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. Version 3.1 and later of @value{NGCC},
1877 the @sc{gnu} C compiler, provides macro information if you are using
1878 the DWARF debugging format, and specify the option @option{-g3}.
1880 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1881 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1882 information on @value{NGCC} options affecting debug information.
1884 You will have the best debugging experience if you use the latest
1885 version of the DWARF debugging format that your compiler supports.
1886 DWARF is currently the most expressive and best supported debugging
1887 format in @value{GDBN}.
1891 @section Starting your Program
1897 @kindex r @r{(@code{run})}
1900 Use the @code{run} command to start your program under @value{GDBN}.
1901 You must first specify the program name (except on VxWorks) with an
1902 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1903 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1904 (@pxref{Files, ,Commands to Specify Files}).
1908 If you are running your program in an execution environment that
1909 supports processes, @code{run} creates an inferior process and makes
1910 that process run your program. In some environments without processes,
1911 @code{run} jumps to the start of your program. Other targets,
1912 like @samp{remote}, are always running. If you get an error
1913 message like this one:
1916 The "remote" target does not support "run".
1917 Try "help target" or "continue".
1921 then use @code{continue} to run your program. You may need @code{load}
1922 first (@pxref{load}).
1924 The execution of a program is affected by certain information it
1925 receives from its superior. @value{GDBN} provides ways to specify this
1926 information, which you must do @emph{before} starting your program. (You
1927 can change it after starting your program, but such changes only affect
1928 your program the next time you start it.) This information may be
1929 divided into four categories:
1932 @item The @emph{arguments.}
1933 Specify the arguments to give your program as the arguments of the
1934 @code{run} command. If a shell is available on your target, the shell
1935 is used to pass the arguments, so that you may use normal conventions
1936 (such as wildcard expansion or variable substitution) in describing
1938 In Unix systems, you can control which shell is used with the
1939 @code{SHELL} environment variable.
1940 @xref{Arguments, ,Your Program's Arguments}.
1942 @item The @emph{environment.}
1943 Your program normally inherits its environment from @value{GDBN}, but you can
1944 use the @value{GDBN} commands @code{set environment} and @code{unset
1945 environment} to change parts of the environment that affect
1946 your program. @xref{Environment, ,Your Program's Environment}.
1948 @item The @emph{working directory.}
1949 Your program inherits its working directory from @value{GDBN}. You can set
1950 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1951 @xref{Working Directory, ,Your Program's Working Directory}.
1953 @item The @emph{standard input and output.}
1954 Your program normally uses the same device for standard input and
1955 standard output as @value{GDBN} is using. You can redirect input and output
1956 in the @code{run} command line, or you can use the @code{tty} command to
1957 set a different device for your program.
1958 @xref{Input/Output, ,Your Program's Input and Output}.
1961 @emph{Warning:} While input and output redirection work, you cannot use
1962 pipes to pass the output of the program you are debugging to another
1963 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1967 When you issue the @code{run} command, your program begins to execute
1968 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1969 of how to arrange for your program to stop. Once your program has
1970 stopped, you may call functions in your program, using the @code{print}
1971 or @code{call} commands. @xref{Data, ,Examining Data}.
1973 If the modification time of your symbol file has changed since the last
1974 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1975 table, and reads it again. When it does this, @value{GDBN} tries to retain
1976 your current breakpoints.
1981 @cindex run to main procedure
1982 The name of the main procedure can vary from language to language.
1983 With C or C@t{++}, the main procedure name is always @code{main}, but
1984 other languages such as Ada do not require a specific name for their
1985 main procedure. The debugger provides a convenient way to start the
1986 execution of the program and to stop at the beginning of the main
1987 procedure, depending on the language used.
1989 The @samp{start} command does the equivalent of setting a temporary
1990 breakpoint at the beginning of the main procedure and then invoking
1991 the @samp{run} command.
1993 @cindex elaboration phase
1994 Some programs contain an @dfn{elaboration} phase where some startup code is
1995 executed before the main procedure is called. This depends on the
1996 languages used to write your program. In C@t{++}, for instance,
1997 constructors for static and global objects are executed before
1998 @code{main} is called. It is therefore possible that the debugger stops
1999 before reaching the main procedure. However, the temporary breakpoint
2000 will remain to halt execution.
2002 Specify the arguments to give to your program as arguments to the
2003 @samp{start} command. These arguments will be given verbatim to the
2004 underlying @samp{run} command. Note that the same arguments will be
2005 reused if no argument is provided during subsequent calls to
2006 @samp{start} or @samp{run}.
2008 It is sometimes necessary to debug the program during elaboration. In
2009 these cases, using the @code{start} command would stop the execution of
2010 your program too late, as the program would have already completed the
2011 elaboration phase. Under these circumstances, insert breakpoints in your
2012 elaboration code before running your program.
2014 @kindex set exec-wrapper
2015 @item set exec-wrapper @var{wrapper}
2016 @itemx show exec-wrapper
2017 @itemx unset exec-wrapper
2018 When @samp{exec-wrapper} is set, the specified wrapper is used to
2019 launch programs for debugging. @value{GDBN} starts your program
2020 with a shell command of the form @kbd{exec @var{wrapper}
2021 @var{program}}. Quoting is added to @var{program} and its
2022 arguments, but not to @var{wrapper}, so you should add quotes if
2023 appropriate for your shell. The wrapper runs until it executes
2024 your program, and then @value{GDBN} takes control.
2026 You can use any program that eventually calls @code{execve} with
2027 its arguments as a wrapper. Several standard Unix utilities do
2028 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2029 with @code{exec "$@@"} will also work.
2031 For example, you can use @code{env} to pass an environment variable to
2032 the debugged program, without setting the variable in your shell's
2036 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2040 This command is available when debugging locally on most targets, excluding
2041 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2043 @kindex set disable-randomization
2044 @item set disable-randomization
2045 @itemx set disable-randomization on
2046 This option (enabled by default in @value{GDBN}) will turn off the native
2047 randomization of the virtual address space of the started program. This option
2048 is useful for multiple debugging sessions to make the execution better
2049 reproducible and memory addresses reusable across debugging sessions.
2051 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2052 On @sc{gnu}/Linux you can get the same behavior using
2055 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2058 @item set disable-randomization off
2059 Leave the behavior of the started executable unchanged. Some bugs rear their
2060 ugly heads only when the program is loaded at certain addresses. If your bug
2061 disappears when you run the program under @value{GDBN}, that might be because
2062 @value{GDBN} by default disables the address randomization on platforms, such
2063 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2064 disable-randomization off} to try to reproduce such elusive bugs.
2066 On targets where it is available, virtual address space randomization
2067 protects the programs against certain kinds of security attacks. In these
2068 cases the attacker needs to know the exact location of a concrete executable
2069 code. Randomizing its location makes it impossible to inject jumps misusing
2070 a code at its expected addresses.
2072 Prelinking shared libraries provides a startup performance advantage but it
2073 makes addresses in these libraries predictable for privileged processes by
2074 having just unprivileged access at the target system. Reading the shared
2075 library binary gives enough information for assembling the malicious code
2076 misusing it. Still even a prelinked shared library can get loaded at a new
2077 random address just requiring the regular relocation process during the
2078 startup. Shared libraries not already prelinked are always loaded at
2079 a randomly chosen address.
2081 Position independent executables (PIE) contain position independent code
2082 similar to the shared libraries and therefore such executables get loaded at
2083 a randomly chosen address upon startup. PIE executables always load even
2084 already prelinked shared libraries at a random address. You can build such
2085 executable using @command{gcc -fPIE -pie}.
2087 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2088 (as long as the randomization is enabled).
2090 @item show disable-randomization
2091 Show the current setting of the explicit disable of the native randomization of
2092 the virtual address space of the started program.
2097 @section Your Program's Arguments
2099 @cindex arguments (to your program)
2100 The arguments to your program can be specified by the arguments of the
2102 They are passed to a shell, which expands wildcard characters and
2103 performs redirection of I/O, and thence to your program. Your
2104 @code{SHELL} environment variable (if it exists) specifies what shell
2105 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2106 the default shell (@file{/bin/sh} on Unix).
2108 On non-Unix systems, the program is usually invoked directly by
2109 @value{GDBN}, which emulates I/O redirection via the appropriate system
2110 calls, and the wildcard characters are expanded by the startup code of
2111 the program, not by the shell.
2113 @code{run} with no arguments uses the same arguments used by the previous
2114 @code{run}, or those set by the @code{set args} command.
2119 Specify the arguments to be used the next time your program is run. If
2120 @code{set args} has no arguments, @code{run} executes your program
2121 with no arguments. Once you have run your program with arguments,
2122 using @code{set args} before the next @code{run} is the only way to run
2123 it again without arguments.
2127 Show the arguments to give your program when it is started.
2131 @section Your Program's Environment
2133 @cindex environment (of your program)
2134 The @dfn{environment} consists of a set of environment variables and
2135 their values. Environment variables conventionally record such things as
2136 your user name, your home directory, your terminal type, and your search
2137 path for programs to run. Usually you set up environment variables with
2138 the shell and they are inherited by all the other programs you run. When
2139 debugging, it can be useful to try running your program with a modified
2140 environment without having to start @value{GDBN} over again.
2144 @item path @var{directory}
2145 Add @var{directory} to the front of the @code{PATH} environment variable
2146 (the search path for executables) that will be passed to your program.
2147 The value of @code{PATH} used by @value{GDBN} does not change.
2148 You may specify several directory names, separated by whitespace or by a
2149 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2150 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2151 is moved to the front, so it is searched sooner.
2153 You can use the string @samp{$cwd} to refer to whatever is the current
2154 working directory at the time @value{GDBN} searches the path. If you
2155 use @samp{.} instead, it refers to the directory where you executed the
2156 @code{path} command. @value{GDBN} replaces @samp{.} in the
2157 @var{directory} argument (with the current path) before adding
2158 @var{directory} to the search path.
2159 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2160 @c document that, since repeating it would be a no-op.
2164 Display the list of search paths for executables (the @code{PATH}
2165 environment variable).
2167 @kindex show environment
2168 @item show environment @r{[}@var{varname}@r{]}
2169 Print the value of environment variable @var{varname} to be given to
2170 your program when it starts. If you do not supply @var{varname},
2171 print the names and values of all environment variables to be given to
2172 your program. You can abbreviate @code{environment} as @code{env}.
2174 @kindex set environment
2175 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2176 Set environment variable @var{varname} to @var{value}. The value
2177 changes for your program only, not for @value{GDBN} itself. @var{value} may
2178 be any string; the values of environment variables are just strings, and
2179 any interpretation is supplied by your program itself. The @var{value}
2180 parameter is optional; if it is eliminated, the variable is set to a
2182 @c "any string" here does not include leading, trailing
2183 @c blanks. Gnu asks: does anyone care?
2185 For example, this command:
2192 tells the debugged program, when subsequently run, that its user is named
2193 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2194 are not actually required.)
2196 @kindex unset environment
2197 @item unset environment @var{varname}
2198 Remove variable @var{varname} from the environment to be passed to your
2199 program. This is different from @samp{set env @var{varname} =};
2200 @code{unset environment} removes the variable from the environment,
2201 rather than assigning it an empty value.
2204 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2206 by your @code{SHELL} environment variable if it exists (or
2207 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2208 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2209 @file{.bashrc} for BASH---any variables you set in that file affect
2210 your program. You may wish to move setting of environment variables to
2211 files that are only run when you sign on, such as @file{.login} or
2214 @node Working Directory
2215 @section Your Program's Working Directory
2217 @cindex working directory (of your program)
2218 Each time you start your program with @code{run}, it inherits its
2219 working directory from the current working directory of @value{GDBN}.
2220 The @value{GDBN} working directory is initially whatever it inherited
2221 from its parent process (typically the shell), but you can specify a new
2222 working directory in @value{GDBN} with the @code{cd} command.
2224 The @value{GDBN} working directory also serves as a default for the commands
2225 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2230 @cindex change working directory
2231 @item cd @var{directory}
2232 Set the @value{GDBN} working directory to @var{directory}.
2236 Print the @value{GDBN} working directory.
2239 It is generally impossible to find the current working directory of
2240 the process being debugged (since a program can change its directory
2241 during its run). If you work on a system where @value{GDBN} is
2242 configured with the @file{/proc} support, you can use the @code{info
2243 proc} command (@pxref{SVR4 Process Information}) to find out the
2244 current working directory of the debuggee.
2247 @section Your Program's Input and Output
2252 By default, the program you run under @value{GDBN} does input and output to
2253 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2254 to its own terminal modes to interact with you, but it records the terminal
2255 modes your program was using and switches back to them when you continue
2256 running your program.
2259 @kindex info terminal
2261 Displays information recorded by @value{GDBN} about the terminal modes your
2265 You can redirect your program's input and/or output using shell
2266 redirection with the @code{run} command. For example,
2273 starts your program, diverting its output to the file @file{outfile}.
2276 @cindex controlling terminal
2277 Another way to specify where your program should do input and output is
2278 with the @code{tty} command. This command accepts a file name as
2279 argument, and causes this file to be the default for future @code{run}
2280 commands. It also resets the controlling terminal for the child
2281 process, for future @code{run} commands. For example,
2288 directs that processes started with subsequent @code{run} commands
2289 default to do input and output on the terminal @file{/dev/ttyb} and have
2290 that as their controlling terminal.
2292 An explicit redirection in @code{run} overrides the @code{tty} command's
2293 effect on the input/output device, but not its effect on the controlling
2296 When you use the @code{tty} command or redirect input in the @code{run}
2297 command, only the input @emph{for your program} is affected. The input
2298 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2299 for @code{set inferior-tty}.
2301 @cindex inferior tty
2302 @cindex set inferior controlling terminal
2303 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2304 display the name of the terminal that will be used for future runs of your
2308 @item set inferior-tty /dev/ttyb
2309 @kindex set inferior-tty
2310 Set the tty for the program being debugged to /dev/ttyb.
2312 @item show inferior-tty
2313 @kindex show inferior-tty
2314 Show the current tty for the program being debugged.
2318 @section Debugging an Already-running Process
2323 @item attach @var{process-id}
2324 This command attaches to a running process---one that was started
2325 outside @value{GDBN}. (@code{info files} shows your active
2326 targets.) The command takes as argument a process ID. The usual way to
2327 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2328 or with the @samp{jobs -l} shell command.
2330 @code{attach} does not repeat if you press @key{RET} a second time after
2331 executing the command.
2334 To use @code{attach}, your program must be running in an environment
2335 which supports processes; for example, @code{attach} does not work for
2336 programs on bare-board targets that lack an operating system. You must
2337 also have permission to send the process a signal.
2339 When you use @code{attach}, the debugger finds the program running in
2340 the process first by looking in the current working directory, then (if
2341 the program is not found) by using the source file search path
2342 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2343 the @code{file} command to load the program. @xref{Files, ,Commands to
2346 The first thing @value{GDBN} does after arranging to debug the specified
2347 process is to stop it. You can examine and modify an attached process
2348 with all the @value{GDBN} commands that are ordinarily available when
2349 you start processes with @code{run}. You can insert breakpoints; you
2350 can step and continue; you can modify storage. If you would rather the
2351 process continue running, you may use the @code{continue} command after
2352 attaching @value{GDBN} to the process.
2357 When you have finished debugging the attached process, you can use the
2358 @code{detach} command to release it from @value{GDBN} control. Detaching
2359 the process continues its execution. After the @code{detach} command,
2360 that process and @value{GDBN} become completely independent once more, and you
2361 are ready to @code{attach} another process or start one with @code{run}.
2362 @code{detach} does not repeat if you press @key{RET} again after
2363 executing the command.
2366 If you exit @value{GDBN} while you have an attached process, you detach
2367 that process. If you use the @code{run} command, you kill that process.
2368 By default, @value{GDBN} asks for confirmation if you try to do either of these
2369 things; you can control whether or not you need to confirm by using the
2370 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2374 @section Killing the Child Process
2379 Kill the child process in which your program is running under @value{GDBN}.
2382 This command is useful if you wish to debug a core dump instead of a
2383 running process. @value{GDBN} ignores any core dump file while your program
2386 On some operating systems, a program cannot be executed outside @value{GDBN}
2387 while you have breakpoints set on it inside @value{GDBN}. You can use the
2388 @code{kill} command in this situation to permit running your program
2389 outside the debugger.
2391 The @code{kill} command is also useful if you wish to recompile and
2392 relink your program, since on many systems it is impossible to modify an
2393 executable file while it is running in a process. In this case, when you
2394 next type @code{run}, @value{GDBN} notices that the file has changed, and
2395 reads the symbol table again (while trying to preserve your current
2396 breakpoint settings).
2398 @node Inferiors and Programs
2399 @section Debugging Multiple Inferiors and Programs
2401 @value{GDBN} lets you run and debug multiple programs in a single
2402 session. In addition, @value{GDBN} on some systems may let you run
2403 several programs simultaneously (otherwise you have to exit from one
2404 before starting another). In the most general case, you can have
2405 multiple threads of execution in each of multiple processes, launched
2406 from multiple executables.
2409 @value{GDBN} represents the state of each program execution with an
2410 object called an @dfn{inferior}. An inferior typically corresponds to
2411 a process, but is more general and applies also to targets that do not
2412 have processes. Inferiors may be created before a process runs, and
2413 may be retained after a process exits. Inferiors have unique
2414 identifiers that are different from process ids. Usually each
2415 inferior will also have its own distinct address space, although some
2416 embedded targets may have several inferiors running in different parts
2417 of a single address space. Each inferior may in turn have multiple
2418 threads running in it.
2420 To find out what inferiors exist at any moment, use @w{@code{info
2424 @kindex info inferiors
2425 @item info inferiors
2426 Print a list of all inferiors currently being managed by @value{GDBN}.
2428 @value{GDBN} displays for each inferior (in this order):
2432 the inferior number assigned by @value{GDBN}
2435 the target system's inferior identifier
2438 the name of the executable the inferior is running.
2443 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2444 indicates the current inferior.
2448 @c end table here to get a little more width for example
2451 (@value{GDBP}) info inferiors
2452 Num Description Executable
2453 2 process 2307 hello
2454 * 1 process 3401 goodbye
2457 To switch focus between inferiors, use the @code{inferior} command:
2460 @kindex inferior @var{infno}
2461 @item inferior @var{infno}
2462 Make inferior number @var{infno} the current inferior. The argument
2463 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2464 in the first field of the @samp{info inferiors} display.
2468 You can get multiple executables into a debugging session via the
2469 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2470 systems @value{GDBN} can add inferiors to the debug session
2471 automatically by following calls to @code{fork} and @code{exec}. To
2472 remove inferiors from the debugging session use the
2473 @w{@code{remove-inferiors}} command.
2476 @kindex add-inferior
2477 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2478 Adds @var{n} inferiors to be run using @var{executable} as the
2479 executable. @var{n} defaults to 1. If no executable is specified,
2480 the inferiors begins empty, with no program. You can still assign or
2481 change the program assigned to the inferior at any time by using the
2482 @code{file} command with the executable name as its argument.
2484 @kindex clone-inferior
2485 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2486 Adds @var{n} inferiors ready to execute the same program as inferior
2487 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2488 number of the current inferior. This is a convenient command when you
2489 want to run another instance of the inferior you are debugging.
2492 (@value{GDBP}) info inferiors
2493 Num Description Executable
2494 * 1 process 29964 helloworld
2495 (@value{GDBP}) clone-inferior
2498 (@value{GDBP}) info inferiors
2499 Num Description Executable
2501 * 1 process 29964 helloworld
2504 You can now simply switch focus to inferior 2 and run it.
2506 @kindex remove-inferiors
2507 @item remove-inferiors @var{infno}@dots{}
2508 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2509 possible to remove an inferior that is running with this command. For
2510 those, use the @code{kill} or @code{detach} command first.
2514 To quit debugging one of the running inferiors that is not the current
2515 inferior, you can either detach from it by using the @w{@code{detach
2516 inferior}} command (allowing it to run independently), or kill it
2517 using the @w{@code{kill inferiors}} command:
2520 @kindex detach inferiors @var{infno}@dots{}
2521 @item detach inferior @var{infno}@dots{}
2522 Detach from the inferior or inferiors identified by @value{GDBN}
2523 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2524 still stays on the list of inferiors shown by @code{info inferiors},
2525 but its Description will show @samp{<null>}.
2527 @kindex kill inferiors @var{infno}@dots{}
2528 @item kill inferiors @var{infno}@dots{}
2529 Kill the inferior or inferiors identified by @value{GDBN} inferior
2530 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2531 stays on the list of inferiors shown by @code{info inferiors}, but its
2532 Description will show @samp{<null>}.
2535 After the successful completion of a command such as @code{detach},
2536 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2537 a normal process exit, the inferior is still valid and listed with
2538 @code{info inferiors}, ready to be restarted.
2541 To be notified when inferiors are started or exit under @value{GDBN}'s
2542 control use @w{@code{set print inferior-events}}:
2545 @kindex set print inferior-events
2546 @cindex print messages on inferior start and exit
2547 @item set print inferior-events
2548 @itemx set print inferior-events on
2549 @itemx set print inferior-events off
2550 The @code{set print inferior-events} command allows you to enable or
2551 disable printing of messages when @value{GDBN} notices that new
2552 inferiors have started or that inferiors have exited or have been
2553 detached. By default, these messages will not be printed.
2555 @kindex show print inferior-events
2556 @item show print inferior-events
2557 Show whether messages will be printed when @value{GDBN} detects that
2558 inferiors have started, exited or have been detached.
2561 Many commands will work the same with multiple programs as with a
2562 single program: e.g., @code{print myglobal} will simply display the
2563 value of @code{myglobal} in the current inferior.
2566 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2567 get more info about the relationship of inferiors, programs, address
2568 spaces in a debug session. You can do that with the @w{@code{maint
2569 info program-spaces}} command.
2572 @kindex maint info program-spaces
2573 @item maint info program-spaces
2574 Print a list of all program spaces currently being managed by
2577 @value{GDBN} displays for each program space (in this order):
2581 the program space number assigned by @value{GDBN}
2584 the name of the executable loaded into the program space, with e.g.,
2585 the @code{file} command.
2590 An asterisk @samp{*} preceding the @value{GDBN} program space number
2591 indicates the current program space.
2593 In addition, below each program space line, @value{GDBN} prints extra
2594 information that isn't suitable to display in tabular form. For
2595 example, the list of inferiors bound to the program space.
2598 (@value{GDBP}) maint info program-spaces
2601 Bound inferiors: ID 1 (process 21561)
2605 Here we can see that no inferior is running the program @code{hello},
2606 while @code{process 21561} is running the program @code{goodbye}. On
2607 some targets, it is possible that multiple inferiors are bound to the
2608 same program space. The most common example is that of debugging both
2609 the parent and child processes of a @code{vfork} call. For example,
2612 (@value{GDBP}) maint info program-spaces
2615 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2618 Here, both inferior 2 and inferior 1 are running in the same program
2619 space as a result of inferior 1 having executed a @code{vfork} call.
2623 @section Debugging Programs with Multiple Threads
2625 @cindex threads of execution
2626 @cindex multiple threads
2627 @cindex switching threads
2628 In some operating systems, such as HP-UX and Solaris, a single program
2629 may have more than one @dfn{thread} of execution. The precise semantics
2630 of threads differ from one operating system to another, but in general
2631 the threads of a single program are akin to multiple processes---except
2632 that they share one address space (that is, they can all examine and
2633 modify the same variables). On the other hand, each thread has its own
2634 registers and execution stack, and perhaps private memory.
2636 @value{GDBN} provides these facilities for debugging multi-thread
2640 @item automatic notification of new threads
2641 @item @samp{thread @var{threadno}}, a command to switch among threads
2642 @item @samp{info threads}, a command to inquire about existing threads
2643 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2644 a command to apply a command to a list of threads
2645 @item thread-specific breakpoints
2646 @item @samp{set print thread-events}, which controls printing of
2647 messages on thread start and exit.
2648 @item @samp{set libthread-db-search-path @var{path}}, which lets
2649 the user specify which @code{libthread_db} to use if the default choice
2650 isn't compatible with the program.
2654 @emph{Warning:} These facilities are not yet available on every
2655 @value{GDBN} configuration where the operating system supports threads.
2656 If your @value{GDBN} does not support threads, these commands have no
2657 effect. For example, a system without thread support shows no output
2658 from @samp{info threads}, and always rejects the @code{thread} command,
2662 (@value{GDBP}) info threads
2663 (@value{GDBP}) thread 1
2664 Thread ID 1 not known. Use the "info threads" command to
2665 see the IDs of currently known threads.
2667 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2668 @c doesn't support threads"?
2671 @cindex focus of debugging
2672 @cindex current thread
2673 The @value{GDBN} thread debugging facility allows you to observe all
2674 threads while your program runs---but whenever @value{GDBN} takes
2675 control, one thread in particular is always the focus of debugging.
2676 This thread is called the @dfn{current thread}. Debugging commands show
2677 program information from the perspective of the current thread.
2679 @cindex @code{New} @var{systag} message
2680 @cindex thread identifier (system)
2681 @c FIXME-implementors!! It would be more helpful if the [New...] message
2682 @c included GDB's numeric thread handle, so you could just go to that
2683 @c thread without first checking `info threads'.
2684 Whenever @value{GDBN} detects a new thread in your program, it displays
2685 the target system's identification for the thread with a message in the
2686 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2687 whose form varies depending on the particular system. For example, on
2688 @sc{gnu}/Linux, you might see
2691 [New Thread 0x41e02940 (LWP 25582)]
2695 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2696 the @var{systag} is simply something like @samp{process 368}, with no
2699 @c FIXME!! (1) Does the [New...] message appear even for the very first
2700 @c thread of a program, or does it only appear for the
2701 @c second---i.e.@: when it becomes obvious we have a multithread
2703 @c (2) *Is* there necessarily a first thread always? Or do some
2704 @c multithread systems permit starting a program with multiple
2705 @c threads ab initio?
2707 @cindex thread number
2708 @cindex thread identifier (GDB)
2709 For debugging purposes, @value{GDBN} associates its own thread
2710 number---always a single integer---with each thread in your program.
2713 @kindex info threads
2714 @item info threads @r{[}@var{id}@dots{}@r{]}
2715 Display a summary of all threads currently in your program. Optional
2716 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2717 means to print information only about the specified thread or threads.
2718 @value{GDBN} displays for each thread (in this order):
2722 the thread number assigned by @value{GDBN}
2725 the target system's thread identifier (@var{systag})
2728 the thread's name, if one is known. A thread can either be named by
2729 the user (see @code{thread name}, below), or, in some cases, by the
2733 the current stack frame summary for that thread
2737 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2738 indicates the current thread.
2742 @c end table here to get a little more width for example
2745 (@value{GDBP}) info threads
2747 3 process 35 thread 27 0x34e5 in sigpause ()
2748 2 process 35 thread 23 0x34e5 in sigpause ()
2749 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2753 On Solaris, you can display more information about user threads with a
2754 Solaris-specific command:
2757 @item maint info sol-threads
2758 @kindex maint info sol-threads
2759 @cindex thread info (Solaris)
2760 Display info on Solaris user threads.
2764 @kindex thread @var{threadno}
2765 @item thread @var{threadno}
2766 Make thread number @var{threadno} the current thread. The command
2767 argument @var{threadno} is the internal @value{GDBN} thread number, as
2768 shown in the first field of the @samp{info threads} display.
2769 @value{GDBN} responds by displaying the system identifier of the thread
2770 you selected, and its current stack frame summary:
2773 (@value{GDBP}) thread 2
2774 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2775 #0 some_function (ignore=0x0) at example.c:8
2776 8 printf ("hello\n");
2780 As with the @samp{[New @dots{}]} message, the form of the text after
2781 @samp{Switching to} depends on your system's conventions for identifying
2784 @vindex $_thread@r{, convenience variable}
2785 The debugger convenience variable @samp{$_thread} contains the number
2786 of the current thread. You may find this useful in writing breakpoint
2787 conditional expressions, command scripts, and so forth. See
2788 @xref{Convenience Vars,, Convenience Variables}, for general
2789 information on convenience variables.
2791 @kindex thread apply
2792 @cindex apply command to several threads
2793 @item thread apply [@var{threadno} | all] @var{command}
2794 The @code{thread apply} command allows you to apply the named
2795 @var{command} to one or more threads. Specify the numbers of the
2796 threads that you want affected with the command argument
2797 @var{threadno}. It can be a single thread number, one of the numbers
2798 shown in the first field of the @samp{info threads} display; or it
2799 could be a range of thread numbers, as in @code{2-4}. To apply a
2800 command to all threads, type @kbd{thread apply all @var{command}}.
2803 @cindex name a thread
2804 @item thread name [@var{name}]
2805 This command assigns a name to the current thread. If no argument is
2806 given, any existing user-specified name is removed. The thread name
2807 appears in the @samp{info threads} display.
2809 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2810 determine the name of the thread as given by the OS. On these
2811 systems, a name specified with @samp{thread name} will override the
2812 system-give name, and removing the user-specified name will cause
2813 @value{GDBN} to once again display the system-specified name.
2816 @cindex search for a thread
2817 @item thread find [@var{regexp}]
2818 Search for and display thread ids whose name or @var{systag}
2819 matches the supplied regular expression.
2821 As well as being the complement to the @samp{thread name} command,
2822 this command also allows you to identify a thread by its target
2823 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2827 (@value{GDBN}) thread find 26688
2828 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2829 (@value{GDBN}) info thread 4
2831 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
2834 @kindex set print thread-events
2835 @cindex print messages on thread start and exit
2836 @item set print thread-events
2837 @itemx set print thread-events on
2838 @itemx set print thread-events off
2839 The @code{set print thread-events} command allows you to enable or
2840 disable printing of messages when @value{GDBN} notices that new threads have
2841 started or that threads have exited. By default, these messages will
2842 be printed if detection of these events is supported by the target.
2843 Note that these messages cannot be disabled on all targets.
2845 @kindex show print thread-events
2846 @item show print thread-events
2847 Show whether messages will be printed when @value{GDBN} detects that threads
2848 have started and exited.
2851 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2852 more information about how @value{GDBN} behaves when you stop and start
2853 programs with multiple threads.
2855 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2856 watchpoints in programs with multiple threads.
2859 @kindex set libthread-db-search-path
2860 @cindex search path for @code{libthread_db}
2861 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2862 If this variable is set, @var{path} is a colon-separated list of
2863 directories @value{GDBN} will use to search for @code{libthread_db}.
2864 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2865 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
2866 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
2869 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2870 @code{libthread_db} library to obtain information about threads in the
2871 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2872 to find @code{libthread_db}.
2874 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
2875 refers to the default system directories that are
2876 normally searched for loading shared libraries.
2878 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
2879 refers to the directory from which @code{libpthread}
2880 was loaded in the inferior process.
2882 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2883 @value{GDBN} attempts to initialize it with the current inferior process.
2884 If this initialization fails (which could happen because of a version
2885 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2886 will unload @code{libthread_db}, and continue with the next directory.
2887 If none of @code{libthread_db} libraries initialize successfully,
2888 @value{GDBN} will issue a warning and thread debugging will be disabled.
2890 Setting @code{libthread-db-search-path} is currently implemented
2891 only on some platforms.
2893 @kindex show libthread-db-search-path
2894 @item show libthread-db-search-path
2895 Display current libthread_db search path.
2897 @kindex set debug libthread-db
2898 @kindex show debug libthread-db
2899 @cindex debugging @code{libthread_db}
2900 @item set debug libthread-db
2901 @itemx show debug libthread-db
2902 Turns on or off display of @code{libthread_db}-related events.
2903 Use @code{1} to enable, @code{0} to disable.
2907 @section Debugging Forks
2909 @cindex fork, debugging programs which call
2910 @cindex multiple processes
2911 @cindex processes, multiple
2912 On most systems, @value{GDBN} has no special support for debugging
2913 programs which create additional processes using the @code{fork}
2914 function. When a program forks, @value{GDBN} will continue to debug the
2915 parent process and the child process will run unimpeded. If you have
2916 set a breakpoint in any code which the child then executes, the child
2917 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2918 will cause it to terminate.
2920 However, if you want to debug the child process there is a workaround
2921 which isn't too painful. Put a call to @code{sleep} in the code which
2922 the child process executes after the fork. It may be useful to sleep
2923 only if a certain environment variable is set, or a certain file exists,
2924 so that the delay need not occur when you don't want to run @value{GDBN}
2925 on the child. While the child is sleeping, use the @code{ps} program to
2926 get its process ID. Then tell @value{GDBN} (a new invocation of
2927 @value{GDBN} if you are also debugging the parent process) to attach to
2928 the child process (@pxref{Attach}). From that point on you can debug
2929 the child process just like any other process which you attached to.
2931 On some systems, @value{GDBN} provides support for debugging programs that
2932 create additional processes using the @code{fork} or @code{vfork} functions.
2933 Currently, the only platforms with this feature are HP-UX (11.x and later
2934 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2936 By default, when a program forks, @value{GDBN} will continue to debug
2937 the parent process and the child process will run unimpeded.
2939 If you want to follow the child process instead of the parent process,
2940 use the command @w{@code{set follow-fork-mode}}.
2943 @kindex set follow-fork-mode
2944 @item set follow-fork-mode @var{mode}
2945 Set the debugger response to a program call of @code{fork} or
2946 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2947 process. The @var{mode} argument can be:
2951 The original process is debugged after a fork. The child process runs
2952 unimpeded. This is the default.
2955 The new process is debugged after a fork. The parent process runs
2960 @kindex show follow-fork-mode
2961 @item show follow-fork-mode
2962 Display the current debugger response to a @code{fork} or @code{vfork} call.
2965 @cindex debugging multiple processes
2966 On Linux, if you want to debug both the parent and child processes, use the
2967 command @w{@code{set detach-on-fork}}.
2970 @kindex set detach-on-fork
2971 @item set detach-on-fork @var{mode}
2972 Tells gdb whether to detach one of the processes after a fork, or
2973 retain debugger control over them both.
2977 The child process (or parent process, depending on the value of
2978 @code{follow-fork-mode}) will be detached and allowed to run
2979 independently. This is the default.
2982 Both processes will be held under the control of @value{GDBN}.
2983 One process (child or parent, depending on the value of
2984 @code{follow-fork-mode}) is debugged as usual, while the other
2989 @kindex show detach-on-fork
2990 @item show detach-on-fork
2991 Show whether detach-on-fork mode is on/off.
2994 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
2995 will retain control of all forked processes (including nested forks).
2996 You can list the forked processes under the control of @value{GDBN} by
2997 using the @w{@code{info inferiors}} command, and switch from one fork
2998 to another by using the @code{inferior} command (@pxref{Inferiors and
2999 Programs, ,Debugging Multiple Inferiors and Programs}).
3001 To quit debugging one of the forked processes, you can either detach
3002 from it by using the @w{@code{detach inferiors}} command (allowing it
3003 to run independently), or kill it using the @w{@code{kill inferiors}}
3004 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3007 If you ask to debug a child process and a @code{vfork} is followed by an
3008 @code{exec}, @value{GDBN} executes the new target up to the first
3009 breakpoint in the new target. If you have a breakpoint set on
3010 @code{main} in your original program, the breakpoint will also be set on
3011 the child process's @code{main}.
3013 On some systems, when a child process is spawned by @code{vfork}, you
3014 cannot debug the child or parent until an @code{exec} call completes.
3016 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3017 call executes, the new target restarts. To restart the parent
3018 process, use the @code{file} command with the parent executable name
3019 as its argument. By default, after an @code{exec} call executes,
3020 @value{GDBN} discards the symbols of the previous executable image.
3021 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3025 @kindex set follow-exec-mode
3026 @item set follow-exec-mode @var{mode}
3028 Set debugger response to a program call of @code{exec}. An
3029 @code{exec} call replaces the program image of a process.
3031 @code{follow-exec-mode} can be:
3035 @value{GDBN} creates a new inferior and rebinds the process to this
3036 new inferior. The program the process was running before the
3037 @code{exec} call can be restarted afterwards by restarting the
3043 (@value{GDBP}) info inferiors
3045 Id Description Executable
3048 process 12020 is executing new program: prog2
3049 Program exited normally.
3050 (@value{GDBP}) info inferiors
3051 Id Description Executable
3057 @value{GDBN} keeps the process bound to the same inferior. The new
3058 executable image replaces the previous executable loaded in the
3059 inferior. Restarting the inferior after the @code{exec} call, with
3060 e.g., the @code{run} command, restarts the executable the process was
3061 running after the @code{exec} call. This is the default mode.
3066 (@value{GDBP}) info inferiors
3067 Id Description Executable
3070 process 12020 is executing new program: prog2
3071 Program exited normally.
3072 (@value{GDBP}) info inferiors
3073 Id Description Executable
3080 You can use the @code{catch} command to make @value{GDBN} stop whenever
3081 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3082 Catchpoints, ,Setting Catchpoints}.
3084 @node Checkpoint/Restart
3085 @section Setting a @emph{Bookmark} to Return to Later
3090 @cindex snapshot of a process
3091 @cindex rewind program state
3093 On certain operating systems@footnote{Currently, only
3094 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3095 program's state, called a @dfn{checkpoint}, and come back to it
3098 Returning to a checkpoint effectively undoes everything that has
3099 happened in the program since the @code{checkpoint} was saved. This
3100 includes changes in memory, registers, and even (within some limits)
3101 system state. Effectively, it is like going back in time to the
3102 moment when the checkpoint was saved.
3104 Thus, if you're stepping thru a program and you think you're
3105 getting close to the point where things go wrong, you can save
3106 a checkpoint. Then, if you accidentally go too far and miss
3107 the critical statement, instead of having to restart your program
3108 from the beginning, you can just go back to the checkpoint and
3109 start again from there.
3111 This can be especially useful if it takes a lot of time or
3112 steps to reach the point where you think the bug occurs.
3114 To use the @code{checkpoint}/@code{restart} method of debugging:
3119 Save a snapshot of the debugged program's current execution state.
3120 The @code{checkpoint} command takes no arguments, but each checkpoint
3121 is assigned a small integer id, similar to a breakpoint id.
3123 @kindex info checkpoints
3124 @item info checkpoints
3125 List the checkpoints that have been saved in the current debugging
3126 session. For each checkpoint, the following information will be
3133 @item Source line, or label
3136 @kindex restart @var{checkpoint-id}
3137 @item restart @var{checkpoint-id}
3138 Restore the program state that was saved as checkpoint number
3139 @var{checkpoint-id}. All program variables, registers, stack frames
3140 etc.@: will be returned to the values that they had when the checkpoint
3141 was saved. In essence, gdb will ``wind back the clock'' to the point
3142 in time when the checkpoint was saved.
3144 Note that breakpoints, @value{GDBN} variables, command history etc.
3145 are not affected by restoring a checkpoint. In general, a checkpoint
3146 only restores things that reside in the program being debugged, not in
3149 @kindex delete checkpoint @var{checkpoint-id}
3150 @item delete checkpoint @var{checkpoint-id}
3151 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3155 Returning to a previously saved checkpoint will restore the user state
3156 of the program being debugged, plus a significant subset of the system
3157 (OS) state, including file pointers. It won't ``un-write'' data from
3158 a file, but it will rewind the file pointer to the previous location,
3159 so that the previously written data can be overwritten. For files
3160 opened in read mode, the pointer will also be restored so that the
3161 previously read data can be read again.
3163 Of course, characters that have been sent to a printer (or other
3164 external device) cannot be ``snatched back'', and characters received
3165 from eg.@: a serial device can be removed from internal program buffers,
3166 but they cannot be ``pushed back'' into the serial pipeline, ready to
3167 be received again. Similarly, the actual contents of files that have
3168 been changed cannot be restored (at this time).
3170 However, within those constraints, you actually can ``rewind'' your
3171 program to a previously saved point in time, and begin debugging it
3172 again --- and you can change the course of events so as to debug a
3173 different execution path this time.
3175 @cindex checkpoints and process id
3176 Finally, there is one bit of internal program state that will be
3177 different when you return to a checkpoint --- the program's process
3178 id. Each checkpoint will have a unique process id (or @var{pid}),
3179 and each will be different from the program's original @var{pid}.
3180 If your program has saved a local copy of its process id, this could
3181 potentially pose a problem.
3183 @subsection A Non-obvious Benefit of Using Checkpoints
3185 On some systems such as @sc{gnu}/Linux, address space randomization
3186 is performed on new processes for security reasons. This makes it
3187 difficult or impossible to set a breakpoint, or watchpoint, on an
3188 absolute address if you have to restart the program, since the
3189 absolute location of a symbol will change from one execution to the
3192 A checkpoint, however, is an @emph{identical} copy of a process.
3193 Therefore if you create a checkpoint at (eg.@:) the start of main,
3194 and simply return to that checkpoint instead of restarting the
3195 process, you can avoid the effects of address randomization and
3196 your symbols will all stay in the same place.
3199 @chapter Stopping and Continuing
3201 The principal purposes of using a debugger are so that you can stop your
3202 program before it terminates; or so that, if your program runs into
3203 trouble, you can investigate and find out why.
3205 Inside @value{GDBN}, your program may stop for any of several reasons,
3206 such as a signal, a breakpoint, or reaching a new line after a
3207 @value{GDBN} command such as @code{step}. You may then examine and
3208 change variables, set new breakpoints or remove old ones, and then
3209 continue execution. Usually, the messages shown by @value{GDBN} provide
3210 ample explanation of the status of your program---but you can also
3211 explicitly request this information at any time.
3214 @kindex info program
3216 Display information about the status of your program: whether it is
3217 running or not, what process it is, and why it stopped.
3221 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3222 * Continuing and Stepping:: Resuming execution
3223 * Skipping Over Functions and Files::
3224 Skipping over functions and files
3226 * Thread Stops:: Stopping and starting multi-thread programs
3230 @section Breakpoints, Watchpoints, and Catchpoints
3233 A @dfn{breakpoint} makes your program stop whenever a certain point in
3234 the program is reached. For each breakpoint, you can add conditions to
3235 control in finer detail whether your program stops. You can set
3236 breakpoints with the @code{break} command and its variants (@pxref{Set
3237 Breaks, ,Setting Breakpoints}), to specify the place where your program
3238 should stop by line number, function name or exact address in the
3241 On some systems, you can set breakpoints in shared libraries before
3242 the executable is run. There is a minor limitation on HP-UX systems:
3243 you must wait until the executable is run in order to set breakpoints
3244 in shared library routines that are not called directly by the program
3245 (for example, routines that are arguments in a @code{pthread_create}
3249 @cindex data breakpoints
3250 @cindex memory tracing
3251 @cindex breakpoint on memory address
3252 @cindex breakpoint on variable modification
3253 A @dfn{watchpoint} is a special breakpoint that stops your program
3254 when the value of an expression changes. The expression may be a value
3255 of a variable, or it could involve values of one or more variables
3256 combined by operators, such as @samp{a + b}. This is sometimes called
3257 @dfn{data breakpoints}. You must use a different command to set
3258 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3259 from that, you can manage a watchpoint like any other breakpoint: you
3260 enable, disable, and delete both breakpoints and watchpoints using the
3263 You can arrange to have values from your program displayed automatically
3264 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3268 @cindex breakpoint on events
3269 A @dfn{catchpoint} is another special breakpoint that stops your program
3270 when a certain kind of event occurs, such as the throwing of a C@t{++}
3271 exception or the loading of a library. As with watchpoints, you use a
3272 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3273 Catchpoints}), but aside from that, you can manage a catchpoint like any
3274 other breakpoint. (To stop when your program receives a signal, use the
3275 @code{handle} command; see @ref{Signals, ,Signals}.)
3277 @cindex breakpoint numbers
3278 @cindex numbers for breakpoints
3279 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3280 catchpoint when you create it; these numbers are successive integers
3281 starting with one. In many of the commands for controlling various
3282 features of breakpoints you use the breakpoint number to say which
3283 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3284 @dfn{disabled}; if disabled, it has no effect on your program until you
3287 @cindex breakpoint ranges
3288 @cindex ranges of breakpoints
3289 Some @value{GDBN} commands accept a range of breakpoints on which to
3290 operate. A breakpoint range is either a single breakpoint number, like
3291 @samp{5}, or two such numbers, in increasing order, separated by a
3292 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3293 all breakpoints in that range are operated on.
3296 * Set Breaks:: Setting breakpoints
3297 * Set Watchpoints:: Setting watchpoints
3298 * Set Catchpoints:: Setting catchpoints
3299 * Delete Breaks:: Deleting breakpoints
3300 * Disabling:: Disabling breakpoints
3301 * Conditions:: Break conditions
3302 * Break Commands:: Breakpoint command lists
3303 * Save Breakpoints:: How to save breakpoints in a file
3304 * Error in Breakpoints:: ``Cannot insert breakpoints''
3305 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3309 @subsection Setting Breakpoints
3311 @c FIXME LMB what does GDB do if no code on line of breakpt?
3312 @c consider in particular declaration with/without initialization.
3314 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3317 @kindex b @r{(@code{break})}
3318 @vindex $bpnum@r{, convenience variable}
3319 @cindex latest breakpoint
3320 Breakpoints are set with the @code{break} command (abbreviated
3321 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3322 number of the breakpoint you've set most recently; see @ref{Convenience
3323 Vars,, Convenience Variables}, for a discussion of what you can do with
3324 convenience variables.
3327 @item break @var{location}
3328 Set a breakpoint at the given @var{location}, which can specify a
3329 function name, a line number, or an address of an instruction.
3330 (@xref{Specify Location}, for a list of all the possible ways to
3331 specify a @var{location}.) The breakpoint will stop your program just
3332 before it executes any of the code in the specified @var{location}.
3334 When using source languages that permit overloading of symbols, such as
3335 C@t{++}, a function name may refer to more than one possible place to break.
3336 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3339 It is also possible to insert a breakpoint that will stop the program
3340 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3341 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3344 When called without any arguments, @code{break} sets a breakpoint at
3345 the next instruction to be executed in the selected stack frame
3346 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3347 innermost, this makes your program stop as soon as control
3348 returns to that frame. This is similar to the effect of a
3349 @code{finish} command in the frame inside the selected frame---except
3350 that @code{finish} does not leave an active breakpoint. If you use
3351 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3352 the next time it reaches the current location; this may be useful
3355 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3356 least one instruction has been executed. If it did not do this, you
3357 would be unable to proceed past a breakpoint without first disabling the
3358 breakpoint. This rule applies whether or not the breakpoint already
3359 existed when your program stopped.
3361 @item break @dots{} if @var{cond}
3362 Set a breakpoint with condition @var{cond}; evaluate the expression
3363 @var{cond} each time the breakpoint is reached, and stop only if the
3364 value is nonzero---that is, if @var{cond} evaluates as true.
3365 @samp{@dots{}} stands for one of the possible arguments described
3366 above (or no argument) specifying where to break. @xref{Conditions,
3367 ,Break Conditions}, for more information on breakpoint conditions.
3370 @item tbreak @var{args}
3371 Set a breakpoint enabled only for one stop. @var{args} are the
3372 same as for the @code{break} command, and the breakpoint is set in the same
3373 way, but the breakpoint is automatically deleted after the first time your
3374 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3377 @cindex hardware breakpoints
3378 @item hbreak @var{args}
3379 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3380 @code{break} command and the breakpoint is set in the same way, but the
3381 breakpoint requires hardware support and some target hardware may not
3382 have this support. The main purpose of this is EPROM/ROM code
3383 debugging, so you can set a breakpoint at an instruction without
3384 changing the instruction. This can be used with the new trap-generation
3385 provided by SPARClite DSU and most x86-based targets. These targets
3386 will generate traps when a program accesses some data or instruction
3387 address that is assigned to the debug registers. However the hardware
3388 breakpoint registers can take a limited number of breakpoints. For
3389 example, on the DSU, only two data breakpoints can be set at a time, and
3390 @value{GDBN} will reject this command if more than two are used. Delete
3391 or disable unused hardware breakpoints before setting new ones
3392 (@pxref{Disabling, ,Disabling Breakpoints}).
3393 @xref{Conditions, ,Break Conditions}.
3394 For remote targets, you can restrict the number of hardware
3395 breakpoints @value{GDBN} will use, see @ref{set remote
3396 hardware-breakpoint-limit}.
3399 @item thbreak @var{args}
3400 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3401 are the same as for the @code{hbreak} command and the breakpoint is set in
3402 the same way. However, like the @code{tbreak} command,
3403 the breakpoint is automatically deleted after the
3404 first time your program stops there. Also, like the @code{hbreak}
3405 command, the breakpoint requires hardware support and some target hardware
3406 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3407 See also @ref{Conditions, ,Break Conditions}.
3410 @cindex regular expression
3411 @cindex breakpoints at functions matching a regexp
3412 @cindex set breakpoints in many functions
3413 @item rbreak @var{regex}
3414 Set breakpoints on all functions matching the regular expression
3415 @var{regex}. This command sets an unconditional breakpoint on all
3416 matches, printing a list of all breakpoints it set. Once these
3417 breakpoints are set, they are treated just like the breakpoints set with
3418 the @code{break} command. You can delete them, disable them, or make
3419 them conditional the same way as any other breakpoint.
3421 The syntax of the regular expression is the standard one used with tools
3422 like @file{grep}. Note that this is different from the syntax used by
3423 shells, so for instance @code{foo*} matches all functions that include
3424 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3425 @code{.*} leading and trailing the regular expression you supply, so to
3426 match only functions that begin with @code{foo}, use @code{^foo}.
3428 @cindex non-member C@t{++} functions, set breakpoint in
3429 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3430 breakpoints on overloaded functions that are not members of any special
3433 @cindex set breakpoints on all functions
3434 The @code{rbreak} command can be used to set breakpoints in
3435 @strong{all} the functions in a program, like this:
3438 (@value{GDBP}) rbreak .
3441 @item rbreak @var{file}:@var{regex}
3442 If @code{rbreak} is called with a filename qualification, it limits
3443 the search for functions matching the given regular expression to the
3444 specified @var{file}. This can be used, for example, to set breakpoints on
3445 every function in a given file:
3448 (@value{GDBP}) rbreak file.c:.
3451 The colon separating the filename qualifier from the regex may
3452 optionally be surrounded by spaces.
3454 @kindex info breakpoints
3455 @cindex @code{$_} and @code{info breakpoints}
3456 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3457 @itemx info break @r{[}@var{n}@dots{}@r{]}
3458 Print a table of all breakpoints, watchpoints, and catchpoints set and
3459 not deleted. Optional argument @var{n} means print information only
3460 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3461 For each breakpoint, following columns are printed:
3464 @item Breakpoint Numbers
3466 Breakpoint, watchpoint, or catchpoint.
3468 Whether the breakpoint is marked to be disabled or deleted when hit.
3469 @item Enabled or Disabled
3470 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3471 that are not enabled.
3473 Where the breakpoint is in your program, as a memory address. For a
3474 pending breakpoint whose address is not yet known, this field will
3475 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3476 library that has the symbol or line referred by breakpoint is loaded.
3477 See below for details. A breakpoint with several locations will
3478 have @samp{<MULTIPLE>} in this field---see below for details.
3480 Where the breakpoint is in the source for your program, as a file and
3481 line number. For a pending breakpoint, the original string passed to
3482 the breakpoint command will be listed as it cannot be resolved until
3483 the appropriate shared library is loaded in the future.
3487 If a breakpoint is conditional, @code{info break} shows the condition on
3488 the line following the affected breakpoint; breakpoint commands, if any,
3489 are listed after that. A pending breakpoint is allowed to have a condition
3490 specified for it. The condition is not parsed for validity until a shared
3491 library is loaded that allows the pending breakpoint to resolve to a
3495 @code{info break} with a breakpoint
3496 number @var{n} as argument lists only that breakpoint. The
3497 convenience variable @code{$_} and the default examining-address for
3498 the @code{x} command are set to the address of the last breakpoint
3499 listed (@pxref{Memory, ,Examining Memory}).
3502 @code{info break} displays a count of the number of times the breakpoint
3503 has been hit. This is especially useful in conjunction with the
3504 @code{ignore} command. You can ignore a large number of breakpoint
3505 hits, look at the breakpoint info to see how many times the breakpoint
3506 was hit, and then run again, ignoring one less than that number. This
3507 will get you quickly to the last hit of that breakpoint.
3510 @value{GDBN} allows you to set any number of breakpoints at the same place in
3511 your program. There is nothing silly or meaningless about this. When
3512 the breakpoints are conditional, this is even useful
3513 (@pxref{Conditions, ,Break Conditions}).
3515 @cindex multiple locations, breakpoints
3516 @cindex breakpoints, multiple locations
3517 It is possible that a breakpoint corresponds to several locations
3518 in your program. Examples of this situation are:
3522 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3523 instances of the function body, used in different cases.
3526 For a C@t{++} template function, a given line in the function can
3527 correspond to any number of instantiations.
3530 For an inlined function, a given source line can correspond to
3531 several places where that function is inlined.
3534 In all those cases, @value{GDBN} will insert a breakpoint at all
3535 the relevant locations@footnote{
3536 As of this writing, multiple-location breakpoints work only if there's
3537 line number information for all the locations. This means that they
3538 will generally not work in system libraries, unless you have debug
3539 info with line numbers for them.}.
3541 A breakpoint with multiple locations is displayed in the breakpoint
3542 table using several rows---one header row, followed by one row for
3543 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3544 address column. The rows for individual locations contain the actual
3545 addresses for locations, and show the functions to which those
3546 locations belong. The number column for a location is of the form
3547 @var{breakpoint-number}.@var{location-number}.
3552 Num Type Disp Enb Address What
3553 1 breakpoint keep y <MULTIPLE>
3555 breakpoint already hit 1 time
3556 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3557 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3560 Each location can be individually enabled or disabled by passing
3561 @var{breakpoint-number}.@var{location-number} as argument to the
3562 @code{enable} and @code{disable} commands. Note that you cannot
3563 delete the individual locations from the list, you can only delete the
3564 entire list of locations that belong to their parent breakpoint (with
3565 the @kbd{delete @var{num}} command, where @var{num} is the number of
3566 the parent breakpoint, 1 in the above example). Disabling or enabling
3567 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3568 that belong to that breakpoint.
3570 @cindex pending breakpoints
3571 It's quite common to have a breakpoint inside a shared library.
3572 Shared libraries can be loaded and unloaded explicitly,
3573 and possibly repeatedly, as the program is executed. To support
3574 this use case, @value{GDBN} updates breakpoint locations whenever
3575 any shared library is loaded or unloaded. Typically, you would
3576 set a breakpoint in a shared library at the beginning of your
3577 debugging session, when the library is not loaded, and when the
3578 symbols from the library are not available. When you try to set
3579 breakpoint, @value{GDBN} will ask you if you want to set
3580 a so called @dfn{pending breakpoint}---breakpoint whose address
3581 is not yet resolved.
3583 After the program is run, whenever a new shared library is loaded,
3584 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3585 shared library contains the symbol or line referred to by some
3586 pending breakpoint, that breakpoint is resolved and becomes an
3587 ordinary breakpoint. When a library is unloaded, all breakpoints
3588 that refer to its symbols or source lines become pending again.
3590 This logic works for breakpoints with multiple locations, too. For
3591 example, if you have a breakpoint in a C@t{++} template function, and
3592 a newly loaded shared library has an instantiation of that template,
3593 a new location is added to the list of locations for the breakpoint.
3595 Except for having unresolved address, pending breakpoints do not
3596 differ from regular breakpoints. You can set conditions or commands,
3597 enable and disable them and perform other breakpoint operations.
3599 @value{GDBN} provides some additional commands for controlling what
3600 happens when the @samp{break} command cannot resolve breakpoint
3601 address specification to an address:
3603 @kindex set breakpoint pending
3604 @kindex show breakpoint pending
3606 @item set breakpoint pending auto
3607 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3608 location, it queries you whether a pending breakpoint should be created.
3610 @item set breakpoint pending on
3611 This indicates that an unrecognized breakpoint location should automatically
3612 result in a pending breakpoint being created.
3614 @item set breakpoint pending off
3615 This indicates that pending breakpoints are not to be created. Any
3616 unrecognized breakpoint location results in an error. This setting does
3617 not affect any pending breakpoints previously created.
3619 @item show breakpoint pending
3620 Show the current behavior setting for creating pending breakpoints.
3623 The settings above only affect the @code{break} command and its
3624 variants. Once breakpoint is set, it will be automatically updated
3625 as shared libraries are loaded and unloaded.
3627 @cindex automatic hardware breakpoints
3628 For some targets, @value{GDBN} can automatically decide if hardware or
3629 software breakpoints should be used, depending on whether the
3630 breakpoint address is read-only or read-write. This applies to
3631 breakpoints set with the @code{break} command as well as to internal
3632 breakpoints set by commands like @code{next} and @code{finish}. For
3633 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3636 You can control this automatic behaviour with the following commands::
3638 @kindex set breakpoint auto-hw
3639 @kindex show breakpoint auto-hw
3641 @item set breakpoint auto-hw on
3642 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3643 will try to use the target memory map to decide if software or hardware
3644 breakpoint must be used.
3646 @item set breakpoint auto-hw off
3647 This indicates @value{GDBN} should not automatically select breakpoint
3648 type. If the target provides a memory map, @value{GDBN} will warn when
3649 trying to set software breakpoint at a read-only address.
3652 @value{GDBN} normally implements breakpoints by replacing the program code
3653 at the breakpoint address with a special instruction, which, when
3654 executed, given control to the debugger. By default, the program
3655 code is so modified only when the program is resumed. As soon as
3656 the program stops, @value{GDBN} restores the original instructions. This
3657 behaviour guards against leaving breakpoints inserted in the
3658 target should gdb abrubptly disconnect. However, with slow remote
3659 targets, inserting and removing breakpoint can reduce the performance.
3660 This behavior can be controlled with the following commands::
3662 @kindex set breakpoint always-inserted
3663 @kindex show breakpoint always-inserted
3665 @item set breakpoint always-inserted off
3666 All breakpoints, including newly added by the user, are inserted in
3667 the target only when the target is resumed. All breakpoints are
3668 removed from the target when it stops.
3670 @item set breakpoint always-inserted on
3671 Causes all breakpoints to be inserted in the target at all times. If
3672 the user adds a new breakpoint, or changes an existing breakpoint, the
3673 breakpoints in the target are updated immediately. A breakpoint is
3674 removed from the target only when breakpoint itself is removed.
3676 @cindex non-stop mode, and @code{breakpoint always-inserted}
3677 @item set breakpoint always-inserted auto
3678 This is the default mode. If @value{GDBN} is controlling the inferior
3679 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3680 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3681 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3682 @code{breakpoint always-inserted} mode is off.
3685 @cindex negative breakpoint numbers
3686 @cindex internal @value{GDBN} breakpoints
3687 @value{GDBN} itself sometimes sets breakpoints in your program for
3688 special purposes, such as proper handling of @code{longjmp} (in C
3689 programs). These internal breakpoints are assigned negative numbers,
3690 starting with @code{-1}; @samp{info breakpoints} does not display them.
3691 You can see these breakpoints with the @value{GDBN} maintenance command
3692 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3695 @node Set Watchpoints
3696 @subsection Setting Watchpoints
3698 @cindex setting watchpoints
3699 You can use a watchpoint to stop execution whenever the value of an
3700 expression changes, without having to predict a particular place where
3701 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3702 The expression may be as simple as the value of a single variable, or
3703 as complex as many variables combined by operators. Examples include:
3707 A reference to the value of a single variable.
3710 An address cast to an appropriate data type. For example,
3711 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3712 address (assuming an @code{int} occupies 4 bytes).
3715 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3716 expression can use any operators valid in the program's native
3717 language (@pxref{Languages}).
3720 You can set a watchpoint on an expression even if the expression can
3721 not be evaluated yet. For instance, you can set a watchpoint on
3722 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3723 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3724 the expression produces a valid value. If the expression becomes
3725 valid in some other way than changing a variable (e.g.@: if the memory
3726 pointed to by @samp{*global_ptr} becomes readable as the result of a
3727 @code{malloc} call), @value{GDBN} may not stop until the next time
3728 the expression changes.
3730 @cindex software watchpoints
3731 @cindex hardware watchpoints
3732 Depending on your system, watchpoints may be implemented in software or
3733 hardware. @value{GDBN} does software watchpointing by single-stepping your
3734 program and testing the variable's value each time, which is hundreds of
3735 times slower than normal execution. (But this may still be worth it, to
3736 catch errors where you have no clue what part of your program is the
3739 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3740 x86-based targets, @value{GDBN} includes support for hardware
3741 watchpoints, which do not slow down the running of your program.
3745 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3746 Set a watchpoint for an expression. @value{GDBN} will break when the
3747 expression @var{expr} is written into by the program and its value
3748 changes. The simplest (and the most popular) use of this command is
3749 to watch the value of a single variable:
3752 (@value{GDBP}) watch foo
3755 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3756 argument, @value{GDBN} breaks only when the thread identified by
3757 @var{threadnum} changes the value of @var{expr}. If any other threads
3758 change the value of @var{expr}, @value{GDBN} will not break. Note
3759 that watchpoints restricted to a single thread in this way only work
3760 with Hardware Watchpoints.
3762 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3763 (see below). The @code{-location} argument tells @value{GDBN} to
3764 instead watch the memory referred to by @var{expr}. In this case,
3765 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3766 and watch the memory at that address. The type of the result is used
3767 to determine the size of the watched memory. If the expression's
3768 result does not have an address, then @value{GDBN} will print an
3771 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3772 of masked watchpoints, if the current architecture supports this
3773 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3774 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
3775 to an address to watch. The mask specifies that some bits of an address
3776 (the bits which are reset in the mask) should be ignored when matching
3777 the address accessed by the inferior against the watchpoint address.
3778 Thus, a masked watchpoint watches many addresses simultaneously---those
3779 addresses whose unmasked bits are identical to the unmasked bits in the
3780 watchpoint address. The @code{mask} argument implies @code{-location}.
3784 (@value{GDBP}) watch foo mask 0xffff00ff
3785 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
3789 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3790 Set a watchpoint that will break when the value of @var{expr} is read
3794 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3795 Set a watchpoint that will break when @var{expr} is either read from
3796 or written into by the program.
3798 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
3799 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
3800 This command prints a list of watchpoints, using the same format as
3801 @code{info break} (@pxref{Set Breaks}).
3804 If you watch for a change in a numerically entered address you need to
3805 dereference it, as the address itself is just a constant number which will
3806 never change. @value{GDBN} refuses to create a watchpoint that watches
3807 a never-changing value:
3810 (@value{GDBP}) watch 0x600850
3811 Cannot watch constant value 0x600850.
3812 (@value{GDBP}) watch *(int *) 0x600850
3813 Watchpoint 1: *(int *) 6293584
3816 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3817 watchpoints execute very quickly, and the debugger reports a change in
3818 value at the exact instruction where the change occurs. If @value{GDBN}
3819 cannot set a hardware watchpoint, it sets a software watchpoint, which
3820 executes more slowly and reports the change in value at the next
3821 @emph{statement}, not the instruction, after the change occurs.
3823 @cindex use only software watchpoints
3824 You can force @value{GDBN} to use only software watchpoints with the
3825 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3826 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3827 the underlying system supports them. (Note that hardware-assisted
3828 watchpoints that were set @emph{before} setting
3829 @code{can-use-hw-watchpoints} to zero will still use the hardware
3830 mechanism of watching expression values.)
3833 @item set can-use-hw-watchpoints
3834 @kindex set can-use-hw-watchpoints
3835 Set whether or not to use hardware watchpoints.
3837 @item show can-use-hw-watchpoints
3838 @kindex show can-use-hw-watchpoints
3839 Show the current mode of using hardware watchpoints.
3842 For remote targets, you can restrict the number of hardware
3843 watchpoints @value{GDBN} will use, see @ref{set remote
3844 hardware-breakpoint-limit}.
3846 When you issue the @code{watch} command, @value{GDBN} reports
3849 Hardware watchpoint @var{num}: @var{expr}
3853 if it was able to set a hardware watchpoint.
3855 Currently, the @code{awatch} and @code{rwatch} commands can only set
3856 hardware watchpoints, because accesses to data that don't change the
3857 value of the watched expression cannot be detected without examining
3858 every instruction as it is being executed, and @value{GDBN} does not do
3859 that currently. If @value{GDBN} finds that it is unable to set a
3860 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3861 will print a message like this:
3864 Expression cannot be implemented with read/access watchpoint.
3867 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3868 data type of the watched expression is wider than what a hardware
3869 watchpoint on the target machine can handle. For example, some systems
3870 can only watch regions that are up to 4 bytes wide; on such systems you
3871 cannot set hardware watchpoints for an expression that yields a
3872 double-precision floating-point number (which is typically 8 bytes
3873 wide). As a work-around, it might be possible to break the large region
3874 into a series of smaller ones and watch them with separate watchpoints.
3876 If you set too many hardware watchpoints, @value{GDBN} might be unable
3877 to insert all of them when you resume the execution of your program.
3878 Since the precise number of active watchpoints is unknown until such
3879 time as the program is about to be resumed, @value{GDBN} might not be
3880 able to warn you about this when you set the watchpoints, and the
3881 warning will be printed only when the program is resumed:
3884 Hardware watchpoint @var{num}: Could not insert watchpoint
3888 If this happens, delete or disable some of the watchpoints.
3890 Watching complex expressions that reference many variables can also
3891 exhaust the resources available for hardware-assisted watchpoints.
3892 That's because @value{GDBN} needs to watch every variable in the
3893 expression with separately allocated resources.
3895 If you call a function interactively using @code{print} or @code{call},
3896 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3897 kind of breakpoint or the call completes.
3899 @value{GDBN} automatically deletes watchpoints that watch local
3900 (automatic) variables, or expressions that involve such variables, when
3901 they go out of scope, that is, when the execution leaves the block in
3902 which these variables were defined. In particular, when the program
3903 being debugged terminates, @emph{all} local variables go out of scope,
3904 and so only watchpoints that watch global variables remain set. If you
3905 rerun the program, you will need to set all such watchpoints again. One
3906 way of doing that would be to set a code breakpoint at the entry to the
3907 @code{main} function and when it breaks, set all the watchpoints.
3909 @cindex watchpoints and threads
3910 @cindex threads and watchpoints
3911 In multi-threaded programs, watchpoints will detect changes to the
3912 watched expression from every thread.
3915 @emph{Warning:} In multi-threaded programs, software watchpoints
3916 have only limited usefulness. If @value{GDBN} creates a software
3917 watchpoint, it can only watch the value of an expression @emph{in a
3918 single thread}. If you are confident that the expression can only
3919 change due to the current thread's activity (and if you are also
3920 confident that no other thread can become current), then you can use
3921 software watchpoints as usual. However, @value{GDBN} may not notice
3922 when a non-current thread's activity changes the expression. (Hardware
3923 watchpoints, in contrast, watch an expression in all threads.)
3926 @xref{set remote hardware-watchpoint-limit}.
3928 @node Set Catchpoints
3929 @subsection Setting Catchpoints
3930 @cindex catchpoints, setting
3931 @cindex exception handlers
3932 @cindex event handling
3934 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3935 kinds of program events, such as C@t{++} exceptions or the loading of a
3936 shared library. Use the @code{catch} command to set a catchpoint.
3940 @item catch @var{event}
3941 Stop when @var{event} occurs. @var{event} can be any of the following:
3944 @cindex stop on C@t{++} exceptions
3945 The throwing of a C@t{++} exception.
3948 The catching of a C@t{++} exception.
3951 @cindex Ada exception catching
3952 @cindex catch Ada exceptions
3953 An Ada exception being raised. If an exception name is specified
3954 at the end of the command (eg @code{catch exception Program_Error}),
3955 the debugger will stop only when this specific exception is raised.
3956 Otherwise, the debugger stops execution when any Ada exception is raised.
3958 When inserting an exception catchpoint on a user-defined exception whose
3959 name is identical to one of the exceptions defined by the language, the
3960 fully qualified name must be used as the exception name. Otherwise,
3961 @value{GDBN} will assume that it should stop on the pre-defined exception
3962 rather than the user-defined one. For instance, assuming an exception
3963 called @code{Constraint_Error} is defined in package @code{Pck}, then
3964 the command to use to catch such exceptions is @kbd{catch exception
3965 Pck.Constraint_Error}.
3967 @item exception unhandled
3968 An exception that was raised but is not handled by the program.
3971 A failed Ada assertion.
3974 @cindex break on fork/exec
3975 A call to @code{exec}. This is currently only available for HP-UX
3979 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
3980 @cindex break on a system call.
3981 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
3982 syscall is a mechanism for application programs to request a service
3983 from the operating system (OS) or one of the OS system services.
3984 @value{GDBN} can catch some or all of the syscalls issued by the
3985 debuggee, and show the related information for each syscall. If no
3986 argument is specified, calls to and returns from all system calls
3989 @var{name} can be any system call name that is valid for the
3990 underlying OS. Just what syscalls are valid depends on the OS. On
3991 GNU and Unix systems, you can find the full list of valid syscall
3992 names on @file{/usr/include/asm/unistd.h}.
3994 @c For MS-Windows, the syscall names and the corresponding numbers
3995 @c can be found, e.g., on this URL:
3996 @c http://www.metasploit.com/users/opcode/syscalls.html
3997 @c but we don't support Windows syscalls yet.
3999 Normally, @value{GDBN} knows in advance which syscalls are valid for
4000 each OS, so you can use the @value{GDBN} command-line completion
4001 facilities (@pxref{Completion,, command completion}) to list the
4004 You may also specify the system call numerically. A syscall's
4005 number is the value passed to the OS's syscall dispatcher to
4006 identify the requested service. When you specify the syscall by its
4007 name, @value{GDBN} uses its database of syscalls to convert the name
4008 into the corresponding numeric code, but using the number directly
4009 may be useful if @value{GDBN}'s database does not have the complete
4010 list of syscalls on your system (e.g., because @value{GDBN} lags
4011 behind the OS upgrades).
4013 The example below illustrates how this command works if you don't provide
4017 (@value{GDBP}) catch syscall
4018 Catchpoint 1 (syscall)
4020 Starting program: /tmp/catch-syscall
4022 Catchpoint 1 (call to syscall 'close'), \
4023 0xffffe424 in __kernel_vsyscall ()
4027 Catchpoint 1 (returned from syscall 'close'), \
4028 0xffffe424 in __kernel_vsyscall ()
4032 Here is an example of catching a system call by name:
4035 (@value{GDBP}) catch syscall chroot
4036 Catchpoint 1 (syscall 'chroot' [61])
4038 Starting program: /tmp/catch-syscall
4040 Catchpoint 1 (call to syscall 'chroot'), \
4041 0xffffe424 in __kernel_vsyscall ()
4045 Catchpoint 1 (returned from syscall 'chroot'), \
4046 0xffffe424 in __kernel_vsyscall ()
4050 An example of specifying a system call numerically. In the case
4051 below, the syscall number has a corresponding entry in the XML
4052 file, so @value{GDBN} finds its name and prints it:
4055 (@value{GDBP}) catch syscall 252
4056 Catchpoint 1 (syscall(s) 'exit_group')
4058 Starting program: /tmp/catch-syscall
4060 Catchpoint 1 (call to syscall 'exit_group'), \
4061 0xffffe424 in __kernel_vsyscall ()
4065 Program exited normally.
4069 However, there can be situations when there is no corresponding name
4070 in XML file for that syscall number. In this case, @value{GDBN} prints
4071 a warning message saying that it was not able to find the syscall name,
4072 but the catchpoint will be set anyway. See the example below:
4075 (@value{GDBP}) catch syscall 764
4076 warning: The number '764' does not represent a known syscall.
4077 Catchpoint 2 (syscall 764)
4081 If you configure @value{GDBN} using the @samp{--without-expat} option,
4082 it will not be able to display syscall names. Also, if your
4083 architecture does not have an XML file describing its system calls,
4084 you will not be able to see the syscall names. It is important to
4085 notice that these two features are used for accessing the syscall
4086 name database. In either case, you will see a warning like this:
4089 (@value{GDBP}) catch syscall
4090 warning: Could not open "syscalls/i386-linux.xml"
4091 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4092 GDB will not be able to display syscall names.
4093 Catchpoint 1 (syscall)
4097 Of course, the file name will change depending on your architecture and system.
4099 Still using the example above, you can also try to catch a syscall by its
4100 number. In this case, you would see something like:
4103 (@value{GDBP}) catch syscall 252
4104 Catchpoint 1 (syscall(s) 252)
4107 Again, in this case @value{GDBN} would not be able to display syscall's names.
4110 A call to @code{fork}. This is currently only available for HP-UX
4114 A call to @code{vfork}. This is currently only available for HP-UX
4119 @item tcatch @var{event}
4120 Set a catchpoint that is enabled only for one stop. The catchpoint is
4121 automatically deleted after the first time the event is caught.
4125 Use the @code{info break} command to list the current catchpoints.
4127 There are currently some limitations to C@t{++} exception handling
4128 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4132 If you call a function interactively, @value{GDBN} normally returns
4133 control to you when the function has finished executing. If the call
4134 raises an exception, however, the call may bypass the mechanism that
4135 returns control to you and cause your program either to abort or to
4136 simply continue running until it hits a breakpoint, catches a signal
4137 that @value{GDBN} is listening for, or exits. This is the case even if
4138 you set a catchpoint for the exception; catchpoints on exceptions are
4139 disabled within interactive calls.
4142 You cannot raise an exception interactively.
4145 You cannot install an exception handler interactively.
4148 @cindex raise exceptions
4149 Sometimes @code{catch} is not the best way to debug exception handling:
4150 if you need to know exactly where an exception is raised, it is better to
4151 stop @emph{before} the exception handler is called, since that way you
4152 can see the stack before any unwinding takes place. If you set a
4153 breakpoint in an exception handler instead, it may not be easy to find
4154 out where the exception was raised.
4156 To stop just before an exception handler is called, you need some
4157 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4158 raised by calling a library function named @code{__raise_exception}
4159 which has the following ANSI C interface:
4162 /* @var{addr} is where the exception identifier is stored.
4163 @var{id} is the exception identifier. */
4164 void __raise_exception (void **addr, void *id);
4168 To make the debugger catch all exceptions before any stack
4169 unwinding takes place, set a breakpoint on @code{__raise_exception}
4170 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4172 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4173 that depends on the value of @var{id}, you can stop your program when
4174 a specific exception is raised. You can use multiple conditional
4175 breakpoints to stop your program when any of a number of exceptions are
4180 @subsection Deleting Breakpoints
4182 @cindex clearing breakpoints, watchpoints, catchpoints
4183 @cindex deleting breakpoints, watchpoints, catchpoints
4184 It is often necessary to eliminate a breakpoint, watchpoint, or
4185 catchpoint once it has done its job and you no longer want your program
4186 to stop there. This is called @dfn{deleting} the breakpoint. A
4187 breakpoint that has been deleted no longer exists; it is forgotten.
4189 With the @code{clear} command you can delete breakpoints according to
4190 where they are in your program. With the @code{delete} command you can
4191 delete individual breakpoints, watchpoints, or catchpoints by specifying
4192 their breakpoint numbers.
4194 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4195 automatically ignores breakpoints on the first instruction to be executed
4196 when you continue execution without changing the execution address.
4201 Delete any breakpoints at the next instruction to be executed in the
4202 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4203 the innermost frame is selected, this is a good way to delete a
4204 breakpoint where your program just stopped.
4206 @item clear @var{location}
4207 Delete any breakpoints set at the specified @var{location}.
4208 @xref{Specify Location}, for the various forms of @var{location}; the
4209 most useful ones are listed below:
4212 @item clear @var{function}
4213 @itemx clear @var{filename}:@var{function}
4214 Delete any breakpoints set at entry to the named @var{function}.
4216 @item clear @var{linenum}
4217 @itemx clear @var{filename}:@var{linenum}
4218 Delete any breakpoints set at or within the code of the specified
4219 @var{linenum} of the specified @var{filename}.
4222 @cindex delete breakpoints
4224 @kindex d @r{(@code{delete})}
4225 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4226 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4227 ranges specified as arguments. If no argument is specified, delete all
4228 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4229 confirm off}). You can abbreviate this command as @code{d}.
4233 @subsection Disabling Breakpoints
4235 @cindex enable/disable a breakpoint
4236 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4237 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4238 it had been deleted, but remembers the information on the breakpoint so
4239 that you can @dfn{enable} it again later.
4241 You disable and enable breakpoints, watchpoints, and catchpoints with
4242 the @code{enable} and @code{disable} commands, optionally specifying
4243 one or more breakpoint numbers as arguments. Use @code{info break} to
4244 print a list of all breakpoints, watchpoints, and catchpoints if you
4245 do not know which numbers to use.
4247 Disabling and enabling a breakpoint that has multiple locations
4248 affects all of its locations.
4250 A breakpoint, watchpoint, or catchpoint can have any of four different
4251 states of enablement:
4255 Enabled. The breakpoint stops your program. A breakpoint set
4256 with the @code{break} command starts out in this state.
4258 Disabled. The breakpoint has no effect on your program.
4260 Enabled once. The breakpoint stops your program, but then becomes
4263 Enabled for deletion. The breakpoint stops your program, but
4264 immediately after it does so it is deleted permanently. A breakpoint
4265 set with the @code{tbreak} command starts out in this state.
4268 You can use the following commands to enable or disable breakpoints,
4269 watchpoints, and catchpoints:
4273 @kindex dis @r{(@code{disable})}
4274 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4275 Disable the specified breakpoints---or all breakpoints, if none are
4276 listed. A disabled breakpoint has no effect but is not forgotten. All
4277 options such as ignore-counts, conditions and commands are remembered in
4278 case the breakpoint is enabled again later. You may abbreviate
4279 @code{disable} as @code{dis}.
4282 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4283 Enable the specified breakpoints (or all defined breakpoints). They
4284 become effective once again in stopping your program.
4286 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4287 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4288 of these breakpoints immediately after stopping your program.
4290 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4291 Enable the specified breakpoints to work once, then die. @value{GDBN}
4292 deletes any of these breakpoints as soon as your program stops there.
4293 Breakpoints set by the @code{tbreak} command start out in this state.
4296 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4297 @c confusing: tbreak is also initially enabled.
4298 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4299 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4300 subsequently, they become disabled or enabled only when you use one of
4301 the commands above. (The command @code{until} can set and delete a
4302 breakpoint of its own, but it does not change the state of your other
4303 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4307 @subsection Break Conditions
4308 @cindex conditional breakpoints
4309 @cindex breakpoint conditions
4311 @c FIXME what is scope of break condition expr? Context where wanted?
4312 @c in particular for a watchpoint?
4313 The simplest sort of breakpoint breaks every time your program reaches a
4314 specified place. You can also specify a @dfn{condition} for a
4315 breakpoint. A condition is just a Boolean expression in your
4316 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4317 a condition evaluates the expression each time your program reaches it,
4318 and your program stops only if the condition is @emph{true}.
4320 This is the converse of using assertions for program validation; in that
4321 situation, you want to stop when the assertion is violated---that is,
4322 when the condition is false. In C, if you want to test an assertion expressed
4323 by the condition @var{assert}, you should set the condition
4324 @samp{! @var{assert}} on the appropriate breakpoint.
4326 Conditions are also accepted for watchpoints; you may not need them,
4327 since a watchpoint is inspecting the value of an expression anyhow---but
4328 it might be simpler, say, to just set a watchpoint on a variable name,
4329 and specify a condition that tests whether the new value is an interesting
4332 Break conditions can have side effects, and may even call functions in
4333 your program. This can be useful, for example, to activate functions
4334 that log program progress, or to use your own print functions to
4335 format special data structures. The effects are completely predictable
4336 unless there is another enabled breakpoint at the same address. (In
4337 that case, @value{GDBN} might see the other breakpoint first and stop your
4338 program without checking the condition of this one.) Note that
4339 breakpoint commands are usually more convenient and flexible than break
4341 purpose of performing side effects when a breakpoint is reached
4342 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4344 Break conditions can be specified when a breakpoint is set, by using
4345 @samp{if} in the arguments to the @code{break} command. @xref{Set
4346 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4347 with the @code{condition} command.
4349 You can also use the @code{if} keyword with the @code{watch} command.
4350 The @code{catch} command does not recognize the @code{if} keyword;
4351 @code{condition} is the only way to impose a further condition on a
4356 @item condition @var{bnum} @var{expression}
4357 Specify @var{expression} as the break condition for breakpoint,
4358 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4359 breakpoint @var{bnum} stops your program only if the value of
4360 @var{expression} is true (nonzero, in C). When you use
4361 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4362 syntactic correctness, and to determine whether symbols in it have
4363 referents in the context of your breakpoint. If @var{expression} uses
4364 symbols not referenced in the context of the breakpoint, @value{GDBN}
4365 prints an error message:
4368 No symbol "foo" in current context.
4373 not actually evaluate @var{expression} at the time the @code{condition}
4374 command (or a command that sets a breakpoint with a condition, like
4375 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4377 @item condition @var{bnum}
4378 Remove the condition from breakpoint number @var{bnum}. It becomes
4379 an ordinary unconditional breakpoint.
4382 @cindex ignore count (of breakpoint)
4383 A special case of a breakpoint condition is to stop only when the
4384 breakpoint has been reached a certain number of times. This is so
4385 useful that there is a special way to do it, using the @dfn{ignore
4386 count} of the breakpoint. Every breakpoint has an ignore count, which
4387 is an integer. Most of the time, the ignore count is zero, and
4388 therefore has no effect. But if your program reaches a breakpoint whose
4389 ignore count is positive, then instead of stopping, it just decrements
4390 the ignore count by one and continues. As a result, if the ignore count
4391 value is @var{n}, the breakpoint does not stop the next @var{n} times
4392 your program reaches it.
4396 @item ignore @var{bnum} @var{count}
4397 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4398 The next @var{count} times the breakpoint is reached, your program's
4399 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4402 To make the breakpoint stop the next time it is reached, specify
4405 When you use @code{continue} to resume execution of your program from a
4406 breakpoint, you can specify an ignore count directly as an argument to
4407 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4408 Stepping,,Continuing and Stepping}.
4410 If a breakpoint has a positive ignore count and a condition, the
4411 condition is not checked. Once the ignore count reaches zero,
4412 @value{GDBN} resumes checking the condition.
4414 You could achieve the effect of the ignore count with a condition such
4415 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4416 is decremented each time. @xref{Convenience Vars, ,Convenience
4420 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4423 @node Break Commands
4424 @subsection Breakpoint Command Lists
4426 @cindex breakpoint commands
4427 You can give any breakpoint (or watchpoint or catchpoint) a series of
4428 commands to execute when your program stops due to that breakpoint. For
4429 example, you might want to print the values of certain expressions, or
4430 enable other breakpoints.
4434 @kindex end@r{ (breakpoint commands)}
4435 @item commands @r{[}@var{range}@dots{}@r{]}
4436 @itemx @dots{} @var{command-list} @dots{}
4438 Specify a list of commands for the given breakpoints. The commands
4439 themselves appear on the following lines. Type a line containing just
4440 @code{end} to terminate the commands.
4442 To remove all commands from a breakpoint, type @code{commands} and
4443 follow it immediately with @code{end}; that is, give no commands.
4445 With no argument, @code{commands} refers to the last breakpoint,
4446 watchpoint, or catchpoint set (not to the breakpoint most recently
4447 encountered). If the most recent breakpoints were set with a single
4448 command, then the @code{commands} will apply to all the breakpoints
4449 set by that command. This applies to breakpoints set by
4450 @code{rbreak}, and also applies when a single @code{break} command
4451 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4455 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4456 disabled within a @var{command-list}.
4458 You can use breakpoint commands to start your program up again. Simply
4459 use the @code{continue} command, or @code{step}, or any other command
4460 that resumes execution.
4462 Any other commands in the command list, after a command that resumes
4463 execution, are ignored. This is because any time you resume execution
4464 (even with a simple @code{next} or @code{step}), you may encounter
4465 another breakpoint---which could have its own command list, leading to
4466 ambiguities about which list to execute.
4469 If the first command you specify in a command list is @code{silent}, the
4470 usual message about stopping at a breakpoint is not printed. This may
4471 be desirable for breakpoints that are to print a specific message and
4472 then continue. If none of the remaining commands print anything, you
4473 see no sign that the breakpoint was reached. @code{silent} is
4474 meaningful only at the beginning of a breakpoint command list.
4476 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4477 print precisely controlled output, and are often useful in silent
4478 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4480 For example, here is how you could use breakpoint commands to print the
4481 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4487 printf "x is %d\n",x
4492 One application for breakpoint commands is to compensate for one bug so
4493 you can test for another. Put a breakpoint just after the erroneous line
4494 of code, give it a condition to detect the case in which something
4495 erroneous has been done, and give it commands to assign correct values
4496 to any variables that need them. End with the @code{continue} command
4497 so that your program does not stop, and start with the @code{silent}
4498 command so that no output is produced. Here is an example:
4509 @node Save Breakpoints
4510 @subsection How to save breakpoints to a file
4512 To save breakpoint definitions to a file use the @w{@code{save
4513 breakpoints}} command.
4516 @kindex save breakpoints
4517 @cindex save breakpoints to a file for future sessions
4518 @item save breakpoints [@var{filename}]
4519 This command saves all current breakpoint definitions together with
4520 their commands and ignore counts, into a file @file{@var{filename}}
4521 suitable for use in a later debugging session. This includes all
4522 types of breakpoints (breakpoints, watchpoints, catchpoints,
4523 tracepoints). To read the saved breakpoint definitions, use the
4524 @code{source} command (@pxref{Command Files}). Note that watchpoints
4525 with expressions involving local variables may fail to be recreated
4526 because it may not be possible to access the context where the
4527 watchpoint is valid anymore. Because the saved breakpoint definitions
4528 are simply a sequence of @value{GDBN} commands that recreate the
4529 breakpoints, you can edit the file in your favorite editing program,
4530 and remove the breakpoint definitions you're not interested in, or
4531 that can no longer be recreated.
4534 @c @ifclear BARETARGET
4535 @node Error in Breakpoints
4536 @subsection ``Cannot insert breakpoints''
4538 If you request too many active hardware-assisted breakpoints and
4539 watchpoints, you will see this error message:
4541 @c FIXME: the precise wording of this message may change; the relevant
4542 @c source change is not committed yet (Sep 3, 1999).
4544 Stopped; cannot insert breakpoints.
4545 You may have requested too many hardware breakpoints and watchpoints.
4549 This message is printed when you attempt to resume the program, since
4550 only then @value{GDBN} knows exactly how many hardware breakpoints and
4551 watchpoints it needs to insert.
4553 When this message is printed, you need to disable or remove some of the
4554 hardware-assisted breakpoints and watchpoints, and then continue.
4556 @node Breakpoint-related Warnings
4557 @subsection ``Breakpoint address adjusted...''
4558 @cindex breakpoint address adjusted
4560 Some processor architectures place constraints on the addresses at
4561 which breakpoints may be placed. For architectures thus constrained,
4562 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4563 with the constraints dictated by the architecture.
4565 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4566 a VLIW architecture in which a number of RISC-like instructions may be
4567 bundled together for parallel execution. The FR-V architecture
4568 constrains the location of a breakpoint instruction within such a
4569 bundle to the instruction with the lowest address. @value{GDBN}
4570 honors this constraint by adjusting a breakpoint's address to the
4571 first in the bundle.
4573 It is not uncommon for optimized code to have bundles which contain
4574 instructions from different source statements, thus it may happen that
4575 a breakpoint's address will be adjusted from one source statement to
4576 another. Since this adjustment may significantly alter @value{GDBN}'s
4577 breakpoint related behavior from what the user expects, a warning is
4578 printed when the breakpoint is first set and also when the breakpoint
4581 A warning like the one below is printed when setting a breakpoint
4582 that's been subject to address adjustment:
4585 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4588 Such warnings are printed both for user settable and @value{GDBN}'s
4589 internal breakpoints. If you see one of these warnings, you should
4590 verify that a breakpoint set at the adjusted address will have the
4591 desired affect. If not, the breakpoint in question may be removed and
4592 other breakpoints may be set which will have the desired behavior.
4593 E.g., it may be sufficient to place the breakpoint at a later
4594 instruction. A conditional breakpoint may also be useful in some
4595 cases to prevent the breakpoint from triggering too often.
4597 @value{GDBN} will also issue a warning when stopping at one of these
4598 adjusted breakpoints:
4601 warning: Breakpoint 1 address previously adjusted from 0x00010414
4605 When this warning is encountered, it may be too late to take remedial
4606 action except in cases where the breakpoint is hit earlier or more
4607 frequently than expected.
4609 @node Continuing and Stepping
4610 @section Continuing and Stepping
4614 @cindex resuming execution
4615 @dfn{Continuing} means resuming program execution until your program
4616 completes normally. In contrast, @dfn{stepping} means executing just
4617 one more ``step'' of your program, where ``step'' may mean either one
4618 line of source code, or one machine instruction (depending on what
4619 particular command you use). Either when continuing or when stepping,
4620 your program may stop even sooner, due to a breakpoint or a signal. (If
4621 it stops due to a signal, you may want to use @code{handle}, or use
4622 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4626 @kindex c @r{(@code{continue})}
4627 @kindex fg @r{(resume foreground execution)}
4628 @item continue @r{[}@var{ignore-count}@r{]}
4629 @itemx c @r{[}@var{ignore-count}@r{]}
4630 @itemx fg @r{[}@var{ignore-count}@r{]}
4631 Resume program execution, at the address where your program last stopped;
4632 any breakpoints set at that address are bypassed. The optional argument
4633 @var{ignore-count} allows you to specify a further number of times to
4634 ignore a breakpoint at this location; its effect is like that of
4635 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4637 The argument @var{ignore-count} is meaningful only when your program
4638 stopped due to a breakpoint. At other times, the argument to
4639 @code{continue} is ignored.
4641 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4642 debugged program is deemed to be the foreground program) are provided
4643 purely for convenience, and have exactly the same behavior as
4647 To resume execution at a different place, you can use @code{return}
4648 (@pxref{Returning, ,Returning from a Function}) to go back to the
4649 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4650 Different Address}) to go to an arbitrary location in your program.
4652 A typical technique for using stepping is to set a breakpoint
4653 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4654 beginning of the function or the section of your program where a problem
4655 is believed to lie, run your program until it stops at that breakpoint,
4656 and then step through the suspect area, examining the variables that are
4657 interesting, until you see the problem happen.
4661 @kindex s @r{(@code{step})}
4663 Continue running your program until control reaches a different source
4664 line, then stop it and return control to @value{GDBN}. This command is
4665 abbreviated @code{s}.
4668 @c "without debugging information" is imprecise; actually "without line
4669 @c numbers in the debugging information". (gcc -g1 has debugging info but
4670 @c not line numbers). But it seems complex to try to make that
4671 @c distinction here.
4672 @emph{Warning:} If you use the @code{step} command while control is
4673 within a function that was compiled without debugging information,
4674 execution proceeds until control reaches a function that does have
4675 debugging information. Likewise, it will not step into a function which
4676 is compiled without debugging information. To step through functions
4677 without debugging information, use the @code{stepi} command, described
4681 The @code{step} command only stops at the first instruction of a source
4682 line. This prevents the multiple stops that could otherwise occur in
4683 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4684 to stop if a function that has debugging information is called within
4685 the line. In other words, @code{step} @emph{steps inside} any functions
4686 called within the line.
4688 Also, the @code{step} command only enters a function if there is line
4689 number information for the function. Otherwise it acts like the
4690 @code{next} command. This avoids problems when using @code{cc -gl}
4691 on MIPS machines. Previously, @code{step} entered subroutines if there
4692 was any debugging information about the routine.
4694 @item step @var{count}
4695 Continue running as in @code{step}, but do so @var{count} times. If a
4696 breakpoint is reached, or a signal not related to stepping occurs before
4697 @var{count} steps, stepping stops right away.
4700 @kindex n @r{(@code{next})}
4701 @item next @r{[}@var{count}@r{]}
4702 Continue to the next source line in the current (innermost) stack frame.
4703 This is similar to @code{step}, but function calls that appear within
4704 the line of code are executed without stopping. Execution stops when
4705 control reaches a different line of code at the original stack level
4706 that was executing when you gave the @code{next} command. This command
4707 is abbreviated @code{n}.
4709 An argument @var{count} is a repeat count, as for @code{step}.
4712 @c FIX ME!! Do we delete this, or is there a way it fits in with
4713 @c the following paragraph? --- Vctoria
4715 @c @code{next} within a function that lacks debugging information acts like
4716 @c @code{step}, but any function calls appearing within the code of the
4717 @c function are executed without stopping.
4719 The @code{next} command only stops at the first instruction of a
4720 source line. This prevents multiple stops that could otherwise occur in
4721 @code{switch} statements, @code{for} loops, etc.
4723 @kindex set step-mode
4725 @cindex functions without line info, and stepping
4726 @cindex stepping into functions with no line info
4727 @itemx set step-mode on
4728 The @code{set step-mode on} command causes the @code{step} command to
4729 stop at the first instruction of a function which contains no debug line
4730 information rather than stepping over it.
4732 This is useful in cases where you may be interested in inspecting the
4733 machine instructions of a function which has no symbolic info and do not
4734 want @value{GDBN} to automatically skip over this function.
4736 @item set step-mode off
4737 Causes the @code{step} command to step over any functions which contains no
4738 debug information. This is the default.
4740 @item show step-mode
4741 Show whether @value{GDBN} will stop in or step over functions without
4742 source line debug information.
4745 @kindex fin @r{(@code{finish})}
4747 Continue running until just after function in the selected stack frame
4748 returns. Print the returned value (if any). This command can be
4749 abbreviated as @code{fin}.
4751 Contrast this with the @code{return} command (@pxref{Returning,
4752 ,Returning from a Function}).
4755 @kindex u @r{(@code{until})}
4756 @cindex run until specified location
4759 Continue running until a source line past the current line, in the
4760 current stack frame, is reached. This command is used to avoid single
4761 stepping through a loop more than once. It is like the @code{next}
4762 command, except that when @code{until} encounters a jump, it
4763 automatically continues execution until the program counter is greater
4764 than the address of the jump.
4766 This means that when you reach the end of a loop after single stepping
4767 though it, @code{until} makes your program continue execution until it
4768 exits the loop. In contrast, a @code{next} command at the end of a loop
4769 simply steps back to the beginning of the loop, which forces you to step
4770 through the next iteration.
4772 @code{until} always stops your program if it attempts to exit the current
4775 @code{until} may produce somewhat counterintuitive results if the order
4776 of machine code does not match the order of the source lines. For
4777 example, in the following excerpt from a debugging session, the @code{f}
4778 (@code{frame}) command shows that execution is stopped at line
4779 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4783 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4785 (@value{GDBP}) until
4786 195 for ( ; argc > 0; NEXTARG) @{
4789 This happened because, for execution efficiency, the compiler had
4790 generated code for the loop closure test at the end, rather than the
4791 start, of the loop---even though the test in a C @code{for}-loop is
4792 written before the body of the loop. The @code{until} command appeared
4793 to step back to the beginning of the loop when it advanced to this
4794 expression; however, it has not really gone to an earlier
4795 statement---not in terms of the actual machine code.
4797 @code{until} with no argument works by means of single
4798 instruction stepping, and hence is slower than @code{until} with an
4801 @item until @var{location}
4802 @itemx u @var{location}
4803 Continue running your program until either the specified location is
4804 reached, or the current stack frame returns. @var{location} is any of
4805 the forms described in @ref{Specify Location}.
4806 This form of the command uses temporary breakpoints, and
4807 hence is quicker than @code{until} without an argument. The specified
4808 location is actually reached only if it is in the current frame. This
4809 implies that @code{until} can be used to skip over recursive function
4810 invocations. For instance in the code below, if the current location is
4811 line @code{96}, issuing @code{until 99} will execute the program up to
4812 line @code{99} in the same invocation of factorial, i.e., after the inner
4813 invocations have returned.
4816 94 int factorial (int value)
4818 96 if (value > 1) @{
4819 97 value *= factorial (value - 1);
4826 @kindex advance @var{location}
4827 @itemx advance @var{location}
4828 Continue running the program up to the given @var{location}. An argument is
4829 required, which should be of one of the forms described in
4830 @ref{Specify Location}.
4831 Execution will also stop upon exit from the current stack
4832 frame. This command is similar to @code{until}, but @code{advance} will
4833 not skip over recursive function calls, and the target location doesn't
4834 have to be in the same frame as the current one.
4838 @kindex si @r{(@code{stepi})}
4840 @itemx stepi @var{arg}
4842 Execute one machine instruction, then stop and return to the debugger.
4844 It is often useful to do @samp{display/i $pc} when stepping by machine
4845 instructions. This makes @value{GDBN} automatically display the next
4846 instruction to be executed, each time your program stops. @xref{Auto
4847 Display,, Automatic Display}.
4849 An argument is a repeat count, as in @code{step}.
4853 @kindex ni @r{(@code{nexti})}
4855 @itemx nexti @var{arg}
4857 Execute one machine instruction, but if it is a function call,
4858 proceed until the function returns.
4860 An argument is a repeat count, as in @code{next}.
4863 @node Skipping Over Functions and Files
4864 @section Skipping Over Functions and Files
4865 @cindex skipping over functions and files
4867 The program you are debugging may contain some functions which are
4868 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
4869 skip a function or all functions in a file when stepping.
4871 For example, consider the following C function:
4882 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
4883 are not interested in stepping through @code{boring}. If you run @code{step}
4884 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
4885 step over both @code{foo} and @code{boring}!
4887 One solution is to @code{step} into @code{boring} and use the @code{finish}
4888 command to immediately exit it. But this can become tedious if @code{boring}
4889 is called from many places.
4891 A more flexible solution is to execute @kbd{skip boring}. This instructs
4892 @value{GDBN} never to step into @code{boring}. Now when you execute
4893 @code{step} at line 103, you'll step over @code{boring} and directly into
4896 You can also instruct @value{GDBN} to skip all functions in a file, with, for
4897 example, @code{skip file boring.c}.
4900 @kindex skip function
4901 @item skip @r{[}@var{linespec}@r{]}
4902 @itemx skip function @r{[}@var{linespec}@r{]}
4903 After running this command, the function named by @var{linespec} or the
4904 function containing the line named by @var{linespec} will be skipped over when
4905 stepping. @xref{Specify Location}.
4907 If you do not specify @var{linespec}, the function you're currently debugging
4910 (If you have a function called @code{file} that you want to skip, use
4911 @kbd{skip function file}.)
4914 @item skip file @r{[}@var{filename}@r{]}
4915 After running this command, any function whose source lives in @var{filename}
4916 will be skipped over when stepping.
4918 If you do not specify @var{filename}, functions whose source lives in the file
4919 you're currently debugging will be skipped.
4922 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
4923 These are the commands for managing your list of skips:
4927 @item info skip @r{[}@var{range}@r{]}
4928 Print details about the specified skip(s). If @var{range} is not specified,
4929 print a table with details about all functions and files marked for skipping.
4930 @code{info skip} prints the following information about each skip:
4934 A number identifying this skip.
4936 The type of this skip, either @samp{function} or @samp{file}.
4937 @item Enabled or Disabled
4938 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
4940 For function skips, this column indicates the address in memory of the function
4941 being skipped. If you've set a function skip on a function which has not yet
4942 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
4943 which has the function is loaded, @code{info skip} will show the function's
4946 For file skips, this field contains the filename being skipped. For functions
4947 skips, this field contains the function name and its line number in the file
4948 where it is defined.
4952 @item skip delete @r{[}@var{range}@r{]}
4953 Delete the specified skip(s). If @var{range} is not specified, delete all
4957 @item skip enable @r{[}@var{range}@r{]}
4958 Enable the specified skip(s). If @var{range} is not specified, enable all
4961 @kindex skip disable
4962 @item skip disable @r{[}@var{range}@r{]}
4963 Disable the specified skip(s). If @var{range} is not specified, disable all
4972 A signal is an asynchronous event that can happen in a program. The
4973 operating system defines the possible kinds of signals, and gives each
4974 kind a name and a number. For example, in Unix @code{SIGINT} is the
4975 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4976 @code{SIGSEGV} is the signal a program gets from referencing a place in
4977 memory far away from all the areas in use; @code{SIGALRM} occurs when
4978 the alarm clock timer goes off (which happens only if your program has
4979 requested an alarm).
4981 @cindex fatal signals
4982 Some signals, including @code{SIGALRM}, are a normal part of the
4983 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4984 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4985 program has not specified in advance some other way to handle the signal.
4986 @code{SIGINT} does not indicate an error in your program, but it is normally
4987 fatal so it can carry out the purpose of the interrupt: to kill the program.
4989 @value{GDBN} has the ability to detect any occurrence of a signal in your
4990 program. You can tell @value{GDBN} in advance what to do for each kind of
4993 @cindex handling signals
4994 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4995 @code{SIGALRM} be silently passed to your program
4996 (so as not to interfere with their role in the program's functioning)
4997 but to stop your program immediately whenever an error signal happens.
4998 You can change these settings with the @code{handle} command.
5001 @kindex info signals
5005 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5006 handle each one. You can use this to see the signal numbers of all
5007 the defined types of signals.
5009 @item info signals @var{sig}
5010 Similar, but print information only about the specified signal number.
5012 @code{info handle} is an alias for @code{info signals}.
5015 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5016 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
5017 can be the number of a signal or its name (with or without the
5018 @samp{SIG} at the beginning); a list of signal numbers of the form
5019 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5020 known signals. Optional arguments @var{keywords}, described below,
5021 say what change to make.
5025 The keywords allowed by the @code{handle} command can be abbreviated.
5026 Their full names are:
5030 @value{GDBN} should not stop your program when this signal happens. It may
5031 still print a message telling you that the signal has come in.
5034 @value{GDBN} should stop your program when this signal happens. This implies
5035 the @code{print} keyword as well.
5038 @value{GDBN} should print a message when this signal happens.
5041 @value{GDBN} should not mention the occurrence of the signal at all. This
5042 implies the @code{nostop} keyword as well.
5046 @value{GDBN} should allow your program to see this signal; your program
5047 can handle the signal, or else it may terminate if the signal is fatal
5048 and not handled. @code{pass} and @code{noignore} are synonyms.
5052 @value{GDBN} should not allow your program to see this signal.
5053 @code{nopass} and @code{ignore} are synonyms.
5057 When a signal stops your program, the signal is not visible to the
5059 continue. Your program sees the signal then, if @code{pass} is in
5060 effect for the signal in question @emph{at that time}. In other words,
5061 after @value{GDBN} reports a signal, you can use the @code{handle}
5062 command with @code{pass} or @code{nopass} to control whether your
5063 program sees that signal when you continue.
5065 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5066 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5067 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5070 You can also use the @code{signal} command to prevent your program from
5071 seeing a signal, or cause it to see a signal it normally would not see,
5072 or to give it any signal at any time. For example, if your program stopped
5073 due to some sort of memory reference error, you might store correct
5074 values into the erroneous variables and continue, hoping to see more
5075 execution; but your program would probably terminate immediately as
5076 a result of the fatal signal once it saw the signal. To prevent this,
5077 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5080 @cindex extra signal information
5081 @anchor{extra signal information}
5083 On some targets, @value{GDBN} can inspect extra signal information
5084 associated with the intercepted signal, before it is actually
5085 delivered to the program being debugged. This information is exported
5086 by the convenience variable @code{$_siginfo}, and consists of data
5087 that is passed by the kernel to the signal handler at the time of the
5088 receipt of a signal. The data type of the information itself is
5089 target dependent. You can see the data type using the @code{ptype
5090 $_siginfo} command. On Unix systems, it typically corresponds to the
5091 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5094 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5095 referenced address that raised a segmentation fault.
5099 (@value{GDBP}) continue
5100 Program received signal SIGSEGV, Segmentation fault.
5101 0x0000000000400766 in main ()
5103 (@value{GDBP}) ptype $_siginfo
5110 struct @{...@} _kill;
5111 struct @{...@} _timer;
5113 struct @{...@} _sigchld;
5114 struct @{...@} _sigfault;
5115 struct @{...@} _sigpoll;
5118 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5122 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5123 $1 = (void *) 0x7ffff7ff7000
5127 Depending on target support, @code{$_siginfo} may also be writable.
5130 @section Stopping and Starting Multi-thread Programs
5132 @cindex stopped threads
5133 @cindex threads, stopped
5135 @cindex continuing threads
5136 @cindex threads, continuing
5138 @value{GDBN} supports debugging programs with multiple threads
5139 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5140 are two modes of controlling execution of your program within the
5141 debugger. In the default mode, referred to as @dfn{all-stop mode},
5142 when any thread in your program stops (for example, at a breakpoint
5143 or while being stepped), all other threads in the program are also stopped by
5144 @value{GDBN}. On some targets, @value{GDBN} also supports
5145 @dfn{non-stop mode}, in which other threads can continue to run freely while
5146 you examine the stopped thread in the debugger.
5149 * All-Stop Mode:: All threads stop when GDB takes control
5150 * Non-Stop Mode:: Other threads continue to execute
5151 * Background Execution:: Running your program asynchronously
5152 * Thread-Specific Breakpoints:: Controlling breakpoints
5153 * Interrupted System Calls:: GDB may interfere with system calls
5154 * Observer Mode:: GDB does not alter program behavior
5158 @subsection All-Stop Mode
5160 @cindex all-stop mode
5162 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5163 @emph{all} threads of execution stop, not just the current thread. This
5164 allows you to examine the overall state of the program, including
5165 switching between threads, without worrying that things may change
5168 Conversely, whenever you restart the program, @emph{all} threads start
5169 executing. @emph{This is true even when single-stepping} with commands
5170 like @code{step} or @code{next}.
5172 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5173 Since thread scheduling is up to your debugging target's operating
5174 system (not controlled by @value{GDBN}), other threads may
5175 execute more than one statement while the current thread completes a
5176 single step. Moreover, in general other threads stop in the middle of a
5177 statement, rather than at a clean statement boundary, when the program
5180 You might even find your program stopped in another thread after
5181 continuing or even single-stepping. This happens whenever some other
5182 thread runs into a breakpoint, a signal, or an exception before the
5183 first thread completes whatever you requested.
5185 @cindex automatic thread selection
5186 @cindex switching threads automatically
5187 @cindex threads, automatic switching
5188 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5189 signal, it automatically selects the thread where that breakpoint or
5190 signal happened. @value{GDBN} alerts you to the context switch with a
5191 message such as @samp{[Switching to Thread @var{n}]} to identify the
5194 On some OSes, you can modify @value{GDBN}'s default behavior by
5195 locking the OS scheduler to allow only a single thread to run.
5198 @item set scheduler-locking @var{mode}
5199 @cindex scheduler locking mode
5200 @cindex lock scheduler
5201 Set the scheduler locking mode. If it is @code{off}, then there is no
5202 locking and any thread may run at any time. If @code{on}, then only the
5203 current thread may run when the inferior is resumed. The @code{step}
5204 mode optimizes for single-stepping; it prevents other threads
5205 from preempting the current thread while you are stepping, so that
5206 the focus of debugging does not change unexpectedly.
5207 Other threads only rarely (or never) get a chance to run
5208 when you step. They are more likely to run when you @samp{next} over a
5209 function call, and they are completely free to run when you use commands
5210 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5211 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5212 the current thread away from the thread that you are debugging.
5214 @item show scheduler-locking
5215 Display the current scheduler locking mode.
5218 @cindex resume threads of multiple processes simultaneously
5219 By default, when you issue one of the execution commands such as
5220 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5221 threads of the current inferior to run. For example, if @value{GDBN}
5222 is attached to two inferiors, each with two threads, the
5223 @code{continue} command resumes only the two threads of the current
5224 inferior. This is useful, for example, when you debug a program that
5225 forks and you want to hold the parent stopped (so that, for instance,
5226 it doesn't run to exit), while you debug the child. In other
5227 situations, you may not be interested in inspecting the current state
5228 of any of the processes @value{GDBN} is attached to, and you may want
5229 to resume them all until some breakpoint is hit. In the latter case,
5230 you can instruct @value{GDBN} to allow all threads of all the
5231 inferiors to run with the @w{@code{set schedule-multiple}} command.
5234 @kindex set schedule-multiple
5235 @item set schedule-multiple
5236 Set the mode for allowing threads of multiple processes to be resumed
5237 when an execution command is issued. When @code{on}, all threads of
5238 all processes are allowed to run. When @code{off}, only the threads
5239 of the current process are resumed. The default is @code{off}. The
5240 @code{scheduler-locking} mode takes precedence when set to @code{on},
5241 or while you are stepping and set to @code{step}.
5243 @item show schedule-multiple
5244 Display the current mode for resuming the execution of threads of
5249 @subsection Non-Stop Mode
5251 @cindex non-stop mode
5253 @c This section is really only a place-holder, and needs to be expanded
5254 @c with more details.
5256 For some multi-threaded targets, @value{GDBN} supports an optional
5257 mode of operation in which you can examine stopped program threads in
5258 the debugger while other threads continue to execute freely. This
5259 minimizes intrusion when debugging live systems, such as programs
5260 where some threads have real-time constraints or must continue to
5261 respond to external events. This is referred to as @dfn{non-stop} mode.
5263 In non-stop mode, when a thread stops to report a debugging event,
5264 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5265 threads as well, in contrast to the all-stop mode behavior. Additionally,
5266 execution commands such as @code{continue} and @code{step} apply by default
5267 only to the current thread in non-stop mode, rather than all threads as
5268 in all-stop mode. This allows you to control threads explicitly in
5269 ways that are not possible in all-stop mode --- for example, stepping
5270 one thread while allowing others to run freely, stepping
5271 one thread while holding all others stopped, or stepping several threads
5272 independently and simultaneously.
5274 To enter non-stop mode, use this sequence of commands before you run
5275 or attach to your program:
5278 # Enable the async interface.
5281 # If using the CLI, pagination breaks non-stop.
5284 # Finally, turn it on!
5288 You can use these commands to manipulate the non-stop mode setting:
5291 @kindex set non-stop
5292 @item set non-stop on
5293 Enable selection of non-stop mode.
5294 @item set non-stop off
5295 Disable selection of non-stop mode.
5296 @kindex show non-stop
5298 Show the current non-stop enablement setting.
5301 Note these commands only reflect whether non-stop mode is enabled,
5302 not whether the currently-executing program is being run in non-stop mode.
5303 In particular, the @code{set non-stop} preference is only consulted when
5304 @value{GDBN} starts or connects to the target program, and it is generally
5305 not possible to switch modes once debugging has started. Furthermore,
5306 since not all targets support non-stop mode, even when you have enabled
5307 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5310 In non-stop mode, all execution commands apply only to the current thread
5311 by default. That is, @code{continue} only continues one thread.
5312 To continue all threads, issue @code{continue -a} or @code{c -a}.
5314 You can use @value{GDBN}'s background execution commands
5315 (@pxref{Background Execution}) to run some threads in the background
5316 while you continue to examine or step others from @value{GDBN}.
5317 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5318 always executed asynchronously in non-stop mode.
5320 Suspending execution is done with the @code{interrupt} command when
5321 running in the background, or @kbd{Ctrl-c} during foreground execution.
5322 In all-stop mode, this stops the whole process;
5323 but in non-stop mode the interrupt applies only to the current thread.
5324 To stop the whole program, use @code{interrupt -a}.
5326 Other execution commands do not currently support the @code{-a} option.
5328 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5329 that thread current, as it does in all-stop mode. This is because the
5330 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5331 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5332 changed to a different thread just as you entered a command to operate on the
5333 previously current thread.
5335 @node Background Execution
5336 @subsection Background Execution
5338 @cindex foreground execution
5339 @cindex background execution
5340 @cindex asynchronous execution
5341 @cindex execution, foreground, background and asynchronous
5343 @value{GDBN}'s execution commands have two variants: the normal
5344 foreground (synchronous) behavior, and a background
5345 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5346 the program to report that some thread has stopped before prompting for
5347 another command. In background execution, @value{GDBN} immediately gives
5348 a command prompt so that you can issue other commands while your program runs.
5350 You need to explicitly enable asynchronous mode before you can use
5351 background execution commands. You can use these commands to
5352 manipulate the asynchronous mode setting:
5355 @kindex set target-async
5356 @item set target-async on
5357 Enable asynchronous mode.
5358 @item set target-async off
5359 Disable asynchronous mode.
5360 @kindex show target-async
5361 @item show target-async
5362 Show the current target-async setting.
5365 If the target doesn't support async mode, @value{GDBN} issues an error
5366 message if you attempt to use the background execution commands.
5368 To specify background execution, add a @code{&} to the command. For example,
5369 the background form of the @code{continue} command is @code{continue&}, or
5370 just @code{c&}. The execution commands that accept background execution
5376 @xref{Starting, , Starting your Program}.
5380 @xref{Attach, , Debugging an Already-running Process}.
5384 @xref{Continuing and Stepping, step}.
5388 @xref{Continuing and Stepping, stepi}.
5392 @xref{Continuing and Stepping, next}.
5396 @xref{Continuing and Stepping, nexti}.
5400 @xref{Continuing and Stepping, continue}.
5404 @xref{Continuing and Stepping, finish}.
5408 @xref{Continuing and Stepping, until}.
5412 Background execution is especially useful in conjunction with non-stop
5413 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5414 However, you can also use these commands in the normal all-stop mode with
5415 the restriction that you cannot issue another execution command until the
5416 previous one finishes. Examples of commands that are valid in all-stop
5417 mode while the program is running include @code{help} and @code{info break}.
5419 You can interrupt your program while it is running in the background by
5420 using the @code{interrupt} command.
5427 Suspend execution of the running program. In all-stop mode,
5428 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5429 only the current thread. To stop the whole program in non-stop mode,
5430 use @code{interrupt -a}.
5433 @node Thread-Specific Breakpoints
5434 @subsection Thread-Specific Breakpoints
5436 When your program has multiple threads (@pxref{Threads,, Debugging
5437 Programs with Multiple Threads}), you can choose whether to set
5438 breakpoints on all threads, or on a particular thread.
5441 @cindex breakpoints and threads
5442 @cindex thread breakpoints
5443 @kindex break @dots{} thread @var{threadno}
5444 @item break @var{linespec} thread @var{threadno}
5445 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5446 @var{linespec} specifies source lines; there are several ways of
5447 writing them (@pxref{Specify Location}), but the effect is always to
5448 specify some source line.
5450 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5451 to specify that you only want @value{GDBN} to stop the program when a
5452 particular thread reaches this breakpoint. @var{threadno} is one of the
5453 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5454 column of the @samp{info threads} display.
5456 If you do not specify @samp{thread @var{threadno}} when you set a
5457 breakpoint, the breakpoint applies to @emph{all} threads of your
5460 You can use the @code{thread} qualifier on conditional breakpoints as
5461 well; in this case, place @samp{thread @var{threadno}} before or
5462 after the breakpoint condition, like this:
5465 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5470 @node Interrupted System Calls
5471 @subsection Interrupted System Calls
5473 @cindex thread breakpoints and system calls
5474 @cindex system calls and thread breakpoints
5475 @cindex premature return from system calls
5476 There is an unfortunate side effect when using @value{GDBN} to debug
5477 multi-threaded programs. If one thread stops for a
5478 breakpoint, or for some other reason, and another thread is blocked in a
5479 system call, then the system call may return prematurely. This is a
5480 consequence of the interaction between multiple threads and the signals
5481 that @value{GDBN} uses to implement breakpoints and other events that
5484 To handle this problem, your program should check the return value of
5485 each system call and react appropriately. This is good programming
5488 For example, do not write code like this:
5494 The call to @code{sleep} will return early if a different thread stops
5495 at a breakpoint or for some other reason.
5497 Instead, write this:
5502 unslept = sleep (unslept);
5505 A system call is allowed to return early, so the system is still
5506 conforming to its specification. But @value{GDBN} does cause your
5507 multi-threaded program to behave differently than it would without
5510 Also, @value{GDBN} uses internal breakpoints in the thread library to
5511 monitor certain events such as thread creation and thread destruction.
5512 When such an event happens, a system call in another thread may return
5513 prematurely, even though your program does not appear to stop.
5516 @subsection Observer Mode
5518 If you want to build on non-stop mode and observe program behavior
5519 without any chance of disruption by @value{GDBN}, you can set
5520 variables to disable all of the debugger's attempts to modify state,
5521 whether by writing memory, inserting breakpoints, etc. These operate
5522 at a low level, intercepting operations from all commands.
5524 When all of these are set to @code{off}, then @value{GDBN} is said to
5525 be @dfn{observer mode}. As a convenience, the variable
5526 @code{observer} can be set to disable these, plus enable non-stop
5529 Note that @value{GDBN} will not prevent you from making nonsensical
5530 combinations of these settings. For instance, if you have enabled
5531 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5532 then breakpoints that work by writing trap instructions into the code
5533 stream will still not be able to be placed.
5538 @item set observer on
5539 @itemx set observer off
5540 When set to @code{on}, this disables all the permission variables
5541 below (except for @code{insert-fast-tracepoints}), plus enables
5542 non-stop debugging. Setting this to @code{off} switches back to
5543 normal debugging, though remaining in non-stop mode.
5546 Show whether observer mode is on or off.
5548 @kindex may-write-registers
5549 @item set may-write-registers on
5550 @itemx set may-write-registers off
5551 This controls whether @value{GDBN} will attempt to alter the values of
5552 registers, such as with assignment expressions in @code{print}, or the
5553 @code{jump} command. It defaults to @code{on}.
5555 @item show may-write-registers
5556 Show the current permission to write registers.
5558 @kindex may-write-memory
5559 @item set may-write-memory on
5560 @itemx set may-write-memory off
5561 This controls whether @value{GDBN} will attempt to alter the contents
5562 of memory, such as with assignment expressions in @code{print}. It
5563 defaults to @code{on}.
5565 @item show may-write-memory
5566 Show the current permission to write memory.
5568 @kindex may-insert-breakpoints
5569 @item set may-insert-breakpoints on
5570 @itemx set may-insert-breakpoints off
5571 This controls whether @value{GDBN} will attempt to insert breakpoints.
5572 This affects all breakpoints, including internal breakpoints defined
5573 by @value{GDBN}. It defaults to @code{on}.
5575 @item show may-insert-breakpoints
5576 Show the current permission to insert breakpoints.
5578 @kindex may-insert-tracepoints
5579 @item set may-insert-tracepoints on
5580 @itemx set may-insert-tracepoints off
5581 This controls whether @value{GDBN} will attempt to insert (regular)
5582 tracepoints at the beginning of a tracing experiment. It affects only
5583 non-fast tracepoints, fast tracepoints being under the control of
5584 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5586 @item show may-insert-tracepoints
5587 Show the current permission to insert tracepoints.
5589 @kindex may-insert-fast-tracepoints
5590 @item set may-insert-fast-tracepoints on
5591 @itemx set may-insert-fast-tracepoints off
5592 This controls whether @value{GDBN} will attempt to insert fast
5593 tracepoints at the beginning of a tracing experiment. It affects only
5594 fast tracepoints, regular (non-fast) tracepoints being under the
5595 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5597 @item show may-insert-fast-tracepoints
5598 Show the current permission to insert fast tracepoints.
5600 @kindex may-interrupt
5601 @item set may-interrupt on
5602 @itemx set may-interrupt off
5603 This controls whether @value{GDBN} will attempt to interrupt or stop
5604 program execution. When this variable is @code{off}, the
5605 @code{interrupt} command will have no effect, nor will
5606 @kbd{Ctrl-c}. It defaults to @code{on}.
5608 @item show may-interrupt
5609 Show the current permission to interrupt or stop the program.
5613 @node Reverse Execution
5614 @chapter Running programs backward
5615 @cindex reverse execution
5616 @cindex running programs backward
5618 When you are debugging a program, it is not unusual to realize that
5619 you have gone too far, and some event of interest has already happened.
5620 If the target environment supports it, @value{GDBN} can allow you to
5621 ``rewind'' the program by running it backward.
5623 A target environment that supports reverse execution should be able
5624 to ``undo'' the changes in machine state that have taken place as the
5625 program was executing normally. Variables, registers etc.@: should
5626 revert to their previous values. Obviously this requires a great
5627 deal of sophistication on the part of the target environment; not
5628 all target environments can support reverse execution.
5630 When a program is executed in reverse, the instructions that
5631 have most recently been executed are ``un-executed'', in reverse
5632 order. The program counter runs backward, following the previous
5633 thread of execution in reverse. As each instruction is ``un-executed'',
5634 the values of memory and/or registers that were changed by that
5635 instruction are reverted to their previous states. After executing
5636 a piece of source code in reverse, all side effects of that code
5637 should be ``undone'', and all variables should be returned to their
5638 prior values@footnote{
5639 Note that some side effects are easier to undo than others. For instance,
5640 memory and registers are relatively easy, but device I/O is hard. Some
5641 targets may be able undo things like device I/O, and some may not.
5643 The contract between @value{GDBN} and the reverse executing target
5644 requires only that the target do something reasonable when
5645 @value{GDBN} tells it to execute backwards, and then report the
5646 results back to @value{GDBN}. Whatever the target reports back to
5647 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5648 assumes that the memory and registers that the target reports are in a
5649 consistant state, but @value{GDBN} accepts whatever it is given.
5652 If you are debugging in a target environment that supports
5653 reverse execution, @value{GDBN} provides the following commands.
5656 @kindex reverse-continue
5657 @kindex rc @r{(@code{reverse-continue})}
5658 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5659 @itemx rc @r{[}@var{ignore-count}@r{]}
5660 Beginning at the point where your program last stopped, start executing
5661 in reverse. Reverse execution will stop for breakpoints and synchronous
5662 exceptions (signals), just like normal execution. Behavior of
5663 asynchronous signals depends on the target environment.
5665 @kindex reverse-step
5666 @kindex rs @r{(@code{step})}
5667 @item reverse-step @r{[}@var{count}@r{]}
5668 Run the program backward until control reaches the start of a
5669 different source line; then stop it, and return control to @value{GDBN}.
5671 Like the @code{step} command, @code{reverse-step} will only stop
5672 at the beginning of a source line. It ``un-executes'' the previously
5673 executed source line. If the previous source line included calls to
5674 debuggable functions, @code{reverse-step} will step (backward) into
5675 the called function, stopping at the beginning of the @emph{last}
5676 statement in the called function (typically a return statement).
5678 Also, as with the @code{step} command, if non-debuggable functions are
5679 called, @code{reverse-step} will run thru them backward without stopping.
5681 @kindex reverse-stepi
5682 @kindex rsi @r{(@code{reverse-stepi})}
5683 @item reverse-stepi @r{[}@var{count}@r{]}
5684 Reverse-execute one machine instruction. Note that the instruction
5685 to be reverse-executed is @emph{not} the one pointed to by the program
5686 counter, but the instruction executed prior to that one. For instance,
5687 if the last instruction was a jump, @code{reverse-stepi} will take you
5688 back from the destination of the jump to the jump instruction itself.
5690 @kindex reverse-next
5691 @kindex rn @r{(@code{reverse-next})}
5692 @item reverse-next @r{[}@var{count}@r{]}
5693 Run backward to the beginning of the previous line executed in
5694 the current (innermost) stack frame. If the line contains function
5695 calls, they will be ``un-executed'' without stopping. Starting from
5696 the first line of a function, @code{reverse-next} will take you back
5697 to the caller of that function, @emph{before} the function was called,
5698 just as the normal @code{next} command would take you from the last
5699 line of a function back to its return to its caller
5700 @footnote{Unless the code is too heavily optimized.}.
5702 @kindex reverse-nexti
5703 @kindex rni @r{(@code{reverse-nexti})}
5704 @item reverse-nexti @r{[}@var{count}@r{]}
5705 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5706 in reverse, except that called functions are ``un-executed'' atomically.
5707 That is, if the previously executed instruction was a return from
5708 another function, @code{reverse-nexti} will continue to execute
5709 in reverse until the call to that function (from the current stack
5712 @kindex reverse-finish
5713 @item reverse-finish
5714 Just as the @code{finish} command takes you to the point where the
5715 current function returns, @code{reverse-finish} takes you to the point
5716 where it was called. Instead of ending up at the end of the current
5717 function invocation, you end up at the beginning.
5719 @kindex set exec-direction
5720 @item set exec-direction
5721 Set the direction of target execution.
5722 @itemx set exec-direction reverse
5723 @cindex execute forward or backward in time
5724 @value{GDBN} will perform all execution commands in reverse, until the
5725 exec-direction mode is changed to ``forward''. Affected commands include
5726 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5727 command cannot be used in reverse mode.
5728 @item set exec-direction forward
5729 @value{GDBN} will perform all execution commands in the normal fashion.
5730 This is the default.
5734 @node Process Record and Replay
5735 @chapter Recording Inferior's Execution and Replaying It
5736 @cindex process record and replay
5737 @cindex recording inferior's execution and replaying it
5739 On some platforms, @value{GDBN} provides a special @dfn{process record
5740 and replay} target that can record a log of the process execution, and
5741 replay it later with both forward and reverse execution commands.
5744 When this target is in use, if the execution log includes the record
5745 for the next instruction, @value{GDBN} will debug in @dfn{replay
5746 mode}. In the replay mode, the inferior does not really execute code
5747 instructions. Instead, all the events that normally happen during
5748 code execution are taken from the execution log. While code is not
5749 really executed in replay mode, the values of registers (including the
5750 program counter register) and the memory of the inferior are still
5751 changed as they normally would. Their contents are taken from the
5755 If the record for the next instruction is not in the execution log,
5756 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5757 inferior executes normally, and @value{GDBN} records the execution log
5760 The process record and replay target supports reverse execution
5761 (@pxref{Reverse Execution}), even if the platform on which the
5762 inferior runs does not. However, the reverse execution is limited in
5763 this case by the range of the instructions recorded in the execution
5764 log. In other words, reverse execution on platforms that don't
5765 support it directly can only be done in the replay mode.
5767 When debugging in the reverse direction, @value{GDBN} will work in
5768 replay mode as long as the execution log includes the record for the
5769 previous instruction; otherwise, it will work in record mode, if the
5770 platform supports reverse execution, or stop if not.
5772 For architecture environments that support process record and replay,
5773 @value{GDBN} provides the following commands:
5776 @kindex target record
5780 This command starts the process record and replay target. The process
5781 record and replay target can only debug a process that is already
5782 running. Therefore, you need first to start the process with the
5783 @kbd{run} or @kbd{start} commands, and then start the recording with
5784 the @kbd{target record} command.
5786 Both @code{record} and @code{rec} are aliases of @code{target record}.
5788 @cindex displaced stepping, and process record and replay
5789 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5790 will be automatically disabled when process record and replay target
5791 is started. That's because the process record and replay target
5792 doesn't support displaced stepping.
5794 @cindex non-stop mode, and process record and replay
5795 @cindex asynchronous execution, and process record and replay
5796 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5797 the asynchronous execution mode (@pxref{Background Execution}), the
5798 process record and replay target cannot be started because it doesn't
5799 support these two modes.
5804 Stop the process record and replay target. When process record and
5805 replay target stops, the entire execution log will be deleted and the
5806 inferior will either be terminated, or will remain in its final state.
5808 When you stop the process record and replay target in record mode (at
5809 the end of the execution log), the inferior will be stopped at the
5810 next instruction that would have been recorded. In other words, if
5811 you record for a while and then stop recording, the inferior process
5812 will be left in the same state as if the recording never happened.
5814 On the other hand, if the process record and replay target is stopped
5815 while in replay mode (that is, not at the end of the execution log,
5816 but at some earlier point), the inferior process will become ``live''
5817 at that earlier state, and it will then be possible to continue the
5818 usual ``live'' debugging of the process from that state.
5820 When the inferior process exits, or @value{GDBN} detaches from it,
5821 process record and replay target will automatically stop itself.
5824 @item record save @var{filename}
5825 Save the execution log to a file @file{@var{filename}}.
5826 Default filename is @file{gdb_record.@var{process_id}}, where
5827 @var{process_id} is the process ID of the inferior.
5829 @kindex record restore
5830 @item record restore @var{filename}
5831 Restore the execution log from a file @file{@var{filename}}.
5832 File must have been created with @code{record save}.
5834 @kindex set record insn-number-max
5835 @item set record insn-number-max @var{limit}
5836 Set the limit of instructions to be recorded. Default value is 200000.
5838 If @var{limit} is a positive number, then @value{GDBN} will start
5839 deleting instructions from the log once the number of the record
5840 instructions becomes greater than @var{limit}. For every new recorded
5841 instruction, @value{GDBN} will delete the earliest recorded
5842 instruction to keep the number of recorded instructions at the limit.
5843 (Since deleting recorded instructions loses information, @value{GDBN}
5844 lets you control what happens when the limit is reached, by means of
5845 the @code{stop-at-limit} option, described below.)
5847 If @var{limit} is zero, @value{GDBN} will never delete recorded
5848 instructions from the execution log. The number of recorded
5849 instructions is unlimited in this case.
5851 @kindex show record insn-number-max
5852 @item show record insn-number-max
5853 Show the limit of instructions to be recorded.
5855 @kindex set record stop-at-limit
5856 @item set record stop-at-limit
5857 Control the behavior when the number of recorded instructions reaches
5858 the limit. If ON (the default), @value{GDBN} will stop when the limit
5859 is reached for the first time and ask you whether you want to stop the
5860 inferior or continue running it and recording the execution log. If
5861 you decide to continue recording, each new recorded instruction will
5862 cause the oldest one to be deleted.
5864 If this option is OFF, @value{GDBN} will automatically delete the
5865 oldest record to make room for each new one, without asking.
5867 @kindex show record stop-at-limit
5868 @item show record stop-at-limit
5869 Show the current setting of @code{stop-at-limit}.
5871 @kindex set record memory-query
5872 @item set record memory-query
5873 Control the behavior when @value{GDBN} is unable to record memory
5874 changes caused by an instruction. If ON, @value{GDBN} will query
5875 whether to stop the inferior in that case.
5877 If this option is OFF (the default), @value{GDBN} will automatically
5878 ignore the effect of such instructions on memory. Later, when
5879 @value{GDBN} replays this execution log, it will mark the log of this
5880 instruction as not accessible, and it will not affect the replay
5883 @kindex show record memory-query
5884 @item show record memory-query
5885 Show the current setting of @code{memory-query}.
5889 Show various statistics about the state of process record and its
5890 in-memory execution log buffer, including:
5894 Whether in record mode or replay mode.
5896 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
5898 Highest recorded instruction number.
5900 Current instruction about to be replayed (if in replay mode).
5902 Number of instructions contained in the execution log.
5904 Maximum number of instructions that may be contained in the execution log.
5907 @kindex record delete
5910 When record target runs in replay mode (``in the past''), delete the
5911 subsequent execution log and begin to record a new execution log starting
5912 from the current address. This means you will abandon the previously
5913 recorded ``future'' and begin recording a new ``future''.
5918 @chapter Examining the Stack
5920 When your program has stopped, the first thing you need to know is where it
5921 stopped and how it got there.
5924 Each time your program performs a function call, information about the call
5926 That information includes the location of the call in your program,
5927 the arguments of the call,
5928 and the local variables of the function being called.
5929 The information is saved in a block of data called a @dfn{stack frame}.
5930 The stack frames are allocated in a region of memory called the @dfn{call
5933 When your program stops, the @value{GDBN} commands for examining the
5934 stack allow you to see all of this information.
5936 @cindex selected frame
5937 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5938 @value{GDBN} commands refer implicitly to the selected frame. In
5939 particular, whenever you ask @value{GDBN} for the value of a variable in
5940 your program, the value is found in the selected frame. There are
5941 special @value{GDBN} commands to select whichever frame you are
5942 interested in. @xref{Selection, ,Selecting a Frame}.
5944 When your program stops, @value{GDBN} automatically selects the
5945 currently executing frame and describes it briefly, similar to the
5946 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5949 * Frames:: Stack frames
5950 * Backtrace:: Backtraces
5951 * Selection:: Selecting a frame
5952 * Frame Info:: Information on a frame
5957 @section Stack Frames
5959 @cindex frame, definition
5961 The call stack is divided up into contiguous pieces called @dfn{stack
5962 frames}, or @dfn{frames} for short; each frame is the data associated
5963 with one call to one function. The frame contains the arguments given
5964 to the function, the function's local variables, and the address at
5965 which the function is executing.
5967 @cindex initial frame
5968 @cindex outermost frame
5969 @cindex innermost frame
5970 When your program is started, the stack has only one frame, that of the
5971 function @code{main}. This is called the @dfn{initial} frame or the
5972 @dfn{outermost} frame. Each time a function is called, a new frame is
5973 made. Each time a function returns, the frame for that function invocation
5974 is eliminated. If a function is recursive, there can be many frames for
5975 the same function. The frame for the function in which execution is
5976 actually occurring is called the @dfn{innermost} frame. This is the most
5977 recently created of all the stack frames that still exist.
5979 @cindex frame pointer
5980 Inside your program, stack frames are identified by their addresses. A
5981 stack frame consists of many bytes, each of which has its own address; each
5982 kind of computer has a convention for choosing one byte whose
5983 address serves as the address of the frame. Usually this address is kept
5984 in a register called the @dfn{frame pointer register}
5985 (@pxref{Registers, $fp}) while execution is going on in that frame.
5987 @cindex frame number
5988 @value{GDBN} assigns numbers to all existing stack frames, starting with
5989 zero for the innermost frame, one for the frame that called it,
5990 and so on upward. These numbers do not really exist in your program;
5991 they are assigned by @value{GDBN} to give you a way of designating stack
5992 frames in @value{GDBN} commands.
5994 @c The -fomit-frame-pointer below perennially causes hbox overflow
5995 @c underflow problems.
5996 @cindex frameless execution
5997 Some compilers provide a way to compile functions so that they operate
5998 without stack frames. (For example, the @value{NGCC} option
6000 @samp{-fomit-frame-pointer}
6002 generates functions without a frame.)
6003 This is occasionally done with heavily used library functions to save
6004 the frame setup time. @value{GDBN} has limited facilities for dealing
6005 with these function invocations. If the innermost function invocation
6006 has no stack frame, @value{GDBN} nevertheless regards it as though
6007 it had a separate frame, which is numbered zero as usual, allowing
6008 correct tracing of the function call chain. However, @value{GDBN} has
6009 no provision for frameless functions elsewhere in the stack.
6012 @kindex frame@r{, command}
6013 @cindex current stack frame
6014 @item frame @var{args}
6015 The @code{frame} command allows you to move from one stack frame to another,
6016 and to print the stack frame you select. @var{args} may be either the
6017 address of the frame or the stack frame number. Without an argument,
6018 @code{frame} prints the current stack frame.
6020 @kindex select-frame
6021 @cindex selecting frame silently
6023 The @code{select-frame} command allows you to move from one stack frame
6024 to another without printing the frame. This is the silent version of
6032 @cindex call stack traces
6033 A backtrace is a summary of how your program got where it is. It shows one
6034 line per frame, for many frames, starting with the currently executing
6035 frame (frame zero), followed by its caller (frame one), and on up the
6040 @kindex bt @r{(@code{backtrace})}
6043 Print a backtrace of the entire stack: one line per frame for all
6044 frames in the stack.
6046 You can stop the backtrace at any time by typing the system interrupt
6047 character, normally @kbd{Ctrl-c}.
6049 @item backtrace @var{n}
6051 Similar, but print only the innermost @var{n} frames.
6053 @item backtrace -@var{n}
6055 Similar, but print only the outermost @var{n} frames.
6057 @item backtrace full
6059 @itemx bt full @var{n}
6060 @itemx bt full -@var{n}
6061 Print the values of the local variables also. @var{n} specifies the
6062 number of frames to print, as described above.
6067 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6068 are additional aliases for @code{backtrace}.
6070 @cindex multiple threads, backtrace
6071 In a multi-threaded program, @value{GDBN} by default shows the
6072 backtrace only for the current thread. To display the backtrace for
6073 several or all of the threads, use the command @code{thread apply}
6074 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6075 apply all backtrace}, @value{GDBN} will display the backtrace for all
6076 the threads; this is handy when you debug a core dump of a
6077 multi-threaded program.
6079 Each line in the backtrace shows the frame number and the function name.
6080 The program counter value is also shown---unless you use @code{set
6081 print address off}. The backtrace also shows the source file name and
6082 line number, as well as the arguments to the function. The program
6083 counter value is omitted if it is at the beginning of the code for that
6086 Here is an example of a backtrace. It was made with the command
6087 @samp{bt 3}, so it shows the innermost three frames.
6091 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6093 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6094 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6096 (More stack frames follow...)
6101 The display for frame zero does not begin with a program counter
6102 value, indicating that your program has stopped at the beginning of the
6103 code for line @code{993} of @code{builtin.c}.
6106 The value of parameter @code{data} in frame 1 has been replaced by
6107 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6108 only if it is a scalar (integer, pointer, enumeration, etc). See command
6109 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6110 on how to configure the way function parameter values are printed.
6112 @cindex optimized out, in backtrace
6113 @cindex function call arguments, optimized out
6114 If your program was compiled with optimizations, some compilers will
6115 optimize away arguments passed to functions if those arguments are
6116 never used after the call. Such optimizations generate code that
6117 passes arguments through registers, but doesn't store those arguments
6118 in the stack frame. @value{GDBN} has no way of displaying such
6119 arguments in stack frames other than the innermost one. Here's what
6120 such a backtrace might look like:
6124 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6126 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6127 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6129 (More stack frames follow...)
6134 The values of arguments that were not saved in their stack frames are
6135 shown as @samp{<optimized out>}.
6137 If you need to display the values of such optimized-out arguments,
6138 either deduce that from other variables whose values depend on the one
6139 you are interested in, or recompile without optimizations.
6141 @cindex backtrace beyond @code{main} function
6142 @cindex program entry point
6143 @cindex startup code, and backtrace
6144 Most programs have a standard user entry point---a place where system
6145 libraries and startup code transition into user code. For C this is
6146 @code{main}@footnote{
6147 Note that embedded programs (the so-called ``free-standing''
6148 environment) are not required to have a @code{main} function as the
6149 entry point. They could even have multiple entry points.}.
6150 When @value{GDBN} finds the entry function in a backtrace
6151 it will terminate the backtrace, to avoid tracing into highly
6152 system-specific (and generally uninteresting) code.
6154 If you need to examine the startup code, or limit the number of levels
6155 in a backtrace, you can change this behavior:
6158 @item set backtrace past-main
6159 @itemx set backtrace past-main on
6160 @kindex set backtrace
6161 Backtraces will continue past the user entry point.
6163 @item set backtrace past-main off
6164 Backtraces will stop when they encounter the user entry point. This is the
6167 @item show backtrace past-main
6168 @kindex show backtrace
6169 Display the current user entry point backtrace policy.
6171 @item set backtrace past-entry
6172 @itemx set backtrace past-entry on
6173 Backtraces will continue past the internal entry point of an application.
6174 This entry point is encoded by the linker when the application is built,
6175 and is likely before the user entry point @code{main} (or equivalent) is called.
6177 @item set backtrace past-entry off
6178 Backtraces will stop when they encounter the internal entry point of an
6179 application. This is the default.
6181 @item show backtrace past-entry
6182 Display the current internal entry point backtrace policy.
6184 @item set backtrace limit @var{n}
6185 @itemx set backtrace limit 0
6186 @cindex backtrace limit
6187 Limit the backtrace to @var{n} levels. A value of zero means
6190 @item show backtrace limit
6191 Display the current limit on backtrace levels.
6195 @section Selecting a Frame
6197 Most commands for examining the stack and other data in your program work on
6198 whichever stack frame is selected at the moment. Here are the commands for
6199 selecting a stack frame; all of them finish by printing a brief description
6200 of the stack frame just selected.
6203 @kindex frame@r{, selecting}
6204 @kindex f @r{(@code{frame})}
6207 Select frame number @var{n}. Recall that frame zero is the innermost
6208 (currently executing) frame, frame one is the frame that called the
6209 innermost one, and so on. The highest-numbered frame is the one for
6212 @item frame @var{addr}
6214 Select the frame at address @var{addr}. This is useful mainly if the
6215 chaining of stack frames has been damaged by a bug, making it
6216 impossible for @value{GDBN} to assign numbers properly to all frames. In
6217 addition, this can be useful when your program has multiple stacks and
6218 switches between them.
6220 On the SPARC architecture, @code{frame} needs two addresses to
6221 select an arbitrary frame: a frame pointer and a stack pointer.
6223 On the MIPS and Alpha architecture, it needs two addresses: a stack
6224 pointer and a program counter.
6226 On the 29k architecture, it needs three addresses: a register stack
6227 pointer, a program counter, and a memory stack pointer.
6231 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6232 advances toward the outermost frame, to higher frame numbers, to frames
6233 that have existed longer. @var{n} defaults to one.
6236 @kindex do @r{(@code{down})}
6238 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6239 advances toward the innermost frame, to lower frame numbers, to frames
6240 that were created more recently. @var{n} defaults to one. You may
6241 abbreviate @code{down} as @code{do}.
6244 All of these commands end by printing two lines of output describing the
6245 frame. The first line shows the frame number, the function name, the
6246 arguments, and the source file and line number of execution in that
6247 frame. The second line shows the text of that source line.
6255 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6257 10 read_input_file (argv[i]);
6261 After such a printout, the @code{list} command with no arguments
6262 prints ten lines centered on the point of execution in the frame.
6263 You can also edit the program at the point of execution with your favorite
6264 editing program by typing @code{edit}.
6265 @xref{List, ,Printing Source Lines},
6269 @kindex down-silently
6271 @item up-silently @var{n}
6272 @itemx down-silently @var{n}
6273 These two commands are variants of @code{up} and @code{down},
6274 respectively; they differ in that they do their work silently, without
6275 causing display of the new frame. They are intended primarily for use
6276 in @value{GDBN} command scripts, where the output might be unnecessary and
6281 @section Information About a Frame
6283 There are several other commands to print information about the selected
6289 When used without any argument, this command does not change which
6290 frame is selected, but prints a brief description of the currently
6291 selected stack frame. It can be abbreviated @code{f}. With an
6292 argument, this command is used to select a stack frame.
6293 @xref{Selection, ,Selecting a Frame}.
6296 @kindex info f @r{(@code{info frame})}
6299 This command prints a verbose description of the selected stack frame,
6304 the address of the frame
6306 the address of the next frame down (called by this frame)
6308 the address of the next frame up (caller of this frame)
6310 the language in which the source code corresponding to this frame is written
6312 the address of the frame's arguments
6314 the address of the frame's local variables
6316 the program counter saved in it (the address of execution in the caller frame)
6318 which registers were saved in the frame
6321 @noindent The verbose description is useful when
6322 something has gone wrong that has made the stack format fail to fit
6323 the usual conventions.
6325 @item info frame @var{addr}
6326 @itemx info f @var{addr}
6327 Print a verbose description of the frame at address @var{addr}, without
6328 selecting that frame. The selected frame remains unchanged by this
6329 command. This requires the same kind of address (more than one for some
6330 architectures) that you specify in the @code{frame} command.
6331 @xref{Selection, ,Selecting a Frame}.
6335 Print the arguments of the selected frame, each on a separate line.
6339 Print the local variables of the selected frame, each on a separate
6340 line. These are all variables (declared either static or automatic)
6341 accessible at the point of execution of the selected frame.
6344 @cindex catch exceptions, list active handlers
6345 @cindex exception handlers, how to list
6347 Print a list of all the exception handlers that are active in the
6348 current stack frame at the current point of execution. To see other
6349 exception handlers, visit the associated frame (using the @code{up},
6350 @code{down}, or @code{frame} commands); then type @code{info catch}.
6351 @xref{Set Catchpoints, , Setting Catchpoints}.
6357 @chapter Examining Source Files
6359 @value{GDBN} can print parts of your program's source, since the debugging
6360 information recorded in the program tells @value{GDBN} what source files were
6361 used to build it. When your program stops, @value{GDBN} spontaneously prints
6362 the line where it stopped. Likewise, when you select a stack frame
6363 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6364 execution in that frame has stopped. You can print other portions of
6365 source files by explicit command.
6367 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6368 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6369 @value{GDBN} under @sc{gnu} Emacs}.
6372 * List:: Printing source lines
6373 * Specify Location:: How to specify code locations
6374 * Edit:: Editing source files
6375 * Search:: Searching source files
6376 * Source Path:: Specifying source directories
6377 * Machine Code:: Source and machine code
6381 @section Printing Source Lines
6384 @kindex l @r{(@code{list})}
6385 To print lines from a source file, use the @code{list} command
6386 (abbreviated @code{l}). By default, ten lines are printed.
6387 There are several ways to specify what part of the file you want to
6388 print; see @ref{Specify Location}, for the full list.
6390 Here are the forms of the @code{list} command most commonly used:
6393 @item list @var{linenum}
6394 Print lines centered around line number @var{linenum} in the
6395 current source file.
6397 @item list @var{function}
6398 Print lines centered around the beginning of function
6402 Print more lines. If the last lines printed were printed with a
6403 @code{list} command, this prints lines following the last lines
6404 printed; however, if the last line printed was a solitary line printed
6405 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6406 Stack}), this prints lines centered around that line.
6409 Print lines just before the lines last printed.
6412 @cindex @code{list}, how many lines to display
6413 By default, @value{GDBN} prints ten source lines with any of these forms of
6414 the @code{list} command. You can change this using @code{set listsize}:
6417 @kindex set listsize
6418 @item set listsize @var{count}
6419 Make the @code{list} command display @var{count} source lines (unless
6420 the @code{list} argument explicitly specifies some other number).
6422 @kindex show listsize
6424 Display the number of lines that @code{list} prints.
6427 Repeating a @code{list} command with @key{RET} discards the argument,
6428 so it is equivalent to typing just @code{list}. This is more useful
6429 than listing the same lines again. An exception is made for an
6430 argument of @samp{-}; that argument is preserved in repetition so that
6431 each repetition moves up in the source file.
6433 In general, the @code{list} command expects you to supply zero, one or two
6434 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6435 of writing them (@pxref{Specify Location}), but the effect is always
6436 to specify some source line.
6438 Here is a complete description of the possible arguments for @code{list}:
6441 @item list @var{linespec}
6442 Print lines centered around the line specified by @var{linespec}.
6444 @item list @var{first},@var{last}
6445 Print lines from @var{first} to @var{last}. Both arguments are
6446 linespecs. When a @code{list} command has two linespecs, and the
6447 source file of the second linespec is omitted, this refers to
6448 the same source file as the first linespec.
6450 @item list ,@var{last}
6451 Print lines ending with @var{last}.
6453 @item list @var{first},
6454 Print lines starting with @var{first}.
6457 Print lines just after the lines last printed.
6460 Print lines just before the lines last printed.
6463 As described in the preceding table.
6466 @node Specify Location
6467 @section Specifying a Location
6468 @cindex specifying location
6471 Several @value{GDBN} commands accept arguments that specify a location
6472 of your program's code. Since @value{GDBN} is a source-level
6473 debugger, a location usually specifies some line in the source code;
6474 for that reason, locations are also known as @dfn{linespecs}.
6476 Here are all the different ways of specifying a code location that
6477 @value{GDBN} understands:
6481 Specifies the line number @var{linenum} of the current source file.
6484 @itemx +@var{offset}
6485 Specifies the line @var{offset} lines before or after the @dfn{current
6486 line}. For the @code{list} command, the current line is the last one
6487 printed; for the breakpoint commands, this is the line at which
6488 execution stopped in the currently selected @dfn{stack frame}
6489 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6490 used as the second of the two linespecs in a @code{list} command,
6491 this specifies the line @var{offset} lines up or down from the first
6494 @item @var{filename}:@var{linenum}
6495 Specifies the line @var{linenum} in the source file @var{filename}.
6497 @item @var{function}
6498 Specifies the line that begins the body of the function @var{function}.
6499 For example, in C, this is the line with the open brace.
6501 @item @var{function}:@var{label}
6502 Specifies the line where @var{label} appears in @var{function}.
6504 @item @var{filename}:@var{function}
6505 Specifies the line that begins the body of the function @var{function}
6506 in the file @var{filename}. You only need the file name with a
6507 function name to avoid ambiguity when there are identically named
6508 functions in different source files.
6511 Specifies the line at which the label named @var{label} appears.
6512 @value{GDBN} searches for the label in the function corresponding to
6513 the currently selected stack frame. If there is no current selected
6514 stack frame (for instance, if the inferior is not running), then
6515 @value{GDBN} will not search for a label.
6517 @item *@var{address}
6518 Specifies the program address @var{address}. For line-oriented
6519 commands, such as @code{list} and @code{edit}, this specifies a source
6520 line that contains @var{address}. For @code{break} and other
6521 breakpoint oriented commands, this can be used to set breakpoints in
6522 parts of your program which do not have debugging information or
6525 Here @var{address} may be any expression valid in the current working
6526 language (@pxref{Languages, working language}) that specifies a code
6527 address. In addition, as a convenience, @value{GDBN} extends the
6528 semantics of expressions used in locations to cover the situations
6529 that frequently happen during debugging. Here are the various forms
6533 @item @var{expression}
6534 Any expression valid in the current working language.
6536 @item @var{funcaddr}
6537 An address of a function or procedure derived from its name. In C,
6538 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6539 simply the function's name @var{function} (and actually a special case
6540 of a valid expression). In Pascal and Modula-2, this is
6541 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6542 (although the Pascal form also works).
6544 This form specifies the address of the function's first instruction,
6545 before the stack frame and arguments have been set up.
6547 @item '@var{filename}'::@var{funcaddr}
6548 Like @var{funcaddr} above, but also specifies the name of the source
6549 file explicitly. This is useful if the name of the function does not
6550 specify the function unambiguously, e.g., if there are several
6551 functions with identical names in different source files.
6558 @section Editing Source Files
6559 @cindex editing source files
6562 @kindex e @r{(@code{edit})}
6563 To edit the lines in a source file, use the @code{edit} command.
6564 The editing program of your choice
6565 is invoked with the current line set to
6566 the active line in the program.
6567 Alternatively, there are several ways to specify what part of the file you
6568 want to print if you want to see other parts of the program:
6571 @item edit @var{location}
6572 Edit the source file specified by @code{location}. Editing starts at
6573 that @var{location}, e.g., at the specified source line of the
6574 specified file. @xref{Specify Location}, for all the possible forms
6575 of the @var{location} argument; here are the forms of the @code{edit}
6576 command most commonly used:
6579 @item edit @var{number}
6580 Edit the current source file with @var{number} as the active line number.
6582 @item edit @var{function}
6583 Edit the file containing @var{function} at the beginning of its definition.
6588 @subsection Choosing your Editor
6589 You can customize @value{GDBN} to use any editor you want
6591 The only restriction is that your editor (say @code{ex}), recognizes the
6592 following command-line syntax:
6594 ex +@var{number} file
6596 The optional numeric value +@var{number} specifies the number of the line in
6597 the file where to start editing.}.
6598 By default, it is @file{@value{EDITOR}}, but you can change this
6599 by setting the environment variable @code{EDITOR} before using
6600 @value{GDBN}. For example, to configure @value{GDBN} to use the
6601 @code{vi} editor, you could use these commands with the @code{sh} shell:
6607 or in the @code{csh} shell,
6609 setenv EDITOR /usr/bin/vi
6614 @section Searching Source Files
6615 @cindex searching source files
6617 There are two commands for searching through the current source file for a
6622 @kindex forward-search
6623 @item forward-search @var{regexp}
6624 @itemx search @var{regexp}
6625 The command @samp{forward-search @var{regexp}} checks each line,
6626 starting with the one following the last line listed, for a match for
6627 @var{regexp}. It lists the line that is found. You can use the
6628 synonym @samp{search @var{regexp}} or abbreviate the command name as
6631 @kindex reverse-search
6632 @item reverse-search @var{regexp}
6633 The command @samp{reverse-search @var{regexp}} checks each line, starting
6634 with the one before the last line listed and going backward, for a match
6635 for @var{regexp}. It lists the line that is found. You can abbreviate
6636 this command as @code{rev}.
6640 @section Specifying Source Directories
6643 @cindex directories for source files
6644 Executable programs sometimes do not record the directories of the source
6645 files from which they were compiled, just the names. Even when they do,
6646 the directories could be moved between the compilation and your debugging
6647 session. @value{GDBN} has a list of directories to search for source files;
6648 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6649 it tries all the directories in the list, in the order they are present
6650 in the list, until it finds a file with the desired name.
6652 For example, suppose an executable references the file
6653 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6654 @file{/mnt/cross}. The file is first looked up literally; if this
6655 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6656 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6657 message is printed. @value{GDBN} does not look up the parts of the
6658 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6659 Likewise, the subdirectories of the source path are not searched: if
6660 the source path is @file{/mnt/cross}, and the binary refers to
6661 @file{foo.c}, @value{GDBN} would not find it under
6662 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6664 Plain file names, relative file names with leading directories, file
6665 names containing dots, etc.@: are all treated as described above; for
6666 instance, if the source path is @file{/mnt/cross}, and the source file
6667 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6668 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6669 that---@file{/mnt/cross/foo.c}.
6671 Note that the executable search path is @emph{not} used to locate the
6674 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6675 any information it has cached about where source files are found and where
6676 each line is in the file.
6680 When you start @value{GDBN}, its source path includes only @samp{cdir}
6681 and @samp{cwd}, in that order.
6682 To add other directories, use the @code{directory} command.
6684 The search path is used to find both program source files and @value{GDBN}
6685 script files (read using the @samp{-command} option and @samp{source} command).
6687 In addition to the source path, @value{GDBN} provides a set of commands
6688 that manage a list of source path substitution rules. A @dfn{substitution
6689 rule} specifies how to rewrite source directories stored in the program's
6690 debug information in case the sources were moved to a different
6691 directory between compilation and debugging. A rule is made of
6692 two strings, the first specifying what needs to be rewritten in
6693 the path, and the second specifying how it should be rewritten.
6694 In @ref{set substitute-path}, we name these two parts @var{from} and
6695 @var{to} respectively. @value{GDBN} does a simple string replacement
6696 of @var{from} with @var{to} at the start of the directory part of the
6697 source file name, and uses that result instead of the original file
6698 name to look up the sources.
6700 Using the previous example, suppose the @file{foo-1.0} tree has been
6701 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6702 @value{GDBN} to replace @file{/usr/src} in all source path names with
6703 @file{/mnt/cross}. The first lookup will then be
6704 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6705 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6706 substitution rule, use the @code{set substitute-path} command
6707 (@pxref{set substitute-path}).
6709 To avoid unexpected substitution results, a rule is applied only if the
6710 @var{from} part of the directory name ends at a directory separator.
6711 For instance, a rule substituting @file{/usr/source} into
6712 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6713 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6714 is applied only at the beginning of the directory name, this rule will
6715 not be applied to @file{/root/usr/source/baz.c} either.
6717 In many cases, you can achieve the same result using the @code{directory}
6718 command. However, @code{set substitute-path} can be more efficient in
6719 the case where the sources are organized in a complex tree with multiple
6720 subdirectories. With the @code{directory} command, you need to add each
6721 subdirectory of your project. If you moved the entire tree while
6722 preserving its internal organization, then @code{set substitute-path}
6723 allows you to direct the debugger to all the sources with one single
6726 @code{set substitute-path} is also more than just a shortcut command.
6727 The source path is only used if the file at the original location no
6728 longer exists. On the other hand, @code{set substitute-path} modifies
6729 the debugger behavior to look at the rewritten location instead. So, if
6730 for any reason a source file that is not relevant to your executable is
6731 located at the original location, a substitution rule is the only
6732 method available to point @value{GDBN} at the new location.
6734 @cindex @samp{--with-relocated-sources}
6735 @cindex default source path substitution
6736 You can configure a default source path substitution rule by
6737 configuring @value{GDBN} with the
6738 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6739 should be the name of a directory under @value{GDBN}'s configured
6740 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6741 directory names in debug information under @var{dir} will be adjusted
6742 automatically if the installed @value{GDBN} is moved to a new
6743 location. This is useful if @value{GDBN}, libraries or executables
6744 with debug information and corresponding source code are being moved
6748 @item directory @var{dirname} @dots{}
6749 @item dir @var{dirname} @dots{}
6750 Add directory @var{dirname} to the front of the source path. Several
6751 directory names may be given to this command, separated by @samp{:}
6752 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6753 part of absolute file names) or
6754 whitespace. You may specify a directory that is already in the source
6755 path; this moves it forward, so @value{GDBN} searches it sooner.
6759 @vindex $cdir@r{, convenience variable}
6760 @vindex $cwd@r{, convenience variable}
6761 @cindex compilation directory
6762 @cindex current directory
6763 @cindex working directory
6764 @cindex directory, current
6765 @cindex directory, compilation
6766 You can use the string @samp{$cdir} to refer to the compilation
6767 directory (if one is recorded), and @samp{$cwd} to refer to the current
6768 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6769 tracks the current working directory as it changes during your @value{GDBN}
6770 session, while the latter is immediately expanded to the current
6771 directory at the time you add an entry to the source path.
6774 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6776 @c RET-repeat for @code{directory} is explicitly disabled, but since
6777 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6779 @item set directories @var{path-list}
6780 @kindex set directories
6781 Set the source path to @var{path-list}.
6782 @samp{$cdir:$cwd} are added if missing.
6784 @item show directories
6785 @kindex show directories
6786 Print the source path: show which directories it contains.
6788 @anchor{set substitute-path}
6789 @item set substitute-path @var{from} @var{to}
6790 @kindex set substitute-path
6791 Define a source path substitution rule, and add it at the end of the
6792 current list of existing substitution rules. If a rule with the same
6793 @var{from} was already defined, then the old rule is also deleted.
6795 For example, if the file @file{/foo/bar/baz.c} was moved to
6796 @file{/mnt/cross/baz.c}, then the command
6799 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6803 will tell @value{GDBN} to replace @samp{/usr/src} with
6804 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6805 @file{baz.c} even though it was moved.
6807 In the case when more than one substitution rule have been defined,
6808 the rules are evaluated one by one in the order where they have been
6809 defined. The first one matching, if any, is selected to perform
6812 For instance, if we had entered the following commands:
6815 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6816 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6820 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6821 @file{/mnt/include/defs.h} by using the first rule. However, it would
6822 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6823 @file{/mnt/src/lib/foo.c}.
6826 @item unset substitute-path [path]
6827 @kindex unset substitute-path
6828 If a path is specified, search the current list of substitution rules
6829 for a rule that would rewrite that path. Delete that rule if found.
6830 A warning is emitted by the debugger if no rule could be found.
6832 If no path is specified, then all substitution rules are deleted.
6834 @item show substitute-path [path]
6835 @kindex show substitute-path
6836 If a path is specified, then print the source path substitution rule
6837 which would rewrite that path, if any.
6839 If no path is specified, then print all existing source path substitution
6844 If your source path is cluttered with directories that are no longer of
6845 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6846 versions of source. You can correct the situation as follows:
6850 Use @code{directory} with no argument to reset the source path to its default value.
6853 Use @code{directory} with suitable arguments to reinstall the
6854 directories you want in the source path. You can add all the
6855 directories in one command.
6859 @section Source and Machine Code
6860 @cindex source line and its code address
6862 You can use the command @code{info line} to map source lines to program
6863 addresses (and vice versa), and the command @code{disassemble} to display
6864 a range of addresses as machine instructions. You can use the command
6865 @code{set disassemble-next-line} to set whether to disassemble next
6866 source line when execution stops. When run under @sc{gnu} Emacs
6867 mode, the @code{info line} command causes the arrow to point to the
6868 line specified. Also, @code{info line} prints addresses in symbolic form as
6873 @item info line @var{linespec}
6874 Print the starting and ending addresses of the compiled code for
6875 source line @var{linespec}. You can specify source lines in any of
6876 the ways documented in @ref{Specify Location}.
6879 For example, we can use @code{info line} to discover the location of
6880 the object code for the first line of function
6881 @code{m4_changequote}:
6883 @c FIXME: I think this example should also show the addresses in
6884 @c symbolic form, as they usually would be displayed.
6886 (@value{GDBP}) info line m4_changequote
6887 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6891 @cindex code address and its source line
6892 We can also inquire (using @code{*@var{addr}} as the form for
6893 @var{linespec}) what source line covers a particular address:
6895 (@value{GDBP}) info line *0x63ff
6896 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6899 @cindex @code{$_} and @code{info line}
6900 @cindex @code{x} command, default address
6901 @kindex x@r{(examine), and} info line
6902 After @code{info line}, the default address for the @code{x} command
6903 is changed to the starting address of the line, so that @samp{x/i} is
6904 sufficient to begin examining the machine code (@pxref{Memory,
6905 ,Examining Memory}). Also, this address is saved as the value of the
6906 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6911 @cindex assembly instructions
6912 @cindex instructions, assembly
6913 @cindex machine instructions
6914 @cindex listing machine instructions
6916 @itemx disassemble /m
6917 @itemx disassemble /r
6918 This specialized command dumps a range of memory as machine
6919 instructions. It can also print mixed source+disassembly by specifying
6920 the @code{/m} modifier and print the raw instructions in hex as well as
6921 in symbolic form by specifying the @code{/r}.
6922 The default memory range is the function surrounding the
6923 program counter of the selected frame. A single argument to this
6924 command is a program counter value; @value{GDBN} dumps the function
6925 surrounding this value. When two arguments are given, they should
6926 be separated by a comma, possibly surrounded by whitespace. The
6927 arguments specify a range of addresses to dump, in one of two forms:
6930 @item @var{start},@var{end}
6931 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
6932 @item @var{start},+@var{length}
6933 the addresses from @var{start} (inclusive) to
6934 @code{@var{start}+@var{length}} (exclusive).
6938 When 2 arguments are specified, the name of the function is also
6939 printed (since there could be several functions in the given range).
6941 The argument(s) can be any expression yielding a numeric value, such as
6942 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
6944 If the range of memory being disassembled contains current program counter,
6945 the instruction at that location is shown with a @code{=>} marker.
6948 The following example shows the disassembly of a range of addresses of
6949 HP PA-RISC 2.0 code:
6952 (@value{GDBP}) disas 0x32c4, 0x32e4
6953 Dump of assembler code from 0x32c4 to 0x32e4:
6954 0x32c4 <main+204>: addil 0,dp
6955 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6956 0x32cc <main+212>: ldil 0x3000,r31
6957 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6958 0x32d4 <main+220>: ldo 0(r31),rp
6959 0x32d8 <main+224>: addil -0x800,dp
6960 0x32dc <main+228>: ldo 0x588(r1),r26
6961 0x32e0 <main+232>: ldil 0x3000,r31
6962 End of assembler dump.
6965 Here is an example showing mixed source+assembly for Intel x86, when the
6966 program is stopped just after function prologue:
6969 (@value{GDBP}) disas /m main
6970 Dump of assembler code for function main:
6972 0x08048330 <+0>: push %ebp
6973 0x08048331 <+1>: mov %esp,%ebp
6974 0x08048333 <+3>: sub $0x8,%esp
6975 0x08048336 <+6>: and $0xfffffff0,%esp
6976 0x08048339 <+9>: sub $0x10,%esp
6978 6 printf ("Hello.\n");
6979 => 0x0804833c <+12>: movl $0x8048440,(%esp)
6980 0x08048343 <+19>: call 0x8048284 <puts@@plt>
6984 0x08048348 <+24>: mov $0x0,%eax
6985 0x0804834d <+29>: leave
6986 0x0804834e <+30>: ret
6988 End of assembler dump.
6991 Here is another example showing raw instructions in hex for AMD x86-64,
6994 (gdb) disas /r 0x400281,+10
6995 Dump of assembler code from 0x400281 to 0x40028b:
6996 0x0000000000400281: 38 36 cmp %dh,(%rsi)
6997 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
6998 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
6999 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7000 End of assembler dump.
7003 Some architectures have more than one commonly-used set of instruction
7004 mnemonics or other syntax.
7006 For programs that were dynamically linked and use shared libraries,
7007 instructions that call functions or branch to locations in the shared
7008 libraries might show a seemingly bogus location---it's actually a
7009 location of the relocation table. On some architectures, @value{GDBN}
7010 might be able to resolve these to actual function names.
7013 @kindex set disassembly-flavor
7014 @cindex Intel disassembly flavor
7015 @cindex AT&T disassembly flavor
7016 @item set disassembly-flavor @var{instruction-set}
7017 Select the instruction set to use when disassembling the
7018 program via the @code{disassemble} or @code{x/i} commands.
7020 Currently this command is only defined for the Intel x86 family. You
7021 can set @var{instruction-set} to either @code{intel} or @code{att}.
7022 The default is @code{att}, the AT&T flavor used by default by Unix
7023 assemblers for x86-based targets.
7025 @kindex show disassembly-flavor
7026 @item show disassembly-flavor
7027 Show the current setting of the disassembly flavor.
7031 @kindex set disassemble-next-line
7032 @kindex show disassemble-next-line
7033 @item set disassemble-next-line
7034 @itemx show disassemble-next-line
7035 Control whether or not @value{GDBN} will disassemble the next source
7036 line or instruction when execution stops. If ON, @value{GDBN} will
7037 display disassembly of the next source line when execution of the
7038 program being debugged stops. This is @emph{in addition} to
7039 displaying the source line itself, which @value{GDBN} always does if
7040 possible. If the next source line cannot be displayed for some reason
7041 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7042 info in the debug info), @value{GDBN} will display disassembly of the
7043 next @emph{instruction} instead of showing the next source line. If
7044 AUTO, @value{GDBN} will display disassembly of next instruction only
7045 if the source line cannot be displayed. This setting causes
7046 @value{GDBN} to display some feedback when you step through a function
7047 with no line info or whose source file is unavailable. The default is
7048 OFF, which means never display the disassembly of the next line or
7054 @chapter Examining Data
7056 @cindex printing data
7057 @cindex examining data
7060 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
7061 @c document because it is nonstandard... Under Epoch it displays in a
7062 @c different window or something like that.
7063 The usual way to examine data in your program is with the @code{print}
7064 command (abbreviated @code{p}), or its synonym @code{inspect}. It
7065 evaluates and prints the value of an expression of the language your
7066 program is written in (@pxref{Languages, ,Using @value{GDBN} with
7067 Different Languages}). It may also print the expression using a
7068 Python-based pretty-printer (@pxref{Pretty Printing}).
7071 @item print @var{expr}
7072 @itemx print /@var{f} @var{expr}
7073 @var{expr} is an expression (in the source language). By default the
7074 value of @var{expr} is printed in a format appropriate to its data type;
7075 you can choose a different format by specifying @samp{/@var{f}}, where
7076 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
7080 @itemx print /@var{f}
7081 @cindex reprint the last value
7082 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
7083 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
7084 conveniently inspect the same value in an alternative format.
7087 A more low-level way of examining data is with the @code{x} command.
7088 It examines data in memory at a specified address and prints it in a
7089 specified format. @xref{Memory, ,Examining Memory}.
7091 If you are interested in information about types, or about how the
7092 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
7093 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
7097 * Expressions:: Expressions
7098 * Ambiguous Expressions:: Ambiguous Expressions
7099 * Variables:: Program variables
7100 * Arrays:: Artificial arrays
7101 * Output Formats:: Output formats
7102 * Memory:: Examining memory
7103 * Auto Display:: Automatic display
7104 * Print Settings:: Print settings
7105 * Pretty Printing:: Python pretty printing
7106 * Value History:: Value history
7107 * Convenience Vars:: Convenience variables
7108 * Registers:: Registers
7109 * Floating Point Hardware:: Floating point hardware
7110 * Vector Unit:: Vector Unit
7111 * OS Information:: Auxiliary data provided by operating system
7112 * Memory Region Attributes:: Memory region attributes
7113 * Dump/Restore Files:: Copy between memory and a file
7114 * Core File Generation:: Cause a program dump its core
7115 * Character Sets:: Debugging programs that use a different
7116 character set than GDB does
7117 * Caching Remote Data:: Data caching for remote targets
7118 * Searching Memory:: Searching memory for a sequence of bytes
7122 @section Expressions
7125 @code{print} and many other @value{GDBN} commands accept an expression and
7126 compute its value. Any kind of constant, variable or operator defined
7127 by the programming language you are using is valid in an expression in
7128 @value{GDBN}. This includes conditional expressions, function calls,
7129 casts, and string constants. It also includes preprocessor macros, if
7130 you compiled your program to include this information; see
7133 @cindex arrays in expressions
7134 @value{GDBN} supports array constants in expressions input by
7135 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
7136 you can use the command @code{print @{1, 2, 3@}} to create an array
7137 of three integers. If you pass an array to a function or assign it
7138 to a program variable, @value{GDBN} copies the array to memory that
7139 is @code{malloc}ed in the target program.
7141 Because C is so widespread, most of the expressions shown in examples in
7142 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
7143 Languages}, for information on how to use expressions in other
7146 In this section, we discuss operators that you can use in @value{GDBN}
7147 expressions regardless of your programming language.
7149 @cindex casts, in expressions
7150 Casts are supported in all languages, not just in C, because it is so
7151 useful to cast a number into a pointer in order to examine a structure
7152 at that address in memory.
7153 @c FIXME: casts supported---Mod2 true?
7155 @value{GDBN} supports these operators, in addition to those common
7156 to programming languages:
7160 @samp{@@} is a binary operator for treating parts of memory as arrays.
7161 @xref{Arrays, ,Artificial Arrays}, for more information.
7164 @samp{::} allows you to specify a variable in terms of the file or
7165 function where it is defined. @xref{Variables, ,Program Variables}.
7167 @cindex @{@var{type}@}
7168 @cindex type casting memory
7169 @cindex memory, viewing as typed object
7170 @cindex casts, to view memory
7171 @item @{@var{type}@} @var{addr}
7172 Refers to an object of type @var{type} stored at address @var{addr} in
7173 memory. @var{addr} may be any expression whose value is an integer or
7174 pointer (but parentheses are required around binary operators, just as in
7175 a cast). This construct is allowed regardless of what kind of data is
7176 normally supposed to reside at @var{addr}.
7179 @node Ambiguous Expressions
7180 @section Ambiguous Expressions
7181 @cindex ambiguous expressions
7183 Expressions can sometimes contain some ambiguous elements. For instance,
7184 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7185 a single function name to be defined several times, for application in
7186 different contexts. This is called @dfn{overloading}. Another example
7187 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7188 templates and is typically instantiated several times, resulting in
7189 the same function name being defined in different contexts.
7191 In some cases and depending on the language, it is possible to adjust
7192 the expression to remove the ambiguity. For instance in C@t{++}, you
7193 can specify the signature of the function you want to break on, as in
7194 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7195 qualified name of your function often makes the expression unambiguous
7198 When an ambiguity that needs to be resolved is detected, the debugger
7199 has the capability to display a menu of numbered choices for each
7200 possibility, and then waits for the selection with the prompt @samp{>}.
7201 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7202 aborts the current command. If the command in which the expression was
7203 used allows more than one choice to be selected, the next option in the
7204 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7207 For example, the following session excerpt shows an attempt to set a
7208 breakpoint at the overloaded symbol @code{String::after}.
7209 We choose three particular definitions of that function name:
7211 @c FIXME! This is likely to change to show arg type lists, at least
7214 (@value{GDBP}) b String::after
7217 [2] file:String.cc; line number:867
7218 [3] file:String.cc; line number:860
7219 [4] file:String.cc; line number:875
7220 [5] file:String.cc; line number:853
7221 [6] file:String.cc; line number:846
7222 [7] file:String.cc; line number:735
7224 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7225 Breakpoint 2 at 0xb344: file String.cc, line 875.
7226 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7227 Multiple breakpoints were set.
7228 Use the "delete" command to delete unwanted
7235 @kindex set multiple-symbols
7236 @item set multiple-symbols @var{mode}
7237 @cindex multiple-symbols menu
7239 This option allows you to adjust the debugger behavior when an expression
7242 By default, @var{mode} is set to @code{all}. If the command with which
7243 the expression is used allows more than one choice, then @value{GDBN}
7244 automatically selects all possible choices. For instance, inserting
7245 a breakpoint on a function using an ambiguous name results in a breakpoint
7246 inserted on each possible match. However, if a unique choice must be made,
7247 then @value{GDBN} uses the menu to help you disambiguate the expression.
7248 For instance, printing the address of an overloaded function will result
7249 in the use of the menu.
7251 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7252 when an ambiguity is detected.
7254 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7255 an error due to the ambiguity and the command is aborted.
7257 @kindex show multiple-symbols
7258 @item show multiple-symbols
7259 Show the current value of the @code{multiple-symbols} setting.
7263 @section Program Variables
7265 The most common kind of expression to use is the name of a variable
7268 Variables in expressions are understood in the selected stack frame
7269 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7273 global (or file-static)
7280 visible according to the scope rules of the
7281 programming language from the point of execution in that frame
7284 @noindent This means that in the function
7299 you can examine and use the variable @code{a} whenever your program is
7300 executing within the function @code{foo}, but you can only use or
7301 examine the variable @code{b} while your program is executing inside
7302 the block where @code{b} is declared.
7304 @cindex variable name conflict
7305 There is an exception: you can refer to a variable or function whose
7306 scope is a single source file even if the current execution point is not
7307 in this file. But it is possible to have more than one such variable or
7308 function with the same name (in different source files). If that
7309 happens, referring to that name has unpredictable effects. If you wish,
7310 you can specify a static variable in a particular function or file,
7311 using the colon-colon (@code{::}) notation:
7313 @cindex colon-colon, context for variables/functions
7315 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7316 @cindex @code{::}, context for variables/functions
7319 @var{file}::@var{variable}
7320 @var{function}::@var{variable}
7324 Here @var{file} or @var{function} is the name of the context for the
7325 static @var{variable}. In the case of file names, you can use quotes to
7326 make sure @value{GDBN} parses the file name as a single word---for example,
7327 to print a global value of @code{x} defined in @file{f2.c}:
7330 (@value{GDBP}) p 'f2.c'::x
7333 @cindex C@t{++} scope resolution
7334 This use of @samp{::} is very rarely in conflict with the very similar
7335 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7336 scope resolution operator in @value{GDBN} expressions.
7337 @c FIXME: Um, so what happens in one of those rare cases where it's in
7340 @cindex wrong values
7341 @cindex variable values, wrong
7342 @cindex function entry/exit, wrong values of variables
7343 @cindex optimized code, wrong values of variables
7345 @emph{Warning:} Occasionally, a local variable may appear to have the
7346 wrong value at certain points in a function---just after entry to a new
7347 scope, and just before exit.
7349 You may see this problem when you are stepping by machine instructions.
7350 This is because, on most machines, it takes more than one instruction to
7351 set up a stack frame (including local variable definitions); if you are
7352 stepping by machine instructions, variables may appear to have the wrong
7353 values until the stack frame is completely built. On exit, it usually
7354 also takes more than one machine instruction to destroy a stack frame;
7355 after you begin stepping through that group of instructions, local
7356 variable definitions may be gone.
7358 This may also happen when the compiler does significant optimizations.
7359 To be sure of always seeing accurate values, turn off all optimization
7362 @cindex ``No symbol "foo" in current context''
7363 Another possible effect of compiler optimizations is to optimize
7364 unused variables out of existence, or assign variables to registers (as
7365 opposed to memory addresses). Depending on the support for such cases
7366 offered by the debug info format used by the compiler, @value{GDBN}
7367 might not be able to display values for such local variables. If that
7368 happens, @value{GDBN} will print a message like this:
7371 No symbol "foo" in current context.
7374 To solve such problems, either recompile without optimizations, or use a
7375 different debug info format, if the compiler supports several such
7376 formats. @xref{Compilation}, for more information on choosing compiler
7377 options. @xref{C, ,C and C@t{++}}, for more information about debug
7378 info formats that are best suited to C@t{++} programs.
7380 If you ask to print an object whose contents are unknown to
7381 @value{GDBN}, e.g., because its data type is not completely specified
7382 by the debug information, @value{GDBN} will say @samp{<incomplete
7383 type>}. @xref{Symbols, incomplete type}, for more about this.
7385 If you append @kbd{@@entry} string to a function parameter name you get its
7386 value at the time the function got called. If the value is not available an
7387 error message is printed. Entry values are available only with some compilers.
7388 Entry values are normally also printed at the function parameter list according
7389 to @ref{set print entry-values}.
7392 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
7398 (gdb) print i@@entry
7402 Strings are identified as arrays of @code{char} values without specified
7403 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7404 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7405 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7406 defines literal string type @code{"char"} as @code{char} without a sign.
7411 signed char var1[] = "A";
7414 You get during debugging
7419 $2 = @{65 'A', 0 '\0'@}
7423 @section Artificial Arrays
7425 @cindex artificial array
7427 @kindex @@@r{, referencing memory as an array}
7428 It is often useful to print out several successive objects of the
7429 same type in memory; a section of an array, or an array of
7430 dynamically determined size for which only a pointer exists in the
7433 You can do this by referring to a contiguous span of memory as an
7434 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7435 operand of @samp{@@} should be the first element of the desired array
7436 and be an individual object. The right operand should be the desired length
7437 of the array. The result is an array value whose elements are all of
7438 the type of the left argument. The first element is actually the left
7439 argument; the second element comes from bytes of memory immediately
7440 following those that hold the first element, and so on. Here is an
7441 example. If a program says
7444 int *array = (int *) malloc (len * sizeof (int));
7448 you can print the contents of @code{array} with
7454 The left operand of @samp{@@} must reside in memory. Array values made
7455 with @samp{@@} in this way behave just like other arrays in terms of
7456 subscripting, and are coerced to pointers when used in expressions.
7457 Artificial arrays most often appear in expressions via the value history
7458 (@pxref{Value History, ,Value History}), after printing one out.
7460 Another way to create an artificial array is to use a cast.
7461 This re-interprets a value as if it were an array.
7462 The value need not be in memory:
7464 (@value{GDBP}) p/x (short[2])0x12345678
7465 $1 = @{0x1234, 0x5678@}
7468 As a convenience, if you leave the array length out (as in
7469 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7470 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7472 (@value{GDBP}) p/x (short[])0x12345678
7473 $2 = @{0x1234, 0x5678@}
7476 Sometimes the artificial array mechanism is not quite enough; in
7477 moderately complex data structures, the elements of interest may not
7478 actually be adjacent---for example, if you are interested in the values
7479 of pointers in an array. One useful work-around in this situation is
7480 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7481 Variables}) as a counter in an expression that prints the first
7482 interesting value, and then repeat that expression via @key{RET}. For
7483 instance, suppose you have an array @code{dtab} of pointers to
7484 structures, and you are interested in the values of a field @code{fv}
7485 in each structure. Here is an example of what you might type:
7495 @node Output Formats
7496 @section Output Formats
7498 @cindex formatted output
7499 @cindex output formats
7500 By default, @value{GDBN} prints a value according to its data type. Sometimes
7501 this is not what you want. For example, you might want to print a number
7502 in hex, or a pointer in decimal. Or you might want to view data in memory
7503 at a certain address as a character string or as an instruction. To do
7504 these things, specify an @dfn{output format} when you print a value.
7506 The simplest use of output formats is to say how to print a value
7507 already computed. This is done by starting the arguments of the
7508 @code{print} command with a slash and a format letter. The format
7509 letters supported are:
7513 Regard the bits of the value as an integer, and print the integer in
7517 Print as integer in signed decimal.
7520 Print as integer in unsigned decimal.
7523 Print as integer in octal.
7526 Print as integer in binary. The letter @samp{t} stands for ``two''.
7527 @footnote{@samp{b} cannot be used because these format letters are also
7528 used with the @code{x} command, where @samp{b} stands for ``byte'';
7529 see @ref{Memory,,Examining Memory}.}
7532 @cindex unknown address, locating
7533 @cindex locate address
7534 Print as an address, both absolute in hexadecimal and as an offset from
7535 the nearest preceding symbol. You can use this format used to discover
7536 where (in what function) an unknown address is located:
7539 (@value{GDBP}) p/a 0x54320
7540 $3 = 0x54320 <_initialize_vx+396>
7544 The command @code{info symbol 0x54320} yields similar results.
7545 @xref{Symbols, info symbol}.
7548 Regard as an integer and print it as a character constant. This
7549 prints both the numerical value and its character representation. The
7550 character representation is replaced with the octal escape @samp{\nnn}
7551 for characters outside the 7-bit @sc{ascii} range.
7553 Without this format, @value{GDBN} displays @code{char},
7554 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7555 constants. Single-byte members of vectors are displayed as integer
7559 Regard the bits of the value as a floating point number and print
7560 using typical floating point syntax.
7563 @cindex printing strings
7564 @cindex printing byte arrays
7565 Regard as a string, if possible. With this format, pointers to single-byte
7566 data are displayed as null-terminated strings and arrays of single-byte data
7567 are displayed as fixed-length strings. Other values are displayed in their
7570 Without this format, @value{GDBN} displays pointers to and arrays of
7571 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7572 strings. Single-byte members of a vector are displayed as an integer
7576 @cindex raw printing
7577 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7578 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7579 Printing}). This typically results in a higher-level display of the
7580 value's contents. The @samp{r} format bypasses any Python
7581 pretty-printer which might exist.
7584 For example, to print the program counter in hex (@pxref{Registers}), type
7591 Note that no space is required before the slash; this is because command
7592 names in @value{GDBN} cannot contain a slash.
7594 To reprint the last value in the value history with a different format,
7595 you can use the @code{print} command with just a format and no
7596 expression. For example, @samp{p/x} reprints the last value in hex.
7599 @section Examining Memory
7601 You can use the command @code{x} (for ``examine'') to examine memory in
7602 any of several formats, independently of your program's data types.
7604 @cindex examining memory
7606 @kindex x @r{(examine memory)}
7607 @item x/@var{nfu} @var{addr}
7610 Use the @code{x} command to examine memory.
7613 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7614 much memory to display and how to format it; @var{addr} is an
7615 expression giving the address where you want to start displaying memory.
7616 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7617 Several commands set convenient defaults for @var{addr}.
7620 @item @var{n}, the repeat count
7621 The repeat count is a decimal integer; the default is 1. It specifies
7622 how much memory (counting by units @var{u}) to display.
7623 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7626 @item @var{f}, the display format
7627 The display format is one of the formats used by @code{print}
7628 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7629 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7630 The default is @samp{x} (hexadecimal) initially. The default changes
7631 each time you use either @code{x} or @code{print}.
7633 @item @var{u}, the unit size
7634 The unit size is any of
7640 Halfwords (two bytes).
7642 Words (four bytes). This is the initial default.
7644 Giant words (eight bytes).
7647 Each time you specify a unit size with @code{x}, that size becomes the
7648 default unit the next time you use @code{x}. For the @samp{i} format,
7649 the unit size is ignored and is normally not written. For the @samp{s} format,
7650 the unit size defaults to @samp{b}, unless it is explicitly given.
7651 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
7652 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
7653 Note that the results depend on the programming language of the
7654 current compilation unit. If the language is C, the @samp{s}
7655 modifier will use the UTF-16 encoding while @samp{w} will use
7656 UTF-32. The encoding is set by the programming language and cannot
7659 @item @var{addr}, starting display address
7660 @var{addr} is the address where you want @value{GDBN} to begin displaying
7661 memory. The expression need not have a pointer value (though it may);
7662 it is always interpreted as an integer address of a byte of memory.
7663 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7664 @var{addr} is usually just after the last address examined---but several
7665 other commands also set the default address: @code{info breakpoints} (to
7666 the address of the last breakpoint listed), @code{info line} (to the
7667 starting address of a line), and @code{print} (if you use it to display
7668 a value from memory).
7671 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7672 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7673 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7674 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7675 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7677 Since the letters indicating unit sizes are all distinct from the
7678 letters specifying output formats, you do not have to remember whether
7679 unit size or format comes first; either order works. The output
7680 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7681 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7683 Even though the unit size @var{u} is ignored for the formats @samp{s}
7684 and @samp{i}, you might still want to use a count @var{n}; for example,
7685 @samp{3i} specifies that you want to see three machine instructions,
7686 including any operands. For convenience, especially when used with
7687 the @code{display} command, the @samp{i} format also prints branch delay
7688 slot instructions, if any, beyond the count specified, which immediately
7689 follow the last instruction that is within the count. The command
7690 @code{disassemble} gives an alternative way of inspecting machine
7691 instructions; see @ref{Machine Code,,Source and Machine Code}.
7693 All the defaults for the arguments to @code{x} are designed to make it
7694 easy to continue scanning memory with minimal specifications each time
7695 you use @code{x}. For example, after you have inspected three machine
7696 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7697 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7698 the repeat count @var{n} is used again; the other arguments default as
7699 for successive uses of @code{x}.
7701 When examining machine instructions, the instruction at current program
7702 counter is shown with a @code{=>} marker. For example:
7705 (@value{GDBP}) x/5i $pc-6
7706 0x804837f <main+11>: mov %esp,%ebp
7707 0x8048381 <main+13>: push %ecx
7708 0x8048382 <main+14>: sub $0x4,%esp
7709 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
7710 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
7713 @cindex @code{$_}, @code{$__}, and value history
7714 The addresses and contents printed by the @code{x} command are not saved
7715 in the value history because there is often too much of them and they
7716 would get in the way. Instead, @value{GDBN} makes these values available for
7717 subsequent use in expressions as values of the convenience variables
7718 @code{$_} and @code{$__}. After an @code{x} command, the last address
7719 examined is available for use in expressions in the convenience variable
7720 @code{$_}. The contents of that address, as examined, are available in
7721 the convenience variable @code{$__}.
7723 If the @code{x} command has a repeat count, the address and contents saved
7724 are from the last memory unit printed; this is not the same as the last
7725 address printed if several units were printed on the last line of output.
7727 @cindex remote memory comparison
7728 @cindex verify remote memory image
7729 When you are debugging a program running on a remote target machine
7730 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7731 remote machine's memory against the executable file you downloaded to
7732 the target. The @code{compare-sections} command is provided for such
7736 @kindex compare-sections
7737 @item compare-sections @r{[}@var{section-name}@r{]}
7738 Compare the data of a loadable section @var{section-name} in the
7739 executable file of the program being debugged with the same section in
7740 the remote machine's memory, and report any mismatches. With no
7741 arguments, compares all loadable sections. This command's
7742 availability depends on the target's support for the @code{"qCRC"}
7747 @section Automatic Display
7748 @cindex automatic display
7749 @cindex display of expressions
7751 If you find that you want to print the value of an expression frequently
7752 (to see how it changes), you might want to add it to the @dfn{automatic
7753 display list} so that @value{GDBN} prints its value each time your program stops.
7754 Each expression added to the list is given a number to identify it;
7755 to remove an expression from the list, you specify that number.
7756 The automatic display looks like this:
7760 3: bar[5] = (struct hack *) 0x3804
7764 This display shows item numbers, expressions and their current values. As with
7765 displays you request manually using @code{x} or @code{print}, you can
7766 specify the output format you prefer; in fact, @code{display} decides
7767 whether to use @code{print} or @code{x} depending your format
7768 specification---it uses @code{x} if you specify either the @samp{i}
7769 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7773 @item display @var{expr}
7774 Add the expression @var{expr} to the list of expressions to display
7775 each time your program stops. @xref{Expressions, ,Expressions}.
7777 @code{display} does not repeat if you press @key{RET} again after using it.
7779 @item display/@var{fmt} @var{expr}
7780 For @var{fmt} specifying only a display format and not a size or
7781 count, add the expression @var{expr} to the auto-display list but
7782 arrange to display it each time in the specified format @var{fmt}.
7783 @xref{Output Formats,,Output Formats}.
7785 @item display/@var{fmt} @var{addr}
7786 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7787 number of units, add the expression @var{addr} as a memory address to
7788 be examined each time your program stops. Examining means in effect
7789 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7792 For example, @samp{display/i $pc} can be helpful, to see the machine
7793 instruction about to be executed each time execution stops (@samp{$pc}
7794 is a common name for the program counter; @pxref{Registers, ,Registers}).
7797 @kindex delete display
7799 @item undisplay @var{dnums}@dots{}
7800 @itemx delete display @var{dnums}@dots{}
7801 Remove items from the list of expressions to display. Specify the
7802 numbers of the displays that you want affected with the command
7803 argument @var{dnums}. It can be a single display number, one of the
7804 numbers shown in the first field of the @samp{info display} display;
7805 or it could be a range of display numbers, as in @code{2-4}.
7807 @code{undisplay} does not repeat if you press @key{RET} after using it.
7808 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7810 @kindex disable display
7811 @item disable display @var{dnums}@dots{}
7812 Disable the display of item numbers @var{dnums}. A disabled display
7813 item is not printed automatically, but is not forgotten. It may be
7814 enabled again later. Specify the numbers of the displays that you
7815 want affected with the command argument @var{dnums}. It can be a
7816 single display number, one of the numbers shown in the first field of
7817 the @samp{info display} display; or it could be a range of display
7818 numbers, as in @code{2-4}.
7820 @kindex enable display
7821 @item enable display @var{dnums}@dots{}
7822 Enable display of item numbers @var{dnums}. It becomes effective once
7823 again in auto display of its expression, until you specify otherwise.
7824 Specify the numbers of the displays that you want affected with the
7825 command argument @var{dnums}. It can be a single display number, one
7826 of the numbers shown in the first field of the @samp{info display}
7827 display; or it could be a range of display numbers, as in @code{2-4}.
7830 Display the current values of the expressions on the list, just as is
7831 done when your program stops.
7833 @kindex info display
7835 Print the list of expressions previously set up to display
7836 automatically, each one with its item number, but without showing the
7837 values. This includes disabled expressions, which are marked as such.
7838 It also includes expressions which would not be displayed right now
7839 because they refer to automatic variables not currently available.
7842 @cindex display disabled out of scope
7843 If a display expression refers to local variables, then it does not make
7844 sense outside the lexical context for which it was set up. Such an
7845 expression is disabled when execution enters a context where one of its
7846 variables is not defined. For example, if you give the command
7847 @code{display last_char} while inside a function with an argument
7848 @code{last_char}, @value{GDBN} displays this argument while your program
7849 continues to stop inside that function. When it stops elsewhere---where
7850 there is no variable @code{last_char}---the display is disabled
7851 automatically. The next time your program stops where @code{last_char}
7852 is meaningful, you can enable the display expression once again.
7854 @node Print Settings
7855 @section Print Settings
7857 @cindex format options
7858 @cindex print settings
7859 @value{GDBN} provides the following ways to control how arrays, structures,
7860 and symbols are printed.
7863 These settings are useful for debugging programs in any language:
7867 @item set print address
7868 @itemx set print address on
7869 @cindex print/don't print memory addresses
7870 @value{GDBN} prints memory addresses showing the location of stack
7871 traces, structure values, pointer values, breakpoints, and so forth,
7872 even when it also displays the contents of those addresses. The default
7873 is @code{on}. For example, this is what a stack frame display looks like with
7874 @code{set print address on}:
7879 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7881 530 if (lquote != def_lquote)
7885 @item set print address off
7886 Do not print addresses when displaying their contents. For example,
7887 this is the same stack frame displayed with @code{set print address off}:
7891 (@value{GDBP}) set print addr off
7893 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7894 530 if (lquote != def_lquote)
7898 You can use @samp{set print address off} to eliminate all machine
7899 dependent displays from the @value{GDBN} interface. For example, with
7900 @code{print address off}, you should get the same text for backtraces on
7901 all machines---whether or not they involve pointer arguments.
7904 @item show print address
7905 Show whether or not addresses are to be printed.
7908 When @value{GDBN} prints a symbolic address, it normally prints the
7909 closest earlier symbol plus an offset. If that symbol does not uniquely
7910 identify the address (for example, it is a name whose scope is a single
7911 source file), you may need to clarify. One way to do this is with
7912 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7913 you can set @value{GDBN} to print the source file and line number when
7914 it prints a symbolic address:
7917 @item set print symbol-filename on
7918 @cindex source file and line of a symbol
7919 @cindex symbol, source file and line
7920 Tell @value{GDBN} to print the source file name and line number of a
7921 symbol in the symbolic form of an address.
7923 @item set print symbol-filename off
7924 Do not print source file name and line number of a symbol. This is the
7927 @item show print symbol-filename
7928 Show whether or not @value{GDBN} will print the source file name and
7929 line number of a symbol in the symbolic form of an address.
7932 Another situation where it is helpful to show symbol filenames and line
7933 numbers is when disassembling code; @value{GDBN} shows you the line
7934 number and source file that corresponds to each instruction.
7936 Also, you may wish to see the symbolic form only if the address being
7937 printed is reasonably close to the closest earlier symbol:
7940 @item set print max-symbolic-offset @var{max-offset}
7941 @cindex maximum value for offset of closest symbol
7942 Tell @value{GDBN} to only display the symbolic form of an address if the
7943 offset between the closest earlier symbol and the address is less than
7944 @var{max-offset}. The default is 0, which tells @value{GDBN}
7945 to always print the symbolic form of an address if any symbol precedes it.
7947 @item show print max-symbolic-offset
7948 Ask how large the maximum offset is that @value{GDBN} prints in a
7952 @cindex wild pointer, interpreting
7953 @cindex pointer, finding referent
7954 If you have a pointer and you are not sure where it points, try
7955 @samp{set print symbol-filename on}. Then you can determine the name
7956 and source file location of the variable where it points, using
7957 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7958 For example, here @value{GDBN} shows that a variable @code{ptt} points
7959 at another variable @code{t}, defined in @file{hi2.c}:
7962 (@value{GDBP}) set print symbol-filename on
7963 (@value{GDBP}) p/a ptt
7964 $4 = 0xe008 <t in hi2.c>
7968 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
7969 does not show the symbol name and filename of the referent, even with
7970 the appropriate @code{set print} options turned on.
7973 Other settings control how different kinds of objects are printed:
7976 @item set print array
7977 @itemx set print array on
7978 @cindex pretty print arrays
7979 Pretty print arrays. This format is more convenient to read,
7980 but uses more space. The default is off.
7982 @item set print array off
7983 Return to compressed format for arrays.
7985 @item show print array
7986 Show whether compressed or pretty format is selected for displaying
7989 @cindex print array indexes
7990 @item set print array-indexes
7991 @itemx set print array-indexes on
7992 Print the index of each element when displaying arrays. May be more
7993 convenient to locate a given element in the array or quickly find the
7994 index of a given element in that printed array. The default is off.
7996 @item set print array-indexes off
7997 Stop printing element indexes when displaying arrays.
7999 @item show print array-indexes
8000 Show whether the index of each element is printed when displaying
8003 @item set print elements @var{number-of-elements}
8004 @cindex number of array elements to print
8005 @cindex limit on number of printed array elements
8006 Set a limit on how many elements of an array @value{GDBN} will print.
8007 If @value{GDBN} is printing a large array, it stops printing after it has
8008 printed the number of elements set by the @code{set print elements} command.
8009 This limit also applies to the display of strings.
8010 When @value{GDBN} starts, this limit is set to 200.
8011 Setting @var{number-of-elements} to zero means that the printing is unlimited.
8013 @item show print elements
8014 Display the number of elements of a large array that @value{GDBN} will print.
8015 If the number is 0, then the printing is unlimited.
8017 @item set print frame-arguments @var{value}
8018 @kindex set print frame-arguments
8019 @cindex printing frame argument values
8020 @cindex print all frame argument values
8021 @cindex print frame argument values for scalars only
8022 @cindex do not print frame argument values
8023 This command allows to control how the values of arguments are printed
8024 when the debugger prints a frame (@pxref{Frames}). The possible
8029 The values of all arguments are printed.
8032 Print the value of an argument only if it is a scalar. The value of more
8033 complex arguments such as arrays, structures, unions, etc, is replaced
8034 by @code{@dots{}}. This is the default. Here is an example where
8035 only scalar arguments are shown:
8038 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
8043 None of the argument values are printed. Instead, the value of each argument
8044 is replaced by @code{@dots{}}. In this case, the example above now becomes:
8047 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
8052 By default, only scalar arguments are printed. This command can be used
8053 to configure the debugger to print the value of all arguments, regardless
8054 of their type. However, it is often advantageous to not print the value
8055 of more complex parameters. For instance, it reduces the amount of
8056 information printed in each frame, making the backtrace more readable.
8057 Also, it improves performance when displaying Ada frames, because
8058 the computation of large arguments can sometimes be CPU-intensive,
8059 especially in large applications. Setting @code{print frame-arguments}
8060 to @code{scalars} (the default) or @code{none} avoids this computation,
8061 thus speeding up the display of each Ada frame.
8063 @item show print frame-arguments
8064 Show how the value of arguments should be displayed when printing a frame.
8066 @anchor{set print entry-values}
8067 @item set print entry-values @var{value}
8068 @kindex set print entry-values
8069 Set printing of frame argument values at function entry. In some cases
8070 @value{GDBN} can determine the value of function argument which was passed by
8071 the function caller, even if the value was modified inside the called function
8072 and therefore is different. With optimized code, the current value could be
8073 unavailable, but the entry value may still be known.
8075 The default value is @code{default} (see below for its description). Older
8076 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
8077 this feature will behave in the @code{default} setting the same way as with the
8080 This functionality is currently supported only by DWARF 2 debugging format and
8081 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
8082 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
8085 The @var{value} parameter can be one of the following:
8089 Print only actual parameter values, never print values from function entry
8093 #0 different (val=6)
8094 #0 lost (val=<optimized out>)
8096 #0 invalid (val=<optimized out>)
8100 Print only parameter values from function entry point. The actual parameter
8101 values are never printed.
8103 #0 equal (val@@entry=5)
8104 #0 different (val@@entry=5)
8105 #0 lost (val@@entry=5)
8106 #0 born (val@@entry=<optimized out>)
8107 #0 invalid (val@@entry=<optimized out>)
8111 Print only parameter values from function entry point. If value from function
8112 entry point is not known while the actual value is known, print the actual
8113 value for such parameter.
8115 #0 equal (val@@entry=5)
8116 #0 different (val@@entry=5)
8117 #0 lost (val@@entry=5)
8119 #0 invalid (val@@entry=<optimized out>)
8123 Print actual parameter values. If actual parameter value is not known while
8124 value from function entry point is known, print the entry point value for such
8128 #0 different (val=6)
8129 #0 lost (val@@entry=5)
8131 #0 invalid (val=<optimized out>)
8135 Always print both the actual parameter value and its value from function entry
8136 point, even if values of one or both are not available due to compiler
8139 #0 equal (val=5, val@@entry=5)
8140 #0 different (val=6, val@@entry=5)
8141 #0 lost (val=<optimized out>, val@@entry=5)
8142 #0 born (val=10, val@@entry=<optimized out>)
8143 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
8147 Print the actual parameter value if it is known and also its value from
8148 function entry point if it is known. If neither is known, print for the actual
8149 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
8150 values are known and identical, print the shortened
8151 @code{param=param@@entry=VALUE} notation.
8153 #0 equal (val=val@@entry=5)
8154 #0 different (val=6, val@@entry=5)
8155 #0 lost (val@@entry=5)
8157 #0 invalid (val=<optimized out>)
8161 Always print the actual parameter value. Print also its value from function
8162 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
8163 if both values are known and identical, print the shortened
8164 @code{param=param@@entry=VALUE} notation.
8166 #0 equal (val=val@@entry=5)
8167 #0 different (val=6, val@@entry=5)
8168 #0 lost (val=<optimized out>, val@@entry=5)
8170 #0 invalid (val=<optimized out>)
8174 For analysis messages on possible failures of frame argument values at function
8175 entry resolution see @ref{set debug entry-values}.
8177 @item show print entry-values
8178 Show the method being used for printing of frame argument values at function
8181 @item set print repeats
8182 @cindex repeated array elements
8183 Set the threshold for suppressing display of repeated array
8184 elements. When the number of consecutive identical elements of an
8185 array exceeds the threshold, @value{GDBN} prints the string
8186 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
8187 identical repetitions, instead of displaying the identical elements
8188 themselves. Setting the threshold to zero will cause all elements to
8189 be individually printed. The default threshold is 10.
8191 @item show print repeats
8192 Display the current threshold for printing repeated identical
8195 @item set print null-stop
8196 @cindex @sc{null} elements in arrays
8197 Cause @value{GDBN} to stop printing the characters of an array when the first
8198 @sc{null} is encountered. This is useful when large arrays actually
8199 contain only short strings.
8202 @item show print null-stop
8203 Show whether @value{GDBN} stops printing an array on the first
8204 @sc{null} character.
8206 @item set print pretty on
8207 @cindex print structures in indented form
8208 @cindex indentation in structure display
8209 Cause @value{GDBN} to print structures in an indented format with one member
8210 per line, like this:
8225 @item set print pretty off
8226 Cause @value{GDBN} to print structures in a compact format, like this:
8230 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
8231 meat = 0x54 "Pork"@}
8236 This is the default format.
8238 @item show print pretty
8239 Show which format @value{GDBN} is using to print structures.
8241 @item set print sevenbit-strings on
8242 @cindex eight-bit characters in strings
8243 @cindex octal escapes in strings
8244 Print using only seven-bit characters; if this option is set,
8245 @value{GDBN} displays any eight-bit characters (in strings or
8246 character values) using the notation @code{\}@var{nnn}. This setting is
8247 best if you are working in English (@sc{ascii}) and you use the
8248 high-order bit of characters as a marker or ``meta'' bit.
8250 @item set print sevenbit-strings off
8251 Print full eight-bit characters. This allows the use of more
8252 international character sets, and is the default.
8254 @item show print sevenbit-strings
8255 Show whether or not @value{GDBN} is printing only seven-bit characters.
8257 @item set print union on
8258 @cindex unions in structures, printing
8259 Tell @value{GDBN} to print unions which are contained in structures
8260 and other unions. This is the default setting.
8262 @item set print union off
8263 Tell @value{GDBN} not to print unions which are contained in
8264 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
8267 @item show print union
8268 Ask @value{GDBN} whether or not it will print unions which are contained in
8269 structures and other unions.
8271 For example, given the declarations
8274 typedef enum @{Tree, Bug@} Species;
8275 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
8276 typedef enum @{Caterpillar, Cocoon, Butterfly@}
8287 struct thing foo = @{Tree, @{Acorn@}@};
8291 with @code{set print union on} in effect @samp{p foo} would print
8294 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
8298 and with @code{set print union off} in effect it would print
8301 $1 = @{it = Tree, form = @{...@}@}
8305 @code{set print union} affects programs written in C-like languages
8311 These settings are of interest when debugging C@t{++} programs:
8314 @cindex demangling C@t{++} names
8315 @item set print demangle
8316 @itemx set print demangle on
8317 Print C@t{++} names in their source form rather than in the encoded
8318 (``mangled'') form passed to the assembler and linker for type-safe
8319 linkage. The default is on.
8321 @item show print demangle
8322 Show whether C@t{++} names are printed in mangled or demangled form.
8324 @item set print asm-demangle
8325 @itemx set print asm-demangle on
8326 Print C@t{++} names in their source form rather than their mangled form, even
8327 in assembler code printouts such as instruction disassemblies.
8330 @item show print asm-demangle
8331 Show whether C@t{++} names in assembly listings are printed in mangled
8334 @cindex C@t{++} symbol decoding style
8335 @cindex symbol decoding style, C@t{++}
8336 @kindex set demangle-style
8337 @item set demangle-style @var{style}
8338 Choose among several encoding schemes used by different compilers to
8339 represent C@t{++} names. The choices for @var{style} are currently:
8343 Allow @value{GDBN} to choose a decoding style by inspecting your program.
8346 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
8347 This is the default.
8350 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
8353 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
8356 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
8357 @strong{Warning:} this setting alone is not sufficient to allow
8358 debugging @code{cfront}-generated executables. @value{GDBN} would
8359 require further enhancement to permit that.
8362 If you omit @var{style}, you will see a list of possible formats.
8364 @item show demangle-style
8365 Display the encoding style currently in use for decoding C@t{++} symbols.
8367 @item set print object
8368 @itemx set print object on
8369 @cindex derived type of an object, printing
8370 @cindex display derived types
8371 When displaying a pointer to an object, identify the @emph{actual}
8372 (derived) type of the object rather than the @emph{declared} type, using
8373 the virtual function table. Note that the virtual function table is
8374 required---this feature can only work for objects that have run-time
8375 type identification; a single virtual method in the object's declared
8378 @item set print object off
8379 Display only the declared type of objects, without reference to the
8380 virtual function table. This is the default setting.
8382 @item show print object
8383 Show whether actual, or declared, object types are displayed.
8385 @item set print static-members
8386 @itemx set print static-members on
8387 @cindex static members of C@t{++} objects
8388 Print static members when displaying a C@t{++} object. The default is on.
8390 @item set print static-members off
8391 Do not print static members when displaying a C@t{++} object.
8393 @item show print static-members
8394 Show whether C@t{++} static members are printed or not.
8396 @item set print pascal_static-members
8397 @itemx set print pascal_static-members on
8398 @cindex static members of Pascal objects
8399 @cindex Pascal objects, static members display
8400 Print static members when displaying a Pascal object. The default is on.
8402 @item set print pascal_static-members off
8403 Do not print static members when displaying a Pascal object.
8405 @item show print pascal_static-members
8406 Show whether Pascal static members are printed or not.
8408 @c These don't work with HP ANSI C++ yet.
8409 @item set print vtbl
8410 @itemx set print vtbl on
8411 @cindex pretty print C@t{++} virtual function tables
8412 @cindex virtual functions (C@t{++}) display
8413 @cindex VTBL display
8414 Pretty print C@t{++} virtual function tables. The default is off.
8415 (The @code{vtbl} commands do not work on programs compiled with the HP
8416 ANSI C@t{++} compiler (@code{aCC}).)
8418 @item set print vtbl off
8419 Do not pretty print C@t{++} virtual function tables.
8421 @item show print vtbl
8422 Show whether C@t{++} virtual function tables are pretty printed, or not.
8425 @node Pretty Printing
8426 @section Pretty Printing
8428 @value{GDBN} provides a mechanism to allow pretty-printing of values using
8429 Python code. It greatly simplifies the display of complex objects. This
8430 mechanism works for both MI and the CLI.
8433 * Pretty-Printer Introduction:: Introduction to pretty-printers
8434 * Pretty-Printer Example:: An example pretty-printer
8435 * Pretty-Printer Commands:: Pretty-printer commands
8438 @node Pretty-Printer Introduction
8439 @subsection Pretty-Printer Introduction
8441 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
8442 registered for the value. If there is then @value{GDBN} invokes the
8443 pretty-printer to print the value. Otherwise the value is printed normally.
8445 Pretty-printers are normally named. This makes them easy to manage.
8446 The @samp{info pretty-printer} command will list all the installed
8447 pretty-printers with their names.
8448 If a pretty-printer can handle multiple data types, then its
8449 @dfn{subprinters} are the printers for the individual data types.
8450 Each such subprinter has its own name.
8451 The format of the name is @var{printer-name};@var{subprinter-name}.
8453 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
8454 Typically they are automatically loaded and registered when the corresponding
8455 debug information is loaded, thus making them available without having to
8456 do anything special.
8458 There are three places where a pretty-printer can be registered.
8462 Pretty-printers registered globally are available when debugging
8466 Pretty-printers registered with a program space are available only
8467 when debugging that program.
8468 @xref{Progspaces In Python}, for more details on program spaces in Python.
8471 Pretty-printers registered with an objfile are loaded and unloaded
8472 with the corresponding objfile (e.g., shared library).
8473 @xref{Objfiles In Python}, for more details on objfiles in Python.
8476 @xref{Selecting Pretty-Printers}, for further information on how
8477 pretty-printers are selected,
8479 @xref{Writing a Pretty-Printer}, for implementing pretty printers
8482 @node Pretty-Printer Example
8483 @subsection Pretty-Printer Example
8485 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
8488 (@value{GDBP}) print s
8490 static npos = 4294967295,
8492 <std::allocator<char>> = @{
8493 <__gnu_cxx::new_allocator<char>> = @{
8494 <No data fields>@}, <No data fields>
8496 members of std::basic_string<char, std::char_traits<char>,
8497 std::allocator<char> >::_Alloc_hider:
8498 _M_p = 0x804a014 "abcd"
8503 With a pretty-printer for @code{std::string} only the contents are printed:
8506 (@value{GDBP}) print s
8510 @node Pretty-Printer Commands
8511 @subsection Pretty-Printer Commands
8512 @cindex pretty-printer commands
8515 @kindex info pretty-printer
8516 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8517 Print the list of installed pretty-printers.
8518 This includes disabled pretty-printers, which are marked as such.
8520 @var{object-regexp} is a regular expression matching the objects
8521 whose pretty-printers to list.
8522 Objects can be @code{global}, the program space's file
8523 (@pxref{Progspaces In Python}),
8524 and the object files within that program space (@pxref{Objfiles In Python}).
8525 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
8526 looks up a printer from these three objects.
8528 @var{name-regexp} is a regular expression matching the name of the printers
8531 @kindex disable pretty-printer
8532 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8533 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8534 A disabled pretty-printer is not forgotten, it may be enabled again later.
8536 @kindex enable pretty-printer
8537 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8538 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8543 Suppose we have three pretty-printers installed: one from library1.so
8544 named @code{foo} that prints objects of type @code{foo}, and
8545 another from library2.so named @code{bar} that prints two types of objects,
8546 @code{bar1} and @code{bar2}.
8549 (gdb) info pretty-printer
8556 (gdb) info pretty-printer library2
8561 (gdb) disable pretty-printer library1
8563 2 of 3 printers enabled
8564 (gdb) info pretty-printer
8571 (gdb) disable pretty-printer library2 bar:bar1
8573 1 of 3 printers enabled
8574 (gdb) info pretty-printer library2
8581 (gdb) disable pretty-printer library2 bar
8583 0 of 3 printers enabled
8584 (gdb) info pretty-printer library2
8593 Note that for @code{bar} the entire printer can be disabled,
8594 as can each individual subprinter.
8597 @section Value History
8599 @cindex value history
8600 @cindex history of values printed by @value{GDBN}
8601 Values printed by the @code{print} command are saved in the @value{GDBN}
8602 @dfn{value history}. This allows you to refer to them in other expressions.
8603 Values are kept until the symbol table is re-read or discarded
8604 (for example with the @code{file} or @code{symbol-file} commands).
8605 When the symbol table changes, the value history is discarded,
8606 since the values may contain pointers back to the types defined in the
8611 @cindex history number
8612 The values printed are given @dfn{history numbers} by which you can
8613 refer to them. These are successive integers starting with one.
8614 @code{print} shows you the history number assigned to a value by
8615 printing @samp{$@var{num} = } before the value; here @var{num} is the
8618 To refer to any previous value, use @samp{$} followed by the value's
8619 history number. The way @code{print} labels its output is designed to
8620 remind you of this. Just @code{$} refers to the most recent value in
8621 the history, and @code{$$} refers to the value before that.
8622 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
8623 is the value just prior to @code{$$}, @code{$$1} is equivalent to
8624 @code{$$}, and @code{$$0} is equivalent to @code{$}.
8626 For example, suppose you have just printed a pointer to a structure and
8627 want to see the contents of the structure. It suffices to type
8633 If you have a chain of structures where the component @code{next} points
8634 to the next one, you can print the contents of the next one with this:
8641 You can print successive links in the chain by repeating this
8642 command---which you can do by just typing @key{RET}.
8644 Note that the history records values, not expressions. If the value of
8645 @code{x} is 4 and you type these commands:
8653 then the value recorded in the value history by the @code{print} command
8654 remains 4 even though the value of @code{x} has changed.
8659 Print the last ten values in the value history, with their item numbers.
8660 This is like @samp{p@ $$9} repeated ten times, except that @code{show
8661 values} does not change the history.
8663 @item show values @var{n}
8664 Print ten history values centered on history item number @var{n}.
8667 Print ten history values just after the values last printed. If no more
8668 values are available, @code{show values +} produces no display.
8671 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
8672 same effect as @samp{show values +}.
8674 @node Convenience Vars
8675 @section Convenience Variables
8677 @cindex convenience variables
8678 @cindex user-defined variables
8679 @value{GDBN} provides @dfn{convenience variables} that you can use within
8680 @value{GDBN} to hold on to a value and refer to it later. These variables
8681 exist entirely within @value{GDBN}; they are not part of your program, and
8682 setting a convenience variable has no direct effect on further execution
8683 of your program. That is why you can use them freely.
8685 Convenience variables are prefixed with @samp{$}. Any name preceded by
8686 @samp{$} can be used for a convenience variable, unless it is one of
8687 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
8688 (Value history references, in contrast, are @emph{numbers} preceded
8689 by @samp{$}. @xref{Value History, ,Value History}.)
8691 You can save a value in a convenience variable with an assignment
8692 expression, just as you would set a variable in your program.
8696 set $foo = *object_ptr
8700 would save in @code{$foo} the value contained in the object pointed to by
8703 Using a convenience variable for the first time creates it, but its
8704 value is @code{void} until you assign a new value. You can alter the
8705 value with another assignment at any time.
8707 Convenience variables have no fixed types. You can assign a convenience
8708 variable any type of value, including structures and arrays, even if
8709 that variable already has a value of a different type. The convenience
8710 variable, when used as an expression, has the type of its current value.
8713 @kindex show convenience
8714 @cindex show all user variables
8715 @item show convenience
8716 Print a list of convenience variables used so far, and their values.
8717 Abbreviated @code{show conv}.
8719 @kindex init-if-undefined
8720 @cindex convenience variables, initializing
8721 @item init-if-undefined $@var{variable} = @var{expression}
8722 Set a convenience variable if it has not already been set. This is useful
8723 for user-defined commands that keep some state. It is similar, in concept,
8724 to using local static variables with initializers in C (except that
8725 convenience variables are global). It can also be used to allow users to
8726 override default values used in a command script.
8728 If the variable is already defined then the expression is not evaluated so
8729 any side-effects do not occur.
8732 One of the ways to use a convenience variable is as a counter to be
8733 incremented or a pointer to be advanced. For example, to print
8734 a field from successive elements of an array of structures:
8738 print bar[$i++]->contents
8742 Repeat that command by typing @key{RET}.
8744 Some convenience variables are created automatically by @value{GDBN} and given
8745 values likely to be useful.
8748 @vindex $_@r{, convenience variable}
8750 The variable @code{$_} is automatically set by the @code{x} command to
8751 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8752 commands which provide a default address for @code{x} to examine also
8753 set @code{$_} to that address; these commands include @code{info line}
8754 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8755 except when set by the @code{x} command, in which case it is a pointer
8756 to the type of @code{$__}.
8758 @vindex $__@r{, convenience variable}
8760 The variable @code{$__} is automatically set by the @code{x} command
8761 to the value found in the last address examined. Its type is chosen
8762 to match the format in which the data was printed.
8765 @vindex $_exitcode@r{, convenience variable}
8766 The variable @code{$_exitcode} is automatically set to the exit code when
8767 the program being debugged terminates.
8770 @vindex $_sdata@r{, inspect, convenience variable}
8771 The variable @code{$_sdata} contains extra collected static tracepoint
8772 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
8773 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
8774 if extra static tracepoint data has not been collected.
8777 @vindex $_siginfo@r{, convenience variable}
8778 The variable @code{$_siginfo} contains extra signal information
8779 (@pxref{extra signal information}). Note that @code{$_siginfo}
8780 could be empty, if the application has not yet received any signals.
8781 For example, it will be empty before you execute the @code{run} command.
8784 @vindex $_tlb@r{, convenience variable}
8785 The variable @code{$_tlb} is automatically set when debugging
8786 applications running on MS-Windows in native mode or connected to
8787 gdbserver that supports the @code{qGetTIBAddr} request.
8788 @xref{General Query Packets}.
8789 This variable contains the address of the thread information block.
8793 On HP-UX systems, if you refer to a function or variable name that
8794 begins with a dollar sign, @value{GDBN} searches for a user or system
8795 name first, before it searches for a convenience variable.
8797 @cindex convenience functions
8798 @value{GDBN} also supplies some @dfn{convenience functions}. These
8799 have a syntax similar to convenience variables. A convenience
8800 function can be used in an expression just like an ordinary function;
8801 however, a convenience function is implemented internally to
8806 @kindex help function
8807 @cindex show all convenience functions
8808 Print a list of all convenience functions.
8815 You can refer to machine register contents, in expressions, as variables
8816 with names starting with @samp{$}. The names of registers are different
8817 for each machine; use @code{info registers} to see the names used on
8821 @kindex info registers
8822 @item info registers
8823 Print the names and values of all registers except floating-point
8824 and vector registers (in the selected stack frame).
8826 @kindex info all-registers
8827 @cindex floating point registers
8828 @item info all-registers
8829 Print the names and values of all registers, including floating-point
8830 and vector registers (in the selected stack frame).
8832 @item info registers @var{regname} @dots{}
8833 Print the @dfn{relativized} value of each specified register @var{regname}.
8834 As discussed in detail below, register values are normally relative to
8835 the selected stack frame. @var{regname} may be any register name valid on
8836 the machine you are using, with or without the initial @samp{$}.
8839 @cindex stack pointer register
8840 @cindex program counter register
8841 @cindex process status register
8842 @cindex frame pointer register
8843 @cindex standard registers
8844 @value{GDBN} has four ``standard'' register names that are available (in
8845 expressions) on most machines---whenever they do not conflict with an
8846 architecture's canonical mnemonics for registers. The register names
8847 @code{$pc} and @code{$sp} are used for the program counter register and
8848 the stack pointer. @code{$fp} is used for a register that contains a
8849 pointer to the current stack frame, and @code{$ps} is used for a
8850 register that contains the processor status. For example,
8851 you could print the program counter in hex with
8858 or print the instruction to be executed next with
8865 or add four to the stack pointer@footnote{This is a way of removing
8866 one word from the stack, on machines where stacks grow downward in
8867 memory (most machines, nowadays). This assumes that the innermost
8868 stack frame is selected; setting @code{$sp} is not allowed when other
8869 stack frames are selected. To pop entire frames off the stack,
8870 regardless of machine architecture, use @code{return};
8871 see @ref{Returning, ,Returning from a Function}.} with
8877 Whenever possible, these four standard register names are available on
8878 your machine even though the machine has different canonical mnemonics,
8879 so long as there is no conflict. The @code{info registers} command
8880 shows the canonical names. For example, on the SPARC, @code{info
8881 registers} displays the processor status register as @code{$psr} but you
8882 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
8883 is an alias for the @sc{eflags} register.
8885 @value{GDBN} always considers the contents of an ordinary register as an
8886 integer when the register is examined in this way. Some machines have
8887 special registers which can hold nothing but floating point; these
8888 registers are considered to have floating point values. There is no way
8889 to refer to the contents of an ordinary register as floating point value
8890 (although you can @emph{print} it as a floating point value with
8891 @samp{print/f $@var{regname}}).
8893 Some registers have distinct ``raw'' and ``virtual'' data formats. This
8894 means that the data format in which the register contents are saved by
8895 the operating system is not the same one that your program normally
8896 sees. For example, the registers of the 68881 floating point
8897 coprocessor are always saved in ``extended'' (raw) format, but all C
8898 programs expect to work with ``double'' (virtual) format. In such
8899 cases, @value{GDBN} normally works with the virtual format only (the format
8900 that makes sense for your program), but the @code{info registers} command
8901 prints the data in both formats.
8903 @cindex SSE registers (x86)
8904 @cindex MMX registers (x86)
8905 Some machines have special registers whose contents can be interpreted
8906 in several different ways. For example, modern x86-based machines
8907 have SSE and MMX registers that can hold several values packed
8908 together in several different formats. @value{GDBN} refers to such
8909 registers in @code{struct} notation:
8912 (@value{GDBP}) print $xmm1
8914 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
8915 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
8916 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
8917 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
8918 v4_int32 = @{0, 20657912, 11, 13@},
8919 v2_int64 = @{88725056443645952, 55834574859@},
8920 uint128 = 0x0000000d0000000b013b36f800000000
8925 To set values of such registers, you need to tell @value{GDBN} which
8926 view of the register you wish to change, as if you were assigning
8927 value to a @code{struct} member:
8930 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
8933 Normally, register values are relative to the selected stack frame
8934 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
8935 value that the register would contain if all stack frames farther in
8936 were exited and their saved registers restored. In order to see the
8937 true contents of hardware registers, you must select the innermost
8938 frame (with @samp{frame 0}).
8940 However, @value{GDBN} must deduce where registers are saved, from the machine
8941 code generated by your compiler. If some registers are not saved, or if
8942 @value{GDBN} is unable to locate the saved registers, the selected stack
8943 frame makes no difference.
8945 @node Floating Point Hardware
8946 @section Floating Point Hardware
8947 @cindex floating point
8949 Depending on the configuration, @value{GDBN} may be able to give
8950 you more information about the status of the floating point hardware.
8955 Display hardware-dependent information about the floating
8956 point unit. The exact contents and layout vary depending on the
8957 floating point chip. Currently, @samp{info float} is supported on
8958 the ARM and x86 machines.
8962 @section Vector Unit
8965 Depending on the configuration, @value{GDBN} may be able to give you
8966 more information about the status of the vector unit.
8971 Display information about the vector unit. The exact contents and
8972 layout vary depending on the hardware.
8975 @node OS Information
8976 @section Operating System Auxiliary Information
8977 @cindex OS information
8979 @value{GDBN} provides interfaces to useful OS facilities that can help
8980 you debug your program.
8982 @cindex @code{ptrace} system call
8983 @cindex @code{struct user} contents
8984 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
8985 machines), it interfaces with the inferior via the @code{ptrace}
8986 system call. The operating system creates a special sata structure,
8987 called @code{struct user}, for this interface. You can use the
8988 command @code{info udot} to display the contents of this data
8994 Display the contents of the @code{struct user} maintained by the OS
8995 kernel for the program being debugged. @value{GDBN} displays the
8996 contents of @code{struct user} as a list of hex numbers, similar to
8997 the @code{examine} command.
9000 @cindex auxiliary vector
9001 @cindex vector, auxiliary
9002 Some operating systems supply an @dfn{auxiliary vector} to programs at
9003 startup. This is akin to the arguments and environment that you
9004 specify for a program, but contains a system-dependent variety of
9005 binary values that tell system libraries important details about the
9006 hardware, operating system, and process. Each value's purpose is
9007 identified by an integer tag; the meanings are well-known but system-specific.
9008 Depending on the configuration and operating system facilities,
9009 @value{GDBN} may be able to show you this information. For remote
9010 targets, this functionality may further depend on the remote stub's
9011 support of the @samp{qXfer:auxv:read} packet, see
9012 @ref{qXfer auxiliary vector read}.
9017 Display the auxiliary vector of the inferior, which can be either a
9018 live process or a core dump file. @value{GDBN} prints each tag value
9019 numerically, and also shows names and text descriptions for recognized
9020 tags. Some values in the vector are numbers, some bit masks, and some
9021 pointers to strings or other data. @value{GDBN} displays each value in the
9022 most appropriate form for a recognized tag, and in hexadecimal for
9023 an unrecognized tag.
9026 On some targets, @value{GDBN} can access operating-system-specific information
9027 and display it to user, without interpretation. For remote targets,
9028 this functionality depends on the remote stub's support of the
9029 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
9034 List the types of OS information available for the target. If the
9035 target does not return a list of possible types, this command will
9038 @kindex info os processes
9039 @item info os processes
9040 Display the list of processes on the target. For each process,
9041 @value{GDBN} prints the process identifier, the name of the user, and
9042 the command corresponding to the process.
9045 @node Memory Region Attributes
9046 @section Memory Region Attributes
9047 @cindex memory region attributes
9049 @dfn{Memory region attributes} allow you to describe special handling
9050 required by regions of your target's memory. @value{GDBN} uses
9051 attributes to determine whether to allow certain types of memory
9052 accesses; whether to use specific width accesses; and whether to cache
9053 target memory. By default the description of memory regions is
9054 fetched from the target (if the current target supports this), but the
9055 user can override the fetched regions.
9057 Defined memory regions can be individually enabled and disabled. When a
9058 memory region is disabled, @value{GDBN} uses the default attributes when
9059 accessing memory in that region. Similarly, if no memory regions have
9060 been defined, @value{GDBN} uses the default attributes when accessing
9063 When a memory region is defined, it is given a number to identify it;
9064 to enable, disable, or remove a memory region, you specify that number.
9068 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
9069 Define a memory region bounded by @var{lower} and @var{upper} with
9070 attributes @var{attributes}@dots{}, and add it to the list of regions
9071 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
9072 case: it is treated as the target's maximum memory address.
9073 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
9076 Discard any user changes to the memory regions and use target-supplied
9077 regions, if available, or no regions if the target does not support.
9080 @item delete mem @var{nums}@dots{}
9081 Remove memory regions @var{nums}@dots{} from the list of regions
9082 monitored by @value{GDBN}.
9085 @item disable mem @var{nums}@dots{}
9086 Disable monitoring of memory regions @var{nums}@dots{}.
9087 A disabled memory region is not forgotten.
9088 It may be enabled again later.
9091 @item enable mem @var{nums}@dots{}
9092 Enable monitoring of memory regions @var{nums}@dots{}.
9096 Print a table of all defined memory regions, with the following columns
9100 @item Memory Region Number
9101 @item Enabled or Disabled.
9102 Enabled memory regions are marked with @samp{y}.
9103 Disabled memory regions are marked with @samp{n}.
9106 The address defining the inclusive lower bound of the memory region.
9109 The address defining the exclusive upper bound of the memory region.
9112 The list of attributes set for this memory region.
9117 @subsection Attributes
9119 @subsubsection Memory Access Mode
9120 The access mode attributes set whether @value{GDBN} may make read or
9121 write accesses to a memory region.
9123 While these attributes prevent @value{GDBN} from performing invalid
9124 memory accesses, they do nothing to prevent the target system, I/O DMA,
9125 etc.@: from accessing memory.
9129 Memory is read only.
9131 Memory is write only.
9133 Memory is read/write. This is the default.
9136 @subsubsection Memory Access Size
9137 The access size attribute tells @value{GDBN} to use specific sized
9138 accesses in the memory region. Often memory mapped device registers
9139 require specific sized accesses. If no access size attribute is
9140 specified, @value{GDBN} may use accesses of any size.
9144 Use 8 bit memory accesses.
9146 Use 16 bit memory accesses.
9148 Use 32 bit memory accesses.
9150 Use 64 bit memory accesses.
9153 @c @subsubsection Hardware/Software Breakpoints
9154 @c The hardware/software breakpoint attributes set whether @value{GDBN}
9155 @c will use hardware or software breakpoints for the internal breakpoints
9156 @c used by the step, next, finish, until, etc. commands.
9160 @c Always use hardware breakpoints
9161 @c @item swbreak (default)
9164 @subsubsection Data Cache
9165 The data cache attributes set whether @value{GDBN} will cache target
9166 memory. While this generally improves performance by reducing debug
9167 protocol overhead, it can lead to incorrect results because @value{GDBN}
9168 does not know about volatile variables or memory mapped device
9173 Enable @value{GDBN} to cache target memory.
9175 Disable @value{GDBN} from caching target memory. This is the default.
9178 @subsection Memory Access Checking
9179 @value{GDBN} can be instructed to refuse accesses to memory that is
9180 not explicitly described. This can be useful if accessing such
9181 regions has undesired effects for a specific target, or to provide
9182 better error checking. The following commands control this behaviour.
9185 @kindex set mem inaccessible-by-default
9186 @item set mem inaccessible-by-default [on|off]
9187 If @code{on} is specified, make @value{GDBN} treat memory not
9188 explicitly described by the memory ranges as non-existent and refuse accesses
9189 to such memory. The checks are only performed if there's at least one
9190 memory range defined. If @code{off} is specified, make @value{GDBN}
9191 treat the memory not explicitly described by the memory ranges as RAM.
9192 The default value is @code{on}.
9193 @kindex show mem inaccessible-by-default
9194 @item show mem inaccessible-by-default
9195 Show the current handling of accesses to unknown memory.
9199 @c @subsubsection Memory Write Verification
9200 @c The memory write verification attributes set whether @value{GDBN}
9201 @c will re-reads data after each write to verify the write was successful.
9205 @c @item noverify (default)
9208 @node Dump/Restore Files
9209 @section Copy Between Memory and a File
9210 @cindex dump/restore files
9211 @cindex append data to a file
9212 @cindex dump data to a file
9213 @cindex restore data from a file
9215 You can use the commands @code{dump}, @code{append}, and
9216 @code{restore} to copy data between target memory and a file. The
9217 @code{dump} and @code{append} commands write data to a file, and the
9218 @code{restore} command reads data from a file back into the inferior's
9219 memory. Files may be in binary, Motorola S-record, Intel hex, or
9220 Tektronix Hex format; however, @value{GDBN} can only append to binary
9226 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9227 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
9228 Dump the contents of memory from @var{start_addr} to @var{end_addr},
9229 or the value of @var{expr}, to @var{filename} in the given format.
9231 The @var{format} parameter may be any one of:
9238 Motorola S-record format.
9240 Tektronix Hex format.
9243 @value{GDBN} uses the same definitions of these formats as the
9244 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
9245 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
9249 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9250 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
9251 Append the contents of memory from @var{start_addr} to @var{end_addr},
9252 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
9253 (@value{GDBN} can only append data to files in raw binary form.)
9256 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
9257 Restore the contents of file @var{filename} into memory. The
9258 @code{restore} command can automatically recognize any known @sc{bfd}
9259 file format, except for raw binary. To restore a raw binary file you
9260 must specify the optional keyword @code{binary} after the filename.
9262 If @var{bias} is non-zero, its value will be added to the addresses
9263 contained in the file. Binary files always start at address zero, so
9264 they will be restored at address @var{bias}. Other bfd files have
9265 a built-in location; they will be restored at offset @var{bias}
9268 If @var{start} and/or @var{end} are non-zero, then only data between
9269 file offset @var{start} and file offset @var{end} will be restored.
9270 These offsets are relative to the addresses in the file, before
9271 the @var{bias} argument is applied.
9275 @node Core File Generation
9276 @section How to Produce a Core File from Your Program
9277 @cindex dump core from inferior
9279 A @dfn{core file} or @dfn{core dump} is a file that records the memory
9280 image of a running process and its process status (register values
9281 etc.). Its primary use is post-mortem debugging of a program that
9282 crashed while it ran outside a debugger. A program that crashes
9283 automatically produces a core file, unless this feature is disabled by
9284 the user. @xref{Files}, for information on invoking @value{GDBN} in
9285 the post-mortem debugging mode.
9287 Occasionally, you may wish to produce a core file of the program you
9288 are debugging in order to preserve a snapshot of its state.
9289 @value{GDBN} has a special command for that.
9293 @kindex generate-core-file
9294 @item generate-core-file [@var{file}]
9295 @itemx gcore [@var{file}]
9296 Produce a core dump of the inferior process. The optional argument
9297 @var{file} specifies the file name where to put the core dump. If not
9298 specified, the file name defaults to @file{core.@var{pid}}, where
9299 @var{pid} is the inferior process ID.
9301 Note that this command is implemented only for some systems (as of
9302 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
9305 @node Character Sets
9306 @section Character Sets
9307 @cindex character sets
9309 @cindex translating between character sets
9310 @cindex host character set
9311 @cindex target character set
9313 If the program you are debugging uses a different character set to
9314 represent characters and strings than the one @value{GDBN} uses itself,
9315 @value{GDBN} can automatically translate between the character sets for
9316 you. The character set @value{GDBN} uses we call the @dfn{host
9317 character set}; the one the inferior program uses we call the
9318 @dfn{target character set}.
9320 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
9321 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
9322 remote protocol (@pxref{Remote Debugging}) to debug a program
9323 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
9324 then the host character set is Latin-1, and the target character set is
9325 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
9326 target-charset EBCDIC-US}, then @value{GDBN} translates between
9327 @sc{ebcdic} and Latin 1 as you print character or string values, or use
9328 character and string literals in expressions.
9330 @value{GDBN} has no way to automatically recognize which character set
9331 the inferior program uses; you must tell it, using the @code{set
9332 target-charset} command, described below.
9334 Here are the commands for controlling @value{GDBN}'s character set
9338 @item set target-charset @var{charset}
9339 @kindex set target-charset
9340 Set the current target character set to @var{charset}. To display the
9341 list of supported target character sets, type
9342 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
9344 @item set host-charset @var{charset}
9345 @kindex set host-charset
9346 Set the current host character set to @var{charset}.
9348 By default, @value{GDBN} uses a host character set appropriate to the
9349 system it is running on; you can override that default using the
9350 @code{set host-charset} command. On some systems, @value{GDBN} cannot
9351 automatically determine the appropriate host character set. In this
9352 case, @value{GDBN} uses @samp{UTF-8}.
9354 @value{GDBN} can only use certain character sets as its host character
9355 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
9356 @value{GDBN} will list the host character sets it supports.
9358 @item set charset @var{charset}
9360 Set the current host and target character sets to @var{charset}. As
9361 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
9362 @value{GDBN} will list the names of the character sets that can be used
9363 for both host and target.
9366 @kindex show charset
9367 Show the names of the current host and target character sets.
9369 @item show host-charset
9370 @kindex show host-charset
9371 Show the name of the current host character set.
9373 @item show target-charset
9374 @kindex show target-charset
9375 Show the name of the current target character set.
9377 @item set target-wide-charset @var{charset}
9378 @kindex set target-wide-charset
9379 Set the current target's wide character set to @var{charset}. This is
9380 the character set used by the target's @code{wchar_t} type. To
9381 display the list of supported wide character sets, type
9382 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
9384 @item show target-wide-charset
9385 @kindex show target-wide-charset
9386 Show the name of the current target's wide character set.
9389 Here is an example of @value{GDBN}'s character set support in action.
9390 Assume that the following source code has been placed in the file
9391 @file{charset-test.c}:
9397 = @{72, 101, 108, 108, 111, 44, 32, 119,
9398 111, 114, 108, 100, 33, 10, 0@};
9399 char ibm1047_hello[]
9400 = @{200, 133, 147, 147, 150, 107, 64, 166,
9401 150, 153, 147, 132, 90, 37, 0@};
9405 printf ("Hello, world!\n");
9409 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
9410 containing the string @samp{Hello, world!} followed by a newline,
9411 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
9413 We compile the program, and invoke the debugger on it:
9416 $ gcc -g charset-test.c -o charset-test
9417 $ gdb -nw charset-test
9418 GNU gdb 2001-12-19-cvs
9419 Copyright 2001 Free Software Foundation, Inc.
9424 We can use the @code{show charset} command to see what character sets
9425 @value{GDBN} is currently using to interpret and display characters and
9429 (@value{GDBP}) show charset
9430 The current host and target character set is `ISO-8859-1'.
9434 For the sake of printing this manual, let's use @sc{ascii} as our
9435 initial character set:
9437 (@value{GDBP}) set charset ASCII
9438 (@value{GDBP}) show charset
9439 The current host and target character set is `ASCII'.
9443 Let's assume that @sc{ascii} is indeed the correct character set for our
9444 host system --- in other words, let's assume that if @value{GDBN} prints
9445 characters using the @sc{ascii} character set, our terminal will display
9446 them properly. Since our current target character set is also
9447 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
9450 (@value{GDBP}) print ascii_hello
9451 $1 = 0x401698 "Hello, world!\n"
9452 (@value{GDBP}) print ascii_hello[0]
9457 @value{GDBN} uses the target character set for character and string
9458 literals you use in expressions:
9461 (@value{GDBP}) print '+'
9466 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
9469 @value{GDBN} relies on the user to tell it which character set the
9470 target program uses. If we print @code{ibm1047_hello} while our target
9471 character set is still @sc{ascii}, we get jibberish:
9474 (@value{GDBP}) print ibm1047_hello
9475 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
9476 (@value{GDBP}) print ibm1047_hello[0]
9481 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
9482 @value{GDBN} tells us the character sets it supports:
9485 (@value{GDBP}) set target-charset
9486 ASCII EBCDIC-US IBM1047 ISO-8859-1
9487 (@value{GDBP}) set target-charset
9490 We can select @sc{ibm1047} as our target character set, and examine the
9491 program's strings again. Now the @sc{ascii} string is wrong, but
9492 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
9493 target character set, @sc{ibm1047}, to the host character set,
9494 @sc{ascii}, and they display correctly:
9497 (@value{GDBP}) set target-charset IBM1047
9498 (@value{GDBP}) show charset
9499 The current host character set is `ASCII'.
9500 The current target character set is `IBM1047'.
9501 (@value{GDBP}) print ascii_hello
9502 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
9503 (@value{GDBP}) print ascii_hello[0]
9505 (@value{GDBP}) print ibm1047_hello
9506 $8 = 0x4016a8 "Hello, world!\n"
9507 (@value{GDBP}) print ibm1047_hello[0]
9512 As above, @value{GDBN} uses the target character set for character and
9513 string literals you use in expressions:
9516 (@value{GDBP}) print '+'
9521 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
9524 @node Caching Remote Data
9525 @section Caching Data of Remote Targets
9526 @cindex caching data of remote targets
9528 @value{GDBN} caches data exchanged between the debugger and a
9529 remote target (@pxref{Remote Debugging}). Such caching generally improves
9530 performance, because it reduces the overhead of the remote protocol by
9531 bundling memory reads and writes into large chunks. Unfortunately, simply
9532 caching everything would lead to incorrect results, since @value{GDBN}
9533 does not necessarily know anything about volatile values, memory-mapped I/O
9534 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
9535 memory can be changed @emph{while} a gdb command is executing.
9536 Therefore, by default, @value{GDBN} only caches data
9537 known to be on the stack@footnote{In non-stop mode, it is moderately
9538 rare for a running thread to modify the stack of a stopped thread
9539 in a way that would interfere with a backtrace, and caching of
9540 stack reads provides a significant speed up of remote backtraces.}.
9541 Other regions of memory can be explicitly marked as
9542 cacheable; see @pxref{Memory Region Attributes}.
9545 @kindex set remotecache
9546 @item set remotecache on
9547 @itemx set remotecache off
9548 This option no longer does anything; it exists for compatibility
9551 @kindex show remotecache
9552 @item show remotecache
9553 Show the current state of the obsolete remotecache flag.
9555 @kindex set stack-cache
9556 @item set stack-cache on
9557 @itemx set stack-cache off
9558 Enable or disable caching of stack accesses. When @code{ON}, use
9559 caching. By default, this option is @code{ON}.
9561 @kindex show stack-cache
9562 @item show stack-cache
9563 Show the current state of data caching for memory accesses.
9566 @item info dcache @r{[}line@r{]}
9567 Print the information about the data cache performance. The
9568 information displayed includes the dcache width and depth, and for
9569 each cache line, its number, address, and how many times it was
9570 referenced. This command is useful for debugging the data cache
9573 If a line number is specified, the contents of that line will be
9576 @item set dcache size @var{size}
9578 @kindex set dcache size
9579 Set maximum number of entries in dcache (dcache depth above).
9581 @item set dcache line-size @var{line-size}
9582 @cindex dcache line-size
9583 @kindex set dcache line-size
9584 Set number of bytes each dcache entry caches (dcache width above).
9585 Must be a power of 2.
9587 @item show dcache size
9588 @kindex show dcache size
9589 Show maximum number of dcache entries. See also @ref{Caching Remote Data, info dcache}.
9591 @item show dcache line-size
9592 @kindex show dcache line-size
9593 Show default size of dcache lines. See also @ref{Caching Remote Data, info dcache}.
9597 @node Searching Memory
9598 @section Search Memory
9599 @cindex searching memory
9601 Memory can be searched for a particular sequence of bytes with the
9602 @code{find} command.
9606 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9607 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9608 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
9609 etc. The search begins at address @var{start_addr} and continues for either
9610 @var{len} bytes or through to @var{end_addr} inclusive.
9613 @var{s} and @var{n} are optional parameters.
9614 They may be specified in either order, apart or together.
9617 @item @var{s}, search query size
9618 The size of each search query value.
9624 halfwords (two bytes)
9628 giant words (eight bytes)
9631 All values are interpreted in the current language.
9632 This means, for example, that if the current source language is C/C@t{++}
9633 then searching for the string ``hello'' includes the trailing '\0'.
9635 If the value size is not specified, it is taken from the
9636 value's type in the current language.
9637 This is useful when one wants to specify the search
9638 pattern as a mixture of types.
9639 Note that this means, for example, that in the case of C-like languages
9640 a search for an untyped 0x42 will search for @samp{(int) 0x42}
9641 which is typically four bytes.
9643 @item @var{n}, maximum number of finds
9644 The maximum number of matches to print. The default is to print all finds.
9647 You can use strings as search values. Quote them with double-quotes
9649 The string value is copied into the search pattern byte by byte,
9650 regardless of the endianness of the target and the size specification.
9652 The address of each match found is printed as well as a count of the
9653 number of matches found.
9655 The address of the last value found is stored in convenience variable
9657 A count of the number of matches is stored in @samp{$numfound}.
9659 For example, if stopped at the @code{printf} in this function:
9665 static char hello[] = "hello-hello";
9666 static struct @{ char c; short s; int i; @}
9667 __attribute__ ((packed)) mixed
9668 = @{ 'c', 0x1234, 0x87654321 @};
9669 printf ("%s\n", hello);
9674 you get during debugging:
9677 (gdb) find &hello[0], +sizeof(hello), "hello"
9678 0x804956d <hello.1620+6>
9680 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
9681 0x8049567 <hello.1620>
9682 0x804956d <hello.1620+6>
9684 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
9685 0x8049567 <hello.1620>
9687 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
9688 0x8049560 <mixed.1625>
9690 (gdb) print $numfound
9693 $2 = (void *) 0x8049560
9696 @node Optimized Code
9697 @chapter Debugging Optimized Code
9698 @cindex optimized code, debugging
9699 @cindex debugging optimized code
9701 Almost all compilers support optimization. With optimization
9702 disabled, the compiler generates assembly code that corresponds
9703 directly to your source code, in a simplistic way. As the compiler
9704 applies more powerful optimizations, the generated assembly code
9705 diverges from your original source code. With help from debugging
9706 information generated by the compiler, @value{GDBN} can map from
9707 the running program back to constructs from your original source.
9709 @value{GDBN} is more accurate with optimization disabled. If you
9710 can recompile without optimization, it is easier to follow the
9711 progress of your program during debugging. But, there are many cases
9712 where you may need to debug an optimized version.
9714 When you debug a program compiled with @samp{-g -O}, remember that the
9715 optimizer has rearranged your code; the debugger shows you what is
9716 really there. Do not be too surprised when the execution path does not
9717 exactly match your source file! An extreme example: if you define a
9718 variable, but never use it, @value{GDBN} never sees that
9719 variable---because the compiler optimizes it out of existence.
9721 Some things do not work as well with @samp{-g -O} as with just
9722 @samp{-g}, particularly on machines with instruction scheduling. If in
9723 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
9724 please report it to us as a bug (including a test case!).
9725 @xref{Variables}, for more information about debugging optimized code.
9728 * Inline Functions:: How @value{GDBN} presents inlining
9729 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
9732 @node Inline Functions
9733 @section Inline Functions
9734 @cindex inline functions, debugging
9736 @dfn{Inlining} is an optimization that inserts a copy of the function
9737 body directly at each call site, instead of jumping to a shared
9738 routine. @value{GDBN} displays inlined functions just like
9739 non-inlined functions. They appear in backtraces. You can view their
9740 arguments and local variables, step into them with @code{step}, skip
9741 them with @code{next}, and escape from them with @code{finish}.
9742 You can check whether a function was inlined by using the
9743 @code{info frame} command.
9745 For @value{GDBN} to support inlined functions, the compiler must
9746 record information about inlining in the debug information ---
9747 @value{NGCC} using the @sc{dwarf 2} format does this, and several
9748 other compilers do also. @value{GDBN} only supports inlined functions
9749 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
9750 do not emit two required attributes (@samp{DW_AT_call_file} and
9751 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
9752 function calls with earlier versions of @value{NGCC}. It instead
9753 displays the arguments and local variables of inlined functions as
9754 local variables in the caller.
9756 The body of an inlined function is directly included at its call site;
9757 unlike a non-inlined function, there are no instructions devoted to
9758 the call. @value{GDBN} still pretends that the call site and the
9759 start of the inlined function are different instructions. Stepping to
9760 the call site shows the call site, and then stepping again shows
9761 the first line of the inlined function, even though no additional
9762 instructions are executed.
9764 This makes source-level debugging much clearer; you can see both the
9765 context of the call and then the effect of the call. Only stepping by
9766 a single instruction using @code{stepi} or @code{nexti} does not do
9767 this; single instruction steps always show the inlined body.
9769 There are some ways that @value{GDBN} does not pretend that inlined
9770 function calls are the same as normal calls:
9774 You cannot set breakpoints on inlined functions. @value{GDBN}
9775 either reports that there is no symbol with that name, or else sets the
9776 breakpoint only on non-inlined copies of the function. This limitation
9777 will be removed in a future version of @value{GDBN}; until then,
9778 set a breakpoint by line number on the first line of the inlined
9782 Setting breakpoints at the call site of an inlined function may not
9783 work, because the call site does not contain any code. @value{GDBN}
9784 may incorrectly move the breakpoint to the next line of the enclosing
9785 function, after the call. This limitation will be removed in a future
9786 version of @value{GDBN}; until then, set a breakpoint on an earlier line
9787 or inside the inlined function instead.
9790 @value{GDBN} cannot locate the return value of inlined calls after
9791 using the @code{finish} command. This is a limitation of compiler-generated
9792 debugging information; after @code{finish}, you can step to the next line
9793 and print a variable where your program stored the return value.
9797 @node Tail Call Frames
9798 @section Tail Call Frames
9799 @cindex tail call frames, debugging
9801 Function @code{B} can call function @code{C} in its very last statement. In
9802 unoptimized compilation the call of @code{C} is immediately followed by return
9803 instruction at the end of @code{B} code. Optimizing compiler may replace the
9804 call and return in function @code{B} into one jump to function @code{C}
9805 instead. Such use of a jump instruction is called @dfn{tail call}.
9807 During execution of function @code{C}, there will be no indication in the
9808 function call stack frames that it was tail-called from @code{B}. If function
9809 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
9810 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
9811 some cases @value{GDBN} can determine that @code{C} was tail-called from
9812 @code{B}, and it will then create fictitious call frame for that, with the
9813 return address set up as if @code{B} called @code{C} normally.
9815 This functionality is currently supported only by DWARF 2 debugging format and
9816 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9817 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9820 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
9821 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
9825 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
9827 Stack level 1, frame at 0x7fffffffda30:
9828 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
9829 tail call frame, caller of frame at 0x7fffffffda30
9830 source language c++.
9831 Arglist at unknown address.
9832 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
9835 The detection of all the possible code path executions can find them ambiguous.
9836 There is no execution history stored (possible @ref{Reverse Execution} is never
9837 used for this purpose) and the last known caller could have reached the known
9838 callee by multiple different jump sequences. In such case @value{GDBN} still
9839 tries to show at least all the unambiguous top tail callers and all the
9840 unambiguous bottom tail calees, if any.
9843 @anchor{set debug entry-values}
9844 @item set debug entry-values
9845 @kindex set debug entry-values
9846 When set to on, enables printing of analysis messages for both frame argument
9847 values at function entry and tail calls. It will show all the possible valid
9848 tail calls code paths it has considered. It will also print the intersection
9849 of them with the final unambiguous (possibly partial or even empty) code path
9852 @item show debug entry-values
9853 @kindex show debug entry-values
9854 Show the current state of analysis messages printing for both frame argument
9855 values at function entry and tail calls.
9858 The analysis messages for tail calls can for example show why the virtual tail
9859 call frame for function @code{c} has not been recognized (due to the indirect
9860 reference by variable @code{x}):
9863 static void __attribute__((noinline, noclone)) c (void);
9864 void (*x) (void) = c;
9865 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
9866 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
9867 int main (void) @{ x (); return 0; @}
9869 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
9870 DW_TAG_GNU_call_site 0x40039a in main
9872 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
9875 #1 0x000000000040039a in main () at t.c:5
9878 Another possibility is an ambiguous virtual tail call frames resolution:
9882 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
9883 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
9884 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
9885 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
9886 static void __attribute__((noinline, noclone)) b (void)
9887 @{ if (i) c (); else e (); @}
9888 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
9889 int main (void) @{ a (); return 0; @}
9891 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
9892 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
9893 tailcall: reduced: 0x4004d2(a) |
9896 #1 0x00000000004004d2 in a () at t.c:8
9897 #2 0x0000000000400395 in main () at t.c:9
9900 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
9901 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
9903 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
9904 @ifset HAVE_MAKEINFO_CLICK
9906 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
9907 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
9909 @ifclear HAVE_MAKEINFO_CLICK
9911 @set CALLSEQ1B @value{CALLSEQ1A}
9912 @set CALLSEQ2B @value{CALLSEQ2A}
9915 Frames #0 and #2 are real, #1 is a virtual tail call frame.
9916 The code can have possible execution paths @value{CALLSEQ1B} or
9917 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
9919 @code{initial:} state shows some random possible calling sequence @value{GDBN}
9920 has found. It then finds another possible calling sequcen - that one is
9921 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
9922 printed as the @code{reduced:} calling sequence. That one could have many
9923 futher @code{compare:} and @code{reduced:} statements as long as there remain
9924 any non-ambiguous sequence entries.
9926 For the frame of function @code{b} in both cases there are different possible
9927 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
9928 also ambigous. The only non-ambiguous frame is the one for function @code{a},
9929 therefore this one is displayed to the user while the ambiguous frames are
9932 There can be also reasons why printing of frame argument values at function
9937 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
9938 static void __attribute__((noinline, noclone)) a (int i);
9939 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
9940 static void __attribute__((noinline, noclone)) a (int i)
9941 @{ if (i) b (i - 1); else c (0); @}
9942 int main (void) @{ a (5); return 0; @}
9945 #0 c (i=i@@entry=0) at t.c:2
9946 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
9947 function "a" at 0x400420 can call itself via tail calls
9948 i=<optimized out>) at t.c:6
9949 #2 0x000000000040036e in main () at t.c:7
9952 @value{GDBN} cannot find out from the inferior state if and how many times did
9953 function @code{a} call itself (via function @code{b}) as these calls would be
9954 tail calls. Such tail calls would modify thue @code{i} variable, therefore
9955 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
9956 prints @code{<optimized out>} instead.
9959 @chapter C Preprocessor Macros
9961 Some languages, such as C and C@t{++}, provide a way to define and invoke
9962 ``preprocessor macros'' which expand into strings of tokens.
9963 @value{GDBN} can evaluate expressions containing macro invocations, show
9964 the result of macro expansion, and show a macro's definition, including
9965 where it was defined.
9967 You may need to compile your program specially to provide @value{GDBN}
9968 with information about preprocessor macros. Most compilers do not
9969 include macros in their debugging information, even when you compile
9970 with the @option{-g} flag. @xref{Compilation}.
9972 A program may define a macro at one point, remove that definition later,
9973 and then provide a different definition after that. Thus, at different
9974 points in the program, a macro may have different definitions, or have
9975 no definition at all. If there is a current stack frame, @value{GDBN}
9976 uses the macros in scope at that frame's source code line. Otherwise,
9977 @value{GDBN} uses the macros in scope at the current listing location;
9980 Whenever @value{GDBN} evaluates an expression, it always expands any
9981 macro invocations present in the expression. @value{GDBN} also provides
9982 the following commands for working with macros explicitly.
9986 @kindex macro expand
9987 @cindex macro expansion, showing the results of preprocessor
9988 @cindex preprocessor macro expansion, showing the results of
9989 @cindex expanding preprocessor macros
9990 @item macro expand @var{expression}
9991 @itemx macro exp @var{expression}
9992 Show the results of expanding all preprocessor macro invocations in
9993 @var{expression}. Since @value{GDBN} simply expands macros, but does
9994 not parse the result, @var{expression} need not be a valid expression;
9995 it can be any string of tokens.
9998 @item macro expand-once @var{expression}
9999 @itemx macro exp1 @var{expression}
10000 @cindex expand macro once
10001 @i{(This command is not yet implemented.)} Show the results of
10002 expanding those preprocessor macro invocations that appear explicitly in
10003 @var{expression}. Macro invocations appearing in that expansion are
10004 left unchanged. This command allows you to see the effect of a
10005 particular macro more clearly, without being confused by further
10006 expansions. Since @value{GDBN} simply expands macros, but does not
10007 parse the result, @var{expression} need not be a valid expression; it
10008 can be any string of tokens.
10011 @cindex macro definition, showing
10012 @cindex definition of a macro, showing
10013 @cindex macros, from debug info
10014 @item info macro @var{macro}
10015 Show the current definition of the named @var{macro}, and describe the
10016 source location or compiler command-line where that definition was established.
10018 @kindex info macros
10019 @item info macros @var{linespec}
10020 Show all macro definitions that are in effect at the location specified
10021 by @var{linespec}, and describe the source location or compiler
10022 command-line where those definitions were established.
10024 @kindex info definitions
10025 @item info definitions @var{macro}
10026 Show all definitions of the named @var{macro} that are defined in the current
10027 compilation unit, and describe the source location or compiler command-line
10028 where those definitions were established.
10030 @kindex macro define
10031 @cindex user-defined macros
10032 @cindex defining macros interactively
10033 @cindex macros, user-defined
10034 @item macro define @var{macro} @var{replacement-list}
10035 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
10036 Introduce a definition for a preprocessor macro named @var{macro},
10037 invocations of which are replaced by the tokens given in
10038 @var{replacement-list}. The first form of this command defines an
10039 ``object-like'' macro, which takes no arguments; the second form
10040 defines a ``function-like'' macro, which takes the arguments given in
10043 A definition introduced by this command is in scope in every
10044 expression evaluated in @value{GDBN}, until it is removed with the
10045 @code{macro undef} command, described below. The definition overrides
10046 all definitions for @var{macro} present in the program being debugged,
10047 as well as any previous user-supplied definition.
10049 @kindex macro undef
10050 @item macro undef @var{macro}
10051 Remove any user-supplied definition for the macro named @var{macro}.
10052 This command only affects definitions provided with the @code{macro
10053 define} command, described above; it cannot remove definitions present
10054 in the program being debugged.
10058 List all the macros defined using the @code{macro define} command.
10061 @cindex macros, example of debugging with
10062 Here is a transcript showing the above commands in action. First, we
10063 show our source files:
10068 #include "sample.h"
10071 #define ADD(x) (M + x)
10076 printf ("Hello, world!\n");
10078 printf ("We're so creative.\n");
10080 printf ("Goodbye, world!\n");
10087 Now, we compile the program using the @sc{gnu} C compiler,
10088 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
10089 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
10090 and @option{-gdwarf-4}; we recommend always choosing the most recent
10091 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
10092 includes information about preprocessor macros in the debugging
10096 $ gcc -gdwarf-2 -g3 sample.c -o sample
10100 Now, we start @value{GDBN} on our sample program:
10104 GNU gdb 2002-05-06-cvs
10105 Copyright 2002 Free Software Foundation, Inc.
10106 GDB is free software, @dots{}
10110 We can expand macros and examine their definitions, even when the
10111 program is not running. @value{GDBN} uses the current listing position
10112 to decide which macro definitions are in scope:
10115 (@value{GDBP}) list main
10118 5 #define ADD(x) (M + x)
10123 10 printf ("Hello, world!\n");
10125 12 printf ("We're so creative.\n");
10126 (@value{GDBP}) info macro ADD
10127 Defined at /home/jimb/gdb/macros/play/sample.c:5
10128 #define ADD(x) (M + x)
10129 (@value{GDBP}) info macro Q
10130 Defined at /home/jimb/gdb/macros/play/sample.h:1
10131 included at /home/jimb/gdb/macros/play/sample.c:2
10133 (@value{GDBP}) macro expand ADD(1)
10134 expands to: (42 + 1)
10135 (@value{GDBP}) macro expand-once ADD(1)
10136 expands to: once (M + 1)
10140 In the example above, note that @code{macro expand-once} expands only
10141 the macro invocation explicit in the original text --- the invocation of
10142 @code{ADD} --- but does not expand the invocation of the macro @code{M},
10143 which was introduced by @code{ADD}.
10145 Once the program is running, @value{GDBN} uses the macro definitions in
10146 force at the source line of the current stack frame:
10149 (@value{GDBP}) break main
10150 Breakpoint 1 at 0x8048370: file sample.c, line 10.
10152 Starting program: /home/jimb/gdb/macros/play/sample
10154 Breakpoint 1, main () at sample.c:10
10155 10 printf ("Hello, world!\n");
10159 At line 10, the definition of the macro @code{N} at line 9 is in force:
10162 (@value{GDBP}) info macro N
10163 Defined at /home/jimb/gdb/macros/play/sample.c:9
10165 (@value{GDBP}) macro expand N Q M
10166 expands to: 28 < 42
10167 (@value{GDBP}) print N Q M
10172 As we step over directives that remove @code{N}'s definition, and then
10173 give it a new definition, @value{GDBN} finds the definition (or lack
10174 thereof) in force at each point:
10177 (@value{GDBP}) next
10179 12 printf ("We're so creative.\n");
10180 (@value{GDBP}) info macro N
10181 The symbol `N' has no definition as a C/C++ preprocessor macro
10182 at /home/jimb/gdb/macros/play/sample.c:12
10183 (@value{GDBP}) next
10185 14 printf ("Goodbye, world!\n");
10186 (@value{GDBP}) info macro N
10187 Defined at /home/jimb/gdb/macros/play/sample.c:13
10189 (@value{GDBP}) macro expand N Q M
10190 expands to: 1729 < 42
10191 (@value{GDBP}) print N Q M
10196 In addition to source files, macros can be defined on the compilation command
10197 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
10198 such a way, @value{GDBN} displays the location of their definition as line zero
10199 of the source file submitted to the compiler.
10202 (@value{GDBP}) info macro __STDC__
10203 Defined at /home/jimb/gdb/macros/play/sample.c:0
10210 @chapter Tracepoints
10211 @c This chapter is based on the documentation written by Michael
10212 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
10214 @cindex tracepoints
10215 In some applications, it is not feasible for the debugger to interrupt
10216 the program's execution long enough for the developer to learn
10217 anything helpful about its behavior. If the program's correctness
10218 depends on its real-time behavior, delays introduced by a debugger
10219 might cause the program to change its behavior drastically, or perhaps
10220 fail, even when the code itself is correct. It is useful to be able
10221 to observe the program's behavior without interrupting it.
10223 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
10224 specify locations in the program, called @dfn{tracepoints}, and
10225 arbitrary expressions to evaluate when those tracepoints are reached.
10226 Later, using the @code{tfind} command, you can examine the values
10227 those expressions had when the program hit the tracepoints. The
10228 expressions may also denote objects in memory---structures or arrays,
10229 for example---whose values @value{GDBN} should record; while visiting
10230 a particular tracepoint, you may inspect those objects as if they were
10231 in memory at that moment. However, because @value{GDBN} records these
10232 values without interacting with you, it can do so quickly and
10233 unobtrusively, hopefully not disturbing the program's behavior.
10235 The tracepoint facility is currently available only for remote
10236 targets. @xref{Targets}. In addition, your remote target must know
10237 how to collect trace data. This functionality is implemented in the
10238 remote stub; however, none of the stubs distributed with @value{GDBN}
10239 support tracepoints as of this writing. The format of the remote
10240 packets used to implement tracepoints are described in @ref{Tracepoint
10243 It is also possible to get trace data from a file, in a manner reminiscent
10244 of corefiles; you specify the filename, and use @code{tfind} to search
10245 through the file. @xref{Trace Files}, for more details.
10247 This chapter describes the tracepoint commands and features.
10250 * Set Tracepoints::
10251 * Analyze Collected Data::
10252 * Tracepoint Variables::
10256 @node Set Tracepoints
10257 @section Commands to Set Tracepoints
10259 Before running such a @dfn{trace experiment}, an arbitrary number of
10260 tracepoints can be set. A tracepoint is actually a special type of
10261 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
10262 standard breakpoint commands. For instance, as with breakpoints,
10263 tracepoint numbers are successive integers starting from one, and many
10264 of the commands associated with tracepoints take the tracepoint number
10265 as their argument, to identify which tracepoint to work on.
10267 For each tracepoint, you can specify, in advance, some arbitrary set
10268 of data that you want the target to collect in the trace buffer when
10269 it hits that tracepoint. The collected data can include registers,
10270 local variables, or global data. Later, you can use @value{GDBN}
10271 commands to examine the values these data had at the time the
10272 tracepoint was hit.
10274 Tracepoints do not support every breakpoint feature. Ignore counts on
10275 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
10276 commands when they are hit. Tracepoints may not be thread-specific
10279 @cindex fast tracepoints
10280 Some targets may support @dfn{fast tracepoints}, which are inserted in
10281 a different way (such as with a jump instead of a trap), that is
10282 faster but possibly restricted in where they may be installed.
10284 @cindex static tracepoints
10285 @cindex markers, static tracepoints
10286 @cindex probing markers, static tracepoints
10287 Regular and fast tracepoints are dynamic tracing facilities, meaning
10288 that they can be used to insert tracepoints at (almost) any location
10289 in the target. Some targets may also support controlling @dfn{static
10290 tracepoints} from @value{GDBN}. With static tracing, a set of
10291 instrumentation points, also known as @dfn{markers}, are embedded in
10292 the target program, and can be activated or deactivated by name or
10293 address. These are usually placed at locations which facilitate
10294 investigating what the target is actually doing. @value{GDBN}'s
10295 support for static tracing includes being able to list instrumentation
10296 points, and attach them with @value{GDBN} defined high level
10297 tracepoints that expose the whole range of convenience of
10298 @value{GDBN}'s tracepoints support. Namely, support for collecting
10299 registers values and values of global or local (to the instrumentation
10300 point) variables; tracepoint conditions and trace state variables.
10301 The act of installing a @value{GDBN} static tracepoint on an
10302 instrumentation point, or marker, is referred to as @dfn{probing} a
10303 static tracepoint marker.
10305 @code{gdbserver} supports tracepoints on some target systems.
10306 @xref{Server,,Tracepoints support in @code{gdbserver}}.
10308 This section describes commands to set tracepoints and associated
10309 conditions and actions.
10312 * Create and Delete Tracepoints::
10313 * Enable and Disable Tracepoints::
10314 * Tracepoint Passcounts::
10315 * Tracepoint Conditions::
10316 * Trace State Variables::
10317 * Tracepoint Actions::
10318 * Listing Tracepoints::
10319 * Listing Static Tracepoint Markers::
10320 * Starting and Stopping Trace Experiments::
10321 * Tracepoint Restrictions::
10324 @node Create and Delete Tracepoints
10325 @subsection Create and Delete Tracepoints
10328 @cindex set tracepoint
10330 @item trace @var{location}
10331 The @code{trace} command is very similar to the @code{break} command.
10332 Its argument @var{location} can be a source line, a function name, or
10333 an address in the target program. @xref{Specify Location}. The
10334 @code{trace} command defines a tracepoint, which is a point in the
10335 target program where the debugger will briefly stop, collect some
10336 data, and then allow the program to continue. Setting a tracepoint or
10337 changing its actions doesn't take effect until the next @code{tstart}
10338 command, and once a trace experiment is running, further changes will
10339 not have any effect until the next trace experiment starts.
10341 Here are some examples of using the @code{trace} command:
10344 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
10346 (@value{GDBP}) @b{trace +2} // 2 lines forward
10348 (@value{GDBP}) @b{trace my_function} // first source line of function
10350 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
10352 (@value{GDBP}) @b{trace *0x2117c4} // an address
10356 You can abbreviate @code{trace} as @code{tr}.
10358 @item trace @var{location} if @var{cond}
10359 Set a tracepoint with condition @var{cond}; evaluate the expression
10360 @var{cond} each time the tracepoint is reached, and collect data only
10361 if the value is nonzero---that is, if @var{cond} evaluates as true.
10362 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
10363 information on tracepoint conditions.
10365 @item ftrace @var{location} [ if @var{cond} ]
10366 @cindex set fast tracepoint
10367 @cindex fast tracepoints, setting
10369 The @code{ftrace} command sets a fast tracepoint. For targets that
10370 support them, fast tracepoints will use a more efficient but possibly
10371 less general technique to trigger data collection, such as a jump
10372 instruction instead of a trap, or some sort of hardware support. It
10373 may not be possible to create a fast tracepoint at the desired
10374 location, in which case the command will exit with an explanatory
10377 @value{GDBN} handles arguments to @code{ftrace} exactly as for
10380 @item strace @var{location} [ if @var{cond} ]
10381 @cindex set static tracepoint
10382 @cindex static tracepoints, setting
10383 @cindex probe static tracepoint marker
10385 The @code{strace} command sets a static tracepoint. For targets that
10386 support it, setting a static tracepoint probes a static
10387 instrumentation point, or marker, found at @var{location}. It may not
10388 be possible to set a static tracepoint at the desired location, in
10389 which case the command will exit with an explanatory message.
10391 @value{GDBN} handles arguments to @code{strace} exactly as for
10392 @code{trace}, with the addition that the user can also specify
10393 @code{-m @var{marker}} as @var{location}. This probes the marker
10394 identified by the @var{marker} string identifier. This identifier
10395 depends on the static tracepoint backend library your program is
10396 using. You can find all the marker identifiers in the @samp{ID} field
10397 of the @code{info static-tracepoint-markers} command output.
10398 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
10399 Markers}. For example, in the following small program using the UST
10405 trace_mark(ust, bar33, "str %s", "FOOBAZ");
10410 the marker id is composed of joining the first two arguments to the
10411 @code{trace_mark} call with a slash, which translates to:
10414 (@value{GDBP}) info static-tracepoint-markers
10415 Cnt Enb ID Address What
10416 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
10422 so you may probe the marker above with:
10425 (@value{GDBP}) strace -m ust/bar33
10428 Static tracepoints accept an extra collect action --- @code{collect
10429 $_sdata}. This collects arbitrary user data passed in the probe point
10430 call to the tracing library. In the UST example above, you'll see
10431 that the third argument to @code{trace_mark} is a printf-like format
10432 string. The user data is then the result of running that formating
10433 string against the following arguments. Note that @code{info
10434 static-tracepoint-markers} command output lists that format string in
10435 the @samp{Data:} field.
10437 You can inspect this data when analyzing the trace buffer, by printing
10438 the $_sdata variable like any other variable available to
10439 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
10442 @cindex last tracepoint number
10443 @cindex recent tracepoint number
10444 @cindex tracepoint number
10445 The convenience variable @code{$tpnum} records the tracepoint number
10446 of the most recently set tracepoint.
10448 @kindex delete tracepoint
10449 @cindex tracepoint deletion
10450 @item delete tracepoint @r{[}@var{num}@r{]}
10451 Permanently delete one or more tracepoints. With no argument, the
10452 default is to delete all tracepoints. Note that the regular
10453 @code{delete} command can remove tracepoints also.
10458 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
10460 (@value{GDBP}) @b{delete trace} // remove all tracepoints
10464 You can abbreviate this command as @code{del tr}.
10467 @node Enable and Disable Tracepoints
10468 @subsection Enable and Disable Tracepoints
10470 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
10473 @kindex disable tracepoint
10474 @item disable tracepoint @r{[}@var{num}@r{]}
10475 Disable tracepoint @var{num}, or all tracepoints if no argument
10476 @var{num} is given. A disabled tracepoint will have no effect during
10477 a trace experiment, but it is not forgotten. You can re-enable
10478 a disabled tracepoint using the @code{enable tracepoint} command.
10479 If the command is issued during a trace experiment and the debug target
10480 has support for disabling tracepoints during a trace experiment, then the
10481 change will be effective immediately. Otherwise, it will be applied to the
10482 next trace experiment.
10484 @kindex enable tracepoint
10485 @item enable tracepoint @r{[}@var{num}@r{]}
10486 Enable tracepoint @var{num}, or all tracepoints. If this command is
10487 issued during a trace experiment and the debug target supports enabling
10488 tracepoints during a trace experiment, then the enabled tracepoints will
10489 become effective immediately. Otherwise, they will become effective the
10490 next time a trace experiment is run.
10493 @node Tracepoint Passcounts
10494 @subsection Tracepoint Passcounts
10498 @cindex tracepoint pass count
10499 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
10500 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
10501 automatically stop a trace experiment. If a tracepoint's passcount is
10502 @var{n}, then the trace experiment will be automatically stopped on
10503 the @var{n}'th time that tracepoint is hit. If the tracepoint number
10504 @var{num} is not specified, the @code{passcount} command sets the
10505 passcount of the most recently defined tracepoint. If no passcount is
10506 given, the trace experiment will run until stopped explicitly by the
10512 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
10513 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
10515 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
10516 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
10517 (@value{GDBP}) @b{trace foo}
10518 (@value{GDBP}) @b{pass 3}
10519 (@value{GDBP}) @b{trace bar}
10520 (@value{GDBP}) @b{pass 2}
10521 (@value{GDBP}) @b{trace baz}
10522 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
10523 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
10524 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
10525 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
10529 @node Tracepoint Conditions
10530 @subsection Tracepoint Conditions
10531 @cindex conditional tracepoints
10532 @cindex tracepoint conditions
10534 The simplest sort of tracepoint collects data every time your program
10535 reaches a specified place. You can also specify a @dfn{condition} for
10536 a tracepoint. A condition is just a Boolean expression in your
10537 programming language (@pxref{Expressions, ,Expressions}). A
10538 tracepoint with a condition evaluates the expression each time your
10539 program reaches it, and data collection happens only if the condition
10542 Tracepoint conditions can be specified when a tracepoint is set, by
10543 using @samp{if} in the arguments to the @code{trace} command.
10544 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
10545 also be set or changed at any time with the @code{condition} command,
10546 just as with breakpoints.
10548 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
10549 the conditional expression itself. Instead, @value{GDBN} encodes the
10550 expression into an agent expression (@pxref{Agent Expressions})
10551 suitable for execution on the target, independently of @value{GDBN}.
10552 Global variables become raw memory locations, locals become stack
10553 accesses, and so forth.
10555 For instance, suppose you have a function that is usually called
10556 frequently, but should not be called after an error has occurred. You
10557 could use the following tracepoint command to collect data about calls
10558 of that function that happen while the error code is propagating
10559 through the program; an unconditional tracepoint could end up
10560 collecting thousands of useless trace frames that you would have to
10564 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
10567 @node Trace State Variables
10568 @subsection Trace State Variables
10569 @cindex trace state variables
10571 A @dfn{trace state variable} is a special type of variable that is
10572 created and managed by target-side code. The syntax is the same as
10573 that for GDB's convenience variables (a string prefixed with ``$''),
10574 but they are stored on the target. They must be created explicitly,
10575 using a @code{tvariable} command. They are always 64-bit signed
10578 Trace state variables are remembered by @value{GDBN}, and downloaded
10579 to the target along with tracepoint information when the trace
10580 experiment starts. There are no intrinsic limits on the number of
10581 trace state variables, beyond memory limitations of the target.
10583 @cindex convenience variables, and trace state variables
10584 Although trace state variables are managed by the target, you can use
10585 them in print commands and expressions as if they were convenience
10586 variables; @value{GDBN} will get the current value from the target
10587 while the trace experiment is running. Trace state variables share
10588 the same namespace as other ``$'' variables, which means that you
10589 cannot have trace state variables with names like @code{$23} or
10590 @code{$pc}, nor can you have a trace state variable and a convenience
10591 variable with the same name.
10595 @item tvariable $@var{name} [ = @var{expression} ]
10597 The @code{tvariable} command creates a new trace state variable named
10598 @code{$@var{name}}, and optionally gives it an initial value of
10599 @var{expression}. @var{expression} is evaluated when this command is
10600 entered; the result will be converted to an integer if possible,
10601 otherwise @value{GDBN} will report an error. A subsequent
10602 @code{tvariable} command specifying the same name does not create a
10603 variable, but instead assigns the supplied initial value to the
10604 existing variable of that name, overwriting any previous initial
10605 value. The default initial value is 0.
10607 @item info tvariables
10608 @kindex info tvariables
10609 List all the trace state variables along with their initial values.
10610 Their current values may also be displayed, if the trace experiment is
10613 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
10614 @kindex delete tvariable
10615 Delete the given trace state variables, or all of them if no arguments
10620 @node Tracepoint Actions
10621 @subsection Tracepoint Action Lists
10625 @cindex tracepoint actions
10626 @item actions @r{[}@var{num}@r{]}
10627 This command will prompt for a list of actions to be taken when the
10628 tracepoint is hit. If the tracepoint number @var{num} is not
10629 specified, this command sets the actions for the one that was most
10630 recently defined (so that you can define a tracepoint and then say
10631 @code{actions} without bothering about its number). You specify the
10632 actions themselves on the following lines, one action at a time, and
10633 terminate the actions list with a line containing just @code{end}. So
10634 far, the only defined actions are @code{collect}, @code{teval}, and
10635 @code{while-stepping}.
10637 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
10638 Commands, ,Breakpoint Command Lists}), except that only the defined
10639 actions are allowed; any other @value{GDBN} command is rejected.
10641 @cindex remove actions from a tracepoint
10642 To remove all actions from a tracepoint, type @samp{actions @var{num}}
10643 and follow it immediately with @samp{end}.
10646 (@value{GDBP}) @b{collect @var{data}} // collect some data
10648 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
10650 (@value{GDBP}) @b{end} // signals the end of actions.
10653 In the following example, the action list begins with @code{collect}
10654 commands indicating the things to be collected when the tracepoint is
10655 hit. Then, in order to single-step and collect additional data
10656 following the tracepoint, a @code{while-stepping} command is used,
10657 followed by the list of things to be collected after each step in a
10658 sequence of single steps. The @code{while-stepping} command is
10659 terminated by its own separate @code{end} command. Lastly, the action
10660 list is terminated by an @code{end} command.
10663 (@value{GDBP}) @b{trace foo}
10664 (@value{GDBP}) @b{actions}
10665 Enter actions for tracepoint 1, one per line:
10668 > while-stepping 12
10669 > collect $pc, arr[i]
10674 @kindex collect @r{(tracepoints)}
10675 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
10676 Collect values of the given expressions when the tracepoint is hit.
10677 This command accepts a comma-separated list of any valid expressions.
10678 In addition to global, static, or local variables, the following
10679 special arguments are supported:
10683 Collect all registers.
10686 Collect all function arguments.
10689 Collect all local variables.
10692 Collect the return address. This is helpful if you want to see more
10696 @vindex $_sdata@r{, collect}
10697 Collect static tracepoint marker specific data. Only available for
10698 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
10699 Lists}. On the UST static tracepoints library backend, an
10700 instrumentation point resembles a @code{printf} function call. The
10701 tracing library is able to collect user specified data formatted to a
10702 character string using the format provided by the programmer that
10703 instrumented the program. Other backends have similar mechanisms.
10704 Here's an example of a UST marker call:
10707 const char master_name[] = "$your_name";
10708 trace_mark(channel1, marker1, "hello %s", master_name)
10711 In this case, collecting @code{$_sdata} collects the string
10712 @samp{hello $yourname}. When analyzing the trace buffer, you can
10713 inspect @samp{$_sdata} like any other variable available to
10717 You can give several consecutive @code{collect} commands, each one
10718 with a single argument, or one @code{collect} command with several
10719 arguments separated by commas; the effect is the same.
10721 The optional @var{mods} changes the usual handling of the arguments.
10722 @code{s} requests that pointers to chars be handled as strings, in
10723 particular collecting the contents of the memory being pointed at, up
10724 to the first zero. The upper bound is by default the value of the
10725 @code{print elements} variable; if @code{s} is followed by a decimal
10726 number, that is the upper bound instead. So for instance
10727 @samp{collect/s25 mystr} collects as many as 25 characters at
10730 The command @code{info scope} (@pxref{Symbols, info scope}) is
10731 particularly useful for figuring out what data to collect.
10733 @kindex teval @r{(tracepoints)}
10734 @item teval @var{expr1}, @var{expr2}, @dots{}
10735 Evaluate the given expressions when the tracepoint is hit. This
10736 command accepts a comma-separated list of expressions. The results
10737 are discarded, so this is mainly useful for assigning values to trace
10738 state variables (@pxref{Trace State Variables}) without adding those
10739 values to the trace buffer, as would be the case if the @code{collect}
10742 @kindex while-stepping @r{(tracepoints)}
10743 @item while-stepping @var{n}
10744 Perform @var{n} single-step instruction traces after the tracepoint,
10745 collecting new data after each step. The @code{while-stepping}
10746 command is followed by the list of what to collect while stepping
10747 (followed by its own @code{end} command):
10750 > while-stepping 12
10751 > collect $regs, myglobal
10757 Note that @code{$pc} is not automatically collected by
10758 @code{while-stepping}; you need to explicitly collect that register if
10759 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
10762 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
10763 @kindex set default-collect
10764 @cindex default collection action
10765 This variable is a list of expressions to collect at each tracepoint
10766 hit. It is effectively an additional @code{collect} action prepended
10767 to every tracepoint action list. The expressions are parsed
10768 individually for each tracepoint, so for instance a variable named
10769 @code{xyz} may be interpreted as a global for one tracepoint, and a
10770 local for another, as appropriate to the tracepoint's location.
10772 @item show default-collect
10773 @kindex show default-collect
10774 Show the list of expressions that are collected by default at each
10779 @node Listing Tracepoints
10780 @subsection Listing Tracepoints
10783 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
10784 @kindex info tp @r{[}@var{n}@dots{}@r{]}
10785 @cindex information about tracepoints
10786 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
10787 Display information about the tracepoint @var{num}. If you don't
10788 specify a tracepoint number, displays information about all the
10789 tracepoints defined so far. The format is similar to that used for
10790 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
10791 command, simply restricting itself to tracepoints.
10793 A tracepoint's listing may include additional information specific to
10798 its passcount as given by the @code{passcount @var{n}} command
10802 (@value{GDBP}) @b{info trace}
10803 Num Type Disp Enb Address What
10804 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
10806 collect globfoo, $regs
10815 This command can be abbreviated @code{info tp}.
10818 @node Listing Static Tracepoint Markers
10819 @subsection Listing Static Tracepoint Markers
10822 @kindex info static-tracepoint-markers
10823 @cindex information about static tracepoint markers
10824 @item info static-tracepoint-markers
10825 Display information about all static tracepoint markers defined in the
10828 For each marker, the following columns are printed:
10832 An incrementing counter, output to help readability. This is not a
10835 The marker ID, as reported by the target.
10836 @item Enabled or Disabled
10837 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
10838 that are not enabled.
10840 Where the marker is in your program, as a memory address.
10842 Where the marker is in the source for your program, as a file and line
10843 number. If the debug information included in the program does not
10844 allow @value{GDBN} to locate the source of the marker, this column
10845 will be left blank.
10849 In addition, the following information may be printed for each marker:
10853 User data passed to the tracing library by the marker call. In the
10854 UST backend, this is the format string passed as argument to the
10856 @item Static tracepoints probing the marker
10857 The list of static tracepoints attached to the marker.
10861 (@value{GDBP}) info static-tracepoint-markers
10862 Cnt ID Enb Address What
10863 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
10864 Data: number1 %d number2 %d
10865 Probed by static tracepoints: #2
10866 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
10872 @node Starting and Stopping Trace Experiments
10873 @subsection Starting and Stopping Trace Experiments
10877 @cindex start a new trace experiment
10878 @cindex collected data discarded
10880 This command takes no arguments. It starts the trace experiment, and
10881 begins collecting data. This has the side effect of discarding all
10882 the data collected in the trace buffer during the previous trace
10886 @cindex stop a running trace experiment
10888 This command takes no arguments. It ends the trace experiment, and
10889 stops collecting data.
10891 @strong{Note}: a trace experiment and data collection may stop
10892 automatically if any tracepoint's passcount is reached
10893 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
10896 @cindex status of trace data collection
10897 @cindex trace experiment, status of
10899 This command displays the status of the current trace data
10903 Here is an example of the commands we described so far:
10906 (@value{GDBP}) @b{trace gdb_c_test}
10907 (@value{GDBP}) @b{actions}
10908 Enter actions for tracepoint #1, one per line.
10909 > collect $regs,$locals,$args
10910 > while-stepping 11
10914 (@value{GDBP}) @b{tstart}
10915 [time passes @dots{}]
10916 (@value{GDBP}) @b{tstop}
10919 @anchor{disconnected tracing}
10920 @cindex disconnected tracing
10921 You can choose to continue running the trace experiment even if
10922 @value{GDBN} disconnects from the target, voluntarily or
10923 involuntarily. For commands such as @code{detach}, the debugger will
10924 ask what you want to do with the trace. But for unexpected
10925 terminations (@value{GDBN} crash, network outage), it would be
10926 unfortunate to lose hard-won trace data, so the variable
10927 @code{disconnected-tracing} lets you decide whether the trace should
10928 continue running without @value{GDBN}.
10931 @item set disconnected-tracing on
10932 @itemx set disconnected-tracing off
10933 @kindex set disconnected-tracing
10934 Choose whether a tracing run should continue to run if @value{GDBN}
10935 has disconnected from the target. Note that @code{detach} or
10936 @code{quit} will ask you directly what to do about a running trace no
10937 matter what this variable's setting, so the variable is mainly useful
10938 for handling unexpected situations, such as loss of the network.
10940 @item show disconnected-tracing
10941 @kindex show disconnected-tracing
10942 Show the current choice for disconnected tracing.
10946 When you reconnect to the target, the trace experiment may or may not
10947 still be running; it might have filled the trace buffer in the
10948 meantime, or stopped for one of the other reasons. If it is running,
10949 it will continue after reconnection.
10951 Upon reconnection, the target will upload information about the
10952 tracepoints in effect. @value{GDBN} will then compare that
10953 information to the set of tracepoints currently defined, and attempt
10954 to match them up, allowing for the possibility that the numbers may
10955 have changed due to creation and deletion in the meantime. If one of
10956 the target's tracepoints does not match any in @value{GDBN}, the
10957 debugger will create a new tracepoint, so that you have a number with
10958 which to specify that tracepoint. This matching-up process is
10959 necessarily heuristic, and it may result in useless tracepoints being
10960 created; you may simply delete them if they are of no use.
10962 @cindex circular trace buffer
10963 If your target agent supports a @dfn{circular trace buffer}, then you
10964 can run a trace experiment indefinitely without filling the trace
10965 buffer; when space runs out, the agent deletes already-collected trace
10966 frames, oldest first, until there is enough room to continue
10967 collecting. This is especially useful if your tracepoints are being
10968 hit too often, and your trace gets terminated prematurely because the
10969 buffer is full. To ask for a circular trace buffer, simply set
10970 @samp{circular-trace-buffer} to on. You can set this at any time,
10971 including during tracing; if the agent can do it, it will change
10972 buffer handling on the fly, otherwise it will not take effect until
10976 @item set circular-trace-buffer on
10977 @itemx set circular-trace-buffer off
10978 @kindex set circular-trace-buffer
10979 Choose whether a tracing run should use a linear or circular buffer
10980 for trace data. A linear buffer will not lose any trace data, but may
10981 fill up prematurely, while a circular buffer will discard old trace
10982 data, but it will have always room for the latest tracepoint hits.
10984 @item show circular-trace-buffer
10985 @kindex show circular-trace-buffer
10986 Show the current choice for the trace buffer. Note that this may not
10987 match the agent's current buffer handling, nor is it guaranteed to
10988 match the setting that might have been in effect during a past run,
10989 for instance if you are looking at frames from a trace file.
10993 @node Tracepoint Restrictions
10994 @subsection Tracepoint Restrictions
10996 @cindex tracepoint restrictions
10997 There are a number of restrictions on the use of tracepoints. As
10998 described above, tracepoint data gathering occurs on the target
10999 without interaction from @value{GDBN}. Thus the full capabilities of
11000 the debugger are not available during data gathering, and then at data
11001 examination time, you will be limited by only having what was
11002 collected. The following items describe some common problems, but it
11003 is not exhaustive, and you may run into additional difficulties not
11009 Tracepoint expressions are intended to gather objects (lvalues). Thus
11010 the full flexibility of GDB's expression evaluator is not available.
11011 You cannot call functions, cast objects to aggregate types, access
11012 convenience variables or modify values (except by assignment to trace
11013 state variables). Some language features may implicitly call
11014 functions (for instance Objective-C fields with accessors), and therefore
11015 cannot be collected either.
11018 Collection of local variables, either individually or in bulk with
11019 @code{$locals} or @code{$args}, during @code{while-stepping} may
11020 behave erratically. The stepping action may enter a new scope (for
11021 instance by stepping into a function), or the location of the variable
11022 may change (for instance it is loaded into a register). The
11023 tracepoint data recorded uses the location information for the
11024 variables that is correct for the tracepoint location. When the
11025 tracepoint is created, it is not possible, in general, to determine
11026 where the steps of a @code{while-stepping} sequence will advance the
11027 program---particularly if a conditional branch is stepped.
11030 Collection of an incompletely-initialized or partially-destroyed object
11031 may result in something that @value{GDBN} cannot display, or displays
11032 in a misleading way.
11035 When @value{GDBN} displays a pointer to character it automatically
11036 dereferences the pointer to also display characters of the string
11037 being pointed to. However, collecting the pointer during tracing does
11038 not automatically collect the string. You need to explicitly
11039 dereference the pointer and provide size information if you want to
11040 collect not only the pointer, but the memory pointed to. For example,
11041 @code{*ptr@@50} can be used to collect the 50 element array pointed to
11045 It is not possible to collect a complete stack backtrace at a
11046 tracepoint. Instead, you may collect the registers and a few hundred
11047 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
11048 (adjust to use the name of the actual stack pointer register on your
11049 target architecture, and the amount of stack you wish to capture).
11050 Then the @code{backtrace} command will show a partial backtrace when
11051 using a trace frame. The number of stack frames that can be examined
11052 depends on the sizes of the frames in the collected stack. Note that
11053 if you ask for a block so large that it goes past the bottom of the
11054 stack, the target agent may report an error trying to read from an
11058 If you do not collect registers at a tracepoint, @value{GDBN} can
11059 infer that the value of @code{$pc} must be the same as the address of
11060 the tracepoint and use that when you are looking at a trace frame
11061 for that tracepoint. However, this cannot work if the tracepoint has
11062 multiple locations (for instance if it was set in a function that was
11063 inlined), or if it has a @code{while-stepping} loop. In those cases
11064 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
11069 @node Analyze Collected Data
11070 @section Using the Collected Data
11072 After the tracepoint experiment ends, you use @value{GDBN} commands
11073 for examining the trace data. The basic idea is that each tracepoint
11074 collects a trace @dfn{snapshot} every time it is hit and another
11075 snapshot every time it single-steps. All these snapshots are
11076 consecutively numbered from zero and go into a buffer, and you can
11077 examine them later. The way you examine them is to @dfn{focus} on a
11078 specific trace snapshot. When the remote stub is focused on a trace
11079 snapshot, it will respond to all @value{GDBN} requests for memory and
11080 registers by reading from the buffer which belongs to that snapshot,
11081 rather than from @emph{real} memory or registers of the program being
11082 debugged. This means that @strong{all} @value{GDBN} commands
11083 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
11084 behave as if we were currently debugging the program state as it was
11085 when the tracepoint occurred. Any requests for data that are not in
11086 the buffer will fail.
11089 * tfind:: How to select a trace snapshot
11090 * tdump:: How to display all data for a snapshot
11091 * save tracepoints:: How to save tracepoints for a future run
11095 @subsection @code{tfind @var{n}}
11098 @cindex select trace snapshot
11099 @cindex find trace snapshot
11100 The basic command for selecting a trace snapshot from the buffer is
11101 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
11102 counting from zero. If no argument @var{n} is given, the next
11103 snapshot is selected.
11105 Here are the various forms of using the @code{tfind} command.
11109 Find the first snapshot in the buffer. This is a synonym for
11110 @code{tfind 0} (since 0 is the number of the first snapshot).
11113 Stop debugging trace snapshots, resume @emph{live} debugging.
11116 Same as @samp{tfind none}.
11119 No argument means find the next trace snapshot.
11122 Find the previous trace snapshot before the current one. This permits
11123 retracing earlier steps.
11125 @item tfind tracepoint @var{num}
11126 Find the next snapshot associated with tracepoint @var{num}. Search
11127 proceeds forward from the last examined trace snapshot. If no
11128 argument @var{num} is given, it means find the next snapshot collected
11129 for the same tracepoint as the current snapshot.
11131 @item tfind pc @var{addr}
11132 Find the next snapshot associated with the value @var{addr} of the
11133 program counter. Search proceeds forward from the last examined trace
11134 snapshot. If no argument @var{addr} is given, it means find the next
11135 snapshot with the same value of PC as the current snapshot.
11137 @item tfind outside @var{addr1}, @var{addr2}
11138 Find the next snapshot whose PC is outside the given range of
11139 addresses (exclusive).
11141 @item tfind range @var{addr1}, @var{addr2}
11142 Find the next snapshot whose PC is between @var{addr1} and
11143 @var{addr2} (inclusive).
11145 @item tfind line @r{[}@var{file}:@r{]}@var{n}
11146 Find the next snapshot associated with the source line @var{n}. If
11147 the optional argument @var{file} is given, refer to line @var{n} in
11148 that source file. Search proceeds forward from the last examined
11149 trace snapshot. If no argument @var{n} is given, it means find the
11150 next line other than the one currently being examined; thus saying
11151 @code{tfind line} repeatedly can appear to have the same effect as
11152 stepping from line to line in a @emph{live} debugging session.
11155 The default arguments for the @code{tfind} commands are specifically
11156 designed to make it easy to scan through the trace buffer. For
11157 instance, @code{tfind} with no argument selects the next trace
11158 snapshot, and @code{tfind -} with no argument selects the previous
11159 trace snapshot. So, by giving one @code{tfind} command, and then
11160 simply hitting @key{RET} repeatedly you can examine all the trace
11161 snapshots in order. Or, by saying @code{tfind -} and then hitting
11162 @key{RET} repeatedly you can examine the snapshots in reverse order.
11163 The @code{tfind line} command with no argument selects the snapshot
11164 for the next source line executed. The @code{tfind pc} command with
11165 no argument selects the next snapshot with the same program counter
11166 (PC) as the current frame. The @code{tfind tracepoint} command with
11167 no argument selects the next trace snapshot collected by the same
11168 tracepoint as the current one.
11170 In addition to letting you scan through the trace buffer manually,
11171 these commands make it easy to construct @value{GDBN} scripts that
11172 scan through the trace buffer and print out whatever collected data
11173 you are interested in. Thus, if we want to examine the PC, FP, and SP
11174 registers from each trace frame in the buffer, we can say this:
11177 (@value{GDBP}) @b{tfind start}
11178 (@value{GDBP}) @b{while ($trace_frame != -1)}
11179 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
11180 $trace_frame, $pc, $sp, $fp
11184 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
11185 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
11186 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
11187 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
11188 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
11189 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
11190 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
11191 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
11192 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
11193 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
11194 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
11197 Or, if we want to examine the variable @code{X} at each source line in
11201 (@value{GDBP}) @b{tfind start}
11202 (@value{GDBP}) @b{while ($trace_frame != -1)}
11203 > printf "Frame %d, X == %d\n", $trace_frame, X
11213 @subsection @code{tdump}
11215 @cindex dump all data collected at tracepoint
11216 @cindex tracepoint data, display
11218 This command takes no arguments. It prints all the data collected at
11219 the current trace snapshot.
11222 (@value{GDBP}) @b{trace 444}
11223 (@value{GDBP}) @b{actions}
11224 Enter actions for tracepoint #2, one per line:
11225 > collect $regs, $locals, $args, gdb_long_test
11228 (@value{GDBP}) @b{tstart}
11230 (@value{GDBP}) @b{tfind line 444}
11231 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
11233 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
11235 (@value{GDBP}) @b{tdump}
11236 Data collected at tracepoint 2, trace frame 1:
11237 d0 0xc4aa0085 -995491707
11241 d4 0x71aea3d 119204413
11244 d7 0x380035 3670069
11245 a0 0x19e24a 1696330
11246 a1 0x3000668 50333288
11248 a3 0x322000 3284992
11249 a4 0x3000698 50333336
11250 a5 0x1ad3cc 1758156
11251 fp 0x30bf3c 0x30bf3c
11252 sp 0x30bf34 0x30bf34
11254 pc 0x20b2c8 0x20b2c8
11258 p = 0x20e5b4 "gdb-test"
11265 gdb_long_test = 17 '\021'
11270 @code{tdump} works by scanning the tracepoint's current collection
11271 actions and printing the value of each expression listed. So
11272 @code{tdump} can fail, if after a run, you change the tracepoint's
11273 actions to mention variables that were not collected during the run.
11275 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
11276 uses the collected value of @code{$pc} to distinguish between trace
11277 frames that were collected at the tracepoint hit, and frames that were
11278 collected while stepping. This allows it to correctly choose whether
11279 to display the basic list of collections, or the collections from the
11280 body of the while-stepping loop. However, if @code{$pc} was not collected,
11281 then @code{tdump} will always attempt to dump using the basic collection
11282 list, and may fail if a while-stepping frame does not include all the
11283 same data that is collected at the tracepoint hit.
11284 @c This is getting pretty arcane, example would be good.
11286 @node save tracepoints
11287 @subsection @code{save tracepoints @var{filename}}
11288 @kindex save tracepoints
11289 @kindex save-tracepoints
11290 @cindex save tracepoints for future sessions
11292 This command saves all current tracepoint definitions together with
11293 their actions and passcounts, into a file @file{@var{filename}}
11294 suitable for use in a later debugging session. To read the saved
11295 tracepoint definitions, use the @code{source} command (@pxref{Command
11296 Files}). The @w{@code{save-tracepoints}} command is a deprecated
11297 alias for @w{@code{save tracepoints}}
11299 @node Tracepoint Variables
11300 @section Convenience Variables for Tracepoints
11301 @cindex tracepoint variables
11302 @cindex convenience variables for tracepoints
11305 @vindex $trace_frame
11306 @item (int) $trace_frame
11307 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
11308 snapshot is selected.
11310 @vindex $tracepoint
11311 @item (int) $tracepoint
11312 The tracepoint for the current trace snapshot.
11314 @vindex $trace_line
11315 @item (int) $trace_line
11316 The line number for the current trace snapshot.
11318 @vindex $trace_file
11319 @item (char []) $trace_file
11320 The source file for the current trace snapshot.
11322 @vindex $trace_func
11323 @item (char []) $trace_func
11324 The name of the function containing @code{$tracepoint}.
11327 Note: @code{$trace_file} is not suitable for use in @code{printf},
11328 use @code{output} instead.
11330 Here's a simple example of using these convenience variables for
11331 stepping through all the trace snapshots and printing some of their
11332 data. Note that these are not the same as trace state variables,
11333 which are managed by the target.
11336 (@value{GDBP}) @b{tfind start}
11338 (@value{GDBP}) @b{while $trace_frame != -1}
11339 > output $trace_file
11340 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
11346 @section Using Trace Files
11347 @cindex trace files
11349 In some situations, the target running a trace experiment may no
11350 longer be available; perhaps it crashed, or the hardware was needed
11351 for a different activity. To handle these cases, you can arrange to
11352 dump the trace data into a file, and later use that file as a source
11353 of trace data, via the @code{target tfile} command.
11358 @item tsave [ -r ] @var{filename}
11359 Save the trace data to @var{filename}. By default, this command
11360 assumes that @var{filename} refers to the host filesystem, so if
11361 necessary @value{GDBN} will copy raw trace data up from the target and
11362 then save it. If the target supports it, you can also supply the
11363 optional argument @code{-r} (``remote'') to direct the target to save
11364 the data directly into @var{filename} in its own filesystem, which may be
11365 more efficient if the trace buffer is very large. (Note, however, that
11366 @code{target tfile} can only read from files accessible to the host.)
11368 @kindex target tfile
11370 @item target tfile @var{filename}
11371 Use the file named @var{filename} as a source of trace data. Commands
11372 that examine data work as they do with a live target, but it is not
11373 possible to run any new trace experiments. @code{tstatus} will report
11374 the state of the trace run at the moment the data was saved, as well
11375 as the current trace frame you are examining. @var{filename} must be
11376 on a filesystem accessible to the host.
11381 @chapter Debugging Programs That Use Overlays
11384 If your program is too large to fit completely in your target system's
11385 memory, you can sometimes use @dfn{overlays} to work around this
11386 problem. @value{GDBN} provides some support for debugging programs that
11390 * How Overlays Work:: A general explanation of overlays.
11391 * Overlay Commands:: Managing overlays in @value{GDBN}.
11392 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
11393 mapped by asking the inferior.
11394 * Overlay Sample Program:: A sample program using overlays.
11397 @node How Overlays Work
11398 @section How Overlays Work
11399 @cindex mapped overlays
11400 @cindex unmapped overlays
11401 @cindex load address, overlay's
11402 @cindex mapped address
11403 @cindex overlay area
11405 Suppose you have a computer whose instruction address space is only 64
11406 kilobytes long, but which has much more memory which can be accessed by
11407 other means: special instructions, segment registers, or memory
11408 management hardware, for example. Suppose further that you want to
11409 adapt a program which is larger than 64 kilobytes to run on this system.
11411 One solution is to identify modules of your program which are relatively
11412 independent, and need not call each other directly; call these modules
11413 @dfn{overlays}. Separate the overlays from the main program, and place
11414 their machine code in the larger memory. Place your main program in
11415 instruction memory, but leave at least enough space there to hold the
11416 largest overlay as well.
11418 Now, to call a function located in an overlay, you must first copy that
11419 overlay's machine code from the large memory into the space set aside
11420 for it in the instruction memory, and then jump to its entry point
11423 @c NB: In the below the mapped area's size is greater or equal to the
11424 @c size of all overlays. This is intentional to remind the developer
11425 @c that overlays don't necessarily need to be the same size.
11429 Data Instruction Larger
11430 Address Space Address Space Address Space
11431 +-----------+ +-----------+ +-----------+
11433 +-----------+ +-----------+ +-----------+<-- overlay 1
11434 | program | | main | .----| overlay 1 | load address
11435 | variables | | program | | +-----------+
11436 | and heap | | | | | |
11437 +-----------+ | | | +-----------+<-- overlay 2
11438 | | +-----------+ | | | load address
11439 +-----------+ | | | .-| overlay 2 |
11441 mapped --->+-----------+ | | +-----------+
11442 address | | | | | |
11443 | overlay | <-' | | |
11444 | area | <---' +-----------+<-- overlay 3
11445 | | <---. | | load address
11446 +-----------+ `--| overlay 3 |
11453 @anchor{A code overlay}A code overlay
11457 The diagram (@pxref{A code overlay}) shows a system with separate data
11458 and instruction address spaces. To map an overlay, the program copies
11459 its code from the larger address space to the instruction address space.
11460 Since the overlays shown here all use the same mapped address, only one
11461 may be mapped at a time. For a system with a single address space for
11462 data and instructions, the diagram would be similar, except that the
11463 program variables and heap would share an address space with the main
11464 program and the overlay area.
11466 An overlay loaded into instruction memory and ready for use is called a
11467 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
11468 instruction memory. An overlay not present (or only partially present)
11469 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
11470 is its address in the larger memory. The mapped address is also called
11471 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
11472 called the @dfn{load memory address}, or @dfn{LMA}.
11474 Unfortunately, overlays are not a completely transparent way to adapt a
11475 program to limited instruction memory. They introduce a new set of
11476 global constraints you must keep in mind as you design your program:
11481 Before calling or returning to a function in an overlay, your program
11482 must make sure that overlay is actually mapped. Otherwise, the call or
11483 return will transfer control to the right address, but in the wrong
11484 overlay, and your program will probably crash.
11487 If the process of mapping an overlay is expensive on your system, you
11488 will need to choose your overlays carefully to minimize their effect on
11489 your program's performance.
11492 The executable file you load onto your system must contain each
11493 overlay's instructions, appearing at the overlay's load address, not its
11494 mapped address. However, each overlay's instructions must be relocated
11495 and its symbols defined as if the overlay were at its mapped address.
11496 You can use GNU linker scripts to specify different load and relocation
11497 addresses for pieces of your program; see @ref{Overlay Description,,,
11498 ld.info, Using ld: the GNU linker}.
11501 The procedure for loading executable files onto your system must be able
11502 to load their contents into the larger address space as well as the
11503 instruction and data spaces.
11507 The overlay system described above is rather simple, and could be
11508 improved in many ways:
11513 If your system has suitable bank switch registers or memory management
11514 hardware, you could use those facilities to make an overlay's load area
11515 contents simply appear at their mapped address in instruction space.
11516 This would probably be faster than copying the overlay to its mapped
11517 area in the usual way.
11520 If your overlays are small enough, you could set aside more than one
11521 overlay area, and have more than one overlay mapped at a time.
11524 You can use overlays to manage data, as well as instructions. In
11525 general, data overlays are even less transparent to your design than
11526 code overlays: whereas code overlays only require care when you call or
11527 return to functions, data overlays require care every time you access
11528 the data. Also, if you change the contents of a data overlay, you
11529 must copy its contents back out to its load address before you can copy a
11530 different data overlay into the same mapped area.
11535 @node Overlay Commands
11536 @section Overlay Commands
11538 To use @value{GDBN}'s overlay support, each overlay in your program must
11539 correspond to a separate section of the executable file. The section's
11540 virtual memory address and load memory address must be the overlay's
11541 mapped and load addresses. Identifying overlays with sections allows
11542 @value{GDBN} to determine the appropriate address of a function or
11543 variable, depending on whether the overlay is mapped or not.
11545 @value{GDBN}'s overlay commands all start with the word @code{overlay};
11546 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
11551 Disable @value{GDBN}'s overlay support. When overlay support is
11552 disabled, @value{GDBN} assumes that all functions and variables are
11553 always present at their mapped addresses. By default, @value{GDBN}'s
11554 overlay support is disabled.
11556 @item overlay manual
11557 @cindex manual overlay debugging
11558 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
11559 relies on you to tell it which overlays are mapped, and which are not,
11560 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
11561 commands described below.
11563 @item overlay map-overlay @var{overlay}
11564 @itemx overlay map @var{overlay}
11565 @cindex map an overlay
11566 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
11567 be the name of the object file section containing the overlay. When an
11568 overlay is mapped, @value{GDBN} assumes it can find the overlay's
11569 functions and variables at their mapped addresses. @value{GDBN} assumes
11570 that any other overlays whose mapped ranges overlap that of
11571 @var{overlay} are now unmapped.
11573 @item overlay unmap-overlay @var{overlay}
11574 @itemx overlay unmap @var{overlay}
11575 @cindex unmap an overlay
11576 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
11577 must be the name of the object file section containing the overlay.
11578 When an overlay is unmapped, @value{GDBN} assumes it can find the
11579 overlay's functions and variables at their load addresses.
11582 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
11583 consults a data structure the overlay manager maintains in the inferior
11584 to see which overlays are mapped. For details, see @ref{Automatic
11585 Overlay Debugging}.
11587 @item overlay load-target
11588 @itemx overlay load
11589 @cindex reloading the overlay table
11590 Re-read the overlay table from the inferior. Normally, @value{GDBN}
11591 re-reads the table @value{GDBN} automatically each time the inferior
11592 stops, so this command should only be necessary if you have changed the
11593 overlay mapping yourself using @value{GDBN}. This command is only
11594 useful when using automatic overlay debugging.
11596 @item overlay list-overlays
11597 @itemx overlay list
11598 @cindex listing mapped overlays
11599 Display a list of the overlays currently mapped, along with their mapped
11600 addresses, load addresses, and sizes.
11604 Normally, when @value{GDBN} prints a code address, it includes the name
11605 of the function the address falls in:
11608 (@value{GDBP}) print main
11609 $3 = @{int ()@} 0x11a0 <main>
11612 When overlay debugging is enabled, @value{GDBN} recognizes code in
11613 unmapped overlays, and prints the names of unmapped functions with
11614 asterisks around them. For example, if @code{foo} is a function in an
11615 unmapped overlay, @value{GDBN} prints it this way:
11618 (@value{GDBP}) overlay list
11619 No sections are mapped.
11620 (@value{GDBP}) print foo
11621 $5 = @{int (int)@} 0x100000 <*foo*>
11624 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
11628 (@value{GDBP}) overlay list
11629 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
11630 mapped at 0x1016 - 0x104a
11631 (@value{GDBP}) print foo
11632 $6 = @{int (int)@} 0x1016 <foo>
11635 When overlay debugging is enabled, @value{GDBN} can find the correct
11636 address for functions and variables in an overlay, whether or not the
11637 overlay is mapped. This allows most @value{GDBN} commands, like
11638 @code{break} and @code{disassemble}, to work normally, even on unmapped
11639 code. However, @value{GDBN}'s breakpoint support has some limitations:
11643 @cindex breakpoints in overlays
11644 @cindex overlays, setting breakpoints in
11645 You can set breakpoints in functions in unmapped overlays, as long as
11646 @value{GDBN} can write to the overlay at its load address.
11648 @value{GDBN} can not set hardware or simulator-based breakpoints in
11649 unmapped overlays. However, if you set a breakpoint at the end of your
11650 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
11651 you are using manual overlay management), @value{GDBN} will re-set its
11652 breakpoints properly.
11656 @node Automatic Overlay Debugging
11657 @section Automatic Overlay Debugging
11658 @cindex automatic overlay debugging
11660 @value{GDBN} can automatically track which overlays are mapped and which
11661 are not, given some simple co-operation from the overlay manager in the
11662 inferior. If you enable automatic overlay debugging with the
11663 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
11664 looks in the inferior's memory for certain variables describing the
11665 current state of the overlays.
11667 Here are the variables your overlay manager must define to support
11668 @value{GDBN}'s automatic overlay debugging:
11672 @item @code{_ovly_table}:
11673 This variable must be an array of the following structures:
11678 /* The overlay's mapped address. */
11681 /* The size of the overlay, in bytes. */
11682 unsigned long size;
11684 /* The overlay's load address. */
11687 /* Non-zero if the overlay is currently mapped;
11689 unsigned long mapped;
11693 @item @code{_novlys}:
11694 This variable must be a four-byte signed integer, holding the total
11695 number of elements in @code{_ovly_table}.
11699 To decide whether a particular overlay is mapped or not, @value{GDBN}
11700 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
11701 @code{lma} members equal the VMA and LMA of the overlay's section in the
11702 executable file. When @value{GDBN} finds a matching entry, it consults
11703 the entry's @code{mapped} member to determine whether the overlay is
11706 In addition, your overlay manager may define a function called
11707 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
11708 will silently set a breakpoint there. If the overlay manager then
11709 calls this function whenever it has changed the overlay table, this
11710 will enable @value{GDBN} to accurately keep track of which overlays
11711 are in program memory, and update any breakpoints that may be set
11712 in overlays. This will allow breakpoints to work even if the
11713 overlays are kept in ROM or other non-writable memory while they
11714 are not being executed.
11716 @node Overlay Sample Program
11717 @section Overlay Sample Program
11718 @cindex overlay example program
11720 When linking a program which uses overlays, you must place the overlays
11721 at their load addresses, while relocating them to run at their mapped
11722 addresses. To do this, you must write a linker script (@pxref{Overlay
11723 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
11724 since linker scripts are specific to a particular host system, target
11725 architecture, and target memory layout, this manual cannot provide
11726 portable sample code demonstrating @value{GDBN}'s overlay support.
11728 However, the @value{GDBN} source distribution does contain an overlaid
11729 program, with linker scripts for a few systems, as part of its test
11730 suite. The program consists of the following files from
11731 @file{gdb/testsuite/gdb.base}:
11735 The main program file.
11737 A simple overlay manager, used by @file{overlays.c}.
11742 Overlay modules, loaded and used by @file{overlays.c}.
11745 Linker scripts for linking the test program on the @code{d10v-elf}
11746 and @code{m32r-elf} targets.
11749 You can build the test program using the @code{d10v-elf} GCC
11750 cross-compiler like this:
11753 $ d10v-elf-gcc -g -c overlays.c
11754 $ d10v-elf-gcc -g -c ovlymgr.c
11755 $ d10v-elf-gcc -g -c foo.c
11756 $ d10v-elf-gcc -g -c bar.c
11757 $ d10v-elf-gcc -g -c baz.c
11758 $ d10v-elf-gcc -g -c grbx.c
11759 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
11760 baz.o grbx.o -Wl,-Td10v.ld -o overlays
11763 The build process is identical for any other architecture, except that
11764 you must substitute the appropriate compiler and linker script for the
11765 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
11769 @chapter Using @value{GDBN} with Different Languages
11772 Although programming languages generally have common aspects, they are
11773 rarely expressed in the same manner. For instance, in ANSI C,
11774 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
11775 Modula-2, it is accomplished by @code{p^}. Values can also be
11776 represented (and displayed) differently. Hex numbers in C appear as
11777 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
11779 @cindex working language
11780 Language-specific information is built into @value{GDBN} for some languages,
11781 allowing you to express operations like the above in your program's
11782 native language, and allowing @value{GDBN} to output values in a manner
11783 consistent with the syntax of your program's native language. The
11784 language you use to build expressions is called the @dfn{working
11788 * Setting:: Switching between source languages
11789 * Show:: Displaying the language
11790 * Checks:: Type and range checks
11791 * Supported Languages:: Supported languages
11792 * Unsupported Languages:: Unsupported languages
11796 @section Switching Between Source Languages
11798 There are two ways to control the working language---either have @value{GDBN}
11799 set it automatically, or select it manually yourself. You can use the
11800 @code{set language} command for either purpose. On startup, @value{GDBN}
11801 defaults to setting the language automatically. The working language is
11802 used to determine how expressions you type are interpreted, how values
11805 In addition to the working language, every source file that
11806 @value{GDBN} knows about has its own working language. For some object
11807 file formats, the compiler might indicate which language a particular
11808 source file is in. However, most of the time @value{GDBN} infers the
11809 language from the name of the file. The language of a source file
11810 controls whether C@t{++} names are demangled---this way @code{backtrace} can
11811 show each frame appropriately for its own language. There is no way to
11812 set the language of a source file from within @value{GDBN}, but you can
11813 set the language associated with a filename extension. @xref{Show, ,
11814 Displaying the Language}.
11816 This is most commonly a problem when you use a program, such
11817 as @code{cfront} or @code{f2c}, that generates C but is written in
11818 another language. In that case, make the
11819 program use @code{#line} directives in its C output; that way
11820 @value{GDBN} will know the correct language of the source code of the original
11821 program, and will display that source code, not the generated C code.
11824 * Filenames:: Filename extensions and languages.
11825 * Manually:: Setting the working language manually
11826 * Automatically:: Having @value{GDBN} infer the source language
11830 @subsection List of Filename Extensions and Languages
11832 If a source file name ends in one of the following extensions, then
11833 @value{GDBN} infers that its language is the one indicated.
11851 C@t{++} source file
11857 Objective-C source file
11861 Fortran source file
11864 Modula-2 source file
11868 Assembler source file. This actually behaves almost like C, but
11869 @value{GDBN} does not skip over function prologues when stepping.
11872 In addition, you may set the language associated with a filename
11873 extension. @xref{Show, , Displaying the Language}.
11876 @subsection Setting the Working Language
11878 If you allow @value{GDBN} to set the language automatically,
11879 expressions are interpreted the same way in your debugging session and
11882 @kindex set language
11883 If you wish, you may set the language manually. To do this, issue the
11884 command @samp{set language @var{lang}}, where @var{lang} is the name of
11885 a language, such as
11886 @code{c} or @code{modula-2}.
11887 For a list of the supported languages, type @samp{set language}.
11889 Setting the language manually prevents @value{GDBN} from updating the working
11890 language automatically. This can lead to confusion if you try
11891 to debug a program when the working language is not the same as the
11892 source language, when an expression is acceptable to both
11893 languages---but means different things. For instance, if the current
11894 source file were written in C, and @value{GDBN} was parsing Modula-2, a
11902 might not have the effect you intended. In C, this means to add
11903 @code{b} and @code{c} and place the result in @code{a}. The result
11904 printed would be the value of @code{a}. In Modula-2, this means to compare
11905 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
11907 @node Automatically
11908 @subsection Having @value{GDBN} Infer the Source Language
11910 To have @value{GDBN} set the working language automatically, use
11911 @samp{set language local} or @samp{set language auto}. @value{GDBN}
11912 then infers the working language. That is, when your program stops in a
11913 frame (usually by encountering a breakpoint), @value{GDBN} sets the
11914 working language to the language recorded for the function in that
11915 frame. If the language for a frame is unknown (that is, if the function
11916 or block corresponding to the frame was defined in a source file that
11917 does not have a recognized extension), the current working language is
11918 not changed, and @value{GDBN} issues a warning.
11920 This may not seem necessary for most programs, which are written
11921 entirely in one source language. However, program modules and libraries
11922 written in one source language can be used by a main program written in
11923 a different source language. Using @samp{set language auto} in this
11924 case frees you from having to set the working language manually.
11927 @section Displaying the Language
11929 The following commands help you find out which language is the
11930 working language, and also what language source files were written in.
11933 @item show language
11934 @kindex show language
11935 Display the current working language. This is the
11936 language you can use with commands such as @code{print} to
11937 build and compute expressions that may involve variables in your program.
11940 @kindex info frame@r{, show the source language}
11941 Display the source language for this frame. This language becomes the
11942 working language if you use an identifier from this frame.
11943 @xref{Frame Info, ,Information about a Frame}, to identify the other
11944 information listed here.
11947 @kindex info source@r{, show the source language}
11948 Display the source language of this source file.
11949 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
11950 information listed here.
11953 In unusual circumstances, you may have source files with extensions
11954 not in the standard list. You can then set the extension associated
11955 with a language explicitly:
11958 @item set extension-language @var{ext} @var{language}
11959 @kindex set extension-language
11960 Tell @value{GDBN} that source files with extension @var{ext} are to be
11961 assumed as written in the source language @var{language}.
11963 @item info extensions
11964 @kindex info extensions
11965 List all the filename extensions and the associated languages.
11969 @section Type and Range Checking
11972 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
11973 checking are included, but they do not yet have any effect. This
11974 section documents the intended facilities.
11976 @c FIXME remove warning when type/range code added
11978 Some languages are designed to guard you against making seemingly common
11979 errors through a series of compile- and run-time checks. These include
11980 checking the type of arguments to functions and operators, and making
11981 sure mathematical overflows are caught at run time. Checks such as
11982 these help to ensure a program's correctness once it has been compiled
11983 by eliminating type mismatches, and providing active checks for range
11984 errors when your program is running.
11986 @value{GDBN} can check for conditions like the above if you wish.
11987 Although @value{GDBN} does not check the statements in your program,
11988 it can check expressions entered directly into @value{GDBN} for
11989 evaluation via the @code{print} command, for example. As with the
11990 working language, @value{GDBN} can also decide whether or not to check
11991 automatically based on your program's source language.
11992 @xref{Supported Languages, ,Supported Languages}, for the default
11993 settings of supported languages.
11996 * Type Checking:: An overview of type checking
11997 * Range Checking:: An overview of range checking
12000 @cindex type checking
12001 @cindex checks, type
12002 @node Type Checking
12003 @subsection An Overview of Type Checking
12005 Some languages, such as Modula-2, are strongly typed, meaning that the
12006 arguments to operators and functions have to be of the correct type,
12007 otherwise an error occurs. These checks prevent type mismatch
12008 errors from ever causing any run-time problems. For example,
12016 The second example fails because the @code{CARDINAL} 1 is not
12017 type-compatible with the @code{REAL} 2.3.
12019 For the expressions you use in @value{GDBN} commands, you can tell the
12020 @value{GDBN} type checker to skip checking;
12021 to treat any mismatches as errors and abandon the expression;
12022 or to only issue warnings when type mismatches occur,
12023 but evaluate the expression anyway. When you choose the last of
12024 these, @value{GDBN} evaluates expressions like the second example above, but
12025 also issues a warning.
12027 Even if you turn type checking off, there may be other reasons
12028 related to type that prevent @value{GDBN} from evaluating an expression.
12029 For instance, @value{GDBN} does not know how to add an @code{int} and
12030 a @code{struct foo}. These particular type errors have nothing to do
12031 with the language in use, and usually arise from expressions, such as
12032 the one described above, which make little sense to evaluate anyway.
12034 Each language defines to what degree it is strict about type. For
12035 instance, both Modula-2 and C require the arguments to arithmetical
12036 operators to be numbers. In C, enumerated types and pointers can be
12037 represented as numbers, so that they are valid arguments to mathematical
12038 operators. @xref{Supported Languages, ,Supported Languages}, for further
12039 details on specific languages.
12041 @value{GDBN} provides some additional commands for controlling the type checker:
12043 @kindex set check type
12044 @kindex show check type
12046 @item set check type auto
12047 Set type checking on or off based on the current working language.
12048 @xref{Supported Languages, ,Supported Languages}, for the default settings for
12051 @item set check type on
12052 @itemx set check type off
12053 Set type checking on or off, overriding the default setting for the
12054 current working language. Issue a warning if the setting does not
12055 match the language default. If any type mismatches occur in
12056 evaluating an expression while type checking is on, @value{GDBN} prints a
12057 message and aborts evaluation of the expression.
12059 @item set check type warn
12060 Cause the type checker to issue warnings, but to always attempt to
12061 evaluate the expression. Evaluating the expression may still
12062 be impossible for other reasons. For example, @value{GDBN} cannot add
12063 numbers and structures.
12066 Show the current setting of the type checker, and whether or not @value{GDBN}
12067 is setting it automatically.
12070 @cindex range checking
12071 @cindex checks, range
12072 @node Range Checking
12073 @subsection An Overview of Range Checking
12075 In some languages (such as Modula-2), it is an error to exceed the
12076 bounds of a type; this is enforced with run-time checks. Such range
12077 checking is meant to ensure program correctness by making sure
12078 computations do not overflow, or indices on an array element access do
12079 not exceed the bounds of the array.
12081 For expressions you use in @value{GDBN} commands, you can tell
12082 @value{GDBN} to treat range errors in one of three ways: ignore them,
12083 always treat them as errors and abandon the expression, or issue
12084 warnings but evaluate the expression anyway.
12086 A range error can result from numerical overflow, from exceeding an
12087 array index bound, or when you type a constant that is not a member
12088 of any type. Some languages, however, do not treat overflows as an
12089 error. In many implementations of C, mathematical overflow causes the
12090 result to ``wrap around'' to lower values---for example, if @var{m} is
12091 the largest integer value, and @var{s} is the smallest, then
12094 @var{m} + 1 @result{} @var{s}
12097 This, too, is specific to individual languages, and in some cases
12098 specific to individual compilers or machines. @xref{Supported Languages, ,
12099 Supported Languages}, for further details on specific languages.
12101 @value{GDBN} provides some additional commands for controlling the range checker:
12103 @kindex set check range
12104 @kindex show check range
12106 @item set check range auto
12107 Set range checking on or off based on the current working language.
12108 @xref{Supported Languages, ,Supported Languages}, for the default settings for
12111 @item set check range on
12112 @itemx set check range off
12113 Set range checking on or off, overriding the default setting for the
12114 current working language. A warning is issued if the setting does not
12115 match the language default. If a range error occurs and range checking is on,
12116 then a message is printed and evaluation of the expression is aborted.
12118 @item set check range warn
12119 Output messages when the @value{GDBN} range checker detects a range error,
12120 but attempt to evaluate the expression anyway. Evaluating the
12121 expression may still be impossible for other reasons, such as accessing
12122 memory that the process does not own (a typical example from many Unix
12126 Show the current setting of the range checker, and whether or not it is
12127 being set automatically by @value{GDBN}.
12130 @node Supported Languages
12131 @section Supported Languages
12133 @value{GDBN} supports C, C@t{++}, D, Objective-C, Fortran, Java, OpenCL C, Pascal,
12134 assembly, Modula-2, and Ada.
12135 @c This is false ...
12136 Some @value{GDBN} features may be used in expressions regardless of the
12137 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
12138 and the @samp{@{type@}addr} construct (@pxref{Expressions,
12139 ,Expressions}) can be used with the constructs of any supported
12142 The following sections detail to what degree each source language is
12143 supported by @value{GDBN}. These sections are not meant to be language
12144 tutorials or references, but serve only as a reference guide to what the
12145 @value{GDBN} expression parser accepts, and what input and output
12146 formats should look like for different languages. There are many good
12147 books written on each of these languages; please look to these for a
12148 language reference or tutorial.
12151 * C:: C and C@t{++}
12153 * Objective-C:: Objective-C
12154 * OpenCL C:: OpenCL C
12155 * Fortran:: Fortran
12157 * Modula-2:: Modula-2
12162 @subsection C and C@t{++}
12164 @cindex C and C@t{++}
12165 @cindex expressions in C or C@t{++}
12167 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
12168 to both languages. Whenever this is the case, we discuss those languages
12172 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
12173 @cindex @sc{gnu} C@t{++}
12174 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
12175 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
12176 effectively, you must compile your C@t{++} programs with a supported
12177 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
12178 compiler (@code{aCC}).
12181 * C Operators:: C and C@t{++} operators
12182 * C Constants:: C and C@t{++} constants
12183 * C Plus Plus Expressions:: C@t{++} expressions
12184 * C Defaults:: Default settings for C and C@t{++}
12185 * C Checks:: C and C@t{++} type and range checks
12186 * Debugging C:: @value{GDBN} and C
12187 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
12188 * Decimal Floating Point:: Numbers in Decimal Floating Point format
12192 @subsubsection C and C@t{++} Operators
12194 @cindex C and C@t{++} operators
12196 Operators must be defined on values of specific types. For instance,
12197 @code{+} is defined on numbers, but not on structures. Operators are
12198 often defined on groups of types.
12200 For the purposes of C and C@t{++}, the following definitions hold:
12205 @emph{Integral types} include @code{int} with any of its storage-class
12206 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
12209 @emph{Floating-point types} include @code{float}, @code{double}, and
12210 @code{long double} (if supported by the target platform).
12213 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
12216 @emph{Scalar types} include all of the above.
12221 The following operators are supported. They are listed here
12222 in order of increasing precedence:
12226 The comma or sequencing operator. Expressions in a comma-separated list
12227 are evaluated from left to right, with the result of the entire
12228 expression being the last expression evaluated.
12231 Assignment. The value of an assignment expression is the value
12232 assigned. Defined on scalar types.
12235 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
12236 and translated to @w{@code{@var{a} = @var{a op b}}}.
12237 @w{@code{@var{op}=}} and @code{=} have the same precedence.
12238 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
12239 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
12242 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
12243 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
12247 Logical @sc{or}. Defined on integral types.
12250 Logical @sc{and}. Defined on integral types.
12253 Bitwise @sc{or}. Defined on integral types.
12256 Bitwise exclusive-@sc{or}. Defined on integral types.
12259 Bitwise @sc{and}. Defined on integral types.
12262 Equality and inequality. Defined on scalar types. The value of these
12263 expressions is 0 for false and non-zero for true.
12265 @item <@r{, }>@r{, }<=@r{, }>=
12266 Less than, greater than, less than or equal, greater than or equal.
12267 Defined on scalar types. The value of these expressions is 0 for false
12268 and non-zero for true.
12271 left shift, and right shift. Defined on integral types.
12274 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12277 Addition and subtraction. Defined on integral types, floating-point types and
12280 @item *@r{, }/@r{, }%
12281 Multiplication, division, and modulus. Multiplication and division are
12282 defined on integral and floating-point types. Modulus is defined on
12286 Increment and decrement. When appearing before a variable, the
12287 operation is performed before the variable is used in an expression;
12288 when appearing after it, the variable's value is used before the
12289 operation takes place.
12292 Pointer dereferencing. Defined on pointer types. Same precedence as
12296 Address operator. Defined on variables. Same precedence as @code{++}.
12298 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
12299 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
12300 to examine the address
12301 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
12305 Negative. Defined on integral and floating-point types. Same
12306 precedence as @code{++}.
12309 Logical negation. Defined on integral types. Same precedence as
12313 Bitwise complement operator. Defined on integral types. Same precedence as
12318 Structure member, and pointer-to-structure member. For convenience,
12319 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
12320 pointer based on the stored type information.
12321 Defined on @code{struct} and @code{union} data.
12324 Dereferences of pointers to members.
12327 Array indexing. @code{@var{a}[@var{i}]} is defined as
12328 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
12331 Function parameter list. Same precedence as @code{->}.
12334 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
12335 and @code{class} types.
12338 Doubled colons also represent the @value{GDBN} scope operator
12339 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
12343 If an operator is redefined in the user code, @value{GDBN} usually
12344 attempts to invoke the redefined version instead of using the operator's
12345 predefined meaning.
12348 @subsubsection C and C@t{++} Constants
12350 @cindex C and C@t{++} constants
12352 @value{GDBN} allows you to express the constants of C and C@t{++} in the
12357 Integer constants are a sequence of digits. Octal constants are
12358 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
12359 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
12360 @samp{l}, specifying that the constant should be treated as a
12364 Floating point constants are a sequence of digits, followed by a decimal
12365 point, followed by a sequence of digits, and optionally followed by an
12366 exponent. An exponent is of the form:
12367 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
12368 sequence of digits. The @samp{+} is optional for positive exponents.
12369 A floating-point constant may also end with a letter @samp{f} or
12370 @samp{F}, specifying that the constant should be treated as being of
12371 the @code{float} (as opposed to the default @code{double}) type; or with
12372 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
12376 Enumerated constants consist of enumerated identifiers, or their
12377 integral equivalents.
12380 Character constants are a single character surrounded by single quotes
12381 (@code{'}), or a number---the ordinal value of the corresponding character
12382 (usually its @sc{ascii} value). Within quotes, the single character may
12383 be represented by a letter or by @dfn{escape sequences}, which are of
12384 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
12385 of the character's ordinal value; or of the form @samp{\@var{x}}, where
12386 @samp{@var{x}} is a predefined special character---for example,
12387 @samp{\n} for newline.
12389 Wide character constants can be written by prefixing a character
12390 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
12391 form of @samp{x}. The target wide character set is used when
12392 computing the value of this constant (@pxref{Character Sets}).
12395 String constants are a sequence of character constants surrounded by
12396 double quotes (@code{"}). Any valid character constant (as described
12397 above) may appear. Double quotes within the string must be preceded by
12398 a backslash, so for instance @samp{"a\"b'c"} is a string of five
12401 Wide string constants can be written by prefixing a string constant
12402 with @samp{L}, as in C. The target wide character set is used when
12403 computing the value of this constant (@pxref{Character Sets}).
12406 Pointer constants are an integral value. You can also write pointers
12407 to constants using the C operator @samp{&}.
12410 Array constants are comma-separated lists surrounded by braces @samp{@{}
12411 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
12412 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
12413 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
12416 @node C Plus Plus Expressions
12417 @subsubsection C@t{++} Expressions
12419 @cindex expressions in C@t{++}
12420 @value{GDBN} expression handling can interpret most C@t{++} expressions.
12422 @cindex debugging C@t{++} programs
12423 @cindex C@t{++} compilers
12424 @cindex debug formats and C@t{++}
12425 @cindex @value{NGCC} and C@t{++}
12427 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
12428 the proper compiler and the proper debug format. Currently,
12429 @value{GDBN} works best when debugging C@t{++} code that is compiled
12430 with the most recent version of @value{NGCC} possible. The DWARF
12431 debugging format is preferred; @value{NGCC} defaults to this on most
12432 popular platforms. Other compilers and/or debug formats are likely to
12433 work badly or not at all when using @value{GDBN} to debug C@t{++}
12434 code. @xref{Compilation}.
12439 @cindex member functions
12441 Member function calls are allowed; you can use expressions like
12444 count = aml->GetOriginal(x, y)
12447 @vindex this@r{, inside C@t{++} member functions}
12448 @cindex namespace in C@t{++}
12450 While a member function is active (in the selected stack frame), your
12451 expressions have the same namespace available as the member function;
12452 that is, @value{GDBN} allows implicit references to the class instance
12453 pointer @code{this} following the same rules as C@t{++}. @code{using}
12454 declarations in the current scope are also respected by @value{GDBN}.
12456 @cindex call overloaded functions
12457 @cindex overloaded functions, calling
12458 @cindex type conversions in C@t{++}
12460 You can call overloaded functions; @value{GDBN} resolves the function
12461 call to the right definition, with some restrictions. @value{GDBN} does not
12462 perform overload resolution involving user-defined type conversions,
12463 calls to constructors, or instantiations of templates that do not exist
12464 in the program. It also cannot handle ellipsis argument lists or
12467 It does perform integral conversions and promotions, floating-point
12468 promotions, arithmetic conversions, pointer conversions, conversions of
12469 class objects to base classes, and standard conversions such as those of
12470 functions or arrays to pointers; it requires an exact match on the
12471 number of function arguments.
12473 Overload resolution is always performed, unless you have specified
12474 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
12475 ,@value{GDBN} Features for C@t{++}}.
12477 You must specify @code{set overload-resolution off} in order to use an
12478 explicit function signature to call an overloaded function, as in
12480 p 'foo(char,int)'('x', 13)
12483 The @value{GDBN} command-completion facility can simplify this;
12484 see @ref{Completion, ,Command Completion}.
12486 @cindex reference declarations
12488 @value{GDBN} understands variables declared as C@t{++} references; you can use
12489 them in expressions just as you do in C@t{++} source---they are automatically
12492 In the parameter list shown when @value{GDBN} displays a frame, the values of
12493 reference variables are not displayed (unlike other variables); this
12494 avoids clutter, since references are often used for large structures.
12495 The @emph{address} of a reference variable is always shown, unless
12496 you have specified @samp{set print address off}.
12499 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
12500 expressions can use it just as expressions in your program do. Since
12501 one scope may be defined in another, you can use @code{::} repeatedly if
12502 necessary, for example in an expression like
12503 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
12504 resolving name scope by reference to source files, in both C and C@t{++}
12505 debugging (@pxref{Variables, ,Program Variables}).
12508 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
12513 @subsubsection C and C@t{++} Defaults
12515 @cindex C and C@t{++} defaults
12517 If you allow @value{GDBN} to set type and range checking automatically, they
12518 both default to @code{off} whenever the working language changes to
12519 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
12520 selects the working language.
12522 If you allow @value{GDBN} to set the language automatically, it
12523 recognizes source files whose names end with @file{.c}, @file{.C}, or
12524 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
12525 these files, it sets the working language to C or C@t{++}.
12526 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
12527 for further details.
12529 @c Type checking is (a) primarily motivated by Modula-2, and (b)
12530 @c unimplemented. If (b) changes, it might make sense to let this node
12531 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
12534 @subsubsection C and C@t{++} Type and Range Checks
12536 @cindex C and C@t{++} checks
12538 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
12539 is not used. However, if you turn type checking on, @value{GDBN}
12540 considers two variables type equivalent if:
12544 The two variables are structured and have the same structure, union, or
12548 The two variables have the same type name, or types that have been
12549 declared equivalent through @code{typedef}.
12552 @c leaving this out because neither J Gilmore nor R Pesch understand it.
12555 The two @code{struct}, @code{union}, or @code{enum} variables are
12556 declared in the same declaration. (Note: this may not be true for all C
12561 Range checking, if turned on, is done on mathematical operations. Array
12562 indices are not checked, since they are often used to index a pointer
12563 that is not itself an array.
12566 @subsubsection @value{GDBN} and C
12568 The @code{set print union} and @code{show print union} commands apply to
12569 the @code{union} type. When set to @samp{on}, any @code{union} that is
12570 inside a @code{struct} or @code{class} is also printed. Otherwise, it
12571 appears as @samp{@{...@}}.
12573 The @code{@@} operator aids in the debugging of dynamic arrays, formed
12574 with pointers and a memory allocation function. @xref{Expressions,
12577 @node Debugging C Plus Plus
12578 @subsubsection @value{GDBN} Features for C@t{++}
12580 @cindex commands for C@t{++}
12582 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
12583 designed specifically for use with C@t{++}. Here is a summary:
12586 @cindex break in overloaded functions
12587 @item @r{breakpoint menus}
12588 When you want a breakpoint in a function whose name is overloaded,
12589 @value{GDBN} has the capability to display a menu of possible breakpoint
12590 locations to help you specify which function definition you want.
12591 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
12593 @cindex overloading in C@t{++}
12594 @item rbreak @var{regex}
12595 Setting breakpoints using regular expressions is helpful for setting
12596 breakpoints on overloaded functions that are not members of any special
12598 @xref{Set Breaks, ,Setting Breakpoints}.
12600 @cindex C@t{++} exception handling
12603 Debug C@t{++} exception handling using these commands. @xref{Set
12604 Catchpoints, , Setting Catchpoints}.
12606 @cindex inheritance
12607 @item ptype @var{typename}
12608 Print inheritance relationships as well as other information for type
12610 @xref{Symbols, ,Examining the Symbol Table}.
12612 @cindex C@t{++} symbol display
12613 @item set print demangle
12614 @itemx show print demangle
12615 @itemx set print asm-demangle
12616 @itemx show print asm-demangle
12617 Control whether C@t{++} symbols display in their source form, both when
12618 displaying code as C@t{++} source and when displaying disassemblies.
12619 @xref{Print Settings, ,Print Settings}.
12621 @item set print object
12622 @itemx show print object
12623 Choose whether to print derived (actual) or declared types of objects.
12624 @xref{Print Settings, ,Print Settings}.
12626 @item set print vtbl
12627 @itemx show print vtbl
12628 Control the format for printing virtual function tables.
12629 @xref{Print Settings, ,Print Settings}.
12630 (The @code{vtbl} commands do not work on programs compiled with the HP
12631 ANSI C@t{++} compiler (@code{aCC}).)
12633 @kindex set overload-resolution
12634 @cindex overloaded functions, overload resolution
12635 @item set overload-resolution on
12636 Enable overload resolution for C@t{++} expression evaluation. The default
12637 is on. For overloaded functions, @value{GDBN} evaluates the arguments
12638 and searches for a function whose signature matches the argument types,
12639 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
12640 Expressions, ,C@t{++} Expressions}, for details).
12641 If it cannot find a match, it emits a message.
12643 @item set overload-resolution off
12644 Disable overload resolution for C@t{++} expression evaluation. For
12645 overloaded functions that are not class member functions, @value{GDBN}
12646 chooses the first function of the specified name that it finds in the
12647 symbol table, whether or not its arguments are of the correct type. For
12648 overloaded functions that are class member functions, @value{GDBN}
12649 searches for a function whose signature @emph{exactly} matches the
12652 @kindex show overload-resolution
12653 @item show overload-resolution
12654 Show the current setting of overload resolution.
12656 @item @r{Overloaded symbol names}
12657 You can specify a particular definition of an overloaded symbol, using
12658 the same notation that is used to declare such symbols in C@t{++}: type
12659 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
12660 also use the @value{GDBN} command-line word completion facilities to list the
12661 available choices, or to finish the type list for you.
12662 @xref{Completion,, Command Completion}, for details on how to do this.
12665 @node Decimal Floating Point
12666 @subsubsection Decimal Floating Point format
12667 @cindex decimal floating point format
12669 @value{GDBN} can examine, set and perform computations with numbers in
12670 decimal floating point format, which in the C language correspond to the
12671 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
12672 specified by the extension to support decimal floating-point arithmetic.
12674 There are two encodings in use, depending on the architecture: BID (Binary
12675 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
12676 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
12679 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
12680 to manipulate decimal floating point numbers, it is not possible to convert
12681 (using a cast, for example) integers wider than 32-bit to decimal float.
12683 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
12684 point computations, error checking in decimal float operations ignores
12685 underflow, overflow and divide by zero exceptions.
12687 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
12688 to inspect @code{_Decimal128} values stored in floating point registers.
12689 See @ref{PowerPC,,PowerPC} for more details.
12695 @value{GDBN} can be used to debug programs written in D and compiled with
12696 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
12697 specific feature --- dynamic arrays.
12700 @subsection Objective-C
12702 @cindex Objective-C
12703 This section provides information about some commands and command
12704 options that are useful for debugging Objective-C code. See also
12705 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
12706 few more commands specific to Objective-C support.
12709 * Method Names in Commands::
12710 * The Print Command with Objective-C::
12713 @node Method Names in Commands
12714 @subsubsection Method Names in Commands
12716 The following commands have been extended to accept Objective-C method
12717 names as line specifications:
12719 @kindex clear@r{, and Objective-C}
12720 @kindex break@r{, and Objective-C}
12721 @kindex info line@r{, and Objective-C}
12722 @kindex jump@r{, and Objective-C}
12723 @kindex list@r{, and Objective-C}
12727 @item @code{info line}
12732 A fully qualified Objective-C method name is specified as
12735 -[@var{Class} @var{methodName}]
12738 where the minus sign is used to indicate an instance method and a
12739 plus sign (not shown) is used to indicate a class method. The class
12740 name @var{Class} and method name @var{methodName} are enclosed in
12741 brackets, similar to the way messages are specified in Objective-C
12742 source code. For example, to set a breakpoint at the @code{create}
12743 instance method of class @code{Fruit} in the program currently being
12747 break -[Fruit create]
12750 To list ten program lines around the @code{initialize} class method,
12754 list +[NSText initialize]
12757 In the current version of @value{GDBN}, the plus or minus sign is
12758 required. In future versions of @value{GDBN}, the plus or minus
12759 sign will be optional, but you can use it to narrow the search. It
12760 is also possible to specify just a method name:
12766 You must specify the complete method name, including any colons. If
12767 your program's source files contain more than one @code{create} method,
12768 you'll be presented with a numbered list of classes that implement that
12769 method. Indicate your choice by number, or type @samp{0} to exit if
12772 As another example, to clear a breakpoint established at the
12773 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
12776 clear -[NSWindow makeKeyAndOrderFront:]
12779 @node The Print Command with Objective-C
12780 @subsubsection The Print Command With Objective-C
12781 @cindex Objective-C, print objects
12782 @kindex print-object
12783 @kindex po @r{(@code{print-object})}
12785 The print command has also been extended to accept methods. For example:
12788 print -[@var{object} hash]
12791 @cindex print an Objective-C object description
12792 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
12794 will tell @value{GDBN} to send the @code{hash} message to @var{object}
12795 and print the result. Also, an additional command has been added,
12796 @code{print-object} or @code{po} for short, which is meant to print
12797 the description of an object. However, this command may only work
12798 with certain Objective-C libraries that have a particular hook
12799 function, @code{_NSPrintForDebugger}, defined.
12802 @subsection OpenCL C
12805 This section provides information about @value{GDBN}s OpenCL C support.
12808 * OpenCL C Datatypes::
12809 * OpenCL C Expressions::
12810 * OpenCL C Operators::
12813 @node OpenCL C Datatypes
12814 @subsubsection OpenCL C Datatypes
12816 @cindex OpenCL C Datatypes
12817 @value{GDBN} supports the builtin scalar and vector datatypes specified
12818 by OpenCL 1.1. In addition the half- and double-precision floating point
12819 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
12820 extensions are also known to @value{GDBN}.
12822 @node OpenCL C Expressions
12823 @subsubsection OpenCL C Expressions
12825 @cindex OpenCL C Expressions
12826 @value{GDBN} supports accesses to vector components including the access as
12827 lvalue where possible. Since OpenCL C is based on C99 most C expressions
12828 supported by @value{GDBN} can be used as well.
12830 @node OpenCL C Operators
12831 @subsubsection OpenCL C Operators
12833 @cindex OpenCL C Operators
12834 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
12838 @subsection Fortran
12839 @cindex Fortran-specific support in @value{GDBN}
12841 @value{GDBN} can be used to debug programs written in Fortran, but it
12842 currently supports only the features of Fortran 77 language.
12844 @cindex trailing underscore, in Fortran symbols
12845 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
12846 among them) append an underscore to the names of variables and
12847 functions. When you debug programs compiled by those compilers, you
12848 will need to refer to variables and functions with a trailing
12852 * Fortran Operators:: Fortran operators and expressions
12853 * Fortran Defaults:: Default settings for Fortran
12854 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
12857 @node Fortran Operators
12858 @subsubsection Fortran Operators and Expressions
12860 @cindex Fortran operators and expressions
12862 Operators must be defined on values of specific types. For instance,
12863 @code{+} is defined on numbers, but not on characters or other non-
12864 arithmetic types. Operators are often defined on groups of types.
12868 The exponentiation operator. It raises the first operand to the power
12872 The range operator. Normally used in the form of array(low:high) to
12873 represent a section of array.
12876 The access component operator. Normally used to access elements in derived
12877 types. Also suitable for unions. As unions aren't part of regular Fortran,
12878 this can only happen when accessing a register that uses a gdbarch-defined
12882 @node Fortran Defaults
12883 @subsubsection Fortran Defaults
12885 @cindex Fortran Defaults
12887 Fortran symbols are usually case-insensitive, so @value{GDBN} by
12888 default uses case-insensitive matches for Fortran symbols. You can
12889 change that with the @samp{set case-insensitive} command, see
12890 @ref{Symbols}, for the details.
12892 @node Special Fortran Commands
12893 @subsubsection Special Fortran Commands
12895 @cindex Special Fortran commands
12897 @value{GDBN} has some commands to support Fortran-specific features,
12898 such as displaying common blocks.
12901 @cindex @code{COMMON} blocks, Fortran
12902 @kindex info common
12903 @item info common @r{[}@var{common-name}@r{]}
12904 This command prints the values contained in the Fortran @code{COMMON}
12905 block whose name is @var{common-name}. With no argument, the names of
12906 all @code{COMMON} blocks visible at the current program location are
12913 @cindex Pascal support in @value{GDBN}, limitations
12914 Debugging Pascal programs which use sets, subranges, file variables, or
12915 nested functions does not currently work. @value{GDBN} does not support
12916 entering expressions, printing values, or similar features using Pascal
12919 The Pascal-specific command @code{set print pascal_static-members}
12920 controls whether static members of Pascal objects are displayed.
12921 @xref{Print Settings, pascal_static-members}.
12924 @subsection Modula-2
12926 @cindex Modula-2, @value{GDBN} support
12928 The extensions made to @value{GDBN} to support Modula-2 only support
12929 output from the @sc{gnu} Modula-2 compiler (which is currently being
12930 developed). Other Modula-2 compilers are not currently supported, and
12931 attempting to debug executables produced by them is most likely
12932 to give an error as @value{GDBN} reads in the executable's symbol
12935 @cindex expressions in Modula-2
12937 * M2 Operators:: Built-in operators
12938 * Built-In Func/Proc:: Built-in functions and procedures
12939 * M2 Constants:: Modula-2 constants
12940 * M2 Types:: Modula-2 types
12941 * M2 Defaults:: Default settings for Modula-2
12942 * Deviations:: Deviations from standard Modula-2
12943 * M2 Checks:: Modula-2 type and range checks
12944 * M2 Scope:: The scope operators @code{::} and @code{.}
12945 * GDB/M2:: @value{GDBN} and Modula-2
12949 @subsubsection Operators
12950 @cindex Modula-2 operators
12952 Operators must be defined on values of specific types. For instance,
12953 @code{+} is defined on numbers, but not on structures. Operators are
12954 often defined on groups of types. For the purposes of Modula-2, the
12955 following definitions hold:
12960 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
12964 @emph{Character types} consist of @code{CHAR} and its subranges.
12967 @emph{Floating-point types} consist of @code{REAL}.
12970 @emph{Pointer types} consist of anything declared as @code{POINTER TO
12974 @emph{Scalar types} consist of all of the above.
12977 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
12980 @emph{Boolean types} consist of @code{BOOLEAN}.
12984 The following operators are supported, and appear in order of
12985 increasing precedence:
12989 Function argument or array index separator.
12992 Assignment. The value of @var{var} @code{:=} @var{value} is
12996 Less than, greater than on integral, floating-point, or enumerated
13000 Less than or equal to, greater than or equal to
13001 on integral, floating-point and enumerated types, or set inclusion on
13002 set types. Same precedence as @code{<}.
13004 @item =@r{, }<>@r{, }#
13005 Equality and two ways of expressing inequality, valid on scalar types.
13006 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
13007 available for inequality, since @code{#} conflicts with the script
13011 Set membership. Defined on set types and the types of their members.
13012 Same precedence as @code{<}.
13015 Boolean disjunction. Defined on boolean types.
13018 Boolean conjunction. Defined on boolean types.
13021 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13024 Addition and subtraction on integral and floating-point types, or union
13025 and difference on set types.
13028 Multiplication on integral and floating-point types, or set intersection
13032 Division on floating-point types, or symmetric set difference on set
13033 types. Same precedence as @code{*}.
13036 Integer division and remainder. Defined on integral types. Same
13037 precedence as @code{*}.
13040 Negative. Defined on @code{INTEGER} and @code{REAL} data.
13043 Pointer dereferencing. Defined on pointer types.
13046 Boolean negation. Defined on boolean types. Same precedence as
13050 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
13051 precedence as @code{^}.
13054 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
13057 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
13061 @value{GDBN} and Modula-2 scope operators.
13065 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
13066 treats the use of the operator @code{IN}, or the use of operators
13067 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
13068 @code{<=}, and @code{>=} on sets as an error.
13072 @node Built-In Func/Proc
13073 @subsubsection Built-in Functions and Procedures
13074 @cindex Modula-2 built-ins
13076 Modula-2 also makes available several built-in procedures and functions.
13077 In describing these, the following metavariables are used:
13082 represents an @code{ARRAY} variable.
13085 represents a @code{CHAR} constant or variable.
13088 represents a variable or constant of integral type.
13091 represents an identifier that belongs to a set. Generally used in the
13092 same function with the metavariable @var{s}. The type of @var{s} should
13093 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
13096 represents a variable or constant of integral or floating-point type.
13099 represents a variable or constant of floating-point type.
13105 represents a variable.
13108 represents a variable or constant of one of many types. See the
13109 explanation of the function for details.
13112 All Modula-2 built-in procedures also return a result, described below.
13116 Returns the absolute value of @var{n}.
13119 If @var{c} is a lower case letter, it returns its upper case
13120 equivalent, otherwise it returns its argument.
13123 Returns the character whose ordinal value is @var{i}.
13126 Decrements the value in the variable @var{v} by one. Returns the new value.
13128 @item DEC(@var{v},@var{i})
13129 Decrements the value in the variable @var{v} by @var{i}. Returns the
13132 @item EXCL(@var{m},@var{s})
13133 Removes the element @var{m} from the set @var{s}. Returns the new
13136 @item FLOAT(@var{i})
13137 Returns the floating point equivalent of the integer @var{i}.
13139 @item HIGH(@var{a})
13140 Returns the index of the last member of @var{a}.
13143 Increments the value in the variable @var{v} by one. Returns the new value.
13145 @item INC(@var{v},@var{i})
13146 Increments the value in the variable @var{v} by @var{i}. Returns the
13149 @item INCL(@var{m},@var{s})
13150 Adds the element @var{m} to the set @var{s} if it is not already
13151 there. Returns the new set.
13154 Returns the maximum value of the type @var{t}.
13157 Returns the minimum value of the type @var{t}.
13160 Returns boolean TRUE if @var{i} is an odd number.
13163 Returns the ordinal value of its argument. For example, the ordinal
13164 value of a character is its @sc{ascii} value (on machines supporting the
13165 @sc{ascii} character set). @var{x} must be of an ordered type, which include
13166 integral, character and enumerated types.
13168 @item SIZE(@var{x})
13169 Returns the size of its argument. @var{x} can be a variable or a type.
13171 @item TRUNC(@var{r})
13172 Returns the integral part of @var{r}.
13174 @item TSIZE(@var{x})
13175 Returns the size of its argument. @var{x} can be a variable or a type.
13177 @item VAL(@var{t},@var{i})
13178 Returns the member of the type @var{t} whose ordinal value is @var{i}.
13182 @emph{Warning:} Sets and their operations are not yet supported, so
13183 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
13187 @cindex Modula-2 constants
13189 @subsubsection Constants
13191 @value{GDBN} allows you to express the constants of Modula-2 in the following
13197 Integer constants are simply a sequence of digits. When used in an
13198 expression, a constant is interpreted to be type-compatible with the
13199 rest of the expression. Hexadecimal integers are specified by a
13200 trailing @samp{H}, and octal integers by a trailing @samp{B}.
13203 Floating point constants appear as a sequence of digits, followed by a
13204 decimal point and another sequence of digits. An optional exponent can
13205 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
13206 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
13207 digits of the floating point constant must be valid decimal (base 10)
13211 Character constants consist of a single character enclosed by a pair of
13212 like quotes, either single (@code{'}) or double (@code{"}). They may
13213 also be expressed by their ordinal value (their @sc{ascii} value, usually)
13214 followed by a @samp{C}.
13217 String constants consist of a sequence of characters enclosed by a
13218 pair of like quotes, either single (@code{'}) or double (@code{"}).
13219 Escape sequences in the style of C are also allowed. @xref{C
13220 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
13224 Enumerated constants consist of an enumerated identifier.
13227 Boolean constants consist of the identifiers @code{TRUE} and
13231 Pointer constants consist of integral values only.
13234 Set constants are not yet supported.
13238 @subsubsection Modula-2 Types
13239 @cindex Modula-2 types
13241 Currently @value{GDBN} can print the following data types in Modula-2
13242 syntax: array types, record types, set types, pointer types, procedure
13243 types, enumerated types, subrange types and base types. You can also
13244 print the contents of variables declared using these type.
13245 This section gives a number of simple source code examples together with
13246 sample @value{GDBN} sessions.
13248 The first example contains the following section of code:
13257 and you can request @value{GDBN} to interrogate the type and value of
13258 @code{r} and @code{s}.
13261 (@value{GDBP}) print s
13263 (@value{GDBP}) ptype s
13265 (@value{GDBP}) print r
13267 (@value{GDBP}) ptype r
13272 Likewise if your source code declares @code{s} as:
13276 s: SET ['A'..'Z'] ;
13280 then you may query the type of @code{s} by:
13283 (@value{GDBP}) ptype s
13284 type = SET ['A'..'Z']
13288 Note that at present you cannot interactively manipulate set
13289 expressions using the debugger.
13291 The following example shows how you might declare an array in Modula-2
13292 and how you can interact with @value{GDBN} to print its type and contents:
13296 s: ARRAY [-10..10] OF CHAR ;
13300 (@value{GDBP}) ptype s
13301 ARRAY [-10..10] OF CHAR
13304 Note that the array handling is not yet complete and although the type
13305 is printed correctly, expression handling still assumes that all
13306 arrays have a lower bound of zero and not @code{-10} as in the example
13309 Here are some more type related Modula-2 examples:
13313 colour = (blue, red, yellow, green) ;
13314 t = [blue..yellow] ;
13322 The @value{GDBN} interaction shows how you can query the data type
13323 and value of a variable.
13326 (@value{GDBP}) print s
13328 (@value{GDBP}) ptype t
13329 type = [blue..yellow]
13333 In this example a Modula-2 array is declared and its contents
13334 displayed. Observe that the contents are written in the same way as
13335 their @code{C} counterparts.
13339 s: ARRAY [1..5] OF CARDINAL ;
13345 (@value{GDBP}) print s
13346 $1 = @{1, 0, 0, 0, 0@}
13347 (@value{GDBP}) ptype s
13348 type = ARRAY [1..5] OF CARDINAL
13351 The Modula-2 language interface to @value{GDBN} also understands
13352 pointer types as shown in this example:
13356 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
13363 and you can request that @value{GDBN} describes the type of @code{s}.
13366 (@value{GDBP}) ptype s
13367 type = POINTER TO ARRAY [1..5] OF CARDINAL
13370 @value{GDBN} handles compound types as we can see in this example.
13371 Here we combine array types, record types, pointer types and subrange
13382 myarray = ARRAY myrange OF CARDINAL ;
13383 myrange = [-2..2] ;
13385 s: POINTER TO ARRAY myrange OF foo ;
13389 and you can ask @value{GDBN} to describe the type of @code{s} as shown
13393 (@value{GDBP}) ptype s
13394 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
13397 f3 : ARRAY [-2..2] OF CARDINAL;
13402 @subsubsection Modula-2 Defaults
13403 @cindex Modula-2 defaults
13405 If type and range checking are set automatically by @value{GDBN}, they
13406 both default to @code{on} whenever the working language changes to
13407 Modula-2. This happens regardless of whether you or @value{GDBN}
13408 selected the working language.
13410 If you allow @value{GDBN} to set the language automatically, then entering
13411 code compiled from a file whose name ends with @file{.mod} sets the
13412 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
13413 Infer the Source Language}, for further details.
13416 @subsubsection Deviations from Standard Modula-2
13417 @cindex Modula-2, deviations from
13419 A few changes have been made to make Modula-2 programs easier to debug.
13420 This is done primarily via loosening its type strictness:
13424 Unlike in standard Modula-2, pointer constants can be formed by
13425 integers. This allows you to modify pointer variables during
13426 debugging. (In standard Modula-2, the actual address contained in a
13427 pointer variable is hidden from you; it can only be modified
13428 through direct assignment to another pointer variable or expression that
13429 returned a pointer.)
13432 C escape sequences can be used in strings and characters to represent
13433 non-printable characters. @value{GDBN} prints out strings with these
13434 escape sequences embedded. Single non-printable characters are
13435 printed using the @samp{CHR(@var{nnn})} format.
13438 The assignment operator (@code{:=}) returns the value of its right-hand
13442 All built-in procedures both modify @emph{and} return their argument.
13446 @subsubsection Modula-2 Type and Range Checks
13447 @cindex Modula-2 checks
13450 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
13453 @c FIXME remove warning when type/range checks added
13455 @value{GDBN} considers two Modula-2 variables type equivalent if:
13459 They are of types that have been declared equivalent via a @code{TYPE
13460 @var{t1} = @var{t2}} statement
13463 They have been declared on the same line. (Note: This is true of the
13464 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
13467 As long as type checking is enabled, any attempt to combine variables
13468 whose types are not equivalent is an error.
13470 Range checking is done on all mathematical operations, assignment, array
13471 index bounds, and all built-in functions and procedures.
13474 @subsubsection The Scope Operators @code{::} and @code{.}
13476 @cindex @code{.}, Modula-2 scope operator
13477 @cindex colon, doubled as scope operator
13479 @vindex colon-colon@r{, in Modula-2}
13480 @c Info cannot handle :: but TeX can.
13483 @vindex ::@r{, in Modula-2}
13486 There are a few subtle differences between the Modula-2 scope operator
13487 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
13492 @var{module} . @var{id}
13493 @var{scope} :: @var{id}
13497 where @var{scope} is the name of a module or a procedure,
13498 @var{module} the name of a module, and @var{id} is any declared
13499 identifier within your program, except another module.
13501 Using the @code{::} operator makes @value{GDBN} search the scope
13502 specified by @var{scope} for the identifier @var{id}. If it is not
13503 found in the specified scope, then @value{GDBN} searches all scopes
13504 enclosing the one specified by @var{scope}.
13506 Using the @code{.} operator makes @value{GDBN} search the current scope for
13507 the identifier specified by @var{id} that was imported from the
13508 definition module specified by @var{module}. With this operator, it is
13509 an error if the identifier @var{id} was not imported from definition
13510 module @var{module}, or if @var{id} is not an identifier in
13514 @subsubsection @value{GDBN} and Modula-2
13516 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
13517 Five subcommands of @code{set print} and @code{show print} apply
13518 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
13519 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
13520 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
13521 analogue in Modula-2.
13523 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
13524 with any language, is not useful with Modula-2. Its
13525 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
13526 created in Modula-2 as they can in C or C@t{++}. However, because an
13527 address can be specified by an integral constant, the construct
13528 @samp{@{@var{type}@}@var{adrexp}} is still useful.
13530 @cindex @code{#} in Modula-2
13531 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
13532 interpreted as the beginning of a comment. Use @code{<>} instead.
13538 The extensions made to @value{GDBN} for Ada only support
13539 output from the @sc{gnu} Ada (GNAT) compiler.
13540 Other Ada compilers are not currently supported, and
13541 attempting to debug executables produced by them is most likely
13545 @cindex expressions in Ada
13547 * Ada Mode Intro:: General remarks on the Ada syntax
13548 and semantics supported by Ada mode
13550 * Omissions from Ada:: Restrictions on the Ada expression syntax.
13551 * Additions to Ada:: Extensions of the Ada expression syntax.
13552 * Stopping Before Main Program:: Debugging the program during elaboration.
13553 * Ada Tasks:: Listing and setting breakpoints in tasks.
13554 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
13555 * Ravenscar Profile:: Tasking Support when using the Ravenscar
13557 * Ada Glitches:: Known peculiarities of Ada mode.
13560 @node Ada Mode Intro
13561 @subsubsection Introduction
13562 @cindex Ada mode, general
13564 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
13565 syntax, with some extensions.
13566 The philosophy behind the design of this subset is
13570 That @value{GDBN} should provide basic literals and access to operations for
13571 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
13572 leaving more sophisticated computations to subprograms written into the
13573 program (which therefore may be called from @value{GDBN}).
13576 That type safety and strict adherence to Ada language restrictions
13577 are not particularly important to the @value{GDBN} user.
13580 That brevity is important to the @value{GDBN} user.
13583 Thus, for brevity, the debugger acts as if all names declared in
13584 user-written packages are directly visible, even if they are not visible
13585 according to Ada rules, thus making it unnecessary to fully qualify most
13586 names with their packages, regardless of context. Where this causes
13587 ambiguity, @value{GDBN} asks the user's intent.
13589 The debugger will start in Ada mode if it detects an Ada main program.
13590 As for other languages, it will enter Ada mode when stopped in a program that
13591 was translated from an Ada source file.
13593 While in Ada mode, you may use `@t{--}' for comments. This is useful
13594 mostly for documenting command files. The standard @value{GDBN} comment
13595 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
13596 middle (to allow based literals).
13598 The debugger supports limited overloading. Given a subprogram call in which
13599 the function symbol has multiple definitions, it will use the number of
13600 actual parameters and some information about their types to attempt to narrow
13601 the set of definitions. It also makes very limited use of context, preferring
13602 procedures to functions in the context of the @code{call} command, and
13603 functions to procedures elsewhere.
13605 @node Omissions from Ada
13606 @subsubsection Omissions from Ada
13607 @cindex Ada, omissions from
13609 Here are the notable omissions from the subset:
13613 Only a subset of the attributes are supported:
13617 @t{'First}, @t{'Last}, and @t{'Length}
13618 on array objects (not on types and subtypes).
13621 @t{'Min} and @t{'Max}.
13624 @t{'Pos} and @t{'Val}.
13630 @t{'Range} on array objects (not subtypes), but only as the right
13631 operand of the membership (@code{in}) operator.
13634 @t{'Access}, @t{'Unchecked_Access}, and
13635 @t{'Unrestricted_Access} (a GNAT extension).
13643 @code{Characters.Latin_1} are not available and
13644 concatenation is not implemented. Thus, escape characters in strings are
13645 not currently available.
13648 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
13649 equality of representations. They will generally work correctly
13650 for strings and arrays whose elements have integer or enumeration types.
13651 They may not work correctly for arrays whose element
13652 types have user-defined equality, for arrays of real values
13653 (in particular, IEEE-conformant floating point, because of negative
13654 zeroes and NaNs), and for arrays whose elements contain unused bits with
13655 indeterminate values.
13658 The other component-by-component array operations (@code{and}, @code{or},
13659 @code{xor}, @code{not}, and relational tests other than equality)
13660 are not implemented.
13663 @cindex array aggregates (Ada)
13664 @cindex record aggregates (Ada)
13665 @cindex aggregates (Ada)
13666 There is limited support for array and record aggregates. They are
13667 permitted only on the right sides of assignments, as in these examples:
13670 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
13671 (@value{GDBP}) set An_Array := (1, others => 0)
13672 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
13673 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
13674 (@value{GDBP}) set A_Record := (1, "Peter", True);
13675 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
13679 discriminant's value by assigning an aggregate has an
13680 undefined effect if that discriminant is used within the record.
13681 However, you can first modify discriminants by directly assigning to
13682 them (which normally would not be allowed in Ada), and then performing an
13683 aggregate assignment. For example, given a variable @code{A_Rec}
13684 declared to have a type such as:
13687 type Rec (Len : Small_Integer := 0) is record
13689 Vals : IntArray (1 .. Len);
13693 you can assign a value with a different size of @code{Vals} with two
13697 (@value{GDBP}) set A_Rec.Len := 4
13698 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
13701 As this example also illustrates, @value{GDBN} is very loose about the usual
13702 rules concerning aggregates. You may leave out some of the
13703 components of an array or record aggregate (such as the @code{Len}
13704 component in the assignment to @code{A_Rec} above); they will retain their
13705 original values upon assignment. You may freely use dynamic values as
13706 indices in component associations. You may even use overlapping or
13707 redundant component associations, although which component values are
13708 assigned in such cases is not defined.
13711 Calls to dispatching subprograms are not implemented.
13714 The overloading algorithm is much more limited (i.e., less selective)
13715 than that of real Ada. It makes only limited use of the context in
13716 which a subexpression appears to resolve its meaning, and it is much
13717 looser in its rules for allowing type matches. As a result, some
13718 function calls will be ambiguous, and the user will be asked to choose
13719 the proper resolution.
13722 The @code{new} operator is not implemented.
13725 Entry calls are not implemented.
13728 Aside from printing, arithmetic operations on the native VAX floating-point
13729 formats are not supported.
13732 It is not possible to slice a packed array.
13735 The names @code{True} and @code{False}, when not part of a qualified name,
13736 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
13738 Should your program
13739 redefine these names in a package or procedure (at best a dubious practice),
13740 you will have to use fully qualified names to access their new definitions.
13743 @node Additions to Ada
13744 @subsubsection Additions to Ada
13745 @cindex Ada, deviations from
13747 As it does for other languages, @value{GDBN} makes certain generic
13748 extensions to Ada (@pxref{Expressions}):
13752 If the expression @var{E} is a variable residing in memory (typically
13753 a local variable or array element) and @var{N} is a positive integer,
13754 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
13755 @var{N}-1 adjacent variables following it in memory as an array. In
13756 Ada, this operator is generally not necessary, since its prime use is
13757 in displaying parts of an array, and slicing will usually do this in
13758 Ada. However, there are occasional uses when debugging programs in
13759 which certain debugging information has been optimized away.
13762 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
13763 appears in function or file @var{B}.'' When @var{B} is a file name,
13764 you must typically surround it in single quotes.
13767 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
13768 @var{type} that appears at address @var{addr}.''
13771 A name starting with @samp{$} is a convenience variable
13772 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
13775 In addition, @value{GDBN} provides a few other shortcuts and outright
13776 additions specific to Ada:
13780 The assignment statement is allowed as an expression, returning
13781 its right-hand operand as its value. Thus, you may enter
13784 (@value{GDBP}) set x := y + 3
13785 (@value{GDBP}) print A(tmp := y + 1)
13789 The semicolon is allowed as an ``operator,'' returning as its value
13790 the value of its right-hand operand.
13791 This allows, for example,
13792 complex conditional breaks:
13795 (@value{GDBP}) break f
13796 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
13800 Rather than use catenation and symbolic character names to introduce special
13801 characters into strings, one may instead use a special bracket notation,
13802 which is also used to print strings. A sequence of characters of the form
13803 @samp{["@var{XX}"]} within a string or character literal denotes the
13804 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
13805 sequence of characters @samp{["""]} also denotes a single quotation mark
13806 in strings. For example,
13808 "One line.["0a"]Next line.["0a"]"
13811 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
13815 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
13816 @t{'Max} is optional (and is ignored in any case). For example, it is valid
13820 (@value{GDBP}) print 'max(x, y)
13824 When printing arrays, @value{GDBN} uses positional notation when the
13825 array has a lower bound of 1, and uses a modified named notation otherwise.
13826 For example, a one-dimensional array of three integers with a lower bound
13827 of 3 might print as
13834 That is, in contrast to valid Ada, only the first component has a @code{=>}
13838 You may abbreviate attributes in expressions with any unique,
13839 multi-character subsequence of
13840 their names (an exact match gets preference).
13841 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
13842 in place of @t{a'length}.
13845 @cindex quoting Ada internal identifiers
13846 Since Ada is case-insensitive, the debugger normally maps identifiers you type
13847 to lower case. The GNAT compiler uses upper-case characters for
13848 some of its internal identifiers, which are normally of no interest to users.
13849 For the rare occasions when you actually have to look at them,
13850 enclose them in angle brackets to avoid the lower-case mapping.
13853 (@value{GDBP}) print <JMPBUF_SAVE>[0]
13857 Printing an object of class-wide type or dereferencing an
13858 access-to-class-wide value will display all the components of the object's
13859 specific type (as indicated by its run-time tag). Likewise, component
13860 selection on such a value will operate on the specific type of the
13865 @node Stopping Before Main Program
13866 @subsubsection Stopping at the Very Beginning
13868 @cindex breakpointing Ada elaboration code
13869 It is sometimes necessary to debug the program during elaboration, and
13870 before reaching the main procedure.
13871 As defined in the Ada Reference
13872 Manual, the elaboration code is invoked from a procedure called
13873 @code{adainit}. To run your program up to the beginning of
13874 elaboration, simply use the following two commands:
13875 @code{tbreak adainit} and @code{run}.
13878 @subsubsection Extensions for Ada Tasks
13879 @cindex Ada, tasking
13881 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
13882 @value{GDBN} provides the following task-related commands:
13887 This command shows a list of current Ada tasks, as in the following example:
13894 (@value{GDBP}) info tasks
13895 ID TID P-ID Pri State Name
13896 1 8088000 0 15 Child Activation Wait main_task
13897 2 80a4000 1 15 Accept Statement b
13898 3 809a800 1 15 Child Activation Wait a
13899 * 4 80ae800 3 15 Runnable c
13904 In this listing, the asterisk before the last task indicates it to be the
13905 task currently being inspected.
13909 Represents @value{GDBN}'s internal task number.
13915 The parent's task ID (@value{GDBN}'s internal task number).
13918 The base priority of the task.
13921 Current state of the task.
13925 The task has been created but has not been activated. It cannot be
13929 The task is not blocked for any reason known to Ada. (It may be waiting
13930 for a mutex, though.) It is conceptually "executing" in normal mode.
13933 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
13934 that were waiting on terminate alternatives have been awakened and have
13935 terminated themselves.
13937 @item Child Activation Wait
13938 The task is waiting for created tasks to complete activation.
13940 @item Accept Statement
13941 The task is waiting on an accept or selective wait statement.
13943 @item Waiting on entry call
13944 The task is waiting on an entry call.
13946 @item Async Select Wait
13947 The task is waiting to start the abortable part of an asynchronous
13951 The task is waiting on a select statement with only a delay
13954 @item Child Termination Wait
13955 The task is sleeping having completed a master within itself, and is
13956 waiting for the tasks dependent on that master to become terminated or
13957 waiting on a terminate Phase.
13959 @item Wait Child in Term Alt
13960 The task is sleeping waiting for tasks on terminate alternatives to
13961 finish terminating.
13963 @item Accepting RV with @var{taskno}
13964 The task is accepting a rendez-vous with the task @var{taskno}.
13968 Name of the task in the program.
13972 @kindex info task @var{taskno}
13973 @item info task @var{taskno}
13974 This command shows detailled informations on the specified task, as in
13975 the following example:
13980 (@value{GDBP}) info tasks
13981 ID TID P-ID Pri State Name
13982 1 8077880 0 15 Child Activation Wait main_task
13983 * 2 807c468 1 15 Runnable task_1
13984 (@value{GDBP}) info task 2
13985 Ada Task: 0x807c468
13988 Parent: 1 (main_task)
13994 @kindex task@r{ (Ada)}
13995 @cindex current Ada task ID
13996 This command prints the ID of the current task.
14002 (@value{GDBP}) info tasks
14003 ID TID P-ID Pri State Name
14004 1 8077870 0 15 Child Activation Wait main_task
14005 * 2 807c458 1 15 Runnable t
14006 (@value{GDBP}) task
14007 [Current task is 2]
14010 @item task @var{taskno}
14011 @cindex Ada task switching
14012 This command is like the @code{thread @var{threadno}}
14013 command (@pxref{Threads}). It switches the context of debugging
14014 from the current task to the given task.
14020 (@value{GDBP}) info tasks
14021 ID TID P-ID Pri State Name
14022 1 8077870 0 15 Child Activation Wait main_task
14023 * 2 807c458 1 15 Runnable t
14024 (@value{GDBP}) task 1
14025 [Switching to task 1]
14026 #0 0x8067726 in pthread_cond_wait ()
14028 #0 0x8067726 in pthread_cond_wait ()
14029 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
14030 #2 0x805cb63 in system.task_primitives.operations.sleep ()
14031 #3 0x806153e in system.tasking.stages.activate_tasks ()
14032 #4 0x804aacc in un () at un.adb:5
14035 @item break @var{linespec} task @var{taskno}
14036 @itemx break @var{linespec} task @var{taskno} if @dots{}
14037 @cindex breakpoints and tasks, in Ada
14038 @cindex task breakpoints, in Ada
14039 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
14040 These commands are like the @code{break @dots{} thread @dots{}}
14041 command (@pxref{Thread Stops}).
14042 @var{linespec} specifies source lines, as described
14043 in @ref{Specify Location}.
14045 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
14046 to specify that you only want @value{GDBN} to stop the program when a
14047 particular Ada task reaches this breakpoint. @var{taskno} is one of the
14048 numeric task identifiers assigned by @value{GDBN}, shown in the first
14049 column of the @samp{info tasks} display.
14051 If you do not specify @samp{task @var{taskno}} when you set a
14052 breakpoint, the breakpoint applies to @emph{all} tasks of your
14055 You can use the @code{task} qualifier on conditional breakpoints as
14056 well; in this case, place @samp{task @var{taskno}} before the
14057 breakpoint condition (before the @code{if}).
14065 (@value{GDBP}) info tasks
14066 ID TID P-ID Pri State Name
14067 1 140022020 0 15 Child Activation Wait main_task
14068 2 140045060 1 15 Accept/Select Wait t2
14069 3 140044840 1 15 Runnable t1
14070 * 4 140056040 1 15 Runnable t3
14071 (@value{GDBP}) b 15 task 2
14072 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
14073 (@value{GDBP}) cont
14078 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
14080 (@value{GDBP}) info tasks
14081 ID TID P-ID Pri State Name
14082 1 140022020 0 15 Child Activation Wait main_task
14083 * 2 140045060 1 15 Runnable t2
14084 3 140044840 1 15 Runnable t1
14085 4 140056040 1 15 Delay Sleep t3
14089 @node Ada Tasks and Core Files
14090 @subsubsection Tasking Support when Debugging Core Files
14091 @cindex Ada tasking and core file debugging
14093 When inspecting a core file, as opposed to debugging a live program,
14094 tasking support may be limited or even unavailable, depending on
14095 the platform being used.
14096 For instance, on x86-linux, the list of tasks is available, but task
14097 switching is not supported. On Tru64, however, task switching will work
14100 On certain platforms, including Tru64, the debugger needs to perform some
14101 memory writes in order to provide Ada tasking support. When inspecting
14102 a core file, this means that the core file must be opened with read-write
14103 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
14104 Under these circumstances, you should make a backup copy of the core
14105 file before inspecting it with @value{GDBN}.
14107 @node Ravenscar Profile
14108 @subsubsection Tasking Support when using the Ravenscar Profile
14109 @cindex Ravenscar Profile
14111 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
14112 specifically designed for systems with safety-critical real-time
14116 @kindex set ravenscar task-switching on
14117 @cindex task switching with program using Ravenscar Profile
14118 @item set ravenscar task-switching on
14119 Allows task switching when debugging a program that uses the Ravenscar
14120 Profile. This is the default.
14122 @kindex set ravenscar task-switching off
14123 @item set ravenscar task-switching off
14124 Turn off task switching when debugging a program that uses the Ravenscar
14125 Profile. This is mostly intended to disable the code that adds support
14126 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
14127 the Ravenscar runtime is preventing @value{GDBN} from working properly.
14128 To be effective, this command should be run before the program is started.
14130 @kindex show ravenscar task-switching
14131 @item show ravenscar task-switching
14132 Show whether it is possible to switch from task to task in a program
14133 using the Ravenscar Profile.
14138 @subsubsection Known Peculiarities of Ada Mode
14139 @cindex Ada, problems
14141 Besides the omissions listed previously (@pxref{Omissions from Ada}),
14142 we know of several problems with and limitations of Ada mode in
14144 some of which will be fixed with planned future releases of the debugger
14145 and the GNU Ada compiler.
14149 Static constants that the compiler chooses not to materialize as objects in
14150 storage are invisible to the debugger.
14153 Named parameter associations in function argument lists are ignored (the
14154 argument lists are treated as positional).
14157 Many useful library packages are currently invisible to the debugger.
14160 Fixed-point arithmetic, conversions, input, and output is carried out using
14161 floating-point arithmetic, and may give results that only approximate those on
14165 The GNAT compiler never generates the prefix @code{Standard} for any of
14166 the standard symbols defined by the Ada language. @value{GDBN} knows about
14167 this: it will strip the prefix from names when you use it, and will never
14168 look for a name you have so qualified among local symbols, nor match against
14169 symbols in other packages or subprograms. If you have
14170 defined entities anywhere in your program other than parameters and
14171 local variables whose simple names match names in @code{Standard},
14172 GNAT's lack of qualification here can cause confusion. When this happens,
14173 you can usually resolve the confusion
14174 by qualifying the problematic names with package
14175 @code{Standard} explicitly.
14178 Older versions of the compiler sometimes generate erroneous debugging
14179 information, resulting in the debugger incorrectly printing the value
14180 of affected entities. In some cases, the debugger is able to work
14181 around an issue automatically. In other cases, the debugger is able
14182 to work around the issue, but the work-around has to be specifically
14185 @kindex set ada trust-PAD-over-XVS
14186 @kindex show ada trust-PAD-over-XVS
14189 @item set ada trust-PAD-over-XVS on
14190 Configure GDB to strictly follow the GNAT encoding when computing the
14191 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
14192 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
14193 a complete description of the encoding used by the GNAT compiler).
14194 This is the default.
14196 @item set ada trust-PAD-over-XVS off
14197 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
14198 sometimes prints the wrong value for certain entities, changing @code{ada
14199 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
14200 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
14201 @code{off}, but this incurs a slight performance penalty, so it is
14202 recommended to leave this setting to @code{on} unless necessary.
14206 @node Unsupported Languages
14207 @section Unsupported Languages
14209 @cindex unsupported languages
14210 @cindex minimal language
14211 In addition to the other fully-supported programming languages,
14212 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
14213 It does not represent a real programming language, but provides a set
14214 of capabilities close to what the C or assembly languages provide.
14215 This should allow most simple operations to be performed while debugging
14216 an application that uses a language currently not supported by @value{GDBN}.
14218 If the language is set to @code{auto}, @value{GDBN} will automatically
14219 select this language if the current frame corresponds to an unsupported
14223 @chapter Examining the Symbol Table
14225 The commands described in this chapter allow you to inquire about the
14226 symbols (names of variables, functions and types) defined in your
14227 program. This information is inherent in the text of your program and
14228 does not change as your program executes. @value{GDBN} finds it in your
14229 program's symbol table, in the file indicated when you started @value{GDBN}
14230 (@pxref{File Options, ,Choosing Files}), or by one of the
14231 file-management commands (@pxref{Files, ,Commands to Specify Files}).
14233 @cindex symbol names
14234 @cindex names of symbols
14235 @cindex quoting names
14236 Occasionally, you may need to refer to symbols that contain unusual
14237 characters, which @value{GDBN} ordinarily treats as word delimiters. The
14238 most frequent case is in referring to static variables in other
14239 source files (@pxref{Variables,,Program Variables}). File names
14240 are recorded in object files as debugging symbols, but @value{GDBN} would
14241 ordinarily parse a typical file name, like @file{foo.c}, as the three words
14242 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
14243 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
14250 looks up the value of @code{x} in the scope of the file @file{foo.c}.
14253 @cindex case-insensitive symbol names
14254 @cindex case sensitivity in symbol names
14255 @kindex set case-sensitive
14256 @item set case-sensitive on
14257 @itemx set case-sensitive off
14258 @itemx set case-sensitive auto
14259 Normally, when @value{GDBN} looks up symbols, it matches their names
14260 with case sensitivity determined by the current source language.
14261 Occasionally, you may wish to control that. The command @code{set
14262 case-sensitive} lets you do that by specifying @code{on} for
14263 case-sensitive matches or @code{off} for case-insensitive ones. If
14264 you specify @code{auto}, case sensitivity is reset to the default
14265 suitable for the source language. The default is case-sensitive
14266 matches for all languages except for Fortran, for which the default is
14267 case-insensitive matches.
14269 @kindex show case-sensitive
14270 @item show case-sensitive
14271 This command shows the current setting of case sensitivity for symbols
14274 @kindex info address
14275 @cindex address of a symbol
14276 @item info address @var{symbol}
14277 Describe where the data for @var{symbol} is stored. For a register
14278 variable, this says which register it is kept in. For a non-register
14279 local variable, this prints the stack-frame offset at which the variable
14282 Note the contrast with @samp{print &@var{symbol}}, which does not work
14283 at all for a register variable, and for a stack local variable prints
14284 the exact address of the current instantiation of the variable.
14286 @kindex info symbol
14287 @cindex symbol from address
14288 @cindex closest symbol and offset for an address
14289 @item info symbol @var{addr}
14290 Print the name of a symbol which is stored at the address @var{addr}.
14291 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
14292 nearest symbol and an offset from it:
14295 (@value{GDBP}) info symbol 0x54320
14296 _initialize_vx + 396 in section .text
14300 This is the opposite of the @code{info address} command. You can use
14301 it to find out the name of a variable or a function given its address.
14303 For dynamically linked executables, the name of executable or shared
14304 library containing the symbol is also printed:
14307 (@value{GDBP}) info symbol 0x400225
14308 _start + 5 in section .text of /tmp/a.out
14309 (@value{GDBP}) info symbol 0x2aaaac2811cf
14310 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
14314 @item whatis [@var{arg}]
14315 Print the data type of @var{arg}, which can be either an expression
14316 or a name of a data type. With no argument, print the data type of
14317 @code{$}, the last value in the value history.
14319 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
14320 is not actually evaluated, and any side-effecting operations (such as
14321 assignments or function calls) inside it do not take place.
14323 If @var{arg} is a variable or an expression, @code{whatis} prints its
14324 literal type as it is used in the source code. If the type was
14325 defined using a @code{typedef}, @code{whatis} will @emph{not} print
14326 the data type underlying the @code{typedef}. If the type of the
14327 variable or the expression is a compound data type, such as
14328 @code{struct} or @code{class}, @code{whatis} never prints their
14329 fields or methods. It just prints the @code{struct}/@code{class}
14330 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
14331 such a compound data type, use @code{ptype}.
14333 If @var{arg} is a type name that was defined using @code{typedef},
14334 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
14335 Unrolling means that @code{whatis} will show the underlying type used
14336 in the @code{typedef} declaration of @var{arg}. However, if that
14337 underlying type is also a @code{typedef}, @code{whatis} will not
14340 For C code, the type names may also have the form @samp{class
14341 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
14342 @var{union-tag}} or @samp{enum @var{enum-tag}}.
14345 @item ptype [@var{arg}]
14346 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
14347 detailed description of the type, instead of just the name of the type.
14348 @xref{Expressions, ,Expressions}.
14350 Contrary to @code{whatis}, @code{ptype} always unrolls any
14351 @code{typedef}s in its argument declaration, whether the argument is
14352 a variable, expression, or a data type. This means that @code{ptype}
14353 of a variable or an expression will not print literally its type as
14354 present in the source code---use @code{whatis} for that. @code{typedef}s at
14355 the pointer or reference targets are also unrolled. Only @code{typedef}s of
14356 fields, methods and inner @code{class typedef}s of @code{struct}s,
14357 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
14359 For example, for this variable declaration:
14362 typedef double real_t;
14363 struct complex @{ real_t real; double imag; @};
14364 typedef struct complex complex_t;
14366 real_t *real_pointer_var;
14370 the two commands give this output:
14374 (@value{GDBP}) whatis var
14376 (@value{GDBP}) ptype var
14377 type = struct complex @{
14381 (@value{GDBP}) whatis complex_t
14382 type = struct complex
14383 (@value{GDBP}) whatis struct complex
14384 type = struct complex
14385 (@value{GDBP}) ptype struct complex
14386 type = struct complex @{
14390 (@value{GDBP}) whatis real_pointer_var
14392 (@value{GDBP}) ptype real_pointer_var
14398 As with @code{whatis}, using @code{ptype} without an argument refers to
14399 the type of @code{$}, the last value in the value history.
14401 @cindex incomplete type
14402 Sometimes, programs use opaque data types or incomplete specifications
14403 of complex data structure. If the debug information included in the
14404 program does not allow @value{GDBN} to display a full declaration of
14405 the data type, it will say @samp{<incomplete type>}. For example,
14406 given these declarations:
14410 struct foo *fooptr;
14414 but no definition for @code{struct foo} itself, @value{GDBN} will say:
14417 (@value{GDBP}) ptype foo
14418 $1 = <incomplete type>
14422 ``Incomplete type'' is C terminology for data types that are not
14423 completely specified.
14426 @item info types @var{regexp}
14428 Print a brief description of all types whose names match the regular
14429 expression @var{regexp} (or all types in your program, if you supply
14430 no argument). Each complete typename is matched as though it were a
14431 complete line; thus, @samp{i type value} gives information on all
14432 types in your program whose names include the string @code{value}, but
14433 @samp{i type ^value$} gives information only on types whose complete
14434 name is @code{value}.
14436 This command differs from @code{ptype} in two ways: first, like
14437 @code{whatis}, it does not print a detailed description; second, it
14438 lists all source files where a type is defined.
14441 @cindex local variables
14442 @item info scope @var{location}
14443 List all the variables local to a particular scope. This command
14444 accepts a @var{location} argument---a function name, a source line, or
14445 an address preceded by a @samp{*}, and prints all the variables local
14446 to the scope defined by that location. (@xref{Specify Location}, for
14447 details about supported forms of @var{location}.) For example:
14450 (@value{GDBP}) @b{info scope command_line_handler}
14451 Scope for command_line_handler:
14452 Symbol rl is an argument at stack/frame offset 8, length 4.
14453 Symbol linebuffer is in static storage at address 0x150a18, length 4.
14454 Symbol linelength is in static storage at address 0x150a1c, length 4.
14455 Symbol p is a local variable in register $esi, length 4.
14456 Symbol p1 is a local variable in register $ebx, length 4.
14457 Symbol nline is a local variable in register $edx, length 4.
14458 Symbol repeat is a local variable at frame offset -8, length 4.
14462 This command is especially useful for determining what data to collect
14463 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
14466 @kindex info source
14468 Show information about the current source file---that is, the source file for
14469 the function containing the current point of execution:
14472 the name of the source file, and the directory containing it,
14474 the directory it was compiled in,
14476 its length, in lines,
14478 which programming language it is written in,
14480 whether the executable includes debugging information for that file, and
14481 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
14483 whether the debugging information includes information about
14484 preprocessor macros.
14488 @kindex info sources
14490 Print the names of all source files in your program for which there is
14491 debugging information, organized into two lists: files whose symbols
14492 have already been read, and files whose symbols will be read when needed.
14494 @kindex info functions
14495 @item info functions
14496 Print the names and data types of all defined functions.
14498 @item info functions @var{regexp}
14499 Print the names and data types of all defined functions
14500 whose names contain a match for regular expression @var{regexp}.
14501 Thus, @samp{info fun step} finds all functions whose names
14502 include @code{step}; @samp{info fun ^step} finds those whose names
14503 start with @code{step}. If a function name contains characters
14504 that conflict with the regular expression language (e.g.@:
14505 @samp{operator*()}), they may be quoted with a backslash.
14507 @kindex info variables
14508 @item info variables
14509 Print the names and data types of all variables that are defined
14510 outside of functions (i.e.@: excluding local variables).
14512 @item info variables @var{regexp}
14513 Print the names and data types of all variables (except for local
14514 variables) whose names contain a match for regular expression
14517 @kindex info classes
14518 @cindex Objective-C, classes and selectors
14520 @itemx info classes @var{regexp}
14521 Display all Objective-C classes in your program, or
14522 (with the @var{regexp} argument) all those matching a particular regular
14525 @kindex info selectors
14526 @item info selectors
14527 @itemx info selectors @var{regexp}
14528 Display all Objective-C selectors in your program, or
14529 (with the @var{regexp} argument) all those matching a particular regular
14533 This was never implemented.
14534 @kindex info methods
14536 @itemx info methods @var{regexp}
14537 The @code{info methods} command permits the user to examine all defined
14538 methods within C@t{++} program, or (with the @var{regexp} argument) a
14539 specific set of methods found in the various C@t{++} classes. Many
14540 C@t{++} classes provide a large number of methods. Thus, the output
14541 from the @code{ptype} command can be overwhelming and hard to use. The
14542 @code{info-methods} command filters the methods, printing only those
14543 which match the regular-expression @var{regexp}.
14546 @cindex reloading symbols
14547 Some systems allow individual object files that make up your program to
14548 be replaced without stopping and restarting your program. For example,
14549 in VxWorks you can simply recompile a defective object file and keep on
14550 running. If you are running on one of these systems, you can allow
14551 @value{GDBN} to reload the symbols for automatically relinked modules:
14554 @kindex set symbol-reloading
14555 @item set symbol-reloading on
14556 Replace symbol definitions for the corresponding source file when an
14557 object file with a particular name is seen again.
14559 @item set symbol-reloading off
14560 Do not replace symbol definitions when encountering object files of the
14561 same name more than once. This is the default state; if you are not
14562 running on a system that permits automatic relinking of modules, you
14563 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
14564 may discard symbols when linking large programs, that may contain
14565 several modules (from different directories or libraries) with the same
14568 @kindex show symbol-reloading
14569 @item show symbol-reloading
14570 Show the current @code{on} or @code{off} setting.
14573 @cindex opaque data types
14574 @kindex set opaque-type-resolution
14575 @item set opaque-type-resolution on
14576 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
14577 declared as a pointer to a @code{struct}, @code{class}, or
14578 @code{union}---for example, @code{struct MyType *}---that is used in one
14579 source file although the full declaration of @code{struct MyType} is in
14580 another source file. The default is on.
14582 A change in the setting of this subcommand will not take effect until
14583 the next time symbols for a file are loaded.
14585 @item set opaque-type-resolution off
14586 Tell @value{GDBN} not to resolve opaque types. In this case, the type
14587 is printed as follows:
14589 @{<no data fields>@}
14592 @kindex show opaque-type-resolution
14593 @item show opaque-type-resolution
14594 Show whether opaque types are resolved or not.
14596 @kindex maint print symbols
14597 @cindex symbol dump
14598 @kindex maint print psymbols
14599 @cindex partial symbol dump
14600 @item maint print symbols @var{filename}
14601 @itemx maint print psymbols @var{filename}
14602 @itemx maint print msymbols @var{filename}
14603 Write a dump of debugging symbol data into the file @var{filename}.
14604 These commands are used to debug the @value{GDBN} symbol-reading code. Only
14605 symbols with debugging data are included. If you use @samp{maint print
14606 symbols}, @value{GDBN} includes all the symbols for which it has already
14607 collected full details: that is, @var{filename} reflects symbols for
14608 only those files whose symbols @value{GDBN} has read. You can use the
14609 command @code{info sources} to find out which files these are. If you
14610 use @samp{maint print psymbols} instead, the dump shows information about
14611 symbols that @value{GDBN} only knows partially---that is, symbols defined in
14612 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
14613 @samp{maint print msymbols} dumps just the minimal symbol information
14614 required for each object file from which @value{GDBN} has read some symbols.
14615 @xref{Files, ,Commands to Specify Files}, for a discussion of how
14616 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
14618 @kindex maint info symtabs
14619 @kindex maint info psymtabs
14620 @cindex listing @value{GDBN}'s internal symbol tables
14621 @cindex symbol tables, listing @value{GDBN}'s internal
14622 @cindex full symbol tables, listing @value{GDBN}'s internal
14623 @cindex partial symbol tables, listing @value{GDBN}'s internal
14624 @item maint info symtabs @r{[} @var{regexp} @r{]}
14625 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
14627 List the @code{struct symtab} or @code{struct partial_symtab}
14628 structures whose names match @var{regexp}. If @var{regexp} is not
14629 given, list them all. The output includes expressions which you can
14630 copy into a @value{GDBN} debugging this one to examine a particular
14631 structure in more detail. For example:
14634 (@value{GDBP}) maint info psymtabs dwarf2read
14635 @{ objfile /home/gnu/build/gdb/gdb
14636 ((struct objfile *) 0x82e69d0)
14637 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
14638 ((struct partial_symtab *) 0x8474b10)
14641 text addresses 0x814d3c8 -- 0x8158074
14642 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
14643 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
14644 dependencies (none)
14647 (@value{GDBP}) maint info symtabs
14651 We see that there is one partial symbol table whose filename contains
14652 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
14653 and we see that @value{GDBN} has not read in any symtabs yet at all.
14654 If we set a breakpoint on a function, that will cause @value{GDBN} to
14655 read the symtab for the compilation unit containing that function:
14658 (@value{GDBP}) break dwarf2_psymtab_to_symtab
14659 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
14661 (@value{GDBP}) maint info symtabs
14662 @{ objfile /home/gnu/build/gdb/gdb
14663 ((struct objfile *) 0x82e69d0)
14664 @{ symtab /home/gnu/src/gdb/dwarf2read.c
14665 ((struct symtab *) 0x86c1f38)
14668 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
14669 linetable ((struct linetable *) 0x8370fa0)
14670 debugformat DWARF 2
14679 @chapter Altering Execution
14681 Once you think you have found an error in your program, you might want to
14682 find out for certain whether correcting the apparent error would lead to
14683 correct results in the rest of the run. You can find the answer by
14684 experiment, using the @value{GDBN} features for altering execution of the
14687 For example, you can store new values into variables or memory
14688 locations, give your program a signal, restart it at a different
14689 address, or even return prematurely from a function.
14692 * Assignment:: Assignment to variables
14693 * Jumping:: Continuing at a different address
14694 * Signaling:: Giving your program a signal
14695 * Returning:: Returning from a function
14696 * Calling:: Calling your program's functions
14697 * Patching:: Patching your program
14701 @section Assignment to Variables
14704 @cindex setting variables
14705 To alter the value of a variable, evaluate an assignment expression.
14706 @xref{Expressions, ,Expressions}. For example,
14713 stores the value 4 into the variable @code{x}, and then prints the
14714 value of the assignment expression (which is 4).
14715 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
14716 information on operators in supported languages.
14718 @kindex set variable
14719 @cindex variables, setting
14720 If you are not interested in seeing the value of the assignment, use the
14721 @code{set} command instead of the @code{print} command. @code{set} is
14722 really the same as @code{print} except that the expression's value is
14723 not printed and is not put in the value history (@pxref{Value History,
14724 ,Value History}). The expression is evaluated only for its effects.
14726 If the beginning of the argument string of the @code{set} command
14727 appears identical to a @code{set} subcommand, use the @code{set
14728 variable} command instead of just @code{set}. This command is identical
14729 to @code{set} except for its lack of subcommands. For example, if your
14730 program has a variable @code{width}, you get an error if you try to set
14731 a new value with just @samp{set width=13}, because @value{GDBN} has the
14732 command @code{set width}:
14735 (@value{GDBP}) whatis width
14737 (@value{GDBP}) p width
14739 (@value{GDBP}) set width=47
14740 Invalid syntax in expression.
14744 The invalid expression, of course, is @samp{=47}. In
14745 order to actually set the program's variable @code{width}, use
14748 (@value{GDBP}) set var width=47
14751 Because the @code{set} command has many subcommands that can conflict
14752 with the names of program variables, it is a good idea to use the
14753 @code{set variable} command instead of just @code{set}. For example, if
14754 your program has a variable @code{g}, you run into problems if you try
14755 to set a new value with just @samp{set g=4}, because @value{GDBN} has
14756 the command @code{set gnutarget}, abbreviated @code{set g}:
14760 (@value{GDBP}) whatis g
14764 (@value{GDBP}) set g=4
14768 The program being debugged has been started already.
14769 Start it from the beginning? (y or n) y
14770 Starting program: /home/smith/cc_progs/a.out
14771 "/home/smith/cc_progs/a.out": can't open to read symbols:
14772 Invalid bfd target.
14773 (@value{GDBP}) show g
14774 The current BFD target is "=4".
14779 The program variable @code{g} did not change, and you silently set the
14780 @code{gnutarget} to an invalid value. In order to set the variable
14784 (@value{GDBP}) set var g=4
14787 @value{GDBN} allows more implicit conversions in assignments than C; you can
14788 freely store an integer value into a pointer variable or vice versa,
14789 and you can convert any structure to any other structure that is the
14790 same length or shorter.
14791 @comment FIXME: how do structs align/pad in these conversions?
14792 @comment /doc@cygnus.com 18dec1990
14794 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
14795 construct to generate a value of specified type at a specified address
14796 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
14797 to memory location @code{0x83040} as an integer (which implies a certain size
14798 and representation in memory), and
14801 set @{int@}0x83040 = 4
14805 stores the value 4 into that memory location.
14808 @section Continuing at a Different Address
14810 Ordinarily, when you continue your program, you do so at the place where
14811 it stopped, with the @code{continue} command. You can instead continue at
14812 an address of your own choosing, with the following commands:
14816 @item jump @var{linespec}
14817 @itemx jump @var{location}
14818 Resume execution at line @var{linespec} or at address given by
14819 @var{location}. Execution stops again immediately if there is a
14820 breakpoint there. @xref{Specify Location}, for a description of the
14821 different forms of @var{linespec} and @var{location}. It is common
14822 practice to use the @code{tbreak} command in conjunction with
14823 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
14825 The @code{jump} command does not change the current stack frame, or
14826 the stack pointer, or the contents of any memory location or any
14827 register other than the program counter. If line @var{linespec} is in
14828 a different function from the one currently executing, the results may
14829 be bizarre if the two functions expect different patterns of arguments or
14830 of local variables. For this reason, the @code{jump} command requests
14831 confirmation if the specified line is not in the function currently
14832 executing. However, even bizarre results are predictable if you are
14833 well acquainted with the machine-language code of your program.
14836 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
14837 On many systems, you can get much the same effect as the @code{jump}
14838 command by storing a new value into the register @code{$pc}. The
14839 difference is that this does not start your program running; it only
14840 changes the address of where it @emph{will} run when you continue. For
14848 makes the next @code{continue} command or stepping command execute at
14849 address @code{0x485}, rather than at the address where your program stopped.
14850 @xref{Continuing and Stepping, ,Continuing and Stepping}.
14852 The most common occasion to use the @code{jump} command is to back
14853 up---perhaps with more breakpoints set---over a portion of a program
14854 that has already executed, in order to examine its execution in more
14859 @section Giving your Program a Signal
14860 @cindex deliver a signal to a program
14864 @item signal @var{signal}
14865 Resume execution where your program stopped, but immediately give it the
14866 signal @var{signal}. @var{signal} can be the name or the number of a
14867 signal. For example, on many systems @code{signal 2} and @code{signal
14868 SIGINT} are both ways of sending an interrupt signal.
14870 Alternatively, if @var{signal} is zero, continue execution without
14871 giving a signal. This is useful when your program stopped on account of
14872 a signal and would ordinary see the signal when resumed with the
14873 @code{continue} command; @samp{signal 0} causes it to resume without a
14876 @code{signal} does not repeat when you press @key{RET} a second time
14877 after executing the command.
14881 Invoking the @code{signal} command is not the same as invoking the
14882 @code{kill} utility from the shell. Sending a signal with @code{kill}
14883 causes @value{GDBN} to decide what to do with the signal depending on
14884 the signal handling tables (@pxref{Signals}). The @code{signal} command
14885 passes the signal directly to your program.
14889 @section Returning from a Function
14892 @cindex returning from a function
14895 @itemx return @var{expression}
14896 You can cancel execution of a function call with the @code{return}
14897 command. If you give an
14898 @var{expression} argument, its value is used as the function's return
14902 When you use @code{return}, @value{GDBN} discards the selected stack frame
14903 (and all frames within it). You can think of this as making the
14904 discarded frame return prematurely. If you wish to specify a value to
14905 be returned, give that value as the argument to @code{return}.
14907 This pops the selected stack frame (@pxref{Selection, ,Selecting a
14908 Frame}), and any other frames inside of it, leaving its caller as the
14909 innermost remaining frame. That frame becomes selected. The
14910 specified value is stored in the registers used for returning values
14913 The @code{return} command does not resume execution; it leaves the
14914 program stopped in the state that would exist if the function had just
14915 returned. In contrast, the @code{finish} command (@pxref{Continuing
14916 and Stepping, ,Continuing and Stepping}) resumes execution until the
14917 selected stack frame returns naturally.
14919 @value{GDBN} needs to know how the @var{expression} argument should be set for
14920 the inferior. The concrete registers assignment depends on the OS ABI and the
14921 type being returned by the selected stack frame. For example it is common for
14922 OS ABI to return floating point values in FPU registers while integer values in
14923 CPU registers. Still some ABIs return even floating point values in CPU
14924 registers. Larger integer widths (such as @code{long long int}) also have
14925 specific placement rules. @value{GDBN} already knows the OS ABI from its
14926 current target so it needs to find out also the type being returned to make the
14927 assignment into the right register(s).
14929 Normally, the selected stack frame has debug info. @value{GDBN} will always
14930 use the debug info instead of the implicit type of @var{expression} when the
14931 debug info is available. For example, if you type @kbd{return -1}, and the
14932 function in the current stack frame is declared to return a @code{long long
14933 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
14934 into a @code{long long int}:
14937 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
14939 (@value{GDBP}) return -1
14940 Make func return now? (y or n) y
14941 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
14942 43 printf ("result=%lld\n", func ());
14946 However, if the selected stack frame does not have a debug info, e.g., if the
14947 function was compiled without debug info, @value{GDBN} has to find out the type
14948 to return from user. Specifying a different type by mistake may set the value
14949 in different inferior registers than the caller code expects. For example,
14950 typing @kbd{return -1} with its implicit type @code{int} would set only a part
14951 of a @code{long long int} result for a debug info less function (on 32-bit
14952 architectures). Therefore the user is required to specify the return type by
14953 an appropriate cast explicitly:
14956 Breakpoint 2, 0x0040050b in func ()
14957 (@value{GDBP}) return -1
14958 Return value type not available for selected stack frame.
14959 Please use an explicit cast of the value to return.
14960 (@value{GDBP}) return (long long int) -1
14961 Make selected stack frame return now? (y or n) y
14962 #0 0x00400526 in main ()
14967 @section Calling Program Functions
14970 @cindex calling functions
14971 @cindex inferior functions, calling
14972 @item print @var{expr}
14973 Evaluate the expression @var{expr} and display the resulting value.
14974 @var{expr} may include calls to functions in the program being
14978 @item call @var{expr}
14979 Evaluate the expression @var{expr} without displaying @code{void}
14982 You can use this variant of the @code{print} command if you want to
14983 execute a function from your program that does not return anything
14984 (a.k.a.@: @dfn{a void function}), but without cluttering the output
14985 with @code{void} returned values that @value{GDBN} will otherwise
14986 print. If the result is not void, it is printed and saved in the
14990 It is possible for the function you call via the @code{print} or
14991 @code{call} command to generate a signal (e.g., if there's a bug in
14992 the function, or if you passed it incorrect arguments). What happens
14993 in that case is controlled by the @code{set unwindonsignal} command.
14995 Similarly, with a C@t{++} program it is possible for the function you
14996 call via the @code{print} or @code{call} command to generate an
14997 exception that is not handled due to the constraints of the dummy
14998 frame. In this case, any exception that is raised in the frame, but has
14999 an out-of-frame exception handler will not be found. GDB builds a
15000 dummy-frame for the inferior function call, and the unwinder cannot
15001 seek for exception handlers outside of this dummy-frame. What happens
15002 in that case is controlled by the
15003 @code{set unwind-on-terminating-exception} command.
15006 @item set unwindonsignal
15007 @kindex set unwindonsignal
15008 @cindex unwind stack in called functions
15009 @cindex call dummy stack unwinding
15010 Set unwinding of the stack if a signal is received while in a function
15011 that @value{GDBN} called in the program being debugged. If set to on,
15012 @value{GDBN} unwinds the stack it created for the call and restores
15013 the context to what it was before the call. If set to off (the
15014 default), @value{GDBN} stops in the frame where the signal was
15017 @item show unwindonsignal
15018 @kindex show unwindonsignal
15019 Show the current setting of stack unwinding in the functions called by
15022 @item set unwind-on-terminating-exception
15023 @kindex set unwind-on-terminating-exception
15024 @cindex unwind stack in called functions with unhandled exceptions
15025 @cindex call dummy stack unwinding on unhandled exception.
15026 Set unwinding of the stack if a C@t{++} exception is raised, but left
15027 unhandled while in a function that @value{GDBN} called in the program being
15028 debugged. If set to on (the default), @value{GDBN} unwinds the stack
15029 it created for the call and restores the context to what it was before
15030 the call. If set to off, @value{GDBN} the exception is delivered to
15031 the default C@t{++} exception handler and the inferior terminated.
15033 @item show unwind-on-terminating-exception
15034 @kindex show unwind-on-terminating-exception
15035 Show the current setting of stack unwinding in the functions called by
15040 @cindex weak alias functions
15041 Sometimes, a function you wish to call is actually a @dfn{weak alias}
15042 for another function. In such case, @value{GDBN} might not pick up
15043 the type information, including the types of the function arguments,
15044 which causes @value{GDBN} to call the inferior function incorrectly.
15045 As a result, the called function will function erroneously and may
15046 even crash. A solution to that is to use the name of the aliased
15050 @section Patching Programs
15052 @cindex patching binaries
15053 @cindex writing into executables
15054 @cindex writing into corefiles
15056 By default, @value{GDBN} opens the file containing your program's
15057 executable code (or the corefile) read-only. This prevents accidental
15058 alterations to machine code; but it also prevents you from intentionally
15059 patching your program's binary.
15061 If you'd like to be able to patch the binary, you can specify that
15062 explicitly with the @code{set write} command. For example, you might
15063 want to turn on internal debugging flags, or even to make emergency
15069 @itemx set write off
15070 If you specify @samp{set write on}, @value{GDBN} opens executable and
15071 core files for both reading and writing; if you specify @kbd{set write
15072 off} (the default), @value{GDBN} opens them read-only.
15074 If you have already loaded a file, you must load it again (using the
15075 @code{exec-file} or @code{core-file} command) after changing @code{set
15076 write}, for your new setting to take effect.
15080 Display whether executable files and core files are opened for writing
15081 as well as reading.
15085 @chapter @value{GDBN} Files
15087 @value{GDBN} needs to know the file name of the program to be debugged,
15088 both in order to read its symbol table and in order to start your
15089 program. To debug a core dump of a previous run, you must also tell
15090 @value{GDBN} the name of the core dump file.
15093 * Files:: Commands to specify files
15094 * Separate Debug Files:: Debugging information in separate files
15095 * Index Files:: Index files speed up GDB
15096 * Symbol Errors:: Errors reading symbol files
15097 * Data Files:: GDB data files
15101 @section Commands to Specify Files
15103 @cindex symbol table
15104 @cindex core dump file
15106 You may want to specify executable and core dump file names. The usual
15107 way to do this is at start-up time, using the arguments to
15108 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
15109 Out of @value{GDBN}}).
15111 Occasionally it is necessary to change to a different file during a
15112 @value{GDBN} session. Or you may run @value{GDBN} and forget to
15113 specify a file you want to use. Or you are debugging a remote target
15114 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
15115 Program}). In these situations the @value{GDBN} commands to specify
15116 new files are useful.
15119 @cindex executable file
15121 @item file @var{filename}
15122 Use @var{filename} as the program to be debugged. It is read for its
15123 symbols and for the contents of pure memory. It is also the program
15124 executed when you use the @code{run} command. If you do not specify a
15125 directory and the file is not found in the @value{GDBN} working directory,
15126 @value{GDBN} uses the environment variable @code{PATH} as a list of
15127 directories to search, just as the shell does when looking for a program
15128 to run. You can change the value of this variable, for both @value{GDBN}
15129 and your program, using the @code{path} command.
15131 @cindex unlinked object files
15132 @cindex patching object files
15133 You can load unlinked object @file{.o} files into @value{GDBN} using
15134 the @code{file} command. You will not be able to ``run'' an object
15135 file, but you can disassemble functions and inspect variables. Also,
15136 if the underlying BFD functionality supports it, you could use
15137 @kbd{gdb -write} to patch object files using this technique. Note
15138 that @value{GDBN} can neither interpret nor modify relocations in this
15139 case, so branches and some initialized variables will appear to go to
15140 the wrong place. But this feature is still handy from time to time.
15143 @code{file} with no argument makes @value{GDBN} discard any information it
15144 has on both executable file and the symbol table.
15147 @item exec-file @r{[} @var{filename} @r{]}
15148 Specify that the program to be run (but not the symbol table) is found
15149 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
15150 if necessary to locate your program. Omitting @var{filename} means to
15151 discard information on the executable file.
15153 @kindex symbol-file
15154 @item symbol-file @r{[} @var{filename} @r{]}
15155 Read symbol table information from file @var{filename}. @code{PATH} is
15156 searched when necessary. Use the @code{file} command to get both symbol
15157 table and program to run from the same file.
15159 @code{symbol-file} with no argument clears out @value{GDBN} information on your
15160 program's symbol table.
15162 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
15163 some breakpoints and auto-display expressions. This is because they may
15164 contain pointers to the internal data recording symbols and data types,
15165 which are part of the old symbol table data being discarded inside
15168 @code{symbol-file} does not repeat if you press @key{RET} again after
15171 When @value{GDBN} is configured for a particular environment, it
15172 understands debugging information in whatever format is the standard
15173 generated for that environment; you may use either a @sc{gnu} compiler, or
15174 other compilers that adhere to the local conventions.
15175 Best results are usually obtained from @sc{gnu} compilers; for example,
15176 using @code{@value{NGCC}} you can generate debugging information for
15179 For most kinds of object files, with the exception of old SVR3 systems
15180 using COFF, the @code{symbol-file} command does not normally read the
15181 symbol table in full right away. Instead, it scans the symbol table
15182 quickly to find which source files and which symbols are present. The
15183 details are read later, one source file at a time, as they are needed.
15185 The purpose of this two-stage reading strategy is to make @value{GDBN}
15186 start up faster. For the most part, it is invisible except for
15187 occasional pauses while the symbol table details for a particular source
15188 file are being read. (The @code{set verbose} command can turn these
15189 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
15190 Warnings and Messages}.)
15192 We have not implemented the two-stage strategy for COFF yet. When the
15193 symbol table is stored in COFF format, @code{symbol-file} reads the
15194 symbol table data in full right away. Note that ``stabs-in-COFF''
15195 still does the two-stage strategy, since the debug info is actually
15199 @cindex reading symbols immediately
15200 @cindex symbols, reading immediately
15201 @item symbol-file @r{[} -readnow @r{]} @var{filename}
15202 @itemx file @r{[} -readnow @r{]} @var{filename}
15203 You can override the @value{GDBN} two-stage strategy for reading symbol
15204 tables by using the @samp{-readnow} option with any of the commands that
15205 load symbol table information, if you want to be sure @value{GDBN} has the
15206 entire symbol table available.
15208 @c FIXME: for now no mention of directories, since this seems to be in
15209 @c flux. 13mar1992 status is that in theory GDB would look either in
15210 @c current dir or in same dir as myprog; but issues like competing
15211 @c GDB's, or clutter in system dirs, mean that in practice right now
15212 @c only current dir is used. FFish says maybe a special GDB hierarchy
15213 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
15217 @item core-file @r{[}@var{filename}@r{]}
15219 Specify the whereabouts of a core dump file to be used as the ``contents
15220 of memory''. Traditionally, core files contain only some parts of the
15221 address space of the process that generated them; @value{GDBN} can access the
15222 executable file itself for other parts.
15224 @code{core-file} with no argument specifies that no core file is
15227 Note that the core file is ignored when your program is actually running
15228 under @value{GDBN}. So, if you have been running your program and you
15229 wish to debug a core file instead, you must kill the subprocess in which
15230 the program is running. To do this, use the @code{kill} command
15231 (@pxref{Kill Process, ,Killing the Child Process}).
15233 @kindex add-symbol-file
15234 @cindex dynamic linking
15235 @item add-symbol-file @var{filename} @var{address}
15236 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
15237 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
15238 The @code{add-symbol-file} command reads additional symbol table
15239 information from the file @var{filename}. You would use this command
15240 when @var{filename} has been dynamically loaded (by some other means)
15241 into the program that is running. @var{address} should be the memory
15242 address at which the file has been loaded; @value{GDBN} cannot figure
15243 this out for itself. You can additionally specify an arbitrary number
15244 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
15245 section name and base address for that section. You can specify any
15246 @var{address} as an expression.
15248 The symbol table of the file @var{filename} is added to the symbol table
15249 originally read with the @code{symbol-file} command. You can use the
15250 @code{add-symbol-file} command any number of times; the new symbol data
15251 thus read keeps adding to the old. To discard all old symbol data
15252 instead, use the @code{symbol-file} command without any arguments.
15254 @cindex relocatable object files, reading symbols from
15255 @cindex object files, relocatable, reading symbols from
15256 @cindex reading symbols from relocatable object files
15257 @cindex symbols, reading from relocatable object files
15258 @cindex @file{.o} files, reading symbols from
15259 Although @var{filename} is typically a shared library file, an
15260 executable file, or some other object file which has been fully
15261 relocated for loading into a process, you can also load symbolic
15262 information from relocatable @file{.o} files, as long as:
15266 the file's symbolic information refers only to linker symbols defined in
15267 that file, not to symbols defined by other object files,
15269 every section the file's symbolic information refers to has actually
15270 been loaded into the inferior, as it appears in the file, and
15272 you can determine the address at which every section was loaded, and
15273 provide these to the @code{add-symbol-file} command.
15277 Some embedded operating systems, like Sun Chorus and VxWorks, can load
15278 relocatable files into an already running program; such systems
15279 typically make the requirements above easy to meet. However, it's
15280 important to recognize that many native systems use complex link
15281 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
15282 assembly, for example) that make the requirements difficult to meet. In
15283 general, one cannot assume that using @code{add-symbol-file} to read a
15284 relocatable object file's symbolic information will have the same effect
15285 as linking the relocatable object file into the program in the normal
15288 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
15290 @kindex add-symbol-file-from-memory
15291 @cindex @code{syscall DSO}
15292 @cindex load symbols from memory
15293 @item add-symbol-file-from-memory @var{address}
15294 Load symbols from the given @var{address} in a dynamically loaded
15295 object file whose image is mapped directly into the inferior's memory.
15296 For example, the Linux kernel maps a @code{syscall DSO} into each
15297 process's address space; this DSO provides kernel-specific code for
15298 some system calls. The argument can be any expression whose
15299 evaluation yields the address of the file's shared object file header.
15300 For this command to work, you must have used @code{symbol-file} or
15301 @code{exec-file} commands in advance.
15303 @kindex add-shared-symbol-files
15305 @item add-shared-symbol-files @var{library-file}
15306 @itemx assf @var{library-file}
15307 The @code{add-shared-symbol-files} command can currently be used only
15308 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
15309 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
15310 @value{GDBN} automatically looks for shared libraries, however if
15311 @value{GDBN} does not find yours, you can invoke
15312 @code{add-shared-symbol-files}. It takes one argument: the shared
15313 library's file name. @code{assf} is a shorthand alias for
15314 @code{add-shared-symbol-files}.
15317 @item section @var{section} @var{addr}
15318 The @code{section} command changes the base address of the named
15319 @var{section} of the exec file to @var{addr}. This can be used if the
15320 exec file does not contain section addresses, (such as in the
15321 @code{a.out} format), or when the addresses specified in the file
15322 itself are wrong. Each section must be changed separately. The
15323 @code{info files} command, described below, lists all the sections and
15327 @kindex info target
15330 @code{info files} and @code{info target} are synonymous; both print the
15331 current target (@pxref{Targets, ,Specifying a Debugging Target}),
15332 including the names of the executable and core dump files currently in
15333 use by @value{GDBN}, and the files from which symbols were loaded. The
15334 command @code{help target} lists all possible targets rather than
15337 @kindex maint info sections
15338 @item maint info sections
15339 Another command that can give you extra information about program sections
15340 is @code{maint info sections}. In addition to the section information
15341 displayed by @code{info files}, this command displays the flags and file
15342 offset of each section in the executable and core dump files. In addition,
15343 @code{maint info sections} provides the following command options (which
15344 may be arbitrarily combined):
15348 Display sections for all loaded object files, including shared libraries.
15349 @item @var{sections}
15350 Display info only for named @var{sections}.
15351 @item @var{section-flags}
15352 Display info only for sections for which @var{section-flags} are true.
15353 The section flags that @value{GDBN} currently knows about are:
15356 Section will have space allocated in the process when loaded.
15357 Set for all sections except those containing debug information.
15359 Section will be loaded from the file into the child process memory.
15360 Set for pre-initialized code and data, clear for @code{.bss} sections.
15362 Section needs to be relocated before loading.
15364 Section cannot be modified by the child process.
15366 Section contains executable code only.
15368 Section contains data only (no executable code).
15370 Section will reside in ROM.
15372 Section contains data for constructor/destructor lists.
15374 Section is not empty.
15376 An instruction to the linker to not output the section.
15377 @item COFF_SHARED_LIBRARY
15378 A notification to the linker that the section contains
15379 COFF shared library information.
15381 Section contains common symbols.
15384 @kindex set trust-readonly-sections
15385 @cindex read-only sections
15386 @item set trust-readonly-sections on
15387 Tell @value{GDBN} that readonly sections in your object file
15388 really are read-only (i.e.@: that their contents will not change).
15389 In that case, @value{GDBN} can fetch values from these sections
15390 out of the object file, rather than from the target program.
15391 For some targets (notably embedded ones), this can be a significant
15392 enhancement to debugging performance.
15394 The default is off.
15396 @item set trust-readonly-sections off
15397 Tell @value{GDBN} not to trust readonly sections. This means that
15398 the contents of the section might change while the program is running,
15399 and must therefore be fetched from the target when needed.
15401 @item show trust-readonly-sections
15402 Show the current setting of trusting readonly sections.
15405 All file-specifying commands allow both absolute and relative file names
15406 as arguments. @value{GDBN} always converts the file name to an absolute file
15407 name and remembers it that way.
15409 @cindex shared libraries
15410 @anchor{Shared Libraries}
15411 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
15412 and IBM RS/6000 AIX shared libraries.
15414 On MS-Windows @value{GDBN} must be linked with the Expat library to support
15415 shared libraries. @xref{Expat}.
15417 @value{GDBN} automatically loads symbol definitions from shared libraries
15418 when you use the @code{run} command, or when you examine a core file.
15419 (Before you issue the @code{run} command, @value{GDBN} does not understand
15420 references to a function in a shared library, however---unless you are
15421 debugging a core file).
15423 On HP-UX, if the program loads a library explicitly, @value{GDBN}
15424 automatically loads the symbols at the time of the @code{shl_load} call.
15426 @c FIXME: some @value{GDBN} release may permit some refs to undef
15427 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
15428 @c FIXME...lib; check this from time to time when updating manual
15430 There are times, however, when you may wish to not automatically load
15431 symbol definitions from shared libraries, such as when they are
15432 particularly large or there are many of them.
15434 To control the automatic loading of shared library symbols, use the
15438 @kindex set auto-solib-add
15439 @item set auto-solib-add @var{mode}
15440 If @var{mode} is @code{on}, symbols from all shared object libraries
15441 will be loaded automatically when the inferior begins execution, you
15442 attach to an independently started inferior, or when the dynamic linker
15443 informs @value{GDBN} that a new library has been loaded. If @var{mode}
15444 is @code{off}, symbols must be loaded manually, using the
15445 @code{sharedlibrary} command. The default value is @code{on}.
15447 @cindex memory used for symbol tables
15448 If your program uses lots of shared libraries with debug info that
15449 takes large amounts of memory, you can decrease the @value{GDBN}
15450 memory footprint by preventing it from automatically loading the
15451 symbols from shared libraries. To that end, type @kbd{set
15452 auto-solib-add off} before running the inferior, then load each
15453 library whose debug symbols you do need with @kbd{sharedlibrary
15454 @var{regexp}}, where @var{regexp} is a regular expression that matches
15455 the libraries whose symbols you want to be loaded.
15457 @kindex show auto-solib-add
15458 @item show auto-solib-add
15459 Display the current autoloading mode.
15462 @cindex load shared library
15463 To explicitly load shared library symbols, use the @code{sharedlibrary}
15467 @kindex info sharedlibrary
15469 @item info share @var{regex}
15470 @itemx info sharedlibrary @var{regex}
15471 Print the names of the shared libraries which are currently loaded
15472 that match @var{regex}. If @var{regex} is omitted then print
15473 all shared libraries that are loaded.
15475 @kindex sharedlibrary
15477 @item sharedlibrary @var{regex}
15478 @itemx share @var{regex}
15479 Load shared object library symbols for files matching a
15480 Unix regular expression.
15481 As with files loaded automatically, it only loads shared libraries
15482 required by your program for a core file or after typing @code{run}. If
15483 @var{regex} is omitted all shared libraries required by your program are
15486 @item nosharedlibrary
15487 @kindex nosharedlibrary
15488 @cindex unload symbols from shared libraries
15489 Unload all shared object library symbols. This discards all symbols
15490 that have been loaded from all shared libraries. Symbols from shared
15491 libraries that were loaded by explicit user requests are not
15495 Sometimes you may wish that @value{GDBN} stops and gives you control
15496 when any of shared library events happen. Use the @code{set
15497 stop-on-solib-events} command for this:
15500 @item set stop-on-solib-events
15501 @kindex set stop-on-solib-events
15502 This command controls whether @value{GDBN} should give you control
15503 when the dynamic linker notifies it about some shared library event.
15504 The most common event of interest is loading or unloading of a new
15507 @item show stop-on-solib-events
15508 @kindex show stop-on-solib-events
15509 Show whether @value{GDBN} stops and gives you control when shared
15510 library events happen.
15513 Shared libraries are also supported in many cross or remote debugging
15514 configurations. @value{GDBN} needs to have access to the target's libraries;
15515 this can be accomplished either by providing copies of the libraries
15516 on the host system, or by asking @value{GDBN} to automatically retrieve the
15517 libraries from the target. If copies of the target libraries are
15518 provided, they need to be the same as the target libraries, although the
15519 copies on the target can be stripped as long as the copies on the host are
15522 @cindex where to look for shared libraries
15523 For remote debugging, you need to tell @value{GDBN} where the target
15524 libraries are, so that it can load the correct copies---otherwise, it
15525 may try to load the host's libraries. @value{GDBN} has two variables
15526 to specify the search directories for target libraries.
15529 @cindex prefix for shared library file names
15530 @cindex system root, alternate
15531 @kindex set solib-absolute-prefix
15532 @kindex set sysroot
15533 @item set sysroot @var{path}
15534 Use @var{path} as the system root for the program being debugged. Any
15535 absolute shared library paths will be prefixed with @var{path}; many
15536 runtime loaders store the absolute paths to the shared library in the
15537 target program's memory. If you use @code{set sysroot} to find shared
15538 libraries, they need to be laid out in the same way that they are on
15539 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
15542 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
15543 retrieve the target libraries from the remote system. This is only
15544 supported when using a remote target that supports the @code{remote get}
15545 command (@pxref{File Transfer,,Sending files to a remote system}).
15546 The part of @var{path} following the initial @file{remote:}
15547 (if present) is used as system root prefix on the remote file system.
15548 @footnote{If you want to specify a local system root using a directory
15549 that happens to be named @file{remote:}, you need to use some equivalent
15550 variant of the name like @file{./remote:}.}
15552 For targets with an MS-DOS based filesystem, such as MS-Windows and
15553 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
15554 absolute file name with @var{path}. But first, on Unix hosts,
15555 @value{GDBN} converts all backslash directory separators into forward
15556 slashes, because the backslash is not a directory separator on Unix:
15559 c:\foo\bar.dll @result{} c:/foo/bar.dll
15562 Then, @value{GDBN} attempts prefixing the target file name with
15563 @var{path}, and looks for the resulting file name in the host file
15567 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
15570 If that does not find the shared library, @value{GDBN} tries removing
15571 the @samp{:} character from the drive spec, both for convenience, and,
15572 for the case of the host file system not supporting file names with
15576 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
15579 This makes it possible to have a system root that mirrors a target
15580 with more than one drive. E.g., you may want to setup your local
15581 copies of the target system shared libraries like so (note @samp{c} vs
15585 @file{/path/to/sysroot/c/sys/bin/foo.dll}
15586 @file{/path/to/sysroot/c/sys/bin/bar.dll}
15587 @file{/path/to/sysroot/z/sys/bin/bar.dll}
15591 and point the system root at @file{/path/to/sysroot}, so that
15592 @value{GDBN} can find the correct copies of both
15593 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
15595 If that still does not find the shared library, @value{GDBN} tries
15596 removing the whole drive spec from the target file name:
15599 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
15602 This last lookup makes it possible to not care about the drive name,
15603 if you don't want or need to.
15605 The @code{set solib-absolute-prefix} command is an alias for @code{set
15608 @cindex default system root
15609 @cindex @samp{--with-sysroot}
15610 You can set the default system root by using the configure-time
15611 @samp{--with-sysroot} option. If the system root is inside
15612 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15613 @samp{--exec-prefix}), then the default system root will be updated
15614 automatically if the installed @value{GDBN} is moved to a new
15617 @kindex show sysroot
15619 Display the current shared library prefix.
15621 @kindex set solib-search-path
15622 @item set solib-search-path @var{path}
15623 If this variable is set, @var{path} is a colon-separated list of
15624 directories to search for shared libraries. @samp{solib-search-path}
15625 is used after @samp{sysroot} fails to locate the library, or if the
15626 path to the library is relative instead of absolute. If you want to
15627 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
15628 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
15629 finding your host's libraries. @samp{sysroot} is preferred; setting
15630 it to a nonexistent directory may interfere with automatic loading
15631 of shared library symbols.
15633 @kindex show solib-search-path
15634 @item show solib-search-path
15635 Display the current shared library search path.
15637 @cindex DOS file-name semantics of file names.
15638 @kindex set target-file-system-kind (unix|dos-based|auto)
15639 @kindex show target-file-system-kind
15640 @item set target-file-system-kind @var{kind}
15641 Set assumed file system kind for target reported file names.
15643 Shared library file names as reported by the target system may not
15644 make sense as is on the system @value{GDBN} is running on. For
15645 example, when remote debugging a target that has MS-DOS based file
15646 system semantics, from a Unix host, the target may be reporting to
15647 @value{GDBN} a list of loaded shared libraries with file names such as
15648 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
15649 drive letters, so the @samp{c:\} prefix is not normally understood as
15650 indicating an absolute file name, and neither is the backslash
15651 normally considered a directory separator character. In that case,
15652 the native file system would interpret this whole absolute file name
15653 as a relative file name with no directory components. This would make
15654 it impossible to point @value{GDBN} at a copy of the remote target's
15655 shared libraries on the host using @code{set sysroot}, and impractical
15656 with @code{set solib-search-path}. Setting
15657 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
15658 to interpret such file names similarly to how the target would, and to
15659 map them to file names valid on @value{GDBN}'s native file system
15660 semantics. The value of @var{kind} can be @code{"auto"}, in addition
15661 to one of the supported file system kinds. In that case, @value{GDBN}
15662 tries to determine the appropriate file system variant based on the
15663 current target's operating system (@pxref{ABI, ,Configuring the
15664 Current ABI}). The supported file system settings are:
15668 Instruct @value{GDBN} to assume the target file system is of Unix
15669 kind. Only file names starting the forward slash (@samp{/}) character
15670 are considered absolute, and the directory separator character is also
15674 Instruct @value{GDBN} to assume the target file system is DOS based.
15675 File names starting with either a forward slash, or a drive letter
15676 followed by a colon (e.g., @samp{c:}), are considered absolute, and
15677 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
15678 considered directory separators.
15681 Instruct @value{GDBN} to use the file system kind associated with the
15682 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
15683 This is the default.
15688 @node Separate Debug Files
15689 @section Debugging Information in Separate Files
15690 @cindex separate debugging information files
15691 @cindex debugging information in separate files
15692 @cindex @file{.debug} subdirectories
15693 @cindex debugging information directory, global
15694 @cindex global debugging information directory
15695 @cindex build ID, and separate debugging files
15696 @cindex @file{.build-id} directory
15698 @value{GDBN} allows you to put a program's debugging information in a
15699 file separate from the executable itself, in a way that allows
15700 @value{GDBN} to find and load the debugging information automatically.
15701 Since debugging information can be very large---sometimes larger
15702 than the executable code itself---some systems distribute debugging
15703 information for their executables in separate files, which users can
15704 install only when they need to debug a problem.
15706 @value{GDBN} supports two ways of specifying the separate debug info
15711 The executable contains a @dfn{debug link} that specifies the name of
15712 the separate debug info file. The separate debug file's name is
15713 usually @file{@var{executable}.debug}, where @var{executable} is the
15714 name of the corresponding executable file without leading directories
15715 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
15716 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
15717 checksum for the debug file, which @value{GDBN} uses to validate that
15718 the executable and the debug file came from the same build.
15721 The executable contains a @dfn{build ID}, a unique bit string that is
15722 also present in the corresponding debug info file. (This is supported
15723 only on some operating systems, notably those which use the ELF format
15724 for binary files and the @sc{gnu} Binutils.) For more details about
15725 this feature, see the description of the @option{--build-id}
15726 command-line option in @ref{Options, , Command Line Options, ld.info,
15727 The GNU Linker}. The debug info file's name is not specified
15728 explicitly by the build ID, but can be computed from the build ID, see
15732 Depending on the way the debug info file is specified, @value{GDBN}
15733 uses two different methods of looking for the debug file:
15737 For the ``debug link'' method, @value{GDBN} looks up the named file in
15738 the directory of the executable file, then in a subdirectory of that
15739 directory named @file{.debug}, and finally under the global debug
15740 directory, in a subdirectory whose name is identical to the leading
15741 directories of the executable's absolute file name.
15744 For the ``build ID'' method, @value{GDBN} looks in the
15745 @file{.build-id} subdirectory of the global debug directory for a file
15746 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
15747 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
15748 are the rest of the bit string. (Real build ID strings are 32 or more
15749 hex characters, not 10.)
15752 So, for example, suppose you ask @value{GDBN} to debug
15753 @file{/usr/bin/ls}, which has a debug link that specifies the
15754 file @file{ls.debug}, and a build ID whose value in hex is
15755 @code{abcdef1234}. If the global debug directory is
15756 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
15757 debug information files, in the indicated order:
15761 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
15763 @file{/usr/bin/ls.debug}
15765 @file{/usr/bin/.debug/ls.debug}
15767 @file{/usr/lib/debug/usr/bin/ls.debug}.
15770 You can set the global debugging info directory's name, and view the
15771 name @value{GDBN} is currently using.
15775 @kindex set debug-file-directory
15776 @item set debug-file-directory @var{directories}
15777 Set the directories which @value{GDBN} searches for separate debugging
15778 information files to @var{directory}. Multiple directory components can be set
15779 concatenating them by a directory separator.
15781 @kindex show debug-file-directory
15782 @item show debug-file-directory
15783 Show the directories @value{GDBN} searches for separate debugging
15788 @cindex @code{.gnu_debuglink} sections
15789 @cindex debug link sections
15790 A debug link is a special section of the executable file named
15791 @code{.gnu_debuglink}. The section must contain:
15795 A filename, with any leading directory components removed, followed by
15798 zero to three bytes of padding, as needed to reach the next four-byte
15799 boundary within the section, and
15801 a four-byte CRC checksum, stored in the same endianness used for the
15802 executable file itself. The checksum is computed on the debugging
15803 information file's full contents by the function given below, passing
15804 zero as the @var{crc} argument.
15807 Any executable file format can carry a debug link, as long as it can
15808 contain a section named @code{.gnu_debuglink} with the contents
15811 @cindex @code{.note.gnu.build-id} sections
15812 @cindex build ID sections
15813 The build ID is a special section in the executable file (and in other
15814 ELF binary files that @value{GDBN} may consider). This section is
15815 often named @code{.note.gnu.build-id}, but that name is not mandatory.
15816 It contains unique identification for the built files---the ID remains
15817 the same across multiple builds of the same build tree. The default
15818 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
15819 content for the build ID string. The same section with an identical
15820 value is present in the original built binary with symbols, in its
15821 stripped variant, and in the separate debugging information file.
15823 The debugging information file itself should be an ordinary
15824 executable, containing a full set of linker symbols, sections, and
15825 debugging information. The sections of the debugging information file
15826 should have the same names, addresses, and sizes as the original file,
15827 but they need not contain any data---much like a @code{.bss} section
15828 in an ordinary executable.
15830 The @sc{gnu} binary utilities (Binutils) package includes the
15831 @samp{objcopy} utility that can produce
15832 the separated executable / debugging information file pairs using the
15833 following commands:
15836 @kbd{objcopy --only-keep-debug foo foo.debug}
15841 These commands remove the debugging
15842 information from the executable file @file{foo} and place it in the file
15843 @file{foo.debug}. You can use the first, second or both methods to link the
15848 The debug link method needs the following additional command to also leave
15849 behind a debug link in @file{foo}:
15852 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
15855 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
15856 a version of the @code{strip} command such that the command @kbd{strip foo -f
15857 foo.debug} has the same functionality as the two @code{objcopy} commands and
15858 the @code{ln -s} command above, together.
15861 Build ID gets embedded into the main executable using @code{ld --build-id} or
15862 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
15863 compatibility fixes for debug files separation are present in @sc{gnu} binary
15864 utilities (Binutils) package since version 2.18.
15869 @cindex CRC algorithm definition
15870 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
15871 IEEE 802.3 using the polynomial:
15873 @c TexInfo requires naked braces for multi-digit exponents for Tex
15874 @c output, but this causes HTML output to barf. HTML has to be set using
15875 @c raw commands. So we end up having to specify this equation in 2
15880 <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>
15881 + <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
15887 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
15888 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
15892 The function is computed byte at a time, taking the least
15893 significant bit of each byte first. The initial pattern
15894 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
15895 the final result is inverted to ensure trailing zeros also affect the
15898 @emph{Note:} This is the same CRC polynomial as used in handling the
15899 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
15900 , @value{GDBN} Remote Serial Protocol}). However in the
15901 case of the Remote Serial Protocol, the CRC is computed @emph{most}
15902 significant bit first, and the result is not inverted, so trailing
15903 zeros have no effect on the CRC value.
15905 To complete the description, we show below the code of the function
15906 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
15907 initially supplied @code{crc} argument means that an initial call to
15908 this function passing in zero will start computing the CRC using
15911 @kindex gnu_debuglink_crc32
15914 gnu_debuglink_crc32 (unsigned long crc,
15915 unsigned char *buf, size_t len)
15917 static const unsigned long crc32_table[256] =
15919 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
15920 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
15921 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
15922 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
15923 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
15924 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
15925 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
15926 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
15927 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
15928 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
15929 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
15930 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
15931 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
15932 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
15933 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
15934 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
15935 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
15936 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
15937 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
15938 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
15939 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
15940 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
15941 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
15942 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
15943 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
15944 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
15945 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
15946 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
15947 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
15948 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
15949 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
15950 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
15951 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
15952 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
15953 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
15954 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
15955 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
15956 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
15957 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
15958 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
15959 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
15960 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
15961 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
15962 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
15963 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
15964 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
15965 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
15966 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
15967 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
15968 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
15969 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
15972 unsigned char *end;
15974 crc = ~crc & 0xffffffff;
15975 for (end = buf + len; buf < end; ++buf)
15976 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
15977 return ~crc & 0xffffffff;
15982 This computation does not apply to the ``build ID'' method.
15986 @section Index Files Speed Up @value{GDBN}
15987 @cindex index files
15988 @cindex @samp{.gdb_index} section
15990 When @value{GDBN} finds a symbol file, it scans the symbols in the
15991 file in order to construct an internal symbol table. This lets most
15992 @value{GDBN} operations work quickly---at the cost of a delay early
15993 on. For large programs, this delay can be quite lengthy, so
15994 @value{GDBN} provides a way to build an index, which speeds up
15997 The index is stored as a section in the symbol file. @value{GDBN} can
15998 write the index to a file, then you can put it into the symbol file
15999 using @command{objcopy}.
16001 To create an index file, use the @code{save gdb-index} command:
16004 @item save gdb-index @var{directory}
16005 @kindex save gdb-index
16006 Create an index file for each symbol file currently known by
16007 @value{GDBN}. Each file is named after its corresponding symbol file,
16008 with @samp{.gdb-index} appended, and is written into the given
16012 Once you have created an index file you can merge it into your symbol
16013 file, here named @file{symfile}, using @command{objcopy}:
16016 $ objcopy --add-section .gdb_index=symfile.gdb-index \
16017 --set-section-flags .gdb_index=readonly symfile symfile
16020 There are currently some limitation on indices. They only work when
16021 for DWARF debugging information, not stabs. And, they do not
16022 currently work for programs using Ada.
16024 @node Symbol Errors
16025 @section Errors Reading Symbol Files
16027 While reading a symbol file, @value{GDBN} occasionally encounters problems,
16028 such as symbol types it does not recognize, or known bugs in compiler
16029 output. By default, @value{GDBN} does not notify you of such problems, since
16030 they are relatively common and primarily of interest to people
16031 debugging compilers. If you are interested in seeing information
16032 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
16033 only one message about each such type of problem, no matter how many
16034 times the problem occurs; or you can ask @value{GDBN} to print more messages,
16035 to see how many times the problems occur, with the @code{set
16036 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
16039 The messages currently printed, and their meanings, include:
16042 @item inner block not inside outer block in @var{symbol}
16044 The symbol information shows where symbol scopes begin and end
16045 (such as at the start of a function or a block of statements). This
16046 error indicates that an inner scope block is not fully contained
16047 in its outer scope blocks.
16049 @value{GDBN} circumvents the problem by treating the inner block as if it had
16050 the same scope as the outer block. In the error message, @var{symbol}
16051 may be shown as ``@code{(don't know)}'' if the outer block is not a
16054 @item block at @var{address} out of order
16056 The symbol information for symbol scope blocks should occur in
16057 order of increasing addresses. This error indicates that it does not
16060 @value{GDBN} does not circumvent this problem, and has trouble
16061 locating symbols in the source file whose symbols it is reading. (You
16062 can often determine what source file is affected by specifying
16063 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
16066 @item bad block start address patched
16068 The symbol information for a symbol scope block has a start address
16069 smaller than the address of the preceding source line. This is known
16070 to occur in the SunOS 4.1.1 (and earlier) C compiler.
16072 @value{GDBN} circumvents the problem by treating the symbol scope block as
16073 starting on the previous source line.
16075 @item bad string table offset in symbol @var{n}
16078 Symbol number @var{n} contains a pointer into the string table which is
16079 larger than the size of the string table.
16081 @value{GDBN} circumvents the problem by considering the symbol to have the
16082 name @code{foo}, which may cause other problems if many symbols end up
16085 @item unknown symbol type @code{0x@var{nn}}
16087 The symbol information contains new data types that @value{GDBN} does
16088 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
16089 uncomprehended information, in hexadecimal.
16091 @value{GDBN} circumvents the error by ignoring this symbol information.
16092 This usually allows you to debug your program, though certain symbols
16093 are not accessible. If you encounter such a problem and feel like
16094 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
16095 on @code{complain}, then go up to the function @code{read_dbx_symtab}
16096 and examine @code{*bufp} to see the symbol.
16098 @item stub type has NULL name
16100 @value{GDBN} could not find the full definition for a struct or class.
16102 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
16103 The symbol information for a C@t{++} member function is missing some
16104 information that recent versions of the compiler should have output for
16107 @item info mismatch between compiler and debugger
16109 @value{GDBN} could not parse a type specification output by the compiler.
16114 @section GDB Data Files
16116 @cindex prefix for data files
16117 @value{GDBN} will sometimes read an auxiliary data file. These files
16118 are kept in a directory known as the @dfn{data directory}.
16120 You can set the data directory's name, and view the name @value{GDBN}
16121 is currently using.
16124 @kindex set data-directory
16125 @item set data-directory @var{directory}
16126 Set the directory which @value{GDBN} searches for auxiliary data files
16127 to @var{directory}.
16129 @kindex show data-directory
16130 @item show data-directory
16131 Show the directory @value{GDBN} searches for auxiliary data files.
16134 @cindex default data directory
16135 @cindex @samp{--with-gdb-datadir}
16136 You can set the default data directory by using the configure-time
16137 @samp{--with-gdb-datadir} option. If the data directory is inside
16138 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
16139 @samp{--exec-prefix}), then the default data directory will be updated
16140 automatically if the installed @value{GDBN} is moved to a new
16143 The data directory may also be specified with the
16144 @code{--data-directory} command line option.
16145 @xref{Mode Options}.
16148 @chapter Specifying a Debugging Target
16150 @cindex debugging target
16151 A @dfn{target} is the execution environment occupied by your program.
16153 Often, @value{GDBN} runs in the same host environment as your program;
16154 in that case, the debugging target is specified as a side effect when
16155 you use the @code{file} or @code{core} commands. When you need more
16156 flexibility---for example, running @value{GDBN} on a physically separate
16157 host, or controlling a standalone system over a serial port or a
16158 realtime system over a TCP/IP connection---you can use the @code{target}
16159 command to specify one of the target types configured for @value{GDBN}
16160 (@pxref{Target Commands, ,Commands for Managing Targets}).
16162 @cindex target architecture
16163 It is possible to build @value{GDBN} for several different @dfn{target
16164 architectures}. When @value{GDBN} is built like that, you can choose
16165 one of the available architectures with the @kbd{set architecture}
16169 @kindex set architecture
16170 @kindex show architecture
16171 @item set architecture @var{arch}
16172 This command sets the current target architecture to @var{arch}. The
16173 value of @var{arch} can be @code{"auto"}, in addition to one of the
16174 supported architectures.
16176 @item show architecture
16177 Show the current target architecture.
16179 @item set processor
16181 @kindex set processor
16182 @kindex show processor
16183 These are alias commands for, respectively, @code{set architecture}
16184 and @code{show architecture}.
16188 * Active Targets:: Active targets
16189 * Target Commands:: Commands for managing targets
16190 * Byte Order:: Choosing target byte order
16193 @node Active Targets
16194 @section Active Targets
16196 @cindex stacking targets
16197 @cindex active targets
16198 @cindex multiple targets
16200 There are multiple classes of targets such as: processes, executable files or
16201 recording sessions. Core files belong to the process class, making core file
16202 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
16203 on multiple active targets, one in each class. This allows you to (for
16204 example) start a process and inspect its activity, while still having access to
16205 the executable file after the process finishes. Or if you start process
16206 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
16207 presented a virtual layer of the recording target, while the process target
16208 remains stopped at the chronologically last point of the process execution.
16210 Use the @code{core-file} and @code{exec-file} commands to select a new core
16211 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
16212 specify as a target a process that is already running, use the @code{attach}
16213 command (@pxref{Attach, ,Debugging an Already-running Process}).
16215 @node Target Commands
16216 @section Commands for Managing Targets
16219 @item target @var{type} @var{parameters}
16220 Connects the @value{GDBN} host environment to a target machine or
16221 process. A target is typically a protocol for talking to debugging
16222 facilities. You use the argument @var{type} to specify the type or
16223 protocol of the target machine.
16225 Further @var{parameters} are interpreted by the target protocol, but
16226 typically include things like device names or host names to connect
16227 with, process numbers, and baud rates.
16229 The @code{target} command does not repeat if you press @key{RET} again
16230 after executing the command.
16232 @kindex help target
16234 Displays the names of all targets available. To display targets
16235 currently selected, use either @code{info target} or @code{info files}
16236 (@pxref{Files, ,Commands to Specify Files}).
16238 @item help target @var{name}
16239 Describe a particular target, including any parameters necessary to
16242 @kindex set gnutarget
16243 @item set gnutarget @var{args}
16244 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
16245 knows whether it is reading an @dfn{executable},
16246 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
16247 with the @code{set gnutarget} command. Unlike most @code{target} commands,
16248 with @code{gnutarget} the @code{target} refers to a program, not a machine.
16251 @emph{Warning:} To specify a file format with @code{set gnutarget},
16252 you must know the actual BFD name.
16256 @xref{Files, , Commands to Specify Files}.
16258 @kindex show gnutarget
16259 @item show gnutarget
16260 Use the @code{show gnutarget} command to display what file format
16261 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
16262 @value{GDBN} will determine the file format for each file automatically,
16263 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
16266 @cindex common targets
16267 Here are some common targets (available, or not, depending on the GDB
16272 @item target exec @var{program}
16273 @cindex executable file target
16274 An executable file. @samp{target exec @var{program}} is the same as
16275 @samp{exec-file @var{program}}.
16277 @item target core @var{filename}
16278 @cindex core dump file target
16279 A core dump file. @samp{target core @var{filename}} is the same as
16280 @samp{core-file @var{filename}}.
16282 @item target remote @var{medium}
16283 @cindex remote target
16284 A remote system connected to @value{GDBN} via a serial line or network
16285 connection. This command tells @value{GDBN} to use its own remote
16286 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
16288 For example, if you have a board connected to @file{/dev/ttya} on the
16289 machine running @value{GDBN}, you could say:
16292 target remote /dev/ttya
16295 @code{target remote} supports the @code{load} command. This is only
16296 useful if you have some other way of getting the stub to the target
16297 system, and you can put it somewhere in memory where it won't get
16298 clobbered by the download.
16300 @item target sim @r{[}@var{simargs}@r{]} @dots{}
16301 @cindex built-in simulator target
16302 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
16310 works; however, you cannot assume that a specific memory map, device
16311 drivers, or even basic I/O is available, although some simulators do
16312 provide these. For info about any processor-specific simulator details,
16313 see the appropriate section in @ref{Embedded Processors, ,Embedded
16318 Some configurations may include these targets as well:
16322 @item target nrom @var{dev}
16323 @cindex NetROM ROM emulator target
16324 NetROM ROM emulator. This target only supports downloading.
16328 Different targets are available on different configurations of @value{GDBN};
16329 your configuration may have more or fewer targets.
16331 Many remote targets require you to download the executable's code once
16332 you've successfully established a connection. You may wish to control
16333 various aspects of this process.
16338 @kindex set hash@r{, for remote monitors}
16339 @cindex hash mark while downloading
16340 This command controls whether a hash mark @samp{#} is displayed while
16341 downloading a file to the remote monitor. If on, a hash mark is
16342 displayed after each S-record is successfully downloaded to the
16346 @kindex show hash@r{, for remote monitors}
16347 Show the current status of displaying the hash mark.
16349 @item set debug monitor
16350 @kindex set debug monitor
16351 @cindex display remote monitor communications
16352 Enable or disable display of communications messages between
16353 @value{GDBN} and the remote monitor.
16355 @item show debug monitor
16356 @kindex show debug monitor
16357 Show the current status of displaying communications between
16358 @value{GDBN} and the remote monitor.
16363 @kindex load @var{filename}
16364 @item load @var{filename}
16366 Depending on what remote debugging facilities are configured into
16367 @value{GDBN}, the @code{load} command may be available. Where it exists, it
16368 is meant to make @var{filename} (an executable) available for debugging
16369 on the remote system---by downloading, or dynamic linking, for example.
16370 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
16371 the @code{add-symbol-file} command.
16373 If your @value{GDBN} does not have a @code{load} command, attempting to
16374 execute it gets the error message ``@code{You can't do that when your
16375 target is @dots{}}''
16377 The file is loaded at whatever address is specified in the executable.
16378 For some object file formats, you can specify the load address when you
16379 link the program; for other formats, like a.out, the object file format
16380 specifies a fixed address.
16381 @c FIXME! This would be a good place for an xref to the GNU linker doc.
16383 Depending on the remote side capabilities, @value{GDBN} may be able to
16384 load programs into flash memory.
16386 @code{load} does not repeat if you press @key{RET} again after using it.
16390 @section Choosing Target Byte Order
16392 @cindex choosing target byte order
16393 @cindex target byte order
16395 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
16396 offer the ability to run either big-endian or little-endian byte
16397 orders. Usually the executable or symbol will include a bit to
16398 designate the endian-ness, and you will not need to worry about
16399 which to use. However, you may still find it useful to adjust
16400 @value{GDBN}'s idea of processor endian-ness manually.
16404 @item set endian big
16405 Instruct @value{GDBN} to assume the target is big-endian.
16407 @item set endian little
16408 Instruct @value{GDBN} to assume the target is little-endian.
16410 @item set endian auto
16411 Instruct @value{GDBN} to use the byte order associated with the
16415 Display @value{GDBN}'s current idea of the target byte order.
16419 Note that these commands merely adjust interpretation of symbolic
16420 data on the host, and that they have absolutely no effect on the
16424 @node Remote Debugging
16425 @chapter Debugging Remote Programs
16426 @cindex remote debugging
16428 If you are trying to debug a program running on a machine that cannot run
16429 @value{GDBN} in the usual way, it is often useful to use remote debugging.
16430 For example, you might use remote debugging on an operating system kernel,
16431 or on a small system which does not have a general purpose operating system
16432 powerful enough to run a full-featured debugger.
16434 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
16435 to make this work with particular debugging targets. In addition,
16436 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
16437 but not specific to any particular target system) which you can use if you
16438 write the remote stubs---the code that runs on the remote system to
16439 communicate with @value{GDBN}.
16441 Other remote targets may be available in your
16442 configuration of @value{GDBN}; use @code{help target} to list them.
16445 * Connecting:: Connecting to a remote target
16446 * File Transfer:: Sending files to a remote system
16447 * Server:: Using the gdbserver program
16448 * Remote Configuration:: Remote configuration
16449 * Remote Stub:: Implementing a remote stub
16453 @section Connecting to a Remote Target
16455 On the @value{GDBN} host machine, you will need an unstripped copy of
16456 your program, since @value{GDBN} needs symbol and debugging information.
16457 Start up @value{GDBN} as usual, using the name of the local copy of your
16458 program as the first argument.
16460 @cindex @code{target remote}
16461 @value{GDBN} can communicate with the target over a serial line, or
16462 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
16463 each case, @value{GDBN} uses the same protocol for debugging your
16464 program; only the medium carrying the debugging packets varies. The
16465 @code{target remote} command establishes a connection to the target.
16466 Its arguments indicate which medium to use:
16470 @item target remote @var{serial-device}
16471 @cindex serial line, @code{target remote}
16472 Use @var{serial-device} to communicate with the target. For example,
16473 to use a serial line connected to the device named @file{/dev/ttyb}:
16476 target remote /dev/ttyb
16479 If you're using a serial line, you may want to give @value{GDBN} the
16480 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
16481 (@pxref{Remote Configuration, set remotebaud}) before the
16482 @code{target} command.
16484 @item target remote @code{@var{host}:@var{port}}
16485 @itemx target remote @code{tcp:@var{host}:@var{port}}
16486 @cindex @acronym{TCP} port, @code{target remote}
16487 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
16488 The @var{host} may be either a host name or a numeric @acronym{IP}
16489 address; @var{port} must be a decimal number. The @var{host} could be
16490 the target machine itself, if it is directly connected to the net, or
16491 it might be a terminal server which in turn has a serial line to the
16494 For example, to connect to port 2828 on a terminal server named
16498 target remote manyfarms:2828
16501 If your remote target is actually running on the same machine as your
16502 debugger session (e.g.@: a simulator for your target running on the
16503 same host), you can omit the hostname. For example, to connect to
16504 port 1234 on your local machine:
16507 target remote :1234
16511 Note that the colon is still required here.
16513 @item target remote @code{udp:@var{host}:@var{port}}
16514 @cindex @acronym{UDP} port, @code{target remote}
16515 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
16516 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
16519 target remote udp:manyfarms:2828
16522 When using a @acronym{UDP} connection for remote debugging, you should
16523 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
16524 can silently drop packets on busy or unreliable networks, which will
16525 cause havoc with your debugging session.
16527 @item target remote | @var{command}
16528 @cindex pipe, @code{target remote} to
16529 Run @var{command} in the background and communicate with it using a
16530 pipe. The @var{command} is a shell command, to be parsed and expanded
16531 by the system's command shell, @code{/bin/sh}; it should expect remote
16532 protocol packets on its standard input, and send replies on its
16533 standard output. You could use this to run a stand-alone simulator
16534 that speaks the remote debugging protocol, to make net connections
16535 using programs like @code{ssh}, or for other similar tricks.
16537 If @var{command} closes its standard output (perhaps by exiting),
16538 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
16539 program has already exited, this will have no effect.)
16543 Once the connection has been established, you can use all the usual
16544 commands to examine and change data. The remote program is already
16545 running; you can use @kbd{step} and @kbd{continue}, and you do not
16546 need to use @kbd{run}.
16548 @cindex interrupting remote programs
16549 @cindex remote programs, interrupting
16550 Whenever @value{GDBN} is waiting for the remote program, if you type the
16551 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
16552 program. This may or may not succeed, depending in part on the hardware
16553 and the serial drivers the remote system uses. If you type the
16554 interrupt character once again, @value{GDBN} displays this prompt:
16557 Interrupted while waiting for the program.
16558 Give up (and stop debugging it)? (y or n)
16561 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
16562 (If you decide you want to try again later, you can use @samp{target
16563 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
16564 goes back to waiting.
16567 @kindex detach (remote)
16569 When you have finished debugging the remote program, you can use the
16570 @code{detach} command to release it from @value{GDBN} control.
16571 Detaching from the target normally resumes its execution, but the results
16572 will depend on your particular remote stub. After the @code{detach}
16573 command, @value{GDBN} is free to connect to another target.
16577 The @code{disconnect} command behaves like @code{detach}, except that
16578 the target is generally not resumed. It will wait for @value{GDBN}
16579 (this instance or another one) to connect and continue debugging. After
16580 the @code{disconnect} command, @value{GDBN} is again free to connect to
16583 @cindex send command to remote monitor
16584 @cindex extend @value{GDBN} for remote targets
16585 @cindex add new commands for external monitor
16587 @item monitor @var{cmd}
16588 This command allows you to send arbitrary commands directly to the
16589 remote monitor. Since @value{GDBN} doesn't care about the commands it
16590 sends like this, this command is the way to extend @value{GDBN}---you
16591 can add new commands that only the external monitor will understand
16595 @node File Transfer
16596 @section Sending files to a remote system
16597 @cindex remote target, file transfer
16598 @cindex file transfer
16599 @cindex sending files to remote systems
16601 Some remote targets offer the ability to transfer files over the same
16602 connection used to communicate with @value{GDBN}. This is convenient
16603 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
16604 running @code{gdbserver} over a network interface. For other targets,
16605 e.g.@: embedded devices with only a single serial port, this may be
16606 the only way to upload or download files.
16608 Not all remote targets support these commands.
16612 @item remote put @var{hostfile} @var{targetfile}
16613 Copy file @var{hostfile} from the host system (the machine running
16614 @value{GDBN}) to @var{targetfile} on the target system.
16617 @item remote get @var{targetfile} @var{hostfile}
16618 Copy file @var{targetfile} from the target system to @var{hostfile}
16619 on the host system.
16621 @kindex remote delete
16622 @item remote delete @var{targetfile}
16623 Delete @var{targetfile} from the target system.
16628 @section Using the @code{gdbserver} Program
16631 @cindex remote connection without stubs
16632 @code{gdbserver} is a control program for Unix-like systems, which
16633 allows you to connect your program with a remote @value{GDBN} via
16634 @code{target remote}---but without linking in the usual debugging stub.
16636 @code{gdbserver} is not a complete replacement for the debugging stubs,
16637 because it requires essentially the same operating-system facilities
16638 that @value{GDBN} itself does. In fact, a system that can run
16639 @code{gdbserver} to connect to a remote @value{GDBN} could also run
16640 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
16641 because it is a much smaller program than @value{GDBN} itself. It is
16642 also easier to port than all of @value{GDBN}, so you may be able to get
16643 started more quickly on a new system by using @code{gdbserver}.
16644 Finally, if you develop code for real-time systems, you may find that
16645 the tradeoffs involved in real-time operation make it more convenient to
16646 do as much development work as possible on another system, for example
16647 by cross-compiling. You can use @code{gdbserver} to make a similar
16648 choice for debugging.
16650 @value{GDBN} and @code{gdbserver} communicate via either a serial line
16651 or a TCP connection, using the standard @value{GDBN} remote serial
16655 @emph{Warning:} @code{gdbserver} does not have any built-in security.
16656 Do not run @code{gdbserver} connected to any public network; a
16657 @value{GDBN} connection to @code{gdbserver} provides access to the
16658 target system with the same privileges as the user running
16662 @subsection Running @code{gdbserver}
16663 @cindex arguments, to @code{gdbserver}
16664 @cindex @code{gdbserver}, command-line arguments
16666 Run @code{gdbserver} on the target system. You need a copy of the
16667 program you want to debug, including any libraries it requires.
16668 @code{gdbserver} does not need your program's symbol table, so you can
16669 strip the program if necessary to save space. @value{GDBN} on the host
16670 system does all the symbol handling.
16672 To use the server, you must tell it how to communicate with @value{GDBN};
16673 the name of your program; and the arguments for your program. The usual
16677 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
16680 @var{comm} is either a device name (to use a serial line) or a TCP
16681 hostname and portnumber. For example, to debug Emacs with the argument
16682 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
16686 target> gdbserver /dev/com1 emacs foo.txt
16689 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
16692 To use a TCP connection instead of a serial line:
16695 target> gdbserver host:2345 emacs foo.txt
16698 The only difference from the previous example is the first argument,
16699 specifying that you are communicating with the host @value{GDBN} via
16700 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
16701 expect a TCP connection from machine @samp{host} to local TCP port 2345.
16702 (Currently, the @samp{host} part is ignored.) You can choose any number
16703 you want for the port number as long as it does not conflict with any
16704 TCP ports already in use on the target system (for example, @code{23} is
16705 reserved for @code{telnet}).@footnote{If you choose a port number that
16706 conflicts with another service, @code{gdbserver} prints an error message
16707 and exits.} You must use the same port number with the host @value{GDBN}
16708 @code{target remote} command.
16710 @subsubsection Attaching to a Running Program
16711 @cindex attach to a program, @code{gdbserver}
16712 @cindex @option{--attach}, @code{gdbserver} option
16714 On some targets, @code{gdbserver} can also attach to running programs.
16715 This is accomplished via the @code{--attach} argument. The syntax is:
16718 target> gdbserver --attach @var{comm} @var{pid}
16721 @var{pid} is the process ID of a currently running process. It isn't necessary
16722 to point @code{gdbserver} at a binary for the running process.
16725 You can debug processes by name instead of process ID if your target has the
16726 @code{pidof} utility:
16729 target> gdbserver --attach @var{comm} `pidof @var{program}`
16732 In case more than one copy of @var{program} is running, or @var{program}
16733 has multiple threads, most versions of @code{pidof} support the
16734 @code{-s} option to only return the first process ID.
16736 @subsubsection Multi-Process Mode for @code{gdbserver}
16737 @cindex @code{gdbserver}, multiple processes
16738 @cindex multiple processes with @code{gdbserver}
16740 When you connect to @code{gdbserver} using @code{target remote},
16741 @code{gdbserver} debugs the specified program only once. When the
16742 program exits, or you detach from it, @value{GDBN} closes the connection
16743 and @code{gdbserver} exits.
16745 If you connect using @kbd{target extended-remote}, @code{gdbserver}
16746 enters multi-process mode. When the debugged program exits, or you
16747 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
16748 though no program is running. The @code{run} and @code{attach}
16749 commands instruct @code{gdbserver} to run or attach to a new program.
16750 The @code{run} command uses @code{set remote exec-file} (@pxref{set
16751 remote exec-file}) to select the program to run. Command line
16752 arguments are supported, except for wildcard expansion and I/O
16753 redirection (@pxref{Arguments}).
16755 @cindex @option{--multi}, @code{gdbserver} option
16756 To start @code{gdbserver} without supplying an initial command to run
16757 or process ID to attach, use the @option{--multi} command line option.
16758 Then you can connect using @kbd{target extended-remote} and start
16759 the program you want to debug.
16761 In multi-process mode @code{gdbserver} does not automatically exit unless you
16762 use the option @option{--once}. You can terminate it by using
16763 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
16764 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
16765 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
16766 @option{--multi} option to @code{gdbserver} has no influence on that.
16768 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
16770 This section applies only when @code{gdbserver} is run to listen on a TCP port.
16772 @code{gdbserver} normally terminates after all of its debugged processes have
16773 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
16774 extended-remote}, @code{gdbserver} stays running even with no processes left.
16775 @value{GDBN} normally terminates the spawned debugged process on its exit,
16776 which normally also terminates @code{gdbserver} in the @kbd{target remote}
16777 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
16778 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
16779 stays running even in the @kbd{target remote} mode.
16781 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
16782 Such reconnecting is useful for features like @ref{disconnected tracing}. For
16783 completeness, at most one @value{GDBN} can be connected at a time.
16785 @cindex @option{--once}, @code{gdbserver} option
16786 By default, @code{gdbserver} keeps the listening TCP port open, so that
16787 additional connections are possible. However, if you start @code{gdbserver}
16788 with the @option{--once} option, it will stop listening for any further
16789 connection attempts after connecting to the first @value{GDBN} session. This
16790 means no further connections to @code{gdbserver} will be possible after the
16791 first one. It also means @code{gdbserver} will terminate after the first
16792 connection with remote @value{GDBN} has closed, even for unexpectedly closed
16793 connections and even in the @kbd{target extended-remote} mode. The
16794 @option{--once} option allows reusing the same port number for connecting to
16795 multiple instances of @code{gdbserver} running on the same host, since each
16796 instance closes its port after the first connection.
16798 @subsubsection Other Command-Line Arguments for @code{gdbserver}
16800 @cindex @option{--debug}, @code{gdbserver} option
16801 The @option{--debug} option tells @code{gdbserver} to display extra
16802 status information about the debugging process.
16803 @cindex @option{--remote-debug}, @code{gdbserver} option
16804 The @option{--remote-debug} option tells @code{gdbserver} to display
16805 remote protocol debug output. These options are intended for
16806 @code{gdbserver} development and for bug reports to the developers.
16808 @cindex @option{--wrapper}, @code{gdbserver} option
16809 The @option{--wrapper} option specifies a wrapper to launch programs
16810 for debugging. The option should be followed by the name of the
16811 wrapper, then any command-line arguments to pass to the wrapper, then
16812 @kbd{--} indicating the end of the wrapper arguments.
16814 @code{gdbserver} runs the specified wrapper program with a combined
16815 command line including the wrapper arguments, then the name of the
16816 program to debug, then any arguments to the program. The wrapper
16817 runs until it executes your program, and then @value{GDBN} gains control.
16819 You can use any program that eventually calls @code{execve} with
16820 its arguments as a wrapper. Several standard Unix utilities do
16821 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
16822 with @code{exec "$@@"} will also work.
16824 For example, you can use @code{env} to pass an environment variable to
16825 the debugged program, without setting the variable in @code{gdbserver}'s
16829 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
16832 @subsection Connecting to @code{gdbserver}
16834 Run @value{GDBN} on the host system.
16836 First make sure you have the necessary symbol files. Load symbols for
16837 your application using the @code{file} command before you connect. Use
16838 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
16839 was compiled with the correct sysroot using @code{--with-sysroot}).
16841 The symbol file and target libraries must exactly match the executable
16842 and libraries on the target, with one exception: the files on the host
16843 system should not be stripped, even if the files on the target system
16844 are. Mismatched or missing files will lead to confusing results
16845 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
16846 files may also prevent @code{gdbserver} from debugging multi-threaded
16849 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
16850 For TCP connections, you must start up @code{gdbserver} prior to using
16851 the @code{target remote} command. Otherwise you may get an error whose
16852 text depends on the host system, but which usually looks something like
16853 @samp{Connection refused}. Don't use the @code{load}
16854 command in @value{GDBN} when using @code{gdbserver}, since the program is
16855 already on the target.
16857 @subsection Monitor Commands for @code{gdbserver}
16858 @cindex monitor commands, for @code{gdbserver}
16859 @anchor{Monitor Commands for gdbserver}
16861 During a @value{GDBN} session using @code{gdbserver}, you can use the
16862 @code{monitor} command to send special requests to @code{gdbserver}.
16863 Here are the available commands.
16867 List the available monitor commands.
16869 @item monitor set debug 0
16870 @itemx monitor set debug 1
16871 Disable or enable general debugging messages.
16873 @item monitor set remote-debug 0
16874 @itemx monitor set remote-debug 1
16875 Disable or enable specific debugging messages associated with the remote
16876 protocol (@pxref{Remote Protocol}).
16878 @item monitor set libthread-db-search-path [PATH]
16879 @cindex gdbserver, search path for @code{libthread_db}
16880 When this command is issued, @var{path} is a colon-separated list of
16881 directories to search for @code{libthread_db} (@pxref{Threads,,set
16882 libthread-db-search-path}). If you omit @var{path},
16883 @samp{libthread-db-search-path} will be reset to its default value.
16885 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
16886 not supported in @code{gdbserver}.
16889 Tell gdbserver to exit immediately. This command should be followed by
16890 @code{disconnect} to close the debugging session. @code{gdbserver} will
16891 detach from any attached processes and kill any processes it created.
16892 Use @code{monitor exit} to terminate @code{gdbserver} at the end
16893 of a multi-process mode debug session.
16897 @subsection Tracepoints support in @code{gdbserver}
16898 @cindex tracepoints support in @code{gdbserver}
16900 On some targets, @code{gdbserver} supports tracepoints, fast
16901 tracepoints and static tracepoints.
16903 For fast or static tracepoints to work, a special library called the
16904 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
16905 This library is built and distributed as an integral part of
16906 @code{gdbserver}. In addition, support for static tracepoints
16907 requires building the in-process agent library with static tracepoints
16908 support. At present, the UST (LTTng Userspace Tracer,
16909 @url{http://lttng.org/ust}) tracing engine is supported. This support
16910 is automatically available if UST development headers are found in the
16911 standard include path when @code{gdbserver} is built, or if
16912 @code{gdbserver} was explicitly configured using @option{--with-ust}
16913 to point at such headers. You can explicitly disable the support
16914 using @option{--with-ust=no}.
16916 There are several ways to load the in-process agent in your program:
16919 @item Specifying it as dependency at link time
16921 You can link your program dynamically with the in-process agent
16922 library. On most systems, this is accomplished by adding
16923 @code{-linproctrace} to the link command.
16925 @item Using the system's preloading mechanisms
16927 You can force loading the in-process agent at startup time by using
16928 your system's support for preloading shared libraries. Many Unixes
16929 support the concept of preloading user defined libraries. In most
16930 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
16931 in the environment. See also the description of @code{gdbserver}'s
16932 @option{--wrapper} command line option.
16934 @item Using @value{GDBN} to force loading the agent at run time
16936 On some systems, you can force the inferior to load a shared library,
16937 by calling a dynamic loader function in the inferior that takes care
16938 of dynamically looking up and loading a shared library. On most Unix
16939 systems, the function is @code{dlopen}. You'll use the @code{call}
16940 command for that. For example:
16943 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
16946 Note that on most Unix systems, for the @code{dlopen} function to be
16947 available, the program needs to be linked with @code{-ldl}.
16950 On systems that have a userspace dynamic loader, like most Unix
16951 systems, when you connect to @code{gdbserver} using @code{target
16952 remote}, you'll find that the program is stopped at the dynamic
16953 loader's entry point, and no shared library has been loaded in the
16954 program's address space yet, including the in-process agent. In that
16955 case, before being able to use any of the fast or static tracepoints
16956 features, you need to let the loader run and load the shared
16957 libraries. The simplest way to do that is to run the program to the
16958 main procedure. E.g., if debugging a C or C@t{++} program, start
16959 @code{gdbserver} like so:
16962 $ gdbserver :9999 myprogram
16965 Start GDB and connect to @code{gdbserver} like so, and run to main:
16969 (@value{GDBP}) target remote myhost:9999
16970 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
16971 (@value{GDBP}) b main
16972 (@value{GDBP}) continue
16975 The in-process tracing agent library should now be loaded into the
16976 process; you can confirm it with the @code{info sharedlibrary}
16977 command, which will list @file{libinproctrace.so} as loaded in the
16978 process. You are now ready to install fast tracepoints, list static
16979 tracepoint markers, probe static tracepoints markers, and start
16982 @node Remote Configuration
16983 @section Remote Configuration
16986 @kindex show remote
16987 This section documents the configuration options available when
16988 debugging remote programs. For the options related to the File I/O
16989 extensions of the remote protocol, see @ref{system,
16990 system-call-allowed}.
16993 @item set remoteaddresssize @var{bits}
16994 @cindex address size for remote targets
16995 @cindex bits in remote address
16996 Set the maximum size of address in a memory packet to the specified
16997 number of bits. @value{GDBN} will mask off the address bits above
16998 that number, when it passes addresses to the remote target. The
16999 default value is the number of bits in the target's address.
17001 @item show remoteaddresssize
17002 Show the current value of remote address size in bits.
17004 @item set remotebaud @var{n}
17005 @cindex baud rate for remote targets
17006 Set the baud rate for the remote serial I/O to @var{n} baud. The
17007 value is used to set the speed of the serial port used for debugging
17010 @item show remotebaud
17011 Show the current speed of the remote connection.
17013 @item set remotebreak
17014 @cindex interrupt remote programs
17015 @cindex BREAK signal instead of Ctrl-C
17016 @anchor{set remotebreak}
17017 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
17018 when you type @kbd{Ctrl-c} to interrupt the program running
17019 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
17020 character instead. The default is off, since most remote systems
17021 expect to see @samp{Ctrl-C} as the interrupt signal.
17023 @item show remotebreak
17024 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
17025 interrupt the remote program.
17027 @item set remoteflow on
17028 @itemx set remoteflow off
17029 @kindex set remoteflow
17030 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
17031 on the serial port used to communicate to the remote target.
17033 @item show remoteflow
17034 @kindex show remoteflow
17035 Show the current setting of hardware flow control.
17037 @item set remotelogbase @var{base}
17038 Set the base (a.k.a.@: radix) of logging serial protocol
17039 communications to @var{base}. Supported values of @var{base} are:
17040 @code{ascii}, @code{octal}, and @code{hex}. The default is
17043 @item show remotelogbase
17044 Show the current setting of the radix for logging remote serial
17047 @item set remotelogfile @var{file}
17048 @cindex record serial communications on file
17049 Record remote serial communications on the named @var{file}. The
17050 default is not to record at all.
17052 @item show remotelogfile.
17053 Show the current setting of the file name on which to record the
17054 serial communications.
17056 @item set remotetimeout @var{num}
17057 @cindex timeout for serial communications
17058 @cindex remote timeout
17059 Set the timeout limit to wait for the remote target to respond to
17060 @var{num} seconds. The default is 2 seconds.
17062 @item show remotetimeout
17063 Show the current number of seconds to wait for the remote target
17066 @cindex limit hardware breakpoints and watchpoints
17067 @cindex remote target, limit break- and watchpoints
17068 @anchor{set remote hardware-watchpoint-limit}
17069 @anchor{set remote hardware-breakpoint-limit}
17070 @item set remote hardware-watchpoint-limit @var{limit}
17071 @itemx set remote hardware-breakpoint-limit @var{limit}
17072 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
17073 watchpoints. A limit of -1, the default, is treated as unlimited.
17075 @cindex limit hardware watchpoints length
17076 @cindex remote target, limit watchpoints length
17077 @anchor{set remote hardware-watchpoint-length-limit}
17078 @item set remote hardware-watchpoint-length-limit @var{limit}
17079 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
17080 a remote hardware watchpoint. A limit of -1, the default, is treated
17083 @item show remote hardware-watchpoint-length-limit
17084 Show the current limit (in bytes) of the maximum length of
17085 a remote hardware watchpoint.
17087 @item set remote exec-file @var{filename}
17088 @itemx show remote exec-file
17089 @anchor{set remote exec-file}
17090 @cindex executable file, for remote target
17091 Select the file used for @code{run} with @code{target
17092 extended-remote}. This should be set to a filename valid on the
17093 target system. If it is not set, the target will use a default
17094 filename (e.g.@: the last program run).
17096 @item set remote interrupt-sequence
17097 @cindex interrupt remote programs
17098 @cindex select Ctrl-C, BREAK or BREAK-g
17099 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
17100 @samp{BREAK-g} as the
17101 sequence to the remote target in order to interrupt the execution.
17102 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
17103 is high level of serial line for some certain time.
17104 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
17105 It is @code{BREAK} signal followed by character @code{g}.
17107 @item show interrupt-sequence
17108 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
17109 is sent by @value{GDBN} to interrupt the remote program.
17110 @code{BREAK-g} is BREAK signal followed by @code{g} and
17111 also known as Magic SysRq g.
17113 @item set remote interrupt-on-connect
17114 @cindex send interrupt-sequence on start
17115 Specify whether interrupt-sequence is sent to remote target when
17116 @value{GDBN} connects to it. This is mostly needed when you debug
17117 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
17118 which is known as Magic SysRq g in order to connect @value{GDBN}.
17120 @item show interrupt-on-connect
17121 Show whether interrupt-sequence is sent
17122 to remote target when @value{GDBN} connects to it.
17126 @item set tcp auto-retry on
17127 @cindex auto-retry, for remote TCP target
17128 Enable auto-retry for remote TCP connections. This is useful if the remote
17129 debugging agent is launched in parallel with @value{GDBN}; there is a race
17130 condition because the agent may not become ready to accept the connection
17131 before @value{GDBN} attempts to connect. When auto-retry is
17132 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
17133 to establish the connection using the timeout specified by
17134 @code{set tcp connect-timeout}.
17136 @item set tcp auto-retry off
17137 Do not auto-retry failed TCP connections.
17139 @item show tcp auto-retry
17140 Show the current auto-retry setting.
17142 @item set tcp connect-timeout @var{seconds}
17143 @cindex connection timeout, for remote TCP target
17144 @cindex timeout, for remote target connection
17145 Set the timeout for establishing a TCP connection to the remote target to
17146 @var{seconds}. The timeout affects both polling to retry failed connections
17147 (enabled by @code{set tcp auto-retry on}) and waiting for connections
17148 that are merely slow to complete, and represents an approximate cumulative
17151 @item show tcp connect-timeout
17152 Show the current connection timeout setting.
17155 @cindex remote packets, enabling and disabling
17156 The @value{GDBN} remote protocol autodetects the packets supported by
17157 your debugging stub. If you need to override the autodetection, you
17158 can use these commands to enable or disable individual packets. Each
17159 packet can be set to @samp{on} (the remote target supports this
17160 packet), @samp{off} (the remote target does not support this packet),
17161 or @samp{auto} (detect remote target support for this packet). They
17162 all default to @samp{auto}. For more information about each packet,
17163 see @ref{Remote Protocol}.
17165 During normal use, you should not have to use any of these commands.
17166 If you do, that may be a bug in your remote debugging stub, or a bug
17167 in @value{GDBN}. You may want to report the problem to the
17168 @value{GDBN} developers.
17170 For each packet @var{name}, the command to enable or disable the
17171 packet is @code{set remote @var{name}-packet}. The available settings
17174 @multitable @columnfractions 0.28 0.32 0.25
17177 @tab Related Features
17179 @item @code{fetch-register}
17181 @tab @code{info registers}
17183 @item @code{set-register}
17187 @item @code{binary-download}
17189 @tab @code{load}, @code{set}
17191 @item @code{read-aux-vector}
17192 @tab @code{qXfer:auxv:read}
17193 @tab @code{info auxv}
17195 @item @code{symbol-lookup}
17196 @tab @code{qSymbol}
17197 @tab Detecting multiple threads
17199 @item @code{attach}
17200 @tab @code{vAttach}
17203 @item @code{verbose-resume}
17205 @tab Stepping or resuming multiple threads
17211 @item @code{software-breakpoint}
17215 @item @code{hardware-breakpoint}
17219 @item @code{write-watchpoint}
17223 @item @code{read-watchpoint}
17227 @item @code{access-watchpoint}
17231 @item @code{target-features}
17232 @tab @code{qXfer:features:read}
17233 @tab @code{set architecture}
17235 @item @code{library-info}
17236 @tab @code{qXfer:libraries:read}
17237 @tab @code{info sharedlibrary}
17239 @item @code{memory-map}
17240 @tab @code{qXfer:memory-map:read}
17241 @tab @code{info mem}
17243 @item @code{read-sdata-object}
17244 @tab @code{qXfer:sdata:read}
17245 @tab @code{print $_sdata}
17247 @item @code{read-spu-object}
17248 @tab @code{qXfer:spu:read}
17249 @tab @code{info spu}
17251 @item @code{write-spu-object}
17252 @tab @code{qXfer:spu:write}
17253 @tab @code{info spu}
17255 @item @code{read-siginfo-object}
17256 @tab @code{qXfer:siginfo:read}
17257 @tab @code{print $_siginfo}
17259 @item @code{write-siginfo-object}
17260 @tab @code{qXfer:siginfo:write}
17261 @tab @code{set $_siginfo}
17263 @item @code{threads}
17264 @tab @code{qXfer:threads:read}
17265 @tab @code{info threads}
17267 @item @code{get-thread-local-@*storage-address}
17268 @tab @code{qGetTLSAddr}
17269 @tab Displaying @code{__thread} variables
17271 @item @code{get-thread-information-block-address}
17272 @tab @code{qGetTIBAddr}
17273 @tab Display MS-Windows Thread Information Block.
17275 @item @code{search-memory}
17276 @tab @code{qSearch:memory}
17279 @item @code{supported-packets}
17280 @tab @code{qSupported}
17281 @tab Remote communications parameters
17283 @item @code{pass-signals}
17284 @tab @code{QPassSignals}
17285 @tab @code{handle @var{signal}}
17287 @item @code{hostio-close-packet}
17288 @tab @code{vFile:close}
17289 @tab @code{remote get}, @code{remote put}
17291 @item @code{hostio-open-packet}
17292 @tab @code{vFile:open}
17293 @tab @code{remote get}, @code{remote put}
17295 @item @code{hostio-pread-packet}
17296 @tab @code{vFile:pread}
17297 @tab @code{remote get}, @code{remote put}
17299 @item @code{hostio-pwrite-packet}
17300 @tab @code{vFile:pwrite}
17301 @tab @code{remote get}, @code{remote put}
17303 @item @code{hostio-unlink-packet}
17304 @tab @code{vFile:unlink}
17305 @tab @code{remote delete}
17307 @item @code{noack-packet}
17308 @tab @code{QStartNoAckMode}
17309 @tab Packet acknowledgment
17311 @item @code{osdata}
17312 @tab @code{qXfer:osdata:read}
17313 @tab @code{info os}
17315 @item @code{query-attached}
17316 @tab @code{qAttached}
17317 @tab Querying remote process attach state.
17319 @item @code{traceframe-info}
17320 @tab @code{qXfer:traceframe-info:read}
17321 @tab Traceframe info
17323 @item @code{disable-randomization}
17324 @tab @code{QDisableRandomization}
17325 @tab @code{set disable-randomization}
17329 @section Implementing a Remote Stub
17331 @cindex debugging stub, example
17332 @cindex remote stub, example
17333 @cindex stub example, remote debugging
17334 The stub files provided with @value{GDBN} implement the target side of the
17335 communication protocol, and the @value{GDBN} side is implemented in the
17336 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
17337 these subroutines to communicate, and ignore the details. (If you're
17338 implementing your own stub file, you can still ignore the details: start
17339 with one of the existing stub files. @file{sparc-stub.c} is the best
17340 organized, and therefore the easiest to read.)
17342 @cindex remote serial debugging, overview
17343 To debug a program running on another machine (the debugging
17344 @dfn{target} machine), you must first arrange for all the usual
17345 prerequisites for the program to run by itself. For example, for a C
17350 A startup routine to set up the C runtime environment; these usually
17351 have a name like @file{crt0}. The startup routine may be supplied by
17352 your hardware supplier, or you may have to write your own.
17355 A C subroutine library to support your program's
17356 subroutine calls, notably managing input and output.
17359 A way of getting your program to the other machine---for example, a
17360 download program. These are often supplied by the hardware
17361 manufacturer, but you may have to write your own from hardware
17365 The next step is to arrange for your program to use a serial port to
17366 communicate with the machine where @value{GDBN} is running (the @dfn{host}
17367 machine). In general terms, the scheme looks like this:
17371 @value{GDBN} already understands how to use this protocol; when everything
17372 else is set up, you can simply use the @samp{target remote} command
17373 (@pxref{Targets,,Specifying a Debugging Target}).
17375 @item On the target,
17376 you must link with your program a few special-purpose subroutines that
17377 implement the @value{GDBN} remote serial protocol. The file containing these
17378 subroutines is called a @dfn{debugging stub}.
17380 On certain remote targets, you can use an auxiliary program
17381 @code{gdbserver} instead of linking a stub into your program.
17382 @xref{Server,,Using the @code{gdbserver} Program}, for details.
17385 The debugging stub is specific to the architecture of the remote
17386 machine; for example, use @file{sparc-stub.c} to debug programs on
17389 @cindex remote serial stub list
17390 These working remote stubs are distributed with @value{GDBN}:
17395 @cindex @file{i386-stub.c}
17398 For Intel 386 and compatible architectures.
17401 @cindex @file{m68k-stub.c}
17402 @cindex Motorola 680x0
17404 For Motorola 680x0 architectures.
17407 @cindex @file{sh-stub.c}
17410 For Renesas SH architectures.
17413 @cindex @file{sparc-stub.c}
17415 For @sc{sparc} architectures.
17417 @item sparcl-stub.c
17418 @cindex @file{sparcl-stub.c}
17421 For Fujitsu @sc{sparclite} architectures.
17425 The @file{README} file in the @value{GDBN} distribution may list other
17426 recently added stubs.
17429 * Stub Contents:: What the stub can do for you
17430 * Bootstrapping:: What you must do for the stub
17431 * Debug Session:: Putting it all together
17434 @node Stub Contents
17435 @subsection What the Stub Can Do for You
17437 @cindex remote serial stub
17438 The debugging stub for your architecture supplies these three
17442 @item set_debug_traps
17443 @findex set_debug_traps
17444 @cindex remote serial stub, initialization
17445 This routine arranges for @code{handle_exception} to run when your
17446 program stops. You must call this subroutine explicitly near the
17447 beginning of your program.
17449 @item handle_exception
17450 @findex handle_exception
17451 @cindex remote serial stub, main routine
17452 This is the central workhorse, but your program never calls it
17453 explicitly---the setup code arranges for @code{handle_exception} to
17454 run when a trap is triggered.
17456 @code{handle_exception} takes control when your program stops during
17457 execution (for example, on a breakpoint), and mediates communications
17458 with @value{GDBN} on the host machine. This is where the communications
17459 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
17460 representative on the target machine. It begins by sending summary
17461 information on the state of your program, then continues to execute,
17462 retrieving and transmitting any information @value{GDBN} needs, until you
17463 execute a @value{GDBN} command that makes your program resume; at that point,
17464 @code{handle_exception} returns control to your own code on the target
17468 @cindex @code{breakpoint} subroutine, remote
17469 Use this auxiliary subroutine to make your program contain a
17470 breakpoint. Depending on the particular situation, this may be the only
17471 way for @value{GDBN} to get control. For instance, if your target
17472 machine has some sort of interrupt button, you won't need to call this;
17473 pressing the interrupt button transfers control to
17474 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
17475 simply receiving characters on the serial port may also trigger a trap;
17476 again, in that situation, you don't need to call @code{breakpoint} from
17477 your own program---simply running @samp{target remote} from the host
17478 @value{GDBN} session gets control.
17480 Call @code{breakpoint} if none of these is true, or if you simply want
17481 to make certain your program stops at a predetermined point for the
17482 start of your debugging session.
17485 @node Bootstrapping
17486 @subsection What You Must Do for the Stub
17488 @cindex remote stub, support routines
17489 The debugging stubs that come with @value{GDBN} are set up for a particular
17490 chip architecture, but they have no information about the rest of your
17491 debugging target machine.
17493 First of all you need to tell the stub how to communicate with the
17497 @item int getDebugChar()
17498 @findex getDebugChar
17499 Write this subroutine to read a single character from the serial port.
17500 It may be identical to @code{getchar} for your target system; a
17501 different name is used to allow you to distinguish the two if you wish.
17503 @item void putDebugChar(int)
17504 @findex putDebugChar
17505 Write this subroutine to write a single character to the serial port.
17506 It may be identical to @code{putchar} for your target system; a
17507 different name is used to allow you to distinguish the two if you wish.
17510 @cindex control C, and remote debugging
17511 @cindex interrupting remote targets
17512 If you want @value{GDBN} to be able to stop your program while it is
17513 running, you need to use an interrupt-driven serial driver, and arrange
17514 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
17515 character). That is the character which @value{GDBN} uses to tell the
17516 remote system to stop.
17518 Getting the debugging target to return the proper status to @value{GDBN}
17519 probably requires changes to the standard stub; one quick and dirty way
17520 is to just execute a breakpoint instruction (the ``dirty'' part is that
17521 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
17523 Other routines you need to supply are:
17526 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
17527 @findex exceptionHandler
17528 Write this function to install @var{exception_address} in the exception
17529 handling tables. You need to do this because the stub does not have any
17530 way of knowing what the exception handling tables on your target system
17531 are like (for example, the processor's table might be in @sc{rom},
17532 containing entries which point to a table in @sc{ram}).
17533 @var{exception_number} is the exception number which should be changed;
17534 its meaning is architecture-dependent (for example, different numbers
17535 might represent divide by zero, misaligned access, etc). When this
17536 exception occurs, control should be transferred directly to
17537 @var{exception_address}, and the processor state (stack, registers,
17538 and so on) should be just as it is when a processor exception occurs. So if
17539 you want to use a jump instruction to reach @var{exception_address}, it
17540 should be a simple jump, not a jump to subroutine.
17542 For the 386, @var{exception_address} should be installed as an interrupt
17543 gate so that interrupts are masked while the handler runs. The gate
17544 should be at privilege level 0 (the most privileged level). The
17545 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
17546 help from @code{exceptionHandler}.
17548 @item void flush_i_cache()
17549 @findex flush_i_cache
17550 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
17551 instruction cache, if any, on your target machine. If there is no
17552 instruction cache, this subroutine may be a no-op.
17554 On target machines that have instruction caches, @value{GDBN} requires this
17555 function to make certain that the state of your program is stable.
17559 You must also make sure this library routine is available:
17562 @item void *memset(void *, int, int)
17564 This is the standard library function @code{memset} that sets an area of
17565 memory to a known value. If you have one of the free versions of
17566 @code{libc.a}, @code{memset} can be found there; otherwise, you must
17567 either obtain it from your hardware manufacturer, or write your own.
17570 If you do not use the GNU C compiler, you may need other standard
17571 library subroutines as well; this varies from one stub to another,
17572 but in general the stubs are likely to use any of the common library
17573 subroutines which @code{@value{NGCC}} generates as inline code.
17576 @node Debug Session
17577 @subsection Putting it All Together
17579 @cindex remote serial debugging summary
17580 In summary, when your program is ready to debug, you must follow these
17585 Make sure you have defined the supporting low-level routines
17586 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
17588 @code{getDebugChar}, @code{putDebugChar},
17589 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
17593 Insert these lines near the top of your program:
17601 For the 680x0 stub only, you need to provide a variable called
17602 @code{exceptionHook}. Normally you just use:
17605 void (*exceptionHook)() = 0;
17609 but if before calling @code{set_debug_traps}, you set it to point to a
17610 function in your program, that function is called when
17611 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
17612 error). The function indicated by @code{exceptionHook} is called with
17613 one parameter: an @code{int} which is the exception number.
17616 Compile and link together: your program, the @value{GDBN} debugging stub for
17617 your target architecture, and the supporting subroutines.
17620 Make sure you have a serial connection between your target machine and
17621 the @value{GDBN} host, and identify the serial port on the host.
17624 @c The "remote" target now provides a `load' command, so we should
17625 @c document that. FIXME.
17626 Download your program to your target machine (or get it there by
17627 whatever means the manufacturer provides), and start it.
17630 Start @value{GDBN} on the host, and connect to the target
17631 (@pxref{Connecting,,Connecting to a Remote Target}).
17635 @node Configurations
17636 @chapter Configuration-Specific Information
17638 While nearly all @value{GDBN} commands are available for all native and
17639 cross versions of the debugger, there are some exceptions. This chapter
17640 describes things that are only available in certain configurations.
17642 There are three major categories of configurations: native
17643 configurations, where the host and target are the same, embedded
17644 operating system configurations, which are usually the same for several
17645 different processor architectures, and bare embedded processors, which
17646 are quite different from each other.
17651 * Embedded Processors::
17658 This section describes details specific to particular native
17663 * BSD libkvm Interface:: Debugging BSD kernel memory images
17664 * SVR4 Process Information:: SVR4 process information
17665 * DJGPP Native:: Features specific to the DJGPP port
17666 * Cygwin Native:: Features specific to the Cygwin port
17667 * Hurd Native:: Features specific to @sc{gnu} Hurd
17668 * Neutrino:: Features specific to QNX Neutrino
17669 * Darwin:: Features specific to Darwin
17675 On HP-UX systems, if you refer to a function or variable name that
17676 begins with a dollar sign, @value{GDBN} searches for a user or system
17677 name first, before it searches for a convenience variable.
17680 @node BSD libkvm Interface
17681 @subsection BSD libkvm Interface
17684 @cindex kernel memory image
17685 @cindex kernel crash dump
17687 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
17688 interface that provides a uniform interface for accessing kernel virtual
17689 memory images, including live systems and crash dumps. @value{GDBN}
17690 uses this interface to allow you to debug live kernels and kernel crash
17691 dumps on many native BSD configurations. This is implemented as a
17692 special @code{kvm} debugging target. For debugging a live system, load
17693 the currently running kernel into @value{GDBN} and connect to the
17697 (@value{GDBP}) @b{target kvm}
17700 For debugging crash dumps, provide the file name of the crash dump as an
17704 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
17707 Once connected to the @code{kvm} target, the following commands are
17713 Set current context from the @dfn{Process Control Block} (PCB) address.
17716 Set current context from proc address. This command isn't available on
17717 modern FreeBSD systems.
17720 @node SVR4 Process Information
17721 @subsection SVR4 Process Information
17723 @cindex examine process image
17724 @cindex process info via @file{/proc}
17726 Many versions of SVR4 and compatible systems provide a facility called
17727 @samp{/proc} that can be used to examine the image of a running
17728 process using file-system subroutines. If @value{GDBN} is configured
17729 for an operating system with this facility, the command @code{info
17730 proc} is available to report information about the process running
17731 your program, or about any process running on your system. @code{info
17732 proc} works only on SVR4 systems that include the @code{procfs} code.
17733 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
17734 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
17740 @itemx info proc @var{process-id}
17741 Summarize available information about any running process. If a
17742 process ID is specified by @var{process-id}, display information about
17743 that process; otherwise display information about the program being
17744 debugged. The summary includes the debugged process ID, the command
17745 line used to invoke it, its current working directory, and its
17746 executable file's absolute file name.
17748 On some systems, @var{process-id} can be of the form
17749 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
17750 within a process. If the optional @var{pid} part is missing, it means
17751 a thread from the process being debugged (the leading @samp{/} still
17752 needs to be present, or else @value{GDBN} will interpret the number as
17753 a process ID rather than a thread ID).
17755 @item info proc mappings
17756 @cindex memory address space mappings
17757 Report the memory address space ranges accessible in the program, with
17758 information on whether the process has read, write, or execute access
17759 rights to each range. On @sc{gnu}/Linux systems, each memory range
17760 includes the object file which is mapped to that range, instead of the
17761 memory access rights to that range.
17763 @item info proc stat
17764 @itemx info proc status
17765 @cindex process detailed status information
17766 These subcommands are specific to @sc{gnu}/Linux systems. They show
17767 the process-related information, including the user ID and group ID;
17768 how many threads are there in the process; its virtual memory usage;
17769 the signals that are pending, blocked, and ignored; its TTY; its
17770 consumption of system and user time; its stack size; its @samp{nice}
17771 value; etc. For more information, see the @samp{proc} man page
17772 (type @kbd{man 5 proc} from your shell prompt).
17774 @item info proc all
17775 Show all the information about the process described under all of the
17776 above @code{info proc} subcommands.
17779 @comment These sub-options of 'info proc' were not included when
17780 @comment procfs.c was re-written. Keep their descriptions around
17781 @comment against the day when someone finds the time to put them back in.
17782 @kindex info proc times
17783 @item info proc times
17784 Starting time, user CPU time, and system CPU time for your program and
17787 @kindex info proc id
17789 Report on the process IDs related to your program: its own process ID,
17790 the ID of its parent, the process group ID, and the session ID.
17793 @item set procfs-trace
17794 @kindex set procfs-trace
17795 @cindex @code{procfs} API calls
17796 This command enables and disables tracing of @code{procfs} API calls.
17798 @item show procfs-trace
17799 @kindex show procfs-trace
17800 Show the current state of @code{procfs} API call tracing.
17802 @item set procfs-file @var{file}
17803 @kindex set procfs-file
17804 Tell @value{GDBN} to write @code{procfs} API trace to the named
17805 @var{file}. @value{GDBN} appends the trace info to the previous
17806 contents of the file. The default is to display the trace on the
17809 @item show procfs-file
17810 @kindex show procfs-file
17811 Show the file to which @code{procfs} API trace is written.
17813 @item proc-trace-entry
17814 @itemx proc-trace-exit
17815 @itemx proc-untrace-entry
17816 @itemx proc-untrace-exit
17817 @kindex proc-trace-entry
17818 @kindex proc-trace-exit
17819 @kindex proc-untrace-entry
17820 @kindex proc-untrace-exit
17821 These commands enable and disable tracing of entries into and exits
17822 from the @code{syscall} interface.
17825 @kindex info pidlist
17826 @cindex process list, QNX Neutrino
17827 For QNX Neutrino only, this command displays the list of all the
17828 processes and all the threads within each process.
17831 @kindex info meminfo
17832 @cindex mapinfo list, QNX Neutrino
17833 For QNX Neutrino only, this command displays the list of all mapinfos.
17837 @subsection Features for Debugging @sc{djgpp} Programs
17838 @cindex @sc{djgpp} debugging
17839 @cindex native @sc{djgpp} debugging
17840 @cindex MS-DOS-specific commands
17843 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
17844 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
17845 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
17846 top of real-mode DOS systems and their emulations.
17848 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
17849 defines a few commands specific to the @sc{djgpp} port. This
17850 subsection describes those commands.
17855 This is a prefix of @sc{djgpp}-specific commands which print
17856 information about the target system and important OS structures.
17859 @cindex MS-DOS system info
17860 @cindex free memory information (MS-DOS)
17861 @item info dos sysinfo
17862 This command displays assorted information about the underlying
17863 platform: the CPU type and features, the OS version and flavor, the
17864 DPMI version, and the available conventional and DPMI memory.
17869 @cindex segment descriptor tables
17870 @cindex descriptor tables display
17872 @itemx info dos ldt
17873 @itemx info dos idt
17874 These 3 commands display entries from, respectively, Global, Local,
17875 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
17876 tables are data structures which store a descriptor for each segment
17877 that is currently in use. The segment's selector is an index into a
17878 descriptor table; the table entry for that index holds the
17879 descriptor's base address and limit, and its attributes and access
17882 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
17883 segment (used for both data and the stack), and a DOS segment (which
17884 allows access to DOS/BIOS data structures and absolute addresses in
17885 conventional memory). However, the DPMI host will usually define
17886 additional segments in order to support the DPMI environment.
17888 @cindex garbled pointers
17889 These commands allow to display entries from the descriptor tables.
17890 Without an argument, all entries from the specified table are
17891 displayed. An argument, which should be an integer expression, means
17892 display a single entry whose index is given by the argument. For
17893 example, here's a convenient way to display information about the
17894 debugged program's data segment:
17897 @exdent @code{(@value{GDBP}) info dos ldt $ds}
17898 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
17902 This comes in handy when you want to see whether a pointer is outside
17903 the data segment's limit (i.e.@: @dfn{garbled}).
17905 @cindex page tables display (MS-DOS)
17907 @itemx info dos pte
17908 These two commands display entries from, respectively, the Page
17909 Directory and the Page Tables. Page Directories and Page Tables are
17910 data structures which control how virtual memory addresses are mapped
17911 into physical addresses. A Page Table includes an entry for every
17912 page of memory that is mapped into the program's address space; there
17913 may be several Page Tables, each one holding up to 4096 entries. A
17914 Page Directory has up to 4096 entries, one each for every Page Table
17915 that is currently in use.
17917 Without an argument, @kbd{info dos pde} displays the entire Page
17918 Directory, and @kbd{info dos pte} displays all the entries in all of
17919 the Page Tables. An argument, an integer expression, given to the
17920 @kbd{info dos pde} command means display only that entry from the Page
17921 Directory table. An argument given to the @kbd{info dos pte} command
17922 means display entries from a single Page Table, the one pointed to by
17923 the specified entry in the Page Directory.
17925 @cindex direct memory access (DMA) on MS-DOS
17926 These commands are useful when your program uses @dfn{DMA} (Direct
17927 Memory Access), which needs physical addresses to program the DMA
17930 These commands are supported only with some DPMI servers.
17932 @cindex physical address from linear address
17933 @item info dos address-pte @var{addr}
17934 This command displays the Page Table entry for a specified linear
17935 address. The argument @var{addr} is a linear address which should
17936 already have the appropriate segment's base address added to it,
17937 because this command accepts addresses which may belong to @emph{any}
17938 segment. For example, here's how to display the Page Table entry for
17939 the page where a variable @code{i} is stored:
17942 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
17943 @exdent @code{Page Table entry for address 0x11a00d30:}
17944 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
17948 This says that @code{i} is stored at offset @code{0xd30} from the page
17949 whose physical base address is @code{0x02698000}, and shows all the
17950 attributes of that page.
17952 Note that you must cast the addresses of variables to a @code{char *},
17953 since otherwise the value of @code{__djgpp_base_address}, the base
17954 address of all variables and functions in a @sc{djgpp} program, will
17955 be added using the rules of C pointer arithmetics: if @code{i} is
17956 declared an @code{int}, @value{GDBN} will add 4 times the value of
17957 @code{__djgpp_base_address} to the address of @code{i}.
17959 Here's another example, it displays the Page Table entry for the
17963 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
17964 @exdent @code{Page Table entry for address 0x29110:}
17965 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
17969 (The @code{+ 3} offset is because the transfer buffer's address is the
17970 3rd member of the @code{_go32_info_block} structure.) The output
17971 clearly shows that this DPMI server maps the addresses in conventional
17972 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
17973 linear (@code{0x29110}) addresses are identical.
17975 This command is supported only with some DPMI servers.
17978 @cindex DOS serial data link, remote debugging
17979 In addition to native debugging, the DJGPP port supports remote
17980 debugging via a serial data link. The following commands are specific
17981 to remote serial debugging in the DJGPP port of @value{GDBN}.
17984 @kindex set com1base
17985 @kindex set com1irq
17986 @kindex set com2base
17987 @kindex set com2irq
17988 @kindex set com3base
17989 @kindex set com3irq
17990 @kindex set com4base
17991 @kindex set com4irq
17992 @item set com1base @var{addr}
17993 This command sets the base I/O port address of the @file{COM1} serial
17996 @item set com1irq @var{irq}
17997 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
17998 for the @file{COM1} serial port.
18000 There are similar commands @samp{set com2base}, @samp{set com3irq},
18001 etc.@: for setting the port address and the @code{IRQ} lines for the
18004 @kindex show com1base
18005 @kindex show com1irq
18006 @kindex show com2base
18007 @kindex show com2irq
18008 @kindex show com3base
18009 @kindex show com3irq
18010 @kindex show com4base
18011 @kindex show com4irq
18012 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
18013 display the current settings of the base address and the @code{IRQ}
18014 lines used by the COM ports.
18017 @kindex info serial
18018 @cindex DOS serial port status
18019 This command prints the status of the 4 DOS serial ports. For each
18020 port, it prints whether it's active or not, its I/O base address and
18021 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
18022 counts of various errors encountered so far.
18026 @node Cygwin Native
18027 @subsection Features for Debugging MS Windows PE Executables
18028 @cindex MS Windows debugging
18029 @cindex native Cygwin debugging
18030 @cindex Cygwin-specific commands
18032 @value{GDBN} supports native debugging of MS Windows programs, including
18033 DLLs with and without symbolic debugging information.
18035 @cindex Ctrl-BREAK, MS-Windows
18036 @cindex interrupt debuggee on MS-Windows
18037 MS-Windows programs that call @code{SetConsoleMode} to switch off the
18038 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
18039 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
18040 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
18041 sequence, which can be used to interrupt the debuggee even if it
18044 There are various additional Cygwin-specific commands, described in
18045 this section. Working with DLLs that have no debugging symbols is
18046 described in @ref{Non-debug DLL Symbols}.
18051 This is a prefix of MS Windows-specific commands which print
18052 information about the target system and important OS structures.
18054 @item info w32 selector
18055 This command displays information returned by
18056 the Win32 API @code{GetThreadSelectorEntry} function.
18057 It takes an optional argument that is evaluated to
18058 a long value to give the information about this given selector.
18059 Without argument, this command displays information
18060 about the six segment registers.
18062 @item info w32 thread-information-block
18063 This command displays thread specific information stored in the
18064 Thread Information Block (readable on the X86 CPU family using @code{$fs}
18065 selector for 32-bit programs and @code{$gs} for 64-bit programs).
18069 This is a Cygwin-specific alias of @code{info shared}.
18071 @kindex dll-symbols
18073 This command loads symbols from a dll similarly to
18074 add-sym command but without the need to specify a base address.
18076 @kindex set cygwin-exceptions
18077 @cindex debugging the Cygwin DLL
18078 @cindex Cygwin DLL, debugging
18079 @item set cygwin-exceptions @var{mode}
18080 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
18081 happen inside the Cygwin DLL. If @var{mode} is @code{off},
18082 @value{GDBN} will delay recognition of exceptions, and may ignore some
18083 exceptions which seem to be caused by internal Cygwin DLL
18084 ``bookkeeping''. This option is meant primarily for debugging the
18085 Cygwin DLL itself; the default value is @code{off} to avoid annoying
18086 @value{GDBN} users with false @code{SIGSEGV} signals.
18088 @kindex show cygwin-exceptions
18089 @item show cygwin-exceptions
18090 Displays whether @value{GDBN} will break on exceptions that happen
18091 inside the Cygwin DLL itself.
18093 @kindex set new-console
18094 @item set new-console @var{mode}
18095 If @var{mode} is @code{on} the debuggee will
18096 be started in a new console on next start.
18097 If @var{mode} is @code{off}, the debuggee will
18098 be started in the same console as the debugger.
18100 @kindex show new-console
18101 @item show new-console
18102 Displays whether a new console is used
18103 when the debuggee is started.
18105 @kindex set new-group
18106 @item set new-group @var{mode}
18107 This boolean value controls whether the debuggee should
18108 start a new group or stay in the same group as the debugger.
18109 This affects the way the Windows OS handles
18112 @kindex show new-group
18113 @item show new-group
18114 Displays current value of new-group boolean.
18116 @kindex set debugevents
18117 @item set debugevents
18118 This boolean value adds debug output concerning kernel events related
18119 to the debuggee seen by the debugger. This includes events that
18120 signal thread and process creation and exit, DLL loading and
18121 unloading, console interrupts, and debugging messages produced by the
18122 Windows @code{OutputDebugString} API call.
18124 @kindex set debugexec
18125 @item set debugexec
18126 This boolean value adds debug output concerning execute events
18127 (such as resume thread) seen by the debugger.
18129 @kindex set debugexceptions
18130 @item set debugexceptions
18131 This boolean value adds debug output concerning exceptions in the
18132 debuggee seen by the debugger.
18134 @kindex set debugmemory
18135 @item set debugmemory
18136 This boolean value adds debug output concerning debuggee memory reads
18137 and writes by the debugger.
18141 This boolean values specifies whether the debuggee is called
18142 via a shell or directly (default value is on).
18146 Displays if the debuggee will be started with a shell.
18151 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
18154 @node Non-debug DLL Symbols
18155 @subsubsection Support for DLLs without Debugging Symbols
18156 @cindex DLLs with no debugging symbols
18157 @cindex Minimal symbols and DLLs
18159 Very often on windows, some of the DLLs that your program relies on do
18160 not include symbolic debugging information (for example,
18161 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
18162 symbols in a DLL, it relies on the minimal amount of symbolic
18163 information contained in the DLL's export table. This section
18164 describes working with such symbols, known internally to @value{GDBN} as
18165 ``minimal symbols''.
18167 Note that before the debugged program has started execution, no DLLs
18168 will have been loaded. The easiest way around this problem is simply to
18169 start the program --- either by setting a breakpoint or letting the
18170 program run once to completion. It is also possible to force
18171 @value{GDBN} to load a particular DLL before starting the executable ---
18172 see the shared library information in @ref{Files}, or the
18173 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
18174 explicitly loading symbols from a DLL with no debugging information will
18175 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
18176 which may adversely affect symbol lookup performance.
18178 @subsubsection DLL Name Prefixes
18180 In keeping with the naming conventions used by the Microsoft debugging
18181 tools, DLL export symbols are made available with a prefix based on the
18182 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
18183 also entered into the symbol table, so @code{CreateFileA} is often
18184 sufficient. In some cases there will be name clashes within a program
18185 (particularly if the executable itself includes full debugging symbols)
18186 necessitating the use of the fully qualified name when referring to the
18187 contents of the DLL. Use single-quotes around the name to avoid the
18188 exclamation mark (``!'') being interpreted as a language operator.
18190 Note that the internal name of the DLL may be all upper-case, even
18191 though the file name of the DLL is lower-case, or vice-versa. Since
18192 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
18193 some confusion. If in doubt, try the @code{info functions} and
18194 @code{info variables} commands or even @code{maint print msymbols}
18195 (@pxref{Symbols}). Here's an example:
18198 (@value{GDBP}) info function CreateFileA
18199 All functions matching regular expression "CreateFileA":
18201 Non-debugging symbols:
18202 0x77e885f4 CreateFileA
18203 0x77e885f4 KERNEL32!CreateFileA
18207 (@value{GDBP}) info function !
18208 All functions matching regular expression "!":
18210 Non-debugging symbols:
18211 0x6100114c cygwin1!__assert
18212 0x61004034 cygwin1!_dll_crt0@@0
18213 0x61004240 cygwin1!dll_crt0(per_process *)
18217 @subsubsection Working with Minimal Symbols
18219 Symbols extracted from a DLL's export table do not contain very much
18220 type information. All that @value{GDBN} can do is guess whether a symbol
18221 refers to a function or variable depending on the linker section that
18222 contains the symbol. Also note that the actual contents of the memory
18223 contained in a DLL are not available unless the program is running. This
18224 means that you cannot examine the contents of a variable or disassemble
18225 a function within a DLL without a running program.
18227 Variables are generally treated as pointers and dereferenced
18228 automatically. For this reason, it is often necessary to prefix a
18229 variable name with the address-of operator (``&'') and provide explicit
18230 type information in the command. Here's an example of the type of
18234 (@value{GDBP}) print 'cygwin1!__argv'
18239 (@value{GDBP}) x 'cygwin1!__argv'
18240 0x10021610: "\230y\""
18243 And two possible solutions:
18246 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
18247 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
18251 (@value{GDBP}) x/2x &'cygwin1!__argv'
18252 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
18253 (@value{GDBP}) x/x 0x10021608
18254 0x10021608: 0x0022fd98
18255 (@value{GDBP}) x/s 0x0022fd98
18256 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
18259 Setting a break point within a DLL is possible even before the program
18260 starts execution. However, under these circumstances, @value{GDBN} can't
18261 examine the initial instructions of the function in order to skip the
18262 function's frame set-up code. You can work around this by using ``*&''
18263 to set the breakpoint at a raw memory address:
18266 (@value{GDBP}) break *&'python22!PyOS_Readline'
18267 Breakpoint 1 at 0x1e04eff0
18270 The author of these extensions is not entirely convinced that setting a
18271 break point within a shared DLL like @file{kernel32.dll} is completely
18275 @subsection Commands Specific to @sc{gnu} Hurd Systems
18276 @cindex @sc{gnu} Hurd debugging
18278 This subsection describes @value{GDBN} commands specific to the
18279 @sc{gnu} Hurd native debugging.
18284 @kindex set signals@r{, Hurd command}
18285 @kindex set sigs@r{, Hurd command}
18286 This command toggles the state of inferior signal interception by
18287 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
18288 affected by this command. @code{sigs} is a shorthand alias for
18293 @kindex show signals@r{, Hurd command}
18294 @kindex show sigs@r{, Hurd command}
18295 Show the current state of intercepting inferior's signals.
18297 @item set signal-thread
18298 @itemx set sigthread
18299 @kindex set signal-thread
18300 @kindex set sigthread
18301 This command tells @value{GDBN} which thread is the @code{libc} signal
18302 thread. That thread is run when a signal is delivered to a running
18303 process. @code{set sigthread} is the shorthand alias of @code{set
18306 @item show signal-thread
18307 @itemx show sigthread
18308 @kindex show signal-thread
18309 @kindex show sigthread
18310 These two commands show which thread will run when the inferior is
18311 delivered a signal.
18314 @kindex set stopped@r{, Hurd command}
18315 This commands tells @value{GDBN} that the inferior process is stopped,
18316 as with the @code{SIGSTOP} signal. The stopped process can be
18317 continued by delivering a signal to it.
18320 @kindex show stopped@r{, Hurd command}
18321 This command shows whether @value{GDBN} thinks the debuggee is
18324 @item set exceptions
18325 @kindex set exceptions@r{, Hurd command}
18326 Use this command to turn off trapping of exceptions in the inferior.
18327 When exception trapping is off, neither breakpoints nor
18328 single-stepping will work. To restore the default, set exception
18331 @item show exceptions
18332 @kindex show exceptions@r{, Hurd command}
18333 Show the current state of trapping exceptions in the inferior.
18335 @item set task pause
18336 @kindex set task@r{, Hurd commands}
18337 @cindex task attributes (@sc{gnu} Hurd)
18338 @cindex pause current task (@sc{gnu} Hurd)
18339 This command toggles task suspension when @value{GDBN} has control.
18340 Setting it to on takes effect immediately, and the task is suspended
18341 whenever @value{GDBN} gets control. Setting it to off will take
18342 effect the next time the inferior is continued. If this option is set
18343 to off, you can use @code{set thread default pause on} or @code{set
18344 thread pause on} (see below) to pause individual threads.
18346 @item show task pause
18347 @kindex show task@r{, Hurd commands}
18348 Show the current state of task suspension.
18350 @item set task detach-suspend-count
18351 @cindex task suspend count
18352 @cindex detach from task, @sc{gnu} Hurd
18353 This command sets the suspend count the task will be left with when
18354 @value{GDBN} detaches from it.
18356 @item show task detach-suspend-count
18357 Show the suspend count the task will be left with when detaching.
18359 @item set task exception-port
18360 @itemx set task excp
18361 @cindex task exception port, @sc{gnu} Hurd
18362 This command sets the task exception port to which @value{GDBN} will
18363 forward exceptions. The argument should be the value of the @dfn{send
18364 rights} of the task. @code{set task excp} is a shorthand alias.
18366 @item set noninvasive
18367 @cindex noninvasive task options
18368 This command switches @value{GDBN} to a mode that is the least
18369 invasive as far as interfering with the inferior is concerned. This
18370 is the same as using @code{set task pause}, @code{set exceptions}, and
18371 @code{set signals} to values opposite to the defaults.
18373 @item info send-rights
18374 @itemx info receive-rights
18375 @itemx info port-rights
18376 @itemx info port-sets
18377 @itemx info dead-names
18380 @cindex send rights, @sc{gnu} Hurd
18381 @cindex receive rights, @sc{gnu} Hurd
18382 @cindex port rights, @sc{gnu} Hurd
18383 @cindex port sets, @sc{gnu} Hurd
18384 @cindex dead names, @sc{gnu} Hurd
18385 These commands display information about, respectively, send rights,
18386 receive rights, port rights, port sets, and dead names of a task.
18387 There are also shorthand aliases: @code{info ports} for @code{info
18388 port-rights} and @code{info psets} for @code{info port-sets}.
18390 @item set thread pause
18391 @kindex set thread@r{, Hurd command}
18392 @cindex thread properties, @sc{gnu} Hurd
18393 @cindex pause current thread (@sc{gnu} Hurd)
18394 This command toggles current thread suspension when @value{GDBN} has
18395 control. Setting it to on takes effect immediately, and the current
18396 thread is suspended whenever @value{GDBN} gets control. Setting it to
18397 off will take effect the next time the inferior is continued.
18398 Normally, this command has no effect, since when @value{GDBN} has
18399 control, the whole task is suspended. However, if you used @code{set
18400 task pause off} (see above), this command comes in handy to suspend
18401 only the current thread.
18403 @item show thread pause
18404 @kindex show thread@r{, Hurd command}
18405 This command shows the state of current thread suspension.
18407 @item set thread run
18408 This command sets whether the current thread is allowed to run.
18410 @item show thread run
18411 Show whether the current thread is allowed to run.
18413 @item set thread detach-suspend-count
18414 @cindex thread suspend count, @sc{gnu} Hurd
18415 @cindex detach from thread, @sc{gnu} Hurd
18416 This command sets the suspend count @value{GDBN} will leave on a
18417 thread when detaching. This number is relative to the suspend count
18418 found by @value{GDBN} when it notices the thread; use @code{set thread
18419 takeover-suspend-count} to force it to an absolute value.
18421 @item show thread detach-suspend-count
18422 Show the suspend count @value{GDBN} will leave on the thread when
18425 @item set thread exception-port
18426 @itemx set thread excp
18427 Set the thread exception port to which to forward exceptions. This
18428 overrides the port set by @code{set task exception-port} (see above).
18429 @code{set thread excp} is the shorthand alias.
18431 @item set thread takeover-suspend-count
18432 Normally, @value{GDBN}'s thread suspend counts are relative to the
18433 value @value{GDBN} finds when it notices each thread. This command
18434 changes the suspend counts to be absolute instead.
18436 @item set thread default
18437 @itemx show thread default
18438 @cindex thread default settings, @sc{gnu} Hurd
18439 Each of the above @code{set thread} commands has a @code{set thread
18440 default} counterpart (e.g., @code{set thread default pause}, @code{set
18441 thread default exception-port}, etc.). The @code{thread default}
18442 variety of commands sets the default thread properties for all
18443 threads; you can then change the properties of individual threads with
18444 the non-default commands.
18449 @subsection QNX Neutrino
18450 @cindex QNX Neutrino
18452 @value{GDBN} provides the following commands specific to the QNX
18456 @item set debug nto-debug
18457 @kindex set debug nto-debug
18458 When set to on, enables debugging messages specific to the QNX
18461 @item show debug nto-debug
18462 @kindex show debug nto-debug
18463 Show the current state of QNX Neutrino messages.
18470 @value{GDBN} provides the following commands specific to the Darwin target:
18473 @item set debug darwin @var{num}
18474 @kindex set debug darwin
18475 When set to a non zero value, enables debugging messages specific to
18476 the Darwin support. Higher values produce more verbose output.
18478 @item show debug darwin
18479 @kindex show debug darwin
18480 Show the current state of Darwin messages.
18482 @item set debug mach-o @var{num}
18483 @kindex set debug mach-o
18484 When set to a non zero value, enables debugging messages while
18485 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
18486 file format used on Darwin for object and executable files.) Higher
18487 values produce more verbose output. This is a command to diagnose
18488 problems internal to @value{GDBN} and should not be needed in normal
18491 @item show debug mach-o
18492 @kindex show debug mach-o
18493 Show the current state of Mach-O file messages.
18495 @item set mach-exceptions on
18496 @itemx set mach-exceptions off
18497 @kindex set mach-exceptions
18498 On Darwin, faults are first reported as a Mach exception and are then
18499 mapped to a Posix signal. Use this command to turn on trapping of
18500 Mach exceptions in the inferior. This might be sometimes useful to
18501 better understand the cause of a fault. The default is off.
18503 @item show mach-exceptions
18504 @kindex show mach-exceptions
18505 Show the current state of exceptions trapping.
18510 @section Embedded Operating Systems
18512 This section describes configurations involving the debugging of
18513 embedded operating systems that are available for several different
18517 * VxWorks:: Using @value{GDBN} with VxWorks
18520 @value{GDBN} includes the ability to debug programs running on
18521 various real-time operating systems.
18524 @subsection Using @value{GDBN} with VxWorks
18530 @kindex target vxworks
18531 @item target vxworks @var{machinename}
18532 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
18533 is the target system's machine name or IP address.
18537 On VxWorks, @code{load} links @var{filename} dynamically on the
18538 current target system as well as adding its symbols in @value{GDBN}.
18540 @value{GDBN} enables developers to spawn and debug tasks running on networked
18541 VxWorks targets from a Unix host. Already-running tasks spawned from
18542 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
18543 both the Unix host and on the VxWorks target. The program
18544 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
18545 installed with the name @code{vxgdb}, to distinguish it from a
18546 @value{GDBN} for debugging programs on the host itself.)
18549 @item VxWorks-timeout @var{args}
18550 @kindex vxworks-timeout
18551 All VxWorks-based targets now support the option @code{vxworks-timeout}.
18552 This option is set by the user, and @var{args} represents the number of
18553 seconds @value{GDBN} waits for responses to rpc's. You might use this if
18554 your VxWorks target is a slow software simulator or is on the far side
18555 of a thin network line.
18558 The following information on connecting to VxWorks was current when
18559 this manual was produced; newer releases of VxWorks may use revised
18562 @findex INCLUDE_RDB
18563 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
18564 to include the remote debugging interface routines in the VxWorks
18565 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
18566 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
18567 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
18568 source debugging task @code{tRdbTask} when VxWorks is booted. For more
18569 information on configuring and remaking VxWorks, see the manufacturer's
18571 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
18573 Once you have included @file{rdb.a} in your VxWorks system image and set
18574 your Unix execution search path to find @value{GDBN}, you are ready to
18575 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
18576 @code{vxgdb}, depending on your installation).
18578 @value{GDBN} comes up showing the prompt:
18585 * VxWorks Connection:: Connecting to VxWorks
18586 * VxWorks Download:: VxWorks download
18587 * VxWorks Attach:: Running tasks
18590 @node VxWorks Connection
18591 @subsubsection Connecting to VxWorks
18593 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
18594 network. To connect to a target whose host name is ``@code{tt}'', type:
18597 (vxgdb) target vxworks tt
18601 @value{GDBN} displays messages like these:
18604 Attaching remote machine across net...
18609 @value{GDBN} then attempts to read the symbol tables of any object modules
18610 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
18611 these files by searching the directories listed in the command search
18612 path (@pxref{Environment, ,Your Program's Environment}); if it fails
18613 to find an object file, it displays a message such as:
18616 prog.o: No such file or directory.
18619 When this happens, add the appropriate directory to the search path with
18620 the @value{GDBN} command @code{path}, and execute the @code{target}
18623 @node VxWorks Download
18624 @subsubsection VxWorks Download
18626 @cindex download to VxWorks
18627 If you have connected to the VxWorks target and you want to debug an
18628 object that has not yet been loaded, you can use the @value{GDBN}
18629 @code{load} command to download a file from Unix to VxWorks
18630 incrementally. The object file given as an argument to the @code{load}
18631 command is actually opened twice: first by the VxWorks target in order
18632 to download the code, then by @value{GDBN} in order to read the symbol
18633 table. This can lead to problems if the current working directories on
18634 the two systems differ. If both systems have NFS mounted the same
18635 filesystems, you can avoid these problems by using absolute paths.
18636 Otherwise, it is simplest to set the working directory on both systems
18637 to the directory in which the object file resides, and then to reference
18638 the file by its name, without any path. For instance, a program
18639 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
18640 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
18641 program, type this on VxWorks:
18644 -> cd "@var{vxpath}/vw/demo/rdb"
18648 Then, in @value{GDBN}, type:
18651 (vxgdb) cd @var{hostpath}/vw/demo/rdb
18652 (vxgdb) load prog.o
18655 @value{GDBN} displays a response similar to this:
18658 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
18661 You can also use the @code{load} command to reload an object module
18662 after editing and recompiling the corresponding source file. Note that
18663 this makes @value{GDBN} delete all currently-defined breakpoints,
18664 auto-displays, and convenience variables, and to clear the value
18665 history. (This is necessary in order to preserve the integrity of
18666 debugger's data structures that reference the target system's symbol
18669 @node VxWorks Attach
18670 @subsubsection Running Tasks
18672 @cindex running VxWorks tasks
18673 You can also attach to an existing task using the @code{attach} command as
18677 (vxgdb) attach @var{task}
18681 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
18682 or suspended when you attach to it. Running tasks are suspended at
18683 the time of attachment.
18685 @node Embedded Processors
18686 @section Embedded Processors
18688 This section goes into details specific to particular embedded
18691 @cindex send command to simulator
18692 Whenever a specific embedded processor has a simulator, @value{GDBN}
18693 allows to send an arbitrary command to the simulator.
18696 @item sim @var{command}
18697 @kindex sim@r{, a command}
18698 Send an arbitrary @var{command} string to the simulator. Consult the
18699 documentation for the specific simulator in use for information about
18700 acceptable commands.
18706 * M32R/D:: Renesas M32R/D
18707 * M68K:: Motorola M68K
18708 * MicroBlaze:: Xilinx MicroBlaze
18709 * MIPS Embedded:: MIPS Embedded
18710 * OpenRISC 1000:: OpenRisc 1000
18711 * PA:: HP PA Embedded
18712 * PowerPC Embedded:: PowerPC Embedded
18713 * Sparclet:: Tsqware Sparclet
18714 * Sparclite:: Fujitsu Sparclite
18715 * Z8000:: Zilog Z8000
18718 * Super-H:: Renesas Super-H
18727 @item target rdi @var{dev}
18728 ARM Angel monitor, via RDI library interface to ADP protocol. You may
18729 use this target to communicate with both boards running the Angel
18730 monitor, or with the EmbeddedICE JTAG debug device.
18733 @item target rdp @var{dev}
18738 @value{GDBN} provides the following ARM-specific commands:
18741 @item set arm disassembler
18743 This commands selects from a list of disassembly styles. The
18744 @code{"std"} style is the standard style.
18746 @item show arm disassembler
18748 Show the current disassembly style.
18750 @item set arm apcs32
18751 @cindex ARM 32-bit mode
18752 This command toggles ARM operation mode between 32-bit and 26-bit.
18754 @item show arm apcs32
18755 Display the current usage of the ARM 32-bit mode.
18757 @item set arm fpu @var{fputype}
18758 This command sets the ARM floating-point unit (FPU) type. The
18759 argument @var{fputype} can be one of these:
18763 Determine the FPU type by querying the OS ABI.
18765 Software FPU, with mixed-endian doubles on little-endian ARM
18768 GCC-compiled FPA co-processor.
18770 Software FPU with pure-endian doubles.
18776 Show the current type of the FPU.
18779 This command forces @value{GDBN} to use the specified ABI.
18782 Show the currently used ABI.
18784 @item set arm fallback-mode (arm|thumb|auto)
18785 @value{GDBN} uses the symbol table, when available, to determine
18786 whether instructions are ARM or Thumb. This command controls
18787 @value{GDBN}'s default behavior when the symbol table is not
18788 available. The default is @samp{auto}, which causes @value{GDBN} to
18789 use the current execution mode (from the @code{T} bit in the @code{CPSR}
18792 @item show arm fallback-mode
18793 Show the current fallback instruction mode.
18795 @item set arm force-mode (arm|thumb|auto)
18796 This command overrides use of the symbol table to determine whether
18797 instructions are ARM or Thumb. The default is @samp{auto}, which
18798 causes @value{GDBN} to use the symbol table and then the setting
18799 of @samp{set arm fallback-mode}.
18801 @item show arm force-mode
18802 Show the current forced instruction mode.
18804 @item set debug arm
18805 Toggle whether to display ARM-specific debugging messages from the ARM
18806 target support subsystem.
18808 @item show debug arm
18809 Show whether ARM-specific debugging messages are enabled.
18812 The following commands are available when an ARM target is debugged
18813 using the RDI interface:
18816 @item rdilogfile @r{[}@var{file}@r{]}
18818 @cindex ADP (Angel Debugger Protocol) logging
18819 Set the filename for the ADP (Angel Debugger Protocol) packet log.
18820 With an argument, sets the log file to the specified @var{file}. With
18821 no argument, show the current log file name. The default log file is
18824 @item rdilogenable @r{[}@var{arg}@r{]}
18825 @kindex rdilogenable
18826 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
18827 enables logging, with an argument 0 or @code{"no"} disables it. With
18828 no arguments displays the current setting. When logging is enabled,
18829 ADP packets exchanged between @value{GDBN} and the RDI target device
18830 are logged to a file.
18832 @item set rdiromatzero
18833 @kindex set rdiromatzero
18834 @cindex ROM at zero address, RDI
18835 Tell @value{GDBN} whether the target has ROM at address 0. If on,
18836 vector catching is disabled, so that zero address can be used. If off
18837 (the default), vector catching is enabled. For this command to take
18838 effect, it needs to be invoked prior to the @code{target rdi} command.
18840 @item show rdiromatzero
18841 @kindex show rdiromatzero
18842 Show the current setting of ROM at zero address.
18844 @item set rdiheartbeat
18845 @kindex set rdiheartbeat
18846 @cindex RDI heartbeat
18847 Enable or disable RDI heartbeat packets. It is not recommended to
18848 turn on this option, since it confuses ARM and EPI JTAG interface, as
18849 well as the Angel monitor.
18851 @item show rdiheartbeat
18852 @kindex show rdiheartbeat
18853 Show the setting of RDI heartbeat packets.
18857 @item target sim @r{[}@var{simargs}@r{]} @dots{}
18858 The @value{GDBN} ARM simulator accepts the following optional arguments.
18861 @item --swi-support=@var{type}
18862 Tell the simulator which SWI interfaces to support.
18863 @var{type} may be a comma separated list of the following values.
18864 The default value is @code{all}.
18877 @subsection Renesas M32R/D and M32R/SDI
18880 @kindex target m32r
18881 @item target m32r @var{dev}
18882 Renesas M32R/D ROM monitor.
18884 @kindex target m32rsdi
18885 @item target m32rsdi @var{dev}
18886 Renesas M32R SDI server, connected via parallel port to the board.
18889 The following @value{GDBN} commands are specific to the M32R monitor:
18892 @item set download-path @var{path}
18893 @kindex set download-path
18894 @cindex find downloadable @sc{srec} files (M32R)
18895 Set the default path for finding downloadable @sc{srec} files.
18897 @item show download-path
18898 @kindex show download-path
18899 Show the default path for downloadable @sc{srec} files.
18901 @item set board-address @var{addr}
18902 @kindex set board-address
18903 @cindex M32-EVA target board address
18904 Set the IP address for the M32R-EVA target board.
18906 @item show board-address
18907 @kindex show board-address
18908 Show the current IP address of the target board.
18910 @item set server-address @var{addr}
18911 @kindex set server-address
18912 @cindex download server address (M32R)
18913 Set the IP address for the download server, which is the @value{GDBN}'s
18916 @item show server-address
18917 @kindex show server-address
18918 Display the IP address of the download server.
18920 @item upload @r{[}@var{file}@r{]}
18921 @kindex upload@r{, M32R}
18922 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
18923 upload capability. If no @var{file} argument is given, the current
18924 executable file is uploaded.
18926 @item tload @r{[}@var{file}@r{]}
18927 @kindex tload@r{, M32R}
18928 Test the @code{upload} command.
18931 The following commands are available for M32R/SDI:
18936 @cindex reset SDI connection, M32R
18937 This command resets the SDI connection.
18941 This command shows the SDI connection status.
18944 @kindex debug_chaos
18945 @cindex M32R/Chaos debugging
18946 Instructs the remote that M32R/Chaos debugging is to be used.
18948 @item use_debug_dma
18949 @kindex use_debug_dma
18950 Instructs the remote to use the DEBUG_DMA method of accessing memory.
18953 @kindex use_mon_code
18954 Instructs the remote to use the MON_CODE method of accessing memory.
18957 @kindex use_ib_break
18958 Instructs the remote to set breakpoints by IB break.
18960 @item use_dbt_break
18961 @kindex use_dbt_break
18962 Instructs the remote to set breakpoints by DBT.
18968 The Motorola m68k configuration includes ColdFire support, and a
18969 target command for the following ROM monitor.
18973 @kindex target dbug
18974 @item target dbug @var{dev}
18975 dBUG ROM monitor for Motorola ColdFire.
18980 @subsection MicroBlaze
18981 @cindex Xilinx MicroBlaze
18982 @cindex XMD, Xilinx Microprocessor Debugger
18984 The MicroBlaze is a soft-core processor supported on various Xilinx
18985 FPGAs, such as Spartan or Virtex series. Boards with these processors
18986 usually have JTAG ports which connect to a host system running the Xilinx
18987 Embedded Development Kit (EDK) or Software Development Kit (SDK).
18988 This host system is used to download the configuration bitstream to
18989 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
18990 communicates with the target board using the JTAG interface and
18991 presents a @code{gdbserver} interface to the board. By default
18992 @code{xmd} uses port @code{1234}. (While it is possible to change
18993 this default port, it requires the use of undocumented @code{xmd}
18994 commands. Contact Xilinx support if you need to do this.)
18996 Use these GDB commands to connect to the MicroBlaze target processor.
18999 @item target remote :1234
19000 Use this command to connect to the target if you are running @value{GDBN}
19001 on the same system as @code{xmd}.
19003 @item target remote @var{xmd-host}:1234
19004 Use this command to connect to the target if it is connected to @code{xmd}
19005 running on a different system named @var{xmd-host}.
19008 Use this command to download a program to the MicroBlaze target.
19010 @item set debug microblaze @var{n}
19011 Enable MicroBlaze-specific debugging messages if non-zero.
19013 @item show debug microblaze @var{n}
19014 Show MicroBlaze-specific debugging level.
19017 @node MIPS Embedded
19018 @subsection MIPS Embedded
19020 @cindex MIPS boards
19021 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
19022 MIPS board attached to a serial line. This is available when
19023 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
19026 Use these @value{GDBN} commands to specify the connection to your target board:
19029 @item target mips @var{port}
19030 @kindex target mips @var{port}
19031 To run a program on the board, start up @code{@value{GDBP}} with the
19032 name of your program as the argument. To connect to the board, use the
19033 command @samp{target mips @var{port}}, where @var{port} is the name of
19034 the serial port connected to the board. If the program has not already
19035 been downloaded to the board, you may use the @code{load} command to
19036 download it. You can then use all the usual @value{GDBN} commands.
19038 For example, this sequence connects to the target board through a serial
19039 port, and loads and runs a program called @var{prog} through the
19043 host$ @value{GDBP} @var{prog}
19044 @value{GDBN} is free software and @dots{}
19045 (@value{GDBP}) target mips /dev/ttyb
19046 (@value{GDBP}) load @var{prog}
19050 @item target mips @var{hostname}:@var{portnumber}
19051 On some @value{GDBN} host configurations, you can specify a TCP
19052 connection (for instance, to a serial line managed by a terminal
19053 concentrator) instead of a serial port, using the syntax
19054 @samp{@var{hostname}:@var{portnumber}}.
19056 @item target pmon @var{port}
19057 @kindex target pmon @var{port}
19060 @item target ddb @var{port}
19061 @kindex target ddb @var{port}
19062 NEC's DDB variant of PMON for Vr4300.
19064 @item target lsi @var{port}
19065 @kindex target lsi @var{port}
19066 LSI variant of PMON.
19068 @kindex target r3900
19069 @item target r3900 @var{dev}
19070 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
19072 @kindex target array
19073 @item target array @var{dev}
19074 Array Tech LSI33K RAID controller board.
19080 @value{GDBN} also supports these special commands for MIPS targets:
19083 @item set mipsfpu double
19084 @itemx set mipsfpu single
19085 @itemx set mipsfpu none
19086 @itemx set mipsfpu auto
19087 @itemx show mipsfpu
19088 @kindex set mipsfpu
19089 @kindex show mipsfpu
19090 @cindex MIPS remote floating point
19091 @cindex floating point, MIPS remote
19092 If your target board does not support the MIPS floating point
19093 coprocessor, you should use the command @samp{set mipsfpu none} (if you
19094 need this, you may wish to put the command in your @value{GDBN} init
19095 file). This tells @value{GDBN} how to find the return value of
19096 functions which return floating point values. It also allows
19097 @value{GDBN} to avoid saving the floating point registers when calling
19098 functions on the board. If you are using a floating point coprocessor
19099 with only single precision floating point support, as on the @sc{r4650}
19100 processor, use the command @samp{set mipsfpu single}. The default
19101 double precision floating point coprocessor may be selected using
19102 @samp{set mipsfpu double}.
19104 In previous versions the only choices were double precision or no
19105 floating point, so @samp{set mipsfpu on} will select double precision
19106 and @samp{set mipsfpu off} will select no floating point.
19108 As usual, you can inquire about the @code{mipsfpu} variable with
19109 @samp{show mipsfpu}.
19111 @item set timeout @var{seconds}
19112 @itemx set retransmit-timeout @var{seconds}
19113 @itemx show timeout
19114 @itemx show retransmit-timeout
19115 @cindex @code{timeout}, MIPS protocol
19116 @cindex @code{retransmit-timeout}, MIPS protocol
19117 @kindex set timeout
19118 @kindex show timeout
19119 @kindex set retransmit-timeout
19120 @kindex show retransmit-timeout
19121 You can control the timeout used while waiting for a packet, in the MIPS
19122 remote protocol, with the @code{set timeout @var{seconds}} command. The
19123 default is 5 seconds. Similarly, you can control the timeout used while
19124 waiting for an acknowledgment of a packet with the @code{set
19125 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
19126 You can inspect both values with @code{show timeout} and @code{show
19127 retransmit-timeout}. (These commands are @emph{only} available when
19128 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
19130 The timeout set by @code{set timeout} does not apply when @value{GDBN}
19131 is waiting for your program to stop. In that case, @value{GDBN} waits
19132 forever because it has no way of knowing how long the program is going
19133 to run before stopping.
19135 @item set syn-garbage-limit @var{num}
19136 @kindex set syn-garbage-limit@r{, MIPS remote}
19137 @cindex synchronize with remote MIPS target
19138 Limit the maximum number of characters @value{GDBN} should ignore when
19139 it tries to synchronize with the remote target. The default is 10
19140 characters. Setting the limit to -1 means there's no limit.
19142 @item show syn-garbage-limit
19143 @kindex show syn-garbage-limit@r{, MIPS remote}
19144 Show the current limit on the number of characters to ignore when
19145 trying to synchronize with the remote system.
19147 @item set monitor-prompt @var{prompt}
19148 @kindex set monitor-prompt@r{, MIPS remote}
19149 @cindex remote monitor prompt
19150 Tell @value{GDBN} to expect the specified @var{prompt} string from the
19151 remote monitor. The default depends on the target:
19161 @item show monitor-prompt
19162 @kindex show monitor-prompt@r{, MIPS remote}
19163 Show the current strings @value{GDBN} expects as the prompt from the
19166 @item set monitor-warnings
19167 @kindex set monitor-warnings@r{, MIPS remote}
19168 Enable or disable monitor warnings about hardware breakpoints. This
19169 has effect only for the @code{lsi} target. When on, @value{GDBN} will
19170 display warning messages whose codes are returned by the @code{lsi}
19171 PMON monitor for breakpoint commands.
19173 @item show monitor-warnings
19174 @kindex show monitor-warnings@r{, MIPS remote}
19175 Show the current setting of printing monitor warnings.
19177 @item pmon @var{command}
19178 @kindex pmon@r{, MIPS remote}
19179 @cindex send PMON command
19180 This command allows sending an arbitrary @var{command} string to the
19181 monitor. The monitor must be in debug mode for this to work.
19184 @node OpenRISC 1000
19185 @subsection OpenRISC 1000
19186 @cindex OpenRISC 1000
19188 @cindex or1k boards
19189 See OR1k Architecture document (@uref{www.opencores.org}) for more information
19190 about platform and commands.
19194 @kindex target jtag
19195 @item target jtag jtag://@var{host}:@var{port}
19197 Connects to remote JTAG server.
19198 JTAG remote server can be either an or1ksim or JTAG server,
19199 connected via parallel port to the board.
19201 Example: @code{target jtag jtag://localhost:9999}
19204 @item or1ksim @var{command}
19205 If connected to @code{or1ksim} OpenRISC 1000 Architectural
19206 Simulator, proprietary commands can be executed.
19208 @kindex info or1k spr
19209 @item info or1k spr
19210 Displays spr groups.
19212 @item info or1k spr @var{group}
19213 @itemx info or1k spr @var{groupno}
19214 Displays register names in selected group.
19216 @item info or1k spr @var{group} @var{register}
19217 @itemx info or1k spr @var{register}
19218 @itemx info or1k spr @var{groupno} @var{registerno}
19219 @itemx info or1k spr @var{registerno}
19220 Shows information about specified spr register.
19223 @item spr @var{group} @var{register} @var{value}
19224 @itemx spr @var{register @var{value}}
19225 @itemx spr @var{groupno} @var{registerno @var{value}}
19226 @itemx spr @var{registerno @var{value}}
19227 Writes @var{value} to specified spr register.
19230 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
19231 It is very similar to @value{GDBN} trace, except it does not interfere with normal
19232 program execution and is thus much faster. Hardware breakpoints/watchpoint
19233 triggers can be set using:
19236 Load effective address/data
19238 Store effective address/data
19240 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
19245 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
19246 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
19248 @code{htrace} commands:
19249 @cindex OpenRISC 1000 htrace
19252 @item hwatch @var{conditional}
19253 Set hardware watchpoint on combination of Load/Store Effective Address(es)
19254 or Data. For example:
19256 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
19258 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
19262 Display information about current HW trace configuration.
19264 @item htrace trigger @var{conditional}
19265 Set starting criteria for HW trace.
19267 @item htrace qualifier @var{conditional}
19268 Set acquisition qualifier for HW trace.
19270 @item htrace stop @var{conditional}
19271 Set HW trace stopping criteria.
19273 @item htrace record [@var{data}]*
19274 Selects the data to be recorded, when qualifier is met and HW trace was
19277 @item htrace enable
19278 @itemx htrace disable
19279 Enables/disables the HW trace.
19281 @item htrace rewind [@var{filename}]
19282 Clears currently recorded trace data.
19284 If filename is specified, new trace file is made and any newly collected data
19285 will be written there.
19287 @item htrace print [@var{start} [@var{len}]]
19288 Prints trace buffer, using current record configuration.
19290 @item htrace mode continuous
19291 Set continuous trace mode.
19293 @item htrace mode suspend
19294 Set suspend trace mode.
19298 @node PowerPC Embedded
19299 @subsection PowerPC Embedded
19301 @cindex DVC register
19302 @value{GDBN} supports using the DVC (Data Value Compare) register to
19303 implement in hardware simple hardware watchpoint conditions of the form:
19306 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
19307 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
19310 The DVC register will be automatically used when @value{GDBN} detects
19311 such pattern in a condition expression, and the created watchpoint uses one
19312 debug register (either the @code{exact-watchpoints} option is on and the
19313 variable is scalar, or the variable has a length of one byte). This feature
19314 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
19317 When running on PowerPC embedded processors, @value{GDBN} automatically uses
19318 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
19319 in which case watchpoints using only one debug register are created when
19320 watching variables of scalar types.
19322 You can create an artificial array to watch an arbitrary memory
19323 region using one of the following commands (@pxref{Expressions}):
19326 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
19327 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
19330 PowerPC embedded processors support masked watchpoints. See the discussion
19331 about the @code{mask} argument in @ref{Set Watchpoints}.
19333 @cindex ranged breakpoint
19334 PowerPC embedded processors support hardware accelerated
19335 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
19336 the inferior whenever it executes an instruction at any address within
19337 the range it specifies. To set a ranged breakpoint in @value{GDBN},
19338 use the @code{break-range} command.
19340 @value{GDBN} provides the following PowerPC-specific commands:
19343 @kindex break-range
19344 @item break-range @var{start-location}, @var{end-location}
19345 Set a breakpoint for an address range.
19346 @var{start-location} and @var{end-location} can specify a function name,
19347 a line number, an offset of lines from the current line or from the start
19348 location, or an address of an instruction (see @ref{Specify Location},
19349 for a list of all the possible ways to specify a @var{location}.)
19350 The breakpoint will stop execution of the inferior whenever it
19351 executes an instruction at any address within the specified range,
19352 (including @var{start-location} and @var{end-location}.)
19354 @kindex set powerpc
19355 @item set powerpc soft-float
19356 @itemx show powerpc soft-float
19357 Force @value{GDBN} to use (or not use) a software floating point calling
19358 convention. By default, @value{GDBN} selects the calling convention based
19359 on the selected architecture and the provided executable file.
19361 @item set powerpc vector-abi
19362 @itemx show powerpc vector-abi
19363 Force @value{GDBN} to use the specified calling convention for vector
19364 arguments and return values. The valid options are @samp{auto};
19365 @samp{generic}, to avoid vector registers even if they are present;
19366 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
19367 registers. By default, @value{GDBN} selects the calling convention
19368 based on the selected architecture and the provided executable file.
19370 @item set powerpc exact-watchpoints
19371 @itemx show powerpc exact-watchpoints
19372 Allow @value{GDBN} to use only one debug register when watching a variable
19373 of scalar type, thus assuming that the variable is accessed through the
19374 address of its first byte.
19376 @kindex target dink32
19377 @item target dink32 @var{dev}
19378 DINK32 ROM monitor.
19380 @kindex target ppcbug
19381 @item target ppcbug @var{dev}
19382 @kindex target ppcbug1
19383 @item target ppcbug1 @var{dev}
19384 PPCBUG ROM monitor for PowerPC.
19387 @item target sds @var{dev}
19388 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
19391 @cindex SDS protocol
19392 The following commands specific to the SDS protocol are supported
19396 @item set sdstimeout @var{nsec}
19397 @kindex set sdstimeout
19398 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
19399 default is 2 seconds.
19401 @item show sdstimeout
19402 @kindex show sdstimeout
19403 Show the current value of the SDS timeout.
19405 @item sds @var{command}
19406 @kindex sds@r{, a command}
19407 Send the specified @var{command} string to the SDS monitor.
19412 @subsection HP PA Embedded
19416 @kindex target op50n
19417 @item target op50n @var{dev}
19418 OP50N monitor, running on an OKI HPPA board.
19420 @kindex target w89k
19421 @item target w89k @var{dev}
19422 W89K monitor, running on a Winbond HPPA board.
19427 @subsection Tsqware Sparclet
19431 @value{GDBN} enables developers to debug tasks running on
19432 Sparclet targets from a Unix host.
19433 @value{GDBN} uses code that runs on
19434 both the Unix host and on the Sparclet target. The program
19435 @code{@value{GDBP}} is installed and executed on the Unix host.
19438 @item remotetimeout @var{args}
19439 @kindex remotetimeout
19440 @value{GDBN} supports the option @code{remotetimeout}.
19441 This option is set by the user, and @var{args} represents the number of
19442 seconds @value{GDBN} waits for responses.
19445 @cindex compiling, on Sparclet
19446 When compiling for debugging, include the options @samp{-g} to get debug
19447 information and @samp{-Ttext} to relocate the program to where you wish to
19448 load it on the target. You may also want to add the options @samp{-n} or
19449 @samp{-N} in order to reduce the size of the sections. Example:
19452 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
19455 You can use @code{objdump} to verify that the addresses are what you intended:
19458 sparclet-aout-objdump --headers --syms prog
19461 @cindex running, on Sparclet
19463 your Unix execution search path to find @value{GDBN}, you are ready to
19464 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
19465 (or @code{sparclet-aout-gdb}, depending on your installation).
19467 @value{GDBN} comes up showing the prompt:
19474 * Sparclet File:: Setting the file to debug
19475 * Sparclet Connection:: Connecting to Sparclet
19476 * Sparclet Download:: Sparclet download
19477 * Sparclet Execution:: Running and debugging
19480 @node Sparclet File
19481 @subsubsection Setting File to Debug
19483 The @value{GDBN} command @code{file} lets you choose with program to debug.
19486 (gdbslet) file prog
19490 @value{GDBN} then attempts to read the symbol table of @file{prog}.
19491 @value{GDBN} locates
19492 the file by searching the directories listed in the command search
19494 If the file was compiled with debug information (option @samp{-g}), source
19495 files will be searched as well.
19496 @value{GDBN} locates
19497 the source files by searching the directories listed in the directory search
19498 path (@pxref{Environment, ,Your Program's Environment}).
19500 to find a file, it displays a message such as:
19503 prog: No such file or directory.
19506 When this happens, add the appropriate directories to the search paths with
19507 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
19508 @code{target} command again.
19510 @node Sparclet Connection
19511 @subsubsection Connecting to Sparclet
19513 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
19514 To connect to a target on serial port ``@code{ttya}'', type:
19517 (gdbslet) target sparclet /dev/ttya
19518 Remote target sparclet connected to /dev/ttya
19519 main () at ../prog.c:3
19523 @value{GDBN} displays messages like these:
19529 @node Sparclet Download
19530 @subsubsection Sparclet Download
19532 @cindex download to Sparclet
19533 Once connected to the Sparclet target,
19534 you can use the @value{GDBN}
19535 @code{load} command to download the file from the host to the target.
19536 The file name and load offset should be given as arguments to the @code{load}
19538 Since the file format is aout, the program must be loaded to the starting
19539 address. You can use @code{objdump} to find out what this value is. The load
19540 offset is an offset which is added to the VMA (virtual memory address)
19541 of each of the file's sections.
19542 For instance, if the program
19543 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
19544 and bss at 0x12010170, in @value{GDBN}, type:
19547 (gdbslet) load prog 0x12010000
19548 Loading section .text, size 0xdb0 vma 0x12010000
19551 If the code is loaded at a different address then what the program was linked
19552 to, you may need to use the @code{section} and @code{add-symbol-file} commands
19553 to tell @value{GDBN} where to map the symbol table.
19555 @node Sparclet Execution
19556 @subsubsection Running and Debugging
19558 @cindex running and debugging Sparclet programs
19559 You can now begin debugging the task using @value{GDBN}'s execution control
19560 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
19561 manual for the list of commands.
19565 Breakpoint 1 at 0x12010000: file prog.c, line 3.
19567 Starting program: prog
19568 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
19569 3 char *symarg = 0;
19571 4 char *execarg = "hello!";
19576 @subsection Fujitsu Sparclite
19580 @kindex target sparclite
19581 @item target sparclite @var{dev}
19582 Fujitsu sparclite boards, used only for the purpose of loading.
19583 You must use an additional command to debug the program.
19584 For example: target remote @var{dev} using @value{GDBN} standard
19590 @subsection Zilog Z8000
19593 @cindex simulator, Z8000
19594 @cindex Zilog Z8000 simulator
19596 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
19599 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
19600 unsegmented variant of the Z8000 architecture) or the Z8001 (the
19601 segmented variant). The simulator recognizes which architecture is
19602 appropriate by inspecting the object code.
19605 @item target sim @var{args}
19607 @kindex target sim@r{, with Z8000}
19608 Debug programs on a simulated CPU. If the simulator supports setup
19609 options, specify them via @var{args}.
19613 After specifying this target, you can debug programs for the simulated
19614 CPU in the same style as programs for your host computer; use the
19615 @code{file} command to load a new program image, the @code{run} command
19616 to run your program, and so on.
19618 As well as making available all the usual machine registers
19619 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
19620 additional items of information as specially named registers:
19625 Counts clock-ticks in the simulator.
19628 Counts instructions run in the simulator.
19631 Execution time in 60ths of a second.
19635 You can refer to these values in @value{GDBN} expressions with the usual
19636 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
19637 conditional breakpoint that suspends only after at least 5000
19638 simulated clock ticks.
19641 @subsection Atmel AVR
19644 When configured for debugging the Atmel AVR, @value{GDBN} supports the
19645 following AVR-specific commands:
19648 @item info io_registers
19649 @kindex info io_registers@r{, AVR}
19650 @cindex I/O registers (Atmel AVR)
19651 This command displays information about the AVR I/O registers. For
19652 each register, @value{GDBN} prints its number and value.
19659 When configured for debugging CRIS, @value{GDBN} provides the
19660 following CRIS-specific commands:
19663 @item set cris-version @var{ver}
19664 @cindex CRIS version
19665 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
19666 The CRIS version affects register names and sizes. This command is useful in
19667 case autodetection of the CRIS version fails.
19669 @item show cris-version
19670 Show the current CRIS version.
19672 @item set cris-dwarf2-cfi
19673 @cindex DWARF-2 CFI and CRIS
19674 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
19675 Change to @samp{off} when using @code{gcc-cris} whose version is below
19678 @item show cris-dwarf2-cfi
19679 Show the current state of using DWARF-2 CFI.
19681 @item set cris-mode @var{mode}
19683 Set the current CRIS mode to @var{mode}. It should only be changed when
19684 debugging in guru mode, in which case it should be set to
19685 @samp{guru} (the default is @samp{normal}).
19687 @item show cris-mode
19688 Show the current CRIS mode.
19692 @subsection Renesas Super-H
19695 For the Renesas Super-H processor, @value{GDBN} provides these
19700 @kindex regs@r{, Super-H}
19701 Show the values of all Super-H registers.
19703 @item set sh calling-convention @var{convention}
19704 @kindex set sh calling-convention
19705 Set the calling-convention used when calling functions from @value{GDBN}.
19706 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
19707 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
19708 convention. If the DWARF-2 information of the called function specifies
19709 that the function follows the Renesas calling convention, the function
19710 is called using the Renesas calling convention. If the calling convention
19711 is set to @samp{renesas}, the Renesas calling convention is always used,
19712 regardless of the DWARF-2 information. This can be used to override the
19713 default of @samp{gcc} if debug information is missing, or the compiler
19714 does not emit the DWARF-2 calling convention entry for a function.
19716 @item show sh calling-convention
19717 @kindex show sh calling-convention
19718 Show the current calling convention setting.
19723 @node Architectures
19724 @section Architectures
19726 This section describes characteristics of architectures that affect
19727 all uses of @value{GDBN} with the architecture, both native and cross.
19734 * HPPA:: HP PA architecture
19735 * SPU:: Cell Broadband Engine SPU architecture
19740 @subsection x86 Architecture-specific Issues
19743 @item set struct-convention @var{mode}
19744 @kindex set struct-convention
19745 @cindex struct return convention
19746 @cindex struct/union returned in registers
19747 Set the convention used by the inferior to return @code{struct}s and
19748 @code{union}s from functions to @var{mode}. Possible values of
19749 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
19750 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
19751 are returned on the stack, while @code{"reg"} means that a
19752 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
19753 be returned in a register.
19755 @item show struct-convention
19756 @kindex show struct-convention
19757 Show the current setting of the convention to return @code{struct}s
19766 @kindex set rstack_high_address
19767 @cindex AMD 29K register stack
19768 @cindex register stack, AMD29K
19769 @item set rstack_high_address @var{address}
19770 On AMD 29000 family processors, registers are saved in a separate
19771 @dfn{register stack}. There is no way for @value{GDBN} to determine the
19772 extent of this stack. Normally, @value{GDBN} just assumes that the
19773 stack is ``large enough''. This may result in @value{GDBN} referencing
19774 memory locations that do not exist. If necessary, you can get around
19775 this problem by specifying the ending address of the register stack with
19776 the @code{set rstack_high_address} command. The argument should be an
19777 address, which you probably want to precede with @samp{0x} to specify in
19780 @kindex show rstack_high_address
19781 @item show rstack_high_address
19782 Display the current limit of the register stack, on AMD 29000 family
19790 See the following section.
19795 @cindex stack on Alpha
19796 @cindex stack on MIPS
19797 @cindex Alpha stack
19799 Alpha- and MIPS-based computers use an unusual stack frame, which
19800 sometimes requires @value{GDBN} to search backward in the object code to
19801 find the beginning of a function.
19803 @cindex response time, MIPS debugging
19804 To improve response time (especially for embedded applications, where
19805 @value{GDBN} may be restricted to a slow serial line for this search)
19806 you may want to limit the size of this search, using one of these
19810 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
19811 @item set heuristic-fence-post @var{limit}
19812 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
19813 search for the beginning of a function. A value of @var{0} (the
19814 default) means there is no limit. However, except for @var{0}, the
19815 larger the limit the more bytes @code{heuristic-fence-post} must search
19816 and therefore the longer it takes to run. You should only need to use
19817 this command when debugging a stripped executable.
19819 @item show heuristic-fence-post
19820 Display the current limit.
19824 These commands are available @emph{only} when @value{GDBN} is configured
19825 for debugging programs on Alpha or MIPS processors.
19827 Several MIPS-specific commands are available when debugging MIPS
19831 @item set mips abi @var{arg}
19832 @kindex set mips abi
19833 @cindex set ABI for MIPS
19834 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
19835 values of @var{arg} are:
19839 The default ABI associated with the current binary (this is the
19849 @item show mips abi
19850 @kindex show mips abi
19851 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
19854 @itemx show mipsfpu
19855 @xref{MIPS Embedded, set mipsfpu}.
19857 @item set mips mask-address @var{arg}
19858 @kindex set mips mask-address
19859 @cindex MIPS addresses, masking
19860 This command determines whether the most-significant 32 bits of 64-bit
19861 MIPS addresses are masked off. The argument @var{arg} can be
19862 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
19863 setting, which lets @value{GDBN} determine the correct value.
19865 @item show mips mask-address
19866 @kindex show mips mask-address
19867 Show whether the upper 32 bits of MIPS addresses are masked off or
19870 @item set remote-mips64-transfers-32bit-regs
19871 @kindex set remote-mips64-transfers-32bit-regs
19872 This command controls compatibility with 64-bit MIPS targets that
19873 transfer data in 32-bit quantities. If you have an old MIPS 64 target
19874 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
19875 and 64 bits for other registers, set this option to @samp{on}.
19877 @item show remote-mips64-transfers-32bit-regs
19878 @kindex show remote-mips64-transfers-32bit-regs
19879 Show the current setting of compatibility with older MIPS 64 targets.
19881 @item set debug mips
19882 @kindex set debug mips
19883 This command turns on and off debugging messages for the MIPS-specific
19884 target code in @value{GDBN}.
19886 @item show debug mips
19887 @kindex show debug mips
19888 Show the current setting of MIPS debugging messages.
19894 @cindex HPPA support
19896 When @value{GDBN} is debugging the HP PA architecture, it provides the
19897 following special commands:
19900 @item set debug hppa
19901 @kindex set debug hppa
19902 This command determines whether HPPA architecture-specific debugging
19903 messages are to be displayed.
19905 @item show debug hppa
19906 Show whether HPPA debugging messages are displayed.
19908 @item maint print unwind @var{address}
19909 @kindex maint print unwind@r{, HPPA}
19910 This command displays the contents of the unwind table entry at the
19911 given @var{address}.
19917 @subsection Cell Broadband Engine SPU architecture
19918 @cindex Cell Broadband Engine
19921 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
19922 it provides the following special commands:
19925 @item info spu event
19927 Display SPU event facility status. Shows current event mask
19928 and pending event status.
19930 @item info spu signal
19931 Display SPU signal notification facility status. Shows pending
19932 signal-control word and signal notification mode of both signal
19933 notification channels.
19935 @item info spu mailbox
19936 Display SPU mailbox facility status. Shows all pending entries,
19937 in order of processing, in each of the SPU Write Outbound,
19938 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
19941 Display MFC DMA status. Shows all pending commands in the MFC
19942 DMA queue. For each entry, opcode, tag, class IDs, effective
19943 and local store addresses and transfer size are shown.
19945 @item info spu proxydma
19946 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
19947 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
19948 and local store addresses and transfer size are shown.
19952 When @value{GDBN} is debugging a combined PowerPC/SPU application
19953 on the Cell Broadband Engine, it provides in addition the following
19957 @item set spu stop-on-load @var{arg}
19959 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
19960 will give control to the user when a new SPE thread enters its @code{main}
19961 function. The default is @code{off}.
19963 @item show spu stop-on-load
19965 Show whether to stop for new SPE threads.
19967 @item set spu auto-flush-cache @var{arg}
19968 Set whether to automatically flush the software-managed cache. When set to
19969 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
19970 cache to be flushed whenever SPE execution stops. This provides a consistent
19971 view of PowerPC memory that is accessed via the cache. If an application
19972 does not use the software-managed cache, this option has no effect.
19974 @item show spu auto-flush-cache
19975 Show whether to automatically flush the software-managed cache.
19980 @subsection PowerPC
19981 @cindex PowerPC architecture
19983 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
19984 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
19985 numbers stored in the floating point registers. These values must be stored
19986 in two consecutive registers, always starting at an even register like
19987 @code{f0} or @code{f2}.
19989 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
19990 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
19991 @code{f2} and @code{f3} for @code{$dl1} and so on.
19993 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
19994 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
19997 @node Controlling GDB
19998 @chapter Controlling @value{GDBN}
20000 You can alter the way @value{GDBN} interacts with you by using the
20001 @code{set} command. For commands controlling how @value{GDBN} displays
20002 data, see @ref{Print Settings, ,Print Settings}. Other settings are
20007 * Editing:: Command editing
20008 * Command History:: Command history
20009 * Screen Size:: Screen size
20010 * Numbers:: Numbers
20011 * ABI:: Configuring the current ABI
20012 * Messages/Warnings:: Optional warnings and messages
20013 * Debugging Output:: Optional messages about internal happenings
20014 * Other Misc Settings:: Other Miscellaneous Settings
20022 @value{GDBN} indicates its readiness to read a command by printing a string
20023 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
20024 can change the prompt string with the @code{set prompt} command. For
20025 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
20026 the prompt in one of the @value{GDBN} sessions so that you can always tell
20027 which one you are talking to.
20029 @emph{Note:} @code{set prompt} does not add a space for you after the
20030 prompt you set. This allows you to set a prompt which ends in a space
20031 or a prompt that does not.
20035 @item set prompt @var{newprompt}
20036 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
20038 @kindex show prompt
20040 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
20043 Versions of @value{GDBN} that ship with Python scripting enabled have
20044 prompt extensions. The commands for interacting with these extensions
20048 @kindex set extended-prompt
20049 @item set extended-prompt @var{prompt}
20050 Set an extended prompt that allows for substitutions.
20051 @xref{gdb.prompt}, for a list of escape sequences that can be used for
20052 substitution. Any escape sequences specified as part of the prompt
20053 string are replaced with the corresponding strings each time the prompt
20059 set extended-prompt Current working directory: \w (gdb)
20062 Note that when an extended-prompt is set, it takes control of the
20063 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
20065 @kindex show extended-prompt
20066 @item show extended-prompt
20067 Prints the extended prompt. Any escape sequences specified as part of
20068 the prompt string with @code{set extended-prompt}, are replaced with the
20069 corresponding strings each time the prompt is displayed.
20073 @section Command Editing
20075 @cindex command line editing
20077 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
20078 @sc{gnu} library provides consistent behavior for programs which provide a
20079 command line interface to the user. Advantages are @sc{gnu} Emacs-style
20080 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
20081 substitution, and a storage and recall of command history across
20082 debugging sessions.
20084 You may control the behavior of command line editing in @value{GDBN} with the
20085 command @code{set}.
20088 @kindex set editing
20091 @itemx set editing on
20092 Enable command line editing (enabled by default).
20094 @item set editing off
20095 Disable command line editing.
20097 @kindex show editing
20099 Show whether command line editing is enabled.
20102 @ifset SYSTEM_READLINE
20103 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
20105 @ifclear SYSTEM_READLINE
20106 @xref{Command Line Editing},
20108 for more details about the Readline
20109 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
20110 encouraged to read that chapter.
20112 @node Command History
20113 @section Command History
20114 @cindex command history
20116 @value{GDBN} can keep track of the commands you type during your
20117 debugging sessions, so that you can be certain of precisely what
20118 happened. Use these commands to manage the @value{GDBN} command
20121 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
20122 package, to provide the history facility.
20123 @ifset SYSTEM_READLINE
20124 @xref{Using History Interactively, , , history, GNU History Library},
20126 @ifclear SYSTEM_READLINE
20127 @xref{Using History Interactively},
20129 for the detailed description of the History library.
20131 To issue a command to @value{GDBN} without affecting certain aspects of
20132 the state which is seen by users, prefix it with @samp{server }
20133 (@pxref{Server Prefix}). This
20134 means that this command will not affect the command history, nor will it
20135 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
20136 pressed on a line by itself.
20138 @cindex @code{server}, command prefix
20139 The server prefix does not affect the recording of values into the value
20140 history; to print a value without recording it into the value history,
20141 use the @code{output} command instead of the @code{print} command.
20143 Here is the description of @value{GDBN} commands related to command
20147 @cindex history substitution
20148 @cindex history file
20149 @kindex set history filename
20150 @cindex @env{GDBHISTFILE}, environment variable
20151 @item set history filename @var{fname}
20152 Set the name of the @value{GDBN} command history file to @var{fname}.
20153 This is the file where @value{GDBN} reads an initial command history
20154 list, and where it writes the command history from this session when it
20155 exits. You can access this list through history expansion or through
20156 the history command editing characters listed below. This file defaults
20157 to the value of the environment variable @code{GDBHISTFILE}, or to
20158 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
20161 @cindex save command history
20162 @kindex set history save
20163 @item set history save
20164 @itemx set history save on
20165 Record command history in a file, whose name may be specified with the
20166 @code{set history filename} command. By default, this option is disabled.
20168 @item set history save off
20169 Stop recording command history in a file.
20171 @cindex history size
20172 @kindex set history size
20173 @cindex @env{HISTSIZE}, environment variable
20174 @item set history size @var{size}
20175 Set the number of commands which @value{GDBN} keeps in its history list.
20176 This defaults to the value of the environment variable
20177 @code{HISTSIZE}, or to 256 if this variable is not set.
20180 History expansion assigns special meaning to the character @kbd{!}.
20181 @ifset SYSTEM_READLINE
20182 @xref{Event Designators, , , history, GNU History Library},
20184 @ifclear SYSTEM_READLINE
20185 @xref{Event Designators},
20189 @cindex history expansion, turn on/off
20190 Since @kbd{!} is also the logical not operator in C, history expansion
20191 is off by default. If you decide to enable history expansion with the
20192 @code{set history expansion on} command, you may sometimes need to
20193 follow @kbd{!} (when it is used as logical not, in an expression) with
20194 a space or a tab to prevent it from being expanded. The readline
20195 history facilities do not attempt substitution on the strings
20196 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
20198 The commands to control history expansion are:
20201 @item set history expansion on
20202 @itemx set history expansion
20203 @kindex set history expansion
20204 Enable history expansion. History expansion is off by default.
20206 @item set history expansion off
20207 Disable history expansion.
20210 @kindex show history
20212 @itemx show history filename
20213 @itemx show history save
20214 @itemx show history size
20215 @itemx show history expansion
20216 These commands display the state of the @value{GDBN} history parameters.
20217 @code{show history} by itself displays all four states.
20222 @kindex show commands
20223 @cindex show last commands
20224 @cindex display command history
20225 @item show commands
20226 Display the last ten commands in the command history.
20228 @item show commands @var{n}
20229 Print ten commands centered on command number @var{n}.
20231 @item show commands +
20232 Print ten commands just after the commands last printed.
20236 @section Screen Size
20237 @cindex size of screen
20238 @cindex pauses in output
20240 Certain commands to @value{GDBN} may produce large amounts of
20241 information output to the screen. To help you read all of it,
20242 @value{GDBN} pauses and asks you for input at the end of each page of
20243 output. Type @key{RET} when you want to continue the output, or @kbd{q}
20244 to discard the remaining output. Also, the screen width setting
20245 determines when to wrap lines of output. Depending on what is being
20246 printed, @value{GDBN} tries to break the line at a readable place,
20247 rather than simply letting it overflow onto the following line.
20249 Normally @value{GDBN} knows the size of the screen from the terminal
20250 driver software. For example, on Unix @value{GDBN} uses the termcap data base
20251 together with the value of the @code{TERM} environment variable and the
20252 @code{stty rows} and @code{stty cols} settings. If this is not correct,
20253 you can override it with the @code{set height} and @code{set
20260 @kindex show height
20261 @item set height @var{lpp}
20263 @itemx set width @var{cpl}
20265 These @code{set} commands specify a screen height of @var{lpp} lines and
20266 a screen width of @var{cpl} characters. The associated @code{show}
20267 commands display the current settings.
20269 If you specify a height of zero lines, @value{GDBN} does not pause during
20270 output no matter how long the output is. This is useful if output is to a
20271 file or to an editor buffer.
20273 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
20274 from wrapping its output.
20276 @item set pagination on
20277 @itemx set pagination off
20278 @kindex set pagination
20279 Turn the output pagination on or off; the default is on. Turning
20280 pagination off is the alternative to @code{set height 0}. Note that
20281 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
20282 Options, -batch}) also automatically disables pagination.
20284 @item show pagination
20285 @kindex show pagination
20286 Show the current pagination mode.
20291 @cindex number representation
20292 @cindex entering numbers
20294 You can always enter numbers in octal, decimal, or hexadecimal in
20295 @value{GDBN} by the usual conventions: octal numbers begin with
20296 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
20297 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
20298 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
20299 10; likewise, the default display for numbers---when no particular
20300 format is specified---is base 10. You can change the default base for
20301 both input and output with the commands described below.
20304 @kindex set input-radix
20305 @item set input-radix @var{base}
20306 Set the default base for numeric input. Supported choices
20307 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
20308 specified either unambiguously or using the current input radix; for
20312 set input-radix 012
20313 set input-radix 10.
20314 set input-radix 0xa
20318 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
20319 leaves the input radix unchanged, no matter what it was, since
20320 @samp{10}, being without any leading or trailing signs of its base, is
20321 interpreted in the current radix. Thus, if the current radix is 16,
20322 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
20325 @kindex set output-radix
20326 @item set output-radix @var{base}
20327 Set the default base for numeric display. Supported choices
20328 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
20329 specified either unambiguously or using the current input radix.
20331 @kindex show input-radix
20332 @item show input-radix
20333 Display the current default base for numeric input.
20335 @kindex show output-radix
20336 @item show output-radix
20337 Display the current default base for numeric display.
20339 @item set radix @r{[}@var{base}@r{]}
20343 These commands set and show the default base for both input and output
20344 of numbers. @code{set radix} sets the radix of input and output to
20345 the same base; without an argument, it resets the radix back to its
20346 default value of 10.
20351 @section Configuring the Current ABI
20353 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
20354 application automatically. However, sometimes you need to override its
20355 conclusions. Use these commands to manage @value{GDBN}'s view of the
20362 One @value{GDBN} configuration can debug binaries for multiple operating
20363 system targets, either via remote debugging or native emulation.
20364 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
20365 but you can override its conclusion using the @code{set osabi} command.
20366 One example where this is useful is in debugging of binaries which use
20367 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
20368 not have the same identifying marks that the standard C library for your
20373 Show the OS ABI currently in use.
20376 With no argument, show the list of registered available OS ABI's.
20378 @item set osabi @var{abi}
20379 Set the current OS ABI to @var{abi}.
20382 @cindex float promotion
20384 Generally, the way that an argument of type @code{float} is passed to a
20385 function depends on whether the function is prototyped. For a prototyped
20386 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
20387 according to the architecture's convention for @code{float}. For unprototyped
20388 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
20389 @code{double} and then passed.
20391 Unfortunately, some forms of debug information do not reliably indicate whether
20392 a function is prototyped. If @value{GDBN} calls a function that is not marked
20393 as prototyped, it consults @kbd{set coerce-float-to-double}.
20396 @kindex set coerce-float-to-double
20397 @item set coerce-float-to-double
20398 @itemx set coerce-float-to-double on
20399 Arguments of type @code{float} will be promoted to @code{double} when passed
20400 to an unprototyped function. This is the default setting.
20402 @item set coerce-float-to-double off
20403 Arguments of type @code{float} will be passed directly to unprototyped
20406 @kindex show coerce-float-to-double
20407 @item show coerce-float-to-double
20408 Show the current setting of promoting @code{float} to @code{double}.
20412 @kindex show cp-abi
20413 @value{GDBN} needs to know the ABI used for your program's C@t{++}
20414 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
20415 used to build your application. @value{GDBN} only fully supports
20416 programs with a single C@t{++} ABI; if your program contains code using
20417 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
20418 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
20419 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
20420 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
20421 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
20422 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
20427 Show the C@t{++} ABI currently in use.
20430 With no argument, show the list of supported C@t{++} ABI's.
20432 @item set cp-abi @var{abi}
20433 @itemx set cp-abi auto
20434 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
20437 @node Messages/Warnings
20438 @section Optional Warnings and Messages
20440 @cindex verbose operation
20441 @cindex optional warnings
20442 By default, @value{GDBN} is silent about its inner workings. If you are
20443 running on a slow machine, you may want to use the @code{set verbose}
20444 command. This makes @value{GDBN} tell you when it does a lengthy
20445 internal operation, so you will not think it has crashed.
20447 Currently, the messages controlled by @code{set verbose} are those
20448 which announce that the symbol table for a source file is being read;
20449 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
20452 @kindex set verbose
20453 @item set verbose on
20454 Enables @value{GDBN} output of certain informational messages.
20456 @item set verbose off
20457 Disables @value{GDBN} output of certain informational messages.
20459 @kindex show verbose
20461 Displays whether @code{set verbose} is on or off.
20464 By default, if @value{GDBN} encounters bugs in the symbol table of an
20465 object file, it is silent; but if you are debugging a compiler, you may
20466 find this information useful (@pxref{Symbol Errors, ,Errors Reading
20471 @kindex set complaints
20472 @item set complaints @var{limit}
20473 Permits @value{GDBN} to output @var{limit} complaints about each type of
20474 unusual symbols before becoming silent about the problem. Set
20475 @var{limit} to zero to suppress all complaints; set it to a large number
20476 to prevent complaints from being suppressed.
20478 @kindex show complaints
20479 @item show complaints
20480 Displays how many symbol complaints @value{GDBN} is permitted to produce.
20484 @anchor{confirmation requests}
20485 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
20486 lot of stupid questions to confirm certain commands. For example, if
20487 you try to run a program which is already running:
20491 The program being debugged has been started already.
20492 Start it from the beginning? (y or n)
20495 If you are willing to unflinchingly face the consequences of your own
20496 commands, you can disable this ``feature'':
20500 @kindex set confirm
20502 @cindex confirmation
20503 @cindex stupid questions
20504 @item set confirm off
20505 Disables confirmation requests. Note that running @value{GDBN} with
20506 the @option{--batch} option (@pxref{Mode Options, -batch}) also
20507 automatically disables confirmation requests.
20509 @item set confirm on
20510 Enables confirmation requests (the default).
20512 @kindex show confirm
20514 Displays state of confirmation requests.
20518 @cindex command tracing
20519 If you need to debug user-defined commands or sourced files you may find it
20520 useful to enable @dfn{command tracing}. In this mode each command will be
20521 printed as it is executed, prefixed with one or more @samp{+} symbols, the
20522 quantity denoting the call depth of each command.
20525 @kindex set trace-commands
20526 @cindex command scripts, debugging
20527 @item set trace-commands on
20528 Enable command tracing.
20529 @item set trace-commands off
20530 Disable command tracing.
20531 @item show trace-commands
20532 Display the current state of command tracing.
20535 @node Debugging Output
20536 @section Optional Messages about Internal Happenings
20537 @cindex optional debugging messages
20539 @value{GDBN} has commands that enable optional debugging messages from
20540 various @value{GDBN} subsystems; normally these commands are of
20541 interest to @value{GDBN} maintainers, or when reporting a bug. This
20542 section documents those commands.
20545 @kindex set exec-done-display
20546 @item set exec-done-display
20547 Turns on or off the notification of asynchronous commands'
20548 completion. When on, @value{GDBN} will print a message when an
20549 asynchronous command finishes its execution. The default is off.
20550 @kindex show exec-done-display
20551 @item show exec-done-display
20552 Displays the current setting of asynchronous command completion
20555 @cindex gdbarch debugging info
20556 @cindex architecture debugging info
20557 @item set debug arch
20558 Turns on or off display of gdbarch debugging info. The default is off
20560 @item show debug arch
20561 Displays the current state of displaying gdbarch debugging info.
20562 @item set debug aix-thread
20563 @cindex AIX threads
20564 Display debugging messages about inner workings of the AIX thread
20566 @item show debug aix-thread
20567 Show the current state of AIX thread debugging info display.
20568 @item set debug check-physname
20570 Check the results of the ``physname'' computation. When reading DWARF
20571 debugging information for C@t{++}, @value{GDBN} attempts to compute
20572 each entity's name. @value{GDBN} can do this computation in two
20573 different ways, depending on exactly what information is present.
20574 When enabled, this setting causes @value{GDBN} to compute the names
20575 both ways and display any discrepancies.
20576 @item show debug check-physname
20577 Show the current state of ``physname'' checking.
20578 @item set debug dwarf2-die
20579 @cindex DWARF2 DIEs
20580 Dump DWARF2 DIEs after they are read in.
20581 The value is the number of nesting levels to print.
20582 A value of zero turns off the display.
20583 @item show debug dwarf2-die
20584 Show the current state of DWARF2 DIE debugging.
20585 @item set debug displaced
20586 @cindex displaced stepping debugging info
20587 Turns on or off display of @value{GDBN} debugging info for the
20588 displaced stepping support. The default is off.
20589 @item show debug displaced
20590 Displays the current state of displaying @value{GDBN} debugging info
20591 related to displaced stepping.
20592 @item set debug event
20593 @cindex event debugging info
20594 Turns on or off display of @value{GDBN} event debugging info. The
20596 @item show debug event
20597 Displays the current state of displaying @value{GDBN} event debugging
20599 @item set debug expression
20600 @cindex expression debugging info
20601 Turns on or off display of debugging info about @value{GDBN}
20602 expression parsing. The default is off.
20603 @item show debug expression
20604 Displays the current state of displaying debugging info about
20605 @value{GDBN} expression parsing.
20606 @item set debug frame
20607 @cindex frame debugging info
20608 Turns on or off display of @value{GDBN} frame debugging info. The
20610 @item show debug frame
20611 Displays the current state of displaying @value{GDBN} frame debugging
20613 @item set debug gnu-nat
20614 @cindex @sc{gnu}/Hurd debug messages
20615 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
20616 @item show debug gnu-nat
20617 Show the current state of @sc{gnu}/Hurd debugging messages.
20618 @item set debug infrun
20619 @cindex inferior debugging info
20620 Turns on or off display of @value{GDBN} debugging info for running the inferior.
20621 The default is off. @file{infrun.c} contains GDB's runtime state machine used
20622 for implementing operations such as single-stepping the inferior.
20623 @item show debug infrun
20624 Displays the current state of @value{GDBN} inferior debugging.
20625 @item set debug jit
20626 @cindex just-in-time compilation, debugging messages
20627 Turns on or off debugging messages from JIT debug support.
20628 @item show debug jit
20629 Displays the current state of @value{GDBN} JIT debugging.
20630 @item set debug lin-lwp
20631 @cindex @sc{gnu}/Linux LWP debug messages
20632 @cindex Linux lightweight processes
20633 Turns on or off debugging messages from the Linux LWP debug support.
20634 @item show debug lin-lwp
20635 Show the current state of Linux LWP debugging messages.
20636 @item set debug observer
20637 @cindex observer debugging info
20638 Turns on or off display of @value{GDBN} observer debugging. This
20639 includes info such as the notification of observable events.
20640 @item show debug observer
20641 Displays the current state of observer debugging.
20642 @item set debug overload
20643 @cindex C@t{++} overload debugging info
20644 Turns on or off display of @value{GDBN} C@t{++} overload debugging
20645 info. This includes info such as ranking of functions, etc. The default
20647 @item show debug overload
20648 Displays the current state of displaying @value{GDBN} C@t{++} overload
20650 @cindex expression parser, debugging info
20651 @cindex debug expression parser
20652 @item set debug parser
20653 Turns on or off the display of expression parser debugging output.
20654 Internally, this sets the @code{yydebug} variable in the expression
20655 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
20656 details. The default is off.
20657 @item show debug parser
20658 Show the current state of expression parser debugging.
20659 @cindex packets, reporting on stdout
20660 @cindex serial connections, debugging
20661 @cindex debug remote protocol
20662 @cindex remote protocol debugging
20663 @cindex display remote packets
20664 @item set debug remote
20665 Turns on or off display of reports on all packets sent back and forth across
20666 the serial line to the remote machine. The info is printed on the
20667 @value{GDBN} standard output stream. The default is off.
20668 @item show debug remote
20669 Displays the state of display of remote packets.
20670 @item set debug serial
20671 Turns on or off display of @value{GDBN} serial debugging info. The
20673 @item show debug serial
20674 Displays the current state of displaying @value{GDBN} serial debugging
20676 @item set debug solib-frv
20677 @cindex FR-V shared-library debugging
20678 Turns on or off debugging messages for FR-V shared-library code.
20679 @item show debug solib-frv
20680 Display the current state of FR-V shared-library code debugging
20682 @item set debug target
20683 @cindex target debugging info
20684 Turns on or off display of @value{GDBN} target debugging info. This info
20685 includes what is going on at the target level of GDB, as it happens. The
20686 default is 0. Set it to 1 to track events, and to 2 to also track the
20687 value of large memory transfers. Changes to this flag do not take effect
20688 until the next time you connect to a target or use the @code{run} command.
20689 @item show debug target
20690 Displays the current state of displaying @value{GDBN} target debugging
20692 @item set debug timestamp
20693 @cindex timestampping debugging info
20694 Turns on or off display of timestamps with @value{GDBN} debugging info.
20695 When enabled, seconds and microseconds are displayed before each debugging
20697 @item show debug timestamp
20698 Displays the current state of displaying timestamps with @value{GDBN}
20700 @item set debugvarobj
20701 @cindex variable object debugging info
20702 Turns on or off display of @value{GDBN} variable object debugging
20703 info. The default is off.
20704 @item show debugvarobj
20705 Displays the current state of displaying @value{GDBN} variable object
20707 @item set debug xml
20708 @cindex XML parser debugging
20709 Turns on or off debugging messages for built-in XML parsers.
20710 @item show debug xml
20711 Displays the current state of XML debugging messages.
20714 @node Other Misc Settings
20715 @section Other Miscellaneous Settings
20716 @cindex miscellaneous settings
20719 @kindex set interactive-mode
20720 @item set interactive-mode
20721 If @code{on}, forces @value{GDBN} to assume that GDB was started
20722 in a terminal. In practice, this means that @value{GDBN} should wait
20723 for the user to answer queries generated by commands entered at
20724 the command prompt. If @code{off}, forces @value{GDBN} to operate
20725 in the opposite mode, and it uses the default answers to all queries.
20726 If @code{auto} (the default), @value{GDBN} tries to determine whether
20727 its standard input is a terminal, and works in interactive-mode if it
20728 is, non-interactively otherwise.
20730 In the vast majority of cases, the debugger should be able to guess
20731 correctly which mode should be used. But this setting can be useful
20732 in certain specific cases, such as running a MinGW @value{GDBN}
20733 inside a cygwin window.
20735 @kindex show interactive-mode
20736 @item show interactive-mode
20737 Displays whether the debugger is operating in interactive mode or not.
20740 @node Extending GDB
20741 @chapter Extending @value{GDBN}
20742 @cindex extending GDB
20744 @value{GDBN} provides three mechanisms for extension. The first is based
20745 on composition of @value{GDBN} commands, the second is based on the
20746 Python scripting language, and the third is for defining new aliases of
20749 To facilitate the use of the first two extensions, @value{GDBN} is capable
20750 of evaluating the contents of a file. When doing so, @value{GDBN}
20751 can recognize which scripting language is being used by looking at
20752 the filename extension. Files with an unrecognized filename extension
20753 are always treated as a @value{GDBN} Command Files.
20754 @xref{Command Files,, Command files}.
20756 You can control how @value{GDBN} evaluates these files with the following
20760 @kindex set script-extension
20761 @kindex show script-extension
20762 @item set script-extension off
20763 All scripts are always evaluated as @value{GDBN} Command Files.
20765 @item set script-extension soft
20766 The debugger determines the scripting language based on filename
20767 extension. If this scripting language is supported, @value{GDBN}
20768 evaluates the script using that language. Otherwise, it evaluates
20769 the file as a @value{GDBN} Command File.
20771 @item set script-extension strict
20772 The debugger determines the scripting language based on filename
20773 extension, and evaluates the script using that language. If the
20774 language is not supported, then the evaluation fails.
20776 @item show script-extension
20777 Display the current value of the @code{script-extension} option.
20782 * Sequences:: Canned Sequences of Commands
20783 * Python:: Scripting @value{GDBN} using Python
20784 * Aliases:: Creating new spellings of existing commands
20788 @section Canned Sequences of Commands
20790 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
20791 Command Lists}), @value{GDBN} provides two ways to store sequences of
20792 commands for execution as a unit: user-defined commands and command
20796 * Define:: How to define your own commands
20797 * Hooks:: Hooks for user-defined commands
20798 * Command Files:: How to write scripts of commands to be stored in a file
20799 * Output:: Commands for controlled output
20803 @subsection User-defined Commands
20805 @cindex user-defined command
20806 @cindex arguments, to user-defined commands
20807 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
20808 which you assign a new name as a command. This is done with the
20809 @code{define} command. User commands may accept up to 10 arguments
20810 separated by whitespace. Arguments are accessed within the user command
20811 via @code{$arg0@dots{}$arg9}. A trivial example:
20815 print $arg0 + $arg1 + $arg2
20820 To execute the command use:
20827 This defines the command @code{adder}, which prints the sum of
20828 its three arguments. Note the arguments are text substitutions, so they may
20829 reference variables, use complex expressions, or even perform inferior
20832 @cindex argument count in user-defined commands
20833 @cindex how many arguments (user-defined commands)
20834 In addition, @code{$argc} may be used to find out how many arguments have
20835 been passed. This expands to a number in the range 0@dots{}10.
20840 print $arg0 + $arg1
20843 print $arg0 + $arg1 + $arg2
20851 @item define @var{commandname}
20852 Define a command named @var{commandname}. If there is already a command
20853 by that name, you are asked to confirm that you want to redefine it.
20854 @var{commandname} may be a bare command name consisting of letters,
20855 numbers, dashes, and underscores. It may also start with any predefined
20856 prefix command. For example, @samp{define target my-target} creates
20857 a user-defined @samp{target my-target} command.
20859 The definition of the command is made up of other @value{GDBN} command lines,
20860 which are given following the @code{define} command. The end of these
20861 commands is marked by a line containing @code{end}.
20864 @kindex end@r{ (user-defined commands)}
20865 @item document @var{commandname}
20866 Document the user-defined command @var{commandname}, so that it can be
20867 accessed by @code{help}. The command @var{commandname} must already be
20868 defined. This command reads lines of documentation just as @code{define}
20869 reads the lines of the command definition, ending with @code{end}.
20870 After the @code{document} command is finished, @code{help} on command
20871 @var{commandname} displays the documentation you have written.
20873 You may use the @code{document} command again to change the
20874 documentation of a command. Redefining the command with @code{define}
20875 does not change the documentation.
20877 @kindex dont-repeat
20878 @cindex don't repeat command
20880 Used inside a user-defined command, this tells @value{GDBN} that this
20881 command should not be repeated when the user hits @key{RET}
20882 (@pxref{Command Syntax, repeat last command}).
20884 @kindex help user-defined
20885 @item help user-defined
20886 List all user-defined commands, with the first line of the documentation
20891 @itemx show user @var{commandname}
20892 Display the @value{GDBN} commands used to define @var{commandname} (but
20893 not its documentation). If no @var{commandname} is given, display the
20894 definitions for all user-defined commands.
20896 @cindex infinite recursion in user-defined commands
20897 @kindex show max-user-call-depth
20898 @kindex set max-user-call-depth
20899 @item show max-user-call-depth
20900 @itemx set max-user-call-depth
20901 The value of @code{max-user-call-depth} controls how many recursion
20902 levels are allowed in user-defined commands before @value{GDBN} suspects an
20903 infinite recursion and aborts the command.
20906 In addition to the above commands, user-defined commands frequently
20907 use control flow commands, described in @ref{Command Files}.
20909 When user-defined commands are executed, the
20910 commands of the definition are not printed. An error in any command
20911 stops execution of the user-defined command.
20913 If used interactively, commands that would ask for confirmation proceed
20914 without asking when used inside a user-defined command. Many @value{GDBN}
20915 commands that normally print messages to say what they are doing omit the
20916 messages when used in a user-defined command.
20919 @subsection User-defined Command Hooks
20920 @cindex command hooks
20921 @cindex hooks, for commands
20922 @cindex hooks, pre-command
20925 You may define @dfn{hooks}, which are a special kind of user-defined
20926 command. Whenever you run the command @samp{foo}, if the user-defined
20927 command @samp{hook-foo} exists, it is executed (with no arguments)
20928 before that command.
20930 @cindex hooks, post-command
20932 A hook may also be defined which is run after the command you executed.
20933 Whenever you run the command @samp{foo}, if the user-defined command
20934 @samp{hookpost-foo} exists, it is executed (with no arguments) after
20935 that command. Post-execution hooks may exist simultaneously with
20936 pre-execution hooks, for the same command.
20938 It is valid for a hook to call the command which it hooks. If this
20939 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
20941 @c It would be nice if hookpost could be passed a parameter indicating
20942 @c if the command it hooks executed properly or not. FIXME!
20944 @kindex stop@r{, a pseudo-command}
20945 In addition, a pseudo-command, @samp{stop} exists. Defining
20946 (@samp{hook-stop}) makes the associated commands execute every time
20947 execution stops in your program: before breakpoint commands are run,
20948 displays are printed, or the stack frame is printed.
20950 For example, to ignore @code{SIGALRM} signals while
20951 single-stepping, but treat them normally during normal execution,
20956 handle SIGALRM nopass
20960 handle SIGALRM pass
20963 define hook-continue
20964 handle SIGALRM pass
20968 As a further example, to hook at the beginning and end of the @code{echo}
20969 command, and to add extra text to the beginning and end of the message,
20977 define hookpost-echo
20981 (@value{GDBP}) echo Hello World
20982 <<<---Hello World--->>>
20987 You can define a hook for any single-word command in @value{GDBN}, but
20988 not for command aliases; you should define a hook for the basic command
20989 name, e.g.@: @code{backtrace} rather than @code{bt}.
20990 @c FIXME! So how does Joe User discover whether a command is an alias
20992 You can hook a multi-word command by adding @code{hook-} or
20993 @code{hookpost-} to the last word of the command, e.g.@:
20994 @samp{define target hook-remote} to add a hook to @samp{target remote}.
20996 If an error occurs during the execution of your hook, execution of
20997 @value{GDBN} commands stops and @value{GDBN} issues a prompt
20998 (before the command that you actually typed had a chance to run).
21000 If you try to define a hook which does not match any known command, you
21001 get a warning from the @code{define} command.
21003 @node Command Files
21004 @subsection Command Files
21006 @cindex command files
21007 @cindex scripting commands
21008 A command file for @value{GDBN} is a text file made of lines that are
21009 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
21010 also be included. An empty line in a command file does nothing; it
21011 does not mean to repeat the last command, as it would from the
21014 You can request the execution of a command file with the @code{source}
21015 command. Note that the @code{source} command is also used to evaluate
21016 scripts that are not Command Files. The exact behavior can be configured
21017 using the @code{script-extension} setting.
21018 @xref{Extending GDB,, Extending GDB}.
21022 @cindex execute commands from a file
21023 @item source [-s] [-v] @var{filename}
21024 Execute the command file @var{filename}.
21027 The lines in a command file are generally executed sequentially,
21028 unless the order of execution is changed by one of the
21029 @emph{flow-control commands} described below. The commands are not
21030 printed as they are executed. An error in any command terminates
21031 execution of the command file and control is returned to the console.
21033 @value{GDBN} first searches for @var{filename} in the current directory.
21034 If the file is not found there, and @var{filename} does not specify a
21035 directory, then @value{GDBN} also looks for the file on the source search path
21036 (specified with the @samp{directory} command);
21037 except that @file{$cdir} is not searched because the compilation directory
21038 is not relevant to scripts.
21040 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
21041 on the search path even if @var{filename} specifies a directory.
21042 The search is done by appending @var{filename} to each element of the
21043 search path. So, for example, if @var{filename} is @file{mylib/myscript}
21044 and the search path contains @file{/home/user} then @value{GDBN} will
21045 look for the script @file{/home/user/mylib/myscript}.
21046 The search is also done if @var{filename} is an absolute path.
21047 For example, if @var{filename} is @file{/tmp/myscript} and
21048 the search path contains @file{/home/user} then @value{GDBN} will
21049 look for the script @file{/home/user/tmp/myscript}.
21050 For DOS-like systems, if @var{filename} contains a drive specification,
21051 it is stripped before concatenation. For example, if @var{filename} is
21052 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
21053 will look for the script @file{c:/tmp/myscript}.
21055 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
21056 each command as it is executed. The option must be given before
21057 @var{filename}, and is interpreted as part of the filename anywhere else.
21059 Commands that would ask for confirmation if used interactively proceed
21060 without asking when used in a command file. Many @value{GDBN} commands that
21061 normally print messages to say what they are doing omit the messages
21062 when called from command files.
21064 @value{GDBN} also accepts command input from standard input. In this
21065 mode, normal output goes to standard output and error output goes to
21066 standard error. Errors in a command file supplied on standard input do
21067 not terminate execution of the command file---execution continues with
21071 gdb < cmds > log 2>&1
21074 (The syntax above will vary depending on the shell used.) This example
21075 will execute commands from the file @file{cmds}. All output and errors
21076 would be directed to @file{log}.
21078 Since commands stored on command files tend to be more general than
21079 commands typed interactively, they frequently need to deal with
21080 complicated situations, such as different or unexpected values of
21081 variables and symbols, changes in how the program being debugged is
21082 built, etc. @value{GDBN} provides a set of flow-control commands to
21083 deal with these complexities. Using these commands, you can write
21084 complex scripts that loop over data structures, execute commands
21085 conditionally, etc.
21092 This command allows to include in your script conditionally executed
21093 commands. The @code{if} command takes a single argument, which is an
21094 expression to evaluate. It is followed by a series of commands that
21095 are executed only if the expression is true (its value is nonzero).
21096 There can then optionally be an @code{else} line, followed by a series
21097 of commands that are only executed if the expression was false. The
21098 end of the list is marked by a line containing @code{end}.
21102 This command allows to write loops. Its syntax is similar to
21103 @code{if}: the command takes a single argument, which is an expression
21104 to evaluate, and must be followed by the commands to execute, one per
21105 line, terminated by an @code{end}. These commands are called the
21106 @dfn{body} of the loop. The commands in the body of @code{while} are
21107 executed repeatedly as long as the expression evaluates to true.
21111 This command exits the @code{while} loop in whose body it is included.
21112 Execution of the script continues after that @code{while}s @code{end}
21115 @kindex loop_continue
21116 @item loop_continue
21117 This command skips the execution of the rest of the body of commands
21118 in the @code{while} loop in whose body it is included. Execution
21119 branches to the beginning of the @code{while} loop, where it evaluates
21120 the controlling expression.
21122 @kindex end@r{ (if/else/while commands)}
21124 Terminate the block of commands that are the body of @code{if},
21125 @code{else}, or @code{while} flow-control commands.
21130 @subsection Commands for Controlled Output
21132 During the execution of a command file or a user-defined command, normal
21133 @value{GDBN} output is suppressed; the only output that appears is what is
21134 explicitly printed by the commands in the definition. This section
21135 describes three commands useful for generating exactly the output you
21140 @item echo @var{text}
21141 @c I do not consider backslash-space a standard C escape sequence
21142 @c because it is not in ANSI.
21143 Print @var{text}. Nonprinting characters can be included in
21144 @var{text} using C escape sequences, such as @samp{\n} to print a
21145 newline. @strong{No newline is printed unless you specify one.}
21146 In addition to the standard C escape sequences, a backslash followed
21147 by a space stands for a space. This is useful for displaying a
21148 string with spaces at the beginning or the end, since leading and
21149 trailing spaces are otherwise trimmed from all arguments.
21150 To print @samp{@w{ }and foo =@w{ }}, use the command
21151 @samp{echo \@w{ }and foo = \@w{ }}.
21153 A backslash at the end of @var{text} can be used, as in C, to continue
21154 the command onto subsequent lines. For example,
21157 echo This is some text\n\
21158 which is continued\n\
21159 onto several lines.\n
21162 produces the same output as
21165 echo This is some text\n
21166 echo which is continued\n
21167 echo onto several lines.\n
21171 @item output @var{expression}
21172 Print the value of @var{expression} and nothing but that value: no
21173 newlines, no @samp{$@var{nn} = }. The value is not entered in the
21174 value history either. @xref{Expressions, ,Expressions}, for more information
21177 @item output/@var{fmt} @var{expression}
21178 Print the value of @var{expression} in format @var{fmt}. You can use
21179 the same formats as for @code{print}. @xref{Output Formats,,Output
21180 Formats}, for more information.
21183 @item printf @var{template}, @var{expressions}@dots{}
21184 Print the values of one or more @var{expressions} under the control of
21185 the string @var{template}. To print several values, make
21186 @var{expressions} be a comma-separated list of individual expressions,
21187 which may be either numbers or pointers. Their values are printed as
21188 specified by @var{template}, exactly as a C program would do by
21189 executing the code below:
21192 printf (@var{template}, @var{expressions}@dots{});
21195 As in @code{C} @code{printf}, ordinary characters in @var{template}
21196 are printed verbatim, while @dfn{conversion specification} introduced
21197 by the @samp{%} character cause subsequent @var{expressions} to be
21198 evaluated, their values converted and formatted according to type and
21199 style information encoded in the conversion specifications, and then
21202 For example, you can print two values in hex like this:
21205 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
21208 @code{printf} supports all the standard @code{C} conversion
21209 specifications, including the flags and modifiers between the @samp{%}
21210 character and the conversion letter, with the following exceptions:
21214 The argument-ordering modifiers, such as @samp{2$}, are not supported.
21217 The modifier @samp{*} is not supported for specifying precision or
21221 The @samp{'} flag (for separation of digits into groups according to
21222 @code{LC_NUMERIC'}) is not supported.
21225 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
21229 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
21232 The conversion letters @samp{a} and @samp{A} are not supported.
21236 Note that the @samp{ll} type modifier is supported only if the
21237 underlying @code{C} implementation used to build @value{GDBN} supports
21238 the @code{long long int} type, and the @samp{L} type modifier is
21239 supported only if @code{long double} type is available.
21241 As in @code{C}, @code{printf} supports simple backslash-escape
21242 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
21243 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
21244 single character. Octal and hexadecimal escape sequences are not
21247 Additionally, @code{printf} supports conversion specifications for DFP
21248 (@dfn{Decimal Floating Point}) types using the following length modifiers
21249 together with a floating point specifier.
21254 @samp{H} for printing @code{Decimal32} types.
21257 @samp{D} for printing @code{Decimal64} types.
21260 @samp{DD} for printing @code{Decimal128} types.
21263 If the underlying @code{C} implementation used to build @value{GDBN} has
21264 support for the three length modifiers for DFP types, other modifiers
21265 such as width and precision will also be available for @value{GDBN} to use.
21267 In case there is no such @code{C} support, no additional modifiers will be
21268 available and the value will be printed in the standard way.
21270 Here's an example of printing DFP types using the above conversion letters:
21272 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
21276 @item eval @var{template}, @var{expressions}@dots{}
21277 Convert the values of one or more @var{expressions} under the control of
21278 the string @var{template} to a command line, and call it.
21283 @section Scripting @value{GDBN} using Python
21284 @cindex python scripting
21285 @cindex scripting with python
21287 You can script @value{GDBN} using the @uref{http://www.python.org/,
21288 Python programming language}. This feature is available only if
21289 @value{GDBN} was configured using @option{--with-python}.
21291 @cindex python directory
21292 Python scripts used by @value{GDBN} should be installed in
21293 @file{@var{data-directory}/python}, where @var{data-directory} is
21294 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
21295 This directory, known as the @dfn{python directory},
21296 is automatically added to the Python Search Path in order to allow
21297 the Python interpreter to locate all scripts installed at this location.
21299 Additionally, @value{GDBN} commands and convenience functions which
21300 are written in Python and are located in the
21301 @file{@var{data-directory}/python/gdb/command} or
21302 @file{@var{data-directory}/python/gdb/function} directories are
21303 automatically imported when @value{GDBN} starts.
21306 * Python Commands:: Accessing Python from @value{GDBN}.
21307 * Python API:: Accessing @value{GDBN} from Python.
21308 * Auto-loading:: Automatically loading Python code.
21309 * Python modules:: Python modules provided by @value{GDBN}.
21312 @node Python Commands
21313 @subsection Python Commands
21314 @cindex python commands
21315 @cindex commands to access python
21317 @value{GDBN} provides one command for accessing the Python interpreter,
21318 and one related setting:
21322 @item python @r{[}@var{code}@r{]}
21323 The @code{python} command can be used to evaluate Python code.
21325 If given an argument, the @code{python} command will evaluate the
21326 argument as a Python command. For example:
21329 (@value{GDBP}) python print 23
21333 If you do not provide an argument to @code{python}, it will act as a
21334 multi-line command, like @code{define}. In this case, the Python
21335 script is made up of subsequent command lines, given after the
21336 @code{python} command. This command list is terminated using a line
21337 containing @code{end}. For example:
21340 (@value{GDBP}) python
21342 End with a line saying just "end".
21348 @kindex maint set python print-stack
21349 @item maint set python print-stack
21350 This command is now deprecated. Instead use @code{set python
21353 @kindex set python print-stack
21354 @item set python print-stack
21355 By default, @value{GDBN} will not print a stack trace when an error
21356 occurs in a Python script. This can be controlled using @code{set
21357 python print-stack}: if @code{on}, then Python stack printing is
21358 enabled; if @code{off}, the default, then Python stack printing is
21362 It is also possible to execute a Python script from the @value{GDBN}
21366 @item source @file{script-name}
21367 The script name must end with @samp{.py} and @value{GDBN} must be configured
21368 to recognize the script language based on filename extension using
21369 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
21371 @item python execfile ("script-name")
21372 This method is based on the @code{execfile} Python built-in function,
21373 and thus is always available.
21377 @subsection Python API
21379 @cindex programming in python
21381 @cindex python stdout
21382 @cindex python pagination
21383 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
21384 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
21385 A Python program which outputs to one of these streams may have its
21386 output interrupted by the user (@pxref{Screen Size}). In this
21387 situation, a Python @code{KeyboardInterrupt} exception is thrown.
21390 * Basic Python:: Basic Python Functions.
21391 * Exception Handling:: How Python exceptions are translated.
21392 * Values From Inferior:: Python representation of values.
21393 * Types In Python:: Python representation of types.
21394 * Pretty Printing API:: Pretty-printing values.
21395 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
21396 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
21397 * Inferiors In Python:: Python representation of inferiors (processes)
21398 * Events In Python:: Listening for events from @value{GDBN}.
21399 * Threads In Python:: Accessing inferior threads from Python.
21400 * Commands In Python:: Implementing new commands in Python.
21401 * Parameters In Python:: Adding new @value{GDBN} parameters.
21402 * Functions In Python:: Writing new convenience functions.
21403 * Progspaces In Python:: Program spaces.
21404 * Objfiles In Python:: Object files.
21405 * Frames In Python:: Accessing inferior stack frames from Python.
21406 * Blocks In Python:: Accessing frame blocks from Python.
21407 * Symbols In Python:: Python representation of symbols.
21408 * Symbol Tables In Python:: Python representation of symbol tables.
21409 * Lazy Strings In Python:: Python representation of lazy strings.
21410 * Breakpoints In Python:: Manipulating breakpoints using Python.
21414 @subsubsection Basic Python
21416 @cindex python functions
21417 @cindex python module
21419 @value{GDBN} introduces a new Python module, named @code{gdb}. All
21420 methods and classes added by @value{GDBN} are placed in this module.
21421 @value{GDBN} automatically @code{import}s the @code{gdb} module for
21422 use in all scripts evaluated by the @code{python} command.
21424 @findex gdb.PYTHONDIR
21425 @defvar gdb.PYTHONDIR
21426 A string containing the python directory (@pxref{Python}).
21429 @findex gdb.execute
21430 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
21431 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
21432 If a GDB exception happens while @var{command} runs, it is
21433 translated as described in @ref{Exception Handling,,Exception Handling}.
21435 @var{from_tty} specifies whether @value{GDBN} ought to consider this
21436 command as having originated from the user invoking it interactively.
21437 It must be a boolean value. If omitted, it defaults to @code{False}.
21439 By default, any output produced by @var{command} is sent to
21440 @value{GDBN}'s standard output. If the @var{to_string} parameter is
21441 @code{True}, then output will be collected by @code{gdb.execute} and
21442 returned as a string. The default is @code{False}, in which case the
21443 return value is @code{None}. If @var{to_string} is @code{True}, the
21444 @value{GDBN} virtual terminal will be temporarily set to unlimited width
21445 and height, and its pagination will be disabled; @pxref{Screen Size}.
21448 @findex gdb.breakpoints
21449 @defun gdb.breakpoints ()
21450 Return a sequence holding all of @value{GDBN}'s breakpoints.
21451 @xref{Breakpoints In Python}, for more information.
21454 @findex gdb.parameter
21455 @defun gdb.parameter (parameter)
21456 Return the value of a @value{GDBN} parameter. @var{parameter} is a
21457 string naming the parameter to look up; @var{parameter} may contain
21458 spaces if the parameter has a multi-part name. For example,
21459 @samp{print object} is a valid parameter name.
21461 If the named parameter does not exist, this function throws a
21462 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
21463 parameter's value is converted to a Python value of the appropriate
21464 type, and returned.
21467 @findex gdb.history
21468 @defun gdb.history (number)
21469 Return a value from @value{GDBN}'s value history (@pxref{Value
21470 History}). @var{number} indicates which history element to return.
21471 If @var{number} is negative, then @value{GDBN} will take its absolute value
21472 and count backward from the last element (i.e., the most recent element) to
21473 find the value to return. If @var{number} is zero, then @value{GDBN} will
21474 return the most recent element. If the element specified by @var{number}
21475 doesn't exist in the value history, a @code{gdb.error} exception will be
21478 If no exception is raised, the return value is always an instance of
21479 @code{gdb.Value} (@pxref{Values From Inferior}).
21482 @findex gdb.parse_and_eval
21483 @defun gdb.parse_and_eval (expression)
21484 Parse @var{expression} as an expression in the current language,
21485 evaluate it, and return the result as a @code{gdb.Value}.
21486 @var{expression} must be a string.
21488 This function can be useful when implementing a new command
21489 (@pxref{Commands In Python}), as it provides a way to parse the
21490 command's argument as an expression. It is also useful simply to
21491 compute values, for example, it is the only way to get the value of a
21492 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
21495 @findex gdb.post_event
21496 @defun gdb.post_event (event)
21497 Put @var{event}, a callable object taking no arguments, into
21498 @value{GDBN}'s internal event queue. This callable will be invoked at
21499 some later point, during @value{GDBN}'s event processing. Events
21500 posted using @code{post_event} will be run in the order in which they
21501 were posted; however, there is no way to know when they will be
21502 processed relative to other events inside @value{GDBN}.
21504 @value{GDBN} is not thread-safe. If your Python program uses multiple
21505 threads, you must be careful to only call @value{GDBN}-specific
21506 functions in the main @value{GDBN} thread. @code{post_event} ensures
21510 (@value{GDBP}) python
21514 > def __init__(self, message):
21515 > self.message = message;
21516 > def __call__(self):
21517 > gdb.write(self.message)
21519 >class MyThread1 (threading.Thread):
21521 > gdb.post_event(Writer("Hello "))
21523 >class MyThread2 (threading.Thread):
21525 > gdb.post_event(Writer("World\n"))
21527 >MyThread1().start()
21528 >MyThread2().start()
21530 (@value{GDBP}) Hello World
21535 @defun gdb.write (string @r{[}, stream{]})
21536 Print a string to @value{GDBN}'s paginated output stream. The
21537 optional @var{stream} determines the stream to print to. The default
21538 stream is @value{GDBN}'s standard output stream. Possible stream
21545 @value{GDBN}'s standard output stream.
21550 @value{GDBN}'s standard error stream.
21555 @value{GDBN}'s log stream (@pxref{Logging Output}).
21558 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
21559 call this function and will automatically direct the output to the
21564 @defun gdb.flush ()
21565 Flush the buffer of a @value{GDBN} paginated stream so that the
21566 contents are displayed immediately. @value{GDBN} will flush the
21567 contents of a stream automatically when it encounters a newline in the
21568 buffer. The optional @var{stream} determines the stream to flush. The
21569 default stream is @value{GDBN}'s standard output stream. Possible
21576 @value{GDBN}'s standard output stream.
21581 @value{GDBN}'s standard error stream.
21586 @value{GDBN}'s log stream (@pxref{Logging Output}).
21590 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
21591 call this function for the relevant stream.
21594 @findex gdb.target_charset
21595 @defun gdb.target_charset ()
21596 Return the name of the current target character set (@pxref{Character
21597 Sets}). This differs from @code{gdb.parameter('target-charset')} in
21598 that @samp{auto} is never returned.
21601 @findex gdb.target_wide_charset
21602 @defun gdb.target_wide_charset ()
21603 Return the name of the current target wide character set
21604 (@pxref{Character Sets}). This differs from
21605 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
21609 @findex gdb.solib_name
21610 @defun gdb.solib_name (address)
21611 Return the name of the shared library holding the given @var{address}
21612 as a string, or @code{None}.
21615 @findex gdb.decode_line
21616 @defun gdb.decode_line @r{[}expression@r{]}
21617 Return locations of the line specified by @var{expression}, or of the
21618 current line if no argument was given. This function returns a Python
21619 tuple containing two elements. The first element contains a string
21620 holding any unparsed section of @var{expression} (or @code{None} if
21621 the expression has been fully parsed). The second element contains
21622 either @code{None} or another tuple that contains all the locations
21623 that match the expression represented as @code{gdb.Symtab_and_line}
21624 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
21625 provided, it is decoded the way that @value{GDBN}'s inbuilt
21626 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
21629 @defun gdb.prompt_hook (current_prompt)
21630 @anchor{prompt_hook}
21632 If @var{prompt_hook} is callable, @value{GDBN} will call the method
21633 assigned to this operation before a prompt is displayed by
21636 The parameter @code{current_prompt} contains the current @value{GDBN}
21637 prompt. This method must return a Python string, or @code{None}. If
21638 a string is returned, the @value{GDBN} prompt will be set to that
21639 string. If @code{None} is returned, @value{GDBN} will continue to use
21640 the current prompt.
21642 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
21643 such as those used by readline for command input, and annotation
21644 related prompts are prohibited from being changed.
21647 @node Exception Handling
21648 @subsubsection Exception Handling
21649 @cindex python exceptions
21650 @cindex exceptions, python
21652 When executing the @code{python} command, Python exceptions
21653 uncaught within the Python code are translated to calls to
21654 @value{GDBN} error-reporting mechanism. If the command that called
21655 @code{python} does not handle the error, @value{GDBN} will
21656 terminate it and print an error message containing the Python
21657 exception name, the associated value, and the Python call stack
21658 backtrace at the point where the exception was raised. Example:
21661 (@value{GDBP}) python print foo
21662 Traceback (most recent call last):
21663 File "<string>", line 1, in <module>
21664 NameError: name 'foo' is not defined
21667 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
21668 Python code are converted to Python exceptions. The type of the
21669 Python exception depends on the error.
21673 This is the base class for most exceptions generated by @value{GDBN}.
21674 It is derived from @code{RuntimeError}, for compatibility with earlier
21675 versions of @value{GDBN}.
21677 If an error occurring in @value{GDBN} does not fit into some more
21678 specific category, then the generated exception will have this type.
21680 @item gdb.MemoryError
21681 This is a subclass of @code{gdb.error} which is thrown when an
21682 operation tried to access invalid memory in the inferior.
21684 @item KeyboardInterrupt
21685 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
21686 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
21689 In all cases, your exception handler will see the @value{GDBN} error
21690 message as its value and the Python call stack backtrace at the Python
21691 statement closest to where the @value{GDBN} error occured as the
21694 @findex gdb.GdbError
21695 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
21696 it is useful to be able to throw an exception that doesn't cause a
21697 traceback to be printed. For example, the user may have invoked the
21698 command incorrectly. Use the @code{gdb.GdbError} exception
21699 to handle this case. Example:
21703 >class HelloWorld (gdb.Command):
21704 > """Greet the whole world."""
21705 > def __init__ (self):
21706 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
21707 > def invoke (self, args, from_tty):
21708 > argv = gdb.string_to_argv (args)
21709 > if len (argv) != 0:
21710 > raise gdb.GdbError ("hello-world takes no arguments")
21711 > print "Hello, World!"
21714 (gdb) hello-world 42
21715 hello-world takes no arguments
21718 @node Values From Inferior
21719 @subsubsection Values From Inferior
21720 @cindex values from inferior, with Python
21721 @cindex python, working with values from inferior
21723 @cindex @code{gdb.Value}
21724 @value{GDBN} provides values it obtains from the inferior program in
21725 an object of type @code{gdb.Value}. @value{GDBN} uses this object
21726 for its internal bookkeeping of the inferior's values, and for
21727 fetching values when necessary.
21729 Inferior values that are simple scalars can be used directly in
21730 Python expressions that are valid for the value's data type. Here's
21731 an example for an integer or floating-point value @code{some_val}:
21738 As result of this, @code{bar} will also be a @code{gdb.Value} object
21739 whose values are of the same type as those of @code{some_val}.
21741 Inferior values that are structures or instances of some class can
21742 be accessed using the Python @dfn{dictionary syntax}. For example, if
21743 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
21744 can access its @code{foo} element with:
21747 bar = some_val['foo']
21750 Again, @code{bar} will also be a @code{gdb.Value} object.
21752 A @code{gdb.Value} that represents a function can be executed via
21753 inferior function call. Any arguments provided to the call must match
21754 the function's prototype, and must be provided in the order specified
21757 For example, @code{some_val} is a @code{gdb.Value} instance
21758 representing a function that takes two integers as arguments. To
21759 execute this function, call it like so:
21762 result = some_val (10,20)
21765 Any values returned from a function call will be stored as a
21768 The following attributes are provided:
21771 @defvar Value.address
21772 If this object is addressable, this read-only attribute holds a
21773 @code{gdb.Value} object representing the address. Otherwise,
21774 this attribute holds @code{None}.
21777 @cindex optimized out value in Python
21778 @defvar Value.is_optimized_out
21779 This read-only boolean attribute is true if the compiler optimized out
21780 this value, thus it is not available for fetching from the inferior.
21784 The type of this @code{gdb.Value}. The value of this attribute is a
21785 @code{gdb.Type} object (@pxref{Types In Python}).
21788 @defvar Value.dynamic_type
21789 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
21790 type information (@acronym{RTTI}) to determine the dynamic type of the
21791 value. If this value is of class type, it will return the class in
21792 which the value is embedded, if any. If this value is of pointer or
21793 reference to a class type, it will compute the dynamic type of the
21794 referenced object, and return a pointer or reference to that type,
21795 respectively. In all other cases, it will return the value's static
21798 Note that this feature will only work when debugging a C@t{++} program
21799 that includes @acronym{RTTI} for the object in question. Otherwise,
21800 it will just return the static type of the value as in @kbd{ptype foo}
21801 (@pxref{Symbols, ptype}).
21804 @defvar Value.is_lazy
21805 The value of this read-only boolean attribute is @code{True} if this
21806 @code{gdb.Value} has not yet been fetched from the inferior.
21807 @value{GDBN} does not fetch values until necessary, for efficiency.
21811 myval = gdb.parse_and_eval ('somevar')
21814 The value of @code{somevar} is not fetched at this time. It will be
21815 fetched when the value is needed, or when the @code{fetch_lazy}
21820 The following methods are provided:
21823 @defun Value.__init__ (@var{val})
21824 Many Python values can be converted directly to a @code{gdb.Value} via
21825 this object initializer. Specifically:
21828 @item Python boolean
21829 A Python boolean is converted to the boolean type from the current
21832 @item Python integer
21833 A Python integer is converted to the C @code{long} type for the
21834 current architecture.
21837 A Python long is converted to the C @code{long long} type for the
21838 current architecture.
21841 A Python float is converted to the C @code{double} type for the
21842 current architecture.
21844 @item Python string
21845 A Python string is converted to a target string, using the current
21848 @item @code{gdb.Value}
21849 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
21851 @item @code{gdb.LazyString}
21852 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
21853 Python}), then the lazy string's @code{value} method is called, and
21854 its result is used.
21858 @defun Value.cast (type)
21859 Return a new instance of @code{gdb.Value} that is the result of
21860 casting this instance to the type described by @var{type}, which must
21861 be a @code{gdb.Type} object. If the cast cannot be performed for some
21862 reason, this method throws an exception.
21865 @defun Value.dereference ()
21866 For pointer data types, this method returns a new @code{gdb.Value} object
21867 whose contents is the object pointed to by the pointer. For example, if
21868 @code{foo} is a C pointer to an @code{int}, declared in your C program as
21875 then you can use the corresponding @code{gdb.Value} to access what
21876 @code{foo} points to like this:
21879 bar = foo.dereference ()
21882 The result @code{bar} will be a @code{gdb.Value} object holding the
21883 value pointed to by @code{foo}.
21886 @defun Value.dynamic_cast (type)
21887 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
21888 operator were used. Consult a C@t{++} reference for details.
21891 @defun Value.reinterpret_cast (type)
21892 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
21893 operator were used. Consult a C@t{++} reference for details.
21896 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
21897 If this @code{gdb.Value} represents a string, then this method
21898 converts the contents to a Python string. Otherwise, this method will
21899 throw an exception.
21901 Strings are recognized in a language-specific way; whether a given
21902 @code{gdb.Value} represents a string is determined by the current
21905 For C-like languages, a value is a string if it is a pointer to or an
21906 array of characters or ints. The string is assumed to be terminated
21907 by a zero of the appropriate width. However if the optional length
21908 argument is given, the string will be converted to that given length,
21909 ignoring any embedded zeros that the string may contain.
21911 If the optional @var{encoding} argument is given, it must be a string
21912 naming the encoding of the string in the @code{gdb.Value}, such as
21913 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
21914 the same encodings as the corresponding argument to Python's
21915 @code{string.decode} method, and the Python codec machinery will be used
21916 to convert the string. If @var{encoding} is not given, or if
21917 @var{encoding} is the empty string, then either the @code{target-charset}
21918 (@pxref{Character Sets}) will be used, or a language-specific encoding
21919 will be used, if the current language is able to supply one.
21921 The optional @var{errors} argument is the same as the corresponding
21922 argument to Python's @code{string.decode} method.
21924 If the optional @var{length} argument is given, the string will be
21925 fetched and converted to the given length.
21928 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
21929 If this @code{gdb.Value} represents a string, then this method
21930 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
21931 In Python}). Otherwise, this method will throw an exception.
21933 If the optional @var{encoding} argument is given, it must be a string
21934 naming the encoding of the @code{gdb.LazyString}. Some examples are:
21935 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
21936 @var{encoding} argument is an encoding that @value{GDBN} does
21937 recognize, @value{GDBN} will raise an error.
21939 When a lazy string is printed, the @value{GDBN} encoding machinery is
21940 used to convert the string during printing. If the optional
21941 @var{encoding} argument is not provided, or is an empty string,
21942 @value{GDBN} will automatically select the encoding most suitable for
21943 the string type. For further information on encoding in @value{GDBN}
21944 please see @ref{Character Sets}.
21946 If the optional @var{length} argument is given, the string will be
21947 fetched and encoded to the length of characters specified. If
21948 the @var{length} argument is not provided, the string will be fetched
21949 and encoded until a null of appropriate width is found.
21952 @defun Value.fetch_lazy ()
21953 If the @code{gdb.Value} object is currently a lazy value
21954 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
21955 fetched from the inferior. Any errors that occur in the process
21956 will produce a Python exception.
21958 If the @code{gdb.Value} object is not a lazy value, this method
21961 This method does not return a value.
21966 @node Types In Python
21967 @subsubsection Types In Python
21968 @cindex types in Python
21969 @cindex Python, working with types
21972 @value{GDBN} represents types from the inferior using the class
21975 The following type-related functions are available in the @code{gdb}
21978 @findex gdb.lookup_type
21979 @defun gdb.lookup_type (name @r{[}, block@r{]})
21980 This function looks up a type by name. @var{name} is the name of the
21981 type to look up. It must be a string.
21983 If @var{block} is given, then @var{name} is looked up in that scope.
21984 Otherwise, it is searched for globally.
21986 Ordinarily, this function will return an instance of @code{gdb.Type}.
21987 If the named type cannot be found, it will throw an exception.
21990 If the type is a structure or class type, or an enum type, the fields
21991 of that type can be accessed using the Python @dfn{dictionary syntax}.
21992 For example, if @code{some_type} is a @code{gdb.Type} instance holding
21993 a structure type, you can access its @code{foo} field with:
21996 bar = some_type['foo']
21999 @code{bar} will be a @code{gdb.Field} object; see below under the
22000 description of the @code{Type.fields} method for a description of the
22001 @code{gdb.Field} class.
22003 An instance of @code{Type} has the following attributes:
22007 The type code for this type. The type code will be one of the
22008 @code{TYPE_CODE_} constants defined below.
22011 @defvar Type.sizeof
22012 The size of this type, in target @code{char} units. Usually, a
22013 target's @code{char} type will be an 8-bit byte. However, on some
22014 unusual platforms, this type may have a different size.
22018 The tag name for this type. The tag name is the name after
22019 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
22020 languages have this concept. If this type has no tag name, then
22021 @code{None} is returned.
22025 The following methods are provided:
22028 @defun Type.fields ()
22029 For structure and union types, this method returns the fields. Range
22030 types have two fields, the minimum and maximum values. Enum types
22031 have one field per enum constant. Function and method types have one
22032 field per parameter. The base types of C@t{++} classes are also
22033 represented as fields. If the type has no fields, or does not fit
22034 into one of these categories, an empty sequence will be returned.
22036 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
22039 This attribute is not available for @code{static} fields (as in
22040 C@t{++} or Java). For non-@code{static} fields, the value is the bit
22041 position of the field. For @code{enum} fields, the value is the
22042 enumeration member's integer representation.
22045 The name of the field, or @code{None} for anonymous fields.
22048 This is @code{True} if the field is artificial, usually meaning that
22049 it was provided by the compiler and not the user. This attribute is
22050 always provided, and is @code{False} if the field is not artificial.
22052 @item is_base_class
22053 This is @code{True} if the field represents a base class of a C@t{++}
22054 structure. This attribute is always provided, and is @code{False}
22055 if the field is not a base class of the type that is the argument of
22056 @code{fields}, or if that type was not a C@t{++} class.
22059 If the field is packed, or is a bitfield, then this will have a
22060 non-zero value, which is the size of the field in bits. Otherwise,
22061 this will be zero; in this case the field's size is given by its type.
22064 The type of the field. This is usually an instance of @code{Type},
22065 but it can be @code{None} in some situations.
22069 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
22070 Return a new @code{gdb.Type} object which represents an array of this
22071 type. If one argument is given, it is the inclusive upper bound of
22072 the array; in this case the lower bound is zero. If two arguments are
22073 given, the first argument is the lower bound of the array, and the
22074 second argument is the upper bound of the array. An array's length
22075 must not be negative, but the bounds can be.
22078 @defun Type.const ()
22079 Return a new @code{gdb.Type} object which represents a
22080 @code{const}-qualified variant of this type.
22083 @defun Type.volatile ()
22084 Return a new @code{gdb.Type} object which represents a
22085 @code{volatile}-qualified variant of this type.
22088 @defun Type.unqualified ()
22089 Return a new @code{gdb.Type} object which represents an unqualified
22090 variant of this type. That is, the result is neither @code{const} nor
22094 @defun Type.range ()
22095 Return a Python @code{Tuple} object that contains two elements: the
22096 low bound of the argument type and the high bound of that type. If
22097 the type does not have a range, @value{GDBN} will raise a
22098 @code{gdb.error} exception (@pxref{Exception Handling}).
22101 @defun Type.reference ()
22102 Return a new @code{gdb.Type} object which represents a reference to this
22106 @defun Type.pointer ()
22107 Return a new @code{gdb.Type} object which represents a pointer to this
22111 @defun Type.strip_typedefs ()
22112 Return a new @code{gdb.Type} that represents the real type,
22113 after removing all layers of typedefs.
22116 @defun Type.target ()
22117 Return a new @code{gdb.Type} object which represents the target type
22120 For a pointer type, the target type is the type of the pointed-to
22121 object. For an array type (meaning C-like arrays), the target type is
22122 the type of the elements of the array. For a function or method type,
22123 the target type is the type of the return value. For a complex type,
22124 the target type is the type of the elements. For a typedef, the
22125 target type is the aliased type.
22127 If the type does not have a target, this method will throw an
22131 @defun Type.template_argument (n @r{[}, block@r{]})
22132 If this @code{gdb.Type} is an instantiation of a template, this will
22133 return a new @code{gdb.Type} which represents the type of the
22134 @var{n}th template argument.
22136 If this @code{gdb.Type} is not a template type, this will throw an
22137 exception. Ordinarily, only C@t{++} code will have template types.
22139 If @var{block} is given, then @var{name} is looked up in that scope.
22140 Otherwise, it is searched for globally.
22145 Each type has a code, which indicates what category this type falls
22146 into. The available type categories are represented by constants
22147 defined in the @code{gdb} module:
22150 @findex TYPE_CODE_PTR
22151 @findex gdb.TYPE_CODE_PTR
22152 @item gdb.TYPE_CODE_PTR
22153 The type is a pointer.
22155 @findex TYPE_CODE_ARRAY
22156 @findex gdb.TYPE_CODE_ARRAY
22157 @item gdb.TYPE_CODE_ARRAY
22158 The type is an array.
22160 @findex TYPE_CODE_STRUCT
22161 @findex gdb.TYPE_CODE_STRUCT
22162 @item gdb.TYPE_CODE_STRUCT
22163 The type is a structure.
22165 @findex TYPE_CODE_UNION
22166 @findex gdb.TYPE_CODE_UNION
22167 @item gdb.TYPE_CODE_UNION
22168 The type is a union.
22170 @findex TYPE_CODE_ENUM
22171 @findex gdb.TYPE_CODE_ENUM
22172 @item gdb.TYPE_CODE_ENUM
22173 The type is an enum.
22175 @findex TYPE_CODE_FLAGS
22176 @findex gdb.TYPE_CODE_FLAGS
22177 @item gdb.TYPE_CODE_FLAGS
22178 A bit flags type, used for things such as status registers.
22180 @findex TYPE_CODE_FUNC
22181 @findex gdb.TYPE_CODE_FUNC
22182 @item gdb.TYPE_CODE_FUNC
22183 The type is a function.
22185 @findex TYPE_CODE_INT
22186 @findex gdb.TYPE_CODE_INT
22187 @item gdb.TYPE_CODE_INT
22188 The type is an integer type.
22190 @findex TYPE_CODE_FLT
22191 @findex gdb.TYPE_CODE_FLT
22192 @item gdb.TYPE_CODE_FLT
22193 A floating point type.
22195 @findex TYPE_CODE_VOID
22196 @findex gdb.TYPE_CODE_VOID
22197 @item gdb.TYPE_CODE_VOID
22198 The special type @code{void}.
22200 @findex TYPE_CODE_SET
22201 @findex gdb.TYPE_CODE_SET
22202 @item gdb.TYPE_CODE_SET
22205 @findex TYPE_CODE_RANGE
22206 @findex gdb.TYPE_CODE_RANGE
22207 @item gdb.TYPE_CODE_RANGE
22208 A range type, that is, an integer type with bounds.
22210 @findex TYPE_CODE_STRING
22211 @findex gdb.TYPE_CODE_STRING
22212 @item gdb.TYPE_CODE_STRING
22213 A string type. Note that this is only used for certain languages with
22214 language-defined string types; C strings are not represented this way.
22216 @findex TYPE_CODE_BITSTRING
22217 @findex gdb.TYPE_CODE_BITSTRING
22218 @item gdb.TYPE_CODE_BITSTRING
22221 @findex TYPE_CODE_ERROR
22222 @findex gdb.TYPE_CODE_ERROR
22223 @item gdb.TYPE_CODE_ERROR
22224 An unknown or erroneous type.
22226 @findex TYPE_CODE_METHOD
22227 @findex gdb.TYPE_CODE_METHOD
22228 @item gdb.TYPE_CODE_METHOD
22229 A method type, as found in C@t{++} or Java.
22231 @findex TYPE_CODE_METHODPTR
22232 @findex gdb.TYPE_CODE_METHODPTR
22233 @item gdb.TYPE_CODE_METHODPTR
22234 A pointer-to-member-function.
22236 @findex TYPE_CODE_MEMBERPTR
22237 @findex gdb.TYPE_CODE_MEMBERPTR
22238 @item gdb.TYPE_CODE_MEMBERPTR
22239 A pointer-to-member.
22241 @findex TYPE_CODE_REF
22242 @findex gdb.TYPE_CODE_REF
22243 @item gdb.TYPE_CODE_REF
22246 @findex TYPE_CODE_CHAR
22247 @findex gdb.TYPE_CODE_CHAR
22248 @item gdb.TYPE_CODE_CHAR
22251 @findex TYPE_CODE_BOOL
22252 @findex gdb.TYPE_CODE_BOOL
22253 @item gdb.TYPE_CODE_BOOL
22256 @findex TYPE_CODE_COMPLEX
22257 @findex gdb.TYPE_CODE_COMPLEX
22258 @item gdb.TYPE_CODE_COMPLEX
22259 A complex float type.
22261 @findex TYPE_CODE_TYPEDEF
22262 @findex gdb.TYPE_CODE_TYPEDEF
22263 @item gdb.TYPE_CODE_TYPEDEF
22264 A typedef to some other type.
22266 @findex TYPE_CODE_NAMESPACE
22267 @findex gdb.TYPE_CODE_NAMESPACE
22268 @item gdb.TYPE_CODE_NAMESPACE
22269 A C@t{++} namespace.
22271 @findex TYPE_CODE_DECFLOAT
22272 @findex gdb.TYPE_CODE_DECFLOAT
22273 @item gdb.TYPE_CODE_DECFLOAT
22274 A decimal floating point type.
22276 @findex TYPE_CODE_INTERNAL_FUNCTION
22277 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
22278 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
22279 A function internal to @value{GDBN}. This is the type used to represent
22280 convenience functions.
22283 Further support for types is provided in the @code{gdb.types}
22284 Python module (@pxref{gdb.types}).
22286 @node Pretty Printing API
22287 @subsubsection Pretty Printing API
22289 An example output is provided (@pxref{Pretty Printing}).
22291 A pretty-printer is just an object that holds a value and implements a
22292 specific interface, defined here.
22294 @defun pretty_printer.children (self)
22295 @value{GDBN} will call this method on a pretty-printer to compute the
22296 children of the pretty-printer's value.
22298 This method must return an object conforming to the Python iterator
22299 protocol. Each item returned by the iterator must be a tuple holding
22300 two elements. The first element is the ``name'' of the child; the
22301 second element is the child's value. The value can be any Python
22302 object which is convertible to a @value{GDBN} value.
22304 This method is optional. If it does not exist, @value{GDBN} will act
22305 as though the value has no children.
22308 @defun pretty_printer.display_hint (self)
22309 The CLI may call this method and use its result to change the
22310 formatting of a value. The result will also be supplied to an MI
22311 consumer as a @samp{displayhint} attribute of the variable being
22314 This method is optional. If it does exist, this method must return a
22317 Some display hints are predefined by @value{GDBN}:
22321 Indicate that the object being printed is ``array-like''. The CLI
22322 uses this to respect parameters such as @code{set print elements} and
22323 @code{set print array}.
22326 Indicate that the object being printed is ``map-like'', and that the
22327 children of this value can be assumed to alternate between keys and
22331 Indicate that the object being printed is ``string-like''. If the
22332 printer's @code{to_string} method returns a Python string of some
22333 kind, then @value{GDBN} will call its internal language-specific
22334 string-printing function to format the string. For the CLI this means
22335 adding quotation marks, possibly escaping some characters, respecting
22336 @code{set print elements}, and the like.
22340 @defun pretty_printer.to_string (self)
22341 @value{GDBN} will call this method to display the string
22342 representation of the value passed to the object's constructor.
22344 When printing from the CLI, if the @code{to_string} method exists,
22345 then @value{GDBN} will prepend its result to the values returned by
22346 @code{children}. Exactly how this formatting is done is dependent on
22347 the display hint, and may change as more hints are added. Also,
22348 depending on the print settings (@pxref{Print Settings}), the CLI may
22349 print just the result of @code{to_string} in a stack trace, omitting
22350 the result of @code{children}.
22352 If this method returns a string, it is printed verbatim.
22354 Otherwise, if this method returns an instance of @code{gdb.Value},
22355 then @value{GDBN} prints this value. This may result in a call to
22356 another pretty-printer.
22358 If instead the method returns a Python value which is convertible to a
22359 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
22360 the resulting value. Again, this may result in a call to another
22361 pretty-printer. Python scalars (integers, floats, and booleans) and
22362 strings are convertible to @code{gdb.Value}; other types are not.
22364 Finally, if this method returns @code{None} then no further operations
22365 are peformed in this method and nothing is printed.
22367 If the result is not one of these types, an exception is raised.
22370 @value{GDBN} provides a function which can be used to look up the
22371 default pretty-printer for a @code{gdb.Value}:
22373 @findex gdb.default_visualizer
22374 @defun gdb.default_visualizer (value)
22375 This function takes a @code{gdb.Value} object as an argument. If a
22376 pretty-printer for this value exists, then it is returned. If no such
22377 printer exists, then this returns @code{None}.
22380 @node Selecting Pretty-Printers
22381 @subsubsection Selecting Pretty-Printers
22383 The Python list @code{gdb.pretty_printers} contains an array of
22384 functions or callable objects that have been registered via addition
22385 as a pretty-printer. Printers in this list are called @code{global}
22386 printers, they're available when debugging all inferiors.
22387 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
22388 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
22391 Each function on these lists is passed a single @code{gdb.Value}
22392 argument and should return a pretty-printer object conforming to the
22393 interface definition above (@pxref{Pretty Printing API}). If a function
22394 cannot create a pretty-printer for the value, it should return
22397 @value{GDBN} first checks the @code{pretty_printers} attribute of each
22398 @code{gdb.Objfile} in the current program space and iteratively calls
22399 each enabled lookup routine in the list for that @code{gdb.Objfile}
22400 until it receives a pretty-printer object.
22401 If no pretty-printer is found in the objfile lists, @value{GDBN} then
22402 searches the pretty-printer list of the current program space,
22403 calling each enabled function until an object is returned.
22404 After these lists have been exhausted, it tries the global
22405 @code{gdb.pretty_printers} list, again calling each enabled function until an
22406 object is returned.
22408 The order in which the objfiles are searched is not specified. For a
22409 given list, functions are always invoked from the head of the list,
22410 and iterated over sequentially until the end of the list, or a printer
22411 object is returned.
22413 For various reasons a pretty-printer may not work.
22414 For example, the underlying data structure may have changed and
22415 the pretty-printer is out of date.
22417 The consequences of a broken pretty-printer are severe enough that
22418 @value{GDBN} provides support for enabling and disabling individual
22419 printers. For example, if @code{print frame-arguments} is on,
22420 a backtrace can become highly illegible if any argument is printed
22421 with a broken printer.
22423 Pretty-printers are enabled and disabled by attaching an @code{enabled}
22424 attribute to the registered function or callable object. If this attribute
22425 is present and its value is @code{False}, the printer is disabled, otherwise
22426 the printer is enabled.
22428 @node Writing a Pretty-Printer
22429 @subsubsection Writing a Pretty-Printer
22430 @cindex writing a pretty-printer
22432 A pretty-printer consists of two parts: a lookup function to detect
22433 if the type is supported, and the printer itself.
22435 Here is an example showing how a @code{std::string} printer might be
22436 written. @xref{Pretty Printing API}, for details on the API this class
22440 class StdStringPrinter(object):
22441 "Print a std::string"
22443 def __init__(self, val):
22446 def to_string(self):
22447 return self.val['_M_dataplus']['_M_p']
22449 def display_hint(self):
22453 And here is an example showing how a lookup function for the printer
22454 example above might be written.
22457 def str_lookup_function(val):
22458 lookup_tag = val.type.tag
22459 if lookup_tag == None:
22461 regex = re.compile("^std::basic_string<char,.*>$")
22462 if regex.match(lookup_tag):
22463 return StdStringPrinter(val)
22467 The example lookup function extracts the value's type, and attempts to
22468 match it to a type that it can pretty-print. If it is a type the
22469 printer can pretty-print, it will return a printer object. If not, it
22470 returns @code{None}.
22472 We recommend that you put your core pretty-printers into a Python
22473 package. If your pretty-printers are for use with a library, we
22474 further recommend embedding a version number into the package name.
22475 This practice will enable @value{GDBN} to load multiple versions of
22476 your pretty-printers at the same time, because they will have
22479 You should write auto-loaded code (@pxref{Auto-loading}) such that it
22480 can be evaluated multiple times without changing its meaning. An
22481 ideal auto-load file will consist solely of @code{import}s of your
22482 printer modules, followed by a call to a register pretty-printers with
22483 the current objfile.
22485 Taken as a whole, this approach will scale nicely to multiple
22486 inferiors, each potentially using a different library version.
22487 Embedding a version number in the Python package name will ensure that
22488 @value{GDBN} is able to load both sets of printers simultaneously.
22489 Then, because the search for pretty-printers is done by objfile, and
22490 because your auto-loaded code took care to register your library's
22491 printers with a specific objfile, @value{GDBN} will find the correct
22492 printers for the specific version of the library used by each
22495 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
22496 this code might appear in @code{gdb.libstdcxx.v6}:
22499 def register_printers(objfile):
22500 objfile.pretty_printers.add(str_lookup_function)
22504 And then the corresponding contents of the auto-load file would be:
22507 import gdb.libstdcxx.v6
22508 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
22511 The previous example illustrates a basic pretty-printer.
22512 There are a few things that can be improved on.
22513 The printer doesn't have a name, making it hard to identify in a
22514 list of installed printers. The lookup function has a name, but
22515 lookup functions can have arbitrary, even identical, names.
22517 Second, the printer only handles one type, whereas a library typically has
22518 several types. One could install a lookup function for each desired type
22519 in the library, but one could also have a single lookup function recognize
22520 several types. The latter is the conventional way this is handled.
22521 If a pretty-printer can handle multiple data types, then its
22522 @dfn{subprinters} are the printers for the individual data types.
22524 The @code{gdb.printing} module provides a formal way of solving these
22525 problems (@pxref{gdb.printing}).
22526 Here is another example that handles multiple types.
22528 These are the types we are going to pretty-print:
22531 struct foo @{ int a, b; @};
22532 struct bar @{ struct foo x, y; @};
22535 Here are the printers:
22539 """Print a foo object."""
22541 def __init__(self, val):
22544 def to_string(self):
22545 return ("a=<" + str(self.val["a"]) +
22546 "> b=<" + str(self.val["b"]) + ">")
22549 """Print a bar object."""
22551 def __init__(self, val):
22554 def to_string(self):
22555 return ("x=<" + str(self.val["x"]) +
22556 "> y=<" + str(self.val["y"]) + ">")
22559 This example doesn't need a lookup function, that is handled by the
22560 @code{gdb.printing} module. Instead a function is provided to build up
22561 the object that handles the lookup.
22564 import gdb.printing
22566 def build_pretty_printer():
22567 pp = gdb.printing.RegexpCollectionPrettyPrinter(
22569 pp.add_printer('foo', '^foo$', fooPrinter)
22570 pp.add_printer('bar', '^bar$', barPrinter)
22574 And here is the autoload support:
22577 import gdb.printing
22579 gdb.printing.register_pretty_printer(
22580 gdb.current_objfile(),
22581 my_library.build_pretty_printer())
22584 Finally, when this printer is loaded into @value{GDBN}, here is the
22585 corresponding output of @samp{info pretty-printer}:
22588 (gdb) info pretty-printer
22595 @node Inferiors In Python
22596 @subsubsection Inferiors In Python
22597 @cindex inferiors in Python
22599 @findex gdb.Inferior
22600 Programs which are being run under @value{GDBN} are called inferiors
22601 (@pxref{Inferiors and Programs}). Python scripts can access
22602 information about and manipulate inferiors controlled by @value{GDBN}
22603 via objects of the @code{gdb.Inferior} class.
22605 The following inferior-related functions are available in the @code{gdb}
22608 @defun gdb.inferiors ()
22609 Return a tuple containing all inferior objects.
22612 @defun gdb.selected_inferior ()
22613 Return an object representing the current inferior.
22616 A @code{gdb.Inferior} object has the following attributes:
22619 @defvar Inferior.num
22620 ID of inferior, as assigned by GDB.
22623 @defvar Inferior.pid
22624 Process ID of the inferior, as assigned by the underlying operating
22628 @defvar Inferior.was_attached
22629 Boolean signaling whether the inferior was created using `attach', or
22630 started by @value{GDBN} itself.
22634 A @code{gdb.Inferior} object has the following methods:
22637 @defun Inferior.is_valid ()
22638 Returns @code{True} if the @code{gdb.Inferior} object is valid,
22639 @code{False} if not. A @code{gdb.Inferior} object will become invalid
22640 if the inferior no longer exists within @value{GDBN}. All other
22641 @code{gdb.Inferior} methods will throw an exception if it is invalid
22642 at the time the method is called.
22645 @defun Inferior.threads ()
22646 This method returns a tuple holding all the threads which are valid
22647 when it is called. If there are no valid threads, the method will
22648 return an empty tuple.
22651 @findex gdb.read_memory
22652 @defun Inferior.read_memory (address, length)
22653 Read @var{length} bytes of memory from the inferior, starting at
22654 @var{address}. Returns a buffer object, which behaves much like an array
22655 or a string. It can be modified and given to the @code{gdb.write_memory}
22659 @findex gdb.write_memory
22660 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
22661 Write the contents of @var{buffer} to the inferior, starting at
22662 @var{address}. The @var{buffer} parameter must be a Python object
22663 which supports the buffer protocol, i.e., a string, an array or the
22664 object returned from @code{gdb.read_memory}. If given, @var{length}
22665 determines the number of bytes from @var{buffer} to be written.
22668 @findex gdb.search_memory
22669 @defun Inferior.search_memory (address, length, pattern)
22670 Search a region of the inferior memory starting at @var{address} with
22671 the given @var{length} using the search pattern supplied in
22672 @var{pattern}. The @var{pattern} parameter must be a Python object
22673 which supports the buffer protocol, i.e., a string, an array or the
22674 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
22675 containing the address where the pattern was found, or @code{None} if
22676 the pattern could not be found.
22680 @node Events In Python
22681 @subsubsection Events In Python
22682 @cindex inferior events in Python
22684 @value{GDBN} provides a general event facility so that Python code can be
22685 notified of various state changes, particularly changes that occur in
22688 An @dfn{event} is just an object that describes some state change. The
22689 type of the object and its attributes will vary depending on the details
22690 of the change. All the existing events are described below.
22692 In order to be notified of an event, you must register an event handler
22693 with an @dfn{event registry}. An event registry is an object in the
22694 @code{gdb.events} module which dispatches particular events. A registry
22695 provides methods to register and unregister event handlers:
22698 @defun EventRegistry.connect (object)
22699 Add the given callable @var{object} to the registry. This object will be
22700 called when an event corresponding to this registry occurs.
22703 @defun EventRegistry.disconnect (object)
22704 Remove the given @var{object} from the registry. Once removed, the object
22705 will no longer receive notifications of events.
22709 Here is an example:
22712 def exit_handler (event):
22713 print "event type: exit"
22714 print "exit code: %d" % (event.exit_code)
22716 gdb.events.exited.connect (exit_handler)
22719 In the above example we connect our handler @code{exit_handler} to the
22720 registry @code{events.exited}. Once connected, @code{exit_handler} gets
22721 called when the inferior exits. The argument @dfn{event} in this example is
22722 of type @code{gdb.ExitedEvent}. As you can see in the example the
22723 @code{ExitedEvent} object has an attribute which indicates the exit code of
22726 The following is a listing of the event registries that are available and
22727 details of the events they emit:
22732 Emits @code{gdb.ThreadEvent}.
22734 Some events can be thread specific when @value{GDBN} is running in non-stop
22735 mode. When represented in Python, these events all extend
22736 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
22737 events which are emitted by this or other modules might extend this event.
22738 Examples of these events are @code{gdb.BreakpointEvent} and
22739 @code{gdb.ContinueEvent}.
22742 @defvar ThreadEvent.inferior_thread
22743 In non-stop mode this attribute will be set to the specific thread which was
22744 involved in the emitted event. Otherwise, it will be set to @code{None}.
22748 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
22750 This event indicates that the inferior has been continued after a stop. For
22751 inherited attribute refer to @code{gdb.ThreadEvent} above.
22753 @item events.exited
22754 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
22755 @code{events.ExitedEvent} has two attributes:
22757 @defvar ExitedEvent.exit_code
22758 An integer representing the exit code, if available, which the inferior
22759 has returned. (The exit code could be unavailable if, for example,
22760 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
22761 the attribute does not exist.
22763 @defvar ExitedEvent inferior
22764 A reference to the inferior which triggered the @code{exited} event.
22769 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
22771 Indicates that the inferior has stopped. All events emitted by this registry
22772 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
22773 will indicate the stopped thread when @value{GDBN} is running in non-stop
22774 mode. Refer to @code{gdb.ThreadEvent} above for more details.
22776 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
22778 This event indicates that the inferior or one of its threads has received as
22779 signal. @code{gdb.SignalEvent} has the following attributes:
22782 @defvar SignalEvent.stop_signal
22783 A string representing the signal received by the inferior. A list of possible
22784 signal values can be obtained by running the command @code{info signals} in
22785 the @value{GDBN} command prompt.
22789 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
22791 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
22792 been hit, and has the following attributes:
22795 @defvar BreakpointEvent.breakpoints
22796 A sequence containing references to all the breakpoints (type
22797 @code{gdb.Breakpoint}) that were hit.
22798 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
22800 @defvar BreakpointEvent.breakpoint
22801 A reference to the first breakpoint that was hit.
22802 This function is maintained for backward compatibility and is now deprecated
22803 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
22807 @item events.new_objfile
22808 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
22809 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
22812 @defvar NewObjFileEvent.new_objfile
22813 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
22814 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
22820 @node Threads In Python
22821 @subsubsection Threads In Python
22822 @cindex threads in python
22824 @findex gdb.InferiorThread
22825 Python scripts can access information about, and manipulate inferior threads
22826 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
22828 The following thread-related functions are available in the @code{gdb}
22831 @findex gdb.selected_thread
22832 @defun gdb.selected_thread ()
22833 This function returns the thread object for the selected thread. If there
22834 is no selected thread, this will return @code{None}.
22837 A @code{gdb.InferiorThread} object has the following attributes:
22840 @defvar InferiorThread.name
22841 The name of the thread. If the user specified a name using
22842 @code{thread name}, then this returns that name. Otherwise, if an
22843 OS-supplied name is available, then it is returned. Otherwise, this
22844 returns @code{None}.
22846 This attribute can be assigned to. The new value must be a string
22847 object, which sets the new name, or @code{None}, which removes any
22848 user-specified thread name.
22851 @defvar InferiorThread.num
22852 ID of the thread, as assigned by GDB.
22855 @defvar InferiorThread.ptid
22856 ID of the thread, as assigned by the operating system. This attribute is a
22857 tuple containing three integers. The first is the Process ID (PID); the second
22858 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
22859 Either the LWPID or TID may be 0, which indicates that the operating system
22860 does not use that identifier.
22864 A @code{gdb.InferiorThread} object has the following methods:
22867 @defun InferiorThread.is_valid ()
22868 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
22869 @code{False} if not. A @code{gdb.InferiorThread} object will become
22870 invalid if the thread exits, or the inferior that the thread belongs
22871 is deleted. All other @code{gdb.InferiorThread} methods will throw an
22872 exception if it is invalid at the time the method is called.
22875 @defun InferiorThread.switch ()
22876 This changes @value{GDBN}'s currently selected thread to the one represented
22880 @defun InferiorThread.is_stopped ()
22881 Return a Boolean indicating whether the thread is stopped.
22884 @defun InferiorThread.is_running ()
22885 Return a Boolean indicating whether the thread is running.
22888 @defun InferiorThread.is_exited ()
22889 Return a Boolean indicating whether the thread is exited.
22893 @node Commands In Python
22894 @subsubsection Commands In Python
22896 @cindex commands in python
22897 @cindex python commands
22898 You can implement new @value{GDBN} CLI commands in Python. A CLI
22899 command is implemented using an instance of the @code{gdb.Command}
22900 class, most commonly using a subclass.
22902 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
22903 The object initializer for @code{Command} registers the new command
22904 with @value{GDBN}. This initializer is normally invoked from the
22905 subclass' own @code{__init__} method.
22907 @var{name} is the name of the command. If @var{name} consists of
22908 multiple words, then the initial words are looked for as prefix
22909 commands. In this case, if one of the prefix commands does not exist,
22910 an exception is raised.
22912 There is no support for multi-line commands.
22914 @var{command_class} should be one of the @samp{COMMAND_} constants
22915 defined below. This argument tells @value{GDBN} how to categorize the
22916 new command in the help system.
22918 @var{completer_class} is an optional argument. If given, it should be
22919 one of the @samp{COMPLETE_} constants defined below. This argument
22920 tells @value{GDBN} how to perform completion for this command. If not
22921 given, @value{GDBN} will attempt to complete using the object's
22922 @code{complete} method (see below); if no such method is found, an
22923 error will occur when completion is attempted.
22925 @var{prefix} is an optional argument. If @code{True}, then the new
22926 command is a prefix command; sub-commands of this command may be
22929 The help text for the new command is taken from the Python
22930 documentation string for the command's class, if there is one. If no
22931 documentation string is provided, the default value ``This command is
22932 not documented.'' is used.
22935 @cindex don't repeat Python command
22936 @defun Command.dont_repeat ()
22937 By default, a @value{GDBN} command is repeated when the user enters a
22938 blank line at the command prompt. A command can suppress this
22939 behavior by invoking the @code{dont_repeat} method. This is similar
22940 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
22943 @defun Command.invoke (argument, from_tty)
22944 This method is called by @value{GDBN} when this command is invoked.
22946 @var{argument} is a string. It is the argument to the command, after
22947 leading and trailing whitespace has been stripped.
22949 @var{from_tty} is a boolean argument. When true, this means that the
22950 command was entered by the user at the terminal; when false it means
22951 that the command came from elsewhere.
22953 If this method throws an exception, it is turned into a @value{GDBN}
22954 @code{error} call. Otherwise, the return value is ignored.
22956 @findex gdb.string_to_argv
22957 To break @var{argument} up into an argv-like string use
22958 @code{gdb.string_to_argv}. This function behaves identically to
22959 @value{GDBN}'s internal argument lexer @code{buildargv}.
22960 It is recommended to use this for consistency.
22961 Arguments are separated by spaces and may be quoted.
22965 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
22966 ['1', '2 "3', '4 "5', "6 '7"]
22971 @cindex completion of Python commands
22972 @defun Command.complete (text, word)
22973 This method is called by @value{GDBN} when the user attempts
22974 completion on this command. All forms of completion are handled by
22975 this method, that is, the @key{TAB} and @key{M-?} key bindings
22976 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
22979 The arguments @var{text} and @var{word} are both strings. @var{text}
22980 holds the complete command line up to the cursor's location.
22981 @var{word} holds the last word of the command line; this is computed
22982 using a word-breaking heuristic.
22984 The @code{complete} method can return several values:
22987 If the return value is a sequence, the contents of the sequence are
22988 used as the completions. It is up to @code{complete} to ensure that the
22989 contents actually do complete the word. A zero-length sequence is
22990 allowed, it means that there were no completions available. Only
22991 string elements of the sequence are used; other elements in the
22992 sequence are ignored.
22995 If the return value is one of the @samp{COMPLETE_} constants defined
22996 below, then the corresponding @value{GDBN}-internal completion
22997 function is invoked, and its result is used.
23000 All other results are treated as though there were no available
23005 When a new command is registered, it must be declared as a member of
23006 some general class of commands. This is used to classify top-level
23007 commands in the on-line help system; note that prefix commands are not
23008 listed under their own category but rather that of their top-level
23009 command. The available classifications are represented by constants
23010 defined in the @code{gdb} module:
23013 @findex COMMAND_NONE
23014 @findex gdb.COMMAND_NONE
23015 @item gdb.COMMAND_NONE
23016 The command does not belong to any particular class. A command in
23017 this category will not be displayed in any of the help categories.
23019 @findex COMMAND_RUNNING
23020 @findex gdb.COMMAND_RUNNING
23021 @item gdb.COMMAND_RUNNING
23022 The command is related to running the inferior. For example,
23023 @code{start}, @code{step}, and @code{continue} are in this category.
23024 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
23025 commands in this category.
23027 @findex COMMAND_DATA
23028 @findex gdb.COMMAND_DATA
23029 @item gdb.COMMAND_DATA
23030 The command is related to data or variables. For example,
23031 @code{call}, @code{find}, and @code{print} are in this category. Type
23032 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
23035 @findex COMMAND_STACK
23036 @findex gdb.COMMAND_STACK
23037 @item gdb.COMMAND_STACK
23038 The command has to do with manipulation of the stack. For example,
23039 @code{backtrace}, @code{frame}, and @code{return} are in this
23040 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
23041 list of commands in this category.
23043 @findex COMMAND_FILES
23044 @findex gdb.COMMAND_FILES
23045 @item gdb.COMMAND_FILES
23046 This class is used for file-related commands. For example,
23047 @code{file}, @code{list} and @code{section} are in this category.
23048 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
23049 commands in this category.
23051 @findex COMMAND_SUPPORT
23052 @findex gdb.COMMAND_SUPPORT
23053 @item gdb.COMMAND_SUPPORT
23054 This should be used for ``support facilities'', generally meaning
23055 things that are useful to the user when interacting with @value{GDBN},
23056 but not related to the state of the inferior. For example,
23057 @code{help}, @code{make}, and @code{shell} are in this category. Type
23058 @kbd{help support} at the @value{GDBN} prompt to see a list of
23059 commands in this category.
23061 @findex COMMAND_STATUS
23062 @findex gdb.COMMAND_STATUS
23063 @item gdb.COMMAND_STATUS
23064 The command is an @samp{info}-related command, that is, related to the
23065 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
23066 and @code{show} are in this category. Type @kbd{help status} at the
23067 @value{GDBN} prompt to see a list of commands in this category.
23069 @findex COMMAND_BREAKPOINTS
23070 @findex gdb.COMMAND_BREAKPOINTS
23071 @item gdb.COMMAND_BREAKPOINTS
23072 The command has to do with breakpoints. For example, @code{break},
23073 @code{clear}, and @code{delete} are in this category. Type @kbd{help
23074 breakpoints} at the @value{GDBN} prompt to see a list of commands in
23077 @findex COMMAND_TRACEPOINTS
23078 @findex gdb.COMMAND_TRACEPOINTS
23079 @item gdb.COMMAND_TRACEPOINTS
23080 The command has to do with tracepoints. For example, @code{trace},
23081 @code{actions}, and @code{tfind} are in this category. Type
23082 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
23083 commands in this category.
23085 @findex COMMAND_OBSCURE
23086 @findex gdb.COMMAND_OBSCURE
23087 @item gdb.COMMAND_OBSCURE
23088 The command is only used in unusual circumstances, or is not of
23089 general interest to users. For example, @code{checkpoint},
23090 @code{fork}, and @code{stop} are in this category. Type @kbd{help
23091 obscure} at the @value{GDBN} prompt to see a list of commands in this
23094 @findex COMMAND_MAINTENANCE
23095 @findex gdb.COMMAND_MAINTENANCE
23096 @item gdb.COMMAND_MAINTENANCE
23097 The command is only useful to @value{GDBN} maintainers. The
23098 @code{maintenance} and @code{flushregs} commands are in this category.
23099 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
23100 commands in this category.
23103 A new command can use a predefined completion function, either by
23104 specifying it via an argument at initialization, or by returning it
23105 from the @code{complete} method. These predefined completion
23106 constants are all defined in the @code{gdb} module:
23109 @findex COMPLETE_NONE
23110 @findex gdb.COMPLETE_NONE
23111 @item gdb.COMPLETE_NONE
23112 This constant means that no completion should be done.
23114 @findex COMPLETE_FILENAME
23115 @findex gdb.COMPLETE_FILENAME
23116 @item gdb.COMPLETE_FILENAME
23117 This constant means that filename completion should be performed.
23119 @findex COMPLETE_LOCATION
23120 @findex gdb.COMPLETE_LOCATION
23121 @item gdb.COMPLETE_LOCATION
23122 This constant means that location completion should be done.
23123 @xref{Specify Location}.
23125 @findex COMPLETE_COMMAND
23126 @findex gdb.COMPLETE_COMMAND
23127 @item gdb.COMPLETE_COMMAND
23128 This constant means that completion should examine @value{GDBN}
23131 @findex COMPLETE_SYMBOL
23132 @findex gdb.COMPLETE_SYMBOL
23133 @item gdb.COMPLETE_SYMBOL
23134 This constant means that completion should be done using symbol names
23138 The following code snippet shows how a trivial CLI command can be
23139 implemented in Python:
23142 class HelloWorld (gdb.Command):
23143 """Greet the whole world."""
23145 def __init__ (self):
23146 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
23148 def invoke (self, arg, from_tty):
23149 print "Hello, World!"
23154 The last line instantiates the class, and is necessary to trigger the
23155 registration of the command with @value{GDBN}. Depending on how the
23156 Python code is read into @value{GDBN}, you may need to import the
23157 @code{gdb} module explicitly.
23159 @node Parameters In Python
23160 @subsubsection Parameters In Python
23162 @cindex parameters in python
23163 @cindex python parameters
23164 @tindex gdb.Parameter
23166 You can implement new @value{GDBN} parameters using Python. A new
23167 parameter is implemented as an instance of the @code{gdb.Parameter}
23170 Parameters are exposed to the user via the @code{set} and
23171 @code{show} commands. @xref{Help}.
23173 There are many parameters that already exist and can be set in
23174 @value{GDBN}. Two examples are: @code{set follow fork} and
23175 @code{set charset}. Setting these parameters influences certain
23176 behavior in @value{GDBN}. Similarly, you can define parameters that
23177 can be used to influence behavior in custom Python scripts and commands.
23179 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
23180 The object initializer for @code{Parameter} registers the new
23181 parameter with @value{GDBN}. This initializer is normally invoked
23182 from the subclass' own @code{__init__} method.
23184 @var{name} is the name of the new parameter. If @var{name} consists
23185 of multiple words, then the initial words are looked for as prefix
23186 parameters. An example of this can be illustrated with the
23187 @code{set print} set of parameters. If @var{name} is
23188 @code{print foo}, then @code{print} will be searched as the prefix
23189 parameter. In this case the parameter can subsequently be accessed in
23190 @value{GDBN} as @code{set print foo}.
23192 If @var{name} consists of multiple words, and no prefix parameter group
23193 can be found, an exception is raised.
23195 @var{command-class} should be one of the @samp{COMMAND_} constants
23196 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
23197 categorize the new parameter in the help system.
23199 @var{parameter-class} should be one of the @samp{PARAM_} constants
23200 defined below. This argument tells @value{GDBN} the type of the new
23201 parameter; this information is used for input validation and
23204 If @var{parameter-class} is @code{PARAM_ENUM}, then
23205 @var{enum-sequence} must be a sequence of strings. These strings
23206 represent the possible values for the parameter.
23208 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
23209 of a fourth argument will cause an exception to be thrown.
23211 The help text for the new parameter is taken from the Python
23212 documentation string for the parameter's class, if there is one. If
23213 there is no documentation string, a default value is used.
23216 @defvar Parameter.set_doc
23217 If this attribute exists, and is a string, then its value is used as
23218 the help text for this parameter's @code{set} command. The value is
23219 examined when @code{Parameter.__init__} is invoked; subsequent changes
23223 @defvar Parameter.show_doc
23224 If this attribute exists, and is a string, then its value is used as
23225 the help text for this parameter's @code{show} command. The value is
23226 examined when @code{Parameter.__init__} is invoked; subsequent changes
23230 @defvar Parameter.value
23231 The @code{value} attribute holds the underlying value of the
23232 parameter. It can be read and assigned to just as any other
23233 attribute. @value{GDBN} does validation when assignments are made.
23236 There are two methods that should be implemented in any
23237 @code{Parameter} class. These are:
23239 @defun Parameter.get_set_string (self)
23240 @value{GDBN} will call this method when a @var{parameter}'s value has
23241 been changed via the @code{set} API (for example, @kbd{set foo off}).
23242 The @code{value} attribute has already been populated with the new
23243 value and may be used in output. This method must return a string.
23246 @defun Parameter.get_show_string (self, svalue)
23247 @value{GDBN} will call this method when a @var{parameter}'s
23248 @code{show} API has been invoked (for example, @kbd{show foo}). The
23249 argument @code{svalue} receives the string representation of the
23250 current value. This method must return a string.
23253 When a new parameter is defined, its type must be specified. The
23254 available types are represented by constants defined in the @code{gdb}
23258 @findex PARAM_BOOLEAN
23259 @findex gdb.PARAM_BOOLEAN
23260 @item gdb.PARAM_BOOLEAN
23261 The value is a plain boolean. The Python boolean values, @code{True}
23262 and @code{False} are the only valid values.
23264 @findex PARAM_AUTO_BOOLEAN
23265 @findex gdb.PARAM_AUTO_BOOLEAN
23266 @item gdb.PARAM_AUTO_BOOLEAN
23267 The value has three possible states: true, false, and @samp{auto}. In
23268 Python, true and false are represented using boolean constants, and
23269 @samp{auto} is represented using @code{None}.
23271 @findex PARAM_UINTEGER
23272 @findex gdb.PARAM_UINTEGER
23273 @item gdb.PARAM_UINTEGER
23274 The value is an unsigned integer. The value of 0 should be
23275 interpreted to mean ``unlimited''.
23277 @findex PARAM_INTEGER
23278 @findex gdb.PARAM_INTEGER
23279 @item gdb.PARAM_INTEGER
23280 The value is a signed integer. The value of 0 should be interpreted
23281 to mean ``unlimited''.
23283 @findex PARAM_STRING
23284 @findex gdb.PARAM_STRING
23285 @item gdb.PARAM_STRING
23286 The value is a string. When the user modifies the string, any escape
23287 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
23288 translated into corresponding characters and encoded into the current
23291 @findex PARAM_STRING_NOESCAPE
23292 @findex gdb.PARAM_STRING_NOESCAPE
23293 @item gdb.PARAM_STRING_NOESCAPE
23294 The value is a string. When the user modifies the string, escapes are
23295 passed through untranslated.
23297 @findex PARAM_OPTIONAL_FILENAME
23298 @findex gdb.PARAM_OPTIONAL_FILENAME
23299 @item gdb.PARAM_OPTIONAL_FILENAME
23300 The value is a either a filename (a string), or @code{None}.
23302 @findex PARAM_FILENAME
23303 @findex gdb.PARAM_FILENAME
23304 @item gdb.PARAM_FILENAME
23305 The value is a filename. This is just like
23306 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
23308 @findex PARAM_ZINTEGER
23309 @findex gdb.PARAM_ZINTEGER
23310 @item gdb.PARAM_ZINTEGER
23311 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
23312 is interpreted as itself.
23315 @findex gdb.PARAM_ENUM
23316 @item gdb.PARAM_ENUM
23317 The value is a string, which must be one of a collection string
23318 constants provided when the parameter is created.
23321 @node Functions In Python
23322 @subsubsection Writing new convenience functions
23324 @cindex writing convenience functions
23325 @cindex convenience functions in python
23326 @cindex python convenience functions
23327 @tindex gdb.Function
23329 You can implement new convenience functions (@pxref{Convenience Vars})
23330 in Python. A convenience function is an instance of a subclass of the
23331 class @code{gdb.Function}.
23333 @defun Function.__init__ (name)
23334 The initializer for @code{Function} registers the new function with
23335 @value{GDBN}. The argument @var{name} is the name of the function,
23336 a string. The function will be visible to the user as a convenience
23337 variable of type @code{internal function}, whose name is the same as
23338 the given @var{name}.
23340 The documentation for the new function is taken from the documentation
23341 string for the new class.
23344 @defun Function.invoke (@var{*args})
23345 When a convenience function is evaluated, its arguments are converted
23346 to instances of @code{gdb.Value}, and then the function's
23347 @code{invoke} method is called. Note that @value{GDBN} does not
23348 predetermine the arity of convenience functions. Instead, all
23349 available arguments are passed to @code{invoke}, following the
23350 standard Python calling convention. In particular, a convenience
23351 function can have default values for parameters without ill effect.
23353 The return value of this method is used as its value in the enclosing
23354 expression. If an ordinary Python value is returned, it is converted
23355 to a @code{gdb.Value} following the usual rules.
23358 The following code snippet shows how a trivial convenience function can
23359 be implemented in Python:
23362 class Greet (gdb.Function):
23363 """Return string to greet someone.
23364 Takes a name as argument."""
23366 def __init__ (self):
23367 super (Greet, self).__init__ ("greet")
23369 def invoke (self, name):
23370 return "Hello, %s!" % name.string ()
23375 The last line instantiates the class, and is necessary to trigger the
23376 registration of the function with @value{GDBN}. Depending on how the
23377 Python code is read into @value{GDBN}, you may need to import the
23378 @code{gdb} module explicitly.
23380 @node Progspaces In Python
23381 @subsubsection Program Spaces In Python
23383 @cindex progspaces in python
23384 @tindex gdb.Progspace
23386 A program space, or @dfn{progspace}, represents a symbolic view
23387 of an address space.
23388 It consists of all of the objfiles of the program.
23389 @xref{Objfiles In Python}.
23390 @xref{Inferiors and Programs, program spaces}, for more details
23391 about program spaces.
23393 The following progspace-related functions are available in the
23396 @findex gdb.current_progspace
23397 @defun gdb.current_progspace ()
23398 This function returns the program space of the currently selected inferior.
23399 @xref{Inferiors and Programs}.
23402 @findex gdb.progspaces
23403 @defun gdb.progspaces ()
23404 Return a sequence of all the progspaces currently known to @value{GDBN}.
23407 Each progspace is represented by an instance of the @code{gdb.Progspace}
23410 @defvar Progspace.filename
23411 The file name of the progspace as a string.
23414 @defvar Progspace.pretty_printers
23415 The @code{pretty_printers} attribute is a list of functions. It is
23416 used to look up pretty-printers. A @code{Value} is passed to each
23417 function in order; if the function returns @code{None}, then the
23418 search continues. Otherwise, the return value should be an object
23419 which is used to format the value. @xref{Pretty Printing API}, for more
23423 @node Objfiles In Python
23424 @subsubsection Objfiles In Python
23426 @cindex objfiles in python
23427 @tindex gdb.Objfile
23429 @value{GDBN} loads symbols for an inferior from various
23430 symbol-containing files (@pxref{Files}). These include the primary
23431 executable file, any shared libraries used by the inferior, and any
23432 separate debug info files (@pxref{Separate Debug Files}).
23433 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
23435 The following objfile-related functions are available in the
23438 @findex gdb.current_objfile
23439 @defun gdb.current_objfile ()
23440 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
23441 sets the ``current objfile'' to the corresponding objfile. This
23442 function returns the current objfile. If there is no current objfile,
23443 this function returns @code{None}.
23446 @findex gdb.objfiles
23447 @defun gdb.objfiles ()
23448 Return a sequence of all the objfiles current known to @value{GDBN}.
23449 @xref{Objfiles In Python}.
23452 Each objfile is represented by an instance of the @code{gdb.Objfile}
23455 @defvar Objfile.filename
23456 The file name of the objfile as a string.
23459 @defvar Objfile.pretty_printers
23460 The @code{pretty_printers} attribute is a list of functions. It is
23461 used to look up pretty-printers. A @code{Value} is passed to each
23462 function in order; if the function returns @code{None}, then the
23463 search continues. Otherwise, the return value should be an object
23464 which is used to format the value. @xref{Pretty Printing API}, for more
23468 A @code{gdb.Objfile} object has the following methods:
23470 @defun Objfile.is_valid ()
23471 Returns @code{True} if the @code{gdb.Objfile} object is valid,
23472 @code{False} if not. A @code{gdb.Objfile} object can become invalid
23473 if the object file it refers to is not loaded in @value{GDBN} any
23474 longer. All other @code{gdb.Objfile} methods will throw an exception
23475 if it is invalid at the time the method is called.
23478 @node Frames In Python
23479 @subsubsection Accessing inferior stack frames from Python.
23481 @cindex frames in python
23482 When the debugged program stops, @value{GDBN} is able to analyze its call
23483 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
23484 represents a frame in the stack. A @code{gdb.Frame} object is only valid
23485 while its corresponding frame exists in the inferior's stack. If you try
23486 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
23487 exception (@pxref{Exception Handling}).
23489 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
23493 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
23497 The following frame-related functions are available in the @code{gdb} module:
23499 @findex gdb.selected_frame
23500 @defun gdb.selected_frame ()
23501 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
23504 @findex gdb.newest_frame
23505 @defun gdb.newest_frame ()
23506 Return the newest frame object for the selected thread.
23509 @defun gdb.frame_stop_reason_string (reason)
23510 Return a string explaining the reason why @value{GDBN} stopped unwinding
23511 frames, as expressed by the given @var{reason} code (an integer, see the
23512 @code{unwind_stop_reason} method further down in this section).
23515 A @code{gdb.Frame} object has the following methods:
23518 @defun Frame.is_valid ()
23519 Returns true if the @code{gdb.Frame} object is valid, false if not.
23520 A frame object can become invalid if the frame it refers to doesn't
23521 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
23522 an exception if it is invalid at the time the method is called.
23525 @defun Frame.name ()
23526 Returns the function name of the frame, or @code{None} if it can't be
23530 @defun Frame.type ()
23531 Returns the type of the frame. The value can be one of:
23533 @item gdb.NORMAL_FRAME
23534 An ordinary stack frame.
23536 @item gdb.DUMMY_FRAME
23537 A fake stack frame that was created by @value{GDBN} when performing an
23538 inferior function call.
23540 @item gdb.INLINE_FRAME
23541 A frame representing an inlined function. The function was inlined
23542 into a @code{gdb.NORMAL_FRAME} that is older than this one.
23544 @item gdb.TAILCALL_FRAME
23545 A frame representing a tail call. @xref{Tail Call Frames}.
23547 @item gdb.SIGTRAMP_FRAME
23548 A signal trampoline frame. This is the frame created by the OS when
23549 it calls into a signal handler.
23551 @item gdb.ARCH_FRAME
23552 A fake stack frame representing a cross-architecture call.
23554 @item gdb.SENTINEL_FRAME
23555 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
23560 @defun Frame.unwind_stop_reason ()
23561 Return an integer representing the reason why it's not possible to find
23562 more frames toward the outermost frame. Use
23563 @code{gdb.frame_stop_reason_string} to convert the value returned by this
23564 function to a string. The value can be one of:
23567 @item gdb.FRAME_UNWIND_NO_REASON
23568 No particular reason (older frames should be available).
23570 @item gdb.FRAME_UNWIND_NULL_ID
23571 The previous frame's analyzer returns an invalid result.
23573 @item gdb.FRAME_UNWIND_OUTERMOST
23574 This frame is the outermost.
23576 @item gdb.FRAME_UNWIND_UNAVAILABLE
23577 Cannot unwind further, because that would require knowing the
23578 values of registers or memory that have not been collected.
23580 @item gdb.FRAME_UNWIND_INNER_ID
23581 This frame ID looks like it ought to belong to a NEXT frame,
23582 but we got it for a PREV frame. Normally, this is a sign of
23583 unwinder failure. It could also indicate stack corruption.
23585 @item gdb.FRAME_UNWIND_SAME_ID
23586 This frame has the same ID as the previous one. That means
23587 that unwinding further would almost certainly give us another
23588 frame with exactly the same ID, so break the chain. Normally,
23589 this is a sign of unwinder failure. It could also indicate
23592 @item gdb.FRAME_UNWIND_NO_SAVED_PC
23593 The frame unwinder did not find any saved PC, but we needed
23594 one to unwind further.
23596 @item gdb.FRAME_UNWIND_FIRST_ERROR
23597 Any stop reason greater or equal to this value indicates some kind
23598 of error. This special value facilitates writing code that tests
23599 for errors in unwinding in a way that will work correctly even if
23600 the list of the other values is modified in future @value{GDBN}
23601 versions. Using it, you could write:
23603 reason = gdb.selected_frame().unwind_stop_reason ()
23604 reason_str = gdb.frame_stop_reason_string (reason)
23605 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
23606 print "An error occured: %s" % reason_str
23613 Returns the frame's resume address.
23616 @defun Frame.block ()
23617 Return the frame's code block. @xref{Blocks In Python}.
23620 @defun Frame.function ()
23621 Return the symbol for the function corresponding to this frame.
23622 @xref{Symbols In Python}.
23625 @defun Frame.older ()
23626 Return the frame that called this frame.
23629 @defun Frame.newer ()
23630 Return the frame called by this frame.
23633 @defun Frame.find_sal ()
23634 Return the frame's symtab and line object.
23635 @xref{Symbol Tables In Python}.
23638 @defun Frame.read_var (variable @r{[}, block@r{]})
23639 Return the value of @var{variable} in this frame. If the optional
23640 argument @var{block} is provided, search for the variable from that
23641 block; otherwise start at the frame's current block (which is
23642 determined by the frame's current program counter). @var{variable}
23643 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
23644 @code{gdb.Block} object.
23647 @defun Frame.select ()
23648 Set this frame to be the selected frame. @xref{Stack, ,Examining the
23653 @node Blocks In Python
23654 @subsubsection Accessing frame blocks from Python.
23656 @cindex blocks in python
23659 Within each frame, @value{GDBN} maintains information on each block
23660 stored in that frame. These blocks are organized hierarchically, and
23661 are represented individually in Python as a @code{gdb.Block}.
23662 Please see @ref{Frames In Python}, for a more in-depth discussion on
23663 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
23664 detailed technical information on @value{GDBN}'s book-keeping of the
23667 The following block-related functions are available in the @code{gdb}
23670 @findex gdb.block_for_pc
23671 @defun gdb.block_for_pc (pc)
23672 Return the @code{gdb.Block} containing the given @var{pc} value. If the
23673 block cannot be found for the @var{pc} value specified, the function
23674 will return @code{None}.
23677 A @code{gdb.Block} object has the following methods:
23680 @defun Block.is_valid ()
23681 Returns @code{True} if the @code{gdb.Block} object is valid,
23682 @code{False} if not. A block object can become invalid if the block it
23683 refers to doesn't exist anymore in the inferior. All other
23684 @code{gdb.Block} methods will throw an exception if it is invalid at
23685 the time the method is called. This method is also made available to
23686 the Python iterator object that @code{gdb.Block} provides in an iteration
23687 context and via the Python @code{iter} built-in function.
23691 A @code{gdb.Block} object has the following attributes:
23694 @defvar Block.start
23695 The start address of the block. This attribute is not writable.
23699 The end address of the block. This attribute is not writable.
23702 @defvar Block.function
23703 The name of the block represented as a @code{gdb.Symbol}. If the
23704 block is not named, then this attribute holds @code{None}. This
23705 attribute is not writable.
23708 @defvar Block.superblock
23709 The block containing this block. If this parent block does not exist,
23710 this attribute holds @code{None}. This attribute is not writable.
23713 @defvar Block.global_block
23714 The global block associated with this block. This attribute is not
23718 @defvar Block.static_block
23719 The static block associated with this block. This attribute is not
23723 @defvar Block.is_global
23724 @code{True} if the @code{gdb.Block} object is a global block,
23725 @code{False} if not. This attribute is not
23729 @defvar Block.is_static
23730 @code{True} if the @code{gdb.Block} object is a static block,
23731 @code{False} if not. This attribute is not writable.
23735 @node Symbols In Python
23736 @subsubsection Python representation of Symbols.
23738 @cindex symbols in python
23741 @value{GDBN} represents every variable, function and type as an
23742 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
23743 Similarly, Python represents these symbols in @value{GDBN} with the
23744 @code{gdb.Symbol} object.
23746 The following symbol-related functions are available in the @code{gdb}
23749 @findex gdb.lookup_symbol
23750 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
23751 This function searches for a symbol by name. The search scope can be
23752 restricted to the parameters defined in the optional domain and block
23755 @var{name} is the name of the symbol. It must be a string. The
23756 optional @var{block} argument restricts the search to symbols visible
23757 in that @var{block}. The @var{block} argument must be a
23758 @code{gdb.Block} object. If omitted, the block for the current frame
23759 is used. The optional @var{domain} argument restricts
23760 the search to the domain type. The @var{domain} argument must be a
23761 domain constant defined in the @code{gdb} module and described later
23764 The result is a tuple of two elements.
23765 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
23767 If the symbol is found, the second element is @code{True} if the symbol
23768 is a field of a method's object (e.g., @code{this} in C@t{++}),
23769 otherwise it is @code{False}.
23770 If the symbol is not found, the second element is @code{False}.
23773 @findex gdb.lookup_global_symbol
23774 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
23775 This function searches for a global symbol by name.
23776 The search scope can be restricted to by the domain argument.
23778 @var{name} is the name of the symbol. It must be a string.
23779 The optional @var{domain} argument restricts the search to the domain type.
23780 The @var{domain} argument must be a domain constant defined in the @code{gdb}
23781 module and described later in this chapter.
23783 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
23787 A @code{gdb.Symbol} object has the following attributes:
23790 @defvar Symbol.type
23791 The type of the symbol or @code{None} if no type is recorded.
23792 This attribute is represented as a @code{gdb.Type} object.
23793 @xref{Types In Python}. This attribute is not writable.
23796 @defvar Symbol.symtab
23797 The symbol table in which the symbol appears. This attribute is
23798 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
23799 Python}. This attribute is not writable.
23802 @defvar Symbol.name
23803 The name of the symbol as a string. This attribute is not writable.
23806 @defvar Symbol.linkage_name
23807 The name of the symbol, as used by the linker (i.e., may be mangled).
23808 This attribute is not writable.
23811 @defvar Symbol.print_name
23812 The name of the symbol in a form suitable for output. This is either
23813 @code{name} or @code{linkage_name}, depending on whether the user
23814 asked @value{GDBN} to display demangled or mangled names.
23817 @defvar Symbol.addr_class
23818 The address class of the symbol. This classifies how to find the value
23819 of a symbol. Each address class is a constant defined in the
23820 @code{gdb} module and described later in this chapter.
23823 @defvar Symbol.is_argument
23824 @code{True} if the symbol is an argument of a function.
23827 @defvar Symbol.is_constant
23828 @code{True} if the symbol is a constant.
23831 @defvar Symbol.is_function
23832 @code{True} if the symbol is a function or a method.
23835 @defvar Symbol.is_variable
23836 @code{True} if the symbol is a variable.
23840 A @code{gdb.Symbol} object has the following methods:
23843 @defun Symbol.is_valid ()
23844 Returns @code{True} if the @code{gdb.Symbol} object is valid,
23845 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
23846 the symbol it refers to does not exist in @value{GDBN} any longer.
23847 All other @code{gdb.Symbol} methods will throw an exception if it is
23848 invalid at the time the method is called.
23852 The available domain categories in @code{gdb.Symbol} are represented
23853 as constants in the @code{gdb} module:
23856 @findex SYMBOL_UNDEF_DOMAIN
23857 @findex gdb.SYMBOL_UNDEF_DOMAIN
23858 @item gdb.SYMBOL_UNDEF_DOMAIN
23859 This is used when a domain has not been discovered or none of the
23860 following domains apply. This usually indicates an error either
23861 in the symbol information or in @value{GDBN}'s handling of symbols.
23862 @findex SYMBOL_VAR_DOMAIN
23863 @findex gdb.SYMBOL_VAR_DOMAIN
23864 @item gdb.SYMBOL_VAR_DOMAIN
23865 This domain contains variables, function names, typedef names and enum
23867 @findex SYMBOL_STRUCT_DOMAIN
23868 @findex gdb.SYMBOL_STRUCT_DOMAIN
23869 @item gdb.SYMBOL_STRUCT_DOMAIN
23870 This domain holds struct, union and enum type names.
23871 @findex SYMBOL_LABEL_DOMAIN
23872 @findex gdb.SYMBOL_LABEL_DOMAIN
23873 @item gdb.SYMBOL_LABEL_DOMAIN
23874 This domain contains names of labels (for gotos).
23875 @findex SYMBOL_VARIABLES_DOMAIN
23876 @findex gdb.SYMBOL_VARIABLES_DOMAIN
23877 @item gdb.SYMBOL_VARIABLES_DOMAIN
23878 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
23879 contains everything minus functions and types.
23880 @findex SYMBOL_FUNCTIONS_DOMAIN
23881 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
23882 @item gdb.SYMBOL_FUNCTION_DOMAIN
23883 This domain contains all functions.
23884 @findex SYMBOL_TYPES_DOMAIN
23885 @findex gdb.SYMBOL_TYPES_DOMAIN
23886 @item gdb.SYMBOL_TYPES_DOMAIN
23887 This domain contains all types.
23890 The available address class categories in @code{gdb.Symbol} are represented
23891 as constants in the @code{gdb} module:
23894 @findex SYMBOL_LOC_UNDEF
23895 @findex gdb.SYMBOL_LOC_UNDEF
23896 @item gdb.SYMBOL_LOC_UNDEF
23897 If this is returned by address class, it indicates an error either in
23898 the symbol information or in @value{GDBN}'s handling of symbols.
23899 @findex SYMBOL_LOC_CONST
23900 @findex gdb.SYMBOL_LOC_CONST
23901 @item gdb.SYMBOL_LOC_CONST
23902 Value is constant int.
23903 @findex SYMBOL_LOC_STATIC
23904 @findex gdb.SYMBOL_LOC_STATIC
23905 @item gdb.SYMBOL_LOC_STATIC
23906 Value is at a fixed address.
23907 @findex SYMBOL_LOC_REGISTER
23908 @findex gdb.SYMBOL_LOC_REGISTER
23909 @item gdb.SYMBOL_LOC_REGISTER
23910 Value is in a register.
23911 @findex SYMBOL_LOC_ARG
23912 @findex gdb.SYMBOL_LOC_ARG
23913 @item gdb.SYMBOL_LOC_ARG
23914 Value is an argument. This value is at the offset stored within the
23915 symbol inside the frame's argument list.
23916 @findex SYMBOL_LOC_REF_ARG
23917 @findex gdb.SYMBOL_LOC_REF_ARG
23918 @item gdb.SYMBOL_LOC_REF_ARG
23919 Value address is stored in the frame's argument list. Just like
23920 @code{LOC_ARG} except that the value's address is stored at the
23921 offset, not the value itself.
23922 @findex SYMBOL_LOC_REGPARM_ADDR
23923 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
23924 @item gdb.SYMBOL_LOC_REGPARM_ADDR
23925 Value is a specified register. Just like @code{LOC_REGISTER} except
23926 the register holds the address of the argument instead of the argument
23928 @findex SYMBOL_LOC_LOCAL
23929 @findex gdb.SYMBOL_LOC_LOCAL
23930 @item gdb.SYMBOL_LOC_LOCAL
23931 Value is a local variable.
23932 @findex SYMBOL_LOC_TYPEDEF
23933 @findex gdb.SYMBOL_LOC_TYPEDEF
23934 @item gdb.SYMBOL_LOC_TYPEDEF
23935 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
23937 @findex SYMBOL_LOC_BLOCK
23938 @findex gdb.SYMBOL_LOC_BLOCK
23939 @item gdb.SYMBOL_LOC_BLOCK
23941 @findex SYMBOL_LOC_CONST_BYTES
23942 @findex gdb.SYMBOL_LOC_CONST_BYTES
23943 @item gdb.SYMBOL_LOC_CONST_BYTES
23944 Value is a byte-sequence.
23945 @findex SYMBOL_LOC_UNRESOLVED
23946 @findex gdb.SYMBOL_LOC_UNRESOLVED
23947 @item gdb.SYMBOL_LOC_UNRESOLVED
23948 Value is at a fixed address, but the address of the variable has to be
23949 determined from the minimal symbol table whenever the variable is
23951 @findex SYMBOL_LOC_OPTIMIZED_OUT
23952 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
23953 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
23954 The value does not actually exist in the program.
23955 @findex SYMBOL_LOC_COMPUTED
23956 @findex gdb.SYMBOL_LOC_COMPUTED
23957 @item gdb.SYMBOL_LOC_COMPUTED
23958 The value's address is a computed location.
23961 @node Symbol Tables In Python
23962 @subsubsection Symbol table representation in Python.
23964 @cindex symbol tables in python
23966 @tindex gdb.Symtab_and_line
23968 Access to symbol table data maintained by @value{GDBN} on the inferior
23969 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
23970 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
23971 from the @code{find_sal} method in @code{gdb.Frame} object.
23972 @xref{Frames In Python}.
23974 For more information on @value{GDBN}'s symbol table management, see
23975 @ref{Symbols, ,Examining the Symbol Table}, for more information.
23977 A @code{gdb.Symtab_and_line} object has the following attributes:
23980 @defvar Symtab_and_line.symtab
23981 The symbol table object (@code{gdb.Symtab}) for this frame.
23982 This attribute is not writable.
23985 @defvar Symtab_and_line.pc
23986 Indicates the current program counter address. This attribute is not
23990 @defvar Symtab_and_line.line
23991 Indicates the current line number for this object. This
23992 attribute is not writable.
23996 A @code{gdb.Symtab_and_line} object has the following methods:
23999 @defun Symtab_and_line.is_valid ()
24000 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
24001 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
24002 invalid if the Symbol table and line object it refers to does not
24003 exist in @value{GDBN} any longer. All other
24004 @code{gdb.Symtab_and_line} methods will throw an exception if it is
24005 invalid at the time the method is called.
24009 A @code{gdb.Symtab} object has the following attributes:
24012 @defvar Symtab.filename
24013 The symbol table's source filename. This attribute is not writable.
24016 @defvar Symtab.objfile
24017 The symbol table's backing object file. @xref{Objfiles In Python}.
24018 This attribute is not writable.
24022 A @code{gdb.Symtab} object has the following methods:
24025 @defun Symtab.is_valid ()
24026 Returns @code{True} if the @code{gdb.Symtab} object is valid,
24027 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
24028 the symbol table it refers to does not exist in @value{GDBN} any
24029 longer. All other @code{gdb.Symtab} methods will throw an exception
24030 if it is invalid at the time the method is called.
24033 @defun Symtab.fullname ()
24034 Return the symbol table's source absolute file name.
24038 @node Breakpoints In Python
24039 @subsubsection Manipulating breakpoints using Python
24041 @cindex breakpoints in python
24042 @tindex gdb.Breakpoint
24044 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
24047 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal@r{]]]})
24048 Create a new breakpoint. @var{spec} is a string naming the
24049 location of the breakpoint, or an expression that defines a
24050 watchpoint. The contents can be any location recognized by the
24051 @code{break} command, or in the case of a watchpoint, by the @code{watch}
24052 command. The optional @var{type} denotes the breakpoint to create
24053 from the types defined later in this chapter. This argument can be
24054 either: @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
24055 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal} argument
24056 allows the breakpoint to become invisible to the user. The breakpoint
24057 will neither be reported when created, nor will it be listed in the
24058 output from @code{info breakpoints} (but will be listed with the
24059 @code{maint info breakpoints} command). The optional @var{wp_class}
24060 argument defines the class of watchpoint to create, if @var{type} is
24061 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it is
24062 assumed to be a @code{gdb.WP_WRITE} class.
24065 @defun Breakpoint.stop (self)
24066 The @code{gdb.Breakpoint} class can be sub-classed and, in
24067 particular, you may choose to implement the @code{stop} method.
24068 If this method is defined as a sub-class of @code{gdb.Breakpoint},
24069 it will be called when the inferior reaches any location of a
24070 breakpoint which instantiates that sub-class. If the method returns
24071 @code{True}, the inferior will be stopped at the location of the
24072 breakpoint, otherwise the inferior will continue.
24074 If there are multiple breakpoints at the same location with a
24075 @code{stop} method, each one will be called regardless of the
24076 return status of the previous. This ensures that all @code{stop}
24077 methods have a chance to execute at that location. In this scenario
24078 if one of the methods returns @code{True} but the others return
24079 @code{False}, the inferior will still be stopped.
24081 You should not alter the execution state of the inferior (i.e.@:, step,
24082 next, etc.), alter the current frame context (i.e.@:, change the current
24083 active frame), or alter, add or delete any breakpoint. As a general
24084 rule, you should not alter any data within @value{GDBN} or the inferior
24087 Example @code{stop} implementation:
24090 class MyBreakpoint (gdb.Breakpoint):
24092 inf_val = gdb.parse_and_eval("foo")
24099 The available watchpoint types represented by constants are defined in the
24104 @findex gdb.WP_READ
24106 Read only watchpoint.
24109 @findex gdb.WP_WRITE
24111 Write only watchpoint.
24114 @findex gdb.WP_ACCESS
24115 @item gdb.WP_ACCESS
24116 Read/Write watchpoint.
24119 @defun Breakpoint.is_valid ()
24120 Return @code{True} if this @code{Breakpoint} object is valid,
24121 @code{False} otherwise. A @code{Breakpoint} object can become invalid
24122 if the user deletes the breakpoint. In this case, the object still
24123 exists, but the underlying breakpoint does not. In the cases of
24124 watchpoint scope, the watchpoint remains valid even if execution of the
24125 inferior leaves the scope of that watchpoint.
24128 @defun Breakpoint.delete
24129 Permanently deletes the @value{GDBN} breakpoint. This also
24130 invalidates the Python @code{Breakpoint} object. Any further access
24131 to this object's attributes or methods will raise an error.
24134 @defvar Breakpoint.enabled
24135 This attribute is @code{True} if the breakpoint is enabled, and
24136 @code{False} otherwise. This attribute is writable.
24139 @defvar Breakpoint.silent
24140 This attribute is @code{True} if the breakpoint is silent, and
24141 @code{False} otherwise. This attribute is writable.
24143 Note that a breakpoint can also be silent if it has commands and the
24144 first command is @code{silent}. This is not reported by the
24145 @code{silent} attribute.
24148 @defvar Breakpoint.thread
24149 If the breakpoint is thread-specific, this attribute holds the thread
24150 id. If the breakpoint is not thread-specific, this attribute is
24151 @code{None}. This attribute is writable.
24154 @defvar Breakpoint.task
24155 If the breakpoint is Ada task-specific, this attribute holds the Ada task
24156 id. If the breakpoint is not task-specific (or the underlying
24157 language is not Ada), this attribute is @code{None}. This attribute
24161 @defvar Breakpoint.ignore_count
24162 This attribute holds the ignore count for the breakpoint, an integer.
24163 This attribute is writable.
24166 @defvar Breakpoint.number
24167 This attribute holds the breakpoint's number --- the identifier used by
24168 the user to manipulate the breakpoint. This attribute is not writable.
24171 @defvar Breakpoint.type
24172 This attribute holds the breakpoint's type --- the identifier used to
24173 determine the actual breakpoint type or use-case. This attribute is not
24177 @defvar Breakpoint.visible
24178 This attribute tells whether the breakpoint is visible to the user
24179 when set, or when the @samp{info breakpoints} command is run. This
24180 attribute is not writable.
24183 The available types are represented by constants defined in the @code{gdb}
24187 @findex BP_BREAKPOINT
24188 @findex gdb.BP_BREAKPOINT
24189 @item gdb.BP_BREAKPOINT
24190 Normal code breakpoint.
24192 @findex BP_WATCHPOINT
24193 @findex gdb.BP_WATCHPOINT
24194 @item gdb.BP_WATCHPOINT
24195 Watchpoint breakpoint.
24197 @findex BP_HARDWARE_WATCHPOINT
24198 @findex gdb.BP_HARDWARE_WATCHPOINT
24199 @item gdb.BP_HARDWARE_WATCHPOINT
24200 Hardware assisted watchpoint.
24202 @findex BP_READ_WATCHPOINT
24203 @findex gdb.BP_READ_WATCHPOINT
24204 @item gdb.BP_READ_WATCHPOINT
24205 Hardware assisted read watchpoint.
24207 @findex BP_ACCESS_WATCHPOINT
24208 @findex gdb.BP_ACCESS_WATCHPOINT
24209 @item gdb.BP_ACCESS_WATCHPOINT
24210 Hardware assisted access watchpoint.
24213 @defvar Breakpoint.hit_count
24214 This attribute holds the hit count for the breakpoint, an integer.
24215 This attribute is writable, but currently it can only be set to zero.
24218 @defvar Breakpoint.location
24219 This attribute holds the location of the breakpoint, as specified by
24220 the user. It is a string. If the breakpoint does not have a location
24221 (that is, it is a watchpoint) the attribute's value is @code{None}. This
24222 attribute is not writable.
24225 @defvar Breakpoint.expression
24226 This attribute holds a breakpoint expression, as specified by
24227 the user. It is a string. If the breakpoint does not have an
24228 expression (the breakpoint is not a watchpoint) the attribute's value
24229 is @code{None}. This attribute is not writable.
24232 @defvar Breakpoint.condition
24233 This attribute holds the condition of the breakpoint, as specified by
24234 the user. It is a string. If there is no condition, this attribute's
24235 value is @code{None}. This attribute is writable.
24238 @defvar Breakpoint.commands
24239 This attribute holds the commands attached to the breakpoint. If
24240 there are commands, this attribute's value is a string holding all the
24241 commands, separated by newlines. If there are no commands, this
24242 attribute is @code{None}. This attribute is not writable.
24245 @node Lazy Strings In Python
24246 @subsubsection Python representation of lazy strings.
24248 @cindex lazy strings in python
24249 @tindex gdb.LazyString
24251 A @dfn{lazy string} is a string whose contents is not retrieved or
24252 encoded until it is needed.
24254 A @code{gdb.LazyString} is represented in @value{GDBN} as an
24255 @code{address} that points to a region of memory, an @code{encoding}
24256 that will be used to encode that region of memory, and a @code{length}
24257 to delimit the region of memory that represents the string. The
24258 difference between a @code{gdb.LazyString} and a string wrapped within
24259 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
24260 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
24261 retrieved and encoded during printing, while a @code{gdb.Value}
24262 wrapping a string is immediately retrieved and encoded on creation.
24264 A @code{gdb.LazyString} object has the following functions:
24266 @defun LazyString.value ()
24267 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
24268 will point to the string in memory, but will lose all the delayed
24269 retrieval, encoding and handling that @value{GDBN} applies to a
24270 @code{gdb.LazyString}.
24273 @defvar LazyString.address
24274 This attribute holds the address of the string. This attribute is not
24278 @defvar LazyString.length
24279 This attribute holds the length of the string in characters. If the
24280 length is -1, then the string will be fetched and encoded up to the
24281 first null of appropriate width. This attribute is not writable.
24284 @defvar LazyString.encoding
24285 This attribute holds the encoding that will be applied to the string
24286 when the string is printed by @value{GDBN}. If the encoding is not
24287 set, or contains an empty string, then @value{GDBN} will select the
24288 most appropriate encoding when the string is printed. This attribute
24292 @defvar LazyString.type
24293 This attribute holds the type that is represented by the lazy string's
24294 type. For a lazy string this will always be a pointer type. To
24295 resolve this to the lazy string's character type, use the type's
24296 @code{target} method. @xref{Types In Python}. This attribute is not
24301 @subsection Auto-loading
24302 @cindex auto-loading, Python
24304 When a new object file is read (for example, due to the @code{file}
24305 command, or because the inferior has loaded a shared library),
24306 @value{GDBN} will look for Python support scripts in several ways:
24307 @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section.
24310 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
24311 * .debug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
24312 * Which flavor to choose?::
24315 The auto-loading feature is useful for supplying application-specific
24316 debugging commands and scripts.
24318 Auto-loading can be enabled or disabled,
24319 and the list of auto-loaded scripts can be printed.
24322 @kindex set auto-load-scripts
24323 @item set auto-load-scripts [yes|no]
24324 Enable or disable the auto-loading of Python scripts.
24326 @kindex show auto-load-scripts
24327 @item show auto-load-scripts
24328 Show whether auto-loading of Python scripts is enabled or disabled.
24330 @kindex info auto-load-scripts
24331 @cindex print list of auto-loaded scripts
24332 @item info auto-load-scripts [@var{regexp}]
24333 Print the list of all scripts that @value{GDBN} auto-loaded.
24335 Also printed is the list of scripts that were mentioned in
24336 the @code{.debug_gdb_scripts} section and were not found
24337 (@pxref{.debug_gdb_scripts section}).
24338 This is useful because their names are not printed when @value{GDBN}
24339 tries to load them and fails. There may be many of them, and printing
24340 an error message for each one is problematic.
24342 If @var{regexp} is supplied only scripts with matching names are printed.
24347 (gdb) info auto-load-scripts
24349 Yes py-section-script.py
24350 full name: /tmp/py-section-script.py
24351 Missing my-foo-pretty-printers.py
24355 When reading an auto-loaded file, @value{GDBN} sets the
24356 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
24357 function (@pxref{Objfiles In Python}). This can be useful for
24358 registering objfile-specific pretty-printers.
24360 @node objfile-gdb.py file
24361 @subsubsection The @file{@var{objfile}-gdb.py} file
24362 @cindex @file{@var{objfile}-gdb.py}
24364 When a new object file is read, @value{GDBN} looks for
24365 a file named @file{@var{objfile}-gdb.py},
24366 where @var{objfile} is the object file's real name, formed by ensuring
24367 that the file name is absolute, following all symlinks, and resolving
24368 @code{.} and @code{..} components. If this file exists and is
24369 readable, @value{GDBN} will evaluate it as a Python script.
24371 If this file does not exist, and if the parameter
24372 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
24373 then @value{GDBN} will look for @var{real-name} in all of the
24374 directories mentioned in the value of @code{debug-file-directory}.
24376 Finally, if this file does not exist, then @value{GDBN} will look for
24377 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
24378 @var{data-directory} is @value{GDBN}'s data directory (available via
24379 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
24380 is the object file's real name, as described above.
24382 @value{GDBN} does not track which files it has already auto-loaded this way.
24383 @value{GDBN} will load the associated script every time the corresponding
24384 @var{objfile} is opened.
24385 So your @file{-gdb.py} file should be careful to avoid errors if it
24386 is evaluated more than once.
24388 @node .debug_gdb_scripts section
24389 @subsubsection The @code{.debug_gdb_scripts} section
24390 @cindex @code{.debug_gdb_scripts} section
24392 For systems using file formats like ELF and COFF,
24393 when @value{GDBN} loads a new object file
24394 it will look for a special section named @samp{.debug_gdb_scripts}.
24395 If this section exists, its contents is a list of names of scripts to load.
24397 @value{GDBN} will look for each specified script file first in the
24398 current directory and then along the source search path
24399 (@pxref{Source Path, ,Specifying Source Directories}),
24400 except that @file{$cdir} is not searched, since the compilation
24401 directory is not relevant to scripts.
24403 Entries can be placed in section @code{.debug_gdb_scripts} with,
24404 for example, this GCC macro:
24407 /* Note: The "MS" section flags are to remove duplicates. */
24408 #define DEFINE_GDB_SCRIPT(script_name) \
24410 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
24412 .asciz \"" script_name "\"\n\
24418 Then one can reference the macro in a header or source file like this:
24421 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
24424 The script name may include directories if desired.
24426 If the macro is put in a header, any application or library
24427 using this header will get a reference to the specified script.
24429 @node Which flavor to choose?
24430 @subsubsection Which flavor to choose?
24432 Given the multiple ways of auto-loading Python scripts, it might not always
24433 be clear which one to choose. This section provides some guidance.
24435 Benefits of the @file{-gdb.py} way:
24439 Can be used with file formats that don't support multiple sections.
24442 Ease of finding scripts for public libraries.
24444 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
24445 in the source search path.
24446 For publicly installed libraries, e.g., @file{libstdc++}, there typically
24447 isn't a source directory in which to find the script.
24450 Doesn't require source code additions.
24453 Benefits of the @code{.debug_gdb_scripts} way:
24457 Works with static linking.
24459 Scripts for libraries done the @file{-gdb.py} way require an objfile to
24460 trigger their loading. When an application is statically linked the only
24461 objfile available is the executable, and it is cumbersome to attach all the
24462 scripts from all the input libraries to the executable's @file{-gdb.py} script.
24465 Works with classes that are entirely inlined.
24467 Some classes can be entirely inlined, and thus there may not be an associated
24468 shared library to attach a @file{-gdb.py} script to.
24471 Scripts needn't be copied out of the source tree.
24473 In some circumstances, apps can be built out of large collections of internal
24474 libraries, and the build infrastructure necessary to install the
24475 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
24476 cumbersome. It may be easier to specify the scripts in the
24477 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
24478 top of the source tree to the source search path.
24481 @node Python modules
24482 @subsection Python modules
24483 @cindex python modules
24485 @value{GDBN} comes with several modules to assist writing Python code.
24488 * gdb.printing:: Building and registering pretty-printers.
24489 * gdb.types:: Utilities for working with types.
24490 * gdb.prompt:: Utilities for prompt value substitution.
24494 @subsubsection gdb.printing
24495 @cindex gdb.printing
24497 This module provides a collection of utilities for working with
24501 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
24502 This class specifies the API that makes @samp{info pretty-printer},
24503 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
24504 Pretty-printers should generally inherit from this class.
24506 @item SubPrettyPrinter (@var{name})
24507 For printers that handle multiple types, this class specifies the
24508 corresponding API for the subprinters.
24510 @item RegexpCollectionPrettyPrinter (@var{name})
24511 Utility class for handling multiple printers, all recognized via
24512 regular expressions.
24513 @xref{Writing a Pretty-Printer}, for an example.
24515 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
24516 Register @var{printer} with the pretty-printer list of @var{obj}.
24517 If @var{replace} is @code{True} then any existing copy of the printer
24518 is replaced. Otherwise a @code{RuntimeError} exception is raised
24519 if a printer with the same name already exists.
24523 @subsubsection gdb.types
24526 This module provides a collection of utilities for working with
24527 @code{gdb.Types} objects.
24530 @item get_basic_type (@var{type})
24531 Return @var{type} with const and volatile qualifiers stripped,
24532 and with typedefs and C@t{++} references converted to the underlying type.
24537 typedef const int const_int;
24539 const_int& foo_ref (foo);
24540 int main () @{ return 0; @}
24547 (gdb) python import gdb.types
24548 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
24549 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
24553 @item has_field (@var{type}, @var{field})
24554 Return @code{True} if @var{type}, assumed to be a type with fields
24555 (e.g., a structure or union), has field @var{field}.
24557 @item make_enum_dict (@var{enum_type})
24558 Return a Python @code{dictionary} type produced from @var{enum_type}.
24560 @item deep_items (@var{type})
24561 Returns a Python iterator similar to the standard
24562 @code{gdb.Type.iteritems} method, except that the iterator returned
24563 by @code{deep_items} will recursively traverse anonymous struct or
24564 union fields. For example:
24578 Then in @value{GDBN}:
24580 (@value{GDBP}) python import gdb.types
24581 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
24582 (@value{GDBP}) python print struct_a.keys ()
24584 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
24585 @{['a', 'b0', 'b1']@}
24591 @subsubsection gdb.prompt
24594 This module provides a method for prompt value-substitution.
24597 @item substitute_prompt (@var{string})
24598 Return @var{string} with escape sequences substituted by values. Some
24599 escape sequences take arguments. You can specify arguments inside
24600 ``@{@}'' immediately following the escape sequence.
24602 The escape sequences you can pass to this function are:
24606 Substitute a backslash.
24608 Substitute an ESC character.
24610 Substitute the selected frame; an argument names a frame parameter.
24612 Substitute a newline.
24614 Substitute a parameter's value; the argument names the parameter.
24616 Substitute a carriage return.
24618 Substitute the selected thread; an argument names a thread parameter.
24620 Substitute the version of GDB.
24622 Substitute the current working directory.
24624 Begin a sequence of non-printing characters. These sequences are
24625 typically used with the ESC character, and are not counted in the string
24626 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
24627 blue-colored ``(gdb)'' prompt where the length is five.
24629 End a sequence of non-printing characters.
24635 substitute_prompt (``frame: \f,
24636 print arguments: \p@{print frame-arguments@}'')
24639 @exdent will return the string:
24642 "frame: main, print arguments: scalars"
24647 @section Creating new spellings of existing commands
24648 @cindex aliases for commands
24650 It is often useful to define alternate spellings of existing commands.
24651 For example, if a new @value{GDBN} command defined in Python has
24652 a long name to type, it is handy to have an abbreviated version of it
24653 that involves less typing.
24655 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
24656 of the @samp{step} command even though it is otherwise an ambiguous
24657 abbreviation of other commands like @samp{set} and @samp{show}.
24659 Aliases are also used to provide shortened or more common versions
24660 of multi-word commands. For example, @value{GDBN} provides the
24661 @samp{tty} alias of the @samp{set inferior-tty} command.
24663 You can define a new alias with the @samp{alias} command.
24668 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
24672 @var{ALIAS} specifies the name of the new alias.
24673 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
24676 @var{COMMAND} specifies the name of an existing command
24677 that is being aliased.
24679 The @samp{-a} option specifies that the new alias is an abbreviation
24680 of the command. Abbreviations are not shown in command
24681 lists displayed by the @samp{help} command.
24683 The @samp{--} option specifies the end of options,
24684 and is useful when @var{ALIAS} begins with a dash.
24686 Here is a simple example showing how to make an abbreviation
24687 of a command so that there is less to type.
24688 Suppose you were tired of typing @samp{disas}, the current
24689 shortest unambiguous abbreviation of the @samp{disassemble} command
24690 and you wanted an even shorter version named @samp{di}.
24691 The following will accomplish this.
24694 (gdb) alias -a di = disas
24697 Note that aliases are different from user-defined commands.
24698 With a user-defined command, you also need to write documentation
24699 for it with the @samp{document} command.
24700 An alias automatically picks up the documentation of the existing command.
24702 Here is an example where we make @samp{elms} an abbreviation of
24703 @samp{elements} in the @samp{set print elements} command.
24704 This is to show that you can make an abbreviation of any part
24708 (gdb) alias -a set print elms = set print elements
24709 (gdb) alias -a show print elms = show print elements
24710 (gdb) set p elms 20
24712 Limit on string chars or array elements to print is 200.
24715 Note that if you are defining an alias of a @samp{set} command,
24716 and you want to have an alias for the corresponding @samp{show}
24717 command, then you need to define the latter separately.
24719 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
24720 @var{ALIAS}, just as they are normally.
24723 (gdb) alias -a set pr elms = set p ele
24726 Finally, here is an example showing the creation of a one word
24727 alias for a more complex command.
24728 This creates alias @samp{spe} of the command @samp{set print elements}.
24731 (gdb) alias spe = set print elements
24736 @chapter Command Interpreters
24737 @cindex command interpreters
24739 @value{GDBN} supports multiple command interpreters, and some command
24740 infrastructure to allow users or user interface writers to switch
24741 between interpreters or run commands in other interpreters.
24743 @value{GDBN} currently supports two command interpreters, the console
24744 interpreter (sometimes called the command-line interpreter or @sc{cli})
24745 and the machine interface interpreter (or @sc{gdb/mi}). This manual
24746 describes both of these interfaces in great detail.
24748 By default, @value{GDBN} will start with the console interpreter.
24749 However, the user may choose to start @value{GDBN} with another
24750 interpreter by specifying the @option{-i} or @option{--interpreter}
24751 startup options. Defined interpreters include:
24755 @cindex console interpreter
24756 The traditional console or command-line interpreter. This is the most often
24757 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
24758 @value{GDBN} will use this interpreter.
24761 @cindex mi interpreter
24762 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
24763 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
24764 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
24768 @cindex mi2 interpreter
24769 The current @sc{gdb/mi} interface.
24772 @cindex mi1 interpreter
24773 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
24777 @cindex invoke another interpreter
24778 The interpreter being used by @value{GDBN} may not be dynamically
24779 switched at runtime. Although possible, this could lead to a very
24780 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
24781 enters the command "interpreter-set console" in a console view,
24782 @value{GDBN} would switch to using the console interpreter, rendering
24783 the IDE inoperable!
24785 @kindex interpreter-exec
24786 Although you may only choose a single interpreter at startup, you may execute
24787 commands in any interpreter from the current interpreter using the appropriate
24788 command. If you are running the console interpreter, simply use the
24789 @code{interpreter-exec} command:
24792 interpreter-exec mi "-data-list-register-names"
24795 @sc{gdb/mi} has a similar command, although it is only available in versions of
24796 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
24799 @chapter @value{GDBN} Text User Interface
24801 @cindex Text User Interface
24804 * TUI Overview:: TUI overview
24805 * TUI Keys:: TUI key bindings
24806 * TUI Single Key Mode:: TUI single key mode
24807 * TUI Commands:: TUI-specific commands
24808 * TUI Configuration:: TUI configuration variables
24811 The @value{GDBN} Text User Interface (TUI) is a terminal
24812 interface which uses the @code{curses} library to show the source
24813 file, the assembly output, the program registers and @value{GDBN}
24814 commands in separate text windows. The TUI mode is supported only
24815 on platforms where a suitable version of the @code{curses} library
24818 @pindex @value{GDBTUI}
24819 The TUI mode is enabled by default when you invoke @value{GDBN} as
24820 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
24821 You can also switch in and out of TUI mode while @value{GDBN} runs by
24822 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
24823 @xref{TUI Keys, ,TUI Key Bindings}.
24826 @section TUI Overview
24828 In TUI mode, @value{GDBN} can display several text windows:
24832 This window is the @value{GDBN} command window with the @value{GDBN}
24833 prompt and the @value{GDBN} output. The @value{GDBN} input is still
24834 managed using readline.
24837 The source window shows the source file of the program. The current
24838 line and active breakpoints are displayed in this window.
24841 The assembly window shows the disassembly output of the program.
24844 This window shows the processor registers. Registers are highlighted
24845 when their values change.
24848 The source and assembly windows show the current program position
24849 by highlighting the current line and marking it with a @samp{>} marker.
24850 Breakpoints are indicated with two markers. The first marker
24851 indicates the breakpoint type:
24855 Breakpoint which was hit at least once.
24858 Breakpoint which was never hit.
24861 Hardware breakpoint which was hit at least once.
24864 Hardware breakpoint which was never hit.
24867 The second marker indicates whether the breakpoint is enabled or not:
24871 Breakpoint is enabled.
24874 Breakpoint is disabled.
24877 The source, assembly and register windows are updated when the current
24878 thread changes, when the frame changes, or when the program counter
24881 These windows are not all visible at the same time. The command
24882 window is always visible. The others can be arranged in several
24893 source and assembly,
24896 source and registers, or
24899 assembly and registers.
24902 A status line above the command window shows the following information:
24906 Indicates the current @value{GDBN} target.
24907 (@pxref{Targets, ,Specifying a Debugging Target}).
24910 Gives the current process or thread number.
24911 When no process is being debugged, this field is set to @code{No process}.
24914 Gives the current function name for the selected frame.
24915 The name is demangled if demangling is turned on (@pxref{Print Settings}).
24916 When there is no symbol corresponding to the current program counter,
24917 the string @code{??} is displayed.
24920 Indicates the current line number for the selected frame.
24921 When the current line number is not known, the string @code{??} is displayed.
24924 Indicates the current program counter address.
24928 @section TUI Key Bindings
24929 @cindex TUI key bindings
24931 The TUI installs several key bindings in the readline keymaps
24932 @ifset SYSTEM_READLINE
24933 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
24935 @ifclear SYSTEM_READLINE
24936 (@pxref{Command Line Editing}).
24938 The following key bindings are installed for both TUI mode and the
24939 @value{GDBN} standard mode.
24948 Enter or leave the TUI mode. When leaving the TUI mode,
24949 the curses window management stops and @value{GDBN} operates using
24950 its standard mode, writing on the terminal directly. When reentering
24951 the TUI mode, control is given back to the curses windows.
24952 The screen is then refreshed.
24956 Use a TUI layout with only one window. The layout will
24957 either be @samp{source} or @samp{assembly}. When the TUI mode
24958 is not active, it will switch to the TUI mode.
24960 Think of this key binding as the Emacs @kbd{C-x 1} binding.
24964 Use a TUI layout with at least two windows. When the current
24965 layout already has two windows, the next layout with two windows is used.
24966 When a new layout is chosen, one window will always be common to the
24967 previous layout and the new one.
24969 Think of it as the Emacs @kbd{C-x 2} binding.
24973 Change the active window. The TUI associates several key bindings
24974 (like scrolling and arrow keys) with the active window. This command
24975 gives the focus to the next TUI window.
24977 Think of it as the Emacs @kbd{C-x o} binding.
24981 Switch in and out of the TUI SingleKey mode that binds single
24982 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
24985 The following key bindings only work in the TUI mode:
24990 Scroll the active window one page up.
24994 Scroll the active window one page down.
24998 Scroll the active window one line up.
25002 Scroll the active window one line down.
25006 Scroll the active window one column left.
25010 Scroll the active window one column right.
25014 Refresh the screen.
25017 Because the arrow keys scroll the active window in the TUI mode, they
25018 are not available for their normal use by readline unless the command
25019 window has the focus. When another window is active, you must use
25020 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
25021 and @kbd{C-f} to control the command window.
25023 @node TUI Single Key Mode
25024 @section TUI Single Key Mode
25025 @cindex TUI single key mode
25027 The TUI also provides a @dfn{SingleKey} mode, which binds several
25028 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
25029 switch into this mode, where the following key bindings are used:
25032 @kindex c @r{(SingleKey TUI key)}
25036 @kindex d @r{(SingleKey TUI key)}
25040 @kindex f @r{(SingleKey TUI key)}
25044 @kindex n @r{(SingleKey TUI key)}
25048 @kindex q @r{(SingleKey TUI key)}
25050 exit the SingleKey mode.
25052 @kindex r @r{(SingleKey TUI key)}
25056 @kindex s @r{(SingleKey TUI key)}
25060 @kindex u @r{(SingleKey TUI key)}
25064 @kindex v @r{(SingleKey TUI key)}
25068 @kindex w @r{(SingleKey TUI key)}
25073 Other keys temporarily switch to the @value{GDBN} command prompt.
25074 The key that was pressed is inserted in the editing buffer so that
25075 it is possible to type most @value{GDBN} commands without interaction
25076 with the TUI SingleKey mode. Once the command is entered the TUI
25077 SingleKey mode is restored. The only way to permanently leave
25078 this mode is by typing @kbd{q} or @kbd{C-x s}.
25082 @section TUI-specific Commands
25083 @cindex TUI commands
25085 The TUI has specific commands to control the text windows.
25086 These commands are always available, even when @value{GDBN} is not in
25087 the TUI mode. When @value{GDBN} is in the standard mode, most
25088 of these commands will automatically switch to the TUI mode.
25090 Note that if @value{GDBN}'s @code{stdout} is not connected to a
25091 terminal, or @value{GDBN} has been started with the machine interface
25092 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
25093 these commands will fail with an error, because it would not be
25094 possible or desirable to enable curses window management.
25099 List and give the size of all displayed windows.
25103 Display the next layout.
25106 Display the previous layout.
25109 Display the source window only.
25112 Display the assembly window only.
25115 Display the source and assembly window.
25118 Display the register window together with the source or assembly window.
25122 Make the next window active for scrolling.
25125 Make the previous window active for scrolling.
25128 Make the source window active for scrolling.
25131 Make the assembly window active for scrolling.
25134 Make the register window active for scrolling.
25137 Make the command window active for scrolling.
25141 Refresh the screen. This is similar to typing @kbd{C-L}.
25143 @item tui reg float
25145 Show the floating point registers in the register window.
25147 @item tui reg general
25148 Show the general registers in the register window.
25151 Show the next register group. The list of register groups as well as
25152 their order is target specific. The predefined register groups are the
25153 following: @code{general}, @code{float}, @code{system}, @code{vector},
25154 @code{all}, @code{save}, @code{restore}.
25156 @item tui reg system
25157 Show the system registers in the register window.
25161 Update the source window and the current execution point.
25163 @item winheight @var{name} +@var{count}
25164 @itemx winheight @var{name} -@var{count}
25166 Change the height of the window @var{name} by @var{count}
25167 lines. Positive counts increase the height, while negative counts
25170 @item tabset @var{nchars}
25172 Set the width of tab stops to be @var{nchars} characters.
25175 @node TUI Configuration
25176 @section TUI Configuration Variables
25177 @cindex TUI configuration variables
25179 Several configuration variables control the appearance of TUI windows.
25182 @item set tui border-kind @var{kind}
25183 @kindex set tui border-kind
25184 Select the border appearance for the source, assembly and register windows.
25185 The possible values are the following:
25188 Use a space character to draw the border.
25191 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
25194 Use the Alternate Character Set to draw the border. The border is
25195 drawn using character line graphics if the terminal supports them.
25198 @item set tui border-mode @var{mode}
25199 @kindex set tui border-mode
25200 @itemx set tui active-border-mode @var{mode}
25201 @kindex set tui active-border-mode
25202 Select the display attributes for the borders of the inactive windows
25203 or the active window. The @var{mode} can be one of the following:
25206 Use normal attributes to display the border.
25212 Use reverse video mode.
25215 Use half bright mode.
25217 @item half-standout
25218 Use half bright and standout mode.
25221 Use extra bright or bold mode.
25223 @item bold-standout
25224 Use extra bright or bold and standout mode.
25229 @chapter Using @value{GDBN} under @sc{gnu} Emacs
25232 @cindex @sc{gnu} Emacs
25233 A special interface allows you to use @sc{gnu} Emacs to view (and
25234 edit) the source files for the program you are debugging with
25237 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
25238 executable file you want to debug as an argument. This command starts
25239 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
25240 created Emacs buffer.
25241 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
25243 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
25248 All ``terminal'' input and output goes through an Emacs buffer, called
25251 This applies both to @value{GDBN} commands and their output, and to the input
25252 and output done by the program you are debugging.
25254 This is useful because it means that you can copy the text of previous
25255 commands and input them again; you can even use parts of the output
25258 All the facilities of Emacs' Shell mode are available for interacting
25259 with your program. In particular, you can send signals the usual
25260 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
25264 @value{GDBN} displays source code through Emacs.
25266 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
25267 source file for that frame and puts an arrow (@samp{=>}) at the
25268 left margin of the current line. Emacs uses a separate buffer for
25269 source display, and splits the screen to show both your @value{GDBN} session
25272 Explicit @value{GDBN} @code{list} or search commands still produce output as
25273 usual, but you probably have no reason to use them from Emacs.
25276 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
25277 a graphical mode, enabled by default, which provides further buffers
25278 that can control the execution and describe the state of your program.
25279 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
25281 If you specify an absolute file name when prompted for the @kbd{M-x
25282 gdb} argument, then Emacs sets your current working directory to where
25283 your program resides. If you only specify the file name, then Emacs
25284 sets your current working directory to the directory associated
25285 with the previous buffer. In this case, @value{GDBN} may find your
25286 program by searching your environment's @code{PATH} variable, but on
25287 some operating systems it might not find the source. So, although the
25288 @value{GDBN} input and output session proceeds normally, the auxiliary
25289 buffer does not display the current source and line of execution.
25291 The initial working directory of @value{GDBN} is printed on the top
25292 line of the GUD buffer and this serves as a default for the commands
25293 that specify files for @value{GDBN} to operate on. @xref{Files,
25294 ,Commands to Specify Files}.
25296 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
25297 need to call @value{GDBN} by a different name (for example, if you
25298 keep several configurations around, with different names) you can
25299 customize the Emacs variable @code{gud-gdb-command-name} to run the
25302 In the GUD buffer, you can use these special Emacs commands in
25303 addition to the standard Shell mode commands:
25307 Describe the features of Emacs' GUD Mode.
25310 Execute to another source line, like the @value{GDBN} @code{step} command; also
25311 update the display window to show the current file and location.
25314 Execute to next source line in this function, skipping all function
25315 calls, like the @value{GDBN} @code{next} command. Then update the display window
25316 to show the current file and location.
25319 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
25320 display window accordingly.
25323 Execute until exit from the selected stack frame, like the @value{GDBN}
25324 @code{finish} command.
25327 Continue execution of your program, like the @value{GDBN} @code{continue}
25331 Go up the number of frames indicated by the numeric argument
25332 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
25333 like the @value{GDBN} @code{up} command.
25336 Go down the number of frames indicated by the numeric argument, like the
25337 @value{GDBN} @code{down} command.
25340 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
25341 tells @value{GDBN} to set a breakpoint on the source line point is on.
25343 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
25344 separate frame which shows a backtrace when the GUD buffer is current.
25345 Move point to any frame in the stack and type @key{RET} to make it
25346 become the current frame and display the associated source in the
25347 source buffer. Alternatively, click @kbd{Mouse-2} to make the
25348 selected frame become the current one. In graphical mode, the
25349 speedbar displays watch expressions.
25351 If you accidentally delete the source-display buffer, an easy way to get
25352 it back is to type the command @code{f} in the @value{GDBN} buffer, to
25353 request a frame display; when you run under Emacs, this recreates
25354 the source buffer if necessary to show you the context of the current
25357 The source files displayed in Emacs are in ordinary Emacs buffers
25358 which are visiting the source files in the usual way. You can edit
25359 the files with these buffers if you wish; but keep in mind that @value{GDBN}
25360 communicates with Emacs in terms of line numbers. If you add or
25361 delete lines from the text, the line numbers that @value{GDBN} knows cease
25362 to correspond properly with the code.
25364 A more detailed description of Emacs' interaction with @value{GDBN} is
25365 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
25368 @c The following dropped because Epoch is nonstandard. Reactivate
25369 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
25371 @kindex Emacs Epoch environment
25375 Version 18 of @sc{gnu} Emacs has a built-in window system
25376 called the @code{epoch}
25377 environment. Users of this environment can use a new command,
25378 @code{inspect} which performs identically to @code{print} except that
25379 each value is printed in its own window.
25384 @chapter The @sc{gdb/mi} Interface
25386 @unnumberedsec Function and Purpose
25388 @cindex @sc{gdb/mi}, its purpose
25389 @sc{gdb/mi} is a line based machine oriented text interface to
25390 @value{GDBN} and is activated by specifying using the
25391 @option{--interpreter} command line option (@pxref{Mode Options}). It
25392 is specifically intended to support the development of systems which
25393 use the debugger as just one small component of a larger system.
25395 This chapter is a specification of the @sc{gdb/mi} interface. It is written
25396 in the form of a reference manual.
25398 Note that @sc{gdb/mi} is still under construction, so some of the
25399 features described below are incomplete and subject to change
25400 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
25402 @unnumberedsec Notation and Terminology
25404 @cindex notational conventions, for @sc{gdb/mi}
25405 This chapter uses the following notation:
25409 @code{|} separates two alternatives.
25412 @code{[ @var{something} ]} indicates that @var{something} is optional:
25413 it may or may not be given.
25416 @code{( @var{group} )*} means that @var{group} inside the parentheses
25417 may repeat zero or more times.
25420 @code{( @var{group} )+} means that @var{group} inside the parentheses
25421 may repeat one or more times.
25424 @code{"@var{string}"} means a literal @var{string}.
25428 @heading Dependencies
25432 * GDB/MI General Design::
25433 * GDB/MI Command Syntax::
25434 * GDB/MI Compatibility with CLI::
25435 * GDB/MI Development and Front Ends::
25436 * GDB/MI Output Records::
25437 * GDB/MI Simple Examples::
25438 * GDB/MI Command Description Format::
25439 * GDB/MI Breakpoint Commands::
25440 * GDB/MI Program Context::
25441 * GDB/MI Thread Commands::
25442 * GDB/MI Ada Tasking Commands::
25443 * GDB/MI Program Execution::
25444 * GDB/MI Stack Manipulation::
25445 * GDB/MI Variable Objects::
25446 * GDB/MI Data Manipulation::
25447 * GDB/MI Tracepoint Commands::
25448 * GDB/MI Symbol Query::
25449 * GDB/MI File Commands::
25451 * GDB/MI Kod Commands::
25452 * GDB/MI Memory Overlay Commands::
25453 * GDB/MI Signal Handling Commands::
25455 * GDB/MI Target Manipulation::
25456 * GDB/MI File Transfer Commands::
25457 * GDB/MI Miscellaneous Commands::
25460 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25461 @node GDB/MI General Design
25462 @section @sc{gdb/mi} General Design
25463 @cindex GDB/MI General Design
25465 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
25466 parts---commands sent to @value{GDBN}, responses to those commands
25467 and notifications. Each command results in exactly one response,
25468 indicating either successful completion of the command, or an error.
25469 For the commands that do not resume the target, the response contains the
25470 requested information. For the commands that resume the target, the
25471 response only indicates whether the target was successfully resumed.
25472 Notifications is the mechanism for reporting changes in the state of the
25473 target, or in @value{GDBN} state, that cannot conveniently be associated with
25474 a command and reported as part of that command response.
25476 The important examples of notifications are:
25480 Exec notifications. These are used to report changes in
25481 target state---when a target is resumed, or stopped. It would not
25482 be feasible to include this information in response of resuming
25483 commands, because one resume commands can result in multiple events in
25484 different threads. Also, quite some time may pass before any event
25485 happens in the target, while a frontend needs to know whether the resuming
25486 command itself was successfully executed.
25489 Console output, and status notifications. Console output
25490 notifications are used to report output of CLI commands, as well as
25491 diagnostics for other commands. Status notifications are used to
25492 report the progress of a long-running operation. Naturally, including
25493 this information in command response would mean no output is produced
25494 until the command is finished, which is undesirable.
25497 General notifications. Commands may have various side effects on
25498 the @value{GDBN} or target state beyond their official purpose. For example,
25499 a command may change the selected thread. Although such changes can
25500 be included in command response, using notification allows for more
25501 orthogonal frontend design.
25505 There's no guarantee that whenever an MI command reports an error,
25506 @value{GDBN} or the target are in any specific state, and especially,
25507 the state is not reverted to the state before the MI command was
25508 processed. Therefore, whenever an MI command results in an error,
25509 we recommend that the frontend refreshes all the information shown in
25510 the user interface.
25514 * Context management::
25515 * Asynchronous and non-stop modes::
25519 @node Context management
25520 @subsection Context management
25522 In most cases when @value{GDBN} accesses the target, this access is
25523 done in context of a specific thread and frame (@pxref{Frames}).
25524 Often, even when accessing global data, the target requires that a thread
25525 be specified. The CLI interface maintains the selected thread and frame,
25526 and supplies them to target on each command. This is convenient,
25527 because a command line user would not want to specify that information
25528 explicitly on each command, and because user interacts with
25529 @value{GDBN} via a single terminal, so no confusion is possible as
25530 to what thread and frame are the current ones.
25532 In the case of MI, the concept of selected thread and frame is less
25533 useful. First, a frontend can easily remember this information
25534 itself. Second, a graphical frontend can have more than one window,
25535 each one used for debugging a different thread, and the frontend might
25536 want to access additional threads for internal purposes. This
25537 increases the risk that by relying on implicitly selected thread, the
25538 frontend may be operating on a wrong one. Therefore, each MI command
25539 should explicitly specify which thread and frame to operate on. To
25540 make it possible, each MI command accepts the @samp{--thread} and
25541 @samp{--frame} options, the value to each is @value{GDBN} identifier
25542 for thread and frame to operate on.
25544 Usually, each top-level window in a frontend allows the user to select
25545 a thread and a frame, and remembers the user selection for further
25546 operations. However, in some cases @value{GDBN} may suggest that the
25547 current thread be changed. For example, when stopping on a breakpoint
25548 it is reasonable to switch to the thread where breakpoint is hit. For
25549 another example, if the user issues the CLI @samp{thread} command via
25550 the frontend, it is desirable to change the frontend's selected thread to the
25551 one specified by user. @value{GDBN} communicates the suggestion to
25552 change current thread using the @samp{=thread-selected} notification.
25553 No such notification is available for the selected frame at the moment.
25555 Note that historically, MI shares the selected thread with CLI, so
25556 frontends used the @code{-thread-select} to execute commands in the
25557 right context. However, getting this to work right is cumbersome. The
25558 simplest way is for frontend to emit @code{-thread-select} command
25559 before every command. This doubles the number of commands that need
25560 to be sent. The alternative approach is to suppress @code{-thread-select}
25561 if the selected thread in @value{GDBN} is supposed to be identical to the
25562 thread the frontend wants to operate on. However, getting this
25563 optimization right can be tricky. In particular, if the frontend
25564 sends several commands to @value{GDBN}, and one of the commands changes the
25565 selected thread, then the behaviour of subsequent commands will
25566 change. So, a frontend should either wait for response from such
25567 problematic commands, or explicitly add @code{-thread-select} for
25568 all subsequent commands. No frontend is known to do this exactly
25569 right, so it is suggested to just always pass the @samp{--thread} and
25570 @samp{--frame} options.
25572 @node Asynchronous and non-stop modes
25573 @subsection Asynchronous command execution and non-stop mode
25575 On some targets, @value{GDBN} is capable of processing MI commands
25576 even while the target is running. This is called @dfn{asynchronous
25577 command execution} (@pxref{Background Execution}). The frontend may
25578 specify a preferrence for asynchronous execution using the
25579 @code{-gdb-set target-async 1} command, which should be emitted before
25580 either running the executable or attaching to the target. After the
25581 frontend has started the executable or attached to the target, it can
25582 find if asynchronous execution is enabled using the
25583 @code{-list-target-features} command.
25585 Even if @value{GDBN} can accept a command while target is running,
25586 many commands that access the target do not work when the target is
25587 running. Therefore, asynchronous command execution is most useful
25588 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
25589 it is possible to examine the state of one thread, while other threads
25592 When a given thread is running, MI commands that try to access the
25593 target in the context of that thread may not work, or may work only on
25594 some targets. In particular, commands that try to operate on thread's
25595 stack will not work, on any target. Commands that read memory, or
25596 modify breakpoints, may work or not work, depending on the target. Note
25597 that even commands that operate on global state, such as @code{print},
25598 @code{set}, and breakpoint commands, still access the target in the
25599 context of a specific thread, so frontend should try to find a
25600 stopped thread and perform the operation on that thread (using the
25601 @samp{--thread} option).
25603 Which commands will work in the context of a running thread is
25604 highly target dependent. However, the two commands
25605 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
25606 to find the state of a thread, will always work.
25608 @node Thread groups
25609 @subsection Thread groups
25610 @value{GDBN} may be used to debug several processes at the same time.
25611 On some platfroms, @value{GDBN} may support debugging of several
25612 hardware systems, each one having several cores with several different
25613 processes running on each core. This section describes the MI
25614 mechanism to support such debugging scenarios.
25616 The key observation is that regardless of the structure of the
25617 target, MI can have a global list of threads, because most commands that
25618 accept the @samp{--thread} option do not need to know what process that
25619 thread belongs to. Therefore, it is not necessary to introduce
25620 neither additional @samp{--process} option, nor an notion of the
25621 current process in the MI interface. The only strictly new feature
25622 that is required is the ability to find how the threads are grouped
25625 To allow the user to discover such grouping, and to support arbitrary
25626 hierarchy of machines/cores/processes, MI introduces the concept of a
25627 @dfn{thread group}. Thread group is a collection of threads and other
25628 thread groups. A thread group always has a string identifier, a type,
25629 and may have additional attributes specific to the type. A new
25630 command, @code{-list-thread-groups}, returns the list of top-level
25631 thread groups, which correspond to processes that @value{GDBN} is
25632 debugging at the moment. By passing an identifier of a thread group
25633 to the @code{-list-thread-groups} command, it is possible to obtain
25634 the members of specific thread group.
25636 To allow the user to easily discover processes, and other objects, he
25637 wishes to debug, a concept of @dfn{available thread group} is
25638 introduced. Available thread group is an thread group that
25639 @value{GDBN} is not debugging, but that can be attached to, using the
25640 @code{-target-attach} command. The list of available top-level thread
25641 groups can be obtained using @samp{-list-thread-groups --available}.
25642 In general, the content of a thread group may be only retrieved only
25643 after attaching to that thread group.
25645 Thread groups are related to inferiors (@pxref{Inferiors and
25646 Programs}). Each inferior corresponds to a thread group of a special
25647 type @samp{process}, and some additional operations are permitted on
25648 such thread groups.
25650 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25651 @node GDB/MI Command Syntax
25652 @section @sc{gdb/mi} Command Syntax
25655 * GDB/MI Input Syntax::
25656 * GDB/MI Output Syntax::
25659 @node GDB/MI Input Syntax
25660 @subsection @sc{gdb/mi} Input Syntax
25662 @cindex input syntax for @sc{gdb/mi}
25663 @cindex @sc{gdb/mi}, input syntax
25665 @item @var{command} @expansion{}
25666 @code{@var{cli-command} | @var{mi-command}}
25668 @item @var{cli-command} @expansion{}
25669 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
25670 @var{cli-command} is any existing @value{GDBN} CLI command.
25672 @item @var{mi-command} @expansion{}
25673 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
25674 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
25676 @item @var{token} @expansion{}
25677 "any sequence of digits"
25679 @item @var{option} @expansion{}
25680 @code{"-" @var{parameter} [ " " @var{parameter} ]}
25682 @item @var{parameter} @expansion{}
25683 @code{@var{non-blank-sequence} | @var{c-string}}
25685 @item @var{operation} @expansion{}
25686 @emph{any of the operations described in this chapter}
25688 @item @var{non-blank-sequence} @expansion{}
25689 @emph{anything, provided it doesn't contain special characters such as
25690 "-", @var{nl}, """ and of course " "}
25692 @item @var{c-string} @expansion{}
25693 @code{""" @var{seven-bit-iso-c-string-content} """}
25695 @item @var{nl} @expansion{}
25704 The CLI commands are still handled by the @sc{mi} interpreter; their
25705 output is described below.
25708 The @code{@var{token}}, when present, is passed back when the command
25712 Some @sc{mi} commands accept optional arguments as part of the parameter
25713 list. Each option is identified by a leading @samp{-} (dash) and may be
25714 followed by an optional argument parameter. Options occur first in the
25715 parameter list and can be delimited from normal parameters using
25716 @samp{--} (this is useful when some parameters begin with a dash).
25723 We want easy access to the existing CLI syntax (for debugging).
25726 We want it to be easy to spot a @sc{mi} operation.
25729 @node GDB/MI Output Syntax
25730 @subsection @sc{gdb/mi} Output Syntax
25732 @cindex output syntax of @sc{gdb/mi}
25733 @cindex @sc{gdb/mi}, output syntax
25734 The output from @sc{gdb/mi} consists of zero or more out-of-band records
25735 followed, optionally, by a single result record. This result record
25736 is for the most recent command. The sequence of output records is
25737 terminated by @samp{(gdb)}.
25739 If an input command was prefixed with a @code{@var{token}} then the
25740 corresponding output for that command will also be prefixed by that same
25744 @item @var{output} @expansion{}
25745 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
25747 @item @var{result-record} @expansion{}
25748 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
25750 @item @var{out-of-band-record} @expansion{}
25751 @code{@var{async-record} | @var{stream-record}}
25753 @item @var{async-record} @expansion{}
25754 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
25756 @item @var{exec-async-output} @expansion{}
25757 @code{[ @var{token} ] "*" @var{async-output}}
25759 @item @var{status-async-output} @expansion{}
25760 @code{[ @var{token} ] "+" @var{async-output}}
25762 @item @var{notify-async-output} @expansion{}
25763 @code{[ @var{token} ] "=" @var{async-output}}
25765 @item @var{async-output} @expansion{}
25766 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
25768 @item @var{result-class} @expansion{}
25769 @code{"done" | "running" | "connected" | "error" | "exit"}
25771 @item @var{async-class} @expansion{}
25772 @code{"stopped" | @var{others}} (where @var{others} will be added
25773 depending on the needs---this is still in development).
25775 @item @var{result} @expansion{}
25776 @code{ @var{variable} "=" @var{value}}
25778 @item @var{variable} @expansion{}
25779 @code{ @var{string} }
25781 @item @var{value} @expansion{}
25782 @code{ @var{const} | @var{tuple} | @var{list} }
25784 @item @var{const} @expansion{}
25785 @code{@var{c-string}}
25787 @item @var{tuple} @expansion{}
25788 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
25790 @item @var{list} @expansion{}
25791 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
25792 @var{result} ( "," @var{result} )* "]" }
25794 @item @var{stream-record} @expansion{}
25795 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
25797 @item @var{console-stream-output} @expansion{}
25798 @code{"~" @var{c-string}}
25800 @item @var{target-stream-output} @expansion{}
25801 @code{"@@" @var{c-string}}
25803 @item @var{log-stream-output} @expansion{}
25804 @code{"&" @var{c-string}}
25806 @item @var{nl} @expansion{}
25809 @item @var{token} @expansion{}
25810 @emph{any sequence of digits}.
25818 All output sequences end in a single line containing a period.
25821 The @code{@var{token}} is from the corresponding request. Note that
25822 for all async output, while the token is allowed by the grammar and
25823 may be output by future versions of @value{GDBN} for select async
25824 output messages, it is generally omitted. Frontends should treat
25825 all async output as reporting general changes in the state of the
25826 target and there should be no need to associate async output to any
25830 @cindex status output in @sc{gdb/mi}
25831 @var{status-async-output} contains on-going status information about the
25832 progress of a slow operation. It can be discarded. All status output is
25833 prefixed by @samp{+}.
25836 @cindex async output in @sc{gdb/mi}
25837 @var{exec-async-output} contains asynchronous state change on the target
25838 (stopped, started, disappeared). All async output is prefixed by
25842 @cindex notify output in @sc{gdb/mi}
25843 @var{notify-async-output} contains supplementary information that the
25844 client should handle (e.g., a new breakpoint information). All notify
25845 output is prefixed by @samp{=}.
25848 @cindex console output in @sc{gdb/mi}
25849 @var{console-stream-output} is output that should be displayed as is in the
25850 console. It is the textual response to a CLI command. All the console
25851 output is prefixed by @samp{~}.
25854 @cindex target output in @sc{gdb/mi}
25855 @var{target-stream-output} is the output produced by the target program.
25856 All the target output is prefixed by @samp{@@}.
25859 @cindex log output in @sc{gdb/mi}
25860 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
25861 instance messages that should be displayed as part of an error log. All
25862 the log output is prefixed by @samp{&}.
25865 @cindex list output in @sc{gdb/mi}
25866 New @sc{gdb/mi} commands should only output @var{lists} containing
25872 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
25873 details about the various output records.
25875 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25876 @node GDB/MI Compatibility with CLI
25877 @section @sc{gdb/mi} Compatibility with CLI
25879 @cindex compatibility, @sc{gdb/mi} and CLI
25880 @cindex @sc{gdb/mi}, compatibility with CLI
25882 For the developers convenience CLI commands can be entered directly,
25883 but there may be some unexpected behaviour. For example, commands
25884 that query the user will behave as if the user replied yes, breakpoint
25885 command lists are not executed and some CLI commands, such as
25886 @code{if}, @code{when} and @code{define}, prompt for further input with
25887 @samp{>}, which is not valid MI output.
25889 This feature may be removed at some stage in the future and it is
25890 recommended that front ends use the @code{-interpreter-exec} command
25891 (@pxref{-interpreter-exec}).
25893 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25894 @node GDB/MI Development and Front Ends
25895 @section @sc{gdb/mi} Development and Front Ends
25896 @cindex @sc{gdb/mi} development
25898 The application which takes the MI output and presents the state of the
25899 program being debugged to the user is called a @dfn{front end}.
25901 Although @sc{gdb/mi} is still incomplete, it is currently being used
25902 by a variety of front ends to @value{GDBN}. This makes it difficult
25903 to introduce new functionality without breaking existing usage. This
25904 section tries to minimize the problems by describing how the protocol
25907 Some changes in MI need not break a carefully designed front end, and
25908 for these the MI version will remain unchanged. The following is a
25909 list of changes that may occur within one level, so front ends should
25910 parse MI output in a way that can handle them:
25914 New MI commands may be added.
25917 New fields may be added to the output of any MI command.
25920 The range of values for fields with specified values, e.g.,
25921 @code{in_scope} (@pxref{-var-update}) may be extended.
25923 @c The format of field's content e.g type prefix, may change so parse it
25924 @c at your own risk. Yes, in general?
25926 @c The order of fields may change? Shouldn't really matter but it might
25927 @c resolve inconsistencies.
25930 If the changes are likely to break front ends, the MI version level
25931 will be increased by one. This will allow the front end to parse the
25932 output according to the MI version. Apart from mi0, new versions of
25933 @value{GDBN} will not support old versions of MI and it will be the
25934 responsibility of the front end to work with the new one.
25936 @c Starting with mi3, add a new command -mi-version that prints the MI
25939 The best way to avoid unexpected changes in MI that might break your front
25940 end is to make your project known to @value{GDBN} developers and
25941 follow development on @email{gdb@@sourceware.org} and
25942 @email{gdb-patches@@sourceware.org}.
25943 @cindex mailing lists
25945 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25946 @node GDB/MI Output Records
25947 @section @sc{gdb/mi} Output Records
25950 * GDB/MI Result Records::
25951 * GDB/MI Stream Records::
25952 * GDB/MI Async Records::
25953 * GDB/MI Frame Information::
25954 * GDB/MI Thread Information::
25955 * GDB/MI Ada Exception Information::
25958 @node GDB/MI Result Records
25959 @subsection @sc{gdb/mi} Result Records
25961 @cindex result records in @sc{gdb/mi}
25962 @cindex @sc{gdb/mi}, result records
25963 In addition to a number of out-of-band notifications, the response to a
25964 @sc{gdb/mi} command includes one of the following result indications:
25968 @item "^done" [ "," @var{results} ]
25969 The synchronous operation was successful, @code{@var{results}} are the return
25974 This result record is equivalent to @samp{^done}. Historically, it
25975 was output instead of @samp{^done} if the command has resumed the
25976 target. This behaviour is maintained for backward compatibility, but
25977 all frontends should treat @samp{^done} and @samp{^running}
25978 identically and rely on the @samp{*running} output record to determine
25979 which threads are resumed.
25983 @value{GDBN} has connected to a remote target.
25985 @item "^error" "," @var{c-string}
25987 The operation failed. The @code{@var{c-string}} contains the corresponding
25992 @value{GDBN} has terminated.
25996 @node GDB/MI Stream Records
25997 @subsection @sc{gdb/mi} Stream Records
25999 @cindex @sc{gdb/mi}, stream records
26000 @cindex stream records in @sc{gdb/mi}
26001 @value{GDBN} internally maintains a number of output streams: the console, the
26002 target, and the log. The output intended for each of these streams is
26003 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
26005 Each stream record begins with a unique @dfn{prefix character} which
26006 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
26007 Syntax}). In addition to the prefix, each stream record contains a
26008 @code{@var{string-output}}. This is either raw text (with an implicit new
26009 line) or a quoted C string (which does not contain an implicit newline).
26012 @item "~" @var{string-output}
26013 The console output stream contains text that should be displayed in the
26014 CLI console window. It contains the textual responses to CLI commands.
26016 @item "@@" @var{string-output}
26017 The target output stream contains any textual output from the running
26018 target. This is only present when GDB's event loop is truly
26019 asynchronous, which is currently only the case for remote targets.
26021 @item "&" @var{string-output}
26022 The log stream contains debugging messages being produced by @value{GDBN}'s
26026 @node GDB/MI Async Records
26027 @subsection @sc{gdb/mi} Async Records
26029 @cindex async records in @sc{gdb/mi}
26030 @cindex @sc{gdb/mi}, async records
26031 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
26032 additional changes that have occurred. Those changes can either be a
26033 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
26034 target activity (e.g., target stopped).
26036 The following is the list of possible async records:
26040 @item *running,thread-id="@var{thread}"
26041 The target is now running. The @var{thread} field tells which
26042 specific thread is now running, and can be @samp{all} if all threads
26043 are running. The frontend should assume that no interaction with a
26044 running thread is possible after this notification is produced.
26045 The frontend should not assume that this notification is output
26046 only once for any command. @value{GDBN} may emit this notification
26047 several times, either for different threads, because it cannot resume
26048 all threads together, or even for a single thread, if the thread must
26049 be stepped though some code before letting it run freely.
26051 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
26052 The target has stopped. The @var{reason} field can have one of the
26056 @item breakpoint-hit
26057 A breakpoint was reached.
26058 @item watchpoint-trigger
26059 A watchpoint was triggered.
26060 @item read-watchpoint-trigger
26061 A read watchpoint was triggered.
26062 @item access-watchpoint-trigger
26063 An access watchpoint was triggered.
26064 @item function-finished
26065 An -exec-finish or similar CLI command was accomplished.
26066 @item location-reached
26067 An -exec-until or similar CLI command was accomplished.
26068 @item watchpoint-scope
26069 A watchpoint has gone out of scope.
26070 @item end-stepping-range
26071 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
26072 similar CLI command was accomplished.
26073 @item exited-signalled
26074 The inferior exited because of a signal.
26076 The inferior exited.
26077 @item exited-normally
26078 The inferior exited normally.
26079 @item signal-received
26080 A signal was received by the inferior.
26083 The @var{id} field identifies the thread that directly caused the stop
26084 -- for example by hitting a breakpoint. Depending on whether all-stop
26085 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
26086 stop all threads, or only the thread that directly triggered the stop.
26087 If all threads are stopped, the @var{stopped} field will have the
26088 value of @code{"all"}. Otherwise, the value of the @var{stopped}
26089 field will be a list of thread identifiers. Presently, this list will
26090 always include a single thread, but frontend should be prepared to see
26091 several threads in the list. The @var{core} field reports the
26092 processor core on which the stop event has happened. This field may be absent
26093 if such information is not available.
26095 @item =thread-group-added,id="@var{id}"
26096 @itemx =thread-group-removed,id="@var{id}"
26097 A thread group was either added or removed. The @var{id} field
26098 contains the @value{GDBN} identifier of the thread group. When a thread
26099 group is added, it generally might not be associated with a running
26100 process. When a thread group is removed, its id becomes invalid and
26101 cannot be used in any way.
26103 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
26104 A thread group became associated with a running program,
26105 either because the program was just started or the thread group
26106 was attached to a program. The @var{id} field contains the
26107 @value{GDBN} identifier of the thread group. The @var{pid} field
26108 contains process identifier, specific to the operating system.
26110 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
26111 A thread group is no longer associated with a running program,
26112 either because the program has exited, or because it was detached
26113 from. The @var{id} field contains the @value{GDBN} identifier of the
26114 thread group. @var{code} is the exit code of the inferior; it exists
26115 only when the inferior exited with some code.
26117 @item =thread-created,id="@var{id}",group-id="@var{gid}"
26118 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
26119 A thread either was created, or has exited. The @var{id} field
26120 contains the @value{GDBN} identifier of the thread. The @var{gid}
26121 field identifies the thread group this thread belongs to.
26123 @item =thread-selected,id="@var{id}"
26124 Informs that the selected thread was changed as result of the last
26125 command. This notification is not emitted as result of @code{-thread-select}
26126 command but is emitted whenever an MI command that is not documented
26127 to change the selected thread actually changes it. In particular,
26128 invoking, directly or indirectly (via user-defined command), the CLI
26129 @code{thread} command, will generate this notification.
26131 We suggest that in response to this notification, front ends
26132 highlight the selected thread and cause subsequent commands to apply to
26135 @item =library-loaded,...
26136 Reports that a new library file was loaded by the program. This
26137 notification has 4 fields---@var{id}, @var{target-name},
26138 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
26139 opaque identifier of the library. For remote debugging case,
26140 @var{target-name} and @var{host-name} fields give the name of the
26141 library file on the target, and on the host respectively. For native
26142 debugging, both those fields have the same value. The
26143 @var{symbols-loaded} field is emitted only for backward compatibility
26144 and should not be relied on to convey any useful information. The
26145 @var{thread-group} field, if present, specifies the id of the thread
26146 group in whose context the library was loaded. If the field is
26147 absent, it means the library was loaded in the context of all present
26150 @item =library-unloaded,...
26151 Reports that a library was unloaded by the program. This notification
26152 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
26153 the same meaning as for the @code{=library-loaded} notification.
26154 The @var{thread-group} field, if present, specifies the id of the
26155 thread group in whose context the library was unloaded. If the field is
26156 absent, it means the library was unloaded in the context of all present
26159 @item =breakpoint-created,bkpt=@{...@}
26160 @itemx =breakpoint-modified,bkpt=@{...@}
26161 @itemx =breakpoint-deleted,bkpt=@{...@}
26162 Reports that a breakpoint was created, modified, or deleted,
26163 respectively. Only user-visible breakpoints are reported to the MI
26166 The @var{bkpt} argument is of the same form as returned by the various
26167 breakpoint commands; @xref{GDB/MI Breakpoint Commands}.
26169 Note that if a breakpoint is emitted in the result record of a
26170 command, then it will not also be emitted in an async record.
26174 @node GDB/MI Frame Information
26175 @subsection @sc{gdb/mi} Frame Information
26177 Response from many MI commands includes an information about stack
26178 frame. This information is a tuple that may have the following
26183 The level of the stack frame. The innermost frame has the level of
26184 zero. This field is always present.
26187 The name of the function corresponding to the frame. This field may
26188 be absent if @value{GDBN} is unable to determine the function name.
26191 The code address for the frame. This field is always present.
26194 The name of the source files that correspond to the frame's code
26195 address. This field may be absent.
26198 The source line corresponding to the frames' code address. This field
26202 The name of the binary file (either executable or shared library) the
26203 corresponds to the frame's code address. This field may be absent.
26207 @node GDB/MI Thread Information
26208 @subsection @sc{gdb/mi} Thread Information
26210 Whenever @value{GDBN} has to report an information about a thread, it
26211 uses a tuple with the following fields:
26215 The numeric id assigned to the thread by @value{GDBN}. This field is
26219 Target-specific string identifying the thread. This field is always present.
26222 Additional information about the thread provided by the target.
26223 It is supposed to be human-readable and not interpreted by the
26224 frontend. This field is optional.
26227 Either @samp{stopped} or @samp{running}, depending on whether the
26228 thread is presently running. This field is always present.
26231 The value of this field is an integer number of the processor core the
26232 thread was last seen on. This field is optional.
26235 @node GDB/MI Ada Exception Information
26236 @subsection @sc{gdb/mi} Ada Exception Information
26238 Whenever a @code{*stopped} record is emitted because the program
26239 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
26240 @value{GDBN} provides the name of the exception that was raised via
26241 the @code{exception-name} field.
26243 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26244 @node GDB/MI Simple Examples
26245 @section Simple Examples of @sc{gdb/mi} Interaction
26246 @cindex @sc{gdb/mi}, simple examples
26248 This subsection presents several simple examples of interaction using
26249 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
26250 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
26251 the output received from @sc{gdb/mi}.
26253 Note the line breaks shown in the examples are here only for
26254 readability, they don't appear in the real output.
26256 @subheading Setting a Breakpoint
26258 Setting a breakpoint generates synchronous output which contains detailed
26259 information of the breakpoint.
26262 -> -break-insert main
26263 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26264 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26265 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
26269 @subheading Program Execution
26271 Program execution generates asynchronous records and MI gives the
26272 reason that execution stopped.
26278 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
26279 frame=@{addr="0x08048564",func="main",
26280 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
26281 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
26286 <- *stopped,reason="exited-normally"
26290 @subheading Quitting @value{GDBN}
26292 Quitting @value{GDBN} just prints the result class @samp{^exit}.
26300 Please note that @samp{^exit} is printed immediately, but it might
26301 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
26302 performs necessary cleanups, including killing programs being debugged
26303 or disconnecting from debug hardware, so the frontend should wait till
26304 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
26305 fails to exit in reasonable time.
26307 @subheading A Bad Command
26309 Here's what happens if you pass a non-existent command:
26313 <- ^error,msg="Undefined MI command: rubbish"
26318 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26319 @node GDB/MI Command Description Format
26320 @section @sc{gdb/mi} Command Description Format
26322 The remaining sections describe blocks of commands. Each block of
26323 commands is laid out in a fashion similar to this section.
26325 @subheading Motivation
26327 The motivation for this collection of commands.
26329 @subheading Introduction
26331 A brief introduction to this collection of commands as a whole.
26333 @subheading Commands
26335 For each command in the block, the following is described:
26337 @subsubheading Synopsis
26340 -command @var{args}@dots{}
26343 @subsubheading Result
26345 @subsubheading @value{GDBN} Command
26347 The corresponding @value{GDBN} CLI command(s), if any.
26349 @subsubheading Example
26351 Example(s) formatted for readability. Some of the described commands have
26352 not been implemented yet and these are labeled N.A.@: (not available).
26355 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26356 @node GDB/MI Breakpoint Commands
26357 @section @sc{gdb/mi} Breakpoint Commands
26359 @cindex breakpoint commands for @sc{gdb/mi}
26360 @cindex @sc{gdb/mi}, breakpoint commands
26361 This section documents @sc{gdb/mi} commands for manipulating
26364 @subheading The @code{-break-after} Command
26365 @findex -break-after
26367 @subsubheading Synopsis
26370 -break-after @var{number} @var{count}
26373 The breakpoint number @var{number} is not in effect until it has been
26374 hit @var{count} times. To see how this is reflected in the output of
26375 the @samp{-break-list} command, see the description of the
26376 @samp{-break-list} command below.
26378 @subsubheading @value{GDBN} Command
26380 The corresponding @value{GDBN} command is @samp{ignore}.
26382 @subsubheading Example
26387 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26388 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26389 fullname="/home/foo/hello.c",line="5",times="0"@}
26396 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26397 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26398 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26399 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26400 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26401 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26402 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26403 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26404 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26405 line="5",times="0",ignore="3"@}]@}
26410 @subheading The @code{-break-catch} Command
26411 @findex -break-catch
26414 @subheading The @code{-break-commands} Command
26415 @findex -break-commands
26417 @subsubheading Synopsis
26420 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
26423 Specifies the CLI commands that should be executed when breakpoint
26424 @var{number} is hit. The parameters @var{command1} to @var{commandN}
26425 are the commands. If no command is specified, any previously-set
26426 commands are cleared. @xref{Break Commands}. Typical use of this
26427 functionality is tracing a program, that is, printing of values of
26428 some variables whenever breakpoint is hit and then continuing.
26430 @subsubheading @value{GDBN} Command
26432 The corresponding @value{GDBN} command is @samp{commands}.
26434 @subsubheading Example
26439 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26440 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26441 fullname="/home/foo/hello.c",line="5",times="0"@}
26443 -break-commands 1 "print v" "continue"
26448 @subheading The @code{-break-condition} Command
26449 @findex -break-condition
26451 @subsubheading Synopsis
26454 -break-condition @var{number} @var{expr}
26457 Breakpoint @var{number} will stop the program only if the condition in
26458 @var{expr} is true. The condition becomes part of the
26459 @samp{-break-list} output (see the description of the @samp{-break-list}
26462 @subsubheading @value{GDBN} Command
26464 The corresponding @value{GDBN} command is @samp{condition}.
26466 @subsubheading Example
26470 -break-condition 1 1
26474 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26475 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26476 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26477 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26478 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26479 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26480 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26481 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26482 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26483 line="5",cond="1",times="0",ignore="3"@}]@}
26487 @subheading The @code{-break-delete} Command
26488 @findex -break-delete
26490 @subsubheading Synopsis
26493 -break-delete ( @var{breakpoint} )+
26496 Delete the breakpoint(s) whose number(s) are specified in the argument
26497 list. This is obviously reflected in the breakpoint list.
26499 @subsubheading @value{GDBN} Command
26501 The corresponding @value{GDBN} command is @samp{delete}.
26503 @subsubheading Example
26511 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26512 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26513 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26514 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26515 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26516 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26517 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26522 @subheading The @code{-break-disable} Command
26523 @findex -break-disable
26525 @subsubheading Synopsis
26528 -break-disable ( @var{breakpoint} )+
26531 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
26532 break list is now set to @samp{n} for the named @var{breakpoint}(s).
26534 @subsubheading @value{GDBN} Command
26536 The corresponding @value{GDBN} command is @samp{disable}.
26538 @subsubheading Example
26546 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26547 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26548 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26549 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26550 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26551 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26552 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26553 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
26554 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26555 line="5",times="0"@}]@}
26559 @subheading The @code{-break-enable} Command
26560 @findex -break-enable
26562 @subsubheading Synopsis
26565 -break-enable ( @var{breakpoint} )+
26568 Enable (previously disabled) @var{breakpoint}(s).
26570 @subsubheading @value{GDBN} Command
26572 The corresponding @value{GDBN} command is @samp{enable}.
26574 @subsubheading Example
26582 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26583 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26584 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26585 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26586 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26587 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26588 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26589 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26590 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26591 line="5",times="0"@}]@}
26595 @subheading The @code{-break-info} Command
26596 @findex -break-info
26598 @subsubheading Synopsis
26601 -break-info @var{breakpoint}
26605 Get information about a single breakpoint.
26607 @subsubheading @value{GDBN} Command
26609 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
26611 @subsubheading Example
26614 @subheading The @code{-break-insert} Command
26615 @findex -break-insert
26617 @subsubheading Synopsis
26620 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
26621 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26622 [ -p @var{thread} ] [ @var{location} ]
26626 If specified, @var{location}, can be one of:
26633 @item filename:linenum
26634 @item filename:function
26638 The possible optional parameters of this command are:
26642 Insert a temporary breakpoint.
26644 Insert a hardware breakpoint.
26645 @item -c @var{condition}
26646 Make the breakpoint conditional on @var{condition}.
26647 @item -i @var{ignore-count}
26648 Initialize the @var{ignore-count}.
26650 If @var{location} cannot be parsed (for example if it
26651 refers to unknown files or functions), create a pending
26652 breakpoint. Without this flag, @value{GDBN} will report
26653 an error, and won't create a breakpoint, if @var{location}
26656 Create a disabled breakpoint.
26658 Create a tracepoint. @xref{Tracepoints}. When this parameter
26659 is used together with @samp{-h}, a fast tracepoint is created.
26662 @subsubheading Result
26664 The result is in the form:
26667 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
26668 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
26669 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
26670 times="@var{times}"@}
26674 where @var{number} is the @value{GDBN} number for this breakpoint,
26675 @var{funcname} is the name of the function where the breakpoint was
26676 inserted, @var{filename} is the name of the source file which contains
26677 this function, @var{lineno} is the source line number within that file
26678 and @var{times} the number of times that the breakpoint has been hit
26679 (always 0 for -break-insert but may be greater for -break-info or -break-list
26680 which use the same output).
26682 Note: this format is open to change.
26683 @c An out-of-band breakpoint instead of part of the result?
26685 @subsubheading @value{GDBN} Command
26687 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
26688 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
26690 @subsubheading Example
26695 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
26696 fullname="/home/foo/recursive2.c,line="4",times="0"@}
26698 -break-insert -t foo
26699 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
26700 fullname="/home/foo/recursive2.c,line="11",times="0"@}
26703 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26704 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26705 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26706 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26707 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26708 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26709 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26710 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26711 addr="0x0001072c", func="main",file="recursive2.c",
26712 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
26713 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
26714 addr="0x00010774",func="foo",file="recursive2.c",
26715 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
26717 -break-insert -r foo.*
26718 ~int foo(int, int);
26719 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
26720 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
26724 @subheading The @code{-break-list} Command
26725 @findex -break-list
26727 @subsubheading Synopsis
26733 Displays the list of inserted breakpoints, showing the following fields:
26737 number of the breakpoint
26739 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
26741 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
26744 is the breakpoint enabled or no: @samp{y} or @samp{n}
26746 memory location at which the breakpoint is set
26748 logical location of the breakpoint, expressed by function name, file
26751 number of times the breakpoint has been hit
26754 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
26755 @code{body} field is an empty list.
26757 @subsubheading @value{GDBN} Command
26759 The corresponding @value{GDBN} command is @samp{info break}.
26761 @subsubheading Example
26766 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26767 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26768 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26769 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26770 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26771 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26772 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26773 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26774 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
26775 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26776 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
26777 line="13",times="0"@}]@}
26781 Here's an example of the result when there are no breakpoints:
26786 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26787 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26788 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26789 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26790 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26791 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26792 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26797 @subheading The @code{-break-passcount} Command
26798 @findex -break-passcount
26800 @subsubheading Synopsis
26803 -break-passcount @var{tracepoint-number} @var{passcount}
26806 Set the passcount for tracepoint @var{tracepoint-number} to
26807 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
26808 is not a tracepoint, error is emitted. This corresponds to CLI
26809 command @samp{passcount}.
26811 @subheading The @code{-break-watch} Command
26812 @findex -break-watch
26814 @subsubheading Synopsis
26817 -break-watch [ -a | -r ]
26820 Create a watchpoint. With the @samp{-a} option it will create an
26821 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
26822 read from or on a write to the memory location. With the @samp{-r}
26823 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
26824 trigger only when the memory location is accessed for reading. Without
26825 either of the options, the watchpoint created is a regular watchpoint,
26826 i.e., it will trigger when the memory location is accessed for writing.
26827 @xref{Set Watchpoints, , Setting Watchpoints}.
26829 Note that @samp{-break-list} will report a single list of watchpoints and
26830 breakpoints inserted.
26832 @subsubheading @value{GDBN} Command
26834 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
26837 @subsubheading Example
26839 Setting a watchpoint on a variable in the @code{main} function:
26844 ^done,wpt=@{number="2",exp="x"@}
26849 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
26850 value=@{old="-268439212",new="55"@},
26851 frame=@{func="main",args=[],file="recursive2.c",
26852 fullname="/home/foo/bar/recursive2.c",line="5"@}
26856 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
26857 the program execution twice: first for the variable changing value, then
26858 for the watchpoint going out of scope.
26863 ^done,wpt=@{number="5",exp="C"@}
26868 *stopped,reason="watchpoint-trigger",
26869 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
26870 frame=@{func="callee4",args=[],
26871 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26872 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
26877 *stopped,reason="watchpoint-scope",wpnum="5",
26878 frame=@{func="callee3",args=[@{name="strarg",
26879 value="0x11940 \"A string argument.\""@}],
26880 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26881 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26885 Listing breakpoints and watchpoints, at different points in the program
26886 execution. Note that once the watchpoint goes out of scope, it is
26892 ^done,wpt=@{number="2",exp="C"@}
26895 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26896 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26897 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26898 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26899 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26900 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26901 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26902 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26903 addr="0x00010734",func="callee4",
26904 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26905 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
26906 bkpt=@{number="2",type="watchpoint",disp="keep",
26907 enabled="y",addr="",what="C",times="0"@}]@}
26912 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
26913 value=@{old="-276895068",new="3"@},
26914 frame=@{func="callee4",args=[],
26915 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26916 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
26919 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26920 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26921 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26922 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26923 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26924 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26925 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26926 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26927 addr="0x00010734",func="callee4",
26928 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26929 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
26930 bkpt=@{number="2",type="watchpoint",disp="keep",
26931 enabled="y",addr="",what="C",times="-5"@}]@}
26935 ^done,reason="watchpoint-scope",wpnum="2",
26936 frame=@{func="callee3",args=[@{name="strarg",
26937 value="0x11940 \"A string argument.\""@}],
26938 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26939 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26942 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26943 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26944 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26945 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26946 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26947 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26948 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26949 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26950 addr="0x00010734",func="callee4",
26951 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26952 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
26957 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26958 @node GDB/MI Program Context
26959 @section @sc{gdb/mi} Program Context
26961 @subheading The @code{-exec-arguments} Command
26962 @findex -exec-arguments
26965 @subsubheading Synopsis
26968 -exec-arguments @var{args}
26971 Set the inferior program arguments, to be used in the next
26974 @subsubheading @value{GDBN} Command
26976 The corresponding @value{GDBN} command is @samp{set args}.
26978 @subsubheading Example
26982 -exec-arguments -v word
26989 @subheading The @code{-exec-show-arguments} Command
26990 @findex -exec-show-arguments
26992 @subsubheading Synopsis
26995 -exec-show-arguments
26998 Print the arguments of the program.
27000 @subsubheading @value{GDBN} Command
27002 The corresponding @value{GDBN} command is @samp{show args}.
27004 @subsubheading Example
27009 @subheading The @code{-environment-cd} Command
27010 @findex -environment-cd
27012 @subsubheading Synopsis
27015 -environment-cd @var{pathdir}
27018 Set @value{GDBN}'s working directory.
27020 @subsubheading @value{GDBN} Command
27022 The corresponding @value{GDBN} command is @samp{cd}.
27024 @subsubheading Example
27028 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27034 @subheading The @code{-environment-directory} Command
27035 @findex -environment-directory
27037 @subsubheading Synopsis
27040 -environment-directory [ -r ] [ @var{pathdir} ]+
27043 Add directories @var{pathdir} to beginning of search path for source files.
27044 If the @samp{-r} option is used, the search path is reset to the default
27045 search path. If directories @var{pathdir} are supplied in addition to the
27046 @samp{-r} option, the search path is first reset and then addition
27048 Multiple directories may be specified, separated by blanks. Specifying
27049 multiple directories in a single command
27050 results in the directories added to the beginning of the
27051 search path in the same order they were presented in the command.
27052 If blanks are needed as
27053 part of a directory name, double-quotes should be used around
27054 the name. In the command output, the path will show up separated
27055 by the system directory-separator character. The directory-separator
27056 character must not be used
27057 in any directory name.
27058 If no directories are specified, the current search path is displayed.
27060 @subsubheading @value{GDBN} Command
27062 The corresponding @value{GDBN} command is @samp{dir}.
27064 @subsubheading Example
27068 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27069 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27071 -environment-directory ""
27072 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27074 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
27075 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
27077 -environment-directory -r
27078 ^done,source-path="$cdir:$cwd"
27083 @subheading The @code{-environment-path} Command
27084 @findex -environment-path
27086 @subsubheading Synopsis
27089 -environment-path [ -r ] [ @var{pathdir} ]+
27092 Add directories @var{pathdir} to beginning of search path for object files.
27093 If the @samp{-r} option is used, the search path is reset to the original
27094 search path that existed at gdb start-up. If directories @var{pathdir} are
27095 supplied in addition to the
27096 @samp{-r} option, the search path is first reset and then addition
27098 Multiple directories may be specified, separated by blanks. Specifying
27099 multiple directories in a single command
27100 results in the directories added to the beginning of the
27101 search path in the same order they were presented in the command.
27102 If blanks are needed as
27103 part of a directory name, double-quotes should be used around
27104 the name. In the command output, the path will show up separated
27105 by the system directory-separator character. The directory-separator
27106 character must not be used
27107 in any directory name.
27108 If no directories are specified, the current path is displayed.
27111 @subsubheading @value{GDBN} Command
27113 The corresponding @value{GDBN} command is @samp{path}.
27115 @subsubheading Example
27120 ^done,path="/usr/bin"
27122 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
27123 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
27125 -environment-path -r /usr/local/bin
27126 ^done,path="/usr/local/bin:/usr/bin"
27131 @subheading The @code{-environment-pwd} Command
27132 @findex -environment-pwd
27134 @subsubheading Synopsis
27140 Show the current working directory.
27142 @subsubheading @value{GDBN} Command
27144 The corresponding @value{GDBN} command is @samp{pwd}.
27146 @subsubheading Example
27151 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
27155 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27156 @node GDB/MI Thread Commands
27157 @section @sc{gdb/mi} Thread Commands
27160 @subheading The @code{-thread-info} Command
27161 @findex -thread-info
27163 @subsubheading Synopsis
27166 -thread-info [ @var{thread-id} ]
27169 Reports information about either a specific thread, if
27170 the @var{thread-id} parameter is present, or about all
27171 threads. When printing information about all threads,
27172 also reports the current thread.
27174 @subsubheading @value{GDBN} Command
27176 The @samp{info thread} command prints the same information
27179 @subsubheading Result
27181 The result is a list of threads. The following attributes are
27182 defined for a given thread:
27186 This field exists only for the current thread. It has the value @samp{*}.
27189 The identifier that @value{GDBN} uses to refer to the thread.
27192 The identifier that the target uses to refer to the thread.
27195 Extra information about the thread, in a target-specific format. This
27199 The name of the thread. If the user specified a name using the
27200 @code{thread name} command, then this name is given. Otherwise, if
27201 @value{GDBN} can extract the thread name from the target, then that
27202 name is given. If @value{GDBN} cannot find the thread name, then this
27206 The stack frame currently executing in the thread.
27209 The thread's state. The @samp{state} field may have the following
27214 The thread is stopped. Frame information is available for stopped
27218 The thread is running. There's no frame information for running
27224 If @value{GDBN} can find the CPU core on which this thread is running,
27225 then this field is the core identifier. This field is optional.
27229 @subsubheading Example
27234 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
27235 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
27236 args=[]@},state="running"@},
27237 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
27238 frame=@{level="0",addr="0x0804891f",func="foo",
27239 args=[@{name="i",value="10"@}],
27240 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
27241 state="running"@}],
27242 current-thread-id="1"
27246 @subheading The @code{-thread-list-ids} Command
27247 @findex -thread-list-ids
27249 @subsubheading Synopsis
27255 Produces a list of the currently known @value{GDBN} thread ids. At the
27256 end of the list it also prints the total number of such threads.
27258 This command is retained for historical reasons, the
27259 @code{-thread-info} command should be used instead.
27261 @subsubheading @value{GDBN} Command
27263 Part of @samp{info threads} supplies the same information.
27265 @subsubheading Example
27270 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27271 current-thread-id="1",number-of-threads="3"
27276 @subheading The @code{-thread-select} Command
27277 @findex -thread-select
27279 @subsubheading Synopsis
27282 -thread-select @var{threadnum}
27285 Make @var{threadnum} the current thread. It prints the number of the new
27286 current thread, and the topmost frame for that thread.
27288 This command is deprecated in favor of explicitly using the
27289 @samp{--thread} option to each command.
27291 @subsubheading @value{GDBN} Command
27293 The corresponding @value{GDBN} command is @samp{thread}.
27295 @subsubheading Example
27302 *stopped,reason="end-stepping-range",thread-id="2",line="187",
27303 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
27307 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27308 number-of-threads="3"
27311 ^done,new-thread-id="3",
27312 frame=@{level="0",func="vprintf",
27313 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
27314 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
27318 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27319 @node GDB/MI Ada Tasking Commands
27320 @section @sc{gdb/mi} Ada Tasking Commands
27322 @subheading The @code{-ada-task-info} Command
27323 @findex -ada-task-info
27325 @subsubheading Synopsis
27328 -ada-task-info [ @var{task-id} ]
27331 Reports information about either a specific Ada task, if the
27332 @var{task-id} parameter is present, or about all Ada tasks.
27334 @subsubheading @value{GDBN} Command
27336 The @samp{info tasks} command prints the same information
27337 about all Ada tasks (@pxref{Ada Tasks}).
27339 @subsubheading Result
27341 The result is a table of Ada tasks. The following columns are
27342 defined for each Ada task:
27346 This field exists only for the current thread. It has the value @samp{*}.
27349 The identifier that @value{GDBN} uses to refer to the Ada task.
27352 The identifier that the target uses to refer to the Ada task.
27355 The identifier of the thread corresponding to the Ada task.
27357 This field should always exist, as Ada tasks are always implemented
27358 on top of a thread. But if @value{GDBN} cannot find this corresponding
27359 thread for any reason, the field is omitted.
27362 This field exists only when the task was created by another task.
27363 In this case, it provides the ID of the parent task.
27366 The base priority of the task.
27369 The current state of the task. For a detailed description of the
27370 possible states, see @ref{Ada Tasks}.
27373 The name of the task.
27377 @subsubheading Example
27381 ^done,tasks=@{nr_rows="3",nr_cols="8",
27382 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
27383 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
27384 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
27385 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
27386 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
27387 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
27388 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
27389 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
27390 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
27391 state="Child Termination Wait",name="main_task"@}]@}
27395 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27396 @node GDB/MI Program Execution
27397 @section @sc{gdb/mi} Program Execution
27399 These are the asynchronous commands which generate the out-of-band
27400 record @samp{*stopped}. Currently @value{GDBN} only really executes
27401 asynchronously with remote targets and this interaction is mimicked in
27404 @subheading The @code{-exec-continue} Command
27405 @findex -exec-continue
27407 @subsubheading Synopsis
27410 -exec-continue [--reverse] [--all|--thread-group N]
27413 Resumes the execution of the inferior program, which will continue
27414 to execute until it reaches a debugger stop event. If the
27415 @samp{--reverse} option is specified, execution resumes in reverse until
27416 it reaches a stop event. Stop events may include
27419 breakpoints or watchpoints
27421 signals or exceptions
27423 the end of the process (or its beginning under @samp{--reverse})
27425 the end or beginning of a replay log if one is being used.
27427 In all-stop mode (@pxref{All-Stop
27428 Mode}), may resume only one thread, or all threads, depending on the
27429 value of the @samp{scheduler-locking} variable. If @samp{--all} is
27430 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
27431 ignored in all-stop mode. If the @samp{--thread-group} options is
27432 specified, then all threads in that thread group are resumed.
27434 @subsubheading @value{GDBN} Command
27436 The corresponding @value{GDBN} corresponding is @samp{continue}.
27438 @subsubheading Example
27445 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
27446 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
27452 @subheading The @code{-exec-finish} Command
27453 @findex -exec-finish
27455 @subsubheading Synopsis
27458 -exec-finish [--reverse]
27461 Resumes the execution of the inferior program until the current
27462 function is exited. Displays the results returned by the function.
27463 If the @samp{--reverse} option is specified, resumes the reverse
27464 execution of the inferior program until the point where current
27465 function was called.
27467 @subsubheading @value{GDBN} Command
27469 The corresponding @value{GDBN} command is @samp{finish}.
27471 @subsubheading Example
27473 Function returning @code{void}.
27480 *stopped,reason="function-finished",frame=@{func="main",args=[],
27481 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
27485 Function returning other than @code{void}. The name of the internal
27486 @value{GDBN} variable storing the result is printed, together with the
27493 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
27494 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
27495 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27496 gdb-result-var="$1",return-value="0"
27501 @subheading The @code{-exec-interrupt} Command
27502 @findex -exec-interrupt
27504 @subsubheading Synopsis
27507 -exec-interrupt [--all|--thread-group N]
27510 Interrupts the background execution of the target. Note how the token
27511 associated with the stop message is the one for the execution command
27512 that has been interrupted. The token for the interrupt itself only
27513 appears in the @samp{^done} output. If the user is trying to
27514 interrupt a non-running program, an error message will be printed.
27516 Note that when asynchronous execution is enabled, this command is
27517 asynchronous just like other execution commands. That is, first the
27518 @samp{^done} response will be printed, and the target stop will be
27519 reported after that using the @samp{*stopped} notification.
27521 In non-stop mode, only the context thread is interrupted by default.
27522 All threads (in all inferiors) will be interrupted if the
27523 @samp{--all} option is specified. If the @samp{--thread-group}
27524 option is specified, all threads in that group will be interrupted.
27526 @subsubheading @value{GDBN} Command
27528 The corresponding @value{GDBN} command is @samp{interrupt}.
27530 @subsubheading Example
27541 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
27542 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
27543 fullname="/home/foo/bar/try.c",line="13"@}
27548 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
27552 @subheading The @code{-exec-jump} Command
27555 @subsubheading Synopsis
27558 -exec-jump @var{location}
27561 Resumes execution of the inferior program at the location specified by
27562 parameter. @xref{Specify Location}, for a description of the
27563 different forms of @var{location}.
27565 @subsubheading @value{GDBN} Command
27567 The corresponding @value{GDBN} command is @samp{jump}.
27569 @subsubheading Example
27572 -exec-jump foo.c:10
27573 *running,thread-id="all"
27578 @subheading The @code{-exec-next} Command
27581 @subsubheading Synopsis
27584 -exec-next [--reverse]
27587 Resumes execution of the inferior program, stopping when the beginning
27588 of the next source line is reached.
27590 If the @samp{--reverse} option is specified, resumes reverse execution
27591 of the inferior program, stopping at the beginning of the previous
27592 source line. If you issue this command on the first line of a
27593 function, it will take you back to the caller of that function, to the
27594 source line where the function was called.
27597 @subsubheading @value{GDBN} Command
27599 The corresponding @value{GDBN} command is @samp{next}.
27601 @subsubheading Example
27607 *stopped,reason="end-stepping-range",line="8",file="hello.c"
27612 @subheading The @code{-exec-next-instruction} Command
27613 @findex -exec-next-instruction
27615 @subsubheading Synopsis
27618 -exec-next-instruction [--reverse]
27621 Executes one machine instruction. If the instruction is a function
27622 call, continues until the function returns. If the program stops at an
27623 instruction in the middle of a source line, the address will be
27626 If the @samp{--reverse} option is specified, resumes reverse execution
27627 of the inferior program, stopping at the previous instruction. If the
27628 previously executed instruction was a return from another function,
27629 it will continue to execute in reverse until the call to that function
27630 (from the current stack frame) is reached.
27632 @subsubheading @value{GDBN} Command
27634 The corresponding @value{GDBN} command is @samp{nexti}.
27636 @subsubheading Example
27640 -exec-next-instruction
27644 *stopped,reason="end-stepping-range",
27645 addr="0x000100d4",line="5",file="hello.c"
27650 @subheading The @code{-exec-return} Command
27651 @findex -exec-return
27653 @subsubheading Synopsis
27659 Makes current function return immediately. Doesn't execute the inferior.
27660 Displays the new current frame.
27662 @subsubheading @value{GDBN} Command
27664 The corresponding @value{GDBN} command is @samp{return}.
27666 @subsubheading Example
27670 200-break-insert callee4
27671 200^done,bkpt=@{number="1",addr="0x00010734",
27672 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27677 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27678 frame=@{func="callee4",args=[],
27679 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27680 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27686 111^done,frame=@{level="0",func="callee3",
27687 args=[@{name="strarg",
27688 value="0x11940 \"A string argument.\""@}],
27689 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27690 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27695 @subheading The @code{-exec-run} Command
27698 @subsubheading Synopsis
27701 -exec-run [--all | --thread-group N]
27704 Starts execution of the inferior from the beginning. The inferior
27705 executes until either a breakpoint is encountered or the program
27706 exits. In the latter case the output will include an exit code, if
27707 the program has exited exceptionally.
27709 When no option is specified, the current inferior is started. If the
27710 @samp{--thread-group} option is specified, it should refer to a thread
27711 group of type @samp{process}, and that thread group will be started.
27712 If the @samp{--all} option is specified, then all inferiors will be started.
27714 @subsubheading @value{GDBN} Command
27716 The corresponding @value{GDBN} command is @samp{run}.
27718 @subsubheading Examples
27723 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
27728 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27729 frame=@{func="main",args=[],file="recursive2.c",
27730 fullname="/home/foo/bar/recursive2.c",line="4"@}
27735 Program exited normally:
27743 *stopped,reason="exited-normally"
27748 Program exited exceptionally:
27756 *stopped,reason="exited",exit-code="01"
27760 Another way the program can terminate is if it receives a signal such as
27761 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
27765 *stopped,reason="exited-signalled",signal-name="SIGINT",
27766 signal-meaning="Interrupt"
27770 @c @subheading -exec-signal
27773 @subheading The @code{-exec-step} Command
27776 @subsubheading Synopsis
27779 -exec-step [--reverse]
27782 Resumes execution of the inferior program, stopping when the beginning
27783 of the next source line is reached, if the next source line is not a
27784 function call. If it is, stop at the first instruction of the called
27785 function. If the @samp{--reverse} option is specified, resumes reverse
27786 execution of the inferior program, stopping at the beginning of the
27787 previously executed source line.
27789 @subsubheading @value{GDBN} Command
27791 The corresponding @value{GDBN} command is @samp{step}.
27793 @subsubheading Example
27795 Stepping into a function:
27801 *stopped,reason="end-stepping-range",
27802 frame=@{func="foo",args=[@{name="a",value="10"@},
27803 @{name="b",value="0"@}],file="recursive2.c",
27804 fullname="/home/foo/bar/recursive2.c",line="11"@}
27814 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
27819 @subheading The @code{-exec-step-instruction} Command
27820 @findex -exec-step-instruction
27822 @subsubheading Synopsis
27825 -exec-step-instruction [--reverse]
27828 Resumes the inferior which executes one machine instruction. If the
27829 @samp{--reverse} option is specified, resumes reverse execution of the
27830 inferior program, stopping at the previously executed instruction.
27831 The output, once @value{GDBN} has stopped, will vary depending on
27832 whether we have stopped in the middle of a source line or not. In the
27833 former case, the address at which the program stopped will be printed
27836 @subsubheading @value{GDBN} Command
27838 The corresponding @value{GDBN} command is @samp{stepi}.
27840 @subsubheading Example
27844 -exec-step-instruction
27848 *stopped,reason="end-stepping-range",
27849 frame=@{func="foo",args=[],file="try.c",
27850 fullname="/home/foo/bar/try.c",line="10"@}
27852 -exec-step-instruction
27856 *stopped,reason="end-stepping-range",
27857 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
27858 fullname="/home/foo/bar/try.c",line="10"@}
27863 @subheading The @code{-exec-until} Command
27864 @findex -exec-until
27866 @subsubheading Synopsis
27869 -exec-until [ @var{location} ]
27872 Executes the inferior until the @var{location} specified in the
27873 argument is reached. If there is no argument, the inferior executes
27874 until a source line greater than the current one is reached. The
27875 reason for stopping in this case will be @samp{location-reached}.
27877 @subsubheading @value{GDBN} Command
27879 The corresponding @value{GDBN} command is @samp{until}.
27881 @subsubheading Example
27885 -exec-until recursive2.c:6
27889 *stopped,reason="location-reached",frame=@{func="main",args=[],
27890 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
27895 @subheading -file-clear
27896 Is this going away????
27899 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27900 @node GDB/MI Stack Manipulation
27901 @section @sc{gdb/mi} Stack Manipulation Commands
27904 @subheading The @code{-stack-info-frame} Command
27905 @findex -stack-info-frame
27907 @subsubheading Synopsis
27913 Get info on the selected frame.
27915 @subsubheading @value{GDBN} Command
27917 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
27918 (without arguments).
27920 @subsubheading Example
27925 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
27926 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27927 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
27931 @subheading The @code{-stack-info-depth} Command
27932 @findex -stack-info-depth
27934 @subsubheading Synopsis
27937 -stack-info-depth [ @var{max-depth} ]
27940 Return the depth of the stack. If the integer argument @var{max-depth}
27941 is specified, do not count beyond @var{max-depth} frames.
27943 @subsubheading @value{GDBN} Command
27945 There's no equivalent @value{GDBN} command.
27947 @subsubheading Example
27949 For a stack with frame levels 0 through 11:
27956 -stack-info-depth 4
27959 -stack-info-depth 12
27962 -stack-info-depth 11
27965 -stack-info-depth 13
27970 @subheading The @code{-stack-list-arguments} Command
27971 @findex -stack-list-arguments
27973 @subsubheading Synopsis
27976 -stack-list-arguments @var{print-values}
27977 [ @var{low-frame} @var{high-frame} ]
27980 Display a list of the arguments for the frames between @var{low-frame}
27981 and @var{high-frame} (inclusive). If @var{low-frame} and
27982 @var{high-frame} are not provided, list the arguments for the whole
27983 call stack. If the two arguments are equal, show the single frame
27984 at the corresponding level. It is an error if @var{low-frame} is
27985 larger than the actual number of frames. On the other hand,
27986 @var{high-frame} may be larger than the actual number of frames, in
27987 which case only existing frames will be returned.
27989 If @var{print-values} is 0 or @code{--no-values}, print only the names of
27990 the variables; if it is 1 or @code{--all-values}, print also their
27991 values; and if it is 2 or @code{--simple-values}, print the name,
27992 type and value for simple data types, and the name and type for arrays,
27993 structures and unions.
27995 Use of this command to obtain arguments in a single frame is
27996 deprecated in favor of the @samp{-stack-list-variables} command.
27998 @subsubheading @value{GDBN} Command
28000 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
28001 @samp{gdb_get_args} command which partially overlaps with the
28002 functionality of @samp{-stack-list-arguments}.
28004 @subsubheading Example
28011 frame=@{level="0",addr="0x00010734",func="callee4",
28012 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28013 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
28014 frame=@{level="1",addr="0x0001076c",func="callee3",
28015 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28016 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
28017 frame=@{level="2",addr="0x0001078c",func="callee2",
28018 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28019 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
28020 frame=@{level="3",addr="0x000107b4",func="callee1",
28021 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28022 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
28023 frame=@{level="4",addr="0x000107e0",func="main",
28024 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28025 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
28027 -stack-list-arguments 0
28030 frame=@{level="0",args=[]@},
28031 frame=@{level="1",args=[name="strarg"]@},
28032 frame=@{level="2",args=[name="intarg",name="strarg"]@},
28033 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
28034 frame=@{level="4",args=[]@}]
28036 -stack-list-arguments 1
28039 frame=@{level="0",args=[]@},
28041 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28042 frame=@{level="2",args=[
28043 @{name="intarg",value="2"@},
28044 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28045 @{frame=@{level="3",args=[
28046 @{name="intarg",value="2"@},
28047 @{name="strarg",value="0x11940 \"A string argument.\""@},
28048 @{name="fltarg",value="3.5"@}]@},
28049 frame=@{level="4",args=[]@}]
28051 -stack-list-arguments 0 2 2
28052 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
28054 -stack-list-arguments 1 2 2
28055 ^done,stack-args=[frame=@{level="2",
28056 args=[@{name="intarg",value="2"@},
28057 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
28061 @c @subheading -stack-list-exception-handlers
28064 @subheading The @code{-stack-list-frames} Command
28065 @findex -stack-list-frames
28067 @subsubheading Synopsis
28070 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
28073 List the frames currently on the stack. For each frame it displays the
28078 The frame number, 0 being the topmost frame, i.e., the innermost function.
28080 The @code{$pc} value for that frame.
28084 File name of the source file where the function lives.
28085 @item @var{fullname}
28086 The full file name of the source file where the function lives.
28088 Line number corresponding to the @code{$pc}.
28090 The shared library where this function is defined. This is only given
28091 if the frame's function is not known.
28094 If invoked without arguments, this command prints a backtrace for the
28095 whole stack. If given two integer arguments, it shows the frames whose
28096 levels are between the two arguments (inclusive). If the two arguments
28097 are equal, it shows the single frame at the corresponding level. It is
28098 an error if @var{low-frame} is larger than the actual number of
28099 frames. On the other hand, @var{high-frame} may be larger than the
28100 actual number of frames, in which case only existing frames will be returned.
28102 @subsubheading @value{GDBN} Command
28104 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
28106 @subsubheading Example
28108 Full stack backtrace:
28114 [frame=@{level="0",addr="0x0001076c",func="foo",
28115 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
28116 frame=@{level="1",addr="0x000107a4",func="foo",
28117 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28118 frame=@{level="2",addr="0x000107a4",func="foo",
28119 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28120 frame=@{level="3",addr="0x000107a4",func="foo",
28121 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28122 frame=@{level="4",addr="0x000107a4",func="foo",
28123 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28124 frame=@{level="5",addr="0x000107a4",func="foo",
28125 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28126 frame=@{level="6",addr="0x000107a4",func="foo",
28127 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28128 frame=@{level="7",addr="0x000107a4",func="foo",
28129 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28130 frame=@{level="8",addr="0x000107a4",func="foo",
28131 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28132 frame=@{level="9",addr="0x000107a4",func="foo",
28133 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28134 frame=@{level="10",addr="0x000107a4",func="foo",
28135 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28136 frame=@{level="11",addr="0x00010738",func="main",
28137 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
28141 Show frames between @var{low_frame} and @var{high_frame}:
28145 -stack-list-frames 3 5
28147 [frame=@{level="3",addr="0x000107a4",func="foo",
28148 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28149 frame=@{level="4",addr="0x000107a4",func="foo",
28150 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28151 frame=@{level="5",addr="0x000107a4",func="foo",
28152 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28156 Show a single frame:
28160 -stack-list-frames 3 3
28162 [frame=@{level="3",addr="0x000107a4",func="foo",
28163 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28168 @subheading The @code{-stack-list-locals} Command
28169 @findex -stack-list-locals
28171 @subsubheading Synopsis
28174 -stack-list-locals @var{print-values}
28177 Display the local variable names for the selected frame. If
28178 @var{print-values} is 0 or @code{--no-values}, print only the names of
28179 the variables; if it is 1 or @code{--all-values}, print also their
28180 values; and if it is 2 or @code{--simple-values}, print the name,
28181 type and value for simple data types, and the name and type for arrays,
28182 structures and unions. In this last case, a frontend can immediately
28183 display the value of simple data types and create variable objects for
28184 other data types when the user wishes to explore their values in
28187 This command is deprecated in favor of the
28188 @samp{-stack-list-variables} command.
28190 @subsubheading @value{GDBN} Command
28192 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
28194 @subsubheading Example
28198 -stack-list-locals 0
28199 ^done,locals=[name="A",name="B",name="C"]
28201 -stack-list-locals --all-values
28202 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
28203 @{name="C",value="@{1, 2, 3@}"@}]
28204 -stack-list-locals --simple-values
28205 ^done,locals=[@{name="A",type="int",value="1"@},
28206 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
28210 @subheading The @code{-stack-list-variables} Command
28211 @findex -stack-list-variables
28213 @subsubheading Synopsis
28216 -stack-list-variables @var{print-values}
28219 Display the names of local variables and function arguments for the selected frame. If
28220 @var{print-values} is 0 or @code{--no-values}, print only the names of
28221 the variables; if it is 1 or @code{--all-values}, print also their
28222 values; and if it is 2 or @code{--simple-values}, print the name,
28223 type and value for simple data types, and the name and type for arrays,
28224 structures and unions.
28226 @subsubheading Example
28230 -stack-list-variables --thread 1 --frame 0 --all-values
28231 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
28236 @subheading The @code{-stack-select-frame} Command
28237 @findex -stack-select-frame
28239 @subsubheading Synopsis
28242 -stack-select-frame @var{framenum}
28245 Change the selected frame. Select a different frame @var{framenum} on
28248 This command in deprecated in favor of passing the @samp{--frame}
28249 option to every command.
28251 @subsubheading @value{GDBN} Command
28253 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
28254 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
28256 @subsubheading Example
28260 -stack-select-frame 2
28265 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28266 @node GDB/MI Variable Objects
28267 @section @sc{gdb/mi} Variable Objects
28271 @subheading Motivation for Variable Objects in @sc{gdb/mi}
28273 For the implementation of a variable debugger window (locals, watched
28274 expressions, etc.), we are proposing the adaptation of the existing code
28275 used by @code{Insight}.
28277 The two main reasons for that are:
28281 It has been proven in practice (it is already on its second generation).
28284 It will shorten development time (needless to say how important it is
28288 The original interface was designed to be used by Tcl code, so it was
28289 slightly changed so it could be used through @sc{gdb/mi}. This section
28290 describes the @sc{gdb/mi} operations that will be available and gives some
28291 hints about their use.
28293 @emph{Note}: In addition to the set of operations described here, we
28294 expect the @sc{gui} implementation of a variable window to require, at
28295 least, the following operations:
28298 @item @code{-gdb-show} @code{output-radix}
28299 @item @code{-stack-list-arguments}
28300 @item @code{-stack-list-locals}
28301 @item @code{-stack-select-frame}
28306 @subheading Introduction to Variable Objects
28308 @cindex variable objects in @sc{gdb/mi}
28310 Variable objects are "object-oriented" MI interface for examining and
28311 changing values of expressions. Unlike some other MI interfaces that
28312 work with expressions, variable objects are specifically designed for
28313 simple and efficient presentation in the frontend. A variable object
28314 is identified by string name. When a variable object is created, the
28315 frontend specifies the expression for that variable object. The
28316 expression can be a simple variable, or it can be an arbitrary complex
28317 expression, and can even involve CPU registers. After creating a
28318 variable object, the frontend can invoke other variable object
28319 operations---for example to obtain or change the value of a variable
28320 object, or to change display format.
28322 Variable objects have hierarchical tree structure. Any variable object
28323 that corresponds to a composite type, such as structure in C, has
28324 a number of child variable objects, for example corresponding to each
28325 element of a structure. A child variable object can itself have
28326 children, recursively. Recursion ends when we reach
28327 leaf variable objects, which always have built-in types. Child variable
28328 objects are created only by explicit request, so if a frontend
28329 is not interested in the children of a particular variable object, no
28330 child will be created.
28332 For a leaf variable object it is possible to obtain its value as a
28333 string, or set the value from a string. String value can be also
28334 obtained for a non-leaf variable object, but it's generally a string
28335 that only indicates the type of the object, and does not list its
28336 contents. Assignment to a non-leaf variable object is not allowed.
28338 A frontend does not need to read the values of all variable objects each time
28339 the program stops. Instead, MI provides an update command that lists all
28340 variable objects whose values has changed since the last update
28341 operation. This considerably reduces the amount of data that must
28342 be transferred to the frontend. As noted above, children variable
28343 objects are created on demand, and only leaf variable objects have a
28344 real value. As result, gdb will read target memory only for leaf
28345 variables that frontend has created.
28347 The automatic update is not always desirable. For example, a frontend
28348 might want to keep a value of some expression for future reference,
28349 and never update it. For another example, fetching memory is
28350 relatively slow for embedded targets, so a frontend might want
28351 to disable automatic update for the variables that are either not
28352 visible on the screen, or ``closed''. This is possible using so
28353 called ``frozen variable objects''. Such variable objects are never
28354 implicitly updated.
28356 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
28357 fixed variable object, the expression is parsed when the variable
28358 object is created, including associating identifiers to specific
28359 variables. The meaning of expression never changes. For a floating
28360 variable object the values of variables whose names appear in the
28361 expressions are re-evaluated every time in the context of the current
28362 frame. Consider this example:
28367 struct work_state state;
28374 If a fixed variable object for the @code{state} variable is created in
28375 this function, and we enter the recursive call, the variable
28376 object will report the value of @code{state} in the top-level
28377 @code{do_work} invocation. On the other hand, a floating variable
28378 object will report the value of @code{state} in the current frame.
28380 If an expression specified when creating a fixed variable object
28381 refers to a local variable, the variable object becomes bound to the
28382 thread and frame in which the variable object is created. When such
28383 variable object is updated, @value{GDBN} makes sure that the
28384 thread/frame combination the variable object is bound to still exists,
28385 and re-evaluates the variable object in context of that thread/frame.
28387 The following is the complete set of @sc{gdb/mi} operations defined to
28388 access this functionality:
28390 @multitable @columnfractions .4 .6
28391 @item @strong{Operation}
28392 @tab @strong{Description}
28394 @item @code{-enable-pretty-printing}
28395 @tab enable Python-based pretty-printing
28396 @item @code{-var-create}
28397 @tab create a variable object
28398 @item @code{-var-delete}
28399 @tab delete the variable object and/or its children
28400 @item @code{-var-set-format}
28401 @tab set the display format of this variable
28402 @item @code{-var-show-format}
28403 @tab show the display format of this variable
28404 @item @code{-var-info-num-children}
28405 @tab tells how many children this object has
28406 @item @code{-var-list-children}
28407 @tab return a list of the object's children
28408 @item @code{-var-info-type}
28409 @tab show the type of this variable object
28410 @item @code{-var-info-expression}
28411 @tab print parent-relative expression that this variable object represents
28412 @item @code{-var-info-path-expression}
28413 @tab print full expression that this variable object represents
28414 @item @code{-var-show-attributes}
28415 @tab is this variable editable? does it exist here?
28416 @item @code{-var-evaluate-expression}
28417 @tab get the value of this variable
28418 @item @code{-var-assign}
28419 @tab set the value of this variable
28420 @item @code{-var-update}
28421 @tab update the variable and its children
28422 @item @code{-var-set-frozen}
28423 @tab set frozeness attribute
28424 @item @code{-var-set-update-range}
28425 @tab set range of children to display on update
28428 In the next subsection we describe each operation in detail and suggest
28429 how it can be used.
28431 @subheading Description And Use of Operations on Variable Objects
28433 @subheading The @code{-enable-pretty-printing} Command
28434 @findex -enable-pretty-printing
28437 -enable-pretty-printing
28440 @value{GDBN} allows Python-based visualizers to affect the output of the
28441 MI variable object commands. However, because there was no way to
28442 implement this in a fully backward-compatible way, a front end must
28443 request that this functionality be enabled.
28445 Once enabled, this feature cannot be disabled.
28447 Note that if Python support has not been compiled into @value{GDBN},
28448 this command will still succeed (and do nothing).
28450 This feature is currently (as of @value{GDBN} 7.0) experimental, and
28451 may work differently in future versions of @value{GDBN}.
28453 @subheading The @code{-var-create} Command
28454 @findex -var-create
28456 @subsubheading Synopsis
28459 -var-create @{@var{name} | "-"@}
28460 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
28463 This operation creates a variable object, which allows the monitoring of
28464 a variable, the result of an expression, a memory cell or a CPU
28467 The @var{name} parameter is the string by which the object can be
28468 referenced. It must be unique. If @samp{-} is specified, the varobj
28469 system will generate a string ``varNNNNNN'' automatically. It will be
28470 unique provided that one does not specify @var{name} of that format.
28471 The command fails if a duplicate name is found.
28473 The frame under which the expression should be evaluated can be
28474 specified by @var{frame-addr}. A @samp{*} indicates that the current
28475 frame should be used. A @samp{@@} indicates that a floating variable
28476 object must be created.
28478 @var{expression} is any expression valid on the current language set (must not
28479 begin with a @samp{*}), or one of the following:
28483 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
28486 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
28489 @samp{$@var{regname}} --- a CPU register name
28492 @cindex dynamic varobj
28493 A varobj's contents may be provided by a Python-based pretty-printer. In this
28494 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
28495 have slightly different semantics in some cases. If the
28496 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
28497 will never create a dynamic varobj. This ensures backward
28498 compatibility for existing clients.
28500 @subsubheading Result
28502 This operation returns attributes of the newly-created varobj. These
28507 The name of the varobj.
28510 The number of children of the varobj. This number is not necessarily
28511 reliable for a dynamic varobj. Instead, you must examine the
28512 @samp{has_more} attribute.
28515 The varobj's scalar value. For a varobj whose type is some sort of
28516 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
28517 will not be interesting.
28520 The varobj's type. This is a string representation of the type, as
28521 would be printed by the @value{GDBN} CLI.
28524 If a variable object is bound to a specific thread, then this is the
28525 thread's identifier.
28528 For a dynamic varobj, this indicates whether there appear to be any
28529 children available. For a non-dynamic varobj, this will be 0.
28532 This attribute will be present and have the value @samp{1} if the
28533 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28534 then this attribute will not be present.
28537 A dynamic varobj can supply a display hint to the front end. The
28538 value comes directly from the Python pretty-printer object's
28539 @code{display_hint} method. @xref{Pretty Printing API}.
28542 Typical output will look like this:
28545 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
28546 has_more="@var{has_more}"
28550 @subheading The @code{-var-delete} Command
28551 @findex -var-delete
28553 @subsubheading Synopsis
28556 -var-delete [ -c ] @var{name}
28559 Deletes a previously created variable object and all of its children.
28560 With the @samp{-c} option, just deletes the children.
28562 Returns an error if the object @var{name} is not found.
28565 @subheading The @code{-var-set-format} Command
28566 @findex -var-set-format
28568 @subsubheading Synopsis
28571 -var-set-format @var{name} @var{format-spec}
28574 Sets the output format for the value of the object @var{name} to be
28577 @anchor{-var-set-format}
28578 The syntax for the @var{format-spec} is as follows:
28581 @var{format-spec} @expansion{}
28582 @{binary | decimal | hexadecimal | octal | natural@}
28585 The natural format is the default format choosen automatically
28586 based on the variable type (like decimal for an @code{int}, hex
28587 for pointers, etc.).
28589 For a variable with children, the format is set only on the
28590 variable itself, and the children are not affected.
28592 @subheading The @code{-var-show-format} Command
28593 @findex -var-show-format
28595 @subsubheading Synopsis
28598 -var-show-format @var{name}
28601 Returns the format used to display the value of the object @var{name}.
28604 @var{format} @expansion{}
28609 @subheading The @code{-var-info-num-children} Command
28610 @findex -var-info-num-children
28612 @subsubheading Synopsis
28615 -var-info-num-children @var{name}
28618 Returns the number of children of a variable object @var{name}:
28624 Note that this number is not completely reliable for a dynamic varobj.
28625 It will return the current number of children, but more children may
28629 @subheading The @code{-var-list-children} Command
28630 @findex -var-list-children
28632 @subsubheading Synopsis
28635 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
28637 @anchor{-var-list-children}
28639 Return a list of the children of the specified variable object and
28640 create variable objects for them, if they do not already exist. With
28641 a single argument or if @var{print-values} has a value of 0 or
28642 @code{--no-values}, print only the names of the variables; if
28643 @var{print-values} is 1 or @code{--all-values}, also print their
28644 values; and if it is 2 or @code{--simple-values} print the name and
28645 value for simple data types and just the name for arrays, structures
28648 @var{from} and @var{to}, if specified, indicate the range of children
28649 to report. If @var{from} or @var{to} is less than zero, the range is
28650 reset and all children will be reported. Otherwise, children starting
28651 at @var{from} (zero-based) and up to and excluding @var{to} will be
28654 If a child range is requested, it will only affect the current call to
28655 @code{-var-list-children}, but not future calls to @code{-var-update}.
28656 For this, you must instead use @code{-var-set-update-range}. The
28657 intent of this approach is to enable a front end to implement any
28658 update approach it likes; for example, scrolling a view may cause the
28659 front end to request more children with @code{-var-list-children}, and
28660 then the front end could call @code{-var-set-update-range} with a
28661 different range to ensure that future updates are restricted to just
28664 For each child the following results are returned:
28669 Name of the variable object created for this child.
28672 The expression to be shown to the user by the front end to designate this child.
28673 For example this may be the name of a structure member.
28675 For a dynamic varobj, this value cannot be used to form an
28676 expression. There is no way to do this at all with a dynamic varobj.
28678 For C/C@t{++} structures there are several pseudo children returned to
28679 designate access qualifiers. For these pseudo children @var{exp} is
28680 @samp{public}, @samp{private}, or @samp{protected}. In this case the
28681 type and value are not present.
28683 A dynamic varobj will not report the access qualifying
28684 pseudo-children, regardless of the language. This information is not
28685 available at all with a dynamic varobj.
28688 Number of children this child has. For a dynamic varobj, this will be
28692 The type of the child.
28695 If values were requested, this is the value.
28698 If this variable object is associated with a thread, this is the thread id.
28699 Otherwise this result is not present.
28702 If the variable object is frozen, this variable will be present with a value of 1.
28705 The result may have its own attributes:
28709 A dynamic varobj can supply a display hint to the front end. The
28710 value comes directly from the Python pretty-printer object's
28711 @code{display_hint} method. @xref{Pretty Printing API}.
28714 This is an integer attribute which is nonzero if there are children
28715 remaining after the end of the selected range.
28718 @subsubheading Example
28722 -var-list-children n
28723 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28724 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
28726 -var-list-children --all-values n
28727 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28728 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
28732 @subheading The @code{-var-info-type} Command
28733 @findex -var-info-type
28735 @subsubheading Synopsis
28738 -var-info-type @var{name}
28741 Returns the type of the specified variable @var{name}. The type is
28742 returned as a string in the same format as it is output by the
28746 type=@var{typename}
28750 @subheading The @code{-var-info-expression} Command
28751 @findex -var-info-expression
28753 @subsubheading Synopsis
28756 -var-info-expression @var{name}
28759 Returns a string that is suitable for presenting this
28760 variable object in user interface. The string is generally
28761 not valid expression in the current language, and cannot be evaluated.
28763 For example, if @code{a} is an array, and variable object
28764 @code{A} was created for @code{a}, then we'll get this output:
28767 (gdb) -var-info-expression A.1
28768 ^done,lang="C",exp="1"
28772 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
28774 Note that the output of the @code{-var-list-children} command also
28775 includes those expressions, so the @code{-var-info-expression} command
28778 @subheading The @code{-var-info-path-expression} Command
28779 @findex -var-info-path-expression
28781 @subsubheading Synopsis
28784 -var-info-path-expression @var{name}
28787 Returns an expression that can be evaluated in the current
28788 context and will yield the same value that a variable object has.
28789 Compare this with the @code{-var-info-expression} command, which
28790 result can be used only for UI presentation. Typical use of
28791 the @code{-var-info-path-expression} command is creating a
28792 watchpoint from a variable object.
28794 This command is currently not valid for children of a dynamic varobj,
28795 and will give an error when invoked on one.
28797 For example, suppose @code{C} is a C@t{++} class, derived from class
28798 @code{Base}, and that the @code{Base} class has a member called
28799 @code{m_size}. Assume a variable @code{c} is has the type of
28800 @code{C} and a variable object @code{C} was created for variable
28801 @code{c}. Then, we'll get this output:
28803 (gdb) -var-info-path-expression C.Base.public.m_size
28804 ^done,path_expr=((Base)c).m_size)
28807 @subheading The @code{-var-show-attributes} Command
28808 @findex -var-show-attributes
28810 @subsubheading Synopsis
28813 -var-show-attributes @var{name}
28816 List attributes of the specified variable object @var{name}:
28819 status=@var{attr} [ ( ,@var{attr} )* ]
28823 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
28825 @subheading The @code{-var-evaluate-expression} Command
28826 @findex -var-evaluate-expression
28828 @subsubheading Synopsis
28831 -var-evaluate-expression [-f @var{format-spec}] @var{name}
28834 Evaluates the expression that is represented by the specified variable
28835 object and returns its value as a string. The format of the string
28836 can be specified with the @samp{-f} option. The possible values of
28837 this option are the same as for @code{-var-set-format}
28838 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
28839 the current display format will be used. The current display format
28840 can be changed using the @code{-var-set-format} command.
28846 Note that one must invoke @code{-var-list-children} for a variable
28847 before the value of a child variable can be evaluated.
28849 @subheading The @code{-var-assign} Command
28850 @findex -var-assign
28852 @subsubheading Synopsis
28855 -var-assign @var{name} @var{expression}
28858 Assigns the value of @var{expression} to the variable object specified
28859 by @var{name}. The object must be @samp{editable}. If the variable's
28860 value is altered by the assign, the variable will show up in any
28861 subsequent @code{-var-update} list.
28863 @subsubheading Example
28871 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
28875 @subheading The @code{-var-update} Command
28876 @findex -var-update
28878 @subsubheading Synopsis
28881 -var-update [@var{print-values}] @{@var{name} | "*"@}
28884 Reevaluate the expressions corresponding to the variable object
28885 @var{name} and all its direct and indirect children, and return the
28886 list of variable objects whose values have changed; @var{name} must
28887 be a root variable object. Here, ``changed'' means that the result of
28888 @code{-var-evaluate-expression} before and after the
28889 @code{-var-update} is different. If @samp{*} is used as the variable
28890 object names, all existing variable objects are updated, except
28891 for frozen ones (@pxref{-var-set-frozen}). The option
28892 @var{print-values} determines whether both names and values, or just
28893 names are printed. The possible values of this option are the same
28894 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
28895 recommended to use the @samp{--all-values} option, to reduce the
28896 number of MI commands needed on each program stop.
28898 With the @samp{*} parameter, if a variable object is bound to a
28899 currently running thread, it will not be updated, without any
28902 If @code{-var-set-update-range} was previously used on a varobj, then
28903 only the selected range of children will be reported.
28905 @code{-var-update} reports all the changed varobjs in a tuple named
28908 Each item in the change list is itself a tuple holding:
28912 The name of the varobj.
28915 If values were requested for this update, then this field will be
28916 present and will hold the value of the varobj.
28919 @anchor{-var-update}
28920 This field is a string which may take one of three values:
28924 The variable object's current value is valid.
28927 The variable object does not currently hold a valid value but it may
28928 hold one in the future if its associated expression comes back into
28932 The variable object no longer holds a valid value.
28933 This can occur when the executable file being debugged has changed,
28934 either through recompilation or by using the @value{GDBN} @code{file}
28935 command. The front end should normally choose to delete these variable
28939 In the future new values may be added to this list so the front should
28940 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
28943 This is only present if the varobj is still valid. If the type
28944 changed, then this will be the string @samp{true}; otherwise it will
28948 If the varobj's type changed, then this field will be present and will
28951 @item new_num_children
28952 For a dynamic varobj, if the number of children changed, or if the
28953 type changed, this will be the new number of children.
28955 The @samp{numchild} field in other varobj responses is generally not
28956 valid for a dynamic varobj -- it will show the number of children that
28957 @value{GDBN} knows about, but because dynamic varobjs lazily
28958 instantiate their children, this will not reflect the number of
28959 children which may be available.
28961 The @samp{new_num_children} attribute only reports changes to the
28962 number of children known by @value{GDBN}. This is the only way to
28963 detect whether an update has removed children (which necessarily can
28964 only happen at the end of the update range).
28967 The display hint, if any.
28970 This is an integer value, which will be 1 if there are more children
28971 available outside the varobj's update range.
28974 This attribute will be present and have the value @samp{1} if the
28975 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28976 then this attribute will not be present.
28979 If new children were added to a dynamic varobj within the selected
28980 update range (as set by @code{-var-set-update-range}), then they will
28981 be listed in this attribute.
28984 @subsubheading Example
28991 -var-update --all-values var1
28992 ^done,changelist=[@{name="var1",value="3",in_scope="true",
28993 type_changed="false"@}]
28997 @subheading The @code{-var-set-frozen} Command
28998 @findex -var-set-frozen
28999 @anchor{-var-set-frozen}
29001 @subsubheading Synopsis
29004 -var-set-frozen @var{name} @var{flag}
29007 Set the frozenness flag on the variable object @var{name}. The
29008 @var{flag} parameter should be either @samp{1} to make the variable
29009 frozen or @samp{0} to make it unfrozen. If a variable object is
29010 frozen, then neither itself, nor any of its children, are
29011 implicitly updated by @code{-var-update} of
29012 a parent variable or by @code{-var-update *}. Only
29013 @code{-var-update} of the variable itself will update its value and
29014 values of its children. After a variable object is unfrozen, it is
29015 implicitly updated by all subsequent @code{-var-update} operations.
29016 Unfreezing a variable does not update it, only subsequent
29017 @code{-var-update} does.
29019 @subsubheading Example
29023 -var-set-frozen V 1
29028 @subheading The @code{-var-set-update-range} command
29029 @findex -var-set-update-range
29030 @anchor{-var-set-update-range}
29032 @subsubheading Synopsis
29035 -var-set-update-range @var{name} @var{from} @var{to}
29038 Set the range of children to be returned by future invocations of
29039 @code{-var-update}.
29041 @var{from} and @var{to} indicate the range of children to report. If
29042 @var{from} or @var{to} is less than zero, the range is reset and all
29043 children will be reported. Otherwise, children starting at @var{from}
29044 (zero-based) and up to and excluding @var{to} will be reported.
29046 @subsubheading Example
29050 -var-set-update-range V 1 2
29054 @subheading The @code{-var-set-visualizer} command
29055 @findex -var-set-visualizer
29056 @anchor{-var-set-visualizer}
29058 @subsubheading Synopsis
29061 -var-set-visualizer @var{name} @var{visualizer}
29064 Set a visualizer for the variable object @var{name}.
29066 @var{visualizer} is the visualizer to use. The special value
29067 @samp{None} means to disable any visualizer in use.
29069 If not @samp{None}, @var{visualizer} must be a Python expression.
29070 This expression must evaluate to a callable object which accepts a
29071 single argument. @value{GDBN} will call this object with the value of
29072 the varobj @var{name} as an argument (this is done so that the same
29073 Python pretty-printing code can be used for both the CLI and MI).
29074 When called, this object must return an object which conforms to the
29075 pretty-printing interface (@pxref{Pretty Printing API}).
29077 The pre-defined function @code{gdb.default_visualizer} may be used to
29078 select a visualizer by following the built-in process
29079 (@pxref{Selecting Pretty-Printers}). This is done automatically when
29080 a varobj is created, and so ordinarily is not needed.
29082 This feature is only available if Python support is enabled. The MI
29083 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
29084 can be used to check this.
29086 @subsubheading Example
29088 Resetting the visualizer:
29092 -var-set-visualizer V None
29096 Reselecting the default (type-based) visualizer:
29100 -var-set-visualizer V gdb.default_visualizer
29104 Suppose @code{SomeClass} is a visualizer class. A lambda expression
29105 can be used to instantiate this class for a varobj:
29109 -var-set-visualizer V "lambda val: SomeClass()"
29113 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29114 @node GDB/MI Data Manipulation
29115 @section @sc{gdb/mi} Data Manipulation
29117 @cindex data manipulation, in @sc{gdb/mi}
29118 @cindex @sc{gdb/mi}, data manipulation
29119 This section describes the @sc{gdb/mi} commands that manipulate data:
29120 examine memory and registers, evaluate expressions, etc.
29122 @c REMOVED FROM THE INTERFACE.
29123 @c @subheading -data-assign
29124 @c Change the value of a program variable. Plenty of side effects.
29125 @c @subsubheading GDB Command
29127 @c @subsubheading Example
29130 @subheading The @code{-data-disassemble} Command
29131 @findex -data-disassemble
29133 @subsubheading Synopsis
29137 [ -s @var{start-addr} -e @var{end-addr} ]
29138 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
29146 @item @var{start-addr}
29147 is the beginning address (or @code{$pc})
29148 @item @var{end-addr}
29150 @item @var{filename}
29151 is the name of the file to disassemble
29152 @item @var{linenum}
29153 is the line number to disassemble around
29155 is the number of disassembly lines to be produced. If it is -1,
29156 the whole function will be disassembled, in case no @var{end-addr} is
29157 specified. If @var{end-addr} is specified as a non-zero value, and
29158 @var{lines} is lower than the number of disassembly lines between
29159 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
29160 displayed; if @var{lines} is higher than the number of lines between
29161 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
29164 is either 0 (meaning only disassembly), 1 (meaning mixed source and
29165 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
29166 mixed source and disassembly with raw opcodes).
29169 @subsubheading Result
29171 The output for each instruction is composed of four fields:
29180 Note that whatever included in the instruction field, is not manipulated
29181 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
29183 @subsubheading @value{GDBN} Command
29185 There's no direct mapping from this command to the CLI.
29187 @subsubheading Example
29189 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
29193 -data-disassemble -s $pc -e "$pc + 20" -- 0
29196 @{address="0x000107c0",func-name="main",offset="4",
29197 inst="mov 2, %o0"@},
29198 @{address="0x000107c4",func-name="main",offset="8",
29199 inst="sethi %hi(0x11800), %o2"@},
29200 @{address="0x000107c8",func-name="main",offset="12",
29201 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
29202 @{address="0x000107cc",func-name="main",offset="16",
29203 inst="sethi %hi(0x11800), %o2"@},
29204 @{address="0x000107d0",func-name="main",offset="20",
29205 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
29209 Disassemble the whole @code{main} function. Line 32 is part of
29213 -data-disassemble -f basics.c -l 32 -- 0
29215 @{address="0x000107bc",func-name="main",offset="0",
29216 inst="save %sp, -112, %sp"@},
29217 @{address="0x000107c0",func-name="main",offset="4",
29218 inst="mov 2, %o0"@},
29219 @{address="0x000107c4",func-name="main",offset="8",
29220 inst="sethi %hi(0x11800), %o2"@},
29222 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
29223 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
29227 Disassemble 3 instructions from the start of @code{main}:
29231 -data-disassemble -f basics.c -l 32 -n 3 -- 0
29233 @{address="0x000107bc",func-name="main",offset="0",
29234 inst="save %sp, -112, %sp"@},
29235 @{address="0x000107c0",func-name="main",offset="4",
29236 inst="mov 2, %o0"@},
29237 @{address="0x000107c4",func-name="main",offset="8",
29238 inst="sethi %hi(0x11800), %o2"@}]
29242 Disassemble 3 instructions from the start of @code{main} in mixed mode:
29246 -data-disassemble -f basics.c -l 32 -n 3 -- 1
29248 src_and_asm_line=@{line="31",
29249 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
29250 testsuite/gdb.mi/basics.c",line_asm_insn=[
29251 @{address="0x000107bc",func-name="main",offset="0",
29252 inst="save %sp, -112, %sp"@}]@},
29253 src_and_asm_line=@{line="32",
29254 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
29255 testsuite/gdb.mi/basics.c",line_asm_insn=[
29256 @{address="0x000107c0",func-name="main",offset="4",
29257 inst="mov 2, %o0"@},
29258 @{address="0x000107c4",func-name="main",offset="8",
29259 inst="sethi %hi(0x11800), %o2"@}]@}]
29264 @subheading The @code{-data-evaluate-expression} Command
29265 @findex -data-evaluate-expression
29267 @subsubheading Synopsis
29270 -data-evaluate-expression @var{expr}
29273 Evaluate @var{expr} as an expression. The expression could contain an
29274 inferior function call. The function call will execute synchronously.
29275 If the expression contains spaces, it must be enclosed in double quotes.
29277 @subsubheading @value{GDBN} Command
29279 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
29280 @samp{call}. In @code{gdbtk} only, there's a corresponding
29281 @samp{gdb_eval} command.
29283 @subsubheading Example
29285 In the following example, the numbers that precede the commands are the
29286 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
29287 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
29291 211-data-evaluate-expression A
29294 311-data-evaluate-expression &A
29295 311^done,value="0xefffeb7c"
29297 411-data-evaluate-expression A+3
29300 511-data-evaluate-expression "A + 3"
29306 @subheading The @code{-data-list-changed-registers} Command
29307 @findex -data-list-changed-registers
29309 @subsubheading Synopsis
29312 -data-list-changed-registers
29315 Display a list of the registers that have changed.
29317 @subsubheading @value{GDBN} Command
29319 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
29320 has the corresponding command @samp{gdb_changed_register_list}.
29322 @subsubheading Example
29324 On a PPC MBX board:
29332 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
29333 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
29336 -data-list-changed-registers
29337 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
29338 "10","11","13","14","15","16","17","18","19","20","21","22","23",
29339 "24","25","26","27","28","30","31","64","65","66","67","69"]
29344 @subheading The @code{-data-list-register-names} Command
29345 @findex -data-list-register-names
29347 @subsubheading Synopsis
29350 -data-list-register-names [ ( @var{regno} )+ ]
29353 Show a list of register names for the current target. If no arguments
29354 are given, it shows a list of the names of all the registers. If
29355 integer numbers are given as arguments, it will print a list of the
29356 names of the registers corresponding to the arguments. To ensure
29357 consistency between a register name and its number, the output list may
29358 include empty register names.
29360 @subsubheading @value{GDBN} Command
29362 @value{GDBN} does not have a command which corresponds to
29363 @samp{-data-list-register-names}. In @code{gdbtk} there is a
29364 corresponding command @samp{gdb_regnames}.
29366 @subsubheading Example
29368 For the PPC MBX board:
29371 -data-list-register-names
29372 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
29373 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
29374 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
29375 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
29376 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
29377 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
29378 "", "pc","ps","cr","lr","ctr","xer"]
29380 -data-list-register-names 1 2 3
29381 ^done,register-names=["r1","r2","r3"]
29385 @subheading The @code{-data-list-register-values} Command
29386 @findex -data-list-register-values
29388 @subsubheading Synopsis
29391 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
29394 Display the registers' contents. @var{fmt} is the format according to
29395 which the registers' contents are to be returned, followed by an optional
29396 list of numbers specifying the registers to display. A missing list of
29397 numbers indicates that the contents of all the registers must be returned.
29399 Allowed formats for @var{fmt} are:
29416 @subsubheading @value{GDBN} Command
29418 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
29419 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
29421 @subsubheading Example
29423 For a PPC MBX board (note: line breaks are for readability only, they
29424 don't appear in the actual output):
29428 -data-list-register-values r 64 65
29429 ^done,register-values=[@{number="64",value="0xfe00a300"@},
29430 @{number="65",value="0x00029002"@}]
29432 -data-list-register-values x
29433 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
29434 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
29435 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
29436 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
29437 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
29438 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
29439 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
29440 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
29441 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
29442 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
29443 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
29444 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
29445 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
29446 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
29447 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
29448 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
29449 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
29450 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
29451 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
29452 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
29453 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
29454 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
29455 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
29456 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
29457 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
29458 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
29459 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
29460 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
29461 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
29462 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
29463 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
29464 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
29465 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
29466 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
29467 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
29468 @{number="69",value="0x20002b03"@}]
29473 @subheading The @code{-data-read-memory} Command
29474 @findex -data-read-memory
29476 This command is deprecated, use @code{-data-read-memory-bytes} instead.
29478 @subsubheading Synopsis
29481 -data-read-memory [ -o @var{byte-offset} ]
29482 @var{address} @var{word-format} @var{word-size}
29483 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
29490 @item @var{address}
29491 An expression specifying the address of the first memory word to be
29492 read. Complex expressions containing embedded white space should be
29493 quoted using the C convention.
29495 @item @var{word-format}
29496 The format to be used to print the memory words. The notation is the
29497 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
29500 @item @var{word-size}
29501 The size of each memory word in bytes.
29503 @item @var{nr-rows}
29504 The number of rows in the output table.
29506 @item @var{nr-cols}
29507 The number of columns in the output table.
29510 If present, indicates that each row should include an @sc{ascii} dump. The
29511 value of @var{aschar} is used as a padding character when a byte is not a
29512 member of the printable @sc{ascii} character set (printable @sc{ascii}
29513 characters are those whose code is between 32 and 126, inclusively).
29515 @item @var{byte-offset}
29516 An offset to add to the @var{address} before fetching memory.
29519 This command displays memory contents as a table of @var{nr-rows} by
29520 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
29521 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
29522 (returned as @samp{total-bytes}). Should less than the requested number
29523 of bytes be returned by the target, the missing words are identified
29524 using @samp{N/A}. The number of bytes read from the target is returned
29525 in @samp{nr-bytes} and the starting address used to read memory in
29528 The address of the next/previous row or page is available in
29529 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
29532 @subsubheading @value{GDBN} Command
29534 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
29535 @samp{gdb_get_mem} memory read command.
29537 @subsubheading Example
29539 Read six bytes of memory starting at @code{bytes+6} but then offset by
29540 @code{-6} bytes. Format as three rows of two columns. One byte per
29541 word. Display each word in hex.
29545 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
29546 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
29547 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
29548 prev-page="0x0000138a",memory=[
29549 @{addr="0x00001390",data=["0x00","0x01"]@},
29550 @{addr="0x00001392",data=["0x02","0x03"]@},
29551 @{addr="0x00001394",data=["0x04","0x05"]@}]
29555 Read two bytes of memory starting at address @code{shorts + 64} and
29556 display as a single word formatted in decimal.
29560 5-data-read-memory shorts+64 d 2 1 1
29561 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
29562 next-row="0x00001512",prev-row="0x0000150e",
29563 next-page="0x00001512",prev-page="0x0000150e",memory=[
29564 @{addr="0x00001510",data=["128"]@}]
29568 Read thirty two bytes of memory starting at @code{bytes+16} and format
29569 as eight rows of four columns. Include a string encoding with @samp{x}
29570 used as the non-printable character.
29574 4-data-read-memory bytes+16 x 1 8 4 x
29575 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
29576 next-row="0x000013c0",prev-row="0x0000139c",
29577 next-page="0x000013c0",prev-page="0x00001380",memory=[
29578 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
29579 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
29580 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
29581 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
29582 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
29583 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
29584 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
29585 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
29589 @subheading The @code{-data-read-memory-bytes} Command
29590 @findex -data-read-memory-bytes
29592 @subsubheading Synopsis
29595 -data-read-memory-bytes [ -o @var{byte-offset} ]
29596 @var{address} @var{count}
29603 @item @var{address}
29604 An expression specifying the address of the first memory word to be
29605 read. Complex expressions containing embedded white space should be
29606 quoted using the C convention.
29609 The number of bytes to read. This should be an integer literal.
29611 @item @var{byte-offset}
29612 The offsets in bytes relative to @var{address} at which to start
29613 reading. This should be an integer literal. This option is provided
29614 so that a frontend is not required to first evaluate address and then
29615 perform address arithmetics itself.
29619 This command attempts to read all accessible memory regions in the
29620 specified range. First, all regions marked as unreadable in the memory
29621 map (if one is defined) will be skipped. @xref{Memory Region
29622 Attributes}. Second, @value{GDBN} will attempt to read the remaining
29623 regions. For each one, if reading full region results in an errors,
29624 @value{GDBN} will try to read a subset of the region.
29626 In general, every single byte in the region may be readable or not,
29627 and the only way to read every readable byte is to try a read at
29628 every address, which is not practical. Therefore, @value{GDBN} will
29629 attempt to read all accessible bytes at either beginning or the end
29630 of the region, using a binary division scheme. This heuristic works
29631 well for reading accross a memory map boundary. Note that if a region
29632 has a readable range that is neither at the beginning or the end,
29633 @value{GDBN} will not read it.
29635 The result record (@pxref{GDB/MI Result Records}) that is output of
29636 the command includes a field named @samp{memory} whose content is a
29637 list of tuples. Each tuple represent a successfully read memory block
29638 and has the following fields:
29642 The start address of the memory block, as hexadecimal literal.
29645 The end address of the memory block, as hexadecimal literal.
29648 The offset of the memory block, as hexadecimal literal, relative to
29649 the start address passed to @code{-data-read-memory-bytes}.
29652 The contents of the memory block, in hex.
29658 @subsubheading @value{GDBN} Command
29660 The corresponding @value{GDBN} command is @samp{x}.
29662 @subsubheading Example
29666 -data-read-memory-bytes &a 10
29667 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
29669 contents="01000000020000000300"@}]
29674 @subheading The @code{-data-write-memory-bytes} Command
29675 @findex -data-write-memory-bytes
29677 @subsubheading Synopsis
29680 -data-write-memory-bytes @var{address} @var{contents}
29687 @item @var{address}
29688 An expression specifying the address of the first memory word to be
29689 read. Complex expressions containing embedded white space should be
29690 quoted using the C convention.
29692 @item @var{contents}
29693 The hex-encoded bytes to write.
29697 @subsubheading @value{GDBN} Command
29699 There's no corresponding @value{GDBN} command.
29701 @subsubheading Example
29705 -data-write-memory-bytes &a "aabbccdd"
29711 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29712 @node GDB/MI Tracepoint Commands
29713 @section @sc{gdb/mi} Tracepoint Commands
29715 The commands defined in this section implement MI support for
29716 tracepoints. For detailed introduction, see @ref{Tracepoints}.
29718 @subheading The @code{-trace-find} Command
29719 @findex -trace-find
29721 @subsubheading Synopsis
29724 -trace-find @var{mode} [@var{parameters}@dots{}]
29727 Find a trace frame using criteria defined by @var{mode} and
29728 @var{parameters}. The following table lists permissible
29729 modes and their parameters. For details of operation, see @ref{tfind}.
29734 No parameters are required. Stops examining trace frames.
29737 An integer is required as parameter. Selects tracepoint frame with
29740 @item tracepoint-number
29741 An integer is required as parameter. Finds next
29742 trace frame that corresponds to tracepoint with the specified number.
29745 An address is required as parameter. Finds
29746 next trace frame that corresponds to any tracepoint at the specified
29749 @item pc-inside-range
29750 Two addresses are required as parameters. Finds next trace
29751 frame that corresponds to a tracepoint at an address inside the
29752 specified range. Both bounds are considered to be inside the range.
29754 @item pc-outside-range
29755 Two addresses are required as parameters. Finds
29756 next trace frame that corresponds to a tracepoint at an address outside
29757 the specified range. Both bounds are considered to be inside the range.
29760 Line specification is required as parameter. @xref{Specify Location}.
29761 Finds next trace frame that corresponds to a tracepoint at
29762 the specified location.
29766 If @samp{none} was passed as @var{mode}, the response does not
29767 have fields. Otherwise, the response may have the following fields:
29771 This field has either @samp{0} or @samp{1} as the value, depending
29772 on whether a matching tracepoint was found.
29775 The index of the found traceframe. This field is present iff
29776 the @samp{found} field has value of @samp{1}.
29779 The index of the found tracepoint. This field is present iff
29780 the @samp{found} field has value of @samp{1}.
29783 The information about the frame corresponding to the found trace
29784 frame. This field is present only if a trace frame was found.
29785 @xref{GDB/MI Frame Information}, for description of this field.
29789 @subsubheading @value{GDBN} Command
29791 The corresponding @value{GDBN} command is @samp{tfind}.
29793 @subheading -trace-define-variable
29794 @findex -trace-define-variable
29796 @subsubheading Synopsis
29799 -trace-define-variable @var{name} [ @var{value} ]
29802 Create trace variable @var{name} if it does not exist. If
29803 @var{value} is specified, sets the initial value of the specified
29804 trace variable to that value. Note that the @var{name} should start
29805 with the @samp{$} character.
29807 @subsubheading @value{GDBN} Command
29809 The corresponding @value{GDBN} command is @samp{tvariable}.
29811 @subheading -trace-list-variables
29812 @findex -trace-list-variables
29814 @subsubheading Synopsis
29817 -trace-list-variables
29820 Return a table of all defined trace variables. Each element of the
29821 table has the following fields:
29825 The name of the trace variable. This field is always present.
29828 The initial value. This is a 64-bit signed integer. This
29829 field is always present.
29832 The value the trace variable has at the moment. This is a 64-bit
29833 signed integer. This field is absent iff current value is
29834 not defined, for example if the trace was never run, or is
29839 @subsubheading @value{GDBN} Command
29841 The corresponding @value{GDBN} command is @samp{tvariables}.
29843 @subsubheading Example
29847 -trace-list-variables
29848 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
29849 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
29850 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
29851 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
29852 body=[variable=@{name="$trace_timestamp",initial="0"@}
29853 variable=@{name="$foo",initial="10",current="15"@}]@}
29857 @subheading -trace-save
29858 @findex -trace-save
29860 @subsubheading Synopsis
29863 -trace-save [-r ] @var{filename}
29866 Saves the collected trace data to @var{filename}. Without the
29867 @samp{-r} option, the data is downloaded from the target and saved
29868 in a local file. With the @samp{-r} option the target is asked
29869 to perform the save.
29871 @subsubheading @value{GDBN} Command
29873 The corresponding @value{GDBN} command is @samp{tsave}.
29876 @subheading -trace-start
29877 @findex -trace-start
29879 @subsubheading Synopsis
29885 Starts a tracing experiments. The result of this command does not
29888 @subsubheading @value{GDBN} Command
29890 The corresponding @value{GDBN} command is @samp{tstart}.
29892 @subheading -trace-status
29893 @findex -trace-status
29895 @subsubheading Synopsis
29901 Obtains the status of a tracing experiment. The result may include
29902 the following fields:
29907 May have a value of either @samp{0}, when no tracing operations are
29908 supported, @samp{1}, when all tracing operations are supported, or
29909 @samp{file} when examining trace file. In the latter case, examining
29910 of trace frame is possible but new tracing experiement cannot be
29911 started. This field is always present.
29914 May have a value of either @samp{0} or @samp{1} depending on whether
29915 tracing experiement is in progress on target. This field is present
29916 if @samp{supported} field is not @samp{0}.
29919 Report the reason why the tracing was stopped last time. This field
29920 may be absent iff tracing was never stopped on target yet. The
29921 value of @samp{request} means the tracing was stopped as result of
29922 the @code{-trace-stop} command. The value of @samp{overflow} means
29923 the tracing buffer is full. The value of @samp{disconnection} means
29924 tracing was automatically stopped when @value{GDBN} has disconnected.
29925 The value of @samp{passcount} means tracing was stopped when a
29926 tracepoint was passed a maximal number of times for that tracepoint.
29927 This field is present if @samp{supported} field is not @samp{0}.
29929 @item stopping-tracepoint
29930 The number of tracepoint whose passcount as exceeded. This field is
29931 present iff the @samp{stop-reason} field has the value of
29935 @itemx frames-created
29936 The @samp{frames} field is a count of the total number of trace frames
29937 in the trace buffer, while @samp{frames-created} is the total created
29938 during the run, including ones that were discarded, such as when a
29939 circular trace buffer filled up. Both fields are optional.
29943 These fields tell the current size of the tracing buffer and the
29944 remaining space. These fields are optional.
29947 The value of the circular trace buffer flag. @code{1} means that the
29948 trace buffer is circular and old trace frames will be discarded if
29949 necessary to make room, @code{0} means that the trace buffer is linear
29953 The value of the disconnected tracing flag. @code{1} means that
29954 tracing will continue after @value{GDBN} disconnects, @code{0} means
29955 that the trace run will stop.
29959 @subsubheading @value{GDBN} Command
29961 The corresponding @value{GDBN} command is @samp{tstatus}.
29963 @subheading -trace-stop
29964 @findex -trace-stop
29966 @subsubheading Synopsis
29972 Stops a tracing experiment. The result of this command has the same
29973 fields as @code{-trace-status}, except that the @samp{supported} and
29974 @samp{running} fields are not output.
29976 @subsubheading @value{GDBN} Command
29978 The corresponding @value{GDBN} command is @samp{tstop}.
29981 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29982 @node GDB/MI Symbol Query
29983 @section @sc{gdb/mi} Symbol Query Commands
29987 @subheading The @code{-symbol-info-address} Command
29988 @findex -symbol-info-address
29990 @subsubheading Synopsis
29993 -symbol-info-address @var{symbol}
29996 Describe where @var{symbol} is stored.
29998 @subsubheading @value{GDBN} Command
30000 The corresponding @value{GDBN} command is @samp{info address}.
30002 @subsubheading Example
30006 @subheading The @code{-symbol-info-file} Command
30007 @findex -symbol-info-file
30009 @subsubheading Synopsis
30015 Show the file for the symbol.
30017 @subsubheading @value{GDBN} Command
30019 There's no equivalent @value{GDBN} command. @code{gdbtk} has
30020 @samp{gdb_find_file}.
30022 @subsubheading Example
30026 @subheading The @code{-symbol-info-function} Command
30027 @findex -symbol-info-function
30029 @subsubheading Synopsis
30032 -symbol-info-function
30035 Show which function the symbol lives in.
30037 @subsubheading @value{GDBN} Command
30039 @samp{gdb_get_function} in @code{gdbtk}.
30041 @subsubheading Example
30045 @subheading The @code{-symbol-info-line} Command
30046 @findex -symbol-info-line
30048 @subsubheading Synopsis
30054 Show the core addresses of the code for a source line.
30056 @subsubheading @value{GDBN} Command
30058 The corresponding @value{GDBN} command is @samp{info line}.
30059 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
30061 @subsubheading Example
30065 @subheading The @code{-symbol-info-symbol} Command
30066 @findex -symbol-info-symbol
30068 @subsubheading Synopsis
30071 -symbol-info-symbol @var{addr}
30074 Describe what symbol is at location @var{addr}.
30076 @subsubheading @value{GDBN} Command
30078 The corresponding @value{GDBN} command is @samp{info symbol}.
30080 @subsubheading Example
30084 @subheading The @code{-symbol-list-functions} Command
30085 @findex -symbol-list-functions
30087 @subsubheading Synopsis
30090 -symbol-list-functions
30093 List the functions in the executable.
30095 @subsubheading @value{GDBN} Command
30097 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
30098 @samp{gdb_search} in @code{gdbtk}.
30100 @subsubheading Example
30105 @subheading The @code{-symbol-list-lines} Command
30106 @findex -symbol-list-lines
30108 @subsubheading Synopsis
30111 -symbol-list-lines @var{filename}
30114 Print the list of lines that contain code and their associated program
30115 addresses for the given source filename. The entries are sorted in
30116 ascending PC order.
30118 @subsubheading @value{GDBN} Command
30120 There is no corresponding @value{GDBN} command.
30122 @subsubheading Example
30125 -symbol-list-lines basics.c
30126 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
30132 @subheading The @code{-symbol-list-types} Command
30133 @findex -symbol-list-types
30135 @subsubheading Synopsis
30141 List all the type names.
30143 @subsubheading @value{GDBN} Command
30145 The corresponding commands are @samp{info types} in @value{GDBN},
30146 @samp{gdb_search} in @code{gdbtk}.
30148 @subsubheading Example
30152 @subheading The @code{-symbol-list-variables} Command
30153 @findex -symbol-list-variables
30155 @subsubheading Synopsis
30158 -symbol-list-variables
30161 List all the global and static variable names.
30163 @subsubheading @value{GDBN} Command
30165 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
30167 @subsubheading Example
30171 @subheading The @code{-symbol-locate} Command
30172 @findex -symbol-locate
30174 @subsubheading Synopsis
30180 @subsubheading @value{GDBN} Command
30182 @samp{gdb_loc} in @code{gdbtk}.
30184 @subsubheading Example
30188 @subheading The @code{-symbol-type} Command
30189 @findex -symbol-type
30191 @subsubheading Synopsis
30194 -symbol-type @var{variable}
30197 Show type of @var{variable}.
30199 @subsubheading @value{GDBN} Command
30201 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
30202 @samp{gdb_obj_variable}.
30204 @subsubheading Example
30209 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30210 @node GDB/MI File Commands
30211 @section @sc{gdb/mi} File Commands
30213 This section describes the GDB/MI commands to specify executable file names
30214 and to read in and obtain symbol table information.
30216 @subheading The @code{-file-exec-and-symbols} Command
30217 @findex -file-exec-and-symbols
30219 @subsubheading Synopsis
30222 -file-exec-and-symbols @var{file}
30225 Specify the executable file to be debugged. This file is the one from
30226 which the symbol table is also read. If no file is specified, the
30227 command clears the executable and symbol information. If breakpoints
30228 are set when using this command with no arguments, @value{GDBN} will produce
30229 error messages. Otherwise, no output is produced, except a completion
30232 @subsubheading @value{GDBN} Command
30234 The corresponding @value{GDBN} command is @samp{file}.
30236 @subsubheading Example
30240 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30246 @subheading The @code{-file-exec-file} Command
30247 @findex -file-exec-file
30249 @subsubheading Synopsis
30252 -file-exec-file @var{file}
30255 Specify the executable file to be debugged. Unlike
30256 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
30257 from this file. If used without argument, @value{GDBN} clears the information
30258 about the executable file. No output is produced, except a completion
30261 @subsubheading @value{GDBN} Command
30263 The corresponding @value{GDBN} command is @samp{exec-file}.
30265 @subsubheading Example
30269 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30276 @subheading The @code{-file-list-exec-sections} Command
30277 @findex -file-list-exec-sections
30279 @subsubheading Synopsis
30282 -file-list-exec-sections
30285 List the sections of the current executable file.
30287 @subsubheading @value{GDBN} Command
30289 The @value{GDBN} command @samp{info file} shows, among the rest, the same
30290 information as this command. @code{gdbtk} has a corresponding command
30291 @samp{gdb_load_info}.
30293 @subsubheading Example
30298 @subheading The @code{-file-list-exec-source-file} Command
30299 @findex -file-list-exec-source-file
30301 @subsubheading Synopsis
30304 -file-list-exec-source-file
30307 List the line number, the current source file, and the absolute path
30308 to the current source file for the current executable. The macro
30309 information field has a value of @samp{1} or @samp{0} depending on
30310 whether or not the file includes preprocessor macro information.
30312 @subsubheading @value{GDBN} Command
30314 The @value{GDBN} equivalent is @samp{info source}
30316 @subsubheading Example
30320 123-file-list-exec-source-file
30321 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
30326 @subheading The @code{-file-list-exec-source-files} Command
30327 @findex -file-list-exec-source-files
30329 @subsubheading Synopsis
30332 -file-list-exec-source-files
30335 List the source files for the current executable.
30337 It will always output the filename, but only when @value{GDBN} can find
30338 the absolute file name of a source file, will it output the fullname.
30340 @subsubheading @value{GDBN} Command
30342 The @value{GDBN} equivalent is @samp{info sources}.
30343 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
30345 @subsubheading Example
30348 -file-list-exec-source-files
30350 @{file=foo.c,fullname=/home/foo.c@},
30351 @{file=/home/bar.c,fullname=/home/bar.c@},
30352 @{file=gdb_could_not_find_fullpath.c@}]
30357 @subheading The @code{-file-list-shared-libraries} Command
30358 @findex -file-list-shared-libraries
30360 @subsubheading Synopsis
30363 -file-list-shared-libraries
30366 List the shared libraries in the program.
30368 @subsubheading @value{GDBN} Command
30370 The corresponding @value{GDBN} command is @samp{info shared}.
30372 @subsubheading Example
30376 @subheading The @code{-file-list-symbol-files} Command
30377 @findex -file-list-symbol-files
30379 @subsubheading Synopsis
30382 -file-list-symbol-files
30387 @subsubheading @value{GDBN} Command
30389 The corresponding @value{GDBN} command is @samp{info file} (part of it).
30391 @subsubheading Example
30396 @subheading The @code{-file-symbol-file} Command
30397 @findex -file-symbol-file
30399 @subsubheading Synopsis
30402 -file-symbol-file @var{file}
30405 Read symbol table info from the specified @var{file} argument. When
30406 used without arguments, clears @value{GDBN}'s symbol table info. No output is
30407 produced, except for a completion notification.
30409 @subsubheading @value{GDBN} Command
30411 The corresponding @value{GDBN} command is @samp{symbol-file}.
30413 @subsubheading Example
30417 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30423 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30424 @node GDB/MI Memory Overlay Commands
30425 @section @sc{gdb/mi} Memory Overlay Commands
30427 The memory overlay commands are not implemented.
30429 @c @subheading -overlay-auto
30431 @c @subheading -overlay-list-mapping-state
30433 @c @subheading -overlay-list-overlays
30435 @c @subheading -overlay-map
30437 @c @subheading -overlay-off
30439 @c @subheading -overlay-on
30441 @c @subheading -overlay-unmap
30443 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30444 @node GDB/MI Signal Handling Commands
30445 @section @sc{gdb/mi} Signal Handling Commands
30447 Signal handling commands are not implemented.
30449 @c @subheading -signal-handle
30451 @c @subheading -signal-list-handle-actions
30453 @c @subheading -signal-list-signal-types
30457 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30458 @node GDB/MI Target Manipulation
30459 @section @sc{gdb/mi} Target Manipulation Commands
30462 @subheading The @code{-target-attach} Command
30463 @findex -target-attach
30465 @subsubheading Synopsis
30468 -target-attach @var{pid} | @var{gid} | @var{file}
30471 Attach to a process @var{pid} or a file @var{file} outside of
30472 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
30473 group, the id previously returned by
30474 @samp{-list-thread-groups --available} must be used.
30476 @subsubheading @value{GDBN} Command
30478 The corresponding @value{GDBN} command is @samp{attach}.
30480 @subsubheading Example
30484 =thread-created,id="1"
30485 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
30491 @subheading The @code{-target-compare-sections} Command
30492 @findex -target-compare-sections
30494 @subsubheading Synopsis
30497 -target-compare-sections [ @var{section} ]
30500 Compare data of section @var{section} on target to the exec file.
30501 Without the argument, all sections are compared.
30503 @subsubheading @value{GDBN} Command
30505 The @value{GDBN} equivalent is @samp{compare-sections}.
30507 @subsubheading Example
30512 @subheading The @code{-target-detach} Command
30513 @findex -target-detach
30515 @subsubheading Synopsis
30518 -target-detach [ @var{pid} | @var{gid} ]
30521 Detach from the remote target which normally resumes its execution.
30522 If either @var{pid} or @var{gid} is specified, detaches from either
30523 the specified process, or specified thread group. There's no output.
30525 @subsubheading @value{GDBN} Command
30527 The corresponding @value{GDBN} command is @samp{detach}.
30529 @subsubheading Example
30539 @subheading The @code{-target-disconnect} Command
30540 @findex -target-disconnect
30542 @subsubheading Synopsis
30548 Disconnect from the remote target. There's no output and the target is
30549 generally not resumed.
30551 @subsubheading @value{GDBN} Command
30553 The corresponding @value{GDBN} command is @samp{disconnect}.
30555 @subsubheading Example
30565 @subheading The @code{-target-download} Command
30566 @findex -target-download
30568 @subsubheading Synopsis
30574 Loads the executable onto the remote target.
30575 It prints out an update message every half second, which includes the fields:
30579 The name of the section.
30581 The size of what has been sent so far for that section.
30583 The size of the section.
30585 The total size of what was sent so far (the current and the previous sections).
30587 The size of the overall executable to download.
30591 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
30592 @sc{gdb/mi} Output Syntax}).
30594 In addition, it prints the name and size of the sections, as they are
30595 downloaded. These messages include the following fields:
30599 The name of the section.
30601 The size of the section.
30603 The size of the overall executable to download.
30607 At the end, a summary is printed.
30609 @subsubheading @value{GDBN} Command
30611 The corresponding @value{GDBN} command is @samp{load}.
30613 @subsubheading Example
30615 Note: each status message appears on a single line. Here the messages
30616 have been broken down so that they can fit onto a page.
30621 +download,@{section=".text",section-size="6668",total-size="9880"@}
30622 +download,@{section=".text",section-sent="512",section-size="6668",
30623 total-sent="512",total-size="9880"@}
30624 +download,@{section=".text",section-sent="1024",section-size="6668",
30625 total-sent="1024",total-size="9880"@}
30626 +download,@{section=".text",section-sent="1536",section-size="6668",
30627 total-sent="1536",total-size="9880"@}
30628 +download,@{section=".text",section-sent="2048",section-size="6668",
30629 total-sent="2048",total-size="9880"@}
30630 +download,@{section=".text",section-sent="2560",section-size="6668",
30631 total-sent="2560",total-size="9880"@}
30632 +download,@{section=".text",section-sent="3072",section-size="6668",
30633 total-sent="3072",total-size="9880"@}
30634 +download,@{section=".text",section-sent="3584",section-size="6668",
30635 total-sent="3584",total-size="9880"@}
30636 +download,@{section=".text",section-sent="4096",section-size="6668",
30637 total-sent="4096",total-size="9880"@}
30638 +download,@{section=".text",section-sent="4608",section-size="6668",
30639 total-sent="4608",total-size="9880"@}
30640 +download,@{section=".text",section-sent="5120",section-size="6668",
30641 total-sent="5120",total-size="9880"@}
30642 +download,@{section=".text",section-sent="5632",section-size="6668",
30643 total-sent="5632",total-size="9880"@}
30644 +download,@{section=".text",section-sent="6144",section-size="6668",
30645 total-sent="6144",total-size="9880"@}
30646 +download,@{section=".text",section-sent="6656",section-size="6668",
30647 total-sent="6656",total-size="9880"@}
30648 +download,@{section=".init",section-size="28",total-size="9880"@}
30649 +download,@{section=".fini",section-size="28",total-size="9880"@}
30650 +download,@{section=".data",section-size="3156",total-size="9880"@}
30651 +download,@{section=".data",section-sent="512",section-size="3156",
30652 total-sent="7236",total-size="9880"@}
30653 +download,@{section=".data",section-sent="1024",section-size="3156",
30654 total-sent="7748",total-size="9880"@}
30655 +download,@{section=".data",section-sent="1536",section-size="3156",
30656 total-sent="8260",total-size="9880"@}
30657 +download,@{section=".data",section-sent="2048",section-size="3156",
30658 total-sent="8772",total-size="9880"@}
30659 +download,@{section=".data",section-sent="2560",section-size="3156",
30660 total-sent="9284",total-size="9880"@}
30661 +download,@{section=".data",section-sent="3072",section-size="3156",
30662 total-sent="9796",total-size="9880"@}
30663 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
30670 @subheading The @code{-target-exec-status} Command
30671 @findex -target-exec-status
30673 @subsubheading Synopsis
30676 -target-exec-status
30679 Provide information on the state of the target (whether it is running or
30680 not, for instance).
30682 @subsubheading @value{GDBN} Command
30684 There's no equivalent @value{GDBN} command.
30686 @subsubheading Example
30690 @subheading The @code{-target-list-available-targets} Command
30691 @findex -target-list-available-targets
30693 @subsubheading Synopsis
30696 -target-list-available-targets
30699 List the possible targets to connect to.
30701 @subsubheading @value{GDBN} Command
30703 The corresponding @value{GDBN} command is @samp{help target}.
30705 @subsubheading Example
30709 @subheading The @code{-target-list-current-targets} Command
30710 @findex -target-list-current-targets
30712 @subsubheading Synopsis
30715 -target-list-current-targets
30718 Describe the current target.
30720 @subsubheading @value{GDBN} Command
30722 The corresponding information is printed by @samp{info file} (among
30725 @subsubheading Example
30729 @subheading The @code{-target-list-parameters} Command
30730 @findex -target-list-parameters
30732 @subsubheading Synopsis
30735 -target-list-parameters
30741 @subsubheading @value{GDBN} Command
30745 @subsubheading Example
30749 @subheading The @code{-target-select} Command
30750 @findex -target-select
30752 @subsubheading Synopsis
30755 -target-select @var{type} @var{parameters @dots{}}
30758 Connect @value{GDBN} to the remote target. This command takes two args:
30762 The type of target, for instance @samp{remote}, etc.
30763 @item @var{parameters}
30764 Device names, host names and the like. @xref{Target Commands, ,
30765 Commands for Managing Targets}, for more details.
30768 The output is a connection notification, followed by the address at
30769 which the target program is, in the following form:
30772 ^connected,addr="@var{address}",func="@var{function name}",
30773 args=[@var{arg list}]
30776 @subsubheading @value{GDBN} Command
30778 The corresponding @value{GDBN} command is @samp{target}.
30780 @subsubheading Example
30784 -target-select remote /dev/ttya
30785 ^connected,addr="0xfe00a300",func="??",args=[]
30789 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30790 @node GDB/MI File Transfer Commands
30791 @section @sc{gdb/mi} File Transfer Commands
30794 @subheading The @code{-target-file-put} Command
30795 @findex -target-file-put
30797 @subsubheading Synopsis
30800 -target-file-put @var{hostfile} @var{targetfile}
30803 Copy file @var{hostfile} from the host system (the machine running
30804 @value{GDBN}) to @var{targetfile} on the target system.
30806 @subsubheading @value{GDBN} Command
30808 The corresponding @value{GDBN} command is @samp{remote put}.
30810 @subsubheading Example
30814 -target-file-put localfile remotefile
30820 @subheading The @code{-target-file-get} Command
30821 @findex -target-file-get
30823 @subsubheading Synopsis
30826 -target-file-get @var{targetfile} @var{hostfile}
30829 Copy file @var{targetfile} from the target system to @var{hostfile}
30830 on the host system.
30832 @subsubheading @value{GDBN} Command
30834 The corresponding @value{GDBN} command is @samp{remote get}.
30836 @subsubheading Example
30840 -target-file-get remotefile localfile
30846 @subheading The @code{-target-file-delete} Command
30847 @findex -target-file-delete
30849 @subsubheading Synopsis
30852 -target-file-delete @var{targetfile}
30855 Delete @var{targetfile} from the target system.
30857 @subsubheading @value{GDBN} Command
30859 The corresponding @value{GDBN} command is @samp{remote delete}.
30861 @subsubheading Example
30865 -target-file-delete remotefile
30871 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30872 @node GDB/MI Miscellaneous Commands
30873 @section Miscellaneous @sc{gdb/mi} Commands
30875 @c @subheading -gdb-complete
30877 @subheading The @code{-gdb-exit} Command
30880 @subsubheading Synopsis
30886 Exit @value{GDBN} immediately.
30888 @subsubheading @value{GDBN} Command
30890 Approximately corresponds to @samp{quit}.
30892 @subsubheading Example
30902 @subheading The @code{-exec-abort} Command
30903 @findex -exec-abort
30905 @subsubheading Synopsis
30911 Kill the inferior running program.
30913 @subsubheading @value{GDBN} Command
30915 The corresponding @value{GDBN} command is @samp{kill}.
30917 @subsubheading Example
30922 @subheading The @code{-gdb-set} Command
30925 @subsubheading Synopsis
30931 Set an internal @value{GDBN} variable.
30932 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
30934 @subsubheading @value{GDBN} Command
30936 The corresponding @value{GDBN} command is @samp{set}.
30938 @subsubheading Example
30948 @subheading The @code{-gdb-show} Command
30951 @subsubheading Synopsis
30957 Show the current value of a @value{GDBN} variable.
30959 @subsubheading @value{GDBN} Command
30961 The corresponding @value{GDBN} command is @samp{show}.
30963 @subsubheading Example
30972 @c @subheading -gdb-source
30975 @subheading The @code{-gdb-version} Command
30976 @findex -gdb-version
30978 @subsubheading Synopsis
30984 Show version information for @value{GDBN}. Used mostly in testing.
30986 @subsubheading @value{GDBN} Command
30988 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
30989 default shows this information when you start an interactive session.
30991 @subsubheading Example
30993 @c This example modifies the actual output from GDB to avoid overfull
30999 ~Copyright 2000 Free Software Foundation, Inc.
31000 ~GDB is free software, covered by the GNU General Public License, and
31001 ~you are welcome to change it and/or distribute copies of it under
31002 ~ certain conditions.
31003 ~Type "show copying" to see the conditions.
31004 ~There is absolutely no warranty for GDB. Type "show warranty" for
31006 ~This GDB was configured as
31007 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
31012 @subheading The @code{-list-features} Command
31013 @findex -list-features
31015 Returns a list of particular features of the MI protocol that
31016 this version of gdb implements. A feature can be a command,
31017 or a new field in an output of some command, or even an
31018 important bugfix. While a frontend can sometimes detect presence
31019 of a feature at runtime, it is easier to perform detection at debugger
31022 The command returns a list of strings, with each string naming an
31023 available feature. Each returned string is just a name, it does not
31024 have any internal structure. The list of possible feature names
31030 (gdb) -list-features
31031 ^done,result=["feature1","feature2"]
31034 The current list of features is:
31037 @item frozen-varobjs
31038 Indicates support for the @code{-var-set-frozen} command, as well
31039 as possible presense of the @code{frozen} field in the output
31040 of @code{-varobj-create}.
31041 @item pending-breakpoints
31042 Indicates support for the @option{-f} option to the @code{-break-insert}
31045 Indicates Python scripting support, Python-based
31046 pretty-printing commands, and possible presence of the
31047 @samp{display_hint} field in the output of @code{-var-list-children}
31049 Indicates support for the @code{-thread-info} command.
31050 @item data-read-memory-bytes
31051 Indicates support for the @code{-data-read-memory-bytes} and the
31052 @code{-data-write-memory-bytes} commands.
31053 @item breakpoint-notifications
31054 Indicates that changes to breakpoints and breakpoints created via the
31055 CLI will be announced via async records.
31056 @item ada-task-info
31057 Indicates support for the @code{-ada-task-info} command.
31060 @subheading The @code{-list-target-features} Command
31061 @findex -list-target-features
31063 Returns a list of particular features that are supported by the
31064 target. Those features affect the permitted MI commands, but
31065 unlike the features reported by the @code{-list-features} command, the
31066 features depend on which target GDB is using at the moment. Whenever
31067 a target can change, due to commands such as @code{-target-select},
31068 @code{-target-attach} or @code{-exec-run}, the list of target features
31069 may change, and the frontend should obtain it again.
31073 (gdb) -list-features
31074 ^done,result=["async"]
31077 The current list of features is:
31081 Indicates that the target is capable of asynchronous command
31082 execution, which means that @value{GDBN} will accept further commands
31083 while the target is running.
31086 Indicates that the target is capable of reverse execution.
31087 @xref{Reverse Execution}, for more information.
31091 @subheading The @code{-list-thread-groups} Command
31092 @findex -list-thread-groups
31094 @subheading Synopsis
31097 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
31100 Lists thread groups (@pxref{Thread groups}). When a single thread
31101 group is passed as the argument, lists the children of that group.
31102 When several thread group are passed, lists information about those
31103 thread groups. Without any parameters, lists information about all
31104 top-level thread groups.
31106 Normally, thread groups that are being debugged are reported.
31107 With the @samp{--available} option, @value{GDBN} reports thread groups
31108 available on the target.
31110 The output of this command may have either a @samp{threads} result or
31111 a @samp{groups} result. The @samp{thread} result has a list of tuples
31112 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
31113 Information}). The @samp{groups} result has a list of tuples as value,
31114 each tuple describing a thread group. If top-level groups are
31115 requested (that is, no parameter is passed), or when several groups
31116 are passed, the output always has a @samp{groups} result. The format
31117 of the @samp{group} result is described below.
31119 To reduce the number of roundtrips it's possible to list thread groups
31120 together with their children, by passing the @samp{--recurse} option
31121 and the recursion depth. Presently, only recursion depth of 1 is
31122 permitted. If this option is present, then every reported thread group
31123 will also include its children, either as @samp{group} or
31124 @samp{threads} field.
31126 In general, any combination of option and parameters is permitted, with
31127 the following caveats:
31131 When a single thread group is passed, the output will typically
31132 be the @samp{threads} result. Because threads may not contain
31133 anything, the @samp{recurse} option will be ignored.
31136 When the @samp{--available} option is passed, limited information may
31137 be available. In particular, the list of threads of a process might
31138 be inaccessible. Further, specifying specific thread groups might
31139 not give any performance advantage over listing all thread groups.
31140 The frontend should assume that @samp{-list-thread-groups --available}
31141 is always an expensive operation and cache the results.
31145 The @samp{groups} result is a list of tuples, where each tuple may
31146 have the following fields:
31150 Identifier of the thread group. This field is always present.
31151 The identifier is an opaque string; frontends should not try to
31152 convert it to an integer, even though it might look like one.
31155 The type of the thread group. At present, only @samp{process} is a
31159 The target-specific process identifier. This field is only present
31160 for thread groups of type @samp{process} and only if the process exists.
31163 The number of children this thread group has. This field may be
31164 absent for an available thread group.
31167 This field has a list of tuples as value, each tuple describing a
31168 thread. It may be present if the @samp{--recurse} option is
31169 specified, and it's actually possible to obtain the threads.
31172 This field is a list of integers, each identifying a core that one
31173 thread of the group is running on. This field may be absent if
31174 such information is not available.
31177 The name of the executable file that corresponds to this thread group.
31178 The field is only present for thread groups of type @samp{process},
31179 and only if there is a corresponding executable file.
31183 @subheading Example
31187 -list-thread-groups
31188 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
31189 -list-thread-groups 17
31190 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31191 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
31192 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31193 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
31194 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
31195 -list-thread-groups --available
31196 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
31197 -list-thread-groups --available --recurse 1
31198 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31199 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31200 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
31201 -list-thread-groups --available --recurse 1 17 18
31202 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31203 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31204 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
31208 @subheading The @code{-add-inferior} Command
31209 @findex -add-inferior
31211 @subheading Synopsis
31217 Creates a new inferior (@pxref{Inferiors and Programs}). The created
31218 inferior is not associated with any executable. Such association may
31219 be established with the @samp{-file-exec-and-symbols} command
31220 (@pxref{GDB/MI File Commands}). The command response has a single
31221 field, @samp{thread-group}, whose value is the identifier of the
31222 thread group corresponding to the new inferior.
31224 @subheading Example
31229 ^done,thread-group="i3"
31232 @subheading The @code{-interpreter-exec} Command
31233 @findex -interpreter-exec
31235 @subheading Synopsis
31238 -interpreter-exec @var{interpreter} @var{command}
31240 @anchor{-interpreter-exec}
31242 Execute the specified @var{command} in the given @var{interpreter}.
31244 @subheading @value{GDBN} Command
31246 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
31248 @subheading Example
31252 -interpreter-exec console "break main"
31253 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
31254 &"During symbol reading, bad structure-type format.\n"
31255 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
31260 @subheading The @code{-inferior-tty-set} Command
31261 @findex -inferior-tty-set
31263 @subheading Synopsis
31266 -inferior-tty-set /dev/pts/1
31269 Set terminal for future runs of the program being debugged.
31271 @subheading @value{GDBN} Command
31273 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
31275 @subheading Example
31279 -inferior-tty-set /dev/pts/1
31284 @subheading The @code{-inferior-tty-show} Command
31285 @findex -inferior-tty-show
31287 @subheading Synopsis
31293 Show terminal for future runs of program being debugged.
31295 @subheading @value{GDBN} Command
31297 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
31299 @subheading Example
31303 -inferior-tty-set /dev/pts/1
31307 ^done,inferior_tty_terminal="/dev/pts/1"
31311 @subheading The @code{-enable-timings} Command
31312 @findex -enable-timings
31314 @subheading Synopsis
31317 -enable-timings [yes | no]
31320 Toggle the printing of the wallclock, user and system times for an MI
31321 command as a field in its output. This command is to help frontend
31322 developers optimize the performance of their code. No argument is
31323 equivalent to @samp{yes}.
31325 @subheading @value{GDBN} Command
31329 @subheading Example
31337 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31338 addr="0x080484ed",func="main",file="myprog.c",
31339 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
31340 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
31348 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
31349 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
31350 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
31351 fullname="/home/nickrob/myprog.c",line="73"@}
31356 @chapter @value{GDBN} Annotations
31358 This chapter describes annotations in @value{GDBN}. Annotations were
31359 designed to interface @value{GDBN} to graphical user interfaces or other
31360 similar programs which want to interact with @value{GDBN} at a
31361 relatively high level.
31363 The annotation mechanism has largely been superseded by @sc{gdb/mi}
31367 This is Edition @value{EDITION}, @value{DATE}.
31371 * Annotations Overview:: What annotations are; the general syntax.
31372 * Server Prefix:: Issuing a command without affecting user state.
31373 * Prompting:: Annotations marking @value{GDBN}'s need for input.
31374 * Errors:: Annotations for error messages.
31375 * Invalidation:: Some annotations describe things now invalid.
31376 * Annotations for Running::
31377 Whether the program is running, how it stopped, etc.
31378 * Source Annotations:: Annotations describing source code.
31381 @node Annotations Overview
31382 @section What is an Annotation?
31383 @cindex annotations
31385 Annotations start with a newline character, two @samp{control-z}
31386 characters, and the name of the annotation. If there is no additional
31387 information associated with this annotation, the name of the annotation
31388 is followed immediately by a newline. If there is additional
31389 information, the name of the annotation is followed by a space, the
31390 additional information, and a newline. The additional information
31391 cannot contain newline characters.
31393 Any output not beginning with a newline and two @samp{control-z}
31394 characters denotes literal output from @value{GDBN}. Currently there is
31395 no need for @value{GDBN} to output a newline followed by two
31396 @samp{control-z} characters, but if there was such a need, the
31397 annotations could be extended with an @samp{escape} annotation which
31398 means those three characters as output.
31400 The annotation @var{level}, which is specified using the
31401 @option{--annotate} command line option (@pxref{Mode Options}), controls
31402 how much information @value{GDBN} prints together with its prompt,
31403 values of expressions, source lines, and other types of output. Level 0
31404 is for no annotations, level 1 is for use when @value{GDBN} is run as a
31405 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
31406 for programs that control @value{GDBN}, and level 2 annotations have
31407 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
31408 Interface, annotate, GDB's Obsolete Annotations}).
31411 @kindex set annotate
31412 @item set annotate @var{level}
31413 The @value{GDBN} command @code{set annotate} sets the level of
31414 annotations to the specified @var{level}.
31416 @item show annotate
31417 @kindex show annotate
31418 Show the current annotation level.
31421 This chapter describes level 3 annotations.
31423 A simple example of starting up @value{GDBN} with annotations is:
31426 $ @kbd{gdb --annotate=3}
31428 Copyright 2003 Free Software Foundation, Inc.
31429 GDB is free software, covered by the GNU General Public License,
31430 and you are welcome to change it and/or distribute copies of it
31431 under certain conditions.
31432 Type "show copying" to see the conditions.
31433 There is absolutely no warranty for GDB. Type "show warranty"
31435 This GDB was configured as "i386-pc-linux-gnu"
31446 Here @samp{quit} is input to @value{GDBN}; the rest is output from
31447 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
31448 denotes a @samp{control-z} character) are annotations; the rest is
31449 output from @value{GDBN}.
31451 @node Server Prefix
31452 @section The Server Prefix
31453 @cindex server prefix
31455 If you prefix a command with @samp{server } then it will not affect
31456 the command history, nor will it affect @value{GDBN}'s notion of which
31457 command to repeat if @key{RET} is pressed on a line by itself. This
31458 means that commands can be run behind a user's back by a front-end in
31459 a transparent manner.
31461 The @code{server } prefix does not affect the recording of values into
31462 the value history; to print a value without recording it into the
31463 value history, use the @code{output} command instead of the
31464 @code{print} command.
31466 Using this prefix also disables confirmation requests
31467 (@pxref{confirmation requests}).
31470 @section Annotation for @value{GDBN} Input
31472 @cindex annotations for prompts
31473 When @value{GDBN} prompts for input, it annotates this fact so it is possible
31474 to know when to send output, when the output from a given command is
31477 Different kinds of input each have a different @dfn{input type}. Each
31478 input type has three annotations: a @code{pre-} annotation, which
31479 denotes the beginning of any prompt which is being output, a plain
31480 annotation, which denotes the end of the prompt, and then a @code{post-}
31481 annotation which denotes the end of any echo which may (or may not) be
31482 associated with the input. For example, the @code{prompt} input type
31483 features the following annotations:
31491 The input types are
31494 @findex pre-prompt annotation
31495 @findex prompt annotation
31496 @findex post-prompt annotation
31498 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
31500 @findex pre-commands annotation
31501 @findex commands annotation
31502 @findex post-commands annotation
31504 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
31505 command. The annotations are repeated for each command which is input.
31507 @findex pre-overload-choice annotation
31508 @findex overload-choice annotation
31509 @findex post-overload-choice annotation
31510 @item overload-choice
31511 When @value{GDBN} wants the user to select between various overloaded functions.
31513 @findex pre-query annotation
31514 @findex query annotation
31515 @findex post-query annotation
31517 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
31519 @findex pre-prompt-for-continue annotation
31520 @findex prompt-for-continue annotation
31521 @findex post-prompt-for-continue annotation
31522 @item prompt-for-continue
31523 When @value{GDBN} is asking the user to press return to continue. Note: Don't
31524 expect this to work well; instead use @code{set height 0} to disable
31525 prompting. This is because the counting of lines is buggy in the
31526 presence of annotations.
31531 @cindex annotations for errors, warnings and interrupts
31533 @findex quit annotation
31538 This annotation occurs right before @value{GDBN} responds to an interrupt.
31540 @findex error annotation
31545 This annotation occurs right before @value{GDBN} responds to an error.
31547 Quit and error annotations indicate that any annotations which @value{GDBN} was
31548 in the middle of may end abruptly. For example, if a
31549 @code{value-history-begin} annotation is followed by a @code{error}, one
31550 cannot expect to receive the matching @code{value-history-end}. One
31551 cannot expect not to receive it either, however; an error annotation
31552 does not necessarily mean that @value{GDBN} is immediately returning all the way
31555 @findex error-begin annotation
31556 A quit or error annotation may be preceded by
31562 Any output between that and the quit or error annotation is the error
31565 Warning messages are not yet annotated.
31566 @c If we want to change that, need to fix warning(), type_error(),
31567 @c range_error(), and possibly other places.
31570 @section Invalidation Notices
31572 @cindex annotations for invalidation messages
31573 The following annotations say that certain pieces of state may have
31577 @findex frames-invalid annotation
31578 @item ^Z^Zframes-invalid
31580 The frames (for example, output from the @code{backtrace} command) may
31583 @findex breakpoints-invalid annotation
31584 @item ^Z^Zbreakpoints-invalid
31586 The breakpoints may have changed. For example, the user just added or
31587 deleted a breakpoint.
31590 @node Annotations for Running
31591 @section Running the Program
31592 @cindex annotations for running programs
31594 @findex starting annotation
31595 @findex stopping annotation
31596 When the program starts executing due to a @value{GDBN} command such as
31597 @code{step} or @code{continue},
31603 is output. When the program stops,
31609 is output. Before the @code{stopped} annotation, a variety of
31610 annotations describe how the program stopped.
31613 @findex exited annotation
31614 @item ^Z^Zexited @var{exit-status}
31615 The program exited, and @var{exit-status} is the exit status (zero for
31616 successful exit, otherwise nonzero).
31618 @findex signalled annotation
31619 @findex signal-name annotation
31620 @findex signal-name-end annotation
31621 @findex signal-string annotation
31622 @findex signal-string-end annotation
31623 @item ^Z^Zsignalled
31624 The program exited with a signal. After the @code{^Z^Zsignalled}, the
31625 annotation continues:
31631 ^Z^Zsignal-name-end
31635 ^Z^Zsignal-string-end
31640 where @var{name} is the name of the signal, such as @code{SIGILL} or
31641 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
31642 as @code{Illegal Instruction} or @code{Segmentation fault}.
31643 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
31644 user's benefit and have no particular format.
31646 @findex signal annotation
31648 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
31649 just saying that the program received the signal, not that it was
31650 terminated with it.
31652 @findex breakpoint annotation
31653 @item ^Z^Zbreakpoint @var{number}
31654 The program hit breakpoint number @var{number}.
31656 @findex watchpoint annotation
31657 @item ^Z^Zwatchpoint @var{number}
31658 The program hit watchpoint number @var{number}.
31661 @node Source Annotations
31662 @section Displaying Source
31663 @cindex annotations for source display
31665 @findex source annotation
31666 The following annotation is used instead of displaying source code:
31669 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
31672 where @var{filename} is an absolute file name indicating which source
31673 file, @var{line} is the line number within that file (where 1 is the
31674 first line in the file), @var{character} is the character position
31675 within the file (where 0 is the first character in the file) (for most
31676 debug formats this will necessarily point to the beginning of a line),
31677 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
31678 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
31679 @var{addr} is the address in the target program associated with the
31680 source which is being displayed. @var{addr} is in the form @samp{0x}
31681 followed by one or more lowercase hex digits (note that this does not
31682 depend on the language).
31684 @node JIT Interface
31685 @chapter JIT Compilation Interface
31686 @cindex just-in-time compilation
31687 @cindex JIT compilation interface
31689 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
31690 interface. A JIT compiler is a program or library that generates native
31691 executable code at runtime and executes it, usually in order to achieve good
31692 performance while maintaining platform independence.
31694 Programs that use JIT compilation are normally difficult to debug because
31695 portions of their code are generated at runtime, instead of being loaded from
31696 object files, which is where @value{GDBN} normally finds the program's symbols
31697 and debug information. In order to debug programs that use JIT compilation,
31698 @value{GDBN} has an interface that allows the program to register in-memory
31699 symbol files with @value{GDBN} at runtime.
31701 If you are using @value{GDBN} to debug a program that uses this interface, then
31702 it should work transparently so long as you have not stripped the binary. If
31703 you are developing a JIT compiler, then the interface is documented in the rest
31704 of this chapter. At this time, the only known client of this interface is the
31707 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
31708 JIT compiler communicates with @value{GDBN} by writing data into a global
31709 variable and calling a fuction at a well-known symbol. When @value{GDBN}
31710 attaches, it reads a linked list of symbol files from the global variable to
31711 find existing code, and puts a breakpoint in the function so that it can find
31712 out about additional code.
31715 * Declarations:: Relevant C struct declarations
31716 * Registering Code:: Steps to register code
31717 * Unregistering Code:: Steps to unregister code
31721 @section JIT Declarations
31723 These are the relevant struct declarations that a C program should include to
31724 implement the interface:
31734 struct jit_code_entry
31736 struct jit_code_entry *next_entry;
31737 struct jit_code_entry *prev_entry;
31738 const char *symfile_addr;
31739 uint64_t symfile_size;
31742 struct jit_descriptor
31745 /* This type should be jit_actions_t, but we use uint32_t
31746 to be explicit about the bitwidth. */
31747 uint32_t action_flag;
31748 struct jit_code_entry *relevant_entry;
31749 struct jit_code_entry *first_entry;
31752 /* GDB puts a breakpoint in this function. */
31753 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
31755 /* Make sure to specify the version statically, because the
31756 debugger may check the version before we can set it. */
31757 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
31760 If the JIT is multi-threaded, then it is important that the JIT synchronize any
31761 modifications to this global data properly, which can easily be done by putting
31762 a global mutex around modifications to these structures.
31764 @node Registering Code
31765 @section Registering Code
31767 To register code with @value{GDBN}, the JIT should follow this protocol:
31771 Generate an object file in memory with symbols and other desired debug
31772 information. The file must include the virtual addresses of the sections.
31775 Create a code entry for the file, which gives the start and size of the symbol
31779 Add it to the linked list in the JIT descriptor.
31782 Point the relevant_entry field of the descriptor at the entry.
31785 Set @code{action_flag} to @code{JIT_REGISTER} and call
31786 @code{__jit_debug_register_code}.
31789 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
31790 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
31791 new code. However, the linked list must still be maintained in order to allow
31792 @value{GDBN} to attach to a running process and still find the symbol files.
31794 @node Unregistering Code
31795 @section Unregistering Code
31797 If code is freed, then the JIT should use the following protocol:
31801 Remove the code entry corresponding to the code from the linked list.
31804 Point the @code{relevant_entry} field of the descriptor at the code entry.
31807 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
31808 @code{__jit_debug_register_code}.
31811 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
31812 and the JIT will leak the memory used for the associated symbol files.
31815 @chapter Reporting Bugs in @value{GDBN}
31816 @cindex bugs in @value{GDBN}
31817 @cindex reporting bugs in @value{GDBN}
31819 Your bug reports play an essential role in making @value{GDBN} reliable.
31821 Reporting a bug may help you by bringing a solution to your problem, or it
31822 may not. But in any case the principal function of a bug report is to help
31823 the entire community by making the next version of @value{GDBN} work better. Bug
31824 reports are your contribution to the maintenance of @value{GDBN}.
31826 In order for a bug report to serve its purpose, you must include the
31827 information that enables us to fix the bug.
31830 * Bug Criteria:: Have you found a bug?
31831 * Bug Reporting:: How to report bugs
31835 @section Have You Found a Bug?
31836 @cindex bug criteria
31838 If you are not sure whether you have found a bug, here are some guidelines:
31841 @cindex fatal signal
31842 @cindex debugger crash
31843 @cindex crash of debugger
31845 If the debugger gets a fatal signal, for any input whatever, that is a
31846 @value{GDBN} bug. Reliable debuggers never crash.
31848 @cindex error on valid input
31850 If @value{GDBN} produces an error message for valid input, that is a
31851 bug. (Note that if you're cross debugging, the problem may also be
31852 somewhere in the connection to the target.)
31854 @cindex invalid input
31856 If @value{GDBN} does not produce an error message for invalid input,
31857 that is a bug. However, you should note that your idea of
31858 ``invalid input'' might be our idea of ``an extension'' or ``support
31859 for traditional practice''.
31862 If you are an experienced user of debugging tools, your suggestions
31863 for improvement of @value{GDBN} are welcome in any case.
31866 @node Bug Reporting
31867 @section How to Report Bugs
31868 @cindex bug reports
31869 @cindex @value{GDBN} bugs, reporting
31871 A number of companies and individuals offer support for @sc{gnu} products.
31872 If you obtained @value{GDBN} from a support organization, we recommend you
31873 contact that organization first.
31875 You can find contact information for many support companies and
31876 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
31878 @c should add a web page ref...
31881 @ifset BUGURL_DEFAULT
31882 In any event, we also recommend that you submit bug reports for
31883 @value{GDBN}. The preferred method is to submit them directly using
31884 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
31885 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
31888 @strong{Do not send bug reports to @samp{info-gdb}, or to
31889 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
31890 not want to receive bug reports. Those that do have arranged to receive
31893 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
31894 serves as a repeater. The mailing list and the newsgroup carry exactly
31895 the same messages. Often people think of posting bug reports to the
31896 newsgroup instead of mailing them. This appears to work, but it has one
31897 problem which can be crucial: a newsgroup posting often lacks a mail
31898 path back to the sender. Thus, if we need to ask for more information,
31899 we may be unable to reach you. For this reason, it is better to send
31900 bug reports to the mailing list.
31902 @ifclear BUGURL_DEFAULT
31903 In any event, we also recommend that you submit bug reports for
31904 @value{GDBN} to @value{BUGURL}.
31908 The fundamental principle of reporting bugs usefully is this:
31909 @strong{report all the facts}. If you are not sure whether to state a
31910 fact or leave it out, state it!
31912 Often people omit facts because they think they know what causes the
31913 problem and assume that some details do not matter. Thus, you might
31914 assume that the name of the variable you use in an example does not matter.
31915 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
31916 stray memory reference which happens to fetch from the location where that
31917 name is stored in memory; perhaps, if the name were different, the contents
31918 of that location would fool the debugger into doing the right thing despite
31919 the bug. Play it safe and give a specific, complete example. That is the
31920 easiest thing for you to do, and the most helpful.
31922 Keep in mind that the purpose of a bug report is to enable us to fix the
31923 bug. It may be that the bug has been reported previously, but neither
31924 you nor we can know that unless your bug report is complete and
31927 Sometimes people give a few sketchy facts and ask, ``Does this ring a
31928 bell?'' Those bug reports are useless, and we urge everyone to
31929 @emph{refuse to respond to them} except to chide the sender to report
31932 To enable us to fix the bug, you should include all these things:
31936 The version of @value{GDBN}. @value{GDBN} announces it if you start
31937 with no arguments; you can also print it at any time using @code{show
31940 Without this, we will not know whether there is any point in looking for
31941 the bug in the current version of @value{GDBN}.
31944 The type of machine you are using, and the operating system name and
31948 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
31949 ``@value{GCC}--2.8.1''.
31952 What compiler (and its version) was used to compile the program you are
31953 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
31954 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
31955 to get this information; for other compilers, see the documentation for
31959 The command arguments you gave the compiler to compile your example and
31960 observe the bug. For example, did you use @samp{-O}? To guarantee
31961 you will not omit something important, list them all. A copy of the
31962 Makefile (or the output from make) is sufficient.
31964 If we were to try to guess the arguments, we would probably guess wrong
31965 and then we might not encounter the bug.
31968 A complete input script, and all necessary source files, that will
31972 A description of what behavior you observe that you believe is
31973 incorrect. For example, ``It gets a fatal signal.''
31975 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
31976 will certainly notice it. But if the bug is incorrect output, we might
31977 not notice unless it is glaringly wrong. You might as well not give us
31978 a chance to make a mistake.
31980 Even if the problem you experience is a fatal signal, you should still
31981 say so explicitly. Suppose something strange is going on, such as, your
31982 copy of @value{GDBN} is out of synch, or you have encountered a bug in
31983 the C library on your system. (This has happened!) Your copy might
31984 crash and ours would not. If you told us to expect a crash, then when
31985 ours fails to crash, we would know that the bug was not happening for
31986 us. If you had not told us to expect a crash, then we would not be able
31987 to draw any conclusion from our observations.
31990 @cindex recording a session script
31991 To collect all this information, you can use a session recording program
31992 such as @command{script}, which is available on many Unix systems.
31993 Just run your @value{GDBN} session inside @command{script} and then
31994 include the @file{typescript} file with your bug report.
31996 Another way to record a @value{GDBN} session is to run @value{GDBN}
31997 inside Emacs and then save the entire buffer to a file.
32000 If you wish to suggest changes to the @value{GDBN} source, send us context
32001 diffs. If you even discuss something in the @value{GDBN} source, refer to
32002 it by context, not by line number.
32004 The line numbers in our development sources will not match those in your
32005 sources. Your line numbers would convey no useful information to us.
32009 Here are some things that are not necessary:
32013 A description of the envelope of the bug.
32015 Often people who encounter a bug spend a lot of time investigating
32016 which changes to the input file will make the bug go away and which
32017 changes will not affect it.
32019 This is often time consuming and not very useful, because the way we
32020 will find the bug is by running a single example under the debugger
32021 with breakpoints, not by pure deduction from a series of examples.
32022 We recommend that you save your time for something else.
32024 Of course, if you can find a simpler example to report @emph{instead}
32025 of the original one, that is a convenience for us. Errors in the
32026 output will be easier to spot, running under the debugger will take
32027 less time, and so on.
32029 However, simplification is not vital; if you do not want to do this,
32030 report the bug anyway and send us the entire test case you used.
32033 A patch for the bug.
32035 A patch for the bug does help us if it is a good one. But do not omit
32036 the necessary information, such as the test case, on the assumption that
32037 a patch is all we need. We might see problems with your patch and decide
32038 to fix the problem another way, or we might not understand it at all.
32040 Sometimes with a program as complicated as @value{GDBN} it is very hard to
32041 construct an example that will make the program follow a certain path
32042 through the code. If you do not send us the example, we will not be able
32043 to construct one, so we will not be able to verify that the bug is fixed.
32045 And if we cannot understand what bug you are trying to fix, or why your
32046 patch should be an improvement, we will not install it. A test case will
32047 help us to understand.
32050 A guess about what the bug is or what it depends on.
32052 Such guesses are usually wrong. Even we cannot guess right about such
32053 things without first using the debugger to find the facts.
32056 @c The readline documentation is distributed with the readline code
32057 @c and consists of the two following files:
32060 @c Use -I with makeinfo to point to the appropriate directory,
32061 @c environment var TEXINPUTS with TeX.
32062 @ifclear SYSTEM_READLINE
32063 @include rluser.texi
32064 @include hsuser.texi
32068 @appendix In Memoriam
32070 The @value{GDBN} project mourns the loss of the following long-time
32075 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
32076 to Free Software in general. Outside of @value{GDBN}, he was known in
32077 the Amiga world for his series of Fish Disks, and the GeekGadget project.
32079 @item Michael Snyder
32080 Michael was one of the Global Maintainers of the @value{GDBN} project,
32081 with contributions recorded as early as 1996, until 2011. In addition
32082 to his day to day participation, he was a large driving force behind
32083 adding Reverse Debugging to @value{GDBN}.
32086 Beyond their technical contributions to the project, they were also
32087 enjoyable members of the Free Software Community. We will miss them.
32089 @node Formatting Documentation
32090 @appendix Formatting Documentation
32092 @cindex @value{GDBN} reference card
32093 @cindex reference card
32094 The @value{GDBN} 4 release includes an already-formatted reference card, ready
32095 for printing with PostScript or Ghostscript, in the @file{gdb}
32096 subdirectory of the main source directory@footnote{In
32097 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
32098 release.}. If you can use PostScript or Ghostscript with your printer,
32099 you can print the reference card immediately with @file{refcard.ps}.
32101 The release also includes the source for the reference card. You
32102 can format it, using @TeX{}, by typing:
32108 The @value{GDBN} reference card is designed to print in @dfn{landscape}
32109 mode on US ``letter'' size paper;
32110 that is, on a sheet 11 inches wide by 8.5 inches
32111 high. You will need to specify this form of printing as an option to
32112 your @sc{dvi} output program.
32114 @cindex documentation
32116 All the documentation for @value{GDBN} comes as part of the machine-readable
32117 distribution. The documentation is written in Texinfo format, which is
32118 a documentation system that uses a single source file to produce both
32119 on-line information and a printed manual. You can use one of the Info
32120 formatting commands to create the on-line version of the documentation
32121 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
32123 @value{GDBN} includes an already formatted copy of the on-line Info
32124 version of this manual in the @file{gdb} subdirectory. The main Info
32125 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
32126 subordinate files matching @samp{gdb.info*} in the same directory. If
32127 necessary, you can print out these files, or read them with any editor;
32128 but they are easier to read using the @code{info} subsystem in @sc{gnu}
32129 Emacs or the standalone @code{info} program, available as part of the
32130 @sc{gnu} Texinfo distribution.
32132 If you want to format these Info files yourself, you need one of the
32133 Info formatting programs, such as @code{texinfo-format-buffer} or
32136 If you have @code{makeinfo} installed, and are in the top level
32137 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
32138 version @value{GDBVN}), you can make the Info file by typing:
32145 If you want to typeset and print copies of this manual, you need @TeX{},
32146 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
32147 Texinfo definitions file.
32149 @TeX{} is a typesetting program; it does not print files directly, but
32150 produces output files called @sc{dvi} files. To print a typeset
32151 document, you need a program to print @sc{dvi} files. If your system
32152 has @TeX{} installed, chances are it has such a program. The precise
32153 command to use depends on your system; @kbd{lpr -d} is common; another
32154 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
32155 require a file name without any extension or a @samp{.dvi} extension.
32157 @TeX{} also requires a macro definitions file called
32158 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
32159 written in Texinfo format. On its own, @TeX{} cannot either read or
32160 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
32161 and is located in the @file{gdb-@var{version-number}/texinfo}
32164 If you have @TeX{} and a @sc{dvi} printer program installed, you can
32165 typeset and print this manual. First switch to the @file{gdb}
32166 subdirectory of the main source directory (for example, to
32167 @file{gdb-@value{GDBVN}/gdb}) and type:
32173 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
32175 @node Installing GDB
32176 @appendix Installing @value{GDBN}
32177 @cindex installation
32180 * Requirements:: Requirements for building @value{GDBN}
32181 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
32182 * Separate Objdir:: Compiling @value{GDBN} in another directory
32183 * Config Names:: Specifying names for hosts and targets
32184 * Configure Options:: Summary of options for configure
32185 * System-wide configuration:: Having a system-wide init file
32189 @section Requirements for Building @value{GDBN}
32190 @cindex building @value{GDBN}, requirements for
32192 Building @value{GDBN} requires various tools and packages to be available.
32193 Other packages will be used only if they are found.
32195 @heading Tools/Packages Necessary for Building @value{GDBN}
32197 @item ISO C90 compiler
32198 @value{GDBN} is written in ISO C90. It should be buildable with any
32199 working C90 compiler, e.g.@: GCC.
32203 @heading Tools/Packages Optional for Building @value{GDBN}
32207 @value{GDBN} can use the Expat XML parsing library. This library may be
32208 included with your operating system distribution; if it is not, you
32209 can get the latest version from @url{http://expat.sourceforge.net}.
32210 The @file{configure} script will search for this library in several
32211 standard locations; if it is installed in an unusual path, you can
32212 use the @option{--with-libexpat-prefix} option to specify its location.
32218 Remote protocol memory maps (@pxref{Memory Map Format})
32220 Target descriptions (@pxref{Target Descriptions})
32222 Remote shared library lists (@pxref{Library List Format})
32224 MS-Windows shared libraries (@pxref{Shared Libraries})
32226 Traceframe info (@pxref{Traceframe Info Format})
32230 @cindex compressed debug sections
32231 @value{GDBN} will use the @samp{zlib} library, if available, to read
32232 compressed debug sections. Some linkers, such as GNU gold, are capable
32233 of producing binaries with compressed debug sections. If @value{GDBN}
32234 is compiled with @samp{zlib}, it will be able to read the debug
32235 information in such binaries.
32237 The @samp{zlib} library is likely included with your operating system
32238 distribution; if it is not, you can get the latest version from
32239 @url{http://zlib.net}.
32242 @value{GDBN}'s features related to character sets (@pxref{Character
32243 Sets}) require a functioning @code{iconv} implementation. If you are
32244 on a GNU system, then this is provided by the GNU C Library. Some
32245 other systems also provide a working @code{iconv}.
32247 If @value{GDBN} is using the @code{iconv} program which is installed
32248 in a non-standard place, you will need to tell @value{GDBN} where to find it.
32249 This is done with @option{--with-iconv-bin} which specifies the
32250 directory that contains the @code{iconv} program.
32252 On systems without @code{iconv}, you can install GNU Libiconv. If you
32253 have previously installed Libiconv, you can use the
32254 @option{--with-libiconv-prefix} option to configure.
32256 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
32257 arrange to build Libiconv if a directory named @file{libiconv} appears
32258 in the top-most source directory. If Libiconv is built this way, and
32259 if the operating system does not provide a suitable @code{iconv}
32260 implementation, then the just-built library will automatically be used
32261 by @value{GDBN}. One easy way to set this up is to download GNU
32262 Libiconv, unpack it, and then rename the directory holding the
32263 Libiconv source code to @samp{libiconv}.
32266 @node Running Configure
32267 @section Invoking the @value{GDBN} @file{configure} Script
32268 @cindex configuring @value{GDBN}
32269 @value{GDBN} comes with a @file{configure} script that automates the process
32270 of preparing @value{GDBN} for installation; you can then use @code{make} to
32271 build the @code{gdb} program.
32273 @c irrelevant in info file; it's as current as the code it lives with.
32274 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
32275 look at the @file{README} file in the sources; we may have improved the
32276 installation procedures since publishing this manual.}
32279 The @value{GDBN} distribution includes all the source code you need for
32280 @value{GDBN} in a single directory, whose name is usually composed by
32281 appending the version number to @samp{gdb}.
32283 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
32284 @file{gdb-@value{GDBVN}} directory. That directory contains:
32287 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
32288 script for configuring @value{GDBN} and all its supporting libraries
32290 @item gdb-@value{GDBVN}/gdb
32291 the source specific to @value{GDBN} itself
32293 @item gdb-@value{GDBVN}/bfd
32294 source for the Binary File Descriptor library
32296 @item gdb-@value{GDBVN}/include
32297 @sc{gnu} include files
32299 @item gdb-@value{GDBVN}/libiberty
32300 source for the @samp{-liberty} free software library
32302 @item gdb-@value{GDBVN}/opcodes
32303 source for the library of opcode tables and disassemblers
32305 @item gdb-@value{GDBVN}/readline
32306 source for the @sc{gnu} command-line interface
32308 @item gdb-@value{GDBVN}/glob
32309 source for the @sc{gnu} filename pattern-matching subroutine
32311 @item gdb-@value{GDBVN}/mmalloc
32312 source for the @sc{gnu} memory-mapped malloc package
32315 The simplest way to configure and build @value{GDBN} is to run @file{configure}
32316 from the @file{gdb-@var{version-number}} source directory, which in
32317 this example is the @file{gdb-@value{GDBVN}} directory.
32319 First switch to the @file{gdb-@var{version-number}} source directory
32320 if you are not already in it; then run @file{configure}. Pass the
32321 identifier for the platform on which @value{GDBN} will run as an
32327 cd gdb-@value{GDBVN}
32328 ./configure @var{host}
32333 where @var{host} is an identifier such as @samp{sun4} or
32334 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
32335 (You can often leave off @var{host}; @file{configure} tries to guess the
32336 correct value by examining your system.)
32338 Running @samp{configure @var{host}} and then running @code{make} builds the
32339 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
32340 libraries, then @code{gdb} itself. The configured source files, and the
32341 binaries, are left in the corresponding source directories.
32344 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
32345 system does not recognize this automatically when you run a different
32346 shell, you may need to run @code{sh} on it explicitly:
32349 sh configure @var{host}
32352 If you run @file{configure} from a directory that contains source
32353 directories for multiple libraries or programs, such as the
32354 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
32356 creates configuration files for every directory level underneath (unless
32357 you tell it not to, with the @samp{--norecursion} option).
32359 You should run the @file{configure} script from the top directory in the
32360 source tree, the @file{gdb-@var{version-number}} directory. If you run
32361 @file{configure} from one of the subdirectories, you will configure only
32362 that subdirectory. That is usually not what you want. In particular,
32363 if you run the first @file{configure} from the @file{gdb} subdirectory
32364 of the @file{gdb-@var{version-number}} directory, you will omit the
32365 configuration of @file{bfd}, @file{readline}, and other sibling
32366 directories of the @file{gdb} subdirectory. This leads to build errors
32367 about missing include files such as @file{bfd/bfd.h}.
32369 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
32370 However, you should make sure that the shell on your path (named by
32371 the @samp{SHELL} environment variable) is publicly readable. Remember
32372 that @value{GDBN} uses the shell to start your program---some systems refuse to
32373 let @value{GDBN} debug child processes whose programs are not readable.
32375 @node Separate Objdir
32376 @section Compiling @value{GDBN} in Another Directory
32378 If you want to run @value{GDBN} versions for several host or target machines,
32379 you need a different @code{gdb} compiled for each combination of
32380 host and target. @file{configure} is designed to make this easy by
32381 allowing you to generate each configuration in a separate subdirectory,
32382 rather than in the source directory. If your @code{make} program
32383 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
32384 @code{make} in each of these directories builds the @code{gdb}
32385 program specified there.
32387 To build @code{gdb} in a separate directory, run @file{configure}
32388 with the @samp{--srcdir} option to specify where to find the source.
32389 (You also need to specify a path to find @file{configure}
32390 itself from your working directory. If the path to @file{configure}
32391 would be the same as the argument to @samp{--srcdir}, you can leave out
32392 the @samp{--srcdir} option; it is assumed.)
32394 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
32395 separate directory for a Sun 4 like this:
32399 cd gdb-@value{GDBVN}
32402 ../gdb-@value{GDBVN}/configure sun4
32407 When @file{configure} builds a configuration using a remote source
32408 directory, it creates a tree for the binaries with the same structure
32409 (and using the same names) as the tree under the source directory. In
32410 the example, you'd find the Sun 4 library @file{libiberty.a} in the
32411 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
32412 @file{gdb-sun4/gdb}.
32414 Make sure that your path to the @file{configure} script has just one
32415 instance of @file{gdb} in it. If your path to @file{configure} looks
32416 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
32417 one subdirectory of @value{GDBN}, not the whole package. This leads to
32418 build errors about missing include files such as @file{bfd/bfd.h}.
32420 One popular reason to build several @value{GDBN} configurations in separate
32421 directories is to configure @value{GDBN} for cross-compiling (where
32422 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
32423 programs that run on another machine---the @dfn{target}).
32424 You specify a cross-debugging target by
32425 giving the @samp{--target=@var{target}} option to @file{configure}.
32427 When you run @code{make} to build a program or library, you must run
32428 it in a configured directory---whatever directory you were in when you
32429 called @file{configure} (or one of its subdirectories).
32431 The @code{Makefile} that @file{configure} generates in each source
32432 directory also runs recursively. If you type @code{make} in a source
32433 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
32434 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
32435 will build all the required libraries, and then build GDB.
32437 When you have multiple hosts or targets configured in separate
32438 directories, you can run @code{make} on them in parallel (for example,
32439 if they are NFS-mounted on each of the hosts); they will not interfere
32443 @section Specifying Names for Hosts and Targets
32445 The specifications used for hosts and targets in the @file{configure}
32446 script are based on a three-part naming scheme, but some short predefined
32447 aliases are also supported. The full naming scheme encodes three pieces
32448 of information in the following pattern:
32451 @var{architecture}-@var{vendor}-@var{os}
32454 For example, you can use the alias @code{sun4} as a @var{host} argument,
32455 or as the value for @var{target} in a @code{--target=@var{target}}
32456 option. The equivalent full name is @samp{sparc-sun-sunos4}.
32458 The @file{configure} script accompanying @value{GDBN} does not provide
32459 any query facility to list all supported host and target names or
32460 aliases. @file{configure} calls the Bourne shell script
32461 @code{config.sub} to map abbreviations to full names; you can read the
32462 script, if you wish, or you can use it to test your guesses on
32463 abbreviations---for example:
32466 % sh config.sub i386-linux
32468 % sh config.sub alpha-linux
32469 alpha-unknown-linux-gnu
32470 % sh config.sub hp9k700
32472 % sh config.sub sun4
32473 sparc-sun-sunos4.1.1
32474 % sh config.sub sun3
32475 m68k-sun-sunos4.1.1
32476 % sh config.sub i986v
32477 Invalid configuration `i986v': machine `i986v' not recognized
32481 @code{config.sub} is also distributed in the @value{GDBN} source
32482 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
32484 @node Configure Options
32485 @section @file{configure} Options
32487 Here is a summary of the @file{configure} options and arguments that
32488 are most often useful for building @value{GDBN}. @file{configure} also has
32489 several other options not listed here. @inforef{What Configure
32490 Does,,configure.info}, for a full explanation of @file{configure}.
32493 configure @r{[}--help@r{]}
32494 @r{[}--prefix=@var{dir}@r{]}
32495 @r{[}--exec-prefix=@var{dir}@r{]}
32496 @r{[}--srcdir=@var{dirname}@r{]}
32497 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
32498 @r{[}--target=@var{target}@r{]}
32503 You may introduce options with a single @samp{-} rather than
32504 @samp{--} if you prefer; but you may abbreviate option names if you use
32509 Display a quick summary of how to invoke @file{configure}.
32511 @item --prefix=@var{dir}
32512 Configure the source to install programs and files under directory
32515 @item --exec-prefix=@var{dir}
32516 Configure the source to install programs under directory
32519 @c avoid splitting the warning from the explanation:
32521 @item --srcdir=@var{dirname}
32522 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
32523 @code{make} that implements the @code{VPATH} feature.}@*
32524 Use this option to make configurations in directories separate from the
32525 @value{GDBN} source directories. Among other things, you can use this to
32526 build (or maintain) several configurations simultaneously, in separate
32527 directories. @file{configure} writes configuration-specific files in
32528 the current directory, but arranges for them to use the source in the
32529 directory @var{dirname}. @file{configure} creates directories under
32530 the working directory in parallel to the source directories below
32533 @item --norecursion
32534 Configure only the directory level where @file{configure} is executed; do not
32535 propagate configuration to subdirectories.
32537 @item --target=@var{target}
32538 Configure @value{GDBN} for cross-debugging programs running on the specified
32539 @var{target}. Without this option, @value{GDBN} is configured to debug
32540 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
32542 There is no convenient way to generate a list of all available targets.
32544 @item @var{host} @dots{}
32545 Configure @value{GDBN} to run on the specified @var{host}.
32547 There is no convenient way to generate a list of all available hosts.
32550 There are many other options available as well, but they are generally
32551 needed for special purposes only.
32553 @node System-wide configuration
32554 @section System-wide configuration and settings
32555 @cindex system-wide init file
32557 @value{GDBN} can be configured to have a system-wide init file;
32558 this file will be read and executed at startup (@pxref{Startup, , What
32559 @value{GDBN} does during startup}).
32561 Here is the corresponding configure option:
32564 @item --with-system-gdbinit=@var{file}
32565 Specify that the default location of the system-wide init file is
32569 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
32570 it may be subject to relocation. Two possible cases:
32574 If the default location of this init file contains @file{$prefix},
32575 it will be subject to relocation. Suppose that the configure options
32576 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
32577 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
32578 init file is looked for as @file{$install/etc/gdbinit} instead of
32579 @file{$prefix/etc/gdbinit}.
32582 By contrast, if the default location does not contain the prefix,
32583 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
32584 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
32585 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
32586 wherever @value{GDBN} is installed.
32589 @node Maintenance Commands
32590 @appendix Maintenance Commands
32591 @cindex maintenance commands
32592 @cindex internal commands
32594 In addition to commands intended for @value{GDBN} users, @value{GDBN}
32595 includes a number of commands intended for @value{GDBN} developers,
32596 that are not documented elsewhere in this manual. These commands are
32597 provided here for reference. (For commands that turn on debugging
32598 messages, see @ref{Debugging Output}.)
32601 @kindex maint agent
32602 @kindex maint agent-eval
32603 @item maint agent @var{expression}
32604 @itemx maint agent-eval @var{expression}
32605 Translate the given @var{expression} into remote agent bytecodes.
32606 This command is useful for debugging the Agent Expression mechanism
32607 (@pxref{Agent Expressions}). The @samp{agent} version produces an
32608 expression useful for data collection, such as by tracepoints, while
32609 @samp{maint agent-eval} produces an expression that evaluates directly
32610 to a result. For instance, a collection expression for @code{globa +
32611 globb} will include bytecodes to record four bytes of memory at each
32612 of the addresses of @code{globa} and @code{globb}, while discarding
32613 the result of the addition, while an evaluation expression will do the
32614 addition and return the sum.
32616 @kindex maint info breakpoints
32617 @item @anchor{maint info breakpoints}maint info breakpoints
32618 Using the same format as @samp{info breakpoints}, display both the
32619 breakpoints you've set explicitly, and those @value{GDBN} is using for
32620 internal purposes. Internal breakpoints are shown with negative
32621 breakpoint numbers. The type column identifies what kind of breakpoint
32626 Normal, explicitly set breakpoint.
32629 Normal, explicitly set watchpoint.
32632 Internal breakpoint, used to handle correctly stepping through
32633 @code{longjmp} calls.
32635 @item longjmp resume
32636 Internal breakpoint at the target of a @code{longjmp}.
32639 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
32642 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
32645 Shared library events.
32649 @kindex set displaced-stepping
32650 @kindex show displaced-stepping
32651 @cindex displaced stepping support
32652 @cindex out-of-line single-stepping
32653 @item set displaced-stepping
32654 @itemx show displaced-stepping
32655 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
32656 if the target supports it. Displaced stepping is a way to single-step
32657 over breakpoints without removing them from the inferior, by executing
32658 an out-of-line copy of the instruction that was originally at the
32659 breakpoint location. It is also known as out-of-line single-stepping.
32662 @item set displaced-stepping on
32663 If the target architecture supports it, @value{GDBN} will use
32664 displaced stepping to step over breakpoints.
32666 @item set displaced-stepping off
32667 @value{GDBN} will not use displaced stepping to step over breakpoints,
32668 even if such is supported by the target architecture.
32670 @cindex non-stop mode, and @samp{set displaced-stepping}
32671 @item set displaced-stepping auto
32672 This is the default mode. @value{GDBN} will use displaced stepping
32673 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
32674 architecture supports displaced stepping.
32677 @kindex maint check-symtabs
32678 @item maint check-symtabs
32679 Check the consistency of psymtabs and symtabs.
32681 @kindex maint cplus first_component
32682 @item maint cplus first_component @var{name}
32683 Print the first C@t{++} class/namespace component of @var{name}.
32685 @kindex maint cplus namespace
32686 @item maint cplus namespace
32687 Print the list of possible C@t{++} namespaces.
32689 @kindex maint demangle
32690 @item maint demangle @var{name}
32691 Demangle a C@t{++} or Objective-C mangled @var{name}.
32693 @kindex maint deprecate
32694 @kindex maint undeprecate
32695 @cindex deprecated commands
32696 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
32697 @itemx maint undeprecate @var{command}
32698 Deprecate or undeprecate the named @var{command}. Deprecated commands
32699 cause @value{GDBN} to issue a warning when you use them. The optional
32700 argument @var{replacement} says which newer command should be used in
32701 favor of the deprecated one; if it is given, @value{GDBN} will mention
32702 the replacement as part of the warning.
32704 @kindex maint dump-me
32705 @item maint dump-me
32706 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
32707 Cause a fatal signal in the debugger and force it to dump its core.
32708 This is supported only on systems which support aborting a program
32709 with the @code{SIGQUIT} signal.
32711 @kindex maint internal-error
32712 @kindex maint internal-warning
32713 @item maint internal-error @r{[}@var{message-text}@r{]}
32714 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
32715 Cause @value{GDBN} to call the internal function @code{internal_error}
32716 or @code{internal_warning} and hence behave as though an internal error
32717 or internal warning has been detected. In addition to reporting the
32718 internal problem, these functions give the user the opportunity to
32719 either quit @value{GDBN} or create a core file of the current
32720 @value{GDBN} session.
32722 These commands take an optional parameter @var{message-text} that is
32723 used as the text of the error or warning message.
32725 Here's an example of using @code{internal-error}:
32728 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
32729 @dots{}/maint.c:121: internal-error: testing, 1, 2
32730 A problem internal to GDB has been detected. Further
32731 debugging may prove unreliable.
32732 Quit this debugging session? (y or n) @kbd{n}
32733 Create a core file? (y or n) @kbd{n}
32737 @cindex @value{GDBN} internal error
32738 @cindex internal errors, control of @value{GDBN} behavior
32740 @kindex maint set internal-error
32741 @kindex maint show internal-error
32742 @kindex maint set internal-warning
32743 @kindex maint show internal-warning
32744 @item maint set internal-error @var{action} [ask|yes|no]
32745 @itemx maint show internal-error @var{action}
32746 @itemx maint set internal-warning @var{action} [ask|yes|no]
32747 @itemx maint show internal-warning @var{action}
32748 When @value{GDBN} reports an internal problem (error or warning) it
32749 gives the user the opportunity to both quit @value{GDBN} and create a
32750 core file of the current @value{GDBN} session. These commands let you
32751 override the default behaviour for each particular @var{action},
32752 described in the table below.
32756 You can specify that @value{GDBN} should always (yes) or never (no)
32757 quit. The default is to ask the user what to do.
32760 You can specify that @value{GDBN} should always (yes) or never (no)
32761 create a core file. The default is to ask the user what to do.
32764 @kindex maint packet
32765 @item maint packet @var{text}
32766 If @value{GDBN} is talking to an inferior via the serial protocol,
32767 then this command sends the string @var{text} to the inferior, and
32768 displays the response packet. @value{GDBN} supplies the initial
32769 @samp{$} character, the terminating @samp{#} character, and the
32772 @kindex maint print architecture
32773 @item maint print architecture @r{[}@var{file}@r{]}
32774 Print the entire architecture configuration. The optional argument
32775 @var{file} names the file where the output goes.
32777 @kindex maint print c-tdesc
32778 @item maint print c-tdesc
32779 Print the current target description (@pxref{Target Descriptions}) as
32780 a C source file. The created source file can be used in @value{GDBN}
32781 when an XML parser is not available to parse the description.
32783 @kindex maint print dummy-frames
32784 @item maint print dummy-frames
32785 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
32788 (@value{GDBP}) @kbd{b add}
32790 (@value{GDBP}) @kbd{print add(2,3)}
32791 Breakpoint 2, add (a=2, b=3) at @dots{}
32793 The program being debugged stopped while in a function called from GDB.
32795 (@value{GDBP}) @kbd{maint print dummy-frames}
32796 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
32797 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
32798 call_lo=0x01014000 call_hi=0x01014001
32802 Takes an optional file parameter.
32804 @kindex maint print registers
32805 @kindex maint print raw-registers
32806 @kindex maint print cooked-registers
32807 @kindex maint print register-groups
32808 @kindex maint print remote-registers
32809 @item maint print registers @r{[}@var{file}@r{]}
32810 @itemx maint print raw-registers @r{[}@var{file}@r{]}
32811 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
32812 @itemx maint print register-groups @r{[}@var{file}@r{]}
32813 @itemx maint print remote-registers @r{[}@var{file}@r{]}
32814 Print @value{GDBN}'s internal register data structures.
32816 The command @code{maint print raw-registers} includes the contents of
32817 the raw register cache; the command @code{maint print
32818 cooked-registers} includes the (cooked) value of all registers,
32819 including registers which aren't available on the target nor visible
32820 to user; the command @code{maint print register-groups} includes the
32821 groups that each register is a member of; and the command @code{maint
32822 print remote-registers} includes the remote target's register numbers
32823 and offsets in the `G' packets. @xref{Registers,, Registers, gdbint,
32824 @value{GDBN} Internals}.
32826 These commands take an optional parameter, a file name to which to
32827 write the information.
32829 @kindex maint print reggroups
32830 @item maint print reggroups @r{[}@var{file}@r{]}
32831 Print @value{GDBN}'s internal register group data structures. The
32832 optional argument @var{file} tells to what file to write the
32835 The register groups info looks like this:
32838 (@value{GDBP}) @kbd{maint print reggroups}
32851 This command forces @value{GDBN} to flush its internal register cache.
32853 @kindex maint print objfiles
32854 @cindex info for known object files
32855 @item maint print objfiles
32856 Print a dump of all known object files. For each object file, this
32857 command prints its name, address in memory, and all of its psymtabs
32860 @kindex maint print section-scripts
32861 @cindex info for known .debug_gdb_scripts-loaded scripts
32862 @item maint print section-scripts [@var{regexp}]
32863 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
32864 If @var{regexp} is specified, only print scripts loaded by object files
32865 matching @var{regexp}.
32866 For each script, this command prints its name as specified in the objfile,
32867 and the full path if known.
32868 @xref{.debug_gdb_scripts section}.
32870 @kindex maint print statistics
32871 @cindex bcache statistics
32872 @item maint print statistics
32873 This command prints, for each object file in the program, various data
32874 about that object file followed by the byte cache (@dfn{bcache})
32875 statistics for the object file. The objfile data includes the number
32876 of minimal, partial, full, and stabs symbols, the number of types
32877 defined by the objfile, the number of as yet unexpanded psym tables,
32878 the number of line tables and string tables, and the amount of memory
32879 used by the various tables. The bcache statistics include the counts,
32880 sizes, and counts of duplicates of all and unique objects, max,
32881 average, and median entry size, total memory used and its overhead and
32882 savings, and various measures of the hash table size and chain
32885 @kindex maint print target-stack
32886 @cindex target stack description
32887 @item maint print target-stack
32888 A @dfn{target} is an interface between the debugger and a particular
32889 kind of file or process. Targets can be stacked in @dfn{strata},
32890 so that more than one target can potentially respond to a request.
32891 In particular, memory accesses will walk down the stack of targets
32892 until they find a target that is interested in handling that particular
32895 This command prints a short description of each layer that was pushed on
32896 the @dfn{target stack}, starting from the top layer down to the bottom one.
32898 @kindex maint print type
32899 @cindex type chain of a data type
32900 @item maint print type @var{expr}
32901 Print the type chain for a type specified by @var{expr}. The argument
32902 can be either a type name or a symbol. If it is a symbol, the type of
32903 that symbol is described. The type chain produced by this command is
32904 a recursive definition of the data type as stored in @value{GDBN}'s
32905 data structures, including its flags and contained types.
32907 @kindex maint set dwarf2 always-disassemble
32908 @kindex maint show dwarf2 always-disassemble
32909 @item maint set dwarf2 always-disassemble
32910 @item maint show dwarf2 always-disassemble
32911 Control the behavior of @code{info address} when using DWARF debugging
32914 The default is @code{off}, which means that @value{GDBN} should try to
32915 describe a variable's location in an easily readable format. When
32916 @code{on}, @value{GDBN} will instead display the DWARF location
32917 expression in an assembly-like format. Note that some locations are
32918 too complex for @value{GDBN} to describe simply; in this case you will
32919 always see the disassembly form.
32921 Here is an example of the resulting disassembly:
32924 (gdb) info addr argc
32925 Symbol "argc" is a complex DWARF expression:
32929 For more information on these expressions, see
32930 @uref{http://www.dwarfstd.org/, the DWARF standard}.
32932 @kindex maint set dwarf2 max-cache-age
32933 @kindex maint show dwarf2 max-cache-age
32934 @item maint set dwarf2 max-cache-age
32935 @itemx maint show dwarf2 max-cache-age
32936 Control the DWARF 2 compilation unit cache.
32938 @cindex DWARF 2 compilation units cache
32939 In object files with inter-compilation-unit references, such as those
32940 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
32941 reader needs to frequently refer to previously read compilation units.
32942 This setting controls how long a compilation unit will remain in the
32943 cache if it is not referenced. A higher limit means that cached
32944 compilation units will be stored in memory longer, and more total
32945 memory will be used. Setting it to zero disables caching, which will
32946 slow down @value{GDBN} startup, but reduce memory consumption.
32948 @kindex maint set profile
32949 @kindex maint show profile
32950 @cindex profiling GDB
32951 @item maint set profile
32952 @itemx maint show profile
32953 Control profiling of @value{GDBN}.
32955 Profiling will be disabled until you use the @samp{maint set profile}
32956 command to enable it. When you enable profiling, the system will begin
32957 collecting timing and execution count data; when you disable profiling or
32958 exit @value{GDBN}, the results will be written to a log file. Remember that
32959 if you use profiling, @value{GDBN} will overwrite the profiling log file
32960 (often called @file{gmon.out}). If you have a record of important profiling
32961 data in a @file{gmon.out} file, be sure to move it to a safe location.
32963 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
32964 compiled with the @samp{-pg} compiler option.
32966 @kindex maint set show-debug-regs
32967 @kindex maint show show-debug-regs
32968 @cindex hardware debug registers
32969 @item maint set show-debug-regs
32970 @itemx maint show show-debug-regs
32971 Control whether to show variables that mirror the hardware debug
32972 registers. Use @code{ON} to enable, @code{OFF} to disable. If
32973 enabled, the debug registers values are shown when @value{GDBN} inserts or
32974 removes a hardware breakpoint or watchpoint, and when the inferior
32975 triggers a hardware-assisted breakpoint or watchpoint.
32977 @kindex maint set show-all-tib
32978 @kindex maint show show-all-tib
32979 @item maint set show-all-tib
32980 @itemx maint show show-all-tib
32981 Control whether to show all non zero areas within a 1k block starting
32982 at thread local base, when using the @samp{info w32 thread-information-block}
32985 @kindex maint space
32986 @cindex memory used by commands
32988 Control whether to display memory usage for each command. If set to a
32989 nonzero value, @value{GDBN} will display how much memory each command
32990 took, following the command's own output. This can also be requested
32991 by invoking @value{GDBN} with the @option{--statistics} command-line
32992 switch (@pxref{Mode Options}).
32995 @cindex time of command execution
32997 Control whether to display the execution time of @value{GDBN} for each command.
32998 If set to a nonzero value, @value{GDBN} will display how much time it
32999 took to execute each command, following the command's own output.
33000 Both CPU time and wallclock time are printed.
33001 Printing both is useful when trying to determine whether the cost is
33002 CPU or, e.g., disk/network, latency.
33003 Note that the CPU time printed is for @value{GDBN} only, it does not include
33004 the execution time of the inferior because there's no mechanism currently
33005 to compute how much time was spent by @value{GDBN} and how much time was
33006 spent by the program been debugged.
33007 This can also be requested by invoking @value{GDBN} with the
33008 @option{--statistics} command-line switch (@pxref{Mode Options}).
33010 @kindex maint translate-address
33011 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
33012 Find the symbol stored at the location specified by the address
33013 @var{addr} and an optional section name @var{section}. If found,
33014 @value{GDBN} prints the name of the closest symbol and an offset from
33015 the symbol's location to the specified address. This is similar to
33016 the @code{info address} command (@pxref{Symbols}), except that this
33017 command also allows to find symbols in other sections.
33019 If section was not specified, the section in which the symbol was found
33020 is also printed. For dynamically linked executables, the name of
33021 executable or shared library containing the symbol is printed as well.
33025 The following command is useful for non-interactive invocations of
33026 @value{GDBN}, such as in the test suite.
33029 @item set watchdog @var{nsec}
33030 @kindex set watchdog
33031 @cindex watchdog timer
33032 @cindex timeout for commands
33033 Set the maximum number of seconds @value{GDBN} will wait for the
33034 target operation to finish. If this time expires, @value{GDBN}
33035 reports and error and the command is aborted.
33037 @item show watchdog
33038 Show the current setting of the target wait timeout.
33041 @node Remote Protocol
33042 @appendix @value{GDBN} Remote Serial Protocol
33047 * Stop Reply Packets::
33048 * General Query Packets::
33049 * Architecture-Specific Protocol Details::
33050 * Tracepoint Packets::
33051 * Host I/O Packets::
33053 * Notification Packets::
33054 * Remote Non-Stop::
33055 * Packet Acknowledgment::
33057 * File-I/O Remote Protocol Extension::
33058 * Library List Format::
33059 * Memory Map Format::
33060 * Thread List Format::
33061 * Traceframe Info Format::
33067 There may be occasions when you need to know something about the
33068 protocol---for example, if there is only one serial port to your target
33069 machine, you might want your program to do something special if it
33070 recognizes a packet meant for @value{GDBN}.
33072 In the examples below, @samp{->} and @samp{<-} are used to indicate
33073 transmitted and received data, respectively.
33075 @cindex protocol, @value{GDBN} remote serial
33076 @cindex serial protocol, @value{GDBN} remote
33077 @cindex remote serial protocol
33078 All @value{GDBN} commands and responses (other than acknowledgments
33079 and notifications, see @ref{Notification Packets}) are sent as a
33080 @var{packet}. A @var{packet} is introduced with the character
33081 @samp{$}, the actual @var{packet-data}, and the terminating character
33082 @samp{#} followed by a two-digit @var{checksum}:
33085 @code{$}@var{packet-data}@code{#}@var{checksum}
33089 @cindex checksum, for @value{GDBN} remote
33091 The two-digit @var{checksum} is computed as the modulo 256 sum of all
33092 characters between the leading @samp{$} and the trailing @samp{#} (an
33093 eight bit unsigned checksum).
33095 Implementors should note that prior to @value{GDBN} 5.0 the protocol
33096 specification also included an optional two-digit @var{sequence-id}:
33099 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
33102 @cindex sequence-id, for @value{GDBN} remote
33104 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
33105 has never output @var{sequence-id}s. Stubs that handle packets added
33106 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
33108 When either the host or the target machine receives a packet, the first
33109 response expected is an acknowledgment: either @samp{+} (to indicate
33110 the package was received correctly) or @samp{-} (to request
33114 -> @code{$}@var{packet-data}@code{#}@var{checksum}
33119 The @samp{+}/@samp{-} acknowledgments can be disabled
33120 once a connection is established.
33121 @xref{Packet Acknowledgment}, for details.
33123 The host (@value{GDBN}) sends @var{command}s, and the target (the
33124 debugging stub incorporated in your program) sends a @var{response}. In
33125 the case of step and continue @var{command}s, the response is only sent
33126 when the operation has completed, and the target has again stopped all
33127 threads in all attached processes. This is the default all-stop mode
33128 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
33129 execution mode; see @ref{Remote Non-Stop}, for details.
33131 @var{packet-data} consists of a sequence of characters with the
33132 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
33135 @cindex remote protocol, field separator
33136 Fields within the packet should be separated using @samp{,} @samp{;} or
33137 @samp{:}. Except where otherwise noted all numbers are represented in
33138 @sc{hex} with leading zeros suppressed.
33140 Implementors should note that prior to @value{GDBN} 5.0, the character
33141 @samp{:} could not appear as the third character in a packet (as it
33142 would potentially conflict with the @var{sequence-id}).
33144 @cindex remote protocol, binary data
33145 @anchor{Binary Data}
33146 Binary data in most packets is encoded either as two hexadecimal
33147 digits per byte of binary data. This allowed the traditional remote
33148 protocol to work over connections which were only seven-bit clean.
33149 Some packets designed more recently assume an eight-bit clean
33150 connection, and use a more efficient encoding to send and receive
33153 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
33154 as an escape character. Any escaped byte is transmitted as the escape
33155 character followed by the original character XORed with @code{0x20}.
33156 For example, the byte @code{0x7d} would be transmitted as the two
33157 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
33158 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
33159 @samp{@}}) must always be escaped. Responses sent by the stub
33160 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
33161 is not interpreted as the start of a run-length encoded sequence
33164 Response @var{data} can be run-length encoded to save space.
33165 Run-length encoding replaces runs of identical characters with one
33166 instance of the repeated character, followed by a @samp{*} and a
33167 repeat count. The repeat count is itself sent encoded, to avoid
33168 binary characters in @var{data}: a value of @var{n} is sent as
33169 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
33170 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
33171 code 32) for a repeat count of 3. (This is because run-length
33172 encoding starts to win for counts 3 or more.) Thus, for example,
33173 @samp{0* } is a run-length encoding of ``0000'': the space character
33174 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
33177 The printable characters @samp{#} and @samp{$} or with a numeric value
33178 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
33179 seven repeats (@samp{$}) can be expanded using a repeat count of only
33180 five (@samp{"}). For example, @samp{00000000} can be encoded as
33183 The error response returned for some packets includes a two character
33184 error number. That number is not well defined.
33186 @cindex empty response, for unsupported packets
33187 For any @var{command} not supported by the stub, an empty response
33188 (@samp{$#00}) should be returned. That way it is possible to extend the
33189 protocol. A newer @value{GDBN} can tell if a packet is supported based
33192 At a minimum, a stub is required to support the @samp{g} and @samp{G}
33193 commands for register access, and the @samp{m} and @samp{M} commands
33194 for memory access. Stubs that only control single-threaded targets
33195 can implement run control with the @samp{c} (continue), and @samp{s}
33196 (step) commands. Stubs that support multi-threading targets should
33197 support the @samp{vCont} command. All other commands are optional.
33202 The following table provides a complete list of all currently defined
33203 @var{command}s and their corresponding response @var{data}.
33204 @xref{File-I/O Remote Protocol Extension}, for details about the File
33205 I/O extension of the remote protocol.
33207 Each packet's description has a template showing the packet's overall
33208 syntax, followed by an explanation of the packet's meaning. We
33209 include spaces in some of the templates for clarity; these are not
33210 part of the packet's syntax. No @value{GDBN} packet uses spaces to
33211 separate its components. For example, a template like @samp{foo
33212 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
33213 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
33214 @var{baz}. @value{GDBN} does not transmit a space character between the
33215 @samp{foo} and the @var{bar}, or between the @var{bar} and the
33218 @cindex @var{thread-id}, in remote protocol
33219 @anchor{thread-id syntax}
33220 Several packets and replies include a @var{thread-id} field to identify
33221 a thread. Normally these are positive numbers with a target-specific
33222 interpretation, formatted as big-endian hex strings. A @var{thread-id}
33223 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
33226 In addition, the remote protocol supports a multiprocess feature in
33227 which the @var{thread-id} syntax is extended to optionally include both
33228 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
33229 The @var{pid} (process) and @var{tid} (thread) components each have the
33230 format described above: a positive number with target-specific
33231 interpretation formatted as a big-endian hex string, literal @samp{-1}
33232 to indicate all processes or threads (respectively), or @samp{0} to
33233 indicate an arbitrary process or thread. Specifying just a process, as
33234 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
33235 error to specify all processes but a specific thread, such as
33236 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
33237 for those packets and replies explicitly documented to include a process
33238 ID, rather than a @var{thread-id}.
33240 The multiprocess @var{thread-id} syntax extensions are only used if both
33241 @value{GDBN} and the stub report support for the @samp{multiprocess}
33242 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
33245 Note that all packet forms beginning with an upper- or lower-case
33246 letter, other than those described here, are reserved for future use.
33248 Here are the packet descriptions.
33253 @cindex @samp{!} packet
33254 @anchor{extended mode}
33255 Enable extended mode. In extended mode, the remote server is made
33256 persistent. The @samp{R} packet is used to restart the program being
33262 The remote target both supports and has enabled extended mode.
33266 @cindex @samp{?} packet
33267 Indicate the reason the target halted. The reply is the same as for
33268 step and continue. This packet has a special interpretation when the
33269 target is in non-stop mode; see @ref{Remote Non-Stop}.
33272 @xref{Stop Reply Packets}, for the reply specifications.
33274 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
33275 @cindex @samp{A} packet
33276 Initialized @code{argv[]} array passed into program. @var{arglen}
33277 specifies the number of bytes in the hex encoded byte stream
33278 @var{arg}. See @code{gdbserver} for more details.
33283 The arguments were set.
33289 @cindex @samp{b} packet
33290 (Don't use this packet; its behavior is not well-defined.)
33291 Change the serial line speed to @var{baud}.
33293 JTC: @emph{When does the transport layer state change? When it's
33294 received, or after the ACK is transmitted. In either case, there are
33295 problems if the command or the acknowledgment packet is dropped.}
33297 Stan: @emph{If people really wanted to add something like this, and get
33298 it working for the first time, they ought to modify ser-unix.c to send
33299 some kind of out-of-band message to a specially-setup stub and have the
33300 switch happen "in between" packets, so that from remote protocol's point
33301 of view, nothing actually happened.}
33303 @item B @var{addr},@var{mode}
33304 @cindex @samp{B} packet
33305 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
33306 breakpoint at @var{addr}.
33308 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
33309 (@pxref{insert breakpoint or watchpoint packet}).
33311 @cindex @samp{bc} packet
33314 Backward continue. Execute the target system in reverse. No parameter.
33315 @xref{Reverse Execution}, for more information.
33318 @xref{Stop Reply Packets}, for the reply specifications.
33320 @cindex @samp{bs} packet
33323 Backward single step. Execute one instruction in reverse. No parameter.
33324 @xref{Reverse Execution}, for more information.
33327 @xref{Stop Reply Packets}, for the reply specifications.
33329 @item c @r{[}@var{addr}@r{]}
33330 @cindex @samp{c} packet
33331 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
33332 resume at current address.
33334 This packet is deprecated for multi-threading support. @xref{vCont
33338 @xref{Stop Reply Packets}, for the reply specifications.
33340 @item C @var{sig}@r{[};@var{addr}@r{]}
33341 @cindex @samp{C} packet
33342 Continue with signal @var{sig} (hex signal number). If
33343 @samp{;@var{addr}} is omitted, resume at same address.
33345 This packet is deprecated for multi-threading support. @xref{vCont
33349 @xref{Stop Reply Packets}, for the reply specifications.
33352 @cindex @samp{d} packet
33355 Don't use this packet; instead, define a general set packet
33356 (@pxref{General Query Packets}).
33360 @cindex @samp{D} packet
33361 The first form of the packet is used to detach @value{GDBN} from the
33362 remote system. It is sent to the remote target
33363 before @value{GDBN} disconnects via the @code{detach} command.
33365 The second form, including a process ID, is used when multiprocess
33366 protocol extensions are enabled (@pxref{multiprocess extensions}), to
33367 detach only a specific process. The @var{pid} is specified as a
33368 big-endian hex string.
33378 @item F @var{RC},@var{EE},@var{CF};@var{XX}
33379 @cindex @samp{F} packet
33380 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
33381 This is part of the File-I/O protocol extension. @xref{File-I/O
33382 Remote Protocol Extension}, for the specification.
33385 @anchor{read registers packet}
33386 @cindex @samp{g} packet
33387 Read general registers.
33391 @item @var{XX@dots{}}
33392 Each byte of register data is described by two hex digits. The bytes
33393 with the register are transmitted in target byte order. The size of
33394 each register and their position within the @samp{g} packet are
33395 determined by the @value{GDBN} internal gdbarch functions
33396 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
33397 specification of several standard @samp{g} packets is specified below.
33399 When reading registers from a trace frame (@pxref{Analyze Collected
33400 Data,,Using the Collected Data}), the stub may also return a string of
33401 literal @samp{x}'s in place of the register data digits, to indicate
33402 that the corresponding register has not been collected, thus its value
33403 is unavailable. For example, for an architecture with 4 registers of
33404 4 bytes each, the following reply indicates to @value{GDBN} that
33405 registers 0 and 2 have not been collected, while registers 1 and 3
33406 have been collected, and both have zero value:
33410 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
33417 @item G @var{XX@dots{}}
33418 @cindex @samp{G} packet
33419 Write general registers. @xref{read registers packet}, for a
33420 description of the @var{XX@dots{}} data.
33430 @item H @var{op} @var{thread-id}
33431 @cindex @samp{H} packet
33432 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
33433 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
33434 it should be @samp{c} for step and continue operations (note that this
33435 is deprecated, supporting the @samp{vCont} command is a better
33436 option), @samp{g} for other operations. The thread designator
33437 @var{thread-id} has the format and interpretation described in
33438 @ref{thread-id syntax}.
33449 @c 'H': How restrictive (or permissive) is the thread model. If a
33450 @c thread is selected and stopped, are other threads allowed
33451 @c to continue to execute? As I mentioned above, I think the
33452 @c semantics of each command when a thread is selected must be
33453 @c described. For example:
33455 @c 'g': If the stub supports threads and a specific thread is
33456 @c selected, returns the register block from that thread;
33457 @c otherwise returns current registers.
33459 @c 'G' If the stub supports threads and a specific thread is
33460 @c selected, sets the registers of the register block of
33461 @c that thread; otherwise sets current registers.
33463 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
33464 @anchor{cycle step packet}
33465 @cindex @samp{i} packet
33466 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
33467 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
33468 step starting at that address.
33471 @cindex @samp{I} packet
33472 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
33476 @cindex @samp{k} packet
33479 FIXME: @emph{There is no description of how to operate when a specific
33480 thread context has been selected (i.e.@: does 'k' kill only that
33483 @item m @var{addr},@var{length}
33484 @cindex @samp{m} packet
33485 Read @var{length} bytes of memory starting at address @var{addr}.
33486 Note that @var{addr} may not be aligned to any particular boundary.
33488 The stub need not use any particular size or alignment when gathering
33489 data from memory for the response; even if @var{addr} is word-aligned
33490 and @var{length} is a multiple of the word size, the stub is free to
33491 use byte accesses, or not. For this reason, this packet may not be
33492 suitable for accessing memory-mapped I/O devices.
33493 @cindex alignment of remote memory accesses
33494 @cindex size of remote memory accesses
33495 @cindex memory, alignment and size of remote accesses
33499 @item @var{XX@dots{}}
33500 Memory contents; each byte is transmitted as a two-digit hexadecimal
33501 number. The reply may contain fewer bytes than requested if the
33502 server was able to read only part of the region of memory.
33507 @item M @var{addr},@var{length}:@var{XX@dots{}}
33508 @cindex @samp{M} packet
33509 Write @var{length} bytes of memory starting at address @var{addr}.
33510 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
33511 hexadecimal number.
33518 for an error (this includes the case where only part of the data was
33523 @cindex @samp{p} packet
33524 Read the value of register @var{n}; @var{n} is in hex.
33525 @xref{read registers packet}, for a description of how the returned
33526 register value is encoded.
33530 @item @var{XX@dots{}}
33531 the register's value
33535 Indicating an unrecognized @var{query}.
33538 @item P @var{n@dots{}}=@var{r@dots{}}
33539 @anchor{write register packet}
33540 @cindex @samp{P} packet
33541 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
33542 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
33543 digits for each byte in the register (target byte order).
33553 @item q @var{name} @var{params}@dots{}
33554 @itemx Q @var{name} @var{params}@dots{}
33555 @cindex @samp{q} packet
33556 @cindex @samp{Q} packet
33557 General query (@samp{q}) and set (@samp{Q}). These packets are
33558 described fully in @ref{General Query Packets}.
33561 @cindex @samp{r} packet
33562 Reset the entire system.
33564 Don't use this packet; use the @samp{R} packet instead.
33567 @cindex @samp{R} packet
33568 Restart the program being debugged. @var{XX}, while needed, is ignored.
33569 This packet is only available in extended mode (@pxref{extended mode}).
33571 The @samp{R} packet has no reply.
33573 @item s @r{[}@var{addr}@r{]}
33574 @cindex @samp{s} packet
33575 Single step. @var{addr} is the address at which to resume. If
33576 @var{addr} is omitted, resume at same address.
33578 This packet is deprecated for multi-threading support. @xref{vCont
33582 @xref{Stop Reply Packets}, for the reply specifications.
33584 @item S @var{sig}@r{[};@var{addr}@r{]}
33585 @anchor{step with signal packet}
33586 @cindex @samp{S} packet
33587 Step with signal. This is analogous to the @samp{C} packet, but
33588 requests a single-step, rather than a normal resumption of execution.
33590 This packet is deprecated for multi-threading support. @xref{vCont
33594 @xref{Stop Reply Packets}, for the reply specifications.
33596 @item t @var{addr}:@var{PP},@var{MM}
33597 @cindex @samp{t} packet
33598 Search backwards starting at address @var{addr} for a match with pattern
33599 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
33600 @var{addr} must be at least 3 digits.
33602 @item T @var{thread-id}
33603 @cindex @samp{T} packet
33604 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
33609 thread is still alive
33615 Packets starting with @samp{v} are identified by a multi-letter name,
33616 up to the first @samp{;} or @samp{?} (or the end of the packet).
33618 @item vAttach;@var{pid}
33619 @cindex @samp{vAttach} packet
33620 Attach to a new process with the specified process ID @var{pid}.
33621 The process ID is a
33622 hexadecimal integer identifying the process. In all-stop mode, all
33623 threads in the attached process are stopped; in non-stop mode, it may be
33624 attached without being stopped if that is supported by the target.
33626 @c In non-stop mode, on a successful vAttach, the stub should set the
33627 @c current thread to a thread of the newly-attached process. After
33628 @c attaching, GDB queries for the attached process's thread ID with qC.
33629 @c Also note that, from a user perspective, whether or not the
33630 @c target is stopped on attach in non-stop mode depends on whether you
33631 @c use the foreground or background version of the attach command, not
33632 @c on what vAttach does; GDB does the right thing with respect to either
33633 @c stopping or restarting threads.
33635 This packet is only available in extended mode (@pxref{extended mode}).
33641 @item @r{Any stop packet}
33642 for success in all-stop mode (@pxref{Stop Reply Packets})
33644 for success in non-stop mode (@pxref{Remote Non-Stop})
33647 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
33648 @cindex @samp{vCont} packet
33649 @anchor{vCont packet}
33650 Resume the inferior, specifying different actions for each thread.
33651 If an action is specified with no @var{thread-id}, then it is applied to any
33652 threads that don't have a specific action specified; if no default action is
33653 specified then other threads should remain stopped in all-stop mode and
33654 in their current state in non-stop mode.
33655 Specifying multiple
33656 default actions is an error; specifying no actions is also an error.
33657 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
33659 Currently supported actions are:
33665 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
33669 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
33674 The optional argument @var{addr} normally associated with the
33675 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
33676 not supported in @samp{vCont}.
33678 The @samp{t} action is only relevant in non-stop mode
33679 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
33680 A stop reply should be generated for any affected thread not already stopped.
33681 When a thread is stopped by means of a @samp{t} action,
33682 the corresponding stop reply should indicate that the thread has stopped with
33683 signal @samp{0}, regardless of whether the target uses some other signal
33684 as an implementation detail.
33687 @xref{Stop Reply Packets}, for the reply specifications.
33690 @cindex @samp{vCont?} packet
33691 Request a list of actions supported by the @samp{vCont} packet.
33695 @item vCont@r{[};@var{action}@dots{}@r{]}
33696 The @samp{vCont} packet is supported. Each @var{action} is a supported
33697 command in the @samp{vCont} packet.
33699 The @samp{vCont} packet is not supported.
33702 @item vFile:@var{operation}:@var{parameter}@dots{}
33703 @cindex @samp{vFile} packet
33704 Perform a file operation on the target system. For details,
33705 see @ref{Host I/O Packets}.
33707 @item vFlashErase:@var{addr},@var{length}
33708 @cindex @samp{vFlashErase} packet
33709 Direct the stub to erase @var{length} bytes of flash starting at
33710 @var{addr}. The region may enclose any number of flash blocks, but
33711 its start and end must fall on block boundaries, as indicated by the
33712 flash block size appearing in the memory map (@pxref{Memory Map
33713 Format}). @value{GDBN} groups flash memory programming operations
33714 together, and sends a @samp{vFlashDone} request after each group; the
33715 stub is allowed to delay erase operation until the @samp{vFlashDone}
33716 packet is received.
33718 The stub must support @samp{vCont} if it reports support for
33719 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
33720 this case @samp{vCont} actions can be specified to apply to all threads
33721 in a process by using the @samp{p@var{pid}.-1} form of the
33732 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
33733 @cindex @samp{vFlashWrite} packet
33734 Direct the stub to write data to flash address @var{addr}. The data
33735 is passed in binary form using the same encoding as for the @samp{X}
33736 packet (@pxref{Binary Data}). The memory ranges specified by
33737 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
33738 not overlap, and must appear in order of increasing addresses
33739 (although @samp{vFlashErase} packets for higher addresses may already
33740 have been received; the ordering is guaranteed only between
33741 @samp{vFlashWrite} packets). If a packet writes to an address that was
33742 neither erased by a preceding @samp{vFlashErase} packet nor by some other
33743 target-specific method, the results are unpredictable.
33751 for vFlashWrite addressing non-flash memory
33757 @cindex @samp{vFlashDone} packet
33758 Indicate to the stub that flash programming operation is finished.
33759 The stub is permitted to delay or batch the effects of a group of
33760 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
33761 @samp{vFlashDone} packet is received. The contents of the affected
33762 regions of flash memory are unpredictable until the @samp{vFlashDone}
33763 request is completed.
33765 @item vKill;@var{pid}
33766 @cindex @samp{vKill} packet
33767 Kill the process with the specified process ID. @var{pid} is a
33768 hexadecimal integer identifying the process. This packet is used in
33769 preference to @samp{k} when multiprocess protocol extensions are
33770 supported; see @ref{multiprocess extensions}.
33780 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
33781 @cindex @samp{vRun} packet
33782 Run the program @var{filename}, passing it each @var{argument} on its
33783 command line. The file and arguments are hex-encoded strings. If
33784 @var{filename} is an empty string, the stub may use a default program
33785 (e.g.@: the last program run). The program is created in the stopped
33788 @c FIXME: What about non-stop mode?
33790 This packet is only available in extended mode (@pxref{extended mode}).
33796 @item @r{Any stop packet}
33797 for success (@pxref{Stop Reply Packets})
33801 @anchor{vStopped packet}
33802 @cindex @samp{vStopped} packet
33804 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
33805 reply and prompt for the stub to report another one.
33809 @item @r{Any stop packet}
33810 if there is another unreported stop event (@pxref{Stop Reply Packets})
33812 if there are no unreported stop events
33815 @item X @var{addr},@var{length}:@var{XX@dots{}}
33817 @cindex @samp{X} packet
33818 Write data to memory, where the data is transmitted in binary.
33819 @var{addr} is address, @var{length} is number of bytes,
33820 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
33830 @item z @var{type},@var{addr},@var{kind}
33831 @itemx Z @var{type},@var{addr},@var{kind}
33832 @anchor{insert breakpoint or watchpoint packet}
33833 @cindex @samp{z} packet
33834 @cindex @samp{Z} packets
33835 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
33836 watchpoint starting at address @var{address} of kind @var{kind}.
33838 Each breakpoint and watchpoint packet @var{type} is documented
33841 @emph{Implementation notes: A remote target shall return an empty string
33842 for an unrecognized breakpoint or watchpoint packet @var{type}. A
33843 remote target shall support either both or neither of a given
33844 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
33845 avoid potential problems with duplicate packets, the operations should
33846 be implemented in an idempotent way.}
33848 @item z0,@var{addr},@var{kind}
33849 @itemx Z0,@var{addr},@var{kind}
33850 @cindex @samp{z0} packet
33851 @cindex @samp{Z0} packet
33852 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
33853 @var{addr} of type @var{kind}.
33855 A memory breakpoint is implemented by replacing the instruction at
33856 @var{addr} with a software breakpoint or trap instruction. The
33857 @var{kind} is target-specific and typically indicates the size of
33858 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
33859 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
33860 architectures have additional meanings for @var{kind};
33861 see @ref{Architecture-Specific Protocol Details}.
33863 @emph{Implementation note: It is possible for a target to copy or move
33864 code that contains memory breakpoints (e.g., when implementing
33865 overlays). The behavior of this packet, in the presence of such a
33866 target, is not defined.}
33878 @item z1,@var{addr},@var{kind}
33879 @itemx Z1,@var{addr},@var{kind}
33880 @cindex @samp{z1} packet
33881 @cindex @samp{Z1} packet
33882 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
33883 address @var{addr}.
33885 A hardware breakpoint is implemented using a mechanism that is not
33886 dependant on being able to modify the target's memory. @var{kind}
33887 has the same meaning as in @samp{Z0} packets.
33889 @emph{Implementation note: A hardware breakpoint is not affected by code
33902 @item z2,@var{addr},@var{kind}
33903 @itemx Z2,@var{addr},@var{kind}
33904 @cindex @samp{z2} packet
33905 @cindex @samp{Z2} packet
33906 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
33907 @var{kind} is interpreted as the number of bytes to watch.
33919 @item z3,@var{addr},@var{kind}
33920 @itemx Z3,@var{addr},@var{kind}
33921 @cindex @samp{z3} packet
33922 @cindex @samp{Z3} packet
33923 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
33924 @var{kind} is interpreted as the number of bytes to watch.
33936 @item z4,@var{addr},@var{kind}
33937 @itemx Z4,@var{addr},@var{kind}
33938 @cindex @samp{z4} packet
33939 @cindex @samp{Z4} packet
33940 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
33941 @var{kind} is interpreted as the number of bytes to watch.
33955 @node Stop Reply Packets
33956 @section Stop Reply Packets
33957 @cindex stop reply packets
33959 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
33960 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
33961 receive any of the below as a reply. Except for @samp{?}
33962 and @samp{vStopped}, that reply is only returned
33963 when the target halts. In the below the exact meaning of @dfn{signal
33964 number} is defined by the header @file{include/gdb/signals.h} in the
33965 @value{GDBN} source code.
33967 As in the description of request packets, we include spaces in the
33968 reply templates for clarity; these are not part of the reply packet's
33969 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
33975 The program received signal number @var{AA} (a two-digit hexadecimal
33976 number). This is equivalent to a @samp{T} response with no
33977 @var{n}:@var{r} pairs.
33979 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
33980 @cindex @samp{T} packet reply
33981 The program received signal number @var{AA} (a two-digit hexadecimal
33982 number). This is equivalent to an @samp{S} response, except that the
33983 @samp{@var{n}:@var{r}} pairs can carry values of important registers
33984 and other information directly in the stop reply packet, reducing
33985 round-trip latency. Single-step and breakpoint traps are reported
33986 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
33990 If @var{n} is a hexadecimal number, it is a register number, and the
33991 corresponding @var{r} gives that register's value. @var{r} is a
33992 series of bytes in target byte order, with each byte given by a
33993 two-digit hex number.
33996 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
33997 the stopped thread, as specified in @ref{thread-id syntax}.
34000 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
34001 the core on which the stop event was detected.
34004 If @var{n} is a recognized @dfn{stop reason}, it describes a more
34005 specific event that stopped the target. The currently defined stop
34006 reasons are listed below. @var{aa} should be @samp{05}, the trap
34007 signal. At most one stop reason should be present.
34010 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
34011 and go on to the next; this allows us to extend the protocol in the
34015 The currently defined stop reasons are:
34021 The packet indicates a watchpoint hit, and @var{r} is the data address, in
34024 @cindex shared library events, remote reply
34026 The packet indicates that the loaded libraries have changed.
34027 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
34028 list of loaded libraries. @var{r} is ignored.
34030 @cindex replay log events, remote reply
34032 The packet indicates that the target cannot continue replaying
34033 logged execution events, because it has reached the end (or the
34034 beginning when executing backward) of the log. The value of @var{r}
34035 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
34036 for more information.
34040 @itemx W @var{AA} ; process:@var{pid}
34041 The process exited, and @var{AA} is the exit status. This is only
34042 applicable to certain targets.
34044 The second form of the response, including the process ID of the exited
34045 process, can be used only when @value{GDBN} has reported support for
34046 multiprocess protocol extensions; see @ref{multiprocess extensions}.
34047 The @var{pid} is formatted as a big-endian hex string.
34050 @itemx X @var{AA} ; process:@var{pid}
34051 The process terminated with signal @var{AA}.
34053 The second form of the response, including the process ID of the
34054 terminated process, can be used only when @value{GDBN} has reported
34055 support for multiprocess protocol extensions; see @ref{multiprocess
34056 extensions}. The @var{pid} is formatted as a big-endian hex string.
34058 @item O @var{XX}@dots{}
34059 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
34060 written as the program's console output. This can happen at any time
34061 while the program is running and the debugger should continue to wait
34062 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
34064 @item F @var{call-id},@var{parameter}@dots{}
34065 @var{call-id} is the identifier which says which host system call should
34066 be called. This is just the name of the function. Translation into the
34067 correct system call is only applicable as it's defined in @value{GDBN}.
34068 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
34071 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
34072 this very system call.
34074 The target replies with this packet when it expects @value{GDBN} to
34075 call a host system call on behalf of the target. @value{GDBN} replies
34076 with an appropriate @samp{F} packet and keeps up waiting for the next
34077 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
34078 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
34079 Protocol Extension}, for more details.
34083 @node General Query Packets
34084 @section General Query Packets
34085 @cindex remote query requests
34087 Packets starting with @samp{q} are @dfn{general query packets};
34088 packets starting with @samp{Q} are @dfn{general set packets}. General
34089 query and set packets are a semi-unified form for retrieving and
34090 sending information to and from the stub.
34092 The initial letter of a query or set packet is followed by a name
34093 indicating what sort of thing the packet applies to. For example,
34094 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
34095 definitions with the stub. These packet names follow some
34100 The name must not contain commas, colons or semicolons.
34102 Most @value{GDBN} query and set packets have a leading upper case
34105 The names of custom vendor packets should use a company prefix, in
34106 lower case, followed by a period. For example, packets designed at
34107 the Acme Corporation might begin with @samp{qacme.foo} (for querying
34108 foos) or @samp{Qacme.bar} (for setting bars).
34111 The name of a query or set packet should be separated from any
34112 parameters by a @samp{:}; the parameters themselves should be
34113 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
34114 full packet name, and check for a separator or the end of the packet,
34115 in case two packet names share a common prefix. New packets should not begin
34116 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
34117 packets predate these conventions, and have arguments without any terminator
34118 for the packet name; we suspect they are in widespread use in places that
34119 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
34120 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
34123 Like the descriptions of the other packets, each description here
34124 has a template showing the packet's overall syntax, followed by an
34125 explanation of the packet's meaning. We include spaces in some of the
34126 templates for clarity; these are not part of the packet's syntax. No
34127 @value{GDBN} packet uses spaces to separate its components.
34129 Here are the currently defined query and set packets:
34133 @item QAllow:@var{op}:@var{val}@dots{}
34134 @cindex @samp{QAllow} packet
34135 Specify which operations @value{GDBN} expects to request of the
34136 target, as a semicolon-separated list of operation name and value
34137 pairs. Possible values for @var{op} include @samp{WriteReg},
34138 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
34139 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
34140 indicating that @value{GDBN} will not request the operation, or 1,
34141 indicating that it may. (The target can then use this to set up its
34142 own internals optimally, for instance if the debugger never expects to
34143 insert breakpoints, it may not need to install its own trap handler.)
34146 @cindex current thread, remote request
34147 @cindex @samp{qC} packet
34148 Return the current thread ID.
34152 @item QC @var{thread-id}
34153 Where @var{thread-id} is a thread ID as documented in
34154 @ref{thread-id syntax}.
34155 @item @r{(anything else)}
34156 Any other reply implies the old thread ID.
34159 @item qCRC:@var{addr},@var{length}
34160 @cindex CRC of memory block, remote request
34161 @cindex @samp{qCRC} packet
34162 Compute the CRC checksum of a block of memory using CRC-32 defined in
34163 IEEE 802.3. The CRC is computed byte at a time, taking the most
34164 significant bit of each byte first. The initial pattern code
34165 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
34167 @emph{Note:} This is the same CRC used in validating separate debug
34168 files (@pxref{Separate Debug Files, , Debugging Information in Separate
34169 Files}). However the algorithm is slightly different. When validating
34170 separate debug files, the CRC is computed taking the @emph{least}
34171 significant bit of each byte first, and the final result is inverted to
34172 detect trailing zeros.
34177 An error (such as memory fault)
34178 @item C @var{crc32}
34179 The specified memory region's checksum is @var{crc32}.
34182 @item QDisableRandomization:@var{value}
34183 @cindex disable address space randomization, remote request
34184 @cindex @samp{QDisableRandomization} packet
34185 Some target operating systems will randomize the virtual address space
34186 of the inferior process as a security feature, but provide a feature
34187 to disable such randomization, e.g.@: to allow for a more deterministic
34188 debugging experience. On such systems, this packet with a @var{value}
34189 of 1 directs the target to disable address space randomization for
34190 processes subsequently started via @samp{vRun} packets, while a packet
34191 with a @var{value} of 0 tells the target to enable address space
34194 This packet is only available in extended mode (@pxref{extended mode}).
34199 The request succeeded.
34202 An error occurred. @var{nn} are hex digits.
34205 An empty reply indicates that @samp{QDisableRandomization} is not supported
34209 This packet is not probed by default; the remote stub must request it,
34210 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34211 This should only be done on targets that actually support disabling
34212 address space randomization.
34215 @itemx qsThreadInfo
34216 @cindex list active threads, remote request
34217 @cindex @samp{qfThreadInfo} packet
34218 @cindex @samp{qsThreadInfo} packet
34219 Obtain a list of all active thread IDs from the target (OS). Since there
34220 may be too many active threads to fit into one reply packet, this query
34221 works iteratively: it may require more than one query/reply sequence to
34222 obtain the entire list of threads. The first query of the sequence will
34223 be the @samp{qfThreadInfo} query; subsequent queries in the
34224 sequence will be the @samp{qsThreadInfo} query.
34226 NOTE: This packet replaces the @samp{qL} query (see below).
34230 @item m @var{thread-id}
34232 @item m @var{thread-id},@var{thread-id}@dots{}
34233 a comma-separated list of thread IDs
34235 (lower case letter @samp{L}) denotes end of list.
34238 In response to each query, the target will reply with a list of one or
34239 more thread IDs, separated by commas.
34240 @value{GDBN} will respond to each reply with a request for more thread
34241 ids (using the @samp{qs} form of the query), until the target responds
34242 with @samp{l} (lower-case ell, for @dfn{last}).
34243 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
34246 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
34247 @cindex get thread-local storage address, remote request
34248 @cindex @samp{qGetTLSAddr} packet
34249 Fetch the address associated with thread local storage specified
34250 by @var{thread-id}, @var{offset}, and @var{lm}.
34252 @var{thread-id} is the thread ID associated with the
34253 thread for which to fetch the TLS address. @xref{thread-id syntax}.
34255 @var{offset} is the (big endian, hex encoded) offset associated with the
34256 thread local variable. (This offset is obtained from the debug
34257 information associated with the variable.)
34259 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
34260 load module associated with the thread local storage. For example,
34261 a @sc{gnu}/Linux system will pass the link map address of the shared
34262 object associated with the thread local storage under consideration.
34263 Other operating environments may choose to represent the load module
34264 differently, so the precise meaning of this parameter will vary.
34268 @item @var{XX}@dots{}
34269 Hex encoded (big endian) bytes representing the address of the thread
34270 local storage requested.
34273 An error occurred. @var{nn} are hex digits.
34276 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
34279 @item qGetTIBAddr:@var{thread-id}
34280 @cindex get thread information block address
34281 @cindex @samp{qGetTIBAddr} packet
34282 Fetch address of the Windows OS specific Thread Information Block.
34284 @var{thread-id} is the thread ID associated with the thread.
34288 @item @var{XX}@dots{}
34289 Hex encoded (big endian) bytes representing the linear address of the
34290 thread information block.
34293 An error occured. This means that either the thread was not found, or the
34294 address could not be retrieved.
34297 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
34300 @item qL @var{startflag} @var{threadcount} @var{nextthread}
34301 Obtain thread information from RTOS. Where: @var{startflag} (one hex
34302 digit) is one to indicate the first query and zero to indicate a
34303 subsequent query; @var{threadcount} (two hex digits) is the maximum
34304 number of threads the response packet can contain; and @var{nextthread}
34305 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
34306 returned in the response as @var{argthread}.
34308 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
34312 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
34313 Where: @var{count} (two hex digits) is the number of threads being
34314 returned; @var{done} (one hex digit) is zero to indicate more threads
34315 and one indicates no further threads; @var{argthreadid} (eight hex
34316 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
34317 is a sequence of thread IDs from the target. @var{threadid} (eight hex
34318 digits). See @code{remote.c:parse_threadlist_response()}.
34322 @cindex section offsets, remote request
34323 @cindex @samp{qOffsets} packet
34324 Get section offsets that the target used when relocating the downloaded
34329 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
34330 Relocate the @code{Text} section by @var{xxx} from its original address.
34331 Relocate the @code{Data} section by @var{yyy} from its original address.
34332 If the object file format provides segment information (e.g.@: @sc{elf}
34333 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
34334 segments by the supplied offsets.
34336 @emph{Note: while a @code{Bss} offset may be included in the response,
34337 @value{GDBN} ignores this and instead applies the @code{Data} offset
34338 to the @code{Bss} section.}
34340 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
34341 Relocate the first segment of the object file, which conventionally
34342 contains program code, to a starting address of @var{xxx}. If
34343 @samp{DataSeg} is specified, relocate the second segment, which
34344 conventionally contains modifiable data, to a starting address of
34345 @var{yyy}. @value{GDBN} will report an error if the object file
34346 does not contain segment information, or does not contain at least
34347 as many segments as mentioned in the reply. Extra segments are
34348 kept at fixed offsets relative to the last relocated segment.
34351 @item qP @var{mode} @var{thread-id}
34352 @cindex thread information, remote request
34353 @cindex @samp{qP} packet
34354 Returns information on @var{thread-id}. Where: @var{mode} is a hex
34355 encoded 32 bit mode; @var{thread-id} is a thread ID
34356 (@pxref{thread-id syntax}).
34358 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
34361 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
34365 @cindex non-stop mode, remote request
34366 @cindex @samp{QNonStop} packet
34368 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
34369 @xref{Remote Non-Stop}, for more information.
34374 The request succeeded.
34377 An error occurred. @var{nn} are hex digits.
34380 An empty reply indicates that @samp{QNonStop} is not supported by
34384 This packet is not probed by default; the remote stub must request it,
34385 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34386 Use of this packet is controlled by the @code{set non-stop} command;
34387 @pxref{Non-Stop Mode}.
34389 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
34390 @cindex pass signals to inferior, remote request
34391 @cindex @samp{QPassSignals} packet
34392 @anchor{QPassSignals}
34393 Each listed @var{signal} should be passed directly to the inferior process.
34394 Signals are numbered identically to continue packets and stop replies
34395 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
34396 strictly greater than the previous item. These signals do not need to stop
34397 the inferior, or be reported to @value{GDBN}. All other signals should be
34398 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
34399 combine; any earlier @samp{QPassSignals} list is completely replaced by the
34400 new list. This packet improves performance when using @samp{handle
34401 @var{signal} nostop noprint pass}.
34406 The request succeeded.
34409 An error occurred. @var{nn} are hex digits.
34412 An empty reply indicates that @samp{QPassSignals} is not supported by
34416 Use of this packet is controlled by the @code{set remote pass-signals}
34417 command (@pxref{Remote Configuration, set remote pass-signals}).
34418 This packet is not probed by default; the remote stub must request it,
34419 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34421 @item qRcmd,@var{command}
34422 @cindex execute remote command, remote request
34423 @cindex @samp{qRcmd} packet
34424 @var{command} (hex encoded) is passed to the local interpreter for
34425 execution. Invalid commands should be reported using the output
34426 string. Before the final result packet, the target may also respond
34427 with a number of intermediate @samp{O@var{output}} console output
34428 packets. @emph{Implementors should note that providing access to a
34429 stubs's interpreter may have security implications}.
34434 A command response with no output.
34436 A command response with the hex encoded output string @var{OUTPUT}.
34438 Indicate a badly formed request.
34440 An empty reply indicates that @samp{qRcmd} is not recognized.
34443 (Note that the @code{qRcmd} packet's name is separated from the
34444 command by a @samp{,}, not a @samp{:}, contrary to the naming
34445 conventions above. Please don't use this packet as a model for new
34448 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
34449 @cindex searching memory, in remote debugging
34450 @cindex @samp{qSearch:memory} packet
34451 @anchor{qSearch memory}
34452 Search @var{length} bytes at @var{address} for @var{search-pattern}.
34453 @var{address} and @var{length} are encoded in hex.
34454 @var{search-pattern} is a sequence of bytes, hex encoded.
34459 The pattern was not found.
34461 The pattern was found at @var{address}.
34463 A badly formed request or an error was encountered while searching memory.
34465 An empty reply indicates that @samp{qSearch:memory} is not recognized.
34468 @item QStartNoAckMode
34469 @cindex @samp{QStartNoAckMode} packet
34470 @anchor{QStartNoAckMode}
34471 Request that the remote stub disable the normal @samp{+}/@samp{-}
34472 protocol acknowledgments (@pxref{Packet Acknowledgment}).
34477 The stub has switched to no-acknowledgment mode.
34478 @value{GDBN} acknowledges this reponse,
34479 but neither the stub nor @value{GDBN} shall send or expect further
34480 @samp{+}/@samp{-} acknowledgments in the current connection.
34482 An empty reply indicates that the stub does not support no-acknowledgment mode.
34485 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
34486 @cindex supported packets, remote query
34487 @cindex features of the remote protocol
34488 @cindex @samp{qSupported} packet
34489 @anchor{qSupported}
34490 Tell the remote stub about features supported by @value{GDBN}, and
34491 query the stub for features it supports. This packet allows
34492 @value{GDBN} and the remote stub to take advantage of each others'
34493 features. @samp{qSupported} also consolidates multiple feature probes
34494 at startup, to improve @value{GDBN} performance---a single larger
34495 packet performs better than multiple smaller probe packets on
34496 high-latency links. Some features may enable behavior which must not
34497 be on by default, e.g.@: because it would confuse older clients or
34498 stubs. Other features may describe packets which could be
34499 automatically probed for, but are not. These features must be
34500 reported before @value{GDBN} will use them. This ``default
34501 unsupported'' behavior is not appropriate for all packets, but it
34502 helps to keep the initial connection time under control with new
34503 versions of @value{GDBN} which support increasing numbers of packets.
34507 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
34508 The stub supports or does not support each returned @var{stubfeature},
34509 depending on the form of each @var{stubfeature} (see below for the
34512 An empty reply indicates that @samp{qSupported} is not recognized,
34513 or that no features needed to be reported to @value{GDBN}.
34516 The allowed forms for each feature (either a @var{gdbfeature} in the
34517 @samp{qSupported} packet, or a @var{stubfeature} in the response)
34521 @item @var{name}=@var{value}
34522 The remote protocol feature @var{name} is supported, and associated
34523 with the specified @var{value}. The format of @var{value} depends
34524 on the feature, but it must not include a semicolon.
34526 The remote protocol feature @var{name} is supported, and does not
34527 need an associated value.
34529 The remote protocol feature @var{name} is not supported.
34531 The remote protocol feature @var{name} may be supported, and
34532 @value{GDBN} should auto-detect support in some other way when it is
34533 needed. This form will not be used for @var{gdbfeature} notifications,
34534 but may be used for @var{stubfeature} responses.
34537 Whenever the stub receives a @samp{qSupported} request, the
34538 supplied set of @value{GDBN} features should override any previous
34539 request. This allows @value{GDBN} to put the stub in a known
34540 state, even if the stub had previously been communicating with
34541 a different version of @value{GDBN}.
34543 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
34548 This feature indicates whether @value{GDBN} supports multiprocess
34549 extensions to the remote protocol. @value{GDBN} does not use such
34550 extensions unless the stub also reports that it supports them by
34551 including @samp{multiprocess+} in its @samp{qSupported} reply.
34552 @xref{multiprocess extensions}, for details.
34555 This feature indicates that @value{GDBN} supports the XML target
34556 description. If the stub sees @samp{xmlRegisters=} with target
34557 specific strings separated by a comma, it will report register
34561 This feature indicates whether @value{GDBN} supports the
34562 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
34563 instruction reply packet}).
34566 Stubs should ignore any unknown values for
34567 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
34568 packet supports receiving packets of unlimited length (earlier
34569 versions of @value{GDBN} may reject overly long responses). Additional values
34570 for @var{gdbfeature} may be defined in the future to let the stub take
34571 advantage of new features in @value{GDBN}, e.g.@: incompatible
34572 improvements in the remote protocol---the @samp{multiprocess} feature is
34573 an example of such a feature. The stub's reply should be independent
34574 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
34575 describes all the features it supports, and then the stub replies with
34576 all the features it supports.
34578 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
34579 responses, as long as each response uses one of the standard forms.
34581 Some features are flags. A stub which supports a flag feature
34582 should respond with a @samp{+} form response. Other features
34583 require values, and the stub should respond with an @samp{=}
34586 Each feature has a default value, which @value{GDBN} will use if
34587 @samp{qSupported} is not available or if the feature is not mentioned
34588 in the @samp{qSupported} response. The default values are fixed; a
34589 stub is free to omit any feature responses that match the defaults.
34591 Not all features can be probed, but for those which can, the probing
34592 mechanism is useful: in some cases, a stub's internal
34593 architecture may not allow the protocol layer to know some information
34594 about the underlying target in advance. This is especially common in
34595 stubs which may be configured for multiple targets.
34597 These are the currently defined stub features and their properties:
34599 @multitable @columnfractions 0.35 0.2 0.12 0.2
34600 @c NOTE: The first row should be @headitem, but we do not yet require
34601 @c a new enough version of Texinfo (4.7) to use @headitem.
34603 @tab Value Required
34607 @item @samp{PacketSize}
34612 @item @samp{qXfer:auxv:read}
34617 @item @samp{qXfer:features:read}
34622 @item @samp{qXfer:libraries:read}
34627 @item @samp{qXfer:memory-map:read}
34632 @item @samp{qXfer:sdata:read}
34637 @item @samp{qXfer:spu:read}
34642 @item @samp{qXfer:spu:write}
34647 @item @samp{qXfer:siginfo:read}
34652 @item @samp{qXfer:siginfo:write}
34657 @item @samp{qXfer:threads:read}
34662 @item @samp{qXfer:traceframe-info:read}
34667 @item @samp{qXfer:fdpic:read}
34672 @item @samp{QNonStop}
34677 @item @samp{QPassSignals}
34682 @item @samp{QStartNoAckMode}
34687 @item @samp{multiprocess}
34692 @item @samp{ConditionalTracepoints}
34697 @item @samp{ReverseContinue}
34702 @item @samp{ReverseStep}
34707 @item @samp{TracepointSource}
34712 @item @samp{QAllow}
34717 @item @samp{QDisableRandomization}
34722 @item @samp{EnableDisableTracepoints}
34727 @item @samp{tracenz}
34734 These are the currently defined stub features, in more detail:
34737 @cindex packet size, remote protocol
34738 @item PacketSize=@var{bytes}
34739 The remote stub can accept packets up to at least @var{bytes} in
34740 length. @value{GDBN} will send packets up to this size for bulk
34741 transfers, and will never send larger packets. This is a limit on the
34742 data characters in the packet, including the frame and checksum.
34743 There is no trailing NUL byte in a remote protocol packet; if the stub
34744 stores packets in a NUL-terminated format, it should allow an extra
34745 byte in its buffer for the NUL. If this stub feature is not supported,
34746 @value{GDBN} guesses based on the size of the @samp{g} packet response.
34748 @item qXfer:auxv:read
34749 The remote stub understands the @samp{qXfer:auxv:read} packet
34750 (@pxref{qXfer auxiliary vector read}).
34752 @item qXfer:features:read
34753 The remote stub understands the @samp{qXfer:features:read} packet
34754 (@pxref{qXfer target description read}).
34756 @item qXfer:libraries:read
34757 The remote stub understands the @samp{qXfer:libraries:read} packet
34758 (@pxref{qXfer library list read}).
34760 @item qXfer:memory-map:read
34761 The remote stub understands the @samp{qXfer:memory-map:read} packet
34762 (@pxref{qXfer memory map read}).
34764 @item qXfer:sdata:read
34765 The remote stub understands the @samp{qXfer:sdata:read} packet
34766 (@pxref{qXfer sdata read}).
34768 @item qXfer:spu:read
34769 The remote stub understands the @samp{qXfer:spu:read} packet
34770 (@pxref{qXfer spu read}).
34772 @item qXfer:spu:write
34773 The remote stub understands the @samp{qXfer:spu:write} packet
34774 (@pxref{qXfer spu write}).
34776 @item qXfer:siginfo:read
34777 The remote stub understands the @samp{qXfer:siginfo:read} packet
34778 (@pxref{qXfer siginfo read}).
34780 @item qXfer:siginfo:write
34781 The remote stub understands the @samp{qXfer:siginfo:write} packet
34782 (@pxref{qXfer siginfo write}).
34784 @item qXfer:threads:read
34785 The remote stub understands the @samp{qXfer:threads:read} packet
34786 (@pxref{qXfer threads read}).
34788 @item qXfer:traceframe-info:read
34789 The remote stub understands the @samp{qXfer:traceframe-info:read}
34790 packet (@pxref{qXfer traceframe info read}).
34792 @item qXfer:fdpic:read
34793 The remote stub understands the @samp{qXfer:fdpic:read}
34794 packet (@pxref{qXfer fdpic loadmap read}).
34797 The remote stub understands the @samp{QNonStop} packet
34798 (@pxref{QNonStop}).
34801 The remote stub understands the @samp{QPassSignals} packet
34802 (@pxref{QPassSignals}).
34804 @item QStartNoAckMode
34805 The remote stub understands the @samp{QStartNoAckMode} packet and
34806 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
34809 @anchor{multiprocess extensions}
34810 @cindex multiprocess extensions, in remote protocol
34811 The remote stub understands the multiprocess extensions to the remote
34812 protocol syntax. The multiprocess extensions affect the syntax of
34813 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
34814 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
34815 replies. Note that reporting this feature indicates support for the
34816 syntactic extensions only, not that the stub necessarily supports
34817 debugging of more than one process at a time. The stub must not use
34818 multiprocess extensions in packet replies unless @value{GDBN} has also
34819 indicated it supports them in its @samp{qSupported} request.
34821 @item qXfer:osdata:read
34822 The remote stub understands the @samp{qXfer:osdata:read} packet
34823 ((@pxref{qXfer osdata read}).
34825 @item ConditionalTracepoints
34826 The remote stub accepts and implements conditional expressions defined
34827 for tracepoints (@pxref{Tracepoint Conditions}).
34829 @item ReverseContinue
34830 The remote stub accepts and implements the reverse continue packet
34834 The remote stub accepts and implements the reverse step packet
34837 @item TracepointSource
34838 The remote stub understands the @samp{QTDPsrc} packet that supplies
34839 the source form of tracepoint definitions.
34842 The remote stub understands the @samp{QAllow} packet.
34844 @item QDisableRandomization
34845 The remote stub understands the @samp{QDisableRandomization} packet.
34847 @item StaticTracepoint
34848 @cindex static tracepoints, in remote protocol
34849 The remote stub supports static tracepoints.
34851 @item EnableDisableTracepoints
34852 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
34853 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
34854 to be enabled and disabled while a trace experiment is running.
34857 @cindex string tracing, in remote protocol
34858 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
34859 See @ref{Bytecode Descriptions} for details about the bytecode.
34864 @cindex symbol lookup, remote request
34865 @cindex @samp{qSymbol} packet
34866 Notify the target that @value{GDBN} is prepared to serve symbol lookup
34867 requests. Accept requests from the target for the values of symbols.
34872 The target does not need to look up any (more) symbols.
34873 @item qSymbol:@var{sym_name}
34874 The target requests the value of symbol @var{sym_name} (hex encoded).
34875 @value{GDBN} may provide the value by using the
34876 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
34880 @item qSymbol:@var{sym_value}:@var{sym_name}
34881 Set the value of @var{sym_name} to @var{sym_value}.
34883 @var{sym_name} (hex encoded) is the name of a symbol whose value the
34884 target has previously requested.
34886 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
34887 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
34893 The target does not need to look up any (more) symbols.
34894 @item qSymbol:@var{sym_name}
34895 The target requests the value of a new symbol @var{sym_name} (hex
34896 encoded). @value{GDBN} will continue to supply the values of symbols
34897 (if available), until the target ceases to request them.
34902 @item QTDisconnected
34909 @xref{Tracepoint Packets}.
34911 @item qThreadExtraInfo,@var{thread-id}
34912 @cindex thread attributes info, remote request
34913 @cindex @samp{qThreadExtraInfo} packet
34914 Obtain a printable string description of a thread's attributes from
34915 the target OS. @var{thread-id} is a thread ID;
34916 see @ref{thread-id syntax}. This
34917 string may contain anything that the target OS thinks is interesting
34918 for @value{GDBN} to tell the user about the thread. The string is
34919 displayed in @value{GDBN}'s @code{info threads} display. Some
34920 examples of possible thread extra info strings are @samp{Runnable}, or
34921 @samp{Blocked on Mutex}.
34925 @item @var{XX}@dots{}
34926 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
34927 comprising the printable string containing the extra information about
34928 the thread's attributes.
34931 (Note that the @code{qThreadExtraInfo} packet's name is separated from
34932 the command by a @samp{,}, not a @samp{:}, contrary to the naming
34933 conventions above. Please don't use this packet as a model for new
34950 @xref{Tracepoint Packets}.
34952 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
34953 @cindex read special object, remote request
34954 @cindex @samp{qXfer} packet
34955 @anchor{qXfer read}
34956 Read uninterpreted bytes from the target's special data area
34957 identified by the keyword @var{object}. Request @var{length} bytes
34958 starting at @var{offset} bytes into the data. The content and
34959 encoding of @var{annex} is specific to @var{object}; it can supply
34960 additional details about what data to access.
34962 Here are the specific requests of this form defined so far. All
34963 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
34964 formats, listed below.
34967 @item qXfer:auxv:read::@var{offset},@var{length}
34968 @anchor{qXfer auxiliary vector read}
34969 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
34970 auxiliary vector}. Note @var{annex} must be empty.
34972 This packet is not probed by default; the remote stub must request it,
34973 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34975 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
34976 @anchor{qXfer target description read}
34977 Access the @dfn{target description}. @xref{Target Descriptions}. The
34978 annex specifies which XML document to access. The main description is
34979 always loaded from the @samp{target.xml} annex.
34981 This packet is not probed by default; the remote stub must request it,
34982 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34984 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
34985 @anchor{qXfer library list read}
34986 Access the target's list of loaded libraries. @xref{Library List Format}.
34987 The annex part of the generic @samp{qXfer} packet must be empty
34988 (@pxref{qXfer read}).
34990 Targets which maintain a list of libraries in the program's memory do
34991 not need to implement this packet; it is designed for platforms where
34992 the operating system manages the list of loaded libraries.
34994 This packet is not probed by default; the remote stub must request it,
34995 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34997 @item qXfer:memory-map:read::@var{offset},@var{length}
34998 @anchor{qXfer memory map read}
34999 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
35000 annex part of the generic @samp{qXfer} packet must be empty
35001 (@pxref{qXfer read}).
35003 This packet is not probed by default; the remote stub must request it,
35004 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35006 @item qXfer:sdata:read::@var{offset},@var{length}
35007 @anchor{qXfer sdata read}
35009 Read contents of the extra collected static tracepoint marker
35010 information. The annex part of the generic @samp{qXfer} packet must
35011 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
35014 This packet is not probed by default; the remote stub must request it,
35015 by supplying an appropriate @samp{qSupported} response
35016 (@pxref{qSupported}).
35018 @item qXfer:siginfo:read::@var{offset},@var{length}
35019 @anchor{qXfer siginfo read}
35020 Read contents of the extra signal information on the target
35021 system. The annex part of the generic @samp{qXfer} packet must be
35022 empty (@pxref{qXfer read}).
35024 This packet is not probed by default; the remote stub must request it,
35025 by supplying an appropriate @samp{qSupported} response
35026 (@pxref{qSupported}).
35028 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
35029 @anchor{qXfer spu read}
35030 Read contents of an @code{spufs} file on the target system. The
35031 annex specifies which file to read; it must be of the form
35032 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
35033 in the target process, and @var{name} identifes the @code{spufs} file
35034 in that context to be accessed.
35036 This packet is not probed by default; the remote stub must request it,
35037 by supplying an appropriate @samp{qSupported} response
35038 (@pxref{qSupported}).
35040 @item qXfer:threads:read::@var{offset},@var{length}
35041 @anchor{qXfer threads read}
35042 Access the list of threads on target. @xref{Thread List Format}. The
35043 annex part of the generic @samp{qXfer} packet must be empty
35044 (@pxref{qXfer read}).
35046 This packet is not probed by default; the remote stub must request it,
35047 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35049 @item qXfer:traceframe-info:read::@var{offset},@var{length}
35050 @anchor{qXfer traceframe info read}
35052 Return a description of the current traceframe's contents.
35053 @xref{Traceframe Info Format}. The annex part of the generic
35054 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
35056 This packet is not probed by default; the remote stub must request it,
35057 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35059 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
35060 @anchor{qXfer fdpic loadmap read}
35061 Read contents of @code{loadmap}s on the target system. The
35062 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
35063 executable @code{loadmap} or interpreter @code{loadmap} to read.
35065 This packet is not probed by default; the remote stub must request it,
35066 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35068 @item qXfer:osdata:read::@var{offset},@var{length}
35069 @anchor{qXfer osdata read}
35070 Access the target's @dfn{operating system information}.
35071 @xref{Operating System Information}.
35078 Data @var{data} (@pxref{Binary Data}) has been read from the
35079 target. There may be more data at a higher address (although
35080 it is permitted to return @samp{m} even for the last valid
35081 block of data, as long as at least one byte of data was read).
35082 @var{data} may have fewer bytes than the @var{length} in the
35086 Data @var{data} (@pxref{Binary Data}) has been read from the target.
35087 There is no more data to be read. @var{data} may have fewer bytes
35088 than the @var{length} in the request.
35091 The @var{offset} in the request is at the end of the data.
35092 There is no more data to be read.
35095 The request was malformed, or @var{annex} was invalid.
35098 The offset was invalid, or there was an error encountered reading the data.
35099 @var{nn} is a hex-encoded @code{errno} value.
35102 An empty reply indicates the @var{object} string was not recognized by
35103 the stub, or that the object does not support reading.
35106 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
35107 @cindex write data into object, remote request
35108 @anchor{qXfer write}
35109 Write uninterpreted bytes into the target's special data area
35110 identified by the keyword @var{object}, starting at @var{offset} bytes
35111 into the data. @var{data}@dots{} is the binary-encoded data
35112 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
35113 is specific to @var{object}; it can supply additional details about what data
35116 Here are the specific requests of this form defined so far. All
35117 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
35118 formats, listed below.
35121 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
35122 @anchor{qXfer siginfo write}
35123 Write @var{data} to the extra signal information on the target system.
35124 The annex part of the generic @samp{qXfer} packet must be
35125 empty (@pxref{qXfer write}).
35127 This packet is not probed by default; the remote stub must request it,
35128 by supplying an appropriate @samp{qSupported} response
35129 (@pxref{qSupported}).
35131 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
35132 @anchor{qXfer spu write}
35133 Write @var{data} to an @code{spufs} file on the target system. The
35134 annex specifies which file to write; it must be of the form
35135 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
35136 in the target process, and @var{name} identifes the @code{spufs} file
35137 in that context to be accessed.
35139 This packet is not probed by default; the remote stub must request it,
35140 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35146 @var{nn} (hex encoded) is the number of bytes written.
35147 This may be fewer bytes than supplied in the request.
35150 The request was malformed, or @var{annex} was invalid.
35153 The offset was invalid, or there was an error encountered writing the data.
35154 @var{nn} is a hex-encoded @code{errno} value.
35157 An empty reply indicates the @var{object} string was not
35158 recognized by the stub, or that the object does not support writing.
35161 @item qXfer:@var{object}:@var{operation}:@dots{}
35162 Requests of this form may be added in the future. When a stub does
35163 not recognize the @var{object} keyword, or its support for
35164 @var{object} does not recognize the @var{operation} keyword, the stub
35165 must respond with an empty packet.
35167 @item qAttached:@var{pid}
35168 @cindex query attached, remote request
35169 @cindex @samp{qAttached} packet
35170 Return an indication of whether the remote server attached to an
35171 existing process or created a new process. When the multiprocess
35172 protocol extensions are supported (@pxref{multiprocess extensions}),
35173 @var{pid} is an integer in hexadecimal format identifying the target
35174 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
35175 the query packet will be simplified as @samp{qAttached}.
35177 This query is used, for example, to know whether the remote process
35178 should be detached or killed when a @value{GDBN} session is ended with
35179 the @code{quit} command.
35184 The remote server attached to an existing process.
35186 The remote server created a new process.
35188 A badly formed request or an error was encountered.
35193 @node Architecture-Specific Protocol Details
35194 @section Architecture-Specific Protocol Details
35196 This section describes how the remote protocol is applied to specific
35197 target architectures. Also see @ref{Standard Target Features}, for
35198 details of XML target descriptions for each architecture.
35202 @subsubsection Breakpoint Kinds
35204 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
35209 16-bit Thumb mode breakpoint.
35212 32-bit Thumb mode (Thumb-2) breakpoint.
35215 32-bit ARM mode breakpoint.
35221 @subsubsection Register Packet Format
35223 The following @code{g}/@code{G} packets have previously been defined.
35224 In the below, some thirty-two bit registers are transferred as
35225 sixty-four bits. Those registers should be zero/sign extended (which?)
35226 to fill the space allocated. Register bytes are transferred in target
35227 byte order. The two nibbles within a register byte are transferred
35228 most-significant - least-significant.
35234 All registers are transferred as thirty-two bit quantities in the order:
35235 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
35236 registers; fsr; fir; fp.
35240 All registers are transferred as sixty-four bit quantities (including
35241 thirty-two bit registers such as @code{sr}). The ordering is the same
35246 @node Tracepoint Packets
35247 @section Tracepoint Packets
35248 @cindex tracepoint packets
35249 @cindex packets, tracepoint
35251 Here we describe the packets @value{GDBN} uses to implement
35252 tracepoints (@pxref{Tracepoints}).
35256 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
35257 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
35258 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
35259 the tracepoint is disabled. @var{step} is the tracepoint's step
35260 count, and @var{pass} is its pass count. If an @samp{F} is present,
35261 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
35262 the number of bytes that the target should copy elsewhere to make room
35263 for the tracepoint. If an @samp{X} is present, it introduces a
35264 tracepoint condition, which consists of a hexadecimal length, followed
35265 by a comma and hex-encoded bytes, in a manner similar to action
35266 encodings as described below. If the trailing @samp{-} is present,
35267 further @samp{QTDP} packets will follow to specify this tracepoint's
35273 The packet was understood and carried out.
35275 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
35277 The packet was not recognized.
35280 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
35281 Define actions to be taken when a tracepoint is hit. @var{n} and
35282 @var{addr} must be the same as in the initial @samp{QTDP} packet for
35283 this tracepoint. This packet may only be sent immediately after
35284 another @samp{QTDP} packet that ended with a @samp{-}. If the
35285 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
35286 specifying more actions for this tracepoint.
35288 In the series of action packets for a given tracepoint, at most one
35289 can have an @samp{S} before its first @var{action}. If such a packet
35290 is sent, it and the following packets define ``while-stepping''
35291 actions. Any prior packets define ordinary actions --- that is, those
35292 taken when the tracepoint is first hit. If no action packet has an
35293 @samp{S}, then all the packets in the series specify ordinary
35294 tracepoint actions.
35296 The @samp{@var{action}@dots{}} portion of the packet is a series of
35297 actions, concatenated without separators. Each action has one of the
35303 Collect the registers whose bits are set in @var{mask}. @var{mask} is
35304 a hexadecimal number whose @var{i}'th bit is set if register number
35305 @var{i} should be collected. (The least significant bit is numbered
35306 zero.) Note that @var{mask} may be any number of digits long; it may
35307 not fit in a 32-bit word.
35309 @item M @var{basereg},@var{offset},@var{len}
35310 Collect @var{len} bytes of memory starting at the address in register
35311 number @var{basereg}, plus @var{offset}. If @var{basereg} is
35312 @samp{-1}, then the range has a fixed address: @var{offset} is the
35313 address of the lowest byte to collect. The @var{basereg},
35314 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
35315 values (the @samp{-1} value for @var{basereg} is a special case).
35317 @item X @var{len},@var{expr}
35318 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
35319 it directs. @var{expr} is an agent expression, as described in
35320 @ref{Agent Expressions}. Each byte of the expression is encoded as a
35321 two-digit hex number in the packet; @var{len} is the number of bytes
35322 in the expression (and thus one-half the number of hex digits in the
35327 Any number of actions may be packed together in a single @samp{QTDP}
35328 packet, as long as the packet does not exceed the maximum packet
35329 length (400 bytes, for many stubs). There may be only one @samp{R}
35330 action per tracepoint, and it must precede any @samp{M} or @samp{X}
35331 actions. Any registers referred to by @samp{M} and @samp{X} actions
35332 must be collected by a preceding @samp{R} action. (The
35333 ``while-stepping'' actions are treated as if they were attached to a
35334 separate tracepoint, as far as these restrictions are concerned.)
35339 The packet was understood and carried out.
35341 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
35343 The packet was not recognized.
35346 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
35347 @cindex @samp{QTDPsrc} packet
35348 Specify a source string of tracepoint @var{n} at address @var{addr}.
35349 This is useful to get accurate reproduction of the tracepoints
35350 originally downloaded at the beginning of the trace run. @var{type}
35351 is the name of the tracepoint part, such as @samp{cond} for the
35352 tracepoint's conditional expression (see below for a list of types), while
35353 @var{bytes} is the string, encoded in hexadecimal.
35355 @var{start} is the offset of the @var{bytes} within the overall source
35356 string, while @var{slen} is the total length of the source string.
35357 This is intended for handling source strings that are longer than will
35358 fit in a single packet.
35359 @c Add detailed example when this info is moved into a dedicated
35360 @c tracepoint descriptions section.
35362 The available string types are @samp{at} for the location,
35363 @samp{cond} for the conditional, and @samp{cmd} for an action command.
35364 @value{GDBN} sends a separate packet for each command in the action
35365 list, in the same order in which the commands are stored in the list.
35367 The target does not need to do anything with source strings except
35368 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
35371 Although this packet is optional, and @value{GDBN} will only send it
35372 if the target replies with @samp{TracepointSource} @xref{General
35373 Query Packets}, it makes both disconnected tracing and trace files
35374 much easier to use. Otherwise the user must be careful that the
35375 tracepoints in effect while looking at trace frames are identical to
35376 the ones in effect during the trace run; even a small discrepancy
35377 could cause @samp{tdump} not to work, or a particular trace frame not
35380 @item QTDV:@var{n}:@var{value}
35381 @cindex define trace state variable, remote request
35382 @cindex @samp{QTDV} packet
35383 Create a new trace state variable, number @var{n}, with an initial
35384 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
35385 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
35386 the option of not using this packet for initial values of zero; the
35387 target should simply create the trace state variables as they are
35388 mentioned in expressions.
35390 @item QTFrame:@var{n}
35391 Select the @var{n}'th tracepoint frame from the buffer, and use the
35392 register and memory contents recorded there to answer subsequent
35393 request packets from @value{GDBN}.
35395 A successful reply from the stub indicates that the stub has found the
35396 requested frame. The response is a series of parts, concatenated
35397 without separators, describing the frame we selected. Each part has
35398 one of the following forms:
35402 The selected frame is number @var{n} in the trace frame buffer;
35403 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
35404 was no frame matching the criteria in the request packet.
35407 The selected trace frame records a hit of tracepoint number @var{t};
35408 @var{t} is a hexadecimal number.
35412 @item QTFrame:pc:@var{addr}
35413 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
35414 currently selected frame whose PC is @var{addr};
35415 @var{addr} is a hexadecimal number.
35417 @item QTFrame:tdp:@var{t}
35418 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
35419 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
35420 is a hexadecimal number.
35422 @item QTFrame:range:@var{start}:@var{end}
35423 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
35424 currently selected frame whose PC is between @var{start} (inclusive)
35425 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
35428 @item QTFrame:outside:@var{start}:@var{end}
35429 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
35430 frame @emph{outside} the given range of addresses (exclusive).
35433 Begin the tracepoint experiment. Begin collecting data from
35434 tracepoint hits in the trace frame buffer. This packet supports the
35435 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
35436 instruction reply packet}).
35439 End the tracepoint experiment. Stop collecting trace frames.
35441 @item QTEnable:@var{n}:@var{addr}
35443 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
35444 experiment. If the tracepoint was previously disabled, then collection
35445 of data from it will resume.
35447 @item QTDisable:@var{n}:@var{addr}
35449 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
35450 experiment. No more data will be collected from the tracepoint unless
35451 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
35454 Clear the table of tracepoints, and empty the trace frame buffer.
35456 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
35457 Establish the given ranges of memory as ``transparent''. The stub
35458 will answer requests for these ranges from memory's current contents,
35459 if they were not collected as part of the tracepoint hit.
35461 @value{GDBN} uses this to mark read-only regions of memory, like those
35462 containing program code. Since these areas never change, they should
35463 still have the same contents they did when the tracepoint was hit, so
35464 there's no reason for the stub to refuse to provide their contents.
35466 @item QTDisconnected:@var{value}
35467 Set the choice to what to do with the tracing run when @value{GDBN}
35468 disconnects from the target. A @var{value} of 1 directs the target to
35469 continue the tracing run, while 0 tells the target to stop tracing if
35470 @value{GDBN} is no longer in the picture.
35473 Ask the stub if there is a trace experiment running right now.
35475 The reply has the form:
35479 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
35480 @var{running} is a single digit @code{1} if the trace is presently
35481 running, or @code{0} if not. It is followed by semicolon-separated
35482 optional fields that an agent may use to report additional status.
35486 If the trace is not running, the agent may report any of several
35487 explanations as one of the optional fields:
35492 No trace has been run yet.
35495 The trace was stopped by a user-originated stop command.
35498 The trace stopped because the trace buffer filled up.
35500 @item tdisconnected:0
35501 The trace stopped because @value{GDBN} disconnected from the target.
35503 @item tpasscount:@var{tpnum}
35504 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
35506 @item terror:@var{text}:@var{tpnum}
35507 The trace stopped because tracepoint @var{tpnum} had an error. The
35508 string @var{text} is available to describe the nature of the error
35509 (for instance, a divide by zero in the condition expression).
35510 @var{text} is hex encoded.
35513 The trace stopped for some other reason.
35517 Additional optional fields supply statistical and other information.
35518 Although not required, they are extremely useful for users monitoring
35519 the progress of a trace run. If a trace has stopped, and these
35520 numbers are reported, they must reflect the state of the just-stopped
35525 @item tframes:@var{n}
35526 The number of trace frames in the buffer.
35528 @item tcreated:@var{n}
35529 The total number of trace frames created during the run. This may
35530 be larger than the trace frame count, if the buffer is circular.
35532 @item tsize:@var{n}
35533 The total size of the trace buffer, in bytes.
35535 @item tfree:@var{n}
35536 The number of bytes still unused in the buffer.
35538 @item circular:@var{n}
35539 The value of the circular trace buffer flag. @code{1} means that the
35540 trace buffer is circular and old trace frames will be discarded if
35541 necessary to make room, @code{0} means that the trace buffer is linear
35544 @item disconn:@var{n}
35545 The value of the disconnected tracing flag. @code{1} means that
35546 tracing will continue after @value{GDBN} disconnects, @code{0} means
35547 that the trace run will stop.
35551 @item qTV:@var{var}
35552 @cindex trace state variable value, remote request
35553 @cindex @samp{qTV} packet
35554 Ask the stub for the value of the trace state variable number @var{var}.
35559 The value of the variable is @var{value}. This will be the current
35560 value of the variable if the user is examining a running target, or a
35561 saved value if the variable was collected in the trace frame that the
35562 user is looking at. Note that multiple requests may result in
35563 different reply values, such as when requesting values while the
35564 program is running.
35567 The value of the variable is unknown. This would occur, for example,
35568 if the user is examining a trace frame in which the requested variable
35574 These packets request data about tracepoints that are being used by
35575 the target. @value{GDBN} sends @code{qTfP} to get the first piece
35576 of data, and multiple @code{qTsP} to get additional pieces. Replies
35577 to these packets generally take the form of the @code{QTDP} packets
35578 that define tracepoints. (FIXME add detailed syntax)
35582 These packets request data about trace state variables that are on the
35583 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
35584 and multiple @code{qTsV} to get additional variables. Replies to
35585 these packets follow the syntax of the @code{QTDV} packets that define
35586 trace state variables.
35590 These packets request data about static tracepoint markers that exist
35591 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
35592 first piece of data, and multiple @code{qTsSTM} to get additional
35593 pieces. Replies to these packets take the following form:
35597 @item m @var{address}:@var{id}:@var{extra}
35599 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
35600 a comma-separated list of markers
35602 (lower case letter @samp{L}) denotes end of list.
35604 An error occurred. @var{nn} are hex digits.
35606 An empty reply indicates that the request is not supported by the
35610 @var{address} is encoded in hex.
35611 @var{id} and @var{extra} are strings encoded in hex.
35613 In response to each query, the target will reply with a list of one or
35614 more markers, separated by commas. @value{GDBN} will respond to each
35615 reply with a request for more markers (using the @samp{qs} form of the
35616 query), until the target responds with @samp{l} (lower-case ell, for
35619 @item qTSTMat:@var{address}
35620 This packets requests data about static tracepoint markers in the
35621 target program at @var{address}. Replies to this packet follow the
35622 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
35623 tracepoint markers.
35625 @item QTSave:@var{filename}
35626 This packet directs the target to save trace data to the file name
35627 @var{filename} in the target's filesystem. @var{filename} is encoded
35628 as a hex string; the interpretation of the file name (relative vs
35629 absolute, wild cards, etc) is up to the target.
35631 @item qTBuffer:@var{offset},@var{len}
35632 Return up to @var{len} bytes of the current contents of trace buffer,
35633 starting at @var{offset}. The trace buffer is treated as if it were
35634 a contiguous collection of traceframes, as per the trace file format.
35635 The reply consists as many hex-encoded bytes as the target can deliver
35636 in a packet; it is not an error to return fewer than were asked for.
35637 A reply consisting of just @code{l} indicates that no bytes are
35640 @item QTBuffer:circular:@var{value}
35641 This packet directs the target to use a circular trace buffer if
35642 @var{value} is 1, or a linear buffer if the value is 0.
35646 @subsection Relocate instruction reply packet
35647 When installing fast tracepoints in memory, the target may need to
35648 relocate the instruction currently at the tracepoint address to a
35649 different address in memory. For most instructions, a simple copy is
35650 enough, but, for example, call instructions that implicitly push the
35651 return address on the stack, and relative branches or other
35652 PC-relative instructions require offset adjustment, so that the effect
35653 of executing the instruction at a different address is the same as if
35654 it had executed in the original location.
35656 In response to several of the tracepoint packets, the target may also
35657 respond with a number of intermediate @samp{qRelocInsn} request
35658 packets before the final result packet, to have @value{GDBN} handle
35659 this relocation operation. If a packet supports this mechanism, its
35660 documentation will explicitly say so. See for example the above
35661 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
35662 format of the request is:
35665 @item qRelocInsn:@var{from};@var{to}
35667 This requests @value{GDBN} to copy instruction at address @var{from}
35668 to address @var{to}, possibly adjusted so that executing the
35669 instruction at @var{to} has the same effect as executing it at
35670 @var{from}. @value{GDBN} writes the adjusted instruction to target
35671 memory starting at @var{to}.
35676 @item qRelocInsn:@var{adjusted_size}
35677 Informs the stub the relocation is complete. @var{adjusted_size} is
35678 the length in bytes of resulting relocated instruction sequence.
35680 A badly formed request was detected, or an error was encountered while
35681 relocating the instruction.
35684 @node Host I/O Packets
35685 @section Host I/O Packets
35686 @cindex Host I/O, remote protocol
35687 @cindex file transfer, remote protocol
35689 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
35690 operations on the far side of a remote link. For example, Host I/O is
35691 used to upload and download files to a remote target with its own
35692 filesystem. Host I/O uses the same constant values and data structure
35693 layout as the target-initiated File-I/O protocol. However, the
35694 Host I/O packets are structured differently. The target-initiated
35695 protocol relies on target memory to store parameters and buffers.
35696 Host I/O requests are initiated by @value{GDBN}, and the
35697 target's memory is not involved. @xref{File-I/O Remote Protocol
35698 Extension}, for more details on the target-initiated protocol.
35700 The Host I/O request packets all encode a single operation along with
35701 its arguments. They have this format:
35705 @item vFile:@var{operation}: @var{parameter}@dots{}
35706 @var{operation} is the name of the particular request; the target
35707 should compare the entire packet name up to the second colon when checking
35708 for a supported operation. The format of @var{parameter} depends on
35709 the operation. Numbers are always passed in hexadecimal. Negative
35710 numbers have an explicit minus sign (i.e.@: two's complement is not
35711 used). Strings (e.g.@: filenames) are encoded as a series of
35712 hexadecimal bytes. The last argument to a system call may be a
35713 buffer of escaped binary data (@pxref{Binary Data}).
35717 The valid responses to Host I/O packets are:
35721 @item F @var{result} [, @var{errno}] [; @var{attachment}]
35722 @var{result} is the integer value returned by this operation, usually
35723 non-negative for success and -1 for errors. If an error has occured,
35724 @var{errno} will be included in the result. @var{errno} will have a
35725 value defined by the File-I/O protocol (@pxref{Errno Values}). For
35726 operations which return data, @var{attachment} supplies the data as a
35727 binary buffer. Binary buffers in response packets are escaped in the
35728 normal way (@pxref{Binary Data}). See the individual packet
35729 documentation for the interpretation of @var{result} and
35733 An empty response indicates that this operation is not recognized.
35737 These are the supported Host I/O operations:
35740 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
35741 Open a file at @var{pathname} and return a file descriptor for it, or
35742 return -1 if an error occurs. @var{pathname} is a string,
35743 @var{flags} is an integer indicating a mask of open flags
35744 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
35745 of mode bits to use if the file is created (@pxref{mode_t Values}).
35746 @xref{open}, for details of the open flags and mode values.
35748 @item vFile:close: @var{fd}
35749 Close the open file corresponding to @var{fd} and return 0, or
35750 -1 if an error occurs.
35752 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
35753 Read data from the open file corresponding to @var{fd}. Up to
35754 @var{count} bytes will be read from the file, starting at @var{offset}
35755 relative to the start of the file. The target may read fewer bytes;
35756 common reasons include packet size limits and an end-of-file
35757 condition. The number of bytes read is returned. Zero should only be
35758 returned for a successful read at the end of the file, or if
35759 @var{count} was zero.
35761 The data read should be returned as a binary attachment on success.
35762 If zero bytes were read, the response should include an empty binary
35763 attachment (i.e.@: a trailing semicolon). The return value is the
35764 number of target bytes read; the binary attachment may be longer if
35765 some characters were escaped.
35767 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
35768 Write @var{data} (a binary buffer) to the open file corresponding
35769 to @var{fd}. Start the write at @var{offset} from the start of the
35770 file. Unlike many @code{write} system calls, there is no
35771 separate @var{count} argument; the length of @var{data} in the
35772 packet is used. @samp{vFile:write} returns the number of bytes written,
35773 which may be shorter than the length of @var{data}, or -1 if an
35776 @item vFile:unlink: @var{pathname}
35777 Delete the file at @var{pathname} on the target. Return 0,
35778 or -1 if an error occurs. @var{pathname} is a string.
35783 @section Interrupts
35784 @cindex interrupts (remote protocol)
35786 When a program on the remote target is running, @value{GDBN} may
35787 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
35788 a @code{BREAK} followed by @code{g},
35789 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
35791 The precise meaning of @code{BREAK} is defined by the transport
35792 mechanism and may, in fact, be undefined. @value{GDBN} does not
35793 currently define a @code{BREAK} mechanism for any of the network
35794 interfaces except for TCP, in which case @value{GDBN} sends the
35795 @code{telnet} BREAK sequence.
35797 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
35798 transport mechanisms. It is represented by sending the single byte
35799 @code{0x03} without any of the usual packet overhead described in
35800 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
35801 transmitted as part of a packet, it is considered to be packet data
35802 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
35803 (@pxref{X packet}), used for binary downloads, may include an unescaped
35804 @code{0x03} as part of its packet.
35806 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
35807 When Linux kernel receives this sequence from serial port,
35808 it stops execution and connects to gdb.
35810 Stubs are not required to recognize these interrupt mechanisms and the
35811 precise meaning associated with receipt of the interrupt is
35812 implementation defined. If the target supports debugging of multiple
35813 threads and/or processes, it should attempt to interrupt all
35814 currently-executing threads and processes.
35815 If the stub is successful at interrupting the
35816 running program, it should send one of the stop
35817 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
35818 of successfully stopping the program in all-stop mode, and a stop reply
35819 for each stopped thread in non-stop mode.
35820 Interrupts received while the
35821 program is stopped are discarded.
35823 @node Notification Packets
35824 @section Notification Packets
35825 @cindex notification packets
35826 @cindex packets, notification
35828 The @value{GDBN} remote serial protocol includes @dfn{notifications},
35829 packets that require no acknowledgment. Both the GDB and the stub
35830 may send notifications (although the only notifications defined at
35831 present are sent by the stub). Notifications carry information
35832 without incurring the round-trip latency of an acknowledgment, and so
35833 are useful for low-impact communications where occasional packet loss
35836 A notification packet has the form @samp{% @var{data} #
35837 @var{checksum}}, where @var{data} is the content of the notification,
35838 and @var{checksum} is a checksum of @var{data}, computed and formatted
35839 as for ordinary @value{GDBN} packets. A notification's @var{data}
35840 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
35841 receiving a notification, the recipient sends no @samp{+} or @samp{-}
35842 to acknowledge the notification's receipt or to report its corruption.
35844 Every notification's @var{data} begins with a name, which contains no
35845 colon characters, followed by a colon character.
35847 Recipients should silently ignore corrupted notifications and
35848 notifications they do not understand. Recipients should restart
35849 timeout periods on receipt of a well-formed notification, whether or
35850 not they understand it.
35852 Senders should only send the notifications described here when this
35853 protocol description specifies that they are permitted. In the
35854 future, we may extend the protocol to permit existing notifications in
35855 new contexts; this rule helps older senders avoid confusing newer
35858 (Older versions of @value{GDBN} ignore bytes received until they see
35859 the @samp{$} byte that begins an ordinary packet, so new stubs may
35860 transmit notifications without fear of confusing older clients. There
35861 are no notifications defined for @value{GDBN} to send at the moment, but we
35862 assume that most older stubs would ignore them, as well.)
35864 The following notification packets from the stub to @value{GDBN} are
35868 @item Stop: @var{reply}
35869 Report an asynchronous stop event in non-stop mode.
35870 The @var{reply} has the form of a stop reply, as
35871 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
35872 for information on how these notifications are acknowledged by
35876 @node Remote Non-Stop
35877 @section Remote Protocol Support for Non-Stop Mode
35879 @value{GDBN}'s remote protocol supports non-stop debugging of
35880 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
35881 supports non-stop mode, it should report that to @value{GDBN} by including
35882 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
35884 @value{GDBN} typically sends a @samp{QNonStop} packet only when
35885 establishing a new connection with the stub. Entering non-stop mode
35886 does not alter the state of any currently-running threads, but targets
35887 must stop all threads in any already-attached processes when entering
35888 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
35889 probe the target state after a mode change.
35891 In non-stop mode, when an attached process encounters an event that
35892 would otherwise be reported with a stop reply, it uses the
35893 asynchronous notification mechanism (@pxref{Notification Packets}) to
35894 inform @value{GDBN}. In contrast to all-stop mode, where all threads
35895 in all processes are stopped when a stop reply is sent, in non-stop
35896 mode only the thread reporting the stop event is stopped. That is,
35897 when reporting a @samp{S} or @samp{T} response to indicate completion
35898 of a step operation, hitting a breakpoint, or a fault, only the
35899 affected thread is stopped; any other still-running threads continue
35900 to run. When reporting a @samp{W} or @samp{X} response, all running
35901 threads belonging to other attached processes continue to run.
35903 Only one stop reply notification at a time may be pending; if
35904 additional stop events occur before @value{GDBN} has acknowledged the
35905 previous notification, they must be queued by the stub for later
35906 synchronous transmission in response to @samp{vStopped} packets from
35907 @value{GDBN}. Because the notification mechanism is unreliable,
35908 the stub is permitted to resend a stop reply notification
35909 if it believes @value{GDBN} may not have received it. @value{GDBN}
35910 ignores additional stop reply notifications received before it has
35911 finished processing a previous notification and the stub has completed
35912 sending any queued stop events.
35914 Otherwise, @value{GDBN} must be prepared to receive a stop reply
35915 notification at any time. Specifically, they may appear when
35916 @value{GDBN} is not otherwise reading input from the stub, or when
35917 @value{GDBN} is expecting to read a normal synchronous response or a
35918 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
35919 Notification packets are distinct from any other communication from
35920 the stub so there is no ambiguity.
35922 After receiving a stop reply notification, @value{GDBN} shall
35923 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
35924 as a regular, synchronous request to the stub. Such acknowledgment
35925 is not required to happen immediately, as @value{GDBN} is permitted to
35926 send other, unrelated packets to the stub first, which the stub should
35929 Upon receiving a @samp{vStopped} packet, if the stub has other queued
35930 stop events to report to @value{GDBN}, it shall respond by sending a
35931 normal stop reply response. @value{GDBN} shall then send another
35932 @samp{vStopped} packet to solicit further responses; again, it is
35933 permitted to send other, unrelated packets as well which the stub
35934 should process normally.
35936 If the stub receives a @samp{vStopped} packet and there are no
35937 additional stop events to report, the stub shall return an @samp{OK}
35938 response. At this point, if further stop events occur, the stub shall
35939 send a new stop reply notification, @value{GDBN} shall accept the
35940 notification, and the process shall be repeated.
35942 In non-stop mode, the target shall respond to the @samp{?} packet as
35943 follows. First, any incomplete stop reply notification/@samp{vStopped}
35944 sequence in progress is abandoned. The target must begin a new
35945 sequence reporting stop events for all stopped threads, whether or not
35946 it has previously reported those events to @value{GDBN}. The first
35947 stop reply is sent as a synchronous reply to the @samp{?} packet, and
35948 subsequent stop replies are sent as responses to @samp{vStopped} packets
35949 using the mechanism described above. The target must not send
35950 asynchronous stop reply notifications until the sequence is complete.
35951 If all threads are running when the target receives the @samp{?} packet,
35952 or if the target is not attached to any process, it shall respond
35955 @node Packet Acknowledgment
35956 @section Packet Acknowledgment
35958 @cindex acknowledgment, for @value{GDBN} remote
35959 @cindex packet acknowledgment, for @value{GDBN} remote
35960 By default, when either the host or the target machine receives a packet,
35961 the first response expected is an acknowledgment: either @samp{+} (to indicate
35962 the package was received correctly) or @samp{-} (to request retransmission).
35963 This mechanism allows the @value{GDBN} remote protocol to operate over
35964 unreliable transport mechanisms, such as a serial line.
35966 In cases where the transport mechanism is itself reliable (such as a pipe or
35967 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
35968 It may be desirable to disable them in that case to reduce communication
35969 overhead, or for other reasons. This can be accomplished by means of the
35970 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
35972 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
35973 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
35974 and response format still includes the normal checksum, as described in
35975 @ref{Overview}, but the checksum may be ignored by the receiver.
35977 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
35978 no-acknowledgment mode, it should report that to @value{GDBN}
35979 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
35980 @pxref{qSupported}.
35981 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
35982 disabled via the @code{set remote noack-packet off} command
35983 (@pxref{Remote Configuration}),
35984 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
35985 Only then may the stub actually turn off packet acknowledgments.
35986 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
35987 response, which can be safely ignored by the stub.
35989 Note that @code{set remote noack-packet} command only affects negotiation
35990 between @value{GDBN} and the stub when subsequent connections are made;
35991 it does not affect the protocol acknowledgment state for any current
35993 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
35994 new connection is established,
35995 there is also no protocol request to re-enable the acknowledgments
35996 for the current connection, once disabled.
36001 Example sequence of a target being re-started. Notice how the restart
36002 does not get any direct output:
36007 @emph{target restarts}
36010 <- @code{T001:1234123412341234}
36014 Example sequence of a target being stepped by a single instruction:
36017 -> @code{G1445@dots{}}
36022 <- @code{T001:1234123412341234}
36026 <- @code{1455@dots{}}
36030 @node File-I/O Remote Protocol Extension
36031 @section File-I/O Remote Protocol Extension
36032 @cindex File-I/O remote protocol extension
36035 * File-I/O Overview::
36036 * Protocol Basics::
36037 * The F Request Packet::
36038 * The F Reply Packet::
36039 * The Ctrl-C Message::
36041 * List of Supported Calls::
36042 * Protocol-specific Representation of Datatypes::
36044 * File-I/O Examples::
36047 @node File-I/O Overview
36048 @subsection File-I/O Overview
36049 @cindex file-i/o overview
36051 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
36052 target to use the host's file system and console I/O to perform various
36053 system calls. System calls on the target system are translated into a
36054 remote protocol packet to the host system, which then performs the needed
36055 actions and returns a response packet to the target system.
36056 This simulates file system operations even on targets that lack file systems.
36058 The protocol is defined to be independent of both the host and target systems.
36059 It uses its own internal representation of datatypes and values. Both
36060 @value{GDBN} and the target's @value{GDBN} stub are responsible for
36061 translating the system-dependent value representations into the internal
36062 protocol representations when data is transmitted.
36064 The communication is synchronous. A system call is possible only when
36065 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
36066 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
36067 the target is stopped to allow deterministic access to the target's
36068 memory. Therefore File-I/O is not interruptible by target signals. On
36069 the other hand, it is possible to interrupt File-I/O by a user interrupt
36070 (@samp{Ctrl-C}) within @value{GDBN}.
36072 The target's request to perform a host system call does not finish
36073 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
36074 after finishing the system call, the target returns to continuing the
36075 previous activity (continue, step). No additional continue or step
36076 request from @value{GDBN} is required.
36079 (@value{GDBP}) continue
36080 <- target requests 'system call X'
36081 target is stopped, @value{GDBN} executes system call
36082 -> @value{GDBN} returns result
36083 ... target continues, @value{GDBN} returns to wait for the target
36084 <- target hits breakpoint and sends a Txx packet
36087 The protocol only supports I/O on the console and to regular files on
36088 the host file system. Character or block special devices, pipes,
36089 named pipes, sockets or any other communication method on the host
36090 system are not supported by this protocol.
36092 File I/O is not supported in non-stop mode.
36094 @node Protocol Basics
36095 @subsection Protocol Basics
36096 @cindex protocol basics, file-i/o
36098 The File-I/O protocol uses the @code{F} packet as the request as well
36099 as reply packet. Since a File-I/O system call can only occur when
36100 @value{GDBN} is waiting for a response from the continuing or stepping target,
36101 the File-I/O request is a reply that @value{GDBN} has to expect as a result
36102 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
36103 This @code{F} packet contains all information needed to allow @value{GDBN}
36104 to call the appropriate host system call:
36108 A unique identifier for the requested system call.
36111 All parameters to the system call. Pointers are given as addresses
36112 in the target memory address space. Pointers to strings are given as
36113 pointer/length pair. Numerical values are given as they are.
36114 Numerical control flags are given in a protocol-specific representation.
36118 At this point, @value{GDBN} has to perform the following actions.
36122 If the parameters include pointer values to data needed as input to a
36123 system call, @value{GDBN} requests this data from the target with a
36124 standard @code{m} packet request. This additional communication has to be
36125 expected by the target implementation and is handled as any other @code{m}
36129 @value{GDBN} translates all value from protocol representation to host
36130 representation as needed. Datatypes are coerced into the host types.
36133 @value{GDBN} calls the system call.
36136 It then coerces datatypes back to protocol representation.
36139 If the system call is expected to return data in buffer space specified
36140 by pointer parameters to the call, the data is transmitted to the
36141 target using a @code{M} or @code{X} packet. This packet has to be expected
36142 by the target implementation and is handled as any other @code{M} or @code{X}
36147 Eventually @value{GDBN} replies with another @code{F} packet which contains all
36148 necessary information for the target to continue. This at least contains
36155 @code{errno}, if has been changed by the system call.
36162 After having done the needed type and value coercion, the target continues
36163 the latest continue or step action.
36165 @node The F Request Packet
36166 @subsection The @code{F} Request Packet
36167 @cindex file-i/o request packet
36168 @cindex @code{F} request packet
36170 The @code{F} request packet has the following format:
36173 @item F@var{call-id},@var{parameter@dots{}}
36175 @var{call-id} is the identifier to indicate the host system call to be called.
36176 This is just the name of the function.
36178 @var{parameter@dots{}} are the parameters to the system call.
36179 Parameters are hexadecimal integer values, either the actual values in case
36180 of scalar datatypes, pointers to target buffer space in case of compound
36181 datatypes and unspecified memory areas, or pointer/length pairs in case
36182 of string parameters. These are appended to the @var{call-id} as a
36183 comma-delimited list. All values are transmitted in ASCII
36184 string representation, pointer/length pairs separated by a slash.
36190 @node The F Reply Packet
36191 @subsection The @code{F} Reply Packet
36192 @cindex file-i/o reply packet
36193 @cindex @code{F} reply packet
36195 The @code{F} reply packet has the following format:
36199 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
36201 @var{retcode} is the return code of the system call as hexadecimal value.
36203 @var{errno} is the @code{errno} set by the call, in protocol-specific
36205 This parameter can be omitted if the call was successful.
36207 @var{Ctrl-C flag} is only sent if the user requested a break. In this
36208 case, @var{errno} must be sent as well, even if the call was successful.
36209 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
36216 or, if the call was interrupted before the host call has been performed:
36223 assuming 4 is the protocol-specific representation of @code{EINTR}.
36228 @node The Ctrl-C Message
36229 @subsection The @samp{Ctrl-C} Message
36230 @cindex ctrl-c message, in file-i/o protocol
36232 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
36233 reply packet (@pxref{The F Reply Packet}),
36234 the target should behave as if it had
36235 gotten a break message. The meaning for the target is ``system call
36236 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
36237 (as with a break message) and return to @value{GDBN} with a @code{T02}
36240 It's important for the target to know in which
36241 state the system call was interrupted. There are two possible cases:
36245 The system call hasn't been performed on the host yet.
36248 The system call on the host has been finished.
36252 These two states can be distinguished by the target by the value of the
36253 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
36254 call hasn't been performed. This is equivalent to the @code{EINTR} handling
36255 on POSIX systems. In any other case, the target may presume that the
36256 system call has been finished --- successfully or not --- and should behave
36257 as if the break message arrived right after the system call.
36259 @value{GDBN} must behave reliably. If the system call has not been called
36260 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
36261 @code{errno} in the packet. If the system call on the host has been finished
36262 before the user requests a break, the full action must be finished by
36263 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
36264 The @code{F} packet may only be sent when either nothing has happened
36265 or the full action has been completed.
36268 @subsection Console I/O
36269 @cindex console i/o as part of file-i/o
36271 By default and if not explicitly closed by the target system, the file
36272 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
36273 on the @value{GDBN} console is handled as any other file output operation
36274 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
36275 by @value{GDBN} so that after the target read request from file descriptor
36276 0 all following typing is buffered until either one of the following
36281 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
36283 system call is treated as finished.
36286 The user presses @key{RET}. This is treated as end of input with a trailing
36290 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
36291 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
36295 If the user has typed more characters than fit in the buffer given to
36296 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
36297 either another @code{read(0, @dots{})} is requested by the target, or debugging
36298 is stopped at the user's request.
36301 @node List of Supported Calls
36302 @subsection List of Supported Calls
36303 @cindex list of supported file-i/o calls
36320 @unnumberedsubsubsec open
36321 @cindex open, file-i/o system call
36326 int open(const char *pathname, int flags);
36327 int open(const char *pathname, int flags, mode_t mode);
36331 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
36334 @var{flags} is the bitwise @code{OR} of the following values:
36338 If the file does not exist it will be created. The host
36339 rules apply as far as file ownership and time stamps
36343 When used with @code{O_CREAT}, if the file already exists it is
36344 an error and open() fails.
36347 If the file already exists and the open mode allows
36348 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
36349 truncated to zero length.
36352 The file is opened in append mode.
36355 The file is opened for reading only.
36358 The file is opened for writing only.
36361 The file is opened for reading and writing.
36365 Other bits are silently ignored.
36369 @var{mode} is the bitwise @code{OR} of the following values:
36373 User has read permission.
36376 User has write permission.
36379 Group has read permission.
36382 Group has write permission.
36385 Others have read permission.
36388 Others have write permission.
36392 Other bits are silently ignored.
36395 @item Return value:
36396 @code{open} returns the new file descriptor or -1 if an error
36403 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
36406 @var{pathname} refers to a directory.
36409 The requested access is not allowed.
36412 @var{pathname} was too long.
36415 A directory component in @var{pathname} does not exist.
36418 @var{pathname} refers to a device, pipe, named pipe or socket.
36421 @var{pathname} refers to a file on a read-only filesystem and
36422 write access was requested.
36425 @var{pathname} is an invalid pointer value.
36428 No space on device to create the file.
36431 The process already has the maximum number of files open.
36434 The limit on the total number of files open on the system
36438 The call was interrupted by the user.
36444 @unnumberedsubsubsec close
36445 @cindex close, file-i/o system call
36454 @samp{Fclose,@var{fd}}
36456 @item Return value:
36457 @code{close} returns zero on success, or -1 if an error occurred.
36463 @var{fd} isn't a valid open file descriptor.
36466 The call was interrupted by the user.
36472 @unnumberedsubsubsec read
36473 @cindex read, file-i/o system call
36478 int read(int fd, void *buf, unsigned int count);
36482 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
36484 @item Return value:
36485 On success, the number of bytes read is returned.
36486 Zero indicates end of file. If count is zero, read
36487 returns zero as well. On error, -1 is returned.
36493 @var{fd} is not a valid file descriptor or is not open for
36497 @var{bufptr} is an invalid pointer value.
36500 The call was interrupted by the user.
36506 @unnumberedsubsubsec write
36507 @cindex write, file-i/o system call
36512 int write(int fd, const void *buf, unsigned int count);
36516 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
36518 @item Return value:
36519 On success, the number of bytes written are returned.
36520 Zero indicates nothing was written. On error, -1
36527 @var{fd} is not a valid file descriptor or is not open for
36531 @var{bufptr} is an invalid pointer value.
36534 An attempt was made to write a file that exceeds the
36535 host-specific maximum file size allowed.
36538 No space on device to write the data.
36541 The call was interrupted by the user.
36547 @unnumberedsubsubsec lseek
36548 @cindex lseek, file-i/o system call
36553 long lseek (int fd, long offset, int flag);
36557 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
36559 @var{flag} is one of:
36563 The offset is set to @var{offset} bytes.
36566 The offset is set to its current location plus @var{offset}
36570 The offset is set to the size of the file plus @var{offset}
36574 @item Return value:
36575 On success, the resulting unsigned offset in bytes from
36576 the beginning of the file is returned. Otherwise, a
36577 value of -1 is returned.
36583 @var{fd} is not a valid open file descriptor.
36586 @var{fd} is associated with the @value{GDBN} console.
36589 @var{flag} is not a proper value.
36592 The call was interrupted by the user.
36598 @unnumberedsubsubsec rename
36599 @cindex rename, file-i/o system call
36604 int rename(const char *oldpath, const char *newpath);
36608 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
36610 @item Return value:
36611 On success, zero is returned. On error, -1 is returned.
36617 @var{newpath} is an existing directory, but @var{oldpath} is not a
36621 @var{newpath} is a non-empty directory.
36624 @var{oldpath} or @var{newpath} is a directory that is in use by some
36628 An attempt was made to make a directory a subdirectory
36632 A component used as a directory in @var{oldpath} or new
36633 path is not a directory. Or @var{oldpath} is a directory
36634 and @var{newpath} exists but is not a directory.
36637 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
36640 No access to the file or the path of the file.
36644 @var{oldpath} or @var{newpath} was too long.
36647 A directory component in @var{oldpath} or @var{newpath} does not exist.
36650 The file is on a read-only filesystem.
36653 The device containing the file has no room for the new
36657 The call was interrupted by the user.
36663 @unnumberedsubsubsec unlink
36664 @cindex unlink, file-i/o system call
36669 int unlink(const char *pathname);
36673 @samp{Funlink,@var{pathnameptr}/@var{len}}
36675 @item Return value:
36676 On success, zero is returned. On error, -1 is returned.
36682 No access to the file or the path of the file.
36685 The system does not allow unlinking of directories.
36688 The file @var{pathname} cannot be unlinked because it's
36689 being used by another process.
36692 @var{pathnameptr} is an invalid pointer value.
36695 @var{pathname} was too long.
36698 A directory component in @var{pathname} does not exist.
36701 A component of the path is not a directory.
36704 The file is on a read-only filesystem.
36707 The call was interrupted by the user.
36713 @unnumberedsubsubsec stat/fstat
36714 @cindex fstat, file-i/o system call
36715 @cindex stat, file-i/o system call
36720 int stat(const char *pathname, struct stat *buf);
36721 int fstat(int fd, struct stat *buf);
36725 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
36726 @samp{Ffstat,@var{fd},@var{bufptr}}
36728 @item Return value:
36729 On success, zero is returned. On error, -1 is returned.
36735 @var{fd} is not a valid open file.
36738 A directory component in @var{pathname} does not exist or the
36739 path is an empty string.
36742 A component of the path is not a directory.
36745 @var{pathnameptr} is an invalid pointer value.
36748 No access to the file or the path of the file.
36751 @var{pathname} was too long.
36754 The call was interrupted by the user.
36760 @unnumberedsubsubsec gettimeofday
36761 @cindex gettimeofday, file-i/o system call
36766 int gettimeofday(struct timeval *tv, void *tz);
36770 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
36772 @item Return value:
36773 On success, 0 is returned, -1 otherwise.
36779 @var{tz} is a non-NULL pointer.
36782 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
36788 @unnumberedsubsubsec isatty
36789 @cindex isatty, file-i/o system call
36794 int isatty(int fd);
36798 @samp{Fisatty,@var{fd}}
36800 @item Return value:
36801 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
36807 The call was interrupted by the user.
36812 Note that the @code{isatty} call is treated as a special case: it returns
36813 1 to the target if the file descriptor is attached
36814 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
36815 would require implementing @code{ioctl} and would be more complex than
36820 @unnumberedsubsubsec system
36821 @cindex system, file-i/o system call
36826 int system(const char *command);
36830 @samp{Fsystem,@var{commandptr}/@var{len}}
36832 @item Return value:
36833 If @var{len} is zero, the return value indicates whether a shell is
36834 available. A zero return value indicates a shell is not available.
36835 For non-zero @var{len}, the value returned is -1 on error and the
36836 return status of the command otherwise. Only the exit status of the
36837 command is returned, which is extracted from the host's @code{system}
36838 return value by calling @code{WEXITSTATUS(retval)}. In case
36839 @file{/bin/sh} could not be executed, 127 is returned.
36845 The call was interrupted by the user.
36850 @value{GDBN} takes over the full task of calling the necessary host calls
36851 to perform the @code{system} call. The return value of @code{system} on
36852 the host is simplified before it's returned
36853 to the target. Any termination signal information from the child process
36854 is discarded, and the return value consists
36855 entirely of the exit status of the called command.
36857 Due to security concerns, the @code{system} call is by default refused
36858 by @value{GDBN}. The user has to allow this call explicitly with the
36859 @code{set remote system-call-allowed 1} command.
36862 @item set remote system-call-allowed
36863 @kindex set remote system-call-allowed
36864 Control whether to allow the @code{system} calls in the File I/O
36865 protocol for the remote target. The default is zero (disabled).
36867 @item show remote system-call-allowed
36868 @kindex show remote system-call-allowed
36869 Show whether the @code{system} calls are allowed in the File I/O
36873 @node Protocol-specific Representation of Datatypes
36874 @subsection Protocol-specific Representation of Datatypes
36875 @cindex protocol-specific representation of datatypes, in file-i/o protocol
36878 * Integral Datatypes::
36880 * Memory Transfer::
36885 @node Integral Datatypes
36886 @unnumberedsubsubsec Integral Datatypes
36887 @cindex integral datatypes, in file-i/o protocol
36889 The integral datatypes used in the system calls are @code{int},
36890 @code{unsigned int}, @code{long}, @code{unsigned long},
36891 @code{mode_t}, and @code{time_t}.
36893 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
36894 implemented as 32 bit values in this protocol.
36896 @code{long} and @code{unsigned long} are implemented as 64 bit types.
36898 @xref{Limits}, for corresponding MIN and MAX values (similar to those
36899 in @file{limits.h}) to allow range checking on host and target.
36901 @code{time_t} datatypes are defined as seconds since the Epoch.
36903 All integral datatypes transferred as part of a memory read or write of a
36904 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
36907 @node Pointer Values
36908 @unnumberedsubsubsec Pointer Values
36909 @cindex pointer values, in file-i/o protocol
36911 Pointers to target data are transmitted as they are. An exception
36912 is made for pointers to buffers for which the length isn't
36913 transmitted as part of the function call, namely strings. Strings
36914 are transmitted as a pointer/length pair, both as hex values, e.g.@:
36921 which is a pointer to data of length 18 bytes at position 0x1aaf.
36922 The length is defined as the full string length in bytes, including
36923 the trailing null byte. For example, the string @code{"hello world"}
36924 at address 0x123456 is transmitted as
36930 @node Memory Transfer
36931 @unnumberedsubsubsec Memory Transfer
36932 @cindex memory transfer, in file-i/o protocol
36934 Structured data which is transferred using a memory read or write (for
36935 example, a @code{struct stat}) is expected to be in a protocol-specific format
36936 with all scalar multibyte datatypes being big endian. Translation to
36937 this representation needs to be done both by the target before the @code{F}
36938 packet is sent, and by @value{GDBN} before
36939 it transfers memory to the target. Transferred pointers to structured
36940 data should point to the already-coerced data at any time.
36944 @unnumberedsubsubsec struct stat
36945 @cindex struct stat, in file-i/o protocol
36947 The buffer of type @code{struct stat} used by the target and @value{GDBN}
36948 is defined as follows:
36952 unsigned int st_dev; /* device */
36953 unsigned int st_ino; /* inode */
36954 mode_t st_mode; /* protection */
36955 unsigned int st_nlink; /* number of hard links */
36956 unsigned int st_uid; /* user ID of owner */
36957 unsigned int st_gid; /* group ID of owner */
36958 unsigned int st_rdev; /* device type (if inode device) */
36959 unsigned long st_size; /* total size, in bytes */
36960 unsigned long st_blksize; /* blocksize for filesystem I/O */
36961 unsigned long st_blocks; /* number of blocks allocated */
36962 time_t st_atime; /* time of last access */
36963 time_t st_mtime; /* time of last modification */
36964 time_t st_ctime; /* time of last change */
36968 The integral datatypes conform to the definitions given in the
36969 appropriate section (see @ref{Integral Datatypes}, for details) so this
36970 structure is of size 64 bytes.
36972 The values of several fields have a restricted meaning and/or
36978 A value of 0 represents a file, 1 the console.
36981 No valid meaning for the target. Transmitted unchanged.
36984 Valid mode bits are described in @ref{Constants}. Any other
36985 bits have currently no meaning for the target.
36990 No valid meaning for the target. Transmitted unchanged.
36995 These values have a host and file system dependent
36996 accuracy. Especially on Windows hosts, the file system may not
36997 support exact timing values.
37000 The target gets a @code{struct stat} of the above representation and is
37001 responsible for coercing it to the target representation before
37004 Note that due to size differences between the host, target, and protocol
37005 representations of @code{struct stat} members, these members could eventually
37006 get truncated on the target.
37008 @node struct timeval
37009 @unnumberedsubsubsec struct timeval
37010 @cindex struct timeval, in file-i/o protocol
37012 The buffer of type @code{struct timeval} used by the File-I/O protocol
37013 is defined as follows:
37017 time_t tv_sec; /* second */
37018 long tv_usec; /* microsecond */
37022 The integral datatypes conform to the definitions given in the
37023 appropriate section (see @ref{Integral Datatypes}, for details) so this
37024 structure is of size 8 bytes.
37027 @subsection Constants
37028 @cindex constants, in file-i/o protocol
37030 The following values are used for the constants inside of the
37031 protocol. @value{GDBN} and target are responsible for translating these
37032 values before and after the call as needed.
37043 @unnumberedsubsubsec Open Flags
37044 @cindex open flags, in file-i/o protocol
37046 All values are given in hexadecimal representation.
37058 @node mode_t Values
37059 @unnumberedsubsubsec mode_t Values
37060 @cindex mode_t values, in file-i/o protocol
37062 All values are given in octal representation.
37079 @unnumberedsubsubsec Errno Values
37080 @cindex errno values, in file-i/o protocol
37082 All values are given in decimal representation.
37107 @code{EUNKNOWN} is used as a fallback error value if a host system returns
37108 any error value not in the list of supported error numbers.
37111 @unnumberedsubsubsec Lseek Flags
37112 @cindex lseek flags, in file-i/o protocol
37121 @unnumberedsubsubsec Limits
37122 @cindex limits, in file-i/o protocol
37124 All values are given in decimal representation.
37127 INT_MIN -2147483648
37129 UINT_MAX 4294967295
37130 LONG_MIN -9223372036854775808
37131 LONG_MAX 9223372036854775807
37132 ULONG_MAX 18446744073709551615
37135 @node File-I/O Examples
37136 @subsection File-I/O Examples
37137 @cindex file-i/o examples
37139 Example sequence of a write call, file descriptor 3, buffer is at target
37140 address 0x1234, 6 bytes should be written:
37143 <- @code{Fwrite,3,1234,6}
37144 @emph{request memory read from target}
37147 @emph{return "6 bytes written"}
37151 Example sequence of a read call, file descriptor 3, buffer is at target
37152 address 0x1234, 6 bytes should be read:
37155 <- @code{Fread,3,1234,6}
37156 @emph{request memory write to target}
37157 -> @code{X1234,6:XXXXXX}
37158 @emph{return "6 bytes read"}
37162 Example sequence of a read call, call fails on the host due to invalid
37163 file descriptor (@code{EBADF}):
37166 <- @code{Fread,3,1234,6}
37170 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
37174 <- @code{Fread,3,1234,6}
37179 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
37183 <- @code{Fread,3,1234,6}
37184 -> @code{X1234,6:XXXXXX}
37188 @node Library List Format
37189 @section Library List Format
37190 @cindex library list format, remote protocol
37192 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
37193 same process as your application to manage libraries. In this case,
37194 @value{GDBN} can use the loader's symbol table and normal memory
37195 operations to maintain a list of shared libraries. On other
37196 platforms, the operating system manages loaded libraries.
37197 @value{GDBN} can not retrieve the list of currently loaded libraries
37198 through memory operations, so it uses the @samp{qXfer:libraries:read}
37199 packet (@pxref{qXfer library list read}) instead. The remote stub
37200 queries the target's operating system and reports which libraries
37203 The @samp{qXfer:libraries:read} packet returns an XML document which
37204 lists loaded libraries and their offsets. Each library has an
37205 associated name and one or more segment or section base addresses,
37206 which report where the library was loaded in memory.
37208 For the common case of libraries that are fully linked binaries, the
37209 library should have a list of segments. If the target supports
37210 dynamic linking of a relocatable object file, its library XML element
37211 should instead include a list of allocated sections. The segment or
37212 section bases are start addresses, not relocation offsets; they do not
37213 depend on the library's link-time base addresses.
37215 @value{GDBN} must be linked with the Expat library to support XML
37216 library lists. @xref{Expat}.
37218 A simple memory map, with one loaded library relocated by a single
37219 offset, looks like this:
37223 <library name="/lib/libc.so.6">
37224 <segment address="0x10000000"/>
37229 Another simple memory map, with one loaded library with three
37230 allocated sections (.text, .data, .bss), looks like this:
37234 <library name="sharedlib.o">
37235 <section address="0x10000000"/>
37236 <section address="0x20000000"/>
37237 <section address="0x30000000"/>
37242 The format of a library list is described by this DTD:
37245 <!-- library-list: Root element with versioning -->
37246 <!ELEMENT library-list (library)*>
37247 <!ATTLIST library-list version CDATA #FIXED "1.0">
37248 <!ELEMENT library (segment*, section*)>
37249 <!ATTLIST library name CDATA #REQUIRED>
37250 <!ELEMENT segment EMPTY>
37251 <!ATTLIST segment address CDATA #REQUIRED>
37252 <!ELEMENT section EMPTY>
37253 <!ATTLIST section address CDATA #REQUIRED>
37256 In addition, segments and section descriptors cannot be mixed within a
37257 single library element, and you must supply at least one segment or
37258 section for each library.
37260 @node Memory Map Format
37261 @section Memory Map Format
37262 @cindex memory map format
37264 To be able to write into flash memory, @value{GDBN} needs to obtain a
37265 memory map from the target. This section describes the format of the
37268 The memory map is obtained using the @samp{qXfer:memory-map:read}
37269 (@pxref{qXfer memory map read}) packet and is an XML document that
37270 lists memory regions.
37272 @value{GDBN} must be linked with the Expat library to support XML
37273 memory maps. @xref{Expat}.
37275 The top-level structure of the document is shown below:
37278 <?xml version="1.0"?>
37279 <!DOCTYPE memory-map
37280 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
37281 "http://sourceware.org/gdb/gdb-memory-map.dtd">
37287 Each region can be either:
37292 A region of RAM starting at @var{addr} and extending for @var{length}
37296 <memory type="ram" start="@var{addr}" length="@var{length}"/>
37301 A region of read-only memory:
37304 <memory type="rom" start="@var{addr}" length="@var{length}"/>
37309 A region of flash memory, with erasure blocks @var{blocksize}
37313 <memory type="flash" start="@var{addr}" length="@var{length}">
37314 <property name="blocksize">@var{blocksize}</property>
37320 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
37321 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
37322 packets to write to addresses in such ranges.
37324 The formal DTD for memory map format is given below:
37327 <!-- ................................................... -->
37328 <!-- Memory Map XML DTD ................................ -->
37329 <!-- File: memory-map.dtd .............................. -->
37330 <!-- .................................... .............. -->
37331 <!-- memory-map.dtd -->
37332 <!-- memory-map: Root element with versioning -->
37333 <!ELEMENT memory-map (memory | property)>
37334 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
37335 <!ELEMENT memory (property)>
37336 <!-- memory: Specifies a memory region,
37337 and its type, or device. -->
37338 <!ATTLIST memory type CDATA #REQUIRED
37339 start CDATA #REQUIRED
37340 length CDATA #REQUIRED
37341 device CDATA #IMPLIED>
37342 <!-- property: Generic attribute tag -->
37343 <!ELEMENT property (#PCDATA | property)*>
37344 <!ATTLIST property name CDATA #REQUIRED>
37347 @node Thread List Format
37348 @section Thread List Format
37349 @cindex thread list format
37351 To efficiently update the list of threads and their attributes,
37352 @value{GDBN} issues the @samp{qXfer:threads:read} packet
37353 (@pxref{qXfer threads read}) and obtains the XML document with
37354 the following structure:
37357 <?xml version="1.0"?>
37359 <thread id="id" core="0">
37360 ... description ...
37365 Each @samp{thread} element must have the @samp{id} attribute that
37366 identifies the thread (@pxref{thread-id syntax}). The
37367 @samp{core} attribute, if present, specifies which processor core
37368 the thread was last executing on. The content of the of @samp{thread}
37369 element is interpreted as human-readable auxilliary information.
37371 @node Traceframe Info Format
37372 @section Traceframe Info Format
37373 @cindex traceframe info format
37375 To be able to know which objects in the inferior can be examined when
37376 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
37377 memory ranges, registers and trace state variables that have been
37378 collected in a traceframe.
37380 This list is obtained using the @samp{qXfer:traceframe-info:read}
37381 (@pxref{qXfer traceframe info read}) packet and is an XML document.
37383 @value{GDBN} must be linked with the Expat library to support XML
37384 traceframe info discovery. @xref{Expat}.
37386 The top-level structure of the document is shown below:
37389 <?xml version="1.0"?>
37390 <!DOCTYPE traceframe-info
37391 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
37392 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
37398 Each traceframe block can be either:
37403 A region of collected memory starting at @var{addr} and extending for
37404 @var{length} bytes from there:
37407 <memory start="@var{addr}" length="@var{length}"/>
37412 The formal DTD for the traceframe info format is given below:
37415 <!ELEMENT traceframe-info (memory)* >
37416 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
37418 <!ELEMENT memory EMPTY>
37419 <!ATTLIST memory start CDATA #REQUIRED
37420 length CDATA #REQUIRED>
37423 @include agentexpr.texi
37425 @node Target Descriptions
37426 @appendix Target Descriptions
37427 @cindex target descriptions
37429 One of the challenges of using @value{GDBN} to debug embedded systems
37430 is that there are so many minor variants of each processor
37431 architecture in use. It is common practice for vendors to start with
37432 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
37433 and then make changes to adapt it to a particular market niche. Some
37434 architectures have hundreds of variants, available from dozens of
37435 vendors. This leads to a number of problems:
37439 With so many different customized processors, it is difficult for
37440 the @value{GDBN} maintainers to keep up with the changes.
37442 Since individual variants may have short lifetimes or limited
37443 audiences, it may not be worthwhile to carry information about every
37444 variant in the @value{GDBN} source tree.
37446 When @value{GDBN} does support the architecture of the embedded system
37447 at hand, the task of finding the correct architecture name to give the
37448 @command{set architecture} command can be error-prone.
37451 To address these problems, the @value{GDBN} remote protocol allows a
37452 target system to not only identify itself to @value{GDBN}, but to
37453 actually describe its own features. This lets @value{GDBN} support
37454 processor variants it has never seen before --- to the extent that the
37455 descriptions are accurate, and that @value{GDBN} understands them.
37457 @value{GDBN} must be linked with the Expat library to support XML
37458 target descriptions. @xref{Expat}.
37461 * Retrieving Descriptions:: How descriptions are fetched from a target.
37462 * Target Description Format:: The contents of a target description.
37463 * Predefined Target Types:: Standard types available for target
37465 * Standard Target Features:: Features @value{GDBN} knows about.
37468 @node Retrieving Descriptions
37469 @section Retrieving Descriptions
37471 Target descriptions can be read from the target automatically, or
37472 specified by the user manually. The default behavior is to read the
37473 description from the target. @value{GDBN} retrieves it via the remote
37474 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
37475 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
37476 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
37477 XML document, of the form described in @ref{Target Description
37480 Alternatively, you can specify a file to read for the target description.
37481 If a file is set, the target will not be queried. The commands to
37482 specify a file are:
37485 @cindex set tdesc filename
37486 @item set tdesc filename @var{path}
37487 Read the target description from @var{path}.
37489 @cindex unset tdesc filename
37490 @item unset tdesc filename
37491 Do not read the XML target description from a file. @value{GDBN}
37492 will use the description supplied by the current target.
37494 @cindex show tdesc filename
37495 @item show tdesc filename
37496 Show the filename to read for a target description, if any.
37500 @node Target Description Format
37501 @section Target Description Format
37502 @cindex target descriptions, XML format
37504 A target description annex is an @uref{http://www.w3.org/XML/, XML}
37505 document which complies with the Document Type Definition provided in
37506 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
37507 means you can use generally available tools like @command{xmllint} to
37508 check that your feature descriptions are well-formed and valid.
37509 However, to help people unfamiliar with XML write descriptions for
37510 their targets, we also describe the grammar here.
37512 Target descriptions can identify the architecture of the remote target
37513 and (for some architectures) provide information about custom register
37514 sets. They can also identify the OS ABI of the remote target.
37515 @value{GDBN} can use this information to autoconfigure for your
37516 target, or to warn you if you connect to an unsupported target.
37518 Here is a simple target description:
37521 <target version="1.0">
37522 <architecture>i386:x86-64</architecture>
37527 This minimal description only says that the target uses
37528 the x86-64 architecture.
37530 A target description has the following overall form, with [ ] marking
37531 optional elements and @dots{} marking repeatable elements. The elements
37532 are explained further below.
37535 <?xml version="1.0"?>
37536 <!DOCTYPE target SYSTEM "gdb-target.dtd">
37537 <target version="1.0">
37538 @r{[}@var{architecture}@r{]}
37539 @r{[}@var{osabi}@r{]}
37540 @r{[}@var{compatible}@r{]}
37541 @r{[}@var{feature}@dots{}@r{]}
37546 The description is generally insensitive to whitespace and line
37547 breaks, under the usual common-sense rules. The XML version
37548 declaration and document type declaration can generally be omitted
37549 (@value{GDBN} does not require them), but specifying them may be
37550 useful for XML validation tools. The @samp{version} attribute for
37551 @samp{<target>} may also be omitted, but we recommend
37552 including it; if future versions of @value{GDBN} use an incompatible
37553 revision of @file{gdb-target.dtd}, they will detect and report
37554 the version mismatch.
37556 @subsection Inclusion
37557 @cindex target descriptions, inclusion
37560 @cindex <xi:include>
37563 It can sometimes be valuable to split a target description up into
37564 several different annexes, either for organizational purposes, or to
37565 share files between different possible target descriptions. You can
37566 divide a description into multiple files by replacing any element of
37567 the target description with an inclusion directive of the form:
37570 <xi:include href="@var{document}"/>
37574 When @value{GDBN} encounters an element of this form, it will retrieve
37575 the named XML @var{document}, and replace the inclusion directive with
37576 the contents of that document. If the current description was read
37577 using @samp{qXfer}, then so will be the included document;
37578 @var{document} will be interpreted as the name of an annex. If the
37579 current description was read from a file, @value{GDBN} will look for
37580 @var{document} as a file in the same directory where it found the
37581 original description.
37583 @subsection Architecture
37584 @cindex <architecture>
37586 An @samp{<architecture>} element has this form:
37589 <architecture>@var{arch}</architecture>
37592 @var{arch} is one of the architectures from the set accepted by
37593 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
37596 @cindex @code{<osabi>}
37598 This optional field was introduced in @value{GDBN} version 7.0.
37599 Previous versions of @value{GDBN} ignore it.
37601 An @samp{<osabi>} element has this form:
37604 <osabi>@var{abi-name}</osabi>
37607 @var{abi-name} is an OS ABI name from the same selection accepted by
37608 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
37610 @subsection Compatible Architecture
37611 @cindex @code{<compatible>}
37613 This optional field was introduced in @value{GDBN} version 7.0.
37614 Previous versions of @value{GDBN} ignore it.
37616 A @samp{<compatible>} element has this form:
37619 <compatible>@var{arch}</compatible>
37622 @var{arch} is one of the architectures from the set accepted by
37623 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
37625 A @samp{<compatible>} element is used to specify that the target
37626 is able to run binaries in some other than the main target architecture
37627 given by the @samp{<architecture>} element. For example, on the
37628 Cell Broadband Engine, the main architecture is @code{powerpc:common}
37629 or @code{powerpc:common64}, but the system is able to run binaries
37630 in the @code{spu} architecture as well. The way to describe this
37631 capability with @samp{<compatible>} is as follows:
37634 <architecture>powerpc:common</architecture>
37635 <compatible>spu</compatible>
37638 @subsection Features
37641 Each @samp{<feature>} describes some logical portion of the target
37642 system. Features are currently used to describe available CPU
37643 registers and the types of their contents. A @samp{<feature>} element
37647 <feature name="@var{name}">
37648 @r{[}@var{type}@dots{}@r{]}
37654 Each feature's name should be unique within the description. The name
37655 of a feature does not matter unless @value{GDBN} has some special
37656 knowledge of the contents of that feature; if it does, the feature
37657 should have its standard name. @xref{Standard Target Features}.
37661 Any register's value is a collection of bits which @value{GDBN} must
37662 interpret. The default interpretation is a two's complement integer,
37663 but other types can be requested by name in the register description.
37664 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
37665 Target Types}), and the description can define additional composite types.
37667 Each type element must have an @samp{id} attribute, which gives
37668 a unique (within the containing @samp{<feature>}) name to the type.
37669 Types must be defined before they are used.
37672 Some targets offer vector registers, which can be treated as arrays
37673 of scalar elements. These types are written as @samp{<vector>} elements,
37674 specifying the array element type, @var{type}, and the number of elements,
37678 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
37682 If a register's value is usefully viewed in multiple ways, define it
37683 with a union type containing the useful representations. The
37684 @samp{<union>} element contains one or more @samp{<field>} elements,
37685 each of which has a @var{name} and a @var{type}:
37688 <union id="@var{id}">
37689 <field name="@var{name}" type="@var{type}"/>
37695 If a register's value is composed from several separate values, define
37696 it with a structure type. There are two forms of the @samp{<struct>}
37697 element; a @samp{<struct>} element must either contain only bitfields
37698 or contain no bitfields. If the structure contains only bitfields,
37699 its total size in bytes must be specified, each bitfield must have an
37700 explicit start and end, and bitfields are automatically assigned an
37701 integer type. The field's @var{start} should be less than or
37702 equal to its @var{end}, and zero represents the least significant bit.
37705 <struct id="@var{id}" size="@var{size}">
37706 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
37711 If the structure contains no bitfields, then each field has an
37712 explicit type, and no implicit padding is added.
37715 <struct id="@var{id}">
37716 <field name="@var{name}" type="@var{type}"/>
37722 If a register's value is a series of single-bit flags, define it with
37723 a flags type. The @samp{<flags>} element has an explicit @var{size}
37724 and contains one or more @samp{<field>} elements. Each field has a
37725 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
37729 <flags id="@var{id}" size="@var{size}">
37730 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
37735 @subsection Registers
37738 Each register is represented as an element with this form:
37741 <reg name="@var{name}"
37742 bitsize="@var{size}"
37743 @r{[}regnum="@var{num}"@r{]}
37744 @r{[}save-restore="@var{save-restore}"@r{]}
37745 @r{[}type="@var{type}"@r{]}
37746 @r{[}group="@var{group}"@r{]}/>
37750 The components are as follows:
37755 The register's name; it must be unique within the target description.
37758 The register's size, in bits.
37761 The register's number. If omitted, a register's number is one greater
37762 than that of the previous register (either in the current feature or in
37763 a preceding feature); the first register in the target description
37764 defaults to zero. This register number is used to read or write
37765 the register; e.g.@: it is used in the remote @code{p} and @code{P}
37766 packets, and registers appear in the @code{g} and @code{G} packets
37767 in order of increasing register number.
37770 Whether the register should be preserved across inferior function
37771 calls; this must be either @code{yes} or @code{no}. The default is
37772 @code{yes}, which is appropriate for most registers except for
37773 some system control registers; this is not related to the target's
37777 The type of the register. @var{type} may be a predefined type, a type
37778 defined in the current feature, or one of the special types @code{int}
37779 and @code{float}. @code{int} is an integer type of the correct size
37780 for @var{bitsize}, and @code{float} is a floating point type (in the
37781 architecture's normal floating point format) of the correct size for
37782 @var{bitsize}. The default is @code{int}.
37785 The register group to which this register belongs. @var{group} must
37786 be either @code{general}, @code{float}, or @code{vector}. If no
37787 @var{group} is specified, @value{GDBN} will not display the register
37788 in @code{info registers}.
37792 @node Predefined Target Types
37793 @section Predefined Target Types
37794 @cindex target descriptions, predefined types
37796 Type definitions in the self-description can build up composite types
37797 from basic building blocks, but can not define fundamental types. Instead,
37798 standard identifiers are provided by @value{GDBN} for the fundamental
37799 types. The currently supported types are:
37808 Signed integer types holding the specified number of bits.
37815 Unsigned integer types holding the specified number of bits.
37819 Pointers to unspecified code and data. The program counter and
37820 any dedicated return address register may be marked as code
37821 pointers; printing a code pointer converts it into a symbolic
37822 address. The stack pointer and any dedicated address registers
37823 may be marked as data pointers.
37826 Single precision IEEE floating point.
37829 Double precision IEEE floating point.
37832 The 12-byte extended precision format used by ARM FPA registers.
37835 The 10-byte extended precision format used by x87 registers.
37838 32bit @sc{eflags} register used by x86.
37841 32bit @sc{mxcsr} register used by x86.
37845 @node Standard Target Features
37846 @section Standard Target Features
37847 @cindex target descriptions, standard features
37849 A target description must contain either no registers or all the
37850 target's registers. If the description contains no registers, then
37851 @value{GDBN} will assume a default register layout, selected based on
37852 the architecture. If the description contains any registers, the
37853 default layout will not be used; the standard registers must be
37854 described in the target description, in such a way that @value{GDBN}
37855 can recognize them.
37857 This is accomplished by giving specific names to feature elements
37858 which contain standard registers. @value{GDBN} will look for features
37859 with those names and verify that they contain the expected registers;
37860 if any known feature is missing required registers, or if any required
37861 feature is missing, @value{GDBN} will reject the target
37862 description. You can add additional registers to any of the
37863 standard features --- @value{GDBN} will display them just as if
37864 they were added to an unrecognized feature.
37866 This section lists the known features and their expected contents.
37867 Sample XML documents for these features are included in the
37868 @value{GDBN} source tree, in the directory @file{gdb/features}.
37870 Names recognized by @value{GDBN} should include the name of the
37871 company or organization which selected the name, and the overall
37872 architecture to which the feature applies; so e.g.@: the feature
37873 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
37875 The names of registers are not case sensitive for the purpose
37876 of recognizing standard features, but @value{GDBN} will only display
37877 registers using the capitalization used in the description.
37884 * PowerPC Features::
37890 @subsection ARM Features
37891 @cindex target descriptions, ARM features
37893 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
37895 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
37896 @samp{lr}, @samp{pc}, and @samp{cpsr}.
37898 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
37899 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
37900 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
37903 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
37904 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
37906 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
37907 it should contain at least registers @samp{wR0} through @samp{wR15} and
37908 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
37909 @samp{wCSSF}, and @samp{wCASF} registers are optional.
37911 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
37912 should contain at least registers @samp{d0} through @samp{d15}. If
37913 they are present, @samp{d16} through @samp{d31} should also be included.
37914 @value{GDBN} will synthesize the single-precision registers from
37915 halves of the double-precision registers.
37917 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
37918 need to contain registers; it instructs @value{GDBN} to display the
37919 VFP double-precision registers as vectors and to synthesize the
37920 quad-precision registers from pairs of double-precision registers.
37921 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
37922 be present and include 32 double-precision registers.
37924 @node i386 Features
37925 @subsection i386 Features
37926 @cindex target descriptions, i386 features
37928 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
37929 targets. It should describe the following registers:
37933 @samp{eax} through @samp{edi} plus @samp{eip} for i386
37935 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
37937 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
37938 @samp{fs}, @samp{gs}
37940 @samp{st0} through @samp{st7}
37942 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
37943 @samp{foseg}, @samp{fooff} and @samp{fop}
37946 The register sets may be different, depending on the target.
37948 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
37949 describe registers:
37953 @samp{xmm0} through @samp{xmm7} for i386
37955 @samp{xmm0} through @samp{xmm15} for amd64
37960 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
37961 @samp{org.gnu.gdb.i386.sse} feature. It should
37962 describe the upper 128 bits of @sc{ymm} registers:
37966 @samp{ymm0h} through @samp{ymm7h} for i386
37968 @samp{ymm0h} through @samp{ymm15h} for amd64
37971 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
37972 describe a single register, @samp{orig_eax}.
37974 @node MIPS Features
37975 @subsection MIPS Features
37976 @cindex target descriptions, MIPS features
37978 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
37979 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
37980 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
37983 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
37984 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
37985 registers. They may be 32-bit or 64-bit depending on the target.
37987 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
37988 it may be optional in a future version of @value{GDBN}. It should
37989 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
37990 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
37992 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
37993 contain a single register, @samp{restart}, which is used by the
37994 Linux kernel to control restartable syscalls.
37996 @node M68K Features
37997 @subsection M68K Features
37998 @cindex target descriptions, M68K features
38001 @item @samp{org.gnu.gdb.m68k.core}
38002 @itemx @samp{org.gnu.gdb.coldfire.core}
38003 @itemx @samp{org.gnu.gdb.fido.core}
38004 One of those features must be always present.
38005 The feature that is present determines which flavor of m68k is
38006 used. The feature that is present should contain registers
38007 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
38008 @samp{sp}, @samp{ps} and @samp{pc}.
38010 @item @samp{org.gnu.gdb.coldfire.fp}
38011 This feature is optional. If present, it should contain registers
38012 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
38016 @node PowerPC Features
38017 @subsection PowerPC Features
38018 @cindex target descriptions, PowerPC features
38020 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
38021 targets. It should contain registers @samp{r0} through @samp{r31},
38022 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
38023 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
38025 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
38026 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
38028 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
38029 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
38032 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
38033 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
38034 will combine these registers with the floating point registers
38035 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
38036 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
38037 through @samp{vs63}, the set of vector registers for POWER7.
38039 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
38040 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
38041 @samp{spefscr}. SPE targets should provide 32-bit registers in
38042 @samp{org.gnu.gdb.power.core} and provide the upper halves in
38043 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
38044 these to present registers @samp{ev0} through @samp{ev31} to the
38047 @node TIC6x Features
38048 @subsection TMS320C6x Features
38049 @cindex target descriptions, TIC6x features
38050 @cindex target descriptions, TMS320C6x features
38051 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
38052 targets. It should contain registers @samp{A0} through @samp{A15},
38053 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
38055 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
38056 contain registers @samp{A16} through @samp{A31} and @samp{B16}
38057 through @samp{B31}.
38059 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
38060 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
38062 @node Operating System Information
38063 @appendix Operating System Information
38064 @cindex operating system information
38070 Users of @value{GDBN} often wish to obtain information about the state of
38071 the operating system running on the target---for example the list of
38072 processes, or the list of open files. This section describes the
38073 mechanism that makes it possible. This mechanism is similar to the
38074 target features mechanism (@pxref{Target Descriptions}), but focuses
38075 on a different aspect of target.
38077 Operating system information is retrived from the target via the
38078 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
38079 read}). The object name in the request should be @samp{osdata}, and
38080 the @var{annex} identifies the data to be fetched.
38083 @appendixsection Process list
38084 @cindex operating system information, process list
38086 When requesting the process list, the @var{annex} field in the
38087 @samp{qXfer} request should be @samp{processes}. The returned data is
38088 an XML document. The formal syntax of this document is defined in
38089 @file{gdb/features/osdata.dtd}.
38091 An example document is:
38094 <?xml version="1.0"?>
38095 <!DOCTYPE target SYSTEM "osdata.dtd">
38096 <osdata type="processes">
38098 <column name="pid">1</column>
38099 <column name="user">root</column>
38100 <column name="command">/sbin/init</column>
38101 <column name="cores">1,2,3</column>
38106 Each item should include a column whose name is @samp{pid}. The value
38107 of that column should identify the process on the target. The
38108 @samp{user} and @samp{command} columns are optional, and will be
38109 displayed by @value{GDBN}. The @samp{cores} column, if present,
38110 should contain a comma-separated list of cores that this process
38111 is running on. Target may provide additional columns,
38112 which @value{GDBN} currently ignores.
38114 @node Trace File Format
38115 @appendix Trace File Format
38116 @cindex trace file format
38118 The trace file comes in three parts: a header, a textual description
38119 section, and a trace frame section with binary data.
38121 The header has the form @code{\x7fTRACE0\n}. The first byte is
38122 @code{0x7f} so as to indicate that the file contains binary data,
38123 while the @code{0} is a version number that may have different values
38126 The description section consists of multiple lines of @sc{ascii} text
38127 separated by newline characters (@code{0xa}). The lines may include a
38128 variety of optional descriptive or context-setting information, such
38129 as tracepoint definitions or register set size. @value{GDBN} will
38130 ignore any line that it does not recognize. An empty line marks the end
38133 @c FIXME add some specific types of data
38135 The trace frame section consists of a number of consecutive frames.
38136 Each frame begins with a two-byte tracepoint number, followed by a
38137 four-byte size giving the amount of data in the frame. The data in
38138 the frame consists of a number of blocks, each introduced by a
38139 character indicating its type (at least register, memory, and trace
38140 state variable). The data in this section is raw binary, not a
38141 hexadecimal or other encoding; its endianness matches the target's
38144 @c FIXME bi-arch may require endianness/arch info in description section
38147 @item R @var{bytes}
38148 Register block. The number and ordering of bytes matches that of a
38149 @code{g} packet in the remote protocol. Note that these are the
38150 actual bytes, in target order and @value{GDBN} register order, not a
38151 hexadecimal encoding.
38153 @item M @var{address} @var{length} @var{bytes}...
38154 Memory block. This is a contiguous block of memory, at the 8-byte
38155 address @var{address}, with a 2-byte length @var{length}, followed by
38156 @var{length} bytes.
38158 @item V @var{number} @var{value}
38159 Trace state variable block. This records the 8-byte signed value
38160 @var{value} of trace state variable numbered @var{number}.
38164 Future enhancements of the trace file format may include additional types
38167 @node Index Section Format
38168 @appendix @code{.gdb_index} section format
38169 @cindex .gdb_index section format
38170 @cindex index section format
38172 This section documents the index section that is created by @code{save
38173 gdb-index} (@pxref{Index Files}). The index section is
38174 DWARF-specific; some knowledge of DWARF is assumed in this
38177 The mapped index file format is designed to be directly
38178 @code{mmap}able on any architecture. In most cases, a datum is
38179 represented using a little-endian 32-bit integer value, called an
38180 @code{offset_type}. Big endian machines must byte-swap the values
38181 before using them. Exceptions to this rule are noted. The data is
38182 laid out such that alignment is always respected.
38184 A mapped index consists of several areas, laid out in order.
38188 The file header. This is a sequence of values, of @code{offset_type}
38189 unless otherwise noted:
38193 The version number, currently 5. Versions 1, 2 and 3 are obsolete.
38194 Version 4 differs by its hashing function.
38197 The offset, from the start of the file, of the CU list.
38200 The offset, from the start of the file, of the types CU list. Note
38201 that this area can be empty, in which case this offset will be equal
38202 to the next offset.
38205 The offset, from the start of the file, of the address area.
38208 The offset, from the start of the file, of the symbol table.
38211 The offset, from the start of the file, of the constant pool.
38215 The CU list. This is a sequence of pairs of 64-bit little-endian
38216 values, sorted by the CU offset. The first element in each pair is
38217 the offset of a CU in the @code{.debug_info} section. The second
38218 element in each pair is the length of that CU. References to a CU
38219 elsewhere in the map are done using a CU index, which is just the
38220 0-based index into this table. Note that if there are type CUs, then
38221 conceptually CUs and type CUs form a single list for the purposes of
38225 The types CU list. This is a sequence of triplets of 64-bit
38226 little-endian values. In a triplet, the first value is the CU offset,
38227 the second value is the type offset in the CU, and the third value is
38228 the type signature. The types CU list is not sorted.
38231 The address area. The address area consists of a sequence of address
38232 entries. Each address entry has three elements:
38236 The low address. This is a 64-bit little-endian value.
38239 The high address. This is a 64-bit little-endian value. Like
38240 @code{DW_AT_high_pc}, the value is one byte beyond the end.
38243 The CU index. This is an @code{offset_type} value.
38247 The symbol table. This is an open-addressed hash table. The size of
38248 the hash table is always a power of 2.
38250 Each slot in the hash table consists of a pair of @code{offset_type}
38251 values. The first value is the offset of the symbol's name in the
38252 constant pool. The second value is the offset of the CU vector in the
38255 If both values are 0, then this slot in the hash table is empty. This
38256 is ok because while 0 is a valid constant pool index, it cannot be a
38257 valid index for both a string and a CU vector.
38259 The hash value for a table entry is computed by applying an
38260 iterative hash function to the symbol's name. Starting with an
38261 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
38262 the string is incorporated into the hash using the formula depending on the
38267 The formula is @code{r = r * 67 + c - 113}.
38270 The formula is @code{r = r * 67 + tolower (c) - 113}.
38273 The terminating @samp{\0} is not incorporated into the hash.
38275 The step size used in the hash table is computed via
38276 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
38277 value, and @samp{size} is the size of the hash table. The step size
38278 is used to find the next candidate slot when handling a hash
38281 The names of C@t{++} symbols in the hash table are canonicalized. We
38282 don't currently have a simple description of the canonicalization
38283 algorithm; if you intend to create new index sections, you must read
38287 The constant pool. This is simply a bunch of bytes. It is organized
38288 so that alignment is correct: CU vectors are stored first, followed by
38291 A CU vector in the constant pool is a sequence of @code{offset_type}
38292 values. The first value is the number of CU indices in the vector.
38293 Each subsequent value is the index of a CU in the CU list. This
38294 element in the hash table is used to indicate which CUs define the
38297 A string in the constant pool is zero-terminated.
38302 @node GNU Free Documentation License
38303 @appendix GNU Free Documentation License
38312 % I think something like @colophon should be in texinfo. In the
38314 \long\def\colophon{\hbox to0pt{}\vfill
38315 \centerline{The body of this manual is set in}
38316 \centerline{\fontname\tenrm,}
38317 \centerline{with headings in {\bf\fontname\tenbf}}
38318 \centerline{and examples in {\tt\fontname\tentt}.}
38319 \centerline{{\it\fontname\tenit\/},}
38320 \centerline{{\bf\fontname\tenbf}, and}
38321 \centerline{{\sl\fontname\tensl\/}}
38322 \centerline{are used for emphasis.}\vfill}
38324 % Blame: doc@cygnus.com, 1991.