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 @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 command @code{info scope} (@pxref{Symbols, info scope}) is
10716 particularly useful for figuring out what data to collect.
10718 @kindex teval @r{(tracepoints)}
10719 @item teval @var{expr1}, @var{expr2}, @dots{}
10720 Evaluate the given expressions when the tracepoint is hit. This
10721 command accepts a comma-separated list of expressions. The results
10722 are discarded, so this is mainly useful for assigning values to trace
10723 state variables (@pxref{Trace State Variables}) without adding those
10724 values to the trace buffer, as would be the case if the @code{collect}
10727 @kindex while-stepping @r{(tracepoints)}
10728 @item while-stepping @var{n}
10729 Perform @var{n} single-step instruction traces after the tracepoint,
10730 collecting new data after each step. The @code{while-stepping}
10731 command is followed by the list of what to collect while stepping
10732 (followed by its own @code{end} command):
10735 > while-stepping 12
10736 > collect $regs, myglobal
10742 Note that @code{$pc} is not automatically collected by
10743 @code{while-stepping}; you need to explicitly collect that register if
10744 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
10747 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
10748 @kindex set default-collect
10749 @cindex default collection action
10750 This variable is a list of expressions to collect at each tracepoint
10751 hit. It is effectively an additional @code{collect} action prepended
10752 to every tracepoint action list. The expressions are parsed
10753 individually for each tracepoint, so for instance a variable named
10754 @code{xyz} may be interpreted as a global for one tracepoint, and a
10755 local for another, as appropriate to the tracepoint's location.
10757 @item show default-collect
10758 @kindex show default-collect
10759 Show the list of expressions that are collected by default at each
10764 @node Listing Tracepoints
10765 @subsection Listing Tracepoints
10768 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
10769 @kindex info tp @r{[}@var{n}@dots{}@r{]}
10770 @cindex information about tracepoints
10771 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
10772 Display information about the tracepoint @var{num}. If you don't
10773 specify a tracepoint number, displays information about all the
10774 tracepoints defined so far. The format is similar to that used for
10775 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
10776 command, simply restricting itself to tracepoints.
10778 A tracepoint's listing may include additional information specific to
10783 its passcount as given by the @code{passcount @var{n}} command
10787 (@value{GDBP}) @b{info trace}
10788 Num Type Disp Enb Address What
10789 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
10791 collect globfoo, $regs
10800 This command can be abbreviated @code{info tp}.
10803 @node Listing Static Tracepoint Markers
10804 @subsection Listing Static Tracepoint Markers
10807 @kindex info static-tracepoint-markers
10808 @cindex information about static tracepoint markers
10809 @item info static-tracepoint-markers
10810 Display information about all static tracepoint markers defined in the
10813 For each marker, the following columns are printed:
10817 An incrementing counter, output to help readability. This is not a
10820 The marker ID, as reported by the target.
10821 @item Enabled or Disabled
10822 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
10823 that are not enabled.
10825 Where the marker is in your program, as a memory address.
10827 Where the marker is in the source for your program, as a file and line
10828 number. If the debug information included in the program does not
10829 allow @value{GDBN} to locate the source of the marker, this column
10830 will be left blank.
10834 In addition, the following information may be printed for each marker:
10838 User data passed to the tracing library by the marker call. In the
10839 UST backend, this is the format string passed as argument to the
10841 @item Static tracepoints probing the marker
10842 The list of static tracepoints attached to the marker.
10846 (@value{GDBP}) info static-tracepoint-markers
10847 Cnt ID Enb Address What
10848 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
10849 Data: number1 %d number2 %d
10850 Probed by static tracepoints: #2
10851 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
10857 @node Starting and Stopping Trace Experiments
10858 @subsection Starting and Stopping Trace Experiments
10862 @cindex start a new trace experiment
10863 @cindex collected data discarded
10865 This command takes no arguments. It starts the trace experiment, and
10866 begins collecting data. This has the side effect of discarding all
10867 the data collected in the trace buffer during the previous trace
10871 @cindex stop a running trace experiment
10873 This command takes no arguments. It ends the trace experiment, and
10874 stops collecting data.
10876 @strong{Note}: a trace experiment and data collection may stop
10877 automatically if any tracepoint's passcount is reached
10878 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
10881 @cindex status of trace data collection
10882 @cindex trace experiment, status of
10884 This command displays the status of the current trace data
10888 Here is an example of the commands we described so far:
10891 (@value{GDBP}) @b{trace gdb_c_test}
10892 (@value{GDBP}) @b{actions}
10893 Enter actions for tracepoint #1, one per line.
10894 > collect $regs,$locals,$args
10895 > while-stepping 11
10899 (@value{GDBP}) @b{tstart}
10900 [time passes @dots{}]
10901 (@value{GDBP}) @b{tstop}
10904 @anchor{disconnected tracing}
10905 @cindex disconnected tracing
10906 You can choose to continue running the trace experiment even if
10907 @value{GDBN} disconnects from the target, voluntarily or
10908 involuntarily. For commands such as @code{detach}, the debugger will
10909 ask what you want to do with the trace. But for unexpected
10910 terminations (@value{GDBN} crash, network outage), it would be
10911 unfortunate to lose hard-won trace data, so the variable
10912 @code{disconnected-tracing} lets you decide whether the trace should
10913 continue running without @value{GDBN}.
10916 @item set disconnected-tracing on
10917 @itemx set disconnected-tracing off
10918 @kindex set disconnected-tracing
10919 Choose whether a tracing run should continue to run if @value{GDBN}
10920 has disconnected from the target. Note that @code{detach} or
10921 @code{quit} will ask you directly what to do about a running trace no
10922 matter what this variable's setting, so the variable is mainly useful
10923 for handling unexpected situations, such as loss of the network.
10925 @item show disconnected-tracing
10926 @kindex show disconnected-tracing
10927 Show the current choice for disconnected tracing.
10931 When you reconnect to the target, the trace experiment may or may not
10932 still be running; it might have filled the trace buffer in the
10933 meantime, or stopped for one of the other reasons. If it is running,
10934 it will continue after reconnection.
10936 Upon reconnection, the target will upload information about the
10937 tracepoints in effect. @value{GDBN} will then compare that
10938 information to the set of tracepoints currently defined, and attempt
10939 to match them up, allowing for the possibility that the numbers may
10940 have changed due to creation and deletion in the meantime. If one of
10941 the target's tracepoints does not match any in @value{GDBN}, the
10942 debugger will create a new tracepoint, so that you have a number with
10943 which to specify that tracepoint. This matching-up process is
10944 necessarily heuristic, and it may result in useless tracepoints being
10945 created; you may simply delete them if they are of no use.
10947 @cindex circular trace buffer
10948 If your target agent supports a @dfn{circular trace buffer}, then you
10949 can run a trace experiment indefinitely without filling the trace
10950 buffer; when space runs out, the agent deletes already-collected trace
10951 frames, oldest first, until there is enough room to continue
10952 collecting. This is especially useful if your tracepoints are being
10953 hit too often, and your trace gets terminated prematurely because the
10954 buffer is full. To ask for a circular trace buffer, simply set
10955 @samp{circular-trace-buffer} to on. You can set this at any time,
10956 including during tracing; if the agent can do it, it will change
10957 buffer handling on the fly, otherwise it will not take effect until
10961 @item set circular-trace-buffer on
10962 @itemx set circular-trace-buffer off
10963 @kindex set circular-trace-buffer
10964 Choose whether a tracing run should use a linear or circular buffer
10965 for trace data. A linear buffer will not lose any trace data, but may
10966 fill up prematurely, while a circular buffer will discard old trace
10967 data, but it will have always room for the latest tracepoint hits.
10969 @item show circular-trace-buffer
10970 @kindex show circular-trace-buffer
10971 Show the current choice for the trace buffer. Note that this may not
10972 match the agent's current buffer handling, nor is it guaranteed to
10973 match the setting that might have been in effect during a past run,
10974 for instance if you are looking at frames from a trace file.
10978 @node Tracepoint Restrictions
10979 @subsection Tracepoint Restrictions
10981 @cindex tracepoint restrictions
10982 There are a number of restrictions on the use of tracepoints. As
10983 described above, tracepoint data gathering occurs on the target
10984 without interaction from @value{GDBN}. Thus the full capabilities of
10985 the debugger are not available during data gathering, and then at data
10986 examination time, you will be limited by only having what was
10987 collected. The following items describe some common problems, but it
10988 is not exhaustive, and you may run into additional difficulties not
10994 Tracepoint expressions are intended to gather objects (lvalues). Thus
10995 the full flexibility of GDB's expression evaluator is not available.
10996 You cannot call functions, cast objects to aggregate types, access
10997 convenience variables or modify values (except by assignment to trace
10998 state variables). Some language features may implicitly call
10999 functions (for instance Objective-C fields with accessors), and therefore
11000 cannot be collected either.
11003 Collection of local variables, either individually or in bulk with
11004 @code{$locals} or @code{$args}, during @code{while-stepping} may
11005 behave erratically. The stepping action may enter a new scope (for
11006 instance by stepping into a function), or the location of the variable
11007 may change (for instance it is loaded into a register). The
11008 tracepoint data recorded uses the location information for the
11009 variables that is correct for the tracepoint location. When the
11010 tracepoint is created, it is not possible, in general, to determine
11011 where the steps of a @code{while-stepping} sequence will advance the
11012 program---particularly if a conditional branch is stepped.
11015 Collection of an incompletely-initialized or partially-destroyed object
11016 may result in something that @value{GDBN} cannot display, or displays
11017 in a misleading way.
11020 When @value{GDBN} displays a pointer to character it automatically
11021 dereferences the pointer to also display characters of the string
11022 being pointed to. However, collecting the pointer during tracing does
11023 not automatically collect the string. You need to explicitly
11024 dereference the pointer and provide size information if you want to
11025 collect not only the pointer, but the memory pointed to. For example,
11026 @code{*ptr@@50} can be used to collect the 50 element array pointed to
11030 It is not possible to collect a complete stack backtrace at a
11031 tracepoint. Instead, you may collect the registers and a few hundred
11032 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
11033 (adjust to use the name of the actual stack pointer register on your
11034 target architecture, and the amount of stack you wish to capture).
11035 Then the @code{backtrace} command will show a partial backtrace when
11036 using a trace frame. The number of stack frames that can be examined
11037 depends on the sizes of the frames in the collected stack. Note that
11038 if you ask for a block so large that it goes past the bottom of the
11039 stack, the target agent may report an error trying to read from an
11043 If you do not collect registers at a tracepoint, @value{GDBN} can
11044 infer that the value of @code{$pc} must be the same as the address of
11045 the tracepoint and use that when you are looking at a trace frame
11046 for that tracepoint. However, this cannot work if the tracepoint has
11047 multiple locations (for instance if it was set in a function that was
11048 inlined), or if it has a @code{while-stepping} loop. In those cases
11049 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
11054 @node Analyze Collected Data
11055 @section Using the Collected Data
11057 After the tracepoint experiment ends, you use @value{GDBN} commands
11058 for examining the trace data. The basic idea is that each tracepoint
11059 collects a trace @dfn{snapshot} every time it is hit and another
11060 snapshot every time it single-steps. All these snapshots are
11061 consecutively numbered from zero and go into a buffer, and you can
11062 examine them later. The way you examine them is to @dfn{focus} on a
11063 specific trace snapshot. When the remote stub is focused on a trace
11064 snapshot, it will respond to all @value{GDBN} requests for memory and
11065 registers by reading from the buffer which belongs to that snapshot,
11066 rather than from @emph{real} memory or registers of the program being
11067 debugged. This means that @strong{all} @value{GDBN} commands
11068 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
11069 behave as if we were currently debugging the program state as it was
11070 when the tracepoint occurred. Any requests for data that are not in
11071 the buffer will fail.
11074 * tfind:: How to select a trace snapshot
11075 * tdump:: How to display all data for a snapshot
11076 * save tracepoints:: How to save tracepoints for a future run
11080 @subsection @code{tfind @var{n}}
11083 @cindex select trace snapshot
11084 @cindex find trace snapshot
11085 The basic command for selecting a trace snapshot from the buffer is
11086 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
11087 counting from zero. If no argument @var{n} is given, the next
11088 snapshot is selected.
11090 Here are the various forms of using the @code{tfind} command.
11094 Find the first snapshot in the buffer. This is a synonym for
11095 @code{tfind 0} (since 0 is the number of the first snapshot).
11098 Stop debugging trace snapshots, resume @emph{live} debugging.
11101 Same as @samp{tfind none}.
11104 No argument means find the next trace snapshot.
11107 Find the previous trace snapshot before the current one. This permits
11108 retracing earlier steps.
11110 @item tfind tracepoint @var{num}
11111 Find the next snapshot associated with tracepoint @var{num}. Search
11112 proceeds forward from the last examined trace snapshot. If no
11113 argument @var{num} is given, it means find the next snapshot collected
11114 for the same tracepoint as the current snapshot.
11116 @item tfind pc @var{addr}
11117 Find the next snapshot associated with the value @var{addr} of the
11118 program counter. Search proceeds forward from the last examined trace
11119 snapshot. If no argument @var{addr} is given, it means find the next
11120 snapshot with the same value of PC as the current snapshot.
11122 @item tfind outside @var{addr1}, @var{addr2}
11123 Find the next snapshot whose PC is outside the given range of
11124 addresses (exclusive).
11126 @item tfind range @var{addr1}, @var{addr2}
11127 Find the next snapshot whose PC is between @var{addr1} and
11128 @var{addr2} (inclusive).
11130 @item tfind line @r{[}@var{file}:@r{]}@var{n}
11131 Find the next snapshot associated with the source line @var{n}. If
11132 the optional argument @var{file} is given, refer to line @var{n} in
11133 that source file. Search proceeds forward from the last examined
11134 trace snapshot. If no argument @var{n} is given, it means find the
11135 next line other than the one currently being examined; thus saying
11136 @code{tfind line} repeatedly can appear to have the same effect as
11137 stepping from line to line in a @emph{live} debugging session.
11140 The default arguments for the @code{tfind} commands are specifically
11141 designed to make it easy to scan through the trace buffer. For
11142 instance, @code{tfind} with no argument selects the next trace
11143 snapshot, and @code{tfind -} with no argument selects the previous
11144 trace snapshot. So, by giving one @code{tfind} command, and then
11145 simply hitting @key{RET} repeatedly you can examine all the trace
11146 snapshots in order. Or, by saying @code{tfind -} and then hitting
11147 @key{RET} repeatedly you can examine the snapshots in reverse order.
11148 The @code{tfind line} command with no argument selects the snapshot
11149 for the next source line executed. The @code{tfind pc} command with
11150 no argument selects the next snapshot with the same program counter
11151 (PC) as the current frame. The @code{tfind tracepoint} command with
11152 no argument selects the next trace snapshot collected by the same
11153 tracepoint as the current one.
11155 In addition to letting you scan through the trace buffer manually,
11156 these commands make it easy to construct @value{GDBN} scripts that
11157 scan through the trace buffer and print out whatever collected data
11158 you are interested in. Thus, if we want to examine the PC, FP, and SP
11159 registers from each trace frame in the buffer, we can say this:
11162 (@value{GDBP}) @b{tfind start}
11163 (@value{GDBP}) @b{while ($trace_frame != -1)}
11164 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
11165 $trace_frame, $pc, $sp, $fp
11169 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
11170 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
11171 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
11172 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
11173 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
11174 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
11175 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
11176 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
11177 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
11178 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
11179 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
11182 Or, if we want to examine the variable @code{X} at each source line in
11186 (@value{GDBP}) @b{tfind start}
11187 (@value{GDBP}) @b{while ($trace_frame != -1)}
11188 > printf "Frame %d, X == %d\n", $trace_frame, X
11198 @subsection @code{tdump}
11200 @cindex dump all data collected at tracepoint
11201 @cindex tracepoint data, display
11203 This command takes no arguments. It prints all the data collected at
11204 the current trace snapshot.
11207 (@value{GDBP}) @b{trace 444}
11208 (@value{GDBP}) @b{actions}
11209 Enter actions for tracepoint #2, one per line:
11210 > collect $regs, $locals, $args, gdb_long_test
11213 (@value{GDBP}) @b{tstart}
11215 (@value{GDBP}) @b{tfind line 444}
11216 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
11218 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
11220 (@value{GDBP}) @b{tdump}
11221 Data collected at tracepoint 2, trace frame 1:
11222 d0 0xc4aa0085 -995491707
11226 d4 0x71aea3d 119204413
11229 d7 0x380035 3670069
11230 a0 0x19e24a 1696330
11231 a1 0x3000668 50333288
11233 a3 0x322000 3284992
11234 a4 0x3000698 50333336
11235 a5 0x1ad3cc 1758156
11236 fp 0x30bf3c 0x30bf3c
11237 sp 0x30bf34 0x30bf34
11239 pc 0x20b2c8 0x20b2c8
11243 p = 0x20e5b4 "gdb-test"
11250 gdb_long_test = 17 '\021'
11255 @code{tdump} works by scanning the tracepoint's current collection
11256 actions and printing the value of each expression listed. So
11257 @code{tdump} can fail, if after a run, you change the tracepoint's
11258 actions to mention variables that were not collected during the run.
11260 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
11261 uses the collected value of @code{$pc} to distinguish between trace
11262 frames that were collected at the tracepoint hit, and frames that were
11263 collected while stepping. This allows it to correctly choose whether
11264 to display the basic list of collections, or the collections from the
11265 body of the while-stepping loop. However, if @code{$pc} was not collected,
11266 then @code{tdump} will always attempt to dump using the basic collection
11267 list, and may fail if a while-stepping frame does not include all the
11268 same data that is collected at the tracepoint hit.
11269 @c This is getting pretty arcane, example would be good.
11271 @node save tracepoints
11272 @subsection @code{save tracepoints @var{filename}}
11273 @kindex save tracepoints
11274 @kindex save-tracepoints
11275 @cindex save tracepoints for future sessions
11277 This command saves all current tracepoint definitions together with
11278 their actions and passcounts, into a file @file{@var{filename}}
11279 suitable for use in a later debugging session. To read the saved
11280 tracepoint definitions, use the @code{source} command (@pxref{Command
11281 Files}). The @w{@code{save-tracepoints}} command is a deprecated
11282 alias for @w{@code{save tracepoints}}
11284 @node Tracepoint Variables
11285 @section Convenience Variables for Tracepoints
11286 @cindex tracepoint variables
11287 @cindex convenience variables for tracepoints
11290 @vindex $trace_frame
11291 @item (int) $trace_frame
11292 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
11293 snapshot is selected.
11295 @vindex $tracepoint
11296 @item (int) $tracepoint
11297 The tracepoint for the current trace snapshot.
11299 @vindex $trace_line
11300 @item (int) $trace_line
11301 The line number for the current trace snapshot.
11303 @vindex $trace_file
11304 @item (char []) $trace_file
11305 The source file for the current trace snapshot.
11307 @vindex $trace_func
11308 @item (char []) $trace_func
11309 The name of the function containing @code{$tracepoint}.
11312 Note: @code{$trace_file} is not suitable for use in @code{printf},
11313 use @code{output} instead.
11315 Here's a simple example of using these convenience variables for
11316 stepping through all the trace snapshots and printing some of their
11317 data. Note that these are not the same as trace state variables,
11318 which are managed by the target.
11321 (@value{GDBP}) @b{tfind start}
11323 (@value{GDBP}) @b{while $trace_frame != -1}
11324 > output $trace_file
11325 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
11331 @section Using Trace Files
11332 @cindex trace files
11334 In some situations, the target running a trace experiment may no
11335 longer be available; perhaps it crashed, or the hardware was needed
11336 for a different activity. To handle these cases, you can arrange to
11337 dump the trace data into a file, and later use that file as a source
11338 of trace data, via the @code{target tfile} command.
11343 @item tsave [ -r ] @var{filename}
11344 Save the trace data to @var{filename}. By default, this command
11345 assumes that @var{filename} refers to the host filesystem, so if
11346 necessary @value{GDBN} will copy raw trace data up from the target and
11347 then save it. If the target supports it, you can also supply the
11348 optional argument @code{-r} (``remote'') to direct the target to save
11349 the data directly into @var{filename} in its own filesystem, which may be
11350 more efficient if the trace buffer is very large. (Note, however, that
11351 @code{target tfile} can only read from files accessible to the host.)
11353 @kindex target tfile
11355 @item target tfile @var{filename}
11356 Use the file named @var{filename} as a source of trace data. Commands
11357 that examine data work as they do with a live target, but it is not
11358 possible to run any new trace experiments. @code{tstatus} will report
11359 the state of the trace run at the moment the data was saved, as well
11360 as the current trace frame you are examining. @var{filename} must be
11361 on a filesystem accessible to the host.
11366 @chapter Debugging Programs That Use Overlays
11369 If your program is too large to fit completely in your target system's
11370 memory, you can sometimes use @dfn{overlays} to work around this
11371 problem. @value{GDBN} provides some support for debugging programs that
11375 * How Overlays Work:: A general explanation of overlays.
11376 * Overlay Commands:: Managing overlays in @value{GDBN}.
11377 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
11378 mapped by asking the inferior.
11379 * Overlay Sample Program:: A sample program using overlays.
11382 @node How Overlays Work
11383 @section How Overlays Work
11384 @cindex mapped overlays
11385 @cindex unmapped overlays
11386 @cindex load address, overlay's
11387 @cindex mapped address
11388 @cindex overlay area
11390 Suppose you have a computer whose instruction address space is only 64
11391 kilobytes long, but which has much more memory which can be accessed by
11392 other means: special instructions, segment registers, or memory
11393 management hardware, for example. Suppose further that you want to
11394 adapt a program which is larger than 64 kilobytes to run on this system.
11396 One solution is to identify modules of your program which are relatively
11397 independent, and need not call each other directly; call these modules
11398 @dfn{overlays}. Separate the overlays from the main program, and place
11399 their machine code in the larger memory. Place your main program in
11400 instruction memory, but leave at least enough space there to hold the
11401 largest overlay as well.
11403 Now, to call a function located in an overlay, you must first copy that
11404 overlay's machine code from the large memory into the space set aside
11405 for it in the instruction memory, and then jump to its entry point
11408 @c NB: In the below the mapped area's size is greater or equal to the
11409 @c size of all overlays. This is intentional to remind the developer
11410 @c that overlays don't necessarily need to be the same size.
11414 Data Instruction Larger
11415 Address Space Address Space Address Space
11416 +-----------+ +-----------+ +-----------+
11418 +-----------+ +-----------+ +-----------+<-- overlay 1
11419 | program | | main | .----| overlay 1 | load address
11420 | variables | | program | | +-----------+
11421 | and heap | | | | | |
11422 +-----------+ | | | +-----------+<-- overlay 2
11423 | | +-----------+ | | | load address
11424 +-----------+ | | | .-| overlay 2 |
11426 mapped --->+-----------+ | | +-----------+
11427 address | | | | | |
11428 | overlay | <-' | | |
11429 | area | <---' +-----------+<-- overlay 3
11430 | | <---. | | load address
11431 +-----------+ `--| overlay 3 |
11438 @anchor{A code overlay}A code overlay
11442 The diagram (@pxref{A code overlay}) shows a system with separate data
11443 and instruction address spaces. To map an overlay, the program copies
11444 its code from the larger address space to the instruction address space.
11445 Since the overlays shown here all use the same mapped address, only one
11446 may be mapped at a time. For a system with a single address space for
11447 data and instructions, the diagram would be similar, except that the
11448 program variables and heap would share an address space with the main
11449 program and the overlay area.
11451 An overlay loaded into instruction memory and ready for use is called a
11452 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
11453 instruction memory. An overlay not present (or only partially present)
11454 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
11455 is its address in the larger memory. The mapped address is also called
11456 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
11457 called the @dfn{load memory address}, or @dfn{LMA}.
11459 Unfortunately, overlays are not a completely transparent way to adapt a
11460 program to limited instruction memory. They introduce a new set of
11461 global constraints you must keep in mind as you design your program:
11466 Before calling or returning to a function in an overlay, your program
11467 must make sure that overlay is actually mapped. Otherwise, the call or
11468 return will transfer control to the right address, but in the wrong
11469 overlay, and your program will probably crash.
11472 If the process of mapping an overlay is expensive on your system, you
11473 will need to choose your overlays carefully to minimize their effect on
11474 your program's performance.
11477 The executable file you load onto your system must contain each
11478 overlay's instructions, appearing at the overlay's load address, not its
11479 mapped address. However, each overlay's instructions must be relocated
11480 and its symbols defined as if the overlay were at its mapped address.
11481 You can use GNU linker scripts to specify different load and relocation
11482 addresses for pieces of your program; see @ref{Overlay Description,,,
11483 ld.info, Using ld: the GNU linker}.
11486 The procedure for loading executable files onto your system must be able
11487 to load their contents into the larger address space as well as the
11488 instruction and data spaces.
11492 The overlay system described above is rather simple, and could be
11493 improved in many ways:
11498 If your system has suitable bank switch registers or memory management
11499 hardware, you could use those facilities to make an overlay's load area
11500 contents simply appear at their mapped address in instruction space.
11501 This would probably be faster than copying the overlay to its mapped
11502 area in the usual way.
11505 If your overlays are small enough, you could set aside more than one
11506 overlay area, and have more than one overlay mapped at a time.
11509 You can use overlays to manage data, as well as instructions. In
11510 general, data overlays are even less transparent to your design than
11511 code overlays: whereas code overlays only require care when you call or
11512 return to functions, data overlays require care every time you access
11513 the data. Also, if you change the contents of a data overlay, you
11514 must copy its contents back out to its load address before you can copy a
11515 different data overlay into the same mapped area.
11520 @node Overlay Commands
11521 @section Overlay Commands
11523 To use @value{GDBN}'s overlay support, each overlay in your program must
11524 correspond to a separate section of the executable file. The section's
11525 virtual memory address and load memory address must be the overlay's
11526 mapped and load addresses. Identifying overlays with sections allows
11527 @value{GDBN} to determine the appropriate address of a function or
11528 variable, depending on whether the overlay is mapped or not.
11530 @value{GDBN}'s overlay commands all start with the word @code{overlay};
11531 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
11536 Disable @value{GDBN}'s overlay support. When overlay support is
11537 disabled, @value{GDBN} assumes that all functions and variables are
11538 always present at their mapped addresses. By default, @value{GDBN}'s
11539 overlay support is disabled.
11541 @item overlay manual
11542 @cindex manual overlay debugging
11543 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
11544 relies on you to tell it which overlays are mapped, and which are not,
11545 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
11546 commands described below.
11548 @item overlay map-overlay @var{overlay}
11549 @itemx overlay map @var{overlay}
11550 @cindex map an overlay
11551 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
11552 be the name of the object file section containing the overlay. When an
11553 overlay is mapped, @value{GDBN} assumes it can find the overlay's
11554 functions and variables at their mapped addresses. @value{GDBN} assumes
11555 that any other overlays whose mapped ranges overlap that of
11556 @var{overlay} are now unmapped.
11558 @item overlay unmap-overlay @var{overlay}
11559 @itemx overlay unmap @var{overlay}
11560 @cindex unmap an overlay
11561 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
11562 must be the name of the object file section containing the overlay.
11563 When an overlay is unmapped, @value{GDBN} assumes it can find the
11564 overlay's functions and variables at their load addresses.
11567 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
11568 consults a data structure the overlay manager maintains in the inferior
11569 to see which overlays are mapped. For details, see @ref{Automatic
11570 Overlay Debugging}.
11572 @item overlay load-target
11573 @itemx overlay load
11574 @cindex reloading the overlay table
11575 Re-read the overlay table from the inferior. Normally, @value{GDBN}
11576 re-reads the table @value{GDBN} automatically each time the inferior
11577 stops, so this command should only be necessary if you have changed the
11578 overlay mapping yourself using @value{GDBN}. This command is only
11579 useful when using automatic overlay debugging.
11581 @item overlay list-overlays
11582 @itemx overlay list
11583 @cindex listing mapped overlays
11584 Display a list of the overlays currently mapped, along with their mapped
11585 addresses, load addresses, and sizes.
11589 Normally, when @value{GDBN} prints a code address, it includes the name
11590 of the function the address falls in:
11593 (@value{GDBP}) print main
11594 $3 = @{int ()@} 0x11a0 <main>
11597 When overlay debugging is enabled, @value{GDBN} recognizes code in
11598 unmapped overlays, and prints the names of unmapped functions with
11599 asterisks around them. For example, if @code{foo} is a function in an
11600 unmapped overlay, @value{GDBN} prints it this way:
11603 (@value{GDBP}) overlay list
11604 No sections are mapped.
11605 (@value{GDBP}) print foo
11606 $5 = @{int (int)@} 0x100000 <*foo*>
11609 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
11613 (@value{GDBP}) overlay list
11614 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
11615 mapped at 0x1016 - 0x104a
11616 (@value{GDBP}) print foo
11617 $6 = @{int (int)@} 0x1016 <foo>
11620 When overlay debugging is enabled, @value{GDBN} can find the correct
11621 address for functions and variables in an overlay, whether or not the
11622 overlay is mapped. This allows most @value{GDBN} commands, like
11623 @code{break} and @code{disassemble}, to work normally, even on unmapped
11624 code. However, @value{GDBN}'s breakpoint support has some limitations:
11628 @cindex breakpoints in overlays
11629 @cindex overlays, setting breakpoints in
11630 You can set breakpoints in functions in unmapped overlays, as long as
11631 @value{GDBN} can write to the overlay at its load address.
11633 @value{GDBN} can not set hardware or simulator-based breakpoints in
11634 unmapped overlays. However, if you set a breakpoint at the end of your
11635 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
11636 you are using manual overlay management), @value{GDBN} will re-set its
11637 breakpoints properly.
11641 @node Automatic Overlay Debugging
11642 @section Automatic Overlay Debugging
11643 @cindex automatic overlay debugging
11645 @value{GDBN} can automatically track which overlays are mapped and which
11646 are not, given some simple co-operation from the overlay manager in the
11647 inferior. If you enable automatic overlay debugging with the
11648 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
11649 looks in the inferior's memory for certain variables describing the
11650 current state of the overlays.
11652 Here are the variables your overlay manager must define to support
11653 @value{GDBN}'s automatic overlay debugging:
11657 @item @code{_ovly_table}:
11658 This variable must be an array of the following structures:
11663 /* The overlay's mapped address. */
11666 /* The size of the overlay, in bytes. */
11667 unsigned long size;
11669 /* The overlay's load address. */
11672 /* Non-zero if the overlay is currently mapped;
11674 unsigned long mapped;
11678 @item @code{_novlys}:
11679 This variable must be a four-byte signed integer, holding the total
11680 number of elements in @code{_ovly_table}.
11684 To decide whether a particular overlay is mapped or not, @value{GDBN}
11685 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
11686 @code{lma} members equal the VMA and LMA of the overlay's section in the
11687 executable file. When @value{GDBN} finds a matching entry, it consults
11688 the entry's @code{mapped} member to determine whether the overlay is
11691 In addition, your overlay manager may define a function called
11692 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
11693 will silently set a breakpoint there. If the overlay manager then
11694 calls this function whenever it has changed the overlay table, this
11695 will enable @value{GDBN} to accurately keep track of which overlays
11696 are in program memory, and update any breakpoints that may be set
11697 in overlays. This will allow breakpoints to work even if the
11698 overlays are kept in ROM or other non-writable memory while they
11699 are not being executed.
11701 @node Overlay Sample Program
11702 @section Overlay Sample Program
11703 @cindex overlay example program
11705 When linking a program which uses overlays, you must place the overlays
11706 at their load addresses, while relocating them to run at their mapped
11707 addresses. To do this, you must write a linker script (@pxref{Overlay
11708 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
11709 since linker scripts are specific to a particular host system, target
11710 architecture, and target memory layout, this manual cannot provide
11711 portable sample code demonstrating @value{GDBN}'s overlay support.
11713 However, the @value{GDBN} source distribution does contain an overlaid
11714 program, with linker scripts for a few systems, as part of its test
11715 suite. The program consists of the following files from
11716 @file{gdb/testsuite/gdb.base}:
11720 The main program file.
11722 A simple overlay manager, used by @file{overlays.c}.
11727 Overlay modules, loaded and used by @file{overlays.c}.
11730 Linker scripts for linking the test program on the @code{d10v-elf}
11731 and @code{m32r-elf} targets.
11734 You can build the test program using the @code{d10v-elf} GCC
11735 cross-compiler like this:
11738 $ d10v-elf-gcc -g -c overlays.c
11739 $ d10v-elf-gcc -g -c ovlymgr.c
11740 $ d10v-elf-gcc -g -c foo.c
11741 $ d10v-elf-gcc -g -c bar.c
11742 $ d10v-elf-gcc -g -c baz.c
11743 $ d10v-elf-gcc -g -c grbx.c
11744 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
11745 baz.o grbx.o -Wl,-Td10v.ld -o overlays
11748 The build process is identical for any other architecture, except that
11749 you must substitute the appropriate compiler and linker script for the
11750 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
11754 @chapter Using @value{GDBN} with Different Languages
11757 Although programming languages generally have common aspects, they are
11758 rarely expressed in the same manner. For instance, in ANSI C,
11759 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
11760 Modula-2, it is accomplished by @code{p^}. Values can also be
11761 represented (and displayed) differently. Hex numbers in C appear as
11762 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
11764 @cindex working language
11765 Language-specific information is built into @value{GDBN} for some languages,
11766 allowing you to express operations like the above in your program's
11767 native language, and allowing @value{GDBN} to output values in a manner
11768 consistent with the syntax of your program's native language. The
11769 language you use to build expressions is called the @dfn{working
11773 * Setting:: Switching between source languages
11774 * Show:: Displaying the language
11775 * Checks:: Type and range checks
11776 * Supported Languages:: Supported languages
11777 * Unsupported Languages:: Unsupported languages
11781 @section Switching Between Source Languages
11783 There are two ways to control the working language---either have @value{GDBN}
11784 set it automatically, or select it manually yourself. You can use the
11785 @code{set language} command for either purpose. On startup, @value{GDBN}
11786 defaults to setting the language automatically. The working language is
11787 used to determine how expressions you type are interpreted, how values
11790 In addition to the working language, every source file that
11791 @value{GDBN} knows about has its own working language. For some object
11792 file formats, the compiler might indicate which language a particular
11793 source file is in. However, most of the time @value{GDBN} infers the
11794 language from the name of the file. The language of a source file
11795 controls whether C@t{++} names are demangled---this way @code{backtrace} can
11796 show each frame appropriately for its own language. There is no way to
11797 set the language of a source file from within @value{GDBN}, but you can
11798 set the language associated with a filename extension. @xref{Show, ,
11799 Displaying the Language}.
11801 This is most commonly a problem when you use a program, such
11802 as @code{cfront} or @code{f2c}, that generates C but is written in
11803 another language. In that case, make the
11804 program use @code{#line} directives in its C output; that way
11805 @value{GDBN} will know the correct language of the source code of the original
11806 program, and will display that source code, not the generated C code.
11809 * Filenames:: Filename extensions and languages.
11810 * Manually:: Setting the working language manually
11811 * Automatically:: Having @value{GDBN} infer the source language
11815 @subsection List of Filename Extensions and Languages
11817 If a source file name ends in one of the following extensions, then
11818 @value{GDBN} infers that its language is the one indicated.
11836 C@t{++} source file
11842 Objective-C source file
11846 Fortran source file
11849 Modula-2 source file
11853 Assembler source file. This actually behaves almost like C, but
11854 @value{GDBN} does not skip over function prologues when stepping.
11857 In addition, you may set the language associated with a filename
11858 extension. @xref{Show, , Displaying the Language}.
11861 @subsection Setting the Working Language
11863 If you allow @value{GDBN} to set the language automatically,
11864 expressions are interpreted the same way in your debugging session and
11867 @kindex set language
11868 If you wish, you may set the language manually. To do this, issue the
11869 command @samp{set language @var{lang}}, where @var{lang} is the name of
11870 a language, such as
11871 @code{c} or @code{modula-2}.
11872 For a list of the supported languages, type @samp{set language}.
11874 Setting the language manually prevents @value{GDBN} from updating the working
11875 language automatically. This can lead to confusion if you try
11876 to debug a program when the working language is not the same as the
11877 source language, when an expression is acceptable to both
11878 languages---but means different things. For instance, if the current
11879 source file were written in C, and @value{GDBN} was parsing Modula-2, a
11887 might not have the effect you intended. In C, this means to add
11888 @code{b} and @code{c} and place the result in @code{a}. The result
11889 printed would be the value of @code{a}. In Modula-2, this means to compare
11890 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
11892 @node Automatically
11893 @subsection Having @value{GDBN} Infer the Source Language
11895 To have @value{GDBN} set the working language automatically, use
11896 @samp{set language local} or @samp{set language auto}. @value{GDBN}
11897 then infers the working language. That is, when your program stops in a
11898 frame (usually by encountering a breakpoint), @value{GDBN} sets the
11899 working language to the language recorded for the function in that
11900 frame. If the language for a frame is unknown (that is, if the function
11901 or block corresponding to the frame was defined in a source file that
11902 does not have a recognized extension), the current working language is
11903 not changed, and @value{GDBN} issues a warning.
11905 This may not seem necessary for most programs, which are written
11906 entirely in one source language. However, program modules and libraries
11907 written in one source language can be used by a main program written in
11908 a different source language. Using @samp{set language auto} in this
11909 case frees you from having to set the working language manually.
11912 @section Displaying the Language
11914 The following commands help you find out which language is the
11915 working language, and also what language source files were written in.
11918 @item show language
11919 @kindex show language
11920 Display the current working language. This is the
11921 language you can use with commands such as @code{print} to
11922 build and compute expressions that may involve variables in your program.
11925 @kindex info frame@r{, show the source language}
11926 Display the source language for this frame. This language becomes the
11927 working language if you use an identifier from this frame.
11928 @xref{Frame Info, ,Information about a Frame}, to identify the other
11929 information listed here.
11932 @kindex info source@r{, show the source language}
11933 Display the source language of this source file.
11934 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
11935 information listed here.
11938 In unusual circumstances, you may have source files with extensions
11939 not in the standard list. You can then set the extension associated
11940 with a language explicitly:
11943 @item set extension-language @var{ext} @var{language}
11944 @kindex set extension-language
11945 Tell @value{GDBN} that source files with extension @var{ext} are to be
11946 assumed as written in the source language @var{language}.
11948 @item info extensions
11949 @kindex info extensions
11950 List all the filename extensions and the associated languages.
11954 @section Type and Range Checking
11957 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
11958 checking are included, but they do not yet have any effect. This
11959 section documents the intended facilities.
11961 @c FIXME remove warning when type/range code added
11963 Some languages are designed to guard you against making seemingly common
11964 errors through a series of compile- and run-time checks. These include
11965 checking the type of arguments to functions and operators, and making
11966 sure mathematical overflows are caught at run time. Checks such as
11967 these help to ensure a program's correctness once it has been compiled
11968 by eliminating type mismatches, and providing active checks for range
11969 errors when your program is running.
11971 @value{GDBN} can check for conditions like the above if you wish.
11972 Although @value{GDBN} does not check the statements in your program,
11973 it can check expressions entered directly into @value{GDBN} for
11974 evaluation via the @code{print} command, for example. As with the
11975 working language, @value{GDBN} can also decide whether or not to check
11976 automatically based on your program's source language.
11977 @xref{Supported Languages, ,Supported Languages}, for the default
11978 settings of supported languages.
11981 * Type Checking:: An overview of type checking
11982 * Range Checking:: An overview of range checking
11985 @cindex type checking
11986 @cindex checks, type
11987 @node Type Checking
11988 @subsection An Overview of Type Checking
11990 Some languages, such as Modula-2, are strongly typed, meaning that the
11991 arguments to operators and functions have to be of the correct type,
11992 otherwise an error occurs. These checks prevent type mismatch
11993 errors from ever causing any run-time problems. For example,
12001 The second example fails because the @code{CARDINAL} 1 is not
12002 type-compatible with the @code{REAL} 2.3.
12004 For the expressions you use in @value{GDBN} commands, you can tell the
12005 @value{GDBN} type checker to skip checking;
12006 to treat any mismatches as errors and abandon the expression;
12007 or to only issue warnings when type mismatches occur,
12008 but evaluate the expression anyway. When you choose the last of
12009 these, @value{GDBN} evaluates expressions like the second example above, but
12010 also issues a warning.
12012 Even if you turn type checking off, there may be other reasons
12013 related to type that prevent @value{GDBN} from evaluating an expression.
12014 For instance, @value{GDBN} does not know how to add an @code{int} and
12015 a @code{struct foo}. These particular type errors have nothing to do
12016 with the language in use, and usually arise from expressions, such as
12017 the one described above, which make little sense to evaluate anyway.
12019 Each language defines to what degree it is strict about type. For
12020 instance, both Modula-2 and C require the arguments to arithmetical
12021 operators to be numbers. In C, enumerated types and pointers can be
12022 represented as numbers, so that they are valid arguments to mathematical
12023 operators. @xref{Supported Languages, ,Supported Languages}, for further
12024 details on specific languages.
12026 @value{GDBN} provides some additional commands for controlling the type checker:
12028 @kindex set check type
12029 @kindex show check type
12031 @item set check type auto
12032 Set type checking on or off based on the current working language.
12033 @xref{Supported Languages, ,Supported Languages}, for the default settings for
12036 @item set check type on
12037 @itemx set check type off
12038 Set type checking on or off, overriding the default setting for the
12039 current working language. Issue a warning if the setting does not
12040 match the language default. If any type mismatches occur in
12041 evaluating an expression while type checking is on, @value{GDBN} prints a
12042 message and aborts evaluation of the expression.
12044 @item set check type warn
12045 Cause the type checker to issue warnings, but to always attempt to
12046 evaluate the expression. Evaluating the expression may still
12047 be impossible for other reasons. For example, @value{GDBN} cannot add
12048 numbers and structures.
12051 Show the current setting of the type checker, and whether or not @value{GDBN}
12052 is setting it automatically.
12055 @cindex range checking
12056 @cindex checks, range
12057 @node Range Checking
12058 @subsection An Overview of Range Checking
12060 In some languages (such as Modula-2), it is an error to exceed the
12061 bounds of a type; this is enforced with run-time checks. Such range
12062 checking is meant to ensure program correctness by making sure
12063 computations do not overflow, or indices on an array element access do
12064 not exceed the bounds of the array.
12066 For expressions you use in @value{GDBN} commands, you can tell
12067 @value{GDBN} to treat range errors in one of three ways: ignore them,
12068 always treat them as errors and abandon the expression, or issue
12069 warnings but evaluate the expression anyway.
12071 A range error can result from numerical overflow, from exceeding an
12072 array index bound, or when you type a constant that is not a member
12073 of any type. Some languages, however, do not treat overflows as an
12074 error. In many implementations of C, mathematical overflow causes the
12075 result to ``wrap around'' to lower values---for example, if @var{m} is
12076 the largest integer value, and @var{s} is the smallest, then
12079 @var{m} + 1 @result{} @var{s}
12082 This, too, is specific to individual languages, and in some cases
12083 specific to individual compilers or machines. @xref{Supported Languages, ,
12084 Supported Languages}, for further details on specific languages.
12086 @value{GDBN} provides some additional commands for controlling the range checker:
12088 @kindex set check range
12089 @kindex show check range
12091 @item set check range auto
12092 Set range checking on or off based on the current working language.
12093 @xref{Supported Languages, ,Supported Languages}, for the default settings for
12096 @item set check range on
12097 @itemx set check range off
12098 Set range checking on or off, overriding the default setting for the
12099 current working language. A warning is issued if the setting does not
12100 match the language default. If a range error occurs and range checking is on,
12101 then a message is printed and evaluation of the expression is aborted.
12103 @item set check range warn
12104 Output messages when the @value{GDBN} range checker detects a range error,
12105 but attempt to evaluate the expression anyway. Evaluating the
12106 expression may still be impossible for other reasons, such as accessing
12107 memory that the process does not own (a typical example from many Unix
12111 Show the current setting of the range checker, and whether or not it is
12112 being set automatically by @value{GDBN}.
12115 @node Supported Languages
12116 @section Supported Languages
12118 @value{GDBN} supports C, C@t{++}, D, Objective-C, Fortran, Java, OpenCL C, Pascal,
12119 assembly, Modula-2, and Ada.
12120 @c This is false ...
12121 Some @value{GDBN} features may be used in expressions regardless of the
12122 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
12123 and the @samp{@{type@}addr} construct (@pxref{Expressions,
12124 ,Expressions}) can be used with the constructs of any supported
12127 The following sections detail to what degree each source language is
12128 supported by @value{GDBN}. These sections are not meant to be language
12129 tutorials or references, but serve only as a reference guide to what the
12130 @value{GDBN} expression parser accepts, and what input and output
12131 formats should look like for different languages. There are many good
12132 books written on each of these languages; please look to these for a
12133 language reference or tutorial.
12136 * C:: C and C@t{++}
12138 * Objective-C:: Objective-C
12139 * OpenCL C:: OpenCL C
12140 * Fortran:: Fortran
12142 * Modula-2:: Modula-2
12147 @subsection C and C@t{++}
12149 @cindex C and C@t{++}
12150 @cindex expressions in C or C@t{++}
12152 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
12153 to both languages. Whenever this is the case, we discuss those languages
12157 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
12158 @cindex @sc{gnu} C@t{++}
12159 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
12160 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
12161 effectively, you must compile your C@t{++} programs with a supported
12162 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
12163 compiler (@code{aCC}).
12165 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
12166 format; if it doesn't work on your system, try the stabs+ debugging
12167 format. You can select those formats explicitly with the @code{g++}
12168 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
12169 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
12170 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
12173 * C Operators:: C and C@t{++} operators
12174 * C Constants:: C and C@t{++} constants
12175 * C Plus Plus Expressions:: C@t{++} expressions
12176 * C Defaults:: Default settings for C and C@t{++}
12177 * C Checks:: C and C@t{++} type and range checks
12178 * Debugging C:: @value{GDBN} and C
12179 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
12180 * Decimal Floating Point:: Numbers in Decimal Floating Point format
12184 @subsubsection C and C@t{++} Operators
12186 @cindex C and C@t{++} operators
12188 Operators must be defined on values of specific types. For instance,
12189 @code{+} is defined on numbers, but not on structures. Operators are
12190 often defined on groups of types.
12192 For the purposes of C and C@t{++}, the following definitions hold:
12197 @emph{Integral types} include @code{int} with any of its storage-class
12198 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
12201 @emph{Floating-point types} include @code{float}, @code{double}, and
12202 @code{long double} (if supported by the target platform).
12205 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
12208 @emph{Scalar types} include all of the above.
12213 The following operators are supported. They are listed here
12214 in order of increasing precedence:
12218 The comma or sequencing operator. Expressions in a comma-separated list
12219 are evaluated from left to right, with the result of the entire
12220 expression being the last expression evaluated.
12223 Assignment. The value of an assignment expression is the value
12224 assigned. Defined on scalar types.
12227 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
12228 and translated to @w{@code{@var{a} = @var{a op b}}}.
12229 @w{@code{@var{op}=}} and @code{=} have the same precedence.
12230 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
12231 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
12234 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
12235 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
12239 Logical @sc{or}. Defined on integral types.
12242 Logical @sc{and}. Defined on integral types.
12245 Bitwise @sc{or}. Defined on integral types.
12248 Bitwise exclusive-@sc{or}. Defined on integral types.
12251 Bitwise @sc{and}. Defined on integral types.
12254 Equality and inequality. Defined on scalar types. The value of these
12255 expressions is 0 for false and non-zero for true.
12257 @item <@r{, }>@r{, }<=@r{, }>=
12258 Less than, greater than, less than or equal, greater than or equal.
12259 Defined on scalar types. The value of these expressions is 0 for false
12260 and non-zero for true.
12263 left shift, and right shift. Defined on integral types.
12266 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12269 Addition and subtraction. Defined on integral types, floating-point types and
12272 @item *@r{, }/@r{, }%
12273 Multiplication, division, and modulus. Multiplication and division are
12274 defined on integral and floating-point types. Modulus is defined on
12278 Increment and decrement. When appearing before a variable, the
12279 operation is performed before the variable is used in an expression;
12280 when appearing after it, the variable's value is used before the
12281 operation takes place.
12284 Pointer dereferencing. Defined on pointer types. Same precedence as
12288 Address operator. Defined on variables. Same precedence as @code{++}.
12290 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
12291 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
12292 to examine the address
12293 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
12297 Negative. Defined on integral and floating-point types. Same
12298 precedence as @code{++}.
12301 Logical negation. Defined on integral types. Same precedence as
12305 Bitwise complement operator. Defined on integral types. Same precedence as
12310 Structure member, and pointer-to-structure member. For convenience,
12311 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
12312 pointer based on the stored type information.
12313 Defined on @code{struct} and @code{union} data.
12316 Dereferences of pointers to members.
12319 Array indexing. @code{@var{a}[@var{i}]} is defined as
12320 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
12323 Function parameter list. Same precedence as @code{->}.
12326 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
12327 and @code{class} types.
12330 Doubled colons also represent the @value{GDBN} scope operator
12331 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
12335 If an operator is redefined in the user code, @value{GDBN} usually
12336 attempts to invoke the redefined version instead of using the operator's
12337 predefined meaning.
12340 @subsubsection C and C@t{++} Constants
12342 @cindex C and C@t{++} constants
12344 @value{GDBN} allows you to express the constants of C and C@t{++} in the
12349 Integer constants are a sequence of digits. Octal constants are
12350 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
12351 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
12352 @samp{l}, specifying that the constant should be treated as a
12356 Floating point constants are a sequence of digits, followed by a decimal
12357 point, followed by a sequence of digits, and optionally followed by an
12358 exponent. An exponent is of the form:
12359 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
12360 sequence of digits. The @samp{+} is optional for positive exponents.
12361 A floating-point constant may also end with a letter @samp{f} or
12362 @samp{F}, specifying that the constant should be treated as being of
12363 the @code{float} (as opposed to the default @code{double}) type; or with
12364 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
12368 Enumerated constants consist of enumerated identifiers, or their
12369 integral equivalents.
12372 Character constants are a single character surrounded by single quotes
12373 (@code{'}), or a number---the ordinal value of the corresponding character
12374 (usually its @sc{ascii} value). Within quotes, the single character may
12375 be represented by a letter or by @dfn{escape sequences}, which are of
12376 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
12377 of the character's ordinal value; or of the form @samp{\@var{x}}, where
12378 @samp{@var{x}} is a predefined special character---for example,
12379 @samp{\n} for newline.
12382 String constants are a sequence of character constants surrounded by
12383 double quotes (@code{"}). Any valid character constant (as described
12384 above) may appear. Double quotes within the string must be preceded by
12385 a backslash, so for instance @samp{"a\"b'c"} is a string of five
12389 Pointer constants are an integral value. You can also write pointers
12390 to constants using the C operator @samp{&}.
12393 Array constants are comma-separated lists surrounded by braces @samp{@{}
12394 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
12395 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
12396 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
12399 @node C Plus Plus Expressions
12400 @subsubsection C@t{++} Expressions
12402 @cindex expressions in C@t{++}
12403 @value{GDBN} expression handling can interpret most C@t{++} expressions.
12405 @cindex debugging C@t{++} programs
12406 @cindex C@t{++} compilers
12407 @cindex debug formats and C@t{++}
12408 @cindex @value{NGCC} and C@t{++}
12410 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
12411 proper compiler and the proper debug format. Currently, @value{GDBN}
12412 works best when debugging C@t{++} code that is compiled with
12413 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
12414 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
12415 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
12416 stabs+ as their default debug format, so you usually don't need to
12417 specify a debug format explicitly. Other compilers and/or debug formats
12418 are likely to work badly or not at all when using @value{GDBN} to debug
12424 @cindex member functions
12426 Member function calls are allowed; you can use expressions like
12429 count = aml->GetOriginal(x, y)
12432 @vindex this@r{, inside C@t{++} member functions}
12433 @cindex namespace in C@t{++}
12435 While a member function is active (in the selected stack frame), your
12436 expressions have the same namespace available as the member function;
12437 that is, @value{GDBN} allows implicit references to the class instance
12438 pointer @code{this} following the same rules as C@t{++}.
12440 @cindex call overloaded functions
12441 @cindex overloaded functions, calling
12442 @cindex type conversions in C@t{++}
12444 You can call overloaded functions; @value{GDBN} resolves the function
12445 call to the right definition, with some restrictions. @value{GDBN} does not
12446 perform overload resolution involving user-defined type conversions,
12447 calls to constructors, or instantiations of templates that do not exist
12448 in the program. It also cannot handle ellipsis argument lists or
12451 It does perform integral conversions and promotions, floating-point
12452 promotions, arithmetic conversions, pointer conversions, conversions of
12453 class objects to base classes, and standard conversions such as those of
12454 functions or arrays to pointers; it requires an exact match on the
12455 number of function arguments.
12457 Overload resolution is always performed, unless you have specified
12458 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
12459 ,@value{GDBN} Features for C@t{++}}.
12461 You must specify @code{set overload-resolution off} in order to use an
12462 explicit function signature to call an overloaded function, as in
12464 p 'foo(char,int)'('x', 13)
12467 The @value{GDBN} command-completion facility can simplify this;
12468 see @ref{Completion, ,Command Completion}.
12470 @cindex reference declarations
12472 @value{GDBN} understands variables declared as C@t{++} references; you can use
12473 them in expressions just as you do in C@t{++} source---they are automatically
12476 In the parameter list shown when @value{GDBN} displays a frame, the values of
12477 reference variables are not displayed (unlike other variables); this
12478 avoids clutter, since references are often used for large structures.
12479 The @emph{address} of a reference variable is always shown, unless
12480 you have specified @samp{set print address off}.
12483 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
12484 expressions can use it just as expressions in your program do. Since
12485 one scope may be defined in another, you can use @code{::} repeatedly if
12486 necessary, for example in an expression like
12487 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
12488 resolving name scope by reference to source files, in both C and C@t{++}
12489 debugging (@pxref{Variables, ,Program Variables}).
12492 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
12493 calling virtual functions correctly, printing out virtual bases of
12494 objects, calling functions in a base subobject, casting objects, and
12495 invoking user-defined operators.
12498 @subsubsection C and C@t{++} Defaults
12500 @cindex C and C@t{++} defaults
12502 If you allow @value{GDBN} to set type and range checking automatically, they
12503 both default to @code{off} whenever the working language changes to
12504 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
12505 selects the working language.
12507 If you allow @value{GDBN} to set the language automatically, it
12508 recognizes source files whose names end with @file{.c}, @file{.C}, or
12509 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
12510 these files, it sets the working language to C or C@t{++}.
12511 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
12512 for further details.
12514 @c Type checking is (a) primarily motivated by Modula-2, and (b)
12515 @c unimplemented. If (b) changes, it might make sense to let this node
12516 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
12519 @subsubsection C and C@t{++} Type and Range Checks
12521 @cindex C and C@t{++} checks
12523 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
12524 is not used. However, if you turn type checking on, @value{GDBN}
12525 considers two variables type equivalent if:
12529 The two variables are structured and have the same structure, union, or
12533 The two variables have the same type name, or types that have been
12534 declared equivalent through @code{typedef}.
12537 @c leaving this out because neither J Gilmore nor R Pesch understand it.
12540 The two @code{struct}, @code{union}, or @code{enum} variables are
12541 declared in the same declaration. (Note: this may not be true for all C
12546 Range checking, if turned on, is done on mathematical operations. Array
12547 indices are not checked, since they are often used to index a pointer
12548 that is not itself an array.
12551 @subsubsection @value{GDBN} and C
12553 The @code{set print union} and @code{show print union} commands apply to
12554 the @code{union} type. When set to @samp{on}, any @code{union} that is
12555 inside a @code{struct} or @code{class} is also printed. Otherwise, it
12556 appears as @samp{@{...@}}.
12558 The @code{@@} operator aids in the debugging of dynamic arrays, formed
12559 with pointers and a memory allocation function. @xref{Expressions,
12562 @node Debugging C Plus Plus
12563 @subsubsection @value{GDBN} Features for C@t{++}
12565 @cindex commands for C@t{++}
12567 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
12568 designed specifically for use with C@t{++}. Here is a summary:
12571 @cindex break in overloaded functions
12572 @item @r{breakpoint menus}
12573 When you want a breakpoint in a function whose name is overloaded,
12574 @value{GDBN} has the capability to display a menu of possible breakpoint
12575 locations to help you specify which function definition you want.
12576 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
12578 @cindex overloading in C@t{++}
12579 @item rbreak @var{regex}
12580 Setting breakpoints using regular expressions is helpful for setting
12581 breakpoints on overloaded functions that are not members of any special
12583 @xref{Set Breaks, ,Setting Breakpoints}.
12585 @cindex C@t{++} exception handling
12588 Debug C@t{++} exception handling using these commands. @xref{Set
12589 Catchpoints, , Setting Catchpoints}.
12591 @cindex inheritance
12592 @item ptype @var{typename}
12593 Print inheritance relationships as well as other information for type
12595 @xref{Symbols, ,Examining the Symbol Table}.
12597 @cindex C@t{++} symbol display
12598 @item set print demangle
12599 @itemx show print demangle
12600 @itemx set print asm-demangle
12601 @itemx show print asm-demangle
12602 Control whether C@t{++} symbols display in their source form, both when
12603 displaying code as C@t{++} source and when displaying disassemblies.
12604 @xref{Print Settings, ,Print Settings}.
12606 @item set print object
12607 @itemx show print object
12608 Choose whether to print derived (actual) or declared types of objects.
12609 @xref{Print Settings, ,Print Settings}.
12611 @item set print vtbl
12612 @itemx show print vtbl
12613 Control the format for printing virtual function tables.
12614 @xref{Print Settings, ,Print Settings}.
12615 (The @code{vtbl} commands do not work on programs compiled with the HP
12616 ANSI C@t{++} compiler (@code{aCC}).)
12618 @kindex set overload-resolution
12619 @cindex overloaded functions, overload resolution
12620 @item set overload-resolution on
12621 Enable overload resolution for C@t{++} expression evaluation. The default
12622 is on. For overloaded functions, @value{GDBN} evaluates the arguments
12623 and searches for a function whose signature matches the argument types,
12624 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
12625 Expressions, ,C@t{++} Expressions}, for details).
12626 If it cannot find a match, it emits a message.
12628 @item set overload-resolution off
12629 Disable overload resolution for C@t{++} expression evaluation. For
12630 overloaded functions that are not class member functions, @value{GDBN}
12631 chooses the first function of the specified name that it finds in the
12632 symbol table, whether or not its arguments are of the correct type. For
12633 overloaded functions that are class member functions, @value{GDBN}
12634 searches for a function whose signature @emph{exactly} matches the
12637 @kindex show overload-resolution
12638 @item show overload-resolution
12639 Show the current setting of overload resolution.
12641 @item @r{Overloaded symbol names}
12642 You can specify a particular definition of an overloaded symbol, using
12643 the same notation that is used to declare such symbols in C@t{++}: type
12644 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
12645 also use the @value{GDBN} command-line word completion facilities to list the
12646 available choices, or to finish the type list for you.
12647 @xref{Completion,, Command Completion}, for details on how to do this.
12650 @node Decimal Floating Point
12651 @subsubsection Decimal Floating Point format
12652 @cindex decimal floating point format
12654 @value{GDBN} can examine, set and perform computations with numbers in
12655 decimal floating point format, which in the C language correspond to the
12656 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
12657 specified by the extension to support decimal floating-point arithmetic.
12659 There are two encodings in use, depending on the architecture: BID (Binary
12660 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
12661 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
12664 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
12665 to manipulate decimal floating point numbers, it is not possible to convert
12666 (using a cast, for example) integers wider than 32-bit to decimal float.
12668 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
12669 point computations, error checking in decimal float operations ignores
12670 underflow, overflow and divide by zero exceptions.
12672 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
12673 to inspect @code{_Decimal128} values stored in floating point registers.
12674 See @ref{PowerPC,,PowerPC} for more details.
12680 @value{GDBN} can be used to debug programs written in D and compiled with
12681 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
12682 specific feature --- dynamic arrays.
12685 @subsection Objective-C
12687 @cindex Objective-C
12688 This section provides information about some commands and command
12689 options that are useful for debugging Objective-C code. See also
12690 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
12691 few more commands specific to Objective-C support.
12694 * Method Names in Commands::
12695 * The Print Command with Objective-C::
12698 @node Method Names in Commands
12699 @subsubsection Method Names in Commands
12701 The following commands have been extended to accept Objective-C method
12702 names as line specifications:
12704 @kindex clear@r{, and Objective-C}
12705 @kindex break@r{, and Objective-C}
12706 @kindex info line@r{, and Objective-C}
12707 @kindex jump@r{, and Objective-C}
12708 @kindex list@r{, and Objective-C}
12712 @item @code{info line}
12717 A fully qualified Objective-C method name is specified as
12720 -[@var{Class} @var{methodName}]
12723 where the minus sign is used to indicate an instance method and a
12724 plus sign (not shown) is used to indicate a class method. The class
12725 name @var{Class} and method name @var{methodName} are enclosed in
12726 brackets, similar to the way messages are specified in Objective-C
12727 source code. For example, to set a breakpoint at the @code{create}
12728 instance method of class @code{Fruit} in the program currently being
12732 break -[Fruit create]
12735 To list ten program lines around the @code{initialize} class method,
12739 list +[NSText initialize]
12742 In the current version of @value{GDBN}, the plus or minus sign is
12743 required. In future versions of @value{GDBN}, the plus or minus
12744 sign will be optional, but you can use it to narrow the search. It
12745 is also possible to specify just a method name:
12751 You must specify the complete method name, including any colons. If
12752 your program's source files contain more than one @code{create} method,
12753 you'll be presented with a numbered list of classes that implement that
12754 method. Indicate your choice by number, or type @samp{0} to exit if
12757 As another example, to clear a breakpoint established at the
12758 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
12761 clear -[NSWindow makeKeyAndOrderFront:]
12764 @node The Print Command with Objective-C
12765 @subsubsection The Print Command With Objective-C
12766 @cindex Objective-C, print objects
12767 @kindex print-object
12768 @kindex po @r{(@code{print-object})}
12770 The print command has also been extended to accept methods. For example:
12773 print -[@var{object} hash]
12776 @cindex print an Objective-C object description
12777 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
12779 will tell @value{GDBN} to send the @code{hash} message to @var{object}
12780 and print the result. Also, an additional command has been added,
12781 @code{print-object} or @code{po} for short, which is meant to print
12782 the description of an object. However, this command may only work
12783 with certain Objective-C libraries that have a particular hook
12784 function, @code{_NSPrintForDebugger}, defined.
12787 @subsection OpenCL C
12790 This section provides information about @value{GDBN}s OpenCL C support.
12793 * OpenCL C Datatypes::
12794 * OpenCL C Expressions::
12795 * OpenCL C Operators::
12798 @node OpenCL C Datatypes
12799 @subsubsection OpenCL C Datatypes
12801 @cindex OpenCL C Datatypes
12802 @value{GDBN} supports the builtin scalar and vector datatypes specified
12803 by OpenCL 1.1. In addition the half- and double-precision floating point
12804 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
12805 extensions are also known to @value{GDBN}.
12807 @node OpenCL C Expressions
12808 @subsubsection OpenCL C Expressions
12810 @cindex OpenCL C Expressions
12811 @value{GDBN} supports accesses to vector components including the access as
12812 lvalue where possible. Since OpenCL C is based on C99 most C expressions
12813 supported by @value{GDBN} can be used as well.
12815 @node OpenCL C Operators
12816 @subsubsection OpenCL C Operators
12818 @cindex OpenCL C Operators
12819 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
12823 @subsection Fortran
12824 @cindex Fortran-specific support in @value{GDBN}
12826 @value{GDBN} can be used to debug programs written in Fortran, but it
12827 currently supports only the features of Fortran 77 language.
12829 @cindex trailing underscore, in Fortran symbols
12830 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
12831 among them) append an underscore to the names of variables and
12832 functions. When you debug programs compiled by those compilers, you
12833 will need to refer to variables and functions with a trailing
12837 * Fortran Operators:: Fortran operators and expressions
12838 * Fortran Defaults:: Default settings for Fortran
12839 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
12842 @node Fortran Operators
12843 @subsubsection Fortran Operators and Expressions
12845 @cindex Fortran operators and expressions
12847 Operators must be defined on values of specific types. For instance,
12848 @code{+} is defined on numbers, but not on characters or other non-
12849 arithmetic types. Operators are often defined on groups of types.
12853 The exponentiation operator. It raises the first operand to the power
12857 The range operator. Normally used in the form of array(low:high) to
12858 represent a section of array.
12861 The access component operator. Normally used to access elements in derived
12862 types. Also suitable for unions. As unions aren't part of regular Fortran,
12863 this can only happen when accessing a register that uses a gdbarch-defined
12867 @node Fortran Defaults
12868 @subsubsection Fortran Defaults
12870 @cindex Fortran Defaults
12872 Fortran symbols are usually case-insensitive, so @value{GDBN} by
12873 default uses case-insensitive matches for Fortran symbols. You can
12874 change that with the @samp{set case-insensitive} command, see
12875 @ref{Symbols}, for the details.
12877 @node Special Fortran Commands
12878 @subsubsection Special Fortran Commands
12880 @cindex Special Fortran commands
12882 @value{GDBN} has some commands to support Fortran-specific features,
12883 such as displaying common blocks.
12886 @cindex @code{COMMON} blocks, Fortran
12887 @kindex info common
12888 @item info common @r{[}@var{common-name}@r{]}
12889 This command prints the values contained in the Fortran @code{COMMON}
12890 block whose name is @var{common-name}. With no argument, the names of
12891 all @code{COMMON} blocks visible at the current program location are
12898 @cindex Pascal support in @value{GDBN}, limitations
12899 Debugging Pascal programs which use sets, subranges, file variables, or
12900 nested functions does not currently work. @value{GDBN} does not support
12901 entering expressions, printing values, or similar features using Pascal
12904 The Pascal-specific command @code{set print pascal_static-members}
12905 controls whether static members of Pascal objects are displayed.
12906 @xref{Print Settings, pascal_static-members}.
12909 @subsection Modula-2
12911 @cindex Modula-2, @value{GDBN} support
12913 The extensions made to @value{GDBN} to support Modula-2 only support
12914 output from the @sc{gnu} Modula-2 compiler (which is currently being
12915 developed). Other Modula-2 compilers are not currently supported, and
12916 attempting to debug executables produced by them is most likely
12917 to give an error as @value{GDBN} reads in the executable's symbol
12920 @cindex expressions in Modula-2
12922 * M2 Operators:: Built-in operators
12923 * Built-In Func/Proc:: Built-in functions and procedures
12924 * M2 Constants:: Modula-2 constants
12925 * M2 Types:: Modula-2 types
12926 * M2 Defaults:: Default settings for Modula-2
12927 * Deviations:: Deviations from standard Modula-2
12928 * M2 Checks:: Modula-2 type and range checks
12929 * M2 Scope:: The scope operators @code{::} and @code{.}
12930 * GDB/M2:: @value{GDBN} and Modula-2
12934 @subsubsection Operators
12935 @cindex Modula-2 operators
12937 Operators must be defined on values of specific types. For instance,
12938 @code{+} is defined on numbers, but not on structures. Operators are
12939 often defined on groups of types. For the purposes of Modula-2, the
12940 following definitions hold:
12945 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
12949 @emph{Character types} consist of @code{CHAR} and its subranges.
12952 @emph{Floating-point types} consist of @code{REAL}.
12955 @emph{Pointer types} consist of anything declared as @code{POINTER TO
12959 @emph{Scalar types} consist of all of the above.
12962 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
12965 @emph{Boolean types} consist of @code{BOOLEAN}.
12969 The following operators are supported, and appear in order of
12970 increasing precedence:
12974 Function argument or array index separator.
12977 Assignment. The value of @var{var} @code{:=} @var{value} is
12981 Less than, greater than on integral, floating-point, or enumerated
12985 Less than or equal to, greater than or equal to
12986 on integral, floating-point and enumerated types, or set inclusion on
12987 set types. Same precedence as @code{<}.
12989 @item =@r{, }<>@r{, }#
12990 Equality and two ways of expressing inequality, valid on scalar types.
12991 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
12992 available for inequality, since @code{#} conflicts with the script
12996 Set membership. Defined on set types and the types of their members.
12997 Same precedence as @code{<}.
13000 Boolean disjunction. Defined on boolean types.
13003 Boolean conjunction. Defined on boolean types.
13006 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13009 Addition and subtraction on integral and floating-point types, or union
13010 and difference on set types.
13013 Multiplication on integral and floating-point types, or set intersection
13017 Division on floating-point types, or symmetric set difference on set
13018 types. Same precedence as @code{*}.
13021 Integer division and remainder. Defined on integral types. Same
13022 precedence as @code{*}.
13025 Negative. Defined on @code{INTEGER} and @code{REAL} data.
13028 Pointer dereferencing. Defined on pointer types.
13031 Boolean negation. Defined on boolean types. Same precedence as
13035 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
13036 precedence as @code{^}.
13039 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
13042 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
13046 @value{GDBN} and Modula-2 scope operators.
13050 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
13051 treats the use of the operator @code{IN}, or the use of operators
13052 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
13053 @code{<=}, and @code{>=} on sets as an error.
13057 @node Built-In Func/Proc
13058 @subsubsection Built-in Functions and Procedures
13059 @cindex Modula-2 built-ins
13061 Modula-2 also makes available several built-in procedures and functions.
13062 In describing these, the following metavariables are used:
13067 represents an @code{ARRAY} variable.
13070 represents a @code{CHAR} constant or variable.
13073 represents a variable or constant of integral type.
13076 represents an identifier that belongs to a set. Generally used in the
13077 same function with the metavariable @var{s}. The type of @var{s} should
13078 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
13081 represents a variable or constant of integral or floating-point type.
13084 represents a variable or constant of floating-point type.
13090 represents a variable.
13093 represents a variable or constant of one of many types. See the
13094 explanation of the function for details.
13097 All Modula-2 built-in procedures also return a result, described below.
13101 Returns the absolute value of @var{n}.
13104 If @var{c} is a lower case letter, it returns its upper case
13105 equivalent, otherwise it returns its argument.
13108 Returns the character whose ordinal value is @var{i}.
13111 Decrements the value in the variable @var{v} by one. Returns the new value.
13113 @item DEC(@var{v},@var{i})
13114 Decrements the value in the variable @var{v} by @var{i}. Returns the
13117 @item EXCL(@var{m},@var{s})
13118 Removes the element @var{m} from the set @var{s}. Returns the new
13121 @item FLOAT(@var{i})
13122 Returns the floating point equivalent of the integer @var{i}.
13124 @item HIGH(@var{a})
13125 Returns the index of the last member of @var{a}.
13128 Increments the value in the variable @var{v} by one. Returns the new value.
13130 @item INC(@var{v},@var{i})
13131 Increments the value in the variable @var{v} by @var{i}. Returns the
13134 @item INCL(@var{m},@var{s})
13135 Adds the element @var{m} to the set @var{s} if it is not already
13136 there. Returns the new set.
13139 Returns the maximum value of the type @var{t}.
13142 Returns the minimum value of the type @var{t}.
13145 Returns boolean TRUE if @var{i} is an odd number.
13148 Returns the ordinal value of its argument. For example, the ordinal
13149 value of a character is its @sc{ascii} value (on machines supporting the
13150 @sc{ascii} character set). @var{x} must be of an ordered type, which include
13151 integral, character and enumerated types.
13153 @item SIZE(@var{x})
13154 Returns the size of its argument. @var{x} can be a variable or a type.
13156 @item TRUNC(@var{r})
13157 Returns the integral part of @var{r}.
13159 @item TSIZE(@var{x})
13160 Returns the size of its argument. @var{x} can be a variable or a type.
13162 @item VAL(@var{t},@var{i})
13163 Returns the member of the type @var{t} whose ordinal value is @var{i}.
13167 @emph{Warning:} Sets and their operations are not yet supported, so
13168 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
13172 @cindex Modula-2 constants
13174 @subsubsection Constants
13176 @value{GDBN} allows you to express the constants of Modula-2 in the following
13182 Integer constants are simply a sequence of digits. When used in an
13183 expression, a constant is interpreted to be type-compatible with the
13184 rest of the expression. Hexadecimal integers are specified by a
13185 trailing @samp{H}, and octal integers by a trailing @samp{B}.
13188 Floating point constants appear as a sequence of digits, followed by a
13189 decimal point and another sequence of digits. An optional exponent can
13190 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
13191 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
13192 digits of the floating point constant must be valid decimal (base 10)
13196 Character constants consist of a single character enclosed by a pair of
13197 like quotes, either single (@code{'}) or double (@code{"}). They may
13198 also be expressed by their ordinal value (their @sc{ascii} value, usually)
13199 followed by a @samp{C}.
13202 String constants consist of a sequence of characters enclosed by a
13203 pair of like quotes, either single (@code{'}) or double (@code{"}).
13204 Escape sequences in the style of C are also allowed. @xref{C
13205 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
13209 Enumerated constants consist of an enumerated identifier.
13212 Boolean constants consist of the identifiers @code{TRUE} and
13216 Pointer constants consist of integral values only.
13219 Set constants are not yet supported.
13223 @subsubsection Modula-2 Types
13224 @cindex Modula-2 types
13226 Currently @value{GDBN} can print the following data types in Modula-2
13227 syntax: array types, record types, set types, pointer types, procedure
13228 types, enumerated types, subrange types and base types. You can also
13229 print the contents of variables declared using these type.
13230 This section gives a number of simple source code examples together with
13231 sample @value{GDBN} sessions.
13233 The first example contains the following section of code:
13242 and you can request @value{GDBN} to interrogate the type and value of
13243 @code{r} and @code{s}.
13246 (@value{GDBP}) print s
13248 (@value{GDBP}) ptype s
13250 (@value{GDBP}) print r
13252 (@value{GDBP}) ptype r
13257 Likewise if your source code declares @code{s} as:
13261 s: SET ['A'..'Z'] ;
13265 then you may query the type of @code{s} by:
13268 (@value{GDBP}) ptype s
13269 type = SET ['A'..'Z']
13273 Note that at present you cannot interactively manipulate set
13274 expressions using the debugger.
13276 The following example shows how you might declare an array in Modula-2
13277 and how you can interact with @value{GDBN} to print its type and contents:
13281 s: ARRAY [-10..10] OF CHAR ;
13285 (@value{GDBP}) ptype s
13286 ARRAY [-10..10] OF CHAR
13289 Note that the array handling is not yet complete and although the type
13290 is printed correctly, expression handling still assumes that all
13291 arrays have a lower bound of zero and not @code{-10} as in the example
13294 Here are some more type related Modula-2 examples:
13298 colour = (blue, red, yellow, green) ;
13299 t = [blue..yellow] ;
13307 The @value{GDBN} interaction shows how you can query the data type
13308 and value of a variable.
13311 (@value{GDBP}) print s
13313 (@value{GDBP}) ptype t
13314 type = [blue..yellow]
13318 In this example a Modula-2 array is declared and its contents
13319 displayed. Observe that the contents are written in the same way as
13320 their @code{C} counterparts.
13324 s: ARRAY [1..5] OF CARDINAL ;
13330 (@value{GDBP}) print s
13331 $1 = @{1, 0, 0, 0, 0@}
13332 (@value{GDBP}) ptype s
13333 type = ARRAY [1..5] OF CARDINAL
13336 The Modula-2 language interface to @value{GDBN} also understands
13337 pointer types as shown in this example:
13341 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
13348 and you can request that @value{GDBN} describes the type of @code{s}.
13351 (@value{GDBP}) ptype s
13352 type = POINTER TO ARRAY [1..5] OF CARDINAL
13355 @value{GDBN} handles compound types as we can see in this example.
13356 Here we combine array types, record types, pointer types and subrange
13367 myarray = ARRAY myrange OF CARDINAL ;
13368 myrange = [-2..2] ;
13370 s: POINTER TO ARRAY myrange OF foo ;
13374 and you can ask @value{GDBN} to describe the type of @code{s} as shown
13378 (@value{GDBP}) ptype s
13379 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
13382 f3 : ARRAY [-2..2] OF CARDINAL;
13387 @subsubsection Modula-2 Defaults
13388 @cindex Modula-2 defaults
13390 If type and range checking are set automatically by @value{GDBN}, they
13391 both default to @code{on} whenever the working language changes to
13392 Modula-2. This happens regardless of whether you or @value{GDBN}
13393 selected the working language.
13395 If you allow @value{GDBN} to set the language automatically, then entering
13396 code compiled from a file whose name ends with @file{.mod} sets the
13397 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
13398 Infer the Source Language}, for further details.
13401 @subsubsection Deviations from Standard Modula-2
13402 @cindex Modula-2, deviations from
13404 A few changes have been made to make Modula-2 programs easier to debug.
13405 This is done primarily via loosening its type strictness:
13409 Unlike in standard Modula-2, pointer constants can be formed by
13410 integers. This allows you to modify pointer variables during
13411 debugging. (In standard Modula-2, the actual address contained in a
13412 pointer variable is hidden from you; it can only be modified
13413 through direct assignment to another pointer variable or expression that
13414 returned a pointer.)
13417 C escape sequences can be used in strings and characters to represent
13418 non-printable characters. @value{GDBN} prints out strings with these
13419 escape sequences embedded. Single non-printable characters are
13420 printed using the @samp{CHR(@var{nnn})} format.
13423 The assignment operator (@code{:=}) returns the value of its right-hand
13427 All built-in procedures both modify @emph{and} return their argument.
13431 @subsubsection Modula-2 Type and Range Checks
13432 @cindex Modula-2 checks
13435 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
13438 @c FIXME remove warning when type/range checks added
13440 @value{GDBN} considers two Modula-2 variables type equivalent if:
13444 They are of types that have been declared equivalent via a @code{TYPE
13445 @var{t1} = @var{t2}} statement
13448 They have been declared on the same line. (Note: This is true of the
13449 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
13452 As long as type checking is enabled, any attempt to combine variables
13453 whose types are not equivalent is an error.
13455 Range checking is done on all mathematical operations, assignment, array
13456 index bounds, and all built-in functions and procedures.
13459 @subsubsection The Scope Operators @code{::} and @code{.}
13461 @cindex @code{.}, Modula-2 scope operator
13462 @cindex colon, doubled as scope operator
13464 @vindex colon-colon@r{, in Modula-2}
13465 @c Info cannot handle :: but TeX can.
13468 @vindex ::@r{, in Modula-2}
13471 There are a few subtle differences between the Modula-2 scope operator
13472 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
13477 @var{module} . @var{id}
13478 @var{scope} :: @var{id}
13482 where @var{scope} is the name of a module or a procedure,
13483 @var{module} the name of a module, and @var{id} is any declared
13484 identifier within your program, except another module.
13486 Using the @code{::} operator makes @value{GDBN} search the scope
13487 specified by @var{scope} for the identifier @var{id}. If it is not
13488 found in the specified scope, then @value{GDBN} searches all scopes
13489 enclosing the one specified by @var{scope}.
13491 Using the @code{.} operator makes @value{GDBN} search the current scope for
13492 the identifier specified by @var{id} that was imported from the
13493 definition module specified by @var{module}. With this operator, it is
13494 an error if the identifier @var{id} was not imported from definition
13495 module @var{module}, or if @var{id} is not an identifier in
13499 @subsubsection @value{GDBN} and Modula-2
13501 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
13502 Five subcommands of @code{set print} and @code{show print} apply
13503 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
13504 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
13505 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
13506 analogue in Modula-2.
13508 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
13509 with any language, is not useful with Modula-2. Its
13510 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
13511 created in Modula-2 as they can in C or C@t{++}. However, because an
13512 address can be specified by an integral constant, the construct
13513 @samp{@{@var{type}@}@var{adrexp}} is still useful.
13515 @cindex @code{#} in Modula-2
13516 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
13517 interpreted as the beginning of a comment. Use @code{<>} instead.
13523 The extensions made to @value{GDBN} for Ada only support
13524 output from the @sc{gnu} Ada (GNAT) compiler.
13525 Other Ada compilers are not currently supported, and
13526 attempting to debug executables produced by them is most likely
13530 @cindex expressions in Ada
13532 * Ada Mode Intro:: General remarks on the Ada syntax
13533 and semantics supported by Ada mode
13535 * Omissions from Ada:: Restrictions on the Ada expression syntax.
13536 * Additions to Ada:: Extensions of the Ada expression syntax.
13537 * Stopping Before Main Program:: Debugging the program during elaboration.
13538 * Ada Tasks:: Listing and setting breakpoints in tasks.
13539 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
13540 * Ravenscar Profile:: Tasking Support when using the Ravenscar
13542 * Ada Glitches:: Known peculiarities of Ada mode.
13545 @node Ada Mode Intro
13546 @subsubsection Introduction
13547 @cindex Ada mode, general
13549 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
13550 syntax, with some extensions.
13551 The philosophy behind the design of this subset is
13555 That @value{GDBN} should provide basic literals and access to operations for
13556 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
13557 leaving more sophisticated computations to subprograms written into the
13558 program (which therefore may be called from @value{GDBN}).
13561 That type safety and strict adherence to Ada language restrictions
13562 are not particularly important to the @value{GDBN} user.
13565 That brevity is important to the @value{GDBN} user.
13568 Thus, for brevity, the debugger acts as if all names declared in
13569 user-written packages are directly visible, even if they are not visible
13570 according to Ada rules, thus making it unnecessary to fully qualify most
13571 names with their packages, regardless of context. Where this causes
13572 ambiguity, @value{GDBN} asks the user's intent.
13574 The debugger will start in Ada mode if it detects an Ada main program.
13575 As for other languages, it will enter Ada mode when stopped in a program that
13576 was translated from an Ada source file.
13578 While in Ada mode, you may use `@t{--}' for comments. This is useful
13579 mostly for documenting command files. The standard @value{GDBN} comment
13580 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
13581 middle (to allow based literals).
13583 The debugger supports limited overloading. Given a subprogram call in which
13584 the function symbol has multiple definitions, it will use the number of
13585 actual parameters and some information about their types to attempt to narrow
13586 the set of definitions. It also makes very limited use of context, preferring
13587 procedures to functions in the context of the @code{call} command, and
13588 functions to procedures elsewhere.
13590 @node Omissions from Ada
13591 @subsubsection Omissions from Ada
13592 @cindex Ada, omissions from
13594 Here are the notable omissions from the subset:
13598 Only a subset of the attributes are supported:
13602 @t{'First}, @t{'Last}, and @t{'Length}
13603 on array objects (not on types and subtypes).
13606 @t{'Min} and @t{'Max}.
13609 @t{'Pos} and @t{'Val}.
13615 @t{'Range} on array objects (not subtypes), but only as the right
13616 operand of the membership (@code{in}) operator.
13619 @t{'Access}, @t{'Unchecked_Access}, and
13620 @t{'Unrestricted_Access} (a GNAT extension).
13628 @code{Characters.Latin_1} are not available and
13629 concatenation is not implemented. Thus, escape characters in strings are
13630 not currently available.
13633 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
13634 equality of representations. They will generally work correctly
13635 for strings and arrays whose elements have integer or enumeration types.
13636 They may not work correctly for arrays whose element
13637 types have user-defined equality, for arrays of real values
13638 (in particular, IEEE-conformant floating point, because of negative
13639 zeroes and NaNs), and for arrays whose elements contain unused bits with
13640 indeterminate values.
13643 The other component-by-component array operations (@code{and}, @code{or},
13644 @code{xor}, @code{not}, and relational tests other than equality)
13645 are not implemented.
13648 @cindex array aggregates (Ada)
13649 @cindex record aggregates (Ada)
13650 @cindex aggregates (Ada)
13651 There is limited support for array and record aggregates. They are
13652 permitted only on the right sides of assignments, as in these examples:
13655 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
13656 (@value{GDBP}) set An_Array := (1, others => 0)
13657 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
13658 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
13659 (@value{GDBP}) set A_Record := (1, "Peter", True);
13660 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
13664 discriminant's value by assigning an aggregate has an
13665 undefined effect if that discriminant is used within the record.
13666 However, you can first modify discriminants by directly assigning to
13667 them (which normally would not be allowed in Ada), and then performing an
13668 aggregate assignment. For example, given a variable @code{A_Rec}
13669 declared to have a type such as:
13672 type Rec (Len : Small_Integer := 0) is record
13674 Vals : IntArray (1 .. Len);
13678 you can assign a value with a different size of @code{Vals} with two
13682 (@value{GDBP}) set A_Rec.Len := 4
13683 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
13686 As this example also illustrates, @value{GDBN} is very loose about the usual
13687 rules concerning aggregates. You may leave out some of the
13688 components of an array or record aggregate (such as the @code{Len}
13689 component in the assignment to @code{A_Rec} above); they will retain their
13690 original values upon assignment. You may freely use dynamic values as
13691 indices in component associations. You may even use overlapping or
13692 redundant component associations, although which component values are
13693 assigned in such cases is not defined.
13696 Calls to dispatching subprograms are not implemented.
13699 The overloading algorithm is much more limited (i.e., less selective)
13700 than that of real Ada. It makes only limited use of the context in
13701 which a subexpression appears to resolve its meaning, and it is much
13702 looser in its rules for allowing type matches. As a result, some
13703 function calls will be ambiguous, and the user will be asked to choose
13704 the proper resolution.
13707 The @code{new} operator is not implemented.
13710 Entry calls are not implemented.
13713 Aside from printing, arithmetic operations on the native VAX floating-point
13714 formats are not supported.
13717 It is not possible to slice a packed array.
13720 The names @code{True} and @code{False}, when not part of a qualified name,
13721 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
13723 Should your program
13724 redefine these names in a package or procedure (at best a dubious practice),
13725 you will have to use fully qualified names to access their new definitions.
13728 @node Additions to Ada
13729 @subsubsection Additions to Ada
13730 @cindex Ada, deviations from
13732 As it does for other languages, @value{GDBN} makes certain generic
13733 extensions to Ada (@pxref{Expressions}):
13737 If the expression @var{E} is a variable residing in memory (typically
13738 a local variable or array element) and @var{N} is a positive integer,
13739 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
13740 @var{N}-1 adjacent variables following it in memory as an array. In
13741 Ada, this operator is generally not necessary, since its prime use is
13742 in displaying parts of an array, and slicing will usually do this in
13743 Ada. However, there are occasional uses when debugging programs in
13744 which certain debugging information has been optimized away.
13747 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
13748 appears in function or file @var{B}.'' When @var{B} is a file name,
13749 you must typically surround it in single quotes.
13752 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
13753 @var{type} that appears at address @var{addr}.''
13756 A name starting with @samp{$} is a convenience variable
13757 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
13760 In addition, @value{GDBN} provides a few other shortcuts and outright
13761 additions specific to Ada:
13765 The assignment statement is allowed as an expression, returning
13766 its right-hand operand as its value. Thus, you may enter
13769 (@value{GDBP}) set x := y + 3
13770 (@value{GDBP}) print A(tmp := y + 1)
13774 The semicolon is allowed as an ``operator,'' returning as its value
13775 the value of its right-hand operand.
13776 This allows, for example,
13777 complex conditional breaks:
13780 (@value{GDBP}) break f
13781 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
13785 Rather than use catenation and symbolic character names to introduce special
13786 characters into strings, one may instead use a special bracket notation,
13787 which is also used to print strings. A sequence of characters of the form
13788 @samp{["@var{XX}"]} within a string or character literal denotes the
13789 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
13790 sequence of characters @samp{["""]} also denotes a single quotation mark
13791 in strings. For example,
13793 "One line.["0a"]Next line.["0a"]"
13796 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
13800 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
13801 @t{'Max} is optional (and is ignored in any case). For example, it is valid
13805 (@value{GDBP}) print 'max(x, y)
13809 When printing arrays, @value{GDBN} uses positional notation when the
13810 array has a lower bound of 1, and uses a modified named notation otherwise.
13811 For example, a one-dimensional array of three integers with a lower bound
13812 of 3 might print as
13819 That is, in contrast to valid Ada, only the first component has a @code{=>}
13823 You may abbreviate attributes in expressions with any unique,
13824 multi-character subsequence of
13825 their names (an exact match gets preference).
13826 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
13827 in place of @t{a'length}.
13830 @cindex quoting Ada internal identifiers
13831 Since Ada is case-insensitive, the debugger normally maps identifiers you type
13832 to lower case. The GNAT compiler uses upper-case characters for
13833 some of its internal identifiers, which are normally of no interest to users.
13834 For the rare occasions when you actually have to look at them,
13835 enclose them in angle brackets to avoid the lower-case mapping.
13838 (@value{GDBP}) print <JMPBUF_SAVE>[0]
13842 Printing an object of class-wide type or dereferencing an
13843 access-to-class-wide value will display all the components of the object's
13844 specific type (as indicated by its run-time tag). Likewise, component
13845 selection on such a value will operate on the specific type of the
13850 @node Stopping Before Main Program
13851 @subsubsection Stopping at the Very Beginning
13853 @cindex breakpointing Ada elaboration code
13854 It is sometimes necessary to debug the program during elaboration, and
13855 before reaching the main procedure.
13856 As defined in the Ada Reference
13857 Manual, the elaboration code is invoked from a procedure called
13858 @code{adainit}. To run your program up to the beginning of
13859 elaboration, simply use the following two commands:
13860 @code{tbreak adainit} and @code{run}.
13863 @subsubsection Extensions for Ada Tasks
13864 @cindex Ada, tasking
13866 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
13867 @value{GDBN} provides the following task-related commands:
13872 This command shows a list of current Ada tasks, as in the following example:
13879 (@value{GDBP}) info tasks
13880 ID TID P-ID Pri State Name
13881 1 8088000 0 15 Child Activation Wait main_task
13882 2 80a4000 1 15 Accept Statement b
13883 3 809a800 1 15 Child Activation Wait a
13884 * 4 80ae800 3 15 Runnable c
13889 In this listing, the asterisk before the last task indicates it to be the
13890 task currently being inspected.
13894 Represents @value{GDBN}'s internal task number.
13900 The parent's task ID (@value{GDBN}'s internal task number).
13903 The base priority of the task.
13906 Current state of the task.
13910 The task has been created but has not been activated. It cannot be
13914 The task is not blocked for any reason known to Ada. (It may be waiting
13915 for a mutex, though.) It is conceptually "executing" in normal mode.
13918 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
13919 that were waiting on terminate alternatives have been awakened and have
13920 terminated themselves.
13922 @item Child Activation Wait
13923 The task is waiting for created tasks to complete activation.
13925 @item Accept Statement
13926 The task is waiting on an accept or selective wait statement.
13928 @item Waiting on entry call
13929 The task is waiting on an entry call.
13931 @item Async Select Wait
13932 The task is waiting to start the abortable part of an asynchronous
13936 The task is waiting on a select statement with only a delay
13939 @item Child Termination Wait
13940 The task is sleeping having completed a master within itself, and is
13941 waiting for the tasks dependent on that master to become terminated or
13942 waiting on a terminate Phase.
13944 @item Wait Child in Term Alt
13945 The task is sleeping waiting for tasks on terminate alternatives to
13946 finish terminating.
13948 @item Accepting RV with @var{taskno}
13949 The task is accepting a rendez-vous with the task @var{taskno}.
13953 Name of the task in the program.
13957 @kindex info task @var{taskno}
13958 @item info task @var{taskno}
13959 This command shows detailled informations on the specified task, as in
13960 the following example:
13965 (@value{GDBP}) info tasks
13966 ID TID P-ID Pri State Name
13967 1 8077880 0 15 Child Activation Wait main_task
13968 * 2 807c468 1 15 Runnable task_1
13969 (@value{GDBP}) info task 2
13970 Ada Task: 0x807c468
13973 Parent: 1 (main_task)
13979 @kindex task@r{ (Ada)}
13980 @cindex current Ada task ID
13981 This command prints the ID of the current task.
13987 (@value{GDBP}) info tasks
13988 ID TID P-ID Pri State Name
13989 1 8077870 0 15 Child Activation Wait main_task
13990 * 2 807c458 1 15 Runnable t
13991 (@value{GDBP}) task
13992 [Current task is 2]
13995 @item task @var{taskno}
13996 @cindex Ada task switching
13997 This command is like the @code{thread @var{threadno}}
13998 command (@pxref{Threads}). It switches the context of debugging
13999 from the current task to the given task.
14005 (@value{GDBP}) info tasks
14006 ID TID P-ID Pri State Name
14007 1 8077870 0 15 Child Activation Wait main_task
14008 * 2 807c458 1 15 Runnable t
14009 (@value{GDBP}) task 1
14010 [Switching to task 1]
14011 #0 0x8067726 in pthread_cond_wait ()
14013 #0 0x8067726 in pthread_cond_wait ()
14014 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
14015 #2 0x805cb63 in system.task_primitives.operations.sleep ()
14016 #3 0x806153e in system.tasking.stages.activate_tasks ()
14017 #4 0x804aacc in un () at un.adb:5
14020 @item break @var{linespec} task @var{taskno}
14021 @itemx break @var{linespec} task @var{taskno} if @dots{}
14022 @cindex breakpoints and tasks, in Ada
14023 @cindex task breakpoints, in Ada
14024 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
14025 These commands are like the @code{break @dots{} thread @dots{}}
14026 command (@pxref{Thread Stops}).
14027 @var{linespec} specifies source lines, as described
14028 in @ref{Specify Location}.
14030 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
14031 to specify that you only want @value{GDBN} to stop the program when a
14032 particular Ada task reaches this breakpoint. @var{taskno} is one of the
14033 numeric task identifiers assigned by @value{GDBN}, shown in the first
14034 column of the @samp{info tasks} display.
14036 If you do not specify @samp{task @var{taskno}} when you set a
14037 breakpoint, the breakpoint applies to @emph{all} tasks of your
14040 You can use the @code{task} qualifier on conditional breakpoints as
14041 well; in this case, place @samp{task @var{taskno}} before the
14042 breakpoint condition (before the @code{if}).
14050 (@value{GDBP}) info tasks
14051 ID TID P-ID Pri State Name
14052 1 140022020 0 15 Child Activation Wait main_task
14053 2 140045060 1 15 Accept/Select Wait t2
14054 3 140044840 1 15 Runnable t1
14055 * 4 140056040 1 15 Runnable t3
14056 (@value{GDBP}) b 15 task 2
14057 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
14058 (@value{GDBP}) cont
14063 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
14065 (@value{GDBP}) info tasks
14066 ID TID P-ID Pri State Name
14067 1 140022020 0 15 Child Activation Wait main_task
14068 * 2 140045060 1 15 Runnable t2
14069 3 140044840 1 15 Runnable t1
14070 4 140056040 1 15 Delay Sleep t3
14074 @node Ada Tasks and Core Files
14075 @subsubsection Tasking Support when Debugging Core Files
14076 @cindex Ada tasking and core file debugging
14078 When inspecting a core file, as opposed to debugging a live program,
14079 tasking support may be limited or even unavailable, depending on
14080 the platform being used.
14081 For instance, on x86-linux, the list of tasks is available, but task
14082 switching is not supported. On Tru64, however, task switching will work
14085 On certain platforms, including Tru64, the debugger needs to perform some
14086 memory writes in order to provide Ada tasking support. When inspecting
14087 a core file, this means that the core file must be opened with read-write
14088 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
14089 Under these circumstances, you should make a backup copy of the core
14090 file before inspecting it with @value{GDBN}.
14092 @node Ravenscar Profile
14093 @subsubsection Tasking Support when using the Ravenscar Profile
14094 @cindex Ravenscar Profile
14096 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
14097 specifically designed for systems with safety-critical real-time
14101 @kindex set ravenscar task-switching on
14102 @cindex task switching with program using Ravenscar Profile
14103 @item set ravenscar task-switching on
14104 Allows task switching when debugging a program that uses the Ravenscar
14105 Profile. This is the default.
14107 @kindex set ravenscar task-switching off
14108 @item set ravenscar task-switching off
14109 Turn off task switching when debugging a program that uses the Ravenscar
14110 Profile. This is mostly intended to disable the code that adds support
14111 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
14112 the Ravenscar runtime is preventing @value{GDBN} from working properly.
14113 To be effective, this command should be run before the program is started.
14115 @kindex show ravenscar task-switching
14116 @item show ravenscar task-switching
14117 Show whether it is possible to switch from task to task in a program
14118 using the Ravenscar Profile.
14123 @subsubsection Known Peculiarities of Ada Mode
14124 @cindex Ada, problems
14126 Besides the omissions listed previously (@pxref{Omissions from Ada}),
14127 we know of several problems with and limitations of Ada mode in
14129 some of which will be fixed with planned future releases of the debugger
14130 and the GNU Ada compiler.
14134 Static constants that the compiler chooses not to materialize as objects in
14135 storage are invisible to the debugger.
14138 Named parameter associations in function argument lists are ignored (the
14139 argument lists are treated as positional).
14142 Many useful library packages are currently invisible to the debugger.
14145 Fixed-point arithmetic, conversions, input, and output is carried out using
14146 floating-point arithmetic, and may give results that only approximate those on
14150 The GNAT compiler never generates the prefix @code{Standard} for any of
14151 the standard symbols defined by the Ada language. @value{GDBN} knows about
14152 this: it will strip the prefix from names when you use it, and will never
14153 look for a name you have so qualified among local symbols, nor match against
14154 symbols in other packages or subprograms. If you have
14155 defined entities anywhere in your program other than parameters and
14156 local variables whose simple names match names in @code{Standard},
14157 GNAT's lack of qualification here can cause confusion. When this happens,
14158 you can usually resolve the confusion
14159 by qualifying the problematic names with package
14160 @code{Standard} explicitly.
14163 Older versions of the compiler sometimes generate erroneous debugging
14164 information, resulting in the debugger incorrectly printing the value
14165 of affected entities. In some cases, the debugger is able to work
14166 around an issue automatically. In other cases, the debugger is able
14167 to work around the issue, but the work-around has to be specifically
14170 @kindex set ada trust-PAD-over-XVS
14171 @kindex show ada trust-PAD-over-XVS
14174 @item set ada trust-PAD-over-XVS on
14175 Configure GDB to strictly follow the GNAT encoding when computing the
14176 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
14177 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
14178 a complete description of the encoding used by the GNAT compiler).
14179 This is the default.
14181 @item set ada trust-PAD-over-XVS off
14182 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
14183 sometimes prints the wrong value for certain entities, changing @code{ada
14184 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
14185 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
14186 @code{off}, but this incurs a slight performance penalty, so it is
14187 recommended to leave this setting to @code{on} unless necessary.
14191 @node Unsupported Languages
14192 @section Unsupported Languages
14194 @cindex unsupported languages
14195 @cindex minimal language
14196 In addition to the other fully-supported programming languages,
14197 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
14198 It does not represent a real programming language, but provides a set
14199 of capabilities close to what the C or assembly languages provide.
14200 This should allow most simple operations to be performed while debugging
14201 an application that uses a language currently not supported by @value{GDBN}.
14203 If the language is set to @code{auto}, @value{GDBN} will automatically
14204 select this language if the current frame corresponds to an unsupported
14208 @chapter Examining the Symbol Table
14210 The commands described in this chapter allow you to inquire about the
14211 symbols (names of variables, functions and types) defined in your
14212 program. This information is inherent in the text of your program and
14213 does not change as your program executes. @value{GDBN} finds it in your
14214 program's symbol table, in the file indicated when you started @value{GDBN}
14215 (@pxref{File Options, ,Choosing Files}), or by one of the
14216 file-management commands (@pxref{Files, ,Commands to Specify Files}).
14218 @cindex symbol names
14219 @cindex names of symbols
14220 @cindex quoting names
14221 Occasionally, you may need to refer to symbols that contain unusual
14222 characters, which @value{GDBN} ordinarily treats as word delimiters. The
14223 most frequent case is in referring to static variables in other
14224 source files (@pxref{Variables,,Program Variables}). File names
14225 are recorded in object files as debugging symbols, but @value{GDBN} would
14226 ordinarily parse a typical file name, like @file{foo.c}, as the three words
14227 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
14228 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
14235 looks up the value of @code{x} in the scope of the file @file{foo.c}.
14238 @cindex case-insensitive symbol names
14239 @cindex case sensitivity in symbol names
14240 @kindex set case-sensitive
14241 @item set case-sensitive on
14242 @itemx set case-sensitive off
14243 @itemx set case-sensitive auto
14244 Normally, when @value{GDBN} looks up symbols, it matches their names
14245 with case sensitivity determined by the current source language.
14246 Occasionally, you may wish to control that. The command @code{set
14247 case-sensitive} lets you do that by specifying @code{on} for
14248 case-sensitive matches or @code{off} for case-insensitive ones. If
14249 you specify @code{auto}, case sensitivity is reset to the default
14250 suitable for the source language. The default is case-sensitive
14251 matches for all languages except for Fortran, for which the default is
14252 case-insensitive matches.
14254 @kindex show case-sensitive
14255 @item show case-sensitive
14256 This command shows the current setting of case sensitivity for symbols
14259 @kindex info address
14260 @cindex address of a symbol
14261 @item info address @var{symbol}
14262 Describe where the data for @var{symbol} is stored. For a register
14263 variable, this says which register it is kept in. For a non-register
14264 local variable, this prints the stack-frame offset at which the variable
14267 Note the contrast with @samp{print &@var{symbol}}, which does not work
14268 at all for a register variable, and for a stack local variable prints
14269 the exact address of the current instantiation of the variable.
14271 @kindex info symbol
14272 @cindex symbol from address
14273 @cindex closest symbol and offset for an address
14274 @item info symbol @var{addr}
14275 Print the name of a symbol which is stored at the address @var{addr}.
14276 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
14277 nearest symbol and an offset from it:
14280 (@value{GDBP}) info symbol 0x54320
14281 _initialize_vx + 396 in section .text
14285 This is the opposite of the @code{info address} command. You can use
14286 it to find out the name of a variable or a function given its address.
14288 For dynamically linked executables, the name of executable or shared
14289 library containing the symbol is also printed:
14292 (@value{GDBP}) info symbol 0x400225
14293 _start + 5 in section .text of /tmp/a.out
14294 (@value{GDBP}) info symbol 0x2aaaac2811cf
14295 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
14299 @item whatis [@var{arg}]
14300 Print the data type of @var{arg}, which can be either an expression
14301 or a name of a data type. With no argument, print the data type of
14302 @code{$}, the last value in the value history.
14304 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
14305 is not actually evaluated, and any side-effecting operations (such as
14306 assignments or function calls) inside it do not take place.
14308 If @var{arg} is a variable or an expression, @code{whatis} prints its
14309 literal type as it is used in the source code. If the type was
14310 defined using a @code{typedef}, @code{whatis} will @emph{not} print
14311 the data type underlying the @code{typedef}. If the type of the
14312 variable or the expression is a compound data type, such as
14313 @code{struct} or @code{class}, @code{whatis} never prints their
14314 fields or methods. It just prints the @code{struct}/@code{class}
14315 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
14316 such a compound data type, use @code{ptype}.
14318 If @var{arg} is a type name that was defined using @code{typedef},
14319 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
14320 Unrolling means that @code{whatis} will show the underlying type used
14321 in the @code{typedef} declaration of @var{arg}. However, if that
14322 underlying type is also a @code{typedef}, @code{whatis} will not
14325 For C code, the type names may also have the form @samp{class
14326 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
14327 @var{union-tag}} or @samp{enum @var{enum-tag}}.
14330 @item ptype [@var{arg}]
14331 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
14332 detailed description of the type, instead of just the name of the type.
14333 @xref{Expressions, ,Expressions}.
14335 Contrary to @code{whatis}, @code{ptype} always unrolls any
14336 @code{typedef}s in its argument declaration, whether the argument is
14337 a variable, expression, or a data type. This means that @code{ptype}
14338 of a variable or an expression will not print literally its type as
14339 present in the source code---use @code{whatis} for that. @code{typedef}s at
14340 the pointer or reference targets are also unrolled. Only @code{typedef}s of
14341 fields, methods and inner @code{class typedef}s of @code{struct}s,
14342 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
14344 For example, for this variable declaration:
14347 typedef double real_t;
14348 struct complex @{ real_t real; double imag; @};
14349 typedef struct complex complex_t;
14351 real_t *real_pointer_var;
14355 the two commands give this output:
14359 (@value{GDBP}) whatis var
14361 (@value{GDBP}) ptype var
14362 type = struct complex @{
14366 (@value{GDBP}) whatis complex_t
14367 type = struct complex
14368 (@value{GDBP}) whatis struct complex
14369 type = struct complex
14370 (@value{GDBP}) ptype struct complex
14371 type = struct complex @{
14375 (@value{GDBP}) whatis real_pointer_var
14377 (@value{GDBP}) ptype real_pointer_var
14383 As with @code{whatis}, using @code{ptype} without an argument refers to
14384 the type of @code{$}, the last value in the value history.
14386 @cindex incomplete type
14387 Sometimes, programs use opaque data types or incomplete specifications
14388 of complex data structure. If the debug information included in the
14389 program does not allow @value{GDBN} to display a full declaration of
14390 the data type, it will say @samp{<incomplete type>}. For example,
14391 given these declarations:
14395 struct foo *fooptr;
14399 but no definition for @code{struct foo} itself, @value{GDBN} will say:
14402 (@value{GDBP}) ptype foo
14403 $1 = <incomplete type>
14407 ``Incomplete type'' is C terminology for data types that are not
14408 completely specified.
14411 @item info types @var{regexp}
14413 Print a brief description of all types whose names match the regular
14414 expression @var{regexp} (or all types in your program, if you supply
14415 no argument). Each complete typename is matched as though it were a
14416 complete line; thus, @samp{i type value} gives information on all
14417 types in your program whose names include the string @code{value}, but
14418 @samp{i type ^value$} gives information only on types whose complete
14419 name is @code{value}.
14421 This command differs from @code{ptype} in two ways: first, like
14422 @code{whatis}, it does not print a detailed description; second, it
14423 lists all source files where a type is defined.
14426 @cindex local variables
14427 @item info scope @var{location}
14428 List all the variables local to a particular scope. This command
14429 accepts a @var{location} argument---a function name, a source line, or
14430 an address preceded by a @samp{*}, and prints all the variables local
14431 to the scope defined by that location. (@xref{Specify Location}, for
14432 details about supported forms of @var{location}.) For example:
14435 (@value{GDBP}) @b{info scope command_line_handler}
14436 Scope for command_line_handler:
14437 Symbol rl is an argument at stack/frame offset 8, length 4.
14438 Symbol linebuffer is in static storage at address 0x150a18, length 4.
14439 Symbol linelength is in static storage at address 0x150a1c, length 4.
14440 Symbol p is a local variable in register $esi, length 4.
14441 Symbol p1 is a local variable in register $ebx, length 4.
14442 Symbol nline is a local variable in register $edx, length 4.
14443 Symbol repeat is a local variable at frame offset -8, length 4.
14447 This command is especially useful for determining what data to collect
14448 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
14451 @kindex info source
14453 Show information about the current source file---that is, the source file for
14454 the function containing the current point of execution:
14457 the name of the source file, and the directory containing it,
14459 the directory it was compiled in,
14461 its length, in lines,
14463 which programming language it is written in,
14465 whether the executable includes debugging information for that file, and
14466 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
14468 whether the debugging information includes information about
14469 preprocessor macros.
14473 @kindex info sources
14475 Print the names of all source files in your program for which there is
14476 debugging information, organized into two lists: files whose symbols
14477 have already been read, and files whose symbols will be read when needed.
14479 @kindex info functions
14480 @item info functions
14481 Print the names and data types of all defined functions.
14483 @item info functions @var{regexp}
14484 Print the names and data types of all defined functions
14485 whose names contain a match for regular expression @var{regexp}.
14486 Thus, @samp{info fun step} finds all functions whose names
14487 include @code{step}; @samp{info fun ^step} finds those whose names
14488 start with @code{step}. If a function name contains characters
14489 that conflict with the regular expression language (e.g.@:
14490 @samp{operator*()}), they may be quoted with a backslash.
14492 @kindex info variables
14493 @item info variables
14494 Print the names and data types of all variables that are defined
14495 outside of functions (i.e.@: excluding local variables).
14497 @item info variables @var{regexp}
14498 Print the names and data types of all variables (except for local
14499 variables) whose names contain a match for regular expression
14502 @kindex info classes
14503 @cindex Objective-C, classes and selectors
14505 @itemx info classes @var{regexp}
14506 Display all Objective-C classes in your program, or
14507 (with the @var{regexp} argument) all those matching a particular regular
14510 @kindex info selectors
14511 @item info selectors
14512 @itemx info selectors @var{regexp}
14513 Display all Objective-C selectors in your program, or
14514 (with the @var{regexp} argument) all those matching a particular regular
14518 This was never implemented.
14519 @kindex info methods
14521 @itemx info methods @var{regexp}
14522 The @code{info methods} command permits the user to examine all defined
14523 methods within C@t{++} program, or (with the @var{regexp} argument) a
14524 specific set of methods found in the various C@t{++} classes. Many
14525 C@t{++} classes provide a large number of methods. Thus, the output
14526 from the @code{ptype} command can be overwhelming and hard to use. The
14527 @code{info-methods} command filters the methods, printing only those
14528 which match the regular-expression @var{regexp}.
14531 @cindex reloading symbols
14532 Some systems allow individual object files that make up your program to
14533 be replaced without stopping and restarting your program. For example,
14534 in VxWorks you can simply recompile a defective object file and keep on
14535 running. If you are running on one of these systems, you can allow
14536 @value{GDBN} to reload the symbols for automatically relinked modules:
14539 @kindex set symbol-reloading
14540 @item set symbol-reloading on
14541 Replace symbol definitions for the corresponding source file when an
14542 object file with a particular name is seen again.
14544 @item set symbol-reloading off
14545 Do not replace symbol definitions when encountering object files of the
14546 same name more than once. This is the default state; if you are not
14547 running on a system that permits automatic relinking of modules, you
14548 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
14549 may discard symbols when linking large programs, that may contain
14550 several modules (from different directories or libraries) with the same
14553 @kindex show symbol-reloading
14554 @item show symbol-reloading
14555 Show the current @code{on} or @code{off} setting.
14558 @cindex opaque data types
14559 @kindex set opaque-type-resolution
14560 @item set opaque-type-resolution on
14561 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
14562 declared as a pointer to a @code{struct}, @code{class}, or
14563 @code{union}---for example, @code{struct MyType *}---that is used in one
14564 source file although the full declaration of @code{struct MyType} is in
14565 another source file. The default is on.
14567 A change in the setting of this subcommand will not take effect until
14568 the next time symbols for a file are loaded.
14570 @item set opaque-type-resolution off
14571 Tell @value{GDBN} not to resolve opaque types. In this case, the type
14572 is printed as follows:
14574 @{<no data fields>@}
14577 @kindex show opaque-type-resolution
14578 @item show opaque-type-resolution
14579 Show whether opaque types are resolved or not.
14581 @kindex maint print symbols
14582 @cindex symbol dump
14583 @kindex maint print psymbols
14584 @cindex partial symbol dump
14585 @item maint print symbols @var{filename}
14586 @itemx maint print psymbols @var{filename}
14587 @itemx maint print msymbols @var{filename}
14588 Write a dump of debugging symbol data into the file @var{filename}.
14589 These commands are used to debug the @value{GDBN} symbol-reading code. Only
14590 symbols with debugging data are included. If you use @samp{maint print
14591 symbols}, @value{GDBN} includes all the symbols for which it has already
14592 collected full details: that is, @var{filename} reflects symbols for
14593 only those files whose symbols @value{GDBN} has read. You can use the
14594 command @code{info sources} to find out which files these are. If you
14595 use @samp{maint print psymbols} instead, the dump shows information about
14596 symbols that @value{GDBN} only knows partially---that is, symbols defined in
14597 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
14598 @samp{maint print msymbols} dumps just the minimal symbol information
14599 required for each object file from which @value{GDBN} has read some symbols.
14600 @xref{Files, ,Commands to Specify Files}, for a discussion of how
14601 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
14603 @kindex maint info symtabs
14604 @kindex maint info psymtabs
14605 @cindex listing @value{GDBN}'s internal symbol tables
14606 @cindex symbol tables, listing @value{GDBN}'s internal
14607 @cindex full symbol tables, listing @value{GDBN}'s internal
14608 @cindex partial symbol tables, listing @value{GDBN}'s internal
14609 @item maint info symtabs @r{[} @var{regexp} @r{]}
14610 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
14612 List the @code{struct symtab} or @code{struct partial_symtab}
14613 structures whose names match @var{regexp}. If @var{regexp} is not
14614 given, list them all. The output includes expressions which you can
14615 copy into a @value{GDBN} debugging this one to examine a particular
14616 structure in more detail. For example:
14619 (@value{GDBP}) maint info psymtabs dwarf2read
14620 @{ objfile /home/gnu/build/gdb/gdb
14621 ((struct objfile *) 0x82e69d0)
14622 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
14623 ((struct partial_symtab *) 0x8474b10)
14626 text addresses 0x814d3c8 -- 0x8158074
14627 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
14628 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
14629 dependencies (none)
14632 (@value{GDBP}) maint info symtabs
14636 We see that there is one partial symbol table whose filename contains
14637 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
14638 and we see that @value{GDBN} has not read in any symtabs yet at all.
14639 If we set a breakpoint on a function, that will cause @value{GDBN} to
14640 read the symtab for the compilation unit containing that function:
14643 (@value{GDBP}) break dwarf2_psymtab_to_symtab
14644 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
14646 (@value{GDBP}) maint info symtabs
14647 @{ objfile /home/gnu/build/gdb/gdb
14648 ((struct objfile *) 0x82e69d0)
14649 @{ symtab /home/gnu/src/gdb/dwarf2read.c
14650 ((struct symtab *) 0x86c1f38)
14653 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
14654 linetable ((struct linetable *) 0x8370fa0)
14655 debugformat DWARF 2
14664 @chapter Altering Execution
14666 Once you think you have found an error in your program, you might want to
14667 find out for certain whether correcting the apparent error would lead to
14668 correct results in the rest of the run. You can find the answer by
14669 experiment, using the @value{GDBN} features for altering execution of the
14672 For example, you can store new values into variables or memory
14673 locations, give your program a signal, restart it at a different
14674 address, or even return prematurely from a function.
14677 * Assignment:: Assignment to variables
14678 * Jumping:: Continuing at a different address
14679 * Signaling:: Giving your program a signal
14680 * Returning:: Returning from a function
14681 * Calling:: Calling your program's functions
14682 * Patching:: Patching your program
14686 @section Assignment to Variables
14689 @cindex setting variables
14690 To alter the value of a variable, evaluate an assignment expression.
14691 @xref{Expressions, ,Expressions}. For example,
14698 stores the value 4 into the variable @code{x}, and then prints the
14699 value of the assignment expression (which is 4).
14700 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
14701 information on operators in supported languages.
14703 @kindex set variable
14704 @cindex variables, setting
14705 If you are not interested in seeing the value of the assignment, use the
14706 @code{set} command instead of the @code{print} command. @code{set} is
14707 really the same as @code{print} except that the expression's value is
14708 not printed and is not put in the value history (@pxref{Value History,
14709 ,Value History}). The expression is evaluated only for its effects.
14711 If the beginning of the argument string of the @code{set} command
14712 appears identical to a @code{set} subcommand, use the @code{set
14713 variable} command instead of just @code{set}. This command is identical
14714 to @code{set} except for its lack of subcommands. For example, if your
14715 program has a variable @code{width}, you get an error if you try to set
14716 a new value with just @samp{set width=13}, because @value{GDBN} has the
14717 command @code{set width}:
14720 (@value{GDBP}) whatis width
14722 (@value{GDBP}) p width
14724 (@value{GDBP}) set width=47
14725 Invalid syntax in expression.
14729 The invalid expression, of course, is @samp{=47}. In
14730 order to actually set the program's variable @code{width}, use
14733 (@value{GDBP}) set var width=47
14736 Because the @code{set} command has many subcommands that can conflict
14737 with the names of program variables, it is a good idea to use the
14738 @code{set variable} command instead of just @code{set}. For example, if
14739 your program has a variable @code{g}, you run into problems if you try
14740 to set a new value with just @samp{set g=4}, because @value{GDBN} has
14741 the command @code{set gnutarget}, abbreviated @code{set g}:
14745 (@value{GDBP}) whatis g
14749 (@value{GDBP}) set g=4
14753 The program being debugged has been started already.
14754 Start it from the beginning? (y or n) y
14755 Starting program: /home/smith/cc_progs/a.out
14756 "/home/smith/cc_progs/a.out": can't open to read symbols:
14757 Invalid bfd target.
14758 (@value{GDBP}) show g
14759 The current BFD target is "=4".
14764 The program variable @code{g} did not change, and you silently set the
14765 @code{gnutarget} to an invalid value. In order to set the variable
14769 (@value{GDBP}) set var g=4
14772 @value{GDBN} allows more implicit conversions in assignments than C; you can
14773 freely store an integer value into a pointer variable or vice versa,
14774 and you can convert any structure to any other structure that is the
14775 same length or shorter.
14776 @comment FIXME: how do structs align/pad in these conversions?
14777 @comment /doc@cygnus.com 18dec1990
14779 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
14780 construct to generate a value of specified type at a specified address
14781 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
14782 to memory location @code{0x83040} as an integer (which implies a certain size
14783 and representation in memory), and
14786 set @{int@}0x83040 = 4
14790 stores the value 4 into that memory location.
14793 @section Continuing at a Different Address
14795 Ordinarily, when you continue your program, you do so at the place where
14796 it stopped, with the @code{continue} command. You can instead continue at
14797 an address of your own choosing, with the following commands:
14801 @item jump @var{linespec}
14802 @itemx jump @var{location}
14803 Resume execution at line @var{linespec} or at address given by
14804 @var{location}. Execution stops again immediately if there is a
14805 breakpoint there. @xref{Specify Location}, for a description of the
14806 different forms of @var{linespec} and @var{location}. It is common
14807 practice to use the @code{tbreak} command in conjunction with
14808 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
14810 The @code{jump} command does not change the current stack frame, or
14811 the stack pointer, or the contents of any memory location or any
14812 register other than the program counter. If line @var{linespec} is in
14813 a different function from the one currently executing, the results may
14814 be bizarre if the two functions expect different patterns of arguments or
14815 of local variables. For this reason, the @code{jump} command requests
14816 confirmation if the specified line is not in the function currently
14817 executing. However, even bizarre results are predictable if you are
14818 well acquainted with the machine-language code of your program.
14821 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
14822 On many systems, you can get much the same effect as the @code{jump}
14823 command by storing a new value into the register @code{$pc}. The
14824 difference is that this does not start your program running; it only
14825 changes the address of where it @emph{will} run when you continue. For
14833 makes the next @code{continue} command or stepping command execute at
14834 address @code{0x485}, rather than at the address where your program stopped.
14835 @xref{Continuing and Stepping, ,Continuing and Stepping}.
14837 The most common occasion to use the @code{jump} command is to back
14838 up---perhaps with more breakpoints set---over a portion of a program
14839 that has already executed, in order to examine its execution in more
14844 @section Giving your Program a Signal
14845 @cindex deliver a signal to a program
14849 @item signal @var{signal}
14850 Resume execution where your program stopped, but immediately give it the
14851 signal @var{signal}. @var{signal} can be the name or the number of a
14852 signal. For example, on many systems @code{signal 2} and @code{signal
14853 SIGINT} are both ways of sending an interrupt signal.
14855 Alternatively, if @var{signal} is zero, continue execution without
14856 giving a signal. This is useful when your program stopped on account of
14857 a signal and would ordinary see the signal when resumed with the
14858 @code{continue} command; @samp{signal 0} causes it to resume without a
14861 @code{signal} does not repeat when you press @key{RET} a second time
14862 after executing the command.
14866 Invoking the @code{signal} command is not the same as invoking the
14867 @code{kill} utility from the shell. Sending a signal with @code{kill}
14868 causes @value{GDBN} to decide what to do with the signal depending on
14869 the signal handling tables (@pxref{Signals}). The @code{signal} command
14870 passes the signal directly to your program.
14874 @section Returning from a Function
14877 @cindex returning from a function
14880 @itemx return @var{expression}
14881 You can cancel execution of a function call with the @code{return}
14882 command. If you give an
14883 @var{expression} argument, its value is used as the function's return
14887 When you use @code{return}, @value{GDBN} discards the selected stack frame
14888 (and all frames within it). You can think of this as making the
14889 discarded frame return prematurely. If you wish to specify a value to
14890 be returned, give that value as the argument to @code{return}.
14892 This pops the selected stack frame (@pxref{Selection, ,Selecting a
14893 Frame}), and any other frames inside of it, leaving its caller as the
14894 innermost remaining frame. That frame becomes selected. The
14895 specified value is stored in the registers used for returning values
14898 The @code{return} command does not resume execution; it leaves the
14899 program stopped in the state that would exist if the function had just
14900 returned. In contrast, the @code{finish} command (@pxref{Continuing
14901 and Stepping, ,Continuing and Stepping}) resumes execution until the
14902 selected stack frame returns naturally.
14904 @value{GDBN} needs to know how the @var{expression} argument should be set for
14905 the inferior. The concrete registers assignment depends on the OS ABI and the
14906 type being returned by the selected stack frame. For example it is common for
14907 OS ABI to return floating point values in FPU registers while integer values in
14908 CPU registers. Still some ABIs return even floating point values in CPU
14909 registers. Larger integer widths (such as @code{long long int}) also have
14910 specific placement rules. @value{GDBN} already knows the OS ABI from its
14911 current target so it needs to find out also the type being returned to make the
14912 assignment into the right register(s).
14914 Normally, the selected stack frame has debug info. @value{GDBN} will always
14915 use the debug info instead of the implicit type of @var{expression} when the
14916 debug info is available. For example, if you type @kbd{return -1}, and the
14917 function in the current stack frame is declared to return a @code{long long
14918 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
14919 into a @code{long long int}:
14922 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
14924 (@value{GDBP}) return -1
14925 Make func return now? (y or n) y
14926 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
14927 43 printf ("result=%lld\n", func ());
14931 However, if the selected stack frame does not have a debug info, e.g., if the
14932 function was compiled without debug info, @value{GDBN} has to find out the type
14933 to return from user. Specifying a different type by mistake may set the value
14934 in different inferior registers than the caller code expects. For example,
14935 typing @kbd{return -1} with its implicit type @code{int} would set only a part
14936 of a @code{long long int} result for a debug info less function (on 32-bit
14937 architectures). Therefore the user is required to specify the return type by
14938 an appropriate cast explicitly:
14941 Breakpoint 2, 0x0040050b in func ()
14942 (@value{GDBP}) return -1
14943 Return value type not available for selected stack frame.
14944 Please use an explicit cast of the value to return.
14945 (@value{GDBP}) return (long long int) -1
14946 Make selected stack frame return now? (y or n) y
14947 #0 0x00400526 in main ()
14952 @section Calling Program Functions
14955 @cindex calling functions
14956 @cindex inferior functions, calling
14957 @item print @var{expr}
14958 Evaluate the expression @var{expr} and display the resulting value.
14959 @var{expr} may include calls to functions in the program being
14963 @item call @var{expr}
14964 Evaluate the expression @var{expr} without displaying @code{void}
14967 You can use this variant of the @code{print} command if you want to
14968 execute a function from your program that does not return anything
14969 (a.k.a.@: @dfn{a void function}), but without cluttering the output
14970 with @code{void} returned values that @value{GDBN} will otherwise
14971 print. If the result is not void, it is printed and saved in the
14975 It is possible for the function you call via the @code{print} or
14976 @code{call} command to generate a signal (e.g., if there's a bug in
14977 the function, or if you passed it incorrect arguments). What happens
14978 in that case is controlled by the @code{set unwindonsignal} command.
14980 Similarly, with a C@t{++} program it is possible for the function you
14981 call via the @code{print} or @code{call} command to generate an
14982 exception that is not handled due to the constraints of the dummy
14983 frame. In this case, any exception that is raised in the frame, but has
14984 an out-of-frame exception handler will not be found. GDB builds a
14985 dummy-frame for the inferior function call, and the unwinder cannot
14986 seek for exception handlers outside of this dummy-frame. What happens
14987 in that case is controlled by the
14988 @code{set unwind-on-terminating-exception} command.
14991 @item set unwindonsignal
14992 @kindex set unwindonsignal
14993 @cindex unwind stack in called functions
14994 @cindex call dummy stack unwinding
14995 Set unwinding of the stack if a signal is received while in a function
14996 that @value{GDBN} called in the program being debugged. If set to on,
14997 @value{GDBN} unwinds the stack it created for the call and restores
14998 the context to what it was before the call. If set to off (the
14999 default), @value{GDBN} stops in the frame where the signal was
15002 @item show unwindonsignal
15003 @kindex show unwindonsignal
15004 Show the current setting of stack unwinding in the functions called by
15007 @item set unwind-on-terminating-exception
15008 @kindex set unwind-on-terminating-exception
15009 @cindex unwind stack in called functions with unhandled exceptions
15010 @cindex call dummy stack unwinding on unhandled exception.
15011 Set unwinding of the stack if a C@t{++} exception is raised, but left
15012 unhandled while in a function that @value{GDBN} called in the program being
15013 debugged. If set to on (the default), @value{GDBN} unwinds the stack
15014 it created for the call and restores the context to what it was before
15015 the call. If set to off, @value{GDBN} the exception is delivered to
15016 the default C@t{++} exception handler and the inferior terminated.
15018 @item show unwind-on-terminating-exception
15019 @kindex show unwind-on-terminating-exception
15020 Show the current setting of stack unwinding in the functions called by
15025 @cindex weak alias functions
15026 Sometimes, a function you wish to call is actually a @dfn{weak alias}
15027 for another function. In such case, @value{GDBN} might not pick up
15028 the type information, including the types of the function arguments,
15029 which causes @value{GDBN} to call the inferior function incorrectly.
15030 As a result, the called function will function erroneously and may
15031 even crash. A solution to that is to use the name of the aliased
15035 @section Patching Programs
15037 @cindex patching binaries
15038 @cindex writing into executables
15039 @cindex writing into corefiles
15041 By default, @value{GDBN} opens the file containing your program's
15042 executable code (or the corefile) read-only. This prevents accidental
15043 alterations to machine code; but it also prevents you from intentionally
15044 patching your program's binary.
15046 If you'd like to be able to patch the binary, you can specify that
15047 explicitly with the @code{set write} command. For example, you might
15048 want to turn on internal debugging flags, or even to make emergency
15054 @itemx set write off
15055 If you specify @samp{set write on}, @value{GDBN} opens executable and
15056 core files for both reading and writing; if you specify @kbd{set write
15057 off} (the default), @value{GDBN} opens them read-only.
15059 If you have already loaded a file, you must load it again (using the
15060 @code{exec-file} or @code{core-file} command) after changing @code{set
15061 write}, for your new setting to take effect.
15065 Display whether executable files and core files are opened for writing
15066 as well as reading.
15070 @chapter @value{GDBN} Files
15072 @value{GDBN} needs to know the file name of the program to be debugged,
15073 both in order to read its symbol table and in order to start your
15074 program. To debug a core dump of a previous run, you must also tell
15075 @value{GDBN} the name of the core dump file.
15078 * Files:: Commands to specify files
15079 * Separate Debug Files:: Debugging information in separate files
15080 * Index Files:: Index files speed up GDB
15081 * Symbol Errors:: Errors reading symbol files
15082 * Data Files:: GDB data files
15086 @section Commands to Specify Files
15088 @cindex symbol table
15089 @cindex core dump file
15091 You may want to specify executable and core dump file names. The usual
15092 way to do this is at start-up time, using the arguments to
15093 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
15094 Out of @value{GDBN}}).
15096 Occasionally it is necessary to change to a different file during a
15097 @value{GDBN} session. Or you may run @value{GDBN} and forget to
15098 specify a file you want to use. Or you are debugging a remote target
15099 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
15100 Program}). In these situations the @value{GDBN} commands to specify
15101 new files are useful.
15104 @cindex executable file
15106 @item file @var{filename}
15107 Use @var{filename} as the program to be debugged. It is read for its
15108 symbols and for the contents of pure memory. It is also the program
15109 executed when you use the @code{run} command. If you do not specify a
15110 directory and the file is not found in the @value{GDBN} working directory,
15111 @value{GDBN} uses the environment variable @code{PATH} as a list of
15112 directories to search, just as the shell does when looking for a program
15113 to run. You can change the value of this variable, for both @value{GDBN}
15114 and your program, using the @code{path} command.
15116 @cindex unlinked object files
15117 @cindex patching object files
15118 You can load unlinked object @file{.o} files into @value{GDBN} using
15119 the @code{file} command. You will not be able to ``run'' an object
15120 file, but you can disassemble functions and inspect variables. Also,
15121 if the underlying BFD functionality supports it, you could use
15122 @kbd{gdb -write} to patch object files using this technique. Note
15123 that @value{GDBN} can neither interpret nor modify relocations in this
15124 case, so branches and some initialized variables will appear to go to
15125 the wrong place. But this feature is still handy from time to time.
15128 @code{file} with no argument makes @value{GDBN} discard any information it
15129 has on both executable file and the symbol table.
15132 @item exec-file @r{[} @var{filename} @r{]}
15133 Specify that the program to be run (but not the symbol table) is found
15134 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
15135 if necessary to locate your program. Omitting @var{filename} means to
15136 discard information on the executable file.
15138 @kindex symbol-file
15139 @item symbol-file @r{[} @var{filename} @r{]}
15140 Read symbol table information from file @var{filename}. @code{PATH} is
15141 searched when necessary. Use the @code{file} command to get both symbol
15142 table and program to run from the same file.
15144 @code{symbol-file} with no argument clears out @value{GDBN} information on your
15145 program's symbol table.
15147 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
15148 some breakpoints and auto-display expressions. This is because they may
15149 contain pointers to the internal data recording symbols and data types,
15150 which are part of the old symbol table data being discarded inside
15153 @code{symbol-file} does not repeat if you press @key{RET} again after
15156 When @value{GDBN} is configured for a particular environment, it
15157 understands debugging information in whatever format is the standard
15158 generated for that environment; you may use either a @sc{gnu} compiler, or
15159 other compilers that adhere to the local conventions.
15160 Best results are usually obtained from @sc{gnu} compilers; for example,
15161 using @code{@value{NGCC}} you can generate debugging information for
15164 For most kinds of object files, with the exception of old SVR3 systems
15165 using COFF, the @code{symbol-file} command does not normally read the
15166 symbol table in full right away. Instead, it scans the symbol table
15167 quickly to find which source files and which symbols are present. The
15168 details are read later, one source file at a time, as they are needed.
15170 The purpose of this two-stage reading strategy is to make @value{GDBN}
15171 start up faster. For the most part, it is invisible except for
15172 occasional pauses while the symbol table details for a particular source
15173 file are being read. (The @code{set verbose} command can turn these
15174 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
15175 Warnings and Messages}.)
15177 We have not implemented the two-stage strategy for COFF yet. When the
15178 symbol table is stored in COFF format, @code{symbol-file} reads the
15179 symbol table data in full right away. Note that ``stabs-in-COFF''
15180 still does the two-stage strategy, since the debug info is actually
15184 @cindex reading symbols immediately
15185 @cindex symbols, reading immediately
15186 @item symbol-file @r{[} -readnow @r{]} @var{filename}
15187 @itemx file @r{[} -readnow @r{]} @var{filename}
15188 You can override the @value{GDBN} two-stage strategy for reading symbol
15189 tables by using the @samp{-readnow} option with any of the commands that
15190 load symbol table information, if you want to be sure @value{GDBN} has the
15191 entire symbol table available.
15193 @c FIXME: for now no mention of directories, since this seems to be in
15194 @c flux. 13mar1992 status is that in theory GDB would look either in
15195 @c current dir or in same dir as myprog; but issues like competing
15196 @c GDB's, or clutter in system dirs, mean that in practice right now
15197 @c only current dir is used. FFish says maybe a special GDB hierarchy
15198 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
15202 @item core-file @r{[}@var{filename}@r{]}
15204 Specify the whereabouts of a core dump file to be used as the ``contents
15205 of memory''. Traditionally, core files contain only some parts of the
15206 address space of the process that generated them; @value{GDBN} can access the
15207 executable file itself for other parts.
15209 @code{core-file} with no argument specifies that no core file is
15212 Note that the core file is ignored when your program is actually running
15213 under @value{GDBN}. So, if you have been running your program and you
15214 wish to debug a core file instead, you must kill the subprocess in which
15215 the program is running. To do this, use the @code{kill} command
15216 (@pxref{Kill Process, ,Killing the Child Process}).
15218 @kindex add-symbol-file
15219 @cindex dynamic linking
15220 @item add-symbol-file @var{filename} @var{address}
15221 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
15222 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
15223 The @code{add-symbol-file} command reads additional symbol table
15224 information from the file @var{filename}. You would use this command
15225 when @var{filename} has been dynamically loaded (by some other means)
15226 into the program that is running. @var{address} should be the memory
15227 address at which the file has been loaded; @value{GDBN} cannot figure
15228 this out for itself. You can additionally specify an arbitrary number
15229 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
15230 section name and base address for that section. You can specify any
15231 @var{address} as an expression.
15233 The symbol table of the file @var{filename} is added to the symbol table
15234 originally read with the @code{symbol-file} command. You can use the
15235 @code{add-symbol-file} command any number of times; the new symbol data
15236 thus read keeps adding to the old. To discard all old symbol data
15237 instead, use the @code{symbol-file} command without any arguments.
15239 @cindex relocatable object files, reading symbols from
15240 @cindex object files, relocatable, reading symbols from
15241 @cindex reading symbols from relocatable object files
15242 @cindex symbols, reading from relocatable object files
15243 @cindex @file{.o} files, reading symbols from
15244 Although @var{filename} is typically a shared library file, an
15245 executable file, or some other object file which has been fully
15246 relocated for loading into a process, you can also load symbolic
15247 information from relocatable @file{.o} files, as long as:
15251 the file's symbolic information refers only to linker symbols defined in
15252 that file, not to symbols defined by other object files,
15254 every section the file's symbolic information refers to has actually
15255 been loaded into the inferior, as it appears in the file, and
15257 you can determine the address at which every section was loaded, and
15258 provide these to the @code{add-symbol-file} command.
15262 Some embedded operating systems, like Sun Chorus and VxWorks, can load
15263 relocatable files into an already running program; such systems
15264 typically make the requirements above easy to meet. However, it's
15265 important to recognize that many native systems use complex link
15266 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
15267 assembly, for example) that make the requirements difficult to meet. In
15268 general, one cannot assume that using @code{add-symbol-file} to read a
15269 relocatable object file's symbolic information will have the same effect
15270 as linking the relocatable object file into the program in the normal
15273 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
15275 @kindex add-symbol-file-from-memory
15276 @cindex @code{syscall DSO}
15277 @cindex load symbols from memory
15278 @item add-symbol-file-from-memory @var{address}
15279 Load symbols from the given @var{address} in a dynamically loaded
15280 object file whose image is mapped directly into the inferior's memory.
15281 For example, the Linux kernel maps a @code{syscall DSO} into each
15282 process's address space; this DSO provides kernel-specific code for
15283 some system calls. The argument can be any expression whose
15284 evaluation yields the address of the file's shared object file header.
15285 For this command to work, you must have used @code{symbol-file} or
15286 @code{exec-file} commands in advance.
15288 @kindex add-shared-symbol-files
15290 @item add-shared-symbol-files @var{library-file}
15291 @itemx assf @var{library-file}
15292 The @code{add-shared-symbol-files} command can currently be used only
15293 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
15294 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
15295 @value{GDBN} automatically looks for shared libraries, however if
15296 @value{GDBN} does not find yours, you can invoke
15297 @code{add-shared-symbol-files}. It takes one argument: the shared
15298 library's file name. @code{assf} is a shorthand alias for
15299 @code{add-shared-symbol-files}.
15302 @item section @var{section} @var{addr}
15303 The @code{section} command changes the base address of the named
15304 @var{section} of the exec file to @var{addr}. This can be used if the
15305 exec file does not contain section addresses, (such as in the
15306 @code{a.out} format), or when the addresses specified in the file
15307 itself are wrong. Each section must be changed separately. The
15308 @code{info files} command, described below, lists all the sections and
15312 @kindex info target
15315 @code{info files} and @code{info target} are synonymous; both print the
15316 current target (@pxref{Targets, ,Specifying a Debugging Target}),
15317 including the names of the executable and core dump files currently in
15318 use by @value{GDBN}, and the files from which symbols were loaded. The
15319 command @code{help target} lists all possible targets rather than
15322 @kindex maint info sections
15323 @item maint info sections
15324 Another command that can give you extra information about program sections
15325 is @code{maint info sections}. In addition to the section information
15326 displayed by @code{info files}, this command displays the flags and file
15327 offset of each section in the executable and core dump files. In addition,
15328 @code{maint info sections} provides the following command options (which
15329 may be arbitrarily combined):
15333 Display sections for all loaded object files, including shared libraries.
15334 @item @var{sections}
15335 Display info only for named @var{sections}.
15336 @item @var{section-flags}
15337 Display info only for sections for which @var{section-flags} are true.
15338 The section flags that @value{GDBN} currently knows about are:
15341 Section will have space allocated in the process when loaded.
15342 Set for all sections except those containing debug information.
15344 Section will be loaded from the file into the child process memory.
15345 Set for pre-initialized code and data, clear for @code{.bss} sections.
15347 Section needs to be relocated before loading.
15349 Section cannot be modified by the child process.
15351 Section contains executable code only.
15353 Section contains data only (no executable code).
15355 Section will reside in ROM.
15357 Section contains data for constructor/destructor lists.
15359 Section is not empty.
15361 An instruction to the linker to not output the section.
15362 @item COFF_SHARED_LIBRARY
15363 A notification to the linker that the section contains
15364 COFF shared library information.
15366 Section contains common symbols.
15369 @kindex set trust-readonly-sections
15370 @cindex read-only sections
15371 @item set trust-readonly-sections on
15372 Tell @value{GDBN} that readonly sections in your object file
15373 really are read-only (i.e.@: that their contents will not change).
15374 In that case, @value{GDBN} can fetch values from these sections
15375 out of the object file, rather than from the target program.
15376 For some targets (notably embedded ones), this can be a significant
15377 enhancement to debugging performance.
15379 The default is off.
15381 @item set trust-readonly-sections off
15382 Tell @value{GDBN} not to trust readonly sections. This means that
15383 the contents of the section might change while the program is running,
15384 and must therefore be fetched from the target when needed.
15386 @item show trust-readonly-sections
15387 Show the current setting of trusting readonly sections.
15390 All file-specifying commands allow both absolute and relative file names
15391 as arguments. @value{GDBN} always converts the file name to an absolute file
15392 name and remembers it that way.
15394 @cindex shared libraries
15395 @anchor{Shared Libraries}
15396 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
15397 and IBM RS/6000 AIX shared libraries.
15399 On MS-Windows @value{GDBN} must be linked with the Expat library to support
15400 shared libraries. @xref{Expat}.
15402 @value{GDBN} automatically loads symbol definitions from shared libraries
15403 when you use the @code{run} command, or when you examine a core file.
15404 (Before you issue the @code{run} command, @value{GDBN} does not understand
15405 references to a function in a shared library, however---unless you are
15406 debugging a core file).
15408 On HP-UX, if the program loads a library explicitly, @value{GDBN}
15409 automatically loads the symbols at the time of the @code{shl_load} call.
15411 @c FIXME: some @value{GDBN} release may permit some refs to undef
15412 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
15413 @c FIXME...lib; check this from time to time when updating manual
15415 There are times, however, when you may wish to not automatically load
15416 symbol definitions from shared libraries, such as when they are
15417 particularly large or there are many of them.
15419 To control the automatic loading of shared library symbols, use the
15423 @kindex set auto-solib-add
15424 @item set auto-solib-add @var{mode}
15425 If @var{mode} is @code{on}, symbols from all shared object libraries
15426 will be loaded automatically when the inferior begins execution, you
15427 attach to an independently started inferior, or when the dynamic linker
15428 informs @value{GDBN} that a new library has been loaded. If @var{mode}
15429 is @code{off}, symbols must be loaded manually, using the
15430 @code{sharedlibrary} command. The default value is @code{on}.
15432 @cindex memory used for symbol tables
15433 If your program uses lots of shared libraries with debug info that
15434 takes large amounts of memory, you can decrease the @value{GDBN}
15435 memory footprint by preventing it from automatically loading the
15436 symbols from shared libraries. To that end, type @kbd{set
15437 auto-solib-add off} before running the inferior, then load each
15438 library whose debug symbols you do need with @kbd{sharedlibrary
15439 @var{regexp}}, where @var{regexp} is a regular expression that matches
15440 the libraries whose symbols you want to be loaded.
15442 @kindex show auto-solib-add
15443 @item show auto-solib-add
15444 Display the current autoloading mode.
15447 @cindex load shared library
15448 To explicitly load shared library symbols, use the @code{sharedlibrary}
15452 @kindex info sharedlibrary
15454 @item info share @var{regex}
15455 @itemx info sharedlibrary @var{regex}
15456 Print the names of the shared libraries which are currently loaded
15457 that match @var{regex}. If @var{regex} is omitted then print
15458 all shared libraries that are loaded.
15460 @kindex sharedlibrary
15462 @item sharedlibrary @var{regex}
15463 @itemx share @var{regex}
15464 Load shared object library symbols for files matching a
15465 Unix regular expression.
15466 As with files loaded automatically, it only loads shared libraries
15467 required by your program for a core file or after typing @code{run}. If
15468 @var{regex} is omitted all shared libraries required by your program are
15471 @item nosharedlibrary
15472 @kindex nosharedlibrary
15473 @cindex unload symbols from shared libraries
15474 Unload all shared object library symbols. This discards all symbols
15475 that have been loaded from all shared libraries. Symbols from shared
15476 libraries that were loaded by explicit user requests are not
15480 Sometimes you may wish that @value{GDBN} stops and gives you control
15481 when any of shared library events happen. Use the @code{set
15482 stop-on-solib-events} command for this:
15485 @item set stop-on-solib-events
15486 @kindex set stop-on-solib-events
15487 This command controls whether @value{GDBN} should give you control
15488 when the dynamic linker notifies it about some shared library event.
15489 The most common event of interest is loading or unloading of a new
15492 @item show stop-on-solib-events
15493 @kindex show stop-on-solib-events
15494 Show whether @value{GDBN} stops and gives you control when shared
15495 library events happen.
15498 Shared libraries are also supported in many cross or remote debugging
15499 configurations. @value{GDBN} needs to have access to the target's libraries;
15500 this can be accomplished either by providing copies of the libraries
15501 on the host system, or by asking @value{GDBN} to automatically retrieve the
15502 libraries from the target. If copies of the target libraries are
15503 provided, they need to be the same as the target libraries, although the
15504 copies on the target can be stripped as long as the copies on the host are
15507 @cindex where to look for shared libraries
15508 For remote debugging, you need to tell @value{GDBN} where the target
15509 libraries are, so that it can load the correct copies---otherwise, it
15510 may try to load the host's libraries. @value{GDBN} has two variables
15511 to specify the search directories for target libraries.
15514 @cindex prefix for shared library file names
15515 @cindex system root, alternate
15516 @kindex set solib-absolute-prefix
15517 @kindex set sysroot
15518 @item set sysroot @var{path}
15519 Use @var{path} as the system root for the program being debugged. Any
15520 absolute shared library paths will be prefixed with @var{path}; many
15521 runtime loaders store the absolute paths to the shared library in the
15522 target program's memory. If you use @code{set sysroot} to find shared
15523 libraries, they need to be laid out in the same way that they are on
15524 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
15527 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
15528 retrieve the target libraries from the remote system. This is only
15529 supported when using a remote target that supports the @code{remote get}
15530 command (@pxref{File Transfer,,Sending files to a remote system}).
15531 The part of @var{path} following the initial @file{remote:}
15532 (if present) is used as system root prefix on the remote file system.
15533 @footnote{If you want to specify a local system root using a directory
15534 that happens to be named @file{remote:}, you need to use some equivalent
15535 variant of the name like @file{./remote:}.}
15537 For targets with an MS-DOS based filesystem, such as MS-Windows and
15538 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
15539 absolute file name with @var{path}. But first, on Unix hosts,
15540 @value{GDBN} converts all backslash directory separators into forward
15541 slashes, because the backslash is not a directory separator on Unix:
15544 c:\foo\bar.dll @result{} c:/foo/bar.dll
15547 Then, @value{GDBN} attempts prefixing the target file name with
15548 @var{path}, and looks for the resulting file name in the host file
15552 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
15555 If that does not find the shared library, @value{GDBN} tries removing
15556 the @samp{:} character from the drive spec, both for convenience, and,
15557 for the case of the host file system not supporting file names with
15561 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
15564 This makes it possible to have a system root that mirrors a target
15565 with more than one drive. E.g., you may want to setup your local
15566 copies of the target system shared libraries like so (note @samp{c} vs
15570 @file{/path/to/sysroot/c/sys/bin/foo.dll}
15571 @file{/path/to/sysroot/c/sys/bin/bar.dll}
15572 @file{/path/to/sysroot/z/sys/bin/bar.dll}
15576 and point the system root at @file{/path/to/sysroot}, so that
15577 @value{GDBN} can find the correct copies of both
15578 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
15580 If that still does not find the shared library, @value{GDBN} tries
15581 removing the whole drive spec from the target file name:
15584 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
15587 This last lookup makes it possible to not care about the drive name,
15588 if you don't want or need to.
15590 The @code{set solib-absolute-prefix} command is an alias for @code{set
15593 @cindex default system root
15594 @cindex @samp{--with-sysroot}
15595 You can set the default system root by using the configure-time
15596 @samp{--with-sysroot} option. If the system root is inside
15597 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15598 @samp{--exec-prefix}), then the default system root will be updated
15599 automatically if the installed @value{GDBN} is moved to a new
15602 @kindex show sysroot
15604 Display the current shared library prefix.
15606 @kindex set solib-search-path
15607 @item set solib-search-path @var{path}
15608 If this variable is set, @var{path} is a colon-separated list of
15609 directories to search for shared libraries. @samp{solib-search-path}
15610 is used after @samp{sysroot} fails to locate the library, or if the
15611 path to the library is relative instead of absolute. If you want to
15612 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
15613 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
15614 finding your host's libraries. @samp{sysroot} is preferred; setting
15615 it to a nonexistent directory may interfere with automatic loading
15616 of shared library symbols.
15618 @kindex show solib-search-path
15619 @item show solib-search-path
15620 Display the current shared library search path.
15622 @cindex DOS file-name semantics of file names.
15623 @kindex set target-file-system-kind (unix|dos-based|auto)
15624 @kindex show target-file-system-kind
15625 @item set target-file-system-kind @var{kind}
15626 Set assumed file system kind for target reported file names.
15628 Shared library file names as reported by the target system may not
15629 make sense as is on the system @value{GDBN} is running on. For
15630 example, when remote debugging a target that has MS-DOS based file
15631 system semantics, from a Unix host, the target may be reporting to
15632 @value{GDBN} a list of loaded shared libraries with file names such as
15633 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
15634 drive letters, so the @samp{c:\} prefix is not normally understood as
15635 indicating an absolute file name, and neither is the backslash
15636 normally considered a directory separator character. In that case,
15637 the native file system would interpret this whole absolute file name
15638 as a relative file name with no directory components. This would make
15639 it impossible to point @value{GDBN} at a copy of the remote target's
15640 shared libraries on the host using @code{set sysroot}, and impractical
15641 with @code{set solib-search-path}. Setting
15642 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
15643 to interpret such file names similarly to how the target would, and to
15644 map them to file names valid on @value{GDBN}'s native file system
15645 semantics. The value of @var{kind} can be @code{"auto"}, in addition
15646 to one of the supported file system kinds. In that case, @value{GDBN}
15647 tries to determine the appropriate file system variant based on the
15648 current target's operating system (@pxref{ABI, ,Configuring the
15649 Current ABI}). The supported file system settings are:
15653 Instruct @value{GDBN} to assume the target file system is of Unix
15654 kind. Only file names starting the forward slash (@samp{/}) character
15655 are considered absolute, and the directory separator character is also
15659 Instruct @value{GDBN} to assume the target file system is DOS based.
15660 File names starting with either a forward slash, or a drive letter
15661 followed by a colon (e.g., @samp{c:}), are considered absolute, and
15662 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
15663 considered directory separators.
15666 Instruct @value{GDBN} to use the file system kind associated with the
15667 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
15668 This is the default.
15673 @node Separate Debug Files
15674 @section Debugging Information in Separate Files
15675 @cindex separate debugging information files
15676 @cindex debugging information in separate files
15677 @cindex @file{.debug} subdirectories
15678 @cindex debugging information directory, global
15679 @cindex global debugging information directory
15680 @cindex build ID, and separate debugging files
15681 @cindex @file{.build-id} directory
15683 @value{GDBN} allows you to put a program's debugging information in a
15684 file separate from the executable itself, in a way that allows
15685 @value{GDBN} to find and load the debugging information automatically.
15686 Since debugging information can be very large---sometimes larger
15687 than the executable code itself---some systems distribute debugging
15688 information for their executables in separate files, which users can
15689 install only when they need to debug a problem.
15691 @value{GDBN} supports two ways of specifying the separate debug info
15696 The executable contains a @dfn{debug link} that specifies the name of
15697 the separate debug info file. The separate debug file's name is
15698 usually @file{@var{executable}.debug}, where @var{executable} is the
15699 name of the corresponding executable file without leading directories
15700 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
15701 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
15702 checksum for the debug file, which @value{GDBN} uses to validate that
15703 the executable and the debug file came from the same build.
15706 The executable contains a @dfn{build ID}, a unique bit string that is
15707 also present in the corresponding debug info file. (This is supported
15708 only on some operating systems, notably those which use the ELF format
15709 for binary files and the @sc{gnu} Binutils.) For more details about
15710 this feature, see the description of the @option{--build-id}
15711 command-line option in @ref{Options, , Command Line Options, ld.info,
15712 The GNU Linker}. The debug info file's name is not specified
15713 explicitly by the build ID, but can be computed from the build ID, see
15717 Depending on the way the debug info file is specified, @value{GDBN}
15718 uses two different methods of looking for the debug file:
15722 For the ``debug link'' method, @value{GDBN} looks up the named file in
15723 the directory of the executable file, then in a subdirectory of that
15724 directory named @file{.debug}, and finally under the global debug
15725 directory, in a subdirectory whose name is identical to the leading
15726 directories of the executable's absolute file name.
15729 For the ``build ID'' method, @value{GDBN} looks in the
15730 @file{.build-id} subdirectory of the global debug directory for a file
15731 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
15732 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
15733 are the rest of the bit string. (Real build ID strings are 32 or more
15734 hex characters, not 10.)
15737 So, for example, suppose you ask @value{GDBN} to debug
15738 @file{/usr/bin/ls}, which has a debug link that specifies the
15739 file @file{ls.debug}, and a build ID whose value in hex is
15740 @code{abcdef1234}. If the global debug directory is
15741 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
15742 debug information files, in the indicated order:
15746 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
15748 @file{/usr/bin/ls.debug}
15750 @file{/usr/bin/.debug/ls.debug}
15752 @file{/usr/lib/debug/usr/bin/ls.debug}.
15755 You can set the global debugging info directory's name, and view the
15756 name @value{GDBN} is currently using.
15760 @kindex set debug-file-directory
15761 @item set debug-file-directory @var{directories}
15762 Set the directories which @value{GDBN} searches for separate debugging
15763 information files to @var{directory}. Multiple directory components can be set
15764 concatenating them by a directory separator.
15766 @kindex show debug-file-directory
15767 @item show debug-file-directory
15768 Show the directories @value{GDBN} searches for separate debugging
15773 @cindex @code{.gnu_debuglink} sections
15774 @cindex debug link sections
15775 A debug link is a special section of the executable file named
15776 @code{.gnu_debuglink}. The section must contain:
15780 A filename, with any leading directory components removed, followed by
15783 zero to three bytes of padding, as needed to reach the next four-byte
15784 boundary within the section, and
15786 a four-byte CRC checksum, stored in the same endianness used for the
15787 executable file itself. The checksum is computed on the debugging
15788 information file's full contents by the function given below, passing
15789 zero as the @var{crc} argument.
15792 Any executable file format can carry a debug link, as long as it can
15793 contain a section named @code{.gnu_debuglink} with the contents
15796 @cindex @code{.note.gnu.build-id} sections
15797 @cindex build ID sections
15798 The build ID is a special section in the executable file (and in other
15799 ELF binary files that @value{GDBN} may consider). This section is
15800 often named @code{.note.gnu.build-id}, but that name is not mandatory.
15801 It contains unique identification for the built files---the ID remains
15802 the same across multiple builds of the same build tree. The default
15803 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
15804 content for the build ID string. The same section with an identical
15805 value is present in the original built binary with symbols, in its
15806 stripped variant, and in the separate debugging information file.
15808 The debugging information file itself should be an ordinary
15809 executable, containing a full set of linker symbols, sections, and
15810 debugging information. The sections of the debugging information file
15811 should have the same names, addresses, and sizes as the original file,
15812 but they need not contain any data---much like a @code{.bss} section
15813 in an ordinary executable.
15815 The @sc{gnu} binary utilities (Binutils) package includes the
15816 @samp{objcopy} utility that can produce
15817 the separated executable / debugging information file pairs using the
15818 following commands:
15821 @kbd{objcopy --only-keep-debug foo foo.debug}
15826 These commands remove the debugging
15827 information from the executable file @file{foo} and place it in the file
15828 @file{foo.debug}. You can use the first, second or both methods to link the
15833 The debug link method needs the following additional command to also leave
15834 behind a debug link in @file{foo}:
15837 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
15840 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
15841 a version of the @code{strip} command such that the command @kbd{strip foo -f
15842 foo.debug} has the same functionality as the two @code{objcopy} commands and
15843 the @code{ln -s} command above, together.
15846 Build ID gets embedded into the main executable using @code{ld --build-id} or
15847 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
15848 compatibility fixes for debug files separation are present in @sc{gnu} binary
15849 utilities (Binutils) package since version 2.18.
15854 @cindex CRC algorithm definition
15855 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
15856 IEEE 802.3 using the polynomial:
15858 @c TexInfo requires naked braces for multi-digit exponents for Tex
15859 @c output, but this causes HTML output to barf. HTML has to be set using
15860 @c raw commands. So we end up having to specify this equation in 2
15865 <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>
15866 + <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
15872 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
15873 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
15877 The function is computed byte at a time, taking the least
15878 significant bit of each byte first. The initial pattern
15879 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
15880 the final result is inverted to ensure trailing zeros also affect the
15883 @emph{Note:} This is the same CRC polynomial as used in handling the
15884 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
15885 , @value{GDBN} Remote Serial Protocol}). However in the
15886 case of the Remote Serial Protocol, the CRC is computed @emph{most}
15887 significant bit first, and the result is not inverted, so trailing
15888 zeros have no effect on the CRC value.
15890 To complete the description, we show below the code of the function
15891 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
15892 initially supplied @code{crc} argument means that an initial call to
15893 this function passing in zero will start computing the CRC using
15896 @kindex gnu_debuglink_crc32
15899 gnu_debuglink_crc32 (unsigned long crc,
15900 unsigned char *buf, size_t len)
15902 static const unsigned long crc32_table[256] =
15904 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
15905 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
15906 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
15907 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
15908 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
15909 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
15910 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
15911 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
15912 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
15913 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
15914 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
15915 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
15916 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
15917 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
15918 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
15919 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
15920 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
15921 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
15922 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
15923 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
15924 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
15925 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
15926 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
15927 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
15928 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
15929 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
15930 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
15931 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
15932 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
15933 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
15934 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
15935 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
15936 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
15937 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
15938 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
15939 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
15940 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
15941 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
15942 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
15943 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
15944 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
15945 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
15946 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
15947 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
15948 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
15949 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
15950 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
15951 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
15952 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
15953 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
15954 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
15957 unsigned char *end;
15959 crc = ~crc & 0xffffffff;
15960 for (end = buf + len; buf < end; ++buf)
15961 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
15962 return ~crc & 0xffffffff;
15967 This computation does not apply to the ``build ID'' method.
15971 @section Index Files Speed Up @value{GDBN}
15972 @cindex index files
15973 @cindex @samp{.gdb_index} section
15975 When @value{GDBN} finds a symbol file, it scans the symbols in the
15976 file in order to construct an internal symbol table. This lets most
15977 @value{GDBN} operations work quickly---at the cost of a delay early
15978 on. For large programs, this delay can be quite lengthy, so
15979 @value{GDBN} provides a way to build an index, which speeds up
15982 The index is stored as a section in the symbol file. @value{GDBN} can
15983 write the index to a file, then you can put it into the symbol file
15984 using @command{objcopy}.
15986 To create an index file, use the @code{save gdb-index} command:
15989 @item save gdb-index @var{directory}
15990 @kindex save gdb-index
15991 Create an index file for each symbol file currently known by
15992 @value{GDBN}. Each file is named after its corresponding symbol file,
15993 with @samp{.gdb-index} appended, and is written into the given
15997 Once you have created an index file you can merge it into your symbol
15998 file, here named @file{symfile}, using @command{objcopy}:
16001 $ objcopy --add-section .gdb_index=symfile.gdb-index \
16002 --set-section-flags .gdb_index=readonly symfile symfile
16005 There are currently some limitation on indices. They only work when
16006 for DWARF debugging information, not stabs. And, they do not
16007 currently work for programs using Ada.
16009 @node Symbol Errors
16010 @section Errors Reading Symbol Files
16012 While reading a symbol file, @value{GDBN} occasionally encounters problems,
16013 such as symbol types it does not recognize, or known bugs in compiler
16014 output. By default, @value{GDBN} does not notify you of such problems, since
16015 they are relatively common and primarily of interest to people
16016 debugging compilers. If you are interested in seeing information
16017 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
16018 only one message about each such type of problem, no matter how many
16019 times the problem occurs; or you can ask @value{GDBN} to print more messages,
16020 to see how many times the problems occur, with the @code{set
16021 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
16024 The messages currently printed, and their meanings, include:
16027 @item inner block not inside outer block in @var{symbol}
16029 The symbol information shows where symbol scopes begin and end
16030 (such as at the start of a function or a block of statements). This
16031 error indicates that an inner scope block is not fully contained
16032 in its outer scope blocks.
16034 @value{GDBN} circumvents the problem by treating the inner block as if it had
16035 the same scope as the outer block. In the error message, @var{symbol}
16036 may be shown as ``@code{(don't know)}'' if the outer block is not a
16039 @item block at @var{address} out of order
16041 The symbol information for symbol scope blocks should occur in
16042 order of increasing addresses. This error indicates that it does not
16045 @value{GDBN} does not circumvent this problem, and has trouble
16046 locating symbols in the source file whose symbols it is reading. (You
16047 can often determine what source file is affected by specifying
16048 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
16051 @item bad block start address patched
16053 The symbol information for a symbol scope block has a start address
16054 smaller than the address of the preceding source line. This is known
16055 to occur in the SunOS 4.1.1 (and earlier) C compiler.
16057 @value{GDBN} circumvents the problem by treating the symbol scope block as
16058 starting on the previous source line.
16060 @item bad string table offset in symbol @var{n}
16063 Symbol number @var{n} contains a pointer into the string table which is
16064 larger than the size of the string table.
16066 @value{GDBN} circumvents the problem by considering the symbol to have the
16067 name @code{foo}, which may cause other problems if many symbols end up
16070 @item unknown symbol type @code{0x@var{nn}}
16072 The symbol information contains new data types that @value{GDBN} does
16073 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
16074 uncomprehended information, in hexadecimal.
16076 @value{GDBN} circumvents the error by ignoring this symbol information.
16077 This usually allows you to debug your program, though certain symbols
16078 are not accessible. If you encounter such a problem and feel like
16079 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
16080 on @code{complain}, then go up to the function @code{read_dbx_symtab}
16081 and examine @code{*bufp} to see the symbol.
16083 @item stub type has NULL name
16085 @value{GDBN} could not find the full definition for a struct or class.
16087 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
16088 The symbol information for a C@t{++} member function is missing some
16089 information that recent versions of the compiler should have output for
16092 @item info mismatch between compiler and debugger
16094 @value{GDBN} could not parse a type specification output by the compiler.
16099 @section GDB Data Files
16101 @cindex prefix for data files
16102 @value{GDBN} will sometimes read an auxiliary data file. These files
16103 are kept in a directory known as the @dfn{data directory}.
16105 You can set the data directory's name, and view the name @value{GDBN}
16106 is currently using.
16109 @kindex set data-directory
16110 @item set data-directory @var{directory}
16111 Set the directory which @value{GDBN} searches for auxiliary data files
16112 to @var{directory}.
16114 @kindex show data-directory
16115 @item show data-directory
16116 Show the directory @value{GDBN} searches for auxiliary data files.
16119 @cindex default data directory
16120 @cindex @samp{--with-gdb-datadir}
16121 You can set the default data directory by using the configure-time
16122 @samp{--with-gdb-datadir} option. If the data directory is inside
16123 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
16124 @samp{--exec-prefix}), then the default data directory will be updated
16125 automatically if the installed @value{GDBN} is moved to a new
16128 The data directory may also be specified with the
16129 @code{--data-directory} command line option.
16130 @xref{Mode Options}.
16133 @chapter Specifying a Debugging Target
16135 @cindex debugging target
16136 A @dfn{target} is the execution environment occupied by your program.
16138 Often, @value{GDBN} runs in the same host environment as your program;
16139 in that case, the debugging target is specified as a side effect when
16140 you use the @code{file} or @code{core} commands. When you need more
16141 flexibility---for example, running @value{GDBN} on a physically separate
16142 host, or controlling a standalone system over a serial port or a
16143 realtime system over a TCP/IP connection---you can use the @code{target}
16144 command to specify one of the target types configured for @value{GDBN}
16145 (@pxref{Target Commands, ,Commands for Managing Targets}).
16147 @cindex target architecture
16148 It is possible to build @value{GDBN} for several different @dfn{target
16149 architectures}. When @value{GDBN} is built like that, you can choose
16150 one of the available architectures with the @kbd{set architecture}
16154 @kindex set architecture
16155 @kindex show architecture
16156 @item set architecture @var{arch}
16157 This command sets the current target architecture to @var{arch}. The
16158 value of @var{arch} can be @code{"auto"}, in addition to one of the
16159 supported architectures.
16161 @item show architecture
16162 Show the current target architecture.
16164 @item set processor
16166 @kindex set processor
16167 @kindex show processor
16168 These are alias commands for, respectively, @code{set architecture}
16169 and @code{show architecture}.
16173 * Active Targets:: Active targets
16174 * Target Commands:: Commands for managing targets
16175 * Byte Order:: Choosing target byte order
16178 @node Active Targets
16179 @section Active Targets
16181 @cindex stacking targets
16182 @cindex active targets
16183 @cindex multiple targets
16185 There are multiple classes of targets such as: processes, executable files or
16186 recording sessions. Core files belong to the process class, making core file
16187 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
16188 on multiple active targets, one in each class. This allows you to (for
16189 example) start a process and inspect its activity, while still having access to
16190 the executable file after the process finishes. Or if you start process
16191 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
16192 presented a virtual layer of the recording target, while the process target
16193 remains stopped at the chronologically last point of the process execution.
16195 Use the @code{core-file} and @code{exec-file} commands to select a new core
16196 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
16197 specify as a target a process that is already running, use the @code{attach}
16198 command (@pxref{Attach, ,Debugging an Already-running Process}).
16200 @node Target Commands
16201 @section Commands for Managing Targets
16204 @item target @var{type} @var{parameters}
16205 Connects the @value{GDBN} host environment to a target machine or
16206 process. A target is typically a protocol for talking to debugging
16207 facilities. You use the argument @var{type} to specify the type or
16208 protocol of the target machine.
16210 Further @var{parameters} are interpreted by the target protocol, but
16211 typically include things like device names or host names to connect
16212 with, process numbers, and baud rates.
16214 The @code{target} command does not repeat if you press @key{RET} again
16215 after executing the command.
16217 @kindex help target
16219 Displays the names of all targets available. To display targets
16220 currently selected, use either @code{info target} or @code{info files}
16221 (@pxref{Files, ,Commands to Specify Files}).
16223 @item help target @var{name}
16224 Describe a particular target, including any parameters necessary to
16227 @kindex set gnutarget
16228 @item set gnutarget @var{args}
16229 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
16230 knows whether it is reading an @dfn{executable},
16231 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
16232 with the @code{set gnutarget} command. Unlike most @code{target} commands,
16233 with @code{gnutarget} the @code{target} refers to a program, not a machine.
16236 @emph{Warning:} To specify a file format with @code{set gnutarget},
16237 you must know the actual BFD name.
16241 @xref{Files, , Commands to Specify Files}.
16243 @kindex show gnutarget
16244 @item show gnutarget
16245 Use the @code{show gnutarget} command to display what file format
16246 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
16247 @value{GDBN} will determine the file format for each file automatically,
16248 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
16251 @cindex common targets
16252 Here are some common targets (available, or not, depending on the GDB
16257 @item target exec @var{program}
16258 @cindex executable file target
16259 An executable file. @samp{target exec @var{program}} is the same as
16260 @samp{exec-file @var{program}}.
16262 @item target core @var{filename}
16263 @cindex core dump file target
16264 A core dump file. @samp{target core @var{filename}} is the same as
16265 @samp{core-file @var{filename}}.
16267 @item target remote @var{medium}
16268 @cindex remote target
16269 A remote system connected to @value{GDBN} via a serial line or network
16270 connection. This command tells @value{GDBN} to use its own remote
16271 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
16273 For example, if you have a board connected to @file{/dev/ttya} on the
16274 machine running @value{GDBN}, you could say:
16277 target remote /dev/ttya
16280 @code{target remote} supports the @code{load} command. This is only
16281 useful if you have some other way of getting the stub to the target
16282 system, and you can put it somewhere in memory where it won't get
16283 clobbered by the download.
16285 @item target sim @r{[}@var{simargs}@r{]} @dots{}
16286 @cindex built-in simulator target
16287 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
16295 works; however, you cannot assume that a specific memory map, device
16296 drivers, or even basic I/O is available, although some simulators do
16297 provide these. For info about any processor-specific simulator details,
16298 see the appropriate section in @ref{Embedded Processors, ,Embedded
16303 Some configurations may include these targets as well:
16307 @item target nrom @var{dev}
16308 @cindex NetROM ROM emulator target
16309 NetROM ROM emulator. This target only supports downloading.
16313 Different targets are available on different configurations of @value{GDBN};
16314 your configuration may have more or fewer targets.
16316 Many remote targets require you to download the executable's code once
16317 you've successfully established a connection. You may wish to control
16318 various aspects of this process.
16323 @kindex set hash@r{, for remote monitors}
16324 @cindex hash mark while downloading
16325 This command controls whether a hash mark @samp{#} is displayed while
16326 downloading a file to the remote monitor. If on, a hash mark is
16327 displayed after each S-record is successfully downloaded to the
16331 @kindex show hash@r{, for remote monitors}
16332 Show the current status of displaying the hash mark.
16334 @item set debug monitor
16335 @kindex set debug monitor
16336 @cindex display remote monitor communications
16337 Enable or disable display of communications messages between
16338 @value{GDBN} and the remote monitor.
16340 @item show debug monitor
16341 @kindex show debug monitor
16342 Show the current status of displaying communications between
16343 @value{GDBN} and the remote monitor.
16348 @kindex load @var{filename}
16349 @item load @var{filename}
16351 Depending on what remote debugging facilities are configured into
16352 @value{GDBN}, the @code{load} command may be available. Where it exists, it
16353 is meant to make @var{filename} (an executable) available for debugging
16354 on the remote system---by downloading, or dynamic linking, for example.
16355 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
16356 the @code{add-symbol-file} command.
16358 If your @value{GDBN} does not have a @code{load} command, attempting to
16359 execute it gets the error message ``@code{You can't do that when your
16360 target is @dots{}}''
16362 The file is loaded at whatever address is specified in the executable.
16363 For some object file formats, you can specify the load address when you
16364 link the program; for other formats, like a.out, the object file format
16365 specifies a fixed address.
16366 @c FIXME! This would be a good place for an xref to the GNU linker doc.
16368 Depending on the remote side capabilities, @value{GDBN} may be able to
16369 load programs into flash memory.
16371 @code{load} does not repeat if you press @key{RET} again after using it.
16375 @section Choosing Target Byte Order
16377 @cindex choosing target byte order
16378 @cindex target byte order
16380 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
16381 offer the ability to run either big-endian or little-endian byte
16382 orders. Usually the executable or symbol will include a bit to
16383 designate the endian-ness, and you will not need to worry about
16384 which to use. However, you may still find it useful to adjust
16385 @value{GDBN}'s idea of processor endian-ness manually.
16389 @item set endian big
16390 Instruct @value{GDBN} to assume the target is big-endian.
16392 @item set endian little
16393 Instruct @value{GDBN} to assume the target is little-endian.
16395 @item set endian auto
16396 Instruct @value{GDBN} to use the byte order associated with the
16400 Display @value{GDBN}'s current idea of the target byte order.
16404 Note that these commands merely adjust interpretation of symbolic
16405 data on the host, and that they have absolutely no effect on the
16409 @node Remote Debugging
16410 @chapter Debugging Remote Programs
16411 @cindex remote debugging
16413 If you are trying to debug a program running on a machine that cannot run
16414 @value{GDBN} in the usual way, it is often useful to use remote debugging.
16415 For example, you might use remote debugging on an operating system kernel,
16416 or on a small system which does not have a general purpose operating system
16417 powerful enough to run a full-featured debugger.
16419 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
16420 to make this work with particular debugging targets. In addition,
16421 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
16422 but not specific to any particular target system) which you can use if you
16423 write the remote stubs---the code that runs on the remote system to
16424 communicate with @value{GDBN}.
16426 Other remote targets may be available in your
16427 configuration of @value{GDBN}; use @code{help target} to list them.
16430 * Connecting:: Connecting to a remote target
16431 * File Transfer:: Sending files to a remote system
16432 * Server:: Using the gdbserver program
16433 * Remote Configuration:: Remote configuration
16434 * Remote Stub:: Implementing a remote stub
16438 @section Connecting to a Remote Target
16440 On the @value{GDBN} host machine, you will need an unstripped copy of
16441 your program, since @value{GDBN} needs symbol and debugging information.
16442 Start up @value{GDBN} as usual, using the name of the local copy of your
16443 program as the first argument.
16445 @cindex @code{target remote}
16446 @value{GDBN} can communicate with the target over a serial line, or
16447 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
16448 each case, @value{GDBN} uses the same protocol for debugging your
16449 program; only the medium carrying the debugging packets varies. The
16450 @code{target remote} command establishes a connection to the target.
16451 Its arguments indicate which medium to use:
16455 @item target remote @var{serial-device}
16456 @cindex serial line, @code{target remote}
16457 Use @var{serial-device} to communicate with the target. For example,
16458 to use a serial line connected to the device named @file{/dev/ttyb}:
16461 target remote /dev/ttyb
16464 If you're using a serial line, you may want to give @value{GDBN} the
16465 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
16466 (@pxref{Remote Configuration, set remotebaud}) before the
16467 @code{target} command.
16469 @item target remote @code{@var{host}:@var{port}}
16470 @itemx target remote @code{tcp:@var{host}:@var{port}}
16471 @cindex @acronym{TCP} port, @code{target remote}
16472 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
16473 The @var{host} may be either a host name or a numeric @acronym{IP}
16474 address; @var{port} must be a decimal number. The @var{host} could be
16475 the target machine itself, if it is directly connected to the net, or
16476 it might be a terminal server which in turn has a serial line to the
16479 For example, to connect to port 2828 on a terminal server named
16483 target remote manyfarms:2828
16486 If your remote target is actually running on the same machine as your
16487 debugger session (e.g.@: a simulator for your target running on the
16488 same host), you can omit the hostname. For example, to connect to
16489 port 1234 on your local machine:
16492 target remote :1234
16496 Note that the colon is still required here.
16498 @item target remote @code{udp:@var{host}:@var{port}}
16499 @cindex @acronym{UDP} port, @code{target remote}
16500 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
16501 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
16504 target remote udp:manyfarms:2828
16507 When using a @acronym{UDP} connection for remote debugging, you should
16508 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
16509 can silently drop packets on busy or unreliable networks, which will
16510 cause havoc with your debugging session.
16512 @item target remote | @var{command}
16513 @cindex pipe, @code{target remote} to
16514 Run @var{command} in the background and communicate with it using a
16515 pipe. The @var{command} is a shell command, to be parsed and expanded
16516 by the system's command shell, @code{/bin/sh}; it should expect remote
16517 protocol packets on its standard input, and send replies on its
16518 standard output. You could use this to run a stand-alone simulator
16519 that speaks the remote debugging protocol, to make net connections
16520 using programs like @code{ssh}, or for other similar tricks.
16522 If @var{command} closes its standard output (perhaps by exiting),
16523 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
16524 program has already exited, this will have no effect.)
16528 Once the connection has been established, you can use all the usual
16529 commands to examine and change data. The remote program is already
16530 running; you can use @kbd{step} and @kbd{continue}, and you do not
16531 need to use @kbd{run}.
16533 @cindex interrupting remote programs
16534 @cindex remote programs, interrupting
16535 Whenever @value{GDBN} is waiting for the remote program, if you type the
16536 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
16537 program. This may or may not succeed, depending in part on the hardware
16538 and the serial drivers the remote system uses. If you type the
16539 interrupt character once again, @value{GDBN} displays this prompt:
16542 Interrupted while waiting for the program.
16543 Give up (and stop debugging it)? (y or n)
16546 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
16547 (If you decide you want to try again later, you can use @samp{target
16548 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
16549 goes back to waiting.
16552 @kindex detach (remote)
16554 When you have finished debugging the remote program, you can use the
16555 @code{detach} command to release it from @value{GDBN} control.
16556 Detaching from the target normally resumes its execution, but the results
16557 will depend on your particular remote stub. After the @code{detach}
16558 command, @value{GDBN} is free to connect to another target.
16562 The @code{disconnect} command behaves like @code{detach}, except that
16563 the target is generally not resumed. It will wait for @value{GDBN}
16564 (this instance or another one) to connect and continue debugging. After
16565 the @code{disconnect} command, @value{GDBN} is again free to connect to
16568 @cindex send command to remote monitor
16569 @cindex extend @value{GDBN} for remote targets
16570 @cindex add new commands for external monitor
16572 @item monitor @var{cmd}
16573 This command allows you to send arbitrary commands directly to the
16574 remote monitor. Since @value{GDBN} doesn't care about the commands it
16575 sends like this, this command is the way to extend @value{GDBN}---you
16576 can add new commands that only the external monitor will understand
16580 @node File Transfer
16581 @section Sending files to a remote system
16582 @cindex remote target, file transfer
16583 @cindex file transfer
16584 @cindex sending files to remote systems
16586 Some remote targets offer the ability to transfer files over the same
16587 connection used to communicate with @value{GDBN}. This is convenient
16588 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
16589 running @code{gdbserver} over a network interface. For other targets,
16590 e.g.@: embedded devices with only a single serial port, this may be
16591 the only way to upload or download files.
16593 Not all remote targets support these commands.
16597 @item remote put @var{hostfile} @var{targetfile}
16598 Copy file @var{hostfile} from the host system (the machine running
16599 @value{GDBN}) to @var{targetfile} on the target system.
16602 @item remote get @var{targetfile} @var{hostfile}
16603 Copy file @var{targetfile} from the target system to @var{hostfile}
16604 on the host system.
16606 @kindex remote delete
16607 @item remote delete @var{targetfile}
16608 Delete @var{targetfile} from the target system.
16613 @section Using the @code{gdbserver} Program
16616 @cindex remote connection without stubs
16617 @code{gdbserver} is a control program for Unix-like systems, which
16618 allows you to connect your program with a remote @value{GDBN} via
16619 @code{target remote}---but without linking in the usual debugging stub.
16621 @code{gdbserver} is not a complete replacement for the debugging stubs,
16622 because it requires essentially the same operating-system facilities
16623 that @value{GDBN} itself does. In fact, a system that can run
16624 @code{gdbserver} to connect to a remote @value{GDBN} could also run
16625 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
16626 because it is a much smaller program than @value{GDBN} itself. It is
16627 also easier to port than all of @value{GDBN}, so you may be able to get
16628 started more quickly on a new system by using @code{gdbserver}.
16629 Finally, if you develop code for real-time systems, you may find that
16630 the tradeoffs involved in real-time operation make it more convenient to
16631 do as much development work as possible on another system, for example
16632 by cross-compiling. You can use @code{gdbserver} to make a similar
16633 choice for debugging.
16635 @value{GDBN} and @code{gdbserver} communicate via either a serial line
16636 or a TCP connection, using the standard @value{GDBN} remote serial
16640 @emph{Warning:} @code{gdbserver} does not have any built-in security.
16641 Do not run @code{gdbserver} connected to any public network; a
16642 @value{GDBN} connection to @code{gdbserver} provides access to the
16643 target system with the same privileges as the user running
16647 @subsection Running @code{gdbserver}
16648 @cindex arguments, to @code{gdbserver}
16649 @cindex @code{gdbserver}, command-line arguments
16651 Run @code{gdbserver} on the target system. You need a copy of the
16652 program you want to debug, including any libraries it requires.
16653 @code{gdbserver} does not need your program's symbol table, so you can
16654 strip the program if necessary to save space. @value{GDBN} on the host
16655 system does all the symbol handling.
16657 To use the server, you must tell it how to communicate with @value{GDBN};
16658 the name of your program; and the arguments for your program. The usual
16662 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
16665 @var{comm} is either a device name (to use a serial line) or a TCP
16666 hostname and portnumber. For example, to debug Emacs with the argument
16667 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
16671 target> gdbserver /dev/com1 emacs foo.txt
16674 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
16677 To use a TCP connection instead of a serial line:
16680 target> gdbserver host:2345 emacs foo.txt
16683 The only difference from the previous example is the first argument,
16684 specifying that you are communicating with the host @value{GDBN} via
16685 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
16686 expect a TCP connection from machine @samp{host} to local TCP port 2345.
16687 (Currently, the @samp{host} part is ignored.) You can choose any number
16688 you want for the port number as long as it does not conflict with any
16689 TCP ports already in use on the target system (for example, @code{23} is
16690 reserved for @code{telnet}).@footnote{If you choose a port number that
16691 conflicts with another service, @code{gdbserver} prints an error message
16692 and exits.} You must use the same port number with the host @value{GDBN}
16693 @code{target remote} command.
16695 @subsubsection Attaching to a Running Program
16696 @cindex attach to a program, @code{gdbserver}
16697 @cindex @option{--attach}, @code{gdbserver} option
16699 On some targets, @code{gdbserver} can also attach to running programs.
16700 This is accomplished via the @code{--attach} argument. The syntax is:
16703 target> gdbserver --attach @var{comm} @var{pid}
16706 @var{pid} is the process ID of a currently running process. It isn't necessary
16707 to point @code{gdbserver} at a binary for the running process.
16710 You can debug processes by name instead of process ID if your target has the
16711 @code{pidof} utility:
16714 target> gdbserver --attach @var{comm} `pidof @var{program}`
16717 In case more than one copy of @var{program} is running, or @var{program}
16718 has multiple threads, most versions of @code{pidof} support the
16719 @code{-s} option to only return the first process ID.
16721 @subsubsection Multi-Process Mode for @code{gdbserver}
16722 @cindex @code{gdbserver}, multiple processes
16723 @cindex multiple processes with @code{gdbserver}
16725 When you connect to @code{gdbserver} using @code{target remote},
16726 @code{gdbserver} debugs the specified program only once. When the
16727 program exits, or you detach from it, @value{GDBN} closes the connection
16728 and @code{gdbserver} exits.
16730 If you connect using @kbd{target extended-remote}, @code{gdbserver}
16731 enters multi-process mode. When the debugged program exits, or you
16732 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
16733 though no program is running. The @code{run} and @code{attach}
16734 commands instruct @code{gdbserver} to run or attach to a new program.
16735 The @code{run} command uses @code{set remote exec-file} (@pxref{set
16736 remote exec-file}) to select the program to run. Command line
16737 arguments are supported, except for wildcard expansion and I/O
16738 redirection (@pxref{Arguments}).
16740 @cindex @option{--multi}, @code{gdbserver} option
16741 To start @code{gdbserver} without supplying an initial command to run
16742 or process ID to attach, use the @option{--multi} command line option.
16743 Then you can connect using @kbd{target extended-remote} and start
16744 the program you want to debug.
16746 In multi-process mode @code{gdbserver} does not automatically exit unless you
16747 use the option @option{--once}. You can terminate it by using
16748 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
16749 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
16750 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
16751 @option{--multi} option to @code{gdbserver} has no influence on that.
16753 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
16755 This section applies only when @code{gdbserver} is run to listen on a TCP port.
16757 @code{gdbserver} normally terminates after all of its debugged processes have
16758 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
16759 extended-remote}, @code{gdbserver} stays running even with no processes left.
16760 @value{GDBN} normally terminates the spawned debugged process on its exit,
16761 which normally also terminates @code{gdbserver} in the @kbd{target remote}
16762 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
16763 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
16764 stays running even in the @kbd{target remote} mode.
16766 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
16767 Such reconnecting is useful for features like @ref{disconnected tracing}. For
16768 completeness, at most one @value{GDBN} can be connected at a time.
16770 @cindex @option{--once}, @code{gdbserver} option
16771 By default, @code{gdbserver} keeps the listening TCP port open, so that
16772 additional connections are possible. However, if you start @code{gdbserver}
16773 with the @option{--once} option, it will stop listening for any further
16774 connection attempts after connecting to the first @value{GDBN} session. This
16775 means no further connections to @code{gdbserver} will be possible after the
16776 first one. It also means @code{gdbserver} will terminate after the first
16777 connection with remote @value{GDBN} has closed, even for unexpectedly closed
16778 connections and even in the @kbd{target extended-remote} mode. The
16779 @option{--once} option allows reusing the same port number for connecting to
16780 multiple instances of @code{gdbserver} running on the same host, since each
16781 instance closes its port after the first connection.
16783 @subsubsection Other Command-Line Arguments for @code{gdbserver}
16785 @cindex @option{--debug}, @code{gdbserver} option
16786 The @option{--debug} option tells @code{gdbserver} to display extra
16787 status information about the debugging process.
16788 @cindex @option{--remote-debug}, @code{gdbserver} option
16789 The @option{--remote-debug} option tells @code{gdbserver} to display
16790 remote protocol debug output. These options are intended for
16791 @code{gdbserver} development and for bug reports to the developers.
16793 @cindex @option{--wrapper}, @code{gdbserver} option
16794 The @option{--wrapper} option specifies a wrapper to launch programs
16795 for debugging. The option should be followed by the name of the
16796 wrapper, then any command-line arguments to pass to the wrapper, then
16797 @kbd{--} indicating the end of the wrapper arguments.
16799 @code{gdbserver} runs the specified wrapper program with a combined
16800 command line including the wrapper arguments, then the name of the
16801 program to debug, then any arguments to the program. The wrapper
16802 runs until it executes your program, and then @value{GDBN} gains control.
16804 You can use any program that eventually calls @code{execve} with
16805 its arguments as a wrapper. Several standard Unix utilities do
16806 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
16807 with @code{exec "$@@"} will also work.
16809 For example, you can use @code{env} to pass an environment variable to
16810 the debugged program, without setting the variable in @code{gdbserver}'s
16814 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
16817 @subsection Connecting to @code{gdbserver}
16819 Run @value{GDBN} on the host system.
16821 First make sure you have the necessary symbol files. Load symbols for
16822 your application using the @code{file} command before you connect. Use
16823 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
16824 was compiled with the correct sysroot using @code{--with-sysroot}).
16826 The symbol file and target libraries must exactly match the executable
16827 and libraries on the target, with one exception: the files on the host
16828 system should not be stripped, even if the files on the target system
16829 are. Mismatched or missing files will lead to confusing results
16830 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
16831 files may also prevent @code{gdbserver} from debugging multi-threaded
16834 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
16835 For TCP connections, you must start up @code{gdbserver} prior to using
16836 the @code{target remote} command. Otherwise you may get an error whose
16837 text depends on the host system, but which usually looks something like
16838 @samp{Connection refused}. Don't use the @code{load}
16839 command in @value{GDBN} when using @code{gdbserver}, since the program is
16840 already on the target.
16842 @subsection Monitor Commands for @code{gdbserver}
16843 @cindex monitor commands, for @code{gdbserver}
16844 @anchor{Monitor Commands for gdbserver}
16846 During a @value{GDBN} session using @code{gdbserver}, you can use the
16847 @code{monitor} command to send special requests to @code{gdbserver}.
16848 Here are the available commands.
16852 List the available monitor commands.
16854 @item monitor set debug 0
16855 @itemx monitor set debug 1
16856 Disable or enable general debugging messages.
16858 @item monitor set remote-debug 0
16859 @itemx monitor set remote-debug 1
16860 Disable or enable specific debugging messages associated with the remote
16861 protocol (@pxref{Remote Protocol}).
16863 @item monitor set libthread-db-search-path [PATH]
16864 @cindex gdbserver, search path for @code{libthread_db}
16865 When this command is issued, @var{path} is a colon-separated list of
16866 directories to search for @code{libthread_db} (@pxref{Threads,,set
16867 libthread-db-search-path}). If you omit @var{path},
16868 @samp{libthread-db-search-path} will be reset to its default value.
16870 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
16871 not supported in @code{gdbserver}.
16874 Tell gdbserver to exit immediately. This command should be followed by
16875 @code{disconnect} to close the debugging session. @code{gdbserver} will
16876 detach from any attached processes and kill any processes it created.
16877 Use @code{monitor exit} to terminate @code{gdbserver} at the end
16878 of a multi-process mode debug session.
16882 @subsection Tracepoints support in @code{gdbserver}
16883 @cindex tracepoints support in @code{gdbserver}
16885 On some targets, @code{gdbserver} supports tracepoints, fast
16886 tracepoints and static tracepoints.
16888 For fast or static tracepoints to work, a special library called the
16889 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
16890 This library is built and distributed as an integral part of
16891 @code{gdbserver}. In addition, support for static tracepoints
16892 requires building the in-process agent library with static tracepoints
16893 support. At present, the UST (LTTng Userspace Tracer,
16894 @url{http://lttng.org/ust}) tracing engine is supported. This support
16895 is automatically available if UST development headers are found in the
16896 standard include path when @code{gdbserver} is built, or if
16897 @code{gdbserver} was explicitly configured using @option{--with-ust}
16898 to point at such headers. You can explicitly disable the support
16899 using @option{--with-ust=no}.
16901 There are several ways to load the in-process agent in your program:
16904 @item Specifying it as dependency at link time
16906 You can link your program dynamically with the in-process agent
16907 library. On most systems, this is accomplished by adding
16908 @code{-linproctrace} to the link command.
16910 @item Using the system's preloading mechanisms
16912 You can force loading the in-process agent at startup time by using
16913 your system's support for preloading shared libraries. Many Unixes
16914 support the concept of preloading user defined libraries. In most
16915 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
16916 in the environment. See also the description of @code{gdbserver}'s
16917 @option{--wrapper} command line option.
16919 @item Using @value{GDBN} to force loading the agent at run time
16921 On some systems, you can force the inferior to load a shared library,
16922 by calling a dynamic loader function in the inferior that takes care
16923 of dynamically looking up and loading a shared library. On most Unix
16924 systems, the function is @code{dlopen}. You'll use the @code{call}
16925 command for that. For example:
16928 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
16931 Note that on most Unix systems, for the @code{dlopen} function to be
16932 available, the program needs to be linked with @code{-ldl}.
16935 On systems that have a userspace dynamic loader, like most Unix
16936 systems, when you connect to @code{gdbserver} using @code{target
16937 remote}, you'll find that the program is stopped at the dynamic
16938 loader's entry point, and no shared library has been loaded in the
16939 program's address space yet, including the in-process agent. In that
16940 case, before being able to use any of the fast or static tracepoints
16941 features, you need to let the loader run and load the shared
16942 libraries. The simplest way to do that is to run the program to the
16943 main procedure. E.g., if debugging a C or C@t{++} program, start
16944 @code{gdbserver} like so:
16947 $ gdbserver :9999 myprogram
16950 Start GDB and connect to @code{gdbserver} like so, and run to main:
16954 (@value{GDBP}) target remote myhost:9999
16955 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
16956 (@value{GDBP}) b main
16957 (@value{GDBP}) continue
16960 The in-process tracing agent library should now be loaded into the
16961 process; you can confirm it with the @code{info sharedlibrary}
16962 command, which will list @file{libinproctrace.so} as loaded in the
16963 process. You are now ready to install fast tracepoints, list static
16964 tracepoint markers, probe static tracepoints markers, and start
16967 @node Remote Configuration
16968 @section Remote Configuration
16971 @kindex show remote
16972 This section documents the configuration options available when
16973 debugging remote programs. For the options related to the File I/O
16974 extensions of the remote protocol, see @ref{system,
16975 system-call-allowed}.
16978 @item set remoteaddresssize @var{bits}
16979 @cindex address size for remote targets
16980 @cindex bits in remote address
16981 Set the maximum size of address in a memory packet to the specified
16982 number of bits. @value{GDBN} will mask off the address bits above
16983 that number, when it passes addresses to the remote target. The
16984 default value is the number of bits in the target's address.
16986 @item show remoteaddresssize
16987 Show the current value of remote address size in bits.
16989 @item set remotebaud @var{n}
16990 @cindex baud rate for remote targets
16991 Set the baud rate for the remote serial I/O to @var{n} baud. The
16992 value is used to set the speed of the serial port used for debugging
16995 @item show remotebaud
16996 Show the current speed of the remote connection.
16998 @item set remotebreak
16999 @cindex interrupt remote programs
17000 @cindex BREAK signal instead of Ctrl-C
17001 @anchor{set remotebreak}
17002 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
17003 when you type @kbd{Ctrl-c} to interrupt the program running
17004 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
17005 character instead. The default is off, since most remote systems
17006 expect to see @samp{Ctrl-C} as the interrupt signal.
17008 @item show remotebreak
17009 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
17010 interrupt the remote program.
17012 @item set remoteflow on
17013 @itemx set remoteflow off
17014 @kindex set remoteflow
17015 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
17016 on the serial port used to communicate to the remote target.
17018 @item show remoteflow
17019 @kindex show remoteflow
17020 Show the current setting of hardware flow control.
17022 @item set remotelogbase @var{base}
17023 Set the base (a.k.a.@: radix) of logging serial protocol
17024 communications to @var{base}. Supported values of @var{base} are:
17025 @code{ascii}, @code{octal}, and @code{hex}. The default is
17028 @item show remotelogbase
17029 Show the current setting of the radix for logging remote serial
17032 @item set remotelogfile @var{file}
17033 @cindex record serial communications on file
17034 Record remote serial communications on the named @var{file}. The
17035 default is not to record at all.
17037 @item show remotelogfile.
17038 Show the current setting of the file name on which to record the
17039 serial communications.
17041 @item set remotetimeout @var{num}
17042 @cindex timeout for serial communications
17043 @cindex remote timeout
17044 Set the timeout limit to wait for the remote target to respond to
17045 @var{num} seconds. The default is 2 seconds.
17047 @item show remotetimeout
17048 Show the current number of seconds to wait for the remote target
17051 @cindex limit hardware breakpoints and watchpoints
17052 @cindex remote target, limit break- and watchpoints
17053 @anchor{set remote hardware-watchpoint-limit}
17054 @anchor{set remote hardware-breakpoint-limit}
17055 @item set remote hardware-watchpoint-limit @var{limit}
17056 @itemx set remote hardware-breakpoint-limit @var{limit}
17057 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
17058 watchpoints. A limit of -1, the default, is treated as unlimited.
17060 @cindex limit hardware watchpoints length
17061 @cindex remote target, limit watchpoints length
17062 @anchor{set remote hardware-watchpoint-length-limit}
17063 @item set remote hardware-watchpoint-length-limit @var{limit}
17064 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
17065 a remote hardware watchpoint. A limit of -1, the default, is treated
17068 @item show remote hardware-watchpoint-length-limit
17069 Show the current limit (in bytes) of the maximum length of
17070 a remote hardware watchpoint.
17072 @item set remote exec-file @var{filename}
17073 @itemx show remote exec-file
17074 @anchor{set remote exec-file}
17075 @cindex executable file, for remote target
17076 Select the file used for @code{run} with @code{target
17077 extended-remote}. This should be set to a filename valid on the
17078 target system. If it is not set, the target will use a default
17079 filename (e.g.@: the last program run).
17081 @item set remote interrupt-sequence
17082 @cindex interrupt remote programs
17083 @cindex select Ctrl-C, BREAK or BREAK-g
17084 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
17085 @samp{BREAK-g} as the
17086 sequence to the remote target in order to interrupt the execution.
17087 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
17088 is high level of serial line for some certain time.
17089 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
17090 It is @code{BREAK} signal followed by character @code{g}.
17092 @item show interrupt-sequence
17093 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
17094 is sent by @value{GDBN} to interrupt the remote program.
17095 @code{BREAK-g} is BREAK signal followed by @code{g} and
17096 also known as Magic SysRq g.
17098 @item set remote interrupt-on-connect
17099 @cindex send interrupt-sequence on start
17100 Specify whether interrupt-sequence is sent to remote target when
17101 @value{GDBN} connects to it. This is mostly needed when you debug
17102 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
17103 which is known as Magic SysRq g in order to connect @value{GDBN}.
17105 @item show interrupt-on-connect
17106 Show whether interrupt-sequence is sent
17107 to remote target when @value{GDBN} connects to it.
17111 @item set tcp auto-retry on
17112 @cindex auto-retry, for remote TCP target
17113 Enable auto-retry for remote TCP connections. This is useful if the remote
17114 debugging agent is launched in parallel with @value{GDBN}; there is a race
17115 condition because the agent may not become ready to accept the connection
17116 before @value{GDBN} attempts to connect. When auto-retry is
17117 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
17118 to establish the connection using the timeout specified by
17119 @code{set tcp connect-timeout}.
17121 @item set tcp auto-retry off
17122 Do not auto-retry failed TCP connections.
17124 @item show tcp auto-retry
17125 Show the current auto-retry setting.
17127 @item set tcp connect-timeout @var{seconds}
17128 @cindex connection timeout, for remote TCP target
17129 @cindex timeout, for remote target connection
17130 Set the timeout for establishing a TCP connection to the remote target to
17131 @var{seconds}. The timeout affects both polling to retry failed connections
17132 (enabled by @code{set tcp auto-retry on}) and waiting for connections
17133 that are merely slow to complete, and represents an approximate cumulative
17136 @item show tcp connect-timeout
17137 Show the current connection timeout setting.
17140 @cindex remote packets, enabling and disabling
17141 The @value{GDBN} remote protocol autodetects the packets supported by
17142 your debugging stub. If you need to override the autodetection, you
17143 can use these commands to enable or disable individual packets. Each
17144 packet can be set to @samp{on} (the remote target supports this
17145 packet), @samp{off} (the remote target does not support this packet),
17146 or @samp{auto} (detect remote target support for this packet). They
17147 all default to @samp{auto}. For more information about each packet,
17148 see @ref{Remote Protocol}.
17150 During normal use, you should not have to use any of these commands.
17151 If you do, that may be a bug in your remote debugging stub, or a bug
17152 in @value{GDBN}. You may want to report the problem to the
17153 @value{GDBN} developers.
17155 For each packet @var{name}, the command to enable or disable the
17156 packet is @code{set remote @var{name}-packet}. The available settings
17159 @multitable @columnfractions 0.28 0.32 0.25
17162 @tab Related Features
17164 @item @code{fetch-register}
17166 @tab @code{info registers}
17168 @item @code{set-register}
17172 @item @code{binary-download}
17174 @tab @code{load}, @code{set}
17176 @item @code{read-aux-vector}
17177 @tab @code{qXfer:auxv:read}
17178 @tab @code{info auxv}
17180 @item @code{symbol-lookup}
17181 @tab @code{qSymbol}
17182 @tab Detecting multiple threads
17184 @item @code{attach}
17185 @tab @code{vAttach}
17188 @item @code{verbose-resume}
17190 @tab Stepping or resuming multiple threads
17196 @item @code{software-breakpoint}
17200 @item @code{hardware-breakpoint}
17204 @item @code{write-watchpoint}
17208 @item @code{read-watchpoint}
17212 @item @code{access-watchpoint}
17216 @item @code{target-features}
17217 @tab @code{qXfer:features:read}
17218 @tab @code{set architecture}
17220 @item @code{library-info}
17221 @tab @code{qXfer:libraries:read}
17222 @tab @code{info sharedlibrary}
17224 @item @code{memory-map}
17225 @tab @code{qXfer:memory-map:read}
17226 @tab @code{info mem}
17228 @item @code{read-sdata-object}
17229 @tab @code{qXfer:sdata:read}
17230 @tab @code{print $_sdata}
17232 @item @code{read-spu-object}
17233 @tab @code{qXfer:spu:read}
17234 @tab @code{info spu}
17236 @item @code{write-spu-object}
17237 @tab @code{qXfer:spu:write}
17238 @tab @code{info spu}
17240 @item @code{read-siginfo-object}
17241 @tab @code{qXfer:siginfo:read}
17242 @tab @code{print $_siginfo}
17244 @item @code{write-siginfo-object}
17245 @tab @code{qXfer:siginfo:write}
17246 @tab @code{set $_siginfo}
17248 @item @code{threads}
17249 @tab @code{qXfer:threads:read}
17250 @tab @code{info threads}
17252 @item @code{get-thread-local-@*storage-address}
17253 @tab @code{qGetTLSAddr}
17254 @tab Displaying @code{__thread} variables
17256 @item @code{get-thread-information-block-address}
17257 @tab @code{qGetTIBAddr}
17258 @tab Display MS-Windows Thread Information Block.
17260 @item @code{search-memory}
17261 @tab @code{qSearch:memory}
17264 @item @code{supported-packets}
17265 @tab @code{qSupported}
17266 @tab Remote communications parameters
17268 @item @code{pass-signals}
17269 @tab @code{QPassSignals}
17270 @tab @code{handle @var{signal}}
17272 @item @code{hostio-close-packet}
17273 @tab @code{vFile:close}
17274 @tab @code{remote get}, @code{remote put}
17276 @item @code{hostio-open-packet}
17277 @tab @code{vFile:open}
17278 @tab @code{remote get}, @code{remote put}
17280 @item @code{hostio-pread-packet}
17281 @tab @code{vFile:pread}
17282 @tab @code{remote get}, @code{remote put}
17284 @item @code{hostio-pwrite-packet}
17285 @tab @code{vFile:pwrite}
17286 @tab @code{remote get}, @code{remote put}
17288 @item @code{hostio-unlink-packet}
17289 @tab @code{vFile:unlink}
17290 @tab @code{remote delete}
17292 @item @code{noack-packet}
17293 @tab @code{QStartNoAckMode}
17294 @tab Packet acknowledgment
17296 @item @code{osdata}
17297 @tab @code{qXfer:osdata:read}
17298 @tab @code{info os}
17300 @item @code{query-attached}
17301 @tab @code{qAttached}
17302 @tab Querying remote process attach state.
17304 @item @code{traceframe-info}
17305 @tab @code{qXfer:traceframe-info:read}
17306 @tab Traceframe info
17308 @item @code{disable-randomization}
17309 @tab @code{QDisableRandomization}
17310 @tab @code{set disable-randomization}
17314 @section Implementing a Remote Stub
17316 @cindex debugging stub, example
17317 @cindex remote stub, example
17318 @cindex stub example, remote debugging
17319 The stub files provided with @value{GDBN} implement the target side of the
17320 communication protocol, and the @value{GDBN} side is implemented in the
17321 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
17322 these subroutines to communicate, and ignore the details. (If you're
17323 implementing your own stub file, you can still ignore the details: start
17324 with one of the existing stub files. @file{sparc-stub.c} is the best
17325 organized, and therefore the easiest to read.)
17327 @cindex remote serial debugging, overview
17328 To debug a program running on another machine (the debugging
17329 @dfn{target} machine), you must first arrange for all the usual
17330 prerequisites for the program to run by itself. For example, for a C
17335 A startup routine to set up the C runtime environment; these usually
17336 have a name like @file{crt0}. The startup routine may be supplied by
17337 your hardware supplier, or you may have to write your own.
17340 A C subroutine library to support your program's
17341 subroutine calls, notably managing input and output.
17344 A way of getting your program to the other machine---for example, a
17345 download program. These are often supplied by the hardware
17346 manufacturer, but you may have to write your own from hardware
17350 The next step is to arrange for your program to use a serial port to
17351 communicate with the machine where @value{GDBN} is running (the @dfn{host}
17352 machine). In general terms, the scheme looks like this:
17356 @value{GDBN} already understands how to use this protocol; when everything
17357 else is set up, you can simply use the @samp{target remote} command
17358 (@pxref{Targets,,Specifying a Debugging Target}).
17360 @item On the target,
17361 you must link with your program a few special-purpose subroutines that
17362 implement the @value{GDBN} remote serial protocol. The file containing these
17363 subroutines is called a @dfn{debugging stub}.
17365 On certain remote targets, you can use an auxiliary program
17366 @code{gdbserver} instead of linking a stub into your program.
17367 @xref{Server,,Using the @code{gdbserver} Program}, for details.
17370 The debugging stub is specific to the architecture of the remote
17371 machine; for example, use @file{sparc-stub.c} to debug programs on
17374 @cindex remote serial stub list
17375 These working remote stubs are distributed with @value{GDBN}:
17380 @cindex @file{i386-stub.c}
17383 For Intel 386 and compatible architectures.
17386 @cindex @file{m68k-stub.c}
17387 @cindex Motorola 680x0
17389 For Motorola 680x0 architectures.
17392 @cindex @file{sh-stub.c}
17395 For Renesas SH architectures.
17398 @cindex @file{sparc-stub.c}
17400 For @sc{sparc} architectures.
17402 @item sparcl-stub.c
17403 @cindex @file{sparcl-stub.c}
17406 For Fujitsu @sc{sparclite} architectures.
17410 The @file{README} file in the @value{GDBN} distribution may list other
17411 recently added stubs.
17414 * Stub Contents:: What the stub can do for you
17415 * Bootstrapping:: What you must do for the stub
17416 * Debug Session:: Putting it all together
17419 @node Stub Contents
17420 @subsection What the Stub Can Do for You
17422 @cindex remote serial stub
17423 The debugging stub for your architecture supplies these three
17427 @item set_debug_traps
17428 @findex set_debug_traps
17429 @cindex remote serial stub, initialization
17430 This routine arranges for @code{handle_exception} to run when your
17431 program stops. You must call this subroutine explicitly near the
17432 beginning of your program.
17434 @item handle_exception
17435 @findex handle_exception
17436 @cindex remote serial stub, main routine
17437 This is the central workhorse, but your program never calls it
17438 explicitly---the setup code arranges for @code{handle_exception} to
17439 run when a trap is triggered.
17441 @code{handle_exception} takes control when your program stops during
17442 execution (for example, on a breakpoint), and mediates communications
17443 with @value{GDBN} on the host machine. This is where the communications
17444 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
17445 representative on the target machine. It begins by sending summary
17446 information on the state of your program, then continues to execute,
17447 retrieving and transmitting any information @value{GDBN} needs, until you
17448 execute a @value{GDBN} command that makes your program resume; at that point,
17449 @code{handle_exception} returns control to your own code on the target
17453 @cindex @code{breakpoint} subroutine, remote
17454 Use this auxiliary subroutine to make your program contain a
17455 breakpoint. Depending on the particular situation, this may be the only
17456 way for @value{GDBN} to get control. For instance, if your target
17457 machine has some sort of interrupt button, you won't need to call this;
17458 pressing the interrupt button transfers control to
17459 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
17460 simply receiving characters on the serial port may also trigger a trap;
17461 again, in that situation, you don't need to call @code{breakpoint} from
17462 your own program---simply running @samp{target remote} from the host
17463 @value{GDBN} session gets control.
17465 Call @code{breakpoint} if none of these is true, or if you simply want
17466 to make certain your program stops at a predetermined point for the
17467 start of your debugging session.
17470 @node Bootstrapping
17471 @subsection What You Must Do for the Stub
17473 @cindex remote stub, support routines
17474 The debugging stubs that come with @value{GDBN} are set up for a particular
17475 chip architecture, but they have no information about the rest of your
17476 debugging target machine.
17478 First of all you need to tell the stub how to communicate with the
17482 @item int getDebugChar()
17483 @findex getDebugChar
17484 Write this subroutine to read a single character from the serial port.
17485 It may be identical to @code{getchar} for your target system; a
17486 different name is used to allow you to distinguish the two if you wish.
17488 @item void putDebugChar(int)
17489 @findex putDebugChar
17490 Write this subroutine to write a single character to the serial port.
17491 It may be identical to @code{putchar} for your target system; a
17492 different name is used to allow you to distinguish the two if you wish.
17495 @cindex control C, and remote debugging
17496 @cindex interrupting remote targets
17497 If you want @value{GDBN} to be able to stop your program while it is
17498 running, you need to use an interrupt-driven serial driver, and arrange
17499 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
17500 character). That is the character which @value{GDBN} uses to tell the
17501 remote system to stop.
17503 Getting the debugging target to return the proper status to @value{GDBN}
17504 probably requires changes to the standard stub; one quick and dirty way
17505 is to just execute a breakpoint instruction (the ``dirty'' part is that
17506 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
17508 Other routines you need to supply are:
17511 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
17512 @findex exceptionHandler
17513 Write this function to install @var{exception_address} in the exception
17514 handling tables. You need to do this because the stub does not have any
17515 way of knowing what the exception handling tables on your target system
17516 are like (for example, the processor's table might be in @sc{rom},
17517 containing entries which point to a table in @sc{ram}).
17518 @var{exception_number} is the exception number which should be changed;
17519 its meaning is architecture-dependent (for example, different numbers
17520 might represent divide by zero, misaligned access, etc). When this
17521 exception occurs, control should be transferred directly to
17522 @var{exception_address}, and the processor state (stack, registers,
17523 and so on) should be just as it is when a processor exception occurs. So if
17524 you want to use a jump instruction to reach @var{exception_address}, it
17525 should be a simple jump, not a jump to subroutine.
17527 For the 386, @var{exception_address} should be installed as an interrupt
17528 gate so that interrupts are masked while the handler runs. The gate
17529 should be at privilege level 0 (the most privileged level). The
17530 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
17531 help from @code{exceptionHandler}.
17533 @item void flush_i_cache()
17534 @findex flush_i_cache
17535 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
17536 instruction cache, if any, on your target machine. If there is no
17537 instruction cache, this subroutine may be a no-op.
17539 On target machines that have instruction caches, @value{GDBN} requires this
17540 function to make certain that the state of your program is stable.
17544 You must also make sure this library routine is available:
17547 @item void *memset(void *, int, int)
17549 This is the standard library function @code{memset} that sets an area of
17550 memory to a known value. If you have one of the free versions of
17551 @code{libc.a}, @code{memset} can be found there; otherwise, you must
17552 either obtain it from your hardware manufacturer, or write your own.
17555 If you do not use the GNU C compiler, you may need other standard
17556 library subroutines as well; this varies from one stub to another,
17557 but in general the stubs are likely to use any of the common library
17558 subroutines which @code{@value{NGCC}} generates as inline code.
17561 @node Debug Session
17562 @subsection Putting it All Together
17564 @cindex remote serial debugging summary
17565 In summary, when your program is ready to debug, you must follow these
17570 Make sure you have defined the supporting low-level routines
17571 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
17573 @code{getDebugChar}, @code{putDebugChar},
17574 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
17578 Insert these lines near the top of your program:
17586 For the 680x0 stub only, you need to provide a variable called
17587 @code{exceptionHook}. Normally you just use:
17590 void (*exceptionHook)() = 0;
17594 but if before calling @code{set_debug_traps}, you set it to point to a
17595 function in your program, that function is called when
17596 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
17597 error). The function indicated by @code{exceptionHook} is called with
17598 one parameter: an @code{int} which is the exception number.
17601 Compile and link together: your program, the @value{GDBN} debugging stub for
17602 your target architecture, and the supporting subroutines.
17605 Make sure you have a serial connection between your target machine and
17606 the @value{GDBN} host, and identify the serial port on the host.
17609 @c The "remote" target now provides a `load' command, so we should
17610 @c document that. FIXME.
17611 Download your program to your target machine (or get it there by
17612 whatever means the manufacturer provides), and start it.
17615 Start @value{GDBN} on the host, and connect to the target
17616 (@pxref{Connecting,,Connecting to a Remote Target}).
17620 @node Configurations
17621 @chapter Configuration-Specific Information
17623 While nearly all @value{GDBN} commands are available for all native and
17624 cross versions of the debugger, there are some exceptions. This chapter
17625 describes things that are only available in certain configurations.
17627 There are three major categories of configurations: native
17628 configurations, where the host and target are the same, embedded
17629 operating system configurations, which are usually the same for several
17630 different processor architectures, and bare embedded processors, which
17631 are quite different from each other.
17636 * Embedded Processors::
17643 This section describes details specific to particular native
17648 * BSD libkvm Interface:: Debugging BSD kernel memory images
17649 * SVR4 Process Information:: SVR4 process information
17650 * DJGPP Native:: Features specific to the DJGPP port
17651 * Cygwin Native:: Features specific to the Cygwin port
17652 * Hurd Native:: Features specific to @sc{gnu} Hurd
17653 * Neutrino:: Features specific to QNX Neutrino
17654 * Darwin:: Features specific to Darwin
17660 On HP-UX systems, if you refer to a function or variable name that
17661 begins with a dollar sign, @value{GDBN} searches for a user or system
17662 name first, before it searches for a convenience variable.
17665 @node BSD libkvm Interface
17666 @subsection BSD libkvm Interface
17669 @cindex kernel memory image
17670 @cindex kernel crash dump
17672 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
17673 interface that provides a uniform interface for accessing kernel virtual
17674 memory images, including live systems and crash dumps. @value{GDBN}
17675 uses this interface to allow you to debug live kernels and kernel crash
17676 dumps on many native BSD configurations. This is implemented as a
17677 special @code{kvm} debugging target. For debugging a live system, load
17678 the currently running kernel into @value{GDBN} and connect to the
17682 (@value{GDBP}) @b{target kvm}
17685 For debugging crash dumps, provide the file name of the crash dump as an
17689 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
17692 Once connected to the @code{kvm} target, the following commands are
17698 Set current context from the @dfn{Process Control Block} (PCB) address.
17701 Set current context from proc address. This command isn't available on
17702 modern FreeBSD systems.
17705 @node SVR4 Process Information
17706 @subsection SVR4 Process Information
17708 @cindex examine process image
17709 @cindex process info via @file{/proc}
17711 Many versions of SVR4 and compatible systems provide a facility called
17712 @samp{/proc} that can be used to examine the image of a running
17713 process using file-system subroutines. If @value{GDBN} is configured
17714 for an operating system with this facility, the command @code{info
17715 proc} is available to report information about the process running
17716 your program, or about any process running on your system. @code{info
17717 proc} works only on SVR4 systems that include the @code{procfs} code.
17718 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
17719 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
17725 @itemx info proc @var{process-id}
17726 Summarize available information about any running process. If a
17727 process ID is specified by @var{process-id}, display information about
17728 that process; otherwise display information about the program being
17729 debugged. The summary includes the debugged process ID, the command
17730 line used to invoke it, its current working directory, and its
17731 executable file's absolute file name.
17733 On some systems, @var{process-id} can be of the form
17734 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
17735 within a process. If the optional @var{pid} part is missing, it means
17736 a thread from the process being debugged (the leading @samp{/} still
17737 needs to be present, or else @value{GDBN} will interpret the number as
17738 a process ID rather than a thread ID).
17740 @item info proc mappings
17741 @cindex memory address space mappings
17742 Report the memory address space ranges accessible in the program, with
17743 information on whether the process has read, write, or execute access
17744 rights to each range. On @sc{gnu}/Linux systems, each memory range
17745 includes the object file which is mapped to that range, instead of the
17746 memory access rights to that range.
17748 @item info proc stat
17749 @itemx info proc status
17750 @cindex process detailed status information
17751 These subcommands are specific to @sc{gnu}/Linux systems. They show
17752 the process-related information, including the user ID and group ID;
17753 how many threads are there in the process; its virtual memory usage;
17754 the signals that are pending, blocked, and ignored; its TTY; its
17755 consumption of system and user time; its stack size; its @samp{nice}
17756 value; etc. For more information, see the @samp{proc} man page
17757 (type @kbd{man 5 proc} from your shell prompt).
17759 @item info proc all
17760 Show all the information about the process described under all of the
17761 above @code{info proc} subcommands.
17764 @comment These sub-options of 'info proc' were not included when
17765 @comment procfs.c was re-written. Keep their descriptions around
17766 @comment against the day when someone finds the time to put them back in.
17767 @kindex info proc times
17768 @item info proc times
17769 Starting time, user CPU time, and system CPU time for your program and
17772 @kindex info proc id
17774 Report on the process IDs related to your program: its own process ID,
17775 the ID of its parent, the process group ID, and the session ID.
17778 @item set procfs-trace
17779 @kindex set procfs-trace
17780 @cindex @code{procfs} API calls
17781 This command enables and disables tracing of @code{procfs} API calls.
17783 @item show procfs-trace
17784 @kindex show procfs-trace
17785 Show the current state of @code{procfs} API call tracing.
17787 @item set procfs-file @var{file}
17788 @kindex set procfs-file
17789 Tell @value{GDBN} to write @code{procfs} API trace to the named
17790 @var{file}. @value{GDBN} appends the trace info to the previous
17791 contents of the file. The default is to display the trace on the
17794 @item show procfs-file
17795 @kindex show procfs-file
17796 Show the file to which @code{procfs} API trace is written.
17798 @item proc-trace-entry
17799 @itemx proc-trace-exit
17800 @itemx proc-untrace-entry
17801 @itemx proc-untrace-exit
17802 @kindex proc-trace-entry
17803 @kindex proc-trace-exit
17804 @kindex proc-untrace-entry
17805 @kindex proc-untrace-exit
17806 These commands enable and disable tracing of entries into and exits
17807 from the @code{syscall} interface.
17810 @kindex info pidlist
17811 @cindex process list, QNX Neutrino
17812 For QNX Neutrino only, this command displays the list of all the
17813 processes and all the threads within each process.
17816 @kindex info meminfo
17817 @cindex mapinfo list, QNX Neutrino
17818 For QNX Neutrino only, this command displays the list of all mapinfos.
17822 @subsection Features for Debugging @sc{djgpp} Programs
17823 @cindex @sc{djgpp} debugging
17824 @cindex native @sc{djgpp} debugging
17825 @cindex MS-DOS-specific commands
17828 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
17829 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
17830 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
17831 top of real-mode DOS systems and their emulations.
17833 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
17834 defines a few commands specific to the @sc{djgpp} port. This
17835 subsection describes those commands.
17840 This is a prefix of @sc{djgpp}-specific commands which print
17841 information about the target system and important OS structures.
17844 @cindex MS-DOS system info
17845 @cindex free memory information (MS-DOS)
17846 @item info dos sysinfo
17847 This command displays assorted information about the underlying
17848 platform: the CPU type and features, the OS version and flavor, the
17849 DPMI version, and the available conventional and DPMI memory.
17854 @cindex segment descriptor tables
17855 @cindex descriptor tables display
17857 @itemx info dos ldt
17858 @itemx info dos idt
17859 These 3 commands display entries from, respectively, Global, Local,
17860 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
17861 tables are data structures which store a descriptor for each segment
17862 that is currently in use. The segment's selector is an index into a
17863 descriptor table; the table entry for that index holds the
17864 descriptor's base address and limit, and its attributes and access
17867 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
17868 segment (used for both data and the stack), and a DOS segment (which
17869 allows access to DOS/BIOS data structures and absolute addresses in
17870 conventional memory). However, the DPMI host will usually define
17871 additional segments in order to support the DPMI environment.
17873 @cindex garbled pointers
17874 These commands allow to display entries from the descriptor tables.
17875 Without an argument, all entries from the specified table are
17876 displayed. An argument, which should be an integer expression, means
17877 display a single entry whose index is given by the argument. For
17878 example, here's a convenient way to display information about the
17879 debugged program's data segment:
17882 @exdent @code{(@value{GDBP}) info dos ldt $ds}
17883 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
17887 This comes in handy when you want to see whether a pointer is outside
17888 the data segment's limit (i.e.@: @dfn{garbled}).
17890 @cindex page tables display (MS-DOS)
17892 @itemx info dos pte
17893 These two commands display entries from, respectively, the Page
17894 Directory and the Page Tables. Page Directories and Page Tables are
17895 data structures which control how virtual memory addresses are mapped
17896 into physical addresses. A Page Table includes an entry for every
17897 page of memory that is mapped into the program's address space; there
17898 may be several Page Tables, each one holding up to 4096 entries. A
17899 Page Directory has up to 4096 entries, one each for every Page Table
17900 that is currently in use.
17902 Without an argument, @kbd{info dos pde} displays the entire Page
17903 Directory, and @kbd{info dos pte} displays all the entries in all of
17904 the Page Tables. An argument, an integer expression, given to the
17905 @kbd{info dos pde} command means display only that entry from the Page
17906 Directory table. An argument given to the @kbd{info dos pte} command
17907 means display entries from a single Page Table, the one pointed to by
17908 the specified entry in the Page Directory.
17910 @cindex direct memory access (DMA) on MS-DOS
17911 These commands are useful when your program uses @dfn{DMA} (Direct
17912 Memory Access), which needs physical addresses to program the DMA
17915 These commands are supported only with some DPMI servers.
17917 @cindex physical address from linear address
17918 @item info dos address-pte @var{addr}
17919 This command displays the Page Table entry for a specified linear
17920 address. The argument @var{addr} is a linear address which should
17921 already have the appropriate segment's base address added to it,
17922 because this command accepts addresses which may belong to @emph{any}
17923 segment. For example, here's how to display the Page Table entry for
17924 the page where a variable @code{i} is stored:
17927 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
17928 @exdent @code{Page Table entry for address 0x11a00d30:}
17929 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
17933 This says that @code{i} is stored at offset @code{0xd30} from the page
17934 whose physical base address is @code{0x02698000}, and shows all the
17935 attributes of that page.
17937 Note that you must cast the addresses of variables to a @code{char *},
17938 since otherwise the value of @code{__djgpp_base_address}, the base
17939 address of all variables and functions in a @sc{djgpp} program, will
17940 be added using the rules of C pointer arithmetics: if @code{i} is
17941 declared an @code{int}, @value{GDBN} will add 4 times the value of
17942 @code{__djgpp_base_address} to the address of @code{i}.
17944 Here's another example, it displays the Page Table entry for the
17948 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
17949 @exdent @code{Page Table entry for address 0x29110:}
17950 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
17954 (The @code{+ 3} offset is because the transfer buffer's address is the
17955 3rd member of the @code{_go32_info_block} structure.) The output
17956 clearly shows that this DPMI server maps the addresses in conventional
17957 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
17958 linear (@code{0x29110}) addresses are identical.
17960 This command is supported only with some DPMI servers.
17963 @cindex DOS serial data link, remote debugging
17964 In addition to native debugging, the DJGPP port supports remote
17965 debugging via a serial data link. The following commands are specific
17966 to remote serial debugging in the DJGPP port of @value{GDBN}.
17969 @kindex set com1base
17970 @kindex set com1irq
17971 @kindex set com2base
17972 @kindex set com2irq
17973 @kindex set com3base
17974 @kindex set com3irq
17975 @kindex set com4base
17976 @kindex set com4irq
17977 @item set com1base @var{addr}
17978 This command sets the base I/O port address of the @file{COM1} serial
17981 @item set com1irq @var{irq}
17982 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
17983 for the @file{COM1} serial port.
17985 There are similar commands @samp{set com2base}, @samp{set com3irq},
17986 etc.@: for setting the port address and the @code{IRQ} lines for the
17989 @kindex show com1base
17990 @kindex show com1irq
17991 @kindex show com2base
17992 @kindex show com2irq
17993 @kindex show com3base
17994 @kindex show com3irq
17995 @kindex show com4base
17996 @kindex show com4irq
17997 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
17998 display the current settings of the base address and the @code{IRQ}
17999 lines used by the COM ports.
18002 @kindex info serial
18003 @cindex DOS serial port status
18004 This command prints the status of the 4 DOS serial ports. For each
18005 port, it prints whether it's active or not, its I/O base address and
18006 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
18007 counts of various errors encountered so far.
18011 @node Cygwin Native
18012 @subsection Features for Debugging MS Windows PE Executables
18013 @cindex MS Windows debugging
18014 @cindex native Cygwin debugging
18015 @cindex Cygwin-specific commands
18017 @value{GDBN} supports native debugging of MS Windows programs, including
18018 DLLs with and without symbolic debugging information.
18020 @cindex Ctrl-BREAK, MS-Windows
18021 @cindex interrupt debuggee on MS-Windows
18022 MS-Windows programs that call @code{SetConsoleMode} to switch off the
18023 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
18024 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
18025 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
18026 sequence, which can be used to interrupt the debuggee even if it
18029 There are various additional Cygwin-specific commands, described in
18030 this section. Working with DLLs that have no debugging symbols is
18031 described in @ref{Non-debug DLL Symbols}.
18036 This is a prefix of MS Windows-specific commands which print
18037 information about the target system and important OS structures.
18039 @item info w32 selector
18040 This command displays information returned by
18041 the Win32 API @code{GetThreadSelectorEntry} function.
18042 It takes an optional argument that is evaluated to
18043 a long value to give the information about this given selector.
18044 Without argument, this command displays information
18045 about the six segment registers.
18047 @item info w32 thread-information-block
18048 This command displays thread specific information stored in the
18049 Thread Information Block (readable on the X86 CPU family using @code{$fs}
18050 selector for 32-bit programs and @code{$gs} for 64-bit programs).
18054 This is a Cygwin-specific alias of @code{info shared}.
18056 @kindex dll-symbols
18058 This command loads symbols from a dll similarly to
18059 add-sym command but without the need to specify a base address.
18061 @kindex set cygwin-exceptions
18062 @cindex debugging the Cygwin DLL
18063 @cindex Cygwin DLL, debugging
18064 @item set cygwin-exceptions @var{mode}
18065 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
18066 happen inside the Cygwin DLL. If @var{mode} is @code{off},
18067 @value{GDBN} will delay recognition of exceptions, and may ignore some
18068 exceptions which seem to be caused by internal Cygwin DLL
18069 ``bookkeeping''. This option is meant primarily for debugging the
18070 Cygwin DLL itself; the default value is @code{off} to avoid annoying
18071 @value{GDBN} users with false @code{SIGSEGV} signals.
18073 @kindex show cygwin-exceptions
18074 @item show cygwin-exceptions
18075 Displays whether @value{GDBN} will break on exceptions that happen
18076 inside the Cygwin DLL itself.
18078 @kindex set new-console
18079 @item set new-console @var{mode}
18080 If @var{mode} is @code{on} the debuggee will
18081 be started in a new console on next start.
18082 If @var{mode} is @code{off}, the debuggee will
18083 be started in the same console as the debugger.
18085 @kindex show new-console
18086 @item show new-console
18087 Displays whether a new console is used
18088 when the debuggee is started.
18090 @kindex set new-group
18091 @item set new-group @var{mode}
18092 This boolean value controls whether the debuggee should
18093 start a new group or stay in the same group as the debugger.
18094 This affects the way the Windows OS handles
18097 @kindex show new-group
18098 @item show new-group
18099 Displays current value of new-group boolean.
18101 @kindex set debugevents
18102 @item set debugevents
18103 This boolean value adds debug output concerning kernel events related
18104 to the debuggee seen by the debugger. This includes events that
18105 signal thread and process creation and exit, DLL loading and
18106 unloading, console interrupts, and debugging messages produced by the
18107 Windows @code{OutputDebugString} API call.
18109 @kindex set debugexec
18110 @item set debugexec
18111 This boolean value adds debug output concerning execute events
18112 (such as resume thread) seen by the debugger.
18114 @kindex set debugexceptions
18115 @item set debugexceptions
18116 This boolean value adds debug output concerning exceptions in the
18117 debuggee seen by the debugger.
18119 @kindex set debugmemory
18120 @item set debugmemory
18121 This boolean value adds debug output concerning debuggee memory reads
18122 and writes by the debugger.
18126 This boolean values specifies whether the debuggee is called
18127 via a shell or directly (default value is on).
18131 Displays if the debuggee will be started with a shell.
18136 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
18139 @node Non-debug DLL Symbols
18140 @subsubsection Support for DLLs without Debugging Symbols
18141 @cindex DLLs with no debugging symbols
18142 @cindex Minimal symbols and DLLs
18144 Very often on windows, some of the DLLs that your program relies on do
18145 not include symbolic debugging information (for example,
18146 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
18147 symbols in a DLL, it relies on the minimal amount of symbolic
18148 information contained in the DLL's export table. This section
18149 describes working with such symbols, known internally to @value{GDBN} as
18150 ``minimal symbols''.
18152 Note that before the debugged program has started execution, no DLLs
18153 will have been loaded. The easiest way around this problem is simply to
18154 start the program --- either by setting a breakpoint or letting the
18155 program run once to completion. It is also possible to force
18156 @value{GDBN} to load a particular DLL before starting the executable ---
18157 see the shared library information in @ref{Files}, or the
18158 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
18159 explicitly loading symbols from a DLL with no debugging information will
18160 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
18161 which may adversely affect symbol lookup performance.
18163 @subsubsection DLL Name Prefixes
18165 In keeping with the naming conventions used by the Microsoft debugging
18166 tools, DLL export symbols are made available with a prefix based on the
18167 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
18168 also entered into the symbol table, so @code{CreateFileA} is often
18169 sufficient. In some cases there will be name clashes within a program
18170 (particularly if the executable itself includes full debugging symbols)
18171 necessitating the use of the fully qualified name when referring to the
18172 contents of the DLL. Use single-quotes around the name to avoid the
18173 exclamation mark (``!'') being interpreted as a language operator.
18175 Note that the internal name of the DLL may be all upper-case, even
18176 though the file name of the DLL is lower-case, or vice-versa. Since
18177 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
18178 some confusion. If in doubt, try the @code{info functions} and
18179 @code{info variables} commands or even @code{maint print msymbols}
18180 (@pxref{Symbols}). Here's an example:
18183 (@value{GDBP}) info function CreateFileA
18184 All functions matching regular expression "CreateFileA":
18186 Non-debugging symbols:
18187 0x77e885f4 CreateFileA
18188 0x77e885f4 KERNEL32!CreateFileA
18192 (@value{GDBP}) info function !
18193 All functions matching regular expression "!":
18195 Non-debugging symbols:
18196 0x6100114c cygwin1!__assert
18197 0x61004034 cygwin1!_dll_crt0@@0
18198 0x61004240 cygwin1!dll_crt0(per_process *)
18202 @subsubsection Working with Minimal Symbols
18204 Symbols extracted from a DLL's export table do not contain very much
18205 type information. All that @value{GDBN} can do is guess whether a symbol
18206 refers to a function or variable depending on the linker section that
18207 contains the symbol. Also note that the actual contents of the memory
18208 contained in a DLL are not available unless the program is running. This
18209 means that you cannot examine the contents of a variable or disassemble
18210 a function within a DLL without a running program.
18212 Variables are generally treated as pointers and dereferenced
18213 automatically. For this reason, it is often necessary to prefix a
18214 variable name with the address-of operator (``&'') and provide explicit
18215 type information in the command. Here's an example of the type of
18219 (@value{GDBP}) print 'cygwin1!__argv'
18224 (@value{GDBP}) x 'cygwin1!__argv'
18225 0x10021610: "\230y\""
18228 And two possible solutions:
18231 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
18232 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
18236 (@value{GDBP}) x/2x &'cygwin1!__argv'
18237 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
18238 (@value{GDBP}) x/x 0x10021608
18239 0x10021608: 0x0022fd98
18240 (@value{GDBP}) x/s 0x0022fd98
18241 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
18244 Setting a break point within a DLL is possible even before the program
18245 starts execution. However, under these circumstances, @value{GDBN} can't
18246 examine the initial instructions of the function in order to skip the
18247 function's frame set-up code. You can work around this by using ``*&''
18248 to set the breakpoint at a raw memory address:
18251 (@value{GDBP}) break *&'python22!PyOS_Readline'
18252 Breakpoint 1 at 0x1e04eff0
18255 The author of these extensions is not entirely convinced that setting a
18256 break point within a shared DLL like @file{kernel32.dll} is completely
18260 @subsection Commands Specific to @sc{gnu} Hurd Systems
18261 @cindex @sc{gnu} Hurd debugging
18263 This subsection describes @value{GDBN} commands specific to the
18264 @sc{gnu} Hurd native debugging.
18269 @kindex set signals@r{, Hurd command}
18270 @kindex set sigs@r{, Hurd command}
18271 This command toggles the state of inferior signal interception by
18272 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
18273 affected by this command. @code{sigs} is a shorthand alias for
18278 @kindex show signals@r{, Hurd command}
18279 @kindex show sigs@r{, Hurd command}
18280 Show the current state of intercepting inferior's signals.
18282 @item set signal-thread
18283 @itemx set sigthread
18284 @kindex set signal-thread
18285 @kindex set sigthread
18286 This command tells @value{GDBN} which thread is the @code{libc} signal
18287 thread. That thread is run when a signal is delivered to a running
18288 process. @code{set sigthread} is the shorthand alias of @code{set
18291 @item show signal-thread
18292 @itemx show sigthread
18293 @kindex show signal-thread
18294 @kindex show sigthread
18295 These two commands show which thread will run when the inferior is
18296 delivered a signal.
18299 @kindex set stopped@r{, Hurd command}
18300 This commands tells @value{GDBN} that the inferior process is stopped,
18301 as with the @code{SIGSTOP} signal. The stopped process can be
18302 continued by delivering a signal to it.
18305 @kindex show stopped@r{, Hurd command}
18306 This command shows whether @value{GDBN} thinks the debuggee is
18309 @item set exceptions
18310 @kindex set exceptions@r{, Hurd command}
18311 Use this command to turn off trapping of exceptions in the inferior.
18312 When exception trapping is off, neither breakpoints nor
18313 single-stepping will work. To restore the default, set exception
18316 @item show exceptions
18317 @kindex show exceptions@r{, Hurd command}
18318 Show the current state of trapping exceptions in the inferior.
18320 @item set task pause
18321 @kindex set task@r{, Hurd commands}
18322 @cindex task attributes (@sc{gnu} Hurd)
18323 @cindex pause current task (@sc{gnu} Hurd)
18324 This command toggles task suspension when @value{GDBN} has control.
18325 Setting it to on takes effect immediately, and the task is suspended
18326 whenever @value{GDBN} gets control. Setting it to off will take
18327 effect the next time the inferior is continued. If this option is set
18328 to off, you can use @code{set thread default pause on} or @code{set
18329 thread pause on} (see below) to pause individual threads.
18331 @item show task pause
18332 @kindex show task@r{, Hurd commands}
18333 Show the current state of task suspension.
18335 @item set task detach-suspend-count
18336 @cindex task suspend count
18337 @cindex detach from task, @sc{gnu} Hurd
18338 This command sets the suspend count the task will be left with when
18339 @value{GDBN} detaches from it.
18341 @item show task detach-suspend-count
18342 Show the suspend count the task will be left with when detaching.
18344 @item set task exception-port
18345 @itemx set task excp
18346 @cindex task exception port, @sc{gnu} Hurd
18347 This command sets the task exception port to which @value{GDBN} will
18348 forward exceptions. The argument should be the value of the @dfn{send
18349 rights} of the task. @code{set task excp} is a shorthand alias.
18351 @item set noninvasive
18352 @cindex noninvasive task options
18353 This command switches @value{GDBN} to a mode that is the least
18354 invasive as far as interfering with the inferior is concerned. This
18355 is the same as using @code{set task pause}, @code{set exceptions}, and
18356 @code{set signals} to values opposite to the defaults.
18358 @item info send-rights
18359 @itemx info receive-rights
18360 @itemx info port-rights
18361 @itemx info port-sets
18362 @itemx info dead-names
18365 @cindex send rights, @sc{gnu} Hurd
18366 @cindex receive rights, @sc{gnu} Hurd
18367 @cindex port rights, @sc{gnu} Hurd
18368 @cindex port sets, @sc{gnu} Hurd
18369 @cindex dead names, @sc{gnu} Hurd
18370 These commands display information about, respectively, send rights,
18371 receive rights, port rights, port sets, and dead names of a task.
18372 There are also shorthand aliases: @code{info ports} for @code{info
18373 port-rights} and @code{info psets} for @code{info port-sets}.
18375 @item set thread pause
18376 @kindex set thread@r{, Hurd command}
18377 @cindex thread properties, @sc{gnu} Hurd
18378 @cindex pause current thread (@sc{gnu} Hurd)
18379 This command toggles current thread suspension when @value{GDBN} has
18380 control. Setting it to on takes effect immediately, and the current
18381 thread is suspended whenever @value{GDBN} gets control. Setting it to
18382 off will take effect the next time the inferior is continued.
18383 Normally, this command has no effect, since when @value{GDBN} has
18384 control, the whole task is suspended. However, if you used @code{set
18385 task pause off} (see above), this command comes in handy to suspend
18386 only the current thread.
18388 @item show thread pause
18389 @kindex show thread@r{, Hurd command}
18390 This command shows the state of current thread suspension.
18392 @item set thread run
18393 This command sets whether the current thread is allowed to run.
18395 @item show thread run
18396 Show whether the current thread is allowed to run.
18398 @item set thread detach-suspend-count
18399 @cindex thread suspend count, @sc{gnu} Hurd
18400 @cindex detach from thread, @sc{gnu} Hurd
18401 This command sets the suspend count @value{GDBN} will leave on a
18402 thread when detaching. This number is relative to the suspend count
18403 found by @value{GDBN} when it notices the thread; use @code{set thread
18404 takeover-suspend-count} to force it to an absolute value.
18406 @item show thread detach-suspend-count
18407 Show the suspend count @value{GDBN} will leave on the thread when
18410 @item set thread exception-port
18411 @itemx set thread excp
18412 Set the thread exception port to which to forward exceptions. This
18413 overrides the port set by @code{set task exception-port} (see above).
18414 @code{set thread excp} is the shorthand alias.
18416 @item set thread takeover-suspend-count
18417 Normally, @value{GDBN}'s thread suspend counts are relative to the
18418 value @value{GDBN} finds when it notices each thread. This command
18419 changes the suspend counts to be absolute instead.
18421 @item set thread default
18422 @itemx show thread default
18423 @cindex thread default settings, @sc{gnu} Hurd
18424 Each of the above @code{set thread} commands has a @code{set thread
18425 default} counterpart (e.g., @code{set thread default pause}, @code{set
18426 thread default exception-port}, etc.). The @code{thread default}
18427 variety of commands sets the default thread properties for all
18428 threads; you can then change the properties of individual threads with
18429 the non-default commands.
18434 @subsection QNX Neutrino
18435 @cindex QNX Neutrino
18437 @value{GDBN} provides the following commands specific to the QNX
18441 @item set debug nto-debug
18442 @kindex set debug nto-debug
18443 When set to on, enables debugging messages specific to the QNX
18446 @item show debug nto-debug
18447 @kindex show debug nto-debug
18448 Show the current state of QNX Neutrino messages.
18455 @value{GDBN} provides the following commands specific to the Darwin target:
18458 @item set debug darwin @var{num}
18459 @kindex set debug darwin
18460 When set to a non zero value, enables debugging messages specific to
18461 the Darwin support. Higher values produce more verbose output.
18463 @item show debug darwin
18464 @kindex show debug darwin
18465 Show the current state of Darwin messages.
18467 @item set debug mach-o @var{num}
18468 @kindex set debug mach-o
18469 When set to a non zero value, enables debugging messages while
18470 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
18471 file format used on Darwin for object and executable files.) Higher
18472 values produce more verbose output. This is a command to diagnose
18473 problems internal to @value{GDBN} and should not be needed in normal
18476 @item show debug mach-o
18477 @kindex show debug mach-o
18478 Show the current state of Mach-O file messages.
18480 @item set mach-exceptions on
18481 @itemx set mach-exceptions off
18482 @kindex set mach-exceptions
18483 On Darwin, faults are first reported as a Mach exception and are then
18484 mapped to a Posix signal. Use this command to turn on trapping of
18485 Mach exceptions in the inferior. This might be sometimes useful to
18486 better understand the cause of a fault. The default is off.
18488 @item show mach-exceptions
18489 @kindex show mach-exceptions
18490 Show the current state of exceptions trapping.
18495 @section Embedded Operating Systems
18497 This section describes configurations involving the debugging of
18498 embedded operating systems that are available for several different
18502 * VxWorks:: Using @value{GDBN} with VxWorks
18505 @value{GDBN} includes the ability to debug programs running on
18506 various real-time operating systems.
18509 @subsection Using @value{GDBN} with VxWorks
18515 @kindex target vxworks
18516 @item target vxworks @var{machinename}
18517 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
18518 is the target system's machine name or IP address.
18522 On VxWorks, @code{load} links @var{filename} dynamically on the
18523 current target system as well as adding its symbols in @value{GDBN}.
18525 @value{GDBN} enables developers to spawn and debug tasks running on networked
18526 VxWorks targets from a Unix host. Already-running tasks spawned from
18527 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
18528 both the Unix host and on the VxWorks target. The program
18529 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
18530 installed with the name @code{vxgdb}, to distinguish it from a
18531 @value{GDBN} for debugging programs on the host itself.)
18534 @item VxWorks-timeout @var{args}
18535 @kindex vxworks-timeout
18536 All VxWorks-based targets now support the option @code{vxworks-timeout}.
18537 This option is set by the user, and @var{args} represents the number of
18538 seconds @value{GDBN} waits for responses to rpc's. You might use this if
18539 your VxWorks target is a slow software simulator or is on the far side
18540 of a thin network line.
18543 The following information on connecting to VxWorks was current when
18544 this manual was produced; newer releases of VxWorks may use revised
18547 @findex INCLUDE_RDB
18548 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
18549 to include the remote debugging interface routines in the VxWorks
18550 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
18551 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
18552 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
18553 source debugging task @code{tRdbTask} when VxWorks is booted. For more
18554 information on configuring and remaking VxWorks, see the manufacturer's
18556 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
18558 Once you have included @file{rdb.a} in your VxWorks system image and set
18559 your Unix execution search path to find @value{GDBN}, you are ready to
18560 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
18561 @code{vxgdb}, depending on your installation).
18563 @value{GDBN} comes up showing the prompt:
18570 * VxWorks Connection:: Connecting to VxWorks
18571 * VxWorks Download:: VxWorks download
18572 * VxWorks Attach:: Running tasks
18575 @node VxWorks Connection
18576 @subsubsection Connecting to VxWorks
18578 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
18579 network. To connect to a target whose host name is ``@code{tt}'', type:
18582 (vxgdb) target vxworks tt
18586 @value{GDBN} displays messages like these:
18589 Attaching remote machine across net...
18594 @value{GDBN} then attempts to read the symbol tables of any object modules
18595 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
18596 these files by searching the directories listed in the command search
18597 path (@pxref{Environment, ,Your Program's Environment}); if it fails
18598 to find an object file, it displays a message such as:
18601 prog.o: No such file or directory.
18604 When this happens, add the appropriate directory to the search path with
18605 the @value{GDBN} command @code{path}, and execute the @code{target}
18608 @node VxWorks Download
18609 @subsubsection VxWorks Download
18611 @cindex download to VxWorks
18612 If you have connected to the VxWorks target and you want to debug an
18613 object that has not yet been loaded, you can use the @value{GDBN}
18614 @code{load} command to download a file from Unix to VxWorks
18615 incrementally. The object file given as an argument to the @code{load}
18616 command is actually opened twice: first by the VxWorks target in order
18617 to download the code, then by @value{GDBN} in order to read the symbol
18618 table. This can lead to problems if the current working directories on
18619 the two systems differ. If both systems have NFS mounted the same
18620 filesystems, you can avoid these problems by using absolute paths.
18621 Otherwise, it is simplest to set the working directory on both systems
18622 to the directory in which the object file resides, and then to reference
18623 the file by its name, without any path. For instance, a program
18624 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
18625 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
18626 program, type this on VxWorks:
18629 -> cd "@var{vxpath}/vw/demo/rdb"
18633 Then, in @value{GDBN}, type:
18636 (vxgdb) cd @var{hostpath}/vw/demo/rdb
18637 (vxgdb) load prog.o
18640 @value{GDBN} displays a response similar to this:
18643 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
18646 You can also use the @code{load} command to reload an object module
18647 after editing and recompiling the corresponding source file. Note that
18648 this makes @value{GDBN} delete all currently-defined breakpoints,
18649 auto-displays, and convenience variables, and to clear the value
18650 history. (This is necessary in order to preserve the integrity of
18651 debugger's data structures that reference the target system's symbol
18654 @node VxWorks Attach
18655 @subsubsection Running Tasks
18657 @cindex running VxWorks tasks
18658 You can also attach to an existing task using the @code{attach} command as
18662 (vxgdb) attach @var{task}
18666 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
18667 or suspended when you attach to it. Running tasks are suspended at
18668 the time of attachment.
18670 @node Embedded Processors
18671 @section Embedded Processors
18673 This section goes into details specific to particular embedded
18676 @cindex send command to simulator
18677 Whenever a specific embedded processor has a simulator, @value{GDBN}
18678 allows to send an arbitrary command to the simulator.
18681 @item sim @var{command}
18682 @kindex sim@r{, a command}
18683 Send an arbitrary @var{command} string to the simulator. Consult the
18684 documentation for the specific simulator in use for information about
18685 acceptable commands.
18691 * M32R/D:: Renesas M32R/D
18692 * M68K:: Motorola M68K
18693 * MicroBlaze:: Xilinx MicroBlaze
18694 * MIPS Embedded:: MIPS Embedded
18695 * OpenRISC 1000:: OpenRisc 1000
18696 * PA:: HP PA Embedded
18697 * PowerPC Embedded:: PowerPC Embedded
18698 * Sparclet:: Tsqware Sparclet
18699 * Sparclite:: Fujitsu Sparclite
18700 * Z8000:: Zilog Z8000
18703 * Super-H:: Renesas Super-H
18712 @item target rdi @var{dev}
18713 ARM Angel monitor, via RDI library interface to ADP protocol. You may
18714 use this target to communicate with both boards running the Angel
18715 monitor, or with the EmbeddedICE JTAG debug device.
18718 @item target rdp @var{dev}
18723 @value{GDBN} provides the following ARM-specific commands:
18726 @item set arm disassembler
18728 This commands selects from a list of disassembly styles. The
18729 @code{"std"} style is the standard style.
18731 @item show arm disassembler
18733 Show the current disassembly style.
18735 @item set arm apcs32
18736 @cindex ARM 32-bit mode
18737 This command toggles ARM operation mode between 32-bit and 26-bit.
18739 @item show arm apcs32
18740 Display the current usage of the ARM 32-bit mode.
18742 @item set arm fpu @var{fputype}
18743 This command sets the ARM floating-point unit (FPU) type. The
18744 argument @var{fputype} can be one of these:
18748 Determine the FPU type by querying the OS ABI.
18750 Software FPU, with mixed-endian doubles on little-endian ARM
18753 GCC-compiled FPA co-processor.
18755 Software FPU with pure-endian doubles.
18761 Show the current type of the FPU.
18764 This command forces @value{GDBN} to use the specified ABI.
18767 Show the currently used ABI.
18769 @item set arm fallback-mode (arm|thumb|auto)
18770 @value{GDBN} uses the symbol table, when available, to determine
18771 whether instructions are ARM or Thumb. This command controls
18772 @value{GDBN}'s default behavior when the symbol table is not
18773 available. The default is @samp{auto}, which causes @value{GDBN} to
18774 use the current execution mode (from the @code{T} bit in the @code{CPSR}
18777 @item show arm fallback-mode
18778 Show the current fallback instruction mode.
18780 @item set arm force-mode (arm|thumb|auto)
18781 This command overrides use of the symbol table to determine whether
18782 instructions are ARM or Thumb. The default is @samp{auto}, which
18783 causes @value{GDBN} to use the symbol table and then the setting
18784 of @samp{set arm fallback-mode}.
18786 @item show arm force-mode
18787 Show the current forced instruction mode.
18789 @item set debug arm
18790 Toggle whether to display ARM-specific debugging messages from the ARM
18791 target support subsystem.
18793 @item show debug arm
18794 Show whether ARM-specific debugging messages are enabled.
18797 The following commands are available when an ARM target is debugged
18798 using the RDI interface:
18801 @item rdilogfile @r{[}@var{file}@r{]}
18803 @cindex ADP (Angel Debugger Protocol) logging
18804 Set the filename for the ADP (Angel Debugger Protocol) packet log.
18805 With an argument, sets the log file to the specified @var{file}. With
18806 no argument, show the current log file name. The default log file is
18809 @item rdilogenable @r{[}@var{arg}@r{]}
18810 @kindex rdilogenable
18811 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
18812 enables logging, with an argument 0 or @code{"no"} disables it. With
18813 no arguments displays the current setting. When logging is enabled,
18814 ADP packets exchanged between @value{GDBN} and the RDI target device
18815 are logged to a file.
18817 @item set rdiromatzero
18818 @kindex set rdiromatzero
18819 @cindex ROM at zero address, RDI
18820 Tell @value{GDBN} whether the target has ROM at address 0. If on,
18821 vector catching is disabled, so that zero address can be used. If off
18822 (the default), vector catching is enabled. For this command to take
18823 effect, it needs to be invoked prior to the @code{target rdi} command.
18825 @item show rdiromatzero
18826 @kindex show rdiromatzero
18827 Show the current setting of ROM at zero address.
18829 @item set rdiheartbeat
18830 @kindex set rdiheartbeat
18831 @cindex RDI heartbeat
18832 Enable or disable RDI heartbeat packets. It is not recommended to
18833 turn on this option, since it confuses ARM and EPI JTAG interface, as
18834 well as the Angel monitor.
18836 @item show rdiheartbeat
18837 @kindex show rdiheartbeat
18838 Show the setting of RDI heartbeat packets.
18842 @item target sim @r{[}@var{simargs}@r{]} @dots{}
18843 The @value{GDBN} ARM simulator accepts the following optional arguments.
18846 @item --swi-support=@var{type}
18847 Tell the simulator which SWI interfaces to support.
18848 @var{type} may be a comma separated list of the following values.
18849 The default value is @code{all}.
18862 @subsection Renesas M32R/D and M32R/SDI
18865 @kindex target m32r
18866 @item target m32r @var{dev}
18867 Renesas M32R/D ROM monitor.
18869 @kindex target m32rsdi
18870 @item target m32rsdi @var{dev}
18871 Renesas M32R SDI server, connected via parallel port to the board.
18874 The following @value{GDBN} commands are specific to the M32R monitor:
18877 @item set download-path @var{path}
18878 @kindex set download-path
18879 @cindex find downloadable @sc{srec} files (M32R)
18880 Set the default path for finding downloadable @sc{srec} files.
18882 @item show download-path
18883 @kindex show download-path
18884 Show the default path for downloadable @sc{srec} files.
18886 @item set board-address @var{addr}
18887 @kindex set board-address
18888 @cindex M32-EVA target board address
18889 Set the IP address for the M32R-EVA target board.
18891 @item show board-address
18892 @kindex show board-address
18893 Show the current IP address of the target board.
18895 @item set server-address @var{addr}
18896 @kindex set server-address
18897 @cindex download server address (M32R)
18898 Set the IP address for the download server, which is the @value{GDBN}'s
18901 @item show server-address
18902 @kindex show server-address
18903 Display the IP address of the download server.
18905 @item upload @r{[}@var{file}@r{]}
18906 @kindex upload@r{, M32R}
18907 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
18908 upload capability. If no @var{file} argument is given, the current
18909 executable file is uploaded.
18911 @item tload @r{[}@var{file}@r{]}
18912 @kindex tload@r{, M32R}
18913 Test the @code{upload} command.
18916 The following commands are available for M32R/SDI:
18921 @cindex reset SDI connection, M32R
18922 This command resets the SDI connection.
18926 This command shows the SDI connection status.
18929 @kindex debug_chaos
18930 @cindex M32R/Chaos debugging
18931 Instructs the remote that M32R/Chaos debugging is to be used.
18933 @item use_debug_dma
18934 @kindex use_debug_dma
18935 Instructs the remote to use the DEBUG_DMA method of accessing memory.
18938 @kindex use_mon_code
18939 Instructs the remote to use the MON_CODE method of accessing memory.
18942 @kindex use_ib_break
18943 Instructs the remote to set breakpoints by IB break.
18945 @item use_dbt_break
18946 @kindex use_dbt_break
18947 Instructs the remote to set breakpoints by DBT.
18953 The Motorola m68k configuration includes ColdFire support, and a
18954 target command for the following ROM monitor.
18958 @kindex target dbug
18959 @item target dbug @var{dev}
18960 dBUG ROM monitor for Motorola ColdFire.
18965 @subsection MicroBlaze
18966 @cindex Xilinx MicroBlaze
18967 @cindex XMD, Xilinx Microprocessor Debugger
18969 The MicroBlaze is a soft-core processor supported on various Xilinx
18970 FPGAs, such as Spartan or Virtex series. Boards with these processors
18971 usually have JTAG ports which connect to a host system running the Xilinx
18972 Embedded Development Kit (EDK) or Software Development Kit (SDK).
18973 This host system is used to download the configuration bitstream to
18974 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
18975 communicates with the target board using the JTAG interface and
18976 presents a @code{gdbserver} interface to the board. By default
18977 @code{xmd} uses port @code{1234}. (While it is possible to change
18978 this default port, it requires the use of undocumented @code{xmd}
18979 commands. Contact Xilinx support if you need to do this.)
18981 Use these GDB commands to connect to the MicroBlaze target processor.
18984 @item target remote :1234
18985 Use this command to connect to the target if you are running @value{GDBN}
18986 on the same system as @code{xmd}.
18988 @item target remote @var{xmd-host}:1234
18989 Use this command to connect to the target if it is connected to @code{xmd}
18990 running on a different system named @var{xmd-host}.
18993 Use this command to download a program to the MicroBlaze target.
18995 @item set debug microblaze @var{n}
18996 Enable MicroBlaze-specific debugging messages if non-zero.
18998 @item show debug microblaze @var{n}
18999 Show MicroBlaze-specific debugging level.
19002 @node MIPS Embedded
19003 @subsection MIPS Embedded
19005 @cindex MIPS boards
19006 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
19007 MIPS board attached to a serial line. This is available when
19008 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
19011 Use these @value{GDBN} commands to specify the connection to your target board:
19014 @item target mips @var{port}
19015 @kindex target mips @var{port}
19016 To run a program on the board, start up @code{@value{GDBP}} with the
19017 name of your program as the argument. To connect to the board, use the
19018 command @samp{target mips @var{port}}, where @var{port} is the name of
19019 the serial port connected to the board. If the program has not already
19020 been downloaded to the board, you may use the @code{load} command to
19021 download it. You can then use all the usual @value{GDBN} commands.
19023 For example, this sequence connects to the target board through a serial
19024 port, and loads and runs a program called @var{prog} through the
19028 host$ @value{GDBP} @var{prog}
19029 @value{GDBN} is free software and @dots{}
19030 (@value{GDBP}) target mips /dev/ttyb
19031 (@value{GDBP}) load @var{prog}
19035 @item target mips @var{hostname}:@var{portnumber}
19036 On some @value{GDBN} host configurations, you can specify a TCP
19037 connection (for instance, to a serial line managed by a terminal
19038 concentrator) instead of a serial port, using the syntax
19039 @samp{@var{hostname}:@var{portnumber}}.
19041 @item target pmon @var{port}
19042 @kindex target pmon @var{port}
19045 @item target ddb @var{port}
19046 @kindex target ddb @var{port}
19047 NEC's DDB variant of PMON for Vr4300.
19049 @item target lsi @var{port}
19050 @kindex target lsi @var{port}
19051 LSI variant of PMON.
19053 @kindex target r3900
19054 @item target r3900 @var{dev}
19055 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
19057 @kindex target array
19058 @item target array @var{dev}
19059 Array Tech LSI33K RAID controller board.
19065 @value{GDBN} also supports these special commands for MIPS targets:
19068 @item set mipsfpu double
19069 @itemx set mipsfpu single
19070 @itemx set mipsfpu none
19071 @itemx set mipsfpu auto
19072 @itemx show mipsfpu
19073 @kindex set mipsfpu
19074 @kindex show mipsfpu
19075 @cindex MIPS remote floating point
19076 @cindex floating point, MIPS remote
19077 If your target board does not support the MIPS floating point
19078 coprocessor, you should use the command @samp{set mipsfpu none} (if you
19079 need this, you may wish to put the command in your @value{GDBN} init
19080 file). This tells @value{GDBN} how to find the return value of
19081 functions which return floating point values. It also allows
19082 @value{GDBN} to avoid saving the floating point registers when calling
19083 functions on the board. If you are using a floating point coprocessor
19084 with only single precision floating point support, as on the @sc{r4650}
19085 processor, use the command @samp{set mipsfpu single}. The default
19086 double precision floating point coprocessor may be selected using
19087 @samp{set mipsfpu double}.
19089 In previous versions the only choices were double precision or no
19090 floating point, so @samp{set mipsfpu on} will select double precision
19091 and @samp{set mipsfpu off} will select no floating point.
19093 As usual, you can inquire about the @code{mipsfpu} variable with
19094 @samp{show mipsfpu}.
19096 @item set timeout @var{seconds}
19097 @itemx set retransmit-timeout @var{seconds}
19098 @itemx show timeout
19099 @itemx show retransmit-timeout
19100 @cindex @code{timeout}, MIPS protocol
19101 @cindex @code{retransmit-timeout}, MIPS protocol
19102 @kindex set timeout
19103 @kindex show timeout
19104 @kindex set retransmit-timeout
19105 @kindex show retransmit-timeout
19106 You can control the timeout used while waiting for a packet, in the MIPS
19107 remote protocol, with the @code{set timeout @var{seconds}} command. The
19108 default is 5 seconds. Similarly, you can control the timeout used while
19109 waiting for an acknowledgment of a packet with the @code{set
19110 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
19111 You can inspect both values with @code{show timeout} and @code{show
19112 retransmit-timeout}. (These commands are @emph{only} available when
19113 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
19115 The timeout set by @code{set timeout} does not apply when @value{GDBN}
19116 is waiting for your program to stop. In that case, @value{GDBN} waits
19117 forever because it has no way of knowing how long the program is going
19118 to run before stopping.
19120 @item set syn-garbage-limit @var{num}
19121 @kindex set syn-garbage-limit@r{, MIPS remote}
19122 @cindex synchronize with remote MIPS target
19123 Limit the maximum number of characters @value{GDBN} should ignore when
19124 it tries to synchronize with the remote target. The default is 10
19125 characters. Setting the limit to -1 means there's no limit.
19127 @item show syn-garbage-limit
19128 @kindex show syn-garbage-limit@r{, MIPS remote}
19129 Show the current limit on the number of characters to ignore when
19130 trying to synchronize with the remote system.
19132 @item set monitor-prompt @var{prompt}
19133 @kindex set monitor-prompt@r{, MIPS remote}
19134 @cindex remote monitor prompt
19135 Tell @value{GDBN} to expect the specified @var{prompt} string from the
19136 remote monitor. The default depends on the target:
19146 @item show monitor-prompt
19147 @kindex show monitor-prompt@r{, MIPS remote}
19148 Show the current strings @value{GDBN} expects as the prompt from the
19151 @item set monitor-warnings
19152 @kindex set monitor-warnings@r{, MIPS remote}
19153 Enable or disable monitor warnings about hardware breakpoints. This
19154 has effect only for the @code{lsi} target. When on, @value{GDBN} will
19155 display warning messages whose codes are returned by the @code{lsi}
19156 PMON monitor for breakpoint commands.
19158 @item show monitor-warnings
19159 @kindex show monitor-warnings@r{, MIPS remote}
19160 Show the current setting of printing monitor warnings.
19162 @item pmon @var{command}
19163 @kindex pmon@r{, MIPS remote}
19164 @cindex send PMON command
19165 This command allows sending an arbitrary @var{command} string to the
19166 monitor. The monitor must be in debug mode for this to work.
19169 @node OpenRISC 1000
19170 @subsection OpenRISC 1000
19171 @cindex OpenRISC 1000
19173 @cindex or1k boards
19174 See OR1k Architecture document (@uref{www.opencores.org}) for more information
19175 about platform and commands.
19179 @kindex target jtag
19180 @item target jtag jtag://@var{host}:@var{port}
19182 Connects to remote JTAG server.
19183 JTAG remote server can be either an or1ksim or JTAG server,
19184 connected via parallel port to the board.
19186 Example: @code{target jtag jtag://localhost:9999}
19189 @item or1ksim @var{command}
19190 If connected to @code{or1ksim} OpenRISC 1000 Architectural
19191 Simulator, proprietary commands can be executed.
19193 @kindex info or1k spr
19194 @item info or1k spr
19195 Displays spr groups.
19197 @item info or1k spr @var{group}
19198 @itemx info or1k spr @var{groupno}
19199 Displays register names in selected group.
19201 @item info or1k spr @var{group} @var{register}
19202 @itemx info or1k spr @var{register}
19203 @itemx info or1k spr @var{groupno} @var{registerno}
19204 @itemx info or1k spr @var{registerno}
19205 Shows information about specified spr register.
19208 @item spr @var{group} @var{register} @var{value}
19209 @itemx spr @var{register @var{value}}
19210 @itemx spr @var{groupno} @var{registerno @var{value}}
19211 @itemx spr @var{registerno @var{value}}
19212 Writes @var{value} to specified spr register.
19215 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
19216 It is very similar to @value{GDBN} trace, except it does not interfere with normal
19217 program execution and is thus much faster. Hardware breakpoints/watchpoint
19218 triggers can be set using:
19221 Load effective address/data
19223 Store effective address/data
19225 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
19230 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
19231 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
19233 @code{htrace} commands:
19234 @cindex OpenRISC 1000 htrace
19237 @item hwatch @var{conditional}
19238 Set hardware watchpoint on combination of Load/Store Effective Address(es)
19239 or Data. For example:
19241 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
19243 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
19247 Display information about current HW trace configuration.
19249 @item htrace trigger @var{conditional}
19250 Set starting criteria for HW trace.
19252 @item htrace qualifier @var{conditional}
19253 Set acquisition qualifier for HW trace.
19255 @item htrace stop @var{conditional}
19256 Set HW trace stopping criteria.
19258 @item htrace record [@var{data}]*
19259 Selects the data to be recorded, when qualifier is met and HW trace was
19262 @item htrace enable
19263 @itemx htrace disable
19264 Enables/disables the HW trace.
19266 @item htrace rewind [@var{filename}]
19267 Clears currently recorded trace data.
19269 If filename is specified, new trace file is made and any newly collected data
19270 will be written there.
19272 @item htrace print [@var{start} [@var{len}]]
19273 Prints trace buffer, using current record configuration.
19275 @item htrace mode continuous
19276 Set continuous trace mode.
19278 @item htrace mode suspend
19279 Set suspend trace mode.
19283 @node PowerPC Embedded
19284 @subsection PowerPC Embedded
19286 @cindex DVC register
19287 @value{GDBN} supports using the DVC (Data Value Compare) register to
19288 implement in hardware simple hardware watchpoint conditions of the form:
19291 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
19292 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
19295 The DVC register will be automatically used when @value{GDBN} detects
19296 such pattern in a condition expression, and the created watchpoint uses one
19297 debug register (either the @code{exact-watchpoints} option is on and the
19298 variable is scalar, or the variable has a length of one byte). This feature
19299 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
19302 When running on PowerPC embedded processors, @value{GDBN} automatically uses
19303 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
19304 in which case watchpoints using only one debug register are created when
19305 watching variables of scalar types.
19307 You can create an artificial array to watch an arbitrary memory
19308 region using one of the following commands (@pxref{Expressions}):
19311 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
19312 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
19315 PowerPC embedded processors support masked watchpoints. See the discussion
19316 about the @code{mask} argument in @ref{Set Watchpoints}.
19318 @cindex ranged breakpoint
19319 PowerPC embedded processors support hardware accelerated
19320 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
19321 the inferior whenever it executes an instruction at any address within
19322 the range it specifies. To set a ranged breakpoint in @value{GDBN},
19323 use the @code{break-range} command.
19325 @value{GDBN} provides the following PowerPC-specific commands:
19328 @kindex break-range
19329 @item break-range @var{start-location}, @var{end-location}
19330 Set a breakpoint for an address range.
19331 @var{start-location} and @var{end-location} can specify a function name,
19332 a line number, an offset of lines from the current line or from the start
19333 location, or an address of an instruction (see @ref{Specify Location},
19334 for a list of all the possible ways to specify a @var{location}.)
19335 The breakpoint will stop execution of the inferior whenever it
19336 executes an instruction at any address within the specified range,
19337 (including @var{start-location} and @var{end-location}.)
19339 @kindex set powerpc
19340 @item set powerpc soft-float
19341 @itemx show powerpc soft-float
19342 Force @value{GDBN} to use (or not use) a software floating point calling
19343 convention. By default, @value{GDBN} selects the calling convention based
19344 on the selected architecture and the provided executable file.
19346 @item set powerpc vector-abi
19347 @itemx show powerpc vector-abi
19348 Force @value{GDBN} to use the specified calling convention for vector
19349 arguments and return values. The valid options are @samp{auto};
19350 @samp{generic}, to avoid vector registers even if they are present;
19351 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
19352 registers. By default, @value{GDBN} selects the calling convention
19353 based on the selected architecture and the provided executable file.
19355 @item set powerpc exact-watchpoints
19356 @itemx show powerpc exact-watchpoints
19357 Allow @value{GDBN} to use only one debug register when watching a variable
19358 of scalar type, thus assuming that the variable is accessed through the
19359 address of its first byte.
19361 @kindex target dink32
19362 @item target dink32 @var{dev}
19363 DINK32 ROM monitor.
19365 @kindex target ppcbug
19366 @item target ppcbug @var{dev}
19367 @kindex target ppcbug1
19368 @item target ppcbug1 @var{dev}
19369 PPCBUG ROM monitor for PowerPC.
19372 @item target sds @var{dev}
19373 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
19376 @cindex SDS protocol
19377 The following commands specific to the SDS protocol are supported
19381 @item set sdstimeout @var{nsec}
19382 @kindex set sdstimeout
19383 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
19384 default is 2 seconds.
19386 @item show sdstimeout
19387 @kindex show sdstimeout
19388 Show the current value of the SDS timeout.
19390 @item sds @var{command}
19391 @kindex sds@r{, a command}
19392 Send the specified @var{command} string to the SDS monitor.
19397 @subsection HP PA Embedded
19401 @kindex target op50n
19402 @item target op50n @var{dev}
19403 OP50N monitor, running on an OKI HPPA board.
19405 @kindex target w89k
19406 @item target w89k @var{dev}
19407 W89K monitor, running on a Winbond HPPA board.
19412 @subsection Tsqware Sparclet
19416 @value{GDBN} enables developers to debug tasks running on
19417 Sparclet targets from a Unix host.
19418 @value{GDBN} uses code that runs on
19419 both the Unix host and on the Sparclet target. The program
19420 @code{@value{GDBP}} is installed and executed on the Unix host.
19423 @item remotetimeout @var{args}
19424 @kindex remotetimeout
19425 @value{GDBN} supports the option @code{remotetimeout}.
19426 This option is set by the user, and @var{args} represents the number of
19427 seconds @value{GDBN} waits for responses.
19430 @cindex compiling, on Sparclet
19431 When compiling for debugging, include the options @samp{-g} to get debug
19432 information and @samp{-Ttext} to relocate the program to where you wish to
19433 load it on the target. You may also want to add the options @samp{-n} or
19434 @samp{-N} in order to reduce the size of the sections. Example:
19437 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
19440 You can use @code{objdump} to verify that the addresses are what you intended:
19443 sparclet-aout-objdump --headers --syms prog
19446 @cindex running, on Sparclet
19448 your Unix execution search path to find @value{GDBN}, you are ready to
19449 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
19450 (or @code{sparclet-aout-gdb}, depending on your installation).
19452 @value{GDBN} comes up showing the prompt:
19459 * Sparclet File:: Setting the file to debug
19460 * Sparclet Connection:: Connecting to Sparclet
19461 * Sparclet Download:: Sparclet download
19462 * Sparclet Execution:: Running and debugging
19465 @node Sparclet File
19466 @subsubsection Setting File to Debug
19468 The @value{GDBN} command @code{file} lets you choose with program to debug.
19471 (gdbslet) file prog
19475 @value{GDBN} then attempts to read the symbol table of @file{prog}.
19476 @value{GDBN} locates
19477 the file by searching the directories listed in the command search
19479 If the file was compiled with debug information (option @samp{-g}), source
19480 files will be searched as well.
19481 @value{GDBN} locates
19482 the source files by searching the directories listed in the directory search
19483 path (@pxref{Environment, ,Your Program's Environment}).
19485 to find a file, it displays a message such as:
19488 prog: No such file or directory.
19491 When this happens, add the appropriate directories to the search paths with
19492 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
19493 @code{target} command again.
19495 @node Sparclet Connection
19496 @subsubsection Connecting to Sparclet
19498 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
19499 To connect to a target on serial port ``@code{ttya}'', type:
19502 (gdbslet) target sparclet /dev/ttya
19503 Remote target sparclet connected to /dev/ttya
19504 main () at ../prog.c:3
19508 @value{GDBN} displays messages like these:
19514 @node Sparclet Download
19515 @subsubsection Sparclet Download
19517 @cindex download to Sparclet
19518 Once connected to the Sparclet target,
19519 you can use the @value{GDBN}
19520 @code{load} command to download the file from the host to the target.
19521 The file name and load offset should be given as arguments to the @code{load}
19523 Since the file format is aout, the program must be loaded to the starting
19524 address. You can use @code{objdump} to find out what this value is. The load
19525 offset is an offset which is added to the VMA (virtual memory address)
19526 of each of the file's sections.
19527 For instance, if the program
19528 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
19529 and bss at 0x12010170, in @value{GDBN}, type:
19532 (gdbslet) load prog 0x12010000
19533 Loading section .text, size 0xdb0 vma 0x12010000
19536 If the code is loaded at a different address then what the program was linked
19537 to, you may need to use the @code{section} and @code{add-symbol-file} commands
19538 to tell @value{GDBN} where to map the symbol table.
19540 @node Sparclet Execution
19541 @subsubsection Running and Debugging
19543 @cindex running and debugging Sparclet programs
19544 You can now begin debugging the task using @value{GDBN}'s execution control
19545 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
19546 manual for the list of commands.
19550 Breakpoint 1 at 0x12010000: file prog.c, line 3.
19552 Starting program: prog
19553 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
19554 3 char *symarg = 0;
19556 4 char *execarg = "hello!";
19561 @subsection Fujitsu Sparclite
19565 @kindex target sparclite
19566 @item target sparclite @var{dev}
19567 Fujitsu sparclite boards, used only for the purpose of loading.
19568 You must use an additional command to debug the program.
19569 For example: target remote @var{dev} using @value{GDBN} standard
19575 @subsection Zilog Z8000
19578 @cindex simulator, Z8000
19579 @cindex Zilog Z8000 simulator
19581 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
19584 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
19585 unsegmented variant of the Z8000 architecture) or the Z8001 (the
19586 segmented variant). The simulator recognizes which architecture is
19587 appropriate by inspecting the object code.
19590 @item target sim @var{args}
19592 @kindex target sim@r{, with Z8000}
19593 Debug programs on a simulated CPU. If the simulator supports setup
19594 options, specify them via @var{args}.
19598 After specifying this target, you can debug programs for the simulated
19599 CPU in the same style as programs for your host computer; use the
19600 @code{file} command to load a new program image, the @code{run} command
19601 to run your program, and so on.
19603 As well as making available all the usual machine registers
19604 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
19605 additional items of information as specially named registers:
19610 Counts clock-ticks in the simulator.
19613 Counts instructions run in the simulator.
19616 Execution time in 60ths of a second.
19620 You can refer to these values in @value{GDBN} expressions with the usual
19621 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
19622 conditional breakpoint that suspends only after at least 5000
19623 simulated clock ticks.
19626 @subsection Atmel AVR
19629 When configured for debugging the Atmel AVR, @value{GDBN} supports the
19630 following AVR-specific commands:
19633 @item info io_registers
19634 @kindex info io_registers@r{, AVR}
19635 @cindex I/O registers (Atmel AVR)
19636 This command displays information about the AVR I/O registers. For
19637 each register, @value{GDBN} prints its number and value.
19644 When configured for debugging CRIS, @value{GDBN} provides the
19645 following CRIS-specific commands:
19648 @item set cris-version @var{ver}
19649 @cindex CRIS version
19650 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
19651 The CRIS version affects register names and sizes. This command is useful in
19652 case autodetection of the CRIS version fails.
19654 @item show cris-version
19655 Show the current CRIS version.
19657 @item set cris-dwarf2-cfi
19658 @cindex DWARF-2 CFI and CRIS
19659 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
19660 Change to @samp{off} when using @code{gcc-cris} whose version is below
19663 @item show cris-dwarf2-cfi
19664 Show the current state of using DWARF-2 CFI.
19666 @item set cris-mode @var{mode}
19668 Set the current CRIS mode to @var{mode}. It should only be changed when
19669 debugging in guru mode, in which case it should be set to
19670 @samp{guru} (the default is @samp{normal}).
19672 @item show cris-mode
19673 Show the current CRIS mode.
19677 @subsection Renesas Super-H
19680 For the Renesas Super-H processor, @value{GDBN} provides these
19685 @kindex regs@r{, Super-H}
19686 Show the values of all Super-H registers.
19688 @item set sh calling-convention @var{convention}
19689 @kindex set sh calling-convention
19690 Set the calling-convention used when calling functions from @value{GDBN}.
19691 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
19692 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
19693 convention. If the DWARF-2 information of the called function specifies
19694 that the function follows the Renesas calling convention, the function
19695 is called using the Renesas calling convention. If the calling convention
19696 is set to @samp{renesas}, the Renesas calling convention is always used,
19697 regardless of the DWARF-2 information. This can be used to override the
19698 default of @samp{gcc} if debug information is missing, or the compiler
19699 does not emit the DWARF-2 calling convention entry for a function.
19701 @item show sh calling-convention
19702 @kindex show sh calling-convention
19703 Show the current calling convention setting.
19708 @node Architectures
19709 @section Architectures
19711 This section describes characteristics of architectures that affect
19712 all uses of @value{GDBN} with the architecture, both native and cross.
19719 * HPPA:: HP PA architecture
19720 * SPU:: Cell Broadband Engine SPU architecture
19725 @subsection x86 Architecture-specific Issues
19728 @item set struct-convention @var{mode}
19729 @kindex set struct-convention
19730 @cindex struct return convention
19731 @cindex struct/union returned in registers
19732 Set the convention used by the inferior to return @code{struct}s and
19733 @code{union}s from functions to @var{mode}. Possible values of
19734 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
19735 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
19736 are returned on the stack, while @code{"reg"} means that a
19737 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
19738 be returned in a register.
19740 @item show struct-convention
19741 @kindex show struct-convention
19742 Show the current setting of the convention to return @code{struct}s
19751 @kindex set rstack_high_address
19752 @cindex AMD 29K register stack
19753 @cindex register stack, AMD29K
19754 @item set rstack_high_address @var{address}
19755 On AMD 29000 family processors, registers are saved in a separate
19756 @dfn{register stack}. There is no way for @value{GDBN} to determine the
19757 extent of this stack. Normally, @value{GDBN} just assumes that the
19758 stack is ``large enough''. This may result in @value{GDBN} referencing
19759 memory locations that do not exist. If necessary, you can get around
19760 this problem by specifying the ending address of the register stack with
19761 the @code{set rstack_high_address} command. The argument should be an
19762 address, which you probably want to precede with @samp{0x} to specify in
19765 @kindex show rstack_high_address
19766 @item show rstack_high_address
19767 Display the current limit of the register stack, on AMD 29000 family
19775 See the following section.
19780 @cindex stack on Alpha
19781 @cindex stack on MIPS
19782 @cindex Alpha stack
19784 Alpha- and MIPS-based computers use an unusual stack frame, which
19785 sometimes requires @value{GDBN} to search backward in the object code to
19786 find the beginning of a function.
19788 @cindex response time, MIPS debugging
19789 To improve response time (especially for embedded applications, where
19790 @value{GDBN} may be restricted to a slow serial line for this search)
19791 you may want to limit the size of this search, using one of these
19795 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
19796 @item set heuristic-fence-post @var{limit}
19797 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
19798 search for the beginning of a function. A value of @var{0} (the
19799 default) means there is no limit. However, except for @var{0}, the
19800 larger the limit the more bytes @code{heuristic-fence-post} must search
19801 and therefore the longer it takes to run. You should only need to use
19802 this command when debugging a stripped executable.
19804 @item show heuristic-fence-post
19805 Display the current limit.
19809 These commands are available @emph{only} when @value{GDBN} is configured
19810 for debugging programs on Alpha or MIPS processors.
19812 Several MIPS-specific commands are available when debugging MIPS
19816 @item set mips abi @var{arg}
19817 @kindex set mips abi
19818 @cindex set ABI for MIPS
19819 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
19820 values of @var{arg} are:
19824 The default ABI associated with the current binary (this is the
19835 @item show mips abi
19836 @kindex show mips abi
19837 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
19840 @itemx show mipsfpu
19841 @xref{MIPS Embedded, set mipsfpu}.
19843 @item set mips mask-address @var{arg}
19844 @kindex set mips mask-address
19845 @cindex MIPS addresses, masking
19846 This command determines whether the most-significant 32 bits of 64-bit
19847 MIPS addresses are masked off. The argument @var{arg} can be
19848 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
19849 setting, which lets @value{GDBN} determine the correct value.
19851 @item show mips mask-address
19852 @kindex show mips mask-address
19853 Show whether the upper 32 bits of MIPS addresses are masked off or
19856 @item set remote-mips64-transfers-32bit-regs
19857 @kindex set remote-mips64-transfers-32bit-regs
19858 This command controls compatibility with 64-bit MIPS targets that
19859 transfer data in 32-bit quantities. If you have an old MIPS 64 target
19860 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
19861 and 64 bits for other registers, set this option to @samp{on}.
19863 @item show remote-mips64-transfers-32bit-regs
19864 @kindex show remote-mips64-transfers-32bit-regs
19865 Show the current setting of compatibility with older MIPS 64 targets.
19867 @item set debug mips
19868 @kindex set debug mips
19869 This command turns on and off debugging messages for the MIPS-specific
19870 target code in @value{GDBN}.
19872 @item show debug mips
19873 @kindex show debug mips
19874 Show the current setting of MIPS debugging messages.
19880 @cindex HPPA support
19882 When @value{GDBN} is debugging the HP PA architecture, it provides the
19883 following special commands:
19886 @item set debug hppa
19887 @kindex set debug hppa
19888 This command determines whether HPPA architecture-specific debugging
19889 messages are to be displayed.
19891 @item show debug hppa
19892 Show whether HPPA debugging messages are displayed.
19894 @item maint print unwind @var{address}
19895 @kindex maint print unwind@r{, HPPA}
19896 This command displays the contents of the unwind table entry at the
19897 given @var{address}.
19903 @subsection Cell Broadband Engine SPU architecture
19904 @cindex Cell Broadband Engine
19907 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
19908 it provides the following special commands:
19911 @item info spu event
19913 Display SPU event facility status. Shows current event mask
19914 and pending event status.
19916 @item info spu signal
19917 Display SPU signal notification facility status. Shows pending
19918 signal-control word and signal notification mode of both signal
19919 notification channels.
19921 @item info spu mailbox
19922 Display SPU mailbox facility status. Shows all pending entries,
19923 in order of processing, in each of the SPU Write Outbound,
19924 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
19927 Display MFC DMA status. Shows all pending commands in the MFC
19928 DMA queue. For each entry, opcode, tag, class IDs, effective
19929 and local store addresses and transfer size are shown.
19931 @item info spu proxydma
19932 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
19933 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
19934 and local store addresses and transfer size are shown.
19938 When @value{GDBN} is debugging a combined PowerPC/SPU application
19939 on the Cell Broadband Engine, it provides in addition the following
19943 @item set spu stop-on-load @var{arg}
19945 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
19946 will give control to the user when a new SPE thread enters its @code{main}
19947 function. The default is @code{off}.
19949 @item show spu stop-on-load
19951 Show whether to stop for new SPE threads.
19953 @item set spu auto-flush-cache @var{arg}
19954 Set whether to automatically flush the software-managed cache. When set to
19955 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
19956 cache to be flushed whenever SPE execution stops. This provides a consistent
19957 view of PowerPC memory that is accessed via the cache. If an application
19958 does not use the software-managed cache, this option has no effect.
19960 @item show spu auto-flush-cache
19961 Show whether to automatically flush the software-managed cache.
19966 @subsection PowerPC
19967 @cindex PowerPC architecture
19969 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
19970 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
19971 numbers stored in the floating point registers. These values must be stored
19972 in two consecutive registers, always starting at an even register like
19973 @code{f0} or @code{f2}.
19975 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
19976 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
19977 @code{f2} and @code{f3} for @code{$dl1} and so on.
19979 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
19980 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
19983 @node Controlling GDB
19984 @chapter Controlling @value{GDBN}
19986 You can alter the way @value{GDBN} interacts with you by using the
19987 @code{set} command. For commands controlling how @value{GDBN} displays
19988 data, see @ref{Print Settings, ,Print Settings}. Other settings are
19993 * Editing:: Command editing
19994 * Command History:: Command history
19995 * Screen Size:: Screen size
19996 * Numbers:: Numbers
19997 * ABI:: Configuring the current ABI
19998 * Messages/Warnings:: Optional warnings and messages
19999 * Debugging Output:: Optional messages about internal happenings
20000 * Other Misc Settings:: Other Miscellaneous Settings
20008 @value{GDBN} indicates its readiness to read a command by printing a string
20009 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
20010 can change the prompt string with the @code{set prompt} command. For
20011 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
20012 the prompt in one of the @value{GDBN} sessions so that you can always tell
20013 which one you are talking to.
20015 @emph{Note:} @code{set prompt} does not add a space for you after the
20016 prompt you set. This allows you to set a prompt which ends in a space
20017 or a prompt that does not.
20021 @item set prompt @var{newprompt}
20022 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
20024 @kindex show prompt
20026 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
20029 Versions of @value{GDBN} that ship with Python scripting enabled have
20030 prompt extensions. The commands for interacting with these extensions
20034 @kindex set extended-prompt
20035 @item set extended-prompt @var{prompt}
20036 Set an extended prompt that allows for substitutions.
20037 @xref{gdb.prompt}, for a list of escape sequences that can be used for
20038 substitution. Any escape sequences specified as part of the prompt
20039 string are replaced with the corresponding strings each time the prompt
20045 set extended-prompt Current working directory: \w (gdb)
20048 Note that when an extended-prompt is set, it takes control of the
20049 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
20051 @kindex show extended-prompt
20052 @item show extended-prompt
20053 Prints the extended prompt. Any escape sequences specified as part of
20054 the prompt string with @code{set extended-prompt}, are replaced with the
20055 corresponding strings each time the prompt is displayed.
20059 @section Command Editing
20061 @cindex command line editing
20063 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
20064 @sc{gnu} library provides consistent behavior for programs which provide a
20065 command line interface to the user. Advantages are @sc{gnu} Emacs-style
20066 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
20067 substitution, and a storage and recall of command history across
20068 debugging sessions.
20070 You may control the behavior of command line editing in @value{GDBN} with the
20071 command @code{set}.
20074 @kindex set editing
20077 @itemx set editing on
20078 Enable command line editing (enabled by default).
20080 @item set editing off
20081 Disable command line editing.
20083 @kindex show editing
20085 Show whether command line editing is enabled.
20088 @ifset SYSTEM_READLINE
20089 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
20091 @ifclear SYSTEM_READLINE
20092 @xref{Command Line Editing},
20094 for more details about the Readline
20095 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
20096 encouraged to read that chapter.
20098 @node Command History
20099 @section Command History
20100 @cindex command history
20102 @value{GDBN} can keep track of the commands you type during your
20103 debugging sessions, so that you can be certain of precisely what
20104 happened. Use these commands to manage the @value{GDBN} command
20107 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
20108 package, to provide the history facility.
20109 @ifset SYSTEM_READLINE
20110 @xref{Using History Interactively, , , history, GNU History Library},
20112 @ifclear SYSTEM_READLINE
20113 @xref{Using History Interactively},
20115 for the detailed description of the History library.
20117 To issue a command to @value{GDBN} without affecting certain aspects of
20118 the state which is seen by users, prefix it with @samp{server }
20119 (@pxref{Server Prefix}). This
20120 means that this command will not affect the command history, nor will it
20121 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
20122 pressed on a line by itself.
20124 @cindex @code{server}, command prefix
20125 The server prefix does not affect the recording of values into the value
20126 history; to print a value without recording it into the value history,
20127 use the @code{output} command instead of the @code{print} command.
20129 Here is the description of @value{GDBN} commands related to command
20133 @cindex history substitution
20134 @cindex history file
20135 @kindex set history filename
20136 @cindex @env{GDBHISTFILE}, environment variable
20137 @item set history filename @var{fname}
20138 Set the name of the @value{GDBN} command history file to @var{fname}.
20139 This is the file where @value{GDBN} reads an initial command history
20140 list, and where it writes the command history from this session when it
20141 exits. You can access this list through history expansion or through
20142 the history command editing characters listed below. This file defaults
20143 to the value of the environment variable @code{GDBHISTFILE}, or to
20144 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
20147 @cindex save command history
20148 @kindex set history save
20149 @item set history save
20150 @itemx set history save on
20151 Record command history in a file, whose name may be specified with the
20152 @code{set history filename} command. By default, this option is disabled.
20154 @item set history save off
20155 Stop recording command history in a file.
20157 @cindex history size
20158 @kindex set history size
20159 @cindex @env{HISTSIZE}, environment variable
20160 @item set history size @var{size}
20161 Set the number of commands which @value{GDBN} keeps in its history list.
20162 This defaults to the value of the environment variable
20163 @code{HISTSIZE}, or to 256 if this variable is not set.
20166 History expansion assigns special meaning to the character @kbd{!}.
20167 @ifset SYSTEM_READLINE
20168 @xref{Event Designators, , , history, GNU History Library},
20170 @ifclear SYSTEM_READLINE
20171 @xref{Event Designators},
20175 @cindex history expansion, turn on/off
20176 Since @kbd{!} is also the logical not operator in C, history expansion
20177 is off by default. If you decide to enable history expansion with the
20178 @code{set history expansion on} command, you may sometimes need to
20179 follow @kbd{!} (when it is used as logical not, in an expression) with
20180 a space or a tab to prevent it from being expanded. The readline
20181 history facilities do not attempt substitution on the strings
20182 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
20184 The commands to control history expansion are:
20187 @item set history expansion on
20188 @itemx set history expansion
20189 @kindex set history expansion
20190 Enable history expansion. History expansion is off by default.
20192 @item set history expansion off
20193 Disable history expansion.
20196 @kindex show history
20198 @itemx show history filename
20199 @itemx show history save
20200 @itemx show history size
20201 @itemx show history expansion
20202 These commands display the state of the @value{GDBN} history parameters.
20203 @code{show history} by itself displays all four states.
20208 @kindex show commands
20209 @cindex show last commands
20210 @cindex display command history
20211 @item show commands
20212 Display the last ten commands in the command history.
20214 @item show commands @var{n}
20215 Print ten commands centered on command number @var{n}.
20217 @item show commands +
20218 Print ten commands just after the commands last printed.
20222 @section Screen Size
20223 @cindex size of screen
20224 @cindex pauses in output
20226 Certain commands to @value{GDBN} may produce large amounts of
20227 information output to the screen. To help you read all of it,
20228 @value{GDBN} pauses and asks you for input at the end of each page of
20229 output. Type @key{RET} when you want to continue the output, or @kbd{q}
20230 to discard the remaining output. Also, the screen width setting
20231 determines when to wrap lines of output. Depending on what is being
20232 printed, @value{GDBN} tries to break the line at a readable place,
20233 rather than simply letting it overflow onto the following line.
20235 Normally @value{GDBN} knows the size of the screen from the terminal
20236 driver software. For example, on Unix @value{GDBN} uses the termcap data base
20237 together with the value of the @code{TERM} environment variable and the
20238 @code{stty rows} and @code{stty cols} settings. If this is not correct,
20239 you can override it with the @code{set height} and @code{set
20246 @kindex show height
20247 @item set height @var{lpp}
20249 @itemx set width @var{cpl}
20251 These @code{set} commands specify a screen height of @var{lpp} lines and
20252 a screen width of @var{cpl} characters. The associated @code{show}
20253 commands display the current settings.
20255 If you specify a height of zero lines, @value{GDBN} does not pause during
20256 output no matter how long the output is. This is useful if output is to a
20257 file or to an editor buffer.
20259 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
20260 from wrapping its output.
20262 @item set pagination on
20263 @itemx set pagination off
20264 @kindex set pagination
20265 Turn the output pagination on or off; the default is on. Turning
20266 pagination off is the alternative to @code{set height 0}. Note that
20267 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
20268 Options, -batch}) also automatically disables pagination.
20270 @item show pagination
20271 @kindex show pagination
20272 Show the current pagination mode.
20277 @cindex number representation
20278 @cindex entering numbers
20280 You can always enter numbers in octal, decimal, or hexadecimal in
20281 @value{GDBN} by the usual conventions: octal numbers begin with
20282 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
20283 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
20284 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
20285 10; likewise, the default display for numbers---when no particular
20286 format is specified---is base 10. You can change the default base for
20287 both input and output with the commands described below.
20290 @kindex set input-radix
20291 @item set input-radix @var{base}
20292 Set the default base for numeric input. Supported choices
20293 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
20294 specified either unambiguously or using the current input radix; for
20298 set input-radix 012
20299 set input-radix 10.
20300 set input-radix 0xa
20304 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
20305 leaves the input radix unchanged, no matter what it was, since
20306 @samp{10}, being without any leading or trailing signs of its base, is
20307 interpreted in the current radix. Thus, if the current radix is 16,
20308 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
20311 @kindex set output-radix
20312 @item set output-radix @var{base}
20313 Set the default base for numeric display. Supported choices
20314 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
20315 specified either unambiguously or using the current input radix.
20317 @kindex show input-radix
20318 @item show input-radix
20319 Display the current default base for numeric input.
20321 @kindex show output-radix
20322 @item show output-radix
20323 Display the current default base for numeric display.
20325 @item set radix @r{[}@var{base}@r{]}
20329 These commands set and show the default base for both input and output
20330 of numbers. @code{set radix} sets the radix of input and output to
20331 the same base; without an argument, it resets the radix back to its
20332 default value of 10.
20337 @section Configuring the Current ABI
20339 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
20340 application automatically. However, sometimes you need to override its
20341 conclusions. Use these commands to manage @value{GDBN}'s view of the
20348 One @value{GDBN} configuration can debug binaries for multiple operating
20349 system targets, either via remote debugging or native emulation.
20350 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
20351 but you can override its conclusion using the @code{set osabi} command.
20352 One example where this is useful is in debugging of binaries which use
20353 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
20354 not have the same identifying marks that the standard C library for your
20359 Show the OS ABI currently in use.
20362 With no argument, show the list of registered available OS ABI's.
20364 @item set osabi @var{abi}
20365 Set the current OS ABI to @var{abi}.
20368 @cindex float promotion
20370 Generally, the way that an argument of type @code{float} is passed to a
20371 function depends on whether the function is prototyped. For a prototyped
20372 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
20373 according to the architecture's convention for @code{float}. For unprototyped
20374 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
20375 @code{double} and then passed.
20377 Unfortunately, some forms of debug information do not reliably indicate whether
20378 a function is prototyped. If @value{GDBN} calls a function that is not marked
20379 as prototyped, it consults @kbd{set coerce-float-to-double}.
20382 @kindex set coerce-float-to-double
20383 @item set coerce-float-to-double
20384 @itemx set coerce-float-to-double on
20385 Arguments of type @code{float} will be promoted to @code{double} when passed
20386 to an unprototyped function. This is the default setting.
20388 @item set coerce-float-to-double off
20389 Arguments of type @code{float} will be passed directly to unprototyped
20392 @kindex show coerce-float-to-double
20393 @item show coerce-float-to-double
20394 Show the current setting of promoting @code{float} to @code{double}.
20398 @kindex show cp-abi
20399 @value{GDBN} needs to know the ABI used for your program's C@t{++}
20400 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
20401 used to build your application. @value{GDBN} only fully supports
20402 programs with a single C@t{++} ABI; if your program contains code using
20403 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
20404 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
20405 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
20406 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
20407 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
20408 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
20413 Show the C@t{++} ABI currently in use.
20416 With no argument, show the list of supported C@t{++} ABI's.
20418 @item set cp-abi @var{abi}
20419 @itemx set cp-abi auto
20420 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
20423 @node Messages/Warnings
20424 @section Optional Warnings and Messages
20426 @cindex verbose operation
20427 @cindex optional warnings
20428 By default, @value{GDBN} is silent about its inner workings. If you are
20429 running on a slow machine, you may want to use the @code{set verbose}
20430 command. This makes @value{GDBN} tell you when it does a lengthy
20431 internal operation, so you will not think it has crashed.
20433 Currently, the messages controlled by @code{set verbose} are those
20434 which announce that the symbol table for a source file is being read;
20435 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
20438 @kindex set verbose
20439 @item set verbose on
20440 Enables @value{GDBN} output of certain informational messages.
20442 @item set verbose off
20443 Disables @value{GDBN} output of certain informational messages.
20445 @kindex show verbose
20447 Displays whether @code{set verbose} is on or off.
20450 By default, if @value{GDBN} encounters bugs in the symbol table of an
20451 object file, it is silent; but if you are debugging a compiler, you may
20452 find this information useful (@pxref{Symbol Errors, ,Errors Reading
20457 @kindex set complaints
20458 @item set complaints @var{limit}
20459 Permits @value{GDBN} to output @var{limit} complaints about each type of
20460 unusual symbols before becoming silent about the problem. Set
20461 @var{limit} to zero to suppress all complaints; set it to a large number
20462 to prevent complaints from being suppressed.
20464 @kindex show complaints
20465 @item show complaints
20466 Displays how many symbol complaints @value{GDBN} is permitted to produce.
20470 @anchor{confirmation requests}
20471 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
20472 lot of stupid questions to confirm certain commands. For example, if
20473 you try to run a program which is already running:
20477 The program being debugged has been started already.
20478 Start it from the beginning? (y or n)
20481 If you are willing to unflinchingly face the consequences of your own
20482 commands, you can disable this ``feature'':
20486 @kindex set confirm
20488 @cindex confirmation
20489 @cindex stupid questions
20490 @item set confirm off
20491 Disables confirmation requests. Note that running @value{GDBN} with
20492 the @option{--batch} option (@pxref{Mode Options, -batch}) also
20493 automatically disables confirmation requests.
20495 @item set confirm on
20496 Enables confirmation requests (the default).
20498 @kindex show confirm
20500 Displays state of confirmation requests.
20504 @cindex command tracing
20505 If you need to debug user-defined commands or sourced files you may find it
20506 useful to enable @dfn{command tracing}. In this mode each command will be
20507 printed as it is executed, prefixed with one or more @samp{+} symbols, the
20508 quantity denoting the call depth of each command.
20511 @kindex set trace-commands
20512 @cindex command scripts, debugging
20513 @item set trace-commands on
20514 Enable command tracing.
20515 @item set trace-commands off
20516 Disable command tracing.
20517 @item show trace-commands
20518 Display the current state of command tracing.
20521 @node Debugging Output
20522 @section Optional Messages about Internal Happenings
20523 @cindex optional debugging messages
20525 @value{GDBN} has commands that enable optional debugging messages from
20526 various @value{GDBN} subsystems; normally these commands are of
20527 interest to @value{GDBN} maintainers, or when reporting a bug. This
20528 section documents those commands.
20531 @kindex set exec-done-display
20532 @item set exec-done-display
20533 Turns on or off the notification of asynchronous commands'
20534 completion. When on, @value{GDBN} will print a message when an
20535 asynchronous command finishes its execution. The default is off.
20536 @kindex show exec-done-display
20537 @item show exec-done-display
20538 Displays the current setting of asynchronous command completion
20541 @cindex gdbarch debugging info
20542 @cindex architecture debugging info
20543 @item set debug arch
20544 Turns on or off display of gdbarch debugging info. The default is off
20546 @item show debug arch
20547 Displays the current state of displaying gdbarch debugging info.
20548 @item set debug aix-thread
20549 @cindex AIX threads
20550 Display debugging messages about inner workings of the AIX thread
20552 @item show debug aix-thread
20553 Show the current state of AIX thread debugging info display.
20554 @item set debug check-physname
20556 Check the results of the ``physname'' computation. When reading DWARF
20557 debugging information for C@t{++}, @value{GDBN} attempts to compute
20558 each entity's name. @value{GDBN} can do this computation in two
20559 different ways, depending on exactly what information is present.
20560 When enabled, this setting causes @value{GDBN} to compute the names
20561 both ways and display any discrepancies.
20562 @item show debug check-physname
20563 Show the current state of ``physname'' checking.
20564 @item set debug dwarf2-die
20565 @cindex DWARF2 DIEs
20566 Dump DWARF2 DIEs after they are read in.
20567 The value is the number of nesting levels to print.
20568 A value of zero turns off the display.
20569 @item show debug dwarf2-die
20570 Show the current state of DWARF2 DIE debugging.
20571 @item set debug displaced
20572 @cindex displaced stepping debugging info
20573 Turns on or off display of @value{GDBN} debugging info for the
20574 displaced stepping support. The default is off.
20575 @item show debug displaced
20576 Displays the current state of displaying @value{GDBN} debugging info
20577 related to displaced stepping.
20578 @item set debug event
20579 @cindex event debugging info
20580 Turns on or off display of @value{GDBN} event debugging info. The
20582 @item show debug event
20583 Displays the current state of displaying @value{GDBN} event debugging
20585 @item set debug expression
20586 @cindex expression debugging info
20587 Turns on or off display of debugging info about @value{GDBN}
20588 expression parsing. The default is off.
20589 @item show debug expression
20590 Displays the current state of displaying debugging info about
20591 @value{GDBN} expression parsing.
20592 @item set debug frame
20593 @cindex frame debugging info
20594 Turns on or off display of @value{GDBN} frame debugging info. The
20596 @item show debug frame
20597 Displays the current state of displaying @value{GDBN} frame debugging
20599 @item set debug gnu-nat
20600 @cindex @sc{gnu}/Hurd debug messages
20601 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
20602 @item show debug gnu-nat
20603 Show the current state of @sc{gnu}/Hurd debugging messages.
20604 @item set debug infrun
20605 @cindex inferior debugging info
20606 Turns on or off display of @value{GDBN} debugging info for running the inferior.
20607 The default is off. @file{infrun.c} contains GDB's runtime state machine used
20608 for implementing operations such as single-stepping the inferior.
20609 @item show debug infrun
20610 Displays the current state of @value{GDBN} inferior debugging.
20611 @item set debug jit
20612 @cindex just-in-time compilation, debugging messages
20613 Turns on or off debugging messages from JIT debug support.
20614 @item show debug jit
20615 Displays the current state of @value{GDBN} JIT debugging.
20616 @item set debug lin-lwp
20617 @cindex @sc{gnu}/Linux LWP debug messages
20618 @cindex Linux lightweight processes
20619 Turns on or off debugging messages from the Linux LWP debug support.
20620 @item show debug lin-lwp
20621 Show the current state of Linux LWP debugging messages.
20622 @item set debug observer
20623 @cindex observer debugging info
20624 Turns on or off display of @value{GDBN} observer debugging. This
20625 includes info such as the notification of observable events.
20626 @item show debug observer
20627 Displays the current state of observer debugging.
20628 @item set debug overload
20629 @cindex C@t{++} overload debugging info
20630 Turns on or off display of @value{GDBN} C@t{++} overload debugging
20631 info. This includes info such as ranking of functions, etc. The default
20633 @item show debug overload
20634 Displays the current state of displaying @value{GDBN} C@t{++} overload
20636 @cindex expression parser, debugging info
20637 @cindex debug expression parser
20638 @item set debug parser
20639 Turns on or off the display of expression parser debugging output.
20640 Internally, this sets the @code{yydebug} variable in the expression
20641 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
20642 details. The default is off.
20643 @item show debug parser
20644 Show the current state of expression parser debugging.
20645 @cindex packets, reporting on stdout
20646 @cindex serial connections, debugging
20647 @cindex debug remote protocol
20648 @cindex remote protocol debugging
20649 @cindex display remote packets
20650 @item set debug remote
20651 Turns on or off display of reports on all packets sent back and forth across
20652 the serial line to the remote machine. The info is printed on the
20653 @value{GDBN} standard output stream. The default is off.
20654 @item show debug remote
20655 Displays the state of display of remote packets.
20656 @item set debug serial
20657 Turns on or off display of @value{GDBN} serial debugging info. The
20659 @item show debug serial
20660 Displays the current state of displaying @value{GDBN} serial debugging
20662 @item set debug solib-frv
20663 @cindex FR-V shared-library debugging
20664 Turns on or off debugging messages for FR-V shared-library code.
20665 @item show debug solib-frv
20666 Display the current state of FR-V shared-library code debugging
20668 @item set debug target
20669 @cindex target debugging info
20670 Turns on or off display of @value{GDBN} target debugging info. This info
20671 includes what is going on at the target level of GDB, as it happens. The
20672 default is 0. Set it to 1 to track events, and to 2 to also track the
20673 value of large memory transfers. Changes to this flag do not take effect
20674 until the next time you connect to a target or use the @code{run} command.
20675 @item show debug target
20676 Displays the current state of displaying @value{GDBN} target debugging
20678 @item set debug timestamp
20679 @cindex timestampping debugging info
20680 Turns on or off display of timestamps with @value{GDBN} debugging info.
20681 When enabled, seconds and microseconds are displayed before each debugging
20683 @item show debug timestamp
20684 Displays the current state of displaying timestamps with @value{GDBN}
20686 @item set debugvarobj
20687 @cindex variable object debugging info
20688 Turns on or off display of @value{GDBN} variable object debugging
20689 info. The default is off.
20690 @item show debugvarobj
20691 Displays the current state of displaying @value{GDBN} variable object
20693 @item set debug xml
20694 @cindex XML parser debugging
20695 Turns on or off debugging messages for built-in XML parsers.
20696 @item show debug xml
20697 Displays the current state of XML debugging messages.
20700 @node Other Misc Settings
20701 @section Other Miscellaneous Settings
20702 @cindex miscellaneous settings
20705 @kindex set interactive-mode
20706 @item set interactive-mode
20707 If @code{on}, forces @value{GDBN} to assume that GDB was started
20708 in a terminal. In practice, this means that @value{GDBN} should wait
20709 for the user to answer queries generated by commands entered at
20710 the command prompt. If @code{off}, forces @value{GDBN} to operate
20711 in the opposite mode, and it uses the default answers to all queries.
20712 If @code{auto} (the default), @value{GDBN} tries to determine whether
20713 its standard input is a terminal, and works in interactive-mode if it
20714 is, non-interactively otherwise.
20716 In the vast majority of cases, the debugger should be able to guess
20717 correctly which mode should be used. But this setting can be useful
20718 in certain specific cases, such as running a MinGW @value{GDBN}
20719 inside a cygwin window.
20721 @kindex show interactive-mode
20722 @item show interactive-mode
20723 Displays whether the debugger is operating in interactive mode or not.
20726 @node Extending GDB
20727 @chapter Extending @value{GDBN}
20728 @cindex extending GDB
20730 @value{GDBN} provides three mechanisms for extension. The first is based
20731 on composition of @value{GDBN} commands, the second is based on the
20732 Python scripting language, and the third is for defining new aliases of
20735 To facilitate the use of the first two extensions, @value{GDBN} is capable
20736 of evaluating the contents of a file. When doing so, @value{GDBN}
20737 can recognize which scripting language is being used by looking at
20738 the filename extension. Files with an unrecognized filename extension
20739 are always treated as a @value{GDBN} Command Files.
20740 @xref{Command Files,, Command files}.
20742 You can control how @value{GDBN} evaluates these files with the following
20746 @kindex set script-extension
20747 @kindex show script-extension
20748 @item set script-extension off
20749 All scripts are always evaluated as @value{GDBN} Command Files.
20751 @item set script-extension soft
20752 The debugger determines the scripting language based on filename
20753 extension. If this scripting language is supported, @value{GDBN}
20754 evaluates the script using that language. Otherwise, it evaluates
20755 the file as a @value{GDBN} Command File.
20757 @item set script-extension strict
20758 The debugger determines the scripting language based on filename
20759 extension, and evaluates the script using that language. If the
20760 language is not supported, then the evaluation fails.
20762 @item show script-extension
20763 Display the current value of the @code{script-extension} option.
20768 * Sequences:: Canned Sequences of Commands
20769 * Python:: Scripting @value{GDBN} using Python
20770 * Aliases:: Creating new spellings of existing commands
20774 @section Canned Sequences of Commands
20776 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
20777 Command Lists}), @value{GDBN} provides two ways to store sequences of
20778 commands for execution as a unit: user-defined commands and command
20782 * Define:: How to define your own commands
20783 * Hooks:: Hooks for user-defined commands
20784 * Command Files:: How to write scripts of commands to be stored in a file
20785 * Output:: Commands for controlled output
20789 @subsection User-defined Commands
20791 @cindex user-defined command
20792 @cindex arguments, to user-defined commands
20793 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
20794 which you assign a new name as a command. This is done with the
20795 @code{define} command. User commands may accept up to 10 arguments
20796 separated by whitespace. Arguments are accessed within the user command
20797 via @code{$arg0@dots{}$arg9}. A trivial example:
20801 print $arg0 + $arg1 + $arg2
20806 To execute the command use:
20813 This defines the command @code{adder}, which prints the sum of
20814 its three arguments. Note the arguments are text substitutions, so they may
20815 reference variables, use complex expressions, or even perform inferior
20818 @cindex argument count in user-defined commands
20819 @cindex how many arguments (user-defined commands)
20820 In addition, @code{$argc} may be used to find out how many arguments have
20821 been passed. This expands to a number in the range 0@dots{}10.
20826 print $arg0 + $arg1
20829 print $arg0 + $arg1 + $arg2
20837 @item define @var{commandname}
20838 Define a command named @var{commandname}. If there is already a command
20839 by that name, you are asked to confirm that you want to redefine it.
20840 @var{commandname} may be a bare command name consisting of letters,
20841 numbers, dashes, and underscores. It may also start with any predefined
20842 prefix command. For example, @samp{define target my-target} creates
20843 a user-defined @samp{target my-target} command.
20845 The definition of the command is made up of other @value{GDBN} command lines,
20846 which are given following the @code{define} command. The end of these
20847 commands is marked by a line containing @code{end}.
20850 @kindex end@r{ (user-defined commands)}
20851 @item document @var{commandname}
20852 Document the user-defined command @var{commandname}, so that it can be
20853 accessed by @code{help}. The command @var{commandname} must already be
20854 defined. This command reads lines of documentation just as @code{define}
20855 reads the lines of the command definition, ending with @code{end}.
20856 After the @code{document} command is finished, @code{help} on command
20857 @var{commandname} displays the documentation you have written.
20859 You may use the @code{document} command again to change the
20860 documentation of a command. Redefining the command with @code{define}
20861 does not change the documentation.
20863 @kindex dont-repeat
20864 @cindex don't repeat command
20866 Used inside a user-defined command, this tells @value{GDBN} that this
20867 command should not be repeated when the user hits @key{RET}
20868 (@pxref{Command Syntax, repeat last command}).
20870 @kindex help user-defined
20871 @item help user-defined
20872 List all user-defined commands, with the first line of the documentation
20877 @itemx show user @var{commandname}
20878 Display the @value{GDBN} commands used to define @var{commandname} (but
20879 not its documentation). If no @var{commandname} is given, display the
20880 definitions for all user-defined commands.
20882 @cindex infinite recursion in user-defined commands
20883 @kindex show max-user-call-depth
20884 @kindex set max-user-call-depth
20885 @item show max-user-call-depth
20886 @itemx set max-user-call-depth
20887 The value of @code{max-user-call-depth} controls how many recursion
20888 levels are allowed in user-defined commands before @value{GDBN} suspects an
20889 infinite recursion and aborts the command.
20892 In addition to the above commands, user-defined commands frequently
20893 use control flow commands, described in @ref{Command Files}.
20895 When user-defined commands are executed, the
20896 commands of the definition are not printed. An error in any command
20897 stops execution of the user-defined command.
20899 If used interactively, commands that would ask for confirmation proceed
20900 without asking when used inside a user-defined command. Many @value{GDBN}
20901 commands that normally print messages to say what they are doing omit the
20902 messages when used in a user-defined command.
20905 @subsection User-defined Command Hooks
20906 @cindex command hooks
20907 @cindex hooks, for commands
20908 @cindex hooks, pre-command
20911 You may define @dfn{hooks}, which are a special kind of user-defined
20912 command. Whenever you run the command @samp{foo}, if the user-defined
20913 command @samp{hook-foo} exists, it is executed (with no arguments)
20914 before that command.
20916 @cindex hooks, post-command
20918 A hook may also be defined which is run after the command you executed.
20919 Whenever you run the command @samp{foo}, if the user-defined command
20920 @samp{hookpost-foo} exists, it is executed (with no arguments) after
20921 that command. Post-execution hooks may exist simultaneously with
20922 pre-execution hooks, for the same command.
20924 It is valid for a hook to call the command which it hooks. If this
20925 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
20927 @c It would be nice if hookpost could be passed a parameter indicating
20928 @c if the command it hooks executed properly or not. FIXME!
20930 @kindex stop@r{, a pseudo-command}
20931 In addition, a pseudo-command, @samp{stop} exists. Defining
20932 (@samp{hook-stop}) makes the associated commands execute every time
20933 execution stops in your program: before breakpoint commands are run,
20934 displays are printed, or the stack frame is printed.
20936 For example, to ignore @code{SIGALRM} signals while
20937 single-stepping, but treat them normally during normal execution,
20942 handle SIGALRM nopass
20946 handle SIGALRM pass
20949 define hook-continue
20950 handle SIGALRM pass
20954 As a further example, to hook at the beginning and end of the @code{echo}
20955 command, and to add extra text to the beginning and end of the message,
20963 define hookpost-echo
20967 (@value{GDBP}) echo Hello World
20968 <<<---Hello World--->>>
20973 You can define a hook for any single-word command in @value{GDBN}, but
20974 not for command aliases; you should define a hook for the basic command
20975 name, e.g.@: @code{backtrace} rather than @code{bt}.
20976 @c FIXME! So how does Joe User discover whether a command is an alias
20978 You can hook a multi-word command by adding @code{hook-} or
20979 @code{hookpost-} to the last word of the command, e.g.@:
20980 @samp{define target hook-remote} to add a hook to @samp{target remote}.
20982 If an error occurs during the execution of your hook, execution of
20983 @value{GDBN} commands stops and @value{GDBN} issues a prompt
20984 (before the command that you actually typed had a chance to run).
20986 If you try to define a hook which does not match any known command, you
20987 get a warning from the @code{define} command.
20989 @node Command Files
20990 @subsection Command Files
20992 @cindex command files
20993 @cindex scripting commands
20994 A command file for @value{GDBN} is a text file made of lines that are
20995 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
20996 also be included. An empty line in a command file does nothing; it
20997 does not mean to repeat the last command, as it would from the
21000 You can request the execution of a command file with the @code{source}
21001 command. Note that the @code{source} command is also used to evaluate
21002 scripts that are not Command Files. The exact behavior can be configured
21003 using the @code{script-extension} setting.
21004 @xref{Extending GDB,, Extending GDB}.
21008 @cindex execute commands from a file
21009 @item source [-s] [-v] @var{filename}
21010 Execute the command file @var{filename}.
21013 The lines in a command file are generally executed sequentially,
21014 unless the order of execution is changed by one of the
21015 @emph{flow-control commands} described below. The commands are not
21016 printed as they are executed. An error in any command terminates
21017 execution of the command file and control is returned to the console.
21019 @value{GDBN} first searches for @var{filename} in the current directory.
21020 If the file is not found there, and @var{filename} does not specify a
21021 directory, then @value{GDBN} also looks for the file on the source search path
21022 (specified with the @samp{directory} command);
21023 except that @file{$cdir} is not searched because the compilation directory
21024 is not relevant to scripts.
21026 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
21027 on the search path even if @var{filename} specifies a directory.
21028 The search is done by appending @var{filename} to each element of the
21029 search path. So, for example, if @var{filename} is @file{mylib/myscript}
21030 and the search path contains @file{/home/user} then @value{GDBN} will
21031 look for the script @file{/home/user/mylib/myscript}.
21032 The search is also done if @var{filename} is an absolute path.
21033 For example, if @var{filename} is @file{/tmp/myscript} and
21034 the search path contains @file{/home/user} then @value{GDBN} will
21035 look for the script @file{/home/user/tmp/myscript}.
21036 For DOS-like systems, if @var{filename} contains a drive specification,
21037 it is stripped before concatenation. For example, if @var{filename} is
21038 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
21039 will look for the script @file{c:/tmp/myscript}.
21041 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
21042 each command as it is executed. The option must be given before
21043 @var{filename}, and is interpreted as part of the filename anywhere else.
21045 Commands that would ask for confirmation if used interactively proceed
21046 without asking when used in a command file. Many @value{GDBN} commands that
21047 normally print messages to say what they are doing omit the messages
21048 when called from command files.
21050 @value{GDBN} also accepts command input from standard input. In this
21051 mode, normal output goes to standard output and error output goes to
21052 standard error. Errors in a command file supplied on standard input do
21053 not terminate execution of the command file---execution continues with
21057 gdb < cmds > log 2>&1
21060 (The syntax above will vary depending on the shell used.) This example
21061 will execute commands from the file @file{cmds}. All output and errors
21062 would be directed to @file{log}.
21064 Since commands stored on command files tend to be more general than
21065 commands typed interactively, they frequently need to deal with
21066 complicated situations, such as different or unexpected values of
21067 variables and symbols, changes in how the program being debugged is
21068 built, etc. @value{GDBN} provides a set of flow-control commands to
21069 deal with these complexities. Using these commands, you can write
21070 complex scripts that loop over data structures, execute commands
21071 conditionally, etc.
21078 This command allows to include in your script conditionally executed
21079 commands. The @code{if} command takes a single argument, which is an
21080 expression to evaluate. It is followed by a series of commands that
21081 are executed only if the expression is true (its value is nonzero).
21082 There can then optionally be an @code{else} line, followed by a series
21083 of commands that are only executed if the expression was false. The
21084 end of the list is marked by a line containing @code{end}.
21088 This command allows to write loops. Its syntax is similar to
21089 @code{if}: the command takes a single argument, which is an expression
21090 to evaluate, and must be followed by the commands to execute, one per
21091 line, terminated by an @code{end}. These commands are called the
21092 @dfn{body} of the loop. The commands in the body of @code{while} are
21093 executed repeatedly as long as the expression evaluates to true.
21097 This command exits the @code{while} loop in whose body it is included.
21098 Execution of the script continues after that @code{while}s @code{end}
21101 @kindex loop_continue
21102 @item loop_continue
21103 This command skips the execution of the rest of the body of commands
21104 in the @code{while} loop in whose body it is included. Execution
21105 branches to the beginning of the @code{while} loop, where it evaluates
21106 the controlling expression.
21108 @kindex end@r{ (if/else/while commands)}
21110 Terminate the block of commands that are the body of @code{if},
21111 @code{else}, or @code{while} flow-control commands.
21116 @subsection Commands for Controlled Output
21118 During the execution of a command file or a user-defined command, normal
21119 @value{GDBN} output is suppressed; the only output that appears is what is
21120 explicitly printed by the commands in the definition. This section
21121 describes three commands useful for generating exactly the output you
21126 @item echo @var{text}
21127 @c I do not consider backslash-space a standard C escape sequence
21128 @c because it is not in ANSI.
21129 Print @var{text}. Nonprinting characters can be included in
21130 @var{text} using C escape sequences, such as @samp{\n} to print a
21131 newline. @strong{No newline is printed unless you specify one.}
21132 In addition to the standard C escape sequences, a backslash followed
21133 by a space stands for a space. This is useful for displaying a
21134 string with spaces at the beginning or the end, since leading and
21135 trailing spaces are otherwise trimmed from all arguments.
21136 To print @samp{@w{ }and foo =@w{ }}, use the command
21137 @samp{echo \@w{ }and foo = \@w{ }}.
21139 A backslash at the end of @var{text} can be used, as in C, to continue
21140 the command onto subsequent lines. For example,
21143 echo This is some text\n\
21144 which is continued\n\
21145 onto several lines.\n
21148 produces the same output as
21151 echo This is some text\n
21152 echo which is continued\n
21153 echo onto several lines.\n
21157 @item output @var{expression}
21158 Print the value of @var{expression} and nothing but that value: no
21159 newlines, no @samp{$@var{nn} = }. The value is not entered in the
21160 value history either. @xref{Expressions, ,Expressions}, for more information
21163 @item output/@var{fmt} @var{expression}
21164 Print the value of @var{expression} in format @var{fmt}. You can use
21165 the same formats as for @code{print}. @xref{Output Formats,,Output
21166 Formats}, for more information.
21169 @item printf @var{template}, @var{expressions}@dots{}
21170 Print the values of one or more @var{expressions} under the control of
21171 the string @var{template}. To print several values, make
21172 @var{expressions} be a comma-separated list of individual expressions,
21173 which may be either numbers or pointers. Their values are printed as
21174 specified by @var{template}, exactly as a C program would do by
21175 executing the code below:
21178 printf (@var{template}, @var{expressions}@dots{});
21181 As in @code{C} @code{printf}, ordinary characters in @var{template}
21182 are printed verbatim, while @dfn{conversion specification} introduced
21183 by the @samp{%} character cause subsequent @var{expressions} to be
21184 evaluated, their values converted and formatted according to type and
21185 style information encoded in the conversion specifications, and then
21188 For example, you can print two values in hex like this:
21191 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
21194 @code{printf} supports all the standard @code{C} conversion
21195 specifications, including the flags and modifiers between the @samp{%}
21196 character and the conversion letter, with the following exceptions:
21200 The argument-ordering modifiers, such as @samp{2$}, are not supported.
21203 The modifier @samp{*} is not supported for specifying precision or
21207 The @samp{'} flag (for separation of digits into groups according to
21208 @code{LC_NUMERIC'}) is not supported.
21211 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
21215 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
21218 The conversion letters @samp{a} and @samp{A} are not supported.
21222 Note that the @samp{ll} type modifier is supported only if the
21223 underlying @code{C} implementation used to build @value{GDBN} supports
21224 the @code{long long int} type, and the @samp{L} type modifier is
21225 supported only if @code{long double} type is available.
21227 As in @code{C}, @code{printf} supports simple backslash-escape
21228 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
21229 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
21230 single character. Octal and hexadecimal escape sequences are not
21233 Additionally, @code{printf} supports conversion specifications for DFP
21234 (@dfn{Decimal Floating Point}) types using the following length modifiers
21235 together with a floating point specifier.
21240 @samp{H} for printing @code{Decimal32} types.
21243 @samp{D} for printing @code{Decimal64} types.
21246 @samp{DD} for printing @code{Decimal128} types.
21249 If the underlying @code{C} implementation used to build @value{GDBN} has
21250 support for the three length modifiers for DFP types, other modifiers
21251 such as width and precision will also be available for @value{GDBN} to use.
21253 In case there is no such @code{C} support, no additional modifiers will be
21254 available and the value will be printed in the standard way.
21256 Here's an example of printing DFP types using the above conversion letters:
21258 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
21262 @item eval @var{template}, @var{expressions}@dots{}
21263 Convert the values of one or more @var{expressions} under the control of
21264 the string @var{template} to a command line, and call it.
21269 @section Scripting @value{GDBN} using Python
21270 @cindex python scripting
21271 @cindex scripting with python
21273 You can script @value{GDBN} using the @uref{http://www.python.org/,
21274 Python programming language}. This feature is available only if
21275 @value{GDBN} was configured using @option{--with-python}.
21277 @cindex python directory
21278 Python scripts used by @value{GDBN} should be installed in
21279 @file{@var{data-directory}/python}, where @var{data-directory} is
21280 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
21281 This directory, known as the @dfn{python directory},
21282 is automatically added to the Python Search Path in order to allow
21283 the Python interpreter to locate all scripts installed at this location.
21285 Additionally, @value{GDBN} commands and convenience functions which
21286 are written in Python and are located in the
21287 @file{@var{data-directory}/python/gdb/command} or
21288 @file{@var{data-directory}/python/gdb/function} directories are
21289 automatically imported when @value{GDBN} starts.
21292 * Python Commands:: Accessing Python from @value{GDBN}.
21293 * Python API:: Accessing @value{GDBN} from Python.
21294 * Auto-loading:: Automatically loading Python code.
21295 * Python modules:: Python modules provided by @value{GDBN}.
21298 @node Python Commands
21299 @subsection Python Commands
21300 @cindex python commands
21301 @cindex commands to access python
21303 @value{GDBN} provides one command for accessing the Python interpreter,
21304 and one related setting:
21308 @item python @r{[}@var{code}@r{]}
21309 The @code{python} command can be used to evaluate Python code.
21311 If given an argument, the @code{python} command will evaluate the
21312 argument as a Python command. For example:
21315 (@value{GDBP}) python print 23
21319 If you do not provide an argument to @code{python}, it will act as a
21320 multi-line command, like @code{define}. In this case, the Python
21321 script is made up of subsequent command lines, given after the
21322 @code{python} command. This command list is terminated using a line
21323 containing @code{end}. For example:
21326 (@value{GDBP}) python
21328 End with a line saying just "end".
21334 @kindex maint set python print-stack
21335 @item maint set python print-stack
21336 This command is now deprecated. Instead use @code{set python
21339 @kindex set python print-stack
21340 @item set python print-stack
21341 By default, @value{GDBN} will not print a stack trace when an error
21342 occurs in a Python script. This can be controlled using @code{set
21343 python print-stack}: if @code{on}, then Python stack printing is
21344 enabled; if @code{off}, the default, then Python stack printing is
21348 It is also possible to execute a Python script from the @value{GDBN}
21352 @item source @file{script-name}
21353 The script name must end with @samp{.py} and @value{GDBN} must be configured
21354 to recognize the script language based on filename extension using
21355 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
21357 @item python execfile ("script-name")
21358 This method is based on the @code{execfile} Python built-in function,
21359 and thus is always available.
21363 @subsection Python API
21365 @cindex programming in python
21367 @cindex python stdout
21368 @cindex python pagination
21369 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
21370 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
21371 A Python program which outputs to one of these streams may have its
21372 output interrupted by the user (@pxref{Screen Size}). In this
21373 situation, a Python @code{KeyboardInterrupt} exception is thrown.
21376 * Basic Python:: Basic Python Functions.
21377 * Exception Handling:: How Python exceptions are translated.
21378 * Values From Inferior:: Python representation of values.
21379 * Types In Python:: Python representation of types.
21380 * Pretty Printing API:: Pretty-printing values.
21381 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
21382 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
21383 * Inferiors In Python:: Python representation of inferiors (processes)
21384 * Events In Python:: Listening for events from @value{GDBN}.
21385 * Threads In Python:: Accessing inferior threads from Python.
21386 * Commands In Python:: Implementing new commands in Python.
21387 * Parameters In Python:: Adding new @value{GDBN} parameters.
21388 * Functions In Python:: Writing new convenience functions.
21389 * Progspaces In Python:: Program spaces.
21390 * Objfiles In Python:: Object files.
21391 * Frames In Python:: Accessing inferior stack frames from Python.
21392 * Blocks In Python:: Accessing frame blocks from Python.
21393 * Symbols In Python:: Python representation of symbols.
21394 * Symbol Tables In Python:: Python representation of symbol tables.
21395 * Lazy Strings In Python:: Python representation of lazy strings.
21396 * Breakpoints In Python:: Manipulating breakpoints using Python.
21400 @subsubsection Basic Python
21402 @cindex python functions
21403 @cindex python module
21405 @value{GDBN} introduces a new Python module, named @code{gdb}. All
21406 methods and classes added by @value{GDBN} are placed in this module.
21407 @value{GDBN} automatically @code{import}s the @code{gdb} module for
21408 use in all scripts evaluated by the @code{python} command.
21410 @findex gdb.PYTHONDIR
21411 @defvar gdb.PYTHONDIR
21412 A string containing the python directory (@pxref{Python}).
21415 @findex gdb.execute
21416 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
21417 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
21418 If a GDB exception happens while @var{command} runs, it is
21419 translated as described in @ref{Exception Handling,,Exception Handling}.
21421 @var{from_tty} specifies whether @value{GDBN} ought to consider this
21422 command as having originated from the user invoking it interactively.
21423 It must be a boolean value. If omitted, it defaults to @code{False}.
21425 By default, any output produced by @var{command} is sent to
21426 @value{GDBN}'s standard output. If the @var{to_string} parameter is
21427 @code{True}, then output will be collected by @code{gdb.execute} and
21428 returned as a string. The default is @code{False}, in which case the
21429 return value is @code{None}. If @var{to_string} is @code{True}, the
21430 @value{GDBN} virtual terminal will be temporarily set to unlimited width
21431 and height, and its pagination will be disabled; @pxref{Screen Size}.
21434 @findex gdb.breakpoints
21435 @defun gdb.breakpoints ()
21436 Return a sequence holding all of @value{GDBN}'s breakpoints.
21437 @xref{Breakpoints In Python}, for more information.
21440 @findex gdb.parameter
21441 @defun gdb.parameter (parameter)
21442 Return the value of a @value{GDBN} parameter. @var{parameter} is a
21443 string naming the parameter to look up; @var{parameter} may contain
21444 spaces if the parameter has a multi-part name. For example,
21445 @samp{print object} is a valid parameter name.
21447 If the named parameter does not exist, this function throws a
21448 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
21449 parameter's value is converted to a Python value of the appropriate
21450 type, and returned.
21453 @findex gdb.history
21454 @defun gdb.history (number)
21455 Return a value from @value{GDBN}'s value history (@pxref{Value
21456 History}). @var{number} indicates which history element to return.
21457 If @var{number} is negative, then @value{GDBN} will take its absolute value
21458 and count backward from the last element (i.e., the most recent element) to
21459 find the value to return. If @var{number} is zero, then @value{GDBN} will
21460 return the most recent element. If the element specified by @var{number}
21461 doesn't exist in the value history, a @code{gdb.error} exception will be
21464 If no exception is raised, the return value is always an instance of
21465 @code{gdb.Value} (@pxref{Values From Inferior}).
21468 @findex gdb.parse_and_eval
21469 @defun gdb.parse_and_eval (expression)
21470 Parse @var{expression} as an expression in the current language,
21471 evaluate it, and return the result as a @code{gdb.Value}.
21472 @var{expression} must be a string.
21474 This function can be useful when implementing a new command
21475 (@pxref{Commands In Python}), as it provides a way to parse the
21476 command's argument as an expression. It is also useful simply to
21477 compute values, for example, it is the only way to get the value of a
21478 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
21481 @findex gdb.post_event
21482 @defun gdb.post_event (event)
21483 Put @var{event}, a callable object taking no arguments, into
21484 @value{GDBN}'s internal event queue. This callable will be invoked at
21485 some later point, during @value{GDBN}'s event processing. Events
21486 posted using @code{post_event} will be run in the order in which they
21487 were posted; however, there is no way to know when they will be
21488 processed relative to other events inside @value{GDBN}.
21490 @value{GDBN} is not thread-safe. If your Python program uses multiple
21491 threads, you must be careful to only call @value{GDBN}-specific
21492 functions in the main @value{GDBN} thread. @code{post_event} ensures
21496 (@value{GDBP}) python
21500 > def __init__(self, message):
21501 > self.message = message;
21502 > def __call__(self):
21503 > gdb.write(self.message)
21505 >class MyThread1 (threading.Thread):
21507 > gdb.post_event(Writer("Hello "))
21509 >class MyThread2 (threading.Thread):
21511 > gdb.post_event(Writer("World\n"))
21513 >MyThread1().start()
21514 >MyThread2().start()
21516 (@value{GDBP}) Hello World
21521 @defun gdb.write (string @r{[}, stream{]})
21522 Print a string to @value{GDBN}'s paginated output stream. The
21523 optional @var{stream} determines the stream to print to. The default
21524 stream is @value{GDBN}'s standard output stream. Possible stream
21531 @value{GDBN}'s standard output stream.
21536 @value{GDBN}'s standard error stream.
21541 @value{GDBN}'s log stream (@pxref{Logging Output}).
21544 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
21545 call this function and will automatically direct the output to the
21550 @defun gdb.flush ()
21551 Flush the buffer of a @value{GDBN} paginated stream so that the
21552 contents are displayed immediately. @value{GDBN} will flush the
21553 contents of a stream automatically when it encounters a newline in the
21554 buffer. The optional @var{stream} determines the stream to flush. The
21555 default stream is @value{GDBN}'s standard output stream. Possible
21562 @value{GDBN}'s standard output stream.
21567 @value{GDBN}'s standard error stream.
21572 @value{GDBN}'s log stream (@pxref{Logging Output}).
21576 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
21577 call this function for the relevant stream.
21580 @findex gdb.target_charset
21581 @defun gdb.target_charset ()
21582 Return the name of the current target character set (@pxref{Character
21583 Sets}). This differs from @code{gdb.parameter('target-charset')} in
21584 that @samp{auto} is never returned.
21587 @findex gdb.target_wide_charset
21588 @defun gdb.target_wide_charset ()
21589 Return the name of the current target wide character set
21590 (@pxref{Character Sets}). This differs from
21591 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
21595 @findex gdb.solib_name
21596 @defun gdb.solib_name (address)
21597 Return the name of the shared library holding the given @var{address}
21598 as a string, or @code{None}.
21601 @findex gdb.decode_line
21602 @defun gdb.decode_line @r{[}expression@r{]}
21603 Return locations of the line specified by @var{expression}, or of the
21604 current line if no argument was given. This function returns a Python
21605 tuple containing two elements. The first element contains a string
21606 holding any unparsed section of @var{expression} (or @code{None} if
21607 the expression has been fully parsed). The second element contains
21608 either @code{None} or another tuple that contains all the locations
21609 that match the expression represented as @code{gdb.Symtab_and_line}
21610 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
21611 provided, it is decoded the way that @value{GDBN}'s inbuilt
21612 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
21615 @defun gdb.prompt_hook (current_prompt)
21616 @anchor{prompt_hook}
21618 If @var{prompt_hook} is callable, @value{GDBN} will call the method
21619 assigned to this operation before a prompt is displayed by
21622 The parameter @code{current_prompt} contains the current @value{GDBN}
21623 prompt. This method must return a Python string, or @code{None}. If
21624 a string is returned, the @value{GDBN} prompt will be set to that
21625 string. If @code{None} is returned, @value{GDBN} will continue to use
21626 the current prompt.
21628 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
21629 such as those used by readline for command input, and annotation
21630 related prompts are prohibited from being changed.
21633 @node Exception Handling
21634 @subsubsection Exception Handling
21635 @cindex python exceptions
21636 @cindex exceptions, python
21638 When executing the @code{python} command, Python exceptions
21639 uncaught within the Python code are translated to calls to
21640 @value{GDBN} error-reporting mechanism. If the command that called
21641 @code{python} does not handle the error, @value{GDBN} will
21642 terminate it and print an error message containing the Python
21643 exception name, the associated value, and the Python call stack
21644 backtrace at the point where the exception was raised. Example:
21647 (@value{GDBP}) python print foo
21648 Traceback (most recent call last):
21649 File "<string>", line 1, in <module>
21650 NameError: name 'foo' is not defined
21653 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
21654 Python code are converted to Python exceptions. The type of the
21655 Python exception depends on the error.
21659 This is the base class for most exceptions generated by @value{GDBN}.
21660 It is derived from @code{RuntimeError}, for compatibility with earlier
21661 versions of @value{GDBN}.
21663 If an error occurring in @value{GDBN} does not fit into some more
21664 specific category, then the generated exception will have this type.
21666 @item gdb.MemoryError
21667 This is a subclass of @code{gdb.error} which is thrown when an
21668 operation tried to access invalid memory in the inferior.
21670 @item KeyboardInterrupt
21671 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
21672 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
21675 In all cases, your exception handler will see the @value{GDBN} error
21676 message as its value and the Python call stack backtrace at the Python
21677 statement closest to where the @value{GDBN} error occured as the
21680 @findex gdb.GdbError
21681 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
21682 it is useful to be able to throw an exception that doesn't cause a
21683 traceback to be printed. For example, the user may have invoked the
21684 command incorrectly. Use the @code{gdb.GdbError} exception
21685 to handle this case. Example:
21689 >class HelloWorld (gdb.Command):
21690 > """Greet the whole world."""
21691 > def __init__ (self):
21692 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
21693 > def invoke (self, args, from_tty):
21694 > argv = gdb.string_to_argv (args)
21695 > if len (argv) != 0:
21696 > raise gdb.GdbError ("hello-world takes no arguments")
21697 > print "Hello, World!"
21700 (gdb) hello-world 42
21701 hello-world takes no arguments
21704 @node Values From Inferior
21705 @subsubsection Values From Inferior
21706 @cindex values from inferior, with Python
21707 @cindex python, working with values from inferior
21709 @cindex @code{gdb.Value}
21710 @value{GDBN} provides values it obtains from the inferior program in
21711 an object of type @code{gdb.Value}. @value{GDBN} uses this object
21712 for its internal bookkeeping of the inferior's values, and for
21713 fetching values when necessary.
21715 Inferior values that are simple scalars can be used directly in
21716 Python expressions that are valid for the value's data type. Here's
21717 an example for an integer or floating-point value @code{some_val}:
21724 As result of this, @code{bar} will also be a @code{gdb.Value} object
21725 whose values are of the same type as those of @code{some_val}.
21727 Inferior values that are structures or instances of some class can
21728 be accessed using the Python @dfn{dictionary syntax}. For example, if
21729 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
21730 can access its @code{foo} element with:
21733 bar = some_val['foo']
21736 Again, @code{bar} will also be a @code{gdb.Value} object.
21738 A @code{gdb.Value} that represents a function can be executed via
21739 inferior function call. Any arguments provided to the call must match
21740 the function's prototype, and must be provided in the order specified
21743 For example, @code{some_val} is a @code{gdb.Value} instance
21744 representing a function that takes two integers as arguments. To
21745 execute this function, call it like so:
21748 result = some_val (10,20)
21751 Any values returned from a function call will be stored as a
21754 The following attributes are provided:
21757 @defvar Value.address
21758 If this object is addressable, this read-only attribute holds a
21759 @code{gdb.Value} object representing the address. Otherwise,
21760 this attribute holds @code{None}.
21763 @cindex optimized out value in Python
21764 @defvar Value.is_optimized_out
21765 This read-only boolean attribute is true if the compiler optimized out
21766 this value, thus it is not available for fetching from the inferior.
21770 The type of this @code{gdb.Value}. The value of this attribute is a
21771 @code{gdb.Type} object (@pxref{Types In Python}).
21774 @defvar Value.dynamic_type
21775 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
21776 type information (@acronym{RTTI}) to determine the dynamic type of the
21777 value. If this value is of class type, it will return the class in
21778 which the value is embedded, if any. If this value is of pointer or
21779 reference to a class type, it will compute the dynamic type of the
21780 referenced object, and return a pointer or reference to that type,
21781 respectively. In all other cases, it will return the value's static
21784 Note that this feature will only work when debugging a C@t{++} program
21785 that includes @acronym{RTTI} for the object in question. Otherwise,
21786 it will just return the static type of the value as in @kbd{ptype foo}
21787 (@pxref{Symbols, ptype}).
21790 @defvar Value.is_lazy
21791 The value of this read-only boolean attribute is @code{True} if this
21792 @code{gdb.Value} has not yet been fetched from the inferior.
21793 @value{GDBN} does not fetch values until necessary, for efficiency.
21797 myval = gdb.parse_and_eval ('somevar')
21800 The value of @code{somevar} is not fetched at this time. It will be
21801 fetched when the value is needed, or when the @code{fetch_lazy}
21806 The following methods are provided:
21809 @defun Value.__init__ (@var{val})
21810 Many Python values can be converted directly to a @code{gdb.Value} via
21811 this object initializer. Specifically:
21814 @item Python boolean
21815 A Python boolean is converted to the boolean type from the current
21818 @item Python integer
21819 A Python integer is converted to the C @code{long} type for the
21820 current architecture.
21823 A Python long is converted to the C @code{long long} type for the
21824 current architecture.
21827 A Python float is converted to the C @code{double} type for the
21828 current architecture.
21830 @item Python string
21831 A Python string is converted to a target string, using the current
21834 @item @code{gdb.Value}
21835 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
21837 @item @code{gdb.LazyString}
21838 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
21839 Python}), then the lazy string's @code{value} method is called, and
21840 its result is used.
21844 @defun Value.cast (type)
21845 Return a new instance of @code{gdb.Value} that is the result of
21846 casting this instance to the type described by @var{type}, which must
21847 be a @code{gdb.Type} object. If the cast cannot be performed for some
21848 reason, this method throws an exception.
21851 @defun Value.dereference ()
21852 For pointer data types, this method returns a new @code{gdb.Value} object
21853 whose contents is the object pointed to by the pointer. For example, if
21854 @code{foo} is a C pointer to an @code{int}, declared in your C program as
21861 then you can use the corresponding @code{gdb.Value} to access what
21862 @code{foo} points to like this:
21865 bar = foo.dereference ()
21868 The result @code{bar} will be a @code{gdb.Value} object holding the
21869 value pointed to by @code{foo}.
21872 @defun Value.dynamic_cast (type)
21873 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
21874 operator were used. Consult a C@t{++} reference for details.
21877 @defun Value.reinterpret_cast (type)
21878 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
21879 operator were used. Consult a C@t{++} reference for details.
21882 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
21883 If this @code{gdb.Value} represents a string, then this method
21884 converts the contents to a Python string. Otherwise, this method will
21885 throw an exception.
21887 Strings are recognized in a language-specific way; whether a given
21888 @code{gdb.Value} represents a string is determined by the current
21891 For C-like languages, a value is a string if it is a pointer to or an
21892 array of characters or ints. The string is assumed to be terminated
21893 by a zero of the appropriate width. However if the optional length
21894 argument is given, the string will be converted to that given length,
21895 ignoring any embedded zeros that the string may contain.
21897 If the optional @var{encoding} argument is given, it must be a string
21898 naming the encoding of the string in the @code{gdb.Value}, such as
21899 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
21900 the same encodings as the corresponding argument to Python's
21901 @code{string.decode} method, and the Python codec machinery will be used
21902 to convert the string. If @var{encoding} is not given, or if
21903 @var{encoding} is the empty string, then either the @code{target-charset}
21904 (@pxref{Character Sets}) will be used, or a language-specific encoding
21905 will be used, if the current language is able to supply one.
21907 The optional @var{errors} argument is the same as the corresponding
21908 argument to Python's @code{string.decode} method.
21910 If the optional @var{length} argument is given, the string will be
21911 fetched and converted to the given length.
21914 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
21915 If this @code{gdb.Value} represents a string, then this method
21916 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
21917 In Python}). Otherwise, this method will throw an exception.
21919 If the optional @var{encoding} argument is given, it must be a string
21920 naming the encoding of the @code{gdb.LazyString}. Some examples are:
21921 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
21922 @var{encoding} argument is an encoding that @value{GDBN} does
21923 recognize, @value{GDBN} will raise an error.
21925 When a lazy string is printed, the @value{GDBN} encoding machinery is
21926 used to convert the string during printing. If the optional
21927 @var{encoding} argument is not provided, or is an empty string,
21928 @value{GDBN} will automatically select the encoding most suitable for
21929 the string type. For further information on encoding in @value{GDBN}
21930 please see @ref{Character Sets}.
21932 If the optional @var{length} argument is given, the string will be
21933 fetched and encoded to the length of characters specified. If
21934 the @var{length} argument is not provided, the string will be fetched
21935 and encoded until a null of appropriate width is found.
21938 @defun Value.fetch_lazy ()
21939 If the @code{gdb.Value} object is currently a lazy value
21940 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
21941 fetched from the inferior. Any errors that occur in the process
21942 will produce a Python exception.
21944 If the @code{gdb.Value} object is not a lazy value, this method
21947 This method does not return a value.
21952 @node Types In Python
21953 @subsubsection Types In Python
21954 @cindex types in Python
21955 @cindex Python, working with types
21958 @value{GDBN} represents types from the inferior using the class
21961 The following type-related functions are available in the @code{gdb}
21964 @findex gdb.lookup_type
21965 @defun gdb.lookup_type (name @r{[}, block@r{]})
21966 This function looks up a type by name. @var{name} is the name of the
21967 type to look up. It must be a string.
21969 If @var{block} is given, then @var{name} is looked up in that scope.
21970 Otherwise, it is searched for globally.
21972 Ordinarily, this function will return an instance of @code{gdb.Type}.
21973 If the named type cannot be found, it will throw an exception.
21976 If the type is a structure or class type, or an enum type, the fields
21977 of that type can be accessed using the Python @dfn{dictionary syntax}.
21978 For example, if @code{some_type} is a @code{gdb.Type} instance holding
21979 a structure type, you can access its @code{foo} field with:
21982 bar = some_type['foo']
21985 @code{bar} will be a @code{gdb.Field} object; see below under the
21986 description of the @code{Type.fields} method for a description of the
21987 @code{gdb.Field} class.
21989 An instance of @code{Type} has the following attributes:
21993 The type code for this type. The type code will be one of the
21994 @code{TYPE_CODE_} constants defined below.
21997 @defvar Type.sizeof
21998 The size of this type, in target @code{char} units. Usually, a
21999 target's @code{char} type will be an 8-bit byte. However, on some
22000 unusual platforms, this type may have a different size.
22004 The tag name for this type. The tag name is the name after
22005 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
22006 languages have this concept. If this type has no tag name, then
22007 @code{None} is returned.
22011 The following methods are provided:
22014 @defun Type.fields ()
22015 For structure and union types, this method returns the fields. Range
22016 types have two fields, the minimum and maximum values. Enum types
22017 have one field per enum constant. Function and method types have one
22018 field per parameter. The base types of C@t{++} classes are also
22019 represented as fields. If the type has no fields, or does not fit
22020 into one of these categories, an empty sequence will be returned.
22022 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
22025 This attribute is not available for @code{static} fields (as in
22026 C@t{++} or Java). For non-@code{static} fields, the value is the bit
22027 position of the field. For @code{enum} fields, the value is the
22028 enumeration member's integer representation.
22031 The name of the field, or @code{None} for anonymous fields.
22034 This is @code{True} if the field is artificial, usually meaning that
22035 it was provided by the compiler and not the user. This attribute is
22036 always provided, and is @code{False} if the field is not artificial.
22038 @item is_base_class
22039 This is @code{True} if the field represents a base class of a C@t{++}
22040 structure. This attribute is always provided, and is @code{False}
22041 if the field is not a base class of the type that is the argument of
22042 @code{fields}, or if that type was not a C@t{++} class.
22045 If the field is packed, or is a bitfield, then this will have a
22046 non-zero value, which is the size of the field in bits. Otherwise,
22047 this will be zero; in this case the field's size is given by its type.
22050 The type of the field. This is usually an instance of @code{Type},
22051 but it can be @code{None} in some situations.
22055 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
22056 Return a new @code{gdb.Type} object which represents an array of this
22057 type. If one argument is given, it is the inclusive upper bound of
22058 the array; in this case the lower bound is zero. If two arguments are
22059 given, the first argument is the lower bound of the array, and the
22060 second argument is the upper bound of the array. An array's length
22061 must not be negative, but the bounds can be.
22064 @defun Type.const ()
22065 Return a new @code{gdb.Type} object which represents a
22066 @code{const}-qualified variant of this type.
22069 @defun Type.volatile ()
22070 Return a new @code{gdb.Type} object which represents a
22071 @code{volatile}-qualified variant of this type.
22074 @defun Type.unqualified ()
22075 Return a new @code{gdb.Type} object which represents an unqualified
22076 variant of this type. That is, the result is neither @code{const} nor
22080 @defun Type.range ()
22081 Return a Python @code{Tuple} object that contains two elements: the
22082 low bound of the argument type and the high bound of that type. If
22083 the type does not have a range, @value{GDBN} will raise a
22084 @code{gdb.error} exception (@pxref{Exception Handling}).
22087 @defun Type.reference ()
22088 Return a new @code{gdb.Type} object which represents a reference to this
22092 @defun Type.pointer ()
22093 Return a new @code{gdb.Type} object which represents a pointer to this
22097 @defun Type.strip_typedefs ()
22098 Return a new @code{gdb.Type} that represents the real type,
22099 after removing all layers of typedefs.
22102 @defun Type.target ()
22103 Return a new @code{gdb.Type} object which represents the target type
22106 For a pointer type, the target type is the type of the pointed-to
22107 object. For an array type (meaning C-like arrays), the target type is
22108 the type of the elements of the array. For a function or method type,
22109 the target type is the type of the return value. For a complex type,
22110 the target type is the type of the elements. For a typedef, the
22111 target type is the aliased type.
22113 If the type does not have a target, this method will throw an
22117 @defun Type.template_argument (n @r{[}, block@r{]})
22118 If this @code{gdb.Type} is an instantiation of a template, this will
22119 return a new @code{gdb.Type} which represents the type of the
22120 @var{n}th template argument.
22122 If this @code{gdb.Type} is not a template type, this will throw an
22123 exception. Ordinarily, only C@t{++} code will have template types.
22125 If @var{block} is given, then @var{name} is looked up in that scope.
22126 Otherwise, it is searched for globally.
22131 Each type has a code, which indicates what category this type falls
22132 into. The available type categories are represented by constants
22133 defined in the @code{gdb} module:
22136 @findex TYPE_CODE_PTR
22137 @findex gdb.TYPE_CODE_PTR
22138 @item gdb.TYPE_CODE_PTR
22139 The type is a pointer.
22141 @findex TYPE_CODE_ARRAY
22142 @findex gdb.TYPE_CODE_ARRAY
22143 @item gdb.TYPE_CODE_ARRAY
22144 The type is an array.
22146 @findex TYPE_CODE_STRUCT
22147 @findex gdb.TYPE_CODE_STRUCT
22148 @item gdb.TYPE_CODE_STRUCT
22149 The type is a structure.
22151 @findex TYPE_CODE_UNION
22152 @findex gdb.TYPE_CODE_UNION
22153 @item gdb.TYPE_CODE_UNION
22154 The type is a union.
22156 @findex TYPE_CODE_ENUM
22157 @findex gdb.TYPE_CODE_ENUM
22158 @item gdb.TYPE_CODE_ENUM
22159 The type is an enum.
22161 @findex TYPE_CODE_FLAGS
22162 @findex gdb.TYPE_CODE_FLAGS
22163 @item gdb.TYPE_CODE_FLAGS
22164 A bit flags type, used for things such as status registers.
22166 @findex TYPE_CODE_FUNC
22167 @findex gdb.TYPE_CODE_FUNC
22168 @item gdb.TYPE_CODE_FUNC
22169 The type is a function.
22171 @findex TYPE_CODE_INT
22172 @findex gdb.TYPE_CODE_INT
22173 @item gdb.TYPE_CODE_INT
22174 The type is an integer type.
22176 @findex TYPE_CODE_FLT
22177 @findex gdb.TYPE_CODE_FLT
22178 @item gdb.TYPE_CODE_FLT
22179 A floating point type.
22181 @findex TYPE_CODE_VOID
22182 @findex gdb.TYPE_CODE_VOID
22183 @item gdb.TYPE_CODE_VOID
22184 The special type @code{void}.
22186 @findex TYPE_CODE_SET
22187 @findex gdb.TYPE_CODE_SET
22188 @item gdb.TYPE_CODE_SET
22191 @findex TYPE_CODE_RANGE
22192 @findex gdb.TYPE_CODE_RANGE
22193 @item gdb.TYPE_CODE_RANGE
22194 A range type, that is, an integer type with bounds.
22196 @findex TYPE_CODE_STRING
22197 @findex gdb.TYPE_CODE_STRING
22198 @item gdb.TYPE_CODE_STRING
22199 A string type. Note that this is only used for certain languages with
22200 language-defined string types; C strings are not represented this way.
22202 @findex TYPE_CODE_BITSTRING
22203 @findex gdb.TYPE_CODE_BITSTRING
22204 @item gdb.TYPE_CODE_BITSTRING
22207 @findex TYPE_CODE_ERROR
22208 @findex gdb.TYPE_CODE_ERROR
22209 @item gdb.TYPE_CODE_ERROR
22210 An unknown or erroneous type.
22212 @findex TYPE_CODE_METHOD
22213 @findex gdb.TYPE_CODE_METHOD
22214 @item gdb.TYPE_CODE_METHOD
22215 A method type, as found in C@t{++} or Java.
22217 @findex TYPE_CODE_METHODPTR
22218 @findex gdb.TYPE_CODE_METHODPTR
22219 @item gdb.TYPE_CODE_METHODPTR
22220 A pointer-to-member-function.
22222 @findex TYPE_CODE_MEMBERPTR
22223 @findex gdb.TYPE_CODE_MEMBERPTR
22224 @item gdb.TYPE_CODE_MEMBERPTR
22225 A pointer-to-member.
22227 @findex TYPE_CODE_REF
22228 @findex gdb.TYPE_CODE_REF
22229 @item gdb.TYPE_CODE_REF
22232 @findex TYPE_CODE_CHAR
22233 @findex gdb.TYPE_CODE_CHAR
22234 @item gdb.TYPE_CODE_CHAR
22237 @findex TYPE_CODE_BOOL
22238 @findex gdb.TYPE_CODE_BOOL
22239 @item gdb.TYPE_CODE_BOOL
22242 @findex TYPE_CODE_COMPLEX
22243 @findex gdb.TYPE_CODE_COMPLEX
22244 @item gdb.TYPE_CODE_COMPLEX
22245 A complex float type.
22247 @findex TYPE_CODE_TYPEDEF
22248 @findex gdb.TYPE_CODE_TYPEDEF
22249 @item gdb.TYPE_CODE_TYPEDEF
22250 A typedef to some other type.
22252 @findex TYPE_CODE_NAMESPACE
22253 @findex gdb.TYPE_CODE_NAMESPACE
22254 @item gdb.TYPE_CODE_NAMESPACE
22255 A C@t{++} namespace.
22257 @findex TYPE_CODE_DECFLOAT
22258 @findex gdb.TYPE_CODE_DECFLOAT
22259 @item gdb.TYPE_CODE_DECFLOAT
22260 A decimal floating point type.
22262 @findex TYPE_CODE_INTERNAL_FUNCTION
22263 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
22264 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
22265 A function internal to @value{GDBN}. This is the type used to represent
22266 convenience functions.
22269 Further support for types is provided in the @code{gdb.types}
22270 Python module (@pxref{gdb.types}).
22272 @node Pretty Printing API
22273 @subsubsection Pretty Printing API
22275 An example output is provided (@pxref{Pretty Printing}).
22277 A pretty-printer is just an object that holds a value and implements a
22278 specific interface, defined here.
22280 @defun pretty_printer.children (self)
22281 @value{GDBN} will call this method on a pretty-printer to compute the
22282 children of the pretty-printer's value.
22284 This method must return an object conforming to the Python iterator
22285 protocol. Each item returned by the iterator must be a tuple holding
22286 two elements. The first element is the ``name'' of the child; the
22287 second element is the child's value. The value can be any Python
22288 object which is convertible to a @value{GDBN} value.
22290 This method is optional. If it does not exist, @value{GDBN} will act
22291 as though the value has no children.
22294 @defun pretty_printer.display_hint (self)
22295 The CLI may call this method and use its result to change the
22296 formatting of a value. The result will also be supplied to an MI
22297 consumer as a @samp{displayhint} attribute of the variable being
22300 This method is optional. If it does exist, this method must return a
22303 Some display hints are predefined by @value{GDBN}:
22307 Indicate that the object being printed is ``array-like''. The CLI
22308 uses this to respect parameters such as @code{set print elements} and
22309 @code{set print array}.
22312 Indicate that the object being printed is ``map-like'', and that the
22313 children of this value can be assumed to alternate between keys and
22317 Indicate that the object being printed is ``string-like''. If the
22318 printer's @code{to_string} method returns a Python string of some
22319 kind, then @value{GDBN} will call its internal language-specific
22320 string-printing function to format the string. For the CLI this means
22321 adding quotation marks, possibly escaping some characters, respecting
22322 @code{set print elements}, and the like.
22326 @defun pretty_printer.to_string (self)
22327 @value{GDBN} will call this method to display the string
22328 representation of the value passed to the object's constructor.
22330 When printing from the CLI, if the @code{to_string} method exists,
22331 then @value{GDBN} will prepend its result to the values returned by
22332 @code{children}. Exactly how this formatting is done is dependent on
22333 the display hint, and may change as more hints are added. Also,
22334 depending on the print settings (@pxref{Print Settings}), the CLI may
22335 print just the result of @code{to_string} in a stack trace, omitting
22336 the result of @code{children}.
22338 If this method returns a string, it is printed verbatim.
22340 Otherwise, if this method returns an instance of @code{gdb.Value},
22341 then @value{GDBN} prints this value. This may result in a call to
22342 another pretty-printer.
22344 If instead the method returns a Python value which is convertible to a
22345 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
22346 the resulting value. Again, this may result in a call to another
22347 pretty-printer. Python scalars (integers, floats, and booleans) and
22348 strings are convertible to @code{gdb.Value}; other types are not.
22350 Finally, if this method returns @code{None} then no further operations
22351 are peformed in this method and nothing is printed.
22353 If the result is not one of these types, an exception is raised.
22356 @value{GDBN} provides a function which can be used to look up the
22357 default pretty-printer for a @code{gdb.Value}:
22359 @findex gdb.default_visualizer
22360 @defun gdb.default_visualizer (value)
22361 This function takes a @code{gdb.Value} object as an argument. If a
22362 pretty-printer for this value exists, then it is returned. If no such
22363 printer exists, then this returns @code{None}.
22366 @node Selecting Pretty-Printers
22367 @subsubsection Selecting Pretty-Printers
22369 The Python list @code{gdb.pretty_printers} contains an array of
22370 functions or callable objects that have been registered via addition
22371 as a pretty-printer. Printers in this list are called @code{global}
22372 printers, they're available when debugging all inferiors.
22373 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
22374 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
22377 Each function on these lists is passed a single @code{gdb.Value}
22378 argument and should return a pretty-printer object conforming to the
22379 interface definition above (@pxref{Pretty Printing API}). If a function
22380 cannot create a pretty-printer for the value, it should return
22383 @value{GDBN} first checks the @code{pretty_printers} attribute of each
22384 @code{gdb.Objfile} in the current program space and iteratively calls
22385 each enabled lookup routine in the list for that @code{gdb.Objfile}
22386 until it receives a pretty-printer object.
22387 If no pretty-printer is found in the objfile lists, @value{GDBN} then
22388 searches the pretty-printer list of the current program space,
22389 calling each enabled function until an object is returned.
22390 After these lists have been exhausted, it tries the global
22391 @code{gdb.pretty_printers} list, again calling each enabled function until an
22392 object is returned.
22394 The order in which the objfiles are searched is not specified. For a
22395 given list, functions are always invoked from the head of the list,
22396 and iterated over sequentially until the end of the list, or a printer
22397 object is returned.
22399 For various reasons a pretty-printer may not work.
22400 For example, the underlying data structure may have changed and
22401 the pretty-printer is out of date.
22403 The consequences of a broken pretty-printer are severe enough that
22404 @value{GDBN} provides support for enabling and disabling individual
22405 printers. For example, if @code{print frame-arguments} is on,
22406 a backtrace can become highly illegible if any argument is printed
22407 with a broken printer.
22409 Pretty-printers are enabled and disabled by attaching an @code{enabled}
22410 attribute to the registered function or callable object. If this attribute
22411 is present and its value is @code{False}, the printer is disabled, otherwise
22412 the printer is enabled.
22414 @node Writing a Pretty-Printer
22415 @subsubsection Writing a Pretty-Printer
22416 @cindex writing a pretty-printer
22418 A pretty-printer consists of two parts: a lookup function to detect
22419 if the type is supported, and the printer itself.
22421 Here is an example showing how a @code{std::string} printer might be
22422 written. @xref{Pretty Printing API}, for details on the API this class
22426 class StdStringPrinter(object):
22427 "Print a std::string"
22429 def __init__(self, val):
22432 def to_string(self):
22433 return self.val['_M_dataplus']['_M_p']
22435 def display_hint(self):
22439 And here is an example showing how a lookup function for the printer
22440 example above might be written.
22443 def str_lookup_function(val):
22444 lookup_tag = val.type.tag
22445 if lookup_tag == None:
22447 regex = re.compile("^std::basic_string<char,.*>$")
22448 if regex.match(lookup_tag):
22449 return StdStringPrinter(val)
22453 The example lookup function extracts the value's type, and attempts to
22454 match it to a type that it can pretty-print. If it is a type the
22455 printer can pretty-print, it will return a printer object. If not, it
22456 returns @code{None}.
22458 We recommend that you put your core pretty-printers into a Python
22459 package. If your pretty-printers are for use with a library, we
22460 further recommend embedding a version number into the package name.
22461 This practice will enable @value{GDBN} to load multiple versions of
22462 your pretty-printers at the same time, because they will have
22465 You should write auto-loaded code (@pxref{Auto-loading}) such that it
22466 can be evaluated multiple times without changing its meaning. An
22467 ideal auto-load file will consist solely of @code{import}s of your
22468 printer modules, followed by a call to a register pretty-printers with
22469 the current objfile.
22471 Taken as a whole, this approach will scale nicely to multiple
22472 inferiors, each potentially using a different library version.
22473 Embedding a version number in the Python package name will ensure that
22474 @value{GDBN} is able to load both sets of printers simultaneously.
22475 Then, because the search for pretty-printers is done by objfile, and
22476 because your auto-loaded code took care to register your library's
22477 printers with a specific objfile, @value{GDBN} will find the correct
22478 printers for the specific version of the library used by each
22481 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
22482 this code might appear in @code{gdb.libstdcxx.v6}:
22485 def register_printers(objfile):
22486 objfile.pretty_printers.add(str_lookup_function)
22490 And then the corresponding contents of the auto-load file would be:
22493 import gdb.libstdcxx.v6
22494 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
22497 The previous example illustrates a basic pretty-printer.
22498 There are a few things that can be improved on.
22499 The printer doesn't have a name, making it hard to identify in a
22500 list of installed printers. The lookup function has a name, but
22501 lookup functions can have arbitrary, even identical, names.
22503 Second, the printer only handles one type, whereas a library typically has
22504 several types. One could install a lookup function for each desired type
22505 in the library, but one could also have a single lookup function recognize
22506 several types. The latter is the conventional way this is handled.
22507 If a pretty-printer can handle multiple data types, then its
22508 @dfn{subprinters} are the printers for the individual data types.
22510 The @code{gdb.printing} module provides a formal way of solving these
22511 problems (@pxref{gdb.printing}).
22512 Here is another example that handles multiple types.
22514 These are the types we are going to pretty-print:
22517 struct foo @{ int a, b; @};
22518 struct bar @{ struct foo x, y; @};
22521 Here are the printers:
22525 """Print a foo object."""
22527 def __init__(self, val):
22530 def to_string(self):
22531 return ("a=<" + str(self.val["a"]) +
22532 "> b=<" + str(self.val["b"]) + ">")
22535 """Print a bar object."""
22537 def __init__(self, val):
22540 def to_string(self):
22541 return ("x=<" + str(self.val["x"]) +
22542 "> y=<" + str(self.val["y"]) + ">")
22545 This example doesn't need a lookup function, that is handled by the
22546 @code{gdb.printing} module. Instead a function is provided to build up
22547 the object that handles the lookup.
22550 import gdb.printing
22552 def build_pretty_printer():
22553 pp = gdb.printing.RegexpCollectionPrettyPrinter(
22555 pp.add_printer('foo', '^foo$', fooPrinter)
22556 pp.add_printer('bar', '^bar$', barPrinter)
22560 And here is the autoload support:
22563 import gdb.printing
22565 gdb.printing.register_pretty_printer(
22566 gdb.current_objfile(),
22567 my_library.build_pretty_printer())
22570 Finally, when this printer is loaded into @value{GDBN}, here is the
22571 corresponding output of @samp{info pretty-printer}:
22574 (gdb) info pretty-printer
22581 @node Inferiors In Python
22582 @subsubsection Inferiors In Python
22583 @cindex inferiors in Python
22585 @findex gdb.Inferior
22586 Programs which are being run under @value{GDBN} are called inferiors
22587 (@pxref{Inferiors and Programs}). Python scripts can access
22588 information about and manipulate inferiors controlled by @value{GDBN}
22589 via objects of the @code{gdb.Inferior} class.
22591 The following inferior-related functions are available in the @code{gdb}
22594 @defun gdb.inferiors ()
22595 Return a tuple containing all inferior objects.
22598 @defun gdb.selected_inferior ()
22599 Return an object representing the current inferior.
22602 A @code{gdb.Inferior} object has the following attributes:
22605 @defvar Inferior.num
22606 ID of inferior, as assigned by GDB.
22609 @defvar Inferior.pid
22610 Process ID of the inferior, as assigned by the underlying operating
22614 @defvar Inferior.was_attached
22615 Boolean signaling whether the inferior was created using `attach', or
22616 started by @value{GDBN} itself.
22620 A @code{gdb.Inferior} object has the following methods:
22623 @defun Inferior.is_valid ()
22624 Returns @code{True} if the @code{gdb.Inferior} object is valid,
22625 @code{False} if not. A @code{gdb.Inferior} object will become invalid
22626 if the inferior no longer exists within @value{GDBN}. All other
22627 @code{gdb.Inferior} methods will throw an exception if it is invalid
22628 at the time the method is called.
22631 @defun Inferior.threads ()
22632 This method returns a tuple holding all the threads which are valid
22633 when it is called. If there are no valid threads, the method will
22634 return an empty tuple.
22637 @findex gdb.read_memory
22638 @defun Inferior.read_memory (address, length)
22639 Read @var{length} bytes of memory from the inferior, starting at
22640 @var{address}. Returns a buffer object, which behaves much like an array
22641 or a string. It can be modified and given to the @code{gdb.write_memory}
22645 @findex gdb.write_memory
22646 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
22647 Write the contents of @var{buffer} to the inferior, starting at
22648 @var{address}. The @var{buffer} parameter must be a Python object
22649 which supports the buffer protocol, i.e., a string, an array or the
22650 object returned from @code{gdb.read_memory}. If given, @var{length}
22651 determines the number of bytes from @var{buffer} to be written.
22654 @findex gdb.search_memory
22655 @defun Inferior.search_memory (address, length, pattern)
22656 Search a region of the inferior memory starting at @var{address} with
22657 the given @var{length} using the search pattern supplied in
22658 @var{pattern}. The @var{pattern} parameter must be a Python object
22659 which supports the buffer protocol, i.e., a string, an array or the
22660 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
22661 containing the address where the pattern was found, or @code{None} if
22662 the pattern could not be found.
22666 @node Events In Python
22667 @subsubsection Events In Python
22668 @cindex inferior events in Python
22670 @value{GDBN} provides a general event facility so that Python code can be
22671 notified of various state changes, particularly changes that occur in
22674 An @dfn{event} is just an object that describes some state change. The
22675 type of the object and its attributes will vary depending on the details
22676 of the change. All the existing events are described below.
22678 In order to be notified of an event, you must register an event handler
22679 with an @dfn{event registry}. An event registry is an object in the
22680 @code{gdb.events} module which dispatches particular events. A registry
22681 provides methods to register and unregister event handlers:
22684 @defun EventRegistry.connect (object)
22685 Add the given callable @var{object} to the registry. This object will be
22686 called when an event corresponding to this registry occurs.
22689 @defun EventRegistry.disconnect (object)
22690 Remove the given @var{object} from the registry. Once removed, the object
22691 will no longer receive notifications of events.
22695 Here is an example:
22698 def exit_handler (event):
22699 print "event type: exit"
22700 print "exit code: %d" % (event.exit_code)
22702 gdb.events.exited.connect (exit_handler)
22705 In the above example we connect our handler @code{exit_handler} to the
22706 registry @code{events.exited}. Once connected, @code{exit_handler} gets
22707 called when the inferior exits. The argument @dfn{event} in this example is
22708 of type @code{gdb.ExitedEvent}. As you can see in the example the
22709 @code{ExitedEvent} object has an attribute which indicates the exit code of
22712 The following is a listing of the event registries that are available and
22713 details of the events they emit:
22718 Emits @code{gdb.ThreadEvent}.
22720 Some events can be thread specific when @value{GDBN} is running in non-stop
22721 mode. When represented in Python, these events all extend
22722 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
22723 events which are emitted by this or other modules might extend this event.
22724 Examples of these events are @code{gdb.BreakpointEvent} and
22725 @code{gdb.ContinueEvent}.
22728 @defvar ThreadEvent.inferior_thread
22729 In non-stop mode this attribute will be set to the specific thread which was
22730 involved in the emitted event. Otherwise, it will be set to @code{None}.
22734 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
22736 This event indicates that the inferior has been continued after a stop. For
22737 inherited attribute refer to @code{gdb.ThreadEvent} above.
22739 @item events.exited
22740 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
22741 @code{events.ExitedEvent} has two attributes:
22743 @defvar ExitedEvent.exit_code
22744 An integer representing the exit code, if available, which the inferior
22745 has returned. (The exit code could be unavailable if, for example,
22746 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
22747 the attribute does not exist.
22749 @defvar ExitedEvent inferior
22750 A reference to the inferior which triggered the @code{exited} event.
22755 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
22757 Indicates that the inferior has stopped. All events emitted by this registry
22758 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
22759 will indicate the stopped thread when @value{GDBN} is running in non-stop
22760 mode. Refer to @code{gdb.ThreadEvent} above for more details.
22762 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
22764 This event indicates that the inferior or one of its threads has received as
22765 signal. @code{gdb.SignalEvent} has the following attributes:
22768 @defvar SignalEvent.stop_signal
22769 A string representing the signal received by the inferior. A list of possible
22770 signal values can be obtained by running the command @code{info signals} in
22771 the @value{GDBN} command prompt.
22775 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
22777 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
22778 been hit, and has the following attributes:
22781 @defvar BreakpointEvent.breakpoints
22782 A sequence containing references to all the breakpoints (type
22783 @code{gdb.Breakpoint}) that were hit.
22784 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
22786 @defvar BreakpointEvent.breakpoint
22787 A reference to the first breakpoint that was hit.
22788 This function is maintained for backward compatibility and is now deprecated
22789 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
22793 @item events.new_objfile
22794 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
22795 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
22798 @defvar NewObjFileEvent.new_objfile
22799 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
22800 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
22806 @node Threads In Python
22807 @subsubsection Threads In Python
22808 @cindex threads in python
22810 @findex gdb.InferiorThread
22811 Python scripts can access information about, and manipulate inferior threads
22812 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
22814 The following thread-related functions are available in the @code{gdb}
22817 @findex gdb.selected_thread
22818 @defun gdb.selected_thread ()
22819 This function returns the thread object for the selected thread. If there
22820 is no selected thread, this will return @code{None}.
22823 A @code{gdb.InferiorThread} object has the following attributes:
22826 @defvar InferiorThread.name
22827 The name of the thread. If the user specified a name using
22828 @code{thread name}, then this returns that name. Otherwise, if an
22829 OS-supplied name is available, then it is returned. Otherwise, this
22830 returns @code{None}.
22832 This attribute can be assigned to. The new value must be a string
22833 object, which sets the new name, or @code{None}, which removes any
22834 user-specified thread name.
22837 @defvar InferiorThread.num
22838 ID of the thread, as assigned by GDB.
22841 @defvar InferiorThread.ptid
22842 ID of the thread, as assigned by the operating system. This attribute is a
22843 tuple containing three integers. The first is the Process ID (PID); the second
22844 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
22845 Either the LWPID or TID may be 0, which indicates that the operating system
22846 does not use that identifier.
22850 A @code{gdb.InferiorThread} object has the following methods:
22853 @defun InferiorThread.is_valid ()
22854 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
22855 @code{False} if not. A @code{gdb.InferiorThread} object will become
22856 invalid if the thread exits, or the inferior that the thread belongs
22857 is deleted. All other @code{gdb.InferiorThread} methods will throw an
22858 exception if it is invalid at the time the method is called.
22861 @defun InferiorThread.switch ()
22862 This changes @value{GDBN}'s currently selected thread to the one represented
22866 @defun InferiorThread.is_stopped ()
22867 Return a Boolean indicating whether the thread is stopped.
22870 @defun InferiorThread.is_running ()
22871 Return a Boolean indicating whether the thread is running.
22874 @defun InferiorThread.is_exited ()
22875 Return a Boolean indicating whether the thread is exited.
22879 @node Commands In Python
22880 @subsubsection Commands In Python
22882 @cindex commands in python
22883 @cindex python commands
22884 You can implement new @value{GDBN} CLI commands in Python. A CLI
22885 command is implemented using an instance of the @code{gdb.Command}
22886 class, most commonly using a subclass.
22888 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
22889 The object initializer for @code{Command} registers the new command
22890 with @value{GDBN}. This initializer is normally invoked from the
22891 subclass' own @code{__init__} method.
22893 @var{name} is the name of the command. If @var{name} consists of
22894 multiple words, then the initial words are looked for as prefix
22895 commands. In this case, if one of the prefix commands does not exist,
22896 an exception is raised.
22898 There is no support for multi-line commands.
22900 @var{command_class} should be one of the @samp{COMMAND_} constants
22901 defined below. This argument tells @value{GDBN} how to categorize the
22902 new command in the help system.
22904 @var{completer_class} is an optional argument. If given, it should be
22905 one of the @samp{COMPLETE_} constants defined below. This argument
22906 tells @value{GDBN} how to perform completion for this command. If not
22907 given, @value{GDBN} will attempt to complete using the object's
22908 @code{complete} method (see below); if no such method is found, an
22909 error will occur when completion is attempted.
22911 @var{prefix} is an optional argument. If @code{True}, then the new
22912 command is a prefix command; sub-commands of this command may be
22915 The help text for the new command is taken from the Python
22916 documentation string for the command's class, if there is one. If no
22917 documentation string is provided, the default value ``This command is
22918 not documented.'' is used.
22921 @cindex don't repeat Python command
22922 @defun Command.dont_repeat ()
22923 By default, a @value{GDBN} command is repeated when the user enters a
22924 blank line at the command prompt. A command can suppress this
22925 behavior by invoking the @code{dont_repeat} method. This is similar
22926 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
22929 @defun Command.invoke (argument, from_tty)
22930 This method is called by @value{GDBN} when this command is invoked.
22932 @var{argument} is a string. It is the argument to the command, after
22933 leading and trailing whitespace has been stripped.
22935 @var{from_tty} is a boolean argument. When true, this means that the
22936 command was entered by the user at the terminal; when false it means
22937 that the command came from elsewhere.
22939 If this method throws an exception, it is turned into a @value{GDBN}
22940 @code{error} call. Otherwise, the return value is ignored.
22942 @findex gdb.string_to_argv
22943 To break @var{argument} up into an argv-like string use
22944 @code{gdb.string_to_argv}. This function behaves identically to
22945 @value{GDBN}'s internal argument lexer @code{buildargv}.
22946 It is recommended to use this for consistency.
22947 Arguments are separated by spaces and may be quoted.
22951 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
22952 ['1', '2 "3', '4 "5', "6 '7"]
22957 @cindex completion of Python commands
22958 @defun Command.complete (text, word)
22959 This method is called by @value{GDBN} when the user attempts
22960 completion on this command. All forms of completion are handled by
22961 this method, that is, the @key{TAB} and @key{M-?} key bindings
22962 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
22965 The arguments @var{text} and @var{word} are both strings. @var{text}
22966 holds the complete command line up to the cursor's location.
22967 @var{word} holds the last word of the command line; this is computed
22968 using a word-breaking heuristic.
22970 The @code{complete} method can return several values:
22973 If the return value is a sequence, the contents of the sequence are
22974 used as the completions. It is up to @code{complete} to ensure that the
22975 contents actually do complete the word. A zero-length sequence is
22976 allowed, it means that there were no completions available. Only
22977 string elements of the sequence are used; other elements in the
22978 sequence are ignored.
22981 If the return value is one of the @samp{COMPLETE_} constants defined
22982 below, then the corresponding @value{GDBN}-internal completion
22983 function is invoked, and its result is used.
22986 All other results are treated as though there were no available
22991 When a new command is registered, it must be declared as a member of
22992 some general class of commands. This is used to classify top-level
22993 commands in the on-line help system; note that prefix commands are not
22994 listed under their own category but rather that of their top-level
22995 command. The available classifications are represented by constants
22996 defined in the @code{gdb} module:
22999 @findex COMMAND_NONE
23000 @findex gdb.COMMAND_NONE
23001 @item gdb.COMMAND_NONE
23002 The command does not belong to any particular class. A command in
23003 this category will not be displayed in any of the help categories.
23005 @findex COMMAND_RUNNING
23006 @findex gdb.COMMAND_RUNNING
23007 @item gdb.COMMAND_RUNNING
23008 The command is related to running the inferior. For example,
23009 @code{start}, @code{step}, and @code{continue} are in this category.
23010 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
23011 commands in this category.
23013 @findex COMMAND_DATA
23014 @findex gdb.COMMAND_DATA
23015 @item gdb.COMMAND_DATA
23016 The command is related to data or variables. For example,
23017 @code{call}, @code{find}, and @code{print} are in this category. Type
23018 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
23021 @findex COMMAND_STACK
23022 @findex gdb.COMMAND_STACK
23023 @item gdb.COMMAND_STACK
23024 The command has to do with manipulation of the stack. For example,
23025 @code{backtrace}, @code{frame}, and @code{return} are in this
23026 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
23027 list of commands in this category.
23029 @findex COMMAND_FILES
23030 @findex gdb.COMMAND_FILES
23031 @item gdb.COMMAND_FILES
23032 This class is used for file-related commands. For example,
23033 @code{file}, @code{list} and @code{section} are in this category.
23034 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
23035 commands in this category.
23037 @findex COMMAND_SUPPORT
23038 @findex gdb.COMMAND_SUPPORT
23039 @item gdb.COMMAND_SUPPORT
23040 This should be used for ``support facilities'', generally meaning
23041 things that are useful to the user when interacting with @value{GDBN},
23042 but not related to the state of the inferior. For example,
23043 @code{help}, @code{make}, and @code{shell} are in this category. Type
23044 @kbd{help support} at the @value{GDBN} prompt to see a list of
23045 commands in this category.
23047 @findex COMMAND_STATUS
23048 @findex gdb.COMMAND_STATUS
23049 @item gdb.COMMAND_STATUS
23050 The command is an @samp{info}-related command, that is, related to the
23051 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
23052 and @code{show} are in this category. Type @kbd{help status} at the
23053 @value{GDBN} prompt to see a list of commands in this category.
23055 @findex COMMAND_BREAKPOINTS
23056 @findex gdb.COMMAND_BREAKPOINTS
23057 @item gdb.COMMAND_BREAKPOINTS
23058 The command has to do with breakpoints. For example, @code{break},
23059 @code{clear}, and @code{delete} are in this category. Type @kbd{help
23060 breakpoints} at the @value{GDBN} prompt to see a list of commands in
23063 @findex COMMAND_TRACEPOINTS
23064 @findex gdb.COMMAND_TRACEPOINTS
23065 @item gdb.COMMAND_TRACEPOINTS
23066 The command has to do with tracepoints. For example, @code{trace},
23067 @code{actions}, and @code{tfind} are in this category. Type
23068 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
23069 commands in this category.
23071 @findex COMMAND_OBSCURE
23072 @findex gdb.COMMAND_OBSCURE
23073 @item gdb.COMMAND_OBSCURE
23074 The command is only used in unusual circumstances, or is not of
23075 general interest to users. For example, @code{checkpoint},
23076 @code{fork}, and @code{stop} are in this category. Type @kbd{help
23077 obscure} at the @value{GDBN} prompt to see a list of commands in this
23080 @findex COMMAND_MAINTENANCE
23081 @findex gdb.COMMAND_MAINTENANCE
23082 @item gdb.COMMAND_MAINTENANCE
23083 The command is only useful to @value{GDBN} maintainers. The
23084 @code{maintenance} and @code{flushregs} commands are in this category.
23085 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
23086 commands in this category.
23089 A new command can use a predefined completion function, either by
23090 specifying it via an argument at initialization, or by returning it
23091 from the @code{complete} method. These predefined completion
23092 constants are all defined in the @code{gdb} module:
23095 @findex COMPLETE_NONE
23096 @findex gdb.COMPLETE_NONE
23097 @item gdb.COMPLETE_NONE
23098 This constant means that no completion should be done.
23100 @findex COMPLETE_FILENAME
23101 @findex gdb.COMPLETE_FILENAME
23102 @item gdb.COMPLETE_FILENAME
23103 This constant means that filename completion should be performed.
23105 @findex COMPLETE_LOCATION
23106 @findex gdb.COMPLETE_LOCATION
23107 @item gdb.COMPLETE_LOCATION
23108 This constant means that location completion should be done.
23109 @xref{Specify Location}.
23111 @findex COMPLETE_COMMAND
23112 @findex gdb.COMPLETE_COMMAND
23113 @item gdb.COMPLETE_COMMAND
23114 This constant means that completion should examine @value{GDBN}
23117 @findex COMPLETE_SYMBOL
23118 @findex gdb.COMPLETE_SYMBOL
23119 @item gdb.COMPLETE_SYMBOL
23120 This constant means that completion should be done using symbol names
23124 The following code snippet shows how a trivial CLI command can be
23125 implemented in Python:
23128 class HelloWorld (gdb.Command):
23129 """Greet the whole world."""
23131 def __init__ (self):
23132 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
23134 def invoke (self, arg, from_tty):
23135 print "Hello, World!"
23140 The last line instantiates the class, and is necessary to trigger the
23141 registration of the command with @value{GDBN}. Depending on how the
23142 Python code is read into @value{GDBN}, you may need to import the
23143 @code{gdb} module explicitly.
23145 @node Parameters In Python
23146 @subsubsection Parameters In Python
23148 @cindex parameters in python
23149 @cindex python parameters
23150 @tindex gdb.Parameter
23152 You can implement new @value{GDBN} parameters using Python. A new
23153 parameter is implemented as an instance of the @code{gdb.Parameter}
23156 Parameters are exposed to the user via the @code{set} and
23157 @code{show} commands. @xref{Help}.
23159 There are many parameters that already exist and can be set in
23160 @value{GDBN}. Two examples are: @code{set follow fork} and
23161 @code{set charset}. Setting these parameters influences certain
23162 behavior in @value{GDBN}. Similarly, you can define parameters that
23163 can be used to influence behavior in custom Python scripts and commands.
23165 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
23166 The object initializer for @code{Parameter} registers the new
23167 parameter with @value{GDBN}. This initializer is normally invoked
23168 from the subclass' own @code{__init__} method.
23170 @var{name} is the name of the new parameter. If @var{name} consists
23171 of multiple words, then the initial words are looked for as prefix
23172 parameters. An example of this can be illustrated with the
23173 @code{set print} set of parameters. If @var{name} is
23174 @code{print foo}, then @code{print} will be searched as the prefix
23175 parameter. In this case the parameter can subsequently be accessed in
23176 @value{GDBN} as @code{set print foo}.
23178 If @var{name} consists of multiple words, and no prefix parameter group
23179 can be found, an exception is raised.
23181 @var{command-class} should be one of the @samp{COMMAND_} constants
23182 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
23183 categorize the new parameter in the help system.
23185 @var{parameter-class} should be one of the @samp{PARAM_} constants
23186 defined below. This argument tells @value{GDBN} the type of the new
23187 parameter; this information is used for input validation and
23190 If @var{parameter-class} is @code{PARAM_ENUM}, then
23191 @var{enum-sequence} must be a sequence of strings. These strings
23192 represent the possible values for the parameter.
23194 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
23195 of a fourth argument will cause an exception to be thrown.
23197 The help text for the new parameter is taken from the Python
23198 documentation string for the parameter's class, if there is one. If
23199 there is no documentation string, a default value is used.
23202 @defvar Parameter.set_doc
23203 If this attribute exists, and is a string, then its value is used as
23204 the help text for this parameter's @code{set} command. The value is
23205 examined when @code{Parameter.__init__} is invoked; subsequent changes
23209 @defvar Parameter.show_doc
23210 If this attribute exists, and is a string, then its value is used as
23211 the help text for this parameter's @code{show} command. The value is
23212 examined when @code{Parameter.__init__} is invoked; subsequent changes
23216 @defvar Parameter.value
23217 The @code{value} attribute holds the underlying value of the
23218 parameter. It can be read and assigned to just as any other
23219 attribute. @value{GDBN} does validation when assignments are made.
23222 There are two methods that should be implemented in any
23223 @code{Parameter} class. These are:
23225 @defun Parameter.get_set_string (self)
23226 @value{GDBN} will call this method when a @var{parameter}'s value has
23227 been changed via the @code{set} API (for example, @kbd{set foo off}).
23228 The @code{value} attribute has already been populated with the new
23229 value and may be used in output. This method must return a string.
23232 @defun Parameter.get_show_string (self, svalue)
23233 @value{GDBN} will call this method when a @var{parameter}'s
23234 @code{show} API has been invoked (for example, @kbd{show foo}). The
23235 argument @code{svalue} receives the string representation of the
23236 current value. This method must return a string.
23239 When a new parameter is defined, its type must be specified. The
23240 available types are represented by constants defined in the @code{gdb}
23244 @findex PARAM_BOOLEAN
23245 @findex gdb.PARAM_BOOLEAN
23246 @item gdb.PARAM_BOOLEAN
23247 The value is a plain boolean. The Python boolean values, @code{True}
23248 and @code{False} are the only valid values.
23250 @findex PARAM_AUTO_BOOLEAN
23251 @findex gdb.PARAM_AUTO_BOOLEAN
23252 @item gdb.PARAM_AUTO_BOOLEAN
23253 The value has three possible states: true, false, and @samp{auto}. In
23254 Python, true and false are represented using boolean constants, and
23255 @samp{auto} is represented using @code{None}.
23257 @findex PARAM_UINTEGER
23258 @findex gdb.PARAM_UINTEGER
23259 @item gdb.PARAM_UINTEGER
23260 The value is an unsigned integer. The value of 0 should be
23261 interpreted to mean ``unlimited''.
23263 @findex PARAM_INTEGER
23264 @findex gdb.PARAM_INTEGER
23265 @item gdb.PARAM_INTEGER
23266 The value is a signed integer. The value of 0 should be interpreted
23267 to mean ``unlimited''.
23269 @findex PARAM_STRING
23270 @findex gdb.PARAM_STRING
23271 @item gdb.PARAM_STRING
23272 The value is a string. When the user modifies the string, any escape
23273 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
23274 translated into corresponding characters and encoded into the current
23277 @findex PARAM_STRING_NOESCAPE
23278 @findex gdb.PARAM_STRING_NOESCAPE
23279 @item gdb.PARAM_STRING_NOESCAPE
23280 The value is a string. When the user modifies the string, escapes are
23281 passed through untranslated.
23283 @findex PARAM_OPTIONAL_FILENAME
23284 @findex gdb.PARAM_OPTIONAL_FILENAME
23285 @item gdb.PARAM_OPTIONAL_FILENAME
23286 The value is a either a filename (a string), or @code{None}.
23288 @findex PARAM_FILENAME
23289 @findex gdb.PARAM_FILENAME
23290 @item gdb.PARAM_FILENAME
23291 The value is a filename. This is just like
23292 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
23294 @findex PARAM_ZINTEGER
23295 @findex gdb.PARAM_ZINTEGER
23296 @item gdb.PARAM_ZINTEGER
23297 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
23298 is interpreted as itself.
23301 @findex gdb.PARAM_ENUM
23302 @item gdb.PARAM_ENUM
23303 The value is a string, which must be one of a collection string
23304 constants provided when the parameter is created.
23307 @node Functions In Python
23308 @subsubsection Writing new convenience functions
23310 @cindex writing convenience functions
23311 @cindex convenience functions in python
23312 @cindex python convenience functions
23313 @tindex gdb.Function
23315 You can implement new convenience functions (@pxref{Convenience Vars})
23316 in Python. A convenience function is an instance of a subclass of the
23317 class @code{gdb.Function}.
23319 @defun Function.__init__ (name)
23320 The initializer for @code{Function} registers the new function with
23321 @value{GDBN}. The argument @var{name} is the name of the function,
23322 a string. The function will be visible to the user as a convenience
23323 variable of type @code{internal function}, whose name is the same as
23324 the given @var{name}.
23326 The documentation for the new function is taken from the documentation
23327 string for the new class.
23330 @defun Function.invoke (@var{*args})
23331 When a convenience function is evaluated, its arguments are converted
23332 to instances of @code{gdb.Value}, and then the function's
23333 @code{invoke} method is called. Note that @value{GDBN} does not
23334 predetermine the arity of convenience functions. Instead, all
23335 available arguments are passed to @code{invoke}, following the
23336 standard Python calling convention. In particular, a convenience
23337 function can have default values for parameters without ill effect.
23339 The return value of this method is used as its value in the enclosing
23340 expression. If an ordinary Python value is returned, it is converted
23341 to a @code{gdb.Value} following the usual rules.
23344 The following code snippet shows how a trivial convenience function can
23345 be implemented in Python:
23348 class Greet (gdb.Function):
23349 """Return string to greet someone.
23350 Takes a name as argument."""
23352 def __init__ (self):
23353 super (Greet, self).__init__ ("greet")
23355 def invoke (self, name):
23356 return "Hello, %s!" % name.string ()
23361 The last line instantiates the class, and is necessary to trigger the
23362 registration of the function with @value{GDBN}. Depending on how the
23363 Python code is read into @value{GDBN}, you may need to import the
23364 @code{gdb} module explicitly.
23366 @node Progspaces In Python
23367 @subsubsection Program Spaces In Python
23369 @cindex progspaces in python
23370 @tindex gdb.Progspace
23372 A program space, or @dfn{progspace}, represents a symbolic view
23373 of an address space.
23374 It consists of all of the objfiles of the program.
23375 @xref{Objfiles In Python}.
23376 @xref{Inferiors and Programs, program spaces}, for more details
23377 about program spaces.
23379 The following progspace-related functions are available in the
23382 @findex gdb.current_progspace
23383 @defun gdb.current_progspace ()
23384 This function returns the program space of the currently selected inferior.
23385 @xref{Inferiors and Programs}.
23388 @findex gdb.progspaces
23389 @defun gdb.progspaces ()
23390 Return a sequence of all the progspaces currently known to @value{GDBN}.
23393 Each progspace is represented by an instance of the @code{gdb.Progspace}
23396 @defvar Progspace.filename
23397 The file name of the progspace as a string.
23400 @defvar Progspace.pretty_printers
23401 The @code{pretty_printers} attribute is a list of functions. It is
23402 used to look up pretty-printers. A @code{Value} is passed to each
23403 function in order; if the function returns @code{None}, then the
23404 search continues. Otherwise, the return value should be an object
23405 which is used to format the value. @xref{Pretty Printing API}, for more
23409 @node Objfiles In Python
23410 @subsubsection Objfiles In Python
23412 @cindex objfiles in python
23413 @tindex gdb.Objfile
23415 @value{GDBN} loads symbols for an inferior from various
23416 symbol-containing files (@pxref{Files}). These include the primary
23417 executable file, any shared libraries used by the inferior, and any
23418 separate debug info files (@pxref{Separate Debug Files}).
23419 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
23421 The following objfile-related functions are available in the
23424 @findex gdb.current_objfile
23425 @defun gdb.current_objfile ()
23426 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
23427 sets the ``current objfile'' to the corresponding objfile. This
23428 function returns the current objfile. If there is no current objfile,
23429 this function returns @code{None}.
23432 @findex gdb.objfiles
23433 @defun gdb.objfiles ()
23434 Return a sequence of all the objfiles current known to @value{GDBN}.
23435 @xref{Objfiles In Python}.
23438 Each objfile is represented by an instance of the @code{gdb.Objfile}
23441 @defvar Objfile.filename
23442 The file name of the objfile as a string.
23445 @defvar Objfile.pretty_printers
23446 The @code{pretty_printers} attribute is a list of functions. It is
23447 used to look up pretty-printers. A @code{Value} is passed to each
23448 function in order; if the function returns @code{None}, then the
23449 search continues. Otherwise, the return value should be an object
23450 which is used to format the value. @xref{Pretty Printing API}, for more
23454 A @code{gdb.Objfile} object has the following methods:
23456 @defun Objfile.is_valid ()
23457 Returns @code{True} if the @code{gdb.Objfile} object is valid,
23458 @code{False} if not. A @code{gdb.Objfile} object can become invalid
23459 if the object file it refers to is not loaded in @value{GDBN} any
23460 longer. All other @code{gdb.Objfile} methods will throw an exception
23461 if it is invalid at the time the method is called.
23464 @node Frames In Python
23465 @subsubsection Accessing inferior stack frames from Python.
23467 @cindex frames in python
23468 When the debugged program stops, @value{GDBN} is able to analyze its call
23469 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
23470 represents a frame in the stack. A @code{gdb.Frame} object is only valid
23471 while its corresponding frame exists in the inferior's stack. If you try
23472 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
23473 exception (@pxref{Exception Handling}).
23475 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
23479 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
23483 The following frame-related functions are available in the @code{gdb} module:
23485 @findex gdb.selected_frame
23486 @defun gdb.selected_frame ()
23487 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
23490 @findex gdb.newest_frame
23491 @defun gdb.newest_frame ()
23492 Return the newest frame object for the selected thread.
23495 @defun gdb.frame_stop_reason_string (reason)
23496 Return a string explaining the reason why @value{GDBN} stopped unwinding
23497 frames, as expressed by the given @var{reason} code (an integer, see the
23498 @code{unwind_stop_reason} method further down in this section).
23501 A @code{gdb.Frame} object has the following methods:
23504 @defun Frame.is_valid ()
23505 Returns true if the @code{gdb.Frame} object is valid, false if not.
23506 A frame object can become invalid if the frame it refers to doesn't
23507 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
23508 an exception if it is invalid at the time the method is called.
23511 @defun Frame.name ()
23512 Returns the function name of the frame, or @code{None} if it can't be
23516 @defun Frame.type ()
23517 Returns the type of the frame. The value can be one of:
23519 @item gdb.NORMAL_FRAME
23520 An ordinary stack frame.
23522 @item gdb.DUMMY_FRAME
23523 A fake stack frame that was created by @value{GDBN} when performing an
23524 inferior function call.
23526 @item gdb.INLINE_FRAME
23527 A frame representing an inlined function. The function was inlined
23528 into a @code{gdb.NORMAL_FRAME} that is older than this one.
23530 @item gdb.TAILCALL_FRAME
23531 A frame representing a tail call. @xref{Tail Call Frames}.
23533 @item gdb.SIGTRAMP_FRAME
23534 A signal trampoline frame. This is the frame created by the OS when
23535 it calls into a signal handler.
23537 @item gdb.ARCH_FRAME
23538 A fake stack frame representing a cross-architecture call.
23540 @item gdb.SENTINEL_FRAME
23541 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
23546 @defun Frame.unwind_stop_reason ()
23547 Return an integer representing the reason why it's not possible to find
23548 more frames toward the outermost frame. Use
23549 @code{gdb.frame_stop_reason_string} to convert the value returned by this
23550 function to a string. The value can be one of:
23553 @item gdb.FRAME_UNWIND_NO_REASON
23554 No particular reason (older frames should be available).
23556 @item gdb.FRAME_UNWIND_NULL_ID
23557 The previous frame's analyzer returns an invalid result.
23559 @item gdb.FRAME_UNWIND_OUTERMOST
23560 This frame is the outermost.
23562 @item gdb.FRAME_UNWIND_UNAVAILABLE
23563 Cannot unwind further, because that would require knowing the
23564 values of registers or memory that have not been collected.
23566 @item gdb.FRAME_UNWIND_INNER_ID
23567 This frame ID looks like it ought to belong to a NEXT frame,
23568 but we got it for a PREV frame. Normally, this is a sign of
23569 unwinder failure. It could also indicate stack corruption.
23571 @item gdb.FRAME_UNWIND_SAME_ID
23572 This frame has the same ID as the previous one. That means
23573 that unwinding further would almost certainly give us another
23574 frame with exactly the same ID, so break the chain. Normally,
23575 this is a sign of unwinder failure. It could also indicate
23578 @item gdb.FRAME_UNWIND_NO_SAVED_PC
23579 The frame unwinder did not find any saved PC, but we needed
23580 one to unwind further.
23582 @item gdb.FRAME_UNWIND_FIRST_ERROR
23583 Any stop reason greater or equal to this value indicates some kind
23584 of error. This special value facilitates writing code that tests
23585 for errors in unwinding in a way that will work correctly even if
23586 the list of the other values is modified in future @value{GDBN}
23587 versions. Using it, you could write:
23589 reason = gdb.selected_frame().unwind_stop_reason ()
23590 reason_str = gdb.frame_stop_reason_string (reason)
23591 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
23592 print "An error occured: %s" % reason_str
23599 Returns the frame's resume address.
23602 @defun Frame.block ()
23603 Return the frame's code block. @xref{Blocks In Python}.
23606 @defun Frame.function ()
23607 Return the symbol for the function corresponding to this frame.
23608 @xref{Symbols In Python}.
23611 @defun Frame.older ()
23612 Return the frame that called this frame.
23615 @defun Frame.newer ()
23616 Return the frame called by this frame.
23619 @defun Frame.find_sal ()
23620 Return the frame's symtab and line object.
23621 @xref{Symbol Tables In Python}.
23624 @defun Frame.read_var (variable @r{[}, block@r{]})
23625 Return the value of @var{variable} in this frame. If the optional
23626 argument @var{block} is provided, search for the variable from that
23627 block; otherwise start at the frame's current block (which is
23628 determined by the frame's current program counter). @var{variable}
23629 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
23630 @code{gdb.Block} object.
23633 @defun Frame.select ()
23634 Set this frame to be the selected frame. @xref{Stack, ,Examining the
23639 @node Blocks In Python
23640 @subsubsection Accessing frame blocks from Python.
23642 @cindex blocks in python
23645 Within each frame, @value{GDBN} maintains information on each block
23646 stored in that frame. These blocks are organized hierarchically, and
23647 are represented individually in Python as a @code{gdb.Block}.
23648 Please see @ref{Frames In Python}, for a more in-depth discussion on
23649 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
23650 detailed technical information on @value{GDBN}'s book-keeping of the
23653 The following block-related functions are available in the @code{gdb}
23656 @findex gdb.block_for_pc
23657 @defun gdb.block_for_pc (pc)
23658 Return the @code{gdb.Block} containing the given @var{pc} value. If the
23659 block cannot be found for the @var{pc} value specified, the function
23660 will return @code{None}.
23663 A @code{gdb.Block} object has the following methods:
23666 @defun Block.is_valid ()
23667 Returns @code{True} if the @code{gdb.Block} object is valid,
23668 @code{False} if not. A block object can become invalid if the block it
23669 refers to doesn't exist anymore in the inferior. All other
23670 @code{gdb.Block} methods will throw an exception if it is invalid at
23671 the time the method is called. This method is also made available to
23672 the Python iterator object that @code{gdb.Block} provides in an iteration
23673 context and via the Python @code{iter} built-in function.
23677 A @code{gdb.Block} object has the following attributes:
23680 @defvar Block.start
23681 The start address of the block. This attribute is not writable.
23685 The end address of the block. This attribute is not writable.
23688 @defvar Block.function
23689 The name of the block represented as a @code{gdb.Symbol}. If the
23690 block is not named, then this attribute holds @code{None}. This
23691 attribute is not writable.
23694 @defvar Block.superblock
23695 The block containing this block. If this parent block does not exist,
23696 this attribute holds @code{None}. This attribute is not writable.
23699 @defvar Block.global_block
23700 The global block associated with this block. This attribute is not
23704 @defvar Block.static_block
23705 The static block associated with this block. This attribute is not
23709 @defvar Block.is_global
23710 @code{True} if the @code{gdb.Block} object is a global block,
23711 @code{False} if not. This attribute is not
23715 @defvar Block.is_static
23716 @code{True} if the @code{gdb.Block} object is a static block,
23717 @code{False} if not. This attribute is not writable.
23721 @node Symbols In Python
23722 @subsubsection Python representation of Symbols.
23724 @cindex symbols in python
23727 @value{GDBN} represents every variable, function and type as an
23728 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
23729 Similarly, Python represents these symbols in @value{GDBN} with the
23730 @code{gdb.Symbol} object.
23732 The following symbol-related functions are available in the @code{gdb}
23735 @findex gdb.lookup_symbol
23736 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
23737 This function searches for a symbol by name. The search scope can be
23738 restricted to the parameters defined in the optional domain and block
23741 @var{name} is the name of the symbol. It must be a string. The
23742 optional @var{block} argument restricts the search to symbols visible
23743 in that @var{block}. The @var{block} argument must be a
23744 @code{gdb.Block} object. If omitted, the block for the current frame
23745 is used. The optional @var{domain} argument restricts
23746 the search to the domain type. The @var{domain} argument must be a
23747 domain constant defined in the @code{gdb} module and described later
23750 The result is a tuple of two elements.
23751 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
23753 If the symbol is found, the second element is @code{True} if the symbol
23754 is a field of a method's object (e.g., @code{this} in C@t{++}),
23755 otherwise it is @code{False}.
23756 If the symbol is not found, the second element is @code{False}.
23759 @findex gdb.lookup_global_symbol
23760 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
23761 This function searches for a global symbol by name.
23762 The search scope can be restricted to by the domain argument.
23764 @var{name} is the name of the symbol. It must be a string.
23765 The optional @var{domain} argument restricts the search to the domain type.
23766 The @var{domain} argument must be a domain constant defined in the @code{gdb}
23767 module and described later in this chapter.
23769 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
23773 A @code{gdb.Symbol} object has the following attributes:
23776 @defvar Symbol.type
23777 The type of the symbol or @code{None} if no type is recorded.
23778 This attribute is represented as a @code{gdb.Type} object.
23779 @xref{Types In Python}. This attribute is not writable.
23782 @defvar Symbol.symtab
23783 The symbol table in which the symbol appears. This attribute is
23784 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
23785 Python}. This attribute is not writable.
23788 @defvar Symbol.name
23789 The name of the symbol as a string. This attribute is not writable.
23792 @defvar Symbol.linkage_name
23793 The name of the symbol, as used by the linker (i.e., may be mangled).
23794 This attribute is not writable.
23797 @defvar Symbol.print_name
23798 The name of the symbol in a form suitable for output. This is either
23799 @code{name} or @code{linkage_name}, depending on whether the user
23800 asked @value{GDBN} to display demangled or mangled names.
23803 @defvar Symbol.addr_class
23804 The address class of the symbol. This classifies how to find the value
23805 of a symbol. Each address class is a constant defined in the
23806 @code{gdb} module and described later in this chapter.
23809 @defvar Symbol.is_argument
23810 @code{True} if the symbol is an argument of a function.
23813 @defvar Symbol.is_constant
23814 @code{True} if the symbol is a constant.
23817 @defvar Symbol.is_function
23818 @code{True} if the symbol is a function or a method.
23821 @defvar Symbol.is_variable
23822 @code{True} if the symbol is a variable.
23826 A @code{gdb.Symbol} object has the following methods:
23829 @defun Symbol.is_valid ()
23830 Returns @code{True} if the @code{gdb.Symbol} object is valid,
23831 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
23832 the symbol it refers to does not exist in @value{GDBN} any longer.
23833 All other @code{gdb.Symbol} methods will throw an exception if it is
23834 invalid at the time the method is called.
23838 The available domain categories in @code{gdb.Symbol} are represented
23839 as constants in the @code{gdb} module:
23842 @findex SYMBOL_UNDEF_DOMAIN
23843 @findex gdb.SYMBOL_UNDEF_DOMAIN
23844 @item gdb.SYMBOL_UNDEF_DOMAIN
23845 This is used when a domain has not been discovered or none of the
23846 following domains apply. This usually indicates an error either
23847 in the symbol information or in @value{GDBN}'s handling of symbols.
23848 @findex SYMBOL_VAR_DOMAIN
23849 @findex gdb.SYMBOL_VAR_DOMAIN
23850 @item gdb.SYMBOL_VAR_DOMAIN
23851 This domain contains variables, function names, typedef names and enum
23853 @findex SYMBOL_STRUCT_DOMAIN
23854 @findex gdb.SYMBOL_STRUCT_DOMAIN
23855 @item gdb.SYMBOL_STRUCT_DOMAIN
23856 This domain holds struct, union and enum type names.
23857 @findex SYMBOL_LABEL_DOMAIN
23858 @findex gdb.SYMBOL_LABEL_DOMAIN
23859 @item gdb.SYMBOL_LABEL_DOMAIN
23860 This domain contains names of labels (for gotos).
23861 @findex SYMBOL_VARIABLES_DOMAIN
23862 @findex gdb.SYMBOL_VARIABLES_DOMAIN
23863 @item gdb.SYMBOL_VARIABLES_DOMAIN
23864 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
23865 contains everything minus functions and types.
23866 @findex SYMBOL_FUNCTIONS_DOMAIN
23867 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
23868 @item gdb.SYMBOL_FUNCTION_DOMAIN
23869 This domain contains all functions.
23870 @findex SYMBOL_TYPES_DOMAIN
23871 @findex gdb.SYMBOL_TYPES_DOMAIN
23872 @item gdb.SYMBOL_TYPES_DOMAIN
23873 This domain contains all types.
23876 The available address class categories in @code{gdb.Symbol} are represented
23877 as constants in the @code{gdb} module:
23880 @findex SYMBOL_LOC_UNDEF
23881 @findex gdb.SYMBOL_LOC_UNDEF
23882 @item gdb.SYMBOL_LOC_UNDEF
23883 If this is returned by address class, it indicates an error either in
23884 the symbol information or in @value{GDBN}'s handling of symbols.
23885 @findex SYMBOL_LOC_CONST
23886 @findex gdb.SYMBOL_LOC_CONST
23887 @item gdb.SYMBOL_LOC_CONST
23888 Value is constant int.
23889 @findex SYMBOL_LOC_STATIC
23890 @findex gdb.SYMBOL_LOC_STATIC
23891 @item gdb.SYMBOL_LOC_STATIC
23892 Value is at a fixed address.
23893 @findex SYMBOL_LOC_REGISTER
23894 @findex gdb.SYMBOL_LOC_REGISTER
23895 @item gdb.SYMBOL_LOC_REGISTER
23896 Value is in a register.
23897 @findex SYMBOL_LOC_ARG
23898 @findex gdb.SYMBOL_LOC_ARG
23899 @item gdb.SYMBOL_LOC_ARG
23900 Value is an argument. This value is at the offset stored within the
23901 symbol inside the frame's argument list.
23902 @findex SYMBOL_LOC_REF_ARG
23903 @findex gdb.SYMBOL_LOC_REF_ARG
23904 @item gdb.SYMBOL_LOC_REF_ARG
23905 Value address is stored in the frame's argument list. Just like
23906 @code{LOC_ARG} except that the value's address is stored at the
23907 offset, not the value itself.
23908 @findex SYMBOL_LOC_REGPARM_ADDR
23909 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
23910 @item gdb.SYMBOL_LOC_REGPARM_ADDR
23911 Value is a specified register. Just like @code{LOC_REGISTER} except
23912 the register holds the address of the argument instead of the argument
23914 @findex SYMBOL_LOC_LOCAL
23915 @findex gdb.SYMBOL_LOC_LOCAL
23916 @item gdb.SYMBOL_LOC_LOCAL
23917 Value is a local variable.
23918 @findex SYMBOL_LOC_TYPEDEF
23919 @findex gdb.SYMBOL_LOC_TYPEDEF
23920 @item gdb.SYMBOL_LOC_TYPEDEF
23921 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
23923 @findex SYMBOL_LOC_BLOCK
23924 @findex gdb.SYMBOL_LOC_BLOCK
23925 @item gdb.SYMBOL_LOC_BLOCK
23927 @findex SYMBOL_LOC_CONST_BYTES
23928 @findex gdb.SYMBOL_LOC_CONST_BYTES
23929 @item gdb.SYMBOL_LOC_CONST_BYTES
23930 Value is a byte-sequence.
23931 @findex SYMBOL_LOC_UNRESOLVED
23932 @findex gdb.SYMBOL_LOC_UNRESOLVED
23933 @item gdb.SYMBOL_LOC_UNRESOLVED
23934 Value is at a fixed address, but the address of the variable has to be
23935 determined from the minimal symbol table whenever the variable is
23937 @findex SYMBOL_LOC_OPTIMIZED_OUT
23938 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
23939 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
23940 The value does not actually exist in the program.
23941 @findex SYMBOL_LOC_COMPUTED
23942 @findex gdb.SYMBOL_LOC_COMPUTED
23943 @item gdb.SYMBOL_LOC_COMPUTED
23944 The value's address is a computed location.
23947 @node Symbol Tables In Python
23948 @subsubsection Symbol table representation in Python.
23950 @cindex symbol tables in python
23952 @tindex gdb.Symtab_and_line
23954 Access to symbol table data maintained by @value{GDBN} on the inferior
23955 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
23956 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
23957 from the @code{find_sal} method in @code{gdb.Frame} object.
23958 @xref{Frames In Python}.
23960 For more information on @value{GDBN}'s symbol table management, see
23961 @ref{Symbols, ,Examining the Symbol Table}, for more information.
23963 A @code{gdb.Symtab_and_line} object has the following attributes:
23966 @defvar Symtab_and_line.symtab
23967 The symbol table object (@code{gdb.Symtab}) for this frame.
23968 This attribute is not writable.
23971 @defvar Symtab_and_line.pc
23972 Indicates the current program counter address. This attribute is not
23976 @defvar Symtab_and_line.line
23977 Indicates the current line number for this object. This
23978 attribute is not writable.
23982 A @code{gdb.Symtab_and_line} object has the following methods:
23985 @defun Symtab_and_line.is_valid ()
23986 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
23987 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
23988 invalid if the Symbol table and line object it refers to does not
23989 exist in @value{GDBN} any longer. All other
23990 @code{gdb.Symtab_and_line} methods will throw an exception if it is
23991 invalid at the time the method is called.
23995 A @code{gdb.Symtab} object has the following attributes:
23998 @defvar Symtab.filename
23999 The symbol table's source filename. This attribute is not writable.
24002 @defvar Symtab.objfile
24003 The symbol table's backing object file. @xref{Objfiles In Python}.
24004 This attribute is not writable.
24008 A @code{gdb.Symtab} object has the following methods:
24011 @defun Symtab.is_valid ()
24012 Returns @code{True} if the @code{gdb.Symtab} object is valid,
24013 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
24014 the symbol table it refers to does not exist in @value{GDBN} any
24015 longer. All other @code{gdb.Symtab} methods will throw an exception
24016 if it is invalid at the time the method is called.
24019 @defun Symtab.fullname ()
24020 Return the symbol table's source absolute file name.
24024 @node Breakpoints In Python
24025 @subsubsection Manipulating breakpoints using Python
24027 @cindex breakpoints in python
24028 @tindex gdb.Breakpoint
24030 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
24033 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal@r{]]]})
24034 Create a new breakpoint. @var{spec} is a string naming the
24035 location of the breakpoint, or an expression that defines a
24036 watchpoint. The contents can be any location recognized by the
24037 @code{break} command, or in the case of a watchpoint, by the @code{watch}
24038 command. The optional @var{type} denotes the breakpoint to create
24039 from the types defined later in this chapter. This argument can be
24040 either: @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
24041 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal} argument
24042 allows the breakpoint to become invisible to the user. The breakpoint
24043 will neither be reported when created, nor will it be listed in the
24044 output from @code{info breakpoints} (but will be listed with the
24045 @code{maint info breakpoints} command). The optional @var{wp_class}
24046 argument defines the class of watchpoint to create, if @var{type} is
24047 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it is
24048 assumed to be a @code{gdb.WP_WRITE} class.
24051 @defun Breakpoint.stop (self)
24052 The @code{gdb.Breakpoint} class can be sub-classed and, in
24053 particular, you may choose to implement the @code{stop} method.
24054 If this method is defined as a sub-class of @code{gdb.Breakpoint},
24055 it will be called when the inferior reaches any location of a
24056 breakpoint which instantiates that sub-class. If the method returns
24057 @code{True}, the inferior will be stopped at the location of the
24058 breakpoint, otherwise the inferior will continue.
24060 If there are multiple breakpoints at the same location with a
24061 @code{stop} method, each one will be called regardless of the
24062 return status of the previous. This ensures that all @code{stop}
24063 methods have a chance to execute at that location. In this scenario
24064 if one of the methods returns @code{True} but the others return
24065 @code{False}, the inferior will still be stopped.
24067 You should not alter the execution state of the inferior (i.e.@:, step,
24068 next, etc.), alter the current frame context (i.e.@:, change the current
24069 active frame), or alter, add or delete any breakpoint. As a general
24070 rule, you should not alter any data within @value{GDBN} or the inferior
24073 Example @code{stop} implementation:
24076 class MyBreakpoint (gdb.Breakpoint):
24078 inf_val = gdb.parse_and_eval("foo")
24085 The available watchpoint types represented by constants are defined in the
24090 @findex gdb.WP_READ
24092 Read only watchpoint.
24095 @findex gdb.WP_WRITE
24097 Write only watchpoint.
24100 @findex gdb.WP_ACCESS
24101 @item gdb.WP_ACCESS
24102 Read/Write watchpoint.
24105 @defun Breakpoint.is_valid ()
24106 Return @code{True} if this @code{Breakpoint} object is valid,
24107 @code{False} otherwise. A @code{Breakpoint} object can become invalid
24108 if the user deletes the breakpoint. In this case, the object still
24109 exists, but the underlying breakpoint does not. In the cases of
24110 watchpoint scope, the watchpoint remains valid even if execution of the
24111 inferior leaves the scope of that watchpoint.
24114 @defun Breakpoint.delete
24115 Permanently deletes the @value{GDBN} breakpoint. This also
24116 invalidates the Python @code{Breakpoint} object. Any further access
24117 to this object's attributes or methods will raise an error.
24120 @defvar Breakpoint.enabled
24121 This attribute is @code{True} if the breakpoint is enabled, and
24122 @code{False} otherwise. This attribute is writable.
24125 @defvar Breakpoint.silent
24126 This attribute is @code{True} if the breakpoint is silent, and
24127 @code{False} otherwise. This attribute is writable.
24129 Note that a breakpoint can also be silent if it has commands and the
24130 first command is @code{silent}. This is not reported by the
24131 @code{silent} attribute.
24134 @defvar Breakpoint.thread
24135 If the breakpoint is thread-specific, this attribute holds the thread
24136 id. If the breakpoint is not thread-specific, this attribute is
24137 @code{None}. This attribute is writable.
24140 @defvar Breakpoint.task
24141 If the breakpoint is Ada task-specific, this attribute holds the Ada task
24142 id. If the breakpoint is not task-specific (or the underlying
24143 language is not Ada), this attribute is @code{None}. This attribute
24147 @defvar Breakpoint.ignore_count
24148 This attribute holds the ignore count for the breakpoint, an integer.
24149 This attribute is writable.
24152 @defvar Breakpoint.number
24153 This attribute holds the breakpoint's number --- the identifier used by
24154 the user to manipulate the breakpoint. This attribute is not writable.
24157 @defvar Breakpoint.type
24158 This attribute holds the breakpoint's type --- the identifier used to
24159 determine the actual breakpoint type or use-case. This attribute is not
24163 @defvar Breakpoint.visible
24164 This attribute tells whether the breakpoint is visible to the user
24165 when set, or when the @samp{info breakpoints} command is run. This
24166 attribute is not writable.
24169 The available types are represented by constants defined in the @code{gdb}
24173 @findex BP_BREAKPOINT
24174 @findex gdb.BP_BREAKPOINT
24175 @item gdb.BP_BREAKPOINT
24176 Normal code breakpoint.
24178 @findex BP_WATCHPOINT
24179 @findex gdb.BP_WATCHPOINT
24180 @item gdb.BP_WATCHPOINT
24181 Watchpoint breakpoint.
24183 @findex BP_HARDWARE_WATCHPOINT
24184 @findex gdb.BP_HARDWARE_WATCHPOINT
24185 @item gdb.BP_HARDWARE_WATCHPOINT
24186 Hardware assisted watchpoint.
24188 @findex BP_READ_WATCHPOINT
24189 @findex gdb.BP_READ_WATCHPOINT
24190 @item gdb.BP_READ_WATCHPOINT
24191 Hardware assisted read watchpoint.
24193 @findex BP_ACCESS_WATCHPOINT
24194 @findex gdb.BP_ACCESS_WATCHPOINT
24195 @item gdb.BP_ACCESS_WATCHPOINT
24196 Hardware assisted access watchpoint.
24199 @defvar Breakpoint.hit_count
24200 This attribute holds the hit count for the breakpoint, an integer.
24201 This attribute is writable, but currently it can only be set to zero.
24204 @defvar Breakpoint.location
24205 This attribute holds the location of the breakpoint, as specified by
24206 the user. It is a string. If the breakpoint does not have a location
24207 (that is, it is a watchpoint) the attribute's value is @code{None}. This
24208 attribute is not writable.
24211 @defvar Breakpoint.expression
24212 This attribute holds a breakpoint expression, as specified by
24213 the user. It is a string. If the breakpoint does not have an
24214 expression (the breakpoint is not a watchpoint) the attribute's value
24215 is @code{None}. This attribute is not writable.
24218 @defvar Breakpoint.condition
24219 This attribute holds the condition of the breakpoint, as specified by
24220 the user. It is a string. If there is no condition, this attribute's
24221 value is @code{None}. This attribute is writable.
24224 @defvar Breakpoint.commands
24225 This attribute holds the commands attached to the breakpoint. If
24226 there are commands, this attribute's value is a string holding all the
24227 commands, separated by newlines. If there are no commands, this
24228 attribute is @code{None}. This attribute is not writable.
24231 @node Lazy Strings In Python
24232 @subsubsection Python representation of lazy strings.
24234 @cindex lazy strings in python
24235 @tindex gdb.LazyString
24237 A @dfn{lazy string} is a string whose contents is not retrieved or
24238 encoded until it is needed.
24240 A @code{gdb.LazyString} is represented in @value{GDBN} as an
24241 @code{address} that points to a region of memory, an @code{encoding}
24242 that will be used to encode that region of memory, and a @code{length}
24243 to delimit the region of memory that represents the string. The
24244 difference between a @code{gdb.LazyString} and a string wrapped within
24245 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
24246 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
24247 retrieved and encoded during printing, while a @code{gdb.Value}
24248 wrapping a string is immediately retrieved and encoded on creation.
24250 A @code{gdb.LazyString} object has the following functions:
24252 @defun LazyString.value ()
24253 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
24254 will point to the string in memory, but will lose all the delayed
24255 retrieval, encoding and handling that @value{GDBN} applies to a
24256 @code{gdb.LazyString}.
24259 @defvar LazyString.address
24260 This attribute holds the address of the string. This attribute is not
24264 @defvar LazyString.length
24265 This attribute holds the length of the string in characters. If the
24266 length is -1, then the string will be fetched and encoded up to the
24267 first null of appropriate width. This attribute is not writable.
24270 @defvar LazyString.encoding
24271 This attribute holds the encoding that will be applied to the string
24272 when the string is printed by @value{GDBN}. If the encoding is not
24273 set, or contains an empty string, then @value{GDBN} will select the
24274 most appropriate encoding when the string is printed. This attribute
24278 @defvar LazyString.type
24279 This attribute holds the type that is represented by the lazy string's
24280 type. For a lazy string this will always be a pointer type. To
24281 resolve this to the lazy string's character type, use the type's
24282 @code{target} method. @xref{Types In Python}. This attribute is not
24287 @subsection Auto-loading
24288 @cindex auto-loading, Python
24290 When a new object file is read (for example, due to the @code{file}
24291 command, or because the inferior has loaded a shared library),
24292 @value{GDBN} will look for Python support scripts in several ways:
24293 @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section.
24296 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
24297 * .debug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
24298 * Which flavor to choose?::
24301 The auto-loading feature is useful for supplying application-specific
24302 debugging commands and scripts.
24304 Auto-loading can be enabled or disabled,
24305 and the list of auto-loaded scripts can be printed.
24308 @kindex set auto-load-scripts
24309 @item set auto-load-scripts [yes|no]
24310 Enable or disable the auto-loading of Python scripts.
24312 @kindex show auto-load-scripts
24313 @item show auto-load-scripts
24314 Show whether auto-loading of Python scripts is enabled or disabled.
24316 @kindex info auto-load-scripts
24317 @cindex print list of auto-loaded scripts
24318 @item info auto-load-scripts [@var{regexp}]
24319 Print the list of all scripts that @value{GDBN} auto-loaded.
24321 Also printed is the list of scripts that were mentioned in
24322 the @code{.debug_gdb_scripts} section and were not found
24323 (@pxref{.debug_gdb_scripts section}).
24324 This is useful because their names are not printed when @value{GDBN}
24325 tries to load them and fails. There may be many of them, and printing
24326 an error message for each one is problematic.
24328 If @var{regexp} is supplied only scripts with matching names are printed.
24333 (gdb) info auto-load-scripts
24335 Yes py-section-script.py
24336 full name: /tmp/py-section-script.py
24337 Missing my-foo-pretty-printers.py
24341 When reading an auto-loaded file, @value{GDBN} sets the
24342 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
24343 function (@pxref{Objfiles In Python}). This can be useful for
24344 registering objfile-specific pretty-printers.
24346 @node objfile-gdb.py file
24347 @subsubsection The @file{@var{objfile}-gdb.py} file
24348 @cindex @file{@var{objfile}-gdb.py}
24350 When a new object file is read, @value{GDBN} looks for
24351 a file named @file{@var{objfile}-gdb.py},
24352 where @var{objfile} is the object file's real name, formed by ensuring
24353 that the file name is absolute, following all symlinks, and resolving
24354 @code{.} and @code{..} components. If this file exists and is
24355 readable, @value{GDBN} will evaluate it as a Python script.
24357 If this file does not exist, and if the parameter
24358 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
24359 then @value{GDBN} will look for @var{real-name} in all of the
24360 directories mentioned in the value of @code{debug-file-directory}.
24362 Finally, if this file does not exist, then @value{GDBN} will look for
24363 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
24364 @var{data-directory} is @value{GDBN}'s data directory (available via
24365 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
24366 is the object file's real name, as described above.
24368 @value{GDBN} does not track which files it has already auto-loaded this way.
24369 @value{GDBN} will load the associated script every time the corresponding
24370 @var{objfile} is opened.
24371 So your @file{-gdb.py} file should be careful to avoid errors if it
24372 is evaluated more than once.
24374 @node .debug_gdb_scripts section
24375 @subsubsection The @code{.debug_gdb_scripts} section
24376 @cindex @code{.debug_gdb_scripts} section
24378 For systems using file formats like ELF and COFF,
24379 when @value{GDBN} loads a new object file
24380 it will look for a special section named @samp{.debug_gdb_scripts}.
24381 If this section exists, its contents is a list of names of scripts to load.
24383 @value{GDBN} will look for each specified script file first in the
24384 current directory and then along the source search path
24385 (@pxref{Source Path, ,Specifying Source Directories}),
24386 except that @file{$cdir} is not searched, since the compilation
24387 directory is not relevant to scripts.
24389 Entries can be placed in section @code{.debug_gdb_scripts} with,
24390 for example, this GCC macro:
24393 /* Note: The "MS" section flags are to remove duplicates. */
24394 #define DEFINE_GDB_SCRIPT(script_name) \
24396 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
24398 .asciz \"" script_name "\"\n\
24404 Then one can reference the macro in a header or source file like this:
24407 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
24410 The script name may include directories if desired.
24412 If the macro is put in a header, any application or library
24413 using this header will get a reference to the specified script.
24415 @node Which flavor to choose?
24416 @subsubsection Which flavor to choose?
24418 Given the multiple ways of auto-loading Python scripts, it might not always
24419 be clear which one to choose. This section provides some guidance.
24421 Benefits of the @file{-gdb.py} way:
24425 Can be used with file formats that don't support multiple sections.
24428 Ease of finding scripts for public libraries.
24430 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
24431 in the source search path.
24432 For publicly installed libraries, e.g., @file{libstdc++}, there typically
24433 isn't a source directory in which to find the script.
24436 Doesn't require source code additions.
24439 Benefits of the @code{.debug_gdb_scripts} way:
24443 Works with static linking.
24445 Scripts for libraries done the @file{-gdb.py} way require an objfile to
24446 trigger their loading. When an application is statically linked the only
24447 objfile available is the executable, and it is cumbersome to attach all the
24448 scripts from all the input libraries to the executable's @file{-gdb.py} script.
24451 Works with classes that are entirely inlined.
24453 Some classes can be entirely inlined, and thus there may not be an associated
24454 shared library to attach a @file{-gdb.py} script to.
24457 Scripts needn't be copied out of the source tree.
24459 In some circumstances, apps can be built out of large collections of internal
24460 libraries, and the build infrastructure necessary to install the
24461 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
24462 cumbersome. It may be easier to specify the scripts in the
24463 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
24464 top of the source tree to the source search path.
24467 @node Python modules
24468 @subsection Python modules
24469 @cindex python modules
24471 @value{GDBN} comes with several modules to assist writing Python code.
24474 * gdb.printing:: Building and registering pretty-printers.
24475 * gdb.types:: Utilities for working with types.
24476 * gdb.prompt:: Utilities for prompt value substitution.
24480 @subsubsection gdb.printing
24481 @cindex gdb.printing
24483 This module provides a collection of utilities for working with
24487 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
24488 This class specifies the API that makes @samp{info pretty-printer},
24489 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
24490 Pretty-printers should generally inherit from this class.
24492 @item SubPrettyPrinter (@var{name})
24493 For printers that handle multiple types, this class specifies the
24494 corresponding API for the subprinters.
24496 @item RegexpCollectionPrettyPrinter (@var{name})
24497 Utility class for handling multiple printers, all recognized via
24498 regular expressions.
24499 @xref{Writing a Pretty-Printer}, for an example.
24501 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
24502 Register @var{printer} with the pretty-printer list of @var{obj}.
24503 If @var{replace} is @code{True} then any existing copy of the printer
24504 is replaced. Otherwise a @code{RuntimeError} exception is raised
24505 if a printer with the same name already exists.
24509 @subsubsection gdb.types
24512 This module provides a collection of utilities for working with
24513 @code{gdb.Types} objects.
24516 @item get_basic_type (@var{type})
24517 Return @var{type} with const and volatile qualifiers stripped,
24518 and with typedefs and C@t{++} references converted to the underlying type.
24523 typedef const int const_int;
24525 const_int& foo_ref (foo);
24526 int main () @{ return 0; @}
24533 (gdb) python import gdb.types
24534 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
24535 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
24539 @item has_field (@var{type}, @var{field})
24540 Return @code{True} if @var{type}, assumed to be a type with fields
24541 (e.g., a structure or union), has field @var{field}.
24543 @item make_enum_dict (@var{enum_type})
24544 Return a Python @code{dictionary} type produced from @var{enum_type}.
24546 @item deep_items (@var{type})
24547 Returns a Python iterator similar to the standard
24548 @code{gdb.Type.iteritems} method, except that the iterator returned
24549 by @code{deep_items} will recursively traverse anonymous struct or
24550 union fields. For example:
24564 Then in @value{GDBN}:
24566 (@value{GDBP}) python import gdb.types
24567 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
24568 (@value{GDBP}) python print struct_a.keys ()
24570 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
24571 @{['a', 'b0', 'b1']@}
24577 @subsubsection gdb.prompt
24580 This module provides a method for prompt value-substitution.
24583 @item substitute_prompt (@var{string})
24584 Return @var{string} with escape sequences substituted by values. Some
24585 escape sequences take arguments. You can specify arguments inside
24586 ``@{@}'' immediately following the escape sequence.
24588 The escape sequences you can pass to this function are:
24592 Substitute a backslash.
24594 Substitute an ESC character.
24596 Substitute the selected frame; an argument names a frame parameter.
24598 Substitute a newline.
24600 Substitute a parameter's value; the argument names the parameter.
24602 Substitute a carriage return.
24604 Substitute the selected thread; an argument names a thread parameter.
24606 Substitute the version of GDB.
24608 Substitute the current working directory.
24610 Begin a sequence of non-printing characters. These sequences are
24611 typically used with the ESC character, and are not counted in the string
24612 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
24613 blue-colored ``(gdb)'' prompt where the length is five.
24615 End a sequence of non-printing characters.
24621 substitute_prompt (``frame: \f,
24622 print arguments: \p@{print frame-arguments@}'')
24625 @exdent will return the string:
24628 "frame: main, print arguments: scalars"
24633 @section Creating new spellings of existing commands
24634 @cindex aliases for commands
24636 It is often useful to define alternate spellings of existing commands.
24637 For example, if a new @value{GDBN} command defined in Python has
24638 a long name to type, it is handy to have an abbreviated version of it
24639 that involves less typing.
24641 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
24642 of the @samp{step} command even though it is otherwise an ambiguous
24643 abbreviation of other commands like @samp{set} and @samp{show}.
24645 Aliases are also used to provide shortened or more common versions
24646 of multi-word commands. For example, @value{GDBN} provides the
24647 @samp{tty} alias of the @samp{set inferior-tty} command.
24649 You can define a new alias with the @samp{alias} command.
24654 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
24658 @var{ALIAS} specifies the name of the new alias.
24659 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
24662 @var{COMMAND} specifies the name of an existing command
24663 that is being aliased.
24665 The @samp{-a} option specifies that the new alias is an abbreviation
24666 of the command. Abbreviations are not shown in command
24667 lists displayed by the @samp{help} command.
24669 The @samp{--} option specifies the end of options,
24670 and is useful when @var{ALIAS} begins with a dash.
24672 Here is a simple example showing how to make an abbreviation
24673 of a command so that there is less to type.
24674 Suppose you were tired of typing @samp{disas}, the current
24675 shortest unambiguous abbreviation of the @samp{disassemble} command
24676 and you wanted an even shorter version named @samp{di}.
24677 The following will accomplish this.
24680 (gdb) alias -a di = disas
24683 Note that aliases are different from user-defined commands.
24684 With a user-defined command, you also need to write documentation
24685 for it with the @samp{document} command.
24686 An alias automatically picks up the documentation of the existing command.
24688 Here is an example where we make @samp{elms} an abbreviation of
24689 @samp{elements} in the @samp{set print elements} command.
24690 This is to show that you can make an abbreviation of any part
24694 (gdb) alias -a set print elms = set print elements
24695 (gdb) alias -a show print elms = show print elements
24696 (gdb) set p elms 20
24698 Limit on string chars or array elements to print is 200.
24701 Note that if you are defining an alias of a @samp{set} command,
24702 and you want to have an alias for the corresponding @samp{show}
24703 command, then you need to define the latter separately.
24705 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
24706 @var{ALIAS}, just as they are normally.
24709 (gdb) alias -a set pr elms = set p ele
24712 Finally, here is an example showing the creation of a one word
24713 alias for a more complex command.
24714 This creates alias @samp{spe} of the command @samp{set print elements}.
24717 (gdb) alias spe = set print elements
24722 @chapter Command Interpreters
24723 @cindex command interpreters
24725 @value{GDBN} supports multiple command interpreters, and some command
24726 infrastructure to allow users or user interface writers to switch
24727 between interpreters or run commands in other interpreters.
24729 @value{GDBN} currently supports two command interpreters, the console
24730 interpreter (sometimes called the command-line interpreter or @sc{cli})
24731 and the machine interface interpreter (or @sc{gdb/mi}). This manual
24732 describes both of these interfaces in great detail.
24734 By default, @value{GDBN} will start with the console interpreter.
24735 However, the user may choose to start @value{GDBN} with another
24736 interpreter by specifying the @option{-i} or @option{--interpreter}
24737 startup options. Defined interpreters include:
24741 @cindex console interpreter
24742 The traditional console or command-line interpreter. This is the most often
24743 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
24744 @value{GDBN} will use this interpreter.
24747 @cindex mi interpreter
24748 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
24749 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
24750 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
24754 @cindex mi2 interpreter
24755 The current @sc{gdb/mi} interface.
24758 @cindex mi1 interpreter
24759 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
24763 @cindex invoke another interpreter
24764 The interpreter being used by @value{GDBN} may not be dynamically
24765 switched at runtime. Although possible, this could lead to a very
24766 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
24767 enters the command "interpreter-set console" in a console view,
24768 @value{GDBN} would switch to using the console interpreter, rendering
24769 the IDE inoperable!
24771 @kindex interpreter-exec
24772 Although you may only choose a single interpreter at startup, you may execute
24773 commands in any interpreter from the current interpreter using the appropriate
24774 command. If you are running the console interpreter, simply use the
24775 @code{interpreter-exec} command:
24778 interpreter-exec mi "-data-list-register-names"
24781 @sc{gdb/mi} has a similar command, although it is only available in versions of
24782 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
24785 @chapter @value{GDBN} Text User Interface
24787 @cindex Text User Interface
24790 * TUI Overview:: TUI overview
24791 * TUI Keys:: TUI key bindings
24792 * TUI Single Key Mode:: TUI single key mode
24793 * TUI Commands:: TUI-specific commands
24794 * TUI Configuration:: TUI configuration variables
24797 The @value{GDBN} Text User Interface (TUI) is a terminal
24798 interface which uses the @code{curses} library to show the source
24799 file, the assembly output, the program registers and @value{GDBN}
24800 commands in separate text windows. The TUI mode is supported only
24801 on platforms where a suitable version of the @code{curses} library
24804 @pindex @value{GDBTUI}
24805 The TUI mode is enabled by default when you invoke @value{GDBN} as
24806 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
24807 You can also switch in and out of TUI mode while @value{GDBN} runs by
24808 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
24809 @xref{TUI Keys, ,TUI Key Bindings}.
24812 @section TUI Overview
24814 In TUI mode, @value{GDBN} can display several text windows:
24818 This window is the @value{GDBN} command window with the @value{GDBN}
24819 prompt and the @value{GDBN} output. The @value{GDBN} input is still
24820 managed using readline.
24823 The source window shows the source file of the program. The current
24824 line and active breakpoints are displayed in this window.
24827 The assembly window shows the disassembly output of the program.
24830 This window shows the processor registers. Registers are highlighted
24831 when their values change.
24834 The source and assembly windows show the current program position
24835 by highlighting the current line and marking it with a @samp{>} marker.
24836 Breakpoints are indicated with two markers. The first marker
24837 indicates the breakpoint type:
24841 Breakpoint which was hit at least once.
24844 Breakpoint which was never hit.
24847 Hardware breakpoint which was hit at least once.
24850 Hardware breakpoint which was never hit.
24853 The second marker indicates whether the breakpoint is enabled or not:
24857 Breakpoint is enabled.
24860 Breakpoint is disabled.
24863 The source, assembly and register windows are updated when the current
24864 thread changes, when the frame changes, or when the program counter
24867 These windows are not all visible at the same time. The command
24868 window is always visible. The others can be arranged in several
24879 source and assembly,
24882 source and registers, or
24885 assembly and registers.
24888 A status line above the command window shows the following information:
24892 Indicates the current @value{GDBN} target.
24893 (@pxref{Targets, ,Specifying a Debugging Target}).
24896 Gives the current process or thread number.
24897 When no process is being debugged, this field is set to @code{No process}.
24900 Gives the current function name for the selected frame.
24901 The name is demangled if demangling is turned on (@pxref{Print Settings}).
24902 When there is no symbol corresponding to the current program counter,
24903 the string @code{??} is displayed.
24906 Indicates the current line number for the selected frame.
24907 When the current line number is not known, the string @code{??} is displayed.
24910 Indicates the current program counter address.
24914 @section TUI Key Bindings
24915 @cindex TUI key bindings
24917 The TUI installs several key bindings in the readline keymaps
24918 @ifset SYSTEM_READLINE
24919 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
24921 @ifclear SYSTEM_READLINE
24922 (@pxref{Command Line Editing}).
24924 The following key bindings are installed for both TUI mode and the
24925 @value{GDBN} standard mode.
24934 Enter or leave the TUI mode. When leaving the TUI mode,
24935 the curses window management stops and @value{GDBN} operates using
24936 its standard mode, writing on the terminal directly. When reentering
24937 the TUI mode, control is given back to the curses windows.
24938 The screen is then refreshed.
24942 Use a TUI layout with only one window. The layout will
24943 either be @samp{source} or @samp{assembly}. When the TUI mode
24944 is not active, it will switch to the TUI mode.
24946 Think of this key binding as the Emacs @kbd{C-x 1} binding.
24950 Use a TUI layout with at least two windows. When the current
24951 layout already has two windows, the next layout with two windows is used.
24952 When a new layout is chosen, one window will always be common to the
24953 previous layout and the new one.
24955 Think of it as the Emacs @kbd{C-x 2} binding.
24959 Change the active window. The TUI associates several key bindings
24960 (like scrolling and arrow keys) with the active window. This command
24961 gives the focus to the next TUI window.
24963 Think of it as the Emacs @kbd{C-x o} binding.
24967 Switch in and out of the TUI SingleKey mode that binds single
24968 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
24971 The following key bindings only work in the TUI mode:
24976 Scroll the active window one page up.
24980 Scroll the active window one page down.
24984 Scroll the active window one line up.
24988 Scroll the active window one line down.
24992 Scroll the active window one column left.
24996 Scroll the active window one column right.
25000 Refresh the screen.
25003 Because the arrow keys scroll the active window in the TUI mode, they
25004 are not available for their normal use by readline unless the command
25005 window has the focus. When another window is active, you must use
25006 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
25007 and @kbd{C-f} to control the command window.
25009 @node TUI Single Key Mode
25010 @section TUI Single Key Mode
25011 @cindex TUI single key mode
25013 The TUI also provides a @dfn{SingleKey} mode, which binds several
25014 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
25015 switch into this mode, where the following key bindings are used:
25018 @kindex c @r{(SingleKey TUI key)}
25022 @kindex d @r{(SingleKey TUI key)}
25026 @kindex f @r{(SingleKey TUI key)}
25030 @kindex n @r{(SingleKey TUI key)}
25034 @kindex q @r{(SingleKey TUI key)}
25036 exit the SingleKey mode.
25038 @kindex r @r{(SingleKey TUI key)}
25042 @kindex s @r{(SingleKey TUI key)}
25046 @kindex u @r{(SingleKey TUI key)}
25050 @kindex v @r{(SingleKey TUI key)}
25054 @kindex w @r{(SingleKey TUI key)}
25059 Other keys temporarily switch to the @value{GDBN} command prompt.
25060 The key that was pressed is inserted in the editing buffer so that
25061 it is possible to type most @value{GDBN} commands without interaction
25062 with the TUI SingleKey mode. Once the command is entered the TUI
25063 SingleKey mode is restored. The only way to permanently leave
25064 this mode is by typing @kbd{q} or @kbd{C-x s}.
25068 @section TUI-specific Commands
25069 @cindex TUI commands
25071 The TUI has specific commands to control the text windows.
25072 These commands are always available, even when @value{GDBN} is not in
25073 the TUI mode. When @value{GDBN} is in the standard mode, most
25074 of these commands will automatically switch to the TUI mode.
25076 Note that if @value{GDBN}'s @code{stdout} is not connected to a
25077 terminal, or @value{GDBN} has been started with the machine interface
25078 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
25079 these commands will fail with an error, because it would not be
25080 possible or desirable to enable curses window management.
25085 List and give the size of all displayed windows.
25089 Display the next layout.
25092 Display the previous layout.
25095 Display the source window only.
25098 Display the assembly window only.
25101 Display the source and assembly window.
25104 Display the register window together with the source or assembly window.
25108 Make the next window active for scrolling.
25111 Make the previous window active for scrolling.
25114 Make the source window active for scrolling.
25117 Make the assembly window active for scrolling.
25120 Make the register window active for scrolling.
25123 Make the command window active for scrolling.
25127 Refresh the screen. This is similar to typing @kbd{C-L}.
25129 @item tui reg float
25131 Show the floating point registers in the register window.
25133 @item tui reg general
25134 Show the general registers in the register window.
25137 Show the next register group. The list of register groups as well as
25138 their order is target specific. The predefined register groups are the
25139 following: @code{general}, @code{float}, @code{system}, @code{vector},
25140 @code{all}, @code{save}, @code{restore}.
25142 @item tui reg system
25143 Show the system registers in the register window.
25147 Update the source window and the current execution point.
25149 @item winheight @var{name} +@var{count}
25150 @itemx winheight @var{name} -@var{count}
25152 Change the height of the window @var{name} by @var{count}
25153 lines. Positive counts increase the height, while negative counts
25156 @item tabset @var{nchars}
25158 Set the width of tab stops to be @var{nchars} characters.
25161 @node TUI Configuration
25162 @section TUI Configuration Variables
25163 @cindex TUI configuration variables
25165 Several configuration variables control the appearance of TUI windows.
25168 @item set tui border-kind @var{kind}
25169 @kindex set tui border-kind
25170 Select the border appearance for the source, assembly and register windows.
25171 The possible values are the following:
25174 Use a space character to draw the border.
25177 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
25180 Use the Alternate Character Set to draw the border. The border is
25181 drawn using character line graphics if the terminal supports them.
25184 @item set tui border-mode @var{mode}
25185 @kindex set tui border-mode
25186 @itemx set tui active-border-mode @var{mode}
25187 @kindex set tui active-border-mode
25188 Select the display attributes for the borders of the inactive windows
25189 or the active window. The @var{mode} can be one of the following:
25192 Use normal attributes to display the border.
25198 Use reverse video mode.
25201 Use half bright mode.
25203 @item half-standout
25204 Use half bright and standout mode.
25207 Use extra bright or bold mode.
25209 @item bold-standout
25210 Use extra bright or bold and standout mode.
25215 @chapter Using @value{GDBN} under @sc{gnu} Emacs
25218 @cindex @sc{gnu} Emacs
25219 A special interface allows you to use @sc{gnu} Emacs to view (and
25220 edit) the source files for the program you are debugging with
25223 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
25224 executable file you want to debug as an argument. This command starts
25225 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
25226 created Emacs buffer.
25227 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
25229 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
25234 All ``terminal'' input and output goes through an Emacs buffer, called
25237 This applies both to @value{GDBN} commands and their output, and to the input
25238 and output done by the program you are debugging.
25240 This is useful because it means that you can copy the text of previous
25241 commands and input them again; you can even use parts of the output
25244 All the facilities of Emacs' Shell mode are available for interacting
25245 with your program. In particular, you can send signals the usual
25246 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
25250 @value{GDBN} displays source code through Emacs.
25252 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
25253 source file for that frame and puts an arrow (@samp{=>}) at the
25254 left margin of the current line. Emacs uses a separate buffer for
25255 source display, and splits the screen to show both your @value{GDBN} session
25258 Explicit @value{GDBN} @code{list} or search commands still produce output as
25259 usual, but you probably have no reason to use them from Emacs.
25262 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
25263 a graphical mode, enabled by default, which provides further buffers
25264 that can control the execution and describe the state of your program.
25265 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
25267 If you specify an absolute file name when prompted for the @kbd{M-x
25268 gdb} argument, then Emacs sets your current working directory to where
25269 your program resides. If you only specify the file name, then Emacs
25270 sets your current working directory to the directory associated
25271 with the previous buffer. In this case, @value{GDBN} may find your
25272 program by searching your environment's @code{PATH} variable, but on
25273 some operating systems it might not find the source. So, although the
25274 @value{GDBN} input and output session proceeds normally, the auxiliary
25275 buffer does not display the current source and line of execution.
25277 The initial working directory of @value{GDBN} is printed on the top
25278 line of the GUD buffer and this serves as a default for the commands
25279 that specify files for @value{GDBN} to operate on. @xref{Files,
25280 ,Commands to Specify Files}.
25282 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
25283 need to call @value{GDBN} by a different name (for example, if you
25284 keep several configurations around, with different names) you can
25285 customize the Emacs variable @code{gud-gdb-command-name} to run the
25288 In the GUD buffer, you can use these special Emacs commands in
25289 addition to the standard Shell mode commands:
25293 Describe the features of Emacs' GUD Mode.
25296 Execute to another source line, like the @value{GDBN} @code{step} command; also
25297 update the display window to show the current file and location.
25300 Execute to next source line in this function, skipping all function
25301 calls, like the @value{GDBN} @code{next} command. Then update the display window
25302 to show the current file and location.
25305 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
25306 display window accordingly.
25309 Execute until exit from the selected stack frame, like the @value{GDBN}
25310 @code{finish} command.
25313 Continue execution of your program, like the @value{GDBN} @code{continue}
25317 Go up the number of frames indicated by the numeric argument
25318 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
25319 like the @value{GDBN} @code{up} command.
25322 Go down the number of frames indicated by the numeric argument, like the
25323 @value{GDBN} @code{down} command.
25326 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
25327 tells @value{GDBN} to set a breakpoint on the source line point is on.
25329 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
25330 separate frame which shows a backtrace when the GUD buffer is current.
25331 Move point to any frame in the stack and type @key{RET} to make it
25332 become the current frame and display the associated source in the
25333 source buffer. Alternatively, click @kbd{Mouse-2} to make the
25334 selected frame become the current one. In graphical mode, the
25335 speedbar displays watch expressions.
25337 If you accidentally delete the source-display buffer, an easy way to get
25338 it back is to type the command @code{f} in the @value{GDBN} buffer, to
25339 request a frame display; when you run under Emacs, this recreates
25340 the source buffer if necessary to show you the context of the current
25343 The source files displayed in Emacs are in ordinary Emacs buffers
25344 which are visiting the source files in the usual way. You can edit
25345 the files with these buffers if you wish; but keep in mind that @value{GDBN}
25346 communicates with Emacs in terms of line numbers. If you add or
25347 delete lines from the text, the line numbers that @value{GDBN} knows cease
25348 to correspond properly with the code.
25350 A more detailed description of Emacs' interaction with @value{GDBN} is
25351 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
25354 @c The following dropped because Epoch is nonstandard. Reactivate
25355 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
25357 @kindex Emacs Epoch environment
25361 Version 18 of @sc{gnu} Emacs has a built-in window system
25362 called the @code{epoch}
25363 environment. Users of this environment can use a new command,
25364 @code{inspect} which performs identically to @code{print} except that
25365 each value is printed in its own window.
25370 @chapter The @sc{gdb/mi} Interface
25372 @unnumberedsec Function and Purpose
25374 @cindex @sc{gdb/mi}, its purpose
25375 @sc{gdb/mi} is a line based machine oriented text interface to
25376 @value{GDBN} and is activated by specifying using the
25377 @option{--interpreter} command line option (@pxref{Mode Options}). It
25378 is specifically intended to support the development of systems which
25379 use the debugger as just one small component of a larger system.
25381 This chapter is a specification of the @sc{gdb/mi} interface. It is written
25382 in the form of a reference manual.
25384 Note that @sc{gdb/mi} is still under construction, so some of the
25385 features described below are incomplete and subject to change
25386 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
25388 @unnumberedsec Notation and Terminology
25390 @cindex notational conventions, for @sc{gdb/mi}
25391 This chapter uses the following notation:
25395 @code{|} separates two alternatives.
25398 @code{[ @var{something} ]} indicates that @var{something} is optional:
25399 it may or may not be given.
25402 @code{( @var{group} )*} means that @var{group} inside the parentheses
25403 may repeat zero or more times.
25406 @code{( @var{group} )+} means that @var{group} inside the parentheses
25407 may repeat one or more times.
25410 @code{"@var{string}"} means a literal @var{string}.
25414 @heading Dependencies
25418 * GDB/MI General Design::
25419 * GDB/MI Command Syntax::
25420 * GDB/MI Compatibility with CLI::
25421 * GDB/MI Development and Front Ends::
25422 * GDB/MI Output Records::
25423 * GDB/MI Simple Examples::
25424 * GDB/MI Command Description Format::
25425 * GDB/MI Breakpoint Commands::
25426 * GDB/MI Program Context::
25427 * GDB/MI Thread Commands::
25428 * GDB/MI Ada Tasking Commands::
25429 * GDB/MI Program Execution::
25430 * GDB/MI Stack Manipulation::
25431 * GDB/MI Variable Objects::
25432 * GDB/MI Data Manipulation::
25433 * GDB/MI Tracepoint Commands::
25434 * GDB/MI Symbol Query::
25435 * GDB/MI File Commands::
25437 * GDB/MI Kod Commands::
25438 * GDB/MI Memory Overlay Commands::
25439 * GDB/MI Signal Handling Commands::
25441 * GDB/MI Target Manipulation::
25442 * GDB/MI File Transfer Commands::
25443 * GDB/MI Miscellaneous Commands::
25446 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25447 @node GDB/MI General Design
25448 @section @sc{gdb/mi} General Design
25449 @cindex GDB/MI General Design
25451 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
25452 parts---commands sent to @value{GDBN}, responses to those commands
25453 and notifications. Each command results in exactly one response,
25454 indicating either successful completion of the command, or an error.
25455 For the commands that do not resume the target, the response contains the
25456 requested information. For the commands that resume the target, the
25457 response only indicates whether the target was successfully resumed.
25458 Notifications is the mechanism for reporting changes in the state of the
25459 target, or in @value{GDBN} state, that cannot conveniently be associated with
25460 a command and reported as part of that command response.
25462 The important examples of notifications are:
25466 Exec notifications. These are used to report changes in
25467 target state---when a target is resumed, or stopped. It would not
25468 be feasible to include this information in response of resuming
25469 commands, because one resume commands can result in multiple events in
25470 different threads. Also, quite some time may pass before any event
25471 happens in the target, while a frontend needs to know whether the resuming
25472 command itself was successfully executed.
25475 Console output, and status notifications. Console output
25476 notifications are used to report output of CLI commands, as well as
25477 diagnostics for other commands. Status notifications are used to
25478 report the progress of a long-running operation. Naturally, including
25479 this information in command response would mean no output is produced
25480 until the command is finished, which is undesirable.
25483 General notifications. Commands may have various side effects on
25484 the @value{GDBN} or target state beyond their official purpose. For example,
25485 a command may change the selected thread. Although such changes can
25486 be included in command response, using notification allows for more
25487 orthogonal frontend design.
25491 There's no guarantee that whenever an MI command reports an error,
25492 @value{GDBN} or the target are in any specific state, and especially,
25493 the state is not reverted to the state before the MI command was
25494 processed. Therefore, whenever an MI command results in an error,
25495 we recommend that the frontend refreshes all the information shown in
25496 the user interface.
25500 * Context management::
25501 * Asynchronous and non-stop modes::
25505 @node Context management
25506 @subsection Context management
25508 In most cases when @value{GDBN} accesses the target, this access is
25509 done in context of a specific thread and frame (@pxref{Frames}).
25510 Often, even when accessing global data, the target requires that a thread
25511 be specified. The CLI interface maintains the selected thread and frame,
25512 and supplies them to target on each command. This is convenient,
25513 because a command line user would not want to specify that information
25514 explicitly on each command, and because user interacts with
25515 @value{GDBN} via a single terminal, so no confusion is possible as
25516 to what thread and frame are the current ones.
25518 In the case of MI, the concept of selected thread and frame is less
25519 useful. First, a frontend can easily remember this information
25520 itself. Second, a graphical frontend can have more than one window,
25521 each one used for debugging a different thread, and the frontend might
25522 want to access additional threads for internal purposes. This
25523 increases the risk that by relying on implicitly selected thread, the
25524 frontend may be operating on a wrong one. Therefore, each MI command
25525 should explicitly specify which thread and frame to operate on. To
25526 make it possible, each MI command accepts the @samp{--thread} and
25527 @samp{--frame} options, the value to each is @value{GDBN} identifier
25528 for thread and frame to operate on.
25530 Usually, each top-level window in a frontend allows the user to select
25531 a thread and a frame, and remembers the user selection for further
25532 operations. However, in some cases @value{GDBN} may suggest that the
25533 current thread be changed. For example, when stopping on a breakpoint
25534 it is reasonable to switch to the thread where breakpoint is hit. For
25535 another example, if the user issues the CLI @samp{thread} command via
25536 the frontend, it is desirable to change the frontend's selected thread to the
25537 one specified by user. @value{GDBN} communicates the suggestion to
25538 change current thread using the @samp{=thread-selected} notification.
25539 No such notification is available for the selected frame at the moment.
25541 Note that historically, MI shares the selected thread with CLI, so
25542 frontends used the @code{-thread-select} to execute commands in the
25543 right context. However, getting this to work right is cumbersome. The
25544 simplest way is for frontend to emit @code{-thread-select} command
25545 before every command. This doubles the number of commands that need
25546 to be sent. The alternative approach is to suppress @code{-thread-select}
25547 if the selected thread in @value{GDBN} is supposed to be identical to the
25548 thread the frontend wants to operate on. However, getting this
25549 optimization right can be tricky. In particular, if the frontend
25550 sends several commands to @value{GDBN}, and one of the commands changes the
25551 selected thread, then the behaviour of subsequent commands will
25552 change. So, a frontend should either wait for response from such
25553 problematic commands, or explicitly add @code{-thread-select} for
25554 all subsequent commands. No frontend is known to do this exactly
25555 right, so it is suggested to just always pass the @samp{--thread} and
25556 @samp{--frame} options.
25558 @node Asynchronous and non-stop modes
25559 @subsection Asynchronous command execution and non-stop mode
25561 On some targets, @value{GDBN} is capable of processing MI commands
25562 even while the target is running. This is called @dfn{asynchronous
25563 command execution} (@pxref{Background Execution}). The frontend may
25564 specify a preferrence for asynchronous execution using the
25565 @code{-gdb-set target-async 1} command, which should be emitted before
25566 either running the executable or attaching to the target. After the
25567 frontend has started the executable or attached to the target, it can
25568 find if asynchronous execution is enabled using the
25569 @code{-list-target-features} command.
25571 Even if @value{GDBN} can accept a command while target is running,
25572 many commands that access the target do not work when the target is
25573 running. Therefore, asynchronous command execution is most useful
25574 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
25575 it is possible to examine the state of one thread, while other threads
25578 When a given thread is running, MI commands that try to access the
25579 target in the context of that thread may not work, or may work only on
25580 some targets. In particular, commands that try to operate on thread's
25581 stack will not work, on any target. Commands that read memory, or
25582 modify breakpoints, may work or not work, depending on the target. Note
25583 that even commands that operate on global state, such as @code{print},
25584 @code{set}, and breakpoint commands, still access the target in the
25585 context of a specific thread, so frontend should try to find a
25586 stopped thread and perform the operation on that thread (using the
25587 @samp{--thread} option).
25589 Which commands will work in the context of a running thread is
25590 highly target dependent. However, the two commands
25591 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
25592 to find the state of a thread, will always work.
25594 @node Thread groups
25595 @subsection Thread groups
25596 @value{GDBN} may be used to debug several processes at the same time.
25597 On some platfroms, @value{GDBN} may support debugging of several
25598 hardware systems, each one having several cores with several different
25599 processes running on each core. This section describes the MI
25600 mechanism to support such debugging scenarios.
25602 The key observation is that regardless of the structure of the
25603 target, MI can have a global list of threads, because most commands that
25604 accept the @samp{--thread} option do not need to know what process that
25605 thread belongs to. Therefore, it is not necessary to introduce
25606 neither additional @samp{--process} option, nor an notion of the
25607 current process in the MI interface. The only strictly new feature
25608 that is required is the ability to find how the threads are grouped
25611 To allow the user to discover such grouping, and to support arbitrary
25612 hierarchy of machines/cores/processes, MI introduces the concept of a
25613 @dfn{thread group}. Thread group is a collection of threads and other
25614 thread groups. A thread group always has a string identifier, a type,
25615 and may have additional attributes specific to the type. A new
25616 command, @code{-list-thread-groups}, returns the list of top-level
25617 thread groups, which correspond to processes that @value{GDBN} is
25618 debugging at the moment. By passing an identifier of a thread group
25619 to the @code{-list-thread-groups} command, it is possible to obtain
25620 the members of specific thread group.
25622 To allow the user to easily discover processes, and other objects, he
25623 wishes to debug, a concept of @dfn{available thread group} is
25624 introduced. Available thread group is an thread group that
25625 @value{GDBN} is not debugging, but that can be attached to, using the
25626 @code{-target-attach} command. The list of available top-level thread
25627 groups can be obtained using @samp{-list-thread-groups --available}.
25628 In general, the content of a thread group may be only retrieved only
25629 after attaching to that thread group.
25631 Thread groups are related to inferiors (@pxref{Inferiors and
25632 Programs}). Each inferior corresponds to a thread group of a special
25633 type @samp{process}, and some additional operations are permitted on
25634 such thread groups.
25636 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25637 @node GDB/MI Command Syntax
25638 @section @sc{gdb/mi} Command Syntax
25641 * GDB/MI Input Syntax::
25642 * GDB/MI Output Syntax::
25645 @node GDB/MI Input Syntax
25646 @subsection @sc{gdb/mi} Input Syntax
25648 @cindex input syntax for @sc{gdb/mi}
25649 @cindex @sc{gdb/mi}, input syntax
25651 @item @var{command} @expansion{}
25652 @code{@var{cli-command} | @var{mi-command}}
25654 @item @var{cli-command} @expansion{}
25655 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
25656 @var{cli-command} is any existing @value{GDBN} CLI command.
25658 @item @var{mi-command} @expansion{}
25659 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
25660 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
25662 @item @var{token} @expansion{}
25663 "any sequence of digits"
25665 @item @var{option} @expansion{}
25666 @code{"-" @var{parameter} [ " " @var{parameter} ]}
25668 @item @var{parameter} @expansion{}
25669 @code{@var{non-blank-sequence} | @var{c-string}}
25671 @item @var{operation} @expansion{}
25672 @emph{any of the operations described in this chapter}
25674 @item @var{non-blank-sequence} @expansion{}
25675 @emph{anything, provided it doesn't contain special characters such as
25676 "-", @var{nl}, """ and of course " "}
25678 @item @var{c-string} @expansion{}
25679 @code{""" @var{seven-bit-iso-c-string-content} """}
25681 @item @var{nl} @expansion{}
25690 The CLI commands are still handled by the @sc{mi} interpreter; their
25691 output is described below.
25694 The @code{@var{token}}, when present, is passed back when the command
25698 Some @sc{mi} commands accept optional arguments as part of the parameter
25699 list. Each option is identified by a leading @samp{-} (dash) and may be
25700 followed by an optional argument parameter. Options occur first in the
25701 parameter list and can be delimited from normal parameters using
25702 @samp{--} (this is useful when some parameters begin with a dash).
25709 We want easy access to the existing CLI syntax (for debugging).
25712 We want it to be easy to spot a @sc{mi} operation.
25715 @node GDB/MI Output Syntax
25716 @subsection @sc{gdb/mi} Output Syntax
25718 @cindex output syntax of @sc{gdb/mi}
25719 @cindex @sc{gdb/mi}, output syntax
25720 The output from @sc{gdb/mi} consists of zero or more out-of-band records
25721 followed, optionally, by a single result record. This result record
25722 is for the most recent command. The sequence of output records is
25723 terminated by @samp{(gdb)}.
25725 If an input command was prefixed with a @code{@var{token}} then the
25726 corresponding output for that command will also be prefixed by that same
25730 @item @var{output} @expansion{}
25731 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
25733 @item @var{result-record} @expansion{}
25734 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
25736 @item @var{out-of-band-record} @expansion{}
25737 @code{@var{async-record} | @var{stream-record}}
25739 @item @var{async-record} @expansion{}
25740 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
25742 @item @var{exec-async-output} @expansion{}
25743 @code{[ @var{token} ] "*" @var{async-output}}
25745 @item @var{status-async-output} @expansion{}
25746 @code{[ @var{token} ] "+" @var{async-output}}
25748 @item @var{notify-async-output} @expansion{}
25749 @code{[ @var{token} ] "=" @var{async-output}}
25751 @item @var{async-output} @expansion{}
25752 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
25754 @item @var{result-class} @expansion{}
25755 @code{"done" | "running" | "connected" | "error" | "exit"}
25757 @item @var{async-class} @expansion{}
25758 @code{"stopped" | @var{others}} (where @var{others} will be added
25759 depending on the needs---this is still in development).
25761 @item @var{result} @expansion{}
25762 @code{ @var{variable} "=" @var{value}}
25764 @item @var{variable} @expansion{}
25765 @code{ @var{string} }
25767 @item @var{value} @expansion{}
25768 @code{ @var{const} | @var{tuple} | @var{list} }
25770 @item @var{const} @expansion{}
25771 @code{@var{c-string}}
25773 @item @var{tuple} @expansion{}
25774 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
25776 @item @var{list} @expansion{}
25777 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
25778 @var{result} ( "," @var{result} )* "]" }
25780 @item @var{stream-record} @expansion{}
25781 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
25783 @item @var{console-stream-output} @expansion{}
25784 @code{"~" @var{c-string}}
25786 @item @var{target-stream-output} @expansion{}
25787 @code{"@@" @var{c-string}}
25789 @item @var{log-stream-output} @expansion{}
25790 @code{"&" @var{c-string}}
25792 @item @var{nl} @expansion{}
25795 @item @var{token} @expansion{}
25796 @emph{any sequence of digits}.
25804 All output sequences end in a single line containing a period.
25807 The @code{@var{token}} is from the corresponding request. Note that
25808 for all async output, while the token is allowed by the grammar and
25809 may be output by future versions of @value{GDBN} for select async
25810 output messages, it is generally omitted. Frontends should treat
25811 all async output as reporting general changes in the state of the
25812 target and there should be no need to associate async output to any
25816 @cindex status output in @sc{gdb/mi}
25817 @var{status-async-output} contains on-going status information about the
25818 progress of a slow operation. It can be discarded. All status output is
25819 prefixed by @samp{+}.
25822 @cindex async output in @sc{gdb/mi}
25823 @var{exec-async-output} contains asynchronous state change on the target
25824 (stopped, started, disappeared). All async output is prefixed by
25828 @cindex notify output in @sc{gdb/mi}
25829 @var{notify-async-output} contains supplementary information that the
25830 client should handle (e.g., a new breakpoint information). All notify
25831 output is prefixed by @samp{=}.
25834 @cindex console output in @sc{gdb/mi}
25835 @var{console-stream-output} is output that should be displayed as is in the
25836 console. It is the textual response to a CLI command. All the console
25837 output is prefixed by @samp{~}.
25840 @cindex target output in @sc{gdb/mi}
25841 @var{target-stream-output} is the output produced by the target program.
25842 All the target output is prefixed by @samp{@@}.
25845 @cindex log output in @sc{gdb/mi}
25846 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
25847 instance messages that should be displayed as part of an error log. All
25848 the log output is prefixed by @samp{&}.
25851 @cindex list output in @sc{gdb/mi}
25852 New @sc{gdb/mi} commands should only output @var{lists} containing
25858 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
25859 details about the various output records.
25861 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25862 @node GDB/MI Compatibility with CLI
25863 @section @sc{gdb/mi} Compatibility with CLI
25865 @cindex compatibility, @sc{gdb/mi} and CLI
25866 @cindex @sc{gdb/mi}, compatibility with CLI
25868 For the developers convenience CLI commands can be entered directly,
25869 but there may be some unexpected behaviour. For example, commands
25870 that query the user will behave as if the user replied yes, breakpoint
25871 command lists are not executed and some CLI commands, such as
25872 @code{if}, @code{when} and @code{define}, prompt for further input with
25873 @samp{>}, which is not valid MI output.
25875 This feature may be removed at some stage in the future and it is
25876 recommended that front ends use the @code{-interpreter-exec} command
25877 (@pxref{-interpreter-exec}).
25879 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25880 @node GDB/MI Development and Front Ends
25881 @section @sc{gdb/mi} Development and Front Ends
25882 @cindex @sc{gdb/mi} development
25884 The application which takes the MI output and presents the state of the
25885 program being debugged to the user is called a @dfn{front end}.
25887 Although @sc{gdb/mi} is still incomplete, it is currently being used
25888 by a variety of front ends to @value{GDBN}. This makes it difficult
25889 to introduce new functionality without breaking existing usage. This
25890 section tries to minimize the problems by describing how the protocol
25893 Some changes in MI need not break a carefully designed front end, and
25894 for these the MI version will remain unchanged. The following is a
25895 list of changes that may occur within one level, so front ends should
25896 parse MI output in a way that can handle them:
25900 New MI commands may be added.
25903 New fields may be added to the output of any MI command.
25906 The range of values for fields with specified values, e.g.,
25907 @code{in_scope} (@pxref{-var-update}) may be extended.
25909 @c The format of field's content e.g type prefix, may change so parse it
25910 @c at your own risk. Yes, in general?
25912 @c The order of fields may change? Shouldn't really matter but it might
25913 @c resolve inconsistencies.
25916 If the changes are likely to break front ends, the MI version level
25917 will be increased by one. This will allow the front end to parse the
25918 output according to the MI version. Apart from mi0, new versions of
25919 @value{GDBN} will not support old versions of MI and it will be the
25920 responsibility of the front end to work with the new one.
25922 @c Starting with mi3, add a new command -mi-version that prints the MI
25925 The best way to avoid unexpected changes in MI that might break your front
25926 end is to make your project known to @value{GDBN} developers and
25927 follow development on @email{gdb@@sourceware.org} and
25928 @email{gdb-patches@@sourceware.org}.
25929 @cindex mailing lists
25931 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25932 @node GDB/MI Output Records
25933 @section @sc{gdb/mi} Output Records
25936 * GDB/MI Result Records::
25937 * GDB/MI Stream Records::
25938 * GDB/MI Async Records::
25939 * GDB/MI Frame Information::
25940 * GDB/MI Thread Information::
25941 * GDB/MI Ada Exception Information::
25944 @node GDB/MI Result Records
25945 @subsection @sc{gdb/mi} Result Records
25947 @cindex result records in @sc{gdb/mi}
25948 @cindex @sc{gdb/mi}, result records
25949 In addition to a number of out-of-band notifications, the response to a
25950 @sc{gdb/mi} command includes one of the following result indications:
25954 @item "^done" [ "," @var{results} ]
25955 The synchronous operation was successful, @code{@var{results}} are the return
25960 This result record is equivalent to @samp{^done}. Historically, it
25961 was output instead of @samp{^done} if the command has resumed the
25962 target. This behaviour is maintained for backward compatibility, but
25963 all frontends should treat @samp{^done} and @samp{^running}
25964 identically and rely on the @samp{*running} output record to determine
25965 which threads are resumed.
25969 @value{GDBN} has connected to a remote target.
25971 @item "^error" "," @var{c-string}
25973 The operation failed. The @code{@var{c-string}} contains the corresponding
25978 @value{GDBN} has terminated.
25982 @node GDB/MI Stream Records
25983 @subsection @sc{gdb/mi} Stream Records
25985 @cindex @sc{gdb/mi}, stream records
25986 @cindex stream records in @sc{gdb/mi}
25987 @value{GDBN} internally maintains a number of output streams: the console, the
25988 target, and the log. The output intended for each of these streams is
25989 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
25991 Each stream record begins with a unique @dfn{prefix character} which
25992 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
25993 Syntax}). In addition to the prefix, each stream record contains a
25994 @code{@var{string-output}}. This is either raw text (with an implicit new
25995 line) or a quoted C string (which does not contain an implicit newline).
25998 @item "~" @var{string-output}
25999 The console output stream contains text that should be displayed in the
26000 CLI console window. It contains the textual responses to CLI commands.
26002 @item "@@" @var{string-output}
26003 The target output stream contains any textual output from the running
26004 target. This is only present when GDB's event loop is truly
26005 asynchronous, which is currently only the case for remote targets.
26007 @item "&" @var{string-output}
26008 The log stream contains debugging messages being produced by @value{GDBN}'s
26012 @node GDB/MI Async Records
26013 @subsection @sc{gdb/mi} Async Records
26015 @cindex async records in @sc{gdb/mi}
26016 @cindex @sc{gdb/mi}, async records
26017 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
26018 additional changes that have occurred. Those changes can either be a
26019 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
26020 target activity (e.g., target stopped).
26022 The following is the list of possible async records:
26026 @item *running,thread-id="@var{thread}"
26027 The target is now running. The @var{thread} field tells which
26028 specific thread is now running, and can be @samp{all} if all threads
26029 are running. The frontend should assume that no interaction with a
26030 running thread is possible after this notification is produced.
26031 The frontend should not assume that this notification is output
26032 only once for any command. @value{GDBN} may emit this notification
26033 several times, either for different threads, because it cannot resume
26034 all threads together, or even for a single thread, if the thread must
26035 be stepped though some code before letting it run freely.
26037 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
26038 The target has stopped. The @var{reason} field can have one of the
26042 @item breakpoint-hit
26043 A breakpoint was reached.
26044 @item watchpoint-trigger
26045 A watchpoint was triggered.
26046 @item read-watchpoint-trigger
26047 A read watchpoint was triggered.
26048 @item access-watchpoint-trigger
26049 An access watchpoint was triggered.
26050 @item function-finished
26051 An -exec-finish or similar CLI command was accomplished.
26052 @item location-reached
26053 An -exec-until or similar CLI command was accomplished.
26054 @item watchpoint-scope
26055 A watchpoint has gone out of scope.
26056 @item end-stepping-range
26057 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
26058 similar CLI command was accomplished.
26059 @item exited-signalled
26060 The inferior exited because of a signal.
26062 The inferior exited.
26063 @item exited-normally
26064 The inferior exited normally.
26065 @item signal-received
26066 A signal was received by the inferior.
26069 The @var{id} field identifies the thread that directly caused the stop
26070 -- for example by hitting a breakpoint. Depending on whether all-stop
26071 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
26072 stop all threads, or only the thread that directly triggered the stop.
26073 If all threads are stopped, the @var{stopped} field will have the
26074 value of @code{"all"}. Otherwise, the value of the @var{stopped}
26075 field will be a list of thread identifiers. Presently, this list will
26076 always include a single thread, but frontend should be prepared to see
26077 several threads in the list. The @var{core} field reports the
26078 processor core on which the stop event has happened. This field may be absent
26079 if such information is not available.
26081 @item =thread-group-added,id="@var{id}"
26082 @itemx =thread-group-removed,id="@var{id}"
26083 A thread group was either added or removed. The @var{id} field
26084 contains the @value{GDBN} identifier of the thread group. When a thread
26085 group is added, it generally might not be associated with a running
26086 process. When a thread group is removed, its id becomes invalid and
26087 cannot be used in any way.
26089 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
26090 A thread group became associated with a running program,
26091 either because the program was just started or the thread group
26092 was attached to a program. The @var{id} field contains the
26093 @value{GDBN} identifier of the thread group. The @var{pid} field
26094 contains process identifier, specific to the operating system.
26096 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
26097 A thread group is no longer associated with a running program,
26098 either because the program has exited, or because it was detached
26099 from. The @var{id} field contains the @value{GDBN} identifier of the
26100 thread group. @var{code} is the exit code of the inferior; it exists
26101 only when the inferior exited with some code.
26103 @item =thread-created,id="@var{id}",group-id="@var{gid}"
26104 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
26105 A thread either was created, or has exited. The @var{id} field
26106 contains the @value{GDBN} identifier of the thread. The @var{gid}
26107 field identifies the thread group this thread belongs to.
26109 @item =thread-selected,id="@var{id}"
26110 Informs that the selected thread was changed as result of the last
26111 command. This notification is not emitted as result of @code{-thread-select}
26112 command but is emitted whenever an MI command that is not documented
26113 to change the selected thread actually changes it. In particular,
26114 invoking, directly or indirectly (via user-defined command), the CLI
26115 @code{thread} command, will generate this notification.
26117 We suggest that in response to this notification, front ends
26118 highlight the selected thread and cause subsequent commands to apply to
26121 @item =library-loaded,...
26122 Reports that a new library file was loaded by the program. This
26123 notification has 4 fields---@var{id}, @var{target-name},
26124 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
26125 opaque identifier of the library. For remote debugging case,
26126 @var{target-name} and @var{host-name} fields give the name of the
26127 library file on the target, and on the host respectively. For native
26128 debugging, both those fields have the same value. The
26129 @var{symbols-loaded} field is emitted only for backward compatibility
26130 and should not be relied on to convey any useful information. The
26131 @var{thread-group} field, if present, specifies the id of the thread
26132 group in whose context the library was loaded. If the field is
26133 absent, it means the library was loaded in the context of all present
26136 @item =library-unloaded,...
26137 Reports that a library was unloaded by the program. This notification
26138 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
26139 the same meaning as for the @code{=library-loaded} notification.
26140 The @var{thread-group} field, if present, specifies the id of the
26141 thread group in whose context the library was unloaded. If the field is
26142 absent, it means the library was unloaded in the context of all present
26145 @item =breakpoint-created,bkpt=@{...@}
26146 @itemx =breakpoint-modified,bkpt=@{...@}
26147 @itemx =breakpoint-deleted,bkpt=@{...@}
26148 Reports that a breakpoint was created, modified, or deleted,
26149 respectively. Only user-visible breakpoints are reported to the MI
26152 The @var{bkpt} argument is of the same form as returned by the various
26153 breakpoint commands; @xref{GDB/MI Breakpoint Commands}.
26155 Note that if a breakpoint is emitted in the result record of a
26156 command, then it will not also be emitted in an async record.
26160 @node GDB/MI Frame Information
26161 @subsection @sc{gdb/mi} Frame Information
26163 Response from many MI commands includes an information about stack
26164 frame. This information is a tuple that may have the following
26169 The level of the stack frame. The innermost frame has the level of
26170 zero. This field is always present.
26173 The name of the function corresponding to the frame. This field may
26174 be absent if @value{GDBN} is unable to determine the function name.
26177 The code address for the frame. This field is always present.
26180 The name of the source files that correspond to the frame's code
26181 address. This field may be absent.
26184 The source line corresponding to the frames' code address. This field
26188 The name of the binary file (either executable or shared library) the
26189 corresponds to the frame's code address. This field may be absent.
26193 @node GDB/MI Thread Information
26194 @subsection @sc{gdb/mi} Thread Information
26196 Whenever @value{GDBN} has to report an information about a thread, it
26197 uses a tuple with the following fields:
26201 The numeric id assigned to the thread by @value{GDBN}. This field is
26205 Target-specific string identifying the thread. This field is always present.
26208 Additional information about the thread provided by the target.
26209 It is supposed to be human-readable and not interpreted by the
26210 frontend. This field is optional.
26213 Either @samp{stopped} or @samp{running}, depending on whether the
26214 thread is presently running. This field is always present.
26217 The value of this field is an integer number of the processor core the
26218 thread was last seen on. This field is optional.
26221 @node GDB/MI Ada Exception Information
26222 @subsection @sc{gdb/mi} Ada Exception Information
26224 Whenever a @code{*stopped} record is emitted because the program
26225 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
26226 @value{GDBN} provides the name of the exception that was raised via
26227 the @code{exception-name} field.
26229 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26230 @node GDB/MI Simple Examples
26231 @section Simple Examples of @sc{gdb/mi} Interaction
26232 @cindex @sc{gdb/mi}, simple examples
26234 This subsection presents several simple examples of interaction using
26235 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
26236 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
26237 the output received from @sc{gdb/mi}.
26239 Note the line breaks shown in the examples are here only for
26240 readability, they don't appear in the real output.
26242 @subheading Setting a Breakpoint
26244 Setting a breakpoint generates synchronous output which contains detailed
26245 information of the breakpoint.
26248 -> -break-insert main
26249 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26250 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26251 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
26255 @subheading Program Execution
26257 Program execution generates asynchronous records and MI gives the
26258 reason that execution stopped.
26264 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
26265 frame=@{addr="0x08048564",func="main",
26266 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
26267 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
26272 <- *stopped,reason="exited-normally"
26276 @subheading Quitting @value{GDBN}
26278 Quitting @value{GDBN} just prints the result class @samp{^exit}.
26286 Please note that @samp{^exit} is printed immediately, but it might
26287 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
26288 performs necessary cleanups, including killing programs being debugged
26289 or disconnecting from debug hardware, so the frontend should wait till
26290 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
26291 fails to exit in reasonable time.
26293 @subheading A Bad Command
26295 Here's what happens if you pass a non-existent command:
26299 <- ^error,msg="Undefined MI command: rubbish"
26304 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26305 @node GDB/MI Command Description Format
26306 @section @sc{gdb/mi} Command Description Format
26308 The remaining sections describe blocks of commands. Each block of
26309 commands is laid out in a fashion similar to this section.
26311 @subheading Motivation
26313 The motivation for this collection of commands.
26315 @subheading Introduction
26317 A brief introduction to this collection of commands as a whole.
26319 @subheading Commands
26321 For each command in the block, the following is described:
26323 @subsubheading Synopsis
26326 -command @var{args}@dots{}
26329 @subsubheading Result
26331 @subsubheading @value{GDBN} Command
26333 The corresponding @value{GDBN} CLI command(s), if any.
26335 @subsubheading Example
26337 Example(s) formatted for readability. Some of the described commands have
26338 not been implemented yet and these are labeled N.A.@: (not available).
26341 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26342 @node GDB/MI Breakpoint Commands
26343 @section @sc{gdb/mi} Breakpoint Commands
26345 @cindex breakpoint commands for @sc{gdb/mi}
26346 @cindex @sc{gdb/mi}, breakpoint commands
26347 This section documents @sc{gdb/mi} commands for manipulating
26350 @subheading The @code{-break-after} Command
26351 @findex -break-after
26353 @subsubheading Synopsis
26356 -break-after @var{number} @var{count}
26359 The breakpoint number @var{number} is not in effect until it has been
26360 hit @var{count} times. To see how this is reflected in the output of
26361 the @samp{-break-list} command, see the description of the
26362 @samp{-break-list} command below.
26364 @subsubheading @value{GDBN} Command
26366 The corresponding @value{GDBN} command is @samp{ignore}.
26368 @subsubheading Example
26373 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26374 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26375 fullname="/home/foo/hello.c",line="5",times="0"@}
26382 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26383 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26384 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26385 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26386 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26387 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26388 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26389 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26390 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26391 line="5",times="0",ignore="3"@}]@}
26396 @subheading The @code{-break-catch} Command
26397 @findex -break-catch
26400 @subheading The @code{-break-commands} Command
26401 @findex -break-commands
26403 @subsubheading Synopsis
26406 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
26409 Specifies the CLI commands that should be executed when breakpoint
26410 @var{number} is hit. The parameters @var{command1} to @var{commandN}
26411 are the commands. If no command is specified, any previously-set
26412 commands are cleared. @xref{Break Commands}. Typical use of this
26413 functionality is tracing a program, that is, printing of values of
26414 some variables whenever breakpoint is hit and then continuing.
26416 @subsubheading @value{GDBN} Command
26418 The corresponding @value{GDBN} command is @samp{commands}.
26420 @subsubheading Example
26425 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26426 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26427 fullname="/home/foo/hello.c",line="5",times="0"@}
26429 -break-commands 1 "print v" "continue"
26434 @subheading The @code{-break-condition} Command
26435 @findex -break-condition
26437 @subsubheading Synopsis
26440 -break-condition @var{number} @var{expr}
26443 Breakpoint @var{number} will stop the program only if the condition in
26444 @var{expr} is true. The condition becomes part of the
26445 @samp{-break-list} output (see the description of the @samp{-break-list}
26448 @subsubheading @value{GDBN} Command
26450 The corresponding @value{GDBN} command is @samp{condition}.
26452 @subsubheading Example
26456 -break-condition 1 1
26460 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26461 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26462 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26463 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26464 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26465 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26466 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26467 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26468 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26469 line="5",cond="1",times="0",ignore="3"@}]@}
26473 @subheading The @code{-break-delete} Command
26474 @findex -break-delete
26476 @subsubheading Synopsis
26479 -break-delete ( @var{breakpoint} )+
26482 Delete the breakpoint(s) whose number(s) are specified in the argument
26483 list. This is obviously reflected in the breakpoint list.
26485 @subsubheading @value{GDBN} Command
26487 The corresponding @value{GDBN} command is @samp{delete}.
26489 @subsubheading Example
26497 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26498 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26499 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26500 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26501 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26502 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26503 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26508 @subheading The @code{-break-disable} Command
26509 @findex -break-disable
26511 @subsubheading Synopsis
26514 -break-disable ( @var{breakpoint} )+
26517 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
26518 break list is now set to @samp{n} for the named @var{breakpoint}(s).
26520 @subsubheading @value{GDBN} Command
26522 The corresponding @value{GDBN} command is @samp{disable}.
26524 @subsubheading Example
26532 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26533 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26534 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26535 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26536 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26537 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26538 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26539 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
26540 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26541 line="5",times="0"@}]@}
26545 @subheading The @code{-break-enable} Command
26546 @findex -break-enable
26548 @subsubheading Synopsis
26551 -break-enable ( @var{breakpoint} )+
26554 Enable (previously disabled) @var{breakpoint}(s).
26556 @subsubheading @value{GDBN} Command
26558 The corresponding @value{GDBN} command is @samp{enable}.
26560 @subsubheading Example
26568 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26569 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26570 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26571 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26572 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26573 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26574 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26575 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26576 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26577 line="5",times="0"@}]@}
26581 @subheading The @code{-break-info} Command
26582 @findex -break-info
26584 @subsubheading Synopsis
26587 -break-info @var{breakpoint}
26591 Get information about a single breakpoint.
26593 @subsubheading @value{GDBN} Command
26595 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
26597 @subsubheading Example
26600 @subheading The @code{-break-insert} Command
26601 @findex -break-insert
26603 @subsubheading Synopsis
26606 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
26607 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26608 [ -p @var{thread} ] [ @var{location} ]
26612 If specified, @var{location}, can be one of:
26619 @item filename:linenum
26620 @item filename:function
26624 The possible optional parameters of this command are:
26628 Insert a temporary breakpoint.
26630 Insert a hardware breakpoint.
26631 @item -c @var{condition}
26632 Make the breakpoint conditional on @var{condition}.
26633 @item -i @var{ignore-count}
26634 Initialize the @var{ignore-count}.
26636 If @var{location} cannot be parsed (for example if it
26637 refers to unknown files or functions), create a pending
26638 breakpoint. Without this flag, @value{GDBN} will report
26639 an error, and won't create a breakpoint, if @var{location}
26642 Create a disabled breakpoint.
26644 Create a tracepoint. @xref{Tracepoints}. When this parameter
26645 is used together with @samp{-h}, a fast tracepoint is created.
26648 @subsubheading Result
26650 The result is in the form:
26653 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
26654 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
26655 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
26656 times="@var{times}"@}
26660 where @var{number} is the @value{GDBN} number for this breakpoint,
26661 @var{funcname} is the name of the function where the breakpoint was
26662 inserted, @var{filename} is the name of the source file which contains
26663 this function, @var{lineno} is the source line number within that file
26664 and @var{times} the number of times that the breakpoint has been hit
26665 (always 0 for -break-insert but may be greater for -break-info or -break-list
26666 which use the same output).
26668 Note: this format is open to change.
26669 @c An out-of-band breakpoint instead of part of the result?
26671 @subsubheading @value{GDBN} Command
26673 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
26674 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
26676 @subsubheading Example
26681 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
26682 fullname="/home/foo/recursive2.c,line="4",times="0"@}
26684 -break-insert -t foo
26685 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
26686 fullname="/home/foo/recursive2.c,line="11",times="0"@}
26689 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26690 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26691 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26692 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26693 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26694 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26695 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26696 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26697 addr="0x0001072c", func="main",file="recursive2.c",
26698 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
26699 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
26700 addr="0x00010774",func="foo",file="recursive2.c",
26701 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
26703 -break-insert -r foo.*
26704 ~int foo(int, int);
26705 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
26706 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
26710 @subheading The @code{-break-list} Command
26711 @findex -break-list
26713 @subsubheading Synopsis
26719 Displays the list of inserted breakpoints, showing the following fields:
26723 number of the breakpoint
26725 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
26727 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
26730 is the breakpoint enabled or no: @samp{y} or @samp{n}
26732 memory location at which the breakpoint is set
26734 logical location of the breakpoint, expressed by function name, file
26737 number of times the breakpoint has been hit
26740 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
26741 @code{body} field is an empty list.
26743 @subsubheading @value{GDBN} Command
26745 The corresponding @value{GDBN} command is @samp{info break}.
26747 @subsubheading Example
26752 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26753 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26754 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26755 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26756 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26757 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26758 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26759 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26760 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
26761 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26762 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
26763 line="13",times="0"@}]@}
26767 Here's an example of the result when there are no breakpoints:
26772 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26773 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26774 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26775 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26776 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26777 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26778 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26783 @subheading The @code{-break-passcount} Command
26784 @findex -break-passcount
26786 @subsubheading Synopsis
26789 -break-passcount @var{tracepoint-number} @var{passcount}
26792 Set the passcount for tracepoint @var{tracepoint-number} to
26793 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
26794 is not a tracepoint, error is emitted. This corresponds to CLI
26795 command @samp{passcount}.
26797 @subheading The @code{-break-watch} Command
26798 @findex -break-watch
26800 @subsubheading Synopsis
26803 -break-watch [ -a | -r ]
26806 Create a watchpoint. With the @samp{-a} option it will create an
26807 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
26808 read from or on a write to the memory location. With the @samp{-r}
26809 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
26810 trigger only when the memory location is accessed for reading. Without
26811 either of the options, the watchpoint created is a regular watchpoint,
26812 i.e., it will trigger when the memory location is accessed for writing.
26813 @xref{Set Watchpoints, , Setting Watchpoints}.
26815 Note that @samp{-break-list} will report a single list of watchpoints and
26816 breakpoints inserted.
26818 @subsubheading @value{GDBN} Command
26820 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
26823 @subsubheading Example
26825 Setting a watchpoint on a variable in the @code{main} function:
26830 ^done,wpt=@{number="2",exp="x"@}
26835 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
26836 value=@{old="-268439212",new="55"@},
26837 frame=@{func="main",args=[],file="recursive2.c",
26838 fullname="/home/foo/bar/recursive2.c",line="5"@}
26842 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
26843 the program execution twice: first for the variable changing value, then
26844 for the watchpoint going out of scope.
26849 ^done,wpt=@{number="5",exp="C"@}
26854 *stopped,reason="watchpoint-trigger",
26855 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
26856 frame=@{func="callee4",args=[],
26857 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26858 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
26863 *stopped,reason="watchpoint-scope",wpnum="5",
26864 frame=@{func="callee3",args=[@{name="strarg",
26865 value="0x11940 \"A string argument.\""@}],
26866 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26867 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26871 Listing breakpoints and watchpoints, at different points in the program
26872 execution. Note that once the watchpoint goes out of scope, it is
26878 ^done,wpt=@{number="2",exp="C"@}
26881 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26882 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26883 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26884 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26885 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26886 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26887 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26888 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26889 addr="0x00010734",func="callee4",
26890 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26891 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
26892 bkpt=@{number="2",type="watchpoint",disp="keep",
26893 enabled="y",addr="",what="C",times="0"@}]@}
26898 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
26899 value=@{old="-276895068",new="3"@},
26900 frame=@{func="callee4",args=[],
26901 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26902 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
26905 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
26906 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26907 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26908 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26909 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26910 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26911 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26912 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26913 addr="0x00010734",func="callee4",
26914 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26915 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
26916 bkpt=@{number="2",type="watchpoint",disp="keep",
26917 enabled="y",addr="",what="C",times="-5"@}]@}
26921 ^done,reason="watchpoint-scope",wpnum="2",
26922 frame=@{func="callee3",args=[@{name="strarg",
26923 value="0x11940 \"A string argument.\""@}],
26924 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26925 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26928 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26929 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26930 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26931 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26932 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26933 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26934 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26935 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26936 addr="0x00010734",func="callee4",
26937 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26938 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
26943 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26944 @node GDB/MI Program Context
26945 @section @sc{gdb/mi} Program Context
26947 @subheading The @code{-exec-arguments} Command
26948 @findex -exec-arguments
26951 @subsubheading Synopsis
26954 -exec-arguments @var{args}
26957 Set the inferior program arguments, to be used in the next
26960 @subsubheading @value{GDBN} Command
26962 The corresponding @value{GDBN} command is @samp{set args}.
26964 @subsubheading Example
26968 -exec-arguments -v word
26975 @subheading The @code{-exec-show-arguments} Command
26976 @findex -exec-show-arguments
26978 @subsubheading Synopsis
26981 -exec-show-arguments
26984 Print the arguments of the program.
26986 @subsubheading @value{GDBN} Command
26988 The corresponding @value{GDBN} command is @samp{show args}.
26990 @subsubheading Example
26995 @subheading The @code{-environment-cd} Command
26996 @findex -environment-cd
26998 @subsubheading Synopsis
27001 -environment-cd @var{pathdir}
27004 Set @value{GDBN}'s working directory.
27006 @subsubheading @value{GDBN} Command
27008 The corresponding @value{GDBN} command is @samp{cd}.
27010 @subsubheading Example
27014 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27020 @subheading The @code{-environment-directory} Command
27021 @findex -environment-directory
27023 @subsubheading Synopsis
27026 -environment-directory [ -r ] [ @var{pathdir} ]+
27029 Add directories @var{pathdir} to beginning of search path for source files.
27030 If the @samp{-r} option is used, the search path is reset to the default
27031 search path. If directories @var{pathdir} are supplied in addition to the
27032 @samp{-r} option, the search path is first reset and then addition
27034 Multiple directories may be specified, separated by blanks. Specifying
27035 multiple directories in a single command
27036 results in the directories added to the beginning of the
27037 search path in the same order they were presented in the command.
27038 If blanks are needed as
27039 part of a directory name, double-quotes should be used around
27040 the name. In the command output, the path will show up separated
27041 by the system directory-separator character. The directory-separator
27042 character must not be used
27043 in any directory name.
27044 If no directories are specified, the current search path is displayed.
27046 @subsubheading @value{GDBN} Command
27048 The corresponding @value{GDBN} command is @samp{dir}.
27050 @subsubheading Example
27054 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27055 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27057 -environment-directory ""
27058 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27060 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
27061 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
27063 -environment-directory -r
27064 ^done,source-path="$cdir:$cwd"
27069 @subheading The @code{-environment-path} Command
27070 @findex -environment-path
27072 @subsubheading Synopsis
27075 -environment-path [ -r ] [ @var{pathdir} ]+
27078 Add directories @var{pathdir} to beginning of search path for object files.
27079 If the @samp{-r} option is used, the search path is reset to the original
27080 search path that existed at gdb start-up. If directories @var{pathdir} are
27081 supplied in addition to the
27082 @samp{-r} option, the search path is first reset and then addition
27084 Multiple directories may be specified, separated by blanks. Specifying
27085 multiple directories in a single command
27086 results in the directories added to the beginning of the
27087 search path in the same order they were presented in the command.
27088 If blanks are needed as
27089 part of a directory name, double-quotes should be used around
27090 the name. In the command output, the path will show up separated
27091 by the system directory-separator character. The directory-separator
27092 character must not be used
27093 in any directory name.
27094 If no directories are specified, the current path is displayed.
27097 @subsubheading @value{GDBN} Command
27099 The corresponding @value{GDBN} command is @samp{path}.
27101 @subsubheading Example
27106 ^done,path="/usr/bin"
27108 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
27109 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
27111 -environment-path -r /usr/local/bin
27112 ^done,path="/usr/local/bin:/usr/bin"
27117 @subheading The @code{-environment-pwd} Command
27118 @findex -environment-pwd
27120 @subsubheading Synopsis
27126 Show the current working directory.
27128 @subsubheading @value{GDBN} Command
27130 The corresponding @value{GDBN} command is @samp{pwd}.
27132 @subsubheading Example
27137 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
27141 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27142 @node GDB/MI Thread Commands
27143 @section @sc{gdb/mi} Thread Commands
27146 @subheading The @code{-thread-info} Command
27147 @findex -thread-info
27149 @subsubheading Synopsis
27152 -thread-info [ @var{thread-id} ]
27155 Reports information about either a specific thread, if
27156 the @var{thread-id} parameter is present, or about all
27157 threads. When printing information about all threads,
27158 also reports the current thread.
27160 @subsubheading @value{GDBN} Command
27162 The @samp{info thread} command prints the same information
27165 @subsubheading Result
27167 The result is a list of threads. The following attributes are
27168 defined for a given thread:
27172 This field exists only for the current thread. It has the value @samp{*}.
27175 The identifier that @value{GDBN} uses to refer to the thread.
27178 The identifier that the target uses to refer to the thread.
27181 Extra information about the thread, in a target-specific format. This
27185 The name of the thread. If the user specified a name using the
27186 @code{thread name} command, then this name is given. Otherwise, if
27187 @value{GDBN} can extract the thread name from the target, then that
27188 name is given. If @value{GDBN} cannot find the thread name, then this
27192 The stack frame currently executing in the thread.
27195 The thread's state. The @samp{state} field may have the following
27200 The thread is stopped. Frame information is available for stopped
27204 The thread is running. There's no frame information for running
27210 If @value{GDBN} can find the CPU core on which this thread is running,
27211 then this field is the core identifier. This field is optional.
27215 @subsubheading Example
27220 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
27221 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
27222 args=[]@},state="running"@},
27223 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
27224 frame=@{level="0",addr="0x0804891f",func="foo",
27225 args=[@{name="i",value="10"@}],
27226 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
27227 state="running"@}],
27228 current-thread-id="1"
27232 @subheading The @code{-thread-list-ids} Command
27233 @findex -thread-list-ids
27235 @subsubheading Synopsis
27241 Produces a list of the currently known @value{GDBN} thread ids. At the
27242 end of the list it also prints the total number of such threads.
27244 This command is retained for historical reasons, the
27245 @code{-thread-info} command should be used instead.
27247 @subsubheading @value{GDBN} Command
27249 Part of @samp{info threads} supplies the same information.
27251 @subsubheading Example
27256 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27257 current-thread-id="1",number-of-threads="3"
27262 @subheading The @code{-thread-select} Command
27263 @findex -thread-select
27265 @subsubheading Synopsis
27268 -thread-select @var{threadnum}
27271 Make @var{threadnum} the current thread. It prints the number of the new
27272 current thread, and the topmost frame for that thread.
27274 This command is deprecated in favor of explicitly using the
27275 @samp{--thread} option to each command.
27277 @subsubheading @value{GDBN} Command
27279 The corresponding @value{GDBN} command is @samp{thread}.
27281 @subsubheading Example
27288 *stopped,reason="end-stepping-range",thread-id="2",line="187",
27289 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
27293 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27294 number-of-threads="3"
27297 ^done,new-thread-id="3",
27298 frame=@{level="0",func="vprintf",
27299 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
27300 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
27304 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27305 @node GDB/MI Ada Tasking Commands
27306 @section @sc{gdb/mi} Ada Tasking Commands
27308 @subheading The @code{-ada-task-info} Command
27309 @findex -ada-task-info
27311 @subsubheading Synopsis
27314 -ada-task-info [ @var{task-id} ]
27317 Reports information about either a specific Ada task, if the
27318 @var{task-id} parameter is present, or about all Ada tasks.
27320 @subsubheading @value{GDBN} Command
27322 The @samp{info tasks} command prints the same information
27323 about all Ada tasks (@pxref{Ada Tasks}).
27325 @subsubheading Result
27327 The result is a table of Ada tasks. The following columns are
27328 defined for each Ada task:
27332 This field exists only for the current thread. It has the value @samp{*}.
27335 The identifier that @value{GDBN} uses to refer to the Ada task.
27338 The identifier that the target uses to refer to the Ada task.
27341 The identifier of the thread corresponding to the Ada task.
27343 This field should always exist, as Ada tasks are always implemented
27344 on top of a thread. But if @value{GDBN} cannot find this corresponding
27345 thread for any reason, the field is omitted.
27348 This field exists only when the task was created by another task.
27349 In this case, it provides the ID of the parent task.
27352 The base priority of the task.
27355 The current state of the task. For a detailed description of the
27356 possible states, see @ref{Ada Tasks}.
27359 The name of the task.
27363 @subsubheading Example
27367 ^done,tasks=@{nr_rows="3",nr_cols="8",
27368 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
27369 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
27370 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
27371 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
27372 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
27373 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
27374 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
27375 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
27376 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
27377 state="Child Termination Wait",name="main_task"@}]@}
27381 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27382 @node GDB/MI Program Execution
27383 @section @sc{gdb/mi} Program Execution
27385 These are the asynchronous commands which generate the out-of-band
27386 record @samp{*stopped}. Currently @value{GDBN} only really executes
27387 asynchronously with remote targets and this interaction is mimicked in
27390 @subheading The @code{-exec-continue} Command
27391 @findex -exec-continue
27393 @subsubheading Synopsis
27396 -exec-continue [--reverse] [--all|--thread-group N]
27399 Resumes the execution of the inferior program, which will continue
27400 to execute until it reaches a debugger stop event. If the
27401 @samp{--reverse} option is specified, execution resumes in reverse until
27402 it reaches a stop event. Stop events may include
27405 breakpoints or watchpoints
27407 signals or exceptions
27409 the end of the process (or its beginning under @samp{--reverse})
27411 the end or beginning of a replay log if one is being used.
27413 In all-stop mode (@pxref{All-Stop
27414 Mode}), may resume only one thread, or all threads, depending on the
27415 value of the @samp{scheduler-locking} variable. If @samp{--all} is
27416 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
27417 ignored in all-stop mode. If the @samp{--thread-group} options is
27418 specified, then all threads in that thread group are resumed.
27420 @subsubheading @value{GDBN} Command
27422 The corresponding @value{GDBN} corresponding is @samp{continue}.
27424 @subsubheading Example
27431 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
27432 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
27438 @subheading The @code{-exec-finish} Command
27439 @findex -exec-finish
27441 @subsubheading Synopsis
27444 -exec-finish [--reverse]
27447 Resumes the execution of the inferior program until the current
27448 function is exited. Displays the results returned by the function.
27449 If the @samp{--reverse} option is specified, resumes the reverse
27450 execution of the inferior program until the point where current
27451 function was called.
27453 @subsubheading @value{GDBN} Command
27455 The corresponding @value{GDBN} command is @samp{finish}.
27457 @subsubheading Example
27459 Function returning @code{void}.
27466 *stopped,reason="function-finished",frame=@{func="main",args=[],
27467 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
27471 Function returning other than @code{void}. The name of the internal
27472 @value{GDBN} variable storing the result is printed, together with the
27479 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
27480 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
27481 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27482 gdb-result-var="$1",return-value="0"
27487 @subheading The @code{-exec-interrupt} Command
27488 @findex -exec-interrupt
27490 @subsubheading Synopsis
27493 -exec-interrupt [--all|--thread-group N]
27496 Interrupts the background execution of the target. Note how the token
27497 associated with the stop message is the one for the execution command
27498 that has been interrupted. The token for the interrupt itself only
27499 appears in the @samp{^done} output. If the user is trying to
27500 interrupt a non-running program, an error message will be printed.
27502 Note that when asynchronous execution is enabled, this command is
27503 asynchronous just like other execution commands. That is, first the
27504 @samp{^done} response will be printed, and the target stop will be
27505 reported after that using the @samp{*stopped} notification.
27507 In non-stop mode, only the context thread is interrupted by default.
27508 All threads (in all inferiors) will be interrupted if the
27509 @samp{--all} option is specified. If the @samp{--thread-group}
27510 option is specified, all threads in that group will be interrupted.
27512 @subsubheading @value{GDBN} Command
27514 The corresponding @value{GDBN} command is @samp{interrupt}.
27516 @subsubheading Example
27527 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
27528 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
27529 fullname="/home/foo/bar/try.c",line="13"@}
27534 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
27538 @subheading The @code{-exec-jump} Command
27541 @subsubheading Synopsis
27544 -exec-jump @var{location}
27547 Resumes execution of the inferior program at the location specified by
27548 parameter. @xref{Specify Location}, for a description of the
27549 different forms of @var{location}.
27551 @subsubheading @value{GDBN} Command
27553 The corresponding @value{GDBN} command is @samp{jump}.
27555 @subsubheading Example
27558 -exec-jump foo.c:10
27559 *running,thread-id="all"
27564 @subheading The @code{-exec-next} Command
27567 @subsubheading Synopsis
27570 -exec-next [--reverse]
27573 Resumes execution of the inferior program, stopping when the beginning
27574 of the next source line is reached.
27576 If the @samp{--reverse} option is specified, resumes reverse execution
27577 of the inferior program, stopping at the beginning of the previous
27578 source line. If you issue this command on the first line of a
27579 function, it will take you back to the caller of that function, to the
27580 source line where the function was called.
27583 @subsubheading @value{GDBN} Command
27585 The corresponding @value{GDBN} command is @samp{next}.
27587 @subsubheading Example
27593 *stopped,reason="end-stepping-range",line="8",file="hello.c"
27598 @subheading The @code{-exec-next-instruction} Command
27599 @findex -exec-next-instruction
27601 @subsubheading Synopsis
27604 -exec-next-instruction [--reverse]
27607 Executes one machine instruction. If the instruction is a function
27608 call, continues until the function returns. If the program stops at an
27609 instruction in the middle of a source line, the address will be
27612 If the @samp{--reverse} option is specified, resumes reverse execution
27613 of the inferior program, stopping at the previous instruction. If the
27614 previously executed instruction was a return from another function,
27615 it will continue to execute in reverse until the call to that function
27616 (from the current stack frame) is reached.
27618 @subsubheading @value{GDBN} Command
27620 The corresponding @value{GDBN} command is @samp{nexti}.
27622 @subsubheading Example
27626 -exec-next-instruction
27630 *stopped,reason="end-stepping-range",
27631 addr="0x000100d4",line="5",file="hello.c"
27636 @subheading The @code{-exec-return} Command
27637 @findex -exec-return
27639 @subsubheading Synopsis
27645 Makes current function return immediately. Doesn't execute the inferior.
27646 Displays the new current frame.
27648 @subsubheading @value{GDBN} Command
27650 The corresponding @value{GDBN} command is @samp{return}.
27652 @subsubheading Example
27656 200-break-insert callee4
27657 200^done,bkpt=@{number="1",addr="0x00010734",
27658 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27663 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27664 frame=@{func="callee4",args=[],
27665 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27666 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
27672 111^done,frame=@{level="0",func="callee3",
27673 args=[@{name="strarg",
27674 value="0x11940 \"A string argument.\""@}],
27675 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27676 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27681 @subheading The @code{-exec-run} Command
27684 @subsubheading Synopsis
27687 -exec-run [--all | --thread-group N]
27690 Starts execution of the inferior from the beginning. The inferior
27691 executes until either a breakpoint is encountered or the program
27692 exits. In the latter case the output will include an exit code, if
27693 the program has exited exceptionally.
27695 When no option is specified, the current inferior is started. If the
27696 @samp{--thread-group} option is specified, it should refer to a thread
27697 group of type @samp{process}, and that thread group will be started.
27698 If the @samp{--all} option is specified, then all inferiors will be started.
27700 @subsubheading @value{GDBN} Command
27702 The corresponding @value{GDBN} command is @samp{run}.
27704 @subsubheading Examples
27709 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
27714 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
27715 frame=@{func="main",args=[],file="recursive2.c",
27716 fullname="/home/foo/bar/recursive2.c",line="4"@}
27721 Program exited normally:
27729 *stopped,reason="exited-normally"
27734 Program exited exceptionally:
27742 *stopped,reason="exited",exit-code="01"
27746 Another way the program can terminate is if it receives a signal such as
27747 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
27751 *stopped,reason="exited-signalled",signal-name="SIGINT",
27752 signal-meaning="Interrupt"
27756 @c @subheading -exec-signal
27759 @subheading The @code{-exec-step} Command
27762 @subsubheading Synopsis
27765 -exec-step [--reverse]
27768 Resumes execution of the inferior program, stopping when the beginning
27769 of the next source line is reached, if the next source line is not a
27770 function call. If it is, stop at the first instruction of the called
27771 function. If the @samp{--reverse} option is specified, resumes reverse
27772 execution of the inferior program, stopping at the beginning of the
27773 previously executed source line.
27775 @subsubheading @value{GDBN} Command
27777 The corresponding @value{GDBN} command is @samp{step}.
27779 @subsubheading Example
27781 Stepping into a function:
27787 *stopped,reason="end-stepping-range",
27788 frame=@{func="foo",args=[@{name="a",value="10"@},
27789 @{name="b",value="0"@}],file="recursive2.c",
27790 fullname="/home/foo/bar/recursive2.c",line="11"@}
27800 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
27805 @subheading The @code{-exec-step-instruction} Command
27806 @findex -exec-step-instruction
27808 @subsubheading Synopsis
27811 -exec-step-instruction [--reverse]
27814 Resumes the inferior which executes one machine instruction. If the
27815 @samp{--reverse} option is specified, resumes reverse execution of the
27816 inferior program, stopping at the previously executed instruction.
27817 The output, once @value{GDBN} has stopped, will vary depending on
27818 whether we have stopped in the middle of a source line or not. In the
27819 former case, the address at which the program stopped will be printed
27822 @subsubheading @value{GDBN} Command
27824 The corresponding @value{GDBN} command is @samp{stepi}.
27826 @subsubheading Example
27830 -exec-step-instruction
27834 *stopped,reason="end-stepping-range",
27835 frame=@{func="foo",args=[],file="try.c",
27836 fullname="/home/foo/bar/try.c",line="10"@}
27838 -exec-step-instruction
27842 *stopped,reason="end-stepping-range",
27843 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
27844 fullname="/home/foo/bar/try.c",line="10"@}
27849 @subheading The @code{-exec-until} Command
27850 @findex -exec-until
27852 @subsubheading Synopsis
27855 -exec-until [ @var{location} ]
27858 Executes the inferior until the @var{location} specified in the
27859 argument is reached. If there is no argument, the inferior executes
27860 until a source line greater than the current one is reached. The
27861 reason for stopping in this case will be @samp{location-reached}.
27863 @subsubheading @value{GDBN} Command
27865 The corresponding @value{GDBN} command is @samp{until}.
27867 @subsubheading Example
27871 -exec-until recursive2.c:6
27875 *stopped,reason="location-reached",frame=@{func="main",args=[],
27876 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
27881 @subheading -file-clear
27882 Is this going away????
27885 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27886 @node GDB/MI Stack Manipulation
27887 @section @sc{gdb/mi} Stack Manipulation Commands
27890 @subheading The @code{-stack-info-frame} Command
27891 @findex -stack-info-frame
27893 @subsubheading Synopsis
27899 Get info on the selected frame.
27901 @subsubheading @value{GDBN} Command
27903 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
27904 (without arguments).
27906 @subsubheading Example
27911 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
27912 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27913 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
27917 @subheading The @code{-stack-info-depth} Command
27918 @findex -stack-info-depth
27920 @subsubheading Synopsis
27923 -stack-info-depth [ @var{max-depth} ]
27926 Return the depth of the stack. If the integer argument @var{max-depth}
27927 is specified, do not count beyond @var{max-depth} frames.
27929 @subsubheading @value{GDBN} Command
27931 There's no equivalent @value{GDBN} command.
27933 @subsubheading Example
27935 For a stack with frame levels 0 through 11:
27942 -stack-info-depth 4
27945 -stack-info-depth 12
27948 -stack-info-depth 11
27951 -stack-info-depth 13
27956 @subheading The @code{-stack-list-arguments} Command
27957 @findex -stack-list-arguments
27959 @subsubheading Synopsis
27962 -stack-list-arguments @var{print-values}
27963 [ @var{low-frame} @var{high-frame} ]
27966 Display a list of the arguments for the frames between @var{low-frame}
27967 and @var{high-frame} (inclusive). If @var{low-frame} and
27968 @var{high-frame} are not provided, list the arguments for the whole
27969 call stack. If the two arguments are equal, show the single frame
27970 at the corresponding level. It is an error if @var{low-frame} is
27971 larger than the actual number of frames. On the other hand,
27972 @var{high-frame} may be larger than the actual number of frames, in
27973 which case only existing frames will be returned.
27975 If @var{print-values} is 0 or @code{--no-values}, print only the names of
27976 the variables; if it is 1 or @code{--all-values}, print also their
27977 values; and if it is 2 or @code{--simple-values}, print the name,
27978 type and value for simple data types, and the name and type for arrays,
27979 structures and unions.
27981 Use of this command to obtain arguments in a single frame is
27982 deprecated in favor of the @samp{-stack-list-variables} command.
27984 @subsubheading @value{GDBN} Command
27986 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
27987 @samp{gdb_get_args} command which partially overlaps with the
27988 functionality of @samp{-stack-list-arguments}.
27990 @subsubheading Example
27997 frame=@{level="0",addr="0x00010734",func="callee4",
27998 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27999 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
28000 frame=@{level="1",addr="0x0001076c",func="callee3",
28001 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28002 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
28003 frame=@{level="2",addr="0x0001078c",func="callee2",
28004 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28005 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
28006 frame=@{level="3",addr="0x000107b4",func="callee1",
28007 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28008 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
28009 frame=@{level="4",addr="0x000107e0",func="main",
28010 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28011 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
28013 -stack-list-arguments 0
28016 frame=@{level="0",args=[]@},
28017 frame=@{level="1",args=[name="strarg"]@},
28018 frame=@{level="2",args=[name="intarg",name="strarg"]@},
28019 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
28020 frame=@{level="4",args=[]@}]
28022 -stack-list-arguments 1
28025 frame=@{level="0",args=[]@},
28027 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28028 frame=@{level="2",args=[
28029 @{name="intarg",value="2"@},
28030 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28031 @{frame=@{level="3",args=[
28032 @{name="intarg",value="2"@},
28033 @{name="strarg",value="0x11940 \"A string argument.\""@},
28034 @{name="fltarg",value="3.5"@}]@},
28035 frame=@{level="4",args=[]@}]
28037 -stack-list-arguments 0 2 2
28038 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
28040 -stack-list-arguments 1 2 2
28041 ^done,stack-args=[frame=@{level="2",
28042 args=[@{name="intarg",value="2"@},
28043 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
28047 @c @subheading -stack-list-exception-handlers
28050 @subheading The @code{-stack-list-frames} Command
28051 @findex -stack-list-frames
28053 @subsubheading Synopsis
28056 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
28059 List the frames currently on the stack. For each frame it displays the
28064 The frame number, 0 being the topmost frame, i.e., the innermost function.
28066 The @code{$pc} value for that frame.
28070 File name of the source file where the function lives.
28071 @item @var{fullname}
28072 The full file name of the source file where the function lives.
28074 Line number corresponding to the @code{$pc}.
28076 The shared library where this function is defined. This is only given
28077 if the frame's function is not known.
28080 If invoked without arguments, this command prints a backtrace for the
28081 whole stack. If given two integer arguments, it shows the frames whose
28082 levels are between the two arguments (inclusive). If the two arguments
28083 are equal, it shows the single frame at the corresponding level. It is
28084 an error if @var{low-frame} is larger than the actual number of
28085 frames. On the other hand, @var{high-frame} may be larger than the
28086 actual number of frames, in which case only existing frames will be returned.
28088 @subsubheading @value{GDBN} Command
28090 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
28092 @subsubheading Example
28094 Full stack backtrace:
28100 [frame=@{level="0",addr="0x0001076c",func="foo",
28101 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
28102 frame=@{level="1",addr="0x000107a4",func="foo",
28103 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28104 frame=@{level="2",addr="0x000107a4",func="foo",
28105 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28106 frame=@{level="3",addr="0x000107a4",func="foo",
28107 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28108 frame=@{level="4",addr="0x000107a4",func="foo",
28109 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28110 frame=@{level="5",addr="0x000107a4",func="foo",
28111 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28112 frame=@{level="6",addr="0x000107a4",func="foo",
28113 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28114 frame=@{level="7",addr="0x000107a4",func="foo",
28115 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28116 frame=@{level="8",addr="0x000107a4",func="foo",
28117 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28118 frame=@{level="9",addr="0x000107a4",func="foo",
28119 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28120 frame=@{level="10",addr="0x000107a4",func="foo",
28121 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28122 frame=@{level="11",addr="0x00010738",func="main",
28123 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
28127 Show frames between @var{low_frame} and @var{high_frame}:
28131 -stack-list-frames 3 5
28133 [frame=@{level="3",addr="0x000107a4",func="foo",
28134 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28135 frame=@{level="4",addr="0x000107a4",func="foo",
28136 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28137 frame=@{level="5",addr="0x000107a4",func="foo",
28138 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28142 Show a single frame:
28146 -stack-list-frames 3 3
28148 [frame=@{level="3",addr="0x000107a4",func="foo",
28149 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28154 @subheading The @code{-stack-list-locals} Command
28155 @findex -stack-list-locals
28157 @subsubheading Synopsis
28160 -stack-list-locals @var{print-values}
28163 Display the local variable names for the selected frame. If
28164 @var{print-values} is 0 or @code{--no-values}, print only the names of
28165 the variables; if it is 1 or @code{--all-values}, print also their
28166 values; and if it is 2 or @code{--simple-values}, print the name,
28167 type and value for simple data types, and the name and type for arrays,
28168 structures and unions. In this last case, a frontend can immediately
28169 display the value of simple data types and create variable objects for
28170 other data types when the user wishes to explore their values in
28173 This command is deprecated in favor of the
28174 @samp{-stack-list-variables} command.
28176 @subsubheading @value{GDBN} Command
28178 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
28180 @subsubheading Example
28184 -stack-list-locals 0
28185 ^done,locals=[name="A",name="B",name="C"]
28187 -stack-list-locals --all-values
28188 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
28189 @{name="C",value="@{1, 2, 3@}"@}]
28190 -stack-list-locals --simple-values
28191 ^done,locals=[@{name="A",type="int",value="1"@},
28192 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
28196 @subheading The @code{-stack-list-variables} Command
28197 @findex -stack-list-variables
28199 @subsubheading Synopsis
28202 -stack-list-variables @var{print-values}
28205 Display the names of local variables and function arguments for the selected frame. If
28206 @var{print-values} is 0 or @code{--no-values}, print only the names of
28207 the variables; if it is 1 or @code{--all-values}, print also their
28208 values; and if it is 2 or @code{--simple-values}, print the name,
28209 type and value for simple data types, and the name and type for arrays,
28210 structures and unions.
28212 @subsubheading Example
28216 -stack-list-variables --thread 1 --frame 0 --all-values
28217 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
28222 @subheading The @code{-stack-select-frame} Command
28223 @findex -stack-select-frame
28225 @subsubheading Synopsis
28228 -stack-select-frame @var{framenum}
28231 Change the selected frame. Select a different frame @var{framenum} on
28234 This command in deprecated in favor of passing the @samp{--frame}
28235 option to every command.
28237 @subsubheading @value{GDBN} Command
28239 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
28240 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
28242 @subsubheading Example
28246 -stack-select-frame 2
28251 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28252 @node GDB/MI Variable Objects
28253 @section @sc{gdb/mi} Variable Objects
28257 @subheading Motivation for Variable Objects in @sc{gdb/mi}
28259 For the implementation of a variable debugger window (locals, watched
28260 expressions, etc.), we are proposing the adaptation of the existing code
28261 used by @code{Insight}.
28263 The two main reasons for that are:
28267 It has been proven in practice (it is already on its second generation).
28270 It will shorten development time (needless to say how important it is
28274 The original interface was designed to be used by Tcl code, so it was
28275 slightly changed so it could be used through @sc{gdb/mi}. This section
28276 describes the @sc{gdb/mi} operations that will be available and gives some
28277 hints about their use.
28279 @emph{Note}: In addition to the set of operations described here, we
28280 expect the @sc{gui} implementation of a variable window to require, at
28281 least, the following operations:
28284 @item @code{-gdb-show} @code{output-radix}
28285 @item @code{-stack-list-arguments}
28286 @item @code{-stack-list-locals}
28287 @item @code{-stack-select-frame}
28292 @subheading Introduction to Variable Objects
28294 @cindex variable objects in @sc{gdb/mi}
28296 Variable objects are "object-oriented" MI interface for examining and
28297 changing values of expressions. Unlike some other MI interfaces that
28298 work with expressions, variable objects are specifically designed for
28299 simple and efficient presentation in the frontend. A variable object
28300 is identified by string name. When a variable object is created, the
28301 frontend specifies the expression for that variable object. The
28302 expression can be a simple variable, or it can be an arbitrary complex
28303 expression, and can even involve CPU registers. After creating a
28304 variable object, the frontend can invoke other variable object
28305 operations---for example to obtain or change the value of a variable
28306 object, or to change display format.
28308 Variable objects have hierarchical tree structure. Any variable object
28309 that corresponds to a composite type, such as structure in C, has
28310 a number of child variable objects, for example corresponding to each
28311 element of a structure. A child variable object can itself have
28312 children, recursively. Recursion ends when we reach
28313 leaf variable objects, which always have built-in types. Child variable
28314 objects are created only by explicit request, so if a frontend
28315 is not interested in the children of a particular variable object, no
28316 child will be created.
28318 For a leaf variable object it is possible to obtain its value as a
28319 string, or set the value from a string. String value can be also
28320 obtained for a non-leaf variable object, but it's generally a string
28321 that only indicates the type of the object, and does not list its
28322 contents. Assignment to a non-leaf variable object is not allowed.
28324 A frontend does not need to read the values of all variable objects each time
28325 the program stops. Instead, MI provides an update command that lists all
28326 variable objects whose values has changed since the last update
28327 operation. This considerably reduces the amount of data that must
28328 be transferred to the frontend. As noted above, children variable
28329 objects are created on demand, and only leaf variable objects have a
28330 real value. As result, gdb will read target memory only for leaf
28331 variables that frontend has created.
28333 The automatic update is not always desirable. For example, a frontend
28334 might want to keep a value of some expression for future reference,
28335 and never update it. For another example, fetching memory is
28336 relatively slow for embedded targets, so a frontend might want
28337 to disable automatic update for the variables that are either not
28338 visible on the screen, or ``closed''. This is possible using so
28339 called ``frozen variable objects''. Such variable objects are never
28340 implicitly updated.
28342 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
28343 fixed variable object, the expression is parsed when the variable
28344 object is created, including associating identifiers to specific
28345 variables. The meaning of expression never changes. For a floating
28346 variable object the values of variables whose names appear in the
28347 expressions are re-evaluated every time in the context of the current
28348 frame. Consider this example:
28353 struct work_state state;
28360 If a fixed variable object for the @code{state} variable is created in
28361 this function, and we enter the recursive call, the variable
28362 object will report the value of @code{state} in the top-level
28363 @code{do_work} invocation. On the other hand, a floating variable
28364 object will report the value of @code{state} in the current frame.
28366 If an expression specified when creating a fixed variable object
28367 refers to a local variable, the variable object becomes bound to the
28368 thread and frame in which the variable object is created. When such
28369 variable object is updated, @value{GDBN} makes sure that the
28370 thread/frame combination the variable object is bound to still exists,
28371 and re-evaluates the variable object in context of that thread/frame.
28373 The following is the complete set of @sc{gdb/mi} operations defined to
28374 access this functionality:
28376 @multitable @columnfractions .4 .6
28377 @item @strong{Operation}
28378 @tab @strong{Description}
28380 @item @code{-enable-pretty-printing}
28381 @tab enable Python-based pretty-printing
28382 @item @code{-var-create}
28383 @tab create a variable object
28384 @item @code{-var-delete}
28385 @tab delete the variable object and/or its children
28386 @item @code{-var-set-format}
28387 @tab set the display format of this variable
28388 @item @code{-var-show-format}
28389 @tab show the display format of this variable
28390 @item @code{-var-info-num-children}
28391 @tab tells how many children this object has
28392 @item @code{-var-list-children}
28393 @tab return a list of the object's children
28394 @item @code{-var-info-type}
28395 @tab show the type of this variable object
28396 @item @code{-var-info-expression}
28397 @tab print parent-relative expression that this variable object represents
28398 @item @code{-var-info-path-expression}
28399 @tab print full expression that this variable object represents
28400 @item @code{-var-show-attributes}
28401 @tab is this variable editable? does it exist here?
28402 @item @code{-var-evaluate-expression}
28403 @tab get the value of this variable
28404 @item @code{-var-assign}
28405 @tab set the value of this variable
28406 @item @code{-var-update}
28407 @tab update the variable and its children
28408 @item @code{-var-set-frozen}
28409 @tab set frozeness attribute
28410 @item @code{-var-set-update-range}
28411 @tab set range of children to display on update
28414 In the next subsection we describe each operation in detail and suggest
28415 how it can be used.
28417 @subheading Description And Use of Operations on Variable Objects
28419 @subheading The @code{-enable-pretty-printing} Command
28420 @findex -enable-pretty-printing
28423 -enable-pretty-printing
28426 @value{GDBN} allows Python-based visualizers to affect the output of the
28427 MI variable object commands. However, because there was no way to
28428 implement this in a fully backward-compatible way, a front end must
28429 request that this functionality be enabled.
28431 Once enabled, this feature cannot be disabled.
28433 Note that if Python support has not been compiled into @value{GDBN},
28434 this command will still succeed (and do nothing).
28436 This feature is currently (as of @value{GDBN} 7.0) experimental, and
28437 may work differently in future versions of @value{GDBN}.
28439 @subheading The @code{-var-create} Command
28440 @findex -var-create
28442 @subsubheading Synopsis
28445 -var-create @{@var{name} | "-"@}
28446 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
28449 This operation creates a variable object, which allows the monitoring of
28450 a variable, the result of an expression, a memory cell or a CPU
28453 The @var{name} parameter is the string by which the object can be
28454 referenced. It must be unique. If @samp{-} is specified, the varobj
28455 system will generate a string ``varNNNNNN'' automatically. It will be
28456 unique provided that one does not specify @var{name} of that format.
28457 The command fails if a duplicate name is found.
28459 The frame under which the expression should be evaluated can be
28460 specified by @var{frame-addr}. A @samp{*} indicates that the current
28461 frame should be used. A @samp{@@} indicates that a floating variable
28462 object must be created.
28464 @var{expression} is any expression valid on the current language set (must not
28465 begin with a @samp{*}), or one of the following:
28469 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
28472 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
28475 @samp{$@var{regname}} --- a CPU register name
28478 @cindex dynamic varobj
28479 A varobj's contents may be provided by a Python-based pretty-printer. In this
28480 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
28481 have slightly different semantics in some cases. If the
28482 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
28483 will never create a dynamic varobj. This ensures backward
28484 compatibility for existing clients.
28486 @subsubheading Result
28488 This operation returns attributes of the newly-created varobj. These
28493 The name of the varobj.
28496 The number of children of the varobj. This number is not necessarily
28497 reliable for a dynamic varobj. Instead, you must examine the
28498 @samp{has_more} attribute.
28501 The varobj's scalar value. For a varobj whose type is some sort of
28502 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
28503 will not be interesting.
28506 The varobj's type. This is a string representation of the type, as
28507 would be printed by the @value{GDBN} CLI.
28510 If a variable object is bound to a specific thread, then this is the
28511 thread's identifier.
28514 For a dynamic varobj, this indicates whether there appear to be any
28515 children available. For a non-dynamic varobj, this will be 0.
28518 This attribute will be present and have the value @samp{1} if the
28519 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28520 then this attribute will not be present.
28523 A dynamic varobj can supply a display hint to the front end. The
28524 value comes directly from the Python pretty-printer object's
28525 @code{display_hint} method. @xref{Pretty Printing API}.
28528 Typical output will look like this:
28531 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
28532 has_more="@var{has_more}"
28536 @subheading The @code{-var-delete} Command
28537 @findex -var-delete
28539 @subsubheading Synopsis
28542 -var-delete [ -c ] @var{name}
28545 Deletes a previously created variable object and all of its children.
28546 With the @samp{-c} option, just deletes the children.
28548 Returns an error if the object @var{name} is not found.
28551 @subheading The @code{-var-set-format} Command
28552 @findex -var-set-format
28554 @subsubheading Synopsis
28557 -var-set-format @var{name} @var{format-spec}
28560 Sets the output format for the value of the object @var{name} to be
28563 @anchor{-var-set-format}
28564 The syntax for the @var{format-spec} is as follows:
28567 @var{format-spec} @expansion{}
28568 @{binary | decimal | hexadecimal | octal | natural@}
28571 The natural format is the default format choosen automatically
28572 based on the variable type (like decimal for an @code{int}, hex
28573 for pointers, etc.).
28575 For a variable with children, the format is set only on the
28576 variable itself, and the children are not affected.
28578 @subheading The @code{-var-show-format} Command
28579 @findex -var-show-format
28581 @subsubheading Synopsis
28584 -var-show-format @var{name}
28587 Returns the format used to display the value of the object @var{name}.
28590 @var{format} @expansion{}
28595 @subheading The @code{-var-info-num-children} Command
28596 @findex -var-info-num-children
28598 @subsubheading Synopsis
28601 -var-info-num-children @var{name}
28604 Returns the number of children of a variable object @var{name}:
28610 Note that this number is not completely reliable for a dynamic varobj.
28611 It will return the current number of children, but more children may
28615 @subheading The @code{-var-list-children} Command
28616 @findex -var-list-children
28618 @subsubheading Synopsis
28621 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
28623 @anchor{-var-list-children}
28625 Return a list of the children of the specified variable object and
28626 create variable objects for them, if they do not already exist. With
28627 a single argument or if @var{print-values} has a value of 0 or
28628 @code{--no-values}, print only the names of the variables; if
28629 @var{print-values} is 1 or @code{--all-values}, also print their
28630 values; and if it is 2 or @code{--simple-values} print the name and
28631 value for simple data types and just the name for arrays, structures
28634 @var{from} and @var{to}, if specified, indicate the range of children
28635 to report. If @var{from} or @var{to} is less than zero, the range is
28636 reset and all children will be reported. Otherwise, children starting
28637 at @var{from} (zero-based) and up to and excluding @var{to} will be
28640 If a child range is requested, it will only affect the current call to
28641 @code{-var-list-children}, but not future calls to @code{-var-update}.
28642 For this, you must instead use @code{-var-set-update-range}. The
28643 intent of this approach is to enable a front end to implement any
28644 update approach it likes; for example, scrolling a view may cause the
28645 front end to request more children with @code{-var-list-children}, and
28646 then the front end could call @code{-var-set-update-range} with a
28647 different range to ensure that future updates are restricted to just
28650 For each child the following results are returned:
28655 Name of the variable object created for this child.
28658 The expression to be shown to the user by the front end to designate this child.
28659 For example this may be the name of a structure member.
28661 For a dynamic varobj, this value cannot be used to form an
28662 expression. There is no way to do this at all with a dynamic varobj.
28664 For C/C@t{++} structures there are several pseudo children returned to
28665 designate access qualifiers. For these pseudo children @var{exp} is
28666 @samp{public}, @samp{private}, or @samp{protected}. In this case the
28667 type and value are not present.
28669 A dynamic varobj will not report the access qualifying
28670 pseudo-children, regardless of the language. This information is not
28671 available at all with a dynamic varobj.
28674 Number of children this child has. For a dynamic varobj, this will be
28678 The type of the child.
28681 If values were requested, this is the value.
28684 If this variable object is associated with a thread, this is the thread id.
28685 Otherwise this result is not present.
28688 If the variable object is frozen, this variable will be present with a value of 1.
28691 The result may have its own attributes:
28695 A dynamic varobj can supply a display hint to the front end. The
28696 value comes directly from the Python pretty-printer object's
28697 @code{display_hint} method. @xref{Pretty Printing API}.
28700 This is an integer attribute which is nonzero if there are children
28701 remaining after the end of the selected range.
28704 @subsubheading Example
28708 -var-list-children n
28709 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28710 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
28712 -var-list-children --all-values n
28713 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
28714 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
28718 @subheading The @code{-var-info-type} Command
28719 @findex -var-info-type
28721 @subsubheading Synopsis
28724 -var-info-type @var{name}
28727 Returns the type of the specified variable @var{name}. The type is
28728 returned as a string in the same format as it is output by the
28732 type=@var{typename}
28736 @subheading The @code{-var-info-expression} Command
28737 @findex -var-info-expression
28739 @subsubheading Synopsis
28742 -var-info-expression @var{name}
28745 Returns a string that is suitable for presenting this
28746 variable object in user interface. The string is generally
28747 not valid expression in the current language, and cannot be evaluated.
28749 For example, if @code{a} is an array, and variable object
28750 @code{A} was created for @code{a}, then we'll get this output:
28753 (gdb) -var-info-expression A.1
28754 ^done,lang="C",exp="1"
28758 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
28760 Note that the output of the @code{-var-list-children} command also
28761 includes those expressions, so the @code{-var-info-expression} command
28764 @subheading The @code{-var-info-path-expression} Command
28765 @findex -var-info-path-expression
28767 @subsubheading Synopsis
28770 -var-info-path-expression @var{name}
28773 Returns an expression that can be evaluated in the current
28774 context and will yield the same value that a variable object has.
28775 Compare this with the @code{-var-info-expression} command, which
28776 result can be used only for UI presentation. Typical use of
28777 the @code{-var-info-path-expression} command is creating a
28778 watchpoint from a variable object.
28780 This command is currently not valid for children of a dynamic varobj,
28781 and will give an error when invoked on one.
28783 For example, suppose @code{C} is a C@t{++} class, derived from class
28784 @code{Base}, and that the @code{Base} class has a member called
28785 @code{m_size}. Assume a variable @code{c} is has the type of
28786 @code{C} and a variable object @code{C} was created for variable
28787 @code{c}. Then, we'll get this output:
28789 (gdb) -var-info-path-expression C.Base.public.m_size
28790 ^done,path_expr=((Base)c).m_size)
28793 @subheading The @code{-var-show-attributes} Command
28794 @findex -var-show-attributes
28796 @subsubheading Synopsis
28799 -var-show-attributes @var{name}
28802 List attributes of the specified variable object @var{name}:
28805 status=@var{attr} [ ( ,@var{attr} )* ]
28809 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
28811 @subheading The @code{-var-evaluate-expression} Command
28812 @findex -var-evaluate-expression
28814 @subsubheading Synopsis
28817 -var-evaluate-expression [-f @var{format-spec}] @var{name}
28820 Evaluates the expression that is represented by the specified variable
28821 object and returns its value as a string. The format of the string
28822 can be specified with the @samp{-f} option. The possible values of
28823 this option are the same as for @code{-var-set-format}
28824 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
28825 the current display format will be used. The current display format
28826 can be changed using the @code{-var-set-format} command.
28832 Note that one must invoke @code{-var-list-children} for a variable
28833 before the value of a child variable can be evaluated.
28835 @subheading The @code{-var-assign} Command
28836 @findex -var-assign
28838 @subsubheading Synopsis
28841 -var-assign @var{name} @var{expression}
28844 Assigns the value of @var{expression} to the variable object specified
28845 by @var{name}. The object must be @samp{editable}. If the variable's
28846 value is altered by the assign, the variable will show up in any
28847 subsequent @code{-var-update} list.
28849 @subsubheading Example
28857 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
28861 @subheading The @code{-var-update} Command
28862 @findex -var-update
28864 @subsubheading Synopsis
28867 -var-update [@var{print-values}] @{@var{name} | "*"@}
28870 Reevaluate the expressions corresponding to the variable object
28871 @var{name} and all its direct and indirect children, and return the
28872 list of variable objects whose values have changed; @var{name} must
28873 be a root variable object. Here, ``changed'' means that the result of
28874 @code{-var-evaluate-expression} before and after the
28875 @code{-var-update} is different. If @samp{*} is used as the variable
28876 object names, all existing variable objects are updated, except
28877 for frozen ones (@pxref{-var-set-frozen}). The option
28878 @var{print-values} determines whether both names and values, or just
28879 names are printed. The possible values of this option are the same
28880 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
28881 recommended to use the @samp{--all-values} option, to reduce the
28882 number of MI commands needed on each program stop.
28884 With the @samp{*} parameter, if a variable object is bound to a
28885 currently running thread, it will not be updated, without any
28888 If @code{-var-set-update-range} was previously used on a varobj, then
28889 only the selected range of children will be reported.
28891 @code{-var-update} reports all the changed varobjs in a tuple named
28894 Each item in the change list is itself a tuple holding:
28898 The name of the varobj.
28901 If values were requested for this update, then this field will be
28902 present and will hold the value of the varobj.
28905 @anchor{-var-update}
28906 This field is a string which may take one of three values:
28910 The variable object's current value is valid.
28913 The variable object does not currently hold a valid value but it may
28914 hold one in the future if its associated expression comes back into
28918 The variable object no longer holds a valid value.
28919 This can occur when the executable file being debugged has changed,
28920 either through recompilation or by using the @value{GDBN} @code{file}
28921 command. The front end should normally choose to delete these variable
28925 In the future new values may be added to this list so the front should
28926 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
28929 This is only present if the varobj is still valid. If the type
28930 changed, then this will be the string @samp{true}; otherwise it will
28934 If the varobj's type changed, then this field will be present and will
28937 @item new_num_children
28938 For a dynamic varobj, if the number of children changed, or if the
28939 type changed, this will be the new number of children.
28941 The @samp{numchild} field in other varobj responses is generally not
28942 valid for a dynamic varobj -- it will show the number of children that
28943 @value{GDBN} knows about, but because dynamic varobjs lazily
28944 instantiate their children, this will not reflect the number of
28945 children which may be available.
28947 The @samp{new_num_children} attribute only reports changes to the
28948 number of children known by @value{GDBN}. This is the only way to
28949 detect whether an update has removed children (which necessarily can
28950 only happen at the end of the update range).
28953 The display hint, if any.
28956 This is an integer value, which will be 1 if there are more children
28957 available outside the varobj's update range.
28960 This attribute will be present and have the value @samp{1} if the
28961 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28962 then this attribute will not be present.
28965 If new children were added to a dynamic varobj within the selected
28966 update range (as set by @code{-var-set-update-range}), then they will
28967 be listed in this attribute.
28970 @subsubheading Example
28977 -var-update --all-values var1
28978 ^done,changelist=[@{name="var1",value="3",in_scope="true",
28979 type_changed="false"@}]
28983 @subheading The @code{-var-set-frozen} Command
28984 @findex -var-set-frozen
28985 @anchor{-var-set-frozen}
28987 @subsubheading Synopsis
28990 -var-set-frozen @var{name} @var{flag}
28993 Set the frozenness flag on the variable object @var{name}. The
28994 @var{flag} parameter should be either @samp{1} to make the variable
28995 frozen or @samp{0} to make it unfrozen. If a variable object is
28996 frozen, then neither itself, nor any of its children, are
28997 implicitly updated by @code{-var-update} of
28998 a parent variable or by @code{-var-update *}. Only
28999 @code{-var-update} of the variable itself will update its value and
29000 values of its children. After a variable object is unfrozen, it is
29001 implicitly updated by all subsequent @code{-var-update} operations.
29002 Unfreezing a variable does not update it, only subsequent
29003 @code{-var-update} does.
29005 @subsubheading Example
29009 -var-set-frozen V 1
29014 @subheading The @code{-var-set-update-range} command
29015 @findex -var-set-update-range
29016 @anchor{-var-set-update-range}
29018 @subsubheading Synopsis
29021 -var-set-update-range @var{name} @var{from} @var{to}
29024 Set the range of children to be returned by future invocations of
29025 @code{-var-update}.
29027 @var{from} and @var{to} indicate the range of children to report. If
29028 @var{from} or @var{to} is less than zero, the range is reset and all
29029 children will be reported. Otherwise, children starting at @var{from}
29030 (zero-based) and up to and excluding @var{to} will be reported.
29032 @subsubheading Example
29036 -var-set-update-range V 1 2
29040 @subheading The @code{-var-set-visualizer} command
29041 @findex -var-set-visualizer
29042 @anchor{-var-set-visualizer}
29044 @subsubheading Synopsis
29047 -var-set-visualizer @var{name} @var{visualizer}
29050 Set a visualizer for the variable object @var{name}.
29052 @var{visualizer} is the visualizer to use. The special value
29053 @samp{None} means to disable any visualizer in use.
29055 If not @samp{None}, @var{visualizer} must be a Python expression.
29056 This expression must evaluate to a callable object which accepts a
29057 single argument. @value{GDBN} will call this object with the value of
29058 the varobj @var{name} as an argument (this is done so that the same
29059 Python pretty-printing code can be used for both the CLI and MI).
29060 When called, this object must return an object which conforms to the
29061 pretty-printing interface (@pxref{Pretty Printing API}).
29063 The pre-defined function @code{gdb.default_visualizer} may be used to
29064 select a visualizer by following the built-in process
29065 (@pxref{Selecting Pretty-Printers}). This is done automatically when
29066 a varobj is created, and so ordinarily is not needed.
29068 This feature is only available if Python support is enabled. The MI
29069 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
29070 can be used to check this.
29072 @subsubheading Example
29074 Resetting the visualizer:
29078 -var-set-visualizer V None
29082 Reselecting the default (type-based) visualizer:
29086 -var-set-visualizer V gdb.default_visualizer
29090 Suppose @code{SomeClass} is a visualizer class. A lambda expression
29091 can be used to instantiate this class for a varobj:
29095 -var-set-visualizer V "lambda val: SomeClass()"
29099 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29100 @node GDB/MI Data Manipulation
29101 @section @sc{gdb/mi} Data Manipulation
29103 @cindex data manipulation, in @sc{gdb/mi}
29104 @cindex @sc{gdb/mi}, data manipulation
29105 This section describes the @sc{gdb/mi} commands that manipulate data:
29106 examine memory and registers, evaluate expressions, etc.
29108 @c REMOVED FROM THE INTERFACE.
29109 @c @subheading -data-assign
29110 @c Change the value of a program variable. Plenty of side effects.
29111 @c @subsubheading GDB Command
29113 @c @subsubheading Example
29116 @subheading The @code{-data-disassemble} Command
29117 @findex -data-disassemble
29119 @subsubheading Synopsis
29123 [ -s @var{start-addr} -e @var{end-addr} ]
29124 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
29132 @item @var{start-addr}
29133 is the beginning address (or @code{$pc})
29134 @item @var{end-addr}
29136 @item @var{filename}
29137 is the name of the file to disassemble
29138 @item @var{linenum}
29139 is the line number to disassemble around
29141 is the number of disassembly lines to be produced. If it is -1,
29142 the whole function will be disassembled, in case no @var{end-addr} is
29143 specified. If @var{end-addr} is specified as a non-zero value, and
29144 @var{lines} is lower than the number of disassembly lines between
29145 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
29146 displayed; if @var{lines} is higher than the number of lines between
29147 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
29150 is either 0 (meaning only disassembly), 1 (meaning mixed source and
29151 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
29152 mixed source and disassembly with raw opcodes).
29155 @subsubheading Result
29157 The output for each instruction is composed of four fields:
29166 Note that whatever included in the instruction field, is not manipulated
29167 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
29169 @subsubheading @value{GDBN} Command
29171 There's no direct mapping from this command to the CLI.
29173 @subsubheading Example
29175 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
29179 -data-disassemble -s $pc -e "$pc + 20" -- 0
29182 @{address="0x000107c0",func-name="main",offset="4",
29183 inst="mov 2, %o0"@},
29184 @{address="0x000107c4",func-name="main",offset="8",
29185 inst="sethi %hi(0x11800), %o2"@},
29186 @{address="0x000107c8",func-name="main",offset="12",
29187 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
29188 @{address="0x000107cc",func-name="main",offset="16",
29189 inst="sethi %hi(0x11800), %o2"@},
29190 @{address="0x000107d0",func-name="main",offset="20",
29191 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
29195 Disassemble the whole @code{main} function. Line 32 is part of
29199 -data-disassemble -f basics.c -l 32 -- 0
29201 @{address="0x000107bc",func-name="main",offset="0",
29202 inst="save %sp, -112, %sp"@},
29203 @{address="0x000107c0",func-name="main",offset="4",
29204 inst="mov 2, %o0"@},
29205 @{address="0x000107c4",func-name="main",offset="8",
29206 inst="sethi %hi(0x11800), %o2"@},
29208 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
29209 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
29213 Disassemble 3 instructions from the start of @code{main}:
29217 -data-disassemble -f basics.c -l 32 -n 3 -- 0
29219 @{address="0x000107bc",func-name="main",offset="0",
29220 inst="save %sp, -112, %sp"@},
29221 @{address="0x000107c0",func-name="main",offset="4",
29222 inst="mov 2, %o0"@},
29223 @{address="0x000107c4",func-name="main",offset="8",
29224 inst="sethi %hi(0x11800), %o2"@}]
29228 Disassemble 3 instructions from the start of @code{main} in mixed mode:
29232 -data-disassemble -f basics.c -l 32 -n 3 -- 1
29234 src_and_asm_line=@{line="31",
29235 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
29236 testsuite/gdb.mi/basics.c",line_asm_insn=[
29237 @{address="0x000107bc",func-name="main",offset="0",
29238 inst="save %sp, -112, %sp"@}]@},
29239 src_and_asm_line=@{line="32",
29240 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
29241 testsuite/gdb.mi/basics.c",line_asm_insn=[
29242 @{address="0x000107c0",func-name="main",offset="4",
29243 inst="mov 2, %o0"@},
29244 @{address="0x000107c4",func-name="main",offset="8",
29245 inst="sethi %hi(0x11800), %o2"@}]@}]
29250 @subheading The @code{-data-evaluate-expression} Command
29251 @findex -data-evaluate-expression
29253 @subsubheading Synopsis
29256 -data-evaluate-expression @var{expr}
29259 Evaluate @var{expr} as an expression. The expression could contain an
29260 inferior function call. The function call will execute synchronously.
29261 If the expression contains spaces, it must be enclosed in double quotes.
29263 @subsubheading @value{GDBN} Command
29265 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
29266 @samp{call}. In @code{gdbtk} only, there's a corresponding
29267 @samp{gdb_eval} command.
29269 @subsubheading Example
29271 In the following example, the numbers that precede the commands are the
29272 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
29273 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
29277 211-data-evaluate-expression A
29280 311-data-evaluate-expression &A
29281 311^done,value="0xefffeb7c"
29283 411-data-evaluate-expression A+3
29286 511-data-evaluate-expression "A + 3"
29292 @subheading The @code{-data-list-changed-registers} Command
29293 @findex -data-list-changed-registers
29295 @subsubheading Synopsis
29298 -data-list-changed-registers
29301 Display a list of the registers that have changed.
29303 @subsubheading @value{GDBN} Command
29305 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
29306 has the corresponding command @samp{gdb_changed_register_list}.
29308 @subsubheading Example
29310 On a PPC MBX board:
29318 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
29319 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
29322 -data-list-changed-registers
29323 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
29324 "10","11","13","14","15","16","17","18","19","20","21","22","23",
29325 "24","25","26","27","28","30","31","64","65","66","67","69"]
29330 @subheading The @code{-data-list-register-names} Command
29331 @findex -data-list-register-names
29333 @subsubheading Synopsis
29336 -data-list-register-names [ ( @var{regno} )+ ]
29339 Show a list of register names for the current target. If no arguments
29340 are given, it shows a list of the names of all the registers. If
29341 integer numbers are given as arguments, it will print a list of the
29342 names of the registers corresponding to the arguments. To ensure
29343 consistency between a register name and its number, the output list may
29344 include empty register names.
29346 @subsubheading @value{GDBN} Command
29348 @value{GDBN} does not have a command which corresponds to
29349 @samp{-data-list-register-names}. In @code{gdbtk} there is a
29350 corresponding command @samp{gdb_regnames}.
29352 @subsubheading Example
29354 For the PPC MBX board:
29357 -data-list-register-names
29358 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
29359 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
29360 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
29361 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
29362 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
29363 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
29364 "", "pc","ps","cr","lr","ctr","xer"]
29366 -data-list-register-names 1 2 3
29367 ^done,register-names=["r1","r2","r3"]
29371 @subheading The @code{-data-list-register-values} Command
29372 @findex -data-list-register-values
29374 @subsubheading Synopsis
29377 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
29380 Display the registers' contents. @var{fmt} is the format according to
29381 which the registers' contents are to be returned, followed by an optional
29382 list of numbers specifying the registers to display. A missing list of
29383 numbers indicates that the contents of all the registers must be returned.
29385 Allowed formats for @var{fmt} are:
29402 @subsubheading @value{GDBN} Command
29404 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
29405 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
29407 @subsubheading Example
29409 For a PPC MBX board (note: line breaks are for readability only, they
29410 don't appear in the actual output):
29414 -data-list-register-values r 64 65
29415 ^done,register-values=[@{number="64",value="0xfe00a300"@},
29416 @{number="65",value="0x00029002"@}]
29418 -data-list-register-values x
29419 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
29420 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
29421 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
29422 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
29423 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
29424 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
29425 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
29426 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
29427 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
29428 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
29429 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
29430 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
29431 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
29432 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
29433 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
29434 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
29435 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
29436 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
29437 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
29438 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
29439 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
29440 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
29441 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
29442 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
29443 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
29444 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
29445 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
29446 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
29447 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
29448 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
29449 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
29450 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
29451 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
29452 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
29453 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
29454 @{number="69",value="0x20002b03"@}]
29459 @subheading The @code{-data-read-memory} Command
29460 @findex -data-read-memory
29462 This command is deprecated, use @code{-data-read-memory-bytes} instead.
29464 @subsubheading Synopsis
29467 -data-read-memory [ -o @var{byte-offset} ]
29468 @var{address} @var{word-format} @var{word-size}
29469 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
29476 @item @var{address}
29477 An expression specifying the address of the first memory word to be
29478 read. Complex expressions containing embedded white space should be
29479 quoted using the C convention.
29481 @item @var{word-format}
29482 The format to be used to print the memory words. The notation is the
29483 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
29486 @item @var{word-size}
29487 The size of each memory word in bytes.
29489 @item @var{nr-rows}
29490 The number of rows in the output table.
29492 @item @var{nr-cols}
29493 The number of columns in the output table.
29496 If present, indicates that each row should include an @sc{ascii} dump. The
29497 value of @var{aschar} is used as a padding character when a byte is not a
29498 member of the printable @sc{ascii} character set (printable @sc{ascii}
29499 characters are those whose code is between 32 and 126, inclusively).
29501 @item @var{byte-offset}
29502 An offset to add to the @var{address} before fetching memory.
29505 This command displays memory contents as a table of @var{nr-rows} by
29506 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
29507 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
29508 (returned as @samp{total-bytes}). Should less than the requested number
29509 of bytes be returned by the target, the missing words are identified
29510 using @samp{N/A}. The number of bytes read from the target is returned
29511 in @samp{nr-bytes} and the starting address used to read memory in
29514 The address of the next/previous row or page is available in
29515 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
29518 @subsubheading @value{GDBN} Command
29520 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
29521 @samp{gdb_get_mem} memory read command.
29523 @subsubheading Example
29525 Read six bytes of memory starting at @code{bytes+6} but then offset by
29526 @code{-6} bytes. Format as three rows of two columns. One byte per
29527 word. Display each word in hex.
29531 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
29532 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
29533 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
29534 prev-page="0x0000138a",memory=[
29535 @{addr="0x00001390",data=["0x00","0x01"]@},
29536 @{addr="0x00001392",data=["0x02","0x03"]@},
29537 @{addr="0x00001394",data=["0x04","0x05"]@}]
29541 Read two bytes of memory starting at address @code{shorts + 64} and
29542 display as a single word formatted in decimal.
29546 5-data-read-memory shorts+64 d 2 1 1
29547 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
29548 next-row="0x00001512",prev-row="0x0000150e",
29549 next-page="0x00001512",prev-page="0x0000150e",memory=[
29550 @{addr="0x00001510",data=["128"]@}]
29554 Read thirty two bytes of memory starting at @code{bytes+16} and format
29555 as eight rows of four columns. Include a string encoding with @samp{x}
29556 used as the non-printable character.
29560 4-data-read-memory bytes+16 x 1 8 4 x
29561 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
29562 next-row="0x000013c0",prev-row="0x0000139c",
29563 next-page="0x000013c0",prev-page="0x00001380",memory=[
29564 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
29565 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
29566 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
29567 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
29568 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
29569 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
29570 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
29571 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
29575 @subheading The @code{-data-read-memory-bytes} Command
29576 @findex -data-read-memory-bytes
29578 @subsubheading Synopsis
29581 -data-read-memory-bytes [ -o @var{byte-offset} ]
29582 @var{address} @var{count}
29589 @item @var{address}
29590 An expression specifying the address of the first memory word to be
29591 read. Complex expressions containing embedded white space should be
29592 quoted using the C convention.
29595 The number of bytes to read. This should be an integer literal.
29597 @item @var{byte-offset}
29598 The offsets in bytes relative to @var{address} at which to start
29599 reading. This should be an integer literal. This option is provided
29600 so that a frontend is not required to first evaluate address and then
29601 perform address arithmetics itself.
29605 This command attempts to read all accessible memory regions in the
29606 specified range. First, all regions marked as unreadable in the memory
29607 map (if one is defined) will be skipped. @xref{Memory Region
29608 Attributes}. Second, @value{GDBN} will attempt to read the remaining
29609 regions. For each one, if reading full region results in an errors,
29610 @value{GDBN} will try to read a subset of the region.
29612 In general, every single byte in the region may be readable or not,
29613 and the only way to read every readable byte is to try a read at
29614 every address, which is not practical. Therefore, @value{GDBN} will
29615 attempt to read all accessible bytes at either beginning or the end
29616 of the region, using a binary division scheme. This heuristic works
29617 well for reading accross a memory map boundary. Note that if a region
29618 has a readable range that is neither at the beginning or the end,
29619 @value{GDBN} will not read it.
29621 The result record (@pxref{GDB/MI Result Records}) that is output of
29622 the command includes a field named @samp{memory} whose content is a
29623 list of tuples. Each tuple represent a successfully read memory block
29624 and has the following fields:
29628 The start address of the memory block, as hexadecimal literal.
29631 The end address of the memory block, as hexadecimal literal.
29634 The offset of the memory block, as hexadecimal literal, relative to
29635 the start address passed to @code{-data-read-memory-bytes}.
29638 The contents of the memory block, in hex.
29644 @subsubheading @value{GDBN} Command
29646 The corresponding @value{GDBN} command is @samp{x}.
29648 @subsubheading Example
29652 -data-read-memory-bytes &a 10
29653 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
29655 contents="01000000020000000300"@}]
29660 @subheading The @code{-data-write-memory-bytes} Command
29661 @findex -data-write-memory-bytes
29663 @subsubheading Synopsis
29666 -data-write-memory-bytes @var{address} @var{contents}
29673 @item @var{address}
29674 An expression specifying the address of the first memory word to be
29675 read. Complex expressions containing embedded white space should be
29676 quoted using the C convention.
29678 @item @var{contents}
29679 The hex-encoded bytes to write.
29683 @subsubheading @value{GDBN} Command
29685 There's no corresponding @value{GDBN} command.
29687 @subsubheading Example
29691 -data-write-memory-bytes &a "aabbccdd"
29697 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29698 @node GDB/MI Tracepoint Commands
29699 @section @sc{gdb/mi} Tracepoint Commands
29701 The commands defined in this section implement MI support for
29702 tracepoints. For detailed introduction, see @ref{Tracepoints}.
29704 @subheading The @code{-trace-find} Command
29705 @findex -trace-find
29707 @subsubheading Synopsis
29710 -trace-find @var{mode} [@var{parameters}@dots{}]
29713 Find a trace frame using criteria defined by @var{mode} and
29714 @var{parameters}. The following table lists permissible
29715 modes and their parameters. For details of operation, see @ref{tfind}.
29720 No parameters are required. Stops examining trace frames.
29723 An integer is required as parameter. Selects tracepoint frame with
29726 @item tracepoint-number
29727 An integer is required as parameter. Finds next
29728 trace frame that corresponds to tracepoint with the specified number.
29731 An address is required as parameter. Finds
29732 next trace frame that corresponds to any tracepoint at the specified
29735 @item pc-inside-range
29736 Two addresses are required as parameters. Finds next trace
29737 frame that corresponds to a tracepoint at an address inside the
29738 specified range. Both bounds are considered to be inside the range.
29740 @item pc-outside-range
29741 Two addresses are required as parameters. Finds
29742 next trace frame that corresponds to a tracepoint at an address outside
29743 the specified range. Both bounds are considered to be inside the range.
29746 Line specification is required as parameter. @xref{Specify Location}.
29747 Finds next trace frame that corresponds to a tracepoint at
29748 the specified location.
29752 If @samp{none} was passed as @var{mode}, the response does not
29753 have fields. Otherwise, the response may have the following fields:
29757 This field has either @samp{0} or @samp{1} as the value, depending
29758 on whether a matching tracepoint was found.
29761 The index of the found traceframe. This field is present iff
29762 the @samp{found} field has value of @samp{1}.
29765 The index of the found tracepoint. This field is present iff
29766 the @samp{found} field has value of @samp{1}.
29769 The information about the frame corresponding to the found trace
29770 frame. This field is present only if a trace frame was found.
29771 @xref{GDB/MI Frame Information}, for description of this field.
29775 @subsubheading @value{GDBN} Command
29777 The corresponding @value{GDBN} command is @samp{tfind}.
29779 @subheading -trace-define-variable
29780 @findex -trace-define-variable
29782 @subsubheading Synopsis
29785 -trace-define-variable @var{name} [ @var{value} ]
29788 Create trace variable @var{name} if it does not exist. If
29789 @var{value} is specified, sets the initial value of the specified
29790 trace variable to that value. Note that the @var{name} should start
29791 with the @samp{$} character.
29793 @subsubheading @value{GDBN} Command
29795 The corresponding @value{GDBN} command is @samp{tvariable}.
29797 @subheading -trace-list-variables
29798 @findex -trace-list-variables
29800 @subsubheading Synopsis
29803 -trace-list-variables
29806 Return a table of all defined trace variables. Each element of the
29807 table has the following fields:
29811 The name of the trace variable. This field is always present.
29814 The initial value. This is a 64-bit signed integer. This
29815 field is always present.
29818 The value the trace variable has at the moment. This is a 64-bit
29819 signed integer. This field is absent iff current value is
29820 not defined, for example if the trace was never run, or is
29825 @subsubheading @value{GDBN} Command
29827 The corresponding @value{GDBN} command is @samp{tvariables}.
29829 @subsubheading Example
29833 -trace-list-variables
29834 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
29835 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
29836 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
29837 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
29838 body=[variable=@{name="$trace_timestamp",initial="0"@}
29839 variable=@{name="$foo",initial="10",current="15"@}]@}
29843 @subheading -trace-save
29844 @findex -trace-save
29846 @subsubheading Synopsis
29849 -trace-save [-r ] @var{filename}
29852 Saves the collected trace data to @var{filename}. Without the
29853 @samp{-r} option, the data is downloaded from the target and saved
29854 in a local file. With the @samp{-r} option the target is asked
29855 to perform the save.
29857 @subsubheading @value{GDBN} Command
29859 The corresponding @value{GDBN} command is @samp{tsave}.
29862 @subheading -trace-start
29863 @findex -trace-start
29865 @subsubheading Synopsis
29871 Starts a tracing experiments. The result of this command does not
29874 @subsubheading @value{GDBN} Command
29876 The corresponding @value{GDBN} command is @samp{tstart}.
29878 @subheading -trace-status
29879 @findex -trace-status
29881 @subsubheading Synopsis
29887 Obtains the status of a tracing experiment. The result may include
29888 the following fields:
29893 May have a value of either @samp{0}, when no tracing operations are
29894 supported, @samp{1}, when all tracing operations are supported, or
29895 @samp{file} when examining trace file. In the latter case, examining
29896 of trace frame is possible but new tracing experiement cannot be
29897 started. This field is always present.
29900 May have a value of either @samp{0} or @samp{1} depending on whether
29901 tracing experiement is in progress on target. This field is present
29902 if @samp{supported} field is not @samp{0}.
29905 Report the reason why the tracing was stopped last time. This field
29906 may be absent iff tracing was never stopped on target yet. The
29907 value of @samp{request} means the tracing was stopped as result of
29908 the @code{-trace-stop} command. The value of @samp{overflow} means
29909 the tracing buffer is full. The value of @samp{disconnection} means
29910 tracing was automatically stopped when @value{GDBN} has disconnected.
29911 The value of @samp{passcount} means tracing was stopped when a
29912 tracepoint was passed a maximal number of times for that tracepoint.
29913 This field is present if @samp{supported} field is not @samp{0}.
29915 @item stopping-tracepoint
29916 The number of tracepoint whose passcount as exceeded. This field is
29917 present iff the @samp{stop-reason} field has the value of
29921 @itemx frames-created
29922 The @samp{frames} field is a count of the total number of trace frames
29923 in the trace buffer, while @samp{frames-created} is the total created
29924 during the run, including ones that were discarded, such as when a
29925 circular trace buffer filled up. Both fields are optional.
29929 These fields tell the current size of the tracing buffer and the
29930 remaining space. These fields are optional.
29933 The value of the circular trace buffer flag. @code{1} means that the
29934 trace buffer is circular and old trace frames will be discarded if
29935 necessary to make room, @code{0} means that the trace buffer is linear
29939 The value of the disconnected tracing flag. @code{1} means that
29940 tracing will continue after @value{GDBN} disconnects, @code{0} means
29941 that the trace run will stop.
29945 @subsubheading @value{GDBN} Command
29947 The corresponding @value{GDBN} command is @samp{tstatus}.
29949 @subheading -trace-stop
29950 @findex -trace-stop
29952 @subsubheading Synopsis
29958 Stops a tracing experiment. The result of this command has the same
29959 fields as @code{-trace-status}, except that the @samp{supported} and
29960 @samp{running} fields are not output.
29962 @subsubheading @value{GDBN} Command
29964 The corresponding @value{GDBN} command is @samp{tstop}.
29967 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29968 @node GDB/MI Symbol Query
29969 @section @sc{gdb/mi} Symbol Query Commands
29973 @subheading The @code{-symbol-info-address} Command
29974 @findex -symbol-info-address
29976 @subsubheading Synopsis
29979 -symbol-info-address @var{symbol}
29982 Describe where @var{symbol} is stored.
29984 @subsubheading @value{GDBN} Command
29986 The corresponding @value{GDBN} command is @samp{info address}.
29988 @subsubheading Example
29992 @subheading The @code{-symbol-info-file} Command
29993 @findex -symbol-info-file
29995 @subsubheading Synopsis
30001 Show the file for the symbol.
30003 @subsubheading @value{GDBN} Command
30005 There's no equivalent @value{GDBN} command. @code{gdbtk} has
30006 @samp{gdb_find_file}.
30008 @subsubheading Example
30012 @subheading The @code{-symbol-info-function} Command
30013 @findex -symbol-info-function
30015 @subsubheading Synopsis
30018 -symbol-info-function
30021 Show which function the symbol lives in.
30023 @subsubheading @value{GDBN} Command
30025 @samp{gdb_get_function} in @code{gdbtk}.
30027 @subsubheading Example
30031 @subheading The @code{-symbol-info-line} Command
30032 @findex -symbol-info-line
30034 @subsubheading Synopsis
30040 Show the core addresses of the code for a source line.
30042 @subsubheading @value{GDBN} Command
30044 The corresponding @value{GDBN} command is @samp{info line}.
30045 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
30047 @subsubheading Example
30051 @subheading The @code{-symbol-info-symbol} Command
30052 @findex -symbol-info-symbol
30054 @subsubheading Synopsis
30057 -symbol-info-symbol @var{addr}
30060 Describe what symbol is at location @var{addr}.
30062 @subsubheading @value{GDBN} Command
30064 The corresponding @value{GDBN} command is @samp{info symbol}.
30066 @subsubheading Example
30070 @subheading The @code{-symbol-list-functions} Command
30071 @findex -symbol-list-functions
30073 @subsubheading Synopsis
30076 -symbol-list-functions
30079 List the functions in the executable.
30081 @subsubheading @value{GDBN} Command
30083 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
30084 @samp{gdb_search} in @code{gdbtk}.
30086 @subsubheading Example
30091 @subheading The @code{-symbol-list-lines} Command
30092 @findex -symbol-list-lines
30094 @subsubheading Synopsis
30097 -symbol-list-lines @var{filename}
30100 Print the list of lines that contain code and their associated program
30101 addresses for the given source filename. The entries are sorted in
30102 ascending PC order.
30104 @subsubheading @value{GDBN} Command
30106 There is no corresponding @value{GDBN} command.
30108 @subsubheading Example
30111 -symbol-list-lines basics.c
30112 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
30118 @subheading The @code{-symbol-list-types} Command
30119 @findex -symbol-list-types
30121 @subsubheading Synopsis
30127 List all the type names.
30129 @subsubheading @value{GDBN} Command
30131 The corresponding commands are @samp{info types} in @value{GDBN},
30132 @samp{gdb_search} in @code{gdbtk}.
30134 @subsubheading Example
30138 @subheading The @code{-symbol-list-variables} Command
30139 @findex -symbol-list-variables
30141 @subsubheading Synopsis
30144 -symbol-list-variables
30147 List all the global and static variable names.
30149 @subsubheading @value{GDBN} Command
30151 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
30153 @subsubheading Example
30157 @subheading The @code{-symbol-locate} Command
30158 @findex -symbol-locate
30160 @subsubheading Synopsis
30166 @subsubheading @value{GDBN} Command
30168 @samp{gdb_loc} in @code{gdbtk}.
30170 @subsubheading Example
30174 @subheading The @code{-symbol-type} Command
30175 @findex -symbol-type
30177 @subsubheading Synopsis
30180 -symbol-type @var{variable}
30183 Show type of @var{variable}.
30185 @subsubheading @value{GDBN} Command
30187 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
30188 @samp{gdb_obj_variable}.
30190 @subsubheading Example
30195 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30196 @node GDB/MI File Commands
30197 @section @sc{gdb/mi} File Commands
30199 This section describes the GDB/MI commands to specify executable file names
30200 and to read in and obtain symbol table information.
30202 @subheading The @code{-file-exec-and-symbols} Command
30203 @findex -file-exec-and-symbols
30205 @subsubheading Synopsis
30208 -file-exec-and-symbols @var{file}
30211 Specify the executable file to be debugged. This file is the one from
30212 which the symbol table is also read. If no file is specified, the
30213 command clears the executable and symbol information. If breakpoints
30214 are set when using this command with no arguments, @value{GDBN} will produce
30215 error messages. Otherwise, no output is produced, except a completion
30218 @subsubheading @value{GDBN} Command
30220 The corresponding @value{GDBN} command is @samp{file}.
30222 @subsubheading Example
30226 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30232 @subheading The @code{-file-exec-file} Command
30233 @findex -file-exec-file
30235 @subsubheading Synopsis
30238 -file-exec-file @var{file}
30241 Specify the executable file to be debugged. Unlike
30242 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
30243 from this file. If used without argument, @value{GDBN} clears the information
30244 about the executable file. No output is produced, except a completion
30247 @subsubheading @value{GDBN} Command
30249 The corresponding @value{GDBN} command is @samp{exec-file}.
30251 @subsubheading Example
30255 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30262 @subheading The @code{-file-list-exec-sections} Command
30263 @findex -file-list-exec-sections
30265 @subsubheading Synopsis
30268 -file-list-exec-sections
30271 List the sections of the current executable file.
30273 @subsubheading @value{GDBN} Command
30275 The @value{GDBN} command @samp{info file} shows, among the rest, the same
30276 information as this command. @code{gdbtk} has a corresponding command
30277 @samp{gdb_load_info}.
30279 @subsubheading Example
30284 @subheading The @code{-file-list-exec-source-file} Command
30285 @findex -file-list-exec-source-file
30287 @subsubheading Synopsis
30290 -file-list-exec-source-file
30293 List the line number, the current source file, and the absolute path
30294 to the current source file for the current executable. The macro
30295 information field has a value of @samp{1} or @samp{0} depending on
30296 whether or not the file includes preprocessor macro information.
30298 @subsubheading @value{GDBN} Command
30300 The @value{GDBN} equivalent is @samp{info source}
30302 @subsubheading Example
30306 123-file-list-exec-source-file
30307 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
30312 @subheading The @code{-file-list-exec-source-files} Command
30313 @findex -file-list-exec-source-files
30315 @subsubheading Synopsis
30318 -file-list-exec-source-files
30321 List the source files for the current executable.
30323 It will always output the filename, but only when @value{GDBN} can find
30324 the absolute file name of a source file, will it output the fullname.
30326 @subsubheading @value{GDBN} Command
30328 The @value{GDBN} equivalent is @samp{info sources}.
30329 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
30331 @subsubheading Example
30334 -file-list-exec-source-files
30336 @{file=foo.c,fullname=/home/foo.c@},
30337 @{file=/home/bar.c,fullname=/home/bar.c@},
30338 @{file=gdb_could_not_find_fullpath.c@}]
30343 @subheading The @code{-file-list-shared-libraries} Command
30344 @findex -file-list-shared-libraries
30346 @subsubheading Synopsis
30349 -file-list-shared-libraries
30352 List the shared libraries in the program.
30354 @subsubheading @value{GDBN} Command
30356 The corresponding @value{GDBN} command is @samp{info shared}.
30358 @subsubheading Example
30362 @subheading The @code{-file-list-symbol-files} Command
30363 @findex -file-list-symbol-files
30365 @subsubheading Synopsis
30368 -file-list-symbol-files
30373 @subsubheading @value{GDBN} Command
30375 The corresponding @value{GDBN} command is @samp{info file} (part of it).
30377 @subsubheading Example
30382 @subheading The @code{-file-symbol-file} Command
30383 @findex -file-symbol-file
30385 @subsubheading Synopsis
30388 -file-symbol-file @var{file}
30391 Read symbol table info from the specified @var{file} argument. When
30392 used without arguments, clears @value{GDBN}'s symbol table info. No output is
30393 produced, except for a completion notification.
30395 @subsubheading @value{GDBN} Command
30397 The corresponding @value{GDBN} command is @samp{symbol-file}.
30399 @subsubheading Example
30403 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30409 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30410 @node GDB/MI Memory Overlay Commands
30411 @section @sc{gdb/mi} Memory Overlay Commands
30413 The memory overlay commands are not implemented.
30415 @c @subheading -overlay-auto
30417 @c @subheading -overlay-list-mapping-state
30419 @c @subheading -overlay-list-overlays
30421 @c @subheading -overlay-map
30423 @c @subheading -overlay-off
30425 @c @subheading -overlay-on
30427 @c @subheading -overlay-unmap
30429 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30430 @node GDB/MI Signal Handling Commands
30431 @section @sc{gdb/mi} Signal Handling Commands
30433 Signal handling commands are not implemented.
30435 @c @subheading -signal-handle
30437 @c @subheading -signal-list-handle-actions
30439 @c @subheading -signal-list-signal-types
30443 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30444 @node GDB/MI Target Manipulation
30445 @section @sc{gdb/mi} Target Manipulation Commands
30448 @subheading The @code{-target-attach} Command
30449 @findex -target-attach
30451 @subsubheading Synopsis
30454 -target-attach @var{pid} | @var{gid} | @var{file}
30457 Attach to a process @var{pid} or a file @var{file} outside of
30458 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
30459 group, the id previously returned by
30460 @samp{-list-thread-groups --available} must be used.
30462 @subsubheading @value{GDBN} Command
30464 The corresponding @value{GDBN} command is @samp{attach}.
30466 @subsubheading Example
30470 =thread-created,id="1"
30471 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
30477 @subheading The @code{-target-compare-sections} Command
30478 @findex -target-compare-sections
30480 @subsubheading Synopsis
30483 -target-compare-sections [ @var{section} ]
30486 Compare data of section @var{section} on target to the exec file.
30487 Without the argument, all sections are compared.
30489 @subsubheading @value{GDBN} Command
30491 The @value{GDBN} equivalent is @samp{compare-sections}.
30493 @subsubheading Example
30498 @subheading The @code{-target-detach} Command
30499 @findex -target-detach
30501 @subsubheading Synopsis
30504 -target-detach [ @var{pid} | @var{gid} ]
30507 Detach from the remote target which normally resumes its execution.
30508 If either @var{pid} or @var{gid} is specified, detaches from either
30509 the specified process, or specified thread group. There's no output.
30511 @subsubheading @value{GDBN} Command
30513 The corresponding @value{GDBN} command is @samp{detach}.
30515 @subsubheading Example
30525 @subheading The @code{-target-disconnect} Command
30526 @findex -target-disconnect
30528 @subsubheading Synopsis
30534 Disconnect from the remote target. There's no output and the target is
30535 generally not resumed.
30537 @subsubheading @value{GDBN} Command
30539 The corresponding @value{GDBN} command is @samp{disconnect}.
30541 @subsubheading Example
30551 @subheading The @code{-target-download} Command
30552 @findex -target-download
30554 @subsubheading Synopsis
30560 Loads the executable onto the remote target.
30561 It prints out an update message every half second, which includes the fields:
30565 The name of the section.
30567 The size of what has been sent so far for that section.
30569 The size of the section.
30571 The total size of what was sent so far (the current and the previous sections).
30573 The size of the overall executable to download.
30577 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
30578 @sc{gdb/mi} Output Syntax}).
30580 In addition, it prints the name and size of the sections, as they are
30581 downloaded. These messages include the following fields:
30585 The name of the section.
30587 The size of the section.
30589 The size of the overall executable to download.
30593 At the end, a summary is printed.
30595 @subsubheading @value{GDBN} Command
30597 The corresponding @value{GDBN} command is @samp{load}.
30599 @subsubheading Example
30601 Note: each status message appears on a single line. Here the messages
30602 have been broken down so that they can fit onto a page.
30607 +download,@{section=".text",section-size="6668",total-size="9880"@}
30608 +download,@{section=".text",section-sent="512",section-size="6668",
30609 total-sent="512",total-size="9880"@}
30610 +download,@{section=".text",section-sent="1024",section-size="6668",
30611 total-sent="1024",total-size="9880"@}
30612 +download,@{section=".text",section-sent="1536",section-size="6668",
30613 total-sent="1536",total-size="9880"@}
30614 +download,@{section=".text",section-sent="2048",section-size="6668",
30615 total-sent="2048",total-size="9880"@}
30616 +download,@{section=".text",section-sent="2560",section-size="6668",
30617 total-sent="2560",total-size="9880"@}
30618 +download,@{section=".text",section-sent="3072",section-size="6668",
30619 total-sent="3072",total-size="9880"@}
30620 +download,@{section=".text",section-sent="3584",section-size="6668",
30621 total-sent="3584",total-size="9880"@}
30622 +download,@{section=".text",section-sent="4096",section-size="6668",
30623 total-sent="4096",total-size="9880"@}
30624 +download,@{section=".text",section-sent="4608",section-size="6668",
30625 total-sent="4608",total-size="9880"@}
30626 +download,@{section=".text",section-sent="5120",section-size="6668",
30627 total-sent="5120",total-size="9880"@}
30628 +download,@{section=".text",section-sent="5632",section-size="6668",
30629 total-sent="5632",total-size="9880"@}
30630 +download,@{section=".text",section-sent="6144",section-size="6668",
30631 total-sent="6144",total-size="9880"@}
30632 +download,@{section=".text",section-sent="6656",section-size="6668",
30633 total-sent="6656",total-size="9880"@}
30634 +download,@{section=".init",section-size="28",total-size="9880"@}
30635 +download,@{section=".fini",section-size="28",total-size="9880"@}
30636 +download,@{section=".data",section-size="3156",total-size="9880"@}
30637 +download,@{section=".data",section-sent="512",section-size="3156",
30638 total-sent="7236",total-size="9880"@}
30639 +download,@{section=".data",section-sent="1024",section-size="3156",
30640 total-sent="7748",total-size="9880"@}
30641 +download,@{section=".data",section-sent="1536",section-size="3156",
30642 total-sent="8260",total-size="9880"@}
30643 +download,@{section=".data",section-sent="2048",section-size="3156",
30644 total-sent="8772",total-size="9880"@}
30645 +download,@{section=".data",section-sent="2560",section-size="3156",
30646 total-sent="9284",total-size="9880"@}
30647 +download,@{section=".data",section-sent="3072",section-size="3156",
30648 total-sent="9796",total-size="9880"@}
30649 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
30656 @subheading The @code{-target-exec-status} Command
30657 @findex -target-exec-status
30659 @subsubheading Synopsis
30662 -target-exec-status
30665 Provide information on the state of the target (whether it is running or
30666 not, for instance).
30668 @subsubheading @value{GDBN} Command
30670 There's no equivalent @value{GDBN} command.
30672 @subsubheading Example
30676 @subheading The @code{-target-list-available-targets} Command
30677 @findex -target-list-available-targets
30679 @subsubheading Synopsis
30682 -target-list-available-targets
30685 List the possible targets to connect to.
30687 @subsubheading @value{GDBN} Command
30689 The corresponding @value{GDBN} command is @samp{help target}.
30691 @subsubheading Example
30695 @subheading The @code{-target-list-current-targets} Command
30696 @findex -target-list-current-targets
30698 @subsubheading Synopsis
30701 -target-list-current-targets
30704 Describe the current target.
30706 @subsubheading @value{GDBN} Command
30708 The corresponding information is printed by @samp{info file} (among
30711 @subsubheading Example
30715 @subheading The @code{-target-list-parameters} Command
30716 @findex -target-list-parameters
30718 @subsubheading Synopsis
30721 -target-list-parameters
30727 @subsubheading @value{GDBN} Command
30731 @subsubheading Example
30735 @subheading The @code{-target-select} Command
30736 @findex -target-select
30738 @subsubheading Synopsis
30741 -target-select @var{type} @var{parameters @dots{}}
30744 Connect @value{GDBN} to the remote target. This command takes two args:
30748 The type of target, for instance @samp{remote}, etc.
30749 @item @var{parameters}
30750 Device names, host names and the like. @xref{Target Commands, ,
30751 Commands for Managing Targets}, for more details.
30754 The output is a connection notification, followed by the address at
30755 which the target program is, in the following form:
30758 ^connected,addr="@var{address}",func="@var{function name}",
30759 args=[@var{arg list}]
30762 @subsubheading @value{GDBN} Command
30764 The corresponding @value{GDBN} command is @samp{target}.
30766 @subsubheading Example
30770 -target-select remote /dev/ttya
30771 ^connected,addr="0xfe00a300",func="??",args=[]
30775 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30776 @node GDB/MI File Transfer Commands
30777 @section @sc{gdb/mi} File Transfer Commands
30780 @subheading The @code{-target-file-put} Command
30781 @findex -target-file-put
30783 @subsubheading Synopsis
30786 -target-file-put @var{hostfile} @var{targetfile}
30789 Copy file @var{hostfile} from the host system (the machine running
30790 @value{GDBN}) to @var{targetfile} on the target system.
30792 @subsubheading @value{GDBN} Command
30794 The corresponding @value{GDBN} command is @samp{remote put}.
30796 @subsubheading Example
30800 -target-file-put localfile remotefile
30806 @subheading The @code{-target-file-get} Command
30807 @findex -target-file-get
30809 @subsubheading Synopsis
30812 -target-file-get @var{targetfile} @var{hostfile}
30815 Copy file @var{targetfile} from the target system to @var{hostfile}
30816 on the host system.
30818 @subsubheading @value{GDBN} Command
30820 The corresponding @value{GDBN} command is @samp{remote get}.
30822 @subsubheading Example
30826 -target-file-get remotefile localfile
30832 @subheading The @code{-target-file-delete} Command
30833 @findex -target-file-delete
30835 @subsubheading Synopsis
30838 -target-file-delete @var{targetfile}
30841 Delete @var{targetfile} from the target system.
30843 @subsubheading @value{GDBN} Command
30845 The corresponding @value{GDBN} command is @samp{remote delete}.
30847 @subsubheading Example
30851 -target-file-delete remotefile
30857 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30858 @node GDB/MI Miscellaneous Commands
30859 @section Miscellaneous @sc{gdb/mi} Commands
30861 @c @subheading -gdb-complete
30863 @subheading The @code{-gdb-exit} Command
30866 @subsubheading Synopsis
30872 Exit @value{GDBN} immediately.
30874 @subsubheading @value{GDBN} Command
30876 Approximately corresponds to @samp{quit}.
30878 @subsubheading Example
30888 @subheading The @code{-exec-abort} Command
30889 @findex -exec-abort
30891 @subsubheading Synopsis
30897 Kill the inferior running program.
30899 @subsubheading @value{GDBN} Command
30901 The corresponding @value{GDBN} command is @samp{kill}.
30903 @subsubheading Example
30908 @subheading The @code{-gdb-set} Command
30911 @subsubheading Synopsis
30917 Set an internal @value{GDBN} variable.
30918 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
30920 @subsubheading @value{GDBN} Command
30922 The corresponding @value{GDBN} command is @samp{set}.
30924 @subsubheading Example
30934 @subheading The @code{-gdb-show} Command
30937 @subsubheading Synopsis
30943 Show the current value of a @value{GDBN} variable.
30945 @subsubheading @value{GDBN} Command
30947 The corresponding @value{GDBN} command is @samp{show}.
30949 @subsubheading Example
30958 @c @subheading -gdb-source
30961 @subheading The @code{-gdb-version} Command
30962 @findex -gdb-version
30964 @subsubheading Synopsis
30970 Show version information for @value{GDBN}. Used mostly in testing.
30972 @subsubheading @value{GDBN} Command
30974 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
30975 default shows this information when you start an interactive session.
30977 @subsubheading Example
30979 @c This example modifies the actual output from GDB to avoid overfull
30985 ~Copyright 2000 Free Software Foundation, Inc.
30986 ~GDB is free software, covered by the GNU General Public License, and
30987 ~you are welcome to change it and/or distribute copies of it under
30988 ~ certain conditions.
30989 ~Type "show copying" to see the conditions.
30990 ~There is absolutely no warranty for GDB. Type "show warranty" for
30992 ~This GDB was configured as
30993 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
30998 @subheading The @code{-list-features} Command
30999 @findex -list-features
31001 Returns a list of particular features of the MI protocol that
31002 this version of gdb implements. A feature can be a command,
31003 or a new field in an output of some command, or even an
31004 important bugfix. While a frontend can sometimes detect presence
31005 of a feature at runtime, it is easier to perform detection at debugger
31008 The command returns a list of strings, with each string naming an
31009 available feature. Each returned string is just a name, it does not
31010 have any internal structure. The list of possible feature names
31016 (gdb) -list-features
31017 ^done,result=["feature1","feature2"]
31020 The current list of features is:
31023 @item frozen-varobjs
31024 Indicates support for the @code{-var-set-frozen} command, as well
31025 as possible presense of the @code{frozen} field in the output
31026 of @code{-varobj-create}.
31027 @item pending-breakpoints
31028 Indicates support for the @option{-f} option to the @code{-break-insert}
31031 Indicates Python scripting support, Python-based
31032 pretty-printing commands, and possible presence of the
31033 @samp{display_hint} field in the output of @code{-var-list-children}
31035 Indicates support for the @code{-thread-info} command.
31036 @item data-read-memory-bytes
31037 Indicates support for the @code{-data-read-memory-bytes} and the
31038 @code{-data-write-memory-bytes} commands.
31039 @item breakpoint-notifications
31040 Indicates that changes to breakpoints and breakpoints created via the
31041 CLI will be announced via async records.
31042 @item ada-task-info
31043 Indicates support for the @code{-ada-task-info} command.
31046 @subheading The @code{-list-target-features} Command
31047 @findex -list-target-features
31049 Returns a list of particular features that are supported by the
31050 target. Those features affect the permitted MI commands, but
31051 unlike the features reported by the @code{-list-features} command, the
31052 features depend on which target GDB is using at the moment. Whenever
31053 a target can change, due to commands such as @code{-target-select},
31054 @code{-target-attach} or @code{-exec-run}, the list of target features
31055 may change, and the frontend should obtain it again.
31059 (gdb) -list-features
31060 ^done,result=["async"]
31063 The current list of features is:
31067 Indicates that the target is capable of asynchronous command
31068 execution, which means that @value{GDBN} will accept further commands
31069 while the target is running.
31072 Indicates that the target is capable of reverse execution.
31073 @xref{Reverse Execution}, for more information.
31077 @subheading The @code{-list-thread-groups} Command
31078 @findex -list-thread-groups
31080 @subheading Synopsis
31083 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
31086 Lists thread groups (@pxref{Thread groups}). When a single thread
31087 group is passed as the argument, lists the children of that group.
31088 When several thread group are passed, lists information about those
31089 thread groups. Without any parameters, lists information about all
31090 top-level thread groups.
31092 Normally, thread groups that are being debugged are reported.
31093 With the @samp{--available} option, @value{GDBN} reports thread groups
31094 available on the target.
31096 The output of this command may have either a @samp{threads} result or
31097 a @samp{groups} result. The @samp{thread} result has a list of tuples
31098 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
31099 Information}). The @samp{groups} result has a list of tuples as value,
31100 each tuple describing a thread group. If top-level groups are
31101 requested (that is, no parameter is passed), or when several groups
31102 are passed, the output always has a @samp{groups} result. The format
31103 of the @samp{group} result is described below.
31105 To reduce the number of roundtrips it's possible to list thread groups
31106 together with their children, by passing the @samp{--recurse} option
31107 and the recursion depth. Presently, only recursion depth of 1 is
31108 permitted. If this option is present, then every reported thread group
31109 will also include its children, either as @samp{group} or
31110 @samp{threads} field.
31112 In general, any combination of option and parameters is permitted, with
31113 the following caveats:
31117 When a single thread group is passed, the output will typically
31118 be the @samp{threads} result. Because threads may not contain
31119 anything, the @samp{recurse} option will be ignored.
31122 When the @samp{--available} option is passed, limited information may
31123 be available. In particular, the list of threads of a process might
31124 be inaccessible. Further, specifying specific thread groups might
31125 not give any performance advantage over listing all thread groups.
31126 The frontend should assume that @samp{-list-thread-groups --available}
31127 is always an expensive operation and cache the results.
31131 The @samp{groups} result is a list of tuples, where each tuple may
31132 have the following fields:
31136 Identifier of the thread group. This field is always present.
31137 The identifier is an opaque string; frontends should not try to
31138 convert it to an integer, even though it might look like one.
31141 The type of the thread group. At present, only @samp{process} is a
31145 The target-specific process identifier. This field is only present
31146 for thread groups of type @samp{process} and only if the process exists.
31149 The number of children this thread group has. This field may be
31150 absent for an available thread group.
31153 This field has a list of tuples as value, each tuple describing a
31154 thread. It may be present if the @samp{--recurse} option is
31155 specified, and it's actually possible to obtain the threads.
31158 This field is a list of integers, each identifying a core that one
31159 thread of the group is running on. This field may be absent if
31160 such information is not available.
31163 The name of the executable file that corresponds to this thread group.
31164 The field is only present for thread groups of type @samp{process},
31165 and only if there is a corresponding executable file.
31169 @subheading Example
31173 -list-thread-groups
31174 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
31175 -list-thread-groups 17
31176 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31177 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
31178 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31179 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
31180 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
31181 -list-thread-groups --available
31182 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
31183 -list-thread-groups --available --recurse 1
31184 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31185 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31186 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
31187 -list-thread-groups --available --recurse 1 17 18
31188 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31189 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31190 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
31194 @subheading The @code{-add-inferior} Command
31195 @findex -add-inferior
31197 @subheading Synopsis
31203 Creates a new inferior (@pxref{Inferiors and Programs}). The created
31204 inferior is not associated with any executable. Such association may
31205 be established with the @samp{-file-exec-and-symbols} command
31206 (@pxref{GDB/MI File Commands}). The command response has a single
31207 field, @samp{thread-group}, whose value is the identifier of the
31208 thread group corresponding to the new inferior.
31210 @subheading Example
31215 ^done,thread-group="i3"
31218 @subheading The @code{-interpreter-exec} Command
31219 @findex -interpreter-exec
31221 @subheading Synopsis
31224 -interpreter-exec @var{interpreter} @var{command}
31226 @anchor{-interpreter-exec}
31228 Execute the specified @var{command} in the given @var{interpreter}.
31230 @subheading @value{GDBN} Command
31232 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
31234 @subheading Example
31238 -interpreter-exec console "break main"
31239 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
31240 &"During symbol reading, bad structure-type format.\n"
31241 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
31246 @subheading The @code{-inferior-tty-set} Command
31247 @findex -inferior-tty-set
31249 @subheading Synopsis
31252 -inferior-tty-set /dev/pts/1
31255 Set terminal for future runs of the program being debugged.
31257 @subheading @value{GDBN} Command
31259 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
31261 @subheading Example
31265 -inferior-tty-set /dev/pts/1
31270 @subheading The @code{-inferior-tty-show} Command
31271 @findex -inferior-tty-show
31273 @subheading Synopsis
31279 Show terminal for future runs of program being debugged.
31281 @subheading @value{GDBN} Command
31283 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
31285 @subheading Example
31289 -inferior-tty-set /dev/pts/1
31293 ^done,inferior_tty_terminal="/dev/pts/1"
31297 @subheading The @code{-enable-timings} Command
31298 @findex -enable-timings
31300 @subheading Synopsis
31303 -enable-timings [yes | no]
31306 Toggle the printing of the wallclock, user and system times for an MI
31307 command as a field in its output. This command is to help frontend
31308 developers optimize the performance of their code. No argument is
31309 equivalent to @samp{yes}.
31311 @subheading @value{GDBN} Command
31315 @subheading Example
31323 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31324 addr="0x080484ed",func="main",file="myprog.c",
31325 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
31326 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
31334 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
31335 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
31336 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
31337 fullname="/home/nickrob/myprog.c",line="73"@}
31342 @chapter @value{GDBN} Annotations
31344 This chapter describes annotations in @value{GDBN}. Annotations were
31345 designed to interface @value{GDBN} to graphical user interfaces or other
31346 similar programs which want to interact with @value{GDBN} at a
31347 relatively high level.
31349 The annotation mechanism has largely been superseded by @sc{gdb/mi}
31353 This is Edition @value{EDITION}, @value{DATE}.
31357 * Annotations Overview:: What annotations are; the general syntax.
31358 * Server Prefix:: Issuing a command without affecting user state.
31359 * Prompting:: Annotations marking @value{GDBN}'s need for input.
31360 * Errors:: Annotations for error messages.
31361 * Invalidation:: Some annotations describe things now invalid.
31362 * Annotations for Running::
31363 Whether the program is running, how it stopped, etc.
31364 * Source Annotations:: Annotations describing source code.
31367 @node Annotations Overview
31368 @section What is an Annotation?
31369 @cindex annotations
31371 Annotations start with a newline character, two @samp{control-z}
31372 characters, and the name of the annotation. If there is no additional
31373 information associated with this annotation, the name of the annotation
31374 is followed immediately by a newline. If there is additional
31375 information, the name of the annotation is followed by a space, the
31376 additional information, and a newline. The additional information
31377 cannot contain newline characters.
31379 Any output not beginning with a newline and two @samp{control-z}
31380 characters denotes literal output from @value{GDBN}. Currently there is
31381 no need for @value{GDBN} to output a newline followed by two
31382 @samp{control-z} characters, but if there was such a need, the
31383 annotations could be extended with an @samp{escape} annotation which
31384 means those three characters as output.
31386 The annotation @var{level}, which is specified using the
31387 @option{--annotate} command line option (@pxref{Mode Options}), controls
31388 how much information @value{GDBN} prints together with its prompt,
31389 values of expressions, source lines, and other types of output. Level 0
31390 is for no annotations, level 1 is for use when @value{GDBN} is run as a
31391 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
31392 for programs that control @value{GDBN}, and level 2 annotations have
31393 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
31394 Interface, annotate, GDB's Obsolete Annotations}).
31397 @kindex set annotate
31398 @item set annotate @var{level}
31399 The @value{GDBN} command @code{set annotate} sets the level of
31400 annotations to the specified @var{level}.
31402 @item show annotate
31403 @kindex show annotate
31404 Show the current annotation level.
31407 This chapter describes level 3 annotations.
31409 A simple example of starting up @value{GDBN} with annotations is:
31412 $ @kbd{gdb --annotate=3}
31414 Copyright 2003 Free Software Foundation, Inc.
31415 GDB is free software, covered by the GNU General Public License,
31416 and you are welcome to change it and/or distribute copies of it
31417 under certain conditions.
31418 Type "show copying" to see the conditions.
31419 There is absolutely no warranty for GDB. Type "show warranty"
31421 This GDB was configured as "i386-pc-linux-gnu"
31432 Here @samp{quit} is input to @value{GDBN}; the rest is output from
31433 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
31434 denotes a @samp{control-z} character) are annotations; the rest is
31435 output from @value{GDBN}.
31437 @node Server Prefix
31438 @section The Server Prefix
31439 @cindex server prefix
31441 If you prefix a command with @samp{server } then it will not affect
31442 the command history, nor will it affect @value{GDBN}'s notion of which
31443 command to repeat if @key{RET} is pressed on a line by itself. This
31444 means that commands can be run behind a user's back by a front-end in
31445 a transparent manner.
31447 The @code{server } prefix does not affect the recording of values into
31448 the value history; to print a value without recording it into the
31449 value history, use the @code{output} command instead of the
31450 @code{print} command.
31452 Using this prefix also disables confirmation requests
31453 (@pxref{confirmation requests}).
31456 @section Annotation for @value{GDBN} Input
31458 @cindex annotations for prompts
31459 When @value{GDBN} prompts for input, it annotates this fact so it is possible
31460 to know when to send output, when the output from a given command is
31463 Different kinds of input each have a different @dfn{input type}. Each
31464 input type has three annotations: a @code{pre-} annotation, which
31465 denotes the beginning of any prompt which is being output, a plain
31466 annotation, which denotes the end of the prompt, and then a @code{post-}
31467 annotation which denotes the end of any echo which may (or may not) be
31468 associated with the input. For example, the @code{prompt} input type
31469 features the following annotations:
31477 The input types are
31480 @findex pre-prompt annotation
31481 @findex prompt annotation
31482 @findex post-prompt annotation
31484 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
31486 @findex pre-commands annotation
31487 @findex commands annotation
31488 @findex post-commands annotation
31490 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
31491 command. The annotations are repeated for each command which is input.
31493 @findex pre-overload-choice annotation
31494 @findex overload-choice annotation
31495 @findex post-overload-choice annotation
31496 @item overload-choice
31497 When @value{GDBN} wants the user to select between various overloaded functions.
31499 @findex pre-query annotation
31500 @findex query annotation
31501 @findex post-query annotation
31503 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
31505 @findex pre-prompt-for-continue annotation
31506 @findex prompt-for-continue annotation
31507 @findex post-prompt-for-continue annotation
31508 @item prompt-for-continue
31509 When @value{GDBN} is asking the user to press return to continue. Note: Don't
31510 expect this to work well; instead use @code{set height 0} to disable
31511 prompting. This is because the counting of lines is buggy in the
31512 presence of annotations.
31517 @cindex annotations for errors, warnings and interrupts
31519 @findex quit annotation
31524 This annotation occurs right before @value{GDBN} responds to an interrupt.
31526 @findex error annotation
31531 This annotation occurs right before @value{GDBN} responds to an error.
31533 Quit and error annotations indicate that any annotations which @value{GDBN} was
31534 in the middle of may end abruptly. For example, if a
31535 @code{value-history-begin} annotation is followed by a @code{error}, one
31536 cannot expect to receive the matching @code{value-history-end}. One
31537 cannot expect not to receive it either, however; an error annotation
31538 does not necessarily mean that @value{GDBN} is immediately returning all the way
31541 @findex error-begin annotation
31542 A quit or error annotation may be preceded by
31548 Any output between that and the quit or error annotation is the error
31551 Warning messages are not yet annotated.
31552 @c If we want to change that, need to fix warning(), type_error(),
31553 @c range_error(), and possibly other places.
31556 @section Invalidation Notices
31558 @cindex annotations for invalidation messages
31559 The following annotations say that certain pieces of state may have
31563 @findex frames-invalid annotation
31564 @item ^Z^Zframes-invalid
31566 The frames (for example, output from the @code{backtrace} command) may
31569 @findex breakpoints-invalid annotation
31570 @item ^Z^Zbreakpoints-invalid
31572 The breakpoints may have changed. For example, the user just added or
31573 deleted a breakpoint.
31576 @node Annotations for Running
31577 @section Running the Program
31578 @cindex annotations for running programs
31580 @findex starting annotation
31581 @findex stopping annotation
31582 When the program starts executing due to a @value{GDBN} command such as
31583 @code{step} or @code{continue},
31589 is output. When the program stops,
31595 is output. Before the @code{stopped} annotation, a variety of
31596 annotations describe how the program stopped.
31599 @findex exited annotation
31600 @item ^Z^Zexited @var{exit-status}
31601 The program exited, and @var{exit-status} is the exit status (zero for
31602 successful exit, otherwise nonzero).
31604 @findex signalled annotation
31605 @findex signal-name annotation
31606 @findex signal-name-end annotation
31607 @findex signal-string annotation
31608 @findex signal-string-end annotation
31609 @item ^Z^Zsignalled
31610 The program exited with a signal. After the @code{^Z^Zsignalled}, the
31611 annotation continues:
31617 ^Z^Zsignal-name-end
31621 ^Z^Zsignal-string-end
31626 where @var{name} is the name of the signal, such as @code{SIGILL} or
31627 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
31628 as @code{Illegal Instruction} or @code{Segmentation fault}.
31629 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
31630 user's benefit and have no particular format.
31632 @findex signal annotation
31634 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
31635 just saying that the program received the signal, not that it was
31636 terminated with it.
31638 @findex breakpoint annotation
31639 @item ^Z^Zbreakpoint @var{number}
31640 The program hit breakpoint number @var{number}.
31642 @findex watchpoint annotation
31643 @item ^Z^Zwatchpoint @var{number}
31644 The program hit watchpoint number @var{number}.
31647 @node Source Annotations
31648 @section Displaying Source
31649 @cindex annotations for source display
31651 @findex source annotation
31652 The following annotation is used instead of displaying source code:
31655 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
31658 where @var{filename} is an absolute file name indicating which source
31659 file, @var{line} is the line number within that file (where 1 is the
31660 first line in the file), @var{character} is the character position
31661 within the file (where 0 is the first character in the file) (for most
31662 debug formats this will necessarily point to the beginning of a line),
31663 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
31664 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
31665 @var{addr} is the address in the target program associated with the
31666 source which is being displayed. @var{addr} is in the form @samp{0x}
31667 followed by one or more lowercase hex digits (note that this does not
31668 depend on the language).
31670 @node JIT Interface
31671 @chapter JIT Compilation Interface
31672 @cindex just-in-time compilation
31673 @cindex JIT compilation interface
31675 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
31676 interface. A JIT compiler is a program or library that generates native
31677 executable code at runtime and executes it, usually in order to achieve good
31678 performance while maintaining platform independence.
31680 Programs that use JIT compilation are normally difficult to debug because
31681 portions of their code are generated at runtime, instead of being loaded from
31682 object files, which is where @value{GDBN} normally finds the program's symbols
31683 and debug information. In order to debug programs that use JIT compilation,
31684 @value{GDBN} has an interface that allows the program to register in-memory
31685 symbol files with @value{GDBN} at runtime.
31687 If you are using @value{GDBN} to debug a program that uses this interface, then
31688 it should work transparently so long as you have not stripped the binary. If
31689 you are developing a JIT compiler, then the interface is documented in the rest
31690 of this chapter. At this time, the only known client of this interface is the
31693 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
31694 JIT compiler communicates with @value{GDBN} by writing data into a global
31695 variable and calling a fuction at a well-known symbol. When @value{GDBN}
31696 attaches, it reads a linked list of symbol files from the global variable to
31697 find existing code, and puts a breakpoint in the function so that it can find
31698 out about additional code.
31701 * Declarations:: Relevant C struct declarations
31702 * Registering Code:: Steps to register code
31703 * Unregistering Code:: Steps to unregister code
31707 @section JIT Declarations
31709 These are the relevant struct declarations that a C program should include to
31710 implement the interface:
31720 struct jit_code_entry
31722 struct jit_code_entry *next_entry;
31723 struct jit_code_entry *prev_entry;
31724 const char *symfile_addr;
31725 uint64_t symfile_size;
31728 struct jit_descriptor
31731 /* This type should be jit_actions_t, but we use uint32_t
31732 to be explicit about the bitwidth. */
31733 uint32_t action_flag;
31734 struct jit_code_entry *relevant_entry;
31735 struct jit_code_entry *first_entry;
31738 /* GDB puts a breakpoint in this function. */
31739 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
31741 /* Make sure to specify the version statically, because the
31742 debugger may check the version before we can set it. */
31743 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
31746 If the JIT is multi-threaded, then it is important that the JIT synchronize any
31747 modifications to this global data properly, which can easily be done by putting
31748 a global mutex around modifications to these structures.
31750 @node Registering Code
31751 @section Registering Code
31753 To register code with @value{GDBN}, the JIT should follow this protocol:
31757 Generate an object file in memory with symbols and other desired debug
31758 information. The file must include the virtual addresses of the sections.
31761 Create a code entry for the file, which gives the start and size of the symbol
31765 Add it to the linked list in the JIT descriptor.
31768 Point the relevant_entry field of the descriptor at the entry.
31771 Set @code{action_flag} to @code{JIT_REGISTER} and call
31772 @code{__jit_debug_register_code}.
31775 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
31776 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
31777 new code. However, the linked list must still be maintained in order to allow
31778 @value{GDBN} to attach to a running process and still find the symbol files.
31780 @node Unregistering Code
31781 @section Unregistering Code
31783 If code is freed, then the JIT should use the following protocol:
31787 Remove the code entry corresponding to the code from the linked list.
31790 Point the @code{relevant_entry} field of the descriptor at the code entry.
31793 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
31794 @code{__jit_debug_register_code}.
31797 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
31798 and the JIT will leak the memory used for the associated symbol files.
31801 @chapter Reporting Bugs in @value{GDBN}
31802 @cindex bugs in @value{GDBN}
31803 @cindex reporting bugs in @value{GDBN}
31805 Your bug reports play an essential role in making @value{GDBN} reliable.
31807 Reporting a bug may help you by bringing a solution to your problem, or it
31808 may not. But in any case the principal function of a bug report is to help
31809 the entire community by making the next version of @value{GDBN} work better. Bug
31810 reports are your contribution to the maintenance of @value{GDBN}.
31812 In order for a bug report to serve its purpose, you must include the
31813 information that enables us to fix the bug.
31816 * Bug Criteria:: Have you found a bug?
31817 * Bug Reporting:: How to report bugs
31821 @section Have You Found a Bug?
31822 @cindex bug criteria
31824 If you are not sure whether you have found a bug, here are some guidelines:
31827 @cindex fatal signal
31828 @cindex debugger crash
31829 @cindex crash of debugger
31831 If the debugger gets a fatal signal, for any input whatever, that is a
31832 @value{GDBN} bug. Reliable debuggers never crash.
31834 @cindex error on valid input
31836 If @value{GDBN} produces an error message for valid input, that is a
31837 bug. (Note that if you're cross debugging, the problem may also be
31838 somewhere in the connection to the target.)
31840 @cindex invalid input
31842 If @value{GDBN} does not produce an error message for invalid input,
31843 that is a bug. However, you should note that your idea of
31844 ``invalid input'' might be our idea of ``an extension'' or ``support
31845 for traditional practice''.
31848 If you are an experienced user of debugging tools, your suggestions
31849 for improvement of @value{GDBN} are welcome in any case.
31852 @node Bug Reporting
31853 @section How to Report Bugs
31854 @cindex bug reports
31855 @cindex @value{GDBN} bugs, reporting
31857 A number of companies and individuals offer support for @sc{gnu} products.
31858 If you obtained @value{GDBN} from a support organization, we recommend you
31859 contact that organization first.
31861 You can find contact information for many support companies and
31862 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
31864 @c should add a web page ref...
31867 @ifset BUGURL_DEFAULT
31868 In any event, we also recommend that you submit bug reports for
31869 @value{GDBN}. The preferred method is to submit them directly using
31870 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
31871 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
31874 @strong{Do not send bug reports to @samp{info-gdb}, or to
31875 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
31876 not want to receive bug reports. Those that do have arranged to receive
31879 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
31880 serves as a repeater. The mailing list and the newsgroup carry exactly
31881 the same messages. Often people think of posting bug reports to the
31882 newsgroup instead of mailing them. This appears to work, but it has one
31883 problem which can be crucial: a newsgroup posting often lacks a mail
31884 path back to the sender. Thus, if we need to ask for more information,
31885 we may be unable to reach you. For this reason, it is better to send
31886 bug reports to the mailing list.
31888 @ifclear BUGURL_DEFAULT
31889 In any event, we also recommend that you submit bug reports for
31890 @value{GDBN} to @value{BUGURL}.
31894 The fundamental principle of reporting bugs usefully is this:
31895 @strong{report all the facts}. If you are not sure whether to state a
31896 fact or leave it out, state it!
31898 Often people omit facts because they think they know what causes the
31899 problem and assume that some details do not matter. Thus, you might
31900 assume that the name of the variable you use in an example does not matter.
31901 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
31902 stray memory reference which happens to fetch from the location where that
31903 name is stored in memory; perhaps, if the name were different, the contents
31904 of that location would fool the debugger into doing the right thing despite
31905 the bug. Play it safe and give a specific, complete example. That is the
31906 easiest thing for you to do, and the most helpful.
31908 Keep in mind that the purpose of a bug report is to enable us to fix the
31909 bug. It may be that the bug has been reported previously, but neither
31910 you nor we can know that unless your bug report is complete and
31913 Sometimes people give a few sketchy facts and ask, ``Does this ring a
31914 bell?'' Those bug reports are useless, and we urge everyone to
31915 @emph{refuse to respond to them} except to chide the sender to report
31918 To enable us to fix the bug, you should include all these things:
31922 The version of @value{GDBN}. @value{GDBN} announces it if you start
31923 with no arguments; you can also print it at any time using @code{show
31926 Without this, we will not know whether there is any point in looking for
31927 the bug in the current version of @value{GDBN}.
31930 The type of machine you are using, and the operating system name and
31934 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
31935 ``@value{GCC}--2.8.1''.
31938 What compiler (and its version) was used to compile the program you are
31939 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
31940 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
31941 to get this information; for other compilers, see the documentation for
31945 The command arguments you gave the compiler to compile your example and
31946 observe the bug. For example, did you use @samp{-O}? To guarantee
31947 you will not omit something important, list them all. A copy of the
31948 Makefile (or the output from make) is sufficient.
31950 If we were to try to guess the arguments, we would probably guess wrong
31951 and then we might not encounter the bug.
31954 A complete input script, and all necessary source files, that will
31958 A description of what behavior you observe that you believe is
31959 incorrect. For example, ``It gets a fatal signal.''
31961 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
31962 will certainly notice it. But if the bug is incorrect output, we might
31963 not notice unless it is glaringly wrong. You might as well not give us
31964 a chance to make a mistake.
31966 Even if the problem you experience is a fatal signal, you should still
31967 say so explicitly. Suppose something strange is going on, such as, your
31968 copy of @value{GDBN} is out of synch, or you have encountered a bug in
31969 the C library on your system. (This has happened!) Your copy might
31970 crash and ours would not. If you told us to expect a crash, then when
31971 ours fails to crash, we would know that the bug was not happening for
31972 us. If you had not told us to expect a crash, then we would not be able
31973 to draw any conclusion from our observations.
31976 @cindex recording a session script
31977 To collect all this information, you can use a session recording program
31978 such as @command{script}, which is available on many Unix systems.
31979 Just run your @value{GDBN} session inside @command{script} and then
31980 include the @file{typescript} file with your bug report.
31982 Another way to record a @value{GDBN} session is to run @value{GDBN}
31983 inside Emacs and then save the entire buffer to a file.
31986 If you wish to suggest changes to the @value{GDBN} source, send us context
31987 diffs. If you even discuss something in the @value{GDBN} source, refer to
31988 it by context, not by line number.
31990 The line numbers in our development sources will not match those in your
31991 sources. Your line numbers would convey no useful information to us.
31995 Here are some things that are not necessary:
31999 A description of the envelope of the bug.
32001 Often people who encounter a bug spend a lot of time investigating
32002 which changes to the input file will make the bug go away and which
32003 changes will not affect it.
32005 This is often time consuming and not very useful, because the way we
32006 will find the bug is by running a single example under the debugger
32007 with breakpoints, not by pure deduction from a series of examples.
32008 We recommend that you save your time for something else.
32010 Of course, if you can find a simpler example to report @emph{instead}
32011 of the original one, that is a convenience for us. Errors in the
32012 output will be easier to spot, running under the debugger will take
32013 less time, and so on.
32015 However, simplification is not vital; if you do not want to do this,
32016 report the bug anyway and send us the entire test case you used.
32019 A patch for the bug.
32021 A patch for the bug does help us if it is a good one. But do not omit
32022 the necessary information, such as the test case, on the assumption that
32023 a patch is all we need. We might see problems with your patch and decide
32024 to fix the problem another way, or we might not understand it at all.
32026 Sometimes with a program as complicated as @value{GDBN} it is very hard to
32027 construct an example that will make the program follow a certain path
32028 through the code. If you do not send us the example, we will not be able
32029 to construct one, so we will not be able to verify that the bug is fixed.
32031 And if we cannot understand what bug you are trying to fix, or why your
32032 patch should be an improvement, we will not install it. A test case will
32033 help us to understand.
32036 A guess about what the bug is or what it depends on.
32038 Such guesses are usually wrong. Even we cannot guess right about such
32039 things without first using the debugger to find the facts.
32042 @c The readline documentation is distributed with the readline code
32043 @c and consists of the two following files:
32046 @c Use -I with makeinfo to point to the appropriate directory,
32047 @c environment var TEXINPUTS with TeX.
32048 @ifclear SYSTEM_READLINE
32049 @include rluser.texi
32050 @include hsuser.texi
32054 @appendix In Memoriam
32056 The @value{GDBN} project mourns the loss of the following long-time
32061 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
32062 to Free Software in general. Outside of @value{GDBN}, he was known in
32063 the Amiga world for his series of Fish Disks, and the GeekGadget project.
32065 @item Michael Snyder
32066 Michael was one of the Global Maintainers of the @value{GDBN} project,
32067 with contributions recorded as early as 1996, until 2011. In addition
32068 to his day to day participation, he was a large driving force behind
32069 adding Reverse Debugging to @value{GDBN}.
32072 Beyond their technical contributions to the project, they were also
32073 enjoyable members of the Free Software Community. We will miss them.
32075 @node Formatting Documentation
32076 @appendix Formatting Documentation
32078 @cindex @value{GDBN} reference card
32079 @cindex reference card
32080 The @value{GDBN} 4 release includes an already-formatted reference card, ready
32081 for printing with PostScript or Ghostscript, in the @file{gdb}
32082 subdirectory of the main source directory@footnote{In
32083 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
32084 release.}. If you can use PostScript or Ghostscript with your printer,
32085 you can print the reference card immediately with @file{refcard.ps}.
32087 The release also includes the source for the reference card. You
32088 can format it, using @TeX{}, by typing:
32094 The @value{GDBN} reference card is designed to print in @dfn{landscape}
32095 mode on US ``letter'' size paper;
32096 that is, on a sheet 11 inches wide by 8.5 inches
32097 high. You will need to specify this form of printing as an option to
32098 your @sc{dvi} output program.
32100 @cindex documentation
32102 All the documentation for @value{GDBN} comes as part of the machine-readable
32103 distribution. The documentation is written in Texinfo format, which is
32104 a documentation system that uses a single source file to produce both
32105 on-line information and a printed manual. You can use one of the Info
32106 formatting commands to create the on-line version of the documentation
32107 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
32109 @value{GDBN} includes an already formatted copy of the on-line Info
32110 version of this manual in the @file{gdb} subdirectory. The main Info
32111 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
32112 subordinate files matching @samp{gdb.info*} in the same directory. If
32113 necessary, you can print out these files, or read them with any editor;
32114 but they are easier to read using the @code{info} subsystem in @sc{gnu}
32115 Emacs or the standalone @code{info} program, available as part of the
32116 @sc{gnu} Texinfo distribution.
32118 If you want to format these Info files yourself, you need one of the
32119 Info formatting programs, such as @code{texinfo-format-buffer} or
32122 If you have @code{makeinfo} installed, and are in the top level
32123 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
32124 version @value{GDBVN}), you can make the Info file by typing:
32131 If you want to typeset and print copies of this manual, you need @TeX{},
32132 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
32133 Texinfo definitions file.
32135 @TeX{} is a typesetting program; it does not print files directly, but
32136 produces output files called @sc{dvi} files. To print a typeset
32137 document, you need a program to print @sc{dvi} files. If your system
32138 has @TeX{} installed, chances are it has such a program. The precise
32139 command to use depends on your system; @kbd{lpr -d} is common; another
32140 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
32141 require a file name without any extension or a @samp{.dvi} extension.
32143 @TeX{} also requires a macro definitions file called
32144 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
32145 written in Texinfo format. On its own, @TeX{} cannot either read or
32146 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
32147 and is located in the @file{gdb-@var{version-number}/texinfo}
32150 If you have @TeX{} and a @sc{dvi} printer program installed, you can
32151 typeset and print this manual. First switch to the @file{gdb}
32152 subdirectory of the main source directory (for example, to
32153 @file{gdb-@value{GDBVN}/gdb}) and type:
32159 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
32161 @node Installing GDB
32162 @appendix Installing @value{GDBN}
32163 @cindex installation
32166 * Requirements:: Requirements for building @value{GDBN}
32167 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
32168 * Separate Objdir:: Compiling @value{GDBN} in another directory
32169 * Config Names:: Specifying names for hosts and targets
32170 * Configure Options:: Summary of options for configure
32171 * System-wide configuration:: Having a system-wide init file
32175 @section Requirements for Building @value{GDBN}
32176 @cindex building @value{GDBN}, requirements for
32178 Building @value{GDBN} requires various tools and packages to be available.
32179 Other packages will be used only if they are found.
32181 @heading Tools/Packages Necessary for Building @value{GDBN}
32183 @item ISO C90 compiler
32184 @value{GDBN} is written in ISO C90. It should be buildable with any
32185 working C90 compiler, e.g.@: GCC.
32189 @heading Tools/Packages Optional for Building @value{GDBN}
32193 @value{GDBN} can use the Expat XML parsing library. This library may be
32194 included with your operating system distribution; if it is not, you
32195 can get the latest version from @url{http://expat.sourceforge.net}.
32196 The @file{configure} script will search for this library in several
32197 standard locations; if it is installed in an unusual path, you can
32198 use the @option{--with-libexpat-prefix} option to specify its location.
32204 Remote protocol memory maps (@pxref{Memory Map Format})
32206 Target descriptions (@pxref{Target Descriptions})
32208 Remote shared library lists (@pxref{Library List Format})
32210 MS-Windows shared libraries (@pxref{Shared Libraries})
32212 Traceframe info (@pxref{Traceframe Info Format})
32216 @cindex compressed debug sections
32217 @value{GDBN} will use the @samp{zlib} library, if available, to read
32218 compressed debug sections. Some linkers, such as GNU gold, are capable
32219 of producing binaries with compressed debug sections. If @value{GDBN}
32220 is compiled with @samp{zlib}, it will be able to read the debug
32221 information in such binaries.
32223 The @samp{zlib} library is likely included with your operating system
32224 distribution; if it is not, you can get the latest version from
32225 @url{http://zlib.net}.
32228 @value{GDBN}'s features related to character sets (@pxref{Character
32229 Sets}) require a functioning @code{iconv} implementation. If you are
32230 on a GNU system, then this is provided by the GNU C Library. Some
32231 other systems also provide a working @code{iconv}.
32233 If @value{GDBN} is using the @code{iconv} program which is installed
32234 in a non-standard place, you will need to tell @value{GDBN} where to find it.
32235 This is done with @option{--with-iconv-bin} which specifies the
32236 directory that contains the @code{iconv} program.
32238 On systems without @code{iconv}, you can install GNU Libiconv. If you
32239 have previously installed Libiconv, you can use the
32240 @option{--with-libiconv-prefix} option to configure.
32242 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
32243 arrange to build Libiconv if a directory named @file{libiconv} appears
32244 in the top-most source directory. If Libiconv is built this way, and
32245 if the operating system does not provide a suitable @code{iconv}
32246 implementation, then the just-built library will automatically be used
32247 by @value{GDBN}. One easy way to set this up is to download GNU
32248 Libiconv, unpack it, and then rename the directory holding the
32249 Libiconv source code to @samp{libiconv}.
32252 @node Running Configure
32253 @section Invoking the @value{GDBN} @file{configure} Script
32254 @cindex configuring @value{GDBN}
32255 @value{GDBN} comes with a @file{configure} script that automates the process
32256 of preparing @value{GDBN} for installation; you can then use @code{make} to
32257 build the @code{gdb} program.
32259 @c irrelevant in info file; it's as current as the code it lives with.
32260 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
32261 look at the @file{README} file in the sources; we may have improved the
32262 installation procedures since publishing this manual.}
32265 The @value{GDBN} distribution includes all the source code you need for
32266 @value{GDBN} in a single directory, whose name is usually composed by
32267 appending the version number to @samp{gdb}.
32269 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
32270 @file{gdb-@value{GDBVN}} directory. That directory contains:
32273 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
32274 script for configuring @value{GDBN} and all its supporting libraries
32276 @item gdb-@value{GDBVN}/gdb
32277 the source specific to @value{GDBN} itself
32279 @item gdb-@value{GDBVN}/bfd
32280 source for the Binary File Descriptor library
32282 @item gdb-@value{GDBVN}/include
32283 @sc{gnu} include files
32285 @item gdb-@value{GDBVN}/libiberty
32286 source for the @samp{-liberty} free software library
32288 @item gdb-@value{GDBVN}/opcodes
32289 source for the library of opcode tables and disassemblers
32291 @item gdb-@value{GDBVN}/readline
32292 source for the @sc{gnu} command-line interface
32294 @item gdb-@value{GDBVN}/glob
32295 source for the @sc{gnu} filename pattern-matching subroutine
32297 @item gdb-@value{GDBVN}/mmalloc
32298 source for the @sc{gnu} memory-mapped malloc package
32301 The simplest way to configure and build @value{GDBN} is to run @file{configure}
32302 from the @file{gdb-@var{version-number}} source directory, which in
32303 this example is the @file{gdb-@value{GDBVN}} directory.
32305 First switch to the @file{gdb-@var{version-number}} source directory
32306 if you are not already in it; then run @file{configure}. Pass the
32307 identifier for the platform on which @value{GDBN} will run as an
32313 cd gdb-@value{GDBVN}
32314 ./configure @var{host}
32319 where @var{host} is an identifier such as @samp{sun4} or
32320 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
32321 (You can often leave off @var{host}; @file{configure} tries to guess the
32322 correct value by examining your system.)
32324 Running @samp{configure @var{host}} and then running @code{make} builds the
32325 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
32326 libraries, then @code{gdb} itself. The configured source files, and the
32327 binaries, are left in the corresponding source directories.
32330 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
32331 system does not recognize this automatically when you run a different
32332 shell, you may need to run @code{sh} on it explicitly:
32335 sh configure @var{host}
32338 If you run @file{configure} from a directory that contains source
32339 directories for multiple libraries or programs, such as the
32340 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
32342 creates configuration files for every directory level underneath (unless
32343 you tell it not to, with the @samp{--norecursion} option).
32345 You should run the @file{configure} script from the top directory in the
32346 source tree, the @file{gdb-@var{version-number}} directory. If you run
32347 @file{configure} from one of the subdirectories, you will configure only
32348 that subdirectory. That is usually not what you want. In particular,
32349 if you run the first @file{configure} from the @file{gdb} subdirectory
32350 of the @file{gdb-@var{version-number}} directory, you will omit the
32351 configuration of @file{bfd}, @file{readline}, and other sibling
32352 directories of the @file{gdb} subdirectory. This leads to build errors
32353 about missing include files such as @file{bfd/bfd.h}.
32355 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
32356 However, you should make sure that the shell on your path (named by
32357 the @samp{SHELL} environment variable) is publicly readable. Remember
32358 that @value{GDBN} uses the shell to start your program---some systems refuse to
32359 let @value{GDBN} debug child processes whose programs are not readable.
32361 @node Separate Objdir
32362 @section Compiling @value{GDBN} in Another Directory
32364 If you want to run @value{GDBN} versions for several host or target machines,
32365 you need a different @code{gdb} compiled for each combination of
32366 host and target. @file{configure} is designed to make this easy by
32367 allowing you to generate each configuration in a separate subdirectory,
32368 rather than in the source directory. If your @code{make} program
32369 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
32370 @code{make} in each of these directories builds the @code{gdb}
32371 program specified there.
32373 To build @code{gdb} in a separate directory, run @file{configure}
32374 with the @samp{--srcdir} option to specify where to find the source.
32375 (You also need to specify a path to find @file{configure}
32376 itself from your working directory. If the path to @file{configure}
32377 would be the same as the argument to @samp{--srcdir}, you can leave out
32378 the @samp{--srcdir} option; it is assumed.)
32380 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
32381 separate directory for a Sun 4 like this:
32385 cd gdb-@value{GDBVN}
32388 ../gdb-@value{GDBVN}/configure sun4
32393 When @file{configure} builds a configuration using a remote source
32394 directory, it creates a tree for the binaries with the same structure
32395 (and using the same names) as the tree under the source directory. In
32396 the example, you'd find the Sun 4 library @file{libiberty.a} in the
32397 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
32398 @file{gdb-sun4/gdb}.
32400 Make sure that your path to the @file{configure} script has just one
32401 instance of @file{gdb} in it. If your path to @file{configure} looks
32402 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
32403 one subdirectory of @value{GDBN}, not the whole package. This leads to
32404 build errors about missing include files such as @file{bfd/bfd.h}.
32406 One popular reason to build several @value{GDBN} configurations in separate
32407 directories is to configure @value{GDBN} for cross-compiling (where
32408 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
32409 programs that run on another machine---the @dfn{target}).
32410 You specify a cross-debugging target by
32411 giving the @samp{--target=@var{target}} option to @file{configure}.
32413 When you run @code{make} to build a program or library, you must run
32414 it in a configured directory---whatever directory you were in when you
32415 called @file{configure} (or one of its subdirectories).
32417 The @code{Makefile} that @file{configure} generates in each source
32418 directory also runs recursively. If you type @code{make} in a source
32419 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
32420 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
32421 will build all the required libraries, and then build GDB.
32423 When you have multiple hosts or targets configured in separate
32424 directories, you can run @code{make} on them in parallel (for example,
32425 if they are NFS-mounted on each of the hosts); they will not interfere
32429 @section Specifying Names for Hosts and Targets
32431 The specifications used for hosts and targets in the @file{configure}
32432 script are based on a three-part naming scheme, but some short predefined
32433 aliases are also supported. The full naming scheme encodes three pieces
32434 of information in the following pattern:
32437 @var{architecture}-@var{vendor}-@var{os}
32440 For example, you can use the alias @code{sun4} as a @var{host} argument,
32441 or as the value for @var{target} in a @code{--target=@var{target}}
32442 option. The equivalent full name is @samp{sparc-sun-sunos4}.
32444 The @file{configure} script accompanying @value{GDBN} does not provide
32445 any query facility to list all supported host and target names or
32446 aliases. @file{configure} calls the Bourne shell script
32447 @code{config.sub} to map abbreviations to full names; you can read the
32448 script, if you wish, or you can use it to test your guesses on
32449 abbreviations---for example:
32452 % sh config.sub i386-linux
32454 % sh config.sub alpha-linux
32455 alpha-unknown-linux-gnu
32456 % sh config.sub hp9k700
32458 % sh config.sub sun4
32459 sparc-sun-sunos4.1.1
32460 % sh config.sub sun3
32461 m68k-sun-sunos4.1.1
32462 % sh config.sub i986v
32463 Invalid configuration `i986v': machine `i986v' not recognized
32467 @code{config.sub} is also distributed in the @value{GDBN} source
32468 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
32470 @node Configure Options
32471 @section @file{configure} Options
32473 Here is a summary of the @file{configure} options and arguments that
32474 are most often useful for building @value{GDBN}. @file{configure} also has
32475 several other options not listed here. @inforef{What Configure
32476 Does,,configure.info}, for a full explanation of @file{configure}.
32479 configure @r{[}--help@r{]}
32480 @r{[}--prefix=@var{dir}@r{]}
32481 @r{[}--exec-prefix=@var{dir}@r{]}
32482 @r{[}--srcdir=@var{dirname}@r{]}
32483 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
32484 @r{[}--target=@var{target}@r{]}
32489 You may introduce options with a single @samp{-} rather than
32490 @samp{--} if you prefer; but you may abbreviate option names if you use
32495 Display a quick summary of how to invoke @file{configure}.
32497 @item --prefix=@var{dir}
32498 Configure the source to install programs and files under directory
32501 @item --exec-prefix=@var{dir}
32502 Configure the source to install programs under directory
32505 @c avoid splitting the warning from the explanation:
32507 @item --srcdir=@var{dirname}
32508 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
32509 @code{make} that implements the @code{VPATH} feature.}@*
32510 Use this option to make configurations in directories separate from the
32511 @value{GDBN} source directories. Among other things, you can use this to
32512 build (or maintain) several configurations simultaneously, in separate
32513 directories. @file{configure} writes configuration-specific files in
32514 the current directory, but arranges for them to use the source in the
32515 directory @var{dirname}. @file{configure} creates directories under
32516 the working directory in parallel to the source directories below
32519 @item --norecursion
32520 Configure only the directory level where @file{configure} is executed; do not
32521 propagate configuration to subdirectories.
32523 @item --target=@var{target}
32524 Configure @value{GDBN} for cross-debugging programs running on the specified
32525 @var{target}. Without this option, @value{GDBN} is configured to debug
32526 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
32528 There is no convenient way to generate a list of all available targets.
32530 @item @var{host} @dots{}
32531 Configure @value{GDBN} to run on the specified @var{host}.
32533 There is no convenient way to generate a list of all available hosts.
32536 There are many other options available as well, but they are generally
32537 needed for special purposes only.
32539 @node System-wide configuration
32540 @section System-wide configuration and settings
32541 @cindex system-wide init file
32543 @value{GDBN} can be configured to have a system-wide init file;
32544 this file will be read and executed at startup (@pxref{Startup, , What
32545 @value{GDBN} does during startup}).
32547 Here is the corresponding configure option:
32550 @item --with-system-gdbinit=@var{file}
32551 Specify that the default location of the system-wide init file is
32555 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
32556 it may be subject to relocation. Two possible cases:
32560 If the default location of this init file contains @file{$prefix},
32561 it will be subject to relocation. Suppose that the configure options
32562 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
32563 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
32564 init file is looked for as @file{$install/etc/gdbinit} instead of
32565 @file{$prefix/etc/gdbinit}.
32568 By contrast, if the default location does not contain the prefix,
32569 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
32570 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
32571 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
32572 wherever @value{GDBN} is installed.
32575 @node Maintenance Commands
32576 @appendix Maintenance Commands
32577 @cindex maintenance commands
32578 @cindex internal commands
32580 In addition to commands intended for @value{GDBN} users, @value{GDBN}
32581 includes a number of commands intended for @value{GDBN} developers,
32582 that are not documented elsewhere in this manual. These commands are
32583 provided here for reference. (For commands that turn on debugging
32584 messages, see @ref{Debugging Output}.)
32587 @kindex maint agent
32588 @kindex maint agent-eval
32589 @item maint agent @var{expression}
32590 @itemx maint agent-eval @var{expression}
32591 Translate the given @var{expression} into remote agent bytecodes.
32592 This command is useful for debugging the Agent Expression mechanism
32593 (@pxref{Agent Expressions}). The @samp{agent} version produces an
32594 expression useful for data collection, such as by tracepoints, while
32595 @samp{maint agent-eval} produces an expression that evaluates directly
32596 to a result. For instance, a collection expression for @code{globa +
32597 globb} will include bytecodes to record four bytes of memory at each
32598 of the addresses of @code{globa} and @code{globb}, while discarding
32599 the result of the addition, while an evaluation expression will do the
32600 addition and return the sum.
32602 @kindex maint info breakpoints
32603 @item @anchor{maint info breakpoints}maint info breakpoints
32604 Using the same format as @samp{info breakpoints}, display both the
32605 breakpoints you've set explicitly, and those @value{GDBN} is using for
32606 internal purposes. Internal breakpoints are shown with negative
32607 breakpoint numbers. The type column identifies what kind of breakpoint
32612 Normal, explicitly set breakpoint.
32615 Normal, explicitly set watchpoint.
32618 Internal breakpoint, used to handle correctly stepping through
32619 @code{longjmp} calls.
32621 @item longjmp resume
32622 Internal breakpoint at the target of a @code{longjmp}.
32625 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
32628 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
32631 Shared library events.
32635 @kindex set displaced-stepping
32636 @kindex show displaced-stepping
32637 @cindex displaced stepping support
32638 @cindex out-of-line single-stepping
32639 @item set displaced-stepping
32640 @itemx show displaced-stepping
32641 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
32642 if the target supports it. Displaced stepping is a way to single-step
32643 over breakpoints without removing them from the inferior, by executing
32644 an out-of-line copy of the instruction that was originally at the
32645 breakpoint location. It is also known as out-of-line single-stepping.
32648 @item set displaced-stepping on
32649 If the target architecture supports it, @value{GDBN} will use
32650 displaced stepping to step over breakpoints.
32652 @item set displaced-stepping off
32653 @value{GDBN} will not use displaced stepping to step over breakpoints,
32654 even if such is supported by the target architecture.
32656 @cindex non-stop mode, and @samp{set displaced-stepping}
32657 @item set displaced-stepping auto
32658 This is the default mode. @value{GDBN} will use displaced stepping
32659 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
32660 architecture supports displaced stepping.
32663 @kindex maint check-symtabs
32664 @item maint check-symtabs
32665 Check the consistency of psymtabs and symtabs.
32667 @kindex maint cplus first_component
32668 @item maint cplus first_component @var{name}
32669 Print the first C@t{++} class/namespace component of @var{name}.
32671 @kindex maint cplus namespace
32672 @item maint cplus namespace
32673 Print the list of possible C@t{++} namespaces.
32675 @kindex maint demangle
32676 @item maint demangle @var{name}
32677 Demangle a C@t{++} or Objective-C mangled @var{name}.
32679 @kindex maint deprecate
32680 @kindex maint undeprecate
32681 @cindex deprecated commands
32682 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
32683 @itemx maint undeprecate @var{command}
32684 Deprecate or undeprecate the named @var{command}. Deprecated commands
32685 cause @value{GDBN} to issue a warning when you use them. The optional
32686 argument @var{replacement} says which newer command should be used in
32687 favor of the deprecated one; if it is given, @value{GDBN} will mention
32688 the replacement as part of the warning.
32690 @kindex maint dump-me
32691 @item maint dump-me
32692 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
32693 Cause a fatal signal in the debugger and force it to dump its core.
32694 This is supported only on systems which support aborting a program
32695 with the @code{SIGQUIT} signal.
32697 @kindex maint internal-error
32698 @kindex maint internal-warning
32699 @item maint internal-error @r{[}@var{message-text}@r{]}
32700 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
32701 Cause @value{GDBN} to call the internal function @code{internal_error}
32702 or @code{internal_warning} and hence behave as though an internal error
32703 or internal warning has been detected. In addition to reporting the
32704 internal problem, these functions give the user the opportunity to
32705 either quit @value{GDBN} or create a core file of the current
32706 @value{GDBN} session.
32708 These commands take an optional parameter @var{message-text} that is
32709 used as the text of the error or warning message.
32711 Here's an example of using @code{internal-error}:
32714 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
32715 @dots{}/maint.c:121: internal-error: testing, 1, 2
32716 A problem internal to GDB has been detected. Further
32717 debugging may prove unreliable.
32718 Quit this debugging session? (y or n) @kbd{n}
32719 Create a core file? (y or n) @kbd{n}
32723 @cindex @value{GDBN} internal error
32724 @cindex internal errors, control of @value{GDBN} behavior
32726 @kindex maint set internal-error
32727 @kindex maint show internal-error
32728 @kindex maint set internal-warning
32729 @kindex maint show internal-warning
32730 @item maint set internal-error @var{action} [ask|yes|no]
32731 @itemx maint show internal-error @var{action}
32732 @itemx maint set internal-warning @var{action} [ask|yes|no]
32733 @itemx maint show internal-warning @var{action}
32734 When @value{GDBN} reports an internal problem (error or warning) it
32735 gives the user the opportunity to both quit @value{GDBN} and create a
32736 core file of the current @value{GDBN} session. These commands let you
32737 override the default behaviour for each particular @var{action},
32738 described in the table below.
32742 You can specify that @value{GDBN} should always (yes) or never (no)
32743 quit. The default is to ask the user what to do.
32746 You can specify that @value{GDBN} should always (yes) or never (no)
32747 create a core file. The default is to ask the user what to do.
32750 @kindex maint packet
32751 @item maint packet @var{text}
32752 If @value{GDBN} is talking to an inferior via the serial protocol,
32753 then this command sends the string @var{text} to the inferior, and
32754 displays the response packet. @value{GDBN} supplies the initial
32755 @samp{$} character, the terminating @samp{#} character, and the
32758 @kindex maint print architecture
32759 @item maint print architecture @r{[}@var{file}@r{]}
32760 Print the entire architecture configuration. The optional argument
32761 @var{file} names the file where the output goes.
32763 @kindex maint print c-tdesc
32764 @item maint print c-tdesc
32765 Print the current target description (@pxref{Target Descriptions}) as
32766 a C source file. The created source file can be used in @value{GDBN}
32767 when an XML parser is not available to parse the description.
32769 @kindex maint print dummy-frames
32770 @item maint print dummy-frames
32771 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
32774 (@value{GDBP}) @kbd{b add}
32776 (@value{GDBP}) @kbd{print add(2,3)}
32777 Breakpoint 2, add (a=2, b=3) at @dots{}
32779 The program being debugged stopped while in a function called from GDB.
32781 (@value{GDBP}) @kbd{maint print dummy-frames}
32782 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
32783 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
32784 call_lo=0x01014000 call_hi=0x01014001
32788 Takes an optional file parameter.
32790 @kindex maint print registers
32791 @kindex maint print raw-registers
32792 @kindex maint print cooked-registers
32793 @kindex maint print register-groups
32794 @kindex maint print remote-registers
32795 @item maint print registers @r{[}@var{file}@r{]}
32796 @itemx maint print raw-registers @r{[}@var{file}@r{]}
32797 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
32798 @itemx maint print register-groups @r{[}@var{file}@r{]}
32799 @itemx maint print remote-registers @r{[}@var{file}@r{]}
32800 Print @value{GDBN}'s internal register data structures.
32802 The command @code{maint print raw-registers} includes the contents of
32803 the raw register cache; the command @code{maint print
32804 cooked-registers} includes the (cooked) value of all registers,
32805 including registers which aren't available on the target nor visible
32806 to user; the command @code{maint print register-groups} includes the
32807 groups that each register is a member of; and the command @code{maint
32808 print remote-registers} includes the remote target's register numbers
32809 and offsets in the `G' packets. @xref{Registers,, Registers, gdbint,
32810 @value{GDBN} Internals}.
32812 These commands take an optional parameter, a file name to which to
32813 write the information.
32815 @kindex maint print reggroups
32816 @item maint print reggroups @r{[}@var{file}@r{]}
32817 Print @value{GDBN}'s internal register group data structures. The
32818 optional argument @var{file} tells to what file to write the
32821 The register groups info looks like this:
32824 (@value{GDBP}) @kbd{maint print reggroups}
32837 This command forces @value{GDBN} to flush its internal register cache.
32839 @kindex maint print objfiles
32840 @cindex info for known object files
32841 @item maint print objfiles
32842 Print a dump of all known object files. For each object file, this
32843 command prints its name, address in memory, and all of its psymtabs
32846 @kindex maint print section-scripts
32847 @cindex info for known .debug_gdb_scripts-loaded scripts
32848 @item maint print section-scripts [@var{regexp}]
32849 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
32850 If @var{regexp} is specified, only print scripts loaded by object files
32851 matching @var{regexp}.
32852 For each script, this command prints its name as specified in the objfile,
32853 and the full path if known.
32854 @xref{.debug_gdb_scripts section}.
32856 @kindex maint print statistics
32857 @cindex bcache statistics
32858 @item maint print statistics
32859 This command prints, for each object file in the program, various data
32860 about that object file followed by the byte cache (@dfn{bcache})
32861 statistics for the object file. The objfile data includes the number
32862 of minimal, partial, full, and stabs symbols, the number of types
32863 defined by the objfile, the number of as yet unexpanded psym tables,
32864 the number of line tables and string tables, and the amount of memory
32865 used by the various tables. The bcache statistics include the counts,
32866 sizes, and counts of duplicates of all and unique objects, max,
32867 average, and median entry size, total memory used and its overhead and
32868 savings, and various measures of the hash table size and chain
32871 @kindex maint print target-stack
32872 @cindex target stack description
32873 @item maint print target-stack
32874 A @dfn{target} is an interface between the debugger and a particular
32875 kind of file or process. Targets can be stacked in @dfn{strata},
32876 so that more than one target can potentially respond to a request.
32877 In particular, memory accesses will walk down the stack of targets
32878 until they find a target that is interested in handling that particular
32881 This command prints a short description of each layer that was pushed on
32882 the @dfn{target stack}, starting from the top layer down to the bottom one.
32884 @kindex maint print type
32885 @cindex type chain of a data type
32886 @item maint print type @var{expr}
32887 Print the type chain for a type specified by @var{expr}. The argument
32888 can be either a type name or a symbol. If it is a symbol, the type of
32889 that symbol is described. The type chain produced by this command is
32890 a recursive definition of the data type as stored in @value{GDBN}'s
32891 data structures, including its flags and contained types.
32893 @kindex maint set dwarf2 always-disassemble
32894 @kindex maint show dwarf2 always-disassemble
32895 @item maint set dwarf2 always-disassemble
32896 @item maint show dwarf2 always-disassemble
32897 Control the behavior of @code{info address} when using DWARF debugging
32900 The default is @code{off}, which means that @value{GDBN} should try to
32901 describe a variable's location in an easily readable format. When
32902 @code{on}, @value{GDBN} will instead display the DWARF location
32903 expression in an assembly-like format. Note that some locations are
32904 too complex for @value{GDBN} to describe simply; in this case you will
32905 always see the disassembly form.
32907 Here is an example of the resulting disassembly:
32910 (gdb) info addr argc
32911 Symbol "argc" is a complex DWARF expression:
32915 For more information on these expressions, see
32916 @uref{http://www.dwarfstd.org/, the DWARF standard}.
32918 @kindex maint set dwarf2 max-cache-age
32919 @kindex maint show dwarf2 max-cache-age
32920 @item maint set dwarf2 max-cache-age
32921 @itemx maint show dwarf2 max-cache-age
32922 Control the DWARF 2 compilation unit cache.
32924 @cindex DWARF 2 compilation units cache
32925 In object files with inter-compilation-unit references, such as those
32926 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
32927 reader needs to frequently refer to previously read compilation units.
32928 This setting controls how long a compilation unit will remain in the
32929 cache if it is not referenced. A higher limit means that cached
32930 compilation units will be stored in memory longer, and more total
32931 memory will be used. Setting it to zero disables caching, which will
32932 slow down @value{GDBN} startup, but reduce memory consumption.
32934 @kindex maint set profile
32935 @kindex maint show profile
32936 @cindex profiling GDB
32937 @item maint set profile
32938 @itemx maint show profile
32939 Control profiling of @value{GDBN}.
32941 Profiling will be disabled until you use the @samp{maint set profile}
32942 command to enable it. When you enable profiling, the system will begin
32943 collecting timing and execution count data; when you disable profiling or
32944 exit @value{GDBN}, the results will be written to a log file. Remember that
32945 if you use profiling, @value{GDBN} will overwrite the profiling log file
32946 (often called @file{gmon.out}). If you have a record of important profiling
32947 data in a @file{gmon.out} file, be sure to move it to a safe location.
32949 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
32950 compiled with the @samp{-pg} compiler option.
32952 @kindex maint set show-debug-regs
32953 @kindex maint show show-debug-regs
32954 @cindex hardware debug registers
32955 @item maint set show-debug-regs
32956 @itemx maint show show-debug-regs
32957 Control whether to show variables that mirror the hardware debug
32958 registers. Use @code{ON} to enable, @code{OFF} to disable. If
32959 enabled, the debug registers values are shown when @value{GDBN} inserts or
32960 removes a hardware breakpoint or watchpoint, and when the inferior
32961 triggers a hardware-assisted breakpoint or watchpoint.
32963 @kindex maint set show-all-tib
32964 @kindex maint show show-all-tib
32965 @item maint set show-all-tib
32966 @itemx maint show show-all-tib
32967 Control whether to show all non zero areas within a 1k block starting
32968 at thread local base, when using the @samp{info w32 thread-information-block}
32971 @kindex maint space
32972 @cindex memory used by commands
32974 Control whether to display memory usage for each command. If set to a
32975 nonzero value, @value{GDBN} will display how much memory each command
32976 took, following the command's own output. This can also be requested
32977 by invoking @value{GDBN} with the @option{--statistics} command-line
32978 switch (@pxref{Mode Options}).
32981 @cindex time of command execution
32983 Control whether to display the execution time for each command. If
32984 set to a nonzero value, @value{GDBN} will display how much time it
32985 took to execute each command, following the command's own output.
32986 The time is not printed for the commands that run the target, since
32987 there's no mechanism currently to compute how much time was spend
32988 by @value{GDBN} and how much time was spend by the program been debugged.
32989 it's not possibly currently
32990 This can also be requested by invoking @value{GDBN} with the
32991 @option{--statistics} command-line switch (@pxref{Mode Options}).
32993 @kindex maint translate-address
32994 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
32995 Find the symbol stored at the location specified by the address
32996 @var{addr} and an optional section name @var{section}. If found,
32997 @value{GDBN} prints the name of the closest symbol and an offset from
32998 the symbol's location to the specified address. This is similar to
32999 the @code{info address} command (@pxref{Symbols}), except that this
33000 command also allows to find symbols in other sections.
33002 If section was not specified, the section in which the symbol was found
33003 is also printed. For dynamically linked executables, the name of
33004 executable or shared library containing the symbol is printed as well.
33008 The following command is useful for non-interactive invocations of
33009 @value{GDBN}, such as in the test suite.
33012 @item set watchdog @var{nsec}
33013 @kindex set watchdog
33014 @cindex watchdog timer
33015 @cindex timeout for commands
33016 Set the maximum number of seconds @value{GDBN} will wait for the
33017 target operation to finish. If this time expires, @value{GDBN}
33018 reports and error and the command is aborted.
33020 @item show watchdog
33021 Show the current setting of the target wait timeout.
33024 @node Remote Protocol
33025 @appendix @value{GDBN} Remote Serial Protocol
33030 * Stop Reply Packets::
33031 * General Query Packets::
33032 * Architecture-Specific Protocol Details::
33033 * Tracepoint Packets::
33034 * Host I/O Packets::
33036 * Notification Packets::
33037 * Remote Non-Stop::
33038 * Packet Acknowledgment::
33040 * File-I/O Remote Protocol Extension::
33041 * Library List Format::
33042 * Memory Map Format::
33043 * Thread List Format::
33044 * Traceframe Info Format::
33050 There may be occasions when you need to know something about the
33051 protocol---for example, if there is only one serial port to your target
33052 machine, you might want your program to do something special if it
33053 recognizes a packet meant for @value{GDBN}.
33055 In the examples below, @samp{->} and @samp{<-} are used to indicate
33056 transmitted and received data, respectively.
33058 @cindex protocol, @value{GDBN} remote serial
33059 @cindex serial protocol, @value{GDBN} remote
33060 @cindex remote serial protocol
33061 All @value{GDBN} commands and responses (other than acknowledgments
33062 and notifications, see @ref{Notification Packets}) are sent as a
33063 @var{packet}. A @var{packet} is introduced with the character
33064 @samp{$}, the actual @var{packet-data}, and the terminating character
33065 @samp{#} followed by a two-digit @var{checksum}:
33068 @code{$}@var{packet-data}@code{#}@var{checksum}
33072 @cindex checksum, for @value{GDBN} remote
33074 The two-digit @var{checksum} is computed as the modulo 256 sum of all
33075 characters between the leading @samp{$} and the trailing @samp{#} (an
33076 eight bit unsigned checksum).
33078 Implementors should note that prior to @value{GDBN} 5.0 the protocol
33079 specification also included an optional two-digit @var{sequence-id}:
33082 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
33085 @cindex sequence-id, for @value{GDBN} remote
33087 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
33088 has never output @var{sequence-id}s. Stubs that handle packets added
33089 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
33091 When either the host or the target machine receives a packet, the first
33092 response expected is an acknowledgment: either @samp{+} (to indicate
33093 the package was received correctly) or @samp{-} (to request
33097 -> @code{$}@var{packet-data}@code{#}@var{checksum}
33102 The @samp{+}/@samp{-} acknowledgments can be disabled
33103 once a connection is established.
33104 @xref{Packet Acknowledgment}, for details.
33106 The host (@value{GDBN}) sends @var{command}s, and the target (the
33107 debugging stub incorporated in your program) sends a @var{response}. In
33108 the case of step and continue @var{command}s, the response is only sent
33109 when the operation has completed, and the target has again stopped all
33110 threads in all attached processes. This is the default all-stop mode
33111 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
33112 execution mode; see @ref{Remote Non-Stop}, for details.
33114 @var{packet-data} consists of a sequence of characters with the
33115 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
33118 @cindex remote protocol, field separator
33119 Fields within the packet should be separated using @samp{,} @samp{;} or
33120 @samp{:}. Except where otherwise noted all numbers are represented in
33121 @sc{hex} with leading zeros suppressed.
33123 Implementors should note that prior to @value{GDBN} 5.0, the character
33124 @samp{:} could not appear as the third character in a packet (as it
33125 would potentially conflict with the @var{sequence-id}).
33127 @cindex remote protocol, binary data
33128 @anchor{Binary Data}
33129 Binary data in most packets is encoded either as two hexadecimal
33130 digits per byte of binary data. This allowed the traditional remote
33131 protocol to work over connections which were only seven-bit clean.
33132 Some packets designed more recently assume an eight-bit clean
33133 connection, and use a more efficient encoding to send and receive
33136 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
33137 as an escape character. Any escaped byte is transmitted as the escape
33138 character followed by the original character XORed with @code{0x20}.
33139 For example, the byte @code{0x7d} would be transmitted as the two
33140 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
33141 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
33142 @samp{@}}) must always be escaped. Responses sent by the stub
33143 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
33144 is not interpreted as the start of a run-length encoded sequence
33147 Response @var{data} can be run-length encoded to save space.
33148 Run-length encoding replaces runs of identical characters with one
33149 instance of the repeated character, followed by a @samp{*} and a
33150 repeat count. The repeat count is itself sent encoded, to avoid
33151 binary characters in @var{data}: a value of @var{n} is sent as
33152 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
33153 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
33154 code 32) for a repeat count of 3. (This is because run-length
33155 encoding starts to win for counts 3 or more.) Thus, for example,
33156 @samp{0* } is a run-length encoding of ``0000'': the space character
33157 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
33160 The printable characters @samp{#} and @samp{$} or with a numeric value
33161 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
33162 seven repeats (@samp{$}) can be expanded using a repeat count of only
33163 five (@samp{"}). For example, @samp{00000000} can be encoded as
33166 The error response returned for some packets includes a two character
33167 error number. That number is not well defined.
33169 @cindex empty response, for unsupported packets
33170 For any @var{command} not supported by the stub, an empty response
33171 (@samp{$#00}) should be returned. That way it is possible to extend the
33172 protocol. A newer @value{GDBN} can tell if a packet is supported based
33175 At a minimum, a stub is required to support the @samp{g} and @samp{G}
33176 commands for register access, and the @samp{m} and @samp{M} commands
33177 for memory access. Stubs that only control single-threaded targets
33178 can implement run control with the @samp{c} (continue), and @samp{s}
33179 (step) commands. Stubs that support multi-threading targets should
33180 support the @samp{vCont} command. All other commands are optional.
33185 The following table provides a complete list of all currently defined
33186 @var{command}s and their corresponding response @var{data}.
33187 @xref{File-I/O Remote Protocol Extension}, for details about the File
33188 I/O extension of the remote protocol.
33190 Each packet's description has a template showing the packet's overall
33191 syntax, followed by an explanation of the packet's meaning. We
33192 include spaces in some of the templates for clarity; these are not
33193 part of the packet's syntax. No @value{GDBN} packet uses spaces to
33194 separate its components. For example, a template like @samp{foo
33195 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
33196 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
33197 @var{baz}. @value{GDBN} does not transmit a space character between the
33198 @samp{foo} and the @var{bar}, or between the @var{bar} and the
33201 @cindex @var{thread-id}, in remote protocol
33202 @anchor{thread-id syntax}
33203 Several packets and replies include a @var{thread-id} field to identify
33204 a thread. Normally these are positive numbers with a target-specific
33205 interpretation, formatted as big-endian hex strings. A @var{thread-id}
33206 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
33209 In addition, the remote protocol supports a multiprocess feature in
33210 which the @var{thread-id} syntax is extended to optionally include both
33211 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
33212 The @var{pid} (process) and @var{tid} (thread) components each have the
33213 format described above: a positive number with target-specific
33214 interpretation formatted as a big-endian hex string, literal @samp{-1}
33215 to indicate all processes or threads (respectively), or @samp{0} to
33216 indicate an arbitrary process or thread. Specifying just a process, as
33217 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
33218 error to specify all processes but a specific thread, such as
33219 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
33220 for those packets and replies explicitly documented to include a process
33221 ID, rather than a @var{thread-id}.
33223 The multiprocess @var{thread-id} syntax extensions are only used if both
33224 @value{GDBN} and the stub report support for the @samp{multiprocess}
33225 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
33228 Note that all packet forms beginning with an upper- or lower-case
33229 letter, other than those described here, are reserved for future use.
33231 Here are the packet descriptions.
33236 @cindex @samp{!} packet
33237 @anchor{extended mode}
33238 Enable extended mode. In extended mode, the remote server is made
33239 persistent. The @samp{R} packet is used to restart the program being
33245 The remote target both supports and has enabled extended mode.
33249 @cindex @samp{?} packet
33250 Indicate the reason the target halted. The reply is the same as for
33251 step and continue. This packet has a special interpretation when the
33252 target is in non-stop mode; see @ref{Remote Non-Stop}.
33255 @xref{Stop Reply Packets}, for the reply specifications.
33257 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
33258 @cindex @samp{A} packet
33259 Initialized @code{argv[]} array passed into program. @var{arglen}
33260 specifies the number of bytes in the hex encoded byte stream
33261 @var{arg}. See @code{gdbserver} for more details.
33266 The arguments were set.
33272 @cindex @samp{b} packet
33273 (Don't use this packet; its behavior is not well-defined.)
33274 Change the serial line speed to @var{baud}.
33276 JTC: @emph{When does the transport layer state change? When it's
33277 received, or after the ACK is transmitted. In either case, there are
33278 problems if the command or the acknowledgment packet is dropped.}
33280 Stan: @emph{If people really wanted to add something like this, and get
33281 it working for the first time, they ought to modify ser-unix.c to send
33282 some kind of out-of-band message to a specially-setup stub and have the
33283 switch happen "in between" packets, so that from remote protocol's point
33284 of view, nothing actually happened.}
33286 @item B @var{addr},@var{mode}
33287 @cindex @samp{B} packet
33288 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
33289 breakpoint at @var{addr}.
33291 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
33292 (@pxref{insert breakpoint or watchpoint packet}).
33294 @cindex @samp{bc} packet
33297 Backward continue. Execute the target system in reverse. No parameter.
33298 @xref{Reverse Execution}, for more information.
33301 @xref{Stop Reply Packets}, for the reply specifications.
33303 @cindex @samp{bs} packet
33306 Backward single step. Execute one instruction in reverse. No parameter.
33307 @xref{Reverse Execution}, for more information.
33310 @xref{Stop Reply Packets}, for the reply specifications.
33312 @item c @r{[}@var{addr}@r{]}
33313 @cindex @samp{c} packet
33314 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
33315 resume at current address.
33317 This packet is deprecated for multi-threading support. @xref{vCont
33321 @xref{Stop Reply Packets}, for the reply specifications.
33323 @item C @var{sig}@r{[};@var{addr}@r{]}
33324 @cindex @samp{C} packet
33325 Continue with signal @var{sig} (hex signal number). If
33326 @samp{;@var{addr}} is omitted, resume at same address.
33328 This packet is deprecated for multi-threading support. @xref{vCont
33332 @xref{Stop Reply Packets}, for the reply specifications.
33335 @cindex @samp{d} packet
33338 Don't use this packet; instead, define a general set packet
33339 (@pxref{General Query Packets}).
33343 @cindex @samp{D} packet
33344 The first form of the packet is used to detach @value{GDBN} from the
33345 remote system. It is sent to the remote target
33346 before @value{GDBN} disconnects via the @code{detach} command.
33348 The second form, including a process ID, is used when multiprocess
33349 protocol extensions are enabled (@pxref{multiprocess extensions}), to
33350 detach only a specific process. The @var{pid} is specified as a
33351 big-endian hex string.
33361 @item F @var{RC},@var{EE},@var{CF};@var{XX}
33362 @cindex @samp{F} packet
33363 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
33364 This is part of the File-I/O protocol extension. @xref{File-I/O
33365 Remote Protocol Extension}, for the specification.
33368 @anchor{read registers packet}
33369 @cindex @samp{g} packet
33370 Read general registers.
33374 @item @var{XX@dots{}}
33375 Each byte of register data is described by two hex digits. The bytes
33376 with the register are transmitted in target byte order. The size of
33377 each register and their position within the @samp{g} packet are
33378 determined by the @value{GDBN} internal gdbarch functions
33379 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
33380 specification of several standard @samp{g} packets is specified below.
33382 When reading registers from a trace frame (@pxref{Analyze Collected
33383 Data,,Using the Collected Data}), the stub may also return a string of
33384 literal @samp{x}'s in place of the register data digits, to indicate
33385 that the corresponding register has not been collected, thus its value
33386 is unavailable. For example, for an architecture with 4 registers of
33387 4 bytes each, the following reply indicates to @value{GDBN} that
33388 registers 0 and 2 have not been collected, while registers 1 and 3
33389 have been collected, and both have zero value:
33393 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
33400 @item G @var{XX@dots{}}
33401 @cindex @samp{G} packet
33402 Write general registers. @xref{read registers packet}, for a
33403 description of the @var{XX@dots{}} data.
33413 @item H @var{op} @var{thread-id}
33414 @cindex @samp{H} packet
33415 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
33416 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
33417 it should be @samp{c} for step and continue operations (note that this
33418 is deprecated, supporting the @samp{vCont} command is a better
33419 option), @samp{g} for other operations. The thread designator
33420 @var{thread-id} has the format and interpretation described in
33421 @ref{thread-id syntax}.
33432 @c 'H': How restrictive (or permissive) is the thread model. If a
33433 @c thread is selected and stopped, are other threads allowed
33434 @c to continue to execute? As I mentioned above, I think the
33435 @c semantics of each command when a thread is selected must be
33436 @c described. For example:
33438 @c 'g': If the stub supports threads and a specific thread is
33439 @c selected, returns the register block from that thread;
33440 @c otherwise returns current registers.
33442 @c 'G' If the stub supports threads and a specific thread is
33443 @c selected, sets the registers of the register block of
33444 @c that thread; otherwise sets current registers.
33446 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
33447 @anchor{cycle step packet}
33448 @cindex @samp{i} packet
33449 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
33450 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
33451 step starting at that address.
33454 @cindex @samp{I} packet
33455 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
33459 @cindex @samp{k} packet
33462 FIXME: @emph{There is no description of how to operate when a specific
33463 thread context has been selected (i.e.@: does 'k' kill only that
33466 @item m @var{addr},@var{length}
33467 @cindex @samp{m} packet
33468 Read @var{length} bytes of memory starting at address @var{addr}.
33469 Note that @var{addr} may not be aligned to any particular boundary.
33471 The stub need not use any particular size or alignment when gathering
33472 data from memory for the response; even if @var{addr} is word-aligned
33473 and @var{length} is a multiple of the word size, the stub is free to
33474 use byte accesses, or not. For this reason, this packet may not be
33475 suitable for accessing memory-mapped I/O devices.
33476 @cindex alignment of remote memory accesses
33477 @cindex size of remote memory accesses
33478 @cindex memory, alignment and size of remote accesses
33482 @item @var{XX@dots{}}
33483 Memory contents; each byte is transmitted as a two-digit hexadecimal
33484 number. The reply may contain fewer bytes than requested if the
33485 server was able to read only part of the region of memory.
33490 @item M @var{addr},@var{length}:@var{XX@dots{}}
33491 @cindex @samp{M} packet
33492 Write @var{length} bytes of memory starting at address @var{addr}.
33493 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
33494 hexadecimal number.
33501 for an error (this includes the case where only part of the data was
33506 @cindex @samp{p} packet
33507 Read the value of register @var{n}; @var{n} is in hex.
33508 @xref{read registers packet}, for a description of how the returned
33509 register value is encoded.
33513 @item @var{XX@dots{}}
33514 the register's value
33518 Indicating an unrecognized @var{query}.
33521 @item P @var{n@dots{}}=@var{r@dots{}}
33522 @anchor{write register packet}
33523 @cindex @samp{P} packet
33524 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
33525 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
33526 digits for each byte in the register (target byte order).
33536 @item q @var{name} @var{params}@dots{}
33537 @itemx Q @var{name} @var{params}@dots{}
33538 @cindex @samp{q} packet
33539 @cindex @samp{Q} packet
33540 General query (@samp{q}) and set (@samp{Q}). These packets are
33541 described fully in @ref{General Query Packets}.
33544 @cindex @samp{r} packet
33545 Reset the entire system.
33547 Don't use this packet; use the @samp{R} packet instead.
33550 @cindex @samp{R} packet
33551 Restart the program being debugged. @var{XX}, while needed, is ignored.
33552 This packet is only available in extended mode (@pxref{extended mode}).
33554 The @samp{R} packet has no reply.
33556 @item s @r{[}@var{addr}@r{]}
33557 @cindex @samp{s} packet
33558 Single step. @var{addr} is the address at which to resume. If
33559 @var{addr} is omitted, resume at same address.
33561 This packet is deprecated for multi-threading support. @xref{vCont
33565 @xref{Stop Reply Packets}, for the reply specifications.
33567 @item S @var{sig}@r{[};@var{addr}@r{]}
33568 @anchor{step with signal packet}
33569 @cindex @samp{S} packet
33570 Step with signal. This is analogous to the @samp{C} packet, but
33571 requests a single-step, rather than a normal resumption of execution.
33573 This packet is deprecated for multi-threading support. @xref{vCont
33577 @xref{Stop Reply Packets}, for the reply specifications.
33579 @item t @var{addr}:@var{PP},@var{MM}
33580 @cindex @samp{t} packet
33581 Search backwards starting at address @var{addr} for a match with pattern
33582 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
33583 @var{addr} must be at least 3 digits.
33585 @item T @var{thread-id}
33586 @cindex @samp{T} packet
33587 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
33592 thread is still alive
33598 Packets starting with @samp{v} are identified by a multi-letter name,
33599 up to the first @samp{;} or @samp{?} (or the end of the packet).
33601 @item vAttach;@var{pid}
33602 @cindex @samp{vAttach} packet
33603 Attach to a new process with the specified process ID @var{pid}.
33604 The process ID is a
33605 hexadecimal integer identifying the process. In all-stop mode, all
33606 threads in the attached process are stopped; in non-stop mode, it may be
33607 attached without being stopped if that is supported by the target.
33609 @c In non-stop mode, on a successful vAttach, the stub should set the
33610 @c current thread to a thread of the newly-attached process. After
33611 @c attaching, GDB queries for the attached process's thread ID with qC.
33612 @c Also note that, from a user perspective, whether or not the
33613 @c target is stopped on attach in non-stop mode depends on whether you
33614 @c use the foreground or background version of the attach command, not
33615 @c on what vAttach does; GDB does the right thing with respect to either
33616 @c stopping or restarting threads.
33618 This packet is only available in extended mode (@pxref{extended mode}).
33624 @item @r{Any stop packet}
33625 for success in all-stop mode (@pxref{Stop Reply Packets})
33627 for success in non-stop mode (@pxref{Remote Non-Stop})
33630 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
33631 @cindex @samp{vCont} packet
33632 @anchor{vCont packet}
33633 Resume the inferior, specifying different actions for each thread.
33634 If an action is specified with no @var{thread-id}, then it is applied to any
33635 threads that don't have a specific action specified; if no default action is
33636 specified then other threads should remain stopped in all-stop mode and
33637 in their current state in non-stop mode.
33638 Specifying multiple
33639 default actions is an error; specifying no actions is also an error.
33640 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
33642 Currently supported actions are:
33648 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
33652 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
33657 The optional argument @var{addr} normally associated with the
33658 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
33659 not supported in @samp{vCont}.
33661 The @samp{t} action is only relevant in non-stop mode
33662 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
33663 A stop reply should be generated for any affected thread not already stopped.
33664 When a thread is stopped by means of a @samp{t} action,
33665 the corresponding stop reply should indicate that the thread has stopped with
33666 signal @samp{0}, regardless of whether the target uses some other signal
33667 as an implementation detail.
33670 @xref{Stop Reply Packets}, for the reply specifications.
33673 @cindex @samp{vCont?} packet
33674 Request a list of actions supported by the @samp{vCont} packet.
33678 @item vCont@r{[};@var{action}@dots{}@r{]}
33679 The @samp{vCont} packet is supported. Each @var{action} is a supported
33680 command in the @samp{vCont} packet.
33682 The @samp{vCont} packet is not supported.
33685 @item vFile:@var{operation}:@var{parameter}@dots{}
33686 @cindex @samp{vFile} packet
33687 Perform a file operation on the target system. For details,
33688 see @ref{Host I/O Packets}.
33690 @item vFlashErase:@var{addr},@var{length}
33691 @cindex @samp{vFlashErase} packet
33692 Direct the stub to erase @var{length} bytes of flash starting at
33693 @var{addr}. The region may enclose any number of flash blocks, but
33694 its start and end must fall on block boundaries, as indicated by the
33695 flash block size appearing in the memory map (@pxref{Memory Map
33696 Format}). @value{GDBN} groups flash memory programming operations
33697 together, and sends a @samp{vFlashDone} request after each group; the
33698 stub is allowed to delay erase operation until the @samp{vFlashDone}
33699 packet is received.
33701 The stub must support @samp{vCont} if it reports support for
33702 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
33703 this case @samp{vCont} actions can be specified to apply to all threads
33704 in a process by using the @samp{p@var{pid}.-1} form of the
33715 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
33716 @cindex @samp{vFlashWrite} packet
33717 Direct the stub to write data to flash address @var{addr}. The data
33718 is passed in binary form using the same encoding as for the @samp{X}
33719 packet (@pxref{Binary Data}). The memory ranges specified by
33720 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
33721 not overlap, and must appear in order of increasing addresses
33722 (although @samp{vFlashErase} packets for higher addresses may already
33723 have been received; the ordering is guaranteed only between
33724 @samp{vFlashWrite} packets). If a packet writes to an address that was
33725 neither erased by a preceding @samp{vFlashErase} packet nor by some other
33726 target-specific method, the results are unpredictable.
33734 for vFlashWrite addressing non-flash memory
33740 @cindex @samp{vFlashDone} packet
33741 Indicate to the stub that flash programming operation is finished.
33742 The stub is permitted to delay or batch the effects of a group of
33743 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
33744 @samp{vFlashDone} packet is received. The contents of the affected
33745 regions of flash memory are unpredictable until the @samp{vFlashDone}
33746 request is completed.
33748 @item vKill;@var{pid}
33749 @cindex @samp{vKill} packet
33750 Kill the process with the specified process ID. @var{pid} is a
33751 hexadecimal integer identifying the process. This packet is used in
33752 preference to @samp{k} when multiprocess protocol extensions are
33753 supported; see @ref{multiprocess extensions}.
33763 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
33764 @cindex @samp{vRun} packet
33765 Run the program @var{filename}, passing it each @var{argument} on its
33766 command line. The file and arguments are hex-encoded strings. If
33767 @var{filename} is an empty string, the stub may use a default program
33768 (e.g.@: the last program run). The program is created in the stopped
33771 @c FIXME: What about non-stop mode?
33773 This packet is only available in extended mode (@pxref{extended mode}).
33779 @item @r{Any stop packet}
33780 for success (@pxref{Stop Reply Packets})
33784 @anchor{vStopped packet}
33785 @cindex @samp{vStopped} packet
33787 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
33788 reply and prompt for the stub to report another one.
33792 @item @r{Any stop packet}
33793 if there is another unreported stop event (@pxref{Stop Reply Packets})
33795 if there are no unreported stop events
33798 @item X @var{addr},@var{length}:@var{XX@dots{}}
33800 @cindex @samp{X} packet
33801 Write data to memory, where the data is transmitted in binary.
33802 @var{addr} is address, @var{length} is number of bytes,
33803 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
33813 @item z @var{type},@var{addr},@var{kind}
33814 @itemx Z @var{type},@var{addr},@var{kind}
33815 @anchor{insert breakpoint or watchpoint packet}
33816 @cindex @samp{z} packet
33817 @cindex @samp{Z} packets
33818 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
33819 watchpoint starting at address @var{address} of kind @var{kind}.
33821 Each breakpoint and watchpoint packet @var{type} is documented
33824 @emph{Implementation notes: A remote target shall return an empty string
33825 for an unrecognized breakpoint or watchpoint packet @var{type}. A
33826 remote target shall support either both or neither of a given
33827 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
33828 avoid potential problems with duplicate packets, the operations should
33829 be implemented in an idempotent way.}
33831 @item z0,@var{addr},@var{kind}
33832 @itemx Z0,@var{addr},@var{kind}
33833 @cindex @samp{z0} packet
33834 @cindex @samp{Z0} packet
33835 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
33836 @var{addr} of type @var{kind}.
33838 A memory breakpoint is implemented by replacing the instruction at
33839 @var{addr} with a software breakpoint or trap instruction. The
33840 @var{kind} is target-specific and typically indicates the size of
33841 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
33842 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
33843 architectures have additional meanings for @var{kind};
33844 see @ref{Architecture-Specific Protocol Details}.
33846 @emph{Implementation note: It is possible for a target to copy or move
33847 code that contains memory breakpoints (e.g., when implementing
33848 overlays). The behavior of this packet, in the presence of such a
33849 target, is not defined.}
33861 @item z1,@var{addr},@var{kind}
33862 @itemx Z1,@var{addr},@var{kind}
33863 @cindex @samp{z1} packet
33864 @cindex @samp{Z1} packet
33865 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
33866 address @var{addr}.
33868 A hardware breakpoint is implemented using a mechanism that is not
33869 dependant on being able to modify the target's memory. @var{kind}
33870 has the same meaning as in @samp{Z0} packets.
33872 @emph{Implementation note: A hardware breakpoint is not affected by code
33885 @item z2,@var{addr},@var{kind}
33886 @itemx Z2,@var{addr},@var{kind}
33887 @cindex @samp{z2} packet
33888 @cindex @samp{Z2} packet
33889 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
33890 @var{kind} is interpreted as the number of bytes to watch.
33902 @item z3,@var{addr},@var{kind}
33903 @itemx Z3,@var{addr},@var{kind}
33904 @cindex @samp{z3} packet
33905 @cindex @samp{Z3} packet
33906 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
33907 @var{kind} is interpreted as the number of bytes to watch.
33919 @item z4,@var{addr},@var{kind}
33920 @itemx Z4,@var{addr},@var{kind}
33921 @cindex @samp{z4} packet
33922 @cindex @samp{Z4} packet
33923 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
33924 @var{kind} is interpreted as the number of bytes to watch.
33938 @node Stop Reply Packets
33939 @section Stop Reply Packets
33940 @cindex stop reply packets
33942 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
33943 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
33944 receive any of the below as a reply. Except for @samp{?}
33945 and @samp{vStopped}, that reply is only returned
33946 when the target halts. In the below the exact meaning of @dfn{signal
33947 number} is defined by the header @file{include/gdb/signals.h} in the
33948 @value{GDBN} source code.
33950 As in the description of request packets, we include spaces in the
33951 reply templates for clarity; these are not part of the reply packet's
33952 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
33958 The program received signal number @var{AA} (a two-digit hexadecimal
33959 number). This is equivalent to a @samp{T} response with no
33960 @var{n}:@var{r} pairs.
33962 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
33963 @cindex @samp{T} packet reply
33964 The program received signal number @var{AA} (a two-digit hexadecimal
33965 number). This is equivalent to an @samp{S} response, except that the
33966 @samp{@var{n}:@var{r}} pairs can carry values of important registers
33967 and other information directly in the stop reply packet, reducing
33968 round-trip latency. Single-step and breakpoint traps are reported
33969 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
33973 If @var{n} is a hexadecimal number, it is a register number, and the
33974 corresponding @var{r} gives that register's value. @var{r} is a
33975 series of bytes in target byte order, with each byte given by a
33976 two-digit hex number.
33979 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
33980 the stopped thread, as specified in @ref{thread-id syntax}.
33983 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
33984 the core on which the stop event was detected.
33987 If @var{n} is a recognized @dfn{stop reason}, it describes a more
33988 specific event that stopped the target. The currently defined stop
33989 reasons are listed below. @var{aa} should be @samp{05}, the trap
33990 signal. At most one stop reason should be present.
33993 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
33994 and go on to the next; this allows us to extend the protocol in the
33998 The currently defined stop reasons are:
34004 The packet indicates a watchpoint hit, and @var{r} is the data address, in
34007 @cindex shared library events, remote reply
34009 The packet indicates that the loaded libraries have changed.
34010 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
34011 list of loaded libraries. @var{r} is ignored.
34013 @cindex replay log events, remote reply
34015 The packet indicates that the target cannot continue replaying
34016 logged execution events, because it has reached the end (or the
34017 beginning when executing backward) of the log. The value of @var{r}
34018 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
34019 for more information.
34023 @itemx W @var{AA} ; process:@var{pid}
34024 The process exited, and @var{AA} is the exit status. This is only
34025 applicable to certain targets.
34027 The second form of the response, including the process ID of the exited
34028 process, can be used only when @value{GDBN} has reported support for
34029 multiprocess protocol extensions; see @ref{multiprocess extensions}.
34030 The @var{pid} is formatted as a big-endian hex string.
34033 @itemx X @var{AA} ; process:@var{pid}
34034 The process terminated with signal @var{AA}.
34036 The second form of the response, including the process ID of the
34037 terminated process, can be used only when @value{GDBN} has reported
34038 support for multiprocess protocol extensions; see @ref{multiprocess
34039 extensions}. The @var{pid} is formatted as a big-endian hex string.
34041 @item O @var{XX}@dots{}
34042 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
34043 written as the program's console output. This can happen at any time
34044 while the program is running and the debugger should continue to wait
34045 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
34047 @item F @var{call-id},@var{parameter}@dots{}
34048 @var{call-id} is the identifier which says which host system call should
34049 be called. This is just the name of the function. Translation into the
34050 correct system call is only applicable as it's defined in @value{GDBN}.
34051 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
34054 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
34055 this very system call.
34057 The target replies with this packet when it expects @value{GDBN} to
34058 call a host system call on behalf of the target. @value{GDBN} replies
34059 with an appropriate @samp{F} packet and keeps up waiting for the next
34060 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
34061 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
34062 Protocol Extension}, for more details.
34066 @node General Query Packets
34067 @section General Query Packets
34068 @cindex remote query requests
34070 Packets starting with @samp{q} are @dfn{general query packets};
34071 packets starting with @samp{Q} are @dfn{general set packets}. General
34072 query and set packets are a semi-unified form for retrieving and
34073 sending information to and from the stub.
34075 The initial letter of a query or set packet is followed by a name
34076 indicating what sort of thing the packet applies to. For example,
34077 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
34078 definitions with the stub. These packet names follow some
34083 The name must not contain commas, colons or semicolons.
34085 Most @value{GDBN} query and set packets have a leading upper case
34088 The names of custom vendor packets should use a company prefix, in
34089 lower case, followed by a period. For example, packets designed at
34090 the Acme Corporation might begin with @samp{qacme.foo} (for querying
34091 foos) or @samp{Qacme.bar} (for setting bars).
34094 The name of a query or set packet should be separated from any
34095 parameters by a @samp{:}; the parameters themselves should be
34096 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
34097 full packet name, and check for a separator or the end of the packet,
34098 in case two packet names share a common prefix. New packets should not begin
34099 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
34100 packets predate these conventions, and have arguments without any terminator
34101 for the packet name; we suspect they are in widespread use in places that
34102 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
34103 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
34106 Like the descriptions of the other packets, each description here
34107 has a template showing the packet's overall syntax, followed by an
34108 explanation of the packet's meaning. We include spaces in some of the
34109 templates for clarity; these are not part of the packet's syntax. No
34110 @value{GDBN} packet uses spaces to separate its components.
34112 Here are the currently defined query and set packets:
34116 @item QAllow:@var{op}:@var{val}@dots{}
34117 @cindex @samp{QAllow} packet
34118 Specify which operations @value{GDBN} expects to request of the
34119 target, as a semicolon-separated list of operation name and value
34120 pairs. Possible values for @var{op} include @samp{WriteReg},
34121 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
34122 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
34123 indicating that @value{GDBN} will not request the operation, or 1,
34124 indicating that it may. (The target can then use this to set up its
34125 own internals optimally, for instance if the debugger never expects to
34126 insert breakpoints, it may not need to install its own trap handler.)
34129 @cindex current thread, remote request
34130 @cindex @samp{qC} packet
34131 Return the current thread ID.
34135 @item QC @var{thread-id}
34136 Where @var{thread-id} is a thread ID as documented in
34137 @ref{thread-id syntax}.
34138 @item @r{(anything else)}
34139 Any other reply implies the old thread ID.
34142 @item qCRC:@var{addr},@var{length}
34143 @cindex CRC of memory block, remote request
34144 @cindex @samp{qCRC} packet
34145 Compute the CRC checksum of a block of memory using CRC-32 defined in
34146 IEEE 802.3. The CRC is computed byte at a time, taking the most
34147 significant bit of each byte first. The initial pattern code
34148 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
34150 @emph{Note:} This is the same CRC used in validating separate debug
34151 files (@pxref{Separate Debug Files, , Debugging Information in Separate
34152 Files}). However the algorithm is slightly different. When validating
34153 separate debug files, the CRC is computed taking the @emph{least}
34154 significant bit of each byte first, and the final result is inverted to
34155 detect trailing zeros.
34160 An error (such as memory fault)
34161 @item C @var{crc32}
34162 The specified memory region's checksum is @var{crc32}.
34165 @item QDisableRandomization:@var{value}
34166 @cindex disable address space randomization, remote request
34167 @cindex @samp{QDisableRandomization} packet
34168 Some target operating systems will randomize the virtual address space
34169 of the inferior process as a security feature, but provide a feature
34170 to disable such randomization, e.g.@: to allow for a more deterministic
34171 debugging experience. On such systems, this packet with a @var{value}
34172 of 1 directs the target to disable address space randomization for
34173 processes subsequently started via @samp{vRun} packets, while a packet
34174 with a @var{value} of 0 tells the target to enable address space
34177 This packet is only available in extended mode (@pxref{extended mode}).
34182 The request succeeded.
34185 An error occurred. @var{nn} are hex digits.
34188 An empty reply indicates that @samp{QDisableRandomization} is not supported
34192 This packet is not probed by default; the remote stub must request it,
34193 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34194 This should only be done on targets that actually support disabling
34195 address space randomization.
34198 @itemx qsThreadInfo
34199 @cindex list active threads, remote request
34200 @cindex @samp{qfThreadInfo} packet
34201 @cindex @samp{qsThreadInfo} packet
34202 Obtain a list of all active thread IDs from the target (OS). Since there
34203 may be too many active threads to fit into one reply packet, this query
34204 works iteratively: it may require more than one query/reply sequence to
34205 obtain the entire list of threads. The first query of the sequence will
34206 be the @samp{qfThreadInfo} query; subsequent queries in the
34207 sequence will be the @samp{qsThreadInfo} query.
34209 NOTE: This packet replaces the @samp{qL} query (see below).
34213 @item m @var{thread-id}
34215 @item m @var{thread-id},@var{thread-id}@dots{}
34216 a comma-separated list of thread IDs
34218 (lower case letter @samp{L}) denotes end of list.
34221 In response to each query, the target will reply with a list of one or
34222 more thread IDs, separated by commas.
34223 @value{GDBN} will respond to each reply with a request for more thread
34224 ids (using the @samp{qs} form of the query), until the target responds
34225 with @samp{l} (lower-case ell, for @dfn{last}).
34226 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
34229 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
34230 @cindex get thread-local storage address, remote request
34231 @cindex @samp{qGetTLSAddr} packet
34232 Fetch the address associated with thread local storage specified
34233 by @var{thread-id}, @var{offset}, and @var{lm}.
34235 @var{thread-id} is the thread ID associated with the
34236 thread for which to fetch the TLS address. @xref{thread-id syntax}.
34238 @var{offset} is the (big endian, hex encoded) offset associated with the
34239 thread local variable. (This offset is obtained from the debug
34240 information associated with the variable.)
34242 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
34243 load module associated with the thread local storage. For example,
34244 a @sc{gnu}/Linux system will pass the link map address of the shared
34245 object associated with the thread local storage under consideration.
34246 Other operating environments may choose to represent the load module
34247 differently, so the precise meaning of this parameter will vary.
34251 @item @var{XX}@dots{}
34252 Hex encoded (big endian) bytes representing the address of the thread
34253 local storage requested.
34256 An error occurred. @var{nn} are hex digits.
34259 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
34262 @item qGetTIBAddr:@var{thread-id}
34263 @cindex get thread information block address
34264 @cindex @samp{qGetTIBAddr} packet
34265 Fetch address of the Windows OS specific Thread Information Block.
34267 @var{thread-id} is the thread ID associated with the thread.
34271 @item @var{XX}@dots{}
34272 Hex encoded (big endian) bytes representing the linear address of the
34273 thread information block.
34276 An error occured. This means that either the thread was not found, or the
34277 address could not be retrieved.
34280 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
34283 @item qL @var{startflag} @var{threadcount} @var{nextthread}
34284 Obtain thread information from RTOS. Where: @var{startflag} (one hex
34285 digit) is one to indicate the first query and zero to indicate a
34286 subsequent query; @var{threadcount} (two hex digits) is the maximum
34287 number of threads the response packet can contain; and @var{nextthread}
34288 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
34289 returned in the response as @var{argthread}.
34291 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
34295 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
34296 Where: @var{count} (two hex digits) is the number of threads being
34297 returned; @var{done} (one hex digit) is zero to indicate more threads
34298 and one indicates no further threads; @var{argthreadid} (eight hex
34299 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
34300 is a sequence of thread IDs from the target. @var{threadid} (eight hex
34301 digits). See @code{remote.c:parse_threadlist_response()}.
34305 @cindex section offsets, remote request
34306 @cindex @samp{qOffsets} packet
34307 Get section offsets that the target used when relocating the downloaded
34312 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
34313 Relocate the @code{Text} section by @var{xxx} from its original address.
34314 Relocate the @code{Data} section by @var{yyy} from its original address.
34315 If the object file format provides segment information (e.g.@: @sc{elf}
34316 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
34317 segments by the supplied offsets.
34319 @emph{Note: while a @code{Bss} offset may be included in the response,
34320 @value{GDBN} ignores this and instead applies the @code{Data} offset
34321 to the @code{Bss} section.}
34323 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
34324 Relocate the first segment of the object file, which conventionally
34325 contains program code, to a starting address of @var{xxx}. If
34326 @samp{DataSeg} is specified, relocate the second segment, which
34327 conventionally contains modifiable data, to a starting address of
34328 @var{yyy}. @value{GDBN} will report an error if the object file
34329 does not contain segment information, or does not contain at least
34330 as many segments as mentioned in the reply. Extra segments are
34331 kept at fixed offsets relative to the last relocated segment.
34334 @item qP @var{mode} @var{thread-id}
34335 @cindex thread information, remote request
34336 @cindex @samp{qP} packet
34337 Returns information on @var{thread-id}. Where: @var{mode} is a hex
34338 encoded 32 bit mode; @var{thread-id} is a thread ID
34339 (@pxref{thread-id syntax}).
34341 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
34344 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
34348 @cindex non-stop mode, remote request
34349 @cindex @samp{QNonStop} packet
34351 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
34352 @xref{Remote Non-Stop}, for more information.
34357 The request succeeded.
34360 An error occurred. @var{nn} are hex digits.
34363 An empty reply indicates that @samp{QNonStop} is not supported by
34367 This packet is not probed by default; the remote stub must request it,
34368 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34369 Use of this packet is controlled by the @code{set non-stop} command;
34370 @pxref{Non-Stop Mode}.
34372 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
34373 @cindex pass signals to inferior, remote request
34374 @cindex @samp{QPassSignals} packet
34375 @anchor{QPassSignals}
34376 Each listed @var{signal} should be passed directly to the inferior process.
34377 Signals are numbered identically to continue packets and stop replies
34378 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
34379 strictly greater than the previous item. These signals do not need to stop
34380 the inferior, or be reported to @value{GDBN}. All other signals should be
34381 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
34382 combine; any earlier @samp{QPassSignals} list is completely replaced by the
34383 new list. This packet improves performance when using @samp{handle
34384 @var{signal} nostop noprint pass}.
34389 The request succeeded.
34392 An error occurred. @var{nn} are hex digits.
34395 An empty reply indicates that @samp{QPassSignals} is not supported by
34399 Use of this packet is controlled by the @code{set remote pass-signals}
34400 command (@pxref{Remote Configuration, set remote pass-signals}).
34401 This packet is not probed by default; the remote stub must request it,
34402 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34404 @item qRcmd,@var{command}
34405 @cindex execute remote command, remote request
34406 @cindex @samp{qRcmd} packet
34407 @var{command} (hex encoded) is passed to the local interpreter for
34408 execution. Invalid commands should be reported using the output
34409 string. Before the final result packet, the target may also respond
34410 with a number of intermediate @samp{O@var{output}} console output
34411 packets. @emph{Implementors should note that providing access to a
34412 stubs's interpreter may have security implications}.
34417 A command response with no output.
34419 A command response with the hex encoded output string @var{OUTPUT}.
34421 Indicate a badly formed request.
34423 An empty reply indicates that @samp{qRcmd} is not recognized.
34426 (Note that the @code{qRcmd} packet's name is separated from the
34427 command by a @samp{,}, not a @samp{:}, contrary to the naming
34428 conventions above. Please don't use this packet as a model for new
34431 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
34432 @cindex searching memory, in remote debugging
34433 @cindex @samp{qSearch:memory} packet
34434 @anchor{qSearch memory}
34435 Search @var{length} bytes at @var{address} for @var{search-pattern}.
34436 @var{address} and @var{length} are encoded in hex.
34437 @var{search-pattern} is a sequence of bytes, hex encoded.
34442 The pattern was not found.
34444 The pattern was found at @var{address}.
34446 A badly formed request or an error was encountered while searching memory.
34448 An empty reply indicates that @samp{qSearch:memory} is not recognized.
34451 @item QStartNoAckMode
34452 @cindex @samp{QStartNoAckMode} packet
34453 @anchor{QStartNoAckMode}
34454 Request that the remote stub disable the normal @samp{+}/@samp{-}
34455 protocol acknowledgments (@pxref{Packet Acknowledgment}).
34460 The stub has switched to no-acknowledgment mode.
34461 @value{GDBN} acknowledges this reponse,
34462 but neither the stub nor @value{GDBN} shall send or expect further
34463 @samp{+}/@samp{-} acknowledgments in the current connection.
34465 An empty reply indicates that the stub does not support no-acknowledgment mode.
34468 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
34469 @cindex supported packets, remote query
34470 @cindex features of the remote protocol
34471 @cindex @samp{qSupported} packet
34472 @anchor{qSupported}
34473 Tell the remote stub about features supported by @value{GDBN}, and
34474 query the stub for features it supports. This packet allows
34475 @value{GDBN} and the remote stub to take advantage of each others'
34476 features. @samp{qSupported} also consolidates multiple feature probes
34477 at startup, to improve @value{GDBN} performance---a single larger
34478 packet performs better than multiple smaller probe packets on
34479 high-latency links. Some features may enable behavior which must not
34480 be on by default, e.g.@: because it would confuse older clients or
34481 stubs. Other features may describe packets which could be
34482 automatically probed for, but are not. These features must be
34483 reported before @value{GDBN} will use them. This ``default
34484 unsupported'' behavior is not appropriate for all packets, but it
34485 helps to keep the initial connection time under control with new
34486 versions of @value{GDBN} which support increasing numbers of packets.
34490 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
34491 The stub supports or does not support each returned @var{stubfeature},
34492 depending on the form of each @var{stubfeature} (see below for the
34495 An empty reply indicates that @samp{qSupported} is not recognized,
34496 or that no features needed to be reported to @value{GDBN}.
34499 The allowed forms for each feature (either a @var{gdbfeature} in the
34500 @samp{qSupported} packet, or a @var{stubfeature} in the response)
34504 @item @var{name}=@var{value}
34505 The remote protocol feature @var{name} is supported, and associated
34506 with the specified @var{value}. The format of @var{value} depends
34507 on the feature, but it must not include a semicolon.
34509 The remote protocol feature @var{name} is supported, and does not
34510 need an associated value.
34512 The remote protocol feature @var{name} is not supported.
34514 The remote protocol feature @var{name} may be supported, and
34515 @value{GDBN} should auto-detect support in some other way when it is
34516 needed. This form will not be used for @var{gdbfeature} notifications,
34517 but may be used for @var{stubfeature} responses.
34520 Whenever the stub receives a @samp{qSupported} request, the
34521 supplied set of @value{GDBN} features should override any previous
34522 request. This allows @value{GDBN} to put the stub in a known
34523 state, even if the stub had previously been communicating with
34524 a different version of @value{GDBN}.
34526 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
34531 This feature indicates whether @value{GDBN} supports multiprocess
34532 extensions to the remote protocol. @value{GDBN} does not use such
34533 extensions unless the stub also reports that it supports them by
34534 including @samp{multiprocess+} in its @samp{qSupported} reply.
34535 @xref{multiprocess extensions}, for details.
34538 This feature indicates that @value{GDBN} supports the XML target
34539 description. If the stub sees @samp{xmlRegisters=} with target
34540 specific strings separated by a comma, it will report register
34544 This feature indicates whether @value{GDBN} supports the
34545 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
34546 instruction reply packet}).
34549 Stubs should ignore any unknown values for
34550 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
34551 packet supports receiving packets of unlimited length (earlier
34552 versions of @value{GDBN} may reject overly long responses). Additional values
34553 for @var{gdbfeature} may be defined in the future to let the stub take
34554 advantage of new features in @value{GDBN}, e.g.@: incompatible
34555 improvements in the remote protocol---the @samp{multiprocess} feature is
34556 an example of such a feature. The stub's reply should be independent
34557 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
34558 describes all the features it supports, and then the stub replies with
34559 all the features it supports.
34561 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
34562 responses, as long as each response uses one of the standard forms.
34564 Some features are flags. A stub which supports a flag feature
34565 should respond with a @samp{+} form response. Other features
34566 require values, and the stub should respond with an @samp{=}
34569 Each feature has a default value, which @value{GDBN} will use if
34570 @samp{qSupported} is not available or if the feature is not mentioned
34571 in the @samp{qSupported} response. The default values are fixed; a
34572 stub is free to omit any feature responses that match the defaults.
34574 Not all features can be probed, but for those which can, the probing
34575 mechanism is useful: in some cases, a stub's internal
34576 architecture may not allow the protocol layer to know some information
34577 about the underlying target in advance. This is especially common in
34578 stubs which may be configured for multiple targets.
34580 These are the currently defined stub features and their properties:
34582 @multitable @columnfractions 0.35 0.2 0.12 0.2
34583 @c NOTE: The first row should be @headitem, but we do not yet require
34584 @c a new enough version of Texinfo (4.7) to use @headitem.
34586 @tab Value Required
34590 @item @samp{PacketSize}
34595 @item @samp{qXfer:auxv:read}
34600 @item @samp{qXfer:features:read}
34605 @item @samp{qXfer:libraries:read}
34610 @item @samp{qXfer:memory-map:read}
34615 @item @samp{qXfer:sdata:read}
34620 @item @samp{qXfer:spu:read}
34625 @item @samp{qXfer:spu:write}
34630 @item @samp{qXfer:siginfo:read}
34635 @item @samp{qXfer:siginfo:write}
34640 @item @samp{qXfer:threads:read}
34645 @item @samp{qXfer:traceframe-info:read}
34650 @item @samp{qXfer:fdpic:read}
34655 @item @samp{QNonStop}
34660 @item @samp{QPassSignals}
34665 @item @samp{QStartNoAckMode}
34670 @item @samp{multiprocess}
34675 @item @samp{ConditionalTracepoints}
34680 @item @samp{ReverseContinue}
34685 @item @samp{ReverseStep}
34690 @item @samp{TracepointSource}
34695 @item @samp{QAllow}
34700 @item @samp{QDisableRandomization}
34705 @item @samp{EnableDisableTracepoints}
34712 These are the currently defined stub features, in more detail:
34715 @cindex packet size, remote protocol
34716 @item PacketSize=@var{bytes}
34717 The remote stub can accept packets up to at least @var{bytes} in
34718 length. @value{GDBN} will send packets up to this size for bulk
34719 transfers, and will never send larger packets. This is a limit on the
34720 data characters in the packet, including the frame and checksum.
34721 There is no trailing NUL byte in a remote protocol packet; if the stub
34722 stores packets in a NUL-terminated format, it should allow an extra
34723 byte in its buffer for the NUL. If this stub feature is not supported,
34724 @value{GDBN} guesses based on the size of the @samp{g} packet response.
34726 @item qXfer:auxv:read
34727 The remote stub understands the @samp{qXfer:auxv:read} packet
34728 (@pxref{qXfer auxiliary vector read}).
34730 @item qXfer:features:read
34731 The remote stub understands the @samp{qXfer:features:read} packet
34732 (@pxref{qXfer target description read}).
34734 @item qXfer:libraries:read
34735 The remote stub understands the @samp{qXfer:libraries:read} packet
34736 (@pxref{qXfer library list read}).
34738 @item qXfer:memory-map:read
34739 The remote stub understands the @samp{qXfer:memory-map:read} packet
34740 (@pxref{qXfer memory map read}).
34742 @item qXfer:sdata:read
34743 The remote stub understands the @samp{qXfer:sdata:read} packet
34744 (@pxref{qXfer sdata read}).
34746 @item qXfer:spu:read
34747 The remote stub understands the @samp{qXfer:spu:read} packet
34748 (@pxref{qXfer spu read}).
34750 @item qXfer:spu:write
34751 The remote stub understands the @samp{qXfer:spu:write} packet
34752 (@pxref{qXfer spu write}).
34754 @item qXfer:siginfo:read
34755 The remote stub understands the @samp{qXfer:siginfo:read} packet
34756 (@pxref{qXfer siginfo read}).
34758 @item qXfer:siginfo:write
34759 The remote stub understands the @samp{qXfer:siginfo:write} packet
34760 (@pxref{qXfer siginfo write}).
34762 @item qXfer:threads:read
34763 The remote stub understands the @samp{qXfer:threads:read} packet
34764 (@pxref{qXfer threads read}).
34766 @item qXfer:traceframe-info:read
34767 The remote stub understands the @samp{qXfer:traceframe-info:read}
34768 packet (@pxref{qXfer traceframe info read}).
34770 @item qXfer:fdpic:read
34771 The remote stub understands the @samp{qXfer:fdpic:read}
34772 packet (@pxref{qXfer fdpic loadmap read}).
34775 The remote stub understands the @samp{QNonStop} packet
34776 (@pxref{QNonStop}).
34779 The remote stub understands the @samp{QPassSignals} packet
34780 (@pxref{QPassSignals}).
34782 @item QStartNoAckMode
34783 The remote stub understands the @samp{QStartNoAckMode} packet and
34784 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
34787 @anchor{multiprocess extensions}
34788 @cindex multiprocess extensions, in remote protocol
34789 The remote stub understands the multiprocess extensions to the remote
34790 protocol syntax. The multiprocess extensions affect the syntax of
34791 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
34792 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
34793 replies. Note that reporting this feature indicates support for the
34794 syntactic extensions only, not that the stub necessarily supports
34795 debugging of more than one process at a time. The stub must not use
34796 multiprocess extensions in packet replies unless @value{GDBN} has also
34797 indicated it supports them in its @samp{qSupported} request.
34799 @item qXfer:osdata:read
34800 The remote stub understands the @samp{qXfer:osdata:read} packet
34801 ((@pxref{qXfer osdata read}).
34803 @item ConditionalTracepoints
34804 The remote stub accepts and implements conditional expressions defined
34805 for tracepoints (@pxref{Tracepoint Conditions}).
34807 @item ReverseContinue
34808 The remote stub accepts and implements the reverse continue packet
34812 The remote stub accepts and implements the reverse step packet
34815 @item TracepointSource
34816 The remote stub understands the @samp{QTDPsrc} packet that supplies
34817 the source form of tracepoint definitions.
34820 The remote stub understands the @samp{QAllow} packet.
34822 @item QDisableRandomization
34823 The remote stub understands the @samp{QDisableRandomization} packet.
34825 @item StaticTracepoint
34826 @cindex static tracepoints, in remote protocol
34827 The remote stub supports static tracepoints.
34829 @item EnableDisableTracepoints
34830 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
34831 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
34832 to be enabled and disabled while a trace experiment is running.
34837 @cindex symbol lookup, remote request
34838 @cindex @samp{qSymbol} packet
34839 Notify the target that @value{GDBN} is prepared to serve symbol lookup
34840 requests. Accept requests from the target for the values of symbols.
34845 The target does not need to look up any (more) symbols.
34846 @item qSymbol:@var{sym_name}
34847 The target requests the value of symbol @var{sym_name} (hex encoded).
34848 @value{GDBN} may provide the value by using the
34849 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
34853 @item qSymbol:@var{sym_value}:@var{sym_name}
34854 Set the value of @var{sym_name} to @var{sym_value}.
34856 @var{sym_name} (hex encoded) is the name of a symbol whose value the
34857 target has previously requested.
34859 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
34860 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
34866 The target does not need to look up any (more) symbols.
34867 @item qSymbol:@var{sym_name}
34868 The target requests the value of a new symbol @var{sym_name} (hex
34869 encoded). @value{GDBN} will continue to supply the values of symbols
34870 (if available), until the target ceases to request them.
34875 @item QTDisconnected
34882 @xref{Tracepoint Packets}.
34884 @item qThreadExtraInfo,@var{thread-id}
34885 @cindex thread attributes info, remote request
34886 @cindex @samp{qThreadExtraInfo} packet
34887 Obtain a printable string description of a thread's attributes from
34888 the target OS. @var{thread-id} is a thread ID;
34889 see @ref{thread-id syntax}. This
34890 string may contain anything that the target OS thinks is interesting
34891 for @value{GDBN} to tell the user about the thread. The string is
34892 displayed in @value{GDBN}'s @code{info threads} display. Some
34893 examples of possible thread extra info strings are @samp{Runnable}, or
34894 @samp{Blocked on Mutex}.
34898 @item @var{XX}@dots{}
34899 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
34900 comprising the printable string containing the extra information about
34901 the thread's attributes.
34904 (Note that the @code{qThreadExtraInfo} packet's name is separated from
34905 the command by a @samp{,}, not a @samp{:}, contrary to the naming
34906 conventions above. Please don't use this packet as a model for new
34923 @xref{Tracepoint Packets}.
34925 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
34926 @cindex read special object, remote request
34927 @cindex @samp{qXfer} packet
34928 @anchor{qXfer read}
34929 Read uninterpreted bytes from the target's special data area
34930 identified by the keyword @var{object}. Request @var{length} bytes
34931 starting at @var{offset} bytes into the data. The content and
34932 encoding of @var{annex} is specific to @var{object}; it can supply
34933 additional details about what data to access.
34935 Here are the specific requests of this form defined so far. All
34936 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
34937 formats, listed below.
34940 @item qXfer:auxv:read::@var{offset},@var{length}
34941 @anchor{qXfer auxiliary vector read}
34942 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
34943 auxiliary vector}. Note @var{annex} must be empty.
34945 This packet is not probed by default; the remote stub must request it,
34946 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34948 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
34949 @anchor{qXfer target description read}
34950 Access the @dfn{target description}. @xref{Target Descriptions}. The
34951 annex specifies which XML document to access. The main description is
34952 always loaded from the @samp{target.xml} annex.
34954 This packet is not probed by default; the remote stub must request it,
34955 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34957 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
34958 @anchor{qXfer library list read}
34959 Access the target's list of loaded libraries. @xref{Library List Format}.
34960 The annex part of the generic @samp{qXfer} packet must be empty
34961 (@pxref{qXfer read}).
34963 Targets which maintain a list of libraries in the program's memory do
34964 not need to implement this packet; it is designed for platforms where
34965 the operating system manages the list of loaded libraries.
34967 This packet is not probed by default; the remote stub must request it,
34968 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34970 @item qXfer:memory-map:read::@var{offset},@var{length}
34971 @anchor{qXfer memory map read}
34972 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
34973 annex part of the generic @samp{qXfer} packet must be empty
34974 (@pxref{qXfer read}).
34976 This packet is not probed by default; the remote stub must request it,
34977 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34979 @item qXfer:sdata:read::@var{offset},@var{length}
34980 @anchor{qXfer sdata read}
34982 Read contents of the extra collected static tracepoint marker
34983 information. The annex part of the generic @samp{qXfer} packet must
34984 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
34987 This packet is not probed by default; the remote stub must request it,
34988 by supplying an appropriate @samp{qSupported} response
34989 (@pxref{qSupported}).
34991 @item qXfer:siginfo:read::@var{offset},@var{length}
34992 @anchor{qXfer siginfo read}
34993 Read contents of the extra signal information on the target
34994 system. The annex part of the generic @samp{qXfer} packet must be
34995 empty (@pxref{qXfer read}).
34997 This packet is not probed by default; the remote stub must request it,
34998 by supplying an appropriate @samp{qSupported} response
34999 (@pxref{qSupported}).
35001 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
35002 @anchor{qXfer spu read}
35003 Read contents of an @code{spufs} file on the target system. The
35004 annex specifies which file to read; it must be of the form
35005 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
35006 in the target process, and @var{name} identifes the @code{spufs} file
35007 in that context to be accessed.
35009 This packet is not probed by default; the remote stub must request it,
35010 by supplying an appropriate @samp{qSupported} response
35011 (@pxref{qSupported}).
35013 @item qXfer:threads:read::@var{offset},@var{length}
35014 @anchor{qXfer threads read}
35015 Access the list of threads on target. @xref{Thread List Format}. The
35016 annex part of the generic @samp{qXfer} packet must be empty
35017 (@pxref{qXfer read}).
35019 This packet is not probed by default; the remote stub must request it,
35020 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35022 @item qXfer:traceframe-info:read::@var{offset},@var{length}
35023 @anchor{qXfer traceframe info read}
35025 Return a description of the current traceframe's contents.
35026 @xref{Traceframe Info Format}. The annex part of the generic
35027 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
35029 This packet is not probed by default; the remote stub must request it,
35030 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35032 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
35033 @anchor{qXfer fdpic loadmap read}
35034 Read contents of @code{loadmap}s on the target system. The
35035 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
35036 executable @code{loadmap} or interpreter @code{loadmap} to 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:osdata:read::@var{offset},@var{length}
35042 @anchor{qXfer osdata read}
35043 Access the target's @dfn{operating system information}.
35044 @xref{Operating System Information}.
35051 Data @var{data} (@pxref{Binary Data}) has been read from the
35052 target. There may be more data at a higher address (although
35053 it is permitted to return @samp{m} even for the last valid
35054 block of data, as long as at least one byte of data was read).
35055 @var{data} may have fewer bytes than the @var{length} in the
35059 Data @var{data} (@pxref{Binary Data}) has been read from the target.
35060 There is no more data to be read. @var{data} may have fewer bytes
35061 than the @var{length} in the request.
35064 The @var{offset} in the request is at the end of the data.
35065 There is no more data to be read.
35068 The request was malformed, or @var{annex} was invalid.
35071 The offset was invalid, or there was an error encountered reading the data.
35072 @var{nn} is a hex-encoded @code{errno} value.
35075 An empty reply indicates the @var{object} string was not recognized by
35076 the stub, or that the object does not support reading.
35079 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
35080 @cindex write data into object, remote request
35081 @anchor{qXfer write}
35082 Write uninterpreted bytes into the target's special data area
35083 identified by the keyword @var{object}, starting at @var{offset} bytes
35084 into the data. @var{data}@dots{} is the binary-encoded data
35085 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
35086 is specific to @var{object}; it can supply additional details about what data
35089 Here are the specific requests of this form defined so far. All
35090 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
35091 formats, listed below.
35094 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
35095 @anchor{qXfer siginfo write}
35096 Write @var{data} to the extra signal information on the target system.
35097 The annex part of the generic @samp{qXfer} packet must be
35098 empty (@pxref{qXfer write}).
35100 This packet is not probed by default; the remote stub must request it,
35101 by supplying an appropriate @samp{qSupported} response
35102 (@pxref{qSupported}).
35104 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
35105 @anchor{qXfer spu write}
35106 Write @var{data} to an @code{spufs} file on the target system. The
35107 annex specifies which file to write; it must be of the form
35108 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
35109 in the target process, and @var{name} identifes the @code{spufs} file
35110 in that context to be accessed.
35112 This packet is not probed by default; the remote stub must request it,
35113 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35119 @var{nn} (hex encoded) is the number of bytes written.
35120 This may be fewer bytes than supplied in the request.
35123 The request was malformed, or @var{annex} was invalid.
35126 The offset was invalid, or there was an error encountered writing the data.
35127 @var{nn} is a hex-encoded @code{errno} value.
35130 An empty reply indicates the @var{object} string was not
35131 recognized by the stub, or that the object does not support writing.
35134 @item qXfer:@var{object}:@var{operation}:@dots{}
35135 Requests of this form may be added in the future. When a stub does
35136 not recognize the @var{object} keyword, or its support for
35137 @var{object} does not recognize the @var{operation} keyword, the stub
35138 must respond with an empty packet.
35140 @item qAttached:@var{pid}
35141 @cindex query attached, remote request
35142 @cindex @samp{qAttached} packet
35143 Return an indication of whether the remote server attached to an
35144 existing process or created a new process. When the multiprocess
35145 protocol extensions are supported (@pxref{multiprocess extensions}),
35146 @var{pid} is an integer in hexadecimal format identifying the target
35147 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
35148 the query packet will be simplified as @samp{qAttached}.
35150 This query is used, for example, to know whether the remote process
35151 should be detached or killed when a @value{GDBN} session is ended with
35152 the @code{quit} command.
35157 The remote server attached to an existing process.
35159 The remote server created a new process.
35161 A badly formed request or an error was encountered.
35166 @node Architecture-Specific Protocol Details
35167 @section Architecture-Specific Protocol Details
35169 This section describes how the remote protocol is applied to specific
35170 target architectures. Also see @ref{Standard Target Features}, for
35171 details of XML target descriptions for each architecture.
35175 @subsubsection Breakpoint Kinds
35177 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
35182 16-bit Thumb mode breakpoint.
35185 32-bit Thumb mode (Thumb-2) breakpoint.
35188 32-bit ARM mode breakpoint.
35194 @subsubsection Register Packet Format
35196 The following @code{g}/@code{G} packets have previously been defined.
35197 In the below, some thirty-two bit registers are transferred as
35198 sixty-four bits. Those registers should be zero/sign extended (which?)
35199 to fill the space allocated. Register bytes are transferred in target
35200 byte order. The two nibbles within a register byte are transferred
35201 most-significant - least-significant.
35207 All registers are transferred as thirty-two bit quantities in the order:
35208 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
35209 registers; fsr; fir; fp.
35213 All registers are transferred as sixty-four bit quantities (including
35214 thirty-two bit registers such as @code{sr}). The ordering is the same
35219 @node Tracepoint Packets
35220 @section Tracepoint Packets
35221 @cindex tracepoint packets
35222 @cindex packets, tracepoint
35224 Here we describe the packets @value{GDBN} uses to implement
35225 tracepoints (@pxref{Tracepoints}).
35229 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
35230 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
35231 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
35232 the tracepoint is disabled. @var{step} is the tracepoint's step
35233 count, and @var{pass} is its pass count. If an @samp{F} is present,
35234 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
35235 the number of bytes that the target should copy elsewhere to make room
35236 for the tracepoint. If an @samp{X} is present, it introduces a
35237 tracepoint condition, which consists of a hexadecimal length, followed
35238 by a comma and hex-encoded bytes, in a manner similar to action
35239 encodings as described below. If the trailing @samp{-} is present,
35240 further @samp{QTDP} packets will follow to specify this tracepoint's
35246 The packet was understood and carried out.
35248 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
35250 The packet was not recognized.
35253 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
35254 Define actions to be taken when a tracepoint is hit. @var{n} and
35255 @var{addr} must be the same as in the initial @samp{QTDP} packet for
35256 this tracepoint. This packet may only be sent immediately after
35257 another @samp{QTDP} packet that ended with a @samp{-}. If the
35258 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
35259 specifying more actions for this tracepoint.
35261 In the series of action packets for a given tracepoint, at most one
35262 can have an @samp{S} before its first @var{action}. If such a packet
35263 is sent, it and the following packets define ``while-stepping''
35264 actions. Any prior packets define ordinary actions --- that is, those
35265 taken when the tracepoint is first hit. If no action packet has an
35266 @samp{S}, then all the packets in the series specify ordinary
35267 tracepoint actions.
35269 The @samp{@var{action}@dots{}} portion of the packet is a series of
35270 actions, concatenated without separators. Each action has one of the
35276 Collect the registers whose bits are set in @var{mask}. @var{mask} is
35277 a hexadecimal number whose @var{i}'th bit is set if register number
35278 @var{i} should be collected. (The least significant bit is numbered
35279 zero.) Note that @var{mask} may be any number of digits long; it may
35280 not fit in a 32-bit word.
35282 @item M @var{basereg},@var{offset},@var{len}
35283 Collect @var{len} bytes of memory starting at the address in register
35284 number @var{basereg}, plus @var{offset}. If @var{basereg} is
35285 @samp{-1}, then the range has a fixed address: @var{offset} is the
35286 address of the lowest byte to collect. The @var{basereg},
35287 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
35288 values (the @samp{-1} value for @var{basereg} is a special case).
35290 @item X @var{len},@var{expr}
35291 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
35292 it directs. @var{expr} is an agent expression, as described in
35293 @ref{Agent Expressions}. Each byte of the expression is encoded as a
35294 two-digit hex number in the packet; @var{len} is the number of bytes
35295 in the expression (and thus one-half the number of hex digits in the
35300 Any number of actions may be packed together in a single @samp{QTDP}
35301 packet, as long as the packet does not exceed the maximum packet
35302 length (400 bytes, for many stubs). There may be only one @samp{R}
35303 action per tracepoint, and it must precede any @samp{M} or @samp{X}
35304 actions. Any registers referred to by @samp{M} and @samp{X} actions
35305 must be collected by a preceding @samp{R} action. (The
35306 ``while-stepping'' actions are treated as if they were attached to a
35307 separate tracepoint, as far as these restrictions are concerned.)
35312 The packet was understood and carried out.
35314 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
35316 The packet was not recognized.
35319 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
35320 @cindex @samp{QTDPsrc} packet
35321 Specify a source string of tracepoint @var{n} at address @var{addr}.
35322 This is useful to get accurate reproduction of the tracepoints
35323 originally downloaded at the beginning of the trace run. @var{type}
35324 is the name of the tracepoint part, such as @samp{cond} for the
35325 tracepoint's conditional expression (see below for a list of types), while
35326 @var{bytes} is the string, encoded in hexadecimal.
35328 @var{start} is the offset of the @var{bytes} within the overall source
35329 string, while @var{slen} is the total length of the source string.
35330 This is intended for handling source strings that are longer than will
35331 fit in a single packet.
35332 @c Add detailed example when this info is moved into a dedicated
35333 @c tracepoint descriptions section.
35335 The available string types are @samp{at} for the location,
35336 @samp{cond} for the conditional, and @samp{cmd} for an action command.
35337 @value{GDBN} sends a separate packet for each command in the action
35338 list, in the same order in which the commands are stored in the list.
35340 The target does not need to do anything with source strings except
35341 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
35344 Although this packet is optional, and @value{GDBN} will only send it
35345 if the target replies with @samp{TracepointSource} @xref{General
35346 Query Packets}, it makes both disconnected tracing and trace files
35347 much easier to use. Otherwise the user must be careful that the
35348 tracepoints in effect while looking at trace frames are identical to
35349 the ones in effect during the trace run; even a small discrepancy
35350 could cause @samp{tdump} not to work, or a particular trace frame not
35353 @item QTDV:@var{n}:@var{value}
35354 @cindex define trace state variable, remote request
35355 @cindex @samp{QTDV} packet
35356 Create a new trace state variable, number @var{n}, with an initial
35357 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
35358 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
35359 the option of not using this packet for initial values of zero; the
35360 target should simply create the trace state variables as they are
35361 mentioned in expressions.
35363 @item QTFrame:@var{n}
35364 Select the @var{n}'th tracepoint frame from the buffer, and use the
35365 register and memory contents recorded there to answer subsequent
35366 request packets from @value{GDBN}.
35368 A successful reply from the stub indicates that the stub has found the
35369 requested frame. The response is a series of parts, concatenated
35370 without separators, describing the frame we selected. Each part has
35371 one of the following forms:
35375 The selected frame is number @var{n} in the trace frame buffer;
35376 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
35377 was no frame matching the criteria in the request packet.
35380 The selected trace frame records a hit of tracepoint number @var{t};
35381 @var{t} is a hexadecimal number.
35385 @item QTFrame:pc:@var{addr}
35386 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
35387 currently selected frame whose PC is @var{addr};
35388 @var{addr} is a hexadecimal number.
35390 @item QTFrame:tdp:@var{t}
35391 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
35392 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
35393 is a hexadecimal number.
35395 @item QTFrame:range:@var{start}:@var{end}
35396 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
35397 currently selected frame whose PC is between @var{start} (inclusive)
35398 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
35401 @item QTFrame:outside:@var{start}:@var{end}
35402 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
35403 frame @emph{outside} the given range of addresses (exclusive).
35406 Begin the tracepoint experiment. Begin collecting data from
35407 tracepoint hits in the trace frame buffer. This packet supports the
35408 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
35409 instruction reply packet}).
35412 End the tracepoint experiment. Stop collecting trace frames.
35414 @item QTEnable:@var{n}:@var{addr}
35416 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
35417 experiment. If the tracepoint was previously disabled, then collection
35418 of data from it will resume.
35420 @item QTDisable:@var{n}:@var{addr}
35422 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
35423 experiment. No more data will be collected from the tracepoint unless
35424 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
35427 Clear the table of tracepoints, and empty the trace frame buffer.
35429 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
35430 Establish the given ranges of memory as ``transparent''. The stub
35431 will answer requests for these ranges from memory's current contents,
35432 if they were not collected as part of the tracepoint hit.
35434 @value{GDBN} uses this to mark read-only regions of memory, like those
35435 containing program code. Since these areas never change, they should
35436 still have the same contents they did when the tracepoint was hit, so
35437 there's no reason for the stub to refuse to provide their contents.
35439 @item QTDisconnected:@var{value}
35440 Set the choice to what to do with the tracing run when @value{GDBN}
35441 disconnects from the target. A @var{value} of 1 directs the target to
35442 continue the tracing run, while 0 tells the target to stop tracing if
35443 @value{GDBN} is no longer in the picture.
35446 Ask the stub if there is a trace experiment running right now.
35448 The reply has the form:
35452 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
35453 @var{running} is a single digit @code{1} if the trace is presently
35454 running, or @code{0} if not. It is followed by semicolon-separated
35455 optional fields that an agent may use to report additional status.
35459 If the trace is not running, the agent may report any of several
35460 explanations as one of the optional fields:
35465 No trace has been run yet.
35468 The trace was stopped by a user-originated stop command.
35471 The trace stopped because the trace buffer filled up.
35473 @item tdisconnected:0
35474 The trace stopped because @value{GDBN} disconnected from the target.
35476 @item tpasscount:@var{tpnum}
35477 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
35479 @item terror:@var{text}:@var{tpnum}
35480 The trace stopped because tracepoint @var{tpnum} had an error. The
35481 string @var{text} is available to describe the nature of the error
35482 (for instance, a divide by zero in the condition expression).
35483 @var{text} is hex encoded.
35486 The trace stopped for some other reason.
35490 Additional optional fields supply statistical and other information.
35491 Although not required, they are extremely useful for users monitoring
35492 the progress of a trace run. If a trace has stopped, and these
35493 numbers are reported, they must reflect the state of the just-stopped
35498 @item tframes:@var{n}
35499 The number of trace frames in the buffer.
35501 @item tcreated:@var{n}
35502 The total number of trace frames created during the run. This may
35503 be larger than the trace frame count, if the buffer is circular.
35505 @item tsize:@var{n}
35506 The total size of the trace buffer, in bytes.
35508 @item tfree:@var{n}
35509 The number of bytes still unused in the buffer.
35511 @item circular:@var{n}
35512 The value of the circular trace buffer flag. @code{1} means that the
35513 trace buffer is circular and old trace frames will be discarded if
35514 necessary to make room, @code{0} means that the trace buffer is linear
35517 @item disconn:@var{n}
35518 The value of the disconnected tracing flag. @code{1} means that
35519 tracing will continue after @value{GDBN} disconnects, @code{0} means
35520 that the trace run will stop.
35524 @item qTV:@var{var}
35525 @cindex trace state variable value, remote request
35526 @cindex @samp{qTV} packet
35527 Ask the stub for the value of the trace state variable number @var{var}.
35532 The value of the variable is @var{value}. This will be the current
35533 value of the variable if the user is examining a running target, or a
35534 saved value if the variable was collected in the trace frame that the
35535 user is looking at. Note that multiple requests may result in
35536 different reply values, such as when requesting values while the
35537 program is running.
35540 The value of the variable is unknown. This would occur, for example,
35541 if the user is examining a trace frame in which the requested variable
35547 These packets request data about tracepoints that are being used by
35548 the target. @value{GDBN} sends @code{qTfP} to get the first piece
35549 of data, and multiple @code{qTsP} to get additional pieces. Replies
35550 to these packets generally take the form of the @code{QTDP} packets
35551 that define tracepoints. (FIXME add detailed syntax)
35555 These packets request data about trace state variables that are on the
35556 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
35557 and multiple @code{qTsV} to get additional variables. Replies to
35558 these packets follow the syntax of the @code{QTDV} packets that define
35559 trace state variables.
35563 These packets request data about static tracepoint markers that exist
35564 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
35565 first piece of data, and multiple @code{qTsSTM} to get additional
35566 pieces. Replies to these packets take the following form:
35570 @item m @var{address}:@var{id}:@var{extra}
35572 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
35573 a comma-separated list of markers
35575 (lower case letter @samp{L}) denotes end of list.
35577 An error occurred. @var{nn} are hex digits.
35579 An empty reply indicates that the request is not supported by the
35583 @var{address} is encoded in hex.
35584 @var{id} and @var{extra} are strings encoded in hex.
35586 In response to each query, the target will reply with a list of one or
35587 more markers, separated by commas. @value{GDBN} will respond to each
35588 reply with a request for more markers (using the @samp{qs} form of the
35589 query), until the target responds with @samp{l} (lower-case ell, for
35592 @item qTSTMat:@var{address}
35593 This packets requests data about static tracepoint markers in the
35594 target program at @var{address}. Replies to this packet follow the
35595 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
35596 tracepoint markers.
35598 @item QTSave:@var{filename}
35599 This packet directs the target to save trace data to the file name
35600 @var{filename} in the target's filesystem. @var{filename} is encoded
35601 as a hex string; the interpretation of the file name (relative vs
35602 absolute, wild cards, etc) is up to the target.
35604 @item qTBuffer:@var{offset},@var{len}
35605 Return up to @var{len} bytes of the current contents of trace buffer,
35606 starting at @var{offset}. The trace buffer is treated as if it were
35607 a contiguous collection of traceframes, as per the trace file format.
35608 The reply consists as many hex-encoded bytes as the target can deliver
35609 in a packet; it is not an error to return fewer than were asked for.
35610 A reply consisting of just @code{l} indicates that no bytes are
35613 @item QTBuffer:circular:@var{value}
35614 This packet directs the target to use a circular trace buffer if
35615 @var{value} is 1, or a linear buffer if the value is 0.
35619 @subsection Relocate instruction reply packet
35620 When installing fast tracepoints in memory, the target may need to
35621 relocate the instruction currently at the tracepoint address to a
35622 different address in memory. For most instructions, a simple copy is
35623 enough, but, for example, call instructions that implicitly push the
35624 return address on the stack, and relative branches or other
35625 PC-relative instructions require offset adjustment, so that the effect
35626 of executing the instruction at a different address is the same as if
35627 it had executed in the original location.
35629 In response to several of the tracepoint packets, the target may also
35630 respond with a number of intermediate @samp{qRelocInsn} request
35631 packets before the final result packet, to have @value{GDBN} handle
35632 this relocation operation. If a packet supports this mechanism, its
35633 documentation will explicitly say so. See for example the above
35634 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
35635 format of the request is:
35638 @item qRelocInsn:@var{from};@var{to}
35640 This requests @value{GDBN} to copy instruction at address @var{from}
35641 to address @var{to}, possibly adjusted so that executing the
35642 instruction at @var{to} has the same effect as executing it at
35643 @var{from}. @value{GDBN} writes the adjusted instruction to target
35644 memory starting at @var{to}.
35649 @item qRelocInsn:@var{adjusted_size}
35650 Informs the stub the relocation is complete. @var{adjusted_size} is
35651 the length in bytes of resulting relocated instruction sequence.
35653 A badly formed request was detected, or an error was encountered while
35654 relocating the instruction.
35657 @node Host I/O Packets
35658 @section Host I/O Packets
35659 @cindex Host I/O, remote protocol
35660 @cindex file transfer, remote protocol
35662 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
35663 operations on the far side of a remote link. For example, Host I/O is
35664 used to upload and download files to a remote target with its own
35665 filesystem. Host I/O uses the same constant values and data structure
35666 layout as the target-initiated File-I/O protocol. However, the
35667 Host I/O packets are structured differently. The target-initiated
35668 protocol relies on target memory to store parameters and buffers.
35669 Host I/O requests are initiated by @value{GDBN}, and the
35670 target's memory is not involved. @xref{File-I/O Remote Protocol
35671 Extension}, for more details on the target-initiated protocol.
35673 The Host I/O request packets all encode a single operation along with
35674 its arguments. They have this format:
35678 @item vFile:@var{operation}: @var{parameter}@dots{}
35679 @var{operation} is the name of the particular request; the target
35680 should compare the entire packet name up to the second colon when checking
35681 for a supported operation. The format of @var{parameter} depends on
35682 the operation. Numbers are always passed in hexadecimal. Negative
35683 numbers have an explicit minus sign (i.e.@: two's complement is not
35684 used). Strings (e.g.@: filenames) are encoded as a series of
35685 hexadecimal bytes. The last argument to a system call may be a
35686 buffer of escaped binary data (@pxref{Binary Data}).
35690 The valid responses to Host I/O packets are:
35694 @item F @var{result} [, @var{errno}] [; @var{attachment}]
35695 @var{result} is the integer value returned by this operation, usually
35696 non-negative for success and -1 for errors. If an error has occured,
35697 @var{errno} will be included in the result. @var{errno} will have a
35698 value defined by the File-I/O protocol (@pxref{Errno Values}). For
35699 operations which return data, @var{attachment} supplies the data as a
35700 binary buffer. Binary buffers in response packets are escaped in the
35701 normal way (@pxref{Binary Data}). See the individual packet
35702 documentation for the interpretation of @var{result} and
35706 An empty response indicates that this operation is not recognized.
35710 These are the supported Host I/O operations:
35713 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
35714 Open a file at @var{pathname} and return a file descriptor for it, or
35715 return -1 if an error occurs. @var{pathname} is a string,
35716 @var{flags} is an integer indicating a mask of open flags
35717 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
35718 of mode bits to use if the file is created (@pxref{mode_t Values}).
35719 @xref{open}, for details of the open flags and mode values.
35721 @item vFile:close: @var{fd}
35722 Close the open file corresponding to @var{fd} and return 0, or
35723 -1 if an error occurs.
35725 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
35726 Read data from the open file corresponding to @var{fd}. Up to
35727 @var{count} bytes will be read from the file, starting at @var{offset}
35728 relative to the start of the file. The target may read fewer bytes;
35729 common reasons include packet size limits and an end-of-file
35730 condition. The number of bytes read is returned. Zero should only be
35731 returned for a successful read at the end of the file, or if
35732 @var{count} was zero.
35734 The data read should be returned as a binary attachment on success.
35735 If zero bytes were read, the response should include an empty binary
35736 attachment (i.e.@: a trailing semicolon). The return value is the
35737 number of target bytes read; the binary attachment may be longer if
35738 some characters were escaped.
35740 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
35741 Write @var{data} (a binary buffer) to the open file corresponding
35742 to @var{fd}. Start the write at @var{offset} from the start of the
35743 file. Unlike many @code{write} system calls, there is no
35744 separate @var{count} argument; the length of @var{data} in the
35745 packet is used. @samp{vFile:write} returns the number of bytes written,
35746 which may be shorter than the length of @var{data}, or -1 if an
35749 @item vFile:unlink: @var{pathname}
35750 Delete the file at @var{pathname} on the target. Return 0,
35751 or -1 if an error occurs. @var{pathname} is a string.
35756 @section Interrupts
35757 @cindex interrupts (remote protocol)
35759 When a program on the remote target is running, @value{GDBN} may
35760 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
35761 a @code{BREAK} followed by @code{g},
35762 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
35764 The precise meaning of @code{BREAK} is defined by the transport
35765 mechanism and may, in fact, be undefined. @value{GDBN} does not
35766 currently define a @code{BREAK} mechanism for any of the network
35767 interfaces except for TCP, in which case @value{GDBN} sends the
35768 @code{telnet} BREAK sequence.
35770 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
35771 transport mechanisms. It is represented by sending the single byte
35772 @code{0x03} without any of the usual packet overhead described in
35773 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
35774 transmitted as part of a packet, it is considered to be packet data
35775 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
35776 (@pxref{X packet}), used for binary downloads, may include an unescaped
35777 @code{0x03} as part of its packet.
35779 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
35780 When Linux kernel receives this sequence from serial port,
35781 it stops execution and connects to gdb.
35783 Stubs are not required to recognize these interrupt mechanisms and the
35784 precise meaning associated with receipt of the interrupt is
35785 implementation defined. If the target supports debugging of multiple
35786 threads and/or processes, it should attempt to interrupt all
35787 currently-executing threads and processes.
35788 If the stub is successful at interrupting the
35789 running program, it should send one of the stop
35790 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
35791 of successfully stopping the program in all-stop mode, and a stop reply
35792 for each stopped thread in non-stop mode.
35793 Interrupts received while the
35794 program is stopped are discarded.
35796 @node Notification Packets
35797 @section Notification Packets
35798 @cindex notification packets
35799 @cindex packets, notification
35801 The @value{GDBN} remote serial protocol includes @dfn{notifications},
35802 packets that require no acknowledgment. Both the GDB and the stub
35803 may send notifications (although the only notifications defined at
35804 present are sent by the stub). Notifications carry information
35805 without incurring the round-trip latency of an acknowledgment, and so
35806 are useful for low-impact communications where occasional packet loss
35809 A notification packet has the form @samp{% @var{data} #
35810 @var{checksum}}, where @var{data} is the content of the notification,
35811 and @var{checksum} is a checksum of @var{data}, computed and formatted
35812 as for ordinary @value{GDBN} packets. A notification's @var{data}
35813 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
35814 receiving a notification, the recipient sends no @samp{+} or @samp{-}
35815 to acknowledge the notification's receipt or to report its corruption.
35817 Every notification's @var{data} begins with a name, which contains no
35818 colon characters, followed by a colon character.
35820 Recipients should silently ignore corrupted notifications and
35821 notifications they do not understand. Recipients should restart
35822 timeout periods on receipt of a well-formed notification, whether or
35823 not they understand it.
35825 Senders should only send the notifications described here when this
35826 protocol description specifies that they are permitted. In the
35827 future, we may extend the protocol to permit existing notifications in
35828 new contexts; this rule helps older senders avoid confusing newer
35831 (Older versions of @value{GDBN} ignore bytes received until they see
35832 the @samp{$} byte that begins an ordinary packet, so new stubs may
35833 transmit notifications without fear of confusing older clients. There
35834 are no notifications defined for @value{GDBN} to send at the moment, but we
35835 assume that most older stubs would ignore them, as well.)
35837 The following notification packets from the stub to @value{GDBN} are
35841 @item Stop: @var{reply}
35842 Report an asynchronous stop event in non-stop mode.
35843 The @var{reply} has the form of a stop reply, as
35844 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
35845 for information on how these notifications are acknowledged by
35849 @node Remote Non-Stop
35850 @section Remote Protocol Support for Non-Stop Mode
35852 @value{GDBN}'s remote protocol supports non-stop debugging of
35853 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
35854 supports non-stop mode, it should report that to @value{GDBN} by including
35855 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
35857 @value{GDBN} typically sends a @samp{QNonStop} packet only when
35858 establishing a new connection with the stub. Entering non-stop mode
35859 does not alter the state of any currently-running threads, but targets
35860 must stop all threads in any already-attached processes when entering
35861 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
35862 probe the target state after a mode change.
35864 In non-stop mode, when an attached process encounters an event that
35865 would otherwise be reported with a stop reply, it uses the
35866 asynchronous notification mechanism (@pxref{Notification Packets}) to
35867 inform @value{GDBN}. In contrast to all-stop mode, where all threads
35868 in all processes are stopped when a stop reply is sent, in non-stop
35869 mode only the thread reporting the stop event is stopped. That is,
35870 when reporting a @samp{S} or @samp{T} response to indicate completion
35871 of a step operation, hitting a breakpoint, or a fault, only the
35872 affected thread is stopped; any other still-running threads continue
35873 to run. When reporting a @samp{W} or @samp{X} response, all running
35874 threads belonging to other attached processes continue to run.
35876 Only one stop reply notification at a time may be pending; if
35877 additional stop events occur before @value{GDBN} has acknowledged the
35878 previous notification, they must be queued by the stub for later
35879 synchronous transmission in response to @samp{vStopped} packets from
35880 @value{GDBN}. Because the notification mechanism is unreliable,
35881 the stub is permitted to resend a stop reply notification
35882 if it believes @value{GDBN} may not have received it. @value{GDBN}
35883 ignores additional stop reply notifications received before it has
35884 finished processing a previous notification and the stub has completed
35885 sending any queued stop events.
35887 Otherwise, @value{GDBN} must be prepared to receive a stop reply
35888 notification at any time. Specifically, they may appear when
35889 @value{GDBN} is not otherwise reading input from the stub, or when
35890 @value{GDBN} is expecting to read a normal synchronous response or a
35891 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
35892 Notification packets are distinct from any other communication from
35893 the stub so there is no ambiguity.
35895 After receiving a stop reply notification, @value{GDBN} shall
35896 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
35897 as a regular, synchronous request to the stub. Such acknowledgment
35898 is not required to happen immediately, as @value{GDBN} is permitted to
35899 send other, unrelated packets to the stub first, which the stub should
35902 Upon receiving a @samp{vStopped} packet, if the stub has other queued
35903 stop events to report to @value{GDBN}, it shall respond by sending a
35904 normal stop reply response. @value{GDBN} shall then send another
35905 @samp{vStopped} packet to solicit further responses; again, it is
35906 permitted to send other, unrelated packets as well which the stub
35907 should process normally.
35909 If the stub receives a @samp{vStopped} packet and there are no
35910 additional stop events to report, the stub shall return an @samp{OK}
35911 response. At this point, if further stop events occur, the stub shall
35912 send a new stop reply notification, @value{GDBN} shall accept the
35913 notification, and the process shall be repeated.
35915 In non-stop mode, the target shall respond to the @samp{?} packet as
35916 follows. First, any incomplete stop reply notification/@samp{vStopped}
35917 sequence in progress is abandoned. The target must begin a new
35918 sequence reporting stop events for all stopped threads, whether or not
35919 it has previously reported those events to @value{GDBN}. The first
35920 stop reply is sent as a synchronous reply to the @samp{?} packet, and
35921 subsequent stop replies are sent as responses to @samp{vStopped} packets
35922 using the mechanism described above. The target must not send
35923 asynchronous stop reply notifications until the sequence is complete.
35924 If all threads are running when the target receives the @samp{?} packet,
35925 or if the target is not attached to any process, it shall respond
35928 @node Packet Acknowledgment
35929 @section Packet Acknowledgment
35931 @cindex acknowledgment, for @value{GDBN} remote
35932 @cindex packet acknowledgment, for @value{GDBN} remote
35933 By default, when either the host or the target machine receives a packet,
35934 the first response expected is an acknowledgment: either @samp{+} (to indicate
35935 the package was received correctly) or @samp{-} (to request retransmission).
35936 This mechanism allows the @value{GDBN} remote protocol to operate over
35937 unreliable transport mechanisms, such as a serial line.
35939 In cases where the transport mechanism is itself reliable (such as a pipe or
35940 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
35941 It may be desirable to disable them in that case to reduce communication
35942 overhead, or for other reasons. This can be accomplished by means of the
35943 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
35945 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
35946 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
35947 and response format still includes the normal checksum, as described in
35948 @ref{Overview}, but the checksum may be ignored by the receiver.
35950 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
35951 no-acknowledgment mode, it should report that to @value{GDBN}
35952 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
35953 @pxref{qSupported}.
35954 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
35955 disabled via the @code{set remote noack-packet off} command
35956 (@pxref{Remote Configuration}),
35957 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
35958 Only then may the stub actually turn off packet acknowledgments.
35959 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
35960 response, which can be safely ignored by the stub.
35962 Note that @code{set remote noack-packet} command only affects negotiation
35963 between @value{GDBN} and the stub when subsequent connections are made;
35964 it does not affect the protocol acknowledgment state for any current
35966 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
35967 new connection is established,
35968 there is also no protocol request to re-enable the acknowledgments
35969 for the current connection, once disabled.
35974 Example sequence of a target being re-started. Notice how the restart
35975 does not get any direct output:
35980 @emph{target restarts}
35983 <- @code{T001:1234123412341234}
35987 Example sequence of a target being stepped by a single instruction:
35990 -> @code{G1445@dots{}}
35995 <- @code{T001:1234123412341234}
35999 <- @code{1455@dots{}}
36003 @node File-I/O Remote Protocol Extension
36004 @section File-I/O Remote Protocol Extension
36005 @cindex File-I/O remote protocol extension
36008 * File-I/O Overview::
36009 * Protocol Basics::
36010 * The F Request Packet::
36011 * The F Reply Packet::
36012 * The Ctrl-C Message::
36014 * List of Supported Calls::
36015 * Protocol-specific Representation of Datatypes::
36017 * File-I/O Examples::
36020 @node File-I/O Overview
36021 @subsection File-I/O Overview
36022 @cindex file-i/o overview
36024 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
36025 target to use the host's file system and console I/O to perform various
36026 system calls. System calls on the target system are translated into a
36027 remote protocol packet to the host system, which then performs the needed
36028 actions and returns a response packet to the target system.
36029 This simulates file system operations even on targets that lack file systems.
36031 The protocol is defined to be independent of both the host and target systems.
36032 It uses its own internal representation of datatypes and values. Both
36033 @value{GDBN} and the target's @value{GDBN} stub are responsible for
36034 translating the system-dependent value representations into the internal
36035 protocol representations when data is transmitted.
36037 The communication is synchronous. A system call is possible only when
36038 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
36039 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
36040 the target is stopped to allow deterministic access to the target's
36041 memory. Therefore File-I/O is not interruptible by target signals. On
36042 the other hand, it is possible to interrupt File-I/O by a user interrupt
36043 (@samp{Ctrl-C}) within @value{GDBN}.
36045 The target's request to perform a host system call does not finish
36046 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
36047 after finishing the system call, the target returns to continuing the
36048 previous activity (continue, step). No additional continue or step
36049 request from @value{GDBN} is required.
36052 (@value{GDBP}) continue
36053 <- target requests 'system call X'
36054 target is stopped, @value{GDBN} executes system call
36055 -> @value{GDBN} returns result
36056 ... target continues, @value{GDBN} returns to wait for the target
36057 <- target hits breakpoint and sends a Txx packet
36060 The protocol only supports I/O on the console and to regular files on
36061 the host file system. Character or block special devices, pipes,
36062 named pipes, sockets or any other communication method on the host
36063 system are not supported by this protocol.
36065 File I/O is not supported in non-stop mode.
36067 @node Protocol Basics
36068 @subsection Protocol Basics
36069 @cindex protocol basics, file-i/o
36071 The File-I/O protocol uses the @code{F} packet as the request as well
36072 as reply packet. Since a File-I/O system call can only occur when
36073 @value{GDBN} is waiting for a response from the continuing or stepping target,
36074 the File-I/O request is a reply that @value{GDBN} has to expect as a result
36075 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
36076 This @code{F} packet contains all information needed to allow @value{GDBN}
36077 to call the appropriate host system call:
36081 A unique identifier for the requested system call.
36084 All parameters to the system call. Pointers are given as addresses
36085 in the target memory address space. Pointers to strings are given as
36086 pointer/length pair. Numerical values are given as they are.
36087 Numerical control flags are given in a protocol-specific representation.
36091 At this point, @value{GDBN} has to perform the following actions.
36095 If the parameters include pointer values to data needed as input to a
36096 system call, @value{GDBN} requests this data from the target with a
36097 standard @code{m} packet request. This additional communication has to be
36098 expected by the target implementation and is handled as any other @code{m}
36102 @value{GDBN} translates all value from protocol representation to host
36103 representation as needed. Datatypes are coerced into the host types.
36106 @value{GDBN} calls the system call.
36109 It then coerces datatypes back to protocol representation.
36112 If the system call is expected to return data in buffer space specified
36113 by pointer parameters to the call, the data is transmitted to the
36114 target using a @code{M} or @code{X} packet. This packet has to be expected
36115 by the target implementation and is handled as any other @code{M} or @code{X}
36120 Eventually @value{GDBN} replies with another @code{F} packet which contains all
36121 necessary information for the target to continue. This at least contains
36128 @code{errno}, if has been changed by the system call.
36135 After having done the needed type and value coercion, the target continues
36136 the latest continue or step action.
36138 @node The F Request Packet
36139 @subsection The @code{F} Request Packet
36140 @cindex file-i/o request packet
36141 @cindex @code{F} request packet
36143 The @code{F} request packet has the following format:
36146 @item F@var{call-id},@var{parameter@dots{}}
36148 @var{call-id} is the identifier to indicate the host system call to be called.
36149 This is just the name of the function.
36151 @var{parameter@dots{}} are the parameters to the system call.
36152 Parameters are hexadecimal integer values, either the actual values in case
36153 of scalar datatypes, pointers to target buffer space in case of compound
36154 datatypes and unspecified memory areas, or pointer/length pairs in case
36155 of string parameters. These are appended to the @var{call-id} as a
36156 comma-delimited list. All values are transmitted in ASCII
36157 string representation, pointer/length pairs separated by a slash.
36163 @node The F Reply Packet
36164 @subsection The @code{F} Reply Packet
36165 @cindex file-i/o reply packet
36166 @cindex @code{F} reply packet
36168 The @code{F} reply packet has the following format:
36172 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
36174 @var{retcode} is the return code of the system call as hexadecimal value.
36176 @var{errno} is the @code{errno} set by the call, in protocol-specific
36178 This parameter can be omitted if the call was successful.
36180 @var{Ctrl-C flag} is only sent if the user requested a break. In this
36181 case, @var{errno} must be sent as well, even if the call was successful.
36182 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
36189 or, if the call was interrupted before the host call has been performed:
36196 assuming 4 is the protocol-specific representation of @code{EINTR}.
36201 @node The Ctrl-C Message
36202 @subsection The @samp{Ctrl-C} Message
36203 @cindex ctrl-c message, in file-i/o protocol
36205 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
36206 reply packet (@pxref{The F Reply Packet}),
36207 the target should behave as if it had
36208 gotten a break message. The meaning for the target is ``system call
36209 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
36210 (as with a break message) and return to @value{GDBN} with a @code{T02}
36213 It's important for the target to know in which
36214 state the system call was interrupted. There are two possible cases:
36218 The system call hasn't been performed on the host yet.
36221 The system call on the host has been finished.
36225 These two states can be distinguished by the target by the value of the
36226 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
36227 call hasn't been performed. This is equivalent to the @code{EINTR} handling
36228 on POSIX systems. In any other case, the target may presume that the
36229 system call has been finished --- successfully or not --- and should behave
36230 as if the break message arrived right after the system call.
36232 @value{GDBN} must behave reliably. If the system call has not been called
36233 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
36234 @code{errno} in the packet. If the system call on the host has been finished
36235 before the user requests a break, the full action must be finished by
36236 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
36237 The @code{F} packet may only be sent when either nothing has happened
36238 or the full action has been completed.
36241 @subsection Console I/O
36242 @cindex console i/o as part of file-i/o
36244 By default and if not explicitly closed by the target system, the file
36245 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
36246 on the @value{GDBN} console is handled as any other file output operation
36247 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
36248 by @value{GDBN} so that after the target read request from file descriptor
36249 0 all following typing is buffered until either one of the following
36254 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
36256 system call is treated as finished.
36259 The user presses @key{RET}. This is treated as end of input with a trailing
36263 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
36264 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
36268 If the user has typed more characters than fit in the buffer given to
36269 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
36270 either another @code{read(0, @dots{})} is requested by the target, or debugging
36271 is stopped at the user's request.
36274 @node List of Supported Calls
36275 @subsection List of Supported Calls
36276 @cindex list of supported file-i/o calls
36293 @unnumberedsubsubsec open
36294 @cindex open, file-i/o system call
36299 int open(const char *pathname, int flags);
36300 int open(const char *pathname, int flags, mode_t mode);
36304 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
36307 @var{flags} is the bitwise @code{OR} of the following values:
36311 If the file does not exist it will be created. The host
36312 rules apply as far as file ownership and time stamps
36316 When used with @code{O_CREAT}, if the file already exists it is
36317 an error and open() fails.
36320 If the file already exists and the open mode allows
36321 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
36322 truncated to zero length.
36325 The file is opened in append mode.
36328 The file is opened for reading only.
36331 The file is opened for writing only.
36334 The file is opened for reading and writing.
36338 Other bits are silently ignored.
36342 @var{mode} is the bitwise @code{OR} of the following values:
36346 User has read permission.
36349 User has write permission.
36352 Group has read permission.
36355 Group has write permission.
36358 Others have read permission.
36361 Others have write permission.
36365 Other bits are silently ignored.
36368 @item Return value:
36369 @code{open} returns the new file descriptor or -1 if an error
36376 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
36379 @var{pathname} refers to a directory.
36382 The requested access is not allowed.
36385 @var{pathname} was too long.
36388 A directory component in @var{pathname} does not exist.
36391 @var{pathname} refers to a device, pipe, named pipe or socket.
36394 @var{pathname} refers to a file on a read-only filesystem and
36395 write access was requested.
36398 @var{pathname} is an invalid pointer value.
36401 No space on device to create the file.
36404 The process already has the maximum number of files open.
36407 The limit on the total number of files open on the system
36411 The call was interrupted by the user.
36417 @unnumberedsubsubsec close
36418 @cindex close, file-i/o system call
36427 @samp{Fclose,@var{fd}}
36429 @item Return value:
36430 @code{close} returns zero on success, or -1 if an error occurred.
36436 @var{fd} isn't a valid open file descriptor.
36439 The call was interrupted by the user.
36445 @unnumberedsubsubsec read
36446 @cindex read, file-i/o system call
36451 int read(int fd, void *buf, unsigned int count);
36455 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
36457 @item Return value:
36458 On success, the number of bytes read is returned.
36459 Zero indicates end of file. If count is zero, read
36460 returns zero as well. On error, -1 is returned.
36466 @var{fd} is not a valid file descriptor or is not open for
36470 @var{bufptr} is an invalid pointer value.
36473 The call was interrupted by the user.
36479 @unnumberedsubsubsec write
36480 @cindex write, file-i/o system call
36485 int write(int fd, const void *buf, unsigned int count);
36489 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
36491 @item Return value:
36492 On success, the number of bytes written are returned.
36493 Zero indicates nothing was written. On error, -1
36500 @var{fd} is not a valid file descriptor or is not open for
36504 @var{bufptr} is an invalid pointer value.
36507 An attempt was made to write a file that exceeds the
36508 host-specific maximum file size allowed.
36511 No space on device to write the data.
36514 The call was interrupted by the user.
36520 @unnumberedsubsubsec lseek
36521 @cindex lseek, file-i/o system call
36526 long lseek (int fd, long offset, int flag);
36530 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
36532 @var{flag} is one of:
36536 The offset is set to @var{offset} bytes.
36539 The offset is set to its current location plus @var{offset}
36543 The offset is set to the size of the file plus @var{offset}
36547 @item Return value:
36548 On success, the resulting unsigned offset in bytes from
36549 the beginning of the file is returned. Otherwise, a
36550 value of -1 is returned.
36556 @var{fd} is not a valid open file descriptor.
36559 @var{fd} is associated with the @value{GDBN} console.
36562 @var{flag} is not a proper value.
36565 The call was interrupted by the user.
36571 @unnumberedsubsubsec rename
36572 @cindex rename, file-i/o system call
36577 int rename(const char *oldpath, const char *newpath);
36581 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
36583 @item Return value:
36584 On success, zero is returned. On error, -1 is returned.
36590 @var{newpath} is an existing directory, but @var{oldpath} is not a
36594 @var{newpath} is a non-empty directory.
36597 @var{oldpath} or @var{newpath} is a directory that is in use by some
36601 An attempt was made to make a directory a subdirectory
36605 A component used as a directory in @var{oldpath} or new
36606 path is not a directory. Or @var{oldpath} is a directory
36607 and @var{newpath} exists but is not a directory.
36610 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
36613 No access to the file or the path of the file.
36617 @var{oldpath} or @var{newpath} was too long.
36620 A directory component in @var{oldpath} or @var{newpath} does not exist.
36623 The file is on a read-only filesystem.
36626 The device containing the file has no room for the new
36630 The call was interrupted by the user.
36636 @unnumberedsubsubsec unlink
36637 @cindex unlink, file-i/o system call
36642 int unlink(const char *pathname);
36646 @samp{Funlink,@var{pathnameptr}/@var{len}}
36648 @item Return value:
36649 On success, zero is returned. On error, -1 is returned.
36655 No access to the file or the path of the file.
36658 The system does not allow unlinking of directories.
36661 The file @var{pathname} cannot be unlinked because it's
36662 being used by another process.
36665 @var{pathnameptr} is an invalid pointer value.
36668 @var{pathname} was too long.
36671 A directory component in @var{pathname} does not exist.
36674 A component of the path is not a directory.
36677 The file is on a read-only filesystem.
36680 The call was interrupted by the user.
36686 @unnumberedsubsubsec stat/fstat
36687 @cindex fstat, file-i/o system call
36688 @cindex stat, file-i/o system call
36693 int stat(const char *pathname, struct stat *buf);
36694 int fstat(int fd, struct stat *buf);
36698 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
36699 @samp{Ffstat,@var{fd},@var{bufptr}}
36701 @item Return value:
36702 On success, zero is returned. On error, -1 is returned.
36708 @var{fd} is not a valid open file.
36711 A directory component in @var{pathname} does not exist or the
36712 path is an empty string.
36715 A component of the path is not a directory.
36718 @var{pathnameptr} is an invalid pointer value.
36721 No access to the file or the path of the file.
36724 @var{pathname} was too long.
36727 The call was interrupted by the user.
36733 @unnumberedsubsubsec gettimeofday
36734 @cindex gettimeofday, file-i/o system call
36739 int gettimeofday(struct timeval *tv, void *tz);
36743 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
36745 @item Return value:
36746 On success, 0 is returned, -1 otherwise.
36752 @var{tz} is a non-NULL pointer.
36755 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
36761 @unnumberedsubsubsec isatty
36762 @cindex isatty, file-i/o system call
36767 int isatty(int fd);
36771 @samp{Fisatty,@var{fd}}
36773 @item Return value:
36774 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
36780 The call was interrupted by the user.
36785 Note that the @code{isatty} call is treated as a special case: it returns
36786 1 to the target if the file descriptor is attached
36787 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
36788 would require implementing @code{ioctl} and would be more complex than
36793 @unnumberedsubsubsec system
36794 @cindex system, file-i/o system call
36799 int system(const char *command);
36803 @samp{Fsystem,@var{commandptr}/@var{len}}
36805 @item Return value:
36806 If @var{len} is zero, the return value indicates whether a shell is
36807 available. A zero return value indicates a shell is not available.
36808 For non-zero @var{len}, the value returned is -1 on error and the
36809 return status of the command otherwise. Only the exit status of the
36810 command is returned, which is extracted from the host's @code{system}
36811 return value by calling @code{WEXITSTATUS(retval)}. In case
36812 @file{/bin/sh} could not be executed, 127 is returned.
36818 The call was interrupted by the user.
36823 @value{GDBN} takes over the full task of calling the necessary host calls
36824 to perform the @code{system} call. The return value of @code{system} on
36825 the host is simplified before it's returned
36826 to the target. Any termination signal information from the child process
36827 is discarded, and the return value consists
36828 entirely of the exit status of the called command.
36830 Due to security concerns, the @code{system} call is by default refused
36831 by @value{GDBN}. The user has to allow this call explicitly with the
36832 @code{set remote system-call-allowed 1} command.
36835 @item set remote system-call-allowed
36836 @kindex set remote system-call-allowed
36837 Control whether to allow the @code{system} calls in the File I/O
36838 protocol for the remote target. The default is zero (disabled).
36840 @item show remote system-call-allowed
36841 @kindex show remote system-call-allowed
36842 Show whether the @code{system} calls are allowed in the File I/O
36846 @node Protocol-specific Representation of Datatypes
36847 @subsection Protocol-specific Representation of Datatypes
36848 @cindex protocol-specific representation of datatypes, in file-i/o protocol
36851 * Integral Datatypes::
36853 * Memory Transfer::
36858 @node Integral Datatypes
36859 @unnumberedsubsubsec Integral Datatypes
36860 @cindex integral datatypes, in file-i/o protocol
36862 The integral datatypes used in the system calls are @code{int},
36863 @code{unsigned int}, @code{long}, @code{unsigned long},
36864 @code{mode_t}, and @code{time_t}.
36866 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
36867 implemented as 32 bit values in this protocol.
36869 @code{long} and @code{unsigned long} are implemented as 64 bit types.
36871 @xref{Limits}, for corresponding MIN and MAX values (similar to those
36872 in @file{limits.h}) to allow range checking on host and target.
36874 @code{time_t} datatypes are defined as seconds since the Epoch.
36876 All integral datatypes transferred as part of a memory read or write of a
36877 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
36880 @node Pointer Values
36881 @unnumberedsubsubsec Pointer Values
36882 @cindex pointer values, in file-i/o protocol
36884 Pointers to target data are transmitted as they are. An exception
36885 is made for pointers to buffers for which the length isn't
36886 transmitted as part of the function call, namely strings. Strings
36887 are transmitted as a pointer/length pair, both as hex values, e.g.@:
36894 which is a pointer to data of length 18 bytes at position 0x1aaf.
36895 The length is defined as the full string length in bytes, including
36896 the trailing null byte. For example, the string @code{"hello world"}
36897 at address 0x123456 is transmitted as
36903 @node Memory Transfer
36904 @unnumberedsubsubsec Memory Transfer
36905 @cindex memory transfer, in file-i/o protocol
36907 Structured data which is transferred using a memory read or write (for
36908 example, a @code{struct stat}) is expected to be in a protocol-specific format
36909 with all scalar multibyte datatypes being big endian. Translation to
36910 this representation needs to be done both by the target before the @code{F}
36911 packet is sent, and by @value{GDBN} before
36912 it transfers memory to the target. Transferred pointers to structured
36913 data should point to the already-coerced data at any time.
36917 @unnumberedsubsubsec struct stat
36918 @cindex struct stat, in file-i/o protocol
36920 The buffer of type @code{struct stat} used by the target and @value{GDBN}
36921 is defined as follows:
36925 unsigned int st_dev; /* device */
36926 unsigned int st_ino; /* inode */
36927 mode_t st_mode; /* protection */
36928 unsigned int st_nlink; /* number of hard links */
36929 unsigned int st_uid; /* user ID of owner */
36930 unsigned int st_gid; /* group ID of owner */
36931 unsigned int st_rdev; /* device type (if inode device) */
36932 unsigned long st_size; /* total size, in bytes */
36933 unsigned long st_blksize; /* blocksize for filesystem I/O */
36934 unsigned long st_blocks; /* number of blocks allocated */
36935 time_t st_atime; /* time of last access */
36936 time_t st_mtime; /* time of last modification */
36937 time_t st_ctime; /* time of last change */
36941 The integral datatypes conform to the definitions given in the
36942 appropriate section (see @ref{Integral Datatypes}, for details) so this
36943 structure is of size 64 bytes.
36945 The values of several fields have a restricted meaning and/or
36951 A value of 0 represents a file, 1 the console.
36954 No valid meaning for the target. Transmitted unchanged.
36957 Valid mode bits are described in @ref{Constants}. Any other
36958 bits have currently no meaning for the target.
36963 No valid meaning for the target. Transmitted unchanged.
36968 These values have a host and file system dependent
36969 accuracy. Especially on Windows hosts, the file system may not
36970 support exact timing values.
36973 The target gets a @code{struct stat} of the above representation and is
36974 responsible for coercing it to the target representation before
36977 Note that due to size differences between the host, target, and protocol
36978 representations of @code{struct stat} members, these members could eventually
36979 get truncated on the target.
36981 @node struct timeval
36982 @unnumberedsubsubsec struct timeval
36983 @cindex struct timeval, in file-i/o protocol
36985 The buffer of type @code{struct timeval} used by the File-I/O protocol
36986 is defined as follows:
36990 time_t tv_sec; /* second */
36991 long tv_usec; /* microsecond */
36995 The integral datatypes conform to the definitions given in the
36996 appropriate section (see @ref{Integral Datatypes}, for details) so this
36997 structure is of size 8 bytes.
37000 @subsection Constants
37001 @cindex constants, in file-i/o protocol
37003 The following values are used for the constants inside of the
37004 protocol. @value{GDBN} and target are responsible for translating these
37005 values before and after the call as needed.
37016 @unnumberedsubsubsec Open Flags
37017 @cindex open flags, in file-i/o protocol
37019 All values are given in hexadecimal representation.
37031 @node mode_t Values
37032 @unnumberedsubsubsec mode_t Values
37033 @cindex mode_t values, in file-i/o protocol
37035 All values are given in octal representation.
37052 @unnumberedsubsubsec Errno Values
37053 @cindex errno values, in file-i/o protocol
37055 All values are given in decimal representation.
37080 @code{EUNKNOWN} is used as a fallback error value if a host system returns
37081 any error value not in the list of supported error numbers.
37084 @unnumberedsubsubsec Lseek Flags
37085 @cindex lseek flags, in file-i/o protocol
37094 @unnumberedsubsubsec Limits
37095 @cindex limits, in file-i/o protocol
37097 All values are given in decimal representation.
37100 INT_MIN -2147483648
37102 UINT_MAX 4294967295
37103 LONG_MIN -9223372036854775808
37104 LONG_MAX 9223372036854775807
37105 ULONG_MAX 18446744073709551615
37108 @node File-I/O Examples
37109 @subsection File-I/O Examples
37110 @cindex file-i/o examples
37112 Example sequence of a write call, file descriptor 3, buffer is at target
37113 address 0x1234, 6 bytes should be written:
37116 <- @code{Fwrite,3,1234,6}
37117 @emph{request memory read from target}
37120 @emph{return "6 bytes written"}
37124 Example sequence of a read call, file descriptor 3, buffer is at target
37125 address 0x1234, 6 bytes should be read:
37128 <- @code{Fread,3,1234,6}
37129 @emph{request memory write to target}
37130 -> @code{X1234,6:XXXXXX}
37131 @emph{return "6 bytes read"}
37135 Example sequence of a read call, call fails on the host due to invalid
37136 file descriptor (@code{EBADF}):
37139 <- @code{Fread,3,1234,6}
37143 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
37147 <- @code{Fread,3,1234,6}
37152 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
37156 <- @code{Fread,3,1234,6}
37157 -> @code{X1234,6:XXXXXX}
37161 @node Library List Format
37162 @section Library List Format
37163 @cindex library list format, remote protocol
37165 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
37166 same process as your application to manage libraries. In this case,
37167 @value{GDBN} can use the loader's symbol table and normal memory
37168 operations to maintain a list of shared libraries. On other
37169 platforms, the operating system manages loaded libraries.
37170 @value{GDBN} can not retrieve the list of currently loaded libraries
37171 through memory operations, so it uses the @samp{qXfer:libraries:read}
37172 packet (@pxref{qXfer library list read}) instead. The remote stub
37173 queries the target's operating system and reports which libraries
37176 The @samp{qXfer:libraries:read} packet returns an XML document which
37177 lists loaded libraries and their offsets. Each library has an
37178 associated name and one or more segment or section base addresses,
37179 which report where the library was loaded in memory.
37181 For the common case of libraries that are fully linked binaries, the
37182 library should have a list of segments. If the target supports
37183 dynamic linking of a relocatable object file, its library XML element
37184 should instead include a list of allocated sections. The segment or
37185 section bases are start addresses, not relocation offsets; they do not
37186 depend on the library's link-time base addresses.
37188 @value{GDBN} must be linked with the Expat library to support XML
37189 library lists. @xref{Expat}.
37191 A simple memory map, with one loaded library relocated by a single
37192 offset, looks like this:
37196 <library name="/lib/libc.so.6">
37197 <segment address="0x10000000"/>
37202 Another simple memory map, with one loaded library with three
37203 allocated sections (.text, .data, .bss), looks like this:
37207 <library name="sharedlib.o">
37208 <section address="0x10000000"/>
37209 <section address="0x20000000"/>
37210 <section address="0x30000000"/>
37215 The format of a library list is described by this DTD:
37218 <!-- library-list: Root element with versioning -->
37219 <!ELEMENT library-list (library)*>
37220 <!ATTLIST library-list version CDATA #FIXED "1.0">
37221 <!ELEMENT library (segment*, section*)>
37222 <!ATTLIST library name CDATA #REQUIRED>
37223 <!ELEMENT segment EMPTY>
37224 <!ATTLIST segment address CDATA #REQUIRED>
37225 <!ELEMENT section EMPTY>
37226 <!ATTLIST section address CDATA #REQUIRED>
37229 In addition, segments and section descriptors cannot be mixed within a
37230 single library element, and you must supply at least one segment or
37231 section for each library.
37233 @node Memory Map Format
37234 @section Memory Map Format
37235 @cindex memory map format
37237 To be able to write into flash memory, @value{GDBN} needs to obtain a
37238 memory map from the target. This section describes the format of the
37241 The memory map is obtained using the @samp{qXfer:memory-map:read}
37242 (@pxref{qXfer memory map read}) packet and is an XML document that
37243 lists memory regions.
37245 @value{GDBN} must be linked with the Expat library to support XML
37246 memory maps. @xref{Expat}.
37248 The top-level structure of the document is shown below:
37251 <?xml version="1.0"?>
37252 <!DOCTYPE memory-map
37253 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
37254 "http://sourceware.org/gdb/gdb-memory-map.dtd">
37260 Each region can be either:
37265 A region of RAM starting at @var{addr} and extending for @var{length}
37269 <memory type="ram" start="@var{addr}" length="@var{length}"/>
37274 A region of read-only memory:
37277 <memory type="rom" start="@var{addr}" length="@var{length}"/>
37282 A region of flash memory, with erasure blocks @var{blocksize}
37286 <memory type="flash" start="@var{addr}" length="@var{length}">
37287 <property name="blocksize">@var{blocksize}</property>
37293 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
37294 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
37295 packets to write to addresses in such ranges.
37297 The formal DTD for memory map format is given below:
37300 <!-- ................................................... -->
37301 <!-- Memory Map XML DTD ................................ -->
37302 <!-- File: memory-map.dtd .............................. -->
37303 <!-- .................................... .............. -->
37304 <!-- memory-map.dtd -->
37305 <!-- memory-map: Root element with versioning -->
37306 <!ELEMENT memory-map (memory | property)>
37307 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
37308 <!ELEMENT memory (property)>
37309 <!-- memory: Specifies a memory region,
37310 and its type, or device. -->
37311 <!ATTLIST memory type CDATA #REQUIRED
37312 start CDATA #REQUIRED
37313 length CDATA #REQUIRED
37314 device CDATA #IMPLIED>
37315 <!-- property: Generic attribute tag -->
37316 <!ELEMENT property (#PCDATA | property)*>
37317 <!ATTLIST property name CDATA #REQUIRED>
37320 @node Thread List Format
37321 @section Thread List Format
37322 @cindex thread list format
37324 To efficiently update the list of threads and their attributes,
37325 @value{GDBN} issues the @samp{qXfer:threads:read} packet
37326 (@pxref{qXfer threads read}) and obtains the XML document with
37327 the following structure:
37330 <?xml version="1.0"?>
37332 <thread id="id" core="0">
37333 ... description ...
37338 Each @samp{thread} element must have the @samp{id} attribute that
37339 identifies the thread (@pxref{thread-id syntax}). The
37340 @samp{core} attribute, if present, specifies which processor core
37341 the thread was last executing on. The content of the of @samp{thread}
37342 element is interpreted as human-readable auxilliary information.
37344 @node Traceframe Info Format
37345 @section Traceframe Info Format
37346 @cindex traceframe info format
37348 To be able to know which objects in the inferior can be examined when
37349 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
37350 memory ranges, registers and trace state variables that have been
37351 collected in a traceframe.
37353 This list is obtained using the @samp{qXfer:traceframe-info:read}
37354 (@pxref{qXfer traceframe info read}) packet and is an XML document.
37356 @value{GDBN} must be linked with the Expat library to support XML
37357 traceframe info discovery. @xref{Expat}.
37359 The top-level structure of the document is shown below:
37362 <?xml version="1.0"?>
37363 <!DOCTYPE traceframe-info
37364 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
37365 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
37371 Each traceframe block can be either:
37376 A region of collected memory starting at @var{addr} and extending for
37377 @var{length} bytes from there:
37380 <memory start="@var{addr}" length="@var{length}"/>
37385 The formal DTD for the traceframe info format is given below:
37388 <!ELEMENT traceframe-info (memory)* >
37389 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
37391 <!ELEMENT memory EMPTY>
37392 <!ATTLIST memory start CDATA #REQUIRED
37393 length CDATA #REQUIRED>
37396 @include agentexpr.texi
37398 @node Target Descriptions
37399 @appendix Target Descriptions
37400 @cindex target descriptions
37402 One of the challenges of using @value{GDBN} to debug embedded systems
37403 is that there are so many minor variants of each processor
37404 architecture in use. It is common practice for vendors to start with
37405 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
37406 and then make changes to adapt it to a particular market niche. Some
37407 architectures have hundreds of variants, available from dozens of
37408 vendors. This leads to a number of problems:
37412 With so many different customized processors, it is difficult for
37413 the @value{GDBN} maintainers to keep up with the changes.
37415 Since individual variants may have short lifetimes or limited
37416 audiences, it may not be worthwhile to carry information about every
37417 variant in the @value{GDBN} source tree.
37419 When @value{GDBN} does support the architecture of the embedded system
37420 at hand, the task of finding the correct architecture name to give the
37421 @command{set architecture} command can be error-prone.
37424 To address these problems, the @value{GDBN} remote protocol allows a
37425 target system to not only identify itself to @value{GDBN}, but to
37426 actually describe its own features. This lets @value{GDBN} support
37427 processor variants it has never seen before --- to the extent that the
37428 descriptions are accurate, and that @value{GDBN} understands them.
37430 @value{GDBN} must be linked with the Expat library to support XML
37431 target descriptions. @xref{Expat}.
37434 * Retrieving Descriptions:: How descriptions are fetched from a target.
37435 * Target Description Format:: The contents of a target description.
37436 * Predefined Target Types:: Standard types available for target
37438 * Standard Target Features:: Features @value{GDBN} knows about.
37441 @node Retrieving Descriptions
37442 @section Retrieving Descriptions
37444 Target descriptions can be read from the target automatically, or
37445 specified by the user manually. The default behavior is to read the
37446 description from the target. @value{GDBN} retrieves it via the remote
37447 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
37448 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
37449 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
37450 XML document, of the form described in @ref{Target Description
37453 Alternatively, you can specify a file to read for the target description.
37454 If a file is set, the target will not be queried. The commands to
37455 specify a file are:
37458 @cindex set tdesc filename
37459 @item set tdesc filename @var{path}
37460 Read the target description from @var{path}.
37462 @cindex unset tdesc filename
37463 @item unset tdesc filename
37464 Do not read the XML target description from a file. @value{GDBN}
37465 will use the description supplied by the current target.
37467 @cindex show tdesc filename
37468 @item show tdesc filename
37469 Show the filename to read for a target description, if any.
37473 @node Target Description Format
37474 @section Target Description Format
37475 @cindex target descriptions, XML format
37477 A target description annex is an @uref{http://www.w3.org/XML/, XML}
37478 document which complies with the Document Type Definition provided in
37479 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
37480 means you can use generally available tools like @command{xmllint} to
37481 check that your feature descriptions are well-formed and valid.
37482 However, to help people unfamiliar with XML write descriptions for
37483 their targets, we also describe the grammar here.
37485 Target descriptions can identify the architecture of the remote target
37486 and (for some architectures) provide information about custom register
37487 sets. They can also identify the OS ABI of the remote target.
37488 @value{GDBN} can use this information to autoconfigure for your
37489 target, or to warn you if you connect to an unsupported target.
37491 Here is a simple target description:
37494 <target version="1.0">
37495 <architecture>i386:x86-64</architecture>
37500 This minimal description only says that the target uses
37501 the x86-64 architecture.
37503 A target description has the following overall form, with [ ] marking
37504 optional elements and @dots{} marking repeatable elements. The elements
37505 are explained further below.
37508 <?xml version="1.0"?>
37509 <!DOCTYPE target SYSTEM "gdb-target.dtd">
37510 <target version="1.0">
37511 @r{[}@var{architecture}@r{]}
37512 @r{[}@var{osabi}@r{]}
37513 @r{[}@var{compatible}@r{]}
37514 @r{[}@var{feature}@dots{}@r{]}
37519 The description is generally insensitive to whitespace and line
37520 breaks, under the usual common-sense rules. The XML version
37521 declaration and document type declaration can generally be omitted
37522 (@value{GDBN} does not require them), but specifying them may be
37523 useful for XML validation tools. The @samp{version} attribute for
37524 @samp{<target>} may also be omitted, but we recommend
37525 including it; if future versions of @value{GDBN} use an incompatible
37526 revision of @file{gdb-target.dtd}, they will detect and report
37527 the version mismatch.
37529 @subsection Inclusion
37530 @cindex target descriptions, inclusion
37533 @cindex <xi:include>
37536 It can sometimes be valuable to split a target description up into
37537 several different annexes, either for organizational purposes, or to
37538 share files between different possible target descriptions. You can
37539 divide a description into multiple files by replacing any element of
37540 the target description with an inclusion directive of the form:
37543 <xi:include href="@var{document}"/>
37547 When @value{GDBN} encounters an element of this form, it will retrieve
37548 the named XML @var{document}, and replace the inclusion directive with
37549 the contents of that document. If the current description was read
37550 using @samp{qXfer}, then so will be the included document;
37551 @var{document} will be interpreted as the name of an annex. If the
37552 current description was read from a file, @value{GDBN} will look for
37553 @var{document} as a file in the same directory where it found the
37554 original description.
37556 @subsection Architecture
37557 @cindex <architecture>
37559 An @samp{<architecture>} element has this form:
37562 <architecture>@var{arch}</architecture>
37565 @var{arch} is one of the architectures from the set accepted by
37566 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
37569 @cindex @code{<osabi>}
37571 This optional field was introduced in @value{GDBN} version 7.0.
37572 Previous versions of @value{GDBN} ignore it.
37574 An @samp{<osabi>} element has this form:
37577 <osabi>@var{abi-name}</osabi>
37580 @var{abi-name} is an OS ABI name from the same selection accepted by
37581 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
37583 @subsection Compatible Architecture
37584 @cindex @code{<compatible>}
37586 This optional field was introduced in @value{GDBN} version 7.0.
37587 Previous versions of @value{GDBN} ignore it.
37589 A @samp{<compatible>} element has this form:
37592 <compatible>@var{arch}</compatible>
37595 @var{arch} is one of the architectures from the set accepted by
37596 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
37598 A @samp{<compatible>} element is used to specify that the target
37599 is able to run binaries in some other than the main target architecture
37600 given by the @samp{<architecture>} element. For example, on the
37601 Cell Broadband Engine, the main architecture is @code{powerpc:common}
37602 or @code{powerpc:common64}, but the system is able to run binaries
37603 in the @code{spu} architecture as well. The way to describe this
37604 capability with @samp{<compatible>} is as follows:
37607 <architecture>powerpc:common</architecture>
37608 <compatible>spu</compatible>
37611 @subsection Features
37614 Each @samp{<feature>} describes some logical portion of the target
37615 system. Features are currently used to describe available CPU
37616 registers and the types of their contents. A @samp{<feature>} element
37620 <feature name="@var{name}">
37621 @r{[}@var{type}@dots{}@r{]}
37627 Each feature's name should be unique within the description. The name
37628 of a feature does not matter unless @value{GDBN} has some special
37629 knowledge of the contents of that feature; if it does, the feature
37630 should have its standard name. @xref{Standard Target Features}.
37634 Any register's value is a collection of bits which @value{GDBN} must
37635 interpret. The default interpretation is a two's complement integer,
37636 but other types can be requested by name in the register description.
37637 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
37638 Target Types}), and the description can define additional composite types.
37640 Each type element must have an @samp{id} attribute, which gives
37641 a unique (within the containing @samp{<feature>}) name to the type.
37642 Types must be defined before they are used.
37645 Some targets offer vector registers, which can be treated as arrays
37646 of scalar elements. These types are written as @samp{<vector>} elements,
37647 specifying the array element type, @var{type}, and the number of elements,
37651 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
37655 If a register's value is usefully viewed in multiple ways, define it
37656 with a union type containing the useful representations. The
37657 @samp{<union>} element contains one or more @samp{<field>} elements,
37658 each of which has a @var{name} and a @var{type}:
37661 <union id="@var{id}">
37662 <field name="@var{name}" type="@var{type}"/>
37668 If a register's value is composed from several separate values, define
37669 it with a structure type. There are two forms of the @samp{<struct>}
37670 element; a @samp{<struct>} element must either contain only bitfields
37671 or contain no bitfields. If the structure contains only bitfields,
37672 its total size in bytes must be specified, each bitfield must have an
37673 explicit start and end, and bitfields are automatically assigned an
37674 integer type. The field's @var{start} should be less than or
37675 equal to its @var{end}, and zero represents the least significant bit.
37678 <struct id="@var{id}" size="@var{size}">
37679 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
37684 If the structure contains no bitfields, then each field has an
37685 explicit type, and no implicit padding is added.
37688 <struct id="@var{id}">
37689 <field name="@var{name}" type="@var{type}"/>
37695 If a register's value is a series of single-bit flags, define it with
37696 a flags type. The @samp{<flags>} element has an explicit @var{size}
37697 and contains one or more @samp{<field>} elements. Each field has a
37698 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
37702 <flags id="@var{id}" size="@var{size}">
37703 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
37708 @subsection Registers
37711 Each register is represented as an element with this form:
37714 <reg name="@var{name}"
37715 bitsize="@var{size}"
37716 @r{[}regnum="@var{num}"@r{]}
37717 @r{[}save-restore="@var{save-restore}"@r{]}
37718 @r{[}type="@var{type}"@r{]}
37719 @r{[}group="@var{group}"@r{]}/>
37723 The components are as follows:
37728 The register's name; it must be unique within the target description.
37731 The register's size, in bits.
37734 The register's number. If omitted, a register's number is one greater
37735 than that of the previous register (either in the current feature or in
37736 a preceding feature); the first register in the target description
37737 defaults to zero. This register number is used to read or write
37738 the register; e.g.@: it is used in the remote @code{p} and @code{P}
37739 packets, and registers appear in the @code{g} and @code{G} packets
37740 in order of increasing register number.
37743 Whether the register should be preserved across inferior function
37744 calls; this must be either @code{yes} or @code{no}. The default is
37745 @code{yes}, which is appropriate for most registers except for
37746 some system control registers; this is not related to the target's
37750 The type of the register. @var{type} may be a predefined type, a type
37751 defined in the current feature, or one of the special types @code{int}
37752 and @code{float}. @code{int} is an integer type of the correct size
37753 for @var{bitsize}, and @code{float} is a floating point type (in the
37754 architecture's normal floating point format) of the correct size for
37755 @var{bitsize}. The default is @code{int}.
37758 The register group to which this register belongs. @var{group} must
37759 be either @code{general}, @code{float}, or @code{vector}. If no
37760 @var{group} is specified, @value{GDBN} will not display the register
37761 in @code{info registers}.
37765 @node Predefined Target Types
37766 @section Predefined Target Types
37767 @cindex target descriptions, predefined types
37769 Type definitions in the self-description can build up composite types
37770 from basic building blocks, but can not define fundamental types. Instead,
37771 standard identifiers are provided by @value{GDBN} for the fundamental
37772 types. The currently supported types are:
37781 Signed integer types holding the specified number of bits.
37788 Unsigned integer types holding the specified number of bits.
37792 Pointers to unspecified code and data. The program counter and
37793 any dedicated return address register may be marked as code
37794 pointers; printing a code pointer converts it into a symbolic
37795 address. The stack pointer and any dedicated address registers
37796 may be marked as data pointers.
37799 Single precision IEEE floating point.
37802 Double precision IEEE floating point.
37805 The 12-byte extended precision format used by ARM FPA registers.
37808 The 10-byte extended precision format used by x87 registers.
37811 32bit @sc{eflags} register used by x86.
37814 32bit @sc{mxcsr} register used by x86.
37818 @node Standard Target Features
37819 @section Standard Target Features
37820 @cindex target descriptions, standard features
37822 A target description must contain either no registers or all the
37823 target's registers. If the description contains no registers, then
37824 @value{GDBN} will assume a default register layout, selected based on
37825 the architecture. If the description contains any registers, the
37826 default layout will not be used; the standard registers must be
37827 described in the target description, in such a way that @value{GDBN}
37828 can recognize them.
37830 This is accomplished by giving specific names to feature elements
37831 which contain standard registers. @value{GDBN} will look for features
37832 with those names and verify that they contain the expected registers;
37833 if any known feature is missing required registers, or if any required
37834 feature is missing, @value{GDBN} will reject the target
37835 description. You can add additional registers to any of the
37836 standard features --- @value{GDBN} will display them just as if
37837 they were added to an unrecognized feature.
37839 This section lists the known features and their expected contents.
37840 Sample XML documents for these features are included in the
37841 @value{GDBN} source tree, in the directory @file{gdb/features}.
37843 Names recognized by @value{GDBN} should include the name of the
37844 company or organization which selected the name, and the overall
37845 architecture to which the feature applies; so e.g.@: the feature
37846 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
37848 The names of registers are not case sensitive for the purpose
37849 of recognizing standard features, but @value{GDBN} will only display
37850 registers using the capitalization used in the description.
37857 * PowerPC Features::
37863 @subsection ARM Features
37864 @cindex target descriptions, ARM features
37866 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
37868 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
37869 @samp{lr}, @samp{pc}, and @samp{cpsr}.
37871 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
37872 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
37873 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
37876 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
37877 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
37879 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
37880 it should contain at least registers @samp{wR0} through @samp{wR15} and
37881 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
37882 @samp{wCSSF}, and @samp{wCASF} registers are optional.
37884 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
37885 should contain at least registers @samp{d0} through @samp{d15}. If
37886 they are present, @samp{d16} through @samp{d31} should also be included.
37887 @value{GDBN} will synthesize the single-precision registers from
37888 halves of the double-precision registers.
37890 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
37891 need to contain registers; it instructs @value{GDBN} to display the
37892 VFP double-precision registers as vectors and to synthesize the
37893 quad-precision registers from pairs of double-precision registers.
37894 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
37895 be present and include 32 double-precision registers.
37897 @node i386 Features
37898 @subsection i386 Features
37899 @cindex target descriptions, i386 features
37901 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
37902 targets. It should describe the following registers:
37906 @samp{eax} through @samp{edi} plus @samp{eip} for i386
37908 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
37910 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
37911 @samp{fs}, @samp{gs}
37913 @samp{st0} through @samp{st7}
37915 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
37916 @samp{foseg}, @samp{fooff} and @samp{fop}
37919 The register sets may be different, depending on the target.
37921 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
37922 describe registers:
37926 @samp{xmm0} through @samp{xmm7} for i386
37928 @samp{xmm0} through @samp{xmm15} for amd64
37933 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
37934 @samp{org.gnu.gdb.i386.sse} feature. It should
37935 describe the upper 128 bits of @sc{ymm} registers:
37939 @samp{ymm0h} through @samp{ymm7h} for i386
37941 @samp{ymm0h} through @samp{ymm15h} for amd64
37944 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
37945 describe a single register, @samp{orig_eax}.
37947 @node MIPS Features
37948 @subsection MIPS Features
37949 @cindex target descriptions, MIPS features
37951 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
37952 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
37953 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
37956 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
37957 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
37958 registers. They may be 32-bit or 64-bit depending on the target.
37960 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
37961 it may be optional in a future version of @value{GDBN}. It should
37962 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
37963 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
37965 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
37966 contain a single register, @samp{restart}, which is used by the
37967 Linux kernel to control restartable syscalls.
37969 @node M68K Features
37970 @subsection M68K Features
37971 @cindex target descriptions, M68K features
37974 @item @samp{org.gnu.gdb.m68k.core}
37975 @itemx @samp{org.gnu.gdb.coldfire.core}
37976 @itemx @samp{org.gnu.gdb.fido.core}
37977 One of those features must be always present.
37978 The feature that is present determines which flavor of m68k is
37979 used. The feature that is present should contain registers
37980 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
37981 @samp{sp}, @samp{ps} and @samp{pc}.
37983 @item @samp{org.gnu.gdb.coldfire.fp}
37984 This feature is optional. If present, it should contain registers
37985 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
37989 @node PowerPC Features
37990 @subsection PowerPC Features
37991 @cindex target descriptions, PowerPC features
37993 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
37994 targets. It should contain registers @samp{r0} through @samp{r31},
37995 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
37996 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
37998 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
37999 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
38001 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
38002 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
38005 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
38006 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
38007 will combine these registers with the floating point registers
38008 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
38009 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
38010 through @samp{vs63}, the set of vector registers for POWER7.
38012 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
38013 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
38014 @samp{spefscr}. SPE targets should provide 32-bit registers in
38015 @samp{org.gnu.gdb.power.core} and provide the upper halves in
38016 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
38017 these to present registers @samp{ev0} through @samp{ev31} to the
38020 @node TIC6x Features
38021 @subsection TMS320C6x Features
38022 @cindex target descriptions, TIC6x features
38023 @cindex target descriptions, TMS320C6x features
38024 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
38025 targets. It should contain registers @samp{A0} through @samp{A15},
38026 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
38028 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
38029 contain registers @samp{A16} through @samp{A31} and @samp{B16}
38030 through @samp{B31}.
38032 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
38033 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
38035 @node Operating System Information
38036 @appendix Operating System Information
38037 @cindex operating system information
38043 Users of @value{GDBN} often wish to obtain information about the state of
38044 the operating system running on the target---for example the list of
38045 processes, or the list of open files. This section describes the
38046 mechanism that makes it possible. This mechanism is similar to the
38047 target features mechanism (@pxref{Target Descriptions}), but focuses
38048 on a different aspect of target.
38050 Operating system information is retrived from the target via the
38051 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
38052 read}). The object name in the request should be @samp{osdata}, and
38053 the @var{annex} identifies the data to be fetched.
38056 @appendixsection Process list
38057 @cindex operating system information, process list
38059 When requesting the process list, the @var{annex} field in the
38060 @samp{qXfer} request should be @samp{processes}. The returned data is
38061 an XML document. The formal syntax of this document is defined in
38062 @file{gdb/features/osdata.dtd}.
38064 An example document is:
38067 <?xml version="1.0"?>
38068 <!DOCTYPE target SYSTEM "osdata.dtd">
38069 <osdata type="processes">
38071 <column name="pid">1</column>
38072 <column name="user">root</column>
38073 <column name="command">/sbin/init</column>
38074 <column name="cores">1,2,3</column>
38079 Each item should include a column whose name is @samp{pid}. The value
38080 of that column should identify the process on the target. The
38081 @samp{user} and @samp{command} columns are optional, and will be
38082 displayed by @value{GDBN}. The @samp{cores} column, if present,
38083 should contain a comma-separated list of cores that this process
38084 is running on. Target may provide additional columns,
38085 which @value{GDBN} currently ignores.
38087 @node Trace File Format
38088 @appendix Trace File Format
38089 @cindex trace file format
38091 The trace file comes in three parts: a header, a textual description
38092 section, and a trace frame section with binary data.
38094 The header has the form @code{\x7fTRACE0\n}. The first byte is
38095 @code{0x7f} so as to indicate that the file contains binary data,
38096 while the @code{0} is a version number that may have different values
38099 The description section consists of multiple lines of @sc{ascii} text
38100 separated by newline characters (@code{0xa}). The lines may include a
38101 variety of optional descriptive or context-setting information, such
38102 as tracepoint definitions or register set size. @value{GDBN} will
38103 ignore any line that it does not recognize. An empty line marks the end
38106 @c FIXME add some specific types of data
38108 The trace frame section consists of a number of consecutive frames.
38109 Each frame begins with a two-byte tracepoint number, followed by a
38110 four-byte size giving the amount of data in the frame. The data in
38111 the frame consists of a number of blocks, each introduced by a
38112 character indicating its type (at least register, memory, and trace
38113 state variable). The data in this section is raw binary, not a
38114 hexadecimal or other encoding; its endianness matches the target's
38117 @c FIXME bi-arch may require endianness/arch info in description section
38120 @item R @var{bytes}
38121 Register block. The number and ordering of bytes matches that of a
38122 @code{g} packet in the remote protocol. Note that these are the
38123 actual bytes, in target order and @value{GDBN} register order, not a
38124 hexadecimal encoding.
38126 @item M @var{address} @var{length} @var{bytes}...
38127 Memory block. This is a contiguous block of memory, at the 8-byte
38128 address @var{address}, with a 2-byte length @var{length}, followed by
38129 @var{length} bytes.
38131 @item V @var{number} @var{value}
38132 Trace state variable block. This records the 8-byte signed value
38133 @var{value} of trace state variable numbered @var{number}.
38137 Future enhancements of the trace file format may include additional types
38140 @node Index Section Format
38141 @appendix @code{.gdb_index} section format
38142 @cindex .gdb_index section format
38143 @cindex index section format
38145 This section documents the index section that is created by @code{save
38146 gdb-index} (@pxref{Index Files}). The index section is
38147 DWARF-specific; some knowledge of DWARF is assumed in this
38150 The mapped index file format is designed to be directly
38151 @code{mmap}able on any architecture. In most cases, a datum is
38152 represented using a little-endian 32-bit integer value, called an
38153 @code{offset_type}. Big endian machines must byte-swap the values
38154 before using them. Exceptions to this rule are noted. The data is
38155 laid out such that alignment is always respected.
38157 A mapped index consists of several areas, laid out in order.
38161 The file header. This is a sequence of values, of @code{offset_type}
38162 unless otherwise noted:
38166 The version number, currently 5. Versions 1, 2 and 3 are obsolete.
38167 Version 4 differs by its hashing function.
38170 The offset, from the start of the file, of the CU list.
38173 The offset, from the start of the file, of the types CU list. Note
38174 that this area can be empty, in which case this offset will be equal
38175 to the next offset.
38178 The offset, from the start of the file, of the address area.
38181 The offset, from the start of the file, of the symbol table.
38184 The offset, from the start of the file, of the constant pool.
38188 The CU list. This is a sequence of pairs of 64-bit little-endian
38189 values, sorted by the CU offset. The first element in each pair is
38190 the offset of a CU in the @code{.debug_info} section. The second
38191 element in each pair is the length of that CU. References to a CU
38192 elsewhere in the map are done using a CU index, which is just the
38193 0-based index into this table. Note that if there are type CUs, then
38194 conceptually CUs and type CUs form a single list for the purposes of
38198 The types CU list. This is a sequence of triplets of 64-bit
38199 little-endian values. In a triplet, the first value is the CU offset,
38200 the second value is the type offset in the CU, and the third value is
38201 the type signature. The types CU list is not sorted.
38204 The address area. The address area consists of a sequence of address
38205 entries. Each address entry has three elements:
38209 The low address. This is a 64-bit little-endian value.
38212 The high address. This is a 64-bit little-endian value. Like
38213 @code{DW_AT_high_pc}, the value is one byte beyond the end.
38216 The CU index. This is an @code{offset_type} value.
38220 The symbol table. This is an open-addressed hash table. The size of
38221 the hash table is always a power of 2.
38223 Each slot in the hash table consists of a pair of @code{offset_type}
38224 values. The first value is the offset of the symbol's name in the
38225 constant pool. The second value is the offset of the CU vector in the
38228 If both values are 0, then this slot in the hash table is empty. This
38229 is ok because while 0 is a valid constant pool index, it cannot be a
38230 valid index for both a string and a CU vector.
38232 The hash value for a table entry is computed by applying an
38233 iterative hash function to the symbol's name. Starting with an
38234 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
38235 the string is incorporated into the hash using the formula depending on the
38240 The formula is @code{r = r * 67 + c - 113}.
38243 The formula is @code{r = r * 67 + tolower (c) - 113}.
38246 The terminating @samp{\0} is not incorporated into the hash.
38248 The step size used in the hash table is computed via
38249 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
38250 value, and @samp{size} is the size of the hash table. The step size
38251 is used to find the next candidate slot when handling a hash
38254 The names of C@t{++} symbols in the hash table are canonicalized. We
38255 don't currently have a simple description of the canonicalization
38256 algorithm; if you intend to create new index sections, you must read
38260 The constant pool. This is simply a bunch of bytes. It is organized
38261 so that alignment is correct: CU vectors are stored first, followed by
38264 A CU vector in the constant pool is a sequence of @code{offset_type}
38265 values. The first value is the number of CU indices in the vector.
38266 Each subsequent value is the index of a CU in the CU list. This
38267 element in the hash table is used to indicate which CUs define the
38270 A string in the constant pool is zero-terminated.
38275 @node GNU Free Documentation License
38276 @appendix GNU Free Documentation License
38285 % I think something like @colophon should be in texinfo. In the
38287 \long\def\colophon{\hbox to0pt{}\vfill
38288 \centerline{The body of this manual is set in}
38289 \centerline{\fontname\tenrm,}
38290 \centerline{with headings in {\bf\fontname\tenbf}}
38291 \centerline{and examples in {\tt\fontname\tentt}.}
38292 \centerline{{\it\fontname\tenit\/},}
38293 \centerline{{\bf\fontname\tenbf}, and}
38294 \centerline{{\sl\fontname\tensl\/}}
38295 \centerline{are used for emphasis.}\vfill}
38297 % Blame: doc@cygnus.com, 1991.