1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,
3 @c 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009
4 @c 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
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 1.1 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 1-882114-77-9 @*
104 This edition of the GDB manual is dedicated to the memory of Fred
105 Fish. Fred was a long-standing contributor to GDB and to Free
106 software in general. We will miss him.
111 @node Top, Summary, (dir), (dir)
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN}
118 @ifset VERSION_PACKAGE
119 @value{VERSION_PACKAGE}
121 Version @value{GDBVN}.
123 Copyright (C) 1988-2009 Free Software Foundation, Inc.
125 This edition of the GDB manual is dedicated to the memory of Fred
126 Fish. Fred was a long-standing contributor to GDB and to Free
127 software in general. We will miss him.
130 * Summary:: Summary of @value{GDBN}
131 * Sample Session:: A sample @value{GDBN} session
133 * Invocation:: Getting in and out of @value{GDBN}
134 * Commands:: @value{GDBN} commands
135 * Running:: Running programs under @value{GDBN}
136 * Stopping:: Stopping and continuing
137 * Reverse Execution:: Running programs backward
138 * Process Record and Replay:: Recording inferior's execution and replaying it
139 * Stack:: Examining the stack
140 * Source:: Examining source files
141 * Data:: Examining data
142 * Optimized Code:: Debugging optimized code
143 * Macros:: Preprocessor Macros
144 * Tracepoints:: Debugging remote targets non-intrusively
145 * Overlays:: Debugging programs that use overlays
147 * Languages:: Using @value{GDBN} with different languages
149 * Symbols:: Examining the symbol table
150 * Altering:: Altering execution
151 * GDB Files:: @value{GDBN} files
152 * Targets:: Specifying a debugging target
153 * Remote Debugging:: Debugging remote programs
154 * Configurations:: Configuration-specific information
155 * Controlling GDB:: Controlling @value{GDBN}
156 * Extending GDB:: Extending @value{GDBN}
157 * Interpreters:: Command Interpreters
158 * TUI:: @value{GDBN} Text User Interface
159 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
160 * GDB/MI:: @value{GDBN}'s Machine Interface.
161 * Annotations:: @value{GDBN}'s annotation interface.
162 * JIT Interface:: Using the JIT debugging interface.
164 * GDB Bugs:: Reporting bugs in @value{GDBN}
166 * Command Line Editing:: Command Line Editing
167 * Using History Interactively:: Using History Interactively
168 * Formatting Documentation:: How to format and print @value{GDBN} documentation
169 * Installing GDB:: Installing GDB
170 * Maintenance Commands:: Maintenance Commands
171 * Remote Protocol:: GDB Remote Serial Protocol
172 * Agent Expressions:: The GDB Agent Expression Mechanism
173 * Target Descriptions:: How targets can describe themselves to
175 * Operating System Information:: Getting additional information from
177 * Copying:: GNU General Public License says
178 how you can copy and share GDB
179 * GNU Free Documentation License:: The license for this documentation
188 @unnumbered Summary of @value{GDBN}
190 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
191 going on ``inside'' another program while it executes---or what another
192 program was doing at the moment it crashed.
194 @value{GDBN} can do four main kinds of things (plus other things in support of
195 these) to help you catch bugs in the act:
199 Start your program, specifying anything that might affect its behavior.
202 Make your program stop on specified conditions.
205 Examine what has happened, when your program has stopped.
208 Change things in your program, so you can experiment with correcting the
209 effects of one bug and go on to learn about another.
212 You can use @value{GDBN} to debug programs written in C and C@t{++}.
213 For more information, see @ref{Supported Languages,,Supported Languages}.
214 For more information, see @ref{C,,C and C++}.
217 Support for Modula-2 is partial. For information on Modula-2, see
218 @ref{Modula-2,,Modula-2}.
221 Debugging Pascal programs which use sets, subranges, file variables, or
222 nested functions does not currently work. @value{GDBN} does not support
223 entering expressions, printing values, or similar features using Pascal
227 @value{GDBN} can be used to debug programs written in Fortran, although
228 it may be necessary to refer to some variables with a trailing
231 @value{GDBN} can be used to debug programs written in Objective-C,
232 using either the Apple/NeXT or the GNU Objective-C runtime.
235 * Free Software:: Freely redistributable software
236 * Contributors:: Contributors to GDB
240 @unnumberedsec Free Software
242 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
243 General Public License
244 (GPL). The GPL gives you the freedom to copy or adapt a licensed
245 program---but every person getting a copy also gets with it the
246 freedom to modify that copy (which means that they must get access to
247 the source code), and the freedom to distribute further copies.
248 Typical software companies use copyrights to limit your freedoms; the
249 Free Software Foundation uses the GPL to preserve these freedoms.
251 Fundamentally, the General Public License is a license which says that
252 you have these freedoms and that you cannot take these freedoms away
255 @unnumberedsec Free Software Needs Free Documentation
257 The biggest deficiency in the free software community today is not in
258 the software---it is the lack of good free documentation that we can
259 include with the free software. Many of our most important
260 programs do not come with free reference manuals and free introductory
261 texts. Documentation is an essential part of any software package;
262 when an important free software package does not come with a free
263 manual and a free tutorial, that is a major gap. We have many such
266 Consider Perl, for instance. The tutorial manuals that people
267 normally use are non-free. How did this come about? Because the
268 authors of those manuals published them with restrictive terms---no
269 copying, no modification, source files not available---which exclude
270 them from the free software world.
272 That wasn't the first time this sort of thing happened, and it was far
273 from the last. Many times we have heard a GNU user eagerly describe a
274 manual that he is writing, his intended contribution to the community,
275 only to learn that he had ruined everything by signing a publication
276 contract to make it non-free.
278 Free documentation, like free software, is a matter of freedom, not
279 price. The problem with the non-free manual is not that publishers
280 charge a price for printed copies---that in itself is fine. (The Free
281 Software Foundation sells printed copies of manuals, too.) The
282 problem is the restrictions on the use of the manual. Free manuals
283 are available in source code form, and give you permission to copy and
284 modify. Non-free manuals do not allow this.
286 The criteria of freedom for a free manual are roughly the same as for
287 free software. Redistribution (including the normal kinds of
288 commercial redistribution) must be permitted, so that the manual can
289 accompany every copy of the program, both on-line and on paper.
291 Permission for modification of the technical content is crucial too.
292 When people modify the software, adding or changing features, if they
293 are conscientious they will change the manual too---so they can
294 provide accurate and clear documentation for the modified program. A
295 manual that leaves you no choice but to write a new manual to document
296 a changed version of the program is not really available to our
299 Some kinds of limits on the way modification is handled are
300 acceptable. For example, requirements to preserve the original
301 author's copyright notice, the distribution terms, or the list of
302 authors, are ok. It is also no problem to require modified versions
303 to include notice that they were modified. Even entire sections that
304 may not be deleted or changed are acceptable, as long as they deal
305 with nontechnical topics (like this one). These kinds of restrictions
306 are acceptable because they don't obstruct the community's normal use
309 However, it must be possible to modify all the @emph{technical}
310 content of the manual, and then distribute the result in all the usual
311 media, through all the usual channels. Otherwise, the restrictions
312 obstruct the use of the manual, it is not free, and we need another
313 manual to replace it.
315 Please spread the word about this issue. Our community continues to
316 lose manuals to proprietary publishing. If we spread the word that
317 free software needs free reference manuals and free tutorials, perhaps
318 the next person who wants to contribute by writing documentation will
319 realize, before it is too late, that only free manuals contribute to
320 the free software community.
322 If you are writing documentation, please insist on publishing it under
323 the GNU Free Documentation License or another free documentation
324 license. Remember that this decision requires your approval---you
325 don't have to let the publisher decide. Some commercial publishers
326 will use a free license if you insist, but they will not propose the
327 option; it is up to you to raise the issue and say firmly that this is
328 what you want. If the publisher you are dealing with refuses, please
329 try other publishers. If you're not sure whether a proposed license
330 is free, write to @email{licensing@@gnu.org}.
332 You can encourage commercial publishers to sell more free, copylefted
333 manuals and tutorials by buying them, and particularly by buying
334 copies from the publishers that paid for their writing or for major
335 improvements. Meanwhile, try to avoid buying non-free documentation
336 at all. Check the distribution terms of a manual before you buy it,
337 and insist that whoever seeks your business must respect your freedom.
338 Check the history of the book, and try to reward the publishers that
339 have paid or pay the authors to work on it.
341 The Free Software Foundation maintains a list of free documentation
342 published by other publishers, at
343 @url{http://www.fsf.org/doc/other-free-books.html}.
346 @unnumberedsec Contributors to @value{GDBN}
348 Richard Stallman was the original author of @value{GDBN}, and of many
349 other @sc{gnu} programs. Many others have contributed to its
350 development. This section attempts to credit major contributors. One
351 of the virtues of free software is that everyone is free to contribute
352 to it; with regret, we cannot actually acknowledge everyone here. The
353 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
354 blow-by-blow account.
356 Changes much prior to version 2.0 are lost in the mists of time.
359 @emph{Plea:} Additions to this section are particularly welcome. If you
360 or your friends (or enemies, to be evenhanded) have been unfairly
361 omitted from this list, we would like to add your names!
364 So that they may not regard their many labors as thankless, we
365 particularly thank those who shepherded @value{GDBN} through major
367 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
368 Jim Blandy (release 4.18);
369 Jason Molenda (release 4.17);
370 Stan Shebs (release 4.14);
371 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
372 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
373 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
374 Jim Kingdon (releases 3.5, 3.4, and 3.3);
375 and Randy Smith (releases 3.2, 3.1, and 3.0).
377 Richard Stallman, assisted at various times by Peter TerMaat, Chris
378 Hanson, and Richard Mlynarik, handled releases through 2.8.
380 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
381 in @value{GDBN}, with significant additional contributions from Per
382 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
383 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
384 much general update work leading to release 3.0).
386 @value{GDBN} uses the BFD subroutine library to examine multiple
387 object-file formats; BFD was a joint project of David V.
388 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
390 David Johnson wrote the original COFF support; Pace Willison did
391 the original support for encapsulated COFF.
393 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
395 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
396 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
398 Jean-Daniel Fekete contributed Sun 386i support.
399 Chris Hanson improved the HP9000 support.
400 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
401 David Johnson contributed Encore Umax support.
402 Jyrki Kuoppala contributed Altos 3068 support.
403 Jeff Law contributed HP PA and SOM support.
404 Keith Packard contributed NS32K support.
405 Doug Rabson contributed Acorn Risc Machine support.
406 Bob Rusk contributed Harris Nighthawk CX-UX support.
407 Chris Smith contributed Convex support (and Fortran debugging).
408 Jonathan Stone contributed Pyramid support.
409 Michael Tiemann contributed SPARC support.
410 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
411 Pace Willison contributed Intel 386 support.
412 Jay Vosburgh contributed Symmetry support.
413 Marko Mlinar contributed OpenRISC 1000 support.
415 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
417 Rich Schaefer and Peter Schauer helped with support of SunOS shared
420 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
421 about several machine instruction sets.
423 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
424 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
425 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
426 and RDI targets, respectively.
428 Brian Fox is the author of the readline libraries providing
429 command-line editing and command history.
431 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
432 Modula-2 support, and contributed the Languages chapter of this manual.
434 Fred Fish wrote most of the support for Unix System Vr4.
435 He also enhanced the command-completion support to cover C@t{++} overloaded
438 Hitachi America (now Renesas America), Ltd. sponsored the support for
439 H8/300, H8/500, and Super-H processors.
441 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
443 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
446 Toshiba sponsored the support for the TX39 Mips processor.
448 Matsushita sponsored the support for the MN10200 and MN10300 processors.
450 Fujitsu sponsored the support for SPARClite and FR30 processors.
452 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
455 Michael Snyder added support for tracepoints.
457 Stu Grossman wrote gdbserver.
459 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
460 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
462 The following people at the Hewlett-Packard Company contributed
463 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
464 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
465 compiler, and the Text User Interface (nee Terminal User Interface):
466 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
467 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
468 provided HP-specific information in this manual.
470 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
471 Robert Hoehne made significant contributions to the DJGPP port.
473 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
474 development since 1991. Cygnus engineers who have worked on @value{GDBN}
475 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
476 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
477 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
478 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
479 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
480 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
481 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
482 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
483 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
484 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
485 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
486 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
487 Zuhn have made contributions both large and small.
489 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
490 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
492 Jim Blandy added support for preprocessor macros, while working for Red
495 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
496 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
497 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
498 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
499 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
500 with the migration of old architectures to this new framework.
502 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
503 unwinder framework, this consisting of a fresh new design featuring
504 frame IDs, independent frame sniffers, and the sentinel frame. Mark
505 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
506 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
507 trad unwinders. The architecture-specific changes, each involving a
508 complete rewrite of the architecture's frame code, were carried out by
509 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
510 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
511 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
512 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
515 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
516 Tensilica, Inc.@: contributed support for Xtensa processors. Others
517 who have worked on the Xtensa port of @value{GDBN} in the past include
518 Steve Tjiang, John Newlin, and Scott Foehner.
520 Michael Eager and staff of Xilinx, Inc., contributed support for the
521 Xilinx MicroBlaze architecture.
524 @chapter A Sample @value{GDBN} Session
526 You can use this manual at your leisure to read all about @value{GDBN}.
527 However, a handful of commands are enough to get started using the
528 debugger. This chapter illustrates those commands.
531 In this sample session, we emphasize user input like this: @b{input},
532 to make it easier to pick out from the surrounding output.
535 @c FIXME: this example may not be appropriate for some configs, where
536 @c FIXME...primary interest is in remote use.
538 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
539 processor) exhibits the following bug: sometimes, when we change its
540 quote strings from the default, the commands used to capture one macro
541 definition within another stop working. In the following short @code{m4}
542 session, we define a macro @code{foo} which expands to @code{0000}; we
543 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
544 same thing. However, when we change the open quote string to
545 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
546 procedure fails to define a new synonym @code{baz}:
555 @b{define(bar,defn(`foo'))}
559 @b{changequote(<QUOTE>,<UNQUOTE>)}
561 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
564 m4: End of input: 0: fatal error: EOF in string
568 Let us use @value{GDBN} to try to see what is going on.
571 $ @b{@value{GDBP} m4}
572 @c FIXME: this falsifies the exact text played out, to permit smallbook
573 @c FIXME... format to come out better.
574 @value{GDBN} is free software and you are welcome to distribute copies
575 of it under certain conditions; type "show copying" to see
577 There is absolutely no warranty for @value{GDBN}; type "show warranty"
580 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
585 @value{GDBN} reads only enough symbol data to know where to find the
586 rest when needed; as a result, the first prompt comes up very quickly.
587 We now tell @value{GDBN} to use a narrower display width than usual, so
588 that examples fit in this manual.
591 (@value{GDBP}) @b{set width 70}
595 We need to see how the @code{m4} built-in @code{changequote} works.
596 Having looked at the source, we know the relevant subroutine is
597 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
598 @code{break} command.
601 (@value{GDBP}) @b{break m4_changequote}
602 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
606 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
607 control; as long as control does not reach the @code{m4_changequote}
608 subroutine, the program runs as usual:
611 (@value{GDBP}) @b{run}
612 Starting program: /work/Editorial/gdb/gnu/m4/m4
620 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
621 suspends execution of @code{m4}, displaying information about the
622 context where it stops.
625 @b{changequote(<QUOTE>,<UNQUOTE>)}
627 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
629 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
633 Now we use the command @code{n} (@code{next}) to advance execution to
634 the next line of the current function.
638 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
643 @code{set_quotes} looks like a promising subroutine. We can go into it
644 by using the command @code{s} (@code{step}) instead of @code{next}.
645 @code{step} goes to the next line to be executed in @emph{any}
646 subroutine, so it steps into @code{set_quotes}.
650 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
652 530 if (lquote != def_lquote)
656 The display that shows the subroutine where @code{m4} is now
657 suspended (and its arguments) is called a stack frame display. It
658 shows a summary of the stack. We can use the @code{backtrace}
659 command (which can also be spelled @code{bt}), to see where we are
660 in the stack as a whole: the @code{backtrace} command displays a
661 stack frame for each active subroutine.
664 (@value{GDBP}) @b{bt}
665 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
667 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
669 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
670 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
672 #4 0x79dc in expand_input () at macro.c:40
673 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
677 We step through a few more lines to see what happens. The first two
678 times, we can use @samp{s}; the next two times we use @code{n} to avoid
679 falling into the @code{xstrdup} subroutine.
683 0x3b5c 532 if (rquote != def_rquote)
685 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
686 def_lquote : xstrdup(lq);
688 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
691 538 len_lquote = strlen(rquote);
695 The last line displayed looks a little odd; we can examine the variables
696 @code{lquote} and @code{rquote} to see if they are in fact the new left
697 and right quotes we specified. We use the command @code{p}
698 (@code{print}) to see their values.
701 (@value{GDBP}) @b{p lquote}
702 $1 = 0x35d40 "<QUOTE>"
703 (@value{GDBP}) @b{p rquote}
704 $2 = 0x35d50 "<UNQUOTE>"
708 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
709 To look at some context, we can display ten lines of source
710 surrounding the current line with the @code{l} (@code{list}) command.
716 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
718 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
721 538 len_lquote = strlen(rquote);
722 539 len_rquote = strlen(lquote);
729 Let us step past the two lines that set @code{len_lquote} and
730 @code{len_rquote}, and then examine the values of those variables.
734 539 len_rquote = strlen(lquote);
737 (@value{GDBP}) @b{p len_lquote}
739 (@value{GDBP}) @b{p len_rquote}
744 That certainly looks wrong, assuming @code{len_lquote} and
745 @code{len_rquote} are meant to be the lengths of @code{lquote} and
746 @code{rquote} respectively. We can set them to better values using
747 the @code{p} command, since it can print the value of
748 any expression---and that expression can include subroutine calls and
752 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
754 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
759 Is that enough to fix the problem of using the new quotes with the
760 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
761 executing with the @code{c} (@code{continue}) command, and then try the
762 example that caused trouble initially:
768 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
775 Success! The new quotes now work just as well as the default ones. The
776 problem seems to have been just the two typos defining the wrong
777 lengths. We allow @code{m4} exit by giving it an EOF as input:
781 Program exited normally.
785 The message @samp{Program exited normally.} is from @value{GDBN}; it
786 indicates @code{m4} has finished executing. We can end our @value{GDBN}
787 session with the @value{GDBN} @code{quit} command.
790 (@value{GDBP}) @b{quit}
794 @chapter Getting In and Out of @value{GDBN}
796 This chapter discusses how to start @value{GDBN}, and how to get out of it.
800 type @samp{@value{GDBP}} to start @value{GDBN}.
802 type @kbd{quit} or @kbd{Ctrl-d} to exit.
806 * Invoking GDB:: How to start @value{GDBN}
807 * Quitting GDB:: How to quit @value{GDBN}
808 * Shell Commands:: How to use shell commands inside @value{GDBN}
809 * Logging Output:: How to log @value{GDBN}'s output to a file
813 @section Invoking @value{GDBN}
815 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
816 @value{GDBN} reads commands from the terminal until you tell it to exit.
818 You can also run @code{@value{GDBP}} with a variety of arguments and options,
819 to specify more of your debugging environment at the outset.
821 The command-line options described here are designed
822 to cover a variety of situations; in some environments, some of these
823 options may effectively be unavailable.
825 The most usual way to start @value{GDBN} is with one argument,
826 specifying an executable program:
829 @value{GDBP} @var{program}
833 You can also start with both an executable program and a core file
837 @value{GDBP} @var{program} @var{core}
840 You can, instead, specify a process ID as a second argument, if you want
841 to debug a running process:
844 @value{GDBP} @var{program} 1234
848 would attach @value{GDBN} to process @code{1234} (unless you also have a file
849 named @file{1234}; @value{GDBN} does check for a core file first).
851 Taking advantage of the second command-line argument requires a fairly
852 complete operating system; when you use @value{GDBN} as a remote
853 debugger attached to a bare board, there may not be any notion of
854 ``process'', and there is often no way to get a core dump. @value{GDBN}
855 will warn you if it is unable to attach or to read core dumps.
857 You can optionally have @code{@value{GDBP}} pass any arguments after the
858 executable file to the inferior using @code{--args}. This option stops
861 @value{GDBP} --args gcc -O2 -c foo.c
863 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
864 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
866 You can run @code{@value{GDBP}} without printing the front material, which describes
867 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
874 You can further control how @value{GDBN} starts up by using command-line
875 options. @value{GDBN} itself can remind you of the options available.
885 to display all available options and briefly describe their use
886 (@samp{@value{GDBP} -h} is a shorter equivalent).
888 All options and command line arguments you give are processed
889 in sequential order. The order makes a difference when the
890 @samp{-x} option is used.
894 * File Options:: Choosing files
895 * Mode Options:: Choosing modes
896 * Startup:: What @value{GDBN} does during startup
900 @subsection Choosing Files
902 When @value{GDBN} starts, it reads any arguments other than options as
903 specifying an executable file and core file (or process ID). This is
904 the same as if the arguments were specified by the @samp{-se} and
905 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
906 first argument that does not have an associated option flag as
907 equivalent to the @samp{-se} option followed by that argument; and the
908 second argument that does not have an associated option flag, if any, as
909 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
910 If the second argument begins with a decimal digit, @value{GDBN} will
911 first attempt to attach to it as a process, and if that fails, attempt
912 to open it as a corefile. If you have a corefile whose name begins with
913 a digit, you can prevent @value{GDBN} from treating it as a pid by
914 prefixing it with @file{./}, e.g.@: @file{./12345}.
916 If @value{GDBN} has not been configured to included core file support,
917 such as for most embedded targets, then it will complain about a second
918 argument and ignore it.
920 Many options have both long and short forms; both are shown in the
921 following list. @value{GDBN} also recognizes the long forms if you truncate
922 them, so long as enough of the option is present to be unambiguous.
923 (If you prefer, you can flag option arguments with @samp{--} rather
924 than @samp{-}, though we illustrate the more usual convention.)
926 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
927 @c way, both those who look for -foo and --foo in the index, will find
931 @item -symbols @var{file}
933 @cindex @code{--symbols}
935 Read symbol table from file @var{file}.
937 @item -exec @var{file}
939 @cindex @code{--exec}
941 Use file @var{file} as the executable file to execute when appropriate,
942 and for examining pure data in conjunction with a core dump.
946 Read symbol table from file @var{file} and use it as the executable
949 @item -core @var{file}
951 @cindex @code{--core}
953 Use file @var{file} as a core dump to examine.
955 @item -pid @var{number}
956 @itemx -p @var{number}
959 Connect to process ID @var{number}, as with the @code{attach} command.
961 @item -command @var{file}
963 @cindex @code{--command}
965 Execute @value{GDBN} commands from file @var{file}. @xref{Command
966 Files,, Command files}.
968 @item -eval-command @var{command}
969 @itemx -ex @var{command}
970 @cindex @code{--eval-command}
972 Execute a single @value{GDBN} command.
974 This option may be used multiple times to call multiple commands. It may
975 also be interleaved with @samp{-command} as required.
978 @value{GDBP} -ex 'target sim' -ex 'load' \
979 -x setbreakpoints -ex 'run' a.out
982 @item -directory @var{directory}
983 @itemx -d @var{directory}
984 @cindex @code{--directory}
986 Add @var{directory} to the path to search for source and script files.
990 @cindex @code{--readnow}
992 Read each symbol file's entire symbol table immediately, rather than
993 the default, which is to read it incrementally as it is needed.
994 This makes startup slower, but makes future operations faster.
999 @subsection Choosing Modes
1001 You can run @value{GDBN} in various alternative modes---for example, in
1002 batch mode or quiet mode.
1009 Do not execute commands found in any initialization files. Normally,
1010 @value{GDBN} executes the commands in these files after all the command
1011 options and arguments have been processed. @xref{Command Files,,Command
1017 @cindex @code{--quiet}
1018 @cindex @code{--silent}
1020 ``Quiet''. Do not print the introductory and copyright messages. These
1021 messages are also suppressed in batch mode.
1024 @cindex @code{--batch}
1025 Run in batch mode. Exit with status @code{0} after processing all the
1026 command files specified with @samp{-x} (and all commands from
1027 initialization files, if not inhibited with @samp{-n}). Exit with
1028 nonzero status if an error occurs in executing the @value{GDBN} commands
1029 in the command files.
1031 Batch mode may be useful for running @value{GDBN} as a filter, for
1032 example to download and run a program on another computer; in order to
1033 make this more useful, the message
1036 Program exited normally.
1040 (which is ordinarily issued whenever a program running under
1041 @value{GDBN} control terminates) is not issued when running in batch
1045 @cindex @code{--batch-silent}
1046 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1047 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1048 unaffected). This is much quieter than @samp{-silent} and would be useless
1049 for an interactive session.
1051 This is particularly useful when using targets that give @samp{Loading section}
1052 messages, for example.
1054 Note that targets that give their output via @value{GDBN}, as opposed to
1055 writing directly to @code{stdout}, will also be made silent.
1057 @item -return-child-result
1058 @cindex @code{--return-child-result}
1059 The return code from @value{GDBN} will be the return code from the child
1060 process (the process being debugged), with the following exceptions:
1064 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1065 internal error. In this case the exit code is the same as it would have been
1066 without @samp{-return-child-result}.
1068 The user quits with an explicit value. E.g., @samp{quit 1}.
1070 The child process never runs, or is not allowed to terminate, in which case
1071 the exit code will be -1.
1074 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1075 when @value{GDBN} is being used as a remote program loader or simulator
1080 @cindex @code{--nowindows}
1082 ``No windows''. If @value{GDBN} comes with a graphical user interface
1083 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1084 interface. If no GUI is available, this option has no effect.
1088 @cindex @code{--windows}
1090 If @value{GDBN} includes a GUI, then this option requires it to be
1093 @item -cd @var{directory}
1095 Run @value{GDBN} using @var{directory} as its working directory,
1096 instead of the current directory.
1100 @cindex @code{--fullname}
1102 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1103 subprocess. It tells @value{GDBN} to output the full file name and line
1104 number in a standard, recognizable fashion each time a stack frame is
1105 displayed (which includes each time your program stops). This
1106 recognizable format looks like two @samp{\032} characters, followed by
1107 the file name, line number and character position separated by colons,
1108 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1109 @samp{\032} characters as a signal to display the source code for the
1113 @cindex @code{--epoch}
1114 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1115 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1116 routines so as to allow Epoch to display values of expressions in a
1119 @item -annotate @var{level}
1120 @cindex @code{--annotate}
1121 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1122 effect is identical to using @samp{set annotate @var{level}}
1123 (@pxref{Annotations}). The annotation @var{level} controls how much
1124 information @value{GDBN} prints together with its prompt, values of
1125 expressions, source lines, and other types of output. Level 0 is the
1126 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1127 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1128 that control @value{GDBN}, and level 2 has been deprecated.
1130 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1134 @cindex @code{--args}
1135 Change interpretation of command line so that arguments following the
1136 executable file are passed as command line arguments to the inferior.
1137 This option stops option processing.
1139 @item -baud @var{bps}
1141 @cindex @code{--baud}
1143 Set the line speed (baud rate or bits per second) of any serial
1144 interface used by @value{GDBN} for remote debugging.
1146 @item -l @var{timeout}
1148 Set the timeout (in seconds) of any communication used by @value{GDBN}
1149 for remote debugging.
1151 @item -tty @var{device}
1152 @itemx -t @var{device}
1153 @cindex @code{--tty}
1155 Run using @var{device} for your program's standard input and output.
1156 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1158 @c resolve the situation of these eventually
1160 @cindex @code{--tui}
1161 Activate the @dfn{Text User Interface} when starting. The Text User
1162 Interface manages several text windows on the terminal, showing
1163 source, assembly, registers and @value{GDBN} command outputs
1164 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1165 Text User Interface can be enabled by invoking the program
1166 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1167 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1170 @c @cindex @code{--xdb}
1171 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1172 @c For information, see the file @file{xdb_trans.html}, which is usually
1173 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1176 @item -interpreter @var{interp}
1177 @cindex @code{--interpreter}
1178 Use the interpreter @var{interp} for interface with the controlling
1179 program or device. This option is meant to be set by programs which
1180 communicate with @value{GDBN} using it as a back end.
1181 @xref{Interpreters, , Command Interpreters}.
1183 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1184 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1185 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1186 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1187 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1188 @sc{gdb/mi} interfaces are no longer supported.
1191 @cindex @code{--write}
1192 Open the executable and core files for both reading and writing. This
1193 is equivalent to the @samp{set write on} command inside @value{GDBN}
1197 @cindex @code{--statistics}
1198 This option causes @value{GDBN} to print statistics about time and
1199 memory usage after it completes each command and returns to the prompt.
1202 @cindex @code{--version}
1203 This option causes @value{GDBN} to print its version number and
1204 no-warranty blurb, and exit.
1209 @subsection What @value{GDBN} Does During Startup
1210 @cindex @value{GDBN} startup
1212 Here's the description of what @value{GDBN} does during session startup:
1216 Sets up the command interpreter as specified by the command line
1217 (@pxref{Mode Options, interpreter}).
1221 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1222 used when building @value{GDBN}; @pxref{System-wide configuration,
1223 ,System-wide configuration and settings}) and executes all the commands in
1227 Reads the init file (if any) in your home directory@footnote{On
1228 DOS/Windows systems, the home directory is the one pointed to by the
1229 @code{HOME} environment variable.} and executes all the commands in
1233 Processes command line options and operands.
1236 Reads and executes the commands from init file (if any) in the current
1237 working directory. This is only done if the current directory is
1238 different from your home directory. Thus, you can have more than one
1239 init file, one generic in your home directory, and another, specific
1240 to the program you are debugging, in the directory where you invoke
1244 Reads command files specified by the @samp{-x} option. @xref{Command
1245 Files}, for more details about @value{GDBN} command files.
1248 Reads the command history recorded in the @dfn{history file}.
1249 @xref{Command History}, for more details about the command history and the
1250 files where @value{GDBN} records it.
1253 Init files use the same syntax as @dfn{command files} (@pxref{Command
1254 Files}) and are processed by @value{GDBN} in the same way. The init
1255 file in your home directory can set options (such as @samp{set
1256 complaints}) that affect subsequent processing of command line options
1257 and operands. Init files are not executed if you use the @samp{-nx}
1258 option (@pxref{Mode Options, ,Choosing Modes}).
1260 To display the list of init files loaded by gdb at startup, you
1261 can use @kbd{gdb --help}.
1263 @cindex init file name
1264 @cindex @file{.gdbinit}
1265 @cindex @file{gdb.ini}
1266 The @value{GDBN} init files are normally called @file{.gdbinit}.
1267 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1268 the limitations of file names imposed by DOS filesystems. The Windows
1269 ports of @value{GDBN} use the standard name, but if they find a
1270 @file{gdb.ini} file, they warn you about that and suggest to rename
1271 the file to the standard name.
1275 @section Quitting @value{GDBN}
1276 @cindex exiting @value{GDBN}
1277 @cindex leaving @value{GDBN}
1280 @kindex quit @r{[}@var{expression}@r{]}
1281 @kindex q @r{(@code{quit})}
1282 @item quit @r{[}@var{expression}@r{]}
1284 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1285 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1286 do not supply @var{expression}, @value{GDBN} will terminate normally;
1287 otherwise it will terminate using the result of @var{expression} as the
1292 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1293 terminates the action of any @value{GDBN} command that is in progress and
1294 returns to @value{GDBN} command level. It is safe to type the interrupt
1295 character at any time because @value{GDBN} does not allow it to take effect
1296 until a time when it is safe.
1298 If you have been using @value{GDBN} to control an attached process or
1299 device, you can release it with the @code{detach} command
1300 (@pxref{Attach, ,Debugging an Already-running Process}).
1302 @node Shell Commands
1303 @section Shell Commands
1305 If you need to execute occasional shell commands during your
1306 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1307 just use the @code{shell} command.
1311 @cindex shell escape
1312 @item shell @var{command string}
1313 Invoke a standard shell to execute @var{command string}.
1314 If it exists, the environment variable @code{SHELL} determines which
1315 shell to run. Otherwise @value{GDBN} uses the default shell
1316 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1319 The utility @code{make} is often needed in development environments.
1320 You do not have to use the @code{shell} command for this purpose in
1325 @cindex calling make
1326 @item make @var{make-args}
1327 Execute the @code{make} program with the specified
1328 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1331 @node Logging Output
1332 @section Logging Output
1333 @cindex logging @value{GDBN} output
1334 @cindex save @value{GDBN} output to a file
1336 You may want to save the output of @value{GDBN} commands to a file.
1337 There are several commands to control @value{GDBN}'s logging.
1341 @item set logging on
1343 @item set logging off
1345 @cindex logging file name
1346 @item set logging file @var{file}
1347 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1348 @item set logging overwrite [on|off]
1349 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1350 you want @code{set logging on} to overwrite the logfile instead.
1351 @item set logging redirect [on|off]
1352 By default, @value{GDBN} output will go to both the terminal and the logfile.
1353 Set @code{redirect} if you want output to go only to the log file.
1354 @kindex show logging
1356 Show the current values of the logging settings.
1360 @chapter @value{GDBN} Commands
1362 You can abbreviate a @value{GDBN} command to the first few letters of the command
1363 name, if that abbreviation is unambiguous; and you can repeat certain
1364 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1365 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1366 show you the alternatives available, if there is more than one possibility).
1369 * Command Syntax:: How to give commands to @value{GDBN}
1370 * Completion:: Command completion
1371 * Help:: How to ask @value{GDBN} for help
1374 @node Command Syntax
1375 @section Command Syntax
1377 A @value{GDBN} command is a single line of input. There is no limit on
1378 how long it can be. It starts with a command name, which is followed by
1379 arguments whose meaning depends on the command name. For example, the
1380 command @code{step} accepts an argument which is the number of times to
1381 step, as in @samp{step 5}. You can also use the @code{step} command
1382 with no arguments. Some commands do not allow any arguments.
1384 @cindex abbreviation
1385 @value{GDBN} command names may always be truncated if that abbreviation is
1386 unambiguous. Other possible command abbreviations are listed in the
1387 documentation for individual commands. In some cases, even ambiguous
1388 abbreviations are allowed; for example, @code{s} is specially defined as
1389 equivalent to @code{step} even though there are other commands whose
1390 names start with @code{s}. You can test abbreviations by using them as
1391 arguments to the @code{help} command.
1393 @cindex repeating commands
1394 @kindex RET @r{(repeat last command)}
1395 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1396 repeat the previous command. Certain commands (for example, @code{run})
1397 will not repeat this way; these are commands whose unintentional
1398 repetition might cause trouble and which you are unlikely to want to
1399 repeat. User-defined commands can disable this feature; see
1400 @ref{Define, dont-repeat}.
1402 The @code{list} and @code{x} commands, when you repeat them with
1403 @key{RET}, construct new arguments rather than repeating
1404 exactly as typed. This permits easy scanning of source or memory.
1406 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1407 output, in a way similar to the common utility @code{more}
1408 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1409 @key{RET} too many in this situation, @value{GDBN} disables command
1410 repetition after any command that generates this sort of display.
1412 @kindex # @r{(a comment)}
1414 Any text from a @kbd{#} to the end of the line is a comment; it does
1415 nothing. This is useful mainly in command files (@pxref{Command
1416 Files,,Command Files}).
1418 @cindex repeating command sequences
1419 @kindex Ctrl-o @r{(operate-and-get-next)}
1420 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1421 commands. This command accepts the current line, like @key{RET}, and
1422 then fetches the next line relative to the current line from the history
1426 @section Command Completion
1429 @cindex word completion
1430 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1431 only one possibility; it can also show you what the valid possibilities
1432 are for the next word in a command, at any time. This works for @value{GDBN}
1433 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1435 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1436 of a word. If there is only one possibility, @value{GDBN} fills in the
1437 word, and waits for you to finish the command (or press @key{RET} to
1438 enter it). For example, if you type
1440 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1441 @c complete accuracy in these examples; space introduced for clarity.
1442 @c If texinfo enhancements make it unnecessary, it would be nice to
1443 @c replace " @key" by "@key" in the following...
1445 (@value{GDBP}) info bre @key{TAB}
1449 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1450 the only @code{info} subcommand beginning with @samp{bre}:
1453 (@value{GDBP}) info breakpoints
1457 You can either press @key{RET} at this point, to run the @code{info
1458 breakpoints} command, or backspace and enter something else, if
1459 @samp{breakpoints} does not look like the command you expected. (If you
1460 were sure you wanted @code{info breakpoints} in the first place, you
1461 might as well just type @key{RET} immediately after @samp{info bre},
1462 to exploit command abbreviations rather than command completion).
1464 If there is more than one possibility for the next word when you press
1465 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1466 characters and try again, or just press @key{TAB} a second time;
1467 @value{GDBN} displays all the possible completions for that word. For
1468 example, you might want to set a breakpoint on a subroutine whose name
1469 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1470 just sounds the bell. Typing @key{TAB} again displays all the
1471 function names in your program that begin with those characters, for
1475 (@value{GDBP}) b make_ @key{TAB}
1476 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1477 make_a_section_from_file make_environ
1478 make_abs_section make_function_type
1479 make_blockvector make_pointer_type
1480 make_cleanup make_reference_type
1481 make_command make_symbol_completion_list
1482 (@value{GDBP}) b make_
1486 After displaying the available possibilities, @value{GDBN} copies your
1487 partial input (@samp{b make_} in the example) so you can finish the
1490 If you just want to see the list of alternatives in the first place, you
1491 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1492 means @kbd{@key{META} ?}. You can type this either by holding down a
1493 key designated as the @key{META} shift on your keyboard (if there is
1494 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1496 @cindex quotes in commands
1497 @cindex completion of quoted strings
1498 Sometimes the string you need, while logically a ``word'', may contain
1499 parentheses or other characters that @value{GDBN} normally excludes from
1500 its notion of a word. To permit word completion to work in this
1501 situation, you may enclose words in @code{'} (single quote marks) in
1502 @value{GDBN} commands.
1504 The most likely situation where you might need this is in typing the
1505 name of a C@t{++} function. This is because C@t{++} allows function
1506 overloading (multiple definitions of the same function, distinguished
1507 by argument type). For example, when you want to set a breakpoint you
1508 may need to distinguish whether you mean the version of @code{name}
1509 that takes an @code{int} parameter, @code{name(int)}, or the version
1510 that takes a @code{float} parameter, @code{name(float)}. To use the
1511 word-completion facilities in this situation, type a single quote
1512 @code{'} at the beginning of the function name. This alerts
1513 @value{GDBN} that it may need to consider more information than usual
1514 when you press @key{TAB} or @kbd{M-?} to request word completion:
1517 (@value{GDBP}) b 'bubble( @kbd{M-?}
1518 bubble(double,double) bubble(int,int)
1519 (@value{GDBP}) b 'bubble(
1522 In some cases, @value{GDBN} can tell that completing a name requires using
1523 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1524 completing as much as it can) if you do not type the quote in the first
1528 (@value{GDBP}) b bub @key{TAB}
1529 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1530 (@value{GDBP}) b 'bubble(
1534 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1535 you have not yet started typing the argument list when you ask for
1536 completion on an overloaded symbol.
1538 For more information about overloaded functions, see @ref{C Plus Plus
1539 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1540 overload-resolution off} to disable overload resolution;
1541 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1543 @cindex completion of structure field names
1544 @cindex structure field name completion
1545 @cindex completion of union field names
1546 @cindex union field name completion
1547 When completing in an expression which looks up a field in a
1548 structure, @value{GDBN} also tries@footnote{The completer can be
1549 confused by certain kinds of invalid expressions. Also, it only
1550 examines the static type of the expression, not the dynamic type.} to
1551 limit completions to the field names available in the type of the
1555 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1556 magic to_delete to_fputs to_put to_rewind
1557 to_data to_flush to_isatty to_read to_write
1561 This is because the @code{gdb_stdout} is a variable of the type
1562 @code{struct ui_file} that is defined in @value{GDBN} sources as
1569 ui_file_flush_ftype *to_flush;
1570 ui_file_write_ftype *to_write;
1571 ui_file_fputs_ftype *to_fputs;
1572 ui_file_read_ftype *to_read;
1573 ui_file_delete_ftype *to_delete;
1574 ui_file_isatty_ftype *to_isatty;
1575 ui_file_rewind_ftype *to_rewind;
1576 ui_file_put_ftype *to_put;
1583 @section Getting Help
1584 @cindex online documentation
1587 You can always ask @value{GDBN} itself for information on its commands,
1588 using the command @code{help}.
1591 @kindex h @r{(@code{help})}
1594 You can use @code{help} (abbreviated @code{h}) with no arguments to
1595 display a short list of named classes of commands:
1599 List of classes of commands:
1601 aliases -- Aliases of other commands
1602 breakpoints -- Making program stop at certain points
1603 data -- Examining data
1604 files -- Specifying and examining files
1605 internals -- Maintenance commands
1606 obscure -- Obscure features
1607 running -- Running the program
1608 stack -- Examining the stack
1609 status -- Status inquiries
1610 support -- Support facilities
1611 tracepoints -- Tracing of program execution without
1612 stopping the program
1613 user-defined -- User-defined commands
1615 Type "help" followed by a class name for a list of
1616 commands in that class.
1617 Type "help" followed by command name for full
1619 Command name abbreviations are allowed if unambiguous.
1622 @c the above line break eliminates huge line overfull...
1624 @item help @var{class}
1625 Using one of the general help classes as an argument, you can get a
1626 list of the individual commands in that class. For example, here is the
1627 help display for the class @code{status}:
1630 (@value{GDBP}) help status
1635 @c Line break in "show" line falsifies real output, but needed
1636 @c to fit in smallbook page size.
1637 info -- Generic command for showing things
1638 about the program being debugged
1639 show -- Generic command for showing things
1642 Type "help" followed by command name for full
1644 Command name abbreviations are allowed if unambiguous.
1648 @item help @var{command}
1649 With a command name as @code{help} argument, @value{GDBN} displays a
1650 short paragraph on how to use that command.
1653 @item apropos @var{args}
1654 The @code{apropos} command searches through all of the @value{GDBN}
1655 commands, and their documentation, for the regular expression specified in
1656 @var{args}. It prints out all matches found. For example:
1667 set symbol-reloading -- Set dynamic symbol table reloading
1668 multiple times in one run
1669 show symbol-reloading -- Show dynamic symbol table reloading
1670 multiple times in one run
1675 @item complete @var{args}
1676 The @code{complete @var{args}} command lists all the possible completions
1677 for the beginning of a command. Use @var{args} to specify the beginning of the
1678 command you want completed. For example:
1684 @noindent results in:
1695 @noindent This is intended for use by @sc{gnu} Emacs.
1698 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1699 and @code{show} to inquire about the state of your program, or the state
1700 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1701 manual introduces each of them in the appropriate context. The listings
1702 under @code{info} and under @code{show} in the Index point to
1703 all the sub-commands. @xref{Index}.
1708 @kindex i @r{(@code{info})}
1710 This command (abbreviated @code{i}) is for describing the state of your
1711 program. For example, you can show the arguments passed to a function
1712 with @code{info args}, list the registers currently in use with @code{info
1713 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1714 You can get a complete list of the @code{info} sub-commands with
1715 @w{@code{help info}}.
1719 You can assign the result of an expression to an environment variable with
1720 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1721 @code{set prompt $}.
1725 In contrast to @code{info}, @code{show} is for describing the state of
1726 @value{GDBN} itself.
1727 You can change most of the things you can @code{show}, by using the
1728 related command @code{set}; for example, you can control what number
1729 system is used for displays with @code{set radix}, or simply inquire
1730 which is currently in use with @code{show radix}.
1733 To display all the settable parameters and their current
1734 values, you can use @code{show} with no arguments; you may also use
1735 @code{info set}. Both commands produce the same display.
1736 @c FIXME: "info set" violates the rule that "info" is for state of
1737 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1738 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1742 Here are three miscellaneous @code{show} subcommands, all of which are
1743 exceptional in lacking corresponding @code{set} commands:
1746 @kindex show version
1747 @cindex @value{GDBN} version number
1749 Show what version of @value{GDBN} is running. You should include this
1750 information in @value{GDBN} bug-reports. If multiple versions of
1751 @value{GDBN} are in use at your site, you may need to determine which
1752 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1753 commands are introduced, and old ones may wither away. Also, many
1754 system vendors ship variant versions of @value{GDBN}, and there are
1755 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1756 The version number is the same as the one announced when you start
1759 @kindex show copying
1760 @kindex info copying
1761 @cindex display @value{GDBN} copyright
1764 Display information about permission for copying @value{GDBN}.
1766 @kindex show warranty
1767 @kindex info warranty
1769 @itemx info warranty
1770 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1771 if your version of @value{GDBN} comes with one.
1776 @chapter Running Programs Under @value{GDBN}
1778 When you run a program under @value{GDBN}, you must first generate
1779 debugging information when you compile it.
1781 You may start @value{GDBN} with its arguments, if any, in an environment
1782 of your choice. If you are doing native debugging, you may redirect
1783 your program's input and output, debug an already running process, or
1784 kill a child process.
1787 * Compilation:: Compiling for debugging
1788 * Starting:: Starting your program
1789 * Arguments:: Your program's arguments
1790 * Environment:: Your program's environment
1792 * Working Directory:: Your program's working directory
1793 * Input/Output:: Your program's input and output
1794 * Attach:: Debugging an already-running process
1795 * Kill Process:: Killing the child process
1797 * Inferiors and Programs:: Debugging multiple inferiors and programs
1798 * Threads:: Debugging programs with multiple threads
1799 * Forks:: Debugging forks
1800 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1804 @section Compiling for Debugging
1806 In order to debug a program effectively, you need to generate
1807 debugging information when you compile it. This debugging information
1808 is stored in the object file; it describes the data type of each
1809 variable or function and the correspondence between source line numbers
1810 and addresses in the executable code.
1812 To request debugging information, specify the @samp{-g} option when you run
1815 Programs that are to be shipped to your customers are compiled with
1816 optimizations, using the @samp{-O} compiler option. However, some
1817 compilers are unable to handle the @samp{-g} and @samp{-O} options
1818 together. Using those compilers, you cannot generate optimized
1819 executables containing debugging information.
1821 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1822 without @samp{-O}, making it possible to debug optimized code. We
1823 recommend that you @emph{always} use @samp{-g} whenever you compile a
1824 program. You may think your program is correct, but there is no sense
1825 in pushing your luck. For more information, see @ref{Optimized Code}.
1827 Older versions of the @sc{gnu} C compiler permitted a variant option
1828 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1829 format; if your @sc{gnu} C compiler has this option, do not use it.
1831 @value{GDBN} knows about preprocessor macros and can show you their
1832 expansion (@pxref{Macros}). Most compilers do not include information
1833 about preprocessor macros in the debugging information if you specify
1834 the @option{-g} flag alone, because this information is rather large.
1835 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1836 provides macro information if you specify the options
1837 @option{-gdwarf-2} and @option{-g3}; the former option requests
1838 debugging information in the Dwarf 2 format, and the latter requests
1839 ``extra information''. In the future, we hope to find more compact
1840 ways to represent macro information, so that it can be included with
1845 @section Starting your Program
1851 @kindex r @r{(@code{run})}
1854 Use the @code{run} command to start your program under @value{GDBN}.
1855 You must first specify the program name (except on VxWorks) with an
1856 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1857 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1858 (@pxref{Files, ,Commands to Specify Files}).
1862 If you are running your program in an execution environment that
1863 supports processes, @code{run} creates an inferior process and makes
1864 that process run your program. In some environments without processes,
1865 @code{run} jumps to the start of your program. Other targets,
1866 like @samp{remote}, are always running. If you get an error
1867 message like this one:
1870 The "remote" target does not support "run".
1871 Try "help target" or "continue".
1875 then use @code{continue} to run your program. You may need @code{load}
1876 first (@pxref{load}).
1878 The execution of a program is affected by certain information it
1879 receives from its superior. @value{GDBN} provides ways to specify this
1880 information, which you must do @emph{before} starting your program. (You
1881 can change it after starting your program, but such changes only affect
1882 your program the next time you start it.) This information may be
1883 divided into four categories:
1886 @item The @emph{arguments.}
1887 Specify the arguments to give your program as the arguments of the
1888 @code{run} command. If a shell is available on your target, the shell
1889 is used to pass the arguments, so that you may use normal conventions
1890 (such as wildcard expansion or variable substitution) in describing
1892 In Unix systems, you can control which shell is used with the
1893 @code{SHELL} environment variable.
1894 @xref{Arguments, ,Your Program's Arguments}.
1896 @item The @emph{environment.}
1897 Your program normally inherits its environment from @value{GDBN}, but you can
1898 use the @value{GDBN} commands @code{set environment} and @code{unset
1899 environment} to change parts of the environment that affect
1900 your program. @xref{Environment, ,Your Program's Environment}.
1902 @item The @emph{working directory.}
1903 Your program inherits its working directory from @value{GDBN}. You can set
1904 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1905 @xref{Working Directory, ,Your Program's Working Directory}.
1907 @item The @emph{standard input and output.}
1908 Your program normally uses the same device for standard input and
1909 standard output as @value{GDBN} is using. You can redirect input and output
1910 in the @code{run} command line, or you can use the @code{tty} command to
1911 set a different device for your program.
1912 @xref{Input/Output, ,Your Program's Input and Output}.
1915 @emph{Warning:} While input and output redirection work, you cannot use
1916 pipes to pass the output of the program you are debugging to another
1917 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1921 When you issue the @code{run} command, your program begins to execute
1922 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1923 of how to arrange for your program to stop. Once your program has
1924 stopped, you may call functions in your program, using the @code{print}
1925 or @code{call} commands. @xref{Data, ,Examining Data}.
1927 If the modification time of your symbol file has changed since the last
1928 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1929 table, and reads it again. When it does this, @value{GDBN} tries to retain
1930 your current breakpoints.
1935 @cindex run to main procedure
1936 The name of the main procedure can vary from language to language.
1937 With C or C@t{++}, the main procedure name is always @code{main}, but
1938 other languages such as Ada do not require a specific name for their
1939 main procedure. The debugger provides a convenient way to start the
1940 execution of the program and to stop at the beginning of the main
1941 procedure, depending on the language used.
1943 The @samp{start} command does the equivalent of setting a temporary
1944 breakpoint at the beginning of the main procedure and then invoking
1945 the @samp{run} command.
1947 @cindex elaboration phase
1948 Some programs contain an @dfn{elaboration} phase where some startup code is
1949 executed before the main procedure is called. This depends on the
1950 languages used to write your program. In C@t{++}, for instance,
1951 constructors for static and global objects are executed before
1952 @code{main} is called. It is therefore possible that the debugger stops
1953 before reaching the main procedure. However, the temporary breakpoint
1954 will remain to halt execution.
1956 Specify the arguments to give to your program as arguments to the
1957 @samp{start} command. These arguments will be given verbatim to the
1958 underlying @samp{run} command. Note that the same arguments will be
1959 reused if no argument is provided during subsequent calls to
1960 @samp{start} or @samp{run}.
1962 It is sometimes necessary to debug the program during elaboration. In
1963 these cases, using the @code{start} command would stop the execution of
1964 your program too late, as the program would have already completed the
1965 elaboration phase. Under these circumstances, insert breakpoints in your
1966 elaboration code before running your program.
1968 @kindex set exec-wrapper
1969 @item set exec-wrapper @var{wrapper}
1970 @itemx show exec-wrapper
1971 @itemx unset exec-wrapper
1972 When @samp{exec-wrapper} is set, the specified wrapper is used to
1973 launch programs for debugging. @value{GDBN} starts your program
1974 with a shell command of the form @kbd{exec @var{wrapper}
1975 @var{program}}. Quoting is added to @var{program} and its
1976 arguments, but not to @var{wrapper}, so you should add quotes if
1977 appropriate for your shell. The wrapper runs until it executes
1978 your program, and then @value{GDBN} takes control.
1980 You can use any program that eventually calls @code{execve} with
1981 its arguments as a wrapper. Several standard Unix utilities do
1982 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
1983 with @code{exec "$@@"} will also work.
1985 For example, you can use @code{env} to pass an environment variable to
1986 the debugged program, without setting the variable in your shell's
1990 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
1994 This command is available when debugging locally on most targets, excluding
1995 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
1997 @kindex set disable-randomization
1998 @item set disable-randomization
1999 @itemx set disable-randomization on
2000 This option (enabled by default in @value{GDBN}) will turn off the native
2001 randomization of the virtual address space of the started program. This option
2002 is useful for multiple debugging sessions to make the execution better
2003 reproducible and memory addresses reusable across debugging sessions.
2005 This feature is implemented only on @sc{gnu}/Linux. You can get the same
2009 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2012 @item set disable-randomization off
2013 Leave the behavior of the started executable unchanged. Some bugs rear their
2014 ugly heads only when the program is loaded at certain addresses. If your bug
2015 disappears when you run the program under @value{GDBN}, that might be because
2016 @value{GDBN} by default disables the address randomization on platforms, such
2017 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2018 disable-randomization off} to try to reproduce such elusive bugs.
2020 The virtual address space randomization is implemented only on @sc{gnu}/Linux.
2021 It protects the programs against some kinds of security attacks. In these
2022 cases the attacker needs to know the exact location of a concrete executable
2023 code. Randomizing its location makes it impossible to inject jumps misusing
2024 a code at its expected addresses.
2026 Prelinking shared libraries provides a startup performance advantage but it
2027 makes addresses in these libraries predictable for privileged processes by
2028 having just unprivileged access at the target system. Reading the shared
2029 library binary gives enough information for assembling the malicious code
2030 misusing it. Still even a prelinked shared library can get loaded at a new
2031 random address just requiring the regular relocation process during the
2032 startup. Shared libraries not already prelinked are always loaded at
2033 a randomly chosen address.
2035 Position independent executables (PIE) contain position independent code
2036 similar to the shared libraries and therefore such executables get loaded at
2037 a randomly chosen address upon startup. PIE executables always load even
2038 already prelinked shared libraries at a random address. You can build such
2039 executable using @command{gcc -fPIE -pie}.
2041 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2042 (as long as the randomization is enabled).
2044 @item show disable-randomization
2045 Show the current setting of the explicit disable of the native randomization of
2046 the virtual address space of the started program.
2051 @section Your Program's Arguments
2053 @cindex arguments (to your program)
2054 The arguments to your program can be specified by the arguments of the
2056 They are passed to a shell, which expands wildcard characters and
2057 performs redirection of I/O, and thence to your program. Your
2058 @code{SHELL} environment variable (if it exists) specifies what shell
2059 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2060 the default shell (@file{/bin/sh} on Unix).
2062 On non-Unix systems, the program is usually invoked directly by
2063 @value{GDBN}, which emulates I/O redirection via the appropriate system
2064 calls, and the wildcard characters are expanded by the startup code of
2065 the program, not by the shell.
2067 @code{run} with no arguments uses the same arguments used by the previous
2068 @code{run}, or those set by the @code{set args} command.
2073 Specify the arguments to be used the next time your program is run. If
2074 @code{set args} has no arguments, @code{run} executes your program
2075 with no arguments. Once you have run your program with arguments,
2076 using @code{set args} before the next @code{run} is the only way to run
2077 it again without arguments.
2081 Show the arguments to give your program when it is started.
2085 @section Your Program's Environment
2087 @cindex environment (of your program)
2088 The @dfn{environment} consists of a set of environment variables and
2089 their values. Environment variables conventionally record such things as
2090 your user name, your home directory, your terminal type, and your search
2091 path for programs to run. Usually you set up environment variables with
2092 the shell and they are inherited by all the other programs you run. When
2093 debugging, it can be useful to try running your program with a modified
2094 environment without having to start @value{GDBN} over again.
2098 @item path @var{directory}
2099 Add @var{directory} to the front of the @code{PATH} environment variable
2100 (the search path for executables) that will be passed to your program.
2101 The value of @code{PATH} used by @value{GDBN} does not change.
2102 You may specify several directory names, separated by whitespace or by a
2103 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2104 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2105 is moved to the front, so it is searched sooner.
2107 You can use the string @samp{$cwd} to refer to whatever is the current
2108 working directory at the time @value{GDBN} searches the path. If you
2109 use @samp{.} instead, it refers to the directory where you executed the
2110 @code{path} command. @value{GDBN} replaces @samp{.} in the
2111 @var{directory} argument (with the current path) before adding
2112 @var{directory} to the search path.
2113 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2114 @c document that, since repeating it would be a no-op.
2118 Display the list of search paths for executables (the @code{PATH}
2119 environment variable).
2121 @kindex show environment
2122 @item show environment @r{[}@var{varname}@r{]}
2123 Print the value of environment variable @var{varname} to be given to
2124 your program when it starts. If you do not supply @var{varname},
2125 print the names and values of all environment variables to be given to
2126 your program. You can abbreviate @code{environment} as @code{env}.
2128 @kindex set environment
2129 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2130 Set environment variable @var{varname} to @var{value}. The value
2131 changes for your program only, not for @value{GDBN} itself. @var{value} may
2132 be any string; the values of environment variables are just strings, and
2133 any interpretation is supplied by your program itself. The @var{value}
2134 parameter is optional; if it is eliminated, the variable is set to a
2136 @c "any string" here does not include leading, trailing
2137 @c blanks. Gnu asks: does anyone care?
2139 For example, this command:
2146 tells the debugged program, when subsequently run, that its user is named
2147 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2148 are not actually required.)
2150 @kindex unset environment
2151 @item unset environment @var{varname}
2152 Remove variable @var{varname} from the environment to be passed to your
2153 program. This is different from @samp{set env @var{varname} =};
2154 @code{unset environment} removes the variable from the environment,
2155 rather than assigning it an empty value.
2158 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2160 by your @code{SHELL} environment variable if it exists (or
2161 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2162 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2163 @file{.bashrc} for BASH---any variables you set in that file affect
2164 your program. You may wish to move setting of environment variables to
2165 files that are only run when you sign on, such as @file{.login} or
2168 @node Working Directory
2169 @section Your Program's Working Directory
2171 @cindex working directory (of your program)
2172 Each time you start your program with @code{run}, it inherits its
2173 working directory from the current working directory of @value{GDBN}.
2174 The @value{GDBN} working directory is initially whatever it inherited
2175 from its parent process (typically the shell), but you can specify a new
2176 working directory in @value{GDBN} with the @code{cd} command.
2178 The @value{GDBN} working directory also serves as a default for the commands
2179 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2184 @cindex change working directory
2185 @item cd @var{directory}
2186 Set the @value{GDBN} working directory to @var{directory}.
2190 Print the @value{GDBN} working directory.
2193 It is generally impossible to find the current working directory of
2194 the process being debugged (since a program can change its directory
2195 during its run). If you work on a system where @value{GDBN} is
2196 configured with the @file{/proc} support, you can use the @code{info
2197 proc} command (@pxref{SVR4 Process Information}) to find out the
2198 current working directory of the debuggee.
2201 @section Your Program's Input and Output
2206 By default, the program you run under @value{GDBN} does input and output to
2207 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2208 to its own terminal modes to interact with you, but it records the terminal
2209 modes your program was using and switches back to them when you continue
2210 running your program.
2213 @kindex info terminal
2215 Displays information recorded by @value{GDBN} about the terminal modes your
2219 You can redirect your program's input and/or output using shell
2220 redirection with the @code{run} command. For example,
2227 starts your program, diverting its output to the file @file{outfile}.
2230 @cindex controlling terminal
2231 Another way to specify where your program should do input and output is
2232 with the @code{tty} command. This command accepts a file name as
2233 argument, and causes this file to be the default for future @code{run}
2234 commands. It also resets the controlling terminal for the child
2235 process, for future @code{run} commands. For example,
2242 directs that processes started with subsequent @code{run} commands
2243 default to do input and output on the terminal @file{/dev/ttyb} and have
2244 that as their controlling terminal.
2246 An explicit redirection in @code{run} overrides the @code{tty} command's
2247 effect on the input/output device, but not its effect on the controlling
2250 When you use the @code{tty} command or redirect input in the @code{run}
2251 command, only the input @emph{for your program} is affected. The input
2252 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2253 for @code{set inferior-tty}.
2255 @cindex inferior tty
2256 @cindex set inferior controlling terminal
2257 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2258 display the name of the terminal that will be used for future runs of your
2262 @item set inferior-tty /dev/ttyb
2263 @kindex set inferior-tty
2264 Set the tty for the program being debugged to /dev/ttyb.
2266 @item show inferior-tty
2267 @kindex show inferior-tty
2268 Show the current tty for the program being debugged.
2272 @section Debugging an Already-running Process
2277 @item attach @var{process-id}
2278 This command attaches to a running process---one that was started
2279 outside @value{GDBN}. (@code{info files} shows your active
2280 targets.) The command takes as argument a process ID. The usual way to
2281 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2282 or with the @samp{jobs -l} shell command.
2284 @code{attach} does not repeat if you press @key{RET} a second time after
2285 executing the command.
2288 To use @code{attach}, your program must be running in an environment
2289 which supports processes; for example, @code{attach} does not work for
2290 programs on bare-board targets that lack an operating system. You must
2291 also have permission to send the process a signal.
2293 When you use @code{attach}, the debugger finds the program running in
2294 the process first by looking in the current working directory, then (if
2295 the program is not found) by using the source file search path
2296 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2297 the @code{file} command to load the program. @xref{Files, ,Commands to
2300 The first thing @value{GDBN} does after arranging to debug the specified
2301 process is to stop it. You can examine and modify an attached process
2302 with all the @value{GDBN} commands that are ordinarily available when
2303 you start processes with @code{run}. You can insert breakpoints; you
2304 can step and continue; you can modify storage. If you would rather the
2305 process continue running, you may use the @code{continue} command after
2306 attaching @value{GDBN} to the process.
2311 When you have finished debugging the attached process, you can use the
2312 @code{detach} command to release it from @value{GDBN} control. Detaching
2313 the process continues its execution. After the @code{detach} command,
2314 that process and @value{GDBN} become completely independent once more, and you
2315 are ready to @code{attach} another process or start one with @code{run}.
2316 @code{detach} does not repeat if you press @key{RET} again after
2317 executing the command.
2320 If you exit @value{GDBN} while you have an attached process, you detach
2321 that process. If you use the @code{run} command, you kill that process.
2322 By default, @value{GDBN} asks for confirmation if you try to do either of these
2323 things; you can control whether or not you need to confirm by using the
2324 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2328 @section Killing the Child Process
2333 Kill the child process in which your program is running under @value{GDBN}.
2336 This command is useful if you wish to debug a core dump instead of a
2337 running process. @value{GDBN} ignores any core dump file while your program
2340 On some operating systems, a program cannot be executed outside @value{GDBN}
2341 while you have breakpoints set on it inside @value{GDBN}. You can use the
2342 @code{kill} command in this situation to permit running your program
2343 outside the debugger.
2345 The @code{kill} command is also useful if you wish to recompile and
2346 relink your program, since on many systems it is impossible to modify an
2347 executable file while it is running in a process. In this case, when you
2348 next type @code{run}, @value{GDBN} notices that the file has changed, and
2349 reads the symbol table again (while trying to preserve your current
2350 breakpoint settings).
2352 @node Inferiors and Programs
2353 @section Debugging Multiple Inferiors and Programs
2355 @value{GDBN} lets you run and debug multiple programs in a single
2356 session. In addition, @value{GDBN} on some systems may let you run
2357 several programs simultaneously (otherwise you have to exit from one
2358 before starting another). In the most general case, you can have
2359 multiple threads of execution in each of multiple processes, launched
2360 from multiple executables.
2363 @value{GDBN} represents the state of each program execution with an
2364 object called an @dfn{inferior}. An inferior typically corresponds to
2365 a process, but is more general and applies also to targets that do not
2366 have processes. Inferiors may be created before a process runs, and
2367 may be retained after a process exits. Inferiors have unique
2368 identifiers that are different from process ids. Usually each
2369 inferior will also have its own distinct address space, although some
2370 embedded targets may have several inferiors running in different parts
2371 of a single address space. Each inferior may in turn have multiple
2372 threads running in it.
2374 To find out what inferiors exist at any moment, use @w{@code{info
2378 @kindex info inferiors
2379 @item info inferiors
2380 Print a list of all inferiors currently being managed by @value{GDBN}.
2382 @value{GDBN} displays for each inferior (in this order):
2386 the inferior number assigned by @value{GDBN}
2389 the target system's inferior identifier
2392 the name of the executable the inferior is running.
2397 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2398 indicates the current inferior.
2402 @c end table here to get a little more width for example
2405 (@value{GDBP}) info inferiors
2406 Num Description Executable
2407 2 process 2307 hello
2408 * 1 process 3401 goodbye
2411 To switch focus between inferiors, use the @code{inferior} command:
2414 @kindex inferior @var{infno}
2415 @item inferior @var{infno}
2416 Make inferior number @var{infno} the current inferior. The argument
2417 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2418 in the first field of the @samp{info inferiors} display.
2422 You can get multiple executables into a debugging session via the
2423 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2424 systems @value{GDBN} can add inferiors to the debug session
2425 automatically by following calls to @code{fork} and @code{exec}. To
2426 remove inferiors from the debugging session use the
2427 @w{@code{remove-inferior}} command.
2430 @kindex add-inferior
2431 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2432 Adds @var{n} inferiors to be run using @var{executable} as the
2433 executable. @var{n} defaults to 1. If no executable is specified,
2434 the inferiors begins empty, with no program. You can still assign or
2435 change the program assigned to the inferior at any time by using the
2436 @code{file} command with the executable name as its argument.
2438 @kindex clone-inferior
2439 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2440 Adds @var{n} inferiors ready to execute the same program as inferior
2441 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2442 number of the current inferior. This is a convenient command when you
2443 want to run another instance of the inferior you are debugging.
2446 (@value{GDBP}) info inferiors
2447 Num Description Executable
2448 * 1 process 29964 helloworld
2449 (@value{GDBP}) clone-inferior
2452 (@value{GDBP}) info inferiors
2453 Num Description Executable
2455 * 1 process 29964 helloworld
2458 You can now simply switch focus to inferior 2 and run it.
2460 @kindex remove-inferior
2461 @item remove-inferior @var{infno}
2462 Removes the inferior @var{infno}. It is not possible to remove an
2463 inferior that is running with this command. For those, use the
2464 @code{kill} or @code{detach} command first.
2468 To quit debugging one of the running inferiors that is not the current
2469 inferior, you can either detach from it by using the @w{@code{detach
2470 inferior}} command (allowing it to run independently), or kill it
2471 using the @w{@code{kill inferior}} command:
2474 @kindex detach inferior @var{infno}
2475 @item detach inferior @var{infno}
2476 Detach from the inferior identified by @value{GDBN} inferior number
2477 @var{infno}, and remove it from the inferior list.
2479 @kindex kill inferior @var{infno}
2480 @item kill inferior @var{infno}
2481 Kill the inferior identified by @value{GDBN} inferior number
2482 @var{infno}, and remove it from the inferior list.
2485 After the successful completion of a command such as @code{detach},
2486 @code{detach inferior}, @code{kill} or @code{kill inferior}, or after
2487 a normal process exit, the inferior is still valid and listed with
2488 @code{info inferiors}, ready to be restarted.
2491 To be notified when inferiors are started or exit under @value{GDBN}'s
2492 control use @w{@code{set print inferior-events}}:
2495 @kindex set print inferior-events
2496 @cindex print messages on inferior start and exit
2497 @item set print inferior-events
2498 @itemx set print inferior-events on
2499 @itemx set print inferior-events off
2500 The @code{set print inferior-events} command allows you to enable or
2501 disable printing of messages when @value{GDBN} notices that new
2502 inferiors have started or that inferiors have exited or have been
2503 detached. By default, these messages will not be printed.
2505 @kindex show print inferior-events
2506 @item show print inferior-events
2507 Show whether messages will be printed when @value{GDBN} detects that
2508 inferiors have started, exited or have been detached.
2511 Many commands will work the same with multiple programs as with a
2512 single program: e.g., @code{print myglobal} will simply display the
2513 value of @code{myglobal} in the current inferior.
2516 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2517 get more info about the relationship of inferiors, programs, address
2518 spaces in a debug session. You can do that with the @w{@code{maint
2519 info program-spaces}} command.
2522 @kindex maint info program-spaces
2523 @item maint info program-spaces
2524 Print a list of all program spaces currently being managed by
2527 @value{GDBN} displays for each program space (in this order):
2531 the program space number assigned by @value{GDBN}
2534 the name of the executable loaded into the program space, with e.g.,
2535 the @code{file} command.
2540 An asterisk @samp{*} preceding the @value{GDBN} program space number
2541 indicates the current program space.
2543 In addition, below each program space line, @value{GDBN} prints extra
2544 information that isn't suitable to display in tabular form. For
2545 example, the list of inferiors bound to the program space.
2548 (@value{GDBP}) maint info program-spaces
2551 Bound inferiors: ID 1 (process 21561)
2555 Here we can see that no inferior is running the program @code{hello},
2556 while @code{process 21561} is running the program @code{goodbye}. On
2557 some targets, it is possible that multiple inferiors are bound to the
2558 same program space. The most common example is that of debugging both
2559 the parent and child processes of a @code{vfork} call. For example,
2562 (@value{GDBP}) maint info program-spaces
2565 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2568 Here, both inferior 2 and inferior 1 are running in the same program
2569 space as a result of inferior 1 having executed a @code{vfork} call.
2573 @section Debugging Programs with Multiple Threads
2575 @cindex threads of execution
2576 @cindex multiple threads
2577 @cindex switching threads
2578 In some operating systems, such as HP-UX and Solaris, a single program
2579 may have more than one @dfn{thread} of execution. The precise semantics
2580 of threads differ from one operating system to another, but in general
2581 the threads of a single program are akin to multiple processes---except
2582 that they share one address space (that is, they can all examine and
2583 modify the same variables). On the other hand, each thread has its own
2584 registers and execution stack, and perhaps private memory.
2586 @value{GDBN} provides these facilities for debugging multi-thread
2590 @item automatic notification of new threads
2591 @item @samp{thread @var{threadno}}, a command to switch among threads
2592 @item @samp{info threads}, a command to inquire about existing threads
2593 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2594 a command to apply a command to a list of threads
2595 @item thread-specific breakpoints
2596 @item @samp{set print thread-events}, which controls printing of
2597 messages on thread start and exit.
2598 @item @samp{set libthread-db-search-path @var{path}}, which lets
2599 the user specify which @code{libthread_db} to use if the default choice
2600 isn't compatible with the program.
2604 @emph{Warning:} These facilities are not yet available on every
2605 @value{GDBN} configuration where the operating system supports threads.
2606 If your @value{GDBN} does not support threads, these commands have no
2607 effect. For example, a system without thread support shows no output
2608 from @samp{info threads}, and always rejects the @code{thread} command,
2612 (@value{GDBP}) info threads
2613 (@value{GDBP}) thread 1
2614 Thread ID 1 not known. Use the "info threads" command to
2615 see the IDs of currently known threads.
2617 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2618 @c doesn't support threads"?
2621 @cindex focus of debugging
2622 @cindex current thread
2623 The @value{GDBN} thread debugging facility allows you to observe all
2624 threads while your program runs---but whenever @value{GDBN} takes
2625 control, one thread in particular is always the focus of debugging.
2626 This thread is called the @dfn{current thread}. Debugging commands show
2627 program information from the perspective of the current thread.
2629 @cindex @code{New} @var{systag} message
2630 @cindex thread identifier (system)
2631 @c FIXME-implementors!! It would be more helpful if the [New...] message
2632 @c included GDB's numeric thread handle, so you could just go to that
2633 @c thread without first checking `info threads'.
2634 Whenever @value{GDBN} detects a new thread in your program, it displays
2635 the target system's identification for the thread with a message in the
2636 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2637 whose form varies depending on the particular system. For example, on
2638 @sc{gnu}/Linux, you might see
2641 [New Thread 46912507313328 (LWP 25582)]
2645 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2646 the @var{systag} is simply something like @samp{process 368}, with no
2649 @c FIXME!! (1) Does the [New...] message appear even for the very first
2650 @c thread of a program, or does it only appear for the
2651 @c second---i.e.@: when it becomes obvious we have a multithread
2653 @c (2) *Is* there necessarily a first thread always? Or do some
2654 @c multithread systems permit starting a program with multiple
2655 @c threads ab initio?
2657 @cindex thread number
2658 @cindex thread identifier (GDB)
2659 For debugging purposes, @value{GDBN} associates its own thread
2660 number---always a single integer---with each thread in your program.
2663 @kindex info threads
2665 Display a summary of all threads currently in your
2666 program. @value{GDBN} displays for each thread (in this order):
2670 the thread number assigned by @value{GDBN}
2673 the target system's thread identifier (@var{systag})
2676 the current stack frame summary for that thread
2680 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2681 indicates the current thread.
2685 @c end table here to get a little more width for example
2688 (@value{GDBP}) info threads
2689 3 process 35 thread 27 0x34e5 in sigpause ()
2690 2 process 35 thread 23 0x34e5 in sigpause ()
2691 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2697 @cindex debugging multithreaded programs (on HP-UX)
2698 @cindex thread identifier (GDB), on HP-UX
2699 For debugging purposes, @value{GDBN} associates its own thread
2700 number---a small integer assigned in thread-creation order---with each
2701 thread in your program.
2703 @cindex @code{New} @var{systag} message, on HP-UX
2704 @cindex thread identifier (system), on HP-UX
2705 @c FIXME-implementors!! It would be more helpful if the [New...] message
2706 @c included GDB's numeric thread handle, so you could just go to that
2707 @c thread without first checking `info threads'.
2708 Whenever @value{GDBN} detects a new thread in your program, it displays
2709 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2710 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2711 whose form varies depending on the particular system. For example, on
2715 [New thread 2 (system thread 26594)]
2719 when @value{GDBN} notices a new thread.
2722 @kindex info threads (HP-UX)
2724 Display a summary of all threads currently in your
2725 program. @value{GDBN} displays for each thread (in this order):
2728 @item the thread number assigned by @value{GDBN}
2730 @item the target system's thread identifier (@var{systag})
2732 @item the current stack frame summary for that thread
2736 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2737 indicates the current thread.
2741 @c end table here to get a little more width for example
2744 (@value{GDBP}) info threads
2745 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2747 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2748 from /usr/lib/libc.2
2749 1 system thread 27905 0x7b003498 in _brk () \@*
2750 from /usr/lib/libc.2
2753 On Solaris, you can display more information about user threads with a
2754 Solaris-specific command:
2757 @item maint info sol-threads
2758 @kindex maint info sol-threads
2759 @cindex thread info (Solaris)
2760 Display info on Solaris user threads.
2764 @kindex thread @var{threadno}
2765 @item thread @var{threadno}
2766 Make thread number @var{threadno} the current thread. The command
2767 argument @var{threadno} is the internal @value{GDBN} thread number, as
2768 shown in the first field of the @samp{info threads} display.
2769 @value{GDBN} responds by displaying the system identifier of the thread
2770 you selected, and its current stack frame summary:
2773 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2774 (@value{GDBP}) thread 2
2775 [Switching to process 35 thread 23]
2776 0x34e5 in sigpause ()
2780 As with the @samp{[New @dots{}]} message, the form of the text after
2781 @samp{Switching to} depends on your system's conventions for identifying
2784 @kindex thread apply
2785 @cindex apply command to several threads
2786 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2787 The @code{thread apply} command allows you to apply the named
2788 @var{command} to one or more threads. Specify the numbers of the
2789 threads that you want affected with the command argument
2790 @var{threadno}. It can be a single thread number, one of the numbers
2791 shown in the first field of the @samp{info threads} display; or it
2792 could be a range of thread numbers, as in @code{2-4}. To apply a
2793 command to all threads, type @kbd{thread apply all @var{command}}.
2795 @kindex set print thread-events
2796 @cindex print messages on thread start and exit
2797 @item set print thread-events
2798 @itemx set print thread-events on
2799 @itemx set print thread-events off
2800 The @code{set print thread-events} command allows you to enable or
2801 disable printing of messages when @value{GDBN} notices that new threads have
2802 started or that threads have exited. By default, these messages will
2803 be printed if detection of these events is supported by the target.
2804 Note that these messages cannot be disabled on all targets.
2806 @kindex show print thread-events
2807 @item show print thread-events
2808 Show whether messages will be printed when @value{GDBN} detects that threads
2809 have started and exited.
2812 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2813 more information about how @value{GDBN} behaves when you stop and start
2814 programs with multiple threads.
2816 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2817 watchpoints in programs with multiple threads.
2820 @kindex set libthread-db-search-path
2821 @cindex search path for @code{libthread_db}
2822 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2823 If this variable is set, @var{path} is a colon-separated list of
2824 directories @value{GDBN} will use to search for @code{libthread_db}.
2825 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2828 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2829 @code{libthread_db} library to obtain information about threads in the
2830 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2831 to find @code{libthread_db}. If that fails, @value{GDBN} will continue
2832 with default system shared library directories, and finally the directory
2833 from which @code{libpthread} was loaded in the inferior process.
2835 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2836 @value{GDBN} attempts to initialize it with the current inferior process.
2837 If this initialization fails (which could happen because of a version
2838 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2839 will unload @code{libthread_db}, and continue with the next directory.
2840 If none of @code{libthread_db} libraries initialize successfully,
2841 @value{GDBN} will issue a warning and thread debugging will be disabled.
2843 Setting @code{libthread-db-search-path} is currently implemented
2844 only on some platforms.
2846 @kindex show libthread-db-search-path
2847 @item show libthread-db-search-path
2848 Display current libthread_db search path.
2852 @section Debugging Forks
2854 @cindex fork, debugging programs which call
2855 @cindex multiple processes
2856 @cindex processes, multiple
2857 On most systems, @value{GDBN} has no special support for debugging
2858 programs which create additional processes using the @code{fork}
2859 function. When a program forks, @value{GDBN} will continue to debug the
2860 parent process and the child process will run unimpeded. If you have
2861 set a breakpoint in any code which the child then executes, the child
2862 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2863 will cause it to terminate.
2865 However, if you want to debug the child process there is a workaround
2866 which isn't too painful. Put a call to @code{sleep} in the code which
2867 the child process executes after the fork. It may be useful to sleep
2868 only if a certain environment variable is set, or a certain file exists,
2869 so that the delay need not occur when you don't want to run @value{GDBN}
2870 on the child. While the child is sleeping, use the @code{ps} program to
2871 get its process ID. Then tell @value{GDBN} (a new invocation of
2872 @value{GDBN} if you are also debugging the parent process) to attach to
2873 the child process (@pxref{Attach}). From that point on you can debug
2874 the child process just like any other process which you attached to.
2876 On some systems, @value{GDBN} provides support for debugging programs that
2877 create additional processes using the @code{fork} or @code{vfork} functions.
2878 Currently, the only platforms with this feature are HP-UX (11.x and later
2879 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2881 By default, when a program forks, @value{GDBN} will continue to debug
2882 the parent process and the child process will run unimpeded.
2884 If you want to follow the child process instead of the parent process,
2885 use the command @w{@code{set follow-fork-mode}}.
2888 @kindex set follow-fork-mode
2889 @item set follow-fork-mode @var{mode}
2890 Set the debugger response to a program call of @code{fork} or
2891 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2892 process. The @var{mode} argument can be:
2896 The original process is debugged after a fork. The child process runs
2897 unimpeded. This is the default.
2900 The new process is debugged after a fork. The parent process runs
2905 @kindex show follow-fork-mode
2906 @item show follow-fork-mode
2907 Display the current debugger response to a @code{fork} or @code{vfork} call.
2910 @cindex debugging multiple processes
2911 On Linux, if you want to debug both the parent and child processes, use the
2912 command @w{@code{set detach-on-fork}}.
2915 @kindex set detach-on-fork
2916 @item set detach-on-fork @var{mode}
2917 Tells gdb whether to detach one of the processes after a fork, or
2918 retain debugger control over them both.
2922 The child process (or parent process, depending on the value of
2923 @code{follow-fork-mode}) will be detached and allowed to run
2924 independently. This is the default.
2927 Both processes will be held under the control of @value{GDBN}.
2928 One process (child or parent, depending on the value of
2929 @code{follow-fork-mode}) is debugged as usual, while the other
2934 @kindex show detach-on-fork
2935 @item show detach-on-fork
2936 Show whether detach-on-fork mode is on/off.
2939 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
2940 will retain control of all forked processes (including nested forks).
2941 You can list the forked processes under the control of @value{GDBN} by
2942 using the @w{@code{info inferiors}} command, and switch from one fork
2943 to another by using the @code{inferior} command (@pxref{Inferiors and
2944 Programs, ,Debugging Multiple Inferiors and Programs}).
2946 To quit debugging one of the forked processes, you can either detach
2947 from it by using the @w{@code{detach inferior}} command (allowing it
2948 to run independently), or kill it using the @w{@code{kill inferior}}
2949 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
2952 If you ask to debug a child process and a @code{vfork} is followed by an
2953 @code{exec}, @value{GDBN} executes the new target up to the first
2954 breakpoint in the new target. If you have a breakpoint set on
2955 @code{main} in your original program, the breakpoint will also be set on
2956 the child process's @code{main}.
2958 On some systems, when a child process is spawned by @code{vfork}, you
2959 cannot debug the child or parent until an @code{exec} call completes.
2961 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2962 call executes, the new target restarts. To restart the parent
2963 process, use the @code{file} command with the parent executable name
2964 as its argument. By default, after an @code{exec} call executes,
2965 @value{GDBN} discards the symbols of the previous executable image.
2966 You can change this behaviour with the @w{@code{set follow-exec-mode}}
2970 @kindex set follow-exec-mode
2971 @item set follow-exec-mode @var{mode}
2973 Set debugger response to a program call of @code{exec}. An
2974 @code{exec} call replaces the program image of a process.
2976 @code{follow-exec-mode} can be:
2980 @value{GDBN} creates a new inferior and rebinds the process to this
2981 new inferior. The program the process was running before the
2982 @code{exec} call can be restarted afterwards by restarting the
2988 (@value{GDBP}) info inferiors
2990 Id Description Executable
2993 process 12020 is executing new program: prog2
2994 Program exited normally.
2995 (@value{GDBP}) info inferiors
2996 Id Description Executable
3002 @value{GDBN} keeps the process bound to the same inferior. The new
3003 executable image replaces the previous executable loaded in the
3004 inferior. Restarting the inferior after the @code{exec} call, with
3005 e.g., the @code{run} command, restarts the executable the process was
3006 running after the @code{exec} call. This is the default mode.
3011 (@value{GDBP}) info inferiors
3012 Id Description Executable
3015 process 12020 is executing new program: prog2
3016 Program exited normally.
3017 (@value{GDBP}) info inferiors
3018 Id Description Executable
3025 You can use the @code{catch} command to make @value{GDBN} stop whenever
3026 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3027 Catchpoints, ,Setting Catchpoints}.
3029 @node Checkpoint/Restart
3030 @section Setting a @emph{Bookmark} to Return to Later
3035 @cindex snapshot of a process
3036 @cindex rewind program state
3038 On certain operating systems@footnote{Currently, only
3039 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3040 program's state, called a @dfn{checkpoint}, and come back to it
3043 Returning to a checkpoint effectively undoes everything that has
3044 happened in the program since the @code{checkpoint} was saved. This
3045 includes changes in memory, registers, and even (within some limits)
3046 system state. Effectively, it is like going back in time to the
3047 moment when the checkpoint was saved.
3049 Thus, if you're stepping thru a program and you think you're
3050 getting close to the point where things go wrong, you can save
3051 a checkpoint. Then, if you accidentally go too far and miss
3052 the critical statement, instead of having to restart your program
3053 from the beginning, you can just go back to the checkpoint and
3054 start again from there.
3056 This can be especially useful if it takes a lot of time or
3057 steps to reach the point where you think the bug occurs.
3059 To use the @code{checkpoint}/@code{restart} method of debugging:
3064 Save a snapshot of the debugged program's current execution state.
3065 The @code{checkpoint} command takes no arguments, but each checkpoint
3066 is assigned a small integer id, similar to a breakpoint id.
3068 @kindex info checkpoints
3069 @item info checkpoints
3070 List the checkpoints that have been saved in the current debugging
3071 session. For each checkpoint, the following information will be
3078 @item Source line, or label
3081 @kindex restart @var{checkpoint-id}
3082 @item restart @var{checkpoint-id}
3083 Restore the program state that was saved as checkpoint number
3084 @var{checkpoint-id}. All program variables, registers, stack frames
3085 etc.@: will be returned to the values that they had when the checkpoint
3086 was saved. In essence, gdb will ``wind back the clock'' to the point
3087 in time when the checkpoint was saved.
3089 Note that breakpoints, @value{GDBN} variables, command history etc.
3090 are not affected by restoring a checkpoint. In general, a checkpoint
3091 only restores things that reside in the program being debugged, not in
3094 @kindex delete checkpoint @var{checkpoint-id}
3095 @item delete checkpoint @var{checkpoint-id}
3096 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3100 Returning to a previously saved checkpoint will restore the user state
3101 of the program being debugged, plus a significant subset of the system
3102 (OS) state, including file pointers. It won't ``un-write'' data from
3103 a file, but it will rewind the file pointer to the previous location,
3104 so that the previously written data can be overwritten. For files
3105 opened in read mode, the pointer will also be restored so that the
3106 previously read data can be read again.
3108 Of course, characters that have been sent to a printer (or other
3109 external device) cannot be ``snatched back'', and characters received
3110 from eg.@: a serial device can be removed from internal program buffers,
3111 but they cannot be ``pushed back'' into the serial pipeline, ready to
3112 be received again. Similarly, the actual contents of files that have
3113 been changed cannot be restored (at this time).
3115 However, within those constraints, you actually can ``rewind'' your
3116 program to a previously saved point in time, and begin debugging it
3117 again --- and you can change the course of events so as to debug a
3118 different execution path this time.
3120 @cindex checkpoints and process id
3121 Finally, there is one bit of internal program state that will be
3122 different when you return to a checkpoint --- the program's process
3123 id. Each checkpoint will have a unique process id (or @var{pid}),
3124 and each will be different from the program's original @var{pid}.
3125 If your program has saved a local copy of its process id, this could
3126 potentially pose a problem.
3128 @subsection A Non-obvious Benefit of Using Checkpoints
3130 On some systems such as @sc{gnu}/Linux, address space randomization
3131 is performed on new processes for security reasons. This makes it
3132 difficult or impossible to set a breakpoint, or watchpoint, on an
3133 absolute address if you have to restart the program, since the
3134 absolute location of a symbol will change from one execution to the
3137 A checkpoint, however, is an @emph{identical} copy of a process.
3138 Therefore if you create a checkpoint at (eg.@:) the start of main,
3139 and simply return to that checkpoint instead of restarting the
3140 process, you can avoid the effects of address randomization and
3141 your symbols will all stay in the same place.
3144 @chapter Stopping and Continuing
3146 The principal purposes of using a debugger are so that you can stop your
3147 program before it terminates; or so that, if your program runs into
3148 trouble, you can investigate and find out why.
3150 Inside @value{GDBN}, your program may stop for any of several reasons,
3151 such as a signal, a breakpoint, or reaching a new line after a
3152 @value{GDBN} command such as @code{step}. You may then examine and
3153 change variables, set new breakpoints or remove old ones, and then
3154 continue execution. Usually, the messages shown by @value{GDBN} provide
3155 ample explanation of the status of your program---but you can also
3156 explicitly request this information at any time.
3159 @kindex info program
3161 Display information about the status of your program: whether it is
3162 running or not, what process it is, and why it stopped.
3166 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3167 * Continuing and Stepping:: Resuming execution
3169 * Thread Stops:: Stopping and starting multi-thread programs
3173 @section Breakpoints, Watchpoints, and Catchpoints
3176 A @dfn{breakpoint} makes your program stop whenever a certain point in
3177 the program is reached. For each breakpoint, you can add conditions to
3178 control in finer detail whether your program stops. You can set
3179 breakpoints with the @code{break} command and its variants (@pxref{Set
3180 Breaks, ,Setting Breakpoints}), to specify the place where your program
3181 should stop by line number, function name or exact address in the
3184 On some systems, you can set breakpoints in shared libraries before
3185 the executable is run. There is a minor limitation on HP-UX systems:
3186 you must wait until the executable is run in order to set breakpoints
3187 in shared library routines that are not called directly by the program
3188 (for example, routines that are arguments in a @code{pthread_create}
3192 @cindex data breakpoints
3193 @cindex memory tracing
3194 @cindex breakpoint on memory address
3195 @cindex breakpoint on variable modification
3196 A @dfn{watchpoint} is a special breakpoint that stops your program
3197 when the value of an expression changes. The expression may be a value
3198 of a variable, or it could involve values of one or more variables
3199 combined by operators, such as @samp{a + b}. This is sometimes called
3200 @dfn{data breakpoints}. You must use a different command to set
3201 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3202 from that, you can manage a watchpoint like any other breakpoint: you
3203 enable, disable, and delete both breakpoints and watchpoints using the
3206 You can arrange to have values from your program displayed automatically
3207 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3211 @cindex breakpoint on events
3212 A @dfn{catchpoint} is another special breakpoint that stops your program
3213 when a certain kind of event occurs, such as the throwing of a C@t{++}
3214 exception or the loading of a library. As with watchpoints, you use a
3215 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3216 Catchpoints}), but aside from that, you can manage a catchpoint like any
3217 other breakpoint. (To stop when your program receives a signal, use the
3218 @code{handle} command; see @ref{Signals, ,Signals}.)
3220 @cindex breakpoint numbers
3221 @cindex numbers for breakpoints
3222 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3223 catchpoint when you create it; these numbers are successive integers
3224 starting with one. In many of the commands for controlling various
3225 features of breakpoints you use the breakpoint number to say which
3226 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3227 @dfn{disabled}; if disabled, it has no effect on your program until you
3230 @cindex breakpoint ranges
3231 @cindex ranges of breakpoints
3232 Some @value{GDBN} commands accept a range of breakpoints on which to
3233 operate. A breakpoint range is either a single breakpoint number, like
3234 @samp{5}, or two such numbers, in increasing order, separated by a
3235 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3236 all breakpoints in that range are operated on.
3239 * Set Breaks:: Setting breakpoints
3240 * Set Watchpoints:: Setting watchpoints
3241 * Set Catchpoints:: Setting catchpoints
3242 * Delete Breaks:: Deleting breakpoints
3243 * Disabling:: Disabling breakpoints
3244 * Conditions:: Break conditions
3245 * Break Commands:: Breakpoint command lists
3246 * Error in Breakpoints:: ``Cannot insert breakpoints''
3247 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3251 @subsection Setting Breakpoints
3253 @c FIXME LMB what does GDB do if no code on line of breakpt?
3254 @c consider in particular declaration with/without initialization.
3256 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3259 @kindex b @r{(@code{break})}
3260 @vindex $bpnum@r{, convenience variable}
3261 @cindex latest breakpoint
3262 Breakpoints are set with the @code{break} command (abbreviated
3263 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3264 number of the breakpoint you've set most recently; see @ref{Convenience
3265 Vars,, Convenience Variables}, for a discussion of what you can do with
3266 convenience variables.
3269 @item break @var{location}
3270 Set a breakpoint at the given @var{location}, which can specify a
3271 function name, a line number, or an address of an instruction.
3272 (@xref{Specify Location}, for a list of all the possible ways to
3273 specify a @var{location}.) The breakpoint will stop your program just
3274 before it executes any of the code in the specified @var{location}.
3276 When using source languages that permit overloading of symbols, such as
3277 C@t{++}, a function name may refer to more than one possible place to break.
3278 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3281 It is also possible to insert a breakpoint that will stop the program
3282 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3283 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3286 When called without any arguments, @code{break} sets a breakpoint at
3287 the next instruction to be executed in the selected stack frame
3288 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3289 innermost, this makes your program stop as soon as control
3290 returns to that frame. This is similar to the effect of a
3291 @code{finish} command in the frame inside the selected frame---except
3292 that @code{finish} does not leave an active breakpoint. If you use
3293 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3294 the next time it reaches the current location; this may be useful
3297 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3298 least one instruction has been executed. If it did not do this, you
3299 would be unable to proceed past a breakpoint without first disabling the
3300 breakpoint. This rule applies whether or not the breakpoint already
3301 existed when your program stopped.
3303 @item break @dots{} if @var{cond}
3304 Set a breakpoint with condition @var{cond}; evaluate the expression
3305 @var{cond} each time the breakpoint is reached, and stop only if the
3306 value is nonzero---that is, if @var{cond} evaluates as true.
3307 @samp{@dots{}} stands for one of the possible arguments described
3308 above (or no argument) specifying where to break. @xref{Conditions,
3309 ,Break Conditions}, for more information on breakpoint conditions.
3312 @item tbreak @var{args}
3313 Set a breakpoint enabled only for one stop. @var{args} are the
3314 same as for the @code{break} command, and the breakpoint is set in the same
3315 way, but the breakpoint is automatically deleted after the first time your
3316 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3319 @cindex hardware breakpoints
3320 @item hbreak @var{args}
3321 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3322 @code{break} command and the breakpoint is set in the same way, but the
3323 breakpoint requires hardware support and some target hardware may not
3324 have this support. The main purpose of this is EPROM/ROM code
3325 debugging, so you can set a breakpoint at an instruction without
3326 changing the instruction. This can be used with the new trap-generation
3327 provided by SPARClite DSU and most x86-based targets. These targets
3328 will generate traps when a program accesses some data or instruction
3329 address that is assigned to the debug registers. However the hardware
3330 breakpoint registers can take a limited number of breakpoints. For
3331 example, on the DSU, only two data breakpoints can be set at a time, and
3332 @value{GDBN} will reject this command if more than two are used. Delete
3333 or disable unused hardware breakpoints before setting new ones
3334 (@pxref{Disabling, ,Disabling Breakpoints}).
3335 @xref{Conditions, ,Break Conditions}.
3336 For remote targets, you can restrict the number of hardware
3337 breakpoints @value{GDBN} will use, see @ref{set remote
3338 hardware-breakpoint-limit}.
3341 @item thbreak @var{args}
3342 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3343 are the same as for the @code{hbreak} command and the breakpoint is set in
3344 the same way. However, like the @code{tbreak} command,
3345 the breakpoint is automatically deleted after the
3346 first time your program stops there. Also, like the @code{hbreak}
3347 command, the breakpoint requires hardware support and some target hardware
3348 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3349 See also @ref{Conditions, ,Break Conditions}.
3352 @cindex regular expression
3353 @cindex breakpoints in functions matching a regexp
3354 @cindex set breakpoints in many functions
3355 @item rbreak @var{regex}
3356 Set breakpoints on all functions matching the regular expression
3357 @var{regex}. This command sets an unconditional breakpoint on all
3358 matches, printing a list of all breakpoints it set. Once these
3359 breakpoints are set, they are treated just like the breakpoints set with
3360 the @code{break} command. You can delete them, disable them, or make
3361 them conditional the same way as any other breakpoint.
3363 The syntax of the regular expression is the standard one used with tools
3364 like @file{grep}. Note that this is different from the syntax used by
3365 shells, so for instance @code{foo*} matches all functions that include
3366 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3367 @code{.*} leading and trailing the regular expression you supply, so to
3368 match only functions that begin with @code{foo}, use @code{^foo}.
3370 @cindex non-member C@t{++} functions, set breakpoint in
3371 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3372 breakpoints on overloaded functions that are not members of any special
3375 @cindex set breakpoints on all functions
3376 The @code{rbreak} command can be used to set breakpoints in
3377 @strong{all} the functions in a program, like this:
3380 (@value{GDBP}) rbreak .
3383 @kindex info breakpoints
3384 @cindex @code{$_} and @code{info breakpoints}
3385 @item info breakpoints @r{[}@var{n}@r{]}
3386 @itemx info break @r{[}@var{n}@r{]}
3387 @itemx info watchpoints @r{[}@var{n}@r{]}
3388 Print a table of all breakpoints, watchpoints, and catchpoints set and
3389 not deleted. Optional argument @var{n} means print information only
3390 about the specified breakpoint (or watchpoint or catchpoint). For
3391 each breakpoint, following columns are printed:
3394 @item Breakpoint Numbers
3396 Breakpoint, watchpoint, or catchpoint.
3398 Whether the breakpoint is marked to be disabled or deleted when hit.
3399 @item Enabled or Disabled
3400 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3401 that are not enabled.
3403 Where the breakpoint is in your program, as a memory address. For a
3404 pending breakpoint whose address is not yet known, this field will
3405 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3406 library that has the symbol or line referred by breakpoint is loaded.
3407 See below for details. A breakpoint with several locations will
3408 have @samp{<MULTIPLE>} in this field---see below for details.
3410 Where the breakpoint is in the source for your program, as a file and
3411 line number. For a pending breakpoint, the original string passed to
3412 the breakpoint command will be listed as it cannot be resolved until
3413 the appropriate shared library is loaded in the future.
3417 If a breakpoint is conditional, @code{info break} shows the condition on
3418 the line following the affected breakpoint; breakpoint commands, if any,
3419 are listed after that. A pending breakpoint is allowed to have a condition
3420 specified for it. The condition is not parsed for validity until a shared
3421 library is loaded that allows the pending breakpoint to resolve to a
3425 @code{info break} with a breakpoint
3426 number @var{n} as argument lists only that breakpoint. The
3427 convenience variable @code{$_} and the default examining-address for
3428 the @code{x} command are set to the address of the last breakpoint
3429 listed (@pxref{Memory, ,Examining Memory}).
3432 @code{info break} displays a count of the number of times the breakpoint
3433 has been hit. This is especially useful in conjunction with the
3434 @code{ignore} command. You can ignore a large number of breakpoint
3435 hits, look at the breakpoint info to see how many times the breakpoint
3436 was hit, and then run again, ignoring one less than that number. This
3437 will get you quickly to the last hit of that breakpoint.
3440 @value{GDBN} allows you to set any number of breakpoints at the same place in
3441 your program. There is nothing silly or meaningless about this. When
3442 the breakpoints are conditional, this is even useful
3443 (@pxref{Conditions, ,Break Conditions}).
3445 @cindex multiple locations, breakpoints
3446 @cindex breakpoints, multiple locations
3447 It is possible that a breakpoint corresponds to several locations
3448 in your program. Examples of this situation are:
3452 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3453 instances of the function body, used in different cases.
3456 For a C@t{++} template function, a given line in the function can
3457 correspond to any number of instantiations.
3460 For an inlined function, a given source line can correspond to
3461 several places where that function is inlined.
3464 In all those cases, @value{GDBN} will insert a breakpoint at all
3465 the relevant locations@footnote{
3466 As of this writing, multiple-location breakpoints work only if there's
3467 line number information for all the locations. This means that they
3468 will generally not work in system libraries, unless you have debug
3469 info with line numbers for them.}.
3471 A breakpoint with multiple locations is displayed in the breakpoint
3472 table using several rows---one header row, followed by one row for
3473 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3474 address column. The rows for individual locations contain the actual
3475 addresses for locations, and show the functions to which those
3476 locations belong. The number column for a location is of the form
3477 @var{breakpoint-number}.@var{location-number}.
3482 Num Type Disp Enb Address What
3483 1 breakpoint keep y <MULTIPLE>
3485 breakpoint already hit 1 time
3486 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3487 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3490 Each location can be individually enabled or disabled by passing
3491 @var{breakpoint-number}.@var{location-number} as argument to the
3492 @code{enable} and @code{disable} commands. Note that you cannot
3493 delete the individual locations from the list, you can only delete the
3494 entire list of locations that belong to their parent breakpoint (with
3495 the @kbd{delete @var{num}} command, where @var{num} is the number of
3496 the parent breakpoint, 1 in the above example). Disabling or enabling
3497 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3498 that belong to that breakpoint.
3500 @cindex pending breakpoints
3501 It's quite common to have a breakpoint inside a shared library.
3502 Shared libraries can be loaded and unloaded explicitly,
3503 and possibly repeatedly, as the program is executed. To support
3504 this use case, @value{GDBN} updates breakpoint locations whenever
3505 any shared library is loaded or unloaded. Typically, you would
3506 set a breakpoint in a shared library at the beginning of your
3507 debugging session, when the library is not loaded, and when the
3508 symbols from the library are not available. When you try to set
3509 breakpoint, @value{GDBN} will ask you if you want to set
3510 a so called @dfn{pending breakpoint}---breakpoint whose address
3511 is not yet resolved.
3513 After the program is run, whenever a new shared library is loaded,
3514 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3515 shared library contains the symbol or line referred to by some
3516 pending breakpoint, that breakpoint is resolved and becomes an
3517 ordinary breakpoint. When a library is unloaded, all breakpoints
3518 that refer to its symbols or source lines become pending again.
3520 This logic works for breakpoints with multiple locations, too. For
3521 example, if you have a breakpoint in a C@t{++} template function, and
3522 a newly loaded shared library has an instantiation of that template,
3523 a new location is added to the list of locations for the breakpoint.
3525 Except for having unresolved address, pending breakpoints do not
3526 differ from regular breakpoints. You can set conditions or commands,
3527 enable and disable them and perform other breakpoint operations.
3529 @value{GDBN} provides some additional commands for controlling what
3530 happens when the @samp{break} command cannot resolve breakpoint
3531 address specification to an address:
3533 @kindex set breakpoint pending
3534 @kindex show breakpoint pending
3536 @item set breakpoint pending auto
3537 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3538 location, it queries you whether a pending breakpoint should be created.
3540 @item set breakpoint pending on
3541 This indicates that an unrecognized breakpoint location should automatically
3542 result in a pending breakpoint being created.
3544 @item set breakpoint pending off
3545 This indicates that pending breakpoints are not to be created. Any
3546 unrecognized breakpoint location results in an error. This setting does
3547 not affect any pending breakpoints previously created.
3549 @item show breakpoint pending
3550 Show the current behavior setting for creating pending breakpoints.
3553 The settings above only affect the @code{break} command and its
3554 variants. Once breakpoint is set, it will be automatically updated
3555 as shared libraries are loaded and unloaded.
3557 @cindex automatic hardware breakpoints
3558 For some targets, @value{GDBN} can automatically decide if hardware or
3559 software breakpoints should be used, depending on whether the
3560 breakpoint address is read-only or read-write. This applies to
3561 breakpoints set with the @code{break} command as well as to internal
3562 breakpoints set by commands like @code{next} and @code{finish}. For
3563 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3566 You can control this automatic behaviour with the following commands::
3568 @kindex set breakpoint auto-hw
3569 @kindex show breakpoint auto-hw
3571 @item set breakpoint auto-hw on
3572 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3573 will try to use the target memory map to decide if software or hardware
3574 breakpoint must be used.
3576 @item set breakpoint auto-hw off
3577 This indicates @value{GDBN} should not automatically select breakpoint
3578 type. If the target provides a memory map, @value{GDBN} will warn when
3579 trying to set software breakpoint at a read-only address.
3582 @value{GDBN} normally implements breakpoints by replacing the program code
3583 at the breakpoint address with a special instruction, which, when
3584 executed, given control to the debugger. By default, the program
3585 code is so modified only when the program is resumed. As soon as
3586 the program stops, @value{GDBN} restores the original instructions. This
3587 behaviour guards against leaving breakpoints inserted in the
3588 target should gdb abrubptly disconnect. However, with slow remote
3589 targets, inserting and removing breakpoint can reduce the performance.
3590 This behavior can be controlled with the following commands::
3592 @kindex set breakpoint always-inserted
3593 @kindex show breakpoint always-inserted
3595 @item set breakpoint always-inserted off
3596 All breakpoints, including newly added by the user, are inserted in
3597 the target only when the target is resumed. All breakpoints are
3598 removed from the target when it stops.
3600 @item set breakpoint always-inserted on
3601 Causes all breakpoints to be inserted in the target at all times. If
3602 the user adds a new breakpoint, or changes an existing breakpoint, the
3603 breakpoints in the target are updated immediately. A breakpoint is
3604 removed from the target only when breakpoint itself is removed.
3606 @cindex non-stop mode, and @code{breakpoint always-inserted}
3607 @item set breakpoint always-inserted auto
3608 This is the default mode. If @value{GDBN} is controlling the inferior
3609 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3610 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3611 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3612 @code{breakpoint always-inserted} mode is off.
3615 @cindex negative breakpoint numbers
3616 @cindex internal @value{GDBN} breakpoints
3617 @value{GDBN} itself sometimes sets breakpoints in your program for
3618 special purposes, such as proper handling of @code{longjmp} (in C
3619 programs). These internal breakpoints are assigned negative numbers,
3620 starting with @code{-1}; @samp{info breakpoints} does not display them.
3621 You can see these breakpoints with the @value{GDBN} maintenance command
3622 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3625 @node Set Watchpoints
3626 @subsection Setting Watchpoints
3628 @cindex setting watchpoints
3629 You can use a watchpoint to stop execution whenever the value of an
3630 expression changes, without having to predict a particular place where
3631 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3632 The expression may be as simple as the value of a single variable, or
3633 as complex as many variables combined by operators. Examples include:
3637 A reference to the value of a single variable.
3640 An address cast to an appropriate data type. For example,
3641 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3642 address (assuming an @code{int} occupies 4 bytes).
3645 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3646 expression can use any operators valid in the program's native
3647 language (@pxref{Languages}).
3650 You can set a watchpoint on an expression even if the expression can
3651 not be evaluated yet. For instance, you can set a watchpoint on
3652 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3653 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3654 the expression produces a valid value. If the expression becomes
3655 valid in some other way than changing a variable (e.g.@: if the memory
3656 pointed to by @samp{*global_ptr} becomes readable as the result of a
3657 @code{malloc} call), @value{GDBN} may not stop until the next time
3658 the expression changes.
3660 @cindex software watchpoints
3661 @cindex hardware watchpoints
3662 Depending on your system, watchpoints may be implemented in software or
3663 hardware. @value{GDBN} does software watchpointing by single-stepping your
3664 program and testing the variable's value each time, which is hundreds of
3665 times slower than normal execution. (But this may still be worth it, to
3666 catch errors where you have no clue what part of your program is the
3669 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3670 x86-based targets, @value{GDBN} includes support for hardware
3671 watchpoints, which do not slow down the running of your program.
3675 @item watch @var{expr} @r{[}thread @var{threadnum}@r{]}
3676 Set a watchpoint for an expression. @value{GDBN} will break when the
3677 expression @var{expr} is written into by the program and its value
3678 changes. The simplest (and the most popular) use of this command is
3679 to watch the value of a single variable:
3682 (@value{GDBP}) watch foo
3685 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3686 clause, @value{GDBN} breaks only when the thread identified by
3687 @var{threadnum} changes the value of @var{expr}. If any other threads
3688 change the value of @var{expr}, @value{GDBN} will not break. Note
3689 that watchpoints restricted to a single thread in this way only work
3690 with Hardware Watchpoints.
3693 @item rwatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3694 Set a watchpoint that will break when the value of @var{expr} is read
3698 @item awatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3699 Set a watchpoint that will break when @var{expr} is either read from
3700 or written into by the program.
3702 @kindex info watchpoints @r{[}@var{n}@r{]}
3703 @item info watchpoints
3704 This command prints a list of watchpoints, breakpoints, and catchpoints;
3705 it is the same as @code{info break} (@pxref{Set Breaks}).
3708 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3709 watchpoints execute very quickly, and the debugger reports a change in
3710 value at the exact instruction where the change occurs. If @value{GDBN}
3711 cannot set a hardware watchpoint, it sets a software watchpoint, which
3712 executes more slowly and reports the change in value at the next
3713 @emph{statement}, not the instruction, after the change occurs.
3715 @cindex use only software watchpoints
3716 You can force @value{GDBN} to use only software watchpoints with the
3717 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3718 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3719 the underlying system supports them. (Note that hardware-assisted
3720 watchpoints that were set @emph{before} setting
3721 @code{can-use-hw-watchpoints} to zero will still use the hardware
3722 mechanism of watching expression values.)
3725 @item set can-use-hw-watchpoints
3726 @kindex set can-use-hw-watchpoints
3727 Set whether or not to use hardware watchpoints.
3729 @item show can-use-hw-watchpoints
3730 @kindex show can-use-hw-watchpoints
3731 Show the current mode of using hardware watchpoints.
3734 For remote targets, you can restrict the number of hardware
3735 watchpoints @value{GDBN} will use, see @ref{set remote
3736 hardware-breakpoint-limit}.
3738 When you issue the @code{watch} command, @value{GDBN} reports
3741 Hardware watchpoint @var{num}: @var{expr}
3745 if it was able to set a hardware watchpoint.
3747 Currently, the @code{awatch} and @code{rwatch} commands can only set
3748 hardware watchpoints, because accesses to data that don't change the
3749 value of the watched expression cannot be detected without examining
3750 every instruction as it is being executed, and @value{GDBN} does not do
3751 that currently. If @value{GDBN} finds that it is unable to set a
3752 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3753 will print a message like this:
3756 Expression cannot be implemented with read/access watchpoint.
3759 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3760 data type of the watched expression is wider than what a hardware
3761 watchpoint on the target machine can handle. For example, some systems
3762 can only watch regions that are up to 4 bytes wide; on such systems you
3763 cannot set hardware watchpoints for an expression that yields a
3764 double-precision floating-point number (which is typically 8 bytes
3765 wide). As a work-around, it might be possible to break the large region
3766 into a series of smaller ones and watch them with separate watchpoints.
3768 If you set too many hardware watchpoints, @value{GDBN} might be unable
3769 to insert all of them when you resume the execution of your program.
3770 Since the precise number of active watchpoints is unknown until such
3771 time as the program is about to be resumed, @value{GDBN} might not be
3772 able to warn you about this when you set the watchpoints, and the
3773 warning will be printed only when the program is resumed:
3776 Hardware watchpoint @var{num}: Could not insert watchpoint
3780 If this happens, delete or disable some of the watchpoints.
3782 Watching complex expressions that reference many variables can also
3783 exhaust the resources available for hardware-assisted watchpoints.
3784 That's because @value{GDBN} needs to watch every variable in the
3785 expression with separately allocated resources.
3787 If you call a function interactively using @code{print} or @code{call},
3788 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3789 kind of breakpoint or the call completes.
3791 @value{GDBN} automatically deletes watchpoints that watch local
3792 (automatic) variables, or expressions that involve such variables, when
3793 they go out of scope, that is, when the execution leaves the block in
3794 which these variables were defined. In particular, when the program
3795 being debugged terminates, @emph{all} local variables go out of scope,
3796 and so only watchpoints that watch global variables remain set. If you
3797 rerun the program, you will need to set all such watchpoints again. One
3798 way of doing that would be to set a code breakpoint at the entry to the
3799 @code{main} function and when it breaks, set all the watchpoints.
3801 @cindex watchpoints and threads
3802 @cindex threads and watchpoints
3803 In multi-threaded programs, watchpoints will detect changes to the
3804 watched expression from every thread.
3807 @emph{Warning:} In multi-threaded programs, software watchpoints
3808 have only limited usefulness. If @value{GDBN} creates a software
3809 watchpoint, it can only watch the value of an expression @emph{in a
3810 single thread}. If you are confident that the expression can only
3811 change due to the current thread's activity (and if you are also
3812 confident that no other thread can become current), then you can use
3813 software watchpoints as usual. However, @value{GDBN} may not notice
3814 when a non-current thread's activity changes the expression. (Hardware
3815 watchpoints, in contrast, watch an expression in all threads.)
3818 @xref{set remote hardware-watchpoint-limit}.
3820 @node Set Catchpoints
3821 @subsection Setting Catchpoints
3822 @cindex catchpoints, setting
3823 @cindex exception handlers
3824 @cindex event handling
3826 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3827 kinds of program events, such as C@t{++} exceptions or the loading of a
3828 shared library. Use the @code{catch} command to set a catchpoint.
3832 @item catch @var{event}
3833 Stop when @var{event} occurs. @var{event} can be any of the following:
3836 @cindex stop on C@t{++} exceptions
3837 The throwing of a C@t{++} exception.
3840 The catching of a C@t{++} exception.
3843 @cindex Ada exception catching
3844 @cindex catch Ada exceptions
3845 An Ada exception being raised. If an exception name is specified
3846 at the end of the command (eg @code{catch exception Program_Error}),
3847 the debugger will stop only when this specific exception is raised.
3848 Otherwise, the debugger stops execution when any Ada exception is raised.
3850 When inserting an exception catchpoint on a user-defined exception whose
3851 name is identical to one of the exceptions defined by the language, the
3852 fully qualified name must be used as the exception name. Otherwise,
3853 @value{GDBN} will assume that it should stop on the pre-defined exception
3854 rather than the user-defined one. For instance, assuming an exception
3855 called @code{Constraint_Error} is defined in package @code{Pck}, then
3856 the command to use to catch such exceptions is @kbd{catch exception
3857 Pck.Constraint_Error}.
3859 @item exception unhandled
3860 An exception that was raised but is not handled by the program.
3863 A failed Ada assertion.
3866 @cindex break on fork/exec
3867 A call to @code{exec}. This is currently only available for HP-UX
3871 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @r{...}
3872 @cindex break on a system call.
3873 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
3874 syscall is a mechanism for application programs to request a service
3875 from the operating system (OS) or one of the OS system services.
3876 @value{GDBN} can catch some or all of the syscalls issued by the
3877 debuggee, and show the related information for each syscall. If no
3878 argument is specified, calls to and returns from all system calls
3881 @var{name} can be any system call name that is valid for the
3882 underlying OS. Just what syscalls are valid depends on the OS. On
3883 GNU and Unix systems, you can find the full list of valid syscall
3884 names on @file{/usr/include/asm/unistd.h}.
3886 @c For MS-Windows, the syscall names and the corresponding numbers
3887 @c can be found, e.g., on this URL:
3888 @c http://www.metasploit.com/users/opcode/syscalls.html
3889 @c but we don't support Windows syscalls yet.
3891 Normally, @value{GDBN} knows in advance which syscalls are valid for
3892 each OS, so you can use the @value{GDBN} command-line completion
3893 facilities (@pxref{Completion,, command completion}) to list the
3896 You may also specify the system call numerically. A syscall's
3897 number is the value passed to the OS's syscall dispatcher to
3898 identify the requested service. When you specify the syscall by its
3899 name, @value{GDBN} uses its database of syscalls to convert the name
3900 into the corresponding numeric code, but using the number directly
3901 may be useful if @value{GDBN}'s database does not have the complete
3902 list of syscalls on your system (e.g., because @value{GDBN} lags
3903 behind the OS upgrades).
3905 The example below illustrates how this command works if you don't provide
3909 (@value{GDBP}) catch syscall
3910 Catchpoint 1 (syscall)
3912 Starting program: /tmp/catch-syscall
3914 Catchpoint 1 (call to syscall 'close'), \
3915 0xffffe424 in __kernel_vsyscall ()
3919 Catchpoint 1 (returned from syscall 'close'), \
3920 0xffffe424 in __kernel_vsyscall ()
3924 Here is an example of catching a system call by name:
3927 (@value{GDBP}) catch syscall chroot
3928 Catchpoint 1 (syscall 'chroot' [61])
3930 Starting program: /tmp/catch-syscall
3932 Catchpoint 1 (call to syscall 'chroot'), \
3933 0xffffe424 in __kernel_vsyscall ()
3937 Catchpoint 1 (returned from syscall 'chroot'), \
3938 0xffffe424 in __kernel_vsyscall ()
3942 An example of specifying a system call numerically. In the case
3943 below, the syscall number has a corresponding entry in the XML
3944 file, so @value{GDBN} finds its name and prints it:
3947 (@value{GDBP}) catch syscall 252
3948 Catchpoint 1 (syscall(s) 'exit_group')
3950 Starting program: /tmp/catch-syscall
3952 Catchpoint 1 (call to syscall 'exit_group'), \
3953 0xffffe424 in __kernel_vsyscall ()
3957 Program exited normally.
3961 However, there can be situations when there is no corresponding name
3962 in XML file for that syscall number. In this case, @value{GDBN} prints
3963 a warning message saying that it was not able to find the syscall name,
3964 but the catchpoint will be set anyway. See the example below:
3967 (@value{GDBP}) catch syscall 764
3968 warning: The number '764' does not represent a known syscall.
3969 Catchpoint 2 (syscall 764)
3973 If you configure @value{GDBN} using the @samp{--without-expat} option,
3974 it will not be able to display syscall names. Also, if your
3975 architecture does not have an XML file describing its system calls,
3976 you will not be able to see the syscall names. It is important to
3977 notice that these two features are used for accessing the syscall
3978 name database. In either case, you will see a warning like this:
3981 (@value{GDBP}) catch syscall
3982 warning: Could not open "syscalls/i386-linux.xml"
3983 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
3984 GDB will not be able to display syscall names.
3985 Catchpoint 1 (syscall)
3989 Of course, the file name will change depending on your architecture and system.
3991 Still using the example above, you can also try to catch a syscall by its
3992 number. In this case, you would see something like:
3995 (@value{GDBP}) catch syscall 252
3996 Catchpoint 1 (syscall(s) 252)
3999 Again, in this case @value{GDBN} would not be able to display syscall's names.
4002 A call to @code{fork}. This is currently only available for HP-UX
4006 A call to @code{vfork}. This is currently only available for HP-UX
4011 @item tcatch @var{event}
4012 Set a catchpoint that is enabled only for one stop. The catchpoint is
4013 automatically deleted after the first time the event is caught.
4017 Use the @code{info break} command to list the current catchpoints.
4019 There are currently some limitations to C@t{++} exception handling
4020 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4024 If you call a function interactively, @value{GDBN} normally returns
4025 control to you when the function has finished executing. If the call
4026 raises an exception, however, the call may bypass the mechanism that
4027 returns control to you and cause your program either to abort or to
4028 simply continue running until it hits a breakpoint, catches a signal
4029 that @value{GDBN} is listening for, or exits. This is the case even if
4030 you set a catchpoint for the exception; catchpoints on exceptions are
4031 disabled within interactive calls.
4034 You cannot raise an exception interactively.
4037 You cannot install an exception handler interactively.
4040 @cindex raise exceptions
4041 Sometimes @code{catch} is not the best way to debug exception handling:
4042 if you need to know exactly where an exception is raised, it is better to
4043 stop @emph{before} the exception handler is called, since that way you
4044 can see the stack before any unwinding takes place. If you set a
4045 breakpoint in an exception handler instead, it may not be easy to find
4046 out where the exception was raised.
4048 To stop just before an exception handler is called, you need some
4049 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4050 raised by calling a library function named @code{__raise_exception}
4051 which has the following ANSI C interface:
4054 /* @var{addr} is where the exception identifier is stored.
4055 @var{id} is the exception identifier. */
4056 void __raise_exception (void **addr, void *id);
4060 To make the debugger catch all exceptions before any stack
4061 unwinding takes place, set a breakpoint on @code{__raise_exception}
4062 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4064 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4065 that depends on the value of @var{id}, you can stop your program when
4066 a specific exception is raised. You can use multiple conditional
4067 breakpoints to stop your program when any of a number of exceptions are
4072 @subsection Deleting Breakpoints
4074 @cindex clearing breakpoints, watchpoints, catchpoints
4075 @cindex deleting breakpoints, watchpoints, catchpoints
4076 It is often necessary to eliminate a breakpoint, watchpoint, or
4077 catchpoint once it has done its job and you no longer want your program
4078 to stop there. This is called @dfn{deleting} the breakpoint. A
4079 breakpoint that has been deleted no longer exists; it is forgotten.
4081 With the @code{clear} command you can delete breakpoints according to
4082 where they are in your program. With the @code{delete} command you can
4083 delete individual breakpoints, watchpoints, or catchpoints by specifying
4084 their breakpoint numbers.
4086 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4087 automatically ignores breakpoints on the first instruction to be executed
4088 when you continue execution without changing the execution address.
4093 Delete any breakpoints at the next instruction to be executed in the
4094 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4095 the innermost frame is selected, this is a good way to delete a
4096 breakpoint where your program just stopped.
4098 @item clear @var{location}
4099 Delete any breakpoints set at the specified @var{location}.
4100 @xref{Specify Location}, for the various forms of @var{location}; the
4101 most useful ones are listed below:
4104 @item clear @var{function}
4105 @itemx clear @var{filename}:@var{function}
4106 Delete any breakpoints set at entry to the named @var{function}.
4108 @item clear @var{linenum}
4109 @itemx clear @var{filename}:@var{linenum}
4110 Delete any breakpoints set at or within the code of the specified
4111 @var{linenum} of the specified @var{filename}.
4114 @cindex delete breakpoints
4116 @kindex d @r{(@code{delete})}
4117 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4118 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4119 ranges specified as arguments. If no argument is specified, delete all
4120 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4121 confirm off}). You can abbreviate this command as @code{d}.
4125 @subsection Disabling Breakpoints
4127 @cindex enable/disable a breakpoint
4128 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4129 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4130 it had been deleted, but remembers the information on the breakpoint so
4131 that you can @dfn{enable} it again later.
4133 You disable and enable breakpoints, watchpoints, and catchpoints with
4134 the @code{enable} and @code{disable} commands, optionally specifying one
4135 or more breakpoint numbers as arguments. Use @code{info break} or
4136 @code{info watch} to print a list of breakpoints, watchpoints, and
4137 catchpoints if you do not know which numbers to use.
4139 Disabling and enabling a breakpoint that has multiple locations
4140 affects all of its locations.
4142 A breakpoint, watchpoint, or catchpoint can have any of four different
4143 states of enablement:
4147 Enabled. The breakpoint stops your program. A breakpoint set
4148 with the @code{break} command starts out in this state.
4150 Disabled. The breakpoint has no effect on your program.
4152 Enabled once. The breakpoint stops your program, but then becomes
4155 Enabled for deletion. The breakpoint stops your program, but
4156 immediately after it does so it is deleted permanently. A breakpoint
4157 set with the @code{tbreak} command starts out in this state.
4160 You can use the following commands to enable or disable breakpoints,
4161 watchpoints, and catchpoints:
4165 @kindex dis @r{(@code{disable})}
4166 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4167 Disable the specified breakpoints---or all breakpoints, if none are
4168 listed. A disabled breakpoint has no effect but is not forgotten. All
4169 options such as ignore-counts, conditions and commands are remembered in
4170 case the breakpoint is enabled again later. You may abbreviate
4171 @code{disable} as @code{dis}.
4174 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4175 Enable the specified breakpoints (or all defined breakpoints). They
4176 become effective once again in stopping your program.
4178 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4179 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4180 of these breakpoints immediately after stopping your program.
4182 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4183 Enable the specified breakpoints to work once, then die. @value{GDBN}
4184 deletes any of these breakpoints as soon as your program stops there.
4185 Breakpoints set by the @code{tbreak} command start out in this state.
4188 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4189 @c confusing: tbreak is also initially enabled.
4190 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4191 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4192 subsequently, they become disabled or enabled only when you use one of
4193 the commands above. (The command @code{until} can set and delete a
4194 breakpoint of its own, but it does not change the state of your other
4195 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4199 @subsection Break Conditions
4200 @cindex conditional breakpoints
4201 @cindex breakpoint conditions
4203 @c FIXME what is scope of break condition expr? Context where wanted?
4204 @c in particular for a watchpoint?
4205 The simplest sort of breakpoint breaks every time your program reaches a
4206 specified place. You can also specify a @dfn{condition} for a
4207 breakpoint. A condition is just a Boolean expression in your
4208 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4209 a condition evaluates the expression each time your program reaches it,
4210 and your program stops only if the condition is @emph{true}.
4212 This is the converse of using assertions for program validation; in that
4213 situation, you want to stop when the assertion is violated---that is,
4214 when the condition is false. In C, if you want to test an assertion expressed
4215 by the condition @var{assert}, you should set the condition
4216 @samp{! @var{assert}} on the appropriate breakpoint.
4218 Conditions are also accepted for watchpoints; you may not need them,
4219 since a watchpoint is inspecting the value of an expression anyhow---but
4220 it might be simpler, say, to just set a watchpoint on a variable name,
4221 and specify a condition that tests whether the new value is an interesting
4224 Break conditions can have side effects, and may even call functions in
4225 your program. This can be useful, for example, to activate functions
4226 that log program progress, or to use your own print functions to
4227 format special data structures. The effects are completely predictable
4228 unless there is another enabled breakpoint at the same address. (In
4229 that case, @value{GDBN} might see the other breakpoint first and stop your
4230 program without checking the condition of this one.) Note that
4231 breakpoint commands are usually more convenient and flexible than break
4233 purpose of performing side effects when a breakpoint is reached
4234 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4236 Break conditions can be specified when a breakpoint is set, by using
4237 @samp{if} in the arguments to the @code{break} command. @xref{Set
4238 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4239 with the @code{condition} command.
4241 You can also use the @code{if} keyword with the @code{watch} command.
4242 The @code{catch} command does not recognize the @code{if} keyword;
4243 @code{condition} is the only way to impose a further condition on a
4248 @item condition @var{bnum} @var{expression}
4249 Specify @var{expression} as the break condition for breakpoint,
4250 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4251 breakpoint @var{bnum} stops your program only if the value of
4252 @var{expression} is true (nonzero, in C). When you use
4253 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4254 syntactic correctness, and to determine whether symbols in it have
4255 referents in the context of your breakpoint. If @var{expression} uses
4256 symbols not referenced in the context of the breakpoint, @value{GDBN}
4257 prints an error message:
4260 No symbol "foo" in current context.
4265 not actually evaluate @var{expression} at the time the @code{condition}
4266 command (or a command that sets a breakpoint with a condition, like
4267 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4269 @item condition @var{bnum}
4270 Remove the condition from breakpoint number @var{bnum}. It becomes
4271 an ordinary unconditional breakpoint.
4274 @cindex ignore count (of breakpoint)
4275 A special case of a breakpoint condition is to stop only when the
4276 breakpoint has been reached a certain number of times. This is so
4277 useful that there is a special way to do it, using the @dfn{ignore
4278 count} of the breakpoint. Every breakpoint has an ignore count, which
4279 is an integer. Most of the time, the ignore count is zero, and
4280 therefore has no effect. But if your program reaches a breakpoint whose
4281 ignore count is positive, then instead of stopping, it just decrements
4282 the ignore count by one and continues. As a result, if the ignore count
4283 value is @var{n}, the breakpoint does not stop the next @var{n} times
4284 your program reaches it.
4288 @item ignore @var{bnum} @var{count}
4289 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4290 The next @var{count} times the breakpoint is reached, your program's
4291 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4294 To make the breakpoint stop the next time it is reached, specify
4297 When you use @code{continue} to resume execution of your program from a
4298 breakpoint, you can specify an ignore count directly as an argument to
4299 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4300 Stepping,,Continuing and Stepping}.
4302 If a breakpoint has a positive ignore count and a condition, the
4303 condition is not checked. Once the ignore count reaches zero,
4304 @value{GDBN} resumes checking the condition.
4306 You could achieve the effect of the ignore count with a condition such
4307 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4308 is decremented each time. @xref{Convenience Vars, ,Convenience
4312 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4315 @node Break Commands
4316 @subsection Breakpoint Command Lists
4318 @cindex breakpoint commands
4319 You can give any breakpoint (or watchpoint or catchpoint) a series of
4320 commands to execute when your program stops due to that breakpoint. For
4321 example, you might want to print the values of certain expressions, or
4322 enable other breakpoints.
4326 @kindex end@r{ (breakpoint commands)}
4327 @item commands @r{[}@var{bnum}@r{]}
4328 @itemx @dots{} @var{command-list} @dots{}
4330 Specify a list of commands for breakpoint number @var{bnum}. The commands
4331 themselves appear on the following lines. Type a line containing just
4332 @code{end} to terminate the commands.
4334 To remove all commands from a breakpoint, type @code{commands} and
4335 follow it immediately with @code{end}; that is, give no commands.
4337 With no @var{bnum} argument, @code{commands} refers to the last
4338 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
4339 recently encountered).
4342 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4343 disabled within a @var{command-list}.
4345 You can use breakpoint commands to start your program up again. Simply
4346 use the @code{continue} command, or @code{step}, or any other command
4347 that resumes execution.
4349 Any other commands in the command list, after a command that resumes
4350 execution, are ignored. This is because any time you resume execution
4351 (even with a simple @code{next} or @code{step}), you may encounter
4352 another breakpoint---which could have its own command list, leading to
4353 ambiguities about which list to execute.
4356 If the first command you specify in a command list is @code{silent}, the
4357 usual message about stopping at a breakpoint is not printed. This may
4358 be desirable for breakpoints that are to print a specific message and
4359 then continue. If none of the remaining commands print anything, you
4360 see no sign that the breakpoint was reached. @code{silent} is
4361 meaningful only at the beginning of a breakpoint command list.
4363 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4364 print precisely controlled output, and are often useful in silent
4365 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4367 For example, here is how you could use breakpoint commands to print the
4368 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4374 printf "x is %d\n",x
4379 One application for breakpoint commands is to compensate for one bug so
4380 you can test for another. Put a breakpoint just after the erroneous line
4381 of code, give it a condition to detect the case in which something
4382 erroneous has been done, and give it commands to assign correct values
4383 to any variables that need them. End with the @code{continue} command
4384 so that your program does not stop, and start with the @code{silent}
4385 command so that no output is produced. Here is an example:
4396 @c @ifclear BARETARGET
4397 @node Error in Breakpoints
4398 @subsection ``Cannot insert breakpoints''
4400 If you request too many active hardware-assisted breakpoints and
4401 watchpoints, you will see this error message:
4403 @c FIXME: the precise wording of this message may change; the relevant
4404 @c source change is not committed yet (Sep 3, 1999).
4406 Stopped; cannot insert breakpoints.
4407 You may have requested too many hardware breakpoints and watchpoints.
4411 This message is printed when you attempt to resume the program, since
4412 only then @value{GDBN} knows exactly how many hardware breakpoints and
4413 watchpoints it needs to insert.
4415 When this message is printed, you need to disable or remove some of the
4416 hardware-assisted breakpoints and watchpoints, and then continue.
4418 @node Breakpoint-related Warnings
4419 @subsection ``Breakpoint address adjusted...''
4420 @cindex breakpoint address adjusted
4422 Some processor architectures place constraints on the addresses at
4423 which breakpoints may be placed. For architectures thus constrained,
4424 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4425 with the constraints dictated by the architecture.
4427 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4428 a VLIW architecture in which a number of RISC-like instructions may be
4429 bundled together for parallel execution. The FR-V architecture
4430 constrains the location of a breakpoint instruction within such a
4431 bundle to the instruction with the lowest address. @value{GDBN}
4432 honors this constraint by adjusting a breakpoint's address to the
4433 first in the bundle.
4435 It is not uncommon for optimized code to have bundles which contain
4436 instructions from different source statements, thus it may happen that
4437 a breakpoint's address will be adjusted from one source statement to
4438 another. Since this adjustment may significantly alter @value{GDBN}'s
4439 breakpoint related behavior from what the user expects, a warning is
4440 printed when the breakpoint is first set and also when the breakpoint
4443 A warning like the one below is printed when setting a breakpoint
4444 that's been subject to address adjustment:
4447 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4450 Such warnings are printed both for user settable and @value{GDBN}'s
4451 internal breakpoints. If you see one of these warnings, you should
4452 verify that a breakpoint set at the adjusted address will have the
4453 desired affect. If not, the breakpoint in question may be removed and
4454 other breakpoints may be set which will have the desired behavior.
4455 E.g., it may be sufficient to place the breakpoint at a later
4456 instruction. A conditional breakpoint may also be useful in some
4457 cases to prevent the breakpoint from triggering too often.
4459 @value{GDBN} will also issue a warning when stopping at one of these
4460 adjusted breakpoints:
4463 warning: Breakpoint 1 address previously adjusted from 0x00010414
4467 When this warning is encountered, it may be too late to take remedial
4468 action except in cases where the breakpoint is hit earlier or more
4469 frequently than expected.
4471 @node Continuing and Stepping
4472 @section Continuing and Stepping
4476 @cindex resuming execution
4477 @dfn{Continuing} means resuming program execution until your program
4478 completes normally. In contrast, @dfn{stepping} means executing just
4479 one more ``step'' of your program, where ``step'' may mean either one
4480 line of source code, or one machine instruction (depending on what
4481 particular command you use). Either when continuing or when stepping,
4482 your program may stop even sooner, due to a breakpoint or a signal. (If
4483 it stops due to a signal, you may want to use @code{handle}, or use
4484 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4488 @kindex c @r{(@code{continue})}
4489 @kindex fg @r{(resume foreground execution)}
4490 @item continue @r{[}@var{ignore-count}@r{]}
4491 @itemx c @r{[}@var{ignore-count}@r{]}
4492 @itemx fg @r{[}@var{ignore-count}@r{]}
4493 Resume program execution, at the address where your program last stopped;
4494 any breakpoints set at that address are bypassed. The optional argument
4495 @var{ignore-count} allows you to specify a further number of times to
4496 ignore a breakpoint at this location; its effect is like that of
4497 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4499 The argument @var{ignore-count} is meaningful only when your program
4500 stopped due to a breakpoint. At other times, the argument to
4501 @code{continue} is ignored.
4503 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4504 debugged program is deemed to be the foreground program) are provided
4505 purely for convenience, and have exactly the same behavior as
4509 To resume execution at a different place, you can use @code{return}
4510 (@pxref{Returning, ,Returning from a Function}) to go back to the
4511 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4512 Different Address}) to go to an arbitrary location in your program.
4514 A typical technique for using stepping is to set a breakpoint
4515 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4516 beginning of the function or the section of your program where a problem
4517 is believed to lie, run your program until it stops at that breakpoint,
4518 and then step through the suspect area, examining the variables that are
4519 interesting, until you see the problem happen.
4523 @kindex s @r{(@code{step})}
4525 Continue running your program until control reaches a different source
4526 line, then stop it and return control to @value{GDBN}. This command is
4527 abbreviated @code{s}.
4530 @c "without debugging information" is imprecise; actually "without line
4531 @c numbers in the debugging information". (gcc -g1 has debugging info but
4532 @c not line numbers). But it seems complex to try to make that
4533 @c distinction here.
4534 @emph{Warning:} If you use the @code{step} command while control is
4535 within a function that was compiled without debugging information,
4536 execution proceeds until control reaches a function that does have
4537 debugging information. Likewise, it will not step into a function which
4538 is compiled without debugging information. To step through functions
4539 without debugging information, use the @code{stepi} command, described
4543 The @code{step} command only stops at the first instruction of a source
4544 line. This prevents the multiple stops that could otherwise occur in
4545 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4546 to stop if a function that has debugging information is called within
4547 the line. In other words, @code{step} @emph{steps inside} any functions
4548 called within the line.
4550 Also, the @code{step} command only enters a function if there is line
4551 number information for the function. Otherwise it acts like the
4552 @code{next} command. This avoids problems when using @code{cc -gl}
4553 on MIPS machines. Previously, @code{step} entered subroutines if there
4554 was any debugging information about the routine.
4556 @item step @var{count}
4557 Continue running as in @code{step}, but do so @var{count} times. If a
4558 breakpoint is reached, or a signal not related to stepping occurs before
4559 @var{count} steps, stepping stops right away.
4562 @kindex n @r{(@code{next})}
4563 @item next @r{[}@var{count}@r{]}
4564 Continue to the next source line in the current (innermost) stack frame.
4565 This is similar to @code{step}, but function calls that appear within
4566 the line of code are executed without stopping. Execution stops when
4567 control reaches a different line of code at the original stack level
4568 that was executing when you gave the @code{next} command. This command
4569 is abbreviated @code{n}.
4571 An argument @var{count} is a repeat count, as for @code{step}.
4574 @c FIX ME!! Do we delete this, or is there a way it fits in with
4575 @c the following paragraph? --- Vctoria
4577 @c @code{next} within a function that lacks debugging information acts like
4578 @c @code{step}, but any function calls appearing within the code of the
4579 @c function are executed without stopping.
4581 The @code{next} command only stops at the first instruction of a
4582 source line. This prevents multiple stops that could otherwise occur in
4583 @code{switch} statements, @code{for} loops, etc.
4585 @kindex set step-mode
4587 @cindex functions without line info, and stepping
4588 @cindex stepping into functions with no line info
4589 @itemx set step-mode on
4590 The @code{set step-mode on} command causes the @code{step} command to
4591 stop at the first instruction of a function which contains no debug line
4592 information rather than stepping over it.
4594 This is useful in cases where you may be interested in inspecting the
4595 machine instructions of a function which has no symbolic info and do not
4596 want @value{GDBN} to automatically skip over this function.
4598 @item set step-mode off
4599 Causes the @code{step} command to step over any functions which contains no
4600 debug information. This is the default.
4602 @item show step-mode
4603 Show whether @value{GDBN} will stop in or step over functions without
4604 source line debug information.
4607 @kindex fin @r{(@code{finish})}
4609 Continue running until just after function in the selected stack frame
4610 returns. Print the returned value (if any). This command can be
4611 abbreviated as @code{fin}.
4613 Contrast this with the @code{return} command (@pxref{Returning,
4614 ,Returning from a Function}).
4617 @kindex u @r{(@code{until})}
4618 @cindex run until specified location
4621 Continue running until a source line past the current line, in the
4622 current stack frame, is reached. This command is used to avoid single
4623 stepping through a loop more than once. It is like the @code{next}
4624 command, except that when @code{until} encounters a jump, it
4625 automatically continues execution until the program counter is greater
4626 than the address of the jump.
4628 This means that when you reach the end of a loop after single stepping
4629 though it, @code{until} makes your program continue execution until it
4630 exits the loop. In contrast, a @code{next} command at the end of a loop
4631 simply steps back to the beginning of the loop, which forces you to step
4632 through the next iteration.
4634 @code{until} always stops your program if it attempts to exit the current
4637 @code{until} may produce somewhat counterintuitive results if the order
4638 of machine code does not match the order of the source lines. For
4639 example, in the following excerpt from a debugging session, the @code{f}
4640 (@code{frame}) command shows that execution is stopped at line
4641 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4645 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4647 (@value{GDBP}) until
4648 195 for ( ; argc > 0; NEXTARG) @{
4651 This happened because, for execution efficiency, the compiler had
4652 generated code for the loop closure test at the end, rather than the
4653 start, of the loop---even though the test in a C @code{for}-loop is
4654 written before the body of the loop. The @code{until} command appeared
4655 to step back to the beginning of the loop when it advanced to this
4656 expression; however, it has not really gone to an earlier
4657 statement---not in terms of the actual machine code.
4659 @code{until} with no argument works by means of single
4660 instruction stepping, and hence is slower than @code{until} with an
4663 @item until @var{location}
4664 @itemx u @var{location}
4665 Continue running your program until either the specified location is
4666 reached, or the current stack frame returns. @var{location} is any of
4667 the forms described in @ref{Specify Location}.
4668 This form of the command uses temporary breakpoints, and
4669 hence is quicker than @code{until} without an argument. The specified
4670 location is actually reached only if it is in the current frame. This
4671 implies that @code{until} can be used to skip over recursive function
4672 invocations. For instance in the code below, if the current location is
4673 line @code{96}, issuing @code{until 99} will execute the program up to
4674 line @code{99} in the same invocation of factorial, i.e., after the inner
4675 invocations have returned.
4678 94 int factorial (int value)
4680 96 if (value > 1) @{
4681 97 value *= factorial (value - 1);
4688 @kindex advance @var{location}
4689 @itemx advance @var{location}
4690 Continue running the program up to the given @var{location}. An argument is
4691 required, which should be of one of the forms described in
4692 @ref{Specify Location}.
4693 Execution will also stop upon exit from the current stack
4694 frame. This command is similar to @code{until}, but @code{advance} will
4695 not skip over recursive function calls, and the target location doesn't
4696 have to be in the same frame as the current one.
4700 @kindex si @r{(@code{stepi})}
4702 @itemx stepi @var{arg}
4704 Execute one machine instruction, then stop and return to the debugger.
4706 It is often useful to do @samp{display/i $pc} when stepping by machine
4707 instructions. This makes @value{GDBN} automatically display the next
4708 instruction to be executed, each time your program stops. @xref{Auto
4709 Display,, Automatic Display}.
4711 An argument is a repeat count, as in @code{step}.
4715 @kindex ni @r{(@code{nexti})}
4717 @itemx nexti @var{arg}
4719 Execute one machine instruction, but if it is a function call,
4720 proceed until the function returns.
4722 An argument is a repeat count, as in @code{next}.
4729 A signal is an asynchronous event that can happen in a program. The
4730 operating system defines the possible kinds of signals, and gives each
4731 kind a name and a number. For example, in Unix @code{SIGINT} is the
4732 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4733 @code{SIGSEGV} is the signal a program gets from referencing a place in
4734 memory far away from all the areas in use; @code{SIGALRM} occurs when
4735 the alarm clock timer goes off (which happens only if your program has
4736 requested an alarm).
4738 @cindex fatal signals
4739 Some signals, including @code{SIGALRM}, are a normal part of the
4740 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4741 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4742 program has not specified in advance some other way to handle the signal.
4743 @code{SIGINT} does not indicate an error in your program, but it is normally
4744 fatal so it can carry out the purpose of the interrupt: to kill the program.
4746 @value{GDBN} has the ability to detect any occurrence of a signal in your
4747 program. You can tell @value{GDBN} in advance what to do for each kind of
4750 @cindex handling signals
4751 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4752 @code{SIGALRM} be silently passed to your program
4753 (so as not to interfere with their role in the program's functioning)
4754 but to stop your program immediately whenever an error signal happens.
4755 You can change these settings with the @code{handle} command.
4758 @kindex info signals
4762 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4763 handle each one. You can use this to see the signal numbers of all
4764 the defined types of signals.
4766 @item info signals @var{sig}
4767 Similar, but print information only about the specified signal number.
4769 @code{info handle} is an alias for @code{info signals}.
4772 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4773 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4774 can be the number of a signal or its name (with or without the
4775 @samp{SIG} at the beginning); a list of signal numbers of the form
4776 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4777 known signals. Optional arguments @var{keywords}, described below,
4778 say what change to make.
4782 The keywords allowed by the @code{handle} command can be abbreviated.
4783 Their full names are:
4787 @value{GDBN} should not stop your program when this signal happens. It may
4788 still print a message telling you that the signal has come in.
4791 @value{GDBN} should stop your program when this signal happens. This implies
4792 the @code{print} keyword as well.
4795 @value{GDBN} should print a message when this signal happens.
4798 @value{GDBN} should not mention the occurrence of the signal at all. This
4799 implies the @code{nostop} keyword as well.
4803 @value{GDBN} should allow your program to see this signal; your program
4804 can handle the signal, or else it may terminate if the signal is fatal
4805 and not handled. @code{pass} and @code{noignore} are synonyms.
4809 @value{GDBN} should not allow your program to see this signal.
4810 @code{nopass} and @code{ignore} are synonyms.
4814 When a signal stops your program, the signal is not visible to the
4816 continue. Your program sees the signal then, if @code{pass} is in
4817 effect for the signal in question @emph{at that time}. In other words,
4818 after @value{GDBN} reports a signal, you can use the @code{handle}
4819 command with @code{pass} or @code{nopass} to control whether your
4820 program sees that signal when you continue.
4822 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4823 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4824 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4827 You can also use the @code{signal} command to prevent your program from
4828 seeing a signal, or cause it to see a signal it normally would not see,
4829 or to give it any signal at any time. For example, if your program stopped
4830 due to some sort of memory reference error, you might store correct
4831 values into the erroneous variables and continue, hoping to see more
4832 execution; but your program would probably terminate immediately as
4833 a result of the fatal signal once it saw the signal. To prevent this,
4834 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4837 @cindex extra signal information
4838 @anchor{extra signal information}
4840 On some targets, @value{GDBN} can inspect extra signal information
4841 associated with the intercepted signal, before it is actually
4842 delivered to the program being debugged. This information is exported
4843 by the convenience variable @code{$_siginfo}, and consists of data
4844 that is passed by the kernel to the signal handler at the time of the
4845 receipt of a signal. The data type of the information itself is
4846 target dependent. You can see the data type using the @code{ptype
4847 $_siginfo} command. On Unix systems, it typically corresponds to the
4848 standard @code{siginfo_t} type, as defined in the @file{signal.h}
4851 Here's an example, on a @sc{gnu}/Linux system, printing the stray
4852 referenced address that raised a segmentation fault.
4856 (@value{GDBP}) continue
4857 Program received signal SIGSEGV, Segmentation fault.
4858 0x0000000000400766 in main ()
4860 (@value{GDBP}) ptype $_siginfo
4867 struct @{...@} _kill;
4868 struct @{...@} _timer;
4870 struct @{...@} _sigchld;
4871 struct @{...@} _sigfault;
4872 struct @{...@} _sigpoll;
4875 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
4879 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
4880 $1 = (void *) 0x7ffff7ff7000
4884 Depending on target support, @code{$_siginfo} may also be writable.
4887 @section Stopping and Starting Multi-thread Programs
4889 @cindex stopped threads
4890 @cindex threads, stopped
4892 @cindex continuing threads
4893 @cindex threads, continuing
4895 @value{GDBN} supports debugging programs with multiple threads
4896 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
4897 are two modes of controlling execution of your program within the
4898 debugger. In the default mode, referred to as @dfn{all-stop mode},
4899 when any thread in your program stops (for example, at a breakpoint
4900 or while being stepped), all other threads in the program are also stopped by
4901 @value{GDBN}. On some targets, @value{GDBN} also supports
4902 @dfn{non-stop mode}, in which other threads can continue to run freely while
4903 you examine the stopped thread in the debugger.
4906 * All-Stop Mode:: All threads stop when GDB takes control
4907 * Non-Stop Mode:: Other threads continue to execute
4908 * Background Execution:: Running your program asynchronously
4909 * Thread-Specific Breakpoints:: Controlling breakpoints
4910 * Interrupted System Calls:: GDB may interfere with system calls
4914 @subsection All-Stop Mode
4916 @cindex all-stop mode
4918 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
4919 @emph{all} threads of execution stop, not just the current thread. This
4920 allows you to examine the overall state of the program, including
4921 switching between threads, without worrying that things may change
4924 Conversely, whenever you restart the program, @emph{all} threads start
4925 executing. @emph{This is true even when single-stepping} with commands
4926 like @code{step} or @code{next}.
4928 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4929 Since thread scheduling is up to your debugging target's operating
4930 system (not controlled by @value{GDBN}), other threads may
4931 execute more than one statement while the current thread completes a
4932 single step. Moreover, in general other threads stop in the middle of a
4933 statement, rather than at a clean statement boundary, when the program
4936 You might even find your program stopped in another thread after
4937 continuing or even single-stepping. This happens whenever some other
4938 thread runs into a breakpoint, a signal, or an exception before the
4939 first thread completes whatever you requested.
4941 @cindex automatic thread selection
4942 @cindex switching threads automatically
4943 @cindex threads, automatic switching
4944 Whenever @value{GDBN} stops your program, due to a breakpoint or a
4945 signal, it automatically selects the thread where that breakpoint or
4946 signal happened. @value{GDBN} alerts you to the context switch with a
4947 message such as @samp{[Switching to Thread @var{n}]} to identify the
4950 On some OSes, you can modify @value{GDBN}'s default behavior by
4951 locking the OS scheduler to allow only a single thread to run.
4954 @item set scheduler-locking @var{mode}
4955 @cindex scheduler locking mode
4956 @cindex lock scheduler
4957 Set the scheduler locking mode. If it is @code{off}, then there is no
4958 locking and any thread may run at any time. If @code{on}, then only the
4959 current thread may run when the inferior is resumed. The @code{step}
4960 mode optimizes for single-stepping; it prevents other threads
4961 from preempting the current thread while you are stepping, so that
4962 the focus of debugging does not change unexpectedly.
4963 Other threads only rarely (or never) get a chance to run
4964 when you step. They are more likely to run when you @samp{next} over a
4965 function call, and they are completely free to run when you use commands
4966 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4967 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
4968 the current thread away from the thread that you are debugging.
4970 @item show scheduler-locking
4971 Display the current scheduler locking mode.
4974 @cindex resume threads of multiple processes simultaneously
4975 By default, when you issue one of the execution commands such as
4976 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
4977 threads of the current inferior to run. For example, if @value{GDBN}
4978 is attached to two inferiors, each with two threads, the
4979 @code{continue} command resumes only the two threads of the current
4980 inferior. This is useful, for example, when you debug a program that
4981 forks and you want to hold the parent stopped (so that, for instance,
4982 it doesn't run to exit), while you debug the child. In other
4983 situations, you may not be interested in inspecting the current state
4984 of any of the processes @value{GDBN} is attached to, and you may want
4985 to resume them all until some breakpoint is hit. In the latter case,
4986 you can instruct @value{GDBN} to allow all threads of all the
4987 inferiors to run with the @w{@code{set schedule-multiple}} command.
4990 @kindex set schedule-multiple
4991 @item set schedule-multiple
4992 Set the mode for allowing threads of multiple processes to be resumed
4993 when an execution command is issued. When @code{on}, all threads of
4994 all processes are allowed to run. When @code{off}, only the threads
4995 of the current process are resumed. The default is @code{off}. The
4996 @code{scheduler-locking} mode takes precedence when set to @code{on},
4997 or while you are stepping and set to @code{step}.
4999 @item show schedule-multiple
5000 Display the current mode for resuming the execution of threads of
5005 @subsection Non-Stop Mode
5007 @cindex non-stop mode
5009 @c This section is really only a place-holder, and needs to be expanded
5010 @c with more details.
5012 For some multi-threaded targets, @value{GDBN} supports an optional
5013 mode of operation in which you can examine stopped program threads in
5014 the debugger while other threads continue to execute freely. This
5015 minimizes intrusion when debugging live systems, such as programs
5016 where some threads have real-time constraints or must continue to
5017 respond to external events. This is referred to as @dfn{non-stop} mode.
5019 In non-stop mode, when a thread stops to report a debugging event,
5020 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5021 threads as well, in contrast to the all-stop mode behavior. Additionally,
5022 execution commands such as @code{continue} and @code{step} apply by default
5023 only to the current thread in non-stop mode, rather than all threads as
5024 in all-stop mode. This allows you to control threads explicitly in
5025 ways that are not possible in all-stop mode --- for example, stepping
5026 one thread while allowing others to run freely, stepping
5027 one thread while holding all others stopped, or stepping several threads
5028 independently and simultaneously.
5030 To enter non-stop mode, use this sequence of commands before you run
5031 or attach to your program:
5034 # Enable the async interface.
5037 # If using the CLI, pagination breaks non-stop.
5040 # Finally, turn it on!
5044 You can use these commands to manipulate the non-stop mode setting:
5047 @kindex set non-stop
5048 @item set non-stop on
5049 Enable selection of non-stop mode.
5050 @item set non-stop off
5051 Disable selection of non-stop mode.
5052 @kindex show non-stop
5054 Show the current non-stop enablement setting.
5057 Note these commands only reflect whether non-stop mode is enabled,
5058 not whether the currently-executing program is being run in non-stop mode.
5059 In particular, the @code{set non-stop} preference is only consulted when
5060 @value{GDBN} starts or connects to the target program, and it is generally
5061 not possible to switch modes once debugging has started. Furthermore,
5062 since not all targets support non-stop mode, even when you have enabled
5063 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5066 In non-stop mode, all execution commands apply only to the current thread
5067 by default. That is, @code{continue} only continues one thread.
5068 To continue all threads, issue @code{continue -a} or @code{c -a}.
5070 You can use @value{GDBN}'s background execution commands
5071 (@pxref{Background Execution}) to run some threads in the background
5072 while you continue to examine or step others from @value{GDBN}.
5073 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5074 always executed asynchronously in non-stop mode.
5076 Suspending execution is done with the @code{interrupt} command when
5077 running in the background, or @kbd{Ctrl-c} during foreground execution.
5078 In all-stop mode, this stops the whole process;
5079 but in non-stop mode the interrupt applies only to the current thread.
5080 To stop the whole program, use @code{interrupt -a}.
5082 Other execution commands do not currently support the @code{-a} option.
5084 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5085 that thread current, as it does in all-stop mode. This is because the
5086 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5087 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5088 changed to a different thread just as you entered a command to operate on the
5089 previously current thread.
5091 @node Background Execution
5092 @subsection Background Execution
5094 @cindex foreground execution
5095 @cindex background execution
5096 @cindex asynchronous execution
5097 @cindex execution, foreground, background and asynchronous
5099 @value{GDBN}'s execution commands have two variants: the normal
5100 foreground (synchronous) behavior, and a background
5101 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5102 the program to report that some thread has stopped before prompting for
5103 another command. In background execution, @value{GDBN} immediately gives
5104 a command prompt so that you can issue other commands while your program runs.
5106 You need to explicitly enable asynchronous mode before you can use
5107 background execution commands. You can use these commands to
5108 manipulate the asynchronous mode setting:
5111 @kindex set target-async
5112 @item set target-async on
5113 Enable asynchronous mode.
5114 @item set target-async off
5115 Disable asynchronous mode.
5116 @kindex show target-async
5117 @item show target-async
5118 Show the current target-async setting.
5121 If the target doesn't support async mode, @value{GDBN} issues an error
5122 message if you attempt to use the background execution commands.
5124 To specify background execution, add a @code{&} to the command. For example,
5125 the background form of the @code{continue} command is @code{continue&}, or
5126 just @code{c&}. The execution commands that accept background execution
5132 @xref{Starting, , Starting your Program}.
5136 @xref{Attach, , Debugging an Already-running Process}.
5140 @xref{Continuing and Stepping, step}.
5144 @xref{Continuing and Stepping, stepi}.
5148 @xref{Continuing and Stepping, next}.
5152 @xref{Continuing and Stepping, nexti}.
5156 @xref{Continuing and Stepping, continue}.
5160 @xref{Continuing and Stepping, finish}.
5164 @xref{Continuing and Stepping, until}.
5168 Background execution is especially useful in conjunction with non-stop
5169 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5170 However, you can also use these commands in the normal all-stop mode with
5171 the restriction that you cannot issue another execution command until the
5172 previous one finishes. Examples of commands that are valid in all-stop
5173 mode while the program is running include @code{help} and @code{info break}.
5175 You can interrupt your program while it is running in the background by
5176 using the @code{interrupt} command.
5183 Suspend execution of the running program. In all-stop mode,
5184 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5185 only the current thread. To stop the whole program in non-stop mode,
5186 use @code{interrupt -a}.
5189 @node Thread-Specific Breakpoints
5190 @subsection Thread-Specific Breakpoints
5192 When your program has multiple threads (@pxref{Threads,, Debugging
5193 Programs with Multiple Threads}), you can choose whether to set
5194 breakpoints on all threads, or on a particular thread.
5197 @cindex breakpoints and threads
5198 @cindex thread breakpoints
5199 @kindex break @dots{} thread @var{threadno}
5200 @item break @var{linespec} thread @var{threadno}
5201 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5202 @var{linespec} specifies source lines; there are several ways of
5203 writing them (@pxref{Specify Location}), but the effect is always to
5204 specify some source line.
5206 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5207 to specify that you only want @value{GDBN} to stop the program when a
5208 particular thread reaches this breakpoint. @var{threadno} is one of the
5209 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5210 column of the @samp{info threads} display.
5212 If you do not specify @samp{thread @var{threadno}} when you set a
5213 breakpoint, the breakpoint applies to @emph{all} threads of your
5216 You can use the @code{thread} qualifier on conditional breakpoints as
5217 well; in this case, place @samp{thread @var{threadno}} before the
5218 breakpoint condition, like this:
5221 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5226 @node Interrupted System Calls
5227 @subsection Interrupted System Calls
5229 @cindex thread breakpoints and system calls
5230 @cindex system calls and thread breakpoints
5231 @cindex premature return from system calls
5232 There is an unfortunate side effect when using @value{GDBN} to debug
5233 multi-threaded programs. If one thread stops for a
5234 breakpoint, or for some other reason, and another thread is blocked in a
5235 system call, then the system call may return prematurely. This is a
5236 consequence of the interaction between multiple threads and the signals
5237 that @value{GDBN} uses to implement breakpoints and other events that
5240 To handle this problem, your program should check the return value of
5241 each system call and react appropriately. This is good programming
5244 For example, do not write code like this:
5250 The call to @code{sleep} will return early if a different thread stops
5251 at a breakpoint or for some other reason.
5253 Instead, write this:
5258 unslept = sleep (unslept);
5261 A system call is allowed to return early, so the system is still
5262 conforming to its specification. But @value{GDBN} does cause your
5263 multi-threaded program to behave differently than it would without
5266 Also, @value{GDBN} uses internal breakpoints in the thread library to
5267 monitor certain events such as thread creation and thread destruction.
5268 When such an event happens, a system call in another thread may return
5269 prematurely, even though your program does not appear to stop.
5272 @node Reverse Execution
5273 @chapter Running programs backward
5274 @cindex reverse execution
5275 @cindex running programs backward
5277 When you are debugging a program, it is not unusual to realize that
5278 you have gone too far, and some event of interest has already happened.
5279 If the target environment supports it, @value{GDBN} can allow you to
5280 ``rewind'' the program by running it backward.
5282 A target environment that supports reverse execution should be able
5283 to ``undo'' the changes in machine state that have taken place as the
5284 program was executing normally. Variables, registers etc.@: should
5285 revert to their previous values. Obviously this requires a great
5286 deal of sophistication on the part of the target environment; not
5287 all target environments can support reverse execution.
5289 When a program is executed in reverse, the instructions that
5290 have most recently been executed are ``un-executed'', in reverse
5291 order. The program counter runs backward, following the previous
5292 thread of execution in reverse. As each instruction is ``un-executed'',
5293 the values of memory and/or registers that were changed by that
5294 instruction are reverted to their previous states. After executing
5295 a piece of source code in reverse, all side effects of that code
5296 should be ``undone'', and all variables should be returned to their
5297 prior values@footnote{
5298 Note that some side effects are easier to undo than others. For instance,
5299 memory and registers are relatively easy, but device I/O is hard. Some
5300 targets may be able undo things like device I/O, and some may not.
5302 The contract between @value{GDBN} and the reverse executing target
5303 requires only that the target do something reasonable when
5304 @value{GDBN} tells it to execute backwards, and then report the
5305 results back to @value{GDBN}. Whatever the target reports back to
5306 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5307 assumes that the memory and registers that the target reports are in a
5308 consistant state, but @value{GDBN} accepts whatever it is given.
5311 If you are debugging in a target environment that supports
5312 reverse execution, @value{GDBN} provides the following commands.
5315 @kindex reverse-continue
5316 @kindex rc @r{(@code{reverse-continue})}
5317 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5318 @itemx rc @r{[}@var{ignore-count}@r{]}
5319 Beginning at the point where your program last stopped, start executing
5320 in reverse. Reverse execution will stop for breakpoints and synchronous
5321 exceptions (signals), just like normal execution. Behavior of
5322 asynchronous signals depends on the target environment.
5324 @kindex reverse-step
5325 @kindex rs @r{(@code{step})}
5326 @item reverse-step @r{[}@var{count}@r{]}
5327 Run the program backward until control reaches the start of a
5328 different source line; then stop it, and return control to @value{GDBN}.
5330 Like the @code{step} command, @code{reverse-step} will only stop
5331 at the beginning of a source line. It ``un-executes'' the previously
5332 executed source line. If the previous source line included calls to
5333 debuggable functions, @code{reverse-step} will step (backward) into
5334 the called function, stopping at the beginning of the @emph{last}
5335 statement in the called function (typically a return statement).
5337 Also, as with the @code{step} command, if non-debuggable functions are
5338 called, @code{reverse-step} will run thru them backward without stopping.
5340 @kindex reverse-stepi
5341 @kindex rsi @r{(@code{reverse-stepi})}
5342 @item reverse-stepi @r{[}@var{count}@r{]}
5343 Reverse-execute one machine instruction. Note that the instruction
5344 to be reverse-executed is @emph{not} the one pointed to by the program
5345 counter, but the instruction executed prior to that one. For instance,
5346 if the last instruction was a jump, @code{reverse-stepi} will take you
5347 back from the destination of the jump to the jump instruction itself.
5349 @kindex reverse-next
5350 @kindex rn @r{(@code{reverse-next})}
5351 @item reverse-next @r{[}@var{count}@r{]}
5352 Run backward to the beginning of the previous line executed in
5353 the current (innermost) stack frame. If the line contains function
5354 calls, they will be ``un-executed'' without stopping. Starting from
5355 the first line of a function, @code{reverse-next} will take you back
5356 to the caller of that function, @emph{before} the function was called,
5357 just as the normal @code{next} command would take you from the last
5358 line of a function back to its return to its caller
5359 @footnote{Unles the code is too heavily optimized.}.
5361 @kindex reverse-nexti
5362 @kindex rni @r{(@code{reverse-nexti})}
5363 @item reverse-nexti @r{[}@var{count}@r{]}
5364 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5365 in reverse, except that called functions are ``un-executed'' atomically.
5366 That is, if the previously executed instruction was a return from
5367 another instruction, @code{reverse-nexti} will continue to execute
5368 in reverse until the call to that function (from the current stack
5371 @kindex reverse-finish
5372 @item reverse-finish
5373 Just as the @code{finish} command takes you to the point where the
5374 current function returns, @code{reverse-finish} takes you to the point
5375 where it was called. Instead of ending up at the end of the current
5376 function invocation, you end up at the beginning.
5378 @kindex set exec-direction
5379 @item set exec-direction
5380 Set the direction of target execution.
5381 @itemx set exec-direction reverse
5382 @cindex execute forward or backward in time
5383 @value{GDBN} will perform all execution commands in reverse, until the
5384 exec-direction mode is changed to ``forward''. Affected commands include
5385 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5386 command cannot be used in reverse mode.
5387 @item set exec-direction forward
5388 @value{GDBN} will perform all execution commands in the normal fashion.
5389 This is the default.
5393 @node Process Record and Replay
5394 @chapter Recording Inferior's Execution and Replaying It
5395 @cindex process record and replay
5396 @cindex recording inferior's execution and replaying it
5398 On some platforms, @value{GDBN} provides a special @dfn{process record
5399 and replay} target that can record a log of the process execution, and
5400 replay it later with both forward and reverse execution commands.
5403 When this target is in use, if the execution log includes the record
5404 for the next instruction, @value{GDBN} will debug in @dfn{replay
5405 mode}. In the replay mode, the inferior does not really execute code
5406 instructions. Instead, all the events that normally happen during
5407 code execution are taken from the execution log. While code is not
5408 really executed in replay mode, the values of registers (including the
5409 program counter register) and the memory of the inferior are still
5410 changed as they normally would. Their contents are taken from the
5414 If the record for the next instruction is not in the execution log,
5415 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5416 inferior executes normally, and @value{GDBN} records the execution log
5419 The process record and replay target supports reverse execution
5420 (@pxref{Reverse Execution}), even if the platform on which the
5421 inferior runs does not. However, the reverse execution is limited in
5422 this case by the range of the instructions recorded in the execution
5423 log. In other words, reverse execution on platforms that don't
5424 support it directly can only be done in the replay mode.
5426 When debugging in the reverse direction, @value{GDBN} will work in
5427 replay mode as long as the execution log includes the record for the
5428 previous instruction; otherwise, it will work in record mode, if the
5429 platform supports reverse execution, or stop if not.
5431 For architecture environments that support process record and replay,
5432 @value{GDBN} provides the following commands:
5435 @kindex target record
5439 This command starts the process record and replay target. The process
5440 record and replay target can only debug a process that is already
5441 running. Therefore, you need first to start the process with the
5442 @kbd{run} or @kbd{start} commands, and then start the recording with
5443 the @kbd{target record} command.
5445 Both @code{record} and @code{rec} are aliases of @code{target record}.
5447 @cindex displaced stepping, and process record and replay
5448 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5449 will be automatically disabled when process record and replay target
5450 is started. That's because the process record and replay target
5451 doesn't support displaced stepping.
5453 @cindex non-stop mode, and process record and replay
5454 @cindex asynchronous execution, and process record and replay
5455 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5456 the asynchronous execution mode (@pxref{Background Execution}), the
5457 process record and replay target cannot be started because it doesn't
5458 support these two modes.
5463 Stop the process record and replay target. When process record and
5464 replay target stops, the entire execution log will be deleted and the
5465 inferior will either be terminated, or will remain in its final state.
5467 When you stop the process record and replay target in record mode (at
5468 the end of the execution log), the inferior will be stopped at the
5469 next instruction that would have been recorded. In other words, if
5470 you record for a while and then stop recording, the inferior process
5471 will be left in the same state as if the recording never happened.
5473 On the other hand, if the process record and replay target is stopped
5474 while in replay mode (that is, not at the end of the execution log,
5475 but at some earlier point), the inferior process will become ``live''
5476 at that earlier state, and it will then be possible to continue the
5477 usual ``live'' debugging of the process from that state.
5479 When the inferior process exits, or @value{GDBN} detaches from it,
5480 process record and replay target will automatically stop itself.
5482 @kindex set record insn-number-max
5483 @item set record insn-number-max @var{limit}
5484 Set the limit of instructions to be recorded. Default value is 200000.
5486 If @var{limit} is a positive number, then @value{GDBN} will start
5487 deleting instructions from the log once the number of the record
5488 instructions becomes greater than @var{limit}. For every new recorded
5489 instruction, @value{GDBN} will delete the earliest recorded
5490 instruction to keep the number of recorded instructions at the limit.
5491 (Since deleting recorded instructions loses information, @value{GDBN}
5492 lets you control what happens when the limit is reached, by means of
5493 the @code{stop-at-limit} option, described below.)
5495 If @var{limit} is zero, @value{GDBN} will never delete recorded
5496 instructions from the execution log. The number of recorded
5497 instructions is unlimited in this case.
5499 @kindex show record insn-number-max
5500 @item show record insn-number-max
5501 Show the limit of instructions to be recorded.
5503 @kindex set record stop-at-limit
5504 @item set record stop-at-limit
5505 Control the behavior when the number of recorded instructions reaches
5506 the limit. If ON (the default), @value{GDBN} will stop when the limit
5507 is reached for the first time and ask you whether you want to stop the
5508 inferior or continue running it and recording the execution log. If
5509 you decide to continue recording, each new recorded instruction will
5510 cause the oldest one to be deleted.
5512 If this option is OFF, @value{GDBN} will automatically delete the
5513 oldest record to make room for each new one, without asking.
5515 @kindex show record stop-at-limit
5516 @item show record stop-at-limit
5517 Show the current setting of @code{stop-at-limit}.
5521 Show various statistics about the state of process record and its
5522 in-memory execution log buffer, including:
5526 Whether in record mode or replay mode.
5528 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
5530 Highest recorded instruction number.
5532 Current instruction about to be replayed (if in replay mode).
5534 Number of instructions contained in the execution log.
5536 Maximum number of instructions that may be contained in the execution log.
5539 @kindex record delete
5542 When record target runs in replay mode (``in the past''), delete the
5543 subsequent execution log and begin to record a new execution log starting
5544 from the current address. This means you will abandon the previously
5545 recorded ``future'' and begin recording a new ``future''.
5550 @chapter Examining the Stack
5552 When your program has stopped, the first thing you need to know is where it
5553 stopped and how it got there.
5556 Each time your program performs a function call, information about the call
5558 That information includes the location of the call in your program,
5559 the arguments of the call,
5560 and the local variables of the function being called.
5561 The information is saved in a block of data called a @dfn{stack frame}.
5562 The stack frames are allocated in a region of memory called the @dfn{call
5565 When your program stops, the @value{GDBN} commands for examining the
5566 stack allow you to see all of this information.
5568 @cindex selected frame
5569 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5570 @value{GDBN} commands refer implicitly to the selected frame. In
5571 particular, whenever you ask @value{GDBN} for the value of a variable in
5572 your program, the value is found in the selected frame. There are
5573 special @value{GDBN} commands to select whichever frame you are
5574 interested in. @xref{Selection, ,Selecting a Frame}.
5576 When your program stops, @value{GDBN} automatically selects the
5577 currently executing frame and describes it briefly, similar to the
5578 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5581 * Frames:: Stack frames
5582 * Backtrace:: Backtraces
5583 * Selection:: Selecting a frame
5584 * Frame Info:: Information on a frame
5589 @section Stack Frames
5591 @cindex frame, definition
5593 The call stack is divided up into contiguous pieces called @dfn{stack
5594 frames}, or @dfn{frames} for short; each frame is the data associated
5595 with one call to one function. The frame contains the arguments given
5596 to the function, the function's local variables, and the address at
5597 which the function is executing.
5599 @cindex initial frame
5600 @cindex outermost frame
5601 @cindex innermost frame
5602 When your program is started, the stack has only one frame, that of the
5603 function @code{main}. This is called the @dfn{initial} frame or the
5604 @dfn{outermost} frame. Each time a function is called, a new frame is
5605 made. Each time a function returns, the frame for that function invocation
5606 is eliminated. If a function is recursive, there can be many frames for
5607 the same function. The frame for the function in which execution is
5608 actually occurring is called the @dfn{innermost} frame. This is the most
5609 recently created of all the stack frames that still exist.
5611 @cindex frame pointer
5612 Inside your program, stack frames are identified by their addresses. A
5613 stack frame consists of many bytes, each of which has its own address; each
5614 kind of computer has a convention for choosing one byte whose
5615 address serves as the address of the frame. Usually this address is kept
5616 in a register called the @dfn{frame pointer register}
5617 (@pxref{Registers, $fp}) while execution is going on in that frame.
5619 @cindex frame number
5620 @value{GDBN} assigns numbers to all existing stack frames, starting with
5621 zero for the innermost frame, one for the frame that called it,
5622 and so on upward. These numbers do not really exist in your program;
5623 they are assigned by @value{GDBN} to give you a way of designating stack
5624 frames in @value{GDBN} commands.
5626 @c The -fomit-frame-pointer below perennially causes hbox overflow
5627 @c underflow problems.
5628 @cindex frameless execution
5629 Some compilers provide a way to compile functions so that they operate
5630 without stack frames. (For example, the @value{NGCC} option
5632 @samp{-fomit-frame-pointer}
5634 generates functions without a frame.)
5635 This is occasionally done with heavily used library functions to save
5636 the frame setup time. @value{GDBN} has limited facilities for dealing
5637 with these function invocations. If the innermost function invocation
5638 has no stack frame, @value{GDBN} nevertheless regards it as though
5639 it had a separate frame, which is numbered zero as usual, allowing
5640 correct tracing of the function call chain. However, @value{GDBN} has
5641 no provision for frameless functions elsewhere in the stack.
5644 @kindex frame@r{, command}
5645 @cindex current stack frame
5646 @item frame @var{args}
5647 The @code{frame} command allows you to move from one stack frame to another,
5648 and to print the stack frame you select. @var{args} may be either the
5649 address of the frame or the stack frame number. Without an argument,
5650 @code{frame} prints the current stack frame.
5652 @kindex select-frame
5653 @cindex selecting frame silently
5655 The @code{select-frame} command allows you to move from one stack frame
5656 to another without printing the frame. This is the silent version of
5664 @cindex call stack traces
5665 A backtrace is a summary of how your program got where it is. It shows one
5666 line per frame, for many frames, starting with the currently executing
5667 frame (frame zero), followed by its caller (frame one), and on up the
5672 @kindex bt @r{(@code{backtrace})}
5675 Print a backtrace of the entire stack: one line per frame for all
5676 frames in the stack.
5678 You can stop the backtrace at any time by typing the system interrupt
5679 character, normally @kbd{Ctrl-c}.
5681 @item backtrace @var{n}
5683 Similar, but print only the innermost @var{n} frames.
5685 @item backtrace -@var{n}
5687 Similar, but print only the outermost @var{n} frames.
5689 @item backtrace full
5691 @itemx bt full @var{n}
5692 @itemx bt full -@var{n}
5693 Print the values of the local variables also. @var{n} specifies the
5694 number of frames to print, as described above.
5699 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5700 are additional aliases for @code{backtrace}.
5702 @cindex multiple threads, backtrace
5703 In a multi-threaded program, @value{GDBN} by default shows the
5704 backtrace only for the current thread. To display the backtrace for
5705 several or all of the threads, use the command @code{thread apply}
5706 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5707 apply all backtrace}, @value{GDBN} will display the backtrace for all
5708 the threads; this is handy when you debug a core dump of a
5709 multi-threaded program.
5711 Each line in the backtrace shows the frame number and the function name.
5712 The program counter value is also shown---unless you use @code{set
5713 print address off}. The backtrace also shows the source file name and
5714 line number, as well as the arguments to the function. The program
5715 counter value is omitted if it is at the beginning of the code for that
5718 Here is an example of a backtrace. It was made with the command
5719 @samp{bt 3}, so it shows the innermost three frames.
5723 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5725 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
5726 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5728 (More stack frames follow...)
5733 The display for frame zero does not begin with a program counter
5734 value, indicating that your program has stopped at the beginning of the
5735 code for line @code{993} of @code{builtin.c}.
5738 The value of parameter @code{data} in frame 1 has been replaced by
5739 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
5740 only if it is a scalar (integer, pointer, enumeration, etc). See command
5741 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
5742 on how to configure the way function parameter values are printed.
5744 @cindex value optimized out, in backtrace
5745 @cindex function call arguments, optimized out
5746 If your program was compiled with optimizations, some compilers will
5747 optimize away arguments passed to functions if those arguments are
5748 never used after the call. Such optimizations generate code that
5749 passes arguments through registers, but doesn't store those arguments
5750 in the stack frame. @value{GDBN} has no way of displaying such
5751 arguments in stack frames other than the innermost one. Here's what
5752 such a backtrace might look like:
5756 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5758 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
5759 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
5761 (More stack frames follow...)
5766 The values of arguments that were not saved in their stack frames are
5767 shown as @samp{<value optimized out>}.
5769 If you need to display the values of such optimized-out arguments,
5770 either deduce that from other variables whose values depend on the one
5771 you are interested in, or recompile without optimizations.
5773 @cindex backtrace beyond @code{main} function
5774 @cindex program entry point
5775 @cindex startup code, and backtrace
5776 Most programs have a standard user entry point---a place where system
5777 libraries and startup code transition into user code. For C this is
5778 @code{main}@footnote{
5779 Note that embedded programs (the so-called ``free-standing''
5780 environment) are not required to have a @code{main} function as the
5781 entry point. They could even have multiple entry points.}.
5782 When @value{GDBN} finds the entry function in a backtrace
5783 it will terminate the backtrace, to avoid tracing into highly
5784 system-specific (and generally uninteresting) code.
5786 If you need to examine the startup code, or limit the number of levels
5787 in a backtrace, you can change this behavior:
5790 @item set backtrace past-main
5791 @itemx set backtrace past-main on
5792 @kindex set backtrace
5793 Backtraces will continue past the user entry point.
5795 @item set backtrace past-main off
5796 Backtraces will stop when they encounter the user entry point. This is the
5799 @item show backtrace past-main
5800 @kindex show backtrace
5801 Display the current user entry point backtrace policy.
5803 @item set backtrace past-entry
5804 @itemx set backtrace past-entry on
5805 Backtraces will continue past the internal entry point of an application.
5806 This entry point is encoded by the linker when the application is built,
5807 and is likely before the user entry point @code{main} (or equivalent) is called.
5809 @item set backtrace past-entry off
5810 Backtraces will stop when they encounter the internal entry point of an
5811 application. This is the default.
5813 @item show backtrace past-entry
5814 Display the current internal entry point backtrace policy.
5816 @item set backtrace limit @var{n}
5817 @itemx set backtrace limit 0
5818 @cindex backtrace limit
5819 Limit the backtrace to @var{n} levels. A value of zero means
5822 @item show backtrace limit
5823 Display the current limit on backtrace levels.
5827 @section Selecting a Frame
5829 Most commands for examining the stack and other data in your program work on
5830 whichever stack frame is selected at the moment. Here are the commands for
5831 selecting a stack frame; all of them finish by printing a brief description
5832 of the stack frame just selected.
5835 @kindex frame@r{, selecting}
5836 @kindex f @r{(@code{frame})}
5839 Select frame number @var{n}. Recall that frame zero is the innermost
5840 (currently executing) frame, frame one is the frame that called the
5841 innermost one, and so on. The highest-numbered frame is the one for
5844 @item frame @var{addr}
5846 Select the frame at address @var{addr}. This is useful mainly if the
5847 chaining of stack frames has been damaged by a bug, making it
5848 impossible for @value{GDBN} to assign numbers properly to all frames. In
5849 addition, this can be useful when your program has multiple stacks and
5850 switches between them.
5852 On the SPARC architecture, @code{frame} needs two addresses to
5853 select an arbitrary frame: a frame pointer and a stack pointer.
5855 On the MIPS and Alpha architecture, it needs two addresses: a stack
5856 pointer and a program counter.
5858 On the 29k architecture, it needs three addresses: a register stack
5859 pointer, a program counter, and a memory stack pointer.
5863 Move @var{n} frames up the stack. For positive numbers @var{n}, this
5864 advances toward the outermost frame, to higher frame numbers, to frames
5865 that have existed longer. @var{n} defaults to one.
5868 @kindex do @r{(@code{down})}
5870 Move @var{n} frames down the stack. For positive numbers @var{n}, this
5871 advances toward the innermost frame, to lower frame numbers, to frames
5872 that were created more recently. @var{n} defaults to one. You may
5873 abbreviate @code{down} as @code{do}.
5876 All of these commands end by printing two lines of output describing the
5877 frame. The first line shows the frame number, the function name, the
5878 arguments, and the source file and line number of execution in that
5879 frame. The second line shows the text of that source line.
5887 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
5889 10 read_input_file (argv[i]);
5893 After such a printout, the @code{list} command with no arguments
5894 prints ten lines centered on the point of execution in the frame.
5895 You can also edit the program at the point of execution with your favorite
5896 editing program by typing @code{edit}.
5897 @xref{List, ,Printing Source Lines},
5901 @kindex down-silently
5903 @item up-silently @var{n}
5904 @itemx down-silently @var{n}
5905 These two commands are variants of @code{up} and @code{down},
5906 respectively; they differ in that they do their work silently, without
5907 causing display of the new frame. They are intended primarily for use
5908 in @value{GDBN} command scripts, where the output might be unnecessary and
5913 @section Information About a Frame
5915 There are several other commands to print information about the selected
5921 When used without any argument, this command does not change which
5922 frame is selected, but prints a brief description of the currently
5923 selected stack frame. It can be abbreviated @code{f}. With an
5924 argument, this command is used to select a stack frame.
5925 @xref{Selection, ,Selecting a Frame}.
5928 @kindex info f @r{(@code{info frame})}
5931 This command prints a verbose description of the selected stack frame,
5936 the address of the frame
5938 the address of the next frame down (called by this frame)
5940 the address of the next frame up (caller of this frame)
5942 the language in which the source code corresponding to this frame is written
5944 the address of the frame's arguments
5946 the address of the frame's local variables
5948 the program counter saved in it (the address of execution in the caller frame)
5950 which registers were saved in the frame
5953 @noindent The verbose description is useful when
5954 something has gone wrong that has made the stack format fail to fit
5955 the usual conventions.
5957 @item info frame @var{addr}
5958 @itemx info f @var{addr}
5959 Print a verbose description of the frame at address @var{addr}, without
5960 selecting that frame. The selected frame remains unchanged by this
5961 command. This requires the same kind of address (more than one for some
5962 architectures) that you specify in the @code{frame} command.
5963 @xref{Selection, ,Selecting a Frame}.
5967 Print the arguments of the selected frame, each on a separate line.
5971 Print the local variables of the selected frame, each on a separate
5972 line. These are all variables (declared either static or automatic)
5973 accessible at the point of execution of the selected frame.
5976 @cindex catch exceptions, list active handlers
5977 @cindex exception handlers, how to list
5979 Print a list of all the exception handlers that are active in the
5980 current stack frame at the current point of execution. To see other
5981 exception handlers, visit the associated frame (using the @code{up},
5982 @code{down}, or @code{frame} commands); then type @code{info catch}.
5983 @xref{Set Catchpoints, , Setting Catchpoints}.
5989 @chapter Examining Source Files
5991 @value{GDBN} can print parts of your program's source, since the debugging
5992 information recorded in the program tells @value{GDBN} what source files were
5993 used to build it. When your program stops, @value{GDBN} spontaneously prints
5994 the line where it stopped. Likewise, when you select a stack frame
5995 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
5996 execution in that frame has stopped. You can print other portions of
5997 source files by explicit command.
5999 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6000 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6001 @value{GDBN} under @sc{gnu} Emacs}.
6004 * List:: Printing source lines
6005 * Specify Location:: How to specify code locations
6006 * Edit:: Editing source files
6007 * Search:: Searching source files
6008 * Source Path:: Specifying source directories
6009 * Machine Code:: Source and machine code
6013 @section Printing Source Lines
6016 @kindex l @r{(@code{list})}
6017 To print lines from a source file, use the @code{list} command
6018 (abbreviated @code{l}). By default, ten lines are printed.
6019 There are several ways to specify what part of the file you want to
6020 print; see @ref{Specify Location}, for the full list.
6022 Here are the forms of the @code{list} command most commonly used:
6025 @item list @var{linenum}
6026 Print lines centered around line number @var{linenum} in the
6027 current source file.
6029 @item list @var{function}
6030 Print lines centered around the beginning of function
6034 Print more lines. If the last lines printed were printed with a
6035 @code{list} command, this prints lines following the last lines
6036 printed; however, if the last line printed was a solitary line printed
6037 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6038 Stack}), this prints lines centered around that line.
6041 Print lines just before the lines last printed.
6044 @cindex @code{list}, how many lines to display
6045 By default, @value{GDBN} prints ten source lines with any of these forms of
6046 the @code{list} command. You can change this using @code{set listsize}:
6049 @kindex set listsize
6050 @item set listsize @var{count}
6051 Make the @code{list} command display @var{count} source lines (unless
6052 the @code{list} argument explicitly specifies some other number).
6054 @kindex show listsize
6056 Display the number of lines that @code{list} prints.
6059 Repeating a @code{list} command with @key{RET} discards the argument,
6060 so it is equivalent to typing just @code{list}. This is more useful
6061 than listing the same lines again. An exception is made for an
6062 argument of @samp{-}; that argument is preserved in repetition so that
6063 each repetition moves up in the source file.
6065 In general, the @code{list} command expects you to supply zero, one or two
6066 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6067 of writing them (@pxref{Specify Location}), but the effect is always
6068 to specify some source line.
6070 Here is a complete description of the possible arguments for @code{list}:
6073 @item list @var{linespec}
6074 Print lines centered around the line specified by @var{linespec}.
6076 @item list @var{first},@var{last}
6077 Print lines from @var{first} to @var{last}. Both arguments are
6078 linespecs. When a @code{list} command has two linespecs, and the
6079 source file of the second linespec is omitted, this refers to
6080 the same source file as the first linespec.
6082 @item list ,@var{last}
6083 Print lines ending with @var{last}.
6085 @item list @var{first},
6086 Print lines starting with @var{first}.
6089 Print lines just after the lines last printed.
6092 Print lines just before the lines last printed.
6095 As described in the preceding table.
6098 @node Specify Location
6099 @section Specifying a Location
6100 @cindex specifying location
6103 Several @value{GDBN} commands accept arguments that specify a location
6104 of your program's code. Since @value{GDBN} is a source-level
6105 debugger, a location usually specifies some line in the source code;
6106 for that reason, locations are also known as @dfn{linespecs}.
6108 Here are all the different ways of specifying a code location that
6109 @value{GDBN} understands:
6113 Specifies the line number @var{linenum} of the current source file.
6116 @itemx +@var{offset}
6117 Specifies the line @var{offset} lines before or after the @dfn{current
6118 line}. For the @code{list} command, the current line is the last one
6119 printed; for the breakpoint commands, this is the line at which
6120 execution stopped in the currently selected @dfn{stack frame}
6121 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6122 used as the second of the two linespecs in a @code{list} command,
6123 this specifies the line @var{offset} lines up or down from the first
6126 @item @var{filename}:@var{linenum}
6127 Specifies the line @var{linenum} in the source file @var{filename}.
6129 @item @var{function}
6130 Specifies the line that begins the body of the function @var{function}.
6131 For example, in C, this is the line with the open brace.
6133 @item @var{filename}:@var{function}
6134 Specifies the line that begins the body of the function @var{function}
6135 in the file @var{filename}. You only need the file name with a
6136 function name to avoid ambiguity when there are identically named
6137 functions in different source files.
6139 @item *@var{address}
6140 Specifies the program address @var{address}. For line-oriented
6141 commands, such as @code{list} and @code{edit}, this specifies a source
6142 line that contains @var{address}. For @code{break} and other
6143 breakpoint oriented commands, this can be used to set breakpoints in
6144 parts of your program which do not have debugging information or
6147 Here @var{address} may be any expression valid in the current working
6148 language (@pxref{Languages, working language}) that specifies a code
6149 address. In addition, as a convenience, @value{GDBN} extends the
6150 semantics of expressions used in locations to cover the situations
6151 that frequently happen during debugging. Here are the various forms
6155 @item @var{expression}
6156 Any expression valid in the current working language.
6158 @item @var{funcaddr}
6159 An address of a function or procedure derived from its name. In C,
6160 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6161 simply the function's name @var{function} (and actually a special case
6162 of a valid expression). In Pascal and Modula-2, this is
6163 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6164 (although the Pascal form also works).
6166 This form specifies the address of the function's first instruction,
6167 before the stack frame and arguments have been set up.
6169 @item '@var{filename}'::@var{funcaddr}
6170 Like @var{funcaddr} above, but also specifies the name of the source
6171 file explicitly. This is useful if the name of the function does not
6172 specify the function unambiguously, e.g., if there are several
6173 functions with identical names in different source files.
6180 @section Editing Source Files
6181 @cindex editing source files
6184 @kindex e @r{(@code{edit})}
6185 To edit the lines in a source file, use the @code{edit} command.
6186 The editing program of your choice
6187 is invoked with the current line set to
6188 the active line in the program.
6189 Alternatively, there are several ways to specify what part of the file you
6190 want to print if you want to see other parts of the program:
6193 @item edit @var{location}
6194 Edit the source file specified by @code{location}. Editing starts at
6195 that @var{location}, e.g., at the specified source line of the
6196 specified file. @xref{Specify Location}, for all the possible forms
6197 of the @var{location} argument; here are the forms of the @code{edit}
6198 command most commonly used:
6201 @item edit @var{number}
6202 Edit the current source file with @var{number} as the active line number.
6204 @item edit @var{function}
6205 Edit the file containing @var{function} at the beginning of its definition.
6210 @subsection Choosing your Editor
6211 You can customize @value{GDBN} to use any editor you want
6213 The only restriction is that your editor (say @code{ex}), recognizes the
6214 following command-line syntax:
6216 ex +@var{number} file
6218 The optional numeric value +@var{number} specifies the number of the line in
6219 the file where to start editing.}.
6220 By default, it is @file{@value{EDITOR}}, but you can change this
6221 by setting the environment variable @code{EDITOR} before using
6222 @value{GDBN}. For example, to configure @value{GDBN} to use the
6223 @code{vi} editor, you could use these commands with the @code{sh} shell:
6229 or in the @code{csh} shell,
6231 setenv EDITOR /usr/bin/vi
6236 @section Searching Source Files
6237 @cindex searching source files
6239 There are two commands for searching through the current source file for a
6244 @kindex forward-search
6245 @item forward-search @var{regexp}
6246 @itemx search @var{regexp}
6247 The command @samp{forward-search @var{regexp}} checks each line,
6248 starting with the one following the last line listed, for a match for
6249 @var{regexp}. It lists the line that is found. You can use the
6250 synonym @samp{search @var{regexp}} or abbreviate the command name as
6253 @kindex reverse-search
6254 @item reverse-search @var{regexp}
6255 The command @samp{reverse-search @var{regexp}} checks each line, starting
6256 with the one before the last line listed and going backward, for a match
6257 for @var{regexp}. It lists the line that is found. You can abbreviate
6258 this command as @code{rev}.
6262 @section Specifying Source Directories
6265 @cindex directories for source files
6266 Executable programs sometimes do not record the directories of the source
6267 files from which they were compiled, just the names. Even when they do,
6268 the directories could be moved between the compilation and your debugging
6269 session. @value{GDBN} has a list of directories to search for source files;
6270 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6271 it tries all the directories in the list, in the order they are present
6272 in the list, until it finds a file with the desired name.
6274 For example, suppose an executable references the file
6275 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6276 @file{/mnt/cross}. The file is first looked up literally; if this
6277 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6278 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6279 message is printed. @value{GDBN} does not look up the parts of the
6280 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6281 Likewise, the subdirectories of the source path are not searched: if
6282 the source path is @file{/mnt/cross}, and the binary refers to
6283 @file{foo.c}, @value{GDBN} would not find it under
6284 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6286 Plain file names, relative file names with leading directories, file
6287 names containing dots, etc.@: are all treated as described above; for
6288 instance, if the source path is @file{/mnt/cross}, and the source file
6289 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6290 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6291 that---@file{/mnt/cross/foo.c}.
6293 Note that the executable search path is @emph{not} used to locate the
6296 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6297 any information it has cached about where source files are found and where
6298 each line is in the file.
6302 When you start @value{GDBN}, its source path includes only @samp{cdir}
6303 and @samp{cwd}, in that order.
6304 To add other directories, use the @code{directory} command.
6306 The search path is used to find both program source files and @value{GDBN}
6307 script files (read using the @samp{-command} option and @samp{source} command).
6309 In addition to the source path, @value{GDBN} provides a set of commands
6310 that manage a list of source path substitution rules. A @dfn{substitution
6311 rule} specifies how to rewrite source directories stored in the program's
6312 debug information in case the sources were moved to a different
6313 directory between compilation and debugging. A rule is made of
6314 two strings, the first specifying what needs to be rewritten in
6315 the path, and the second specifying how it should be rewritten.
6316 In @ref{set substitute-path}, we name these two parts @var{from} and
6317 @var{to} respectively. @value{GDBN} does a simple string replacement
6318 of @var{from} with @var{to} at the start of the directory part of the
6319 source file name, and uses that result instead of the original file
6320 name to look up the sources.
6322 Using the previous example, suppose the @file{foo-1.0} tree has been
6323 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6324 @value{GDBN} to replace @file{/usr/src} in all source path names with
6325 @file{/mnt/cross}. The first lookup will then be
6326 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6327 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6328 substitution rule, use the @code{set substitute-path} command
6329 (@pxref{set substitute-path}).
6331 To avoid unexpected substitution results, a rule is applied only if the
6332 @var{from} part of the directory name ends at a directory separator.
6333 For instance, a rule substituting @file{/usr/source} into
6334 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6335 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6336 is applied only at the beginning of the directory name, this rule will
6337 not be applied to @file{/root/usr/source/baz.c} either.
6339 In many cases, you can achieve the same result using the @code{directory}
6340 command. However, @code{set substitute-path} can be more efficient in
6341 the case where the sources are organized in a complex tree with multiple
6342 subdirectories. With the @code{directory} command, you need to add each
6343 subdirectory of your project. If you moved the entire tree while
6344 preserving its internal organization, then @code{set substitute-path}
6345 allows you to direct the debugger to all the sources with one single
6348 @code{set substitute-path} is also more than just a shortcut command.
6349 The source path is only used if the file at the original location no
6350 longer exists. On the other hand, @code{set substitute-path} modifies
6351 the debugger behavior to look at the rewritten location instead. So, if
6352 for any reason a source file that is not relevant to your executable is
6353 located at the original location, a substitution rule is the only
6354 method available to point @value{GDBN} at the new location.
6356 @cindex @samp{--with-relocated-sources}
6357 @cindex default source path substitution
6358 You can configure a default source path substitution rule by
6359 configuring @value{GDBN} with the
6360 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6361 should be the name of a directory under @value{GDBN}'s configured
6362 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6363 directory names in debug information under @var{dir} will be adjusted
6364 automatically if the installed @value{GDBN} is moved to a new
6365 location. This is useful if @value{GDBN}, libraries or executables
6366 with debug information and corresponding source code are being moved
6370 @item directory @var{dirname} @dots{}
6371 @item dir @var{dirname} @dots{}
6372 Add directory @var{dirname} to the front of the source path. Several
6373 directory names may be given to this command, separated by @samp{:}
6374 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6375 part of absolute file names) or
6376 whitespace. You may specify a directory that is already in the source
6377 path; this moves it forward, so @value{GDBN} searches it sooner.
6381 @vindex $cdir@r{, convenience variable}
6382 @vindex $cwd@r{, convenience variable}
6383 @cindex compilation directory
6384 @cindex current directory
6385 @cindex working directory
6386 @cindex directory, current
6387 @cindex directory, compilation
6388 You can use the string @samp{$cdir} to refer to the compilation
6389 directory (if one is recorded), and @samp{$cwd} to refer to the current
6390 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6391 tracks the current working directory as it changes during your @value{GDBN}
6392 session, while the latter is immediately expanded to the current
6393 directory at the time you add an entry to the source path.
6396 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6398 @c RET-repeat for @code{directory} is explicitly disabled, but since
6399 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6401 @item show directories
6402 @kindex show directories
6403 Print the source path: show which directories it contains.
6405 @anchor{set substitute-path}
6406 @item set substitute-path @var{from} @var{to}
6407 @kindex set substitute-path
6408 Define a source path substitution rule, and add it at the end of the
6409 current list of existing substitution rules. If a rule with the same
6410 @var{from} was already defined, then the old rule is also deleted.
6412 For example, if the file @file{/foo/bar/baz.c} was moved to
6413 @file{/mnt/cross/baz.c}, then the command
6416 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6420 will tell @value{GDBN} to replace @samp{/usr/src} with
6421 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6422 @file{baz.c} even though it was moved.
6424 In the case when more than one substitution rule have been defined,
6425 the rules are evaluated one by one in the order where they have been
6426 defined. The first one matching, if any, is selected to perform
6429 For instance, if we had entered the following commands:
6432 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6433 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6437 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6438 @file{/mnt/include/defs.h} by using the first rule. However, it would
6439 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6440 @file{/mnt/src/lib/foo.c}.
6443 @item unset substitute-path [path]
6444 @kindex unset substitute-path
6445 If a path is specified, search the current list of substitution rules
6446 for a rule that would rewrite that path. Delete that rule if found.
6447 A warning is emitted by the debugger if no rule could be found.
6449 If no path is specified, then all substitution rules are deleted.
6451 @item show substitute-path [path]
6452 @kindex show substitute-path
6453 If a path is specified, then print the source path substitution rule
6454 which would rewrite that path, if any.
6456 If no path is specified, then print all existing source path substitution
6461 If your source path is cluttered with directories that are no longer of
6462 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6463 versions of source. You can correct the situation as follows:
6467 Use @code{directory} with no argument to reset the source path to its default value.
6470 Use @code{directory} with suitable arguments to reinstall the
6471 directories you want in the source path. You can add all the
6472 directories in one command.
6476 @section Source and Machine Code
6477 @cindex source line and its code address
6479 You can use the command @code{info line} to map source lines to program
6480 addresses (and vice versa), and the command @code{disassemble} to display
6481 a range of addresses as machine instructions. You can use the command
6482 @code{set disassemble-next-line} to set whether to disassemble next
6483 source line when execution stops. When run under @sc{gnu} Emacs
6484 mode, the @code{info line} command causes the arrow to point to the
6485 line specified. Also, @code{info line} prints addresses in symbolic form as
6490 @item info line @var{linespec}
6491 Print the starting and ending addresses of the compiled code for
6492 source line @var{linespec}. You can specify source lines in any of
6493 the ways documented in @ref{Specify Location}.
6496 For example, we can use @code{info line} to discover the location of
6497 the object code for the first line of function
6498 @code{m4_changequote}:
6500 @c FIXME: I think this example should also show the addresses in
6501 @c symbolic form, as they usually would be displayed.
6503 (@value{GDBP}) info line m4_changequote
6504 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6508 @cindex code address and its source line
6509 We can also inquire (using @code{*@var{addr}} as the form for
6510 @var{linespec}) what source line covers a particular address:
6512 (@value{GDBP}) info line *0x63ff
6513 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6516 @cindex @code{$_} and @code{info line}
6517 @cindex @code{x} command, default address
6518 @kindex x@r{(examine), and} info line
6519 After @code{info line}, the default address for the @code{x} command
6520 is changed to the starting address of the line, so that @samp{x/i} is
6521 sufficient to begin examining the machine code (@pxref{Memory,
6522 ,Examining Memory}). Also, this address is saved as the value of the
6523 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6528 @cindex assembly instructions
6529 @cindex instructions, assembly
6530 @cindex machine instructions
6531 @cindex listing machine instructions
6533 @itemx disassemble /m
6534 @itemx disassemble /r
6535 This specialized command dumps a range of memory as machine
6536 instructions. It can also print mixed source+disassembly by specifying
6537 the @code{/m} modifier and print the raw instructions in hex as well as
6538 in symbolic form by specifying the @code{/r}.
6539 The default memory range is the function surrounding the
6540 program counter of the selected frame. A single argument to this
6541 command is a program counter value; @value{GDBN} dumps the function
6542 surrounding this value. Two arguments specify a range of addresses
6543 (first inclusive, second exclusive) to dump. In that case, the name of
6544 the function is also printed (since there could be several functions in
6547 If the range of memory being disassembled contains current program counter,
6548 the instruction at that location is shown with a @code{=>} marker.
6551 The following example shows the disassembly of a range of addresses of
6552 HP PA-RISC 2.0 code:
6555 (@value{GDBP}) disas 0x32c4 0x32e4
6556 Dump of assembler code from 0x32c4 to 0x32e4:
6557 0x32c4 <main+204>: addil 0,dp
6558 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6559 0x32cc <main+212>: ldil 0x3000,r31
6560 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6561 0x32d4 <main+220>: ldo 0(r31),rp
6562 0x32d8 <main+224>: addil -0x800,dp
6563 0x32dc <main+228>: ldo 0x588(r1),r26
6564 0x32e0 <main+232>: ldil 0x3000,r31
6565 End of assembler dump.
6568 Here is an example showing mixed source+assembly for Intel x86, when the
6569 program is stopped just after function prologue:
6572 (@value{GDBP}) disas /m main
6573 Dump of assembler code for function main:
6575 0x08048330 <+0>: push %ebp
6576 0x08048331 <+1>: mov %esp,%ebp
6577 0x08048333 <+3>: sub $0x8,%esp
6578 0x08048336 <+6>: and $0xfffffff0,%esp
6579 0x08048339 <+9>: sub $0x10,%esp
6581 6 printf ("Hello.\n");
6582 => 0x0804833c <+12>: movl $0x8048440,(%esp)
6583 0x08048343 <+19>: call 0x8048284 <puts@@plt>
6587 0x08048348 <+24>: mov $0x0,%eax
6588 0x0804834d <+29>: leave
6589 0x0804834e <+30>: ret
6591 End of assembler dump.
6594 Some architectures have more than one commonly-used set of instruction
6595 mnemonics or other syntax.
6597 For programs that were dynamically linked and use shared libraries,
6598 instructions that call functions or branch to locations in the shared
6599 libraries might show a seemingly bogus location---it's actually a
6600 location of the relocation table. On some architectures, @value{GDBN}
6601 might be able to resolve these to actual function names.
6604 @kindex set disassembly-flavor
6605 @cindex Intel disassembly flavor
6606 @cindex AT&T disassembly flavor
6607 @item set disassembly-flavor @var{instruction-set}
6608 Select the instruction set to use when disassembling the
6609 program via the @code{disassemble} or @code{x/i} commands.
6611 Currently this command is only defined for the Intel x86 family. You
6612 can set @var{instruction-set} to either @code{intel} or @code{att}.
6613 The default is @code{att}, the AT&T flavor used by default by Unix
6614 assemblers for x86-based targets.
6616 @kindex show disassembly-flavor
6617 @item show disassembly-flavor
6618 Show the current setting of the disassembly flavor.
6622 @kindex set disassemble-next-line
6623 @kindex show disassemble-next-line
6624 @item set disassemble-next-line
6625 @itemx show disassemble-next-line
6626 Control whether or not @value{GDBN} will disassemble the next source
6627 line or instruction when execution stops. If ON, @value{GDBN} will
6628 display disassembly of the next source line when execution of the
6629 program being debugged stops. This is @emph{in addition} to
6630 displaying the source line itself, which @value{GDBN} always does if
6631 possible. If the next source line cannot be displayed for some reason
6632 (e.g., if @value{GDBN} cannot find the source file, or there's no line
6633 info in the debug info), @value{GDBN} will display disassembly of the
6634 next @emph{instruction} instead of showing the next source line. If
6635 AUTO, @value{GDBN} will display disassembly of next instruction only
6636 if the source line cannot be displayed. This setting causes
6637 @value{GDBN} to display some feedback when you step through a function
6638 with no line info or whose source file is unavailable. The default is
6639 OFF, which means never display the disassembly of the next line or
6645 @chapter Examining Data
6647 @cindex printing data
6648 @cindex examining data
6651 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6652 @c document because it is nonstandard... Under Epoch it displays in a
6653 @c different window or something like that.
6654 The usual way to examine data in your program is with the @code{print}
6655 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6656 evaluates and prints the value of an expression of the language your
6657 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6658 Different Languages}).
6661 @item print @var{expr}
6662 @itemx print /@var{f} @var{expr}
6663 @var{expr} is an expression (in the source language). By default the
6664 value of @var{expr} is printed in a format appropriate to its data type;
6665 you can choose a different format by specifying @samp{/@var{f}}, where
6666 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6670 @itemx print /@var{f}
6671 @cindex reprint the last value
6672 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6673 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6674 conveniently inspect the same value in an alternative format.
6677 A more low-level way of examining data is with the @code{x} command.
6678 It examines data in memory at a specified address and prints it in a
6679 specified format. @xref{Memory, ,Examining Memory}.
6681 If you are interested in information about types, or about how the
6682 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6683 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6687 * Expressions:: Expressions
6688 * Ambiguous Expressions:: Ambiguous Expressions
6689 * Variables:: Program variables
6690 * Arrays:: Artificial arrays
6691 * Output Formats:: Output formats
6692 * Memory:: Examining memory
6693 * Auto Display:: Automatic display
6694 * Print Settings:: Print settings
6695 * Value History:: Value history
6696 * Convenience Vars:: Convenience variables
6697 * Registers:: Registers
6698 * Floating Point Hardware:: Floating point hardware
6699 * Vector Unit:: Vector Unit
6700 * OS Information:: Auxiliary data provided by operating system
6701 * Memory Region Attributes:: Memory region attributes
6702 * Dump/Restore Files:: Copy between memory and a file
6703 * Core File Generation:: Cause a program dump its core
6704 * Character Sets:: Debugging programs that use a different
6705 character set than GDB does
6706 * Caching Remote Data:: Data caching for remote targets
6707 * Searching Memory:: Searching memory for a sequence of bytes
6711 @section Expressions
6714 @code{print} and many other @value{GDBN} commands accept an expression and
6715 compute its value. Any kind of constant, variable or operator defined
6716 by the programming language you are using is valid in an expression in
6717 @value{GDBN}. This includes conditional expressions, function calls,
6718 casts, and string constants. It also includes preprocessor macros, if
6719 you compiled your program to include this information; see
6722 @cindex arrays in expressions
6723 @value{GDBN} supports array constants in expressions input by
6724 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
6725 you can use the command @code{print @{1, 2, 3@}} to create an array
6726 of three integers. If you pass an array to a function or assign it
6727 to a program variable, @value{GDBN} copies the array to memory that
6728 is @code{malloc}ed in the target program.
6730 Because C is so widespread, most of the expressions shown in examples in
6731 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
6732 Languages}, for information on how to use expressions in other
6735 In this section, we discuss operators that you can use in @value{GDBN}
6736 expressions regardless of your programming language.
6738 @cindex casts, in expressions
6739 Casts are supported in all languages, not just in C, because it is so
6740 useful to cast a number into a pointer in order to examine a structure
6741 at that address in memory.
6742 @c FIXME: casts supported---Mod2 true?
6744 @value{GDBN} supports these operators, in addition to those common
6745 to programming languages:
6749 @samp{@@} is a binary operator for treating parts of memory as arrays.
6750 @xref{Arrays, ,Artificial Arrays}, for more information.
6753 @samp{::} allows you to specify a variable in terms of the file or
6754 function where it is defined. @xref{Variables, ,Program Variables}.
6756 @cindex @{@var{type}@}
6757 @cindex type casting memory
6758 @cindex memory, viewing as typed object
6759 @cindex casts, to view memory
6760 @item @{@var{type}@} @var{addr}
6761 Refers to an object of type @var{type} stored at address @var{addr} in
6762 memory. @var{addr} may be any expression whose value is an integer or
6763 pointer (but parentheses are required around binary operators, just as in
6764 a cast). This construct is allowed regardless of what kind of data is
6765 normally supposed to reside at @var{addr}.
6768 @node Ambiguous Expressions
6769 @section Ambiguous Expressions
6770 @cindex ambiguous expressions
6772 Expressions can sometimes contain some ambiguous elements. For instance,
6773 some programming languages (notably Ada, C@t{++} and Objective-C) permit
6774 a single function name to be defined several times, for application in
6775 different contexts. This is called @dfn{overloading}. Another example
6776 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
6777 templates and is typically instantiated several times, resulting in
6778 the same function name being defined in different contexts.
6780 In some cases and depending on the language, it is possible to adjust
6781 the expression to remove the ambiguity. For instance in C@t{++}, you
6782 can specify the signature of the function you want to break on, as in
6783 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
6784 qualified name of your function often makes the expression unambiguous
6787 When an ambiguity that needs to be resolved is detected, the debugger
6788 has the capability to display a menu of numbered choices for each
6789 possibility, and then waits for the selection with the prompt @samp{>}.
6790 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
6791 aborts the current command. If the command in which the expression was
6792 used allows more than one choice to be selected, the next option in the
6793 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
6796 For example, the following session excerpt shows an attempt to set a
6797 breakpoint at the overloaded symbol @code{String::after}.
6798 We choose three particular definitions of that function name:
6800 @c FIXME! This is likely to change to show arg type lists, at least
6803 (@value{GDBP}) b String::after
6806 [2] file:String.cc; line number:867
6807 [3] file:String.cc; line number:860
6808 [4] file:String.cc; line number:875
6809 [5] file:String.cc; line number:853
6810 [6] file:String.cc; line number:846
6811 [7] file:String.cc; line number:735
6813 Breakpoint 1 at 0xb26c: file String.cc, line 867.
6814 Breakpoint 2 at 0xb344: file String.cc, line 875.
6815 Breakpoint 3 at 0xafcc: file String.cc, line 846.
6816 Multiple breakpoints were set.
6817 Use the "delete" command to delete unwanted
6824 @kindex set multiple-symbols
6825 @item set multiple-symbols @var{mode}
6826 @cindex multiple-symbols menu
6828 This option allows you to adjust the debugger behavior when an expression
6831 By default, @var{mode} is set to @code{all}. If the command with which
6832 the expression is used allows more than one choice, then @value{GDBN}
6833 automatically selects all possible choices. For instance, inserting
6834 a breakpoint on a function using an ambiguous name results in a breakpoint
6835 inserted on each possible match. However, if a unique choice must be made,
6836 then @value{GDBN} uses the menu to help you disambiguate the expression.
6837 For instance, printing the address of an overloaded function will result
6838 in the use of the menu.
6840 When @var{mode} is set to @code{ask}, the debugger always uses the menu
6841 when an ambiguity is detected.
6843 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
6844 an error due to the ambiguity and the command is aborted.
6846 @kindex show multiple-symbols
6847 @item show multiple-symbols
6848 Show the current value of the @code{multiple-symbols} setting.
6852 @section Program Variables
6854 The most common kind of expression to use is the name of a variable
6857 Variables in expressions are understood in the selected stack frame
6858 (@pxref{Selection, ,Selecting a Frame}); they must be either:
6862 global (or file-static)
6869 visible according to the scope rules of the
6870 programming language from the point of execution in that frame
6873 @noindent This means that in the function
6888 you can examine and use the variable @code{a} whenever your program is
6889 executing within the function @code{foo}, but you can only use or
6890 examine the variable @code{b} while your program is executing inside
6891 the block where @code{b} is declared.
6893 @cindex variable name conflict
6894 There is an exception: you can refer to a variable or function whose
6895 scope is a single source file even if the current execution point is not
6896 in this file. But it is possible to have more than one such variable or
6897 function with the same name (in different source files). If that
6898 happens, referring to that name has unpredictable effects. If you wish,
6899 you can specify a static variable in a particular function or file,
6900 using the colon-colon (@code{::}) notation:
6902 @cindex colon-colon, context for variables/functions
6904 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
6905 @cindex @code{::}, context for variables/functions
6908 @var{file}::@var{variable}
6909 @var{function}::@var{variable}
6913 Here @var{file} or @var{function} is the name of the context for the
6914 static @var{variable}. In the case of file names, you can use quotes to
6915 make sure @value{GDBN} parses the file name as a single word---for example,
6916 to print a global value of @code{x} defined in @file{f2.c}:
6919 (@value{GDBP}) p 'f2.c'::x
6922 @cindex C@t{++} scope resolution
6923 This use of @samp{::} is very rarely in conflict with the very similar
6924 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
6925 scope resolution operator in @value{GDBN} expressions.
6926 @c FIXME: Um, so what happens in one of those rare cases where it's in
6929 @cindex wrong values
6930 @cindex variable values, wrong
6931 @cindex function entry/exit, wrong values of variables
6932 @cindex optimized code, wrong values of variables
6934 @emph{Warning:} Occasionally, a local variable may appear to have the
6935 wrong value at certain points in a function---just after entry to a new
6936 scope, and just before exit.
6938 You may see this problem when you are stepping by machine instructions.
6939 This is because, on most machines, it takes more than one instruction to
6940 set up a stack frame (including local variable definitions); if you are
6941 stepping by machine instructions, variables may appear to have the wrong
6942 values until the stack frame is completely built. On exit, it usually
6943 also takes more than one machine instruction to destroy a stack frame;
6944 after you begin stepping through that group of instructions, local
6945 variable definitions may be gone.
6947 This may also happen when the compiler does significant optimizations.
6948 To be sure of always seeing accurate values, turn off all optimization
6951 @cindex ``No symbol "foo" in current context''
6952 Another possible effect of compiler optimizations is to optimize
6953 unused variables out of existence, or assign variables to registers (as
6954 opposed to memory addresses). Depending on the support for such cases
6955 offered by the debug info format used by the compiler, @value{GDBN}
6956 might not be able to display values for such local variables. If that
6957 happens, @value{GDBN} will print a message like this:
6960 No symbol "foo" in current context.
6963 To solve such problems, either recompile without optimizations, or use a
6964 different debug info format, if the compiler supports several such
6965 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
6966 usually supports the @option{-gstabs+} option. @option{-gstabs+}
6967 produces debug info in a format that is superior to formats such as
6968 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
6969 an effective form for debug info. @xref{Debugging Options,,Options
6970 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
6971 Compiler Collection (GCC)}.
6972 @xref{C, ,C and C@t{++}}, for more information about debug info formats
6973 that are best suited to C@t{++} programs.
6975 If you ask to print an object whose contents are unknown to
6976 @value{GDBN}, e.g., because its data type is not completely specified
6977 by the debug information, @value{GDBN} will say @samp{<incomplete
6978 type>}. @xref{Symbols, incomplete type}, for more about this.
6980 Strings are identified as arrays of @code{char} values without specified
6981 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
6982 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
6983 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
6984 defines literal string type @code{"char"} as @code{char} without a sign.
6989 signed char var1[] = "A";
6992 You get during debugging
6997 $2 = @{65 'A', 0 '\0'@}
7001 @section Artificial Arrays
7003 @cindex artificial array
7005 @kindex @@@r{, referencing memory as an array}
7006 It is often useful to print out several successive objects of the
7007 same type in memory; a section of an array, or an array of
7008 dynamically determined size for which only a pointer exists in the
7011 You can do this by referring to a contiguous span of memory as an
7012 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7013 operand of @samp{@@} should be the first element of the desired array
7014 and be an individual object. The right operand should be the desired length
7015 of the array. The result is an array value whose elements are all of
7016 the type of the left argument. The first element is actually the left
7017 argument; the second element comes from bytes of memory immediately
7018 following those that hold the first element, and so on. Here is an
7019 example. If a program says
7022 int *array = (int *) malloc (len * sizeof (int));
7026 you can print the contents of @code{array} with
7032 The left operand of @samp{@@} must reside in memory. Array values made
7033 with @samp{@@} in this way behave just like other arrays in terms of
7034 subscripting, and are coerced to pointers when used in expressions.
7035 Artificial arrays most often appear in expressions via the value history
7036 (@pxref{Value History, ,Value History}), after printing one out.
7038 Another way to create an artificial array is to use a cast.
7039 This re-interprets a value as if it were an array.
7040 The value need not be in memory:
7042 (@value{GDBP}) p/x (short[2])0x12345678
7043 $1 = @{0x1234, 0x5678@}
7046 As a convenience, if you leave the array length out (as in
7047 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7048 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7050 (@value{GDBP}) p/x (short[])0x12345678
7051 $2 = @{0x1234, 0x5678@}
7054 Sometimes the artificial array mechanism is not quite enough; in
7055 moderately complex data structures, the elements of interest may not
7056 actually be adjacent---for example, if you are interested in the values
7057 of pointers in an array. One useful work-around in this situation is
7058 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7059 Variables}) as a counter in an expression that prints the first
7060 interesting value, and then repeat that expression via @key{RET}. For
7061 instance, suppose you have an array @code{dtab} of pointers to
7062 structures, and you are interested in the values of a field @code{fv}
7063 in each structure. Here is an example of what you might type:
7073 @node Output Formats
7074 @section Output Formats
7076 @cindex formatted output
7077 @cindex output formats
7078 By default, @value{GDBN} prints a value according to its data type. Sometimes
7079 this is not what you want. For example, you might want to print a number
7080 in hex, or a pointer in decimal. Or you might want to view data in memory
7081 at a certain address as a character string or as an instruction. To do
7082 these things, specify an @dfn{output format} when you print a value.
7084 The simplest use of output formats is to say how to print a value
7085 already computed. This is done by starting the arguments of the
7086 @code{print} command with a slash and a format letter. The format
7087 letters supported are:
7091 Regard the bits of the value as an integer, and print the integer in
7095 Print as integer in signed decimal.
7098 Print as integer in unsigned decimal.
7101 Print as integer in octal.
7104 Print as integer in binary. The letter @samp{t} stands for ``two''.
7105 @footnote{@samp{b} cannot be used because these format letters are also
7106 used with the @code{x} command, where @samp{b} stands for ``byte'';
7107 see @ref{Memory,,Examining Memory}.}
7110 @cindex unknown address, locating
7111 @cindex locate address
7112 Print as an address, both absolute in hexadecimal and as an offset from
7113 the nearest preceding symbol. You can use this format used to discover
7114 where (in what function) an unknown address is located:
7117 (@value{GDBP}) p/a 0x54320
7118 $3 = 0x54320 <_initialize_vx+396>
7122 The command @code{info symbol 0x54320} yields similar results.
7123 @xref{Symbols, info symbol}.
7126 Regard as an integer and print it as a character constant. This
7127 prints both the numerical value and its character representation. The
7128 character representation is replaced with the octal escape @samp{\nnn}
7129 for characters outside the 7-bit @sc{ascii} range.
7131 Without this format, @value{GDBN} displays @code{char},
7132 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7133 constants. Single-byte members of vectors are displayed as integer
7137 Regard the bits of the value as a floating point number and print
7138 using typical floating point syntax.
7141 @cindex printing strings
7142 @cindex printing byte arrays
7143 Regard as a string, if possible. With this format, pointers to single-byte
7144 data are displayed as null-terminated strings and arrays of single-byte data
7145 are displayed as fixed-length strings. Other values are displayed in their
7148 Without this format, @value{GDBN} displays pointers to and arrays of
7149 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7150 strings. Single-byte members of a vector are displayed as an integer
7154 @cindex raw printing
7155 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7156 use a type-specific pretty-printer. The @samp{r} format bypasses any
7157 pretty-printer which might exist for the value's type.
7160 For example, to print the program counter in hex (@pxref{Registers}), type
7167 Note that no space is required before the slash; this is because command
7168 names in @value{GDBN} cannot contain a slash.
7170 To reprint the last value in the value history with a different format,
7171 you can use the @code{print} command with just a format and no
7172 expression. For example, @samp{p/x} reprints the last value in hex.
7175 @section Examining Memory
7177 You can use the command @code{x} (for ``examine'') to examine memory in
7178 any of several formats, independently of your program's data types.
7180 @cindex examining memory
7182 @kindex x @r{(examine memory)}
7183 @item x/@var{nfu} @var{addr}
7186 Use the @code{x} command to examine memory.
7189 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7190 much memory to display and how to format it; @var{addr} is an
7191 expression giving the address where you want to start displaying memory.
7192 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7193 Several commands set convenient defaults for @var{addr}.
7196 @item @var{n}, the repeat count
7197 The repeat count is a decimal integer; the default is 1. It specifies
7198 how much memory (counting by units @var{u}) to display.
7199 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7202 @item @var{f}, the display format
7203 The display format is one of the formats used by @code{print}
7204 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7205 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7206 The default is @samp{x} (hexadecimal) initially. The default changes
7207 each time you use either @code{x} or @code{print}.
7209 @item @var{u}, the unit size
7210 The unit size is any of
7216 Halfwords (two bytes).
7218 Words (four bytes). This is the initial default.
7220 Giant words (eight bytes).
7223 Each time you specify a unit size with @code{x}, that size becomes the
7224 default unit the next time you use @code{x}. (For the @samp{s} and
7225 @samp{i} formats, the unit size is ignored and is normally not written.)
7227 @item @var{addr}, starting display address
7228 @var{addr} is the address where you want @value{GDBN} to begin displaying
7229 memory. The expression need not have a pointer value (though it may);
7230 it is always interpreted as an integer address of a byte of memory.
7231 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7232 @var{addr} is usually just after the last address examined---but several
7233 other commands also set the default address: @code{info breakpoints} (to
7234 the address of the last breakpoint listed), @code{info line} (to the
7235 starting address of a line), and @code{print} (if you use it to display
7236 a value from memory).
7239 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7240 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7241 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7242 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7243 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7245 Since the letters indicating unit sizes are all distinct from the
7246 letters specifying output formats, you do not have to remember whether
7247 unit size or format comes first; either order works. The output
7248 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7249 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7251 Even though the unit size @var{u} is ignored for the formats @samp{s}
7252 and @samp{i}, you might still want to use a count @var{n}; for example,
7253 @samp{3i} specifies that you want to see three machine instructions,
7254 including any operands. For convenience, especially when used with
7255 the @code{display} command, the @samp{i} format also prints branch delay
7256 slot instructions, if any, beyond the count specified, which immediately
7257 follow the last instruction that is within the count. The command
7258 @code{disassemble} gives an alternative way of inspecting machine
7259 instructions; see @ref{Machine Code,,Source and Machine Code}.
7261 All the defaults for the arguments to @code{x} are designed to make it
7262 easy to continue scanning memory with minimal specifications each time
7263 you use @code{x}. For example, after you have inspected three machine
7264 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7265 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7266 the repeat count @var{n} is used again; the other arguments default as
7267 for successive uses of @code{x}.
7269 When examining machine instructions, the instruction at current program
7270 counter is shown with a @code{=>} marker. For example:
7273 (@value{GDBP}) x/5i $pc-6
7274 0x804837f <main+11>: mov %esp,%ebp
7275 0x8048381 <main+13>: push %ecx
7276 0x8048382 <main+14>: sub $0x4,%esp
7277 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
7278 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
7281 @cindex @code{$_}, @code{$__}, and value history
7282 The addresses and contents printed by the @code{x} command are not saved
7283 in the value history because there is often too much of them and they
7284 would get in the way. Instead, @value{GDBN} makes these values available for
7285 subsequent use in expressions as values of the convenience variables
7286 @code{$_} and @code{$__}. After an @code{x} command, the last address
7287 examined is available for use in expressions in the convenience variable
7288 @code{$_}. The contents of that address, as examined, are available in
7289 the convenience variable @code{$__}.
7291 If the @code{x} command has a repeat count, the address and contents saved
7292 are from the last memory unit printed; this is not the same as the last
7293 address printed if several units were printed on the last line of output.
7295 @cindex remote memory comparison
7296 @cindex verify remote memory image
7297 When you are debugging a program running on a remote target machine
7298 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7299 remote machine's memory against the executable file you downloaded to
7300 the target. The @code{compare-sections} command is provided for such
7304 @kindex compare-sections
7305 @item compare-sections @r{[}@var{section-name}@r{]}
7306 Compare the data of a loadable section @var{section-name} in the
7307 executable file of the program being debugged with the same section in
7308 the remote machine's memory, and report any mismatches. With no
7309 arguments, compares all loadable sections. This command's
7310 availability depends on the target's support for the @code{"qCRC"}
7315 @section Automatic Display
7316 @cindex automatic display
7317 @cindex display of expressions
7319 If you find that you want to print the value of an expression frequently
7320 (to see how it changes), you might want to add it to the @dfn{automatic
7321 display list} so that @value{GDBN} prints its value each time your program stops.
7322 Each expression added to the list is given a number to identify it;
7323 to remove an expression from the list, you specify that number.
7324 The automatic display looks like this:
7328 3: bar[5] = (struct hack *) 0x3804
7332 This display shows item numbers, expressions and their current values. As with
7333 displays you request manually using @code{x} or @code{print}, you can
7334 specify the output format you prefer; in fact, @code{display} decides
7335 whether to use @code{print} or @code{x} depending your format
7336 specification---it uses @code{x} if you specify either the @samp{i}
7337 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7341 @item display @var{expr}
7342 Add the expression @var{expr} to the list of expressions to display
7343 each time your program stops. @xref{Expressions, ,Expressions}.
7345 @code{display} does not repeat if you press @key{RET} again after using it.
7347 @item display/@var{fmt} @var{expr}
7348 For @var{fmt} specifying only a display format and not a size or
7349 count, add the expression @var{expr} to the auto-display list but
7350 arrange to display it each time in the specified format @var{fmt}.
7351 @xref{Output Formats,,Output Formats}.
7353 @item display/@var{fmt} @var{addr}
7354 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7355 number of units, add the expression @var{addr} as a memory address to
7356 be examined each time your program stops. Examining means in effect
7357 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7360 For example, @samp{display/i $pc} can be helpful, to see the machine
7361 instruction about to be executed each time execution stops (@samp{$pc}
7362 is a common name for the program counter; @pxref{Registers, ,Registers}).
7365 @kindex delete display
7367 @item undisplay @var{dnums}@dots{}
7368 @itemx delete display @var{dnums}@dots{}
7369 Remove item numbers @var{dnums} from the list of expressions to display.
7371 @code{undisplay} does not repeat if you press @key{RET} after using it.
7372 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7374 @kindex disable display
7375 @item disable display @var{dnums}@dots{}
7376 Disable the display of item numbers @var{dnums}. A disabled display
7377 item is not printed automatically, but is not forgotten. It may be
7378 enabled again later.
7380 @kindex enable display
7381 @item enable display @var{dnums}@dots{}
7382 Enable display of item numbers @var{dnums}. It becomes effective once
7383 again in auto display of its expression, until you specify otherwise.
7386 Display the current values of the expressions on the list, just as is
7387 done when your program stops.
7389 @kindex info display
7391 Print the list of expressions previously set up to display
7392 automatically, each one with its item number, but without showing the
7393 values. This includes disabled expressions, which are marked as such.
7394 It also includes expressions which would not be displayed right now
7395 because they refer to automatic variables not currently available.
7398 @cindex display disabled out of scope
7399 If a display expression refers to local variables, then it does not make
7400 sense outside the lexical context for which it was set up. Such an
7401 expression is disabled when execution enters a context where one of its
7402 variables is not defined. For example, if you give the command
7403 @code{display last_char} while inside a function with an argument
7404 @code{last_char}, @value{GDBN} displays this argument while your program
7405 continues to stop inside that function. When it stops elsewhere---where
7406 there is no variable @code{last_char}---the display is disabled
7407 automatically. The next time your program stops where @code{last_char}
7408 is meaningful, you can enable the display expression once again.
7410 @node Print Settings
7411 @section Print Settings
7413 @cindex format options
7414 @cindex print settings
7415 @value{GDBN} provides the following ways to control how arrays, structures,
7416 and symbols are printed.
7419 These settings are useful for debugging programs in any language:
7423 @item set print address
7424 @itemx set print address on
7425 @cindex print/don't print memory addresses
7426 @value{GDBN} prints memory addresses showing the location of stack
7427 traces, structure values, pointer values, breakpoints, and so forth,
7428 even when it also displays the contents of those addresses. The default
7429 is @code{on}. For example, this is what a stack frame display looks like with
7430 @code{set print address on}:
7435 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7437 530 if (lquote != def_lquote)
7441 @item set print address off
7442 Do not print addresses when displaying their contents. For example,
7443 this is the same stack frame displayed with @code{set print address off}:
7447 (@value{GDBP}) set print addr off
7449 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7450 530 if (lquote != def_lquote)
7454 You can use @samp{set print address off} to eliminate all machine
7455 dependent displays from the @value{GDBN} interface. For example, with
7456 @code{print address off}, you should get the same text for backtraces on
7457 all machines---whether or not they involve pointer arguments.
7460 @item show print address
7461 Show whether or not addresses are to be printed.
7464 When @value{GDBN} prints a symbolic address, it normally prints the
7465 closest earlier symbol plus an offset. If that symbol does not uniquely
7466 identify the address (for example, it is a name whose scope is a single
7467 source file), you may need to clarify. One way to do this is with
7468 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7469 you can set @value{GDBN} to print the source file and line number when
7470 it prints a symbolic address:
7473 @item set print symbol-filename on
7474 @cindex source file and line of a symbol
7475 @cindex symbol, source file and line
7476 Tell @value{GDBN} to print the source file name and line number of a
7477 symbol in the symbolic form of an address.
7479 @item set print symbol-filename off
7480 Do not print source file name and line number of a symbol. This is the
7483 @item show print symbol-filename
7484 Show whether or not @value{GDBN} will print the source file name and
7485 line number of a symbol in the symbolic form of an address.
7488 Another situation where it is helpful to show symbol filenames and line
7489 numbers is when disassembling code; @value{GDBN} shows you the line
7490 number and source file that corresponds to each instruction.
7492 Also, you may wish to see the symbolic form only if the address being
7493 printed is reasonably close to the closest earlier symbol:
7496 @item set print max-symbolic-offset @var{max-offset}
7497 @cindex maximum value for offset of closest symbol
7498 Tell @value{GDBN} to only display the symbolic form of an address if the
7499 offset between the closest earlier symbol and the address is less than
7500 @var{max-offset}. The default is 0, which tells @value{GDBN}
7501 to always print the symbolic form of an address if any symbol precedes it.
7503 @item show print max-symbolic-offset
7504 Ask how large the maximum offset is that @value{GDBN} prints in a
7508 @cindex wild pointer, interpreting
7509 @cindex pointer, finding referent
7510 If you have a pointer and you are not sure where it points, try
7511 @samp{set print symbol-filename on}. Then you can determine the name
7512 and source file location of the variable where it points, using
7513 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7514 For example, here @value{GDBN} shows that a variable @code{ptt} points
7515 at another variable @code{t}, defined in @file{hi2.c}:
7518 (@value{GDBP}) set print symbol-filename on
7519 (@value{GDBP}) p/a ptt
7520 $4 = 0xe008 <t in hi2.c>
7524 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
7525 does not show the symbol name and filename of the referent, even with
7526 the appropriate @code{set print} options turned on.
7529 Other settings control how different kinds of objects are printed:
7532 @item set print array
7533 @itemx set print array on
7534 @cindex pretty print arrays
7535 Pretty print arrays. This format is more convenient to read,
7536 but uses more space. The default is off.
7538 @item set print array off
7539 Return to compressed format for arrays.
7541 @item show print array
7542 Show whether compressed or pretty format is selected for displaying
7545 @cindex print array indexes
7546 @item set print array-indexes
7547 @itemx set print array-indexes on
7548 Print the index of each element when displaying arrays. May be more
7549 convenient to locate a given element in the array or quickly find the
7550 index of a given element in that printed array. The default is off.
7552 @item set print array-indexes off
7553 Stop printing element indexes when displaying arrays.
7555 @item show print array-indexes
7556 Show whether the index of each element is printed when displaying
7559 @item set print elements @var{number-of-elements}
7560 @cindex number of array elements to print
7561 @cindex limit on number of printed array elements
7562 Set a limit on how many elements of an array @value{GDBN} will print.
7563 If @value{GDBN} is printing a large array, it stops printing after it has
7564 printed the number of elements set by the @code{set print elements} command.
7565 This limit also applies to the display of strings.
7566 When @value{GDBN} starts, this limit is set to 200.
7567 Setting @var{number-of-elements} to zero means that the printing is unlimited.
7569 @item show print elements
7570 Display the number of elements of a large array that @value{GDBN} will print.
7571 If the number is 0, then the printing is unlimited.
7573 @item set print frame-arguments @var{value}
7574 @kindex set print frame-arguments
7575 @cindex printing frame argument values
7576 @cindex print all frame argument values
7577 @cindex print frame argument values for scalars only
7578 @cindex do not print frame argument values
7579 This command allows to control how the values of arguments are printed
7580 when the debugger prints a frame (@pxref{Frames}). The possible
7585 The values of all arguments are printed.
7588 Print the value of an argument only if it is a scalar. The value of more
7589 complex arguments such as arrays, structures, unions, etc, is replaced
7590 by @code{@dots{}}. This is the default. Here is an example where
7591 only scalar arguments are shown:
7594 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
7599 None of the argument values are printed. Instead, the value of each argument
7600 is replaced by @code{@dots{}}. In this case, the example above now becomes:
7603 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
7608 By default, only scalar arguments are printed. This command can be used
7609 to configure the debugger to print the value of all arguments, regardless
7610 of their type. However, it is often advantageous to not print the value
7611 of more complex parameters. For instance, it reduces the amount of
7612 information printed in each frame, making the backtrace more readable.
7613 Also, it improves performance when displaying Ada frames, because
7614 the computation of large arguments can sometimes be CPU-intensive,
7615 especially in large applications. Setting @code{print frame-arguments}
7616 to @code{scalars} (the default) or @code{none} avoids this computation,
7617 thus speeding up the display of each Ada frame.
7619 @item show print frame-arguments
7620 Show how the value of arguments should be displayed when printing a frame.
7622 @item set print repeats
7623 @cindex repeated array elements
7624 Set the threshold for suppressing display of repeated array
7625 elements. When the number of consecutive identical elements of an
7626 array exceeds the threshold, @value{GDBN} prints the string
7627 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
7628 identical repetitions, instead of displaying the identical elements
7629 themselves. Setting the threshold to zero will cause all elements to
7630 be individually printed. The default threshold is 10.
7632 @item show print repeats
7633 Display the current threshold for printing repeated identical
7636 @item set print null-stop
7637 @cindex @sc{null} elements in arrays
7638 Cause @value{GDBN} to stop printing the characters of an array when the first
7639 @sc{null} is encountered. This is useful when large arrays actually
7640 contain only short strings.
7643 @item show print null-stop
7644 Show whether @value{GDBN} stops printing an array on the first
7645 @sc{null} character.
7647 @item set print pretty on
7648 @cindex print structures in indented form
7649 @cindex indentation in structure display
7650 Cause @value{GDBN} to print structures in an indented format with one member
7651 per line, like this:
7666 @item set print pretty off
7667 Cause @value{GDBN} to print structures in a compact format, like this:
7671 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
7672 meat = 0x54 "Pork"@}
7677 This is the default format.
7679 @item show print pretty
7680 Show which format @value{GDBN} is using to print structures.
7682 @item set print sevenbit-strings on
7683 @cindex eight-bit characters in strings
7684 @cindex octal escapes in strings
7685 Print using only seven-bit characters; if this option is set,
7686 @value{GDBN} displays any eight-bit characters (in strings or
7687 character values) using the notation @code{\}@var{nnn}. This setting is
7688 best if you are working in English (@sc{ascii}) and you use the
7689 high-order bit of characters as a marker or ``meta'' bit.
7691 @item set print sevenbit-strings off
7692 Print full eight-bit characters. This allows the use of more
7693 international character sets, and is the default.
7695 @item show print sevenbit-strings
7696 Show whether or not @value{GDBN} is printing only seven-bit characters.
7698 @item set print union on
7699 @cindex unions in structures, printing
7700 Tell @value{GDBN} to print unions which are contained in structures
7701 and other unions. This is the default setting.
7703 @item set print union off
7704 Tell @value{GDBN} not to print unions which are contained in
7705 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
7708 @item show print union
7709 Ask @value{GDBN} whether or not it will print unions which are contained in
7710 structures and other unions.
7712 For example, given the declarations
7715 typedef enum @{Tree, Bug@} Species;
7716 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
7717 typedef enum @{Caterpillar, Cocoon, Butterfly@}
7728 struct thing foo = @{Tree, @{Acorn@}@};
7732 with @code{set print union on} in effect @samp{p foo} would print
7735 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
7739 and with @code{set print union off} in effect it would print
7742 $1 = @{it = Tree, form = @{...@}@}
7746 @code{set print union} affects programs written in C-like languages
7752 These settings are of interest when debugging C@t{++} programs:
7755 @cindex demangling C@t{++} names
7756 @item set print demangle
7757 @itemx set print demangle on
7758 Print C@t{++} names in their source form rather than in the encoded
7759 (``mangled'') form passed to the assembler and linker for type-safe
7760 linkage. The default is on.
7762 @item show print demangle
7763 Show whether C@t{++} names are printed in mangled or demangled form.
7765 @item set print asm-demangle
7766 @itemx set print asm-demangle on
7767 Print C@t{++} names in their source form rather than their mangled form, even
7768 in assembler code printouts such as instruction disassemblies.
7771 @item show print asm-demangle
7772 Show whether C@t{++} names in assembly listings are printed in mangled
7775 @cindex C@t{++} symbol decoding style
7776 @cindex symbol decoding style, C@t{++}
7777 @kindex set demangle-style
7778 @item set demangle-style @var{style}
7779 Choose among several encoding schemes used by different compilers to
7780 represent C@t{++} names. The choices for @var{style} are currently:
7784 Allow @value{GDBN} to choose a decoding style by inspecting your program.
7787 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
7788 This is the default.
7791 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
7794 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
7797 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
7798 @strong{Warning:} this setting alone is not sufficient to allow
7799 debugging @code{cfront}-generated executables. @value{GDBN} would
7800 require further enhancement to permit that.
7803 If you omit @var{style}, you will see a list of possible formats.
7805 @item show demangle-style
7806 Display the encoding style currently in use for decoding C@t{++} symbols.
7808 @item set print object
7809 @itemx set print object on
7810 @cindex derived type of an object, printing
7811 @cindex display derived types
7812 When displaying a pointer to an object, identify the @emph{actual}
7813 (derived) type of the object rather than the @emph{declared} type, using
7814 the virtual function table.
7816 @item set print object off
7817 Display only the declared type of objects, without reference to the
7818 virtual function table. This is the default setting.
7820 @item show print object
7821 Show whether actual, or declared, object types are displayed.
7823 @item set print static-members
7824 @itemx set print static-members on
7825 @cindex static members of C@t{++} objects
7826 Print static members when displaying a C@t{++} object. The default is on.
7828 @item set print static-members off
7829 Do not print static members when displaying a C@t{++} object.
7831 @item show print static-members
7832 Show whether C@t{++} static members are printed or not.
7834 @item set print pascal_static-members
7835 @itemx set print pascal_static-members on
7836 @cindex static members of Pascal objects
7837 @cindex Pascal objects, static members display
7838 Print static members when displaying a Pascal object. The default is on.
7840 @item set print pascal_static-members off
7841 Do not print static members when displaying a Pascal object.
7843 @item show print pascal_static-members
7844 Show whether Pascal static members are printed or not.
7846 @c These don't work with HP ANSI C++ yet.
7847 @item set print vtbl
7848 @itemx set print vtbl on
7849 @cindex pretty print C@t{++} virtual function tables
7850 @cindex virtual functions (C@t{++}) display
7851 @cindex VTBL display
7852 Pretty print C@t{++} virtual function tables. The default is off.
7853 (The @code{vtbl} commands do not work on programs compiled with the HP
7854 ANSI C@t{++} compiler (@code{aCC}).)
7856 @item set print vtbl off
7857 Do not pretty print C@t{++} virtual function tables.
7859 @item show print vtbl
7860 Show whether C@t{++} virtual function tables are pretty printed, or not.
7864 @section Value History
7866 @cindex value history
7867 @cindex history of values printed by @value{GDBN}
7868 Values printed by the @code{print} command are saved in the @value{GDBN}
7869 @dfn{value history}. This allows you to refer to them in other expressions.
7870 Values are kept until the symbol table is re-read or discarded
7871 (for example with the @code{file} or @code{symbol-file} commands).
7872 When the symbol table changes, the value history is discarded,
7873 since the values may contain pointers back to the types defined in the
7878 @cindex history number
7879 The values printed are given @dfn{history numbers} by which you can
7880 refer to them. These are successive integers starting with one.
7881 @code{print} shows you the history number assigned to a value by
7882 printing @samp{$@var{num} = } before the value; here @var{num} is the
7885 To refer to any previous value, use @samp{$} followed by the value's
7886 history number. The way @code{print} labels its output is designed to
7887 remind you of this. Just @code{$} refers to the most recent value in
7888 the history, and @code{$$} refers to the value before that.
7889 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
7890 is the value just prior to @code{$$}, @code{$$1} is equivalent to
7891 @code{$$}, and @code{$$0} is equivalent to @code{$}.
7893 For example, suppose you have just printed a pointer to a structure and
7894 want to see the contents of the structure. It suffices to type
7900 If you have a chain of structures where the component @code{next} points
7901 to the next one, you can print the contents of the next one with this:
7908 You can print successive links in the chain by repeating this
7909 command---which you can do by just typing @key{RET}.
7911 Note that the history records values, not expressions. If the value of
7912 @code{x} is 4 and you type these commands:
7920 then the value recorded in the value history by the @code{print} command
7921 remains 4 even though the value of @code{x} has changed.
7926 Print the last ten values in the value history, with their item numbers.
7927 This is like @samp{p@ $$9} repeated ten times, except that @code{show
7928 values} does not change the history.
7930 @item show values @var{n}
7931 Print ten history values centered on history item number @var{n}.
7934 Print ten history values just after the values last printed. If no more
7935 values are available, @code{show values +} produces no display.
7938 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
7939 same effect as @samp{show values +}.
7941 @node Convenience Vars
7942 @section Convenience Variables
7944 @cindex convenience variables
7945 @cindex user-defined variables
7946 @value{GDBN} provides @dfn{convenience variables} that you can use within
7947 @value{GDBN} to hold on to a value and refer to it later. These variables
7948 exist entirely within @value{GDBN}; they are not part of your program, and
7949 setting a convenience variable has no direct effect on further execution
7950 of your program. That is why you can use them freely.
7952 Convenience variables are prefixed with @samp{$}. Any name preceded by
7953 @samp{$} can be used for a convenience variable, unless it is one of
7954 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
7955 (Value history references, in contrast, are @emph{numbers} preceded
7956 by @samp{$}. @xref{Value History, ,Value History}.)
7958 You can save a value in a convenience variable with an assignment
7959 expression, just as you would set a variable in your program.
7963 set $foo = *object_ptr
7967 would save in @code{$foo} the value contained in the object pointed to by
7970 Using a convenience variable for the first time creates it, but its
7971 value is @code{void} until you assign a new value. You can alter the
7972 value with another assignment at any time.
7974 Convenience variables have no fixed types. You can assign a convenience
7975 variable any type of value, including structures and arrays, even if
7976 that variable already has a value of a different type. The convenience
7977 variable, when used as an expression, has the type of its current value.
7980 @kindex show convenience
7981 @cindex show all user variables
7982 @item show convenience
7983 Print a list of convenience variables used so far, and their values.
7984 Abbreviated @code{show conv}.
7986 @kindex init-if-undefined
7987 @cindex convenience variables, initializing
7988 @item init-if-undefined $@var{variable} = @var{expression}
7989 Set a convenience variable if it has not already been set. This is useful
7990 for user-defined commands that keep some state. It is similar, in concept,
7991 to using local static variables with initializers in C (except that
7992 convenience variables are global). It can also be used to allow users to
7993 override default values used in a command script.
7995 If the variable is already defined then the expression is not evaluated so
7996 any side-effects do not occur.
7999 One of the ways to use a convenience variable is as a counter to be
8000 incremented or a pointer to be advanced. For example, to print
8001 a field from successive elements of an array of structures:
8005 print bar[$i++]->contents
8009 Repeat that command by typing @key{RET}.
8011 Some convenience variables are created automatically by @value{GDBN} and given
8012 values likely to be useful.
8015 @vindex $_@r{, convenience variable}
8017 The variable @code{$_} is automatically set by the @code{x} command to
8018 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8019 commands which provide a default address for @code{x} to examine also
8020 set @code{$_} to that address; these commands include @code{info line}
8021 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8022 except when set by the @code{x} command, in which case it is a pointer
8023 to the type of @code{$__}.
8025 @vindex $__@r{, convenience variable}
8027 The variable @code{$__} is automatically set by the @code{x} command
8028 to the value found in the last address examined. Its type is chosen
8029 to match the format in which the data was printed.
8032 @vindex $_exitcode@r{, convenience variable}
8033 The variable @code{$_exitcode} is automatically set to the exit code when
8034 the program being debugged terminates.
8037 @vindex $_siginfo@r{, convenience variable}
8038 The variable @code{$_siginfo} contains extra signal information
8039 (@pxref{extra signal information}). Note that @code{$_siginfo}
8040 could be empty, if the application has not yet received any signals.
8041 For example, it will be empty before you execute the @code{run} command.
8044 On HP-UX systems, if you refer to a function or variable name that
8045 begins with a dollar sign, @value{GDBN} searches for a user or system
8046 name first, before it searches for a convenience variable.
8048 @cindex convenience functions
8049 @value{GDBN} also supplies some @dfn{convenience functions}. These
8050 have a syntax similar to convenience variables. A convenience
8051 function can be used in an expression just like an ordinary function;
8052 however, a convenience function is implemented internally to
8057 @kindex help function
8058 @cindex show all convenience functions
8059 Print a list of all convenience functions.
8066 You can refer to machine register contents, in expressions, as variables
8067 with names starting with @samp{$}. The names of registers are different
8068 for each machine; use @code{info registers} to see the names used on
8072 @kindex info registers
8073 @item info registers
8074 Print the names and values of all registers except floating-point
8075 and vector registers (in the selected stack frame).
8077 @kindex info all-registers
8078 @cindex floating point registers
8079 @item info all-registers
8080 Print the names and values of all registers, including floating-point
8081 and vector registers (in the selected stack frame).
8083 @item info registers @var{regname} @dots{}
8084 Print the @dfn{relativized} value of each specified register @var{regname}.
8085 As discussed in detail below, register values are normally relative to
8086 the selected stack frame. @var{regname} may be any register name valid on
8087 the machine you are using, with or without the initial @samp{$}.
8090 @cindex stack pointer register
8091 @cindex program counter register
8092 @cindex process status register
8093 @cindex frame pointer register
8094 @cindex standard registers
8095 @value{GDBN} has four ``standard'' register names that are available (in
8096 expressions) on most machines---whenever they do not conflict with an
8097 architecture's canonical mnemonics for registers. The register names
8098 @code{$pc} and @code{$sp} are used for the program counter register and
8099 the stack pointer. @code{$fp} is used for a register that contains a
8100 pointer to the current stack frame, and @code{$ps} is used for a
8101 register that contains the processor status. For example,
8102 you could print the program counter in hex with
8109 or print the instruction to be executed next with
8116 or add four to the stack pointer@footnote{This is a way of removing
8117 one word from the stack, on machines where stacks grow downward in
8118 memory (most machines, nowadays). This assumes that the innermost
8119 stack frame is selected; setting @code{$sp} is not allowed when other
8120 stack frames are selected. To pop entire frames off the stack,
8121 regardless of machine architecture, use @code{return};
8122 see @ref{Returning, ,Returning from a Function}.} with
8128 Whenever possible, these four standard register names are available on
8129 your machine even though the machine has different canonical mnemonics,
8130 so long as there is no conflict. The @code{info registers} command
8131 shows the canonical names. For example, on the SPARC, @code{info
8132 registers} displays the processor status register as @code{$psr} but you
8133 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
8134 is an alias for the @sc{eflags} register.
8136 @value{GDBN} always considers the contents of an ordinary register as an
8137 integer when the register is examined in this way. Some machines have
8138 special registers which can hold nothing but floating point; these
8139 registers are considered to have floating point values. There is no way
8140 to refer to the contents of an ordinary register as floating point value
8141 (although you can @emph{print} it as a floating point value with
8142 @samp{print/f $@var{regname}}).
8144 Some registers have distinct ``raw'' and ``virtual'' data formats. This
8145 means that the data format in which the register contents are saved by
8146 the operating system is not the same one that your program normally
8147 sees. For example, the registers of the 68881 floating point
8148 coprocessor are always saved in ``extended'' (raw) format, but all C
8149 programs expect to work with ``double'' (virtual) format. In such
8150 cases, @value{GDBN} normally works with the virtual format only (the format
8151 that makes sense for your program), but the @code{info registers} command
8152 prints the data in both formats.
8154 @cindex SSE registers (x86)
8155 @cindex MMX registers (x86)
8156 Some machines have special registers whose contents can be interpreted
8157 in several different ways. For example, modern x86-based machines
8158 have SSE and MMX registers that can hold several values packed
8159 together in several different formats. @value{GDBN} refers to such
8160 registers in @code{struct} notation:
8163 (@value{GDBP}) print $xmm1
8165 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
8166 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
8167 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
8168 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
8169 v4_int32 = @{0, 20657912, 11, 13@},
8170 v2_int64 = @{88725056443645952, 55834574859@},
8171 uint128 = 0x0000000d0000000b013b36f800000000
8176 To set values of such registers, you need to tell @value{GDBN} which
8177 view of the register you wish to change, as if you were assigning
8178 value to a @code{struct} member:
8181 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
8184 Normally, register values are relative to the selected stack frame
8185 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
8186 value that the register would contain if all stack frames farther in
8187 were exited and their saved registers restored. In order to see the
8188 true contents of hardware registers, you must select the innermost
8189 frame (with @samp{frame 0}).
8191 However, @value{GDBN} must deduce where registers are saved, from the machine
8192 code generated by your compiler. If some registers are not saved, or if
8193 @value{GDBN} is unable to locate the saved registers, the selected stack
8194 frame makes no difference.
8196 @node Floating Point Hardware
8197 @section Floating Point Hardware
8198 @cindex floating point
8200 Depending on the configuration, @value{GDBN} may be able to give
8201 you more information about the status of the floating point hardware.
8206 Display hardware-dependent information about the floating
8207 point unit. The exact contents and layout vary depending on the
8208 floating point chip. Currently, @samp{info float} is supported on
8209 the ARM and x86 machines.
8213 @section Vector Unit
8216 Depending on the configuration, @value{GDBN} may be able to give you
8217 more information about the status of the vector unit.
8222 Display information about the vector unit. The exact contents and
8223 layout vary depending on the hardware.
8226 @node OS Information
8227 @section Operating System Auxiliary Information
8228 @cindex OS information
8230 @value{GDBN} provides interfaces to useful OS facilities that can help
8231 you debug your program.
8233 @cindex @code{ptrace} system call
8234 @cindex @code{struct user} contents
8235 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
8236 machines), it interfaces with the inferior via the @code{ptrace}
8237 system call. The operating system creates a special sata structure,
8238 called @code{struct user}, for this interface. You can use the
8239 command @code{info udot} to display the contents of this data
8245 Display the contents of the @code{struct user} maintained by the OS
8246 kernel for the program being debugged. @value{GDBN} displays the
8247 contents of @code{struct user} as a list of hex numbers, similar to
8248 the @code{examine} command.
8251 @cindex auxiliary vector
8252 @cindex vector, auxiliary
8253 Some operating systems supply an @dfn{auxiliary vector} to programs at
8254 startup. This is akin to the arguments and environment that you
8255 specify for a program, but contains a system-dependent variety of
8256 binary values that tell system libraries important details about the
8257 hardware, operating system, and process. Each value's purpose is
8258 identified by an integer tag; the meanings are well-known but system-specific.
8259 Depending on the configuration and operating system facilities,
8260 @value{GDBN} may be able to show you this information. For remote
8261 targets, this functionality may further depend on the remote stub's
8262 support of the @samp{qXfer:auxv:read} packet, see
8263 @ref{qXfer auxiliary vector read}.
8268 Display the auxiliary vector of the inferior, which can be either a
8269 live process or a core dump file. @value{GDBN} prints each tag value
8270 numerically, and also shows names and text descriptions for recognized
8271 tags. Some values in the vector are numbers, some bit masks, and some
8272 pointers to strings or other data. @value{GDBN} displays each value in the
8273 most appropriate form for a recognized tag, and in hexadecimal for
8274 an unrecognized tag.
8277 On some targets, @value{GDBN} can access operating-system-specific information
8278 and display it to user, without interpretation. For remote targets,
8279 this functionality depends on the remote stub's support of the
8280 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
8283 @kindex info os processes
8284 @item info os processes
8285 Display the list of processes on the target. For each process,
8286 @value{GDBN} prints the process identifier, the name of the user, and
8287 the command corresponding to the process.
8290 @node Memory Region Attributes
8291 @section Memory Region Attributes
8292 @cindex memory region attributes
8294 @dfn{Memory region attributes} allow you to describe special handling
8295 required by regions of your target's memory. @value{GDBN} uses
8296 attributes to determine whether to allow certain types of memory
8297 accesses; whether to use specific width accesses; and whether to cache
8298 target memory. By default the description of memory regions is
8299 fetched from the target (if the current target supports this), but the
8300 user can override the fetched regions.
8302 Defined memory regions can be individually enabled and disabled. When a
8303 memory region is disabled, @value{GDBN} uses the default attributes when
8304 accessing memory in that region. Similarly, if no memory regions have
8305 been defined, @value{GDBN} uses the default attributes when accessing
8308 When a memory region is defined, it is given a number to identify it;
8309 to enable, disable, or remove a memory region, you specify that number.
8313 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
8314 Define a memory region bounded by @var{lower} and @var{upper} with
8315 attributes @var{attributes}@dots{}, and add it to the list of regions
8316 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
8317 case: it is treated as the target's maximum memory address.
8318 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
8321 Discard any user changes to the memory regions and use target-supplied
8322 regions, if available, or no regions if the target does not support.
8325 @item delete mem @var{nums}@dots{}
8326 Remove memory regions @var{nums}@dots{} from the list of regions
8327 monitored by @value{GDBN}.
8330 @item disable mem @var{nums}@dots{}
8331 Disable monitoring of memory regions @var{nums}@dots{}.
8332 A disabled memory region is not forgotten.
8333 It may be enabled again later.
8336 @item enable mem @var{nums}@dots{}
8337 Enable monitoring of memory regions @var{nums}@dots{}.
8341 Print a table of all defined memory regions, with the following columns
8345 @item Memory Region Number
8346 @item Enabled or Disabled.
8347 Enabled memory regions are marked with @samp{y}.
8348 Disabled memory regions are marked with @samp{n}.
8351 The address defining the inclusive lower bound of the memory region.
8354 The address defining the exclusive upper bound of the memory region.
8357 The list of attributes set for this memory region.
8362 @subsection Attributes
8364 @subsubsection Memory Access Mode
8365 The access mode attributes set whether @value{GDBN} may make read or
8366 write accesses to a memory region.
8368 While these attributes prevent @value{GDBN} from performing invalid
8369 memory accesses, they do nothing to prevent the target system, I/O DMA,
8370 etc.@: from accessing memory.
8374 Memory is read only.
8376 Memory is write only.
8378 Memory is read/write. This is the default.
8381 @subsubsection Memory Access Size
8382 The access size attribute tells @value{GDBN} to use specific sized
8383 accesses in the memory region. Often memory mapped device registers
8384 require specific sized accesses. If no access size attribute is
8385 specified, @value{GDBN} may use accesses of any size.
8389 Use 8 bit memory accesses.
8391 Use 16 bit memory accesses.
8393 Use 32 bit memory accesses.
8395 Use 64 bit memory accesses.
8398 @c @subsubsection Hardware/Software Breakpoints
8399 @c The hardware/software breakpoint attributes set whether @value{GDBN}
8400 @c will use hardware or software breakpoints for the internal breakpoints
8401 @c used by the step, next, finish, until, etc. commands.
8405 @c Always use hardware breakpoints
8406 @c @item swbreak (default)
8409 @subsubsection Data Cache
8410 The data cache attributes set whether @value{GDBN} will cache target
8411 memory. While this generally improves performance by reducing debug
8412 protocol overhead, it can lead to incorrect results because @value{GDBN}
8413 does not know about volatile variables or memory mapped device
8418 Enable @value{GDBN} to cache target memory.
8420 Disable @value{GDBN} from caching target memory. This is the default.
8423 @subsection Memory Access Checking
8424 @value{GDBN} can be instructed to refuse accesses to memory that is
8425 not explicitly described. This can be useful if accessing such
8426 regions has undesired effects for a specific target, or to provide
8427 better error checking. The following commands control this behaviour.
8430 @kindex set mem inaccessible-by-default
8431 @item set mem inaccessible-by-default [on|off]
8432 If @code{on} is specified, make @value{GDBN} treat memory not
8433 explicitly described by the memory ranges as non-existent and refuse accesses
8434 to such memory. The checks are only performed if there's at least one
8435 memory range defined. If @code{off} is specified, make @value{GDBN}
8436 treat the memory not explicitly described by the memory ranges as RAM.
8437 The default value is @code{on}.
8438 @kindex show mem inaccessible-by-default
8439 @item show mem inaccessible-by-default
8440 Show the current handling of accesses to unknown memory.
8444 @c @subsubsection Memory Write Verification
8445 @c The memory write verification attributes set whether @value{GDBN}
8446 @c will re-reads data after each write to verify the write was successful.
8450 @c @item noverify (default)
8453 @node Dump/Restore Files
8454 @section Copy Between Memory and a File
8455 @cindex dump/restore files
8456 @cindex append data to a file
8457 @cindex dump data to a file
8458 @cindex restore data from a file
8460 You can use the commands @code{dump}, @code{append}, and
8461 @code{restore} to copy data between target memory and a file. The
8462 @code{dump} and @code{append} commands write data to a file, and the
8463 @code{restore} command reads data from a file back into the inferior's
8464 memory. Files may be in binary, Motorola S-record, Intel hex, or
8465 Tektronix Hex format; however, @value{GDBN} can only append to binary
8471 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8472 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
8473 Dump the contents of memory from @var{start_addr} to @var{end_addr},
8474 or the value of @var{expr}, to @var{filename} in the given format.
8476 The @var{format} parameter may be any one of:
8483 Motorola S-record format.
8485 Tektronix Hex format.
8488 @value{GDBN} uses the same definitions of these formats as the
8489 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
8490 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
8494 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8495 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
8496 Append the contents of memory from @var{start_addr} to @var{end_addr},
8497 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
8498 (@value{GDBN} can only append data to files in raw binary form.)
8501 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
8502 Restore the contents of file @var{filename} into memory. The
8503 @code{restore} command can automatically recognize any known @sc{bfd}
8504 file format, except for raw binary. To restore a raw binary file you
8505 must specify the optional keyword @code{binary} after the filename.
8507 If @var{bias} is non-zero, its value will be added to the addresses
8508 contained in the file. Binary files always start at address zero, so
8509 they will be restored at address @var{bias}. Other bfd files have
8510 a built-in location; they will be restored at offset @var{bias}
8513 If @var{start} and/or @var{end} are non-zero, then only data between
8514 file offset @var{start} and file offset @var{end} will be restored.
8515 These offsets are relative to the addresses in the file, before
8516 the @var{bias} argument is applied.
8520 @node Core File Generation
8521 @section How to Produce a Core File from Your Program
8522 @cindex dump core from inferior
8524 A @dfn{core file} or @dfn{core dump} is a file that records the memory
8525 image of a running process and its process status (register values
8526 etc.). Its primary use is post-mortem debugging of a program that
8527 crashed while it ran outside a debugger. A program that crashes
8528 automatically produces a core file, unless this feature is disabled by
8529 the user. @xref{Files}, for information on invoking @value{GDBN} in
8530 the post-mortem debugging mode.
8532 Occasionally, you may wish to produce a core file of the program you
8533 are debugging in order to preserve a snapshot of its state.
8534 @value{GDBN} has a special command for that.
8538 @kindex generate-core-file
8539 @item generate-core-file [@var{file}]
8540 @itemx gcore [@var{file}]
8541 Produce a core dump of the inferior process. The optional argument
8542 @var{file} specifies the file name where to put the core dump. If not
8543 specified, the file name defaults to @file{core.@var{pid}}, where
8544 @var{pid} is the inferior process ID.
8546 Note that this command is implemented only for some systems (as of
8547 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
8550 @node Character Sets
8551 @section Character Sets
8552 @cindex character sets
8554 @cindex translating between character sets
8555 @cindex host character set
8556 @cindex target character set
8558 If the program you are debugging uses a different character set to
8559 represent characters and strings than the one @value{GDBN} uses itself,
8560 @value{GDBN} can automatically translate between the character sets for
8561 you. The character set @value{GDBN} uses we call the @dfn{host
8562 character set}; the one the inferior program uses we call the
8563 @dfn{target character set}.
8565 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
8566 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
8567 remote protocol (@pxref{Remote Debugging}) to debug a program
8568 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
8569 then the host character set is Latin-1, and the target character set is
8570 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
8571 target-charset EBCDIC-US}, then @value{GDBN} translates between
8572 @sc{ebcdic} and Latin 1 as you print character or string values, or use
8573 character and string literals in expressions.
8575 @value{GDBN} has no way to automatically recognize which character set
8576 the inferior program uses; you must tell it, using the @code{set
8577 target-charset} command, described below.
8579 Here are the commands for controlling @value{GDBN}'s character set
8583 @item set target-charset @var{charset}
8584 @kindex set target-charset
8585 Set the current target character set to @var{charset}. To display the
8586 list of supported target character sets, type
8587 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
8589 @item set host-charset @var{charset}
8590 @kindex set host-charset
8591 Set the current host character set to @var{charset}.
8593 By default, @value{GDBN} uses a host character set appropriate to the
8594 system it is running on; you can override that default using the
8595 @code{set host-charset} command. On some systems, @value{GDBN} cannot
8596 automatically determine the appropriate host character set. In this
8597 case, @value{GDBN} uses @samp{UTF-8}.
8599 @value{GDBN} can only use certain character sets as its host character
8600 set. If you type @kbd{@w{set target-charset @key{TAB}@key{TAB}}},
8601 @value{GDBN} will list the host character sets it supports.
8603 @item set charset @var{charset}
8605 Set the current host and target character sets to @var{charset}. As
8606 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
8607 @value{GDBN} will list the names of the character sets that can be used
8608 for both host and target.
8611 @kindex show charset
8612 Show the names of the current host and target character sets.
8614 @item show host-charset
8615 @kindex show host-charset
8616 Show the name of the current host character set.
8618 @item show target-charset
8619 @kindex show target-charset
8620 Show the name of the current target character set.
8622 @item set target-wide-charset @var{charset}
8623 @kindex set target-wide-charset
8624 Set the current target's wide character set to @var{charset}. This is
8625 the character set used by the target's @code{wchar_t} type. To
8626 display the list of supported wide character sets, type
8627 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
8629 @item show target-wide-charset
8630 @kindex show target-wide-charset
8631 Show the name of the current target's wide character set.
8634 Here is an example of @value{GDBN}'s character set support in action.
8635 Assume that the following source code has been placed in the file
8636 @file{charset-test.c}:
8642 = @{72, 101, 108, 108, 111, 44, 32, 119,
8643 111, 114, 108, 100, 33, 10, 0@};
8644 char ibm1047_hello[]
8645 = @{200, 133, 147, 147, 150, 107, 64, 166,
8646 150, 153, 147, 132, 90, 37, 0@};
8650 printf ("Hello, world!\n");
8654 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
8655 containing the string @samp{Hello, world!} followed by a newline,
8656 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
8658 We compile the program, and invoke the debugger on it:
8661 $ gcc -g charset-test.c -o charset-test
8662 $ gdb -nw charset-test
8663 GNU gdb 2001-12-19-cvs
8664 Copyright 2001 Free Software Foundation, Inc.
8669 We can use the @code{show charset} command to see what character sets
8670 @value{GDBN} is currently using to interpret and display characters and
8674 (@value{GDBP}) show charset
8675 The current host and target character set is `ISO-8859-1'.
8679 For the sake of printing this manual, let's use @sc{ascii} as our
8680 initial character set:
8682 (@value{GDBP}) set charset ASCII
8683 (@value{GDBP}) show charset
8684 The current host and target character set is `ASCII'.
8688 Let's assume that @sc{ascii} is indeed the correct character set for our
8689 host system --- in other words, let's assume that if @value{GDBN} prints
8690 characters using the @sc{ascii} character set, our terminal will display
8691 them properly. Since our current target character set is also
8692 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
8695 (@value{GDBP}) print ascii_hello
8696 $1 = 0x401698 "Hello, world!\n"
8697 (@value{GDBP}) print ascii_hello[0]
8702 @value{GDBN} uses the target character set for character and string
8703 literals you use in expressions:
8706 (@value{GDBP}) print '+'
8711 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
8714 @value{GDBN} relies on the user to tell it which character set the
8715 target program uses. If we print @code{ibm1047_hello} while our target
8716 character set is still @sc{ascii}, we get jibberish:
8719 (@value{GDBP}) print ibm1047_hello
8720 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
8721 (@value{GDBP}) print ibm1047_hello[0]
8726 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
8727 @value{GDBN} tells us the character sets it supports:
8730 (@value{GDBP}) set target-charset
8731 ASCII EBCDIC-US IBM1047 ISO-8859-1
8732 (@value{GDBP}) set target-charset
8735 We can select @sc{ibm1047} as our target character set, and examine the
8736 program's strings again. Now the @sc{ascii} string is wrong, but
8737 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
8738 target character set, @sc{ibm1047}, to the host character set,
8739 @sc{ascii}, and they display correctly:
8742 (@value{GDBP}) set target-charset IBM1047
8743 (@value{GDBP}) show charset
8744 The current host character set is `ASCII'.
8745 The current target character set is `IBM1047'.
8746 (@value{GDBP}) print ascii_hello
8747 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
8748 (@value{GDBP}) print ascii_hello[0]
8750 (@value{GDBP}) print ibm1047_hello
8751 $8 = 0x4016a8 "Hello, world!\n"
8752 (@value{GDBP}) print ibm1047_hello[0]
8757 As above, @value{GDBN} uses the target character set for character and
8758 string literals you use in expressions:
8761 (@value{GDBP}) print '+'
8766 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
8769 @node Caching Remote Data
8770 @section Caching Data of Remote Targets
8771 @cindex caching data of remote targets
8773 @value{GDBN} caches data exchanged between the debugger and a
8774 remote target (@pxref{Remote Debugging}). Such caching generally improves
8775 performance, because it reduces the overhead of the remote protocol by
8776 bundling memory reads and writes into large chunks. Unfortunately, simply
8777 caching everything would lead to incorrect results, since @value{GDBN}
8778 does not necessarily know anything about volatile values, memory-mapped I/O
8779 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
8780 memory can be changed @emph{while} a gdb command is executing.
8781 Therefore, by default, @value{GDBN} only caches data
8782 known to be on the stack@footnote{In non-stop mode, it is moderately
8783 rare for a running thread to modify the stack of a stopped thread
8784 in a way that would interfere with a backtrace, and caching of
8785 stack reads provides a significant speed up of remote backtraces.}.
8786 Other regions of memory can be explicitly marked as
8787 cacheable; see @pxref{Memory Region Attributes}.
8790 @kindex set remotecache
8791 @item set remotecache on
8792 @itemx set remotecache off
8793 This option no longer does anything; it exists for compatibility
8796 @kindex show remotecache
8797 @item show remotecache
8798 Show the current state of the obsolete remotecache flag.
8800 @kindex set stack-cache
8801 @item set stack-cache on
8802 @itemx set stack-cache off
8803 Enable or disable caching of stack accesses. When @code{ON}, use
8804 caching. By default, this option is @code{ON}.
8806 @kindex show stack-cache
8807 @item show stack-cache
8808 Show the current state of data caching for memory accesses.
8811 @item info dcache @r{[}line@r{]}
8812 Print the information about the data cache performance. The
8813 information displayed includes the dcache width and depth, and for
8814 each cache line, its number, address, and how many times it was
8815 referenced. This command is useful for debugging the data cache
8818 If a line number is specified, the contents of that line will be
8822 @node Searching Memory
8823 @section Search Memory
8824 @cindex searching memory
8826 Memory can be searched for a particular sequence of bytes with the
8827 @code{find} command.
8831 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8832 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8833 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
8834 etc. The search begins at address @var{start_addr} and continues for either
8835 @var{len} bytes or through to @var{end_addr} inclusive.
8838 @var{s} and @var{n} are optional parameters.
8839 They may be specified in either order, apart or together.
8842 @item @var{s}, search query size
8843 The size of each search query value.
8849 halfwords (two bytes)
8853 giant words (eight bytes)
8856 All values are interpreted in the current language.
8857 This means, for example, that if the current source language is C/C@t{++}
8858 then searching for the string ``hello'' includes the trailing '\0'.
8860 If the value size is not specified, it is taken from the
8861 value's type in the current language.
8862 This is useful when one wants to specify the search
8863 pattern as a mixture of types.
8864 Note that this means, for example, that in the case of C-like languages
8865 a search for an untyped 0x42 will search for @samp{(int) 0x42}
8866 which is typically four bytes.
8868 @item @var{n}, maximum number of finds
8869 The maximum number of matches to print. The default is to print all finds.
8872 You can use strings as search values. Quote them with double-quotes
8874 The string value is copied into the search pattern byte by byte,
8875 regardless of the endianness of the target and the size specification.
8877 The address of each match found is printed as well as a count of the
8878 number of matches found.
8880 The address of the last value found is stored in convenience variable
8882 A count of the number of matches is stored in @samp{$numfound}.
8884 For example, if stopped at the @code{printf} in this function:
8890 static char hello[] = "hello-hello";
8891 static struct @{ char c; short s; int i; @}
8892 __attribute__ ((packed)) mixed
8893 = @{ 'c', 0x1234, 0x87654321 @};
8894 printf ("%s\n", hello);
8899 you get during debugging:
8902 (gdb) find &hello[0], +sizeof(hello), "hello"
8903 0x804956d <hello.1620+6>
8905 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
8906 0x8049567 <hello.1620>
8907 0x804956d <hello.1620+6>
8909 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
8910 0x8049567 <hello.1620>
8912 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
8913 0x8049560 <mixed.1625>
8915 (gdb) print $numfound
8918 $2 = (void *) 0x8049560
8921 @node Optimized Code
8922 @chapter Debugging Optimized Code
8923 @cindex optimized code, debugging
8924 @cindex debugging optimized code
8926 Almost all compilers support optimization. With optimization
8927 disabled, the compiler generates assembly code that corresponds
8928 directly to your source code, in a simplistic way. As the compiler
8929 applies more powerful optimizations, the generated assembly code
8930 diverges from your original source code. With help from debugging
8931 information generated by the compiler, @value{GDBN} can map from
8932 the running program back to constructs from your original source.
8934 @value{GDBN} is more accurate with optimization disabled. If you
8935 can recompile without optimization, it is easier to follow the
8936 progress of your program during debugging. But, there are many cases
8937 where you may need to debug an optimized version.
8939 When you debug a program compiled with @samp{-g -O}, remember that the
8940 optimizer has rearranged your code; the debugger shows you what is
8941 really there. Do not be too surprised when the execution path does not
8942 exactly match your source file! An extreme example: if you define a
8943 variable, but never use it, @value{GDBN} never sees that
8944 variable---because the compiler optimizes it out of existence.
8946 Some things do not work as well with @samp{-g -O} as with just
8947 @samp{-g}, particularly on machines with instruction scheduling. If in
8948 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
8949 please report it to us as a bug (including a test case!).
8950 @xref{Variables}, for more information about debugging optimized code.
8953 * Inline Functions:: How @value{GDBN} presents inlining
8956 @node Inline Functions
8957 @section Inline Functions
8958 @cindex inline functions, debugging
8960 @dfn{Inlining} is an optimization that inserts a copy of the function
8961 body directly at each call site, instead of jumping to a shared
8962 routine. @value{GDBN} displays inlined functions just like
8963 non-inlined functions. They appear in backtraces. You can view their
8964 arguments and local variables, step into them with @code{step}, skip
8965 them with @code{next}, and escape from them with @code{finish}.
8966 You can check whether a function was inlined by using the
8967 @code{info frame} command.
8969 For @value{GDBN} to support inlined functions, the compiler must
8970 record information about inlining in the debug information ---
8971 @value{NGCC} using the @sc{dwarf 2} format does this, and several
8972 other compilers do also. @value{GDBN} only supports inlined functions
8973 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
8974 do not emit two required attributes (@samp{DW_AT_call_file} and
8975 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
8976 function calls with earlier versions of @value{NGCC}. It instead
8977 displays the arguments and local variables of inlined functions as
8978 local variables in the caller.
8980 The body of an inlined function is directly included at its call site;
8981 unlike a non-inlined function, there are no instructions devoted to
8982 the call. @value{GDBN} still pretends that the call site and the
8983 start of the inlined function are different instructions. Stepping to
8984 the call site shows the call site, and then stepping again shows
8985 the first line of the inlined function, even though no additional
8986 instructions are executed.
8988 This makes source-level debugging much clearer; you can see both the
8989 context of the call and then the effect of the call. Only stepping by
8990 a single instruction using @code{stepi} or @code{nexti} does not do
8991 this; single instruction steps always show the inlined body.
8993 There are some ways that @value{GDBN} does not pretend that inlined
8994 function calls are the same as normal calls:
8998 You cannot set breakpoints on inlined functions. @value{GDBN}
8999 either reports that there is no symbol with that name, or else sets the
9000 breakpoint only on non-inlined copies of the function. This limitation
9001 will be removed in a future version of @value{GDBN}; until then,
9002 set a breakpoint by line number on the first line of the inlined
9006 Setting breakpoints at the call site of an inlined function may not
9007 work, because the call site does not contain any code. @value{GDBN}
9008 may incorrectly move the breakpoint to the next line of the enclosing
9009 function, after the call. This limitation will be removed in a future
9010 version of @value{GDBN}; until then, set a breakpoint on an earlier line
9011 or inside the inlined function instead.
9014 @value{GDBN} cannot locate the return value of inlined calls after
9015 using the @code{finish} command. This is a limitation of compiler-generated
9016 debugging information; after @code{finish}, you can step to the next line
9017 and print a variable where your program stored the return value.
9023 @chapter C Preprocessor Macros
9025 Some languages, such as C and C@t{++}, provide a way to define and invoke
9026 ``preprocessor macros'' which expand into strings of tokens.
9027 @value{GDBN} can evaluate expressions containing macro invocations, show
9028 the result of macro expansion, and show a macro's definition, including
9029 where it was defined.
9031 You may need to compile your program specially to provide @value{GDBN}
9032 with information about preprocessor macros. Most compilers do not
9033 include macros in their debugging information, even when you compile
9034 with the @option{-g} flag. @xref{Compilation}.
9036 A program may define a macro at one point, remove that definition later,
9037 and then provide a different definition after that. Thus, at different
9038 points in the program, a macro may have different definitions, or have
9039 no definition at all. If there is a current stack frame, @value{GDBN}
9040 uses the macros in scope at that frame's source code line. Otherwise,
9041 @value{GDBN} uses the macros in scope at the current listing location;
9044 Whenever @value{GDBN} evaluates an expression, it always expands any
9045 macro invocations present in the expression. @value{GDBN} also provides
9046 the following commands for working with macros explicitly.
9050 @kindex macro expand
9051 @cindex macro expansion, showing the results of preprocessor
9052 @cindex preprocessor macro expansion, showing the results of
9053 @cindex expanding preprocessor macros
9054 @item macro expand @var{expression}
9055 @itemx macro exp @var{expression}
9056 Show the results of expanding all preprocessor macro invocations in
9057 @var{expression}. Since @value{GDBN} simply expands macros, but does
9058 not parse the result, @var{expression} need not be a valid expression;
9059 it can be any string of tokens.
9062 @item macro expand-once @var{expression}
9063 @itemx macro exp1 @var{expression}
9064 @cindex expand macro once
9065 @i{(This command is not yet implemented.)} Show the results of
9066 expanding those preprocessor macro invocations that appear explicitly in
9067 @var{expression}. Macro invocations appearing in that expansion are
9068 left unchanged. This command allows you to see the effect of a
9069 particular macro more clearly, without being confused by further
9070 expansions. Since @value{GDBN} simply expands macros, but does not
9071 parse the result, @var{expression} need not be a valid expression; it
9072 can be any string of tokens.
9075 @cindex macro definition, showing
9076 @cindex definition, showing a macro's
9077 @item info macro @var{macro}
9078 Show the definition of the macro named @var{macro}, and describe the
9079 source location or compiler command-line where that definition was established.
9081 @kindex macro define
9082 @cindex user-defined macros
9083 @cindex defining macros interactively
9084 @cindex macros, user-defined
9085 @item macro define @var{macro} @var{replacement-list}
9086 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
9087 Introduce a definition for a preprocessor macro named @var{macro},
9088 invocations of which are replaced by the tokens given in
9089 @var{replacement-list}. The first form of this command defines an
9090 ``object-like'' macro, which takes no arguments; the second form
9091 defines a ``function-like'' macro, which takes the arguments given in
9094 A definition introduced by this command is in scope in every
9095 expression evaluated in @value{GDBN}, until it is removed with the
9096 @code{macro undef} command, described below. The definition overrides
9097 all definitions for @var{macro} present in the program being debugged,
9098 as well as any previous user-supplied definition.
9101 @item macro undef @var{macro}
9102 Remove any user-supplied definition for the macro named @var{macro}.
9103 This command only affects definitions provided with the @code{macro
9104 define} command, described above; it cannot remove definitions present
9105 in the program being debugged.
9109 List all the macros defined using the @code{macro define} command.
9112 @cindex macros, example of debugging with
9113 Here is a transcript showing the above commands in action. First, we
9114 show our source files:
9122 #define ADD(x) (M + x)
9127 printf ("Hello, world!\n");
9129 printf ("We're so creative.\n");
9131 printf ("Goodbye, world!\n");
9138 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
9139 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
9140 compiler includes information about preprocessor macros in the debugging
9144 $ gcc -gdwarf-2 -g3 sample.c -o sample
9148 Now, we start @value{GDBN} on our sample program:
9152 GNU gdb 2002-05-06-cvs
9153 Copyright 2002 Free Software Foundation, Inc.
9154 GDB is free software, @dots{}
9158 We can expand macros and examine their definitions, even when the
9159 program is not running. @value{GDBN} uses the current listing position
9160 to decide which macro definitions are in scope:
9163 (@value{GDBP}) list main
9166 5 #define ADD(x) (M + x)
9171 10 printf ("Hello, world!\n");
9173 12 printf ("We're so creative.\n");
9174 (@value{GDBP}) info macro ADD
9175 Defined at /home/jimb/gdb/macros/play/sample.c:5
9176 #define ADD(x) (M + x)
9177 (@value{GDBP}) info macro Q
9178 Defined at /home/jimb/gdb/macros/play/sample.h:1
9179 included at /home/jimb/gdb/macros/play/sample.c:2
9181 (@value{GDBP}) macro expand ADD(1)
9182 expands to: (42 + 1)
9183 (@value{GDBP}) macro expand-once ADD(1)
9184 expands to: once (M + 1)
9188 In the example above, note that @code{macro expand-once} expands only
9189 the macro invocation explicit in the original text --- the invocation of
9190 @code{ADD} --- but does not expand the invocation of the macro @code{M},
9191 which was introduced by @code{ADD}.
9193 Once the program is running, @value{GDBN} uses the macro definitions in
9194 force at the source line of the current stack frame:
9197 (@value{GDBP}) break main
9198 Breakpoint 1 at 0x8048370: file sample.c, line 10.
9200 Starting program: /home/jimb/gdb/macros/play/sample
9202 Breakpoint 1, main () at sample.c:10
9203 10 printf ("Hello, world!\n");
9207 At line 10, the definition of the macro @code{N} at line 9 is in force:
9210 (@value{GDBP}) info macro N
9211 Defined at /home/jimb/gdb/macros/play/sample.c:9
9213 (@value{GDBP}) macro expand N Q M
9215 (@value{GDBP}) print N Q M
9220 As we step over directives that remove @code{N}'s definition, and then
9221 give it a new definition, @value{GDBN} finds the definition (or lack
9222 thereof) in force at each point:
9227 12 printf ("We're so creative.\n");
9228 (@value{GDBP}) info macro N
9229 The symbol `N' has no definition as a C/C++ preprocessor macro
9230 at /home/jimb/gdb/macros/play/sample.c:12
9233 14 printf ("Goodbye, world!\n");
9234 (@value{GDBP}) info macro N
9235 Defined at /home/jimb/gdb/macros/play/sample.c:13
9237 (@value{GDBP}) macro expand N Q M
9238 expands to: 1729 < 42
9239 (@value{GDBP}) print N Q M
9244 In addition to source files, macros can be defined on the compilation command
9245 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
9246 such a way, @value{GDBN} displays the location of their definition as line zero
9247 of the source file submitted to the compiler.
9250 (@value{GDBP}) info macro __STDC__
9251 Defined at /home/jimb/gdb/macros/play/sample.c:0
9258 @chapter Tracepoints
9259 @c This chapter is based on the documentation written by Michael
9260 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
9263 In some applications, it is not feasible for the debugger to interrupt
9264 the program's execution long enough for the developer to learn
9265 anything helpful about its behavior. If the program's correctness
9266 depends on its real-time behavior, delays introduced by a debugger
9267 might cause the program to change its behavior drastically, or perhaps
9268 fail, even when the code itself is correct. It is useful to be able
9269 to observe the program's behavior without interrupting it.
9271 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
9272 specify locations in the program, called @dfn{tracepoints}, and
9273 arbitrary expressions to evaluate when those tracepoints are reached.
9274 Later, using the @code{tfind} command, you can examine the values
9275 those expressions had when the program hit the tracepoints. The
9276 expressions may also denote objects in memory---structures or arrays,
9277 for example---whose values @value{GDBN} should record; while visiting
9278 a particular tracepoint, you may inspect those objects as if they were
9279 in memory at that moment. However, because @value{GDBN} records these
9280 values without interacting with you, it can do so quickly and
9281 unobtrusively, hopefully not disturbing the program's behavior.
9283 The tracepoint facility is currently available only for remote
9284 targets. @xref{Targets}. In addition, your remote target must know
9285 how to collect trace data. This functionality is implemented in the
9286 remote stub; however, none of the stubs distributed with @value{GDBN}
9287 support tracepoints as of this writing. The format of the remote
9288 packets used to implement tracepoints are described in @ref{Tracepoint
9291 This chapter describes the tracepoint commands and features.
9295 * Analyze Collected Data::
9296 * Tracepoint Variables::
9299 @node Set Tracepoints
9300 @section Commands to Set Tracepoints
9302 Before running such a @dfn{trace experiment}, an arbitrary number of
9303 tracepoints can be set. A tracepoint is actually a special type of
9304 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
9305 standard breakpoint commands. For instance, as with breakpoints,
9306 tracepoint numbers are successive integers starting from one, and many
9307 of the commands associated with tracepoints take the tracepoint number
9308 as their argument, to identify which tracepoint to work on.
9310 For each tracepoint, you can specify, in advance, some arbitrary set
9311 of data that you want the target to collect in the trace buffer when
9312 it hits that tracepoint. The collected data can include registers,
9313 local variables, or global data. Later, you can use @value{GDBN}
9314 commands to examine the values these data had at the time the
9317 Tracepoints do not support every breakpoint feature. Conditional
9318 expressions and ignore counts on tracepoints have no effect, and
9319 tracepoints cannot run @value{GDBN} commands when they are
9320 hit. Tracepoints may not be thread-specific either.
9322 This section describes commands to set tracepoints and associated
9323 conditions and actions.
9326 * Create and Delete Tracepoints::
9327 * Enable and Disable Tracepoints::
9328 * Tracepoint Passcounts::
9329 * Tracepoint Conditions::
9330 * Tracepoint Actions::
9331 * Listing Tracepoints::
9332 * Starting and Stopping Trace Experiments::
9335 @node Create and Delete Tracepoints
9336 @subsection Create and Delete Tracepoints
9339 @cindex set tracepoint
9341 @item trace @var{location}
9342 The @code{trace} command is very similar to the @code{break} command.
9343 Its argument @var{location} can be a source line, a function name, or
9344 an address in the target program. @xref{Specify Location}. The
9345 @code{trace} command defines a tracepoint, which is a point in the
9346 target program where the debugger will briefly stop, collect some
9347 data, and then allow the program to continue. Setting a tracepoint or
9348 changing its actions doesn't take effect until the next @code{tstart}
9349 command, and once a trace experiment is running, further changes will
9350 not have any effect until the next trace experiment starts.
9352 Here are some examples of using the @code{trace} command:
9355 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
9357 (@value{GDBP}) @b{trace +2} // 2 lines forward
9359 (@value{GDBP}) @b{trace my_function} // first source line of function
9361 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
9363 (@value{GDBP}) @b{trace *0x2117c4} // an address
9367 You can abbreviate @code{trace} as @code{tr}.
9369 @item trace @var{location} if @var{cond}
9370 Set a tracepoint with condition @var{cond}; evaluate the expression
9371 @var{cond} each time the tracepoint is reached, and collect data only
9372 if the value is nonzero---that is, if @var{cond} evaluates as true.
9373 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
9374 information on tracepoint conditions.
9377 @cindex last tracepoint number
9378 @cindex recent tracepoint number
9379 @cindex tracepoint number
9380 The convenience variable @code{$tpnum} records the tracepoint number
9381 of the most recently set tracepoint.
9383 @kindex delete tracepoint
9384 @cindex tracepoint deletion
9385 @item delete tracepoint @r{[}@var{num}@r{]}
9386 Permanently delete one or more tracepoints. With no argument, the
9387 default is to delete all tracepoints. Note that the regular
9388 @code{delete} command can remove tracepoints also.
9393 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
9395 (@value{GDBP}) @b{delete trace} // remove all tracepoints
9399 You can abbreviate this command as @code{del tr}.
9402 @node Enable and Disable Tracepoints
9403 @subsection Enable and Disable Tracepoints
9405 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
9408 @kindex disable tracepoint
9409 @item disable tracepoint @r{[}@var{num}@r{]}
9410 Disable tracepoint @var{num}, or all tracepoints if no argument
9411 @var{num} is given. A disabled tracepoint will have no effect during
9412 the next trace experiment, but it is not forgotten. You can re-enable
9413 a disabled tracepoint using the @code{enable tracepoint} command.
9415 @kindex enable tracepoint
9416 @item enable tracepoint @r{[}@var{num}@r{]}
9417 Enable tracepoint @var{num}, or all tracepoints. The enabled
9418 tracepoints will become effective the next time a trace experiment is
9422 @node Tracepoint Passcounts
9423 @subsection Tracepoint Passcounts
9427 @cindex tracepoint pass count
9428 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
9429 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
9430 automatically stop a trace experiment. If a tracepoint's passcount is
9431 @var{n}, then the trace experiment will be automatically stopped on
9432 the @var{n}'th time that tracepoint is hit. If the tracepoint number
9433 @var{num} is not specified, the @code{passcount} command sets the
9434 passcount of the most recently defined tracepoint. If no passcount is
9435 given, the trace experiment will run until stopped explicitly by the
9441 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
9442 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
9444 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
9445 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
9446 (@value{GDBP}) @b{trace foo}
9447 (@value{GDBP}) @b{pass 3}
9448 (@value{GDBP}) @b{trace bar}
9449 (@value{GDBP}) @b{pass 2}
9450 (@value{GDBP}) @b{trace baz}
9451 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
9452 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
9453 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
9454 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
9458 @node Tracepoint Conditions
9459 @subsection Tracepoint Conditions
9460 @cindex conditional tracepoints
9461 @cindex tracepoint conditions
9463 The simplest sort of tracepoint collects data every time your program
9464 reaches a specified place. You can also specify a @dfn{condition} for
9465 a tracepoint. A condition is just a Boolean expression in your
9466 programming language (@pxref{Expressions, ,Expressions}). A
9467 tracepoint with a condition evaluates the expression each time your
9468 program reaches it, and data collection happens only if the condition
9471 Tracepoint conditions can be specified when a tracepoint is set, by
9472 using @samp{if} in the arguments to the @code{trace} command.
9473 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
9474 also be set or changed at any time with the @code{condition} command,
9475 just as with breakpoints.
9477 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
9478 the conditional expression itself. Instead, @value{GDBN} encodes the
9479 expression into an agent expression (@pxref{Agent Expressions}
9480 suitable for execution on the target, independently of @value{GDBN}.
9481 Global variables become raw memory locations, locals become stack
9482 accesses, and so forth.
9484 For instance, suppose you have a function that is usually called
9485 frequently, but should not be called after an error has occurred. You
9486 could use the following tracepoint command to collect data about calls
9487 of that function that happen while the error code is propagating
9488 through the program; an unconditional tracepoint could end up
9489 collecting thousands of useless trace frames that you would have to
9493 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
9496 @node Tracepoint Actions
9497 @subsection Tracepoint Action Lists
9501 @cindex tracepoint actions
9502 @item actions @r{[}@var{num}@r{]}
9503 This command will prompt for a list of actions to be taken when the
9504 tracepoint is hit. If the tracepoint number @var{num} is not
9505 specified, this command sets the actions for the one that was most
9506 recently defined (so that you can define a tracepoint and then say
9507 @code{actions} without bothering about its number). You specify the
9508 actions themselves on the following lines, one action at a time, and
9509 terminate the actions list with a line containing just @code{end}. So
9510 far, the only defined actions are @code{collect} and
9511 @code{while-stepping}.
9513 @cindex remove actions from a tracepoint
9514 To remove all actions from a tracepoint, type @samp{actions @var{num}}
9515 and follow it immediately with @samp{end}.
9518 (@value{GDBP}) @b{collect @var{data}} // collect some data
9520 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
9522 (@value{GDBP}) @b{end} // signals the end of actions.
9525 In the following example, the action list begins with @code{collect}
9526 commands indicating the things to be collected when the tracepoint is
9527 hit. Then, in order to single-step and collect additional data
9528 following the tracepoint, a @code{while-stepping} command is used,
9529 followed by the list of things to be collected while stepping. The
9530 @code{while-stepping} command is terminated by its own separate
9531 @code{end} command. Lastly, the action list is terminated by an
9535 (@value{GDBP}) @b{trace foo}
9536 (@value{GDBP}) @b{actions}
9537 Enter actions for tracepoint 1, one per line:
9546 @kindex collect @r{(tracepoints)}
9547 @item collect @var{expr1}, @var{expr2}, @dots{}
9548 Collect values of the given expressions when the tracepoint is hit.
9549 This command accepts a comma-separated list of any valid expressions.
9550 In addition to global, static, or local variables, the following
9551 special arguments are supported:
9555 collect all registers
9558 collect all function arguments
9561 collect all local variables.
9564 You can give several consecutive @code{collect} commands, each one
9565 with a single argument, or one @code{collect} command with several
9566 arguments separated by commas: the effect is the same.
9568 The command @code{info scope} (@pxref{Symbols, info scope}) is
9569 particularly useful for figuring out what data to collect.
9571 @kindex while-stepping @r{(tracepoints)}
9572 @item while-stepping @var{n}
9573 Perform @var{n} single-step traces after the tracepoint, collecting
9574 new data at each step. The @code{while-stepping} command is
9575 followed by the list of what to collect while stepping (followed by
9576 its own @code{end} command):
9580 > collect $regs, myglobal
9586 You may abbreviate @code{while-stepping} as @code{ws} or
9590 @node Listing Tracepoints
9591 @subsection Listing Tracepoints
9594 @kindex info tracepoints
9596 @cindex information about tracepoints
9597 @item info tracepoints @r{[}@var{num}@r{]}
9598 Display information about the tracepoint @var{num}. If you don't
9599 specify a tracepoint number, displays information about all the
9600 tracepoints defined so far. The format is similar to that used for
9601 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
9602 command, simply restricting itself to tracepoints.
9604 A tracepoint's listing may include additional information specific to
9609 its passcount as given by the @code{passcount @var{n}} command
9611 its step count as given by the @code{while-stepping @var{n}} command
9613 its action list as given by the @code{actions} command. The actions
9614 are prefixed with an @samp{A} so as to distinguish them from commands.
9618 (@value{GDBP}) @b{info trace}
9619 Num Type Disp Enb Address What
9620 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
9624 A collect globfoo, $regs
9632 This command can be abbreviated @code{info tp}.
9635 @node Starting and Stopping Trace Experiments
9636 @subsection Starting and Stopping Trace Experiments
9640 @cindex start a new trace experiment
9641 @cindex collected data discarded
9643 This command takes no arguments. It starts the trace experiment, and
9644 begins collecting data. This has the side effect of discarding all
9645 the data collected in the trace buffer during the previous trace
9649 @cindex stop a running trace experiment
9651 This command takes no arguments. It ends the trace experiment, and
9652 stops collecting data.
9654 @strong{Note}: a trace experiment and data collection may stop
9655 automatically if any tracepoint's passcount is reached
9656 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
9659 @cindex status of trace data collection
9660 @cindex trace experiment, status of
9662 This command displays the status of the current trace data
9666 Here is an example of the commands we described so far:
9669 (@value{GDBP}) @b{trace gdb_c_test}
9670 (@value{GDBP}) @b{actions}
9671 Enter actions for tracepoint #1, one per line.
9672 > collect $regs,$locals,$args
9677 (@value{GDBP}) @b{tstart}
9678 [time passes @dots{}]
9679 (@value{GDBP}) @b{tstop}
9683 @node Analyze Collected Data
9684 @section Using the Collected Data
9686 After the tracepoint experiment ends, you use @value{GDBN} commands
9687 for examining the trace data. The basic idea is that each tracepoint
9688 collects a trace @dfn{snapshot} every time it is hit and another
9689 snapshot every time it single-steps. All these snapshots are
9690 consecutively numbered from zero and go into a buffer, and you can
9691 examine them later. The way you examine them is to @dfn{focus} on a
9692 specific trace snapshot. When the remote stub is focused on a trace
9693 snapshot, it will respond to all @value{GDBN} requests for memory and
9694 registers by reading from the buffer which belongs to that snapshot,
9695 rather than from @emph{real} memory or registers of the program being
9696 debugged. This means that @strong{all} @value{GDBN} commands
9697 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
9698 behave as if we were currently debugging the program state as it was
9699 when the tracepoint occurred. Any requests for data that are not in
9700 the buffer will fail.
9703 * tfind:: How to select a trace snapshot
9704 * tdump:: How to display all data for a snapshot
9705 * save-tracepoints:: How to save tracepoints for a future run
9709 @subsection @code{tfind @var{n}}
9712 @cindex select trace snapshot
9713 @cindex find trace snapshot
9714 The basic command for selecting a trace snapshot from the buffer is
9715 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
9716 counting from zero. If no argument @var{n} is given, the next
9717 snapshot is selected.
9719 Here are the various forms of using the @code{tfind} command.
9723 Find the first snapshot in the buffer. This is a synonym for
9724 @code{tfind 0} (since 0 is the number of the first snapshot).
9727 Stop debugging trace snapshots, resume @emph{live} debugging.
9730 Same as @samp{tfind none}.
9733 No argument means find the next trace snapshot.
9736 Find the previous trace snapshot before the current one. This permits
9737 retracing earlier steps.
9739 @item tfind tracepoint @var{num}
9740 Find the next snapshot associated with tracepoint @var{num}. Search
9741 proceeds forward from the last examined trace snapshot. If no
9742 argument @var{num} is given, it means find the next snapshot collected
9743 for the same tracepoint as the current snapshot.
9745 @item tfind pc @var{addr}
9746 Find the next snapshot associated with the value @var{addr} of the
9747 program counter. Search proceeds forward from the last examined trace
9748 snapshot. If no argument @var{addr} is given, it means find the next
9749 snapshot with the same value of PC as the current snapshot.
9751 @item tfind outside @var{addr1}, @var{addr2}
9752 Find the next snapshot whose PC is outside the given range of
9755 @item tfind range @var{addr1}, @var{addr2}
9756 Find the next snapshot whose PC is between @var{addr1} and
9757 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
9759 @item tfind line @r{[}@var{file}:@r{]}@var{n}
9760 Find the next snapshot associated with the source line @var{n}. If
9761 the optional argument @var{file} is given, refer to line @var{n} in
9762 that source file. Search proceeds forward from the last examined
9763 trace snapshot. If no argument @var{n} is given, it means find the
9764 next line other than the one currently being examined; thus saying
9765 @code{tfind line} repeatedly can appear to have the same effect as
9766 stepping from line to line in a @emph{live} debugging session.
9769 The default arguments for the @code{tfind} commands are specifically
9770 designed to make it easy to scan through the trace buffer. For
9771 instance, @code{tfind} with no argument selects the next trace
9772 snapshot, and @code{tfind -} with no argument selects the previous
9773 trace snapshot. So, by giving one @code{tfind} command, and then
9774 simply hitting @key{RET} repeatedly you can examine all the trace
9775 snapshots in order. Or, by saying @code{tfind -} and then hitting
9776 @key{RET} repeatedly you can examine the snapshots in reverse order.
9777 The @code{tfind line} command with no argument selects the snapshot
9778 for the next source line executed. The @code{tfind pc} command with
9779 no argument selects the next snapshot with the same program counter
9780 (PC) as the current frame. The @code{tfind tracepoint} command with
9781 no argument selects the next trace snapshot collected by the same
9782 tracepoint as the current one.
9784 In addition to letting you scan through the trace buffer manually,
9785 these commands make it easy to construct @value{GDBN} scripts that
9786 scan through the trace buffer and print out whatever collected data
9787 you are interested in. Thus, if we want to examine the PC, FP, and SP
9788 registers from each trace frame in the buffer, we can say this:
9791 (@value{GDBP}) @b{tfind start}
9792 (@value{GDBP}) @b{while ($trace_frame != -1)}
9793 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
9794 $trace_frame, $pc, $sp, $fp
9798 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
9799 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
9800 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
9801 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
9802 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
9803 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
9804 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
9805 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
9806 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
9807 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
9808 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
9811 Or, if we want to examine the variable @code{X} at each source line in
9815 (@value{GDBP}) @b{tfind start}
9816 (@value{GDBP}) @b{while ($trace_frame != -1)}
9817 > printf "Frame %d, X == %d\n", $trace_frame, X
9827 @subsection @code{tdump}
9829 @cindex dump all data collected at tracepoint
9830 @cindex tracepoint data, display
9832 This command takes no arguments. It prints all the data collected at
9833 the current trace snapshot.
9836 (@value{GDBP}) @b{trace 444}
9837 (@value{GDBP}) @b{actions}
9838 Enter actions for tracepoint #2, one per line:
9839 > collect $regs, $locals, $args, gdb_long_test
9842 (@value{GDBP}) @b{tstart}
9844 (@value{GDBP}) @b{tfind line 444}
9845 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
9847 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
9849 (@value{GDBP}) @b{tdump}
9850 Data collected at tracepoint 2, trace frame 1:
9851 d0 0xc4aa0085 -995491707
9855 d4 0x71aea3d 119204413
9860 a1 0x3000668 50333288
9863 a4 0x3000698 50333336
9865 fp 0x30bf3c 0x30bf3c
9866 sp 0x30bf34 0x30bf34
9868 pc 0x20b2c8 0x20b2c8
9872 p = 0x20e5b4 "gdb-test"
9879 gdb_long_test = 17 '\021'
9884 @node save-tracepoints
9885 @subsection @code{save-tracepoints @var{filename}}
9886 @kindex save-tracepoints
9887 @cindex save tracepoints for future sessions
9889 This command saves all current tracepoint definitions together with
9890 their actions and passcounts, into a file @file{@var{filename}}
9891 suitable for use in a later debugging session. To read the saved
9892 tracepoint definitions, use the @code{source} command (@pxref{Command
9895 @node Tracepoint Variables
9896 @section Convenience Variables for Tracepoints
9897 @cindex tracepoint variables
9898 @cindex convenience variables for tracepoints
9901 @vindex $trace_frame
9902 @item (int) $trace_frame
9903 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
9904 snapshot is selected.
9907 @item (int) $tracepoint
9908 The tracepoint for the current trace snapshot.
9911 @item (int) $trace_line
9912 The line number for the current trace snapshot.
9915 @item (char []) $trace_file
9916 The source file for the current trace snapshot.
9919 @item (char []) $trace_func
9920 The name of the function containing @code{$tracepoint}.
9923 Note: @code{$trace_file} is not suitable for use in @code{printf},
9924 use @code{output} instead.
9926 Here's a simple example of using these convenience variables for
9927 stepping through all the trace snapshots and printing some of their
9931 (@value{GDBP}) @b{tfind start}
9933 (@value{GDBP}) @b{while $trace_frame != -1}
9934 > output $trace_file
9935 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
9941 @chapter Debugging Programs That Use Overlays
9944 If your program is too large to fit completely in your target system's
9945 memory, you can sometimes use @dfn{overlays} to work around this
9946 problem. @value{GDBN} provides some support for debugging programs that
9950 * How Overlays Work:: A general explanation of overlays.
9951 * Overlay Commands:: Managing overlays in @value{GDBN}.
9952 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
9953 mapped by asking the inferior.
9954 * Overlay Sample Program:: A sample program using overlays.
9957 @node How Overlays Work
9958 @section How Overlays Work
9959 @cindex mapped overlays
9960 @cindex unmapped overlays
9961 @cindex load address, overlay's
9962 @cindex mapped address
9963 @cindex overlay area
9965 Suppose you have a computer whose instruction address space is only 64
9966 kilobytes long, but which has much more memory which can be accessed by
9967 other means: special instructions, segment registers, or memory
9968 management hardware, for example. Suppose further that you want to
9969 adapt a program which is larger than 64 kilobytes to run on this system.
9971 One solution is to identify modules of your program which are relatively
9972 independent, and need not call each other directly; call these modules
9973 @dfn{overlays}. Separate the overlays from the main program, and place
9974 their machine code in the larger memory. Place your main program in
9975 instruction memory, but leave at least enough space there to hold the
9976 largest overlay as well.
9978 Now, to call a function located in an overlay, you must first copy that
9979 overlay's machine code from the large memory into the space set aside
9980 for it in the instruction memory, and then jump to its entry point
9983 @c NB: In the below the mapped area's size is greater or equal to the
9984 @c size of all overlays. This is intentional to remind the developer
9985 @c that overlays don't necessarily need to be the same size.
9989 Data Instruction Larger
9990 Address Space Address Space Address Space
9991 +-----------+ +-----------+ +-----------+
9993 +-----------+ +-----------+ +-----------+<-- overlay 1
9994 | program | | main | .----| overlay 1 | load address
9995 | variables | | program | | +-----------+
9996 | and heap | | | | | |
9997 +-----------+ | | | +-----------+<-- overlay 2
9998 | | +-----------+ | | | load address
9999 +-----------+ | | | .-| overlay 2 |
10001 mapped --->+-----------+ | | +-----------+
10002 address | | | | | |
10003 | overlay | <-' | | |
10004 | area | <---' +-----------+<-- overlay 3
10005 | | <---. | | load address
10006 +-----------+ `--| overlay 3 |
10013 @anchor{A code overlay}A code overlay
10017 The diagram (@pxref{A code overlay}) shows a system with separate data
10018 and instruction address spaces. To map an overlay, the program copies
10019 its code from the larger address space to the instruction address space.
10020 Since the overlays shown here all use the same mapped address, only one
10021 may be mapped at a time. For a system with a single address space for
10022 data and instructions, the diagram would be similar, except that the
10023 program variables and heap would share an address space with the main
10024 program and the overlay area.
10026 An overlay loaded into instruction memory and ready for use is called a
10027 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
10028 instruction memory. An overlay not present (or only partially present)
10029 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
10030 is its address in the larger memory. The mapped address is also called
10031 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
10032 called the @dfn{load memory address}, or @dfn{LMA}.
10034 Unfortunately, overlays are not a completely transparent way to adapt a
10035 program to limited instruction memory. They introduce a new set of
10036 global constraints you must keep in mind as you design your program:
10041 Before calling or returning to a function in an overlay, your program
10042 must make sure that overlay is actually mapped. Otherwise, the call or
10043 return will transfer control to the right address, but in the wrong
10044 overlay, and your program will probably crash.
10047 If the process of mapping an overlay is expensive on your system, you
10048 will need to choose your overlays carefully to minimize their effect on
10049 your program's performance.
10052 The executable file you load onto your system must contain each
10053 overlay's instructions, appearing at the overlay's load address, not its
10054 mapped address. However, each overlay's instructions must be relocated
10055 and its symbols defined as if the overlay were at its mapped address.
10056 You can use GNU linker scripts to specify different load and relocation
10057 addresses for pieces of your program; see @ref{Overlay Description,,,
10058 ld.info, Using ld: the GNU linker}.
10061 The procedure for loading executable files onto your system must be able
10062 to load their contents into the larger address space as well as the
10063 instruction and data spaces.
10067 The overlay system described above is rather simple, and could be
10068 improved in many ways:
10073 If your system has suitable bank switch registers or memory management
10074 hardware, you could use those facilities to make an overlay's load area
10075 contents simply appear at their mapped address in instruction space.
10076 This would probably be faster than copying the overlay to its mapped
10077 area in the usual way.
10080 If your overlays are small enough, you could set aside more than one
10081 overlay area, and have more than one overlay mapped at a time.
10084 You can use overlays to manage data, as well as instructions. In
10085 general, data overlays are even less transparent to your design than
10086 code overlays: whereas code overlays only require care when you call or
10087 return to functions, data overlays require care every time you access
10088 the data. Also, if you change the contents of a data overlay, you
10089 must copy its contents back out to its load address before you can copy a
10090 different data overlay into the same mapped area.
10095 @node Overlay Commands
10096 @section Overlay Commands
10098 To use @value{GDBN}'s overlay support, each overlay in your program must
10099 correspond to a separate section of the executable file. The section's
10100 virtual memory address and load memory address must be the overlay's
10101 mapped and load addresses. Identifying overlays with sections allows
10102 @value{GDBN} to determine the appropriate address of a function or
10103 variable, depending on whether the overlay is mapped or not.
10105 @value{GDBN}'s overlay commands all start with the word @code{overlay};
10106 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
10111 Disable @value{GDBN}'s overlay support. When overlay support is
10112 disabled, @value{GDBN} assumes that all functions and variables are
10113 always present at their mapped addresses. By default, @value{GDBN}'s
10114 overlay support is disabled.
10116 @item overlay manual
10117 @cindex manual overlay debugging
10118 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
10119 relies on you to tell it which overlays are mapped, and which are not,
10120 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
10121 commands described below.
10123 @item overlay map-overlay @var{overlay}
10124 @itemx overlay map @var{overlay}
10125 @cindex map an overlay
10126 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
10127 be the name of the object file section containing the overlay. When an
10128 overlay is mapped, @value{GDBN} assumes it can find the overlay's
10129 functions and variables at their mapped addresses. @value{GDBN} assumes
10130 that any other overlays whose mapped ranges overlap that of
10131 @var{overlay} are now unmapped.
10133 @item overlay unmap-overlay @var{overlay}
10134 @itemx overlay unmap @var{overlay}
10135 @cindex unmap an overlay
10136 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
10137 must be the name of the object file section containing the overlay.
10138 When an overlay is unmapped, @value{GDBN} assumes it can find the
10139 overlay's functions and variables at their load addresses.
10142 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
10143 consults a data structure the overlay manager maintains in the inferior
10144 to see which overlays are mapped. For details, see @ref{Automatic
10145 Overlay Debugging}.
10147 @item overlay load-target
10148 @itemx overlay load
10149 @cindex reloading the overlay table
10150 Re-read the overlay table from the inferior. Normally, @value{GDBN}
10151 re-reads the table @value{GDBN} automatically each time the inferior
10152 stops, so this command should only be necessary if you have changed the
10153 overlay mapping yourself using @value{GDBN}. This command is only
10154 useful when using automatic overlay debugging.
10156 @item overlay list-overlays
10157 @itemx overlay list
10158 @cindex listing mapped overlays
10159 Display a list of the overlays currently mapped, along with their mapped
10160 addresses, load addresses, and sizes.
10164 Normally, when @value{GDBN} prints a code address, it includes the name
10165 of the function the address falls in:
10168 (@value{GDBP}) print main
10169 $3 = @{int ()@} 0x11a0 <main>
10172 When overlay debugging is enabled, @value{GDBN} recognizes code in
10173 unmapped overlays, and prints the names of unmapped functions with
10174 asterisks around them. For example, if @code{foo} is a function in an
10175 unmapped overlay, @value{GDBN} prints it this way:
10178 (@value{GDBP}) overlay list
10179 No sections are mapped.
10180 (@value{GDBP}) print foo
10181 $5 = @{int (int)@} 0x100000 <*foo*>
10184 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
10188 (@value{GDBP}) overlay list
10189 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
10190 mapped at 0x1016 - 0x104a
10191 (@value{GDBP}) print foo
10192 $6 = @{int (int)@} 0x1016 <foo>
10195 When overlay debugging is enabled, @value{GDBN} can find the correct
10196 address for functions and variables in an overlay, whether or not the
10197 overlay is mapped. This allows most @value{GDBN} commands, like
10198 @code{break} and @code{disassemble}, to work normally, even on unmapped
10199 code. However, @value{GDBN}'s breakpoint support has some limitations:
10203 @cindex breakpoints in overlays
10204 @cindex overlays, setting breakpoints in
10205 You can set breakpoints in functions in unmapped overlays, as long as
10206 @value{GDBN} can write to the overlay at its load address.
10208 @value{GDBN} can not set hardware or simulator-based breakpoints in
10209 unmapped overlays. However, if you set a breakpoint at the end of your
10210 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
10211 you are using manual overlay management), @value{GDBN} will re-set its
10212 breakpoints properly.
10216 @node Automatic Overlay Debugging
10217 @section Automatic Overlay Debugging
10218 @cindex automatic overlay debugging
10220 @value{GDBN} can automatically track which overlays are mapped and which
10221 are not, given some simple co-operation from the overlay manager in the
10222 inferior. If you enable automatic overlay debugging with the
10223 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
10224 looks in the inferior's memory for certain variables describing the
10225 current state of the overlays.
10227 Here are the variables your overlay manager must define to support
10228 @value{GDBN}'s automatic overlay debugging:
10232 @item @code{_ovly_table}:
10233 This variable must be an array of the following structures:
10238 /* The overlay's mapped address. */
10241 /* The size of the overlay, in bytes. */
10242 unsigned long size;
10244 /* The overlay's load address. */
10247 /* Non-zero if the overlay is currently mapped;
10249 unsigned long mapped;
10253 @item @code{_novlys}:
10254 This variable must be a four-byte signed integer, holding the total
10255 number of elements in @code{_ovly_table}.
10259 To decide whether a particular overlay is mapped or not, @value{GDBN}
10260 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
10261 @code{lma} members equal the VMA and LMA of the overlay's section in the
10262 executable file. When @value{GDBN} finds a matching entry, it consults
10263 the entry's @code{mapped} member to determine whether the overlay is
10266 In addition, your overlay manager may define a function called
10267 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
10268 will silently set a breakpoint there. If the overlay manager then
10269 calls this function whenever it has changed the overlay table, this
10270 will enable @value{GDBN} to accurately keep track of which overlays
10271 are in program memory, and update any breakpoints that may be set
10272 in overlays. This will allow breakpoints to work even if the
10273 overlays are kept in ROM or other non-writable memory while they
10274 are not being executed.
10276 @node Overlay Sample Program
10277 @section Overlay Sample Program
10278 @cindex overlay example program
10280 When linking a program which uses overlays, you must place the overlays
10281 at their load addresses, while relocating them to run at their mapped
10282 addresses. To do this, you must write a linker script (@pxref{Overlay
10283 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
10284 since linker scripts are specific to a particular host system, target
10285 architecture, and target memory layout, this manual cannot provide
10286 portable sample code demonstrating @value{GDBN}'s overlay support.
10288 However, the @value{GDBN} source distribution does contain an overlaid
10289 program, with linker scripts for a few systems, as part of its test
10290 suite. The program consists of the following files from
10291 @file{gdb/testsuite/gdb.base}:
10295 The main program file.
10297 A simple overlay manager, used by @file{overlays.c}.
10302 Overlay modules, loaded and used by @file{overlays.c}.
10305 Linker scripts for linking the test program on the @code{d10v-elf}
10306 and @code{m32r-elf} targets.
10309 You can build the test program using the @code{d10v-elf} GCC
10310 cross-compiler like this:
10313 $ d10v-elf-gcc -g -c overlays.c
10314 $ d10v-elf-gcc -g -c ovlymgr.c
10315 $ d10v-elf-gcc -g -c foo.c
10316 $ d10v-elf-gcc -g -c bar.c
10317 $ d10v-elf-gcc -g -c baz.c
10318 $ d10v-elf-gcc -g -c grbx.c
10319 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
10320 baz.o grbx.o -Wl,-Td10v.ld -o overlays
10323 The build process is identical for any other architecture, except that
10324 you must substitute the appropriate compiler and linker script for the
10325 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
10329 @chapter Using @value{GDBN} with Different Languages
10332 Although programming languages generally have common aspects, they are
10333 rarely expressed in the same manner. For instance, in ANSI C,
10334 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
10335 Modula-2, it is accomplished by @code{p^}. Values can also be
10336 represented (and displayed) differently. Hex numbers in C appear as
10337 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
10339 @cindex working language
10340 Language-specific information is built into @value{GDBN} for some languages,
10341 allowing you to express operations like the above in your program's
10342 native language, and allowing @value{GDBN} to output values in a manner
10343 consistent with the syntax of your program's native language. The
10344 language you use to build expressions is called the @dfn{working
10348 * Setting:: Switching between source languages
10349 * Show:: Displaying the language
10350 * Checks:: Type and range checks
10351 * Supported Languages:: Supported languages
10352 * Unsupported Languages:: Unsupported languages
10356 @section Switching Between Source Languages
10358 There are two ways to control the working language---either have @value{GDBN}
10359 set it automatically, or select it manually yourself. You can use the
10360 @code{set language} command for either purpose. On startup, @value{GDBN}
10361 defaults to setting the language automatically. The working language is
10362 used to determine how expressions you type are interpreted, how values
10365 In addition to the working language, every source file that
10366 @value{GDBN} knows about has its own working language. For some object
10367 file formats, the compiler might indicate which language a particular
10368 source file is in. However, most of the time @value{GDBN} infers the
10369 language from the name of the file. The language of a source file
10370 controls whether C@t{++} names are demangled---this way @code{backtrace} can
10371 show each frame appropriately for its own language. There is no way to
10372 set the language of a source file from within @value{GDBN}, but you can
10373 set the language associated with a filename extension. @xref{Show, ,
10374 Displaying the Language}.
10376 This is most commonly a problem when you use a program, such
10377 as @code{cfront} or @code{f2c}, that generates C but is written in
10378 another language. In that case, make the
10379 program use @code{#line} directives in its C output; that way
10380 @value{GDBN} will know the correct language of the source code of the original
10381 program, and will display that source code, not the generated C code.
10384 * Filenames:: Filename extensions and languages.
10385 * Manually:: Setting the working language manually
10386 * Automatically:: Having @value{GDBN} infer the source language
10390 @subsection List of Filename Extensions and Languages
10392 If a source file name ends in one of the following extensions, then
10393 @value{GDBN} infers that its language is the one indicated.
10411 C@t{++} source file
10414 Objective-C source file
10418 Fortran source file
10421 Modula-2 source file
10425 Assembler source file. This actually behaves almost like C, but
10426 @value{GDBN} does not skip over function prologues when stepping.
10429 In addition, you may set the language associated with a filename
10430 extension. @xref{Show, , Displaying the Language}.
10433 @subsection Setting the Working Language
10435 If you allow @value{GDBN} to set the language automatically,
10436 expressions are interpreted the same way in your debugging session and
10439 @kindex set language
10440 If you wish, you may set the language manually. To do this, issue the
10441 command @samp{set language @var{lang}}, where @var{lang} is the name of
10442 a language, such as
10443 @code{c} or @code{modula-2}.
10444 For a list of the supported languages, type @samp{set language}.
10446 Setting the language manually prevents @value{GDBN} from updating the working
10447 language automatically. This can lead to confusion if you try
10448 to debug a program when the working language is not the same as the
10449 source language, when an expression is acceptable to both
10450 languages---but means different things. For instance, if the current
10451 source file were written in C, and @value{GDBN} was parsing Modula-2, a
10459 might not have the effect you intended. In C, this means to add
10460 @code{b} and @code{c} and place the result in @code{a}. The result
10461 printed would be the value of @code{a}. In Modula-2, this means to compare
10462 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
10464 @node Automatically
10465 @subsection Having @value{GDBN} Infer the Source Language
10467 To have @value{GDBN} set the working language automatically, use
10468 @samp{set language local} or @samp{set language auto}. @value{GDBN}
10469 then infers the working language. That is, when your program stops in a
10470 frame (usually by encountering a breakpoint), @value{GDBN} sets the
10471 working language to the language recorded for the function in that
10472 frame. If the language for a frame is unknown (that is, if the function
10473 or block corresponding to the frame was defined in a source file that
10474 does not have a recognized extension), the current working language is
10475 not changed, and @value{GDBN} issues a warning.
10477 This may not seem necessary for most programs, which are written
10478 entirely in one source language. However, program modules and libraries
10479 written in one source language can be used by a main program written in
10480 a different source language. Using @samp{set language auto} in this
10481 case frees you from having to set the working language manually.
10484 @section Displaying the Language
10486 The following commands help you find out which language is the
10487 working language, and also what language source files were written in.
10490 @item show language
10491 @kindex show language
10492 Display the current working language. This is the
10493 language you can use with commands such as @code{print} to
10494 build and compute expressions that may involve variables in your program.
10497 @kindex info frame@r{, show the source language}
10498 Display the source language for this frame. This language becomes the
10499 working language if you use an identifier from this frame.
10500 @xref{Frame Info, ,Information about a Frame}, to identify the other
10501 information listed here.
10504 @kindex info source@r{, show the source language}
10505 Display the source language of this source file.
10506 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
10507 information listed here.
10510 In unusual circumstances, you may have source files with extensions
10511 not in the standard list. You can then set the extension associated
10512 with a language explicitly:
10515 @item set extension-language @var{ext} @var{language}
10516 @kindex set extension-language
10517 Tell @value{GDBN} that source files with extension @var{ext} are to be
10518 assumed as written in the source language @var{language}.
10520 @item info extensions
10521 @kindex info extensions
10522 List all the filename extensions and the associated languages.
10526 @section Type and Range Checking
10529 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
10530 checking are included, but they do not yet have any effect. This
10531 section documents the intended facilities.
10533 @c FIXME remove warning when type/range code added
10535 Some languages are designed to guard you against making seemingly common
10536 errors through a series of compile- and run-time checks. These include
10537 checking the type of arguments to functions and operators, and making
10538 sure mathematical overflows are caught at run time. Checks such as
10539 these help to ensure a program's correctness once it has been compiled
10540 by eliminating type mismatches, and providing active checks for range
10541 errors when your program is running.
10543 @value{GDBN} can check for conditions like the above if you wish.
10544 Although @value{GDBN} does not check the statements in your program,
10545 it can check expressions entered directly into @value{GDBN} for
10546 evaluation via the @code{print} command, for example. As with the
10547 working language, @value{GDBN} can also decide whether or not to check
10548 automatically based on your program's source language.
10549 @xref{Supported Languages, ,Supported Languages}, for the default
10550 settings of supported languages.
10553 * Type Checking:: An overview of type checking
10554 * Range Checking:: An overview of range checking
10557 @cindex type checking
10558 @cindex checks, type
10559 @node Type Checking
10560 @subsection An Overview of Type Checking
10562 Some languages, such as Modula-2, are strongly typed, meaning that the
10563 arguments to operators and functions have to be of the correct type,
10564 otherwise an error occurs. These checks prevent type mismatch
10565 errors from ever causing any run-time problems. For example,
10573 The second example fails because the @code{CARDINAL} 1 is not
10574 type-compatible with the @code{REAL} 2.3.
10576 For the expressions you use in @value{GDBN} commands, you can tell the
10577 @value{GDBN} type checker to skip checking;
10578 to treat any mismatches as errors and abandon the expression;
10579 or to only issue warnings when type mismatches occur,
10580 but evaluate the expression anyway. When you choose the last of
10581 these, @value{GDBN} evaluates expressions like the second example above, but
10582 also issues a warning.
10584 Even if you turn type checking off, there may be other reasons
10585 related to type that prevent @value{GDBN} from evaluating an expression.
10586 For instance, @value{GDBN} does not know how to add an @code{int} and
10587 a @code{struct foo}. These particular type errors have nothing to do
10588 with the language in use, and usually arise from expressions, such as
10589 the one described above, which make little sense to evaluate anyway.
10591 Each language defines to what degree it is strict about type. For
10592 instance, both Modula-2 and C require the arguments to arithmetical
10593 operators to be numbers. In C, enumerated types and pointers can be
10594 represented as numbers, so that they are valid arguments to mathematical
10595 operators. @xref{Supported Languages, ,Supported Languages}, for further
10596 details on specific languages.
10598 @value{GDBN} provides some additional commands for controlling the type checker:
10600 @kindex set check type
10601 @kindex show check type
10603 @item set check type auto
10604 Set type checking on or off based on the current working language.
10605 @xref{Supported Languages, ,Supported Languages}, for the default settings for
10608 @item set check type on
10609 @itemx set check type off
10610 Set type checking on or off, overriding the default setting for the
10611 current working language. Issue a warning if the setting does not
10612 match the language default. If any type mismatches occur in
10613 evaluating an expression while type checking is on, @value{GDBN} prints a
10614 message and aborts evaluation of the expression.
10616 @item set check type warn
10617 Cause the type checker to issue warnings, but to always attempt to
10618 evaluate the expression. Evaluating the expression may still
10619 be impossible for other reasons. For example, @value{GDBN} cannot add
10620 numbers and structures.
10623 Show the current setting of the type checker, and whether or not @value{GDBN}
10624 is setting it automatically.
10627 @cindex range checking
10628 @cindex checks, range
10629 @node Range Checking
10630 @subsection An Overview of Range Checking
10632 In some languages (such as Modula-2), it is an error to exceed the
10633 bounds of a type; this is enforced with run-time checks. Such range
10634 checking is meant to ensure program correctness by making sure
10635 computations do not overflow, or indices on an array element access do
10636 not exceed the bounds of the array.
10638 For expressions you use in @value{GDBN} commands, you can tell
10639 @value{GDBN} to treat range errors in one of three ways: ignore them,
10640 always treat them as errors and abandon the expression, or issue
10641 warnings but evaluate the expression anyway.
10643 A range error can result from numerical overflow, from exceeding an
10644 array index bound, or when you type a constant that is not a member
10645 of any type. Some languages, however, do not treat overflows as an
10646 error. In many implementations of C, mathematical overflow causes the
10647 result to ``wrap around'' to lower values---for example, if @var{m} is
10648 the largest integer value, and @var{s} is the smallest, then
10651 @var{m} + 1 @result{} @var{s}
10654 This, too, is specific to individual languages, and in some cases
10655 specific to individual compilers or machines. @xref{Supported Languages, ,
10656 Supported Languages}, for further details on specific languages.
10658 @value{GDBN} provides some additional commands for controlling the range checker:
10660 @kindex set check range
10661 @kindex show check range
10663 @item set check range auto
10664 Set range checking on or off based on the current working language.
10665 @xref{Supported Languages, ,Supported Languages}, for the default settings for
10668 @item set check range on
10669 @itemx set check range off
10670 Set range checking on or off, overriding the default setting for the
10671 current working language. A warning is issued if the setting does not
10672 match the language default. If a range error occurs and range checking is on,
10673 then a message is printed and evaluation of the expression is aborted.
10675 @item set check range warn
10676 Output messages when the @value{GDBN} range checker detects a range error,
10677 but attempt to evaluate the expression anyway. Evaluating the
10678 expression may still be impossible for other reasons, such as accessing
10679 memory that the process does not own (a typical example from many Unix
10683 Show the current setting of the range checker, and whether or not it is
10684 being set automatically by @value{GDBN}.
10687 @node Supported Languages
10688 @section Supported Languages
10690 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
10691 assembly, Modula-2, and Ada.
10692 @c This is false ...
10693 Some @value{GDBN} features may be used in expressions regardless of the
10694 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
10695 and the @samp{@{type@}addr} construct (@pxref{Expressions,
10696 ,Expressions}) can be used with the constructs of any supported
10699 The following sections detail to what degree each source language is
10700 supported by @value{GDBN}. These sections are not meant to be language
10701 tutorials or references, but serve only as a reference guide to what the
10702 @value{GDBN} expression parser accepts, and what input and output
10703 formats should look like for different languages. There are many good
10704 books written on each of these languages; please look to these for a
10705 language reference or tutorial.
10708 * C:: C and C@t{++}
10709 * Objective-C:: Objective-C
10710 * Fortran:: Fortran
10712 * Modula-2:: Modula-2
10717 @subsection C and C@t{++}
10719 @cindex C and C@t{++}
10720 @cindex expressions in C or C@t{++}
10722 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
10723 to both languages. Whenever this is the case, we discuss those languages
10727 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
10728 @cindex @sc{gnu} C@t{++}
10729 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
10730 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
10731 effectively, you must compile your C@t{++} programs with a supported
10732 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
10733 compiler (@code{aCC}).
10735 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
10736 format; if it doesn't work on your system, try the stabs+ debugging
10737 format. You can select those formats explicitly with the @code{g++}
10738 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
10739 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
10740 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
10743 * C Operators:: C and C@t{++} operators
10744 * C Constants:: C and C@t{++} constants
10745 * C Plus Plus Expressions:: C@t{++} expressions
10746 * C Defaults:: Default settings for C and C@t{++}
10747 * C Checks:: C and C@t{++} type and range checks
10748 * Debugging C:: @value{GDBN} and C
10749 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
10750 * Decimal Floating Point:: Numbers in Decimal Floating Point format
10754 @subsubsection C and C@t{++} Operators
10756 @cindex C and C@t{++} operators
10758 Operators must be defined on values of specific types. For instance,
10759 @code{+} is defined on numbers, but not on structures. Operators are
10760 often defined on groups of types.
10762 For the purposes of C and C@t{++}, the following definitions hold:
10767 @emph{Integral types} include @code{int} with any of its storage-class
10768 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
10771 @emph{Floating-point types} include @code{float}, @code{double}, and
10772 @code{long double} (if supported by the target platform).
10775 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
10778 @emph{Scalar types} include all of the above.
10783 The following operators are supported. They are listed here
10784 in order of increasing precedence:
10788 The comma or sequencing operator. Expressions in a comma-separated list
10789 are evaluated from left to right, with the result of the entire
10790 expression being the last expression evaluated.
10793 Assignment. The value of an assignment expression is the value
10794 assigned. Defined on scalar types.
10797 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
10798 and translated to @w{@code{@var{a} = @var{a op b}}}.
10799 @w{@code{@var{op}=}} and @code{=} have the same precedence.
10800 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
10801 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
10804 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
10805 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
10809 Logical @sc{or}. Defined on integral types.
10812 Logical @sc{and}. Defined on integral types.
10815 Bitwise @sc{or}. Defined on integral types.
10818 Bitwise exclusive-@sc{or}. Defined on integral types.
10821 Bitwise @sc{and}. Defined on integral types.
10824 Equality and inequality. Defined on scalar types. The value of these
10825 expressions is 0 for false and non-zero for true.
10827 @item <@r{, }>@r{, }<=@r{, }>=
10828 Less than, greater than, less than or equal, greater than or equal.
10829 Defined on scalar types. The value of these expressions is 0 for false
10830 and non-zero for true.
10833 left shift, and right shift. Defined on integral types.
10836 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
10839 Addition and subtraction. Defined on integral types, floating-point types and
10842 @item *@r{, }/@r{, }%
10843 Multiplication, division, and modulus. Multiplication and division are
10844 defined on integral and floating-point types. Modulus is defined on
10848 Increment and decrement. When appearing before a variable, the
10849 operation is performed before the variable is used in an expression;
10850 when appearing after it, the variable's value is used before the
10851 operation takes place.
10854 Pointer dereferencing. Defined on pointer types. Same precedence as
10858 Address operator. Defined on variables. Same precedence as @code{++}.
10860 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
10861 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
10862 to examine the address
10863 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
10867 Negative. Defined on integral and floating-point types. Same
10868 precedence as @code{++}.
10871 Logical negation. Defined on integral types. Same precedence as
10875 Bitwise complement operator. Defined on integral types. Same precedence as
10880 Structure member, and pointer-to-structure member. For convenience,
10881 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
10882 pointer based on the stored type information.
10883 Defined on @code{struct} and @code{union} data.
10886 Dereferences of pointers to members.
10889 Array indexing. @code{@var{a}[@var{i}]} is defined as
10890 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
10893 Function parameter list. Same precedence as @code{->}.
10896 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
10897 and @code{class} types.
10900 Doubled colons also represent the @value{GDBN} scope operator
10901 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
10905 If an operator is redefined in the user code, @value{GDBN} usually
10906 attempts to invoke the redefined version instead of using the operator's
10907 predefined meaning.
10910 @subsubsection C and C@t{++} Constants
10912 @cindex C and C@t{++} constants
10914 @value{GDBN} allows you to express the constants of C and C@t{++} in the
10919 Integer constants are a sequence of digits. Octal constants are
10920 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
10921 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
10922 @samp{l}, specifying that the constant should be treated as a
10926 Floating point constants are a sequence of digits, followed by a decimal
10927 point, followed by a sequence of digits, and optionally followed by an
10928 exponent. An exponent is of the form:
10929 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
10930 sequence of digits. The @samp{+} is optional for positive exponents.
10931 A floating-point constant may also end with a letter @samp{f} or
10932 @samp{F}, specifying that the constant should be treated as being of
10933 the @code{float} (as opposed to the default @code{double}) type; or with
10934 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
10938 Enumerated constants consist of enumerated identifiers, or their
10939 integral equivalents.
10942 Character constants are a single character surrounded by single quotes
10943 (@code{'}), or a number---the ordinal value of the corresponding character
10944 (usually its @sc{ascii} value). Within quotes, the single character may
10945 be represented by a letter or by @dfn{escape sequences}, which are of
10946 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
10947 of the character's ordinal value; or of the form @samp{\@var{x}}, where
10948 @samp{@var{x}} is a predefined special character---for example,
10949 @samp{\n} for newline.
10952 String constants are a sequence of character constants surrounded by
10953 double quotes (@code{"}). Any valid character constant (as described
10954 above) may appear. Double quotes within the string must be preceded by
10955 a backslash, so for instance @samp{"a\"b'c"} is a string of five
10959 Pointer constants are an integral value. You can also write pointers
10960 to constants using the C operator @samp{&}.
10963 Array constants are comma-separated lists surrounded by braces @samp{@{}
10964 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
10965 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
10966 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
10969 @node C Plus Plus Expressions
10970 @subsubsection C@t{++} Expressions
10972 @cindex expressions in C@t{++}
10973 @value{GDBN} expression handling can interpret most C@t{++} expressions.
10975 @cindex debugging C@t{++} programs
10976 @cindex C@t{++} compilers
10977 @cindex debug formats and C@t{++}
10978 @cindex @value{NGCC} and C@t{++}
10980 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
10981 proper compiler and the proper debug format. Currently, @value{GDBN}
10982 works best when debugging C@t{++} code that is compiled with
10983 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
10984 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
10985 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
10986 stabs+ as their default debug format, so you usually don't need to
10987 specify a debug format explicitly. Other compilers and/or debug formats
10988 are likely to work badly or not at all when using @value{GDBN} to debug
10994 @cindex member functions
10996 Member function calls are allowed; you can use expressions like
10999 count = aml->GetOriginal(x, y)
11002 @vindex this@r{, inside C@t{++} member functions}
11003 @cindex namespace in C@t{++}
11005 While a member function is active (in the selected stack frame), your
11006 expressions have the same namespace available as the member function;
11007 that is, @value{GDBN} allows implicit references to the class instance
11008 pointer @code{this} following the same rules as C@t{++}.
11010 @cindex call overloaded functions
11011 @cindex overloaded functions, calling
11012 @cindex type conversions in C@t{++}
11014 You can call overloaded functions; @value{GDBN} resolves the function
11015 call to the right definition, with some restrictions. @value{GDBN} does not
11016 perform overload resolution involving user-defined type conversions,
11017 calls to constructors, or instantiations of templates that do not exist
11018 in the program. It also cannot handle ellipsis argument lists or
11021 It does perform integral conversions and promotions, floating-point
11022 promotions, arithmetic conversions, pointer conversions, conversions of
11023 class objects to base classes, and standard conversions such as those of
11024 functions or arrays to pointers; it requires an exact match on the
11025 number of function arguments.
11027 Overload resolution is always performed, unless you have specified
11028 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
11029 ,@value{GDBN} Features for C@t{++}}.
11031 You must specify @code{set overload-resolution off} in order to use an
11032 explicit function signature to call an overloaded function, as in
11034 p 'foo(char,int)'('x', 13)
11037 The @value{GDBN} command-completion facility can simplify this;
11038 see @ref{Completion, ,Command Completion}.
11040 @cindex reference declarations
11042 @value{GDBN} understands variables declared as C@t{++} references; you can use
11043 them in expressions just as you do in C@t{++} source---they are automatically
11046 In the parameter list shown when @value{GDBN} displays a frame, the values of
11047 reference variables are not displayed (unlike other variables); this
11048 avoids clutter, since references are often used for large structures.
11049 The @emph{address} of a reference variable is always shown, unless
11050 you have specified @samp{set print address off}.
11053 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
11054 expressions can use it just as expressions in your program do. Since
11055 one scope may be defined in another, you can use @code{::} repeatedly if
11056 necessary, for example in an expression like
11057 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
11058 resolving name scope by reference to source files, in both C and C@t{++}
11059 debugging (@pxref{Variables, ,Program Variables}).
11062 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
11063 calling virtual functions correctly, printing out virtual bases of
11064 objects, calling functions in a base subobject, casting objects, and
11065 invoking user-defined operators.
11068 @subsubsection C and C@t{++} Defaults
11070 @cindex C and C@t{++} defaults
11072 If you allow @value{GDBN} to set type and range checking automatically, they
11073 both default to @code{off} whenever the working language changes to
11074 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
11075 selects the working language.
11077 If you allow @value{GDBN} to set the language automatically, it
11078 recognizes source files whose names end with @file{.c}, @file{.C}, or
11079 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
11080 these files, it sets the working language to C or C@t{++}.
11081 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
11082 for further details.
11084 @c Type checking is (a) primarily motivated by Modula-2, and (b)
11085 @c unimplemented. If (b) changes, it might make sense to let this node
11086 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
11089 @subsubsection C and C@t{++} Type and Range Checks
11091 @cindex C and C@t{++} checks
11093 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
11094 is not used. However, if you turn type checking on, @value{GDBN}
11095 considers two variables type equivalent if:
11099 The two variables are structured and have the same structure, union, or
11103 The two variables have the same type name, or types that have been
11104 declared equivalent through @code{typedef}.
11107 @c leaving this out because neither J Gilmore nor R Pesch understand it.
11110 The two @code{struct}, @code{union}, or @code{enum} variables are
11111 declared in the same declaration. (Note: this may not be true for all C
11116 Range checking, if turned on, is done on mathematical operations. Array
11117 indices are not checked, since they are often used to index a pointer
11118 that is not itself an array.
11121 @subsubsection @value{GDBN} and C
11123 The @code{set print union} and @code{show print union} commands apply to
11124 the @code{union} type. When set to @samp{on}, any @code{union} that is
11125 inside a @code{struct} or @code{class} is also printed. Otherwise, it
11126 appears as @samp{@{...@}}.
11128 The @code{@@} operator aids in the debugging of dynamic arrays, formed
11129 with pointers and a memory allocation function. @xref{Expressions,
11132 @node Debugging C Plus Plus
11133 @subsubsection @value{GDBN} Features for C@t{++}
11135 @cindex commands for C@t{++}
11137 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
11138 designed specifically for use with C@t{++}. Here is a summary:
11141 @cindex break in overloaded functions
11142 @item @r{breakpoint menus}
11143 When you want a breakpoint in a function whose name is overloaded,
11144 @value{GDBN} has the capability to display a menu of possible breakpoint
11145 locations to help you specify which function definition you want.
11146 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
11148 @cindex overloading in C@t{++}
11149 @item rbreak @var{regex}
11150 Setting breakpoints using regular expressions is helpful for setting
11151 breakpoints on overloaded functions that are not members of any special
11153 @xref{Set Breaks, ,Setting Breakpoints}.
11155 @cindex C@t{++} exception handling
11158 Debug C@t{++} exception handling using these commands. @xref{Set
11159 Catchpoints, , Setting Catchpoints}.
11161 @cindex inheritance
11162 @item ptype @var{typename}
11163 Print inheritance relationships as well as other information for type
11165 @xref{Symbols, ,Examining the Symbol Table}.
11167 @cindex C@t{++} symbol display
11168 @item set print demangle
11169 @itemx show print demangle
11170 @itemx set print asm-demangle
11171 @itemx show print asm-demangle
11172 Control whether C@t{++} symbols display in their source form, both when
11173 displaying code as C@t{++} source and when displaying disassemblies.
11174 @xref{Print Settings, ,Print Settings}.
11176 @item set print object
11177 @itemx show print object
11178 Choose whether to print derived (actual) or declared types of objects.
11179 @xref{Print Settings, ,Print Settings}.
11181 @item set print vtbl
11182 @itemx show print vtbl
11183 Control the format for printing virtual function tables.
11184 @xref{Print Settings, ,Print Settings}.
11185 (The @code{vtbl} commands do not work on programs compiled with the HP
11186 ANSI C@t{++} compiler (@code{aCC}).)
11188 @kindex set overload-resolution
11189 @cindex overloaded functions, overload resolution
11190 @item set overload-resolution on
11191 Enable overload resolution for C@t{++} expression evaluation. The default
11192 is on. For overloaded functions, @value{GDBN} evaluates the arguments
11193 and searches for a function whose signature matches the argument types,
11194 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
11195 Expressions, ,C@t{++} Expressions}, for details).
11196 If it cannot find a match, it emits a message.
11198 @item set overload-resolution off
11199 Disable overload resolution for C@t{++} expression evaluation. For
11200 overloaded functions that are not class member functions, @value{GDBN}
11201 chooses the first function of the specified name that it finds in the
11202 symbol table, whether or not its arguments are of the correct type. For
11203 overloaded functions that are class member functions, @value{GDBN}
11204 searches for a function whose signature @emph{exactly} matches the
11207 @kindex show overload-resolution
11208 @item show overload-resolution
11209 Show the current setting of overload resolution.
11211 @item @r{Overloaded symbol names}
11212 You can specify a particular definition of an overloaded symbol, using
11213 the same notation that is used to declare such symbols in C@t{++}: type
11214 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
11215 also use the @value{GDBN} command-line word completion facilities to list the
11216 available choices, or to finish the type list for you.
11217 @xref{Completion,, Command Completion}, for details on how to do this.
11220 @node Decimal Floating Point
11221 @subsubsection Decimal Floating Point format
11222 @cindex decimal floating point format
11224 @value{GDBN} can examine, set and perform computations with numbers in
11225 decimal floating point format, which in the C language correspond to the
11226 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
11227 specified by the extension to support decimal floating-point arithmetic.
11229 There are two encodings in use, depending on the architecture: BID (Binary
11230 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
11231 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
11234 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
11235 to manipulate decimal floating point numbers, it is not possible to convert
11236 (using a cast, for example) integers wider than 32-bit to decimal float.
11238 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
11239 point computations, error checking in decimal float operations ignores
11240 underflow, overflow and divide by zero exceptions.
11242 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
11243 to inspect @code{_Decimal128} values stored in floating point registers.
11244 See @ref{PowerPC,,PowerPC} for more details.
11247 @subsection Objective-C
11249 @cindex Objective-C
11250 This section provides information about some commands and command
11251 options that are useful for debugging Objective-C code. See also
11252 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
11253 few more commands specific to Objective-C support.
11256 * Method Names in Commands::
11257 * The Print Command with Objective-C::
11260 @node Method Names in Commands
11261 @subsubsection Method Names in Commands
11263 The following commands have been extended to accept Objective-C method
11264 names as line specifications:
11266 @kindex clear@r{, and Objective-C}
11267 @kindex break@r{, and Objective-C}
11268 @kindex info line@r{, and Objective-C}
11269 @kindex jump@r{, and Objective-C}
11270 @kindex list@r{, and Objective-C}
11274 @item @code{info line}
11279 A fully qualified Objective-C method name is specified as
11282 -[@var{Class} @var{methodName}]
11285 where the minus sign is used to indicate an instance method and a
11286 plus sign (not shown) is used to indicate a class method. The class
11287 name @var{Class} and method name @var{methodName} are enclosed in
11288 brackets, similar to the way messages are specified in Objective-C
11289 source code. For example, to set a breakpoint at the @code{create}
11290 instance method of class @code{Fruit} in the program currently being
11294 break -[Fruit create]
11297 To list ten program lines around the @code{initialize} class method,
11301 list +[NSText initialize]
11304 In the current version of @value{GDBN}, the plus or minus sign is
11305 required. In future versions of @value{GDBN}, the plus or minus
11306 sign will be optional, but you can use it to narrow the search. It
11307 is also possible to specify just a method name:
11313 You must specify the complete method name, including any colons. If
11314 your program's source files contain more than one @code{create} method,
11315 you'll be presented with a numbered list of classes that implement that
11316 method. Indicate your choice by number, or type @samp{0} to exit if
11319 As another example, to clear a breakpoint established at the
11320 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
11323 clear -[NSWindow makeKeyAndOrderFront:]
11326 @node The Print Command with Objective-C
11327 @subsubsection The Print Command With Objective-C
11328 @cindex Objective-C, print objects
11329 @kindex print-object
11330 @kindex po @r{(@code{print-object})}
11332 The print command has also been extended to accept methods. For example:
11335 print -[@var{object} hash]
11338 @cindex print an Objective-C object description
11339 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
11341 will tell @value{GDBN} to send the @code{hash} message to @var{object}
11342 and print the result. Also, an additional command has been added,
11343 @code{print-object} or @code{po} for short, which is meant to print
11344 the description of an object. However, this command may only work
11345 with certain Objective-C libraries that have a particular hook
11346 function, @code{_NSPrintForDebugger}, defined.
11349 @subsection Fortran
11350 @cindex Fortran-specific support in @value{GDBN}
11352 @value{GDBN} can be used to debug programs written in Fortran, but it
11353 currently supports only the features of Fortran 77 language.
11355 @cindex trailing underscore, in Fortran symbols
11356 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
11357 among them) append an underscore to the names of variables and
11358 functions. When you debug programs compiled by those compilers, you
11359 will need to refer to variables and functions with a trailing
11363 * Fortran Operators:: Fortran operators and expressions
11364 * Fortran Defaults:: Default settings for Fortran
11365 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
11368 @node Fortran Operators
11369 @subsubsection Fortran Operators and Expressions
11371 @cindex Fortran operators and expressions
11373 Operators must be defined on values of specific types. For instance,
11374 @code{+} is defined on numbers, but not on characters or other non-
11375 arithmetic types. Operators are often defined on groups of types.
11379 The exponentiation operator. It raises the first operand to the power
11383 The range operator. Normally used in the form of array(low:high) to
11384 represent a section of array.
11387 The access component operator. Normally used to access elements in derived
11388 types. Also suitable for unions. As unions aren't part of regular Fortran,
11389 this can only happen when accessing a register that uses a gdbarch-defined
11393 @node Fortran Defaults
11394 @subsubsection Fortran Defaults
11396 @cindex Fortran Defaults
11398 Fortran symbols are usually case-insensitive, so @value{GDBN} by
11399 default uses case-insensitive matches for Fortran symbols. You can
11400 change that with the @samp{set case-insensitive} command, see
11401 @ref{Symbols}, for the details.
11403 @node Special Fortran Commands
11404 @subsubsection Special Fortran Commands
11406 @cindex Special Fortran commands
11408 @value{GDBN} has some commands to support Fortran-specific features,
11409 such as displaying common blocks.
11412 @cindex @code{COMMON} blocks, Fortran
11413 @kindex info common
11414 @item info common @r{[}@var{common-name}@r{]}
11415 This command prints the values contained in the Fortran @code{COMMON}
11416 block whose name is @var{common-name}. With no argument, the names of
11417 all @code{COMMON} blocks visible at the current program location are
11424 @cindex Pascal support in @value{GDBN}, limitations
11425 Debugging Pascal programs which use sets, subranges, file variables, or
11426 nested functions does not currently work. @value{GDBN} does not support
11427 entering expressions, printing values, or similar features using Pascal
11430 The Pascal-specific command @code{set print pascal_static-members}
11431 controls whether static members of Pascal objects are displayed.
11432 @xref{Print Settings, pascal_static-members}.
11435 @subsection Modula-2
11437 @cindex Modula-2, @value{GDBN} support
11439 The extensions made to @value{GDBN} to support Modula-2 only support
11440 output from the @sc{gnu} Modula-2 compiler (which is currently being
11441 developed). Other Modula-2 compilers are not currently supported, and
11442 attempting to debug executables produced by them is most likely
11443 to give an error as @value{GDBN} reads in the executable's symbol
11446 @cindex expressions in Modula-2
11448 * M2 Operators:: Built-in operators
11449 * Built-In Func/Proc:: Built-in functions and procedures
11450 * M2 Constants:: Modula-2 constants
11451 * M2 Types:: Modula-2 types
11452 * M2 Defaults:: Default settings for Modula-2
11453 * Deviations:: Deviations from standard Modula-2
11454 * M2 Checks:: Modula-2 type and range checks
11455 * M2 Scope:: The scope operators @code{::} and @code{.}
11456 * GDB/M2:: @value{GDBN} and Modula-2
11460 @subsubsection Operators
11461 @cindex Modula-2 operators
11463 Operators must be defined on values of specific types. For instance,
11464 @code{+} is defined on numbers, but not on structures. Operators are
11465 often defined on groups of types. For the purposes of Modula-2, the
11466 following definitions hold:
11471 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
11475 @emph{Character types} consist of @code{CHAR} and its subranges.
11478 @emph{Floating-point types} consist of @code{REAL}.
11481 @emph{Pointer types} consist of anything declared as @code{POINTER TO
11485 @emph{Scalar types} consist of all of the above.
11488 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
11491 @emph{Boolean types} consist of @code{BOOLEAN}.
11495 The following operators are supported, and appear in order of
11496 increasing precedence:
11500 Function argument or array index separator.
11503 Assignment. The value of @var{var} @code{:=} @var{value} is
11507 Less than, greater than on integral, floating-point, or enumerated
11511 Less than or equal to, greater than or equal to
11512 on integral, floating-point and enumerated types, or set inclusion on
11513 set types. Same precedence as @code{<}.
11515 @item =@r{, }<>@r{, }#
11516 Equality and two ways of expressing inequality, valid on scalar types.
11517 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
11518 available for inequality, since @code{#} conflicts with the script
11522 Set membership. Defined on set types and the types of their members.
11523 Same precedence as @code{<}.
11526 Boolean disjunction. Defined on boolean types.
11529 Boolean conjunction. Defined on boolean types.
11532 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
11535 Addition and subtraction on integral and floating-point types, or union
11536 and difference on set types.
11539 Multiplication on integral and floating-point types, or set intersection
11543 Division on floating-point types, or symmetric set difference on set
11544 types. Same precedence as @code{*}.
11547 Integer division and remainder. Defined on integral types. Same
11548 precedence as @code{*}.
11551 Negative. Defined on @code{INTEGER} and @code{REAL} data.
11554 Pointer dereferencing. Defined on pointer types.
11557 Boolean negation. Defined on boolean types. Same precedence as
11561 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
11562 precedence as @code{^}.
11565 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
11568 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
11572 @value{GDBN} and Modula-2 scope operators.
11576 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
11577 treats the use of the operator @code{IN}, or the use of operators
11578 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
11579 @code{<=}, and @code{>=} on sets as an error.
11583 @node Built-In Func/Proc
11584 @subsubsection Built-in Functions and Procedures
11585 @cindex Modula-2 built-ins
11587 Modula-2 also makes available several built-in procedures and functions.
11588 In describing these, the following metavariables are used:
11593 represents an @code{ARRAY} variable.
11596 represents a @code{CHAR} constant or variable.
11599 represents a variable or constant of integral type.
11602 represents an identifier that belongs to a set. Generally used in the
11603 same function with the metavariable @var{s}. The type of @var{s} should
11604 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
11607 represents a variable or constant of integral or floating-point type.
11610 represents a variable or constant of floating-point type.
11616 represents a variable.
11619 represents a variable or constant of one of many types. See the
11620 explanation of the function for details.
11623 All Modula-2 built-in procedures also return a result, described below.
11627 Returns the absolute value of @var{n}.
11630 If @var{c} is a lower case letter, it returns its upper case
11631 equivalent, otherwise it returns its argument.
11634 Returns the character whose ordinal value is @var{i}.
11637 Decrements the value in the variable @var{v} by one. Returns the new value.
11639 @item DEC(@var{v},@var{i})
11640 Decrements the value in the variable @var{v} by @var{i}. Returns the
11643 @item EXCL(@var{m},@var{s})
11644 Removes the element @var{m} from the set @var{s}. Returns the new
11647 @item FLOAT(@var{i})
11648 Returns the floating point equivalent of the integer @var{i}.
11650 @item HIGH(@var{a})
11651 Returns the index of the last member of @var{a}.
11654 Increments the value in the variable @var{v} by one. Returns the new value.
11656 @item INC(@var{v},@var{i})
11657 Increments the value in the variable @var{v} by @var{i}. Returns the
11660 @item INCL(@var{m},@var{s})
11661 Adds the element @var{m} to the set @var{s} if it is not already
11662 there. Returns the new set.
11665 Returns the maximum value of the type @var{t}.
11668 Returns the minimum value of the type @var{t}.
11671 Returns boolean TRUE if @var{i} is an odd number.
11674 Returns the ordinal value of its argument. For example, the ordinal
11675 value of a character is its @sc{ascii} value (on machines supporting the
11676 @sc{ascii} character set). @var{x} must be of an ordered type, which include
11677 integral, character and enumerated types.
11679 @item SIZE(@var{x})
11680 Returns the size of its argument. @var{x} can be a variable or a type.
11682 @item TRUNC(@var{r})
11683 Returns the integral part of @var{r}.
11685 @item TSIZE(@var{x})
11686 Returns the size of its argument. @var{x} can be a variable or a type.
11688 @item VAL(@var{t},@var{i})
11689 Returns the member of the type @var{t} whose ordinal value is @var{i}.
11693 @emph{Warning:} Sets and their operations are not yet supported, so
11694 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
11698 @cindex Modula-2 constants
11700 @subsubsection Constants
11702 @value{GDBN} allows you to express the constants of Modula-2 in the following
11708 Integer constants are simply a sequence of digits. When used in an
11709 expression, a constant is interpreted to be type-compatible with the
11710 rest of the expression. Hexadecimal integers are specified by a
11711 trailing @samp{H}, and octal integers by a trailing @samp{B}.
11714 Floating point constants appear as a sequence of digits, followed by a
11715 decimal point and another sequence of digits. An optional exponent can
11716 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
11717 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
11718 digits of the floating point constant must be valid decimal (base 10)
11722 Character constants consist of a single character enclosed by a pair of
11723 like quotes, either single (@code{'}) or double (@code{"}). They may
11724 also be expressed by their ordinal value (their @sc{ascii} value, usually)
11725 followed by a @samp{C}.
11728 String constants consist of a sequence of characters enclosed by a
11729 pair of like quotes, either single (@code{'}) or double (@code{"}).
11730 Escape sequences in the style of C are also allowed. @xref{C
11731 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
11735 Enumerated constants consist of an enumerated identifier.
11738 Boolean constants consist of the identifiers @code{TRUE} and
11742 Pointer constants consist of integral values only.
11745 Set constants are not yet supported.
11749 @subsubsection Modula-2 Types
11750 @cindex Modula-2 types
11752 Currently @value{GDBN} can print the following data types in Modula-2
11753 syntax: array types, record types, set types, pointer types, procedure
11754 types, enumerated types, subrange types and base types. You can also
11755 print the contents of variables declared using these type.
11756 This section gives a number of simple source code examples together with
11757 sample @value{GDBN} sessions.
11759 The first example contains the following section of code:
11768 and you can request @value{GDBN} to interrogate the type and value of
11769 @code{r} and @code{s}.
11772 (@value{GDBP}) print s
11774 (@value{GDBP}) ptype s
11776 (@value{GDBP}) print r
11778 (@value{GDBP}) ptype r
11783 Likewise if your source code declares @code{s} as:
11787 s: SET ['A'..'Z'] ;
11791 then you may query the type of @code{s} by:
11794 (@value{GDBP}) ptype s
11795 type = SET ['A'..'Z']
11799 Note that at present you cannot interactively manipulate set
11800 expressions using the debugger.
11802 The following example shows how you might declare an array in Modula-2
11803 and how you can interact with @value{GDBN} to print its type and contents:
11807 s: ARRAY [-10..10] OF CHAR ;
11811 (@value{GDBP}) ptype s
11812 ARRAY [-10..10] OF CHAR
11815 Note that the array handling is not yet complete and although the type
11816 is printed correctly, expression handling still assumes that all
11817 arrays have a lower bound of zero and not @code{-10} as in the example
11820 Here are some more type related Modula-2 examples:
11824 colour = (blue, red, yellow, green) ;
11825 t = [blue..yellow] ;
11833 The @value{GDBN} interaction shows how you can query the data type
11834 and value of a variable.
11837 (@value{GDBP}) print s
11839 (@value{GDBP}) ptype t
11840 type = [blue..yellow]
11844 In this example a Modula-2 array is declared and its contents
11845 displayed. Observe that the contents are written in the same way as
11846 their @code{C} counterparts.
11850 s: ARRAY [1..5] OF CARDINAL ;
11856 (@value{GDBP}) print s
11857 $1 = @{1, 0, 0, 0, 0@}
11858 (@value{GDBP}) ptype s
11859 type = ARRAY [1..5] OF CARDINAL
11862 The Modula-2 language interface to @value{GDBN} also understands
11863 pointer types as shown in this example:
11867 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
11874 and you can request that @value{GDBN} describes the type of @code{s}.
11877 (@value{GDBP}) ptype s
11878 type = POINTER TO ARRAY [1..5] OF CARDINAL
11881 @value{GDBN} handles compound types as we can see in this example.
11882 Here we combine array types, record types, pointer types and subrange
11893 myarray = ARRAY myrange OF CARDINAL ;
11894 myrange = [-2..2] ;
11896 s: POINTER TO ARRAY myrange OF foo ;
11900 and you can ask @value{GDBN} to describe the type of @code{s} as shown
11904 (@value{GDBP}) ptype s
11905 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
11908 f3 : ARRAY [-2..2] OF CARDINAL;
11913 @subsubsection Modula-2 Defaults
11914 @cindex Modula-2 defaults
11916 If type and range checking are set automatically by @value{GDBN}, they
11917 both default to @code{on} whenever the working language changes to
11918 Modula-2. This happens regardless of whether you or @value{GDBN}
11919 selected the working language.
11921 If you allow @value{GDBN} to set the language automatically, then entering
11922 code compiled from a file whose name ends with @file{.mod} sets the
11923 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
11924 Infer the Source Language}, for further details.
11927 @subsubsection Deviations from Standard Modula-2
11928 @cindex Modula-2, deviations from
11930 A few changes have been made to make Modula-2 programs easier to debug.
11931 This is done primarily via loosening its type strictness:
11935 Unlike in standard Modula-2, pointer constants can be formed by
11936 integers. This allows you to modify pointer variables during
11937 debugging. (In standard Modula-2, the actual address contained in a
11938 pointer variable is hidden from you; it can only be modified
11939 through direct assignment to another pointer variable or expression that
11940 returned a pointer.)
11943 C escape sequences can be used in strings and characters to represent
11944 non-printable characters. @value{GDBN} prints out strings with these
11945 escape sequences embedded. Single non-printable characters are
11946 printed using the @samp{CHR(@var{nnn})} format.
11949 The assignment operator (@code{:=}) returns the value of its right-hand
11953 All built-in procedures both modify @emph{and} return their argument.
11957 @subsubsection Modula-2 Type and Range Checks
11958 @cindex Modula-2 checks
11961 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
11964 @c FIXME remove warning when type/range checks added
11966 @value{GDBN} considers two Modula-2 variables type equivalent if:
11970 They are of types that have been declared equivalent via a @code{TYPE
11971 @var{t1} = @var{t2}} statement
11974 They have been declared on the same line. (Note: This is true of the
11975 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
11978 As long as type checking is enabled, any attempt to combine variables
11979 whose types are not equivalent is an error.
11981 Range checking is done on all mathematical operations, assignment, array
11982 index bounds, and all built-in functions and procedures.
11985 @subsubsection The Scope Operators @code{::} and @code{.}
11987 @cindex @code{.}, Modula-2 scope operator
11988 @cindex colon, doubled as scope operator
11990 @vindex colon-colon@r{, in Modula-2}
11991 @c Info cannot handle :: but TeX can.
11994 @vindex ::@r{, in Modula-2}
11997 There are a few subtle differences between the Modula-2 scope operator
11998 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
12003 @var{module} . @var{id}
12004 @var{scope} :: @var{id}
12008 where @var{scope} is the name of a module or a procedure,
12009 @var{module} the name of a module, and @var{id} is any declared
12010 identifier within your program, except another module.
12012 Using the @code{::} operator makes @value{GDBN} search the scope
12013 specified by @var{scope} for the identifier @var{id}. If it is not
12014 found in the specified scope, then @value{GDBN} searches all scopes
12015 enclosing the one specified by @var{scope}.
12017 Using the @code{.} operator makes @value{GDBN} search the current scope for
12018 the identifier specified by @var{id} that was imported from the
12019 definition module specified by @var{module}. With this operator, it is
12020 an error if the identifier @var{id} was not imported from definition
12021 module @var{module}, or if @var{id} is not an identifier in
12025 @subsubsection @value{GDBN} and Modula-2
12027 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
12028 Five subcommands of @code{set print} and @code{show print} apply
12029 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
12030 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
12031 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
12032 analogue in Modula-2.
12034 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
12035 with any language, is not useful with Modula-2. Its
12036 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
12037 created in Modula-2 as they can in C or C@t{++}. However, because an
12038 address can be specified by an integral constant, the construct
12039 @samp{@{@var{type}@}@var{adrexp}} is still useful.
12041 @cindex @code{#} in Modula-2
12042 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
12043 interpreted as the beginning of a comment. Use @code{<>} instead.
12049 The extensions made to @value{GDBN} for Ada only support
12050 output from the @sc{gnu} Ada (GNAT) compiler.
12051 Other Ada compilers are not currently supported, and
12052 attempting to debug executables produced by them is most likely
12056 @cindex expressions in Ada
12058 * Ada Mode Intro:: General remarks on the Ada syntax
12059 and semantics supported by Ada mode
12061 * Omissions from Ada:: Restrictions on the Ada expression syntax.
12062 * Additions to Ada:: Extensions of the Ada expression syntax.
12063 * Stopping Before Main Program:: Debugging the program during elaboration.
12064 * Ada Tasks:: Listing and setting breakpoints in tasks.
12065 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
12066 * Ada Glitches:: Known peculiarities of Ada mode.
12069 @node Ada Mode Intro
12070 @subsubsection Introduction
12071 @cindex Ada mode, general
12073 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
12074 syntax, with some extensions.
12075 The philosophy behind the design of this subset is
12079 That @value{GDBN} should provide basic literals and access to operations for
12080 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
12081 leaving more sophisticated computations to subprograms written into the
12082 program (which therefore may be called from @value{GDBN}).
12085 That type safety and strict adherence to Ada language restrictions
12086 are not particularly important to the @value{GDBN} user.
12089 That brevity is important to the @value{GDBN} user.
12092 Thus, for brevity, the debugger acts as if all names declared in
12093 user-written packages are directly visible, even if they are not visible
12094 according to Ada rules, thus making it unnecessary to fully qualify most
12095 names with their packages, regardless of context. Where this causes
12096 ambiguity, @value{GDBN} asks the user's intent.
12098 The debugger will start in Ada mode if it detects an Ada main program.
12099 As for other languages, it will enter Ada mode when stopped in a program that
12100 was translated from an Ada source file.
12102 While in Ada mode, you may use `@t{--}' for comments. This is useful
12103 mostly for documenting command files. The standard @value{GDBN} comment
12104 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
12105 middle (to allow based literals).
12107 The debugger supports limited overloading. Given a subprogram call in which
12108 the function symbol has multiple definitions, it will use the number of
12109 actual parameters and some information about their types to attempt to narrow
12110 the set of definitions. It also makes very limited use of context, preferring
12111 procedures to functions in the context of the @code{call} command, and
12112 functions to procedures elsewhere.
12114 @node Omissions from Ada
12115 @subsubsection Omissions from Ada
12116 @cindex Ada, omissions from
12118 Here are the notable omissions from the subset:
12122 Only a subset of the attributes are supported:
12126 @t{'First}, @t{'Last}, and @t{'Length}
12127 on array objects (not on types and subtypes).
12130 @t{'Min} and @t{'Max}.
12133 @t{'Pos} and @t{'Val}.
12139 @t{'Range} on array objects (not subtypes), but only as the right
12140 operand of the membership (@code{in}) operator.
12143 @t{'Access}, @t{'Unchecked_Access}, and
12144 @t{'Unrestricted_Access} (a GNAT extension).
12152 @code{Characters.Latin_1} are not available and
12153 concatenation is not implemented. Thus, escape characters in strings are
12154 not currently available.
12157 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
12158 equality of representations. They will generally work correctly
12159 for strings and arrays whose elements have integer or enumeration types.
12160 They may not work correctly for arrays whose element
12161 types have user-defined equality, for arrays of real values
12162 (in particular, IEEE-conformant floating point, because of negative
12163 zeroes and NaNs), and for arrays whose elements contain unused bits with
12164 indeterminate values.
12167 The other component-by-component array operations (@code{and}, @code{or},
12168 @code{xor}, @code{not}, and relational tests other than equality)
12169 are not implemented.
12172 @cindex array aggregates (Ada)
12173 @cindex record aggregates (Ada)
12174 @cindex aggregates (Ada)
12175 There is limited support for array and record aggregates. They are
12176 permitted only on the right sides of assignments, as in these examples:
12179 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
12180 (@value{GDBP}) set An_Array := (1, others => 0)
12181 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
12182 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
12183 (@value{GDBP}) set A_Record := (1, "Peter", True);
12184 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
12188 discriminant's value by assigning an aggregate has an
12189 undefined effect if that discriminant is used within the record.
12190 However, you can first modify discriminants by directly assigning to
12191 them (which normally would not be allowed in Ada), and then performing an
12192 aggregate assignment. For example, given a variable @code{A_Rec}
12193 declared to have a type such as:
12196 type Rec (Len : Small_Integer := 0) is record
12198 Vals : IntArray (1 .. Len);
12202 you can assign a value with a different size of @code{Vals} with two
12206 (@value{GDBP}) set A_Rec.Len := 4
12207 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
12210 As this example also illustrates, @value{GDBN} is very loose about the usual
12211 rules concerning aggregates. You may leave out some of the
12212 components of an array or record aggregate (such as the @code{Len}
12213 component in the assignment to @code{A_Rec} above); they will retain their
12214 original values upon assignment. You may freely use dynamic values as
12215 indices in component associations. You may even use overlapping or
12216 redundant component associations, although which component values are
12217 assigned in such cases is not defined.
12220 Calls to dispatching subprograms are not implemented.
12223 The overloading algorithm is much more limited (i.e., less selective)
12224 than that of real Ada. It makes only limited use of the context in
12225 which a subexpression appears to resolve its meaning, and it is much
12226 looser in its rules for allowing type matches. As a result, some
12227 function calls will be ambiguous, and the user will be asked to choose
12228 the proper resolution.
12231 The @code{new} operator is not implemented.
12234 Entry calls are not implemented.
12237 Aside from printing, arithmetic operations on the native VAX floating-point
12238 formats are not supported.
12241 It is not possible to slice a packed array.
12244 The names @code{True} and @code{False}, when not part of a qualified name,
12245 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
12247 Should your program
12248 redefine these names in a package or procedure (at best a dubious practice),
12249 you will have to use fully qualified names to access their new definitions.
12252 @node Additions to Ada
12253 @subsubsection Additions to Ada
12254 @cindex Ada, deviations from
12256 As it does for other languages, @value{GDBN} makes certain generic
12257 extensions to Ada (@pxref{Expressions}):
12261 If the expression @var{E} is a variable residing in memory (typically
12262 a local variable or array element) and @var{N} is a positive integer,
12263 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
12264 @var{N}-1 adjacent variables following it in memory as an array. In
12265 Ada, this operator is generally not necessary, since its prime use is
12266 in displaying parts of an array, and slicing will usually do this in
12267 Ada. However, there are occasional uses when debugging programs in
12268 which certain debugging information has been optimized away.
12271 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
12272 appears in function or file @var{B}.'' When @var{B} is a file name,
12273 you must typically surround it in single quotes.
12276 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
12277 @var{type} that appears at address @var{addr}.''
12280 A name starting with @samp{$} is a convenience variable
12281 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
12284 In addition, @value{GDBN} provides a few other shortcuts and outright
12285 additions specific to Ada:
12289 The assignment statement is allowed as an expression, returning
12290 its right-hand operand as its value. Thus, you may enter
12293 (@value{GDBP}) set x := y + 3
12294 (@value{GDBP}) print A(tmp := y + 1)
12298 The semicolon is allowed as an ``operator,'' returning as its value
12299 the value of its right-hand operand.
12300 This allows, for example,
12301 complex conditional breaks:
12304 (@value{GDBP}) break f
12305 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
12309 Rather than use catenation and symbolic character names to introduce special
12310 characters into strings, one may instead use a special bracket notation,
12311 which is also used to print strings. A sequence of characters of the form
12312 @samp{["@var{XX}"]} within a string or character literal denotes the
12313 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
12314 sequence of characters @samp{["""]} also denotes a single quotation mark
12315 in strings. For example,
12317 "One line.["0a"]Next line.["0a"]"
12320 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
12324 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
12325 @t{'Max} is optional (and is ignored in any case). For example, it is valid
12329 (@value{GDBP}) print 'max(x, y)
12333 When printing arrays, @value{GDBN} uses positional notation when the
12334 array has a lower bound of 1, and uses a modified named notation otherwise.
12335 For example, a one-dimensional array of three integers with a lower bound
12336 of 3 might print as
12343 That is, in contrast to valid Ada, only the first component has a @code{=>}
12347 You may abbreviate attributes in expressions with any unique,
12348 multi-character subsequence of
12349 their names (an exact match gets preference).
12350 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
12351 in place of @t{a'length}.
12354 @cindex quoting Ada internal identifiers
12355 Since Ada is case-insensitive, the debugger normally maps identifiers you type
12356 to lower case. The GNAT compiler uses upper-case characters for
12357 some of its internal identifiers, which are normally of no interest to users.
12358 For the rare occasions when you actually have to look at them,
12359 enclose them in angle brackets to avoid the lower-case mapping.
12362 (@value{GDBP}) print <JMPBUF_SAVE>[0]
12366 Printing an object of class-wide type or dereferencing an
12367 access-to-class-wide value will display all the components of the object's
12368 specific type (as indicated by its run-time tag). Likewise, component
12369 selection on such a value will operate on the specific type of the
12374 @node Stopping Before Main Program
12375 @subsubsection Stopping at the Very Beginning
12377 @cindex breakpointing Ada elaboration code
12378 It is sometimes necessary to debug the program during elaboration, and
12379 before reaching the main procedure.
12380 As defined in the Ada Reference
12381 Manual, the elaboration code is invoked from a procedure called
12382 @code{adainit}. To run your program up to the beginning of
12383 elaboration, simply use the following two commands:
12384 @code{tbreak adainit} and @code{run}.
12387 @subsubsection Extensions for Ada Tasks
12388 @cindex Ada, tasking
12390 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
12391 @value{GDBN} provides the following task-related commands:
12396 This command shows a list of current Ada tasks, as in the following example:
12403 (@value{GDBP}) info tasks
12404 ID TID P-ID Pri State Name
12405 1 8088000 0 15 Child Activation Wait main_task
12406 2 80a4000 1 15 Accept Statement b
12407 3 809a800 1 15 Child Activation Wait a
12408 * 4 80ae800 3 15 Runnable c
12413 In this listing, the asterisk before the last task indicates it to be the
12414 task currently being inspected.
12418 Represents @value{GDBN}'s internal task number.
12424 The parent's task ID (@value{GDBN}'s internal task number).
12427 The base priority of the task.
12430 Current state of the task.
12434 The task has been created but has not been activated. It cannot be
12438 The task is not blocked for any reason known to Ada. (It may be waiting
12439 for a mutex, though.) It is conceptually "executing" in normal mode.
12442 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
12443 that were waiting on terminate alternatives have been awakened and have
12444 terminated themselves.
12446 @item Child Activation Wait
12447 The task is waiting for created tasks to complete activation.
12449 @item Accept Statement
12450 The task is waiting on an accept or selective wait statement.
12452 @item Waiting on entry call
12453 The task is waiting on an entry call.
12455 @item Async Select Wait
12456 The task is waiting to start the abortable part of an asynchronous
12460 The task is waiting on a select statement with only a delay
12463 @item Child Termination Wait
12464 The task is sleeping having completed a master within itself, and is
12465 waiting for the tasks dependent on that master to become terminated or
12466 waiting on a terminate Phase.
12468 @item Wait Child in Term Alt
12469 The task is sleeping waiting for tasks on terminate alternatives to
12470 finish terminating.
12472 @item Accepting RV with @var{taskno}
12473 The task is accepting a rendez-vous with the task @var{taskno}.
12477 Name of the task in the program.
12481 @kindex info task @var{taskno}
12482 @item info task @var{taskno}
12483 This command shows detailled informations on the specified task, as in
12484 the following example:
12489 (@value{GDBP}) info tasks
12490 ID TID P-ID Pri State Name
12491 1 8077880 0 15 Child Activation Wait main_task
12492 * 2 807c468 1 15 Runnable task_1
12493 (@value{GDBP}) info task 2
12494 Ada Task: 0x807c468
12497 Parent: 1 (main_task)
12503 @kindex task@r{ (Ada)}
12504 @cindex current Ada task ID
12505 This command prints the ID of the current task.
12511 (@value{GDBP}) info tasks
12512 ID TID P-ID Pri State Name
12513 1 8077870 0 15 Child Activation Wait main_task
12514 * 2 807c458 1 15 Runnable t
12515 (@value{GDBP}) task
12516 [Current task is 2]
12519 @item task @var{taskno}
12520 @cindex Ada task switching
12521 This command is like the @code{thread @var{threadno}}
12522 command (@pxref{Threads}). It switches the context of debugging
12523 from the current task to the given task.
12529 (@value{GDBP}) info tasks
12530 ID TID P-ID Pri State Name
12531 1 8077870 0 15 Child Activation Wait main_task
12532 * 2 807c458 1 15 Runnable t
12533 (@value{GDBP}) task 1
12534 [Switching to task 1]
12535 #0 0x8067726 in pthread_cond_wait ()
12537 #0 0x8067726 in pthread_cond_wait ()
12538 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
12539 #2 0x805cb63 in system.task_primitives.operations.sleep ()
12540 #3 0x806153e in system.tasking.stages.activate_tasks ()
12541 #4 0x804aacc in un () at un.adb:5
12544 @item break @var{linespec} task @var{taskno}
12545 @itemx break @var{linespec} task @var{taskno} if @dots{}
12546 @cindex breakpoints and tasks, in Ada
12547 @cindex task breakpoints, in Ada
12548 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
12549 These commands are like the @code{break @dots{} thread @dots{}}
12550 command (@pxref{Thread Stops}).
12551 @var{linespec} specifies source lines, as described
12552 in @ref{Specify Location}.
12554 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
12555 to specify that you only want @value{GDBN} to stop the program when a
12556 particular Ada task reaches this breakpoint. @var{taskno} is one of the
12557 numeric task identifiers assigned by @value{GDBN}, shown in the first
12558 column of the @samp{info tasks} display.
12560 If you do not specify @samp{task @var{taskno}} when you set a
12561 breakpoint, the breakpoint applies to @emph{all} tasks of your
12564 You can use the @code{task} qualifier on conditional breakpoints as
12565 well; in this case, place @samp{task @var{taskno}} before the
12566 breakpoint condition (before the @code{if}).
12574 (@value{GDBP}) info tasks
12575 ID TID P-ID Pri State Name
12576 1 140022020 0 15 Child Activation Wait main_task
12577 2 140045060 1 15 Accept/Select Wait t2
12578 3 140044840 1 15 Runnable t1
12579 * 4 140056040 1 15 Runnable t3
12580 (@value{GDBP}) b 15 task 2
12581 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
12582 (@value{GDBP}) cont
12587 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
12589 (@value{GDBP}) info tasks
12590 ID TID P-ID Pri State Name
12591 1 140022020 0 15 Child Activation Wait main_task
12592 * 2 140045060 1 15 Runnable t2
12593 3 140044840 1 15 Runnable t1
12594 4 140056040 1 15 Delay Sleep t3
12598 @node Ada Tasks and Core Files
12599 @subsubsection Tasking Support when Debugging Core Files
12600 @cindex Ada tasking and core file debugging
12602 When inspecting a core file, as opposed to debugging a live program,
12603 tasking support may be limited or even unavailable, depending on
12604 the platform being used.
12605 For instance, on x86-linux, the list of tasks is available, but task
12606 switching is not supported. On Tru64, however, task switching will work
12609 On certain platforms, including Tru64, the debugger needs to perform some
12610 memory writes in order to provide Ada tasking support. When inspecting
12611 a core file, this means that the core file must be opened with read-write
12612 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
12613 Under these circumstances, you should make a backup copy of the core
12614 file before inspecting it with @value{GDBN}.
12617 @subsubsection Known Peculiarities of Ada Mode
12618 @cindex Ada, problems
12620 Besides the omissions listed previously (@pxref{Omissions from Ada}),
12621 we know of several problems with and limitations of Ada mode in
12623 some of which will be fixed with planned future releases of the debugger
12624 and the GNU Ada compiler.
12628 Currently, the debugger
12629 has insufficient information to determine whether certain pointers represent
12630 pointers to objects or the objects themselves.
12631 Thus, the user may have to tack an extra @code{.all} after an expression
12632 to get it printed properly.
12635 Static constants that the compiler chooses not to materialize as objects in
12636 storage are invisible to the debugger.
12639 Named parameter associations in function argument lists are ignored (the
12640 argument lists are treated as positional).
12643 Many useful library packages are currently invisible to the debugger.
12646 Fixed-point arithmetic, conversions, input, and output is carried out using
12647 floating-point arithmetic, and may give results that only approximate those on
12651 The GNAT compiler never generates the prefix @code{Standard} for any of
12652 the standard symbols defined by the Ada language. @value{GDBN} knows about
12653 this: it will strip the prefix from names when you use it, and will never
12654 look for a name you have so qualified among local symbols, nor match against
12655 symbols in other packages or subprograms. If you have
12656 defined entities anywhere in your program other than parameters and
12657 local variables whose simple names match names in @code{Standard},
12658 GNAT's lack of qualification here can cause confusion. When this happens,
12659 you can usually resolve the confusion
12660 by qualifying the problematic names with package
12661 @code{Standard} explicitly.
12664 @node Unsupported Languages
12665 @section Unsupported Languages
12667 @cindex unsupported languages
12668 @cindex minimal language
12669 In addition to the other fully-supported programming languages,
12670 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
12671 It does not represent a real programming language, but provides a set
12672 of capabilities close to what the C or assembly languages provide.
12673 This should allow most simple operations to be performed while debugging
12674 an application that uses a language currently not supported by @value{GDBN}.
12676 If the language is set to @code{auto}, @value{GDBN} will automatically
12677 select this language if the current frame corresponds to an unsupported
12681 @chapter Examining the Symbol Table
12683 The commands described in this chapter allow you to inquire about the
12684 symbols (names of variables, functions and types) defined in your
12685 program. This information is inherent in the text of your program and
12686 does not change as your program executes. @value{GDBN} finds it in your
12687 program's symbol table, in the file indicated when you started @value{GDBN}
12688 (@pxref{File Options, ,Choosing Files}), or by one of the
12689 file-management commands (@pxref{Files, ,Commands to Specify Files}).
12691 @cindex symbol names
12692 @cindex names of symbols
12693 @cindex quoting names
12694 Occasionally, you may need to refer to symbols that contain unusual
12695 characters, which @value{GDBN} ordinarily treats as word delimiters. The
12696 most frequent case is in referring to static variables in other
12697 source files (@pxref{Variables,,Program Variables}). File names
12698 are recorded in object files as debugging symbols, but @value{GDBN} would
12699 ordinarily parse a typical file name, like @file{foo.c}, as the three words
12700 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
12701 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
12708 looks up the value of @code{x} in the scope of the file @file{foo.c}.
12711 @cindex case-insensitive symbol names
12712 @cindex case sensitivity in symbol names
12713 @kindex set case-sensitive
12714 @item set case-sensitive on
12715 @itemx set case-sensitive off
12716 @itemx set case-sensitive auto
12717 Normally, when @value{GDBN} looks up symbols, it matches their names
12718 with case sensitivity determined by the current source language.
12719 Occasionally, you may wish to control that. The command @code{set
12720 case-sensitive} lets you do that by specifying @code{on} for
12721 case-sensitive matches or @code{off} for case-insensitive ones. If
12722 you specify @code{auto}, case sensitivity is reset to the default
12723 suitable for the source language. The default is case-sensitive
12724 matches for all languages except for Fortran, for which the default is
12725 case-insensitive matches.
12727 @kindex show case-sensitive
12728 @item show case-sensitive
12729 This command shows the current setting of case sensitivity for symbols
12732 @kindex info address
12733 @cindex address of a symbol
12734 @item info address @var{symbol}
12735 Describe where the data for @var{symbol} is stored. For a register
12736 variable, this says which register it is kept in. For a non-register
12737 local variable, this prints the stack-frame offset at which the variable
12740 Note the contrast with @samp{print &@var{symbol}}, which does not work
12741 at all for a register variable, and for a stack local variable prints
12742 the exact address of the current instantiation of the variable.
12744 @kindex info symbol
12745 @cindex symbol from address
12746 @cindex closest symbol and offset for an address
12747 @item info symbol @var{addr}
12748 Print the name of a symbol which is stored at the address @var{addr}.
12749 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
12750 nearest symbol and an offset from it:
12753 (@value{GDBP}) info symbol 0x54320
12754 _initialize_vx + 396 in section .text
12758 This is the opposite of the @code{info address} command. You can use
12759 it to find out the name of a variable or a function given its address.
12761 For dynamically linked executables, the name of executable or shared
12762 library containing the symbol is also printed:
12765 (@value{GDBP}) info symbol 0x400225
12766 _start + 5 in section .text of /tmp/a.out
12767 (@value{GDBP}) info symbol 0x2aaaac2811cf
12768 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
12772 @item whatis [@var{arg}]
12773 Print the data type of @var{arg}, which can be either an expression or
12774 a data type. With no argument, print the data type of @code{$}, the
12775 last value in the value history. If @var{arg} is an expression, it is
12776 not actually evaluated, and any side-effecting operations (such as
12777 assignments or function calls) inside it do not take place. If
12778 @var{arg} is a type name, it may be the name of a type or typedef, or
12779 for C code it may have the form @samp{class @var{class-name}},
12780 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
12781 @samp{enum @var{enum-tag}}.
12782 @xref{Expressions, ,Expressions}.
12785 @item ptype [@var{arg}]
12786 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
12787 detailed description of the type, instead of just the name of the type.
12788 @xref{Expressions, ,Expressions}.
12790 For example, for this variable declaration:
12793 struct complex @{double real; double imag;@} v;
12797 the two commands give this output:
12801 (@value{GDBP}) whatis v
12802 type = struct complex
12803 (@value{GDBP}) ptype v
12804 type = struct complex @{
12812 As with @code{whatis}, using @code{ptype} without an argument refers to
12813 the type of @code{$}, the last value in the value history.
12815 @cindex incomplete type
12816 Sometimes, programs use opaque data types or incomplete specifications
12817 of complex data structure. If the debug information included in the
12818 program does not allow @value{GDBN} to display a full declaration of
12819 the data type, it will say @samp{<incomplete type>}. For example,
12820 given these declarations:
12824 struct foo *fooptr;
12828 but no definition for @code{struct foo} itself, @value{GDBN} will say:
12831 (@value{GDBP}) ptype foo
12832 $1 = <incomplete type>
12836 ``Incomplete type'' is C terminology for data types that are not
12837 completely specified.
12840 @item info types @var{regexp}
12842 Print a brief description of all types whose names match the regular
12843 expression @var{regexp} (or all types in your program, if you supply
12844 no argument). Each complete typename is matched as though it were a
12845 complete line; thus, @samp{i type value} gives information on all
12846 types in your program whose names include the string @code{value}, but
12847 @samp{i type ^value$} gives information only on types whose complete
12848 name is @code{value}.
12850 This command differs from @code{ptype} in two ways: first, like
12851 @code{whatis}, it does not print a detailed description; second, it
12852 lists all source files where a type is defined.
12855 @cindex local variables
12856 @item info scope @var{location}
12857 List all the variables local to a particular scope. This command
12858 accepts a @var{location} argument---a function name, a source line, or
12859 an address preceded by a @samp{*}, and prints all the variables local
12860 to the scope defined by that location. (@xref{Specify Location}, for
12861 details about supported forms of @var{location}.) For example:
12864 (@value{GDBP}) @b{info scope command_line_handler}
12865 Scope for command_line_handler:
12866 Symbol rl is an argument at stack/frame offset 8, length 4.
12867 Symbol linebuffer is in static storage at address 0x150a18, length 4.
12868 Symbol linelength is in static storage at address 0x150a1c, length 4.
12869 Symbol p is a local variable in register $esi, length 4.
12870 Symbol p1 is a local variable in register $ebx, length 4.
12871 Symbol nline is a local variable in register $edx, length 4.
12872 Symbol repeat is a local variable at frame offset -8, length 4.
12876 This command is especially useful for determining what data to collect
12877 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
12880 @kindex info source
12882 Show information about the current source file---that is, the source file for
12883 the function containing the current point of execution:
12886 the name of the source file, and the directory containing it,
12888 the directory it was compiled in,
12890 its length, in lines,
12892 which programming language it is written in,
12894 whether the executable includes debugging information for that file, and
12895 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
12897 whether the debugging information includes information about
12898 preprocessor macros.
12902 @kindex info sources
12904 Print the names of all source files in your program for which there is
12905 debugging information, organized into two lists: files whose symbols
12906 have already been read, and files whose symbols will be read when needed.
12908 @kindex info functions
12909 @item info functions
12910 Print the names and data types of all defined functions.
12912 @item info functions @var{regexp}
12913 Print the names and data types of all defined functions
12914 whose names contain a match for regular expression @var{regexp}.
12915 Thus, @samp{info fun step} finds all functions whose names
12916 include @code{step}; @samp{info fun ^step} finds those whose names
12917 start with @code{step}. If a function name contains characters
12918 that conflict with the regular expression language (e.g.@:
12919 @samp{operator*()}), they may be quoted with a backslash.
12921 @kindex info variables
12922 @item info variables
12923 Print the names and data types of all variables that are declared
12924 outside of functions (i.e.@: excluding local variables).
12926 @item info variables @var{regexp}
12927 Print the names and data types of all variables (except for local
12928 variables) whose names contain a match for regular expression
12931 @kindex info classes
12932 @cindex Objective-C, classes and selectors
12934 @itemx info classes @var{regexp}
12935 Display all Objective-C classes in your program, or
12936 (with the @var{regexp} argument) all those matching a particular regular
12939 @kindex info selectors
12940 @item info selectors
12941 @itemx info selectors @var{regexp}
12942 Display all Objective-C selectors in your program, or
12943 (with the @var{regexp} argument) all those matching a particular regular
12947 This was never implemented.
12948 @kindex info methods
12950 @itemx info methods @var{regexp}
12951 The @code{info methods} command permits the user to examine all defined
12952 methods within C@t{++} program, or (with the @var{regexp} argument) a
12953 specific set of methods found in the various C@t{++} classes. Many
12954 C@t{++} classes provide a large number of methods. Thus, the output
12955 from the @code{ptype} command can be overwhelming and hard to use. The
12956 @code{info-methods} command filters the methods, printing only those
12957 which match the regular-expression @var{regexp}.
12960 @cindex reloading symbols
12961 Some systems allow individual object files that make up your program to
12962 be replaced without stopping and restarting your program. For example,
12963 in VxWorks you can simply recompile a defective object file and keep on
12964 running. If you are running on one of these systems, you can allow
12965 @value{GDBN} to reload the symbols for automatically relinked modules:
12968 @kindex set symbol-reloading
12969 @item set symbol-reloading on
12970 Replace symbol definitions for the corresponding source file when an
12971 object file with a particular name is seen again.
12973 @item set symbol-reloading off
12974 Do not replace symbol definitions when encountering object files of the
12975 same name more than once. This is the default state; if you are not
12976 running on a system that permits automatic relinking of modules, you
12977 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
12978 may discard symbols when linking large programs, that may contain
12979 several modules (from different directories or libraries) with the same
12982 @kindex show symbol-reloading
12983 @item show symbol-reloading
12984 Show the current @code{on} or @code{off} setting.
12987 @cindex opaque data types
12988 @kindex set opaque-type-resolution
12989 @item set opaque-type-resolution on
12990 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
12991 declared as a pointer to a @code{struct}, @code{class}, or
12992 @code{union}---for example, @code{struct MyType *}---that is used in one
12993 source file although the full declaration of @code{struct MyType} is in
12994 another source file. The default is on.
12996 A change in the setting of this subcommand will not take effect until
12997 the next time symbols for a file are loaded.
12999 @item set opaque-type-resolution off
13000 Tell @value{GDBN} not to resolve opaque types. In this case, the type
13001 is printed as follows:
13003 @{<no data fields>@}
13006 @kindex show opaque-type-resolution
13007 @item show opaque-type-resolution
13008 Show whether opaque types are resolved or not.
13010 @kindex maint print symbols
13011 @cindex symbol dump
13012 @kindex maint print psymbols
13013 @cindex partial symbol dump
13014 @item maint print symbols @var{filename}
13015 @itemx maint print psymbols @var{filename}
13016 @itemx maint print msymbols @var{filename}
13017 Write a dump of debugging symbol data into the file @var{filename}.
13018 These commands are used to debug the @value{GDBN} symbol-reading code. Only
13019 symbols with debugging data are included. If you use @samp{maint print
13020 symbols}, @value{GDBN} includes all the symbols for which it has already
13021 collected full details: that is, @var{filename} reflects symbols for
13022 only those files whose symbols @value{GDBN} has read. You can use the
13023 command @code{info sources} to find out which files these are. If you
13024 use @samp{maint print psymbols} instead, the dump shows information about
13025 symbols that @value{GDBN} only knows partially---that is, symbols defined in
13026 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
13027 @samp{maint print msymbols} dumps just the minimal symbol information
13028 required for each object file from which @value{GDBN} has read some symbols.
13029 @xref{Files, ,Commands to Specify Files}, for a discussion of how
13030 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
13032 @kindex maint info symtabs
13033 @kindex maint info psymtabs
13034 @cindex listing @value{GDBN}'s internal symbol tables
13035 @cindex symbol tables, listing @value{GDBN}'s internal
13036 @cindex full symbol tables, listing @value{GDBN}'s internal
13037 @cindex partial symbol tables, listing @value{GDBN}'s internal
13038 @item maint info symtabs @r{[} @var{regexp} @r{]}
13039 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
13041 List the @code{struct symtab} or @code{struct partial_symtab}
13042 structures whose names match @var{regexp}. If @var{regexp} is not
13043 given, list them all. The output includes expressions which you can
13044 copy into a @value{GDBN} debugging this one to examine a particular
13045 structure in more detail. For example:
13048 (@value{GDBP}) maint info psymtabs dwarf2read
13049 @{ objfile /home/gnu/build/gdb/gdb
13050 ((struct objfile *) 0x82e69d0)
13051 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
13052 ((struct partial_symtab *) 0x8474b10)
13055 text addresses 0x814d3c8 -- 0x8158074
13056 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
13057 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
13058 dependencies (none)
13061 (@value{GDBP}) maint info symtabs
13065 We see that there is one partial symbol table whose filename contains
13066 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
13067 and we see that @value{GDBN} has not read in any symtabs yet at all.
13068 If we set a breakpoint on a function, that will cause @value{GDBN} to
13069 read the symtab for the compilation unit containing that function:
13072 (@value{GDBP}) break dwarf2_psymtab_to_symtab
13073 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
13075 (@value{GDBP}) maint info symtabs
13076 @{ objfile /home/gnu/build/gdb/gdb
13077 ((struct objfile *) 0x82e69d0)
13078 @{ symtab /home/gnu/src/gdb/dwarf2read.c
13079 ((struct symtab *) 0x86c1f38)
13082 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
13083 linetable ((struct linetable *) 0x8370fa0)
13084 debugformat DWARF 2
13093 @chapter Altering Execution
13095 Once you think you have found an error in your program, you might want to
13096 find out for certain whether correcting the apparent error would lead to
13097 correct results in the rest of the run. You can find the answer by
13098 experiment, using the @value{GDBN} features for altering execution of the
13101 For example, you can store new values into variables or memory
13102 locations, give your program a signal, restart it at a different
13103 address, or even return prematurely from a function.
13106 * Assignment:: Assignment to variables
13107 * Jumping:: Continuing at a different address
13108 * Signaling:: Giving your program a signal
13109 * Returning:: Returning from a function
13110 * Calling:: Calling your program's functions
13111 * Patching:: Patching your program
13115 @section Assignment to Variables
13118 @cindex setting variables
13119 To alter the value of a variable, evaluate an assignment expression.
13120 @xref{Expressions, ,Expressions}. For example,
13127 stores the value 4 into the variable @code{x}, and then prints the
13128 value of the assignment expression (which is 4).
13129 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
13130 information on operators in supported languages.
13132 @kindex set variable
13133 @cindex variables, setting
13134 If you are not interested in seeing the value of the assignment, use the
13135 @code{set} command instead of the @code{print} command. @code{set} is
13136 really the same as @code{print} except that the expression's value is
13137 not printed and is not put in the value history (@pxref{Value History,
13138 ,Value History}). The expression is evaluated only for its effects.
13140 If the beginning of the argument string of the @code{set} command
13141 appears identical to a @code{set} subcommand, use the @code{set
13142 variable} command instead of just @code{set}. This command is identical
13143 to @code{set} except for its lack of subcommands. For example, if your
13144 program has a variable @code{width}, you get an error if you try to set
13145 a new value with just @samp{set width=13}, because @value{GDBN} has the
13146 command @code{set width}:
13149 (@value{GDBP}) whatis width
13151 (@value{GDBP}) p width
13153 (@value{GDBP}) set width=47
13154 Invalid syntax in expression.
13158 The invalid expression, of course, is @samp{=47}. In
13159 order to actually set the program's variable @code{width}, use
13162 (@value{GDBP}) set var width=47
13165 Because the @code{set} command has many subcommands that can conflict
13166 with the names of program variables, it is a good idea to use the
13167 @code{set variable} command instead of just @code{set}. For example, if
13168 your program has a variable @code{g}, you run into problems if you try
13169 to set a new value with just @samp{set g=4}, because @value{GDBN} has
13170 the command @code{set gnutarget}, abbreviated @code{set g}:
13174 (@value{GDBP}) whatis g
13178 (@value{GDBP}) set g=4
13182 The program being debugged has been started already.
13183 Start it from the beginning? (y or n) y
13184 Starting program: /home/smith/cc_progs/a.out
13185 "/home/smith/cc_progs/a.out": can't open to read symbols:
13186 Invalid bfd target.
13187 (@value{GDBP}) show g
13188 The current BFD target is "=4".
13193 The program variable @code{g} did not change, and you silently set the
13194 @code{gnutarget} to an invalid value. In order to set the variable
13198 (@value{GDBP}) set var g=4
13201 @value{GDBN} allows more implicit conversions in assignments than C; you can
13202 freely store an integer value into a pointer variable or vice versa,
13203 and you can convert any structure to any other structure that is the
13204 same length or shorter.
13205 @comment FIXME: how do structs align/pad in these conversions?
13206 @comment /doc@cygnus.com 18dec1990
13208 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
13209 construct to generate a value of specified type at a specified address
13210 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
13211 to memory location @code{0x83040} as an integer (which implies a certain size
13212 and representation in memory), and
13215 set @{int@}0x83040 = 4
13219 stores the value 4 into that memory location.
13222 @section Continuing at a Different Address
13224 Ordinarily, when you continue your program, you do so at the place where
13225 it stopped, with the @code{continue} command. You can instead continue at
13226 an address of your own choosing, with the following commands:
13230 @item jump @var{linespec}
13231 @itemx jump @var{location}
13232 Resume execution at line @var{linespec} or at address given by
13233 @var{location}. Execution stops again immediately if there is a
13234 breakpoint there. @xref{Specify Location}, for a description of the
13235 different forms of @var{linespec} and @var{location}. It is common
13236 practice to use the @code{tbreak} command in conjunction with
13237 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
13239 The @code{jump} command does not change the current stack frame, or
13240 the stack pointer, or the contents of any memory location or any
13241 register other than the program counter. If line @var{linespec} is in
13242 a different function from the one currently executing, the results may
13243 be bizarre if the two functions expect different patterns of arguments or
13244 of local variables. For this reason, the @code{jump} command requests
13245 confirmation if the specified line is not in the function currently
13246 executing. However, even bizarre results are predictable if you are
13247 well acquainted with the machine-language code of your program.
13250 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
13251 On many systems, you can get much the same effect as the @code{jump}
13252 command by storing a new value into the register @code{$pc}. The
13253 difference is that this does not start your program running; it only
13254 changes the address of where it @emph{will} run when you continue. For
13262 makes the next @code{continue} command or stepping command execute at
13263 address @code{0x485}, rather than at the address where your program stopped.
13264 @xref{Continuing and Stepping, ,Continuing and Stepping}.
13266 The most common occasion to use the @code{jump} command is to back
13267 up---perhaps with more breakpoints set---over a portion of a program
13268 that has already executed, in order to examine its execution in more
13273 @section Giving your Program a Signal
13274 @cindex deliver a signal to a program
13278 @item signal @var{signal}
13279 Resume execution where your program stopped, but immediately give it the
13280 signal @var{signal}. @var{signal} can be the name or the number of a
13281 signal. For example, on many systems @code{signal 2} and @code{signal
13282 SIGINT} are both ways of sending an interrupt signal.
13284 Alternatively, if @var{signal} is zero, continue execution without
13285 giving a signal. This is useful when your program stopped on account of
13286 a signal and would ordinary see the signal when resumed with the
13287 @code{continue} command; @samp{signal 0} causes it to resume without a
13290 @code{signal} does not repeat when you press @key{RET} a second time
13291 after executing the command.
13295 Invoking the @code{signal} command is not the same as invoking the
13296 @code{kill} utility from the shell. Sending a signal with @code{kill}
13297 causes @value{GDBN} to decide what to do with the signal depending on
13298 the signal handling tables (@pxref{Signals}). The @code{signal} command
13299 passes the signal directly to your program.
13303 @section Returning from a Function
13306 @cindex returning from a function
13309 @itemx return @var{expression}
13310 You can cancel execution of a function call with the @code{return}
13311 command. If you give an
13312 @var{expression} argument, its value is used as the function's return
13316 When you use @code{return}, @value{GDBN} discards the selected stack frame
13317 (and all frames within it). You can think of this as making the
13318 discarded frame return prematurely. If you wish to specify a value to
13319 be returned, give that value as the argument to @code{return}.
13321 This pops the selected stack frame (@pxref{Selection, ,Selecting a
13322 Frame}), and any other frames inside of it, leaving its caller as the
13323 innermost remaining frame. That frame becomes selected. The
13324 specified value is stored in the registers used for returning values
13327 The @code{return} command does not resume execution; it leaves the
13328 program stopped in the state that would exist if the function had just
13329 returned. In contrast, the @code{finish} command (@pxref{Continuing
13330 and Stepping, ,Continuing and Stepping}) resumes execution until the
13331 selected stack frame returns naturally.
13333 @value{GDBN} needs to know how the @var{expression} argument should be set for
13334 the inferior. The concrete registers assignment depends on the OS ABI and the
13335 type being returned by the selected stack frame. For example it is common for
13336 OS ABI to return floating point values in FPU registers while integer values in
13337 CPU registers. Still some ABIs return even floating point values in CPU
13338 registers. Larger integer widths (such as @code{long long int}) also have
13339 specific placement rules. @value{GDBN} already knows the OS ABI from its
13340 current target so it needs to find out also the type being returned to make the
13341 assignment into the right register(s).
13343 Normally, the selected stack frame has debug info. @value{GDBN} will always
13344 use the debug info instead of the implicit type of @var{expression} when the
13345 debug info is available. For example, if you type @kbd{return -1}, and the
13346 function in the current stack frame is declared to return a @code{long long
13347 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
13348 into a @code{long long int}:
13351 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
13353 (@value{GDBP}) return -1
13354 Make func return now? (y or n) y
13355 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
13356 43 printf ("result=%lld\n", func ());
13360 However, if the selected stack frame does not have a debug info, e.g., if the
13361 function was compiled without debug info, @value{GDBN} has to find out the type
13362 to return from user. Specifying a different type by mistake may set the value
13363 in different inferior registers than the caller code expects. For example,
13364 typing @kbd{return -1} with its implicit type @code{int} would set only a part
13365 of a @code{long long int} result for a debug info less function (on 32-bit
13366 architectures). Therefore the user is required to specify the return type by
13367 an appropriate cast explicitly:
13370 Breakpoint 2, 0x0040050b in func ()
13371 (@value{GDBP}) return -1
13372 Return value type not available for selected stack frame.
13373 Please use an explicit cast of the value to return.
13374 (@value{GDBP}) return (long long int) -1
13375 Make selected stack frame return now? (y or n) y
13376 #0 0x00400526 in main ()
13381 @section Calling Program Functions
13384 @cindex calling functions
13385 @cindex inferior functions, calling
13386 @item print @var{expr}
13387 Evaluate the expression @var{expr} and display the resulting value.
13388 @var{expr} may include calls to functions in the program being
13392 @item call @var{expr}
13393 Evaluate the expression @var{expr} without displaying @code{void}
13396 You can use this variant of the @code{print} command if you want to
13397 execute a function from your program that does not return anything
13398 (a.k.a.@: @dfn{a void function}), but without cluttering the output
13399 with @code{void} returned values that @value{GDBN} will otherwise
13400 print. If the result is not void, it is printed and saved in the
13404 It is possible for the function you call via the @code{print} or
13405 @code{call} command to generate a signal (e.g., if there's a bug in
13406 the function, or if you passed it incorrect arguments). What happens
13407 in that case is controlled by the @code{set unwindonsignal} command.
13409 Similarly, with a C@t{++} program it is possible for the function you
13410 call via the @code{print} or @code{call} command to generate an
13411 exception that is not handled due to the constraints of the dummy
13412 frame. In this case, any exception that is raised in the frame, but has
13413 an out-of-frame exception handler will not be found. GDB builds a
13414 dummy-frame for the inferior function call, and the unwinder cannot
13415 seek for exception handlers outside of this dummy-frame. What happens
13416 in that case is controlled by the
13417 @code{set unwind-on-terminating-exception} command.
13420 @item set unwindonsignal
13421 @kindex set unwindonsignal
13422 @cindex unwind stack in called functions
13423 @cindex call dummy stack unwinding
13424 Set unwinding of the stack if a signal is received while in a function
13425 that @value{GDBN} called in the program being debugged. If set to on,
13426 @value{GDBN} unwinds the stack it created for the call and restores
13427 the context to what it was before the call. If set to off (the
13428 default), @value{GDBN} stops in the frame where the signal was
13431 @item show unwindonsignal
13432 @kindex show unwindonsignal
13433 Show the current setting of stack unwinding in the functions called by
13436 @item set unwind-on-terminating-exception
13437 @kindex set unwind-on-terminating-exception
13438 @cindex unwind stack in called functions with unhandled exceptions
13439 @cindex call dummy stack unwinding on unhandled exception.
13440 Set unwinding of the stack if a C@t{++} exception is raised, but left
13441 unhandled while in a function that @value{GDBN} called in the program being
13442 debugged. If set to on (the default), @value{GDBN} unwinds the stack
13443 it created for the call and restores the context to what it was before
13444 the call. If set to off, @value{GDBN} the exception is delivered to
13445 the default C@t{++} exception handler and the inferior terminated.
13447 @item show unwind-on-terminating-exception
13448 @kindex show unwind-on-terminating-exception
13449 Show the current setting of stack unwinding in the functions called by
13454 @cindex weak alias functions
13455 Sometimes, a function you wish to call is actually a @dfn{weak alias}
13456 for another function. In such case, @value{GDBN} might not pick up
13457 the type information, including the types of the function arguments,
13458 which causes @value{GDBN} to call the inferior function incorrectly.
13459 As a result, the called function will function erroneously and may
13460 even crash. A solution to that is to use the name of the aliased
13464 @section Patching Programs
13466 @cindex patching binaries
13467 @cindex writing into executables
13468 @cindex writing into corefiles
13470 By default, @value{GDBN} opens the file containing your program's
13471 executable code (or the corefile) read-only. This prevents accidental
13472 alterations to machine code; but it also prevents you from intentionally
13473 patching your program's binary.
13475 If you'd like to be able to patch the binary, you can specify that
13476 explicitly with the @code{set write} command. For example, you might
13477 want to turn on internal debugging flags, or even to make emergency
13483 @itemx set write off
13484 If you specify @samp{set write on}, @value{GDBN} opens executable and
13485 core files for both reading and writing; if you specify @kbd{set write
13486 off} (the default), @value{GDBN} opens them read-only.
13488 If you have already loaded a file, you must load it again (using the
13489 @code{exec-file} or @code{core-file} command) after changing @code{set
13490 write}, for your new setting to take effect.
13494 Display whether executable files and core files are opened for writing
13495 as well as reading.
13499 @chapter @value{GDBN} Files
13501 @value{GDBN} needs to know the file name of the program to be debugged,
13502 both in order to read its symbol table and in order to start your
13503 program. To debug a core dump of a previous run, you must also tell
13504 @value{GDBN} the name of the core dump file.
13507 * Files:: Commands to specify files
13508 * Separate Debug Files:: Debugging information in separate files
13509 * Symbol Errors:: Errors reading symbol files
13510 * Data Files:: GDB data files
13514 @section Commands to Specify Files
13516 @cindex symbol table
13517 @cindex core dump file
13519 You may want to specify executable and core dump file names. The usual
13520 way to do this is at start-up time, using the arguments to
13521 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
13522 Out of @value{GDBN}}).
13524 Occasionally it is necessary to change to a different file during a
13525 @value{GDBN} session. Or you may run @value{GDBN} and forget to
13526 specify a file you want to use. Or you are debugging a remote target
13527 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
13528 Program}). In these situations the @value{GDBN} commands to specify
13529 new files are useful.
13532 @cindex executable file
13534 @item file @var{filename}
13535 Use @var{filename} as the program to be debugged. It is read for its
13536 symbols and for the contents of pure memory. It is also the program
13537 executed when you use the @code{run} command. If you do not specify a
13538 directory and the file is not found in the @value{GDBN} working directory,
13539 @value{GDBN} uses the environment variable @code{PATH} as a list of
13540 directories to search, just as the shell does when looking for a program
13541 to run. You can change the value of this variable, for both @value{GDBN}
13542 and your program, using the @code{path} command.
13544 @cindex unlinked object files
13545 @cindex patching object files
13546 You can load unlinked object @file{.o} files into @value{GDBN} using
13547 the @code{file} command. You will not be able to ``run'' an object
13548 file, but you can disassemble functions and inspect variables. Also,
13549 if the underlying BFD functionality supports it, you could use
13550 @kbd{gdb -write} to patch object files using this technique. Note
13551 that @value{GDBN} can neither interpret nor modify relocations in this
13552 case, so branches and some initialized variables will appear to go to
13553 the wrong place. But this feature is still handy from time to time.
13556 @code{file} with no argument makes @value{GDBN} discard any information it
13557 has on both executable file and the symbol table.
13560 @item exec-file @r{[} @var{filename} @r{]}
13561 Specify that the program to be run (but not the symbol table) is found
13562 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
13563 if necessary to locate your program. Omitting @var{filename} means to
13564 discard information on the executable file.
13566 @kindex symbol-file
13567 @item symbol-file @r{[} @var{filename} @r{]}
13568 Read symbol table information from file @var{filename}. @code{PATH} is
13569 searched when necessary. Use the @code{file} command to get both symbol
13570 table and program to run from the same file.
13572 @code{symbol-file} with no argument clears out @value{GDBN} information on your
13573 program's symbol table.
13575 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
13576 some breakpoints and auto-display expressions. This is because they may
13577 contain pointers to the internal data recording symbols and data types,
13578 which are part of the old symbol table data being discarded inside
13581 @code{symbol-file} does not repeat if you press @key{RET} again after
13584 When @value{GDBN} is configured for a particular environment, it
13585 understands debugging information in whatever format is the standard
13586 generated for that environment; you may use either a @sc{gnu} compiler, or
13587 other compilers that adhere to the local conventions.
13588 Best results are usually obtained from @sc{gnu} compilers; for example,
13589 using @code{@value{NGCC}} you can generate debugging information for
13592 For most kinds of object files, with the exception of old SVR3 systems
13593 using COFF, the @code{symbol-file} command does not normally read the
13594 symbol table in full right away. Instead, it scans the symbol table
13595 quickly to find which source files and which symbols are present. The
13596 details are read later, one source file at a time, as they are needed.
13598 The purpose of this two-stage reading strategy is to make @value{GDBN}
13599 start up faster. For the most part, it is invisible except for
13600 occasional pauses while the symbol table details for a particular source
13601 file are being read. (The @code{set verbose} command can turn these
13602 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
13603 Warnings and Messages}.)
13605 We have not implemented the two-stage strategy for COFF yet. When the
13606 symbol table is stored in COFF format, @code{symbol-file} reads the
13607 symbol table data in full right away. Note that ``stabs-in-COFF''
13608 still does the two-stage strategy, since the debug info is actually
13612 @cindex reading symbols immediately
13613 @cindex symbols, reading immediately
13614 @item symbol-file @var{filename} @r{[} -readnow @r{]}
13615 @itemx file @var{filename} @r{[} -readnow @r{]}
13616 You can override the @value{GDBN} two-stage strategy for reading symbol
13617 tables by using the @samp{-readnow} option with any of the commands that
13618 load symbol table information, if you want to be sure @value{GDBN} has the
13619 entire symbol table available.
13621 @c FIXME: for now no mention of directories, since this seems to be in
13622 @c flux. 13mar1992 status is that in theory GDB would look either in
13623 @c current dir or in same dir as myprog; but issues like competing
13624 @c GDB's, or clutter in system dirs, mean that in practice right now
13625 @c only current dir is used. FFish says maybe a special GDB hierarchy
13626 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
13630 @item core-file @r{[}@var{filename}@r{]}
13632 Specify the whereabouts of a core dump file to be used as the ``contents
13633 of memory''. Traditionally, core files contain only some parts of the
13634 address space of the process that generated them; @value{GDBN} can access the
13635 executable file itself for other parts.
13637 @code{core-file} with no argument specifies that no core file is
13640 Note that the core file is ignored when your program is actually running
13641 under @value{GDBN}. So, if you have been running your program and you
13642 wish to debug a core file instead, you must kill the subprocess in which
13643 the program is running. To do this, use the @code{kill} command
13644 (@pxref{Kill Process, ,Killing the Child Process}).
13646 @kindex add-symbol-file
13647 @cindex dynamic linking
13648 @item add-symbol-file @var{filename} @var{address}
13649 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
13650 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
13651 The @code{add-symbol-file} command reads additional symbol table
13652 information from the file @var{filename}. You would use this command
13653 when @var{filename} has been dynamically loaded (by some other means)
13654 into the program that is running. @var{address} should be the memory
13655 address at which the file has been loaded; @value{GDBN} cannot figure
13656 this out for itself. You can additionally specify an arbitrary number
13657 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
13658 section name and base address for that section. You can specify any
13659 @var{address} as an expression.
13661 The symbol table of the file @var{filename} is added to the symbol table
13662 originally read with the @code{symbol-file} command. You can use the
13663 @code{add-symbol-file} command any number of times; the new symbol data
13664 thus read keeps adding to the old. To discard all old symbol data
13665 instead, use the @code{symbol-file} command without any arguments.
13667 @cindex relocatable object files, reading symbols from
13668 @cindex object files, relocatable, reading symbols from
13669 @cindex reading symbols from relocatable object files
13670 @cindex symbols, reading from relocatable object files
13671 @cindex @file{.o} files, reading symbols from
13672 Although @var{filename} is typically a shared library file, an
13673 executable file, or some other object file which has been fully
13674 relocated for loading into a process, you can also load symbolic
13675 information from relocatable @file{.o} files, as long as:
13679 the file's symbolic information refers only to linker symbols defined in
13680 that file, not to symbols defined by other object files,
13682 every section the file's symbolic information refers to has actually
13683 been loaded into the inferior, as it appears in the file, and
13685 you can determine the address at which every section was loaded, and
13686 provide these to the @code{add-symbol-file} command.
13690 Some embedded operating systems, like Sun Chorus and VxWorks, can load
13691 relocatable files into an already running program; such systems
13692 typically make the requirements above easy to meet. However, it's
13693 important to recognize that many native systems use complex link
13694 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
13695 assembly, for example) that make the requirements difficult to meet. In
13696 general, one cannot assume that using @code{add-symbol-file} to read a
13697 relocatable object file's symbolic information will have the same effect
13698 as linking the relocatable object file into the program in the normal
13701 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
13703 @kindex add-symbol-file-from-memory
13704 @cindex @code{syscall DSO}
13705 @cindex load symbols from memory
13706 @item add-symbol-file-from-memory @var{address}
13707 Load symbols from the given @var{address} in a dynamically loaded
13708 object file whose image is mapped directly into the inferior's memory.
13709 For example, the Linux kernel maps a @code{syscall DSO} into each
13710 process's address space; this DSO provides kernel-specific code for
13711 some system calls. The argument can be any expression whose
13712 evaluation yields the address of the file's shared object file header.
13713 For this command to work, you must have used @code{symbol-file} or
13714 @code{exec-file} commands in advance.
13716 @kindex add-shared-symbol-files
13718 @item add-shared-symbol-files @var{library-file}
13719 @itemx assf @var{library-file}
13720 The @code{add-shared-symbol-files} command can currently be used only
13721 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
13722 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
13723 @value{GDBN} automatically looks for shared libraries, however if
13724 @value{GDBN} does not find yours, you can invoke
13725 @code{add-shared-symbol-files}. It takes one argument: the shared
13726 library's file name. @code{assf} is a shorthand alias for
13727 @code{add-shared-symbol-files}.
13730 @item section @var{section} @var{addr}
13731 The @code{section} command changes the base address of the named
13732 @var{section} of the exec file to @var{addr}. This can be used if the
13733 exec file does not contain section addresses, (such as in the
13734 @code{a.out} format), or when the addresses specified in the file
13735 itself are wrong. Each section must be changed separately. The
13736 @code{info files} command, described below, lists all the sections and
13740 @kindex info target
13743 @code{info files} and @code{info target} are synonymous; both print the
13744 current target (@pxref{Targets, ,Specifying a Debugging Target}),
13745 including the names of the executable and core dump files currently in
13746 use by @value{GDBN}, and the files from which symbols were loaded. The
13747 command @code{help target} lists all possible targets rather than
13750 @kindex maint info sections
13751 @item maint info sections
13752 Another command that can give you extra information about program sections
13753 is @code{maint info sections}. In addition to the section information
13754 displayed by @code{info files}, this command displays the flags and file
13755 offset of each section in the executable and core dump files. In addition,
13756 @code{maint info sections} provides the following command options (which
13757 may be arbitrarily combined):
13761 Display sections for all loaded object files, including shared libraries.
13762 @item @var{sections}
13763 Display info only for named @var{sections}.
13764 @item @var{section-flags}
13765 Display info only for sections for which @var{section-flags} are true.
13766 The section flags that @value{GDBN} currently knows about are:
13769 Section will have space allocated in the process when loaded.
13770 Set for all sections except those containing debug information.
13772 Section will be loaded from the file into the child process memory.
13773 Set for pre-initialized code and data, clear for @code{.bss} sections.
13775 Section needs to be relocated before loading.
13777 Section cannot be modified by the child process.
13779 Section contains executable code only.
13781 Section contains data only (no executable code).
13783 Section will reside in ROM.
13785 Section contains data for constructor/destructor lists.
13787 Section is not empty.
13789 An instruction to the linker to not output the section.
13790 @item COFF_SHARED_LIBRARY
13791 A notification to the linker that the section contains
13792 COFF shared library information.
13794 Section contains common symbols.
13797 @kindex set trust-readonly-sections
13798 @cindex read-only sections
13799 @item set trust-readonly-sections on
13800 Tell @value{GDBN} that readonly sections in your object file
13801 really are read-only (i.e.@: that their contents will not change).
13802 In that case, @value{GDBN} can fetch values from these sections
13803 out of the object file, rather than from the target program.
13804 For some targets (notably embedded ones), this can be a significant
13805 enhancement to debugging performance.
13807 The default is off.
13809 @item set trust-readonly-sections off
13810 Tell @value{GDBN} not to trust readonly sections. This means that
13811 the contents of the section might change while the program is running,
13812 and must therefore be fetched from the target when needed.
13814 @item show trust-readonly-sections
13815 Show the current setting of trusting readonly sections.
13818 All file-specifying commands allow both absolute and relative file names
13819 as arguments. @value{GDBN} always converts the file name to an absolute file
13820 name and remembers it that way.
13822 @cindex shared libraries
13823 @anchor{Shared Libraries}
13824 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
13825 and IBM RS/6000 AIX shared libraries.
13827 On MS-Windows @value{GDBN} must be linked with the Expat library to support
13828 shared libraries. @xref{Expat}.
13830 @value{GDBN} automatically loads symbol definitions from shared libraries
13831 when you use the @code{run} command, or when you examine a core file.
13832 (Before you issue the @code{run} command, @value{GDBN} does not understand
13833 references to a function in a shared library, however---unless you are
13834 debugging a core file).
13836 On HP-UX, if the program loads a library explicitly, @value{GDBN}
13837 automatically loads the symbols at the time of the @code{shl_load} call.
13839 @c FIXME: some @value{GDBN} release may permit some refs to undef
13840 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
13841 @c FIXME...lib; check this from time to time when updating manual
13843 There are times, however, when you may wish to not automatically load
13844 symbol definitions from shared libraries, such as when they are
13845 particularly large or there are many of them.
13847 To control the automatic loading of shared library symbols, use the
13851 @kindex set auto-solib-add
13852 @item set auto-solib-add @var{mode}
13853 If @var{mode} is @code{on}, symbols from all shared object libraries
13854 will be loaded automatically when the inferior begins execution, you
13855 attach to an independently started inferior, or when the dynamic linker
13856 informs @value{GDBN} that a new library has been loaded. If @var{mode}
13857 is @code{off}, symbols must be loaded manually, using the
13858 @code{sharedlibrary} command. The default value is @code{on}.
13860 @cindex memory used for symbol tables
13861 If your program uses lots of shared libraries with debug info that
13862 takes large amounts of memory, you can decrease the @value{GDBN}
13863 memory footprint by preventing it from automatically loading the
13864 symbols from shared libraries. To that end, type @kbd{set
13865 auto-solib-add off} before running the inferior, then load each
13866 library whose debug symbols you do need with @kbd{sharedlibrary
13867 @var{regexp}}, where @var{regexp} is a regular expression that matches
13868 the libraries whose symbols you want to be loaded.
13870 @kindex show auto-solib-add
13871 @item show auto-solib-add
13872 Display the current autoloading mode.
13875 @cindex load shared library
13876 To explicitly load shared library symbols, use the @code{sharedlibrary}
13880 @kindex info sharedlibrary
13882 @item info share @var{regex}
13883 @itemx info sharedlibrary @var{regex}
13884 Print the names of the shared libraries which are currently loaded
13885 that match @var{regex}. If @var{regex} is omitted then print
13886 all shared libraries that are loaded.
13888 @kindex sharedlibrary
13890 @item sharedlibrary @var{regex}
13891 @itemx share @var{regex}
13892 Load shared object library symbols for files matching a
13893 Unix regular expression.
13894 As with files loaded automatically, it only loads shared libraries
13895 required by your program for a core file or after typing @code{run}. If
13896 @var{regex} is omitted all shared libraries required by your program are
13899 @item nosharedlibrary
13900 @kindex nosharedlibrary
13901 @cindex unload symbols from shared libraries
13902 Unload all shared object library symbols. This discards all symbols
13903 that have been loaded from all shared libraries. Symbols from shared
13904 libraries that were loaded by explicit user requests are not
13908 Sometimes you may wish that @value{GDBN} stops and gives you control
13909 when any of shared library events happen. Use the @code{set
13910 stop-on-solib-events} command for this:
13913 @item set stop-on-solib-events
13914 @kindex set stop-on-solib-events
13915 This command controls whether @value{GDBN} should give you control
13916 when the dynamic linker notifies it about some shared library event.
13917 The most common event of interest is loading or unloading of a new
13920 @item show stop-on-solib-events
13921 @kindex show stop-on-solib-events
13922 Show whether @value{GDBN} stops and gives you control when shared
13923 library events happen.
13926 Shared libraries are also supported in many cross or remote debugging
13927 configurations. @value{GDBN} needs to have access to the target's libraries;
13928 this can be accomplished either by providing copies of the libraries
13929 on the host system, or by asking @value{GDBN} to automatically retrieve the
13930 libraries from the target. If copies of the target libraries are
13931 provided, they need to be the same as the target libraries, although the
13932 copies on the target can be stripped as long as the copies on the host are
13935 @cindex where to look for shared libraries
13936 For remote debugging, you need to tell @value{GDBN} where the target
13937 libraries are, so that it can load the correct copies---otherwise, it
13938 may try to load the host's libraries. @value{GDBN} has two variables
13939 to specify the search directories for target libraries.
13942 @cindex prefix for shared library file names
13943 @cindex system root, alternate
13944 @kindex set solib-absolute-prefix
13945 @kindex set sysroot
13946 @item set sysroot @var{path}
13947 Use @var{path} as the system root for the program being debugged. Any
13948 absolute shared library paths will be prefixed with @var{path}; many
13949 runtime loaders store the absolute paths to the shared library in the
13950 target program's memory. If you use @code{set sysroot} to find shared
13951 libraries, they need to be laid out in the same way that they are on
13952 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
13955 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
13956 retrieve the target libraries from the remote system. This is only
13957 supported when using a remote target that supports the @code{remote get}
13958 command (@pxref{File Transfer,,Sending files to a remote system}).
13959 The part of @var{path} following the initial @file{remote:}
13960 (if present) is used as system root prefix on the remote file system.
13961 @footnote{If you want to specify a local system root using a directory
13962 that happens to be named @file{remote:}, you need to use some equivalent
13963 variant of the name like @file{./remote:}.}
13965 The @code{set solib-absolute-prefix} command is an alias for @code{set
13968 @cindex default system root
13969 @cindex @samp{--with-sysroot}
13970 You can set the default system root by using the configure-time
13971 @samp{--with-sysroot} option. If the system root is inside
13972 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
13973 @samp{--exec-prefix}), then the default system root will be updated
13974 automatically if the installed @value{GDBN} is moved to a new
13977 @kindex show sysroot
13979 Display the current shared library prefix.
13981 @kindex set solib-search-path
13982 @item set solib-search-path @var{path}
13983 If this variable is set, @var{path} is a colon-separated list of
13984 directories to search for shared libraries. @samp{solib-search-path}
13985 is used after @samp{sysroot} fails to locate the library, or if the
13986 path to the library is relative instead of absolute. If you want to
13987 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
13988 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
13989 finding your host's libraries. @samp{sysroot} is preferred; setting
13990 it to a nonexistent directory may interfere with automatic loading
13991 of shared library symbols.
13993 @kindex show solib-search-path
13994 @item show solib-search-path
13995 Display the current shared library search path.
13999 @node Separate Debug Files
14000 @section Debugging Information in Separate Files
14001 @cindex separate debugging information files
14002 @cindex debugging information in separate files
14003 @cindex @file{.debug} subdirectories
14004 @cindex debugging information directory, global
14005 @cindex global debugging information directory
14006 @cindex build ID, and separate debugging files
14007 @cindex @file{.build-id} directory
14009 @value{GDBN} allows you to put a program's debugging information in a
14010 file separate from the executable itself, in a way that allows
14011 @value{GDBN} to find and load the debugging information automatically.
14012 Since debugging information can be very large---sometimes larger
14013 than the executable code itself---some systems distribute debugging
14014 information for their executables in separate files, which users can
14015 install only when they need to debug a problem.
14017 @value{GDBN} supports two ways of specifying the separate debug info
14022 The executable contains a @dfn{debug link} that specifies the name of
14023 the separate debug info file. The separate debug file's name is
14024 usually @file{@var{executable}.debug}, where @var{executable} is the
14025 name of the corresponding executable file without leading directories
14026 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
14027 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
14028 checksum for the debug file, which @value{GDBN} uses to validate that
14029 the executable and the debug file came from the same build.
14032 The executable contains a @dfn{build ID}, a unique bit string that is
14033 also present in the corresponding debug info file. (This is supported
14034 only on some operating systems, notably those which use the ELF format
14035 for binary files and the @sc{gnu} Binutils.) For more details about
14036 this feature, see the description of the @option{--build-id}
14037 command-line option in @ref{Options, , Command Line Options, ld.info,
14038 The GNU Linker}. The debug info file's name is not specified
14039 explicitly by the build ID, but can be computed from the build ID, see
14043 Depending on the way the debug info file is specified, @value{GDBN}
14044 uses two different methods of looking for the debug file:
14048 For the ``debug link'' method, @value{GDBN} looks up the named file in
14049 the directory of the executable file, then in a subdirectory of that
14050 directory named @file{.debug}, and finally under the global debug
14051 directory, in a subdirectory whose name is identical to the leading
14052 directories of the executable's absolute file name.
14055 For the ``build ID'' method, @value{GDBN} looks in the
14056 @file{.build-id} subdirectory of the global debug directory for a file
14057 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
14058 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
14059 are the rest of the bit string. (Real build ID strings are 32 or more
14060 hex characters, not 10.)
14063 So, for example, suppose you ask @value{GDBN} to debug
14064 @file{/usr/bin/ls}, which has a debug link that specifies the
14065 file @file{ls.debug}, and a build ID whose value in hex is
14066 @code{abcdef1234}. If the global debug directory is
14067 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
14068 debug information files, in the indicated order:
14072 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
14074 @file{/usr/bin/ls.debug}
14076 @file{/usr/bin/.debug/ls.debug}
14078 @file{/usr/lib/debug/usr/bin/ls.debug}.
14081 You can set the global debugging info directory's name, and view the
14082 name @value{GDBN} is currently using.
14086 @kindex set debug-file-directory
14087 @item set debug-file-directory @var{directory}
14088 Set the directory which @value{GDBN} searches for separate debugging
14089 information files to @var{directory}.
14091 @kindex show debug-file-directory
14092 @item show debug-file-directory
14093 Show the directory @value{GDBN} searches for separate debugging
14098 @cindex @code{.gnu_debuglink} sections
14099 @cindex debug link sections
14100 A debug link is a special section of the executable file named
14101 @code{.gnu_debuglink}. The section must contain:
14105 A filename, with any leading directory components removed, followed by
14108 zero to three bytes of padding, as needed to reach the next four-byte
14109 boundary within the section, and
14111 a four-byte CRC checksum, stored in the same endianness used for the
14112 executable file itself. The checksum is computed on the debugging
14113 information file's full contents by the function given below, passing
14114 zero as the @var{crc} argument.
14117 Any executable file format can carry a debug link, as long as it can
14118 contain a section named @code{.gnu_debuglink} with the contents
14121 @cindex @code{.note.gnu.build-id} sections
14122 @cindex build ID sections
14123 The build ID is a special section in the executable file (and in other
14124 ELF binary files that @value{GDBN} may consider). This section is
14125 often named @code{.note.gnu.build-id}, but that name is not mandatory.
14126 It contains unique identification for the built files---the ID remains
14127 the same across multiple builds of the same build tree. The default
14128 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
14129 content for the build ID string. The same section with an identical
14130 value is present in the original built binary with symbols, in its
14131 stripped variant, and in the separate debugging information file.
14133 The debugging information file itself should be an ordinary
14134 executable, containing a full set of linker symbols, sections, and
14135 debugging information. The sections of the debugging information file
14136 should have the same names, addresses, and sizes as the original file,
14137 but they need not contain any data---much like a @code{.bss} section
14138 in an ordinary executable.
14140 The @sc{gnu} binary utilities (Binutils) package includes the
14141 @samp{objcopy} utility that can produce
14142 the separated executable / debugging information file pairs using the
14143 following commands:
14146 @kbd{objcopy --only-keep-debug foo foo.debug}
14151 These commands remove the debugging
14152 information from the executable file @file{foo} and place it in the file
14153 @file{foo.debug}. You can use the first, second or both methods to link the
14158 The debug link method needs the following additional command to also leave
14159 behind a debug link in @file{foo}:
14162 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
14165 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
14166 a version of the @code{strip} command such that the command @kbd{strip foo -f
14167 foo.debug} has the same functionality as the two @code{objcopy} commands and
14168 the @code{ln -s} command above, together.
14171 Build ID gets embedded into the main executable using @code{ld --build-id} or
14172 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
14173 compatibility fixes for debug files separation are present in @sc{gnu} binary
14174 utilities (Binutils) package since version 2.18.
14179 @cindex CRC algorithm definition
14180 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
14181 IEEE 802.3 using the polynomial:
14183 @c TexInfo requires naked braces for multi-digit exponents for Tex
14184 @c output, but this causes HTML output to barf. HTML has to be set using
14185 @c raw commands. So we end up having to specify this equation in 2
14190 <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>
14191 + <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
14197 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
14198 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
14202 The function is computed byte at a time, taking the least
14203 significant bit of each byte first. The initial pattern
14204 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
14205 the final result is inverted to ensure trailing zeros also affect the
14208 @emph{Note:} This is the same CRC polynomial as used in handling the
14209 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
14210 , @value{GDBN} Remote Serial Protocol}). However in the
14211 case of the Remote Serial Protocol, the CRC is computed @emph{most}
14212 significant bit first, and the result is not inverted, so trailing
14213 zeros have no effect on the CRC value.
14215 To complete the description, we show below the code of the function
14216 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
14217 initially supplied @code{crc} argument means that an initial call to
14218 this function passing in zero will start computing the CRC using
14221 @kindex gnu_debuglink_crc32
14224 gnu_debuglink_crc32 (unsigned long crc,
14225 unsigned char *buf, size_t len)
14227 static const unsigned long crc32_table[256] =
14229 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
14230 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
14231 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
14232 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
14233 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
14234 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
14235 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
14236 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
14237 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
14238 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
14239 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
14240 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
14241 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
14242 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
14243 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
14244 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
14245 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
14246 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
14247 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
14248 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
14249 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
14250 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
14251 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
14252 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
14253 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
14254 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
14255 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
14256 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
14257 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
14258 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
14259 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
14260 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
14261 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
14262 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
14263 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
14264 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
14265 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
14266 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
14267 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
14268 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
14269 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
14270 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
14271 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
14272 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
14273 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
14274 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
14275 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
14276 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
14277 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
14278 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
14279 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
14282 unsigned char *end;
14284 crc = ~crc & 0xffffffff;
14285 for (end = buf + len; buf < end; ++buf)
14286 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
14287 return ~crc & 0xffffffff;
14292 This computation does not apply to the ``build ID'' method.
14295 @node Symbol Errors
14296 @section Errors Reading Symbol Files
14298 While reading a symbol file, @value{GDBN} occasionally encounters problems,
14299 such as symbol types it does not recognize, or known bugs in compiler
14300 output. By default, @value{GDBN} does not notify you of such problems, since
14301 they are relatively common and primarily of interest to people
14302 debugging compilers. If you are interested in seeing information
14303 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
14304 only one message about each such type of problem, no matter how many
14305 times the problem occurs; or you can ask @value{GDBN} to print more messages,
14306 to see how many times the problems occur, with the @code{set
14307 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
14310 The messages currently printed, and their meanings, include:
14313 @item inner block not inside outer block in @var{symbol}
14315 The symbol information shows where symbol scopes begin and end
14316 (such as at the start of a function or a block of statements). This
14317 error indicates that an inner scope block is not fully contained
14318 in its outer scope blocks.
14320 @value{GDBN} circumvents the problem by treating the inner block as if it had
14321 the same scope as the outer block. In the error message, @var{symbol}
14322 may be shown as ``@code{(don't know)}'' if the outer block is not a
14325 @item block at @var{address} out of order
14327 The symbol information for symbol scope blocks should occur in
14328 order of increasing addresses. This error indicates that it does not
14331 @value{GDBN} does not circumvent this problem, and has trouble
14332 locating symbols in the source file whose symbols it is reading. (You
14333 can often determine what source file is affected by specifying
14334 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
14337 @item bad block start address patched
14339 The symbol information for a symbol scope block has a start address
14340 smaller than the address of the preceding source line. This is known
14341 to occur in the SunOS 4.1.1 (and earlier) C compiler.
14343 @value{GDBN} circumvents the problem by treating the symbol scope block as
14344 starting on the previous source line.
14346 @item bad string table offset in symbol @var{n}
14349 Symbol number @var{n} contains a pointer into the string table which is
14350 larger than the size of the string table.
14352 @value{GDBN} circumvents the problem by considering the symbol to have the
14353 name @code{foo}, which may cause other problems if many symbols end up
14356 @item unknown symbol type @code{0x@var{nn}}
14358 The symbol information contains new data types that @value{GDBN} does
14359 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
14360 uncomprehended information, in hexadecimal.
14362 @value{GDBN} circumvents the error by ignoring this symbol information.
14363 This usually allows you to debug your program, though certain symbols
14364 are not accessible. If you encounter such a problem and feel like
14365 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
14366 on @code{complain}, then go up to the function @code{read_dbx_symtab}
14367 and examine @code{*bufp} to see the symbol.
14369 @item stub type has NULL name
14371 @value{GDBN} could not find the full definition for a struct or class.
14373 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
14374 The symbol information for a C@t{++} member function is missing some
14375 information that recent versions of the compiler should have output for
14378 @item info mismatch between compiler and debugger
14380 @value{GDBN} could not parse a type specification output by the compiler.
14385 @section GDB Data Files
14387 @cindex prefix for data files
14388 @value{GDBN} will sometimes read an auxiliary data file. These files
14389 are kept in a directory known as the @dfn{data directory}.
14391 You can set the data directory's name, and view the name @value{GDBN}
14392 is currently using.
14395 @kindex set data-directory
14396 @item set data-directory @var{directory}
14397 Set the directory which @value{GDBN} searches for auxiliary data files
14398 to @var{directory}.
14400 @kindex show data-directory
14401 @item show data-directory
14402 Show the directory @value{GDBN} searches for auxiliary data files.
14405 @cindex default data directory
14406 @cindex @samp{--with-gdb-datadir}
14407 You can set the default data directory by using the configure-time
14408 @samp{--with-gdb-datadir} option. If the data directory is inside
14409 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
14410 @samp{--exec-prefix}), then the default data directory will be updated
14411 automatically if the installed @value{GDBN} is moved to a new
14415 @chapter Specifying a Debugging Target
14417 @cindex debugging target
14418 A @dfn{target} is the execution environment occupied by your program.
14420 Often, @value{GDBN} runs in the same host environment as your program;
14421 in that case, the debugging target is specified as a side effect when
14422 you use the @code{file} or @code{core} commands. When you need more
14423 flexibility---for example, running @value{GDBN} on a physically separate
14424 host, or controlling a standalone system over a serial port or a
14425 realtime system over a TCP/IP connection---you can use the @code{target}
14426 command to specify one of the target types configured for @value{GDBN}
14427 (@pxref{Target Commands, ,Commands for Managing Targets}).
14429 @cindex target architecture
14430 It is possible to build @value{GDBN} for several different @dfn{target
14431 architectures}. When @value{GDBN} is built like that, you can choose
14432 one of the available architectures with the @kbd{set architecture}
14436 @kindex set architecture
14437 @kindex show architecture
14438 @item set architecture @var{arch}
14439 This command sets the current target architecture to @var{arch}. The
14440 value of @var{arch} can be @code{"auto"}, in addition to one of the
14441 supported architectures.
14443 @item show architecture
14444 Show the current target architecture.
14446 @item set processor
14448 @kindex set processor
14449 @kindex show processor
14450 These are alias commands for, respectively, @code{set architecture}
14451 and @code{show architecture}.
14455 * Active Targets:: Active targets
14456 * Target Commands:: Commands for managing targets
14457 * Byte Order:: Choosing target byte order
14460 @node Active Targets
14461 @section Active Targets
14463 @cindex stacking targets
14464 @cindex active targets
14465 @cindex multiple targets
14467 There are three classes of targets: processes, core files, and
14468 executable files. @value{GDBN} can work concurrently on up to three
14469 active targets, one in each class. This allows you to (for example)
14470 start a process and inspect its activity without abandoning your work on
14473 For example, if you execute @samp{gdb a.out}, then the executable file
14474 @code{a.out} is the only active target. If you designate a core file as
14475 well---presumably from a prior run that crashed and coredumped---then
14476 @value{GDBN} has two active targets and uses them in tandem, looking
14477 first in the corefile target, then in the executable file, to satisfy
14478 requests for memory addresses. (Typically, these two classes of target
14479 are complementary, since core files contain only a program's
14480 read-write memory---variables and so on---plus machine status, while
14481 executable files contain only the program text and initialized data.)
14483 When you type @code{run}, your executable file becomes an active process
14484 target as well. When a process target is active, all @value{GDBN}
14485 commands requesting memory addresses refer to that target; addresses in
14486 an active core file or executable file target are obscured while the
14487 process target is active.
14489 Use the @code{core-file} and @code{exec-file} commands to select a new
14490 core file or executable target (@pxref{Files, ,Commands to Specify
14491 Files}). To specify as a target a process that is already running, use
14492 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
14495 @node Target Commands
14496 @section Commands for Managing Targets
14499 @item target @var{type} @var{parameters}
14500 Connects the @value{GDBN} host environment to a target machine or
14501 process. A target is typically a protocol for talking to debugging
14502 facilities. You use the argument @var{type} to specify the type or
14503 protocol of the target machine.
14505 Further @var{parameters} are interpreted by the target protocol, but
14506 typically include things like device names or host names to connect
14507 with, process numbers, and baud rates.
14509 The @code{target} command does not repeat if you press @key{RET} again
14510 after executing the command.
14512 @kindex help target
14514 Displays the names of all targets available. To display targets
14515 currently selected, use either @code{info target} or @code{info files}
14516 (@pxref{Files, ,Commands to Specify Files}).
14518 @item help target @var{name}
14519 Describe a particular target, including any parameters necessary to
14522 @kindex set gnutarget
14523 @item set gnutarget @var{args}
14524 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
14525 knows whether it is reading an @dfn{executable},
14526 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
14527 with the @code{set gnutarget} command. Unlike most @code{target} commands,
14528 with @code{gnutarget} the @code{target} refers to a program, not a machine.
14531 @emph{Warning:} To specify a file format with @code{set gnutarget},
14532 you must know the actual BFD name.
14536 @xref{Files, , Commands to Specify Files}.
14538 @kindex show gnutarget
14539 @item show gnutarget
14540 Use the @code{show gnutarget} command to display what file format
14541 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
14542 @value{GDBN} will determine the file format for each file automatically,
14543 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
14546 @cindex common targets
14547 Here are some common targets (available, or not, depending on the GDB
14552 @item target exec @var{program}
14553 @cindex executable file target
14554 An executable file. @samp{target exec @var{program}} is the same as
14555 @samp{exec-file @var{program}}.
14557 @item target core @var{filename}
14558 @cindex core dump file target
14559 A core dump file. @samp{target core @var{filename}} is the same as
14560 @samp{core-file @var{filename}}.
14562 @item target remote @var{medium}
14563 @cindex remote target
14564 A remote system connected to @value{GDBN} via a serial line or network
14565 connection. This command tells @value{GDBN} to use its own remote
14566 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
14568 For example, if you have a board connected to @file{/dev/ttya} on the
14569 machine running @value{GDBN}, you could say:
14572 target remote /dev/ttya
14575 @code{target remote} supports the @code{load} command. This is only
14576 useful if you have some other way of getting the stub to the target
14577 system, and you can put it somewhere in memory where it won't get
14578 clobbered by the download.
14581 @cindex built-in simulator target
14582 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
14590 works; however, you cannot assume that a specific memory map, device
14591 drivers, or even basic I/O is available, although some simulators do
14592 provide these. For info about any processor-specific simulator details,
14593 see the appropriate section in @ref{Embedded Processors, ,Embedded
14598 Some configurations may include these targets as well:
14602 @item target nrom @var{dev}
14603 @cindex NetROM ROM emulator target
14604 NetROM ROM emulator. This target only supports downloading.
14608 Different targets are available on different configurations of @value{GDBN};
14609 your configuration may have more or fewer targets.
14611 Many remote targets require you to download the executable's code once
14612 you've successfully established a connection. You may wish to control
14613 various aspects of this process.
14618 @kindex set hash@r{, for remote monitors}
14619 @cindex hash mark while downloading
14620 This command controls whether a hash mark @samp{#} is displayed while
14621 downloading a file to the remote monitor. If on, a hash mark is
14622 displayed after each S-record is successfully downloaded to the
14626 @kindex show hash@r{, for remote monitors}
14627 Show the current status of displaying the hash mark.
14629 @item set debug monitor
14630 @kindex set debug monitor
14631 @cindex display remote monitor communications
14632 Enable or disable display of communications messages between
14633 @value{GDBN} and the remote monitor.
14635 @item show debug monitor
14636 @kindex show debug monitor
14637 Show the current status of displaying communications between
14638 @value{GDBN} and the remote monitor.
14643 @kindex load @var{filename}
14644 @item load @var{filename}
14646 Depending on what remote debugging facilities are configured into
14647 @value{GDBN}, the @code{load} command may be available. Where it exists, it
14648 is meant to make @var{filename} (an executable) available for debugging
14649 on the remote system---by downloading, or dynamic linking, for example.
14650 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
14651 the @code{add-symbol-file} command.
14653 If your @value{GDBN} does not have a @code{load} command, attempting to
14654 execute it gets the error message ``@code{You can't do that when your
14655 target is @dots{}}''
14657 The file is loaded at whatever address is specified in the executable.
14658 For some object file formats, you can specify the load address when you
14659 link the program; for other formats, like a.out, the object file format
14660 specifies a fixed address.
14661 @c FIXME! This would be a good place for an xref to the GNU linker doc.
14663 Depending on the remote side capabilities, @value{GDBN} may be able to
14664 load programs into flash memory.
14666 @code{load} does not repeat if you press @key{RET} again after using it.
14670 @section Choosing Target Byte Order
14672 @cindex choosing target byte order
14673 @cindex target byte order
14675 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
14676 offer the ability to run either big-endian or little-endian byte
14677 orders. Usually the executable or symbol will include a bit to
14678 designate the endian-ness, and you will not need to worry about
14679 which to use. However, you may still find it useful to adjust
14680 @value{GDBN}'s idea of processor endian-ness manually.
14684 @item set endian big
14685 Instruct @value{GDBN} to assume the target is big-endian.
14687 @item set endian little
14688 Instruct @value{GDBN} to assume the target is little-endian.
14690 @item set endian auto
14691 Instruct @value{GDBN} to use the byte order associated with the
14695 Display @value{GDBN}'s current idea of the target byte order.
14699 Note that these commands merely adjust interpretation of symbolic
14700 data on the host, and that they have absolutely no effect on the
14704 @node Remote Debugging
14705 @chapter Debugging Remote Programs
14706 @cindex remote debugging
14708 If you are trying to debug a program running on a machine that cannot run
14709 @value{GDBN} in the usual way, it is often useful to use remote debugging.
14710 For example, you might use remote debugging on an operating system kernel,
14711 or on a small system which does not have a general purpose operating system
14712 powerful enough to run a full-featured debugger.
14714 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
14715 to make this work with particular debugging targets. In addition,
14716 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
14717 but not specific to any particular target system) which you can use if you
14718 write the remote stubs---the code that runs on the remote system to
14719 communicate with @value{GDBN}.
14721 Other remote targets may be available in your
14722 configuration of @value{GDBN}; use @code{help target} to list them.
14725 * Connecting:: Connecting to a remote target
14726 * File Transfer:: Sending files to a remote system
14727 * Server:: Using the gdbserver program
14728 * Remote Configuration:: Remote configuration
14729 * Remote Stub:: Implementing a remote stub
14733 @section Connecting to a Remote Target
14735 On the @value{GDBN} host machine, you will need an unstripped copy of
14736 your program, since @value{GDBN} needs symbol and debugging information.
14737 Start up @value{GDBN} as usual, using the name of the local copy of your
14738 program as the first argument.
14740 @cindex @code{target remote}
14741 @value{GDBN} can communicate with the target over a serial line, or
14742 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
14743 each case, @value{GDBN} uses the same protocol for debugging your
14744 program; only the medium carrying the debugging packets varies. The
14745 @code{target remote} command establishes a connection to the target.
14746 Its arguments indicate which medium to use:
14750 @item target remote @var{serial-device}
14751 @cindex serial line, @code{target remote}
14752 Use @var{serial-device} to communicate with the target. For example,
14753 to use a serial line connected to the device named @file{/dev/ttyb}:
14756 target remote /dev/ttyb
14759 If you're using a serial line, you may want to give @value{GDBN} the
14760 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
14761 (@pxref{Remote Configuration, set remotebaud}) before the
14762 @code{target} command.
14764 @item target remote @code{@var{host}:@var{port}}
14765 @itemx target remote @code{tcp:@var{host}:@var{port}}
14766 @cindex @acronym{TCP} port, @code{target remote}
14767 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
14768 The @var{host} may be either a host name or a numeric @acronym{IP}
14769 address; @var{port} must be a decimal number. The @var{host} could be
14770 the target machine itself, if it is directly connected to the net, or
14771 it might be a terminal server which in turn has a serial line to the
14774 For example, to connect to port 2828 on a terminal server named
14778 target remote manyfarms:2828
14781 If your remote target is actually running on the same machine as your
14782 debugger session (e.g.@: a simulator for your target running on the
14783 same host), you can omit the hostname. For example, to connect to
14784 port 1234 on your local machine:
14787 target remote :1234
14791 Note that the colon is still required here.
14793 @item target remote @code{udp:@var{host}:@var{port}}
14794 @cindex @acronym{UDP} port, @code{target remote}
14795 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
14796 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
14799 target remote udp:manyfarms:2828
14802 When using a @acronym{UDP} connection for remote debugging, you should
14803 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
14804 can silently drop packets on busy or unreliable networks, which will
14805 cause havoc with your debugging session.
14807 @item target remote | @var{command}
14808 @cindex pipe, @code{target remote} to
14809 Run @var{command} in the background and communicate with it using a
14810 pipe. The @var{command} is a shell command, to be parsed and expanded
14811 by the system's command shell, @code{/bin/sh}; it should expect remote
14812 protocol packets on its standard input, and send replies on its
14813 standard output. You could use this to run a stand-alone simulator
14814 that speaks the remote debugging protocol, to make net connections
14815 using programs like @code{ssh}, or for other similar tricks.
14817 If @var{command} closes its standard output (perhaps by exiting),
14818 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
14819 program has already exited, this will have no effect.)
14823 Once the connection has been established, you can use all the usual
14824 commands to examine and change data. The remote program is already
14825 running; you can use @kbd{step} and @kbd{continue}, and you do not
14826 need to use @kbd{run}.
14828 @cindex interrupting remote programs
14829 @cindex remote programs, interrupting
14830 Whenever @value{GDBN} is waiting for the remote program, if you type the
14831 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
14832 program. This may or may not succeed, depending in part on the hardware
14833 and the serial drivers the remote system uses. If you type the
14834 interrupt character once again, @value{GDBN} displays this prompt:
14837 Interrupted while waiting for the program.
14838 Give up (and stop debugging it)? (y or n)
14841 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
14842 (If you decide you want to try again later, you can use @samp{target
14843 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
14844 goes back to waiting.
14847 @kindex detach (remote)
14849 When you have finished debugging the remote program, you can use the
14850 @code{detach} command to release it from @value{GDBN} control.
14851 Detaching from the target normally resumes its execution, but the results
14852 will depend on your particular remote stub. After the @code{detach}
14853 command, @value{GDBN} is free to connect to another target.
14857 The @code{disconnect} command behaves like @code{detach}, except that
14858 the target is generally not resumed. It will wait for @value{GDBN}
14859 (this instance or another one) to connect and continue debugging. After
14860 the @code{disconnect} command, @value{GDBN} is again free to connect to
14863 @cindex send command to remote monitor
14864 @cindex extend @value{GDBN} for remote targets
14865 @cindex add new commands for external monitor
14867 @item monitor @var{cmd}
14868 This command allows you to send arbitrary commands directly to the
14869 remote monitor. Since @value{GDBN} doesn't care about the commands it
14870 sends like this, this command is the way to extend @value{GDBN}---you
14871 can add new commands that only the external monitor will understand
14875 @node File Transfer
14876 @section Sending files to a remote system
14877 @cindex remote target, file transfer
14878 @cindex file transfer
14879 @cindex sending files to remote systems
14881 Some remote targets offer the ability to transfer files over the same
14882 connection used to communicate with @value{GDBN}. This is convenient
14883 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
14884 running @code{gdbserver} over a network interface. For other targets,
14885 e.g.@: embedded devices with only a single serial port, this may be
14886 the only way to upload or download files.
14888 Not all remote targets support these commands.
14892 @item remote put @var{hostfile} @var{targetfile}
14893 Copy file @var{hostfile} from the host system (the machine running
14894 @value{GDBN}) to @var{targetfile} on the target system.
14897 @item remote get @var{targetfile} @var{hostfile}
14898 Copy file @var{targetfile} from the target system to @var{hostfile}
14899 on the host system.
14901 @kindex remote delete
14902 @item remote delete @var{targetfile}
14903 Delete @var{targetfile} from the target system.
14908 @section Using the @code{gdbserver} Program
14911 @cindex remote connection without stubs
14912 @code{gdbserver} is a control program for Unix-like systems, which
14913 allows you to connect your program with a remote @value{GDBN} via
14914 @code{target remote}---but without linking in the usual debugging stub.
14916 @code{gdbserver} is not a complete replacement for the debugging stubs,
14917 because it requires essentially the same operating-system facilities
14918 that @value{GDBN} itself does. In fact, a system that can run
14919 @code{gdbserver} to connect to a remote @value{GDBN} could also run
14920 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
14921 because it is a much smaller program than @value{GDBN} itself. It is
14922 also easier to port than all of @value{GDBN}, so you may be able to get
14923 started more quickly on a new system by using @code{gdbserver}.
14924 Finally, if you develop code for real-time systems, you may find that
14925 the tradeoffs involved in real-time operation make it more convenient to
14926 do as much development work as possible on another system, for example
14927 by cross-compiling. You can use @code{gdbserver} to make a similar
14928 choice for debugging.
14930 @value{GDBN} and @code{gdbserver} communicate via either a serial line
14931 or a TCP connection, using the standard @value{GDBN} remote serial
14935 @emph{Warning:} @code{gdbserver} does not have any built-in security.
14936 Do not run @code{gdbserver} connected to any public network; a
14937 @value{GDBN} connection to @code{gdbserver} provides access to the
14938 target system with the same privileges as the user running
14942 @subsection Running @code{gdbserver}
14943 @cindex arguments, to @code{gdbserver}
14945 Run @code{gdbserver} on the target system. You need a copy of the
14946 program you want to debug, including any libraries it requires.
14947 @code{gdbserver} does not need your program's symbol table, so you can
14948 strip the program if necessary to save space. @value{GDBN} on the host
14949 system does all the symbol handling.
14951 To use the server, you must tell it how to communicate with @value{GDBN};
14952 the name of your program; and the arguments for your program. The usual
14956 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
14959 @var{comm} is either a device name (to use a serial line) or a TCP
14960 hostname and portnumber. For example, to debug Emacs with the argument
14961 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
14965 target> gdbserver /dev/com1 emacs foo.txt
14968 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
14971 To use a TCP connection instead of a serial line:
14974 target> gdbserver host:2345 emacs foo.txt
14977 The only difference from the previous example is the first argument,
14978 specifying that you are communicating with the host @value{GDBN} via
14979 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
14980 expect a TCP connection from machine @samp{host} to local TCP port 2345.
14981 (Currently, the @samp{host} part is ignored.) You can choose any number
14982 you want for the port number as long as it does not conflict with any
14983 TCP ports already in use on the target system (for example, @code{23} is
14984 reserved for @code{telnet}).@footnote{If you choose a port number that
14985 conflicts with another service, @code{gdbserver} prints an error message
14986 and exits.} You must use the same port number with the host @value{GDBN}
14987 @code{target remote} command.
14989 @subsubsection Attaching to a Running Program
14991 On some targets, @code{gdbserver} can also attach to running programs.
14992 This is accomplished via the @code{--attach} argument. The syntax is:
14995 target> gdbserver --attach @var{comm} @var{pid}
14998 @var{pid} is the process ID of a currently running process. It isn't necessary
14999 to point @code{gdbserver} at a binary for the running process.
15002 @cindex attach to a program by name
15003 You can debug processes by name instead of process ID if your target has the
15004 @code{pidof} utility:
15007 target> gdbserver --attach @var{comm} `pidof @var{program}`
15010 In case more than one copy of @var{program} is running, or @var{program}
15011 has multiple threads, most versions of @code{pidof} support the
15012 @code{-s} option to only return the first process ID.
15014 @subsubsection Multi-Process Mode for @code{gdbserver}
15015 @cindex gdbserver, multiple processes
15016 @cindex multiple processes with gdbserver
15018 When you connect to @code{gdbserver} using @code{target remote},
15019 @code{gdbserver} debugs the specified program only once. When the
15020 program exits, or you detach from it, @value{GDBN} closes the connection
15021 and @code{gdbserver} exits.
15023 If you connect using @kbd{target extended-remote}, @code{gdbserver}
15024 enters multi-process mode. When the debugged program exits, or you
15025 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
15026 though no program is running. The @code{run} and @code{attach}
15027 commands instruct @code{gdbserver} to run or attach to a new program.
15028 The @code{run} command uses @code{set remote exec-file} (@pxref{set
15029 remote exec-file}) to select the program to run. Command line
15030 arguments are supported, except for wildcard expansion and I/O
15031 redirection (@pxref{Arguments}).
15033 To start @code{gdbserver} without supplying an initial command to run
15034 or process ID to attach, use the @option{--multi} command line option.
15035 Then you can connect using @kbd{target extended-remote} and start
15036 the program you want to debug.
15038 @code{gdbserver} does not automatically exit in multi-process mode.
15039 You can terminate it by using @code{monitor exit}
15040 (@pxref{Monitor Commands for gdbserver}).
15042 @subsubsection Other Command-Line Arguments for @code{gdbserver}
15044 The @option{--debug} option tells @code{gdbserver} to display extra
15045 status information about the debugging process. The
15046 @option{--remote-debug} option tells @code{gdbserver} to display
15047 remote protocol debug output. These options are intended for
15048 @code{gdbserver} development and for bug reports to the developers.
15050 The @option{--wrapper} option specifies a wrapper to launch programs
15051 for debugging. The option should be followed by the name of the
15052 wrapper, then any command-line arguments to pass to the wrapper, then
15053 @kbd{--} indicating the end of the wrapper arguments.
15055 @code{gdbserver} runs the specified wrapper program with a combined
15056 command line including the wrapper arguments, then the name of the
15057 program to debug, then any arguments to the program. The wrapper
15058 runs until it executes your program, and then @value{GDBN} gains control.
15060 You can use any program that eventually calls @code{execve} with
15061 its arguments as a wrapper. Several standard Unix utilities do
15062 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
15063 with @code{exec "$@@"} will also work.
15065 For example, you can use @code{env} to pass an environment variable to
15066 the debugged program, without setting the variable in @code{gdbserver}'s
15070 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
15073 @subsection Connecting to @code{gdbserver}
15075 Run @value{GDBN} on the host system.
15077 First make sure you have the necessary symbol files. Load symbols for
15078 your application using the @code{file} command before you connect. Use
15079 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
15080 was compiled with the correct sysroot using @code{--with-sysroot}).
15082 The symbol file and target libraries must exactly match the executable
15083 and libraries on the target, with one exception: the files on the host
15084 system should not be stripped, even if the files on the target system
15085 are. Mismatched or missing files will lead to confusing results
15086 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
15087 files may also prevent @code{gdbserver} from debugging multi-threaded
15090 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
15091 For TCP connections, you must start up @code{gdbserver} prior to using
15092 the @code{target remote} command. Otherwise you may get an error whose
15093 text depends on the host system, but which usually looks something like
15094 @samp{Connection refused}. Don't use the @code{load}
15095 command in @value{GDBN} when using @code{gdbserver}, since the program is
15096 already on the target.
15098 @subsection Monitor Commands for @code{gdbserver}
15099 @cindex monitor commands, for @code{gdbserver}
15100 @anchor{Monitor Commands for gdbserver}
15102 During a @value{GDBN} session using @code{gdbserver}, you can use the
15103 @code{monitor} command to send special requests to @code{gdbserver}.
15104 Here are the available commands.
15108 List the available monitor commands.
15110 @item monitor set debug 0
15111 @itemx monitor set debug 1
15112 Disable or enable general debugging messages.
15114 @item monitor set remote-debug 0
15115 @itemx monitor set remote-debug 1
15116 Disable or enable specific debugging messages associated with the remote
15117 protocol (@pxref{Remote Protocol}).
15119 @item monitor set libthread-db-search-path [PATH]
15120 @cindex gdbserver, search path for @code{libthread_db}
15121 When this command is issued, @var{path} is a colon-separated list of
15122 directories to search for @code{libthread_db} (@pxref{Threads,,set
15123 libthread-db-search-path}). If you omit @var{path},
15124 @samp{libthread-db-search-path} will be reset to an empty list.
15127 Tell gdbserver to exit immediately. This command should be followed by
15128 @code{disconnect} to close the debugging session. @code{gdbserver} will
15129 detach from any attached processes and kill any processes it created.
15130 Use @code{monitor exit} to terminate @code{gdbserver} at the end
15131 of a multi-process mode debug session.
15135 @node Remote Configuration
15136 @section Remote Configuration
15139 @kindex show remote
15140 This section documents the configuration options available when
15141 debugging remote programs. For the options related to the File I/O
15142 extensions of the remote protocol, see @ref{system,
15143 system-call-allowed}.
15146 @item set remoteaddresssize @var{bits}
15147 @cindex address size for remote targets
15148 @cindex bits in remote address
15149 Set the maximum size of address in a memory packet to the specified
15150 number of bits. @value{GDBN} will mask off the address bits above
15151 that number, when it passes addresses to the remote target. The
15152 default value is the number of bits in the target's address.
15154 @item show remoteaddresssize
15155 Show the current value of remote address size in bits.
15157 @item set remotebaud @var{n}
15158 @cindex baud rate for remote targets
15159 Set the baud rate for the remote serial I/O to @var{n} baud. The
15160 value is used to set the speed of the serial port used for debugging
15163 @item show remotebaud
15164 Show the current speed of the remote connection.
15166 @item set remotebreak
15167 @cindex interrupt remote programs
15168 @cindex BREAK signal instead of Ctrl-C
15169 @anchor{set remotebreak}
15170 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
15171 when you type @kbd{Ctrl-c} to interrupt the program running
15172 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
15173 character instead. The default is off, since most remote systems
15174 expect to see @samp{Ctrl-C} as the interrupt signal.
15176 @item show remotebreak
15177 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
15178 interrupt the remote program.
15180 @item set remoteflow on
15181 @itemx set remoteflow off
15182 @kindex set remoteflow
15183 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
15184 on the serial port used to communicate to the remote target.
15186 @item show remoteflow
15187 @kindex show remoteflow
15188 Show the current setting of hardware flow control.
15190 @item set remotelogbase @var{base}
15191 Set the base (a.k.a.@: radix) of logging serial protocol
15192 communications to @var{base}. Supported values of @var{base} are:
15193 @code{ascii}, @code{octal}, and @code{hex}. The default is
15196 @item show remotelogbase
15197 Show the current setting of the radix for logging remote serial
15200 @item set remotelogfile @var{file}
15201 @cindex record serial communications on file
15202 Record remote serial communications on the named @var{file}. The
15203 default is not to record at all.
15205 @item show remotelogfile.
15206 Show the current setting of the file name on which to record the
15207 serial communications.
15209 @item set remotetimeout @var{num}
15210 @cindex timeout for serial communications
15211 @cindex remote timeout
15212 Set the timeout limit to wait for the remote target to respond to
15213 @var{num} seconds. The default is 2 seconds.
15215 @item show remotetimeout
15216 Show the current number of seconds to wait for the remote target
15219 @cindex limit hardware breakpoints and watchpoints
15220 @cindex remote target, limit break- and watchpoints
15221 @anchor{set remote hardware-watchpoint-limit}
15222 @anchor{set remote hardware-breakpoint-limit}
15223 @item set remote hardware-watchpoint-limit @var{limit}
15224 @itemx set remote hardware-breakpoint-limit @var{limit}
15225 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
15226 watchpoints. A limit of -1, the default, is treated as unlimited.
15228 @item set remote exec-file @var{filename}
15229 @itemx show remote exec-file
15230 @anchor{set remote exec-file}
15231 @cindex executable file, for remote target
15232 Select the file used for @code{run} with @code{target
15233 extended-remote}. This should be set to a filename valid on the
15234 target system. If it is not set, the target will use a default
15235 filename (e.g.@: the last program run).
15239 @item set tcp auto-retry on
15240 @cindex auto-retry, for remote TCP target
15241 Enable auto-retry for remote TCP connections. This is useful if the remote
15242 debugging agent is launched in parallel with @value{GDBN}; there is a race
15243 condition because the agent may not become ready to accept the connection
15244 before @value{GDBN} attempts to connect. When auto-retry is
15245 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
15246 to establish the connection using the timeout specified by
15247 @code{set tcp connect-timeout}.
15249 @item set tcp auto-retry off
15250 Do not auto-retry failed TCP connections.
15252 @item show tcp auto-retry
15253 Show the current auto-retry setting.
15255 @item set tcp connect-timeout @var{seconds}
15256 @cindex connection timeout, for remote TCP target
15257 @cindex timeout, for remote target connection
15258 Set the timeout for establishing a TCP connection to the remote target to
15259 @var{seconds}. The timeout affects both polling to retry failed connections
15260 (enabled by @code{set tcp auto-retry on}) and waiting for connections
15261 that are merely slow to complete, and represents an approximate cumulative
15264 @item show tcp connect-timeout
15265 Show the current connection timeout setting.
15268 @cindex remote packets, enabling and disabling
15269 The @value{GDBN} remote protocol autodetects the packets supported by
15270 your debugging stub. If you need to override the autodetection, you
15271 can use these commands to enable or disable individual packets. Each
15272 packet can be set to @samp{on} (the remote target supports this
15273 packet), @samp{off} (the remote target does not support this packet),
15274 or @samp{auto} (detect remote target support for this packet). They
15275 all default to @samp{auto}. For more information about each packet,
15276 see @ref{Remote Protocol}.
15278 During normal use, you should not have to use any of these commands.
15279 If you do, that may be a bug in your remote debugging stub, or a bug
15280 in @value{GDBN}. You may want to report the problem to the
15281 @value{GDBN} developers.
15283 For each packet @var{name}, the command to enable or disable the
15284 packet is @code{set remote @var{name}-packet}. The available settings
15287 @multitable @columnfractions 0.28 0.32 0.25
15290 @tab Related Features
15292 @item @code{fetch-register}
15294 @tab @code{info registers}
15296 @item @code{set-register}
15300 @item @code{binary-download}
15302 @tab @code{load}, @code{set}
15304 @item @code{read-aux-vector}
15305 @tab @code{qXfer:auxv:read}
15306 @tab @code{info auxv}
15308 @item @code{symbol-lookup}
15309 @tab @code{qSymbol}
15310 @tab Detecting multiple threads
15312 @item @code{attach}
15313 @tab @code{vAttach}
15316 @item @code{verbose-resume}
15318 @tab Stepping or resuming multiple threads
15324 @item @code{software-breakpoint}
15328 @item @code{hardware-breakpoint}
15332 @item @code{write-watchpoint}
15336 @item @code{read-watchpoint}
15340 @item @code{access-watchpoint}
15344 @item @code{target-features}
15345 @tab @code{qXfer:features:read}
15346 @tab @code{set architecture}
15348 @item @code{library-info}
15349 @tab @code{qXfer:libraries:read}
15350 @tab @code{info sharedlibrary}
15352 @item @code{memory-map}
15353 @tab @code{qXfer:memory-map:read}
15354 @tab @code{info mem}
15356 @item @code{read-spu-object}
15357 @tab @code{qXfer:spu:read}
15358 @tab @code{info spu}
15360 @item @code{write-spu-object}
15361 @tab @code{qXfer:spu:write}
15362 @tab @code{info spu}
15364 @item @code{read-siginfo-object}
15365 @tab @code{qXfer:siginfo:read}
15366 @tab @code{print $_siginfo}
15368 @item @code{write-siginfo-object}
15369 @tab @code{qXfer:siginfo:write}
15370 @tab @code{set $_siginfo}
15372 @item @code{get-thread-local-@*storage-address}
15373 @tab @code{qGetTLSAddr}
15374 @tab Displaying @code{__thread} variables
15376 @item @code{search-memory}
15377 @tab @code{qSearch:memory}
15380 @item @code{supported-packets}
15381 @tab @code{qSupported}
15382 @tab Remote communications parameters
15384 @item @code{pass-signals}
15385 @tab @code{QPassSignals}
15386 @tab @code{handle @var{signal}}
15388 @item @code{hostio-close-packet}
15389 @tab @code{vFile:close}
15390 @tab @code{remote get}, @code{remote put}
15392 @item @code{hostio-open-packet}
15393 @tab @code{vFile:open}
15394 @tab @code{remote get}, @code{remote put}
15396 @item @code{hostio-pread-packet}
15397 @tab @code{vFile:pread}
15398 @tab @code{remote get}, @code{remote put}
15400 @item @code{hostio-pwrite-packet}
15401 @tab @code{vFile:pwrite}
15402 @tab @code{remote get}, @code{remote put}
15404 @item @code{hostio-unlink-packet}
15405 @tab @code{vFile:unlink}
15406 @tab @code{remote delete}
15408 @item @code{noack-packet}
15409 @tab @code{QStartNoAckMode}
15410 @tab Packet acknowledgment
15412 @item @code{osdata}
15413 @tab @code{qXfer:osdata:read}
15414 @tab @code{info os}
15416 @item @code{query-attached}
15417 @tab @code{qAttached}
15418 @tab Querying remote process attach state.
15422 @section Implementing a Remote Stub
15424 @cindex debugging stub, example
15425 @cindex remote stub, example
15426 @cindex stub example, remote debugging
15427 The stub files provided with @value{GDBN} implement the target side of the
15428 communication protocol, and the @value{GDBN} side is implemented in the
15429 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
15430 these subroutines to communicate, and ignore the details. (If you're
15431 implementing your own stub file, you can still ignore the details: start
15432 with one of the existing stub files. @file{sparc-stub.c} is the best
15433 organized, and therefore the easiest to read.)
15435 @cindex remote serial debugging, overview
15436 To debug a program running on another machine (the debugging
15437 @dfn{target} machine), you must first arrange for all the usual
15438 prerequisites for the program to run by itself. For example, for a C
15443 A startup routine to set up the C runtime environment; these usually
15444 have a name like @file{crt0}. The startup routine may be supplied by
15445 your hardware supplier, or you may have to write your own.
15448 A C subroutine library to support your program's
15449 subroutine calls, notably managing input and output.
15452 A way of getting your program to the other machine---for example, a
15453 download program. These are often supplied by the hardware
15454 manufacturer, but you may have to write your own from hardware
15458 The next step is to arrange for your program to use a serial port to
15459 communicate with the machine where @value{GDBN} is running (the @dfn{host}
15460 machine). In general terms, the scheme looks like this:
15464 @value{GDBN} already understands how to use this protocol; when everything
15465 else is set up, you can simply use the @samp{target remote} command
15466 (@pxref{Targets,,Specifying a Debugging Target}).
15468 @item On the target,
15469 you must link with your program a few special-purpose subroutines that
15470 implement the @value{GDBN} remote serial protocol. The file containing these
15471 subroutines is called a @dfn{debugging stub}.
15473 On certain remote targets, you can use an auxiliary program
15474 @code{gdbserver} instead of linking a stub into your program.
15475 @xref{Server,,Using the @code{gdbserver} Program}, for details.
15478 The debugging stub is specific to the architecture of the remote
15479 machine; for example, use @file{sparc-stub.c} to debug programs on
15482 @cindex remote serial stub list
15483 These working remote stubs are distributed with @value{GDBN}:
15488 @cindex @file{i386-stub.c}
15491 For Intel 386 and compatible architectures.
15494 @cindex @file{m68k-stub.c}
15495 @cindex Motorola 680x0
15497 For Motorola 680x0 architectures.
15500 @cindex @file{sh-stub.c}
15503 For Renesas SH architectures.
15506 @cindex @file{sparc-stub.c}
15508 For @sc{sparc} architectures.
15510 @item sparcl-stub.c
15511 @cindex @file{sparcl-stub.c}
15514 For Fujitsu @sc{sparclite} architectures.
15518 The @file{README} file in the @value{GDBN} distribution may list other
15519 recently added stubs.
15522 * Stub Contents:: What the stub can do for you
15523 * Bootstrapping:: What you must do for the stub
15524 * Debug Session:: Putting it all together
15527 @node Stub Contents
15528 @subsection What the Stub Can Do for You
15530 @cindex remote serial stub
15531 The debugging stub for your architecture supplies these three
15535 @item set_debug_traps
15536 @findex set_debug_traps
15537 @cindex remote serial stub, initialization
15538 This routine arranges for @code{handle_exception} to run when your
15539 program stops. You must call this subroutine explicitly near the
15540 beginning of your program.
15542 @item handle_exception
15543 @findex handle_exception
15544 @cindex remote serial stub, main routine
15545 This is the central workhorse, but your program never calls it
15546 explicitly---the setup code arranges for @code{handle_exception} to
15547 run when a trap is triggered.
15549 @code{handle_exception} takes control when your program stops during
15550 execution (for example, on a breakpoint), and mediates communications
15551 with @value{GDBN} on the host machine. This is where the communications
15552 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
15553 representative on the target machine. It begins by sending summary
15554 information on the state of your program, then continues to execute,
15555 retrieving and transmitting any information @value{GDBN} needs, until you
15556 execute a @value{GDBN} command that makes your program resume; at that point,
15557 @code{handle_exception} returns control to your own code on the target
15561 @cindex @code{breakpoint} subroutine, remote
15562 Use this auxiliary subroutine to make your program contain a
15563 breakpoint. Depending on the particular situation, this may be the only
15564 way for @value{GDBN} to get control. For instance, if your target
15565 machine has some sort of interrupt button, you won't need to call this;
15566 pressing the interrupt button transfers control to
15567 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
15568 simply receiving characters on the serial port may also trigger a trap;
15569 again, in that situation, you don't need to call @code{breakpoint} from
15570 your own program---simply running @samp{target remote} from the host
15571 @value{GDBN} session gets control.
15573 Call @code{breakpoint} if none of these is true, or if you simply want
15574 to make certain your program stops at a predetermined point for the
15575 start of your debugging session.
15578 @node Bootstrapping
15579 @subsection What You Must Do for the Stub
15581 @cindex remote stub, support routines
15582 The debugging stubs that come with @value{GDBN} are set up for a particular
15583 chip architecture, but they have no information about the rest of your
15584 debugging target machine.
15586 First of all you need to tell the stub how to communicate with the
15590 @item int getDebugChar()
15591 @findex getDebugChar
15592 Write this subroutine to read a single character from the serial port.
15593 It may be identical to @code{getchar} for your target system; a
15594 different name is used to allow you to distinguish the two if you wish.
15596 @item void putDebugChar(int)
15597 @findex putDebugChar
15598 Write this subroutine to write a single character to the serial port.
15599 It may be identical to @code{putchar} for your target system; a
15600 different name is used to allow you to distinguish the two if you wish.
15603 @cindex control C, and remote debugging
15604 @cindex interrupting remote targets
15605 If you want @value{GDBN} to be able to stop your program while it is
15606 running, you need to use an interrupt-driven serial driver, and arrange
15607 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
15608 character). That is the character which @value{GDBN} uses to tell the
15609 remote system to stop.
15611 Getting the debugging target to return the proper status to @value{GDBN}
15612 probably requires changes to the standard stub; one quick and dirty way
15613 is to just execute a breakpoint instruction (the ``dirty'' part is that
15614 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
15616 Other routines you need to supply are:
15619 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
15620 @findex exceptionHandler
15621 Write this function to install @var{exception_address} in the exception
15622 handling tables. You need to do this because the stub does not have any
15623 way of knowing what the exception handling tables on your target system
15624 are like (for example, the processor's table might be in @sc{rom},
15625 containing entries which point to a table in @sc{ram}).
15626 @var{exception_number} is the exception number which should be changed;
15627 its meaning is architecture-dependent (for example, different numbers
15628 might represent divide by zero, misaligned access, etc). When this
15629 exception occurs, control should be transferred directly to
15630 @var{exception_address}, and the processor state (stack, registers,
15631 and so on) should be just as it is when a processor exception occurs. So if
15632 you want to use a jump instruction to reach @var{exception_address}, it
15633 should be a simple jump, not a jump to subroutine.
15635 For the 386, @var{exception_address} should be installed as an interrupt
15636 gate so that interrupts are masked while the handler runs. The gate
15637 should be at privilege level 0 (the most privileged level). The
15638 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
15639 help from @code{exceptionHandler}.
15641 @item void flush_i_cache()
15642 @findex flush_i_cache
15643 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
15644 instruction cache, if any, on your target machine. If there is no
15645 instruction cache, this subroutine may be a no-op.
15647 On target machines that have instruction caches, @value{GDBN} requires this
15648 function to make certain that the state of your program is stable.
15652 You must also make sure this library routine is available:
15655 @item void *memset(void *, int, int)
15657 This is the standard library function @code{memset} that sets an area of
15658 memory to a known value. If you have one of the free versions of
15659 @code{libc.a}, @code{memset} can be found there; otherwise, you must
15660 either obtain it from your hardware manufacturer, or write your own.
15663 If you do not use the GNU C compiler, you may need other standard
15664 library subroutines as well; this varies from one stub to another,
15665 but in general the stubs are likely to use any of the common library
15666 subroutines which @code{@value{NGCC}} generates as inline code.
15669 @node Debug Session
15670 @subsection Putting it All Together
15672 @cindex remote serial debugging summary
15673 In summary, when your program is ready to debug, you must follow these
15678 Make sure you have defined the supporting low-level routines
15679 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
15681 @code{getDebugChar}, @code{putDebugChar},
15682 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
15686 Insert these lines near the top of your program:
15694 For the 680x0 stub only, you need to provide a variable called
15695 @code{exceptionHook}. Normally you just use:
15698 void (*exceptionHook)() = 0;
15702 but if before calling @code{set_debug_traps}, you set it to point to a
15703 function in your program, that function is called when
15704 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
15705 error). The function indicated by @code{exceptionHook} is called with
15706 one parameter: an @code{int} which is the exception number.
15709 Compile and link together: your program, the @value{GDBN} debugging stub for
15710 your target architecture, and the supporting subroutines.
15713 Make sure you have a serial connection between your target machine and
15714 the @value{GDBN} host, and identify the serial port on the host.
15717 @c The "remote" target now provides a `load' command, so we should
15718 @c document that. FIXME.
15719 Download your program to your target machine (or get it there by
15720 whatever means the manufacturer provides), and start it.
15723 Start @value{GDBN} on the host, and connect to the target
15724 (@pxref{Connecting,,Connecting to a Remote Target}).
15728 @node Configurations
15729 @chapter Configuration-Specific Information
15731 While nearly all @value{GDBN} commands are available for all native and
15732 cross versions of the debugger, there are some exceptions. This chapter
15733 describes things that are only available in certain configurations.
15735 There are three major categories of configurations: native
15736 configurations, where the host and target are the same, embedded
15737 operating system configurations, which are usually the same for several
15738 different processor architectures, and bare embedded processors, which
15739 are quite different from each other.
15744 * Embedded Processors::
15751 This section describes details specific to particular native
15756 * BSD libkvm Interface:: Debugging BSD kernel memory images
15757 * SVR4 Process Information:: SVR4 process information
15758 * DJGPP Native:: Features specific to the DJGPP port
15759 * Cygwin Native:: Features specific to the Cygwin port
15760 * Hurd Native:: Features specific to @sc{gnu} Hurd
15761 * Neutrino:: Features specific to QNX Neutrino
15762 * Darwin:: Features specific to Darwin
15768 On HP-UX systems, if you refer to a function or variable name that
15769 begins with a dollar sign, @value{GDBN} searches for a user or system
15770 name first, before it searches for a convenience variable.
15773 @node BSD libkvm Interface
15774 @subsection BSD libkvm Interface
15777 @cindex kernel memory image
15778 @cindex kernel crash dump
15780 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
15781 interface that provides a uniform interface for accessing kernel virtual
15782 memory images, including live systems and crash dumps. @value{GDBN}
15783 uses this interface to allow you to debug live kernels and kernel crash
15784 dumps on many native BSD configurations. This is implemented as a
15785 special @code{kvm} debugging target. For debugging a live system, load
15786 the currently running kernel into @value{GDBN} and connect to the
15790 (@value{GDBP}) @b{target kvm}
15793 For debugging crash dumps, provide the file name of the crash dump as an
15797 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
15800 Once connected to the @code{kvm} target, the following commands are
15806 Set current context from the @dfn{Process Control Block} (PCB) address.
15809 Set current context from proc address. This command isn't available on
15810 modern FreeBSD systems.
15813 @node SVR4 Process Information
15814 @subsection SVR4 Process Information
15816 @cindex examine process image
15817 @cindex process info via @file{/proc}
15819 Many versions of SVR4 and compatible systems provide a facility called
15820 @samp{/proc} that can be used to examine the image of a running
15821 process using file-system subroutines. If @value{GDBN} is configured
15822 for an operating system with this facility, the command @code{info
15823 proc} is available to report information about the process running
15824 your program, or about any process running on your system. @code{info
15825 proc} works only on SVR4 systems that include the @code{procfs} code.
15826 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
15827 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
15833 @itemx info proc @var{process-id}
15834 Summarize available information about any running process. If a
15835 process ID is specified by @var{process-id}, display information about
15836 that process; otherwise display information about the program being
15837 debugged. The summary includes the debugged process ID, the command
15838 line used to invoke it, its current working directory, and its
15839 executable file's absolute file name.
15841 On some systems, @var{process-id} can be of the form
15842 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
15843 within a process. If the optional @var{pid} part is missing, it means
15844 a thread from the process being debugged (the leading @samp{/} still
15845 needs to be present, or else @value{GDBN} will interpret the number as
15846 a process ID rather than a thread ID).
15848 @item info proc mappings
15849 @cindex memory address space mappings
15850 Report the memory address space ranges accessible in the program, with
15851 information on whether the process has read, write, or execute access
15852 rights to each range. On @sc{gnu}/Linux systems, each memory range
15853 includes the object file which is mapped to that range, instead of the
15854 memory access rights to that range.
15856 @item info proc stat
15857 @itemx info proc status
15858 @cindex process detailed status information
15859 These subcommands are specific to @sc{gnu}/Linux systems. They show
15860 the process-related information, including the user ID and group ID;
15861 how many threads are there in the process; its virtual memory usage;
15862 the signals that are pending, blocked, and ignored; its TTY; its
15863 consumption of system and user time; its stack size; its @samp{nice}
15864 value; etc. For more information, see the @samp{proc} man page
15865 (type @kbd{man 5 proc} from your shell prompt).
15867 @item info proc all
15868 Show all the information about the process described under all of the
15869 above @code{info proc} subcommands.
15872 @comment These sub-options of 'info proc' were not included when
15873 @comment procfs.c was re-written. Keep their descriptions around
15874 @comment against the day when someone finds the time to put them back in.
15875 @kindex info proc times
15876 @item info proc times
15877 Starting time, user CPU time, and system CPU time for your program and
15880 @kindex info proc id
15882 Report on the process IDs related to your program: its own process ID,
15883 the ID of its parent, the process group ID, and the session ID.
15886 @item set procfs-trace
15887 @kindex set procfs-trace
15888 @cindex @code{procfs} API calls
15889 This command enables and disables tracing of @code{procfs} API calls.
15891 @item show procfs-trace
15892 @kindex show procfs-trace
15893 Show the current state of @code{procfs} API call tracing.
15895 @item set procfs-file @var{file}
15896 @kindex set procfs-file
15897 Tell @value{GDBN} to write @code{procfs} API trace to the named
15898 @var{file}. @value{GDBN} appends the trace info to the previous
15899 contents of the file. The default is to display the trace on the
15902 @item show procfs-file
15903 @kindex show procfs-file
15904 Show the file to which @code{procfs} API trace is written.
15906 @item proc-trace-entry
15907 @itemx proc-trace-exit
15908 @itemx proc-untrace-entry
15909 @itemx proc-untrace-exit
15910 @kindex proc-trace-entry
15911 @kindex proc-trace-exit
15912 @kindex proc-untrace-entry
15913 @kindex proc-untrace-exit
15914 These commands enable and disable tracing of entries into and exits
15915 from the @code{syscall} interface.
15918 @kindex info pidlist
15919 @cindex process list, QNX Neutrino
15920 For QNX Neutrino only, this command displays the list of all the
15921 processes and all the threads within each process.
15924 @kindex info meminfo
15925 @cindex mapinfo list, QNX Neutrino
15926 For QNX Neutrino only, this command displays the list of all mapinfos.
15930 @subsection Features for Debugging @sc{djgpp} Programs
15931 @cindex @sc{djgpp} debugging
15932 @cindex native @sc{djgpp} debugging
15933 @cindex MS-DOS-specific commands
15936 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
15937 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
15938 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
15939 top of real-mode DOS systems and their emulations.
15941 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
15942 defines a few commands specific to the @sc{djgpp} port. This
15943 subsection describes those commands.
15948 This is a prefix of @sc{djgpp}-specific commands which print
15949 information about the target system and important OS structures.
15952 @cindex MS-DOS system info
15953 @cindex free memory information (MS-DOS)
15954 @item info dos sysinfo
15955 This command displays assorted information about the underlying
15956 platform: the CPU type and features, the OS version and flavor, the
15957 DPMI version, and the available conventional and DPMI memory.
15962 @cindex segment descriptor tables
15963 @cindex descriptor tables display
15965 @itemx info dos ldt
15966 @itemx info dos idt
15967 These 3 commands display entries from, respectively, Global, Local,
15968 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
15969 tables are data structures which store a descriptor for each segment
15970 that is currently in use. The segment's selector is an index into a
15971 descriptor table; the table entry for that index holds the
15972 descriptor's base address and limit, and its attributes and access
15975 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
15976 segment (used for both data and the stack), and a DOS segment (which
15977 allows access to DOS/BIOS data structures and absolute addresses in
15978 conventional memory). However, the DPMI host will usually define
15979 additional segments in order to support the DPMI environment.
15981 @cindex garbled pointers
15982 These commands allow to display entries from the descriptor tables.
15983 Without an argument, all entries from the specified table are
15984 displayed. An argument, which should be an integer expression, means
15985 display a single entry whose index is given by the argument. For
15986 example, here's a convenient way to display information about the
15987 debugged program's data segment:
15990 @exdent @code{(@value{GDBP}) info dos ldt $ds}
15991 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
15995 This comes in handy when you want to see whether a pointer is outside
15996 the data segment's limit (i.e.@: @dfn{garbled}).
15998 @cindex page tables display (MS-DOS)
16000 @itemx info dos pte
16001 These two commands display entries from, respectively, the Page
16002 Directory and the Page Tables. Page Directories and Page Tables are
16003 data structures which control how virtual memory addresses are mapped
16004 into physical addresses. A Page Table includes an entry for every
16005 page of memory that is mapped into the program's address space; there
16006 may be several Page Tables, each one holding up to 4096 entries. A
16007 Page Directory has up to 4096 entries, one each for every Page Table
16008 that is currently in use.
16010 Without an argument, @kbd{info dos pde} displays the entire Page
16011 Directory, and @kbd{info dos pte} displays all the entries in all of
16012 the Page Tables. An argument, an integer expression, given to the
16013 @kbd{info dos pde} command means display only that entry from the Page
16014 Directory table. An argument given to the @kbd{info dos pte} command
16015 means display entries from a single Page Table, the one pointed to by
16016 the specified entry in the Page Directory.
16018 @cindex direct memory access (DMA) on MS-DOS
16019 These commands are useful when your program uses @dfn{DMA} (Direct
16020 Memory Access), which needs physical addresses to program the DMA
16023 These commands are supported only with some DPMI servers.
16025 @cindex physical address from linear address
16026 @item info dos address-pte @var{addr}
16027 This command displays the Page Table entry for a specified linear
16028 address. The argument @var{addr} is a linear address which should
16029 already have the appropriate segment's base address added to it,
16030 because this command accepts addresses which may belong to @emph{any}
16031 segment. For example, here's how to display the Page Table entry for
16032 the page where a variable @code{i} is stored:
16035 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
16036 @exdent @code{Page Table entry for address 0x11a00d30:}
16037 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
16041 This says that @code{i} is stored at offset @code{0xd30} from the page
16042 whose physical base address is @code{0x02698000}, and shows all the
16043 attributes of that page.
16045 Note that you must cast the addresses of variables to a @code{char *},
16046 since otherwise the value of @code{__djgpp_base_address}, the base
16047 address of all variables and functions in a @sc{djgpp} program, will
16048 be added using the rules of C pointer arithmetics: if @code{i} is
16049 declared an @code{int}, @value{GDBN} will add 4 times the value of
16050 @code{__djgpp_base_address} to the address of @code{i}.
16052 Here's another example, it displays the Page Table entry for the
16056 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
16057 @exdent @code{Page Table entry for address 0x29110:}
16058 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
16062 (The @code{+ 3} offset is because the transfer buffer's address is the
16063 3rd member of the @code{_go32_info_block} structure.) The output
16064 clearly shows that this DPMI server maps the addresses in conventional
16065 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
16066 linear (@code{0x29110}) addresses are identical.
16068 This command is supported only with some DPMI servers.
16071 @cindex DOS serial data link, remote debugging
16072 In addition to native debugging, the DJGPP port supports remote
16073 debugging via a serial data link. The following commands are specific
16074 to remote serial debugging in the DJGPP port of @value{GDBN}.
16077 @kindex set com1base
16078 @kindex set com1irq
16079 @kindex set com2base
16080 @kindex set com2irq
16081 @kindex set com3base
16082 @kindex set com3irq
16083 @kindex set com4base
16084 @kindex set com4irq
16085 @item set com1base @var{addr}
16086 This command sets the base I/O port address of the @file{COM1} serial
16089 @item set com1irq @var{irq}
16090 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
16091 for the @file{COM1} serial port.
16093 There are similar commands @samp{set com2base}, @samp{set com3irq},
16094 etc.@: for setting the port address and the @code{IRQ} lines for the
16097 @kindex show com1base
16098 @kindex show com1irq
16099 @kindex show com2base
16100 @kindex show com2irq
16101 @kindex show com3base
16102 @kindex show com3irq
16103 @kindex show com4base
16104 @kindex show com4irq
16105 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
16106 display the current settings of the base address and the @code{IRQ}
16107 lines used by the COM ports.
16110 @kindex info serial
16111 @cindex DOS serial port status
16112 This command prints the status of the 4 DOS serial ports. For each
16113 port, it prints whether it's active or not, its I/O base address and
16114 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
16115 counts of various errors encountered so far.
16119 @node Cygwin Native
16120 @subsection Features for Debugging MS Windows PE Executables
16121 @cindex MS Windows debugging
16122 @cindex native Cygwin debugging
16123 @cindex Cygwin-specific commands
16125 @value{GDBN} supports native debugging of MS Windows programs, including
16126 DLLs with and without symbolic debugging information.
16128 @cindex Ctrl-BREAK, MS-Windows
16129 @cindex interrupt debuggee on MS-Windows
16130 MS-Windows programs that call @code{SetConsoleMode} to switch off the
16131 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
16132 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
16133 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
16134 sequence, which can be used to interrupt the debuggee even if it
16137 There are various additional Cygwin-specific commands, described in
16138 this section. Working with DLLs that have no debugging symbols is
16139 described in @ref{Non-debug DLL Symbols}.
16144 This is a prefix of MS Windows-specific commands which print
16145 information about the target system and important OS structures.
16147 @item info w32 selector
16148 This command displays information returned by
16149 the Win32 API @code{GetThreadSelectorEntry} function.
16150 It takes an optional argument that is evaluated to
16151 a long value to give the information about this given selector.
16152 Without argument, this command displays information
16153 about the six segment registers.
16157 This is a Cygwin-specific alias of @code{info shared}.
16159 @kindex dll-symbols
16161 This command loads symbols from a dll similarly to
16162 add-sym command but without the need to specify a base address.
16164 @kindex set cygwin-exceptions
16165 @cindex debugging the Cygwin DLL
16166 @cindex Cygwin DLL, debugging
16167 @item set cygwin-exceptions @var{mode}
16168 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
16169 happen inside the Cygwin DLL. If @var{mode} is @code{off},
16170 @value{GDBN} will delay recognition of exceptions, and may ignore some
16171 exceptions which seem to be caused by internal Cygwin DLL
16172 ``bookkeeping''. This option is meant primarily for debugging the
16173 Cygwin DLL itself; the default value is @code{off} to avoid annoying
16174 @value{GDBN} users with false @code{SIGSEGV} signals.
16176 @kindex show cygwin-exceptions
16177 @item show cygwin-exceptions
16178 Displays whether @value{GDBN} will break on exceptions that happen
16179 inside the Cygwin DLL itself.
16181 @kindex set new-console
16182 @item set new-console @var{mode}
16183 If @var{mode} is @code{on} the debuggee will
16184 be started in a new console on next start.
16185 If @var{mode} is @code{off}i, the debuggee will
16186 be started in the same console as the debugger.
16188 @kindex show new-console
16189 @item show new-console
16190 Displays whether a new console is used
16191 when the debuggee is started.
16193 @kindex set new-group
16194 @item set new-group @var{mode}
16195 This boolean value controls whether the debuggee should
16196 start a new group or stay in the same group as the debugger.
16197 This affects the way the Windows OS handles
16200 @kindex show new-group
16201 @item show new-group
16202 Displays current value of new-group boolean.
16204 @kindex set debugevents
16205 @item set debugevents
16206 This boolean value adds debug output concerning kernel events related
16207 to the debuggee seen by the debugger. This includes events that
16208 signal thread and process creation and exit, DLL loading and
16209 unloading, console interrupts, and debugging messages produced by the
16210 Windows @code{OutputDebugString} API call.
16212 @kindex set debugexec
16213 @item set debugexec
16214 This boolean value adds debug output concerning execute events
16215 (such as resume thread) seen by the debugger.
16217 @kindex set debugexceptions
16218 @item set debugexceptions
16219 This boolean value adds debug output concerning exceptions in the
16220 debuggee seen by the debugger.
16222 @kindex set debugmemory
16223 @item set debugmemory
16224 This boolean value adds debug output concerning debuggee memory reads
16225 and writes by the debugger.
16229 This boolean values specifies whether the debuggee is called
16230 via a shell or directly (default value is on).
16234 Displays if the debuggee will be started with a shell.
16239 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
16242 @node Non-debug DLL Symbols
16243 @subsubsection Support for DLLs without Debugging Symbols
16244 @cindex DLLs with no debugging symbols
16245 @cindex Minimal symbols and DLLs
16247 Very often on windows, some of the DLLs that your program relies on do
16248 not include symbolic debugging information (for example,
16249 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
16250 symbols in a DLL, it relies on the minimal amount of symbolic
16251 information contained in the DLL's export table. This section
16252 describes working with such symbols, known internally to @value{GDBN} as
16253 ``minimal symbols''.
16255 Note that before the debugged program has started execution, no DLLs
16256 will have been loaded. The easiest way around this problem is simply to
16257 start the program --- either by setting a breakpoint or letting the
16258 program run once to completion. It is also possible to force
16259 @value{GDBN} to load a particular DLL before starting the executable ---
16260 see the shared library information in @ref{Files}, or the
16261 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
16262 explicitly loading symbols from a DLL with no debugging information will
16263 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
16264 which may adversely affect symbol lookup performance.
16266 @subsubsection DLL Name Prefixes
16268 In keeping with the naming conventions used by the Microsoft debugging
16269 tools, DLL export symbols are made available with a prefix based on the
16270 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
16271 also entered into the symbol table, so @code{CreateFileA} is often
16272 sufficient. In some cases there will be name clashes within a program
16273 (particularly if the executable itself includes full debugging symbols)
16274 necessitating the use of the fully qualified name when referring to the
16275 contents of the DLL. Use single-quotes around the name to avoid the
16276 exclamation mark (``!'') being interpreted as a language operator.
16278 Note that the internal name of the DLL may be all upper-case, even
16279 though the file name of the DLL is lower-case, or vice-versa. Since
16280 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
16281 some confusion. If in doubt, try the @code{info functions} and
16282 @code{info variables} commands or even @code{maint print msymbols}
16283 (@pxref{Symbols}). Here's an example:
16286 (@value{GDBP}) info function CreateFileA
16287 All functions matching regular expression "CreateFileA":
16289 Non-debugging symbols:
16290 0x77e885f4 CreateFileA
16291 0x77e885f4 KERNEL32!CreateFileA
16295 (@value{GDBP}) info function !
16296 All functions matching regular expression "!":
16298 Non-debugging symbols:
16299 0x6100114c cygwin1!__assert
16300 0x61004034 cygwin1!_dll_crt0@@0
16301 0x61004240 cygwin1!dll_crt0(per_process *)
16305 @subsubsection Working with Minimal Symbols
16307 Symbols extracted from a DLL's export table do not contain very much
16308 type information. All that @value{GDBN} can do is guess whether a symbol
16309 refers to a function or variable depending on the linker section that
16310 contains the symbol. Also note that the actual contents of the memory
16311 contained in a DLL are not available unless the program is running. This
16312 means that you cannot examine the contents of a variable or disassemble
16313 a function within a DLL without a running program.
16315 Variables are generally treated as pointers and dereferenced
16316 automatically. For this reason, it is often necessary to prefix a
16317 variable name with the address-of operator (``&'') and provide explicit
16318 type information in the command. Here's an example of the type of
16322 (@value{GDBP}) print 'cygwin1!__argv'
16327 (@value{GDBP}) x 'cygwin1!__argv'
16328 0x10021610: "\230y\""
16331 And two possible solutions:
16334 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
16335 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
16339 (@value{GDBP}) x/2x &'cygwin1!__argv'
16340 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
16341 (@value{GDBP}) x/x 0x10021608
16342 0x10021608: 0x0022fd98
16343 (@value{GDBP}) x/s 0x0022fd98
16344 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
16347 Setting a break point within a DLL is possible even before the program
16348 starts execution. However, under these circumstances, @value{GDBN} can't
16349 examine the initial instructions of the function in order to skip the
16350 function's frame set-up code. You can work around this by using ``*&''
16351 to set the breakpoint at a raw memory address:
16354 (@value{GDBP}) break *&'python22!PyOS_Readline'
16355 Breakpoint 1 at 0x1e04eff0
16358 The author of these extensions is not entirely convinced that setting a
16359 break point within a shared DLL like @file{kernel32.dll} is completely
16363 @subsection Commands Specific to @sc{gnu} Hurd Systems
16364 @cindex @sc{gnu} Hurd debugging
16366 This subsection describes @value{GDBN} commands specific to the
16367 @sc{gnu} Hurd native debugging.
16372 @kindex set signals@r{, Hurd command}
16373 @kindex set sigs@r{, Hurd command}
16374 This command toggles the state of inferior signal interception by
16375 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
16376 affected by this command. @code{sigs} is a shorthand alias for
16381 @kindex show signals@r{, Hurd command}
16382 @kindex show sigs@r{, Hurd command}
16383 Show the current state of intercepting inferior's signals.
16385 @item set signal-thread
16386 @itemx set sigthread
16387 @kindex set signal-thread
16388 @kindex set sigthread
16389 This command tells @value{GDBN} which thread is the @code{libc} signal
16390 thread. That thread is run when a signal is delivered to a running
16391 process. @code{set sigthread} is the shorthand alias of @code{set
16394 @item show signal-thread
16395 @itemx show sigthread
16396 @kindex show signal-thread
16397 @kindex show sigthread
16398 These two commands show which thread will run when the inferior is
16399 delivered a signal.
16402 @kindex set stopped@r{, Hurd command}
16403 This commands tells @value{GDBN} that the inferior process is stopped,
16404 as with the @code{SIGSTOP} signal. The stopped process can be
16405 continued by delivering a signal to it.
16408 @kindex show stopped@r{, Hurd command}
16409 This command shows whether @value{GDBN} thinks the debuggee is
16412 @item set exceptions
16413 @kindex set exceptions@r{, Hurd command}
16414 Use this command to turn off trapping of exceptions in the inferior.
16415 When exception trapping is off, neither breakpoints nor
16416 single-stepping will work. To restore the default, set exception
16419 @item show exceptions
16420 @kindex show exceptions@r{, Hurd command}
16421 Show the current state of trapping exceptions in the inferior.
16423 @item set task pause
16424 @kindex set task@r{, Hurd commands}
16425 @cindex task attributes (@sc{gnu} Hurd)
16426 @cindex pause current task (@sc{gnu} Hurd)
16427 This command toggles task suspension when @value{GDBN} has control.
16428 Setting it to on takes effect immediately, and the task is suspended
16429 whenever @value{GDBN} gets control. Setting it to off will take
16430 effect the next time the inferior is continued. If this option is set
16431 to off, you can use @code{set thread default pause on} or @code{set
16432 thread pause on} (see below) to pause individual threads.
16434 @item show task pause
16435 @kindex show task@r{, Hurd commands}
16436 Show the current state of task suspension.
16438 @item set task detach-suspend-count
16439 @cindex task suspend count
16440 @cindex detach from task, @sc{gnu} Hurd
16441 This command sets the suspend count the task will be left with when
16442 @value{GDBN} detaches from it.
16444 @item show task detach-suspend-count
16445 Show the suspend count the task will be left with when detaching.
16447 @item set task exception-port
16448 @itemx set task excp
16449 @cindex task exception port, @sc{gnu} Hurd
16450 This command sets the task exception port to which @value{GDBN} will
16451 forward exceptions. The argument should be the value of the @dfn{send
16452 rights} of the task. @code{set task excp} is a shorthand alias.
16454 @item set noninvasive
16455 @cindex noninvasive task options
16456 This command switches @value{GDBN} to a mode that is the least
16457 invasive as far as interfering with the inferior is concerned. This
16458 is the same as using @code{set task pause}, @code{set exceptions}, and
16459 @code{set signals} to values opposite to the defaults.
16461 @item info send-rights
16462 @itemx info receive-rights
16463 @itemx info port-rights
16464 @itemx info port-sets
16465 @itemx info dead-names
16468 @cindex send rights, @sc{gnu} Hurd
16469 @cindex receive rights, @sc{gnu} Hurd
16470 @cindex port rights, @sc{gnu} Hurd
16471 @cindex port sets, @sc{gnu} Hurd
16472 @cindex dead names, @sc{gnu} Hurd
16473 These commands display information about, respectively, send rights,
16474 receive rights, port rights, port sets, and dead names of a task.
16475 There are also shorthand aliases: @code{info ports} for @code{info
16476 port-rights} and @code{info psets} for @code{info port-sets}.
16478 @item set thread pause
16479 @kindex set thread@r{, Hurd command}
16480 @cindex thread properties, @sc{gnu} Hurd
16481 @cindex pause current thread (@sc{gnu} Hurd)
16482 This command toggles current thread suspension when @value{GDBN} has
16483 control. Setting it to on takes effect immediately, and the current
16484 thread is suspended whenever @value{GDBN} gets control. Setting it to
16485 off will take effect the next time the inferior is continued.
16486 Normally, this command has no effect, since when @value{GDBN} has
16487 control, the whole task is suspended. However, if you used @code{set
16488 task pause off} (see above), this command comes in handy to suspend
16489 only the current thread.
16491 @item show thread pause
16492 @kindex show thread@r{, Hurd command}
16493 This command shows the state of current thread suspension.
16495 @item set thread run
16496 This command sets whether the current thread is allowed to run.
16498 @item show thread run
16499 Show whether the current thread is allowed to run.
16501 @item set thread detach-suspend-count
16502 @cindex thread suspend count, @sc{gnu} Hurd
16503 @cindex detach from thread, @sc{gnu} Hurd
16504 This command sets the suspend count @value{GDBN} will leave on a
16505 thread when detaching. This number is relative to the suspend count
16506 found by @value{GDBN} when it notices the thread; use @code{set thread
16507 takeover-suspend-count} to force it to an absolute value.
16509 @item show thread detach-suspend-count
16510 Show the suspend count @value{GDBN} will leave on the thread when
16513 @item set thread exception-port
16514 @itemx set thread excp
16515 Set the thread exception port to which to forward exceptions. This
16516 overrides the port set by @code{set task exception-port} (see above).
16517 @code{set thread excp} is the shorthand alias.
16519 @item set thread takeover-suspend-count
16520 Normally, @value{GDBN}'s thread suspend counts are relative to the
16521 value @value{GDBN} finds when it notices each thread. This command
16522 changes the suspend counts to be absolute instead.
16524 @item set thread default
16525 @itemx show thread default
16526 @cindex thread default settings, @sc{gnu} Hurd
16527 Each of the above @code{set thread} commands has a @code{set thread
16528 default} counterpart (e.g., @code{set thread default pause}, @code{set
16529 thread default exception-port}, etc.). The @code{thread default}
16530 variety of commands sets the default thread properties for all
16531 threads; you can then change the properties of individual threads with
16532 the non-default commands.
16537 @subsection QNX Neutrino
16538 @cindex QNX Neutrino
16540 @value{GDBN} provides the following commands specific to the QNX
16544 @item set debug nto-debug
16545 @kindex set debug nto-debug
16546 When set to on, enables debugging messages specific to the QNX
16549 @item show debug nto-debug
16550 @kindex show debug nto-debug
16551 Show the current state of QNX Neutrino messages.
16558 @value{GDBN} provides the following commands specific to the Darwin target:
16561 @item set debug darwin @var{num}
16562 @kindex set debug darwin
16563 When set to a non zero value, enables debugging messages specific to
16564 the Darwin support. Higher values produce more verbose output.
16566 @item show debug darwin
16567 @kindex show debug darwin
16568 Show the current state of Darwin messages.
16570 @item set debug mach-o @var{num}
16571 @kindex set debug mach-o
16572 When set to a non zero value, enables debugging messages while
16573 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
16574 file format used on Darwin for object and executable files.) Higher
16575 values produce more verbose output. This is a command to diagnose
16576 problems internal to @value{GDBN} and should not be needed in normal
16579 @item show debug mach-o
16580 @kindex show debug mach-o
16581 Show the current state of Mach-O file messages.
16583 @item set mach-exceptions on
16584 @itemx set mach-exceptions off
16585 @kindex set mach-exceptions
16586 On Darwin, faults are first reported as a Mach exception and are then
16587 mapped to a Posix signal. Use this command to turn on trapping of
16588 Mach exceptions in the inferior. This might be sometimes useful to
16589 better understand the cause of a fault. The default is off.
16591 @item show mach-exceptions
16592 @kindex show mach-exceptions
16593 Show the current state of exceptions trapping.
16598 @section Embedded Operating Systems
16600 This section describes configurations involving the debugging of
16601 embedded operating systems that are available for several different
16605 * VxWorks:: Using @value{GDBN} with VxWorks
16608 @value{GDBN} includes the ability to debug programs running on
16609 various real-time operating systems.
16612 @subsection Using @value{GDBN} with VxWorks
16618 @kindex target vxworks
16619 @item target vxworks @var{machinename}
16620 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
16621 is the target system's machine name or IP address.
16625 On VxWorks, @code{load} links @var{filename} dynamically on the
16626 current target system as well as adding its symbols in @value{GDBN}.
16628 @value{GDBN} enables developers to spawn and debug tasks running on networked
16629 VxWorks targets from a Unix host. Already-running tasks spawned from
16630 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
16631 both the Unix host and on the VxWorks target. The program
16632 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
16633 installed with the name @code{vxgdb}, to distinguish it from a
16634 @value{GDBN} for debugging programs on the host itself.)
16637 @item VxWorks-timeout @var{args}
16638 @kindex vxworks-timeout
16639 All VxWorks-based targets now support the option @code{vxworks-timeout}.
16640 This option is set by the user, and @var{args} represents the number of
16641 seconds @value{GDBN} waits for responses to rpc's. You might use this if
16642 your VxWorks target is a slow software simulator or is on the far side
16643 of a thin network line.
16646 The following information on connecting to VxWorks was current when
16647 this manual was produced; newer releases of VxWorks may use revised
16650 @findex INCLUDE_RDB
16651 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
16652 to include the remote debugging interface routines in the VxWorks
16653 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
16654 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
16655 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
16656 source debugging task @code{tRdbTask} when VxWorks is booted. For more
16657 information on configuring and remaking VxWorks, see the manufacturer's
16659 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
16661 Once you have included @file{rdb.a} in your VxWorks system image and set
16662 your Unix execution search path to find @value{GDBN}, you are ready to
16663 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
16664 @code{vxgdb}, depending on your installation).
16666 @value{GDBN} comes up showing the prompt:
16673 * VxWorks Connection:: Connecting to VxWorks
16674 * VxWorks Download:: VxWorks download
16675 * VxWorks Attach:: Running tasks
16678 @node VxWorks Connection
16679 @subsubsection Connecting to VxWorks
16681 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
16682 network. To connect to a target whose host name is ``@code{tt}'', type:
16685 (vxgdb) target vxworks tt
16689 @value{GDBN} displays messages like these:
16692 Attaching remote machine across net...
16697 @value{GDBN} then attempts to read the symbol tables of any object modules
16698 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
16699 these files by searching the directories listed in the command search
16700 path (@pxref{Environment, ,Your Program's Environment}); if it fails
16701 to find an object file, it displays a message such as:
16704 prog.o: No such file or directory.
16707 When this happens, add the appropriate directory to the search path with
16708 the @value{GDBN} command @code{path}, and execute the @code{target}
16711 @node VxWorks Download
16712 @subsubsection VxWorks Download
16714 @cindex download to VxWorks
16715 If you have connected to the VxWorks target and you want to debug an
16716 object that has not yet been loaded, you can use the @value{GDBN}
16717 @code{load} command to download a file from Unix to VxWorks
16718 incrementally. The object file given as an argument to the @code{load}
16719 command is actually opened twice: first by the VxWorks target in order
16720 to download the code, then by @value{GDBN} in order to read the symbol
16721 table. This can lead to problems if the current working directories on
16722 the two systems differ. If both systems have NFS mounted the same
16723 filesystems, you can avoid these problems by using absolute paths.
16724 Otherwise, it is simplest to set the working directory on both systems
16725 to the directory in which the object file resides, and then to reference
16726 the file by its name, without any path. For instance, a program
16727 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
16728 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
16729 program, type this on VxWorks:
16732 -> cd "@var{vxpath}/vw/demo/rdb"
16736 Then, in @value{GDBN}, type:
16739 (vxgdb) cd @var{hostpath}/vw/demo/rdb
16740 (vxgdb) load prog.o
16743 @value{GDBN} displays a response similar to this:
16746 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
16749 You can also use the @code{load} command to reload an object module
16750 after editing and recompiling the corresponding source file. Note that
16751 this makes @value{GDBN} delete all currently-defined breakpoints,
16752 auto-displays, and convenience variables, and to clear the value
16753 history. (This is necessary in order to preserve the integrity of
16754 debugger's data structures that reference the target system's symbol
16757 @node VxWorks Attach
16758 @subsubsection Running Tasks
16760 @cindex running VxWorks tasks
16761 You can also attach to an existing task using the @code{attach} command as
16765 (vxgdb) attach @var{task}
16769 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
16770 or suspended when you attach to it. Running tasks are suspended at
16771 the time of attachment.
16773 @node Embedded Processors
16774 @section Embedded Processors
16776 This section goes into details specific to particular embedded
16779 @cindex send command to simulator
16780 Whenever a specific embedded processor has a simulator, @value{GDBN}
16781 allows to send an arbitrary command to the simulator.
16784 @item sim @var{command}
16785 @kindex sim@r{, a command}
16786 Send an arbitrary @var{command} string to the simulator. Consult the
16787 documentation for the specific simulator in use for information about
16788 acceptable commands.
16794 * M32R/D:: Renesas M32R/D
16795 * M68K:: Motorola M68K
16796 * MicroBlaze:: Xilinx MicroBlaze
16797 * MIPS Embedded:: MIPS Embedded
16798 * OpenRISC 1000:: OpenRisc 1000
16799 * PA:: HP PA Embedded
16800 * PowerPC Embedded:: PowerPC Embedded
16801 * Sparclet:: Tsqware Sparclet
16802 * Sparclite:: Fujitsu Sparclite
16803 * Z8000:: Zilog Z8000
16806 * Super-H:: Renesas Super-H
16815 @item target rdi @var{dev}
16816 ARM Angel monitor, via RDI library interface to ADP protocol. You may
16817 use this target to communicate with both boards running the Angel
16818 monitor, or with the EmbeddedICE JTAG debug device.
16821 @item target rdp @var{dev}
16826 @value{GDBN} provides the following ARM-specific commands:
16829 @item set arm disassembler
16831 This commands selects from a list of disassembly styles. The
16832 @code{"std"} style is the standard style.
16834 @item show arm disassembler
16836 Show the current disassembly style.
16838 @item set arm apcs32
16839 @cindex ARM 32-bit mode
16840 This command toggles ARM operation mode between 32-bit and 26-bit.
16842 @item show arm apcs32
16843 Display the current usage of the ARM 32-bit mode.
16845 @item set arm fpu @var{fputype}
16846 This command sets the ARM floating-point unit (FPU) type. The
16847 argument @var{fputype} can be one of these:
16851 Determine the FPU type by querying the OS ABI.
16853 Software FPU, with mixed-endian doubles on little-endian ARM
16856 GCC-compiled FPA co-processor.
16858 Software FPU with pure-endian doubles.
16864 Show the current type of the FPU.
16867 This command forces @value{GDBN} to use the specified ABI.
16870 Show the currently used ABI.
16872 @item set arm fallback-mode (arm|thumb|auto)
16873 @value{GDBN} uses the symbol table, when available, to determine
16874 whether instructions are ARM or Thumb. This command controls
16875 @value{GDBN}'s default behavior when the symbol table is not
16876 available. The default is @samp{auto}, which causes @value{GDBN} to
16877 use the current execution mode (from the @code{T} bit in the @code{CPSR}
16880 @item show arm fallback-mode
16881 Show the current fallback instruction mode.
16883 @item set arm force-mode (arm|thumb|auto)
16884 This command overrides use of the symbol table to determine whether
16885 instructions are ARM or Thumb. The default is @samp{auto}, which
16886 causes @value{GDBN} to use the symbol table and then the setting
16887 of @samp{set arm fallback-mode}.
16889 @item show arm force-mode
16890 Show the current forced instruction mode.
16892 @item set debug arm
16893 Toggle whether to display ARM-specific debugging messages from the ARM
16894 target support subsystem.
16896 @item show debug arm
16897 Show whether ARM-specific debugging messages are enabled.
16900 The following commands are available when an ARM target is debugged
16901 using the RDI interface:
16904 @item rdilogfile @r{[}@var{file}@r{]}
16906 @cindex ADP (Angel Debugger Protocol) logging
16907 Set the filename for the ADP (Angel Debugger Protocol) packet log.
16908 With an argument, sets the log file to the specified @var{file}. With
16909 no argument, show the current log file name. The default log file is
16912 @item rdilogenable @r{[}@var{arg}@r{]}
16913 @kindex rdilogenable
16914 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
16915 enables logging, with an argument 0 or @code{"no"} disables it. With
16916 no arguments displays the current setting. When logging is enabled,
16917 ADP packets exchanged between @value{GDBN} and the RDI target device
16918 are logged to a file.
16920 @item set rdiromatzero
16921 @kindex set rdiromatzero
16922 @cindex ROM at zero address, RDI
16923 Tell @value{GDBN} whether the target has ROM at address 0. If on,
16924 vector catching is disabled, so that zero address can be used. If off
16925 (the default), vector catching is enabled. For this command to take
16926 effect, it needs to be invoked prior to the @code{target rdi} command.
16928 @item show rdiromatzero
16929 @kindex show rdiromatzero
16930 Show the current setting of ROM at zero address.
16932 @item set rdiheartbeat
16933 @kindex set rdiheartbeat
16934 @cindex RDI heartbeat
16935 Enable or disable RDI heartbeat packets. It is not recommended to
16936 turn on this option, since it confuses ARM and EPI JTAG interface, as
16937 well as the Angel monitor.
16939 @item show rdiheartbeat
16940 @kindex show rdiheartbeat
16941 Show the setting of RDI heartbeat packets.
16946 @subsection Renesas M32R/D and M32R/SDI
16949 @kindex target m32r
16950 @item target m32r @var{dev}
16951 Renesas M32R/D ROM monitor.
16953 @kindex target m32rsdi
16954 @item target m32rsdi @var{dev}
16955 Renesas M32R SDI server, connected via parallel port to the board.
16958 The following @value{GDBN} commands are specific to the M32R monitor:
16961 @item set download-path @var{path}
16962 @kindex set download-path
16963 @cindex find downloadable @sc{srec} files (M32R)
16964 Set the default path for finding downloadable @sc{srec} files.
16966 @item show download-path
16967 @kindex show download-path
16968 Show the default path for downloadable @sc{srec} files.
16970 @item set board-address @var{addr}
16971 @kindex set board-address
16972 @cindex M32-EVA target board address
16973 Set the IP address for the M32R-EVA target board.
16975 @item show board-address
16976 @kindex show board-address
16977 Show the current IP address of the target board.
16979 @item set server-address @var{addr}
16980 @kindex set server-address
16981 @cindex download server address (M32R)
16982 Set the IP address for the download server, which is the @value{GDBN}'s
16985 @item show server-address
16986 @kindex show server-address
16987 Display the IP address of the download server.
16989 @item upload @r{[}@var{file}@r{]}
16990 @kindex upload@r{, M32R}
16991 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
16992 upload capability. If no @var{file} argument is given, the current
16993 executable file is uploaded.
16995 @item tload @r{[}@var{file}@r{]}
16996 @kindex tload@r{, M32R}
16997 Test the @code{upload} command.
17000 The following commands are available for M32R/SDI:
17005 @cindex reset SDI connection, M32R
17006 This command resets the SDI connection.
17010 This command shows the SDI connection status.
17013 @kindex debug_chaos
17014 @cindex M32R/Chaos debugging
17015 Instructs the remote that M32R/Chaos debugging is to be used.
17017 @item use_debug_dma
17018 @kindex use_debug_dma
17019 Instructs the remote to use the DEBUG_DMA method of accessing memory.
17022 @kindex use_mon_code
17023 Instructs the remote to use the MON_CODE method of accessing memory.
17026 @kindex use_ib_break
17027 Instructs the remote to set breakpoints by IB break.
17029 @item use_dbt_break
17030 @kindex use_dbt_break
17031 Instructs the remote to set breakpoints by DBT.
17037 The Motorola m68k configuration includes ColdFire support, and a
17038 target command for the following ROM monitor.
17042 @kindex target dbug
17043 @item target dbug @var{dev}
17044 dBUG ROM monitor for Motorola ColdFire.
17049 @subsection MicroBlaze
17050 @cindex Xilinx MicroBlaze
17051 @cindex XMD, Xilinx Microprocessor Debugger
17053 The MicroBlaze is a soft-core processor supported on various Xilinx
17054 FPGAs, such as Spartan or Virtex series. Boards with these processors
17055 usually have JTAG ports which connect to a host system running the Xilinx
17056 Embedded Development Kit (EDK) or Software Development Kit (SDK).
17057 This host system is used to download the configuration bitstream to
17058 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
17059 communicates with the target board using the JTAG interface and
17060 presents a @code{gdbserver} interface to the board. By default
17061 @code{xmd} uses port @code{1234}. (While it is possible to change
17062 this default port, it requires the use of undocumented @code{xmd}
17063 commands. Contact Xilinx support if you need to do this.)
17065 Use these GDB commands to connect to the MicroBlaze target processor.
17068 @item target remote :1234
17069 Use this command to connect to the target if you are running @value{GDBN}
17070 on the same system as @code{xmd}.
17072 @item target remote @var{xmd-host}:1234
17073 Use this command to connect to the target if it is connected to @code{xmd}
17074 running on a different system named @var{xmd-host}.
17077 Use this command to download a program to the MicroBlaze target.
17079 @item set debug microblaze @var{n}
17080 Enable MicroBlaze-specific debugging messages if non-zero.
17082 @item show debug microblaze @var{n}
17083 Show MicroBlaze-specific debugging level.
17086 @node MIPS Embedded
17087 @subsection MIPS Embedded
17089 @cindex MIPS boards
17090 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
17091 MIPS board attached to a serial line. This is available when
17092 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
17095 Use these @value{GDBN} commands to specify the connection to your target board:
17098 @item target mips @var{port}
17099 @kindex target mips @var{port}
17100 To run a program on the board, start up @code{@value{GDBP}} with the
17101 name of your program as the argument. To connect to the board, use the
17102 command @samp{target mips @var{port}}, where @var{port} is the name of
17103 the serial port connected to the board. If the program has not already
17104 been downloaded to the board, you may use the @code{load} command to
17105 download it. You can then use all the usual @value{GDBN} commands.
17107 For example, this sequence connects to the target board through a serial
17108 port, and loads and runs a program called @var{prog} through the
17112 host$ @value{GDBP} @var{prog}
17113 @value{GDBN} is free software and @dots{}
17114 (@value{GDBP}) target mips /dev/ttyb
17115 (@value{GDBP}) load @var{prog}
17119 @item target mips @var{hostname}:@var{portnumber}
17120 On some @value{GDBN} host configurations, you can specify a TCP
17121 connection (for instance, to a serial line managed by a terminal
17122 concentrator) instead of a serial port, using the syntax
17123 @samp{@var{hostname}:@var{portnumber}}.
17125 @item target pmon @var{port}
17126 @kindex target pmon @var{port}
17129 @item target ddb @var{port}
17130 @kindex target ddb @var{port}
17131 NEC's DDB variant of PMON for Vr4300.
17133 @item target lsi @var{port}
17134 @kindex target lsi @var{port}
17135 LSI variant of PMON.
17137 @kindex target r3900
17138 @item target r3900 @var{dev}
17139 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
17141 @kindex target array
17142 @item target array @var{dev}
17143 Array Tech LSI33K RAID controller board.
17149 @value{GDBN} also supports these special commands for MIPS targets:
17152 @item set mipsfpu double
17153 @itemx set mipsfpu single
17154 @itemx set mipsfpu none
17155 @itemx set mipsfpu auto
17156 @itemx show mipsfpu
17157 @kindex set mipsfpu
17158 @kindex show mipsfpu
17159 @cindex MIPS remote floating point
17160 @cindex floating point, MIPS remote
17161 If your target board does not support the MIPS floating point
17162 coprocessor, you should use the command @samp{set mipsfpu none} (if you
17163 need this, you may wish to put the command in your @value{GDBN} init
17164 file). This tells @value{GDBN} how to find the return value of
17165 functions which return floating point values. It also allows
17166 @value{GDBN} to avoid saving the floating point registers when calling
17167 functions on the board. If you are using a floating point coprocessor
17168 with only single precision floating point support, as on the @sc{r4650}
17169 processor, use the command @samp{set mipsfpu single}. The default
17170 double precision floating point coprocessor may be selected using
17171 @samp{set mipsfpu double}.
17173 In previous versions the only choices were double precision or no
17174 floating point, so @samp{set mipsfpu on} will select double precision
17175 and @samp{set mipsfpu off} will select no floating point.
17177 As usual, you can inquire about the @code{mipsfpu} variable with
17178 @samp{show mipsfpu}.
17180 @item set timeout @var{seconds}
17181 @itemx set retransmit-timeout @var{seconds}
17182 @itemx show timeout
17183 @itemx show retransmit-timeout
17184 @cindex @code{timeout}, MIPS protocol
17185 @cindex @code{retransmit-timeout}, MIPS protocol
17186 @kindex set timeout
17187 @kindex show timeout
17188 @kindex set retransmit-timeout
17189 @kindex show retransmit-timeout
17190 You can control the timeout used while waiting for a packet, in the MIPS
17191 remote protocol, with the @code{set timeout @var{seconds}} command. The
17192 default is 5 seconds. Similarly, you can control the timeout used while
17193 waiting for an acknowledgment of a packet with the @code{set
17194 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
17195 You can inspect both values with @code{show timeout} and @code{show
17196 retransmit-timeout}. (These commands are @emph{only} available when
17197 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
17199 The timeout set by @code{set timeout} does not apply when @value{GDBN}
17200 is waiting for your program to stop. In that case, @value{GDBN} waits
17201 forever because it has no way of knowing how long the program is going
17202 to run before stopping.
17204 @item set syn-garbage-limit @var{num}
17205 @kindex set syn-garbage-limit@r{, MIPS remote}
17206 @cindex synchronize with remote MIPS target
17207 Limit the maximum number of characters @value{GDBN} should ignore when
17208 it tries to synchronize with the remote target. The default is 10
17209 characters. Setting the limit to -1 means there's no limit.
17211 @item show syn-garbage-limit
17212 @kindex show syn-garbage-limit@r{, MIPS remote}
17213 Show the current limit on the number of characters to ignore when
17214 trying to synchronize with the remote system.
17216 @item set monitor-prompt @var{prompt}
17217 @kindex set monitor-prompt@r{, MIPS remote}
17218 @cindex remote monitor prompt
17219 Tell @value{GDBN} to expect the specified @var{prompt} string from the
17220 remote monitor. The default depends on the target:
17230 @item show monitor-prompt
17231 @kindex show monitor-prompt@r{, MIPS remote}
17232 Show the current strings @value{GDBN} expects as the prompt from the
17235 @item set monitor-warnings
17236 @kindex set monitor-warnings@r{, MIPS remote}
17237 Enable or disable monitor warnings about hardware breakpoints. This
17238 has effect only for the @code{lsi} target. When on, @value{GDBN} will
17239 display warning messages whose codes are returned by the @code{lsi}
17240 PMON monitor for breakpoint commands.
17242 @item show monitor-warnings
17243 @kindex show monitor-warnings@r{, MIPS remote}
17244 Show the current setting of printing monitor warnings.
17246 @item pmon @var{command}
17247 @kindex pmon@r{, MIPS remote}
17248 @cindex send PMON command
17249 This command allows sending an arbitrary @var{command} string to the
17250 monitor. The monitor must be in debug mode for this to work.
17253 @node OpenRISC 1000
17254 @subsection OpenRISC 1000
17255 @cindex OpenRISC 1000
17257 @cindex or1k boards
17258 See OR1k Architecture document (@uref{www.opencores.org}) for more information
17259 about platform and commands.
17263 @kindex target jtag
17264 @item target jtag jtag://@var{host}:@var{port}
17266 Connects to remote JTAG server.
17267 JTAG remote server can be either an or1ksim or JTAG server,
17268 connected via parallel port to the board.
17270 Example: @code{target jtag jtag://localhost:9999}
17273 @item or1ksim @var{command}
17274 If connected to @code{or1ksim} OpenRISC 1000 Architectural
17275 Simulator, proprietary commands can be executed.
17277 @kindex info or1k spr
17278 @item info or1k spr
17279 Displays spr groups.
17281 @item info or1k spr @var{group}
17282 @itemx info or1k spr @var{groupno}
17283 Displays register names in selected group.
17285 @item info or1k spr @var{group} @var{register}
17286 @itemx info or1k spr @var{register}
17287 @itemx info or1k spr @var{groupno} @var{registerno}
17288 @itemx info or1k spr @var{registerno}
17289 Shows information about specified spr register.
17292 @item spr @var{group} @var{register} @var{value}
17293 @itemx spr @var{register @var{value}}
17294 @itemx spr @var{groupno} @var{registerno @var{value}}
17295 @itemx spr @var{registerno @var{value}}
17296 Writes @var{value} to specified spr register.
17299 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
17300 It is very similar to @value{GDBN} trace, except it does not interfere with normal
17301 program execution and is thus much faster. Hardware breakpoints/watchpoint
17302 triggers can be set using:
17305 Load effective address/data
17307 Store effective address/data
17309 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
17314 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
17315 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
17317 @code{htrace} commands:
17318 @cindex OpenRISC 1000 htrace
17321 @item hwatch @var{conditional}
17322 Set hardware watchpoint on combination of Load/Store Effective Address(es)
17323 or Data. For example:
17325 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
17327 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
17331 Display information about current HW trace configuration.
17333 @item htrace trigger @var{conditional}
17334 Set starting criteria for HW trace.
17336 @item htrace qualifier @var{conditional}
17337 Set acquisition qualifier for HW trace.
17339 @item htrace stop @var{conditional}
17340 Set HW trace stopping criteria.
17342 @item htrace record [@var{data}]*
17343 Selects the data to be recorded, when qualifier is met and HW trace was
17346 @item htrace enable
17347 @itemx htrace disable
17348 Enables/disables the HW trace.
17350 @item htrace rewind [@var{filename}]
17351 Clears currently recorded trace data.
17353 If filename is specified, new trace file is made and any newly collected data
17354 will be written there.
17356 @item htrace print [@var{start} [@var{len}]]
17357 Prints trace buffer, using current record configuration.
17359 @item htrace mode continuous
17360 Set continuous trace mode.
17362 @item htrace mode suspend
17363 Set suspend trace mode.
17367 @node PowerPC Embedded
17368 @subsection PowerPC Embedded
17370 @value{GDBN} provides the following PowerPC-specific commands:
17373 @kindex set powerpc
17374 @item set powerpc soft-float
17375 @itemx show powerpc soft-float
17376 Force @value{GDBN} to use (or not use) a software floating point calling
17377 convention. By default, @value{GDBN} selects the calling convention based
17378 on the selected architecture and the provided executable file.
17380 @item set powerpc vector-abi
17381 @itemx show powerpc vector-abi
17382 Force @value{GDBN} to use the specified calling convention for vector
17383 arguments and return values. The valid options are @samp{auto};
17384 @samp{generic}, to avoid vector registers even if they are present;
17385 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
17386 registers. By default, @value{GDBN} selects the calling convention
17387 based on the selected architecture and the provided executable file.
17389 @kindex target dink32
17390 @item target dink32 @var{dev}
17391 DINK32 ROM monitor.
17393 @kindex target ppcbug
17394 @item target ppcbug @var{dev}
17395 @kindex target ppcbug1
17396 @item target ppcbug1 @var{dev}
17397 PPCBUG ROM monitor for PowerPC.
17400 @item target sds @var{dev}
17401 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
17404 @cindex SDS protocol
17405 The following commands specific to the SDS protocol are supported
17409 @item set sdstimeout @var{nsec}
17410 @kindex set sdstimeout
17411 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
17412 default is 2 seconds.
17414 @item show sdstimeout
17415 @kindex show sdstimeout
17416 Show the current value of the SDS timeout.
17418 @item sds @var{command}
17419 @kindex sds@r{, a command}
17420 Send the specified @var{command} string to the SDS monitor.
17425 @subsection HP PA Embedded
17429 @kindex target op50n
17430 @item target op50n @var{dev}
17431 OP50N monitor, running on an OKI HPPA board.
17433 @kindex target w89k
17434 @item target w89k @var{dev}
17435 W89K monitor, running on a Winbond HPPA board.
17440 @subsection Tsqware Sparclet
17444 @value{GDBN} enables developers to debug tasks running on
17445 Sparclet targets from a Unix host.
17446 @value{GDBN} uses code that runs on
17447 both the Unix host and on the Sparclet target. The program
17448 @code{@value{GDBP}} is installed and executed on the Unix host.
17451 @item remotetimeout @var{args}
17452 @kindex remotetimeout
17453 @value{GDBN} supports the option @code{remotetimeout}.
17454 This option is set by the user, and @var{args} represents the number of
17455 seconds @value{GDBN} waits for responses.
17458 @cindex compiling, on Sparclet
17459 When compiling for debugging, include the options @samp{-g} to get debug
17460 information and @samp{-Ttext} to relocate the program to where you wish to
17461 load it on the target. You may also want to add the options @samp{-n} or
17462 @samp{-N} in order to reduce the size of the sections. Example:
17465 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
17468 You can use @code{objdump} to verify that the addresses are what you intended:
17471 sparclet-aout-objdump --headers --syms prog
17474 @cindex running, on Sparclet
17476 your Unix execution search path to find @value{GDBN}, you are ready to
17477 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
17478 (or @code{sparclet-aout-gdb}, depending on your installation).
17480 @value{GDBN} comes up showing the prompt:
17487 * Sparclet File:: Setting the file to debug
17488 * Sparclet Connection:: Connecting to Sparclet
17489 * Sparclet Download:: Sparclet download
17490 * Sparclet Execution:: Running and debugging
17493 @node Sparclet File
17494 @subsubsection Setting File to Debug
17496 The @value{GDBN} command @code{file} lets you choose with program to debug.
17499 (gdbslet) file prog
17503 @value{GDBN} then attempts to read the symbol table of @file{prog}.
17504 @value{GDBN} locates
17505 the file by searching the directories listed in the command search
17507 If the file was compiled with debug information (option @samp{-g}), source
17508 files will be searched as well.
17509 @value{GDBN} locates
17510 the source files by searching the directories listed in the directory search
17511 path (@pxref{Environment, ,Your Program's Environment}).
17513 to find a file, it displays a message such as:
17516 prog: No such file or directory.
17519 When this happens, add the appropriate directories to the search paths with
17520 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
17521 @code{target} command again.
17523 @node Sparclet Connection
17524 @subsubsection Connecting to Sparclet
17526 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
17527 To connect to a target on serial port ``@code{ttya}'', type:
17530 (gdbslet) target sparclet /dev/ttya
17531 Remote target sparclet connected to /dev/ttya
17532 main () at ../prog.c:3
17536 @value{GDBN} displays messages like these:
17542 @node Sparclet Download
17543 @subsubsection Sparclet Download
17545 @cindex download to Sparclet
17546 Once connected to the Sparclet target,
17547 you can use the @value{GDBN}
17548 @code{load} command to download the file from the host to the target.
17549 The file name and load offset should be given as arguments to the @code{load}
17551 Since the file format is aout, the program must be loaded to the starting
17552 address. You can use @code{objdump} to find out what this value is. The load
17553 offset is an offset which is added to the VMA (virtual memory address)
17554 of each of the file's sections.
17555 For instance, if the program
17556 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
17557 and bss at 0x12010170, in @value{GDBN}, type:
17560 (gdbslet) load prog 0x12010000
17561 Loading section .text, size 0xdb0 vma 0x12010000
17564 If the code is loaded at a different address then what the program was linked
17565 to, you may need to use the @code{section} and @code{add-symbol-file} commands
17566 to tell @value{GDBN} where to map the symbol table.
17568 @node Sparclet Execution
17569 @subsubsection Running and Debugging
17571 @cindex running and debugging Sparclet programs
17572 You can now begin debugging the task using @value{GDBN}'s execution control
17573 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
17574 manual for the list of commands.
17578 Breakpoint 1 at 0x12010000: file prog.c, line 3.
17580 Starting program: prog
17581 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
17582 3 char *symarg = 0;
17584 4 char *execarg = "hello!";
17589 @subsection Fujitsu Sparclite
17593 @kindex target sparclite
17594 @item target sparclite @var{dev}
17595 Fujitsu sparclite boards, used only for the purpose of loading.
17596 You must use an additional command to debug the program.
17597 For example: target remote @var{dev} using @value{GDBN} standard
17603 @subsection Zilog Z8000
17606 @cindex simulator, Z8000
17607 @cindex Zilog Z8000 simulator
17609 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
17612 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
17613 unsegmented variant of the Z8000 architecture) or the Z8001 (the
17614 segmented variant). The simulator recognizes which architecture is
17615 appropriate by inspecting the object code.
17618 @item target sim @var{args}
17620 @kindex target sim@r{, with Z8000}
17621 Debug programs on a simulated CPU. If the simulator supports setup
17622 options, specify them via @var{args}.
17626 After specifying this target, you can debug programs for the simulated
17627 CPU in the same style as programs for your host computer; use the
17628 @code{file} command to load a new program image, the @code{run} command
17629 to run your program, and so on.
17631 As well as making available all the usual machine registers
17632 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
17633 additional items of information as specially named registers:
17638 Counts clock-ticks in the simulator.
17641 Counts instructions run in the simulator.
17644 Execution time in 60ths of a second.
17648 You can refer to these values in @value{GDBN} expressions with the usual
17649 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
17650 conditional breakpoint that suspends only after at least 5000
17651 simulated clock ticks.
17654 @subsection Atmel AVR
17657 When configured for debugging the Atmel AVR, @value{GDBN} supports the
17658 following AVR-specific commands:
17661 @item info io_registers
17662 @kindex info io_registers@r{, AVR}
17663 @cindex I/O registers (Atmel AVR)
17664 This command displays information about the AVR I/O registers. For
17665 each register, @value{GDBN} prints its number and value.
17672 When configured for debugging CRIS, @value{GDBN} provides the
17673 following CRIS-specific commands:
17676 @item set cris-version @var{ver}
17677 @cindex CRIS version
17678 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
17679 The CRIS version affects register names and sizes. This command is useful in
17680 case autodetection of the CRIS version fails.
17682 @item show cris-version
17683 Show the current CRIS version.
17685 @item set cris-dwarf2-cfi
17686 @cindex DWARF-2 CFI and CRIS
17687 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
17688 Change to @samp{off} when using @code{gcc-cris} whose version is below
17691 @item show cris-dwarf2-cfi
17692 Show the current state of using DWARF-2 CFI.
17694 @item set cris-mode @var{mode}
17696 Set the current CRIS mode to @var{mode}. It should only be changed when
17697 debugging in guru mode, in which case it should be set to
17698 @samp{guru} (the default is @samp{normal}).
17700 @item show cris-mode
17701 Show the current CRIS mode.
17705 @subsection Renesas Super-H
17708 For the Renesas Super-H processor, @value{GDBN} provides these
17713 @kindex regs@r{, Super-H}
17714 Show the values of all Super-H registers.
17716 @item set sh calling-convention @var{convention}
17717 @kindex set sh calling-convention
17718 Set the calling-convention used when calling functions from @value{GDBN}.
17719 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
17720 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
17721 convention. If the DWARF-2 information of the called function specifies
17722 that the function follows the Renesas calling convention, the function
17723 is called using the Renesas calling convention. If the calling convention
17724 is set to @samp{renesas}, the Renesas calling convention is always used,
17725 regardless of the DWARF-2 information. This can be used to override the
17726 default of @samp{gcc} if debug information is missing, or the compiler
17727 does not emit the DWARF-2 calling convention entry for a function.
17729 @item show sh calling-convention
17730 @kindex show sh calling-convention
17731 Show the current calling convention setting.
17736 @node Architectures
17737 @section Architectures
17739 This section describes characteristics of architectures that affect
17740 all uses of @value{GDBN} with the architecture, both native and cross.
17747 * HPPA:: HP PA architecture
17748 * SPU:: Cell Broadband Engine SPU architecture
17753 @subsection x86 Architecture-specific Issues
17756 @item set struct-convention @var{mode}
17757 @kindex set struct-convention
17758 @cindex struct return convention
17759 @cindex struct/union returned in registers
17760 Set the convention used by the inferior to return @code{struct}s and
17761 @code{union}s from functions to @var{mode}. Possible values of
17762 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
17763 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
17764 are returned on the stack, while @code{"reg"} means that a
17765 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
17766 be returned in a register.
17768 @item show struct-convention
17769 @kindex show struct-convention
17770 Show the current setting of the convention to return @code{struct}s
17779 @kindex set rstack_high_address
17780 @cindex AMD 29K register stack
17781 @cindex register stack, AMD29K
17782 @item set rstack_high_address @var{address}
17783 On AMD 29000 family processors, registers are saved in a separate
17784 @dfn{register stack}. There is no way for @value{GDBN} to determine the
17785 extent of this stack. Normally, @value{GDBN} just assumes that the
17786 stack is ``large enough''. This may result in @value{GDBN} referencing
17787 memory locations that do not exist. If necessary, you can get around
17788 this problem by specifying the ending address of the register stack with
17789 the @code{set rstack_high_address} command. The argument should be an
17790 address, which you probably want to precede with @samp{0x} to specify in
17793 @kindex show rstack_high_address
17794 @item show rstack_high_address
17795 Display the current limit of the register stack, on AMD 29000 family
17803 See the following section.
17808 @cindex stack on Alpha
17809 @cindex stack on MIPS
17810 @cindex Alpha stack
17812 Alpha- and MIPS-based computers use an unusual stack frame, which
17813 sometimes requires @value{GDBN} to search backward in the object code to
17814 find the beginning of a function.
17816 @cindex response time, MIPS debugging
17817 To improve response time (especially for embedded applications, where
17818 @value{GDBN} may be restricted to a slow serial line for this search)
17819 you may want to limit the size of this search, using one of these
17823 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
17824 @item set heuristic-fence-post @var{limit}
17825 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
17826 search for the beginning of a function. A value of @var{0} (the
17827 default) means there is no limit. However, except for @var{0}, the
17828 larger the limit the more bytes @code{heuristic-fence-post} must search
17829 and therefore the longer it takes to run. You should only need to use
17830 this command when debugging a stripped executable.
17832 @item show heuristic-fence-post
17833 Display the current limit.
17837 These commands are available @emph{only} when @value{GDBN} is configured
17838 for debugging programs on Alpha or MIPS processors.
17840 Several MIPS-specific commands are available when debugging MIPS
17844 @item set mips abi @var{arg}
17845 @kindex set mips abi
17846 @cindex set ABI for MIPS
17847 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
17848 values of @var{arg} are:
17852 The default ABI associated with the current binary (this is the
17863 @item show mips abi
17864 @kindex show mips abi
17865 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
17868 @itemx show mipsfpu
17869 @xref{MIPS Embedded, set mipsfpu}.
17871 @item set mips mask-address @var{arg}
17872 @kindex set mips mask-address
17873 @cindex MIPS addresses, masking
17874 This command determines whether the most-significant 32 bits of 64-bit
17875 MIPS addresses are masked off. The argument @var{arg} can be
17876 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
17877 setting, which lets @value{GDBN} determine the correct value.
17879 @item show mips mask-address
17880 @kindex show mips mask-address
17881 Show whether the upper 32 bits of MIPS addresses are masked off or
17884 @item set remote-mips64-transfers-32bit-regs
17885 @kindex set remote-mips64-transfers-32bit-regs
17886 This command controls compatibility with 64-bit MIPS targets that
17887 transfer data in 32-bit quantities. If you have an old MIPS 64 target
17888 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
17889 and 64 bits for other registers, set this option to @samp{on}.
17891 @item show remote-mips64-transfers-32bit-regs
17892 @kindex show remote-mips64-transfers-32bit-regs
17893 Show the current setting of compatibility with older MIPS 64 targets.
17895 @item set debug mips
17896 @kindex set debug mips
17897 This command turns on and off debugging messages for the MIPS-specific
17898 target code in @value{GDBN}.
17900 @item show debug mips
17901 @kindex show debug mips
17902 Show the current setting of MIPS debugging messages.
17908 @cindex HPPA support
17910 When @value{GDBN} is debugging the HP PA architecture, it provides the
17911 following special commands:
17914 @item set debug hppa
17915 @kindex set debug hppa
17916 This command determines whether HPPA architecture-specific debugging
17917 messages are to be displayed.
17919 @item show debug hppa
17920 Show whether HPPA debugging messages are displayed.
17922 @item maint print unwind @var{address}
17923 @kindex maint print unwind@r{, HPPA}
17924 This command displays the contents of the unwind table entry at the
17925 given @var{address}.
17931 @subsection Cell Broadband Engine SPU architecture
17932 @cindex Cell Broadband Engine
17935 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
17936 it provides the following special commands:
17939 @item info spu event
17941 Display SPU event facility status. Shows current event mask
17942 and pending event status.
17944 @item info spu signal
17945 Display SPU signal notification facility status. Shows pending
17946 signal-control word and signal notification mode of both signal
17947 notification channels.
17949 @item info spu mailbox
17950 Display SPU mailbox facility status. Shows all pending entries,
17951 in order of processing, in each of the SPU Write Outbound,
17952 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
17955 Display MFC DMA status. Shows all pending commands in the MFC
17956 DMA queue. For each entry, opcode, tag, class IDs, effective
17957 and local store addresses and transfer size are shown.
17959 @item info spu proxydma
17960 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
17961 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
17962 and local store addresses and transfer size are shown.
17966 When @value{GDBN} is debugging a combined PowerPC/SPU application
17967 on the Cell Broadband Engine, it provides in addition the following
17971 @item set spu stop-on-load @var{arg}
17973 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
17974 will give control to the user when a new SPE thread enters its @code{main}
17975 function. The default is @code{off}.
17977 @item show spu stop-on-load
17979 Show whether to stop for new SPE threads.
17981 @item set spu auto-flush-cache @var{arg}
17982 Set whether to automatically flush the software-managed cache. When set to
17983 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
17984 cache to be flushed whenever SPE execution stops. This provides a consistent
17985 view of PowerPC memory that is accessed via the cache. If an application
17986 does not use the software-managed cache, this option has no effect.
17988 @item show spu auto-flush-cache
17989 Show whether to automatically flush the software-managed cache.
17994 @subsection PowerPC
17995 @cindex PowerPC architecture
17997 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
17998 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
17999 numbers stored in the floating point registers. These values must be stored
18000 in two consecutive registers, always starting at an even register like
18001 @code{f0} or @code{f2}.
18003 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
18004 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
18005 @code{f2} and @code{f3} for @code{$dl1} and so on.
18007 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
18008 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
18011 @node Controlling GDB
18012 @chapter Controlling @value{GDBN}
18014 You can alter the way @value{GDBN} interacts with you by using the
18015 @code{set} command. For commands controlling how @value{GDBN} displays
18016 data, see @ref{Print Settings, ,Print Settings}. Other settings are
18021 * Editing:: Command editing
18022 * Command History:: Command history
18023 * Screen Size:: Screen size
18024 * Numbers:: Numbers
18025 * ABI:: Configuring the current ABI
18026 * Messages/Warnings:: Optional warnings and messages
18027 * Debugging Output:: Optional messages about internal happenings
18028 * Other Misc Settings:: Other Miscellaneous Settings
18036 @value{GDBN} indicates its readiness to read a command by printing a string
18037 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
18038 can change the prompt string with the @code{set prompt} command. For
18039 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
18040 the prompt in one of the @value{GDBN} sessions so that you can always tell
18041 which one you are talking to.
18043 @emph{Note:} @code{set prompt} does not add a space for you after the
18044 prompt you set. This allows you to set a prompt which ends in a space
18045 or a prompt that does not.
18049 @item set prompt @var{newprompt}
18050 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
18052 @kindex show prompt
18054 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
18058 @section Command Editing
18060 @cindex command line editing
18062 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
18063 @sc{gnu} library provides consistent behavior for programs which provide a
18064 command line interface to the user. Advantages are @sc{gnu} Emacs-style
18065 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
18066 substitution, and a storage and recall of command history across
18067 debugging sessions.
18069 You may control the behavior of command line editing in @value{GDBN} with the
18070 command @code{set}.
18073 @kindex set editing
18076 @itemx set editing on
18077 Enable command line editing (enabled by default).
18079 @item set editing off
18080 Disable command line editing.
18082 @kindex show editing
18084 Show whether command line editing is enabled.
18087 @xref{Command Line Editing}, for more details about the Readline
18088 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
18089 encouraged to read that chapter.
18091 @node Command History
18092 @section Command History
18093 @cindex command history
18095 @value{GDBN} can keep track of the commands you type during your
18096 debugging sessions, so that you can be certain of precisely what
18097 happened. Use these commands to manage the @value{GDBN} command
18100 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
18101 package, to provide the history facility. @xref{Using History
18102 Interactively}, for the detailed description of the History library.
18104 To issue a command to @value{GDBN} without affecting certain aspects of
18105 the state which is seen by users, prefix it with @samp{server }
18106 (@pxref{Server Prefix}). This
18107 means that this command will not affect the command history, nor will it
18108 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
18109 pressed on a line by itself.
18111 @cindex @code{server}, command prefix
18112 The server prefix does not affect the recording of values into the value
18113 history; to print a value without recording it into the value history,
18114 use the @code{output} command instead of the @code{print} command.
18116 Here is the description of @value{GDBN} commands related to command
18120 @cindex history substitution
18121 @cindex history file
18122 @kindex set history filename
18123 @cindex @env{GDBHISTFILE}, environment variable
18124 @item set history filename @var{fname}
18125 Set the name of the @value{GDBN} command history file to @var{fname}.
18126 This is the file where @value{GDBN} reads an initial command history
18127 list, and where it writes the command history from this session when it
18128 exits. You can access this list through history expansion or through
18129 the history command editing characters listed below. This file defaults
18130 to the value of the environment variable @code{GDBHISTFILE}, or to
18131 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
18134 @cindex save command history
18135 @kindex set history save
18136 @item set history save
18137 @itemx set history save on
18138 Record command history in a file, whose name may be specified with the
18139 @code{set history filename} command. By default, this option is disabled.
18141 @item set history save off
18142 Stop recording command history in a file.
18144 @cindex history size
18145 @kindex set history size
18146 @cindex @env{HISTSIZE}, environment variable
18147 @item set history size @var{size}
18148 Set the number of commands which @value{GDBN} keeps in its history list.
18149 This defaults to the value of the environment variable
18150 @code{HISTSIZE}, or to 256 if this variable is not set.
18153 History expansion assigns special meaning to the character @kbd{!}.
18154 @xref{Event Designators}, for more details.
18156 @cindex history expansion, turn on/off
18157 Since @kbd{!} is also the logical not operator in C, history expansion
18158 is off by default. If you decide to enable history expansion with the
18159 @code{set history expansion on} command, you may sometimes need to
18160 follow @kbd{!} (when it is used as logical not, in an expression) with
18161 a space or a tab to prevent it from being expanded. The readline
18162 history facilities do not attempt substitution on the strings
18163 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
18165 The commands to control history expansion are:
18168 @item set history expansion on
18169 @itemx set history expansion
18170 @kindex set history expansion
18171 Enable history expansion. History expansion is off by default.
18173 @item set history expansion off
18174 Disable history expansion.
18177 @kindex show history
18179 @itemx show history filename
18180 @itemx show history save
18181 @itemx show history size
18182 @itemx show history expansion
18183 These commands display the state of the @value{GDBN} history parameters.
18184 @code{show history} by itself displays all four states.
18189 @kindex show commands
18190 @cindex show last commands
18191 @cindex display command history
18192 @item show commands
18193 Display the last ten commands in the command history.
18195 @item show commands @var{n}
18196 Print ten commands centered on command number @var{n}.
18198 @item show commands +
18199 Print ten commands just after the commands last printed.
18203 @section Screen Size
18204 @cindex size of screen
18205 @cindex pauses in output
18207 Certain commands to @value{GDBN} may produce large amounts of
18208 information output to the screen. To help you read all of it,
18209 @value{GDBN} pauses and asks you for input at the end of each page of
18210 output. Type @key{RET} when you want to continue the output, or @kbd{q}
18211 to discard the remaining output. Also, the screen width setting
18212 determines when to wrap lines of output. Depending on what is being
18213 printed, @value{GDBN} tries to break the line at a readable place,
18214 rather than simply letting it overflow onto the following line.
18216 Normally @value{GDBN} knows the size of the screen from the terminal
18217 driver software. For example, on Unix @value{GDBN} uses the termcap data base
18218 together with the value of the @code{TERM} environment variable and the
18219 @code{stty rows} and @code{stty cols} settings. If this is not correct,
18220 you can override it with the @code{set height} and @code{set
18227 @kindex show height
18228 @item set height @var{lpp}
18230 @itemx set width @var{cpl}
18232 These @code{set} commands specify a screen height of @var{lpp} lines and
18233 a screen width of @var{cpl} characters. The associated @code{show}
18234 commands display the current settings.
18236 If you specify a height of zero lines, @value{GDBN} does not pause during
18237 output no matter how long the output is. This is useful if output is to a
18238 file or to an editor buffer.
18240 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
18241 from wrapping its output.
18243 @item set pagination on
18244 @itemx set pagination off
18245 @kindex set pagination
18246 Turn the output pagination on or off; the default is on. Turning
18247 pagination off is the alternative to @code{set height 0}.
18249 @item show pagination
18250 @kindex show pagination
18251 Show the current pagination mode.
18256 @cindex number representation
18257 @cindex entering numbers
18259 You can always enter numbers in octal, decimal, or hexadecimal in
18260 @value{GDBN} by the usual conventions: octal numbers begin with
18261 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
18262 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
18263 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
18264 10; likewise, the default display for numbers---when no particular
18265 format is specified---is base 10. You can change the default base for
18266 both input and output with the commands described below.
18269 @kindex set input-radix
18270 @item set input-radix @var{base}
18271 Set the default base for numeric input. Supported choices
18272 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
18273 specified either unambiguously or using the current input radix; for
18277 set input-radix 012
18278 set input-radix 10.
18279 set input-radix 0xa
18283 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
18284 leaves the input radix unchanged, no matter what it was, since
18285 @samp{10}, being without any leading or trailing signs of its base, is
18286 interpreted in the current radix. Thus, if the current radix is 16,
18287 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
18290 @kindex set output-radix
18291 @item set output-radix @var{base}
18292 Set the default base for numeric display. Supported choices
18293 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
18294 specified either unambiguously or using the current input radix.
18296 @kindex show input-radix
18297 @item show input-radix
18298 Display the current default base for numeric input.
18300 @kindex show output-radix
18301 @item show output-radix
18302 Display the current default base for numeric display.
18304 @item set radix @r{[}@var{base}@r{]}
18308 These commands set and show the default base for both input and output
18309 of numbers. @code{set radix} sets the radix of input and output to
18310 the same base; without an argument, it resets the radix back to its
18311 default value of 10.
18316 @section Configuring the Current ABI
18318 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
18319 application automatically. However, sometimes you need to override its
18320 conclusions. Use these commands to manage @value{GDBN}'s view of the
18327 One @value{GDBN} configuration can debug binaries for multiple operating
18328 system targets, either via remote debugging or native emulation.
18329 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
18330 but you can override its conclusion using the @code{set osabi} command.
18331 One example where this is useful is in debugging of binaries which use
18332 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
18333 not have the same identifying marks that the standard C library for your
18338 Show the OS ABI currently in use.
18341 With no argument, show the list of registered available OS ABI's.
18343 @item set osabi @var{abi}
18344 Set the current OS ABI to @var{abi}.
18347 @cindex float promotion
18349 Generally, the way that an argument of type @code{float} is passed to a
18350 function depends on whether the function is prototyped. For a prototyped
18351 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
18352 according to the architecture's convention for @code{float}. For unprototyped
18353 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
18354 @code{double} and then passed.
18356 Unfortunately, some forms of debug information do not reliably indicate whether
18357 a function is prototyped. If @value{GDBN} calls a function that is not marked
18358 as prototyped, it consults @kbd{set coerce-float-to-double}.
18361 @kindex set coerce-float-to-double
18362 @item set coerce-float-to-double
18363 @itemx set coerce-float-to-double on
18364 Arguments of type @code{float} will be promoted to @code{double} when passed
18365 to an unprototyped function. This is the default setting.
18367 @item set coerce-float-to-double off
18368 Arguments of type @code{float} will be passed directly to unprototyped
18371 @kindex show coerce-float-to-double
18372 @item show coerce-float-to-double
18373 Show the current setting of promoting @code{float} to @code{double}.
18377 @kindex show cp-abi
18378 @value{GDBN} needs to know the ABI used for your program's C@t{++}
18379 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
18380 used to build your application. @value{GDBN} only fully supports
18381 programs with a single C@t{++} ABI; if your program contains code using
18382 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
18383 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
18384 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
18385 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
18386 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
18387 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
18392 Show the C@t{++} ABI currently in use.
18395 With no argument, show the list of supported C@t{++} ABI's.
18397 @item set cp-abi @var{abi}
18398 @itemx set cp-abi auto
18399 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
18402 @node Messages/Warnings
18403 @section Optional Warnings and Messages
18405 @cindex verbose operation
18406 @cindex optional warnings
18407 By default, @value{GDBN} is silent about its inner workings. If you are
18408 running on a slow machine, you may want to use the @code{set verbose}
18409 command. This makes @value{GDBN} tell you when it does a lengthy
18410 internal operation, so you will not think it has crashed.
18412 Currently, the messages controlled by @code{set verbose} are those
18413 which announce that the symbol table for a source file is being read;
18414 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
18417 @kindex set verbose
18418 @item set verbose on
18419 Enables @value{GDBN} output of certain informational messages.
18421 @item set verbose off
18422 Disables @value{GDBN} output of certain informational messages.
18424 @kindex show verbose
18426 Displays whether @code{set verbose} is on or off.
18429 By default, if @value{GDBN} encounters bugs in the symbol table of an
18430 object file, it is silent; but if you are debugging a compiler, you may
18431 find this information useful (@pxref{Symbol Errors, ,Errors Reading
18436 @kindex set complaints
18437 @item set complaints @var{limit}
18438 Permits @value{GDBN} to output @var{limit} complaints about each type of
18439 unusual symbols before becoming silent about the problem. Set
18440 @var{limit} to zero to suppress all complaints; set it to a large number
18441 to prevent complaints from being suppressed.
18443 @kindex show complaints
18444 @item show complaints
18445 Displays how many symbol complaints @value{GDBN} is permitted to produce.
18449 @anchor{confirmation requests}
18450 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
18451 lot of stupid questions to confirm certain commands. For example, if
18452 you try to run a program which is already running:
18456 The program being debugged has been started already.
18457 Start it from the beginning? (y or n)
18460 If you are willing to unflinchingly face the consequences of your own
18461 commands, you can disable this ``feature'':
18465 @kindex set confirm
18467 @cindex confirmation
18468 @cindex stupid questions
18469 @item set confirm off
18470 Disables confirmation requests.
18472 @item set confirm on
18473 Enables confirmation requests (the default).
18475 @kindex show confirm
18477 Displays state of confirmation requests.
18481 @cindex command tracing
18482 If you need to debug user-defined commands or sourced files you may find it
18483 useful to enable @dfn{command tracing}. In this mode each command will be
18484 printed as it is executed, prefixed with one or more @samp{+} symbols, the
18485 quantity denoting the call depth of each command.
18488 @kindex set trace-commands
18489 @cindex command scripts, debugging
18490 @item set trace-commands on
18491 Enable command tracing.
18492 @item set trace-commands off
18493 Disable command tracing.
18494 @item show trace-commands
18495 Display the current state of command tracing.
18498 @node Debugging Output
18499 @section Optional Messages about Internal Happenings
18500 @cindex optional debugging messages
18502 @value{GDBN} has commands that enable optional debugging messages from
18503 various @value{GDBN} subsystems; normally these commands are of
18504 interest to @value{GDBN} maintainers, or when reporting a bug. This
18505 section documents those commands.
18508 @kindex set exec-done-display
18509 @item set exec-done-display
18510 Turns on or off the notification of asynchronous commands'
18511 completion. When on, @value{GDBN} will print a message when an
18512 asynchronous command finishes its execution. The default is off.
18513 @kindex show exec-done-display
18514 @item show exec-done-display
18515 Displays the current setting of asynchronous command completion
18518 @cindex gdbarch debugging info
18519 @cindex architecture debugging info
18520 @item set debug arch
18521 Turns on or off display of gdbarch debugging info. The default is off
18523 @item show debug arch
18524 Displays the current state of displaying gdbarch debugging info.
18525 @item set debug aix-thread
18526 @cindex AIX threads
18527 Display debugging messages about inner workings of the AIX thread
18529 @item show debug aix-thread
18530 Show the current state of AIX thread debugging info display.
18531 @item set debug dwarf2-die
18532 @cindex DWARF2 DIEs
18533 Dump DWARF2 DIEs after they are read in.
18534 The value is the number of nesting levels to print.
18535 A value of zero turns off the display.
18536 @item show debug dwarf2-die
18537 Show the current state of DWARF2 DIE debugging.
18538 @item set debug displaced
18539 @cindex displaced stepping debugging info
18540 Turns on or off display of @value{GDBN} debugging info for the
18541 displaced stepping support. The default is off.
18542 @item show debug displaced
18543 Displays the current state of displaying @value{GDBN} debugging info
18544 related to displaced stepping.
18545 @item set debug event
18546 @cindex event debugging info
18547 Turns on or off display of @value{GDBN} event debugging info. The
18549 @item show debug event
18550 Displays the current state of displaying @value{GDBN} event debugging
18552 @item set debug expression
18553 @cindex expression debugging info
18554 Turns on or off display of debugging info about @value{GDBN}
18555 expression parsing. The default is off.
18556 @item show debug expression
18557 Displays the current state of displaying debugging info about
18558 @value{GDBN} expression parsing.
18559 @item set debug frame
18560 @cindex frame debugging info
18561 Turns on or off display of @value{GDBN} frame debugging info. The
18563 @item show debug frame
18564 Displays the current state of displaying @value{GDBN} frame debugging
18566 @item set debug gnu-nat
18567 @cindex @sc{gnu}/Hurd debug messages
18568 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
18569 @item show debug gnu-nat
18570 Show the current state of @sc{gnu}/Hurd debugging messages.
18571 @item set debug infrun
18572 @cindex inferior debugging info
18573 Turns on or off display of @value{GDBN} debugging info for running the inferior.
18574 The default is off. @file{infrun.c} contains GDB's runtime state machine used
18575 for implementing operations such as single-stepping the inferior.
18576 @item show debug infrun
18577 Displays the current state of @value{GDBN} inferior debugging.
18578 @item set debug lin-lwp
18579 @cindex @sc{gnu}/Linux LWP debug messages
18580 @cindex Linux lightweight processes
18581 Turns on or off debugging messages from the Linux LWP debug support.
18582 @item show debug lin-lwp
18583 Show the current state of Linux LWP debugging messages.
18584 @item set debug lin-lwp-async
18585 @cindex @sc{gnu}/Linux LWP async debug messages
18586 @cindex Linux lightweight processes
18587 Turns on or off debugging messages from the Linux LWP async debug support.
18588 @item show debug lin-lwp-async
18589 Show the current state of Linux LWP async debugging messages.
18590 @item set debug observer
18591 @cindex observer debugging info
18592 Turns on or off display of @value{GDBN} observer debugging. This
18593 includes info such as the notification of observable events.
18594 @item show debug observer
18595 Displays the current state of observer debugging.
18596 @item set debug overload
18597 @cindex C@t{++} overload debugging info
18598 Turns on or off display of @value{GDBN} C@t{++} overload debugging
18599 info. This includes info such as ranking of functions, etc. The default
18601 @item show debug overload
18602 Displays the current state of displaying @value{GDBN} C@t{++} overload
18604 @cindex packets, reporting on stdout
18605 @cindex serial connections, debugging
18606 @cindex debug remote protocol
18607 @cindex remote protocol debugging
18608 @cindex display remote packets
18609 @item set debug remote
18610 Turns on or off display of reports on all packets sent back and forth across
18611 the serial line to the remote machine. The info is printed on the
18612 @value{GDBN} standard output stream. The default is off.
18613 @item show debug remote
18614 Displays the state of display of remote packets.
18615 @item set debug serial
18616 Turns on or off display of @value{GDBN} serial debugging info. The
18618 @item show debug serial
18619 Displays the current state of displaying @value{GDBN} serial debugging
18621 @item set debug solib-frv
18622 @cindex FR-V shared-library debugging
18623 Turns on or off debugging messages for FR-V shared-library code.
18624 @item show debug solib-frv
18625 Display the current state of FR-V shared-library code debugging
18627 @item set debug target
18628 @cindex target debugging info
18629 Turns on or off display of @value{GDBN} target debugging info. This info
18630 includes what is going on at the target level of GDB, as it happens. The
18631 default is 0. Set it to 1 to track events, and to 2 to also track the
18632 value of large memory transfers. Changes to this flag do not take effect
18633 until the next time you connect to a target or use the @code{run} command.
18634 @item show debug target
18635 Displays the current state of displaying @value{GDBN} target debugging
18637 @item set debug timestamp
18638 @cindex timestampping debugging info
18639 Turns on or off display of timestamps with @value{GDBN} debugging info.
18640 When enabled, seconds and microseconds are displayed before each debugging
18642 @item show debug timestamp
18643 Displays the current state of displaying timestamps with @value{GDBN}
18645 @item set debugvarobj
18646 @cindex variable object debugging info
18647 Turns on or off display of @value{GDBN} variable object debugging
18648 info. The default is off.
18649 @item show debugvarobj
18650 Displays the current state of displaying @value{GDBN} variable object
18652 @item set debug xml
18653 @cindex XML parser debugging
18654 Turns on or off debugging messages for built-in XML parsers.
18655 @item show debug xml
18656 Displays the current state of XML debugging messages.
18659 @node Other Misc Settings
18660 @section Other Miscellaneous Settings
18661 @cindex miscellaneous settings
18664 @kindex set interactive-mode
18665 @item set interactive-mode
18666 If @code{on}, forces @value{GDBN} to operate interactively.
18667 If @code{off}, forces @value{GDBN} to operate non-interactively,
18668 If @code{auto} (the default), @value{GDBN} guesses which mode to use,
18669 based on whether the debugger was started in a terminal or not.
18671 In the vast majority of cases, the debugger should be able to guess
18672 correctly which mode should be used. But this setting can be useful
18673 in certain specific cases, such as running a MinGW @value{GDBN}
18674 inside a cygwin window.
18676 @kindex show interactive-mode
18677 @item show interactive-mode
18678 Displays whether the debugger is operating in interactive mode or not.
18681 @node Extending GDB
18682 @chapter Extending @value{GDBN}
18683 @cindex extending GDB
18685 @value{GDBN} provides two mechanisms for extension. The first is based
18686 on composition of @value{GDBN} commands, and the second is based on the
18687 Python scripting language.
18690 * Sequences:: Canned Sequences of Commands
18691 * Python:: Scripting @value{GDBN} using Python
18695 @section Canned Sequences of Commands
18697 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
18698 Command Lists}), @value{GDBN} provides two ways to store sequences of
18699 commands for execution as a unit: user-defined commands and command
18703 * Define:: How to define your own commands
18704 * Hooks:: Hooks for user-defined commands
18705 * Command Files:: How to write scripts of commands to be stored in a file
18706 * Output:: Commands for controlled output
18710 @subsection User-defined Commands
18712 @cindex user-defined command
18713 @cindex arguments, to user-defined commands
18714 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
18715 which you assign a new name as a command. This is done with the
18716 @code{define} command. User commands may accept up to 10 arguments
18717 separated by whitespace. Arguments are accessed within the user command
18718 via @code{$arg0@dots{}$arg9}. A trivial example:
18722 print $arg0 + $arg1 + $arg2
18727 To execute the command use:
18734 This defines the command @code{adder}, which prints the sum of
18735 its three arguments. Note the arguments are text substitutions, so they may
18736 reference variables, use complex expressions, or even perform inferior
18739 @cindex argument count in user-defined commands
18740 @cindex how many arguments (user-defined commands)
18741 In addition, @code{$argc} may be used to find out how many arguments have
18742 been passed. This expands to a number in the range 0@dots{}10.
18747 print $arg0 + $arg1
18750 print $arg0 + $arg1 + $arg2
18758 @item define @var{commandname}
18759 Define a command named @var{commandname}. If there is already a command
18760 by that name, you are asked to confirm that you want to redefine it.
18761 @var{commandname} may be a bare command name consisting of letters,
18762 numbers, dashes, and underscores. It may also start with any predefined
18763 prefix command. For example, @samp{define target my-target} creates
18764 a user-defined @samp{target my-target} command.
18766 The definition of the command is made up of other @value{GDBN} command lines,
18767 which are given following the @code{define} command. The end of these
18768 commands is marked by a line containing @code{end}.
18771 @kindex end@r{ (user-defined commands)}
18772 @item document @var{commandname}
18773 Document the user-defined command @var{commandname}, so that it can be
18774 accessed by @code{help}. The command @var{commandname} must already be
18775 defined. This command reads lines of documentation just as @code{define}
18776 reads the lines of the command definition, ending with @code{end}.
18777 After the @code{document} command is finished, @code{help} on command
18778 @var{commandname} displays the documentation you have written.
18780 You may use the @code{document} command again to change the
18781 documentation of a command. Redefining the command with @code{define}
18782 does not change the documentation.
18784 @kindex dont-repeat
18785 @cindex don't repeat command
18787 Used inside a user-defined command, this tells @value{GDBN} that this
18788 command should not be repeated when the user hits @key{RET}
18789 (@pxref{Command Syntax, repeat last command}).
18791 @kindex help user-defined
18792 @item help user-defined
18793 List all user-defined commands, with the first line of the documentation
18798 @itemx show user @var{commandname}
18799 Display the @value{GDBN} commands used to define @var{commandname} (but
18800 not its documentation). If no @var{commandname} is given, display the
18801 definitions for all user-defined commands.
18803 @cindex infinite recursion in user-defined commands
18804 @kindex show max-user-call-depth
18805 @kindex set max-user-call-depth
18806 @item show max-user-call-depth
18807 @itemx set max-user-call-depth
18808 The value of @code{max-user-call-depth} controls how many recursion
18809 levels are allowed in user-defined commands before @value{GDBN} suspects an
18810 infinite recursion and aborts the command.
18813 In addition to the above commands, user-defined commands frequently
18814 use control flow commands, described in @ref{Command Files}.
18816 When user-defined commands are executed, the
18817 commands of the definition are not printed. An error in any command
18818 stops execution of the user-defined command.
18820 If used interactively, commands that would ask for confirmation proceed
18821 without asking when used inside a user-defined command. Many @value{GDBN}
18822 commands that normally print messages to say what they are doing omit the
18823 messages when used in a user-defined command.
18826 @subsection User-defined Command Hooks
18827 @cindex command hooks
18828 @cindex hooks, for commands
18829 @cindex hooks, pre-command
18832 You may define @dfn{hooks}, which are a special kind of user-defined
18833 command. Whenever you run the command @samp{foo}, if the user-defined
18834 command @samp{hook-foo} exists, it is executed (with no arguments)
18835 before that command.
18837 @cindex hooks, post-command
18839 A hook may also be defined which is run after the command you executed.
18840 Whenever you run the command @samp{foo}, if the user-defined command
18841 @samp{hookpost-foo} exists, it is executed (with no arguments) after
18842 that command. Post-execution hooks may exist simultaneously with
18843 pre-execution hooks, for the same command.
18845 It is valid for a hook to call the command which it hooks. If this
18846 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
18848 @c It would be nice if hookpost could be passed a parameter indicating
18849 @c if the command it hooks executed properly or not. FIXME!
18851 @kindex stop@r{, a pseudo-command}
18852 In addition, a pseudo-command, @samp{stop} exists. Defining
18853 (@samp{hook-stop}) makes the associated commands execute every time
18854 execution stops in your program: before breakpoint commands are run,
18855 displays are printed, or the stack frame is printed.
18857 For example, to ignore @code{SIGALRM} signals while
18858 single-stepping, but treat them normally during normal execution,
18863 handle SIGALRM nopass
18867 handle SIGALRM pass
18870 define hook-continue
18871 handle SIGALRM pass
18875 As a further example, to hook at the beginning and end of the @code{echo}
18876 command, and to add extra text to the beginning and end of the message,
18884 define hookpost-echo
18888 (@value{GDBP}) echo Hello World
18889 <<<---Hello World--->>>
18894 You can define a hook for any single-word command in @value{GDBN}, but
18895 not for command aliases; you should define a hook for the basic command
18896 name, e.g.@: @code{backtrace} rather than @code{bt}.
18897 @c FIXME! So how does Joe User discover whether a command is an alias
18899 You can hook a multi-word command by adding @code{hook-} or
18900 @code{hookpost-} to the last word of the command, e.g.@:
18901 @samp{define target hook-remote} to add a hook to @samp{target remote}.
18903 If an error occurs during the execution of your hook, execution of
18904 @value{GDBN} commands stops and @value{GDBN} issues a prompt
18905 (before the command that you actually typed had a chance to run).
18907 If you try to define a hook which does not match any known command, you
18908 get a warning from the @code{define} command.
18910 @node Command Files
18911 @subsection Command Files
18913 @cindex command files
18914 @cindex scripting commands
18915 A command file for @value{GDBN} is a text file made of lines that are
18916 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
18917 also be included. An empty line in a command file does nothing; it
18918 does not mean to repeat the last command, as it would from the
18921 You can request the execution of a command file with the @code{source}
18926 @cindex execute commands from a file
18927 @item source [@code{-v}] @var{filename}
18928 Execute the command file @var{filename}.
18931 The lines in a command file are generally executed sequentially,
18932 unless the order of execution is changed by one of the
18933 @emph{flow-control commands} described below. The commands are not
18934 printed as they are executed. An error in any command terminates
18935 execution of the command file and control is returned to the console.
18937 @value{GDBN} searches for @var{filename} in the current directory and then
18938 on the search path (specified with the @samp{directory} command).
18940 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
18941 each command as it is executed. The option must be given before
18942 @var{filename}, and is interpreted as part of the filename anywhere else.
18944 Commands that would ask for confirmation if used interactively proceed
18945 without asking when used in a command file. Many @value{GDBN} commands that
18946 normally print messages to say what they are doing omit the messages
18947 when called from command files.
18949 @value{GDBN} also accepts command input from standard input. In this
18950 mode, normal output goes to standard output and error output goes to
18951 standard error. Errors in a command file supplied on standard input do
18952 not terminate execution of the command file---execution continues with
18956 gdb < cmds > log 2>&1
18959 (The syntax above will vary depending on the shell used.) This example
18960 will execute commands from the file @file{cmds}. All output and errors
18961 would be directed to @file{log}.
18963 Since commands stored on command files tend to be more general than
18964 commands typed interactively, they frequently need to deal with
18965 complicated situations, such as different or unexpected values of
18966 variables and symbols, changes in how the program being debugged is
18967 built, etc. @value{GDBN} provides a set of flow-control commands to
18968 deal with these complexities. Using these commands, you can write
18969 complex scripts that loop over data structures, execute commands
18970 conditionally, etc.
18977 This command allows to include in your script conditionally executed
18978 commands. The @code{if} command takes a single argument, which is an
18979 expression to evaluate. It is followed by a series of commands that
18980 are executed only if the expression is true (its value is nonzero).
18981 There can then optionally be an @code{else} line, followed by a series
18982 of commands that are only executed if the expression was false. The
18983 end of the list is marked by a line containing @code{end}.
18987 This command allows to write loops. Its syntax is similar to
18988 @code{if}: the command takes a single argument, which is an expression
18989 to evaluate, and must be followed by the commands to execute, one per
18990 line, terminated by an @code{end}. These commands are called the
18991 @dfn{body} of the loop. The commands in the body of @code{while} are
18992 executed repeatedly as long as the expression evaluates to true.
18996 This command exits the @code{while} loop in whose body it is included.
18997 Execution of the script continues after that @code{while}s @code{end}
19000 @kindex loop_continue
19001 @item loop_continue
19002 This command skips the execution of the rest of the body of commands
19003 in the @code{while} loop in whose body it is included. Execution
19004 branches to the beginning of the @code{while} loop, where it evaluates
19005 the controlling expression.
19007 @kindex end@r{ (if/else/while commands)}
19009 Terminate the block of commands that are the body of @code{if},
19010 @code{else}, or @code{while} flow-control commands.
19015 @subsection Commands for Controlled Output
19017 During the execution of a command file or a user-defined command, normal
19018 @value{GDBN} output is suppressed; the only output that appears is what is
19019 explicitly printed by the commands in the definition. This section
19020 describes three commands useful for generating exactly the output you
19025 @item echo @var{text}
19026 @c I do not consider backslash-space a standard C escape sequence
19027 @c because it is not in ANSI.
19028 Print @var{text}. Nonprinting characters can be included in
19029 @var{text} using C escape sequences, such as @samp{\n} to print a
19030 newline. @strong{No newline is printed unless you specify one.}
19031 In addition to the standard C escape sequences, a backslash followed
19032 by a space stands for a space. This is useful for displaying a
19033 string with spaces at the beginning or the end, since leading and
19034 trailing spaces are otherwise trimmed from all arguments.
19035 To print @samp{@w{ }and foo =@w{ }}, use the command
19036 @samp{echo \@w{ }and foo = \@w{ }}.
19038 A backslash at the end of @var{text} can be used, as in C, to continue
19039 the command onto subsequent lines. For example,
19042 echo This is some text\n\
19043 which is continued\n\
19044 onto several lines.\n
19047 produces the same output as
19050 echo This is some text\n
19051 echo which is continued\n
19052 echo onto several lines.\n
19056 @item output @var{expression}
19057 Print the value of @var{expression} and nothing but that value: no
19058 newlines, no @samp{$@var{nn} = }. The value is not entered in the
19059 value history either. @xref{Expressions, ,Expressions}, for more information
19062 @item output/@var{fmt} @var{expression}
19063 Print the value of @var{expression} in format @var{fmt}. You can use
19064 the same formats as for @code{print}. @xref{Output Formats,,Output
19065 Formats}, for more information.
19068 @item printf @var{template}, @var{expressions}@dots{}
19069 Print the values of one or more @var{expressions} under the control of
19070 the string @var{template}. To print several values, make
19071 @var{expressions} be a comma-separated list of individual expressions,
19072 which may be either numbers or pointers. Their values are printed as
19073 specified by @var{template}, exactly as a C program would do by
19074 executing the code below:
19077 printf (@var{template}, @var{expressions}@dots{});
19080 As in @code{C} @code{printf}, ordinary characters in @var{template}
19081 are printed verbatim, while @dfn{conversion specification} introduced
19082 by the @samp{%} character cause subsequent @var{expressions} to be
19083 evaluated, their values converted and formatted according to type and
19084 style information encoded in the conversion specifications, and then
19087 For example, you can print two values in hex like this:
19090 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
19093 @code{printf} supports all the standard @code{C} conversion
19094 specifications, including the flags and modifiers between the @samp{%}
19095 character and the conversion letter, with the following exceptions:
19099 The argument-ordering modifiers, such as @samp{2$}, are not supported.
19102 The modifier @samp{*} is not supported for specifying precision or
19106 The @samp{'} flag (for separation of digits into groups according to
19107 @code{LC_NUMERIC'}) is not supported.
19110 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
19114 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
19117 The conversion letters @samp{a} and @samp{A} are not supported.
19121 Note that the @samp{ll} type modifier is supported only if the
19122 underlying @code{C} implementation used to build @value{GDBN} supports
19123 the @code{long long int} type, and the @samp{L} type modifier is
19124 supported only if @code{long double} type is available.
19126 As in @code{C}, @code{printf} supports simple backslash-escape
19127 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
19128 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
19129 single character. Octal and hexadecimal escape sequences are not
19132 Additionally, @code{printf} supports conversion specifications for DFP
19133 (@dfn{Decimal Floating Point}) types using the following length modifiers
19134 together with a floating point specifier.
19139 @samp{H} for printing @code{Decimal32} types.
19142 @samp{D} for printing @code{Decimal64} types.
19145 @samp{DD} for printing @code{Decimal128} types.
19148 If the underlying @code{C} implementation used to build @value{GDBN} has
19149 support for the three length modifiers for DFP types, other modifiers
19150 such as width and precision will also be available for @value{GDBN} to use.
19152 In case there is no such @code{C} support, no additional modifiers will be
19153 available and the value will be printed in the standard way.
19155 Here's an example of printing DFP types using the above conversion letters:
19157 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
19163 @section Scripting @value{GDBN} using Python
19164 @cindex python scripting
19165 @cindex scripting with python
19167 You can script @value{GDBN} using the @uref{http://www.python.org/,
19168 Python programming language}. This feature is available only if
19169 @value{GDBN} was configured using @option{--with-python}.
19172 * Python Commands:: Accessing Python from @value{GDBN}.
19173 * Python API:: Accessing @value{GDBN} from Python.
19176 @node Python Commands
19177 @subsection Python Commands
19178 @cindex python commands
19179 @cindex commands to access python
19181 @value{GDBN} provides one command for accessing the Python interpreter,
19182 and one related setting:
19186 @item python @r{[}@var{code}@r{]}
19187 The @code{python} command can be used to evaluate Python code.
19189 If given an argument, the @code{python} command will evaluate the
19190 argument as a Python command. For example:
19193 (@value{GDBP}) python print 23
19197 If you do not provide an argument to @code{python}, it will act as a
19198 multi-line command, like @code{define}. In this case, the Python
19199 script is made up of subsequent command lines, given after the
19200 @code{python} command. This command list is terminated using a line
19201 containing @code{end}. For example:
19204 (@value{GDBP}) python
19206 End with a line saying just "end".
19212 @kindex maint set python print-stack
19213 @item maint set python print-stack
19214 By default, @value{GDBN} will print a stack trace when an error occurs
19215 in a Python script. This can be controlled using @code{maint set
19216 python print-stack}: if @code{on}, the default, then Python stack
19217 printing is enabled; if @code{off}, then Python stack printing is
19222 @subsection Python API
19224 @cindex programming in python
19226 @cindex python stdout
19227 @cindex python pagination
19228 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
19229 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
19230 A Python program which outputs to one of these streams may have its
19231 output interrupted by the user (@pxref{Screen Size}). In this
19232 situation, a Python @code{KeyboardInterrupt} exception is thrown.
19235 * Basic Python:: Basic Python Functions.
19236 * Exception Handling::
19237 * Auto-loading:: Automatically loading Python code.
19238 * Values From Inferior::
19239 * Types In Python:: Python representation of types.
19240 * Pretty Printing:: Pretty-printing values.
19241 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
19242 * Commands In Python:: Implementing new commands in Python.
19243 * Functions In Python:: Writing new convenience functions.
19244 * Objfiles In Python:: Object files.
19245 * Frames In Python:: Acessing inferior stack frames from Python.
19249 @subsubsection Basic Python
19251 @cindex python functions
19252 @cindex python module
19254 @value{GDBN} introduces a new Python module, named @code{gdb}. All
19255 methods and classes added by @value{GDBN} are placed in this module.
19256 @value{GDBN} automatically @code{import}s the @code{gdb} module for
19257 use in all scripts evaluated by the @code{python} command.
19259 @findex gdb.execute
19260 @defun execute command [from_tty]
19261 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
19262 If a GDB exception happens while @var{command} runs, it is
19263 translated as described in @ref{Exception Handling,,Exception Handling}.
19264 If no exceptions occur, this function returns @code{None}.
19266 @var{from_tty} specifies whether @value{GDBN} ought to consider this
19267 command as having originated from the user invoking it interactively.
19268 It must be a boolean value. If omitted, it defaults to @code{False}.
19271 @findex gdb.parameter
19272 @defun parameter parameter
19273 Return the value of a @value{GDBN} parameter. @var{parameter} is a
19274 string naming the parameter to look up; @var{parameter} may contain
19275 spaces if the parameter has a multi-part name. For example,
19276 @samp{print object} is a valid parameter name.
19278 If the named parameter does not exist, this function throws a
19279 @code{RuntimeError}. Otherwise, the parameter's value is converted to
19280 a Python value of the appropriate type, and returned.
19283 @findex gdb.history
19284 @defun history number
19285 Return a value from @value{GDBN}'s value history (@pxref{Value
19286 History}). @var{number} indicates which history element to return.
19287 If @var{number} is negative, then @value{GDBN} will take its absolute value
19288 and count backward from the last element (i.e., the most recent element) to
19289 find the value to return. If @var{number} is zero, then @value{GDBN} will
19290 return the most recent element. If the element specified by @var{number}
19291 doesn't exist in the value history, a @code{RuntimeError} exception will be
19294 If no exception is raised, the return value is always an instance of
19295 @code{gdb.Value} (@pxref{Values From Inferior}).
19299 @defun write string
19300 Print a string to @value{GDBN}'s paginated standard output stream.
19301 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
19302 call this function.
19307 Flush @value{GDBN}'s paginated standard output stream. Flushing
19308 @code{sys.stdout} or @code{sys.stderr} will automatically call this
19312 @node Exception Handling
19313 @subsubsection Exception Handling
19314 @cindex python exceptions
19315 @cindex exceptions, python
19317 When executing the @code{python} command, Python exceptions
19318 uncaught within the Python code are translated to calls to
19319 @value{GDBN} error-reporting mechanism. If the command that called
19320 @code{python} does not handle the error, @value{GDBN} will
19321 terminate it and print an error message containing the Python
19322 exception name, the associated value, and the Python call stack
19323 backtrace at the point where the exception was raised. Example:
19326 (@value{GDBP}) python print foo
19327 Traceback (most recent call last):
19328 File "<string>", line 1, in <module>
19329 NameError: name 'foo' is not defined
19332 @value{GDBN} errors that happen in @value{GDBN} commands invoked by Python
19333 code are converted to Python @code{RuntimeError} exceptions. User
19334 interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
19335 prompt) is translated to a Python @code{KeyboardInterrupt}
19336 exception. If you catch these exceptions in your Python code, your
19337 exception handler will see @code{RuntimeError} or
19338 @code{KeyboardInterrupt} as the exception type, the @value{GDBN} error
19339 message as its value, and the Python call stack backtrace at the
19340 Python statement closest to where the @value{GDBN} error occured as the
19344 @subsubsection Auto-loading
19345 @cindex auto-loading, Python
19347 When a new object file is read (for example, due to the @code{file}
19348 command, or because the inferior has loaded a shared library),
19349 @value{GDBN} will look for a file named @file{@var{objfile}-gdb.py},
19350 where @var{objfile} is the object file's real name, formed by ensuring
19351 that the file name is absolute, following all symlinks, and resolving
19352 @code{.} and @code{..} components. If this file exists and is
19353 readable, @value{GDBN} will evaluate it as a Python script.
19355 If this file does not exist, and if the parameter
19356 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
19357 then @value{GDBN} will use the file named
19358 @file{@var{debug-file-directory}/@var{real-name}}, where
19359 @var{real-name} is the object file's real name, as described above.
19361 Finally, if this file does not exist, then @value{GDBN} will look for
19362 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
19363 @var{data-directory} is @value{GDBN}'s data directory (available via
19364 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
19365 is the object file's real name, as described above.
19367 When reading an auto-loaded file, @value{GDBN} sets the ``current
19368 objfile''. This is available via the @code{gdb.current_objfile}
19369 function (@pxref{Objfiles In Python}). This can be useful for
19370 registering objfile-specific pretty-printers.
19372 The auto-loading feature is useful for supplying application-specific
19373 debugging commands and scripts. You can enable or disable this
19374 feature, and view its current state.
19377 @kindex maint set python auto-load
19378 @item maint set python auto-load [yes|no]
19379 Enable or disable the Python auto-loading feature.
19381 @kindex show python auto-load
19382 @item show python auto-load
19383 Show whether Python auto-loading is enabled or disabled.
19386 @value{GDBN} does not track which files it has already auto-loaded.
19387 So, your @samp{-gdb.py} file should take care to ensure that it may be
19388 evaluated multiple times without error.
19390 @node Values From Inferior
19391 @subsubsection Values From Inferior
19392 @cindex values from inferior, with Python
19393 @cindex python, working with values from inferior
19395 @cindex @code{gdb.Value}
19396 @value{GDBN} provides values it obtains from the inferior program in
19397 an object of type @code{gdb.Value}. @value{GDBN} uses this object
19398 for its internal bookkeeping of the inferior's values, and for
19399 fetching values when necessary.
19401 Inferior values that are simple scalars can be used directly in
19402 Python expressions that are valid for the value's data type. Here's
19403 an example for an integer or floating-point value @code{some_val}:
19410 As result of this, @code{bar} will also be a @code{gdb.Value} object
19411 whose values are of the same type as those of @code{some_val}.
19413 Inferior values that are structures or instances of some class can
19414 be accessed using the Python @dfn{dictionary syntax}. For example, if
19415 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
19416 can access its @code{foo} element with:
19419 bar = some_val['foo']
19422 Again, @code{bar} will also be a @code{gdb.Value} object.
19424 The following attributes are provided:
19427 @defivar Value address
19428 If this object is addressable, this read-only attribute holds a
19429 @code{gdb.Value} object representing the address. Otherwise,
19430 this attribute holds @code{None}.
19433 @cindex optimized out value in Python
19434 @defivar Value is_optimized_out
19435 This read-only boolean attribute is true if the compiler optimized out
19436 this value, thus it is not available for fetching from the inferior.
19439 @defivar Value type
19440 The type of this @code{gdb.Value}. The value of this attribute is a
19441 @code{gdb.Type} object.
19445 The following methods are provided:
19448 @defmethod Value cast type
19449 Return a new instance of @code{gdb.Value} that is the result of
19450 casting this instance to the type described by @var{type}, which must
19451 be a @code{gdb.Type} object. If the cast cannot be performed for some
19452 reason, this method throws an exception.
19455 @defmethod Value dereference
19456 For pointer data types, this method returns a new @code{gdb.Value} object
19457 whose contents is the object pointed to by the pointer. For example, if
19458 @code{foo} is a C pointer to an @code{int}, declared in your C program as
19465 then you can use the corresponding @code{gdb.Value} to access what
19466 @code{foo} points to like this:
19469 bar = foo.dereference ()
19472 The result @code{bar} will be a @code{gdb.Value} object holding the
19473 value pointed to by @code{foo}.
19476 @defmethod Value string @r{[}encoding@r{]} @r{[}errors@r{]} @r{[}length@r{]}
19477 If this @code{gdb.Value} represents a string, then this method
19478 converts the contents to a Python string. Otherwise, this method will
19479 throw an exception.
19481 Strings are recognized in a language-specific way; whether a given
19482 @code{gdb.Value} represents a string is determined by the current
19485 For C-like languages, a value is a string if it is a pointer to or an
19486 array of characters or ints. The string is assumed to be terminated
19487 by a zero of the appropriate width. However if the optional length
19488 argument is given, the string will be converted to that given length,
19489 ignoring any embedded zeros that the string may contain.
19491 If the optional @var{encoding} argument is given, it must be a string
19492 naming the encoding of the string in the @code{gdb.Value}, such as
19493 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
19494 the same encodings as the corresponding argument to Python's
19495 @code{string.decode} method, and the Python codec machinery will be used
19496 to convert the string. If @var{encoding} is not given, or if
19497 @var{encoding} is the empty string, then either the @code{target-charset}
19498 (@pxref{Character Sets}) will be used, or a language-specific encoding
19499 will be used, if the current language is able to supply one.
19501 The optional @var{errors} argument is the same as the corresponding
19502 argument to Python's @code{string.decode} method.
19504 If the optional @var{length} argument is given, the string will be
19505 fetched and converted to the given length.
19509 @node Types In Python
19510 @subsubsection Types In Python
19511 @cindex types in Python
19512 @cindex Python, working with types
19515 @value{GDBN} represents types from the inferior using the class
19518 The following type-related functions are available in the @code{gdb}
19521 @findex gdb.lookup_type
19522 @defun lookup_type name [block]
19523 This function looks up a type by name. @var{name} is the name of the
19524 type to look up. It must be a string.
19526 Ordinarily, this function will return an instance of @code{gdb.Type}.
19527 If the named type cannot be found, it will throw an exception.
19530 An instance of @code{Type} has the following attributes:
19534 The type code for this type. The type code will be one of the
19535 @code{TYPE_CODE_} constants defined below.
19538 @defivar Type sizeof
19539 The size of this type, in target @code{char} units. Usually, a
19540 target's @code{char} type will be an 8-bit byte. However, on some
19541 unusual platforms, this type may have a different size.
19545 The tag name for this type. The tag name is the name after
19546 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
19547 languages have this concept. If this type has no tag name, then
19548 @code{None} is returned.
19552 The following methods are provided:
19555 @defmethod Type fields
19556 For structure and union types, this method returns the fields. Range
19557 types have two fields, the minimum and maximum values. Enum types
19558 have one field per enum constant. Function and method types have one
19559 field per parameter. The base types of C@t{++} classes are also
19560 represented as fields. If the type has no fields, or does not fit
19561 into one of these categories, an empty sequence will be returned.
19563 Each field is an object, with some pre-defined attributes:
19566 This attribute is not available for @code{static} fields (as in
19567 C@t{++} or Java). For non-@code{static} fields, the value is the bit
19568 position of the field.
19571 The name of the field, or @code{None} for anonymous fields.
19574 This is @code{True} if the field is artificial, usually meaning that
19575 it was provided by the compiler and not the user. This attribute is
19576 always provided, and is @code{False} if the field is not artificial.
19579 If the field is packed, or is a bitfield, then this will have a
19580 non-zero value, which is the size of the field in bits. Otherwise,
19581 this will be zero; in this case the field's size is given by its type.
19584 The type of the field. This is usually an instance of @code{Type},
19585 but it can be @code{None} in some situations.
19589 @defmethod Type const
19590 Return a new @code{gdb.Type} object which represents a
19591 @code{const}-qualified variant of this type.
19594 @defmethod Type volatile
19595 Return a new @code{gdb.Type} object which represents a
19596 @code{volatile}-qualified variant of this type.
19599 @defmethod Type unqualified
19600 Return a new @code{gdb.Type} object which represents an unqualified
19601 variant of this type. That is, the result is neither @code{const} nor
19605 @defmethod Type reference
19606 Return a new @code{gdb.Type} object which represents a reference to this
19610 @defmethod Type strip_typedefs
19611 Return a new @code{gdb.Type} that represents the real type,
19612 after removing all layers of typedefs.
19615 @defmethod Type target
19616 Return a new @code{gdb.Type} object which represents the target type
19619 For a pointer type, the target type is the type of the pointed-to
19620 object. For an array type (meaning C-like arrays), the target type is
19621 the type of the elements of the array. For a function or method type,
19622 the target type is the type of the return value. For a complex type,
19623 the target type is the type of the elements. For a typedef, the
19624 target type is the aliased type.
19626 If the type does not have a target, this method will throw an
19630 @defmethod Type template_argument n
19631 If this @code{gdb.Type} is an instantiation of a template, this will
19632 return a new @code{gdb.Type} which represents the type of the
19633 @var{n}th template argument.
19635 If this @code{gdb.Type} is not a template type, this will throw an
19636 exception. Ordinarily, only C@t{++} code will have template types.
19638 @var{name} is searched for globally.
19643 Each type has a code, which indicates what category this type falls
19644 into. The available type categories are represented by constants
19645 defined in the @code{gdb} module:
19648 @findex TYPE_CODE_PTR
19649 @findex gdb.TYPE_CODE_PTR
19650 @item TYPE_CODE_PTR
19651 The type is a pointer.
19653 @findex TYPE_CODE_ARRAY
19654 @findex gdb.TYPE_CODE_ARRAY
19655 @item TYPE_CODE_ARRAY
19656 The type is an array.
19658 @findex TYPE_CODE_STRUCT
19659 @findex gdb.TYPE_CODE_STRUCT
19660 @item TYPE_CODE_STRUCT
19661 The type is a structure.
19663 @findex TYPE_CODE_UNION
19664 @findex gdb.TYPE_CODE_UNION
19665 @item TYPE_CODE_UNION
19666 The type is a union.
19668 @findex TYPE_CODE_ENUM
19669 @findex gdb.TYPE_CODE_ENUM
19670 @item TYPE_CODE_ENUM
19671 The type is an enum.
19673 @findex TYPE_CODE_FLAGS
19674 @findex gdb.TYPE_CODE_FLAGS
19675 @item TYPE_CODE_FLAGS
19676 A bit flags type, used for things such as status registers.
19678 @findex TYPE_CODE_FUNC
19679 @findex gdb.TYPE_CODE_FUNC
19680 @item TYPE_CODE_FUNC
19681 The type is a function.
19683 @findex TYPE_CODE_INT
19684 @findex gdb.TYPE_CODE_INT
19685 @item TYPE_CODE_INT
19686 The type is an integer type.
19688 @findex TYPE_CODE_FLT
19689 @findex gdb.TYPE_CODE_FLT
19690 @item TYPE_CODE_FLT
19691 A floating point type.
19693 @findex TYPE_CODE_VOID
19694 @findex gdb.TYPE_CODE_VOID
19695 @item TYPE_CODE_VOID
19696 The special type @code{void}.
19698 @findex TYPE_CODE_SET
19699 @findex gdb.TYPE_CODE_SET
19700 @item TYPE_CODE_SET
19703 @findex TYPE_CODE_RANGE
19704 @findex gdb.TYPE_CODE_RANGE
19705 @item TYPE_CODE_RANGE
19706 A range type, that is, an integer type with bounds.
19708 @findex TYPE_CODE_STRING
19709 @findex gdb.TYPE_CODE_STRING
19710 @item TYPE_CODE_STRING
19711 A string type. Note that this is only used for certain languages with
19712 language-defined string types; C strings are not represented this way.
19714 @findex TYPE_CODE_BITSTRING
19715 @findex gdb.TYPE_CODE_BITSTRING
19716 @item TYPE_CODE_BITSTRING
19719 @findex TYPE_CODE_ERROR
19720 @findex gdb.TYPE_CODE_ERROR
19721 @item TYPE_CODE_ERROR
19722 An unknown or erroneous type.
19724 @findex TYPE_CODE_METHOD
19725 @findex gdb.TYPE_CODE_METHOD
19726 @item TYPE_CODE_METHOD
19727 A method type, as found in C@t{++} or Java.
19729 @findex TYPE_CODE_METHODPTR
19730 @findex gdb.TYPE_CODE_METHODPTR
19731 @item TYPE_CODE_METHODPTR
19732 A pointer-to-member-function.
19734 @findex TYPE_CODE_MEMBERPTR
19735 @findex gdb.TYPE_CODE_MEMBERPTR
19736 @item TYPE_CODE_MEMBERPTR
19737 A pointer-to-member.
19739 @findex TYPE_CODE_REF
19740 @findex gdb.TYPE_CODE_REF
19741 @item TYPE_CODE_REF
19744 @findex TYPE_CODE_CHAR
19745 @findex gdb.TYPE_CODE_CHAR
19746 @item TYPE_CODE_CHAR
19749 @findex TYPE_CODE_BOOL
19750 @findex gdb.TYPE_CODE_BOOL
19751 @item TYPE_CODE_BOOL
19754 @findex TYPE_CODE_COMPLEX
19755 @findex gdb.TYPE_CODE_COMPLEX
19756 @item TYPE_CODE_COMPLEX
19757 A complex float type.
19759 @findex TYPE_CODE_TYPEDEF
19760 @findex gdb.TYPE_CODE_TYPEDEF
19761 @item TYPE_CODE_TYPEDEF
19762 A typedef to some other type.
19764 @findex TYPE_CODE_NAMESPACE
19765 @findex gdb.TYPE_CODE_NAMESPACE
19766 @item TYPE_CODE_NAMESPACE
19767 A C@t{++} namespace.
19769 @findex TYPE_CODE_DECFLOAT
19770 @findex gdb.TYPE_CODE_DECFLOAT
19771 @item TYPE_CODE_DECFLOAT
19772 A decimal floating point type.
19774 @findex TYPE_CODE_INTERNAL_FUNCTION
19775 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
19776 @item TYPE_CODE_INTERNAL_FUNCTION
19777 A function internal to @value{GDBN}. This is the type used to represent
19778 convenience functions.
19781 @node Pretty Printing
19782 @subsubsection Pretty Printing
19784 @value{GDBN} provides a mechanism to allow pretty-printing of values
19785 using Python code. The pretty-printer API allows application-specific
19786 code to greatly simplify the display of complex objects. This
19787 mechanism works for both MI and the CLI.
19789 For example, here is how a C@t{++} @code{std::string} looks without a
19793 (@value{GDBP}) print s
19795 static npos = 4294967295,
19797 <std::allocator<char>> = @{
19798 <__gnu_cxx::new_allocator<char>> = @{<No data fields>@}, <No data fields>@},
19799 members of std::basic_string<char, std::char_traits<char>, std::allocator<char> >::_Alloc_hider:
19800 _M_p = 0x804a014 "abcd"
19805 After a pretty-printer for @code{std::string} has been installed, only
19806 the contents are printed:
19809 (@value{GDBP}) print s
19813 A pretty-printer is just an object that holds a value and implements a
19814 specific interface, defined here.
19816 @defop Operation {pretty printer} children (self)
19817 @value{GDBN} will call this method on a pretty-printer to compute the
19818 children of the pretty-printer's value.
19820 This method must return an object conforming to the Python iterator
19821 protocol. Each item returned by the iterator must be a tuple holding
19822 two elements. The first element is the ``name'' of the child; the
19823 second element is the child's value. The value can be any Python
19824 object which is convertible to a @value{GDBN} value.
19826 This method is optional. If it does not exist, @value{GDBN} will act
19827 as though the value has no children.
19830 @defop Operation {pretty printer} display_hint (self)
19831 The CLI may call this method and use its result to change the
19832 formatting of a value. The result will also be supplied to an MI
19833 consumer as a @samp{displayhint} attribute of the variable being
19836 This method is optional. If it does exist, this method must return a
19839 Some display hints are predefined by @value{GDBN}:
19843 Indicate that the object being printed is ``array-like''. The CLI
19844 uses this to respect parameters such as @code{set print elements} and
19845 @code{set print array}.
19848 Indicate that the object being printed is ``map-like'', and that the
19849 children of this value can be assumed to alternate between keys and
19853 Indicate that the object being printed is ``string-like''. If the
19854 printer's @code{to_string} method returns a Python string of some
19855 kind, then @value{GDBN} will call its internal language-specific
19856 string-printing function to format the string. For the CLI this means
19857 adding quotation marks, possibly escaping some characters, respecting
19858 @code{set print elements}, and the like.
19862 @defop Operation {pretty printer} to_string (self)
19863 @value{GDBN} will call this method to display the string
19864 representation of the value passed to the object's constructor.
19866 When printing from the CLI, if the @code{to_string} method exists,
19867 then @value{GDBN} will prepend its result to the values returned by
19868 @code{children}. Exactly how this formatting is done is dependent on
19869 the display hint, and may change as more hints are added. Also,
19870 depending on the print settings (@pxref{Print Settings}), the CLI may
19871 print just the result of @code{to_string} in a stack trace, omitting
19872 the result of @code{children}.
19874 If this method returns a string, it is printed verbatim.
19876 Otherwise, if this method returns an instance of @code{gdb.Value},
19877 then @value{GDBN} prints this value. This may result in a call to
19878 another pretty-printer.
19880 If instead the method returns a Python value which is convertible to a
19881 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
19882 the resulting value. Again, this may result in a call to another
19883 pretty-printer. Python scalars (integers, floats, and booleans) and
19884 strings are convertible to @code{gdb.Value}; other types are not.
19886 If the result is not one of these types, an exception is raised.
19889 @node Selecting Pretty-Printers
19890 @subsubsection Selecting Pretty-Printers
19892 The Python list @code{gdb.pretty_printers} contains an array of
19893 functions that have been registered via addition as a pretty-printer.
19894 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
19897 A function on one of these lists is passed a single @code{gdb.Value}
19898 argument and should return a pretty-printer object conforming to the
19899 interface definition above (@pxref{Pretty Printing}). If a function
19900 cannot create a pretty-printer for the value, it should return
19903 @value{GDBN} first checks the @code{pretty_printers} attribute of each
19904 @code{gdb.Objfile} and iteratively calls each function in the list for
19905 that @code{gdb.Objfile} until it receives a pretty-printer object.
19906 After these lists have been exhausted, it tries the global
19907 @code{gdb.pretty-printers} list, again calling each function until an
19908 object is returned.
19910 The order in which the objfiles are searched is not specified. For a
19911 given list, functions are always invoked from the head of the list,
19912 and iterated over sequentially until the end of the list, or a printer
19913 object is returned.
19915 Here is an example showing how a @code{std::string} printer might be
19919 class StdStringPrinter:
19920 "Print a std::string"
19922 def __init__ (self, val):
19925 def to_string (self):
19926 return self.val['_M_dataplus']['_M_p']
19928 def display_hint (self):
19932 And here is an example showing how a lookup function for the printer
19933 example above might be written.
19936 def str_lookup_function (val):
19938 lookup_tag = val.type.tag
19939 regex = re.compile ("^std::basic_string<char,.*>$")
19940 if lookup_tag == None:
19942 if regex.match (lookup_tag):
19943 return StdStringPrinter (val)
19948 The example lookup function extracts the value's type, and attempts to
19949 match it to a type that it can pretty-print. If it is a type the
19950 printer can pretty-print, it will return a printer object. If not, it
19951 returns @code{None}.
19953 We recommend that you put your core pretty-printers into a Python
19954 package. If your pretty-printers are for use with a library, we
19955 further recommend embedding a version number into the package name.
19956 This practice will enable @value{GDBN} to load multiple versions of
19957 your pretty-printers at the same time, because they will have
19960 You should write auto-loaded code (@pxref{Auto-loading}) such that it
19961 can be evaluated multiple times without changing its meaning. An
19962 ideal auto-load file will consist solely of @code{import}s of your
19963 printer modules, followed by a call to a register pretty-printers with
19964 the current objfile.
19966 Taken as a whole, this approach will scale nicely to multiple
19967 inferiors, each potentially using a different library version.
19968 Embedding a version number in the Python package name will ensure that
19969 @value{GDBN} is able to load both sets of printers simultaneously.
19970 Then, because the search for pretty-printers is done by objfile, and
19971 because your auto-loaded code took care to register your library's
19972 printers with a specific objfile, @value{GDBN} will find the correct
19973 printers for the specific version of the library used by each
19976 To continue the @code{std::string} example (@pxref{Pretty Printing}),
19977 this code might appear in @code{gdb.libstdcxx.v6}:
19980 def register_printers (objfile):
19981 objfile.pretty_printers.add (str_lookup_function)
19985 And then the corresponding contents of the auto-load file would be:
19988 import gdb.libstdcxx.v6
19989 gdb.libstdcxx.v6.register_printers (gdb.current_objfile ())
19992 @node Commands In Python
19993 @subsubsection Commands In Python
19995 @cindex commands in python
19996 @cindex python commands
19997 You can implement new @value{GDBN} CLI commands in Python. A CLI
19998 command is implemented using an instance of the @code{gdb.Command}
19999 class, most commonly using a subclass.
20001 @defmethod Command __init__ name @var{command_class} @r{[}@var{completer_class}@r{]} @r{[}@var{prefix}@r{]}
20002 The object initializer for @code{Command} registers the new command
20003 with @value{GDBN}. This initializer is normally invoked from the
20004 subclass' own @code{__init__} method.
20006 @var{name} is the name of the command. If @var{name} consists of
20007 multiple words, then the initial words are looked for as prefix
20008 commands. In this case, if one of the prefix commands does not exist,
20009 an exception is raised.
20011 There is no support for multi-line commands.
20013 @var{command_class} should be one of the @samp{COMMAND_} constants
20014 defined below. This argument tells @value{GDBN} how to categorize the
20015 new command in the help system.
20017 @var{completer_class} is an optional argument. If given, it should be
20018 one of the @samp{COMPLETE_} constants defined below. This argument
20019 tells @value{GDBN} how to perform completion for this command. If not
20020 given, @value{GDBN} will attempt to complete using the object's
20021 @code{complete} method (see below); if no such method is found, an
20022 error will occur when completion is attempted.
20024 @var{prefix} is an optional argument. If @code{True}, then the new
20025 command is a prefix command; sub-commands of this command may be
20028 The help text for the new command is taken from the Python
20029 documentation string for the command's class, if there is one. If no
20030 documentation string is provided, the default value ``This command is
20031 not documented.'' is used.
20034 @cindex don't repeat Python command
20035 @defmethod Command dont_repeat
20036 By default, a @value{GDBN} command is repeated when the user enters a
20037 blank line at the command prompt. A command can suppress this
20038 behavior by invoking the @code{dont_repeat} method. This is similar
20039 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
20042 @defmethod Command invoke argument from_tty
20043 This method is called by @value{GDBN} when this command is invoked.
20045 @var{argument} is a string. It is the argument to the command, after
20046 leading and trailing whitespace has been stripped.
20048 @var{from_tty} is a boolean argument. When true, this means that the
20049 command was entered by the user at the terminal; when false it means
20050 that the command came from elsewhere.
20052 If this method throws an exception, it is turned into a @value{GDBN}
20053 @code{error} call. Otherwise, the return value is ignored.
20056 @cindex completion of Python commands
20057 @defmethod Command complete text word
20058 This method is called by @value{GDBN} when the user attempts
20059 completion on this command. All forms of completion are handled by
20060 this method, that is, the @key{TAB} and @key{M-?} key bindings
20061 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
20064 The arguments @var{text} and @var{word} are both strings. @var{text}
20065 holds the complete command line up to the cursor's location.
20066 @var{word} holds the last word of the command line; this is computed
20067 using a word-breaking heuristic.
20069 The @code{complete} method can return several values:
20072 If the return value is a sequence, the contents of the sequence are
20073 used as the completions. It is up to @code{complete} to ensure that the
20074 contents actually do complete the word. A zero-length sequence is
20075 allowed, it means that there were no completions available. Only
20076 string elements of the sequence are used; other elements in the
20077 sequence are ignored.
20080 If the return value is one of the @samp{COMPLETE_} constants defined
20081 below, then the corresponding @value{GDBN}-internal completion
20082 function is invoked, and its result is used.
20085 All other results are treated as though there were no available
20090 When a new command is registered, it must be declared as a member of
20091 some general class of commands. This is used to classify top-level
20092 commands in the on-line help system; note that prefix commands are not
20093 listed under their own category but rather that of their top-level
20094 command. The available classifications are represented by constants
20095 defined in the @code{gdb} module:
20098 @findex COMMAND_NONE
20099 @findex gdb.COMMAND_NONE
20101 The command does not belong to any particular class. A command in
20102 this category will not be displayed in any of the help categories.
20104 @findex COMMAND_RUNNING
20105 @findex gdb.COMMAND_RUNNING
20106 @item COMMAND_RUNNING
20107 The command is related to running the inferior. For example,
20108 @code{start}, @code{step}, and @code{continue} are in this category.
20109 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
20110 commands in this category.
20112 @findex COMMAND_DATA
20113 @findex gdb.COMMAND_DATA
20115 The command is related to data or variables. For example,
20116 @code{call}, @code{find}, and @code{print} are in this category. Type
20117 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
20120 @findex COMMAND_STACK
20121 @findex gdb.COMMAND_STACK
20122 @item COMMAND_STACK
20123 The command has to do with manipulation of the stack. For example,
20124 @code{backtrace}, @code{frame}, and @code{return} are in this
20125 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
20126 list of commands in this category.
20128 @findex COMMAND_FILES
20129 @findex gdb.COMMAND_FILES
20130 @item COMMAND_FILES
20131 This class is used for file-related commands. For example,
20132 @code{file}, @code{list} and @code{section} are in this category.
20133 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
20134 commands in this category.
20136 @findex COMMAND_SUPPORT
20137 @findex gdb.COMMAND_SUPPORT
20138 @item COMMAND_SUPPORT
20139 This should be used for ``support facilities'', generally meaning
20140 things that are useful to the user when interacting with @value{GDBN},
20141 but not related to the state of the inferior. For example,
20142 @code{help}, @code{make}, and @code{shell} are in this category. Type
20143 @kbd{help support} at the @value{GDBN} prompt to see a list of
20144 commands in this category.
20146 @findex COMMAND_STATUS
20147 @findex gdb.COMMAND_STATUS
20148 @item COMMAND_STATUS
20149 The command is an @samp{info}-related command, that is, related to the
20150 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
20151 and @code{show} are in this category. Type @kbd{help status} at the
20152 @value{GDBN} prompt to see a list of commands in this category.
20154 @findex COMMAND_BREAKPOINTS
20155 @findex gdb.COMMAND_BREAKPOINTS
20156 @item COMMAND_BREAKPOINTS
20157 The command has to do with breakpoints. For example, @code{break},
20158 @code{clear}, and @code{delete} are in this category. Type @kbd{help
20159 breakpoints} at the @value{GDBN} prompt to see a list of commands in
20162 @findex COMMAND_TRACEPOINTS
20163 @findex gdb.COMMAND_TRACEPOINTS
20164 @item COMMAND_TRACEPOINTS
20165 The command has to do with tracepoints. For example, @code{trace},
20166 @code{actions}, and @code{tfind} are in this category. Type
20167 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
20168 commands in this category.
20170 @findex COMMAND_OBSCURE
20171 @findex gdb.COMMAND_OBSCURE
20172 @item COMMAND_OBSCURE
20173 The command is only used in unusual circumstances, or is not of
20174 general interest to users. For example, @code{checkpoint},
20175 @code{fork}, and @code{stop} are in this category. Type @kbd{help
20176 obscure} at the @value{GDBN} prompt to see a list of commands in this
20179 @findex COMMAND_MAINTENANCE
20180 @findex gdb.COMMAND_MAINTENANCE
20181 @item COMMAND_MAINTENANCE
20182 The command is only useful to @value{GDBN} maintainers. The
20183 @code{maintenance} and @code{flushregs} commands are in this category.
20184 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
20185 commands in this category.
20188 A new command can use a predefined completion function, either by
20189 specifying it via an argument at initialization, or by returning it
20190 from the @code{complete} method. These predefined completion
20191 constants are all defined in the @code{gdb} module:
20194 @findex COMPLETE_NONE
20195 @findex gdb.COMPLETE_NONE
20196 @item COMPLETE_NONE
20197 This constant means that no completion should be done.
20199 @findex COMPLETE_FILENAME
20200 @findex gdb.COMPLETE_FILENAME
20201 @item COMPLETE_FILENAME
20202 This constant means that filename completion should be performed.
20204 @findex COMPLETE_LOCATION
20205 @findex gdb.COMPLETE_LOCATION
20206 @item COMPLETE_LOCATION
20207 This constant means that location completion should be done.
20208 @xref{Specify Location}.
20210 @findex COMPLETE_COMMAND
20211 @findex gdb.COMPLETE_COMMAND
20212 @item COMPLETE_COMMAND
20213 This constant means that completion should examine @value{GDBN}
20216 @findex COMPLETE_SYMBOL
20217 @findex gdb.COMPLETE_SYMBOL
20218 @item COMPLETE_SYMBOL
20219 This constant means that completion should be done using symbol names
20223 The following code snippet shows how a trivial CLI command can be
20224 implemented in Python:
20227 class HelloWorld (gdb.Command):
20228 """Greet the whole world."""
20230 def __init__ (self):
20231 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
20233 def invoke (self, arg, from_tty):
20234 print "Hello, World!"
20239 The last line instantiates the class, and is necessary to trigger the
20240 registration of the command with @value{GDBN}. Depending on how the
20241 Python code is read into @value{GDBN}, you may need to import the
20242 @code{gdb} module explicitly.
20244 @node Functions In Python
20245 @subsubsection Writing new convenience functions
20247 @cindex writing convenience functions
20248 @cindex convenience functions in python
20249 @cindex python convenience functions
20250 @tindex gdb.Function
20252 You can implement new convenience functions (@pxref{Convenience Vars})
20253 in Python. A convenience function is an instance of a subclass of the
20254 class @code{gdb.Function}.
20256 @defmethod Function __init__ name
20257 The initializer for @code{Function} registers the new function with
20258 @value{GDBN}. The argument @var{name} is the name of the function,
20259 a string. The function will be visible to the user as a convenience
20260 variable of type @code{internal function}, whose name is the same as
20261 the given @var{name}.
20263 The documentation for the new function is taken from the documentation
20264 string for the new class.
20267 @defmethod Function invoke @var{*args}
20268 When a convenience function is evaluated, its arguments are converted
20269 to instances of @code{gdb.Value}, and then the function's
20270 @code{invoke} method is called. Note that @value{GDBN} does not
20271 predetermine the arity of convenience functions. Instead, all
20272 available arguments are passed to @code{invoke}, following the
20273 standard Python calling convention. In particular, a convenience
20274 function can have default values for parameters without ill effect.
20276 The return value of this method is used as its value in the enclosing
20277 expression. If an ordinary Python value is returned, it is converted
20278 to a @code{gdb.Value} following the usual rules.
20281 The following code snippet shows how a trivial convenience function can
20282 be implemented in Python:
20285 class Greet (gdb.Function):
20286 """Return string to greet someone.
20287 Takes a name as argument."""
20289 def __init__ (self):
20290 super (Greet, self).__init__ ("greet")
20292 def invoke (self, name):
20293 return "Hello, %s!" % name.string ()
20298 The last line instantiates the class, and is necessary to trigger the
20299 registration of the function with @value{GDBN}. Depending on how the
20300 Python code is read into @value{GDBN}, you may need to import the
20301 @code{gdb} module explicitly.
20303 @node Objfiles In Python
20304 @subsubsection Objfiles In Python
20306 @cindex objfiles in python
20307 @tindex gdb.Objfile
20309 @value{GDBN} loads symbols for an inferior from various
20310 symbol-containing files (@pxref{Files}). These include the primary
20311 executable file, any shared libraries used by the inferior, and any
20312 separate debug info files (@pxref{Separate Debug Files}).
20313 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
20315 The following objfile-related functions are available in the
20318 @findex gdb.current_objfile
20319 @defun current_objfile
20320 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
20321 sets the ``current objfile'' to the corresponding objfile. This
20322 function returns the current objfile. If there is no current objfile,
20323 this function returns @code{None}.
20326 @findex gdb.objfiles
20328 Return a sequence of all the objfiles current known to @value{GDBN}.
20329 @xref{Objfiles In Python}.
20332 Each objfile is represented by an instance of the @code{gdb.Objfile}
20335 @defivar Objfile filename
20336 The file name of the objfile as a string.
20339 @defivar Objfile pretty_printers
20340 The @code{pretty_printers} attribute is a list of functions. It is
20341 used to look up pretty-printers. A @code{Value} is passed to each
20342 function in order; if the function returns @code{None}, then the
20343 search continues. Otherwise, the return value should be an object
20344 which is used to format the value. @xref{Pretty Printing}, for more
20348 @node Frames In Python
20349 @subsubsection Acessing inferior stack frames from Python.
20351 @cindex frames in python
20352 When the debugged program stops, @value{GDBN} is able to analyze its call
20353 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
20354 represents a frame in the stack. A @code{gdb.Frame} object is only valid
20355 while its corresponding frame exists in the inferior's stack. If you try
20356 to use an invalid frame object, @value{GDBN} will throw a @code{RuntimeError}
20359 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
20363 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
20367 The following frame-related functions are available in the @code{gdb} module:
20369 @findex gdb.selected_frame
20370 @defun selected_frame
20371 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
20374 @defun frame_stop_reason_string reason
20375 Return a string explaining the reason why @value{GDBN} stopped unwinding
20376 frames, as expressed by the given @var{reason} code (an integer, see the
20377 @code{unwind_stop_reason} method further down in this section).
20380 A @code{gdb.Frame} object has the following methods:
20383 @defmethod Frame is_valid
20384 Returns true if the @code{gdb.Frame} object is valid, false if not.
20385 A frame object can become invalid if the frame it refers to doesn't
20386 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
20387 an exception if it is invalid at the time the method is called.
20390 @defmethod Frame name
20391 Returns the function name of the frame, or @code{None} if it can't be
20395 @defmethod Frame type
20396 Returns the type of the frame. The value can be one of
20397 @code{gdb.NORMAL_FRAME}, @code{gdb.DUMMY_FRAME}, @code{gdb.SIGTRAMP_FRAME}
20398 or @code{gdb.SENTINEL_FRAME}.
20401 @defmethod Frame unwind_stop_reason
20402 Return an integer representing the reason why it's not possible to find
20403 more frames toward the outermost frame. Use
20404 @code{gdb.frame_stop_reason_string} to convert the value returned by this
20405 function to a string.
20408 @defmethod Frame pc
20409 Returns the frame's resume address.
20412 @defmethod Frame older
20413 Return the frame that called this frame.
20416 @defmethod Frame newer
20417 Return the frame called by this frame.
20420 @defmethod Frame read_var variable
20421 Return the value of the given variable in this frame. @var{variable} must
20427 @chapter Command Interpreters
20428 @cindex command interpreters
20430 @value{GDBN} supports multiple command interpreters, and some command
20431 infrastructure to allow users or user interface writers to switch
20432 between interpreters or run commands in other interpreters.
20434 @value{GDBN} currently supports two command interpreters, the console
20435 interpreter (sometimes called the command-line interpreter or @sc{cli})
20436 and the machine interface interpreter (or @sc{gdb/mi}). This manual
20437 describes both of these interfaces in great detail.
20439 By default, @value{GDBN} will start with the console interpreter.
20440 However, the user may choose to start @value{GDBN} with another
20441 interpreter by specifying the @option{-i} or @option{--interpreter}
20442 startup options. Defined interpreters include:
20446 @cindex console interpreter
20447 The traditional console or command-line interpreter. This is the most often
20448 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
20449 @value{GDBN} will use this interpreter.
20452 @cindex mi interpreter
20453 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
20454 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
20455 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
20459 @cindex mi2 interpreter
20460 The current @sc{gdb/mi} interface.
20463 @cindex mi1 interpreter
20464 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
20468 @cindex invoke another interpreter
20469 The interpreter being used by @value{GDBN} may not be dynamically
20470 switched at runtime. Although possible, this could lead to a very
20471 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
20472 enters the command "interpreter-set console" in a console view,
20473 @value{GDBN} would switch to using the console interpreter, rendering
20474 the IDE inoperable!
20476 @kindex interpreter-exec
20477 Although you may only choose a single interpreter at startup, you may execute
20478 commands in any interpreter from the current interpreter using the appropriate
20479 command. If you are running the console interpreter, simply use the
20480 @code{interpreter-exec} command:
20483 interpreter-exec mi "-data-list-register-names"
20486 @sc{gdb/mi} has a similar command, although it is only available in versions of
20487 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
20490 @chapter @value{GDBN} Text User Interface
20492 @cindex Text User Interface
20495 * TUI Overview:: TUI overview
20496 * TUI Keys:: TUI key bindings
20497 * TUI Single Key Mode:: TUI single key mode
20498 * TUI Commands:: TUI-specific commands
20499 * TUI Configuration:: TUI configuration variables
20502 The @value{GDBN} Text User Interface (TUI) is a terminal
20503 interface which uses the @code{curses} library to show the source
20504 file, the assembly output, the program registers and @value{GDBN}
20505 commands in separate text windows. The TUI mode is supported only
20506 on platforms where a suitable version of the @code{curses} library
20509 @pindex @value{GDBTUI}
20510 The TUI mode is enabled by default when you invoke @value{GDBN} as
20511 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
20512 You can also switch in and out of TUI mode while @value{GDBN} runs by
20513 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
20514 @xref{TUI Keys, ,TUI Key Bindings}.
20517 @section TUI Overview
20519 In TUI mode, @value{GDBN} can display several text windows:
20523 This window is the @value{GDBN} command window with the @value{GDBN}
20524 prompt and the @value{GDBN} output. The @value{GDBN} input is still
20525 managed using readline.
20528 The source window shows the source file of the program. The current
20529 line and active breakpoints are displayed in this window.
20532 The assembly window shows the disassembly output of the program.
20535 This window shows the processor registers. Registers are highlighted
20536 when their values change.
20539 The source and assembly windows show the current program position
20540 by highlighting the current line and marking it with a @samp{>} marker.
20541 Breakpoints are indicated with two markers. The first marker
20542 indicates the breakpoint type:
20546 Breakpoint which was hit at least once.
20549 Breakpoint which was never hit.
20552 Hardware breakpoint which was hit at least once.
20555 Hardware breakpoint which was never hit.
20558 The second marker indicates whether the breakpoint is enabled or not:
20562 Breakpoint is enabled.
20565 Breakpoint is disabled.
20568 The source, assembly and register windows are updated when the current
20569 thread changes, when the frame changes, or when the program counter
20572 These windows are not all visible at the same time. The command
20573 window is always visible. The others can be arranged in several
20584 source and assembly,
20587 source and registers, or
20590 assembly and registers.
20593 A status line above the command window shows the following information:
20597 Indicates the current @value{GDBN} target.
20598 (@pxref{Targets, ,Specifying a Debugging Target}).
20601 Gives the current process or thread number.
20602 When no process is being debugged, this field is set to @code{No process}.
20605 Gives the current function name for the selected frame.
20606 The name is demangled if demangling is turned on (@pxref{Print Settings}).
20607 When there is no symbol corresponding to the current program counter,
20608 the string @code{??} is displayed.
20611 Indicates the current line number for the selected frame.
20612 When the current line number is not known, the string @code{??} is displayed.
20615 Indicates the current program counter address.
20619 @section TUI Key Bindings
20620 @cindex TUI key bindings
20622 The TUI installs several key bindings in the readline keymaps
20623 (@pxref{Command Line Editing}). The following key bindings
20624 are installed for both TUI mode and the @value{GDBN} standard mode.
20633 Enter or leave the TUI mode. When leaving the TUI mode,
20634 the curses window management stops and @value{GDBN} operates using
20635 its standard mode, writing on the terminal directly. When reentering
20636 the TUI mode, control is given back to the curses windows.
20637 The screen is then refreshed.
20641 Use a TUI layout with only one window. The layout will
20642 either be @samp{source} or @samp{assembly}. When the TUI mode
20643 is not active, it will switch to the TUI mode.
20645 Think of this key binding as the Emacs @kbd{C-x 1} binding.
20649 Use a TUI layout with at least two windows. When the current
20650 layout already has two windows, the next layout with two windows is used.
20651 When a new layout is chosen, one window will always be common to the
20652 previous layout and the new one.
20654 Think of it as the Emacs @kbd{C-x 2} binding.
20658 Change the active window. The TUI associates several key bindings
20659 (like scrolling and arrow keys) with the active window. This command
20660 gives the focus to the next TUI window.
20662 Think of it as the Emacs @kbd{C-x o} binding.
20666 Switch in and out of the TUI SingleKey mode that binds single
20667 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
20670 The following key bindings only work in the TUI mode:
20675 Scroll the active window one page up.
20679 Scroll the active window one page down.
20683 Scroll the active window one line up.
20687 Scroll the active window one line down.
20691 Scroll the active window one column left.
20695 Scroll the active window one column right.
20699 Refresh the screen.
20702 Because the arrow keys scroll the active window in the TUI mode, they
20703 are not available for their normal use by readline unless the command
20704 window has the focus. When another window is active, you must use
20705 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
20706 and @kbd{C-f} to control the command window.
20708 @node TUI Single Key Mode
20709 @section TUI Single Key Mode
20710 @cindex TUI single key mode
20712 The TUI also provides a @dfn{SingleKey} mode, which binds several
20713 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
20714 switch into this mode, where the following key bindings are used:
20717 @kindex c @r{(SingleKey TUI key)}
20721 @kindex d @r{(SingleKey TUI key)}
20725 @kindex f @r{(SingleKey TUI key)}
20729 @kindex n @r{(SingleKey TUI key)}
20733 @kindex q @r{(SingleKey TUI key)}
20735 exit the SingleKey mode.
20737 @kindex r @r{(SingleKey TUI key)}
20741 @kindex s @r{(SingleKey TUI key)}
20745 @kindex u @r{(SingleKey TUI key)}
20749 @kindex v @r{(SingleKey TUI key)}
20753 @kindex w @r{(SingleKey TUI key)}
20758 Other keys temporarily switch to the @value{GDBN} command prompt.
20759 The key that was pressed is inserted in the editing buffer so that
20760 it is possible to type most @value{GDBN} commands without interaction
20761 with the TUI SingleKey mode. Once the command is entered the TUI
20762 SingleKey mode is restored. The only way to permanently leave
20763 this mode is by typing @kbd{q} or @kbd{C-x s}.
20767 @section TUI-specific Commands
20768 @cindex TUI commands
20770 The TUI has specific commands to control the text windows.
20771 These commands are always available, even when @value{GDBN} is not in
20772 the TUI mode. When @value{GDBN} is in the standard mode, most
20773 of these commands will automatically switch to the TUI mode.
20778 List and give the size of all displayed windows.
20782 Display the next layout.
20785 Display the previous layout.
20788 Display the source window only.
20791 Display the assembly window only.
20794 Display the source and assembly window.
20797 Display the register window together with the source or assembly window.
20801 Make the next window active for scrolling.
20804 Make the previous window active for scrolling.
20807 Make the source window active for scrolling.
20810 Make the assembly window active for scrolling.
20813 Make the register window active for scrolling.
20816 Make the command window active for scrolling.
20820 Refresh the screen. This is similar to typing @kbd{C-L}.
20822 @item tui reg float
20824 Show the floating point registers in the register window.
20826 @item tui reg general
20827 Show the general registers in the register window.
20830 Show the next register group. The list of register groups as well as
20831 their order is target specific. The predefined register groups are the
20832 following: @code{general}, @code{float}, @code{system}, @code{vector},
20833 @code{all}, @code{save}, @code{restore}.
20835 @item tui reg system
20836 Show the system registers in the register window.
20840 Update the source window and the current execution point.
20842 @item winheight @var{name} +@var{count}
20843 @itemx winheight @var{name} -@var{count}
20845 Change the height of the window @var{name} by @var{count}
20846 lines. Positive counts increase the height, while negative counts
20849 @item tabset @var{nchars}
20851 Set the width of tab stops to be @var{nchars} characters.
20854 @node TUI Configuration
20855 @section TUI Configuration Variables
20856 @cindex TUI configuration variables
20858 Several configuration variables control the appearance of TUI windows.
20861 @item set tui border-kind @var{kind}
20862 @kindex set tui border-kind
20863 Select the border appearance for the source, assembly and register windows.
20864 The possible values are the following:
20867 Use a space character to draw the border.
20870 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
20873 Use the Alternate Character Set to draw the border. The border is
20874 drawn using character line graphics if the terminal supports them.
20877 @item set tui border-mode @var{mode}
20878 @kindex set tui border-mode
20879 @itemx set tui active-border-mode @var{mode}
20880 @kindex set tui active-border-mode
20881 Select the display attributes for the borders of the inactive windows
20882 or the active window. The @var{mode} can be one of the following:
20885 Use normal attributes to display the border.
20891 Use reverse video mode.
20894 Use half bright mode.
20896 @item half-standout
20897 Use half bright and standout mode.
20900 Use extra bright or bold mode.
20902 @item bold-standout
20903 Use extra bright or bold and standout mode.
20908 @chapter Using @value{GDBN} under @sc{gnu} Emacs
20911 @cindex @sc{gnu} Emacs
20912 A special interface allows you to use @sc{gnu} Emacs to view (and
20913 edit) the source files for the program you are debugging with
20916 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
20917 executable file you want to debug as an argument. This command starts
20918 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
20919 created Emacs buffer.
20920 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
20922 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
20927 All ``terminal'' input and output goes through an Emacs buffer, called
20930 This applies both to @value{GDBN} commands and their output, and to the input
20931 and output done by the program you are debugging.
20933 This is useful because it means that you can copy the text of previous
20934 commands and input them again; you can even use parts of the output
20937 All the facilities of Emacs' Shell mode are available for interacting
20938 with your program. In particular, you can send signals the usual
20939 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
20943 @value{GDBN} displays source code through Emacs.
20945 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
20946 source file for that frame and puts an arrow (@samp{=>}) at the
20947 left margin of the current line. Emacs uses a separate buffer for
20948 source display, and splits the screen to show both your @value{GDBN} session
20951 Explicit @value{GDBN} @code{list} or search commands still produce output as
20952 usual, but you probably have no reason to use them from Emacs.
20955 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
20956 a graphical mode, enabled by default, which provides further buffers
20957 that can control the execution and describe the state of your program.
20958 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
20960 If you specify an absolute file name when prompted for the @kbd{M-x
20961 gdb} argument, then Emacs sets your current working directory to where
20962 your program resides. If you only specify the file name, then Emacs
20963 sets your current working directory to to the directory associated
20964 with the previous buffer. In this case, @value{GDBN} may find your
20965 program by searching your environment's @code{PATH} variable, but on
20966 some operating systems it might not find the source. So, although the
20967 @value{GDBN} input and output session proceeds normally, the auxiliary
20968 buffer does not display the current source and line of execution.
20970 The initial working directory of @value{GDBN} is printed on the top
20971 line of the GUD buffer and this serves as a default for the commands
20972 that specify files for @value{GDBN} to operate on. @xref{Files,
20973 ,Commands to Specify Files}.
20975 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
20976 need to call @value{GDBN} by a different name (for example, if you
20977 keep several configurations around, with different names) you can
20978 customize the Emacs variable @code{gud-gdb-command-name} to run the
20981 In the GUD buffer, you can use these special Emacs commands in
20982 addition to the standard Shell mode commands:
20986 Describe the features of Emacs' GUD Mode.
20989 Execute to another source line, like the @value{GDBN} @code{step} command; also
20990 update the display window to show the current file and location.
20993 Execute to next source line in this function, skipping all function
20994 calls, like the @value{GDBN} @code{next} command. Then update the display window
20995 to show the current file and location.
20998 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
20999 display window accordingly.
21002 Execute until exit from the selected stack frame, like the @value{GDBN}
21003 @code{finish} command.
21006 Continue execution of your program, like the @value{GDBN} @code{continue}
21010 Go up the number of frames indicated by the numeric argument
21011 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
21012 like the @value{GDBN} @code{up} command.
21015 Go down the number of frames indicated by the numeric argument, like the
21016 @value{GDBN} @code{down} command.
21019 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
21020 tells @value{GDBN} to set a breakpoint on the source line point is on.
21022 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
21023 separate frame which shows a backtrace when the GUD buffer is current.
21024 Move point to any frame in the stack and type @key{RET} to make it
21025 become the current frame and display the associated source in the
21026 source buffer. Alternatively, click @kbd{Mouse-2} to make the
21027 selected frame become the current one. In graphical mode, the
21028 speedbar displays watch expressions.
21030 If you accidentally delete the source-display buffer, an easy way to get
21031 it back is to type the command @code{f} in the @value{GDBN} buffer, to
21032 request a frame display; when you run under Emacs, this recreates
21033 the source buffer if necessary to show you the context of the current
21036 The source files displayed in Emacs are in ordinary Emacs buffers
21037 which are visiting the source files in the usual way. You can edit
21038 the files with these buffers if you wish; but keep in mind that @value{GDBN}
21039 communicates with Emacs in terms of line numbers. If you add or
21040 delete lines from the text, the line numbers that @value{GDBN} knows cease
21041 to correspond properly with the code.
21043 A more detailed description of Emacs' interaction with @value{GDBN} is
21044 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
21047 @c The following dropped because Epoch is nonstandard. Reactivate
21048 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
21050 @kindex Emacs Epoch environment
21054 Version 18 of @sc{gnu} Emacs has a built-in window system
21055 called the @code{epoch}
21056 environment. Users of this environment can use a new command,
21057 @code{inspect} which performs identically to @code{print} except that
21058 each value is printed in its own window.
21063 @chapter The @sc{gdb/mi} Interface
21065 @unnumberedsec Function and Purpose
21067 @cindex @sc{gdb/mi}, its purpose
21068 @sc{gdb/mi} is a line based machine oriented text interface to
21069 @value{GDBN} and is activated by specifying using the
21070 @option{--interpreter} command line option (@pxref{Mode Options}). It
21071 is specifically intended to support the development of systems which
21072 use the debugger as just one small component of a larger system.
21074 This chapter is a specification of the @sc{gdb/mi} interface. It is written
21075 in the form of a reference manual.
21077 Note that @sc{gdb/mi} is still under construction, so some of the
21078 features described below are incomplete and subject to change
21079 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
21081 @unnumberedsec Notation and Terminology
21083 @cindex notational conventions, for @sc{gdb/mi}
21084 This chapter uses the following notation:
21088 @code{|} separates two alternatives.
21091 @code{[ @var{something} ]} indicates that @var{something} is optional:
21092 it may or may not be given.
21095 @code{( @var{group} )*} means that @var{group} inside the parentheses
21096 may repeat zero or more times.
21099 @code{( @var{group} )+} means that @var{group} inside the parentheses
21100 may repeat one or more times.
21103 @code{"@var{string}"} means a literal @var{string}.
21107 @heading Dependencies
21111 * GDB/MI General Design::
21112 * GDB/MI Command Syntax::
21113 * GDB/MI Compatibility with CLI::
21114 * GDB/MI Development and Front Ends::
21115 * GDB/MI Output Records::
21116 * GDB/MI Simple Examples::
21117 * GDB/MI Command Description Format::
21118 * GDB/MI Breakpoint Commands::
21119 * GDB/MI Program Context::
21120 * GDB/MI Thread Commands::
21121 * GDB/MI Program Execution::
21122 * GDB/MI Stack Manipulation::
21123 * GDB/MI Variable Objects::
21124 * GDB/MI Data Manipulation::
21125 * GDB/MI Tracepoint Commands::
21126 * GDB/MI Symbol Query::
21127 * GDB/MI File Commands::
21129 * GDB/MI Kod Commands::
21130 * GDB/MI Memory Overlay Commands::
21131 * GDB/MI Signal Handling Commands::
21133 * GDB/MI Target Manipulation::
21134 * GDB/MI File Transfer Commands::
21135 * GDB/MI Miscellaneous Commands::
21138 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21139 @node GDB/MI General Design
21140 @section @sc{gdb/mi} General Design
21141 @cindex GDB/MI General Design
21143 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
21144 parts---commands sent to @value{GDBN}, responses to those commands
21145 and notifications. Each command results in exactly one response,
21146 indicating either successful completion of the command, or an error.
21147 For the commands that do not resume the target, the response contains the
21148 requested information. For the commands that resume the target, the
21149 response only indicates whether the target was successfully resumed.
21150 Notifications is the mechanism for reporting changes in the state of the
21151 target, or in @value{GDBN} state, that cannot conveniently be associated with
21152 a command and reported as part of that command response.
21154 The important examples of notifications are:
21158 Exec notifications. These are used to report changes in
21159 target state---when a target is resumed, or stopped. It would not
21160 be feasible to include this information in response of resuming
21161 commands, because one resume commands can result in multiple events in
21162 different threads. Also, quite some time may pass before any event
21163 happens in the target, while a frontend needs to know whether the resuming
21164 command itself was successfully executed.
21167 Console output, and status notifications. Console output
21168 notifications are used to report output of CLI commands, as well as
21169 diagnostics for other commands. Status notifications are used to
21170 report the progress of a long-running operation. Naturally, including
21171 this information in command response would mean no output is produced
21172 until the command is finished, which is undesirable.
21175 General notifications. Commands may have various side effects on
21176 the @value{GDBN} or target state beyond their official purpose. For example,
21177 a command may change the selected thread. Although such changes can
21178 be included in command response, using notification allows for more
21179 orthogonal frontend design.
21183 There's no guarantee that whenever an MI command reports an error,
21184 @value{GDBN} or the target are in any specific state, and especially,
21185 the state is not reverted to the state before the MI command was
21186 processed. Therefore, whenever an MI command results in an error,
21187 we recommend that the frontend refreshes all the information shown in
21188 the user interface.
21192 * Context management::
21193 * Asynchronous and non-stop modes::
21197 @node Context management
21198 @subsection Context management
21200 In most cases when @value{GDBN} accesses the target, this access is
21201 done in context of a specific thread and frame (@pxref{Frames}).
21202 Often, even when accessing global data, the target requires that a thread
21203 be specified. The CLI interface maintains the selected thread and frame,
21204 and supplies them to target on each command. This is convenient,
21205 because a command line user would not want to specify that information
21206 explicitly on each command, and because user interacts with
21207 @value{GDBN} via a single terminal, so no confusion is possible as
21208 to what thread and frame are the current ones.
21210 In the case of MI, the concept of selected thread and frame is less
21211 useful. First, a frontend can easily remember this information
21212 itself. Second, a graphical frontend can have more than one window,
21213 each one used for debugging a different thread, and the frontend might
21214 want to access additional threads for internal purposes. This
21215 increases the risk that by relying on implicitly selected thread, the
21216 frontend may be operating on a wrong one. Therefore, each MI command
21217 should explicitly specify which thread and frame to operate on. To
21218 make it possible, each MI command accepts the @samp{--thread} and
21219 @samp{--frame} options, the value to each is @value{GDBN} identifier
21220 for thread and frame to operate on.
21222 Usually, each top-level window in a frontend allows the user to select
21223 a thread and a frame, and remembers the user selection for further
21224 operations. However, in some cases @value{GDBN} may suggest that the
21225 current thread be changed. For example, when stopping on a breakpoint
21226 it is reasonable to switch to the thread where breakpoint is hit. For
21227 another example, if the user issues the CLI @samp{thread} command via
21228 the frontend, it is desirable to change the frontend's selected thread to the
21229 one specified by user. @value{GDBN} communicates the suggestion to
21230 change current thread using the @samp{=thread-selected} notification.
21231 No such notification is available for the selected frame at the moment.
21233 Note that historically, MI shares the selected thread with CLI, so
21234 frontends used the @code{-thread-select} to execute commands in the
21235 right context. However, getting this to work right is cumbersome. The
21236 simplest way is for frontend to emit @code{-thread-select} command
21237 before every command. This doubles the number of commands that need
21238 to be sent. The alternative approach is to suppress @code{-thread-select}
21239 if the selected thread in @value{GDBN} is supposed to be identical to the
21240 thread the frontend wants to operate on. However, getting this
21241 optimization right can be tricky. In particular, if the frontend
21242 sends several commands to @value{GDBN}, and one of the commands changes the
21243 selected thread, then the behaviour of subsequent commands will
21244 change. So, a frontend should either wait for response from such
21245 problematic commands, or explicitly add @code{-thread-select} for
21246 all subsequent commands. No frontend is known to do this exactly
21247 right, so it is suggested to just always pass the @samp{--thread} and
21248 @samp{--frame} options.
21250 @node Asynchronous and non-stop modes
21251 @subsection Asynchronous command execution and non-stop mode
21253 On some targets, @value{GDBN} is capable of processing MI commands
21254 even while the target is running. This is called @dfn{asynchronous
21255 command execution} (@pxref{Background Execution}). The frontend may
21256 specify a preferrence for asynchronous execution using the
21257 @code{-gdb-set target-async 1} command, which should be emitted before
21258 either running the executable or attaching to the target. After the
21259 frontend has started the executable or attached to the target, it can
21260 find if asynchronous execution is enabled using the
21261 @code{-list-target-features} command.
21263 Even if @value{GDBN} can accept a command while target is running,
21264 many commands that access the target do not work when the target is
21265 running. Therefore, asynchronous command execution is most useful
21266 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
21267 it is possible to examine the state of one thread, while other threads
21270 When a given thread is running, MI commands that try to access the
21271 target in the context of that thread may not work, or may work only on
21272 some targets. In particular, commands that try to operate on thread's
21273 stack will not work, on any target. Commands that read memory, or
21274 modify breakpoints, may work or not work, depending on the target. Note
21275 that even commands that operate on global state, such as @code{print},
21276 @code{set}, and breakpoint commands, still access the target in the
21277 context of a specific thread, so frontend should try to find a
21278 stopped thread and perform the operation on that thread (using the
21279 @samp{--thread} option).
21281 Which commands will work in the context of a running thread is
21282 highly target dependent. However, the two commands
21283 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
21284 to find the state of a thread, will always work.
21286 @node Thread groups
21287 @subsection Thread groups
21288 @value{GDBN} may be used to debug several processes at the same time.
21289 On some platfroms, @value{GDBN} may support debugging of several
21290 hardware systems, each one having several cores with several different
21291 processes running on each core. This section describes the MI
21292 mechanism to support such debugging scenarios.
21294 The key observation is that regardless of the structure of the
21295 target, MI can have a global list of threads, because most commands that
21296 accept the @samp{--thread} option do not need to know what process that
21297 thread belongs to. Therefore, it is not necessary to introduce
21298 neither additional @samp{--process} option, nor an notion of the
21299 current process in the MI interface. The only strictly new feature
21300 that is required is the ability to find how the threads are grouped
21303 To allow the user to discover such grouping, and to support arbitrary
21304 hierarchy of machines/cores/processes, MI introduces the concept of a
21305 @dfn{thread group}. Thread group is a collection of threads and other
21306 thread groups. A thread group always has a string identifier, a type,
21307 and may have additional attributes specific to the type. A new
21308 command, @code{-list-thread-groups}, returns the list of top-level
21309 thread groups, which correspond to processes that @value{GDBN} is
21310 debugging at the moment. By passing an identifier of a thread group
21311 to the @code{-list-thread-groups} command, it is possible to obtain
21312 the members of specific thread group.
21314 To allow the user to easily discover processes, and other objects, he
21315 wishes to debug, a concept of @dfn{available thread group} is
21316 introduced. Available thread group is an thread group that
21317 @value{GDBN} is not debugging, but that can be attached to, using the
21318 @code{-target-attach} command. The list of available top-level thread
21319 groups can be obtained using @samp{-list-thread-groups --available}.
21320 In general, the content of a thread group may be only retrieved only
21321 after attaching to that thread group.
21323 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21324 @node GDB/MI Command Syntax
21325 @section @sc{gdb/mi} Command Syntax
21328 * GDB/MI Input Syntax::
21329 * GDB/MI Output Syntax::
21332 @node GDB/MI Input Syntax
21333 @subsection @sc{gdb/mi} Input Syntax
21335 @cindex input syntax for @sc{gdb/mi}
21336 @cindex @sc{gdb/mi}, input syntax
21338 @item @var{command} @expansion{}
21339 @code{@var{cli-command} | @var{mi-command}}
21341 @item @var{cli-command} @expansion{}
21342 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
21343 @var{cli-command} is any existing @value{GDBN} CLI command.
21345 @item @var{mi-command} @expansion{}
21346 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
21347 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
21349 @item @var{token} @expansion{}
21350 "any sequence of digits"
21352 @item @var{option} @expansion{}
21353 @code{"-" @var{parameter} [ " " @var{parameter} ]}
21355 @item @var{parameter} @expansion{}
21356 @code{@var{non-blank-sequence} | @var{c-string}}
21358 @item @var{operation} @expansion{}
21359 @emph{any of the operations described in this chapter}
21361 @item @var{non-blank-sequence} @expansion{}
21362 @emph{anything, provided it doesn't contain special characters such as
21363 "-", @var{nl}, """ and of course " "}
21365 @item @var{c-string} @expansion{}
21366 @code{""" @var{seven-bit-iso-c-string-content} """}
21368 @item @var{nl} @expansion{}
21377 The CLI commands are still handled by the @sc{mi} interpreter; their
21378 output is described below.
21381 The @code{@var{token}}, when present, is passed back when the command
21385 Some @sc{mi} commands accept optional arguments as part of the parameter
21386 list. Each option is identified by a leading @samp{-} (dash) and may be
21387 followed by an optional argument parameter. Options occur first in the
21388 parameter list and can be delimited from normal parameters using
21389 @samp{--} (this is useful when some parameters begin with a dash).
21396 We want easy access to the existing CLI syntax (for debugging).
21399 We want it to be easy to spot a @sc{mi} operation.
21402 @node GDB/MI Output Syntax
21403 @subsection @sc{gdb/mi} Output Syntax
21405 @cindex output syntax of @sc{gdb/mi}
21406 @cindex @sc{gdb/mi}, output syntax
21407 The output from @sc{gdb/mi} consists of zero or more out-of-band records
21408 followed, optionally, by a single result record. This result record
21409 is for the most recent command. The sequence of output records is
21410 terminated by @samp{(gdb)}.
21412 If an input command was prefixed with a @code{@var{token}} then the
21413 corresponding output for that command will also be prefixed by that same
21417 @item @var{output} @expansion{}
21418 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
21420 @item @var{result-record} @expansion{}
21421 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
21423 @item @var{out-of-band-record} @expansion{}
21424 @code{@var{async-record} | @var{stream-record}}
21426 @item @var{async-record} @expansion{}
21427 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
21429 @item @var{exec-async-output} @expansion{}
21430 @code{[ @var{token} ] "*" @var{async-output}}
21432 @item @var{status-async-output} @expansion{}
21433 @code{[ @var{token} ] "+" @var{async-output}}
21435 @item @var{notify-async-output} @expansion{}
21436 @code{[ @var{token} ] "=" @var{async-output}}
21438 @item @var{async-output} @expansion{}
21439 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
21441 @item @var{result-class} @expansion{}
21442 @code{"done" | "running" | "connected" | "error" | "exit"}
21444 @item @var{async-class} @expansion{}
21445 @code{"stopped" | @var{others}} (where @var{others} will be added
21446 depending on the needs---this is still in development).
21448 @item @var{result} @expansion{}
21449 @code{ @var{variable} "=" @var{value}}
21451 @item @var{variable} @expansion{}
21452 @code{ @var{string} }
21454 @item @var{value} @expansion{}
21455 @code{ @var{const} | @var{tuple} | @var{list} }
21457 @item @var{const} @expansion{}
21458 @code{@var{c-string}}
21460 @item @var{tuple} @expansion{}
21461 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
21463 @item @var{list} @expansion{}
21464 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
21465 @var{result} ( "," @var{result} )* "]" }
21467 @item @var{stream-record} @expansion{}
21468 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
21470 @item @var{console-stream-output} @expansion{}
21471 @code{"~" @var{c-string}}
21473 @item @var{target-stream-output} @expansion{}
21474 @code{"@@" @var{c-string}}
21476 @item @var{log-stream-output} @expansion{}
21477 @code{"&" @var{c-string}}
21479 @item @var{nl} @expansion{}
21482 @item @var{token} @expansion{}
21483 @emph{any sequence of digits}.
21491 All output sequences end in a single line containing a period.
21494 The @code{@var{token}} is from the corresponding request. Note that
21495 for all async output, while the token is allowed by the grammar and
21496 may be output by future versions of @value{GDBN} for select async
21497 output messages, it is generally omitted. Frontends should treat
21498 all async output as reporting general changes in the state of the
21499 target and there should be no need to associate async output to any
21503 @cindex status output in @sc{gdb/mi}
21504 @var{status-async-output} contains on-going status information about the
21505 progress of a slow operation. It can be discarded. All status output is
21506 prefixed by @samp{+}.
21509 @cindex async output in @sc{gdb/mi}
21510 @var{exec-async-output} contains asynchronous state change on the target
21511 (stopped, started, disappeared). All async output is prefixed by
21515 @cindex notify output in @sc{gdb/mi}
21516 @var{notify-async-output} contains supplementary information that the
21517 client should handle (e.g., a new breakpoint information). All notify
21518 output is prefixed by @samp{=}.
21521 @cindex console output in @sc{gdb/mi}
21522 @var{console-stream-output} is output that should be displayed as is in the
21523 console. It is the textual response to a CLI command. All the console
21524 output is prefixed by @samp{~}.
21527 @cindex target output in @sc{gdb/mi}
21528 @var{target-stream-output} is the output produced by the target program.
21529 All the target output is prefixed by @samp{@@}.
21532 @cindex log output in @sc{gdb/mi}
21533 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
21534 instance messages that should be displayed as part of an error log. All
21535 the log output is prefixed by @samp{&}.
21538 @cindex list output in @sc{gdb/mi}
21539 New @sc{gdb/mi} commands should only output @var{lists} containing
21545 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
21546 details about the various output records.
21548 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21549 @node GDB/MI Compatibility with CLI
21550 @section @sc{gdb/mi} Compatibility with CLI
21552 @cindex compatibility, @sc{gdb/mi} and CLI
21553 @cindex @sc{gdb/mi}, compatibility with CLI
21555 For the developers convenience CLI commands can be entered directly,
21556 but there may be some unexpected behaviour. For example, commands
21557 that query the user will behave as if the user replied yes, breakpoint
21558 command lists are not executed and some CLI commands, such as
21559 @code{if}, @code{when} and @code{define}, prompt for further input with
21560 @samp{>}, which is not valid MI output.
21562 This feature may be removed at some stage in the future and it is
21563 recommended that front ends use the @code{-interpreter-exec} command
21564 (@pxref{-interpreter-exec}).
21566 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21567 @node GDB/MI Development and Front Ends
21568 @section @sc{gdb/mi} Development and Front Ends
21569 @cindex @sc{gdb/mi} development
21571 The application which takes the MI output and presents the state of the
21572 program being debugged to the user is called a @dfn{front end}.
21574 Although @sc{gdb/mi} is still incomplete, it is currently being used
21575 by a variety of front ends to @value{GDBN}. This makes it difficult
21576 to introduce new functionality without breaking existing usage. This
21577 section tries to minimize the problems by describing how the protocol
21580 Some changes in MI need not break a carefully designed front end, and
21581 for these the MI version will remain unchanged. The following is a
21582 list of changes that may occur within one level, so front ends should
21583 parse MI output in a way that can handle them:
21587 New MI commands may be added.
21590 New fields may be added to the output of any MI command.
21593 The range of values for fields with specified values, e.g.,
21594 @code{in_scope} (@pxref{-var-update}) may be extended.
21596 @c The format of field's content e.g type prefix, may change so parse it
21597 @c at your own risk. Yes, in general?
21599 @c The order of fields may change? Shouldn't really matter but it might
21600 @c resolve inconsistencies.
21603 If the changes are likely to break front ends, the MI version level
21604 will be increased by one. This will allow the front end to parse the
21605 output according to the MI version. Apart from mi0, new versions of
21606 @value{GDBN} will not support old versions of MI and it will be the
21607 responsibility of the front end to work with the new one.
21609 @c Starting with mi3, add a new command -mi-version that prints the MI
21612 The best way to avoid unexpected changes in MI that might break your front
21613 end is to make your project known to @value{GDBN} developers and
21614 follow development on @email{gdb@@sourceware.org} and
21615 @email{gdb-patches@@sourceware.org}.
21616 @cindex mailing lists
21618 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21619 @node GDB/MI Output Records
21620 @section @sc{gdb/mi} Output Records
21623 * GDB/MI Result Records::
21624 * GDB/MI Stream Records::
21625 * GDB/MI Async Records::
21626 * GDB/MI Frame Information::
21629 @node GDB/MI Result Records
21630 @subsection @sc{gdb/mi} Result Records
21632 @cindex result records in @sc{gdb/mi}
21633 @cindex @sc{gdb/mi}, result records
21634 In addition to a number of out-of-band notifications, the response to a
21635 @sc{gdb/mi} command includes one of the following result indications:
21639 @item "^done" [ "," @var{results} ]
21640 The synchronous operation was successful, @code{@var{results}} are the return
21645 @c Is this one correct? Should it be an out-of-band notification?
21646 The asynchronous operation was successfully started. The target is
21651 @value{GDBN} has connected to a remote target.
21653 @item "^error" "," @var{c-string}
21655 The operation failed. The @code{@var{c-string}} contains the corresponding
21660 @value{GDBN} has terminated.
21664 @node GDB/MI Stream Records
21665 @subsection @sc{gdb/mi} Stream Records
21667 @cindex @sc{gdb/mi}, stream records
21668 @cindex stream records in @sc{gdb/mi}
21669 @value{GDBN} internally maintains a number of output streams: the console, the
21670 target, and the log. The output intended for each of these streams is
21671 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
21673 Each stream record begins with a unique @dfn{prefix character} which
21674 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
21675 Syntax}). In addition to the prefix, each stream record contains a
21676 @code{@var{string-output}}. This is either raw text (with an implicit new
21677 line) or a quoted C string (which does not contain an implicit newline).
21680 @item "~" @var{string-output}
21681 The console output stream contains text that should be displayed in the
21682 CLI console window. It contains the textual responses to CLI commands.
21684 @item "@@" @var{string-output}
21685 The target output stream contains any textual output from the running
21686 target. This is only present when GDB's event loop is truly
21687 asynchronous, which is currently only the case for remote targets.
21689 @item "&" @var{string-output}
21690 The log stream contains debugging messages being produced by @value{GDBN}'s
21694 @node GDB/MI Async Records
21695 @subsection @sc{gdb/mi} Async Records
21697 @cindex async records in @sc{gdb/mi}
21698 @cindex @sc{gdb/mi}, async records
21699 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
21700 additional changes that have occurred. Those changes can either be a
21701 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
21702 target activity (e.g., target stopped).
21704 The following is the list of possible async records:
21708 @item *running,thread-id="@var{thread}"
21709 The target is now running. The @var{thread} field tells which
21710 specific thread is now running, and can be @samp{all} if all threads
21711 are running. The frontend should assume that no interaction with a
21712 running thread is possible after this notification is produced.
21713 The frontend should not assume that this notification is output
21714 only once for any command. @value{GDBN} may emit this notification
21715 several times, either for different threads, because it cannot resume
21716 all threads together, or even for a single thread, if the thread must
21717 be stepped though some code before letting it run freely.
21719 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}"
21720 The target has stopped. The @var{reason} field can have one of the
21724 @item breakpoint-hit
21725 A breakpoint was reached.
21726 @item watchpoint-trigger
21727 A watchpoint was triggered.
21728 @item read-watchpoint-trigger
21729 A read watchpoint was triggered.
21730 @item access-watchpoint-trigger
21731 An access watchpoint was triggered.
21732 @item function-finished
21733 An -exec-finish or similar CLI command was accomplished.
21734 @item location-reached
21735 An -exec-until or similar CLI command was accomplished.
21736 @item watchpoint-scope
21737 A watchpoint has gone out of scope.
21738 @item end-stepping-range
21739 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
21740 similar CLI command was accomplished.
21741 @item exited-signalled
21742 The inferior exited because of a signal.
21744 The inferior exited.
21745 @item exited-normally
21746 The inferior exited normally.
21747 @item signal-received
21748 A signal was received by the inferior.
21751 The @var{id} field identifies the thread that directly caused the stop
21752 -- for example by hitting a breakpoint. Depending on whether all-stop
21753 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
21754 stop all threads, or only the thread that directly triggered the stop.
21755 If all threads are stopped, the @var{stopped} field will have the
21756 value of @code{"all"}. Otherwise, the value of the @var{stopped}
21757 field will be a list of thread identifiers. Presently, this list will
21758 always include a single thread, but frontend should be prepared to see
21759 several threads in the list.
21761 @item =thread-group-created,id="@var{id}"
21762 @itemx =thread-group-exited,id="@var{id}"
21763 A thread thread group either was attached to, or has exited/detached
21764 from. The @var{id} field contains the @value{GDBN} identifier of the
21767 @item =thread-created,id="@var{id}",group-id="@var{gid}"
21768 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
21769 A thread either was created, or has exited. The @var{id} field
21770 contains the @value{GDBN} identifier of the thread. The @var{gid}
21771 field identifies the thread group this thread belongs to.
21773 @item =thread-selected,id="@var{id}"
21774 Informs that the selected thread was changed as result of the last
21775 command. This notification is not emitted as result of @code{-thread-select}
21776 command but is emitted whenever an MI command that is not documented
21777 to change the selected thread actually changes it. In particular,
21778 invoking, directly or indirectly (via user-defined command), the CLI
21779 @code{thread} command, will generate this notification.
21781 We suggest that in response to this notification, front ends
21782 highlight the selected thread and cause subsequent commands to apply to
21785 @item =library-loaded,...
21786 Reports that a new library file was loaded by the program. This
21787 notification has 4 fields---@var{id}, @var{target-name},
21788 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
21789 opaque identifier of the library. For remote debugging case,
21790 @var{target-name} and @var{host-name} fields give the name of the
21791 library file on the target, and on the host respectively. For native
21792 debugging, both those fields have the same value. The
21793 @var{symbols-loaded} field reports if the debug symbols for this
21794 library are loaded.
21796 @item =library-unloaded,...
21797 Reports that a library was unloaded by the program. This notification
21798 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
21799 the same meaning as for the @code{=library-loaded} notification
21803 @node GDB/MI Frame Information
21804 @subsection @sc{gdb/mi} Frame Information
21806 Response from many MI commands includes an information about stack
21807 frame. This information is a tuple that may have the following
21812 The level of the stack frame. The innermost frame has the level of
21813 zero. This field is always present.
21816 The name of the function corresponding to the frame. This field may
21817 be absent if @value{GDBN} is unable to determine the function name.
21820 The code address for the frame. This field is always present.
21823 The name of the source files that correspond to the frame's code
21824 address. This field may be absent.
21827 The source line corresponding to the frames' code address. This field
21831 The name of the binary file (either executable or shared library) the
21832 corresponds to the frame's code address. This field may be absent.
21837 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21838 @node GDB/MI Simple Examples
21839 @section Simple Examples of @sc{gdb/mi} Interaction
21840 @cindex @sc{gdb/mi}, simple examples
21842 This subsection presents several simple examples of interaction using
21843 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
21844 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
21845 the output received from @sc{gdb/mi}.
21847 Note the line breaks shown in the examples are here only for
21848 readability, they don't appear in the real output.
21850 @subheading Setting a Breakpoint
21852 Setting a breakpoint generates synchronous output which contains detailed
21853 information of the breakpoint.
21856 -> -break-insert main
21857 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
21858 enabled="y",addr="0x08048564",func="main",file="myprog.c",
21859 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
21863 @subheading Program Execution
21865 Program execution generates asynchronous records and MI gives the
21866 reason that execution stopped.
21872 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
21873 frame=@{addr="0x08048564",func="main",
21874 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
21875 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
21880 <- *stopped,reason="exited-normally"
21884 @subheading Quitting @value{GDBN}
21886 Quitting @value{GDBN} just prints the result class @samp{^exit}.
21894 @subheading A Bad Command
21896 Here's what happens if you pass a non-existent command:
21900 <- ^error,msg="Undefined MI command: rubbish"
21905 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21906 @node GDB/MI Command Description Format
21907 @section @sc{gdb/mi} Command Description Format
21909 The remaining sections describe blocks of commands. Each block of
21910 commands is laid out in a fashion similar to this section.
21912 @subheading Motivation
21914 The motivation for this collection of commands.
21916 @subheading Introduction
21918 A brief introduction to this collection of commands as a whole.
21920 @subheading Commands
21922 For each command in the block, the following is described:
21924 @subsubheading Synopsis
21927 -command @var{args}@dots{}
21930 @subsubheading Result
21932 @subsubheading @value{GDBN} Command
21934 The corresponding @value{GDBN} CLI command(s), if any.
21936 @subsubheading Example
21938 Example(s) formatted for readability. Some of the described commands have
21939 not been implemented yet and these are labeled N.A.@: (not available).
21942 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21943 @node GDB/MI Breakpoint Commands
21944 @section @sc{gdb/mi} Breakpoint Commands
21946 @cindex breakpoint commands for @sc{gdb/mi}
21947 @cindex @sc{gdb/mi}, breakpoint commands
21948 This section documents @sc{gdb/mi} commands for manipulating
21951 @subheading The @code{-break-after} Command
21952 @findex -break-after
21954 @subsubheading Synopsis
21957 -break-after @var{number} @var{count}
21960 The breakpoint number @var{number} is not in effect until it has been
21961 hit @var{count} times. To see how this is reflected in the output of
21962 the @samp{-break-list} command, see the description of the
21963 @samp{-break-list} command below.
21965 @subsubheading @value{GDBN} Command
21967 The corresponding @value{GDBN} command is @samp{ignore}.
21969 @subsubheading Example
21974 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
21975 enabled="y",addr="0x000100d0",func="main",file="hello.c",
21976 fullname="/home/foo/hello.c",line="5",times="0"@}
21983 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
21984 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
21985 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
21986 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
21987 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
21988 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
21989 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
21990 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
21991 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
21992 line="5",times="0",ignore="3"@}]@}
21997 @subheading The @code{-break-catch} Command
21998 @findex -break-catch
22001 @subheading The @code{-break-commands} Command
22002 @findex -break-commands
22004 @subsubheading Synopsis
22007 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
22010 Specifies the CLI commands that should be executed when breakpoint
22011 @var{number} is hit. The parameters @var{command1} to @var{commandN}
22012 are the commands. If no command is specified, any previously-set
22013 commands are cleared. @xref{Break Commands}. Typical use of this
22014 functionality is tracing a program, that is, printing of values of
22015 some variables whenever breakpoint is hit and then continuing.
22017 @subsubheading @value{GDBN} Command
22019 The corresponding @value{GDBN} command is @samp{commands}.
22021 @subsubheading Example
22026 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
22027 enabled="y",addr="0x000100d0",func="main",file="hello.c",
22028 fullname="/home/foo/hello.c",line="5",times="0"@}
22030 -break-commands 1 "print v" "continue"
22035 @subheading The @code{-break-condition} Command
22036 @findex -break-condition
22038 @subsubheading Synopsis
22041 -break-condition @var{number} @var{expr}
22044 Breakpoint @var{number} will stop the program only if the condition in
22045 @var{expr} is true. The condition becomes part of the
22046 @samp{-break-list} output (see the description of the @samp{-break-list}
22049 @subsubheading @value{GDBN} Command
22051 The corresponding @value{GDBN} command is @samp{condition}.
22053 @subsubheading Example
22057 -break-condition 1 1
22061 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
22062 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
22063 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
22064 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
22065 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
22066 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
22067 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
22068 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
22069 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
22070 line="5",cond="1",times="0",ignore="3"@}]@}
22074 @subheading The @code{-break-delete} Command
22075 @findex -break-delete
22077 @subsubheading Synopsis
22080 -break-delete ( @var{breakpoint} )+
22083 Delete the breakpoint(s) whose number(s) are specified in the argument
22084 list. This is obviously reflected in the breakpoint list.
22086 @subsubheading @value{GDBN} Command
22088 The corresponding @value{GDBN} command is @samp{delete}.
22090 @subsubheading Example
22098 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
22099 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
22100 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
22101 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
22102 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
22103 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
22104 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
22109 @subheading The @code{-break-disable} Command
22110 @findex -break-disable
22112 @subsubheading Synopsis
22115 -break-disable ( @var{breakpoint} )+
22118 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
22119 break list is now set to @samp{n} for the named @var{breakpoint}(s).
22121 @subsubheading @value{GDBN} Command
22123 The corresponding @value{GDBN} command is @samp{disable}.
22125 @subsubheading Example
22133 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
22134 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
22135 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
22136 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
22137 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
22138 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
22139 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
22140 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
22141 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
22142 line="5",times="0"@}]@}
22146 @subheading The @code{-break-enable} Command
22147 @findex -break-enable
22149 @subsubheading Synopsis
22152 -break-enable ( @var{breakpoint} )+
22155 Enable (previously disabled) @var{breakpoint}(s).
22157 @subsubheading @value{GDBN} Command
22159 The corresponding @value{GDBN} command is @samp{enable}.
22161 @subsubheading Example
22169 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
22170 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
22171 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
22172 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
22173 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
22174 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
22175 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
22176 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
22177 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
22178 line="5",times="0"@}]@}
22182 @subheading The @code{-break-info} Command
22183 @findex -break-info
22185 @subsubheading Synopsis
22188 -break-info @var{breakpoint}
22192 Get information about a single breakpoint.
22194 @subsubheading @value{GDBN} Command
22196 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
22198 @subsubheading Example
22201 @subheading The @code{-break-insert} Command
22202 @findex -break-insert
22204 @subsubheading Synopsis
22207 -break-insert [ -t ] [ -h ] [ -f ] [ -d ]
22208 [ -c @var{condition} ] [ -i @var{ignore-count} ]
22209 [ -p @var{thread} ] [ @var{location} ]
22213 If specified, @var{location}, can be one of:
22220 @item filename:linenum
22221 @item filename:function
22225 The possible optional parameters of this command are:
22229 Insert a temporary breakpoint.
22231 Insert a hardware breakpoint.
22232 @item -c @var{condition}
22233 Make the breakpoint conditional on @var{condition}.
22234 @item -i @var{ignore-count}
22235 Initialize the @var{ignore-count}.
22237 If @var{location} cannot be parsed (for example if it
22238 refers to unknown files or functions), create a pending
22239 breakpoint. Without this flag, @value{GDBN} will report
22240 an error, and won't create a breakpoint, if @var{location}
22243 Create a disabled breakpoint.
22246 @subsubheading Result
22248 The result is in the form:
22251 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
22252 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
22253 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
22254 times="@var{times}"@}
22258 where @var{number} is the @value{GDBN} number for this breakpoint,
22259 @var{funcname} is the name of the function where the breakpoint was
22260 inserted, @var{filename} is the name of the source file which contains
22261 this function, @var{lineno} is the source line number within that file
22262 and @var{times} the number of times that the breakpoint has been hit
22263 (always 0 for -break-insert but may be greater for -break-info or -break-list
22264 which use the same output).
22266 Note: this format is open to change.
22267 @c An out-of-band breakpoint instead of part of the result?
22269 @subsubheading @value{GDBN} Command
22271 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
22272 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
22274 @subsubheading Example
22279 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
22280 fullname="/home/foo/recursive2.c,line="4",times="0"@}
22282 -break-insert -t foo
22283 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
22284 fullname="/home/foo/recursive2.c,line="11",times="0"@}
22287 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
22288 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
22289 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
22290 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
22291 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
22292 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
22293 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
22294 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
22295 addr="0x0001072c", func="main",file="recursive2.c",
22296 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
22297 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
22298 addr="0x00010774",func="foo",file="recursive2.c",
22299 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
22301 -break-insert -r foo.*
22302 ~int foo(int, int);
22303 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
22304 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
22308 @subheading The @code{-break-list} Command
22309 @findex -break-list
22311 @subsubheading Synopsis
22317 Displays the list of inserted breakpoints, showing the following fields:
22321 number of the breakpoint
22323 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
22325 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
22328 is the breakpoint enabled or no: @samp{y} or @samp{n}
22330 memory location at which the breakpoint is set
22332 logical location of the breakpoint, expressed by function name, file
22335 number of times the breakpoint has been hit
22338 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
22339 @code{body} field is an empty list.
22341 @subsubheading @value{GDBN} Command
22343 The corresponding @value{GDBN} command is @samp{info break}.
22345 @subsubheading Example
22350 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
22351 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
22352 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
22353 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
22354 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
22355 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
22356 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
22357 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
22358 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
22359 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
22360 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
22361 line="13",times="0"@}]@}
22365 Here's an example of the result when there are no breakpoints:
22370 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
22371 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
22372 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
22373 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
22374 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
22375 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
22376 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
22381 @subheading The @code{-break-watch} Command
22382 @findex -break-watch
22384 @subsubheading Synopsis
22387 -break-watch [ -a | -r ]
22390 Create a watchpoint. With the @samp{-a} option it will create an
22391 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
22392 read from or on a write to the memory location. With the @samp{-r}
22393 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
22394 trigger only when the memory location is accessed for reading. Without
22395 either of the options, the watchpoint created is a regular watchpoint,
22396 i.e., it will trigger when the memory location is accessed for writing.
22397 @xref{Set Watchpoints, , Setting Watchpoints}.
22399 Note that @samp{-break-list} will report a single list of watchpoints and
22400 breakpoints inserted.
22402 @subsubheading @value{GDBN} Command
22404 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
22407 @subsubheading Example
22409 Setting a watchpoint on a variable in the @code{main} function:
22414 ^done,wpt=@{number="2",exp="x"@}
22419 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
22420 value=@{old="-268439212",new="55"@},
22421 frame=@{func="main",args=[],file="recursive2.c",
22422 fullname="/home/foo/bar/recursive2.c",line="5"@}
22426 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
22427 the program execution twice: first for the variable changing value, then
22428 for the watchpoint going out of scope.
22433 ^done,wpt=@{number="5",exp="C"@}
22438 *stopped,reason="watchpoint-trigger",
22439 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
22440 frame=@{func="callee4",args=[],
22441 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22442 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
22447 *stopped,reason="watchpoint-scope",wpnum="5",
22448 frame=@{func="callee3",args=[@{name="strarg",
22449 value="0x11940 \"A string argument.\""@}],
22450 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22451 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
22455 Listing breakpoints and watchpoints, at different points in the program
22456 execution. Note that once the watchpoint goes out of scope, it is
22462 ^done,wpt=@{number="2",exp="C"@}
22465 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
22466 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
22467 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
22468 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
22469 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
22470 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
22471 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
22472 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
22473 addr="0x00010734",func="callee4",
22474 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22475 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
22476 bkpt=@{number="2",type="watchpoint",disp="keep",
22477 enabled="y",addr="",what="C",times="0"@}]@}
22482 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
22483 value=@{old="-276895068",new="3"@},
22484 frame=@{func="callee4",args=[],
22485 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22486 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
22489 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
22490 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
22491 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
22492 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
22493 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
22494 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
22495 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
22496 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
22497 addr="0x00010734",func="callee4",
22498 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22499 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
22500 bkpt=@{number="2",type="watchpoint",disp="keep",
22501 enabled="y",addr="",what="C",times="-5"@}]@}
22505 ^done,reason="watchpoint-scope",wpnum="2",
22506 frame=@{func="callee3",args=[@{name="strarg",
22507 value="0x11940 \"A string argument.\""@}],
22508 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22509 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
22512 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
22513 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
22514 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
22515 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
22516 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
22517 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
22518 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
22519 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
22520 addr="0x00010734",func="callee4",
22521 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22522 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
22527 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22528 @node GDB/MI Program Context
22529 @section @sc{gdb/mi} Program Context
22531 @subheading The @code{-exec-arguments} Command
22532 @findex -exec-arguments
22535 @subsubheading Synopsis
22538 -exec-arguments @var{args}
22541 Set the inferior program arguments, to be used in the next
22544 @subsubheading @value{GDBN} Command
22546 The corresponding @value{GDBN} command is @samp{set args}.
22548 @subsubheading Example
22552 -exec-arguments -v word
22559 @subheading The @code{-exec-show-arguments} Command
22560 @findex -exec-show-arguments
22562 @subsubheading Synopsis
22565 -exec-show-arguments
22568 Print the arguments of the program.
22570 @subsubheading @value{GDBN} Command
22572 The corresponding @value{GDBN} command is @samp{show args}.
22574 @subsubheading Example
22579 @subheading The @code{-environment-cd} Command
22580 @findex -environment-cd
22582 @subsubheading Synopsis
22585 -environment-cd @var{pathdir}
22588 Set @value{GDBN}'s working directory.
22590 @subsubheading @value{GDBN} Command
22592 The corresponding @value{GDBN} command is @samp{cd}.
22594 @subsubheading Example
22598 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
22604 @subheading The @code{-environment-directory} Command
22605 @findex -environment-directory
22607 @subsubheading Synopsis
22610 -environment-directory [ -r ] [ @var{pathdir} ]+
22613 Add directories @var{pathdir} to beginning of search path for source files.
22614 If the @samp{-r} option is used, the search path is reset to the default
22615 search path. If directories @var{pathdir} are supplied in addition to the
22616 @samp{-r} option, the search path is first reset and then addition
22618 Multiple directories may be specified, separated by blanks. Specifying
22619 multiple directories in a single command
22620 results in the directories added to the beginning of the
22621 search path in the same order they were presented in the command.
22622 If blanks are needed as
22623 part of a directory name, double-quotes should be used around
22624 the name. In the command output, the path will show up separated
22625 by the system directory-separator character. The directory-separator
22626 character must not be used
22627 in any directory name.
22628 If no directories are specified, the current search path is displayed.
22630 @subsubheading @value{GDBN} Command
22632 The corresponding @value{GDBN} command is @samp{dir}.
22634 @subsubheading Example
22638 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
22639 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
22641 -environment-directory ""
22642 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
22644 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
22645 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
22647 -environment-directory -r
22648 ^done,source-path="$cdir:$cwd"
22653 @subheading The @code{-environment-path} Command
22654 @findex -environment-path
22656 @subsubheading Synopsis
22659 -environment-path [ -r ] [ @var{pathdir} ]+
22662 Add directories @var{pathdir} to beginning of search path for object files.
22663 If the @samp{-r} option is used, the search path is reset to the original
22664 search path that existed at gdb start-up. If directories @var{pathdir} are
22665 supplied in addition to the
22666 @samp{-r} option, the search path is first reset and then addition
22668 Multiple directories may be specified, separated by blanks. Specifying
22669 multiple directories in a single command
22670 results in the directories added to the beginning of the
22671 search path in the same order they were presented in the command.
22672 If blanks are needed as
22673 part of a directory name, double-quotes should be used around
22674 the name. In the command output, the path will show up separated
22675 by the system directory-separator character. The directory-separator
22676 character must not be used
22677 in any directory name.
22678 If no directories are specified, the current path is displayed.
22681 @subsubheading @value{GDBN} Command
22683 The corresponding @value{GDBN} command is @samp{path}.
22685 @subsubheading Example
22690 ^done,path="/usr/bin"
22692 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
22693 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
22695 -environment-path -r /usr/local/bin
22696 ^done,path="/usr/local/bin:/usr/bin"
22701 @subheading The @code{-environment-pwd} Command
22702 @findex -environment-pwd
22704 @subsubheading Synopsis
22710 Show the current working directory.
22712 @subsubheading @value{GDBN} Command
22714 The corresponding @value{GDBN} command is @samp{pwd}.
22716 @subsubheading Example
22721 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
22725 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22726 @node GDB/MI Thread Commands
22727 @section @sc{gdb/mi} Thread Commands
22730 @subheading The @code{-thread-info} Command
22731 @findex -thread-info
22733 @subsubheading Synopsis
22736 -thread-info [ @var{thread-id} ]
22739 Reports information about either a specific thread, if
22740 the @var{thread-id} parameter is present, or about all
22741 threads. When printing information about all threads,
22742 also reports the current thread.
22744 @subsubheading @value{GDBN} Command
22746 The @samp{info thread} command prints the same information
22749 @subsubheading Example
22754 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
22755 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
22756 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
22757 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
22758 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}],
22759 current-thread-id="1"
22763 The @samp{state} field may have the following values:
22767 The thread is stopped. Frame information is available for stopped
22771 The thread is running. There's no frame information for running
22776 @subheading The @code{-thread-list-ids} Command
22777 @findex -thread-list-ids
22779 @subsubheading Synopsis
22785 Produces a list of the currently known @value{GDBN} thread ids. At the
22786 end of the list it also prints the total number of such threads.
22788 This command is retained for historical reasons, the
22789 @code{-thread-info} command should be used instead.
22791 @subsubheading @value{GDBN} Command
22793 Part of @samp{info threads} supplies the same information.
22795 @subsubheading Example
22800 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
22801 current-thread-id="1",number-of-threads="3"
22806 @subheading The @code{-thread-select} Command
22807 @findex -thread-select
22809 @subsubheading Synopsis
22812 -thread-select @var{threadnum}
22815 Make @var{threadnum} the current thread. It prints the number of the new
22816 current thread, and the topmost frame for that thread.
22818 This command is deprecated in favor of explicitly using the
22819 @samp{--thread} option to each command.
22821 @subsubheading @value{GDBN} Command
22823 The corresponding @value{GDBN} command is @samp{thread}.
22825 @subsubheading Example
22832 *stopped,reason="end-stepping-range",thread-id="2",line="187",
22833 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
22837 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
22838 number-of-threads="3"
22841 ^done,new-thread-id="3",
22842 frame=@{level="0",func="vprintf",
22843 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
22844 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
22848 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22849 @node GDB/MI Program Execution
22850 @section @sc{gdb/mi} Program Execution
22852 These are the asynchronous commands which generate the out-of-band
22853 record @samp{*stopped}. Currently @value{GDBN} only really executes
22854 asynchronously with remote targets and this interaction is mimicked in
22857 @subheading The @code{-exec-continue} Command
22858 @findex -exec-continue
22860 @subsubheading Synopsis
22863 -exec-continue [--all|--thread-group N]
22866 Resumes the execution of the inferior program until a breakpoint is
22867 encountered, or until the inferior exits. In all-stop mode
22868 (@pxref{All-Stop Mode}), may resume only one thread, or all threads,
22869 depending on the value of the @samp{scheduler-locking} variable. In
22870 non-stop mode (@pxref{Non-Stop Mode}), if the @samp{--all} is not
22871 specified, only the thread specified with the @samp{--thread} option
22872 (or current thread, if no @samp{--thread} is provided) is resumed. If
22873 @samp{--all} is specified, all threads will be resumed. The
22874 @samp{--all} option is ignored in all-stop mode. If the
22875 @samp{--thread-group} options is specified, then all threads in that
22876 thread group are resumed.
22878 @subsubheading @value{GDBN} Command
22880 The corresponding @value{GDBN} corresponding is @samp{continue}.
22882 @subsubheading Example
22889 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
22890 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
22896 @subheading The @code{-exec-finish} Command
22897 @findex -exec-finish
22899 @subsubheading Synopsis
22905 Resumes the execution of the inferior program until the current
22906 function is exited. Displays the results returned by the function.
22908 @subsubheading @value{GDBN} Command
22910 The corresponding @value{GDBN} command is @samp{finish}.
22912 @subsubheading Example
22914 Function returning @code{void}.
22921 *stopped,reason="function-finished",frame=@{func="main",args=[],
22922 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
22926 Function returning other than @code{void}. The name of the internal
22927 @value{GDBN} variable storing the result is printed, together with the
22934 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
22935 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
22936 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
22937 gdb-result-var="$1",return-value="0"
22942 @subheading The @code{-exec-interrupt} Command
22943 @findex -exec-interrupt
22945 @subsubheading Synopsis
22948 -exec-interrupt [--all|--thread-group N]
22951 Interrupts the background execution of the target. Note how the token
22952 associated with the stop message is the one for the execution command
22953 that has been interrupted. The token for the interrupt itself only
22954 appears in the @samp{^done} output. If the user is trying to
22955 interrupt a non-running program, an error message will be printed.
22957 Note that when asynchronous execution is enabled, this command is
22958 asynchronous just like other execution commands. That is, first the
22959 @samp{^done} response will be printed, and the target stop will be
22960 reported after that using the @samp{*stopped} notification.
22962 In non-stop mode, only the context thread is interrupted by default.
22963 All threads will be interrupted if the @samp{--all} option is
22964 specified. If the @samp{--thread-group} option is specified, all
22965 threads in that group will be interrupted.
22967 @subsubheading @value{GDBN} Command
22969 The corresponding @value{GDBN} command is @samp{interrupt}.
22971 @subsubheading Example
22982 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
22983 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
22984 fullname="/home/foo/bar/try.c",line="13"@}
22989 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
22993 @subheading The @code{-exec-jump} Command
22996 @subsubheading Synopsis
22999 -exec-jump @var{location}
23002 Resumes execution of the inferior program at the location specified by
23003 parameter. @xref{Specify Location}, for a description of the
23004 different forms of @var{location}.
23006 @subsubheading @value{GDBN} Command
23008 The corresponding @value{GDBN} command is @samp{jump}.
23010 @subsubheading Example
23013 -exec-jump foo.c:10
23014 *running,thread-id="all"
23019 @subheading The @code{-exec-next} Command
23022 @subsubheading Synopsis
23028 Resumes execution of the inferior program, stopping when the beginning
23029 of the next source line is reached.
23031 @subsubheading @value{GDBN} Command
23033 The corresponding @value{GDBN} command is @samp{next}.
23035 @subsubheading Example
23041 *stopped,reason="end-stepping-range",line="8",file="hello.c"
23046 @subheading The @code{-exec-next-instruction} Command
23047 @findex -exec-next-instruction
23049 @subsubheading Synopsis
23052 -exec-next-instruction
23055 Executes one machine instruction. If the instruction is a function
23056 call, continues until the function returns. If the program stops at an
23057 instruction in the middle of a source line, the address will be
23060 @subsubheading @value{GDBN} Command
23062 The corresponding @value{GDBN} command is @samp{nexti}.
23064 @subsubheading Example
23068 -exec-next-instruction
23072 *stopped,reason="end-stepping-range",
23073 addr="0x000100d4",line="5",file="hello.c"
23078 @subheading The @code{-exec-return} Command
23079 @findex -exec-return
23081 @subsubheading Synopsis
23087 Makes current function return immediately. Doesn't execute the inferior.
23088 Displays the new current frame.
23090 @subsubheading @value{GDBN} Command
23092 The corresponding @value{GDBN} command is @samp{return}.
23094 @subsubheading Example
23098 200-break-insert callee4
23099 200^done,bkpt=@{number="1",addr="0x00010734",
23100 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
23105 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
23106 frame=@{func="callee4",args=[],
23107 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23108 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
23114 111^done,frame=@{level="0",func="callee3",
23115 args=[@{name="strarg",
23116 value="0x11940 \"A string argument.\""@}],
23117 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23118 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
23123 @subheading The @code{-exec-run} Command
23126 @subsubheading Synopsis
23132 Starts execution of the inferior from the beginning. The inferior
23133 executes until either a breakpoint is encountered or the program
23134 exits. In the latter case the output will include an exit code, if
23135 the program has exited exceptionally.
23137 @subsubheading @value{GDBN} Command
23139 The corresponding @value{GDBN} command is @samp{run}.
23141 @subsubheading Examples
23146 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
23151 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
23152 frame=@{func="main",args=[],file="recursive2.c",
23153 fullname="/home/foo/bar/recursive2.c",line="4"@}
23158 Program exited normally:
23166 *stopped,reason="exited-normally"
23171 Program exited exceptionally:
23179 *stopped,reason="exited",exit-code="01"
23183 Another way the program can terminate is if it receives a signal such as
23184 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
23188 *stopped,reason="exited-signalled",signal-name="SIGINT",
23189 signal-meaning="Interrupt"
23193 @c @subheading -exec-signal
23196 @subheading The @code{-exec-step} Command
23199 @subsubheading Synopsis
23205 Resumes execution of the inferior program, stopping when the beginning
23206 of the next source line is reached, if the next source line is not a
23207 function call. If it is, stop at the first instruction of the called
23210 @subsubheading @value{GDBN} Command
23212 The corresponding @value{GDBN} command is @samp{step}.
23214 @subsubheading Example
23216 Stepping into a function:
23222 *stopped,reason="end-stepping-range",
23223 frame=@{func="foo",args=[@{name="a",value="10"@},
23224 @{name="b",value="0"@}],file="recursive2.c",
23225 fullname="/home/foo/bar/recursive2.c",line="11"@}
23235 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
23240 @subheading The @code{-exec-step-instruction} Command
23241 @findex -exec-step-instruction
23243 @subsubheading Synopsis
23246 -exec-step-instruction
23249 Resumes the inferior which executes one machine instruction. The
23250 output, once @value{GDBN} has stopped, will vary depending on whether
23251 we have stopped in the middle of a source line or not. In the former
23252 case, the address at which the program stopped will be printed as
23255 @subsubheading @value{GDBN} Command
23257 The corresponding @value{GDBN} command is @samp{stepi}.
23259 @subsubheading Example
23263 -exec-step-instruction
23267 *stopped,reason="end-stepping-range",
23268 frame=@{func="foo",args=[],file="try.c",
23269 fullname="/home/foo/bar/try.c",line="10"@}
23271 -exec-step-instruction
23275 *stopped,reason="end-stepping-range",
23276 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
23277 fullname="/home/foo/bar/try.c",line="10"@}
23282 @subheading The @code{-exec-until} Command
23283 @findex -exec-until
23285 @subsubheading Synopsis
23288 -exec-until [ @var{location} ]
23291 Executes the inferior until the @var{location} specified in the
23292 argument is reached. If there is no argument, the inferior executes
23293 until a source line greater than the current one is reached. The
23294 reason for stopping in this case will be @samp{location-reached}.
23296 @subsubheading @value{GDBN} Command
23298 The corresponding @value{GDBN} command is @samp{until}.
23300 @subsubheading Example
23304 -exec-until recursive2.c:6
23308 *stopped,reason="location-reached",frame=@{func="main",args=[],
23309 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
23314 @subheading -file-clear
23315 Is this going away????
23318 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23319 @node GDB/MI Stack Manipulation
23320 @section @sc{gdb/mi} Stack Manipulation Commands
23323 @subheading The @code{-stack-info-frame} Command
23324 @findex -stack-info-frame
23326 @subsubheading Synopsis
23332 Get info on the selected frame.
23334 @subsubheading @value{GDBN} Command
23336 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
23337 (without arguments).
23339 @subsubheading Example
23344 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
23345 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23346 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
23350 @subheading The @code{-stack-info-depth} Command
23351 @findex -stack-info-depth
23353 @subsubheading Synopsis
23356 -stack-info-depth [ @var{max-depth} ]
23359 Return the depth of the stack. If the integer argument @var{max-depth}
23360 is specified, do not count beyond @var{max-depth} frames.
23362 @subsubheading @value{GDBN} Command
23364 There's no equivalent @value{GDBN} command.
23366 @subsubheading Example
23368 For a stack with frame levels 0 through 11:
23375 -stack-info-depth 4
23378 -stack-info-depth 12
23381 -stack-info-depth 11
23384 -stack-info-depth 13
23389 @subheading The @code{-stack-list-arguments} Command
23390 @findex -stack-list-arguments
23392 @subsubheading Synopsis
23395 -stack-list-arguments @var{show-values}
23396 [ @var{low-frame} @var{high-frame} ]
23399 Display a list of the arguments for the frames between @var{low-frame}
23400 and @var{high-frame} (inclusive). If @var{low-frame} and
23401 @var{high-frame} are not provided, list the arguments for the whole
23402 call stack. If the two arguments are equal, show the single frame
23403 at the corresponding level. It is an error if @var{low-frame} is
23404 larger than the actual number of frames. On the other hand,
23405 @var{high-frame} may be larger than the actual number of frames, in
23406 which case only existing frames will be returned.
23408 The @var{show-values} argument must have a value of 0 or 1. A value of
23409 0 means that only the names of the arguments are listed, a value of 1
23410 means that both names and values of the arguments are printed.
23412 Use of this command to obtain arguments in a single frame is
23413 deprecated in favor of the @samp{-stack-list-variables} command.
23415 @subsubheading @value{GDBN} Command
23417 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
23418 @samp{gdb_get_args} command which partially overlaps with the
23419 functionality of @samp{-stack-list-arguments}.
23421 @subsubheading Example
23428 frame=@{level="0",addr="0x00010734",func="callee4",
23429 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23430 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
23431 frame=@{level="1",addr="0x0001076c",func="callee3",
23432 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23433 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
23434 frame=@{level="2",addr="0x0001078c",func="callee2",
23435 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23436 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
23437 frame=@{level="3",addr="0x000107b4",func="callee1",
23438 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23439 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
23440 frame=@{level="4",addr="0x000107e0",func="main",
23441 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23442 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
23444 -stack-list-arguments 0
23447 frame=@{level="0",args=[]@},
23448 frame=@{level="1",args=[name="strarg"]@},
23449 frame=@{level="2",args=[name="intarg",name="strarg"]@},
23450 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
23451 frame=@{level="4",args=[]@}]
23453 -stack-list-arguments 1
23456 frame=@{level="0",args=[]@},
23458 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
23459 frame=@{level="2",args=[
23460 @{name="intarg",value="2"@},
23461 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
23462 @{frame=@{level="3",args=[
23463 @{name="intarg",value="2"@},
23464 @{name="strarg",value="0x11940 \"A string argument.\""@},
23465 @{name="fltarg",value="3.5"@}]@},
23466 frame=@{level="4",args=[]@}]
23468 -stack-list-arguments 0 2 2
23469 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
23471 -stack-list-arguments 1 2 2
23472 ^done,stack-args=[frame=@{level="2",
23473 args=[@{name="intarg",value="2"@},
23474 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
23478 @c @subheading -stack-list-exception-handlers
23481 @subheading The @code{-stack-list-frames} Command
23482 @findex -stack-list-frames
23484 @subsubheading Synopsis
23487 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
23490 List the frames currently on the stack. For each frame it displays the
23495 The frame number, 0 being the topmost frame, i.e., the innermost function.
23497 The @code{$pc} value for that frame.
23501 File name of the source file where the function lives.
23503 Line number corresponding to the @code{$pc}.
23506 If invoked without arguments, this command prints a backtrace for the
23507 whole stack. If given two integer arguments, it shows the frames whose
23508 levels are between the two arguments (inclusive). If the two arguments
23509 are equal, it shows the single frame at the corresponding level. It is
23510 an error if @var{low-frame} is larger than the actual number of
23511 frames. On the other hand, @var{high-frame} may be larger than the
23512 actual number of frames, in which case only existing frames will be returned.
23514 @subsubheading @value{GDBN} Command
23516 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
23518 @subsubheading Example
23520 Full stack backtrace:
23526 [frame=@{level="0",addr="0x0001076c",func="foo",
23527 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
23528 frame=@{level="1",addr="0x000107a4",func="foo",
23529 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23530 frame=@{level="2",addr="0x000107a4",func="foo",
23531 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23532 frame=@{level="3",addr="0x000107a4",func="foo",
23533 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23534 frame=@{level="4",addr="0x000107a4",func="foo",
23535 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23536 frame=@{level="5",addr="0x000107a4",func="foo",
23537 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23538 frame=@{level="6",addr="0x000107a4",func="foo",
23539 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23540 frame=@{level="7",addr="0x000107a4",func="foo",
23541 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23542 frame=@{level="8",addr="0x000107a4",func="foo",
23543 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23544 frame=@{level="9",addr="0x000107a4",func="foo",
23545 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23546 frame=@{level="10",addr="0x000107a4",func="foo",
23547 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23548 frame=@{level="11",addr="0x00010738",func="main",
23549 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
23553 Show frames between @var{low_frame} and @var{high_frame}:
23557 -stack-list-frames 3 5
23559 [frame=@{level="3",addr="0x000107a4",func="foo",
23560 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23561 frame=@{level="4",addr="0x000107a4",func="foo",
23562 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23563 frame=@{level="5",addr="0x000107a4",func="foo",
23564 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
23568 Show a single frame:
23572 -stack-list-frames 3 3
23574 [frame=@{level="3",addr="0x000107a4",func="foo",
23575 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
23580 @subheading The @code{-stack-list-locals} Command
23581 @findex -stack-list-locals
23583 @subsubheading Synopsis
23586 -stack-list-locals @var{print-values}
23589 Display the local variable names for the selected frame. If
23590 @var{print-values} is 0 or @code{--no-values}, print only the names of
23591 the variables; if it is 1 or @code{--all-values}, print also their
23592 values; and if it is 2 or @code{--simple-values}, print the name,
23593 type and value for simple data types and the name and type for arrays,
23594 structures and unions. In this last case, a frontend can immediately
23595 display the value of simple data types and create variable objects for
23596 other data types when the user wishes to explore their values in
23599 This command is deprecated in favor of the
23600 @samp{-stack-list-variables} command.
23602 @subsubheading @value{GDBN} Command
23604 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
23606 @subsubheading Example
23610 -stack-list-locals 0
23611 ^done,locals=[name="A",name="B",name="C"]
23613 -stack-list-locals --all-values
23614 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
23615 @{name="C",value="@{1, 2, 3@}"@}]
23616 -stack-list-locals --simple-values
23617 ^done,locals=[@{name="A",type="int",value="1"@},
23618 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
23622 @subheading The @code{-stack-list-variables} Command
23623 @findex -stack-list-variables
23625 @subsubheading Synopsis
23628 -stack-list-variables @var{print-values}
23631 Display the names of local variables and function arguments for the selected frame. If
23632 @var{print-values} is 0 or @code{--no-values}, print only the names of
23633 the variables; if it is 1 or @code{--all-values}, print also their
23634 values; and if it is 2 or @code{--simple-values}, print the name,
23635 type and value for simple data types and the name and type for arrays,
23636 structures and unions.
23638 @subsubheading Example
23642 -stack-list-variables --thread 1 --frame 0 --all-values
23643 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
23648 @subheading The @code{-stack-select-frame} Command
23649 @findex -stack-select-frame
23651 @subsubheading Synopsis
23654 -stack-select-frame @var{framenum}
23657 Change the selected frame. Select a different frame @var{framenum} on
23660 This command in deprecated in favor of passing the @samp{--frame}
23661 option to every command.
23663 @subsubheading @value{GDBN} Command
23665 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
23666 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
23668 @subsubheading Example
23672 -stack-select-frame 2
23677 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23678 @node GDB/MI Variable Objects
23679 @section @sc{gdb/mi} Variable Objects
23683 @subheading Motivation for Variable Objects in @sc{gdb/mi}
23685 For the implementation of a variable debugger window (locals, watched
23686 expressions, etc.), we are proposing the adaptation of the existing code
23687 used by @code{Insight}.
23689 The two main reasons for that are:
23693 It has been proven in practice (it is already on its second generation).
23696 It will shorten development time (needless to say how important it is
23700 The original interface was designed to be used by Tcl code, so it was
23701 slightly changed so it could be used through @sc{gdb/mi}. This section
23702 describes the @sc{gdb/mi} operations that will be available and gives some
23703 hints about their use.
23705 @emph{Note}: In addition to the set of operations described here, we
23706 expect the @sc{gui} implementation of a variable window to require, at
23707 least, the following operations:
23710 @item @code{-gdb-show} @code{output-radix}
23711 @item @code{-stack-list-arguments}
23712 @item @code{-stack-list-locals}
23713 @item @code{-stack-select-frame}
23718 @subheading Introduction to Variable Objects
23720 @cindex variable objects in @sc{gdb/mi}
23722 Variable objects are "object-oriented" MI interface for examining and
23723 changing values of expressions. Unlike some other MI interfaces that
23724 work with expressions, variable objects are specifically designed for
23725 simple and efficient presentation in the frontend. A variable object
23726 is identified by string name. When a variable object is created, the
23727 frontend specifies the expression for that variable object. The
23728 expression can be a simple variable, or it can be an arbitrary complex
23729 expression, and can even involve CPU registers. After creating a
23730 variable object, the frontend can invoke other variable object
23731 operations---for example to obtain or change the value of a variable
23732 object, or to change display format.
23734 Variable objects have hierarchical tree structure. Any variable object
23735 that corresponds to a composite type, such as structure in C, has
23736 a number of child variable objects, for example corresponding to each
23737 element of a structure. A child variable object can itself have
23738 children, recursively. Recursion ends when we reach
23739 leaf variable objects, which always have built-in types. Child variable
23740 objects are created only by explicit request, so if a frontend
23741 is not interested in the children of a particular variable object, no
23742 child will be created.
23744 For a leaf variable object it is possible to obtain its value as a
23745 string, or set the value from a string. String value can be also
23746 obtained for a non-leaf variable object, but it's generally a string
23747 that only indicates the type of the object, and does not list its
23748 contents. Assignment to a non-leaf variable object is not allowed.
23750 A frontend does not need to read the values of all variable objects each time
23751 the program stops. Instead, MI provides an update command that lists all
23752 variable objects whose values has changed since the last update
23753 operation. This considerably reduces the amount of data that must
23754 be transferred to the frontend. As noted above, children variable
23755 objects are created on demand, and only leaf variable objects have a
23756 real value. As result, gdb will read target memory only for leaf
23757 variables that frontend has created.
23759 The automatic update is not always desirable. For example, a frontend
23760 might want to keep a value of some expression for future reference,
23761 and never update it. For another example, fetching memory is
23762 relatively slow for embedded targets, so a frontend might want
23763 to disable automatic update for the variables that are either not
23764 visible on the screen, or ``closed''. This is possible using so
23765 called ``frozen variable objects''. Such variable objects are never
23766 implicitly updated.
23768 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
23769 fixed variable object, the expression is parsed when the variable
23770 object is created, including associating identifiers to specific
23771 variables. The meaning of expression never changes. For a floating
23772 variable object the values of variables whose names appear in the
23773 expressions are re-evaluated every time in the context of the current
23774 frame. Consider this example:
23779 struct work_state state;
23786 If a fixed variable object for the @code{state} variable is created in
23787 this function, and we enter the recursive call, the the variable
23788 object will report the value of @code{state} in the top-level
23789 @code{do_work} invocation. On the other hand, a floating variable
23790 object will report the value of @code{state} in the current frame.
23792 If an expression specified when creating a fixed variable object
23793 refers to a local variable, the variable object becomes bound to the
23794 thread and frame in which the variable object is created. When such
23795 variable object is updated, @value{GDBN} makes sure that the
23796 thread/frame combination the variable object is bound to still exists,
23797 and re-evaluates the variable object in context of that thread/frame.
23799 The following is the complete set of @sc{gdb/mi} operations defined to
23800 access this functionality:
23802 @multitable @columnfractions .4 .6
23803 @item @strong{Operation}
23804 @tab @strong{Description}
23806 @item @code{-enable-pretty-printing}
23807 @tab enable Python-based pretty-printing
23808 @item @code{-var-create}
23809 @tab create a variable object
23810 @item @code{-var-delete}
23811 @tab delete the variable object and/or its children
23812 @item @code{-var-set-format}
23813 @tab set the display format of this variable
23814 @item @code{-var-show-format}
23815 @tab show the display format of this variable
23816 @item @code{-var-info-num-children}
23817 @tab tells how many children this object has
23818 @item @code{-var-list-children}
23819 @tab return a list of the object's children
23820 @item @code{-var-info-type}
23821 @tab show the type of this variable object
23822 @item @code{-var-info-expression}
23823 @tab print parent-relative expression that this variable object represents
23824 @item @code{-var-info-path-expression}
23825 @tab print full expression that this variable object represents
23826 @item @code{-var-show-attributes}
23827 @tab is this variable editable? does it exist here?
23828 @item @code{-var-evaluate-expression}
23829 @tab get the value of this variable
23830 @item @code{-var-assign}
23831 @tab set the value of this variable
23832 @item @code{-var-update}
23833 @tab update the variable and its children
23834 @item @code{-var-set-frozen}
23835 @tab set frozeness attribute
23836 @item @code{-var-set-update-range}
23837 @tab set range of children to display on update
23840 In the next subsection we describe each operation in detail and suggest
23841 how it can be used.
23843 @subheading Description And Use of Operations on Variable Objects
23845 @subheading The @code{-enable-pretty-printing} Command
23846 @findex -enable-pretty-printing
23849 -enable-pretty-printing
23852 @value{GDBN} allows Python-based visualizers to affect the output of the
23853 MI variable object commands. However, because there was no way to
23854 implement this in a fully backward-compatible way, a front end must
23855 request that this functionality be enabled.
23857 Once enabled, this feature cannot be disabled.
23859 Note that if Python support has not been compiled into @value{GDBN},
23860 this command will still succeed (and do nothing).
23862 This feature is currently (as of @value{GDBN} 7.0) experimental, and
23863 may work differently in future versions of @value{GDBN}.
23865 @subheading The @code{-var-create} Command
23866 @findex -var-create
23868 @subsubheading Synopsis
23871 -var-create @{@var{name} | "-"@}
23872 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
23875 This operation creates a variable object, which allows the monitoring of
23876 a variable, the result of an expression, a memory cell or a CPU
23879 The @var{name} parameter is the string by which the object can be
23880 referenced. It must be unique. If @samp{-} is specified, the varobj
23881 system will generate a string ``varNNNNNN'' automatically. It will be
23882 unique provided that one does not specify @var{name} of that format.
23883 The command fails if a duplicate name is found.
23885 The frame under which the expression should be evaluated can be
23886 specified by @var{frame-addr}. A @samp{*} indicates that the current
23887 frame should be used. A @samp{@@} indicates that a floating variable
23888 object must be created.
23890 @var{expression} is any expression valid on the current language set (must not
23891 begin with a @samp{*}), or one of the following:
23895 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
23898 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
23901 @samp{$@var{regname}} --- a CPU register name
23904 @cindex dynamic varobj
23905 A varobj's contents may be provided by a Python-based pretty-printer. In this
23906 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
23907 have slightly different semantics in some cases. If the
23908 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
23909 will never create a dynamic varobj. This ensures backward
23910 compatibility for existing clients.
23912 @subsubheading Result
23914 This operation returns attributes of the newly-created varobj. These
23919 The name of the varobj.
23922 The number of children of the varobj. This number is not necessarily
23923 reliable for a dynamic varobj. Instead, you must examine the
23924 @samp{has_more} attribute.
23927 The varobj's scalar value. For a varobj whose type is some sort of
23928 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
23929 will not be interesting.
23932 The varobj's type. This is a string representation of the type, as
23933 would be printed by the @value{GDBN} CLI.
23936 If a variable object is bound to a specific thread, then this is the
23937 thread's identifier.
23940 For a dynamic varobj, this indicates whether there appear to be any
23941 children available. For a non-dynamic varobj, this will be 0.
23944 This attribute will be present and have the value @samp{1} if the
23945 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
23946 then this attribute will not be present.
23949 A dynamic varobj can supply a display hint to the front end. The
23950 value comes directly from the Python pretty-printer object's
23951 @code{display_hint} method. @xref{Pretty Printing}.
23954 Typical output will look like this:
23957 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
23958 has_more="@var{has_more}"
23962 @subheading The @code{-var-delete} Command
23963 @findex -var-delete
23965 @subsubheading Synopsis
23968 -var-delete [ -c ] @var{name}
23971 Deletes a previously created variable object and all of its children.
23972 With the @samp{-c} option, just deletes the children.
23974 Returns an error if the object @var{name} is not found.
23977 @subheading The @code{-var-set-format} Command
23978 @findex -var-set-format
23980 @subsubheading Synopsis
23983 -var-set-format @var{name} @var{format-spec}
23986 Sets the output format for the value of the object @var{name} to be
23989 @anchor{-var-set-format}
23990 The syntax for the @var{format-spec} is as follows:
23993 @var{format-spec} @expansion{}
23994 @{binary | decimal | hexadecimal | octal | natural@}
23997 The natural format is the default format choosen automatically
23998 based on the variable type (like decimal for an @code{int}, hex
23999 for pointers, etc.).
24001 For a variable with children, the format is set only on the
24002 variable itself, and the children are not affected.
24004 @subheading The @code{-var-show-format} Command
24005 @findex -var-show-format
24007 @subsubheading Synopsis
24010 -var-show-format @var{name}
24013 Returns the format used to display the value of the object @var{name}.
24016 @var{format} @expansion{}
24021 @subheading The @code{-var-info-num-children} Command
24022 @findex -var-info-num-children
24024 @subsubheading Synopsis
24027 -var-info-num-children @var{name}
24030 Returns the number of children of a variable object @var{name}:
24036 Note that this number is not completely reliable for a dynamic varobj.
24037 It will return the current number of children, but more children may
24041 @subheading The @code{-var-list-children} Command
24042 @findex -var-list-children
24044 @subsubheading Synopsis
24047 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
24049 @anchor{-var-list-children}
24051 Return a list of the children of the specified variable object and
24052 create variable objects for them, if they do not already exist. With
24053 a single argument or if @var{print-values} has a value for of 0 or
24054 @code{--no-values}, print only the names of the variables; if
24055 @var{print-values} is 1 or @code{--all-values}, also print their
24056 values; and if it is 2 or @code{--simple-values} print the name and
24057 value for simple data types and just the name for arrays, structures
24060 @var{from} and @var{to}, if specified, indicate the range of children
24061 to report. If @var{from} or @var{to} is less than zero, the range is
24062 reset and all children will be reported. Otherwise, children starting
24063 at @var{from} (zero-based) and up to and excluding @var{to} will be
24066 If a child range is requested, it will only affect the current call to
24067 @code{-var-list-children}, but not future calls to @code{-var-update}.
24068 For this, you must instead use @code{-var-set-update-range}. The
24069 intent of this approach is to enable a front end to implement any
24070 update approach it likes; for example, scrolling a view may cause the
24071 front end to request more children with @code{-var-list-children}, and
24072 then the front end could call @code{-var-set-update-range} with a
24073 different range to ensure that future updates are restricted to just
24076 For each child the following results are returned:
24081 Name of the variable object created for this child.
24084 The expression to be shown to the user by the front end to designate this child.
24085 For example this may be the name of a structure member.
24087 For a dynamic varobj, this value cannot be used to form an
24088 expression. There is no way to do this at all with a dynamic varobj.
24090 For C/C@t{++} structures there are several pseudo children returned to
24091 designate access qualifiers. For these pseudo children @var{exp} is
24092 @samp{public}, @samp{private}, or @samp{protected}. In this case the
24093 type and value are not present.
24095 A dynamic varobj will not report the access qualifying
24096 pseudo-children, regardless of the language. This information is not
24097 available at all with a dynamic varobj.
24100 Number of children this child has. For a dynamic varobj, this will be
24104 The type of the child.
24107 If values were requested, this is the value.
24110 If this variable object is associated with a thread, this is the thread id.
24111 Otherwise this result is not present.
24114 If the variable object is frozen, this variable will be present with a value of 1.
24117 The result may have its own attributes:
24121 A dynamic varobj can supply a display hint to the front end. The
24122 value comes directly from the Python pretty-printer object's
24123 @code{display_hint} method. @xref{Pretty Printing}.
24126 This is an integer attribute which is nonzero if there are children
24127 remaining after the end of the selected range.
24130 @subsubheading Example
24134 -var-list-children n
24135 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
24136 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
24138 -var-list-children --all-values n
24139 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
24140 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
24144 @subheading The @code{-var-info-type} Command
24145 @findex -var-info-type
24147 @subsubheading Synopsis
24150 -var-info-type @var{name}
24153 Returns the type of the specified variable @var{name}. The type is
24154 returned as a string in the same format as it is output by the
24158 type=@var{typename}
24162 @subheading The @code{-var-info-expression} Command
24163 @findex -var-info-expression
24165 @subsubheading Synopsis
24168 -var-info-expression @var{name}
24171 Returns a string that is suitable for presenting this
24172 variable object in user interface. The string is generally
24173 not valid expression in the current language, and cannot be evaluated.
24175 For example, if @code{a} is an array, and variable object
24176 @code{A} was created for @code{a}, then we'll get this output:
24179 (gdb) -var-info-expression A.1
24180 ^done,lang="C",exp="1"
24184 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
24186 Note that the output of the @code{-var-list-children} command also
24187 includes those expressions, so the @code{-var-info-expression} command
24190 @subheading The @code{-var-info-path-expression} Command
24191 @findex -var-info-path-expression
24193 @subsubheading Synopsis
24196 -var-info-path-expression @var{name}
24199 Returns an expression that can be evaluated in the current
24200 context and will yield the same value that a variable object has.
24201 Compare this with the @code{-var-info-expression} command, which
24202 result can be used only for UI presentation. Typical use of
24203 the @code{-var-info-path-expression} command is creating a
24204 watchpoint from a variable object.
24206 This command is currently not valid for children of a dynamic varobj,
24207 and will give an error when invoked on one.
24209 For example, suppose @code{C} is a C@t{++} class, derived from class
24210 @code{Base}, and that the @code{Base} class has a member called
24211 @code{m_size}. Assume a variable @code{c} is has the type of
24212 @code{C} and a variable object @code{C} was created for variable
24213 @code{c}. Then, we'll get this output:
24215 (gdb) -var-info-path-expression C.Base.public.m_size
24216 ^done,path_expr=((Base)c).m_size)
24219 @subheading The @code{-var-show-attributes} Command
24220 @findex -var-show-attributes
24222 @subsubheading Synopsis
24225 -var-show-attributes @var{name}
24228 List attributes of the specified variable object @var{name}:
24231 status=@var{attr} [ ( ,@var{attr} )* ]
24235 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
24237 @subheading The @code{-var-evaluate-expression} Command
24238 @findex -var-evaluate-expression
24240 @subsubheading Synopsis
24243 -var-evaluate-expression [-f @var{format-spec}] @var{name}
24246 Evaluates the expression that is represented by the specified variable
24247 object and returns its value as a string. The format of the string
24248 can be specified with the @samp{-f} option. The possible values of
24249 this option are the same as for @code{-var-set-format}
24250 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
24251 the current display format will be used. The current display format
24252 can be changed using the @code{-var-set-format} command.
24258 Note that one must invoke @code{-var-list-children} for a variable
24259 before the value of a child variable can be evaluated.
24261 @subheading The @code{-var-assign} Command
24262 @findex -var-assign
24264 @subsubheading Synopsis
24267 -var-assign @var{name} @var{expression}
24270 Assigns the value of @var{expression} to the variable object specified
24271 by @var{name}. The object must be @samp{editable}. If the variable's
24272 value is altered by the assign, the variable will show up in any
24273 subsequent @code{-var-update} list.
24275 @subsubheading Example
24283 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
24287 @subheading The @code{-var-update} Command
24288 @findex -var-update
24290 @subsubheading Synopsis
24293 -var-update [@var{print-values}] @{@var{name} | "*"@}
24296 Reevaluate the expressions corresponding to the variable object
24297 @var{name} and all its direct and indirect children, and return the
24298 list of variable objects whose values have changed; @var{name} must
24299 be a root variable object. Here, ``changed'' means that the result of
24300 @code{-var-evaluate-expression} before and after the
24301 @code{-var-update} is different. If @samp{*} is used as the variable
24302 object names, all existing variable objects are updated, except
24303 for frozen ones (@pxref{-var-set-frozen}). The option
24304 @var{print-values} determines whether both names and values, or just
24305 names are printed. The possible values of this option are the same
24306 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
24307 recommended to use the @samp{--all-values} option, to reduce the
24308 number of MI commands needed on each program stop.
24310 With the @samp{*} parameter, if a variable object is bound to a
24311 currently running thread, it will not be updated, without any
24314 If @code{-var-set-update-range} was previously used on a varobj, then
24315 only the selected range of children will be reported.
24317 @code{-var-update} reports all the changed varobjs in a tuple named
24320 Each item in the change list is itself a tuple holding:
24324 The name of the varobj.
24327 If values were requested for this update, then this field will be
24328 present and will hold the value of the varobj.
24331 @anchor{-var-update}
24332 This field is a string which may take one of three values:
24336 The variable object's current value is valid.
24339 The variable object does not currently hold a valid value but it may
24340 hold one in the future if its associated expression comes back into
24344 The variable object no longer holds a valid value.
24345 This can occur when the executable file being debugged has changed,
24346 either through recompilation or by using the @value{GDBN} @code{file}
24347 command. The front end should normally choose to delete these variable
24351 In the future new values may be added to this list so the front should
24352 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
24355 This is only present if the varobj is still valid. If the type
24356 changed, then this will be the string @samp{true}; otherwise it will
24360 If the varobj's type changed, then this field will be present and will
24363 @item new_num_children
24364 For a dynamic varobj, if the number of children changed, or if the
24365 type changed, this will be the new number of children.
24367 The @samp{numchild} field in other varobj responses is generally not
24368 valid for a dynamic varobj -- it will show the number of children that
24369 @value{GDBN} knows about, but because dynamic varobjs lazily
24370 instantiate their children, this will not reflect the number of
24371 children which may be available.
24373 The @samp{new_num_children} attribute only reports changes to the
24374 number of children known by @value{GDBN}. This is the only way to
24375 detect whether an update has removed children (which necessarily can
24376 only happen at the end of the update range).
24379 The display hint, if any.
24382 This is an integer value, which will be 1 if there are more children
24383 available outside the varobj's update range.
24386 This attribute will be present and have the value @samp{1} if the
24387 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
24388 then this attribute will not be present.
24391 If new children were added to a dynamic varobj within the selected
24392 update range (as set by @code{-var-set-update-range}), then they will
24393 be listed in this attribute.
24396 @subsubheading Example
24403 -var-update --all-values var1
24404 ^done,changelist=[@{name="var1",value="3",in_scope="true",
24405 type_changed="false"@}]
24409 @subheading The @code{-var-set-frozen} Command
24410 @findex -var-set-frozen
24411 @anchor{-var-set-frozen}
24413 @subsubheading Synopsis
24416 -var-set-frozen @var{name} @var{flag}
24419 Set the frozenness flag on the variable object @var{name}. The
24420 @var{flag} parameter should be either @samp{1} to make the variable
24421 frozen or @samp{0} to make it unfrozen. If a variable object is
24422 frozen, then neither itself, nor any of its children, are
24423 implicitly updated by @code{-var-update} of
24424 a parent variable or by @code{-var-update *}. Only
24425 @code{-var-update} of the variable itself will update its value and
24426 values of its children. After a variable object is unfrozen, it is
24427 implicitly updated by all subsequent @code{-var-update} operations.
24428 Unfreezing a variable does not update it, only subsequent
24429 @code{-var-update} does.
24431 @subsubheading Example
24435 -var-set-frozen V 1
24440 @subheading The @code{-var-set-update-range} command
24441 @findex -var-set-update-range
24442 @anchor{-var-set-update-range}
24444 @subsubheading Synopsis
24447 -var-set-update-range @var{name} @var{from} @var{to}
24450 Set the range of children to be returned by future invocations of
24451 @code{-var-update}.
24453 @var{from} and @var{to} indicate the range of children to report. If
24454 @var{from} or @var{to} is less than zero, the range is reset and all
24455 children will be reported. Otherwise, children starting at @var{from}
24456 (zero-based) and up to and excluding @var{to} will be reported.
24458 @subsubheading Example
24462 -var-set-update-range V 1 2
24466 @subheading The @code{-var-set-visualizer} command
24467 @findex -var-set-visualizer
24468 @anchor{-var-set-visualizer}
24470 @subsubheading Synopsis
24473 -var-set-visualizer @var{name} @var{visualizer}
24476 Set a visualizer for the variable object @var{name}.
24478 @var{visualizer} is the visualizer to use. The special value
24479 @samp{None} means to disable any visualizer in use.
24481 If not @samp{None}, @var{visualizer} must be a Python expression.
24482 This expression must evaluate to a callable object which accepts a
24483 single argument. @value{GDBN} will call this object with the value of
24484 the varobj @var{name} as an argument (this is done so that the same
24485 Python pretty-printing code can be used for both the CLI and MI).
24486 When called, this object must return an object which conforms to the
24487 pretty-printing interface (@pxref{Pretty Printing}).
24489 The pre-defined function @code{gdb.default_visualizer} may be used to
24490 select a visualizer by following the built-in process
24491 (@pxref{Selecting Pretty-Printers}). This is done automatically when
24492 a varobj is created, and so ordinarily is not needed.
24494 This feature is only available if Python support is enabled. The MI
24495 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
24496 can be used to check this.
24498 @subsubheading Example
24500 Resetting the visualizer:
24504 -var-set-visualizer V None
24508 Reselecting the default (type-based) visualizer:
24512 -var-set-visualizer V gdb.default_visualizer
24516 Suppose @code{SomeClass} is a visualizer class. A lambda expression
24517 can be used to instantiate this class for a varobj:
24521 -var-set-visualizer V "lambda val: SomeClass()"
24525 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24526 @node GDB/MI Data Manipulation
24527 @section @sc{gdb/mi} Data Manipulation
24529 @cindex data manipulation, in @sc{gdb/mi}
24530 @cindex @sc{gdb/mi}, data manipulation
24531 This section describes the @sc{gdb/mi} commands that manipulate data:
24532 examine memory and registers, evaluate expressions, etc.
24534 @c REMOVED FROM THE INTERFACE.
24535 @c @subheading -data-assign
24536 @c Change the value of a program variable. Plenty of side effects.
24537 @c @subsubheading GDB Command
24539 @c @subsubheading Example
24542 @subheading The @code{-data-disassemble} Command
24543 @findex -data-disassemble
24545 @subsubheading Synopsis
24549 [ -s @var{start-addr} -e @var{end-addr} ]
24550 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
24558 @item @var{start-addr}
24559 is the beginning address (or @code{$pc})
24560 @item @var{end-addr}
24562 @item @var{filename}
24563 is the name of the file to disassemble
24564 @item @var{linenum}
24565 is the line number to disassemble around
24567 is the number of disassembly lines to be produced. If it is -1,
24568 the whole function will be disassembled, in case no @var{end-addr} is
24569 specified. If @var{end-addr} is specified as a non-zero value, and
24570 @var{lines} is lower than the number of disassembly lines between
24571 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
24572 displayed; if @var{lines} is higher than the number of lines between
24573 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
24576 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
24580 @subsubheading Result
24582 The output for each instruction is composed of four fields:
24591 Note that whatever included in the instruction field, is not manipulated
24592 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
24594 @subsubheading @value{GDBN} Command
24596 There's no direct mapping from this command to the CLI.
24598 @subsubheading Example
24600 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
24604 -data-disassemble -s $pc -e "$pc + 20" -- 0
24607 @{address="0x000107c0",func-name="main",offset="4",
24608 inst="mov 2, %o0"@},
24609 @{address="0x000107c4",func-name="main",offset="8",
24610 inst="sethi %hi(0x11800), %o2"@},
24611 @{address="0x000107c8",func-name="main",offset="12",
24612 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
24613 @{address="0x000107cc",func-name="main",offset="16",
24614 inst="sethi %hi(0x11800), %o2"@},
24615 @{address="0x000107d0",func-name="main",offset="20",
24616 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
24620 Disassemble the whole @code{main} function. Line 32 is part of
24624 -data-disassemble -f basics.c -l 32 -- 0
24626 @{address="0x000107bc",func-name="main",offset="0",
24627 inst="save %sp, -112, %sp"@},
24628 @{address="0x000107c0",func-name="main",offset="4",
24629 inst="mov 2, %o0"@},
24630 @{address="0x000107c4",func-name="main",offset="8",
24631 inst="sethi %hi(0x11800), %o2"@},
24633 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
24634 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
24638 Disassemble 3 instructions from the start of @code{main}:
24642 -data-disassemble -f basics.c -l 32 -n 3 -- 0
24644 @{address="0x000107bc",func-name="main",offset="0",
24645 inst="save %sp, -112, %sp"@},
24646 @{address="0x000107c0",func-name="main",offset="4",
24647 inst="mov 2, %o0"@},
24648 @{address="0x000107c4",func-name="main",offset="8",
24649 inst="sethi %hi(0x11800), %o2"@}]
24653 Disassemble 3 instructions from the start of @code{main} in mixed mode:
24657 -data-disassemble -f basics.c -l 32 -n 3 -- 1
24659 src_and_asm_line=@{line="31",
24660 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
24661 testsuite/gdb.mi/basics.c",line_asm_insn=[
24662 @{address="0x000107bc",func-name="main",offset="0",
24663 inst="save %sp, -112, %sp"@}]@},
24664 src_and_asm_line=@{line="32",
24665 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
24666 testsuite/gdb.mi/basics.c",line_asm_insn=[
24667 @{address="0x000107c0",func-name="main",offset="4",
24668 inst="mov 2, %o0"@},
24669 @{address="0x000107c4",func-name="main",offset="8",
24670 inst="sethi %hi(0x11800), %o2"@}]@}]
24675 @subheading The @code{-data-evaluate-expression} Command
24676 @findex -data-evaluate-expression
24678 @subsubheading Synopsis
24681 -data-evaluate-expression @var{expr}
24684 Evaluate @var{expr} as an expression. The expression could contain an
24685 inferior function call. The function call will execute synchronously.
24686 If the expression contains spaces, it must be enclosed in double quotes.
24688 @subsubheading @value{GDBN} Command
24690 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
24691 @samp{call}. In @code{gdbtk} only, there's a corresponding
24692 @samp{gdb_eval} command.
24694 @subsubheading Example
24696 In the following example, the numbers that precede the commands are the
24697 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
24698 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
24702 211-data-evaluate-expression A
24705 311-data-evaluate-expression &A
24706 311^done,value="0xefffeb7c"
24708 411-data-evaluate-expression A+3
24711 511-data-evaluate-expression "A + 3"
24717 @subheading The @code{-data-list-changed-registers} Command
24718 @findex -data-list-changed-registers
24720 @subsubheading Synopsis
24723 -data-list-changed-registers
24726 Display a list of the registers that have changed.
24728 @subsubheading @value{GDBN} Command
24730 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
24731 has the corresponding command @samp{gdb_changed_register_list}.
24733 @subsubheading Example
24735 On a PPC MBX board:
24743 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
24744 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
24747 -data-list-changed-registers
24748 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
24749 "10","11","13","14","15","16","17","18","19","20","21","22","23",
24750 "24","25","26","27","28","30","31","64","65","66","67","69"]
24755 @subheading The @code{-data-list-register-names} Command
24756 @findex -data-list-register-names
24758 @subsubheading Synopsis
24761 -data-list-register-names [ ( @var{regno} )+ ]
24764 Show a list of register names for the current target. If no arguments
24765 are given, it shows a list of the names of all the registers. If
24766 integer numbers are given as arguments, it will print a list of the
24767 names of the registers corresponding to the arguments. To ensure
24768 consistency between a register name and its number, the output list may
24769 include empty register names.
24771 @subsubheading @value{GDBN} Command
24773 @value{GDBN} does not have a command which corresponds to
24774 @samp{-data-list-register-names}. In @code{gdbtk} there is a
24775 corresponding command @samp{gdb_regnames}.
24777 @subsubheading Example
24779 For the PPC MBX board:
24782 -data-list-register-names
24783 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
24784 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
24785 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
24786 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
24787 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
24788 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
24789 "", "pc","ps","cr","lr","ctr","xer"]
24791 -data-list-register-names 1 2 3
24792 ^done,register-names=["r1","r2","r3"]
24796 @subheading The @code{-data-list-register-values} Command
24797 @findex -data-list-register-values
24799 @subsubheading Synopsis
24802 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
24805 Display the registers' contents. @var{fmt} is the format according to
24806 which the registers' contents are to be returned, followed by an optional
24807 list of numbers specifying the registers to display. A missing list of
24808 numbers indicates that the contents of all the registers must be returned.
24810 Allowed formats for @var{fmt} are:
24827 @subsubheading @value{GDBN} Command
24829 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
24830 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
24832 @subsubheading Example
24834 For a PPC MBX board (note: line breaks are for readability only, they
24835 don't appear in the actual output):
24839 -data-list-register-values r 64 65
24840 ^done,register-values=[@{number="64",value="0xfe00a300"@},
24841 @{number="65",value="0x00029002"@}]
24843 -data-list-register-values x
24844 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
24845 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
24846 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
24847 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
24848 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
24849 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
24850 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
24851 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
24852 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
24853 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
24854 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
24855 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
24856 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
24857 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
24858 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
24859 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
24860 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
24861 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
24862 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
24863 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
24864 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
24865 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
24866 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
24867 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
24868 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
24869 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
24870 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
24871 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
24872 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
24873 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
24874 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
24875 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
24876 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
24877 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
24878 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
24879 @{number="69",value="0x20002b03"@}]
24884 @subheading The @code{-data-read-memory} Command
24885 @findex -data-read-memory
24887 @subsubheading Synopsis
24890 -data-read-memory [ -o @var{byte-offset} ]
24891 @var{address} @var{word-format} @var{word-size}
24892 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
24899 @item @var{address}
24900 An expression specifying the address of the first memory word to be
24901 read. Complex expressions containing embedded white space should be
24902 quoted using the C convention.
24904 @item @var{word-format}
24905 The format to be used to print the memory words. The notation is the
24906 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
24909 @item @var{word-size}
24910 The size of each memory word in bytes.
24912 @item @var{nr-rows}
24913 The number of rows in the output table.
24915 @item @var{nr-cols}
24916 The number of columns in the output table.
24919 If present, indicates that each row should include an @sc{ascii} dump. The
24920 value of @var{aschar} is used as a padding character when a byte is not a
24921 member of the printable @sc{ascii} character set (printable @sc{ascii}
24922 characters are those whose code is between 32 and 126, inclusively).
24924 @item @var{byte-offset}
24925 An offset to add to the @var{address} before fetching memory.
24928 This command displays memory contents as a table of @var{nr-rows} by
24929 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
24930 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
24931 (returned as @samp{total-bytes}). Should less than the requested number
24932 of bytes be returned by the target, the missing words are identified
24933 using @samp{N/A}. The number of bytes read from the target is returned
24934 in @samp{nr-bytes} and the starting address used to read memory in
24937 The address of the next/previous row or page is available in
24938 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
24941 @subsubheading @value{GDBN} Command
24943 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
24944 @samp{gdb_get_mem} memory read command.
24946 @subsubheading Example
24948 Read six bytes of memory starting at @code{bytes+6} but then offset by
24949 @code{-6} bytes. Format as three rows of two columns. One byte per
24950 word. Display each word in hex.
24954 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
24955 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
24956 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
24957 prev-page="0x0000138a",memory=[
24958 @{addr="0x00001390",data=["0x00","0x01"]@},
24959 @{addr="0x00001392",data=["0x02","0x03"]@},
24960 @{addr="0x00001394",data=["0x04","0x05"]@}]
24964 Read two bytes of memory starting at address @code{shorts + 64} and
24965 display as a single word formatted in decimal.
24969 5-data-read-memory shorts+64 d 2 1 1
24970 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
24971 next-row="0x00001512",prev-row="0x0000150e",
24972 next-page="0x00001512",prev-page="0x0000150e",memory=[
24973 @{addr="0x00001510",data=["128"]@}]
24977 Read thirty two bytes of memory starting at @code{bytes+16} and format
24978 as eight rows of four columns. Include a string encoding with @samp{x}
24979 used as the non-printable character.
24983 4-data-read-memory bytes+16 x 1 8 4 x
24984 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
24985 next-row="0x000013c0",prev-row="0x0000139c",
24986 next-page="0x000013c0",prev-page="0x00001380",memory=[
24987 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
24988 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
24989 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
24990 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
24991 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
24992 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
24993 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
24994 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
24998 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24999 @node GDB/MI Tracepoint Commands
25000 @section @sc{gdb/mi} Tracepoint Commands
25002 The tracepoint commands are not yet implemented.
25004 @c @subheading -trace-actions
25006 @c @subheading -trace-delete
25008 @c @subheading -trace-disable
25010 @c @subheading -trace-dump
25012 @c @subheading -trace-enable
25014 @c @subheading -trace-exists
25016 @c @subheading -trace-find
25018 @c @subheading -trace-frame-number
25020 @c @subheading -trace-info
25022 @c @subheading -trace-insert
25024 @c @subheading -trace-list
25026 @c @subheading -trace-pass-count
25028 @c @subheading -trace-save
25030 @c @subheading -trace-start
25032 @c @subheading -trace-stop
25035 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25036 @node GDB/MI Symbol Query
25037 @section @sc{gdb/mi} Symbol Query Commands
25041 @subheading The @code{-symbol-info-address} Command
25042 @findex -symbol-info-address
25044 @subsubheading Synopsis
25047 -symbol-info-address @var{symbol}
25050 Describe where @var{symbol} is stored.
25052 @subsubheading @value{GDBN} Command
25054 The corresponding @value{GDBN} command is @samp{info address}.
25056 @subsubheading Example
25060 @subheading The @code{-symbol-info-file} Command
25061 @findex -symbol-info-file
25063 @subsubheading Synopsis
25069 Show the file for the symbol.
25071 @subsubheading @value{GDBN} Command
25073 There's no equivalent @value{GDBN} command. @code{gdbtk} has
25074 @samp{gdb_find_file}.
25076 @subsubheading Example
25080 @subheading The @code{-symbol-info-function} Command
25081 @findex -symbol-info-function
25083 @subsubheading Synopsis
25086 -symbol-info-function
25089 Show which function the symbol lives in.
25091 @subsubheading @value{GDBN} Command
25093 @samp{gdb_get_function} in @code{gdbtk}.
25095 @subsubheading Example
25099 @subheading The @code{-symbol-info-line} Command
25100 @findex -symbol-info-line
25102 @subsubheading Synopsis
25108 Show the core addresses of the code for a source line.
25110 @subsubheading @value{GDBN} Command
25112 The corresponding @value{GDBN} command is @samp{info line}.
25113 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
25115 @subsubheading Example
25119 @subheading The @code{-symbol-info-symbol} Command
25120 @findex -symbol-info-symbol
25122 @subsubheading Synopsis
25125 -symbol-info-symbol @var{addr}
25128 Describe what symbol is at location @var{addr}.
25130 @subsubheading @value{GDBN} Command
25132 The corresponding @value{GDBN} command is @samp{info symbol}.
25134 @subsubheading Example
25138 @subheading The @code{-symbol-list-functions} Command
25139 @findex -symbol-list-functions
25141 @subsubheading Synopsis
25144 -symbol-list-functions
25147 List the functions in the executable.
25149 @subsubheading @value{GDBN} Command
25151 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
25152 @samp{gdb_search} in @code{gdbtk}.
25154 @subsubheading Example
25159 @subheading The @code{-symbol-list-lines} Command
25160 @findex -symbol-list-lines
25162 @subsubheading Synopsis
25165 -symbol-list-lines @var{filename}
25168 Print the list of lines that contain code and their associated program
25169 addresses for the given source filename. The entries are sorted in
25170 ascending PC order.
25172 @subsubheading @value{GDBN} Command
25174 There is no corresponding @value{GDBN} command.
25176 @subsubheading Example
25179 -symbol-list-lines basics.c
25180 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
25186 @subheading The @code{-symbol-list-types} Command
25187 @findex -symbol-list-types
25189 @subsubheading Synopsis
25195 List all the type names.
25197 @subsubheading @value{GDBN} Command
25199 The corresponding commands are @samp{info types} in @value{GDBN},
25200 @samp{gdb_search} in @code{gdbtk}.
25202 @subsubheading Example
25206 @subheading The @code{-symbol-list-variables} Command
25207 @findex -symbol-list-variables
25209 @subsubheading Synopsis
25212 -symbol-list-variables
25215 List all the global and static variable names.
25217 @subsubheading @value{GDBN} Command
25219 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
25221 @subsubheading Example
25225 @subheading The @code{-symbol-locate} Command
25226 @findex -symbol-locate
25228 @subsubheading Synopsis
25234 @subsubheading @value{GDBN} Command
25236 @samp{gdb_loc} in @code{gdbtk}.
25238 @subsubheading Example
25242 @subheading The @code{-symbol-type} Command
25243 @findex -symbol-type
25245 @subsubheading Synopsis
25248 -symbol-type @var{variable}
25251 Show type of @var{variable}.
25253 @subsubheading @value{GDBN} Command
25255 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
25256 @samp{gdb_obj_variable}.
25258 @subsubheading Example
25263 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25264 @node GDB/MI File Commands
25265 @section @sc{gdb/mi} File Commands
25267 This section describes the GDB/MI commands to specify executable file names
25268 and to read in and obtain symbol table information.
25270 @subheading The @code{-file-exec-and-symbols} Command
25271 @findex -file-exec-and-symbols
25273 @subsubheading Synopsis
25276 -file-exec-and-symbols @var{file}
25279 Specify the executable file to be debugged. This file is the one from
25280 which the symbol table is also read. If no file is specified, the
25281 command clears the executable and symbol information. If breakpoints
25282 are set when using this command with no arguments, @value{GDBN} will produce
25283 error messages. Otherwise, no output is produced, except a completion
25286 @subsubheading @value{GDBN} Command
25288 The corresponding @value{GDBN} command is @samp{file}.
25290 @subsubheading Example
25294 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
25300 @subheading The @code{-file-exec-file} Command
25301 @findex -file-exec-file
25303 @subsubheading Synopsis
25306 -file-exec-file @var{file}
25309 Specify the executable file to be debugged. Unlike
25310 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
25311 from this file. If used without argument, @value{GDBN} clears the information
25312 about the executable file. No output is produced, except a completion
25315 @subsubheading @value{GDBN} Command
25317 The corresponding @value{GDBN} command is @samp{exec-file}.
25319 @subsubheading Example
25323 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
25330 @subheading The @code{-file-list-exec-sections} Command
25331 @findex -file-list-exec-sections
25333 @subsubheading Synopsis
25336 -file-list-exec-sections
25339 List the sections of the current executable file.
25341 @subsubheading @value{GDBN} Command
25343 The @value{GDBN} command @samp{info file} shows, among the rest, the same
25344 information as this command. @code{gdbtk} has a corresponding command
25345 @samp{gdb_load_info}.
25347 @subsubheading Example
25352 @subheading The @code{-file-list-exec-source-file} Command
25353 @findex -file-list-exec-source-file
25355 @subsubheading Synopsis
25358 -file-list-exec-source-file
25361 List the line number, the current source file, and the absolute path
25362 to the current source file for the current executable. The macro
25363 information field has a value of @samp{1} or @samp{0} depending on
25364 whether or not the file includes preprocessor macro information.
25366 @subsubheading @value{GDBN} Command
25368 The @value{GDBN} equivalent is @samp{info source}
25370 @subsubheading Example
25374 123-file-list-exec-source-file
25375 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
25380 @subheading The @code{-file-list-exec-source-files} Command
25381 @findex -file-list-exec-source-files
25383 @subsubheading Synopsis
25386 -file-list-exec-source-files
25389 List the source files for the current executable.
25391 It will always output the filename, but only when @value{GDBN} can find
25392 the absolute file name of a source file, will it output the fullname.
25394 @subsubheading @value{GDBN} Command
25396 The @value{GDBN} equivalent is @samp{info sources}.
25397 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
25399 @subsubheading Example
25402 -file-list-exec-source-files
25404 @{file=foo.c,fullname=/home/foo.c@},
25405 @{file=/home/bar.c,fullname=/home/bar.c@},
25406 @{file=gdb_could_not_find_fullpath.c@}]
25411 @subheading The @code{-file-list-shared-libraries} Command
25412 @findex -file-list-shared-libraries
25414 @subsubheading Synopsis
25417 -file-list-shared-libraries
25420 List the shared libraries in the program.
25422 @subsubheading @value{GDBN} Command
25424 The corresponding @value{GDBN} command is @samp{info shared}.
25426 @subsubheading Example
25430 @subheading The @code{-file-list-symbol-files} Command
25431 @findex -file-list-symbol-files
25433 @subsubheading Synopsis
25436 -file-list-symbol-files
25441 @subsubheading @value{GDBN} Command
25443 The corresponding @value{GDBN} command is @samp{info file} (part of it).
25445 @subsubheading Example
25450 @subheading The @code{-file-symbol-file} Command
25451 @findex -file-symbol-file
25453 @subsubheading Synopsis
25456 -file-symbol-file @var{file}
25459 Read symbol table info from the specified @var{file} argument. When
25460 used without arguments, clears @value{GDBN}'s symbol table info. No output is
25461 produced, except for a completion notification.
25463 @subsubheading @value{GDBN} Command
25465 The corresponding @value{GDBN} command is @samp{symbol-file}.
25467 @subsubheading Example
25471 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
25477 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25478 @node GDB/MI Memory Overlay Commands
25479 @section @sc{gdb/mi} Memory Overlay Commands
25481 The memory overlay commands are not implemented.
25483 @c @subheading -overlay-auto
25485 @c @subheading -overlay-list-mapping-state
25487 @c @subheading -overlay-list-overlays
25489 @c @subheading -overlay-map
25491 @c @subheading -overlay-off
25493 @c @subheading -overlay-on
25495 @c @subheading -overlay-unmap
25497 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25498 @node GDB/MI Signal Handling Commands
25499 @section @sc{gdb/mi} Signal Handling Commands
25501 Signal handling commands are not implemented.
25503 @c @subheading -signal-handle
25505 @c @subheading -signal-list-handle-actions
25507 @c @subheading -signal-list-signal-types
25511 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25512 @node GDB/MI Target Manipulation
25513 @section @sc{gdb/mi} Target Manipulation Commands
25516 @subheading The @code{-target-attach} Command
25517 @findex -target-attach
25519 @subsubheading Synopsis
25522 -target-attach @var{pid} | @var{gid} | @var{file}
25525 Attach to a process @var{pid} or a file @var{file} outside of
25526 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
25527 group, the id previously returned by
25528 @samp{-list-thread-groups --available} must be used.
25530 @subsubheading @value{GDBN} Command
25532 The corresponding @value{GDBN} command is @samp{attach}.
25534 @subsubheading Example
25538 =thread-created,id="1"
25539 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
25545 @subheading The @code{-target-compare-sections} Command
25546 @findex -target-compare-sections
25548 @subsubheading Synopsis
25551 -target-compare-sections [ @var{section} ]
25554 Compare data of section @var{section} on target to the exec file.
25555 Without the argument, all sections are compared.
25557 @subsubheading @value{GDBN} Command
25559 The @value{GDBN} equivalent is @samp{compare-sections}.
25561 @subsubheading Example
25566 @subheading The @code{-target-detach} Command
25567 @findex -target-detach
25569 @subsubheading Synopsis
25572 -target-detach [ @var{pid} | @var{gid} ]
25575 Detach from the remote target which normally resumes its execution.
25576 If either @var{pid} or @var{gid} is specified, detaches from either
25577 the specified process, or specified thread group. There's no output.
25579 @subsubheading @value{GDBN} Command
25581 The corresponding @value{GDBN} command is @samp{detach}.
25583 @subsubheading Example
25593 @subheading The @code{-target-disconnect} Command
25594 @findex -target-disconnect
25596 @subsubheading Synopsis
25602 Disconnect from the remote target. There's no output and the target is
25603 generally not resumed.
25605 @subsubheading @value{GDBN} Command
25607 The corresponding @value{GDBN} command is @samp{disconnect}.
25609 @subsubheading Example
25619 @subheading The @code{-target-download} Command
25620 @findex -target-download
25622 @subsubheading Synopsis
25628 Loads the executable onto the remote target.
25629 It prints out an update message every half second, which includes the fields:
25633 The name of the section.
25635 The size of what has been sent so far for that section.
25637 The size of the section.
25639 The total size of what was sent so far (the current and the previous sections).
25641 The size of the overall executable to download.
25645 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
25646 @sc{gdb/mi} Output Syntax}).
25648 In addition, it prints the name and size of the sections, as they are
25649 downloaded. These messages include the following fields:
25653 The name of the section.
25655 The size of the section.
25657 The size of the overall executable to download.
25661 At the end, a summary is printed.
25663 @subsubheading @value{GDBN} Command
25665 The corresponding @value{GDBN} command is @samp{load}.
25667 @subsubheading Example
25669 Note: each status message appears on a single line. Here the messages
25670 have been broken down so that they can fit onto a page.
25675 +download,@{section=".text",section-size="6668",total-size="9880"@}
25676 +download,@{section=".text",section-sent="512",section-size="6668",
25677 total-sent="512",total-size="9880"@}
25678 +download,@{section=".text",section-sent="1024",section-size="6668",
25679 total-sent="1024",total-size="9880"@}
25680 +download,@{section=".text",section-sent="1536",section-size="6668",
25681 total-sent="1536",total-size="9880"@}
25682 +download,@{section=".text",section-sent="2048",section-size="6668",
25683 total-sent="2048",total-size="9880"@}
25684 +download,@{section=".text",section-sent="2560",section-size="6668",
25685 total-sent="2560",total-size="9880"@}
25686 +download,@{section=".text",section-sent="3072",section-size="6668",
25687 total-sent="3072",total-size="9880"@}
25688 +download,@{section=".text",section-sent="3584",section-size="6668",
25689 total-sent="3584",total-size="9880"@}
25690 +download,@{section=".text",section-sent="4096",section-size="6668",
25691 total-sent="4096",total-size="9880"@}
25692 +download,@{section=".text",section-sent="4608",section-size="6668",
25693 total-sent="4608",total-size="9880"@}
25694 +download,@{section=".text",section-sent="5120",section-size="6668",
25695 total-sent="5120",total-size="9880"@}
25696 +download,@{section=".text",section-sent="5632",section-size="6668",
25697 total-sent="5632",total-size="9880"@}
25698 +download,@{section=".text",section-sent="6144",section-size="6668",
25699 total-sent="6144",total-size="9880"@}
25700 +download,@{section=".text",section-sent="6656",section-size="6668",
25701 total-sent="6656",total-size="9880"@}
25702 +download,@{section=".init",section-size="28",total-size="9880"@}
25703 +download,@{section=".fini",section-size="28",total-size="9880"@}
25704 +download,@{section=".data",section-size="3156",total-size="9880"@}
25705 +download,@{section=".data",section-sent="512",section-size="3156",
25706 total-sent="7236",total-size="9880"@}
25707 +download,@{section=".data",section-sent="1024",section-size="3156",
25708 total-sent="7748",total-size="9880"@}
25709 +download,@{section=".data",section-sent="1536",section-size="3156",
25710 total-sent="8260",total-size="9880"@}
25711 +download,@{section=".data",section-sent="2048",section-size="3156",
25712 total-sent="8772",total-size="9880"@}
25713 +download,@{section=".data",section-sent="2560",section-size="3156",
25714 total-sent="9284",total-size="9880"@}
25715 +download,@{section=".data",section-sent="3072",section-size="3156",
25716 total-sent="9796",total-size="9880"@}
25717 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
25724 @subheading The @code{-target-exec-status} Command
25725 @findex -target-exec-status
25727 @subsubheading Synopsis
25730 -target-exec-status
25733 Provide information on the state of the target (whether it is running or
25734 not, for instance).
25736 @subsubheading @value{GDBN} Command
25738 There's no equivalent @value{GDBN} command.
25740 @subsubheading Example
25744 @subheading The @code{-target-list-available-targets} Command
25745 @findex -target-list-available-targets
25747 @subsubheading Synopsis
25750 -target-list-available-targets
25753 List the possible targets to connect to.
25755 @subsubheading @value{GDBN} Command
25757 The corresponding @value{GDBN} command is @samp{help target}.
25759 @subsubheading Example
25763 @subheading The @code{-target-list-current-targets} Command
25764 @findex -target-list-current-targets
25766 @subsubheading Synopsis
25769 -target-list-current-targets
25772 Describe the current target.
25774 @subsubheading @value{GDBN} Command
25776 The corresponding information is printed by @samp{info file} (among
25779 @subsubheading Example
25783 @subheading The @code{-target-list-parameters} Command
25784 @findex -target-list-parameters
25786 @subsubheading Synopsis
25789 -target-list-parameters
25795 @subsubheading @value{GDBN} Command
25799 @subsubheading Example
25803 @subheading The @code{-target-select} Command
25804 @findex -target-select
25806 @subsubheading Synopsis
25809 -target-select @var{type} @var{parameters @dots{}}
25812 Connect @value{GDBN} to the remote target. This command takes two args:
25816 The type of target, for instance @samp{remote}, etc.
25817 @item @var{parameters}
25818 Device names, host names and the like. @xref{Target Commands, ,
25819 Commands for Managing Targets}, for more details.
25822 The output is a connection notification, followed by the address at
25823 which the target program is, in the following form:
25826 ^connected,addr="@var{address}",func="@var{function name}",
25827 args=[@var{arg list}]
25830 @subsubheading @value{GDBN} Command
25832 The corresponding @value{GDBN} command is @samp{target}.
25834 @subsubheading Example
25838 -target-select remote /dev/ttya
25839 ^connected,addr="0xfe00a300",func="??",args=[]
25843 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25844 @node GDB/MI File Transfer Commands
25845 @section @sc{gdb/mi} File Transfer Commands
25848 @subheading The @code{-target-file-put} Command
25849 @findex -target-file-put
25851 @subsubheading Synopsis
25854 -target-file-put @var{hostfile} @var{targetfile}
25857 Copy file @var{hostfile} from the host system (the machine running
25858 @value{GDBN}) to @var{targetfile} on the target system.
25860 @subsubheading @value{GDBN} Command
25862 The corresponding @value{GDBN} command is @samp{remote put}.
25864 @subsubheading Example
25868 -target-file-put localfile remotefile
25874 @subheading The @code{-target-file-get} Command
25875 @findex -target-file-get
25877 @subsubheading Synopsis
25880 -target-file-get @var{targetfile} @var{hostfile}
25883 Copy file @var{targetfile} from the target system to @var{hostfile}
25884 on the host system.
25886 @subsubheading @value{GDBN} Command
25888 The corresponding @value{GDBN} command is @samp{remote get}.
25890 @subsubheading Example
25894 -target-file-get remotefile localfile
25900 @subheading The @code{-target-file-delete} Command
25901 @findex -target-file-delete
25903 @subsubheading Synopsis
25906 -target-file-delete @var{targetfile}
25909 Delete @var{targetfile} from the target system.
25911 @subsubheading @value{GDBN} Command
25913 The corresponding @value{GDBN} command is @samp{remote delete}.
25915 @subsubheading Example
25919 -target-file-delete remotefile
25925 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25926 @node GDB/MI Miscellaneous Commands
25927 @section Miscellaneous @sc{gdb/mi} Commands
25929 @c @subheading -gdb-complete
25931 @subheading The @code{-gdb-exit} Command
25934 @subsubheading Synopsis
25940 Exit @value{GDBN} immediately.
25942 @subsubheading @value{GDBN} Command
25944 Approximately corresponds to @samp{quit}.
25946 @subsubheading Example
25956 @subheading The @code{-exec-abort} Command
25957 @findex -exec-abort
25959 @subsubheading Synopsis
25965 Kill the inferior running program.
25967 @subsubheading @value{GDBN} Command
25969 The corresponding @value{GDBN} command is @samp{kill}.
25971 @subsubheading Example
25976 @subheading The @code{-gdb-set} Command
25979 @subsubheading Synopsis
25985 Set an internal @value{GDBN} variable.
25986 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
25988 @subsubheading @value{GDBN} Command
25990 The corresponding @value{GDBN} command is @samp{set}.
25992 @subsubheading Example
26002 @subheading The @code{-gdb-show} Command
26005 @subsubheading Synopsis
26011 Show the current value of a @value{GDBN} variable.
26013 @subsubheading @value{GDBN} Command
26015 The corresponding @value{GDBN} command is @samp{show}.
26017 @subsubheading Example
26026 @c @subheading -gdb-source
26029 @subheading The @code{-gdb-version} Command
26030 @findex -gdb-version
26032 @subsubheading Synopsis
26038 Show version information for @value{GDBN}. Used mostly in testing.
26040 @subsubheading @value{GDBN} Command
26042 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
26043 default shows this information when you start an interactive session.
26045 @subsubheading Example
26047 @c This example modifies the actual output from GDB to avoid overfull
26053 ~Copyright 2000 Free Software Foundation, Inc.
26054 ~GDB is free software, covered by the GNU General Public License, and
26055 ~you are welcome to change it and/or distribute copies of it under
26056 ~ certain conditions.
26057 ~Type "show copying" to see the conditions.
26058 ~There is absolutely no warranty for GDB. Type "show warranty" for
26060 ~This GDB was configured as
26061 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
26066 @subheading The @code{-list-features} Command
26067 @findex -list-features
26069 Returns a list of particular features of the MI protocol that
26070 this version of gdb implements. A feature can be a command,
26071 or a new field in an output of some command, or even an
26072 important bugfix. While a frontend can sometimes detect presence
26073 of a feature at runtime, it is easier to perform detection at debugger
26076 The command returns a list of strings, with each string naming an
26077 available feature. Each returned string is just a name, it does not
26078 have any internal structure. The list of possible feature names
26084 (gdb) -list-features
26085 ^done,result=["feature1","feature2"]
26088 The current list of features is:
26091 @item frozen-varobjs
26092 Indicates presence of the @code{-var-set-frozen} command, as well
26093 as possible presense of the @code{frozen} field in the output
26094 of @code{-varobj-create}.
26095 @item pending-breakpoints
26096 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
26098 Indicates presence of Python scripting support, Python-based
26099 pretty-printing commands, and possible presence of the
26100 @samp{display_hint} field in the output of @code{-var-list-children}
26102 Indicates presence of the @code{-thread-info} command.
26106 @subheading The @code{-list-target-features} Command
26107 @findex -list-target-features
26109 Returns a list of particular features that are supported by the
26110 target. Those features affect the permitted MI commands, but
26111 unlike the features reported by the @code{-list-features} command, the
26112 features depend on which target GDB is using at the moment. Whenever
26113 a target can change, due to commands such as @code{-target-select},
26114 @code{-target-attach} or @code{-exec-run}, the list of target features
26115 may change, and the frontend should obtain it again.
26119 (gdb) -list-features
26120 ^done,result=["async"]
26123 The current list of features is:
26127 Indicates that the target is capable of asynchronous command
26128 execution, which means that @value{GDBN} will accept further commands
26129 while the target is running.
26133 @subheading The @code{-list-thread-groups} Command
26134 @findex -list-thread-groups
26136 @subheading Synopsis
26139 -list-thread-groups [ --available ] [ @var{group} ]
26142 When used without the @var{group} parameter, lists top-level thread
26143 groups that are being debugged. When used with the @var{group}
26144 parameter, the children of the specified group are listed. The
26145 children can be either threads, or other groups. At present,
26146 @value{GDBN} will not report both threads and groups as children at
26147 the same time, but it may change in future.
26149 With the @samp{--available} option, instead of reporting groups that
26150 are been debugged, GDB will report all thread groups available on the
26151 target. Using the @samp{--available} option together with @var{group}
26154 @subheading Example
26158 -list-thread-groups
26159 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
26160 -list-thread-groups 17
26161 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
26162 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
26163 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
26164 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
26165 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
26168 @subheading The @code{-interpreter-exec} Command
26169 @findex -interpreter-exec
26171 @subheading Synopsis
26174 -interpreter-exec @var{interpreter} @var{command}
26176 @anchor{-interpreter-exec}
26178 Execute the specified @var{command} in the given @var{interpreter}.
26180 @subheading @value{GDBN} Command
26182 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
26184 @subheading Example
26188 -interpreter-exec console "break main"
26189 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
26190 &"During symbol reading, bad structure-type format.\n"
26191 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
26196 @subheading The @code{-inferior-tty-set} Command
26197 @findex -inferior-tty-set
26199 @subheading Synopsis
26202 -inferior-tty-set /dev/pts/1
26205 Set terminal for future runs of the program being debugged.
26207 @subheading @value{GDBN} Command
26209 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
26211 @subheading Example
26215 -inferior-tty-set /dev/pts/1
26220 @subheading The @code{-inferior-tty-show} Command
26221 @findex -inferior-tty-show
26223 @subheading Synopsis
26229 Show terminal for future runs of program being debugged.
26231 @subheading @value{GDBN} Command
26233 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
26235 @subheading Example
26239 -inferior-tty-set /dev/pts/1
26243 ^done,inferior_tty_terminal="/dev/pts/1"
26247 @subheading The @code{-enable-timings} Command
26248 @findex -enable-timings
26250 @subheading Synopsis
26253 -enable-timings [yes | no]
26256 Toggle the printing of the wallclock, user and system times for an MI
26257 command as a field in its output. This command is to help frontend
26258 developers optimize the performance of their code. No argument is
26259 equivalent to @samp{yes}.
26261 @subheading @value{GDBN} Command
26265 @subheading Example
26273 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26274 addr="0x080484ed",func="main",file="myprog.c",
26275 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
26276 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
26284 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
26285 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
26286 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
26287 fullname="/home/nickrob/myprog.c",line="73"@}
26292 @chapter @value{GDBN} Annotations
26294 This chapter describes annotations in @value{GDBN}. Annotations were
26295 designed to interface @value{GDBN} to graphical user interfaces or other
26296 similar programs which want to interact with @value{GDBN} at a
26297 relatively high level.
26299 The annotation mechanism has largely been superseded by @sc{gdb/mi}
26303 This is Edition @value{EDITION}, @value{DATE}.
26307 * Annotations Overview:: What annotations are; the general syntax.
26308 * Server Prefix:: Issuing a command without affecting user state.
26309 * Prompting:: Annotations marking @value{GDBN}'s need for input.
26310 * Errors:: Annotations for error messages.
26311 * Invalidation:: Some annotations describe things now invalid.
26312 * Annotations for Running::
26313 Whether the program is running, how it stopped, etc.
26314 * Source Annotations:: Annotations describing source code.
26317 @node Annotations Overview
26318 @section What is an Annotation?
26319 @cindex annotations
26321 Annotations start with a newline character, two @samp{control-z}
26322 characters, and the name of the annotation. If there is no additional
26323 information associated with this annotation, the name of the annotation
26324 is followed immediately by a newline. If there is additional
26325 information, the name of the annotation is followed by a space, the
26326 additional information, and a newline. The additional information
26327 cannot contain newline characters.
26329 Any output not beginning with a newline and two @samp{control-z}
26330 characters denotes literal output from @value{GDBN}. Currently there is
26331 no need for @value{GDBN} to output a newline followed by two
26332 @samp{control-z} characters, but if there was such a need, the
26333 annotations could be extended with an @samp{escape} annotation which
26334 means those three characters as output.
26336 The annotation @var{level}, which is specified using the
26337 @option{--annotate} command line option (@pxref{Mode Options}), controls
26338 how much information @value{GDBN} prints together with its prompt,
26339 values of expressions, source lines, and other types of output. Level 0
26340 is for no annotations, level 1 is for use when @value{GDBN} is run as a
26341 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
26342 for programs that control @value{GDBN}, and level 2 annotations have
26343 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
26344 Interface, annotate, GDB's Obsolete Annotations}).
26347 @kindex set annotate
26348 @item set annotate @var{level}
26349 The @value{GDBN} command @code{set annotate} sets the level of
26350 annotations to the specified @var{level}.
26352 @item show annotate
26353 @kindex show annotate
26354 Show the current annotation level.
26357 This chapter describes level 3 annotations.
26359 A simple example of starting up @value{GDBN} with annotations is:
26362 $ @kbd{gdb --annotate=3}
26364 Copyright 2003 Free Software Foundation, Inc.
26365 GDB is free software, covered by the GNU General Public License,
26366 and you are welcome to change it and/or distribute copies of it
26367 under certain conditions.
26368 Type "show copying" to see the conditions.
26369 There is absolutely no warranty for GDB. Type "show warranty"
26371 This GDB was configured as "i386-pc-linux-gnu"
26382 Here @samp{quit} is input to @value{GDBN}; the rest is output from
26383 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
26384 denotes a @samp{control-z} character) are annotations; the rest is
26385 output from @value{GDBN}.
26387 @node Server Prefix
26388 @section The Server Prefix
26389 @cindex server prefix
26391 If you prefix a command with @samp{server } then it will not affect
26392 the command history, nor will it affect @value{GDBN}'s notion of which
26393 command to repeat if @key{RET} is pressed on a line by itself. This
26394 means that commands can be run behind a user's back by a front-end in
26395 a transparent manner.
26397 The @code{server } prefix does not affect the recording of values into
26398 the value history; to print a value without recording it into the
26399 value history, use the @code{output} command instead of the
26400 @code{print} command.
26402 Using this prefix also disables confirmation requests
26403 (@pxref{confirmation requests}).
26406 @section Annotation for @value{GDBN} Input
26408 @cindex annotations for prompts
26409 When @value{GDBN} prompts for input, it annotates this fact so it is possible
26410 to know when to send output, when the output from a given command is
26413 Different kinds of input each have a different @dfn{input type}. Each
26414 input type has three annotations: a @code{pre-} annotation, which
26415 denotes the beginning of any prompt which is being output, a plain
26416 annotation, which denotes the end of the prompt, and then a @code{post-}
26417 annotation which denotes the end of any echo which may (or may not) be
26418 associated with the input. For example, the @code{prompt} input type
26419 features the following annotations:
26427 The input types are
26430 @findex pre-prompt annotation
26431 @findex prompt annotation
26432 @findex post-prompt annotation
26434 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
26436 @findex pre-commands annotation
26437 @findex commands annotation
26438 @findex post-commands annotation
26440 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
26441 command. The annotations are repeated for each command which is input.
26443 @findex pre-overload-choice annotation
26444 @findex overload-choice annotation
26445 @findex post-overload-choice annotation
26446 @item overload-choice
26447 When @value{GDBN} wants the user to select between various overloaded functions.
26449 @findex pre-query annotation
26450 @findex query annotation
26451 @findex post-query annotation
26453 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
26455 @findex pre-prompt-for-continue annotation
26456 @findex prompt-for-continue annotation
26457 @findex post-prompt-for-continue annotation
26458 @item prompt-for-continue
26459 When @value{GDBN} is asking the user to press return to continue. Note: Don't
26460 expect this to work well; instead use @code{set height 0} to disable
26461 prompting. This is because the counting of lines is buggy in the
26462 presence of annotations.
26467 @cindex annotations for errors, warnings and interrupts
26469 @findex quit annotation
26474 This annotation occurs right before @value{GDBN} responds to an interrupt.
26476 @findex error annotation
26481 This annotation occurs right before @value{GDBN} responds to an error.
26483 Quit and error annotations indicate that any annotations which @value{GDBN} was
26484 in the middle of may end abruptly. For example, if a
26485 @code{value-history-begin} annotation is followed by a @code{error}, one
26486 cannot expect to receive the matching @code{value-history-end}. One
26487 cannot expect not to receive it either, however; an error annotation
26488 does not necessarily mean that @value{GDBN} is immediately returning all the way
26491 @findex error-begin annotation
26492 A quit or error annotation may be preceded by
26498 Any output between that and the quit or error annotation is the error
26501 Warning messages are not yet annotated.
26502 @c If we want to change that, need to fix warning(), type_error(),
26503 @c range_error(), and possibly other places.
26506 @section Invalidation Notices
26508 @cindex annotations for invalidation messages
26509 The following annotations say that certain pieces of state may have
26513 @findex frames-invalid annotation
26514 @item ^Z^Zframes-invalid
26516 The frames (for example, output from the @code{backtrace} command) may
26519 @findex breakpoints-invalid annotation
26520 @item ^Z^Zbreakpoints-invalid
26522 The breakpoints may have changed. For example, the user just added or
26523 deleted a breakpoint.
26526 @node Annotations for Running
26527 @section Running the Program
26528 @cindex annotations for running programs
26530 @findex starting annotation
26531 @findex stopping annotation
26532 When the program starts executing due to a @value{GDBN} command such as
26533 @code{step} or @code{continue},
26539 is output. When the program stops,
26545 is output. Before the @code{stopped} annotation, a variety of
26546 annotations describe how the program stopped.
26549 @findex exited annotation
26550 @item ^Z^Zexited @var{exit-status}
26551 The program exited, and @var{exit-status} is the exit status (zero for
26552 successful exit, otherwise nonzero).
26554 @findex signalled annotation
26555 @findex signal-name annotation
26556 @findex signal-name-end annotation
26557 @findex signal-string annotation
26558 @findex signal-string-end annotation
26559 @item ^Z^Zsignalled
26560 The program exited with a signal. After the @code{^Z^Zsignalled}, the
26561 annotation continues:
26567 ^Z^Zsignal-name-end
26571 ^Z^Zsignal-string-end
26576 where @var{name} is the name of the signal, such as @code{SIGILL} or
26577 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
26578 as @code{Illegal Instruction} or @code{Segmentation fault}.
26579 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
26580 user's benefit and have no particular format.
26582 @findex signal annotation
26584 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
26585 just saying that the program received the signal, not that it was
26586 terminated with it.
26588 @findex breakpoint annotation
26589 @item ^Z^Zbreakpoint @var{number}
26590 The program hit breakpoint number @var{number}.
26592 @findex watchpoint annotation
26593 @item ^Z^Zwatchpoint @var{number}
26594 The program hit watchpoint number @var{number}.
26597 @node Source Annotations
26598 @section Displaying Source
26599 @cindex annotations for source display
26601 @findex source annotation
26602 The following annotation is used instead of displaying source code:
26605 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
26608 where @var{filename} is an absolute file name indicating which source
26609 file, @var{line} is the line number within that file (where 1 is the
26610 first line in the file), @var{character} is the character position
26611 within the file (where 0 is the first character in the file) (for most
26612 debug formats this will necessarily point to the beginning of a line),
26613 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
26614 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
26615 @var{addr} is the address in the target program associated with the
26616 source which is being displayed. @var{addr} is in the form @samp{0x}
26617 followed by one or more lowercase hex digits (note that this does not
26618 depend on the language).
26620 @node JIT Interface
26621 @chapter JIT Compilation Interface
26622 @cindex just-in-time compilation
26623 @cindex JIT compilation interface
26625 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
26626 interface. A JIT compiler is a program or library that generates native
26627 executable code at runtime and executes it, usually in order to achieve good
26628 performance while maintaining platform independence.
26630 Programs that use JIT compilation are normally difficult to debug because
26631 portions of their code are generated at runtime, instead of being loaded from
26632 object files, which is where @value{GDBN} normally finds the program's symbols
26633 and debug information. In order to debug programs that use JIT compilation,
26634 @value{GDBN} has an interface that allows the program to register in-memory
26635 symbol files with @value{GDBN} at runtime.
26637 If you are using @value{GDBN} to debug a program that uses this interface, then
26638 it should work transparently so long as you have not stripped the binary. If
26639 you are developing a JIT compiler, then the interface is documented in the rest
26640 of this chapter. At this time, the only known client of this interface is the
26643 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
26644 JIT compiler communicates with @value{GDBN} by writing data into a global
26645 variable and calling a fuction at a well-known symbol. When @value{GDBN}
26646 attaches, it reads a linked list of symbol files from the global variable to
26647 find existing code, and puts a breakpoint in the function so that it can find
26648 out about additional code.
26651 * Declarations:: Relevant C struct declarations
26652 * Registering Code:: Steps to register code
26653 * Unregistering Code:: Steps to unregister code
26657 @section JIT Declarations
26659 These are the relevant struct declarations that a C program should include to
26660 implement the interface:
26670 struct jit_code_entry
26672 struct jit_code_entry *next_entry;
26673 struct jit_code_entry *prev_entry;
26674 const char *symfile_addr;
26675 uint64_t symfile_size;
26678 struct jit_descriptor
26681 /* This type should be jit_actions_t, but we use uint32_t
26682 to be explicit about the bitwidth. */
26683 uint32_t action_flag;
26684 struct jit_code_entry *relevant_entry;
26685 struct jit_code_entry *first_entry;
26688 /* GDB puts a breakpoint in this function. */
26689 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
26691 /* Make sure to specify the version statically, because the
26692 debugger may check the version before we can set it. */
26693 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
26696 If the JIT is multi-threaded, then it is important that the JIT synchronize any
26697 modifications to this global data properly, which can easily be done by putting
26698 a global mutex around modifications to these structures.
26700 @node Registering Code
26701 @section Registering Code
26703 To register code with @value{GDBN}, the JIT should follow this protocol:
26707 Generate an object file in memory with symbols and other desired debug
26708 information. The file must include the virtual addresses of the sections.
26711 Create a code entry for the file, which gives the start and size of the symbol
26715 Add it to the linked list in the JIT descriptor.
26718 Point the relevant_entry field of the descriptor at the entry.
26721 Set @code{action_flag} to @code{JIT_REGISTER} and call
26722 @code{__jit_debug_register_code}.
26725 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
26726 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
26727 new code. However, the linked list must still be maintained in order to allow
26728 @value{GDBN} to attach to a running process and still find the symbol files.
26730 @node Unregistering Code
26731 @section Unregistering Code
26733 If code is freed, then the JIT should use the following protocol:
26737 Remove the code entry corresponding to the code from the linked list.
26740 Point the @code{relevant_entry} field of the descriptor at the code entry.
26743 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
26744 @code{__jit_debug_register_code}.
26747 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
26748 and the JIT will leak the memory used for the associated symbol files.
26751 @chapter Reporting Bugs in @value{GDBN}
26752 @cindex bugs in @value{GDBN}
26753 @cindex reporting bugs in @value{GDBN}
26755 Your bug reports play an essential role in making @value{GDBN} reliable.
26757 Reporting a bug may help you by bringing a solution to your problem, or it
26758 may not. But in any case the principal function of a bug report is to help
26759 the entire community by making the next version of @value{GDBN} work better. Bug
26760 reports are your contribution to the maintenance of @value{GDBN}.
26762 In order for a bug report to serve its purpose, you must include the
26763 information that enables us to fix the bug.
26766 * Bug Criteria:: Have you found a bug?
26767 * Bug Reporting:: How to report bugs
26771 @section Have You Found a Bug?
26772 @cindex bug criteria
26774 If you are not sure whether you have found a bug, here are some guidelines:
26777 @cindex fatal signal
26778 @cindex debugger crash
26779 @cindex crash of debugger
26781 If the debugger gets a fatal signal, for any input whatever, that is a
26782 @value{GDBN} bug. Reliable debuggers never crash.
26784 @cindex error on valid input
26786 If @value{GDBN} produces an error message for valid input, that is a
26787 bug. (Note that if you're cross debugging, the problem may also be
26788 somewhere in the connection to the target.)
26790 @cindex invalid input
26792 If @value{GDBN} does not produce an error message for invalid input,
26793 that is a bug. However, you should note that your idea of
26794 ``invalid input'' might be our idea of ``an extension'' or ``support
26795 for traditional practice''.
26798 If you are an experienced user of debugging tools, your suggestions
26799 for improvement of @value{GDBN} are welcome in any case.
26802 @node Bug Reporting
26803 @section How to Report Bugs
26804 @cindex bug reports
26805 @cindex @value{GDBN} bugs, reporting
26807 A number of companies and individuals offer support for @sc{gnu} products.
26808 If you obtained @value{GDBN} from a support organization, we recommend you
26809 contact that organization first.
26811 You can find contact information for many support companies and
26812 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
26814 @c should add a web page ref...
26817 @ifset BUGURL_DEFAULT
26818 In any event, we also recommend that you submit bug reports for
26819 @value{GDBN}. The preferred method is to submit them directly using
26820 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
26821 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
26824 @strong{Do not send bug reports to @samp{info-gdb}, or to
26825 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
26826 not want to receive bug reports. Those that do have arranged to receive
26829 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
26830 serves as a repeater. The mailing list and the newsgroup carry exactly
26831 the same messages. Often people think of posting bug reports to the
26832 newsgroup instead of mailing them. This appears to work, but it has one
26833 problem which can be crucial: a newsgroup posting often lacks a mail
26834 path back to the sender. Thus, if we need to ask for more information,
26835 we may be unable to reach you. For this reason, it is better to send
26836 bug reports to the mailing list.
26838 @ifclear BUGURL_DEFAULT
26839 In any event, we also recommend that you submit bug reports for
26840 @value{GDBN} to @value{BUGURL}.
26844 The fundamental principle of reporting bugs usefully is this:
26845 @strong{report all the facts}. If you are not sure whether to state a
26846 fact or leave it out, state it!
26848 Often people omit facts because they think they know what causes the
26849 problem and assume that some details do not matter. Thus, you might
26850 assume that the name of the variable you use in an example does not matter.
26851 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
26852 stray memory reference which happens to fetch from the location where that
26853 name is stored in memory; perhaps, if the name were different, the contents
26854 of that location would fool the debugger into doing the right thing despite
26855 the bug. Play it safe and give a specific, complete example. That is the
26856 easiest thing for you to do, and the most helpful.
26858 Keep in mind that the purpose of a bug report is to enable us to fix the
26859 bug. It may be that the bug has been reported previously, but neither
26860 you nor we can know that unless your bug report is complete and
26863 Sometimes people give a few sketchy facts and ask, ``Does this ring a
26864 bell?'' Those bug reports are useless, and we urge everyone to
26865 @emph{refuse to respond to them} except to chide the sender to report
26868 To enable us to fix the bug, you should include all these things:
26872 The version of @value{GDBN}. @value{GDBN} announces it if you start
26873 with no arguments; you can also print it at any time using @code{show
26876 Without this, we will not know whether there is any point in looking for
26877 the bug in the current version of @value{GDBN}.
26880 The type of machine you are using, and the operating system name and
26884 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
26885 ``@value{GCC}--2.8.1''.
26888 What compiler (and its version) was used to compile the program you are
26889 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
26890 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
26891 to get this information; for other compilers, see the documentation for
26895 The command arguments you gave the compiler to compile your example and
26896 observe the bug. For example, did you use @samp{-O}? To guarantee
26897 you will not omit something important, list them all. A copy of the
26898 Makefile (or the output from make) is sufficient.
26900 If we were to try to guess the arguments, we would probably guess wrong
26901 and then we might not encounter the bug.
26904 A complete input script, and all necessary source files, that will
26908 A description of what behavior you observe that you believe is
26909 incorrect. For example, ``It gets a fatal signal.''
26911 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
26912 will certainly notice it. But if the bug is incorrect output, we might
26913 not notice unless it is glaringly wrong. You might as well not give us
26914 a chance to make a mistake.
26916 Even if the problem you experience is a fatal signal, you should still
26917 say so explicitly. Suppose something strange is going on, such as, your
26918 copy of @value{GDBN} is out of synch, or you have encountered a bug in
26919 the C library on your system. (This has happened!) Your copy might
26920 crash and ours would not. If you told us to expect a crash, then when
26921 ours fails to crash, we would know that the bug was not happening for
26922 us. If you had not told us to expect a crash, then we would not be able
26923 to draw any conclusion from our observations.
26926 @cindex recording a session script
26927 To collect all this information, you can use a session recording program
26928 such as @command{script}, which is available on many Unix systems.
26929 Just run your @value{GDBN} session inside @command{script} and then
26930 include the @file{typescript} file with your bug report.
26932 Another way to record a @value{GDBN} session is to run @value{GDBN}
26933 inside Emacs and then save the entire buffer to a file.
26936 If you wish to suggest changes to the @value{GDBN} source, send us context
26937 diffs. If you even discuss something in the @value{GDBN} source, refer to
26938 it by context, not by line number.
26940 The line numbers in our development sources will not match those in your
26941 sources. Your line numbers would convey no useful information to us.
26945 Here are some things that are not necessary:
26949 A description of the envelope of the bug.
26951 Often people who encounter a bug spend a lot of time investigating
26952 which changes to the input file will make the bug go away and which
26953 changes will not affect it.
26955 This is often time consuming and not very useful, because the way we
26956 will find the bug is by running a single example under the debugger
26957 with breakpoints, not by pure deduction from a series of examples.
26958 We recommend that you save your time for something else.
26960 Of course, if you can find a simpler example to report @emph{instead}
26961 of the original one, that is a convenience for us. Errors in the
26962 output will be easier to spot, running under the debugger will take
26963 less time, and so on.
26965 However, simplification is not vital; if you do not want to do this,
26966 report the bug anyway and send us the entire test case you used.
26969 A patch for the bug.
26971 A patch for the bug does help us if it is a good one. But do not omit
26972 the necessary information, such as the test case, on the assumption that
26973 a patch is all we need. We might see problems with your patch and decide
26974 to fix the problem another way, or we might not understand it at all.
26976 Sometimes with a program as complicated as @value{GDBN} it is very hard to
26977 construct an example that will make the program follow a certain path
26978 through the code. If you do not send us the example, we will not be able
26979 to construct one, so we will not be able to verify that the bug is fixed.
26981 And if we cannot understand what bug you are trying to fix, or why your
26982 patch should be an improvement, we will not install it. A test case will
26983 help us to understand.
26986 A guess about what the bug is or what it depends on.
26988 Such guesses are usually wrong. Even we cannot guess right about such
26989 things without first using the debugger to find the facts.
26992 @c The readline documentation is distributed with the readline code
26993 @c and consists of the two following files:
26995 @c inc-hist.texinfo
26996 @c Use -I with makeinfo to point to the appropriate directory,
26997 @c environment var TEXINPUTS with TeX.
26998 @include rluser.texi
26999 @include inc-hist.texinfo
27002 @node Formatting Documentation
27003 @appendix Formatting Documentation
27005 @cindex @value{GDBN} reference card
27006 @cindex reference card
27007 The @value{GDBN} 4 release includes an already-formatted reference card, ready
27008 for printing with PostScript or Ghostscript, in the @file{gdb}
27009 subdirectory of the main source directory@footnote{In
27010 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
27011 release.}. If you can use PostScript or Ghostscript with your printer,
27012 you can print the reference card immediately with @file{refcard.ps}.
27014 The release also includes the source for the reference card. You
27015 can format it, using @TeX{}, by typing:
27021 The @value{GDBN} reference card is designed to print in @dfn{landscape}
27022 mode on US ``letter'' size paper;
27023 that is, on a sheet 11 inches wide by 8.5 inches
27024 high. You will need to specify this form of printing as an option to
27025 your @sc{dvi} output program.
27027 @cindex documentation
27029 All the documentation for @value{GDBN} comes as part of the machine-readable
27030 distribution. The documentation is written in Texinfo format, which is
27031 a documentation system that uses a single source file to produce both
27032 on-line information and a printed manual. You can use one of the Info
27033 formatting commands to create the on-line version of the documentation
27034 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
27036 @value{GDBN} includes an already formatted copy of the on-line Info
27037 version of this manual in the @file{gdb} subdirectory. The main Info
27038 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
27039 subordinate files matching @samp{gdb.info*} in the same directory. If
27040 necessary, you can print out these files, or read them with any editor;
27041 but they are easier to read using the @code{info} subsystem in @sc{gnu}
27042 Emacs or the standalone @code{info} program, available as part of the
27043 @sc{gnu} Texinfo distribution.
27045 If you want to format these Info files yourself, you need one of the
27046 Info formatting programs, such as @code{texinfo-format-buffer} or
27049 If you have @code{makeinfo} installed, and are in the top level
27050 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
27051 version @value{GDBVN}), you can make the Info file by typing:
27058 If you want to typeset and print copies of this manual, you need @TeX{},
27059 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
27060 Texinfo definitions file.
27062 @TeX{} is a typesetting program; it does not print files directly, but
27063 produces output files called @sc{dvi} files. To print a typeset
27064 document, you need a program to print @sc{dvi} files. If your system
27065 has @TeX{} installed, chances are it has such a program. The precise
27066 command to use depends on your system; @kbd{lpr -d} is common; another
27067 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
27068 require a file name without any extension or a @samp{.dvi} extension.
27070 @TeX{} also requires a macro definitions file called
27071 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
27072 written in Texinfo format. On its own, @TeX{} cannot either read or
27073 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
27074 and is located in the @file{gdb-@var{version-number}/texinfo}
27077 If you have @TeX{} and a @sc{dvi} printer program installed, you can
27078 typeset and print this manual. First switch to the @file{gdb}
27079 subdirectory of the main source directory (for example, to
27080 @file{gdb-@value{GDBVN}/gdb}) and type:
27086 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
27088 @node Installing GDB
27089 @appendix Installing @value{GDBN}
27090 @cindex installation
27093 * Requirements:: Requirements for building @value{GDBN}
27094 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
27095 * Separate Objdir:: Compiling @value{GDBN} in another directory
27096 * Config Names:: Specifying names for hosts and targets
27097 * Configure Options:: Summary of options for configure
27098 * System-wide configuration:: Having a system-wide init file
27102 @section Requirements for Building @value{GDBN}
27103 @cindex building @value{GDBN}, requirements for
27105 Building @value{GDBN} requires various tools and packages to be available.
27106 Other packages will be used only if they are found.
27108 @heading Tools/Packages Necessary for Building @value{GDBN}
27110 @item ISO C90 compiler
27111 @value{GDBN} is written in ISO C90. It should be buildable with any
27112 working C90 compiler, e.g.@: GCC.
27116 @heading Tools/Packages Optional for Building @value{GDBN}
27120 @value{GDBN} can use the Expat XML parsing library. This library may be
27121 included with your operating system distribution; if it is not, you
27122 can get the latest version from @url{http://expat.sourceforge.net}.
27123 The @file{configure} script will search for this library in several
27124 standard locations; if it is installed in an unusual path, you can
27125 use the @option{--with-libexpat-prefix} option to specify its location.
27131 Remote protocol memory maps (@pxref{Memory Map Format})
27133 Target descriptions (@pxref{Target Descriptions})
27135 Remote shared library lists (@pxref{Library List Format})
27137 MS-Windows shared libraries (@pxref{Shared Libraries})
27141 @cindex compressed debug sections
27142 @value{GDBN} will use the @samp{zlib} library, if available, to read
27143 compressed debug sections. Some linkers, such as GNU gold, are capable
27144 of producing binaries with compressed debug sections. If @value{GDBN}
27145 is compiled with @samp{zlib}, it will be able to read the debug
27146 information in such binaries.
27148 The @samp{zlib} library is likely included with your operating system
27149 distribution; if it is not, you can get the latest version from
27150 @url{http://zlib.net}.
27153 @value{GDBN}'s features related to character sets (@pxref{Character
27154 Sets}) require a functioning @code{iconv} implementation. If you are
27155 on a GNU system, then this is provided by the GNU C Library. Some
27156 other systems also provide a working @code{iconv}.
27158 On systems with @code{iconv}, you can install GNU Libiconv. If you
27159 have previously installed Libiconv, you can use the
27160 @option{--with-libiconv-prefix} option to configure.
27162 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
27163 arrange to build Libiconv if a directory named @file{libiconv} appears
27164 in the top-most source directory. If Libiconv is built this way, and
27165 if the operating system does not provide a suitable @code{iconv}
27166 implementation, then the just-built library will automatically be used
27167 by @value{GDBN}. One easy way to set this up is to download GNU
27168 Libiconv, unpack it, and then rename the directory holding the
27169 Libiconv source code to @samp{libiconv}.
27172 @node Running Configure
27173 @section Invoking the @value{GDBN} @file{configure} Script
27174 @cindex configuring @value{GDBN}
27175 @value{GDBN} comes with a @file{configure} script that automates the process
27176 of preparing @value{GDBN} for installation; you can then use @code{make} to
27177 build the @code{gdb} program.
27179 @c irrelevant in info file; it's as current as the code it lives with.
27180 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
27181 look at the @file{README} file in the sources; we may have improved the
27182 installation procedures since publishing this manual.}
27185 The @value{GDBN} distribution includes all the source code you need for
27186 @value{GDBN} in a single directory, whose name is usually composed by
27187 appending the version number to @samp{gdb}.
27189 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
27190 @file{gdb-@value{GDBVN}} directory. That directory contains:
27193 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
27194 script for configuring @value{GDBN} and all its supporting libraries
27196 @item gdb-@value{GDBVN}/gdb
27197 the source specific to @value{GDBN} itself
27199 @item gdb-@value{GDBVN}/bfd
27200 source for the Binary File Descriptor library
27202 @item gdb-@value{GDBVN}/include
27203 @sc{gnu} include files
27205 @item gdb-@value{GDBVN}/libiberty
27206 source for the @samp{-liberty} free software library
27208 @item gdb-@value{GDBVN}/opcodes
27209 source for the library of opcode tables and disassemblers
27211 @item gdb-@value{GDBVN}/readline
27212 source for the @sc{gnu} command-line interface
27214 @item gdb-@value{GDBVN}/glob
27215 source for the @sc{gnu} filename pattern-matching subroutine
27217 @item gdb-@value{GDBVN}/mmalloc
27218 source for the @sc{gnu} memory-mapped malloc package
27221 The simplest way to configure and build @value{GDBN} is to run @file{configure}
27222 from the @file{gdb-@var{version-number}} source directory, which in
27223 this example is the @file{gdb-@value{GDBVN}} directory.
27225 First switch to the @file{gdb-@var{version-number}} source directory
27226 if you are not already in it; then run @file{configure}. Pass the
27227 identifier for the platform on which @value{GDBN} will run as an
27233 cd gdb-@value{GDBVN}
27234 ./configure @var{host}
27239 where @var{host} is an identifier such as @samp{sun4} or
27240 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
27241 (You can often leave off @var{host}; @file{configure} tries to guess the
27242 correct value by examining your system.)
27244 Running @samp{configure @var{host}} and then running @code{make} builds the
27245 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
27246 libraries, then @code{gdb} itself. The configured source files, and the
27247 binaries, are left in the corresponding source directories.
27250 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
27251 system does not recognize this automatically when you run a different
27252 shell, you may need to run @code{sh} on it explicitly:
27255 sh configure @var{host}
27258 If you run @file{configure} from a directory that contains source
27259 directories for multiple libraries or programs, such as the
27260 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
27262 creates configuration files for every directory level underneath (unless
27263 you tell it not to, with the @samp{--norecursion} option).
27265 You should run the @file{configure} script from the top directory in the
27266 source tree, the @file{gdb-@var{version-number}} directory. If you run
27267 @file{configure} from one of the subdirectories, you will configure only
27268 that subdirectory. That is usually not what you want. In particular,
27269 if you run the first @file{configure} from the @file{gdb} subdirectory
27270 of the @file{gdb-@var{version-number}} directory, you will omit the
27271 configuration of @file{bfd}, @file{readline}, and other sibling
27272 directories of the @file{gdb} subdirectory. This leads to build errors
27273 about missing include files such as @file{bfd/bfd.h}.
27275 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
27276 However, you should make sure that the shell on your path (named by
27277 the @samp{SHELL} environment variable) is publicly readable. Remember
27278 that @value{GDBN} uses the shell to start your program---some systems refuse to
27279 let @value{GDBN} debug child processes whose programs are not readable.
27281 @node Separate Objdir
27282 @section Compiling @value{GDBN} in Another Directory
27284 If you want to run @value{GDBN} versions for several host or target machines,
27285 you need a different @code{gdb} compiled for each combination of
27286 host and target. @file{configure} is designed to make this easy by
27287 allowing you to generate each configuration in a separate subdirectory,
27288 rather than in the source directory. If your @code{make} program
27289 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
27290 @code{make} in each of these directories builds the @code{gdb}
27291 program specified there.
27293 To build @code{gdb} in a separate directory, run @file{configure}
27294 with the @samp{--srcdir} option to specify where to find the source.
27295 (You also need to specify a path to find @file{configure}
27296 itself from your working directory. If the path to @file{configure}
27297 would be the same as the argument to @samp{--srcdir}, you can leave out
27298 the @samp{--srcdir} option; it is assumed.)
27300 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
27301 separate directory for a Sun 4 like this:
27305 cd gdb-@value{GDBVN}
27308 ../gdb-@value{GDBVN}/configure sun4
27313 When @file{configure} builds a configuration using a remote source
27314 directory, it creates a tree for the binaries with the same structure
27315 (and using the same names) as the tree under the source directory. In
27316 the example, you'd find the Sun 4 library @file{libiberty.a} in the
27317 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
27318 @file{gdb-sun4/gdb}.
27320 Make sure that your path to the @file{configure} script has just one
27321 instance of @file{gdb} in it. If your path to @file{configure} looks
27322 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
27323 one subdirectory of @value{GDBN}, not the whole package. This leads to
27324 build errors about missing include files such as @file{bfd/bfd.h}.
27326 One popular reason to build several @value{GDBN} configurations in separate
27327 directories is to configure @value{GDBN} for cross-compiling (where
27328 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
27329 programs that run on another machine---the @dfn{target}).
27330 You specify a cross-debugging target by
27331 giving the @samp{--target=@var{target}} option to @file{configure}.
27333 When you run @code{make} to build a program or library, you must run
27334 it in a configured directory---whatever directory you were in when you
27335 called @file{configure} (or one of its subdirectories).
27337 The @code{Makefile} that @file{configure} generates in each source
27338 directory also runs recursively. If you type @code{make} in a source
27339 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
27340 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
27341 will build all the required libraries, and then build GDB.
27343 When you have multiple hosts or targets configured in separate
27344 directories, you can run @code{make} on them in parallel (for example,
27345 if they are NFS-mounted on each of the hosts); they will not interfere
27349 @section Specifying Names for Hosts and Targets
27351 The specifications used for hosts and targets in the @file{configure}
27352 script are based on a three-part naming scheme, but some short predefined
27353 aliases are also supported. The full naming scheme encodes three pieces
27354 of information in the following pattern:
27357 @var{architecture}-@var{vendor}-@var{os}
27360 For example, you can use the alias @code{sun4} as a @var{host} argument,
27361 or as the value for @var{target} in a @code{--target=@var{target}}
27362 option. The equivalent full name is @samp{sparc-sun-sunos4}.
27364 The @file{configure} script accompanying @value{GDBN} does not provide
27365 any query facility to list all supported host and target names or
27366 aliases. @file{configure} calls the Bourne shell script
27367 @code{config.sub} to map abbreviations to full names; you can read the
27368 script, if you wish, or you can use it to test your guesses on
27369 abbreviations---for example:
27372 % sh config.sub i386-linux
27374 % sh config.sub alpha-linux
27375 alpha-unknown-linux-gnu
27376 % sh config.sub hp9k700
27378 % sh config.sub sun4
27379 sparc-sun-sunos4.1.1
27380 % sh config.sub sun3
27381 m68k-sun-sunos4.1.1
27382 % sh config.sub i986v
27383 Invalid configuration `i986v': machine `i986v' not recognized
27387 @code{config.sub} is also distributed in the @value{GDBN} source
27388 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
27390 @node Configure Options
27391 @section @file{configure} Options
27393 Here is a summary of the @file{configure} options and arguments that
27394 are most often useful for building @value{GDBN}. @file{configure} also has
27395 several other options not listed here. @inforef{What Configure
27396 Does,,configure.info}, for a full explanation of @file{configure}.
27399 configure @r{[}--help@r{]}
27400 @r{[}--prefix=@var{dir}@r{]}
27401 @r{[}--exec-prefix=@var{dir}@r{]}
27402 @r{[}--srcdir=@var{dirname}@r{]}
27403 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
27404 @r{[}--target=@var{target}@r{]}
27409 You may introduce options with a single @samp{-} rather than
27410 @samp{--} if you prefer; but you may abbreviate option names if you use
27415 Display a quick summary of how to invoke @file{configure}.
27417 @item --prefix=@var{dir}
27418 Configure the source to install programs and files under directory
27421 @item --exec-prefix=@var{dir}
27422 Configure the source to install programs under directory
27425 @c avoid splitting the warning from the explanation:
27427 @item --srcdir=@var{dirname}
27428 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
27429 @code{make} that implements the @code{VPATH} feature.}@*
27430 Use this option to make configurations in directories separate from the
27431 @value{GDBN} source directories. Among other things, you can use this to
27432 build (or maintain) several configurations simultaneously, in separate
27433 directories. @file{configure} writes configuration-specific files in
27434 the current directory, but arranges for them to use the source in the
27435 directory @var{dirname}. @file{configure} creates directories under
27436 the working directory in parallel to the source directories below
27439 @item --norecursion
27440 Configure only the directory level where @file{configure} is executed; do not
27441 propagate configuration to subdirectories.
27443 @item --target=@var{target}
27444 Configure @value{GDBN} for cross-debugging programs running on the specified
27445 @var{target}. Without this option, @value{GDBN} is configured to debug
27446 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
27448 There is no convenient way to generate a list of all available targets.
27450 @item @var{host} @dots{}
27451 Configure @value{GDBN} to run on the specified @var{host}.
27453 There is no convenient way to generate a list of all available hosts.
27456 There are many other options available as well, but they are generally
27457 needed for special purposes only.
27459 @node System-wide configuration
27460 @section System-wide configuration and settings
27461 @cindex system-wide init file
27463 @value{GDBN} can be configured to have a system-wide init file;
27464 this file will be read and executed at startup (@pxref{Startup, , What
27465 @value{GDBN} does during startup}).
27467 Here is the corresponding configure option:
27470 @item --with-system-gdbinit=@var{file}
27471 Specify that the default location of the system-wide init file is
27475 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
27476 it may be subject to relocation. Two possible cases:
27480 If the default location of this init file contains @file{$prefix},
27481 it will be subject to relocation. Suppose that the configure options
27482 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
27483 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
27484 init file is looked for as @file{$install/etc/gdbinit} instead of
27485 @file{$prefix/etc/gdbinit}.
27488 By contrast, if the default location does not contain the prefix,
27489 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
27490 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
27491 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
27492 wherever @value{GDBN} is installed.
27495 @node Maintenance Commands
27496 @appendix Maintenance Commands
27497 @cindex maintenance commands
27498 @cindex internal commands
27500 In addition to commands intended for @value{GDBN} users, @value{GDBN}
27501 includes a number of commands intended for @value{GDBN} developers,
27502 that are not documented elsewhere in this manual. These commands are
27503 provided here for reference. (For commands that turn on debugging
27504 messages, see @ref{Debugging Output}.)
27507 @kindex maint agent
27508 @kindex maint agent-eval
27509 @item maint agent @var{expression}
27510 @itemx maint agent-eval @var{expression}
27511 Translate the given @var{expression} into remote agent bytecodes.
27512 This command is useful for debugging the Agent Expression mechanism
27513 (@pxref{Agent Expressions}). The @samp{agent} version produces an
27514 expression useful for data collection, such as by tracepoints, while
27515 @samp{maint agent-eval} produces an expression that evaluates directly
27516 to a result. For instance, a collection expression for @code{globa +
27517 globb} will include bytecodes to record four bytes of memory at each
27518 of the addresses of @code{globa} and @code{globb}, while discarding
27519 the result of the addition, while an evaluation expression will do the
27520 addition and return the sum.
27522 @kindex maint info breakpoints
27523 @item @anchor{maint info breakpoints}maint info breakpoints
27524 Using the same format as @samp{info breakpoints}, display both the
27525 breakpoints you've set explicitly, and those @value{GDBN} is using for
27526 internal purposes. Internal breakpoints are shown with negative
27527 breakpoint numbers. The type column identifies what kind of breakpoint
27532 Normal, explicitly set breakpoint.
27535 Normal, explicitly set watchpoint.
27538 Internal breakpoint, used to handle correctly stepping through
27539 @code{longjmp} calls.
27541 @item longjmp resume
27542 Internal breakpoint at the target of a @code{longjmp}.
27545 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
27548 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
27551 Shared library events.
27555 @kindex set displaced-stepping
27556 @kindex show displaced-stepping
27557 @cindex displaced stepping support
27558 @cindex out-of-line single-stepping
27559 @item set displaced-stepping
27560 @itemx show displaced-stepping
27561 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
27562 if the target supports it. Displaced stepping is a way to single-step
27563 over breakpoints without removing them from the inferior, by executing
27564 an out-of-line copy of the instruction that was originally at the
27565 breakpoint location. It is also known as out-of-line single-stepping.
27568 @item set displaced-stepping on
27569 If the target architecture supports it, @value{GDBN} will use
27570 displaced stepping to step over breakpoints.
27572 @item set displaced-stepping off
27573 @value{GDBN} will not use displaced stepping to step over breakpoints,
27574 even if such is supported by the target architecture.
27576 @cindex non-stop mode, and @samp{set displaced-stepping}
27577 @item set displaced-stepping auto
27578 This is the default mode. @value{GDBN} will use displaced stepping
27579 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
27580 architecture supports displaced stepping.
27583 @kindex maint check-symtabs
27584 @item maint check-symtabs
27585 Check the consistency of psymtabs and symtabs.
27587 @kindex maint cplus first_component
27588 @item maint cplus first_component @var{name}
27589 Print the first C@t{++} class/namespace component of @var{name}.
27591 @kindex maint cplus namespace
27592 @item maint cplus namespace
27593 Print the list of possible C@t{++} namespaces.
27595 @kindex maint demangle
27596 @item maint demangle @var{name}
27597 Demangle a C@t{++} or Objective-C mangled @var{name}.
27599 @kindex maint deprecate
27600 @kindex maint undeprecate
27601 @cindex deprecated commands
27602 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
27603 @itemx maint undeprecate @var{command}
27604 Deprecate or undeprecate the named @var{command}. Deprecated commands
27605 cause @value{GDBN} to issue a warning when you use them. The optional
27606 argument @var{replacement} says which newer command should be used in
27607 favor of the deprecated one; if it is given, @value{GDBN} will mention
27608 the replacement as part of the warning.
27610 @kindex maint dump-me
27611 @item maint dump-me
27612 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
27613 Cause a fatal signal in the debugger and force it to dump its core.
27614 This is supported only on systems which support aborting a program
27615 with the @code{SIGQUIT} signal.
27617 @kindex maint internal-error
27618 @kindex maint internal-warning
27619 @item maint internal-error @r{[}@var{message-text}@r{]}
27620 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
27621 Cause @value{GDBN} to call the internal function @code{internal_error}
27622 or @code{internal_warning} and hence behave as though an internal error
27623 or internal warning has been detected. In addition to reporting the
27624 internal problem, these functions give the user the opportunity to
27625 either quit @value{GDBN} or create a core file of the current
27626 @value{GDBN} session.
27628 These commands take an optional parameter @var{message-text} that is
27629 used as the text of the error or warning message.
27631 Here's an example of using @code{internal-error}:
27634 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
27635 @dots{}/maint.c:121: internal-error: testing, 1, 2
27636 A problem internal to GDB has been detected. Further
27637 debugging may prove unreliable.
27638 Quit this debugging session? (y or n) @kbd{n}
27639 Create a core file? (y or n) @kbd{n}
27643 @cindex @value{GDBN} internal error
27644 @cindex internal errors, control of @value{GDBN} behavior
27646 @kindex maint set internal-error
27647 @kindex maint show internal-error
27648 @kindex maint set internal-warning
27649 @kindex maint show internal-warning
27650 @item maint set internal-error @var{action} [ask|yes|no]
27651 @itemx maint show internal-error @var{action}
27652 @itemx maint set internal-warning @var{action} [ask|yes|no]
27653 @itemx maint show internal-warning @var{action}
27654 When @value{GDBN} reports an internal problem (error or warning) it
27655 gives the user the opportunity to both quit @value{GDBN} and create a
27656 core file of the current @value{GDBN} session. These commands let you
27657 override the default behaviour for each particular @var{action},
27658 described in the table below.
27662 You can specify that @value{GDBN} should always (yes) or never (no)
27663 quit. The default is to ask the user what to do.
27666 You can specify that @value{GDBN} should always (yes) or never (no)
27667 create a core file. The default is to ask the user what to do.
27670 @kindex maint packet
27671 @item maint packet @var{text}
27672 If @value{GDBN} is talking to an inferior via the serial protocol,
27673 then this command sends the string @var{text} to the inferior, and
27674 displays the response packet. @value{GDBN} supplies the initial
27675 @samp{$} character, the terminating @samp{#} character, and the
27678 @kindex maint print architecture
27679 @item maint print architecture @r{[}@var{file}@r{]}
27680 Print the entire architecture configuration. The optional argument
27681 @var{file} names the file where the output goes.
27683 @kindex maint print c-tdesc
27684 @item maint print c-tdesc
27685 Print the current target description (@pxref{Target Descriptions}) as
27686 a C source file. The created source file can be used in @value{GDBN}
27687 when an XML parser is not available to parse the description.
27689 @kindex maint print dummy-frames
27690 @item maint print dummy-frames
27691 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
27694 (@value{GDBP}) @kbd{b add}
27696 (@value{GDBP}) @kbd{print add(2,3)}
27697 Breakpoint 2, add (a=2, b=3) at @dots{}
27699 The program being debugged stopped while in a function called from GDB.
27701 (@value{GDBP}) @kbd{maint print dummy-frames}
27702 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
27703 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
27704 call_lo=0x01014000 call_hi=0x01014001
27708 Takes an optional file parameter.
27710 @kindex maint print registers
27711 @kindex maint print raw-registers
27712 @kindex maint print cooked-registers
27713 @kindex maint print register-groups
27714 @item maint print registers @r{[}@var{file}@r{]}
27715 @itemx maint print raw-registers @r{[}@var{file}@r{]}
27716 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
27717 @itemx maint print register-groups @r{[}@var{file}@r{]}
27718 Print @value{GDBN}'s internal register data structures.
27720 The command @code{maint print raw-registers} includes the contents of
27721 the raw register cache; the command @code{maint print cooked-registers}
27722 includes the (cooked) value of all registers; and the command
27723 @code{maint print register-groups} includes the groups that each
27724 register is a member of. @xref{Registers,, Registers, gdbint,
27725 @value{GDBN} Internals}.
27727 These commands take an optional parameter, a file name to which to
27728 write the information.
27730 @kindex maint print reggroups
27731 @item maint print reggroups @r{[}@var{file}@r{]}
27732 Print @value{GDBN}'s internal register group data structures. The
27733 optional argument @var{file} tells to what file to write the
27736 The register groups info looks like this:
27739 (@value{GDBP}) @kbd{maint print reggroups}
27752 This command forces @value{GDBN} to flush its internal register cache.
27754 @kindex maint print objfiles
27755 @cindex info for known object files
27756 @item maint print objfiles
27757 Print a dump of all known object files. For each object file, this
27758 command prints its name, address in memory, and all of its psymtabs
27761 @kindex maint print statistics
27762 @cindex bcache statistics
27763 @item maint print statistics
27764 This command prints, for each object file in the program, various data
27765 about that object file followed by the byte cache (@dfn{bcache})
27766 statistics for the object file. The objfile data includes the number
27767 of minimal, partial, full, and stabs symbols, the number of types
27768 defined by the objfile, the number of as yet unexpanded psym tables,
27769 the number of line tables and string tables, and the amount of memory
27770 used by the various tables. The bcache statistics include the counts,
27771 sizes, and counts of duplicates of all and unique objects, max,
27772 average, and median entry size, total memory used and its overhead and
27773 savings, and various measures of the hash table size and chain
27776 @kindex maint print target-stack
27777 @cindex target stack description
27778 @item maint print target-stack
27779 A @dfn{target} is an interface between the debugger and a particular
27780 kind of file or process. Targets can be stacked in @dfn{strata},
27781 so that more than one target can potentially respond to a request.
27782 In particular, memory accesses will walk down the stack of targets
27783 until they find a target that is interested in handling that particular
27786 This command prints a short description of each layer that was pushed on
27787 the @dfn{target stack}, starting from the top layer down to the bottom one.
27789 @kindex maint print type
27790 @cindex type chain of a data type
27791 @item maint print type @var{expr}
27792 Print the type chain for a type specified by @var{expr}. The argument
27793 can be either a type name or a symbol. If it is a symbol, the type of
27794 that symbol is described. The type chain produced by this command is
27795 a recursive definition of the data type as stored in @value{GDBN}'s
27796 data structures, including its flags and contained types.
27798 @kindex maint set dwarf2 max-cache-age
27799 @kindex maint show dwarf2 max-cache-age
27800 @item maint set dwarf2 max-cache-age
27801 @itemx maint show dwarf2 max-cache-age
27802 Control the DWARF 2 compilation unit cache.
27804 @cindex DWARF 2 compilation units cache
27805 In object files with inter-compilation-unit references, such as those
27806 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
27807 reader needs to frequently refer to previously read compilation units.
27808 This setting controls how long a compilation unit will remain in the
27809 cache if it is not referenced. A higher limit means that cached
27810 compilation units will be stored in memory longer, and more total
27811 memory will be used. Setting it to zero disables caching, which will
27812 slow down @value{GDBN} startup, but reduce memory consumption.
27814 @kindex maint set profile
27815 @kindex maint show profile
27816 @cindex profiling GDB
27817 @item maint set profile
27818 @itemx maint show profile
27819 Control profiling of @value{GDBN}.
27821 Profiling will be disabled until you use the @samp{maint set profile}
27822 command to enable it. When you enable profiling, the system will begin
27823 collecting timing and execution count data; when you disable profiling or
27824 exit @value{GDBN}, the results will be written to a log file. Remember that
27825 if you use profiling, @value{GDBN} will overwrite the profiling log file
27826 (often called @file{gmon.out}). If you have a record of important profiling
27827 data in a @file{gmon.out} file, be sure to move it to a safe location.
27829 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
27830 compiled with the @samp{-pg} compiler option.
27832 @kindex maint set show-debug-regs
27833 @kindex maint show show-debug-regs
27834 @cindex hardware debug registers
27835 @item maint set show-debug-regs
27836 @itemx maint show show-debug-regs
27837 Control whether to show variables that mirror the hardware debug
27838 registers. Use @code{ON} to enable, @code{OFF} to disable. If
27839 enabled, the debug registers values are shown when @value{GDBN} inserts or
27840 removes a hardware breakpoint or watchpoint, and when the inferior
27841 triggers a hardware-assisted breakpoint or watchpoint.
27843 @kindex maint space
27844 @cindex memory used by commands
27846 Control whether to display memory usage for each command. If set to a
27847 nonzero value, @value{GDBN} will display how much memory each command
27848 took, following the command's own output. This can also be requested
27849 by invoking @value{GDBN} with the @option{--statistics} command-line
27850 switch (@pxref{Mode Options}).
27853 @cindex time of command execution
27855 Control whether to display the execution time for each command. If
27856 set to a nonzero value, @value{GDBN} will display how much time it
27857 took to execute each command, following the command's own output.
27858 The time is not printed for the commands that run the target, since
27859 there's no mechanism currently to compute how much time was spend
27860 by @value{GDBN} and how much time was spend by the program been debugged.
27861 it's not possibly currently
27862 This can also be requested by invoking @value{GDBN} with the
27863 @option{--statistics} command-line switch (@pxref{Mode Options}).
27865 @kindex maint translate-address
27866 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
27867 Find the symbol stored at the location specified by the address
27868 @var{addr} and an optional section name @var{section}. If found,
27869 @value{GDBN} prints the name of the closest symbol and an offset from
27870 the symbol's location to the specified address. This is similar to
27871 the @code{info address} command (@pxref{Symbols}), except that this
27872 command also allows to find symbols in other sections.
27874 If section was not specified, the section in which the symbol was found
27875 is also printed. For dynamically linked executables, the name of
27876 executable or shared library containing the symbol is printed as well.
27880 The following command is useful for non-interactive invocations of
27881 @value{GDBN}, such as in the test suite.
27884 @item set watchdog @var{nsec}
27885 @kindex set watchdog
27886 @cindex watchdog timer
27887 @cindex timeout for commands
27888 Set the maximum number of seconds @value{GDBN} will wait for the
27889 target operation to finish. If this time expires, @value{GDBN}
27890 reports and error and the command is aborted.
27892 @item show watchdog
27893 Show the current setting of the target wait timeout.
27896 @node Remote Protocol
27897 @appendix @value{GDBN} Remote Serial Protocol
27902 * Stop Reply Packets::
27903 * General Query Packets::
27904 * Register Packet Format::
27905 * Tracepoint Packets::
27906 * Host I/O Packets::
27908 * Notification Packets::
27909 * Remote Non-Stop::
27910 * Packet Acknowledgment::
27912 * File-I/O Remote Protocol Extension::
27913 * Library List Format::
27914 * Memory Map Format::
27920 There may be occasions when you need to know something about the
27921 protocol---for example, if there is only one serial port to your target
27922 machine, you might want your program to do something special if it
27923 recognizes a packet meant for @value{GDBN}.
27925 In the examples below, @samp{->} and @samp{<-} are used to indicate
27926 transmitted and received data, respectively.
27928 @cindex protocol, @value{GDBN} remote serial
27929 @cindex serial protocol, @value{GDBN} remote
27930 @cindex remote serial protocol
27931 All @value{GDBN} commands and responses (other than acknowledgments
27932 and notifications, see @ref{Notification Packets}) are sent as a
27933 @var{packet}. A @var{packet} is introduced with the character
27934 @samp{$}, the actual @var{packet-data}, and the terminating character
27935 @samp{#} followed by a two-digit @var{checksum}:
27938 @code{$}@var{packet-data}@code{#}@var{checksum}
27942 @cindex checksum, for @value{GDBN} remote
27944 The two-digit @var{checksum} is computed as the modulo 256 sum of all
27945 characters between the leading @samp{$} and the trailing @samp{#} (an
27946 eight bit unsigned checksum).
27948 Implementors should note that prior to @value{GDBN} 5.0 the protocol
27949 specification also included an optional two-digit @var{sequence-id}:
27952 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
27955 @cindex sequence-id, for @value{GDBN} remote
27957 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
27958 has never output @var{sequence-id}s. Stubs that handle packets added
27959 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
27961 When either the host or the target machine receives a packet, the first
27962 response expected is an acknowledgment: either @samp{+} (to indicate
27963 the package was received correctly) or @samp{-} (to request
27967 -> @code{$}@var{packet-data}@code{#}@var{checksum}
27972 The @samp{+}/@samp{-} acknowledgments can be disabled
27973 once a connection is established.
27974 @xref{Packet Acknowledgment}, for details.
27976 The host (@value{GDBN}) sends @var{command}s, and the target (the
27977 debugging stub incorporated in your program) sends a @var{response}. In
27978 the case of step and continue @var{command}s, the response is only sent
27979 when the operation has completed, and the target has again stopped all
27980 threads in all attached processes. This is the default all-stop mode
27981 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
27982 execution mode; see @ref{Remote Non-Stop}, for details.
27984 @var{packet-data} consists of a sequence of characters with the
27985 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
27988 @cindex remote protocol, field separator
27989 Fields within the packet should be separated using @samp{,} @samp{;} or
27990 @samp{:}. Except where otherwise noted all numbers are represented in
27991 @sc{hex} with leading zeros suppressed.
27993 Implementors should note that prior to @value{GDBN} 5.0, the character
27994 @samp{:} could not appear as the third character in a packet (as it
27995 would potentially conflict with the @var{sequence-id}).
27997 @cindex remote protocol, binary data
27998 @anchor{Binary Data}
27999 Binary data in most packets is encoded either as two hexadecimal
28000 digits per byte of binary data. This allowed the traditional remote
28001 protocol to work over connections which were only seven-bit clean.
28002 Some packets designed more recently assume an eight-bit clean
28003 connection, and use a more efficient encoding to send and receive
28006 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
28007 as an escape character. Any escaped byte is transmitted as the escape
28008 character followed by the original character XORed with @code{0x20}.
28009 For example, the byte @code{0x7d} would be transmitted as the two
28010 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
28011 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
28012 @samp{@}}) must always be escaped. Responses sent by the stub
28013 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
28014 is not interpreted as the start of a run-length encoded sequence
28017 Response @var{data} can be run-length encoded to save space.
28018 Run-length encoding replaces runs of identical characters with one
28019 instance of the repeated character, followed by a @samp{*} and a
28020 repeat count. The repeat count is itself sent encoded, to avoid
28021 binary characters in @var{data}: a value of @var{n} is sent as
28022 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
28023 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
28024 code 32) for a repeat count of 3. (This is because run-length
28025 encoding starts to win for counts 3 or more.) Thus, for example,
28026 @samp{0* } is a run-length encoding of ``0000'': the space character
28027 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
28030 The printable characters @samp{#} and @samp{$} or with a numeric value
28031 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
28032 seven repeats (@samp{$}) can be expanded using a repeat count of only
28033 five (@samp{"}). For example, @samp{00000000} can be encoded as
28036 The error response returned for some packets includes a two character
28037 error number. That number is not well defined.
28039 @cindex empty response, for unsupported packets
28040 For any @var{command} not supported by the stub, an empty response
28041 (@samp{$#00}) should be returned. That way it is possible to extend the
28042 protocol. A newer @value{GDBN} can tell if a packet is supported based
28045 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
28046 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
28052 The following table provides a complete list of all currently defined
28053 @var{command}s and their corresponding response @var{data}.
28054 @xref{File-I/O Remote Protocol Extension}, for details about the File
28055 I/O extension of the remote protocol.
28057 Each packet's description has a template showing the packet's overall
28058 syntax, followed by an explanation of the packet's meaning. We
28059 include spaces in some of the templates for clarity; these are not
28060 part of the packet's syntax. No @value{GDBN} packet uses spaces to
28061 separate its components. For example, a template like @samp{foo
28062 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
28063 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
28064 @var{baz}. @value{GDBN} does not transmit a space character between the
28065 @samp{foo} and the @var{bar}, or between the @var{bar} and the
28068 @cindex @var{thread-id}, in remote protocol
28069 @anchor{thread-id syntax}
28070 Several packets and replies include a @var{thread-id} field to identify
28071 a thread. Normally these are positive numbers with a target-specific
28072 interpretation, formatted as big-endian hex strings. A @var{thread-id}
28073 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
28076 In addition, the remote protocol supports a multiprocess feature in
28077 which the @var{thread-id} syntax is extended to optionally include both
28078 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
28079 The @var{pid} (process) and @var{tid} (thread) components each have the
28080 format described above: a positive number with target-specific
28081 interpretation formatted as a big-endian hex string, literal @samp{-1}
28082 to indicate all processes or threads (respectively), or @samp{0} to
28083 indicate an arbitrary process or thread. Specifying just a process, as
28084 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
28085 error to specify all processes but a specific thread, such as
28086 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
28087 for those packets and replies explicitly documented to include a process
28088 ID, rather than a @var{thread-id}.
28090 The multiprocess @var{thread-id} syntax extensions are only used if both
28091 @value{GDBN} and the stub report support for the @samp{multiprocess}
28092 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
28095 Note that all packet forms beginning with an upper- or lower-case
28096 letter, other than those described here, are reserved for future use.
28098 Here are the packet descriptions.
28103 @cindex @samp{!} packet
28104 @anchor{extended mode}
28105 Enable extended mode. In extended mode, the remote server is made
28106 persistent. The @samp{R} packet is used to restart the program being
28112 The remote target both supports and has enabled extended mode.
28116 @cindex @samp{?} packet
28117 Indicate the reason the target halted. The reply is the same as for
28118 step and continue. This packet has a special interpretation when the
28119 target is in non-stop mode; see @ref{Remote Non-Stop}.
28122 @xref{Stop Reply Packets}, for the reply specifications.
28124 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
28125 @cindex @samp{A} packet
28126 Initialized @code{argv[]} array passed into program. @var{arglen}
28127 specifies the number of bytes in the hex encoded byte stream
28128 @var{arg}. See @code{gdbserver} for more details.
28133 The arguments were set.
28139 @cindex @samp{b} packet
28140 (Don't use this packet; its behavior is not well-defined.)
28141 Change the serial line speed to @var{baud}.
28143 JTC: @emph{When does the transport layer state change? When it's
28144 received, or after the ACK is transmitted. In either case, there are
28145 problems if the command or the acknowledgment packet is dropped.}
28147 Stan: @emph{If people really wanted to add something like this, and get
28148 it working for the first time, they ought to modify ser-unix.c to send
28149 some kind of out-of-band message to a specially-setup stub and have the
28150 switch happen "in between" packets, so that from remote protocol's point
28151 of view, nothing actually happened.}
28153 @item B @var{addr},@var{mode}
28154 @cindex @samp{B} packet
28155 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
28156 breakpoint at @var{addr}.
28158 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
28159 (@pxref{insert breakpoint or watchpoint packet}).
28161 @cindex @samp{bc} packet
28164 Backward continue. Execute the target system in reverse. No parameter.
28165 @xref{Reverse Execution}, for more information.
28168 @xref{Stop Reply Packets}, for the reply specifications.
28170 @cindex @samp{bs} packet
28173 Backward single step. Execute one instruction in reverse. No parameter.
28174 @xref{Reverse Execution}, for more information.
28177 @xref{Stop Reply Packets}, for the reply specifications.
28179 @item c @r{[}@var{addr}@r{]}
28180 @cindex @samp{c} packet
28181 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
28182 resume at current address.
28185 @xref{Stop Reply Packets}, for the reply specifications.
28187 @item C @var{sig}@r{[};@var{addr}@r{]}
28188 @cindex @samp{C} packet
28189 Continue with signal @var{sig} (hex signal number). If
28190 @samp{;@var{addr}} is omitted, resume at same address.
28193 @xref{Stop Reply Packets}, for the reply specifications.
28196 @cindex @samp{d} packet
28199 Don't use this packet; instead, define a general set packet
28200 (@pxref{General Query Packets}).
28204 @cindex @samp{D} packet
28205 The first form of the packet is used to detach @value{GDBN} from the
28206 remote system. It is sent to the remote target
28207 before @value{GDBN} disconnects via the @code{detach} command.
28209 The second form, including a process ID, is used when multiprocess
28210 protocol extensions are enabled (@pxref{multiprocess extensions}), to
28211 detach only a specific process. The @var{pid} is specified as a
28212 big-endian hex string.
28222 @item F @var{RC},@var{EE},@var{CF};@var{XX}
28223 @cindex @samp{F} packet
28224 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
28225 This is part of the File-I/O protocol extension. @xref{File-I/O
28226 Remote Protocol Extension}, for the specification.
28229 @anchor{read registers packet}
28230 @cindex @samp{g} packet
28231 Read general registers.
28235 @item @var{XX@dots{}}
28236 Each byte of register data is described by two hex digits. The bytes
28237 with the register are transmitted in target byte order. The size of
28238 each register and their position within the @samp{g} packet are
28239 determined by the @value{GDBN} internal gdbarch functions
28240 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
28241 specification of several standard @samp{g} packets is specified below.
28246 @item G @var{XX@dots{}}
28247 @cindex @samp{G} packet
28248 Write general registers. @xref{read registers packet}, for a
28249 description of the @var{XX@dots{}} data.
28259 @item H @var{c} @var{thread-id}
28260 @cindex @samp{H} packet
28261 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
28262 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
28263 should be @samp{c} for step and continue operations, @samp{g} for other
28264 operations. The thread designator @var{thread-id} has the format and
28265 interpretation described in @ref{thread-id syntax}.
28276 @c 'H': How restrictive (or permissive) is the thread model. If a
28277 @c thread is selected and stopped, are other threads allowed
28278 @c to continue to execute? As I mentioned above, I think the
28279 @c semantics of each command when a thread is selected must be
28280 @c described. For example:
28282 @c 'g': If the stub supports threads and a specific thread is
28283 @c selected, returns the register block from that thread;
28284 @c otherwise returns current registers.
28286 @c 'G' If the stub supports threads and a specific thread is
28287 @c selected, sets the registers of the register block of
28288 @c that thread; otherwise sets current registers.
28290 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
28291 @anchor{cycle step packet}
28292 @cindex @samp{i} packet
28293 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
28294 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
28295 step starting at that address.
28298 @cindex @samp{I} packet
28299 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
28303 @cindex @samp{k} packet
28306 FIXME: @emph{There is no description of how to operate when a specific
28307 thread context has been selected (i.e.@: does 'k' kill only that
28310 @item m @var{addr},@var{length}
28311 @cindex @samp{m} packet
28312 Read @var{length} bytes of memory starting at address @var{addr}.
28313 Note that @var{addr} may not be aligned to any particular boundary.
28315 The stub need not use any particular size or alignment when gathering
28316 data from memory for the response; even if @var{addr} is word-aligned
28317 and @var{length} is a multiple of the word size, the stub is free to
28318 use byte accesses, or not. For this reason, this packet may not be
28319 suitable for accessing memory-mapped I/O devices.
28320 @cindex alignment of remote memory accesses
28321 @cindex size of remote memory accesses
28322 @cindex memory, alignment and size of remote accesses
28326 @item @var{XX@dots{}}
28327 Memory contents; each byte is transmitted as a two-digit hexadecimal
28328 number. The reply may contain fewer bytes than requested if the
28329 server was able to read only part of the region of memory.
28334 @item M @var{addr},@var{length}:@var{XX@dots{}}
28335 @cindex @samp{M} packet
28336 Write @var{length} bytes of memory starting at address @var{addr}.
28337 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
28338 hexadecimal number.
28345 for an error (this includes the case where only part of the data was
28350 @cindex @samp{p} packet
28351 Read the value of register @var{n}; @var{n} is in hex.
28352 @xref{read registers packet}, for a description of how the returned
28353 register value is encoded.
28357 @item @var{XX@dots{}}
28358 the register's value
28362 Indicating an unrecognized @var{query}.
28365 @item P @var{n@dots{}}=@var{r@dots{}}
28366 @anchor{write register packet}
28367 @cindex @samp{P} packet
28368 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
28369 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
28370 digits for each byte in the register (target byte order).
28380 @item q @var{name} @var{params}@dots{}
28381 @itemx Q @var{name} @var{params}@dots{}
28382 @cindex @samp{q} packet
28383 @cindex @samp{Q} packet
28384 General query (@samp{q}) and set (@samp{Q}). These packets are
28385 described fully in @ref{General Query Packets}.
28388 @cindex @samp{r} packet
28389 Reset the entire system.
28391 Don't use this packet; use the @samp{R} packet instead.
28394 @cindex @samp{R} packet
28395 Restart the program being debugged. @var{XX}, while needed, is ignored.
28396 This packet is only available in extended mode (@pxref{extended mode}).
28398 The @samp{R} packet has no reply.
28400 @item s @r{[}@var{addr}@r{]}
28401 @cindex @samp{s} packet
28402 Single step. @var{addr} is the address at which to resume. If
28403 @var{addr} is omitted, resume at same address.
28406 @xref{Stop Reply Packets}, for the reply specifications.
28408 @item S @var{sig}@r{[};@var{addr}@r{]}
28409 @anchor{step with signal packet}
28410 @cindex @samp{S} packet
28411 Step with signal. This is analogous to the @samp{C} packet, but
28412 requests a single-step, rather than a normal resumption of execution.
28415 @xref{Stop Reply Packets}, for the reply specifications.
28417 @item t @var{addr}:@var{PP},@var{MM}
28418 @cindex @samp{t} packet
28419 Search backwards starting at address @var{addr} for a match with pattern
28420 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
28421 @var{addr} must be at least 3 digits.
28423 @item T @var{thread-id}
28424 @cindex @samp{T} packet
28425 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
28430 thread is still alive
28436 Packets starting with @samp{v} are identified by a multi-letter name,
28437 up to the first @samp{;} or @samp{?} (or the end of the packet).
28439 @item vAttach;@var{pid}
28440 @cindex @samp{vAttach} packet
28441 Attach to a new process with the specified process ID @var{pid}.
28442 The process ID is a
28443 hexadecimal integer identifying the process. In all-stop mode, all
28444 threads in the attached process are stopped; in non-stop mode, it may be
28445 attached without being stopped if that is supported by the target.
28447 @c In non-stop mode, on a successful vAttach, the stub should set the
28448 @c current thread to a thread of the newly-attached process. After
28449 @c attaching, GDB queries for the attached process's thread ID with qC.
28450 @c Also note that, from a user perspective, whether or not the
28451 @c target is stopped on attach in non-stop mode depends on whether you
28452 @c use the foreground or background version of the attach command, not
28453 @c on what vAttach does; GDB does the right thing with respect to either
28454 @c stopping or restarting threads.
28456 This packet is only available in extended mode (@pxref{extended mode}).
28462 @item @r{Any stop packet}
28463 for success in all-stop mode (@pxref{Stop Reply Packets})
28465 for success in non-stop mode (@pxref{Remote Non-Stop})
28468 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
28469 @cindex @samp{vCont} packet
28470 Resume the inferior, specifying different actions for each thread.
28471 If an action is specified with no @var{thread-id}, then it is applied to any
28472 threads that don't have a specific action specified; if no default action is
28473 specified then other threads should remain stopped in all-stop mode and
28474 in their current state in non-stop mode.
28475 Specifying multiple
28476 default actions is an error; specifying no actions is also an error.
28477 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
28479 Currently supported actions are:
28485 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
28489 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
28494 The optional argument @var{addr} normally associated with the
28495 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
28496 not supported in @samp{vCont}.
28498 The @samp{t} action is only relevant in non-stop mode
28499 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
28500 A stop reply should be generated for any affected thread not already stopped.
28501 When a thread is stopped by means of a @samp{t} action,
28502 the corresponding stop reply should indicate that the thread has stopped with
28503 signal @samp{0}, regardless of whether the target uses some other signal
28504 as an implementation detail.
28507 @xref{Stop Reply Packets}, for the reply specifications.
28510 @cindex @samp{vCont?} packet
28511 Request a list of actions supported by the @samp{vCont} packet.
28515 @item vCont@r{[};@var{action}@dots{}@r{]}
28516 The @samp{vCont} packet is supported. Each @var{action} is a supported
28517 command in the @samp{vCont} packet.
28519 The @samp{vCont} packet is not supported.
28522 @item vFile:@var{operation}:@var{parameter}@dots{}
28523 @cindex @samp{vFile} packet
28524 Perform a file operation on the target system. For details,
28525 see @ref{Host I/O Packets}.
28527 @item vFlashErase:@var{addr},@var{length}
28528 @cindex @samp{vFlashErase} packet
28529 Direct the stub to erase @var{length} bytes of flash starting at
28530 @var{addr}. The region may enclose any number of flash blocks, but
28531 its start and end must fall on block boundaries, as indicated by the
28532 flash block size appearing in the memory map (@pxref{Memory Map
28533 Format}). @value{GDBN} groups flash memory programming operations
28534 together, and sends a @samp{vFlashDone} request after each group; the
28535 stub is allowed to delay erase operation until the @samp{vFlashDone}
28536 packet is received.
28538 The stub must support @samp{vCont} if it reports support for
28539 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
28540 this case @samp{vCont} actions can be specified to apply to all threads
28541 in a process by using the @samp{p@var{pid}.-1} form of the
28552 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
28553 @cindex @samp{vFlashWrite} packet
28554 Direct the stub to write data to flash address @var{addr}. The data
28555 is passed in binary form using the same encoding as for the @samp{X}
28556 packet (@pxref{Binary Data}). The memory ranges specified by
28557 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
28558 not overlap, and must appear in order of increasing addresses
28559 (although @samp{vFlashErase} packets for higher addresses may already
28560 have been received; the ordering is guaranteed only between
28561 @samp{vFlashWrite} packets). If a packet writes to an address that was
28562 neither erased by a preceding @samp{vFlashErase} packet nor by some other
28563 target-specific method, the results are unpredictable.
28571 for vFlashWrite addressing non-flash memory
28577 @cindex @samp{vFlashDone} packet
28578 Indicate to the stub that flash programming operation is finished.
28579 The stub is permitted to delay or batch the effects of a group of
28580 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
28581 @samp{vFlashDone} packet is received. The contents of the affected
28582 regions of flash memory are unpredictable until the @samp{vFlashDone}
28583 request is completed.
28585 @item vKill;@var{pid}
28586 @cindex @samp{vKill} packet
28587 Kill the process with the specified process ID. @var{pid} is a
28588 hexadecimal integer identifying the process. This packet is used in
28589 preference to @samp{k} when multiprocess protocol extensions are
28590 supported; see @ref{multiprocess extensions}.
28600 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
28601 @cindex @samp{vRun} packet
28602 Run the program @var{filename}, passing it each @var{argument} on its
28603 command line. The file and arguments are hex-encoded strings. If
28604 @var{filename} is an empty string, the stub may use a default program
28605 (e.g.@: the last program run). The program is created in the stopped
28608 @c FIXME: What about non-stop mode?
28610 This packet is only available in extended mode (@pxref{extended mode}).
28616 @item @r{Any stop packet}
28617 for success (@pxref{Stop Reply Packets})
28621 @anchor{vStopped packet}
28622 @cindex @samp{vStopped} packet
28624 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
28625 reply and prompt for the stub to report another one.
28629 @item @r{Any stop packet}
28630 if there is another unreported stop event (@pxref{Stop Reply Packets})
28632 if there are no unreported stop events
28635 @item X @var{addr},@var{length}:@var{XX@dots{}}
28637 @cindex @samp{X} packet
28638 Write data to memory, where the data is transmitted in binary.
28639 @var{addr} is address, @var{length} is number of bytes,
28640 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
28650 @item z @var{type},@var{addr},@var{length}
28651 @itemx Z @var{type},@var{addr},@var{length}
28652 @anchor{insert breakpoint or watchpoint packet}
28653 @cindex @samp{z} packet
28654 @cindex @samp{Z} packets
28655 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
28656 watchpoint starting at address @var{address} and covering the next
28657 @var{length} bytes.
28659 Each breakpoint and watchpoint packet @var{type} is documented
28662 @emph{Implementation notes: A remote target shall return an empty string
28663 for an unrecognized breakpoint or watchpoint packet @var{type}. A
28664 remote target shall support either both or neither of a given
28665 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
28666 avoid potential problems with duplicate packets, the operations should
28667 be implemented in an idempotent way.}
28669 @item z0,@var{addr},@var{length}
28670 @itemx Z0,@var{addr},@var{length}
28671 @cindex @samp{z0} packet
28672 @cindex @samp{Z0} packet
28673 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
28674 @var{addr} of size @var{length}.
28676 A memory breakpoint is implemented by replacing the instruction at
28677 @var{addr} with a software breakpoint or trap instruction. The
28678 @var{length} is used by targets that indicates the size of the
28679 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
28680 @sc{mips} can insert either a 2 or 4 byte breakpoint).
28682 @emph{Implementation note: It is possible for a target to copy or move
28683 code that contains memory breakpoints (e.g., when implementing
28684 overlays). The behavior of this packet, in the presence of such a
28685 target, is not defined.}
28697 @item z1,@var{addr},@var{length}
28698 @itemx Z1,@var{addr},@var{length}
28699 @cindex @samp{z1} packet
28700 @cindex @samp{Z1} packet
28701 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
28702 address @var{addr} of size @var{length}.
28704 A hardware breakpoint is implemented using a mechanism that is not
28705 dependant on being able to modify the target's memory.
28707 @emph{Implementation note: A hardware breakpoint is not affected by code
28720 @item z2,@var{addr},@var{length}
28721 @itemx Z2,@var{addr},@var{length}
28722 @cindex @samp{z2} packet
28723 @cindex @samp{Z2} packet
28724 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
28736 @item z3,@var{addr},@var{length}
28737 @itemx Z3,@var{addr},@var{length}
28738 @cindex @samp{z3} packet
28739 @cindex @samp{Z3} packet
28740 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
28752 @item z4,@var{addr},@var{length}
28753 @itemx Z4,@var{addr},@var{length}
28754 @cindex @samp{z4} packet
28755 @cindex @samp{Z4} packet
28756 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
28770 @node Stop Reply Packets
28771 @section Stop Reply Packets
28772 @cindex stop reply packets
28774 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
28775 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
28776 receive any of the below as a reply. Except for @samp{?}
28777 and @samp{vStopped}, that reply is only returned
28778 when the target halts. In the below the exact meaning of @dfn{signal
28779 number} is defined by the header @file{include/gdb/signals.h} in the
28780 @value{GDBN} source code.
28782 As in the description of request packets, we include spaces in the
28783 reply templates for clarity; these are not part of the reply packet's
28784 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
28790 The program received signal number @var{AA} (a two-digit hexadecimal
28791 number). This is equivalent to a @samp{T} response with no
28792 @var{n}:@var{r} pairs.
28794 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
28795 @cindex @samp{T} packet reply
28796 The program received signal number @var{AA} (a two-digit hexadecimal
28797 number). This is equivalent to an @samp{S} response, except that the
28798 @samp{@var{n}:@var{r}} pairs can carry values of important registers
28799 and other information directly in the stop reply packet, reducing
28800 round-trip latency. Single-step and breakpoint traps are reported
28801 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
28805 If @var{n} is a hexadecimal number, it is a register number, and the
28806 corresponding @var{r} gives that register's value. @var{r} is a
28807 series of bytes in target byte order, with each byte given by a
28808 two-digit hex number.
28811 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
28812 the stopped thread, as specified in @ref{thread-id syntax}.
28815 If @var{n} is a recognized @dfn{stop reason}, it describes a more
28816 specific event that stopped the target. The currently defined stop
28817 reasons are listed below. @var{aa} should be @samp{05}, the trap
28818 signal. At most one stop reason should be present.
28821 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
28822 and go on to the next; this allows us to extend the protocol in the
28826 The currently defined stop reasons are:
28832 The packet indicates a watchpoint hit, and @var{r} is the data address, in
28835 @cindex shared library events, remote reply
28837 The packet indicates that the loaded libraries have changed.
28838 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
28839 list of loaded libraries. @var{r} is ignored.
28841 @cindex replay log events, remote reply
28843 The packet indicates that the target cannot continue replaying
28844 logged execution events, because it has reached the end (or the
28845 beginning when executing backward) of the log. The value of @var{r}
28846 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
28847 for more information.
28853 @itemx W @var{AA} ; process:@var{pid}
28854 The process exited, and @var{AA} is the exit status. This is only
28855 applicable to certain targets.
28857 The second form of the response, including the process ID of the exited
28858 process, can be used only when @value{GDBN} has reported support for
28859 multiprocess protocol extensions; see @ref{multiprocess extensions}.
28860 The @var{pid} is formatted as a big-endian hex string.
28863 @itemx X @var{AA} ; process:@var{pid}
28864 The process terminated with signal @var{AA}.
28866 The second form of the response, including the process ID of the
28867 terminated process, can be used only when @value{GDBN} has reported
28868 support for multiprocess protocol extensions; see @ref{multiprocess
28869 extensions}. The @var{pid} is formatted as a big-endian hex string.
28871 @item O @var{XX}@dots{}
28872 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
28873 written as the program's console output. This can happen at any time
28874 while the program is running and the debugger should continue to wait
28875 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
28877 @item F @var{call-id},@var{parameter}@dots{}
28878 @var{call-id} is the identifier which says which host system call should
28879 be called. This is just the name of the function. Translation into the
28880 correct system call is only applicable as it's defined in @value{GDBN}.
28881 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
28884 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
28885 this very system call.
28887 The target replies with this packet when it expects @value{GDBN} to
28888 call a host system call on behalf of the target. @value{GDBN} replies
28889 with an appropriate @samp{F} packet and keeps up waiting for the next
28890 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
28891 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
28892 Protocol Extension}, for more details.
28896 @node General Query Packets
28897 @section General Query Packets
28898 @cindex remote query requests
28900 Packets starting with @samp{q} are @dfn{general query packets};
28901 packets starting with @samp{Q} are @dfn{general set packets}. General
28902 query and set packets are a semi-unified form for retrieving and
28903 sending information to and from the stub.
28905 The initial letter of a query or set packet is followed by a name
28906 indicating what sort of thing the packet applies to. For example,
28907 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
28908 definitions with the stub. These packet names follow some
28913 The name must not contain commas, colons or semicolons.
28915 Most @value{GDBN} query and set packets have a leading upper case
28918 The names of custom vendor packets should use a company prefix, in
28919 lower case, followed by a period. For example, packets designed at
28920 the Acme Corporation might begin with @samp{qacme.foo} (for querying
28921 foos) or @samp{Qacme.bar} (for setting bars).
28924 The name of a query or set packet should be separated from any
28925 parameters by a @samp{:}; the parameters themselves should be
28926 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
28927 full packet name, and check for a separator or the end of the packet,
28928 in case two packet names share a common prefix. New packets should not begin
28929 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
28930 packets predate these conventions, and have arguments without any terminator
28931 for the packet name; we suspect they are in widespread use in places that
28932 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
28933 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
28936 Like the descriptions of the other packets, each description here
28937 has a template showing the packet's overall syntax, followed by an
28938 explanation of the packet's meaning. We include spaces in some of the
28939 templates for clarity; these are not part of the packet's syntax. No
28940 @value{GDBN} packet uses spaces to separate its components.
28942 Here are the currently defined query and set packets:
28947 @cindex current thread, remote request
28948 @cindex @samp{qC} packet
28949 Return the current thread ID.
28953 @item QC @var{thread-id}
28954 Where @var{thread-id} is a thread ID as documented in
28955 @ref{thread-id syntax}.
28956 @item @r{(anything else)}
28957 Any other reply implies the old thread ID.
28960 @item qCRC:@var{addr},@var{length}
28961 @cindex CRC of memory block, remote request
28962 @cindex @samp{qCRC} packet
28963 Compute the CRC checksum of a block of memory using CRC-32 defined in
28964 IEEE 802.3. The CRC is computed byte at a time, taking the most
28965 significant bit of each byte first. The initial pattern code
28966 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
28968 @emph{Note:} This is the same CRC used in validating separate debug
28969 files (@pxref{Separate Debug Files, , Debugging Information in Separate
28970 Files}). However the algorithm is slightly different. When validating
28971 separate debug files, the CRC is computed taking the @emph{least}
28972 significant bit of each byte first, and the final result is inverted to
28973 detect trailing zeros.
28978 An error (such as memory fault)
28979 @item C @var{crc32}
28980 The specified memory region's checksum is @var{crc32}.
28984 @itemx qsThreadInfo
28985 @cindex list active threads, remote request
28986 @cindex @samp{qfThreadInfo} packet
28987 @cindex @samp{qsThreadInfo} packet
28988 Obtain a list of all active thread IDs from the target (OS). Since there
28989 may be too many active threads to fit into one reply packet, this query
28990 works iteratively: it may require more than one query/reply sequence to
28991 obtain the entire list of threads. The first query of the sequence will
28992 be the @samp{qfThreadInfo} query; subsequent queries in the
28993 sequence will be the @samp{qsThreadInfo} query.
28995 NOTE: This packet replaces the @samp{qL} query (see below).
28999 @item m @var{thread-id}
29001 @item m @var{thread-id},@var{thread-id}@dots{}
29002 a comma-separated list of thread IDs
29004 (lower case letter @samp{L}) denotes end of list.
29007 In response to each query, the target will reply with a list of one or
29008 more thread IDs, separated by commas.
29009 @value{GDBN} will respond to each reply with a request for more thread
29010 ids (using the @samp{qs} form of the query), until the target responds
29011 with @samp{l} (lower-case el, for @dfn{last}).
29012 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
29015 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
29016 @cindex get thread-local storage address, remote request
29017 @cindex @samp{qGetTLSAddr} packet
29018 Fetch the address associated with thread local storage specified
29019 by @var{thread-id}, @var{offset}, and @var{lm}.
29021 @var{thread-id} is the thread ID associated with the
29022 thread for which to fetch the TLS address. @xref{thread-id syntax}.
29024 @var{offset} is the (big endian, hex encoded) offset associated with the
29025 thread local variable. (This offset is obtained from the debug
29026 information associated with the variable.)
29028 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
29029 the load module associated with the thread local storage. For example,
29030 a @sc{gnu}/Linux system will pass the link map address of the shared
29031 object associated with the thread local storage under consideration.
29032 Other operating environments may choose to represent the load module
29033 differently, so the precise meaning of this parameter will vary.
29037 @item @var{XX}@dots{}
29038 Hex encoded (big endian) bytes representing the address of the thread
29039 local storage requested.
29042 An error occurred. @var{nn} are hex digits.
29045 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
29048 @item qL @var{startflag} @var{threadcount} @var{nextthread}
29049 Obtain thread information from RTOS. Where: @var{startflag} (one hex
29050 digit) is one to indicate the first query and zero to indicate a
29051 subsequent query; @var{threadcount} (two hex digits) is the maximum
29052 number of threads the response packet can contain; and @var{nextthread}
29053 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
29054 returned in the response as @var{argthread}.
29056 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
29060 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
29061 Where: @var{count} (two hex digits) is the number of threads being
29062 returned; @var{done} (one hex digit) is zero to indicate more threads
29063 and one indicates no further threads; @var{argthreadid} (eight hex
29064 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
29065 is a sequence of thread IDs from the target. @var{threadid} (eight hex
29066 digits). See @code{remote.c:parse_threadlist_response()}.
29070 @cindex section offsets, remote request
29071 @cindex @samp{qOffsets} packet
29072 Get section offsets that the target used when relocating the downloaded
29077 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
29078 Relocate the @code{Text} section by @var{xxx} from its original address.
29079 Relocate the @code{Data} section by @var{yyy} from its original address.
29080 If the object file format provides segment information (e.g.@: @sc{elf}
29081 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
29082 segments by the supplied offsets.
29084 @emph{Note: while a @code{Bss} offset may be included in the response,
29085 @value{GDBN} ignores this and instead applies the @code{Data} offset
29086 to the @code{Bss} section.}
29088 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
29089 Relocate the first segment of the object file, which conventionally
29090 contains program code, to a starting address of @var{xxx}. If
29091 @samp{DataSeg} is specified, relocate the second segment, which
29092 conventionally contains modifiable data, to a starting address of
29093 @var{yyy}. @value{GDBN} will report an error if the object file
29094 does not contain segment information, or does not contain at least
29095 as many segments as mentioned in the reply. Extra segments are
29096 kept at fixed offsets relative to the last relocated segment.
29099 @item qP @var{mode} @var{thread-id}
29100 @cindex thread information, remote request
29101 @cindex @samp{qP} packet
29102 Returns information on @var{thread-id}. Where: @var{mode} is a hex
29103 encoded 32 bit mode; @var{thread-id} is a thread ID
29104 (@pxref{thread-id syntax}).
29106 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
29109 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
29113 @cindex non-stop mode, remote request
29114 @cindex @samp{QNonStop} packet
29116 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
29117 @xref{Remote Non-Stop}, for more information.
29122 The request succeeded.
29125 An error occurred. @var{nn} are hex digits.
29128 An empty reply indicates that @samp{QNonStop} is not supported by
29132 This packet is not probed by default; the remote stub must request it,
29133 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
29134 Use of this packet is controlled by the @code{set non-stop} command;
29135 @pxref{Non-Stop Mode}.
29137 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
29138 @cindex pass signals to inferior, remote request
29139 @cindex @samp{QPassSignals} packet
29140 @anchor{QPassSignals}
29141 Each listed @var{signal} should be passed directly to the inferior process.
29142 Signals are numbered identically to continue packets and stop replies
29143 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
29144 strictly greater than the previous item. These signals do not need to stop
29145 the inferior, or be reported to @value{GDBN}. All other signals should be
29146 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
29147 combine; any earlier @samp{QPassSignals} list is completely replaced by the
29148 new list. This packet improves performance when using @samp{handle
29149 @var{signal} nostop noprint pass}.
29154 The request succeeded.
29157 An error occurred. @var{nn} are hex digits.
29160 An empty reply indicates that @samp{QPassSignals} is not supported by
29164 Use of this packet is controlled by the @code{set remote pass-signals}
29165 command (@pxref{Remote Configuration, set remote pass-signals}).
29166 This packet is not probed by default; the remote stub must request it,
29167 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
29169 @item qRcmd,@var{command}
29170 @cindex execute remote command, remote request
29171 @cindex @samp{qRcmd} packet
29172 @var{command} (hex encoded) is passed to the local interpreter for
29173 execution. Invalid commands should be reported using the output
29174 string. Before the final result packet, the target may also respond
29175 with a number of intermediate @samp{O@var{output}} console output
29176 packets. @emph{Implementors should note that providing access to a
29177 stubs's interpreter may have security implications}.
29182 A command response with no output.
29184 A command response with the hex encoded output string @var{OUTPUT}.
29186 Indicate a badly formed request.
29188 An empty reply indicates that @samp{qRcmd} is not recognized.
29191 (Note that the @code{qRcmd} packet's name is separated from the
29192 command by a @samp{,}, not a @samp{:}, contrary to the naming
29193 conventions above. Please don't use this packet as a model for new
29196 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
29197 @cindex searching memory, in remote debugging
29198 @cindex @samp{qSearch:memory} packet
29199 @anchor{qSearch memory}
29200 Search @var{length} bytes at @var{address} for @var{search-pattern}.
29201 @var{address} and @var{length} are encoded in hex.
29202 @var{search-pattern} is a sequence of bytes, hex encoded.
29207 The pattern was not found.
29209 The pattern was found at @var{address}.
29211 A badly formed request or an error was encountered while searching memory.
29213 An empty reply indicates that @samp{qSearch:memory} is not recognized.
29216 @item QStartNoAckMode
29217 @cindex @samp{QStartNoAckMode} packet
29218 @anchor{QStartNoAckMode}
29219 Request that the remote stub disable the normal @samp{+}/@samp{-}
29220 protocol acknowledgments (@pxref{Packet Acknowledgment}).
29225 The stub has switched to no-acknowledgment mode.
29226 @value{GDBN} acknowledges this reponse,
29227 but neither the stub nor @value{GDBN} shall send or expect further
29228 @samp{+}/@samp{-} acknowledgments in the current connection.
29230 An empty reply indicates that the stub does not support no-acknowledgment mode.
29233 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
29234 @cindex supported packets, remote query
29235 @cindex features of the remote protocol
29236 @cindex @samp{qSupported} packet
29237 @anchor{qSupported}
29238 Tell the remote stub about features supported by @value{GDBN}, and
29239 query the stub for features it supports. This packet allows
29240 @value{GDBN} and the remote stub to take advantage of each others'
29241 features. @samp{qSupported} also consolidates multiple feature probes
29242 at startup, to improve @value{GDBN} performance---a single larger
29243 packet performs better than multiple smaller probe packets on
29244 high-latency links. Some features may enable behavior which must not
29245 be on by default, e.g.@: because it would confuse older clients or
29246 stubs. Other features may describe packets which could be
29247 automatically probed for, but are not. These features must be
29248 reported before @value{GDBN} will use them. This ``default
29249 unsupported'' behavior is not appropriate for all packets, but it
29250 helps to keep the initial connection time under control with new
29251 versions of @value{GDBN} which support increasing numbers of packets.
29255 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
29256 The stub supports or does not support each returned @var{stubfeature},
29257 depending on the form of each @var{stubfeature} (see below for the
29260 An empty reply indicates that @samp{qSupported} is not recognized,
29261 or that no features needed to be reported to @value{GDBN}.
29264 The allowed forms for each feature (either a @var{gdbfeature} in the
29265 @samp{qSupported} packet, or a @var{stubfeature} in the response)
29269 @item @var{name}=@var{value}
29270 The remote protocol feature @var{name} is supported, and associated
29271 with the specified @var{value}. The format of @var{value} depends
29272 on the feature, but it must not include a semicolon.
29274 The remote protocol feature @var{name} is supported, and does not
29275 need an associated value.
29277 The remote protocol feature @var{name} is not supported.
29279 The remote protocol feature @var{name} may be supported, and
29280 @value{GDBN} should auto-detect support in some other way when it is
29281 needed. This form will not be used for @var{gdbfeature} notifications,
29282 but may be used for @var{stubfeature} responses.
29285 Whenever the stub receives a @samp{qSupported} request, the
29286 supplied set of @value{GDBN} features should override any previous
29287 request. This allows @value{GDBN} to put the stub in a known
29288 state, even if the stub had previously been communicating with
29289 a different version of @value{GDBN}.
29291 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
29296 This feature indicates whether @value{GDBN} supports multiprocess
29297 extensions to the remote protocol. @value{GDBN} does not use such
29298 extensions unless the stub also reports that it supports them by
29299 including @samp{multiprocess+} in its @samp{qSupported} reply.
29300 @xref{multiprocess extensions}, for details.
29303 Stubs should ignore any unknown values for
29304 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
29305 packet supports receiving packets of unlimited length (earlier
29306 versions of @value{GDBN} may reject overly long responses). Additional values
29307 for @var{gdbfeature} may be defined in the future to let the stub take
29308 advantage of new features in @value{GDBN}, e.g.@: incompatible
29309 improvements in the remote protocol---the @samp{multiprocess} feature is
29310 an example of such a feature. The stub's reply should be independent
29311 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
29312 describes all the features it supports, and then the stub replies with
29313 all the features it supports.
29315 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
29316 responses, as long as each response uses one of the standard forms.
29318 Some features are flags. A stub which supports a flag feature
29319 should respond with a @samp{+} form response. Other features
29320 require values, and the stub should respond with an @samp{=}
29323 Each feature has a default value, which @value{GDBN} will use if
29324 @samp{qSupported} is not available or if the feature is not mentioned
29325 in the @samp{qSupported} response. The default values are fixed; a
29326 stub is free to omit any feature responses that match the defaults.
29328 Not all features can be probed, but for those which can, the probing
29329 mechanism is useful: in some cases, a stub's internal
29330 architecture may not allow the protocol layer to know some information
29331 about the underlying target in advance. This is especially common in
29332 stubs which may be configured for multiple targets.
29334 These are the currently defined stub features and their properties:
29336 @multitable @columnfractions 0.35 0.2 0.12 0.2
29337 @c NOTE: The first row should be @headitem, but we do not yet require
29338 @c a new enough version of Texinfo (4.7) to use @headitem.
29340 @tab Value Required
29344 @item @samp{PacketSize}
29349 @item @samp{qXfer:auxv:read}
29354 @item @samp{qXfer:features:read}
29359 @item @samp{qXfer:libraries:read}
29364 @item @samp{qXfer:memory-map:read}
29369 @item @samp{qXfer:spu:read}
29374 @item @samp{qXfer:spu:write}
29379 @item @samp{qXfer:siginfo:read}
29384 @item @samp{qXfer:siginfo:write}
29389 @item @samp{QNonStop}
29394 @item @samp{QPassSignals}
29399 @item @samp{QStartNoAckMode}
29404 @item @samp{multiprocess}
29409 @item @samp{ConditionalTracepoints}
29414 @item @samp{ReverseContinue}
29419 @item @samp{ReverseStep}
29426 These are the currently defined stub features, in more detail:
29429 @cindex packet size, remote protocol
29430 @item PacketSize=@var{bytes}
29431 The remote stub can accept packets up to at least @var{bytes} in
29432 length. @value{GDBN} will send packets up to this size for bulk
29433 transfers, and will never send larger packets. This is a limit on the
29434 data characters in the packet, including the frame and checksum.
29435 There is no trailing NUL byte in a remote protocol packet; if the stub
29436 stores packets in a NUL-terminated format, it should allow an extra
29437 byte in its buffer for the NUL. If this stub feature is not supported,
29438 @value{GDBN} guesses based on the size of the @samp{g} packet response.
29440 @item qXfer:auxv:read
29441 The remote stub understands the @samp{qXfer:auxv:read} packet
29442 (@pxref{qXfer auxiliary vector read}).
29444 @item qXfer:features:read
29445 The remote stub understands the @samp{qXfer:features:read} packet
29446 (@pxref{qXfer target description read}).
29448 @item qXfer:libraries:read
29449 The remote stub understands the @samp{qXfer:libraries:read} packet
29450 (@pxref{qXfer library list read}).
29452 @item qXfer:memory-map:read
29453 The remote stub understands the @samp{qXfer:memory-map:read} packet
29454 (@pxref{qXfer memory map read}).
29456 @item qXfer:spu:read
29457 The remote stub understands the @samp{qXfer:spu:read} packet
29458 (@pxref{qXfer spu read}).
29460 @item qXfer:spu:write
29461 The remote stub understands the @samp{qXfer:spu:write} packet
29462 (@pxref{qXfer spu write}).
29464 @item qXfer:siginfo:read
29465 The remote stub understands the @samp{qXfer:siginfo:read} packet
29466 (@pxref{qXfer siginfo read}).
29468 @item qXfer:siginfo:write
29469 The remote stub understands the @samp{qXfer:siginfo:write} packet
29470 (@pxref{qXfer siginfo write}).
29473 The remote stub understands the @samp{QNonStop} packet
29474 (@pxref{QNonStop}).
29477 The remote stub understands the @samp{QPassSignals} packet
29478 (@pxref{QPassSignals}).
29480 @item QStartNoAckMode
29481 The remote stub understands the @samp{QStartNoAckMode} packet and
29482 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
29485 @anchor{multiprocess extensions}
29486 @cindex multiprocess extensions, in remote protocol
29487 The remote stub understands the multiprocess extensions to the remote
29488 protocol syntax. The multiprocess extensions affect the syntax of
29489 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
29490 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
29491 replies. Note that reporting this feature indicates support for the
29492 syntactic extensions only, not that the stub necessarily supports
29493 debugging of more than one process at a time. The stub must not use
29494 multiprocess extensions in packet replies unless @value{GDBN} has also
29495 indicated it supports them in its @samp{qSupported} request.
29497 @item qXfer:osdata:read
29498 The remote stub understands the @samp{qXfer:osdata:read} packet
29499 ((@pxref{qXfer osdata read}).
29501 @item ConditionalTracepoints
29502 The remote stub accepts and implements conditional expressions defined
29503 for tracepoints (@pxref{Tracepoint Conditions}).
29505 @item ReverseContinue
29506 The remote stub accepts and implements the reverse continue packet
29510 The remote stub accepts and implements the reverse step packet
29516 @cindex symbol lookup, remote request
29517 @cindex @samp{qSymbol} packet
29518 Notify the target that @value{GDBN} is prepared to serve symbol lookup
29519 requests. Accept requests from the target for the values of symbols.
29524 The target does not need to look up any (more) symbols.
29525 @item qSymbol:@var{sym_name}
29526 The target requests the value of symbol @var{sym_name} (hex encoded).
29527 @value{GDBN} may provide the value by using the
29528 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
29532 @item qSymbol:@var{sym_value}:@var{sym_name}
29533 Set the value of @var{sym_name} to @var{sym_value}.
29535 @var{sym_name} (hex encoded) is the name of a symbol whose value the
29536 target has previously requested.
29538 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
29539 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
29545 The target does not need to look up any (more) symbols.
29546 @item qSymbol:@var{sym_name}
29547 The target requests the value of a new symbol @var{sym_name} (hex
29548 encoded). @value{GDBN} will continue to supply the values of symbols
29549 (if available), until the target ceases to request them.
29554 @xref{Tracepoint Packets}.
29556 @item qThreadExtraInfo,@var{thread-id}
29557 @cindex thread attributes info, remote request
29558 @cindex @samp{qThreadExtraInfo} packet
29559 Obtain a printable string description of a thread's attributes from
29560 the target OS. @var{thread-id} is a thread ID;
29561 see @ref{thread-id syntax}. This
29562 string may contain anything that the target OS thinks is interesting
29563 for @value{GDBN} to tell the user about the thread. The string is
29564 displayed in @value{GDBN}'s @code{info threads} display. Some
29565 examples of possible thread extra info strings are @samp{Runnable}, or
29566 @samp{Blocked on Mutex}.
29570 @item @var{XX}@dots{}
29571 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
29572 comprising the printable string containing the extra information about
29573 the thread's attributes.
29576 (Note that the @code{qThreadExtraInfo} packet's name is separated from
29577 the command by a @samp{,}, not a @samp{:}, contrary to the naming
29578 conventions above. Please don't use this packet as a model for new
29586 @xref{Tracepoint Packets}.
29588 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
29589 @cindex read special object, remote request
29590 @cindex @samp{qXfer} packet
29591 @anchor{qXfer read}
29592 Read uninterpreted bytes from the target's special data area
29593 identified by the keyword @var{object}. Request @var{length} bytes
29594 starting at @var{offset} bytes into the data. The content and
29595 encoding of @var{annex} is specific to @var{object}; it can supply
29596 additional details about what data to access.
29598 Here are the specific requests of this form defined so far. All
29599 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
29600 formats, listed below.
29603 @item qXfer:auxv:read::@var{offset},@var{length}
29604 @anchor{qXfer auxiliary vector read}
29605 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
29606 auxiliary vector}. Note @var{annex} must be empty.
29608 This packet is not probed by default; the remote stub must request it,
29609 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
29611 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
29612 @anchor{qXfer target description read}
29613 Access the @dfn{target description}. @xref{Target Descriptions}. The
29614 annex specifies which XML document to access. The main description is
29615 always loaded from the @samp{target.xml} annex.
29617 This packet is not probed by default; the remote stub must request it,
29618 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
29620 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
29621 @anchor{qXfer library list read}
29622 Access the target's list of loaded libraries. @xref{Library List Format}.
29623 The annex part of the generic @samp{qXfer} packet must be empty
29624 (@pxref{qXfer read}).
29626 Targets which maintain a list of libraries in the program's memory do
29627 not need to implement this packet; it is designed for platforms where
29628 the operating system manages the list of loaded libraries.
29630 This packet is not probed by default; the remote stub must request it,
29631 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
29633 @item qXfer:memory-map:read::@var{offset},@var{length}
29634 @anchor{qXfer memory map read}
29635 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
29636 annex part of the generic @samp{qXfer} packet must be empty
29637 (@pxref{qXfer read}).
29639 This packet is not probed by default; the remote stub must request it,
29640 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
29642 @item qXfer:siginfo:read::@var{offset},@var{length}
29643 @anchor{qXfer siginfo read}
29644 Read contents of the extra signal information on the target
29645 system. The annex part of the generic @samp{qXfer} packet must be
29646 empty (@pxref{qXfer read}).
29648 This packet is not probed by default; the remote stub must request it,
29649 by supplying an appropriate @samp{qSupported} response
29650 (@pxref{qSupported}).
29652 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
29653 @anchor{qXfer spu read}
29654 Read contents of an @code{spufs} file on the target system. The
29655 annex specifies which file to read; it must be of the form
29656 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
29657 in the target process, and @var{name} identifes the @code{spufs} file
29658 in that context to be accessed.
29660 This packet is not probed by default; the remote stub must request it,
29661 by supplying an appropriate @samp{qSupported} response
29662 (@pxref{qSupported}).
29664 @item qXfer:osdata:read::@var{offset},@var{length}
29665 @anchor{qXfer osdata read}
29666 Access the target's @dfn{operating system information}.
29667 @xref{Operating System Information}.
29674 Data @var{data} (@pxref{Binary Data}) has been read from the
29675 target. There may be more data at a higher address (although
29676 it is permitted to return @samp{m} even for the last valid
29677 block of data, as long as at least one byte of data was read).
29678 @var{data} may have fewer bytes than the @var{length} in the
29682 Data @var{data} (@pxref{Binary Data}) has been read from the target.
29683 There is no more data to be read. @var{data} may have fewer bytes
29684 than the @var{length} in the request.
29687 The @var{offset} in the request is at the end of the data.
29688 There is no more data to be read.
29691 The request was malformed, or @var{annex} was invalid.
29694 The offset was invalid, or there was an error encountered reading the data.
29695 @var{nn} is a hex-encoded @code{errno} value.
29698 An empty reply indicates the @var{object} string was not recognized by
29699 the stub, or that the object does not support reading.
29702 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
29703 @cindex write data into object, remote request
29704 @anchor{qXfer write}
29705 Write uninterpreted bytes into the target's special data area
29706 identified by the keyword @var{object}, starting at @var{offset} bytes
29707 into the data. @var{data}@dots{} is the binary-encoded data
29708 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
29709 is specific to @var{object}; it can supply additional details about what data
29712 Here are the specific requests of this form defined so far. All
29713 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
29714 formats, listed below.
29717 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
29718 @anchor{qXfer siginfo write}
29719 Write @var{data} to the extra signal information on the target system.
29720 The annex part of the generic @samp{qXfer} packet must be
29721 empty (@pxref{qXfer write}).
29723 This packet is not probed by default; the remote stub must request it,
29724 by supplying an appropriate @samp{qSupported} response
29725 (@pxref{qSupported}).
29727 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
29728 @anchor{qXfer spu write}
29729 Write @var{data} to an @code{spufs} file on the target system. The
29730 annex specifies which file to write; it must be of the form
29731 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
29732 in the target process, and @var{name} identifes the @code{spufs} file
29733 in that context to be accessed.
29735 This packet is not probed by default; the remote stub must request it,
29736 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
29742 @var{nn} (hex encoded) is the number of bytes written.
29743 This may be fewer bytes than supplied in the request.
29746 The request was malformed, or @var{annex} was invalid.
29749 The offset was invalid, or there was an error encountered writing the data.
29750 @var{nn} is a hex-encoded @code{errno} value.
29753 An empty reply indicates the @var{object} string was not
29754 recognized by the stub, or that the object does not support writing.
29757 @item qXfer:@var{object}:@var{operation}:@dots{}
29758 Requests of this form may be added in the future. When a stub does
29759 not recognize the @var{object} keyword, or its support for
29760 @var{object} does not recognize the @var{operation} keyword, the stub
29761 must respond with an empty packet.
29763 @item qAttached:@var{pid}
29764 @cindex query attached, remote request
29765 @cindex @samp{qAttached} packet
29766 Return an indication of whether the remote server attached to an
29767 existing process or created a new process. When the multiprocess
29768 protocol extensions are supported (@pxref{multiprocess extensions}),
29769 @var{pid} is an integer in hexadecimal format identifying the target
29770 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
29771 the query packet will be simplified as @samp{qAttached}.
29773 This query is used, for example, to know whether the remote process
29774 should be detached or killed when a @value{GDBN} session is ended with
29775 the @code{quit} command.
29780 The remote server attached to an existing process.
29782 The remote server created a new process.
29784 A badly formed request or an error was encountered.
29789 @node Register Packet Format
29790 @section Register Packet Format
29792 The following @code{g}/@code{G} packets have previously been defined.
29793 In the below, some thirty-two bit registers are transferred as
29794 sixty-four bits. Those registers should be zero/sign extended (which?)
29795 to fill the space allocated. Register bytes are transferred in target
29796 byte order. The two nibbles within a register byte are transferred
29797 most-significant - least-significant.
29803 All registers are transferred as thirty-two bit quantities in the order:
29804 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
29805 registers; fsr; fir; fp.
29809 All registers are transferred as sixty-four bit quantities (including
29810 thirty-two bit registers such as @code{sr}). The ordering is the same
29815 @node Tracepoint Packets
29816 @section Tracepoint Packets
29817 @cindex tracepoint packets
29818 @cindex packets, tracepoint
29820 Here we describe the packets @value{GDBN} uses to implement
29821 tracepoints (@pxref{Tracepoints}).
29825 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:X@var{len},@var{bytes}]@r{[}-@r{]}
29826 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
29827 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
29828 the tracepoint is disabled. @var{step} is the tracepoint's step
29829 count, and @var{pass} is its pass count. If an @samp{X} is present,
29830 it introduces a tracepoint condition, which consists of a hexadecimal
29831 length, followed by a comma and hex-encoded bytes, in a manner similar
29832 to action encodings as described below. If the trailing @samp{-} is
29833 present, further @samp{QTDP} packets will follow to specify this
29834 tracepoint's actions.
29839 The packet was understood and carried out.
29841 The packet was not recognized.
29844 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
29845 Define actions to be taken when a tracepoint is hit. @var{n} and
29846 @var{addr} must be the same as in the initial @samp{QTDP} packet for
29847 this tracepoint. This packet may only be sent immediately after
29848 another @samp{QTDP} packet that ended with a @samp{-}. If the
29849 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
29850 specifying more actions for this tracepoint.
29852 In the series of action packets for a given tracepoint, at most one
29853 can have an @samp{S} before its first @var{action}. If such a packet
29854 is sent, it and the following packets define ``while-stepping''
29855 actions. Any prior packets define ordinary actions --- that is, those
29856 taken when the tracepoint is first hit. If no action packet has an
29857 @samp{S}, then all the packets in the series specify ordinary
29858 tracepoint actions.
29860 The @samp{@var{action}@dots{}} portion of the packet is a series of
29861 actions, concatenated without separators. Each action has one of the
29867 Collect the registers whose bits are set in @var{mask}. @var{mask} is
29868 a hexadecimal number whose @var{i}'th bit is set if register number
29869 @var{i} should be collected. (The least significant bit is numbered
29870 zero.) Note that @var{mask} may be any number of digits long; it may
29871 not fit in a 32-bit word.
29873 @item M @var{basereg},@var{offset},@var{len}
29874 Collect @var{len} bytes of memory starting at the address in register
29875 number @var{basereg}, plus @var{offset}. If @var{basereg} is
29876 @samp{-1}, then the range has a fixed address: @var{offset} is the
29877 address of the lowest byte to collect. The @var{basereg},
29878 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
29879 values (the @samp{-1} value for @var{basereg} is a special case).
29881 @item X @var{len},@var{expr}
29882 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
29883 it directs. @var{expr} is an agent expression, as described in
29884 @ref{Agent Expressions}. Each byte of the expression is encoded as a
29885 two-digit hex number in the packet; @var{len} is the number of bytes
29886 in the expression (and thus one-half the number of hex digits in the
29891 Any number of actions may be packed together in a single @samp{QTDP}
29892 packet, as long as the packet does not exceed the maximum packet
29893 length (400 bytes, for many stubs). There may be only one @samp{R}
29894 action per tracepoint, and it must precede any @samp{M} or @samp{X}
29895 actions. Any registers referred to by @samp{M} and @samp{X} actions
29896 must be collected by a preceding @samp{R} action. (The
29897 ``while-stepping'' actions are treated as if they were attached to a
29898 separate tracepoint, as far as these restrictions are concerned.)
29903 The packet was understood and carried out.
29905 The packet was not recognized.
29908 @item QTFrame:@var{n}
29909 Select the @var{n}'th tracepoint frame from the buffer, and use the
29910 register and memory contents recorded there to answer subsequent
29911 request packets from @value{GDBN}.
29913 A successful reply from the stub indicates that the stub has found the
29914 requested frame. The response is a series of parts, concatenated
29915 without separators, describing the frame we selected. Each part has
29916 one of the following forms:
29920 The selected frame is number @var{n} in the trace frame buffer;
29921 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
29922 was no frame matching the criteria in the request packet.
29925 The selected trace frame records a hit of tracepoint number @var{t};
29926 @var{t} is a hexadecimal number.
29930 @item QTFrame:pc:@var{addr}
29931 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
29932 currently selected frame whose PC is @var{addr};
29933 @var{addr} is a hexadecimal number.
29935 @item QTFrame:tdp:@var{t}
29936 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
29937 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
29938 is a hexadecimal number.
29940 @item QTFrame:range:@var{start}:@var{end}
29941 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
29942 currently selected frame whose PC is between @var{start} (inclusive)
29943 and @var{end} (exclusive); @var{start} and @var{end} are hexadecimal
29946 @item QTFrame:outside:@var{start}:@var{end}
29947 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
29948 frame @emph{outside} the given range of addresses.
29951 Begin the tracepoint experiment. Begin collecting data from tracepoint
29952 hits in the trace frame buffer.
29955 End the tracepoint experiment. Stop collecting trace frames.
29958 Clear the table of tracepoints, and empty the trace frame buffer.
29960 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
29961 Establish the given ranges of memory as ``transparent''. The stub
29962 will answer requests for these ranges from memory's current contents,
29963 if they were not collected as part of the tracepoint hit.
29965 @value{GDBN} uses this to mark read-only regions of memory, like those
29966 containing program code. Since these areas never change, they should
29967 still have the same contents they did when the tracepoint was hit, so
29968 there's no reason for the stub to refuse to provide their contents.
29971 Ask the stub if there is a trace experiment running right now.
29976 There is no trace experiment running.
29978 There is a trace experiment running.
29984 @node Host I/O Packets
29985 @section Host I/O Packets
29986 @cindex Host I/O, remote protocol
29987 @cindex file transfer, remote protocol
29989 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
29990 operations on the far side of a remote link. For example, Host I/O is
29991 used to upload and download files to a remote target with its own
29992 filesystem. Host I/O uses the same constant values and data structure
29993 layout as the target-initiated File-I/O protocol. However, the
29994 Host I/O packets are structured differently. The target-initiated
29995 protocol relies on target memory to store parameters and buffers.
29996 Host I/O requests are initiated by @value{GDBN}, and the
29997 target's memory is not involved. @xref{File-I/O Remote Protocol
29998 Extension}, for more details on the target-initiated protocol.
30000 The Host I/O request packets all encode a single operation along with
30001 its arguments. They have this format:
30005 @item vFile:@var{operation}: @var{parameter}@dots{}
30006 @var{operation} is the name of the particular request; the target
30007 should compare the entire packet name up to the second colon when checking
30008 for a supported operation. The format of @var{parameter} depends on
30009 the operation. Numbers are always passed in hexadecimal. Negative
30010 numbers have an explicit minus sign (i.e.@: two's complement is not
30011 used). Strings (e.g.@: filenames) are encoded as a series of
30012 hexadecimal bytes. The last argument to a system call may be a
30013 buffer of escaped binary data (@pxref{Binary Data}).
30017 The valid responses to Host I/O packets are:
30021 @item F @var{result} [, @var{errno}] [; @var{attachment}]
30022 @var{result} is the integer value returned by this operation, usually
30023 non-negative for success and -1 for errors. If an error has occured,
30024 @var{errno} will be included in the result. @var{errno} will have a
30025 value defined by the File-I/O protocol (@pxref{Errno Values}). For
30026 operations which return data, @var{attachment} supplies the data as a
30027 binary buffer. Binary buffers in response packets are escaped in the
30028 normal way (@pxref{Binary Data}). See the individual packet
30029 documentation for the interpretation of @var{result} and
30033 An empty response indicates that this operation is not recognized.
30037 These are the supported Host I/O operations:
30040 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
30041 Open a file at @var{pathname} and return a file descriptor for it, or
30042 return -1 if an error occurs. @var{pathname} is a string,
30043 @var{flags} is an integer indicating a mask of open flags
30044 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
30045 of mode bits to use if the file is created (@pxref{mode_t Values}).
30046 @xref{open}, for details of the open flags and mode values.
30048 @item vFile:close: @var{fd}
30049 Close the open file corresponding to @var{fd} and return 0, or
30050 -1 if an error occurs.
30052 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
30053 Read data from the open file corresponding to @var{fd}. Up to
30054 @var{count} bytes will be read from the file, starting at @var{offset}
30055 relative to the start of the file. The target may read fewer bytes;
30056 common reasons include packet size limits and an end-of-file
30057 condition. The number of bytes read is returned. Zero should only be
30058 returned for a successful read at the end of the file, or if
30059 @var{count} was zero.
30061 The data read should be returned as a binary attachment on success.
30062 If zero bytes were read, the response should include an empty binary
30063 attachment (i.e.@: a trailing semicolon). The return value is the
30064 number of target bytes read; the binary attachment may be longer if
30065 some characters were escaped.
30067 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
30068 Write @var{data} (a binary buffer) to the open file corresponding
30069 to @var{fd}. Start the write at @var{offset} from the start of the
30070 file. Unlike many @code{write} system calls, there is no
30071 separate @var{count} argument; the length of @var{data} in the
30072 packet is used. @samp{vFile:write} returns the number of bytes written,
30073 which may be shorter than the length of @var{data}, or -1 if an
30076 @item vFile:unlink: @var{pathname}
30077 Delete the file at @var{pathname} on the target. Return 0,
30078 or -1 if an error occurs. @var{pathname} is a string.
30083 @section Interrupts
30084 @cindex interrupts (remote protocol)
30086 When a program on the remote target is running, @value{GDBN} may
30087 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
30088 control of which is specified via @value{GDBN}'s @samp{remotebreak}
30089 setting (@pxref{set remotebreak}).
30091 The precise meaning of @code{BREAK} is defined by the transport
30092 mechanism and may, in fact, be undefined. @value{GDBN} does not
30093 currently define a @code{BREAK} mechanism for any of the network
30094 interfaces except for TCP, in which case @value{GDBN} sends the
30095 @code{telnet} BREAK sequence.
30097 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
30098 transport mechanisms. It is represented by sending the single byte
30099 @code{0x03} without any of the usual packet overhead described in
30100 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
30101 transmitted as part of a packet, it is considered to be packet data
30102 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
30103 (@pxref{X packet}), used for binary downloads, may include an unescaped
30104 @code{0x03} as part of its packet.
30106 Stubs are not required to recognize these interrupt mechanisms and the
30107 precise meaning associated with receipt of the interrupt is
30108 implementation defined. If the target supports debugging of multiple
30109 threads and/or processes, it should attempt to interrupt all
30110 currently-executing threads and processes.
30111 If the stub is successful at interrupting the
30112 running program, it should send one of the stop
30113 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
30114 of successfully stopping the program in all-stop mode, and a stop reply
30115 for each stopped thread in non-stop mode.
30116 Interrupts received while the
30117 program is stopped are discarded.
30119 @node Notification Packets
30120 @section Notification Packets
30121 @cindex notification packets
30122 @cindex packets, notification
30124 The @value{GDBN} remote serial protocol includes @dfn{notifications},
30125 packets that require no acknowledgment. Both the GDB and the stub
30126 may send notifications (although the only notifications defined at
30127 present are sent by the stub). Notifications carry information
30128 without incurring the round-trip latency of an acknowledgment, and so
30129 are useful for low-impact communications where occasional packet loss
30132 A notification packet has the form @samp{% @var{data} #
30133 @var{checksum}}, where @var{data} is the content of the notification,
30134 and @var{checksum} is a checksum of @var{data}, computed and formatted
30135 as for ordinary @value{GDBN} packets. A notification's @var{data}
30136 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
30137 receiving a notification, the recipient sends no @samp{+} or @samp{-}
30138 to acknowledge the notification's receipt or to report its corruption.
30140 Every notification's @var{data} begins with a name, which contains no
30141 colon characters, followed by a colon character.
30143 Recipients should silently ignore corrupted notifications and
30144 notifications they do not understand. Recipients should restart
30145 timeout periods on receipt of a well-formed notification, whether or
30146 not they understand it.
30148 Senders should only send the notifications described here when this
30149 protocol description specifies that they are permitted. In the
30150 future, we may extend the protocol to permit existing notifications in
30151 new contexts; this rule helps older senders avoid confusing newer
30154 (Older versions of @value{GDBN} ignore bytes received until they see
30155 the @samp{$} byte that begins an ordinary packet, so new stubs may
30156 transmit notifications without fear of confusing older clients. There
30157 are no notifications defined for @value{GDBN} to send at the moment, but we
30158 assume that most older stubs would ignore them, as well.)
30160 The following notification packets from the stub to @value{GDBN} are
30164 @item Stop: @var{reply}
30165 Report an asynchronous stop event in non-stop mode.
30166 The @var{reply} has the form of a stop reply, as
30167 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
30168 for information on how these notifications are acknowledged by
30172 @node Remote Non-Stop
30173 @section Remote Protocol Support for Non-Stop Mode
30175 @value{GDBN}'s remote protocol supports non-stop debugging of
30176 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
30177 supports non-stop mode, it should report that to @value{GDBN} by including
30178 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
30180 @value{GDBN} typically sends a @samp{QNonStop} packet only when
30181 establishing a new connection with the stub. Entering non-stop mode
30182 does not alter the state of any currently-running threads, but targets
30183 must stop all threads in any already-attached processes when entering
30184 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
30185 probe the target state after a mode change.
30187 In non-stop mode, when an attached process encounters an event that
30188 would otherwise be reported with a stop reply, it uses the
30189 asynchronous notification mechanism (@pxref{Notification Packets}) to
30190 inform @value{GDBN}. In contrast to all-stop mode, where all threads
30191 in all processes are stopped when a stop reply is sent, in non-stop
30192 mode only the thread reporting the stop event is stopped. That is,
30193 when reporting a @samp{S} or @samp{T} response to indicate completion
30194 of a step operation, hitting a breakpoint, or a fault, only the
30195 affected thread is stopped; any other still-running threads continue
30196 to run. When reporting a @samp{W} or @samp{X} response, all running
30197 threads belonging to other attached processes continue to run.
30199 Only one stop reply notification at a time may be pending; if
30200 additional stop events occur before @value{GDBN} has acknowledged the
30201 previous notification, they must be queued by the stub for later
30202 synchronous transmission in response to @samp{vStopped} packets from
30203 @value{GDBN}. Because the notification mechanism is unreliable,
30204 the stub is permitted to resend a stop reply notification
30205 if it believes @value{GDBN} may not have received it. @value{GDBN}
30206 ignores additional stop reply notifications received before it has
30207 finished processing a previous notification and the stub has completed
30208 sending any queued stop events.
30210 Otherwise, @value{GDBN} must be prepared to receive a stop reply
30211 notification at any time. Specifically, they may appear when
30212 @value{GDBN} is not otherwise reading input from the stub, or when
30213 @value{GDBN} is expecting to read a normal synchronous response or a
30214 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
30215 Notification packets are distinct from any other communication from
30216 the stub so there is no ambiguity.
30218 After receiving a stop reply notification, @value{GDBN} shall
30219 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
30220 as a regular, synchronous request to the stub. Such acknowledgment
30221 is not required to happen immediately, as @value{GDBN} is permitted to
30222 send other, unrelated packets to the stub first, which the stub should
30225 Upon receiving a @samp{vStopped} packet, if the stub has other queued
30226 stop events to report to @value{GDBN}, it shall respond by sending a
30227 normal stop reply response. @value{GDBN} shall then send another
30228 @samp{vStopped} packet to solicit further responses; again, it is
30229 permitted to send other, unrelated packets as well which the stub
30230 should process normally.
30232 If the stub receives a @samp{vStopped} packet and there are no
30233 additional stop events to report, the stub shall return an @samp{OK}
30234 response. At this point, if further stop events occur, the stub shall
30235 send a new stop reply notification, @value{GDBN} shall accept the
30236 notification, and the process shall be repeated.
30238 In non-stop mode, the target shall respond to the @samp{?} packet as
30239 follows. First, any incomplete stop reply notification/@samp{vStopped}
30240 sequence in progress is abandoned. The target must begin a new
30241 sequence reporting stop events for all stopped threads, whether or not
30242 it has previously reported those events to @value{GDBN}. The first
30243 stop reply is sent as a synchronous reply to the @samp{?} packet, and
30244 subsequent stop replies are sent as responses to @samp{vStopped} packets
30245 using the mechanism described above. The target must not send
30246 asynchronous stop reply notifications until the sequence is complete.
30247 If all threads are running when the target receives the @samp{?} packet,
30248 or if the target is not attached to any process, it shall respond
30251 @node Packet Acknowledgment
30252 @section Packet Acknowledgment
30254 @cindex acknowledgment, for @value{GDBN} remote
30255 @cindex packet acknowledgment, for @value{GDBN} remote
30256 By default, when either the host or the target machine receives a packet,
30257 the first response expected is an acknowledgment: either @samp{+} (to indicate
30258 the package was received correctly) or @samp{-} (to request retransmission).
30259 This mechanism allows the @value{GDBN} remote protocol to operate over
30260 unreliable transport mechanisms, such as a serial line.
30262 In cases where the transport mechanism is itself reliable (such as a pipe or
30263 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
30264 It may be desirable to disable them in that case to reduce communication
30265 overhead, or for other reasons. This can be accomplished by means of the
30266 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
30268 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
30269 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
30270 and response format still includes the normal checksum, as described in
30271 @ref{Overview}, but the checksum may be ignored by the receiver.
30273 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
30274 no-acknowledgment mode, it should report that to @value{GDBN}
30275 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
30276 @pxref{qSupported}.
30277 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
30278 disabled via the @code{set remote noack-packet off} command
30279 (@pxref{Remote Configuration}),
30280 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
30281 Only then may the stub actually turn off packet acknowledgments.
30282 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
30283 response, which can be safely ignored by the stub.
30285 Note that @code{set remote noack-packet} command only affects negotiation
30286 between @value{GDBN} and the stub when subsequent connections are made;
30287 it does not affect the protocol acknowledgment state for any current
30289 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
30290 new connection is established,
30291 there is also no protocol request to re-enable the acknowledgments
30292 for the current connection, once disabled.
30297 Example sequence of a target being re-started. Notice how the restart
30298 does not get any direct output:
30303 @emph{target restarts}
30306 <- @code{T001:1234123412341234}
30310 Example sequence of a target being stepped by a single instruction:
30313 -> @code{G1445@dots{}}
30318 <- @code{T001:1234123412341234}
30322 <- @code{1455@dots{}}
30326 @node File-I/O Remote Protocol Extension
30327 @section File-I/O Remote Protocol Extension
30328 @cindex File-I/O remote protocol extension
30331 * File-I/O Overview::
30332 * Protocol Basics::
30333 * The F Request Packet::
30334 * The F Reply Packet::
30335 * The Ctrl-C Message::
30337 * List of Supported Calls::
30338 * Protocol-specific Representation of Datatypes::
30340 * File-I/O Examples::
30343 @node File-I/O Overview
30344 @subsection File-I/O Overview
30345 @cindex file-i/o overview
30347 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
30348 target to use the host's file system and console I/O to perform various
30349 system calls. System calls on the target system are translated into a
30350 remote protocol packet to the host system, which then performs the needed
30351 actions and returns a response packet to the target system.
30352 This simulates file system operations even on targets that lack file systems.
30354 The protocol is defined to be independent of both the host and target systems.
30355 It uses its own internal representation of datatypes and values. Both
30356 @value{GDBN} and the target's @value{GDBN} stub are responsible for
30357 translating the system-dependent value representations into the internal
30358 protocol representations when data is transmitted.
30360 The communication is synchronous. A system call is possible only when
30361 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
30362 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
30363 the target is stopped to allow deterministic access to the target's
30364 memory. Therefore File-I/O is not interruptible by target signals. On
30365 the other hand, it is possible to interrupt File-I/O by a user interrupt
30366 (@samp{Ctrl-C}) within @value{GDBN}.
30368 The target's request to perform a host system call does not finish
30369 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
30370 after finishing the system call, the target returns to continuing the
30371 previous activity (continue, step). No additional continue or step
30372 request from @value{GDBN} is required.
30375 (@value{GDBP}) continue
30376 <- target requests 'system call X'
30377 target is stopped, @value{GDBN} executes system call
30378 -> @value{GDBN} returns result
30379 ... target continues, @value{GDBN} returns to wait for the target
30380 <- target hits breakpoint and sends a Txx packet
30383 The protocol only supports I/O on the console and to regular files on
30384 the host file system. Character or block special devices, pipes,
30385 named pipes, sockets or any other communication method on the host
30386 system are not supported by this protocol.
30388 File I/O is not supported in non-stop mode.
30390 @node Protocol Basics
30391 @subsection Protocol Basics
30392 @cindex protocol basics, file-i/o
30394 The File-I/O protocol uses the @code{F} packet as the request as well
30395 as reply packet. Since a File-I/O system call can only occur when
30396 @value{GDBN} is waiting for a response from the continuing or stepping target,
30397 the File-I/O request is a reply that @value{GDBN} has to expect as a result
30398 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
30399 This @code{F} packet contains all information needed to allow @value{GDBN}
30400 to call the appropriate host system call:
30404 A unique identifier for the requested system call.
30407 All parameters to the system call. Pointers are given as addresses
30408 in the target memory address space. Pointers to strings are given as
30409 pointer/length pair. Numerical values are given as they are.
30410 Numerical control flags are given in a protocol-specific representation.
30414 At this point, @value{GDBN} has to perform the following actions.
30418 If the parameters include pointer values to data needed as input to a
30419 system call, @value{GDBN} requests this data from the target with a
30420 standard @code{m} packet request. This additional communication has to be
30421 expected by the target implementation and is handled as any other @code{m}
30425 @value{GDBN} translates all value from protocol representation to host
30426 representation as needed. Datatypes are coerced into the host types.
30429 @value{GDBN} calls the system call.
30432 It then coerces datatypes back to protocol representation.
30435 If the system call is expected to return data in buffer space specified
30436 by pointer parameters to the call, the data is transmitted to the
30437 target using a @code{M} or @code{X} packet. This packet has to be expected
30438 by the target implementation and is handled as any other @code{M} or @code{X}
30443 Eventually @value{GDBN} replies with another @code{F} packet which contains all
30444 necessary information for the target to continue. This at least contains
30451 @code{errno}, if has been changed by the system call.
30458 After having done the needed type and value coercion, the target continues
30459 the latest continue or step action.
30461 @node The F Request Packet
30462 @subsection The @code{F} Request Packet
30463 @cindex file-i/o request packet
30464 @cindex @code{F} request packet
30466 The @code{F} request packet has the following format:
30469 @item F@var{call-id},@var{parameter@dots{}}
30471 @var{call-id} is the identifier to indicate the host system call to be called.
30472 This is just the name of the function.
30474 @var{parameter@dots{}} are the parameters to the system call.
30475 Parameters are hexadecimal integer values, either the actual values in case
30476 of scalar datatypes, pointers to target buffer space in case of compound
30477 datatypes and unspecified memory areas, or pointer/length pairs in case
30478 of string parameters. These are appended to the @var{call-id} as a
30479 comma-delimited list. All values are transmitted in ASCII
30480 string representation, pointer/length pairs separated by a slash.
30486 @node The F Reply Packet
30487 @subsection The @code{F} Reply Packet
30488 @cindex file-i/o reply packet
30489 @cindex @code{F} reply packet
30491 The @code{F} reply packet has the following format:
30495 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
30497 @var{retcode} is the return code of the system call as hexadecimal value.
30499 @var{errno} is the @code{errno} set by the call, in protocol-specific
30501 This parameter can be omitted if the call was successful.
30503 @var{Ctrl-C flag} is only sent if the user requested a break. In this
30504 case, @var{errno} must be sent as well, even if the call was successful.
30505 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
30512 or, if the call was interrupted before the host call has been performed:
30519 assuming 4 is the protocol-specific representation of @code{EINTR}.
30524 @node The Ctrl-C Message
30525 @subsection The @samp{Ctrl-C} Message
30526 @cindex ctrl-c message, in file-i/o protocol
30528 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
30529 reply packet (@pxref{The F Reply Packet}),
30530 the target should behave as if it had
30531 gotten a break message. The meaning for the target is ``system call
30532 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
30533 (as with a break message) and return to @value{GDBN} with a @code{T02}
30536 It's important for the target to know in which
30537 state the system call was interrupted. There are two possible cases:
30541 The system call hasn't been performed on the host yet.
30544 The system call on the host has been finished.
30548 These two states can be distinguished by the target by the value of the
30549 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
30550 call hasn't been performed. This is equivalent to the @code{EINTR} handling
30551 on POSIX systems. In any other case, the target may presume that the
30552 system call has been finished --- successfully or not --- and should behave
30553 as if the break message arrived right after the system call.
30555 @value{GDBN} must behave reliably. If the system call has not been called
30556 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
30557 @code{errno} in the packet. If the system call on the host has been finished
30558 before the user requests a break, the full action must be finished by
30559 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
30560 The @code{F} packet may only be sent when either nothing has happened
30561 or the full action has been completed.
30564 @subsection Console I/O
30565 @cindex console i/o as part of file-i/o
30567 By default and if not explicitly closed by the target system, the file
30568 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
30569 on the @value{GDBN} console is handled as any other file output operation
30570 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
30571 by @value{GDBN} so that after the target read request from file descriptor
30572 0 all following typing is buffered until either one of the following
30577 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
30579 system call is treated as finished.
30582 The user presses @key{RET}. This is treated as end of input with a trailing
30586 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
30587 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
30591 If the user has typed more characters than fit in the buffer given to
30592 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
30593 either another @code{read(0, @dots{})} is requested by the target, or debugging
30594 is stopped at the user's request.
30597 @node List of Supported Calls
30598 @subsection List of Supported Calls
30599 @cindex list of supported file-i/o calls
30616 @unnumberedsubsubsec open
30617 @cindex open, file-i/o system call
30622 int open(const char *pathname, int flags);
30623 int open(const char *pathname, int flags, mode_t mode);
30627 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
30630 @var{flags} is the bitwise @code{OR} of the following values:
30634 If the file does not exist it will be created. The host
30635 rules apply as far as file ownership and time stamps
30639 When used with @code{O_CREAT}, if the file already exists it is
30640 an error and open() fails.
30643 If the file already exists and the open mode allows
30644 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
30645 truncated to zero length.
30648 The file is opened in append mode.
30651 The file is opened for reading only.
30654 The file is opened for writing only.
30657 The file is opened for reading and writing.
30661 Other bits are silently ignored.
30665 @var{mode} is the bitwise @code{OR} of the following values:
30669 User has read permission.
30672 User has write permission.
30675 Group has read permission.
30678 Group has write permission.
30681 Others have read permission.
30684 Others have write permission.
30688 Other bits are silently ignored.
30691 @item Return value:
30692 @code{open} returns the new file descriptor or -1 if an error
30699 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
30702 @var{pathname} refers to a directory.
30705 The requested access is not allowed.
30708 @var{pathname} was too long.
30711 A directory component in @var{pathname} does not exist.
30714 @var{pathname} refers to a device, pipe, named pipe or socket.
30717 @var{pathname} refers to a file on a read-only filesystem and
30718 write access was requested.
30721 @var{pathname} is an invalid pointer value.
30724 No space on device to create the file.
30727 The process already has the maximum number of files open.
30730 The limit on the total number of files open on the system
30734 The call was interrupted by the user.
30740 @unnumberedsubsubsec close
30741 @cindex close, file-i/o system call
30750 @samp{Fclose,@var{fd}}
30752 @item Return value:
30753 @code{close} returns zero on success, or -1 if an error occurred.
30759 @var{fd} isn't a valid open file descriptor.
30762 The call was interrupted by the user.
30768 @unnumberedsubsubsec read
30769 @cindex read, file-i/o system call
30774 int read(int fd, void *buf, unsigned int count);
30778 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
30780 @item Return value:
30781 On success, the number of bytes read is returned.
30782 Zero indicates end of file. If count is zero, read
30783 returns zero as well. On error, -1 is returned.
30789 @var{fd} is not a valid file descriptor or is not open for
30793 @var{bufptr} is an invalid pointer value.
30796 The call was interrupted by the user.
30802 @unnumberedsubsubsec write
30803 @cindex write, file-i/o system call
30808 int write(int fd, const void *buf, unsigned int count);
30812 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
30814 @item Return value:
30815 On success, the number of bytes written are returned.
30816 Zero indicates nothing was written. On error, -1
30823 @var{fd} is not a valid file descriptor or is not open for
30827 @var{bufptr} is an invalid pointer value.
30830 An attempt was made to write a file that exceeds the
30831 host-specific maximum file size allowed.
30834 No space on device to write the data.
30837 The call was interrupted by the user.
30843 @unnumberedsubsubsec lseek
30844 @cindex lseek, file-i/o system call
30849 long lseek (int fd, long offset, int flag);
30853 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
30855 @var{flag} is one of:
30859 The offset is set to @var{offset} bytes.
30862 The offset is set to its current location plus @var{offset}
30866 The offset is set to the size of the file plus @var{offset}
30870 @item Return value:
30871 On success, the resulting unsigned offset in bytes from
30872 the beginning of the file is returned. Otherwise, a
30873 value of -1 is returned.
30879 @var{fd} is not a valid open file descriptor.
30882 @var{fd} is associated with the @value{GDBN} console.
30885 @var{flag} is not a proper value.
30888 The call was interrupted by the user.
30894 @unnumberedsubsubsec rename
30895 @cindex rename, file-i/o system call
30900 int rename(const char *oldpath, const char *newpath);
30904 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
30906 @item Return value:
30907 On success, zero is returned. On error, -1 is returned.
30913 @var{newpath} is an existing directory, but @var{oldpath} is not a
30917 @var{newpath} is a non-empty directory.
30920 @var{oldpath} or @var{newpath} is a directory that is in use by some
30924 An attempt was made to make a directory a subdirectory
30928 A component used as a directory in @var{oldpath} or new
30929 path is not a directory. Or @var{oldpath} is a directory
30930 and @var{newpath} exists but is not a directory.
30933 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
30936 No access to the file or the path of the file.
30940 @var{oldpath} or @var{newpath} was too long.
30943 A directory component in @var{oldpath} or @var{newpath} does not exist.
30946 The file is on a read-only filesystem.
30949 The device containing the file has no room for the new
30953 The call was interrupted by the user.
30959 @unnumberedsubsubsec unlink
30960 @cindex unlink, file-i/o system call
30965 int unlink(const char *pathname);
30969 @samp{Funlink,@var{pathnameptr}/@var{len}}
30971 @item Return value:
30972 On success, zero is returned. On error, -1 is returned.
30978 No access to the file or the path of the file.
30981 The system does not allow unlinking of directories.
30984 The file @var{pathname} cannot be unlinked because it's
30985 being used by another process.
30988 @var{pathnameptr} is an invalid pointer value.
30991 @var{pathname} was too long.
30994 A directory component in @var{pathname} does not exist.
30997 A component of the path is not a directory.
31000 The file is on a read-only filesystem.
31003 The call was interrupted by the user.
31009 @unnumberedsubsubsec stat/fstat
31010 @cindex fstat, file-i/o system call
31011 @cindex stat, file-i/o system call
31016 int stat(const char *pathname, struct stat *buf);
31017 int fstat(int fd, struct stat *buf);
31021 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
31022 @samp{Ffstat,@var{fd},@var{bufptr}}
31024 @item Return value:
31025 On success, zero is returned. On error, -1 is returned.
31031 @var{fd} is not a valid open file.
31034 A directory component in @var{pathname} does not exist or the
31035 path is an empty string.
31038 A component of the path is not a directory.
31041 @var{pathnameptr} is an invalid pointer value.
31044 No access to the file or the path of the file.
31047 @var{pathname} was too long.
31050 The call was interrupted by the user.
31056 @unnumberedsubsubsec gettimeofday
31057 @cindex gettimeofday, file-i/o system call
31062 int gettimeofday(struct timeval *tv, void *tz);
31066 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
31068 @item Return value:
31069 On success, 0 is returned, -1 otherwise.
31075 @var{tz} is a non-NULL pointer.
31078 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
31084 @unnumberedsubsubsec isatty
31085 @cindex isatty, file-i/o system call
31090 int isatty(int fd);
31094 @samp{Fisatty,@var{fd}}
31096 @item Return value:
31097 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
31103 The call was interrupted by the user.
31108 Note that the @code{isatty} call is treated as a special case: it returns
31109 1 to the target if the file descriptor is attached
31110 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
31111 would require implementing @code{ioctl} and would be more complex than
31116 @unnumberedsubsubsec system
31117 @cindex system, file-i/o system call
31122 int system(const char *command);
31126 @samp{Fsystem,@var{commandptr}/@var{len}}
31128 @item Return value:
31129 If @var{len} is zero, the return value indicates whether a shell is
31130 available. A zero return value indicates a shell is not available.
31131 For non-zero @var{len}, the value returned is -1 on error and the
31132 return status of the command otherwise. Only the exit status of the
31133 command is returned, which is extracted from the host's @code{system}
31134 return value by calling @code{WEXITSTATUS(retval)}. In case
31135 @file{/bin/sh} could not be executed, 127 is returned.
31141 The call was interrupted by the user.
31146 @value{GDBN} takes over the full task of calling the necessary host calls
31147 to perform the @code{system} call. The return value of @code{system} on
31148 the host is simplified before it's returned
31149 to the target. Any termination signal information from the child process
31150 is discarded, and the return value consists
31151 entirely of the exit status of the called command.
31153 Due to security concerns, the @code{system} call is by default refused
31154 by @value{GDBN}. The user has to allow this call explicitly with the
31155 @code{set remote system-call-allowed 1} command.
31158 @item set remote system-call-allowed
31159 @kindex set remote system-call-allowed
31160 Control whether to allow the @code{system} calls in the File I/O
31161 protocol for the remote target. The default is zero (disabled).
31163 @item show remote system-call-allowed
31164 @kindex show remote system-call-allowed
31165 Show whether the @code{system} calls are allowed in the File I/O
31169 @node Protocol-specific Representation of Datatypes
31170 @subsection Protocol-specific Representation of Datatypes
31171 @cindex protocol-specific representation of datatypes, in file-i/o protocol
31174 * Integral Datatypes::
31176 * Memory Transfer::
31181 @node Integral Datatypes
31182 @unnumberedsubsubsec Integral Datatypes
31183 @cindex integral datatypes, in file-i/o protocol
31185 The integral datatypes used in the system calls are @code{int},
31186 @code{unsigned int}, @code{long}, @code{unsigned long},
31187 @code{mode_t}, and @code{time_t}.
31189 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
31190 implemented as 32 bit values in this protocol.
31192 @code{long} and @code{unsigned long} are implemented as 64 bit types.
31194 @xref{Limits}, for corresponding MIN and MAX values (similar to those
31195 in @file{limits.h}) to allow range checking on host and target.
31197 @code{time_t} datatypes are defined as seconds since the Epoch.
31199 All integral datatypes transferred as part of a memory read or write of a
31200 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
31203 @node Pointer Values
31204 @unnumberedsubsubsec Pointer Values
31205 @cindex pointer values, in file-i/o protocol
31207 Pointers to target data are transmitted as they are. An exception
31208 is made for pointers to buffers for which the length isn't
31209 transmitted as part of the function call, namely strings. Strings
31210 are transmitted as a pointer/length pair, both as hex values, e.g.@:
31217 which is a pointer to data of length 18 bytes at position 0x1aaf.
31218 The length is defined as the full string length in bytes, including
31219 the trailing null byte. For example, the string @code{"hello world"}
31220 at address 0x123456 is transmitted as
31226 @node Memory Transfer
31227 @unnumberedsubsubsec Memory Transfer
31228 @cindex memory transfer, in file-i/o protocol
31230 Structured data which is transferred using a memory read or write (for
31231 example, a @code{struct stat}) is expected to be in a protocol-specific format
31232 with all scalar multibyte datatypes being big endian. Translation to
31233 this representation needs to be done both by the target before the @code{F}
31234 packet is sent, and by @value{GDBN} before
31235 it transfers memory to the target. Transferred pointers to structured
31236 data should point to the already-coerced data at any time.
31240 @unnumberedsubsubsec struct stat
31241 @cindex struct stat, in file-i/o protocol
31243 The buffer of type @code{struct stat} used by the target and @value{GDBN}
31244 is defined as follows:
31248 unsigned int st_dev; /* device */
31249 unsigned int st_ino; /* inode */
31250 mode_t st_mode; /* protection */
31251 unsigned int st_nlink; /* number of hard links */
31252 unsigned int st_uid; /* user ID of owner */
31253 unsigned int st_gid; /* group ID of owner */
31254 unsigned int st_rdev; /* device type (if inode device) */
31255 unsigned long st_size; /* total size, in bytes */
31256 unsigned long st_blksize; /* blocksize for filesystem I/O */
31257 unsigned long st_blocks; /* number of blocks allocated */
31258 time_t st_atime; /* time of last access */
31259 time_t st_mtime; /* time of last modification */
31260 time_t st_ctime; /* time of last change */
31264 The integral datatypes conform to the definitions given in the
31265 appropriate section (see @ref{Integral Datatypes}, for details) so this
31266 structure is of size 64 bytes.
31268 The values of several fields have a restricted meaning and/or
31274 A value of 0 represents a file, 1 the console.
31277 No valid meaning for the target. Transmitted unchanged.
31280 Valid mode bits are described in @ref{Constants}. Any other
31281 bits have currently no meaning for the target.
31286 No valid meaning for the target. Transmitted unchanged.
31291 These values have a host and file system dependent
31292 accuracy. Especially on Windows hosts, the file system may not
31293 support exact timing values.
31296 The target gets a @code{struct stat} of the above representation and is
31297 responsible for coercing it to the target representation before
31300 Note that due to size differences between the host, target, and protocol
31301 representations of @code{struct stat} members, these members could eventually
31302 get truncated on the target.
31304 @node struct timeval
31305 @unnumberedsubsubsec struct timeval
31306 @cindex struct timeval, in file-i/o protocol
31308 The buffer of type @code{struct timeval} used by the File-I/O protocol
31309 is defined as follows:
31313 time_t tv_sec; /* second */
31314 long tv_usec; /* microsecond */
31318 The integral datatypes conform to the definitions given in the
31319 appropriate section (see @ref{Integral Datatypes}, for details) so this
31320 structure is of size 8 bytes.
31323 @subsection Constants
31324 @cindex constants, in file-i/o protocol
31326 The following values are used for the constants inside of the
31327 protocol. @value{GDBN} and target are responsible for translating these
31328 values before and after the call as needed.
31339 @unnumberedsubsubsec Open Flags
31340 @cindex open flags, in file-i/o protocol
31342 All values are given in hexadecimal representation.
31354 @node mode_t Values
31355 @unnumberedsubsubsec mode_t Values
31356 @cindex mode_t values, in file-i/o protocol
31358 All values are given in octal representation.
31375 @unnumberedsubsubsec Errno Values
31376 @cindex errno values, in file-i/o protocol
31378 All values are given in decimal representation.
31403 @code{EUNKNOWN} is used as a fallback error value if a host system returns
31404 any error value not in the list of supported error numbers.
31407 @unnumberedsubsubsec Lseek Flags
31408 @cindex lseek flags, in file-i/o protocol
31417 @unnumberedsubsubsec Limits
31418 @cindex limits, in file-i/o protocol
31420 All values are given in decimal representation.
31423 INT_MIN -2147483648
31425 UINT_MAX 4294967295
31426 LONG_MIN -9223372036854775808
31427 LONG_MAX 9223372036854775807
31428 ULONG_MAX 18446744073709551615
31431 @node File-I/O Examples
31432 @subsection File-I/O Examples
31433 @cindex file-i/o examples
31435 Example sequence of a write call, file descriptor 3, buffer is at target
31436 address 0x1234, 6 bytes should be written:
31439 <- @code{Fwrite,3,1234,6}
31440 @emph{request memory read from target}
31443 @emph{return "6 bytes written"}
31447 Example sequence of a read call, file descriptor 3, buffer is at target
31448 address 0x1234, 6 bytes should be read:
31451 <- @code{Fread,3,1234,6}
31452 @emph{request memory write to target}
31453 -> @code{X1234,6:XXXXXX}
31454 @emph{return "6 bytes read"}
31458 Example sequence of a read call, call fails on the host due to invalid
31459 file descriptor (@code{EBADF}):
31462 <- @code{Fread,3,1234,6}
31466 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
31470 <- @code{Fread,3,1234,6}
31475 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
31479 <- @code{Fread,3,1234,6}
31480 -> @code{X1234,6:XXXXXX}
31484 @node Library List Format
31485 @section Library List Format
31486 @cindex library list format, remote protocol
31488 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
31489 same process as your application to manage libraries. In this case,
31490 @value{GDBN} can use the loader's symbol table and normal memory
31491 operations to maintain a list of shared libraries. On other
31492 platforms, the operating system manages loaded libraries.
31493 @value{GDBN} can not retrieve the list of currently loaded libraries
31494 through memory operations, so it uses the @samp{qXfer:libraries:read}
31495 packet (@pxref{qXfer library list read}) instead. The remote stub
31496 queries the target's operating system and reports which libraries
31499 The @samp{qXfer:libraries:read} packet returns an XML document which
31500 lists loaded libraries and their offsets. Each library has an
31501 associated name and one or more segment or section base addresses,
31502 which report where the library was loaded in memory.
31504 For the common case of libraries that are fully linked binaries, the
31505 library should have a list of segments. If the target supports
31506 dynamic linking of a relocatable object file, its library XML element
31507 should instead include a list of allocated sections. The segment or
31508 section bases are start addresses, not relocation offsets; they do not
31509 depend on the library's link-time base addresses.
31511 @value{GDBN} must be linked with the Expat library to support XML
31512 library lists. @xref{Expat}.
31514 A simple memory map, with one loaded library relocated by a single
31515 offset, looks like this:
31519 <library name="/lib/libc.so.6">
31520 <segment address="0x10000000"/>
31525 Another simple memory map, with one loaded library with three
31526 allocated sections (.text, .data, .bss), looks like this:
31530 <library name="sharedlib.o">
31531 <section address="0x10000000"/>
31532 <section address="0x20000000"/>
31533 <section address="0x30000000"/>
31538 The format of a library list is described by this DTD:
31541 <!-- library-list: Root element with versioning -->
31542 <!ELEMENT library-list (library)*>
31543 <!ATTLIST library-list version CDATA #FIXED "1.0">
31544 <!ELEMENT library (segment*, section*)>
31545 <!ATTLIST library name CDATA #REQUIRED>
31546 <!ELEMENT segment EMPTY>
31547 <!ATTLIST segment address CDATA #REQUIRED>
31548 <!ELEMENT section EMPTY>
31549 <!ATTLIST section address CDATA #REQUIRED>
31552 In addition, segments and section descriptors cannot be mixed within a
31553 single library element, and you must supply at least one segment or
31554 section for each library.
31556 @node Memory Map Format
31557 @section Memory Map Format
31558 @cindex memory map format
31560 To be able to write into flash memory, @value{GDBN} needs to obtain a
31561 memory map from the target. This section describes the format of the
31564 The memory map is obtained using the @samp{qXfer:memory-map:read}
31565 (@pxref{qXfer memory map read}) packet and is an XML document that
31566 lists memory regions.
31568 @value{GDBN} must be linked with the Expat library to support XML
31569 memory maps. @xref{Expat}.
31571 The top-level structure of the document is shown below:
31574 <?xml version="1.0"?>
31575 <!DOCTYPE memory-map
31576 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
31577 "http://sourceware.org/gdb/gdb-memory-map.dtd">
31583 Each region can be either:
31588 A region of RAM starting at @var{addr} and extending for @var{length}
31592 <memory type="ram" start="@var{addr}" length="@var{length}"/>
31597 A region of read-only memory:
31600 <memory type="rom" start="@var{addr}" length="@var{length}"/>
31605 A region of flash memory, with erasure blocks @var{blocksize}
31609 <memory type="flash" start="@var{addr}" length="@var{length}">
31610 <property name="blocksize">@var{blocksize}</property>
31616 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
31617 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
31618 packets to write to addresses in such ranges.
31620 The formal DTD for memory map format is given below:
31623 <!-- ................................................... -->
31624 <!-- Memory Map XML DTD ................................ -->
31625 <!-- File: memory-map.dtd .............................. -->
31626 <!-- .................................... .............. -->
31627 <!-- memory-map.dtd -->
31628 <!-- memory-map: Root element with versioning -->
31629 <!ELEMENT memory-map (memory | property)>
31630 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
31631 <!ELEMENT memory (property)>
31632 <!-- memory: Specifies a memory region,
31633 and its type, or device. -->
31634 <!ATTLIST memory type CDATA #REQUIRED
31635 start CDATA #REQUIRED
31636 length CDATA #REQUIRED
31637 device CDATA #IMPLIED>
31638 <!-- property: Generic attribute tag -->
31639 <!ELEMENT property (#PCDATA | property)*>
31640 <!ATTLIST property name CDATA #REQUIRED>
31643 @include agentexpr.texi
31645 @node Target Descriptions
31646 @appendix Target Descriptions
31647 @cindex target descriptions
31649 @strong{Warning:} target descriptions are still under active development,
31650 and the contents and format may change between @value{GDBN} releases.
31651 The format is expected to stabilize in the future.
31653 One of the challenges of using @value{GDBN} to debug embedded systems
31654 is that there are so many minor variants of each processor
31655 architecture in use. It is common practice for vendors to start with
31656 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
31657 and then make changes to adapt it to a particular market niche. Some
31658 architectures have hundreds of variants, available from dozens of
31659 vendors. This leads to a number of problems:
31663 With so many different customized processors, it is difficult for
31664 the @value{GDBN} maintainers to keep up with the changes.
31666 Since individual variants may have short lifetimes or limited
31667 audiences, it may not be worthwhile to carry information about every
31668 variant in the @value{GDBN} source tree.
31670 When @value{GDBN} does support the architecture of the embedded system
31671 at hand, the task of finding the correct architecture name to give the
31672 @command{set architecture} command can be error-prone.
31675 To address these problems, the @value{GDBN} remote protocol allows a
31676 target system to not only identify itself to @value{GDBN}, but to
31677 actually describe its own features. This lets @value{GDBN} support
31678 processor variants it has never seen before --- to the extent that the
31679 descriptions are accurate, and that @value{GDBN} understands them.
31681 @value{GDBN} must be linked with the Expat library to support XML
31682 target descriptions. @xref{Expat}.
31685 * Retrieving Descriptions:: How descriptions are fetched from a target.
31686 * Target Description Format:: The contents of a target description.
31687 * Predefined Target Types:: Standard types available for target
31689 * Standard Target Features:: Features @value{GDBN} knows about.
31692 @node Retrieving Descriptions
31693 @section Retrieving Descriptions
31695 Target descriptions can be read from the target automatically, or
31696 specified by the user manually. The default behavior is to read the
31697 description from the target. @value{GDBN} retrieves it via the remote
31698 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
31699 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
31700 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
31701 XML document, of the form described in @ref{Target Description
31704 Alternatively, you can specify a file to read for the target description.
31705 If a file is set, the target will not be queried. The commands to
31706 specify a file are:
31709 @cindex set tdesc filename
31710 @item set tdesc filename @var{path}
31711 Read the target description from @var{path}.
31713 @cindex unset tdesc filename
31714 @item unset tdesc filename
31715 Do not read the XML target description from a file. @value{GDBN}
31716 will use the description supplied by the current target.
31718 @cindex show tdesc filename
31719 @item show tdesc filename
31720 Show the filename to read for a target description, if any.
31724 @node Target Description Format
31725 @section Target Description Format
31726 @cindex target descriptions, XML format
31728 A target description annex is an @uref{http://www.w3.org/XML/, XML}
31729 document which complies with the Document Type Definition provided in
31730 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
31731 means you can use generally available tools like @command{xmllint} to
31732 check that your feature descriptions are well-formed and valid.
31733 However, to help people unfamiliar with XML write descriptions for
31734 their targets, we also describe the grammar here.
31736 Target descriptions can identify the architecture of the remote target
31737 and (for some architectures) provide information about custom register
31738 sets. They can also identify the OS ABI of the remote target.
31739 @value{GDBN} can use this information to autoconfigure for your
31740 target, or to warn you if you connect to an unsupported target.
31742 Here is a simple target description:
31745 <target version="1.0">
31746 <architecture>i386:x86-64</architecture>
31751 This minimal description only says that the target uses
31752 the x86-64 architecture.
31754 A target description has the following overall form, with [ ] marking
31755 optional elements and @dots{} marking repeatable elements. The elements
31756 are explained further below.
31759 <?xml version="1.0"?>
31760 <!DOCTYPE target SYSTEM "gdb-target.dtd">
31761 <target version="1.0">
31762 @r{[}@var{architecture}@r{]}
31763 @r{[}@var{osabi}@r{]}
31764 @r{[}@var{compatible}@r{]}
31765 @r{[}@var{feature}@dots{}@r{]}
31770 The description is generally insensitive to whitespace and line
31771 breaks, under the usual common-sense rules. The XML version
31772 declaration and document type declaration can generally be omitted
31773 (@value{GDBN} does not require them), but specifying them may be
31774 useful for XML validation tools. The @samp{version} attribute for
31775 @samp{<target>} may also be omitted, but we recommend
31776 including it; if future versions of @value{GDBN} use an incompatible
31777 revision of @file{gdb-target.dtd}, they will detect and report
31778 the version mismatch.
31780 @subsection Inclusion
31781 @cindex target descriptions, inclusion
31784 @cindex <xi:include>
31787 It can sometimes be valuable to split a target description up into
31788 several different annexes, either for organizational purposes, or to
31789 share files between different possible target descriptions. You can
31790 divide a description into multiple files by replacing any element of
31791 the target description with an inclusion directive of the form:
31794 <xi:include href="@var{document}"/>
31798 When @value{GDBN} encounters an element of this form, it will retrieve
31799 the named XML @var{document}, and replace the inclusion directive with
31800 the contents of that document. If the current description was read
31801 using @samp{qXfer}, then so will be the included document;
31802 @var{document} will be interpreted as the name of an annex. If the
31803 current description was read from a file, @value{GDBN} will look for
31804 @var{document} as a file in the same directory where it found the
31805 original description.
31807 @subsection Architecture
31808 @cindex <architecture>
31810 An @samp{<architecture>} element has this form:
31813 <architecture>@var{arch}</architecture>
31816 @var{arch} is one of the architectures from the set accepted by
31817 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
31820 @cindex @code{<osabi>}
31822 This optional field was introduced in @value{GDBN} version 7.0.
31823 Previous versions of @value{GDBN} ignore it.
31825 An @samp{<osabi>} element has this form:
31828 <osabi>@var{abi-name}</osabi>
31831 @var{abi-name} is an OS ABI name from the same selection accepted by
31832 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
31834 @subsection Compatible Architecture
31835 @cindex @code{<compatible>}
31837 This optional field was introduced in @value{GDBN} version 7.0.
31838 Previous versions of @value{GDBN} ignore it.
31840 A @samp{<compatible>} element has this form:
31843 <compatible>@var{arch}</compatible>
31846 @var{arch} is one of the architectures from the set accepted by
31847 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
31849 A @samp{<compatible>} element is used to specify that the target
31850 is able to run binaries in some other than the main target architecture
31851 given by the @samp{<architecture>} element. For example, on the
31852 Cell Broadband Engine, the main architecture is @code{powerpc:common}
31853 or @code{powerpc:common64}, but the system is able to run binaries
31854 in the @code{spu} architecture as well. The way to describe this
31855 capability with @samp{<compatible>} is as follows:
31858 <architecture>powerpc:common</architecture>
31859 <compatible>spu</compatible>
31862 @subsection Features
31865 Each @samp{<feature>} describes some logical portion of the target
31866 system. Features are currently used to describe available CPU
31867 registers and the types of their contents. A @samp{<feature>} element
31871 <feature name="@var{name}">
31872 @r{[}@var{type}@dots{}@r{]}
31878 Each feature's name should be unique within the description. The name
31879 of a feature does not matter unless @value{GDBN} has some special
31880 knowledge of the contents of that feature; if it does, the feature
31881 should have its standard name. @xref{Standard Target Features}.
31885 Any register's value is a collection of bits which @value{GDBN} must
31886 interpret. The default interpretation is a two's complement integer,
31887 but other types can be requested by name in the register description.
31888 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
31889 Target Types}), and the description can define additional composite types.
31891 Each type element must have an @samp{id} attribute, which gives
31892 a unique (within the containing @samp{<feature>}) name to the type.
31893 Types must be defined before they are used.
31896 Some targets offer vector registers, which can be treated as arrays
31897 of scalar elements. These types are written as @samp{<vector>} elements,
31898 specifying the array element type, @var{type}, and the number of elements,
31902 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
31906 If a register's value is usefully viewed in multiple ways, define it
31907 with a union type containing the useful representations. The
31908 @samp{<union>} element contains one or more @samp{<field>} elements,
31909 each of which has a @var{name} and a @var{type}:
31912 <union id="@var{id}">
31913 <field name="@var{name}" type="@var{type}"/>
31918 @subsection Registers
31921 Each register is represented as an element with this form:
31924 <reg name="@var{name}"
31925 bitsize="@var{size}"
31926 @r{[}regnum="@var{num}"@r{]}
31927 @r{[}save-restore="@var{save-restore}"@r{]}
31928 @r{[}type="@var{type}"@r{]}
31929 @r{[}group="@var{group}"@r{]}/>
31933 The components are as follows:
31938 The register's name; it must be unique within the target description.
31941 The register's size, in bits.
31944 The register's number. If omitted, a register's number is one greater
31945 than that of the previous register (either in the current feature or in
31946 a preceeding feature); the first register in the target description
31947 defaults to zero. This register number is used to read or write
31948 the register; e.g.@: it is used in the remote @code{p} and @code{P}
31949 packets, and registers appear in the @code{g} and @code{G} packets
31950 in order of increasing register number.
31953 Whether the register should be preserved across inferior function
31954 calls; this must be either @code{yes} or @code{no}. The default is
31955 @code{yes}, which is appropriate for most registers except for
31956 some system control registers; this is not related to the target's
31960 The type of the register. @var{type} may be a predefined type, a type
31961 defined in the current feature, or one of the special types @code{int}
31962 and @code{float}. @code{int} is an integer type of the correct size
31963 for @var{bitsize}, and @code{float} is a floating point type (in the
31964 architecture's normal floating point format) of the correct size for
31965 @var{bitsize}. The default is @code{int}.
31968 The register group to which this register belongs. @var{group} must
31969 be either @code{general}, @code{float}, or @code{vector}. If no
31970 @var{group} is specified, @value{GDBN} will not display the register
31971 in @code{info registers}.
31975 @node Predefined Target Types
31976 @section Predefined Target Types
31977 @cindex target descriptions, predefined types
31979 Type definitions in the self-description can build up composite types
31980 from basic building blocks, but can not define fundamental types. Instead,
31981 standard identifiers are provided by @value{GDBN} for the fundamental
31982 types. The currently supported types are:
31991 Signed integer types holding the specified number of bits.
31998 Unsigned integer types holding the specified number of bits.
32002 Pointers to unspecified code and data. The program counter and
32003 any dedicated return address register may be marked as code
32004 pointers; printing a code pointer converts it into a symbolic
32005 address. The stack pointer and any dedicated address registers
32006 may be marked as data pointers.
32009 Single precision IEEE floating point.
32012 Double precision IEEE floating point.
32015 The 12-byte extended precision format used by ARM FPA registers.
32019 @node Standard Target Features
32020 @section Standard Target Features
32021 @cindex target descriptions, standard features
32023 A target description must contain either no registers or all the
32024 target's registers. If the description contains no registers, then
32025 @value{GDBN} will assume a default register layout, selected based on
32026 the architecture. If the description contains any registers, the
32027 default layout will not be used; the standard registers must be
32028 described in the target description, in such a way that @value{GDBN}
32029 can recognize them.
32031 This is accomplished by giving specific names to feature elements
32032 which contain standard registers. @value{GDBN} will look for features
32033 with those names and verify that they contain the expected registers;
32034 if any known feature is missing required registers, or if any required
32035 feature is missing, @value{GDBN} will reject the target
32036 description. You can add additional registers to any of the
32037 standard features --- @value{GDBN} will display them just as if
32038 they were added to an unrecognized feature.
32040 This section lists the known features and their expected contents.
32041 Sample XML documents for these features are included in the
32042 @value{GDBN} source tree, in the directory @file{gdb/features}.
32044 Names recognized by @value{GDBN} should include the name of the
32045 company or organization which selected the name, and the overall
32046 architecture to which the feature applies; so e.g.@: the feature
32047 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
32049 The names of registers are not case sensitive for the purpose
32050 of recognizing standard features, but @value{GDBN} will only display
32051 registers using the capitalization used in the description.
32057 * PowerPC Features::
32062 @subsection ARM Features
32063 @cindex target descriptions, ARM features
32065 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
32066 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
32067 @samp{lr}, @samp{pc}, and @samp{cpsr}.
32069 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
32070 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
32072 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
32073 it should contain at least registers @samp{wR0} through @samp{wR15} and
32074 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
32075 @samp{wCSSF}, and @samp{wCASF} registers are optional.
32077 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
32078 should contain at least registers @samp{d0} through @samp{d15}. If
32079 they are present, @samp{d16} through @samp{d31} should also be included.
32080 @value{GDBN} will synthesize the single-precision registers from
32081 halves of the double-precision registers.
32083 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
32084 need to contain registers; it instructs @value{GDBN} to display the
32085 VFP double-precision registers as vectors and to synthesize the
32086 quad-precision registers from pairs of double-precision registers.
32087 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
32088 be present and include 32 double-precision registers.
32090 @node MIPS Features
32091 @subsection MIPS Features
32092 @cindex target descriptions, MIPS features
32094 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
32095 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
32096 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
32099 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
32100 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
32101 registers. They may be 32-bit or 64-bit depending on the target.
32103 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
32104 it may be optional in a future version of @value{GDBN}. It should
32105 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
32106 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
32108 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
32109 contain a single register, @samp{restart}, which is used by the
32110 Linux kernel to control restartable syscalls.
32112 @node M68K Features
32113 @subsection M68K Features
32114 @cindex target descriptions, M68K features
32117 @item @samp{org.gnu.gdb.m68k.core}
32118 @itemx @samp{org.gnu.gdb.coldfire.core}
32119 @itemx @samp{org.gnu.gdb.fido.core}
32120 One of those features must be always present.
32121 The feature that is present determines which flavor of m68k is
32122 used. The feature that is present should contain registers
32123 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
32124 @samp{sp}, @samp{ps} and @samp{pc}.
32126 @item @samp{org.gnu.gdb.coldfire.fp}
32127 This feature is optional. If present, it should contain registers
32128 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
32132 @node PowerPC Features
32133 @subsection PowerPC Features
32134 @cindex target descriptions, PowerPC features
32136 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
32137 targets. It should contain registers @samp{r0} through @samp{r31},
32138 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
32139 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
32141 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
32142 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
32144 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
32145 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
32148 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
32149 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
32150 will combine these registers with the floating point registers
32151 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
32152 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
32153 through @samp{vs63}, the set of vector registers for POWER7.
32155 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
32156 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
32157 @samp{spefscr}. SPE targets should provide 32-bit registers in
32158 @samp{org.gnu.gdb.power.core} and provide the upper halves in
32159 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
32160 these to present registers @samp{ev0} through @samp{ev31} to the
32163 @node Operating System Information
32164 @appendix Operating System Information
32165 @cindex operating system information
32171 Users of @value{GDBN} often wish to obtain information about the state of
32172 the operating system running on the target---for example the list of
32173 processes, or the list of open files. This section describes the
32174 mechanism that makes it possible. This mechanism is similar to the
32175 target features mechanism (@pxref{Target Descriptions}), but focuses
32176 on a different aspect of target.
32178 Operating system information is retrived from the target via the
32179 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
32180 read}). The object name in the request should be @samp{osdata}, and
32181 the @var{annex} identifies the data to be fetched.
32184 @appendixsection Process list
32185 @cindex operating system information, process list
32187 When requesting the process list, the @var{annex} field in the
32188 @samp{qXfer} request should be @samp{processes}. The returned data is
32189 an XML document. The formal syntax of this document is defined in
32190 @file{gdb/features/osdata.dtd}.
32192 An example document is:
32195 <?xml version="1.0"?>
32196 <!DOCTYPE target SYSTEM "osdata.dtd">
32197 <osdata type="processes">
32199 <column name="pid">1</column>
32200 <column name="user">root</column>
32201 <column name="command">/sbin/init</column>
32206 Each item should include a column whose name is @samp{pid}. The value
32207 of that column should identify the process on the target. The
32208 @samp{user} and @samp{command} columns are optional, and will be
32209 displayed by @value{GDBN}. Target may provide additional columns,
32210 which @value{GDBN} currently ignores.
32224 % I think something like @colophon should be in texinfo. In the
32226 \long\def\colophon{\hbox to0pt{}\vfill
32227 \centerline{The body of this manual is set in}
32228 \centerline{\fontname\tenrm,}
32229 \centerline{with headings in {\bf\fontname\tenbf}}
32230 \centerline{and examples in {\tt\fontname\tentt}.}
32231 \centerline{{\it\fontname\tenit\/},}
32232 \centerline{{\bf\fontname\tenbf}, and}
32233 \centerline{{\sl\fontname\tensl\/}}
32234 \centerline{are used for emphasis.}\vfill}
32236 % Blame: doc@cygnus.com, 1991.