1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
3 @c 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009,
4 @c 2010, 2011 Free Software Foundation, Inc.
7 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
8 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
26 @c readline appendices use @vindex, @findex and @ftable,
27 @c annotate.texi and gdbmi use @findex.
31 @c !!set GDB manual's edition---not the same as GDB version!
32 @c This is updated by GNU Press.
35 @c !!set GDB edit command default editor
38 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
40 @c This is a dir.info fragment to support semi-automated addition of
41 @c manuals to an info tree.
42 @dircategory Software development
44 * Gdb: (gdb). The GNU debugger.
48 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
49 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
50 Free Software Foundation, Inc.
52 Permission is granted to copy, distribute and/or modify this document
53 under the terms of the GNU Free Documentation License, Version 1.3 or
54 any later version published by the Free Software Foundation; with the
55 Invariant Sections being ``Free Software'' and ``Free Software Needs
56 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
57 and with the Back-Cover Texts as in (a) below.
59 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
60 this GNU Manual. Buying copies from GNU Press supports the FSF in
61 developing GNU and promoting software freedom.''
65 This file documents the @sc{gnu} debugger @value{GDBN}.
67 This is the @value{EDITION} Edition, of @cite{Debugging with
68 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
69 @ifset VERSION_PACKAGE
70 @value{VERSION_PACKAGE}
72 Version @value{GDBVN}.
78 @title Debugging with @value{GDBN}
79 @subtitle The @sc{gnu} Source-Level Debugger
81 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
82 @ifset VERSION_PACKAGE
84 @subtitle @value{VERSION_PACKAGE}
86 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
90 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
91 \hfill {\it Debugging with @value{GDBN}}\par
92 \hfill \TeX{}info \texinfoversion\par
96 @vskip 0pt plus 1filll
97 Published by the Free Software Foundation @*
98 51 Franklin Street, Fifth Floor,
99 Boston, MA 02110-1301, USA@*
100 ISBN 978-0-9831592-3-0 @*
107 @node Top, Summary, (dir), (dir)
109 @top Debugging with @value{GDBN}
111 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
113 This is the @value{EDITION} Edition, for @value{GDBN}
114 @ifset VERSION_PACKAGE
115 @value{VERSION_PACKAGE}
117 Version @value{GDBVN}.
119 Copyright (C) 1988-2010 Free Software Foundation, Inc.
121 This edition of the GDB manual is dedicated to the memory of Fred
122 Fish. Fred was a long-standing contributor to GDB and to Free
123 software in general. We will miss him.
126 * Summary:: Summary of @value{GDBN}
127 * Sample Session:: A sample @value{GDBN} session
129 * Invocation:: Getting in and out of @value{GDBN}
130 * Commands:: @value{GDBN} commands
131 * Running:: Running programs under @value{GDBN}
132 * Stopping:: Stopping and continuing
133 * Reverse Execution:: Running programs backward
134 * Process Record and Replay:: Recording inferior's execution and replaying it
135 * Stack:: Examining the stack
136 * Source:: Examining source files
137 * Data:: Examining data
138 * Optimized Code:: Debugging optimized code
139 * Macros:: Preprocessor Macros
140 * Tracepoints:: Debugging remote targets non-intrusively
141 * Overlays:: Debugging programs that use overlays
143 * Languages:: Using @value{GDBN} with different languages
145 * Symbols:: Examining the symbol table
146 * Altering:: Altering execution
147 * GDB Files:: @value{GDBN} files
148 * Targets:: Specifying a debugging target
149 * Remote Debugging:: Debugging remote programs
150 * Configurations:: Configuration-specific information
151 * Controlling GDB:: Controlling @value{GDBN}
152 * Extending GDB:: Extending @value{GDBN}
153 * Interpreters:: Command Interpreters
154 * TUI:: @value{GDBN} Text User Interface
155 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
156 * GDB/MI:: @value{GDBN}'s Machine Interface.
157 * Annotations:: @value{GDBN}'s annotation interface.
158 * JIT Interface:: Using the JIT debugging interface.
160 * GDB Bugs:: Reporting bugs in @value{GDBN}
162 @ifset SYSTEM_READLINE
163 * Command Line Editing: (rluserman). Command Line Editing
164 * Using History Interactively: (history). Using History Interactively
166 @ifclear SYSTEM_READLINE
167 * Command Line Editing:: Command Line Editing
168 * Using History Interactively:: Using History Interactively
170 * In Memoriam:: In Memoriam
171 * Formatting Documentation:: How to format and print @value{GDBN} documentation
172 * Installing GDB:: Installing GDB
173 * Maintenance Commands:: Maintenance Commands
174 * Remote Protocol:: GDB Remote Serial Protocol
175 * Agent Expressions:: The GDB Agent Expression Mechanism
176 * Target Descriptions:: How targets can describe themselves to
178 * Operating System Information:: Getting additional information from
180 * Trace File Format:: GDB trace file format
181 * Index Section Format:: .gdb_index section format
182 * Copying:: GNU General Public License says
183 how you can copy and share GDB
184 * GNU Free Documentation License:: The license for this documentation
193 @unnumbered Summary of @value{GDBN}
195 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
196 going on ``inside'' another program while it executes---or what another
197 program was doing at the moment it crashed.
199 @value{GDBN} can do four main kinds of things (plus other things in support of
200 these) to help you catch bugs in the act:
204 Start your program, specifying anything that might affect its behavior.
207 Make your program stop on specified conditions.
210 Examine what has happened, when your program has stopped.
213 Change things in your program, so you can experiment with correcting the
214 effects of one bug and go on to learn about another.
217 You can use @value{GDBN} to debug programs written in C and C@t{++}.
218 For more information, see @ref{Supported Languages,,Supported Languages}.
219 For more information, see @ref{C,,C and C++}.
221 Support for D is partial. For information on D, see
225 Support for Modula-2 is partial. For information on Modula-2, see
226 @ref{Modula-2,,Modula-2}.
228 Support for OpenCL C is partial. For information on OpenCL C, see
229 @ref{OpenCL C,,OpenCL C}.
232 Debugging Pascal programs which use sets, subranges, file variables, or
233 nested functions does not currently work. @value{GDBN} does not support
234 entering expressions, printing values, or similar features using Pascal
238 @value{GDBN} can be used to debug programs written in Fortran, although
239 it may be necessary to refer to some variables with a trailing
242 @value{GDBN} can be used to debug programs written in Objective-C,
243 using either the Apple/NeXT or the GNU Objective-C runtime.
246 * Free Software:: Freely redistributable software
247 * Contributors:: Contributors to GDB
251 @unnumberedsec Free Software
253 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
254 General Public License
255 (GPL). The GPL gives you the freedom to copy or adapt a licensed
256 program---but every person getting a copy also gets with it the
257 freedom to modify that copy (which means that they must get access to
258 the source code), and the freedom to distribute further copies.
259 Typical software companies use copyrights to limit your freedoms; the
260 Free Software Foundation uses the GPL to preserve these freedoms.
262 Fundamentally, the General Public License is a license which says that
263 you have these freedoms and that you cannot take these freedoms away
266 @unnumberedsec Free Software Needs Free Documentation
268 The biggest deficiency in the free software community today is not in
269 the software---it is the lack of good free documentation that we can
270 include with the free software. Many of our most important
271 programs do not come with free reference manuals and free introductory
272 texts. Documentation is an essential part of any software package;
273 when an important free software package does not come with a free
274 manual and a free tutorial, that is a major gap. We have many such
277 Consider Perl, for instance. The tutorial manuals that people
278 normally use are non-free. How did this come about? Because the
279 authors of those manuals published them with restrictive terms---no
280 copying, no modification, source files not available---which exclude
281 them from the free software world.
283 That wasn't the first time this sort of thing happened, and it was far
284 from the last. Many times we have heard a GNU user eagerly describe a
285 manual that he is writing, his intended contribution to the community,
286 only to learn that he had ruined everything by signing a publication
287 contract to make it non-free.
289 Free documentation, like free software, is a matter of freedom, not
290 price. The problem with the non-free manual is not that publishers
291 charge a price for printed copies---that in itself is fine. (The Free
292 Software Foundation sells printed copies of manuals, too.) The
293 problem is the restrictions on the use of the manual. Free manuals
294 are available in source code form, and give you permission to copy and
295 modify. Non-free manuals do not allow this.
297 The criteria of freedom for a free manual are roughly the same as for
298 free software. Redistribution (including the normal kinds of
299 commercial redistribution) must be permitted, so that the manual can
300 accompany every copy of the program, both on-line and on paper.
302 Permission for modification of the technical content is crucial too.
303 When people modify the software, adding or changing features, if they
304 are conscientious they will change the manual too---so they can
305 provide accurate and clear documentation for the modified program. A
306 manual that leaves you no choice but to write a new manual to document
307 a changed version of the program is not really available to our
310 Some kinds of limits on the way modification is handled are
311 acceptable. For example, requirements to preserve the original
312 author's copyright notice, the distribution terms, or the list of
313 authors, are ok. It is also no problem to require modified versions
314 to include notice that they were modified. Even entire sections that
315 may not be deleted or changed are acceptable, as long as they deal
316 with nontechnical topics (like this one). These kinds of restrictions
317 are acceptable because they don't obstruct the community's normal use
320 However, it must be possible to modify all the @emph{technical}
321 content of the manual, and then distribute the result in all the usual
322 media, through all the usual channels. Otherwise, the restrictions
323 obstruct the use of the manual, it is not free, and we need another
324 manual to replace it.
326 Please spread the word about this issue. Our community continues to
327 lose manuals to proprietary publishing. If we spread the word that
328 free software needs free reference manuals and free tutorials, perhaps
329 the next person who wants to contribute by writing documentation will
330 realize, before it is too late, that only free manuals contribute to
331 the free software community.
333 If you are writing documentation, please insist on publishing it under
334 the GNU Free Documentation License or another free documentation
335 license. Remember that this decision requires your approval---you
336 don't have to let the publisher decide. Some commercial publishers
337 will use a free license if you insist, but they will not propose the
338 option; it is up to you to raise the issue and say firmly that this is
339 what you want. If the publisher you are dealing with refuses, please
340 try other publishers. If you're not sure whether a proposed license
341 is free, write to @email{licensing@@gnu.org}.
343 You can encourage commercial publishers to sell more free, copylefted
344 manuals and tutorials by buying them, and particularly by buying
345 copies from the publishers that paid for their writing or for major
346 improvements. Meanwhile, try to avoid buying non-free documentation
347 at all. Check the distribution terms of a manual before you buy it,
348 and insist that whoever seeks your business must respect your freedom.
349 Check the history of the book, and try to reward the publishers that
350 have paid or pay the authors to work on it.
352 The Free Software Foundation maintains a list of free documentation
353 published by other publishers, at
354 @url{http://www.fsf.org/doc/other-free-books.html}.
357 @unnumberedsec Contributors to @value{GDBN}
359 Richard Stallman was the original author of @value{GDBN}, and of many
360 other @sc{gnu} programs. Many others have contributed to its
361 development. This section attempts to credit major contributors. One
362 of the virtues of free software is that everyone is free to contribute
363 to it; with regret, we cannot actually acknowledge everyone here. The
364 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
365 blow-by-blow account.
367 Changes much prior to version 2.0 are lost in the mists of time.
370 @emph{Plea:} Additions to this section are particularly welcome. If you
371 or your friends (or enemies, to be evenhanded) have been unfairly
372 omitted from this list, we would like to add your names!
375 So that they may not regard their many labors as thankless, we
376 particularly thank those who shepherded @value{GDBN} through major
378 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
379 Jim Blandy (release 4.18);
380 Jason Molenda (release 4.17);
381 Stan Shebs (release 4.14);
382 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
383 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
384 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
385 Jim Kingdon (releases 3.5, 3.4, and 3.3);
386 and Randy Smith (releases 3.2, 3.1, and 3.0).
388 Richard Stallman, assisted at various times by Peter TerMaat, Chris
389 Hanson, and Richard Mlynarik, handled releases through 2.8.
391 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
392 in @value{GDBN}, with significant additional contributions from Per
393 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
394 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
395 much general update work leading to release 3.0).
397 @value{GDBN} uses the BFD subroutine library to examine multiple
398 object-file formats; BFD was a joint project of David V.
399 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
401 David Johnson wrote the original COFF support; Pace Willison did
402 the original support for encapsulated COFF.
404 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
406 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
407 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
409 Jean-Daniel Fekete contributed Sun 386i support.
410 Chris Hanson improved the HP9000 support.
411 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
412 David Johnson contributed Encore Umax support.
413 Jyrki Kuoppala contributed Altos 3068 support.
414 Jeff Law contributed HP PA and SOM support.
415 Keith Packard contributed NS32K support.
416 Doug Rabson contributed Acorn Risc Machine support.
417 Bob Rusk contributed Harris Nighthawk CX-UX support.
418 Chris Smith contributed Convex support (and Fortran debugging).
419 Jonathan Stone contributed Pyramid support.
420 Michael Tiemann contributed SPARC support.
421 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
422 Pace Willison contributed Intel 386 support.
423 Jay Vosburgh contributed Symmetry support.
424 Marko Mlinar contributed OpenRISC 1000 support.
426 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
428 Rich Schaefer and Peter Schauer helped with support of SunOS shared
431 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
432 about several machine instruction sets.
434 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
435 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
436 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
437 and RDI targets, respectively.
439 Brian Fox is the author of the readline libraries providing
440 command-line editing and command history.
442 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
443 Modula-2 support, and contributed the Languages chapter of this manual.
445 Fred Fish wrote most of the support for Unix System Vr4.
446 He also enhanced the command-completion support to cover C@t{++} overloaded
449 Hitachi America (now Renesas America), Ltd. sponsored the support for
450 H8/300, H8/500, and Super-H processors.
452 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
454 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
457 Toshiba sponsored the support for the TX39 Mips processor.
459 Matsushita sponsored the support for the MN10200 and MN10300 processors.
461 Fujitsu sponsored the support for SPARClite and FR30 processors.
463 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
466 Michael Snyder added support for tracepoints.
468 Stu Grossman wrote gdbserver.
470 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
471 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
473 The following people at the Hewlett-Packard Company contributed
474 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
475 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
476 compiler, and the Text User Interface (nee Terminal User Interface):
477 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
478 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
479 provided HP-specific information in this manual.
481 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
482 Robert Hoehne made significant contributions to the DJGPP port.
484 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
485 development since 1991. Cygnus engineers who have worked on @value{GDBN}
486 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
487 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
488 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
489 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
490 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
491 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
492 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
493 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
494 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
495 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
496 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
497 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
498 Zuhn have made contributions both large and small.
500 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
501 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
503 Jim Blandy added support for preprocessor macros, while working for Red
506 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
507 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
508 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
509 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
510 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
511 with the migration of old architectures to this new framework.
513 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
514 unwinder framework, this consisting of a fresh new design featuring
515 frame IDs, independent frame sniffers, and the sentinel frame. Mark
516 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
517 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
518 trad unwinders. The architecture-specific changes, each involving a
519 complete rewrite of the architecture's frame code, were carried out by
520 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
521 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
522 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
523 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
526 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
527 Tensilica, Inc.@: contributed support for Xtensa processors. Others
528 who have worked on the Xtensa port of @value{GDBN} in the past include
529 Steve Tjiang, John Newlin, and Scott Foehner.
531 Michael Eager and staff of Xilinx, Inc., contributed support for the
532 Xilinx MicroBlaze architecture.
535 @chapter A Sample @value{GDBN} Session
537 You can use this manual at your leisure to read all about @value{GDBN}.
538 However, a handful of commands are enough to get started using the
539 debugger. This chapter illustrates those commands.
542 In this sample session, we emphasize user input like this: @b{input},
543 to make it easier to pick out from the surrounding output.
546 @c FIXME: this example may not be appropriate for some configs, where
547 @c FIXME...primary interest is in remote use.
549 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
550 processor) exhibits the following bug: sometimes, when we change its
551 quote strings from the default, the commands used to capture one macro
552 definition within another stop working. In the following short @code{m4}
553 session, we define a macro @code{foo} which expands to @code{0000}; we
554 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
555 same thing. However, when we change the open quote string to
556 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
557 procedure fails to define a new synonym @code{baz}:
566 @b{define(bar,defn(`foo'))}
570 @b{changequote(<QUOTE>,<UNQUOTE>)}
572 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
575 m4: End of input: 0: fatal error: EOF in string
579 Let us use @value{GDBN} to try to see what is going on.
582 $ @b{@value{GDBP} m4}
583 @c FIXME: this falsifies the exact text played out, to permit smallbook
584 @c FIXME... format to come out better.
585 @value{GDBN} is free software and you are welcome to distribute copies
586 of it under certain conditions; type "show copying" to see
588 There is absolutely no warranty for @value{GDBN}; type "show warranty"
591 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
596 @value{GDBN} reads only enough symbol data to know where to find the
597 rest when needed; as a result, the first prompt comes up very quickly.
598 We now tell @value{GDBN} to use a narrower display width than usual, so
599 that examples fit in this manual.
602 (@value{GDBP}) @b{set width 70}
606 We need to see how the @code{m4} built-in @code{changequote} works.
607 Having looked at the source, we know the relevant subroutine is
608 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
609 @code{break} command.
612 (@value{GDBP}) @b{break m4_changequote}
613 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
617 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
618 control; as long as control does not reach the @code{m4_changequote}
619 subroutine, the program runs as usual:
622 (@value{GDBP}) @b{run}
623 Starting program: /work/Editorial/gdb/gnu/m4/m4
631 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
632 suspends execution of @code{m4}, displaying information about the
633 context where it stops.
636 @b{changequote(<QUOTE>,<UNQUOTE>)}
638 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
640 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
644 Now we use the command @code{n} (@code{next}) to advance execution to
645 the next line of the current function.
649 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
654 @code{set_quotes} looks like a promising subroutine. We can go into it
655 by using the command @code{s} (@code{step}) instead of @code{next}.
656 @code{step} goes to the next line to be executed in @emph{any}
657 subroutine, so it steps into @code{set_quotes}.
661 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
663 530 if (lquote != def_lquote)
667 The display that shows the subroutine where @code{m4} is now
668 suspended (and its arguments) is called a stack frame display. It
669 shows a summary of the stack. We can use the @code{backtrace}
670 command (which can also be spelled @code{bt}), to see where we are
671 in the stack as a whole: the @code{backtrace} command displays a
672 stack frame for each active subroutine.
675 (@value{GDBP}) @b{bt}
676 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
678 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
680 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
681 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
683 #4 0x79dc in expand_input () at macro.c:40
684 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
688 We step through a few more lines to see what happens. The first two
689 times, we can use @samp{s}; the next two times we use @code{n} to avoid
690 falling into the @code{xstrdup} subroutine.
694 0x3b5c 532 if (rquote != def_rquote)
696 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
697 def_lquote : xstrdup(lq);
699 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
702 538 len_lquote = strlen(rquote);
706 The last line displayed looks a little odd; we can examine the variables
707 @code{lquote} and @code{rquote} to see if they are in fact the new left
708 and right quotes we specified. We use the command @code{p}
709 (@code{print}) to see their values.
712 (@value{GDBP}) @b{p lquote}
713 $1 = 0x35d40 "<QUOTE>"
714 (@value{GDBP}) @b{p rquote}
715 $2 = 0x35d50 "<UNQUOTE>"
719 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
720 To look at some context, we can display ten lines of source
721 surrounding the current line with the @code{l} (@code{list}) command.
727 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
729 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
732 538 len_lquote = strlen(rquote);
733 539 len_rquote = strlen(lquote);
740 Let us step past the two lines that set @code{len_lquote} and
741 @code{len_rquote}, and then examine the values of those variables.
745 539 len_rquote = strlen(lquote);
748 (@value{GDBP}) @b{p len_lquote}
750 (@value{GDBP}) @b{p len_rquote}
755 That certainly looks wrong, assuming @code{len_lquote} and
756 @code{len_rquote} are meant to be the lengths of @code{lquote} and
757 @code{rquote} respectively. We can set them to better values using
758 the @code{p} command, since it can print the value of
759 any expression---and that expression can include subroutine calls and
763 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
765 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
770 Is that enough to fix the problem of using the new quotes with the
771 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
772 executing with the @code{c} (@code{continue}) command, and then try the
773 example that caused trouble initially:
779 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
786 Success! The new quotes now work just as well as the default ones. The
787 problem seems to have been just the two typos defining the wrong
788 lengths. We allow @code{m4} exit by giving it an EOF as input:
792 Program exited normally.
796 The message @samp{Program exited normally.} is from @value{GDBN}; it
797 indicates @code{m4} has finished executing. We can end our @value{GDBN}
798 session with the @value{GDBN} @code{quit} command.
801 (@value{GDBP}) @b{quit}
805 @chapter Getting In and Out of @value{GDBN}
807 This chapter discusses how to start @value{GDBN}, and how to get out of it.
811 type @samp{@value{GDBP}} to start @value{GDBN}.
813 type @kbd{quit} or @kbd{Ctrl-d} to exit.
817 * Invoking GDB:: How to start @value{GDBN}
818 * Quitting GDB:: How to quit @value{GDBN}
819 * Shell Commands:: How to use shell commands inside @value{GDBN}
820 * Logging Output:: How to log @value{GDBN}'s output to a file
824 @section Invoking @value{GDBN}
826 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
827 @value{GDBN} reads commands from the terminal until you tell it to exit.
829 You can also run @code{@value{GDBP}} with a variety of arguments and options,
830 to specify more of your debugging environment at the outset.
832 The command-line options described here are designed
833 to cover a variety of situations; in some environments, some of these
834 options may effectively be unavailable.
836 The most usual way to start @value{GDBN} is with one argument,
837 specifying an executable program:
840 @value{GDBP} @var{program}
844 You can also start with both an executable program and a core file
848 @value{GDBP} @var{program} @var{core}
851 You can, instead, specify a process ID as a second argument, if you want
852 to debug a running process:
855 @value{GDBP} @var{program} 1234
859 would attach @value{GDBN} to process @code{1234} (unless you also have a file
860 named @file{1234}; @value{GDBN} does check for a core file first).
862 Taking advantage of the second command-line argument requires a fairly
863 complete operating system; when you use @value{GDBN} as a remote
864 debugger attached to a bare board, there may not be any notion of
865 ``process'', and there is often no way to get a core dump. @value{GDBN}
866 will warn you if it is unable to attach or to read core dumps.
868 You can optionally have @code{@value{GDBP}} pass any arguments after the
869 executable file to the inferior using @code{--args}. This option stops
872 @value{GDBP} --args gcc -O2 -c foo.c
874 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
875 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
877 You can run @code{@value{GDBP}} without printing the front material, which describes
878 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
885 You can further control how @value{GDBN} starts up by using command-line
886 options. @value{GDBN} itself can remind you of the options available.
896 to display all available options and briefly describe their use
897 (@samp{@value{GDBP} -h} is a shorter equivalent).
899 All options and command line arguments you give are processed
900 in sequential order. The order makes a difference when the
901 @samp{-x} option is used.
905 * File Options:: Choosing files
906 * Mode Options:: Choosing modes
907 * Startup:: What @value{GDBN} does during startup
911 @subsection Choosing Files
913 When @value{GDBN} starts, it reads any arguments other than options as
914 specifying an executable file and core file (or process ID). This is
915 the same as if the arguments were specified by the @samp{-se} and
916 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
917 first argument that does not have an associated option flag as
918 equivalent to the @samp{-se} option followed by that argument; and the
919 second argument that does not have an associated option flag, if any, as
920 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
921 If the second argument begins with a decimal digit, @value{GDBN} will
922 first attempt to attach to it as a process, and if that fails, attempt
923 to open it as a corefile. If you have a corefile whose name begins with
924 a digit, you can prevent @value{GDBN} from treating it as a pid by
925 prefixing it with @file{./}, e.g.@: @file{./12345}.
927 If @value{GDBN} has not been configured to included core file support,
928 such as for most embedded targets, then it will complain about a second
929 argument and ignore it.
931 Many options have both long and short forms; both are shown in the
932 following list. @value{GDBN} also recognizes the long forms if you truncate
933 them, so long as enough of the option is present to be unambiguous.
934 (If you prefer, you can flag option arguments with @samp{--} rather
935 than @samp{-}, though we illustrate the more usual convention.)
937 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
938 @c way, both those who look for -foo and --foo in the index, will find
942 @item -symbols @var{file}
944 @cindex @code{--symbols}
946 Read symbol table from file @var{file}.
948 @item -exec @var{file}
950 @cindex @code{--exec}
952 Use file @var{file} as the executable file to execute when appropriate,
953 and for examining pure data in conjunction with a core dump.
957 Read symbol table from file @var{file} and use it as the executable
960 @item -core @var{file}
962 @cindex @code{--core}
964 Use file @var{file} as a core dump to examine.
966 @item -pid @var{number}
967 @itemx -p @var{number}
970 Connect to process ID @var{number}, as with the @code{attach} command.
972 @item -command @var{file}
974 @cindex @code{--command}
976 Execute commands from file @var{file}. The contents of this file is
977 evaluated exactly as the @code{source} command would.
978 @xref{Command Files,, Command files}.
980 @item -eval-command @var{command}
981 @itemx -ex @var{command}
982 @cindex @code{--eval-command}
984 Execute a single @value{GDBN} command.
986 This option may be used multiple times to call multiple commands. It may
987 also be interleaved with @samp{-command} as required.
990 @value{GDBP} -ex 'target sim' -ex 'load' \
991 -x setbreakpoints -ex 'run' a.out
994 @item -directory @var{directory}
995 @itemx -d @var{directory}
996 @cindex @code{--directory}
998 Add @var{directory} to the path to search for source and script files.
1002 @cindex @code{--readnow}
1004 Read each symbol file's entire symbol table immediately, rather than
1005 the default, which is to read it incrementally as it is needed.
1006 This makes startup slower, but makes future operations faster.
1011 @subsection Choosing Modes
1013 You can run @value{GDBN} in various alternative modes---for example, in
1014 batch mode or quiet mode.
1021 Do not execute commands found in any initialization files. Normally,
1022 @value{GDBN} executes the commands in these files after all the command
1023 options and arguments have been processed. @xref{Command Files,,Command
1029 @cindex @code{--quiet}
1030 @cindex @code{--silent}
1032 ``Quiet''. Do not print the introductory and copyright messages. These
1033 messages are also suppressed in batch mode.
1036 @cindex @code{--batch}
1037 Run in batch mode. Exit with status @code{0} after processing all the
1038 command files specified with @samp{-x} (and all commands from
1039 initialization files, if not inhibited with @samp{-n}). Exit with
1040 nonzero status if an error occurs in executing the @value{GDBN} commands
1041 in the command files. Batch mode also disables pagination, sets unlimited
1042 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1043 off} were in effect (@pxref{Messages/Warnings}).
1045 Batch mode may be useful for running @value{GDBN} as a filter, for
1046 example to download and run a program on another computer; in order to
1047 make this more useful, the message
1050 Program exited normally.
1054 (which is ordinarily issued whenever a program running under
1055 @value{GDBN} control terminates) is not issued when running in batch
1059 @cindex @code{--batch-silent}
1060 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1061 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1062 unaffected). This is much quieter than @samp{-silent} and would be useless
1063 for an interactive session.
1065 This is particularly useful when using targets that give @samp{Loading section}
1066 messages, for example.
1068 Note that targets that give their output via @value{GDBN}, as opposed to
1069 writing directly to @code{stdout}, will also be made silent.
1071 @item -return-child-result
1072 @cindex @code{--return-child-result}
1073 The return code from @value{GDBN} will be the return code from the child
1074 process (the process being debugged), with the following exceptions:
1078 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1079 internal error. In this case the exit code is the same as it would have been
1080 without @samp{-return-child-result}.
1082 The user quits with an explicit value. E.g., @samp{quit 1}.
1084 The child process never runs, or is not allowed to terminate, in which case
1085 the exit code will be -1.
1088 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1089 when @value{GDBN} is being used as a remote program loader or simulator
1094 @cindex @code{--nowindows}
1096 ``No windows''. If @value{GDBN} comes with a graphical user interface
1097 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1098 interface. If no GUI is available, this option has no effect.
1102 @cindex @code{--windows}
1104 If @value{GDBN} includes a GUI, then this option requires it to be
1107 @item -cd @var{directory}
1109 Run @value{GDBN} using @var{directory} as its working directory,
1110 instead of the current directory.
1112 @item -data-directory @var{directory}
1113 @cindex @code{--data-directory}
1114 Run @value{GDBN} using @var{directory} as its data directory.
1115 The data directory is where @value{GDBN} searches for its
1116 auxiliary files. @xref{Data Files}.
1120 @cindex @code{--fullname}
1122 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1123 subprocess. It tells @value{GDBN} to output the full file name and line
1124 number in a standard, recognizable fashion each time a stack frame is
1125 displayed (which includes each time your program stops). This
1126 recognizable format looks like two @samp{\032} characters, followed by
1127 the file name, line number and character position separated by colons,
1128 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1129 @samp{\032} characters as a signal to display the source code for the
1133 @cindex @code{--epoch}
1134 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1135 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1136 routines so as to allow Epoch to display values of expressions in a
1139 @item -annotate @var{level}
1140 @cindex @code{--annotate}
1141 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1142 effect is identical to using @samp{set annotate @var{level}}
1143 (@pxref{Annotations}). The annotation @var{level} controls how much
1144 information @value{GDBN} prints together with its prompt, values of
1145 expressions, source lines, and other types of output. Level 0 is the
1146 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1147 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1148 that control @value{GDBN}, and level 2 has been deprecated.
1150 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1154 @cindex @code{--args}
1155 Change interpretation of command line so that arguments following the
1156 executable file are passed as command line arguments to the inferior.
1157 This option stops option processing.
1159 @item -baud @var{bps}
1161 @cindex @code{--baud}
1163 Set the line speed (baud rate or bits per second) of any serial
1164 interface used by @value{GDBN} for remote debugging.
1166 @item -l @var{timeout}
1168 Set the timeout (in seconds) of any communication used by @value{GDBN}
1169 for remote debugging.
1171 @item -tty @var{device}
1172 @itemx -t @var{device}
1173 @cindex @code{--tty}
1175 Run using @var{device} for your program's standard input and output.
1176 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1178 @c resolve the situation of these eventually
1180 @cindex @code{--tui}
1181 Activate the @dfn{Text User Interface} when starting. The Text User
1182 Interface manages several text windows on the terminal, showing
1183 source, assembly, registers and @value{GDBN} command outputs
1184 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1185 Text User Interface can be enabled by invoking the program
1186 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1187 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1190 @c @cindex @code{--xdb}
1191 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1192 @c For information, see the file @file{xdb_trans.html}, which is usually
1193 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1196 @item -interpreter @var{interp}
1197 @cindex @code{--interpreter}
1198 Use the interpreter @var{interp} for interface with the controlling
1199 program or device. This option is meant to be set by programs which
1200 communicate with @value{GDBN} using it as a back end.
1201 @xref{Interpreters, , Command Interpreters}.
1203 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1204 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1205 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1206 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1207 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1208 @sc{gdb/mi} interfaces are no longer supported.
1211 @cindex @code{--write}
1212 Open the executable and core files for both reading and writing. This
1213 is equivalent to the @samp{set write on} command inside @value{GDBN}
1217 @cindex @code{--statistics}
1218 This option causes @value{GDBN} to print statistics about time and
1219 memory usage after it completes each command and returns to the prompt.
1222 @cindex @code{--version}
1223 This option causes @value{GDBN} to print its version number and
1224 no-warranty blurb, and exit.
1229 @subsection What @value{GDBN} Does During Startup
1230 @cindex @value{GDBN} startup
1232 Here's the description of what @value{GDBN} does during session startup:
1236 Sets up the command interpreter as specified by the command line
1237 (@pxref{Mode Options, interpreter}).
1241 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1242 used when building @value{GDBN}; @pxref{System-wide configuration,
1243 ,System-wide configuration and settings}) and executes all the commands in
1247 Reads the init file (if any) in your home directory@footnote{On
1248 DOS/Windows systems, the home directory is the one pointed to by the
1249 @code{HOME} environment variable.} and executes all the commands in
1253 Processes command line options and operands.
1256 Reads and executes the commands from init file (if any) in the current
1257 working directory. This is only done if the current directory is
1258 different from your home directory. Thus, you can have more than one
1259 init file, one generic in your home directory, and another, specific
1260 to the program you are debugging, in the directory where you invoke
1264 If the command line specified a program to debug, or a process to
1265 attach to, or a core file, @value{GDBN} loads any auto-loaded
1266 scripts provided for the program or for its loaded shared libraries.
1267 @xref{Auto-loading}.
1269 If you wish to disable the auto-loading during startup,
1270 you must do something like the following:
1273 $ gdb -ex "set auto-load-scripts off" -ex "file myprogram"
1276 The following does not work because the auto-loading is turned off too late:
1279 $ gdb -ex "set auto-load-scripts off" myprogram
1283 Reads command files specified by the @samp{-x} option. @xref{Command
1284 Files}, for more details about @value{GDBN} command files.
1287 Reads the command history recorded in the @dfn{history file}.
1288 @xref{Command History}, for more details about the command history and the
1289 files where @value{GDBN} records it.
1292 Init files use the same syntax as @dfn{command files} (@pxref{Command
1293 Files}) and are processed by @value{GDBN} in the same way. The init
1294 file in your home directory can set options (such as @samp{set
1295 complaints}) that affect subsequent processing of command line options
1296 and operands. Init files are not executed if you use the @samp{-nx}
1297 option (@pxref{Mode Options, ,Choosing Modes}).
1299 To display the list of init files loaded by gdb at startup, you
1300 can use @kbd{gdb --help}.
1302 @cindex init file name
1303 @cindex @file{.gdbinit}
1304 @cindex @file{gdb.ini}
1305 The @value{GDBN} init files are normally called @file{.gdbinit}.
1306 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1307 the limitations of file names imposed by DOS filesystems. The Windows
1308 ports of @value{GDBN} use the standard name, but if they find a
1309 @file{gdb.ini} file, they warn you about that and suggest to rename
1310 the file to the standard name.
1314 @section Quitting @value{GDBN}
1315 @cindex exiting @value{GDBN}
1316 @cindex leaving @value{GDBN}
1319 @kindex quit @r{[}@var{expression}@r{]}
1320 @kindex q @r{(@code{quit})}
1321 @item quit @r{[}@var{expression}@r{]}
1323 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1324 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1325 do not supply @var{expression}, @value{GDBN} will terminate normally;
1326 otherwise it will terminate using the result of @var{expression} as the
1331 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1332 terminates the action of any @value{GDBN} command that is in progress and
1333 returns to @value{GDBN} command level. It is safe to type the interrupt
1334 character at any time because @value{GDBN} does not allow it to take effect
1335 until a time when it is safe.
1337 If you have been using @value{GDBN} to control an attached process or
1338 device, you can release it with the @code{detach} command
1339 (@pxref{Attach, ,Debugging an Already-running Process}).
1341 @node Shell Commands
1342 @section Shell Commands
1344 If you need to execute occasional shell commands during your
1345 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1346 just use the @code{shell} command.
1350 @cindex shell escape
1351 @item shell @var{command string}
1352 Invoke a standard shell to execute @var{command string}.
1353 If it exists, the environment variable @code{SHELL} determines which
1354 shell to run. Otherwise @value{GDBN} uses the default shell
1355 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1358 The utility @code{make} is often needed in development environments.
1359 You do not have to use the @code{shell} command for this purpose in
1364 @cindex calling make
1365 @item make @var{make-args}
1366 Execute the @code{make} program with the specified
1367 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1370 @node Logging Output
1371 @section Logging Output
1372 @cindex logging @value{GDBN} output
1373 @cindex save @value{GDBN} output to a file
1375 You may want to save the output of @value{GDBN} commands to a file.
1376 There are several commands to control @value{GDBN}'s logging.
1380 @item set logging on
1382 @item set logging off
1384 @cindex logging file name
1385 @item set logging file @var{file}
1386 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1387 @item set logging overwrite [on|off]
1388 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1389 you want @code{set logging on} to overwrite the logfile instead.
1390 @item set logging redirect [on|off]
1391 By default, @value{GDBN} output will go to both the terminal and the logfile.
1392 Set @code{redirect} if you want output to go only to the log file.
1393 @kindex show logging
1395 Show the current values of the logging settings.
1399 @chapter @value{GDBN} Commands
1401 You can abbreviate a @value{GDBN} command to the first few letters of the command
1402 name, if that abbreviation is unambiguous; and you can repeat certain
1403 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1404 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1405 show you the alternatives available, if there is more than one possibility).
1408 * Command Syntax:: How to give commands to @value{GDBN}
1409 * Completion:: Command completion
1410 * Help:: How to ask @value{GDBN} for help
1413 @node Command Syntax
1414 @section Command Syntax
1416 A @value{GDBN} command is a single line of input. There is no limit on
1417 how long it can be. It starts with a command name, which is followed by
1418 arguments whose meaning depends on the command name. For example, the
1419 command @code{step} accepts an argument which is the number of times to
1420 step, as in @samp{step 5}. You can also use the @code{step} command
1421 with no arguments. Some commands do not allow any arguments.
1423 @cindex abbreviation
1424 @value{GDBN} command names may always be truncated if that abbreviation is
1425 unambiguous. Other possible command abbreviations are listed in the
1426 documentation for individual commands. In some cases, even ambiguous
1427 abbreviations are allowed; for example, @code{s} is specially defined as
1428 equivalent to @code{step} even though there are other commands whose
1429 names start with @code{s}. You can test abbreviations by using them as
1430 arguments to the @code{help} command.
1432 @cindex repeating commands
1433 @kindex RET @r{(repeat last command)}
1434 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1435 repeat the previous command. Certain commands (for example, @code{run})
1436 will not repeat this way; these are commands whose unintentional
1437 repetition might cause trouble and which you are unlikely to want to
1438 repeat. User-defined commands can disable this feature; see
1439 @ref{Define, dont-repeat}.
1441 The @code{list} and @code{x} commands, when you repeat them with
1442 @key{RET}, construct new arguments rather than repeating
1443 exactly as typed. This permits easy scanning of source or memory.
1445 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1446 output, in a way similar to the common utility @code{more}
1447 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1448 @key{RET} too many in this situation, @value{GDBN} disables command
1449 repetition after any command that generates this sort of display.
1451 @kindex # @r{(a comment)}
1453 Any text from a @kbd{#} to the end of the line is a comment; it does
1454 nothing. This is useful mainly in command files (@pxref{Command
1455 Files,,Command Files}).
1457 @cindex repeating command sequences
1458 @kindex Ctrl-o @r{(operate-and-get-next)}
1459 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1460 commands. This command accepts the current line, like @key{RET}, and
1461 then fetches the next line relative to the current line from the history
1465 @section Command Completion
1468 @cindex word completion
1469 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1470 only one possibility; it can also show you what the valid possibilities
1471 are for the next word in a command, at any time. This works for @value{GDBN}
1472 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1474 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1475 of a word. If there is only one possibility, @value{GDBN} fills in the
1476 word, and waits for you to finish the command (or press @key{RET} to
1477 enter it). For example, if you type
1479 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1480 @c complete accuracy in these examples; space introduced for clarity.
1481 @c If texinfo enhancements make it unnecessary, it would be nice to
1482 @c replace " @key" by "@key" in the following...
1484 (@value{GDBP}) info bre @key{TAB}
1488 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1489 the only @code{info} subcommand beginning with @samp{bre}:
1492 (@value{GDBP}) info breakpoints
1496 You can either press @key{RET} at this point, to run the @code{info
1497 breakpoints} command, or backspace and enter something else, if
1498 @samp{breakpoints} does not look like the command you expected. (If you
1499 were sure you wanted @code{info breakpoints} in the first place, you
1500 might as well just type @key{RET} immediately after @samp{info bre},
1501 to exploit command abbreviations rather than command completion).
1503 If there is more than one possibility for the next word when you press
1504 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1505 characters and try again, or just press @key{TAB} a second time;
1506 @value{GDBN} displays all the possible completions for that word. For
1507 example, you might want to set a breakpoint on a subroutine whose name
1508 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1509 just sounds the bell. Typing @key{TAB} again displays all the
1510 function names in your program that begin with those characters, for
1514 (@value{GDBP}) b make_ @key{TAB}
1515 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1516 make_a_section_from_file make_environ
1517 make_abs_section make_function_type
1518 make_blockvector make_pointer_type
1519 make_cleanup make_reference_type
1520 make_command make_symbol_completion_list
1521 (@value{GDBP}) b make_
1525 After displaying the available possibilities, @value{GDBN} copies your
1526 partial input (@samp{b make_} in the example) so you can finish the
1529 If you just want to see the list of alternatives in the first place, you
1530 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1531 means @kbd{@key{META} ?}. You can type this either by holding down a
1532 key designated as the @key{META} shift on your keyboard (if there is
1533 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1535 @cindex quotes in commands
1536 @cindex completion of quoted strings
1537 Sometimes the string you need, while logically a ``word'', may contain
1538 parentheses or other characters that @value{GDBN} normally excludes from
1539 its notion of a word. To permit word completion to work in this
1540 situation, you may enclose words in @code{'} (single quote marks) in
1541 @value{GDBN} commands.
1543 The most likely situation where you might need this is in typing the
1544 name of a C@t{++} function. This is because C@t{++} allows function
1545 overloading (multiple definitions of the same function, distinguished
1546 by argument type). For example, when you want to set a breakpoint you
1547 may need to distinguish whether you mean the version of @code{name}
1548 that takes an @code{int} parameter, @code{name(int)}, or the version
1549 that takes a @code{float} parameter, @code{name(float)}. To use the
1550 word-completion facilities in this situation, type a single quote
1551 @code{'} at the beginning of the function name. This alerts
1552 @value{GDBN} that it may need to consider more information than usual
1553 when you press @key{TAB} or @kbd{M-?} to request word completion:
1556 (@value{GDBP}) b 'bubble( @kbd{M-?}
1557 bubble(double,double) bubble(int,int)
1558 (@value{GDBP}) b 'bubble(
1561 In some cases, @value{GDBN} can tell that completing a name requires using
1562 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1563 completing as much as it can) if you do not type the quote in the first
1567 (@value{GDBP}) b bub @key{TAB}
1568 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1569 (@value{GDBP}) b 'bubble(
1573 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1574 you have not yet started typing the argument list when you ask for
1575 completion on an overloaded symbol.
1577 For more information about overloaded functions, see @ref{C Plus Plus
1578 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1579 overload-resolution off} to disable overload resolution;
1580 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1582 @cindex completion of structure field names
1583 @cindex structure field name completion
1584 @cindex completion of union field names
1585 @cindex union field name completion
1586 When completing in an expression which looks up a field in a
1587 structure, @value{GDBN} also tries@footnote{The completer can be
1588 confused by certain kinds of invalid expressions. Also, it only
1589 examines the static type of the expression, not the dynamic type.} to
1590 limit completions to the field names available in the type of the
1594 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1595 magic to_fputs to_rewind
1596 to_data to_isatty to_write
1597 to_delete to_put to_write_async_safe
1602 This is because the @code{gdb_stdout} is a variable of the type
1603 @code{struct ui_file} that is defined in @value{GDBN} sources as
1610 ui_file_flush_ftype *to_flush;
1611 ui_file_write_ftype *to_write;
1612 ui_file_write_async_safe_ftype *to_write_async_safe;
1613 ui_file_fputs_ftype *to_fputs;
1614 ui_file_read_ftype *to_read;
1615 ui_file_delete_ftype *to_delete;
1616 ui_file_isatty_ftype *to_isatty;
1617 ui_file_rewind_ftype *to_rewind;
1618 ui_file_put_ftype *to_put;
1625 @section Getting Help
1626 @cindex online documentation
1629 You can always ask @value{GDBN} itself for information on its commands,
1630 using the command @code{help}.
1633 @kindex h @r{(@code{help})}
1636 You can use @code{help} (abbreviated @code{h}) with no arguments to
1637 display a short list of named classes of commands:
1641 List of classes of commands:
1643 aliases -- Aliases of other commands
1644 breakpoints -- Making program stop at certain points
1645 data -- Examining data
1646 files -- Specifying and examining files
1647 internals -- Maintenance commands
1648 obscure -- Obscure features
1649 running -- Running the program
1650 stack -- Examining the stack
1651 status -- Status inquiries
1652 support -- Support facilities
1653 tracepoints -- Tracing of program execution without
1654 stopping the program
1655 user-defined -- User-defined commands
1657 Type "help" followed by a class name for a list of
1658 commands in that class.
1659 Type "help" followed by command name for full
1661 Command name abbreviations are allowed if unambiguous.
1664 @c the above line break eliminates huge line overfull...
1666 @item help @var{class}
1667 Using one of the general help classes as an argument, you can get a
1668 list of the individual commands in that class. For example, here is the
1669 help display for the class @code{status}:
1672 (@value{GDBP}) help status
1677 @c Line break in "show" line falsifies real output, but needed
1678 @c to fit in smallbook page size.
1679 info -- Generic command for showing things
1680 about the program being debugged
1681 show -- Generic command for showing things
1684 Type "help" followed by command name for full
1686 Command name abbreviations are allowed if unambiguous.
1690 @item help @var{command}
1691 With a command name as @code{help} argument, @value{GDBN} displays a
1692 short paragraph on how to use that command.
1695 @item apropos @var{args}
1696 The @code{apropos} command searches through all of the @value{GDBN}
1697 commands, and their documentation, for the regular expression specified in
1698 @var{args}. It prints out all matches found. For example:
1709 set symbol-reloading -- Set dynamic symbol table reloading
1710 multiple times in one run
1711 show symbol-reloading -- Show dynamic symbol table reloading
1712 multiple times in one run
1717 @item complete @var{args}
1718 The @code{complete @var{args}} command lists all the possible completions
1719 for the beginning of a command. Use @var{args} to specify the beginning of the
1720 command you want completed. For example:
1726 @noindent results in:
1737 @noindent This is intended for use by @sc{gnu} Emacs.
1740 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1741 and @code{show} to inquire about the state of your program, or the state
1742 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1743 manual introduces each of them in the appropriate context. The listings
1744 under @code{info} and under @code{show} in the Index point to
1745 all the sub-commands. @xref{Index}.
1750 @kindex i @r{(@code{info})}
1752 This command (abbreviated @code{i}) is for describing the state of your
1753 program. For example, you can show the arguments passed to a function
1754 with @code{info args}, list the registers currently in use with @code{info
1755 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1756 You can get a complete list of the @code{info} sub-commands with
1757 @w{@code{help info}}.
1761 You can assign the result of an expression to an environment variable with
1762 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1763 @code{set prompt $}.
1767 In contrast to @code{info}, @code{show} is for describing the state of
1768 @value{GDBN} itself.
1769 You can change most of the things you can @code{show}, by using the
1770 related command @code{set}; for example, you can control what number
1771 system is used for displays with @code{set radix}, or simply inquire
1772 which is currently in use with @code{show radix}.
1775 To display all the settable parameters and their current
1776 values, you can use @code{show} with no arguments; you may also use
1777 @code{info set}. Both commands produce the same display.
1778 @c FIXME: "info set" violates the rule that "info" is for state of
1779 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1780 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1784 Here are three miscellaneous @code{show} subcommands, all of which are
1785 exceptional in lacking corresponding @code{set} commands:
1788 @kindex show version
1789 @cindex @value{GDBN} version number
1791 Show what version of @value{GDBN} is running. You should include this
1792 information in @value{GDBN} bug-reports. If multiple versions of
1793 @value{GDBN} are in use at your site, you may need to determine which
1794 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1795 commands are introduced, and old ones may wither away. Also, many
1796 system vendors ship variant versions of @value{GDBN}, and there are
1797 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1798 The version number is the same as the one announced when you start
1801 @kindex show copying
1802 @kindex info copying
1803 @cindex display @value{GDBN} copyright
1806 Display information about permission for copying @value{GDBN}.
1808 @kindex show warranty
1809 @kindex info warranty
1811 @itemx info warranty
1812 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1813 if your version of @value{GDBN} comes with one.
1818 @chapter Running Programs Under @value{GDBN}
1820 When you run a program under @value{GDBN}, you must first generate
1821 debugging information when you compile it.
1823 You may start @value{GDBN} with its arguments, if any, in an environment
1824 of your choice. If you are doing native debugging, you may redirect
1825 your program's input and output, debug an already running process, or
1826 kill a child process.
1829 * Compilation:: Compiling for debugging
1830 * Starting:: Starting your program
1831 * Arguments:: Your program's arguments
1832 * Environment:: Your program's environment
1834 * Working Directory:: Your program's working directory
1835 * Input/Output:: Your program's input and output
1836 * Attach:: Debugging an already-running process
1837 * Kill Process:: Killing the child process
1839 * Inferiors and Programs:: Debugging multiple inferiors and programs
1840 * Threads:: Debugging programs with multiple threads
1841 * Forks:: Debugging forks
1842 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1846 @section Compiling for Debugging
1848 In order to debug a program effectively, you need to generate
1849 debugging information when you compile it. This debugging information
1850 is stored in the object file; it describes the data type of each
1851 variable or function and the correspondence between source line numbers
1852 and addresses in the executable code.
1854 To request debugging information, specify the @samp{-g} option when you run
1857 Programs that are to be shipped to your customers are compiled with
1858 optimizations, using the @samp{-O} compiler option. However, some
1859 compilers are unable to handle the @samp{-g} and @samp{-O} options
1860 together. Using those compilers, you cannot generate optimized
1861 executables containing debugging information.
1863 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1864 without @samp{-O}, making it possible to debug optimized code. We
1865 recommend that you @emph{always} use @samp{-g} whenever you compile a
1866 program. You may think your program is correct, but there is no sense
1867 in pushing your luck. For more information, see @ref{Optimized Code}.
1869 Older versions of the @sc{gnu} C compiler permitted a variant option
1870 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1871 format; if your @sc{gnu} C compiler has this option, do not use it.
1873 @value{GDBN} knows about preprocessor macros and can show you their
1874 expansion (@pxref{Macros}). Most compilers do not include information
1875 about preprocessor macros in the debugging information if you specify
1876 the @option{-g} flag alone, because this information is rather large.
1877 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1878 provides macro information if you specify the options
1879 @option{-gdwarf-2} and @option{-g3}; the former option requests
1880 debugging information in the Dwarf 2 format, and the latter requests
1881 ``extra information''. In the future, we hope to find more compact
1882 ways to represent macro information, so that it can be included with
1887 @section Starting your Program
1893 @kindex r @r{(@code{run})}
1896 Use the @code{run} command to start your program under @value{GDBN}.
1897 You must first specify the program name (except on VxWorks) with an
1898 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1899 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1900 (@pxref{Files, ,Commands to Specify Files}).
1904 If you are running your program in an execution environment that
1905 supports processes, @code{run} creates an inferior process and makes
1906 that process run your program. In some environments without processes,
1907 @code{run} jumps to the start of your program. Other targets,
1908 like @samp{remote}, are always running. If you get an error
1909 message like this one:
1912 The "remote" target does not support "run".
1913 Try "help target" or "continue".
1917 then use @code{continue} to run your program. You may need @code{load}
1918 first (@pxref{load}).
1920 The execution of a program is affected by certain information it
1921 receives from its superior. @value{GDBN} provides ways to specify this
1922 information, which you must do @emph{before} starting your program. (You
1923 can change it after starting your program, but such changes only affect
1924 your program the next time you start it.) This information may be
1925 divided into four categories:
1928 @item The @emph{arguments.}
1929 Specify the arguments to give your program as the arguments of the
1930 @code{run} command. If a shell is available on your target, the shell
1931 is used to pass the arguments, so that you may use normal conventions
1932 (such as wildcard expansion or variable substitution) in describing
1934 In Unix systems, you can control which shell is used with the
1935 @code{SHELL} environment variable.
1936 @xref{Arguments, ,Your Program's Arguments}.
1938 @item The @emph{environment.}
1939 Your program normally inherits its environment from @value{GDBN}, but you can
1940 use the @value{GDBN} commands @code{set environment} and @code{unset
1941 environment} to change parts of the environment that affect
1942 your program. @xref{Environment, ,Your Program's Environment}.
1944 @item The @emph{working directory.}
1945 Your program inherits its working directory from @value{GDBN}. You can set
1946 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1947 @xref{Working Directory, ,Your Program's Working Directory}.
1949 @item The @emph{standard input and output.}
1950 Your program normally uses the same device for standard input and
1951 standard output as @value{GDBN} is using. You can redirect input and output
1952 in the @code{run} command line, or you can use the @code{tty} command to
1953 set a different device for your program.
1954 @xref{Input/Output, ,Your Program's Input and Output}.
1957 @emph{Warning:} While input and output redirection work, you cannot use
1958 pipes to pass the output of the program you are debugging to another
1959 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1963 When you issue the @code{run} command, your program begins to execute
1964 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1965 of how to arrange for your program to stop. Once your program has
1966 stopped, you may call functions in your program, using the @code{print}
1967 or @code{call} commands. @xref{Data, ,Examining Data}.
1969 If the modification time of your symbol file has changed since the last
1970 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1971 table, and reads it again. When it does this, @value{GDBN} tries to retain
1972 your current breakpoints.
1977 @cindex run to main procedure
1978 The name of the main procedure can vary from language to language.
1979 With C or C@t{++}, the main procedure name is always @code{main}, but
1980 other languages such as Ada do not require a specific name for their
1981 main procedure. The debugger provides a convenient way to start the
1982 execution of the program and to stop at the beginning of the main
1983 procedure, depending on the language used.
1985 The @samp{start} command does the equivalent of setting a temporary
1986 breakpoint at the beginning of the main procedure and then invoking
1987 the @samp{run} command.
1989 @cindex elaboration phase
1990 Some programs contain an @dfn{elaboration} phase where some startup code is
1991 executed before the main procedure is called. This depends on the
1992 languages used to write your program. In C@t{++}, for instance,
1993 constructors for static and global objects are executed before
1994 @code{main} is called. It is therefore possible that the debugger stops
1995 before reaching the main procedure. However, the temporary breakpoint
1996 will remain to halt execution.
1998 Specify the arguments to give to your program as arguments to the
1999 @samp{start} command. These arguments will be given verbatim to the
2000 underlying @samp{run} command. Note that the same arguments will be
2001 reused if no argument is provided during subsequent calls to
2002 @samp{start} or @samp{run}.
2004 It is sometimes necessary to debug the program during elaboration. In
2005 these cases, using the @code{start} command would stop the execution of
2006 your program too late, as the program would have already completed the
2007 elaboration phase. Under these circumstances, insert breakpoints in your
2008 elaboration code before running your program.
2010 @kindex set exec-wrapper
2011 @item set exec-wrapper @var{wrapper}
2012 @itemx show exec-wrapper
2013 @itemx unset exec-wrapper
2014 When @samp{exec-wrapper} is set, the specified wrapper is used to
2015 launch programs for debugging. @value{GDBN} starts your program
2016 with a shell command of the form @kbd{exec @var{wrapper}
2017 @var{program}}. Quoting is added to @var{program} and its
2018 arguments, but not to @var{wrapper}, so you should add quotes if
2019 appropriate for your shell. The wrapper runs until it executes
2020 your program, and then @value{GDBN} takes control.
2022 You can use any program that eventually calls @code{execve} with
2023 its arguments as a wrapper. Several standard Unix utilities do
2024 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2025 with @code{exec "$@@"} will also work.
2027 For example, you can use @code{env} to pass an environment variable to
2028 the debugged program, without setting the variable in your shell's
2032 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2036 This command is available when debugging locally on most targets, excluding
2037 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2039 @kindex set disable-randomization
2040 @item set disable-randomization
2041 @itemx set disable-randomization on
2042 This option (enabled by default in @value{GDBN}) will turn off the native
2043 randomization of the virtual address space of the started program. This option
2044 is useful for multiple debugging sessions to make the execution better
2045 reproducible and memory addresses reusable across debugging sessions.
2047 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2048 On @sc{gnu}/Linux you can get the same behavior using
2051 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2054 @item set disable-randomization off
2055 Leave the behavior of the started executable unchanged. Some bugs rear their
2056 ugly heads only when the program is loaded at certain addresses. If your bug
2057 disappears when you run the program under @value{GDBN}, that might be because
2058 @value{GDBN} by default disables the address randomization on platforms, such
2059 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2060 disable-randomization off} to try to reproduce such elusive bugs.
2062 On targets where it is available, virtual address space randomization
2063 protects the programs against certain kinds of security attacks. In these
2064 cases the attacker needs to know the exact location of a concrete executable
2065 code. Randomizing its location makes it impossible to inject jumps misusing
2066 a code at its expected addresses.
2068 Prelinking shared libraries provides a startup performance advantage but it
2069 makes addresses in these libraries predictable for privileged processes by
2070 having just unprivileged access at the target system. Reading the shared
2071 library binary gives enough information for assembling the malicious code
2072 misusing it. Still even a prelinked shared library can get loaded at a new
2073 random address just requiring the regular relocation process during the
2074 startup. Shared libraries not already prelinked are always loaded at
2075 a randomly chosen address.
2077 Position independent executables (PIE) contain position independent code
2078 similar to the shared libraries and therefore such executables get loaded at
2079 a randomly chosen address upon startup. PIE executables always load even
2080 already prelinked shared libraries at a random address. You can build such
2081 executable using @command{gcc -fPIE -pie}.
2083 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2084 (as long as the randomization is enabled).
2086 @item show disable-randomization
2087 Show the current setting of the explicit disable of the native randomization of
2088 the virtual address space of the started program.
2093 @section Your Program's Arguments
2095 @cindex arguments (to your program)
2096 The arguments to your program can be specified by the arguments of the
2098 They are passed to a shell, which expands wildcard characters and
2099 performs redirection of I/O, and thence to your program. Your
2100 @code{SHELL} environment variable (if it exists) specifies what shell
2101 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2102 the default shell (@file{/bin/sh} on Unix).
2104 On non-Unix systems, the program is usually invoked directly by
2105 @value{GDBN}, which emulates I/O redirection via the appropriate system
2106 calls, and the wildcard characters are expanded by the startup code of
2107 the program, not by the shell.
2109 @code{run} with no arguments uses the same arguments used by the previous
2110 @code{run}, or those set by the @code{set args} command.
2115 Specify the arguments to be used the next time your program is run. If
2116 @code{set args} has no arguments, @code{run} executes your program
2117 with no arguments. Once you have run your program with arguments,
2118 using @code{set args} before the next @code{run} is the only way to run
2119 it again without arguments.
2123 Show the arguments to give your program when it is started.
2127 @section Your Program's Environment
2129 @cindex environment (of your program)
2130 The @dfn{environment} consists of a set of environment variables and
2131 their values. Environment variables conventionally record such things as
2132 your user name, your home directory, your terminal type, and your search
2133 path for programs to run. Usually you set up environment variables with
2134 the shell and they are inherited by all the other programs you run. When
2135 debugging, it can be useful to try running your program with a modified
2136 environment without having to start @value{GDBN} over again.
2140 @item path @var{directory}
2141 Add @var{directory} to the front of the @code{PATH} environment variable
2142 (the search path for executables) that will be passed to your program.
2143 The value of @code{PATH} used by @value{GDBN} does not change.
2144 You may specify several directory names, separated by whitespace or by a
2145 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2146 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2147 is moved to the front, so it is searched sooner.
2149 You can use the string @samp{$cwd} to refer to whatever is the current
2150 working directory at the time @value{GDBN} searches the path. If you
2151 use @samp{.} instead, it refers to the directory where you executed the
2152 @code{path} command. @value{GDBN} replaces @samp{.} in the
2153 @var{directory} argument (with the current path) before adding
2154 @var{directory} to the search path.
2155 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2156 @c document that, since repeating it would be a no-op.
2160 Display the list of search paths for executables (the @code{PATH}
2161 environment variable).
2163 @kindex show environment
2164 @item show environment @r{[}@var{varname}@r{]}
2165 Print the value of environment variable @var{varname} to be given to
2166 your program when it starts. If you do not supply @var{varname},
2167 print the names and values of all environment variables to be given to
2168 your program. You can abbreviate @code{environment} as @code{env}.
2170 @kindex set environment
2171 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2172 Set environment variable @var{varname} to @var{value}. The value
2173 changes for your program only, not for @value{GDBN} itself. @var{value} may
2174 be any string; the values of environment variables are just strings, and
2175 any interpretation is supplied by your program itself. The @var{value}
2176 parameter is optional; if it is eliminated, the variable is set to a
2178 @c "any string" here does not include leading, trailing
2179 @c blanks. Gnu asks: does anyone care?
2181 For example, this command:
2188 tells the debugged program, when subsequently run, that its user is named
2189 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2190 are not actually required.)
2192 @kindex unset environment
2193 @item unset environment @var{varname}
2194 Remove variable @var{varname} from the environment to be passed to your
2195 program. This is different from @samp{set env @var{varname} =};
2196 @code{unset environment} removes the variable from the environment,
2197 rather than assigning it an empty value.
2200 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2202 by your @code{SHELL} environment variable if it exists (or
2203 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2204 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2205 @file{.bashrc} for BASH---any variables you set in that file affect
2206 your program. You may wish to move setting of environment variables to
2207 files that are only run when you sign on, such as @file{.login} or
2210 @node Working Directory
2211 @section Your Program's Working Directory
2213 @cindex working directory (of your program)
2214 Each time you start your program with @code{run}, it inherits its
2215 working directory from the current working directory of @value{GDBN}.
2216 The @value{GDBN} working directory is initially whatever it inherited
2217 from its parent process (typically the shell), but you can specify a new
2218 working directory in @value{GDBN} with the @code{cd} command.
2220 The @value{GDBN} working directory also serves as a default for the commands
2221 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2226 @cindex change working directory
2227 @item cd @var{directory}
2228 Set the @value{GDBN} working directory to @var{directory}.
2232 Print the @value{GDBN} working directory.
2235 It is generally impossible to find the current working directory of
2236 the process being debugged (since a program can change its directory
2237 during its run). If you work on a system where @value{GDBN} is
2238 configured with the @file{/proc} support, you can use the @code{info
2239 proc} command (@pxref{SVR4 Process Information}) to find out the
2240 current working directory of the debuggee.
2243 @section Your Program's Input and Output
2248 By default, the program you run under @value{GDBN} does input and output to
2249 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2250 to its own terminal modes to interact with you, but it records the terminal
2251 modes your program was using and switches back to them when you continue
2252 running your program.
2255 @kindex info terminal
2257 Displays information recorded by @value{GDBN} about the terminal modes your
2261 You can redirect your program's input and/or output using shell
2262 redirection with the @code{run} command. For example,
2269 starts your program, diverting its output to the file @file{outfile}.
2272 @cindex controlling terminal
2273 Another way to specify where your program should do input and output is
2274 with the @code{tty} command. This command accepts a file name as
2275 argument, and causes this file to be the default for future @code{run}
2276 commands. It also resets the controlling terminal for the child
2277 process, for future @code{run} commands. For example,
2284 directs that processes started with subsequent @code{run} commands
2285 default to do input and output on the terminal @file{/dev/ttyb} and have
2286 that as their controlling terminal.
2288 An explicit redirection in @code{run} overrides the @code{tty} command's
2289 effect on the input/output device, but not its effect on the controlling
2292 When you use the @code{tty} command or redirect input in the @code{run}
2293 command, only the input @emph{for your program} is affected. The input
2294 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2295 for @code{set inferior-tty}.
2297 @cindex inferior tty
2298 @cindex set inferior controlling terminal
2299 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2300 display the name of the terminal that will be used for future runs of your
2304 @item set inferior-tty /dev/ttyb
2305 @kindex set inferior-tty
2306 Set the tty for the program being debugged to /dev/ttyb.
2308 @item show inferior-tty
2309 @kindex show inferior-tty
2310 Show the current tty for the program being debugged.
2314 @section Debugging an Already-running Process
2319 @item attach @var{process-id}
2320 This command attaches to a running process---one that was started
2321 outside @value{GDBN}. (@code{info files} shows your active
2322 targets.) The command takes as argument a process ID. The usual way to
2323 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2324 or with the @samp{jobs -l} shell command.
2326 @code{attach} does not repeat if you press @key{RET} a second time after
2327 executing the command.
2330 To use @code{attach}, your program must be running in an environment
2331 which supports processes; for example, @code{attach} does not work for
2332 programs on bare-board targets that lack an operating system. You must
2333 also have permission to send the process a signal.
2335 When you use @code{attach}, the debugger finds the program running in
2336 the process first by looking in the current working directory, then (if
2337 the program is not found) by using the source file search path
2338 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2339 the @code{file} command to load the program. @xref{Files, ,Commands to
2342 The first thing @value{GDBN} does after arranging to debug the specified
2343 process is to stop it. You can examine and modify an attached process
2344 with all the @value{GDBN} commands that are ordinarily available when
2345 you start processes with @code{run}. You can insert breakpoints; you
2346 can step and continue; you can modify storage. If you would rather the
2347 process continue running, you may use the @code{continue} command after
2348 attaching @value{GDBN} to the process.
2353 When you have finished debugging the attached process, you can use the
2354 @code{detach} command to release it from @value{GDBN} control. Detaching
2355 the process continues its execution. After the @code{detach} command,
2356 that process and @value{GDBN} become completely independent once more, and you
2357 are ready to @code{attach} another process or start one with @code{run}.
2358 @code{detach} does not repeat if you press @key{RET} again after
2359 executing the command.
2362 If you exit @value{GDBN} while you have an attached process, you detach
2363 that process. If you use the @code{run} command, you kill that process.
2364 By default, @value{GDBN} asks for confirmation if you try to do either of these
2365 things; you can control whether or not you need to confirm by using the
2366 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2370 @section Killing the Child Process
2375 Kill the child process in which your program is running under @value{GDBN}.
2378 This command is useful if you wish to debug a core dump instead of a
2379 running process. @value{GDBN} ignores any core dump file while your program
2382 On some operating systems, a program cannot be executed outside @value{GDBN}
2383 while you have breakpoints set on it inside @value{GDBN}. You can use the
2384 @code{kill} command in this situation to permit running your program
2385 outside the debugger.
2387 The @code{kill} command is also useful if you wish to recompile and
2388 relink your program, since on many systems it is impossible to modify an
2389 executable file while it is running in a process. In this case, when you
2390 next type @code{run}, @value{GDBN} notices that the file has changed, and
2391 reads the symbol table again (while trying to preserve your current
2392 breakpoint settings).
2394 @node Inferiors and Programs
2395 @section Debugging Multiple Inferiors and Programs
2397 @value{GDBN} lets you run and debug multiple programs in a single
2398 session. In addition, @value{GDBN} on some systems may let you run
2399 several programs simultaneously (otherwise you have to exit from one
2400 before starting another). In the most general case, you can have
2401 multiple threads of execution in each of multiple processes, launched
2402 from multiple executables.
2405 @value{GDBN} represents the state of each program execution with an
2406 object called an @dfn{inferior}. An inferior typically corresponds to
2407 a process, but is more general and applies also to targets that do not
2408 have processes. Inferiors may be created before a process runs, and
2409 may be retained after a process exits. Inferiors have unique
2410 identifiers that are different from process ids. Usually each
2411 inferior will also have its own distinct address space, although some
2412 embedded targets may have several inferiors running in different parts
2413 of a single address space. Each inferior may in turn have multiple
2414 threads running in it.
2416 To find out what inferiors exist at any moment, use @w{@code{info
2420 @kindex info inferiors
2421 @item info inferiors
2422 Print a list of all inferiors currently being managed by @value{GDBN}.
2424 @value{GDBN} displays for each inferior (in this order):
2428 the inferior number assigned by @value{GDBN}
2431 the target system's inferior identifier
2434 the name of the executable the inferior is running.
2439 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2440 indicates the current inferior.
2444 @c end table here to get a little more width for example
2447 (@value{GDBP}) info inferiors
2448 Num Description Executable
2449 2 process 2307 hello
2450 * 1 process 3401 goodbye
2453 To switch focus between inferiors, use the @code{inferior} command:
2456 @kindex inferior @var{infno}
2457 @item inferior @var{infno}
2458 Make inferior number @var{infno} the current inferior. The argument
2459 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2460 in the first field of the @samp{info inferiors} display.
2464 You can get multiple executables into a debugging session via the
2465 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2466 systems @value{GDBN} can add inferiors to the debug session
2467 automatically by following calls to @code{fork} and @code{exec}. To
2468 remove inferiors from the debugging session use the
2469 @w{@code{remove-inferiors}} command.
2472 @kindex add-inferior
2473 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2474 Adds @var{n} inferiors to be run using @var{executable} as the
2475 executable. @var{n} defaults to 1. If no executable is specified,
2476 the inferiors begins empty, with no program. You can still assign or
2477 change the program assigned to the inferior at any time by using the
2478 @code{file} command with the executable name as its argument.
2480 @kindex clone-inferior
2481 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2482 Adds @var{n} inferiors ready to execute the same program as inferior
2483 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2484 number of the current inferior. This is a convenient command when you
2485 want to run another instance of the inferior you are debugging.
2488 (@value{GDBP}) info inferiors
2489 Num Description Executable
2490 * 1 process 29964 helloworld
2491 (@value{GDBP}) clone-inferior
2494 (@value{GDBP}) info inferiors
2495 Num Description Executable
2497 * 1 process 29964 helloworld
2500 You can now simply switch focus to inferior 2 and run it.
2502 @kindex remove-inferiors
2503 @item remove-inferiors @var{infno}@dots{}
2504 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2505 possible to remove an inferior that is running with this command. For
2506 those, use the @code{kill} or @code{detach} command first.
2510 To quit debugging one of the running inferiors that is not the current
2511 inferior, you can either detach from it by using the @w{@code{detach
2512 inferior}} command (allowing it to run independently), or kill it
2513 using the @w{@code{kill inferiors}} command:
2516 @kindex detach inferiors @var{infno}@dots{}
2517 @item detach inferior @var{infno}@dots{}
2518 Detach from the inferior or inferiors identified by @value{GDBN}
2519 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2520 still stays on the list of inferiors shown by @code{info inferiors},
2521 but its Description will show @samp{<null>}.
2523 @kindex kill inferiors @var{infno}@dots{}
2524 @item kill inferiors @var{infno}@dots{}
2525 Kill the inferior or inferiors identified by @value{GDBN} inferior
2526 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2527 stays on the list of inferiors shown by @code{info inferiors}, but its
2528 Description will show @samp{<null>}.
2531 After the successful completion of a command such as @code{detach},
2532 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2533 a normal process exit, the inferior is still valid and listed with
2534 @code{info inferiors}, ready to be restarted.
2537 To be notified when inferiors are started or exit under @value{GDBN}'s
2538 control use @w{@code{set print inferior-events}}:
2541 @kindex set print inferior-events
2542 @cindex print messages on inferior start and exit
2543 @item set print inferior-events
2544 @itemx set print inferior-events on
2545 @itemx set print inferior-events off
2546 The @code{set print inferior-events} command allows you to enable or
2547 disable printing of messages when @value{GDBN} notices that new
2548 inferiors have started or that inferiors have exited or have been
2549 detached. By default, these messages will not be printed.
2551 @kindex show print inferior-events
2552 @item show print inferior-events
2553 Show whether messages will be printed when @value{GDBN} detects that
2554 inferiors have started, exited or have been detached.
2557 Many commands will work the same with multiple programs as with a
2558 single program: e.g., @code{print myglobal} will simply display the
2559 value of @code{myglobal} in the current inferior.
2562 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2563 get more info about the relationship of inferiors, programs, address
2564 spaces in a debug session. You can do that with the @w{@code{maint
2565 info program-spaces}} command.
2568 @kindex maint info program-spaces
2569 @item maint info program-spaces
2570 Print a list of all program spaces currently being managed by
2573 @value{GDBN} displays for each program space (in this order):
2577 the program space number assigned by @value{GDBN}
2580 the name of the executable loaded into the program space, with e.g.,
2581 the @code{file} command.
2586 An asterisk @samp{*} preceding the @value{GDBN} program space number
2587 indicates the current program space.
2589 In addition, below each program space line, @value{GDBN} prints extra
2590 information that isn't suitable to display in tabular form. For
2591 example, the list of inferiors bound to the program space.
2594 (@value{GDBP}) maint info program-spaces
2597 Bound inferiors: ID 1 (process 21561)
2601 Here we can see that no inferior is running the program @code{hello},
2602 while @code{process 21561} is running the program @code{goodbye}. On
2603 some targets, it is possible that multiple inferiors are bound to the
2604 same program space. The most common example is that of debugging both
2605 the parent and child processes of a @code{vfork} call. For example,
2608 (@value{GDBP}) maint info program-spaces
2611 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2614 Here, both inferior 2 and inferior 1 are running in the same program
2615 space as a result of inferior 1 having executed a @code{vfork} call.
2619 @section Debugging Programs with Multiple Threads
2621 @cindex threads of execution
2622 @cindex multiple threads
2623 @cindex switching threads
2624 In some operating systems, such as HP-UX and Solaris, a single program
2625 may have more than one @dfn{thread} of execution. The precise semantics
2626 of threads differ from one operating system to another, but in general
2627 the threads of a single program are akin to multiple processes---except
2628 that they share one address space (that is, they can all examine and
2629 modify the same variables). On the other hand, each thread has its own
2630 registers and execution stack, and perhaps private memory.
2632 @value{GDBN} provides these facilities for debugging multi-thread
2636 @item automatic notification of new threads
2637 @item @samp{thread @var{threadno}}, a command to switch among threads
2638 @item @samp{info threads}, a command to inquire about existing threads
2639 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2640 a command to apply a command to a list of threads
2641 @item thread-specific breakpoints
2642 @item @samp{set print thread-events}, which controls printing of
2643 messages on thread start and exit.
2644 @item @samp{set libthread-db-search-path @var{path}}, which lets
2645 the user specify which @code{libthread_db} to use if the default choice
2646 isn't compatible with the program.
2650 @emph{Warning:} These facilities are not yet available on every
2651 @value{GDBN} configuration where the operating system supports threads.
2652 If your @value{GDBN} does not support threads, these commands have no
2653 effect. For example, a system without thread support shows no output
2654 from @samp{info threads}, and always rejects the @code{thread} command,
2658 (@value{GDBP}) info threads
2659 (@value{GDBP}) thread 1
2660 Thread ID 1 not known. Use the "info threads" command to
2661 see the IDs of currently known threads.
2663 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2664 @c doesn't support threads"?
2667 @cindex focus of debugging
2668 @cindex current thread
2669 The @value{GDBN} thread debugging facility allows you to observe all
2670 threads while your program runs---but whenever @value{GDBN} takes
2671 control, one thread in particular is always the focus of debugging.
2672 This thread is called the @dfn{current thread}. Debugging commands show
2673 program information from the perspective of the current thread.
2675 @cindex @code{New} @var{systag} message
2676 @cindex thread identifier (system)
2677 @c FIXME-implementors!! It would be more helpful if the [New...] message
2678 @c included GDB's numeric thread handle, so you could just go to that
2679 @c thread without first checking `info threads'.
2680 Whenever @value{GDBN} detects a new thread in your program, it displays
2681 the target system's identification for the thread with a message in the
2682 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2683 whose form varies depending on the particular system. For example, on
2684 @sc{gnu}/Linux, you might see
2687 [New Thread 0x41e02940 (LWP 25582)]
2691 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2692 the @var{systag} is simply something like @samp{process 368}, with no
2695 @c FIXME!! (1) Does the [New...] message appear even for the very first
2696 @c thread of a program, or does it only appear for the
2697 @c second---i.e.@: when it becomes obvious we have a multithread
2699 @c (2) *Is* there necessarily a first thread always? Or do some
2700 @c multithread systems permit starting a program with multiple
2701 @c threads ab initio?
2703 @cindex thread number
2704 @cindex thread identifier (GDB)
2705 For debugging purposes, @value{GDBN} associates its own thread
2706 number---always a single integer---with each thread in your program.
2709 @kindex info threads
2710 @item info threads @r{[}@var{id}@dots{}@r{]}
2711 Display a summary of all threads currently in your program. Optional
2712 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2713 means to print information only about the specified thread or threads.
2714 @value{GDBN} displays for each thread (in this order):
2718 the thread number assigned by @value{GDBN}
2721 the target system's thread identifier (@var{systag})
2724 the thread's name, if one is known. A thread can either be named by
2725 the user (see @code{thread name}, below), or, in some cases, by the
2729 the current stack frame summary for that thread
2733 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2734 indicates the current thread.
2738 @c end table here to get a little more width for example
2741 (@value{GDBP}) info threads
2743 3 process 35 thread 27 0x34e5 in sigpause ()
2744 2 process 35 thread 23 0x34e5 in sigpause ()
2745 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2749 On Solaris, you can display more information about user threads with a
2750 Solaris-specific command:
2753 @item maint info sol-threads
2754 @kindex maint info sol-threads
2755 @cindex thread info (Solaris)
2756 Display info on Solaris user threads.
2760 @kindex thread @var{threadno}
2761 @item thread @var{threadno}
2762 Make thread number @var{threadno} the current thread. The command
2763 argument @var{threadno} is the internal @value{GDBN} thread number, as
2764 shown in the first field of the @samp{info threads} display.
2765 @value{GDBN} responds by displaying the system identifier of the thread
2766 you selected, and its current stack frame summary:
2769 (@value{GDBP}) thread 2
2770 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2771 #0 some_function (ignore=0x0) at example.c:8
2772 8 printf ("hello\n");
2776 As with the @samp{[New @dots{}]} message, the form of the text after
2777 @samp{Switching to} depends on your system's conventions for identifying
2780 @vindex $_thread@r{, convenience variable}
2781 The debugger convenience variable @samp{$_thread} contains the number
2782 of the current thread. You may find this useful in writing breakpoint
2783 conditional expressions, command scripts, and so forth. See
2784 @xref{Convenience Vars,, Convenience Variables}, for general
2785 information on convenience variables.
2787 @kindex thread apply
2788 @cindex apply command to several threads
2789 @item thread apply [@var{threadno} | all] @var{command}
2790 The @code{thread apply} command allows you to apply the named
2791 @var{command} to one or more threads. Specify the numbers of the
2792 threads that you want affected with the command argument
2793 @var{threadno}. It can be a single thread number, one of the numbers
2794 shown in the first field of the @samp{info threads} display; or it
2795 could be a range of thread numbers, as in @code{2-4}. To apply a
2796 command to all threads, type @kbd{thread apply all @var{command}}.
2799 @cindex name a thread
2800 @item thread name [@var{name}]
2801 This command assigns a name to the current thread. If no argument is
2802 given, any existing user-specified name is removed. The thread name
2803 appears in the @samp{info threads} display.
2805 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2806 determine the name of the thread as given by the OS. On these
2807 systems, a name specified with @samp{thread name} will override the
2808 system-give name, and removing the user-specified name will cause
2809 @value{GDBN} to once again display the system-specified name.
2812 @cindex search for a thread
2813 @item thread find [@var{regexp}]
2814 Search for and display thread ids whose name or @var{systag}
2815 matches the supplied regular expression.
2817 As well as being the complement to the @samp{thread name} command,
2818 this command also allows you to identify a thread by its target
2819 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2823 (@value{GDBN}) thread find 26688
2824 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2825 (@value{GDBN}) info thread 4
2827 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
2830 @kindex set print thread-events
2831 @cindex print messages on thread start and exit
2832 @item set print thread-events
2833 @itemx set print thread-events on
2834 @itemx set print thread-events off
2835 The @code{set print thread-events} command allows you to enable or
2836 disable printing of messages when @value{GDBN} notices that new threads have
2837 started or that threads have exited. By default, these messages will
2838 be printed if detection of these events is supported by the target.
2839 Note that these messages cannot be disabled on all targets.
2841 @kindex show print thread-events
2842 @item show print thread-events
2843 Show whether messages will be printed when @value{GDBN} detects that threads
2844 have started and exited.
2847 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2848 more information about how @value{GDBN} behaves when you stop and start
2849 programs with multiple threads.
2851 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2852 watchpoints in programs with multiple threads.
2855 @kindex set libthread-db-search-path
2856 @cindex search path for @code{libthread_db}
2857 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2858 If this variable is set, @var{path} is a colon-separated list of
2859 directories @value{GDBN} will use to search for @code{libthread_db}.
2860 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2861 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
2862 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
2865 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2866 @code{libthread_db} library to obtain information about threads in the
2867 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2868 to find @code{libthread_db}.
2870 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
2871 refers to the default system directories that are
2872 normally searched for loading shared libraries.
2874 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
2875 refers to the directory from which @code{libpthread}
2876 was loaded in the inferior process.
2878 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2879 @value{GDBN} attempts to initialize it with the current inferior process.
2880 If this initialization fails (which could happen because of a version
2881 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2882 will unload @code{libthread_db}, and continue with the next directory.
2883 If none of @code{libthread_db} libraries initialize successfully,
2884 @value{GDBN} will issue a warning and thread debugging will be disabled.
2886 Setting @code{libthread-db-search-path} is currently implemented
2887 only on some platforms.
2889 @kindex show libthread-db-search-path
2890 @item show libthread-db-search-path
2891 Display current libthread_db search path.
2893 @kindex set debug libthread-db
2894 @kindex show debug libthread-db
2895 @cindex debugging @code{libthread_db}
2896 @item set debug libthread-db
2897 @itemx show debug libthread-db
2898 Turns on or off display of @code{libthread_db}-related events.
2899 Use @code{1} to enable, @code{0} to disable.
2903 @section Debugging Forks
2905 @cindex fork, debugging programs which call
2906 @cindex multiple processes
2907 @cindex processes, multiple
2908 On most systems, @value{GDBN} has no special support for debugging
2909 programs which create additional processes using the @code{fork}
2910 function. When a program forks, @value{GDBN} will continue to debug the
2911 parent process and the child process will run unimpeded. If you have
2912 set a breakpoint in any code which the child then executes, the child
2913 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2914 will cause it to terminate.
2916 However, if you want to debug the child process there is a workaround
2917 which isn't too painful. Put a call to @code{sleep} in the code which
2918 the child process executes after the fork. It may be useful to sleep
2919 only if a certain environment variable is set, or a certain file exists,
2920 so that the delay need not occur when you don't want to run @value{GDBN}
2921 on the child. While the child is sleeping, use the @code{ps} program to
2922 get its process ID. Then tell @value{GDBN} (a new invocation of
2923 @value{GDBN} if you are also debugging the parent process) to attach to
2924 the child process (@pxref{Attach}). From that point on you can debug
2925 the child process just like any other process which you attached to.
2927 On some systems, @value{GDBN} provides support for debugging programs that
2928 create additional processes using the @code{fork} or @code{vfork} functions.
2929 Currently, the only platforms with this feature are HP-UX (11.x and later
2930 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2932 By default, when a program forks, @value{GDBN} will continue to debug
2933 the parent process and the child process will run unimpeded.
2935 If you want to follow the child process instead of the parent process,
2936 use the command @w{@code{set follow-fork-mode}}.
2939 @kindex set follow-fork-mode
2940 @item set follow-fork-mode @var{mode}
2941 Set the debugger response to a program call of @code{fork} or
2942 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2943 process. The @var{mode} argument can be:
2947 The original process is debugged after a fork. The child process runs
2948 unimpeded. This is the default.
2951 The new process is debugged after a fork. The parent process runs
2956 @kindex show follow-fork-mode
2957 @item show follow-fork-mode
2958 Display the current debugger response to a @code{fork} or @code{vfork} call.
2961 @cindex debugging multiple processes
2962 On Linux, if you want to debug both the parent and child processes, use the
2963 command @w{@code{set detach-on-fork}}.
2966 @kindex set detach-on-fork
2967 @item set detach-on-fork @var{mode}
2968 Tells gdb whether to detach one of the processes after a fork, or
2969 retain debugger control over them both.
2973 The child process (or parent process, depending on the value of
2974 @code{follow-fork-mode}) will be detached and allowed to run
2975 independently. This is the default.
2978 Both processes will be held under the control of @value{GDBN}.
2979 One process (child or parent, depending on the value of
2980 @code{follow-fork-mode}) is debugged as usual, while the other
2985 @kindex show detach-on-fork
2986 @item show detach-on-fork
2987 Show whether detach-on-fork mode is on/off.
2990 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
2991 will retain control of all forked processes (including nested forks).
2992 You can list the forked processes under the control of @value{GDBN} by
2993 using the @w{@code{info inferiors}} command, and switch from one fork
2994 to another by using the @code{inferior} command (@pxref{Inferiors and
2995 Programs, ,Debugging Multiple Inferiors and Programs}).
2997 To quit debugging one of the forked processes, you can either detach
2998 from it by using the @w{@code{detach inferiors}} command (allowing it
2999 to run independently), or kill it using the @w{@code{kill inferiors}}
3000 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3003 If you ask to debug a child process and a @code{vfork} is followed by an
3004 @code{exec}, @value{GDBN} executes the new target up to the first
3005 breakpoint in the new target. If you have a breakpoint set on
3006 @code{main} in your original program, the breakpoint will also be set on
3007 the child process's @code{main}.
3009 On some systems, when a child process is spawned by @code{vfork}, you
3010 cannot debug the child or parent until an @code{exec} call completes.
3012 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3013 call executes, the new target restarts. To restart the parent
3014 process, use the @code{file} command with the parent executable name
3015 as its argument. By default, after an @code{exec} call executes,
3016 @value{GDBN} discards the symbols of the previous executable image.
3017 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3021 @kindex set follow-exec-mode
3022 @item set follow-exec-mode @var{mode}
3024 Set debugger response to a program call of @code{exec}. An
3025 @code{exec} call replaces the program image of a process.
3027 @code{follow-exec-mode} can be:
3031 @value{GDBN} creates a new inferior and rebinds the process to this
3032 new inferior. The program the process was running before the
3033 @code{exec} call can be restarted afterwards by restarting the
3039 (@value{GDBP}) info inferiors
3041 Id Description Executable
3044 process 12020 is executing new program: prog2
3045 Program exited normally.
3046 (@value{GDBP}) info inferiors
3047 Id Description Executable
3053 @value{GDBN} keeps the process bound to the same inferior. The new
3054 executable image replaces the previous executable loaded in the
3055 inferior. Restarting the inferior after the @code{exec} call, with
3056 e.g., the @code{run} command, restarts the executable the process was
3057 running after the @code{exec} call. This is the default mode.
3062 (@value{GDBP}) info inferiors
3063 Id Description Executable
3066 process 12020 is executing new program: prog2
3067 Program exited normally.
3068 (@value{GDBP}) info inferiors
3069 Id Description Executable
3076 You can use the @code{catch} command to make @value{GDBN} stop whenever
3077 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3078 Catchpoints, ,Setting Catchpoints}.
3080 @node Checkpoint/Restart
3081 @section Setting a @emph{Bookmark} to Return to Later
3086 @cindex snapshot of a process
3087 @cindex rewind program state
3089 On certain operating systems@footnote{Currently, only
3090 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3091 program's state, called a @dfn{checkpoint}, and come back to it
3094 Returning to a checkpoint effectively undoes everything that has
3095 happened in the program since the @code{checkpoint} was saved. This
3096 includes changes in memory, registers, and even (within some limits)
3097 system state. Effectively, it is like going back in time to the
3098 moment when the checkpoint was saved.
3100 Thus, if you're stepping thru a program and you think you're
3101 getting close to the point where things go wrong, you can save
3102 a checkpoint. Then, if you accidentally go too far and miss
3103 the critical statement, instead of having to restart your program
3104 from the beginning, you can just go back to the checkpoint and
3105 start again from there.
3107 This can be especially useful if it takes a lot of time or
3108 steps to reach the point where you think the bug occurs.
3110 To use the @code{checkpoint}/@code{restart} method of debugging:
3115 Save a snapshot of the debugged program's current execution state.
3116 The @code{checkpoint} command takes no arguments, but each checkpoint
3117 is assigned a small integer id, similar to a breakpoint id.
3119 @kindex info checkpoints
3120 @item info checkpoints
3121 List the checkpoints that have been saved in the current debugging
3122 session. For each checkpoint, the following information will be
3129 @item Source line, or label
3132 @kindex restart @var{checkpoint-id}
3133 @item restart @var{checkpoint-id}
3134 Restore the program state that was saved as checkpoint number
3135 @var{checkpoint-id}. All program variables, registers, stack frames
3136 etc.@: will be returned to the values that they had when the checkpoint
3137 was saved. In essence, gdb will ``wind back the clock'' to the point
3138 in time when the checkpoint was saved.
3140 Note that breakpoints, @value{GDBN} variables, command history etc.
3141 are not affected by restoring a checkpoint. In general, a checkpoint
3142 only restores things that reside in the program being debugged, not in
3145 @kindex delete checkpoint @var{checkpoint-id}
3146 @item delete checkpoint @var{checkpoint-id}
3147 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3151 Returning to a previously saved checkpoint will restore the user state
3152 of the program being debugged, plus a significant subset of the system
3153 (OS) state, including file pointers. It won't ``un-write'' data from
3154 a file, but it will rewind the file pointer to the previous location,
3155 so that the previously written data can be overwritten. For files
3156 opened in read mode, the pointer will also be restored so that the
3157 previously read data can be read again.
3159 Of course, characters that have been sent to a printer (or other
3160 external device) cannot be ``snatched back'', and characters received
3161 from eg.@: a serial device can be removed from internal program buffers,
3162 but they cannot be ``pushed back'' into the serial pipeline, ready to
3163 be received again. Similarly, the actual contents of files that have
3164 been changed cannot be restored (at this time).
3166 However, within those constraints, you actually can ``rewind'' your
3167 program to a previously saved point in time, and begin debugging it
3168 again --- and you can change the course of events so as to debug a
3169 different execution path this time.
3171 @cindex checkpoints and process id
3172 Finally, there is one bit of internal program state that will be
3173 different when you return to a checkpoint --- the program's process
3174 id. Each checkpoint will have a unique process id (or @var{pid}),
3175 and each will be different from the program's original @var{pid}.
3176 If your program has saved a local copy of its process id, this could
3177 potentially pose a problem.
3179 @subsection A Non-obvious Benefit of Using Checkpoints
3181 On some systems such as @sc{gnu}/Linux, address space randomization
3182 is performed on new processes for security reasons. This makes it
3183 difficult or impossible to set a breakpoint, or watchpoint, on an
3184 absolute address if you have to restart the program, since the
3185 absolute location of a symbol will change from one execution to the
3188 A checkpoint, however, is an @emph{identical} copy of a process.
3189 Therefore if you create a checkpoint at (eg.@:) the start of main,
3190 and simply return to that checkpoint instead of restarting the
3191 process, you can avoid the effects of address randomization and
3192 your symbols will all stay in the same place.
3195 @chapter Stopping and Continuing
3197 The principal purposes of using a debugger are so that you can stop your
3198 program before it terminates; or so that, if your program runs into
3199 trouble, you can investigate and find out why.
3201 Inside @value{GDBN}, your program may stop for any of several reasons,
3202 such as a signal, a breakpoint, or reaching a new line after a
3203 @value{GDBN} command such as @code{step}. You may then examine and
3204 change variables, set new breakpoints or remove old ones, and then
3205 continue execution. Usually, the messages shown by @value{GDBN} provide
3206 ample explanation of the status of your program---but you can also
3207 explicitly request this information at any time.
3210 @kindex info program
3212 Display information about the status of your program: whether it is
3213 running or not, what process it is, and why it stopped.
3217 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3218 * Continuing and Stepping:: Resuming execution
3220 * Thread Stops:: Stopping and starting multi-thread programs
3224 @section Breakpoints, Watchpoints, and Catchpoints
3227 A @dfn{breakpoint} makes your program stop whenever a certain point in
3228 the program is reached. For each breakpoint, you can add conditions to
3229 control in finer detail whether your program stops. You can set
3230 breakpoints with the @code{break} command and its variants (@pxref{Set
3231 Breaks, ,Setting Breakpoints}), to specify the place where your program
3232 should stop by line number, function name or exact address in the
3235 On some systems, you can set breakpoints in shared libraries before
3236 the executable is run. There is a minor limitation on HP-UX systems:
3237 you must wait until the executable is run in order to set breakpoints
3238 in shared library routines that are not called directly by the program
3239 (for example, routines that are arguments in a @code{pthread_create}
3243 @cindex data breakpoints
3244 @cindex memory tracing
3245 @cindex breakpoint on memory address
3246 @cindex breakpoint on variable modification
3247 A @dfn{watchpoint} is a special breakpoint that stops your program
3248 when the value of an expression changes. The expression may be a value
3249 of a variable, or it could involve values of one or more variables
3250 combined by operators, such as @samp{a + b}. This is sometimes called
3251 @dfn{data breakpoints}. You must use a different command to set
3252 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3253 from that, you can manage a watchpoint like any other breakpoint: you
3254 enable, disable, and delete both breakpoints and watchpoints using the
3257 You can arrange to have values from your program displayed automatically
3258 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3262 @cindex breakpoint on events
3263 A @dfn{catchpoint} is another special breakpoint that stops your program
3264 when a certain kind of event occurs, such as the throwing of a C@t{++}
3265 exception or the loading of a library. As with watchpoints, you use a
3266 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3267 Catchpoints}), but aside from that, you can manage a catchpoint like any
3268 other breakpoint. (To stop when your program receives a signal, use the
3269 @code{handle} command; see @ref{Signals, ,Signals}.)
3271 @cindex breakpoint numbers
3272 @cindex numbers for breakpoints
3273 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3274 catchpoint when you create it; these numbers are successive integers
3275 starting with one. In many of the commands for controlling various
3276 features of breakpoints you use the breakpoint number to say which
3277 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3278 @dfn{disabled}; if disabled, it has no effect on your program until you
3281 @cindex breakpoint ranges
3282 @cindex ranges of breakpoints
3283 Some @value{GDBN} commands accept a range of breakpoints on which to
3284 operate. A breakpoint range is either a single breakpoint number, like
3285 @samp{5}, or two such numbers, in increasing order, separated by a
3286 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3287 all breakpoints in that range are operated on.
3290 * Set Breaks:: Setting breakpoints
3291 * Set Watchpoints:: Setting watchpoints
3292 * Set Catchpoints:: Setting catchpoints
3293 * Delete Breaks:: Deleting breakpoints
3294 * Disabling:: Disabling breakpoints
3295 * Conditions:: Break conditions
3296 * Break Commands:: Breakpoint command lists
3297 * Save Breakpoints:: How to save breakpoints in a file
3298 * Error in Breakpoints:: ``Cannot insert breakpoints''
3299 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3303 @subsection Setting Breakpoints
3305 @c FIXME LMB what does GDB do if no code on line of breakpt?
3306 @c consider in particular declaration with/without initialization.
3308 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3311 @kindex b @r{(@code{break})}
3312 @vindex $bpnum@r{, convenience variable}
3313 @cindex latest breakpoint
3314 Breakpoints are set with the @code{break} command (abbreviated
3315 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3316 number of the breakpoint you've set most recently; see @ref{Convenience
3317 Vars,, Convenience Variables}, for a discussion of what you can do with
3318 convenience variables.
3321 @item break @var{location}
3322 Set a breakpoint at the given @var{location}, which can specify a
3323 function name, a line number, or an address of an instruction.
3324 (@xref{Specify Location}, for a list of all the possible ways to
3325 specify a @var{location}.) The breakpoint will stop your program just
3326 before it executes any of the code in the specified @var{location}.
3328 When using source languages that permit overloading of symbols, such as
3329 C@t{++}, a function name may refer to more than one possible place to break.
3330 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3333 It is also possible to insert a breakpoint that will stop the program
3334 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3335 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3338 When called without any arguments, @code{break} sets a breakpoint at
3339 the next instruction to be executed in the selected stack frame
3340 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3341 innermost, this makes your program stop as soon as control
3342 returns to that frame. This is similar to the effect of a
3343 @code{finish} command in the frame inside the selected frame---except
3344 that @code{finish} does not leave an active breakpoint. If you use
3345 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3346 the next time it reaches the current location; this may be useful
3349 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3350 least one instruction has been executed. If it did not do this, you
3351 would be unable to proceed past a breakpoint without first disabling the
3352 breakpoint. This rule applies whether or not the breakpoint already
3353 existed when your program stopped.
3355 @item break @dots{} if @var{cond}
3356 Set a breakpoint with condition @var{cond}; evaluate the expression
3357 @var{cond} each time the breakpoint is reached, and stop only if the
3358 value is nonzero---that is, if @var{cond} evaluates as true.
3359 @samp{@dots{}} stands for one of the possible arguments described
3360 above (or no argument) specifying where to break. @xref{Conditions,
3361 ,Break Conditions}, for more information on breakpoint conditions.
3364 @item tbreak @var{args}
3365 Set a breakpoint enabled only for one stop. @var{args} are the
3366 same as for the @code{break} command, and the breakpoint is set in the same
3367 way, but the breakpoint is automatically deleted after the first time your
3368 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3371 @cindex hardware breakpoints
3372 @item hbreak @var{args}
3373 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3374 @code{break} command and the breakpoint is set in the same way, but the
3375 breakpoint requires hardware support and some target hardware may not
3376 have this support. The main purpose of this is EPROM/ROM code
3377 debugging, so you can set a breakpoint at an instruction without
3378 changing the instruction. This can be used with the new trap-generation
3379 provided by SPARClite DSU and most x86-based targets. These targets
3380 will generate traps when a program accesses some data or instruction
3381 address that is assigned to the debug registers. However the hardware
3382 breakpoint registers can take a limited number of breakpoints. For
3383 example, on the DSU, only two data breakpoints can be set at a time, and
3384 @value{GDBN} will reject this command if more than two are used. Delete
3385 or disable unused hardware breakpoints before setting new ones
3386 (@pxref{Disabling, ,Disabling Breakpoints}).
3387 @xref{Conditions, ,Break Conditions}.
3388 For remote targets, you can restrict the number of hardware
3389 breakpoints @value{GDBN} will use, see @ref{set remote
3390 hardware-breakpoint-limit}.
3393 @item thbreak @var{args}
3394 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3395 are the same as for the @code{hbreak} command and the breakpoint is set in
3396 the same way. However, like the @code{tbreak} command,
3397 the breakpoint is automatically deleted after the
3398 first time your program stops there. Also, like the @code{hbreak}
3399 command, the breakpoint requires hardware support and some target hardware
3400 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3401 See also @ref{Conditions, ,Break Conditions}.
3404 @cindex regular expression
3405 @cindex breakpoints at functions matching a regexp
3406 @cindex set breakpoints in many functions
3407 @item rbreak @var{regex}
3408 Set breakpoints on all functions matching the regular expression
3409 @var{regex}. This command sets an unconditional breakpoint on all
3410 matches, printing a list of all breakpoints it set. Once these
3411 breakpoints are set, they are treated just like the breakpoints set with
3412 the @code{break} command. You can delete them, disable them, or make
3413 them conditional the same way as any other breakpoint.
3415 The syntax of the regular expression is the standard one used with tools
3416 like @file{grep}. Note that this is different from the syntax used by
3417 shells, so for instance @code{foo*} matches all functions that include
3418 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3419 @code{.*} leading and trailing the regular expression you supply, so to
3420 match only functions that begin with @code{foo}, use @code{^foo}.
3422 @cindex non-member C@t{++} functions, set breakpoint in
3423 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3424 breakpoints on overloaded functions that are not members of any special
3427 @cindex set breakpoints on all functions
3428 The @code{rbreak} command can be used to set breakpoints in
3429 @strong{all} the functions in a program, like this:
3432 (@value{GDBP}) rbreak .
3435 @item rbreak @var{file}:@var{regex}
3436 If @code{rbreak} is called with a filename qualification, it limits
3437 the search for functions matching the given regular expression to the
3438 specified @var{file}. This can be used, for example, to set breakpoints on
3439 every function in a given file:
3442 (@value{GDBP}) rbreak file.c:.
3445 The colon separating the filename qualifier from the regex may
3446 optionally be surrounded by spaces.
3448 @kindex info breakpoints
3449 @cindex @code{$_} and @code{info breakpoints}
3450 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3451 @itemx info break @r{[}@var{n}@dots{}@r{]}
3452 Print a table of all breakpoints, watchpoints, and catchpoints set and
3453 not deleted. Optional argument @var{n} means print information only
3454 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3455 For each breakpoint, following columns are printed:
3458 @item Breakpoint Numbers
3460 Breakpoint, watchpoint, or catchpoint.
3462 Whether the breakpoint is marked to be disabled or deleted when hit.
3463 @item Enabled or Disabled
3464 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3465 that are not enabled.
3467 Where the breakpoint is in your program, as a memory address. For a
3468 pending breakpoint whose address is not yet known, this field will
3469 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3470 library that has the symbol or line referred by breakpoint is loaded.
3471 See below for details. A breakpoint with several locations will
3472 have @samp{<MULTIPLE>} in this field---see below for details.
3474 Where the breakpoint is in the source for your program, as a file and
3475 line number. For a pending breakpoint, the original string passed to
3476 the breakpoint command will be listed as it cannot be resolved until
3477 the appropriate shared library is loaded in the future.
3481 If a breakpoint is conditional, @code{info break} shows the condition on
3482 the line following the affected breakpoint; breakpoint commands, if any,
3483 are listed after that. A pending breakpoint is allowed to have a condition
3484 specified for it. The condition is not parsed for validity until a shared
3485 library is loaded that allows the pending breakpoint to resolve to a
3489 @code{info break} with a breakpoint
3490 number @var{n} as argument lists only that breakpoint. The
3491 convenience variable @code{$_} and the default examining-address for
3492 the @code{x} command are set to the address of the last breakpoint
3493 listed (@pxref{Memory, ,Examining Memory}).
3496 @code{info break} displays a count of the number of times the breakpoint
3497 has been hit. This is especially useful in conjunction with the
3498 @code{ignore} command. You can ignore a large number of breakpoint
3499 hits, look at the breakpoint info to see how many times the breakpoint
3500 was hit, and then run again, ignoring one less than that number. This
3501 will get you quickly to the last hit of that breakpoint.
3504 @value{GDBN} allows you to set any number of breakpoints at the same place in
3505 your program. There is nothing silly or meaningless about this. When
3506 the breakpoints are conditional, this is even useful
3507 (@pxref{Conditions, ,Break Conditions}).
3509 @cindex multiple locations, breakpoints
3510 @cindex breakpoints, multiple locations
3511 It is possible that a breakpoint corresponds to several locations
3512 in your program. Examples of this situation are:
3516 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3517 instances of the function body, used in different cases.
3520 For a C@t{++} template function, a given line in the function can
3521 correspond to any number of instantiations.
3524 For an inlined function, a given source line can correspond to
3525 several places where that function is inlined.
3528 In all those cases, @value{GDBN} will insert a breakpoint at all
3529 the relevant locations@footnote{
3530 As of this writing, multiple-location breakpoints work only if there's
3531 line number information for all the locations. This means that they
3532 will generally not work in system libraries, unless you have debug
3533 info with line numbers for them.}.
3535 A breakpoint with multiple locations is displayed in the breakpoint
3536 table using several rows---one header row, followed by one row for
3537 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3538 address column. The rows for individual locations contain the actual
3539 addresses for locations, and show the functions to which those
3540 locations belong. The number column for a location is of the form
3541 @var{breakpoint-number}.@var{location-number}.
3546 Num Type Disp Enb Address What
3547 1 breakpoint keep y <MULTIPLE>
3549 breakpoint already hit 1 time
3550 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3551 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3554 Each location can be individually enabled or disabled by passing
3555 @var{breakpoint-number}.@var{location-number} as argument to the
3556 @code{enable} and @code{disable} commands. Note that you cannot
3557 delete the individual locations from the list, you can only delete the
3558 entire list of locations that belong to their parent breakpoint (with
3559 the @kbd{delete @var{num}} command, where @var{num} is the number of
3560 the parent breakpoint, 1 in the above example). Disabling or enabling
3561 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3562 that belong to that breakpoint.
3564 @cindex pending breakpoints
3565 It's quite common to have a breakpoint inside a shared library.
3566 Shared libraries can be loaded and unloaded explicitly,
3567 and possibly repeatedly, as the program is executed. To support
3568 this use case, @value{GDBN} updates breakpoint locations whenever
3569 any shared library is loaded or unloaded. Typically, you would
3570 set a breakpoint in a shared library at the beginning of your
3571 debugging session, when the library is not loaded, and when the
3572 symbols from the library are not available. When you try to set
3573 breakpoint, @value{GDBN} will ask you if you want to set
3574 a so called @dfn{pending breakpoint}---breakpoint whose address
3575 is not yet resolved.
3577 After the program is run, whenever a new shared library is loaded,
3578 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3579 shared library contains the symbol or line referred to by some
3580 pending breakpoint, that breakpoint is resolved and becomes an
3581 ordinary breakpoint. When a library is unloaded, all breakpoints
3582 that refer to its symbols or source lines become pending again.
3584 This logic works for breakpoints with multiple locations, too. For
3585 example, if you have a breakpoint in a C@t{++} template function, and
3586 a newly loaded shared library has an instantiation of that template,
3587 a new location is added to the list of locations for the breakpoint.
3589 Except for having unresolved address, pending breakpoints do not
3590 differ from regular breakpoints. You can set conditions or commands,
3591 enable and disable them and perform other breakpoint operations.
3593 @value{GDBN} provides some additional commands for controlling what
3594 happens when the @samp{break} command cannot resolve breakpoint
3595 address specification to an address:
3597 @kindex set breakpoint pending
3598 @kindex show breakpoint pending
3600 @item set breakpoint pending auto
3601 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3602 location, it queries you whether a pending breakpoint should be created.
3604 @item set breakpoint pending on
3605 This indicates that an unrecognized breakpoint location should automatically
3606 result in a pending breakpoint being created.
3608 @item set breakpoint pending off
3609 This indicates that pending breakpoints are not to be created. Any
3610 unrecognized breakpoint location results in an error. This setting does
3611 not affect any pending breakpoints previously created.
3613 @item show breakpoint pending
3614 Show the current behavior setting for creating pending breakpoints.
3617 The settings above only affect the @code{break} command and its
3618 variants. Once breakpoint is set, it will be automatically updated
3619 as shared libraries are loaded and unloaded.
3621 @cindex automatic hardware breakpoints
3622 For some targets, @value{GDBN} can automatically decide if hardware or
3623 software breakpoints should be used, depending on whether the
3624 breakpoint address is read-only or read-write. This applies to
3625 breakpoints set with the @code{break} command as well as to internal
3626 breakpoints set by commands like @code{next} and @code{finish}. For
3627 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3630 You can control this automatic behaviour with the following commands::
3632 @kindex set breakpoint auto-hw
3633 @kindex show breakpoint auto-hw
3635 @item set breakpoint auto-hw on
3636 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3637 will try to use the target memory map to decide if software or hardware
3638 breakpoint must be used.
3640 @item set breakpoint auto-hw off
3641 This indicates @value{GDBN} should not automatically select breakpoint
3642 type. If the target provides a memory map, @value{GDBN} will warn when
3643 trying to set software breakpoint at a read-only address.
3646 @value{GDBN} normally implements breakpoints by replacing the program code
3647 at the breakpoint address with a special instruction, which, when
3648 executed, given control to the debugger. By default, the program
3649 code is so modified only when the program is resumed. As soon as
3650 the program stops, @value{GDBN} restores the original instructions. This
3651 behaviour guards against leaving breakpoints inserted in the
3652 target should gdb abrubptly disconnect. However, with slow remote
3653 targets, inserting and removing breakpoint can reduce the performance.
3654 This behavior can be controlled with the following commands::
3656 @kindex set breakpoint always-inserted
3657 @kindex show breakpoint always-inserted
3659 @item set breakpoint always-inserted off
3660 All breakpoints, including newly added by the user, are inserted in
3661 the target only when the target is resumed. All breakpoints are
3662 removed from the target when it stops.
3664 @item set breakpoint always-inserted on
3665 Causes all breakpoints to be inserted in the target at all times. If
3666 the user adds a new breakpoint, or changes an existing breakpoint, the
3667 breakpoints in the target are updated immediately. A breakpoint is
3668 removed from the target only when breakpoint itself is removed.
3670 @cindex non-stop mode, and @code{breakpoint always-inserted}
3671 @item set breakpoint always-inserted auto
3672 This is the default mode. If @value{GDBN} is controlling the inferior
3673 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3674 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3675 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3676 @code{breakpoint always-inserted} mode is off.
3679 @cindex negative breakpoint numbers
3680 @cindex internal @value{GDBN} breakpoints
3681 @value{GDBN} itself sometimes sets breakpoints in your program for
3682 special purposes, such as proper handling of @code{longjmp} (in C
3683 programs). These internal breakpoints are assigned negative numbers,
3684 starting with @code{-1}; @samp{info breakpoints} does not display them.
3685 You can see these breakpoints with the @value{GDBN} maintenance command
3686 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3689 @node Set Watchpoints
3690 @subsection Setting Watchpoints
3692 @cindex setting watchpoints
3693 You can use a watchpoint to stop execution whenever the value of an
3694 expression changes, without having to predict a particular place where
3695 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3696 The expression may be as simple as the value of a single variable, or
3697 as complex as many variables combined by operators. Examples include:
3701 A reference to the value of a single variable.
3704 An address cast to an appropriate data type. For example,
3705 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3706 address (assuming an @code{int} occupies 4 bytes).
3709 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3710 expression can use any operators valid in the program's native
3711 language (@pxref{Languages}).
3714 You can set a watchpoint on an expression even if the expression can
3715 not be evaluated yet. For instance, you can set a watchpoint on
3716 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3717 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3718 the expression produces a valid value. If the expression becomes
3719 valid in some other way than changing a variable (e.g.@: if the memory
3720 pointed to by @samp{*global_ptr} becomes readable as the result of a
3721 @code{malloc} call), @value{GDBN} may not stop until the next time
3722 the expression changes.
3724 @cindex software watchpoints
3725 @cindex hardware watchpoints
3726 Depending on your system, watchpoints may be implemented in software or
3727 hardware. @value{GDBN} does software watchpointing by single-stepping your
3728 program and testing the variable's value each time, which is hundreds of
3729 times slower than normal execution. (But this may still be worth it, to
3730 catch errors where you have no clue what part of your program is the
3733 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3734 x86-based targets, @value{GDBN} includes support for hardware
3735 watchpoints, which do not slow down the running of your program.
3739 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3740 Set a watchpoint for an expression. @value{GDBN} will break when the
3741 expression @var{expr} is written into by the program and its value
3742 changes. The simplest (and the most popular) use of this command is
3743 to watch the value of a single variable:
3746 (@value{GDBP}) watch foo
3749 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3750 argument, @value{GDBN} breaks only when the thread identified by
3751 @var{threadnum} changes the value of @var{expr}. If any other threads
3752 change the value of @var{expr}, @value{GDBN} will not break. Note
3753 that watchpoints restricted to a single thread in this way only work
3754 with Hardware Watchpoints.
3756 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3757 (see below). The @code{-location} argument tells @value{GDBN} to
3758 instead watch the memory referred to by @var{expr}. In this case,
3759 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3760 and watch the memory at that address. The type of the result is used
3761 to determine the size of the watched memory. If the expression's
3762 result does not have an address, then @value{GDBN} will print an
3765 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3766 of masked watchpoints, if the current architecture supports this
3767 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3768 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
3769 to an address to watch. The mask specifies that some bits of an address
3770 (the bits which are reset in the mask) should be ignored when matching
3771 the address accessed by the inferior against the watchpoint address.
3772 Thus, a masked watchpoint watches many addresses simultaneously---those
3773 addresses whose unmasked bits are identical to the unmasked bits in the
3774 watchpoint address. The @code{mask} argument implies @code{-location}.
3778 (@value{GDBP}) watch foo mask 0xffff00ff
3779 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
3783 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3784 Set a watchpoint that will break when the value of @var{expr} is read
3788 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3789 Set a watchpoint that will break when @var{expr} is either read from
3790 or written into by the program.
3792 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
3793 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
3794 This command prints a list of watchpoints, using the same format as
3795 @code{info break} (@pxref{Set Breaks}).
3798 If you watch for a change in a numerically entered address you need to
3799 dereference it, as the address itself is just a constant number which will
3800 never change. @value{GDBN} refuses to create a watchpoint that watches
3801 a never-changing value:
3804 (@value{GDBP}) watch 0x600850
3805 Cannot watch constant value 0x600850.
3806 (@value{GDBP}) watch *(int *) 0x600850
3807 Watchpoint 1: *(int *) 6293584
3810 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3811 watchpoints execute very quickly, and the debugger reports a change in
3812 value at the exact instruction where the change occurs. If @value{GDBN}
3813 cannot set a hardware watchpoint, it sets a software watchpoint, which
3814 executes more slowly and reports the change in value at the next
3815 @emph{statement}, not the instruction, after the change occurs.
3817 @cindex use only software watchpoints
3818 You can force @value{GDBN} to use only software watchpoints with the
3819 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3820 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3821 the underlying system supports them. (Note that hardware-assisted
3822 watchpoints that were set @emph{before} setting
3823 @code{can-use-hw-watchpoints} to zero will still use the hardware
3824 mechanism of watching expression values.)
3827 @item set can-use-hw-watchpoints
3828 @kindex set can-use-hw-watchpoints
3829 Set whether or not to use hardware watchpoints.
3831 @item show can-use-hw-watchpoints
3832 @kindex show can-use-hw-watchpoints
3833 Show the current mode of using hardware watchpoints.
3836 For remote targets, you can restrict the number of hardware
3837 watchpoints @value{GDBN} will use, see @ref{set remote
3838 hardware-breakpoint-limit}.
3840 When you issue the @code{watch} command, @value{GDBN} reports
3843 Hardware watchpoint @var{num}: @var{expr}
3847 if it was able to set a hardware watchpoint.
3849 Currently, the @code{awatch} and @code{rwatch} commands can only set
3850 hardware watchpoints, because accesses to data that don't change the
3851 value of the watched expression cannot be detected without examining
3852 every instruction as it is being executed, and @value{GDBN} does not do
3853 that currently. If @value{GDBN} finds that it is unable to set a
3854 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3855 will print a message like this:
3858 Expression cannot be implemented with read/access watchpoint.
3861 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3862 data type of the watched expression is wider than what a hardware
3863 watchpoint on the target machine can handle. For example, some systems
3864 can only watch regions that are up to 4 bytes wide; on such systems you
3865 cannot set hardware watchpoints for an expression that yields a
3866 double-precision floating-point number (which is typically 8 bytes
3867 wide). As a work-around, it might be possible to break the large region
3868 into a series of smaller ones and watch them with separate watchpoints.
3870 If you set too many hardware watchpoints, @value{GDBN} might be unable
3871 to insert all of them when you resume the execution of your program.
3872 Since the precise number of active watchpoints is unknown until such
3873 time as the program is about to be resumed, @value{GDBN} might not be
3874 able to warn you about this when you set the watchpoints, and the
3875 warning will be printed only when the program is resumed:
3878 Hardware watchpoint @var{num}: Could not insert watchpoint
3882 If this happens, delete or disable some of the watchpoints.
3884 Watching complex expressions that reference many variables can also
3885 exhaust the resources available for hardware-assisted watchpoints.
3886 That's because @value{GDBN} needs to watch every variable in the
3887 expression with separately allocated resources.
3889 If you call a function interactively using @code{print} or @code{call},
3890 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3891 kind of breakpoint or the call completes.
3893 @value{GDBN} automatically deletes watchpoints that watch local
3894 (automatic) variables, or expressions that involve such variables, when
3895 they go out of scope, that is, when the execution leaves the block in
3896 which these variables were defined. In particular, when the program
3897 being debugged terminates, @emph{all} local variables go out of scope,
3898 and so only watchpoints that watch global variables remain set. If you
3899 rerun the program, you will need to set all such watchpoints again. One
3900 way of doing that would be to set a code breakpoint at the entry to the
3901 @code{main} function and when it breaks, set all the watchpoints.
3903 @cindex watchpoints and threads
3904 @cindex threads and watchpoints
3905 In multi-threaded programs, watchpoints will detect changes to the
3906 watched expression from every thread.
3909 @emph{Warning:} In multi-threaded programs, software watchpoints
3910 have only limited usefulness. If @value{GDBN} creates a software
3911 watchpoint, it can only watch the value of an expression @emph{in a
3912 single thread}. If you are confident that the expression can only
3913 change due to the current thread's activity (and if you are also
3914 confident that no other thread can become current), then you can use
3915 software watchpoints as usual. However, @value{GDBN} may not notice
3916 when a non-current thread's activity changes the expression. (Hardware
3917 watchpoints, in contrast, watch an expression in all threads.)
3920 @xref{set remote hardware-watchpoint-limit}.
3922 @node Set Catchpoints
3923 @subsection Setting Catchpoints
3924 @cindex catchpoints, setting
3925 @cindex exception handlers
3926 @cindex event handling
3928 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3929 kinds of program events, such as C@t{++} exceptions or the loading of a
3930 shared library. Use the @code{catch} command to set a catchpoint.
3934 @item catch @var{event}
3935 Stop when @var{event} occurs. @var{event} can be any of the following:
3938 @cindex stop on C@t{++} exceptions
3939 The throwing of a C@t{++} exception.
3942 The catching of a C@t{++} exception.
3945 @cindex Ada exception catching
3946 @cindex catch Ada exceptions
3947 An Ada exception being raised. If an exception name is specified
3948 at the end of the command (eg @code{catch exception Program_Error}),
3949 the debugger will stop only when this specific exception is raised.
3950 Otherwise, the debugger stops execution when any Ada exception is raised.
3952 When inserting an exception catchpoint on a user-defined exception whose
3953 name is identical to one of the exceptions defined by the language, the
3954 fully qualified name must be used as the exception name. Otherwise,
3955 @value{GDBN} will assume that it should stop on the pre-defined exception
3956 rather than the user-defined one. For instance, assuming an exception
3957 called @code{Constraint_Error} is defined in package @code{Pck}, then
3958 the command to use to catch such exceptions is @kbd{catch exception
3959 Pck.Constraint_Error}.
3961 @item exception unhandled
3962 An exception that was raised but is not handled by the program.
3965 A failed Ada assertion.
3968 @cindex break on fork/exec
3969 A call to @code{exec}. This is currently only available for HP-UX
3973 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
3974 @cindex break on a system call.
3975 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
3976 syscall is a mechanism for application programs to request a service
3977 from the operating system (OS) or one of the OS system services.
3978 @value{GDBN} can catch some or all of the syscalls issued by the
3979 debuggee, and show the related information for each syscall. If no
3980 argument is specified, calls to and returns from all system calls
3983 @var{name} can be any system call name that is valid for the
3984 underlying OS. Just what syscalls are valid depends on the OS. On
3985 GNU and Unix systems, you can find the full list of valid syscall
3986 names on @file{/usr/include/asm/unistd.h}.
3988 @c For MS-Windows, the syscall names and the corresponding numbers
3989 @c can be found, e.g., on this URL:
3990 @c http://www.metasploit.com/users/opcode/syscalls.html
3991 @c but we don't support Windows syscalls yet.
3993 Normally, @value{GDBN} knows in advance which syscalls are valid for
3994 each OS, so you can use the @value{GDBN} command-line completion
3995 facilities (@pxref{Completion,, command completion}) to list the
3998 You may also specify the system call numerically. A syscall's
3999 number is the value passed to the OS's syscall dispatcher to
4000 identify the requested service. When you specify the syscall by its
4001 name, @value{GDBN} uses its database of syscalls to convert the name
4002 into the corresponding numeric code, but using the number directly
4003 may be useful if @value{GDBN}'s database does not have the complete
4004 list of syscalls on your system (e.g., because @value{GDBN} lags
4005 behind the OS upgrades).
4007 The example below illustrates how this command works if you don't provide
4011 (@value{GDBP}) catch syscall
4012 Catchpoint 1 (syscall)
4014 Starting program: /tmp/catch-syscall
4016 Catchpoint 1 (call to syscall 'close'), \
4017 0xffffe424 in __kernel_vsyscall ()
4021 Catchpoint 1 (returned from syscall 'close'), \
4022 0xffffe424 in __kernel_vsyscall ()
4026 Here is an example of catching a system call by name:
4029 (@value{GDBP}) catch syscall chroot
4030 Catchpoint 1 (syscall 'chroot' [61])
4032 Starting program: /tmp/catch-syscall
4034 Catchpoint 1 (call to syscall 'chroot'), \
4035 0xffffe424 in __kernel_vsyscall ()
4039 Catchpoint 1 (returned from syscall 'chroot'), \
4040 0xffffe424 in __kernel_vsyscall ()
4044 An example of specifying a system call numerically. In the case
4045 below, the syscall number has a corresponding entry in the XML
4046 file, so @value{GDBN} finds its name and prints it:
4049 (@value{GDBP}) catch syscall 252
4050 Catchpoint 1 (syscall(s) 'exit_group')
4052 Starting program: /tmp/catch-syscall
4054 Catchpoint 1 (call to syscall 'exit_group'), \
4055 0xffffe424 in __kernel_vsyscall ()
4059 Program exited normally.
4063 However, there can be situations when there is no corresponding name
4064 in XML file for that syscall number. In this case, @value{GDBN} prints
4065 a warning message saying that it was not able to find the syscall name,
4066 but the catchpoint will be set anyway. See the example below:
4069 (@value{GDBP}) catch syscall 764
4070 warning: The number '764' does not represent a known syscall.
4071 Catchpoint 2 (syscall 764)
4075 If you configure @value{GDBN} using the @samp{--without-expat} option,
4076 it will not be able to display syscall names. Also, if your
4077 architecture does not have an XML file describing its system calls,
4078 you will not be able to see the syscall names. It is important to
4079 notice that these two features are used for accessing the syscall
4080 name database. In either case, you will see a warning like this:
4083 (@value{GDBP}) catch syscall
4084 warning: Could not open "syscalls/i386-linux.xml"
4085 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4086 GDB will not be able to display syscall names.
4087 Catchpoint 1 (syscall)
4091 Of course, the file name will change depending on your architecture and system.
4093 Still using the example above, you can also try to catch a syscall by its
4094 number. In this case, you would see something like:
4097 (@value{GDBP}) catch syscall 252
4098 Catchpoint 1 (syscall(s) 252)
4101 Again, in this case @value{GDBN} would not be able to display syscall's names.
4104 A call to @code{fork}. This is currently only available for HP-UX
4108 A call to @code{vfork}. This is currently only available for HP-UX
4113 @item tcatch @var{event}
4114 Set a catchpoint that is enabled only for one stop. The catchpoint is
4115 automatically deleted after the first time the event is caught.
4119 Use the @code{info break} command to list the current catchpoints.
4121 There are currently some limitations to C@t{++} exception handling
4122 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4126 If you call a function interactively, @value{GDBN} normally returns
4127 control to you when the function has finished executing. If the call
4128 raises an exception, however, the call may bypass the mechanism that
4129 returns control to you and cause your program either to abort or to
4130 simply continue running until it hits a breakpoint, catches a signal
4131 that @value{GDBN} is listening for, or exits. This is the case even if
4132 you set a catchpoint for the exception; catchpoints on exceptions are
4133 disabled within interactive calls.
4136 You cannot raise an exception interactively.
4139 You cannot install an exception handler interactively.
4142 @cindex raise exceptions
4143 Sometimes @code{catch} is not the best way to debug exception handling:
4144 if you need to know exactly where an exception is raised, it is better to
4145 stop @emph{before} the exception handler is called, since that way you
4146 can see the stack before any unwinding takes place. If you set a
4147 breakpoint in an exception handler instead, it may not be easy to find
4148 out where the exception was raised.
4150 To stop just before an exception handler is called, you need some
4151 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4152 raised by calling a library function named @code{__raise_exception}
4153 which has the following ANSI C interface:
4156 /* @var{addr} is where the exception identifier is stored.
4157 @var{id} is the exception identifier. */
4158 void __raise_exception (void **addr, void *id);
4162 To make the debugger catch all exceptions before any stack
4163 unwinding takes place, set a breakpoint on @code{__raise_exception}
4164 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4166 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4167 that depends on the value of @var{id}, you can stop your program when
4168 a specific exception is raised. You can use multiple conditional
4169 breakpoints to stop your program when any of a number of exceptions are
4174 @subsection Deleting Breakpoints
4176 @cindex clearing breakpoints, watchpoints, catchpoints
4177 @cindex deleting breakpoints, watchpoints, catchpoints
4178 It is often necessary to eliminate a breakpoint, watchpoint, or
4179 catchpoint once it has done its job and you no longer want your program
4180 to stop there. This is called @dfn{deleting} the breakpoint. A
4181 breakpoint that has been deleted no longer exists; it is forgotten.
4183 With the @code{clear} command you can delete breakpoints according to
4184 where they are in your program. With the @code{delete} command you can
4185 delete individual breakpoints, watchpoints, or catchpoints by specifying
4186 their breakpoint numbers.
4188 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4189 automatically ignores breakpoints on the first instruction to be executed
4190 when you continue execution without changing the execution address.
4195 Delete any breakpoints at the next instruction to be executed in the
4196 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4197 the innermost frame is selected, this is a good way to delete a
4198 breakpoint where your program just stopped.
4200 @item clear @var{location}
4201 Delete any breakpoints set at the specified @var{location}.
4202 @xref{Specify Location}, for the various forms of @var{location}; the
4203 most useful ones are listed below:
4206 @item clear @var{function}
4207 @itemx clear @var{filename}:@var{function}
4208 Delete any breakpoints set at entry to the named @var{function}.
4210 @item clear @var{linenum}
4211 @itemx clear @var{filename}:@var{linenum}
4212 Delete any breakpoints set at or within the code of the specified
4213 @var{linenum} of the specified @var{filename}.
4216 @cindex delete breakpoints
4218 @kindex d @r{(@code{delete})}
4219 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4220 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4221 ranges specified as arguments. If no argument is specified, delete all
4222 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4223 confirm off}). You can abbreviate this command as @code{d}.
4227 @subsection Disabling Breakpoints
4229 @cindex enable/disable a breakpoint
4230 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4231 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4232 it had been deleted, but remembers the information on the breakpoint so
4233 that you can @dfn{enable} it again later.
4235 You disable and enable breakpoints, watchpoints, and catchpoints with
4236 the @code{enable} and @code{disable} commands, optionally specifying
4237 one or more breakpoint numbers as arguments. Use @code{info break} to
4238 print a list of all breakpoints, watchpoints, and catchpoints if you
4239 do not know which numbers to use.
4241 Disabling and enabling a breakpoint that has multiple locations
4242 affects all of its locations.
4244 A breakpoint, watchpoint, or catchpoint can have any of four different
4245 states of enablement:
4249 Enabled. The breakpoint stops your program. A breakpoint set
4250 with the @code{break} command starts out in this state.
4252 Disabled. The breakpoint has no effect on your program.
4254 Enabled once. The breakpoint stops your program, but then becomes
4257 Enabled for deletion. The breakpoint stops your program, but
4258 immediately after it does so it is deleted permanently. A breakpoint
4259 set with the @code{tbreak} command starts out in this state.
4262 You can use the following commands to enable or disable breakpoints,
4263 watchpoints, and catchpoints:
4267 @kindex dis @r{(@code{disable})}
4268 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4269 Disable the specified breakpoints---or all breakpoints, if none are
4270 listed. A disabled breakpoint has no effect but is not forgotten. All
4271 options such as ignore-counts, conditions and commands are remembered in
4272 case the breakpoint is enabled again later. You may abbreviate
4273 @code{disable} as @code{dis}.
4276 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4277 Enable the specified breakpoints (or all defined breakpoints). They
4278 become effective once again in stopping your program.
4280 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4281 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4282 of these breakpoints immediately after stopping your program.
4284 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4285 Enable the specified breakpoints to work once, then die. @value{GDBN}
4286 deletes any of these breakpoints as soon as your program stops there.
4287 Breakpoints set by the @code{tbreak} command start out in this state.
4290 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4291 @c confusing: tbreak is also initially enabled.
4292 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4293 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4294 subsequently, they become disabled or enabled only when you use one of
4295 the commands above. (The command @code{until} can set and delete a
4296 breakpoint of its own, but it does not change the state of your other
4297 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4301 @subsection Break Conditions
4302 @cindex conditional breakpoints
4303 @cindex breakpoint conditions
4305 @c FIXME what is scope of break condition expr? Context where wanted?
4306 @c in particular for a watchpoint?
4307 The simplest sort of breakpoint breaks every time your program reaches a
4308 specified place. You can also specify a @dfn{condition} for a
4309 breakpoint. A condition is just a Boolean expression in your
4310 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4311 a condition evaluates the expression each time your program reaches it,
4312 and your program stops only if the condition is @emph{true}.
4314 This is the converse of using assertions for program validation; in that
4315 situation, you want to stop when the assertion is violated---that is,
4316 when the condition is false. In C, if you want to test an assertion expressed
4317 by the condition @var{assert}, you should set the condition
4318 @samp{! @var{assert}} on the appropriate breakpoint.
4320 Conditions are also accepted for watchpoints; you may not need them,
4321 since a watchpoint is inspecting the value of an expression anyhow---but
4322 it might be simpler, say, to just set a watchpoint on a variable name,
4323 and specify a condition that tests whether the new value is an interesting
4326 Break conditions can have side effects, and may even call functions in
4327 your program. This can be useful, for example, to activate functions
4328 that log program progress, or to use your own print functions to
4329 format special data structures. The effects are completely predictable
4330 unless there is another enabled breakpoint at the same address. (In
4331 that case, @value{GDBN} might see the other breakpoint first and stop your
4332 program without checking the condition of this one.) Note that
4333 breakpoint commands are usually more convenient and flexible than break
4335 purpose of performing side effects when a breakpoint is reached
4336 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4338 Break conditions can be specified when a breakpoint is set, by using
4339 @samp{if} in the arguments to the @code{break} command. @xref{Set
4340 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4341 with the @code{condition} command.
4343 You can also use the @code{if} keyword with the @code{watch} command.
4344 The @code{catch} command does not recognize the @code{if} keyword;
4345 @code{condition} is the only way to impose a further condition on a
4350 @item condition @var{bnum} @var{expression}
4351 Specify @var{expression} as the break condition for breakpoint,
4352 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4353 breakpoint @var{bnum} stops your program only if the value of
4354 @var{expression} is true (nonzero, in C). When you use
4355 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4356 syntactic correctness, and to determine whether symbols in it have
4357 referents in the context of your breakpoint. If @var{expression} uses
4358 symbols not referenced in the context of the breakpoint, @value{GDBN}
4359 prints an error message:
4362 No symbol "foo" in current context.
4367 not actually evaluate @var{expression} at the time the @code{condition}
4368 command (or a command that sets a breakpoint with a condition, like
4369 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4371 @item condition @var{bnum}
4372 Remove the condition from breakpoint number @var{bnum}. It becomes
4373 an ordinary unconditional breakpoint.
4376 @cindex ignore count (of breakpoint)
4377 A special case of a breakpoint condition is to stop only when the
4378 breakpoint has been reached a certain number of times. This is so
4379 useful that there is a special way to do it, using the @dfn{ignore
4380 count} of the breakpoint. Every breakpoint has an ignore count, which
4381 is an integer. Most of the time, the ignore count is zero, and
4382 therefore has no effect. But if your program reaches a breakpoint whose
4383 ignore count is positive, then instead of stopping, it just decrements
4384 the ignore count by one and continues. As a result, if the ignore count
4385 value is @var{n}, the breakpoint does not stop the next @var{n} times
4386 your program reaches it.
4390 @item ignore @var{bnum} @var{count}
4391 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4392 The next @var{count} times the breakpoint is reached, your program's
4393 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4396 To make the breakpoint stop the next time it is reached, specify
4399 When you use @code{continue} to resume execution of your program from a
4400 breakpoint, you can specify an ignore count directly as an argument to
4401 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4402 Stepping,,Continuing and Stepping}.
4404 If a breakpoint has a positive ignore count and a condition, the
4405 condition is not checked. Once the ignore count reaches zero,
4406 @value{GDBN} resumes checking the condition.
4408 You could achieve the effect of the ignore count with a condition such
4409 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4410 is decremented each time. @xref{Convenience Vars, ,Convenience
4414 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4417 @node Break Commands
4418 @subsection Breakpoint Command Lists
4420 @cindex breakpoint commands
4421 You can give any breakpoint (or watchpoint or catchpoint) a series of
4422 commands to execute when your program stops due to that breakpoint. For
4423 example, you might want to print the values of certain expressions, or
4424 enable other breakpoints.
4428 @kindex end@r{ (breakpoint commands)}
4429 @item commands @r{[}@var{range}@dots{}@r{]}
4430 @itemx @dots{} @var{command-list} @dots{}
4432 Specify a list of commands for the given breakpoints. The commands
4433 themselves appear on the following lines. Type a line containing just
4434 @code{end} to terminate the commands.
4436 To remove all commands from a breakpoint, type @code{commands} and
4437 follow it immediately with @code{end}; that is, give no commands.
4439 With no argument, @code{commands} refers to the last breakpoint,
4440 watchpoint, or catchpoint set (not to the breakpoint most recently
4441 encountered). If the most recent breakpoints were set with a single
4442 command, then the @code{commands} will apply to all the breakpoints
4443 set by that command. This applies to breakpoints set by
4444 @code{rbreak}, and also applies when a single @code{break} command
4445 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4449 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4450 disabled within a @var{command-list}.
4452 You can use breakpoint commands to start your program up again. Simply
4453 use the @code{continue} command, or @code{step}, or any other command
4454 that resumes execution.
4456 Any other commands in the command list, after a command that resumes
4457 execution, are ignored. This is because any time you resume execution
4458 (even with a simple @code{next} or @code{step}), you may encounter
4459 another breakpoint---which could have its own command list, leading to
4460 ambiguities about which list to execute.
4463 If the first command you specify in a command list is @code{silent}, the
4464 usual message about stopping at a breakpoint is not printed. This may
4465 be desirable for breakpoints that are to print a specific message and
4466 then continue. If none of the remaining commands print anything, you
4467 see no sign that the breakpoint was reached. @code{silent} is
4468 meaningful only at the beginning of a breakpoint command list.
4470 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4471 print precisely controlled output, and are often useful in silent
4472 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4474 For example, here is how you could use breakpoint commands to print the
4475 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4481 printf "x is %d\n",x
4486 One application for breakpoint commands is to compensate for one bug so
4487 you can test for another. Put a breakpoint just after the erroneous line
4488 of code, give it a condition to detect the case in which something
4489 erroneous has been done, and give it commands to assign correct values
4490 to any variables that need them. End with the @code{continue} command
4491 so that your program does not stop, and start with the @code{silent}
4492 command so that no output is produced. Here is an example:
4503 @node Save Breakpoints
4504 @subsection How to save breakpoints to a file
4506 To save breakpoint definitions to a file use the @w{@code{save
4507 breakpoints}} command.
4510 @kindex save breakpoints
4511 @cindex save breakpoints to a file for future sessions
4512 @item save breakpoints [@var{filename}]
4513 This command saves all current breakpoint definitions together with
4514 their commands and ignore counts, into a file @file{@var{filename}}
4515 suitable for use in a later debugging session. This includes all
4516 types of breakpoints (breakpoints, watchpoints, catchpoints,
4517 tracepoints). To read the saved breakpoint definitions, use the
4518 @code{source} command (@pxref{Command Files}). Note that watchpoints
4519 with expressions involving local variables may fail to be recreated
4520 because it may not be possible to access the context where the
4521 watchpoint is valid anymore. Because the saved breakpoint definitions
4522 are simply a sequence of @value{GDBN} commands that recreate the
4523 breakpoints, you can edit the file in your favorite editing program,
4524 and remove the breakpoint definitions you're not interested in, or
4525 that can no longer be recreated.
4528 @c @ifclear BARETARGET
4529 @node Error in Breakpoints
4530 @subsection ``Cannot insert breakpoints''
4532 If you request too many active hardware-assisted breakpoints and
4533 watchpoints, you will see this error message:
4535 @c FIXME: the precise wording of this message may change; the relevant
4536 @c source change is not committed yet (Sep 3, 1999).
4538 Stopped; cannot insert breakpoints.
4539 You may have requested too many hardware breakpoints and watchpoints.
4543 This message is printed when you attempt to resume the program, since
4544 only then @value{GDBN} knows exactly how many hardware breakpoints and
4545 watchpoints it needs to insert.
4547 When this message is printed, you need to disable or remove some of the
4548 hardware-assisted breakpoints and watchpoints, and then continue.
4550 @node Breakpoint-related Warnings
4551 @subsection ``Breakpoint address adjusted...''
4552 @cindex breakpoint address adjusted
4554 Some processor architectures place constraints on the addresses at
4555 which breakpoints may be placed. For architectures thus constrained,
4556 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4557 with the constraints dictated by the architecture.
4559 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4560 a VLIW architecture in which a number of RISC-like instructions may be
4561 bundled together for parallel execution. The FR-V architecture
4562 constrains the location of a breakpoint instruction within such a
4563 bundle to the instruction with the lowest address. @value{GDBN}
4564 honors this constraint by adjusting a breakpoint's address to the
4565 first in the bundle.
4567 It is not uncommon for optimized code to have bundles which contain
4568 instructions from different source statements, thus it may happen that
4569 a breakpoint's address will be adjusted from one source statement to
4570 another. Since this adjustment may significantly alter @value{GDBN}'s
4571 breakpoint related behavior from what the user expects, a warning is
4572 printed when the breakpoint is first set and also when the breakpoint
4575 A warning like the one below is printed when setting a breakpoint
4576 that's been subject to address adjustment:
4579 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4582 Such warnings are printed both for user settable and @value{GDBN}'s
4583 internal breakpoints. If you see one of these warnings, you should
4584 verify that a breakpoint set at the adjusted address will have the
4585 desired affect. If not, the breakpoint in question may be removed and
4586 other breakpoints may be set which will have the desired behavior.
4587 E.g., it may be sufficient to place the breakpoint at a later
4588 instruction. A conditional breakpoint may also be useful in some
4589 cases to prevent the breakpoint from triggering too often.
4591 @value{GDBN} will also issue a warning when stopping at one of these
4592 adjusted breakpoints:
4595 warning: Breakpoint 1 address previously adjusted from 0x00010414
4599 When this warning is encountered, it may be too late to take remedial
4600 action except in cases where the breakpoint is hit earlier or more
4601 frequently than expected.
4603 @node Continuing and Stepping
4604 @section Continuing and Stepping
4608 @cindex resuming execution
4609 @dfn{Continuing} means resuming program execution until your program
4610 completes normally. In contrast, @dfn{stepping} means executing just
4611 one more ``step'' of your program, where ``step'' may mean either one
4612 line of source code, or one machine instruction (depending on what
4613 particular command you use). Either when continuing or when stepping,
4614 your program may stop even sooner, due to a breakpoint or a signal. (If
4615 it stops due to a signal, you may want to use @code{handle}, or use
4616 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4620 @kindex c @r{(@code{continue})}
4621 @kindex fg @r{(resume foreground execution)}
4622 @item continue @r{[}@var{ignore-count}@r{]}
4623 @itemx c @r{[}@var{ignore-count}@r{]}
4624 @itemx fg @r{[}@var{ignore-count}@r{]}
4625 Resume program execution, at the address where your program last stopped;
4626 any breakpoints set at that address are bypassed. The optional argument
4627 @var{ignore-count} allows you to specify a further number of times to
4628 ignore a breakpoint at this location; its effect is like that of
4629 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4631 The argument @var{ignore-count} is meaningful only when your program
4632 stopped due to a breakpoint. At other times, the argument to
4633 @code{continue} is ignored.
4635 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4636 debugged program is deemed to be the foreground program) are provided
4637 purely for convenience, and have exactly the same behavior as
4641 To resume execution at a different place, you can use @code{return}
4642 (@pxref{Returning, ,Returning from a Function}) to go back to the
4643 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4644 Different Address}) to go to an arbitrary location in your program.
4646 A typical technique for using stepping is to set a breakpoint
4647 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4648 beginning of the function or the section of your program where a problem
4649 is believed to lie, run your program until it stops at that breakpoint,
4650 and then step through the suspect area, examining the variables that are
4651 interesting, until you see the problem happen.
4655 @kindex s @r{(@code{step})}
4657 Continue running your program until control reaches a different source
4658 line, then stop it and return control to @value{GDBN}. This command is
4659 abbreviated @code{s}.
4662 @c "without debugging information" is imprecise; actually "without line
4663 @c numbers in the debugging information". (gcc -g1 has debugging info but
4664 @c not line numbers). But it seems complex to try to make that
4665 @c distinction here.
4666 @emph{Warning:} If you use the @code{step} command while control is
4667 within a function that was compiled without debugging information,
4668 execution proceeds until control reaches a function that does have
4669 debugging information. Likewise, it will not step into a function which
4670 is compiled without debugging information. To step through functions
4671 without debugging information, use the @code{stepi} command, described
4675 The @code{step} command only stops at the first instruction of a source
4676 line. This prevents the multiple stops that could otherwise occur in
4677 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4678 to stop if a function that has debugging information is called within
4679 the line. In other words, @code{step} @emph{steps inside} any functions
4680 called within the line.
4682 Also, the @code{step} command only enters a function if there is line
4683 number information for the function. Otherwise it acts like the
4684 @code{next} command. This avoids problems when using @code{cc -gl}
4685 on MIPS machines. Previously, @code{step} entered subroutines if there
4686 was any debugging information about the routine.
4688 @item step @var{count}
4689 Continue running as in @code{step}, but do so @var{count} times. If a
4690 breakpoint is reached, or a signal not related to stepping occurs before
4691 @var{count} steps, stepping stops right away.
4694 @kindex n @r{(@code{next})}
4695 @item next @r{[}@var{count}@r{]}
4696 Continue to the next source line in the current (innermost) stack frame.
4697 This is similar to @code{step}, but function calls that appear within
4698 the line of code are executed without stopping. Execution stops when
4699 control reaches a different line of code at the original stack level
4700 that was executing when you gave the @code{next} command. This command
4701 is abbreviated @code{n}.
4703 An argument @var{count} is a repeat count, as for @code{step}.
4706 @c FIX ME!! Do we delete this, or is there a way it fits in with
4707 @c the following paragraph? --- Vctoria
4709 @c @code{next} within a function that lacks debugging information acts like
4710 @c @code{step}, but any function calls appearing within the code of the
4711 @c function are executed without stopping.
4713 The @code{next} command only stops at the first instruction of a
4714 source line. This prevents multiple stops that could otherwise occur in
4715 @code{switch} statements, @code{for} loops, etc.
4717 @kindex set step-mode
4719 @cindex functions without line info, and stepping
4720 @cindex stepping into functions with no line info
4721 @itemx set step-mode on
4722 The @code{set step-mode on} command causes the @code{step} command to
4723 stop at the first instruction of a function which contains no debug line
4724 information rather than stepping over it.
4726 This is useful in cases where you may be interested in inspecting the
4727 machine instructions of a function which has no symbolic info and do not
4728 want @value{GDBN} to automatically skip over this function.
4730 @item set step-mode off
4731 Causes the @code{step} command to step over any functions which contains no
4732 debug information. This is the default.
4734 @item show step-mode
4735 Show whether @value{GDBN} will stop in or step over functions without
4736 source line debug information.
4739 @kindex fin @r{(@code{finish})}
4741 Continue running until just after function in the selected stack frame
4742 returns. Print the returned value (if any). This command can be
4743 abbreviated as @code{fin}.
4745 Contrast this with the @code{return} command (@pxref{Returning,
4746 ,Returning from a Function}).
4749 @kindex u @r{(@code{until})}
4750 @cindex run until specified location
4753 Continue running until a source line past the current line, in the
4754 current stack frame, is reached. This command is used to avoid single
4755 stepping through a loop more than once. It is like the @code{next}
4756 command, except that when @code{until} encounters a jump, it
4757 automatically continues execution until the program counter is greater
4758 than the address of the jump.
4760 This means that when you reach the end of a loop after single stepping
4761 though it, @code{until} makes your program continue execution until it
4762 exits the loop. In contrast, a @code{next} command at the end of a loop
4763 simply steps back to the beginning of the loop, which forces you to step
4764 through the next iteration.
4766 @code{until} always stops your program if it attempts to exit the current
4769 @code{until} may produce somewhat counterintuitive results if the order
4770 of machine code does not match the order of the source lines. For
4771 example, in the following excerpt from a debugging session, the @code{f}
4772 (@code{frame}) command shows that execution is stopped at line
4773 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4777 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4779 (@value{GDBP}) until
4780 195 for ( ; argc > 0; NEXTARG) @{
4783 This happened because, for execution efficiency, the compiler had
4784 generated code for the loop closure test at the end, rather than the
4785 start, of the loop---even though the test in a C @code{for}-loop is
4786 written before the body of the loop. The @code{until} command appeared
4787 to step back to the beginning of the loop when it advanced to this
4788 expression; however, it has not really gone to an earlier
4789 statement---not in terms of the actual machine code.
4791 @code{until} with no argument works by means of single
4792 instruction stepping, and hence is slower than @code{until} with an
4795 @item until @var{location}
4796 @itemx u @var{location}
4797 Continue running your program until either the specified location is
4798 reached, or the current stack frame returns. @var{location} is any of
4799 the forms described in @ref{Specify Location}.
4800 This form of the command uses temporary breakpoints, and
4801 hence is quicker than @code{until} without an argument. The specified
4802 location is actually reached only if it is in the current frame. This
4803 implies that @code{until} can be used to skip over recursive function
4804 invocations. For instance in the code below, if the current location is
4805 line @code{96}, issuing @code{until 99} will execute the program up to
4806 line @code{99} in the same invocation of factorial, i.e., after the inner
4807 invocations have returned.
4810 94 int factorial (int value)
4812 96 if (value > 1) @{
4813 97 value *= factorial (value - 1);
4820 @kindex advance @var{location}
4821 @itemx advance @var{location}
4822 Continue running the program up to the given @var{location}. An argument is
4823 required, which should be of one of the forms described in
4824 @ref{Specify Location}.
4825 Execution will also stop upon exit from the current stack
4826 frame. This command is similar to @code{until}, but @code{advance} will
4827 not skip over recursive function calls, and the target location doesn't
4828 have to be in the same frame as the current one.
4832 @kindex si @r{(@code{stepi})}
4834 @itemx stepi @var{arg}
4836 Execute one machine instruction, then stop and return to the debugger.
4838 It is often useful to do @samp{display/i $pc} when stepping by machine
4839 instructions. This makes @value{GDBN} automatically display the next
4840 instruction to be executed, each time your program stops. @xref{Auto
4841 Display,, Automatic Display}.
4843 An argument is a repeat count, as in @code{step}.
4847 @kindex ni @r{(@code{nexti})}
4849 @itemx nexti @var{arg}
4851 Execute one machine instruction, but if it is a function call,
4852 proceed until the function returns.
4854 An argument is a repeat count, as in @code{next}.
4857 @node Skipping Over Functions and Files
4858 @subsection Skipping Over Functions and Files
4859 @cindex skipping over functions and files
4861 The program you are debugging may contain some functions which are
4862 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
4863 skip a function or all functions in a file when stepping.
4865 For example, consider the following C function:
4876 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
4877 are not interested in stepping through @code{boring}. If you run @code{step}
4878 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
4879 step over both @code{foo} and @code{boring}!
4881 One solution is to @code{step} into @code{boring} and use the @code{finish}
4882 command to immediately exit it. But this can become tedious if @code{boring}
4883 is called from many places.
4885 A more flexible solution is to execute @kbd{skip boring}. This instructs
4886 @value{GDBN} never to step into @code{boring}. Now when you execute
4887 @code{step} at line 103, you'll step over @code{boring} and directly into
4890 You can also instruct @value{GDBN} to skip all functions in a file, with, for
4891 example, @code{skip file boring.c}.
4894 @kindex skip function
4895 @item skip @r{[}@var{linespec}@r{]}
4896 @itemx skip function @r{[}@var{linespec}@r{]}
4897 After running this command, the function named by @var{linespec} or the
4898 function containing the line named by @var{linespec} will be skipped over when
4899 stepping. @xref{Specify Location}
4901 If you do not specify @var{linespec}, the function you're currently debugging
4904 (If you have a function called @code{file} that you want to skip, use
4905 @kbd{skip function file}.)
4908 @item skip file @r{[}@var{filename}@r{]}
4909 After running this command, any function whose source lives in @var{filename}
4910 will be skipped over when stepping.
4912 If you do not specify @var{filename}, functions whose source lives in the file
4913 you're currently debugging will be skipped.
4916 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
4917 These are the commands for managing your list of skips:
4921 @item info skip @r{[}@var{range}@r{]}
4922 Print details about the specified skip(s). If @var{range} is not specified,
4923 print a table with details about all functions and files marked for skipping.
4924 @code{info skip} prints the following information about each skip:
4928 A number identifying this skip.
4930 The type of this skip, either @samp{function} or @samp{file}.
4931 @item Enabled or Disabled
4932 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
4934 For function skips, this column indicates the address in memory of the function
4935 being skipped. If you've set a function skip on a function which has not yet
4936 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
4937 which has the function is loaded, @code{info skip} will show the function's
4940 For file skips, this field contains the filename being skipped. For functions
4941 skips, this field contains the function name and its line number in the file
4942 where it is defined.
4946 @item skip delete @r{[}@var{range}@r{]}
4947 Delete the specified skip(s). If @var{range} is not specified, delete all
4951 @item skip enable @r{[}@var{range}@r{]}
4952 Enable the specified skip(s). If @var{range} is not specified, enable all
4955 @kindex skip disable
4956 @item skip disable @r{[}@var{range}@r{]}
4957 Disable the specified skip(s). If @var{range} is not specified, disable all
4966 A signal is an asynchronous event that can happen in a program. The
4967 operating system defines the possible kinds of signals, and gives each
4968 kind a name and a number. For example, in Unix @code{SIGINT} is the
4969 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4970 @code{SIGSEGV} is the signal a program gets from referencing a place in
4971 memory far away from all the areas in use; @code{SIGALRM} occurs when
4972 the alarm clock timer goes off (which happens only if your program has
4973 requested an alarm).
4975 @cindex fatal signals
4976 Some signals, including @code{SIGALRM}, are a normal part of the
4977 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4978 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4979 program has not specified in advance some other way to handle the signal.
4980 @code{SIGINT} does not indicate an error in your program, but it is normally
4981 fatal so it can carry out the purpose of the interrupt: to kill the program.
4983 @value{GDBN} has the ability to detect any occurrence of a signal in your
4984 program. You can tell @value{GDBN} in advance what to do for each kind of
4987 @cindex handling signals
4988 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4989 @code{SIGALRM} be silently passed to your program
4990 (so as not to interfere with their role in the program's functioning)
4991 but to stop your program immediately whenever an error signal happens.
4992 You can change these settings with the @code{handle} command.
4995 @kindex info signals
4999 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5000 handle each one. You can use this to see the signal numbers of all
5001 the defined types of signals.
5003 @item info signals @var{sig}
5004 Similar, but print information only about the specified signal number.
5006 @code{info handle} is an alias for @code{info signals}.
5009 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5010 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
5011 can be the number of a signal or its name (with or without the
5012 @samp{SIG} at the beginning); a list of signal numbers of the form
5013 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5014 known signals. Optional arguments @var{keywords}, described below,
5015 say what change to make.
5019 The keywords allowed by the @code{handle} command can be abbreviated.
5020 Their full names are:
5024 @value{GDBN} should not stop your program when this signal happens. It may
5025 still print a message telling you that the signal has come in.
5028 @value{GDBN} should stop your program when this signal happens. This implies
5029 the @code{print} keyword as well.
5032 @value{GDBN} should print a message when this signal happens.
5035 @value{GDBN} should not mention the occurrence of the signal at all. This
5036 implies the @code{nostop} keyword as well.
5040 @value{GDBN} should allow your program to see this signal; your program
5041 can handle the signal, or else it may terminate if the signal is fatal
5042 and not handled. @code{pass} and @code{noignore} are synonyms.
5046 @value{GDBN} should not allow your program to see this signal.
5047 @code{nopass} and @code{ignore} are synonyms.
5051 When a signal stops your program, the signal is not visible to the
5053 continue. Your program sees the signal then, if @code{pass} is in
5054 effect for the signal in question @emph{at that time}. In other words,
5055 after @value{GDBN} reports a signal, you can use the @code{handle}
5056 command with @code{pass} or @code{nopass} to control whether your
5057 program sees that signal when you continue.
5059 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5060 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5061 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5064 You can also use the @code{signal} command to prevent your program from
5065 seeing a signal, or cause it to see a signal it normally would not see,
5066 or to give it any signal at any time. For example, if your program stopped
5067 due to some sort of memory reference error, you might store correct
5068 values into the erroneous variables and continue, hoping to see more
5069 execution; but your program would probably terminate immediately as
5070 a result of the fatal signal once it saw the signal. To prevent this,
5071 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5074 @cindex extra signal information
5075 @anchor{extra signal information}
5077 On some targets, @value{GDBN} can inspect extra signal information
5078 associated with the intercepted signal, before it is actually
5079 delivered to the program being debugged. This information is exported
5080 by the convenience variable @code{$_siginfo}, and consists of data
5081 that is passed by the kernel to the signal handler at the time of the
5082 receipt of a signal. The data type of the information itself is
5083 target dependent. You can see the data type using the @code{ptype
5084 $_siginfo} command. On Unix systems, it typically corresponds to the
5085 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5088 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5089 referenced address that raised a segmentation fault.
5093 (@value{GDBP}) continue
5094 Program received signal SIGSEGV, Segmentation fault.
5095 0x0000000000400766 in main ()
5097 (@value{GDBP}) ptype $_siginfo
5104 struct @{...@} _kill;
5105 struct @{...@} _timer;
5107 struct @{...@} _sigchld;
5108 struct @{...@} _sigfault;
5109 struct @{...@} _sigpoll;
5112 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5116 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5117 $1 = (void *) 0x7ffff7ff7000
5121 Depending on target support, @code{$_siginfo} may also be writable.
5124 @section Stopping and Starting Multi-thread Programs
5126 @cindex stopped threads
5127 @cindex threads, stopped
5129 @cindex continuing threads
5130 @cindex threads, continuing
5132 @value{GDBN} supports debugging programs with multiple threads
5133 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5134 are two modes of controlling execution of your program within the
5135 debugger. In the default mode, referred to as @dfn{all-stop mode},
5136 when any thread in your program stops (for example, at a breakpoint
5137 or while being stepped), all other threads in the program are also stopped by
5138 @value{GDBN}. On some targets, @value{GDBN} also supports
5139 @dfn{non-stop mode}, in which other threads can continue to run freely while
5140 you examine the stopped thread in the debugger.
5143 * All-Stop Mode:: All threads stop when GDB takes control
5144 * Non-Stop Mode:: Other threads continue to execute
5145 * Background Execution:: Running your program asynchronously
5146 * Thread-Specific Breakpoints:: Controlling breakpoints
5147 * Interrupted System Calls:: GDB may interfere with system calls
5148 * Observer Mode:: GDB does not alter program behavior
5152 @subsection All-Stop Mode
5154 @cindex all-stop mode
5156 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5157 @emph{all} threads of execution stop, not just the current thread. This
5158 allows you to examine the overall state of the program, including
5159 switching between threads, without worrying that things may change
5162 Conversely, whenever you restart the program, @emph{all} threads start
5163 executing. @emph{This is true even when single-stepping} with commands
5164 like @code{step} or @code{next}.
5166 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5167 Since thread scheduling is up to your debugging target's operating
5168 system (not controlled by @value{GDBN}), other threads may
5169 execute more than one statement while the current thread completes a
5170 single step. Moreover, in general other threads stop in the middle of a
5171 statement, rather than at a clean statement boundary, when the program
5174 You might even find your program stopped in another thread after
5175 continuing or even single-stepping. This happens whenever some other
5176 thread runs into a breakpoint, a signal, or an exception before the
5177 first thread completes whatever you requested.
5179 @cindex automatic thread selection
5180 @cindex switching threads automatically
5181 @cindex threads, automatic switching
5182 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5183 signal, it automatically selects the thread where that breakpoint or
5184 signal happened. @value{GDBN} alerts you to the context switch with a
5185 message such as @samp{[Switching to Thread @var{n}]} to identify the
5188 On some OSes, you can modify @value{GDBN}'s default behavior by
5189 locking the OS scheduler to allow only a single thread to run.
5192 @item set scheduler-locking @var{mode}
5193 @cindex scheduler locking mode
5194 @cindex lock scheduler
5195 Set the scheduler locking mode. If it is @code{off}, then there is no
5196 locking and any thread may run at any time. If @code{on}, then only the
5197 current thread may run when the inferior is resumed. The @code{step}
5198 mode optimizes for single-stepping; it prevents other threads
5199 from preempting the current thread while you are stepping, so that
5200 the focus of debugging does not change unexpectedly.
5201 Other threads only rarely (or never) get a chance to run
5202 when you step. They are more likely to run when you @samp{next} over a
5203 function call, and they are completely free to run when you use commands
5204 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5205 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5206 the current thread away from the thread that you are debugging.
5208 @item show scheduler-locking
5209 Display the current scheduler locking mode.
5212 @cindex resume threads of multiple processes simultaneously
5213 By default, when you issue one of the execution commands such as
5214 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5215 threads of the current inferior to run. For example, if @value{GDBN}
5216 is attached to two inferiors, each with two threads, the
5217 @code{continue} command resumes only the two threads of the current
5218 inferior. This is useful, for example, when you debug a program that
5219 forks and you want to hold the parent stopped (so that, for instance,
5220 it doesn't run to exit), while you debug the child. In other
5221 situations, you may not be interested in inspecting the current state
5222 of any of the processes @value{GDBN} is attached to, and you may want
5223 to resume them all until some breakpoint is hit. In the latter case,
5224 you can instruct @value{GDBN} to allow all threads of all the
5225 inferiors to run with the @w{@code{set schedule-multiple}} command.
5228 @kindex set schedule-multiple
5229 @item set schedule-multiple
5230 Set the mode for allowing threads of multiple processes to be resumed
5231 when an execution command is issued. When @code{on}, all threads of
5232 all processes are allowed to run. When @code{off}, only the threads
5233 of the current process are resumed. The default is @code{off}. The
5234 @code{scheduler-locking} mode takes precedence when set to @code{on},
5235 or while you are stepping and set to @code{step}.
5237 @item show schedule-multiple
5238 Display the current mode for resuming the execution of threads of
5243 @subsection Non-Stop Mode
5245 @cindex non-stop mode
5247 @c This section is really only a place-holder, and needs to be expanded
5248 @c with more details.
5250 For some multi-threaded targets, @value{GDBN} supports an optional
5251 mode of operation in which you can examine stopped program threads in
5252 the debugger while other threads continue to execute freely. This
5253 minimizes intrusion when debugging live systems, such as programs
5254 where some threads have real-time constraints or must continue to
5255 respond to external events. This is referred to as @dfn{non-stop} mode.
5257 In non-stop mode, when a thread stops to report a debugging event,
5258 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5259 threads as well, in contrast to the all-stop mode behavior. Additionally,
5260 execution commands such as @code{continue} and @code{step} apply by default
5261 only to the current thread in non-stop mode, rather than all threads as
5262 in all-stop mode. This allows you to control threads explicitly in
5263 ways that are not possible in all-stop mode --- for example, stepping
5264 one thread while allowing others to run freely, stepping
5265 one thread while holding all others stopped, or stepping several threads
5266 independently and simultaneously.
5268 To enter non-stop mode, use this sequence of commands before you run
5269 or attach to your program:
5272 # Enable the async interface.
5275 # If using the CLI, pagination breaks non-stop.
5278 # Finally, turn it on!
5282 You can use these commands to manipulate the non-stop mode setting:
5285 @kindex set non-stop
5286 @item set non-stop on
5287 Enable selection of non-stop mode.
5288 @item set non-stop off
5289 Disable selection of non-stop mode.
5290 @kindex show non-stop
5292 Show the current non-stop enablement setting.
5295 Note these commands only reflect whether non-stop mode is enabled,
5296 not whether the currently-executing program is being run in non-stop mode.
5297 In particular, the @code{set non-stop} preference is only consulted when
5298 @value{GDBN} starts or connects to the target program, and it is generally
5299 not possible to switch modes once debugging has started. Furthermore,
5300 since not all targets support non-stop mode, even when you have enabled
5301 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5304 In non-stop mode, all execution commands apply only to the current thread
5305 by default. That is, @code{continue} only continues one thread.
5306 To continue all threads, issue @code{continue -a} or @code{c -a}.
5308 You can use @value{GDBN}'s background execution commands
5309 (@pxref{Background Execution}) to run some threads in the background
5310 while you continue to examine or step others from @value{GDBN}.
5311 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5312 always executed asynchronously in non-stop mode.
5314 Suspending execution is done with the @code{interrupt} command when
5315 running in the background, or @kbd{Ctrl-c} during foreground execution.
5316 In all-stop mode, this stops the whole process;
5317 but in non-stop mode the interrupt applies only to the current thread.
5318 To stop the whole program, use @code{interrupt -a}.
5320 Other execution commands do not currently support the @code{-a} option.
5322 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5323 that thread current, as it does in all-stop mode. This is because the
5324 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5325 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5326 changed to a different thread just as you entered a command to operate on the
5327 previously current thread.
5329 @node Background Execution
5330 @subsection Background Execution
5332 @cindex foreground execution
5333 @cindex background execution
5334 @cindex asynchronous execution
5335 @cindex execution, foreground, background and asynchronous
5337 @value{GDBN}'s execution commands have two variants: the normal
5338 foreground (synchronous) behavior, and a background
5339 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5340 the program to report that some thread has stopped before prompting for
5341 another command. In background execution, @value{GDBN} immediately gives
5342 a command prompt so that you can issue other commands while your program runs.
5344 You need to explicitly enable asynchronous mode before you can use
5345 background execution commands. You can use these commands to
5346 manipulate the asynchronous mode setting:
5349 @kindex set target-async
5350 @item set target-async on
5351 Enable asynchronous mode.
5352 @item set target-async off
5353 Disable asynchronous mode.
5354 @kindex show target-async
5355 @item show target-async
5356 Show the current target-async setting.
5359 If the target doesn't support async mode, @value{GDBN} issues an error
5360 message if you attempt to use the background execution commands.
5362 To specify background execution, add a @code{&} to the command. For example,
5363 the background form of the @code{continue} command is @code{continue&}, or
5364 just @code{c&}. The execution commands that accept background execution
5370 @xref{Starting, , Starting your Program}.
5374 @xref{Attach, , Debugging an Already-running Process}.
5378 @xref{Continuing and Stepping, step}.
5382 @xref{Continuing and Stepping, stepi}.
5386 @xref{Continuing and Stepping, next}.
5390 @xref{Continuing and Stepping, nexti}.
5394 @xref{Continuing and Stepping, continue}.
5398 @xref{Continuing and Stepping, finish}.
5402 @xref{Continuing and Stepping, until}.
5406 Background execution is especially useful in conjunction with non-stop
5407 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5408 However, you can also use these commands in the normal all-stop mode with
5409 the restriction that you cannot issue another execution command until the
5410 previous one finishes. Examples of commands that are valid in all-stop
5411 mode while the program is running include @code{help} and @code{info break}.
5413 You can interrupt your program while it is running in the background by
5414 using the @code{interrupt} command.
5421 Suspend execution of the running program. In all-stop mode,
5422 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5423 only the current thread. To stop the whole program in non-stop mode,
5424 use @code{interrupt -a}.
5427 @node Thread-Specific Breakpoints
5428 @subsection Thread-Specific Breakpoints
5430 When your program has multiple threads (@pxref{Threads,, Debugging
5431 Programs with Multiple Threads}), you can choose whether to set
5432 breakpoints on all threads, or on a particular thread.
5435 @cindex breakpoints and threads
5436 @cindex thread breakpoints
5437 @kindex break @dots{} thread @var{threadno}
5438 @item break @var{linespec} thread @var{threadno}
5439 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5440 @var{linespec} specifies source lines; there are several ways of
5441 writing them (@pxref{Specify Location}), but the effect is always to
5442 specify some source line.
5444 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5445 to specify that you only want @value{GDBN} to stop the program when a
5446 particular thread reaches this breakpoint. @var{threadno} is one of the
5447 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5448 column of the @samp{info threads} display.
5450 If you do not specify @samp{thread @var{threadno}} when you set a
5451 breakpoint, the breakpoint applies to @emph{all} threads of your
5454 You can use the @code{thread} qualifier on conditional breakpoints as
5455 well; in this case, place @samp{thread @var{threadno}} before or
5456 after the breakpoint condition, like this:
5459 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5464 @node Interrupted System Calls
5465 @subsection Interrupted System Calls
5467 @cindex thread breakpoints and system calls
5468 @cindex system calls and thread breakpoints
5469 @cindex premature return from system calls
5470 There is an unfortunate side effect when using @value{GDBN} to debug
5471 multi-threaded programs. If one thread stops for a
5472 breakpoint, or for some other reason, and another thread is blocked in a
5473 system call, then the system call may return prematurely. This is a
5474 consequence of the interaction between multiple threads and the signals
5475 that @value{GDBN} uses to implement breakpoints and other events that
5478 To handle this problem, your program should check the return value of
5479 each system call and react appropriately. This is good programming
5482 For example, do not write code like this:
5488 The call to @code{sleep} will return early if a different thread stops
5489 at a breakpoint or for some other reason.
5491 Instead, write this:
5496 unslept = sleep (unslept);
5499 A system call is allowed to return early, so the system is still
5500 conforming to its specification. But @value{GDBN} does cause your
5501 multi-threaded program to behave differently than it would without
5504 Also, @value{GDBN} uses internal breakpoints in the thread library to
5505 monitor certain events such as thread creation and thread destruction.
5506 When such an event happens, a system call in another thread may return
5507 prematurely, even though your program does not appear to stop.
5510 @subsection Observer Mode
5512 If you want to build on non-stop mode and observe program behavior
5513 without any chance of disruption by @value{GDBN}, you can set
5514 variables to disable all of the debugger's attempts to modify state,
5515 whether by writing memory, inserting breakpoints, etc. These operate
5516 at a low level, intercepting operations from all commands.
5518 When all of these are set to @code{off}, then @value{GDBN} is said to
5519 be @dfn{observer mode}. As a convenience, the variable
5520 @code{observer} can be set to disable these, plus enable non-stop
5523 Note that @value{GDBN} will not prevent you from making nonsensical
5524 combinations of these settings. For instance, if you have enabled
5525 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5526 then breakpoints that work by writing trap instructions into the code
5527 stream will still not be able to be placed.
5532 @item set observer on
5533 @itemx set observer off
5534 When set to @code{on}, this disables all the permission variables
5535 below (except for @code{insert-fast-tracepoints}), plus enables
5536 non-stop debugging. Setting this to @code{off} switches back to
5537 normal debugging, though remaining in non-stop mode.
5540 Show whether observer mode is on or off.
5542 @kindex may-write-registers
5543 @item set may-write-registers on
5544 @itemx set may-write-registers off
5545 This controls whether @value{GDBN} will attempt to alter the values of
5546 registers, such as with assignment expressions in @code{print}, or the
5547 @code{jump} command. It defaults to @code{on}.
5549 @item show may-write-registers
5550 Show the current permission to write registers.
5552 @kindex may-write-memory
5553 @item set may-write-memory on
5554 @itemx set may-write-memory off
5555 This controls whether @value{GDBN} will attempt to alter the contents
5556 of memory, such as with assignment expressions in @code{print}. It
5557 defaults to @code{on}.
5559 @item show may-write-memory
5560 Show the current permission to write memory.
5562 @kindex may-insert-breakpoints
5563 @item set may-insert-breakpoints on
5564 @itemx set may-insert-breakpoints off
5565 This controls whether @value{GDBN} will attempt to insert breakpoints.
5566 This affects all breakpoints, including internal breakpoints defined
5567 by @value{GDBN}. It defaults to @code{on}.
5569 @item show may-insert-breakpoints
5570 Show the current permission to insert breakpoints.
5572 @kindex may-insert-tracepoints
5573 @item set may-insert-tracepoints on
5574 @itemx set may-insert-tracepoints off
5575 This controls whether @value{GDBN} will attempt to insert (regular)
5576 tracepoints at the beginning of a tracing experiment. It affects only
5577 non-fast tracepoints, fast tracepoints being under the control of
5578 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5580 @item show may-insert-tracepoints
5581 Show the current permission to insert tracepoints.
5583 @kindex may-insert-fast-tracepoints
5584 @item set may-insert-fast-tracepoints on
5585 @itemx set may-insert-fast-tracepoints off
5586 This controls whether @value{GDBN} will attempt to insert fast
5587 tracepoints at the beginning of a tracing experiment. It affects only
5588 fast tracepoints, regular (non-fast) tracepoints being under the
5589 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5591 @item show may-insert-fast-tracepoints
5592 Show the current permission to insert fast tracepoints.
5594 @kindex may-interrupt
5595 @item set may-interrupt on
5596 @itemx set may-interrupt off
5597 This controls whether @value{GDBN} will attempt to interrupt or stop
5598 program execution. When this variable is @code{off}, the
5599 @code{interrupt} command will have no effect, nor will
5600 @kbd{Ctrl-c}. It defaults to @code{on}.
5602 @item show may-interrupt
5603 Show the current permission to interrupt or stop the program.
5607 @node Reverse Execution
5608 @chapter Running programs backward
5609 @cindex reverse execution
5610 @cindex running programs backward
5612 When you are debugging a program, it is not unusual to realize that
5613 you have gone too far, and some event of interest has already happened.
5614 If the target environment supports it, @value{GDBN} can allow you to
5615 ``rewind'' the program by running it backward.
5617 A target environment that supports reverse execution should be able
5618 to ``undo'' the changes in machine state that have taken place as the
5619 program was executing normally. Variables, registers etc.@: should
5620 revert to their previous values. Obviously this requires a great
5621 deal of sophistication on the part of the target environment; not
5622 all target environments can support reverse execution.
5624 When a program is executed in reverse, the instructions that
5625 have most recently been executed are ``un-executed'', in reverse
5626 order. The program counter runs backward, following the previous
5627 thread of execution in reverse. As each instruction is ``un-executed'',
5628 the values of memory and/or registers that were changed by that
5629 instruction are reverted to their previous states. After executing
5630 a piece of source code in reverse, all side effects of that code
5631 should be ``undone'', and all variables should be returned to their
5632 prior values@footnote{
5633 Note that some side effects are easier to undo than others. For instance,
5634 memory and registers are relatively easy, but device I/O is hard. Some
5635 targets may be able undo things like device I/O, and some may not.
5637 The contract between @value{GDBN} and the reverse executing target
5638 requires only that the target do something reasonable when
5639 @value{GDBN} tells it to execute backwards, and then report the
5640 results back to @value{GDBN}. Whatever the target reports back to
5641 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5642 assumes that the memory and registers that the target reports are in a
5643 consistant state, but @value{GDBN} accepts whatever it is given.
5646 If you are debugging in a target environment that supports
5647 reverse execution, @value{GDBN} provides the following commands.
5650 @kindex reverse-continue
5651 @kindex rc @r{(@code{reverse-continue})}
5652 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5653 @itemx rc @r{[}@var{ignore-count}@r{]}
5654 Beginning at the point where your program last stopped, start executing
5655 in reverse. Reverse execution will stop for breakpoints and synchronous
5656 exceptions (signals), just like normal execution. Behavior of
5657 asynchronous signals depends on the target environment.
5659 @kindex reverse-step
5660 @kindex rs @r{(@code{step})}
5661 @item reverse-step @r{[}@var{count}@r{]}
5662 Run the program backward until control reaches the start of a
5663 different source line; then stop it, and return control to @value{GDBN}.
5665 Like the @code{step} command, @code{reverse-step} will only stop
5666 at the beginning of a source line. It ``un-executes'' the previously
5667 executed source line. If the previous source line included calls to
5668 debuggable functions, @code{reverse-step} will step (backward) into
5669 the called function, stopping at the beginning of the @emph{last}
5670 statement in the called function (typically a return statement).
5672 Also, as with the @code{step} command, if non-debuggable functions are
5673 called, @code{reverse-step} will run thru them backward without stopping.
5675 @kindex reverse-stepi
5676 @kindex rsi @r{(@code{reverse-stepi})}
5677 @item reverse-stepi @r{[}@var{count}@r{]}
5678 Reverse-execute one machine instruction. Note that the instruction
5679 to be reverse-executed is @emph{not} the one pointed to by the program
5680 counter, but the instruction executed prior to that one. For instance,
5681 if the last instruction was a jump, @code{reverse-stepi} will take you
5682 back from the destination of the jump to the jump instruction itself.
5684 @kindex reverse-next
5685 @kindex rn @r{(@code{reverse-next})}
5686 @item reverse-next @r{[}@var{count}@r{]}
5687 Run backward to the beginning of the previous line executed in
5688 the current (innermost) stack frame. If the line contains function
5689 calls, they will be ``un-executed'' without stopping. Starting from
5690 the first line of a function, @code{reverse-next} will take you back
5691 to the caller of that function, @emph{before} the function was called,
5692 just as the normal @code{next} command would take you from the last
5693 line of a function back to its return to its caller
5694 @footnote{Unless the code is too heavily optimized.}.
5696 @kindex reverse-nexti
5697 @kindex rni @r{(@code{reverse-nexti})}
5698 @item reverse-nexti @r{[}@var{count}@r{]}
5699 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5700 in reverse, except that called functions are ``un-executed'' atomically.
5701 That is, if the previously executed instruction was a return from
5702 another function, @code{reverse-nexti} will continue to execute
5703 in reverse until the call to that function (from the current stack
5706 @kindex reverse-finish
5707 @item reverse-finish
5708 Just as the @code{finish} command takes you to the point where the
5709 current function returns, @code{reverse-finish} takes you to the point
5710 where it was called. Instead of ending up at the end of the current
5711 function invocation, you end up at the beginning.
5713 @kindex set exec-direction
5714 @item set exec-direction
5715 Set the direction of target execution.
5716 @itemx set exec-direction reverse
5717 @cindex execute forward or backward in time
5718 @value{GDBN} will perform all execution commands in reverse, until the
5719 exec-direction mode is changed to ``forward''. Affected commands include
5720 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5721 command cannot be used in reverse mode.
5722 @item set exec-direction forward
5723 @value{GDBN} will perform all execution commands in the normal fashion.
5724 This is the default.
5728 @node Process Record and Replay
5729 @chapter Recording Inferior's Execution and Replaying It
5730 @cindex process record and replay
5731 @cindex recording inferior's execution and replaying it
5733 On some platforms, @value{GDBN} provides a special @dfn{process record
5734 and replay} target that can record a log of the process execution, and
5735 replay it later with both forward and reverse execution commands.
5738 When this target is in use, if the execution log includes the record
5739 for the next instruction, @value{GDBN} will debug in @dfn{replay
5740 mode}. In the replay mode, the inferior does not really execute code
5741 instructions. Instead, all the events that normally happen during
5742 code execution are taken from the execution log. While code is not
5743 really executed in replay mode, the values of registers (including the
5744 program counter register) and the memory of the inferior are still
5745 changed as they normally would. Their contents are taken from the
5749 If the record for the next instruction is not in the execution log,
5750 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5751 inferior executes normally, and @value{GDBN} records the execution log
5754 The process record and replay target supports reverse execution
5755 (@pxref{Reverse Execution}), even if the platform on which the
5756 inferior runs does not. However, the reverse execution is limited in
5757 this case by the range of the instructions recorded in the execution
5758 log. In other words, reverse execution on platforms that don't
5759 support it directly can only be done in the replay mode.
5761 When debugging in the reverse direction, @value{GDBN} will work in
5762 replay mode as long as the execution log includes the record for the
5763 previous instruction; otherwise, it will work in record mode, if the
5764 platform supports reverse execution, or stop if not.
5766 For architecture environments that support process record and replay,
5767 @value{GDBN} provides the following commands:
5770 @kindex target record
5774 This command starts the process record and replay target. The process
5775 record and replay target can only debug a process that is already
5776 running. Therefore, you need first to start the process with the
5777 @kbd{run} or @kbd{start} commands, and then start the recording with
5778 the @kbd{target record} command.
5780 Both @code{record} and @code{rec} are aliases of @code{target record}.
5782 @cindex displaced stepping, and process record and replay
5783 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5784 will be automatically disabled when process record and replay target
5785 is started. That's because the process record and replay target
5786 doesn't support displaced stepping.
5788 @cindex non-stop mode, and process record and replay
5789 @cindex asynchronous execution, and process record and replay
5790 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5791 the asynchronous execution mode (@pxref{Background Execution}), the
5792 process record and replay target cannot be started because it doesn't
5793 support these two modes.
5798 Stop the process record and replay target. When process record and
5799 replay target stops, the entire execution log will be deleted and the
5800 inferior will either be terminated, or will remain in its final state.
5802 When you stop the process record and replay target in record mode (at
5803 the end of the execution log), the inferior will be stopped at the
5804 next instruction that would have been recorded. In other words, if
5805 you record for a while and then stop recording, the inferior process
5806 will be left in the same state as if the recording never happened.
5808 On the other hand, if the process record and replay target is stopped
5809 while in replay mode (that is, not at the end of the execution log,
5810 but at some earlier point), the inferior process will become ``live''
5811 at that earlier state, and it will then be possible to continue the
5812 usual ``live'' debugging of the process from that state.
5814 When the inferior process exits, or @value{GDBN} detaches from it,
5815 process record and replay target will automatically stop itself.
5818 @item record save @var{filename}
5819 Save the execution log to a file @file{@var{filename}}.
5820 Default filename is @file{gdb_record.@var{process_id}}, where
5821 @var{process_id} is the process ID of the inferior.
5823 @kindex record restore
5824 @item record restore @var{filename}
5825 Restore the execution log from a file @file{@var{filename}}.
5826 File must have been created with @code{record save}.
5828 @kindex set record insn-number-max
5829 @item set record insn-number-max @var{limit}
5830 Set the limit of instructions to be recorded. Default value is 200000.
5832 If @var{limit} is a positive number, then @value{GDBN} will start
5833 deleting instructions from the log once the number of the record
5834 instructions becomes greater than @var{limit}. For every new recorded
5835 instruction, @value{GDBN} will delete the earliest recorded
5836 instruction to keep the number of recorded instructions at the limit.
5837 (Since deleting recorded instructions loses information, @value{GDBN}
5838 lets you control what happens when the limit is reached, by means of
5839 the @code{stop-at-limit} option, described below.)
5841 If @var{limit} is zero, @value{GDBN} will never delete recorded
5842 instructions from the execution log. The number of recorded
5843 instructions is unlimited in this case.
5845 @kindex show record insn-number-max
5846 @item show record insn-number-max
5847 Show the limit of instructions to be recorded.
5849 @kindex set record stop-at-limit
5850 @item set record stop-at-limit
5851 Control the behavior when the number of recorded instructions reaches
5852 the limit. If ON (the default), @value{GDBN} will stop when the limit
5853 is reached for the first time and ask you whether you want to stop the
5854 inferior or continue running it and recording the execution log. If
5855 you decide to continue recording, each new recorded instruction will
5856 cause the oldest one to be deleted.
5858 If this option is OFF, @value{GDBN} will automatically delete the
5859 oldest record to make room for each new one, without asking.
5861 @kindex show record stop-at-limit
5862 @item show record stop-at-limit
5863 Show the current setting of @code{stop-at-limit}.
5865 @kindex set record memory-query
5866 @item set record memory-query
5867 Control the behavior when @value{GDBN} is unable to record memory
5868 changes caused by an instruction. If ON, @value{GDBN} will query
5869 whether to stop the inferior in that case.
5871 If this option is OFF (the default), @value{GDBN} will automatically
5872 ignore the effect of such instructions on memory. Later, when
5873 @value{GDBN} replays this execution log, it will mark the log of this
5874 instruction as not accessible, and it will not affect the replay
5877 @kindex show record memory-query
5878 @item show record memory-query
5879 Show the current setting of @code{memory-query}.
5883 Show various statistics about the state of process record and its
5884 in-memory execution log buffer, including:
5888 Whether in record mode or replay mode.
5890 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
5892 Highest recorded instruction number.
5894 Current instruction about to be replayed (if in replay mode).
5896 Number of instructions contained in the execution log.
5898 Maximum number of instructions that may be contained in the execution log.
5901 @kindex record delete
5904 When record target runs in replay mode (``in the past''), delete the
5905 subsequent execution log and begin to record a new execution log starting
5906 from the current address. This means you will abandon the previously
5907 recorded ``future'' and begin recording a new ``future''.
5912 @chapter Examining the Stack
5914 When your program has stopped, the first thing you need to know is where it
5915 stopped and how it got there.
5918 Each time your program performs a function call, information about the call
5920 That information includes the location of the call in your program,
5921 the arguments of the call,
5922 and the local variables of the function being called.
5923 The information is saved in a block of data called a @dfn{stack frame}.
5924 The stack frames are allocated in a region of memory called the @dfn{call
5927 When your program stops, the @value{GDBN} commands for examining the
5928 stack allow you to see all of this information.
5930 @cindex selected frame
5931 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5932 @value{GDBN} commands refer implicitly to the selected frame. In
5933 particular, whenever you ask @value{GDBN} for the value of a variable in
5934 your program, the value is found in the selected frame. There are
5935 special @value{GDBN} commands to select whichever frame you are
5936 interested in. @xref{Selection, ,Selecting a Frame}.
5938 When your program stops, @value{GDBN} automatically selects the
5939 currently executing frame and describes it briefly, similar to the
5940 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5943 * Frames:: Stack frames
5944 * Backtrace:: Backtraces
5945 * Selection:: Selecting a frame
5946 * Frame Info:: Information on a frame
5951 @section Stack Frames
5953 @cindex frame, definition
5955 The call stack is divided up into contiguous pieces called @dfn{stack
5956 frames}, or @dfn{frames} for short; each frame is the data associated
5957 with one call to one function. The frame contains the arguments given
5958 to the function, the function's local variables, and the address at
5959 which the function is executing.
5961 @cindex initial frame
5962 @cindex outermost frame
5963 @cindex innermost frame
5964 When your program is started, the stack has only one frame, that of the
5965 function @code{main}. This is called the @dfn{initial} frame or the
5966 @dfn{outermost} frame. Each time a function is called, a new frame is
5967 made. Each time a function returns, the frame for that function invocation
5968 is eliminated. If a function is recursive, there can be many frames for
5969 the same function. The frame for the function in which execution is
5970 actually occurring is called the @dfn{innermost} frame. This is the most
5971 recently created of all the stack frames that still exist.
5973 @cindex frame pointer
5974 Inside your program, stack frames are identified by their addresses. A
5975 stack frame consists of many bytes, each of which has its own address; each
5976 kind of computer has a convention for choosing one byte whose
5977 address serves as the address of the frame. Usually this address is kept
5978 in a register called the @dfn{frame pointer register}
5979 (@pxref{Registers, $fp}) while execution is going on in that frame.
5981 @cindex frame number
5982 @value{GDBN} assigns numbers to all existing stack frames, starting with
5983 zero for the innermost frame, one for the frame that called it,
5984 and so on upward. These numbers do not really exist in your program;
5985 they are assigned by @value{GDBN} to give you a way of designating stack
5986 frames in @value{GDBN} commands.
5988 @c The -fomit-frame-pointer below perennially causes hbox overflow
5989 @c underflow problems.
5990 @cindex frameless execution
5991 Some compilers provide a way to compile functions so that they operate
5992 without stack frames. (For example, the @value{NGCC} option
5994 @samp{-fomit-frame-pointer}
5996 generates functions without a frame.)
5997 This is occasionally done with heavily used library functions to save
5998 the frame setup time. @value{GDBN} has limited facilities for dealing
5999 with these function invocations. If the innermost function invocation
6000 has no stack frame, @value{GDBN} nevertheless regards it as though
6001 it had a separate frame, which is numbered zero as usual, allowing
6002 correct tracing of the function call chain. However, @value{GDBN} has
6003 no provision for frameless functions elsewhere in the stack.
6006 @kindex frame@r{, command}
6007 @cindex current stack frame
6008 @item frame @var{args}
6009 The @code{frame} command allows you to move from one stack frame to another,
6010 and to print the stack frame you select. @var{args} may be either the
6011 address of the frame or the stack frame number. Without an argument,
6012 @code{frame} prints the current stack frame.
6014 @kindex select-frame
6015 @cindex selecting frame silently
6017 The @code{select-frame} command allows you to move from one stack frame
6018 to another without printing the frame. This is the silent version of
6026 @cindex call stack traces
6027 A backtrace is a summary of how your program got where it is. It shows one
6028 line per frame, for many frames, starting with the currently executing
6029 frame (frame zero), followed by its caller (frame one), and on up the
6034 @kindex bt @r{(@code{backtrace})}
6037 Print a backtrace of the entire stack: one line per frame for all
6038 frames in the stack.
6040 You can stop the backtrace at any time by typing the system interrupt
6041 character, normally @kbd{Ctrl-c}.
6043 @item backtrace @var{n}
6045 Similar, but print only the innermost @var{n} frames.
6047 @item backtrace -@var{n}
6049 Similar, but print only the outermost @var{n} frames.
6051 @item backtrace full
6053 @itemx bt full @var{n}
6054 @itemx bt full -@var{n}
6055 Print the values of the local variables also. @var{n} specifies the
6056 number of frames to print, as described above.
6061 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6062 are additional aliases for @code{backtrace}.
6064 @cindex multiple threads, backtrace
6065 In a multi-threaded program, @value{GDBN} by default shows the
6066 backtrace only for the current thread. To display the backtrace for
6067 several or all of the threads, use the command @code{thread apply}
6068 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6069 apply all backtrace}, @value{GDBN} will display the backtrace for all
6070 the threads; this is handy when you debug a core dump of a
6071 multi-threaded program.
6073 Each line in the backtrace shows the frame number and the function name.
6074 The program counter value is also shown---unless you use @code{set
6075 print address off}. The backtrace also shows the source file name and
6076 line number, as well as the arguments to the function. The program
6077 counter value is omitted if it is at the beginning of the code for that
6080 Here is an example of a backtrace. It was made with the command
6081 @samp{bt 3}, so it shows the innermost three frames.
6085 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6087 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6088 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6090 (More stack frames follow...)
6095 The display for frame zero does not begin with a program counter
6096 value, indicating that your program has stopped at the beginning of the
6097 code for line @code{993} of @code{builtin.c}.
6100 The value of parameter @code{data} in frame 1 has been replaced by
6101 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6102 only if it is a scalar (integer, pointer, enumeration, etc). See command
6103 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6104 on how to configure the way function parameter values are printed.
6106 @cindex optimized out, in backtrace
6107 @cindex function call arguments, optimized out
6108 If your program was compiled with optimizations, some compilers will
6109 optimize away arguments passed to functions if those arguments are
6110 never used after the call. Such optimizations generate code that
6111 passes arguments through registers, but doesn't store those arguments
6112 in the stack frame. @value{GDBN} has no way of displaying such
6113 arguments in stack frames other than the innermost one. Here's what
6114 such a backtrace might look like:
6118 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6120 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6121 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6123 (More stack frames follow...)
6128 The values of arguments that were not saved in their stack frames are
6129 shown as @samp{<optimized out>}.
6131 If you need to display the values of such optimized-out arguments,
6132 either deduce that from other variables whose values depend on the one
6133 you are interested in, or recompile without optimizations.
6135 @cindex backtrace beyond @code{main} function
6136 @cindex program entry point
6137 @cindex startup code, and backtrace
6138 Most programs have a standard user entry point---a place where system
6139 libraries and startup code transition into user code. For C this is
6140 @code{main}@footnote{
6141 Note that embedded programs (the so-called ``free-standing''
6142 environment) are not required to have a @code{main} function as the
6143 entry point. They could even have multiple entry points.}.
6144 When @value{GDBN} finds the entry function in a backtrace
6145 it will terminate the backtrace, to avoid tracing into highly
6146 system-specific (and generally uninteresting) code.
6148 If you need to examine the startup code, or limit the number of levels
6149 in a backtrace, you can change this behavior:
6152 @item set backtrace past-main
6153 @itemx set backtrace past-main on
6154 @kindex set backtrace
6155 Backtraces will continue past the user entry point.
6157 @item set backtrace past-main off
6158 Backtraces will stop when they encounter the user entry point. This is the
6161 @item show backtrace past-main
6162 @kindex show backtrace
6163 Display the current user entry point backtrace policy.
6165 @item set backtrace past-entry
6166 @itemx set backtrace past-entry on
6167 Backtraces will continue past the internal entry point of an application.
6168 This entry point is encoded by the linker when the application is built,
6169 and is likely before the user entry point @code{main} (or equivalent) is called.
6171 @item set backtrace past-entry off
6172 Backtraces will stop when they encounter the internal entry point of an
6173 application. This is the default.
6175 @item show backtrace past-entry
6176 Display the current internal entry point backtrace policy.
6178 @item set backtrace limit @var{n}
6179 @itemx set backtrace limit 0
6180 @cindex backtrace limit
6181 Limit the backtrace to @var{n} levels. A value of zero means
6184 @item show backtrace limit
6185 Display the current limit on backtrace levels.
6189 @section Selecting a Frame
6191 Most commands for examining the stack and other data in your program work on
6192 whichever stack frame is selected at the moment. Here are the commands for
6193 selecting a stack frame; all of them finish by printing a brief description
6194 of the stack frame just selected.
6197 @kindex frame@r{, selecting}
6198 @kindex f @r{(@code{frame})}
6201 Select frame number @var{n}. Recall that frame zero is the innermost
6202 (currently executing) frame, frame one is the frame that called the
6203 innermost one, and so on. The highest-numbered frame is the one for
6206 @item frame @var{addr}
6208 Select the frame at address @var{addr}. This is useful mainly if the
6209 chaining of stack frames has been damaged by a bug, making it
6210 impossible for @value{GDBN} to assign numbers properly to all frames. In
6211 addition, this can be useful when your program has multiple stacks and
6212 switches between them.
6214 On the SPARC architecture, @code{frame} needs two addresses to
6215 select an arbitrary frame: a frame pointer and a stack pointer.
6217 On the MIPS and Alpha architecture, it needs two addresses: a stack
6218 pointer and a program counter.
6220 On the 29k architecture, it needs three addresses: a register stack
6221 pointer, a program counter, and a memory stack pointer.
6225 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6226 advances toward the outermost frame, to higher frame numbers, to frames
6227 that have existed longer. @var{n} defaults to one.
6230 @kindex do @r{(@code{down})}
6232 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6233 advances toward the innermost frame, to lower frame numbers, to frames
6234 that were created more recently. @var{n} defaults to one. You may
6235 abbreviate @code{down} as @code{do}.
6238 All of these commands end by printing two lines of output describing the
6239 frame. The first line shows the frame number, the function name, the
6240 arguments, and the source file and line number of execution in that
6241 frame. The second line shows the text of that source line.
6249 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6251 10 read_input_file (argv[i]);
6255 After such a printout, the @code{list} command with no arguments
6256 prints ten lines centered on the point of execution in the frame.
6257 You can also edit the program at the point of execution with your favorite
6258 editing program by typing @code{edit}.
6259 @xref{List, ,Printing Source Lines},
6263 @kindex down-silently
6265 @item up-silently @var{n}
6266 @itemx down-silently @var{n}
6267 These two commands are variants of @code{up} and @code{down},
6268 respectively; they differ in that they do their work silently, without
6269 causing display of the new frame. They are intended primarily for use
6270 in @value{GDBN} command scripts, where the output might be unnecessary and
6275 @section Information About a Frame
6277 There are several other commands to print information about the selected
6283 When used without any argument, this command does not change which
6284 frame is selected, but prints a brief description of the currently
6285 selected stack frame. It can be abbreviated @code{f}. With an
6286 argument, this command is used to select a stack frame.
6287 @xref{Selection, ,Selecting a Frame}.
6290 @kindex info f @r{(@code{info frame})}
6293 This command prints a verbose description of the selected stack frame,
6298 the address of the frame
6300 the address of the next frame down (called by this frame)
6302 the address of the next frame up (caller of this frame)
6304 the language in which the source code corresponding to this frame is written
6306 the address of the frame's arguments
6308 the address of the frame's local variables
6310 the program counter saved in it (the address of execution in the caller frame)
6312 which registers were saved in the frame
6315 @noindent The verbose description is useful when
6316 something has gone wrong that has made the stack format fail to fit
6317 the usual conventions.
6319 @item info frame @var{addr}
6320 @itemx info f @var{addr}
6321 Print a verbose description of the frame at address @var{addr}, without
6322 selecting that frame. The selected frame remains unchanged by this
6323 command. This requires the same kind of address (more than one for some
6324 architectures) that you specify in the @code{frame} command.
6325 @xref{Selection, ,Selecting a Frame}.
6329 Print the arguments of the selected frame, each on a separate line.
6333 Print the local variables of the selected frame, each on a separate
6334 line. These are all variables (declared either static or automatic)
6335 accessible at the point of execution of the selected frame.
6338 @cindex catch exceptions, list active handlers
6339 @cindex exception handlers, how to list
6341 Print a list of all the exception handlers that are active in the
6342 current stack frame at the current point of execution. To see other
6343 exception handlers, visit the associated frame (using the @code{up},
6344 @code{down}, or @code{frame} commands); then type @code{info catch}.
6345 @xref{Set Catchpoints, , Setting Catchpoints}.
6351 @chapter Examining Source Files
6353 @value{GDBN} can print parts of your program's source, since the debugging
6354 information recorded in the program tells @value{GDBN} what source files were
6355 used to build it. When your program stops, @value{GDBN} spontaneously prints
6356 the line where it stopped. Likewise, when you select a stack frame
6357 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6358 execution in that frame has stopped. You can print other portions of
6359 source files by explicit command.
6361 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6362 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6363 @value{GDBN} under @sc{gnu} Emacs}.
6366 * List:: Printing source lines
6367 * Specify Location:: How to specify code locations
6368 * Edit:: Editing source files
6369 * Search:: Searching source files
6370 * Source Path:: Specifying source directories
6371 * Machine Code:: Source and machine code
6375 @section Printing Source Lines
6378 @kindex l @r{(@code{list})}
6379 To print lines from a source file, use the @code{list} command
6380 (abbreviated @code{l}). By default, ten lines are printed.
6381 There are several ways to specify what part of the file you want to
6382 print; see @ref{Specify Location}, for the full list.
6384 Here are the forms of the @code{list} command most commonly used:
6387 @item list @var{linenum}
6388 Print lines centered around line number @var{linenum} in the
6389 current source file.
6391 @item list @var{function}
6392 Print lines centered around the beginning of function
6396 Print more lines. If the last lines printed were printed with a
6397 @code{list} command, this prints lines following the last lines
6398 printed; however, if the last line printed was a solitary line printed
6399 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6400 Stack}), this prints lines centered around that line.
6403 Print lines just before the lines last printed.
6406 @cindex @code{list}, how many lines to display
6407 By default, @value{GDBN} prints ten source lines with any of these forms of
6408 the @code{list} command. You can change this using @code{set listsize}:
6411 @kindex set listsize
6412 @item set listsize @var{count}
6413 Make the @code{list} command display @var{count} source lines (unless
6414 the @code{list} argument explicitly specifies some other number).
6416 @kindex show listsize
6418 Display the number of lines that @code{list} prints.
6421 Repeating a @code{list} command with @key{RET} discards the argument,
6422 so it is equivalent to typing just @code{list}. This is more useful
6423 than listing the same lines again. An exception is made for an
6424 argument of @samp{-}; that argument is preserved in repetition so that
6425 each repetition moves up in the source file.
6427 In general, the @code{list} command expects you to supply zero, one or two
6428 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6429 of writing them (@pxref{Specify Location}), but the effect is always
6430 to specify some source line.
6432 Here is a complete description of the possible arguments for @code{list}:
6435 @item list @var{linespec}
6436 Print lines centered around the line specified by @var{linespec}.
6438 @item list @var{first},@var{last}
6439 Print lines from @var{first} to @var{last}. Both arguments are
6440 linespecs. When a @code{list} command has two linespecs, and the
6441 source file of the second linespec is omitted, this refers to
6442 the same source file as the first linespec.
6444 @item list ,@var{last}
6445 Print lines ending with @var{last}.
6447 @item list @var{first},
6448 Print lines starting with @var{first}.
6451 Print lines just after the lines last printed.
6454 Print lines just before the lines last printed.
6457 As described in the preceding table.
6460 @node Specify Location
6461 @section Specifying a Location
6462 @cindex specifying location
6465 Several @value{GDBN} commands accept arguments that specify a location
6466 of your program's code. Since @value{GDBN} is a source-level
6467 debugger, a location usually specifies some line in the source code;
6468 for that reason, locations are also known as @dfn{linespecs}.
6470 Here are all the different ways of specifying a code location that
6471 @value{GDBN} understands:
6475 Specifies the line number @var{linenum} of the current source file.
6478 @itemx +@var{offset}
6479 Specifies the line @var{offset} lines before or after the @dfn{current
6480 line}. For the @code{list} command, the current line is the last one
6481 printed; for the breakpoint commands, this is the line at which
6482 execution stopped in the currently selected @dfn{stack frame}
6483 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6484 used as the second of the two linespecs in a @code{list} command,
6485 this specifies the line @var{offset} lines up or down from the first
6488 @item @var{filename}:@var{linenum}
6489 Specifies the line @var{linenum} in the source file @var{filename}.
6491 @item @var{function}
6492 Specifies the line that begins the body of the function @var{function}.
6493 For example, in C, this is the line with the open brace.
6495 @item @var{function}:@var{label}
6496 Specifies the line where @var{label} appears in @var{function}.
6498 @item @var{filename}:@var{function}
6499 Specifies the line that begins the body of the function @var{function}
6500 in the file @var{filename}. You only need the file name with a
6501 function name to avoid ambiguity when there are identically named
6502 functions in different source files.
6505 Specifies the line at which the label named @var{label} appears.
6506 @value{GDBN} searches for the label in the function corresponding to
6507 the currently selected stack frame. If there is no current selected
6508 stack frame (for instance, if the inferior is not running), then
6509 @value{GDBN} will not search for a label.
6511 @item *@var{address}
6512 Specifies the program address @var{address}. For line-oriented
6513 commands, such as @code{list} and @code{edit}, this specifies a source
6514 line that contains @var{address}. For @code{break} and other
6515 breakpoint oriented commands, this can be used to set breakpoints in
6516 parts of your program which do not have debugging information or
6519 Here @var{address} may be any expression valid in the current working
6520 language (@pxref{Languages, working language}) that specifies a code
6521 address. In addition, as a convenience, @value{GDBN} extends the
6522 semantics of expressions used in locations to cover the situations
6523 that frequently happen during debugging. Here are the various forms
6527 @item @var{expression}
6528 Any expression valid in the current working language.
6530 @item @var{funcaddr}
6531 An address of a function or procedure derived from its name. In C,
6532 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6533 simply the function's name @var{function} (and actually a special case
6534 of a valid expression). In Pascal and Modula-2, this is
6535 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6536 (although the Pascal form also works).
6538 This form specifies the address of the function's first instruction,
6539 before the stack frame and arguments have been set up.
6541 @item '@var{filename}'::@var{funcaddr}
6542 Like @var{funcaddr} above, but also specifies the name of the source
6543 file explicitly. This is useful if the name of the function does not
6544 specify the function unambiguously, e.g., if there are several
6545 functions with identical names in different source files.
6552 @section Editing Source Files
6553 @cindex editing source files
6556 @kindex e @r{(@code{edit})}
6557 To edit the lines in a source file, use the @code{edit} command.
6558 The editing program of your choice
6559 is invoked with the current line set to
6560 the active line in the program.
6561 Alternatively, there are several ways to specify what part of the file you
6562 want to print if you want to see other parts of the program:
6565 @item edit @var{location}
6566 Edit the source file specified by @code{location}. Editing starts at
6567 that @var{location}, e.g., at the specified source line of the
6568 specified file. @xref{Specify Location}, for all the possible forms
6569 of the @var{location} argument; here are the forms of the @code{edit}
6570 command most commonly used:
6573 @item edit @var{number}
6574 Edit the current source file with @var{number} as the active line number.
6576 @item edit @var{function}
6577 Edit the file containing @var{function} at the beginning of its definition.
6582 @subsection Choosing your Editor
6583 You can customize @value{GDBN} to use any editor you want
6585 The only restriction is that your editor (say @code{ex}), recognizes the
6586 following command-line syntax:
6588 ex +@var{number} file
6590 The optional numeric value +@var{number} specifies the number of the line in
6591 the file where to start editing.}.
6592 By default, it is @file{@value{EDITOR}}, but you can change this
6593 by setting the environment variable @code{EDITOR} before using
6594 @value{GDBN}. For example, to configure @value{GDBN} to use the
6595 @code{vi} editor, you could use these commands with the @code{sh} shell:
6601 or in the @code{csh} shell,
6603 setenv EDITOR /usr/bin/vi
6608 @section Searching Source Files
6609 @cindex searching source files
6611 There are two commands for searching through the current source file for a
6616 @kindex forward-search
6617 @item forward-search @var{regexp}
6618 @itemx search @var{regexp}
6619 The command @samp{forward-search @var{regexp}} checks each line,
6620 starting with the one following the last line listed, for a match for
6621 @var{regexp}. It lists the line that is found. You can use the
6622 synonym @samp{search @var{regexp}} or abbreviate the command name as
6625 @kindex reverse-search
6626 @item reverse-search @var{regexp}
6627 The command @samp{reverse-search @var{regexp}} checks each line, starting
6628 with the one before the last line listed and going backward, for a match
6629 for @var{regexp}. It lists the line that is found. You can abbreviate
6630 this command as @code{rev}.
6634 @section Specifying Source Directories
6637 @cindex directories for source files
6638 Executable programs sometimes do not record the directories of the source
6639 files from which they were compiled, just the names. Even when they do,
6640 the directories could be moved between the compilation and your debugging
6641 session. @value{GDBN} has a list of directories to search for source files;
6642 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6643 it tries all the directories in the list, in the order they are present
6644 in the list, until it finds a file with the desired name.
6646 For example, suppose an executable references the file
6647 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6648 @file{/mnt/cross}. The file is first looked up literally; if this
6649 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6650 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6651 message is printed. @value{GDBN} does not look up the parts of the
6652 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6653 Likewise, the subdirectories of the source path are not searched: if
6654 the source path is @file{/mnt/cross}, and the binary refers to
6655 @file{foo.c}, @value{GDBN} would not find it under
6656 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6658 Plain file names, relative file names with leading directories, file
6659 names containing dots, etc.@: are all treated as described above; for
6660 instance, if the source path is @file{/mnt/cross}, and the source file
6661 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6662 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6663 that---@file{/mnt/cross/foo.c}.
6665 Note that the executable search path is @emph{not} used to locate the
6668 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6669 any information it has cached about where source files are found and where
6670 each line is in the file.
6674 When you start @value{GDBN}, its source path includes only @samp{cdir}
6675 and @samp{cwd}, in that order.
6676 To add other directories, use the @code{directory} command.
6678 The search path is used to find both program source files and @value{GDBN}
6679 script files (read using the @samp{-command} option and @samp{source} command).
6681 In addition to the source path, @value{GDBN} provides a set of commands
6682 that manage a list of source path substitution rules. A @dfn{substitution
6683 rule} specifies how to rewrite source directories stored in the program's
6684 debug information in case the sources were moved to a different
6685 directory between compilation and debugging. A rule is made of
6686 two strings, the first specifying what needs to be rewritten in
6687 the path, and the second specifying how it should be rewritten.
6688 In @ref{set substitute-path}, we name these two parts @var{from} and
6689 @var{to} respectively. @value{GDBN} does a simple string replacement
6690 of @var{from} with @var{to} at the start of the directory part of the
6691 source file name, and uses that result instead of the original file
6692 name to look up the sources.
6694 Using the previous example, suppose the @file{foo-1.0} tree has been
6695 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6696 @value{GDBN} to replace @file{/usr/src} in all source path names with
6697 @file{/mnt/cross}. The first lookup will then be
6698 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6699 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6700 substitution rule, use the @code{set substitute-path} command
6701 (@pxref{set substitute-path}).
6703 To avoid unexpected substitution results, a rule is applied only if the
6704 @var{from} part of the directory name ends at a directory separator.
6705 For instance, a rule substituting @file{/usr/source} into
6706 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6707 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6708 is applied only at the beginning of the directory name, this rule will
6709 not be applied to @file{/root/usr/source/baz.c} either.
6711 In many cases, you can achieve the same result using the @code{directory}
6712 command. However, @code{set substitute-path} can be more efficient in
6713 the case where the sources are organized in a complex tree with multiple
6714 subdirectories. With the @code{directory} command, you need to add each
6715 subdirectory of your project. If you moved the entire tree while
6716 preserving its internal organization, then @code{set substitute-path}
6717 allows you to direct the debugger to all the sources with one single
6720 @code{set substitute-path} is also more than just a shortcut command.
6721 The source path is only used if the file at the original location no
6722 longer exists. On the other hand, @code{set substitute-path} modifies
6723 the debugger behavior to look at the rewritten location instead. So, if
6724 for any reason a source file that is not relevant to your executable is
6725 located at the original location, a substitution rule is the only
6726 method available to point @value{GDBN} at the new location.
6728 @cindex @samp{--with-relocated-sources}
6729 @cindex default source path substitution
6730 You can configure a default source path substitution rule by
6731 configuring @value{GDBN} with the
6732 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6733 should be the name of a directory under @value{GDBN}'s configured
6734 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6735 directory names in debug information under @var{dir} will be adjusted
6736 automatically if the installed @value{GDBN} is moved to a new
6737 location. This is useful if @value{GDBN}, libraries or executables
6738 with debug information and corresponding source code are being moved
6742 @item directory @var{dirname} @dots{}
6743 @item dir @var{dirname} @dots{}
6744 Add directory @var{dirname} to the front of the source path. Several
6745 directory names may be given to this command, separated by @samp{:}
6746 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6747 part of absolute file names) or
6748 whitespace. You may specify a directory that is already in the source
6749 path; this moves it forward, so @value{GDBN} searches it sooner.
6753 @vindex $cdir@r{, convenience variable}
6754 @vindex $cwd@r{, convenience variable}
6755 @cindex compilation directory
6756 @cindex current directory
6757 @cindex working directory
6758 @cindex directory, current
6759 @cindex directory, compilation
6760 You can use the string @samp{$cdir} to refer to the compilation
6761 directory (if one is recorded), and @samp{$cwd} to refer to the current
6762 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6763 tracks the current working directory as it changes during your @value{GDBN}
6764 session, while the latter is immediately expanded to the current
6765 directory at the time you add an entry to the source path.
6768 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6770 @c RET-repeat for @code{directory} is explicitly disabled, but since
6771 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6773 @item set directories @var{path-list}
6774 @kindex set directories
6775 Set the source path to @var{path-list}.
6776 @samp{$cdir:$cwd} are added if missing.
6778 @item show directories
6779 @kindex show directories
6780 Print the source path: show which directories it contains.
6782 @anchor{set substitute-path}
6783 @item set substitute-path @var{from} @var{to}
6784 @kindex set substitute-path
6785 Define a source path substitution rule, and add it at the end of the
6786 current list of existing substitution rules. If a rule with the same
6787 @var{from} was already defined, then the old rule is also deleted.
6789 For example, if the file @file{/foo/bar/baz.c} was moved to
6790 @file{/mnt/cross/baz.c}, then the command
6793 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6797 will tell @value{GDBN} to replace @samp{/usr/src} with
6798 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6799 @file{baz.c} even though it was moved.
6801 In the case when more than one substitution rule have been defined,
6802 the rules are evaluated one by one in the order where they have been
6803 defined. The first one matching, if any, is selected to perform
6806 For instance, if we had entered the following commands:
6809 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6810 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6814 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6815 @file{/mnt/include/defs.h} by using the first rule. However, it would
6816 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6817 @file{/mnt/src/lib/foo.c}.
6820 @item unset substitute-path [path]
6821 @kindex unset substitute-path
6822 If a path is specified, search the current list of substitution rules
6823 for a rule that would rewrite that path. Delete that rule if found.
6824 A warning is emitted by the debugger if no rule could be found.
6826 If no path is specified, then all substitution rules are deleted.
6828 @item show substitute-path [path]
6829 @kindex show substitute-path
6830 If a path is specified, then print the source path substitution rule
6831 which would rewrite that path, if any.
6833 If no path is specified, then print all existing source path substitution
6838 If your source path is cluttered with directories that are no longer of
6839 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6840 versions of source. You can correct the situation as follows:
6844 Use @code{directory} with no argument to reset the source path to its default value.
6847 Use @code{directory} with suitable arguments to reinstall the
6848 directories you want in the source path. You can add all the
6849 directories in one command.
6853 @section Source and Machine Code
6854 @cindex source line and its code address
6856 You can use the command @code{info line} to map source lines to program
6857 addresses (and vice versa), and the command @code{disassemble} to display
6858 a range of addresses as machine instructions. You can use the command
6859 @code{set disassemble-next-line} to set whether to disassemble next
6860 source line when execution stops. When run under @sc{gnu} Emacs
6861 mode, the @code{info line} command causes the arrow to point to the
6862 line specified. Also, @code{info line} prints addresses in symbolic form as
6867 @item info line @var{linespec}
6868 Print the starting and ending addresses of the compiled code for
6869 source line @var{linespec}. You can specify source lines in any of
6870 the ways documented in @ref{Specify Location}.
6873 For example, we can use @code{info line} to discover the location of
6874 the object code for the first line of function
6875 @code{m4_changequote}:
6877 @c FIXME: I think this example should also show the addresses in
6878 @c symbolic form, as they usually would be displayed.
6880 (@value{GDBP}) info line m4_changequote
6881 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6885 @cindex code address and its source line
6886 We can also inquire (using @code{*@var{addr}} as the form for
6887 @var{linespec}) what source line covers a particular address:
6889 (@value{GDBP}) info line *0x63ff
6890 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6893 @cindex @code{$_} and @code{info line}
6894 @cindex @code{x} command, default address
6895 @kindex x@r{(examine), and} info line
6896 After @code{info line}, the default address for the @code{x} command
6897 is changed to the starting address of the line, so that @samp{x/i} is
6898 sufficient to begin examining the machine code (@pxref{Memory,
6899 ,Examining Memory}). Also, this address is saved as the value of the
6900 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6905 @cindex assembly instructions
6906 @cindex instructions, assembly
6907 @cindex machine instructions
6908 @cindex listing machine instructions
6910 @itemx disassemble /m
6911 @itemx disassemble /r
6912 This specialized command dumps a range of memory as machine
6913 instructions. It can also print mixed source+disassembly by specifying
6914 the @code{/m} modifier and print the raw instructions in hex as well as
6915 in symbolic form by specifying the @code{/r}.
6916 The default memory range is the function surrounding the
6917 program counter of the selected frame. A single argument to this
6918 command is a program counter value; @value{GDBN} dumps the function
6919 surrounding this value. When two arguments are given, they should
6920 be separated by a comma, possibly surrounded by whitespace. The
6921 arguments specify a range of addresses to dump, in one of two forms:
6924 @item @var{start},@var{end}
6925 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
6926 @item @var{start},+@var{length}
6927 the addresses from @var{start} (inclusive) to
6928 @code{@var{start}+@var{length}} (exclusive).
6932 When 2 arguments are specified, the name of the function is also
6933 printed (since there could be several functions in the given range).
6935 The argument(s) can be any expression yielding a numeric value, such as
6936 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
6938 If the range of memory being disassembled contains current program counter,
6939 the instruction at that location is shown with a @code{=>} marker.
6942 The following example shows the disassembly of a range of addresses of
6943 HP PA-RISC 2.0 code:
6946 (@value{GDBP}) disas 0x32c4, 0x32e4
6947 Dump of assembler code from 0x32c4 to 0x32e4:
6948 0x32c4 <main+204>: addil 0,dp
6949 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6950 0x32cc <main+212>: ldil 0x3000,r31
6951 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6952 0x32d4 <main+220>: ldo 0(r31),rp
6953 0x32d8 <main+224>: addil -0x800,dp
6954 0x32dc <main+228>: ldo 0x588(r1),r26
6955 0x32e0 <main+232>: ldil 0x3000,r31
6956 End of assembler dump.
6959 Here is an example showing mixed source+assembly for Intel x86, when the
6960 program is stopped just after function prologue:
6963 (@value{GDBP}) disas /m main
6964 Dump of assembler code for function main:
6966 0x08048330 <+0>: push %ebp
6967 0x08048331 <+1>: mov %esp,%ebp
6968 0x08048333 <+3>: sub $0x8,%esp
6969 0x08048336 <+6>: and $0xfffffff0,%esp
6970 0x08048339 <+9>: sub $0x10,%esp
6972 6 printf ("Hello.\n");
6973 => 0x0804833c <+12>: movl $0x8048440,(%esp)
6974 0x08048343 <+19>: call 0x8048284 <puts@@plt>
6978 0x08048348 <+24>: mov $0x0,%eax
6979 0x0804834d <+29>: leave
6980 0x0804834e <+30>: ret
6982 End of assembler dump.
6985 Here is another example showing raw instructions in hex for AMD x86-64,
6988 (gdb) disas /r 0x400281,+10
6989 Dump of assembler code from 0x400281 to 0x40028b:
6990 0x0000000000400281: 38 36 cmp %dh,(%rsi)
6991 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
6992 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
6993 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
6994 End of assembler dump.
6997 Some architectures have more than one commonly-used set of instruction
6998 mnemonics or other syntax.
7000 For programs that were dynamically linked and use shared libraries,
7001 instructions that call functions or branch to locations in the shared
7002 libraries might show a seemingly bogus location---it's actually a
7003 location of the relocation table. On some architectures, @value{GDBN}
7004 might be able to resolve these to actual function names.
7007 @kindex set disassembly-flavor
7008 @cindex Intel disassembly flavor
7009 @cindex AT&T disassembly flavor
7010 @item set disassembly-flavor @var{instruction-set}
7011 Select the instruction set to use when disassembling the
7012 program via the @code{disassemble} or @code{x/i} commands.
7014 Currently this command is only defined for the Intel x86 family. You
7015 can set @var{instruction-set} to either @code{intel} or @code{att}.
7016 The default is @code{att}, the AT&T flavor used by default by Unix
7017 assemblers for x86-based targets.
7019 @kindex show disassembly-flavor
7020 @item show disassembly-flavor
7021 Show the current setting of the disassembly flavor.
7025 @kindex set disassemble-next-line
7026 @kindex show disassemble-next-line
7027 @item set disassemble-next-line
7028 @itemx show disassemble-next-line
7029 Control whether or not @value{GDBN} will disassemble the next source
7030 line or instruction when execution stops. If ON, @value{GDBN} will
7031 display disassembly of the next source line when execution of the
7032 program being debugged stops. This is @emph{in addition} to
7033 displaying the source line itself, which @value{GDBN} always does if
7034 possible. If the next source line cannot be displayed for some reason
7035 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7036 info in the debug info), @value{GDBN} will display disassembly of the
7037 next @emph{instruction} instead of showing the next source line. If
7038 AUTO, @value{GDBN} will display disassembly of next instruction only
7039 if the source line cannot be displayed. This setting causes
7040 @value{GDBN} to display some feedback when you step through a function
7041 with no line info or whose source file is unavailable. The default is
7042 OFF, which means never display the disassembly of the next line or
7048 @chapter Examining Data
7050 @cindex printing data
7051 @cindex examining data
7054 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
7055 @c document because it is nonstandard... Under Epoch it displays in a
7056 @c different window or something like that.
7057 The usual way to examine data in your program is with the @code{print}
7058 command (abbreviated @code{p}), or its synonym @code{inspect}. It
7059 evaluates and prints the value of an expression of the language your
7060 program is written in (@pxref{Languages, ,Using @value{GDBN} with
7061 Different Languages}). It may also print the expression using a
7062 Python-based pretty-printer (@pxref{Pretty Printing}).
7065 @item print @var{expr}
7066 @itemx print /@var{f} @var{expr}
7067 @var{expr} is an expression (in the source language). By default the
7068 value of @var{expr} is printed in a format appropriate to its data type;
7069 you can choose a different format by specifying @samp{/@var{f}}, where
7070 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
7074 @itemx print /@var{f}
7075 @cindex reprint the last value
7076 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
7077 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
7078 conveniently inspect the same value in an alternative format.
7081 A more low-level way of examining data is with the @code{x} command.
7082 It examines data in memory at a specified address and prints it in a
7083 specified format. @xref{Memory, ,Examining Memory}.
7085 If you are interested in information about types, or about how the
7086 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
7087 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
7091 * Expressions:: Expressions
7092 * Ambiguous Expressions:: Ambiguous Expressions
7093 * Variables:: Program variables
7094 * Arrays:: Artificial arrays
7095 * Output Formats:: Output formats
7096 * Memory:: Examining memory
7097 * Auto Display:: Automatic display
7098 * Print Settings:: Print settings
7099 * Pretty Printing:: Python pretty printing
7100 * Value History:: Value history
7101 * Convenience Vars:: Convenience variables
7102 * Registers:: Registers
7103 * Floating Point Hardware:: Floating point hardware
7104 * Vector Unit:: Vector Unit
7105 * OS Information:: Auxiliary data provided by operating system
7106 * Memory Region Attributes:: Memory region attributes
7107 * Dump/Restore Files:: Copy between memory and a file
7108 * Core File Generation:: Cause a program dump its core
7109 * Character Sets:: Debugging programs that use a different
7110 character set than GDB does
7111 * Caching Remote Data:: Data caching for remote targets
7112 * Searching Memory:: Searching memory for a sequence of bytes
7116 @section Expressions
7119 @code{print} and many other @value{GDBN} commands accept an expression and
7120 compute its value. Any kind of constant, variable or operator defined
7121 by the programming language you are using is valid in an expression in
7122 @value{GDBN}. This includes conditional expressions, function calls,
7123 casts, and string constants. It also includes preprocessor macros, if
7124 you compiled your program to include this information; see
7127 @cindex arrays in expressions
7128 @value{GDBN} supports array constants in expressions input by
7129 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
7130 you can use the command @code{print @{1, 2, 3@}} to create an array
7131 of three integers. If you pass an array to a function or assign it
7132 to a program variable, @value{GDBN} copies the array to memory that
7133 is @code{malloc}ed in the target program.
7135 Because C is so widespread, most of the expressions shown in examples in
7136 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
7137 Languages}, for information on how to use expressions in other
7140 In this section, we discuss operators that you can use in @value{GDBN}
7141 expressions regardless of your programming language.
7143 @cindex casts, in expressions
7144 Casts are supported in all languages, not just in C, because it is so
7145 useful to cast a number into a pointer in order to examine a structure
7146 at that address in memory.
7147 @c FIXME: casts supported---Mod2 true?
7149 @value{GDBN} supports these operators, in addition to those common
7150 to programming languages:
7154 @samp{@@} is a binary operator for treating parts of memory as arrays.
7155 @xref{Arrays, ,Artificial Arrays}, for more information.
7158 @samp{::} allows you to specify a variable in terms of the file or
7159 function where it is defined. @xref{Variables, ,Program Variables}.
7161 @cindex @{@var{type}@}
7162 @cindex type casting memory
7163 @cindex memory, viewing as typed object
7164 @cindex casts, to view memory
7165 @item @{@var{type}@} @var{addr}
7166 Refers to an object of type @var{type} stored at address @var{addr} in
7167 memory. @var{addr} may be any expression whose value is an integer or
7168 pointer (but parentheses are required around binary operators, just as in
7169 a cast). This construct is allowed regardless of what kind of data is
7170 normally supposed to reside at @var{addr}.
7173 @node Ambiguous Expressions
7174 @section Ambiguous Expressions
7175 @cindex ambiguous expressions
7177 Expressions can sometimes contain some ambiguous elements. For instance,
7178 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7179 a single function name to be defined several times, for application in
7180 different contexts. This is called @dfn{overloading}. Another example
7181 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7182 templates and is typically instantiated several times, resulting in
7183 the same function name being defined in different contexts.
7185 In some cases and depending on the language, it is possible to adjust
7186 the expression to remove the ambiguity. For instance in C@t{++}, you
7187 can specify the signature of the function you want to break on, as in
7188 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7189 qualified name of your function often makes the expression unambiguous
7192 When an ambiguity that needs to be resolved is detected, the debugger
7193 has the capability to display a menu of numbered choices for each
7194 possibility, and then waits for the selection with the prompt @samp{>}.
7195 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7196 aborts the current command. If the command in which the expression was
7197 used allows more than one choice to be selected, the next option in the
7198 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7201 For example, the following session excerpt shows an attempt to set a
7202 breakpoint at the overloaded symbol @code{String::after}.
7203 We choose three particular definitions of that function name:
7205 @c FIXME! This is likely to change to show arg type lists, at least
7208 (@value{GDBP}) b String::after
7211 [2] file:String.cc; line number:867
7212 [3] file:String.cc; line number:860
7213 [4] file:String.cc; line number:875
7214 [5] file:String.cc; line number:853
7215 [6] file:String.cc; line number:846
7216 [7] file:String.cc; line number:735
7218 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7219 Breakpoint 2 at 0xb344: file String.cc, line 875.
7220 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7221 Multiple breakpoints were set.
7222 Use the "delete" command to delete unwanted
7229 @kindex set multiple-symbols
7230 @item set multiple-symbols @var{mode}
7231 @cindex multiple-symbols menu
7233 This option allows you to adjust the debugger behavior when an expression
7236 By default, @var{mode} is set to @code{all}. If the command with which
7237 the expression is used allows more than one choice, then @value{GDBN}
7238 automatically selects all possible choices. For instance, inserting
7239 a breakpoint on a function using an ambiguous name results in a breakpoint
7240 inserted on each possible match. However, if a unique choice must be made,
7241 then @value{GDBN} uses the menu to help you disambiguate the expression.
7242 For instance, printing the address of an overloaded function will result
7243 in the use of the menu.
7245 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7246 when an ambiguity is detected.
7248 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7249 an error due to the ambiguity and the command is aborted.
7251 @kindex show multiple-symbols
7252 @item show multiple-symbols
7253 Show the current value of the @code{multiple-symbols} setting.
7257 @section Program Variables
7259 The most common kind of expression to use is the name of a variable
7262 Variables in expressions are understood in the selected stack frame
7263 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7267 global (or file-static)
7274 visible according to the scope rules of the
7275 programming language from the point of execution in that frame
7278 @noindent This means that in the function
7293 you can examine and use the variable @code{a} whenever your program is
7294 executing within the function @code{foo}, but you can only use or
7295 examine the variable @code{b} while your program is executing inside
7296 the block where @code{b} is declared.
7298 @cindex variable name conflict
7299 There is an exception: you can refer to a variable or function whose
7300 scope is a single source file even if the current execution point is not
7301 in this file. But it is possible to have more than one such variable or
7302 function with the same name (in different source files). If that
7303 happens, referring to that name has unpredictable effects. If you wish,
7304 you can specify a static variable in a particular function or file,
7305 using the colon-colon (@code{::}) notation:
7307 @cindex colon-colon, context for variables/functions
7309 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7310 @cindex @code{::}, context for variables/functions
7313 @var{file}::@var{variable}
7314 @var{function}::@var{variable}
7318 Here @var{file} or @var{function} is the name of the context for the
7319 static @var{variable}. In the case of file names, you can use quotes to
7320 make sure @value{GDBN} parses the file name as a single word---for example,
7321 to print a global value of @code{x} defined in @file{f2.c}:
7324 (@value{GDBP}) p 'f2.c'::x
7327 @cindex C@t{++} scope resolution
7328 This use of @samp{::} is very rarely in conflict with the very similar
7329 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7330 scope resolution operator in @value{GDBN} expressions.
7331 @c FIXME: Um, so what happens in one of those rare cases where it's in
7334 @cindex wrong values
7335 @cindex variable values, wrong
7336 @cindex function entry/exit, wrong values of variables
7337 @cindex optimized code, wrong values of variables
7339 @emph{Warning:} Occasionally, a local variable may appear to have the
7340 wrong value at certain points in a function---just after entry to a new
7341 scope, and just before exit.
7343 You may see this problem when you are stepping by machine instructions.
7344 This is because, on most machines, it takes more than one instruction to
7345 set up a stack frame (including local variable definitions); if you are
7346 stepping by machine instructions, variables may appear to have the wrong
7347 values until the stack frame is completely built. On exit, it usually
7348 also takes more than one machine instruction to destroy a stack frame;
7349 after you begin stepping through that group of instructions, local
7350 variable definitions may be gone.
7352 This may also happen when the compiler does significant optimizations.
7353 To be sure of always seeing accurate values, turn off all optimization
7356 @cindex ``No symbol "foo" in current context''
7357 Another possible effect of compiler optimizations is to optimize
7358 unused variables out of existence, or assign variables to registers (as
7359 opposed to memory addresses). Depending on the support for such cases
7360 offered by the debug info format used by the compiler, @value{GDBN}
7361 might not be able to display values for such local variables. If that
7362 happens, @value{GDBN} will print a message like this:
7365 No symbol "foo" in current context.
7368 To solve such problems, either recompile without optimizations, or use a
7369 different debug info format, if the compiler supports several such
7370 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
7371 usually supports the @option{-gstabs+} option. @option{-gstabs+}
7372 produces debug info in a format that is superior to formats such as
7373 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
7374 an effective form for debug info. @xref{Debugging Options,,Options
7375 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
7376 Compiler Collection (GCC)}.
7377 @xref{C, ,C and C@t{++}}, for more information about debug info formats
7378 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.
8375 @item set print object off
8376 Display only the declared type of objects, without reference to the
8377 virtual function table. This is the default setting.
8379 @item show print object
8380 Show whether actual, or declared, object types are displayed.
8382 @item set print static-members
8383 @itemx set print static-members on
8384 @cindex static members of C@t{++} objects
8385 Print static members when displaying a C@t{++} object. The default is on.
8387 @item set print static-members off
8388 Do not print static members when displaying a C@t{++} object.
8390 @item show print static-members
8391 Show whether C@t{++} static members are printed or not.
8393 @item set print pascal_static-members
8394 @itemx set print pascal_static-members on
8395 @cindex static members of Pascal objects
8396 @cindex Pascal objects, static members display
8397 Print static members when displaying a Pascal object. The default is on.
8399 @item set print pascal_static-members off
8400 Do not print static members when displaying a Pascal object.
8402 @item show print pascal_static-members
8403 Show whether Pascal static members are printed or not.
8405 @c These don't work with HP ANSI C++ yet.
8406 @item set print vtbl
8407 @itemx set print vtbl on
8408 @cindex pretty print C@t{++} virtual function tables
8409 @cindex virtual functions (C@t{++}) display
8410 @cindex VTBL display
8411 Pretty print C@t{++} virtual function tables. The default is off.
8412 (The @code{vtbl} commands do not work on programs compiled with the HP
8413 ANSI C@t{++} compiler (@code{aCC}).)
8415 @item set print vtbl off
8416 Do not pretty print C@t{++} virtual function tables.
8418 @item show print vtbl
8419 Show whether C@t{++} virtual function tables are pretty printed, or not.
8422 @node Pretty Printing
8423 @section Pretty Printing
8425 @value{GDBN} provides a mechanism to allow pretty-printing of values using
8426 Python code. It greatly simplifies the display of complex objects. This
8427 mechanism works for both MI and the CLI.
8430 * Pretty-Printer Introduction:: Introduction to pretty-printers
8431 * Pretty-Printer Example:: An example pretty-printer
8432 * Pretty-Printer Commands:: Pretty-printer commands
8435 @node Pretty-Printer Introduction
8436 @subsection Pretty-Printer Introduction
8438 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
8439 registered for the value. If there is then @value{GDBN} invokes the
8440 pretty-printer to print the value. Otherwise the value is printed normally.
8442 Pretty-printers are normally named. This makes them easy to manage.
8443 The @samp{info pretty-printer} command will list all the installed
8444 pretty-printers with their names.
8445 If a pretty-printer can handle multiple data types, then its
8446 @dfn{subprinters} are the printers for the individual data types.
8447 Each such subprinter has its own name.
8448 The format of the name is @var{printer-name};@var{subprinter-name}.
8450 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
8451 Typically they are automatically loaded and registered when the corresponding
8452 debug information is loaded, thus making them available without having to
8453 do anything special.
8455 There are three places where a pretty-printer can be registered.
8459 Pretty-printers registered globally are available when debugging
8463 Pretty-printers registered with a program space are available only
8464 when debugging that program.
8465 @xref{Progspaces In Python}, for more details on program spaces in Python.
8468 Pretty-printers registered with an objfile are loaded and unloaded
8469 with the corresponding objfile (e.g., shared library).
8470 @xref{Objfiles In Python}, for more details on objfiles in Python.
8473 @xref{Selecting Pretty-Printers}, for further information on how
8474 pretty-printers are selected,
8476 @xref{Writing a Pretty-Printer}, for implementing pretty printers
8479 @node Pretty-Printer Example
8480 @subsection Pretty-Printer Example
8482 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
8485 (@value{GDBP}) print s
8487 static npos = 4294967295,
8489 <std::allocator<char>> = @{
8490 <__gnu_cxx::new_allocator<char>> = @{
8491 <No data fields>@}, <No data fields>
8493 members of std::basic_string<char, std::char_traits<char>,
8494 std::allocator<char> >::_Alloc_hider:
8495 _M_p = 0x804a014 "abcd"
8500 With a pretty-printer for @code{std::string} only the contents are printed:
8503 (@value{GDBP}) print s
8507 @node Pretty-Printer Commands
8508 @subsection Pretty-Printer Commands
8509 @cindex pretty-printer commands
8512 @kindex info pretty-printer
8513 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8514 Print the list of installed pretty-printers.
8515 This includes disabled pretty-printers, which are marked as such.
8517 @var{object-regexp} is a regular expression matching the objects
8518 whose pretty-printers to list.
8519 Objects can be @code{global}, the program space's file
8520 (@pxref{Progspaces In Python}),
8521 and the object files within that program space (@pxref{Objfiles In Python}).
8522 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
8523 looks up a printer from these three objects.
8525 @var{name-regexp} is a regular expression matching the name of the printers
8528 @kindex disable pretty-printer
8529 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8530 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8531 A disabled pretty-printer is not forgotten, it may be enabled again later.
8533 @kindex enable pretty-printer
8534 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8535 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8540 Suppose we have three pretty-printers installed: one from library1.so
8541 named @code{foo} that prints objects of type @code{foo}, and
8542 another from library2.so named @code{bar} that prints two types of objects,
8543 @code{bar1} and @code{bar2}.
8546 (gdb) info pretty-printer
8553 (gdb) info pretty-printer library2
8558 (gdb) disable pretty-printer library1
8560 2 of 3 printers enabled
8561 (gdb) info pretty-printer
8568 (gdb) disable pretty-printer library2 bar:bar1
8570 1 of 3 printers enabled
8571 (gdb) info pretty-printer library2
8578 (gdb) disable pretty-printer library2 bar
8580 0 of 3 printers enabled
8581 (gdb) info pretty-printer library2
8590 Note that for @code{bar} the entire printer can be disabled,
8591 as can each individual subprinter.
8594 @section Value History
8596 @cindex value history
8597 @cindex history of values printed by @value{GDBN}
8598 Values printed by the @code{print} command are saved in the @value{GDBN}
8599 @dfn{value history}. This allows you to refer to them in other expressions.
8600 Values are kept until the symbol table is re-read or discarded
8601 (for example with the @code{file} or @code{symbol-file} commands).
8602 When the symbol table changes, the value history is discarded,
8603 since the values may contain pointers back to the types defined in the
8608 @cindex history number
8609 The values printed are given @dfn{history numbers} by which you can
8610 refer to them. These are successive integers starting with one.
8611 @code{print} shows you the history number assigned to a value by
8612 printing @samp{$@var{num} = } before the value; here @var{num} is the
8615 To refer to any previous value, use @samp{$} followed by the value's
8616 history number. The way @code{print} labels its output is designed to
8617 remind you of this. Just @code{$} refers to the most recent value in
8618 the history, and @code{$$} refers to the value before that.
8619 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
8620 is the value just prior to @code{$$}, @code{$$1} is equivalent to
8621 @code{$$}, and @code{$$0} is equivalent to @code{$}.
8623 For example, suppose you have just printed a pointer to a structure and
8624 want to see the contents of the structure. It suffices to type
8630 If you have a chain of structures where the component @code{next} points
8631 to the next one, you can print the contents of the next one with this:
8638 You can print successive links in the chain by repeating this
8639 command---which you can do by just typing @key{RET}.
8641 Note that the history records values, not expressions. If the value of
8642 @code{x} is 4 and you type these commands:
8650 then the value recorded in the value history by the @code{print} command
8651 remains 4 even though the value of @code{x} has changed.
8656 Print the last ten values in the value history, with their item numbers.
8657 This is like @samp{p@ $$9} repeated ten times, except that @code{show
8658 values} does not change the history.
8660 @item show values @var{n}
8661 Print ten history values centered on history item number @var{n}.
8664 Print ten history values just after the values last printed. If no more
8665 values are available, @code{show values +} produces no display.
8668 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
8669 same effect as @samp{show values +}.
8671 @node Convenience Vars
8672 @section Convenience Variables
8674 @cindex convenience variables
8675 @cindex user-defined variables
8676 @value{GDBN} provides @dfn{convenience variables} that you can use within
8677 @value{GDBN} to hold on to a value and refer to it later. These variables
8678 exist entirely within @value{GDBN}; they are not part of your program, and
8679 setting a convenience variable has no direct effect on further execution
8680 of your program. That is why you can use them freely.
8682 Convenience variables are prefixed with @samp{$}. Any name preceded by
8683 @samp{$} can be used for a convenience variable, unless it is one of
8684 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
8685 (Value history references, in contrast, are @emph{numbers} preceded
8686 by @samp{$}. @xref{Value History, ,Value History}.)
8688 You can save a value in a convenience variable with an assignment
8689 expression, just as you would set a variable in your program.
8693 set $foo = *object_ptr
8697 would save in @code{$foo} the value contained in the object pointed to by
8700 Using a convenience variable for the first time creates it, but its
8701 value is @code{void} until you assign a new value. You can alter the
8702 value with another assignment at any time.
8704 Convenience variables have no fixed types. You can assign a convenience
8705 variable any type of value, including structures and arrays, even if
8706 that variable already has a value of a different type. The convenience
8707 variable, when used as an expression, has the type of its current value.
8710 @kindex show convenience
8711 @cindex show all user variables
8712 @item show convenience
8713 Print a list of convenience variables used so far, and their values.
8714 Abbreviated @code{show conv}.
8716 @kindex init-if-undefined
8717 @cindex convenience variables, initializing
8718 @item init-if-undefined $@var{variable} = @var{expression}
8719 Set a convenience variable if it has not already been set. This is useful
8720 for user-defined commands that keep some state. It is similar, in concept,
8721 to using local static variables with initializers in C (except that
8722 convenience variables are global). It can also be used to allow users to
8723 override default values used in a command script.
8725 If the variable is already defined then the expression is not evaluated so
8726 any side-effects do not occur.
8729 One of the ways to use a convenience variable is as a counter to be
8730 incremented or a pointer to be advanced. For example, to print
8731 a field from successive elements of an array of structures:
8735 print bar[$i++]->contents
8739 Repeat that command by typing @key{RET}.
8741 Some convenience variables are created automatically by @value{GDBN} and given
8742 values likely to be useful.
8745 @vindex $_@r{, convenience variable}
8747 The variable @code{$_} is automatically set by the @code{x} command to
8748 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8749 commands which provide a default address for @code{x} to examine also
8750 set @code{$_} to that address; these commands include @code{info line}
8751 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8752 except when set by the @code{x} command, in which case it is a pointer
8753 to the type of @code{$__}.
8755 @vindex $__@r{, convenience variable}
8757 The variable @code{$__} is automatically set by the @code{x} command
8758 to the value found in the last address examined. Its type is chosen
8759 to match the format in which the data was printed.
8762 @vindex $_exitcode@r{, convenience variable}
8763 The variable @code{$_exitcode} is automatically set to the exit code when
8764 the program being debugged terminates.
8767 @vindex $_sdata@r{, inspect, convenience variable}
8768 The variable @code{$_sdata} contains extra collected static tracepoint
8769 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
8770 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
8771 if extra static tracepoint data has not been collected.
8774 @vindex $_siginfo@r{, convenience variable}
8775 The variable @code{$_siginfo} contains extra signal information
8776 (@pxref{extra signal information}). Note that @code{$_siginfo}
8777 could be empty, if the application has not yet received any signals.
8778 For example, it will be empty before you execute the @code{run} command.
8781 @vindex $_tlb@r{, convenience variable}
8782 The variable @code{$_tlb} is automatically set when debugging
8783 applications running on MS-Windows in native mode or connected to
8784 gdbserver that supports the @code{qGetTIBAddr} request.
8785 @xref{General Query Packets}.
8786 This variable contains the address of the thread information block.
8790 On HP-UX systems, if you refer to a function or variable name that
8791 begins with a dollar sign, @value{GDBN} searches for a user or system
8792 name first, before it searches for a convenience variable.
8794 @cindex convenience functions
8795 @value{GDBN} also supplies some @dfn{convenience functions}. These
8796 have a syntax similar to convenience variables. A convenience
8797 function can be used in an expression just like an ordinary function;
8798 however, a convenience function is implemented internally to
8803 @kindex help function
8804 @cindex show all convenience functions
8805 Print a list of all convenience functions.
8812 You can refer to machine register contents, in expressions, as variables
8813 with names starting with @samp{$}. The names of registers are different
8814 for each machine; use @code{info registers} to see the names used on
8818 @kindex info registers
8819 @item info registers
8820 Print the names and values of all registers except floating-point
8821 and vector registers (in the selected stack frame).
8823 @kindex info all-registers
8824 @cindex floating point registers
8825 @item info all-registers
8826 Print the names and values of all registers, including floating-point
8827 and vector registers (in the selected stack frame).
8829 @item info registers @var{regname} @dots{}
8830 Print the @dfn{relativized} value of each specified register @var{regname}.
8831 As discussed in detail below, register values are normally relative to
8832 the selected stack frame. @var{regname} may be any register name valid on
8833 the machine you are using, with or without the initial @samp{$}.
8836 @cindex stack pointer register
8837 @cindex program counter register
8838 @cindex process status register
8839 @cindex frame pointer register
8840 @cindex standard registers
8841 @value{GDBN} has four ``standard'' register names that are available (in
8842 expressions) on most machines---whenever they do not conflict with an
8843 architecture's canonical mnemonics for registers. The register names
8844 @code{$pc} and @code{$sp} are used for the program counter register and
8845 the stack pointer. @code{$fp} is used for a register that contains a
8846 pointer to the current stack frame, and @code{$ps} is used for a
8847 register that contains the processor status. For example,
8848 you could print the program counter in hex with
8855 or print the instruction to be executed next with
8862 or add four to the stack pointer@footnote{This is a way of removing
8863 one word from the stack, on machines where stacks grow downward in
8864 memory (most machines, nowadays). This assumes that the innermost
8865 stack frame is selected; setting @code{$sp} is not allowed when other
8866 stack frames are selected. To pop entire frames off the stack,
8867 regardless of machine architecture, use @code{return};
8868 see @ref{Returning, ,Returning from a Function}.} with
8874 Whenever possible, these four standard register names are available on
8875 your machine even though the machine has different canonical mnemonics,
8876 so long as there is no conflict. The @code{info registers} command
8877 shows the canonical names. For example, on the SPARC, @code{info
8878 registers} displays the processor status register as @code{$psr} but you
8879 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
8880 is an alias for the @sc{eflags} register.
8882 @value{GDBN} always considers the contents of an ordinary register as an
8883 integer when the register is examined in this way. Some machines have
8884 special registers which can hold nothing but floating point; these
8885 registers are considered to have floating point values. There is no way
8886 to refer to the contents of an ordinary register as floating point value
8887 (although you can @emph{print} it as a floating point value with
8888 @samp{print/f $@var{regname}}).
8890 Some registers have distinct ``raw'' and ``virtual'' data formats. This
8891 means that the data format in which the register contents are saved by
8892 the operating system is not the same one that your program normally
8893 sees. For example, the registers of the 68881 floating point
8894 coprocessor are always saved in ``extended'' (raw) format, but all C
8895 programs expect to work with ``double'' (virtual) format. In such
8896 cases, @value{GDBN} normally works with the virtual format only (the format
8897 that makes sense for your program), but the @code{info registers} command
8898 prints the data in both formats.
8900 @cindex SSE registers (x86)
8901 @cindex MMX registers (x86)
8902 Some machines have special registers whose contents can be interpreted
8903 in several different ways. For example, modern x86-based machines
8904 have SSE and MMX registers that can hold several values packed
8905 together in several different formats. @value{GDBN} refers to such
8906 registers in @code{struct} notation:
8909 (@value{GDBP}) print $xmm1
8911 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
8912 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
8913 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
8914 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
8915 v4_int32 = @{0, 20657912, 11, 13@},
8916 v2_int64 = @{88725056443645952, 55834574859@},
8917 uint128 = 0x0000000d0000000b013b36f800000000
8922 To set values of such registers, you need to tell @value{GDBN} which
8923 view of the register you wish to change, as if you were assigning
8924 value to a @code{struct} member:
8927 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
8930 Normally, register values are relative to the selected stack frame
8931 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
8932 value that the register would contain if all stack frames farther in
8933 were exited and their saved registers restored. In order to see the
8934 true contents of hardware registers, you must select the innermost
8935 frame (with @samp{frame 0}).
8937 However, @value{GDBN} must deduce where registers are saved, from the machine
8938 code generated by your compiler. If some registers are not saved, or if
8939 @value{GDBN} is unable to locate the saved registers, the selected stack
8940 frame makes no difference.
8942 @node Floating Point Hardware
8943 @section Floating Point Hardware
8944 @cindex floating point
8946 Depending on the configuration, @value{GDBN} may be able to give
8947 you more information about the status of the floating point hardware.
8952 Display hardware-dependent information about the floating
8953 point unit. The exact contents and layout vary depending on the
8954 floating point chip. Currently, @samp{info float} is supported on
8955 the ARM and x86 machines.
8959 @section Vector Unit
8962 Depending on the configuration, @value{GDBN} may be able to give you
8963 more information about the status of the vector unit.
8968 Display information about the vector unit. The exact contents and
8969 layout vary depending on the hardware.
8972 @node OS Information
8973 @section Operating System Auxiliary Information
8974 @cindex OS information
8976 @value{GDBN} provides interfaces to useful OS facilities that can help
8977 you debug your program.
8979 @cindex @code{ptrace} system call
8980 @cindex @code{struct user} contents
8981 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
8982 machines), it interfaces with the inferior via the @code{ptrace}
8983 system call. The operating system creates a special sata structure,
8984 called @code{struct user}, for this interface. You can use the
8985 command @code{info udot} to display the contents of this data
8991 Display the contents of the @code{struct user} maintained by the OS
8992 kernel for the program being debugged. @value{GDBN} displays the
8993 contents of @code{struct user} as a list of hex numbers, similar to
8994 the @code{examine} command.
8997 @cindex auxiliary vector
8998 @cindex vector, auxiliary
8999 Some operating systems supply an @dfn{auxiliary vector} to programs at
9000 startup. This is akin to the arguments and environment that you
9001 specify for a program, but contains a system-dependent variety of
9002 binary values that tell system libraries important details about the
9003 hardware, operating system, and process. Each value's purpose is
9004 identified by an integer tag; the meanings are well-known but system-specific.
9005 Depending on the configuration and operating system facilities,
9006 @value{GDBN} may be able to show you this information. For remote
9007 targets, this functionality may further depend on the remote stub's
9008 support of the @samp{qXfer:auxv:read} packet, see
9009 @ref{qXfer auxiliary vector read}.
9014 Display the auxiliary vector of the inferior, which can be either a
9015 live process or a core dump file. @value{GDBN} prints each tag value
9016 numerically, and also shows names and text descriptions for recognized
9017 tags. Some values in the vector are numbers, some bit masks, and some
9018 pointers to strings or other data. @value{GDBN} displays each value in the
9019 most appropriate form for a recognized tag, and in hexadecimal for
9020 an unrecognized tag.
9023 On some targets, @value{GDBN} can access operating-system-specific information
9024 and display it to user, without interpretation. For remote targets,
9025 this functionality depends on the remote stub's support of the
9026 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
9031 List the types of OS information available for the target. If the
9032 target does not return a list of possible types, this command will
9035 @kindex info os processes
9036 @item info os processes
9037 Display the list of processes on the target. For each process,
9038 @value{GDBN} prints the process identifier, the name of the user, and
9039 the command corresponding to the process.
9042 @node Memory Region Attributes
9043 @section Memory Region Attributes
9044 @cindex memory region attributes
9046 @dfn{Memory region attributes} allow you to describe special handling
9047 required by regions of your target's memory. @value{GDBN} uses
9048 attributes to determine whether to allow certain types of memory
9049 accesses; whether to use specific width accesses; and whether to cache
9050 target memory. By default the description of memory regions is
9051 fetched from the target (if the current target supports this), but the
9052 user can override the fetched regions.
9054 Defined memory regions can be individually enabled and disabled. When a
9055 memory region is disabled, @value{GDBN} uses the default attributes when
9056 accessing memory in that region. Similarly, if no memory regions have
9057 been defined, @value{GDBN} uses the default attributes when accessing
9060 When a memory region is defined, it is given a number to identify it;
9061 to enable, disable, or remove a memory region, you specify that number.
9065 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
9066 Define a memory region bounded by @var{lower} and @var{upper} with
9067 attributes @var{attributes}@dots{}, and add it to the list of regions
9068 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
9069 case: it is treated as the target's maximum memory address.
9070 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
9073 Discard any user changes to the memory regions and use target-supplied
9074 regions, if available, or no regions if the target does not support.
9077 @item delete mem @var{nums}@dots{}
9078 Remove memory regions @var{nums}@dots{} from the list of regions
9079 monitored by @value{GDBN}.
9082 @item disable mem @var{nums}@dots{}
9083 Disable monitoring of memory regions @var{nums}@dots{}.
9084 A disabled memory region is not forgotten.
9085 It may be enabled again later.
9088 @item enable mem @var{nums}@dots{}
9089 Enable monitoring of memory regions @var{nums}@dots{}.
9093 Print a table of all defined memory regions, with the following columns
9097 @item Memory Region Number
9098 @item Enabled or Disabled.
9099 Enabled memory regions are marked with @samp{y}.
9100 Disabled memory regions are marked with @samp{n}.
9103 The address defining the inclusive lower bound of the memory region.
9106 The address defining the exclusive upper bound of the memory region.
9109 The list of attributes set for this memory region.
9114 @subsection Attributes
9116 @subsubsection Memory Access Mode
9117 The access mode attributes set whether @value{GDBN} may make read or
9118 write accesses to a memory region.
9120 While these attributes prevent @value{GDBN} from performing invalid
9121 memory accesses, they do nothing to prevent the target system, I/O DMA,
9122 etc.@: from accessing memory.
9126 Memory is read only.
9128 Memory is write only.
9130 Memory is read/write. This is the default.
9133 @subsubsection Memory Access Size
9134 The access size attribute tells @value{GDBN} to use specific sized
9135 accesses in the memory region. Often memory mapped device registers
9136 require specific sized accesses. If no access size attribute is
9137 specified, @value{GDBN} may use accesses of any size.
9141 Use 8 bit memory accesses.
9143 Use 16 bit memory accesses.
9145 Use 32 bit memory accesses.
9147 Use 64 bit memory accesses.
9150 @c @subsubsection Hardware/Software Breakpoints
9151 @c The hardware/software breakpoint attributes set whether @value{GDBN}
9152 @c will use hardware or software breakpoints for the internal breakpoints
9153 @c used by the step, next, finish, until, etc. commands.
9157 @c Always use hardware breakpoints
9158 @c @item swbreak (default)
9161 @subsubsection Data Cache
9162 The data cache attributes set whether @value{GDBN} will cache target
9163 memory. While this generally improves performance by reducing debug
9164 protocol overhead, it can lead to incorrect results because @value{GDBN}
9165 does not know about volatile variables or memory mapped device
9170 Enable @value{GDBN} to cache target memory.
9172 Disable @value{GDBN} from caching target memory. This is the default.
9175 @subsection Memory Access Checking
9176 @value{GDBN} can be instructed to refuse accesses to memory that is
9177 not explicitly described. This can be useful if accessing such
9178 regions has undesired effects for a specific target, or to provide
9179 better error checking. The following commands control this behaviour.
9182 @kindex set mem inaccessible-by-default
9183 @item set mem inaccessible-by-default [on|off]
9184 If @code{on} is specified, make @value{GDBN} treat memory not
9185 explicitly described by the memory ranges as non-existent and refuse accesses
9186 to such memory. The checks are only performed if there's at least one
9187 memory range defined. If @code{off} is specified, make @value{GDBN}
9188 treat the memory not explicitly described by the memory ranges as RAM.
9189 The default value is @code{on}.
9190 @kindex show mem inaccessible-by-default
9191 @item show mem inaccessible-by-default
9192 Show the current handling of accesses to unknown memory.
9196 @c @subsubsection Memory Write Verification
9197 @c The memory write verification attributes set whether @value{GDBN}
9198 @c will re-reads data after each write to verify the write was successful.
9202 @c @item noverify (default)
9205 @node Dump/Restore Files
9206 @section Copy Between Memory and a File
9207 @cindex dump/restore files
9208 @cindex append data to a file
9209 @cindex dump data to a file
9210 @cindex restore data from a file
9212 You can use the commands @code{dump}, @code{append}, and
9213 @code{restore} to copy data between target memory and a file. The
9214 @code{dump} and @code{append} commands write data to a file, and the
9215 @code{restore} command reads data from a file back into the inferior's
9216 memory. Files may be in binary, Motorola S-record, Intel hex, or
9217 Tektronix Hex format; however, @value{GDBN} can only append to binary
9223 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9224 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
9225 Dump the contents of memory from @var{start_addr} to @var{end_addr},
9226 or the value of @var{expr}, to @var{filename} in the given format.
9228 The @var{format} parameter may be any one of:
9235 Motorola S-record format.
9237 Tektronix Hex format.
9240 @value{GDBN} uses the same definitions of these formats as the
9241 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
9242 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
9246 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9247 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
9248 Append the contents of memory from @var{start_addr} to @var{end_addr},
9249 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
9250 (@value{GDBN} can only append data to files in raw binary form.)
9253 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
9254 Restore the contents of file @var{filename} into memory. The
9255 @code{restore} command can automatically recognize any known @sc{bfd}
9256 file format, except for raw binary. To restore a raw binary file you
9257 must specify the optional keyword @code{binary} after the filename.
9259 If @var{bias} is non-zero, its value will be added to the addresses
9260 contained in the file. Binary files always start at address zero, so
9261 they will be restored at address @var{bias}. Other bfd files have
9262 a built-in location; they will be restored at offset @var{bias}
9265 If @var{start} and/or @var{end} are non-zero, then only data between
9266 file offset @var{start} and file offset @var{end} will be restored.
9267 These offsets are relative to the addresses in the file, before
9268 the @var{bias} argument is applied.
9272 @node Core File Generation
9273 @section How to Produce a Core File from Your Program
9274 @cindex dump core from inferior
9276 A @dfn{core file} or @dfn{core dump} is a file that records the memory
9277 image of a running process and its process status (register values
9278 etc.). Its primary use is post-mortem debugging of a program that
9279 crashed while it ran outside a debugger. A program that crashes
9280 automatically produces a core file, unless this feature is disabled by
9281 the user. @xref{Files}, for information on invoking @value{GDBN} in
9282 the post-mortem debugging mode.
9284 Occasionally, you may wish to produce a core file of the program you
9285 are debugging in order to preserve a snapshot of its state.
9286 @value{GDBN} has a special command for that.
9290 @kindex generate-core-file
9291 @item generate-core-file [@var{file}]
9292 @itemx gcore [@var{file}]
9293 Produce a core dump of the inferior process. The optional argument
9294 @var{file} specifies the file name where to put the core dump. If not
9295 specified, the file name defaults to @file{core.@var{pid}}, where
9296 @var{pid} is the inferior process ID.
9298 Note that this command is implemented only for some systems (as of
9299 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
9302 @node Character Sets
9303 @section Character Sets
9304 @cindex character sets
9306 @cindex translating between character sets
9307 @cindex host character set
9308 @cindex target character set
9310 If the program you are debugging uses a different character set to
9311 represent characters and strings than the one @value{GDBN} uses itself,
9312 @value{GDBN} can automatically translate between the character sets for
9313 you. The character set @value{GDBN} uses we call the @dfn{host
9314 character set}; the one the inferior program uses we call the
9315 @dfn{target character set}.
9317 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
9318 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
9319 remote protocol (@pxref{Remote Debugging}) to debug a program
9320 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
9321 then the host character set is Latin-1, and the target character set is
9322 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
9323 target-charset EBCDIC-US}, then @value{GDBN} translates between
9324 @sc{ebcdic} and Latin 1 as you print character or string values, or use
9325 character and string literals in expressions.
9327 @value{GDBN} has no way to automatically recognize which character set
9328 the inferior program uses; you must tell it, using the @code{set
9329 target-charset} command, described below.
9331 Here are the commands for controlling @value{GDBN}'s character set
9335 @item set target-charset @var{charset}
9336 @kindex set target-charset
9337 Set the current target character set to @var{charset}. To display the
9338 list of supported target character sets, type
9339 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
9341 @item set host-charset @var{charset}
9342 @kindex set host-charset
9343 Set the current host character set to @var{charset}.
9345 By default, @value{GDBN} uses a host character set appropriate to the
9346 system it is running on; you can override that default using the
9347 @code{set host-charset} command. On some systems, @value{GDBN} cannot
9348 automatically determine the appropriate host character set. In this
9349 case, @value{GDBN} uses @samp{UTF-8}.
9351 @value{GDBN} can only use certain character sets as its host character
9352 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
9353 @value{GDBN} will list the host character sets it supports.
9355 @item set charset @var{charset}
9357 Set the current host and target character sets to @var{charset}. As
9358 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
9359 @value{GDBN} will list the names of the character sets that can be used
9360 for both host and target.
9363 @kindex show charset
9364 Show the names of the current host and target character sets.
9366 @item show host-charset
9367 @kindex show host-charset
9368 Show the name of the current host character set.
9370 @item show target-charset
9371 @kindex show target-charset
9372 Show the name of the current target character set.
9374 @item set target-wide-charset @var{charset}
9375 @kindex set target-wide-charset
9376 Set the current target's wide character set to @var{charset}. This is
9377 the character set used by the target's @code{wchar_t} type. To
9378 display the list of supported wide character sets, type
9379 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
9381 @item show target-wide-charset
9382 @kindex show target-wide-charset
9383 Show the name of the current target's wide character set.
9386 Here is an example of @value{GDBN}'s character set support in action.
9387 Assume that the following source code has been placed in the file
9388 @file{charset-test.c}:
9394 = @{72, 101, 108, 108, 111, 44, 32, 119,
9395 111, 114, 108, 100, 33, 10, 0@};
9396 char ibm1047_hello[]
9397 = @{200, 133, 147, 147, 150, 107, 64, 166,
9398 150, 153, 147, 132, 90, 37, 0@};
9402 printf ("Hello, world!\n");
9406 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
9407 containing the string @samp{Hello, world!} followed by a newline,
9408 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
9410 We compile the program, and invoke the debugger on it:
9413 $ gcc -g charset-test.c -o charset-test
9414 $ gdb -nw charset-test
9415 GNU gdb 2001-12-19-cvs
9416 Copyright 2001 Free Software Foundation, Inc.
9421 We can use the @code{show charset} command to see what character sets
9422 @value{GDBN} is currently using to interpret and display characters and
9426 (@value{GDBP}) show charset
9427 The current host and target character set is `ISO-8859-1'.
9431 For the sake of printing this manual, let's use @sc{ascii} as our
9432 initial character set:
9434 (@value{GDBP}) set charset ASCII
9435 (@value{GDBP}) show charset
9436 The current host and target character set is `ASCII'.
9440 Let's assume that @sc{ascii} is indeed the correct character set for our
9441 host system --- in other words, let's assume that if @value{GDBN} prints
9442 characters using the @sc{ascii} character set, our terminal will display
9443 them properly. Since our current target character set is also
9444 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
9447 (@value{GDBP}) print ascii_hello
9448 $1 = 0x401698 "Hello, world!\n"
9449 (@value{GDBP}) print ascii_hello[0]
9454 @value{GDBN} uses the target character set for character and string
9455 literals you use in expressions:
9458 (@value{GDBP}) print '+'
9463 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
9466 @value{GDBN} relies on the user to tell it which character set the
9467 target program uses. If we print @code{ibm1047_hello} while our target
9468 character set is still @sc{ascii}, we get jibberish:
9471 (@value{GDBP}) print ibm1047_hello
9472 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
9473 (@value{GDBP}) print ibm1047_hello[0]
9478 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
9479 @value{GDBN} tells us the character sets it supports:
9482 (@value{GDBP}) set target-charset
9483 ASCII EBCDIC-US IBM1047 ISO-8859-1
9484 (@value{GDBP}) set target-charset
9487 We can select @sc{ibm1047} as our target character set, and examine the
9488 program's strings again. Now the @sc{ascii} string is wrong, but
9489 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
9490 target character set, @sc{ibm1047}, to the host character set,
9491 @sc{ascii}, and they display correctly:
9494 (@value{GDBP}) set target-charset IBM1047
9495 (@value{GDBP}) show charset
9496 The current host character set is `ASCII'.
9497 The current target character set is `IBM1047'.
9498 (@value{GDBP}) print ascii_hello
9499 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
9500 (@value{GDBP}) print ascii_hello[0]
9502 (@value{GDBP}) print ibm1047_hello
9503 $8 = 0x4016a8 "Hello, world!\n"
9504 (@value{GDBP}) print ibm1047_hello[0]
9509 As above, @value{GDBN} uses the target character set for character and
9510 string literals you use in expressions:
9513 (@value{GDBP}) print '+'
9518 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
9521 @node Caching Remote Data
9522 @section Caching Data of Remote Targets
9523 @cindex caching data of remote targets
9525 @value{GDBN} caches data exchanged between the debugger and a
9526 remote target (@pxref{Remote Debugging}). Such caching generally improves
9527 performance, because it reduces the overhead of the remote protocol by
9528 bundling memory reads and writes into large chunks. Unfortunately, simply
9529 caching everything would lead to incorrect results, since @value{GDBN}
9530 does not necessarily know anything about volatile values, memory-mapped I/O
9531 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
9532 memory can be changed @emph{while} a gdb command is executing.
9533 Therefore, by default, @value{GDBN} only caches data
9534 known to be on the stack@footnote{In non-stop mode, it is moderately
9535 rare for a running thread to modify the stack of a stopped thread
9536 in a way that would interfere with a backtrace, and caching of
9537 stack reads provides a significant speed up of remote backtraces.}.
9538 Other regions of memory can be explicitly marked as
9539 cacheable; see @pxref{Memory Region Attributes}.
9542 @kindex set remotecache
9543 @item set remotecache on
9544 @itemx set remotecache off
9545 This option no longer does anything; it exists for compatibility
9548 @kindex show remotecache
9549 @item show remotecache
9550 Show the current state of the obsolete remotecache flag.
9552 @kindex set stack-cache
9553 @item set stack-cache on
9554 @itemx set stack-cache off
9555 Enable or disable caching of stack accesses. When @code{ON}, use
9556 caching. By default, this option is @code{ON}.
9558 @kindex show stack-cache
9559 @item show stack-cache
9560 Show the current state of data caching for memory accesses.
9563 @item info dcache @r{[}line@r{]}
9564 Print the information about the data cache performance. The
9565 information displayed includes the dcache width and depth, and for
9566 each cache line, its number, address, and how many times it was
9567 referenced. This command is useful for debugging the data cache
9570 If a line number is specified, the contents of that line will be
9573 @item set dcache size @var{size}
9575 @kindex set dcache size
9576 Set maximum number of entries in dcache (dcache depth above).
9578 @item set dcache line-size @var{line-size}
9579 @cindex dcache line-size
9580 @kindex set dcache line-size
9581 Set number of bytes each dcache entry caches (dcache width above).
9582 Must be a power of 2.
9584 @item show dcache size
9585 @kindex show dcache size
9586 Show maximum number of dcache entries. See also @ref{Caching Remote Data, info dcache}.
9588 @item show dcache line-size
9589 @kindex show dcache line-size
9590 Show default size of dcache lines. See also @ref{Caching Remote Data, info dcache}.
9594 @node Searching Memory
9595 @section Search Memory
9596 @cindex searching memory
9598 Memory can be searched for a particular sequence of bytes with the
9599 @code{find} command.
9603 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9604 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9605 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
9606 etc. The search begins at address @var{start_addr} and continues for either
9607 @var{len} bytes or through to @var{end_addr} inclusive.
9610 @var{s} and @var{n} are optional parameters.
9611 They may be specified in either order, apart or together.
9614 @item @var{s}, search query size
9615 The size of each search query value.
9621 halfwords (two bytes)
9625 giant words (eight bytes)
9628 All values are interpreted in the current language.
9629 This means, for example, that if the current source language is C/C@t{++}
9630 then searching for the string ``hello'' includes the trailing '\0'.
9632 If the value size is not specified, it is taken from the
9633 value's type in the current language.
9634 This is useful when one wants to specify the search
9635 pattern as a mixture of types.
9636 Note that this means, for example, that in the case of C-like languages
9637 a search for an untyped 0x42 will search for @samp{(int) 0x42}
9638 which is typically four bytes.
9640 @item @var{n}, maximum number of finds
9641 The maximum number of matches to print. The default is to print all finds.
9644 You can use strings as search values. Quote them with double-quotes
9646 The string value is copied into the search pattern byte by byte,
9647 regardless of the endianness of the target and the size specification.
9649 The address of each match found is printed as well as a count of the
9650 number of matches found.
9652 The address of the last value found is stored in convenience variable
9654 A count of the number of matches is stored in @samp{$numfound}.
9656 For example, if stopped at the @code{printf} in this function:
9662 static char hello[] = "hello-hello";
9663 static struct @{ char c; short s; int i; @}
9664 __attribute__ ((packed)) mixed
9665 = @{ 'c', 0x1234, 0x87654321 @};
9666 printf ("%s\n", hello);
9671 you get during debugging:
9674 (gdb) find &hello[0], +sizeof(hello), "hello"
9675 0x804956d <hello.1620+6>
9677 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
9678 0x8049567 <hello.1620>
9679 0x804956d <hello.1620+6>
9681 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
9682 0x8049567 <hello.1620>
9684 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
9685 0x8049560 <mixed.1625>
9687 (gdb) print $numfound
9690 $2 = (void *) 0x8049560
9693 @node Optimized Code
9694 @chapter Debugging Optimized Code
9695 @cindex optimized code, debugging
9696 @cindex debugging optimized code
9698 Almost all compilers support optimization. With optimization
9699 disabled, the compiler generates assembly code that corresponds
9700 directly to your source code, in a simplistic way. As the compiler
9701 applies more powerful optimizations, the generated assembly code
9702 diverges from your original source code. With help from debugging
9703 information generated by the compiler, @value{GDBN} can map from
9704 the running program back to constructs from your original source.
9706 @value{GDBN} is more accurate with optimization disabled. If you
9707 can recompile without optimization, it is easier to follow the
9708 progress of your program during debugging. But, there are many cases
9709 where you may need to debug an optimized version.
9711 When you debug a program compiled with @samp{-g -O}, remember that the
9712 optimizer has rearranged your code; the debugger shows you what is
9713 really there. Do not be too surprised when the execution path does not
9714 exactly match your source file! An extreme example: if you define a
9715 variable, but never use it, @value{GDBN} never sees that
9716 variable---because the compiler optimizes it out of existence.
9718 Some things do not work as well with @samp{-g -O} as with just
9719 @samp{-g}, particularly on machines with instruction scheduling. If in
9720 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
9721 please report it to us as a bug (including a test case!).
9722 @xref{Variables}, for more information about debugging optimized code.
9725 * Inline Functions:: How @value{GDBN} presents inlining
9726 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
9729 @node Inline Functions
9730 @section Inline Functions
9731 @cindex inline functions, debugging
9733 @dfn{Inlining} is an optimization that inserts a copy of the function
9734 body directly at each call site, instead of jumping to a shared
9735 routine. @value{GDBN} displays inlined functions just like
9736 non-inlined functions. They appear in backtraces. You can view their
9737 arguments and local variables, step into them with @code{step}, skip
9738 them with @code{next}, and escape from them with @code{finish}.
9739 You can check whether a function was inlined by using the
9740 @code{info frame} command.
9742 For @value{GDBN} to support inlined functions, the compiler must
9743 record information about inlining in the debug information ---
9744 @value{NGCC} using the @sc{dwarf 2} format does this, and several
9745 other compilers do also. @value{GDBN} only supports inlined functions
9746 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
9747 do not emit two required attributes (@samp{DW_AT_call_file} and
9748 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
9749 function calls with earlier versions of @value{NGCC}. It instead
9750 displays the arguments and local variables of inlined functions as
9751 local variables in the caller.
9753 The body of an inlined function is directly included at its call site;
9754 unlike a non-inlined function, there are no instructions devoted to
9755 the call. @value{GDBN} still pretends that the call site and the
9756 start of the inlined function are different instructions. Stepping to
9757 the call site shows the call site, and then stepping again shows
9758 the first line of the inlined function, even though no additional
9759 instructions are executed.
9761 This makes source-level debugging much clearer; you can see both the
9762 context of the call and then the effect of the call. Only stepping by
9763 a single instruction using @code{stepi} or @code{nexti} does not do
9764 this; single instruction steps always show the inlined body.
9766 There are some ways that @value{GDBN} does not pretend that inlined
9767 function calls are the same as normal calls:
9771 You cannot set breakpoints on inlined functions. @value{GDBN}
9772 either reports that there is no symbol with that name, or else sets the
9773 breakpoint only on non-inlined copies of the function. This limitation
9774 will be removed in a future version of @value{GDBN}; until then,
9775 set a breakpoint by line number on the first line of the inlined
9779 Setting breakpoints at the call site of an inlined function may not
9780 work, because the call site does not contain any code. @value{GDBN}
9781 may incorrectly move the breakpoint to the next line of the enclosing
9782 function, after the call. This limitation will be removed in a future
9783 version of @value{GDBN}; until then, set a breakpoint on an earlier line
9784 or inside the inlined function instead.
9787 @value{GDBN} cannot locate the return value of inlined calls after
9788 using the @code{finish} command. This is a limitation of compiler-generated
9789 debugging information; after @code{finish}, you can step to the next line
9790 and print a variable where your program stored the return value.
9794 @node Tail Call Frames
9795 @section Tail Call Frames
9796 @cindex tail call frames, debugging
9798 Function @code{B} can call function @code{C} in its very last statement. In
9799 unoptimized compilation the call of @code{C} is immediately followed by return
9800 instruction at the end of @code{B} code. Optimizing compiler may replace the
9801 call and return in function @code{B} into one jump to function @code{C}
9802 instead. Such use of a jump instruction is called @dfn{tail call}.
9804 During execution of function @code{C}, there will be no indication in the
9805 function call stack frames that it was tail-called from @code{B}. If function
9806 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
9807 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
9808 some cases @value{GDBN} can determine that @code{C} was tail-called from
9809 @code{B}, and it will then create fictitious call frame for that, with the
9810 return address set up as if @code{B} called @code{C} normally.
9812 This functionality is currently supported only by DWARF 2 debugging format and
9813 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9814 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9817 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
9818 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
9822 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
9824 Stack level 1, frame at 0x7fffffffda30:
9825 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
9826 tail call frame, caller of frame at 0x7fffffffda30
9827 source language c++.
9828 Arglist at unknown address.
9829 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
9832 The detection of all the possible code path executions can find them ambiguous.
9833 There is no execution history stored (possible @ref{Reverse Execution} is never
9834 used for this purpose) and the last known caller could have reached the known
9835 callee by multiple different jump sequences. In such case @value{GDBN} still
9836 tries to show at least all the unambiguous top tail callers and all the
9837 unambiguous bottom tail calees, if any.
9840 @anchor{set debug entry-values}
9841 @item set debug entry-values
9842 @kindex set debug entry-values
9843 When set to on, enables printing of analysis messages for both frame argument
9844 values at function entry and tail calls. It will show all the possible valid
9845 tail calls code paths it has considered. It will also print the intersection
9846 of them with the final unambiguous (possibly partial or even empty) code path
9849 @item show debug entry-values
9850 @kindex show debug entry-values
9851 Show the current state of analysis messages printing for both frame argument
9852 values at function entry and tail calls.
9855 The analysis messages for tail calls can for example show why the virtual tail
9856 call frame for function @code{c} has not been recognized (due to the indirect
9857 reference by variable @code{x}):
9860 static void __attribute__((noinline, noclone)) c (void);
9861 void (*x) (void) = c;
9862 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
9863 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
9864 int main (void) @{ x (); return 0; @}
9866 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
9867 DW_TAG_GNU_call_site 0x40039a in main
9869 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
9872 #1 0x000000000040039a in main () at t.c:5
9875 Another possibility is an ambiguous virtual tail call frames resolution:
9879 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
9880 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
9881 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
9882 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
9883 static void __attribute__((noinline, noclone)) b (void)
9884 @{ if (i) c (); else e (); @}
9885 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
9886 int main (void) @{ a (); return 0; @}
9888 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
9889 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
9890 tailcall: reduced: 0x4004d2(a) |
9893 #1 0x00000000004004d2 in a () at t.c:8
9894 #2 0x0000000000400395 in main () at t.c:9
9897 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
9898 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
9900 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
9901 @ifset HAVE_MAKEINFO_CLICK
9903 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
9904 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
9906 @ifclear HAVE_MAKEINFO_CLICK
9908 @set CALLSEQ1B @value{CALLSEQ1A}
9909 @set CALLSEQ2B @value{CALLSEQ2A}
9912 Frames #0 and #2 are real, #1 is a virtual tail call frame.
9913 The code can have possible execution paths @value{CALLSEQ1B} or
9914 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
9916 @code{initial:} state shows some random possible calling sequence @value{GDBN}
9917 has found. It then finds another possible calling sequcen - that one is
9918 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
9919 printed as the @code{reduced:} calling sequence. That one could have many
9920 futher @code{compare:} and @code{reduced:} statements as long as there remain
9921 any non-ambiguous sequence entries.
9923 For the frame of function @code{b} in both cases there are different possible
9924 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
9925 also ambigous. The only non-ambiguous frame is the one for function @code{a},
9926 therefore this one is displayed to the user while the ambiguous frames are
9929 There can be also reasons why printing of frame argument values at function
9934 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
9935 static void __attribute__((noinline, noclone)) a (int i);
9936 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
9937 static void __attribute__((noinline, noclone)) a (int i)
9938 @{ if (i) b (i - 1); else c (0); @}
9939 int main (void) @{ a (5); return 0; @}
9942 #0 c (i=i@@entry=0) at t.c:2
9943 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
9944 function "a" at 0x400420 can call itself via tail calls
9945 i=<optimized out>) at t.c:6
9946 #2 0x000000000040036e in main () at t.c:7
9949 @value{GDBN} cannot find out from the inferior state if and how many times did
9950 function @code{a} call itself (via function @code{b}) as these calls would be
9951 tail calls. Such tail calls would modify thue @code{i} variable, therefore
9952 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
9953 prints @code{<optimized out>} instead.
9956 @chapter C Preprocessor Macros
9958 Some languages, such as C and C@t{++}, provide a way to define and invoke
9959 ``preprocessor macros'' which expand into strings of tokens.
9960 @value{GDBN} can evaluate expressions containing macro invocations, show
9961 the result of macro expansion, and show a macro's definition, including
9962 where it was defined.
9964 You may need to compile your program specially to provide @value{GDBN}
9965 with information about preprocessor macros. Most compilers do not
9966 include macros in their debugging information, even when you compile
9967 with the @option{-g} flag. @xref{Compilation}.
9969 A program may define a macro at one point, remove that definition later,
9970 and then provide a different definition after that. Thus, at different
9971 points in the program, a macro may have different definitions, or have
9972 no definition at all. If there is a current stack frame, @value{GDBN}
9973 uses the macros in scope at that frame's source code line. Otherwise,
9974 @value{GDBN} uses the macros in scope at the current listing location;
9977 Whenever @value{GDBN} evaluates an expression, it always expands any
9978 macro invocations present in the expression. @value{GDBN} also provides
9979 the following commands for working with macros explicitly.
9983 @kindex macro expand
9984 @cindex macro expansion, showing the results of preprocessor
9985 @cindex preprocessor macro expansion, showing the results of
9986 @cindex expanding preprocessor macros
9987 @item macro expand @var{expression}
9988 @itemx macro exp @var{expression}
9989 Show the results of expanding all preprocessor macro invocations in
9990 @var{expression}. Since @value{GDBN} simply expands macros, but does
9991 not parse the result, @var{expression} need not be a valid expression;
9992 it can be any string of tokens.
9995 @item macro expand-once @var{expression}
9996 @itemx macro exp1 @var{expression}
9997 @cindex expand macro once
9998 @i{(This command is not yet implemented.)} Show the results of
9999 expanding those preprocessor macro invocations that appear explicitly in
10000 @var{expression}. Macro invocations appearing in that expansion are
10001 left unchanged. This command allows you to see the effect of a
10002 particular macro more clearly, without being confused by further
10003 expansions. Since @value{GDBN} simply expands macros, but does not
10004 parse the result, @var{expression} need not be a valid expression; it
10005 can be any string of tokens.
10008 @cindex macro definition, showing
10009 @cindex definition of a macro, showing
10010 @cindex macros, from debug info
10011 @item info macro @var{macro}
10012 Show the current definition of the named @var{macro}, and describe the
10013 source location or compiler command-line where that definition was established.
10015 @kindex info macros
10016 @item info macros @var{linespec}
10017 Show all macro definitions that are in effect at the location specified
10018 by @var{linespec}, and describe the source location or compiler
10019 command-line where those definitions were established.
10021 @kindex info definitions
10022 @item info definitions @var{macro}
10023 Show all definitions of the named @var{macro} that are defined in the current
10024 compilation unit, and describe the source location or compiler command-line
10025 where those definitions were established.
10027 @kindex macro define
10028 @cindex user-defined macros
10029 @cindex defining macros interactively
10030 @cindex macros, user-defined
10031 @item macro define @var{macro} @var{replacement-list}
10032 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
10033 Introduce a definition for a preprocessor macro named @var{macro},
10034 invocations of which are replaced by the tokens given in
10035 @var{replacement-list}. The first form of this command defines an
10036 ``object-like'' macro, which takes no arguments; the second form
10037 defines a ``function-like'' macro, which takes the arguments given in
10040 A definition introduced by this command is in scope in every
10041 expression evaluated in @value{GDBN}, until it is removed with the
10042 @code{macro undef} command, described below. The definition overrides
10043 all definitions for @var{macro} present in the program being debugged,
10044 as well as any previous user-supplied definition.
10046 @kindex macro undef
10047 @item macro undef @var{macro}
10048 Remove any user-supplied definition for the macro named @var{macro}.
10049 This command only affects definitions provided with the @code{macro
10050 define} command, described above; it cannot remove definitions present
10051 in the program being debugged.
10055 List all the macros defined using the @code{macro define} command.
10058 @cindex macros, example of debugging with
10059 Here is a transcript showing the above commands in action. First, we
10060 show our source files:
10065 #include "sample.h"
10068 #define ADD(x) (M + x)
10073 printf ("Hello, world!\n");
10075 printf ("We're so creative.\n");
10077 printf ("Goodbye, world!\n");
10084 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
10085 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
10086 compiler includes information about preprocessor macros in the debugging
10090 $ gcc -gdwarf-2 -g3 sample.c -o sample
10094 Now, we start @value{GDBN} on our sample program:
10098 GNU gdb 2002-05-06-cvs
10099 Copyright 2002 Free Software Foundation, Inc.
10100 GDB is free software, @dots{}
10104 We can expand macros and examine their definitions, even when the
10105 program is not running. @value{GDBN} uses the current listing position
10106 to decide which macro definitions are in scope:
10109 (@value{GDBP}) list main
10112 5 #define ADD(x) (M + x)
10117 10 printf ("Hello, world!\n");
10119 12 printf ("We're so creative.\n");
10120 (@value{GDBP}) info macro ADD
10121 Defined at /home/jimb/gdb/macros/play/sample.c:5
10122 #define ADD(x) (M + x)
10123 (@value{GDBP}) info macro Q
10124 Defined at /home/jimb/gdb/macros/play/sample.h:1
10125 included at /home/jimb/gdb/macros/play/sample.c:2
10127 (@value{GDBP}) macro expand ADD(1)
10128 expands to: (42 + 1)
10129 (@value{GDBP}) macro expand-once ADD(1)
10130 expands to: once (M + 1)
10134 In the example above, note that @code{macro expand-once} expands only
10135 the macro invocation explicit in the original text --- the invocation of
10136 @code{ADD} --- but does not expand the invocation of the macro @code{M},
10137 which was introduced by @code{ADD}.
10139 Once the program is running, @value{GDBN} uses the macro definitions in
10140 force at the source line of the current stack frame:
10143 (@value{GDBP}) break main
10144 Breakpoint 1 at 0x8048370: file sample.c, line 10.
10146 Starting program: /home/jimb/gdb/macros/play/sample
10148 Breakpoint 1, main () at sample.c:10
10149 10 printf ("Hello, world!\n");
10153 At line 10, the definition of the macro @code{N} at line 9 is in force:
10156 (@value{GDBP}) info macro N
10157 Defined at /home/jimb/gdb/macros/play/sample.c:9
10159 (@value{GDBP}) macro expand N Q M
10160 expands to: 28 < 42
10161 (@value{GDBP}) print N Q M
10166 As we step over directives that remove @code{N}'s definition, and then
10167 give it a new definition, @value{GDBN} finds the definition (or lack
10168 thereof) in force at each point:
10171 (@value{GDBP}) next
10173 12 printf ("We're so creative.\n");
10174 (@value{GDBP}) info macro N
10175 The symbol `N' has no definition as a C/C++ preprocessor macro
10176 at /home/jimb/gdb/macros/play/sample.c:12
10177 (@value{GDBP}) next
10179 14 printf ("Goodbye, world!\n");
10180 (@value{GDBP}) info macro N
10181 Defined at /home/jimb/gdb/macros/play/sample.c:13
10183 (@value{GDBP}) macro expand N Q M
10184 expands to: 1729 < 42
10185 (@value{GDBP}) print N Q M
10190 In addition to source files, macros can be defined on the compilation command
10191 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
10192 such a way, @value{GDBN} displays the location of their definition as line zero
10193 of the source file submitted to the compiler.
10196 (@value{GDBP}) info macro __STDC__
10197 Defined at /home/jimb/gdb/macros/play/sample.c:0
10204 @chapter Tracepoints
10205 @c This chapter is based on the documentation written by Michael
10206 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
10208 @cindex tracepoints
10209 In some applications, it is not feasible for the debugger to interrupt
10210 the program's execution long enough for the developer to learn
10211 anything helpful about its behavior. If the program's correctness
10212 depends on its real-time behavior, delays introduced by a debugger
10213 might cause the program to change its behavior drastically, or perhaps
10214 fail, even when the code itself is correct. It is useful to be able
10215 to observe the program's behavior without interrupting it.
10217 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
10218 specify locations in the program, called @dfn{tracepoints}, and
10219 arbitrary expressions to evaluate when those tracepoints are reached.
10220 Later, using the @code{tfind} command, you can examine the values
10221 those expressions had when the program hit the tracepoints. The
10222 expressions may also denote objects in memory---structures or arrays,
10223 for example---whose values @value{GDBN} should record; while visiting
10224 a particular tracepoint, you may inspect those objects as if they were
10225 in memory at that moment. However, because @value{GDBN} records these
10226 values without interacting with you, it can do so quickly and
10227 unobtrusively, hopefully not disturbing the program's behavior.
10229 The tracepoint facility is currently available only for remote
10230 targets. @xref{Targets}. In addition, your remote target must know
10231 how to collect trace data. This functionality is implemented in the
10232 remote stub; however, none of the stubs distributed with @value{GDBN}
10233 support tracepoints as of this writing. The format of the remote
10234 packets used to implement tracepoints are described in @ref{Tracepoint
10237 It is also possible to get trace data from a file, in a manner reminiscent
10238 of corefiles; you specify the filename, and use @code{tfind} to search
10239 through the file. @xref{Trace Files}, for more details.
10241 This chapter describes the tracepoint commands and features.
10244 * Set Tracepoints::
10245 * Analyze Collected Data::
10246 * Tracepoint Variables::
10250 @node Set Tracepoints
10251 @section Commands to Set Tracepoints
10253 Before running such a @dfn{trace experiment}, an arbitrary number of
10254 tracepoints can be set. A tracepoint is actually a special type of
10255 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
10256 standard breakpoint commands. For instance, as with breakpoints,
10257 tracepoint numbers are successive integers starting from one, and many
10258 of the commands associated with tracepoints take the tracepoint number
10259 as their argument, to identify which tracepoint to work on.
10261 For each tracepoint, you can specify, in advance, some arbitrary set
10262 of data that you want the target to collect in the trace buffer when
10263 it hits that tracepoint. The collected data can include registers,
10264 local variables, or global data. Later, you can use @value{GDBN}
10265 commands to examine the values these data had at the time the
10266 tracepoint was hit.
10268 Tracepoints do not support every breakpoint feature. Ignore counts on
10269 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
10270 commands when they are hit. Tracepoints may not be thread-specific
10273 @cindex fast tracepoints
10274 Some targets may support @dfn{fast tracepoints}, which are inserted in
10275 a different way (such as with a jump instead of a trap), that is
10276 faster but possibly restricted in where they may be installed.
10278 @cindex static tracepoints
10279 @cindex markers, static tracepoints
10280 @cindex probing markers, static tracepoints
10281 Regular and fast tracepoints are dynamic tracing facilities, meaning
10282 that they can be used to insert tracepoints at (almost) any location
10283 in the target. Some targets may also support controlling @dfn{static
10284 tracepoints} from @value{GDBN}. With static tracing, a set of
10285 instrumentation points, also known as @dfn{markers}, are embedded in
10286 the target program, and can be activated or deactivated by name or
10287 address. These are usually placed at locations which facilitate
10288 investigating what the target is actually doing. @value{GDBN}'s
10289 support for static tracing includes being able to list instrumentation
10290 points, and attach them with @value{GDBN} defined high level
10291 tracepoints that expose the whole range of convenience of
10292 @value{GDBN}'s tracepoints support. Namely, support for collecting
10293 registers values and values of global or local (to the instrumentation
10294 point) variables; tracepoint conditions and trace state variables.
10295 The act of installing a @value{GDBN} static tracepoint on an
10296 instrumentation point, or marker, is referred to as @dfn{probing} a
10297 static tracepoint marker.
10299 @code{gdbserver} supports tracepoints on some target systems.
10300 @xref{Server,,Tracepoints support in @code{gdbserver}}.
10302 This section describes commands to set tracepoints and associated
10303 conditions and actions.
10306 * Create and Delete Tracepoints::
10307 * Enable and Disable Tracepoints::
10308 * Tracepoint Passcounts::
10309 * Tracepoint Conditions::
10310 * Trace State Variables::
10311 * Tracepoint Actions::
10312 * Listing Tracepoints::
10313 * Listing Static Tracepoint Markers::
10314 * Starting and Stopping Trace Experiments::
10315 * Tracepoint Restrictions::
10318 @node Create and Delete Tracepoints
10319 @subsection Create and Delete Tracepoints
10322 @cindex set tracepoint
10324 @item trace @var{location}
10325 The @code{trace} command is very similar to the @code{break} command.
10326 Its argument @var{location} can be a source line, a function name, or
10327 an address in the target program. @xref{Specify Location}. The
10328 @code{trace} command defines a tracepoint, which is a point in the
10329 target program where the debugger will briefly stop, collect some
10330 data, and then allow the program to continue. Setting a tracepoint or
10331 changing its actions doesn't take effect until the next @code{tstart}
10332 command, and once a trace experiment is running, further changes will
10333 not have any effect until the next trace experiment starts.
10335 Here are some examples of using the @code{trace} command:
10338 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
10340 (@value{GDBP}) @b{trace +2} // 2 lines forward
10342 (@value{GDBP}) @b{trace my_function} // first source line of function
10344 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
10346 (@value{GDBP}) @b{trace *0x2117c4} // an address
10350 You can abbreviate @code{trace} as @code{tr}.
10352 @item trace @var{location} if @var{cond}
10353 Set a tracepoint with condition @var{cond}; evaluate the expression
10354 @var{cond} each time the tracepoint is reached, and collect data only
10355 if the value is nonzero---that is, if @var{cond} evaluates as true.
10356 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
10357 information on tracepoint conditions.
10359 @item ftrace @var{location} [ if @var{cond} ]
10360 @cindex set fast tracepoint
10361 @cindex fast tracepoints, setting
10363 The @code{ftrace} command sets a fast tracepoint. For targets that
10364 support them, fast tracepoints will use a more efficient but possibly
10365 less general technique to trigger data collection, such as a jump
10366 instruction instead of a trap, or some sort of hardware support. It
10367 may not be possible to create a fast tracepoint at the desired
10368 location, in which case the command will exit with an explanatory
10371 @value{GDBN} handles arguments to @code{ftrace} exactly as for
10374 @item strace @var{location} [ if @var{cond} ]
10375 @cindex set static tracepoint
10376 @cindex static tracepoints, setting
10377 @cindex probe static tracepoint marker
10379 The @code{strace} command sets a static tracepoint. For targets that
10380 support it, setting a static tracepoint probes a static
10381 instrumentation point, or marker, found at @var{location}. It may not
10382 be possible to set a static tracepoint at the desired location, in
10383 which case the command will exit with an explanatory message.
10385 @value{GDBN} handles arguments to @code{strace} exactly as for
10386 @code{trace}, with the addition that the user can also specify
10387 @code{-m @var{marker}} as @var{location}. This probes the marker
10388 identified by the @var{marker} string identifier. This identifier
10389 depends on the static tracepoint backend library your program is
10390 using. You can find all the marker identifiers in the @samp{ID} field
10391 of the @code{info static-tracepoint-markers} command output.
10392 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
10393 Markers}. For example, in the following small program using the UST
10399 trace_mark(ust, bar33, "str %s", "FOOBAZ");
10404 the marker id is composed of joining the first two arguments to the
10405 @code{trace_mark} call with a slash, which translates to:
10408 (@value{GDBP}) info static-tracepoint-markers
10409 Cnt Enb ID Address What
10410 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
10416 so you may probe the marker above with:
10419 (@value{GDBP}) strace -m ust/bar33
10422 Static tracepoints accept an extra collect action --- @code{collect
10423 $_sdata}. This collects arbitrary user data passed in the probe point
10424 call to the tracing library. In the UST example above, you'll see
10425 that the third argument to @code{trace_mark} is a printf-like format
10426 string. The user data is then the result of running that formating
10427 string against the following arguments. Note that @code{info
10428 static-tracepoint-markers} command output lists that format string in
10429 the @samp{Data:} field.
10431 You can inspect this data when analyzing the trace buffer, by printing
10432 the $_sdata variable like any other variable available to
10433 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
10436 @cindex last tracepoint number
10437 @cindex recent tracepoint number
10438 @cindex tracepoint number
10439 The convenience variable @code{$tpnum} records the tracepoint number
10440 of the most recently set tracepoint.
10442 @kindex delete tracepoint
10443 @cindex tracepoint deletion
10444 @item delete tracepoint @r{[}@var{num}@r{]}
10445 Permanently delete one or more tracepoints. With no argument, the
10446 default is to delete all tracepoints. Note that the regular
10447 @code{delete} command can remove tracepoints also.
10452 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
10454 (@value{GDBP}) @b{delete trace} // remove all tracepoints
10458 You can abbreviate this command as @code{del tr}.
10461 @node Enable and Disable Tracepoints
10462 @subsection Enable and Disable Tracepoints
10464 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
10467 @kindex disable tracepoint
10468 @item disable tracepoint @r{[}@var{num}@r{]}
10469 Disable tracepoint @var{num}, or all tracepoints if no argument
10470 @var{num} is given. A disabled tracepoint will have no effect during
10471 a trace experiment, but it is not forgotten. You can re-enable
10472 a disabled tracepoint using the @code{enable tracepoint} command.
10473 If the command is issued during a trace experiment and the debug target
10474 has support for disabling tracepoints during a trace experiment, then the
10475 change will be effective immediately. Otherwise, it will be applied to the
10476 next trace experiment.
10478 @kindex enable tracepoint
10479 @item enable tracepoint @r{[}@var{num}@r{]}
10480 Enable tracepoint @var{num}, or all tracepoints. If this command is
10481 issued during a trace experiment and the debug target supports enabling
10482 tracepoints during a trace experiment, then the enabled tracepoints will
10483 become effective immediately. Otherwise, they will become effective the
10484 next time a trace experiment is run.
10487 @node Tracepoint Passcounts
10488 @subsection Tracepoint Passcounts
10492 @cindex tracepoint pass count
10493 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
10494 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
10495 automatically stop a trace experiment. If a tracepoint's passcount is
10496 @var{n}, then the trace experiment will be automatically stopped on
10497 the @var{n}'th time that tracepoint is hit. If the tracepoint number
10498 @var{num} is not specified, the @code{passcount} command sets the
10499 passcount of the most recently defined tracepoint. If no passcount is
10500 given, the trace experiment will run until stopped explicitly by the
10506 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
10507 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
10509 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
10510 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
10511 (@value{GDBP}) @b{trace foo}
10512 (@value{GDBP}) @b{pass 3}
10513 (@value{GDBP}) @b{trace bar}
10514 (@value{GDBP}) @b{pass 2}
10515 (@value{GDBP}) @b{trace baz}
10516 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
10517 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
10518 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
10519 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
10523 @node Tracepoint Conditions
10524 @subsection Tracepoint Conditions
10525 @cindex conditional tracepoints
10526 @cindex tracepoint conditions
10528 The simplest sort of tracepoint collects data every time your program
10529 reaches a specified place. You can also specify a @dfn{condition} for
10530 a tracepoint. A condition is just a Boolean expression in your
10531 programming language (@pxref{Expressions, ,Expressions}). A
10532 tracepoint with a condition evaluates the expression each time your
10533 program reaches it, and data collection happens only if the condition
10536 Tracepoint conditions can be specified when a tracepoint is set, by
10537 using @samp{if} in the arguments to the @code{trace} command.
10538 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
10539 also be set or changed at any time with the @code{condition} command,
10540 just as with breakpoints.
10542 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
10543 the conditional expression itself. Instead, @value{GDBN} encodes the
10544 expression into an agent expression (@pxref{Agent Expressions})
10545 suitable for execution on the target, independently of @value{GDBN}.
10546 Global variables become raw memory locations, locals become stack
10547 accesses, and so forth.
10549 For instance, suppose you have a function that is usually called
10550 frequently, but should not be called after an error has occurred. You
10551 could use the following tracepoint command to collect data about calls
10552 of that function that happen while the error code is propagating
10553 through the program; an unconditional tracepoint could end up
10554 collecting thousands of useless trace frames that you would have to
10558 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
10561 @node Trace State Variables
10562 @subsection Trace State Variables
10563 @cindex trace state variables
10565 A @dfn{trace state variable} is a special type of variable that is
10566 created and managed by target-side code. The syntax is the same as
10567 that for GDB's convenience variables (a string prefixed with ``$''),
10568 but they are stored on the target. They must be created explicitly,
10569 using a @code{tvariable} command. They are always 64-bit signed
10572 Trace state variables are remembered by @value{GDBN}, and downloaded
10573 to the target along with tracepoint information when the trace
10574 experiment starts. There are no intrinsic limits on the number of
10575 trace state variables, beyond memory limitations of the target.
10577 @cindex convenience variables, and trace state variables
10578 Although trace state variables are managed by the target, you can use
10579 them in print commands and expressions as if they were convenience
10580 variables; @value{GDBN} will get the current value from the target
10581 while the trace experiment is running. Trace state variables share
10582 the same namespace as other ``$'' variables, which means that you
10583 cannot have trace state variables with names like @code{$23} or
10584 @code{$pc}, nor can you have a trace state variable and a convenience
10585 variable with the same name.
10589 @item tvariable $@var{name} [ = @var{expression} ]
10591 The @code{tvariable} command creates a new trace state variable named
10592 @code{$@var{name}}, and optionally gives it an initial value of
10593 @var{expression}. @var{expression} is evaluated when this command is
10594 entered; the result will be converted to an integer if possible,
10595 otherwise @value{GDBN} will report an error. A subsequent
10596 @code{tvariable} command specifying the same name does not create a
10597 variable, but instead assigns the supplied initial value to the
10598 existing variable of that name, overwriting any previous initial
10599 value. The default initial value is 0.
10601 @item info tvariables
10602 @kindex info tvariables
10603 List all the trace state variables along with their initial values.
10604 Their current values may also be displayed, if the trace experiment is
10607 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
10608 @kindex delete tvariable
10609 Delete the given trace state variables, or all of them if no arguments
10614 @node Tracepoint Actions
10615 @subsection Tracepoint Action Lists
10619 @cindex tracepoint actions
10620 @item actions @r{[}@var{num}@r{]}
10621 This command will prompt for a list of actions to be taken when the
10622 tracepoint is hit. If the tracepoint number @var{num} is not
10623 specified, this command sets the actions for the one that was most
10624 recently defined (so that you can define a tracepoint and then say
10625 @code{actions} without bothering about its number). You specify the
10626 actions themselves on the following lines, one action at a time, and
10627 terminate the actions list with a line containing just @code{end}. So
10628 far, the only defined actions are @code{collect}, @code{teval}, and
10629 @code{while-stepping}.
10631 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
10632 Commands, ,Breakpoint Command Lists}), except that only the defined
10633 actions are allowed; any other @value{GDBN} command is rejected.
10635 @cindex remove actions from a tracepoint
10636 To remove all actions from a tracepoint, type @samp{actions @var{num}}
10637 and follow it immediately with @samp{end}.
10640 (@value{GDBP}) @b{collect @var{data}} // collect some data
10642 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
10644 (@value{GDBP}) @b{end} // signals the end of actions.
10647 In the following example, the action list begins with @code{collect}
10648 commands indicating the things to be collected when the tracepoint is
10649 hit. Then, in order to single-step and collect additional data
10650 following the tracepoint, a @code{while-stepping} command is used,
10651 followed by the list of things to be collected after each step in a
10652 sequence of single steps. The @code{while-stepping} command is
10653 terminated by its own separate @code{end} command. Lastly, the action
10654 list is terminated by an @code{end} command.
10657 (@value{GDBP}) @b{trace foo}
10658 (@value{GDBP}) @b{actions}
10659 Enter actions for tracepoint 1, one per line:
10662 > while-stepping 12
10663 > collect $pc, arr[i]
10668 @kindex collect @r{(tracepoints)}
10669 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
10670 Collect values of the given expressions when the tracepoint is hit.
10671 This command accepts a comma-separated list of any valid expressions.
10672 In addition to global, static, or local variables, the following
10673 special arguments are supported:
10677 Collect all registers.
10680 Collect all function arguments.
10683 Collect all local variables.
10686 Collect the return address. This is helpful if you want to see more
10690 @vindex $_sdata@r{, collect}
10691 Collect static tracepoint marker specific data. Only available for
10692 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
10693 Lists}. On the UST static tracepoints library backend, an
10694 instrumentation point resembles a @code{printf} function call. The
10695 tracing library is able to collect user specified data formatted to a
10696 character string using the format provided by the programmer that
10697 instrumented the program. Other backends have similar mechanisms.
10698 Here's an example of a UST marker call:
10701 const char master_name[] = "$your_name";
10702 trace_mark(channel1, marker1, "hello %s", master_name)
10705 In this case, collecting @code{$_sdata} collects the string
10706 @samp{hello $yourname}. When analyzing the trace buffer, you can
10707 inspect @samp{$_sdata} like any other variable available to
10711 You can give several consecutive @code{collect} commands, each one
10712 with a single argument, or one @code{collect} command with several
10713 arguments separated by commas; the effect is the same.
10715 The optional @var{mods} changes the usual handling of the arguments.
10716 @code{s} requests that pointers to chars be handled as strings, in
10717 particular collecting the contents of the memory being pointed at, up
10718 to the first zero. The upper bound is by default the value of the
10719 @code{print elements} variable; if @code{s} is followed by a decimal
10720 number, that is the upper bound instead. So for instance
10721 @samp{collect/s25 mystr} collects as many as 25 characters at
10724 The command @code{info scope} (@pxref{Symbols, info scope}) is
10725 particularly useful for figuring out what data to collect.
10727 @kindex teval @r{(tracepoints)}
10728 @item teval @var{expr1}, @var{expr2}, @dots{}
10729 Evaluate the given expressions when the tracepoint is hit. This
10730 command accepts a comma-separated list of expressions. The results
10731 are discarded, so this is mainly useful for assigning values to trace
10732 state variables (@pxref{Trace State Variables}) without adding those
10733 values to the trace buffer, as would be the case if the @code{collect}
10736 @kindex while-stepping @r{(tracepoints)}
10737 @item while-stepping @var{n}
10738 Perform @var{n} single-step instruction traces after the tracepoint,
10739 collecting new data after each step. The @code{while-stepping}
10740 command is followed by the list of what to collect while stepping
10741 (followed by its own @code{end} command):
10744 > while-stepping 12
10745 > collect $regs, myglobal
10751 Note that @code{$pc} is not automatically collected by
10752 @code{while-stepping}; you need to explicitly collect that register if
10753 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
10756 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
10757 @kindex set default-collect
10758 @cindex default collection action
10759 This variable is a list of expressions to collect at each tracepoint
10760 hit. It is effectively an additional @code{collect} action prepended
10761 to every tracepoint action list. The expressions are parsed
10762 individually for each tracepoint, so for instance a variable named
10763 @code{xyz} may be interpreted as a global for one tracepoint, and a
10764 local for another, as appropriate to the tracepoint's location.
10766 @item show default-collect
10767 @kindex show default-collect
10768 Show the list of expressions that are collected by default at each
10773 @node Listing Tracepoints
10774 @subsection Listing Tracepoints
10777 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
10778 @kindex info tp @r{[}@var{n}@dots{}@r{]}
10779 @cindex information about tracepoints
10780 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
10781 Display information about the tracepoint @var{num}. If you don't
10782 specify a tracepoint number, displays information about all the
10783 tracepoints defined so far. The format is similar to that used for
10784 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
10785 command, simply restricting itself to tracepoints.
10787 A tracepoint's listing may include additional information specific to
10792 its passcount as given by the @code{passcount @var{n}} command
10796 (@value{GDBP}) @b{info trace}
10797 Num Type Disp Enb Address What
10798 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
10800 collect globfoo, $regs
10809 This command can be abbreviated @code{info tp}.
10812 @node Listing Static Tracepoint Markers
10813 @subsection Listing Static Tracepoint Markers
10816 @kindex info static-tracepoint-markers
10817 @cindex information about static tracepoint markers
10818 @item info static-tracepoint-markers
10819 Display information about all static tracepoint markers defined in the
10822 For each marker, the following columns are printed:
10826 An incrementing counter, output to help readability. This is not a
10829 The marker ID, as reported by the target.
10830 @item Enabled or Disabled
10831 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
10832 that are not enabled.
10834 Where the marker is in your program, as a memory address.
10836 Where the marker is in the source for your program, as a file and line
10837 number. If the debug information included in the program does not
10838 allow @value{GDBN} to locate the source of the marker, this column
10839 will be left blank.
10843 In addition, the following information may be printed for each marker:
10847 User data passed to the tracing library by the marker call. In the
10848 UST backend, this is the format string passed as argument to the
10850 @item Static tracepoints probing the marker
10851 The list of static tracepoints attached to the marker.
10855 (@value{GDBP}) info static-tracepoint-markers
10856 Cnt ID Enb Address What
10857 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
10858 Data: number1 %d number2 %d
10859 Probed by static tracepoints: #2
10860 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
10866 @node Starting and Stopping Trace Experiments
10867 @subsection Starting and Stopping Trace Experiments
10871 @cindex start a new trace experiment
10872 @cindex collected data discarded
10874 This command takes no arguments. It starts the trace experiment, and
10875 begins collecting data. This has the side effect of discarding all
10876 the data collected in the trace buffer during the previous trace
10880 @cindex stop a running trace experiment
10882 This command takes no arguments. It ends the trace experiment, and
10883 stops collecting data.
10885 @strong{Note}: a trace experiment and data collection may stop
10886 automatically if any tracepoint's passcount is reached
10887 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
10890 @cindex status of trace data collection
10891 @cindex trace experiment, status of
10893 This command displays the status of the current trace data
10897 Here is an example of the commands we described so far:
10900 (@value{GDBP}) @b{trace gdb_c_test}
10901 (@value{GDBP}) @b{actions}
10902 Enter actions for tracepoint #1, one per line.
10903 > collect $regs,$locals,$args
10904 > while-stepping 11
10908 (@value{GDBP}) @b{tstart}
10909 [time passes @dots{}]
10910 (@value{GDBP}) @b{tstop}
10913 @anchor{disconnected tracing}
10914 @cindex disconnected tracing
10915 You can choose to continue running the trace experiment even if
10916 @value{GDBN} disconnects from the target, voluntarily or
10917 involuntarily. For commands such as @code{detach}, the debugger will
10918 ask what you want to do with the trace. But for unexpected
10919 terminations (@value{GDBN} crash, network outage), it would be
10920 unfortunate to lose hard-won trace data, so the variable
10921 @code{disconnected-tracing} lets you decide whether the trace should
10922 continue running without @value{GDBN}.
10925 @item set disconnected-tracing on
10926 @itemx set disconnected-tracing off
10927 @kindex set disconnected-tracing
10928 Choose whether a tracing run should continue to run if @value{GDBN}
10929 has disconnected from the target. Note that @code{detach} or
10930 @code{quit} will ask you directly what to do about a running trace no
10931 matter what this variable's setting, so the variable is mainly useful
10932 for handling unexpected situations, such as loss of the network.
10934 @item show disconnected-tracing
10935 @kindex show disconnected-tracing
10936 Show the current choice for disconnected tracing.
10940 When you reconnect to the target, the trace experiment may or may not
10941 still be running; it might have filled the trace buffer in the
10942 meantime, or stopped for one of the other reasons. If it is running,
10943 it will continue after reconnection.
10945 Upon reconnection, the target will upload information about the
10946 tracepoints in effect. @value{GDBN} will then compare that
10947 information to the set of tracepoints currently defined, and attempt
10948 to match them up, allowing for the possibility that the numbers may
10949 have changed due to creation and deletion in the meantime. If one of
10950 the target's tracepoints does not match any in @value{GDBN}, the
10951 debugger will create a new tracepoint, so that you have a number with
10952 which to specify that tracepoint. This matching-up process is
10953 necessarily heuristic, and it may result in useless tracepoints being
10954 created; you may simply delete them if they are of no use.
10956 @cindex circular trace buffer
10957 If your target agent supports a @dfn{circular trace buffer}, then you
10958 can run a trace experiment indefinitely without filling the trace
10959 buffer; when space runs out, the agent deletes already-collected trace
10960 frames, oldest first, until there is enough room to continue
10961 collecting. This is especially useful if your tracepoints are being
10962 hit too often, and your trace gets terminated prematurely because the
10963 buffer is full. To ask for a circular trace buffer, simply set
10964 @samp{circular-trace-buffer} to on. You can set this at any time,
10965 including during tracing; if the agent can do it, it will change
10966 buffer handling on the fly, otherwise it will not take effect until
10970 @item set circular-trace-buffer on
10971 @itemx set circular-trace-buffer off
10972 @kindex set circular-trace-buffer
10973 Choose whether a tracing run should use a linear or circular buffer
10974 for trace data. A linear buffer will not lose any trace data, but may
10975 fill up prematurely, while a circular buffer will discard old trace
10976 data, but it will have always room for the latest tracepoint hits.
10978 @item show circular-trace-buffer
10979 @kindex show circular-trace-buffer
10980 Show the current choice for the trace buffer. Note that this may not
10981 match the agent's current buffer handling, nor is it guaranteed to
10982 match the setting that might have been in effect during a past run,
10983 for instance if you are looking at frames from a trace file.
10987 @node Tracepoint Restrictions
10988 @subsection Tracepoint Restrictions
10990 @cindex tracepoint restrictions
10991 There are a number of restrictions on the use of tracepoints. As
10992 described above, tracepoint data gathering occurs on the target
10993 without interaction from @value{GDBN}. Thus the full capabilities of
10994 the debugger are not available during data gathering, and then at data
10995 examination time, you will be limited by only having what was
10996 collected. The following items describe some common problems, but it
10997 is not exhaustive, and you may run into additional difficulties not
11003 Tracepoint expressions are intended to gather objects (lvalues). Thus
11004 the full flexibility of GDB's expression evaluator is not available.
11005 You cannot call functions, cast objects to aggregate types, access
11006 convenience variables or modify values (except by assignment to trace
11007 state variables). Some language features may implicitly call
11008 functions (for instance Objective-C fields with accessors), and therefore
11009 cannot be collected either.
11012 Collection of local variables, either individually or in bulk with
11013 @code{$locals} or @code{$args}, during @code{while-stepping} may
11014 behave erratically. The stepping action may enter a new scope (for
11015 instance by stepping into a function), or the location of the variable
11016 may change (for instance it is loaded into a register). The
11017 tracepoint data recorded uses the location information for the
11018 variables that is correct for the tracepoint location. When the
11019 tracepoint is created, it is not possible, in general, to determine
11020 where the steps of a @code{while-stepping} sequence will advance the
11021 program---particularly if a conditional branch is stepped.
11024 Collection of an incompletely-initialized or partially-destroyed object
11025 may result in something that @value{GDBN} cannot display, or displays
11026 in a misleading way.
11029 When @value{GDBN} displays a pointer to character it automatically
11030 dereferences the pointer to also display characters of the string
11031 being pointed to. However, collecting the pointer during tracing does
11032 not automatically collect the string. You need to explicitly
11033 dereference the pointer and provide size information if you want to
11034 collect not only the pointer, but the memory pointed to. For example,
11035 @code{*ptr@@50} can be used to collect the 50 element array pointed to
11039 It is not possible to collect a complete stack backtrace at a
11040 tracepoint. Instead, you may collect the registers and a few hundred
11041 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
11042 (adjust to use the name of the actual stack pointer register on your
11043 target architecture, and the amount of stack you wish to capture).
11044 Then the @code{backtrace} command will show a partial backtrace when
11045 using a trace frame. The number of stack frames that can be examined
11046 depends on the sizes of the frames in the collected stack. Note that
11047 if you ask for a block so large that it goes past the bottom of the
11048 stack, the target agent may report an error trying to read from an
11052 If you do not collect registers at a tracepoint, @value{GDBN} can
11053 infer that the value of @code{$pc} must be the same as the address of
11054 the tracepoint and use that when you are looking at a trace frame
11055 for that tracepoint. However, this cannot work if the tracepoint has
11056 multiple locations (for instance if it was set in a function that was
11057 inlined), or if it has a @code{while-stepping} loop. In those cases
11058 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
11063 @node Analyze Collected Data
11064 @section Using the Collected Data
11066 After the tracepoint experiment ends, you use @value{GDBN} commands
11067 for examining the trace data. The basic idea is that each tracepoint
11068 collects a trace @dfn{snapshot} every time it is hit and another
11069 snapshot every time it single-steps. All these snapshots are
11070 consecutively numbered from zero and go into a buffer, and you can
11071 examine them later. The way you examine them is to @dfn{focus} on a
11072 specific trace snapshot. When the remote stub is focused on a trace
11073 snapshot, it will respond to all @value{GDBN} requests for memory and
11074 registers by reading from the buffer which belongs to that snapshot,
11075 rather than from @emph{real} memory or registers of the program being
11076 debugged. This means that @strong{all} @value{GDBN} commands
11077 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
11078 behave as if we were currently debugging the program state as it was
11079 when the tracepoint occurred. Any requests for data that are not in
11080 the buffer will fail.
11083 * tfind:: How to select a trace snapshot
11084 * tdump:: How to display all data for a snapshot
11085 * save tracepoints:: How to save tracepoints for a future run
11089 @subsection @code{tfind @var{n}}
11092 @cindex select trace snapshot
11093 @cindex find trace snapshot
11094 The basic command for selecting a trace snapshot from the buffer is
11095 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
11096 counting from zero. If no argument @var{n} is given, the next
11097 snapshot is selected.
11099 Here are the various forms of using the @code{tfind} command.
11103 Find the first snapshot in the buffer. This is a synonym for
11104 @code{tfind 0} (since 0 is the number of the first snapshot).
11107 Stop debugging trace snapshots, resume @emph{live} debugging.
11110 Same as @samp{tfind none}.
11113 No argument means find the next trace snapshot.
11116 Find the previous trace snapshot before the current one. This permits
11117 retracing earlier steps.
11119 @item tfind tracepoint @var{num}
11120 Find the next snapshot associated with tracepoint @var{num}. Search
11121 proceeds forward from the last examined trace snapshot. If no
11122 argument @var{num} is given, it means find the next snapshot collected
11123 for the same tracepoint as the current snapshot.
11125 @item tfind pc @var{addr}
11126 Find the next snapshot associated with the value @var{addr} of the
11127 program counter. Search proceeds forward from the last examined trace
11128 snapshot. If no argument @var{addr} is given, it means find the next
11129 snapshot with the same value of PC as the current snapshot.
11131 @item tfind outside @var{addr1}, @var{addr2}
11132 Find the next snapshot whose PC is outside the given range of
11133 addresses (exclusive).
11135 @item tfind range @var{addr1}, @var{addr2}
11136 Find the next snapshot whose PC is between @var{addr1} and
11137 @var{addr2} (inclusive).
11139 @item tfind line @r{[}@var{file}:@r{]}@var{n}
11140 Find the next snapshot associated with the source line @var{n}. If
11141 the optional argument @var{file} is given, refer to line @var{n} in
11142 that source file. Search proceeds forward from the last examined
11143 trace snapshot. If no argument @var{n} is given, it means find the
11144 next line other than the one currently being examined; thus saying
11145 @code{tfind line} repeatedly can appear to have the same effect as
11146 stepping from line to line in a @emph{live} debugging session.
11149 The default arguments for the @code{tfind} commands are specifically
11150 designed to make it easy to scan through the trace buffer. For
11151 instance, @code{tfind} with no argument selects the next trace
11152 snapshot, and @code{tfind -} with no argument selects the previous
11153 trace snapshot. So, by giving one @code{tfind} command, and then
11154 simply hitting @key{RET} repeatedly you can examine all the trace
11155 snapshots in order. Or, by saying @code{tfind -} and then hitting
11156 @key{RET} repeatedly you can examine the snapshots in reverse order.
11157 The @code{tfind line} command with no argument selects the snapshot
11158 for the next source line executed. The @code{tfind pc} command with
11159 no argument selects the next snapshot with the same program counter
11160 (PC) as the current frame. The @code{tfind tracepoint} command with
11161 no argument selects the next trace snapshot collected by the same
11162 tracepoint as the current one.
11164 In addition to letting you scan through the trace buffer manually,
11165 these commands make it easy to construct @value{GDBN} scripts that
11166 scan through the trace buffer and print out whatever collected data
11167 you are interested in. Thus, if we want to examine the PC, FP, and SP
11168 registers from each trace frame in the buffer, we can say this:
11171 (@value{GDBP}) @b{tfind start}
11172 (@value{GDBP}) @b{while ($trace_frame != -1)}
11173 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
11174 $trace_frame, $pc, $sp, $fp
11178 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
11179 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
11180 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
11181 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
11182 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
11183 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
11184 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
11185 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
11186 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
11187 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
11188 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
11191 Or, if we want to examine the variable @code{X} at each source line in
11195 (@value{GDBP}) @b{tfind start}
11196 (@value{GDBP}) @b{while ($trace_frame != -1)}
11197 > printf "Frame %d, X == %d\n", $trace_frame, X
11207 @subsection @code{tdump}
11209 @cindex dump all data collected at tracepoint
11210 @cindex tracepoint data, display
11212 This command takes no arguments. It prints all the data collected at
11213 the current trace snapshot.
11216 (@value{GDBP}) @b{trace 444}
11217 (@value{GDBP}) @b{actions}
11218 Enter actions for tracepoint #2, one per line:
11219 > collect $regs, $locals, $args, gdb_long_test
11222 (@value{GDBP}) @b{tstart}
11224 (@value{GDBP}) @b{tfind line 444}
11225 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
11227 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
11229 (@value{GDBP}) @b{tdump}
11230 Data collected at tracepoint 2, trace frame 1:
11231 d0 0xc4aa0085 -995491707
11235 d4 0x71aea3d 119204413
11238 d7 0x380035 3670069
11239 a0 0x19e24a 1696330
11240 a1 0x3000668 50333288
11242 a3 0x322000 3284992
11243 a4 0x3000698 50333336
11244 a5 0x1ad3cc 1758156
11245 fp 0x30bf3c 0x30bf3c
11246 sp 0x30bf34 0x30bf34
11248 pc 0x20b2c8 0x20b2c8
11252 p = 0x20e5b4 "gdb-test"
11259 gdb_long_test = 17 '\021'
11264 @code{tdump} works by scanning the tracepoint's current collection
11265 actions and printing the value of each expression listed. So
11266 @code{tdump} can fail, if after a run, you change the tracepoint's
11267 actions to mention variables that were not collected during the run.
11269 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
11270 uses the collected value of @code{$pc} to distinguish between trace
11271 frames that were collected at the tracepoint hit, and frames that were
11272 collected while stepping. This allows it to correctly choose whether
11273 to display the basic list of collections, or the collections from the
11274 body of the while-stepping loop. However, if @code{$pc} was not collected,
11275 then @code{tdump} will always attempt to dump using the basic collection
11276 list, and may fail if a while-stepping frame does not include all the
11277 same data that is collected at the tracepoint hit.
11278 @c This is getting pretty arcane, example would be good.
11280 @node save tracepoints
11281 @subsection @code{save tracepoints @var{filename}}
11282 @kindex save tracepoints
11283 @kindex save-tracepoints
11284 @cindex save tracepoints for future sessions
11286 This command saves all current tracepoint definitions together with
11287 their actions and passcounts, into a file @file{@var{filename}}
11288 suitable for use in a later debugging session. To read the saved
11289 tracepoint definitions, use the @code{source} command (@pxref{Command
11290 Files}). The @w{@code{save-tracepoints}} command is a deprecated
11291 alias for @w{@code{save tracepoints}}
11293 @node Tracepoint Variables
11294 @section Convenience Variables for Tracepoints
11295 @cindex tracepoint variables
11296 @cindex convenience variables for tracepoints
11299 @vindex $trace_frame
11300 @item (int) $trace_frame
11301 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
11302 snapshot is selected.
11304 @vindex $tracepoint
11305 @item (int) $tracepoint
11306 The tracepoint for the current trace snapshot.
11308 @vindex $trace_line
11309 @item (int) $trace_line
11310 The line number for the current trace snapshot.
11312 @vindex $trace_file
11313 @item (char []) $trace_file
11314 The source file for the current trace snapshot.
11316 @vindex $trace_func
11317 @item (char []) $trace_func
11318 The name of the function containing @code{$tracepoint}.
11321 Note: @code{$trace_file} is not suitable for use in @code{printf},
11322 use @code{output} instead.
11324 Here's a simple example of using these convenience variables for
11325 stepping through all the trace snapshots and printing some of their
11326 data. Note that these are not the same as trace state variables,
11327 which are managed by the target.
11330 (@value{GDBP}) @b{tfind start}
11332 (@value{GDBP}) @b{while $trace_frame != -1}
11333 > output $trace_file
11334 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
11340 @section Using Trace Files
11341 @cindex trace files
11343 In some situations, the target running a trace experiment may no
11344 longer be available; perhaps it crashed, or the hardware was needed
11345 for a different activity. To handle these cases, you can arrange to
11346 dump the trace data into a file, and later use that file as a source
11347 of trace data, via the @code{target tfile} command.
11352 @item tsave [ -r ] @var{filename}
11353 Save the trace data to @var{filename}. By default, this command
11354 assumes that @var{filename} refers to the host filesystem, so if
11355 necessary @value{GDBN} will copy raw trace data up from the target and
11356 then save it. If the target supports it, you can also supply the
11357 optional argument @code{-r} (``remote'') to direct the target to save
11358 the data directly into @var{filename} in its own filesystem, which may be
11359 more efficient if the trace buffer is very large. (Note, however, that
11360 @code{target tfile} can only read from files accessible to the host.)
11362 @kindex target tfile
11364 @item target tfile @var{filename}
11365 Use the file named @var{filename} as a source of trace data. Commands
11366 that examine data work as they do with a live target, but it is not
11367 possible to run any new trace experiments. @code{tstatus} will report
11368 the state of the trace run at the moment the data was saved, as well
11369 as the current trace frame you are examining. @var{filename} must be
11370 on a filesystem accessible to the host.
11375 @chapter Debugging Programs That Use Overlays
11378 If your program is too large to fit completely in your target system's
11379 memory, you can sometimes use @dfn{overlays} to work around this
11380 problem. @value{GDBN} provides some support for debugging programs that
11384 * How Overlays Work:: A general explanation of overlays.
11385 * Overlay Commands:: Managing overlays in @value{GDBN}.
11386 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
11387 mapped by asking the inferior.
11388 * Overlay Sample Program:: A sample program using overlays.
11391 @node How Overlays Work
11392 @section How Overlays Work
11393 @cindex mapped overlays
11394 @cindex unmapped overlays
11395 @cindex load address, overlay's
11396 @cindex mapped address
11397 @cindex overlay area
11399 Suppose you have a computer whose instruction address space is only 64
11400 kilobytes long, but which has much more memory which can be accessed by
11401 other means: special instructions, segment registers, or memory
11402 management hardware, for example. Suppose further that you want to
11403 adapt a program which is larger than 64 kilobytes to run on this system.
11405 One solution is to identify modules of your program which are relatively
11406 independent, and need not call each other directly; call these modules
11407 @dfn{overlays}. Separate the overlays from the main program, and place
11408 their machine code in the larger memory. Place your main program in
11409 instruction memory, but leave at least enough space there to hold the
11410 largest overlay as well.
11412 Now, to call a function located in an overlay, you must first copy that
11413 overlay's machine code from the large memory into the space set aside
11414 for it in the instruction memory, and then jump to its entry point
11417 @c NB: In the below the mapped area's size is greater or equal to the
11418 @c size of all overlays. This is intentional to remind the developer
11419 @c that overlays don't necessarily need to be the same size.
11423 Data Instruction Larger
11424 Address Space Address Space Address Space
11425 +-----------+ +-----------+ +-----------+
11427 +-----------+ +-----------+ +-----------+<-- overlay 1
11428 | program | | main | .----| overlay 1 | load address
11429 | variables | | program | | +-----------+
11430 | and heap | | | | | |
11431 +-----------+ | | | +-----------+<-- overlay 2
11432 | | +-----------+ | | | load address
11433 +-----------+ | | | .-| overlay 2 |
11435 mapped --->+-----------+ | | +-----------+
11436 address | | | | | |
11437 | overlay | <-' | | |
11438 | area | <---' +-----------+<-- overlay 3
11439 | | <---. | | load address
11440 +-----------+ `--| overlay 3 |
11447 @anchor{A code overlay}A code overlay
11451 The diagram (@pxref{A code overlay}) shows a system with separate data
11452 and instruction address spaces. To map an overlay, the program copies
11453 its code from the larger address space to the instruction address space.
11454 Since the overlays shown here all use the same mapped address, only one
11455 may be mapped at a time. For a system with a single address space for
11456 data and instructions, the diagram would be similar, except that the
11457 program variables and heap would share an address space with the main
11458 program and the overlay area.
11460 An overlay loaded into instruction memory and ready for use is called a
11461 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
11462 instruction memory. An overlay not present (or only partially present)
11463 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
11464 is its address in the larger memory. The mapped address is also called
11465 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
11466 called the @dfn{load memory address}, or @dfn{LMA}.
11468 Unfortunately, overlays are not a completely transparent way to adapt a
11469 program to limited instruction memory. They introduce a new set of
11470 global constraints you must keep in mind as you design your program:
11475 Before calling or returning to a function in an overlay, your program
11476 must make sure that overlay is actually mapped. Otherwise, the call or
11477 return will transfer control to the right address, but in the wrong
11478 overlay, and your program will probably crash.
11481 If the process of mapping an overlay is expensive on your system, you
11482 will need to choose your overlays carefully to minimize their effect on
11483 your program's performance.
11486 The executable file you load onto your system must contain each
11487 overlay's instructions, appearing at the overlay's load address, not its
11488 mapped address. However, each overlay's instructions must be relocated
11489 and its symbols defined as if the overlay were at its mapped address.
11490 You can use GNU linker scripts to specify different load and relocation
11491 addresses for pieces of your program; see @ref{Overlay Description,,,
11492 ld.info, Using ld: the GNU linker}.
11495 The procedure for loading executable files onto your system must be able
11496 to load their contents into the larger address space as well as the
11497 instruction and data spaces.
11501 The overlay system described above is rather simple, and could be
11502 improved in many ways:
11507 If your system has suitable bank switch registers or memory management
11508 hardware, you could use those facilities to make an overlay's load area
11509 contents simply appear at their mapped address in instruction space.
11510 This would probably be faster than copying the overlay to its mapped
11511 area in the usual way.
11514 If your overlays are small enough, you could set aside more than one
11515 overlay area, and have more than one overlay mapped at a time.
11518 You can use overlays to manage data, as well as instructions. In
11519 general, data overlays are even less transparent to your design than
11520 code overlays: whereas code overlays only require care when you call or
11521 return to functions, data overlays require care every time you access
11522 the data. Also, if you change the contents of a data overlay, you
11523 must copy its contents back out to its load address before you can copy a
11524 different data overlay into the same mapped area.
11529 @node Overlay Commands
11530 @section Overlay Commands
11532 To use @value{GDBN}'s overlay support, each overlay in your program must
11533 correspond to a separate section of the executable file. The section's
11534 virtual memory address and load memory address must be the overlay's
11535 mapped and load addresses. Identifying overlays with sections allows
11536 @value{GDBN} to determine the appropriate address of a function or
11537 variable, depending on whether the overlay is mapped or not.
11539 @value{GDBN}'s overlay commands all start with the word @code{overlay};
11540 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
11545 Disable @value{GDBN}'s overlay support. When overlay support is
11546 disabled, @value{GDBN} assumes that all functions and variables are
11547 always present at their mapped addresses. By default, @value{GDBN}'s
11548 overlay support is disabled.
11550 @item overlay manual
11551 @cindex manual overlay debugging
11552 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
11553 relies on you to tell it which overlays are mapped, and which are not,
11554 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
11555 commands described below.
11557 @item overlay map-overlay @var{overlay}
11558 @itemx overlay map @var{overlay}
11559 @cindex map an overlay
11560 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
11561 be the name of the object file section containing the overlay. When an
11562 overlay is mapped, @value{GDBN} assumes it can find the overlay's
11563 functions and variables at their mapped addresses. @value{GDBN} assumes
11564 that any other overlays whose mapped ranges overlap that of
11565 @var{overlay} are now unmapped.
11567 @item overlay unmap-overlay @var{overlay}
11568 @itemx overlay unmap @var{overlay}
11569 @cindex unmap an overlay
11570 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
11571 must be the name of the object file section containing the overlay.
11572 When an overlay is unmapped, @value{GDBN} assumes it can find the
11573 overlay's functions and variables at their load addresses.
11576 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
11577 consults a data structure the overlay manager maintains in the inferior
11578 to see which overlays are mapped. For details, see @ref{Automatic
11579 Overlay Debugging}.
11581 @item overlay load-target
11582 @itemx overlay load
11583 @cindex reloading the overlay table
11584 Re-read the overlay table from the inferior. Normally, @value{GDBN}
11585 re-reads the table @value{GDBN} automatically each time the inferior
11586 stops, so this command should only be necessary if you have changed the
11587 overlay mapping yourself using @value{GDBN}. This command is only
11588 useful when using automatic overlay debugging.
11590 @item overlay list-overlays
11591 @itemx overlay list
11592 @cindex listing mapped overlays
11593 Display a list of the overlays currently mapped, along with their mapped
11594 addresses, load addresses, and sizes.
11598 Normally, when @value{GDBN} prints a code address, it includes the name
11599 of the function the address falls in:
11602 (@value{GDBP}) print main
11603 $3 = @{int ()@} 0x11a0 <main>
11606 When overlay debugging is enabled, @value{GDBN} recognizes code in
11607 unmapped overlays, and prints the names of unmapped functions with
11608 asterisks around them. For example, if @code{foo} is a function in an
11609 unmapped overlay, @value{GDBN} prints it this way:
11612 (@value{GDBP}) overlay list
11613 No sections are mapped.
11614 (@value{GDBP}) print foo
11615 $5 = @{int (int)@} 0x100000 <*foo*>
11618 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
11622 (@value{GDBP}) overlay list
11623 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
11624 mapped at 0x1016 - 0x104a
11625 (@value{GDBP}) print foo
11626 $6 = @{int (int)@} 0x1016 <foo>
11629 When overlay debugging is enabled, @value{GDBN} can find the correct
11630 address for functions and variables in an overlay, whether or not the
11631 overlay is mapped. This allows most @value{GDBN} commands, like
11632 @code{break} and @code{disassemble}, to work normally, even on unmapped
11633 code. However, @value{GDBN}'s breakpoint support has some limitations:
11637 @cindex breakpoints in overlays
11638 @cindex overlays, setting breakpoints in
11639 You can set breakpoints in functions in unmapped overlays, as long as
11640 @value{GDBN} can write to the overlay at its load address.
11642 @value{GDBN} can not set hardware or simulator-based breakpoints in
11643 unmapped overlays. However, if you set a breakpoint at the end of your
11644 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
11645 you are using manual overlay management), @value{GDBN} will re-set its
11646 breakpoints properly.
11650 @node Automatic Overlay Debugging
11651 @section Automatic Overlay Debugging
11652 @cindex automatic overlay debugging
11654 @value{GDBN} can automatically track which overlays are mapped and which
11655 are not, given some simple co-operation from the overlay manager in the
11656 inferior. If you enable automatic overlay debugging with the
11657 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
11658 looks in the inferior's memory for certain variables describing the
11659 current state of the overlays.
11661 Here are the variables your overlay manager must define to support
11662 @value{GDBN}'s automatic overlay debugging:
11666 @item @code{_ovly_table}:
11667 This variable must be an array of the following structures:
11672 /* The overlay's mapped address. */
11675 /* The size of the overlay, in bytes. */
11676 unsigned long size;
11678 /* The overlay's load address. */
11681 /* Non-zero if the overlay is currently mapped;
11683 unsigned long mapped;
11687 @item @code{_novlys}:
11688 This variable must be a four-byte signed integer, holding the total
11689 number of elements in @code{_ovly_table}.
11693 To decide whether a particular overlay is mapped or not, @value{GDBN}
11694 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
11695 @code{lma} members equal the VMA and LMA of the overlay's section in the
11696 executable file. When @value{GDBN} finds a matching entry, it consults
11697 the entry's @code{mapped} member to determine whether the overlay is
11700 In addition, your overlay manager may define a function called
11701 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
11702 will silently set a breakpoint there. If the overlay manager then
11703 calls this function whenever it has changed the overlay table, this
11704 will enable @value{GDBN} to accurately keep track of which overlays
11705 are in program memory, and update any breakpoints that may be set
11706 in overlays. This will allow breakpoints to work even if the
11707 overlays are kept in ROM or other non-writable memory while they
11708 are not being executed.
11710 @node Overlay Sample Program
11711 @section Overlay Sample Program
11712 @cindex overlay example program
11714 When linking a program which uses overlays, you must place the overlays
11715 at their load addresses, while relocating them to run at their mapped
11716 addresses. To do this, you must write a linker script (@pxref{Overlay
11717 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
11718 since linker scripts are specific to a particular host system, target
11719 architecture, and target memory layout, this manual cannot provide
11720 portable sample code demonstrating @value{GDBN}'s overlay support.
11722 However, the @value{GDBN} source distribution does contain an overlaid
11723 program, with linker scripts for a few systems, as part of its test
11724 suite. The program consists of the following files from
11725 @file{gdb/testsuite/gdb.base}:
11729 The main program file.
11731 A simple overlay manager, used by @file{overlays.c}.
11736 Overlay modules, loaded and used by @file{overlays.c}.
11739 Linker scripts for linking the test program on the @code{d10v-elf}
11740 and @code{m32r-elf} targets.
11743 You can build the test program using the @code{d10v-elf} GCC
11744 cross-compiler like this:
11747 $ d10v-elf-gcc -g -c overlays.c
11748 $ d10v-elf-gcc -g -c ovlymgr.c
11749 $ d10v-elf-gcc -g -c foo.c
11750 $ d10v-elf-gcc -g -c bar.c
11751 $ d10v-elf-gcc -g -c baz.c
11752 $ d10v-elf-gcc -g -c grbx.c
11753 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
11754 baz.o grbx.o -Wl,-Td10v.ld -o overlays
11757 The build process is identical for any other architecture, except that
11758 you must substitute the appropriate compiler and linker script for the
11759 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
11763 @chapter Using @value{GDBN} with Different Languages
11766 Although programming languages generally have common aspects, they are
11767 rarely expressed in the same manner. For instance, in ANSI C,
11768 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
11769 Modula-2, it is accomplished by @code{p^}. Values can also be
11770 represented (and displayed) differently. Hex numbers in C appear as
11771 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
11773 @cindex working language
11774 Language-specific information is built into @value{GDBN} for some languages,
11775 allowing you to express operations like the above in your program's
11776 native language, and allowing @value{GDBN} to output values in a manner
11777 consistent with the syntax of your program's native language. The
11778 language you use to build expressions is called the @dfn{working
11782 * Setting:: Switching between source languages
11783 * Show:: Displaying the language
11784 * Checks:: Type and range checks
11785 * Supported Languages:: Supported languages
11786 * Unsupported Languages:: Unsupported languages
11790 @section Switching Between Source Languages
11792 There are two ways to control the working language---either have @value{GDBN}
11793 set it automatically, or select it manually yourself. You can use the
11794 @code{set language} command for either purpose. On startup, @value{GDBN}
11795 defaults to setting the language automatically. The working language is
11796 used to determine how expressions you type are interpreted, how values
11799 In addition to the working language, every source file that
11800 @value{GDBN} knows about has its own working language. For some object
11801 file formats, the compiler might indicate which language a particular
11802 source file is in. However, most of the time @value{GDBN} infers the
11803 language from the name of the file. The language of a source file
11804 controls whether C@t{++} names are demangled---this way @code{backtrace} can
11805 show each frame appropriately for its own language. There is no way to
11806 set the language of a source file from within @value{GDBN}, but you can
11807 set the language associated with a filename extension. @xref{Show, ,
11808 Displaying the Language}.
11810 This is most commonly a problem when you use a program, such
11811 as @code{cfront} or @code{f2c}, that generates C but is written in
11812 another language. In that case, make the
11813 program use @code{#line} directives in its C output; that way
11814 @value{GDBN} will know the correct language of the source code of the original
11815 program, and will display that source code, not the generated C code.
11818 * Filenames:: Filename extensions and languages.
11819 * Manually:: Setting the working language manually
11820 * Automatically:: Having @value{GDBN} infer the source language
11824 @subsection List of Filename Extensions and Languages
11826 If a source file name ends in one of the following extensions, then
11827 @value{GDBN} infers that its language is the one indicated.
11845 C@t{++} source file
11851 Objective-C source file
11855 Fortran source file
11858 Modula-2 source file
11862 Assembler source file. This actually behaves almost like C, but
11863 @value{GDBN} does not skip over function prologues when stepping.
11866 In addition, you may set the language associated with a filename
11867 extension. @xref{Show, , Displaying the Language}.
11870 @subsection Setting the Working Language
11872 If you allow @value{GDBN} to set the language automatically,
11873 expressions are interpreted the same way in your debugging session and
11876 @kindex set language
11877 If you wish, you may set the language manually. To do this, issue the
11878 command @samp{set language @var{lang}}, where @var{lang} is the name of
11879 a language, such as
11880 @code{c} or @code{modula-2}.
11881 For a list of the supported languages, type @samp{set language}.
11883 Setting the language manually prevents @value{GDBN} from updating the working
11884 language automatically. This can lead to confusion if you try
11885 to debug a program when the working language is not the same as the
11886 source language, when an expression is acceptable to both
11887 languages---but means different things. For instance, if the current
11888 source file were written in C, and @value{GDBN} was parsing Modula-2, a
11896 might not have the effect you intended. In C, this means to add
11897 @code{b} and @code{c} and place the result in @code{a}. The result
11898 printed would be the value of @code{a}. In Modula-2, this means to compare
11899 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
11901 @node Automatically
11902 @subsection Having @value{GDBN} Infer the Source Language
11904 To have @value{GDBN} set the working language automatically, use
11905 @samp{set language local} or @samp{set language auto}. @value{GDBN}
11906 then infers the working language. That is, when your program stops in a
11907 frame (usually by encountering a breakpoint), @value{GDBN} sets the
11908 working language to the language recorded for the function in that
11909 frame. If the language for a frame is unknown (that is, if the function
11910 or block corresponding to the frame was defined in a source file that
11911 does not have a recognized extension), the current working language is
11912 not changed, and @value{GDBN} issues a warning.
11914 This may not seem necessary for most programs, which are written
11915 entirely in one source language. However, program modules and libraries
11916 written in one source language can be used by a main program written in
11917 a different source language. Using @samp{set language auto} in this
11918 case frees you from having to set the working language manually.
11921 @section Displaying the Language
11923 The following commands help you find out which language is the
11924 working language, and also what language source files were written in.
11927 @item show language
11928 @kindex show language
11929 Display the current working language. This is the
11930 language you can use with commands such as @code{print} to
11931 build and compute expressions that may involve variables in your program.
11934 @kindex info frame@r{, show the source language}
11935 Display the source language for this frame. This language becomes the
11936 working language if you use an identifier from this frame.
11937 @xref{Frame Info, ,Information about a Frame}, to identify the other
11938 information listed here.
11941 @kindex info source@r{, show the source language}
11942 Display the source language of this source file.
11943 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
11944 information listed here.
11947 In unusual circumstances, you may have source files with extensions
11948 not in the standard list. You can then set the extension associated
11949 with a language explicitly:
11952 @item set extension-language @var{ext} @var{language}
11953 @kindex set extension-language
11954 Tell @value{GDBN} that source files with extension @var{ext} are to be
11955 assumed as written in the source language @var{language}.
11957 @item info extensions
11958 @kindex info extensions
11959 List all the filename extensions and the associated languages.
11963 @section Type and Range Checking
11966 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
11967 checking are included, but they do not yet have any effect. This
11968 section documents the intended facilities.
11970 @c FIXME remove warning when type/range code added
11972 Some languages are designed to guard you against making seemingly common
11973 errors through a series of compile- and run-time checks. These include
11974 checking the type of arguments to functions and operators, and making
11975 sure mathematical overflows are caught at run time. Checks such as
11976 these help to ensure a program's correctness once it has been compiled
11977 by eliminating type mismatches, and providing active checks for range
11978 errors when your program is running.
11980 @value{GDBN} can check for conditions like the above if you wish.
11981 Although @value{GDBN} does not check the statements in your program,
11982 it can check expressions entered directly into @value{GDBN} for
11983 evaluation via the @code{print} command, for example. As with the
11984 working language, @value{GDBN} can also decide whether or not to check
11985 automatically based on your program's source language.
11986 @xref{Supported Languages, ,Supported Languages}, for the default
11987 settings of supported languages.
11990 * Type Checking:: An overview of type checking
11991 * Range Checking:: An overview of range checking
11994 @cindex type checking
11995 @cindex checks, type
11996 @node Type Checking
11997 @subsection An Overview of Type Checking
11999 Some languages, such as Modula-2, are strongly typed, meaning that the
12000 arguments to operators and functions have to be of the correct type,
12001 otherwise an error occurs. These checks prevent type mismatch
12002 errors from ever causing any run-time problems. For example,
12010 The second example fails because the @code{CARDINAL} 1 is not
12011 type-compatible with the @code{REAL} 2.3.
12013 For the expressions you use in @value{GDBN} commands, you can tell the
12014 @value{GDBN} type checker to skip checking;
12015 to treat any mismatches as errors and abandon the expression;
12016 or to only issue warnings when type mismatches occur,
12017 but evaluate the expression anyway. When you choose the last of
12018 these, @value{GDBN} evaluates expressions like the second example above, but
12019 also issues a warning.
12021 Even if you turn type checking off, there may be other reasons
12022 related to type that prevent @value{GDBN} from evaluating an expression.
12023 For instance, @value{GDBN} does not know how to add an @code{int} and
12024 a @code{struct foo}. These particular type errors have nothing to do
12025 with the language in use, and usually arise from expressions, such as
12026 the one described above, which make little sense to evaluate anyway.
12028 Each language defines to what degree it is strict about type. For
12029 instance, both Modula-2 and C require the arguments to arithmetical
12030 operators to be numbers. In C, enumerated types and pointers can be
12031 represented as numbers, so that they are valid arguments to mathematical
12032 operators. @xref{Supported Languages, ,Supported Languages}, for further
12033 details on specific languages.
12035 @value{GDBN} provides some additional commands for controlling the type checker:
12037 @kindex set check type
12038 @kindex show check type
12040 @item set check type auto
12041 Set type checking on or off based on the current working language.
12042 @xref{Supported Languages, ,Supported Languages}, for the default settings for
12045 @item set check type on
12046 @itemx set check type off
12047 Set type checking on or off, overriding the default setting for the
12048 current working language. Issue a warning if the setting does not
12049 match the language default. If any type mismatches occur in
12050 evaluating an expression while type checking is on, @value{GDBN} prints a
12051 message and aborts evaluation of the expression.
12053 @item set check type warn
12054 Cause the type checker to issue warnings, but to always attempt to
12055 evaluate the expression. Evaluating the expression may still
12056 be impossible for other reasons. For example, @value{GDBN} cannot add
12057 numbers and structures.
12060 Show the current setting of the type checker, and whether or not @value{GDBN}
12061 is setting it automatically.
12064 @cindex range checking
12065 @cindex checks, range
12066 @node Range Checking
12067 @subsection An Overview of Range Checking
12069 In some languages (such as Modula-2), it is an error to exceed the
12070 bounds of a type; this is enforced with run-time checks. Such range
12071 checking is meant to ensure program correctness by making sure
12072 computations do not overflow, or indices on an array element access do
12073 not exceed the bounds of the array.
12075 For expressions you use in @value{GDBN} commands, you can tell
12076 @value{GDBN} to treat range errors in one of three ways: ignore them,
12077 always treat them as errors and abandon the expression, or issue
12078 warnings but evaluate the expression anyway.
12080 A range error can result from numerical overflow, from exceeding an
12081 array index bound, or when you type a constant that is not a member
12082 of any type. Some languages, however, do not treat overflows as an
12083 error. In many implementations of C, mathematical overflow causes the
12084 result to ``wrap around'' to lower values---for example, if @var{m} is
12085 the largest integer value, and @var{s} is the smallest, then
12088 @var{m} + 1 @result{} @var{s}
12091 This, too, is specific to individual languages, and in some cases
12092 specific to individual compilers or machines. @xref{Supported Languages, ,
12093 Supported Languages}, for further details on specific languages.
12095 @value{GDBN} provides some additional commands for controlling the range checker:
12097 @kindex set check range
12098 @kindex show check range
12100 @item set check range auto
12101 Set range checking on or off based on the current working language.
12102 @xref{Supported Languages, ,Supported Languages}, for the default settings for
12105 @item set check range on
12106 @itemx set check range off
12107 Set range checking on or off, overriding the default setting for the
12108 current working language. A warning is issued if the setting does not
12109 match the language default. If a range error occurs and range checking is on,
12110 then a message is printed and evaluation of the expression is aborted.
12112 @item set check range warn
12113 Output messages when the @value{GDBN} range checker detects a range error,
12114 but attempt to evaluate the expression anyway. Evaluating the
12115 expression may still be impossible for other reasons, such as accessing
12116 memory that the process does not own (a typical example from many Unix
12120 Show the current setting of the range checker, and whether or not it is
12121 being set automatically by @value{GDBN}.
12124 @node Supported Languages
12125 @section Supported Languages
12127 @value{GDBN} supports C, C@t{++}, D, Objective-C, Fortran, Java, OpenCL C, Pascal,
12128 assembly, Modula-2, and Ada.
12129 @c This is false ...
12130 Some @value{GDBN} features may be used in expressions regardless of the
12131 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
12132 and the @samp{@{type@}addr} construct (@pxref{Expressions,
12133 ,Expressions}) can be used with the constructs of any supported
12136 The following sections detail to what degree each source language is
12137 supported by @value{GDBN}. These sections are not meant to be language
12138 tutorials or references, but serve only as a reference guide to what the
12139 @value{GDBN} expression parser accepts, and what input and output
12140 formats should look like for different languages. There are many good
12141 books written on each of these languages; please look to these for a
12142 language reference or tutorial.
12145 * C:: C and C@t{++}
12147 * Objective-C:: Objective-C
12148 * OpenCL C:: OpenCL C
12149 * Fortran:: Fortran
12151 * Modula-2:: Modula-2
12156 @subsection C and C@t{++}
12158 @cindex C and C@t{++}
12159 @cindex expressions in C or C@t{++}
12161 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
12162 to both languages. Whenever this is the case, we discuss those languages
12166 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
12167 @cindex @sc{gnu} C@t{++}
12168 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
12169 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
12170 effectively, you must compile your C@t{++} programs with a supported
12171 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
12172 compiler (@code{aCC}).
12174 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
12175 format; if it doesn't work on your system, try the stabs+ debugging
12176 format. You can select those formats explicitly with the @code{g++}
12177 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
12178 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
12179 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
12182 * C Operators:: C and C@t{++} operators
12183 * C Constants:: C and C@t{++} constants
12184 * C Plus Plus Expressions:: C@t{++} expressions
12185 * C Defaults:: Default settings for C and C@t{++}
12186 * C Checks:: C and C@t{++} type and range checks
12187 * Debugging C:: @value{GDBN} and C
12188 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
12189 * Decimal Floating Point:: Numbers in Decimal Floating Point format
12193 @subsubsection C and C@t{++} Operators
12195 @cindex C and C@t{++} operators
12197 Operators must be defined on values of specific types. For instance,
12198 @code{+} is defined on numbers, but not on structures. Operators are
12199 often defined on groups of types.
12201 For the purposes of C and C@t{++}, the following definitions hold:
12206 @emph{Integral types} include @code{int} with any of its storage-class
12207 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
12210 @emph{Floating-point types} include @code{float}, @code{double}, and
12211 @code{long double} (if supported by the target platform).
12214 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
12217 @emph{Scalar types} include all of the above.
12222 The following operators are supported. They are listed here
12223 in order of increasing precedence:
12227 The comma or sequencing operator. Expressions in a comma-separated list
12228 are evaluated from left to right, with the result of the entire
12229 expression being the last expression evaluated.
12232 Assignment. The value of an assignment expression is the value
12233 assigned. Defined on scalar types.
12236 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
12237 and translated to @w{@code{@var{a} = @var{a op b}}}.
12238 @w{@code{@var{op}=}} and @code{=} have the same precedence.
12239 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
12240 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
12243 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
12244 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
12248 Logical @sc{or}. Defined on integral types.
12251 Logical @sc{and}. Defined on integral types.
12254 Bitwise @sc{or}. Defined on integral types.
12257 Bitwise exclusive-@sc{or}. Defined on integral types.
12260 Bitwise @sc{and}. Defined on integral types.
12263 Equality and inequality. Defined on scalar types. The value of these
12264 expressions is 0 for false and non-zero for true.
12266 @item <@r{, }>@r{, }<=@r{, }>=
12267 Less than, greater than, less than or equal, greater than or equal.
12268 Defined on scalar types. The value of these expressions is 0 for false
12269 and non-zero for true.
12272 left shift, and right shift. Defined on integral types.
12275 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12278 Addition and subtraction. Defined on integral types, floating-point types and
12281 @item *@r{, }/@r{, }%
12282 Multiplication, division, and modulus. Multiplication and division are
12283 defined on integral and floating-point types. Modulus is defined on
12287 Increment and decrement. When appearing before a variable, the
12288 operation is performed before the variable is used in an expression;
12289 when appearing after it, the variable's value is used before the
12290 operation takes place.
12293 Pointer dereferencing. Defined on pointer types. Same precedence as
12297 Address operator. Defined on variables. Same precedence as @code{++}.
12299 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
12300 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
12301 to examine the address
12302 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
12306 Negative. Defined on integral and floating-point types. Same
12307 precedence as @code{++}.
12310 Logical negation. Defined on integral types. Same precedence as
12314 Bitwise complement operator. Defined on integral types. Same precedence as
12319 Structure member, and pointer-to-structure member. For convenience,
12320 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
12321 pointer based on the stored type information.
12322 Defined on @code{struct} and @code{union} data.
12325 Dereferences of pointers to members.
12328 Array indexing. @code{@var{a}[@var{i}]} is defined as
12329 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
12332 Function parameter list. Same precedence as @code{->}.
12335 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
12336 and @code{class} types.
12339 Doubled colons also represent the @value{GDBN} scope operator
12340 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
12344 If an operator is redefined in the user code, @value{GDBN} usually
12345 attempts to invoke the redefined version instead of using the operator's
12346 predefined meaning.
12349 @subsubsection C and C@t{++} Constants
12351 @cindex C and C@t{++} constants
12353 @value{GDBN} allows you to express the constants of C and C@t{++} in the
12358 Integer constants are a sequence of digits. Octal constants are
12359 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
12360 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
12361 @samp{l}, specifying that the constant should be treated as a
12365 Floating point constants are a sequence of digits, followed by a decimal
12366 point, followed by a sequence of digits, and optionally followed by an
12367 exponent. An exponent is of the form:
12368 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
12369 sequence of digits. The @samp{+} is optional for positive exponents.
12370 A floating-point constant may also end with a letter @samp{f} or
12371 @samp{F}, specifying that the constant should be treated as being of
12372 the @code{float} (as opposed to the default @code{double}) type; or with
12373 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
12377 Enumerated constants consist of enumerated identifiers, or their
12378 integral equivalents.
12381 Character constants are a single character surrounded by single quotes
12382 (@code{'}), or a number---the ordinal value of the corresponding character
12383 (usually its @sc{ascii} value). Within quotes, the single character may
12384 be represented by a letter or by @dfn{escape sequences}, which are of
12385 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
12386 of the character's ordinal value; or of the form @samp{\@var{x}}, where
12387 @samp{@var{x}} is a predefined special character---for example,
12388 @samp{\n} for newline.
12391 String constants are a sequence of character constants surrounded by
12392 double quotes (@code{"}). Any valid character constant (as described
12393 above) may appear. Double quotes within the string must be preceded by
12394 a backslash, so for instance @samp{"a\"b'c"} is a string of five
12398 Pointer constants are an integral value. You can also write pointers
12399 to constants using the C operator @samp{&}.
12402 Array constants are comma-separated lists surrounded by braces @samp{@{}
12403 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
12404 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
12405 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
12408 @node C Plus Plus Expressions
12409 @subsubsection C@t{++} Expressions
12411 @cindex expressions in C@t{++}
12412 @value{GDBN} expression handling can interpret most C@t{++} expressions.
12414 @cindex debugging C@t{++} programs
12415 @cindex C@t{++} compilers
12416 @cindex debug formats and C@t{++}
12417 @cindex @value{NGCC} and C@t{++}
12419 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
12420 proper compiler and the proper debug format. Currently, @value{GDBN}
12421 works best when debugging C@t{++} code that is compiled with
12422 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
12423 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
12424 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
12425 stabs+ as their default debug format, so you usually don't need to
12426 specify a debug format explicitly. Other compilers and/or debug formats
12427 are likely to work badly or not at all when using @value{GDBN} to debug
12433 @cindex member functions
12435 Member function calls are allowed; you can use expressions like
12438 count = aml->GetOriginal(x, y)
12441 @vindex this@r{, inside C@t{++} member functions}
12442 @cindex namespace in C@t{++}
12444 While a member function is active (in the selected stack frame), your
12445 expressions have the same namespace available as the member function;
12446 that is, @value{GDBN} allows implicit references to the class instance
12447 pointer @code{this} following the same rules as C@t{++}.
12449 @cindex call overloaded functions
12450 @cindex overloaded functions, calling
12451 @cindex type conversions in C@t{++}
12453 You can call overloaded functions; @value{GDBN} resolves the function
12454 call to the right definition, with some restrictions. @value{GDBN} does not
12455 perform overload resolution involving user-defined type conversions,
12456 calls to constructors, or instantiations of templates that do not exist
12457 in the program. It also cannot handle ellipsis argument lists or
12460 It does perform integral conversions and promotions, floating-point
12461 promotions, arithmetic conversions, pointer conversions, conversions of
12462 class objects to base classes, and standard conversions such as those of
12463 functions or arrays to pointers; it requires an exact match on the
12464 number of function arguments.
12466 Overload resolution is always performed, unless you have specified
12467 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
12468 ,@value{GDBN} Features for C@t{++}}.
12470 You must specify @code{set overload-resolution off} in order to use an
12471 explicit function signature to call an overloaded function, as in
12473 p 'foo(char,int)'('x', 13)
12476 The @value{GDBN} command-completion facility can simplify this;
12477 see @ref{Completion, ,Command Completion}.
12479 @cindex reference declarations
12481 @value{GDBN} understands variables declared as C@t{++} references; you can use
12482 them in expressions just as you do in C@t{++} source---they are automatically
12485 In the parameter list shown when @value{GDBN} displays a frame, the values of
12486 reference variables are not displayed (unlike other variables); this
12487 avoids clutter, since references are often used for large structures.
12488 The @emph{address} of a reference variable is always shown, unless
12489 you have specified @samp{set print address off}.
12492 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
12493 expressions can use it just as expressions in your program do. Since
12494 one scope may be defined in another, you can use @code{::} repeatedly if
12495 necessary, for example in an expression like
12496 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
12497 resolving name scope by reference to source files, in both C and C@t{++}
12498 debugging (@pxref{Variables, ,Program Variables}).
12501 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
12502 calling virtual functions correctly, printing out virtual bases of
12503 objects, calling functions in a base subobject, casting objects, and
12504 invoking user-defined operators.
12507 @subsubsection C and C@t{++} Defaults
12509 @cindex C and C@t{++} defaults
12511 If you allow @value{GDBN} to set type and range checking automatically, they
12512 both default to @code{off} whenever the working language changes to
12513 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
12514 selects the working language.
12516 If you allow @value{GDBN} to set the language automatically, it
12517 recognizes source files whose names end with @file{.c}, @file{.C}, or
12518 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
12519 these files, it sets the working language to C or C@t{++}.
12520 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
12521 for further details.
12523 @c Type checking is (a) primarily motivated by Modula-2, and (b)
12524 @c unimplemented. If (b) changes, it might make sense to let this node
12525 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
12528 @subsubsection C and C@t{++} Type and Range Checks
12530 @cindex C and C@t{++} checks
12532 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
12533 is not used. However, if you turn type checking on, @value{GDBN}
12534 considers two variables type equivalent if:
12538 The two variables are structured and have the same structure, union, or
12542 The two variables have the same type name, or types that have been
12543 declared equivalent through @code{typedef}.
12546 @c leaving this out because neither J Gilmore nor R Pesch understand it.
12549 The two @code{struct}, @code{union}, or @code{enum} variables are
12550 declared in the same declaration. (Note: this may not be true for all C
12555 Range checking, if turned on, is done on mathematical operations. Array
12556 indices are not checked, since they are often used to index a pointer
12557 that is not itself an array.
12560 @subsubsection @value{GDBN} and C
12562 The @code{set print union} and @code{show print union} commands apply to
12563 the @code{union} type. When set to @samp{on}, any @code{union} that is
12564 inside a @code{struct} or @code{class} is also printed. Otherwise, it
12565 appears as @samp{@{...@}}.
12567 The @code{@@} operator aids in the debugging of dynamic arrays, formed
12568 with pointers and a memory allocation function. @xref{Expressions,
12571 @node Debugging C Plus Plus
12572 @subsubsection @value{GDBN} Features for C@t{++}
12574 @cindex commands for C@t{++}
12576 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
12577 designed specifically for use with C@t{++}. Here is a summary:
12580 @cindex break in overloaded functions
12581 @item @r{breakpoint menus}
12582 When you want a breakpoint in a function whose name is overloaded,
12583 @value{GDBN} has the capability to display a menu of possible breakpoint
12584 locations to help you specify which function definition you want.
12585 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
12587 @cindex overloading in C@t{++}
12588 @item rbreak @var{regex}
12589 Setting breakpoints using regular expressions is helpful for setting
12590 breakpoints on overloaded functions that are not members of any special
12592 @xref{Set Breaks, ,Setting Breakpoints}.
12594 @cindex C@t{++} exception handling
12597 Debug C@t{++} exception handling using these commands. @xref{Set
12598 Catchpoints, , Setting Catchpoints}.
12600 @cindex inheritance
12601 @item ptype @var{typename}
12602 Print inheritance relationships as well as other information for type
12604 @xref{Symbols, ,Examining the Symbol Table}.
12606 @cindex C@t{++} symbol display
12607 @item set print demangle
12608 @itemx show print demangle
12609 @itemx set print asm-demangle
12610 @itemx show print asm-demangle
12611 Control whether C@t{++} symbols display in their source form, both when
12612 displaying code as C@t{++} source and when displaying disassemblies.
12613 @xref{Print Settings, ,Print Settings}.
12615 @item set print object
12616 @itemx show print object
12617 Choose whether to print derived (actual) or declared types of objects.
12618 @xref{Print Settings, ,Print Settings}.
12620 @item set print vtbl
12621 @itemx show print vtbl
12622 Control the format for printing virtual function tables.
12623 @xref{Print Settings, ,Print Settings}.
12624 (The @code{vtbl} commands do not work on programs compiled with the HP
12625 ANSI C@t{++} compiler (@code{aCC}).)
12627 @kindex set overload-resolution
12628 @cindex overloaded functions, overload resolution
12629 @item set overload-resolution on
12630 Enable overload resolution for C@t{++} expression evaluation. The default
12631 is on. For overloaded functions, @value{GDBN} evaluates the arguments
12632 and searches for a function whose signature matches the argument types,
12633 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
12634 Expressions, ,C@t{++} Expressions}, for details).
12635 If it cannot find a match, it emits a message.
12637 @item set overload-resolution off
12638 Disable overload resolution for C@t{++} expression evaluation. For
12639 overloaded functions that are not class member functions, @value{GDBN}
12640 chooses the first function of the specified name that it finds in the
12641 symbol table, whether or not its arguments are of the correct type. For
12642 overloaded functions that are class member functions, @value{GDBN}
12643 searches for a function whose signature @emph{exactly} matches the
12646 @kindex show overload-resolution
12647 @item show overload-resolution
12648 Show the current setting of overload resolution.
12650 @item @r{Overloaded symbol names}
12651 You can specify a particular definition of an overloaded symbol, using
12652 the same notation that is used to declare such symbols in C@t{++}: type
12653 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
12654 also use the @value{GDBN} command-line word completion facilities to list the
12655 available choices, or to finish the type list for you.
12656 @xref{Completion,, Command Completion}, for details on how to do this.
12659 @node Decimal Floating Point
12660 @subsubsection Decimal Floating Point format
12661 @cindex decimal floating point format
12663 @value{GDBN} can examine, set and perform computations with numbers in
12664 decimal floating point format, which in the C language correspond to the
12665 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
12666 specified by the extension to support decimal floating-point arithmetic.
12668 There are two encodings in use, depending on the architecture: BID (Binary
12669 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
12670 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
12673 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
12674 to manipulate decimal floating point numbers, it is not possible to convert
12675 (using a cast, for example) integers wider than 32-bit to decimal float.
12677 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
12678 point computations, error checking in decimal float operations ignores
12679 underflow, overflow and divide by zero exceptions.
12681 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
12682 to inspect @code{_Decimal128} values stored in floating point registers.
12683 See @ref{PowerPC,,PowerPC} for more details.
12689 @value{GDBN} can be used to debug programs written in D and compiled with
12690 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
12691 specific feature --- dynamic arrays.
12694 @subsection Objective-C
12696 @cindex Objective-C
12697 This section provides information about some commands and command
12698 options that are useful for debugging Objective-C code. See also
12699 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
12700 few more commands specific to Objective-C support.
12703 * Method Names in Commands::
12704 * The Print Command with Objective-C::
12707 @node Method Names in Commands
12708 @subsubsection Method Names in Commands
12710 The following commands have been extended to accept Objective-C method
12711 names as line specifications:
12713 @kindex clear@r{, and Objective-C}
12714 @kindex break@r{, and Objective-C}
12715 @kindex info line@r{, and Objective-C}
12716 @kindex jump@r{, and Objective-C}
12717 @kindex list@r{, and Objective-C}
12721 @item @code{info line}
12726 A fully qualified Objective-C method name is specified as
12729 -[@var{Class} @var{methodName}]
12732 where the minus sign is used to indicate an instance method and a
12733 plus sign (not shown) is used to indicate a class method. The class
12734 name @var{Class} and method name @var{methodName} are enclosed in
12735 brackets, similar to the way messages are specified in Objective-C
12736 source code. For example, to set a breakpoint at the @code{create}
12737 instance method of class @code{Fruit} in the program currently being
12741 break -[Fruit create]
12744 To list ten program lines around the @code{initialize} class method,
12748 list +[NSText initialize]
12751 In the current version of @value{GDBN}, the plus or minus sign is
12752 required. In future versions of @value{GDBN}, the plus or minus
12753 sign will be optional, but you can use it to narrow the search. It
12754 is also possible to specify just a method name:
12760 You must specify the complete method name, including any colons. If
12761 your program's source files contain more than one @code{create} method,
12762 you'll be presented with a numbered list of classes that implement that
12763 method. Indicate your choice by number, or type @samp{0} to exit if
12766 As another example, to clear a breakpoint established at the
12767 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
12770 clear -[NSWindow makeKeyAndOrderFront:]
12773 @node The Print Command with Objective-C
12774 @subsubsection The Print Command With Objective-C
12775 @cindex Objective-C, print objects
12776 @kindex print-object
12777 @kindex po @r{(@code{print-object})}
12779 The print command has also been extended to accept methods. For example:
12782 print -[@var{object} hash]
12785 @cindex print an Objective-C object description
12786 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
12788 will tell @value{GDBN} to send the @code{hash} message to @var{object}
12789 and print the result. Also, an additional command has been added,
12790 @code{print-object} or @code{po} for short, which is meant to print
12791 the description of an object. However, this command may only work
12792 with certain Objective-C libraries that have a particular hook
12793 function, @code{_NSPrintForDebugger}, defined.
12796 @subsection OpenCL C
12799 This section provides information about @value{GDBN}s OpenCL C support.
12802 * OpenCL C Datatypes::
12803 * OpenCL C Expressions::
12804 * OpenCL C Operators::
12807 @node OpenCL C Datatypes
12808 @subsubsection OpenCL C Datatypes
12810 @cindex OpenCL C Datatypes
12811 @value{GDBN} supports the builtin scalar and vector datatypes specified
12812 by OpenCL 1.1. In addition the half- and double-precision floating point
12813 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
12814 extensions are also known to @value{GDBN}.
12816 @node OpenCL C Expressions
12817 @subsubsection OpenCL C Expressions
12819 @cindex OpenCL C Expressions
12820 @value{GDBN} supports accesses to vector components including the access as
12821 lvalue where possible. Since OpenCL C is based on C99 most C expressions
12822 supported by @value{GDBN} can be used as well.
12824 @node OpenCL C Operators
12825 @subsubsection OpenCL C Operators
12827 @cindex OpenCL C Operators
12828 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
12832 @subsection Fortran
12833 @cindex Fortran-specific support in @value{GDBN}
12835 @value{GDBN} can be used to debug programs written in Fortran, but it
12836 currently supports only the features of Fortran 77 language.
12838 @cindex trailing underscore, in Fortran symbols
12839 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
12840 among them) append an underscore to the names of variables and
12841 functions. When you debug programs compiled by those compilers, you
12842 will need to refer to variables and functions with a trailing
12846 * Fortran Operators:: Fortran operators and expressions
12847 * Fortran Defaults:: Default settings for Fortran
12848 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
12851 @node Fortran Operators
12852 @subsubsection Fortran Operators and Expressions
12854 @cindex Fortran operators and expressions
12856 Operators must be defined on values of specific types. For instance,
12857 @code{+} is defined on numbers, but not on characters or other non-
12858 arithmetic types. Operators are often defined on groups of types.
12862 The exponentiation operator. It raises the first operand to the power
12866 The range operator. Normally used in the form of array(low:high) to
12867 represent a section of array.
12870 The access component operator. Normally used to access elements in derived
12871 types. Also suitable for unions. As unions aren't part of regular Fortran,
12872 this can only happen when accessing a register that uses a gdbarch-defined
12876 @node Fortran Defaults
12877 @subsubsection Fortran Defaults
12879 @cindex Fortran Defaults
12881 Fortran symbols are usually case-insensitive, so @value{GDBN} by
12882 default uses case-insensitive matches for Fortran symbols. You can
12883 change that with the @samp{set case-insensitive} command, see
12884 @ref{Symbols}, for the details.
12886 @node Special Fortran Commands
12887 @subsubsection Special Fortran Commands
12889 @cindex Special Fortran commands
12891 @value{GDBN} has some commands to support Fortran-specific features,
12892 such as displaying common blocks.
12895 @cindex @code{COMMON} blocks, Fortran
12896 @kindex info common
12897 @item info common @r{[}@var{common-name}@r{]}
12898 This command prints the values contained in the Fortran @code{COMMON}
12899 block whose name is @var{common-name}. With no argument, the names of
12900 all @code{COMMON} blocks visible at the current program location are
12907 @cindex Pascal support in @value{GDBN}, limitations
12908 Debugging Pascal programs which use sets, subranges, file variables, or
12909 nested functions does not currently work. @value{GDBN} does not support
12910 entering expressions, printing values, or similar features using Pascal
12913 The Pascal-specific command @code{set print pascal_static-members}
12914 controls whether static members of Pascal objects are displayed.
12915 @xref{Print Settings, pascal_static-members}.
12918 @subsection Modula-2
12920 @cindex Modula-2, @value{GDBN} support
12922 The extensions made to @value{GDBN} to support Modula-2 only support
12923 output from the @sc{gnu} Modula-2 compiler (which is currently being
12924 developed). Other Modula-2 compilers are not currently supported, and
12925 attempting to debug executables produced by them is most likely
12926 to give an error as @value{GDBN} reads in the executable's symbol
12929 @cindex expressions in Modula-2
12931 * M2 Operators:: Built-in operators
12932 * Built-In Func/Proc:: Built-in functions and procedures
12933 * M2 Constants:: Modula-2 constants
12934 * M2 Types:: Modula-2 types
12935 * M2 Defaults:: Default settings for Modula-2
12936 * Deviations:: Deviations from standard Modula-2
12937 * M2 Checks:: Modula-2 type and range checks
12938 * M2 Scope:: The scope operators @code{::} and @code{.}
12939 * GDB/M2:: @value{GDBN} and Modula-2
12943 @subsubsection Operators
12944 @cindex Modula-2 operators
12946 Operators must be defined on values of specific types. For instance,
12947 @code{+} is defined on numbers, but not on structures. Operators are
12948 often defined on groups of types. For the purposes of Modula-2, the
12949 following definitions hold:
12954 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
12958 @emph{Character types} consist of @code{CHAR} and its subranges.
12961 @emph{Floating-point types} consist of @code{REAL}.
12964 @emph{Pointer types} consist of anything declared as @code{POINTER TO
12968 @emph{Scalar types} consist of all of the above.
12971 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
12974 @emph{Boolean types} consist of @code{BOOLEAN}.
12978 The following operators are supported, and appear in order of
12979 increasing precedence:
12983 Function argument or array index separator.
12986 Assignment. The value of @var{var} @code{:=} @var{value} is
12990 Less than, greater than on integral, floating-point, or enumerated
12994 Less than or equal to, greater than or equal to
12995 on integral, floating-point and enumerated types, or set inclusion on
12996 set types. Same precedence as @code{<}.
12998 @item =@r{, }<>@r{, }#
12999 Equality and two ways of expressing inequality, valid on scalar types.
13000 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
13001 available for inequality, since @code{#} conflicts with the script
13005 Set membership. Defined on set types and the types of their members.
13006 Same precedence as @code{<}.
13009 Boolean disjunction. Defined on boolean types.
13012 Boolean conjunction. Defined on boolean types.
13015 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13018 Addition and subtraction on integral and floating-point types, or union
13019 and difference on set types.
13022 Multiplication on integral and floating-point types, or set intersection
13026 Division on floating-point types, or symmetric set difference on set
13027 types. Same precedence as @code{*}.
13030 Integer division and remainder. Defined on integral types. Same
13031 precedence as @code{*}.
13034 Negative. Defined on @code{INTEGER} and @code{REAL} data.
13037 Pointer dereferencing. Defined on pointer types.
13040 Boolean negation. Defined on boolean types. Same precedence as
13044 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
13045 precedence as @code{^}.
13048 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
13051 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
13055 @value{GDBN} and Modula-2 scope operators.
13059 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
13060 treats the use of the operator @code{IN}, or the use of operators
13061 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
13062 @code{<=}, and @code{>=} on sets as an error.
13066 @node Built-In Func/Proc
13067 @subsubsection Built-in Functions and Procedures
13068 @cindex Modula-2 built-ins
13070 Modula-2 also makes available several built-in procedures and functions.
13071 In describing these, the following metavariables are used:
13076 represents an @code{ARRAY} variable.
13079 represents a @code{CHAR} constant or variable.
13082 represents a variable or constant of integral type.
13085 represents an identifier that belongs to a set. Generally used in the
13086 same function with the metavariable @var{s}. The type of @var{s} should
13087 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
13090 represents a variable or constant of integral or floating-point type.
13093 represents a variable or constant of floating-point type.
13099 represents a variable.
13102 represents a variable or constant of one of many types. See the
13103 explanation of the function for details.
13106 All Modula-2 built-in procedures also return a result, described below.
13110 Returns the absolute value of @var{n}.
13113 If @var{c} is a lower case letter, it returns its upper case
13114 equivalent, otherwise it returns its argument.
13117 Returns the character whose ordinal value is @var{i}.
13120 Decrements the value in the variable @var{v} by one. Returns the new value.
13122 @item DEC(@var{v},@var{i})
13123 Decrements the value in the variable @var{v} by @var{i}. Returns the
13126 @item EXCL(@var{m},@var{s})
13127 Removes the element @var{m} from the set @var{s}. Returns the new
13130 @item FLOAT(@var{i})
13131 Returns the floating point equivalent of the integer @var{i}.
13133 @item HIGH(@var{a})
13134 Returns the index of the last member of @var{a}.
13137 Increments the value in the variable @var{v} by one. Returns the new value.
13139 @item INC(@var{v},@var{i})
13140 Increments the value in the variable @var{v} by @var{i}. Returns the
13143 @item INCL(@var{m},@var{s})
13144 Adds the element @var{m} to the set @var{s} if it is not already
13145 there. Returns the new set.
13148 Returns the maximum value of the type @var{t}.
13151 Returns the minimum value of the type @var{t}.
13154 Returns boolean TRUE if @var{i} is an odd number.
13157 Returns the ordinal value of its argument. For example, the ordinal
13158 value of a character is its @sc{ascii} value (on machines supporting the
13159 @sc{ascii} character set). @var{x} must be of an ordered type, which include
13160 integral, character and enumerated types.
13162 @item SIZE(@var{x})
13163 Returns the size of its argument. @var{x} can be a variable or a type.
13165 @item TRUNC(@var{r})
13166 Returns the integral part of @var{r}.
13168 @item TSIZE(@var{x})
13169 Returns the size of its argument. @var{x} can be a variable or a type.
13171 @item VAL(@var{t},@var{i})
13172 Returns the member of the type @var{t} whose ordinal value is @var{i}.
13176 @emph{Warning:} Sets and their operations are not yet supported, so
13177 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
13181 @cindex Modula-2 constants
13183 @subsubsection Constants
13185 @value{GDBN} allows you to express the constants of Modula-2 in the following
13191 Integer constants are simply a sequence of digits. When used in an
13192 expression, a constant is interpreted to be type-compatible with the
13193 rest of the expression. Hexadecimal integers are specified by a
13194 trailing @samp{H}, and octal integers by a trailing @samp{B}.
13197 Floating point constants appear as a sequence of digits, followed by a
13198 decimal point and another sequence of digits. An optional exponent can
13199 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
13200 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
13201 digits of the floating point constant must be valid decimal (base 10)
13205 Character constants consist of a single character enclosed by a pair of
13206 like quotes, either single (@code{'}) or double (@code{"}). They may
13207 also be expressed by their ordinal value (their @sc{ascii} value, usually)
13208 followed by a @samp{C}.
13211 String constants consist of a sequence of characters enclosed by a
13212 pair of like quotes, either single (@code{'}) or double (@code{"}).
13213 Escape sequences in the style of C are also allowed. @xref{C
13214 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
13218 Enumerated constants consist of an enumerated identifier.
13221 Boolean constants consist of the identifiers @code{TRUE} and
13225 Pointer constants consist of integral values only.
13228 Set constants are not yet supported.
13232 @subsubsection Modula-2 Types
13233 @cindex Modula-2 types
13235 Currently @value{GDBN} can print the following data types in Modula-2
13236 syntax: array types, record types, set types, pointer types, procedure
13237 types, enumerated types, subrange types and base types. You can also
13238 print the contents of variables declared using these type.
13239 This section gives a number of simple source code examples together with
13240 sample @value{GDBN} sessions.
13242 The first example contains the following section of code:
13251 and you can request @value{GDBN} to interrogate the type and value of
13252 @code{r} and @code{s}.
13255 (@value{GDBP}) print s
13257 (@value{GDBP}) ptype s
13259 (@value{GDBP}) print r
13261 (@value{GDBP}) ptype r
13266 Likewise if your source code declares @code{s} as:
13270 s: SET ['A'..'Z'] ;
13274 then you may query the type of @code{s} by:
13277 (@value{GDBP}) ptype s
13278 type = SET ['A'..'Z']
13282 Note that at present you cannot interactively manipulate set
13283 expressions using the debugger.
13285 The following example shows how you might declare an array in Modula-2
13286 and how you can interact with @value{GDBN} to print its type and contents:
13290 s: ARRAY [-10..10] OF CHAR ;
13294 (@value{GDBP}) ptype s
13295 ARRAY [-10..10] OF CHAR
13298 Note that the array handling is not yet complete and although the type
13299 is printed correctly, expression handling still assumes that all
13300 arrays have a lower bound of zero and not @code{-10} as in the example
13303 Here are some more type related Modula-2 examples:
13307 colour = (blue, red, yellow, green) ;
13308 t = [blue..yellow] ;
13316 The @value{GDBN} interaction shows how you can query the data type
13317 and value of a variable.
13320 (@value{GDBP}) print s
13322 (@value{GDBP}) ptype t
13323 type = [blue..yellow]
13327 In this example a Modula-2 array is declared and its contents
13328 displayed. Observe that the contents are written in the same way as
13329 their @code{C} counterparts.
13333 s: ARRAY [1..5] OF CARDINAL ;
13339 (@value{GDBP}) print s
13340 $1 = @{1, 0, 0, 0, 0@}
13341 (@value{GDBP}) ptype s
13342 type = ARRAY [1..5] OF CARDINAL
13345 The Modula-2 language interface to @value{GDBN} also understands
13346 pointer types as shown in this example:
13350 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
13357 and you can request that @value{GDBN} describes the type of @code{s}.
13360 (@value{GDBP}) ptype s
13361 type = POINTER TO ARRAY [1..5] OF CARDINAL
13364 @value{GDBN} handles compound types as we can see in this example.
13365 Here we combine array types, record types, pointer types and subrange
13376 myarray = ARRAY myrange OF CARDINAL ;
13377 myrange = [-2..2] ;
13379 s: POINTER TO ARRAY myrange OF foo ;
13383 and you can ask @value{GDBN} to describe the type of @code{s} as shown
13387 (@value{GDBP}) ptype s
13388 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
13391 f3 : ARRAY [-2..2] OF CARDINAL;
13396 @subsubsection Modula-2 Defaults
13397 @cindex Modula-2 defaults
13399 If type and range checking are set automatically by @value{GDBN}, they
13400 both default to @code{on} whenever the working language changes to
13401 Modula-2. This happens regardless of whether you or @value{GDBN}
13402 selected the working language.
13404 If you allow @value{GDBN} to set the language automatically, then entering
13405 code compiled from a file whose name ends with @file{.mod} sets the
13406 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
13407 Infer the Source Language}, for further details.
13410 @subsubsection Deviations from Standard Modula-2
13411 @cindex Modula-2, deviations from
13413 A few changes have been made to make Modula-2 programs easier to debug.
13414 This is done primarily via loosening its type strictness:
13418 Unlike in standard Modula-2, pointer constants can be formed by
13419 integers. This allows you to modify pointer variables during
13420 debugging. (In standard Modula-2, the actual address contained in a
13421 pointer variable is hidden from you; it can only be modified
13422 through direct assignment to another pointer variable or expression that
13423 returned a pointer.)
13426 C escape sequences can be used in strings and characters to represent
13427 non-printable characters. @value{GDBN} prints out strings with these
13428 escape sequences embedded. Single non-printable characters are
13429 printed using the @samp{CHR(@var{nnn})} format.
13432 The assignment operator (@code{:=}) returns the value of its right-hand
13436 All built-in procedures both modify @emph{and} return their argument.
13440 @subsubsection Modula-2 Type and Range Checks
13441 @cindex Modula-2 checks
13444 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
13447 @c FIXME remove warning when type/range checks added
13449 @value{GDBN} considers two Modula-2 variables type equivalent if:
13453 They are of types that have been declared equivalent via a @code{TYPE
13454 @var{t1} = @var{t2}} statement
13457 They have been declared on the same line. (Note: This is true of the
13458 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
13461 As long as type checking is enabled, any attempt to combine variables
13462 whose types are not equivalent is an error.
13464 Range checking is done on all mathematical operations, assignment, array
13465 index bounds, and all built-in functions and procedures.
13468 @subsubsection The Scope Operators @code{::} and @code{.}
13470 @cindex @code{.}, Modula-2 scope operator
13471 @cindex colon, doubled as scope operator
13473 @vindex colon-colon@r{, in Modula-2}
13474 @c Info cannot handle :: but TeX can.
13477 @vindex ::@r{, in Modula-2}
13480 There are a few subtle differences between the Modula-2 scope operator
13481 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
13486 @var{module} . @var{id}
13487 @var{scope} :: @var{id}
13491 where @var{scope} is the name of a module or a procedure,
13492 @var{module} the name of a module, and @var{id} is any declared
13493 identifier within your program, except another module.
13495 Using the @code{::} operator makes @value{GDBN} search the scope
13496 specified by @var{scope} for the identifier @var{id}. If it is not
13497 found in the specified scope, then @value{GDBN} searches all scopes
13498 enclosing the one specified by @var{scope}.
13500 Using the @code{.} operator makes @value{GDBN} search the current scope for
13501 the identifier specified by @var{id} that was imported from the
13502 definition module specified by @var{module}. With this operator, it is
13503 an error if the identifier @var{id} was not imported from definition
13504 module @var{module}, or if @var{id} is not an identifier in
13508 @subsubsection @value{GDBN} and Modula-2
13510 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
13511 Five subcommands of @code{set print} and @code{show print} apply
13512 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
13513 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
13514 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
13515 analogue in Modula-2.
13517 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
13518 with any language, is not useful with Modula-2. Its
13519 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
13520 created in Modula-2 as they can in C or C@t{++}. However, because an
13521 address can be specified by an integral constant, the construct
13522 @samp{@{@var{type}@}@var{adrexp}} is still useful.
13524 @cindex @code{#} in Modula-2
13525 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
13526 interpreted as the beginning of a comment. Use @code{<>} instead.
13532 The extensions made to @value{GDBN} for Ada only support
13533 output from the @sc{gnu} Ada (GNAT) compiler.
13534 Other Ada compilers are not currently supported, and
13535 attempting to debug executables produced by them is most likely
13539 @cindex expressions in Ada
13541 * Ada Mode Intro:: General remarks on the Ada syntax
13542 and semantics supported by Ada mode
13544 * Omissions from Ada:: Restrictions on the Ada expression syntax.
13545 * Additions to Ada:: Extensions of the Ada expression syntax.
13546 * Stopping Before Main Program:: Debugging the program during elaboration.
13547 * Ada Tasks:: Listing and setting breakpoints in tasks.
13548 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
13549 * Ravenscar Profile:: Tasking Support when using the Ravenscar
13551 * Ada Glitches:: Known peculiarities of Ada mode.
13554 @node Ada Mode Intro
13555 @subsubsection Introduction
13556 @cindex Ada mode, general
13558 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
13559 syntax, with some extensions.
13560 The philosophy behind the design of this subset is
13564 That @value{GDBN} should provide basic literals and access to operations for
13565 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
13566 leaving more sophisticated computations to subprograms written into the
13567 program (which therefore may be called from @value{GDBN}).
13570 That type safety and strict adherence to Ada language restrictions
13571 are not particularly important to the @value{GDBN} user.
13574 That brevity is important to the @value{GDBN} user.
13577 Thus, for brevity, the debugger acts as if all names declared in
13578 user-written packages are directly visible, even if they are not visible
13579 according to Ada rules, thus making it unnecessary to fully qualify most
13580 names with their packages, regardless of context. Where this causes
13581 ambiguity, @value{GDBN} asks the user's intent.
13583 The debugger will start in Ada mode if it detects an Ada main program.
13584 As for other languages, it will enter Ada mode when stopped in a program that
13585 was translated from an Ada source file.
13587 While in Ada mode, you may use `@t{--}' for comments. This is useful
13588 mostly for documenting command files. The standard @value{GDBN} comment
13589 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
13590 middle (to allow based literals).
13592 The debugger supports limited overloading. Given a subprogram call in which
13593 the function symbol has multiple definitions, it will use the number of
13594 actual parameters and some information about their types to attempt to narrow
13595 the set of definitions. It also makes very limited use of context, preferring
13596 procedures to functions in the context of the @code{call} command, and
13597 functions to procedures elsewhere.
13599 @node Omissions from Ada
13600 @subsubsection Omissions from Ada
13601 @cindex Ada, omissions from
13603 Here are the notable omissions from the subset:
13607 Only a subset of the attributes are supported:
13611 @t{'First}, @t{'Last}, and @t{'Length}
13612 on array objects (not on types and subtypes).
13615 @t{'Min} and @t{'Max}.
13618 @t{'Pos} and @t{'Val}.
13624 @t{'Range} on array objects (not subtypes), but only as the right
13625 operand of the membership (@code{in}) operator.
13628 @t{'Access}, @t{'Unchecked_Access}, and
13629 @t{'Unrestricted_Access} (a GNAT extension).
13637 @code{Characters.Latin_1} are not available and
13638 concatenation is not implemented. Thus, escape characters in strings are
13639 not currently available.
13642 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
13643 equality of representations. They will generally work correctly
13644 for strings and arrays whose elements have integer or enumeration types.
13645 They may not work correctly for arrays whose element
13646 types have user-defined equality, for arrays of real values
13647 (in particular, IEEE-conformant floating point, because of negative
13648 zeroes and NaNs), and for arrays whose elements contain unused bits with
13649 indeterminate values.
13652 The other component-by-component array operations (@code{and}, @code{or},
13653 @code{xor}, @code{not}, and relational tests other than equality)
13654 are not implemented.
13657 @cindex array aggregates (Ada)
13658 @cindex record aggregates (Ada)
13659 @cindex aggregates (Ada)
13660 There is limited support for array and record aggregates. They are
13661 permitted only on the right sides of assignments, as in these examples:
13664 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
13665 (@value{GDBP}) set An_Array := (1, others => 0)
13666 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
13667 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
13668 (@value{GDBP}) set A_Record := (1, "Peter", True);
13669 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
13673 discriminant's value by assigning an aggregate has an
13674 undefined effect if that discriminant is used within the record.
13675 However, you can first modify discriminants by directly assigning to
13676 them (which normally would not be allowed in Ada), and then performing an
13677 aggregate assignment. For example, given a variable @code{A_Rec}
13678 declared to have a type such as:
13681 type Rec (Len : Small_Integer := 0) is record
13683 Vals : IntArray (1 .. Len);
13687 you can assign a value with a different size of @code{Vals} with two
13691 (@value{GDBP}) set A_Rec.Len := 4
13692 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
13695 As this example also illustrates, @value{GDBN} is very loose about the usual
13696 rules concerning aggregates. You may leave out some of the
13697 components of an array or record aggregate (such as the @code{Len}
13698 component in the assignment to @code{A_Rec} above); they will retain their
13699 original values upon assignment. You may freely use dynamic values as
13700 indices in component associations. You may even use overlapping or
13701 redundant component associations, although which component values are
13702 assigned in such cases is not defined.
13705 Calls to dispatching subprograms are not implemented.
13708 The overloading algorithm is much more limited (i.e., less selective)
13709 than that of real Ada. It makes only limited use of the context in
13710 which a subexpression appears to resolve its meaning, and it is much
13711 looser in its rules for allowing type matches. As a result, some
13712 function calls will be ambiguous, and the user will be asked to choose
13713 the proper resolution.
13716 The @code{new} operator is not implemented.
13719 Entry calls are not implemented.
13722 Aside from printing, arithmetic operations on the native VAX floating-point
13723 formats are not supported.
13726 It is not possible to slice a packed array.
13729 The names @code{True} and @code{False}, when not part of a qualified name,
13730 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
13732 Should your program
13733 redefine these names in a package or procedure (at best a dubious practice),
13734 you will have to use fully qualified names to access their new definitions.
13737 @node Additions to Ada
13738 @subsubsection Additions to Ada
13739 @cindex Ada, deviations from
13741 As it does for other languages, @value{GDBN} makes certain generic
13742 extensions to Ada (@pxref{Expressions}):
13746 If the expression @var{E} is a variable residing in memory (typically
13747 a local variable or array element) and @var{N} is a positive integer,
13748 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
13749 @var{N}-1 adjacent variables following it in memory as an array. In
13750 Ada, this operator is generally not necessary, since its prime use is
13751 in displaying parts of an array, and slicing will usually do this in
13752 Ada. However, there are occasional uses when debugging programs in
13753 which certain debugging information has been optimized away.
13756 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
13757 appears in function or file @var{B}.'' When @var{B} is a file name,
13758 you must typically surround it in single quotes.
13761 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
13762 @var{type} that appears at address @var{addr}.''
13765 A name starting with @samp{$} is a convenience variable
13766 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
13769 In addition, @value{GDBN} provides a few other shortcuts and outright
13770 additions specific to Ada:
13774 The assignment statement is allowed as an expression, returning
13775 its right-hand operand as its value. Thus, you may enter
13778 (@value{GDBP}) set x := y + 3
13779 (@value{GDBP}) print A(tmp := y + 1)
13783 The semicolon is allowed as an ``operator,'' returning as its value
13784 the value of its right-hand operand.
13785 This allows, for example,
13786 complex conditional breaks:
13789 (@value{GDBP}) break f
13790 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
13794 Rather than use catenation and symbolic character names to introduce special
13795 characters into strings, one may instead use a special bracket notation,
13796 which is also used to print strings. A sequence of characters of the form
13797 @samp{["@var{XX}"]} within a string or character literal denotes the
13798 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
13799 sequence of characters @samp{["""]} also denotes a single quotation mark
13800 in strings. For example,
13802 "One line.["0a"]Next line.["0a"]"
13805 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
13809 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
13810 @t{'Max} is optional (and is ignored in any case). For example, it is valid
13814 (@value{GDBP}) print 'max(x, y)
13818 When printing arrays, @value{GDBN} uses positional notation when the
13819 array has a lower bound of 1, and uses a modified named notation otherwise.
13820 For example, a one-dimensional array of three integers with a lower bound
13821 of 3 might print as
13828 That is, in contrast to valid Ada, only the first component has a @code{=>}
13832 You may abbreviate attributes in expressions with any unique,
13833 multi-character subsequence of
13834 their names (an exact match gets preference).
13835 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
13836 in place of @t{a'length}.
13839 @cindex quoting Ada internal identifiers
13840 Since Ada is case-insensitive, the debugger normally maps identifiers you type
13841 to lower case. The GNAT compiler uses upper-case characters for
13842 some of its internal identifiers, which are normally of no interest to users.
13843 For the rare occasions when you actually have to look at them,
13844 enclose them in angle brackets to avoid the lower-case mapping.
13847 (@value{GDBP}) print <JMPBUF_SAVE>[0]
13851 Printing an object of class-wide type or dereferencing an
13852 access-to-class-wide value will display all the components of the object's
13853 specific type (as indicated by its run-time tag). Likewise, component
13854 selection on such a value will operate on the specific type of the
13859 @node Stopping Before Main Program
13860 @subsubsection Stopping at the Very Beginning
13862 @cindex breakpointing Ada elaboration code
13863 It is sometimes necessary to debug the program during elaboration, and
13864 before reaching the main procedure.
13865 As defined in the Ada Reference
13866 Manual, the elaboration code is invoked from a procedure called
13867 @code{adainit}. To run your program up to the beginning of
13868 elaboration, simply use the following two commands:
13869 @code{tbreak adainit} and @code{run}.
13872 @subsubsection Extensions for Ada Tasks
13873 @cindex Ada, tasking
13875 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
13876 @value{GDBN} provides the following task-related commands:
13881 This command shows a list of current Ada tasks, as in the following example:
13888 (@value{GDBP}) info tasks
13889 ID TID P-ID Pri State Name
13890 1 8088000 0 15 Child Activation Wait main_task
13891 2 80a4000 1 15 Accept Statement b
13892 3 809a800 1 15 Child Activation Wait a
13893 * 4 80ae800 3 15 Runnable c
13898 In this listing, the asterisk before the last task indicates it to be the
13899 task currently being inspected.
13903 Represents @value{GDBN}'s internal task number.
13909 The parent's task ID (@value{GDBN}'s internal task number).
13912 The base priority of the task.
13915 Current state of the task.
13919 The task has been created but has not been activated. It cannot be
13923 The task is not blocked for any reason known to Ada. (It may be waiting
13924 for a mutex, though.) It is conceptually "executing" in normal mode.
13927 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
13928 that were waiting on terminate alternatives have been awakened and have
13929 terminated themselves.
13931 @item Child Activation Wait
13932 The task is waiting for created tasks to complete activation.
13934 @item Accept Statement
13935 The task is waiting on an accept or selective wait statement.
13937 @item Waiting on entry call
13938 The task is waiting on an entry call.
13940 @item Async Select Wait
13941 The task is waiting to start the abortable part of an asynchronous
13945 The task is waiting on a select statement with only a delay
13948 @item Child Termination Wait
13949 The task is sleeping having completed a master within itself, and is
13950 waiting for the tasks dependent on that master to become terminated or
13951 waiting on a terminate Phase.
13953 @item Wait Child in Term Alt
13954 The task is sleeping waiting for tasks on terminate alternatives to
13955 finish terminating.
13957 @item Accepting RV with @var{taskno}
13958 The task is accepting a rendez-vous with the task @var{taskno}.
13962 Name of the task in the program.
13966 @kindex info task @var{taskno}
13967 @item info task @var{taskno}
13968 This command shows detailled informations on the specified task, as in
13969 the following example:
13974 (@value{GDBP}) info tasks
13975 ID TID P-ID Pri State Name
13976 1 8077880 0 15 Child Activation Wait main_task
13977 * 2 807c468 1 15 Runnable task_1
13978 (@value{GDBP}) info task 2
13979 Ada Task: 0x807c468
13982 Parent: 1 (main_task)
13988 @kindex task@r{ (Ada)}
13989 @cindex current Ada task ID
13990 This command prints the ID of the current task.
13996 (@value{GDBP}) info tasks
13997 ID TID P-ID Pri State Name
13998 1 8077870 0 15 Child Activation Wait main_task
13999 * 2 807c458 1 15 Runnable t
14000 (@value{GDBP}) task
14001 [Current task is 2]
14004 @item task @var{taskno}
14005 @cindex Ada task switching
14006 This command is like the @code{thread @var{threadno}}
14007 command (@pxref{Threads}). It switches the context of debugging
14008 from the current task to the given task.
14014 (@value{GDBP}) info tasks
14015 ID TID P-ID Pri State Name
14016 1 8077870 0 15 Child Activation Wait main_task
14017 * 2 807c458 1 15 Runnable t
14018 (@value{GDBP}) task 1
14019 [Switching to task 1]
14020 #0 0x8067726 in pthread_cond_wait ()
14022 #0 0x8067726 in pthread_cond_wait ()
14023 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
14024 #2 0x805cb63 in system.task_primitives.operations.sleep ()
14025 #3 0x806153e in system.tasking.stages.activate_tasks ()
14026 #4 0x804aacc in un () at un.adb:5
14029 @item break @var{linespec} task @var{taskno}
14030 @itemx break @var{linespec} task @var{taskno} if @dots{}
14031 @cindex breakpoints and tasks, in Ada
14032 @cindex task breakpoints, in Ada
14033 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
14034 These commands are like the @code{break @dots{} thread @dots{}}
14035 command (@pxref{Thread Stops}).
14036 @var{linespec} specifies source lines, as described
14037 in @ref{Specify Location}.
14039 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
14040 to specify that you only want @value{GDBN} to stop the program when a
14041 particular Ada task reaches this breakpoint. @var{taskno} is one of the
14042 numeric task identifiers assigned by @value{GDBN}, shown in the first
14043 column of the @samp{info tasks} display.
14045 If you do not specify @samp{task @var{taskno}} when you set a
14046 breakpoint, the breakpoint applies to @emph{all} tasks of your
14049 You can use the @code{task} qualifier on conditional breakpoints as
14050 well; in this case, place @samp{task @var{taskno}} before the
14051 breakpoint condition (before the @code{if}).
14059 (@value{GDBP}) info tasks
14060 ID TID P-ID Pri State Name
14061 1 140022020 0 15 Child Activation Wait main_task
14062 2 140045060 1 15 Accept/Select Wait t2
14063 3 140044840 1 15 Runnable t1
14064 * 4 140056040 1 15 Runnable t3
14065 (@value{GDBP}) b 15 task 2
14066 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
14067 (@value{GDBP}) cont
14072 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
14074 (@value{GDBP}) info tasks
14075 ID TID P-ID Pri State Name
14076 1 140022020 0 15 Child Activation Wait main_task
14077 * 2 140045060 1 15 Runnable t2
14078 3 140044840 1 15 Runnable t1
14079 4 140056040 1 15 Delay Sleep t3
14083 @node Ada Tasks and Core Files
14084 @subsubsection Tasking Support when Debugging Core Files
14085 @cindex Ada tasking and core file debugging
14087 When inspecting a core file, as opposed to debugging a live program,
14088 tasking support may be limited or even unavailable, depending on
14089 the platform being used.
14090 For instance, on x86-linux, the list of tasks is available, but task
14091 switching is not supported. On Tru64, however, task switching will work
14094 On certain platforms, including Tru64, the debugger needs to perform some
14095 memory writes in order to provide Ada tasking support. When inspecting
14096 a core file, this means that the core file must be opened with read-write
14097 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
14098 Under these circumstances, you should make a backup copy of the core
14099 file before inspecting it with @value{GDBN}.
14101 @node Ravenscar Profile
14102 @subsubsection Tasking Support when using the Ravenscar Profile
14103 @cindex Ravenscar Profile
14105 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
14106 specifically designed for systems with safety-critical real-time
14110 @kindex set ravenscar task-switching on
14111 @cindex task switching with program using Ravenscar Profile
14112 @item set ravenscar task-switching on
14113 Allows task switching when debugging a program that uses the Ravenscar
14114 Profile. This is the default.
14116 @kindex set ravenscar task-switching off
14117 @item set ravenscar task-switching off
14118 Turn off task switching when debugging a program that uses the Ravenscar
14119 Profile. This is mostly intended to disable the code that adds support
14120 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
14121 the Ravenscar runtime is preventing @value{GDBN} from working properly.
14122 To be effective, this command should be run before the program is started.
14124 @kindex show ravenscar task-switching
14125 @item show ravenscar task-switching
14126 Show whether it is possible to switch from task to task in a program
14127 using the Ravenscar Profile.
14132 @subsubsection Known Peculiarities of Ada Mode
14133 @cindex Ada, problems
14135 Besides the omissions listed previously (@pxref{Omissions from Ada}),
14136 we know of several problems with and limitations of Ada mode in
14138 some of which will be fixed with planned future releases of the debugger
14139 and the GNU Ada compiler.
14143 Static constants that the compiler chooses not to materialize as objects in
14144 storage are invisible to the debugger.
14147 Named parameter associations in function argument lists are ignored (the
14148 argument lists are treated as positional).
14151 Many useful library packages are currently invisible to the debugger.
14154 Fixed-point arithmetic, conversions, input, and output is carried out using
14155 floating-point arithmetic, and may give results that only approximate those on
14159 The GNAT compiler never generates the prefix @code{Standard} for any of
14160 the standard symbols defined by the Ada language. @value{GDBN} knows about
14161 this: it will strip the prefix from names when you use it, and will never
14162 look for a name you have so qualified among local symbols, nor match against
14163 symbols in other packages or subprograms. If you have
14164 defined entities anywhere in your program other than parameters and
14165 local variables whose simple names match names in @code{Standard},
14166 GNAT's lack of qualification here can cause confusion. When this happens,
14167 you can usually resolve the confusion
14168 by qualifying the problematic names with package
14169 @code{Standard} explicitly.
14172 Older versions of the compiler sometimes generate erroneous debugging
14173 information, resulting in the debugger incorrectly printing the value
14174 of affected entities. In some cases, the debugger is able to work
14175 around an issue automatically. In other cases, the debugger is able
14176 to work around the issue, but the work-around has to be specifically
14179 @kindex set ada trust-PAD-over-XVS
14180 @kindex show ada trust-PAD-over-XVS
14183 @item set ada trust-PAD-over-XVS on
14184 Configure GDB to strictly follow the GNAT encoding when computing the
14185 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
14186 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
14187 a complete description of the encoding used by the GNAT compiler).
14188 This is the default.
14190 @item set ada trust-PAD-over-XVS off
14191 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
14192 sometimes prints the wrong value for certain entities, changing @code{ada
14193 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
14194 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
14195 @code{off}, but this incurs a slight performance penalty, so it is
14196 recommended to leave this setting to @code{on} unless necessary.
14200 @node Unsupported Languages
14201 @section Unsupported Languages
14203 @cindex unsupported languages
14204 @cindex minimal language
14205 In addition to the other fully-supported programming languages,
14206 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
14207 It does not represent a real programming language, but provides a set
14208 of capabilities close to what the C or assembly languages provide.
14209 This should allow most simple operations to be performed while debugging
14210 an application that uses a language currently not supported by @value{GDBN}.
14212 If the language is set to @code{auto}, @value{GDBN} will automatically
14213 select this language if the current frame corresponds to an unsupported
14217 @chapter Examining the Symbol Table
14219 The commands described in this chapter allow you to inquire about the
14220 symbols (names of variables, functions and types) defined in your
14221 program. This information is inherent in the text of your program and
14222 does not change as your program executes. @value{GDBN} finds it in your
14223 program's symbol table, in the file indicated when you started @value{GDBN}
14224 (@pxref{File Options, ,Choosing Files}), or by one of the
14225 file-management commands (@pxref{Files, ,Commands to Specify Files}).
14227 @cindex symbol names
14228 @cindex names of symbols
14229 @cindex quoting names
14230 Occasionally, you may need to refer to symbols that contain unusual
14231 characters, which @value{GDBN} ordinarily treats as word delimiters. The
14232 most frequent case is in referring to static variables in other
14233 source files (@pxref{Variables,,Program Variables}). File names
14234 are recorded in object files as debugging symbols, but @value{GDBN} would
14235 ordinarily parse a typical file name, like @file{foo.c}, as the three words
14236 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
14237 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
14244 looks up the value of @code{x} in the scope of the file @file{foo.c}.
14247 @cindex case-insensitive symbol names
14248 @cindex case sensitivity in symbol names
14249 @kindex set case-sensitive
14250 @item set case-sensitive on
14251 @itemx set case-sensitive off
14252 @itemx set case-sensitive auto
14253 Normally, when @value{GDBN} looks up symbols, it matches their names
14254 with case sensitivity determined by the current source language.
14255 Occasionally, you may wish to control that. The command @code{set
14256 case-sensitive} lets you do that by specifying @code{on} for
14257 case-sensitive matches or @code{off} for case-insensitive ones. If
14258 you specify @code{auto}, case sensitivity is reset to the default
14259 suitable for the source language. The default is case-sensitive
14260 matches for all languages except for Fortran, for which the default is
14261 case-insensitive matches.
14263 @kindex show case-sensitive
14264 @item show case-sensitive
14265 This command shows the current setting of case sensitivity for symbols
14268 @kindex info address
14269 @cindex address of a symbol
14270 @item info address @var{symbol}
14271 Describe where the data for @var{symbol} is stored. For a register
14272 variable, this says which register it is kept in. For a non-register
14273 local variable, this prints the stack-frame offset at which the variable
14276 Note the contrast with @samp{print &@var{symbol}}, which does not work
14277 at all for a register variable, and for a stack local variable prints
14278 the exact address of the current instantiation of the variable.
14280 @kindex info symbol
14281 @cindex symbol from address
14282 @cindex closest symbol and offset for an address
14283 @item info symbol @var{addr}
14284 Print the name of a symbol which is stored at the address @var{addr}.
14285 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
14286 nearest symbol and an offset from it:
14289 (@value{GDBP}) info symbol 0x54320
14290 _initialize_vx + 396 in section .text
14294 This is the opposite of the @code{info address} command. You can use
14295 it to find out the name of a variable or a function given its address.
14297 For dynamically linked executables, the name of executable or shared
14298 library containing the symbol is also printed:
14301 (@value{GDBP}) info symbol 0x400225
14302 _start + 5 in section .text of /tmp/a.out
14303 (@value{GDBP}) info symbol 0x2aaaac2811cf
14304 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
14308 @item whatis [@var{arg}]
14309 Print the data type of @var{arg}, which can be either an expression
14310 or a name of a data type. With no argument, print the data type of
14311 @code{$}, the last value in the value history.
14313 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
14314 is not actually evaluated, and any side-effecting operations (such as
14315 assignments or function calls) inside it do not take place.
14317 If @var{arg} is a variable or an expression, @code{whatis} prints its
14318 literal type as it is used in the source code. If the type was
14319 defined using a @code{typedef}, @code{whatis} will @emph{not} print
14320 the data type underlying the @code{typedef}. If the type of the
14321 variable or the expression is a compound data type, such as
14322 @code{struct} or @code{class}, @code{whatis} never prints their
14323 fields or methods. It just prints the @code{struct}/@code{class}
14324 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
14325 such a compound data type, use @code{ptype}.
14327 If @var{arg} is a type name that was defined using @code{typedef},
14328 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
14329 Unrolling means that @code{whatis} will show the underlying type used
14330 in the @code{typedef} declaration of @var{arg}. However, if that
14331 underlying type is also a @code{typedef}, @code{whatis} will not
14334 For C code, the type names may also have the form @samp{class
14335 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
14336 @var{union-tag}} or @samp{enum @var{enum-tag}}.
14339 @item ptype [@var{arg}]
14340 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
14341 detailed description of the type, instead of just the name of the type.
14342 @xref{Expressions, ,Expressions}.
14344 Contrary to @code{whatis}, @code{ptype} always unrolls any
14345 @code{typedef}s in its argument declaration, whether the argument is
14346 a variable, expression, or a data type. This means that @code{ptype}
14347 of a variable or an expression will not print literally its type as
14348 present in the source code---use @code{whatis} for that. @code{typedef}s at
14349 the pointer or reference targets are also unrolled. Only @code{typedef}s of
14350 fields, methods and inner @code{class typedef}s of @code{struct}s,
14351 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
14353 For example, for this variable declaration:
14356 typedef double real_t;
14357 struct complex @{ real_t real; double imag; @};
14358 typedef struct complex complex_t;
14360 real_t *real_pointer_var;
14364 the two commands give this output:
14368 (@value{GDBP}) whatis var
14370 (@value{GDBP}) ptype var
14371 type = struct complex @{
14375 (@value{GDBP}) whatis complex_t
14376 type = struct complex
14377 (@value{GDBP}) whatis struct complex
14378 type = struct complex
14379 (@value{GDBP}) ptype struct complex
14380 type = struct complex @{
14384 (@value{GDBP}) whatis real_pointer_var
14386 (@value{GDBP}) ptype real_pointer_var
14392 As with @code{whatis}, using @code{ptype} without an argument refers to
14393 the type of @code{$}, the last value in the value history.
14395 @cindex incomplete type
14396 Sometimes, programs use opaque data types or incomplete specifications
14397 of complex data structure. If the debug information included in the
14398 program does not allow @value{GDBN} to display a full declaration of
14399 the data type, it will say @samp{<incomplete type>}. For example,
14400 given these declarations:
14404 struct foo *fooptr;
14408 but no definition for @code{struct foo} itself, @value{GDBN} will say:
14411 (@value{GDBP}) ptype foo
14412 $1 = <incomplete type>
14416 ``Incomplete type'' is C terminology for data types that are not
14417 completely specified.
14420 @item info types @var{regexp}
14422 Print a brief description of all types whose names match the regular
14423 expression @var{regexp} (or all types in your program, if you supply
14424 no argument). Each complete typename is matched as though it were a
14425 complete line; thus, @samp{i type value} gives information on all
14426 types in your program whose names include the string @code{value}, but
14427 @samp{i type ^value$} gives information only on types whose complete
14428 name is @code{value}.
14430 This command differs from @code{ptype} in two ways: first, like
14431 @code{whatis}, it does not print a detailed description; second, it
14432 lists all source files where a type is defined.
14435 @cindex local variables
14436 @item info scope @var{location}
14437 List all the variables local to a particular scope. This command
14438 accepts a @var{location} argument---a function name, a source line, or
14439 an address preceded by a @samp{*}, and prints all the variables local
14440 to the scope defined by that location. (@xref{Specify Location}, for
14441 details about supported forms of @var{location}.) For example:
14444 (@value{GDBP}) @b{info scope command_line_handler}
14445 Scope for command_line_handler:
14446 Symbol rl is an argument at stack/frame offset 8, length 4.
14447 Symbol linebuffer is in static storage at address 0x150a18, length 4.
14448 Symbol linelength is in static storage at address 0x150a1c, length 4.
14449 Symbol p is a local variable in register $esi, length 4.
14450 Symbol p1 is a local variable in register $ebx, length 4.
14451 Symbol nline is a local variable in register $edx, length 4.
14452 Symbol repeat is a local variable at frame offset -8, length 4.
14456 This command is especially useful for determining what data to collect
14457 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
14460 @kindex info source
14462 Show information about the current source file---that is, the source file for
14463 the function containing the current point of execution:
14466 the name of the source file, and the directory containing it,
14468 the directory it was compiled in,
14470 its length, in lines,
14472 which programming language it is written in,
14474 whether the executable includes debugging information for that file, and
14475 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
14477 whether the debugging information includes information about
14478 preprocessor macros.
14482 @kindex info sources
14484 Print the names of all source files in your program for which there is
14485 debugging information, organized into two lists: files whose symbols
14486 have already been read, and files whose symbols will be read when needed.
14488 @kindex info functions
14489 @item info functions
14490 Print the names and data types of all defined functions.
14492 @item info functions @var{regexp}
14493 Print the names and data types of all defined functions
14494 whose names contain a match for regular expression @var{regexp}.
14495 Thus, @samp{info fun step} finds all functions whose names
14496 include @code{step}; @samp{info fun ^step} finds those whose names
14497 start with @code{step}. If a function name contains characters
14498 that conflict with the regular expression language (e.g.@:
14499 @samp{operator*()}), they may be quoted with a backslash.
14501 @kindex info variables
14502 @item info variables
14503 Print the names and data types of all variables that are defined
14504 outside of functions (i.e.@: excluding local variables).
14506 @item info variables @var{regexp}
14507 Print the names and data types of all variables (except for local
14508 variables) whose names contain a match for regular expression
14511 @kindex info classes
14512 @cindex Objective-C, classes and selectors
14514 @itemx info classes @var{regexp}
14515 Display all Objective-C classes in your program, or
14516 (with the @var{regexp} argument) all those matching a particular regular
14519 @kindex info selectors
14520 @item info selectors
14521 @itemx info selectors @var{regexp}
14522 Display all Objective-C selectors in your program, or
14523 (with the @var{regexp} argument) all those matching a particular regular
14527 This was never implemented.
14528 @kindex info methods
14530 @itemx info methods @var{regexp}
14531 The @code{info methods} command permits the user to examine all defined
14532 methods within C@t{++} program, or (with the @var{regexp} argument) a
14533 specific set of methods found in the various C@t{++} classes. Many
14534 C@t{++} classes provide a large number of methods. Thus, the output
14535 from the @code{ptype} command can be overwhelming and hard to use. The
14536 @code{info-methods} command filters the methods, printing only those
14537 which match the regular-expression @var{regexp}.
14540 @cindex reloading symbols
14541 Some systems allow individual object files that make up your program to
14542 be replaced without stopping and restarting your program. For example,
14543 in VxWorks you can simply recompile a defective object file and keep on
14544 running. If you are running on one of these systems, you can allow
14545 @value{GDBN} to reload the symbols for automatically relinked modules:
14548 @kindex set symbol-reloading
14549 @item set symbol-reloading on
14550 Replace symbol definitions for the corresponding source file when an
14551 object file with a particular name is seen again.
14553 @item set symbol-reloading off
14554 Do not replace symbol definitions when encountering object files of the
14555 same name more than once. This is the default state; if you are not
14556 running on a system that permits automatic relinking of modules, you
14557 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
14558 may discard symbols when linking large programs, that may contain
14559 several modules (from different directories or libraries) with the same
14562 @kindex show symbol-reloading
14563 @item show symbol-reloading
14564 Show the current @code{on} or @code{off} setting.
14567 @cindex opaque data types
14568 @kindex set opaque-type-resolution
14569 @item set opaque-type-resolution on
14570 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
14571 declared as a pointer to a @code{struct}, @code{class}, or
14572 @code{union}---for example, @code{struct MyType *}---that is used in one
14573 source file although the full declaration of @code{struct MyType} is in
14574 another source file. The default is on.
14576 A change in the setting of this subcommand will not take effect until
14577 the next time symbols for a file are loaded.
14579 @item set opaque-type-resolution off
14580 Tell @value{GDBN} not to resolve opaque types. In this case, the type
14581 is printed as follows:
14583 @{<no data fields>@}
14586 @kindex show opaque-type-resolution
14587 @item show opaque-type-resolution
14588 Show whether opaque types are resolved or not.
14590 @kindex maint print symbols
14591 @cindex symbol dump
14592 @kindex maint print psymbols
14593 @cindex partial symbol dump
14594 @item maint print symbols @var{filename}
14595 @itemx maint print psymbols @var{filename}
14596 @itemx maint print msymbols @var{filename}
14597 Write a dump of debugging symbol data into the file @var{filename}.
14598 These commands are used to debug the @value{GDBN} symbol-reading code. Only
14599 symbols with debugging data are included. If you use @samp{maint print
14600 symbols}, @value{GDBN} includes all the symbols for which it has already
14601 collected full details: that is, @var{filename} reflects symbols for
14602 only those files whose symbols @value{GDBN} has read. You can use the
14603 command @code{info sources} to find out which files these are. If you
14604 use @samp{maint print psymbols} instead, the dump shows information about
14605 symbols that @value{GDBN} only knows partially---that is, symbols defined in
14606 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
14607 @samp{maint print msymbols} dumps just the minimal symbol information
14608 required for each object file from which @value{GDBN} has read some symbols.
14609 @xref{Files, ,Commands to Specify Files}, for a discussion of how
14610 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
14612 @kindex maint info symtabs
14613 @kindex maint info psymtabs
14614 @cindex listing @value{GDBN}'s internal symbol tables
14615 @cindex symbol tables, listing @value{GDBN}'s internal
14616 @cindex full symbol tables, listing @value{GDBN}'s internal
14617 @cindex partial symbol tables, listing @value{GDBN}'s internal
14618 @item maint info symtabs @r{[} @var{regexp} @r{]}
14619 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
14621 List the @code{struct symtab} or @code{struct partial_symtab}
14622 structures whose names match @var{regexp}. If @var{regexp} is not
14623 given, list them all. The output includes expressions which you can
14624 copy into a @value{GDBN} debugging this one to examine a particular
14625 structure in more detail. For example:
14628 (@value{GDBP}) maint info psymtabs dwarf2read
14629 @{ objfile /home/gnu/build/gdb/gdb
14630 ((struct objfile *) 0x82e69d0)
14631 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
14632 ((struct partial_symtab *) 0x8474b10)
14635 text addresses 0x814d3c8 -- 0x8158074
14636 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
14637 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
14638 dependencies (none)
14641 (@value{GDBP}) maint info symtabs
14645 We see that there is one partial symbol table whose filename contains
14646 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
14647 and we see that @value{GDBN} has not read in any symtabs yet at all.
14648 If we set a breakpoint on a function, that will cause @value{GDBN} to
14649 read the symtab for the compilation unit containing that function:
14652 (@value{GDBP}) break dwarf2_psymtab_to_symtab
14653 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
14655 (@value{GDBP}) maint info symtabs
14656 @{ objfile /home/gnu/build/gdb/gdb
14657 ((struct objfile *) 0x82e69d0)
14658 @{ symtab /home/gnu/src/gdb/dwarf2read.c
14659 ((struct symtab *) 0x86c1f38)
14662 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
14663 linetable ((struct linetable *) 0x8370fa0)
14664 debugformat DWARF 2
14673 @chapter Altering Execution
14675 Once you think you have found an error in your program, you might want to
14676 find out for certain whether correcting the apparent error would lead to
14677 correct results in the rest of the run. You can find the answer by
14678 experiment, using the @value{GDBN} features for altering execution of the
14681 For example, you can store new values into variables or memory
14682 locations, give your program a signal, restart it at a different
14683 address, or even return prematurely from a function.
14686 * Assignment:: Assignment to variables
14687 * Jumping:: Continuing at a different address
14688 * Signaling:: Giving your program a signal
14689 * Returning:: Returning from a function
14690 * Calling:: Calling your program's functions
14691 * Patching:: Patching your program
14695 @section Assignment to Variables
14698 @cindex setting variables
14699 To alter the value of a variable, evaluate an assignment expression.
14700 @xref{Expressions, ,Expressions}. For example,
14707 stores the value 4 into the variable @code{x}, and then prints the
14708 value of the assignment expression (which is 4).
14709 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
14710 information on operators in supported languages.
14712 @kindex set variable
14713 @cindex variables, setting
14714 If you are not interested in seeing the value of the assignment, use the
14715 @code{set} command instead of the @code{print} command. @code{set} is
14716 really the same as @code{print} except that the expression's value is
14717 not printed and is not put in the value history (@pxref{Value History,
14718 ,Value History}). The expression is evaluated only for its effects.
14720 If the beginning of the argument string of the @code{set} command
14721 appears identical to a @code{set} subcommand, use the @code{set
14722 variable} command instead of just @code{set}. This command is identical
14723 to @code{set} except for its lack of subcommands. For example, if your
14724 program has a variable @code{width}, you get an error if you try to set
14725 a new value with just @samp{set width=13}, because @value{GDBN} has the
14726 command @code{set width}:
14729 (@value{GDBP}) whatis width
14731 (@value{GDBP}) p width
14733 (@value{GDBP}) set width=47
14734 Invalid syntax in expression.
14738 The invalid expression, of course, is @samp{=47}. In
14739 order to actually set the program's variable @code{width}, use
14742 (@value{GDBP}) set var width=47
14745 Because the @code{set} command has many subcommands that can conflict
14746 with the names of program variables, it is a good idea to use the
14747 @code{set variable} command instead of just @code{set}. For example, if
14748 your program has a variable @code{g}, you run into problems if you try
14749 to set a new value with just @samp{set g=4}, because @value{GDBN} has
14750 the command @code{set gnutarget}, abbreviated @code{set g}:
14754 (@value{GDBP}) whatis g
14758 (@value{GDBP}) set g=4
14762 The program being debugged has been started already.
14763 Start it from the beginning? (y or n) y
14764 Starting program: /home/smith/cc_progs/a.out
14765 "/home/smith/cc_progs/a.out": can't open to read symbols:
14766 Invalid bfd target.
14767 (@value{GDBP}) show g
14768 The current BFD target is "=4".
14773 The program variable @code{g} did not change, and you silently set the
14774 @code{gnutarget} to an invalid value. In order to set the variable
14778 (@value{GDBP}) set var g=4
14781 @value{GDBN} allows more implicit conversions in assignments than C; you can
14782 freely store an integer value into a pointer variable or vice versa,
14783 and you can convert any structure to any other structure that is the
14784 same length or shorter.
14785 @comment FIXME: how do structs align/pad in these conversions?
14786 @comment /doc@cygnus.com 18dec1990
14788 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
14789 construct to generate a value of specified type at a specified address
14790 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
14791 to memory location @code{0x83040} as an integer (which implies a certain size
14792 and representation in memory), and
14795 set @{int@}0x83040 = 4
14799 stores the value 4 into that memory location.
14802 @section Continuing at a Different Address
14804 Ordinarily, when you continue your program, you do so at the place where
14805 it stopped, with the @code{continue} command. You can instead continue at
14806 an address of your own choosing, with the following commands:
14810 @item jump @var{linespec}
14811 @itemx jump @var{location}
14812 Resume execution at line @var{linespec} or at address given by
14813 @var{location}. Execution stops again immediately if there is a
14814 breakpoint there. @xref{Specify Location}, for a description of the
14815 different forms of @var{linespec} and @var{location}. It is common
14816 practice to use the @code{tbreak} command in conjunction with
14817 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
14819 The @code{jump} command does not change the current stack frame, or
14820 the stack pointer, or the contents of any memory location or any
14821 register other than the program counter. If line @var{linespec} is in
14822 a different function from the one currently executing, the results may
14823 be bizarre if the two functions expect different patterns of arguments or
14824 of local variables. For this reason, the @code{jump} command requests
14825 confirmation if the specified line is not in the function currently
14826 executing. However, even bizarre results are predictable if you are
14827 well acquainted with the machine-language code of your program.
14830 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
14831 On many systems, you can get much the same effect as the @code{jump}
14832 command by storing a new value into the register @code{$pc}. The
14833 difference is that this does not start your program running; it only
14834 changes the address of where it @emph{will} run when you continue. For
14842 makes the next @code{continue} command or stepping command execute at
14843 address @code{0x485}, rather than at the address where your program stopped.
14844 @xref{Continuing and Stepping, ,Continuing and Stepping}.
14846 The most common occasion to use the @code{jump} command is to back
14847 up---perhaps with more breakpoints set---over a portion of a program
14848 that has already executed, in order to examine its execution in more
14853 @section Giving your Program a Signal
14854 @cindex deliver a signal to a program
14858 @item signal @var{signal}
14859 Resume execution where your program stopped, but immediately give it the
14860 signal @var{signal}. @var{signal} can be the name or the number of a
14861 signal. For example, on many systems @code{signal 2} and @code{signal
14862 SIGINT} are both ways of sending an interrupt signal.
14864 Alternatively, if @var{signal} is zero, continue execution without
14865 giving a signal. This is useful when your program stopped on account of
14866 a signal and would ordinary see the signal when resumed with the
14867 @code{continue} command; @samp{signal 0} causes it to resume without a
14870 @code{signal} does not repeat when you press @key{RET} a second time
14871 after executing the command.
14875 Invoking the @code{signal} command is not the same as invoking the
14876 @code{kill} utility from the shell. Sending a signal with @code{kill}
14877 causes @value{GDBN} to decide what to do with the signal depending on
14878 the signal handling tables (@pxref{Signals}). The @code{signal} command
14879 passes the signal directly to your program.
14883 @section Returning from a Function
14886 @cindex returning from a function
14889 @itemx return @var{expression}
14890 You can cancel execution of a function call with the @code{return}
14891 command. If you give an
14892 @var{expression} argument, its value is used as the function's return
14896 When you use @code{return}, @value{GDBN} discards the selected stack frame
14897 (and all frames within it). You can think of this as making the
14898 discarded frame return prematurely. If you wish to specify a value to
14899 be returned, give that value as the argument to @code{return}.
14901 This pops the selected stack frame (@pxref{Selection, ,Selecting a
14902 Frame}), and any other frames inside of it, leaving its caller as the
14903 innermost remaining frame. That frame becomes selected. The
14904 specified value is stored in the registers used for returning values
14907 The @code{return} command does not resume execution; it leaves the
14908 program stopped in the state that would exist if the function had just
14909 returned. In contrast, the @code{finish} command (@pxref{Continuing
14910 and Stepping, ,Continuing and Stepping}) resumes execution until the
14911 selected stack frame returns naturally.
14913 @value{GDBN} needs to know how the @var{expression} argument should be set for
14914 the inferior. The concrete registers assignment depends on the OS ABI and the
14915 type being returned by the selected stack frame. For example it is common for
14916 OS ABI to return floating point values in FPU registers while integer values in
14917 CPU registers. Still some ABIs return even floating point values in CPU
14918 registers. Larger integer widths (such as @code{long long int}) also have
14919 specific placement rules. @value{GDBN} already knows the OS ABI from its
14920 current target so it needs to find out also the type being returned to make the
14921 assignment into the right register(s).
14923 Normally, the selected stack frame has debug info. @value{GDBN} will always
14924 use the debug info instead of the implicit type of @var{expression} when the
14925 debug info is available. For example, if you type @kbd{return -1}, and the
14926 function in the current stack frame is declared to return a @code{long long
14927 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
14928 into a @code{long long int}:
14931 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
14933 (@value{GDBP}) return -1
14934 Make func return now? (y or n) y
14935 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
14936 43 printf ("result=%lld\n", func ());
14940 However, if the selected stack frame does not have a debug info, e.g., if the
14941 function was compiled without debug info, @value{GDBN} has to find out the type
14942 to return from user. Specifying a different type by mistake may set the value
14943 in different inferior registers than the caller code expects. For example,
14944 typing @kbd{return -1} with its implicit type @code{int} would set only a part
14945 of a @code{long long int} result for a debug info less function (on 32-bit
14946 architectures). Therefore the user is required to specify the return type by
14947 an appropriate cast explicitly:
14950 Breakpoint 2, 0x0040050b in func ()
14951 (@value{GDBP}) return -1
14952 Return value type not available for selected stack frame.
14953 Please use an explicit cast of the value to return.
14954 (@value{GDBP}) return (long long int) -1
14955 Make selected stack frame return now? (y or n) y
14956 #0 0x00400526 in main ()
14961 @section Calling Program Functions
14964 @cindex calling functions
14965 @cindex inferior functions, calling
14966 @item print @var{expr}
14967 Evaluate the expression @var{expr} and display the resulting value.
14968 @var{expr} may include calls to functions in the program being
14972 @item call @var{expr}
14973 Evaluate the expression @var{expr} without displaying @code{void}
14976 You can use this variant of the @code{print} command if you want to
14977 execute a function from your program that does not return anything
14978 (a.k.a.@: @dfn{a void function}), but without cluttering the output
14979 with @code{void} returned values that @value{GDBN} will otherwise
14980 print. If the result is not void, it is printed and saved in the
14984 It is possible for the function you call via the @code{print} or
14985 @code{call} command to generate a signal (e.g., if there's a bug in
14986 the function, or if you passed it incorrect arguments). What happens
14987 in that case is controlled by the @code{set unwindonsignal} command.
14989 Similarly, with a C@t{++} program it is possible for the function you
14990 call via the @code{print} or @code{call} command to generate an
14991 exception that is not handled due to the constraints of the dummy
14992 frame. In this case, any exception that is raised in the frame, but has
14993 an out-of-frame exception handler will not be found. GDB builds a
14994 dummy-frame for the inferior function call, and the unwinder cannot
14995 seek for exception handlers outside of this dummy-frame. What happens
14996 in that case is controlled by the
14997 @code{set unwind-on-terminating-exception} command.
15000 @item set unwindonsignal
15001 @kindex set unwindonsignal
15002 @cindex unwind stack in called functions
15003 @cindex call dummy stack unwinding
15004 Set unwinding of the stack if a signal is received while in a function
15005 that @value{GDBN} called in the program being debugged. If set to on,
15006 @value{GDBN} unwinds the stack it created for the call and restores
15007 the context to what it was before the call. If set to off (the
15008 default), @value{GDBN} stops in the frame where the signal was
15011 @item show unwindonsignal
15012 @kindex show unwindonsignal
15013 Show the current setting of stack unwinding in the functions called by
15016 @item set unwind-on-terminating-exception
15017 @kindex set unwind-on-terminating-exception
15018 @cindex unwind stack in called functions with unhandled exceptions
15019 @cindex call dummy stack unwinding on unhandled exception.
15020 Set unwinding of the stack if a C@t{++} exception is raised, but left
15021 unhandled while in a function that @value{GDBN} called in the program being
15022 debugged. If set to on (the default), @value{GDBN} unwinds the stack
15023 it created for the call and restores the context to what it was before
15024 the call. If set to off, @value{GDBN} the exception is delivered to
15025 the default C@t{++} exception handler and the inferior terminated.
15027 @item show unwind-on-terminating-exception
15028 @kindex show unwind-on-terminating-exception
15029 Show the current setting of stack unwinding in the functions called by
15034 @cindex weak alias functions
15035 Sometimes, a function you wish to call is actually a @dfn{weak alias}
15036 for another function. In such case, @value{GDBN} might not pick up
15037 the type information, including the types of the function arguments,
15038 which causes @value{GDBN} to call the inferior function incorrectly.
15039 As a result, the called function will function erroneously and may
15040 even crash. A solution to that is to use the name of the aliased
15044 @section Patching Programs
15046 @cindex patching binaries
15047 @cindex writing into executables
15048 @cindex writing into corefiles
15050 By default, @value{GDBN} opens the file containing your program's
15051 executable code (or the corefile) read-only. This prevents accidental
15052 alterations to machine code; but it also prevents you from intentionally
15053 patching your program's binary.
15055 If you'd like to be able to patch the binary, you can specify that
15056 explicitly with the @code{set write} command. For example, you might
15057 want to turn on internal debugging flags, or even to make emergency
15063 @itemx set write off
15064 If you specify @samp{set write on}, @value{GDBN} opens executable and
15065 core files for both reading and writing; if you specify @kbd{set write
15066 off} (the default), @value{GDBN} opens them read-only.
15068 If you have already loaded a file, you must load it again (using the
15069 @code{exec-file} or @code{core-file} command) after changing @code{set
15070 write}, for your new setting to take effect.
15074 Display whether executable files and core files are opened for writing
15075 as well as reading.
15079 @chapter @value{GDBN} Files
15081 @value{GDBN} needs to know the file name of the program to be debugged,
15082 both in order to read its symbol table and in order to start your
15083 program. To debug a core dump of a previous run, you must also tell
15084 @value{GDBN} the name of the core dump file.
15087 * Files:: Commands to specify files
15088 * Separate Debug Files:: Debugging information in separate files
15089 * Index Files:: Index files speed up GDB
15090 * Symbol Errors:: Errors reading symbol files
15091 * Data Files:: GDB data files
15095 @section Commands to Specify Files
15097 @cindex symbol table
15098 @cindex core dump file
15100 You may want to specify executable and core dump file names. The usual
15101 way to do this is at start-up time, using the arguments to
15102 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
15103 Out of @value{GDBN}}).
15105 Occasionally it is necessary to change to a different file during a
15106 @value{GDBN} session. Or you may run @value{GDBN} and forget to
15107 specify a file you want to use. Or you are debugging a remote target
15108 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
15109 Program}). In these situations the @value{GDBN} commands to specify
15110 new files are useful.
15113 @cindex executable file
15115 @item file @var{filename}
15116 Use @var{filename} as the program to be debugged. It is read for its
15117 symbols and for the contents of pure memory. It is also the program
15118 executed when you use the @code{run} command. If you do not specify a
15119 directory and the file is not found in the @value{GDBN} working directory,
15120 @value{GDBN} uses the environment variable @code{PATH} as a list of
15121 directories to search, just as the shell does when looking for a program
15122 to run. You can change the value of this variable, for both @value{GDBN}
15123 and your program, using the @code{path} command.
15125 @cindex unlinked object files
15126 @cindex patching object files
15127 You can load unlinked object @file{.o} files into @value{GDBN} using
15128 the @code{file} command. You will not be able to ``run'' an object
15129 file, but you can disassemble functions and inspect variables. Also,
15130 if the underlying BFD functionality supports it, you could use
15131 @kbd{gdb -write} to patch object files using this technique. Note
15132 that @value{GDBN} can neither interpret nor modify relocations in this
15133 case, so branches and some initialized variables will appear to go to
15134 the wrong place. But this feature is still handy from time to time.
15137 @code{file} with no argument makes @value{GDBN} discard any information it
15138 has on both executable file and the symbol table.
15141 @item exec-file @r{[} @var{filename} @r{]}
15142 Specify that the program to be run (but not the symbol table) is found
15143 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
15144 if necessary to locate your program. Omitting @var{filename} means to
15145 discard information on the executable file.
15147 @kindex symbol-file
15148 @item symbol-file @r{[} @var{filename} @r{]}
15149 Read symbol table information from file @var{filename}. @code{PATH} is
15150 searched when necessary. Use the @code{file} command to get both symbol
15151 table and program to run from the same file.
15153 @code{symbol-file} with no argument clears out @value{GDBN} information on your
15154 program's symbol table.
15156 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
15157 some breakpoints and auto-display expressions. This is because they may
15158 contain pointers to the internal data recording symbols and data types,
15159 which are part of the old symbol table data being discarded inside
15162 @code{symbol-file} does not repeat if you press @key{RET} again after
15165 When @value{GDBN} is configured for a particular environment, it
15166 understands debugging information in whatever format is the standard
15167 generated for that environment; you may use either a @sc{gnu} compiler, or
15168 other compilers that adhere to the local conventions.
15169 Best results are usually obtained from @sc{gnu} compilers; for example,
15170 using @code{@value{NGCC}} you can generate debugging information for
15173 For most kinds of object files, with the exception of old SVR3 systems
15174 using COFF, the @code{symbol-file} command does not normally read the
15175 symbol table in full right away. Instead, it scans the symbol table
15176 quickly to find which source files and which symbols are present. The
15177 details are read later, one source file at a time, as they are needed.
15179 The purpose of this two-stage reading strategy is to make @value{GDBN}
15180 start up faster. For the most part, it is invisible except for
15181 occasional pauses while the symbol table details for a particular source
15182 file are being read. (The @code{set verbose} command can turn these
15183 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
15184 Warnings and Messages}.)
15186 We have not implemented the two-stage strategy for COFF yet. When the
15187 symbol table is stored in COFF format, @code{symbol-file} reads the
15188 symbol table data in full right away. Note that ``stabs-in-COFF''
15189 still does the two-stage strategy, since the debug info is actually
15193 @cindex reading symbols immediately
15194 @cindex symbols, reading immediately
15195 @item symbol-file @r{[} -readnow @r{]} @var{filename}
15196 @itemx file @r{[} -readnow @r{]} @var{filename}
15197 You can override the @value{GDBN} two-stage strategy for reading symbol
15198 tables by using the @samp{-readnow} option with any of the commands that
15199 load symbol table information, if you want to be sure @value{GDBN} has the
15200 entire symbol table available.
15202 @c FIXME: for now no mention of directories, since this seems to be in
15203 @c flux. 13mar1992 status is that in theory GDB would look either in
15204 @c current dir or in same dir as myprog; but issues like competing
15205 @c GDB's, or clutter in system dirs, mean that in practice right now
15206 @c only current dir is used. FFish says maybe a special GDB hierarchy
15207 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
15211 @item core-file @r{[}@var{filename}@r{]}
15213 Specify the whereabouts of a core dump file to be used as the ``contents
15214 of memory''. Traditionally, core files contain only some parts of the
15215 address space of the process that generated them; @value{GDBN} can access the
15216 executable file itself for other parts.
15218 @code{core-file} with no argument specifies that no core file is
15221 Note that the core file is ignored when your program is actually running
15222 under @value{GDBN}. So, if you have been running your program and you
15223 wish to debug a core file instead, you must kill the subprocess in which
15224 the program is running. To do this, use the @code{kill} command
15225 (@pxref{Kill Process, ,Killing the Child Process}).
15227 @kindex add-symbol-file
15228 @cindex dynamic linking
15229 @item add-symbol-file @var{filename} @var{address}
15230 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
15231 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
15232 The @code{add-symbol-file} command reads additional symbol table
15233 information from the file @var{filename}. You would use this command
15234 when @var{filename} has been dynamically loaded (by some other means)
15235 into the program that is running. @var{address} should be the memory
15236 address at which the file has been loaded; @value{GDBN} cannot figure
15237 this out for itself. You can additionally specify an arbitrary number
15238 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
15239 section name and base address for that section. You can specify any
15240 @var{address} as an expression.
15242 The symbol table of the file @var{filename} is added to the symbol table
15243 originally read with the @code{symbol-file} command. You can use the
15244 @code{add-symbol-file} command any number of times; the new symbol data
15245 thus read keeps adding to the old. To discard all old symbol data
15246 instead, use the @code{symbol-file} command without any arguments.
15248 @cindex relocatable object files, reading symbols from
15249 @cindex object files, relocatable, reading symbols from
15250 @cindex reading symbols from relocatable object files
15251 @cindex symbols, reading from relocatable object files
15252 @cindex @file{.o} files, reading symbols from
15253 Although @var{filename} is typically a shared library file, an
15254 executable file, or some other object file which has been fully
15255 relocated for loading into a process, you can also load symbolic
15256 information from relocatable @file{.o} files, as long as:
15260 the file's symbolic information refers only to linker symbols defined in
15261 that file, not to symbols defined by other object files,
15263 every section the file's symbolic information refers to has actually
15264 been loaded into the inferior, as it appears in the file, and
15266 you can determine the address at which every section was loaded, and
15267 provide these to the @code{add-symbol-file} command.
15271 Some embedded operating systems, like Sun Chorus and VxWorks, can load
15272 relocatable files into an already running program; such systems
15273 typically make the requirements above easy to meet. However, it's
15274 important to recognize that many native systems use complex link
15275 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
15276 assembly, for example) that make the requirements difficult to meet. In
15277 general, one cannot assume that using @code{add-symbol-file} to read a
15278 relocatable object file's symbolic information will have the same effect
15279 as linking the relocatable object file into the program in the normal
15282 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
15284 @kindex add-symbol-file-from-memory
15285 @cindex @code{syscall DSO}
15286 @cindex load symbols from memory
15287 @item add-symbol-file-from-memory @var{address}
15288 Load symbols from the given @var{address} in a dynamically loaded
15289 object file whose image is mapped directly into the inferior's memory.
15290 For example, the Linux kernel maps a @code{syscall DSO} into each
15291 process's address space; this DSO provides kernel-specific code for
15292 some system calls. The argument can be any expression whose
15293 evaluation yields the address of the file's shared object file header.
15294 For this command to work, you must have used @code{symbol-file} or
15295 @code{exec-file} commands in advance.
15297 @kindex add-shared-symbol-files
15299 @item add-shared-symbol-files @var{library-file}
15300 @itemx assf @var{library-file}
15301 The @code{add-shared-symbol-files} command can currently be used only
15302 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
15303 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
15304 @value{GDBN} automatically looks for shared libraries, however if
15305 @value{GDBN} does not find yours, you can invoke
15306 @code{add-shared-symbol-files}. It takes one argument: the shared
15307 library's file name. @code{assf} is a shorthand alias for
15308 @code{add-shared-symbol-files}.
15311 @item section @var{section} @var{addr}
15312 The @code{section} command changes the base address of the named
15313 @var{section} of the exec file to @var{addr}. This can be used if the
15314 exec file does not contain section addresses, (such as in the
15315 @code{a.out} format), or when the addresses specified in the file
15316 itself are wrong. Each section must be changed separately. The
15317 @code{info files} command, described below, lists all the sections and
15321 @kindex info target
15324 @code{info files} and @code{info target} are synonymous; both print the
15325 current target (@pxref{Targets, ,Specifying a Debugging Target}),
15326 including the names of the executable and core dump files currently in
15327 use by @value{GDBN}, and the files from which symbols were loaded. The
15328 command @code{help target} lists all possible targets rather than
15331 @kindex maint info sections
15332 @item maint info sections
15333 Another command that can give you extra information about program sections
15334 is @code{maint info sections}. In addition to the section information
15335 displayed by @code{info files}, this command displays the flags and file
15336 offset of each section in the executable and core dump files. In addition,
15337 @code{maint info sections} provides the following command options (which
15338 may be arbitrarily combined):
15342 Display sections for all loaded object files, including shared libraries.
15343 @item @var{sections}
15344 Display info only for named @var{sections}.
15345 @item @var{section-flags}
15346 Display info only for sections for which @var{section-flags} are true.
15347 The section flags that @value{GDBN} currently knows about are:
15350 Section will have space allocated in the process when loaded.
15351 Set for all sections except those containing debug information.
15353 Section will be loaded from the file into the child process memory.
15354 Set for pre-initialized code and data, clear for @code{.bss} sections.
15356 Section needs to be relocated before loading.
15358 Section cannot be modified by the child process.
15360 Section contains executable code only.
15362 Section contains data only (no executable code).
15364 Section will reside in ROM.
15366 Section contains data for constructor/destructor lists.
15368 Section is not empty.
15370 An instruction to the linker to not output the section.
15371 @item COFF_SHARED_LIBRARY
15372 A notification to the linker that the section contains
15373 COFF shared library information.
15375 Section contains common symbols.
15378 @kindex set trust-readonly-sections
15379 @cindex read-only sections
15380 @item set trust-readonly-sections on
15381 Tell @value{GDBN} that readonly sections in your object file
15382 really are read-only (i.e.@: that their contents will not change).
15383 In that case, @value{GDBN} can fetch values from these sections
15384 out of the object file, rather than from the target program.
15385 For some targets (notably embedded ones), this can be a significant
15386 enhancement to debugging performance.
15388 The default is off.
15390 @item set trust-readonly-sections off
15391 Tell @value{GDBN} not to trust readonly sections. This means that
15392 the contents of the section might change while the program is running,
15393 and must therefore be fetched from the target when needed.
15395 @item show trust-readonly-sections
15396 Show the current setting of trusting readonly sections.
15399 All file-specifying commands allow both absolute and relative file names
15400 as arguments. @value{GDBN} always converts the file name to an absolute file
15401 name and remembers it that way.
15403 @cindex shared libraries
15404 @anchor{Shared Libraries}
15405 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
15406 and IBM RS/6000 AIX shared libraries.
15408 On MS-Windows @value{GDBN} must be linked with the Expat library to support
15409 shared libraries. @xref{Expat}.
15411 @value{GDBN} automatically loads symbol definitions from shared libraries
15412 when you use the @code{run} command, or when you examine a core file.
15413 (Before you issue the @code{run} command, @value{GDBN} does not understand
15414 references to a function in a shared library, however---unless you are
15415 debugging a core file).
15417 On HP-UX, if the program loads a library explicitly, @value{GDBN}
15418 automatically loads the symbols at the time of the @code{shl_load} call.
15420 @c FIXME: some @value{GDBN} release may permit some refs to undef
15421 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
15422 @c FIXME...lib; check this from time to time when updating manual
15424 There are times, however, when you may wish to not automatically load
15425 symbol definitions from shared libraries, such as when they are
15426 particularly large or there are many of them.
15428 To control the automatic loading of shared library symbols, use the
15432 @kindex set auto-solib-add
15433 @item set auto-solib-add @var{mode}
15434 If @var{mode} is @code{on}, symbols from all shared object libraries
15435 will be loaded automatically when the inferior begins execution, you
15436 attach to an independently started inferior, or when the dynamic linker
15437 informs @value{GDBN} that a new library has been loaded. If @var{mode}
15438 is @code{off}, symbols must be loaded manually, using the
15439 @code{sharedlibrary} command. The default value is @code{on}.
15441 @cindex memory used for symbol tables
15442 If your program uses lots of shared libraries with debug info that
15443 takes large amounts of memory, you can decrease the @value{GDBN}
15444 memory footprint by preventing it from automatically loading the
15445 symbols from shared libraries. To that end, type @kbd{set
15446 auto-solib-add off} before running the inferior, then load each
15447 library whose debug symbols you do need with @kbd{sharedlibrary
15448 @var{regexp}}, where @var{regexp} is a regular expression that matches
15449 the libraries whose symbols you want to be loaded.
15451 @kindex show auto-solib-add
15452 @item show auto-solib-add
15453 Display the current autoloading mode.
15456 @cindex load shared library
15457 To explicitly load shared library symbols, use the @code{sharedlibrary}
15461 @kindex info sharedlibrary
15463 @item info share @var{regex}
15464 @itemx info sharedlibrary @var{regex}
15465 Print the names of the shared libraries which are currently loaded
15466 that match @var{regex}. If @var{regex} is omitted then print
15467 all shared libraries that are loaded.
15469 @kindex sharedlibrary
15471 @item sharedlibrary @var{regex}
15472 @itemx share @var{regex}
15473 Load shared object library symbols for files matching a
15474 Unix regular expression.
15475 As with files loaded automatically, it only loads shared libraries
15476 required by your program for a core file or after typing @code{run}. If
15477 @var{regex} is omitted all shared libraries required by your program are
15480 @item nosharedlibrary
15481 @kindex nosharedlibrary
15482 @cindex unload symbols from shared libraries
15483 Unload all shared object library symbols. This discards all symbols
15484 that have been loaded from all shared libraries. Symbols from shared
15485 libraries that were loaded by explicit user requests are not
15489 Sometimes you may wish that @value{GDBN} stops and gives you control
15490 when any of shared library events happen. Use the @code{set
15491 stop-on-solib-events} command for this:
15494 @item set stop-on-solib-events
15495 @kindex set stop-on-solib-events
15496 This command controls whether @value{GDBN} should give you control
15497 when the dynamic linker notifies it about some shared library event.
15498 The most common event of interest is loading or unloading of a new
15501 @item show stop-on-solib-events
15502 @kindex show stop-on-solib-events
15503 Show whether @value{GDBN} stops and gives you control when shared
15504 library events happen.
15507 Shared libraries are also supported in many cross or remote debugging
15508 configurations. @value{GDBN} needs to have access to the target's libraries;
15509 this can be accomplished either by providing copies of the libraries
15510 on the host system, or by asking @value{GDBN} to automatically retrieve the
15511 libraries from the target. If copies of the target libraries are
15512 provided, they need to be the same as the target libraries, although the
15513 copies on the target can be stripped as long as the copies on the host are
15516 @cindex where to look for shared libraries
15517 For remote debugging, you need to tell @value{GDBN} where the target
15518 libraries are, so that it can load the correct copies---otherwise, it
15519 may try to load the host's libraries. @value{GDBN} has two variables
15520 to specify the search directories for target libraries.
15523 @cindex prefix for shared library file names
15524 @cindex system root, alternate
15525 @kindex set solib-absolute-prefix
15526 @kindex set sysroot
15527 @item set sysroot @var{path}
15528 Use @var{path} as the system root for the program being debugged. Any
15529 absolute shared library paths will be prefixed with @var{path}; many
15530 runtime loaders store the absolute paths to the shared library in the
15531 target program's memory. If you use @code{set sysroot} to find shared
15532 libraries, they need to be laid out in the same way that they are on
15533 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
15536 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
15537 retrieve the target libraries from the remote system. This is only
15538 supported when using a remote target that supports the @code{remote get}
15539 command (@pxref{File Transfer,,Sending files to a remote system}).
15540 The part of @var{path} following the initial @file{remote:}
15541 (if present) is used as system root prefix on the remote file system.
15542 @footnote{If you want to specify a local system root using a directory
15543 that happens to be named @file{remote:}, you need to use some equivalent
15544 variant of the name like @file{./remote:}.}
15546 For targets with an MS-DOS based filesystem, such as MS-Windows and
15547 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
15548 absolute file name with @var{path}. But first, on Unix hosts,
15549 @value{GDBN} converts all backslash directory separators into forward
15550 slashes, because the backslash is not a directory separator on Unix:
15553 c:\foo\bar.dll @result{} c:/foo/bar.dll
15556 Then, @value{GDBN} attempts prefixing the target file name with
15557 @var{path}, and looks for the resulting file name in the host file
15561 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
15564 If that does not find the shared library, @value{GDBN} tries removing
15565 the @samp{:} character from the drive spec, both for convenience, and,
15566 for the case of the host file system not supporting file names with
15570 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
15573 This makes it possible to have a system root that mirrors a target
15574 with more than one drive. E.g., you may want to setup your local
15575 copies of the target system shared libraries like so (note @samp{c} vs
15579 @file{/path/to/sysroot/c/sys/bin/foo.dll}
15580 @file{/path/to/sysroot/c/sys/bin/bar.dll}
15581 @file{/path/to/sysroot/z/sys/bin/bar.dll}
15585 and point the system root at @file{/path/to/sysroot}, so that
15586 @value{GDBN} can find the correct copies of both
15587 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
15589 If that still does not find the shared library, @value{GDBN} tries
15590 removing the whole drive spec from the target file name:
15593 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
15596 This last lookup makes it possible to not care about the drive name,
15597 if you don't want or need to.
15599 The @code{set solib-absolute-prefix} command is an alias for @code{set
15602 @cindex default system root
15603 @cindex @samp{--with-sysroot}
15604 You can set the default system root by using the configure-time
15605 @samp{--with-sysroot} option. If the system root is inside
15606 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15607 @samp{--exec-prefix}), then the default system root will be updated
15608 automatically if the installed @value{GDBN} is moved to a new
15611 @kindex show sysroot
15613 Display the current shared library prefix.
15615 @kindex set solib-search-path
15616 @item set solib-search-path @var{path}
15617 If this variable is set, @var{path} is a colon-separated list of
15618 directories to search for shared libraries. @samp{solib-search-path}
15619 is used after @samp{sysroot} fails to locate the library, or if the
15620 path to the library is relative instead of absolute. If you want to
15621 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
15622 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
15623 finding your host's libraries. @samp{sysroot} is preferred; setting
15624 it to a nonexistent directory may interfere with automatic loading
15625 of shared library symbols.
15627 @kindex show solib-search-path
15628 @item show solib-search-path
15629 Display the current shared library search path.
15631 @cindex DOS file-name semantics of file names.
15632 @kindex set target-file-system-kind (unix|dos-based|auto)
15633 @kindex show target-file-system-kind
15634 @item set target-file-system-kind @var{kind}
15635 Set assumed file system kind for target reported file names.
15637 Shared library file names as reported by the target system may not
15638 make sense as is on the system @value{GDBN} is running on. For
15639 example, when remote debugging a target that has MS-DOS based file
15640 system semantics, from a Unix host, the target may be reporting to
15641 @value{GDBN} a list of loaded shared libraries with file names such as
15642 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
15643 drive letters, so the @samp{c:\} prefix is not normally understood as
15644 indicating an absolute file name, and neither is the backslash
15645 normally considered a directory separator character. In that case,
15646 the native file system would interpret this whole absolute file name
15647 as a relative file name with no directory components. This would make
15648 it impossible to point @value{GDBN} at a copy of the remote target's
15649 shared libraries on the host using @code{set sysroot}, and impractical
15650 with @code{set solib-search-path}. Setting
15651 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
15652 to interpret such file names similarly to how the target would, and to
15653 map them to file names valid on @value{GDBN}'s native file system
15654 semantics. The value of @var{kind} can be @code{"auto"}, in addition
15655 to one of the supported file system kinds. In that case, @value{GDBN}
15656 tries to determine the appropriate file system variant based on the
15657 current target's operating system (@pxref{ABI, ,Configuring the
15658 Current ABI}). The supported file system settings are:
15662 Instruct @value{GDBN} to assume the target file system is of Unix
15663 kind. Only file names starting the forward slash (@samp{/}) character
15664 are considered absolute, and the directory separator character is also
15668 Instruct @value{GDBN} to assume the target file system is DOS based.
15669 File names starting with either a forward slash, or a drive letter
15670 followed by a colon (e.g., @samp{c:}), are considered absolute, and
15671 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
15672 considered directory separators.
15675 Instruct @value{GDBN} to use the file system kind associated with the
15676 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
15677 This is the default.
15682 @node Separate Debug Files
15683 @section Debugging Information in Separate Files
15684 @cindex separate debugging information files
15685 @cindex debugging information in separate files
15686 @cindex @file{.debug} subdirectories
15687 @cindex debugging information directory, global
15688 @cindex global debugging information directory
15689 @cindex build ID, and separate debugging files
15690 @cindex @file{.build-id} directory
15692 @value{GDBN} allows you to put a program's debugging information in a
15693 file separate from the executable itself, in a way that allows
15694 @value{GDBN} to find and load the debugging information automatically.
15695 Since debugging information can be very large---sometimes larger
15696 than the executable code itself---some systems distribute debugging
15697 information for their executables in separate files, which users can
15698 install only when they need to debug a problem.
15700 @value{GDBN} supports two ways of specifying the separate debug info
15705 The executable contains a @dfn{debug link} that specifies the name of
15706 the separate debug info file. The separate debug file's name is
15707 usually @file{@var{executable}.debug}, where @var{executable} is the
15708 name of the corresponding executable file without leading directories
15709 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
15710 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
15711 checksum for the debug file, which @value{GDBN} uses to validate that
15712 the executable and the debug file came from the same build.
15715 The executable contains a @dfn{build ID}, a unique bit string that is
15716 also present in the corresponding debug info file. (This is supported
15717 only on some operating systems, notably those which use the ELF format
15718 for binary files and the @sc{gnu} Binutils.) For more details about
15719 this feature, see the description of the @option{--build-id}
15720 command-line option in @ref{Options, , Command Line Options, ld.info,
15721 The GNU Linker}. The debug info file's name is not specified
15722 explicitly by the build ID, but can be computed from the build ID, see
15726 Depending on the way the debug info file is specified, @value{GDBN}
15727 uses two different methods of looking for the debug file:
15731 For the ``debug link'' method, @value{GDBN} looks up the named file in
15732 the directory of the executable file, then in a subdirectory of that
15733 directory named @file{.debug}, and finally under the global debug
15734 directory, in a subdirectory whose name is identical to the leading
15735 directories of the executable's absolute file name.
15738 For the ``build ID'' method, @value{GDBN} looks in the
15739 @file{.build-id} subdirectory of the global debug directory for a file
15740 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
15741 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
15742 are the rest of the bit string. (Real build ID strings are 32 or more
15743 hex characters, not 10.)
15746 So, for example, suppose you ask @value{GDBN} to debug
15747 @file{/usr/bin/ls}, which has a debug link that specifies the
15748 file @file{ls.debug}, and a build ID whose value in hex is
15749 @code{abcdef1234}. If the global debug directory is
15750 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
15751 debug information files, in the indicated order:
15755 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
15757 @file{/usr/bin/ls.debug}
15759 @file{/usr/bin/.debug/ls.debug}
15761 @file{/usr/lib/debug/usr/bin/ls.debug}.
15764 You can set the global debugging info directory's name, and view the
15765 name @value{GDBN} is currently using.
15769 @kindex set debug-file-directory
15770 @item set debug-file-directory @var{directories}
15771 Set the directories which @value{GDBN} searches for separate debugging
15772 information files to @var{directory}. Multiple directory components can be set
15773 concatenating them by a directory separator.
15775 @kindex show debug-file-directory
15776 @item show debug-file-directory
15777 Show the directories @value{GDBN} searches for separate debugging
15782 @cindex @code{.gnu_debuglink} sections
15783 @cindex debug link sections
15784 A debug link is a special section of the executable file named
15785 @code{.gnu_debuglink}. The section must contain:
15789 A filename, with any leading directory components removed, followed by
15792 zero to three bytes of padding, as needed to reach the next four-byte
15793 boundary within the section, and
15795 a four-byte CRC checksum, stored in the same endianness used for the
15796 executable file itself. The checksum is computed on the debugging
15797 information file's full contents by the function given below, passing
15798 zero as the @var{crc} argument.
15801 Any executable file format can carry a debug link, as long as it can
15802 contain a section named @code{.gnu_debuglink} with the contents
15805 @cindex @code{.note.gnu.build-id} sections
15806 @cindex build ID sections
15807 The build ID is a special section in the executable file (and in other
15808 ELF binary files that @value{GDBN} may consider). This section is
15809 often named @code{.note.gnu.build-id}, but that name is not mandatory.
15810 It contains unique identification for the built files---the ID remains
15811 the same across multiple builds of the same build tree. The default
15812 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
15813 content for the build ID string. The same section with an identical
15814 value is present in the original built binary with symbols, in its
15815 stripped variant, and in the separate debugging information file.
15817 The debugging information file itself should be an ordinary
15818 executable, containing a full set of linker symbols, sections, and
15819 debugging information. The sections of the debugging information file
15820 should have the same names, addresses, and sizes as the original file,
15821 but they need not contain any data---much like a @code{.bss} section
15822 in an ordinary executable.
15824 The @sc{gnu} binary utilities (Binutils) package includes the
15825 @samp{objcopy} utility that can produce
15826 the separated executable / debugging information file pairs using the
15827 following commands:
15830 @kbd{objcopy --only-keep-debug foo foo.debug}
15835 These commands remove the debugging
15836 information from the executable file @file{foo} and place it in the file
15837 @file{foo.debug}. You can use the first, second or both methods to link the
15842 The debug link method needs the following additional command to also leave
15843 behind a debug link in @file{foo}:
15846 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
15849 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
15850 a version of the @code{strip} command such that the command @kbd{strip foo -f
15851 foo.debug} has the same functionality as the two @code{objcopy} commands and
15852 the @code{ln -s} command above, together.
15855 Build ID gets embedded into the main executable using @code{ld --build-id} or
15856 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
15857 compatibility fixes for debug files separation are present in @sc{gnu} binary
15858 utilities (Binutils) package since version 2.18.
15863 @cindex CRC algorithm definition
15864 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
15865 IEEE 802.3 using the polynomial:
15867 @c TexInfo requires naked braces for multi-digit exponents for Tex
15868 @c output, but this causes HTML output to barf. HTML has to be set using
15869 @c raw commands. So we end up having to specify this equation in 2
15874 <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>
15875 + <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
15881 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
15882 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
15886 The function is computed byte at a time, taking the least
15887 significant bit of each byte first. The initial pattern
15888 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
15889 the final result is inverted to ensure trailing zeros also affect the
15892 @emph{Note:} This is the same CRC polynomial as used in handling the
15893 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
15894 , @value{GDBN} Remote Serial Protocol}). However in the
15895 case of the Remote Serial Protocol, the CRC is computed @emph{most}
15896 significant bit first, and the result is not inverted, so trailing
15897 zeros have no effect on the CRC value.
15899 To complete the description, we show below the code of the function
15900 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
15901 initially supplied @code{crc} argument means that an initial call to
15902 this function passing in zero will start computing the CRC using
15905 @kindex gnu_debuglink_crc32
15908 gnu_debuglink_crc32 (unsigned long crc,
15909 unsigned char *buf, size_t len)
15911 static const unsigned long crc32_table[256] =
15913 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
15914 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
15915 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
15916 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
15917 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
15918 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
15919 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
15920 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
15921 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
15922 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
15923 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
15924 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
15925 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
15926 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
15927 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
15928 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
15929 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
15930 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
15931 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
15932 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
15933 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
15934 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
15935 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
15936 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
15937 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
15938 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
15939 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
15940 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
15941 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
15942 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
15943 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
15944 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
15945 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
15946 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
15947 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
15948 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
15949 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
15950 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
15951 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
15952 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
15953 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
15954 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
15955 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
15956 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
15957 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
15958 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
15959 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
15960 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
15961 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
15962 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
15963 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
15966 unsigned char *end;
15968 crc = ~crc & 0xffffffff;
15969 for (end = buf + len; buf < end; ++buf)
15970 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
15971 return ~crc & 0xffffffff;
15976 This computation does not apply to the ``build ID'' method.
15980 @section Index Files Speed Up @value{GDBN}
15981 @cindex index files
15982 @cindex @samp{.gdb_index} section
15984 When @value{GDBN} finds a symbol file, it scans the symbols in the
15985 file in order to construct an internal symbol table. This lets most
15986 @value{GDBN} operations work quickly---at the cost of a delay early
15987 on. For large programs, this delay can be quite lengthy, so
15988 @value{GDBN} provides a way to build an index, which speeds up
15991 The index is stored as a section in the symbol file. @value{GDBN} can
15992 write the index to a file, then you can put it into the symbol file
15993 using @command{objcopy}.
15995 To create an index file, use the @code{save gdb-index} command:
15998 @item save gdb-index @var{directory}
15999 @kindex save gdb-index
16000 Create an index file for each symbol file currently known by
16001 @value{GDBN}. Each file is named after its corresponding symbol file,
16002 with @samp{.gdb-index} appended, and is written into the given
16006 Once you have created an index file you can merge it into your symbol
16007 file, here named @file{symfile}, using @command{objcopy}:
16010 $ objcopy --add-section .gdb_index=symfile.gdb-index \
16011 --set-section-flags .gdb_index=readonly symfile symfile
16014 There are currently some limitation on indices. They only work when
16015 for DWARF debugging information, not stabs. And, they do not
16016 currently work for programs using Ada.
16018 @node Symbol Errors
16019 @section Errors Reading Symbol Files
16021 While reading a symbol file, @value{GDBN} occasionally encounters problems,
16022 such as symbol types it does not recognize, or known bugs in compiler
16023 output. By default, @value{GDBN} does not notify you of such problems, since
16024 they are relatively common and primarily of interest to people
16025 debugging compilers. If you are interested in seeing information
16026 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
16027 only one message about each such type of problem, no matter how many
16028 times the problem occurs; or you can ask @value{GDBN} to print more messages,
16029 to see how many times the problems occur, with the @code{set
16030 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
16033 The messages currently printed, and their meanings, include:
16036 @item inner block not inside outer block in @var{symbol}
16038 The symbol information shows where symbol scopes begin and end
16039 (such as at the start of a function or a block of statements). This
16040 error indicates that an inner scope block is not fully contained
16041 in its outer scope blocks.
16043 @value{GDBN} circumvents the problem by treating the inner block as if it had
16044 the same scope as the outer block. In the error message, @var{symbol}
16045 may be shown as ``@code{(don't know)}'' if the outer block is not a
16048 @item block at @var{address} out of order
16050 The symbol information for symbol scope blocks should occur in
16051 order of increasing addresses. This error indicates that it does not
16054 @value{GDBN} does not circumvent this problem, and has trouble
16055 locating symbols in the source file whose symbols it is reading. (You
16056 can often determine what source file is affected by specifying
16057 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
16060 @item bad block start address patched
16062 The symbol information for a symbol scope block has a start address
16063 smaller than the address of the preceding source line. This is known
16064 to occur in the SunOS 4.1.1 (and earlier) C compiler.
16066 @value{GDBN} circumvents the problem by treating the symbol scope block as
16067 starting on the previous source line.
16069 @item bad string table offset in symbol @var{n}
16072 Symbol number @var{n} contains a pointer into the string table which is
16073 larger than the size of the string table.
16075 @value{GDBN} circumvents the problem by considering the symbol to have the
16076 name @code{foo}, which may cause other problems if many symbols end up
16079 @item unknown symbol type @code{0x@var{nn}}
16081 The symbol information contains new data types that @value{GDBN} does
16082 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
16083 uncomprehended information, in hexadecimal.
16085 @value{GDBN} circumvents the error by ignoring this symbol information.
16086 This usually allows you to debug your program, though certain symbols
16087 are not accessible. If you encounter such a problem and feel like
16088 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
16089 on @code{complain}, then go up to the function @code{read_dbx_symtab}
16090 and examine @code{*bufp} to see the symbol.
16092 @item stub type has NULL name
16094 @value{GDBN} could not find the full definition for a struct or class.
16096 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
16097 The symbol information for a C@t{++} member function is missing some
16098 information that recent versions of the compiler should have output for
16101 @item info mismatch between compiler and debugger
16103 @value{GDBN} could not parse a type specification output by the compiler.
16108 @section GDB Data Files
16110 @cindex prefix for data files
16111 @value{GDBN} will sometimes read an auxiliary data file. These files
16112 are kept in a directory known as the @dfn{data directory}.
16114 You can set the data directory's name, and view the name @value{GDBN}
16115 is currently using.
16118 @kindex set data-directory
16119 @item set data-directory @var{directory}
16120 Set the directory which @value{GDBN} searches for auxiliary data files
16121 to @var{directory}.
16123 @kindex show data-directory
16124 @item show data-directory
16125 Show the directory @value{GDBN} searches for auxiliary data files.
16128 @cindex default data directory
16129 @cindex @samp{--with-gdb-datadir}
16130 You can set the default data directory by using the configure-time
16131 @samp{--with-gdb-datadir} option. If the data directory is inside
16132 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
16133 @samp{--exec-prefix}), then the default data directory will be updated
16134 automatically if the installed @value{GDBN} is moved to a new
16137 The data directory may also be specified with the
16138 @code{--data-directory} command line option.
16139 @xref{Mode Options}.
16142 @chapter Specifying a Debugging Target
16144 @cindex debugging target
16145 A @dfn{target} is the execution environment occupied by your program.
16147 Often, @value{GDBN} runs in the same host environment as your program;
16148 in that case, the debugging target is specified as a side effect when
16149 you use the @code{file} or @code{core} commands. When you need more
16150 flexibility---for example, running @value{GDBN} on a physically separate
16151 host, or controlling a standalone system over a serial port or a
16152 realtime system over a TCP/IP connection---you can use the @code{target}
16153 command to specify one of the target types configured for @value{GDBN}
16154 (@pxref{Target Commands, ,Commands for Managing Targets}).
16156 @cindex target architecture
16157 It is possible to build @value{GDBN} for several different @dfn{target
16158 architectures}. When @value{GDBN} is built like that, you can choose
16159 one of the available architectures with the @kbd{set architecture}
16163 @kindex set architecture
16164 @kindex show architecture
16165 @item set architecture @var{arch}
16166 This command sets the current target architecture to @var{arch}. The
16167 value of @var{arch} can be @code{"auto"}, in addition to one of the
16168 supported architectures.
16170 @item show architecture
16171 Show the current target architecture.
16173 @item set processor
16175 @kindex set processor
16176 @kindex show processor
16177 These are alias commands for, respectively, @code{set architecture}
16178 and @code{show architecture}.
16182 * Active Targets:: Active targets
16183 * Target Commands:: Commands for managing targets
16184 * Byte Order:: Choosing target byte order
16187 @node Active Targets
16188 @section Active Targets
16190 @cindex stacking targets
16191 @cindex active targets
16192 @cindex multiple targets
16194 There are multiple classes of targets such as: processes, executable files or
16195 recording sessions. Core files belong to the process class, making core file
16196 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
16197 on multiple active targets, one in each class. This allows you to (for
16198 example) start a process and inspect its activity, while still having access to
16199 the executable file after the process finishes. Or if you start process
16200 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
16201 presented a virtual layer of the recording target, while the process target
16202 remains stopped at the chronologically last point of the process execution.
16204 Use the @code{core-file} and @code{exec-file} commands to select a new core
16205 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
16206 specify as a target a process that is already running, use the @code{attach}
16207 command (@pxref{Attach, ,Debugging an Already-running Process}).
16209 @node Target Commands
16210 @section Commands for Managing Targets
16213 @item target @var{type} @var{parameters}
16214 Connects the @value{GDBN} host environment to a target machine or
16215 process. A target is typically a protocol for talking to debugging
16216 facilities. You use the argument @var{type} to specify the type or
16217 protocol of the target machine.
16219 Further @var{parameters} are interpreted by the target protocol, but
16220 typically include things like device names or host names to connect
16221 with, process numbers, and baud rates.
16223 The @code{target} command does not repeat if you press @key{RET} again
16224 after executing the command.
16226 @kindex help target
16228 Displays the names of all targets available. To display targets
16229 currently selected, use either @code{info target} or @code{info files}
16230 (@pxref{Files, ,Commands to Specify Files}).
16232 @item help target @var{name}
16233 Describe a particular target, including any parameters necessary to
16236 @kindex set gnutarget
16237 @item set gnutarget @var{args}
16238 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
16239 knows whether it is reading an @dfn{executable},
16240 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
16241 with the @code{set gnutarget} command. Unlike most @code{target} commands,
16242 with @code{gnutarget} the @code{target} refers to a program, not a machine.
16245 @emph{Warning:} To specify a file format with @code{set gnutarget},
16246 you must know the actual BFD name.
16250 @xref{Files, , Commands to Specify Files}.
16252 @kindex show gnutarget
16253 @item show gnutarget
16254 Use the @code{show gnutarget} command to display what file format
16255 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
16256 @value{GDBN} will determine the file format for each file automatically,
16257 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
16260 @cindex common targets
16261 Here are some common targets (available, or not, depending on the GDB
16266 @item target exec @var{program}
16267 @cindex executable file target
16268 An executable file. @samp{target exec @var{program}} is the same as
16269 @samp{exec-file @var{program}}.
16271 @item target core @var{filename}
16272 @cindex core dump file target
16273 A core dump file. @samp{target core @var{filename}} is the same as
16274 @samp{core-file @var{filename}}.
16276 @item target remote @var{medium}
16277 @cindex remote target
16278 A remote system connected to @value{GDBN} via a serial line or network
16279 connection. This command tells @value{GDBN} to use its own remote
16280 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
16282 For example, if you have a board connected to @file{/dev/ttya} on the
16283 machine running @value{GDBN}, you could say:
16286 target remote /dev/ttya
16289 @code{target remote} supports the @code{load} command. This is only
16290 useful if you have some other way of getting the stub to the target
16291 system, and you can put it somewhere in memory where it won't get
16292 clobbered by the download.
16294 @item target sim @r{[}@var{simargs}@r{]} @dots{}
16295 @cindex built-in simulator target
16296 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
16304 works; however, you cannot assume that a specific memory map, device
16305 drivers, or even basic I/O is available, although some simulators do
16306 provide these. For info about any processor-specific simulator details,
16307 see the appropriate section in @ref{Embedded Processors, ,Embedded
16312 Some configurations may include these targets as well:
16316 @item target nrom @var{dev}
16317 @cindex NetROM ROM emulator target
16318 NetROM ROM emulator. This target only supports downloading.
16322 Different targets are available on different configurations of @value{GDBN};
16323 your configuration may have more or fewer targets.
16325 Many remote targets require you to download the executable's code once
16326 you've successfully established a connection. You may wish to control
16327 various aspects of this process.
16332 @kindex set hash@r{, for remote monitors}
16333 @cindex hash mark while downloading
16334 This command controls whether a hash mark @samp{#} is displayed while
16335 downloading a file to the remote monitor. If on, a hash mark is
16336 displayed after each S-record is successfully downloaded to the
16340 @kindex show hash@r{, for remote monitors}
16341 Show the current status of displaying the hash mark.
16343 @item set debug monitor
16344 @kindex set debug monitor
16345 @cindex display remote monitor communications
16346 Enable or disable display of communications messages between
16347 @value{GDBN} and the remote monitor.
16349 @item show debug monitor
16350 @kindex show debug monitor
16351 Show the current status of displaying communications between
16352 @value{GDBN} and the remote monitor.
16357 @kindex load @var{filename}
16358 @item load @var{filename}
16360 Depending on what remote debugging facilities are configured into
16361 @value{GDBN}, the @code{load} command may be available. Where it exists, it
16362 is meant to make @var{filename} (an executable) available for debugging
16363 on the remote system---by downloading, or dynamic linking, for example.
16364 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
16365 the @code{add-symbol-file} command.
16367 If your @value{GDBN} does not have a @code{load} command, attempting to
16368 execute it gets the error message ``@code{You can't do that when your
16369 target is @dots{}}''
16371 The file is loaded at whatever address is specified in the executable.
16372 For some object file formats, you can specify the load address when you
16373 link the program; for other formats, like a.out, the object file format
16374 specifies a fixed address.
16375 @c FIXME! This would be a good place for an xref to the GNU linker doc.
16377 Depending on the remote side capabilities, @value{GDBN} may be able to
16378 load programs into flash memory.
16380 @code{load} does not repeat if you press @key{RET} again after using it.
16384 @section Choosing Target Byte Order
16386 @cindex choosing target byte order
16387 @cindex target byte order
16389 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
16390 offer the ability to run either big-endian or little-endian byte
16391 orders. Usually the executable or symbol will include a bit to
16392 designate the endian-ness, and you will not need to worry about
16393 which to use. However, you may still find it useful to adjust
16394 @value{GDBN}'s idea of processor endian-ness manually.
16398 @item set endian big
16399 Instruct @value{GDBN} to assume the target is big-endian.
16401 @item set endian little
16402 Instruct @value{GDBN} to assume the target is little-endian.
16404 @item set endian auto
16405 Instruct @value{GDBN} to use the byte order associated with the
16409 Display @value{GDBN}'s current idea of the target byte order.
16413 Note that these commands merely adjust interpretation of symbolic
16414 data on the host, and that they have absolutely no effect on the
16418 @node Remote Debugging
16419 @chapter Debugging Remote Programs
16420 @cindex remote debugging
16422 If you are trying to debug a program running on a machine that cannot run
16423 @value{GDBN} in the usual way, it is often useful to use remote debugging.
16424 For example, you might use remote debugging on an operating system kernel,
16425 or on a small system which does not have a general purpose operating system
16426 powerful enough to run a full-featured debugger.
16428 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
16429 to make this work with particular debugging targets. In addition,
16430 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
16431 but not specific to any particular target system) which you can use if you
16432 write the remote stubs---the code that runs on the remote system to
16433 communicate with @value{GDBN}.
16435 Other remote targets may be available in your
16436 configuration of @value{GDBN}; use @code{help target} to list them.
16439 * Connecting:: Connecting to a remote target
16440 * File Transfer:: Sending files to a remote system
16441 * Server:: Using the gdbserver program
16442 * Remote Configuration:: Remote configuration
16443 * Remote Stub:: Implementing a remote stub
16447 @section Connecting to a Remote Target
16449 On the @value{GDBN} host machine, you will need an unstripped copy of
16450 your program, since @value{GDBN} needs symbol and debugging information.
16451 Start up @value{GDBN} as usual, using the name of the local copy of your
16452 program as the first argument.
16454 @cindex @code{target remote}
16455 @value{GDBN} can communicate with the target over a serial line, or
16456 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
16457 each case, @value{GDBN} uses the same protocol for debugging your
16458 program; only the medium carrying the debugging packets varies. The
16459 @code{target remote} command establishes a connection to the target.
16460 Its arguments indicate which medium to use:
16464 @item target remote @var{serial-device}
16465 @cindex serial line, @code{target remote}
16466 Use @var{serial-device} to communicate with the target. For example,
16467 to use a serial line connected to the device named @file{/dev/ttyb}:
16470 target remote /dev/ttyb
16473 If you're using a serial line, you may want to give @value{GDBN} the
16474 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
16475 (@pxref{Remote Configuration, set remotebaud}) before the
16476 @code{target} command.
16478 @item target remote @code{@var{host}:@var{port}}
16479 @itemx target remote @code{tcp:@var{host}:@var{port}}
16480 @cindex @acronym{TCP} port, @code{target remote}
16481 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
16482 The @var{host} may be either a host name or a numeric @acronym{IP}
16483 address; @var{port} must be a decimal number. The @var{host} could be
16484 the target machine itself, if it is directly connected to the net, or
16485 it might be a terminal server which in turn has a serial line to the
16488 For example, to connect to port 2828 on a terminal server named
16492 target remote manyfarms:2828
16495 If your remote target is actually running on the same machine as your
16496 debugger session (e.g.@: a simulator for your target running on the
16497 same host), you can omit the hostname. For example, to connect to
16498 port 1234 on your local machine:
16501 target remote :1234
16505 Note that the colon is still required here.
16507 @item target remote @code{udp:@var{host}:@var{port}}
16508 @cindex @acronym{UDP} port, @code{target remote}
16509 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
16510 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
16513 target remote udp:manyfarms:2828
16516 When using a @acronym{UDP} connection for remote debugging, you should
16517 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
16518 can silently drop packets on busy or unreliable networks, which will
16519 cause havoc with your debugging session.
16521 @item target remote | @var{command}
16522 @cindex pipe, @code{target remote} to
16523 Run @var{command} in the background and communicate with it using a
16524 pipe. The @var{command} is a shell command, to be parsed and expanded
16525 by the system's command shell, @code{/bin/sh}; it should expect remote
16526 protocol packets on its standard input, and send replies on its
16527 standard output. You could use this to run a stand-alone simulator
16528 that speaks the remote debugging protocol, to make net connections
16529 using programs like @code{ssh}, or for other similar tricks.
16531 If @var{command} closes its standard output (perhaps by exiting),
16532 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
16533 program has already exited, this will have no effect.)
16537 Once the connection has been established, you can use all the usual
16538 commands to examine and change data. The remote program is already
16539 running; you can use @kbd{step} and @kbd{continue}, and you do not
16540 need to use @kbd{run}.
16542 @cindex interrupting remote programs
16543 @cindex remote programs, interrupting
16544 Whenever @value{GDBN} is waiting for the remote program, if you type the
16545 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
16546 program. This may or may not succeed, depending in part on the hardware
16547 and the serial drivers the remote system uses. If you type the
16548 interrupt character once again, @value{GDBN} displays this prompt:
16551 Interrupted while waiting for the program.
16552 Give up (and stop debugging it)? (y or n)
16555 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
16556 (If you decide you want to try again later, you can use @samp{target
16557 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
16558 goes back to waiting.
16561 @kindex detach (remote)
16563 When you have finished debugging the remote program, you can use the
16564 @code{detach} command to release it from @value{GDBN} control.
16565 Detaching from the target normally resumes its execution, but the results
16566 will depend on your particular remote stub. After the @code{detach}
16567 command, @value{GDBN} is free to connect to another target.
16571 The @code{disconnect} command behaves like @code{detach}, except that
16572 the target is generally not resumed. It will wait for @value{GDBN}
16573 (this instance or another one) to connect and continue debugging. After
16574 the @code{disconnect} command, @value{GDBN} is again free to connect to
16577 @cindex send command to remote monitor
16578 @cindex extend @value{GDBN} for remote targets
16579 @cindex add new commands for external monitor
16581 @item monitor @var{cmd}
16582 This command allows you to send arbitrary commands directly to the
16583 remote monitor. Since @value{GDBN} doesn't care about the commands it
16584 sends like this, this command is the way to extend @value{GDBN}---you
16585 can add new commands that only the external monitor will understand
16589 @node File Transfer
16590 @section Sending files to a remote system
16591 @cindex remote target, file transfer
16592 @cindex file transfer
16593 @cindex sending files to remote systems
16595 Some remote targets offer the ability to transfer files over the same
16596 connection used to communicate with @value{GDBN}. This is convenient
16597 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
16598 running @code{gdbserver} over a network interface. For other targets,
16599 e.g.@: embedded devices with only a single serial port, this may be
16600 the only way to upload or download files.
16602 Not all remote targets support these commands.
16606 @item remote put @var{hostfile} @var{targetfile}
16607 Copy file @var{hostfile} from the host system (the machine running
16608 @value{GDBN}) to @var{targetfile} on the target system.
16611 @item remote get @var{targetfile} @var{hostfile}
16612 Copy file @var{targetfile} from the target system to @var{hostfile}
16613 on the host system.
16615 @kindex remote delete
16616 @item remote delete @var{targetfile}
16617 Delete @var{targetfile} from the target system.
16622 @section Using the @code{gdbserver} Program
16625 @cindex remote connection without stubs
16626 @code{gdbserver} is a control program for Unix-like systems, which
16627 allows you to connect your program with a remote @value{GDBN} via
16628 @code{target remote}---but without linking in the usual debugging stub.
16630 @code{gdbserver} is not a complete replacement for the debugging stubs,
16631 because it requires essentially the same operating-system facilities
16632 that @value{GDBN} itself does. In fact, a system that can run
16633 @code{gdbserver} to connect to a remote @value{GDBN} could also run
16634 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
16635 because it is a much smaller program than @value{GDBN} itself. It is
16636 also easier to port than all of @value{GDBN}, so you may be able to get
16637 started more quickly on a new system by using @code{gdbserver}.
16638 Finally, if you develop code for real-time systems, you may find that
16639 the tradeoffs involved in real-time operation make it more convenient to
16640 do as much development work as possible on another system, for example
16641 by cross-compiling. You can use @code{gdbserver} to make a similar
16642 choice for debugging.
16644 @value{GDBN} and @code{gdbserver} communicate via either a serial line
16645 or a TCP connection, using the standard @value{GDBN} remote serial
16649 @emph{Warning:} @code{gdbserver} does not have any built-in security.
16650 Do not run @code{gdbserver} connected to any public network; a
16651 @value{GDBN} connection to @code{gdbserver} provides access to the
16652 target system with the same privileges as the user running
16656 @subsection Running @code{gdbserver}
16657 @cindex arguments, to @code{gdbserver}
16658 @cindex @code{gdbserver}, command-line arguments
16660 Run @code{gdbserver} on the target system. You need a copy of the
16661 program you want to debug, including any libraries it requires.
16662 @code{gdbserver} does not need your program's symbol table, so you can
16663 strip the program if necessary to save space. @value{GDBN} on the host
16664 system does all the symbol handling.
16666 To use the server, you must tell it how to communicate with @value{GDBN};
16667 the name of your program; and the arguments for your program. The usual
16671 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
16674 @var{comm} is either a device name (to use a serial line) or a TCP
16675 hostname and portnumber. For example, to debug Emacs with the argument
16676 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
16680 target> gdbserver /dev/com1 emacs foo.txt
16683 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
16686 To use a TCP connection instead of a serial line:
16689 target> gdbserver host:2345 emacs foo.txt
16692 The only difference from the previous example is the first argument,
16693 specifying that you are communicating with the host @value{GDBN} via
16694 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
16695 expect a TCP connection from machine @samp{host} to local TCP port 2345.
16696 (Currently, the @samp{host} part is ignored.) You can choose any number
16697 you want for the port number as long as it does not conflict with any
16698 TCP ports already in use on the target system (for example, @code{23} is
16699 reserved for @code{telnet}).@footnote{If you choose a port number that
16700 conflicts with another service, @code{gdbserver} prints an error message
16701 and exits.} You must use the same port number with the host @value{GDBN}
16702 @code{target remote} command.
16704 @subsubsection Attaching to a Running Program
16705 @cindex attach to a program, @code{gdbserver}
16706 @cindex @option{--attach}, @code{gdbserver} option
16708 On some targets, @code{gdbserver} can also attach to running programs.
16709 This is accomplished via the @code{--attach} argument. The syntax is:
16712 target> gdbserver --attach @var{comm} @var{pid}
16715 @var{pid} is the process ID of a currently running process. It isn't necessary
16716 to point @code{gdbserver} at a binary for the running process.
16719 You can debug processes by name instead of process ID if your target has the
16720 @code{pidof} utility:
16723 target> gdbserver --attach @var{comm} `pidof @var{program}`
16726 In case more than one copy of @var{program} is running, or @var{program}
16727 has multiple threads, most versions of @code{pidof} support the
16728 @code{-s} option to only return the first process ID.
16730 @subsubsection Multi-Process Mode for @code{gdbserver}
16731 @cindex @code{gdbserver}, multiple processes
16732 @cindex multiple processes with @code{gdbserver}
16734 When you connect to @code{gdbserver} using @code{target remote},
16735 @code{gdbserver} debugs the specified program only once. When the
16736 program exits, or you detach from it, @value{GDBN} closes the connection
16737 and @code{gdbserver} exits.
16739 If you connect using @kbd{target extended-remote}, @code{gdbserver}
16740 enters multi-process mode. When the debugged program exits, or you
16741 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
16742 though no program is running. The @code{run} and @code{attach}
16743 commands instruct @code{gdbserver} to run or attach to a new program.
16744 The @code{run} command uses @code{set remote exec-file} (@pxref{set
16745 remote exec-file}) to select the program to run. Command line
16746 arguments are supported, except for wildcard expansion and I/O
16747 redirection (@pxref{Arguments}).
16749 @cindex @option{--multi}, @code{gdbserver} option
16750 To start @code{gdbserver} without supplying an initial command to run
16751 or process ID to attach, use the @option{--multi} command line option.
16752 Then you can connect using @kbd{target extended-remote} and start
16753 the program you want to debug.
16755 In multi-process mode @code{gdbserver} does not automatically exit unless you
16756 use the option @option{--once}. You can terminate it by using
16757 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
16758 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
16759 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
16760 @option{--multi} option to @code{gdbserver} has no influence on that.
16762 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
16764 This section applies only when @code{gdbserver} is run to listen on a TCP port.
16766 @code{gdbserver} normally terminates after all of its debugged processes have
16767 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
16768 extended-remote}, @code{gdbserver} stays running even with no processes left.
16769 @value{GDBN} normally terminates the spawned debugged process on its exit,
16770 which normally also terminates @code{gdbserver} in the @kbd{target remote}
16771 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
16772 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
16773 stays running even in the @kbd{target remote} mode.
16775 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
16776 Such reconnecting is useful for features like @ref{disconnected tracing}. For
16777 completeness, at most one @value{GDBN} can be connected at a time.
16779 @cindex @option{--once}, @code{gdbserver} option
16780 By default, @code{gdbserver} keeps the listening TCP port open, so that
16781 additional connections are possible. However, if you start @code{gdbserver}
16782 with the @option{--once} option, it will stop listening for any further
16783 connection attempts after connecting to the first @value{GDBN} session. This
16784 means no further connections to @code{gdbserver} will be possible after the
16785 first one. It also means @code{gdbserver} will terminate after the first
16786 connection with remote @value{GDBN} has closed, even for unexpectedly closed
16787 connections and even in the @kbd{target extended-remote} mode. The
16788 @option{--once} option allows reusing the same port number for connecting to
16789 multiple instances of @code{gdbserver} running on the same host, since each
16790 instance closes its port after the first connection.
16792 @subsubsection Other Command-Line Arguments for @code{gdbserver}
16794 @cindex @option{--debug}, @code{gdbserver} option
16795 The @option{--debug} option tells @code{gdbserver} to display extra
16796 status information about the debugging process.
16797 @cindex @option{--remote-debug}, @code{gdbserver} option
16798 The @option{--remote-debug} option tells @code{gdbserver} to display
16799 remote protocol debug output. These options are intended for
16800 @code{gdbserver} development and for bug reports to the developers.
16802 @cindex @option{--wrapper}, @code{gdbserver} option
16803 The @option{--wrapper} option specifies a wrapper to launch programs
16804 for debugging. The option should be followed by the name of the
16805 wrapper, then any command-line arguments to pass to the wrapper, then
16806 @kbd{--} indicating the end of the wrapper arguments.
16808 @code{gdbserver} runs the specified wrapper program with a combined
16809 command line including the wrapper arguments, then the name of the
16810 program to debug, then any arguments to the program. The wrapper
16811 runs until it executes your program, and then @value{GDBN} gains control.
16813 You can use any program that eventually calls @code{execve} with
16814 its arguments as a wrapper. Several standard Unix utilities do
16815 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
16816 with @code{exec "$@@"} will also work.
16818 For example, you can use @code{env} to pass an environment variable to
16819 the debugged program, without setting the variable in @code{gdbserver}'s
16823 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
16826 @subsection Connecting to @code{gdbserver}
16828 Run @value{GDBN} on the host system.
16830 First make sure you have the necessary symbol files. Load symbols for
16831 your application using the @code{file} command before you connect. Use
16832 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
16833 was compiled with the correct sysroot using @code{--with-sysroot}).
16835 The symbol file and target libraries must exactly match the executable
16836 and libraries on the target, with one exception: the files on the host
16837 system should not be stripped, even if the files on the target system
16838 are. Mismatched or missing files will lead to confusing results
16839 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
16840 files may also prevent @code{gdbserver} from debugging multi-threaded
16843 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
16844 For TCP connections, you must start up @code{gdbserver} prior to using
16845 the @code{target remote} command. Otherwise you may get an error whose
16846 text depends on the host system, but which usually looks something like
16847 @samp{Connection refused}. Don't use the @code{load}
16848 command in @value{GDBN} when using @code{gdbserver}, since the program is
16849 already on the target.
16851 @subsection Monitor Commands for @code{gdbserver}
16852 @cindex monitor commands, for @code{gdbserver}
16853 @anchor{Monitor Commands for gdbserver}
16855 During a @value{GDBN} session using @code{gdbserver}, you can use the
16856 @code{monitor} command to send special requests to @code{gdbserver}.
16857 Here are the available commands.
16861 List the available monitor commands.
16863 @item monitor set debug 0
16864 @itemx monitor set debug 1
16865 Disable or enable general debugging messages.
16867 @item monitor set remote-debug 0
16868 @itemx monitor set remote-debug 1
16869 Disable or enable specific debugging messages associated with the remote
16870 protocol (@pxref{Remote Protocol}).
16872 @item monitor set libthread-db-search-path [PATH]
16873 @cindex gdbserver, search path for @code{libthread_db}
16874 When this command is issued, @var{path} is a colon-separated list of
16875 directories to search for @code{libthread_db} (@pxref{Threads,,set
16876 libthread-db-search-path}). If you omit @var{path},
16877 @samp{libthread-db-search-path} will be reset to its default value.
16879 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
16880 not supported in @code{gdbserver}.
16883 Tell gdbserver to exit immediately. This command should be followed by
16884 @code{disconnect} to close the debugging session. @code{gdbserver} will
16885 detach from any attached processes and kill any processes it created.
16886 Use @code{monitor exit} to terminate @code{gdbserver} at the end
16887 of a multi-process mode debug session.
16891 @subsection Tracepoints support in @code{gdbserver}
16892 @cindex tracepoints support in @code{gdbserver}
16894 On some targets, @code{gdbserver} supports tracepoints, fast
16895 tracepoints and static tracepoints.
16897 For fast or static tracepoints to work, a special library called the
16898 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
16899 This library is built and distributed as an integral part of
16900 @code{gdbserver}. In addition, support for static tracepoints
16901 requires building the in-process agent library with static tracepoints
16902 support. At present, the UST (LTTng Userspace Tracer,
16903 @url{http://lttng.org/ust}) tracing engine is supported. This support
16904 is automatically available if UST development headers are found in the
16905 standard include path when @code{gdbserver} is built, or if
16906 @code{gdbserver} was explicitly configured using @option{--with-ust}
16907 to point at such headers. You can explicitly disable the support
16908 using @option{--with-ust=no}.
16910 There are several ways to load the in-process agent in your program:
16913 @item Specifying it as dependency at link time
16915 You can link your program dynamically with the in-process agent
16916 library. On most systems, this is accomplished by adding
16917 @code{-linproctrace} to the link command.
16919 @item Using the system's preloading mechanisms
16921 You can force loading the in-process agent at startup time by using
16922 your system's support for preloading shared libraries. Many Unixes
16923 support the concept of preloading user defined libraries. In most
16924 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
16925 in the environment. See also the description of @code{gdbserver}'s
16926 @option{--wrapper} command line option.
16928 @item Using @value{GDBN} to force loading the agent at run time
16930 On some systems, you can force the inferior to load a shared library,
16931 by calling a dynamic loader function in the inferior that takes care
16932 of dynamically looking up and loading a shared library. On most Unix
16933 systems, the function is @code{dlopen}. You'll use the @code{call}
16934 command for that. For example:
16937 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
16940 Note that on most Unix systems, for the @code{dlopen} function to be
16941 available, the program needs to be linked with @code{-ldl}.
16944 On systems that have a userspace dynamic loader, like most Unix
16945 systems, when you connect to @code{gdbserver} using @code{target
16946 remote}, you'll find that the program is stopped at the dynamic
16947 loader's entry point, and no shared library has been loaded in the
16948 program's address space yet, including the in-process agent. In that
16949 case, before being able to use any of the fast or static tracepoints
16950 features, you need to let the loader run and load the shared
16951 libraries. The simplest way to do that is to run the program to the
16952 main procedure. E.g., if debugging a C or C@t{++} program, start
16953 @code{gdbserver} like so:
16956 $ gdbserver :9999 myprogram
16959 Start GDB and connect to @code{gdbserver} like so, and run to main:
16963 (@value{GDBP}) target remote myhost:9999
16964 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
16965 (@value{GDBP}) b main
16966 (@value{GDBP}) continue
16969 The in-process tracing agent library should now be loaded into the
16970 process; you can confirm it with the @code{info sharedlibrary}
16971 command, which will list @file{libinproctrace.so} as loaded in the
16972 process. You are now ready to install fast tracepoints, list static
16973 tracepoint markers, probe static tracepoints markers, and start
16976 @node Remote Configuration
16977 @section Remote Configuration
16980 @kindex show remote
16981 This section documents the configuration options available when
16982 debugging remote programs. For the options related to the File I/O
16983 extensions of the remote protocol, see @ref{system,
16984 system-call-allowed}.
16987 @item set remoteaddresssize @var{bits}
16988 @cindex address size for remote targets
16989 @cindex bits in remote address
16990 Set the maximum size of address in a memory packet to the specified
16991 number of bits. @value{GDBN} will mask off the address bits above
16992 that number, when it passes addresses to the remote target. The
16993 default value is the number of bits in the target's address.
16995 @item show remoteaddresssize
16996 Show the current value of remote address size in bits.
16998 @item set remotebaud @var{n}
16999 @cindex baud rate for remote targets
17000 Set the baud rate for the remote serial I/O to @var{n} baud. The
17001 value is used to set the speed of the serial port used for debugging
17004 @item show remotebaud
17005 Show the current speed of the remote connection.
17007 @item set remotebreak
17008 @cindex interrupt remote programs
17009 @cindex BREAK signal instead of Ctrl-C
17010 @anchor{set remotebreak}
17011 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
17012 when you type @kbd{Ctrl-c} to interrupt the program running
17013 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
17014 character instead. The default is off, since most remote systems
17015 expect to see @samp{Ctrl-C} as the interrupt signal.
17017 @item show remotebreak
17018 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
17019 interrupt the remote program.
17021 @item set remoteflow on
17022 @itemx set remoteflow off
17023 @kindex set remoteflow
17024 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
17025 on the serial port used to communicate to the remote target.
17027 @item show remoteflow
17028 @kindex show remoteflow
17029 Show the current setting of hardware flow control.
17031 @item set remotelogbase @var{base}
17032 Set the base (a.k.a.@: radix) of logging serial protocol
17033 communications to @var{base}. Supported values of @var{base} are:
17034 @code{ascii}, @code{octal}, and @code{hex}. The default is
17037 @item show remotelogbase
17038 Show the current setting of the radix for logging remote serial
17041 @item set remotelogfile @var{file}
17042 @cindex record serial communications on file
17043 Record remote serial communications on the named @var{file}. The
17044 default is not to record at all.
17046 @item show remotelogfile.
17047 Show the current setting of the file name on which to record the
17048 serial communications.
17050 @item set remotetimeout @var{num}
17051 @cindex timeout for serial communications
17052 @cindex remote timeout
17053 Set the timeout limit to wait for the remote target to respond to
17054 @var{num} seconds. The default is 2 seconds.
17056 @item show remotetimeout
17057 Show the current number of seconds to wait for the remote target
17060 @cindex limit hardware breakpoints and watchpoints
17061 @cindex remote target, limit break- and watchpoints
17062 @anchor{set remote hardware-watchpoint-limit}
17063 @anchor{set remote hardware-breakpoint-limit}
17064 @item set remote hardware-watchpoint-limit @var{limit}
17065 @itemx set remote hardware-breakpoint-limit @var{limit}
17066 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
17067 watchpoints. A limit of -1, the default, is treated as unlimited.
17069 @cindex limit hardware watchpoints length
17070 @cindex remote target, limit watchpoints length
17071 @anchor{set remote hardware-watchpoint-length-limit}
17072 @item set remote hardware-watchpoint-length-limit @var{limit}
17073 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
17074 a remote hardware watchpoint. A limit of -1, the default, is treated
17077 @item show remote hardware-watchpoint-length-limit
17078 Show the current limit (in bytes) of the maximum length of
17079 a remote hardware watchpoint.
17081 @item set remote exec-file @var{filename}
17082 @itemx show remote exec-file
17083 @anchor{set remote exec-file}
17084 @cindex executable file, for remote target
17085 Select the file used for @code{run} with @code{target
17086 extended-remote}. This should be set to a filename valid on the
17087 target system. If it is not set, the target will use a default
17088 filename (e.g.@: the last program run).
17090 @item set remote interrupt-sequence
17091 @cindex interrupt remote programs
17092 @cindex select Ctrl-C, BREAK or BREAK-g
17093 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
17094 @samp{BREAK-g} as the
17095 sequence to the remote target in order to interrupt the execution.
17096 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
17097 is high level of serial line for some certain time.
17098 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
17099 It is @code{BREAK} signal followed by character @code{g}.
17101 @item show interrupt-sequence
17102 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
17103 is sent by @value{GDBN} to interrupt the remote program.
17104 @code{BREAK-g} is BREAK signal followed by @code{g} and
17105 also known as Magic SysRq g.
17107 @item set remote interrupt-on-connect
17108 @cindex send interrupt-sequence on start
17109 Specify whether interrupt-sequence is sent to remote target when
17110 @value{GDBN} connects to it. This is mostly needed when you debug
17111 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
17112 which is known as Magic SysRq g in order to connect @value{GDBN}.
17114 @item show interrupt-on-connect
17115 Show whether interrupt-sequence is sent
17116 to remote target when @value{GDBN} connects to it.
17120 @item set tcp auto-retry on
17121 @cindex auto-retry, for remote TCP target
17122 Enable auto-retry for remote TCP connections. This is useful if the remote
17123 debugging agent is launched in parallel with @value{GDBN}; there is a race
17124 condition because the agent may not become ready to accept the connection
17125 before @value{GDBN} attempts to connect. When auto-retry is
17126 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
17127 to establish the connection using the timeout specified by
17128 @code{set tcp connect-timeout}.
17130 @item set tcp auto-retry off
17131 Do not auto-retry failed TCP connections.
17133 @item show tcp auto-retry
17134 Show the current auto-retry setting.
17136 @item set tcp connect-timeout @var{seconds}
17137 @cindex connection timeout, for remote TCP target
17138 @cindex timeout, for remote target connection
17139 Set the timeout for establishing a TCP connection to the remote target to
17140 @var{seconds}. The timeout affects both polling to retry failed connections
17141 (enabled by @code{set tcp auto-retry on}) and waiting for connections
17142 that are merely slow to complete, and represents an approximate cumulative
17145 @item show tcp connect-timeout
17146 Show the current connection timeout setting.
17149 @cindex remote packets, enabling and disabling
17150 The @value{GDBN} remote protocol autodetects the packets supported by
17151 your debugging stub. If you need to override the autodetection, you
17152 can use these commands to enable or disable individual packets. Each
17153 packet can be set to @samp{on} (the remote target supports this
17154 packet), @samp{off} (the remote target does not support this packet),
17155 or @samp{auto} (detect remote target support for this packet). They
17156 all default to @samp{auto}. For more information about each packet,
17157 see @ref{Remote Protocol}.
17159 During normal use, you should not have to use any of these commands.
17160 If you do, that may be a bug in your remote debugging stub, or a bug
17161 in @value{GDBN}. You may want to report the problem to the
17162 @value{GDBN} developers.
17164 For each packet @var{name}, the command to enable or disable the
17165 packet is @code{set remote @var{name}-packet}. The available settings
17168 @multitable @columnfractions 0.28 0.32 0.25
17171 @tab Related Features
17173 @item @code{fetch-register}
17175 @tab @code{info registers}
17177 @item @code{set-register}
17181 @item @code{binary-download}
17183 @tab @code{load}, @code{set}
17185 @item @code{read-aux-vector}
17186 @tab @code{qXfer:auxv:read}
17187 @tab @code{info auxv}
17189 @item @code{symbol-lookup}
17190 @tab @code{qSymbol}
17191 @tab Detecting multiple threads
17193 @item @code{attach}
17194 @tab @code{vAttach}
17197 @item @code{verbose-resume}
17199 @tab Stepping or resuming multiple threads
17205 @item @code{software-breakpoint}
17209 @item @code{hardware-breakpoint}
17213 @item @code{write-watchpoint}
17217 @item @code{read-watchpoint}
17221 @item @code{access-watchpoint}
17225 @item @code{target-features}
17226 @tab @code{qXfer:features:read}
17227 @tab @code{set architecture}
17229 @item @code{library-info}
17230 @tab @code{qXfer:libraries:read}
17231 @tab @code{info sharedlibrary}
17233 @item @code{memory-map}
17234 @tab @code{qXfer:memory-map:read}
17235 @tab @code{info mem}
17237 @item @code{read-sdata-object}
17238 @tab @code{qXfer:sdata:read}
17239 @tab @code{print $_sdata}
17241 @item @code{read-spu-object}
17242 @tab @code{qXfer:spu:read}
17243 @tab @code{info spu}
17245 @item @code{write-spu-object}
17246 @tab @code{qXfer:spu:write}
17247 @tab @code{info spu}
17249 @item @code{read-siginfo-object}
17250 @tab @code{qXfer:siginfo:read}
17251 @tab @code{print $_siginfo}
17253 @item @code{write-siginfo-object}
17254 @tab @code{qXfer:siginfo:write}
17255 @tab @code{set $_siginfo}
17257 @item @code{threads}
17258 @tab @code{qXfer:threads:read}
17259 @tab @code{info threads}
17261 @item @code{get-thread-local-@*storage-address}
17262 @tab @code{qGetTLSAddr}
17263 @tab Displaying @code{__thread} variables
17265 @item @code{get-thread-information-block-address}
17266 @tab @code{qGetTIBAddr}
17267 @tab Display MS-Windows Thread Information Block.
17269 @item @code{search-memory}
17270 @tab @code{qSearch:memory}
17273 @item @code{supported-packets}
17274 @tab @code{qSupported}
17275 @tab Remote communications parameters
17277 @item @code{pass-signals}
17278 @tab @code{QPassSignals}
17279 @tab @code{handle @var{signal}}
17281 @item @code{hostio-close-packet}
17282 @tab @code{vFile:close}
17283 @tab @code{remote get}, @code{remote put}
17285 @item @code{hostio-open-packet}
17286 @tab @code{vFile:open}
17287 @tab @code{remote get}, @code{remote put}
17289 @item @code{hostio-pread-packet}
17290 @tab @code{vFile:pread}
17291 @tab @code{remote get}, @code{remote put}
17293 @item @code{hostio-pwrite-packet}
17294 @tab @code{vFile:pwrite}
17295 @tab @code{remote get}, @code{remote put}
17297 @item @code{hostio-unlink-packet}
17298 @tab @code{vFile:unlink}
17299 @tab @code{remote delete}
17301 @item @code{noack-packet}
17302 @tab @code{QStartNoAckMode}
17303 @tab Packet acknowledgment
17305 @item @code{osdata}
17306 @tab @code{qXfer:osdata:read}
17307 @tab @code{info os}
17309 @item @code{query-attached}
17310 @tab @code{qAttached}
17311 @tab Querying remote process attach state.
17313 @item @code{traceframe-info}
17314 @tab @code{qXfer:traceframe-info:read}
17315 @tab Traceframe info
17317 @item @code{disable-randomization}
17318 @tab @code{QDisableRandomization}
17319 @tab @code{set disable-randomization}
17323 @section Implementing a Remote Stub
17325 @cindex debugging stub, example
17326 @cindex remote stub, example
17327 @cindex stub example, remote debugging
17328 The stub files provided with @value{GDBN} implement the target side of the
17329 communication protocol, and the @value{GDBN} side is implemented in the
17330 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
17331 these subroutines to communicate, and ignore the details. (If you're
17332 implementing your own stub file, you can still ignore the details: start
17333 with one of the existing stub files. @file{sparc-stub.c} is the best
17334 organized, and therefore the easiest to read.)
17336 @cindex remote serial debugging, overview
17337 To debug a program running on another machine (the debugging
17338 @dfn{target} machine), you must first arrange for all the usual
17339 prerequisites for the program to run by itself. For example, for a C
17344 A startup routine to set up the C runtime environment; these usually
17345 have a name like @file{crt0}. The startup routine may be supplied by
17346 your hardware supplier, or you may have to write your own.
17349 A C subroutine library to support your program's
17350 subroutine calls, notably managing input and output.
17353 A way of getting your program to the other machine---for example, a
17354 download program. These are often supplied by the hardware
17355 manufacturer, but you may have to write your own from hardware
17359 The next step is to arrange for your program to use a serial port to
17360 communicate with the machine where @value{GDBN} is running (the @dfn{host}
17361 machine). In general terms, the scheme looks like this:
17365 @value{GDBN} already understands how to use this protocol; when everything
17366 else is set up, you can simply use the @samp{target remote} command
17367 (@pxref{Targets,,Specifying a Debugging Target}).
17369 @item On the target,
17370 you must link with your program a few special-purpose subroutines that
17371 implement the @value{GDBN} remote serial protocol. The file containing these
17372 subroutines is called a @dfn{debugging stub}.
17374 On certain remote targets, you can use an auxiliary program
17375 @code{gdbserver} instead of linking a stub into your program.
17376 @xref{Server,,Using the @code{gdbserver} Program}, for details.
17379 The debugging stub is specific to the architecture of the remote
17380 machine; for example, use @file{sparc-stub.c} to debug programs on
17383 @cindex remote serial stub list
17384 These working remote stubs are distributed with @value{GDBN}:
17389 @cindex @file{i386-stub.c}
17392 For Intel 386 and compatible architectures.
17395 @cindex @file{m68k-stub.c}
17396 @cindex Motorola 680x0
17398 For Motorola 680x0 architectures.
17401 @cindex @file{sh-stub.c}
17404 For Renesas SH architectures.
17407 @cindex @file{sparc-stub.c}
17409 For @sc{sparc} architectures.
17411 @item sparcl-stub.c
17412 @cindex @file{sparcl-stub.c}
17415 For Fujitsu @sc{sparclite} architectures.
17419 The @file{README} file in the @value{GDBN} distribution may list other
17420 recently added stubs.
17423 * Stub Contents:: What the stub can do for you
17424 * Bootstrapping:: What you must do for the stub
17425 * Debug Session:: Putting it all together
17428 @node Stub Contents
17429 @subsection What the Stub Can Do for You
17431 @cindex remote serial stub
17432 The debugging stub for your architecture supplies these three
17436 @item set_debug_traps
17437 @findex set_debug_traps
17438 @cindex remote serial stub, initialization
17439 This routine arranges for @code{handle_exception} to run when your
17440 program stops. You must call this subroutine explicitly near the
17441 beginning of your program.
17443 @item handle_exception
17444 @findex handle_exception
17445 @cindex remote serial stub, main routine
17446 This is the central workhorse, but your program never calls it
17447 explicitly---the setup code arranges for @code{handle_exception} to
17448 run when a trap is triggered.
17450 @code{handle_exception} takes control when your program stops during
17451 execution (for example, on a breakpoint), and mediates communications
17452 with @value{GDBN} on the host machine. This is where the communications
17453 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
17454 representative on the target machine. It begins by sending summary
17455 information on the state of your program, then continues to execute,
17456 retrieving and transmitting any information @value{GDBN} needs, until you
17457 execute a @value{GDBN} command that makes your program resume; at that point,
17458 @code{handle_exception} returns control to your own code on the target
17462 @cindex @code{breakpoint} subroutine, remote
17463 Use this auxiliary subroutine to make your program contain a
17464 breakpoint. Depending on the particular situation, this may be the only
17465 way for @value{GDBN} to get control. For instance, if your target
17466 machine has some sort of interrupt button, you won't need to call this;
17467 pressing the interrupt button transfers control to
17468 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
17469 simply receiving characters on the serial port may also trigger a trap;
17470 again, in that situation, you don't need to call @code{breakpoint} from
17471 your own program---simply running @samp{target remote} from the host
17472 @value{GDBN} session gets control.
17474 Call @code{breakpoint} if none of these is true, or if you simply want
17475 to make certain your program stops at a predetermined point for the
17476 start of your debugging session.
17479 @node Bootstrapping
17480 @subsection What You Must Do for the Stub
17482 @cindex remote stub, support routines
17483 The debugging stubs that come with @value{GDBN} are set up for a particular
17484 chip architecture, but they have no information about the rest of your
17485 debugging target machine.
17487 First of all you need to tell the stub how to communicate with the
17491 @item int getDebugChar()
17492 @findex getDebugChar
17493 Write this subroutine to read a single character from the serial port.
17494 It may be identical to @code{getchar} for your target system; a
17495 different name is used to allow you to distinguish the two if you wish.
17497 @item void putDebugChar(int)
17498 @findex putDebugChar
17499 Write this subroutine to write a single character to the serial port.
17500 It may be identical to @code{putchar} for your target system; a
17501 different name is used to allow you to distinguish the two if you wish.
17504 @cindex control C, and remote debugging
17505 @cindex interrupting remote targets
17506 If you want @value{GDBN} to be able to stop your program while it is
17507 running, you need to use an interrupt-driven serial driver, and arrange
17508 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
17509 character). That is the character which @value{GDBN} uses to tell the
17510 remote system to stop.
17512 Getting the debugging target to return the proper status to @value{GDBN}
17513 probably requires changes to the standard stub; one quick and dirty way
17514 is to just execute a breakpoint instruction (the ``dirty'' part is that
17515 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
17517 Other routines you need to supply are:
17520 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
17521 @findex exceptionHandler
17522 Write this function to install @var{exception_address} in the exception
17523 handling tables. You need to do this because the stub does not have any
17524 way of knowing what the exception handling tables on your target system
17525 are like (for example, the processor's table might be in @sc{rom},
17526 containing entries which point to a table in @sc{ram}).
17527 @var{exception_number} is the exception number which should be changed;
17528 its meaning is architecture-dependent (for example, different numbers
17529 might represent divide by zero, misaligned access, etc). When this
17530 exception occurs, control should be transferred directly to
17531 @var{exception_address}, and the processor state (stack, registers,
17532 and so on) should be just as it is when a processor exception occurs. So if
17533 you want to use a jump instruction to reach @var{exception_address}, it
17534 should be a simple jump, not a jump to subroutine.
17536 For the 386, @var{exception_address} should be installed as an interrupt
17537 gate so that interrupts are masked while the handler runs. The gate
17538 should be at privilege level 0 (the most privileged level). The
17539 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
17540 help from @code{exceptionHandler}.
17542 @item void flush_i_cache()
17543 @findex flush_i_cache
17544 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
17545 instruction cache, if any, on your target machine. If there is no
17546 instruction cache, this subroutine may be a no-op.
17548 On target machines that have instruction caches, @value{GDBN} requires this
17549 function to make certain that the state of your program is stable.
17553 You must also make sure this library routine is available:
17556 @item void *memset(void *, int, int)
17558 This is the standard library function @code{memset} that sets an area of
17559 memory to a known value. If you have one of the free versions of
17560 @code{libc.a}, @code{memset} can be found there; otherwise, you must
17561 either obtain it from your hardware manufacturer, or write your own.
17564 If you do not use the GNU C compiler, you may need other standard
17565 library subroutines as well; this varies from one stub to another,
17566 but in general the stubs are likely to use any of the common library
17567 subroutines which @code{@value{NGCC}} generates as inline code.
17570 @node Debug Session
17571 @subsection Putting it All Together
17573 @cindex remote serial debugging summary
17574 In summary, when your program is ready to debug, you must follow these
17579 Make sure you have defined the supporting low-level routines
17580 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
17582 @code{getDebugChar}, @code{putDebugChar},
17583 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
17587 Insert these lines near the top of your program:
17595 For the 680x0 stub only, you need to provide a variable called
17596 @code{exceptionHook}. Normally you just use:
17599 void (*exceptionHook)() = 0;
17603 but if before calling @code{set_debug_traps}, you set it to point to a
17604 function in your program, that function is called when
17605 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
17606 error). The function indicated by @code{exceptionHook} is called with
17607 one parameter: an @code{int} which is the exception number.
17610 Compile and link together: your program, the @value{GDBN} debugging stub for
17611 your target architecture, and the supporting subroutines.
17614 Make sure you have a serial connection between your target machine and
17615 the @value{GDBN} host, and identify the serial port on the host.
17618 @c The "remote" target now provides a `load' command, so we should
17619 @c document that. FIXME.
17620 Download your program to your target machine (or get it there by
17621 whatever means the manufacturer provides), and start it.
17624 Start @value{GDBN} on the host, and connect to the target
17625 (@pxref{Connecting,,Connecting to a Remote Target}).
17629 @node Configurations
17630 @chapter Configuration-Specific Information
17632 While nearly all @value{GDBN} commands are available for all native and
17633 cross versions of the debugger, there are some exceptions. This chapter
17634 describes things that are only available in certain configurations.
17636 There are three major categories of configurations: native
17637 configurations, where the host and target are the same, embedded
17638 operating system configurations, which are usually the same for several
17639 different processor architectures, and bare embedded processors, which
17640 are quite different from each other.
17645 * Embedded Processors::
17652 This section describes details specific to particular native
17657 * BSD libkvm Interface:: Debugging BSD kernel memory images
17658 * SVR4 Process Information:: SVR4 process information
17659 * DJGPP Native:: Features specific to the DJGPP port
17660 * Cygwin Native:: Features specific to the Cygwin port
17661 * Hurd Native:: Features specific to @sc{gnu} Hurd
17662 * Neutrino:: Features specific to QNX Neutrino
17663 * Darwin:: Features specific to Darwin
17669 On HP-UX systems, if you refer to a function or variable name that
17670 begins with a dollar sign, @value{GDBN} searches for a user or system
17671 name first, before it searches for a convenience variable.
17674 @node BSD libkvm Interface
17675 @subsection BSD libkvm Interface
17678 @cindex kernel memory image
17679 @cindex kernel crash dump
17681 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
17682 interface that provides a uniform interface for accessing kernel virtual
17683 memory images, including live systems and crash dumps. @value{GDBN}
17684 uses this interface to allow you to debug live kernels and kernel crash
17685 dumps on many native BSD configurations. This is implemented as a
17686 special @code{kvm} debugging target. For debugging a live system, load
17687 the currently running kernel into @value{GDBN} and connect to the
17691 (@value{GDBP}) @b{target kvm}
17694 For debugging crash dumps, provide the file name of the crash dump as an
17698 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
17701 Once connected to the @code{kvm} target, the following commands are
17707 Set current context from the @dfn{Process Control Block} (PCB) address.
17710 Set current context from proc address. This command isn't available on
17711 modern FreeBSD systems.
17714 @node SVR4 Process Information
17715 @subsection SVR4 Process Information
17717 @cindex examine process image
17718 @cindex process info via @file{/proc}
17720 Many versions of SVR4 and compatible systems provide a facility called
17721 @samp{/proc} that can be used to examine the image of a running
17722 process using file-system subroutines. If @value{GDBN} is configured
17723 for an operating system with this facility, the command @code{info
17724 proc} is available to report information about the process running
17725 your program, or about any process running on your system. @code{info
17726 proc} works only on SVR4 systems that include the @code{procfs} code.
17727 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
17728 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
17734 @itemx info proc @var{process-id}
17735 Summarize available information about any running process. If a
17736 process ID is specified by @var{process-id}, display information about
17737 that process; otherwise display information about the program being
17738 debugged. The summary includes the debugged process ID, the command
17739 line used to invoke it, its current working directory, and its
17740 executable file's absolute file name.
17742 On some systems, @var{process-id} can be of the form
17743 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
17744 within a process. If the optional @var{pid} part is missing, it means
17745 a thread from the process being debugged (the leading @samp{/} still
17746 needs to be present, or else @value{GDBN} will interpret the number as
17747 a process ID rather than a thread ID).
17749 @item info proc mappings
17750 @cindex memory address space mappings
17751 Report the memory address space ranges accessible in the program, with
17752 information on whether the process has read, write, or execute access
17753 rights to each range. On @sc{gnu}/Linux systems, each memory range
17754 includes the object file which is mapped to that range, instead of the
17755 memory access rights to that range.
17757 @item info proc stat
17758 @itemx info proc status
17759 @cindex process detailed status information
17760 These subcommands are specific to @sc{gnu}/Linux systems. They show
17761 the process-related information, including the user ID and group ID;
17762 how many threads are there in the process; its virtual memory usage;
17763 the signals that are pending, blocked, and ignored; its TTY; its
17764 consumption of system and user time; its stack size; its @samp{nice}
17765 value; etc. For more information, see the @samp{proc} man page
17766 (type @kbd{man 5 proc} from your shell prompt).
17768 @item info proc all
17769 Show all the information about the process described under all of the
17770 above @code{info proc} subcommands.
17773 @comment These sub-options of 'info proc' were not included when
17774 @comment procfs.c was re-written. Keep their descriptions around
17775 @comment against the day when someone finds the time to put them back in.
17776 @kindex info proc times
17777 @item info proc times
17778 Starting time, user CPU time, and system CPU time for your program and
17781 @kindex info proc id
17783 Report on the process IDs related to your program: its own process ID,
17784 the ID of its parent, the process group ID, and the session ID.
17787 @item set procfs-trace
17788 @kindex set procfs-trace
17789 @cindex @code{procfs} API calls
17790 This command enables and disables tracing of @code{procfs} API calls.
17792 @item show procfs-trace
17793 @kindex show procfs-trace
17794 Show the current state of @code{procfs} API call tracing.
17796 @item set procfs-file @var{file}
17797 @kindex set procfs-file
17798 Tell @value{GDBN} to write @code{procfs} API trace to the named
17799 @var{file}. @value{GDBN} appends the trace info to the previous
17800 contents of the file. The default is to display the trace on the
17803 @item show procfs-file
17804 @kindex show procfs-file
17805 Show the file to which @code{procfs} API trace is written.
17807 @item proc-trace-entry
17808 @itemx proc-trace-exit
17809 @itemx proc-untrace-entry
17810 @itemx proc-untrace-exit
17811 @kindex proc-trace-entry
17812 @kindex proc-trace-exit
17813 @kindex proc-untrace-entry
17814 @kindex proc-untrace-exit
17815 These commands enable and disable tracing of entries into and exits
17816 from the @code{syscall} interface.
17819 @kindex info pidlist
17820 @cindex process list, QNX Neutrino
17821 For QNX Neutrino only, this command displays the list of all the
17822 processes and all the threads within each process.
17825 @kindex info meminfo
17826 @cindex mapinfo list, QNX Neutrino
17827 For QNX Neutrino only, this command displays the list of all mapinfos.
17831 @subsection Features for Debugging @sc{djgpp} Programs
17832 @cindex @sc{djgpp} debugging
17833 @cindex native @sc{djgpp} debugging
17834 @cindex MS-DOS-specific commands
17837 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
17838 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
17839 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
17840 top of real-mode DOS systems and their emulations.
17842 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
17843 defines a few commands specific to the @sc{djgpp} port. This
17844 subsection describes those commands.
17849 This is a prefix of @sc{djgpp}-specific commands which print
17850 information about the target system and important OS structures.
17853 @cindex MS-DOS system info
17854 @cindex free memory information (MS-DOS)
17855 @item info dos sysinfo
17856 This command displays assorted information about the underlying
17857 platform: the CPU type and features, the OS version and flavor, the
17858 DPMI version, and the available conventional and DPMI memory.
17863 @cindex segment descriptor tables
17864 @cindex descriptor tables display
17866 @itemx info dos ldt
17867 @itemx info dos idt
17868 These 3 commands display entries from, respectively, Global, Local,
17869 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
17870 tables are data structures which store a descriptor for each segment
17871 that is currently in use. The segment's selector is an index into a
17872 descriptor table; the table entry for that index holds the
17873 descriptor's base address and limit, and its attributes and access
17876 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
17877 segment (used for both data and the stack), and a DOS segment (which
17878 allows access to DOS/BIOS data structures and absolute addresses in
17879 conventional memory). However, the DPMI host will usually define
17880 additional segments in order to support the DPMI environment.
17882 @cindex garbled pointers
17883 These commands allow to display entries from the descriptor tables.
17884 Without an argument, all entries from the specified table are
17885 displayed. An argument, which should be an integer expression, means
17886 display a single entry whose index is given by the argument. For
17887 example, here's a convenient way to display information about the
17888 debugged program's data segment:
17891 @exdent @code{(@value{GDBP}) info dos ldt $ds}
17892 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
17896 This comes in handy when you want to see whether a pointer is outside
17897 the data segment's limit (i.e.@: @dfn{garbled}).
17899 @cindex page tables display (MS-DOS)
17901 @itemx info dos pte
17902 These two commands display entries from, respectively, the Page
17903 Directory and the Page Tables. Page Directories and Page Tables are
17904 data structures which control how virtual memory addresses are mapped
17905 into physical addresses. A Page Table includes an entry for every
17906 page of memory that is mapped into the program's address space; there
17907 may be several Page Tables, each one holding up to 4096 entries. A
17908 Page Directory has up to 4096 entries, one each for every Page Table
17909 that is currently in use.
17911 Without an argument, @kbd{info dos pde} displays the entire Page
17912 Directory, and @kbd{info dos pte} displays all the entries in all of
17913 the Page Tables. An argument, an integer expression, given to the
17914 @kbd{info dos pde} command means display only that entry from the Page
17915 Directory table. An argument given to the @kbd{info dos pte} command
17916 means display entries from a single Page Table, the one pointed to by
17917 the specified entry in the Page Directory.
17919 @cindex direct memory access (DMA) on MS-DOS
17920 These commands are useful when your program uses @dfn{DMA} (Direct
17921 Memory Access), which needs physical addresses to program the DMA
17924 These commands are supported only with some DPMI servers.
17926 @cindex physical address from linear address
17927 @item info dos address-pte @var{addr}
17928 This command displays the Page Table entry for a specified linear
17929 address. The argument @var{addr} is a linear address which should
17930 already have the appropriate segment's base address added to it,
17931 because this command accepts addresses which may belong to @emph{any}
17932 segment. For example, here's how to display the Page Table entry for
17933 the page where a variable @code{i} is stored:
17936 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
17937 @exdent @code{Page Table entry for address 0x11a00d30:}
17938 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
17942 This says that @code{i} is stored at offset @code{0xd30} from the page
17943 whose physical base address is @code{0x02698000}, and shows all the
17944 attributes of that page.
17946 Note that you must cast the addresses of variables to a @code{char *},
17947 since otherwise the value of @code{__djgpp_base_address}, the base
17948 address of all variables and functions in a @sc{djgpp} program, will
17949 be added using the rules of C pointer arithmetics: if @code{i} is
17950 declared an @code{int}, @value{GDBN} will add 4 times the value of
17951 @code{__djgpp_base_address} to the address of @code{i}.
17953 Here's another example, it displays the Page Table entry for the
17957 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
17958 @exdent @code{Page Table entry for address 0x29110:}
17959 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
17963 (The @code{+ 3} offset is because the transfer buffer's address is the
17964 3rd member of the @code{_go32_info_block} structure.) The output
17965 clearly shows that this DPMI server maps the addresses in conventional
17966 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
17967 linear (@code{0x29110}) addresses are identical.
17969 This command is supported only with some DPMI servers.
17972 @cindex DOS serial data link, remote debugging
17973 In addition to native debugging, the DJGPP port supports remote
17974 debugging via a serial data link. The following commands are specific
17975 to remote serial debugging in the DJGPP port of @value{GDBN}.
17978 @kindex set com1base
17979 @kindex set com1irq
17980 @kindex set com2base
17981 @kindex set com2irq
17982 @kindex set com3base
17983 @kindex set com3irq
17984 @kindex set com4base
17985 @kindex set com4irq
17986 @item set com1base @var{addr}
17987 This command sets the base I/O port address of the @file{COM1} serial
17990 @item set com1irq @var{irq}
17991 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
17992 for the @file{COM1} serial port.
17994 There are similar commands @samp{set com2base}, @samp{set com3irq},
17995 etc.@: for setting the port address and the @code{IRQ} lines for the
17998 @kindex show com1base
17999 @kindex show com1irq
18000 @kindex show com2base
18001 @kindex show com2irq
18002 @kindex show com3base
18003 @kindex show com3irq
18004 @kindex show com4base
18005 @kindex show com4irq
18006 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
18007 display the current settings of the base address and the @code{IRQ}
18008 lines used by the COM ports.
18011 @kindex info serial
18012 @cindex DOS serial port status
18013 This command prints the status of the 4 DOS serial ports. For each
18014 port, it prints whether it's active or not, its I/O base address and
18015 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
18016 counts of various errors encountered so far.
18020 @node Cygwin Native
18021 @subsection Features for Debugging MS Windows PE Executables
18022 @cindex MS Windows debugging
18023 @cindex native Cygwin debugging
18024 @cindex Cygwin-specific commands
18026 @value{GDBN} supports native debugging of MS Windows programs, including
18027 DLLs with and without symbolic debugging information.
18029 @cindex Ctrl-BREAK, MS-Windows
18030 @cindex interrupt debuggee on MS-Windows
18031 MS-Windows programs that call @code{SetConsoleMode} to switch off the
18032 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
18033 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
18034 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
18035 sequence, which can be used to interrupt the debuggee even if it
18038 There are various additional Cygwin-specific commands, described in
18039 this section. Working with DLLs that have no debugging symbols is
18040 described in @ref{Non-debug DLL Symbols}.
18045 This is a prefix of MS Windows-specific commands which print
18046 information about the target system and important OS structures.
18048 @item info w32 selector
18049 This command displays information returned by
18050 the Win32 API @code{GetThreadSelectorEntry} function.
18051 It takes an optional argument that is evaluated to
18052 a long value to give the information about this given selector.
18053 Without argument, this command displays information
18054 about the six segment registers.
18056 @item info w32 thread-information-block
18057 This command displays thread specific information stored in the
18058 Thread Information Block (readable on the X86 CPU family using @code{$fs}
18059 selector for 32-bit programs and @code{$gs} for 64-bit programs).
18063 This is a Cygwin-specific alias of @code{info shared}.
18065 @kindex dll-symbols
18067 This command loads symbols from a dll similarly to
18068 add-sym command but without the need to specify a base address.
18070 @kindex set cygwin-exceptions
18071 @cindex debugging the Cygwin DLL
18072 @cindex Cygwin DLL, debugging
18073 @item set cygwin-exceptions @var{mode}
18074 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
18075 happen inside the Cygwin DLL. If @var{mode} is @code{off},
18076 @value{GDBN} will delay recognition of exceptions, and may ignore some
18077 exceptions which seem to be caused by internal Cygwin DLL
18078 ``bookkeeping''. This option is meant primarily for debugging the
18079 Cygwin DLL itself; the default value is @code{off} to avoid annoying
18080 @value{GDBN} users with false @code{SIGSEGV} signals.
18082 @kindex show cygwin-exceptions
18083 @item show cygwin-exceptions
18084 Displays whether @value{GDBN} will break on exceptions that happen
18085 inside the Cygwin DLL itself.
18087 @kindex set new-console
18088 @item set new-console @var{mode}
18089 If @var{mode} is @code{on} the debuggee will
18090 be started in a new console on next start.
18091 If @var{mode} is @code{off}, the debuggee will
18092 be started in the same console as the debugger.
18094 @kindex show new-console
18095 @item show new-console
18096 Displays whether a new console is used
18097 when the debuggee is started.
18099 @kindex set new-group
18100 @item set new-group @var{mode}
18101 This boolean value controls whether the debuggee should
18102 start a new group or stay in the same group as the debugger.
18103 This affects the way the Windows OS handles
18106 @kindex show new-group
18107 @item show new-group
18108 Displays current value of new-group boolean.
18110 @kindex set debugevents
18111 @item set debugevents
18112 This boolean value adds debug output concerning kernel events related
18113 to the debuggee seen by the debugger. This includes events that
18114 signal thread and process creation and exit, DLL loading and
18115 unloading, console interrupts, and debugging messages produced by the
18116 Windows @code{OutputDebugString} API call.
18118 @kindex set debugexec
18119 @item set debugexec
18120 This boolean value adds debug output concerning execute events
18121 (such as resume thread) seen by the debugger.
18123 @kindex set debugexceptions
18124 @item set debugexceptions
18125 This boolean value adds debug output concerning exceptions in the
18126 debuggee seen by the debugger.
18128 @kindex set debugmemory
18129 @item set debugmemory
18130 This boolean value adds debug output concerning debuggee memory reads
18131 and writes by the debugger.
18135 This boolean values specifies whether the debuggee is called
18136 via a shell or directly (default value is on).
18140 Displays if the debuggee will be started with a shell.
18145 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
18148 @node Non-debug DLL Symbols
18149 @subsubsection Support for DLLs without Debugging Symbols
18150 @cindex DLLs with no debugging symbols
18151 @cindex Minimal symbols and DLLs
18153 Very often on windows, some of the DLLs that your program relies on do
18154 not include symbolic debugging information (for example,
18155 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
18156 symbols in a DLL, it relies on the minimal amount of symbolic
18157 information contained in the DLL's export table. This section
18158 describes working with such symbols, known internally to @value{GDBN} as
18159 ``minimal symbols''.
18161 Note that before the debugged program has started execution, no DLLs
18162 will have been loaded. The easiest way around this problem is simply to
18163 start the program --- either by setting a breakpoint or letting the
18164 program run once to completion. It is also possible to force
18165 @value{GDBN} to load a particular DLL before starting the executable ---
18166 see the shared library information in @ref{Files}, or the
18167 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
18168 explicitly loading symbols from a DLL with no debugging information will
18169 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
18170 which may adversely affect symbol lookup performance.
18172 @subsubsection DLL Name Prefixes
18174 In keeping with the naming conventions used by the Microsoft debugging
18175 tools, DLL export symbols are made available with a prefix based on the
18176 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
18177 also entered into the symbol table, so @code{CreateFileA} is often
18178 sufficient. In some cases there will be name clashes within a program
18179 (particularly if the executable itself includes full debugging symbols)
18180 necessitating the use of the fully qualified name when referring to the
18181 contents of the DLL. Use single-quotes around the name to avoid the
18182 exclamation mark (``!'') being interpreted as a language operator.
18184 Note that the internal name of the DLL may be all upper-case, even
18185 though the file name of the DLL is lower-case, or vice-versa. Since
18186 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
18187 some confusion. If in doubt, try the @code{info functions} and
18188 @code{info variables} commands or even @code{maint print msymbols}
18189 (@pxref{Symbols}). Here's an example:
18192 (@value{GDBP}) info function CreateFileA
18193 All functions matching regular expression "CreateFileA":
18195 Non-debugging symbols:
18196 0x77e885f4 CreateFileA
18197 0x77e885f4 KERNEL32!CreateFileA
18201 (@value{GDBP}) info function !
18202 All functions matching regular expression "!":
18204 Non-debugging symbols:
18205 0x6100114c cygwin1!__assert
18206 0x61004034 cygwin1!_dll_crt0@@0
18207 0x61004240 cygwin1!dll_crt0(per_process *)
18211 @subsubsection Working with Minimal Symbols
18213 Symbols extracted from a DLL's export table do not contain very much
18214 type information. All that @value{GDBN} can do is guess whether a symbol
18215 refers to a function or variable depending on the linker section that
18216 contains the symbol. Also note that the actual contents of the memory
18217 contained in a DLL are not available unless the program is running. This
18218 means that you cannot examine the contents of a variable or disassemble
18219 a function within a DLL without a running program.
18221 Variables are generally treated as pointers and dereferenced
18222 automatically. For this reason, it is often necessary to prefix a
18223 variable name with the address-of operator (``&'') and provide explicit
18224 type information in the command. Here's an example of the type of
18228 (@value{GDBP}) print 'cygwin1!__argv'
18233 (@value{GDBP}) x 'cygwin1!__argv'
18234 0x10021610: "\230y\""
18237 And two possible solutions:
18240 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
18241 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
18245 (@value{GDBP}) x/2x &'cygwin1!__argv'
18246 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
18247 (@value{GDBP}) x/x 0x10021608
18248 0x10021608: 0x0022fd98
18249 (@value{GDBP}) x/s 0x0022fd98
18250 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
18253 Setting a break point within a DLL is possible even before the program
18254 starts execution. However, under these circumstances, @value{GDBN} can't
18255 examine the initial instructions of the function in order to skip the
18256 function's frame set-up code. You can work around this by using ``*&''
18257 to set the breakpoint at a raw memory address:
18260 (@value{GDBP}) break *&'python22!PyOS_Readline'
18261 Breakpoint 1 at 0x1e04eff0
18264 The author of these extensions is not entirely convinced that setting a
18265 break point within a shared DLL like @file{kernel32.dll} is completely
18269 @subsection Commands Specific to @sc{gnu} Hurd Systems
18270 @cindex @sc{gnu} Hurd debugging
18272 This subsection describes @value{GDBN} commands specific to the
18273 @sc{gnu} Hurd native debugging.
18278 @kindex set signals@r{, Hurd command}
18279 @kindex set sigs@r{, Hurd command}
18280 This command toggles the state of inferior signal interception by
18281 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
18282 affected by this command. @code{sigs} is a shorthand alias for
18287 @kindex show signals@r{, Hurd command}
18288 @kindex show sigs@r{, Hurd command}
18289 Show the current state of intercepting inferior's signals.
18291 @item set signal-thread
18292 @itemx set sigthread
18293 @kindex set signal-thread
18294 @kindex set sigthread
18295 This command tells @value{GDBN} which thread is the @code{libc} signal
18296 thread. That thread is run when a signal is delivered to a running
18297 process. @code{set sigthread} is the shorthand alias of @code{set
18300 @item show signal-thread
18301 @itemx show sigthread
18302 @kindex show signal-thread
18303 @kindex show sigthread
18304 These two commands show which thread will run when the inferior is
18305 delivered a signal.
18308 @kindex set stopped@r{, Hurd command}
18309 This commands tells @value{GDBN} that the inferior process is stopped,
18310 as with the @code{SIGSTOP} signal. The stopped process can be
18311 continued by delivering a signal to it.
18314 @kindex show stopped@r{, Hurd command}
18315 This command shows whether @value{GDBN} thinks the debuggee is
18318 @item set exceptions
18319 @kindex set exceptions@r{, Hurd command}
18320 Use this command to turn off trapping of exceptions in the inferior.
18321 When exception trapping is off, neither breakpoints nor
18322 single-stepping will work. To restore the default, set exception
18325 @item show exceptions
18326 @kindex show exceptions@r{, Hurd command}
18327 Show the current state of trapping exceptions in the inferior.
18329 @item set task pause
18330 @kindex set task@r{, Hurd commands}
18331 @cindex task attributes (@sc{gnu} Hurd)
18332 @cindex pause current task (@sc{gnu} Hurd)
18333 This command toggles task suspension when @value{GDBN} has control.
18334 Setting it to on takes effect immediately, and the task is suspended
18335 whenever @value{GDBN} gets control. Setting it to off will take
18336 effect the next time the inferior is continued. If this option is set
18337 to off, you can use @code{set thread default pause on} or @code{set
18338 thread pause on} (see below) to pause individual threads.
18340 @item show task pause
18341 @kindex show task@r{, Hurd commands}
18342 Show the current state of task suspension.
18344 @item set task detach-suspend-count
18345 @cindex task suspend count
18346 @cindex detach from task, @sc{gnu} Hurd
18347 This command sets the suspend count the task will be left with when
18348 @value{GDBN} detaches from it.
18350 @item show task detach-suspend-count
18351 Show the suspend count the task will be left with when detaching.
18353 @item set task exception-port
18354 @itemx set task excp
18355 @cindex task exception port, @sc{gnu} Hurd
18356 This command sets the task exception port to which @value{GDBN} will
18357 forward exceptions. The argument should be the value of the @dfn{send
18358 rights} of the task. @code{set task excp} is a shorthand alias.
18360 @item set noninvasive
18361 @cindex noninvasive task options
18362 This command switches @value{GDBN} to a mode that is the least
18363 invasive as far as interfering with the inferior is concerned. This
18364 is the same as using @code{set task pause}, @code{set exceptions}, and
18365 @code{set signals} to values opposite to the defaults.
18367 @item info send-rights
18368 @itemx info receive-rights
18369 @itemx info port-rights
18370 @itemx info port-sets
18371 @itemx info dead-names
18374 @cindex send rights, @sc{gnu} Hurd
18375 @cindex receive rights, @sc{gnu} Hurd
18376 @cindex port rights, @sc{gnu} Hurd
18377 @cindex port sets, @sc{gnu} Hurd
18378 @cindex dead names, @sc{gnu} Hurd
18379 These commands display information about, respectively, send rights,
18380 receive rights, port rights, port sets, and dead names of a task.
18381 There are also shorthand aliases: @code{info ports} for @code{info
18382 port-rights} and @code{info psets} for @code{info port-sets}.
18384 @item set thread pause
18385 @kindex set thread@r{, Hurd command}
18386 @cindex thread properties, @sc{gnu} Hurd
18387 @cindex pause current thread (@sc{gnu} Hurd)
18388 This command toggles current thread suspension when @value{GDBN} has
18389 control. Setting it to on takes effect immediately, and the current
18390 thread is suspended whenever @value{GDBN} gets control. Setting it to
18391 off will take effect the next time the inferior is continued.
18392 Normally, this command has no effect, since when @value{GDBN} has
18393 control, the whole task is suspended. However, if you used @code{set
18394 task pause off} (see above), this command comes in handy to suspend
18395 only the current thread.
18397 @item show thread pause
18398 @kindex show thread@r{, Hurd command}
18399 This command shows the state of current thread suspension.
18401 @item set thread run
18402 This command sets whether the current thread is allowed to run.
18404 @item show thread run
18405 Show whether the current thread is allowed to run.
18407 @item set thread detach-suspend-count
18408 @cindex thread suspend count, @sc{gnu} Hurd
18409 @cindex detach from thread, @sc{gnu} Hurd
18410 This command sets the suspend count @value{GDBN} will leave on a
18411 thread when detaching. This number is relative to the suspend count
18412 found by @value{GDBN} when it notices the thread; use @code{set thread
18413 takeover-suspend-count} to force it to an absolute value.
18415 @item show thread detach-suspend-count
18416 Show the suspend count @value{GDBN} will leave on the thread when
18419 @item set thread exception-port
18420 @itemx set thread excp
18421 Set the thread exception port to which to forward exceptions. This
18422 overrides the port set by @code{set task exception-port} (see above).
18423 @code{set thread excp} is the shorthand alias.
18425 @item set thread takeover-suspend-count
18426 Normally, @value{GDBN}'s thread suspend counts are relative to the
18427 value @value{GDBN} finds when it notices each thread. This command
18428 changes the suspend counts to be absolute instead.
18430 @item set thread default
18431 @itemx show thread default
18432 @cindex thread default settings, @sc{gnu} Hurd
18433 Each of the above @code{set thread} commands has a @code{set thread
18434 default} counterpart (e.g., @code{set thread default pause}, @code{set
18435 thread default exception-port}, etc.). The @code{thread default}
18436 variety of commands sets the default thread properties for all
18437 threads; you can then change the properties of individual threads with
18438 the non-default commands.
18443 @subsection QNX Neutrino
18444 @cindex QNX Neutrino
18446 @value{GDBN} provides the following commands specific to the QNX
18450 @item set debug nto-debug
18451 @kindex set debug nto-debug
18452 When set to on, enables debugging messages specific to the QNX
18455 @item show debug nto-debug
18456 @kindex show debug nto-debug
18457 Show the current state of QNX Neutrino messages.
18464 @value{GDBN} provides the following commands specific to the Darwin target:
18467 @item set debug darwin @var{num}
18468 @kindex set debug darwin
18469 When set to a non zero value, enables debugging messages specific to
18470 the Darwin support. Higher values produce more verbose output.
18472 @item show debug darwin
18473 @kindex show debug darwin
18474 Show the current state of Darwin messages.
18476 @item set debug mach-o @var{num}
18477 @kindex set debug mach-o
18478 When set to a non zero value, enables debugging messages while
18479 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
18480 file format used on Darwin for object and executable files.) Higher
18481 values produce more verbose output. This is a command to diagnose
18482 problems internal to @value{GDBN} and should not be needed in normal
18485 @item show debug mach-o
18486 @kindex show debug mach-o
18487 Show the current state of Mach-O file messages.
18489 @item set mach-exceptions on
18490 @itemx set mach-exceptions off
18491 @kindex set mach-exceptions
18492 On Darwin, faults are first reported as a Mach exception and are then
18493 mapped to a Posix signal. Use this command to turn on trapping of
18494 Mach exceptions in the inferior. This might be sometimes useful to
18495 better understand the cause of a fault. The default is off.
18497 @item show mach-exceptions
18498 @kindex show mach-exceptions
18499 Show the current state of exceptions trapping.
18504 @section Embedded Operating Systems
18506 This section describes configurations involving the debugging of
18507 embedded operating systems that are available for several different
18511 * VxWorks:: Using @value{GDBN} with VxWorks
18514 @value{GDBN} includes the ability to debug programs running on
18515 various real-time operating systems.
18518 @subsection Using @value{GDBN} with VxWorks
18524 @kindex target vxworks
18525 @item target vxworks @var{machinename}
18526 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
18527 is the target system's machine name or IP address.
18531 On VxWorks, @code{load} links @var{filename} dynamically on the
18532 current target system as well as adding its symbols in @value{GDBN}.
18534 @value{GDBN} enables developers to spawn and debug tasks running on networked
18535 VxWorks targets from a Unix host. Already-running tasks spawned from
18536 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
18537 both the Unix host and on the VxWorks target. The program
18538 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
18539 installed with the name @code{vxgdb}, to distinguish it from a
18540 @value{GDBN} for debugging programs on the host itself.)
18543 @item VxWorks-timeout @var{args}
18544 @kindex vxworks-timeout
18545 All VxWorks-based targets now support the option @code{vxworks-timeout}.
18546 This option is set by the user, and @var{args} represents the number of
18547 seconds @value{GDBN} waits for responses to rpc's. You might use this if
18548 your VxWorks target is a slow software simulator or is on the far side
18549 of a thin network line.
18552 The following information on connecting to VxWorks was current when
18553 this manual was produced; newer releases of VxWorks may use revised
18556 @findex INCLUDE_RDB
18557 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
18558 to include the remote debugging interface routines in the VxWorks
18559 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
18560 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
18561 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
18562 source debugging task @code{tRdbTask} when VxWorks is booted. For more
18563 information on configuring and remaking VxWorks, see the manufacturer's
18565 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
18567 Once you have included @file{rdb.a} in your VxWorks system image and set
18568 your Unix execution search path to find @value{GDBN}, you are ready to
18569 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
18570 @code{vxgdb}, depending on your installation).
18572 @value{GDBN} comes up showing the prompt:
18579 * VxWorks Connection:: Connecting to VxWorks
18580 * VxWorks Download:: VxWorks download
18581 * VxWorks Attach:: Running tasks
18584 @node VxWorks Connection
18585 @subsubsection Connecting to VxWorks
18587 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
18588 network. To connect to a target whose host name is ``@code{tt}'', type:
18591 (vxgdb) target vxworks tt
18595 @value{GDBN} displays messages like these:
18598 Attaching remote machine across net...
18603 @value{GDBN} then attempts to read the symbol tables of any object modules
18604 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
18605 these files by searching the directories listed in the command search
18606 path (@pxref{Environment, ,Your Program's Environment}); if it fails
18607 to find an object file, it displays a message such as:
18610 prog.o: No such file or directory.
18613 When this happens, add the appropriate directory to the search path with
18614 the @value{GDBN} command @code{path}, and execute the @code{target}
18617 @node VxWorks Download
18618 @subsubsection VxWorks Download
18620 @cindex download to VxWorks
18621 If you have connected to the VxWorks target and you want to debug an
18622 object that has not yet been loaded, you can use the @value{GDBN}
18623 @code{load} command to download a file from Unix to VxWorks
18624 incrementally. The object file given as an argument to the @code{load}
18625 command is actually opened twice: first by the VxWorks target in order
18626 to download the code, then by @value{GDBN} in order to read the symbol
18627 table. This can lead to problems if the current working directories on
18628 the two systems differ. If both systems have NFS mounted the same
18629 filesystems, you can avoid these problems by using absolute paths.
18630 Otherwise, it is simplest to set the working directory on both systems
18631 to the directory in which the object file resides, and then to reference
18632 the file by its name, without any path. For instance, a program
18633 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
18634 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
18635 program, type this on VxWorks:
18638 -> cd "@var{vxpath}/vw/demo/rdb"
18642 Then, in @value{GDBN}, type:
18645 (vxgdb) cd @var{hostpath}/vw/demo/rdb
18646 (vxgdb) load prog.o
18649 @value{GDBN} displays a response similar to this:
18652 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
18655 You can also use the @code{load} command to reload an object module
18656 after editing and recompiling the corresponding source file. Note that
18657 this makes @value{GDBN} delete all currently-defined breakpoints,
18658 auto-displays, and convenience variables, and to clear the value
18659 history. (This is necessary in order to preserve the integrity of
18660 debugger's data structures that reference the target system's symbol
18663 @node VxWorks Attach
18664 @subsubsection Running Tasks
18666 @cindex running VxWorks tasks
18667 You can also attach to an existing task using the @code{attach} command as
18671 (vxgdb) attach @var{task}
18675 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
18676 or suspended when you attach to it. Running tasks are suspended at
18677 the time of attachment.
18679 @node Embedded Processors
18680 @section Embedded Processors
18682 This section goes into details specific to particular embedded
18685 @cindex send command to simulator
18686 Whenever a specific embedded processor has a simulator, @value{GDBN}
18687 allows to send an arbitrary command to the simulator.
18690 @item sim @var{command}
18691 @kindex sim@r{, a command}
18692 Send an arbitrary @var{command} string to the simulator. Consult the
18693 documentation for the specific simulator in use for information about
18694 acceptable commands.
18700 * M32R/D:: Renesas M32R/D
18701 * M68K:: Motorola M68K
18702 * MicroBlaze:: Xilinx MicroBlaze
18703 * MIPS Embedded:: MIPS Embedded
18704 * OpenRISC 1000:: OpenRisc 1000
18705 * PA:: HP PA Embedded
18706 * PowerPC Embedded:: PowerPC Embedded
18707 * Sparclet:: Tsqware Sparclet
18708 * Sparclite:: Fujitsu Sparclite
18709 * Z8000:: Zilog Z8000
18712 * Super-H:: Renesas Super-H
18721 @item target rdi @var{dev}
18722 ARM Angel monitor, via RDI library interface to ADP protocol. You may
18723 use this target to communicate with both boards running the Angel
18724 monitor, or with the EmbeddedICE JTAG debug device.
18727 @item target rdp @var{dev}
18732 @value{GDBN} provides the following ARM-specific commands:
18735 @item set arm disassembler
18737 This commands selects from a list of disassembly styles. The
18738 @code{"std"} style is the standard style.
18740 @item show arm disassembler
18742 Show the current disassembly style.
18744 @item set arm apcs32
18745 @cindex ARM 32-bit mode
18746 This command toggles ARM operation mode between 32-bit and 26-bit.
18748 @item show arm apcs32
18749 Display the current usage of the ARM 32-bit mode.
18751 @item set arm fpu @var{fputype}
18752 This command sets the ARM floating-point unit (FPU) type. The
18753 argument @var{fputype} can be one of these:
18757 Determine the FPU type by querying the OS ABI.
18759 Software FPU, with mixed-endian doubles on little-endian ARM
18762 GCC-compiled FPA co-processor.
18764 Software FPU with pure-endian doubles.
18770 Show the current type of the FPU.
18773 This command forces @value{GDBN} to use the specified ABI.
18776 Show the currently used ABI.
18778 @item set arm fallback-mode (arm|thumb|auto)
18779 @value{GDBN} uses the symbol table, when available, to determine
18780 whether instructions are ARM or Thumb. This command controls
18781 @value{GDBN}'s default behavior when the symbol table is not
18782 available. The default is @samp{auto}, which causes @value{GDBN} to
18783 use the current execution mode (from the @code{T} bit in the @code{CPSR}
18786 @item show arm fallback-mode
18787 Show the current fallback instruction mode.
18789 @item set arm force-mode (arm|thumb|auto)
18790 This command overrides use of the symbol table to determine whether
18791 instructions are ARM or Thumb. The default is @samp{auto}, which
18792 causes @value{GDBN} to use the symbol table and then the setting
18793 of @samp{set arm fallback-mode}.
18795 @item show arm force-mode
18796 Show the current forced instruction mode.
18798 @item set debug arm
18799 Toggle whether to display ARM-specific debugging messages from the ARM
18800 target support subsystem.
18802 @item show debug arm
18803 Show whether ARM-specific debugging messages are enabled.
18806 The following commands are available when an ARM target is debugged
18807 using the RDI interface:
18810 @item rdilogfile @r{[}@var{file}@r{]}
18812 @cindex ADP (Angel Debugger Protocol) logging
18813 Set the filename for the ADP (Angel Debugger Protocol) packet log.
18814 With an argument, sets the log file to the specified @var{file}. With
18815 no argument, show the current log file name. The default log file is
18818 @item rdilogenable @r{[}@var{arg}@r{]}
18819 @kindex rdilogenable
18820 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
18821 enables logging, with an argument 0 or @code{"no"} disables it. With
18822 no arguments displays the current setting. When logging is enabled,
18823 ADP packets exchanged between @value{GDBN} and the RDI target device
18824 are logged to a file.
18826 @item set rdiromatzero
18827 @kindex set rdiromatzero
18828 @cindex ROM at zero address, RDI
18829 Tell @value{GDBN} whether the target has ROM at address 0. If on,
18830 vector catching is disabled, so that zero address can be used. If off
18831 (the default), vector catching is enabled. For this command to take
18832 effect, it needs to be invoked prior to the @code{target rdi} command.
18834 @item show rdiromatzero
18835 @kindex show rdiromatzero
18836 Show the current setting of ROM at zero address.
18838 @item set rdiheartbeat
18839 @kindex set rdiheartbeat
18840 @cindex RDI heartbeat
18841 Enable or disable RDI heartbeat packets. It is not recommended to
18842 turn on this option, since it confuses ARM and EPI JTAG interface, as
18843 well as the Angel monitor.
18845 @item show rdiheartbeat
18846 @kindex show rdiheartbeat
18847 Show the setting of RDI heartbeat packets.
18851 @item target sim @r{[}@var{simargs}@r{]} @dots{}
18852 The @value{GDBN} ARM simulator accepts the following optional arguments.
18855 @item --swi-support=@var{type}
18856 Tell the simulator which SWI interfaces to support.
18857 @var{type} may be a comma separated list of the following values.
18858 The default value is @code{all}.
18871 @subsection Renesas M32R/D and M32R/SDI
18874 @kindex target m32r
18875 @item target m32r @var{dev}
18876 Renesas M32R/D ROM monitor.
18878 @kindex target m32rsdi
18879 @item target m32rsdi @var{dev}
18880 Renesas M32R SDI server, connected via parallel port to the board.
18883 The following @value{GDBN} commands are specific to the M32R monitor:
18886 @item set download-path @var{path}
18887 @kindex set download-path
18888 @cindex find downloadable @sc{srec} files (M32R)
18889 Set the default path for finding downloadable @sc{srec} files.
18891 @item show download-path
18892 @kindex show download-path
18893 Show the default path for downloadable @sc{srec} files.
18895 @item set board-address @var{addr}
18896 @kindex set board-address
18897 @cindex M32-EVA target board address
18898 Set the IP address for the M32R-EVA target board.
18900 @item show board-address
18901 @kindex show board-address
18902 Show the current IP address of the target board.
18904 @item set server-address @var{addr}
18905 @kindex set server-address
18906 @cindex download server address (M32R)
18907 Set the IP address for the download server, which is the @value{GDBN}'s
18910 @item show server-address
18911 @kindex show server-address
18912 Display the IP address of the download server.
18914 @item upload @r{[}@var{file}@r{]}
18915 @kindex upload@r{, M32R}
18916 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
18917 upload capability. If no @var{file} argument is given, the current
18918 executable file is uploaded.
18920 @item tload @r{[}@var{file}@r{]}
18921 @kindex tload@r{, M32R}
18922 Test the @code{upload} command.
18925 The following commands are available for M32R/SDI:
18930 @cindex reset SDI connection, M32R
18931 This command resets the SDI connection.
18935 This command shows the SDI connection status.
18938 @kindex debug_chaos
18939 @cindex M32R/Chaos debugging
18940 Instructs the remote that M32R/Chaos debugging is to be used.
18942 @item use_debug_dma
18943 @kindex use_debug_dma
18944 Instructs the remote to use the DEBUG_DMA method of accessing memory.
18947 @kindex use_mon_code
18948 Instructs the remote to use the MON_CODE method of accessing memory.
18951 @kindex use_ib_break
18952 Instructs the remote to set breakpoints by IB break.
18954 @item use_dbt_break
18955 @kindex use_dbt_break
18956 Instructs the remote to set breakpoints by DBT.
18962 The Motorola m68k configuration includes ColdFire support, and a
18963 target command for the following ROM monitor.
18967 @kindex target dbug
18968 @item target dbug @var{dev}
18969 dBUG ROM monitor for Motorola ColdFire.
18974 @subsection MicroBlaze
18975 @cindex Xilinx MicroBlaze
18976 @cindex XMD, Xilinx Microprocessor Debugger
18978 The MicroBlaze is a soft-core processor supported on various Xilinx
18979 FPGAs, such as Spartan or Virtex series. Boards with these processors
18980 usually have JTAG ports which connect to a host system running the Xilinx
18981 Embedded Development Kit (EDK) or Software Development Kit (SDK).
18982 This host system is used to download the configuration bitstream to
18983 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
18984 communicates with the target board using the JTAG interface and
18985 presents a @code{gdbserver} interface to the board. By default
18986 @code{xmd} uses port @code{1234}. (While it is possible to change
18987 this default port, it requires the use of undocumented @code{xmd}
18988 commands. Contact Xilinx support if you need to do this.)
18990 Use these GDB commands to connect to the MicroBlaze target processor.
18993 @item target remote :1234
18994 Use this command to connect to the target if you are running @value{GDBN}
18995 on the same system as @code{xmd}.
18997 @item target remote @var{xmd-host}:1234
18998 Use this command to connect to the target if it is connected to @code{xmd}
18999 running on a different system named @var{xmd-host}.
19002 Use this command to download a program to the MicroBlaze target.
19004 @item set debug microblaze @var{n}
19005 Enable MicroBlaze-specific debugging messages if non-zero.
19007 @item show debug microblaze @var{n}
19008 Show MicroBlaze-specific debugging level.
19011 @node MIPS Embedded
19012 @subsection MIPS Embedded
19014 @cindex MIPS boards
19015 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
19016 MIPS board attached to a serial line. This is available when
19017 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
19020 Use these @value{GDBN} commands to specify the connection to your target board:
19023 @item target mips @var{port}
19024 @kindex target mips @var{port}
19025 To run a program on the board, start up @code{@value{GDBP}} with the
19026 name of your program as the argument. To connect to the board, use the
19027 command @samp{target mips @var{port}}, where @var{port} is the name of
19028 the serial port connected to the board. If the program has not already
19029 been downloaded to the board, you may use the @code{load} command to
19030 download it. You can then use all the usual @value{GDBN} commands.
19032 For example, this sequence connects to the target board through a serial
19033 port, and loads and runs a program called @var{prog} through the
19037 host$ @value{GDBP} @var{prog}
19038 @value{GDBN} is free software and @dots{}
19039 (@value{GDBP}) target mips /dev/ttyb
19040 (@value{GDBP}) load @var{prog}
19044 @item target mips @var{hostname}:@var{portnumber}
19045 On some @value{GDBN} host configurations, you can specify a TCP
19046 connection (for instance, to a serial line managed by a terminal
19047 concentrator) instead of a serial port, using the syntax
19048 @samp{@var{hostname}:@var{portnumber}}.
19050 @item target pmon @var{port}
19051 @kindex target pmon @var{port}
19054 @item target ddb @var{port}
19055 @kindex target ddb @var{port}
19056 NEC's DDB variant of PMON for Vr4300.
19058 @item target lsi @var{port}
19059 @kindex target lsi @var{port}
19060 LSI variant of PMON.
19062 @kindex target r3900
19063 @item target r3900 @var{dev}
19064 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
19066 @kindex target array
19067 @item target array @var{dev}
19068 Array Tech LSI33K RAID controller board.
19074 @value{GDBN} also supports these special commands for MIPS targets:
19077 @item set mipsfpu double
19078 @itemx set mipsfpu single
19079 @itemx set mipsfpu none
19080 @itemx set mipsfpu auto
19081 @itemx show mipsfpu
19082 @kindex set mipsfpu
19083 @kindex show mipsfpu
19084 @cindex MIPS remote floating point
19085 @cindex floating point, MIPS remote
19086 If your target board does not support the MIPS floating point
19087 coprocessor, you should use the command @samp{set mipsfpu none} (if you
19088 need this, you may wish to put the command in your @value{GDBN} init
19089 file). This tells @value{GDBN} how to find the return value of
19090 functions which return floating point values. It also allows
19091 @value{GDBN} to avoid saving the floating point registers when calling
19092 functions on the board. If you are using a floating point coprocessor
19093 with only single precision floating point support, as on the @sc{r4650}
19094 processor, use the command @samp{set mipsfpu single}. The default
19095 double precision floating point coprocessor may be selected using
19096 @samp{set mipsfpu double}.
19098 In previous versions the only choices were double precision or no
19099 floating point, so @samp{set mipsfpu on} will select double precision
19100 and @samp{set mipsfpu off} will select no floating point.
19102 As usual, you can inquire about the @code{mipsfpu} variable with
19103 @samp{show mipsfpu}.
19105 @item set timeout @var{seconds}
19106 @itemx set retransmit-timeout @var{seconds}
19107 @itemx show timeout
19108 @itemx show retransmit-timeout
19109 @cindex @code{timeout}, MIPS protocol
19110 @cindex @code{retransmit-timeout}, MIPS protocol
19111 @kindex set timeout
19112 @kindex show timeout
19113 @kindex set retransmit-timeout
19114 @kindex show retransmit-timeout
19115 You can control the timeout used while waiting for a packet, in the MIPS
19116 remote protocol, with the @code{set timeout @var{seconds}} command. The
19117 default is 5 seconds. Similarly, you can control the timeout used while
19118 waiting for an acknowledgment of a packet with the @code{set
19119 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
19120 You can inspect both values with @code{show timeout} and @code{show
19121 retransmit-timeout}. (These commands are @emph{only} available when
19122 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
19124 The timeout set by @code{set timeout} does not apply when @value{GDBN}
19125 is waiting for your program to stop. In that case, @value{GDBN} waits
19126 forever because it has no way of knowing how long the program is going
19127 to run before stopping.
19129 @item set syn-garbage-limit @var{num}
19130 @kindex set syn-garbage-limit@r{, MIPS remote}
19131 @cindex synchronize with remote MIPS target
19132 Limit the maximum number of characters @value{GDBN} should ignore when
19133 it tries to synchronize with the remote target. The default is 10
19134 characters. Setting the limit to -1 means there's no limit.
19136 @item show syn-garbage-limit
19137 @kindex show syn-garbage-limit@r{, MIPS remote}
19138 Show the current limit on the number of characters to ignore when
19139 trying to synchronize with the remote system.
19141 @item set monitor-prompt @var{prompt}
19142 @kindex set monitor-prompt@r{, MIPS remote}
19143 @cindex remote monitor prompt
19144 Tell @value{GDBN} to expect the specified @var{prompt} string from the
19145 remote monitor. The default depends on the target:
19155 @item show monitor-prompt
19156 @kindex show monitor-prompt@r{, MIPS remote}
19157 Show the current strings @value{GDBN} expects as the prompt from the
19160 @item set monitor-warnings
19161 @kindex set monitor-warnings@r{, MIPS remote}
19162 Enable or disable monitor warnings about hardware breakpoints. This
19163 has effect only for the @code{lsi} target. When on, @value{GDBN} will
19164 display warning messages whose codes are returned by the @code{lsi}
19165 PMON monitor for breakpoint commands.
19167 @item show monitor-warnings
19168 @kindex show monitor-warnings@r{, MIPS remote}
19169 Show the current setting of printing monitor warnings.
19171 @item pmon @var{command}
19172 @kindex pmon@r{, MIPS remote}
19173 @cindex send PMON command
19174 This command allows sending an arbitrary @var{command} string to the
19175 monitor. The monitor must be in debug mode for this to work.
19178 @node OpenRISC 1000
19179 @subsection OpenRISC 1000
19180 @cindex OpenRISC 1000
19182 @cindex or1k boards
19183 See OR1k Architecture document (@uref{www.opencores.org}) for more information
19184 about platform and commands.
19188 @kindex target jtag
19189 @item target jtag jtag://@var{host}:@var{port}
19191 Connects to remote JTAG server.
19192 JTAG remote server can be either an or1ksim or JTAG server,
19193 connected via parallel port to the board.
19195 Example: @code{target jtag jtag://localhost:9999}
19198 @item or1ksim @var{command}
19199 If connected to @code{or1ksim} OpenRISC 1000 Architectural
19200 Simulator, proprietary commands can be executed.
19202 @kindex info or1k spr
19203 @item info or1k spr
19204 Displays spr groups.
19206 @item info or1k spr @var{group}
19207 @itemx info or1k spr @var{groupno}
19208 Displays register names in selected group.
19210 @item info or1k spr @var{group} @var{register}
19211 @itemx info or1k spr @var{register}
19212 @itemx info or1k spr @var{groupno} @var{registerno}
19213 @itemx info or1k spr @var{registerno}
19214 Shows information about specified spr register.
19217 @item spr @var{group} @var{register} @var{value}
19218 @itemx spr @var{register @var{value}}
19219 @itemx spr @var{groupno} @var{registerno @var{value}}
19220 @itemx spr @var{registerno @var{value}}
19221 Writes @var{value} to specified spr register.
19224 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
19225 It is very similar to @value{GDBN} trace, except it does not interfere with normal
19226 program execution and is thus much faster. Hardware breakpoints/watchpoint
19227 triggers can be set using:
19230 Load effective address/data
19232 Store effective address/data
19234 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
19239 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
19240 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
19242 @code{htrace} commands:
19243 @cindex OpenRISC 1000 htrace
19246 @item hwatch @var{conditional}
19247 Set hardware watchpoint on combination of Load/Store Effective Address(es)
19248 or Data. For example:
19250 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
19252 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
19256 Display information about current HW trace configuration.
19258 @item htrace trigger @var{conditional}
19259 Set starting criteria for HW trace.
19261 @item htrace qualifier @var{conditional}
19262 Set acquisition qualifier for HW trace.
19264 @item htrace stop @var{conditional}
19265 Set HW trace stopping criteria.
19267 @item htrace record [@var{data}]*
19268 Selects the data to be recorded, when qualifier is met and HW trace was
19271 @item htrace enable
19272 @itemx htrace disable
19273 Enables/disables the HW trace.
19275 @item htrace rewind [@var{filename}]
19276 Clears currently recorded trace data.
19278 If filename is specified, new trace file is made and any newly collected data
19279 will be written there.
19281 @item htrace print [@var{start} [@var{len}]]
19282 Prints trace buffer, using current record configuration.
19284 @item htrace mode continuous
19285 Set continuous trace mode.
19287 @item htrace mode suspend
19288 Set suspend trace mode.
19292 @node PowerPC Embedded
19293 @subsection PowerPC Embedded
19295 @cindex DVC register
19296 @value{GDBN} supports using the DVC (Data Value Compare) register to
19297 implement in hardware simple hardware watchpoint conditions of the form:
19300 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
19301 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
19304 The DVC register will be automatically used when @value{GDBN} detects
19305 such pattern in a condition expression, and the created watchpoint uses one
19306 debug register (either the @code{exact-watchpoints} option is on and the
19307 variable is scalar, or the variable has a length of one byte). This feature
19308 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
19311 When running on PowerPC embedded processors, @value{GDBN} automatically uses
19312 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
19313 in which case watchpoints using only one debug register are created when
19314 watching variables of scalar types.
19316 You can create an artificial array to watch an arbitrary memory
19317 region using one of the following commands (@pxref{Expressions}):
19320 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
19321 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
19324 PowerPC embedded processors support masked watchpoints. See the discussion
19325 about the @code{mask} argument in @ref{Set Watchpoints}.
19327 @cindex ranged breakpoint
19328 PowerPC embedded processors support hardware accelerated
19329 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
19330 the inferior whenever it executes an instruction at any address within
19331 the range it specifies. To set a ranged breakpoint in @value{GDBN},
19332 use the @code{break-range} command.
19334 @value{GDBN} provides the following PowerPC-specific commands:
19337 @kindex break-range
19338 @item break-range @var{start-location}, @var{end-location}
19339 Set a breakpoint for an address range.
19340 @var{start-location} and @var{end-location} can specify a function name,
19341 a line number, an offset of lines from the current line or from the start
19342 location, or an address of an instruction (see @ref{Specify Location},
19343 for a list of all the possible ways to specify a @var{location}.)
19344 The breakpoint will stop execution of the inferior whenever it
19345 executes an instruction at any address within the specified range,
19346 (including @var{start-location} and @var{end-location}.)
19348 @kindex set powerpc
19349 @item set powerpc soft-float
19350 @itemx show powerpc soft-float
19351 Force @value{GDBN} to use (or not use) a software floating point calling
19352 convention. By default, @value{GDBN} selects the calling convention based
19353 on the selected architecture and the provided executable file.
19355 @item set powerpc vector-abi
19356 @itemx show powerpc vector-abi
19357 Force @value{GDBN} to use the specified calling convention for vector
19358 arguments and return values. The valid options are @samp{auto};
19359 @samp{generic}, to avoid vector registers even if they are present;
19360 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
19361 registers. By default, @value{GDBN} selects the calling convention
19362 based on the selected architecture and the provided executable file.
19364 @item set powerpc exact-watchpoints
19365 @itemx show powerpc exact-watchpoints
19366 Allow @value{GDBN} to use only one debug register when watching a variable
19367 of scalar type, thus assuming that the variable is accessed through the
19368 address of its first byte.
19370 @kindex target dink32
19371 @item target dink32 @var{dev}
19372 DINK32 ROM monitor.
19374 @kindex target ppcbug
19375 @item target ppcbug @var{dev}
19376 @kindex target ppcbug1
19377 @item target ppcbug1 @var{dev}
19378 PPCBUG ROM monitor for PowerPC.
19381 @item target sds @var{dev}
19382 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
19385 @cindex SDS protocol
19386 The following commands specific to the SDS protocol are supported
19390 @item set sdstimeout @var{nsec}
19391 @kindex set sdstimeout
19392 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
19393 default is 2 seconds.
19395 @item show sdstimeout
19396 @kindex show sdstimeout
19397 Show the current value of the SDS timeout.
19399 @item sds @var{command}
19400 @kindex sds@r{, a command}
19401 Send the specified @var{command} string to the SDS monitor.
19406 @subsection HP PA Embedded
19410 @kindex target op50n
19411 @item target op50n @var{dev}
19412 OP50N monitor, running on an OKI HPPA board.
19414 @kindex target w89k
19415 @item target w89k @var{dev}
19416 W89K monitor, running on a Winbond HPPA board.
19421 @subsection Tsqware Sparclet
19425 @value{GDBN} enables developers to debug tasks running on
19426 Sparclet targets from a Unix host.
19427 @value{GDBN} uses code that runs on
19428 both the Unix host and on the Sparclet target. The program
19429 @code{@value{GDBP}} is installed and executed on the Unix host.
19432 @item remotetimeout @var{args}
19433 @kindex remotetimeout
19434 @value{GDBN} supports the option @code{remotetimeout}.
19435 This option is set by the user, and @var{args} represents the number of
19436 seconds @value{GDBN} waits for responses.
19439 @cindex compiling, on Sparclet
19440 When compiling for debugging, include the options @samp{-g} to get debug
19441 information and @samp{-Ttext} to relocate the program to where you wish to
19442 load it on the target. You may also want to add the options @samp{-n} or
19443 @samp{-N} in order to reduce the size of the sections. Example:
19446 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
19449 You can use @code{objdump} to verify that the addresses are what you intended:
19452 sparclet-aout-objdump --headers --syms prog
19455 @cindex running, on Sparclet
19457 your Unix execution search path to find @value{GDBN}, you are ready to
19458 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
19459 (or @code{sparclet-aout-gdb}, depending on your installation).
19461 @value{GDBN} comes up showing the prompt:
19468 * Sparclet File:: Setting the file to debug
19469 * Sparclet Connection:: Connecting to Sparclet
19470 * Sparclet Download:: Sparclet download
19471 * Sparclet Execution:: Running and debugging
19474 @node Sparclet File
19475 @subsubsection Setting File to Debug
19477 The @value{GDBN} command @code{file} lets you choose with program to debug.
19480 (gdbslet) file prog
19484 @value{GDBN} then attempts to read the symbol table of @file{prog}.
19485 @value{GDBN} locates
19486 the file by searching the directories listed in the command search
19488 If the file was compiled with debug information (option @samp{-g}), source
19489 files will be searched as well.
19490 @value{GDBN} locates
19491 the source files by searching the directories listed in the directory search
19492 path (@pxref{Environment, ,Your Program's Environment}).
19494 to find a file, it displays a message such as:
19497 prog: No such file or directory.
19500 When this happens, add the appropriate directories to the search paths with
19501 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
19502 @code{target} command again.
19504 @node Sparclet Connection
19505 @subsubsection Connecting to Sparclet
19507 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
19508 To connect to a target on serial port ``@code{ttya}'', type:
19511 (gdbslet) target sparclet /dev/ttya
19512 Remote target sparclet connected to /dev/ttya
19513 main () at ../prog.c:3
19517 @value{GDBN} displays messages like these:
19523 @node Sparclet Download
19524 @subsubsection Sparclet Download
19526 @cindex download to Sparclet
19527 Once connected to the Sparclet target,
19528 you can use the @value{GDBN}
19529 @code{load} command to download the file from the host to the target.
19530 The file name and load offset should be given as arguments to the @code{load}
19532 Since the file format is aout, the program must be loaded to the starting
19533 address. You can use @code{objdump} to find out what this value is. The load
19534 offset is an offset which is added to the VMA (virtual memory address)
19535 of each of the file's sections.
19536 For instance, if the program
19537 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
19538 and bss at 0x12010170, in @value{GDBN}, type:
19541 (gdbslet) load prog 0x12010000
19542 Loading section .text, size 0xdb0 vma 0x12010000
19545 If the code is loaded at a different address then what the program was linked
19546 to, you may need to use the @code{section} and @code{add-symbol-file} commands
19547 to tell @value{GDBN} where to map the symbol table.
19549 @node Sparclet Execution
19550 @subsubsection Running and Debugging
19552 @cindex running and debugging Sparclet programs
19553 You can now begin debugging the task using @value{GDBN}'s execution control
19554 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
19555 manual for the list of commands.
19559 Breakpoint 1 at 0x12010000: file prog.c, line 3.
19561 Starting program: prog
19562 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
19563 3 char *symarg = 0;
19565 4 char *execarg = "hello!";
19570 @subsection Fujitsu Sparclite
19574 @kindex target sparclite
19575 @item target sparclite @var{dev}
19576 Fujitsu sparclite boards, used only for the purpose of loading.
19577 You must use an additional command to debug the program.
19578 For example: target remote @var{dev} using @value{GDBN} standard
19584 @subsection Zilog Z8000
19587 @cindex simulator, Z8000
19588 @cindex Zilog Z8000 simulator
19590 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
19593 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
19594 unsegmented variant of the Z8000 architecture) or the Z8001 (the
19595 segmented variant). The simulator recognizes which architecture is
19596 appropriate by inspecting the object code.
19599 @item target sim @var{args}
19601 @kindex target sim@r{, with Z8000}
19602 Debug programs on a simulated CPU. If the simulator supports setup
19603 options, specify them via @var{args}.
19607 After specifying this target, you can debug programs for the simulated
19608 CPU in the same style as programs for your host computer; use the
19609 @code{file} command to load a new program image, the @code{run} command
19610 to run your program, and so on.
19612 As well as making available all the usual machine registers
19613 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
19614 additional items of information as specially named registers:
19619 Counts clock-ticks in the simulator.
19622 Counts instructions run in the simulator.
19625 Execution time in 60ths of a second.
19629 You can refer to these values in @value{GDBN} expressions with the usual
19630 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
19631 conditional breakpoint that suspends only after at least 5000
19632 simulated clock ticks.
19635 @subsection Atmel AVR
19638 When configured for debugging the Atmel AVR, @value{GDBN} supports the
19639 following AVR-specific commands:
19642 @item info io_registers
19643 @kindex info io_registers@r{, AVR}
19644 @cindex I/O registers (Atmel AVR)
19645 This command displays information about the AVR I/O registers. For
19646 each register, @value{GDBN} prints its number and value.
19653 When configured for debugging CRIS, @value{GDBN} provides the
19654 following CRIS-specific commands:
19657 @item set cris-version @var{ver}
19658 @cindex CRIS version
19659 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
19660 The CRIS version affects register names and sizes. This command is useful in
19661 case autodetection of the CRIS version fails.
19663 @item show cris-version
19664 Show the current CRIS version.
19666 @item set cris-dwarf2-cfi
19667 @cindex DWARF-2 CFI and CRIS
19668 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
19669 Change to @samp{off} when using @code{gcc-cris} whose version is below
19672 @item show cris-dwarf2-cfi
19673 Show the current state of using DWARF-2 CFI.
19675 @item set cris-mode @var{mode}
19677 Set the current CRIS mode to @var{mode}. It should only be changed when
19678 debugging in guru mode, in which case it should be set to
19679 @samp{guru} (the default is @samp{normal}).
19681 @item show cris-mode
19682 Show the current CRIS mode.
19686 @subsection Renesas Super-H
19689 For the Renesas Super-H processor, @value{GDBN} provides these
19694 @kindex regs@r{, Super-H}
19695 Show the values of all Super-H registers.
19697 @item set sh calling-convention @var{convention}
19698 @kindex set sh calling-convention
19699 Set the calling-convention used when calling functions from @value{GDBN}.
19700 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
19701 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
19702 convention. If the DWARF-2 information of the called function specifies
19703 that the function follows the Renesas calling convention, the function
19704 is called using the Renesas calling convention. If the calling convention
19705 is set to @samp{renesas}, the Renesas calling convention is always used,
19706 regardless of the DWARF-2 information. This can be used to override the
19707 default of @samp{gcc} if debug information is missing, or the compiler
19708 does not emit the DWARF-2 calling convention entry for a function.
19710 @item show sh calling-convention
19711 @kindex show sh calling-convention
19712 Show the current calling convention setting.
19717 @node Architectures
19718 @section Architectures
19720 This section describes characteristics of architectures that affect
19721 all uses of @value{GDBN} with the architecture, both native and cross.
19728 * HPPA:: HP PA architecture
19729 * SPU:: Cell Broadband Engine SPU architecture
19734 @subsection x86 Architecture-specific Issues
19737 @item set struct-convention @var{mode}
19738 @kindex set struct-convention
19739 @cindex struct return convention
19740 @cindex struct/union returned in registers
19741 Set the convention used by the inferior to return @code{struct}s and
19742 @code{union}s from functions to @var{mode}. Possible values of
19743 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
19744 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
19745 are returned on the stack, while @code{"reg"} means that a
19746 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
19747 be returned in a register.
19749 @item show struct-convention
19750 @kindex show struct-convention
19751 Show the current setting of the convention to return @code{struct}s
19760 @kindex set rstack_high_address
19761 @cindex AMD 29K register stack
19762 @cindex register stack, AMD29K
19763 @item set rstack_high_address @var{address}
19764 On AMD 29000 family processors, registers are saved in a separate
19765 @dfn{register stack}. There is no way for @value{GDBN} to determine the
19766 extent of this stack. Normally, @value{GDBN} just assumes that the
19767 stack is ``large enough''. This may result in @value{GDBN} referencing
19768 memory locations that do not exist. If necessary, you can get around
19769 this problem by specifying the ending address of the register stack with
19770 the @code{set rstack_high_address} command. The argument should be an
19771 address, which you probably want to precede with @samp{0x} to specify in
19774 @kindex show rstack_high_address
19775 @item show rstack_high_address
19776 Display the current limit of the register stack, on AMD 29000 family
19784 See the following section.
19789 @cindex stack on Alpha
19790 @cindex stack on MIPS
19791 @cindex Alpha stack
19793 Alpha- and MIPS-based computers use an unusual stack frame, which
19794 sometimes requires @value{GDBN} to search backward in the object code to
19795 find the beginning of a function.
19797 @cindex response time, MIPS debugging
19798 To improve response time (especially for embedded applications, where
19799 @value{GDBN} may be restricted to a slow serial line for this search)
19800 you may want to limit the size of this search, using one of these
19804 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
19805 @item set heuristic-fence-post @var{limit}
19806 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
19807 search for the beginning of a function. A value of @var{0} (the
19808 default) means there is no limit. However, except for @var{0}, the
19809 larger the limit the more bytes @code{heuristic-fence-post} must search
19810 and therefore the longer it takes to run. You should only need to use
19811 this command when debugging a stripped executable.
19813 @item show heuristic-fence-post
19814 Display the current limit.
19818 These commands are available @emph{only} when @value{GDBN} is configured
19819 for debugging programs on Alpha or MIPS processors.
19821 Several MIPS-specific commands are available when debugging MIPS
19825 @item set mips abi @var{arg}
19826 @kindex set mips abi
19827 @cindex set ABI for MIPS
19828 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
19829 values of @var{arg} are:
19833 The default ABI associated with the current binary (this is the
19844 @item show mips abi
19845 @kindex show mips abi
19846 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
19849 @itemx show mipsfpu
19850 @xref{MIPS Embedded, set mipsfpu}.
19852 @item set mips mask-address @var{arg}
19853 @kindex set mips mask-address
19854 @cindex MIPS addresses, masking
19855 This command determines whether the most-significant 32 bits of 64-bit
19856 MIPS addresses are masked off. The argument @var{arg} can be
19857 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
19858 setting, which lets @value{GDBN} determine the correct value.
19860 @item show mips mask-address
19861 @kindex show mips mask-address
19862 Show whether the upper 32 bits of MIPS addresses are masked off or
19865 @item set remote-mips64-transfers-32bit-regs
19866 @kindex set remote-mips64-transfers-32bit-regs
19867 This command controls compatibility with 64-bit MIPS targets that
19868 transfer data in 32-bit quantities. If you have an old MIPS 64 target
19869 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
19870 and 64 bits for other registers, set this option to @samp{on}.
19872 @item show remote-mips64-transfers-32bit-regs
19873 @kindex show remote-mips64-transfers-32bit-regs
19874 Show the current setting of compatibility with older MIPS 64 targets.
19876 @item set debug mips
19877 @kindex set debug mips
19878 This command turns on and off debugging messages for the MIPS-specific
19879 target code in @value{GDBN}.
19881 @item show debug mips
19882 @kindex show debug mips
19883 Show the current setting of MIPS debugging messages.
19889 @cindex HPPA support
19891 When @value{GDBN} is debugging the HP PA architecture, it provides the
19892 following special commands:
19895 @item set debug hppa
19896 @kindex set debug hppa
19897 This command determines whether HPPA architecture-specific debugging
19898 messages are to be displayed.
19900 @item show debug hppa
19901 Show whether HPPA debugging messages are displayed.
19903 @item maint print unwind @var{address}
19904 @kindex maint print unwind@r{, HPPA}
19905 This command displays the contents of the unwind table entry at the
19906 given @var{address}.
19912 @subsection Cell Broadband Engine SPU architecture
19913 @cindex Cell Broadband Engine
19916 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
19917 it provides the following special commands:
19920 @item info spu event
19922 Display SPU event facility status. Shows current event mask
19923 and pending event status.
19925 @item info spu signal
19926 Display SPU signal notification facility status. Shows pending
19927 signal-control word and signal notification mode of both signal
19928 notification channels.
19930 @item info spu mailbox
19931 Display SPU mailbox facility status. Shows all pending entries,
19932 in order of processing, in each of the SPU Write Outbound,
19933 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
19936 Display MFC DMA status. Shows all pending commands in the MFC
19937 DMA queue. For each entry, opcode, tag, class IDs, effective
19938 and local store addresses and transfer size are shown.
19940 @item info spu proxydma
19941 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
19942 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
19943 and local store addresses and transfer size are shown.
19947 When @value{GDBN} is debugging a combined PowerPC/SPU application
19948 on the Cell Broadband Engine, it provides in addition the following
19952 @item set spu stop-on-load @var{arg}
19954 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
19955 will give control to the user when a new SPE thread enters its @code{main}
19956 function. The default is @code{off}.
19958 @item show spu stop-on-load
19960 Show whether to stop for new SPE threads.
19962 @item set spu auto-flush-cache @var{arg}
19963 Set whether to automatically flush the software-managed cache. When set to
19964 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
19965 cache to be flushed whenever SPE execution stops. This provides a consistent
19966 view of PowerPC memory that is accessed via the cache. If an application
19967 does not use the software-managed cache, this option has no effect.
19969 @item show spu auto-flush-cache
19970 Show whether to automatically flush the software-managed cache.
19975 @subsection PowerPC
19976 @cindex PowerPC architecture
19978 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
19979 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
19980 numbers stored in the floating point registers. These values must be stored
19981 in two consecutive registers, always starting at an even register like
19982 @code{f0} or @code{f2}.
19984 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
19985 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
19986 @code{f2} and @code{f3} for @code{$dl1} and so on.
19988 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
19989 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
19992 @node Controlling GDB
19993 @chapter Controlling @value{GDBN}
19995 You can alter the way @value{GDBN} interacts with you by using the
19996 @code{set} command. For commands controlling how @value{GDBN} displays
19997 data, see @ref{Print Settings, ,Print Settings}. Other settings are
20002 * Editing:: Command editing
20003 * Command History:: Command history
20004 * Screen Size:: Screen size
20005 * Numbers:: Numbers
20006 * ABI:: Configuring the current ABI
20007 * Messages/Warnings:: Optional warnings and messages
20008 * Debugging Output:: Optional messages about internal happenings
20009 * Other Misc Settings:: Other Miscellaneous Settings
20017 @value{GDBN} indicates its readiness to read a command by printing a string
20018 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
20019 can change the prompt string with the @code{set prompt} command. For
20020 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
20021 the prompt in one of the @value{GDBN} sessions so that you can always tell
20022 which one you are talking to.
20024 @emph{Note:} @code{set prompt} does not add a space for you after the
20025 prompt you set. This allows you to set a prompt which ends in a space
20026 or a prompt that does not.
20030 @item set prompt @var{newprompt}
20031 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
20033 @kindex show prompt
20035 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
20038 Versions of @value{GDBN} that ship with Python scripting enabled have
20039 prompt extensions. The commands for interacting with these extensions
20043 @kindex set extended-prompt
20044 @item set extended-prompt @var{prompt}
20045 Set an extended prompt that allows for substitutions.
20046 @xref{gdb.prompt}, for a list of escape sequences that can be used for
20047 substitution. Any escape sequences specified as part of the prompt
20048 string are replaced with the corresponding strings each time the prompt
20054 set extended-prompt Current working directory: \w (gdb)
20057 Note that when an extended-prompt is set, it takes control of the
20058 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
20060 @kindex show extended-prompt
20061 @item show extended-prompt
20062 Prints the extended prompt. Any escape sequences specified as part of
20063 the prompt string with @code{set extended-prompt}, are replaced with the
20064 corresponding strings each time the prompt is displayed.
20068 @section Command Editing
20070 @cindex command line editing
20072 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
20073 @sc{gnu} library provides consistent behavior for programs which provide a
20074 command line interface to the user. Advantages are @sc{gnu} Emacs-style
20075 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
20076 substitution, and a storage and recall of command history across
20077 debugging sessions.
20079 You may control the behavior of command line editing in @value{GDBN} with the
20080 command @code{set}.
20083 @kindex set editing
20086 @itemx set editing on
20087 Enable command line editing (enabled by default).
20089 @item set editing off
20090 Disable command line editing.
20092 @kindex show editing
20094 Show whether command line editing is enabled.
20097 @ifset SYSTEM_READLINE
20098 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
20100 @ifclear SYSTEM_READLINE
20101 @xref{Command Line Editing},
20103 for more details about the Readline
20104 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
20105 encouraged to read that chapter.
20107 @node Command History
20108 @section Command History
20109 @cindex command history
20111 @value{GDBN} can keep track of the commands you type during your
20112 debugging sessions, so that you can be certain of precisely what
20113 happened. Use these commands to manage the @value{GDBN} command
20116 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
20117 package, to provide the history facility.
20118 @ifset SYSTEM_READLINE
20119 @xref{Using History Interactively, , , history, GNU History Library},
20121 @ifclear SYSTEM_READLINE
20122 @xref{Using History Interactively},
20124 for the detailed description of the History library.
20126 To issue a command to @value{GDBN} without affecting certain aspects of
20127 the state which is seen by users, prefix it with @samp{server }
20128 (@pxref{Server Prefix}). This
20129 means that this command will not affect the command history, nor will it
20130 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
20131 pressed on a line by itself.
20133 @cindex @code{server}, command prefix
20134 The server prefix does not affect the recording of values into the value
20135 history; to print a value without recording it into the value history,
20136 use the @code{output} command instead of the @code{print} command.
20138 Here is the description of @value{GDBN} commands related to command
20142 @cindex history substitution
20143 @cindex history file
20144 @kindex set history filename
20145 @cindex @env{GDBHISTFILE}, environment variable
20146 @item set history filename @var{fname}
20147 Set the name of the @value{GDBN} command history file to @var{fname}.
20148 This is the file where @value{GDBN} reads an initial command history
20149 list, and where it writes the command history from this session when it
20150 exits. You can access this list through history expansion or through
20151 the history command editing characters listed below. This file defaults
20152 to the value of the environment variable @code{GDBHISTFILE}, or to
20153 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
20156 @cindex save command history
20157 @kindex set history save
20158 @item set history save
20159 @itemx set history save on
20160 Record command history in a file, whose name may be specified with the
20161 @code{set history filename} command. By default, this option is disabled.
20163 @item set history save off
20164 Stop recording command history in a file.
20166 @cindex history size
20167 @kindex set history size
20168 @cindex @env{HISTSIZE}, environment variable
20169 @item set history size @var{size}
20170 Set the number of commands which @value{GDBN} keeps in its history list.
20171 This defaults to the value of the environment variable
20172 @code{HISTSIZE}, or to 256 if this variable is not set.
20175 History expansion assigns special meaning to the character @kbd{!}.
20176 @ifset SYSTEM_READLINE
20177 @xref{Event Designators, , , history, GNU History Library},
20179 @ifclear SYSTEM_READLINE
20180 @xref{Event Designators},
20184 @cindex history expansion, turn on/off
20185 Since @kbd{!} is also the logical not operator in C, history expansion
20186 is off by default. If you decide to enable history expansion with the
20187 @code{set history expansion on} command, you may sometimes need to
20188 follow @kbd{!} (when it is used as logical not, in an expression) with
20189 a space or a tab to prevent it from being expanded. The readline
20190 history facilities do not attempt substitution on the strings
20191 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
20193 The commands to control history expansion are:
20196 @item set history expansion on
20197 @itemx set history expansion
20198 @kindex set history expansion
20199 Enable history expansion. History expansion is off by default.
20201 @item set history expansion off
20202 Disable history expansion.
20205 @kindex show history
20207 @itemx show history filename
20208 @itemx show history save
20209 @itemx show history size
20210 @itemx show history expansion
20211 These commands display the state of the @value{GDBN} history parameters.
20212 @code{show history} by itself displays all four states.
20217 @kindex show commands
20218 @cindex show last commands
20219 @cindex display command history
20220 @item show commands
20221 Display the last ten commands in the command history.
20223 @item show commands @var{n}
20224 Print ten commands centered on command number @var{n}.
20226 @item show commands +
20227 Print ten commands just after the commands last printed.
20231 @section Screen Size
20232 @cindex size of screen
20233 @cindex pauses in output
20235 Certain commands to @value{GDBN} may produce large amounts of
20236 information output to the screen. To help you read all of it,
20237 @value{GDBN} pauses and asks you for input at the end of each page of
20238 output. Type @key{RET} when you want to continue the output, or @kbd{q}
20239 to discard the remaining output. Also, the screen width setting
20240 determines when to wrap lines of output. Depending on what is being
20241 printed, @value{GDBN} tries to break the line at a readable place,
20242 rather than simply letting it overflow onto the following line.
20244 Normally @value{GDBN} knows the size of the screen from the terminal
20245 driver software. For example, on Unix @value{GDBN} uses the termcap data base
20246 together with the value of the @code{TERM} environment variable and the
20247 @code{stty rows} and @code{stty cols} settings. If this is not correct,
20248 you can override it with the @code{set height} and @code{set
20255 @kindex show height
20256 @item set height @var{lpp}
20258 @itemx set width @var{cpl}
20260 These @code{set} commands specify a screen height of @var{lpp} lines and
20261 a screen width of @var{cpl} characters. The associated @code{show}
20262 commands display the current settings.
20264 If you specify a height of zero lines, @value{GDBN} does not pause during
20265 output no matter how long the output is. This is useful if output is to a
20266 file or to an editor buffer.
20268 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
20269 from wrapping its output.
20271 @item set pagination on
20272 @itemx set pagination off
20273 @kindex set pagination
20274 Turn the output pagination on or off; the default is on. Turning
20275 pagination off is the alternative to @code{set height 0}. Note that
20276 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
20277 Options, -batch}) also automatically disables pagination.
20279 @item show pagination
20280 @kindex show pagination
20281 Show the current pagination mode.
20286 @cindex number representation
20287 @cindex entering numbers
20289 You can always enter numbers in octal, decimal, or hexadecimal in
20290 @value{GDBN} by the usual conventions: octal numbers begin with
20291 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
20292 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
20293 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
20294 10; likewise, the default display for numbers---when no particular
20295 format is specified---is base 10. You can change the default base for
20296 both input and output with the commands described below.
20299 @kindex set input-radix
20300 @item set input-radix @var{base}
20301 Set the default base for numeric input. Supported choices
20302 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
20303 specified either unambiguously or using the current input radix; for
20307 set input-radix 012
20308 set input-radix 10.
20309 set input-radix 0xa
20313 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
20314 leaves the input radix unchanged, no matter what it was, since
20315 @samp{10}, being without any leading or trailing signs of its base, is
20316 interpreted in the current radix. Thus, if the current radix is 16,
20317 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
20320 @kindex set output-radix
20321 @item set output-radix @var{base}
20322 Set the default base for numeric display. Supported choices
20323 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
20324 specified either unambiguously or using the current input radix.
20326 @kindex show input-radix
20327 @item show input-radix
20328 Display the current default base for numeric input.
20330 @kindex show output-radix
20331 @item show output-radix
20332 Display the current default base for numeric display.
20334 @item set radix @r{[}@var{base}@r{]}
20338 These commands set and show the default base for both input and output
20339 of numbers. @code{set radix} sets the radix of input and output to
20340 the same base; without an argument, it resets the radix back to its
20341 default value of 10.
20346 @section Configuring the Current ABI
20348 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
20349 application automatically. However, sometimes you need to override its
20350 conclusions. Use these commands to manage @value{GDBN}'s view of the
20357 One @value{GDBN} configuration can debug binaries for multiple operating
20358 system targets, either via remote debugging or native emulation.
20359 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
20360 but you can override its conclusion using the @code{set osabi} command.
20361 One example where this is useful is in debugging of binaries which use
20362 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
20363 not have the same identifying marks that the standard C library for your
20368 Show the OS ABI currently in use.
20371 With no argument, show the list of registered available OS ABI's.
20373 @item set osabi @var{abi}
20374 Set the current OS ABI to @var{abi}.
20377 @cindex float promotion
20379 Generally, the way that an argument of type @code{float} is passed to a
20380 function depends on whether the function is prototyped. For a prototyped
20381 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
20382 according to the architecture's convention for @code{float}. For unprototyped
20383 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
20384 @code{double} and then passed.
20386 Unfortunately, some forms of debug information do not reliably indicate whether
20387 a function is prototyped. If @value{GDBN} calls a function that is not marked
20388 as prototyped, it consults @kbd{set coerce-float-to-double}.
20391 @kindex set coerce-float-to-double
20392 @item set coerce-float-to-double
20393 @itemx set coerce-float-to-double on
20394 Arguments of type @code{float} will be promoted to @code{double} when passed
20395 to an unprototyped function. This is the default setting.
20397 @item set coerce-float-to-double off
20398 Arguments of type @code{float} will be passed directly to unprototyped
20401 @kindex show coerce-float-to-double
20402 @item show coerce-float-to-double
20403 Show the current setting of promoting @code{float} to @code{double}.
20407 @kindex show cp-abi
20408 @value{GDBN} needs to know the ABI used for your program's C@t{++}
20409 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
20410 used to build your application. @value{GDBN} only fully supports
20411 programs with a single C@t{++} ABI; if your program contains code using
20412 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
20413 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
20414 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
20415 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
20416 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
20417 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
20422 Show the C@t{++} ABI currently in use.
20425 With no argument, show the list of supported C@t{++} ABI's.
20427 @item set cp-abi @var{abi}
20428 @itemx set cp-abi auto
20429 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
20432 @node Messages/Warnings
20433 @section Optional Warnings and Messages
20435 @cindex verbose operation
20436 @cindex optional warnings
20437 By default, @value{GDBN} is silent about its inner workings. If you are
20438 running on a slow machine, you may want to use the @code{set verbose}
20439 command. This makes @value{GDBN} tell you when it does a lengthy
20440 internal operation, so you will not think it has crashed.
20442 Currently, the messages controlled by @code{set verbose} are those
20443 which announce that the symbol table for a source file is being read;
20444 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
20447 @kindex set verbose
20448 @item set verbose on
20449 Enables @value{GDBN} output of certain informational messages.
20451 @item set verbose off
20452 Disables @value{GDBN} output of certain informational messages.
20454 @kindex show verbose
20456 Displays whether @code{set verbose} is on or off.
20459 By default, if @value{GDBN} encounters bugs in the symbol table of an
20460 object file, it is silent; but if you are debugging a compiler, you may
20461 find this information useful (@pxref{Symbol Errors, ,Errors Reading
20466 @kindex set complaints
20467 @item set complaints @var{limit}
20468 Permits @value{GDBN} to output @var{limit} complaints about each type of
20469 unusual symbols before becoming silent about the problem. Set
20470 @var{limit} to zero to suppress all complaints; set it to a large number
20471 to prevent complaints from being suppressed.
20473 @kindex show complaints
20474 @item show complaints
20475 Displays how many symbol complaints @value{GDBN} is permitted to produce.
20479 @anchor{confirmation requests}
20480 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
20481 lot of stupid questions to confirm certain commands. For example, if
20482 you try to run a program which is already running:
20486 The program being debugged has been started already.
20487 Start it from the beginning? (y or n)
20490 If you are willing to unflinchingly face the consequences of your own
20491 commands, you can disable this ``feature'':
20495 @kindex set confirm
20497 @cindex confirmation
20498 @cindex stupid questions
20499 @item set confirm off
20500 Disables confirmation requests. Note that running @value{GDBN} with
20501 the @option{--batch} option (@pxref{Mode Options, -batch}) also
20502 automatically disables confirmation requests.
20504 @item set confirm on
20505 Enables confirmation requests (the default).
20507 @kindex show confirm
20509 Displays state of confirmation requests.
20513 @cindex command tracing
20514 If you need to debug user-defined commands or sourced files you may find it
20515 useful to enable @dfn{command tracing}. In this mode each command will be
20516 printed as it is executed, prefixed with one or more @samp{+} symbols, the
20517 quantity denoting the call depth of each command.
20520 @kindex set trace-commands
20521 @cindex command scripts, debugging
20522 @item set trace-commands on
20523 Enable command tracing.
20524 @item set trace-commands off
20525 Disable command tracing.
20526 @item show trace-commands
20527 Display the current state of command tracing.
20530 @node Debugging Output
20531 @section Optional Messages about Internal Happenings
20532 @cindex optional debugging messages
20534 @value{GDBN} has commands that enable optional debugging messages from
20535 various @value{GDBN} subsystems; normally these commands are of
20536 interest to @value{GDBN} maintainers, or when reporting a bug. This
20537 section documents those commands.
20540 @kindex set exec-done-display
20541 @item set exec-done-display
20542 Turns on or off the notification of asynchronous commands'
20543 completion. When on, @value{GDBN} will print a message when an
20544 asynchronous command finishes its execution. The default is off.
20545 @kindex show exec-done-display
20546 @item show exec-done-display
20547 Displays the current setting of asynchronous command completion
20550 @cindex gdbarch debugging info
20551 @cindex architecture debugging info
20552 @item set debug arch
20553 Turns on or off display of gdbarch debugging info. The default is off
20555 @item show debug arch
20556 Displays the current state of displaying gdbarch debugging info.
20557 @item set debug aix-thread
20558 @cindex AIX threads
20559 Display debugging messages about inner workings of the AIX thread
20561 @item show debug aix-thread
20562 Show the current state of AIX thread debugging info display.
20563 @item set debug check-physname
20565 Check the results of the ``physname'' computation. When reading DWARF
20566 debugging information for C@t{++}, @value{GDBN} attempts to compute
20567 each entity's name. @value{GDBN} can do this computation in two
20568 different ways, depending on exactly what information is present.
20569 When enabled, this setting causes @value{GDBN} to compute the names
20570 both ways and display any discrepancies.
20571 @item show debug check-physname
20572 Show the current state of ``physname'' checking.
20573 @item set debug dwarf2-die
20574 @cindex DWARF2 DIEs
20575 Dump DWARF2 DIEs after they are read in.
20576 The value is the number of nesting levels to print.
20577 A value of zero turns off the display.
20578 @item show debug dwarf2-die
20579 Show the current state of DWARF2 DIE debugging.
20580 @item set debug displaced
20581 @cindex displaced stepping debugging info
20582 Turns on or off display of @value{GDBN} debugging info for the
20583 displaced stepping support. The default is off.
20584 @item show debug displaced
20585 Displays the current state of displaying @value{GDBN} debugging info
20586 related to displaced stepping.
20587 @item set debug event
20588 @cindex event debugging info
20589 Turns on or off display of @value{GDBN} event debugging info. The
20591 @item show debug event
20592 Displays the current state of displaying @value{GDBN} event debugging
20594 @item set debug expression
20595 @cindex expression debugging info
20596 Turns on or off display of debugging info about @value{GDBN}
20597 expression parsing. The default is off.
20598 @item show debug expression
20599 Displays the current state of displaying debugging info about
20600 @value{GDBN} expression parsing.
20601 @item set debug frame
20602 @cindex frame debugging info
20603 Turns on or off display of @value{GDBN} frame debugging info. The
20605 @item show debug frame
20606 Displays the current state of displaying @value{GDBN} frame debugging
20608 @item set debug gnu-nat
20609 @cindex @sc{gnu}/Hurd debug messages
20610 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
20611 @item show debug gnu-nat
20612 Show the current state of @sc{gnu}/Hurd debugging messages.
20613 @item set debug infrun
20614 @cindex inferior debugging info
20615 Turns on or off display of @value{GDBN} debugging info for running the inferior.
20616 The default is off. @file{infrun.c} contains GDB's runtime state machine used
20617 for implementing operations such as single-stepping the inferior.
20618 @item show debug infrun
20619 Displays the current state of @value{GDBN} inferior debugging.
20620 @item set debug jit
20621 @cindex just-in-time compilation, debugging messages
20622 Turns on or off debugging messages from JIT debug support.
20623 @item show debug jit
20624 Displays the current state of @value{GDBN} JIT debugging.
20625 @item set debug lin-lwp
20626 @cindex @sc{gnu}/Linux LWP debug messages
20627 @cindex Linux lightweight processes
20628 Turns on or off debugging messages from the Linux LWP debug support.
20629 @item show debug lin-lwp
20630 Show the current state of Linux LWP debugging messages.
20631 @item set debug observer
20632 @cindex observer debugging info
20633 Turns on or off display of @value{GDBN} observer debugging. This
20634 includes info such as the notification of observable events.
20635 @item show debug observer
20636 Displays the current state of observer debugging.
20637 @item set debug overload
20638 @cindex C@t{++} overload debugging info
20639 Turns on or off display of @value{GDBN} C@t{++} overload debugging
20640 info. This includes info such as ranking of functions, etc. The default
20642 @item show debug overload
20643 Displays the current state of displaying @value{GDBN} C@t{++} overload
20645 @cindex expression parser, debugging info
20646 @cindex debug expression parser
20647 @item set debug parser
20648 Turns on or off the display of expression parser debugging output.
20649 Internally, this sets the @code{yydebug} variable in the expression
20650 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
20651 details. The default is off.
20652 @item show debug parser
20653 Show the current state of expression parser debugging.
20654 @cindex packets, reporting on stdout
20655 @cindex serial connections, debugging
20656 @cindex debug remote protocol
20657 @cindex remote protocol debugging
20658 @cindex display remote packets
20659 @item set debug remote
20660 Turns on or off display of reports on all packets sent back and forth across
20661 the serial line to the remote machine. The info is printed on the
20662 @value{GDBN} standard output stream. The default is off.
20663 @item show debug remote
20664 Displays the state of display of remote packets.
20665 @item set debug serial
20666 Turns on or off display of @value{GDBN} serial debugging info. The
20668 @item show debug serial
20669 Displays the current state of displaying @value{GDBN} serial debugging
20671 @item set debug solib-frv
20672 @cindex FR-V shared-library debugging
20673 Turns on or off debugging messages for FR-V shared-library code.
20674 @item show debug solib-frv
20675 Display the current state of FR-V shared-library code debugging
20677 @item set debug target
20678 @cindex target debugging info
20679 Turns on or off display of @value{GDBN} target debugging info. This info
20680 includes what is going on at the target level of GDB, as it happens. The
20681 default is 0. Set it to 1 to track events, and to 2 to also track the
20682 value of large memory transfers. Changes to this flag do not take effect
20683 until the next time you connect to a target or use the @code{run} command.
20684 @item show debug target
20685 Displays the current state of displaying @value{GDBN} target debugging
20687 @item set debug timestamp
20688 @cindex timestampping debugging info
20689 Turns on or off display of timestamps with @value{GDBN} debugging info.
20690 When enabled, seconds and microseconds are displayed before each debugging
20692 @item show debug timestamp
20693 Displays the current state of displaying timestamps with @value{GDBN}
20695 @item set debugvarobj
20696 @cindex variable object debugging info
20697 Turns on or off display of @value{GDBN} variable object debugging
20698 info. The default is off.
20699 @item show debugvarobj
20700 Displays the current state of displaying @value{GDBN} variable object
20702 @item set debug xml
20703 @cindex XML parser debugging
20704 Turns on or off debugging messages for built-in XML parsers.
20705 @item show debug xml
20706 Displays the current state of XML debugging messages.
20709 @node Other Misc Settings
20710 @section Other Miscellaneous Settings
20711 @cindex miscellaneous settings
20714 @kindex set interactive-mode
20715 @item set interactive-mode
20716 If @code{on}, forces @value{GDBN} to assume that GDB was started
20717 in a terminal. In practice, this means that @value{GDBN} should wait
20718 for the user to answer queries generated by commands entered at
20719 the command prompt. If @code{off}, forces @value{GDBN} to operate
20720 in the opposite mode, and it uses the default answers to all queries.
20721 If @code{auto} (the default), @value{GDBN} tries to determine whether
20722 its standard input is a terminal, and works in interactive-mode if it
20723 is, non-interactively otherwise.
20725 In the vast majority of cases, the debugger should be able to guess
20726 correctly which mode should be used. But this setting can be useful
20727 in certain specific cases, such as running a MinGW @value{GDBN}
20728 inside a cygwin window.
20730 @kindex show interactive-mode
20731 @item show interactive-mode
20732 Displays whether the debugger is operating in interactive mode or not.
20735 @node Extending GDB
20736 @chapter Extending @value{GDBN}
20737 @cindex extending GDB
20739 @value{GDBN} provides three mechanisms for extension. The first is based
20740 on composition of @value{GDBN} commands, the second is based on the
20741 Python scripting language, and the third is for defining new aliases of
20744 To facilitate the use of the first two extensions, @value{GDBN} is capable
20745 of evaluating the contents of a file. When doing so, @value{GDBN}
20746 can recognize which scripting language is being used by looking at
20747 the filename extension. Files with an unrecognized filename extension
20748 are always treated as a @value{GDBN} Command Files.
20749 @xref{Command Files,, Command files}.
20751 You can control how @value{GDBN} evaluates these files with the following
20755 @kindex set script-extension
20756 @kindex show script-extension
20757 @item set script-extension off
20758 All scripts are always evaluated as @value{GDBN} Command Files.
20760 @item set script-extension soft
20761 The debugger determines the scripting language based on filename
20762 extension. If this scripting language is supported, @value{GDBN}
20763 evaluates the script using that language. Otherwise, it evaluates
20764 the file as a @value{GDBN} Command File.
20766 @item set script-extension strict
20767 The debugger determines the scripting language based on filename
20768 extension, and evaluates the script using that language. If the
20769 language is not supported, then the evaluation fails.
20771 @item show script-extension
20772 Display the current value of the @code{script-extension} option.
20777 * Sequences:: Canned Sequences of Commands
20778 * Python:: Scripting @value{GDBN} using Python
20779 * Aliases:: Creating new spellings of existing commands
20783 @section Canned Sequences of Commands
20785 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
20786 Command Lists}), @value{GDBN} provides two ways to store sequences of
20787 commands for execution as a unit: user-defined commands and command
20791 * Define:: How to define your own commands
20792 * Hooks:: Hooks for user-defined commands
20793 * Command Files:: How to write scripts of commands to be stored in a file
20794 * Output:: Commands for controlled output
20798 @subsection User-defined Commands
20800 @cindex user-defined command
20801 @cindex arguments, to user-defined commands
20802 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
20803 which you assign a new name as a command. This is done with the
20804 @code{define} command. User commands may accept up to 10 arguments
20805 separated by whitespace. Arguments are accessed within the user command
20806 via @code{$arg0@dots{}$arg9}. A trivial example:
20810 print $arg0 + $arg1 + $arg2
20815 To execute the command use:
20822 This defines the command @code{adder}, which prints the sum of
20823 its three arguments. Note the arguments are text substitutions, so they may
20824 reference variables, use complex expressions, or even perform inferior
20827 @cindex argument count in user-defined commands
20828 @cindex how many arguments (user-defined commands)
20829 In addition, @code{$argc} may be used to find out how many arguments have
20830 been passed. This expands to a number in the range 0@dots{}10.
20835 print $arg0 + $arg1
20838 print $arg0 + $arg1 + $arg2
20846 @item define @var{commandname}
20847 Define a command named @var{commandname}. If there is already a command
20848 by that name, you are asked to confirm that you want to redefine it.
20849 @var{commandname} may be a bare command name consisting of letters,
20850 numbers, dashes, and underscores. It may also start with any predefined
20851 prefix command. For example, @samp{define target my-target} creates
20852 a user-defined @samp{target my-target} command.
20854 The definition of the command is made up of other @value{GDBN} command lines,
20855 which are given following the @code{define} command. The end of these
20856 commands is marked by a line containing @code{end}.
20859 @kindex end@r{ (user-defined commands)}
20860 @item document @var{commandname}
20861 Document the user-defined command @var{commandname}, so that it can be
20862 accessed by @code{help}. The command @var{commandname} must already be
20863 defined. This command reads lines of documentation just as @code{define}
20864 reads the lines of the command definition, ending with @code{end}.
20865 After the @code{document} command is finished, @code{help} on command
20866 @var{commandname} displays the documentation you have written.
20868 You may use the @code{document} command again to change the
20869 documentation of a command. Redefining the command with @code{define}
20870 does not change the documentation.
20872 @kindex dont-repeat
20873 @cindex don't repeat command
20875 Used inside a user-defined command, this tells @value{GDBN} that this
20876 command should not be repeated when the user hits @key{RET}
20877 (@pxref{Command Syntax, repeat last command}).
20879 @kindex help user-defined
20880 @item help user-defined
20881 List all user-defined commands, with the first line of the documentation
20886 @itemx show user @var{commandname}
20887 Display the @value{GDBN} commands used to define @var{commandname} (but
20888 not its documentation). If no @var{commandname} is given, display the
20889 definitions for all user-defined commands.
20891 @cindex infinite recursion in user-defined commands
20892 @kindex show max-user-call-depth
20893 @kindex set max-user-call-depth
20894 @item show max-user-call-depth
20895 @itemx set max-user-call-depth
20896 The value of @code{max-user-call-depth} controls how many recursion
20897 levels are allowed in user-defined commands before @value{GDBN} suspects an
20898 infinite recursion and aborts the command.
20901 In addition to the above commands, user-defined commands frequently
20902 use control flow commands, described in @ref{Command Files}.
20904 When user-defined commands are executed, the
20905 commands of the definition are not printed. An error in any command
20906 stops execution of the user-defined command.
20908 If used interactively, commands that would ask for confirmation proceed
20909 without asking when used inside a user-defined command. Many @value{GDBN}
20910 commands that normally print messages to say what they are doing omit the
20911 messages when used in a user-defined command.
20914 @subsection User-defined Command Hooks
20915 @cindex command hooks
20916 @cindex hooks, for commands
20917 @cindex hooks, pre-command
20920 You may define @dfn{hooks}, which are a special kind of user-defined
20921 command. Whenever you run the command @samp{foo}, if the user-defined
20922 command @samp{hook-foo} exists, it is executed (with no arguments)
20923 before that command.
20925 @cindex hooks, post-command
20927 A hook may also be defined which is run after the command you executed.
20928 Whenever you run the command @samp{foo}, if the user-defined command
20929 @samp{hookpost-foo} exists, it is executed (with no arguments) after
20930 that command. Post-execution hooks may exist simultaneously with
20931 pre-execution hooks, for the same command.
20933 It is valid for a hook to call the command which it hooks. If this
20934 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
20936 @c It would be nice if hookpost could be passed a parameter indicating
20937 @c if the command it hooks executed properly or not. FIXME!
20939 @kindex stop@r{, a pseudo-command}
20940 In addition, a pseudo-command, @samp{stop} exists. Defining
20941 (@samp{hook-stop}) makes the associated commands execute every time
20942 execution stops in your program: before breakpoint commands are run,
20943 displays are printed, or the stack frame is printed.
20945 For example, to ignore @code{SIGALRM} signals while
20946 single-stepping, but treat them normally during normal execution,
20951 handle SIGALRM nopass
20955 handle SIGALRM pass
20958 define hook-continue
20959 handle SIGALRM pass
20963 As a further example, to hook at the beginning and end of the @code{echo}
20964 command, and to add extra text to the beginning and end of the message,
20972 define hookpost-echo
20976 (@value{GDBP}) echo Hello World
20977 <<<---Hello World--->>>
20982 You can define a hook for any single-word command in @value{GDBN}, but
20983 not for command aliases; you should define a hook for the basic command
20984 name, e.g.@: @code{backtrace} rather than @code{bt}.
20985 @c FIXME! So how does Joe User discover whether a command is an alias
20987 You can hook a multi-word command by adding @code{hook-} or
20988 @code{hookpost-} to the last word of the command, e.g.@:
20989 @samp{define target hook-remote} to add a hook to @samp{target remote}.
20991 If an error occurs during the execution of your hook, execution of
20992 @value{GDBN} commands stops and @value{GDBN} issues a prompt
20993 (before the command that you actually typed had a chance to run).
20995 If you try to define a hook which does not match any known command, you
20996 get a warning from the @code{define} command.
20998 @node Command Files
20999 @subsection Command Files
21001 @cindex command files
21002 @cindex scripting commands
21003 A command file for @value{GDBN} is a text file made of lines that are
21004 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
21005 also be included. An empty line in a command file does nothing; it
21006 does not mean to repeat the last command, as it would from the
21009 You can request the execution of a command file with the @code{source}
21010 command. Note that the @code{source} command is also used to evaluate
21011 scripts that are not Command Files. The exact behavior can be configured
21012 using the @code{script-extension} setting.
21013 @xref{Extending GDB,, Extending GDB}.
21017 @cindex execute commands from a file
21018 @item source [-s] [-v] @var{filename}
21019 Execute the command file @var{filename}.
21022 The lines in a command file are generally executed sequentially,
21023 unless the order of execution is changed by one of the
21024 @emph{flow-control commands} described below. The commands are not
21025 printed as they are executed. An error in any command terminates
21026 execution of the command file and control is returned to the console.
21028 @value{GDBN} first searches for @var{filename} in the current directory.
21029 If the file is not found there, and @var{filename} does not specify a
21030 directory, then @value{GDBN} also looks for the file on the source search path
21031 (specified with the @samp{directory} command);
21032 except that @file{$cdir} is not searched because the compilation directory
21033 is not relevant to scripts.
21035 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
21036 on the search path even if @var{filename} specifies a directory.
21037 The search is done by appending @var{filename} to each element of the
21038 search path. So, for example, if @var{filename} is @file{mylib/myscript}
21039 and the search path contains @file{/home/user} then @value{GDBN} will
21040 look for the script @file{/home/user/mylib/myscript}.
21041 The search is also done if @var{filename} is an absolute path.
21042 For example, if @var{filename} is @file{/tmp/myscript} and
21043 the search path contains @file{/home/user} then @value{GDBN} will
21044 look for the script @file{/home/user/tmp/myscript}.
21045 For DOS-like systems, if @var{filename} contains a drive specification,
21046 it is stripped before concatenation. For example, if @var{filename} is
21047 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
21048 will look for the script @file{c:/tmp/myscript}.
21050 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
21051 each command as it is executed. The option must be given before
21052 @var{filename}, and is interpreted as part of the filename anywhere else.
21054 Commands that would ask for confirmation if used interactively proceed
21055 without asking when used in a command file. Many @value{GDBN} commands that
21056 normally print messages to say what they are doing omit the messages
21057 when called from command files.
21059 @value{GDBN} also accepts command input from standard input. In this
21060 mode, normal output goes to standard output and error output goes to
21061 standard error. Errors in a command file supplied on standard input do
21062 not terminate execution of the command file---execution continues with
21066 gdb < cmds > log 2>&1
21069 (The syntax above will vary depending on the shell used.) This example
21070 will execute commands from the file @file{cmds}. All output and errors
21071 would be directed to @file{log}.
21073 Since commands stored on command files tend to be more general than
21074 commands typed interactively, they frequently need to deal with
21075 complicated situations, such as different or unexpected values of
21076 variables and symbols, changes in how the program being debugged is
21077 built, etc. @value{GDBN} provides a set of flow-control commands to
21078 deal with these complexities. Using these commands, you can write
21079 complex scripts that loop over data structures, execute commands
21080 conditionally, etc.
21087 This command allows to include in your script conditionally executed
21088 commands. The @code{if} command takes a single argument, which is an
21089 expression to evaluate. It is followed by a series of commands that
21090 are executed only if the expression is true (its value is nonzero).
21091 There can then optionally be an @code{else} line, followed by a series
21092 of commands that are only executed if the expression was false. The
21093 end of the list is marked by a line containing @code{end}.
21097 This command allows to write loops. Its syntax is similar to
21098 @code{if}: the command takes a single argument, which is an expression
21099 to evaluate, and must be followed by the commands to execute, one per
21100 line, terminated by an @code{end}. These commands are called the
21101 @dfn{body} of the loop. The commands in the body of @code{while} are
21102 executed repeatedly as long as the expression evaluates to true.
21106 This command exits the @code{while} loop in whose body it is included.
21107 Execution of the script continues after that @code{while}s @code{end}
21110 @kindex loop_continue
21111 @item loop_continue
21112 This command skips the execution of the rest of the body of commands
21113 in the @code{while} loop in whose body it is included. Execution
21114 branches to the beginning of the @code{while} loop, where it evaluates
21115 the controlling expression.
21117 @kindex end@r{ (if/else/while commands)}
21119 Terminate the block of commands that are the body of @code{if},
21120 @code{else}, or @code{while} flow-control commands.
21125 @subsection Commands for Controlled Output
21127 During the execution of a command file or a user-defined command, normal
21128 @value{GDBN} output is suppressed; the only output that appears is what is
21129 explicitly printed by the commands in the definition. This section
21130 describes three commands useful for generating exactly the output you
21135 @item echo @var{text}
21136 @c I do not consider backslash-space a standard C escape sequence
21137 @c because it is not in ANSI.
21138 Print @var{text}. Nonprinting characters can be included in
21139 @var{text} using C escape sequences, such as @samp{\n} to print a
21140 newline. @strong{No newline is printed unless you specify one.}
21141 In addition to the standard C escape sequences, a backslash followed
21142 by a space stands for a space. This is useful for displaying a
21143 string with spaces at the beginning or the end, since leading and
21144 trailing spaces are otherwise trimmed from all arguments.
21145 To print @samp{@w{ }and foo =@w{ }}, use the command
21146 @samp{echo \@w{ }and foo = \@w{ }}.
21148 A backslash at the end of @var{text} can be used, as in C, to continue
21149 the command onto subsequent lines. For example,
21152 echo This is some text\n\
21153 which is continued\n\
21154 onto several lines.\n
21157 produces the same output as
21160 echo This is some text\n
21161 echo which is continued\n
21162 echo onto several lines.\n
21166 @item output @var{expression}
21167 Print the value of @var{expression} and nothing but that value: no
21168 newlines, no @samp{$@var{nn} = }. The value is not entered in the
21169 value history either. @xref{Expressions, ,Expressions}, for more information
21172 @item output/@var{fmt} @var{expression}
21173 Print the value of @var{expression} in format @var{fmt}. You can use
21174 the same formats as for @code{print}. @xref{Output Formats,,Output
21175 Formats}, for more information.
21178 @item printf @var{template}, @var{expressions}@dots{}
21179 Print the values of one or more @var{expressions} under the control of
21180 the string @var{template}. To print several values, make
21181 @var{expressions} be a comma-separated list of individual expressions,
21182 which may be either numbers or pointers. Their values are printed as
21183 specified by @var{template}, exactly as a C program would do by
21184 executing the code below:
21187 printf (@var{template}, @var{expressions}@dots{});
21190 As in @code{C} @code{printf}, ordinary characters in @var{template}
21191 are printed verbatim, while @dfn{conversion specification} introduced
21192 by the @samp{%} character cause subsequent @var{expressions} to be
21193 evaluated, their values converted and formatted according to type and
21194 style information encoded in the conversion specifications, and then
21197 For example, you can print two values in hex like this:
21200 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
21203 @code{printf} supports all the standard @code{C} conversion
21204 specifications, including the flags and modifiers between the @samp{%}
21205 character and the conversion letter, with the following exceptions:
21209 The argument-ordering modifiers, such as @samp{2$}, are not supported.
21212 The modifier @samp{*} is not supported for specifying precision or
21216 The @samp{'} flag (for separation of digits into groups according to
21217 @code{LC_NUMERIC'}) is not supported.
21220 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
21224 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
21227 The conversion letters @samp{a} and @samp{A} are not supported.
21231 Note that the @samp{ll} type modifier is supported only if the
21232 underlying @code{C} implementation used to build @value{GDBN} supports
21233 the @code{long long int} type, and the @samp{L} type modifier is
21234 supported only if @code{long double} type is available.
21236 As in @code{C}, @code{printf} supports simple backslash-escape
21237 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
21238 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
21239 single character. Octal and hexadecimal escape sequences are not
21242 Additionally, @code{printf} supports conversion specifications for DFP
21243 (@dfn{Decimal Floating Point}) types using the following length modifiers
21244 together with a floating point specifier.
21249 @samp{H} for printing @code{Decimal32} types.
21252 @samp{D} for printing @code{Decimal64} types.
21255 @samp{DD} for printing @code{Decimal128} types.
21258 If the underlying @code{C} implementation used to build @value{GDBN} has
21259 support for the three length modifiers for DFP types, other modifiers
21260 such as width and precision will also be available for @value{GDBN} to use.
21262 In case there is no such @code{C} support, no additional modifiers will be
21263 available and the value will be printed in the standard way.
21265 Here's an example of printing DFP types using the above conversion letters:
21267 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
21271 @item eval @var{template}, @var{expressions}@dots{}
21272 Convert the values of one or more @var{expressions} under the control of
21273 the string @var{template} to a command line, and call it.
21278 @section Scripting @value{GDBN} using Python
21279 @cindex python scripting
21280 @cindex scripting with python
21282 You can script @value{GDBN} using the @uref{http://www.python.org/,
21283 Python programming language}. This feature is available only if
21284 @value{GDBN} was configured using @option{--with-python}.
21286 @cindex python directory
21287 Python scripts used by @value{GDBN} should be installed in
21288 @file{@var{data-directory}/python}, where @var{data-directory} is
21289 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
21290 This directory, known as the @dfn{python directory},
21291 is automatically added to the Python Search Path in order to allow
21292 the Python interpreter to locate all scripts installed at this location.
21294 Additionally, @value{GDBN} commands and convenience functions which
21295 are written in Python and are located in the
21296 @file{@var{data-directory}/python/gdb/command} or
21297 @file{@var{data-directory}/python/gdb/function} directories are
21298 automatically imported when @value{GDBN} starts.
21301 * Python Commands:: Accessing Python from @value{GDBN}.
21302 * Python API:: Accessing @value{GDBN} from Python.
21303 * Auto-loading:: Automatically loading Python code.
21304 * Python modules:: Python modules provided by @value{GDBN}.
21307 @node Python Commands
21308 @subsection Python Commands
21309 @cindex python commands
21310 @cindex commands to access python
21312 @value{GDBN} provides one command for accessing the Python interpreter,
21313 and one related setting:
21317 @item python @r{[}@var{code}@r{]}
21318 The @code{python} command can be used to evaluate Python code.
21320 If given an argument, the @code{python} command will evaluate the
21321 argument as a Python command. For example:
21324 (@value{GDBP}) python print 23
21328 If you do not provide an argument to @code{python}, it will act as a
21329 multi-line command, like @code{define}. In this case, the Python
21330 script is made up of subsequent command lines, given after the
21331 @code{python} command. This command list is terminated using a line
21332 containing @code{end}. For example:
21335 (@value{GDBP}) python
21337 End with a line saying just "end".
21343 @kindex maint set python print-stack
21344 @item maint set python print-stack
21345 This command is now deprecated. Instead use @code{set python
21348 @kindex set python print-stack
21349 @item set python print-stack
21350 By default, @value{GDBN} will not print a stack trace when an error
21351 occurs in a Python script. This can be controlled using @code{set
21352 python print-stack}: if @code{on}, then Python stack printing is
21353 enabled; if @code{off}, the default, then Python stack printing is
21357 It is also possible to execute a Python script from the @value{GDBN}
21361 @item source @file{script-name}
21362 The script name must end with @samp{.py} and @value{GDBN} must be configured
21363 to recognize the script language based on filename extension using
21364 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
21366 @item python execfile ("script-name")
21367 This method is based on the @code{execfile} Python built-in function,
21368 and thus is always available.
21372 @subsection Python API
21374 @cindex programming in python
21376 @cindex python stdout
21377 @cindex python pagination
21378 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
21379 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
21380 A Python program which outputs to one of these streams may have its
21381 output interrupted by the user (@pxref{Screen Size}). In this
21382 situation, a Python @code{KeyboardInterrupt} exception is thrown.
21385 * Basic Python:: Basic Python Functions.
21386 * Exception Handling:: How Python exceptions are translated.
21387 * Values From Inferior:: Python representation of values.
21388 * Types In Python:: Python representation of types.
21389 * Pretty Printing API:: Pretty-printing values.
21390 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
21391 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
21392 * Inferiors In Python:: Python representation of inferiors (processes)
21393 * Events In Python:: Listening for events from @value{GDBN}.
21394 * Threads In Python:: Accessing inferior threads from Python.
21395 * Commands In Python:: Implementing new commands in Python.
21396 * Parameters In Python:: Adding new @value{GDBN} parameters.
21397 * Functions In Python:: Writing new convenience functions.
21398 * Progspaces In Python:: Program spaces.
21399 * Objfiles In Python:: Object files.
21400 * Frames In Python:: Accessing inferior stack frames from Python.
21401 * Blocks In Python:: Accessing frame blocks from Python.
21402 * Symbols In Python:: Python representation of symbols.
21403 * Symbol Tables In Python:: Python representation of symbol tables.
21404 * Lazy Strings In Python:: Python representation of lazy strings.
21405 * Breakpoints In Python:: Manipulating breakpoints using Python.
21409 @subsubsection Basic Python
21411 @cindex python functions
21412 @cindex python module
21414 @value{GDBN} introduces a new Python module, named @code{gdb}. All
21415 methods and classes added by @value{GDBN} are placed in this module.
21416 @value{GDBN} automatically @code{import}s the @code{gdb} module for
21417 use in all scripts evaluated by the @code{python} command.
21419 @findex gdb.PYTHONDIR
21420 @defvar gdb.PYTHONDIR
21421 A string containing the python directory (@pxref{Python}).
21424 @findex gdb.execute
21425 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
21426 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
21427 If a GDB exception happens while @var{command} runs, it is
21428 translated as described in @ref{Exception Handling,,Exception Handling}.
21430 @var{from_tty} specifies whether @value{GDBN} ought to consider this
21431 command as having originated from the user invoking it interactively.
21432 It must be a boolean value. If omitted, it defaults to @code{False}.
21434 By default, any output produced by @var{command} is sent to
21435 @value{GDBN}'s standard output. If the @var{to_string} parameter is
21436 @code{True}, then output will be collected by @code{gdb.execute} and
21437 returned as a string. The default is @code{False}, in which case the
21438 return value is @code{None}. If @var{to_string} is @code{True}, the
21439 @value{GDBN} virtual terminal will be temporarily set to unlimited width
21440 and height, and its pagination will be disabled; @pxref{Screen Size}.
21443 @findex gdb.breakpoints
21444 @defun gdb.breakpoints ()
21445 Return a sequence holding all of @value{GDBN}'s breakpoints.
21446 @xref{Breakpoints In Python}, for more information.
21449 @findex gdb.parameter
21450 @defun gdb.parameter (parameter)
21451 Return the value of a @value{GDBN} parameter. @var{parameter} is a
21452 string naming the parameter to look up; @var{parameter} may contain
21453 spaces if the parameter has a multi-part name. For example,
21454 @samp{print object} is a valid parameter name.
21456 If the named parameter does not exist, this function throws a
21457 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
21458 parameter's value is converted to a Python value of the appropriate
21459 type, and returned.
21462 @findex gdb.history
21463 @defun gdb.history (number)
21464 Return a value from @value{GDBN}'s value history (@pxref{Value
21465 History}). @var{number} indicates which history element to return.
21466 If @var{number} is negative, then @value{GDBN} will take its absolute value
21467 and count backward from the last element (i.e., the most recent element) to
21468 find the value to return. If @var{number} is zero, then @value{GDBN} will
21469 return the most recent element. If the element specified by @var{number}
21470 doesn't exist in the value history, a @code{gdb.error} exception will be
21473 If no exception is raised, the return value is always an instance of
21474 @code{gdb.Value} (@pxref{Values From Inferior}).
21477 @findex gdb.parse_and_eval
21478 @defun gdb.parse_and_eval (expression)
21479 Parse @var{expression} as an expression in the current language,
21480 evaluate it, and return the result as a @code{gdb.Value}.
21481 @var{expression} must be a string.
21483 This function can be useful when implementing a new command
21484 (@pxref{Commands In Python}), as it provides a way to parse the
21485 command's argument as an expression. It is also useful simply to
21486 compute values, for example, it is the only way to get the value of a
21487 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
21490 @findex gdb.post_event
21491 @defun gdb.post_event (event)
21492 Put @var{event}, a callable object taking no arguments, into
21493 @value{GDBN}'s internal event queue. This callable will be invoked at
21494 some later point, during @value{GDBN}'s event processing. Events
21495 posted using @code{post_event} will be run in the order in which they
21496 were posted; however, there is no way to know when they will be
21497 processed relative to other events inside @value{GDBN}.
21499 @value{GDBN} is not thread-safe. If your Python program uses multiple
21500 threads, you must be careful to only call @value{GDBN}-specific
21501 functions in the main @value{GDBN} thread. @code{post_event} ensures
21505 (@value{GDBP}) python
21509 > def __init__(self, message):
21510 > self.message = message;
21511 > def __call__(self):
21512 > gdb.write(self.message)
21514 >class MyThread1 (threading.Thread):
21516 > gdb.post_event(Writer("Hello "))
21518 >class MyThread2 (threading.Thread):
21520 > gdb.post_event(Writer("World\n"))
21522 >MyThread1().start()
21523 >MyThread2().start()
21525 (@value{GDBP}) Hello World
21530 @defun gdb.write (string @r{[}, stream{]})
21531 Print a string to @value{GDBN}'s paginated output stream. The
21532 optional @var{stream} determines the stream to print to. The default
21533 stream is @value{GDBN}'s standard output stream. Possible stream
21540 @value{GDBN}'s standard output stream.
21545 @value{GDBN}'s standard error stream.
21550 @value{GDBN}'s log stream (@pxref{Logging Output}).
21553 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
21554 call this function and will automatically direct the output to the
21559 @defun gdb.flush ()
21560 Flush the buffer of a @value{GDBN} paginated stream so that the
21561 contents are displayed immediately. @value{GDBN} will flush the
21562 contents of a stream automatically when it encounters a newline in the
21563 buffer. The optional @var{stream} determines the stream to flush. The
21564 default stream is @value{GDBN}'s standard output stream. Possible
21571 @value{GDBN}'s standard output stream.
21576 @value{GDBN}'s standard error stream.
21581 @value{GDBN}'s log stream (@pxref{Logging Output}).
21585 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
21586 call this function for the relevant stream.
21589 @findex gdb.target_charset
21590 @defun gdb.target_charset ()
21591 Return the name of the current target character set (@pxref{Character
21592 Sets}). This differs from @code{gdb.parameter('target-charset')} in
21593 that @samp{auto} is never returned.
21596 @findex gdb.target_wide_charset
21597 @defun gdb.target_wide_charset ()
21598 Return the name of the current target wide character set
21599 (@pxref{Character Sets}). This differs from
21600 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
21604 @findex gdb.solib_name
21605 @defun gdb.solib_name (address)
21606 Return the name of the shared library holding the given @var{address}
21607 as a string, or @code{None}.
21610 @findex gdb.decode_line
21611 @defun gdb.decode_line @r{[}expression@r{]}
21612 Return locations of the line specified by @var{expression}, or of the
21613 current line if no argument was given. This function returns a Python
21614 tuple containing two elements. The first element contains a string
21615 holding any unparsed section of @var{expression} (or @code{None} if
21616 the expression has been fully parsed). The second element contains
21617 either @code{None} or another tuple that contains all the locations
21618 that match the expression represented as @code{gdb.Symtab_and_line}
21619 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
21620 provided, it is decoded the way that @value{GDBN}'s inbuilt
21621 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
21624 @defun gdb.prompt_hook (current_prompt)
21625 @anchor{prompt_hook}
21627 If @var{prompt_hook} is callable, @value{GDBN} will call the method
21628 assigned to this operation before a prompt is displayed by
21631 The parameter @code{current_prompt} contains the current @value{GDBN}
21632 prompt. This method must return a Python string, or @code{None}. If
21633 a string is returned, the @value{GDBN} prompt will be set to that
21634 string. If @code{None} is returned, @value{GDBN} will continue to use
21635 the current prompt.
21637 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
21638 such as those used by readline for command input, and annotation
21639 related prompts are prohibited from being changed.
21642 @node Exception Handling
21643 @subsubsection Exception Handling
21644 @cindex python exceptions
21645 @cindex exceptions, python
21647 When executing the @code{python} command, Python exceptions
21648 uncaught within the Python code are translated to calls to
21649 @value{GDBN} error-reporting mechanism. If the command that called
21650 @code{python} does not handle the error, @value{GDBN} will
21651 terminate it and print an error message containing the Python
21652 exception name, the associated value, and the Python call stack
21653 backtrace at the point where the exception was raised. Example:
21656 (@value{GDBP}) python print foo
21657 Traceback (most recent call last):
21658 File "<string>", line 1, in <module>
21659 NameError: name 'foo' is not defined
21662 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
21663 Python code are converted to Python exceptions. The type of the
21664 Python exception depends on the error.
21668 This is the base class for most exceptions generated by @value{GDBN}.
21669 It is derived from @code{RuntimeError}, for compatibility with earlier
21670 versions of @value{GDBN}.
21672 If an error occurring in @value{GDBN} does not fit into some more
21673 specific category, then the generated exception will have this type.
21675 @item gdb.MemoryError
21676 This is a subclass of @code{gdb.error} which is thrown when an
21677 operation tried to access invalid memory in the inferior.
21679 @item KeyboardInterrupt
21680 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
21681 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
21684 In all cases, your exception handler will see the @value{GDBN} error
21685 message as its value and the Python call stack backtrace at the Python
21686 statement closest to where the @value{GDBN} error occured as the
21689 @findex gdb.GdbError
21690 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
21691 it is useful to be able to throw an exception that doesn't cause a
21692 traceback to be printed. For example, the user may have invoked the
21693 command incorrectly. Use the @code{gdb.GdbError} exception
21694 to handle this case. Example:
21698 >class HelloWorld (gdb.Command):
21699 > """Greet the whole world."""
21700 > def __init__ (self):
21701 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
21702 > def invoke (self, args, from_tty):
21703 > argv = gdb.string_to_argv (args)
21704 > if len (argv) != 0:
21705 > raise gdb.GdbError ("hello-world takes no arguments")
21706 > print "Hello, World!"
21709 (gdb) hello-world 42
21710 hello-world takes no arguments
21713 @node Values From Inferior
21714 @subsubsection Values From Inferior
21715 @cindex values from inferior, with Python
21716 @cindex python, working with values from inferior
21718 @cindex @code{gdb.Value}
21719 @value{GDBN} provides values it obtains from the inferior program in
21720 an object of type @code{gdb.Value}. @value{GDBN} uses this object
21721 for its internal bookkeeping of the inferior's values, and for
21722 fetching values when necessary.
21724 Inferior values that are simple scalars can be used directly in
21725 Python expressions that are valid for the value's data type. Here's
21726 an example for an integer or floating-point value @code{some_val}:
21733 As result of this, @code{bar} will also be a @code{gdb.Value} object
21734 whose values are of the same type as those of @code{some_val}.
21736 Inferior values that are structures or instances of some class can
21737 be accessed using the Python @dfn{dictionary syntax}. For example, if
21738 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
21739 can access its @code{foo} element with:
21742 bar = some_val['foo']
21745 Again, @code{bar} will also be a @code{gdb.Value} object.
21747 A @code{gdb.Value} that represents a function can be executed via
21748 inferior function call. Any arguments provided to the call must match
21749 the function's prototype, and must be provided in the order specified
21752 For example, @code{some_val} is a @code{gdb.Value} instance
21753 representing a function that takes two integers as arguments. To
21754 execute this function, call it like so:
21757 result = some_val (10,20)
21760 Any values returned from a function call will be stored as a
21763 The following attributes are provided:
21766 @defvar Value.address
21767 If this object is addressable, this read-only attribute holds a
21768 @code{gdb.Value} object representing the address. Otherwise,
21769 this attribute holds @code{None}.
21772 @cindex optimized out value in Python
21773 @defvar Value.is_optimized_out
21774 This read-only boolean attribute is true if the compiler optimized out
21775 this value, thus it is not available for fetching from the inferior.
21779 The type of this @code{gdb.Value}. The value of this attribute is a
21780 @code{gdb.Type} object (@pxref{Types In Python}).
21783 @defvar Value.dynamic_type
21784 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
21785 type information (@acronym{RTTI}) to determine the dynamic type of the
21786 value. If this value is of class type, it will return the class in
21787 which the value is embedded, if any. If this value is of pointer or
21788 reference to a class type, it will compute the dynamic type of the
21789 referenced object, and return a pointer or reference to that type,
21790 respectively. In all other cases, it will return the value's static
21793 Note that this feature will only work when debugging a C@t{++} program
21794 that includes @acronym{RTTI} for the object in question. Otherwise,
21795 it will just return the static type of the value as in @kbd{ptype foo}
21796 (@pxref{Symbols, ptype}).
21799 @defvar Value.is_lazy
21800 The value of this read-only boolean attribute is @code{True} if this
21801 @code{gdb.Value} has not yet been fetched from the inferior.
21802 @value{GDBN} does not fetch values until necessary, for efficiency.
21806 myval = gdb.parse_and_eval ('somevar')
21809 The value of @code{somevar} is not fetched at this time. It will be
21810 fetched when the value is needed, or when the @code{fetch_lazy}
21815 The following methods are provided:
21818 @defun Value.__init__ (@var{val})
21819 Many Python values can be converted directly to a @code{gdb.Value} via
21820 this object initializer. Specifically:
21823 @item Python boolean
21824 A Python boolean is converted to the boolean type from the current
21827 @item Python integer
21828 A Python integer is converted to the C @code{long} type for the
21829 current architecture.
21832 A Python long is converted to the C @code{long long} type for the
21833 current architecture.
21836 A Python float is converted to the C @code{double} type for the
21837 current architecture.
21839 @item Python string
21840 A Python string is converted to a target string, using the current
21843 @item @code{gdb.Value}
21844 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
21846 @item @code{gdb.LazyString}
21847 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
21848 Python}), then the lazy string's @code{value} method is called, and
21849 its result is used.
21853 @defun Value.cast (type)
21854 Return a new instance of @code{gdb.Value} that is the result of
21855 casting this instance to the type described by @var{type}, which must
21856 be a @code{gdb.Type} object. If the cast cannot be performed for some
21857 reason, this method throws an exception.
21860 @defun Value.dereference ()
21861 For pointer data types, this method returns a new @code{gdb.Value} object
21862 whose contents is the object pointed to by the pointer. For example, if
21863 @code{foo} is a C pointer to an @code{int}, declared in your C program as
21870 then you can use the corresponding @code{gdb.Value} to access what
21871 @code{foo} points to like this:
21874 bar = foo.dereference ()
21877 The result @code{bar} will be a @code{gdb.Value} object holding the
21878 value pointed to by @code{foo}.
21881 @defun Value.dynamic_cast (type)
21882 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
21883 operator were used. Consult a C@t{++} reference for details.
21886 @defun Value.reinterpret_cast (type)
21887 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
21888 operator were used. Consult a C@t{++} reference for details.
21891 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
21892 If this @code{gdb.Value} represents a string, then this method
21893 converts the contents to a Python string. Otherwise, this method will
21894 throw an exception.
21896 Strings are recognized in a language-specific way; whether a given
21897 @code{gdb.Value} represents a string is determined by the current
21900 For C-like languages, a value is a string if it is a pointer to or an
21901 array of characters or ints. The string is assumed to be terminated
21902 by a zero of the appropriate width. However if the optional length
21903 argument is given, the string will be converted to that given length,
21904 ignoring any embedded zeros that the string may contain.
21906 If the optional @var{encoding} argument is given, it must be a string
21907 naming the encoding of the string in the @code{gdb.Value}, such as
21908 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
21909 the same encodings as the corresponding argument to Python's
21910 @code{string.decode} method, and the Python codec machinery will be used
21911 to convert the string. If @var{encoding} is not given, or if
21912 @var{encoding} is the empty string, then either the @code{target-charset}
21913 (@pxref{Character Sets}) will be used, or a language-specific encoding
21914 will be used, if the current language is able to supply one.
21916 The optional @var{errors} argument is the same as the corresponding
21917 argument to Python's @code{string.decode} method.
21919 If the optional @var{length} argument is given, the string will be
21920 fetched and converted to the given length.
21923 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
21924 If this @code{gdb.Value} represents a string, then this method
21925 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
21926 In Python}). Otherwise, this method will throw an exception.
21928 If the optional @var{encoding} argument is given, it must be a string
21929 naming the encoding of the @code{gdb.LazyString}. Some examples are:
21930 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
21931 @var{encoding} argument is an encoding that @value{GDBN} does
21932 recognize, @value{GDBN} will raise an error.
21934 When a lazy string is printed, the @value{GDBN} encoding machinery is
21935 used to convert the string during printing. If the optional
21936 @var{encoding} argument is not provided, or is an empty string,
21937 @value{GDBN} will automatically select the encoding most suitable for
21938 the string type. For further information on encoding in @value{GDBN}
21939 please see @ref{Character Sets}.
21941 If the optional @var{length} argument is given, the string will be
21942 fetched and encoded to the length of characters specified. If
21943 the @var{length} argument is not provided, the string will be fetched
21944 and encoded until a null of appropriate width is found.
21947 @defun Value.fetch_lazy ()
21948 If the @code{gdb.Value} object is currently a lazy value
21949 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
21950 fetched from the inferior. Any errors that occur in the process
21951 will produce a Python exception.
21953 If the @code{gdb.Value} object is not a lazy value, this method
21956 This method does not return a value.
21961 @node Types In Python
21962 @subsubsection Types In Python
21963 @cindex types in Python
21964 @cindex Python, working with types
21967 @value{GDBN} represents types from the inferior using the class
21970 The following type-related functions are available in the @code{gdb}
21973 @findex gdb.lookup_type
21974 @defun gdb.lookup_type (name @r{[}, block@r{]})
21975 This function looks up a type by name. @var{name} is the name of the
21976 type to look up. It must be a string.
21978 If @var{block} is given, then @var{name} is looked up in that scope.
21979 Otherwise, it is searched for globally.
21981 Ordinarily, this function will return an instance of @code{gdb.Type}.
21982 If the named type cannot be found, it will throw an exception.
21985 If the type is a structure or class type, or an enum type, the fields
21986 of that type can be accessed using the Python @dfn{dictionary syntax}.
21987 For example, if @code{some_type} is a @code{gdb.Type} instance holding
21988 a structure type, you can access its @code{foo} field with:
21991 bar = some_type['foo']
21994 @code{bar} will be a @code{gdb.Field} object; see below under the
21995 description of the @code{Type.fields} method for a description of the
21996 @code{gdb.Field} class.
21998 An instance of @code{Type} has the following attributes:
22002 The type code for this type. The type code will be one of the
22003 @code{TYPE_CODE_} constants defined below.
22006 @defvar Type.sizeof
22007 The size of this type, in target @code{char} units. Usually, a
22008 target's @code{char} type will be an 8-bit byte. However, on some
22009 unusual platforms, this type may have a different size.
22013 The tag name for this type. The tag name is the name after
22014 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
22015 languages have this concept. If this type has no tag name, then
22016 @code{None} is returned.
22020 The following methods are provided:
22023 @defun Type.fields ()
22024 For structure and union types, this method returns the fields. Range
22025 types have two fields, the minimum and maximum values. Enum types
22026 have one field per enum constant. Function and method types have one
22027 field per parameter. The base types of C@t{++} classes are also
22028 represented as fields. If the type has no fields, or does not fit
22029 into one of these categories, an empty sequence will be returned.
22031 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
22034 This attribute is not available for @code{static} fields (as in
22035 C@t{++} or Java). For non-@code{static} fields, the value is the bit
22036 position of the field. For @code{enum} fields, the value is the
22037 enumeration member's integer representation.
22040 The name of the field, or @code{None} for anonymous fields.
22043 This is @code{True} if the field is artificial, usually meaning that
22044 it was provided by the compiler and not the user. This attribute is
22045 always provided, and is @code{False} if the field is not artificial.
22047 @item is_base_class
22048 This is @code{True} if the field represents a base class of a C@t{++}
22049 structure. This attribute is always provided, and is @code{False}
22050 if the field is not a base class of the type that is the argument of
22051 @code{fields}, or if that type was not a C@t{++} class.
22054 If the field is packed, or is a bitfield, then this will have a
22055 non-zero value, which is the size of the field in bits. Otherwise,
22056 this will be zero; in this case the field's size is given by its type.
22059 The type of the field. This is usually an instance of @code{Type},
22060 but it can be @code{None} in some situations.
22064 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
22065 Return a new @code{gdb.Type} object which represents an array of this
22066 type. If one argument is given, it is the inclusive upper bound of
22067 the array; in this case the lower bound is zero. If two arguments are
22068 given, the first argument is the lower bound of the array, and the
22069 second argument is the upper bound of the array. An array's length
22070 must not be negative, but the bounds can be.
22073 @defun Type.const ()
22074 Return a new @code{gdb.Type} object which represents a
22075 @code{const}-qualified variant of this type.
22078 @defun Type.volatile ()
22079 Return a new @code{gdb.Type} object which represents a
22080 @code{volatile}-qualified variant of this type.
22083 @defun Type.unqualified ()
22084 Return a new @code{gdb.Type} object which represents an unqualified
22085 variant of this type. That is, the result is neither @code{const} nor
22089 @defun Type.range ()
22090 Return a Python @code{Tuple} object that contains two elements: the
22091 low bound of the argument type and the high bound of that type. If
22092 the type does not have a range, @value{GDBN} will raise a
22093 @code{gdb.error} exception (@pxref{Exception Handling}).
22096 @defun Type.reference ()
22097 Return a new @code{gdb.Type} object which represents a reference to this
22101 @defun Type.pointer ()
22102 Return a new @code{gdb.Type} object which represents a pointer to this
22106 @defun Type.strip_typedefs ()
22107 Return a new @code{gdb.Type} that represents the real type,
22108 after removing all layers of typedefs.
22111 @defun Type.target ()
22112 Return a new @code{gdb.Type} object which represents the target type
22115 For a pointer type, the target type is the type of the pointed-to
22116 object. For an array type (meaning C-like arrays), the target type is
22117 the type of the elements of the array. For a function or method type,
22118 the target type is the type of the return value. For a complex type,
22119 the target type is the type of the elements. For a typedef, the
22120 target type is the aliased type.
22122 If the type does not have a target, this method will throw an
22126 @defun Type.template_argument (n @r{[}, block@r{]})
22127 If this @code{gdb.Type} is an instantiation of a template, this will
22128 return a new @code{gdb.Type} which represents the type of the
22129 @var{n}th template argument.
22131 If this @code{gdb.Type} is not a template type, this will throw an
22132 exception. Ordinarily, only C@t{++} code will have template types.
22134 If @var{block} is given, then @var{name} is looked up in that scope.
22135 Otherwise, it is searched for globally.
22140 Each type has a code, which indicates what category this type falls
22141 into. The available type categories are represented by constants
22142 defined in the @code{gdb} module:
22145 @findex TYPE_CODE_PTR
22146 @findex gdb.TYPE_CODE_PTR
22147 @item gdb.TYPE_CODE_PTR
22148 The type is a pointer.
22150 @findex TYPE_CODE_ARRAY
22151 @findex gdb.TYPE_CODE_ARRAY
22152 @item gdb.TYPE_CODE_ARRAY
22153 The type is an array.
22155 @findex TYPE_CODE_STRUCT
22156 @findex gdb.TYPE_CODE_STRUCT
22157 @item gdb.TYPE_CODE_STRUCT
22158 The type is a structure.
22160 @findex TYPE_CODE_UNION
22161 @findex gdb.TYPE_CODE_UNION
22162 @item gdb.TYPE_CODE_UNION
22163 The type is a union.
22165 @findex TYPE_CODE_ENUM
22166 @findex gdb.TYPE_CODE_ENUM
22167 @item gdb.TYPE_CODE_ENUM
22168 The type is an enum.
22170 @findex TYPE_CODE_FLAGS
22171 @findex gdb.TYPE_CODE_FLAGS
22172 @item gdb.TYPE_CODE_FLAGS
22173 A bit flags type, used for things such as status registers.
22175 @findex TYPE_CODE_FUNC
22176 @findex gdb.TYPE_CODE_FUNC
22177 @item gdb.TYPE_CODE_FUNC
22178 The type is a function.
22180 @findex TYPE_CODE_INT
22181 @findex gdb.TYPE_CODE_INT
22182 @item gdb.TYPE_CODE_INT
22183 The type is an integer type.
22185 @findex TYPE_CODE_FLT
22186 @findex gdb.TYPE_CODE_FLT
22187 @item gdb.TYPE_CODE_FLT
22188 A floating point type.
22190 @findex TYPE_CODE_VOID
22191 @findex gdb.TYPE_CODE_VOID
22192 @item gdb.TYPE_CODE_VOID
22193 The special type @code{void}.
22195 @findex TYPE_CODE_SET
22196 @findex gdb.TYPE_CODE_SET
22197 @item gdb.TYPE_CODE_SET
22200 @findex TYPE_CODE_RANGE
22201 @findex gdb.TYPE_CODE_RANGE
22202 @item gdb.TYPE_CODE_RANGE
22203 A range type, that is, an integer type with bounds.
22205 @findex TYPE_CODE_STRING
22206 @findex gdb.TYPE_CODE_STRING
22207 @item gdb.TYPE_CODE_STRING
22208 A string type. Note that this is only used for certain languages with
22209 language-defined string types; C strings are not represented this way.
22211 @findex TYPE_CODE_BITSTRING
22212 @findex gdb.TYPE_CODE_BITSTRING
22213 @item gdb.TYPE_CODE_BITSTRING
22216 @findex TYPE_CODE_ERROR
22217 @findex gdb.TYPE_CODE_ERROR
22218 @item gdb.TYPE_CODE_ERROR
22219 An unknown or erroneous type.
22221 @findex TYPE_CODE_METHOD
22222 @findex gdb.TYPE_CODE_METHOD
22223 @item gdb.TYPE_CODE_METHOD
22224 A method type, as found in C@t{++} or Java.
22226 @findex TYPE_CODE_METHODPTR
22227 @findex gdb.TYPE_CODE_METHODPTR
22228 @item gdb.TYPE_CODE_METHODPTR
22229 A pointer-to-member-function.
22231 @findex TYPE_CODE_MEMBERPTR
22232 @findex gdb.TYPE_CODE_MEMBERPTR
22233 @item gdb.TYPE_CODE_MEMBERPTR
22234 A pointer-to-member.
22236 @findex TYPE_CODE_REF
22237 @findex gdb.TYPE_CODE_REF
22238 @item gdb.TYPE_CODE_REF
22241 @findex TYPE_CODE_CHAR
22242 @findex gdb.TYPE_CODE_CHAR
22243 @item gdb.TYPE_CODE_CHAR
22246 @findex TYPE_CODE_BOOL
22247 @findex gdb.TYPE_CODE_BOOL
22248 @item gdb.TYPE_CODE_BOOL
22251 @findex TYPE_CODE_COMPLEX
22252 @findex gdb.TYPE_CODE_COMPLEX
22253 @item gdb.TYPE_CODE_COMPLEX
22254 A complex float type.
22256 @findex TYPE_CODE_TYPEDEF
22257 @findex gdb.TYPE_CODE_TYPEDEF
22258 @item gdb.TYPE_CODE_TYPEDEF
22259 A typedef to some other type.
22261 @findex TYPE_CODE_NAMESPACE
22262 @findex gdb.TYPE_CODE_NAMESPACE
22263 @item gdb.TYPE_CODE_NAMESPACE
22264 A C@t{++} namespace.
22266 @findex TYPE_CODE_DECFLOAT
22267 @findex gdb.TYPE_CODE_DECFLOAT
22268 @item gdb.TYPE_CODE_DECFLOAT
22269 A decimal floating point type.
22271 @findex TYPE_CODE_INTERNAL_FUNCTION
22272 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
22273 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
22274 A function internal to @value{GDBN}. This is the type used to represent
22275 convenience functions.
22278 Further support for types is provided in the @code{gdb.types}
22279 Python module (@pxref{gdb.types}).
22281 @node Pretty Printing API
22282 @subsubsection Pretty Printing API
22284 An example output is provided (@pxref{Pretty Printing}).
22286 A pretty-printer is just an object that holds a value and implements a
22287 specific interface, defined here.
22289 @defun pretty_printer.children (self)
22290 @value{GDBN} will call this method on a pretty-printer to compute the
22291 children of the pretty-printer's value.
22293 This method must return an object conforming to the Python iterator
22294 protocol. Each item returned by the iterator must be a tuple holding
22295 two elements. The first element is the ``name'' of the child; the
22296 second element is the child's value. The value can be any Python
22297 object which is convertible to a @value{GDBN} value.
22299 This method is optional. If it does not exist, @value{GDBN} will act
22300 as though the value has no children.
22303 @defun pretty_printer.display_hint (self)
22304 The CLI may call this method and use its result to change the
22305 formatting of a value. The result will also be supplied to an MI
22306 consumer as a @samp{displayhint} attribute of the variable being
22309 This method is optional. If it does exist, this method must return a
22312 Some display hints are predefined by @value{GDBN}:
22316 Indicate that the object being printed is ``array-like''. The CLI
22317 uses this to respect parameters such as @code{set print elements} and
22318 @code{set print array}.
22321 Indicate that the object being printed is ``map-like'', and that the
22322 children of this value can be assumed to alternate between keys and
22326 Indicate that the object being printed is ``string-like''. If the
22327 printer's @code{to_string} method returns a Python string of some
22328 kind, then @value{GDBN} will call its internal language-specific
22329 string-printing function to format the string. For the CLI this means
22330 adding quotation marks, possibly escaping some characters, respecting
22331 @code{set print elements}, and the like.
22335 @defun pretty_printer.to_string (self)
22336 @value{GDBN} will call this method to display the string
22337 representation of the value passed to the object's constructor.
22339 When printing from the CLI, if the @code{to_string} method exists,
22340 then @value{GDBN} will prepend its result to the values returned by
22341 @code{children}. Exactly how this formatting is done is dependent on
22342 the display hint, and may change as more hints are added. Also,
22343 depending on the print settings (@pxref{Print Settings}), the CLI may
22344 print just the result of @code{to_string} in a stack trace, omitting
22345 the result of @code{children}.
22347 If this method returns a string, it is printed verbatim.
22349 Otherwise, if this method returns an instance of @code{gdb.Value},
22350 then @value{GDBN} prints this value. This may result in a call to
22351 another pretty-printer.
22353 If instead the method returns a Python value which is convertible to a
22354 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
22355 the resulting value. Again, this may result in a call to another
22356 pretty-printer. Python scalars (integers, floats, and booleans) and
22357 strings are convertible to @code{gdb.Value}; other types are not.
22359 Finally, if this method returns @code{None} then no further operations
22360 are peformed in this method and nothing is printed.
22362 If the result is not one of these types, an exception is raised.
22365 @value{GDBN} provides a function which can be used to look up the
22366 default pretty-printer for a @code{gdb.Value}:
22368 @findex gdb.default_visualizer
22369 @defun gdb.default_visualizer (value)
22370 This function takes a @code{gdb.Value} object as an argument. If a
22371 pretty-printer for this value exists, then it is returned. If no such
22372 printer exists, then this returns @code{None}.
22375 @node Selecting Pretty-Printers
22376 @subsubsection Selecting Pretty-Printers
22378 The Python list @code{gdb.pretty_printers} contains an array of
22379 functions or callable objects that have been registered via addition
22380 as a pretty-printer. Printers in this list are called @code{global}
22381 printers, they're available when debugging all inferiors.
22382 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
22383 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
22386 Each function on these lists is passed a single @code{gdb.Value}
22387 argument and should return a pretty-printer object conforming to the
22388 interface definition above (@pxref{Pretty Printing API}). If a function
22389 cannot create a pretty-printer for the value, it should return
22392 @value{GDBN} first checks the @code{pretty_printers} attribute of each
22393 @code{gdb.Objfile} in the current program space and iteratively calls
22394 each enabled lookup routine in the list for that @code{gdb.Objfile}
22395 until it receives a pretty-printer object.
22396 If no pretty-printer is found in the objfile lists, @value{GDBN} then
22397 searches the pretty-printer list of the current program space,
22398 calling each enabled function until an object is returned.
22399 After these lists have been exhausted, it tries the global
22400 @code{gdb.pretty_printers} list, again calling each enabled function until an
22401 object is returned.
22403 The order in which the objfiles are searched is not specified. For a
22404 given list, functions are always invoked from the head of the list,
22405 and iterated over sequentially until the end of the list, or a printer
22406 object is returned.
22408 For various reasons a pretty-printer may not work.
22409 For example, the underlying data structure may have changed and
22410 the pretty-printer is out of date.
22412 The consequences of a broken pretty-printer are severe enough that
22413 @value{GDBN} provides support for enabling and disabling individual
22414 printers. For example, if @code{print frame-arguments} is on,
22415 a backtrace can become highly illegible if any argument is printed
22416 with a broken printer.
22418 Pretty-printers are enabled and disabled by attaching an @code{enabled}
22419 attribute to the registered function or callable object. If this attribute
22420 is present and its value is @code{False}, the printer is disabled, otherwise
22421 the printer is enabled.
22423 @node Writing a Pretty-Printer
22424 @subsubsection Writing a Pretty-Printer
22425 @cindex writing a pretty-printer
22427 A pretty-printer consists of two parts: a lookup function to detect
22428 if the type is supported, and the printer itself.
22430 Here is an example showing how a @code{std::string} printer might be
22431 written. @xref{Pretty Printing API}, for details on the API this class
22435 class StdStringPrinter(object):
22436 "Print a std::string"
22438 def __init__(self, val):
22441 def to_string(self):
22442 return self.val['_M_dataplus']['_M_p']
22444 def display_hint(self):
22448 And here is an example showing how a lookup function for the printer
22449 example above might be written.
22452 def str_lookup_function(val):
22453 lookup_tag = val.type.tag
22454 if lookup_tag == None:
22456 regex = re.compile("^std::basic_string<char,.*>$")
22457 if regex.match(lookup_tag):
22458 return StdStringPrinter(val)
22462 The example lookup function extracts the value's type, and attempts to
22463 match it to a type that it can pretty-print. If it is a type the
22464 printer can pretty-print, it will return a printer object. If not, it
22465 returns @code{None}.
22467 We recommend that you put your core pretty-printers into a Python
22468 package. If your pretty-printers are for use with a library, we
22469 further recommend embedding a version number into the package name.
22470 This practice will enable @value{GDBN} to load multiple versions of
22471 your pretty-printers at the same time, because they will have
22474 You should write auto-loaded code (@pxref{Auto-loading}) such that it
22475 can be evaluated multiple times without changing its meaning. An
22476 ideal auto-load file will consist solely of @code{import}s of your
22477 printer modules, followed by a call to a register pretty-printers with
22478 the current objfile.
22480 Taken as a whole, this approach will scale nicely to multiple
22481 inferiors, each potentially using a different library version.
22482 Embedding a version number in the Python package name will ensure that
22483 @value{GDBN} is able to load both sets of printers simultaneously.
22484 Then, because the search for pretty-printers is done by objfile, and
22485 because your auto-loaded code took care to register your library's
22486 printers with a specific objfile, @value{GDBN} will find the correct
22487 printers for the specific version of the library used by each
22490 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
22491 this code might appear in @code{gdb.libstdcxx.v6}:
22494 def register_printers(objfile):
22495 objfile.pretty_printers.add(str_lookup_function)
22499 And then the corresponding contents of the auto-load file would be:
22502 import gdb.libstdcxx.v6
22503 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
22506 The previous example illustrates a basic pretty-printer.
22507 There are a few things that can be improved on.
22508 The printer doesn't have a name, making it hard to identify in a
22509 list of installed printers. The lookup function has a name, but
22510 lookup functions can have arbitrary, even identical, names.
22512 Second, the printer only handles one type, whereas a library typically has
22513 several types. One could install a lookup function for each desired type
22514 in the library, but one could also have a single lookup function recognize
22515 several types. The latter is the conventional way this is handled.
22516 If a pretty-printer can handle multiple data types, then its
22517 @dfn{subprinters} are the printers for the individual data types.
22519 The @code{gdb.printing} module provides a formal way of solving these
22520 problems (@pxref{gdb.printing}).
22521 Here is another example that handles multiple types.
22523 These are the types we are going to pretty-print:
22526 struct foo @{ int a, b; @};
22527 struct bar @{ struct foo x, y; @};
22530 Here are the printers:
22534 """Print a foo object."""
22536 def __init__(self, val):
22539 def to_string(self):
22540 return ("a=<" + str(self.val["a"]) +
22541 "> b=<" + str(self.val["b"]) + ">")
22544 """Print a bar object."""
22546 def __init__(self, val):
22549 def to_string(self):
22550 return ("x=<" + str(self.val["x"]) +
22551 "> y=<" + str(self.val["y"]) + ">")
22554 This example doesn't need a lookup function, that is handled by the
22555 @code{gdb.printing} module. Instead a function is provided to build up
22556 the object that handles the lookup.
22559 import gdb.printing
22561 def build_pretty_printer():
22562 pp = gdb.printing.RegexpCollectionPrettyPrinter(
22564 pp.add_printer('foo', '^foo$', fooPrinter)
22565 pp.add_printer('bar', '^bar$', barPrinter)
22569 And here is the autoload support:
22572 import gdb.printing
22574 gdb.printing.register_pretty_printer(
22575 gdb.current_objfile(),
22576 my_library.build_pretty_printer())
22579 Finally, when this printer is loaded into @value{GDBN}, here is the
22580 corresponding output of @samp{info pretty-printer}:
22583 (gdb) info pretty-printer
22590 @node Inferiors In Python
22591 @subsubsection Inferiors In Python
22592 @cindex inferiors in Python
22594 @findex gdb.Inferior
22595 Programs which are being run under @value{GDBN} are called inferiors
22596 (@pxref{Inferiors and Programs}). Python scripts can access
22597 information about and manipulate inferiors controlled by @value{GDBN}
22598 via objects of the @code{gdb.Inferior} class.
22600 The following inferior-related functions are available in the @code{gdb}
22603 @defun gdb.inferiors ()
22604 Return a tuple containing all inferior objects.
22607 @defun gdb.selected_inferior ()
22608 Return an object representing the current inferior.
22611 A @code{gdb.Inferior} object has the following attributes:
22614 @defvar Inferior.num
22615 ID of inferior, as assigned by GDB.
22618 @defvar Inferior.pid
22619 Process ID of the inferior, as assigned by the underlying operating
22623 @defvar Inferior.was_attached
22624 Boolean signaling whether the inferior was created using `attach', or
22625 started by @value{GDBN} itself.
22629 A @code{gdb.Inferior} object has the following methods:
22632 @defun Inferior.is_valid ()
22633 Returns @code{True} if the @code{gdb.Inferior} object is valid,
22634 @code{False} if not. A @code{gdb.Inferior} object will become invalid
22635 if the inferior no longer exists within @value{GDBN}. All other
22636 @code{gdb.Inferior} methods will throw an exception if it is invalid
22637 at the time the method is called.
22640 @defun Inferior.threads ()
22641 This method returns a tuple holding all the threads which are valid
22642 when it is called. If there are no valid threads, the method will
22643 return an empty tuple.
22646 @findex gdb.read_memory
22647 @defun Inferior.read_memory (address, length)
22648 Read @var{length} bytes of memory from the inferior, starting at
22649 @var{address}. Returns a buffer object, which behaves much like an array
22650 or a string. It can be modified and given to the @code{gdb.write_memory}
22654 @findex gdb.write_memory
22655 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
22656 Write the contents of @var{buffer} to the inferior, starting at
22657 @var{address}. The @var{buffer} parameter must be a Python object
22658 which supports the buffer protocol, i.e., a string, an array or the
22659 object returned from @code{gdb.read_memory}. If given, @var{length}
22660 determines the number of bytes from @var{buffer} to be written.
22663 @findex gdb.search_memory
22664 @defun Inferior.search_memory (address, length, pattern)
22665 Search a region of the inferior memory starting at @var{address} with
22666 the given @var{length} using the search pattern supplied in
22667 @var{pattern}. The @var{pattern} parameter must be a Python object
22668 which supports the buffer protocol, i.e., a string, an array or the
22669 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
22670 containing the address where the pattern was found, or @code{None} if
22671 the pattern could not be found.
22675 @node Events In Python
22676 @subsubsection Events In Python
22677 @cindex inferior events in Python
22679 @value{GDBN} provides a general event facility so that Python code can be
22680 notified of various state changes, particularly changes that occur in
22683 An @dfn{event} is just an object that describes some state change. The
22684 type of the object and its attributes will vary depending on the details
22685 of the change. All the existing events are described below.
22687 In order to be notified of an event, you must register an event handler
22688 with an @dfn{event registry}. An event registry is an object in the
22689 @code{gdb.events} module which dispatches particular events. A registry
22690 provides methods to register and unregister event handlers:
22693 @defun EventRegistry.connect (object)
22694 Add the given callable @var{object} to the registry. This object will be
22695 called when an event corresponding to this registry occurs.
22698 @defun EventRegistry.disconnect (object)
22699 Remove the given @var{object} from the registry. Once removed, the object
22700 will no longer receive notifications of events.
22704 Here is an example:
22707 def exit_handler (event):
22708 print "event type: exit"
22709 print "exit code: %d" % (event.exit_code)
22711 gdb.events.exited.connect (exit_handler)
22714 In the above example we connect our handler @code{exit_handler} to the
22715 registry @code{events.exited}. Once connected, @code{exit_handler} gets
22716 called when the inferior exits. The argument @dfn{event} in this example is
22717 of type @code{gdb.ExitedEvent}. As you can see in the example the
22718 @code{ExitedEvent} object has an attribute which indicates the exit code of
22721 The following is a listing of the event registries that are available and
22722 details of the events they emit:
22727 Emits @code{gdb.ThreadEvent}.
22729 Some events can be thread specific when @value{GDBN} is running in non-stop
22730 mode. When represented in Python, these events all extend
22731 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
22732 events which are emitted by this or other modules might extend this event.
22733 Examples of these events are @code{gdb.BreakpointEvent} and
22734 @code{gdb.ContinueEvent}.
22737 @defvar ThreadEvent.inferior_thread
22738 In non-stop mode this attribute will be set to the specific thread which was
22739 involved in the emitted event. Otherwise, it will be set to @code{None}.
22743 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
22745 This event indicates that the inferior has been continued after a stop. For
22746 inherited attribute refer to @code{gdb.ThreadEvent} above.
22748 @item events.exited
22749 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
22750 @code{events.ExitedEvent} has two attributes:
22752 @defvar ExitedEvent.exit_code
22753 An integer representing the exit code, if available, which the inferior
22754 has returned. (The exit code could be unavailable if, for example,
22755 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
22756 the attribute does not exist.
22758 @defvar ExitedEvent inferior
22759 A reference to the inferior which triggered the @code{exited} event.
22764 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
22766 Indicates that the inferior has stopped. All events emitted by this registry
22767 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
22768 will indicate the stopped thread when @value{GDBN} is running in non-stop
22769 mode. Refer to @code{gdb.ThreadEvent} above for more details.
22771 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
22773 This event indicates that the inferior or one of its threads has received as
22774 signal. @code{gdb.SignalEvent} has the following attributes:
22777 @defvar SignalEvent.stop_signal
22778 A string representing the signal received by the inferior. A list of possible
22779 signal values can be obtained by running the command @code{info signals} in
22780 the @value{GDBN} command prompt.
22784 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
22786 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
22787 been hit, and has the following attributes:
22790 @defvar BreakpointEvent.breakpoints
22791 A sequence containing references to all the breakpoints (type
22792 @code{gdb.Breakpoint}) that were hit.
22793 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
22795 @defvar BreakpointEvent.breakpoint
22796 A reference to the first breakpoint that was hit.
22797 This function is maintained for backward compatibility and is now deprecated
22798 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
22802 @item events.new_objfile
22803 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
22804 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
22807 @defvar NewObjFileEvent.new_objfile
22808 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
22809 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
22815 @node Threads In Python
22816 @subsubsection Threads In Python
22817 @cindex threads in python
22819 @findex gdb.InferiorThread
22820 Python scripts can access information about, and manipulate inferior threads
22821 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
22823 The following thread-related functions are available in the @code{gdb}
22826 @findex gdb.selected_thread
22827 @defun gdb.selected_thread ()
22828 This function returns the thread object for the selected thread. If there
22829 is no selected thread, this will return @code{None}.
22832 A @code{gdb.InferiorThread} object has the following attributes:
22835 @defvar InferiorThread.name
22836 The name of the thread. If the user specified a name using
22837 @code{thread name}, then this returns that name. Otherwise, if an
22838 OS-supplied name is available, then it is returned. Otherwise, this
22839 returns @code{None}.
22841 This attribute can be assigned to. The new value must be a string
22842 object, which sets the new name, or @code{None}, which removes any
22843 user-specified thread name.
22846 @defvar InferiorThread.num
22847 ID of the thread, as assigned by GDB.
22850 @defvar InferiorThread.ptid
22851 ID of the thread, as assigned by the operating system. This attribute is a
22852 tuple containing three integers. The first is the Process ID (PID); the second
22853 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
22854 Either the LWPID or TID may be 0, which indicates that the operating system
22855 does not use that identifier.
22859 A @code{gdb.InferiorThread} object has the following methods:
22862 @defun InferiorThread.is_valid ()
22863 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
22864 @code{False} if not. A @code{gdb.InferiorThread} object will become
22865 invalid if the thread exits, or the inferior that the thread belongs
22866 is deleted. All other @code{gdb.InferiorThread} methods will throw an
22867 exception if it is invalid at the time the method is called.
22870 @defun InferiorThread.switch ()
22871 This changes @value{GDBN}'s currently selected thread to the one represented
22875 @defun InferiorThread.is_stopped ()
22876 Return a Boolean indicating whether the thread is stopped.
22879 @defun InferiorThread.is_running ()
22880 Return a Boolean indicating whether the thread is running.
22883 @defun InferiorThread.is_exited ()
22884 Return a Boolean indicating whether the thread is exited.
22888 @node Commands In Python
22889 @subsubsection Commands In Python
22891 @cindex commands in python
22892 @cindex python commands
22893 You can implement new @value{GDBN} CLI commands in Python. A CLI
22894 command is implemented using an instance of the @code{gdb.Command}
22895 class, most commonly using a subclass.
22897 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
22898 The object initializer for @code{Command} registers the new command
22899 with @value{GDBN}. This initializer is normally invoked from the
22900 subclass' own @code{__init__} method.
22902 @var{name} is the name of the command. If @var{name} consists of
22903 multiple words, then the initial words are looked for as prefix
22904 commands. In this case, if one of the prefix commands does not exist,
22905 an exception is raised.
22907 There is no support for multi-line commands.
22909 @var{command_class} should be one of the @samp{COMMAND_} constants
22910 defined below. This argument tells @value{GDBN} how to categorize the
22911 new command in the help system.
22913 @var{completer_class} is an optional argument. If given, it should be
22914 one of the @samp{COMPLETE_} constants defined below. This argument
22915 tells @value{GDBN} how to perform completion for this command. If not
22916 given, @value{GDBN} will attempt to complete using the object's
22917 @code{complete} method (see below); if no such method is found, an
22918 error will occur when completion is attempted.
22920 @var{prefix} is an optional argument. If @code{True}, then the new
22921 command is a prefix command; sub-commands of this command may be
22924 The help text for the new command is taken from the Python
22925 documentation string for the command's class, if there is one. If no
22926 documentation string is provided, the default value ``This command is
22927 not documented.'' is used.
22930 @cindex don't repeat Python command
22931 @defun Command.dont_repeat ()
22932 By default, a @value{GDBN} command is repeated when the user enters a
22933 blank line at the command prompt. A command can suppress this
22934 behavior by invoking the @code{dont_repeat} method. This is similar
22935 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
22938 @defun Command.invoke (argument, from_tty)
22939 This method is called by @value{GDBN} when this command is invoked.
22941 @var{argument} is a string. It is the argument to the command, after
22942 leading and trailing whitespace has been stripped.
22944 @var{from_tty} is a boolean argument. When true, this means that the
22945 command was entered by the user at the terminal; when false it means
22946 that the command came from elsewhere.
22948 If this method throws an exception, it is turned into a @value{GDBN}
22949 @code{error} call. Otherwise, the return value is ignored.
22951 @findex gdb.string_to_argv
22952 To break @var{argument} up into an argv-like string use
22953 @code{gdb.string_to_argv}. This function behaves identically to
22954 @value{GDBN}'s internal argument lexer @code{buildargv}.
22955 It is recommended to use this for consistency.
22956 Arguments are separated by spaces and may be quoted.
22960 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
22961 ['1', '2 "3', '4 "5', "6 '7"]
22966 @cindex completion of Python commands
22967 @defun Command.complete (text, word)
22968 This method is called by @value{GDBN} when the user attempts
22969 completion on this command. All forms of completion are handled by
22970 this method, that is, the @key{TAB} and @key{M-?} key bindings
22971 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
22974 The arguments @var{text} and @var{word} are both strings. @var{text}
22975 holds the complete command line up to the cursor's location.
22976 @var{word} holds the last word of the command line; this is computed
22977 using a word-breaking heuristic.
22979 The @code{complete} method can return several values:
22982 If the return value is a sequence, the contents of the sequence are
22983 used as the completions. It is up to @code{complete} to ensure that the
22984 contents actually do complete the word. A zero-length sequence is
22985 allowed, it means that there were no completions available. Only
22986 string elements of the sequence are used; other elements in the
22987 sequence are ignored.
22990 If the return value is one of the @samp{COMPLETE_} constants defined
22991 below, then the corresponding @value{GDBN}-internal completion
22992 function is invoked, and its result is used.
22995 All other results are treated as though there were no available
23000 When a new command is registered, it must be declared as a member of
23001 some general class of commands. This is used to classify top-level
23002 commands in the on-line help system; note that prefix commands are not
23003 listed under their own category but rather that of their top-level
23004 command. The available classifications are represented by constants
23005 defined in the @code{gdb} module:
23008 @findex COMMAND_NONE
23009 @findex gdb.COMMAND_NONE
23010 @item gdb.COMMAND_NONE
23011 The command does not belong to any particular class. A command in
23012 this category will not be displayed in any of the help categories.
23014 @findex COMMAND_RUNNING
23015 @findex gdb.COMMAND_RUNNING
23016 @item gdb.COMMAND_RUNNING
23017 The command is related to running the inferior. For example,
23018 @code{start}, @code{step}, and @code{continue} are in this category.
23019 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
23020 commands in this category.
23022 @findex COMMAND_DATA
23023 @findex gdb.COMMAND_DATA
23024 @item gdb.COMMAND_DATA
23025 The command is related to data or variables. For example,
23026 @code{call}, @code{find}, and @code{print} are in this category. Type
23027 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
23030 @findex COMMAND_STACK
23031 @findex gdb.COMMAND_STACK
23032 @item gdb.COMMAND_STACK
23033 The command has to do with manipulation of the stack. For example,
23034 @code{backtrace}, @code{frame}, and @code{return} are in this
23035 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
23036 list of commands in this category.
23038 @findex COMMAND_FILES
23039 @findex gdb.COMMAND_FILES
23040 @item gdb.COMMAND_FILES
23041 This class is used for file-related commands. For example,
23042 @code{file}, @code{list} and @code{section} are in this category.
23043 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
23044 commands in this category.
23046 @findex COMMAND_SUPPORT
23047 @findex gdb.COMMAND_SUPPORT
23048 @item gdb.COMMAND_SUPPORT
23049 This should be used for ``support facilities'', generally meaning
23050 things that are useful to the user when interacting with @value{GDBN},
23051 but not related to the state of the inferior. For example,
23052 @code{help}, @code{make}, and @code{shell} are in this category. Type
23053 @kbd{help support} at the @value{GDBN} prompt to see a list of
23054 commands in this category.
23056 @findex COMMAND_STATUS
23057 @findex gdb.COMMAND_STATUS
23058 @item gdb.COMMAND_STATUS
23059 The command is an @samp{info}-related command, that is, related to the
23060 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
23061 and @code{show} are in this category. Type @kbd{help status} at the
23062 @value{GDBN} prompt to see a list of commands in this category.
23064 @findex COMMAND_BREAKPOINTS
23065 @findex gdb.COMMAND_BREAKPOINTS
23066 @item gdb.COMMAND_BREAKPOINTS
23067 The command has to do with breakpoints. For example, @code{break},
23068 @code{clear}, and @code{delete} are in this category. Type @kbd{help
23069 breakpoints} at the @value{GDBN} prompt to see a list of commands in
23072 @findex COMMAND_TRACEPOINTS
23073 @findex gdb.COMMAND_TRACEPOINTS
23074 @item gdb.COMMAND_TRACEPOINTS
23075 The command has to do with tracepoints. For example, @code{trace},
23076 @code{actions}, and @code{tfind} are in this category. Type
23077 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
23078 commands in this category.
23080 @findex COMMAND_OBSCURE
23081 @findex gdb.COMMAND_OBSCURE
23082 @item gdb.COMMAND_OBSCURE
23083 The command is only used in unusual circumstances, or is not of
23084 general interest to users. For example, @code{checkpoint},
23085 @code{fork}, and @code{stop} are in this category. Type @kbd{help
23086 obscure} at the @value{GDBN} prompt to see a list of commands in this
23089 @findex COMMAND_MAINTENANCE
23090 @findex gdb.COMMAND_MAINTENANCE
23091 @item gdb.COMMAND_MAINTENANCE
23092 The command is only useful to @value{GDBN} maintainers. The
23093 @code{maintenance} and @code{flushregs} commands are in this category.
23094 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
23095 commands in this category.
23098 A new command can use a predefined completion function, either by
23099 specifying it via an argument at initialization, or by returning it
23100 from the @code{complete} method. These predefined completion
23101 constants are all defined in the @code{gdb} module:
23104 @findex COMPLETE_NONE
23105 @findex gdb.COMPLETE_NONE
23106 @item gdb.COMPLETE_NONE
23107 This constant means that no completion should be done.
23109 @findex COMPLETE_FILENAME
23110 @findex gdb.COMPLETE_FILENAME
23111 @item gdb.COMPLETE_FILENAME
23112 This constant means that filename completion should be performed.
23114 @findex COMPLETE_LOCATION
23115 @findex gdb.COMPLETE_LOCATION
23116 @item gdb.COMPLETE_LOCATION
23117 This constant means that location completion should be done.
23118 @xref{Specify Location}.
23120 @findex COMPLETE_COMMAND
23121 @findex gdb.COMPLETE_COMMAND
23122 @item gdb.COMPLETE_COMMAND
23123 This constant means that completion should examine @value{GDBN}
23126 @findex COMPLETE_SYMBOL
23127 @findex gdb.COMPLETE_SYMBOL
23128 @item gdb.COMPLETE_SYMBOL
23129 This constant means that completion should be done using symbol names
23133 The following code snippet shows how a trivial CLI command can be
23134 implemented in Python:
23137 class HelloWorld (gdb.Command):
23138 """Greet the whole world."""
23140 def __init__ (self):
23141 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
23143 def invoke (self, arg, from_tty):
23144 print "Hello, World!"
23149 The last line instantiates the class, and is necessary to trigger the
23150 registration of the command with @value{GDBN}. Depending on how the
23151 Python code is read into @value{GDBN}, you may need to import the
23152 @code{gdb} module explicitly.
23154 @node Parameters In Python
23155 @subsubsection Parameters In Python
23157 @cindex parameters in python
23158 @cindex python parameters
23159 @tindex gdb.Parameter
23161 You can implement new @value{GDBN} parameters using Python. A new
23162 parameter is implemented as an instance of the @code{gdb.Parameter}
23165 Parameters are exposed to the user via the @code{set} and
23166 @code{show} commands. @xref{Help}.
23168 There are many parameters that already exist and can be set in
23169 @value{GDBN}. Two examples are: @code{set follow fork} and
23170 @code{set charset}. Setting these parameters influences certain
23171 behavior in @value{GDBN}. Similarly, you can define parameters that
23172 can be used to influence behavior in custom Python scripts and commands.
23174 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
23175 The object initializer for @code{Parameter} registers the new
23176 parameter with @value{GDBN}. This initializer is normally invoked
23177 from the subclass' own @code{__init__} method.
23179 @var{name} is the name of the new parameter. If @var{name} consists
23180 of multiple words, then the initial words are looked for as prefix
23181 parameters. An example of this can be illustrated with the
23182 @code{set print} set of parameters. If @var{name} is
23183 @code{print foo}, then @code{print} will be searched as the prefix
23184 parameter. In this case the parameter can subsequently be accessed in
23185 @value{GDBN} as @code{set print foo}.
23187 If @var{name} consists of multiple words, and no prefix parameter group
23188 can be found, an exception is raised.
23190 @var{command-class} should be one of the @samp{COMMAND_} constants
23191 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
23192 categorize the new parameter in the help system.
23194 @var{parameter-class} should be one of the @samp{PARAM_} constants
23195 defined below. This argument tells @value{GDBN} the type of the new
23196 parameter; this information is used for input validation and
23199 If @var{parameter-class} is @code{PARAM_ENUM}, then
23200 @var{enum-sequence} must be a sequence of strings. These strings
23201 represent the possible values for the parameter.
23203 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
23204 of a fourth argument will cause an exception to be thrown.
23206 The help text for the new parameter is taken from the Python
23207 documentation string for the parameter's class, if there is one. If
23208 there is no documentation string, a default value is used.
23211 @defvar Parameter.set_doc
23212 If this attribute exists, and is a string, then its value is used as
23213 the help text for this parameter's @code{set} command. The value is
23214 examined when @code{Parameter.__init__} is invoked; subsequent changes
23218 @defvar Parameter.show_doc
23219 If this attribute exists, and is a string, then its value is used as
23220 the help text for this parameter's @code{show} command. The value is
23221 examined when @code{Parameter.__init__} is invoked; subsequent changes
23225 @defvar Parameter.value
23226 The @code{value} attribute holds the underlying value of the
23227 parameter. It can be read and assigned to just as any other
23228 attribute. @value{GDBN} does validation when assignments are made.
23231 There are two methods that should be implemented in any
23232 @code{Parameter} class. These are:
23234 @defun Parameter.get_set_string (self)
23235 @value{GDBN} will call this method when a @var{parameter}'s value has
23236 been changed via the @code{set} API (for example, @kbd{set foo off}).
23237 The @code{value} attribute has already been populated with the new
23238 value and may be used in output. This method must return a string.
23241 @defun Parameter.get_show_string (self, svalue)
23242 @value{GDBN} will call this method when a @var{parameter}'s
23243 @code{show} API has been invoked (for example, @kbd{show foo}). The
23244 argument @code{svalue} receives the string representation of the
23245 current value. This method must return a string.
23248 When a new parameter is defined, its type must be specified. The
23249 available types are represented by constants defined in the @code{gdb}
23253 @findex PARAM_BOOLEAN
23254 @findex gdb.PARAM_BOOLEAN
23255 @item gdb.PARAM_BOOLEAN
23256 The value is a plain boolean. The Python boolean values, @code{True}
23257 and @code{False} are the only valid values.
23259 @findex PARAM_AUTO_BOOLEAN
23260 @findex gdb.PARAM_AUTO_BOOLEAN
23261 @item gdb.PARAM_AUTO_BOOLEAN
23262 The value has three possible states: true, false, and @samp{auto}. In
23263 Python, true and false are represented using boolean constants, and
23264 @samp{auto} is represented using @code{None}.
23266 @findex PARAM_UINTEGER
23267 @findex gdb.PARAM_UINTEGER
23268 @item gdb.PARAM_UINTEGER
23269 The value is an unsigned integer. The value of 0 should be
23270 interpreted to mean ``unlimited''.
23272 @findex PARAM_INTEGER
23273 @findex gdb.PARAM_INTEGER
23274 @item gdb.PARAM_INTEGER
23275 The value is a signed integer. The value of 0 should be interpreted
23276 to mean ``unlimited''.
23278 @findex PARAM_STRING
23279 @findex gdb.PARAM_STRING
23280 @item gdb.PARAM_STRING
23281 The value is a string. When the user modifies the string, any escape
23282 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
23283 translated into corresponding characters and encoded into the current
23286 @findex PARAM_STRING_NOESCAPE
23287 @findex gdb.PARAM_STRING_NOESCAPE
23288 @item gdb.PARAM_STRING_NOESCAPE
23289 The value is a string. When the user modifies the string, escapes are
23290 passed through untranslated.
23292 @findex PARAM_OPTIONAL_FILENAME
23293 @findex gdb.PARAM_OPTIONAL_FILENAME
23294 @item gdb.PARAM_OPTIONAL_FILENAME
23295 The value is a either a filename (a string), or @code{None}.
23297 @findex PARAM_FILENAME
23298 @findex gdb.PARAM_FILENAME
23299 @item gdb.PARAM_FILENAME
23300 The value is a filename. This is just like
23301 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
23303 @findex PARAM_ZINTEGER
23304 @findex gdb.PARAM_ZINTEGER
23305 @item gdb.PARAM_ZINTEGER
23306 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
23307 is interpreted as itself.
23310 @findex gdb.PARAM_ENUM
23311 @item gdb.PARAM_ENUM
23312 The value is a string, which must be one of a collection string
23313 constants provided when the parameter is created.
23316 @node Functions In Python
23317 @subsubsection Writing new convenience functions
23319 @cindex writing convenience functions
23320 @cindex convenience functions in python
23321 @cindex python convenience functions
23322 @tindex gdb.Function
23324 You can implement new convenience functions (@pxref{Convenience Vars})
23325 in Python. A convenience function is an instance of a subclass of the
23326 class @code{gdb.Function}.
23328 @defun Function.__init__ (name)
23329 The initializer for @code{Function} registers the new function with
23330 @value{GDBN}. The argument @var{name} is the name of the function,
23331 a string. The function will be visible to the user as a convenience
23332 variable of type @code{internal function}, whose name is the same as
23333 the given @var{name}.
23335 The documentation for the new function is taken from the documentation
23336 string for the new class.
23339 @defun Function.invoke (@var{*args})
23340 When a convenience function is evaluated, its arguments are converted
23341 to instances of @code{gdb.Value}, and then the function's
23342 @code{invoke} method is called. Note that @value{GDBN} does not
23343 predetermine the arity of convenience functions. Instead, all
23344 available arguments are passed to @code{invoke}, following the
23345 standard Python calling convention. In particular, a convenience
23346 function can have default values for parameters without ill effect.
23348 The return value of this method is used as its value in the enclosing
23349 expression. If an ordinary Python value is returned, it is converted
23350 to a @code{gdb.Value} following the usual rules.
23353 The following code snippet shows how a trivial convenience function can
23354 be implemented in Python:
23357 class Greet (gdb.Function):
23358 """Return string to greet someone.
23359 Takes a name as argument."""
23361 def __init__ (self):
23362 super (Greet, self).__init__ ("greet")
23364 def invoke (self, name):
23365 return "Hello, %s!" % name.string ()
23370 The last line instantiates the class, and is necessary to trigger the
23371 registration of the function with @value{GDBN}. Depending on how the
23372 Python code is read into @value{GDBN}, you may need to import the
23373 @code{gdb} module explicitly.
23375 @node Progspaces In Python
23376 @subsubsection Program Spaces In Python
23378 @cindex progspaces in python
23379 @tindex gdb.Progspace
23381 A program space, or @dfn{progspace}, represents a symbolic view
23382 of an address space.
23383 It consists of all of the objfiles of the program.
23384 @xref{Objfiles In Python}.
23385 @xref{Inferiors and Programs, program spaces}, for more details
23386 about program spaces.
23388 The following progspace-related functions are available in the
23391 @findex gdb.current_progspace
23392 @defun gdb.current_progspace ()
23393 This function returns the program space of the currently selected inferior.
23394 @xref{Inferiors and Programs}.
23397 @findex gdb.progspaces
23398 @defun gdb.progspaces ()
23399 Return a sequence of all the progspaces currently known to @value{GDBN}.
23402 Each progspace is represented by an instance of the @code{gdb.Progspace}
23405 @defvar Progspace.filename
23406 The file name of the progspace as a string.
23409 @defvar Progspace.pretty_printers
23410 The @code{pretty_printers} attribute is a list of functions. It is
23411 used to look up pretty-printers. A @code{Value} is passed to each
23412 function in order; if the function returns @code{None}, then the
23413 search continues. Otherwise, the return value should be an object
23414 which is used to format the value. @xref{Pretty Printing API}, for more
23418 @node Objfiles In Python
23419 @subsubsection Objfiles In Python
23421 @cindex objfiles in python
23422 @tindex gdb.Objfile
23424 @value{GDBN} loads symbols for an inferior from various
23425 symbol-containing files (@pxref{Files}). These include the primary
23426 executable file, any shared libraries used by the inferior, and any
23427 separate debug info files (@pxref{Separate Debug Files}).
23428 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
23430 The following objfile-related functions are available in the
23433 @findex gdb.current_objfile
23434 @defun gdb.current_objfile ()
23435 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
23436 sets the ``current objfile'' to the corresponding objfile. This
23437 function returns the current objfile. If there is no current objfile,
23438 this function returns @code{None}.
23441 @findex gdb.objfiles
23442 @defun gdb.objfiles ()
23443 Return a sequence of all the objfiles current known to @value{GDBN}.
23444 @xref{Objfiles In Python}.
23447 Each objfile is represented by an instance of the @code{gdb.Objfile}
23450 @defvar Objfile.filename
23451 The file name of the objfile as a string.
23454 @defvar Objfile.pretty_printers
23455 The @code{pretty_printers} attribute is a list of functions. It is
23456 used to look up pretty-printers. A @code{Value} is passed to each
23457 function in order; if the function returns @code{None}, then the
23458 search continues. Otherwise, the return value should be an object
23459 which is used to format the value. @xref{Pretty Printing API}, for more
23463 A @code{gdb.Objfile} object has the following methods:
23465 @defun Objfile.is_valid ()
23466 Returns @code{True} if the @code{gdb.Objfile} object is valid,
23467 @code{False} if not. A @code{gdb.Objfile} object can become invalid
23468 if the object file it refers to is not loaded in @value{GDBN} any
23469 longer. All other @code{gdb.Objfile} methods will throw an exception
23470 if it is invalid at the time the method is called.
23473 @node Frames In Python
23474 @subsubsection Accessing inferior stack frames from Python.
23476 @cindex frames in python
23477 When the debugged program stops, @value{GDBN} is able to analyze its call
23478 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
23479 represents a frame in the stack. A @code{gdb.Frame} object is only valid
23480 while its corresponding frame exists in the inferior's stack. If you try
23481 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
23482 exception (@pxref{Exception Handling}).
23484 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
23488 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
23492 The following frame-related functions are available in the @code{gdb} module:
23494 @findex gdb.selected_frame
23495 @defun gdb.selected_frame ()
23496 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
23499 @findex gdb.newest_frame
23500 @defun gdb.newest_frame ()
23501 Return the newest frame object for the selected thread.
23504 @defun gdb.frame_stop_reason_string (reason)
23505 Return a string explaining the reason why @value{GDBN} stopped unwinding
23506 frames, as expressed by the given @var{reason} code (an integer, see the
23507 @code{unwind_stop_reason} method further down in this section).
23510 A @code{gdb.Frame} object has the following methods:
23513 @defun Frame.is_valid ()
23514 Returns true if the @code{gdb.Frame} object is valid, false if not.
23515 A frame object can become invalid if the frame it refers to doesn't
23516 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
23517 an exception if it is invalid at the time the method is called.
23520 @defun Frame.name ()
23521 Returns the function name of the frame, or @code{None} if it can't be
23525 @defun Frame.type ()
23526 Returns the type of the frame. The value can be one of:
23528 @item gdb.NORMAL_FRAME
23529 An ordinary stack frame.
23531 @item gdb.DUMMY_FRAME
23532 A fake stack frame that was created by @value{GDBN} when performing an
23533 inferior function call.
23535 @item gdb.INLINE_FRAME
23536 A frame representing an inlined function. The function was inlined
23537 into a @code{gdb.NORMAL_FRAME} that is older than this one.
23539 @item gdb.TAILCALL_FRAME
23540 A frame representing a tail call. @xref{Tail Call Frames}.
23542 @item gdb.SIGTRAMP_FRAME
23543 A signal trampoline frame. This is the frame created by the OS when
23544 it calls into a signal handler.
23546 @item gdb.ARCH_FRAME
23547 A fake stack frame representing a cross-architecture call.
23549 @item gdb.SENTINEL_FRAME
23550 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
23555 @defun Frame.unwind_stop_reason ()
23556 Return an integer representing the reason why it's not possible to find
23557 more frames toward the outermost frame. Use
23558 @code{gdb.frame_stop_reason_string} to convert the value returned by this
23559 function to a string. The value can be one of:
23562 @item gdb.FRAME_UNWIND_NO_REASON
23563 No particular reason (older frames should be available).
23565 @item gdb.FRAME_UNWIND_NULL_ID
23566 The previous frame's analyzer returns an invalid result.
23568 @item gdb.FRAME_UNWIND_OUTERMOST
23569 This frame is the outermost.
23571 @item gdb.FRAME_UNWIND_UNAVAILABLE
23572 Cannot unwind further, because that would require knowing the
23573 values of registers or memory that have not been collected.
23575 @item gdb.FRAME_UNWIND_INNER_ID
23576 This frame ID looks like it ought to belong to a NEXT frame,
23577 but we got it for a PREV frame. Normally, this is a sign of
23578 unwinder failure. It could also indicate stack corruption.
23580 @item gdb.FRAME_UNWIND_SAME_ID
23581 This frame has the same ID as the previous one. That means
23582 that unwinding further would almost certainly give us another
23583 frame with exactly the same ID, so break the chain. Normally,
23584 this is a sign of unwinder failure. It could also indicate
23587 @item gdb.FRAME_UNWIND_NO_SAVED_PC
23588 The frame unwinder did not find any saved PC, but we needed
23589 one to unwind further.
23591 @item gdb.FRAME_UNWIND_FIRST_ERROR
23592 Any stop reason greater or equal to this value indicates some kind
23593 of error. This special value facilitates writing code that tests
23594 for errors in unwinding in a way that will work correctly even if
23595 the list of the other values is modified in future @value{GDBN}
23596 versions. Using it, you could write:
23598 reason = gdb.selected_frame().unwind_stop_reason ()
23599 reason_str = gdb.frame_stop_reason_string (reason)
23600 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
23601 print "An error occured: %s" % reason_str
23608 Returns the frame's resume address.
23611 @defun Frame.block ()
23612 Return the frame's code block. @xref{Blocks In Python}.
23615 @defun Frame.function ()
23616 Return the symbol for the function corresponding to this frame.
23617 @xref{Symbols In Python}.
23620 @defun Frame.older ()
23621 Return the frame that called this frame.
23624 @defun Frame.newer ()
23625 Return the frame called by this frame.
23628 @defun Frame.find_sal ()
23629 Return the frame's symtab and line object.
23630 @xref{Symbol Tables In Python}.
23633 @defun Frame.read_var (variable @r{[}, block@r{]})
23634 Return the value of @var{variable} in this frame. If the optional
23635 argument @var{block} is provided, search for the variable from that
23636 block; otherwise start at the frame's current block (which is
23637 determined by the frame's current program counter). @var{variable}
23638 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
23639 @code{gdb.Block} object.
23642 @defun Frame.select ()
23643 Set this frame to be the selected frame. @xref{Stack, ,Examining the
23648 @node Blocks In Python
23649 @subsubsection Accessing frame blocks from Python.
23651 @cindex blocks in python
23654 Within each frame, @value{GDBN} maintains information on each block
23655 stored in that frame. These blocks are organized hierarchically, and
23656 are represented individually in Python as a @code{gdb.Block}.
23657 Please see @ref{Frames In Python}, for a more in-depth discussion on
23658 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
23659 detailed technical information on @value{GDBN}'s book-keeping of the
23662 The following block-related functions are available in the @code{gdb}
23665 @findex gdb.block_for_pc
23666 @defun gdb.block_for_pc (pc)
23667 Return the @code{gdb.Block} containing the given @var{pc} value. If the
23668 block cannot be found for the @var{pc} value specified, the function
23669 will return @code{None}.
23672 A @code{gdb.Block} object has the following methods:
23675 @defun Block.is_valid ()
23676 Returns @code{True} if the @code{gdb.Block} object is valid,
23677 @code{False} if not. A block object can become invalid if the block it
23678 refers to doesn't exist anymore in the inferior. All other
23679 @code{gdb.Block} methods will throw an exception if it is invalid at
23680 the time the method is called. This method is also made available to
23681 the Python iterator object that @code{gdb.Block} provides in an iteration
23682 context and via the Python @code{iter} built-in function.
23686 A @code{gdb.Block} object has the following attributes:
23689 @defvar Block.start
23690 The start address of the block. This attribute is not writable.
23694 The end address of the block. This attribute is not writable.
23697 @defvar Block.function
23698 The name of the block represented as a @code{gdb.Symbol}. If the
23699 block is not named, then this attribute holds @code{None}. This
23700 attribute is not writable.
23703 @defvar Block.superblock
23704 The block containing this block. If this parent block does not exist,
23705 this attribute holds @code{None}. This attribute is not writable.
23708 @defvar Block.global_block
23709 The global block associated with this block. This attribute is not
23713 @defvar Block.static_block
23714 The static block associated with this block. This attribute is not
23718 @defvar Block.is_global
23719 @code{True} if the @code{gdb.Block} object is a global block,
23720 @code{False} if not. This attribute is not
23724 @defvar Block.is_static
23725 @code{True} if the @code{gdb.Block} object is a static block,
23726 @code{False} if not. This attribute is not writable.
23730 @node Symbols In Python
23731 @subsubsection Python representation of Symbols.
23733 @cindex symbols in python
23736 @value{GDBN} represents every variable, function and type as an
23737 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
23738 Similarly, Python represents these symbols in @value{GDBN} with the
23739 @code{gdb.Symbol} object.
23741 The following symbol-related functions are available in the @code{gdb}
23744 @findex gdb.lookup_symbol
23745 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
23746 This function searches for a symbol by name. The search scope can be
23747 restricted to the parameters defined in the optional domain and block
23750 @var{name} is the name of the symbol. It must be a string. The
23751 optional @var{block} argument restricts the search to symbols visible
23752 in that @var{block}. The @var{block} argument must be a
23753 @code{gdb.Block} object. If omitted, the block for the current frame
23754 is used. The optional @var{domain} argument restricts
23755 the search to the domain type. The @var{domain} argument must be a
23756 domain constant defined in the @code{gdb} module and described later
23759 The result is a tuple of two elements.
23760 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
23762 If the symbol is found, the second element is @code{True} if the symbol
23763 is a field of a method's object (e.g., @code{this} in C@t{++}),
23764 otherwise it is @code{False}.
23765 If the symbol is not found, the second element is @code{False}.
23768 @findex gdb.lookup_global_symbol
23769 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
23770 This function searches for a global symbol by name.
23771 The search scope can be restricted to by the domain argument.
23773 @var{name} is the name of the symbol. It must be a string.
23774 The optional @var{domain} argument restricts the search to the domain type.
23775 The @var{domain} argument must be a domain constant defined in the @code{gdb}
23776 module and described later in this chapter.
23778 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
23782 A @code{gdb.Symbol} object has the following attributes:
23785 @defvar Symbol.type
23786 The type of the symbol or @code{None} if no type is recorded.
23787 This attribute is represented as a @code{gdb.Type} object.
23788 @xref{Types In Python}. This attribute is not writable.
23791 @defvar Symbol.symtab
23792 The symbol table in which the symbol appears. This attribute is
23793 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
23794 Python}. This attribute is not writable.
23797 @defvar Symbol.name
23798 The name of the symbol as a string. This attribute is not writable.
23801 @defvar Symbol.linkage_name
23802 The name of the symbol, as used by the linker (i.e., may be mangled).
23803 This attribute is not writable.
23806 @defvar Symbol.print_name
23807 The name of the symbol in a form suitable for output. This is either
23808 @code{name} or @code{linkage_name}, depending on whether the user
23809 asked @value{GDBN} to display demangled or mangled names.
23812 @defvar Symbol.addr_class
23813 The address class of the symbol. This classifies how to find the value
23814 of a symbol. Each address class is a constant defined in the
23815 @code{gdb} module and described later in this chapter.
23818 @defvar Symbol.is_argument
23819 @code{True} if the symbol is an argument of a function.
23822 @defvar Symbol.is_constant
23823 @code{True} if the symbol is a constant.
23826 @defvar Symbol.is_function
23827 @code{True} if the symbol is a function or a method.
23830 @defvar Symbol.is_variable
23831 @code{True} if the symbol is a variable.
23835 A @code{gdb.Symbol} object has the following methods:
23838 @defun Symbol.is_valid ()
23839 Returns @code{True} if the @code{gdb.Symbol} object is valid,
23840 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
23841 the symbol it refers to does not exist in @value{GDBN} any longer.
23842 All other @code{gdb.Symbol} methods will throw an exception if it is
23843 invalid at the time the method is called.
23847 The available domain categories in @code{gdb.Symbol} are represented
23848 as constants in the @code{gdb} module:
23851 @findex SYMBOL_UNDEF_DOMAIN
23852 @findex gdb.SYMBOL_UNDEF_DOMAIN
23853 @item gdb.SYMBOL_UNDEF_DOMAIN
23854 This is used when a domain has not been discovered or none of the
23855 following domains apply. This usually indicates an error either
23856 in the symbol information or in @value{GDBN}'s handling of symbols.
23857 @findex SYMBOL_VAR_DOMAIN
23858 @findex gdb.SYMBOL_VAR_DOMAIN
23859 @item gdb.SYMBOL_VAR_DOMAIN
23860 This domain contains variables, function names, typedef names and enum
23862 @findex SYMBOL_STRUCT_DOMAIN
23863 @findex gdb.SYMBOL_STRUCT_DOMAIN
23864 @item gdb.SYMBOL_STRUCT_DOMAIN
23865 This domain holds struct, union and enum type names.
23866 @findex SYMBOL_LABEL_DOMAIN
23867 @findex gdb.SYMBOL_LABEL_DOMAIN
23868 @item gdb.SYMBOL_LABEL_DOMAIN
23869 This domain contains names of labels (for gotos).
23870 @findex SYMBOL_VARIABLES_DOMAIN
23871 @findex gdb.SYMBOL_VARIABLES_DOMAIN
23872 @item gdb.SYMBOL_VARIABLES_DOMAIN
23873 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
23874 contains everything minus functions and types.
23875 @findex SYMBOL_FUNCTIONS_DOMAIN
23876 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
23877 @item gdb.SYMBOL_FUNCTION_DOMAIN
23878 This domain contains all functions.
23879 @findex SYMBOL_TYPES_DOMAIN
23880 @findex gdb.SYMBOL_TYPES_DOMAIN
23881 @item gdb.SYMBOL_TYPES_DOMAIN
23882 This domain contains all types.
23885 The available address class categories in @code{gdb.Symbol} are represented
23886 as constants in the @code{gdb} module:
23889 @findex SYMBOL_LOC_UNDEF
23890 @findex gdb.SYMBOL_LOC_UNDEF
23891 @item gdb.SYMBOL_LOC_UNDEF
23892 If this is returned by address class, it indicates an error either in
23893 the symbol information or in @value{GDBN}'s handling of symbols.
23894 @findex SYMBOL_LOC_CONST
23895 @findex gdb.SYMBOL_LOC_CONST
23896 @item gdb.SYMBOL_LOC_CONST
23897 Value is constant int.
23898 @findex SYMBOL_LOC_STATIC
23899 @findex gdb.SYMBOL_LOC_STATIC
23900 @item gdb.SYMBOL_LOC_STATIC
23901 Value is at a fixed address.
23902 @findex SYMBOL_LOC_REGISTER
23903 @findex gdb.SYMBOL_LOC_REGISTER
23904 @item gdb.SYMBOL_LOC_REGISTER
23905 Value is in a register.
23906 @findex SYMBOL_LOC_ARG
23907 @findex gdb.SYMBOL_LOC_ARG
23908 @item gdb.SYMBOL_LOC_ARG
23909 Value is an argument. This value is at the offset stored within the
23910 symbol inside the frame's argument list.
23911 @findex SYMBOL_LOC_REF_ARG
23912 @findex gdb.SYMBOL_LOC_REF_ARG
23913 @item gdb.SYMBOL_LOC_REF_ARG
23914 Value address is stored in the frame's argument list. Just like
23915 @code{LOC_ARG} except that the value's address is stored at the
23916 offset, not the value itself.
23917 @findex SYMBOL_LOC_REGPARM_ADDR
23918 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
23919 @item gdb.SYMBOL_LOC_REGPARM_ADDR
23920 Value is a specified register. Just like @code{LOC_REGISTER} except
23921 the register holds the address of the argument instead of the argument
23923 @findex SYMBOL_LOC_LOCAL
23924 @findex gdb.SYMBOL_LOC_LOCAL
23925 @item gdb.SYMBOL_LOC_LOCAL
23926 Value is a local variable.
23927 @findex SYMBOL_LOC_TYPEDEF
23928 @findex gdb.SYMBOL_LOC_TYPEDEF
23929 @item gdb.SYMBOL_LOC_TYPEDEF
23930 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
23932 @findex SYMBOL_LOC_BLOCK
23933 @findex gdb.SYMBOL_LOC_BLOCK
23934 @item gdb.SYMBOL_LOC_BLOCK
23936 @findex SYMBOL_LOC_CONST_BYTES
23937 @findex gdb.SYMBOL_LOC_CONST_BYTES
23938 @item gdb.SYMBOL_LOC_CONST_BYTES
23939 Value is a byte-sequence.
23940 @findex SYMBOL_LOC_UNRESOLVED
23941 @findex gdb.SYMBOL_LOC_UNRESOLVED
23942 @item gdb.SYMBOL_LOC_UNRESOLVED
23943 Value is at a fixed address, but the address of the variable has to be
23944 determined from the minimal symbol table whenever the variable is
23946 @findex SYMBOL_LOC_OPTIMIZED_OUT
23947 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
23948 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
23949 The value does not actually exist in the program.
23950 @findex SYMBOL_LOC_COMPUTED
23951 @findex gdb.SYMBOL_LOC_COMPUTED
23952 @item gdb.SYMBOL_LOC_COMPUTED
23953 The value's address is a computed location.
23956 @node Symbol Tables In Python
23957 @subsubsection Symbol table representation in Python.
23959 @cindex symbol tables in python
23961 @tindex gdb.Symtab_and_line
23963 Access to symbol table data maintained by @value{GDBN} on the inferior
23964 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
23965 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
23966 from the @code{find_sal} method in @code{gdb.Frame} object.
23967 @xref{Frames In Python}.
23969 For more information on @value{GDBN}'s symbol table management, see
23970 @ref{Symbols, ,Examining the Symbol Table}, for more information.
23972 A @code{gdb.Symtab_and_line} object has the following attributes:
23975 @defvar Symtab_and_line.symtab
23976 The symbol table object (@code{gdb.Symtab}) for this frame.
23977 This attribute is not writable.
23980 @defvar Symtab_and_line.pc
23981 Indicates the current program counter address. This attribute is not
23985 @defvar Symtab_and_line.line
23986 Indicates the current line number for this object. This
23987 attribute is not writable.
23991 A @code{gdb.Symtab_and_line} object has the following methods:
23994 @defun Symtab_and_line.is_valid ()
23995 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
23996 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
23997 invalid if the Symbol table and line object it refers to does not
23998 exist in @value{GDBN} any longer. All other
23999 @code{gdb.Symtab_and_line} methods will throw an exception if it is
24000 invalid at the time the method is called.
24004 A @code{gdb.Symtab} object has the following attributes:
24007 @defvar Symtab.filename
24008 The symbol table's source filename. This attribute is not writable.
24011 @defvar Symtab.objfile
24012 The symbol table's backing object file. @xref{Objfiles In Python}.
24013 This attribute is not writable.
24017 A @code{gdb.Symtab} object has the following methods:
24020 @defun Symtab.is_valid ()
24021 Returns @code{True} if the @code{gdb.Symtab} object is valid,
24022 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
24023 the symbol table it refers to does not exist in @value{GDBN} any
24024 longer. All other @code{gdb.Symtab} methods will throw an exception
24025 if it is invalid at the time the method is called.
24028 @defun Symtab.fullname ()
24029 Return the symbol table's source absolute file name.
24033 @node Breakpoints In Python
24034 @subsubsection Manipulating breakpoints using Python
24036 @cindex breakpoints in python
24037 @tindex gdb.Breakpoint
24039 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
24042 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal@r{]]]})
24043 Create a new breakpoint. @var{spec} is a string naming the
24044 location of the breakpoint, or an expression that defines a
24045 watchpoint. The contents can be any location recognized by the
24046 @code{break} command, or in the case of a watchpoint, by the @code{watch}
24047 command. The optional @var{type} denotes the breakpoint to create
24048 from the types defined later in this chapter. This argument can be
24049 either: @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
24050 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal} argument
24051 allows the breakpoint to become invisible to the user. The breakpoint
24052 will neither be reported when created, nor will it be listed in the
24053 output from @code{info breakpoints} (but will be listed with the
24054 @code{maint info breakpoints} command). The optional @var{wp_class}
24055 argument defines the class of watchpoint to create, if @var{type} is
24056 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it is
24057 assumed to be a @code{gdb.WP_WRITE} class.
24060 @defun Breakpoint.stop (self)
24061 The @code{gdb.Breakpoint} class can be sub-classed and, in
24062 particular, you may choose to implement the @code{stop} method.
24063 If this method is defined as a sub-class of @code{gdb.Breakpoint},
24064 it will be called when the inferior reaches any location of a
24065 breakpoint which instantiates that sub-class. If the method returns
24066 @code{True}, the inferior will be stopped at the location of the
24067 breakpoint, otherwise the inferior will continue.
24069 If there are multiple breakpoints at the same location with a
24070 @code{stop} method, each one will be called regardless of the
24071 return status of the previous. This ensures that all @code{stop}
24072 methods have a chance to execute at that location. In this scenario
24073 if one of the methods returns @code{True} but the others return
24074 @code{False}, the inferior will still be stopped.
24076 You should not alter the execution state of the inferior (i.e.@:, step,
24077 next, etc.), alter the current frame context (i.e.@:, change the current
24078 active frame), or alter, add or delete any breakpoint. As a general
24079 rule, you should not alter any data within @value{GDBN} or the inferior
24082 Example @code{stop} implementation:
24085 class MyBreakpoint (gdb.Breakpoint):
24087 inf_val = gdb.parse_and_eval("foo")
24094 The available watchpoint types represented by constants are defined in the
24099 @findex gdb.WP_READ
24101 Read only watchpoint.
24104 @findex gdb.WP_WRITE
24106 Write only watchpoint.
24109 @findex gdb.WP_ACCESS
24110 @item gdb.WP_ACCESS
24111 Read/Write watchpoint.
24114 @defun Breakpoint.is_valid ()
24115 Return @code{True} if this @code{Breakpoint} object is valid,
24116 @code{False} otherwise. A @code{Breakpoint} object can become invalid
24117 if the user deletes the breakpoint. In this case, the object still
24118 exists, but the underlying breakpoint does not. In the cases of
24119 watchpoint scope, the watchpoint remains valid even if execution of the
24120 inferior leaves the scope of that watchpoint.
24123 @defun Breakpoint.delete
24124 Permanently deletes the @value{GDBN} breakpoint. This also
24125 invalidates the Python @code{Breakpoint} object. Any further access
24126 to this object's attributes or methods will raise an error.
24129 @defvar Breakpoint.enabled
24130 This attribute is @code{True} if the breakpoint is enabled, and
24131 @code{False} otherwise. This attribute is writable.
24134 @defvar Breakpoint.silent
24135 This attribute is @code{True} if the breakpoint is silent, and
24136 @code{False} otherwise. This attribute is writable.
24138 Note that a breakpoint can also be silent if it has commands and the
24139 first command is @code{silent}. This is not reported by the
24140 @code{silent} attribute.
24143 @defvar Breakpoint.thread
24144 If the breakpoint is thread-specific, this attribute holds the thread
24145 id. If the breakpoint is not thread-specific, this attribute is
24146 @code{None}. This attribute is writable.
24149 @defvar Breakpoint.task
24150 If the breakpoint is Ada task-specific, this attribute holds the Ada task
24151 id. If the breakpoint is not task-specific (or the underlying
24152 language is not Ada), this attribute is @code{None}. This attribute
24156 @defvar Breakpoint.ignore_count
24157 This attribute holds the ignore count for the breakpoint, an integer.
24158 This attribute is writable.
24161 @defvar Breakpoint.number
24162 This attribute holds the breakpoint's number --- the identifier used by
24163 the user to manipulate the breakpoint. This attribute is not writable.
24166 @defvar Breakpoint.type
24167 This attribute holds the breakpoint's type --- the identifier used to
24168 determine the actual breakpoint type or use-case. This attribute is not
24172 @defvar Breakpoint.visible
24173 This attribute tells whether the breakpoint is visible to the user
24174 when set, or when the @samp{info breakpoints} command is run. This
24175 attribute is not writable.
24178 The available types are represented by constants defined in the @code{gdb}
24182 @findex BP_BREAKPOINT
24183 @findex gdb.BP_BREAKPOINT
24184 @item gdb.BP_BREAKPOINT
24185 Normal code breakpoint.
24187 @findex BP_WATCHPOINT
24188 @findex gdb.BP_WATCHPOINT
24189 @item gdb.BP_WATCHPOINT
24190 Watchpoint breakpoint.
24192 @findex BP_HARDWARE_WATCHPOINT
24193 @findex gdb.BP_HARDWARE_WATCHPOINT
24194 @item gdb.BP_HARDWARE_WATCHPOINT
24195 Hardware assisted watchpoint.
24197 @findex BP_READ_WATCHPOINT
24198 @findex gdb.BP_READ_WATCHPOINT
24199 @item gdb.BP_READ_WATCHPOINT
24200 Hardware assisted read watchpoint.
24202 @findex BP_ACCESS_WATCHPOINT
24203 @findex gdb.BP_ACCESS_WATCHPOINT
24204 @item gdb.BP_ACCESS_WATCHPOINT
24205 Hardware assisted access watchpoint.
24208 @defvar Breakpoint.hit_count
24209 This attribute holds the hit count for the breakpoint, an integer.
24210 This attribute is writable, but currently it can only be set to zero.
24213 @defvar Breakpoint.location
24214 This attribute holds the location of the breakpoint, as specified by
24215 the user. It is a string. If the breakpoint does not have a location
24216 (that is, it is a watchpoint) the attribute's value is @code{None}. This
24217 attribute is not writable.
24220 @defvar Breakpoint.expression
24221 This attribute holds a breakpoint expression, as specified by
24222 the user. It is a string. If the breakpoint does not have an
24223 expression (the breakpoint is not a watchpoint) the attribute's value
24224 is @code{None}. This attribute is not writable.
24227 @defvar Breakpoint.condition
24228 This attribute holds the condition of the breakpoint, as specified by
24229 the user. It is a string. If there is no condition, this attribute's
24230 value is @code{None}. This attribute is writable.
24233 @defvar Breakpoint.commands
24234 This attribute holds the commands attached to the breakpoint. If
24235 there are commands, this attribute's value is a string holding all the
24236 commands, separated by newlines. If there are no commands, this
24237 attribute is @code{None}. This attribute is not writable.
24240 @node Lazy Strings In Python
24241 @subsubsection Python representation of lazy strings.
24243 @cindex lazy strings in python
24244 @tindex gdb.LazyString
24246 A @dfn{lazy string} is a string whose contents is not retrieved or
24247 encoded until it is needed.
24249 A @code{gdb.LazyString} is represented in @value{GDBN} as an
24250 @code{address} that points to a region of memory, an @code{encoding}
24251 that will be used to encode that region of memory, and a @code{length}
24252 to delimit the region of memory that represents the string. The
24253 difference between a @code{gdb.LazyString} and a string wrapped within
24254 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
24255 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
24256 retrieved and encoded during printing, while a @code{gdb.Value}
24257 wrapping a string is immediately retrieved and encoded on creation.
24259 A @code{gdb.LazyString} object has the following functions:
24261 @defun LazyString.value ()
24262 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
24263 will point to the string in memory, but will lose all the delayed
24264 retrieval, encoding and handling that @value{GDBN} applies to a
24265 @code{gdb.LazyString}.
24268 @defvar LazyString.address
24269 This attribute holds the address of the string. This attribute is not
24273 @defvar LazyString.length
24274 This attribute holds the length of the string in characters. If the
24275 length is -1, then the string will be fetched and encoded up to the
24276 first null of appropriate width. This attribute is not writable.
24279 @defvar LazyString.encoding
24280 This attribute holds the encoding that will be applied to the string
24281 when the string is printed by @value{GDBN}. If the encoding is not
24282 set, or contains an empty string, then @value{GDBN} will select the
24283 most appropriate encoding when the string is printed. This attribute
24287 @defvar LazyString.type
24288 This attribute holds the type that is represented by the lazy string's
24289 type. For a lazy string this will always be a pointer type. To
24290 resolve this to the lazy string's character type, use the type's
24291 @code{target} method. @xref{Types In Python}. This attribute is not
24296 @subsection Auto-loading
24297 @cindex auto-loading, Python
24299 When a new object file is read (for example, due to the @code{file}
24300 command, or because the inferior has loaded a shared library),
24301 @value{GDBN} will look for Python support scripts in several ways:
24302 @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section.
24305 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
24306 * .debug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
24307 * Which flavor to choose?::
24310 The auto-loading feature is useful for supplying application-specific
24311 debugging commands and scripts.
24313 Auto-loading can be enabled or disabled,
24314 and the list of auto-loaded scripts can be printed.
24317 @kindex set auto-load-scripts
24318 @item set auto-load-scripts [yes|no]
24319 Enable or disable the auto-loading of Python scripts.
24321 @kindex show auto-load-scripts
24322 @item show auto-load-scripts
24323 Show whether auto-loading of Python scripts is enabled or disabled.
24325 @kindex info auto-load-scripts
24326 @cindex print list of auto-loaded scripts
24327 @item info auto-load-scripts [@var{regexp}]
24328 Print the list of all scripts that @value{GDBN} auto-loaded.
24330 Also printed is the list of scripts that were mentioned in
24331 the @code{.debug_gdb_scripts} section and were not found
24332 (@pxref{.debug_gdb_scripts section}).
24333 This is useful because their names are not printed when @value{GDBN}
24334 tries to load them and fails. There may be many of them, and printing
24335 an error message for each one is problematic.
24337 If @var{regexp} is supplied only scripts with matching names are printed.
24342 (gdb) info auto-load-scripts
24344 Yes py-section-script.py
24345 full name: /tmp/py-section-script.py
24346 Missing my-foo-pretty-printers.py
24350 When reading an auto-loaded file, @value{GDBN} sets the
24351 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
24352 function (@pxref{Objfiles In Python}). This can be useful for
24353 registering objfile-specific pretty-printers.
24355 @node objfile-gdb.py file
24356 @subsubsection The @file{@var{objfile}-gdb.py} file
24357 @cindex @file{@var{objfile}-gdb.py}
24359 When a new object file is read, @value{GDBN} looks for
24360 a file named @file{@var{objfile}-gdb.py},
24361 where @var{objfile} is the object file's real name, formed by ensuring
24362 that the file name is absolute, following all symlinks, and resolving
24363 @code{.} and @code{..} components. If this file exists and is
24364 readable, @value{GDBN} will evaluate it as a Python script.
24366 If this file does not exist, and if the parameter
24367 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
24368 then @value{GDBN} will look for @var{real-name} in all of the
24369 directories mentioned in the value of @code{debug-file-directory}.
24371 Finally, if this file does not exist, then @value{GDBN} will look for
24372 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
24373 @var{data-directory} is @value{GDBN}'s data directory (available via
24374 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
24375 is the object file's real name, as described above.
24377 @value{GDBN} does not track which files it has already auto-loaded this way.
24378 @value{GDBN} will load the associated script every time the corresponding
24379 @var{objfile} is opened.
24380 So your @file{-gdb.py} file should be careful to avoid errors if it
24381 is evaluated more than once.
24383 @node .debug_gdb_scripts section
24384 @subsubsection The @code{.debug_gdb_scripts} section
24385 @cindex @code{.debug_gdb_scripts} section
24387 For systems using file formats like ELF and COFF,
24388 when @value{GDBN} loads a new object file
24389 it will look for a special section named @samp{.debug_gdb_scripts}.
24390 If this section exists, its contents is a list of names of scripts to load.
24392 @value{GDBN} will look for each specified script file first in the
24393 current directory and then along the source search path
24394 (@pxref{Source Path, ,Specifying Source Directories}),
24395 except that @file{$cdir} is not searched, since the compilation
24396 directory is not relevant to scripts.
24398 Entries can be placed in section @code{.debug_gdb_scripts} with,
24399 for example, this GCC macro:
24402 /* Note: The "MS" section flags are to remove duplicates. */
24403 #define DEFINE_GDB_SCRIPT(script_name) \
24405 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
24407 .asciz \"" script_name "\"\n\
24413 Then one can reference the macro in a header or source file like this:
24416 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
24419 The script name may include directories if desired.
24421 If the macro is put in a header, any application or library
24422 using this header will get a reference to the specified script.
24424 @node Which flavor to choose?
24425 @subsubsection Which flavor to choose?
24427 Given the multiple ways of auto-loading Python scripts, it might not always
24428 be clear which one to choose. This section provides some guidance.
24430 Benefits of the @file{-gdb.py} way:
24434 Can be used with file formats that don't support multiple sections.
24437 Ease of finding scripts for public libraries.
24439 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
24440 in the source search path.
24441 For publicly installed libraries, e.g., @file{libstdc++}, there typically
24442 isn't a source directory in which to find the script.
24445 Doesn't require source code additions.
24448 Benefits of the @code{.debug_gdb_scripts} way:
24452 Works with static linking.
24454 Scripts for libraries done the @file{-gdb.py} way require an objfile to
24455 trigger their loading. When an application is statically linked the only
24456 objfile available is the executable, and it is cumbersome to attach all the
24457 scripts from all the input libraries to the executable's @file{-gdb.py} script.
24460 Works with classes that are entirely inlined.
24462 Some classes can be entirely inlined, and thus there may not be an associated
24463 shared library to attach a @file{-gdb.py} script to.
24466 Scripts needn't be copied out of the source tree.
24468 In some circumstances, apps can be built out of large collections of internal
24469 libraries, and the build infrastructure necessary to install the
24470 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
24471 cumbersome. It may be easier to specify the scripts in the
24472 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
24473 top of the source tree to the source search path.
24476 @node Python modules
24477 @subsection Python modules
24478 @cindex python modules
24480 @value{GDBN} comes with several modules to assist writing Python code.
24483 * gdb.printing:: Building and registering pretty-printers.
24484 * gdb.types:: Utilities for working with types.
24485 * gdb.prompt:: Utilities for prompt value substitution.
24489 @subsubsection gdb.printing
24490 @cindex gdb.printing
24492 This module provides a collection of utilities for working with
24496 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
24497 This class specifies the API that makes @samp{info pretty-printer},
24498 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
24499 Pretty-printers should generally inherit from this class.
24501 @item SubPrettyPrinter (@var{name})
24502 For printers that handle multiple types, this class specifies the
24503 corresponding API for the subprinters.
24505 @item RegexpCollectionPrettyPrinter (@var{name})
24506 Utility class for handling multiple printers, all recognized via
24507 regular expressions.
24508 @xref{Writing a Pretty-Printer}, for an example.
24510 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
24511 Register @var{printer} with the pretty-printer list of @var{obj}.
24512 If @var{replace} is @code{True} then any existing copy of the printer
24513 is replaced. Otherwise a @code{RuntimeError} exception is raised
24514 if a printer with the same name already exists.
24518 @subsubsection gdb.types
24521 This module provides a collection of utilities for working with
24522 @code{gdb.Types} objects.
24525 @item get_basic_type (@var{type})
24526 Return @var{type} with const and volatile qualifiers stripped,
24527 and with typedefs and C@t{++} references converted to the underlying type.
24532 typedef const int const_int;
24534 const_int& foo_ref (foo);
24535 int main () @{ return 0; @}
24542 (gdb) python import gdb.types
24543 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
24544 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
24548 @item has_field (@var{type}, @var{field})
24549 Return @code{True} if @var{type}, assumed to be a type with fields
24550 (e.g., a structure or union), has field @var{field}.
24552 @item make_enum_dict (@var{enum_type})
24553 Return a Python @code{dictionary} type produced from @var{enum_type}.
24555 @item deep_items (@var{type})
24556 Returns a Python iterator similar to the standard
24557 @code{gdb.Type.iteritems} method, except that the iterator returned
24558 by @code{deep_items} will recursively traverse anonymous struct or
24559 union fields. For example:
24573 Then in @value{GDBN}:
24575 (@value{GDBP}) python import gdb.types
24576 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
24577 (@value{GDBP}) python print struct_a.keys ()
24579 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
24580 @{['a', 'b0', 'b1']@}
24586 @subsubsection gdb.prompt
24589 This module provides a method for prompt value-substitution.
24592 @item substitute_prompt (@var{string})
24593 Return @var{string} with escape sequences substituted by values. Some
24594 escape sequences take arguments. You can specify arguments inside
24595 ``@{@}'' immediately following the escape sequence.
24597 The escape sequences you can pass to this function are:
24601 Substitute a backslash.
24603 Substitute an ESC character.
24605 Substitute the selected frame; an argument names a frame parameter.
24607 Substitute a newline.
24609 Substitute a parameter's value; the argument names the parameter.
24611 Substitute a carriage return.
24613 Substitute the selected thread; an argument names a thread parameter.
24615 Substitute the version of GDB.
24617 Substitute the current working directory.
24619 Begin a sequence of non-printing characters. These sequences are
24620 typically used with the ESC character, and are not counted in the string
24621 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
24622 blue-colored ``(gdb)'' prompt where the length is five.
24624 End a sequence of non-printing characters.
24630 substitute_prompt (``frame: \f,
24631 print arguments: \p@{print frame-arguments@}'')
24634 @exdent will return the string:
24637 "frame: main, print arguments: scalars"
24642 @section Creating new spellings of existing commands
24643 @cindex aliases for commands
24645 It is often useful to define alternate spellings of existing commands.
24646 For example, if a new @value{GDBN} command defined in Python has
24647 a long name to type, it is handy to have an abbreviated version of it
24648 that involves less typing.
24650 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
24651 of the @samp{step} command even though it is otherwise an ambiguous
24652 abbreviation of other commands like @samp{set} and @samp{show}.
24654 Aliases are also used to provide shortened or more common versions
24655 of multi-word commands. For example, @value{GDBN} provides the
24656 @samp{tty} alias of the @samp{set inferior-tty} command.
24658 You can define a new alias with the @samp{alias} command.
24663 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
24667 @var{ALIAS} specifies the name of the new alias.
24668 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
24671 @var{COMMAND} specifies the name of an existing command
24672 that is being aliased.
24674 The @samp{-a} option specifies that the new alias is an abbreviation
24675 of the command. Abbreviations are not shown in command
24676 lists displayed by the @samp{help} command.
24678 The @samp{--} option specifies the end of options,
24679 and is useful when @var{ALIAS} begins with a dash.
24681 Here is a simple example showing how to make an abbreviation
24682 of a command so that there is less to type.
24683 Suppose you were tired of typing @samp{disas}, the current
24684 shortest unambiguous abbreviation of the @samp{disassemble} command
24685 and you wanted an even shorter version named @samp{di}.
24686 The following will accomplish this.
24689 (gdb) alias -a di = disas
24692 Note that aliases are different from user-defined commands.
24693 With a user-defined command, you also need to write documentation
24694 for it with the @samp{document} command.
24695 An alias automatically picks up the documentation of the existing command.
24697 Here is an example where we make @samp{elms} an abbreviation of
24698 @samp{elements} in the @samp{set print elements} command.
24699 This is to show that you can make an abbreviation of any part
24703 (gdb) alias -a set print elms = set print elements
24704 (gdb) alias -a show print elms = show print elements
24705 (gdb) set p elms 20
24707 Limit on string chars or array elements to print is 200.
24710 Note that if you are defining an alias of a @samp{set} command,
24711 and you want to have an alias for the corresponding @samp{show}
24712 command, then you need to define the latter separately.
24714 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
24715 @var{ALIAS}, just as they are normally.
24718 (gdb) alias -a set pr elms = set p ele
24721 Finally, here is an example showing the creation of a one word
24722 alias for a more complex command.
24723 This creates alias @samp{spe} of the command @samp{set print elements}.
24726 (gdb) alias spe = set print elements
24731 @chapter Command Interpreters
24732 @cindex command interpreters
24734 @value{GDBN} supports multiple command interpreters, and some command
24735 infrastructure to allow users or user interface writers to switch
24736 between interpreters or run commands in other interpreters.
24738 @value{GDBN} currently supports two command interpreters, the console
24739 interpreter (sometimes called the command-line interpreter or @sc{cli})
24740 and the machine interface interpreter (or @sc{gdb/mi}). This manual
24741 describes both of these interfaces in great detail.
24743 By default, @value{GDBN} will start with the console interpreter.
24744 However, the user may choose to start @value{GDBN} with another
24745 interpreter by specifying the @option{-i} or @option{--interpreter}
24746 startup options. Defined interpreters include:
24750 @cindex console interpreter
24751 The traditional console or command-line interpreter. This is the most often
24752 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
24753 @value{GDBN} will use this interpreter.
24756 @cindex mi interpreter
24757 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
24758 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
24759 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
24763 @cindex mi2 interpreter
24764 The current @sc{gdb/mi} interface.
24767 @cindex mi1 interpreter
24768 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
24772 @cindex invoke another interpreter
24773 The interpreter being used by @value{GDBN} may not be dynamically
24774 switched at runtime. Although possible, this could lead to a very
24775 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
24776 enters the command "interpreter-set console" in a console view,
24777 @value{GDBN} would switch to using the console interpreter, rendering
24778 the IDE inoperable!
24780 @kindex interpreter-exec
24781 Although you may only choose a single interpreter at startup, you may execute
24782 commands in any interpreter from the current interpreter using the appropriate
24783 command. If you are running the console interpreter, simply use the
24784 @code{interpreter-exec} command:
24787 interpreter-exec mi "-data-list-register-names"
24790 @sc{gdb/mi} has a similar command, although it is only available in versions of
24791 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
24794 @chapter @value{GDBN} Text User Interface
24796 @cindex Text User Interface
24799 * TUI Overview:: TUI overview
24800 * TUI Keys:: TUI key bindings
24801 * TUI Single Key Mode:: TUI single key mode
24802 * TUI Commands:: TUI-specific commands
24803 * TUI Configuration:: TUI configuration variables
24806 The @value{GDBN} Text User Interface (TUI) is a terminal
24807 interface which uses the @code{curses} library to show the source
24808 file, the assembly output, the program registers and @value{GDBN}
24809 commands in separate text windows. The TUI mode is supported only
24810 on platforms where a suitable version of the @code{curses} library
24813 @pindex @value{GDBTUI}
24814 The TUI mode is enabled by default when you invoke @value{GDBN} as
24815 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
24816 You can also switch in and out of TUI mode while @value{GDBN} runs by
24817 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
24818 @xref{TUI Keys, ,TUI Key Bindings}.
24821 @section TUI Overview
24823 In TUI mode, @value{GDBN} can display several text windows:
24827 This window is the @value{GDBN} command window with the @value{GDBN}
24828 prompt and the @value{GDBN} output. The @value{GDBN} input is still
24829 managed using readline.
24832 The source window shows the source file of the program. The current
24833 line and active breakpoints are displayed in this window.
24836 The assembly window shows the disassembly output of the program.
24839 This window shows the processor registers. Registers are highlighted
24840 when their values change.
24843 The source and assembly windows show the current program position
24844 by highlighting the current line and marking it with a @samp{>} marker.
24845 Breakpoints are indicated with two markers. The first marker
24846 indicates the breakpoint type:
24850 Breakpoint which was hit at least once.
24853 Breakpoint which was never hit.
24856 Hardware breakpoint which was hit at least once.
24859 Hardware breakpoint which was never hit.
24862 The second marker indicates whether the breakpoint is enabled or not:
24866 Breakpoint is enabled.
24869 Breakpoint is disabled.
24872 The source, assembly and register windows are updated when the current
24873 thread changes, when the frame changes, or when the program counter
24876 These windows are not all visible at the same time. The command
24877 window is always visible. The others can be arranged in several
24888 source and assembly,
24891 source and registers, or
24894 assembly and registers.
24897 A status line above the command window shows the following information:
24901 Indicates the current @value{GDBN} target.
24902 (@pxref{Targets, ,Specifying a Debugging Target}).
24905 Gives the current process or thread number.
24906 When no process is being debugged, this field is set to @code{No process}.
24909 Gives the current function name for the selected frame.
24910 The name is demangled if demangling is turned on (@pxref{Print Settings}).
24911 When there is no symbol corresponding to the current program counter,
24912 the string @code{??} is displayed.
24915 Indicates the current line number for the selected frame.
24916 When the current line number is not known, the string @code{??} is displayed.
24919 Indicates the current program counter address.
24923 @section TUI Key Bindings
24924 @cindex TUI key bindings
24926 The TUI installs several key bindings in the readline keymaps
24927 @ifset SYSTEM_READLINE
24928 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
24930 @ifclear SYSTEM_READLINE
24931 (@pxref{Command Line Editing}).
24933 The following key bindings are installed for both TUI mode and the
24934 @value{GDBN} standard mode.
24943 Enter or leave the TUI mode. When leaving the TUI mode,
24944 the curses window management stops and @value{GDBN} operates using
24945 its standard mode, writing on the terminal directly. When reentering
24946 the TUI mode, control is given back to the curses windows.
24947 The screen is then refreshed.
24951 Use a TUI layout with only one window. The layout will
24952 either be @samp{source} or @samp{assembly}. When the TUI mode
24953 is not active, it will switch to the TUI mode.
24955 Think of this key binding as the Emacs @kbd{C-x 1} binding.
24959 Use a TUI layout with at least two windows. When the current
24960 layout already has two windows, the next layout with two windows is used.
24961 When a new layout is chosen, one window will always be common to the
24962 previous layout and the new one.
24964 Think of it as the Emacs @kbd{C-x 2} binding.
24968 Change the active window. The TUI associates several key bindings
24969 (like scrolling and arrow keys) with the active window. This command
24970 gives the focus to the next TUI window.
24972 Think of it as the Emacs @kbd{C-x o} binding.
24976 Switch in and out of the TUI SingleKey mode that binds single
24977 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
24980 The following key bindings only work in the TUI mode:
24985 Scroll the active window one page up.
24989 Scroll the active window one page down.
24993 Scroll the active window one line up.
24997 Scroll the active window one line down.
25001 Scroll the active window one column left.
25005 Scroll the active window one column right.
25009 Refresh the screen.
25012 Because the arrow keys scroll the active window in the TUI mode, they
25013 are not available for their normal use by readline unless the command
25014 window has the focus. When another window is active, you must use
25015 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
25016 and @kbd{C-f} to control the command window.
25018 @node TUI Single Key Mode
25019 @section TUI Single Key Mode
25020 @cindex TUI single key mode
25022 The TUI also provides a @dfn{SingleKey} mode, which binds several
25023 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
25024 switch into this mode, where the following key bindings are used:
25027 @kindex c @r{(SingleKey TUI key)}
25031 @kindex d @r{(SingleKey TUI key)}
25035 @kindex f @r{(SingleKey TUI key)}
25039 @kindex n @r{(SingleKey TUI key)}
25043 @kindex q @r{(SingleKey TUI key)}
25045 exit the SingleKey mode.
25047 @kindex r @r{(SingleKey TUI key)}
25051 @kindex s @r{(SingleKey TUI key)}
25055 @kindex u @r{(SingleKey TUI key)}
25059 @kindex v @r{(SingleKey TUI key)}
25063 @kindex w @r{(SingleKey TUI key)}
25068 Other keys temporarily switch to the @value{GDBN} command prompt.
25069 The key that was pressed is inserted in the editing buffer so that
25070 it is possible to type most @value{GDBN} commands without interaction
25071 with the TUI SingleKey mode. Once the command is entered the TUI
25072 SingleKey mode is restored. The only way to permanently leave
25073 this mode is by typing @kbd{q} or @kbd{C-x s}.
25077 @section TUI-specific Commands
25078 @cindex TUI commands
25080 The TUI has specific commands to control the text windows.
25081 These commands are always available, even when @value{GDBN} is not in
25082 the TUI mode. When @value{GDBN} is in the standard mode, most
25083 of these commands will automatically switch to the TUI mode.
25085 Note that if @value{GDBN}'s @code{stdout} is not connected to a
25086 terminal, or @value{GDBN} has been started with the machine interface
25087 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
25088 these commands will fail with an error, because it would not be
25089 possible or desirable to enable curses window management.
25094 List and give the size of all displayed windows.
25098 Display the next layout.
25101 Display the previous layout.
25104 Display the source window only.
25107 Display the assembly window only.
25110 Display the source and assembly window.
25113 Display the register window together with the source or assembly window.
25117 Make the next window active for scrolling.
25120 Make the previous window active for scrolling.
25123 Make the source window active for scrolling.
25126 Make the assembly window active for scrolling.
25129 Make the register window active for scrolling.
25132 Make the command window active for scrolling.
25136 Refresh the screen. This is similar to typing @kbd{C-L}.
25138 @item tui reg float
25140 Show the floating point registers in the register window.
25142 @item tui reg general
25143 Show the general registers in the register window.
25146 Show the next register group. The list of register groups as well as
25147 their order is target specific. The predefined register groups are the
25148 following: @code{general}, @code{float}, @code{system}, @code{vector},
25149 @code{all}, @code{save}, @code{restore}.
25151 @item tui reg system
25152 Show the system registers in the register window.
25156 Update the source window and the current execution point.
25158 @item winheight @var{name} +@var{count}
25159 @itemx winheight @var{name} -@var{count}
25161 Change the height of the window @var{name} by @var{count}
25162 lines. Positive counts increase the height, while negative counts
25165 @item tabset @var{nchars}
25167 Set the width of tab stops to be @var{nchars} characters.
25170 @node TUI Configuration
25171 @section TUI Configuration Variables
25172 @cindex TUI configuration variables
25174 Several configuration variables control the appearance of TUI windows.
25177 @item set tui border-kind @var{kind}
25178 @kindex set tui border-kind
25179 Select the border appearance for the source, assembly and register windows.
25180 The possible values are the following:
25183 Use a space character to draw the border.
25186 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
25189 Use the Alternate Character Set to draw the border. The border is
25190 drawn using character line graphics if the terminal supports them.
25193 @item set tui border-mode @var{mode}
25194 @kindex set tui border-mode
25195 @itemx set tui active-border-mode @var{mode}
25196 @kindex set tui active-border-mode
25197 Select the display attributes for the borders of the inactive windows
25198 or the active window. The @var{mode} can be one of the following:
25201 Use normal attributes to display the border.
25207 Use reverse video mode.
25210 Use half bright mode.
25212 @item half-standout
25213 Use half bright and standout mode.
25216 Use extra bright or bold mode.
25218 @item bold-standout
25219 Use extra bright or bold and standout mode.
25224 @chapter Using @value{GDBN} under @sc{gnu} Emacs
25227 @cindex @sc{gnu} Emacs
25228 A special interface allows you to use @sc{gnu} Emacs to view (and
25229 edit) the source files for the program you are debugging with
25232 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
25233 executable file you want to debug as an argument. This command starts
25234 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
25235 created Emacs buffer.
25236 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
25238 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
25243 All ``terminal'' input and output goes through an Emacs buffer, called
25246 This applies both to @value{GDBN} commands and their output, and to the input
25247 and output done by the program you are debugging.
25249 This is useful because it means that you can copy the text of previous
25250 commands and input them again; you can even use parts of the output
25253 All the facilities of Emacs' Shell mode are available for interacting
25254 with your program. In particular, you can send signals the usual
25255 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
25259 @value{GDBN} displays source code through Emacs.
25261 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
25262 source file for that frame and puts an arrow (@samp{=>}) at the
25263 left margin of the current line. Emacs uses a separate buffer for
25264 source display, and splits the screen to show both your @value{GDBN} session
25267 Explicit @value{GDBN} @code{list} or search commands still produce output as
25268 usual, but you probably have no reason to use them from Emacs.
25271 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
25272 a graphical mode, enabled by default, which provides further buffers
25273 that can control the execution and describe the state of your program.
25274 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
25276 If you specify an absolute file name when prompted for the @kbd{M-x
25277 gdb} argument, then Emacs sets your current working directory to where
25278 your program resides. If you only specify the file name, then Emacs
25279 sets your current working directory to the directory associated
25280 with the previous buffer. In this case, @value{GDBN} may find your
25281 program by searching your environment's @code{PATH} variable, but on
25282 some operating systems it might not find the source. So, although the
25283 @value{GDBN} input and output session proceeds normally, the auxiliary
25284 buffer does not display the current source and line of execution.
25286 The initial working directory of @value{GDBN} is printed on the top
25287 line of the GUD buffer and this serves as a default for the commands
25288 that specify files for @value{GDBN} to operate on. @xref{Files,
25289 ,Commands to Specify Files}.
25291 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
25292 need to call @value{GDBN} by a different name (for example, if you
25293 keep several configurations around, with different names) you can
25294 customize the Emacs variable @code{gud-gdb-command-name} to run the
25297 In the GUD buffer, you can use these special Emacs commands in
25298 addition to the standard Shell mode commands:
25302 Describe the features of Emacs' GUD Mode.
25305 Execute to another source line, like the @value{GDBN} @code{step} command; also
25306 update the display window to show the current file and location.
25309 Execute to next source line in this function, skipping all function
25310 calls, like the @value{GDBN} @code{next} command. Then update the display window
25311 to show the current file and location.
25314 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
25315 display window accordingly.
25318 Execute until exit from the selected stack frame, like the @value{GDBN}
25319 @code{finish} command.
25322 Continue execution of your program, like the @value{GDBN} @code{continue}
25326 Go up the number of frames indicated by the numeric argument
25327 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
25328 like the @value{GDBN} @code{up} command.
25331 Go down the number of frames indicated by the numeric argument, like the
25332 @value{GDBN} @code{down} command.
25335 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
25336 tells @value{GDBN} to set a breakpoint on the source line point is on.
25338 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
25339 separate frame which shows a backtrace when the GUD buffer is current.
25340 Move point to any frame in the stack and type @key{RET} to make it
25341 become the current frame and display the associated source in the
25342 source buffer. Alternatively, click @kbd{Mouse-2} to make the
25343 selected frame become the current one. In graphical mode, the
25344 speedbar displays watch expressions.
25346 If you accidentally delete the source-display buffer, an easy way to get
25347 it back is to type the command @code{f} in the @value{GDBN} buffer, to
25348 request a frame display; when you run under Emacs, this recreates
25349 the source buffer if necessary to show you the context of the current
25352 The source files displayed in Emacs are in ordinary Emacs buffers
25353 which are visiting the source files in the usual way. You can edit
25354 the files with these buffers if you wish; but keep in mind that @value{GDBN}
25355 communicates with Emacs in terms of line numbers. If you add or
25356 delete lines from the text, the line numbers that @value{GDBN} knows cease
25357 to correspond properly with the code.
25359 A more detailed description of Emacs' interaction with @value{GDBN} is
25360 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
25363 @c The following dropped because Epoch is nonstandard. Reactivate
25364 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
25366 @kindex Emacs Epoch environment
25370 Version 18 of @sc{gnu} Emacs has a built-in window system
25371 called the @code{epoch}
25372 environment. Users of this environment can use a new command,
25373 @code{inspect} which performs identically to @code{print} except that
25374 each value is printed in its own window.
25379 @chapter The @sc{gdb/mi} Interface
25381 @unnumberedsec Function and Purpose
25383 @cindex @sc{gdb/mi}, its purpose
25384 @sc{gdb/mi} is a line based machine oriented text interface to
25385 @value{GDBN} and is activated by specifying using the
25386 @option{--interpreter} command line option (@pxref{Mode Options}). It
25387 is specifically intended to support the development of systems which
25388 use the debugger as just one small component of a larger system.
25390 This chapter is a specification of the @sc{gdb/mi} interface. It is written
25391 in the form of a reference manual.
25393 Note that @sc{gdb/mi} is still under construction, so some of the
25394 features described below are incomplete and subject to change
25395 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
25397 @unnumberedsec Notation and Terminology
25399 @cindex notational conventions, for @sc{gdb/mi}
25400 This chapter uses the following notation:
25404 @code{|} separates two alternatives.
25407 @code{[ @var{something} ]} indicates that @var{something} is optional:
25408 it may or may not be given.
25411 @code{( @var{group} )*} means that @var{group} inside the parentheses
25412 may repeat zero or more times.
25415 @code{( @var{group} )+} means that @var{group} inside the parentheses
25416 may repeat one or more times.
25419 @code{"@var{string}"} means a literal @var{string}.
25423 @heading Dependencies
25427 * GDB/MI General Design::
25428 * GDB/MI Command Syntax::
25429 * GDB/MI Compatibility with CLI::
25430 * GDB/MI Development and Front Ends::
25431 * GDB/MI Output Records::
25432 * GDB/MI Simple Examples::
25433 * GDB/MI Command Description Format::
25434 * GDB/MI Breakpoint Commands::
25435 * GDB/MI Program Context::
25436 * GDB/MI Thread Commands::
25437 * GDB/MI Ada Tasking Commands::
25438 * GDB/MI Program Execution::
25439 * GDB/MI Stack Manipulation::
25440 * GDB/MI Variable Objects::
25441 * GDB/MI Data Manipulation::
25442 * GDB/MI Tracepoint Commands::
25443 * GDB/MI Symbol Query::
25444 * GDB/MI File Commands::
25446 * GDB/MI Kod Commands::
25447 * GDB/MI Memory Overlay Commands::
25448 * GDB/MI Signal Handling Commands::
25450 * GDB/MI Target Manipulation::
25451 * GDB/MI File Transfer Commands::
25452 * GDB/MI Miscellaneous Commands::
25455 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25456 @node GDB/MI General Design
25457 @section @sc{gdb/mi} General Design
25458 @cindex GDB/MI General Design
25460 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
25461 parts---commands sent to @value{GDBN}, responses to those commands
25462 and notifications. Each command results in exactly one response,
25463 indicating either successful completion of the command, or an error.
25464 For the commands that do not resume the target, the response contains the
25465 requested information. For the commands that resume the target, the
25466 response only indicates whether the target was successfully resumed.
25467 Notifications is the mechanism for reporting changes in the state of the
25468 target, or in @value{GDBN} state, that cannot conveniently be associated with
25469 a command and reported as part of that command response.
25471 The important examples of notifications are:
25475 Exec notifications. These are used to report changes in
25476 target state---when a target is resumed, or stopped. It would not
25477 be feasible to include this information in response of resuming
25478 commands, because one resume commands can result in multiple events in
25479 different threads. Also, quite some time may pass before any event
25480 happens in the target, while a frontend needs to know whether the resuming
25481 command itself was successfully executed.
25484 Console output, and status notifications. Console output
25485 notifications are used to report output of CLI commands, as well as
25486 diagnostics for other commands. Status notifications are used to
25487 report the progress of a long-running operation. Naturally, including
25488 this information in command response would mean no output is produced
25489 until the command is finished, which is undesirable.
25492 General notifications. Commands may have various side effects on
25493 the @value{GDBN} or target state beyond their official purpose. For example,
25494 a command may change the selected thread. Although such changes can
25495 be included in command response, using notification allows for more
25496 orthogonal frontend design.
25500 There's no guarantee that whenever an MI command reports an error,
25501 @value{GDBN} or the target are in any specific state, and especially,
25502 the state is not reverted to the state before the MI command was
25503 processed. Therefore, whenever an MI command results in an error,
25504 we recommend that the frontend refreshes all the information shown in
25505 the user interface.
25509 * Context management::
25510 * Asynchronous and non-stop modes::
25514 @node Context management
25515 @subsection Context management
25517 In most cases when @value{GDBN} accesses the target, this access is
25518 done in context of a specific thread and frame (@pxref{Frames}).
25519 Often, even when accessing global data, the target requires that a thread
25520 be specified. The CLI interface maintains the selected thread and frame,
25521 and supplies them to target on each command. This is convenient,
25522 because a command line user would not want to specify that information
25523 explicitly on each command, and because user interacts with
25524 @value{GDBN} via a single terminal, so no confusion is possible as
25525 to what thread and frame are the current ones.
25527 In the case of MI, the concept of selected thread and frame is less
25528 useful. First, a frontend can easily remember this information
25529 itself. Second, a graphical frontend can have more than one window,
25530 each one used for debugging a different thread, and the frontend might
25531 want to access additional threads for internal purposes. This
25532 increases the risk that by relying on implicitly selected thread, the
25533 frontend may be operating on a wrong one. Therefore, each MI command
25534 should explicitly specify which thread and frame to operate on. To
25535 make it possible, each MI command accepts the @samp{--thread} and
25536 @samp{--frame} options, the value to each is @value{GDBN} identifier
25537 for thread and frame to operate on.
25539 Usually, each top-level window in a frontend allows the user to select
25540 a thread and a frame, and remembers the user selection for further
25541 operations. However, in some cases @value{GDBN} may suggest that the
25542 current thread be changed. For example, when stopping on a breakpoint
25543 it is reasonable to switch to the thread where breakpoint is hit. For
25544 another example, if the user issues the CLI @samp{thread} command via
25545 the frontend, it is desirable to change the frontend's selected thread to the
25546 one specified by user. @value{GDBN} communicates the suggestion to
25547 change current thread using the @samp{=thread-selected} notification.
25548 No such notification is available for the selected frame at the moment.
25550 Note that historically, MI shares the selected thread with CLI, so
25551 frontends used the @code{-thread-select} to execute commands in the
25552 right context. However, getting this to work right is cumbersome. The
25553 simplest way is for frontend to emit @code{-thread-select} command
25554 before every command. This doubles the number of commands that need
25555 to be sent. The alternative approach is to suppress @code{-thread-select}
25556 if the selected thread in @value{GDBN} is supposed to be identical to the
25557 thread the frontend wants to operate on. However, getting this
25558 optimization right can be tricky. In particular, if the frontend
25559 sends several commands to @value{GDBN}, and one of the commands changes the
25560 selected thread, then the behaviour of subsequent commands will
25561 change. So, a frontend should either wait for response from such
25562 problematic commands, or explicitly add @code{-thread-select} for
25563 all subsequent commands. No frontend is known to do this exactly
25564 right, so it is suggested to just always pass the @samp{--thread} and
25565 @samp{--frame} options.
25567 @node Asynchronous and non-stop modes
25568 @subsection Asynchronous command execution and non-stop mode
25570 On some targets, @value{GDBN} is capable of processing MI commands
25571 even while the target is running. This is called @dfn{asynchronous
25572 command execution} (@pxref{Background Execution}). The frontend may
25573 specify a preferrence for asynchronous execution using the
25574 @code{-gdb-set target-async 1} command, which should be emitted before
25575 either running the executable or attaching to the target. After the
25576 frontend has started the executable or attached to the target, it can
25577 find if asynchronous execution is enabled using the
25578 @code{-list-target-features} command.
25580 Even if @value{GDBN} can accept a command while target is running,
25581 many commands that access the target do not work when the target is
25582 running. Therefore, asynchronous command execution is most useful
25583 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
25584 it is possible to examine the state of one thread, while other threads
25587 When a given thread is running, MI commands that try to access the
25588 target in the context of that thread may not work, or may work only on
25589 some targets. In particular, commands that try to operate on thread's
25590 stack will not work, on any target. Commands that read memory, or
25591 modify breakpoints, may work or not work, depending on the target. Note
25592 that even commands that operate on global state, such as @code{print},
25593 @code{set}, and breakpoint commands, still access the target in the
25594 context of a specific thread, so frontend should try to find a
25595 stopped thread and perform the operation on that thread (using the
25596 @samp{--thread} option).
25598 Which commands will work in the context of a running thread is
25599 highly target dependent. However, the two commands
25600 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
25601 to find the state of a thread, will always work.
25603 @node Thread groups
25604 @subsection Thread groups
25605 @value{GDBN} may be used to debug several processes at the same time.
25606 On some platfroms, @value{GDBN} may support debugging of several
25607 hardware systems, each one having several cores with several different
25608 processes running on each core. This section describes the MI
25609 mechanism to support such debugging scenarios.
25611 The key observation is that regardless of the structure of the
25612 target, MI can have a global list of threads, because most commands that
25613 accept the @samp{--thread} option do not need to know what process that
25614 thread belongs to. Therefore, it is not necessary to introduce
25615 neither additional @samp{--process} option, nor an notion of the
25616 current process in the MI interface. The only strictly new feature
25617 that is required is the ability to find how the threads are grouped
25620 To allow the user to discover such grouping, and to support arbitrary
25621 hierarchy of machines/cores/processes, MI introduces the concept of a
25622 @dfn{thread group}. Thread group is a collection of threads and other
25623 thread groups. A thread group always has a string identifier, a type,
25624 and may have additional attributes specific to the type. A new
25625 command, @code{-list-thread-groups}, returns the list of top-level
25626 thread groups, which correspond to processes that @value{GDBN} is
25627 debugging at the moment. By passing an identifier of a thread group
25628 to the @code{-list-thread-groups} command, it is possible to obtain
25629 the members of specific thread group.
25631 To allow the user to easily discover processes, and other objects, he
25632 wishes to debug, a concept of @dfn{available thread group} is
25633 introduced. Available thread group is an thread group that
25634 @value{GDBN} is not debugging, but that can be attached to, using the
25635 @code{-target-attach} command. The list of available top-level thread
25636 groups can be obtained using @samp{-list-thread-groups --available}.
25637 In general, the content of a thread group may be only retrieved only
25638 after attaching to that thread group.
25640 Thread groups are related to inferiors (@pxref{Inferiors and
25641 Programs}). Each inferior corresponds to a thread group of a special
25642 type @samp{process}, and some additional operations are permitted on
25643 such thread groups.
25645 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25646 @node GDB/MI Command Syntax
25647 @section @sc{gdb/mi} Command Syntax
25650 * GDB/MI Input Syntax::
25651 * GDB/MI Output Syntax::
25654 @node GDB/MI Input Syntax
25655 @subsection @sc{gdb/mi} Input Syntax
25657 @cindex input syntax for @sc{gdb/mi}
25658 @cindex @sc{gdb/mi}, input syntax
25660 @item @var{command} @expansion{}
25661 @code{@var{cli-command} | @var{mi-command}}
25663 @item @var{cli-command} @expansion{}
25664 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
25665 @var{cli-command} is any existing @value{GDBN} CLI command.
25667 @item @var{mi-command} @expansion{}
25668 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
25669 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
25671 @item @var{token} @expansion{}
25672 "any sequence of digits"
25674 @item @var{option} @expansion{}
25675 @code{"-" @var{parameter} [ " " @var{parameter} ]}
25677 @item @var{parameter} @expansion{}
25678 @code{@var{non-blank-sequence} | @var{c-string}}
25680 @item @var{operation} @expansion{}
25681 @emph{any of the operations described in this chapter}
25683 @item @var{non-blank-sequence} @expansion{}
25684 @emph{anything, provided it doesn't contain special characters such as
25685 "-", @var{nl}, """ and of course " "}
25687 @item @var{c-string} @expansion{}
25688 @code{""" @var{seven-bit-iso-c-string-content} """}
25690 @item @var{nl} @expansion{}
25699 The CLI commands are still handled by the @sc{mi} interpreter; their
25700 output is described below.
25703 The @code{@var{token}}, when present, is passed back when the command
25707 Some @sc{mi} commands accept optional arguments as part of the parameter
25708 list. Each option is identified by a leading @samp{-} (dash) and may be
25709 followed by an optional argument parameter. Options occur first in the
25710 parameter list and can be delimited from normal parameters using
25711 @samp{--} (this is useful when some parameters begin with a dash).
25718 We want easy access to the existing CLI syntax (for debugging).
25721 We want it to be easy to spot a @sc{mi} operation.
25724 @node GDB/MI Output Syntax
25725 @subsection @sc{gdb/mi} Output Syntax
25727 @cindex output syntax of @sc{gdb/mi}
25728 @cindex @sc{gdb/mi}, output syntax
25729 The output from @sc{gdb/mi} consists of zero or more out-of-band records
25730 followed, optionally, by a single result record. This result record
25731 is for the most recent command. The sequence of output records is
25732 terminated by @samp{(gdb)}.
25734 If an input command was prefixed with a @code{@var{token}} then the
25735 corresponding output for that command will also be prefixed by that same
25739 @item @var{output} @expansion{}
25740 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
25742 @item @var{result-record} @expansion{}
25743 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
25745 @item @var{out-of-band-record} @expansion{}
25746 @code{@var{async-record} | @var{stream-record}}
25748 @item @var{async-record} @expansion{}
25749 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
25751 @item @var{exec-async-output} @expansion{}
25752 @code{[ @var{token} ] "*" @var{async-output}}
25754 @item @var{status-async-output} @expansion{}
25755 @code{[ @var{token} ] "+" @var{async-output}}
25757 @item @var{notify-async-output} @expansion{}
25758 @code{[ @var{token} ] "=" @var{async-output}}
25760 @item @var{async-output} @expansion{}
25761 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
25763 @item @var{result-class} @expansion{}
25764 @code{"done" | "running" | "connected" | "error" | "exit"}
25766 @item @var{async-class} @expansion{}
25767 @code{"stopped" | @var{others}} (where @var{others} will be added
25768 depending on the needs---this is still in development).
25770 @item @var{result} @expansion{}
25771 @code{ @var{variable} "=" @var{value}}
25773 @item @var{variable} @expansion{}
25774 @code{ @var{string} }
25776 @item @var{value} @expansion{}
25777 @code{ @var{const} | @var{tuple} | @var{list} }
25779 @item @var{const} @expansion{}
25780 @code{@var{c-string}}
25782 @item @var{tuple} @expansion{}
25783 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
25785 @item @var{list} @expansion{}
25786 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
25787 @var{result} ( "," @var{result} )* "]" }
25789 @item @var{stream-record} @expansion{}
25790 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
25792 @item @var{console-stream-output} @expansion{}
25793 @code{"~" @var{c-string}}
25795 @item @var{target-stream-output} @expansion{}
25796 @code{"@@" @var{c-string}}
25798 @item @var{log-stream-output} @expansion{}
25799 @code{"&" @var{c-string}}
25801 @item @var{nl} @expansion{}
25804 @item @var{token} @expansion{}
25805 @emph{any sequence of digits}.
25813 All output sequences end in a single line containing a period.
25816 The @code{@var{token}} is from the corresponding request. Note that
25817 for all async output, while the token is allowed by the grammar and
25818 may be output by future versions of @value{GDBN} for select async
25819 output messages, it is generally omitted. Frontends should treat
25820 all async output as reporting general changes in the state of the
25821 target and there should be no need to associate async output to any
25825 @cindex status output in @sc{gdb/mi}
25826 @var{status-async-output} contains on-going status information about the
25827 progress of a slow operation. It can be discarded. All status output is
25828 prefixed by @samp{+}.
25831 @cindex async output in @sc{gdb/mi}
25832 @var{exec-async-output} contains asynchronous state change on the target
25833 (stopped, started, disappeared). All async output is prefixed by
25837 @cindex notify output in @sc{gdb/mi}
25838 @var{notify-async-output} contains supplementary information that the
25839 client should handle (e.g., a new breakpoint information). All notify
25840 output is prefixed by @samp{=}.
25843 @cindex console output in @sc{gdb/mi}
25844 @var{console-stream-output} is output that should be displayed as is in the
25845 console. It is the textual response to a CLI command. All the console
25846 output is prefixed by @samp{~}.
25849 @cindex target output in @sc{gdb/mi}
25850 @var{target-stream-output} is the output produced by the target program.
25851 All the target output is prefixed by @samp{@@}.
25854 @cindex log output in @sc{gdb/mi}
25855 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
25856 instance messages that should be displayed as part of an error log. All
25857 the log output is prefixed by @samp{&}.
25860 @cindex list output in @sc{gdb/mi}
25861 New @sc{gdb/mi} commands should only output @var{lists} containing
25867 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
25868 details about the various output records.
25870 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25871 @node GDB/MI Compatibility with CLI
25872 @section @sc{gdb/mi} Compatibility with CLI
25874 @cindex compatibility, @sc{gdb/mi} and CLI
25875 @cindex @sc{gdb/mi}, compatibility with CLI
25877 For the developers convenience CLI commands can be entered directly,
25878 but there may be some unexpected behaviour. For example, commands
25879 that query the user will behave as if the user replied yes, breakpoint
25880 command lists are not executed and some CLI commands, such as
25881 @code{if}, @code{when} and @code{define}, prompt for further input with
25882 @samp{>}, which is not valid MI output.
25884 This feature may be removed at some stage in the future and it is
25885 recommended that front ends use the @code{-interpreter-exec} command
25886 (@pxref{-interpreter-exec}).
25888 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25889 @node GDB/MI Development and Front Ends
25890 @section @sc{gdb/mi} Development and Front Ends
25891 @cindex @sc{gdb/mi} development
25893 The application which takes the MI output and presents the state of the
25894 program being debugged to the user is called a @dfn{front end}.
25896 Although @sc{gdb/mi} is still incomplete, it is currently being used
25897 by a variety of front ends to @value{GDBN}. This makes it difficult
25898 to introduce new functionality without breaking existing usage. This
25899 section tries to minimize the problems by describing how the protocol
25902 Some changes in MI need not break a carefully designed front end, and
25903 for these the MI version will remain unchanged. The following is a
25904 list of changes that may occur within one level, so front ends should
25905 parse MI output in a way that can handle them:
25909 New MI commands may be added.
25912 New fields may be added to the output of any MI command.
25915 The range of values for fields with specified values, e.g.,
25916 @code{in_scope} (@pxref{-var-update}) may be extended.
25918 @c The format of field's content e.g type prefix, may change so parse it
25919 @c at your own risk. Yes, in general?
25921 @c The order of fields may change? Shouldn't really matter but it might
25922 @c resolve inconsistencies.
25925 If the changes are likely to break front ends, the MI version level
25926 will be increased by one. This will allow the front end to parse the
25927 output according to the MI version. Apart from mi0, new versions of
25928 @value{GDBN} will not support old versions of MI and it will be the
25929 responsibility of the front end to work with the new one.
25931 @c Starting with mi3, add a new command -mi-version that prints the MI
25934 The best way to avoid unexpected changes in MI that might break your front
25935 end is to make your project known to @value{GDBN} developers and
25936 follow development on @email{gdb@@sourceware.org} and
25937 @email{gdb-patches@@sourceware.org}.
25938 @cindex mailing lists
25940 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25941 @node GDB/MI Output Records
25942 @section @sc{gdb/mi} Output Records
25945 * GDB/MI Result Records::
25946 * GDB/MI Stream Records::
25947 * GDB/MI Async Records::
25948 * GDB/MI Frame Information::
25949 * GDB/MI Thread Information::
25950 * GDB/MI Ada Exception Information::
25953 @node GDB/MI Result Records
25954 @subsection @sc{gdb/mi} Result Records
25956 @cindex result records in @sc{gdb/mi}
25957 @cindex @sc{gdb/mi}, result records
25958 In addition to a number of out-of-band notifications, the response to a
25959 @sc{gdb/mi} command includes one of the following result indications:
25963 @item "^done" [ "," @var{results} ]
25964 The synchronous operation was successful, @code{@var{results}} are the return
25969 This result record is equivalent to @samp{^done}. Historically, it
25970 was output instead of @samp{^done} if the command has resumed the
25971 target. This behaviour is maintained for backward compatibility, but
25972 all frontends should treat @samp{^done} and @samp{^running}
25973 identically and rely on the @samp{*running} output record to determine
25974 which threads are resumed.
25978 @value{GDBN} has connected to a remote target.
25980 @item "^error" "," @var{c-string}
25982 The operation failed. The @code{@var{c-string}} contains the corresponding
25987 @value{GDBN} has terminated.
25991 @node GDB/MI Stream Records
25992 @subsection @sc{gdb/mi} Stream Records
25994 @cindex @sc{gdb/mi}, stream records
25995 @cindex stream records in @sc{gdb/mi}
25996 @value{GDBN} internally maintains a number of output streams: the console, the
25997 target, and the log. The output intended for each of these streams is
25998 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
26000 Each stream record begins with a unique @dfn{prefix character} which
26001 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
26002 Syntax}). In addition to the prefix, each stream record contains a
26003 @code{@var{string-output}}. This is either raw text (with an implicit new
26004 line) or a quoted C string (which does not contain an implicit newline).
26007 @item "~" @var{string-output}
26008 The console output stream contains text that should be displayed in the
26009 CLI console window. It contains the textual responses to CLI commands.
26011 @item "@@" @var{string-output}
26012 The target output stream contains any textual output from the running
26013 target. This is only present when GDB's event loop is truly
26014 asynchronous, which is currently only the case for remote targets.
26016 @item "&" @var{string-output}
26017 The log stream contains debugging messages being produced by @value{GDBN}'s
26021 @node GDB/MI Async Records
26022 @subsection @sc{gdb/mi} Async Records
26024 @cindex async records in @sc{gdb/mi}
26025 @cindex @sc{gdb/mi}, async records
26026 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
26027 additional changes that have occurred. Those changes can either be a
26028 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
26029 target activity (e.g., target stopped).
26031 The following is the list of possible async records:
26035 @item *running,thread-id="@var{thread}"
26036 The target is now running. The @var{thread} field tells which
26037 specific thread is now running, and can be @samp{all} if all threads
26038 are running. The frontend should assume that no interaction with a
26039 running thread is possible after this notification is produced.
26040 The frontend should not assume that this notification is output
26041 only once for any command. @value{GDBN} may emit this notification
26042 several times, either for different threads, because it cannot resume
26043 all threads together, or even for a single thread, if the thread must
26044 be stepped though some code before letting it run freely.
26046 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
26047 The target has stopped. The @var{reason} field can have one of the
26051 @item breakpoint-hit
26052 A breakpoint was reached.
26053 @item watchpoint-trigger
26054 A watchpoint was triggered.
26055 @item read-watchpoint-trigger
26056 A read watchpoint was triggered.
26057 @item access-watchpoint-trigger
26058 An access watchpoint was triggered.
26059 @item function-finished
26060 An -exec-finish or similar CLI command was accomplished.
26061 @item location-reached
26062 An -exec-until or similar CLI command was accomplished.
26063 @item watchpoint-scope
26064 A watchpoint has gone out of scope.
26065 @item end-stepping-range
26066 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
26067 similar CLI command was accomplished.
26068 @item exited-signalled
26069 The inferior exited because of a signal.
26071 The inferior exited.
26072 @item exited-normally
26073 The inferior exited normally.
26074 @item signal-received
26075 A signal was received by the inferior.
26078 The @var{id} field identifies the thread that directly caused the stop
26079 -- for example by hitting a breakpoint. Depending on whether all-stop
26080 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
26081 stop all threads, or only the thread that directly triggered the stop.
26082 If all threads are stopped, the @var{stopped} field will have the
26083 value of @code{"all"}. Otherwise, the value of the @var{stopped}
26084 field will be a list of thread identifiers. Presently, this list will
26085 always include a single thread, but frontend should be prepared to see
26086 several threads in the list. The @var{core} field reports the
26087 processor core on which the stop event has happened. This field may be absent
26088 if such information is not available.
26090 @item =thread-group-added,id="@var{id}"
26091 @itemx =thread-group-removed,id="@var{id}"
26092 A thread group was either added or removed. The @var{id} field
26093 contains the @value{GDBN} identifier of the thread group. When a thread
26094 group is added, it generally might not be associated with a running
26095 process. When a thread group is removed, its id becomes invalid and
26096 cannot be used in any way.
26098 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
26099 A thread group became associated with a running program,
26100 either because the program was just started or the thread group
26101 was attached to a program. The @var{id} field contains the
26102 @value{GDBN} identifier of the thread group. The @var{pid} field
26103 contains process identifier, specific to the operating system.
26105 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
26106 A thread group is no longer associated with a running program,
26107 either because the program has exited, or because it was detached
26108 from. The @var{id} field contains the @value{GDBN} identifier of the
26109 thread group. @var{code} is the exit code of the inferior; it exists
26110 only when the inferior exited with some code.
26112 @item =thread-created,id="@var{id}",group-id="@var{gid}"
26113 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
26114 A thread either was created, or has exited. The @var{id} field
26115 contains the @value{GDBN} identifier of the thread. The @var{gid}
26116 field identifies the thread group this thread belongs to.
26118 @item =thread-selected,id="@var{id}"
26119 Informs that the selected thread was changed as result of the last
26120 command. This notification is not emitted as result of @code{-thread-select}
26121 command but is emitted whenever an MI command that is not documented
26122 to change the selected thread actually changes it. In particular,
26123 invoking, directly or indirectly (via user-defined command), the CLI
26124 @code{thread} command, will generate this notification.
26126 We suggest that in response to this notification, front ends
26127 highlight the selected thread and cause subsequent commands to apply to
26130 @item =library-loaded,...
26131 Reports that a new library file was loaded by the program. This
26132 notification has 4 fields---@var{id}, @var{target-name},
26133 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
26134 opaque identifier of the library. For remote debugging case,
26135 @var{target-name} and @var{host-name} fields give the name of the
26136 library file on the target, and on the host respectively. For native
26137 debugging, both those fields have the same value. The
26138 @var{symbols-loaded} field is emitted only for backward compatibility
26139 and should not be relied on to convey any useful information. The
26140 @var{thread-group} field, if present, specifies the id of the thread
26141 group in whose context the library was loaded. If the field is
26142 absent, it means the library was loaded in the context of all present
26145 @item =library-unloaded,...
26146 Reports that a library was unloaded by the program. This notification
26147 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
26148 the same meaning as for the @code{=library-loaded} notification.
26149 The @var{thread-group} field, if present, specifies the id of the
26150 thread group in whose context the library was unloaded. If the field is
26151 absent, it means the library was unloaded in the context of all present
26154 @item =breakpoint-created,bkpt=@{...@}
26155 @itemx =breakpoint-modified,bkpt=@{...@}
26156 @itemx =breakpoint-deleted,bkpt=@{...@}
26157 Reports that a breakpoint was created, modified, or deleted,
26158 respectively. Only user-visible breakpoints are reported to the MI
26161 The @var{bkpt} argument is of the same form as returned by the various
26162 breakpoint commands; @xref{GDB/MI Breakpoint Commands}.
26164 Note that if a breakpoint is emitted in the result record of a
26165 command, then it will not also be emitted in an async record.
26169 @node GDB/MI Frame Information
26170 @subsection @sc{gdb/mi} Frame Information
26172 Response from many MI commands includes an information about stack
26173 frame. This information is a tuple that may have the following
26178 The level of the stack frame. The innermost frame has the level of
26179 zero. This field is always present.
26182 The name of the function corresponding to the frame. This field may
26183 be absent if @value{GDBN} is unable to determine the function name.
26186 The code address for the frame. This field is always present.
26189 The name of the source files that correspond to the frame's code
26190 address. This field may be absent.
26193 The source line corresponding to the frames' code address. This field
26197 The name of the binary file (either executable or shared library) the
26198 corresponds to the frame's code address. This field may be absent.
26202 @node GDB/MI Thread Information
26203 @subsection @sc{gdb/mi} Thread Information
26205 Whenever @value{GDBN} has to report an information about a thread, it
26206 uses a tuple with the following fields:
26210 The numeric id assigned to the thread by @value{GDBN}. This field is
26214 Target-specific string identifying the thread. This field is always present.
26217 Additional information about the thread provided by the target.
26218 It is supposed to be human-readable and not interpreted by the
26219 frontend. This field is optional.
26222 Either @samp{stopped} or @samp{running}, depending on whether the
26223 thread is presently running. This field is always present.
26226 The value of this field is an integer number of the processor core the
26227 thread was last seen on. This field is optional.
26230 @node GDB/MI Ada Exception Information
26231 @subsection @sc{gdb/mi} Ada Exception Information
26233 Whenever a @code{*stopped} record is emitted because the program
26234 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
26235 @value{GDBN} provides the name of the exception that was raised via
26236 the @code{exception-name} field.
26238 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26239 @node GDB/MI Simple Examples
26240 @section Simple Examples of @sc{gdb/mi} Interaction
26241 @cindex @sc{gdb/mi}, simple examples
26243 This subsection presents several simple examples of interaction using
26244 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
26245 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
26246 the output received from @sc{gdb/mi}.
26248 Note the line breaks shown in the examples are here only for
26249 readability, they don't appear in the real output.
26251 @subheading Setting a Breakpoint
26253 Setting a breakpoint generates synchronous output which contains detailed
26254 information of the breakpoint.
26257 -> -break-insert main
26258 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26259 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26260 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
26264 @subheading Program Execution
26266 Program execution generates asynchronous records and MI gives the
26267 reason that execution stopped.
26273 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
26274 frame=@{addr="0x08048564",func="main",
26275 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
26276 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
26281 <- *stopped,reason="exited-normally"
26285 @subheading Quitting @value{GDBN}
26287 Quitting @value{GDBN} just prints the result class @samp{^exit}.
26295 Please note that @samp{^exit} is printed immediately, but it might
26296 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
26297 performs necessary cleanups, including killing programs being debugged
26298 or disconnecting from debug hardware, so the frontend should wait till
26299 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
26300 fails to exit in reasonable time.
26302 @subheading A Bad Command
26304 Here's what happens if you pass a non-existent command:
26308 <- ^error,msg="Undefined MI command: rubbish"
26313 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26314 @node GDB/MI Command Description Format
26315 @section @sc{gdb/mi} Command Description Format
26317 The remaining sections describe blocks of commands. Each block of
26318 commands is laid out in a fashion similar to this section.
26320 @subheading Motivation
26322 The motivation for this collection of commands.
26324 @subheading Introduction
26326 A brief introduction to this collection of commands as a whole.
26328 @subheading Commands
26330 For each command in the block, the following is described:
26332 @subsubheading Synopsis
26335 -command @var{args}@dots{}
26338 @subsubheading Result
26340 @subsubheading @value{GDBN} Command
26342 The corresponding @value{GDBN} CLI command(s), if any.
26344 @subsubheading Example
26346 Example(s) formatted for readability. Some of the described commands have
26347 not been implemented yet and these are labeled N.A.@: (not available).
26350 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26351 @node GDB/MI Breakpoint Commands
26352 @section @sc{gdb/mi} Breakpoint Commands
26354 @cindex breakpoint commands for @sc{gdb/mi}
26355 @cindex @sc{gdb/mi}, breakpoint commands
26356 This section documents @sc{gdb/mi} commands for manipulating
26359 @subheading The @code{-break-after} Command
26360 @findex -break-after
26362 @subsubheading Synopsis
26365 -break-after @var{number} @var{count}
26368 The breakpoint number @var{number} is not in effect until it has been
26369 hit @var{count} times. To see how this is reflected in the output of
26370 the @samp{-break-list} command, see the description of the
26371 @samp{-break-list} command below.
26373 @subsubheading @value{GDBN} Command
26375 The corresponding @value{GDBN} command is @samp{ignore}.
26377 @subsubheading Example
26382 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26383 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26384 fullname="/home/foo/hello.c",line="5",times="0"@}
26391 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26392 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26393 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26394 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26395 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26396 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26397 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26398 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26399 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26400 line="5",times="0",ignore="3"@}]@}
26405 @subheading The @code{-break-catch} Command
26406 @findex -break-catch
26409 @subheading The @code{-break-commands} Command
26410 @findex -break-commands
26412 @subsubheading Synopsis
26415 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
26418 Specifies the CLI commands that should be executed when breakpoint
26419 @var{number} is hit. The parameters @var{command1} to @var{commandN}
26420 are the commands. If no command is specified, any previously-set
26421 commands are cleared. @xref{Break Commands}. Typical use of this
26422 functionality is tracing a program, that is, printing of values of
26423 some variables whenever breakpoint is hit and then continuing.
26425 @subsubheading @value{GDBN} Command
26427 The corresponding @value{GDBN} command is @samp{commands}.
26429 @subsubheading Example
26434 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26435 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26436 fullname="/home/foo/hello.c",line="5",times="0"@}
26438 -break-commands 1 "print v" "continue"
26443 @subheading The @code{-break-condition} Command
26444 @findex -break-condition
26446 @subsubheading Synopsis
26449 -break-condition @var{number} @var{expr}
26452 Breakpoint @var{number} will stop the program only if the condition in
26453 @var{expr} is true. The condition becomes part of the
26454 @samp{-break-list} output (see the description of the @samp{-break-list}
26457 @subsubheading @value{GDBN} Command
26459 The corresponding @value{GDBN} command is @samp{condition}.
26461 @subsubheading Example
26465 -break-condition 1 1
26469 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26470 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26471 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26472 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26473 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26474 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26475 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26476 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26477 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26478 line="5",cond="1",times="0",ignore="3"@}]@}
26482 @subheading The @code{-break-delete} Command
26483 @findex -break-delete
26485 @subsubheading Synopsis
26488 -break-delete ( @var{breakpoint} )+
26491 Delete the breakpoint(s) whose number(s) are specified in the argument
26492 list. This is obviously reflected in the breakpoint list.
26494 @subsubheading @value{GDBN} Command
26496 The corresponding @value{GDBN} command is @samp{delete}.
26498 @subsubheading Example
26506 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26507 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26508 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26509 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26510 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26511 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26512 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26517 @subheading The @code{-break-disable} Command
26518 @findex -break-disable
26520 @subsubheading Synopsis
26523 -break-disable ( @var{breakpoint} )+
26526 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
26527 break list is now set to @samp{n} for the named @var{breakpoint}(s).
26529 @subsubheading @value{GDBN} Command
26531 The corresponding @value{GDBN} command is @samp{disable}.
26533 @subsubheading Example
26541 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26542 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26543 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26544 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26545 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26546 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26547 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26548 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
26549 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26550 line="5",times="0"@}]@}
26554 @subheading The @code{-break-enable} Command
26555 @findex -break-enable
26557 @subsubheading Synopsis
26560 -break-enable ( @var{breakpoint} )+
26563 Enable (previously disabled) @var{breakpoint}(s).
26565 @subsubheading @value{GDBN} Command
26567 The corresponding @value{GDBN} command is @samp{enable}.
26569 @subsubheading Example
26577 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26578 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26579 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26580 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26581 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26582 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26583 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26584 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26585 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26586 line="5",times="0"@}]@}
26590 @subheading The @code{-break-info} Command
26591 @findex -break-info
26593 @subsubheading Synopsis
26596 -break-info @var{breakpoint}
26600 Get information about a single breakpoint.
26602 @subsubheading @value{GDBN} Command
26604 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
26606 @subsubheading Example
26609 @subheading The @code{-break-insert} Command
26610 @findex -break-insert
26612 @subsubheading Synopsis
26615 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
26616 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26617 [ -p @var{thread} ] [ @var{location} ]
26621 If specified, @var{location}, can be one of:
26628 @item filename:linenum
26629 @item filename:function
26633 The possible optional parameters of this command are:
26637 Insert a temporary breakpoint.
26639 Insert a hardware breakpoint.
26640 @item -c @var{condition}
26641 Make the breakpoint conditional on @var{condition}.
26642 @item -i @var{ignore-count}
26643 Initialize the @var{ignore-count}.
26645 If @var{location} cannot be parsed (for example if it
26646 refers to unknown files or functions), create a pending
26647 breakpoint. Without this flag, @value{GDBN} will report
26648 an error, and won't create a breakpoint, if @var{location}
26651 Create a disabled breakpoint.
26653 Create a tracepoint. @xref{Tracepoints}. When this parameter
26654 is used together with @samp{-h}, a fast tracepoint is created.
26657 @subsubheading Result
26659 The result is in the form:
26662 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
26663 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
26664 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
26665 times="@var{times}"@}
26669 where @var{number} is the @value{GDBN} number for this breakpoint,
26670 @var{funcname} is the name of the function where the breakpoint was
26671 inserted, @var{filename} is the name of the source file which contains
26672 this function, @var{lineno} is the source line number within that file
26673 and @var{times} the number of times that the breakpoint has been hit
26674 (always 0 for -break-insert but may be greater for -break-info or -break-list
26675 which use the same output).
26677 Note: this format is open to change.
26678 @c An out-of-band breakpoint instead of part of the result?
26680 @subsubheading @value{GDBN} Command
26682 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
26683 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
26685 @subsubheading Example
26690 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
26691 fullname="/home/foo/recursive2.c,line="4",times="0"@}
26693 -break-insert -t foo
26694 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
26695 fullname="/home/foo/recursive2.c,line="11",times="0"@}
26698 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26699 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26700 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26701 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26702 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26703 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26704 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26705 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26706 addr="0x0001072c", func="main",file="recursive2.c",
26707 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
26708 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
26709 addr="0x00010774",func="foo",file="recursive2.c",
26710 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
26712 -break-insert -r foo.*
26713 ~int foo(int, int);
26714 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
26715 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
26719 @subheading The @code{-break-list} Command
26720 @findex -break-list
26722 @subsubheading Synopsis
26728 Displays the list of inserted breakpoints, showing the following fields:
26732 number of the breakpoint
26734 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
26736 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
26739 is the breakpoint enabled or no: @samp{y} or @samp{n}
26741 memory location at which the breakpoint is set
26743 logical location of the breakpoint, expressed by function name, file
26746 number of times the breakpoint has been hit
26749 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
26750 @code{body} field is an empty list.
26752 @subsubheading @value{GDBN} Command
26754 The corresponding @value{GDBN} command is @samp{info break}.
26756 @subsubheading Example
26761 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26762 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26763 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26764 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26765 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26766 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26767 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26768 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26769 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
26770 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26771 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
26772 line="13",times="0"@}]@}
26776 Here's an example of the result when there are no breakpoints:
26781 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26782 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26783 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26784 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26785 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26786 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26787 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26792 @subheading The @code{-break-passcount} Command
26793 @findex -break-passcount
26795 @subsubheading Synopsis
26798 -break-passcount @var{tracepoint-number} @var{passcount}
26801 Set the passcount for tracepoint @var{tracepoint-number} to
26802 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
26803 is not a tracepoint, error is emitted. This corresponds to CLI
26804 command @samp{passcount}.
26806 @subheading The @code{-break-watch} Command
26807 @findex -break-watch
26809 @subsubheading Synopsis
26812 -break-watch [ -a | -r ]
26815 Create a watchpoint. With the @samp{-a} option it will create an
26816 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
26817 read from or on a write to the memory location. With the @samp{-r}
26818 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
26819 trigger only when the memory location is accessed for reading. Without
26820 either of the options, the watchpoint created is a regular watchpoint,
26821 i.e., it will trigger when the memory location is accessed for writing.
26822 @xref{Set Watchpoints, , Setting Watchpoints}.
26824 Note that @samp{-break-list} will report a single list of watchpoints and
26825 breakpoints inserted.
26827 @subsubheading @value{GDBN} Command
26829 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
26832 @subsubheading Example
26834 Setting a watchpoint on a variable in the @code{main} function:
26839 ^done,wpt=@{number="2",exp="x"@}
26844 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
26845 value=@{old="-268439212",new="55"@},
26846 frame=@{func="main",args=[],file="recursive2.c",
26847 fullname="/home/foo/bar/recursive2.c",line="5"@}
26851 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
26852 the program execution twice: first for the variable changing value, then
26853 for the watchpoint going out of scope.
26858 ^done,wpt=@{number="5",exp="C"@}
26863 *stopped,reason="watchpoint-trigger",
26864 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
26865 frame=@{func="callee4",args=[],
26866 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26867 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
26872 *stopped,reason="watchpoint-scope",wpnum="5",
26873 frame=@{func="callee3",args=[@{name="strarg",
26874 value="0x11940 \"A string argument.\""@}],
26875 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26876 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26880 Listing breakpoints and watchpoints, at different points in the program
26881 execution. Note that once the watchpoint goes out of scope, it is
26887 ^done,wpt=@{number="2",exp="C"@}
26890 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26891 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26892 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26893 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26894 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26895 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26896 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26897 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26898 addr="0x00010734",func="callee4",
26899 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26900 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
26901 bkpt=@{number="2",type="watchpoint",disp="keep",
26902 enabled="y",addr="",what="C",times="0"@}]@}
26907 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
26908 value=@{old="-276895068",new="3"@},
26909 frame=@{func="callee4",args=[],
26910 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26911 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
26914 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26915 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26916 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26917 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26918 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26919 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26920 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26921 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26922 addr="0x00010734",func="callee4",
26923 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26924 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
26925 bkpt=@{number="2",type="watchpoint",disp="keep",
26926 enabled="y",addr="",what="C",times="-5"@}]@}
26930 ^done,reason="watchpoint-scope",wpnum="2",
26931 frame=@{func="callee3",args=[@{name="strarg",
26932 value="0x11940 \"A string argument.\""@}],
26933 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26934 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26937 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26938 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26939 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26940 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26941 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26942 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26943 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26944 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26945 addr="0x00010734",func="callee4",
26946 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26947 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
26952 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26953 @node GDB/MI Program Context
26954 @section @sc{gdb/mi} Program Context
26956 @subheading The @code{-exec-arguments} Command
26957 @findex -exec-arguments
26960 @subsubheading Synopsis
26963 -exec-arguments @var{args}
26966 Set the inferior program arguments, to be used in the next
26969 @subsubheading @value{GDBN} Command
26971 The corresponding @value{GDBN} command is @samp{set args}.
26973 @subsubheading Example
26977 -exec-arguments -v word
26984 @subheading The @code{-exec-show-arguments} Command
26985 @findex -exec-show-arguments
26987 @subsubheading Synopsis
26990 -exec-show-arguments
26993 Print the arguments of the program.
26995 @subsubheading @value{GDBN} Command
26997 The corresponding @value{GDBN} command is @samp{show args}.
26999 @subsubheading Example
27004 @subheading The @code{-environment-cd} Command
27005 @findex -environment-cd
27007 @subsubheading Synopsis
27010 -environment-cd @var{pathdir}
27013 Set @value{GDBN}'s working directory.
27015 @subsubheading @value{GDBN} Command
27017 The corresponding @value{GDBN} command is @samp{cd}.
27019 @subsubheading Example
27023 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27029 @subheading The @code{-environment-directory} Command
27030 @findex -environment-directory
27032 @subsubheading Synopsis
27035 -environment-directory [ -r ] [ @var{pathdir} ]+
27038 Add directories @var{pathdir} to beginning of search path for source files.
27039 If the @samp{-r} option is used, the search path is reset to the default
27040 search path. If directories @var{pathdir} are supplied in addition to the
27041 @samp{-r} option, the search path is first reset and then addition
27043 Multiple directories may be specified, separated by blanks. Specifying
27044 multiple directories in a single command
27045 results in the directories added to the beginning of the
27046 search path in the same order they were presented in the command.
27047 If blanks are needed as
27048 part of a directory name, double-quotes should be used around
27049 the name. In the command output, the path will show up separated
27050 by the system directory-separator character. The directory-separator
27051 character must not be used
27052 in any directory name.
27053 If no directories are specified, the current search path is displayed.
27055 @subsubheading @value{GDBN} Command
27057 The corresponding @value{GDBN} command is @samp{dir}.
27059 @subsubheading Example
27063 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27064 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27066 -environment-directory ""
27067 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27069 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
27070 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
27072 -environment-directory -r
27073 ^done,source-path="$cdir:$cwd"
27078 @subheading The @code{-environment-path} Command
27079 @findex -environment-path
27081 @subsubheading Synopsis
27084 -environment-path [ -r ] [ @var{pathdir} ]+
27087 Add directories @var{pathdir} to beginning of search path for object files.
27088 If the @samp{-r} option is used, the search path is reset to the original
27089 search path that existed at gdb start-up. If directories @var{pathdir} are
27090 supplied in addition to the
27091 @samp{-r} option, the search path is first reset and then addition
27093 Multiple directories may be specified, separated by blanks. Specifying
27094 multiple directories in a single command
27095 results in the directories added to the beginning of the
27096 search path in the same order they were presented in the command.
27097 If blanks are needed as
27098 part of a directory name, double-quotes should be used around
27099 the name. In the command output, the path will show up separated
27100 by the system directory-separator character. The directory-separator
27101 character must not be used
27102 in any directory name.
27103 If no directories are specified, the current path is displayed.
27106 @subsubheading @value{GDBN} Command
27108 The corresponding @value{GDBN} command is @samp{path}.
27110 @subsubheading Example
27115 ^done,path="/usr/bin"
27117 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
27118 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
27120 -environment-path -r /usr/local/bin
27121 ^done,path="/usr/local/bin:/usr/bin"
27126 @subheading The @code{-environment-pwd} Command
27127 @findex -environment-pwd
27129 @subsubheading Synopsis
27135 Show the current working directory.
27137 @subsubheading @value{GDBN} Command
27139 The corresponding @value{GDBN} command is @samp{pwd}.
27141 @subsubheading Example
27146 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
27150 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27151 @node GDB/MI Thread Commands
27152 @section @sc{gdb/mi} Thread Commands
27155 @subheading The @code{-thread-info} Command
27156 @findex -thread-info
27158 @subsubheading Synopsis
27161 -thread-info [ @var{thread-id} ]
27164 Reports information about either a specific thread, if
27165 the @var{thread-id} parameter is present, or about all
27166 threads. When printing information about all threads,
27167 also reports the current thread.
27169 @subsubheading @value{GDBN} Command
27171 The @samp{info thread} command prints the same information
27174 @subsubheading Result
27176 The result is a list of threads. The following attributes are
27177 defined for a given thread:
27181 This field exists only for the current thread. It has the value @samp{*}.
27184 The identifier that @value{GDBN} uses to refer to the thread.
27187 The identifier that the target uses to refer to the thread.
27190 Extra information about the thread, in a target-specific format. This
27194 The name of the thread. If the user specified a name using the
27195 @code{thread name} command, then this name is given. Otherwise, if
27196 @value{GDBN} can extract the thread name from the target, then that
27197 name is given. If @value{GDBN} cannot find the thread name, then this
27201 The stack frame currently executing in the thread.
27204 The thread's state. The @samp{state} field may have the following
27209 The thread is stopped. Frame information is available for stopped
27213 The thread is running. There's no frame information for running
27219 If @value{GDBN} can find the CPU core on which this thread is running,
27220 then this field is the core identifier. This field is optional.
27224 @subsubheading Example
27229 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
27230 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
27231 args=[]@},state="running"@},
27232 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
27233 frame=@{level="0",addr="0x0804891f",func="foo",
27234 args=[@{name="i",value="10"@}],
27235 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
27236 state="running"@}],
27237 current-thread-id="1"
27241 @subheading The @code{-thread-list-ids} Command
27242 @findex -thread-list-ids
27244 @subsubheading Synopsis
27250 Produces a list of the currently known @value{GDBN} thread ids. At the
27251 end of the list it also prints the total number of such threads.
27253 This command is retained for historical reasons, the
27254 @code{-thread-info} command should be used instead.
27256 @subsubheading @value{GDBN} Command
27258 Part of @samp{info threads} supplies the same information.
27260 @subsubheading Example
27265 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27266 current-thread-id="1",number-of-threads="3"
27271 @subheading The @code{-thread-select} Command
27272 @findex -thread-select
27274 @subsubheading Synopsis
27277 -thread-select @var{threadnum}
27280 Make @var{threadnum} the current thread. It prints the number of the new
27281 current thread, and the topmost frame for that thread.
27283 This command is deprecated in favor of explicitly using the
27284 @samp{--thread} option to each command.
27286 @subsubheading @value{GDBN} Command
27288 The corresponding @value{GDBN} command is @samp{thread}.
27290 @subsubheading Example
27297 *stopped,reason="end-stepping-range",thread-id="2",line="187",
27298 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
27302 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27303 number-of-threads="3"
27306 ^done,new-thread-id="3",
27307 frame=@{level="0",func="vprintf",
27308 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
27309 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
27313 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27314 @node GDB/MI Ada Tasking Commands
27315 @section @sc{gdb/mi} Ada Tasking Commands
27317 @subheading The @code{-ada-task-info} Command
27318 @findex -ada-task-info
27320 @subsubheading Synopsis
27323 -ada-task-info [ @var{task-id} ]
27326 Reports information about either a specific Ada task, if the
27327 @var{task-id} parameter is present, or about all Ada tasks.
27329 @subsubheading @value{GDBN} Command
27331 The @samp{info tasks} command prints the same information
27332 about all Ada tasks (@pxref{Ada Tasks}).
27334 @subsubheading Result
27336 The result is a table of Ada tasks. The following columns are
27337 defined for each Ada task:
27341 This field exists only for the current thread. It has the value @samp{*}.
27344 The identifier that @value{GDBN} uses to refer to the Ada task.
27347 The identifier that the target uses to refer to the Ada task.
27350 The identifier of the thread corresponding to the Ada task.
27352 This field should always exist, as Ada tasks are always implemented
27353 on top of a thread. But if @value{GDBN} cannot find this corresponding
27354 thread for any reason, the field is omitted.
27357 This field exists only when the task was created by another task.
27358 In this case, it provides the ID of the parent task.
27361 The base priority of the task.
27364 The current state of the task. For a detailed description of the
27365 possible states, see @ref{Ada Tasks}.
27368 The name of the task.
27372 @subsubheading Example
27376 ^done,tasks=@{nr_rows="3",nr_cols="8",
27377 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
27378 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
27379 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
27380 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
27381 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
27382 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
27383 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
27384 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
27385 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
27386 state="Child Termination Wait",name="main_task"@}]@}
27390 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27391 @node GDB/MI Program Execution
27392 @section @sc{gdb/mi} Program Execution
27394 These are the asynchronous commands which generate the out-of-band
27395 record @samp{*stopped}. Currently @value{GDBN} only really executes
27396 asynchronously with remote targets and this interaction is mimicked in
27399 @subheading The @code{-exec-continue} Command
27400 @findex -exec-continue
27402 @subsubheading Synopsis
27405 -exec-continue [--reverse] [--all|--thread-group N]
27408 Resumes the execution of the inferior program, which will continue
27409 to execute until it reaches a debugger stop event. If the
27410 @samp{--reverse} option is specified, execution resumes in reverse until
27411 it reaches a stop event. Stop events may include
27414 breakpoints or watchpoints
27416 signals or exceptions
27418 the end of the process (or its beginning under @samp{--reverse})
27420 the end or beginning of a replay log if one is being used.
27422 In all-stop mode (@pxref{All-Stop
27423 Mode}), may resume only one thread, or all threads, depending on the
27424 value of the @samp{scheduler-locking} variable. If @samp{--all} is
27425 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
27426 ignored in all-stop mode. If the @samp{--thread-group} options is
27427 specified, then all threads in that thread group are resumed.
27429 @subsubheading @value{GDBN} Command
27431 The corresponding @value{GDBN} corresponding is @samp{continue}.
27433 @subsubheading Example
27440 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
27441 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
27447 @subheading The @code{-exec-finish} Command
27448 @findex -exec-finish
27450 @subsubheading Synopsis
27453 -exec-finish [--reverse]
27456 Resumes the execution of the inferior program until the current
27457 function is exited. Displays the results returned by the function.
27458 If the @samp{--reverse} option is specified, resumes the reverse
27459 execution of the inferior program until the point where current
27460 function was called.
27462 @subsubheading @value{GDBN} Command
27464 The corresponding @value{GDBN} command is @samp{finish}.
27466 @subsubheading Example
27468 Function returning @code{void}.
27475 *stopped,reason="function-finished",frame=@{func="main",args=[],
27476 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
27480 Function returning other than @code{void}. The name of the internal
27481 @value{GDBN} variable storing the result is printed, together with the
27488 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
27489 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
27490 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27491 gdb-result-var="$1",return-value="0"
27496 @subheading The @code{-exec-interrupt} Command
27497 @findex -exec-interrupt
27499 @subsubheading Synopsis
27502 -exec-interrupt [--all|--thread-group N]
27505 Interrupts the background execution of the target. Note how the token
27506 associated with the stop message is the one for the execution command
27507 that has been interrupted. The token for the interrupt itself only
27508 appears in the @samp{^done} output. If the user is trying to
27509 interrupt a non-running program, an error message will be printed.
27511 Note that when asynchronous execution is enabled, this command is
27512 asynchronous just like other execution commands. That is, first the
27513 @samp{^done} response will be printed, and the target stop will be
27514 reported after that using the @samp{*stopped} notification.
27516 In non-stop mode, only the context thread is interrupted by default.
27517 All threads (in all inferiors) will be interrupted if the
27518 @samp{--all} option is specified. If the @samp{--thread-group}
27519 option is specified, all threads in that group will be interrupted.
27521 @subsubheading @value{GDBN} Command
27523 The corresponding @value{GDBN} command is @samp{interrupt}.
27525 @subsubheading Example
27536 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
27537 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
27538 fullname="/home/foo/bar/try.c",line="13"@}
27543 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
27547 @subheading The @code{-exec-jump} Command
27550 @subsubheading Synopsis
27553 -exec-jump @var{location}
27556 Resumes execution of the inferior program at the location specified by
27557 parameter. @xref{Specify Location}, for a description of the
27558 different forms of @var{location}.
27560 @subsubheading @value{GDBN} Command
27562 The corresponding @value{GDBN} command is @samp{jump}.
27564 @subsubheading Example
27567 -exec-jump foo.c:10
27568 *running,thread-id="all"
27573 @subheading The @code{-exec-next} Command
27576 @subsubheading Synopsis
27579 -exec-next [--reverse]
27582 Resumes execution of the inferior program, stopping when the beginning
27583 of the next source line is reached.
27585 If the @samp{--reverse} option is specified, resumes reverse execution
27586 of the inferior program, stopping at the beginning of the previous
27587 source line. If you issue this command on the first line of a
27588 function, it will take you back to the caller of that function, to the
27589 source line where the function was called.
27592 @subsubheading @value{GDBN} Command
27594 The corresponding @value{GDBN} command is @samp{next}.
27596 @subsubheading Example
27602 *stopped,reason="end-stepping-range",line="8",file="hello.c"
27607 @subheading The @code{-exec-next-instruction} Command
27608 @findex -exec-next-instruction
27610 @subsubheading Synopsis
27613 -exec-next-instruction [--reverse]
27616 Executes one machine instruction. If the instruction is a function
27617 call, continues until the function returns. If the program stops at an
27618 instruction in the middle of a source line, the address will be
27621 If the @samp{--reverse} option is specified, resumes reverse execution
27622 of the inferior program, stopping at the previous instruction. If the
27623 previously executed instruction was a return from another function,
27624 it will continue to execute in reverse until the call to that function
27625 (from the current stack frame) is reached.
27627 @subsubheading @value{GDBN} Command
27629 The corresponding @value{GDBN} command is @samp{nexti}.
27631 @subsubheading Example
27635 -exec-next-instruction
27639 *stopped,reason="end-stepping-range",
27640 addr="0x000100d4",line="5",file="hello.c"
27645 @subheading The @code{-exec-return} Command
27646 @findex -exec-return
27648 @subsubheading Synopsis
27654 Makes current function return immediately. Doesn't execute the inferior.
27655 Displays the new current frame.
27657 @subsubheading @value{GDBN} Command
27659 The corresponding @value{GDBN} command is @samp{return}.
27661 @subsubheading Example
27665 200-break-insert callee4
27666 200^done,bkpt=@{number="1",addr="0x00010734",
27667 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27672 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27673 frame=@{func="callee4",args=[],
27674 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27675 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27681 111^done,frame=@{level="0",func="callee3",
27682 args=[@{name="strarg",
27683 value="0x11940 \"A string argument.\""@}],
27684 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27685 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27690 @subheading The @code{-exec-run} Command
27693 @subsubheading Synopsis
27696 -exec-run [--all | --thread-group N]
27699 Starts execution of the inferior from the beginning. The inferior
27700 executes until either a breakpoint is encountered or the program
27701 exits. In the latter case the output will include an exit code, if
27702 the program has exited exceptionally.
27704 When no option is specified, the current inferior is started. If the
27705 @samp{--thread-group} option is specified, it should refer to a thread
27706 group of type @samp{process}, and that thread group will be started.
27707 If the @samp{--all} option is specified, then all inferiors will be started.
27709 @subsubheading @value{GDBN} Command
27711 The corresponding @value{GDBN} command is @samp{run}.
27713 @subsubheading Examples
27718 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
27723 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27724 frame=@{func="main",args=[],file="recursive2.c",
27725 fullname="/home/foo/bar/recursive2.c",line="4"@}
27730 Program exited normally:
27738 *stopped,reason="exited-normally"
27743 Program exited exceptionally:
27751 *stopped,reason="exited",exit-code="01"
27755 Another way the program can terminate is if it receives a signal such as
27756 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
27760 *stopped,reason="exited-signalled",signal-name="SIGINT",
27761 signal-meaning="Interrupt"
27765 @c @subheading -exec-signal
27768 @subheading The @code{-exec-step} Command
27771 @subsubheading Synopsis
27774 -exec-step [--reverse]
27777 Resumes execution of the inferior program, stopping when the beginning
27778 of the next source line is reached, if the next source line is not a
27779 function call. If it is, stop at the first instruction of the called
27780 function. If the @samp{--reverse} option is specified, resumes reverse
27781 execution of the inferior program, stopping at the beginning of the
27782 previously executed source line.
27784 @subsubheading @value{GDBN} Command
27786 The corresponding @value{GDBN} command is @samp{step}.
27788 @subsubheading Example
27790 Stepping into a function:
27796 *stopped,reason="end-stepping-range",
27797 frame=@{func="foo",args=[@{name="a",value="10"@},
27798 @{name="b",value="0"@}],file="recursive2.c",
27799 fullname="/home/foo/bar/recursive2.c",line="11"@}
27809 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
27814 @subheading The @code{-exec-step-instruction} Command
27815 @findex -exec-step-instruction
27817 @subsubheading Synopsis
27820 -exec-step-instruction [--reverse]
27823 Resumes the inferior which executes one machine instruction. If the
27824 @samp{--reverse} option is specified, resumes reverse execution of the
27825 inferior program, stopping at the previously executed instruction.
27826 The output, once @value{GDBN} has stopped, will vary depending on
27827 whether we have stopped in the middle of a source line or not. In the
27828 former case, the address at which the program stopped will be printed
27831 @subsubheading @value{GDBN} Command
27833 The corresponding @value{GDBN} command is @samp{stepi}.
27835 @subsubheading Example
27839 -exec-step-instruction
27843 *stopped,reason="end-stepping-range",
27844 frame=@{func="foo",args=[],file="try.c",
27845 fullname="/home/foo/bar/try.c",line="10"@}
27847 -exec-step-instruction
27851 *stopped,reason="end-stepping-range",
27852 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
27853 fullname="/home/foo/bar/try.c",line="10"@}
27858 @subheading The @code{-exec-until} Command
27859 @findex -exec-until
27861 @subsubheading Synopsis
27864 -exec-until [ @var{location} ]
27867 Executes the inferior until the @var{location} specified in the
27868 argument is reached. If there is no argument, the inferior executes
27869 until a source line greater than the current one is reached. The
27870 reason for stopping in this case will be @samp{location-reached}.
27872 @subsubheading @value{GDBN} Command
27874 The corresponding @value{GDBN} command is @samp{until}.
27876 @subsubheading Example
27880 -exec-until recursive2.c:6
27884 *stopped,reason="location-reached",frame=@{func="main",args=[],
27885 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
27890 @subheading -file-clear
27891 Is this going away????
27894 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27895 @node GDB/MI Stack Manipulation
27896 @section @sc{gdb/mi} Stack Manipulation Commands
27899 @subheading The @code{-stack-info-frame} Command
27900 @findex -stack-info-frame
27902 @subsubheading Synopsis
27908 Get info on the selected frame.
27910 @subsubheading @value{GDBN} Command
27912 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
27913 (without arguments).
27915 @subsubheading Example
27920 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
27921 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27922 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
27926 @subheading The @code{-stack-info-depth} Command
27927 @findex -stack-info-depth
27929 @subsubheading Synopsis
27932 -stack-info-depth [ @var{max-depth} ]
27935 Return the depth of the stack. If the integer argument @var{max-depth}
27936 is specified, do not count beyond @var{max-depth} frames.
27938 @subsubheading @value{GDBN} Command
27940 There's no equivalent @value{GDBN} command.
27942 @subsubheading Example
27944 For a stack with frame levels 0 through 11:
27951 -stack-info-depth 4
27954 -stack-info-depth 12
27957 -stack-info-depth 11
27960 -stack-info-depth 13
27965 @subheading The @code{-stack-list-arguments} Command
27966 @findex -stack-list-arguments
27968 @subsubheading Synopsis
27971 -stack-list-arguments @var{print-values}
27972 [ @var{low-frame} @var{high-frame} ]
27975 Display a list of the arguments for the frames between @var{low-frame}
27976 and @var{high-frame} (inclusive). If @var{low-frame} and
27977 @var{high-frame} are not provided, list the arguments for the whole
27978 call stack. If the two arguments are equal, show the single frame
27979 at the corresponding level. It is an error if @var{low-frame} is
27980 larger than the actual number of frames. On the other hand,
27981 @var{high-frame} may be larger than the actual number of frames, in
27982 which case only existing frames will be returned.
27984 If @var{print-values} is 0 or @code{--no-values}, print only the names of
27985 the variables; if it is 1 or @code{--all-values}, print also their
27986 values; and if it is 2 or @code{--simple-values}, print the name,
27987 type and value for simple data types, and the name and type for arrays,
27988 structures and unions.
27990 Use of this command to obtain arguments in a single frame is
27991 deprecated in favor of the @samp{-stack-list-variables} command.
27993 @subsubheading @value{GDBN} Command
27995 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
27996 @samp{gdb_get_args} command which partially overlaps with the
27997 functionality of @samp{-stack-list-arguments}.
27999 @subsubheading Example
28006 frame=@{level="0",addr="0x00010734",func="callee4",
28007 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28008 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
28009 frame=@{level="1",addr="0x0001076c",func="callee3",
28010 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28011 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
28012 frame=@{level="2",addr="0x0001078c",func="callee2",
28013 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28014 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
28015 frame=@{level="3",addr="0x000107b4",func="callee1",
28016 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28017 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
28018 frame=@{level="4",addr="0x000107e0",func="main",
28019 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28020 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
28022 -stack-list-arguments 0
28025 frame=@{level="0",args=[]@},
28026 frame=@{level="1",args=[name="strarg"]@},
28027 frame=@{level="2",args=[name="intarg",name="strarg"]@},
28028 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
28029 frame=@{level="4",args=[]@}]
28031 -stack-list-arguments 1
28034 frame=@{level="0",args=[]@},
28036 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28037 frame=@{level="2",args=[
28038 @{name="intarg",value="2"@},
28039 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28040 @{frame=@{level="3",args=[
28041 @{name="intarg",value="2"@},
28042 @{name="strarg",value="0x11940 \"A string argument.\""@},
28043 @{name="fltarg",value="3.5"@}]@},
28044 frame=@{level="4",args=[]@}]
28046 -stack-list-arguments 0 2 2
28047 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
28049 -stack-list-arguments 1 2 2
28050 ^done,stack-args=[frame=@{level="2",
28051 args=[@{name="intarg",value="2"@},
28052 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
28056 @c @subheading -stack-list-exception-handlers
28059 @subheading The @code{-stack-list-frames} Command
28060 @findex -stack-list-frames
28062 @subsubheading Synopsis
28065 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
28068 List the frames currently on the stack. For each frame it displays the
28073 The frame number, 0 being the topmost frame, i.e., the innermost function.
28075 The @code{$pc} value for that frame.
28079 File name of the source file where the function lives.
28080 @item @var{fullname}
28081 The full file name of the source file where the function lives.
28083 Line number corresponding to the @code{$pc}.
28085 The shared library where this function is defined. This is only given
28086 if the frame's function is not known.
28089 If invoked without arguments, this command prints a backtrace for the
28090 whole stack. If given two integer arguments, it shows the frames whose
28091 levels are between the two arguments (inclusive). If the two arguments
28092 are equal, it shows the single frame at the corresponding level. It is
28093 an error if @var{low-frame} is larger than the actual number of
28094 frames. On the other hand, @var{high-frame} may be larger than the
28095 actual number of frames, in which case only existing frames will be returned.
28097 @subsubheading @value{GDBN} Command
28099 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
28101 @subsubheading Example
28103 Full stack backtrace:
28109 [frame=@{level="0",addr="0x0001076c",func="foo",
28110 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
28111 frame=@{level="1",addr="0x000107a4",func="foo",
28112 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28113 frame=@{level="2",addr="0x000107a4",func="foo",
28114 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28115 frame=@{level="3",addr="0x000107a4",func="foo",
28116 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28117 frame=@{level="4",addr="0x000107a4",func="foo",
28118 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28119 frame=@{level="5",addr="0x000107a4",func="foo",
28120 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28121 frame=@{level="6",addr="0x000107a4",func="foo",
28122 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28123 frame=@{level="7",addr="0x000107a4",func="foo",
28124 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28125 frame=@{level="8",addr="0x000107a4",func="foo",
28126 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28127 frame=@{level="9",addr="0x000107a4",func="foo",
28128 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28129 frame=@{level="10",addr="0x000107a4",func="foo",
28130 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28131 frame=@{level="11",addr="0x00010738",func="main",
28132 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
28136 Show frames between @var{low_frame} and @var{high_frame}:
28140 -stack-list-frames 3 5
28142 [frame=@{level="3",addr="0x000107a4",func="foo",
28143 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28144 frame=@{level="4",addr="0x000107a4",func="foo",
28145 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28146 frame=@{level="5",addr="0x000107a4",func="foo",
28147 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28151 Show a single frame:
28155 -stack-list-frames 3 3
28157 [frame=@{level="3",addr="0x000107a4",func="foo",
28158 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28163 @subheading The @code{-stack-list-locals} Command
28164 @findex -stack-list-locals
28166 @subsubheading Synopsis
28169 -stack-list-locals @var{print-values}
28172 Display the local variable names for the selected frame. If
28173 @var{print-values} is 0 or @code{--no-values}, print only the names of
28174 the variables; if it is 1 or @code{--all-values}, print also their
28175 values; and if it is 2 or @code{--simple-values}, print the name,
28176 type and value for simple data types, and the name and type for arrays,
28177 structures and unions. In this last case, a frontend can immediately
28178 display the value of simple data types and create variable objects for
28179 other data types when the user wishes to explore their values in
28182 This command is deprecated in favor of the
28183 @samp{-stack-list-variables} command.
28185 @subsubheading @value{GDBN} Command
28187 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
28189 @subsubheading Example
28193 -stack-list-locals 0
28194 ^done,locals=[name="A",name="B",name="C"]
28196 -stack-list-locals --all-values
28197 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
28198 @{name="C",value="@{1, 2, 3@}"@}]
28199 -stack-list-locals --simple-values
28200 ^done,locals=[@{name="A",type="int",value="1"@},
28201 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
28205 @subheading The @code{-stack-list-variables} Command
28206 @findex -stack-list-variables
28208 @subsubheading Synopsis
28211 -stack-list-variables @var{print-values}
28214 Display the names of local variables and function arguments for the selected frame. If
28215 @var{print-values} is 0 or @code{--no-values}, print only the names of
28216 the variables; if it is 1 or @code{--all-values}, print also their
28217 values; and if it is 2 or @code{--simple-values}, print the name,
28218 type and value for simple data types, and the name and type for arrays,
28219 structures and unions.
28221 @subsubheading Example
28225 -stack-list-variables --thread 1 --frame 0 --all-values
28226 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
28231 @subheading The @code{-stack-select-frame} Command
28232 @findex -stack-select-frame
28234 @subsubheading Synopsis
28237 -stack-select-frame @var{framenum}
28240 Change the selected frame. Select a different frame @var{framenum} on
28243 This command in deprecated in favor of passing the @samp{--frame}
28244 option to every command.
28246 @subsubheading @value{GDBN} Command
28248 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
28249 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
28251 @subsubheading Example
28255 -stack-select-frame 2
28260 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28261 @node GDB/MI Variable Objects
28262 @section @sc{gdb/mi} Variable Objects
28266 @subheading Motivation for Variable Objects in @sc{gdb/mi}
28268 For the implementation of a variable debugger window (locals, watched
28269 expressions, etc.), we are proposing the adaptation of the existing code
28270 used by @code{Insight}.
28272 The two main reasons for that are:
28276 It has been proven in practice (it is already on its second generation).
28279 It will shorten development time (needless to say how important it is
28283 The original interface was designed to be used by Tcl code, so it was
28284 slightly changed so it could be used through @sc{gdb/mi}. This section
28285 describes the @sc{gdb/mi} operations that will be available and gives some
28286 hints about their use.
28288 @emph{Note}: In addition to the set of operations described here, we
28289 expect the @sc{gui} implementation of a variable window to require, at
28290 least, the following operations:
28293 @item @code{-gdb-show} @code{output-radix}
28294 @item @code{-stack-list-arguments}
28295 @item @code{-stack-list-locals}
28296 @item @code{-stack-select-frame}
28301 @subheading Introduction to Variable Objects
28303 @cindex variable objects in @sc{gdb/mi}
28305 Variable objects are "object-oriented" MI interface for examining and
28306 changing values of expressions. Unlike some other MI interfaces that
28307 work with expressions, variable objects are specifically designed for
28308 simple and efficient presentation in the frontend. A variable object
28309 is identified by string name. When a variable object is created, the
28310 frontend specifies the expression for that variable object. The
28311 expression can be a simple variable, or it can be an arbitrary complex
28312 expression, and can even involve CPU registers. After creating a
28313 variable object, the frontend can invoke other variable object
28314 operations---for example to obtain or change the value of a variable
28315 object, or to change display format.
28317 Variable objects have hierarchical tree structure. Any variable object
28318 that corresponds to a composite type, such as structure in C, has
28319 a number of child variable objects, for example corresponding to each
28320 element of a structure. A child variable object can itself have
28321 children, recursively. Recursion ends when we reach
28322 leaf variable objects, which always have built-in types. Child variable
28323 objects are created only by explicit request, so if a frontend
28324 is not interested in the children of a particular variable object, no
28325 child will be created.
28327 For a leaf variable object it is possible to obtain its value as a
28328 string, or set the value from a string. String value can be also
28329 obtained for a non-leaf variable object, but it's generally a string
28330 that only indicates the type of the object, and does not list its
28331 contents. Assignment to a non-leaf variable object is not allowed.
28333 A frontend does not need to read the values of all variable objects each time
28334 the program stops. Instead, MI provides an update command that lists all
28335 variable objects whose values has changed since the last update
28336 operation. This considerably reduces the amount of data that must
28337 be transferred to the frontend. As noted above, children variable
28338 objects are created on demand, and only leaf variable objects have a
28339 real value. As result, gdb will read target memory only for leaf
28340 variables that frontend has created.
28342 The automatic update is not always desirable. For example, a frontend
28343 might want to keep a value of some expression for future reference,
28344 and never update it. For another example, fetching memory is
28345 relatively slow for embedded targets, so a frontend might want
28346 to disable automatic update for the variables that are either not
28347 visible on the screen, or ``closed''. This is possible using so
28348 called ``frozen variable objects''. Such variable objects are never
28349 implicitly updated.
28351 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
28352 fixed variable object, the expression is parsed when the variable
28353 object is created, including associating identifiers to specific
28354 variables. The meaning of expression never changes. For a floating
28355 variable object the values of variables whose names appear in the
28356 expressions are re-evaluated every time in the context of the current
28357 frame. Consider this example:
28362 struct work_state state;
28369 If a fixed variable object for the @code{state} variable is created in
28370 this function, and we enter the recursive call, the variable
28371 object will report the value of @code{state} in the top-level
28372 @code{do_work} invocation. On the other hand, a floating variable
28373 object will report the value of @code{state} in the current frame.
28375 If an expression specified when creating a fixed variable object
28376 refers to a local variable, the variable object becomes bound to the
28377 thread and frame in which the variable object is created. When such
28378 variable object is updated, @value{GDBN} makes sure that the
28379 thread/frame combination the variable object is bound to still exists,
28380 and re-evaluates the variable object in context of that thread/frame.
28382 The following is the complete set of @sc{gdb/mi} operations defined to
28383 access this functionality:
28385 @multitable @columnfractions .4 .6
28386 @item @strong{Operation}
28387 @tab @strong{Description}
28389 @item @code{-enable-pretty-printing}
28390 @tab enable Python-based pretty-printing
28391 @item @code{-var-create}
28392 @tab create a variable object
28393 @item @code{-var-delete}
28394 @tab delete the variable object and/or its children
28395 @item @code{-var-set-format}
28396 @tab set the display format of this variable
28397 @item @code{-var-show-format}
28398 @tab show the display format of this variable
28399 @item @code{-var-info-num-children}
28400 @tab tells how many children this object has
28401 @item @code{-var-list-children}
28402 @tab return a list of the object's children
28403 @item @code{-var-info-type}
28404 @tab show the type of this variable object
28405 @item @code{-var-info-expression}
28406 @tab print parent-relative expression that this variable object represents
28407 @item @code{-var-info-path-expression}
28408 @tab print full expression that this variable object represents
28409 @item @code{-var-show-attributes}
28410 @tab is this variable editable? does it exist here?
28411 @item @code{-var-evaluate-expression}
28412 @tab get the value of this variable
28413 @item @code{-var-assign}
28414 @tab set the value of this variable
28415 @item @code{-var-update}
28416 @tab update the variable and its children
28417 @item @code{-var-set-frozen}
28418 @tab set frozeness attribute
28419 @item @code{-var-set-update-range}
28420 @tab set range of children to display on update
28423 In the next subsection we describe each operation in detail and suggest
28424 how it can be used.
28426 @subheading Description And Use of Operations on Variable Objects
28428 @subheading The @code{-enable-pretty-printing} Command
28429 @findex -enable-pretty-printing
28432 -enable-pretty-printing
28435 @value{GDBN} allows Python-based visualizers to affect the output of the
28436 MI variable object commands. However, because there was no way to
28437 implement this in a fully backward-compatible way, a front end must
28438 request that this functionality be enabled.
28440 Once enabled, this feature cannot be disabled.
28442 Note that if Python support has not been compiled into @value{GDBN},
28443 this command will still succeed (and do nothing).
28445 This feature is currently (as of @value{GDBN} 7.0) experimental, and
28446 may work differently in future versions of @value{GDBN}.
28448 @subheading The @code{-var-create} Command
28449 @findex -var-create
28451 @subsubheading Synopsis
28454 -var-create @{@var{name} | "-"@}
28455 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
28458 This operation creates a variable object, which allows the monitoring of
28459 a variable, the result of an expression, a memory cell or a CPU
28462 The @var{name} parameter is the string by which the object can be
28463 referenced. It must be unique. If @samp{-} is specified, the varobj
28464 system will generate a string ``varNNNNNN'' automatically. It will be
28465 unique provided that one does not specify @var{name} of that format.
28466 The command fails if a duplicate name is found.
28468 The frame under which the expression should be evaluated can be
28469 specified by @var{frame-addr}. A @samp{*} indicates that the current
28470 frame should be used. A @samp{@@} indicates that a floating variable
28471 object must be created.
28473 @var{expression} is any expression valid on the current language set (must not
28474 begin with a @samp{*}), or one of the following:
28478 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
28481 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
28484 @samp{$@var{regname}} --- a CPU register name
28487 @cindex dynamic varobj
28488 A varobj's contents may be provided by a Python-based pretty-printer. In this
28489 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
28490 have slightly different semantics in some cases. If the
28491 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
28492 will never create a dynamic varobj. This ensures backward
28493 compatibility for existing clients.
28495 @subsubheading Result
28497 This operation returns attributes of the newly-created varobj. These
28502 The name of the varobj.
28505 The number of children of the varobj. This number is not necessarily
28506 reliable for a dynamic varobj. Instead, you must examine the
28507 @samp{has_more} attribute.
28510 The varobj's scalar value. For a varobj whose type is some sort of
28511 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
28512 will not be interesting.
28515 The varobj's type. This is a string representation of the type, as
28516 would be printed by the @value{GDBN} CLI.
28519 If a variable object is bound to a specific thread, then this is the
28520 thread's identifier.
28523 For a dynamic varobj, this indicates whether there appear to be any
28524 children available. For a non-dynamic varobj, this will be 0.
28527 This attribute will be present and have the value @samp{1} if the
28528 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28529 then this attribute will not be present.
28532 A dynamic varobj can supply a display hint to the front end. The
28533 value comes directly from the Python pretty-printer object's
28534 @code{display_hint} method. @xref{Pretty Printing API}.
28537 Typical output will look like this:
28540 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
28541 has_more="@var{has_more}"
28545 @subheading The @code{-var-delete} Command
28546 @findex -var-delete
28548 @subsubheading Synopsis
28551 -var-delete [ -c ] @var{name}
28554 Deletes a previously created variable object and all of its children.
28555 With the @samp{-c} option, just deletes the children.
28557 Returns an error if the object @var{name} is not found.
28560 @subheading The @code{-var-set-format} Command
28561 @findex -var-set-format
28563 @subsubheading Synopsis
28566 -var-set-format @var{name} @var{format-spec}
28569 Sets the output format for the value of the object @var{name} to be
28572 @anchor{-var-set-format}
28573 The syntax for the @var{format-spec} is as follows:
28576 @var{format-spec} @expansion{}
28577 @{binary | decimal | hexadecimal | octal | natural@}
28580 The natural format is the default format choosen automatically
28581 based on the variable type (like decimal for an @code{int}, hex
28582 for pointers, etc.).
28584 For a variable with children, the format is set only on the
28585 variable itself, and the children are not affected.
28587 @subheading The @code{-var-show-format} Command
28588 @findex -var-show-format
28590 @subsubheading Synopsis
28593 -var-show-format @var{name}
28596 Returns the format used to display the value of the object @var{name}.
28599 @var{format} @expansion{}
28604 @subheading The @code{-var-info-num-children} Command
28605 @findex -var-info-num-children
28607 @subsubheading Synopsis
28610 -var-info-num-children @var{name}
28613 Returns the number of children of a variable object @var{name}:
28619 Note that this number is not completely reliable for a dynamic varobj.
28620 It will return the current number of children, but more children may
28624 @subheading The @code{-var-list-children} Command
28625 @findex -var-list-children
28627 @subsubheading Synopsis
28630 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
28632 @anchor{-var-list-children}
28634 Return a list of the children of the specified variable object and
28635 create variable objects for them, if they do not already exist. With
28636 a single argument or if @var{print-values} has a value of 0 or
28637 @code{--no-values}, print only the names of the variables; if
28638 @var{print-values} is 1 or @code{--all-values}, also print their
28639 values; and if it is 2 or @code{--simple-values} print the name and
28640 value for simple data types and just the name for arrays, structures
28643 @var{from} and @var{to}, if specified, indicate the range of children
28644 to report. If @var{from} or @var{to} is less than zero, the range is
28645 reset and all children will be reported. Otherwise, children starting
28646 at @var{from} (zero-based) and up to and excluding @var{to} will be
28649 If a child range is requested, it will only affect the current call to
28650 @code{-var-list-children}, but not future calls to @code{-var-update}.
28651 For this, you must instead use @code{-var-set-update-range}. The
28652 intent of this approach is to enable a front end to implement any
28653 update approach it likes; for example, scrolling a view may cause the
28654 front end to request more children with @code{-var-list-children}, and
28655 then the front end could call @code{-var-set-update-range} with a
28656 different range to ensure that future updates are restricted to just
28659 For each child the following results are returned:
28664 Name of the variable object created for this child.
28667 The expression to be shown to the user by the front end to designate this child.
28668 For example this may be the name of a structure member.
28670 For a dynamic varobj, this value cannot be used to form an
28671 expression. There is no way to do this at all with a dynamic varobj.
28673 For C/C@t{++} structures there are several pseudo children returned to
28674 designate access qualifiers. For these pseudo children @var{exp} is
28675 @samp{public}, @samp{private}, or @samp{protected}. In this case the
28676 type and value are not present.
28678 A dynamic varobj will not report the access qualifying
28679 pseudo-children, regardless of the language. This information is not
28680 available at all with a dynamic varobj.
28683 Number of children this child has. For a dynamic varobj, this will be
28687 The type of the child.
28690 If values were requested, this is the value.
28693 If this variable object is associated with a thread, this is the thread id.
28694 Otherwise this result is not present.
28697 If the variable object is frozen, this variable will be present with a value of 1.
28700 The result may have its own attributes:
28704 A dynamic varobj can supply a display hint to the front end. The
28705 value comes directly from the Python pretty-printer object's
28706 @code{display_hint} method. @xref{Pretty Printing API}.
28709 This is an integer attribute which is nonzero if there are children
28710 remaining after the end of the selected range.
28713 @subsubheading Example
28717 -var-list-children n
28718 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28719 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
28721 -var-list-children --all-values n
28722 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28723 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
28727 @subheading The @code{-var-info-type} Command
28728 @findex -var-info-type
28730 @subsubheading Synopsis
28733 -var-info-type @var{name}
28736 Returns the type of the specified variable @var{name}. The type is
28737 returned as a string in the same format as it is output by the
28741 type=@var{typename}
28745 @subheading The @code{-var-info-expression} Command
28746 @findex -var-info-expression
28748 @subsubheading Synopsis
28751 -var-info-expression @var{name}
28754 Returns a string that is suitable for presenting this
28755 variable object in user interface. The string is generally
28756 not valid expression in the current language, and cannot be evaluated.
28758 For example, if @code{a} is an array, and variable object
28759 @code{A} was created for @code{a}, then we'll get this output:
28762 (gdb) -var-info-expression A.1
28763 ^done,lang="C",exp="1"
28767 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
28769 Note that the output of the @code{-var-list-children} command also
28770 includes those expressions, so the @code{-var-info-expression} command
28773 @subheading The @code{-var-info-path-expression} Command
28774 @findex -var-info-path-expression
28776 @subsubheading Synopsis
28779 -var-info-path-expression @var{name}
28782 Returns an expression that can be evaluated in the current
28783 context and will yield the same value that a variable object has.
28784 Compare this with the @code{-var-info-expression} command, which
28785 result can be used only for UI presentation. Typical use of
28786 the @code{-var-info-path-expression} command is creating a
28787 watchpoint from a variable object.
28789 This command is currently not valid for children of a dynamic varobj,
28790 and will give an error when invoked on one.
28792 For example, suppose @code{C} is a C@t{++} class, derived from class
28793 @code{Base}, and that the @code{Base} class has a member called
28794 @code{m_size}. Assume a variable @code{c} is has the type of
28795 @code{C} and a variable object @code{C} was created for variable
28796 @code{c}. Then, we'll get this output:
28798 (gdb) -var-info-path-expression C.Base.public.m_size
28799 ^done,path_expr=((Base)c).m_size)
28802 @subheading The @code{-var-show-attributes} Command
28803 @findex -var-show-attributes
28805 @subsubheading Synopsis
28808 -var-show-attributes @var{name}
28811 List attributes of the specified variable object @var{name}:
28814 status=@var{attr} [ ( ,@var{attr} )* ]
28818 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
28820 @subheading The @code{-var-evaluate-expression} Command
28821 @findex -var-evaluate-expression
28823 @subsubheading Synopsis
28826 -var-evaluate-expression [-f @var{format-spec}] @var{name}
28829 Evaluates the expression that is represented by the specified variable
28830 object and returns its value as a string. The format of the string
28831 can be specified with the @samp{-f} option. The possible values of
28832 this option are the same as for @code{-var-set-format}
28833 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
28834 the current display format will be used. The current display format
28835 can be changed using the @code{-var-set-format} command.
28841 Note that one must invoke @code{-var-list-children} for a variable
28842 before the value of a child variable can be evaluated.
28844 @subheading The @code{-var-assign} Command
28845 @findex -var-assign
28847 @subsubheading Synopsis
28850 -var-assign @var{name} @var{expression}
28853 Assigns the value of @var{expression} to the variable object specified
28854 by @var{name}. The object must be @samp{editable}. If the variable's
28855 value is altered by the assign, the variable will show up in any
28856 subsequent @code{-var-update} list.
28858 @subsubheading Example
28866 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
28870 @subheading The @code{-var-update} Command
28871 @findex -var-update
28873 @subsubheading Synopsis
28876 -var-update [@var{print-values}] @{@var{name} | "*"@}
28879 Reevaluate the expressions corresponding to the variable object
28880 @var{name} and all its direct and indirect children, and return the
28881 list of variable objects whose values have changed; @var{name} must
28882 be a root variable object. Here, ``changed'' means that the result of
28883 @code{-var-evaluate-expression} before and after the
28884 @code{-var-update} is different. If @samp{*} is used as the variable
28885 object names, all existing variable objects are updated, except
28886 for frozen ones (@pxref{-var-set-frozen}). The option
28887 @var{print-values} determines whether both names and values, or just
28888 names are printed. The possible values of this option are the same
28889 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
28890 recommended to use the @samp{--all-values} option, to reduce the
28891 number of MI commands needed on each program stop.
28893 With the @samp{*} parameter, if a variable object is bound to a
28894 currently running thread, it will not be updated, without any
28897 If @code{-var-set-update-range} was previously used on a varobj, then
28898 only the selected range of children will be reported.
28900 @code{-var-update} reports all the changed varobjs in a tuple named
28903 Each item in the change list is itself a tuple holding:
28907 The name of the varobj.
28910 If values were requested for this update, then this field will be
28911 present and will hold the value of the varobj.
28914 @anchor{-var-update}
28915 This field is a string which may take one of three values:
28919 The variable object's current value is valid.
28922 The variable object does not currently hold a valid value but it may
28923 hold one in the future if its associated expression comes back into
28927 The variable object no longer holds a valid value.
28928 This can occur when the executable file being debugged has changed,
28929 either through recompilation or by using the @value{GDBN} @code{file}
28930 command. The front end should normally choose to delete these variable
28934 In the future new values may be added to this list so the front should
28935 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
28938 This is only present if the varobj is still valid. If the type
28939 changed, then this will be the string @samp{true}; otherwise it will
28943 If the varobj's type changed, then this field will be present and will
28946 @item new_num_children
28947 For a dynamic varobj, if the number of children changed, or if the
28948 type changed, this will be the new number of children.
28950 The @samp{numchild} field in other varobj responses is generally not
28951 valid for a dynamic varobj -- it will show the number of children that
28952 @value{GDBN} knows about, but because dynamic varobjs lazily
28953 instantiate their children, this will not reflect the number of
28954 children which may be available.
28956 The @samp{new_num_children} attribute only reports changes to the
28957 number of children known by @value{GDBN}. This is the only way to
28958 detect whether an update has removed children (which necessarily can
28959 only happen at the end of the update range).
28962 The display hint, if any.
28965 This is an integer value, which will be 1 if there are more children
28966 available outside the varobj's update range.
28969 This attribute will be present and have the value @samp{1} if the
28970 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28971 then this attribute will not be present.
28974 If new children were added to a dynamic varobj within the selected
28975 update range (as set by @code{-var-set-update-range}), then they will
28976 be listed in this attribute.
28979 @subsubheading Example
28986 -var-update --all-values var1
28987 ^done,changelist=[@{name="var1",value="3",in_scope="true",
28988 type_changed="false"@}]
28992 @subheading The @code{-var-set-frozen} Command
28993 @findex -var-set-frozen
28994 @anchor{-var-set-frozen}
28996 @subsubheading Synopsis
28999 -var-set-frozen @var{name} @var{flag}
29002 Set the frozenness flag on the variable object @var{name}. The
29003 @var{flag} parameter should be either @samp{1} to make the variable
29004 frozen or @samp{0} to make it unfrozen. If a variable object is
29005 frozen, then neither itself, nor any of its children, are
29006 implicitly updated by @code{-var-update} of
29007 a parent variable or by @code{-var-update *}. Only
29008 @code{-var-update} of the variable itself will update its value and
29009 values of its children. After a variable object is unfrozen, it is
29010 implicitly updated by all subsequent @code{-var-update} operations.
29011 Unfreezing a variable does not update it, only subsequent
29012 @code{-var-update} does.
29014 @subsubheading Example
29018 -var-set-frozen V 1
29023 @subheading The @code{-var-set-update-range} command
29024 @findex -var-set-update-range
29025 @anchor{-var-set-update-range}
29027 @subsubheading Synopsis
29030 -var-set-update-range @var{name} @var{from} @var{to}
29033 Set the range of children to be returned by future invocations of
29034 @code{-var-update}.
29036 @var{from} and @var{to} indicate the range of children to report. If
29037 @var{from} or @var{to} is less than zero, the range is reset and all
29038 children will be reported. Otherwise, children starting at @var{from}
29039 (zero-based) and up to and excluding @var{to} will be reported.
29041 @subsubheading Example
29045 -var-set-update-range V 1 2
29049 @subheading The @code{-var-set-visualizer} command
29050 @findex -var-set-visualizer
29051 @anchor{-var-set-visualizer}
29053 @subsubheading Synopsis
29056 -var-set-visualizer @var{name} @var{visualizer}
29059 Set a visualizer for the variable object @var{name}.
29061 @var{visualizer} is the visualizer to use. The special value
29062 @samp{None} means to disable any visualizer in use.
29064 If not @samp{None}, @var{visualizer} must be a Python expression.
29065 This expression must evaluate to a callable object which accepts a
29066 single argument. @value{GDBN} will call this object with the value of
29067 the varobj @var{name} as an argument (this is done so that the same
29068 Python pretty-printing code can be used for both the CLI and MI).
29069 When called, this object must return an object which conforms to the
29070 pretty-printing interface (@pxref{Pretty Printing API}).
29072 The pre-defined function @code{gdb.default_visualizer} may be used to
29073 select a visualizer by following the built-in process
29074 (@pxref{Selecting Pretty-Printers}). This is done automatically when
29075 a varobj is created, and so ordinarily is not needed.
29077 This feature is only available if Python support is enabled. The MI
29078 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
29079 can be used to check this.
29081 @subsubheading Example
29083 Resetting the visualizer:
29087 -var-set-visualizer V None
29091 Reselecting the default (type-based) visualizer:
29095 -var-set-visualizer V gdb.default_visualizer
29099 Suppose @code{SomeClass} is a visualizer class. A lambda expression
29100 can be used to instantiate this class for a varobj:
29104 -var-set-visualizer V "lambda val: SomeClass()"
29108 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29109 @node GDB/MI Data Manipulation
29110 @section @sc{gdb/mi} Data Manipulation
29112 @cindex data manipulation, in @sc{gdb/mi}
29113 @cindex @sc{gdb/mi}, data manipulation
29114 This section describes the @sc{gdb/mi} commands that manipulate data:
29115 examine memory and registers, evaluate expressions, etc.
29117 @c REMOVED FROM THE INTERFACE.
29118 @c @subheading -data-assign
29119 @c Change the value of a program variable. Plenty of side effects.
29120 @c @subsubheading GDB Command
29122 @c @subsubheading Example
29125 @subheading The @code{-data-disassemble} Command
29126 @findex -data-disassemble
29128 @subsubheading Synopsis
29132 [ -s @var{start-addr} -e @var{end-addr} ]
29133 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
29141 @item @var{start-addr}
29142 is the beginning address (or @code{$pc})
29143 @item @var{end-addr}
29145 @item @var{filename}
29146 is the name of the file to disassemble
29147 @item @var{linenum}
29148 is the line number to disassemble around
29150 is the number of disassembly lines to be produced. If it is -1,
29151 the whole function will be disassembled, in case no @var{end-addr} is
29152 specified. If @var{end-addr} is specified as a non-zero value, and
29153 @var{lines} is lower than the number of disassembly lines between
29154 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
29155 displayed; if @var{lines} is higher than the number of lines between
29156 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
29159 is either 0 (meaning only disassembly), 1 (meaning mixed source and
29160 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
29161 mixed source and disassembly with raw opcodes).
29164 @subsubheading Result
29166 The output for each instruction is composed of four fields:
29175 Note that whatever included in the instruction field, is not manipulated
29176 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
29178 @subsubheading @value{GDBN} Command
29180 There's no direct mapping from this command to the CLI.
29182 @subsubheading Example
29184 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
29188 -data-disassemble -s $pc -e "$pc + 20" -- 0
29191 @{address="0x000107c0",func-name="main",offset="4",
29192 inst="mov 2, %o0"@},
29193 @{address="0x000107c4",func-name="main",offset="8",
29194 inst="sethi %hi(0x11800), %o2"@},
29195 @{address="0x000107c8",func-name="main",offset="12",
29196 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
29197 @{address="0x000107cc",func-name="main",offset="16",
29198 inst="sethi %hi(0x11800), %o2"@},
29199 @{address="0x000107d0",func-name="main",offset="20",
29200 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
29204 Disassemble the whole @code{main} function. Line 32 is part of
29208 -data-disassemble -f basics.c -l 32 -- 0
29210 @{address="0x000107bc",func-name="main",offset="0",
29211 inst="save %sp, -112, %sp"@},
29212 @{address="0x000107c0",func-name="main",offset="4",
29213 inst="mov 2, %o0"@},
29214 @{address="0x000107c4",func-name="main",offset="8",
29215 inst="sethi %hi(0x11800), %o2"@},
29217 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
29218 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
29222 Disassemble 3 instructions from the start of @code{main}:
29226 -data-disassemble -f basics.c -l 32 -n 3 -- 0
29228 @{address="0x000107bc",func-name="main",offset="0",
29229 inst="save %sp, -112, %sp"@},
29230 @{address="0x000107c0",func-name="main",offset="4",
29231 inst="mov 2, %o0"@},
29232 @{address="0x000107c4",func-name="main",offset="8",
29233 inst="sethi %hi(0x11800), %o2"@}]
29237 Disassemble 3 instructions from the start of @code{main} in mixed mode:
29241 -data-disassemble -f basics.c -l 32 -n 3 -- 1
29243 src_and_asm_line=@{line="31",
29244 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
29245 testsuite/gdb.mi/basics.c",line_asm_insn=[
29246 @{address="0x000107bc",func-name="main",offset="0",
29247 inst="save %sp, -112, %sp"@}]@},
29248 src_and_asm_line=@{line="32",
29249 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
29250 testsuite/gdb.mi/basics.c",line_asm_insn=[
29251 @{address="0x000107c0",func-name="main",offset="4",
29252 inst="mov 2, %o0"@},
29253 @{address="0x000107c4",func-name="main",offset="8",
29254 inst="sethi %hi(0x11800), %o2"@}]@}]
29259 @subheading The @code{-data-evaluate-expression} Command
29260 @findex -data-evaluate-expression
29262 @subsubheading Synopsis
29265 -data-evaluate-expression @var{expr}
29268 Evaluate @var{expr} as an expression. The expression could contain an
29269 inferior function call. The function call will execute synchronously.
29270 If the expression contains spaces, it must be enclosed in double quotes.
29272 @subsubheading @value{GDBN} Command
29274 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
29275 @samp{call}. In @code{gdbtk} only, there's a corresponding
29276 @samp{gdb_eval} command.
29278 @subsubheading Example
29280 In the following example, the numbers that precede the commands are the
29281 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
29282 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
29286 211-data-evaluate-expression A
29289 311-data-evaluate-expression &A
29290 311^done,value="0xefffeb7c"
29292 411-data-evaluate-expression A+3
29295 511-data-evaluate-expression "A + 3"
29301 @subheading The @code{-data-list-changed-registers} Command
29302 @findex -data-list-changed-registers
29304 @subsubheading Synopsis
29307 -data-list-changed-registers
29310 Display a list of the registers that have changed.
29312 @subsubheading @value{GDBN} Command
29314 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
29315 has the corresponding command @samp{gdb_changed_register_list}.
29317 @subsubheading Example
29319 On a PPC MBX board:
29327 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
29328 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
29331 -data-list-changed-registers
29332 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
29333 "10","11","13","14","15","16","17","18","19","20","21","22","23",
29334 "24","25","26","27","28","30","31","64","65","66","67","69"]
29339 @subheading The @code{-data-list-register-names} Command
29340 @findex -data-list-register-names
29342 @subsubheading Synopsis
29345 -data-list-register-names [ ( @var{regno} )+ ]
29348 Show a list of register names for the current target. If no arguments
29349 are given, it shows a list of the names of all the registers. If
29350 integer numbers are given as arguments, it will print a list of the
29351 names of the registers corresponding to the arguments. To ensure
29352 consistency between a register name and its number, the output list may
29353 include empty register names.
29355 @subsubheading @value{GDBN} Command
29357 @value{GDBN} does not have a command which corresponds to
29358 @samp{-data-list-register-names}. In @code{gdbtk} there is a
29359 corresponding command @samp{gdb_regnames}.
29361 @subsubheading Example
29363 For the PPC MBX board:
29366 -data-list-register-names
29367 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
29368 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
29369 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
29370 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
29371 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
29372 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
29373 "", "pc","ps","cr","lr","ctr","xer"]
29375 -data-list-register-names 1 2 3
29376 ^done,register-names=["r1","r2","r3"]
29380 @subheading The @code{-data-list-register-values} Command
29381 @findex -data-list-register-values
29383 @subsubheading Synopsis
29386 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
29389 Display the registers' contents. @var{fmt} is the format according to
29390 which the registers' contents are to be returned, followed by an optional
29391 list of numbers specifying the registers to display. A missing list of
29392 numbers indicates that the contents of all the registers must be returned.
29394 Allowed formats for @var{fmt} are:
29411 @subsubheading @value{GDBN} Command
29413 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
29414 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
29416 @subsubheading Example
29418 For a PPC MBX board (note: line breaks are for readability only, they
29419 don't appear in the actual output):
29423 -data-list-register-values r 64 65
29424 ^done,register-values=[@{number="64",value="0xfe00a300"@},
29425 @{number="65",value="0x00029002"@}]
29427 -data-list-register-values x
29428 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
29429 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
29430 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
29431 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
29432 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
29433 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
29434 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
29435 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
29436 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
29437 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
29438 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
29439 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
29440 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
29441 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
29442 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
29443 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
29444 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
29445 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
29446 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
29447 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
29448 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
29449 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
29450 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
29451 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
29452 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
29453 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
29454 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
29455 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
29456 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
29457 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
29458 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
29459 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
29460 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
29461 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
29462 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
29463 @{number="69",value="0x20002b03"@}]
29468 @subheading The @code{-data-read-memory} Command
29469 @findex -data-read-memory
29471 This command is deprecated, use @code{-data-read-memory-bytes} instead.
29473 @subsubheading Synopsis
29476 -data-read-memory [ -o @var{byte-offset} ]
29477 @var{address} @var{word-format} @var{word-size}
29478 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
29485 @item @var{address}
29486 An expression specifying the address of the first memory word to be
29487 read. Complex expressions containing embedded white space should be
29488 quoted using the C convention.
29490 @item @var{word-format}
29491 The format to be used to print the memory words. The notation is the
29492 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
29495 @item @var{word-size}
29496 The size of each memory word in bytes.
29498 @item @var{nr-rows}
29499 The number of rows in the output table.
29501 @item @var{nr-cols}
29502 The number of columns in the output table.
29505 If present, indicates that each row should include an @sc{ascii} dump. The
29506 value of @var{aschar} is used as a padding character when a byte is not a
29507 member of the printable @sc{ascii} character set (printable @sc{ascii}
29508 characters are those whose code is between 32 and 126, inclusively).
29510 @item @var{byte-offset}
29511 An offset to add to the @var{address} before fetching memory.
29514 This command displays memory contents as a table of @var{nr-rows} by
29515 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
29516 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
29517 (returned as @samp{total-bytes}). Should less than the requested number
29518 of bytes be returned by the target, the missing words are identified
29519 using @samp{N/A}. The number of bytes read from the target is returned
29520 in @samp{nr-bytes} and the starting address used to read memory in
29523 The address of the next/previous row or page is available in
29524 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
29527 @subsubheading @value{GDBN} Command
29529 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
29530 @samp{gdb_get_mem} memory read command.
29532 @subsubheading Example
29534 Read six bytes of memory starting at @code{bytes+6} but then offset by
29535 @code{-6} bytes. Format as three rows of two columns. One byte per
29536 word. Display each word in hex.
29540 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
29541 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
29542 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
29543 prev-page="0x0000138a",memory=[
29544 @{addr="0x00001390",data=["0x00","0x01"]@},
29545 @{addr="0x00001392",data=["0x02","0x03"]@},
29546 @{addr="0x00001394",data=["0x04","0x05"]@}]
29550 Read two bytes of memory starting at address @code{shorts + 64} and
29551 display as a single word formatted in decimal.
29555 5-data-read-memory shorts+64 d 2 1 1
29556 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
29557 next-row="0x00001512",prev-row="0x0000150e",
29558 next-page="0x00001512",prev-page="0x0000150e",memory=[
29559 @{addr="0x00001510",data=["128"]@}]
29563 Read thirty two bytes of memory starting at @code{bytes+16} and format
29564 as eight rows of four columns. Include a string encoding with @samp{x}
29565 used as the non-printable character.
29569 4-data-read-memory bytes+16 x 1 8 4 x
29570 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
29571 next-row="0x000013c0",prev-row="0x0000139c",
29572 next-page="0x000013c0",prev-page="0x00001380",memory=[
29573 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
29574 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
29575 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
29576 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
29577 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
29578 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
29579 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
29580 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
29584 @subheading The @code{-data-read-memory-bytes} Command
29585 @findex -data-read-memory-bytes
29587 @subsubheading Synopsis
29590 -data-read-memory-bytes [ -o @var{byte-offset} ]
29591 @var{address} @var{count}
29598 @item @var{address}
29599 An expression specifying the address of the first memory word to be
29600 read. Complex expressions containing embedded white space should be
29601 quoted using the C convention.
29604 The number of bytes to read. This should be an integer literal.
29606 @item @var{byte-offset}
29607 The offsets in bytes relative to @var{address} at which to start
29608 reading. This should be an integer literal. This option is provided
29609 so that a frontend is not required to first evaluate address and then
29610 perform address arithmetics itself.
29614 This command attempts to read all accessible memory regions in the
29615 specified range. First, all regions marked as unreadable in the memory
29616 map (if one is defined) will be skipped. @xref{Memory Region
29617 Attributes}. Second, @value{GDBN} will attempt to read the remaining
29618 regions. For each one, if reading full region results in an errors,
29619 @value{GDBN} will try to read a subset of the region.
29621 In general, every single byte in the region may be readable or not,
29622 and the only way to read every readable byte is to try a read at
29623 every address, which is not practical. Therefore, @value{GDBN} will
29624 attempt to read all accessible bytes at either beginning or the end
29625 of the region, using a binary division scheme. This heuristic works
29626 well for reading accross a memory map boundary. Note that if a region
29627 has a readable range that is neither at the beginning or the end,
29628 @value{GDBN} will not read it.
29630 The result record (@pxref{GDB/MI Result Records}) that is output of
29631 the command includes a field named @samp{memory} whose content is a
29632 list of tuples. Each tuple represent a successfully read memory block
29633 and has the following fields:
29637 The start address of the memory block, as hexadecimal literal.
29640 The end address of the memory block, as hexadecimal literal.
29643 The offset of the memory block, as hexadecimal literal, relative to
29644 the start address passed to @code{-data-read-memory-bytes}.
29647 The contents of the memory block, in hex.
29653 @subsubheading @value{GDBN} Command
29655 The corresponding @value{GDBN} command is @samp{x}.
29657 @subsubheading Example
29661 -data-read-memory-bytes &a 10
29662 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
29664 contents="01000000020000000300"@}]
29669 @subheading The @code{-data-write-memory-bytes} Command
29670 @findex -data-write-memory-bytes
29672 @subsubheading Synopsis
29675 -data-write-memory-bytes @var{address} @var{contents}
29682 @item @var{address}
29683 An expression specifying the address of the first memory word to be
29684 read. Complex expressions containing embedded white space should be
29685 quoted using the C convention.
29687 @item @var{contents}
29688 The hex-encoded bytes to write.
29692 @subsubheading @value{GDBN} Command
29694 There's no corresponding @value{GDBN} command.
29696 @subsubheading Example
29700 -data-write-memory-bytes &a "aabbccdd"
29706 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29707 @node GDB/MI Tracepoint Commands
29708 @section @sc{gdb/mi} Tracepoint Commands
29710 The commands defined in this section implement MI support for
29711 tracepoints. For detailed introduction, see @ref{Tracepoints}.
29713 @subheading The @code{-trace-find} Command
29714 @findex -trace-find
29716 @subsubheading Synopsis
29719 -trace-find @var{mode} [@var{parameters}@dots{}]
29722 Find a trace frame using criteria defined by @var{mode} and
29723 @var{parameters}. The following table lists permissible
29724 modes and their parameters. For details of operation, see @ref{tfind}.
29729 No parameters are required. Stops examining trace frames.
29732 An integer is required as parameter. Selects tracepoint frame with
29735 @item tracepoint-number
29736 An integer is required as parameter. Finds next
29737 trace frame that corresponds to tracepoint with the specified number.
29740 An address is required as parameter. Finds
29741 next trace frame that corresponds to any tracepoint at the specified
29744 @item pc-inside-range
29745 Two addresses are required as parameters. Finds next trace
29746 frame that corresponds to a tracepoint at an address inside the
29747 specified range. Both bounds are considered to be inside the range.
29749 @item pc-outside-range
29750 Two addresses are required as parameters. Finds
29751 next trace frame that corresponds to a tracepoint at an address outside
29752 the specified range. Both bounds are considered to be inside the range.
29755 Line specification is required as parameter. @xref{Specify Location}.
29756 Finds next trace frame that corresponds to a tracepoint at
29757 the specified location.
29761 If @samp{none} was passed as @var{mode}, the response does not
29762 have fields. Otherwise, the response may have the following fields:
29766 This field has either @samp{0} or @samp{1} as the value, depending
29767 on whether a matching tracepoint was found.
29770 The index of the found traceframe. This field is present iff
29771 the @samp{found} field has value of @samp{1}.
29774 The index of the found tracepoint. This field is present iff
29775 the @samp{found} field has value of @samp{1}.
29778 The information about the frame corresponding to the found trace
29779 frame. This field is present only if a trace frame was found.
29780 @xref{GDB/MI Frame Information}, for description of this field.
29784 @subsubheading @value{GDBN} Command
29786 The corresponding @value{GDBN} command is @samp{tfind}.
29788 @subheading -trace-define-variable
29789 @findex -trace-define-variable
29791 @subsubheading Synopsis
29794 -trace-define-variable @var{name} [ @var{value} ]
29797 Create trace variable @var{name} if it does not exist. If
29798 @var{value} is specified, sets the initial value of the specified
29799 trace variable to that value. Note that the @var{name} should start
29800 with the @samp{$} character.
29802 @subsubheading @value{GDBN} Command
29804 The corresponding @value{GDBN} command is @samp{tvariable}.
29806 @subheading -trace-list-variables
29807 @findex -trace-list-variables
29809 @subsubheading Synopsis
29812 -trace-list-variables
29815 Return a table of all defined trace variables. Each element of the
29816 table has the following fields:
29820 The name of the trace variable. This field is always present.
29823 The initial value. This is a 64-bit signed integer. This
29824 field is always present.
29827 The value the trace variable has at the moment. This is a 64-bit
29828 signed integer. This field is absent iff current value is
29829 not defined, for example if the trace was never run, or is
29834 @subsubheading @value{GDBN} Command
29836 The corresponding @value{GDBN} command is @samp{tvariables}.
29838 @subsubheading Example
29842 -trace-list-variables
29843 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
29844 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
29845 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
29846 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
29847 body=[variable=@{name="$trace_timestamp",initial="0"@}
29848 variable=@{name="$foo",initial="10",current="15"@}]@}
29852 @subheading -trace-save
29853 @findex -trace-save
29855 @subsubheading Synopsis
29858 -trace-save [-r ] @var{filename}
29861 Saves the collected trace data to @var{filename}. Without the
29862 @samp{-r} option, the data is downloaded from the target and saved
29863 in a local file. With the @samp{-r} option the target is asked
29864 to perform the save.
29866 @subsubheading @value{GDBN} Command
29868 The corresponding @value{GDBN} command is @samp{tsave}.
29871 @subheading -trace-start
29872 @findex -trace-start
29874 @subsubheading Synopsis
29880 Starts a tracing experiments. The result of this command does not
29883 @subsubheading @value{GDBN} Command
29885 The corresponding @value{GDBN} command is @samp{tstart}.
29887 @subheading -trace-status
29888 @findex -trace-status
29890 @subsubheading Synopsis
29896 Obtains the status of a tracing experiment. The result may include
29897 the following fields:
29902 May have a value of either @samp{0}, when no tracing operations are
29903 supported, @samp{1}, when all tracing operations are supported, or
29904 @samp{file} when examining trace file. In the latter case, examining
29905 of trace frame is possible but new tracing experiement cannot be
29906 started. This field is always present.
29909 May have a value of either @samp{0} or @samp{1} depending on whether
29910 tracing experiement is in progress on target. This field is present
29911 if @samp{supported} field is not @samp{0}.
29914 Report the reason why the tracing was stopped last time. This field
29915 may be absent iff tracing was never stopped on target yet. The
29916 value of @samp{request} means the tracing was stopped as result of
29917 the @code{-trace-stop} command. The value of @samp{overflow} means
29918 the tracing buffer is full. The value of @samp{disconnection} means
29919 tracing was automatically stopped when @value{GDBN} has disconnected.
29920 The value of @samp{passcount} means tracing was stopped when a
29921 tracepoint was passed a maximal number of times for that tracepoint.
29922 This field is present if @samp{supported} field is not @samp{0}.
29924 @item stopping-tracepoint
29925 The number of tracepoint whose passcount as exceeded. This field is
29926 present iff the @samp{stop-reason} field has the value of
29930 @itemx frames-created
29931 The @samp{frames} field is a count of the total number of trace frames
29932 in the trace buffer, while @samp{frames-created} is the total created
29933 during the run, including ones that were discarded, such as when a
29934 circular trace buffer filled up. Both fields are optional.
29938 These fields tell the current size of the tracing buffer and the
29939 remaining space. These fields are optional.
29942 The value of the circular trace buffer flag. @code{1} means that the
29943 trace buffer is circular and old trace frames will be discarded if
29944 necessary to make room, @code{0} means that the trace buffer is linear
29948 The value of the disconnected tracing flag. @code{1} means that
29949 tracing will continue after @value{GDBN} disconnects, @code{0} means
29950 that the trace run will stop.
29954 @subsubheading @value{GDBN} Command
29956 The corresponding @value{GDBN} command is @samp{tstatus}.
29958 @subheading -trace-stop
29959 @findex -trace-stop
29961 @subsubheading Synopsis
29967 Stops a tracing experiment. The result of this command has the same
29968 fields as @code{-trace-status}, except that the @samp{supported} and
29969 @samp{running} fields are not output.
29971 @subsubheading @value{GDBN} Command
29973 The corresponding @value{GDBN} command is @samp{tstop}.
29976 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29977 @node GDB/MI Symbol Query
29978 @section @sc{gdb/mi} Symbol Query Commands
29982 @subheading The @code{-symbol-info-address} Command
29983 @findex -symbol-info-address
29985 @subsubheading Synopsis
29988 -symbol-info-address @var{symbol}
29991 Describe where @var{symbol} is stored.
29993 @subsubheading @value{GDBN} Command
29995 The corresponding @value{GDBN} command is @samp{info address}.
29997 @subsubheading Example
30001 @subheading The @code{-symbol-info-file} Command
30002 @findex -symbol-info-file
30004 @subsubheading Synopsis
30010 Show the file for the symbol.
30012 @subsubheading @value{GDBN} Command
30014 There's no equivalent @value{GDBN} command. @code{gdbtk} has
30015 @samp{gdb_find_file}.
30017 @subsubheading Example
30021 @subheading The @code{-symbol-info-function} Command
30022 @findex -symbol-info-function
30024 @subsubheading Synopsis
30027 -symbol-info-function
30030 Show which function the symbol lives in.
30032 @subsubheading @value{GDBN} Command
30034 @samp{gdb_get_function} in @code{gdbtk}.
30036 @subsubheading Example
30040 @subheading The @code{-symbol-info-line} Command
30041 @findex -symbol-info-line
30043 @subsubheading Synopsis
30049 Show the core addresses of the code for a source line.
30051 @subsubheading @value{GDBN} Command
30053 The corresponding @value{GDBN} command is @samp{info line}.
30054 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
30056 @subsubheading Example
30060 @subheading The @code{-symbol-info-symbol} Command
30061 @findex -symbol-info-symbol
30063 @subsubheading Synopsis
30066 -symbol-info-symbol @var{addr}
30069 Describe what symbol is at location @var{addr}.
30071 @subsubheading @value{GDBN} Command
30073 The corresponding @value{GDBN} command is @samp{info symbol}.
30075 @subsubheading Example
30079 @subheading The @code{-symbol-list-functions} Command
30080 @findex -symbol-list-functions
30082 @subsubheading Synopsis
30085 -symbol-list-functions
30088 List the functions in the executable.
30090 @subsubheading @value{GDBN} Command
30092 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
30093 @samp{gdb_search} in @code{gdbtk}.
30095 @subsubheading Example
30100 @subheading The @code{-symbol-list-lines} Command
30101 @findex -symbol-list-lines
30103 @subsubheading Synopsis
30106 -symbol-list-lines @var{filename}
30109 Print the list of lines that contain code and their associated program
30110 addresses for the given source filename. The entries are sorted in
30111 ascending PC order.
30113 @subsubheading @value{GDBN} Command
30115 There is no corresponding @value{GDBN} command.
30117 @subsubheading Example
30120 -symbol-list-lines basics.c
30121 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
30127 @subheading The @code{-symbol-list-types} Command
30128 @findex -symbol-list-types
30130 @subsubheading Synopsis
30136 List all the type names.
30138 @subsubheading @value{GDBN} Command
30140 The corresponding commands are @samp{info types} in @value{GDBN},
30141 @samp{gdb_search} in @code{gdbtk}.
30143 @subsubheading Example
30147 @subheading The @code{-symbol-list-variables} Command
30148 @findex -symbol-list-variables
30150 @subsubheading Synopsis
30153 -symbol-list-variables
30156 List all the global and static variable names.
30158 @subsubheading @value{GDBN} Command
30160 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
30162 @subsubheading Example
30166 @subheading The @code{-symbol-locate} Command
30167 @findex -symbol-locate
30169 @subsubheading Synopsis
30175 @subsubheading @value{GDBN} Command
30177 @samp{gdb_loc} in @code{gdbtk}.
30179 @subsubheading Example
30183 @subheading The @code{-symbol-type} Command
30184 @findex -symbol-type
30186 @subsubheading Synopsis
30189 -symbol-type @var{variable}
30192 Show type of @var{variable}.
30194 @subsubheading @value{GDBN} Command
30196 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
30197 @samp{gdb_obj_variable}.
30199 @subsubheading Example
30204 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30205 @node GDB/MI File Commands
30206 @section @sc{gdb/mi} File Commands
30208 This section describes the GDB/MI commands to specify executable file names
30209 and to read in and obtain symbol table information.
30211 @subheading The @code{-file-exec-and-symbols} Command
30212 @findex -file-exec-and-symbols
30214 @subsubheading Synopsis
30217 -file-exec-and-symbols @var{file}
30220 Specify the executable file to be debugged. This file is the one from
30221 which the symbol table is also read. If no file is specified, the
30222 command clears the executable and symbol information. If breakpoints
30223 are set when using this command with no arguments, @value{GDBN} will produce
30224 error messages. Otherwise, no output is produced, except a completion
30227 @subsubheading @value{GDBN} Command
30229 The corresponding @value{GDBN} command is @samp{file}.
30231 @subsubheading Example
30235 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30241 @subheading The @code{-file-exec-file} Command
30242 @findex -file-exec-file
30244 @subsubheading Synopsis
30247 -file-exec-file @var{file}
30250 Specify the executable file to be debugged. Unlike
30251 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
30252 from this file. If used without argument, @value{GDBN} clears the information
30253 about the executable file. No output is produced, except a completion
30256 @subsubheading @value{GDBN} Command
30258 The corresponding @value{GDBN} command is @samp{exec-file}.
30260 @subsubheading Example
30264 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30271 @subheading The @code{-file-list-exec-sections} Command
30272 @findex -file-list-exec-sections
30274 @subsubheading Synopsis
30277 -file-list-exec-sections
30280 List the sections of the current executable file.
30282 @subsubheading @value{GDBN} Command
30284 The @value{GDBN} command @samp{info file} shows, among the rest, the same
30285 information as this command. @code{gdbtk} has a corresponding command
30286 @samp{gdb_load_info}.
30288 @subsubheading Example
30293 @subheading The @code{-file-list-exec-source-file} Command
30294 @findex -file-list-exec-source-file
30296 @subsubheading Synopsis
30299 -file-list-exec-source-file
30302 List the line number, the current source file, and the absolute path
30303 to the current source file for the current executable. The macro
30304 information field has a value of @samp{1} or @samp{0} depending on
30305 whether or not the file includes preprocessor macro information.
30307 @subsubheading @value{GDBN} Command
30309 The @value{GDBN} equivalent is @samp{info source}
30311 @subsubheading Example
30315 123-file-list-exec-source-file
30316 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
30321 @subheading The @code{-file-list-exec-source-files} Command
30322 @findex -file-list-exec-source-files
30324 @subsubheading Synopsis
30327 -file-list-exec-source-files
30330 List the source files for the current executable.
30332 It will always output the filename, but only when @value{GDBN} can find
30333 the absolute file name of a source file, will it output the fullname.
30335 @subsubheading @value{GDBN} Command
30337 The @value{GDBN} equivalent is @samp{info sources}.
30338 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
30340 @subsubheading Example
30343 -file-list-exec-source-files
30345 @{file=foo.c,fullname=/home/foo.c@},
30346 @{file=/home/bar.c,fullname=/home/bar.c@},
30347 @{file=gdb_could_not_find_fullpath.c@}]
30352 @subheading The @code{-file-list-shared-libraries} Command
30353 @findex -file-list-shared-libraries
30355 @subsubheading Synopsis
30358 -file-list-shared-libraries
30361 List the shared libraries in the program.
30363 @subsubheading @value{GDBN} Command
30365 The corresponding @value{GDBN} command is @samp{info shared}.
30367 @subsubheading Example
30371 @subheading The @code{-file-list-symbol-files} Command
30372 @findex -file-list-symbol-files
30374 @subsubheading Synopsis
30377 -file-list-symbol-files
30382 @subsubheading @value{GDBN} Command
30384 The corresponding @value{GDBN} command is @samp{info file} (part of it).
30386 @subsubheading Example
30391 @subheading The @code{-file-symbol-file} Command
30392 @findex -file-symbol-file
30394 @subsubheading Synopsis
30397 -file-symbol-file @var{file}
30400 Read symbol table info from the specified @var{file} argument. When
30401 used without arguments, clears @value{GDBN}'s symbol table info. No output is
30402 produced, except for a completion notification.
30404 @subsubheading @value{GDBN} Command
30406 The corresponding @value{GDBN} command is @samp{symbol-file}.
30408 @subsubheading Example
30412 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30418 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30419 @node GDB/MI Memory Overlay Commands
30420 @section @sc{gdb/mi} Memory Overlay Commands
30422 The memory overlay commands are not implemented.
30424 @c @subheading -overlay-auto
30426 @c @subheading -overlay-list-mapping-state
30428 @c @subheading -overlay-list-overlays
30430 @c @subheading -overlay-map
30432 @c @subheading -overlay-off
30434 @c @subheading -overlay-on
30436 @c @subheading -overlay-unmap
30438 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30439 @node GDB/MI Signal Handling Commands
30440 @section @sc{gdb/mi} Signal Handling Commands
30442 Signal handling commands are not implemented.
30444 @c @subheading -signal-handle
30446 @c @subheading -signal-list-handle-actions
30448 @c @subheading -signal-list-signal-types
30452 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30453 @node GDB/MI Target Manipulation
30454 @section @sc{gdb/mi} Target Manipulation Commands
30457 @subheading The @code{-target-attach} Command
30458 @findex -target-attach
30460 @subsubheading Synopsis
30463 -target-attach @var{pid} | @var{gid} | @var{file}
30466 Attach to a process @var{pid} or a file @var{file} outside of
30467 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
30468 group, the id previously returned by
30469 @samp{-list-thread-groups --available} must be used.
30471 @subsubheading @value{GDBN} Command
30473 The corresponding @value{GDBN} command is @samp{attach}.
30475 @subsubheading Example
30479 =thread-created,id="1"
30480 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
30486 @subheading The @code{-target-compare-sections} Command
30487 @findex -target-compare-sections
30489 @subsubheading Synopsis
30492 -target-compare-sections [ @var{section} ]
30495 Compare data of section @var{section} on target to the exec file.
30496 Without the argument, all sections are compared.
30498 @subsubheading @value{GDBN} Command
30500 The @value{GDBN} equivalent is @samp{compare-sections}.
30502 @subsubheading Example
30507 @subheading The @code{-target-detach} Command
30508 @findex -target-detach
30510 @subsubheading Synopsis
30513 -target-detach [ @var{pid} | @var{gid} ]
30516 Detach from the remote target which normally resumes its execution.
30517 If either @var{pid} or @var{gid} is specified, detaches from either
30518 the specified process, or specified thread group. There's no output.
30520 @subsubheading @value{GDBN} Command
30522 The corresponding @value{GDBN} command is @samp{detach}.
30524 @subsubheading Example
30534 @subheading The @code{-target-disconnect} Command
30535 @findex -target-disconnect
30537 @subsubheading Synopsis
30543 Disconnect from the remote target. There's no output and the target is
30544 generally not resumed.
30546 @subsubheading @value{GDBN} Command
30548 The corresponding @value{GDBN} command is @samp{disconnect}.
30550 @subsubheading Example
30560 @subheading The @code{-target-download} Command
30561 @findex -target-download
30563 @subsubheading Synopsis
30569 Loads the executable onto the remote target.
30570 It prints out an update message every half second, which includes the fields:
30574 The name of the section.
30576 The size of what has been sent so far for that section.
30578 The size of the section.
30580 The total size of what was sent so far (the current and the previous sections).
30582 The size of the overall executable to download.
30586 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
30587 @sc{gdb/mi} Output Syntax}).
30589 In addition, it prints the name and size of the sections, as they are
30590 downloaded. These messages include the following fields:
30594 The name of the section.
30596 The size of the section.
30598 The size of the overall executable to download.
30602 At the end, a summary is printed.
30604 @subsubheading @value{GDBN} Command
30606 The corresponding @value{GDBN} command is @samp{load}.
30608 @subsubheading Example
30610 Note: each status message appears on a single line. Here the messages
30611 have been broken down so that they can fit onto a page.
30616 +download,@{section=".text",section-size="6668",total-size="9880"@}
30617 +download,@{section=".text",section-sent="512",section-size="6668",
30618 total-sent="512",total-size="9880"@}
30619 +download,@{section=".text",section-sent="1024",section-size="6668",
30620 total-sent="1024",total-size="9880"@}
30621 +download,@{section=".text",section-sent="1536",section-size="6668",
30622 total-sent="1536",total-size="9880"@}
30623 +download,@{section=".text",section-sent="2048",section-size="6668",
30624 total-sent="2048",total-size="9880"@}
30625 +download,@{section=".text",section-sent="2560",section-size="6668",
30626 total-sent="2560",total-size="9880"@}
30627 +download,@{section=".text",section-sent="3072",section-size="6668",
30628 total-sent="3072",total-size="9880"@}
30629 +download,@{section=".text",section-sent="3584",section-size="6668",
30630 total-sent="3584",total-size="9880"@}
30631 +download,@{section=".text",section-sent="4096",section-size="6668",
30632 total-sent="4096",total-size="9880"@}
30633 +download,@{section=".text",section-sent="4608",section-size="6668",
30634 total-sent="4608",total-size="9880"@}
30635 +download,@{section=".text",section-sent="5120",section-size="6668",
30636 total-sent="5120",total-size="9880"@}
30637 +download,@{section=".text",section-sent="5632",section-size="6668",
30638 total-sent="5632",total-size="9880"@}
30639 +download,@{section=".text",section-sent="6144",section-size="6668",
30640 total-sent="6144",total-size="9880"@}
30641 +download,@{section=".text",section-sent="6656",section-size="6668",
30642 total-sent="6656",total-size="9880"@}
30643 +download,@{section=".init",section-size="28",total-size="9880"@}
30644 +download,@{section=".fini",section-size="28",total-size="9880"@}
30645 +download,@{section=".data",section-size="3156",total-size="9880"@}
30646 +download,@{section=".data",section-sent="512",section-size="3156",
30647 total-sent="7236",total-size="9880"@}
30648 +download,@{section=".data",section-sent="1024",section-size="3156",
30649 total-sent="7748",total-size="9880"@}
30650 +download,@{section=".data",section-sent="1536",section-size="3156",
30651 total-sent="8260",total-size="9880"@}
30652 +download,@{section=".data",section-sent="2048",section-size="3156",
30653 total-sent="8772",total-size="9880"@}
30654 +download,@{section=".data",section-sent="2560",section-size="3156",
30655 total-sent="9284",total-size="9880"@}
30656 +download,@{section=".data",section-sent="3072",section-size="3156",
30657 total-sent="9796",total-size="9880"@}
30658 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
30665 @subheading The @code{-target-exec-status} Command
30666 @findex -target-exec-status
30668 @subsubheading Synopsis
30671 -target-exec-status
30674 Provide information on the state of the target (whether it is running or
30675 not, for instance).
30677 @subsubheading @value{GDBN} Command
30679 There's no equivalent @value{GDBN} command.
30681 @subsubheading Example
30685 @subheading The @code{-target-list-available-targets} Command
30686 @findex -target-list-available-targets
30688 @subsubheading Synopsis
30691 -target-list-available-targets
30694 List the possible targets to connect to.
30696 @subsubheading @value{GDBN} Command
30698 The corresponding @value{GDBN} command is @samp{help target}.
30700 @subsubheading Example
30704 @subheading The @code{-target-list-current-targets} Command
30705 @findex -target-list-current-targets
30707 @subsubheading Synopsis
30710 -target-list-current-targets
30713 Describe the current target.
30715 @subsubheading @value{GDBN} Command
30717 The corresponding information is printed by @samp{info file} (among
30720 @subsubheading Example
30724 @subheading The @code{-target-list-parameters} Command
30725 @findex -target-list-parameters
30727 @subsubheading Synopsis
30730 -target-list-parameters
30736 @subsubheading @value{GDBN} Command
30740 @subsubheading Example
30744 @subheading The @code{-target-select} Command
30745 @findex -target-select
30747 @subsubheading Synopsis
30750 -target-select @var{type} @var{parameters @dots{}}
30753 Connect @value{GDBN} to the remote target. This command takes two args:
30757 The type of target, for instance @samp{remote}, etc.
30758 @item @var{parameters}
30759 Device names, host names and the like. @xref{Target Commands, ,
30760 Commands for Managing Targets}, for more details.
30763 The output is a connection notification, followed by the address at
30764 which the target program is, in the following form:
30767 ^connected,addr="@var{address}",func="@var{function name}",
30768 args=[@var{arg list}]
30771 @subsubheading @value{GDBN} Command
30773 The corresponding @value{GDBN} command is @samp{target}.
30775 @subsubheading Example
30779 -target-select remote /dev/ttya
30780 ^connected,addr="0xfe00a300",func="??",args=[]
30784 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30785 @node GDB/MI File Transfer Commands
30786 @section @sc{gdb/mi} File Transfer Commands
30789 @subheading The @code{-target-file-put} Command
30790 @findex -target-file-put
30792 @subsubheading Synopsis
30795 -target-file-put @var{hostfile} @var{targetfile}
30798 Copy file @var{hostfile} from the host system (the machine running
30799 @value{GDBN}) to @var{targetfile} on the target system.
30801 @subsubheading @value{GDBN} Command
30803 The corresponding @value{GDBN} command is @samp{remote put}.
30805 @subsubheading Example
30809 -target-file-put localfile remotefile
30815 @subheading The @code{-target-file-get} Command
30816 @findex -target-file-get
30818 @subsubheading Synopsis
30821 -target-file-get @var{targetfile} @var{hostfile}
30824 Copy file @var{targetfile} from the target system to @var{hostfile}
30825 on the host system.
30827 @subsubheading @value{GDBN} Command
30829 The corresponding @value{GDBN} command is @samp{remote get}.
30831 @subsubheading Example
30835 -target-file-get remotefile localfile
30841 @subheading The @code{-target-file-delete} Command
30842 @findex -target-file-delete
30844 @subsubheading Synopsis
30847 -target-file-delete @var{targetfile}
30850 Delete @var{targetfile} from the target system.
30852 @subsubheading @value{GDBN} Command
30854 The corresponding @value{GDBN} command is @samp{remote delete}.
30856 @subsubheading Example
30860 -target-file-delete remotefile
30866 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30867 @node GDB/MI Miscellaneous Commands
30868 @section Miscellaneous @sc{gdb/mi} Commands
30870 @c @subheading -gdb-complete
30872 @subheading The @code{-gdb-exit} Command
30875 @subsubheading Synopsis
30881 Exit @value{GDBN} immediately.
30883 @subsubheading @value{GDBN} Command
30885 Approximately corresponds to @samp{quit}.
30887 @subsubheading Example
30897 @subheading The @code{-exec-abort} Command
30898 @findex -exec-abort
30900 @subsubheading Synopsis
30906 Kill the inferior running program.
30908 @subsubheading @value{GDBN} Command
30910 The corresponding @value{GDBN} command is @samp{kill}.
30912 @subsubheading Example
30917 @subheading The @code{-gdb-set} Command
30920 @subsubheading Synopsis
30926 Set an internal @value{GDBN} variable.
30927 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
30929 @subsubheading @value{GDBN} Command
30931 The corresponding @value{GDBN} command is @samp{set}.
30933 @subsubheading Example
30943 @subheading The @code{-gdb-show} Command
30946 @subsubheading Synopsis
30952 Show the current value of a @value{GDBN} variable.
30954 @subsubheading @value{GDBN} Command
30956 The corresponding @value{GDBN} command is @samp{show}.
30958 @subsubheading Example
30967 @c @subheading -gdb-source
30970 @subheading The @code{-gdb-version} Command
30971 @findex -gdb-version
30973 @subsubheading Synopsis
30979 Show version information for @value{GDBN}. Used mostly in testing.
30981 @subsubheading @value{GDBN} Command
30983 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
30984 default shows this information when you start an interactive session.
30986 @subsubheading Example
30988 @c This example modifies the actual output from GDB to avoid overfull
30994 ~Copyright 2000 Free Software Foundation, Inc.
30995 ~GDB is free software, covered by the GNU General Public License, and
30996 ~you are welcome to change it and/or distribute copies of it under
30997 ~ certain conditions.
30998 ~Type "show copying" to see the conditions.
30999 ~There is absolutely no warranty for GDB. Type "show warranty" for
31001 ~This GDB was configured as
31002 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
31007 @subheading The @code{-list-features} Command
31008 @findex -list-features
31010 Returns a list of particular features of the MI protocol that
31011 this version of gdb implements. A feature can be a command,
31012 or a new field in an output of some command, or even an
31013 important bugfix. While a frontend can sometimes detect presence
31014 of a feature at runtime, it is easier to perform detection at debugger
31017 The command returns a list of strings, with each string naming an
31018 available feature. Each returned string is just a name, it does not
31019 have any internal structure. The list of possible feature names
31025 (gdb) -list-features
31026 ^done,result=["feature1","feature2"]
31029 The current list of features is:
31032 @item frozen-varobjs
31033 Indicates support for the @code{-var-set-frozen} command, as well
31034 as possible presense of the @code{frozen} field in the output
31035 of @code{-varobj-create}.
31036 @item pending-breakpoints
31037 Indicates support for the @option{-f} option to the @code{-break-insert}
31040 Indicates Python scripting support, Python-based
31041 pretty-printing commands, and possible presence of the
31042 @samp{display_hint} field in the output of @code{-var-list-children}
31044 Indicates support for the @code{-thread-info} command.
31045 @item data-read-memory-bytes
31046 Indicates support for the @code{-data-read-memory-bytes} and the
31047 @code{-data-write-memory-bytes} commands.
31048 @item breakpoint-notifications
31049 Indicates that changes to breakpoints and breakpoints created via the
31050 CLI will be announced via async records.
31051 @item ada-task-info
31052 Indicates support for the @code{-ada-task-info} command.
31055 @subheading The @code{-list-target-features} Command
31056 @findex -list-target-features
31058 Returns a list of particular features that are supported by the
31059 target. Those features affect the permitted MI commands, but
31060 unlike the features reported by the @code{-list-features} command, the
31061 features depend on which target GDB is using at the moment. Whenever
31062 a target can change, due to commands such as @code{-target-select},
31063 @code{-target-attach} or @code{-exec-run}, the list of target features
31064 may change, and the frontend should obtain it again.
31068 (gdb) -list-features
31069 ^done,result=["async"]
31072 The current list of features is:
31076 Indicates that the target is capable of asynchronous command
31077 execution, which means that @value{GDBN} will accept further commands
31078 while the target is running.
31081 Indicates that the target is capable of reverse execution.
31082 @xref{Reverse Execution}, for more information.
31086 @subheading The @code{-list-thread-groups} Command
31087 @findex -list-thread-groups
31089 @subheading Synopsis
31092 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
31095 Lists thread groups (@pxref{Thread groups}). When a single thread
31096 group is passed as the argument, lists the children of that group.
31097 When several thread group are passed, lists information about those
31098 thread groups. Without any parameters, lists information about all
31099 top-level thread groups.
31101 Normally, thread groups that are being debugged are reported.
31102 With the @samp{--available} option, @value{GDBN} reports thread groups
31103 available on the target.
31105 The output of this command may have either a @samp{threads} result or
31106 a @samp{groups} result. The @samp{thread} result has a list of tuples
31107 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
31108 Information}). The @samp{groups} result has a list of tuples as value,
31109 each tuple describing a thread group. If top-level groups are
31110 requested (that is, no parameter is passed), or when several groups
31111 are passed, the output always has a @samp{groups} result. The format
31112 of the @samp{group} result is described below.
31114 To reduce the number of roundtrips it's possible to list thread groups
31115 together with their children, by passing the @samp{--recurse} option
31116 and the recursion depth. Presently, only recursion depth of 1 is
31117 permitted. If this option is present, then every reported thread group
31118 will also include its children, either as @samp{group} or
31119 @samp{threads} field.
31121 In general, any combination of option and parameters is permitted, with
31122 the following caveats:
31126 When a single thread group is passed, the output will typically
31127 be the @samp{threads} result. Because threads may not contain
31128 anything, the @samp{recurse} option will be ignored.
31131 When the @samp{--available} option is passed, limited information may
31132 be available. In particular, the list of threads of a process might
31133 be inaccessible. Further, specifying specific thread groups might
31134 not give any performance advantage over listing all thread groups.
31135 The frontend should assume that @samp{-list-thread-groups --available}
31136 is always an expensive operation and cache the results.
31140 The @samp{groups} result is a list of tuples, where each tuple may
31141 have the following fields:
31145 Identifier of the thread group. This field is always present.
31146 The identifier is an opaque string; frontends should not try to
31147 convert it to an integer, even though it might look like one.
31150 The type of the thread group. At present, only @samp{process} is a
31154 The target-specific process identifier. This field is only present
31155 for thread groups of type @samp{process} and only if the process exists.
31158 The number of children this thread group has. This field may be
31159 absent for an available thread group.
31162 This field has a list of tuples as value, each tuple describing a
31163 thread. It may be present if the @samp{--recurse} option is
31164 specified, and it's actually possible to obtain the threads.
31167 This field is a list of integers, each identifying a core that one
31168 thread of the group is running on. This field may be absent if
31169 such information is not available.
31172 The name of the executable file that corresponds to this thread group.
31173 The field is only present for thread groups of type @samp{process},
31174 and only if there is a corresponding executable file.
31178 @subheading Example
31182 -list-thread-groups
31183 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
31184 -list-thread-groups 17
31185 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31186 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
31187 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31188 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
31189 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
31190 -list-thread-groups --available
31191 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
31192 -list-thread-groups --available --recurse 1
31193 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31194 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31195 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
31196 -list-thread-groups --available --recurse 1 17 18
31197 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31198 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31199 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
31203 @subheading The @code{-add-inferior} Command
31204 @findex -add-inferior
31206 @subheading Synopsis
31212 Creates a new inferior (@pxref{Inferiors and Programs}). The created
31213 inferior is not associated with any executable. Such association may
31214 be established with the @samp{-file-exec-and-symbols} command
31215 (@pxref{GDB/MI File Commands}). The command response has a single
31216 field, @samp{thread-group}, whose value is the identifier of the
31217 thread group corresponding to the new inferior.
31219 @subheading Example
31224 ^done,thread-group="i3"
31227 @subheading The @code{-interpreter-exec} Command
31228 @findex -interpreter-exec
31230 @subheading Synopsis
31233 -interpreter-exec @var{interpreter} @var{command}
31235 @anchor{-interpreter-exec}
31237 Execute the specified @var{command} in the given @var{interpreter}.
31239 @subheading @value{GDBN} Command
31241 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
31243 @subheading Example
31247 -interpreter-exec console "break main"
31248 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
31249 &"During symbol reading, bad structure-type format.\n"
31250 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
31255 @subheading The @code{-inferior-tty-set} Command
31256 @findex -inferior-tty-set
31258 @subheading Synopsis
31261 -inferior-tty-set /dev/pts/1
31264 Set terminal for future runs of the program being debugged.
31266 @subheading @value{GDBN} Command
31268 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
31270 @subheading Example
31274 -inferior-tty-set /dev/pts/1
31279 @subheading The @code{-inferior-tty-show} Command
31280 @findex -inferior-tty-show
31282 @subheading Synopsis
31288 Show terminal for future runs of program being debugged.
31290 @subheading @value{GDBN} Command
31292 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
31294 @subheading Example
31298 -inferior-tty-set /dev/pts/1
31302 ^done,inferior_tty_terminal="/dev/pts/1"
31306 @subheading The @code{-enable-timings} Command
31307 @findex -enable-timings
31309 @subheading Synopsis
31312 -enable-timings [yes | no]
31315 Toggle the printing of the wallclock, user and system times for an MI
31316 command as a field in its output. This command is to help frontend
31317 developers optimize the performance of their code. No argument is
31318 equivalent to @samp{yes}.
31320 @subheading @value{GDBN} Command
31324 @subheading Example
31332 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31333 addr="0x080484ed",func="main",file="myprog.c",
31334 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
31335 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
31343 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
31344 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
31345 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
31346 fullname="/home/nickrob/myprog.c",line="73"@}
31351 @chapter @value{GDBN} Annotations
31353 This chapter describes annotations in @value{GDBN}. Annotations were
31354 designed to interface @value{GDBN} to graphical user interfaces or other
31355 similar programs which want to interact with @value{GDBN} at a
31356 relatively high level.
31358 The annotation mechanism has largely been superseded by @sc{gdb/mi}
31362 This is Edition @value{EDITION}, @value{DATE}.
31366 * Annotations Overview:: What annotations are; the general syntax.
31367 * Server Prefix:: Issuing a command without affecting user state.
31368 * Prompting:: Annotations marking @value{GDBN}'s need for input.
31369 * Errors:: Annotations for error messages.
31370 * Invalidation:: Some annotations describe things now invalid.
31371 * Annotations for Running::
31372 Whether the program is running, how it stopped, etc.
31373 * Source Annotations:: Annotations describing source code.
31376 @node Annotations Overview
31377 @section What is an Annotation?
31378 @cindex annotations
31380 Annotations start with a newline character, two @samp{control-z}
31381 characters, and the name of the annotation. If there is no additional
31382 information associated with this annotation, the name of the annotation
31383 is followed immediately by a newline. If there is additional
31384 information, the name of the annotation is followed by a space, the
31385 additional information, and a newline. The additional information
31386 cannot contain newline characters.
31388 Any output not beginning with a newline and two @samp{control-z}
31389 characters denotes literal output from @value{GDBN}. Currently there is
31390 no need for @value{GDBN} to output a newline followed by two
31391 @samp{control-z} characters, but if there was such a need, the
31392 annotations could be extended with an @samp{escape} annotation which
31393 means those three characters as output.
31395 The annotation @var{level}, which is specified using the
31396 @option{--annotate} command line option (@pxref{Mode Options}), controls
31397 how much information @value{GDBN} prints together with its prompt,
31398 values of expressions, source lines, and other types of output. Level 0
31399 is for no annotations, level 1 is for use when @value{GDBN} is run as a
31400 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
31401 for programs that control @value{GDBN}, and level 2 annotations have
31402 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
31403 Interface, annotate, GDB's Obsolete Annotations}).
31406 @kindex set annotate
31407 @item set annotate @var{level}
31408 The @value{GDBN} command @code{set annotate} sets the level of
31409 annotations to the specified @var{level}.
31411 @item show annotate
31412 @kindex show annotate
31413 Show the current annotation level.
31416 This chapter describes level 3 annotations.
31418 A simple example of starting up @value{GDBN} with annotations is:
31421 $ @kbd{gdb --annotate=3}
31423 Copyright 2003 Free Software Foundation, Inc.
31424 GDB is free software, covered by the GNU General Public License,
31425 and you are welcome to change it and/or distribute copies of it
31426 under certain conditions.
31427 Type "show copying" to see the conditions.
31428 There is absolutely no warranty for GDB. Type "show warranty"
31430 This GDB was configured as "i386-pc-linux-gnu"
31441 Here @samp{quit} is input to @value{GDBN}; the rest is output from
31442 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
31443 denotes a @samp{control-z} character) are annotations; the rest is
31444 output from @value{GDBN}.
31446 @node Server Prefix
31447 @section The Server Prefix
31448 @cindex server prefix
31450 If you prefix a command with @samp{server } then it will not affect
31451 the command history, nor will it affect @value{GDBN}'s notion of which
31452 command to repeat if @key{RET} is pressed on a line by itself. This
31453 means that commands can be run behind a user's back by a front-end in
31454 a transparent manner.
31456 The @code{server } prefix does not affect the recording of values into
31457 the value history; to print a value without recording it into the
31458 value history, use the @code{output} command instead of the
31459 @code{print} command.
31461 Using this prefix also disables confirmation requests
31462 (@pxref{confirmation requests}).
31465 @section Annotation for @value{GDBN} Input
31467 @cindex annotations for prompts
31468 When @value{GDBN} prompts for input, it annotates this fact so it is possible
31469 to know when to send output, when the output from a given command is
31472 Different kinds of input each have a different @dfn{input type}. Each
31473 input type has three annotations: a @code{pre-} annotation, which
31474 denotes the beginning of any prompt which is being output, a plain
31475 annotation, which denotes the end of the prompt, and then a @code{post-}
31476 annotation which denotes the end of any echo which may (or may not) be
31477 associated with the input. For example, the @code{prompt} input type
31478 features the following annotations:
31486 The input types are
31489 @findex pre-prompt annotation
31490 @findex prompt annotation
31491 @findex post-prompt annotation
31493 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
31495 @findex pre-commands annotation
31496 @findex commands annotation
31497 @findex post-commands annotation
31499 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
31500 command. The annotations are repeated for each command which is input.
31502 @findex pre-overload-choice annotation
31503 @findex overload-choice annotation
31504 @findex post-overload-choice annotation
31505 @item overload-choice
31506 When @value{GDBN} wants the user to select between various overloaded functions.
31508 @findex pre-query annotation
31509 @findex query annotation
31510 @findex post-query annotation
31512 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
31514 @findex pre-prompt-for-continue annotation
31515 @findex prompt-for-continue annotation
31516 @findex post-prompt-for-continue annotation
31517 @item prompt-for-continue
31518 When @value{GDBN} is asking the user to press return to continue. Note: Don't
31519 expect this to work well; instead use @code{set height 0} to disable
31520 prompting. This is because the counting of lines is buggy in the
31521 presence of annotations.
31526 @cindex annotations for errors, warnings and interrupts
31528 @findex quit annotation
31533 This annotation occurs right before @value{GDBN} responds to an interrupt.
31535 @findex error annotation
31540 This annotation occurs right before @value{GDBN} responds to an error.
31542 Quit and error annotations indicate that any annotations which @value{GDBN} was
31543 in the middle of may end abruptly. For example, if a
31544 @code{value-history-begin} annotation is followed by a @code{error}, one
31545 cannot expect to receive the matching @code{value-history-end}. One
31546 cannot expect not to receive it either, however; an error annotation
31547 does not necessarily mean that @value{GDBN} is immediately returning all the way
31550 @findex error-begin annotation
31551 A quit or error annotation may be preceded by
31557 Any output between that and the quit or error annotation is the error
31560 Warning messages are not yet annotated.
31561 @c If we want to change that, need to fix warning(), type_error(),
31562 @c range_error(), and possibly other places.
31565 @section Invalidation Notices
31567 @cindex annotations for invalidation messages
31568 The following annotations say that certain pieces of state may have
31572 @findex frames-invalid annotation
31573 @item ^Z^Zframes-invalid
31575 The frames (for example, output from the @code{backtrace} command) may
31578 @findex breakpoints-invalid annotation
31579 @item ^Z^Zbreakpoints-invalid
31581 The breakpoints may have changed. For example, the user just added or
31582 deleted a breakpoint.
31585 @node Annotations for Running
31586 @section Running the Program
31587 @cindex annotations for running programs
31589 @findex starting annotation
31590 @findex stopping annotation
31591 When the program starts executing due to a @value{GDBN} command such as
31592 @code{step} or @code{continue},
31598 is output. When the program stops,
31604 is output. Before the @code{stopped} annotation, a variety of
31605 annotations describe how the program stopped.
31608 @findex exited annotation
31609 @item ^Z^Zexited @var{exit-status}
31610 The program exited, and @var{exit-status} is the exit status (zero for
31611 successful exit, otherwise nonzero).
31613 @findex signalled annotation
31614 @findex signal-name annotation
31615 @findex signal-name-end annotation
31616 @findex signal-string annotation
31617 @findex signal-string-end annotation
31618 @item ^Z^Zsignalled
31619 The program exited with a signal. After the @code{^Z^Zsignalled}, the
31620 annotation continues:
31626 ^Z^Zsignal-name-end
31630 ^Z^Zsignal-string-end
31635 where @var{name} is the name of the signal, such as @code{SIGILL} or
31636 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
31637 as @code{Illegal Instruction} or @code{Segmentation fault}.
31638 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
31639 user's benefit and have no particular format.
31641 @findex signal annotation
31643 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
31644 just saying that the program received the signal, not that it was
31645 terminated with it.
31647 @findex breakpoint annotation
31648 @item ^Z^Zbreakpoint @var{number}
31649 The program hit breakpoint number @var{number}.
31651 @findex watchpoint annotation
31652 @item ^Z^Zwatchpoint @var{number}
31653 The program hit watchpoint number @var{number}.
31656 @node Source Annotations
31657 @section Displaying Source
31658 @cindex annotations for source display
31660 @findex source annotation
31661 The following annotation is used instead of displaying source code:
31664 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
31667 where @var{filename} is an absolute file name indicating which source
31668 file, @var{line} is the line number within that file (where 1 is the
31669 first line in the file), @var{character} is the character position
31670 within the file (where 0 is the first character in the file) (for most
31671 debug formats this will necessarily point to the beginning of a line),
31672 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
31673 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
31674 @var{addr} is the address in the target program associated with the
31675 source which is being displayed. @var{addr} is in the form @samp{0x}
31676 followed by one or more lowercase hex digits (note that this does not
31677 depend on the language).
31679 @node JIT Interface
31680 @chapter JIT Compilation Interface
31681 @cindex just-in-time compilation
31682 @cindex JIT compilation interface
31684 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
31685 interface. A JIT compiler is a program or library that generates native
31686 executable code at runtime and executes it, usually in order to achieve good
31687 performance while maintaining platform independence.
31689 Programs that use JIT compilation are normally difficult to debug because
31690 portions of their code are generated at runtime, instead of being loaded from
31691 object files, which is where @value{GDBN} normally finds the program's symbols
31692 and debug information. In order to debug programs that use JIT compilation,
31693 @value{GDBN} has an interface that allows the program to register in-memory
31694 symbol files with @value{GDBN} at runtime.
31696 If you are using @value{GDBN} to debug a program that uses this interface, then
31697 it should work transparently so long as you have not stripped the binary. If
31698 you are developing a JIT compiler, then the interface is documented in the rest
31699 of this chapter. At this time, the only known client of this interface is the
31702 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
31703 JIT compiler communicates with @value{GDBN} by writing data into a global
31704 variable and calling a fuction at a well-known symbol. When @value{GDBN}
31705 attaches, it reads a linked list of symbol files from the global variable to
31706 find existing code, and puts a breakpoint in the function so that it can find
31707 out about additional code.
31710 * Declarations:: Relevant C struct declarations
31711 * Registering Code:: Steps to register code
31712 * Unregistering Code:: Steps to unregister code
31716 @section JIT Declarations
31718 These are the relevant struct declarations that a C program should include to
31719 implement the interface:
31729 struct jit_code_entry
31731 struct jit_code_entry *next_entry;
31732 struct jit_code_entry *prev_entry;
31733 const char *symfile_addr;
31734 uint64_t symfile_size;
31737 struct jit_descriptor
31740 /* This type should be jit_actions_t, but we use uint32_t
31741 to be explicit about the bitwidth. */
31742 uint32_t action_flag;
31743 struct jit_code_entry *relevant_entry;
31744 struct jit_code_entry *first_entry;
31747 /* GDB puts a breakpoint in this function. */
31748 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
31750 /* Make sure to specify the version statically, because the
31751 debugger may check the version before we can set it. */
31752 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
31755 If the JIT is multi-threaded, then it is important that the JIT synchronize any
31756 modifications to this global data properly, which can easily be done by putting
31757 a global mutex around modifications to these structures.
31759 @node Registering Code
31760 @section Registering Code
31762 To register code with @value{GDBN}, the JIT should follow this protocol:
31766 Generate an object file in memory with symbols and other desired debug
31767 information. The file must include the virtual addresses of the sections.
31770 Create a code entry for the file, which gives the start and size of the symbol
31774 Add it to the linked list in the JIT descriptor.
31777 Point the relevant_entry field of the descriptor at the entry.
31780 Set @code{action_flag} to @code{JIT_REGISTER} and call
31781 @code{__jit_debug_register_code}.
31784 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
31785 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
31786 new code. However, the linked list must still be maintained in order to allow
31787 @value{GDBN} to attach to a running process and still find the symbol files.
31789 @node Unregistering Code
31790 @section Unregistering Code
31792 If code is freed, then the JIT should use the following protocol:
31796 Remove the code entry corresponding to the code from the linked list.
31799 Point the @code{relevant_entry} field of the descriptor at the code entry.
31802 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
31803 @code{__jit_debug_register_code}.
31806 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
31807 and the JIT will leak the memory used for the associated symbol files.
31810 @chapter Reporting Bugs in @value{GDBN}
31811 @cindex bugs in @value{GDBN}
31812 @cindex reporting bugs in @value{GDBN}
31814 Your bug reports play an essential role in making @value{GDBN} reliable.
31816 Reporting a bug may help you by bringing a solution to your problem, or it
31817 may not. But in any case the principal function of a bug report is to help
31818 the entire community by making the next version of @value{GDBN} work better. Bug
31819 reports are your contribution to the maintenance of @value{GDBN}.
31821 In order for a bug report to serve its purpose, you must include the
31822 information that enables us to fix the bug.
31825 * Bug Criteria:: Have you found a bug?
31826 * Bug Reporting:: How to report bugs
31830 @section Have You Found a Bug?
31831 @cindex bug criteria
31833 If you are not sure whether you have found a bug, here are some guidelines:
31836 @cindex fatal signal
31837 @cindex debugger crash
31838 @cindex crash of debugger
31840 If the debugger gets a fatal signal, for any input whatever, that is a
31841 @value{GDBN} bug. Reliable debuggers never crash.
31843 @cindex error on valid input
31845 If @value{GDBN} produces an error message for valid input, that is a
31846 bug. (Note that if you're cross debugging, the problem may also be
31847 somewhere in the connection to the target.)
31849 @cindex invalid input
31851 If @value{GDBN} does not produce an error message for invalid input,
31852 that is a bug. However, you should note that your idea of
31853 ``invalid input'' might be our idea of ``an extension'' or ``support
31854 for traditional practice''.
31857 If you are an experienced user of debugging tools, your suggestions
31858 for improvement of @value{GDBN} are welcome in any case.
31861 @node Bug Reporting
31862 @section How to Report Bugs
31863 @cindex bug reports
31864 @cindex @value{GDBN} bugs, reporting
31866 A number of companies and individuals offer support for @sc{gnu} products.
31867 If you obtained @value{GDBN} from a support organization, we recommend you
31868 contact that organization first.
31870 You can find contact information for many support companies and
31871 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
31873 @c should add a web page ref...
31876 @ifset BUGURL_DEFAULT
31877 In any event, we also recommend that you submit bug reports for
31878 @value{GDBN}. The preferred method is to submit them directly using
31879 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
31880 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
31883 @strong{Do not send bug reports to @samp{info-gdb}, or to
31884 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
31885 not want to receive bug reports. Those that do have arranged to receive
31888 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
31889 serves as a repeater. The mailing list and the newsgroup carry exactly
31890 the same messages. Often people think of posting bug reports to the
31891 newsgroup instead of mailing them. This appears to work, but it has one
31892 problem which can be crucial: a newsgroup posting often lacks a mail
31893 path back to the sender. Thus, if we need to ask for more information,
31894 we may be unable to reach you. For this reason, it is better to send
31895 bug reports to the mailing list.
31897 @ifclear BUGURL_DEFAULT
31898 In any event, we also recommend that you submit bug reports for
31899 @value{GDBN} to @value{BUGURL}.
31903 The fundamental principle of reporting bugs usefully is this:
31904 @strong{report all the facts}. If you are not sure whether to state a
31905 fact or leave it out, state it!
31907 Often people omit facts because they think they know what causes the
31908 problem and assume that some details do not matter. Thus, you might
31909 assume that the name of the variable you use in an example does not matter.
31910 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
31911 stray memory reference which happens to fetch from the location where that
31912 name is stored in memory; perhaps, if the name were different, the contents
31913 of that location would fool the debugger into doing the right thing despite
31914 the bug. Play it safe and give a specific, complete example. That is the
31915 easiest thing for you to do, and the most helpful.
31917 Keep in mind that the purpose of a bug report is to enable us to fix the
31918 bug. It may be that the bug has been reported previously, but neither
31919 you nor we can know that unless your bug report is complete and
31922 Sometimes people give a few sketchy facts and ask, ``Does this ring a
31923 bell?'' Those bug reports are useless, and we urge everyone to
31924 @emph{refuse to respond to them} except to chide the sender to report
31927 To enable us to fix the bug, you should include all these things:
31931 The version of @value{GDBN}. @value{GDBN} announces it if you start
31932 with no arguments; you can also print it at any time using @code{show
31935 Without this, we will not know whether there is any point in looking for
31936 the bug in the current version of @value{GDBN}.
31939 The type of machine you are using, and the operating system name and
31943 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
31944 ``@value{GCC}--2.8.1''.
31947 What compiler (and its version) was used to compile the program you are
31948 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
31949 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
31950 to get this information; for other compilers, see the documentation for
31954 The command arguments you gave the compiler to compile your example and
31955 observe the bug. For example, did you use @samp{-O}? To guarantee
31956 you will not omit something important, list them all. A copy of the
31957 Makefile (or the output from make) is sufficient.
31959 If we were to try to guess the arguments, we would probably guess wrong
31960 and then we might not encounter the bug.
31963 A complete input script, and all necessary source files, that will
31967 A description of what behavior you observe that you believe is
31968 incorrect. For example, ``It gets a fatal signal.''
31970 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
31971 will certainly notice it. But if the bug is incorrect output, we might
31972 not notice unless it is glaringly wrong. You might as well not give us
31973 a chance to make a mistake.
31975 Even if the problem you experience is a fatal signal, you should still
31976 say so explicitly. Suppose something strange is going on, such as, your
31977 copy of @value{GDBN} is out of synch, or you have encountered a bug in
31978 the C library on your system. (This has happened!) Your copy might
31979 crash and ours would not. If you told us to expect a crash, then when
31980 ours fails to crash, we would know that the bug was not happening for
31981 us. If you had not told us to expect a crash, then we would not be able
31982 to draw any conclusion from our observations.
31985 @cindex recording a session script
31986 To collect all this information, you can use a session recording program
31987 such as @command{script}, which is available on many Unix systems.
31988 Just run your @value{GDBN} session inside @command{script} and then
31989 include the @file{typescript} file with your bug report.
31991 Another way to record a @value{GDBN} session is to run @value{GDBN}
31992 inside Emacs and then save the entire buffer to a file.
31995 If you wish to suggest changes to the @value{GDBN} source, send us context
31996 diffs. If you even discuss something in the @value{GDBN} source, refer to
31997 it by context, not by line number.
31999 The line numbers in our development sources will not match those in your
32000 sources. Your line numbers would convey no useful information to us.
32004 Here are some things that are not necessary:
32008 A description of the envelope of the bug.
32010 Often people who encounter a bug spend a lot of time investigating
32011 which changes to the input file will make the bug go away and which
32012 changes will not affect it.
32014 This is often time consuming and not very useful, because the way we
32015 will find the bug is by running a single example under the debugger
32016 with breakpoints, not by pure deduction from a series of examples.
32017 We recommend that you save your time for something else.
32019 Of course, if you can find a simpler example to report @emph{instead}
32020 of the original one, that is a convenience for us. Errors in the
32021 output will be easier to spot, running under the debugger will take
32022 less time, and so on.
32024 However, simplification is not vital; if you do not want to do this,
32025 report the bug anyway and send us the entire test case you used.
32028 A patch for the bug.
32030 A patch for the bug does help us if it is a good one. But do not omit
32031 the necessary information, such as the test case, on the assumption that
32032 a patch is all we need. We might see problems with your patch and decide
32033 to fix the problem another way, or we might not understand it at all.
32035 Sometimes with a program as complicated as @value{GDBN} it is very hard to
32036 construct an example that will make the program follow a certain path
32037 through the code. If you do not send us the example, we will not be able
32038 to construct one, so we will not be able to verify that the bug is fixed.
32040 And if we cannot understand what bug you are trying to fix, or why your
32041 patch should be an improvement, we will not install it. A test case will
32042 help us to understand.
32045 A guess about what the bug is or what it depends on.
32047 Such guesses are usually wrong. Even we cannot guess right about such
32048 things without first using the debugger to find the facts.
32051 @c The readline documentation is distributed with the readline code
32052 @c and consists of the two following files:
32055 @c Use -I with makeinfo to point to the appropriate directory,
32056 @c environment var TEXINPUTS with TeX.
32057 @ifclear SYSTEM_READLINE
32058 @include rluser.texi
32059 @include hsuser.texi
32063 @appendix In Memoriam
32065 The @value{GDBN} project mourns the loss of the following long-time
32070 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
32071 to Free Software in general. Outside of @value{GDBN}, he was known in
32072 the Amiga world for his series of Fish Disks, and the GeekGadget project.
32074 @item Michael Snyder
32075 Michael was one of the Global Maintainers of the @value{GDBN} project,
32076 with contributions recorded as early as 1996, until 2011. In addition
32077 to his day to day participation, he was a large driving force behind
32078 adding Reverse Debugging to @value{GDBN}.
32081 Beyond their technical contributions to the project, they were also
32082 enjoyable members of the Free Software Community. We will miss them.
32084 @node Formatting Documentation
32085 @appendix Formatting Documentation
32087 @cindex @value{GDBN} reference card
32088 @cindex reference card
32089 The @value{GDBN} 4 release includes an already-formatted reference card, ready
32090 for printing with PostScript or Ghostscript, in the @file{gdb}
32091 subdirectory of the main source directory@footnote{In
32092 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
32093 release.}. If you can use PostScript or Ghostscript with your printer,
32094 you can print the reference card immediately with @file{refcard.ps}.
32096 The release also includes the source for the reference card. You
32097 can format it, using @TeX{}, by typing:
32103 The @value{GDBN} reference card is designed to print in @dfn{landscape}
32104 mode on US ``letter'' size paper;
32105 that is, on a sheet 11 inches wide by 8.5 inches
32106 high. You will need to specify this form of printing as an option to
32107 your @sc{dvi} output program.
32109 @cindex documentation
32111 All the documentation for @value{GDBN} comes as part of the machine-readable
32112 distribution. The documentation is written in Texinfo format, which is
32113 a documentation system that uses a single source file to produce both
32114 on-line information and a printed manual. You can use one of the Info
32115 formatting commands to create the on-line version of the documentation
32116 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
32118 @value{GDBN} includes an already formatted copy of the on-line Info
32119 version of this manual in the @file{gdb} subdirectory. The main Info
32120 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
32121 subordinate files matching @samp{gdb.info*} in the same directory. If
32122 necessary, you can print out these files, or read them with any editor;
32123 but they are easier to read using the @code{info} subsystem in @sc{gnu}
32124 Emacs or the standalone @code{info} program, available as part of the
32125 @sc{gnu} Texinfo distribution.
32127 If you want to format these Info files yourself, you need one of the
32128 Info formatting programs, such as @code{texinfo-format-buffer} or
32131 If you have @code{makeinfo} installed, and are in the top level
32132 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
32133 version @value{GDBVN}), you can make the Info file by typing:
32140 If you want to typeset and print copies of this manual, you need @TeX{},
32141 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
32142 Texinfo definitions file.
32144 @TeX{} is a typesetting program; it does not print files directly, but
32145 produces output files called @sc{dvi} files. To print a typeset
32146 document, you need a program to print @sc{dvi} files. If your system
32147 has @TeX{} installed, chances are it has such a program. The precise
32148 command to use depends on your system; @kbd{lpr -d} is common; another
32149 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
32150 require a file name without any extension or a @samp{.dvi} extension.
32152 @TeX{} also requires a macro definitions file called
32153 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
32154 written in Texinfo format. On its own, @TeX{} cannot either read or
32155 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
32156 and is located in the @file{gdb-@var{version-number}/texinfo}
32159 If you have @TeX{} and a @sc{dvi} printer program installed, you can
32160 typeset and print this manual. First switch to the @file{gdb}
32161 subdirectory of the main source directory (for example, to
32162 @file{gdb-@value{GDBVN}/gdb}) and type:
32168 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
32170 @node Installing GDB
32171 @appendix Installing @value{GDBN}
32172 @cindex installation
32175 * Requirements:: Requirements for building @value{GDBN}
32176 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
32177 * Separate Objdir:: Compiling @value{GDBN} in another directory
32178 * Config Names:: Specifying names for hosts and targets
32179 * Configure Options:: Summary of options for configure
32180 * System-wide configuration:: Having a system-wide init file
32184 @section Requirements for Building @value{GDBN}
32185 @cindex building @value{GDBN}, requirements for
32187 Building @value{GDBN} requires various tools and packages to be available.
32188 Other packages will be used only if they are found.
32190 @heading Tools/Packages Necessary for Building @value{GDBN}
32192 @item ISO C90 compiler
32193 @value{GDBN} is written in ISO C90. It should be buildable with any
32194 working C90 compiler, e.g.@: GCC.
32198 @heading Tools/Packages Optional for Building @value{GDBN}
32202 @value{GDBN} can use the Expat XML parsing library. This library may be
32203 included with your operating system distribution; if it is not, you
32204 can get the latest version from @url{http://expat.sourceforge.net}.
32205 The @file{configure} script will search for this library in several
32206 standard locations; if it is installed in an unusual path, you can
32207 use the @option{--with-libexpat-prefix} option to specify its location.
32213 Remote protocol memory maps (@pxref{Memory Map Format})
32215 Target descriptions (@pxref{Target Descriptions})
32217 Remote shared library lists (@pxref{Library List Format})
32219 MS-Windows shared libraries (@pxref{Shared Libraries})
32221 Traceframe info (@pxref{Traceframe Info Format})
32225 @cindex compressed debug sections
32226 @value{GDBN} will use the @samp{zlib} library, if available, to read
32227 compressed debug sections. Some linkers, such as GNU gold, are capable
32228 of producing binaries with compressed debug sections. If @value{GDBN}
32229 is compiled with @samp{zlib}, it will be able to read the debug
32230 information in such binaries.
32232 The @samp{zlib} library is likely included with your operating system
32233 distribution; if it is not, you can get the latest version from
32234 @url{http://zlib.net}.
32237 @value{GDBN}'s features related to character sets (@pxref{Character
32238 Sets}) require a functioning @code{iconv} implementation. If you are
32239 on a GNU system, then this is provided by the GNU C Library. Some
32240 other systems also provide a working @code{iconv}.
32242 If @value{GDBN} is using the @code{iconv} program which is installed
32243 in a non-standard place, you will need to tell @value{GDBN} where to find it.
32244 This is done with @option{--with-iconv-bin} which specifies the
32245 directory that contains the @code{iconv} program.
32247 On systems without @code{iconv}, you can install GNU Libiconv. If you
32248 have previously installed Libiconv, you can use the
32249 @option{--with-libiconv-prefix} option to configure.
32251 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
32252 arrange to build Libiconv if a directory named @file{libiconv} appears
32253 in the top-most source directory. If Libiconv is built this way, and
32254 if the operating system does not provide a suitable @code{iconv}
32255 implementation, then the just-built library will automatically be used
32256 by @value{GDBN}. One easy way to set this up is to download GNU
32257 Libiconv, unpack it, and then rename the directory holding the
32258 Libiconv source code to @samp{libiconv}.
32261 @node Running Configure
32262 @section Invoking the @value{GDBN} @file{configure} Script
32263 @cindex configuring @value{GDBN}
32264 @value{GDBN} comes with a @file{configure} script that automates the process
32265 of preparing @value{GDBN} for installation; you can then use @code{make} to
32266 build the @code{gdb} program.
32268 @c irrelevant in info file; it's as current as the code it lives with.
32269 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
32270 look at the @file{README} file in the sources; we may have improved the
32271 installation procedures since publishing this manual.}
32274 The @value{GDBN} distribution includes all the source code you need for
32275 @value{GDBN} in a single directory, whose name is usually composed by
32276 appending the version number to @samp{gdb}.
32278 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
32279 @file{gdb-@value{GDBVN}} directory. That directory contains:
32282 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
32283 script for configuring @value{GDBN} and all its supporting libraries
32285 @item gdb-@value{GDBVN}/gdb
32286 the source specific to @value{GDBN} itself
32288 @item gdb-@value{GDBVN}/bfd
32289 source for the Binary File Descriptor library
32291 @item gdb-@value{GDBVN}/include
32292 @sc{gnu} include files
32294 @item gdb-@value{GDBVN}/libiberty
32295 source for the @samp{-liberty} free software library
32297 @item gdb-@value{GDBVN}/opcodes
32298 source for the library of opcode tables and disassemblers
32300 @item gdb-@value{GDBVN}/readline
32301 source for the @sc{gnu} command-line interface
32303 @item gdb-@value{GDBVN}/glob
32304 source for the @sc{gnu} filename pattern-matching subroutine
32306 @item gdb-@value{GDBVN}/mmalloc
32307 source for the @sc{gnu} memory-mapped malloc package
32310 The simplest way to configure and build @value{GDBN} is to run @file{configure}
32311 from the @file{gdb-@var{version-number}} source directory, which in
32312 this example is the @file{gdb-@value{GDBVN}} directory.
32314 First switch to the @file{gdb-@var{version-number}} source directory
32315 if you are not already in it; then run @file{configure}. Pass the
32316 identifier for the platform on which @value{GDBN} will run as an
32322 cd gdb-@value{GDBVN}
32323 ./configure @var{host}
32328 where @var{host} is an identifier such as @samp{sun4} or
32329 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
32330 (You can often leave off @var{host}; @file{configure} tries to guess the
32331 correct value by examining your system.)
32333 Running @samp{configure @var{host}} and then running @code{make} builds the
32334 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
32335 libraries, then @code{gdb} itself. The configured source files, and the
32336 binaries, are left in the corresponding source directories.
32339 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
32340 system does not recognize this automatically when you run a different
32341 shell, you may need to run @code{sh} on it explicitly:
32344 sh configure @var{host}
32347 If you run @file{configure} from a directory that contains source
32348 directories for multiple libraries or programs, such as the
32349 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
32351 creates configuration files for every directory level underneath (unless
32352 you tell it not to, with the @samp{--norecursion} option).
32354 You should run the @file{configure} script from the top directory in the
32355 source tree, the @file{gdb-@var{version-number}} directory. If you run
32356 @file{configure} from one of the subdirectories, you will configure only
32357 that subdirectory. That is usually not what you want. In particular,
32358 if you run the first @file{configure} from the @file{gdb} subdirectory
32359 of the @file{gdb-@var{version-number}} directory, you will omit the
32360 configuration of @file{bfd}, @file{readline}, and other sibling
32361 directories of the @file{gdb} subdirectory. This leads to build errors
32362 about missing include files such as @file{bfd/bfd.h}.
32364 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
32365 However, you should make sure that the shell on your path (named by
32366 the @samp{SHELL} environment variable) is publicly readable. Remember
32367 that @value{GDBN} uses the shell to start your program---some systems refuse to
32368 let @value{GDBN} debug child processes whose programs are not readable.
32370 @node Separate Objdir
32371 @section Compiling @value{GDBN} in Another Directory
32373 If you want to run @value{GDBN} versions for several host or target machines,
32374 you need a different @code{gdb} compiled for each combination of
32375 host and target. @file{configure} is designed to make this easy by
32376 allowing you to generate each configuration in a separate subdirectory,
32377 rather than in the source directory. If your @code{make} program
32378 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
32379 @code{make} in each of these directories builds the @code{gdb}
32380 program specified there.
32382 To build @code{gdb} in a separate directory, run @file{configure}
32383 with the @samp{--srcdir} option to specify where to find the source.
32384 (You also need to specify a path to find @file{configure}
32385 itself from your working directory. If the path to @file{configure}
32386 would be the same as the argument to @samp{--srcdir}, you can leave out
32387 the @samp{--srcdir} option; it is assumed.)
32389 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
32390 separate directory for a Sun 4 like this:
32394 cd gdb-@value{GDBVN}
32397 ../gdb-@value{GDBVN}/configure sun4
32402 When @file{configure} builds a configuration using a remote source
32403 directory, it creates a tree for the binaries with the same structure
32404 (and using the same names) as the tree under the source directory. In
32405 the example, you'd find the Sun 4 library @file{libiberty.a} in the
32406 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
32407 @file{gdb-sun4/gdb}.
32409 Make sure that your path to the @file{configure} script has just one
32410 instance of @file{gdb} in it. If your path to @file{configure} looks
32411 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
32412 one subdirectory of @value{GDBN}, not the whole package. This leads to
32413 build errors about missing include files such as @file{bfd/bfd.h}.
32415 One popular reason to build several @value{GDBN} configurations in separate
32416 directories is to configure @value{GDBN} for cross-compiling (where
32417 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
32418 programs that run on another machine---the @dfn{target}).
32419 You specify a cross-debugging target by
32420 giving the @samp{--target=@var{target}} option to @file{configure}.
32422 When you run @code{make} to build a program or library, you must run
32423 it in a configured directory---whatever directory you were in when you
32424 called @file{configure} (or one of its subdirectories).
32426 The @code{Makefile} that @file{configure} generates in each source
32427 directory also runs recursively. If you type @code{make} in a source
32428 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
32429 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
32430 will build all the required libraries, and then build GDB.
32432 When you have multiple hosts or targets configured in separate
32433 directories, you can run @code{make} on them in parallel (for example,
32434 if they are NFS-mounted on each of the hosts); they will not interfere
32438 @section Specifying Names for Hosts and Targets
32440 The specifications used for hosts and targets in the @file{configure}
32441 script are based on a three-part naming scheme, but some short predefined
32442 aliases are also supported. The full naming scheme encodes three pieces
32443 of information in the following pattern:
32446 @var{architecture}-@var{vendor}-@var{os}
32449 For example, you can use the alias @code{sun4} as a @var{host} argument,
32450 or as the value for @var{target} in a @code{--target=@var{target}}
32451 option. The equivalent full name is @samp{sparc-sun-sunos4}.
32453 The @file{configure} script accompanying @value{GDBN} does not provide
32454 any query facility to list all supported host and target names or
32455 aliases. @file{configure} calls the Bourne shell script
32456 @code{config.sub} to map abbreviations to full names; you can read the
32457 script, if you wish, or you can use it to test your guesses on
32458 abbreviations---for example:
32461 % sh config.sub i386-linux
32463 % sh config.sub alpha-linux
32464 alpha-unknown-linux-gnu
32465 % sh config.sub hp9k700
32467 % sh config.sub sun4
32468 sparc-sun-sunos4.1.1
32469 % sh config.sub sun3
32470 m68k-sun-sunos4.1.1
32471 % sh config.sub i986v
32472 Invalid configuration `i986v': machine `i986v' not recognized
32476 @code{config.sub} is also distributed in the @value{GDBN} source
32477 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
32479 @node Configure Options
32480 @section @file{configure} Options
32482 Here is a summary of the @file{configure} options and arguments that
32483 are most often useful for building @value{GDBN}. @file{configure} also has
32484 several other options not listed here. @inforef{What Configure
32485 Does,,configure.info}, for a full explanation of @file{configure}.
32488 configure @r{[}--help@r{]}
32489 @r{[}--prefix=@var{dir}@r{]}
32490 @r{[}--exec-prefix=@var{dir}@r{]}
32491 @r{[}--srcdir=@var{dirname}@r{]}
32492 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
32493 @r{[}--target=@var{target}@r{]}
32498 You may introduce options with a single @samp{-} rather than
32499 @samp{--} if you prefer; but you may abbreviate option names if you use
32504 Display a quick summary of how to invoke @file{configure}.
32506 @item --prefix=@var{dir}
32507 Configure the source to install programs and files under directory
32510 @item --exec-prefix=@var{dir}
32511 Configure the source to install programs under directory
32514 @c avoid splitting the warning from the explanation:
32516 @item --srcdir=@var{dirname}
32517 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
32518 @code{make} that implements the @code{VPATH} feature.}@*
32519 Use this option to make configurations in directories separate from the
32520 @value{GDBN} source directories. Among other things, you can use this to
32521 build (or maintain) several configurations simultaneously, in separate
32522 directories. @file{configure} writes configuration-specific files in
32523 the current directory, but arranges for them to use the source in the
32524 directory @var{dirname}. @file{configure} creates directories under
32525 the working directory in parallel to the source directories below
32528 @item --norecursion
32529 Configure only the directory level where @file{configure} is executed; do not
32530 propagate configuration to subdirectories.
32532 @item --target=@var{target}
32533 Configure @value{GDBN} for cross-debugging programs running on the specified
32534 @var{target}. Without this option, @value{GDBN} is configured to debug
32535 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
32537 There is no convenient way to generate a list of all available targets.
32539 @item @var{host} @dots{}
32540 Configure @value{GDBN} to run on the specified @var{host}.
32542 There is no convenient way to generate a list of all available hosts.
32545 There are many other options available as well, but they are generally
32546 needed for special purposes only.
32548 @node System-wide configuration
32549 @section System-wide configuration and settings
32550 @cindex system-wide init file
32552 @value{GDBN} can be configured to have a system-wide init file;
32553 this file will be read and executed at startup (@pxref{Startup, , What
32554 @value{GDBN} does during startup}).
32556 Here is the corresponding configure option:
32559 @item --with-system-gdbinit=@var{file}
32560 Specify that the default location of the system-wide init file is
32564 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
32565 it may be subject to relocation. Two possible cases:
32569 If the default location of this init file contains @file{$prefix},
32570 it will be subject to relocation. Suppose that the configure options
32571 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
32572 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
32573 init file is looked for as @file{$install/etc/gdbinit} instead of
32574 @file{$prefix/etc/gdbinit}.
32577 By contrast, if the default location does not contain the prefix,
32578 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
32579 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
32580 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
32581 wherever @value{GDBN} is installed.
32584 @node Maintenance Commands
32585 @appendix Maintenance Commands
32586 @cindex maintenance commands
32587 @cindex internal commands
32589 In addition to commands intended for @value{GDBN} users, @value{GDBN}
32590 includes a number of commands intended for @value{GDBN} developers,
32591 that are not documented elsewhere in this manual. These commands are
32592 provided here for reference. (For commands that turn on debugging
32593 messages, see @ref{Debugging Output}.)
32596 @kindex maint agent
32597 @kindex maint agent-eval
32598 @item maint agent @var{expression}
32599 @itemx maint agent-eval @var{expression}
32600 Translate the given @var{expression} into remote agent bytecodes.
32601 This command is useful for debugging the Agent Expression mechanism
32602 (@pxref{Agent Expressions}). The @samp{agent} version produces an
32603 expression useful for data collection, such as by tracepoints, while
32604 @samp{maint agent-eval} produces an expression that evaluates directly
32605 to a result. For instance, a collection expression for @code{globa +
32606 globb} will include bytecodes to record four bytes of memory at each
32607 of the addresses of @code{globa} and @code{globb}, while discarding
32608 the result of the addition, while an evaluation expression will do the
32609 addition and return the sum.
32611 @kindex maint info breakpoints
32612 @item @anchor{maint info breakpoints}maint info breakpoints
32613 Using the same format as @samp{info breakpoints}, display both the
32614 breakpoints you've set explicitly, and those @value{GDBN} is using for
32615 internal purposes. Internal breakpoints are shown with negative
32616 breakpoint numbers. The type column identifies what kind of breakpoint
32621 Normal, explicitly set breakpoint.
32624 Normal, explicitly set watchpoint.
32627 Internal breakpoint, used to handle correctly stepping through
32628 @code{longjmp} calls.
32630 @item longjmp resume
32631 Internal breakpoint at the target of a @code{longjmp}.
32634 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
32637 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
32640 Shared library events.
32644 @kindex set displaced-stepping
32645 @kindex show displaced-stepping
32646 @cindex displaced stepping support
32647 @cindex out-of-line single-stepping
32648 @item set displaced-stepping
32649 @itemx show displaced-stepping
32650 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
32651 if the target supports it. Displaced stepping is a way to single-step
32652 over breakpoints without removing them from the inferior, by executing
32653 an out-of-line copy of the instruction that was originally at the
32654 breakpoint location. It is also known as out-of-line single-stepping.
32657 @item set displaced-stepping on
32658 If the target architecture supports it, @value{GDBN} will use
32659 displaced stepping to step over breakpoints.
32661 @item set displaced-stepping off
32662 @value{GDBN} will not use displaced stepping to step over breakpoints,
32663 even if such is supported by the target architecture.
32665 @cindex non-stop mode, and @samp{set displaced-stepping}
32666 @item set displaced-stepping auto
32667 This is the default mode. @value{GDBN} will use displaced stepping
32668 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
32669 architecture supports displaced stepping.
32672 @kindex maint check-symtabs
32673 @item maint check-symtabs
32674 Check the consistency of psymtabs and symtabs.
32676 @kindex maint cplus first_component
32677 @item maint cplus first_component @var{name}
32678 Print the first C@t{++} class/namespace component of @var{name}.
32680 @kindex maint cplus namespace
32681 @item maint cplus namespace
32682 Print the list of possible C@t{++} namespaces.
32684 @kindex maint demangle
32685 @item maint demangle @var{name}
32686 Demangle a C@t{++} or Objective-C mangled @var{name}.
32688 @kindex maint deprecate
32689 @kindex maint undeprecate
32690 @cindex deprecated commands
32691 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
32692 @itemx maint undeprecate @var{command}
32693 Deprecate or undeprecate the named @var{command}. Deprecated commands
32694 cause @value{GDBN} to issue a warning when you use them. The optional
32695 argument @var{replacement} says which newer command should be used in
32696 favor of the deprecated one; if it is given, @value{GDBN} will mention
32697 the replacement as part of the warning.
32699 @kindex maint dump-me
32700 @item maint dump-me
32701 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
32702 Cause a fatal signal in the debugger and force it to dump its core.
32703 This is supported only on systems which support aborting a program
32704 with the @code{SIGQUIT} signal.
32706 @kindex maint internal-error
32707 @kindex maint internal-warning
32708 @item maint internal-error @r{[}@var{message-text}@r{]}
32709 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
32710 Cause @value{GDBN} to call the internal function @code{internal_error}
32711 or @code{internal_warning} and hence behave as though an internal error
32712 or internal warning has been detected. In addition to reporting the
32713 internal problem, these functions give the user the opportunity to
32714 either quit @value{GDBN} or create a core file of the current
32715 @value{GDBN} session.
32717 These commands take an optional parameter @var{message-text} that is
32718 used as the text of the error or warning message.
32720 Here's an example of using @code{internal-error}:
32723 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
32724 @dots{}/maint.c:121: internal-error: testing, 1, 2
32725 A problem internal to GDB has been detected. Further
32726 debugging may prove unreliable.
32727 Quit this debugging session? (y or n) @kbd{n}
32728 Create a core file? (y or n) @kbd{n}
32732 @cindex @value{GDBN} internal error
32733 @cindex internal errors, control of @value{GDBN} behavior
32735 @kindex maint set internal-error
32736 @kindex maint show internal-error
32737 @kindex maint set internal-warning
32738 @kindex maint show internal-warning
32739 @item maint set internal-error @var{action} [ask|yes|no]
32740 @itemx maint show internal-error @var{action}
32741 @itemx maint set internal-warning @var{action} [ask|yes|no]
32742 @itemx maint show internal-warning @var{action}
32743 When @value{GDBN} reports an internal problem (error or warning) it
32744 gives the user the opportunity to both quit @value{GDBN} and create a
32745 core file of the current @value{GDBN} session. These commands let you
32746 override the default behaviour for each particular @var{action},
32747 described in the table below.
32751 You can specify that @value{GDBN} should always (yes) or never (no)
32752 quit. The default is to ask the user what to do.
32755 You can specify that @value{GDBN} should always (yes) or never (no)
32756 create a core file. The default is to ask the user what to do.
32759 @kindex maint packet
32760 @item maint packet @var{text}
32761 If @value{GDBN} is talking to an inferior via the serial protocol,
32762 then this command sends the string @var{text} to the inferior, and
32763 displays the response packet. @value{GDBN} supplies the initial
32764 @samp{$} character, the terminating @samp{#} character, and the
32767 @kindex maint print architecture
32768 @item maint print architecture @r{[}@var{file}@r{]}
32769 Print the entire architecture configuration. The optional argument
32770 @var{file} names the file where the output goes.
32772 @kindex maint print c-tdesc
32773 @item maint print c-tdesc
32774 Print the current target description (@pxref{Target Descriptions}) as
32775 a C source file. The created source file can be used in @value{GDBN}
32776 when an XML parser is not available to parse the description.
32778 @kindex maint print dummy-frames
32779 @item maint print dummy-frames
32780 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
32783 (@value{GDBP}) @kbd{b add}
32785 (@value{GDBP}) @kbd{print add(2,3)}
32786 Breakpoint 2, add (a=2, b=3) at @dots{}
32788 The program being debugged stopped while in a function called from GDB.
32790 (@value{GDBP}) @kbd{maint print dummy-frames}
32791 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
32792 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
32793 call_lo=0x01014000 call_hi=0x01014001
32797 Takes an optional file parameter.
32799 @kindex maint print registers
32800 @kindex maint print raw-registers
32801 @kindex maint print cooked-registers
32802 @kindex maint print register-groups
32803 @kindex maint print remote-registers
32804 @item maint print registers @r{[}@var{file}@r{]}
32805 @itemx maint print raw-registers @r{[}@var{file}@r{]}
32806 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
32807 @itemx maint print register-groups @r{[}@var{file}@r{]}
32808 @itemx maint print remote-registers @r{[}@var{file}@r{]}
32809 Print @value{GDBN}'s internal register data structures.
32811 The command @code{maint print raw-registers} includes the contents of
32812 the raw register cache; the command @code{maint print
32813 cooked-registers} includes the (cooked) value of all registers,
32814 including registers which aren't available on the target nor visible
32815 to user; the command @code{maint print register-groups} includes the
32816 groups that each register is a member of; and the command @code{maint
32817 print remote-registers} includes the remote target's register numbers
32818 and offsets in the `G' packets. @xref{Registers,, Registers, gdbint,
32819 @value{GDBN} Internals}.
32821 These commands take an optional parameter, a file name to which to
32822 write the information.
32824 @kindex maint print reggroups
32825 @item maint print reggroups @r{[}@var{file}@r{]}
32826 Print @value{GDBN}'s internal register group data structures. The
32827 optional argument @var{file} tells to what file to write the
32830 The register groups info looks like this:
32833 (@value{GDBP}) @kbd{maint print reggroups}
32846 This command forces @value{GDBN} to flush its internal register cache.
32848 @kindex maint print objfiles
32849 @cindex info for known object files
32850 @item maint print objfiles
32851 Print a dump of all known object files. For each object file, this
32852 command prints its name, address in memory, and all of its psymtabs
32855 @kindex maint print section-scripts
32856 @cindex info for known .debug_gdb_scripts-loaded scripts
32857 @item maint print section-scripts [@var{regexp}]
32858 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
32859 If @var{regexp} is specified, only print scripts loaded by object files
32860 matching @var{regexp}.
32861 For each script, this command prints its name as specified in the objfile,
32862 and the full path if known.
32863 @xref{.debug_gdb_scripts section}.
32865 @kindex maint print statistics
32866 @cindex bcache statistics
32867 @item maint print statistics
32868 This command prints, for each object file in the program, various data
32869 about that object file followed by the byte cache (@dfn{bcache})
32870 statistics for the object file. The objfile data includes the number
32871 of minimal, partial, full, and stabs symbols, the number of types
32872 defined by the objfile, the number of as yet unexpanded psym tables,
32873 the number of line tables and string tables, and the amount of memory
32874 used by the various tables. The bcache statistics include the counts,
32875 sizes, and counts of duplicates of all and unique objects, max,
32876 average, and median entry size, total memory used and its overhead and
32877 savings, and various measures of the hash table size and chain
32880 @kindex maint print target-stack
32881 @cindex target stack description
32882 @item maint print target-stack
32883 A @dfn{target} is an interface between the debugger and a particular
32884 kind of file or process. Targets can be stacked in @dfn{strata},
32885 so that more than one target can potentially respond to a request.
32886 In particular, memory accesses will walk down the stack of targets
32887 until they find a target that is interested in handling that particular
32890 This command prints a short description of each layer that was pushed on
32891 the @dfn{target stack}, starting from the top layer down to the bottom one.
32893 @kindex maint print type
32894 @cindex type chain of a data type
32895 @item maint print type @var{expr}
32896 Print the type chain for a type specified by @var{expr}. The argument
32897 can be either a type name or a symbol. If it is a symbol, the type of
32898 that symbol is described. The type chain produced by this command is
32899 a recursive definition of the data type as stored in @value{GDBN}'s
32900 data structures, including its flags and contained types.
32902 @kindex maint set dwarf2 always-disassemble
32903 @kindex maint show dwarf2 always-disassemble
32904 @item maint set dwarf2 always-disassemble
32905 @item maint show dwarf2 always-disassemble
32906 Control the behavior of @code{info address} when using DWARF debugging
32909 The default is @code{off}, which means that @value{GDBN} should try to
32910 describe a variable's location in an easily readable format. When
32911 @code{on}, @value{GDBN} will instead display the DWARF location
32912 expression in an assembly-like format. Note that some locations are
32913 too complex for @value{GDBN} to describe simply; in this case you will
32914 always see the disassembly form.
32916 Here is an example of the resulting disassembly:
32919 (gdb) info addr argc
32920 Symbol "argc" is a complex DWARF expression:
32924 For more information on these expressions, see
32925 @uref{http://www.dwarfstd.org/, the DWARF standard}.
32927 @kindex maint set dwarf2 max-cache-age
32928 @kindex maint show dwarf2 max-cache-age
32929 @item maint set dwarf2 max-cache-age
32930 @itemx maint show dwarf2 max-cache-age
32931 Control the DWARF 2 compilation unit cache.
32933 @cindex DWARF 2 compilation units cache
32934 In object files with inter-compilation-unit references, such as those
32935 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
32936 reader needs to frequently refer to previously read compilation units.
32937 This setting controls how long a compilation unit will remain in the
32938 cache if it is not referenced. A higher limit means that cached
32939 compilation units will be stored in memory longer, and more total
32940 memory will be used. Setting it to zero disables caching, which will
32941 slow down @value{GDBN} startup, but reduce memory consumption.
32943 @kindex maint set profile
32944 @kindex maint show profile
32945 @cindex profiling GDB
32946 @item maint set profile
32947 @itemx maint show profile
32948 Control profiling of @value{GDBN}.
32950 Profiling will be disabled until you use the @samp{maint set profile}
32951 command to enable it. When you enable profiling, the system will begin
32952 collecting timing and execution count data; when you disable profiling or
32953 exit @value{GDBN}, the results will be written to a log file. Remember that
32954 if you use profiling, @value{GDBN} will overwrite the profiling log file
32955 (often called @file{gmon.out}). If you have a record of important profiling
32956 data in a @file{gmon.out} file, be sure to move it to a safe location.
32958 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
32959 compiled with the @samp{-pg} compiler option.
32961 @kindex maint set show-debug-regs
32962 @kindex maint show show-debug-regs
32963 @cindex hardware debug registers
32964 @item maint set show-debug-regs
32965 @itemx maint show show-debug-regs
32966 Control whether to show variables that mirror the hardware debug
32967 registers. Use @code{ON} to enable, @code{OFF} to disable. If
32968 enabled, the debug registers values are shown when @value{GDBN} inserts or
32969 removes a hardware breakpoint or watchpoint, and when the inferior
32970 triggers a hardware-assisted breakpoint or watchpoint.
32972 @kindex maint set show-all-tib
32973 @kindex maint show show-all-tib
32974 @item maint set show-all-tib
32975 @itemx maint show show-all-tib
32976 Control whether to show all non zero areas within a 1k block starting
32977 at thread local base, when using the @samp{info w32 thread-information-block}
32980 @kindex maint space
32981 @cindex memory used by commands
32983 Control whether to display memory usage for each command. If set to a
32984 nonzero value, @value{GDBN} will display how much memory each command
32985 took, following the command's own output. This can also be requested
32986 by invoking @value{GDBN} with the @option{--statistics} command-line
32987 switch (@pxref{Mode Options}).
32990 @cindex time of command execution
32992 Control whether to display the execution time for each command. If
32993 set to a nonzero value, @value{GDBN} will display how much time it
32994 took to execute each command, following the command's own output.
32995 The time is not printed for the commands that run the target, since
32996 there's no mechanism currently to compute how much time was spend
32997 by @value{GDBN} and how much time was spend by the program been debugged.
32998 it's not possibly currently
32999 This can also be requested by invoking @value{GDBN} with the
33000 @option{--statistics} command-line switch (@pxref{Mode Options}).
33002 @kindex maint translate-address
33003 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
33004 Find the symbol stored at the location specified by the address
33005 @var{addr} and an optional section name @var{section}. If found,
33006 @value{GDBN} prints the name of the closest symbol and an offset from
33007 the symbol's location to the specified address. This is similar to
33008 the @code{info address} command (@pxref{Symbols}), except that this
33009 command also allows to find symbols in other sections.
33011 If section was not specified, the section in which the symbol was found
33012 is also printed. For dynamically linked executables, the name of
33013 executable or shared library containing the symbol is printed as well.
33017 The following command is useful for non-interactive invocations of
33018 @value{GDBN}, such as in the test suite.
33021 @item set watchdog @var{nsec}
33022 @kindex set watchdog
33023 @cindex watchdog timer
33024 @cindex timeout for commands
33025 Set the maximum number of seconds @value{GDBN} will wait for the
33026 target operation to finish. If this time expires, @value{GDBN}
33027 reports and error and the command is aborted.
33029 @item show watchdog
33030 Show the current setting of the target wait timeout.
33033 @node Remote Protocol
33034 @appendix @value{GDBN} Remote Serial Protocol
33039 * Stop Reply Packets::
33040 * General Query Packets::
33041 * Architecture-Specific Protocol Details::
33042 * Tracepoint Packets::
33043 * Host I/O Packets::
33045 * Notification Packets::
33046 * Remote Non-Stop::
33047 * Packet Acknowledgment::
33049 * File-I/O Remote Protocol Extension::
33050 * Library List Format::
33051 * Memory Map Format::
33052 * Thread List Format::
33053 * Traceframe Info Format::
33059 There may be occasions when you need to know something about the
33060 protocol---for example, if there is only one serial port to your target
33061 machine, you might want your program to do something special if it
33062 recognizes a packet meant for @value{GDBN}.
33064 In the examples below, @samp{->} and @samp{<-} are used to indicate
33065 transmitted and received data, respectively.
33067 @cindex protocol, @value{GDBN} remote serial
33068 @cindex serial protocol, @value{GDBN} remote
33069 @cindex remote serial protocol
33070 All @value{GDBN} commands and responses (other than acknowledgments
33071 and notifications, see @ref{Notification Packets}) are sent as a
33072 @var{packet}. A @var{packet} is introduced with the character
33073 @samp{$}, the actual @var{packet-data}, and the terminating character
33074 @samp{#} followed by a two-digit @var{checksum}:
33077 @code{$}@var{packet-data}@code{#}@var{checksum}
33081 @cindex checksum, for @value{GDBN} remote
33083 The two-digit @var{checksum} is computed as the modulo 256 sum of all
33084 characters between the leading @samp{$} and the trailing @samp{#} (an
33085 eight bit unsigned checksum).
33087 Implementors should note that prior to @value{GDBN} 5.0 the protocol
33088 specification also included an optional two-digit @var{sequence-id}:
33091 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
33094 @cindex sequence-id, for @value{GDBN} remote
33096 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
33097 has never output @var{sequence-id}s. Stubs that handle packets added
33098 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
33100 When either the host or the target machine receives a packet, the first
33101 response expected is an acknowledgment: either @samp{+} (to indicate
33102 the package was received correctly) or @samp{-} (to request
33106 -> @code{$}@var{packet-data}@code{#}@var{checksum}
33111 The @samp{+}/@samp{-} acknowledgments can be disabled
33112 once a connection is established.
33113 @xref{Packet Acknowledgment}, for details.
33115 The host (@value{GDBN}) sends @var{command}s, and the target (the
33116 debugging stub incorporated in your program) sends a @var{response}. In
33117 the case of step and continue @var{command}s, the response is only sent
33118 when the operation has completed, and the target has again stopped all
33119 threads in all attached processes. This is the default all-stop mode
33120 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
33121 execution mode; see @ref{Remote Non-Stop}, for details.
33123 @var{packet-data} consists of a sequence of characters with the
33124 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
33127 @cindex remote protocol, field separator
33128 Fields within the packet should be separated using @samp{,} @samp{;} or
33129 @samp{:}. Except where otherwise noted all numbers are represented in
33130 @sc{hex} with leading zeros suppressed.
33132 Implementors should note that prior to @value{GDBN} 5.0, the character
33133 @samp{:} could not appear as the third character in a packet (as it
33134 would potentially conflict with the @var{sequence-id}).
33136 @cindex remote protocol, binary data
33137 @anchor{Binary Data}
33138 Binary data in most packets is encoded either as two hexadecimal
33139 digits per byte of binary data. This allowed the traditional remote
33140 protocol to work over connections which were only seven-bit clean.
33141 Some packets designed more recently assume an eight-bit clean
33142 connection, and use a more efficient encoding to send and receive
33145 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
33146 as an escape character. Any escaped byte is transmitted as the escape
33147 character followed by the original character XORed with @code{0x20}.
33148 For example, the byte @code{0x7d} would be transmitted as the two
33149 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
33150 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
33151 @samp{@}}) must always be escaped. Responses sent by the stub
33152 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
33153 is not interpreted as the start of a run-length encoded sequence
33156 Response @var{data} can be run-length encoded to save space.
33157 Run-length encoding replaces runs of identical characters with one
33158 instance of the repeated character, followed by a @samp{*} and a
33159 repeat count. The repeat count is itself sent encoded, to avoid
33160 binary characters in @var{data}: a value of @var{n} is sent as
33161 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
33162 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
33163 code 32) for a repeat count of 3. (This is because run-length
33164 encoding starts to win for counts 3 or more.) Thus, for example,
33165 @samp{0* } is a run-length encoding of ``0000'': the space character
33166 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
33169 The printable characters @samp{#} and @samp{$} or with a numeric value
33170 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
33171 seven repeats (@samp{$}) can be expanded using a repeat count of only
33172 five (@samp{"}). For example, @samp{00000000} can be encoded as
33175 The error response returned for some packets includes a two character
33176 error number. That number is not well defined.
33178 @cindex empty response, for unsupported packets
33179 For any @var{command} not supported by the stub, an empty response
33180 (@samp{$#00}) should be returned. That way it is possible to extend the
33181 protocol. A newer @value{GDBN} can tell if a packet is supported based
33184 At a minimum, a stub is required to support the @samp{g} and @samp{G}
33185 commands for register access, and the @samp{m} and @samp{M} commands
33186 for memory access. Stubs that only control single-threaded targets
33187 can implement run control with the @samp{c} (continue), and @samp{s}
33188 (step) commands. Stubs that support multi-threading targets should
33189 support the @samp{vCont} command. All other commands are optional.
33194 The following table provides a complete list of all currently defined
33195 @var{command}s and their corresponding response @var{data}.
33196 @xref{File-I/O Remote Protocol Extension}, for details about the File
33197 I/O extension of the remote protocol.
33199 Each packet's description has a template showing the packet's overall
33200 syntax, followed by an explanation of the packet's meaning. We
33201 include spaces in some of the templates for clarity; these are not
33202 part of the packet's syntax. No @value{GDBN} packet uses spaces to
33203 separate its components. For example, a template like @samp{foo
33204 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
33205 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
33206 @var{baz}. @value{GDBN} does not transmit a space character between the
33207 @samp{foo} and the @var{bar}, or between the @var{bar} and the
33210 @cindex @var{thread-id}, in remote protocol
33211 @anchor{thread-id syntax}
33212 Several packets and replies include a @var{thread-id} field to identify
33213 a thread. Normally these are positive numbers with a target-specific
33214 interpretation, formatted as big-endian hex strings. A @var{thread-id}
33215 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
33218 In addition, the remote protocol supports a multiprocess feature in
33219 which the @var{thread-id} syntax is extended to optionally include both
33220 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
33221 The @var{pid} (process) and @var{tid} (thread) components each have the
33222 format described above: a positive number with target-specific
33223 interpretation formatted as a big-endian hex string, literal @samp{-1}
33224 to indicate all processes or threads (respectively), or @samp{0} to
33225 indicate an arbitrary process or thread. Specifying just a process, as
33226 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
33227 error to specify all processes but a specific thread, such as
33228 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
33229 for those packets and replies explicitly documented to include a process
33230 ID, rather than a @var{thread-id}.
33232 The multiprocess @var{thread-id} syntax extensions are only used if both
33233 @value{GDBN} and the stub report support for the @samp{multiprocess}
33234 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
33237 Note that all packet forms beginning with an upper- or lower-case
33238 letter, other than those described here, are reserved for future use.
33240 Here are the packet descriptions.
33245 @cindex @samp{!} packet
33246 @anchor{extended mode}
33247 Enable extended mode. In extended mode, the remote server is made
33248 persistent. The @samp{R} packet is used to restart the program being
33254 The remote target both supports and has enabled extended mode.
33258 @cindex @samp{?} packet
33259 Indicate the reason the target halted. The reply is the same as for
33260 step and continue. This packet has a special interpretation when the
33261 target is in non-stop mode; see @ref{Remote Non-Stop}.
33264 @xref{Stop Reply Packets}, for the reply specifications.
33266 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
33267 @cindex @samp{A} packet
33268 Initialized @code{argv[]} array passed into program. @var{arglen}
33269 specifies the number of bytes in the hex encoded byte stream
33270 @var{arg}. See @code{gdbserver} for more details.
33275 The arguments were set.
33281 @cindex @samp{b} packet
33282 (Don't use this packet; its behavior is not well-defined.)
33283 Change the serial line speed to @var{baud}.
33285 JTC: @emph{When does the transport layer state change? When it's
33286 received, or after the ACK is transmitted. In either case, there are
33287 problems if the command or the acknowledgment packet is dropped.}
33289 Stan: @emph{If people really wanted to add something like this, and get
33290 it working for the first time, they ought to modify ser-unix.c to send
33291 some kind of out-of-band message to a specially-setup stub and have the
33292 switch happen "in between" packets, so that from remote protocol's point
33293 of view, nothing actually happened.}
33295 @item B @var{addr},@var{mode}
33296 @cindex @samp{B} packet
33297 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
33298 breakpoint at @var{addr}.
33300 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
33301 (@pxref{insert breakpoint or watchpoint packet}).
33303 @cindex @samp{bc} packet
33306 Backward continue. Execute the target system in reverse. No parameter.
33307 @xref{Reverse Execution}, for more information.
33310 @xref{Stop Reply Packets}, for the reply specifications.
33312 @cindex @samp{bs} packet
33315 Backward single step. Execute one instruction in reverse. No parameter.
33316 @xref{Reverse Execution}, for more information.
33319 @xref{Stop Reply Packets}, for the reply specifications.
33321 @item c @r{[}@var{addr}@r{]}
33322 @cindex @samp{c} packet
33323 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
33324 resume at current address.
33326 This packet is deprecated for multi-threading support. @xref{vCont
33330 @xref{Stop Reply Packets}, for the reply specifications.
33332 @item C @var{sig}@r{[};@var{addr}@r{]}
33333 @cindex @samp{C} packet
33334 Continue with signal @var{sig} (hex signal number). If
33335 @samp{;@var{addr}} is omitted, resume at same address.
33337 This packet is deprecated for multi-threading support. @xref{vCont
33341 @xref{Stop Reply Packets}, for the reply specifications.
33344 @cindex @samp{d} packet
33347 Don't use this packet; instead, define a general set packet
33348 (@pxref{General Query Packets}).
33352 @cindex @samp{D} packet
33353 The first form of the packet is used to detach @value{GDBN} from the
33354 remote system. It is sent to the remote target
33355 before @value{GDBN} disconnects via the @code{detach} command.
33357 The second form, including a process ID, is used when multiprocess
33358 protocol extensions are enabled (@pxref{multiprocess extensions}), to
33359 detach only a specific process. The @var{pid} is specified as a
33360 big-endian hex string.
33370 @item F @var{RC},@var{EE},@var{CF};@var{XX}
33371 @cindex @samp{F} packet
33372 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
33373 This is part of the File-I/O protocol extension. @xref{File-I/O
33374 Remote Protocol Extension}, for the specification.
33377 @anchor{read registers packet}
33378 @cindex @samp{g} packet
33379 Read general registers.
33383 @item @var{XX@dots{}}
33384 Each byte of register data is described by two hex digits. The bytes
33385 with the register are transmitted in target byte order. The size of
33386 each register and their position within the @samp{g} packet are
33387 determined by the @value{GDBN} internal gdbarch functions
33388 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
33389 specification of several standard @samp{g} packets is specified below.
33391 When reading registers from a trace frame (@pxref{Analyze Collected
33392 Data,,Using the Collected Data}), the stub may also return a string of
33393 literal @samp{x}'s in place of the register data digits, to indicate
33394 that the corresponding register has not been collected, thus its value
33395 is unavailable. For example, for an architecture with 4 registers of
33396 4 bytes each, the following reply indicates to @value{GDBN} that
33397 registers 0 and 2 have not been collected, while registers 1 and 3
33398 have been collected, and both have zero value:
33402 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
33409 @item G @var{XX@dots{}}
33410 @cindex @samp{G} packet
33411 Write general registers. @xref{read registers packet}, for a
33412 description of the @var{XX@dots{}} data.
33422 @item H @var{op} @var{thread-id}
33423 @cindex @samp{H} packet
33424 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
33425 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
33426 it should be @samp{c} for step and continue operations (note that this
33427 is deprecated, supporting the @samp{vCont} command is a better
33428 option), @samp{g} for other operations. The thread designator
33429 @var{thread-id} has the format and interpretation described in
33430 @ref{thread-id syntax}.
33441 @c 'H': How restrictive (or permissive) is the thread model. If a
33442 @c thread is selected and stopped, are other threads allowed
33443 @c to continue to execute? As I mentioned above, I think the
33444 @c semantics of each command when a thread is selected must be
33445 @c described. For example:
33447 @c 'g': If the stub supports threads and a specific thread is
33448 @c selected, returns the register block from that thread;
33449 @c otherwise returns current registers.
33451 @c 'G' If the stub supports threads and a specific thread is
33452 @c selected, sets the registers of the register block of
33453 @c that thread; otherwise sets current registers.
33455 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
33456 @anchor{cycle step packet}
33457 @cindex @samp{i} packet
33458 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
33459 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
33460 step starting at that address.
33463 @cindex @samp{I} packet
33464 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
33468 @cindex @samp{k} packet
33471 FIXME: @emph{There is no description of how to operate when a specific
33472 thread context has been selected (i.e.@: does 'k' kill only that
33475 @item m @var{addr},@var{length}
33476 @cindex @samp{m} packet
33477 Read @var{length} bytes of memory starting at address @var{addr}.
33478 Note that @var{addr} may not be aligned to any particular boundary.
33480 The stub need not use any particular size or alignment when gathering
33481 data from memory for the response; even if @var{addr} is word-aligned
33482 and @var{length} is a multiple of the word size, the stub is free to
33483 use byte accesses, or not. For this reason, this packet may not be
33484 suitable for accessing memory-mapped I/O devices.
33485 @cindex alignment of remote memory accesses
33486 @cindex size of remote memory accesses
33487 @cindex memory, alignment and size of remote accesses
33491 @item @var{XX@dots{}}
33492 Memory contents; each byte is transmitted as a two-digit hexadecimal
33493 number. The reply may contain fewer bytes than requested if the
33494 server was able to read only part of the region of memory.
33499 @item M @var{addr},@var{length}:@var{XX@dots{}}
33500 @cindex @samp{M} packet
33501 Write @var{length} bytes of memory starting at address @var{addr}.
33502 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
33503 hexadecimal number.
33510 for an error (this includes the case where only part of the data was
33515 @cindex @samp{p} packet
33516 Read the value of register @var{n}; @var{n} is in hex.
33517 @xref{read registers packet}, for a description of how the returned
33518 register value is encoded.
33522 @item @var{XX@dots{}}
33523 the register's value
33527 Indicating an unrecognized @var{query}.
33530 @item P @var{n@dots{}}=@var{r@dots{}}
33531 @anchor{write register packet}
33532 @cindex @samp{P} packet
33533 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
33534 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
33535 digits for each byte in the register (target byte order).
33545 @item q @var{name} @var{params}@dots{}
33546 @itemx Q @var{name} @var{params}@dots{}
33547 @cindex @samp{q} packet
33548 @cindex @samp{Q} packet
33549 General query (@samp{q}) and set (@samp{Q}). These packets are
33550 described fully in @ref{General Query Packets}.
33553 @cindex @samp{r} packet
33554 Reset the entire system.
33556 Don't use this packet; use the @samp{R} packet instead.
33559 @cindex @samp{R} packet
33560 Restart the program being debugged. @var{XX}, while needed, is ignored.
33561 This packet is only available in extended mode (@pxref{extended mode}).
33563 The @samp{R} packet has no reply.
33565 @item s @r{[}@var{addr}@r{]}
33566 @cindex @samp{s} packet
33567 Single step. @var{addr} is the address at which to resume. If
33568 @var{addr} is omitted, resume at same address.
33570 This packet is deprecated for multi-threading support. @xref{vCont
33574 @xref{Stop Reply Packets}, for the reply specifications.
33576 @item S @var{sig}@r{[};@var{addr}@r{]}
33577 @anchor{step with signal packet}
33578 @cindex @samp{S} packet
33579 Step with signal. This is analogous to the @samp{C} packet, but
33580 requests a single-step, rather than a normal resumption of execution.
33582 This packet is deprecated for multi-threading support. @xref{vCont
33586 @xref{Stop Reply Packets}, for the reply specifications.
33588 @item t @var{addr}:@var{PP},@var{MM}
33589 @cindex @samp{t} packet
33590 Search backwards starting at address @var{addr} for a match with pattern
33591 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
33592 @var{addr} must be at least 3 digits.
33594 @item T @var{thread-id}
33595 @cindex @samp{T} packet
33596 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
33601 thread is still alive
33607 Packets starting with @samp{v} are identified by a multi-letter name,
33608 up to the first @samp{;} or @samp{?} (or the end of the packet).
33610 @item vAttach;@var{pid}
33611 @cindex @samp{vAttach} packet
33612 Attach to a new process with the specified process ID @var{pid}.
33613 The process ID is a
33614 hexadecimal integer identifying the process. In all-stop mode, all
33615 threads in the attached process are stopped; in non-stop mode, it may be
33616 attached without being stopped if that is supported by the target.
33618 @c In non-stop mode, on a successful vAttach, the stub should set the
33619 @c current thread to a thread of the newly-attached process. After
33620 @c attaching, GDB queries for the attached process's thread ID with qC.
33621 @c Also note that, from a user perspective, whether or not the
33622 @c target is stopped on attach in non-stop mode depends on whether you
33623 @c use the foreground or background version of the attach command, not
33624 @c on what vAttach does; GDB does the right thing with respect to either
33625 @c stopping or restarting threads.
33627 This packet is only available in extended mode (@pxref{extended mode}).
33633 @item @r{Any stop packet}
33634 for success in all-stop mode (@pxref{Stop Reply Packets})
33636 for success in non-stop mode (@pxref{Remote Non-Stop})
33639 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
33640 @cindex @samp{vCont} packet
33641 @anchor{vCont packet}
33642 Resume the inferior, specifying different actions for each thread.
33643 If an action is specified with no @var{thread-id}, then it is applied to any
33644 threads that don't have a specific action specified; if no default action is
33645 specified then other threads should remain stopped in all-stop mode and
33646 in their current state in non-stop mode.
33647 Specifying multiple
33648 default actions is an error; specifying no actions is also an error.
33649 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
33651 Currently supported actions are:
33657 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
33661 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
33666 The optional argument @var{addr} normally associated with the
33667 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
33668 not supported in @samp{vCont}.
33670 The @samp{t} action is only relevant in non-stop mode
33671 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
33672 A stop reply should be generated for any affected thread not already stopped.
33673 When a thread is stopped by means of a @samp{t} action,
33674 the corresponding stop reply should indicate that the thread has stopped with
33675 signal @samp{0}, regardless of whether the target uses some other signal
33676 as an implementation detail.
33679 @xref{Stop Reply Packets}, for the reply specifications.
33682 @cindex @samp{vCont?} packet
33683 Request a list of actions supported by the @samp{vCont} packet.
33687 @item vCont@r{[};@var{action}@dots{}@r{]}
33688 The @samp{vCont} packet is supported. Each @var{action} is a supported
33689 command in the @samp{vCont} packet.
33691 The @samp{vCont} packet is not supported.
33694 @item vFile:@var{operation}:@var{parameter}@dots{}
33695 @cindex @samp{vFile} packet
33696 Perform a file operation on the target system. For details,
33697 see @ref{Host I/O Packets}.
33699 @item vFlashErase:@var{addr},@var{length}
33700 @cindex @samp{vFlashErase} packet
33701 Direct the stub to erase @var{length} bytes of flash starting at
33702 @var{addr}. The region may enclose any number of flash blocks, but
33703 its start and end must fall on block boundaries, as indicated by the
33704 flash block size appearing in the memory map (@pxref{Memory Map
33705 Format}). @value{GDBN} groups flash memory programming operations
33706 together, and sends a @samp{vFlashDone} request after each group; the
33707 stub is allowed to delay erase operation until the @samp{vFlashDone}
33708 packet is received.
33710 The stub must support @samp{vCont} if it reports support for
33711 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
33712 this case @samp{vCont} actions can be specified to apply to all threads
33713 in a process by using the @samp{p@var{pid}.-1} form of the
33724 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
33725 @cindex @samp{vFlashWrite} packet
33726 Direct the stub to write data to flash address @var{addr}. The data
33727 is passed in binary form using the same encoding as for the @samp{X}
33728 packet (@pxref{Binary Data}). The memory ranges specified by
33729 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
33730 not overlap, and must appear in order of increasing addresses
33731 (although @samp{vFlashErase} packets for higher addresses may already
33732 have been received; the ordering is guaranteed only between
33733 @samp{vFlashWrite} packets). If a packet writes to an address that was
33734 neither erased by a preceding @samp{vFlashErase} packet nor by some other
33735 target-specific method, the results are unpredictable.
33743 for vFlashWrite addressing non-flash memory
33749 @cindex @samp{vFlashDone} packet
33750 Indicate to the stub that flash programming operation is finished.
33751 The stub is permitted to delay or batch the effects of a group of
33752 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
33753 @samp{vFlashDone} packet is received. The contents of the affected
33754 regions of flash memory are unpredictable until the @samp{vFlashDone}
33755 request is completed.
33757 @item vKill;@var{pid}
33758 @cindex @samp{vKill} packet
33759 Kill the process with the specified process ID. @var{pid} is a
33760 hexadecimal integer identifying the process. This packet is used in
33761 preference to @samp{k} when multiprocess protocol extensions are
33762 supported; see @ref{multiprocess extensions}.
33772 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
33773 @cindex @samp{vRun} packet
33774 Run the program @var{filename}, passing it each @var{argument} on its
33775 command line. The file and arguments are hex-encoded strings. If
33776 @var{filename} is an empty string, the stub may use a default program
33777 (e.g.@: the last program run). The program is created in the stopped
33780 @c FIXME: What about non-stop mode?
33782 This packet is only available in extended mode (@pxref{extended mode}).
33788 @item @r{Any stop packet}
33789 for success (@pxref{Stop Reply Packets})
33793 @anchor{vStopped packet}
33794 @cindex @samp{vStopped} packet
33796 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
33797 reply and prompt for the stub to report another one.
33801 @item @r{Any stop packet}
33802 if there is another unreported stop event (@pxref{Stop Reply Packets})
33804 if there are no unreported stop events
33807 @item X @var{addr},@var{length}:@var{XX@dots{}}
33809 @cindex @samp{X} packet
33810 Write data to memory, where the data is transmitted in binary.
33811 @var{addr} is address, @var{length} is number of bytes,
33812 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
33822 @item z @var{type},@var{addr},@var{kind}
33823 @itemx Z @var{type},@var{addr},@var{kind}
33824 @anchor{insert breakpoint or watchpoint packet}
33825 @cindex @samp{z} packet
33826 @cindex @samp{Z} packets
33827 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
33828 watchpoint starting at address @var{address} of kind @var{kind}.
33830 Each breakpoint and watchpoint packet @var{type} is documented
33833 @emph{Implementation notes: A remote target shall return an empty string
33834 for an unrecognized breakpoint or watchpoint packet @var{type}. A
33835 remote target shall support either both or neither of a given
33836 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
33837 avoid potential problems with duplicate packets, the operations should
33838 be implemented in an idempotent way.}
33840 @item z0,@var{addr},@var{kind}
33841 @itemx Z0,@var{addr},@var{kind}
33842 @cindex @samp{z0} packet
33843 @cindex @samp{Z0} packet
33844 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
33845 @var{addr} of type @var{kind}.
33847 A memory breakpoint is implemented by replacing the instruction at
33848 @var{addr} with a software breakpoint or trap instruction. The
33849 @var{kind} is target-specific and typically indicates the size of
33850 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
33851 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
33852 architectures have additional meanings for @var{kind};
33853 see @ref{Architecture-Specific Protocol Details}.
33855 @emph{Implementation note: It is possible for a target to copy or move
33856 code that contains memory breakpoints (e.g., when implementing
33857 overlays). The behavior of this packet, in the presence of such a
33858 target, is not defined.}
33870 @item z1,@var{addr},@var{kind}
33871 @itemx Z1,@var{addr},@var{kind}
33872 @cindex @samp{z1} packet
33873 @cindex @samp{Z1} packet
33874 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
33875 address @var{addr}.
33877 A hardware breakpoint is implemented using a mechanism that is not
33878 dependant on being able to modify the target's memory. @var{kind}
33879 has the same meaning as in @samp{Z0} packets.
33881 @emph{Implementation note: A hardware breakpoint is not affected by code
33894 @item z2,@var{addr},@var{kind}
33895 @itemx Z2,@var{addr},@var{kind}
33896 @cindex @samp{z2} packet
33897 @cindex @samp{Z2} packet
33898 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
33899 @var{kind} is interpreted as the number of bytes to watch.
33911 @item z3,@var{addr},@var{kind}
33912 @itemx Z3,@var{addr},@var{kind}
33913 @cindex @samp{z3} packet
33914 @cindex @samp{Z3} packet
33915 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
33916 @var{kind} is interpreted as the number of bytes to watch.
33928 @item z4,@var{addr},@var{kind}
33929 @itemx Z4,@var{addr},@var{kind}
33930 @cindex @samp{z4} packet
33931 @cindex @samp{Z4} packet
33932 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
33933 @var{kind} is interpreted as the number of bytes to watch.
33947 @node Stop Reply Packets
33948 @section Stop Reply Packets
33949 @cindex stop reply packets
33951 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
33952 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
33953 receive any of the below as a reply. Except for @samp{?}
33954 and @samp{vStopped}, that reply is only returned
33955 when the target halts. In the below the exact meaning of @dfn{signal
33956 number} is defined by the header @file{include/gdb/signals.h} in the
33957 @value{GDBN} source code.
33959 As in the description of request packets, we include spaces in the
33960 reply templates for clarity; these are not part of the reply packet's
33961 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
33967 The program received signal number @var{AA} (a two-digit hexadecimal
33968 number). This is equivalent to a @samp{T} response with no
33969 @var{n}:@var{r} pairs.
33971 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
33972 @cindex @samp{T} packet reply
33973 The program received signal number @var{AA} (a two-digit hexadecimal
33974 number). This is equivalent to an @samp{S} response, except that the
33975 @samp{@var{n}:@var{r}} pairs can carry values of important registers
33976 and other information directly in the stop reply packet, reducing
33977 round-trip latency. Single-step and breakpoint traps are reported
33978 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
33982 If @var{n} is a hexadecimal number, it is a register number, and the
33983 corresponding @var{r} gives that register's value. @var{r} is a
33984 series of bytes in target byte order, with each byte given by a
33985 two-digit hex number.
33988 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
33989 the stopped thread, as specified in @ref{thread-id syntax}.
33992 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
33993 the core on which the stop event was detected.
33996 If @var{n} is a recognized @dfn{stop reason}, it describes a more
33997 specific event that stopped the target. The currently defined stop
33998 reasons are listed below. @var{aa} should be @samp{05}, the trap
33999 signal. At most one stop reason should be present.
34002 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
34003 and go on to the next; this allows us to extend the protocol in the
34007 The currently defined stop reasons are:
34013 The packet indicates a watchpoint hit, and @var{r} is the data address, in
34016 @cindex shared library events, remote reply
34018 The packet indicates that the loaded libraries have changed.
34019 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
34020 list of loaded libraries. @var{r} is ignored.
34022 @cindex replay log events, remote reply
34024 The packet indicates that the target cannot continue replaying
34025 logged execution events, because it has reached the end (or the
34026 beginning when executing backward) of the log. The value of @var{r}
34027 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
34028 for more information.
34032 @itemx W @var{AA} ; process:@var{pid}
34033 The process exited, and @var{AA} is the exit status. This is only
34034 applicable to certain targets.
34036 The second form of the response, including the process ID of the exited
34037 process, can be used only when @value{GDBN} has reported support for
34038 multiprocess protocol extensions; see @ref{multiprocess extensions}.
34039 The @var{pid} is formatted as a big-endian hex string.
34042 @itemx X @var{AA} ; process:@var{pid}
34043 The process terminated with signal @var{AA}.
34045 The second form of the response, including the process ID of the
34046 terminated process, can be used only when @value{GDBN} has reported
34047 support for multiprocess protocol extensions; see @ref{multiprocess
34048 extensions}. The @var{pid} is formatted as a big-endian hex string.
34050 @item O @var{XX}@dots{}
34051 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
34052 written as the program's console output. This can happen at any time
34053 while the program is running and the debugger should continue to wait
34054 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
34056 @item F @var{call-id},@var{parameter}@dots{}
34057 @var{call-id} is the identifier which says which host system call should
34058 be called. This is just the name of the function. Translation into the
34059 correct system call is only applicable as it's defined in @value{GDBN}.
34060 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
34063 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
34064 this very system call.
34066 The target replies with this packet when it expects @value{GDBN} to
34067 call a host system call on behalf of the target. @value{GDBN} replies
34068 with an appropriate @samp{F} packet and keeps up waiting for the next
34069 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
34070 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
34071 Protocol Extension}, for more details.
34075 @node General Query Packets
34076 @section General Query Packets
34077 @cindex remote query requests
34079 Packets starting with @samp{q} are @dfn{general query packets};
34080 packets starting with @samp{Q} are @dfn{general set packets}. General
34081 query and set packets are a semi-unified form for retrieving and
34082 sending information to and from the stub.
34084 The initial letter of a query or set packet is followed by a name
34085 indicating what sort of thing the packet applies to. For example,
34086 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
34087 definitions with the stub. These packet names follow some
34092 The name must not contain commas, colons or semicolons.
34094 Most @value{GDBN} query and set packets have a leading upper case
34097 The names of custom vendor packets should use a company prefix, in
34098 lower case, followed by a period. For example, packets designed at
34099 the Acme Corporation might begin with @samp{qacme.foo} (for querying
34100 foos) or @samp{Qacme.bar} (for setting bars).
34103 The name of a query or set packet should be separated from any
34104 parameters by a @samp{:}; the parameters themselves should be
34105 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
34106 full packet name, and check for a separator or the end of the packet,
34107 in case two packet names share a common prefix. New packets should not begin
34108 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
34109 packets predate these conventions, and have arguments without any terminator
34110 for the packet name; we suspect they are in widespread use in places that
34111 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
34112 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
34115 Like the descriptions of the other packets, each description here
34116 has a template showing the packet's overall syntax, followed by an
34117 explanation of the packet's meaning. We include spaces in some of the
34118 templates for clarity; these are not part of the packet's syntax. No
34119 @value{GDBN} packet uses spaces to separate its components.
34121 Here are the currently defined query and set packets:
34125 @item QAllow:@var{op}:@var{val}@dots{}
34126 @cindex @samp{QAllow} packet
34127 Specify which operations @value{GDBN} expects to request of the
34128 target, as a semicolon-separated list of operation name and value
34129 pairs. Possible values for @var{op} include @samp{WriteReg},
34130 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
34131 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
34132 indicating that @value{GDBN} will not request the operation, or 1,
34133 indicating that it may. (The target can then use this to set up its
34134 own internals optimally, for instance if the debugger never expects to
34135 insert breakpoints, it may not need to install its own trap handler.)
34138 @cindex current thread, remote request
34139 @cindex @samp{qC} packet
34140 Return the current thread ID.
34144 @item QC @var{thread-id}
34145 Where @var{thread-id} is a thread ID as documented in
34146 @ref{thread-id syntax}.
34147 @item @r{(anything else)}
34148 Any other reply implies the old thread ID.
34151 @item qCRC:@var{addr},@var{length}
34152 @cindex CRC of memory block, remote request
34153 @cindex @samp{qCRC} packet
34154 Compute the CRC checksum of a block of memory using CRC-32 defined in
34155 IEEE 802.3. The CRC is computed byte at a time, taking the most
34156 significant bit of each byte first. The initial pattern code
34157 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
34159 @emph{Note:} This is the same CRC used in validating separate debug
34160 files (@pxref{Separate Debug Files, , Debugging Information in Separate
34161 Files}). However the algorithm is slightly different. When validating
34162 separate debug files, the CRC is computed taking the @emph{least}
34163 significant bit of each byte first, and the final result is inverted to
34164 detect trailing zeros.
34169 An error (such as memory fault)
34170 @item C @var{crc32}
34171 The specified memory region's checksum is @var{crc32}.
34174 @item QDisableRandomization:@var{value}
34175 @cindex disable address space randomization, remote request
34176 @cindex @samp{QDisableRandomization} packet
34177 Some target operating systems will randomize the virtual address space
34178 of the inferior process as a security feature, but provide a feature
34179 to disable such randomization, e.g.@: to allow for a more deterministic
34180 debugging experience. On such systems, this packet with a @var{value}
34181 of 1 directs the target to disable address space randomization for
34182 processes subsequently started via @samp{vRun} packets, while a packet
34183 with a @var{value} of 0 tells the target to enable address space
34186 This packet is only available in extended mode (@pxref{extended mode}).
34191 The request succeeded.
34194 An error occurred. @var{nn} are hex digits.
34197 An empty reply indicates that @samp{QDisableRandomization} is not supported
34201 This packet is not probed by default; the remote stub must request it,
34202 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34203 This should only be done on targets that actually support disabling
34204 address space randomization.
34207 @itemx qsThreadInfo
34208 @cindex list active threads, remote request
34209 @cindex @samp{qfThreadInfo} packet
34210 @cindex @samp{qsThreadInfo} packet
34211 Obtain a list of all active thread IDs from the target (OS). Since there
34212 may be too many active threads to fit into one reply packet, this query
34213 works iteratively: it may require more than one query/reply sequence to
34214 obtain the entire list of threads. The first query of the sequence will
34215 be the @samp{qfThreadInfo} query; subsequent queries in the
34216 sequence will be the @samp{qsThreadInfo} query.
34218 NOTE: This packet replaces the @samp{qL} query (see below).
34222 @item m @var{thread-id}
34224 @item m @var{thread-id},@var{thread-id}@dots{}
34225 a comma-separated list of thread IDs
34227 (lower case letter @samp{L}) denotes end of list.
34230 In response to each query, the target will reply with a list of one or
34231 more thread IDs, separated by commas.
34232 @value{GDBN} will respond to each reply with a request for more thread
34233 ids (using the @samp{qs} form of the query), until the target responds
34234 with @samp{l} (lower-case ell, for @dfn{last}).
34235 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
34238 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
34239 @cindex get thread-local storage address, remote request
34240 @cindex @samp{qGetTLSAddr} packet
34241 Fetch the address associated with thread local storage specified
34242 by @var{thread-id}, @var{offset}, and @var{lm}.
34244 @var{thread-id} is the thread ID associated with the
34245 thread for which to fetch the TLS address. @xref{thread-id syntax}.
34247 @var{offset} is the (big endian, hex encoded) offset associated with the
34248 thread local variable. (This offset is obtained from the debug
34249 information associated with the variable.)
34251 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
34252 load module associated with the thread local storage. For example,
34253 a @sc{gnu}/Linux system will pass the link map address of the shared
34254 object associated with the thread local storage under consideration.
34255 Other operating environments may choose to represent the load module
34256 differently, so the precise meaning of this parameter will vary.
34260 @item @var{XX}@dots{}
34261 Hex encoded (big endian) bytes representing the address of the thread
34262 local storage requested.
34265 An error occurred. @var{nn} are hex digits.
34268 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
34271 @item qGetTIBAddr:@var{thread-id}
34272 @cindex get thread information block address
34273 @cindex @samp{qGetTIBAddr} packet
34274 Fetch address of the Windows OS specific Thread Information Block.
34276 @var{thread-id} is the thread ID associated with the thread.
34280 @item @var{XX}@dots{}
34281 Hex encoded (big endian) bytes representing the linear address of the
34282 thread information block.
34285 An error occured. This means that either the thread was not found, or the
34286 address could not be retrieved.
34289 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
34292 @item qL @var{startflag} @var{threadcount} @var{nextthread}
34293 Obtain thread information from RTOS. Where: @var{startflag} (one hex
34294 digit) is one to indicate the first query and zero to indicate a
34295 subsequent query; @var{threadcount} (two hex digits) is the maximum
34296 number of threads the response packet can contain; and @var{nextthread}
34297 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
34298 returned in the response as @var{argthread}.
34300 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
34304 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
34305 Where: @var{count} (two hex digits) is the number of threads being
34306 returned; @var{done} (one hex digit) is zero to indicate more threads
34307 and one indicates no further threads; @var{argthreadid} (eight hex
34308 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
34309 is a sequence of thread IDs from the target. @var{threadid} (eight hex
34310 digits). See @code{remote.c:parse_threadlist_response()}.
34314 @cindex section offsets, remote request
34315 @cindex @samp{qOffsets} packet
34316 Get section offsets that the target used when relocating the downloaded
34321 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
34322 Relocate the @code{Text} section by @var{xxx} from its original address.
34323 Relocate the @code{Data} section by @var{yyy} from its original address.
34324 If the object file format provides segment information (e.g.@: @sc{elf}
34325 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
34326 segments by the supplied offsets.
34328 @emph{Note: while a @code{Bss} offset may be included in the response,
34329 @value{GDBN} ignores this and instead applies the @code{Data} offset
34330 to the @code{Bss} section.}
34332 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
34333 Relocate the first segment of the object file, which conventionally
34334 contains program code, to a starting address of @var{xxx}. If
34335 @samp{DataSeg} is specified, relocate the second segment, which
34336 conventionally contains modifiable data, to a starting address of
34337 @var{yyy}. @value{GDBN} will report an error if the object file
34338 does not contain segment information, or does not contain at least
34339 as many segments as mentioned in the reply. Extra segments are
34340 kept at fixed offsets relative to the last relocated segment.
34343 @item qP @var{mode} @var{thread-id}
34344 @cindex thread information, remote request
34345 @cindex @samp{qP} packet
34346 Returns information on @var{thread-id}. Where: @var{mode} is a hex
34347 encoded 32 bit mode; @var{thread-id} is a thread ID
34348 (@pxref{thread-id syntax}).
34350 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
34353 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
34357 @cindex non-stop mode, remote request
34358 @cindex @samp{QNonStop} packet
34360 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
34361 @xref{Remote Non-Stop}, for more information.
34366 The request succeeded.
34369 An error occurred. @var{nn} are hex digits.
34372 An empty reply indicates that @samp{QNonStop} is not supported by
34376 This packet is not probed by default; the remote stub must request it,
34377 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34378 Use of this packet is controlled by the @code{set non-stop} command;
34379 @pxref{Non-Stop Mode}.
34381 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
34382 @cindex pass signals to inferior, remote request
34383 @cindex @samp{QPassSignals} packet
34384 @anchor{QPassSignals}
34385 Each listed @var{signal} should be passed directly to the inferior process.
34386 Signals are numbered identically to continue packets and stop replies
34387 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
34388 strictly greater than the previous item. These signals do not need to stop
34389 the inferior, or be reported to @value{GDBN}. All other signals should be
34390 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
34391 combine; any earlier @samp{QPassSignals} list is completely replaced by the
34392 new list. This packet improves performance when using @samp{handle
34393 @var{signal} nostop noprint pass}.
34398 The request succeeded.
34401 An error occurred. @var{nn} are hex digits.
34404 An empty reply indicates that @samp{QPassSignals} is not supported by
34408 Use of this packet is controlled by the @code{set remote pass-signals}
34409 command (@pxref{Remote Configuration, set remote pass-signals}).
34410 This packet is not probed by default; the remote stub must request it,
34411 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34413 @item qRcmd,@var{command}
34414 @cindex execute remote command, remote request
34415 @cindex @samp{qRcmd} packet
34416 @var{command} (hex encoded) is passed to the local interpreter for
34417 execution. Invalid commands should be reported using the output
34418 string. Before the final result packet, the target may also respond
34419 with a number of intermediate @samp{O@var{output}} console output
34420 packets. @emph{Implementors should note that providing access to a
34421 stubs's interpreter may have security implications}.
34426 A command response with no output.
34428 A command response with the hex encoded output string @var{OUTPUT}.
34430 Indicate a badly formed request.
34432 An empty reply indicates that @samp{qRcmd} is not recognized.
34435 (Note that the @code{qRcmd} packet's name is separated from the
34436 command by a @samp{,}, not a @samp{:}, contrary to the naming
34437 conventions above. Please don't use this packet as a model for new
34440 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
34441 @cindex searching memory, in remote debugging
34442 @cindex @samp{qSearch:memory} packet
34443 @anchor{qSearch memory}
34444 Search @var{length} bytes at @var{address} for @var{search-pattern}.
34445 @var{address} and @var{length} are encoded in hex.
34446 @var{search-pattern} is a sequence of bytes, hex encoded.
34451 The pattern was not found.
34453 The pattern was found at @var{address}.
34455 A badly formed request or an error was encountered while searching memory.
34457 An empty reply indicates that @samp{qSearch:memory} is not recognized.
34460 @item QStartNoAckMode
34461 @cindex @samp{QStartNoAckMode} packet
34462 @anchor{QStartNoAckMode}
34463 Request that the remote stub disable the normal @samp{+}/@samp{-}
34464 protocol acknowledgments (@pxref{Packet Acknowledgment}).
34469 The stub has switched to no-acknowledgment mode.
34470 @value{GDBN} acknowledges this reponse,
34471 but neither the stub nor @value{GDBN} shall send or expect further
34472 @samp{+}/@samp{-} acknowledgments in the current connection.
34474 An empty reply indicates that the stub does not support no-acknowledgment mode.
34477 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
34478 @cindex supported packets, remote query
34479 @cindex features of the remote protocol
34480 @cindex @samp{qSupported} packet
34481 @anchor{qSupported}
34482 Tell the remote stub about features supported by @value{GDBN}, and
34483 query the stub for features it supports. This packet allows
34484 @value{GDBN} and the remote stub to take advantage of each others'
34485 features. @samp{qSupported} also consolidates multiple feature probes
34486 at startup, to improve @value{GDBN} performance---a single larger
34487 packet performs better than multiple smaller probe packets on
34488 high-latency links. Some features may enable behavior which must not
34489 be on by default, e.g.@: because it would confuse older clients or
34490 stubs. Other features may describe packets which could be
34491 automatically probed for, but are not. These features must be
34492 reported before @value{GDBN} will use them. This ``default
34493 unsupported'' behavior is not appropriate for all packets, but it
34494 helps to keep the initial connection time under control with new
34495 versions of @value{GDBN} which support increasing numbers of packets.
34499 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
34500 The stub supports or does not support each returned @var{stubfeature},
34501 depending on the form of each @var{stubfeature} (see below for the
34504 An empty reply indicates that @samp{qSupported} is not recognized,
34505 or that no features needed to be reported to @value{GDBN}.
34508 The allowed forms for each feature (either a @var{gdbfeature} in the
34509 @samp{qSupported} packet, or a @var{stubfeature} in the response)
34513 @item @var{name}=@var{value}
34514 The remote protocol feature @var{name} is supported, and associated
34515 with the specified @var{value}. The format of @var{value} depends
34516 on the feature, but it must not include a semicolon.
34518 The remote protocol feature @var{name} is supported, and does not
34519 need an associated value.
34521 The remote protocol feature @var{name} is not supported.
34523 The remote protocol feature @var{name} may be supported, and
34524 @value{GDBN} should auto-detect support in some other way when it is
34525 needed. This form will not be used for @var{gdbfeature} notifications,
34526 but may be used for @var{stubfeature} responses.
34529 Whenever the stub receives a @samp{qSupported} request, the
34530 supplied set of @value{GDBN} features should override any previous
34531 request. This allows @value{GDBN} to put the stub in a known
34532 state, even if the stub had previously been communicating with
34533 a different version of @value{GDBN}.
34535 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
34540 This feature indicates whether @value{GDBN} supports multiprocess
34541 extensions to the remote protocol. @value{GDBN} does not use such
34542 extensions unless the stub also reports that it supports them by
34543 including @samp{multiprocess+} in its @samp{qSupported} reply.
34544 @xref{multiprocess extensions}, for details.
34547 This feature indicates that @value{GDBN} supports the XML target
34548 description. If the stub sees @samp{xmlRegisters=} with target
34549 specific strings separated by a comma, it will report register
34553 This feature indicates whether @value{GDBN} supports the
34554 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
34555 instruction reply packet}).
34558 Stubs should ignore any unknown values for
34559 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
34560 packet supports receiving packets of unlimited length (earlier
34561 versions of @value{GDBN} may reject overly long responses). Additional values
34562 for @var{gdbfeature} may be defined in the future to let the stub take
34563 advantage of new features in @value{GDBN}, e.g.@: incompatible
34564 improvements in the remote protocol---the @samp{multiprocess} feature is
34565 an example of such a feature. The stub's reply should be independent
34566 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
34567 describes all the features it supports, and then the stub replies with
34568 all the features it supports.
34570 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
34571 responses, as long as each response uses one of the standard forms.
34573 Some features are flags. A stub which supports a flag feature
34574 should respond with a @samp{+} form response. Other features
34575 require values, and the stub should respond with an @samp{=}
34578 Each feature has a default value, which @value{GDBN} will use if
34579 @samp{qSupported} is not available or if the feature is not mentioned
34580 in the @samp{qSupported} response. The default values are fixed; a
34581 stub is free to omit any feature responses that match the defaults.
34583 Not all features can be probed, but for those which can, the probing
34584 mechanism is useful: in some cases, a stub's internal
34585 architecture may not allow the protocol layer to know some information
34586 about the underlying target in advance. This is especially common in
34587 stubs which may be configured for multiple targets.
34589 These are the currently defined stub features and their properties:
34591 @multitable @columnfractions 0.35 0.2 0.12 0.2
34592 @c NOTE: The first row should be @headitem, but we do not yet require
34593 @c a new enough version of Texinfo (4.7) to use @headitem.
34595 @tab Value Required
34599 @item @samp{PacketSize}
34604 @item @samp{qXfer:auxv:read}
34609 @item @samp{qXfer:features:read}
34614 @item @samp{qXfer:libraries:read}
34619 @item @samp{qXfer:memory-map:read}
34624 @item @samp{qXfer:sdata:read}
34629 @item @samp{qXfer:spu:read}
34634 @item @samp{qXfer:spu:write}
34639 @item @samp{qXfer:siginfo:read}
34644 @item @samp{qXfer:siginfo:write}
34649 @item @samp{qXfer:threads:read}
34654 @item @samp{qXfer:traceframe-info:read}
34659 @item @samp{qXfer:fdpic:read}
34664 @item @samp{QNonStop}
34669 @item @samp{QPassSignals}
34674 @item @samp{QStartNoAckMode}
34679 @item @samp{multiprocess}
34684 @item @samp{ConditionalTracepoints}
34689 @item @samp{ReverseContinue}
34694 @item @samp{ReverseStep}
34699 @item @samp{TracepointSource}
34704 @item @samp{QAllow}
34709 @item @samp{QDisableRandomization}
34714 @item @samp{EnableDisableTracepoints}
34719 @item @samp{tracenz}
34726 These are the currently defined stub features, in more detail:
34729 @cindex packet size, remote protocol
34730 @item PacketSize=@var{bytes}
34731 The remote stub can accept packets up to at least @var{bytes} in
34732 length. @value{GDBN} will send packets up to this size for bulk
34733 transfers, and will never send larger packets. This is a limit on the
34734 data characters in the packet, including the frame and checksum.
34735 There is no trailing NUL byte in a remote protocol packet; if the stub
34736 stores packets in a NUL-terminated format, it should allow an extra
34737 byte in its buffer for the NUL. If this stub feature is not supported,
34738 @value{GDBN} guesses based on the size of the @samp{g} packet response.
34740 @item qXfer:auxv:read
34741 The remote stub understands the @samp{qXfer:auxv:read} packet
34742 (@pxref{qXfer auxiliary vector read}).
34744 @item qXfer:features:read
34745 The remote stub understands the @samp{qXfer:features:read} packet
34746 (@pxref{qXfer target description read}).
34748 @item qXfer:libraries:read
34749 The remote stub understands the @samp{qXfer:libraries:read} packet
34750 (@pxref{qXfer library list read}).
34752 @item qXfer:memory-map:read
34753 The remote stub understands the @samp{qXfer:memory-map:read} packet
34754 (@pxref{qXfer memory map read}).
34756 @item qXfer:sdata:read
34757 The remote stub understands the @samp{qXfer:sdata:read} packet
34758 (@pxref{qXfer sdata read}).
34760 @item qXfer:spu:read
34761 The remote stub understands the @samp{qXfer:spu:read} packet
34762 (@pxref{qXfer spu read}).
34764 @item qXfer:spu:write
34765 The remote stub understands the @samp{qXfer:spu:write} packet
34766 (@pxref{qXfer spu write}).
34768 @item qXfer:siginfo:read
34769 The remote stub understands the @samp{qXfer:siginfo:read} packet
34770 (@pxref{qXfer siginfo read}).
34772 @item qXfer:siginfo:write
34773 The remote stub understands the @samp{qXfer:siginfo:write} packet
34774 (@pxref{qXfer siginfo write}).
34776 @item qXfer:threads:read
34777 The remote stub understands the @samp{qXfer:threads:read} packet
34778 (@pxref{qXfer threads read}).
34780 @item qXfer:traceframe-info:read
34781 The remote stub understands the @samp{qXfer:traceframe-info:read}
34782 packet (@pxref{qXfer traceframe info read}).
34784 @item qXfer:fdpic:read
34785 The remote stub understands the @samp{qXfer:fdpic:read}
34786 packet (@pxref{qXfer fdpic loadmap read}).
34789 The remote stub understands the @samp{QNonStop} packet
34790 (@pxref{QNonStop}).
34793 The remote stub understands the @samp{QPassSignals} packet
34794 (@pxref{QPassSignals}).
34796 @item QStartNoAckMode
34797 The remote stub understands the @samp{QStartNoAckMode} packet and
34798 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
34801 @anchor{multiprocess extensions}
34802 @cindex multiprocess extensions, in remote protocol
34803 The remote stub understands the multiprocess extensions to the remote
34804 protocol syntax. The multiprocess extensions affect the syntax of
34805 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
34806 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
34807 replies. Note that reporting this feature indicates support for the
34808 syntactic extensions only, not that the stub necessarily supports
34809 debugging of more than one process at a time. The stub must not use
34810 multiprocess extensions in packet replies unless @value{GDBN} has also
34811 indicated it supports them in its @samp{qSupported} request.
34813 @item qXfer:osdata:read
34814 The remote stub understands the @samp{qXfer:osdata:read} packet
34815 ((@pxref{qXfer osdata read}).
34817 @item ConditionalTracepoints
34818 The remote stub accepts and implements conditional expressions defined
34819 for tracepoints (@pxref{Tracepoint Conditions}).
34821 @item ReverseContinue
34822 The remote stub accepts and implements the reverse continue packet
34826 The remote stub accepts and implements the reverse step packet
34829 @item TracepointSource
34830 The remote stub understands the @samp{QTDPsrc} packet that supplies
34831 the source form of tracepoint definitions.
34834 The remote stub understands the @samp{QAllow} packet.
34836 @item QDisableRandomization
34837 The remote stub understands the @samp{QDisableRandomization} packet.
34839 @item StaticTracepoint
34840 @cindex static tracepoints, in remote protocol
34841 The remote stub supports static tracepoints.
34843 @item EnableDisableTracepoints
34844 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
34845 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
34846 to be enabled and disabled while a trace experiment is running.
34849 @cindex string tracing, in remote protocol
34850 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
34851 See @ref{Bytecode Descriptions} for details about the bytecode.
34856 @cindex symbol lookup, remote request
34857 @cindex @samp{qSymbol} packet
34858 Notify the target that @value{GDBN} is prepared to serve symbol lookup
34859 requests. Accept requests from the target for the values of symbols.
34864 The target does not need to look up any (more) symbols.
34865 @item qSymbol:@var{sym_name}
34866 The target requests the value of symbol @var{sym_name} (hex encoded).
34867 @value{GDBN} may provide the value by using the
34868 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
34872 @item qSymbol:@var{sym_value}:@var{sym_name}
34873 Set the value of @var{sym_name} to @var{sym_value}.
34875 @var{sym_name} (hex encoded) is the name of a symbol whose value the
34876 target has previously requested.
34878 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
34879 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
34885 The target does not need to look up any (more) symbols.
34886 @item qSymbol:@var{sym_name}
34887 The target requests the value of a new symbol @var{sym_name} (hex
34888 encoded). @value{GDBN} will continue to supply the values of symbols
34889 (if available), until the target ceases to request them.
34894 @item QTDisconnected
34901 @xref{Tracepoint Packets}.
34903 @item qThreadExtraInfo,@var{thread-id}
34904 @cindex thread attributes info, remote request
34905 @cindex @samp{qThreadExtraInfo} packet
34906 Obtain a printable string description of a thread's attributes from
34907 the target OS. @var{thread-id} is a thread ID;
34908 see @ref{thread-id syntax}. This
34909 string may contain anything that the target OS thinks is interesting
34910 for @value{GDBN} to tell the user about the thread. The string is
34911 displayed in @value{GDBN}'s @code{info threads} display. Some
34912 examples of possible thread extra info strings are @samp{Runnable}, or
34913 @samp{Blocked on Mutex}.
34917 @item @var{XX}@dots{}
34918 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
34919 comprising the printable string containing the extra information about
34920 the thread's attributes.
34923 (Note that the @code{qThreadExtraInfo} packet's name is separated from
34924 the command by a @samp{,}, not a @samp{:}, contrary to the naming
34925 conventions above. Please don't use this packet as a model for new
34942 @xref{Tracepoint Packets}.
34944 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
34945 @cindex read special object, remote request
34946 @cindex @samp{qXfer} packet
34947 @anchor{qXfer read}
34948 Read uninterpreted bytes from the target's special data area
34949 identified by the keyword @var{object}. Request @var{length} bytes
34950 starting at @var{offset} bytes into the data. The content and
34951 encoding of @var{annex} is specific to @var{object}; it can supply
34952 additional details about what data to access.
34954 Here are the specific requests of this form defined so far. All
34955 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
34956 formats, listed below.
34959 @item qXfer:auxv:read::@var{offset},@var{length}
34960 @anchor{qXfer auxiliary vector read}
34961 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
34962 auxiliary vector}. Note @var{annex} must be empty.
34964 This packet is not probed by default; the remote stub must request it,
34965 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34967 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
34968 @anchor{qXfer target description read}
34969 Access the @dfn{target description}. @xref{Target Descriptions}. The
34970 annex specifies which XML document to access. The main description is
34971 always loaded from the @samp{target.xml} annex.
34973 This packet is not probed by default; the remote stub must request it,
34974 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34976 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
34977 @anchor{qXfer library list read}
34978 Access the target's list of loaded libraries. @xref{Library List Format}.
34979 The annex part of the generic @samp{qXfer} packet must be empty
34980 (@pxref{qXfer read}).
34982 Targets which maintain a list of libraries in the program's memory do
34983 not need to implement this packet; it is designed for platforms where
34984 the operating system manages the list of loaded libraries.
34986 This packet is not probed by default; the remote stub must request it,
34987 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34989 @item qXfer:memory-map:read::@var{offset},@var{length}
34990 @anchor{qXfer memory map read}
34991 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
34992 annex part of the generic @samp{qXfer} packet must be empty
34993 (@pxref{qXfer read}).
34995 This packet is not probed by default; the remote stub must request it,
34996 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34998 @item qXfer:sdata:read::@var{offset},@var{length}
34999 @anchor{qXfer sdata read}
35001 Read contents of the extra collected static tracepoint marker
35002 information. The annex part of the generic @samp{qXfer} packet must
35003 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
35006 This packet is not probed by default; the remote stub must request it,
35007 by supplying an appropriate @samp{qSupported} response
35008 (@pxref{qSupported}).
35010 @item qXfer:siginfo:read::@var{offset},@var{length}
35011 @anchor{qXfer siginfo read}
35012 Read contents of the extra signal information on the target
35013 system. The annex part of the generic @samp{qXfer} packet must be
35014 empty (@pxref{qXfer read}).
35016 This packet is not probed by default; the remote stub must request it,
35017 by supplying an appropriate @samp{qSupported} response
35018 (@pxref{qSupported}).
35020 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
35021 @anchor{qXfer spu read}
35022 Read contents of an @code{spufs} file on the target system. The
35023 annex specifies which file to read; it must be of the form
35024 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
35025 in the target process, and @var{name} identifes the @code{spufs} file
35026 in that context to be accessed.
35028 This packet is not probed by default; the remote stub must request it,
35029 by supplying an appropriate @samp{qSupported} response
35030 (@pxref{qSupported}).
35032 @item qXfer:threads:read::@var{offset},@var{length}
35033 @anchor{qXfer threads read}
35034 Access the list of threads on target. @xref{Thread List Format}. The
35035 annex part of the generic @samp{qXfer} packet must be empty
35036 (@pxref{qXfer read}).
35038 This packet is not probed by default; the remote stub must request it,
35039 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35041 @item qXfer:traceframe-info:read::@var{offset},@var{length}
35042 @anchor{qXfer traceframe info read}
35044 Return a description of the current traceframe's contents.
35045 @xref{Traceframe Info Format}. The annex part of the generic
35046 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
35048 This packet is not probed by default; the remote stub must request it,
35049 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35051 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
35052 @anchor{qXfer fdpic loadmap read}
35053 Read contents of @code{loadmap}s on the target system. The
35054 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
35055 executable @code{loadmap} or interpreter @code{loadmap} to read.
35057 This packet is not probed by default; the remote stub must request it,
35058 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35060 @item qXfer:osdata:read::@var{offset},@var{length}
35061 @anchor{qXfer osdata read}
35062 Access the target's @dfn{operating system information}.
35063 @xref{Operating System Information}.
35070 Data @var{data} (@pxref{Binary Data}) has been read from the
35071 target. There may be more data at a higher address (although
35072 it is permitted to return @samp{m} even for the last valid
35073 block of data, as long as at least one byte of data was read).
35074 @var{data} may have fewer bytes than the @var{length} in the
35078 Data @var{data} (@pxref{Binary Data}) has been read from the target.
35079 There is no more data to be read. @var{data} may have fewer bytes
35080 than the @var{length} in the request.
35083 The @var{offset} in the request is at the end of the data.
35084 There is no more data to be read.
35087 The request was malformed, or @var{annex} was invalid.
35090 The offset was invalid, or there was an error encountered reading the data.
35091 @var{nn} is a hex-encoded @code{errno} value.
35094 An empty reply indicates the @var{object} string was not recognized by
35095 the stub, or that the object does not support reading.
35098 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
35099 @cindex write data into object, remote request
35100 @anchor{qXfer write}
35101 Write uninterpreted bytes into the target's special data area
35102 identified by the keyword @var{object}, starting at @var{offset} bytes
35103 into the data. @var{data}@dots{} is the binary-encoded data
35104 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
35105 is specific to @var{object}; it can supply additional details about what data
35108 Here are the specific requests of this form defined so far. All
35109 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
35110 formats, listed below.
35113 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
35114 @anchor{qXfer siginfo write}
35115 Write @var{data} to the extra signal information on the target system.
35116 The annex part of the generic @samp{qXfer} packet must be
35117 empty (@pxref{qXfer write}).
35119 This packet is not probed by default; the remote stub must request it,
35120 by supplying an appropriate @samp{qSupported} response
35121 (@pxref{qSupported}).
35123 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
35124 @anchor{qXfer spu write}
35125 Write @var{data} to an @code{spufs} file on the target system. The
35126 annex specifies which file to write; it must be of the form
35127 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
35128 in the target process, and @var{name} identifes the @code{spufs} file
35129 in that context to be accessed.
35131 This packet is not probed by default; the remote stub must request it,
35132 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35138 @var{nn} (hex encoded) is the number of bytes written.
35139 This may be fewer bytes than supplied in the request.
35142 The request was malformed, or @var{annex} was invalid.
35145 The offset was invalid, or there was an error encountered writing the data.
35146 @var{nn} is a hex-encoded @code{errno} value.
35149 An empty reply indicates the @var{object} string was not
35150 recognized by the stub, or that the object does not support writing.
35153 @item qXfer:@var{object}:@var{operation}:@dots{}
35154 Requests of this form may be added in the future. When a stub does
35155 not recognize the @var{object} keyword, or its support for
35156 @var{object} does not recognize the @var{operation} keyword, the stub
35157 must respond with an empty packet.
35159 @item qAttached:@var{pid}
35160 @cindex query attached, remote request
35161 @cindex @samp{qAttached} packet
35162 Return an indication of whether the remote server attached to an
35163 existing process or created a new process. When the multiprocess
35164 protocol extensions are supported (@pxref{multiprocess extensions}),
35165 @var{pid} is an integer in hexadecimal format identifying the target
35166 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
35167 the query packet will be simplified as @samp{qAttached}.
35169 This query is used, for example, to know whether the remote process
35170 should be detached or killed when a @value{GDBN} session is ended with
35171 the @code{quit} command.
35176 The remote server attached to an existing process.
35178 The remote server created a new process.
35180 A badly formed request or an error was encountered.
35185 @node Architecture-Specific Protocol Details
35186 @section Architecture-Specific Protocol Details
35188 This section describes how the remote protocol is applied to specific
35189 target architectures. Also see @ref{Standard Target Features}, for
35190 details of XML target descriptions for each architecture.
35194 @subsubsection Breakpoint Kinds
35196 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
35201 16-bit Thumb mode breakpoint.
35204 32-bit Thumb mode (Thumb-2) breakpoint.
35207 32-bit ARM mode breakpoint.
35213 @subsubsection Register Packet Format
35215 The following @code{g}/@code{G} packets have previously been defined.
35216 In the below, some thirty-two bit registers are transferred as
35217 sixty-four bits. Those registers should be zero/sign extended (which?)
35218 to fill the space allocated. Register bytes are transferred in target
35219 byte order. The two nibbles within a register byte are transferred
35220 most-significant - least-significant.
35226 All registers are transferred as thirty-two bit quantities in the order:
35227 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
35228 registers; fsr; fir; fp.
35232 All registers are transferred as sixty-four bit quantities (including
35233 thirty-two bit registers such as @code{sr}). The ordering is the same
35238 @node Tracepoint Packets
35239 @section Tracepoint Packets
35240 @cindex tracepoint packets
35241 @cindex packets, tracepoint
35243 Here we describe the packets @value{GDBN} uses to implement
35244 tracepoints (@pxref{Tracepoints}).
35248 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
35249 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
35250 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
35251 the tracepoint is disabled. @var{step} is the tracepoint's step
35252 count, and @var{pass} is its pass count. If an @samp{F} is present,
35253 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
35254 the number of bytes that the target should copy elsewhere to make room
35255 for the tracepoint. If an @samp{X} is present, it introduces a
35256 tracepoint condition, which consists of a hexadecimal length, followed
35257 by a comma and hex-encoded bytes, in a manner similar to action
35258 encodings as described below. If the trailing @samp{-} is present,
35259 further @samp{QTDP} packets will follow to specify this tracepoint's
35265 The packet was understood and carried out.
35267 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
35269 The packet was not recognized.
35272 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
35273 Define actions to be taken when a tracepoint is hit. @var{n} and
35274 @var{addr} must be the same as in the initial @samp{QTDP} packet for
35275 this tracepoint. This packet may only be sent immediately after
35276 another @samp{QTDP} packet that ended with a @samp{-}. If the
35277 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
35278 specifying more actions for this tracepoint.
35280 In the series of action packets for a given tracepoint, at most one
35281 can have an @samp{S} before its first @var{action}. If such a packet
35282 is sent, it and the following packets define ``while-stepping''
35283 actions. Any prior packets define ordinary actions --- that is, those
35284 taken when the tracepoint is first hit. If no action packet has an
35285 @samp{S}, then all the packets in the series specify ordinary
35286 tracepoint actions.
35288 The @samp{@var{action}@dots{}} portion of the packet is a series of
35289 actions, concatenated without separators. Each action has one of the
35295 Collect the registers whose bits are set in @var{mask}. @var{mask} is
35296 a hexadecimal number whose @var{i}'th bit is set if register number
35297 @var{i} should be collected. (The least significant bit is numbered
35298 zero.) Note that @var{mask} may be any number of digits long; it may
35299 not fit in a 32-bit word.
35301 @item M @var{basereg},@var{offset},@var{len}
35302 Collect @var{len} bytes of memory starting at the address in register
35303 number @var{basereg}, plus @var{offset}. If @var{basereg} is
35304 @samp{-1}, then the range has a fixed address: @var{offset} is the
35305 address of the lowest byte to collect. The @var{basereg},
35306 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
35307 values (the @samp{-1} value for @var{basereg} is a special case).
35309 @item X @var{len},@var{expr}
35310 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
35311 it directs. @var{expr} is an agent expression, as described in
35312 @ref{Agent Expressions}. Each byte of the expression is encoded as a
35313 two-digit hex number in the packet; @var{len} is the number of bytes
35314 in the expression (and thus one-half the number of hex digits in the
35319 Any number of actions may be packed together in a single @samp{QTDP}
35320 packet, as long as the packet does not exceed the maximum packet
35321 length (400 bytes, for many stubs). There may be only one @samp{R}
35322 action per tracepoint, and it must precede any @samp{M} or @samp{X}
35323 actions. Any registers referred to by @samp{M} and @samp{X} actions
35324 must be collected by a preceding @samp{R} action. (The
35325 ``while-stepping'' actions are treated as if they were attached to a
35326 separate tracepoint, as far as these restrictions are concerned.)
35331 The packet was understood and carried out.
35333 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
35335 The packet was not recognized.
35338 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
35339 @cindex @samp{QTDPsrc} packet
35340 Specify a source string of tracepoint @var{n} at address @var{addr}.
35341 This is useful to get accurate reproduction of the tracepoints
35342 originally downloaded at the beginning of the trace run. @var{type}
35343 is the name of the tracepoint part, such as @samp{cond} for the
35344 tracepoint's conditional expression (see below for a list of types), while
35345 @var{bytes} is the string, encoded in hexadecimal.
35347 @var{start} is the offset of the @var{bytes} within the overall source
35348 string, while @var{slen} is the total length of the source string.
35349 This is intended for handling source strings that are longer than will
35350 fit in a single packet.
35351 @c Add detailed example when this info is moved into a dedicated
35352 @c tracepoint descriptions section.
35354 The available string types are @samp{at} for the location,
35355 @samp{cond} for the conditional, and @samp{cmd} for an action command.
35356 @value{GDBN} sends a separate packet for each command in the action
35357 list, in the same order in which the commands are stored in the list.
35359 The target does not need to do anything with source strings except
35360 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
35363 Although this packet is optional, and @value{GDBN} will only send it
35364 if the target replies with @samp{TracepointSource} @xref{General
35365 Query Packets}, it makes both disconnected tracing and trace files
35366 much easier to use. Otherwise the user must be careful that the
35367 tracepoints in effect while looking at trace frames are identical to
35368 the ones in effect during the trace run; even a small discrepancy
35369 could cause @samp{tdump} not to work, or a particular trace frame not
35372 @item QTDV:@var{n}:@var{value}
35373 @cindex define trace state variable, remote request
35374 @cindex @samp{QTDV} packet
35375 Create a new trace state variable, number @var{n}, with an initial
35376 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
35377 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
35378 the option of not using this packet for initial values of zero; the
35379 target should simply create the trace state variables as they are
35380 mentioned in expressions.
35382 @item QTFrame:@var{n}
35383 Select the @var{n}'th tracepoint frame from the buffer, and use the
35384 register and memory contents recorded there to answer subsequent
35385 request packets from @value{GDBN}.
35387 A successful reply from the stub indicates that the stub has found the
35388 requested frame. The response is a series of parts, concatenated
35389 without separators, describing the frame we selected. Each part has
35390 one of the following forms:
35394 The selected frame is number @var{n} in the trace frame buffer;
35395 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
35396 was no frame matching the criteria in the request packet.
35399 The selected trace frame records a hit of tracepoint number @var{t};
35400 @var{t} is a hexadecimal number.
35404 @item QTFrame:pc:@var{addr}
35405 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
35406 currently selected frame whose PC is @var{addr};
35407 @var{addr} is a hexadecimal number.
35409 @item QTFrame:tdp:@var{t}
35410 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
35411 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
35412 is a hexadecimal number.
35414 @item QTFrame:range:@var{start}:@var{end}
35415 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
35416 currently selected frame whose PC is between @var{start} (inclusive)
35417 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
35420 @item QTFrame:outside:@var{start}:@var{end}
35421 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
35422 frame @emph{outside} the given range of addresses (exclusive).
35425 Begin the tracepoint experiment. Begin collecting data from
35426 tracepoint hits in the trace frame buffer. This packet supports the
35427 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
35428 instruction reply packet}).
35431 End the tracepoint experiment. Stop collecting trace frames.
35433 @item QTEnable:@var{n}:@var{addr}
35435 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
35436 experiment. If the tracepoint was previously disabled, then collection
35437 of data from it will resume.
35439 @item QTDisable:@var{n}:@var{addr}
35441 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
35442 experiment. No more data will be collected from the tracepoint unless
35443 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
35446 Clear the table of tracepoints, and empty the trace frame buffer.
35448 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
35449 Establish the given ranges of memory as ``transparent''. The stub
35450 will answer requests for these ranges from memory's current contents,
35451 if they were not collected as part of the tracepoint hit.
35453 @value{GDBN} uses this to mark read-only regions of memory, like those
35454 containing program code. Since these areas never change, they should
35455 still have the same contents they did when the tracepoint was hit, so
35456 there's no reason for the stub to refuse to provide their contents.
35458 @item QTDisconnected:@var{value}
35459 Set the choice to what to do with the tracing run when @value{GDBN}
35460 disconnects from the target. A @var{value} of 1 directs the target to
35461 continue the tracing run, while 0 tells the target to stop tracing if
35462 @value{GDBN} is no longer in the picture.
35465 Ask the stub if there is a trace experiment running right now.
35467 The reply has the form:
35471 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
35472 @var{running} is a single digit @code{1} if the trace is presently
35473 running, or @code{0} if not. It is followed by semicolon-separated
35474 optional fields that an agent may use to report additional status.
35478 If the trace is not running, the agent may report any of several
35479 explanations as one of the optional fields:
35484 No trace has been run yet.
35487 The trace was stopped by a user-originated stop command.
35490 The trace stopped because the trace buffer filled up.
35492 @item tdisconnected:0
35493 The trace stopped because @value{GDBN} disconnected from the target.
35495 @item tpasscount:@var{tpnum}
35496 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
35498 @item terror:@var{text}:@var{tpnum}
35499 The trace stopped because tracepoint @var{tpnum} had an error. The
35500 string @var{text} is available to describe the nature of the error
35501 (for instance, a divide by zero in the condition expression).
35502 @var{text} is hex encoded.
35505 The trace stopped for some other reason.
35509 Additional optional fields supply statistical and other information.
35510 Although not required, they are extremely useful for users monitoring
35511 the progress of a trace run. If a trace has stopped, and these
35512 numbers are reported, they must reflect the state of the just-stopped
35517 @item tframes:@var{n}
35518 The number of trace frames in the buffer.
35520 @item tcreated:@var{n}
35521 The total number of trace frames created during the run. This may
35522 be larger than the trace frame count, if the buffer is circular.
35524 @item tsize:@var{n}
35525 The total size of the trace buffer, in bytes.
35527 @item tfree:@var{n}
35528 The number of bytes still unused in the buffer.
35530 @item circular:@var{n}
35531 The value of the circular trace buffer flag. @code{1} means that the
35532 trace buffer is circular and old trace frames will be discarded if
35533 necessary to make room, @code{0} means that the trace buffer is linear
35536 @item disconn:@var{n}
35537 The value of the disconnected tracing flag. @code{1} means that
35538 tracing will continue after @value{GDBN} disconnects, @code{0} means
35539 that the trace run will stop.
35543 @item qTV:@var{var}
35544 @cindex trace state variable value, remote request
35545 @cindex @samp{qTV} packet
35546 Ask the stub for the value of the trace state variable number @var{var}.
35551 The value of the variable is @var{value}. This will be the current
35552 value of the variable if the user is examining a running target, or a
35553 saved value if the variable was collected in the trace frame that the
35554 user is looking at. Note that multiple requests may result in
35555 different reply values, such as when requesting values while the
35556 program is running.
35559 The value of the variable is unknown. This would occur, for example,
35560 if the user is examining a trace frame in which the requested variable
35566 These packets request data about tracepoints that are being used by
35567 the target. @value{GDBN} sends @code{qTfP} to get the first piece
35568 of data, and multiple @code{qTsP} to get additional pieces. Replies
35569 to these packets generally take the form of the @code{QTDP} packets
35570 that define tracepoints. (FIXME add detailed syntax)
35574 These packets request data about trace state variables that are on the
35575 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
35576 and multiple @code{qTsV} to get additional variables. Replies to
35577 these packets follow the syntax of the @code{QTDV} packets that define
35578 trace state variables.
35582 These packets request data about static tracepoint markers that exist
35583 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
35584 first piece of data, and multiple @code{qTsSTM} to get additional
35585 pieces. Replies to these packets take the following form:
35589 @item m @var{address}:@var{id}:@var{extra}
35591 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
35592 a comma-separated list of markers
35594 (lower case letter @samp{L}) denotes end of list.
35596 An error occurred. @var{nn} are hex digits.
35598 An empty reply indicates that the request is not supported by the
35602 @var{address} is encoded in hex.
35603 @var{id} and @var{extra} are strings encoded in hex.
35605 In response to each query, the target will reply with a list of one or
35606 more markers, separated by commas. @value{GDBN} will respond to each
35607 reply with a request for more markers (using the @samp{qs} form of the
35608 query), until the target responds with @samp{l} (lower-case ell, for
35611 @item qTSTMat:@var{address}
35612 This packets requests data about static tracepoint markers in the
35613 target program at @var{address}. Replies to this packet follow the
35614 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
35615 tracepoint markers.
35617 @item QTSave:@var{filename}
35618 This packet directs the target to save trace data to the file name
35619 @var{filename} in the target's filesystem. @var{filename} is encoded
35620 as a hex string; the interpretation of the file name (relative vs
35621 absolute, wild cards, etc) is up to the target.
35623 @item qTBuffer:@var{offset},@var{len}
35624 Return up to @var{len} bytes of the current contents of trace buffer,
35625 starting at @var{offset}. The trace buffer is treated as if it were
35626 a contiguous collection of traceframes, as per the trace file format.
35627 The reply consists as many hex-encoded bytes as the target can deliver
35628 in a packet; it is not an error to return fewer than were asked for.
35629 A reply consisting of just @code{l} indicates that no bytes are
35632 @item QTBuffer:circular:@var{value}
35633 This packet directs the target to use a circular trace buffer if
35634 @var{value} is 1, or a linear buffer if the value is 0.
35638 @subsection Relocate instruction reply packet
35639 When installing fast tracepoints in memory, the target may need to
35640 relocate the instruction currently at the tracepoint address to a
35641 different address in memory. For most instructions, a simple copy is
35642 enough, but, for example, call instructions that implicitly push the
35643 return address on the stack, and relative branches or other
35644 PC-relative instructions require offset adjustment, so that the effect
35645 of executing the instruction at a different address is the same as if
35646 it had executed in the original location.
35648 In response to several of the tracepoint packets, the target may also
35649 respond with a number of intermediate @samp{qRelocInsn} request
35650 packets before the final result packet, to have @value{GDBN} handle
35651 this relocation operation. If a packet supports this mechanism, its
35652 documentation will explicitly say so. See for example the above
35653 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
35654 format of the request is:
35657 @item qRelocInsn:@var{from};@var{to}
35659 This requests @value{GDBN} to copy instruction at address @var{from}
35660 to address @var{to}, possibly adjusted so that executing the
35661 instruction at @var{to} has the same effect as executing it at
35662 @var{from}. @value{GDBN} writes the adjusted instruction to target
35663 memory starting at @var{to}.
35668 @item qRelocInsn:@var{adjusted_size}
35669 Informs the stub the relocation is complete. @var{adjusted_size} is
35670 the length in bytes of resulting relocated instruction sequence.
35672 A badly formed request was detected, or an error was encountered while
35673 relocating the instruction.
35676 @node Host I/O Packets
35677 @section Host I/O Packets
35678 @cindex Host I/O, remote protocol
35679 @cindex file transfer, remote protocol
35681 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
35682 operations on the far side of a remote link. For example, Host I/O is
35683 used to upload and download files to a remote target with its own
35684 filesystem. Host I/O uses the same constant values and data structure
35685 layout as the target-initiated File-I/O protocol. However, the
35686 Host I/O packets are structured differently. The target-initiated
35687 protocol relies on target memory to store parameters and buffers.
35688 Host I/O requests are initiated by @value{GDBN}, and the
35689 target's memory is not involved. @xref{File-I/O Remote Protocol
35690 Extension}, for more details on the target-initiated protocol.
35692 The Host I/O request packets all encode a single operation along with
35693 its arguments. They have this format:
35697 @item vFile:@var{operation}: @var{parameter}@dots{}
35698 @var{operation} is the name of the particular request; the target
35699 should compare the entire packet name up to the second colon when checking
35700 for a supported operation. The format of @var{parameter} depends on
35701 the operation. Numbers are always passed in hexadecimal. Negative
35702 numbers have an explicit minus sign (i.e.@: two's complement is not
35703 used). Strings (e.g.@: filenames) are encoded as a series of
35704 hexadecimal bytes. The last argument to a system call may be a
35705 buffer of escaped binary data (@pxref{Binary Data}).
35709 The valid responses to Host I/O packets are:
35713 @item F @var{result} [, @var{errno}] [; @var{attachment}]
35714 @var{result} is the integer value returned by this operation, usually
35715 non-negative for success and -1 for errors. If an error has occured,
35716 @var{errno} will be included in the result. @var{errno} will have a
35717 value defined by the File-I/O protocol (@pxref{Errno Values}). For
35718 operations which return data, @var{attachment} supplies the data as a
35719 binary buffer. Binary buffers in response packets are escaped in the
35720 normal way (@pxref{Binary Data}). See the individual packet
35721 documentation for the interpretation of @var{result} and
35725 An empty response indicates that this operation is not recognized.
35729 These are the supported Host I/O operations:
35732 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
35733 Open a file at @var{pathname} and return a file descriptor for it, or
35734 return -1 if an error occurs. @var{pathname} is a string,
35735 @var{flags} is an integer indicating a mask of open flags
35736 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
35737 of mode bits to use if the file is created (@pxref{mode_t Values}).
35738 @xref{open}, for details of the open flags and mode values.
35740 @item vFile:close: @var{fd}
35741 Close the open file corresponding to @var{fd} and return 0, or
35742 -1 if an error occurs.
35744 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
35745 Read data from the open file corresponding to @var{fd}. Up to
35746 @var{count} bytes will be read from the file, starting at @var{offset}
35747 relative to the start of the file. The target may read fewer bytes;
35748 common reasons include packet size limits and an end-of-file
35749 condition. The number of bytes read is returned. Zero should only be
35750 returned for a successful read at the end of the file, or if
35751 @var{count} was zero.
35753 The data read should be returned as a binary attachment on success.
35754 If zero bytes were read, the response should include an empty binary
35755 attachment (i.e.@: a trailing semicolon). The return value is the
35756 number of target bytes read; the binary attachment may be longer if
35757 some characters were escaped.
35759 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
35760 Write @var{data} (a binary buffer) to the open file corresponding
35761 to @var{fd}. Start the write at @var{offset} from the start of the
35762 file. Unlike many @code{write} system calls, there is no
35763 separate @var{count} argument; the length of @var{data} in the
35764 packet is used. @samp{vFile:write} returns the number of bytes written,
35765 which may be shorter than the length of @var{data}, or -1 if an
35768 @item vFile:unlink: @var{pathname}
35769 Delete the file at @var{pathname} on the target. Return 0,
35770 or -1 if an error occurs. @var{pathname} is a string.
35775 @section Interrupts
35776 @cindex interrupts (remote protocol)
35778 When a program on the remote target is running, @value{GDBN} may
35779 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
35780 a @code{BREAK} followed by @code{g},
35781 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
35783 The precise meaning of @code{BREAK} is defined by the transport
35784 mechanism and may, in fact, be undefined. @value{GDBN} does not
35785 currently define a @code{BREAK} mechanism for any of the network
35786 interfaces except for TCP, in which case @value{GDBN} sends the
35787 @code{telnet} BREAK sequence.
35789 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
35790 transport mechanisms. It is represented by sending the single byte
35791 @code{0x03} without any of the usual packet overhead described in
35792 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
35793 transmitted as part of a packet, it is considered to be packet data
35794 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
35795 (@pxref{X packet}), used for binary downloads, may include an unescaped
35796 @code{0x03} as part of its packet.
35798 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
35799 When Linux kernel receives this sequence from serial port,
35800 it stops execution and connects to gdb.
35802 Stubs are not required to recognize these interrupt mechanisms and the
35803 precise meaning associated with receipt of the interrupt is
35804 implementation defined. If the target supports debugging of multiple
35805 threads and/or processes, it should attempt to interrupt all
35806 currently-executing threads and processes.
35807 If the stub is successful at interrupting the
35808 running program, it should send one of the stop
35809 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
35810 of successfully stopping the program in all-stop mode, and a stop reply
35811 for each stopped thread in non-stop mode.
35812 Interrupts received while the
35813 program is stopped are discarded.
35815 @node Notification Packets
35816 @section Notification Packets
35817 @cindex notification packets
35818 @cindex packets, notification
35820 The @value{GDBN} remote serial protocol includes @dfn{notifications},
35821 packets that require no acknowledgment. Both the GDB and the stub
35822 may send notifications (although the only notifications defined at
35823 present are sent by the stub). Notifications carry information
35824 without incurring the round-trip latency of an acknowledgment, and so
35825 are useful for low-impact communications where occasional packet loss
35828 A notification packet has the form @samp{% @var{data} #
35829 @var{checksum}}, where @var{data} is the content of the notification,
35830 and @var{checksum} is a checksum of @var{data}, computed and formatted
35831 as for ordinary @value{GDBN} packets. A notification's @var{data}
35832 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
35833 receiving a notification, the recipient sends no @samp{+} or @samp{-}
35834 to acknowledge the notification's receipt or to report its corruption.
35836 Every notification's @var{data} begins with a name, which contains no
35837 colon characters, followed by a colon character.
35839 Recipients should silently ignore corrupted notifications and
35840 notifications they do not understand. Recipients should restart
35841 timeout periods on receipt of a well-formed notification, whether or
35842 not they understand it.
35844 Senders should only send the notifications described here when this
35845 protocol description specifies that they are permitted. In the
35846 future, we may extend the protocol to permit existing notifications in
35847 new contexts; this rule helps older senders avoid confusing newer
35850 (Older versions of @value{GDBN} ignore bytes received until they see
35851 the @samp{$} byte that begins an ordinary packet, so new stubs may
35852 transmit notifications without fear of confusing older clients. There
35853 are no notifications defined for @value{GDBN} to send at the moment, but we
35854 assume that most older stubs would ignore them, as well.)
35856 The following notification packets from the stub to @value{GDBN} are
35860 @item Stop: @var{reply}
35861 Report an asynchronous stop event in non-stop mode.
35862 The @var{reply} has the form of a stop reply, as
35863 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
35864 for information on how these notifications are acknowledged by
35868 @node Remote Non-Stop
35869 @section Remote Protocol Support for Non-Stop Mode
35871 @value{GDBN}'s remote protocol supports non-stop debugging of
35872 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
35873 supports non-stop mode, it should report that to @value{GDBN} by including
35874 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
35876 @value{GDBN} typically sends a @samp{QNonStop} packet only when
35877 establishing a new connection with the stub. Entering non-stop mode
35878 does not alter the state of any currently-running threads, but targets
35879 must stop all threads in any already-attached processes when entering
35880 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
35881 probe the target state after a mode change.
35883 In non-stop mode, when an attached process encounters an event that
35884 would otherwise be reported with a stop reply, it uses the
35885 asynchronous notification mechanism (@pxref{Notification Packets}) to
35886 inform @value{GDBN}. In contrast to all-stop mode, where all threads
35887 in all processes are stopped when a stop reply is sent, in non-stop
35888 mode only the thread reporting the stop event is stopped. That is,
35889 when reporting a @samp{S} or @samp{T} response to indicate completion
35890 of a step operation, hitting a breakpoint, or a fault, only the
35891 affected thread is stopped; any other still-running threads continue
35892 to run. When reporting a @samp{W} or @samp{X} response, all running
35893 threads belonging to other attached processes continue to run.
35895 Only one stop reply notification at a time may be pending; if
35896 additional stop events occur before @value{GDBN} has acknowledged the
35897 previous notification, they must be queued by the stub for later
35898 synchronous transmission in response to @samp{vStopped} packets from
35899 @value{GDBN}. Because the notification mechanism is unreliable,
35900 the stub is permitted to resend a stop reply notification
35901 if it believes @value{GDBN} may not have received it. @value{GDBN}
35902 ignores additional stop reply notifications received before it has
35903 finished processing a previous notification and the stub has completed
35904 sending any queued stop events.
35906 Otherwise, @value{GDBN} must be prepared to receive a stop reply
35907 notification at any time. Specifically, they may appear when
35908 @value{GDBN} is not otherwise reading input from the stub, or when
35909 @value{GDBN} is expecting to read a normal synchronous response or a
35910 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
35911 Notification packets are distinct from any other communication from
35912 the stub so there is no ambiguity.
35914 After receiving a stop reply notification, @value{GDBN} shall
35915 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
35916 as a regular, synchronous request to the stub. Such acknowledgment
35917 is not required to happen immediately, as @value{GDBN} is permitted to
35918 send other, unrelated packets to the stub first, which the stub should
35921 Upon receiving a @samp{vStopped} packet, if the stub has other queued
35922 stop events to report to @value{GDBN}, it shall respond by sending a
35923 normal stop reply response. @value{GDBN} shall then send another
35924 @samp{vStopped} packet to solicit further responses; again, it is
35925 permitted to send other, unrelated packets as well which the stub
35926 should process normally.
35928 If the stub receives a @samp{vStopped} packet and there are no
35929 additional stop events to report, the stub shall return an @samp{OK}
35930 response. At this point, if further stop events occur, the stub shall
35931 send a new stop reply notification, @value{GDBN} shall accept the
35932 notification, and the process shall be repeated.
35934 In non-stop mode, the target shall respond to the @samp{?} packet as
35935 follows. First, any incomplete stop reply notification/@samp{vStopped}
35936 sequence in progress is abandoned. The target must begin a new
35937 sequence reporting stop events for all stopped threads, whether or not
35938 it has previously reported those events to @value{GDBN}. The first
35939 stop reply is sent as a synchronous reply to the @samp{?} packet, and
35940 subsequent stop replies are sent as responses to @samp{vStopped} packets
35941 using the mechanism described above. The target must not send
35942 asynchronous stop reply notifications until the sequence is complete.
35943 If all threads are running when the target receives the @samp{?} packet,
35944 or if the target is not attached to any process, it shall respond
35947 @node Packet Acknowledgment
35948 @section Packet Acknowledgment
35950 @cindex acknowledgment, for @value{GDBN} remote
35951 @cindex packet acknowledgment, for @value{GDBN} remote
35952 By default, when either the host or the target machine receives a packet,
35953 the first response expected is an acknowledgment: either @samp{+} (to indicate
35954 the package was received correctly) or @samp{-} (to request retransmission).
35955 This mechanism allows the @value{GDBN} remote protocol to operate over
35956 unreliable transport mechanisms, such as a serial line.
35958 In cases where the transport mechanism is itself reliable (such as a pipe or
35959 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
35960 It may be desirable to disable them in that case to reduce communication
35961 overhead, or for other reasons. This can be accomplished by means of the
35962 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
35964 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
35965 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
35966 and response format still includes the normal checksum, as described in
35967 @ref{Overview}, but the checksum may be ignored by the receiver.
35969 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
35970 no-acknowledgment mode, it should report that to @value{GDBN}
35971 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
35972 @pxref{qSupported}.
35973 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
35974 disabled via the @code{set remote noack-packet off} command
35975 (@pxref{Remote Configuration}),
35976 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
35977 Only then may the stub actually turn off packet acknowledgments.
35978 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
35979 response, which can be safely ignored by the stub.
35981 Note that @code{set remote noack-packet} command only affects negotiation
35982 between @value{GDBN} and the stub when subsequent connections are made;
35983 it does not affect the protocol acknowledgment state for any current
35985 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
35986 new connection is established,
35987 there is also no protocol request to re-enable the acknowledgments
35988 for the current connection, once disabled.
35993 Example sequence of a target being re-started. Notice how the restart
35994 does not get any direct output:
35999 @emph{target restarts}
36002 <- @code{T001:1234123412341234}
36006 Example sequence of a target being stepped by a single instruction:
36009 -> @code{G1445@dots{}}
36014 <- @code{T001:1234123412341234}
36018 <- @code{1455@dots{}}
36022 @node File-I/O Remote Protocol Extension
36023 @section File-I/O Remote Protocol Extension
36024 @cindex File-I/O remote protocol extension
36027 * File-I/O Overview::
36028 * Protocol Basics::
36029 * The F Request Packet::
36030 * The F Reply Packet::
36031 * The Ctrl-C Message::
36033 * List of Supported Calls::
36034 * Protocol-specific Representation of Datatypes::
36036 * File-I/O Examples::
36039 @node File-I/O Overview
36040 @subsection File-I/O Overview
36041 @cindex file-i/o overview
36043 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
36044 target to use the host's file system and console I/O to perform various
36045 system calls. System calls on the target system are translated into a
36046 remote protocol packet to the host system, which then performs the needed
36047 actions and returns a response packet to the target system.
36048 This simulates file system operations even on targets that lack file systems.
36050 The protocol is defined to be independent of both the host and target systems.
36051 It uses its own internal representation of datatypes and values. Both
36052 @value{GDBN} and the target's @value{GDBN} stub are responsible for
36053 translating the system-dependent value representations into the internal
36054 protocol representations when data is transmitted.
36056 The communication is synchronous. A system call is possible only when
36057 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
36058 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
36059 the target is stopped to allow deterministic access to the target's
36060 memory. Therefore File-I/O is not interruptible by target signals. On
36061 the other hand, it is possible to interrupt File-I/O by a user interrupt
36062 (@samp{Ctrl-C}) within @value{GDBN}.
36064 The target's request to perform a host system call does not finish
36065 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
36066 after finishing the system call, the target returns to continuing the
36067 previous activity (continue, step). No additional continue or step
36068 request from @value{GDBN} is required.
36071 (@value{GDBP}) continue
36072 <- target requests 'system call X'
36073 target is stopped, @value{GDBN} executes system call
36074 -> @value{GDBN} returns result
36075 ... target continues, @value{GDBN} returns to wait for the target
36076 <- target hits breakpoint and sends a Txx packet
36079 The protocol only supports I/O on the console and to regular files on
36080 the host file system. Character or block special devices, pipes,
36081 named pipes, sockets or any other communication method on the host
36082 system are not supported by this protocol.
36084 File I/O is not supported in non-stop mode.
36086 @node Protocol Basics
36087 @subsection Protocol Basics
36088 @cindex protocol basics, file-i/o
36090 The File-I/O protocol uses the @code{F} packet as the request as well
36091 as reply packet. Since a File-I/O system call can only occur when
36092 @value{GDBN} is waiting for a response from the continuing or stepping target,
36093 the File-I/O request is a reply that @value{GDBN} has to expect as a result
36094 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
36095 This @code{F} packet contains all information needed to allow @value{GDBN}
36096 to call the appropriate host system call:
36100 A unique identifier for the requested system call.
36103 All parameters to the system call. Pointers are given as addresses
36104 in the target memory address space. Pointers to strings are given as
36105 pointer/length pair. Numerical values are given as they are.
36106 Numerical control flags are given in a protocol-specific representation.
36110 At this point, @value{GDBN} has to perform the following actions.
36114 If the parameters include pointer values to data needed as input to a
36115 system call, @value{GDBN} requests this data from the target with a
36116 standard @code{m} packet request. This additional communication has to be
36117 expected by the target implementation and is handled as any other @code{m}
36121 @value{GDBN} translates all value from protocol representation to host
36122 representation as needed. Datatypes are coerced into the host types.
36125 @value{GDBN} calls the system call.
36128 It then coerces datatypes back to protocol representation.
36131 If the system call is expected to return data in buffer space specified
36132 by pointer parameters to the call, the data is transmitted to the
36133 target using a @code{M} or @code{X} packet. This packet has to be expected
36134 by the target implementation and is handled as any other @code{M} or @code{X}
36139 Eventually @value{GDBN} replies with another @code{F} packet which contains all
36140 necessary information for the target to continue. This at least contains
36147 @code{errno}, if has been changed by the system call.
36154 After having done the needed type and value coercion, the target continues
36155 the latest continue or step action.
36157 @node The F Request Packet
36158 @subsection The @code{F} Request Packet
36159 @cindex file-i/o request packet
36160 @cindex @code{F} request packet
36162 The @code{F} request packet has the following format:
36165 @item F@var{call-id},@var{parameter@dots{}}
36167 @var{call-id} is the identifier to indicate the host system call to be called.
36168 This is just the name of the function.
36170 @var{parameter@dots{}} are the parameters to the system call.
36171 Parameters are hexadecimal integer values, either the actual values in case
36172 of scalar datatypes, pointers to target buffer space in case of compound
36173 datatypes and unspecified memory areas, or pointer/length pairs in case
36174 of string parameters. These are appended to the @var{call-id} as a
36175 comma-delimited list. All values are transmitted in ASCII
36176 string representation, pointer/length pairs separated by a slash.
36182 @node The F Reply Packet
36183 @subsection The @code{F} Reply Packet
36184 @cindex file-i/o reply packet
36185 @cindex @code{F} reply packet
36187 The @code{F} reply packet has the following format:
36191 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
36193 @var{retcode} is the return code of the system call as hexadecimal value.
36195 @var{errno} is the @code{errno} set by the call, in protocol-specific
36197 This parameter can be omitted if the call was successful.
36199 @var{Ctrl-C flag} is only sent if the user requested a break. In this
36200 case, @var{errno} must be sent as well, even if the call was successful.
36201 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
36208 or, if the call was interrupted before the host call has been performed:
36215 assuming 4 is the protocol-specific representation of @code{EINTR}.
36220 @node The Ctrl-C Message
36221 @subsection The @samp{Ctrl-C} Message
36222 @cindex ctrl-c message, in file-i/o protocol
36224 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
36225 reply packet (@pxref{The F Reply Packet}),
36226 the target should behave as if it had
36227 gotten a break message. The meaning for the target is ``system call
36228 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
36229 (as with a break message) and return to @value{GDBN} with a @code{T02}
36232 It's important for the target to know in which
36233 state the system call was interrupted. There are two possible cases:
36237 The system call hasn't been performed on the host yet.
36240 The system call on the host has been finished.
36244 These two states can be distinguished by the target by the value of the
36245 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
36246 call hasn't been performed. This is equivalent to the @code{EINTR} handling
36247 on POSIX systems. In any other case, the target may presume that the
36248 system call has been finished --- successfully or not --- and should behave
36249 as if the break message arrived right after the system call.
36251 @value{GDBN} must behave reliably. If the system call has not been called
36252 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
36253 @code{errno} in the packet. If the system call on the host has been finished
36254 before the user requests a break, the full action must be finished by
36255 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
36256 The @code{F} packet may only be sent when either nothing has happened
36257 or the full action has been completed.
36260 @subsection Console I/O
36261 @cindex console i/o as part of file-i/o
36263 By default and if not explicitly closed by the target system, the file
36264 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
36265 on the @value{GDBN} console is handled as any other file output operation
36266 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
36267 by @value{GDBN} so that after the target read request from file descriptor
36268 0 all following typing is buffered until either one of the following
36273 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
36275 system call is treated as finished.
36278 The user presses @key{RET}. This is treated as end of input with a trailing
36282 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
36283 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
36287 If the user has typed more characters than fit in the buffer given to
36288 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
36289 either another @code{read(0, @dots{})} is requested by the target, or debugging
36290 is stopped at the user's request.
36293 @node List of Supported Calls
36294 @subsection List of Supported Calls
36295 @cindex list of supported file-i/o calls
36312 @unnumberedsubsubsec open
36313 @cindex open, file-i/o system call
36318 int open(const char *pathname, int flags);
36319 int open(const char *pathname, int flags, mode_t mode);
36323 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
36326 @var{flags} is the bitwise @code{OR} of the following values:
36330 If the file does not exist it will be created. The host
36331 rules apply as far as file ownership and time stamps
36335 When used with @code{O_CREAT}, if the file already exists it is
36336 an error and open() fails.
36339 If the file already exists and the open mode allows
36340 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
36341 truncated to zero length.
36344 The file is opened in append mode.
36347 The file is opened for reading only.
36350 The file is opened for writing only.
36353 The file is opened for reading and writing.
36357 Other bits are silently ignored.
36361 @var{mode} is the bitwise @code{OR} of the following values:
36365 User has read permission.
36368 User has write permission.
36371 Group has read permission.
36374 Group has write permission.
36377 Others have read permission.
36380 Others have write permission.
36384 Other bits are silently ignored.
36387 @item Return value:
36388 @code{open} returns the new file descriptor or -1 if an error
36395 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
36398 @var{pathname} refers to a directory.
36401 The requested access is not allowed.
36404 @var{pathname} was too long.
36407 A directory component in @var{pathname} does not exist.
36410 @var{pathname} refers to a device, pipe, named pipe or socket.
36413 @var{pathname} refers to a file on a read-only filesystem and
36414 write access was requested.
36417 @var{pathname} is an invalid pointer value.
36420 No space on device to create the file.
36423 The process already has the maximum number of files open.
36426 The limit on the total number of files open on the system
36430 The call was interrupted by the user.
36436 @unnumberedsubsubsec close
36437 @cindex close, file-i/o system call
36446 @samp{Fclose,@var{fd}}
36448 @item Return value:
36449 @code{close} returns zero on success, or -1 if an error occurred.
36455 @var{fd} isn't a valid open file descriptor.
36458 The call was interrupted by the user.
36464 @unnumberedsubsubsec read
36465 @cindex read, file-i/o system call
36470 int read(int fd, void *buf, unsigned int count);
36474 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
36476 @item Return value:
36477 On success, the number of bytes read is returned.
36478 Zero indicates end of file. If count is zero, read
36479 returns zero as well. On error, -1 is returned.
36485 @var{fd} is not a valid file descriptor or is not open for
36489 @var{bufptr} is an invalid pointer value.
36492 The call was interrupted by the user.
36498 @unnumberedsubsubsec write
36499 @cindex write, file-i/o system call
36504 int write(int fd, const void *buf, unsigned int count);
36508 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
36510 @item Return value:
36511 On success, the number of bytes written are returned.
36512 Zero indicates nothing was written. On error, -1
36519 @var{fd} is not a valid file descriptor or is not open for
36523 @var{bufptr} is an invalid pointer value.
36526 An attempt was made to write a file that exceeds the
36527 host-specific maximum file size allowed.
36530 No space on device to write the data.
36533 The call was interrupted by the user.
36539 @unnumberedsubsubsec lseek
36540 @cindex lseek, file-i/o system call
36545 long lseek (int fd, long offset, int flag);
36549 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
36551 @var{flag} is one of:
36555 The offset is set to @var{offset} bytes.
36558 The offset is set to its current location plus @var{offset}
36562 The offset is set to the size of the file plus @var{offset}
36566 @item Return value:
36567 On success, the resulting unsigned offset in bytes from
36568 the beginning of the file is returned. Otherwise, a
36569 value of -1 is returned.
36575 @var{fd} is not a valid open file descriptor.
36578 @var{fd} is associated with the @value{GDBN} console.
36581 @var{flag} is not a proper value.
36584 The call was interrupted by the user.
36590 @unnumberedsubsubsec rename
36591 @cindex rename, file-i/o system call
36596 int rename(const char *oldpath, const char *newpath);
36600 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
36602 @item Return value:
36603 On success, zero is returned. On error, -1 is returned.
36609 @var{newpath} is an existing directory, but @var{oldpath} is not a
36613 @var{newpath} is a non-empty directory.
36616 @var{oldpath} or @var{newpath} is a directory that is in use by some
36620 An attempt was made to make a directory a subdirectory
36624 A component used as a directory in @var{oldpath} or new
36625 path is not a directory. Or @var{oldpath} is a directory
36626 and @var{newpath} exists but is not a directory.
36629 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
36632 No access to the file or the path of the file.
36636 @var{oldpath} or @var{newpath} was too long.
36639 A directory component in @var{oldpath} or @var{newpath} does not exist.
36642 The file is on a read-only filesystem.
36645 The device containing the file has no room for the new
36649 The call was interrupted by the user.
36655 @unnumberedsubsubsec unlink
36656 @cindex unlink, file-i/o system call
36661 int unlink(const char *pathname);
36665 @samp{Funlink,@var{pathnameptr}/@var{len}}
36667 @item Return value:
36668 On success, zero is returned. On error, -1 is returned.
36674 No access to the file or the path of the file.
36677 The system does not allow unlinking of directories.
36680 The file @var{pathname} cannot be unlinked because it's
36681 being used by another process.
36684 @var{pathnameptr} is an invalid pointer value.
36687 @var{pathname} was too long.
36690 A directory component in @var{pathname} does not exist.
36693 A component of the path is not a directory.
36696 The file is on a read-only filesystem.
36699 The call was interrupted by the user.
36705 @unnumberedsubsubsec stat/fstat
36706 @cindex fstat, file-i/o system call
36707 @cindex stat, file-i/o system call
36712 int stat(const char *pathname, struct stat *buf);
36713 int fstat(int fd, struct stat *buf);
36717 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
36718 @samp{Ffstat,@var{fd},@var{bufptr}}
36720 @item Return value:
36721 On success, zero is returned. On error, -1 is returned.
36727 @var{fd} is not a valid open file.
36730 A directory component in @var{pathname} does not exist or the
36731 path is an empty string.
36734 A component of the path is not a directory.
36737 @var{pathnameptr} is an invalid pointer value.
36740 No access to the file or the path of the file.
36743 @var{pathname} was too long.
36746 The call was interrupted by the user.
36752 @unnumberedsubsubsec gettimeofday
36753 @cindex gettimeofday, file-i/o system call
36758 int gettimeofday(struct timeval *tv, void *tz);
36762 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
36764 @item Return value:
36765 On success, 0 is returned, -1 otherwise.
36771 @var{tz} is a non-NULL pointer.
36774 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
36780 @unnumberedsubsubsec isatty
36781 @cindex isatty, file-i/o system call
36786 int isatty(int fd);
36790 @samp{Fisatty,@var{fd}}
36792 @item Return value:
36793 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
36799 The call was interrupted by the user.
36804 Note that the @code{isatty} call is treated as a special case: it returns
36805 1 to the target if the file descriptor is attached
36806 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
36807 would require implementing @code{ioctl} and would be more complex than
36812 @unnumberedsubsubsec system
36813 @cindex system, file-i/o system call
36818 int system(const char *command);
36822 @samp{Fsystem,@var{commandptr}/@var{len}}
36824 @item Return value:
36825 If @var{len} is zero, the return value indicates whether a shell is
36826 available. A zero return value indicates a shell is not available.
36827 For non-zero @var{len}, the value returned is -1 on error and the
36828 return status of the command otherwise. Only the exit status of the
36829 command is returned, which is extracted from the host's @code{system}
36830 return value by calling @code{WEXITSTATUS(retval)}. In case
36831 @file{/bin/sh} could not be executed, 127 is returned.
36837 The call was interrupted by the user.
36842 @value{GDBN} takes over the full task of calling the necessary host calls
36843 to perform the @code{system} call. The return value of @code{system} on
36844 the host is simplified before it's returned
36845 to the target. Any termination signal information from the child process
36846 is discarded, and the return value consists
36847 entirely of the exit status of the called command.
36849 Due to security concerns, the @code{system} call is by default refused
36850 by @value{GDBN}. The user has to allow this call explicitly with the
36851 @code{set remote system-call-allowed 1} command.
36854 @item set remote system-call-allowed
36855 @kindex set remote system-call-allowed
36856 Control whether to allow the @code{system} calls in the File I/O
36857 protocol for the remote target. The default is zero (disabled).
36859 @item show remote system-call-allowed
36860 @kindex show remote system-call-allowed
36861 Show whether the @code{system} calls are allowed in the File I/O
36865 @node Protocol-specific Representation of Datatypes
36866 @subsection Protocol-specific Representation of Datatypes
36867 @cindex protocol-specific representation of datatypes, in file-i/o protocol
36870 * Integral Datatypes::
36872 * Memory Transfer::
36877 @node Integral Datatypes
36878 @unnumberedsubsubsec Integral Datatypes
36879 @cindex integral datatypes, in file-i/o protocol
36881 The integral datatypes used in the system calls are @code{int},
36882 @code{unsigned int}, @code{long}, @code{unsigned long},
36883 @code{mode_t}, and @code{time_t}.
36885 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
36886 implemented as 32 bit values in this protocol.
36888 @code{long} and @code{unsigned long} are implemented as 64 bit types.
36890 @xref{Limits}, for corresponding MIN and MAX values (similar to those
36891 in @file{limits.h}) to allow range checking on host and target.
36893 @code{time_t} datatypes are defined as seconds since the Epoch.
36895 All integral datatypes transferred as part of a memory read or write of a
36896 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
36899 @node Pointer Values
36900 @unnumberedsubsubsec Pointer Values
36901 @cindex pointer values, in file-i/o protocol
36903 Pointers to target data are transmitted as they are. An exception
36904 is made for pointers to buffers for which the length isn't
36905 transmitted as part of the function call, namely strings. Strings
36906 are transmitted as a pointer/length pair, both as hex values, e.g.@:
36913 which is a pointer to data of length 18 bytes at position 0x1aaf.
36914 The length is defined as the full string length in bytes, including
36915 the trailing null byte. For example, the string @code{"hello world"}
36916 at address 0x123456 is transmitted as
36922 @node Memory Transfer
36923 @unnumberedsubsubsec Memory Transfer
36924 @cindex memory transfer, in file-i/o protocol
36926 Structured data which is transferred using a memory read or write (for
36927 example, a @code{struct stat}) is expected to be in a protocol-specific format
36928 with all scalar multibyte datatypes being big endian. Translation to
36929 this representation needs to be done both by the target before the @code{F}
36930 packet is sent, and by @value{GDBN} before
36931 it transfers memory to the target. Transferred pointers to structured
36932 data should point to the already-coerced data at any time.
36936 @unnumberedsubsubsec struct stat
36937 @cindex struct stat, in file-i/o protocol
36939 The buffer of type @code{struct stat} used by the target and @value{GDBN}
36940 is defined as follows:
36944 unsigned int st_dev; /* device */
36945 unsigned int st_ino; /* inode */
36946 mode_t st_mode; /* protection */
36947 unsigned int st_nlink; /* number of hard links */
36948 unsigned int st_uid; /* user ID of owner */
36949 unsigned int st_gid; /* group ID of owner */
36950 unsigned int st_rdev; /* device type (if inode device) */
36951 unsigned long st_size; /* total size, in bytes */
36952 unsigned long st_blksize; /* blocksize for filesystem I/O */
36953 unsigned long st_blocks; /* number of blocks allocated */
36954 time_t st_atime; /* time of last access */
36955 time_t st_mtime; /* time of last modification */
36956 time_t st_ctime; /* time of last change */
36960 The integral datatypes conform to the definitions given in the
36961 appropriate section (see @ref{Integral Datatypes}, for details) so this
36962 structure is of size 64 bytes.
36964 The values of several fields have a restricted meaning and/or
36970 A value of 0 represents a file, 1 the console.
36973 No valid meaning for the target. Transmitted unchanged.
36976 Valid mode bits are described in @ref{Constants}. Any other
36977 bits have currently no meaning for the target.
36982 No valid meaning for the target. Transmitted unchanged.
36987 These values have a host and file system dependent
36988 accuracy. Especially on Windows hosts, the file system may not
36989 support exact timing values.
36992 The target gets a @code{struct stat} of the above representation and is
36993 responsible for coercing it to the target representation before
36996 Note that due to size differences between the host, target, and protocol
36997 representations of @code{struct stat} members, these members could eventually
36998 get truncated on the target.
37000 @node struct timeval
37001 @unnumberedsubsubsec struct timeval
37002 @cindex struct timeval, in file-i/o protocol
37004 The buffer of type @code{struct timeval} used by the File-I/O protocol
37005 is defined as follows:
37009 time_t tv_sec; /* second */
37010 long tv_usec; /* microsecond */
37014 The integral datatypes conform to the definitions given in the
37015 appropriate section (see @ref{Integral Datatypes}, for details) so this
37016 structure is of size 8 bytes.
37019 @subsection Constants
37020 @cindex constants, in file-i/o protocol
37022 The following values are used for the constants inside of the
37023 protocol. @value{GDBN} and target are responsible for translating these
37024 values before and after the call as needed.
37035 @unnumberedsubsubsec Open Flags
37036 @cindex open flags, in file-i/o protocol
37038 All values are given in hexadecimal representation.
37050 @node mode_t Values
37051 @unnumberedsubsubsec mode_t Values
37052 @cindex mode_t values, in file-i/o protocol
37054 All values are given in octal representation.
37071 @unnumberedsubsubsec Errno Values
37072 @cindex errno values, in file-i/o protocol
37074 All values are given in decimal representation.
37099 @code{EUNKNOWN} is used as a fallback error value if a host system returns
37100 any error value not in the list of supported error numbers.
37103 @unnumberedsubsubsec Lseek Flags
37104 @cindex lseek flags, in file-i/o protocol
37113 @unnumberedsubsubsec Limits
37114 @cindex limits, in file-i/o protocol
37116 All values are given in decimal representation.
37119 INT_MIN -2147483648
37121 UINT_MAX 4294967295
37122 LONG_MIN -9223372036854775808
37123 LONG_MAX 9223372036854775807
37124 ULONG_MAX 18446744073709551615
37127 @node File-I/O Examples
37128 @subsection File-I/O Examples
37129 @cindex file-i/o examples
37131 Example sequence of a write call, file descriptor 3, buffer is at target
37132 address 0x1234, 6 bytes should be written:
37135 <- @code{Fwrite,3,1234,6}
37136 @emph{request memory read from target}
37139 @emph{return "6 bytes written"}
37143 Example sequence of a read call, file descriptor 3, buffer is at target
37144 address 0x1234, 6 bytes should be read:
37147 <- @code{Fread,3,1234,6}
37148 @emph{request memory write to target}
37149 -> @code{X1234,6:XXXXXX}
37150 @emph{return "6 bytes read"}
37154 Example sequence of a read call, call fails on the host due to invalid
37155 file descriptor (@code{EBADF}):
37158 <- @code{Fread,3,1234,6}
37162 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
37166 <- @code{Fread,3,1234,6}
37171 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
37175 <- @code{Fread,3,1234,6}
37176 -> @code{X1234,6:XXXXXX}
37180 @node Library List Format
37181 @section Library List Format
37182 @cindex library list format, remote protocol
37184 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
37185 same process as your application to manage libraries. In this case,
37186 @value{GDBN} can use the loader's symbol table and normal memory
37187 operations to maintain a list of shared libraries. On other
37188 platforms, the operating system manages loaded libraries.
37189 @value{GDBN} can not retrieve the list of currently loaded libraries
37190 through memory operations, so it uses the @samp{qXfer:libraries:read}
37191 packet (@pxref{qXfer library list read}) instead. The remote stub
37192 queries the target's operating system and reports which libraries
37195 The @samp{qXfer:libraries:read} packet returns an XML document which
37196 lists loaded libraries and their offsets. Each library has an
37197 associated name and one or more segment or section base addresses,
37198 which report where the library was loaded in memory.
37200 For the common case of libraries that are fully linked binaries, the
37201 library should have a list of segments. If the target supports
37202 dynamic linking of a relocatable object file, its library XML element
37203 should instead include a list of allocated sections. The segment or
37204 section bases are start addresses, not relocation offsets; they do not
37205 depend on the library's link-time base addresses.
37207 @value{GDBN} must be linked with the Expat library to support XML
37208 library lists. @xref{Expat}.
37210 A simple memory map, with one loaded library relocated by a single
37211 offset, looks like this:
37215 <library name="/lib/libc.so.6">
37216 <segment address="0x10000000"/>
37221 Another simple memory map, with one loaded library with three
37222 allocated sections (.text, .data, .bss), looks like this:
37226 <library name="sharedlib.o">
37227 <section address="0x10000000"/>
37228 <section address="0x20000000"/>
37229 <section address="0x30000000"/>
37234 The format of a library list is described by this DTD:
37237 <!-- library-list: Root element with versioning -->
37238 <!ELEMENT library-list (library)*>
37239 <!ATTLIST library-list version CDATA #FIXED "1.0">
37240 <!ELEMENT library (segment*, section*)>
37241 <!ATTLIST library name CDATA #REQUIRED>
37242 <!ELEMENT segment EMPTY>
37243 <!ATTLIST segment address CDATA #REQUIRED>
37244 <!ELEMENT section EMPTY>
37245 <!ATTLIST section address CDATA #REQUIRED>
37248 In addition, segments and section descriptors cannot be mixed within a
37249 single library element, and you must supply at least one segment or
37250 section for each library.
37252 @node Memory Map Format
37253 @section Memory Map Format
37254 @cindex memory map format
37256 To be able to write into flash memory, @value{GDBN} needs to obtain a
37257 memory map from the target. This section describes the format of the
37260 The memory map is obtained using the @samp{qXfer:memory-map:read}
37261 (@pxref{qXfer memory map read}) packet and is an XML document that
37262 lists memory regions.
37264 @value{GDBN} must be linked with the Expat library to support XML
37265 memory maps. @xref{Expat}.
37267 The top-level structure of the document is shown below:
37270 <?xml version="1.0"?>
37271 <!DOCTYPE memory-map
37272 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
37273 "http://sourceware.org/gdb/gdb-memory-map.dtd">
37279 Each region can be either:
37284 A region of RAM starting at @var{addr} and extending for @var{length}
37288 <memory type="ram" start="@var{addr}" length="@var{length}"/>
37293 A region of read-only memory:
37296 <memory type="rom" start="@var{addr}" length="@var{length}"/>
37301 A region of flash memory, with erasure blocks @var{blocksize}
37305 <memory type="flash" start="@var{addr}" length="@var{length}">
37306 <property name="blocksize">@var{blocksize}</property>
37312 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
37313 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
37314 packets to write to addresses in such ranges.
37316 The formal DTD for memory map format is given below:
37319 <!-- ................................................... -->
37320 <!-- Memory Map XML DTD ................................ -->
37321 <!-- File: memory-map.dtd .............................. -->
37322 <!-- .................................... .............. -->
37323 <!-- memory-map.dtd -->
37324 <!-- memory-map: Root element with versioning -->
37325 <!ELEMENT memory-map (memory | property)>
37326 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
37327 <!ELEMENT memory (property)>
37328 <!-- memory: Specifies a memory region,
37329 and its type, or device. -->
37330 <!ATTLIST memory type CDATA #REQUIRED
37331 start CDATA #REQUIRED
37332 length CDATA #REQUIRED
37333 device CDATA #IMPLIED>
37334 <!-- property: Generic attribute tag -->
37335 <!ELEMENT property (#PCDATA | property)*>
37336 <!ATTLIST property name CDATA #REQUIRED>
37339 @node Thread List Format
37340 @section Thread List Format
37341 @cindex thread list format
37343 To efficiently update the list of threads and their attributes,
37344 @value{GDBN} issues the @samp{qXfer:threads:read} packet
37345 (@pxref{qXfer threads read}) and obtains the XML document with
37346 the following structure:
37349 <?xml version="1.0"?>
37351 <thread id="id" core="0">
37352 ... description ...
37357 Each @samp{thread} element must have the @samp{id} attribute that
37358 identifies the thread (@pxref{thread-id syntax}). The
37359 @samp{core} attribute, if present, specifies which processor core
37360 the thread was last executing on. The content of the of @samp{thread}
37361 element is interpreted as human-readable auxilliary information.
37363 @node Traceframe Info Format
37364 @section Traceframe Info Format
37365 @cindex traceframe info format
37367 To be able to know which objects in the inferior can be examined when
37368 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
37369 memory ranges, registers and trace state variables that have been
37370 collected in a traceframe.
37372 This list is obtained using the @samp{qXfer:traceframe-info:read}
37373 (@pxref{qXfer traceframe info read}) packet and is an XML document.
37375 @value{GDBN} must be linked with the Expat library to support XML
37376 traceframe info discovery. @xref{Expat}.
37378 The top-level structure of the document is shown below:
37381 <?xml version="1.0"?>
37382 <!DOCTYPE traceframe-info
37383 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
37384 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
37390 Each traceframe block can be either:
37395 A region of collected memory starting at @var{addr} and extending for
37396 @var{length} bytes from there:
37399 <memory start="@var{addr}" length="@var{length}"/>
37404 The formal DTD for the traceframe info format is given below:
37407 <!ELEMENT traceframe-info (memory)* >
37408 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
37410 <!ELEMENT memory EMPTY>
37411 <!ATTLIST memory start CDATA #REQUIRED
37412 length CDATA #REQUIRED>
37415 @include agentexpr.texi
37417 @node Target Descriptions
37418 @appendix Target Descriptions
37419 @cindex target descriptions
37421 One of the challenges of using @value{GDBN} to debug embedded systems
37422 is that there are so many minor variants of each processor
37423 architecture in use. It is common practice for vendors to start with
37424 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
37425 and then make changes to adapt it to a particular market niche. Some
37426 architectures have hundreds of variants, available from dozens of
37427 vendors. This leads to a number of problems:
37431 With so many different customized processors, it is difficult for
37432 the @value{GDBN} maintainers to keep up with the changes.
37434 Since individual variants may have short lifetimes or limited
37435 audiences, it may not be worthwhile to carry information about every
37436 variant in the @value{GDBN} source tree.
37438 When @value{GDBN} does support the architecture of the embedded system
37439 at hand, the task of finding the correct architecture name to give the
37440 @command{set architecture} command can be error-prone.
37443 To address these problems, the @value{GDBN} remote protocol allows a
37444 target system to not only identify itself to @value{GDBN}, but to
37445 actually describe its own features. This lets @value{GDBN} support
37446 processor variants it has never seen before --- to the extent that the
37447 descriptions are accurate, and that @value{GDBN} understands them.
37449 @value{GDBN} must be linked with the Expat library to support XML
37450 target descriptions. @xref{Expat}.
37453 * Retrieving Descriptions:: How descriptions are fetched from a target.
37454 * Target Description Format:: The contents of a target description.
37455 * Predefined Target Types:: Standard types available for target
37457 * Standard Target Features:: Features @value{GDBN} knows about.
37460 @node Retrieving Descriptions
37461 @section Retrieving Descriptions
37463 Target descriptions can be read from the target automatically, or
37464 specified by the user manually. The default behavior is to read the
37465 description from the target. @value{GDBN} retrieves it via the remote
37466 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
37467 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
37468 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
37469 XML document, of the form described in @ref{Target Description
37472 Alternatively, you can specify a file to read for the target description.
37473 If a file is set, the target will not be queried. The commands to
37474 specify a file are:
37477 @cindex set tdesc filename
37478 @item set tdesc filename @var{path}
37479 Read the target description from @var{path}.
37481 @cindex unset tdesc filename
37482 @item unset tdesc filename
37483 Do not read the XML target description from a file. @value{GDBN}
37484 will use the description supplied by the current target.
37486 @cindex show tdesc filename
37487 @item show tdesc filename
37488 Show the filename to read for a target description, if any.
37492 @node Target Description Format
37493 @section Target Description Format
37494 @cindex target descriptions, XML format
37496 A target description annex is an @uref{http://www.w3.org/XML/, XML}
37497 document which complies with the Document Type Definition provided in
37498 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
37499 means you can use generally available tools like @command{xmllint} to
37500 check that your feature descriptions are well-formed and valid.
37501 However, to help people unfamiliar with XML write descriptions for
37502 their targets, we also describe the grammar here.
37504 Target descriptions can identify the architecture of the remote target
37505 and (for some architectures) provide information about custom register
37506 sets. They can also identify the OS ABI of the remote target.
37507 @value{GDBN} can use this information to autoconfigure for your
37508 target, or to warn you if you connect to an unsupported target.
37510 Here is a simple target description:
37513 <target version="1.0">
37514 <architecture>i386:x86-64</architecture>
37519 This minimal description only says that the target uses
37520 the x86-64 architecture.
37522 A target description has the following overall form, with [ ] marking
37523 optional elements and @dots{} marking repeatable elements. The elements
37524 are explained further below.
37527 <?xml version="1.0"?>
37528 <!DOCTYPE target SYSTEM "gdb-target.dtd">
37529 <target version="1.0">
37530 @r{[}@var{architecture}@r{]}
37531 @r{[}@var{osabi}@r{]}
37532 @r{[}@var{compatible}@r{]}
37533 @r{[}@var{feature}@dots{}@r{]}
37538 The description is generally insensitive to whitespace and line
37539 breaks, under the usual common-sense rules. The XML version
37540 declaration and document type declaration can generally be omitted
37541 (@value{GDBN} does not require them), but specifying them may be
37542 useful for XML validation tools. The @samp{version} attribute for
37543 @samp{<target>} may also be omitted, but we recommend
37544 including it; if future versions of @value{GDBN} use an incompatible
37545 revision of @file{gdb-target.dtd}, they will detect and report
37546 the version mismatch.
37548 @subsection Inclusion
37549 @cindex target descriptions, inclusion
37552 @cindex <xi:include>
37555 It can sometimes be valuable to split a target description up into
37556 several different annexes, either for organizational purposes, or to
37557 share files between different possible target descriptions. You can
37558 divide a description into multiple files by replacing any element of
37559 the target description with an inclusion directive of the form:
37562 <xi:include href="@var{document}"/>
37566 When @value{GDBN} encounters an element of this form, it will retrieve
37567 the named XML @var{document}, and replace the inclusion directive with
37568 the contents of that document. If the current description was read
37569 using @samp{qXfer}, then so will be the included document;
37570 @var{document} will be interpreted as the name of an annex. If the
37571 current description was read from a file, @value{GDBN} will look for
37572 @var{document} as a file in the same directory where it found the
37573 original description.
37575 @subsection Architecture
37576 @cindex <architecture>
37578 An @samp{<architecture>} element has this form:
37581 <architecture>@var{arch}</architecture>
37584 @var{arch} is one of the architectures from the set accepted by
37585 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
37588 @cindex @code{<osabi>}
37590 This optional field was introduced in @value{GDBN} version 7.0.
37591 Previous versions of @value{GDBN} ignore it.
37593 An @samp{<osabi>} element has this form:
37596 <osabi>@var{abi-name}</osabi>
37599 @var{abi-name} is an OS ABI name from the same selection accepted by
37600 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
37602 @subsection Compatible Architecture
37603 @cindex @code{<compatible>}
37605 This optional field was introduced in @value{GDBN} version 7.0.
37606 Previous versions of @value{GDBN} ignore it.
37608 A @samp{<compatible>} element has this form:
37611 <compatible>@var{arch}</compatible>
37614 @var{arch} is one of the architectures from the set accepted by
37615 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
37617 A @samp{<compatible>} element is used to specify that the target
37618 is able to run binaries in some other than the main target architecture
37619 given by the @samp{<architecture>} element. For example, on the
37620 Cell Broadband Engine, the main architecture is @code{powerpc:common}
37621 or @code{powerpc:common64}, but the system is able to run binaries
37622 in the @code{spu} architecture as well. The way to describe this
37623 capability with @samp{<compatible>} is as follows:
37626 <architecture>powerpc:common</architecture>
37627 <compatible>spu</compatible>
37630 @subsection Features
37633 Each @samp{<feature>} describes some logical portion of the target
37634 system. Features are currently used to describe available CPU
37635 registers and the types of their contents. A @samp{<feature>} element
37639 <feature name="@var{name}">
37640 @r{[}@var{type}@dots{}@r{]}
37646 Each feature's name should be unique within the description. The name
37647 of a feature does not matter unless @value{GDBN} has some special
37648 knowledge of the contents of that feature; if it does, the feature
37649 should have its standard name. @xref{Standard Target Features}.
37653 Any register's value is a collection of bits which @value{GDBN} must
37654 interpret. The default interpretation is a two's complement integer,
37655 but other types can be requested by name in the register description.
37656 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
37657 Target Types}), and the description can define additional composite types.
37659 Each type element must have an @samp{id} attribute, which gives
37660 a unique (within the containing @samp{<feature>}) name to the type.
37661 Types must be defined before they are used.
37664 Some targets offer vector registers, which can be treated as arrays
37665 of scalar elements. These types are written as @samp{<vector>} elements,
37666 specifying the array element type, @var{type}, and the number of elements,
37670 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
37674 If a register's value is usefully viewed in multiple ways, define it
37675 with a union type containing the useful representations. The
37676 @samp{<union>} element contains one or more @samp{<field>} elements,
37677 each of which has a @var{name} and a @var{type}:
37680 <union id="@var{id}">
37681 <field name="@var{name}" type="@var{type}"/>
37687 If a register's value is composed from several separate values, define
37688 it with a structure type. There are two forms of the @samp{<struct>}
37689 element; a @samp{<struct>} element must either contain only bitfields
37690 or contain no bitfields. If the structure contains only bitfields,
37691 its total size in bytes must be specified, each bitfield must have an
37692 explicit start and end, and bitfields are automatically assigned an
37693 integer type. The field's @var{start} should be less than or
37694 equal to its @var{end}, and zero represents the least significant bit.
37697 <struct id="@var{id}" size="@var{size}">
37698 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
37703 If the structure contains no bitfields, then each field has an
37704 explicit type, and no implicit padding is added.
37707 <struct id="@var{id}">
37708 <field name="@var{name}" type="@var{type}"/>
37714 If a register's value is a series of single-bit flags, define it with
37715 a flags type. The @samp{<flags>} element has an explicit @var{size}
37716 and contains one or more @samp{<field>} elements. Each field has a
37717 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
37721 <flags id="@var{id}" size="@var{size}">
37722 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
37727 @subsection Registers
37730 Each register is represented as an element with this form:
37733 <reg name="@var{name}"
37734 bitsize="@var{size}"
37735 @r{[}regnum="@var{num}"@r{]}
37736 @r{[}save-restore="@var{save-restore}"@r{]}
37737 @r{[}type="@var{type}"@r{]}
37738 @r{[}group="@var{group}"@r{]}/>
37742 The components are as follows:
37747 The register's name; it must be unique within the target description.
37750 The register's size, in bits.
37753 The register's number. If omitted, a register's number is one greater
37754 than that of the previous register (either in the current feature or in
37755 a preceding feature); the first register in the target description
37756 defaults to zero. This register number is used to read or write
37757 the register; e.g.@: it is used in the remote @code{p} and @code{P}
37758 packets, and registers appear in the @code{g} and @code{G} packets
37759 in order of increasing register number.
37762 Whether the register should be preserved across inferior function
37763 calls; this must be either @code{yes} or @code{no}. The default is
37764 @code{yes}, which is appropriate for most registers except for
37765 some system control registers; this is not related to the target's
37769 The type of the register. @var{type} may be a predefined type, a type
37770 defined in the current feature, or one of the special types @code{int}
37771 and @code{float}. @code{int} is an integer type of the correct size
37772 for @var{bitsize}, and @code{float} is a floating point type (in the
37773 architecture's normal floating point format) of the correct size for
37774 @var{bitsize}. The default is @code{int}.
37777 The register group to which this register belongs. @var{group} must
37778 be either @code{general}, @code{float}, or @code{vector}. If no
37779 @var{group} is specified, @value{GDBN} will not display the register
37780 in @code{info registers}.
37784 @node Predefined Target Types
37785 @section Predefined Target Types
37786 @cindex target descriptions, predefined types
37788 Type definitions in the self-description can build up composite types
37789 from basic building blocks, but can not define fundamental types. Instead,
37790 standard identifiers are provided by @value{GDBN} for the fundamental
37791 types. The currently supported types are:
37800 Signed integer types holding the specified number of bits.
37807 Unsigned integer types holding the specified number of bits.
37811 Pointers to unspecified code and data. The program counter and
37812 any dedicated return address register may be marked as code
37813 pointers; printing a code pointer converts it into a symbolic
37814 address. The stack pointer and any dedicated address registers
37815 may be marked as data pointers.
37818 Single precision IEEE floating point.
37821 Double precision IEEE floating point.
37824 The 12-byte extended precision format used by ARM FPA registers.
37827 The 10-byte extended precision format used by x87 registers.
37830 32bit @sc{eflags} register used by x86.
37833 32bit @sc{mxcsr} register used by x86.
37837 @node Standard Target Features
37838 @section Standard Target Features
37839 @cindex target descriptions, standard features
37841 A target description must contain either no registers or all the
37842 target's registers. If the description contains no registers, then
37843 @value{GDBN} will assume a default register layout, selected based on
37844 the architecture. If the description contains any registers, the
37845 default layout will not be used; the standard registers must be
37846 described in the target description, in such a way that @value{GDBN}
37847 can recognize them.
37849 This is accomplished by giving specific names to feature elements
37850 which contain standard registers. @value{GDBN} will look for features
37851 with those names and verify that they contain the expected registers;
37852 if any known feature is missing required registers, or if any required
37853 feature is missing, @value{GDBN} will reject the target
37854 description. You can add additional registers to any of the
37855 standard features --- @value{GDBN} will display them just as if
37856 they were added to an unrecognized feature.
37858 This section lists the known features and their expected contents.
37859 Sample XML documents for these features are included in the
37860 @value{GDBN} source tree, in the directory @file{gdb/features}.
37862 Names recognized by @value{GDBN} should include the name of the
37863 company or organization which selected the name, and the overall
37864 architecture to which the feature applies; so e.g.@: the feature
37865 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
37867 The names of registers are not case sensitive for the purpose
37868 of recognizing standard features, but @value{GDBN} will only display
37869 registers using the capitalization used in the description.
37876 * PowerPC Features::
37882 @subsection ARM Features
37883 @cindex target descriptions, ARM features
37885 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
37887 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
37888 @samp{lr}, @samp{pc}, and @samp{cpsr}.
37890 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
37891 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
37892 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
37895 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
37896 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
37898 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
37899 it should contain at least registers @samp{wR0} through @samp{wR15} and
37900 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
37901 @samp{wCSSF}, and @samp{wCASF} registers are optional.
37903 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
37904 should contain at least registers @samp{d0} through @samp{d15}. If
37905 they are present, @samp{d16} through @samp{d31} should also be included.
37906 @value{GDBN} will synthesize the single-precision registers from
37907 halves of the double-precision registers.
37909 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
37910 need to contain registers; it instructs @value{GDBN} to display the
37911 VFP double-precision registers as vectors and to synthesize the
37912 quad-precision registers from pairs of double-precision registers.
37913 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
37914 be present and include 32 double-precision registers.
37916 @node i386 Features
37917 @subsection i386 Features
37918 @cindex target descriptions, i386 features
37920 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
37921 targets. It should describe the following registers:
37925 @samp{eax} through @samp{edi} plus @samp{eip} for i386
37927 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
37929 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
37930 @samp{fs}, @samp{gs}
37932 @samp{st0} through @samp{st7}
37934 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
37935 @samp{foseg}, @samp{fooff} and @samp{fop}
37938 The register sets may be different, depending on the target.
37940 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
37941 describe registers:
37945 @samp{xmm0} through @samp{xmm7} for i386
37947 @samp{xmm0} through @samp{xmm15} for amd64
37952 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
37953 @samp{org.gnu.gdb.i386.sse} feature. It should
37954 describe the upper 128 bits of @sc{ymm} registers:
37958 @samp{ymm0h} through @samp{ymm7h} for i386
37960 @samp{ymm0h} through @samp{ymm15h} for amd64
37963 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
37964 describe a single register, @samp{orig_eax}.
37966 @node MIPS Features
37967 @subsection MIPS Features
37968 @cindex target descriptions, MIPS features
37970 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
37971 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
37972 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
37975 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
37976 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
37977 registers. They may be 32-bit or 64-bit depending on the target.
37979 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
37980 it may be optional in a future version of @value{GDBN}. It should
37981 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
37982 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
37984 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
37985 contain a single register, @samp{restart}, which is used by the
37986 Linux kernel to control restartable syscalls.
37988 @node M68K Features
37989 @subsection M68K Features
37990 @cindex target descriptions, M68K features
37993 @item @samp{org.gnu.gdb.m68k.core}
37994 @itemx @samp{org.gnu.gdb.coldfire.core}
37995 @itemx @samp{org.gnu.gdb.fido.core}
37996 One of those features must be always present.
37997 The feature that is present determines which flavor of m68k is
37998 used. The feature that is present should contain registers
37999 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
38000 @samp{sp}, @samp{ps} and @samp{pc}.
38002 @item @samp{org.gnu.gdb.coldfire.fp}
38003 This feature is optional. If present, it should contain registers
38004 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
38008 @node PowerPC Features
38009 @subsection PowerPC Features
38010 @cindex target descriptions, PowerPC features
38012 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
38013 targets. It should contain registers @samp{r0} through @samp{r31},
38014 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
38015 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
38017 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
38018 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
38020 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
38021 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
38024 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
38025 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
38026 will combine these registers with the floating point registers
38027 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
38028 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
38029 through @samp{vs63}, the set of vector registers for POWER7.
38031 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
38032 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
38033 @samp{spefscr}. SPE targets should provide 32-bit registers in
38034 @samp{org.gnu.gdb.power.core} and provide the upper halves in
38035 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
38036 these to present registers @samp{ev0} through @samp{ev31} to the
38039 @node TIC6x Features
38040 @subsection TMS320C6x Features
38041 @cindex target descriptions, TIC6x features
38042 @cindex target descriptions, TMS320C6x features
38043 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
38044 targets. It should contain registers @samp{A0} through @samp{A15},
38045 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
38047 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
38048 contain registers @samp{A16} through @samp{A31} and @samp{B16}
38049 through @samp{B31}.
38051 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
38052 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
38054 @node Operating System Information
38055 @appendix Operating System Information
38056 @cindex operating system information
38062 Users of @value{GDBN} often wish to obtain information about the state of
38063 the operating system running on the target---for example the list of
38064 processes, or the list of open files. This section describes the
38065 mechanism that makes it possible. This mechanism is similar to the
38066 target features mechanism (@pxref{Target Descriptions}), but focuses
38067 on a different aspect of target.
38069 Operating system information is retrived from the target via the
38070 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
38071 read}). The object name in the request should be @samp{osdata}, and
38072 the @var{annex} identifies the data to be fetched.
38075 @appendixsection Process list
38076 @cindex operating system information, process list
38078 When requesting the process list, the @var{annex} field in the
38079 @samp{qXfer} request should be @samp{processes}. The returned data is
38080 an XML document. The formal syntax of this document is defined in
38081 @file{gdb/features/osdata.dtd}.
38083 An example document is:
38086 <?xml version="1.0"?>
38087 <!DOCTYPE target SYSTEM "osdata.dtd">
38088 <osdata type="processes">
38090 <column name="pid">1</column>
38091 <column name="user">root</column>
38092 <column name="command">/sbin/init</column>
38093 <column name="cores">1,2,3</column>
38098 Each item should include a column whose name is @samp{pid}. The value
38099 of that column should identify the process on the target. The
38100 @samp{user} and @samp{command} columns are optional, and will be
38101 displayed by @value{GDBN}. The @samp{cores} column, if present,
38102 should contain a comma-separated list of cores that this process
38103 is running on. Target may provide additional columns,
38104 which @value{GDBN} currently ignores.
38106 @node Trace File Format
38107 @appendix Trace File Format
38108 @cindex trace file format
38110 The trace file comes in three parts: a header, a textual description
38111 section, and a trace frame section with binary data.
38113 The header has the form @code{\x7fTRACE0\n}. The first byte is
38114 @code{0x7f} so as to indicate that the file contains binary data,
38115 while the @code{0} is a version number that may have different values
38118 The description section consists of multiple lines of @sc{ascii} text
38119 separated by newline characters (@code{0xa}). The lines may include a
38120 variety of optional descriptive or context-setting information, such
38121 as tracepoint definitions or register set size. @value{GDBN} will
38122 ignore any line that it does not recognize. An empty line marks the end
38125 @c FIXME add some specific types of data
38127 The trace frame section consists of a number of consecutive frames.
38128 Each frame begins with a two-byte tracepoint number, followed by a
38129 four-byte size giving the amount of data in the frame. The data in
38130 the frame consists of a number of blocks, each introduced by a
38131 character indicating its type (at least register, memory, and trace
38132 state variable). The data in this section is raw binary, not a
38133 hexadecimal or other encoding; its endianness matches the target's
38136 @c FIXME bi-arch may require endianness/arch info in description section
38139 @item R @var{bytes}
38140 Register block. The number and ordering of bytes matches that of a
38141 @code{g} packet in the remote protocol. Note that these are the
38142 actual bytes, in target order and @value{GDBN} register order, not a
38143 hexadecimal encoding.
38145 @item M @var{address} @var{length} @var{bytes}...
38146 Memory block. This is a contiguous block of memory, at the 8-byte
38147 address @var{address}, with a 2-byte length @var{length}, followed by
38148 @var{length} bytes.
38150 @item V @var{number} @var{value}
38151 Trace state variable block. This records the 8-byte signed value
38152 @var{value} of trace state variable numbered @var{number}.
38156 Future enhancements of the trace file format may include additional types
38159 @node Index Section Format
38160 @appendix @code{.gdb_index} section format
38161 @cindex .gdb_index section format
38162 @cindex index section format
38164 This section documents the index section that is created by @code{save
38165 gdb-index} (@pxref{Index Files}). The index section is
38166 DWARF-specific; some knowledge of DWARF is assumed in this
38169 The mapped index file format is designed to be directly
38170 @code{mmap}able on any architecture. In most cases, a datum is
38171 represented using a little-endian 32-bit integer value, called an
38172 @code{offset_type}. Big endian machines must byte-swap the values
38173 before using them. Exceptions to this rule are noted. The data is
38174 laid out such that alignment is always respected.
38176 A mapped index consists of several areas, laid out in order.
38180 The file header. This is a sequence of values, of @code{offset_type}
38181 unless otherwise noted:
38185 The version number, currently 5. Versions 1, 2 and 3 are obsolete.
38186 Version 4 differs by its hashing function.
38189 The offset, from the start of the file, of the CU list.
38192 The offset, from the start of the file, of the types CU list. Note
38193 that this area can be empty, in which case this offset will be equal
38194 to the next offset.
38197 The offset, from the start of the file, of the address area.
38200 The offset, from the start of the file, of the symbol table.
38203 The offset, from the start of the file, of the constant pool.
38207 The CU list. This is a sequence of pairs of 64-bit little-endian
38208 values, sorted by the CU offset. The first element in each pair is
38209 the offset of a CU in the @code{.debug_info} section. The second
38210 element in each pair is the length of that CU. References to a CU
38211 elsewhere in the map are done using a CU index, which is just the
38212 0-based index into this table. Note that if there are type CUs, then
38213 conceptually CUs and type CUs form a single list for the purposes of
38217 The types CU list. This is a sequence of triplets of 64-bit
38218 little-endian values. In a triplet, the first value is the CU offset,
38219 the second value is the type offset in the CU, and the third value is
38220 the type signature. The types CU list is not sorted.
38223 The address area. The address area consists of a sequence of address
38224 entries. Each address entry has three elements:
38228 The low address. This is a 64-bit little-endian value.
38231 The high address. This is a 64-bit little-endian value. Like
38232 @code{DW_AT_high_pc}, the value is one byte beyond the end.
38235 The CU index. This is an @code{offset_type} value.
38239 The symbol table. This is an open-addressed hash table. The size of
38240 the hash table is always a power of 2.
38242 Each slot in the hash table consists of a pair of @code{offset_type}
38243 values. The first value is the offset of the symbol's name in the
38244 constant pool. The second value is the offset of the CU vector in the
38247 If both values are 0, then this slot in the hash table is empty. This
38248 is ok because while 0 is a valid constant pool index, it cannot be a
38249 valid index for both a string and a CU vector.
38251 The hash value for a table entry is computed by applying an
38252 iterative hash function to the symbol's name. Starting with an
38253 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
38254 the string is incorporated into the hash using the formula depending on the
38259 The formula is @code{r = r * 67 + c - 113}.
38262 The formula is @code{r = r * 67 + tolower (c) - 113}.
38265 The terminating @samp{\0} is not incorporated into the hash.
38267 The step size used in the hash table is computed via
38268 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
38269 value, and @samp{size} is the size of the hash table. The step size
38270 is used to find the next candidate slot when handling a hash
38273 The names of C@t{++} symbols in the hash table are canonicalized. We
38274 don't currently have a simple description of the canonicalization
38275 algorithm; if you intend to create new index sections, you must read
38279 The constant pool. This is simply a bunch of bytes. It is organized
38280 so that alignment is correct: CU vectors are stored first, followed by
38283 A CU vector in the constant pool is a sequence of @code{offset_type}
38284 values. The first value is the number of CU indices in the vector.
38285 Each subsequent value is the index of a CU in the CU list. This
38286 element in the hash table is used to indicate which CUs define the
38289 A string in the constant pool is zero-terminated.
38294 @node GNU Free Documentation License
38295 @appendix GNU Free Documentation License
38304 % I think something like @colophon should be in texinfo. In the
38306 \long\def\colophon{\hbox to0pt{}\vfill
38307 \centerline{The body of this manual is set in}
38308 \centerline{\fontname\tenrm,}
38309 \centerline{with headings in {\bf\fontname\tenbf}}
38310 \centerline{and examples in {\tt\fontname\tentt}.}
38311 \centerline{{\it\fontname\tenit\/},}
38312 \centerline{{\bf\fontname\tenbf}, and}
38313 \centerline{{\sl\fontname\tensl\/}}
38314 \centerline{are used for emphasis.}\vfill}
38316 % Blame: doc@cygnus.com, 1991.