
37285 interpret. The default interpretation is a two's complement integer,
37286 but other types can be requested by name in the register description.
37287 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
37288 Target Types}), and the description can define additional composite types.
37290 Each type element must have an @samp{id} attribute, which gives
37291 a unique (within the containing @samp{<feature>}) name to the type.
37292 Types must be defined before they are used.
37295 Some targets offer vector registers, which can be treated as arrays
37296 of scalar elements. These types are written as @samp{<vector>} elements,
37297 specifying the array element type, @var{type}, and the number of elements,
37301 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
37305 If a register's value is usefully viewed in multiple ways, define it
37306 with a union type containing the useful representations. The
37307 @samp{<union>} element contains one or more @samp{<field>} elements,
37308 each of which has a @var{name} and a @var{type}:
37311 <union id="@var{id}">
37312 <field name="@var{name}" type="@var{type}"/>
37318 If a register's value is composed from several separate values, define
37319 it with a structure type. There are two forms of the @samp{<struct>}
37320 element; a @samp{<struct>} element must either contain only bitfields
37321 or contain no bitfields. If the structure contains only bitfields,
37322 its total size in bytes must be specified, each bitfield must have an
37323 explicit start and end, and bitfields are automatically assigned an
37324 integer type. The field's @var{start} should be less than or
37325 equal to its @var{end}, and zero represents the least significant bit.
37328 <struct id="@var{id}" size="@var{size}">
37329 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
37334 If the structure contains no bitfields, then each field has an
37335 explicit type, and no implicit padding is added.
37338 <struct id="@var{id}">
37339 <field name="@var{name}" type="@var{type}"/>
37345 If a register's value is a series of single-bit flags, define it with
37346 a flags type. The @samp{<flags>} element has an explicit @var{size}
37347 and contains one or more @samp{<field>} elements. Each field has a
37348 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
37352 <flags id="@var{id}" size="@var{size}">
37353 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
37358 @subsection Registers
37361 Each register is represented as an element with this form:
37364 <reg name="@var{name}"
37365 bitsize="@var{size}"
37366 @r{[}regnum="@var{num}"@r{]}
37367 @r{[}save-restore="@var{save-restore}"@r{]}
37368 @r{[}type="@var{type}"@r{]}
37369 @r{[}group="@var{group}"@r{]}/>
37373 The components are as follows:
37378 The register's name; it must be unique within the target description.
37381 The register's size, in bits.
37384 The register's number. If omitted, a register's number is one greater
37385 than that of the previous register (either in the current feature or in
37386 a preceding feature); the first register in the target description
37387 defaults to zero. This register number is used to read or write
37388 the register; e.g.@: it is used in the remote @code{p} and @code{P}
37389 packets, and registers appear in the @code{g} and @code{G} packets
37390 in order of increasing register number.
37393 Whether the register should be preserved across inferior function
37394 calls; this must be either @code{yes} or @code{no}. The default is
37395 @code{yes}, which is appropriate for most registers except for
37396 some system control registers; this is not related to the target's
37400 The type of the register. @var{type} may be a predefined type, a type
37401 defined in the current feature, or one of the special types @code{int}
37402 and @code{float}. @code{int} is an integer type of the correct size
37403 for @var{bitsize}, and @code{float} is a floating point type (in the
37404 architecture's normal floating point format) of the correct size for
37405 @var{bitsize}. The default is @code{int}.
37408 The register group to which this register belongs. @var{group} must
37409 be either @code{general}, @code{float}, or @code{vector}. If no
37410 @var{group} is specified, @value{GDBN} will not display the register
37411 in @code{info registers}.
37415 @node Predefined Target Types
37416 @section Predefined Target Types
37417 @cindex target descriptions, predefined types
37419 Type definitions in the self-description can build up composite types
37420 from basic building blocks, but can not define fundamental types. Instead,
37421 standard identifiers are provided by @value{GDBN} for the fundamental
37422 types. The currently supported types are:
37431 Signed integer types holding the specified number of bits.
37438 Unsigned integer types holding the specified number of bits.
37442 Pointers to unspecified code and data. The program counter and
37443 any dedicated return address register may be marked as code
37444 pointers; printing a code pointer converts it into a symbolic
37445 address. The stack pointer and any dedicated address registers
37446 may be marked as data pointers.
37449 Single precision IEEE floating point.
37452 Double precision IEEE floating point.
37455 The 12-byte extended precision format used by ARM FPA registers.
37458 The 10-byte extended precision format used by x87 registers.
37461 32bit @sc{eflags} register used by x86.
37464 32bit @sc{mxcsr} register used by x86.
37468 @node Standard Target Features
37469 @section Standard Target Features
37470 @cindex target descriptions, standard features
37472 A target description must contain either no registers or all the
37473 target's registers. If the description contains no registers, then
37474 @value{GDBN} will assume a default register layout, selected based on
37475 the architecture. If the description contains any registers, the
37476 default layout will not be used; the standard registers must be
37477 described in the target description, in such a way that @value{GDBN}
37478 can recognize them.
37480 This is accomplished by giving specific names to feature elements
37481 which contain standard registers. @value{GDBN} will look for features
37482 with those names and verify that they contain the expected registers;
37483 if any known feature is missing required registers, or if any required
37484 feature is missing, @value{GDBN} will reject the target
37485 description. You can add additional registers to any of the
37486 standard features --- @value{GDBN} will display them just as if
37487 they were added to an unrecognized feature.
37489 This section lists the known features and their expected contents.
37490 Sample XML documents for these features are included in the
37491 @value{GDBN} source tree, in the directory @file{gdb/features}.
37493 Names recognized by @value{GDBN} should include the name of the
37494 company or organization which selected the name, and the overall
37495 architecture to which the feature applies; so e.g.@: the feature
37496 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
37498 The names of registers are not case sensitive for the purpose
37499 of recognizing standard features, but @value{GDBN} will only display
37500 registers using the capitalization used in the description.
37507 * PowerPC Features::
37513 @subsection ARM Features
37514 @cindex target descriptions, ARM features
37516 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
37518 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
37519 @samp{lr}, @samp{pc}, and @samp{cpsr}.
37521 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
37522 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
37523 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
37526 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
37527 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
37529 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
37530 it should contain at least registers @samp{wR0} through @samp{wR15} and
37531 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
37532 @samp{wCSSF}, and @samp{wCASF} registers are optional.
37534 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
37535 should contain at least registers @samp{d0} through @samp{d15}. If
37536 they are present, @samp{d16} through @samp{d31} should also be included.
37537 @value{GDBN} will synthesize the single-precision registers from
37538 halves of the double-precision registers.
37540 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
37541 need to contain registers; it instructs @value{GDBN} to display the
37542 VFP double-precision registers as vectors and to synthesize the
37543 quad-precision registers from pairs of double-precision registers.
37544 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
37545 be present and include 32 double-precision registers.
37547 @node i386 Features
37548 @subsection i386 Features
37549 @cindex target descriptions, i386 features
37551 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
37552 targets. It should describe the following registers:
37556 @samp{eax} through @samp{edi} plus @samp{eip} for i386
37558 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
37560 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
37561 @samp{fs}, @samp{gs}
37563 @samp{st0} through @samp{st7}
37565 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
37566 @samp{foseg}, @samp{fooff} and @samp{fop}
37569 The register sets may be different, depending on the target.
37571 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
37572 describe registers:
37576 @samp{xmm0} through @samp{xmm7} for i386
37578 @samp{xmm0} through @samp{xmm15} for amd64
37583 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
37584 @samp{org.gnu.gdb.i386.sse} feature. It should
37585 describe the upper 128 bits of @sc{ymm} registers:
37589 @samp{ymm0h} through @samp{ymm7h} for i386
37591 @samp{ymm0h} through @samp{ymm15h} for amd64
37594 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
37595 describe a single register, @samp{orig_eax}.
37597 @node MIPS Features
37598 @subsection MIPS Features
37599 @cindex target descriptions, MIPS features
37601 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
37602 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
37603 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
37606 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
37607 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
37608 registers. They may be 32-bit or 64-bit depending on the target.
37610 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
37611 it may be optional in a future version of @value{GDBN}. It should
37612 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
37613 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
37615 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
37616 contain a single register, @samp{restart}, which is used by the
37617 Linux kernel to control restartable syscalls.
37619 @node M68K Features
37620 @subsection M68K Features
37621 @cindex target descriptions, M68K features
37624 @item @samp{org.gnu.gdb.m68k.core}
37625 @itemx @samp{org.gnu.gdb.coldfire.core}
37626 @itemx @samp{org.gnu.gdb.fido.core}
37627 One of those features must be always present.
37628 The feature that is present determines which flavor of m68k is
37629 used. The feature that is present should contain registers
37630 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
37631 @samp{sp}, @samp{ps} and @samp{pc}.
37633 @item @samp{org.gnu.gdb.coldfire.fp}
37634 This feature is optional. If present, it should contain registers
37635 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
37639 @node PowerPC Features
37640 @subsection PowerPC Features
37641 @cindex target descriptions, PowerPC features
37643 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
37644 targets. It should contain registers @samp{r0} through @samp{r31},
37645 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
37646 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
37648 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
37649 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
37651 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
37652 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
37655 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
37656 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
37657 will combine these registers with the floating point registers
37658 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
37659 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
37660 through @samp{vs63}, the set of vector registers for POWER7.
37662 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
37663 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
37664 @samp{spefscr}. SPE targets should provide 32-bit registers in
37665 @samp{org.gnu.gdb.power.core} and provide the upper halves in
37666 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
37667 these to present registers @samp{ev0} through @samp{ev31} to the
37670 @node TIC6x Features
37671 @subsection TMS320C6x Features
37672 @cindex target descriptions, TIC6x features
37673 @cindex target descriptions, TMS320C6x features
37674 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
37675 targets. It should contain registers @samp{A0} through @samp{A15},
37676 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
37678 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
37679 contain registers @samp{A16} through @samp{A31} and @samp{B16}
37680 through @samp{B31}.
37682 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
37683 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
37685 @node Operating System Information
37686 @appendix Operating System Information
37687 @cindex operating system information
37693 Users of @value{GDBN} often wish to obtain information about the state of
37694 the operating system running on the target---for example the list of
37695 processes, or the list of open files. This section describes the
37696 mechanism that makes it possible. This mechanism is similar to the
37697 target features mechanism (@pxref{Target Descriptions}), but focuses
37698 on a different aspect of target.
37700 Operating system information is retrived from the target via the
37701 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
37702 read}). The object name in the request should be @samp{osdata}, and
37703 the @var{annex} identifies the data to be fetched.
37706 @appendixsection Process list
37707 @cindex operating system information, process list
37709 When requesting the process list, the @var{annex} field in the
37710 @samp{qXfer} request should be @samp{processes}. The returned data is
37711 an XML document. The formal syntax of this document is defined in
37712 @file{gdb/features/osdata.dtd}.
37714 An example document is:
37717 <?xml version="1.0"?>
37718 <!DOCTYPE target SYSTEM "osdata.dtd">
37719 <osdata type="processes">
37721 <column name="pid">1</column>
37722 <column name="user">root</column>
37723 <column name="command">/sbin/init</column>
37724 <column name="cores">1,2,3</column>
37729 Each item should include a column whose name is @samp{pid}. The value
37730 of that column should identify the process on the target. The
37731 @samp{user} and @samp{command} columns are optional, and will be
37732 displayed by @value{GDBN}. The @samp{cores} column, if present,
37733 should contain a comma-separated list of cores that this process
37734 is running on. Target may provide additional columns,
37735 which @value{GDBN} currently ignores.
37737 @node Trace File Format
37738 @appendix Trace File Format
37739 @cindex trace file format
37741 The trace file comes in three parts: a header, a textual description
37742 section, and a trace frame section with binary data.
37744 The header has the form @code{\x7fTRACE0\n}. The first byte is
37745 @code{0x7f} so as to indicate that the file contains binary data,
37746 while the @code{0} is a version number that may have different values
37749 The description section consists of multiple lines of @sc{ascii} text
37750 separated by newline characters (@code{0xa}). The lines may include a
37751 variety of optional descriptive or context-setting information, such
37752 as tracepoint definitions or register set size. @value{GDBN} will
37753 ignore any line that it does not recognize. An empty line marks the end
37756 @c FIXME add some specific types of data
37758 The trace frame section consists of a number of consecutive frames.
37759 Each frame begins with a two-byte tracepoint number, followed by a
37760 four-byte size giving the amount of data in the frame. The data in
37761 the frame consists of a number of blocks, each introduced by a
37762 character indicating its type (at least register, memory, and trace
37763 state variable). The data in this section is raw binary, not a
37764 hexadecimal or other encoding; its endianness matches the target's
37767 @c FIXME bi-arch may require endianness/arch info in description section
37770 @item R @var{bytes}
37771 Register block. The number and ordering of bytes matches that of a
37772 @code{g} packet in the remote protocol. Note that these are the
37773 actual bytes, in target order and @value{GDBN} register order, not a
37774 hexadecimal encoding.
37776 @item M @var{address} @var{length} @var{bytes}...
37777 Memory block. This is a contiguous block of memory, at the 8-byte
37778 address @var{address}, with a 2-byte length @var{length}, followed by
37779 @var{length} bytes.
37781 @item V @var{number} @var{value}
37782 Trace state variable block. This records the 8-byte signed value
37783 @var{value} of trace state variable numbered @var{number}.
37787 Future enhancements of the trace file format may include additional types
37790 @node Index Section Format
37791 @appendix @code{.gdb_index} section format
37792 @cindex .gdb_index section format
37793 @cindex index section format
37795 This section documents the index section that is created by @code{save
37796 gdb-index} (@pxref{Index Files}). The index section is
37797 DWARF-specific; some knowledge of DWARF is assumed in this
37800 The mapped index file format is designed to be directly
37801 @code{mmap}able on any architecture. In most cases, a datum is
37802 represented using a little-endian 32-bit integer value, called an
37803 @code{offset_type}. Big endian machines must byte-swap the values
37804 before using them. Exceptions to this rule are noted. The data is
37805 laid out such that alignment is always respected.
37807 A mapped index consists of several areas, laid out in order.
37811 The file header. This is a sequence of values, of @code{offset_type}
37812 unless otherwise noted:
37816 The version number, currently 5. Versions 1, 2 and 3 are obsolete.
37817 Version 4 differs by its hashing function.
37820 The offset, from the start of the file, of the CU list.
37823 The offset, from the start of the file, of the types CU list. Note
37824 that this area can be empty, in which case this offset will be equal
37825 to the next offset.
37828 The offset, from the start of the file, of the address area.
37831 The offset, from the start of the file, of the symbol table.
37834 The offset, from the start of the file, of the constant pool.
37838 The CU list. This is a sequence of pairs of 64-bit little-endian
37839 values, sorted by the CU offset. The first element in each pair is
37840 the offset of a CU in the @code{.debug_info} section. The second
37841 element in each pair is the length of that CU. References to a CU
37842 elsewhere in the map are done using a CU index, which is just the
37843 0-based index into this table. Note that if there are type CUs, then
37844 conceptually CUs and type CUs form a single list for the purposes of
37848 The types CU list. This is a sequence of triplets of 64-bit
37849 little-endian values. In a triplet, the first value is the CU offset,
37850 the second value is the type offset in the CU, and the third value is
37851 the type signature. The types CU list is not sorted.
37854 The address area. The address area consists of a sequence of address
37855 entries. Each address entry has three elements:
37859 The low address. This is a 64-bit little-endian value.
37862 The high address. This is a 64-bit little-endian value. Like
37863 @code{DW_AT_high_pc}, the value is one byte beyond the end.
37866 The CU index. This is an @code{offset_type} value.
37870 The symbol table. This is an open-addressed hash table. The size of
37871 the hash table is always a power of 2.
37873 Each slot in the hash table consists of a pair of @code{offset_type}
37874 values. The first value is the offset of the symbol's name in the
37875 constant pool. The second value is the offset of the CU vector in the
37878 If both values are 0, then this slot in the hash table is empty. This
37879 is ok because while 0 is a valid constant pool index, it cannot be a
37880 valid index for both a string and a CU vector.
37882 The hash value for a table entry is computed by applying an
37883 iterative hash function to the symbol's name. Starting with an
37884 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
37885 the string is incorporated into the hash using the formula depending on the
37890 The formula is @code{r = r * 67 + c - 113}.
37893 The formula is @code{r = r * 67 + tolower (c) - 113}.
37896 The terminating @samp{\0} is not incorporated into the hash.
37898 The step size used in the hash table is computed via
37899 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
37900 value, and @samp{size} is the size of the hash table. The step size
37901 is used to find the next candidate slot when handling a hash
37904 The names of C@t{++} symbols in the hash table are canonicalized. We
37905 don't currently have a simple description of the canonicalization
37906 algorithm; if you intend to create new index sections, you must read
37910 The constant pool. This is simply a bunch of bytes. It is organized
37911 so that alignment is correct: CU vectors are stored first, followed by
37914 A CU vector in the constant pool is a sequence of @code{offset_type}
37915 values. The first value is the number of CU indices in the vector.
37916 Each subsequent value is the index of a CU in the CU list. This
37917 element in the hash table is used to indicate which CUs define the
37920 A string in the constant pool is zero-terminated.
37925 @node GNU Free Documentation License
37926 @appendix GNU Free Documentation License
37935 % I think something like @colophon should be in texinfo. In the
37937 \long\def\colophon{\hbox to0pt{}\vfill
37938 \centerline{The body of this manual is set in}
37939 \centerline{\fontname\tenrm,}
37940 \centerline{with headings in {\bf\fontname\tenbf}}
37941 \centerline{and examples in {\tt\fontname\tentt}.}
37942 \centerline{{\it\fontname\tenit\/},}
37943 \centerline{{\bf\fontname\tenbf}, and}
37944 \centerline{{\sl\fontname\tensl\/}}
37945 \centerline{are used for emphasis.}\vfill}
37947 % Blame: doc@cygnus.com, 1991.