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.
163 * GDB Bugs:: Reporting bugs in @value{GDBN}
165 * Command Line Editing:: Command Line Editing
166 * Using History Interactively:: Using History Interactively
167 * Formatting Documentation:: How to format and print @value{GDBN} documentation
168 * Installing GDB:: Installing GDB
169 * Maintenance Commands:: Maintenance Commands
170 * Remote Protocol:: GDB Remote Serial Protocol
171 * Agent Expressions:: The GDB Agent Expression Mechanism
172 * Target Descriptions:: How targets can describe themselves to
174 * Operating System Information:: Getting additional information from
176 * Copying:: GNU General Public License says
177 how you can copy and share GDB
178 * GNU Free Documentation License:: The license for this documentation
187 @unnumbered Summary of @value{GDBN}
189 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
190 going on ``inside'' another program while it executes---or what another
191 program was doing at the moment it crashed.
193 @value{GDBN} can do four main kinds of things (plus other things in support of
194 these) to help you catch bugs in the act:
198 Start your program, specifying anything that might affect its behavior.
201 Make your program stop on specified conditions.
204 Examine what has happened, when your program has stopped.
207 Change things in your program, so you can experiment with correcting the
208 effects of one bug and go on to learn about another.
211 You can use @value{GDBN} to debug programs written in C and C@t{++}.
212 For more information, see @ref{Supported Languages,,Supported Languages}.
213 For more information, see @ref{C,,C and C++}.
216 Support for Modula-2 is partial. For information on Modula-2, see
217 @ref{Modula-2,,Modula-2}.
220 Debugging Pascal programs which use sets, subranges, file variables, or
221 nested functions does not currently work. @value{GDBN} does not support
222 entering expressions, printing values, or similar features using Pascal
226 @value{GDBN} can be used to debug programs written in Fortran, although
227 it may be necessary to refer to some variables with a trailing
230 @value{GDBN} can be used to debug programs written in Objective-C,
231 using either the Apple/NeXT or the GNU Objective-C runtime.
234 * Free Software:: Freely redistributable software
235 * Contributors:: Contributors to GDB
239 @unnumberedsec Free Software
241 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
242 General Public License
243 (GPL). The GPL gives you the freedom to copy or adapt a licensed
244 program---but every person getting a copy also gets with it the
245 freedom to modify that copy (which means that they must get access to
246 the source code), and the freedom to distribute further copies.
247 Typical software companies use copyrights to limit your freedoms; the
248 Free Software Foundation uses the GPL to preserve these freedoms.
250 Fundamentally, the General Public License is a license which says that
251 you have these freedoms and that you cannot take these freedoms away
254 @unnumberedsec Free Software Needs Free Documentation
256 The biggest deficiency in the free software community today is not in
257 the software---it is the lack of good free documentation that we can
258 include with the free software. Many of our most important
259 programs do not come with free reference manuals and free introductory
260 texts. Documentation is an essential part of any software package;
261 when an important free software package does not come with a free
262 manual and a free tutorial, that is a major gap. We have many such
265 Consider Perl, for instance. The tutorial manuals that people
266 normally use are non-free. How did this come about? Because the
267 authors of those manuals published them with restrictive terms---no
268 copying, no modification, source files not available---which exclude
269 them from the free software world.
271 That wasn't the first time this sort of thing happened, and it was far
272 from the last. Many times we have heard a GNU user eagerly describe a
273 manual that he is writing, his intended contribution to the community,
274 only to learn that he had ruined everything by signing a publication
275 contract to make it non-free.
277 Free documentation, like free software, is a matter of freedom, not
278 price. The problem with the non-free manual is not that publishers
279 charge a price for printed copies---that in itself is fine. (The Free
280 Software Foundation sells printed copies of manuals, too.) The
281 problem is the restrictions on the use of the manual. Free manuals
282 are available in source code form, and give you permission to copy and
283 modify. Non-free manuals do not allow this.
285 The criteria of freedom for a free manual are roughly the same as for
286 free software. Redistribution (including the normal kinds of
287 commercial redistribution) must be permitted, so that the manual can
288 accompany every copy of the program, both on-line and on paper.
290 Permission for modification of the technical content is crucial too.
291 When people modify the software, adding or changing features, if they
292 are conscientious they will change the manual too---so they can
293 provide accurate and clear documentation for the modified program. A
294 manual that leaves you no choice but to write a new manual to document
295 a changed version of the program is not really available to our
298 Some kinds of limits on the way modification is handled are
299 acceptable. For example, requirements to preserve the original
300 author's copyright notice, the distribution terms, or the list of
301 authors, are ok. It is also no problem to require modified versions
302 to include notice that they were modified. Even entire sections that
303 may not be deleted or changed are acceptable, as long as they deal
304 with nontechnical topics (like this one). These kinds of restrictions
305 are acceptable because they don't obstruct the community's normal use
308 However, it must be possible to modify all the @emph{technical}
309 content of the manual, and then distribute the result in all the usual
310 media, through all the usual channels. Otherwise, the restrictions
311 obstruct the use of the manual, it is not free, and we need another
312 manual to replace it.
314 Please spread the word about this issue. Our community continues to
315 lose manuals to proprietary publishing. If we spread the word that
316 free software needs free reference manuals and free tutorials, perhaps
317 the next person who wants to contribute by writing documentation will
318 realize, before it is too late, that only free manuals contribute to
319 the free software community.
321 If you are writing documentation, please insist on publishing it under
322 the GNU Free Documentation License or another free documentation
323 license. Remember that this decision requires your approval---you
324 don't have to let the publisher decide. Some commercial publishers
325 will use a free license if you insist, but they will not propose the
326 option; it is up to you to raise the issue and say firmly that this is
327 what you want. If the publisher you are dealing with refuses, please
328 try other publishers. If you're not sure whether a proposed license
329 is free, write to @email{licensing@@gnu.org}.
331 You can encourage commercial publishers to sell more free, copylefted
332 manuals and tutorials by buying them, and particularly by buying
333 copies from the publishers that paid for their writing or for major
334 improvements. Meanwhile, try to avoid buying non-free documentation
335 at all. Check the distribution terms of a manual before you buy it,
336 and insist that whoever seeks your business must respect your freedom.
337 Check the history of the book, and try to reward the publishers that
338 have paid or pay the authors to work on it.
340 The Free Software Foundation maintains a list of free documentation
341 published by other publishers, at
342 @url{http://www.fsf.org/doc/other-free-books.html}.
345 @unnumberedsec Contributors to @value{GDBN}
347 Richard Stallman was the original author of @value{GDBN}, and of many
348 other @sc{gnu} programs. Many others have contributed to its
349 development. This section attempts to credit major contributors. One
350 of the virtues of free software is that everyone is free to contribute
351 to it; with regret, we cannot actually acknowledge everyone here. The
352 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
353 blow-by-blow account.
355 Changes much prior to version 2.0 are lost in the mists of time.
358 @emph{Plea:} Additions to this section are particularly welcome. If you
359 or your friends (or enemies, to be evenhanded) have been unfairly
360 omitted from this list, we would like to add your names!
363 So that they may not regard their many labors as thankless, we
364 particularly thank those who shepherded @value{GDBN} through major
366 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
367 Jim Blandy (release 4.18);
368 Jason Molenda (release 4.17);
369 Stan Shebs (release 4.14);
370 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
371 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
372 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
373 Jim Kingdon (releases 3.5, 3.4, and 3.3);
374 and Randy Smith (releases 3.2, 3.1, and 3.0).
376 Richard Stallman, assisted at various times by Peter TerMaat, Chris
377 Hanson, and Richard Mlynarik, handled releases through 2.8.
379 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
380 in @value{GDBN}, with significant additional contributions from Per
381 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
382 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
383 much general update work leading to release 3.0).
385 @value{GDBN} uses the BFD subroutine library to examine multiple
386 object-file formats; BFD was a joint project of David V.
387 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
389 David Johnson wrote the original COFF support; Pace Willison did
390 the original support for encapsulated COFF.
392 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
394 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
395 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
397 Jean-Daniel Fekete contributed Sun 386i support.
398 Chris Hanson improved the HP9000 support.
399 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
400 David Johnson contributed Encore Umax support.
401 Jyrki Kuoppala contributed Altos 3068 support.
402 Jeff Law contributed HP PA and SOM support.
403 Keith Packard contributed NS32K support.
404 Doug Rabson contributed Acorn Risc Machine support.
405 Bob Rusk contributed Harris Nighthawk CX-UX support.
406 Chris Smith contributed Convex support (and Fortran debugging).
407 Jonathan Stone contributed Pyramid support.
408 Michael Tiemann contributed SPARC support.
409 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
410 Pace Willison contributed Intel 386 support.
411 Jay Vosburgh contributed Symmetry support.
412 Marko Mlinar contributed OpenRISC 1000 support.
414 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
416 Rich Schaefer and Peter Schauer helped with support of SunOS shared
419 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
420 about several machine instruction sets.
422 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
423 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
424 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
425 and RDI targets, respectively.
427 Brian Fox is the author of the readline libraries providing
428 command-line editing and command history.
430 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
431 Modula-2 support, and contributed the Languages chapter of this manual.
433 Fred Fish wrote most of the support for Unix System Vr4.
434 He also enhanced the command-completion support to cover C@t{++} overloaded
437 Hitachi America (now Renesas America), Ltd. sponsored the support for
438 H8/300, H8/500, and Super-H processors.
440 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
442 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
445 Toshiba sponsored the support for the TX39 Mips processor.
447 Matsushita sponsored the support for the MN10200 and MN10300 processors.
449 Fujitsu sponsored the support for SPARClite and FR30 processors.
451 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
454 Michael Snyder added support for tracepoints.
456 Stu Grossman wrote gdbserver.
458 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
459 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
461 The following people at the Hewlett-Packard Company contributed
462 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
463 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
464 compiler, and the Text User Interface (nee Terminal User Interface):
465 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
466 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
467 provided HP-specific information in this manual.
469 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
470 Robert Hoehne made significant contributions to the DJGPP port.
472 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
473 development since 1991. Cygnus engineers who have worked on @value{GDBN}
474 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
475 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
476 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
477 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
478 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
479 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
480 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
481 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
482 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
483 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
484 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
485 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
486 Zuhn have made contributions both large and small.
488 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
489 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
491 Jim Blandy added support for preprocessor macros, while working for Red
494 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
495 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
496 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
497 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
498 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
499 with the migration of old architectures to this new framework.
501 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
502 unwinder framework, this consisting of a fresh new design featuring
503 frame IDs, independent frame sniffers, and the sentinel frame. Mark
504 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
505 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
506 trad unwinders. The architecture-specific changes, each involving a
507 complete rewrite of the architecture's frame code, were carried out by
508 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
509 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
510 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
511 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
514 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
515 Tensilica, Inc.@: contributed support for Xtensa processors. Others
516 who have worked on the Xtensa port of @value{GDBN} in the past include
517 Steve Tjiang, John Newlin, and Scott Foehner.
520 @chapter A Sample @value{GDBN} Session
522 You can use this manual at your leisure to read all about @value{GDBN}.
523 However, a handful of commands are enough to get started using the
524 debugger. This chapter illustrates those commands.
527 In this sample session, we emphasize user input like this: @b{input},
528 to make it easier to pick out from the surrounding output.
531 @c FIXME: this example may not be appropriate for some configs, where
532 @c FIXME...primary interest is in remote use.
534 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
535 processor) exhibits the following bug: sometimes, when we change its
536 quote strings from the default, the commands used to capture one macro
537 definition within another stop working. In the following short @code{m4}
538 session, we define a macro @code{foo} which expands to @code{0000}; we
539 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
540 same thing. However, when we change the open quote string to
541 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
542 procedure fails to define a new synonym @code{baz}:
551 @b{define(bar,defn(`foo'))}
555 @b{changequote(<QUOTE>,<UNQUOTE>)}
557 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
560 m4: End of input: 0: fatal error: EOF in string
564 Let us use @value{GDBN} to try to see what is going on.
567 $ @b{@value{GDBP} m4}
568 @c FIXME: this falsifies the exact text played out, to permit smallbook
569 @c FIXME... format to come out better.
570 @value{GDBN} is free software and you are welcome to distribute copies
571 of it under certain conditions; type "show copying" to see
573 There is absolutely no warranty for @value{GDBN}; type "show warranty"
576 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
581 @value{GDBN} reads only enough symbol data to know where to find the
582 rest when needed; as a result, the first prompt comes up very quickly.
583 We now tell @value{GDBN} to use a narrower display width than usual, so
584 that examples fit in this manual.
587 (@value{GDBP}) @b{set width 70}
591 We need to see how the @code{m4} built-in @code{changequote} works.
592 Having looked at the source, we know the relevant subroutine is
593 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
594 @code{break} command.
597 (@value{GDBP}) @b{break m4_changequote}
598 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
602 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
603 control; as long as control does not reach the @code{m4_changequote}
604 subroutine, the program runs as usual:
607 (@value{GDBP}) @b{run}
608 Starting program: /work/Editorial/gdb/gnu/m4/m4
616 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
617 suspends execution of @code{m4}, displaying information about the
618 context where it stops.
621 @b{changequote(<QUOTE>,<UNQUOTE>)}
623 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
625 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
629 Now we use the command @code{n} (@code{next}) to advance execution to
630 the next line of the current function.
634 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
639 @code{set_quotes} looks like a promising subroutine. We can go into it
640 by using the command @code{s} (@code{step}) instead of @code{next}.
641 @code{step} goes to the next line to be executed in @emph{any}
642 subroutine, so it steps into @code{set_quotes}.
646 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
648 530 if (lquote != def_lquote)
652 The display that shows the subroutine where @code{m4} is now
653 suspended (and its arguments) is called a stack frame display. It
654 shows a summary of the stack. We can use the @code{backtrace}
655 command (which can also be spelled @code{bt}), to see where we are
656 in the stack as a whole: the @code{backtrace} command displays a
657 stack frame for each active subroutine.
660 (@value{GDBP}) @b{bt}
661 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
663 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
665 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
666 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
668 #4 0x79dc in expand_input () at macro.c:40
669 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
673 We step through a few more lines to see what happens. The first two
674 times, we can use @samp{s}; the next two times we use @code{n} to avoid
675 falling into the @code{xstrdup} subroutine.
679 0x3b5c 532 if (rquote != def_rquote)
681 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
682 def_lquote : xstrdup(lq);
684 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
687 538 len_lquote = strlen(rquote);
691 The last line displayed looks a little odd; we can examine the variables
692 @code{lquote} and @code{rquote} to see if they are in fact the new left
693 and right quotes we specified. We use the command @code{p}
694 (@code{print}) to see their values.
697 (@value{GDBP}) @b{p lquote}
698 $1 = 0x35d40 "<QUOTE>"
699 (@value{GDBP}) @b{p rquote}
700 $2 = 0x35d50 "<UNQUOTE>"
704 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
705 To look at some context, we can display ten lines of source
706 surrounding the current line with the @code{l} (@code{list}) command.
712 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
714 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
717 538 len_lquote = strlen(rquote);
718 539 len_rquote = strlen(lquote);
725 Let us step past the two lines that set @code{len_lquote} and
726 @code{len_rquote}, and then examine the values of those variables.
730 539 len_rquote = strlen(lquote);
733 (@value{GDBP}) @b{p len_lquote}
735 (@value{GDBP}) @b{p len_rquote}
740 That certainly looks wrong, assuming @code{len_lquote} and
741 @code{len_rquote} are meant to be the lengths of @code{lquote} and
742 @code{rquote} respectively. We can set them to better values using
743 the @code{p} command, since it can print the value of
744 any expression---and that expression can include subroutine calls and
748 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
750 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
755 Is that enough to fix the problem of using the new quotes with the
756 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
757 executing with the @code{c} (@code{continue}) command, and then try the
758 example that caused trouble initially:
764 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
771 Success! The new quotes now work just as well as the default ones. The
772 problem seems to have been just the two typos defining the wrong
773 lengths. We allow @code{m4} exit by giving it an EOF as input:
777 Program exited normally.
781 The message @samp{Program exited normally.} is from @value{GDBN}; it
782 indicates @code{m4} has finished executing. We can end our @value{GDBN}
783 session with the @value{GDBN} @code{quit} command.
786 (@value{GDBP}) @b{quit}
790 @chapter Getting In and Out of @value{GDBN}
792 This chapter discusses how to start @value{GDBN}, and how to get out of it.
796 type @samp{@value{GDBP}} to start @value{GDBN}.
798 type @kbd{quit} or @kbd{Ctrl-d} to exit.
802 * Invoking GDB:: How to start @value{GDBN}
803 * Quitting GDB:: How to quit @value{GDBN}
804 * Shell Commands:: How to use shell commands inside @value{GDBN}
805 * Logging Output:: How to log @value{GDBN}'s output to a file
809 @section Invoking @value{GDBN}
811 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
812 @value{GDBN} reads commands from the terminal until you tell it to exit.
814 You can also run @code{@value{GDBP}} with a variety of arguments and options,
815 to specify more of your debugging environment at the outset.
817 The command-line options described here are designed
818 to cover a variety of situations; in some environments, some of these
819 options may effectively be unavailable.
821 The most usual way to start @value{GDBN} is with one argument,
822 specifying an executable program:
825 @value{GDBP} @var{program}
829 You can also start with both an executable program and a core file
833 @value{GDBP} @var{program} @var{core}
836 You can, instead, specify a process ID as a second argument, if you want
837 to debug a running process:
840 @value{GDBP} @var{program} 1234
844 would attach @value{GDBN} to process @code{1234} (unless you also have a file
845 named @file{1234}; @value{GDBN} does check for a core file first).
847 Taking advantage of the second command-line argument requires a fairly
848 complete operating system; when you use @value{GDBN} as a remote
849 debugger attached to a bare board, there may not be any notion of
850 ``process'', and there is often no way to get a core dump. @value{GDBN}
851 will warn you if it is unable to attach or to read core dumps.
853 You can optionally have @code{@value{GDBP}} pass any arguments after the
854 executable file to the inferior using @code{--args}. This option stops
857 @value{GDBP} --args gcc -O2 -c foo.c
859 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
860 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
862 You can run @code{@value{GDBP}} without printing the front material, which describes
863 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
870 You can further control how @value{GDBN} starts up by using command-line
871 options. @value{GDBN} itself can remind you of the options available.
881 to display all available options and briefly describe their use
882 (@samp{@value{GDBP} -h} is a shorter equivalent).
884 All options and command line arguments you give are processed
885 in sequential order. The order makes a difference when the
886 @samp{-x} option is used.
890 * File Options:: Choosing files
891 * Mode Options:: Choosing modes
892 * Startup:: What @value{GDBN} does during startup
896 @subsection Choosing Files
898 When @value{GDBN} starts, it reads any arguments other than options as
899 specifying an executable file and core file (or process ID). This is
900 the same as if the arguments were specified by the @samp{-se} and
901 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
902 first argument that does not have an associated option flag as
903 equivalent to the @samp{-se} option followed by that argument; and the
904 second argument that does not have an associated option flag, if any, as
905 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
906 If the second argument begins with a decimal digit, @value{GDBN} will
907 first attempt to attach to it as a process, and if that fails, attempt
908 to open it as a corefile. If you have a corefile whose name begins with
909 a digit, you can prevent @value{GDBN} from treating it as a pid by
910 prefixing it with @file{./}, e.g.@: @file{./12345}.
912 If @value{GDBN} has not been configured to included core file support,
913 such as for most embedded targets, then it will complain about a second
914 argument and ignore it.
916 Many options have both long and short forms; both are shown in the
917 following list. @value{GDBN} also recognizes the long forms if you truncate
918 them, so long as enough of the option is present to be unambiguous.
919 (If you prefer, you can flag option arguments with @samp{--} rather
920 than @samp{-}, though we illustrate the more usual convention.)
922 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
923 @c way, both those who look for -foo and --foo in the index, will find
927 @item -symbols @var{file}
929 @cindex @code{--symbols}
931 Read symbol table from file @var{file}.
933 @item -exec @var{file}
935 @cindex @code{--exec}
937 Use file @var{file} as the executable file to execute when appropriate,
938 and for examining pure data in conjunction with a core dump.
942 Read symbol table from file @var{file} and use it as the executable
945 @item -core @var{file}
947 @cindex @code{--core}
949 Use file @var{file} as a core dump to examine.
951 @item -pid @var{number}
952 @itemx -p @var{number}
955 Connect to process ID @var{number}, as with the @code{attach} command.
957 @item -command @var{file}
959 @cindex @code{--command}
961 Execute @value{GDBN} commands from file @var{file}. @xref{Command
962 Files,, Command files}.
964 @item -eval-command @var{command}
965 @itemx -ex @var{command}
966 @cindex @code{--eval-command}
968 Execute a single @value{GDBN} command.
970 This option may be used multiple times to call multiple commands. It may
971 also be interleaved with @samp{-command} as required.
974 @value{GDBP} -ex 'target sim' -ex 'load' \
975 -x setbreakpoints -ex 'run' a.out
978 @item -directory @var{directory}
979 @itemx -d @var{directory}
980 @cindex @code{--directory}
982 Add @var{directory} to the path to search for source and script files.
986 @cindex @code{--readnow}
988 Read each symbol file's entire symbol table immediately, rather than
989 the default, which is to read it incrementally as it is needed.
990 This makes startup slower, but makes future operations faster.
995 @subsection Choosing Modes
997 You can run @value{GDBN} in various alternative modes---for example, in
998 batch mode or quiet mode.
1005 Do not execute commands found in any initialization files. Normally,
1006 @value{GDBN} executes the commands in these files after all the command
1007 options and arguments have been processed. @xref{Command Files,,Command
1013 @cindex @code{--quiet}
1014 @cindex @code{--silent}
1016 ``Quiet''. Do not print the introductory and copyright messages. These
1017 messages are also suppressed in batch mode.
1020 @cindex @code{--batch}
1021 Run in batch mode. Exit with status @code{0} after processing all the
1022 command files specified with @samp{-x} (and all commands from
1023 initialization files, if not inhibited with @samp{-n}). Exit with
1024 nonzero status if an error occurs in executing the @value{GDBN} commands
1025 in the command files.
1027 Batch mode may be useful for running @value{GDBN} as a filter, for
1028 example to download and run a program on another computer; in order to
1029 make this more useful, the message
1032 Program exited normally.
1036 (which is ordinarily issued whenever a program running under
1037 @value{GDBN} control terminates) is not issued when running in batch
1041 @cindex @code{--batch-silent}
1042 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1043 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1044 unaffected). This is much quieter than @samp{-silent} and would be useless
1045 for an interactive session.
1047 This is particularly useful when using targets that give @samp{Loading section}
1048 messages, for example.
1050 Note that targets that give their output via @value{GDBN}, as opposed to
1051 writing directly to @code{stdout}, will also be made silent.
1053 @item -return-child-result
1054 @cindex @code{--return-child-result}
1055 The return code from @value{GDBN} will be the return code from the child
1056 process (the process being debugged), with the following exceptions:
1060 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1061 internal error. In this case the exit code is the same as it would have been
1062 without @samp{-return-child-result}.
1064 The user quits with an explicit value. E.g., @samp{quit 1}.
1066 The child process never runs, or is not allowed to terminate, in which case
1067 the exit code will be -1.
1070 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1071 when @value{GDBN} is being used as a remote program loader or simulator
1076 @cindex @code{--nowindows}
1078 ``No windows''. If @value{GDBN} comes with a graphical user interface
1079 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1080 interface. If no GUI is available, this option has no effect.
1084 @cindex @code{--windows}
1086 If @value{GDBN} includes a GUI, then this option requires it to be
1089 @item -cd @var{directory}
1091 Run @value{GDBN} using @var{directory} as its working directory,
1092 instead of the current directory.
1096 @cindex @code{--fullname}
1098 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1099 subprocess. It tells @value{GDBN} to output the full file name and line
1100 number in a standard, recognizable fashion each time a stack frame is
1101 displayed (which includes each time your program stops). This
1102 recognizable format looks like two @samp{\032} characters, followed by
1103 the file name, line number and character position separated by colons,
1104 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1105 @samp{\032} characters as a signal to display the source code for the
1109 @cindex @code{--epoch}
1110 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1111 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1112 routines so as to allow Epoch to display values of expressions in a
1115 @item -annotate @var{level}
1116 @cindex @code{--annotate}
1117 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1118 effect is identical to using @samp{set annotate @var{level}}
1119 (@pxref{Annotations}). The annotation @var{level} controls how much
1120 information @value{GDBN} prints together with its prompt, values of
1121 expressions, source lines, and other types of output. Level 0 is the
1122 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1123 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1124 that control @value{GDBN}, and level 2 has been deprecated.
1126 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1130 @cindex @code{--args}
1131 Change interpretation of command line so that arguments following the
1132 executable file are passed as command line arguments to the inferior.
1133 This option stops option processing.
1135 @item -baud @var{bps}
1137 @cindex @code{--baud}
1139 Set the line speed (baud rate or bits per second) of any serial
1140 interface used by @value{GDBN} for remote debugging.
1142 @item -l @var{timeout}
1144 Set the timeout (in seconds) of any communication used by @value{GDBN}
1145 for remote debugging.
1147 @item -tty @var{device}
1148 @itemx -t @var{device}
1149 @cindex @code{--tty}
1151 Run using @var{device} for your program's standard input and output.
1152 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1154 @c resolve the situation of these eventually
1156 @cindex @code{--tui}
1157 Activate the @dfn{Text User Interface} when starting. The Text User
1158 Interface manages several text windows on the terminal, showing
1159 source, assembly, registers and @value{GDBN} command outputs
1160 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1161 Text User Interface can be enabled by invoking the program
1162 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1163 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1166 @c @cindex @code{--xdb}
1167 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1168 @c For information, see the file @file{xdb_trans.html}, which is usually
1169 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1172 @item -interpreter @var{interp}
1173 @cindex @code{--interpreter}
1174 Use the interpreter @var{interp} for interface with the controlling
1175 program or device. This option is meant to be set by programs which
1176 communicate with @value{GDBN} using it as a back end.
1177 @xref{Interpreters, , Command Interpreters}.
1179 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1180 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1181 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1182 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1183 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1184 @sc{gdb/mi} interfaces are no longer supported.
1187 @cindex @code{--write}
1188 Open the executable and core files for both reading and writing. This
1189 is equivalent to the @samp{set write on} command inside @value{GDBN}
1193 @cindex @code{--statistics}
1194 This option causes @value{GDBN} to print statistics about time and
1195 memory usage after it completes each command and returns to the prompt.
1198 @cindex @code{--version}
1199 This option causes @value{GDBN} to print its version number and
1200 no-warranty blurb, and exit.
1205 @subsection What @value{GDBN} Does During Startup
1206 @cindex @value{GDBN} startup
1208 Here's the description of what @value{GDBN} does during session startup:
1212 Sets up the command interpreter as specified by the command line
1213 (@pxref{Mode Options, interpreter}).
1217 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1218 used when building @value{GDBN}; @pxref{System-wide configuration,
1219 ,System-wide configuration and settings}) and executes all the commands in
1223 Reads the init file (if any) in your home directory@footnote{On
1224 DOS/Windows systems, the home directory is the one pointed to by the
1225 @code{HOME} environment variable.} and executes all the commands in
1229 Processes command line options and operands.
1232 Reads and executes the commands from init file (if any) in the current
1233 working directory. This is only done if the current directory is
1234 different from your home directory. Thus, you can have more than one
1235 init file, one generic in your home directory, and another, specific
1236 to the program you are debugging, in the directory where you invoke
1240 Reads command files specified by the @samp{-x} option. @xref{Command
1241 Files}, for more details about @value{GDBN} command files.
1244 Reads the command history recorded in the @dfn{history file}.
1245 @xref{Command History}, for more details about the command history and the
1246 files where @value{GDBN} records it.
1249 Init files use the same syntax as @dfn{command files} (@pxref{Command
1250 Files}) and are processed by @value{GDBN} in the same way. The init
1251 file in your home directory can set options (such as @samp{set
1252 complaints}) that affect subsequent processing of command line options
1253 and operands. Init files are not executed if you use the @samp{-nx}
1254 option (@pxref{Mode Options, ,Choosing Modes}).
1256 To display the list of init files loaded by gdb at startup, you
1257 can use @kbd{gdb --help}.
1259 @cindex init file name
1260 @cindex @file{.gdbinit}
1261 @cindex @file{gdb.ini}
1262 The @value{GDBN} init files are normally called @file{.gdbinit}.
1263 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1264 the limitations of file names imposed by DOS filesystems. The Windows
1265 ports of @value{GDBN} use the standard name, but if they find a
1266 @file{gdb.ini} file, they warn you about that and suggest to rename
1267 the file to the standard name.
1271 @section Quitting @value{GDBN}
1272 @cindex exiting @value{GDBN}
1273 @cindex leaving @value{GDBN}
1276 @kindex quit @r{[}@var{expression}@r{]}
1277 @kindex q @r{(@code{quit})}
1278 @item quit @r{[}@var{expression}@r{]}
1280 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1281 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1282 do not supply @var{expression}, @value{GDBN} will terminate normally;
1283 otherwise it will terminate using the result of @var{expression} as the
1288 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1289 terminates the action of any @value{GDBN} command that is in progress and
1290 returns to @value{GDBN} command level. It is safe to type the interrupt
1291 character at any time because @value{GDBN} does not allow it to take effect
1292 until a time when it is safe.
1294 If you have been using @value{GDBN} to control an attached process or
1295 device, you can release it with the @code{detach} command
1296 (@pxref{Attach, ,Debugging an Already-running Process}).
1298 @node Shell Commands
1299 @section Shell Commands
1301 If you need to execute occasional shell commands during your
1302 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1303 just use the @code{shell} command.
1307 @cindex shell escape
1308 @item shell @var{command string}
1309 Invoke a standard shell to execute @var{command string}.
1310 If it exists, the environment variable @code{SHELL} determines which
1311 shell to run. Otherwise @value{GDBN} uses the default shell
1312 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1315 The utility @code{make} is often needed in development environments.
1316 You do not have to use the @code{shell} command for this purpose in
1321 @cindex calling make
1322 @item make @var{make-args}
1323 Execute the @code{make} program with the specified
1324 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1327 @node Logging Output
1328 @section Logging Output
1329 @cindex logging @value{GDBN} output
1330 @cindex save @value{GDBN} output to a file
1332 You may want to save the output of @value{GDBN} commands to a file.
1333 There are several commands to control @value{GDBN}'s logging.
1337 @item set logging on
1339 @item set logging off
1341 @cindex logging file name
1342 @item set logging file @var{file}
1343 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1344 @item set logging overwrite [on|off]
1345 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1346 you want @code{set logging on} to overwrite the logfile instead.
1347 @item set logging redirect [on|off]
1348 By default, @value{GDBN} output will go to both the terminal and the logfile.
1349 Set @code{redirect} if you want output to go only to the log file.
1350 @kindex show logging
1352 Show the current values of the logging settings.
1356 @chapter @value{GDBN} Commands
1358 You can abbreviate a @value{GDBN} command to the first few letters of the command
1359 name, if that abbreviation is unambiguous; and you can repeat certain
1360 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1361 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1362 show you the alternatives available, if there is more than one possibility).
1365 * Command Syntax:: How to give commands to @value{GDBN}
1366 * Completion:: Command completion
1367 * Help:: How to ask @value{GDBN} for help
1370 @node Command Syntax
1371 @section Command Syntax
1373 A @value{GDBN} command is a single line of input. There is no limit on
1374 how long it can be. It starts with a command name, which is followed by
1375 arguments whose meaning depends on the command name. For example, the
1376 command @code{step} accepts an argument which is the number of times to
1377 step, as in @samp{step 5}. You can also use the @code{step} command
1378 with no arguments. Some commands do not allow any arguments.
1380 @cindex abbreviation
1381 @value{GDBN} command names may always be truncated if that abbreviation is
1382 unambiguous. Other possible command abbreviations are listed in the
1383 documentation for individual commands. In some cases, even ambiguous
1384 abbreviations are allowed; for example, @code{s} is specially defined as
1385 equivalent to @code{step} even though there are other commands whose
1386 names start with @code{s}. You can test abbreviations by using them as
1387 arguments to the @code{help} command.
1389 @cindex repeating commands
1390 @kindex RET @r{(repeat last command)}
1391 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1392 repeat the previous command. Certain commands (for example, @code{run})
1393 will not repeat this way; these are commands whose unintentional
1394 repetition might cause trouble and which you are unlikely to want to
1395 repeat. User-defined commands can disable this feature; see
1396 @ref{Define, dont-repeat}.
1398 The @code{list} and @code{x} commands, when you repeat them with
1399 @key{RET}, construct new arguments rather than repeating
1400 exactly as typed. This permits easy scanning of source or memory.
1402 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1403 output, in a way similar to the common utility @code{more}
1404 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1405 @key{RET} too many in this situation, @value{GDBN} disables command
1406 repetition after any command that generates this sort of display.
1408 @kindex # @r{(a comment)}
1410 Any text from a @kbd{#} to the end of the line is a comment; it does
1411 nothing. This is useful mainly in command files (@pxref{Command
1412 Files,,Command Files}).
1414 @cindex repeating command sequences
1415 @kindex Ctrl-o @r{(operate-and-get-next)}
1416 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1417 commands. This command accepts the current line, like @key{RET}, and
1418 then fetches the next line relative to the current line from the history
1422 @section Command Completion
1425 @cindex word completion
1426 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1427 only one possibility; it can also show you what the valid possibilities
1428 are for the next word in a command, at any time. This works for @value{GDBN}
1429 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1431 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1432 of a word. If there is only one possibility, @value{GDBN} fills in the
1433 word, and waits for you to finish the command (or press @key{RET} to
1434 enter it). For example, if you type
1436 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1437 @c complete accuracy in these examples; space introduced for clarity.
1438 @c If texinfo enhancements make it unnecessary, it would be nice to
1439 @c replace " @key" by "@key" in the following...
1441 (@value{GDBP}) info bre @key{TAB}
1445 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1446 the only @code{info} subcommand beginning with @samp{bre}:
1449 (@value{GDBP}) info breakpoints
1453 You can either press @key{RET} at this point, to run the @code{info
1454 breakpoints} command, or backspace and enter something else, if
1455 @samp{breakpoints} does not look like the command you expected. (If you
1456 were sure you wanted @code{info breakpoints} in the first place, you
1457 might as well just type @key{RET} immediately after @samp{info bre},
1458 to exploit command abbreviations rather than command completion).
1460 If there is more than one possibility for the next word when you press
1461 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1462 characters and try again, or just press @key{TAB} a second time;
1463 @value{GDBN} displays all the possible completions for that word. For
1464 example, you might want to set a breakpoint on a subroutine whose name
1465 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1466 just sounds the bell. Typing @key{TAB} again displays all the
1467 function names in your program that begin with those characters, for
1471 (@value{GDBP}) b make_ @key{TAB}
1472 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1473 make_a_section_from_file make_environ
1474 make_abs_section make_function_type
1475 make_blockvector make_pointer_type
1476 make_cleanup make_reference_type
1477 make_command make_symbol_completion_list
1478 (@value{GDBP}) b make_
1482 After displaying the available possibilities, @value{GDBN} copies your
1483 partial input (@samp{b make_} in the example) so you can finish the
1486 If you just want to see the list of alternatives in the first place, you
1487 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1488 means @kbd{@key{META} ?}. You can type this either by holding down a
1489 key designated as the @key{META} shift on your keyboard (if there is
1490 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1492 @cindex quotes in commands
1493 @cindex completion of quoted strings
1494 Sometimes the string you need, while logically a ``word'', may contain
1495 parentheses or other characters that @value{GDBN} normally excludes from
1496 its notion of a word. To permit word completion to work in this
1497 situation, you may enclose words in @code{'} (single quote marks) in
1498 @value{GDBN} commands.
1500 The most likely situation where you might need this is in typing the
1501 name of a C@t{++} function. This is because C@t{++} allows function
1502 overloading (multiple definitions of the same function, distinguished
1503 by argument type). For example, when you want to set a breakpoint you
1504 may need to distinguish whether you mean the version of @code{name}
1505 that takes an @code{int} parameter, @code{name(int)}, or the version
1506 that takes a @code{float} parameter, @code{name(float)}. To use the
1507 word-completion facilities in this situation, type a single quote
1508 @code{'} at the beginning of the function name. This alerts
1509 @value{GDBN} that it may need to consider more information than usual
1510 when you press @key{TAB} or @kbd{M-?} to request word completion:
1513 (@value{GDBP}) b 'bubble( @kbd{M-?}
1514 bubble(double,double) bubble(int,int)
1515 (@value{GDBP}) b 'bubble(
1518 In some cases, @value{GDBN} can tell that completing a name requires using
1519 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1520 completing as much as it can) if you do not type the quote in the first
1524 (@value{GDBP}) b bub @key{TAB}
1525 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1526 (@value{GDBP}) b 'bubble(
1530 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1531 you have not yet started typing the argument list when you ask for
1532 completion on an overloaded symbol.
1534 For more information about overloaded functions, see @ref{C Plus Plus
1535 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1536 overload-resolution off} to disable overload resolution;
1537 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1539 @cindex completion of structure field names
1540 @cindex structure field name completion
1541 @cindex completion of union field names
1542 @cindex union field name completion
1543 When completing in an expression which looks up a field in a
1544 structure, @value{GDBN} also tries@footnote{The completer can be
1545 confused by certain kinds of invalid expressions. Also, it only
1546 examines the static type of the expression, not the dynamic type.} to
1547 limit completions to the field names available in the type of the
1551 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1552 magic to_delete to_fputs to_put to_rewind
1553 to_data to_flush to_isatty to_read to_write
1557 This is because the @code{gdb_stdout} is a variable of the type
1558 @code{struct ui_file} that is defined in @value{GDBN} sources as
1565 ui_file_flush_ftype *to_flush;
1566 ui_file_write_ftype *to_write;
1567 ui_file_fputs_ftype *to_fputs;
1568 ui_file_read_ftype *to_read;
1569 ui_file_delete_ftype *to_delete;
1570 ui_file_isatty_ftype *to_isatty;
1571 ui_file_rewind_ftype *to_rewind;
1572 ui_file_put_ftype *to_put;
1579 @section Getting Help
1580 @cindex online documentation
1583 You can always ask @value{GDBN} itself for information on its commands,
1584 using the command @code{help}.
1587 @kindex h @r{(@code{help})}
1590 You can use @code{help} (abbreviated @code{h}) with no arguments to
1591 display a short list of named classes of commands:
1595 List of classes of commands:
1597 aliases -- Aliases of other commands
1598 breakpoints -- Making program stop at certain points
1599 data -- Examining data
1600 files -- Specifying and examining files
1601 internals -- Maintenance commands
1602 obscure -- Obscure features
1603 running -- Running the program
1604 stack -- Examining the stack
1605 status -- Status inquiries
1606 support -- Support facilities
1607 tracepoints -- Tracing of program execution without
1608 stopping the program
1609 user-defined -- User-defined commands
1611 Type "help" followed by a class name for a list of
1612 commands in that class.
1613 Type "help" followed by command name for full
1615 Command name abbreviations are allowed if unambiguous.
1618 @c the above line break eliminates huge line overfull...
1620 @item help @var{class}
1621 Using one of the general help classes as an argument, you can get a
1622 list of the individual commands in that class. For example, here is the
1623 help display for the class @code{status}:
1626 (@value{GDBP}) help status
1631 @c Line break in "show" line falsifies real output, but needed
1632 @c to fit in smallbook page size.
1633 info -- Generic command for showing things
1634 about the program being debugged
1635 show -- Generic command for showing things
1638 Type "help" followed by command name for full
1640 Command name abbreviations are allowed if unambiguous.
1644 @item help @var{command}
1645 With a command name as @code{help} argument, @value{GDBN} displays a
1646 short paragraph on how to use that command.
1649 @item apropos @var{args}
1650 The @code{apropos} command searches through all of the @value{GDBN}
1651 commands, and their documentation, for the regular expression specified in
1652 @var{args}. It prints out all matches found. For example:
1663 set symbol-reloading -- Set dynamic symbol table reloading
1664 multiple times in one run
1665 show symbol-reloading -- Show dynamic symbol table reloading
1666 multiple times in one run
1671 @item complete @var{args}
1672 The @code{complete @var{args}} command lists all the possible completions
1673 for the beginning of a command. Use @var{args} to specify the beginning of the
1674 command you want completed. For example:
1680 @noindent results in:
1691 @noindent This is intended for use by @sc{gnu} Emacs.
1694 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1695 and @code{show} to inquire about the state of your program, or the state
1696 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1697 manual introduces each of them in the appropriate context. The listings
1698 under @code{info} and under @code{show} in the Index point to
1699 all the sub-commands. @xref{Index}.
1704 @kindex i @r{(@code{info})}
1706 This command (abbreviated @code{i}) is for describing the state of your
1707 program. For example, you can show the arguments passed to a function
1708 with @code{info args}, list the registers currently in use with @code{info
1709 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1710 You can get a complete list of the @code{info} sub-commands with
1711 @w{@code{help info}}.
1715 You can assign the result of an expression to an environment variable with
1716 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1717 @code{set prompt $}.
1721 In contrast to @code{info}, @code{show} is for describing the state of
1722 @value{GDBN} itself.
1723 You can change most of the things you can @code{show}, by using the
1724 related command @code{set}; for example, you can control what number
1725 system is used for displays with @code{set radix}, or simply inquire
1726 which is currently in use with @code{show radix}.
1729 To display all the settable parameters and their current
1730 values, you can use @code{show} with no arguments; you may also use
1731 @code{info set}. Both commands produce the same display.
1732 @c FIXME: "info set" violates the rule that "info" is for state of
1733 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1734 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1738 Here are three miscellaneous @code{show} subcommands, all of which are
1739 exceptional in lacking corresponding @code{set} commands:
1742 @kindex show version
1743 @cindex @value{GDBN} version number
1745 Show what version of @value{GDBN} is running. You should include this
1746 information in @value{GDBN} bug-reports. If multiple versions of
1747 @value{GDBN} are in use at your site, you may need to determine which
1748 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1749 commands are introduced, and old ones may wither away. Also, many
1750 system vendors ship variant versions of @value{GDBN}, and there are
1751 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1752 The version number is the same as the one announced when you start
1755 @kindex show copying
1756 @kindex info copying
1757 @cindex display @value{GDBN} copyright
1760 Display information about permission for copying @value{GDBN}.
1762 @kindex show warranty
1763 @kindex info warranty
1765 @itemx info warranty
1766 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1767 if your version of @value{GDBN} comes with one.
1772 @chapter Running Programs Under @value{GDBN}
1774 When you run a program under @value{GDBN}, you must first generate
1775 debugging information when you compile it.
1777 You may start @value{GDBN} with its arguments, if any, in an environment
1778 of your choice. If you are doing native debugging, you may redirect
1779 your program's input and output, debug an already running process, or
1780 kill a child process.
1783 * Compilation:: Compiling for debugging
1784 * Starting:: Starting your program
1785 * Arguments:: Your program's arguments
1786 * Environment:: Your program's environment
1788 * Working Directory:: Your program's working directory
1789 * Input/Output:: Your program's input and output
1790 * Attach:: Debugging an already-running process
1791 * Kill Process:: Killing the child process
1793 * Inferiors:: Debugging multiple inferiors
1794 * Threads:: Debugging programs with multiple threads
1795 * Processes:: Debugging programs with multiple processes
1796 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1800 @section Compiling for Debugging
1802 In order to debug a program effectively, you need to generate
1803 debugging information when you compile it. This debugging information
1804 is stored in the object file; it describes the data type of each
1805 variable or function and the correspondence between source line numbers
1806 and addresses in the executable code.
1808 To request debugging information, specify the @samp{-g} option when you run
1811 Programs that are to be shipped to your customers are compiled with
1812 optimizations, using the @samp{-O} compiler option. However, some
1813 compilers are unable to handle the @samp{-g} and @samp{-O} options
1814 together. Using those compilers, you cannot generate optimized
1815 executables containing debugging information.
1817 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1818 without @samp{-O}, making it possible to debug optimized code. We
1819 recommend that you @emph{always} use @samp{-g} whenever you compile a
1820 program. You may think your program is correct, but there is no sense
1821 in pushing your luck. For more information, see @ref{Optimized Code}.
1823 Older versions of the @sc{gnu} C compiler permitted a variant option
1824 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1825 format; if your @sc{gnu} C compiler has this option, do not use it.
1827 @value{GDBN} knows about preprocessor macros and can show you their
1828 expansion (@pxref{Macros}). Most compilers do not include information
1829 about preprocessor macros in the debugging information if you specify
1830 the @option{-g} flag alone, because this information is rather large.
1831 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1832 provides macro information if you specify the options
1833 @option{-gdwarf-2} and @option{-g3}; the former option requests
1834 debugging information in the Dwarf 2 format, and the latter requests
1835 ``extra information''. In the future, we hope to find more compact
1836 ways to represent macro information, so that it can be included with
1841 @section Starting your Program
1847 @kindex r @r{(@code{run})}
1850 Use the @code{run} command to start your program under @value{GDBN}.
1851 You must first specify the program name (except on VxWorks) with an
1852 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1853 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1854 (@pxref{Files, ,Commands to Specify Files}).
1858 If you are running your program in an execution environment that
1859 supports processes, @code{run} creates an inferior process and makes
1860 that process run your program. In some environments without processes,
1861 @code{run} jumps to the start of your program. Other targets,
1862 like @samp{remote}, are always running. If you get an error
1863 message like this one:
1866 The "remote" target does not support "run".
1867 Try "help target" or "continue".
1871 then use @code{continue} to run your program. You may need @code{load}
1872 first (@pxref{load}).
1874 The execution of a program is affected by certain information it
1875 receives from its superior. @value{GDBN} provides ways to specify this
1876 information, which you must do @emph{before} starting your program. (You
1877 can change it after starting your program, but such changes only affect
1878 your program the next time you start it.) This information may be
1879 divided into four categories:
1882 @item The @emph{arguments.}
1883 Specify the arguments to give your program as the arguments of the
1884 @code{run} command. If a shell is available on your target, the shell
1885 is used to pass the arguments, so that you may use normal conventions
1886 (such as wildcard expansion or variable substitution) in describing
1888 In Unix systems, you can control which shell is used with the
1889 @code{SHELL} environment variable.
1890 @xref{Arguments, ,Your Program's Arguments}.
1892 @item The @emph{environment.}
1893 Your program normally inherits its environment from @value{GDBN}, but you can
1894 use the @value{GDBN} commands @code{set environment} and @code{unset
1895 environment} to change parts of the environment that affect
1896 your program. @xref{Environment, ,Your Program's Environment}.
1898 @item The @emph{working directory.}
1899 Your program inherits its working directory from @value{GDBN}. You can set
1900 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1901 @xref{Working Directory, ,Your Program's Working Directory}.
1903 @item The @emph{standard input and output.}
1904 Your program normally uses the same device for standard input and
1905 standard output as @value{GDBN} is using. You can redirect input and output
1906 in the @code{run} command line, or you can use the @code{tty} command to
1907 set a different device for your program.
1908 @xref{Input/Output, ,Your Program's Input and Output}.
1911 @emph{Warning:} While input and output redirection work, you cannot use
1912 pipes to pass the output of the program you are debugging to another
1913 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1917 When you issue the @code{run} command, your program begins to execute
1918 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1919 of how to arrange for your program to stop. Once your program has
1920 stopped, you may call functions in your program, using the @code{print}
1921 or @code{call} commands. @xref{Data, ,Examining Data}.
1923 If the modification time of your symbol file has changed since the last
1924 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1925 table, and reads it again. When it does this, @value{GDBN} tries to retain
1926 your current breakpoints.
1931 @cindex run to main procedure
1932 The name of the main procedure can vary from language to language.
1933 With C or C@t{++}, the main procedure name is always @code{main}, but
1934 other languages such as Ada do not require a specific name for their
1935 main procedure. The debugger provides a convenient way to start the
1936 execution of the program and to stop at the beginning of the main
1937 procedure, depending on the language used.
1939 The @samp{start} command does the equivalent of setting a temporary
1940 breakpoint at the beginning of the main procedure and then invoking
1941 the @samp{run} command.
1943 @cindex elaboration phase
1944 Some programs contain an @dfn{elaboration} phase where some startup code is
1945 executed before the main procedure is called. This depends on the
1946 languages used to write your program. In C@t{++}, for instance,
1947 constructors for static and global objects are executed before
1948 @code{main} is called. It is therefore possible that the debugger stops
1949 before reaching the main procedure. However, the temporary breakpoint
1950 will remain to halt execution.
1952 Specify the arguments to give to your program as arguments to the
1953 @samp{start} command. These arguments will be given verbatim to the
1954 underlying @samp{run} command. Note that the same arguments will be
1955 reused if no argument is provided during subsequent calls to
1956 @samp{start} or @samp{run}.
1958 It is sometimes necessary to debug the program during elaboration. In
1959 these cases, using the @code{start} command would stop the execution of
1960 your program too late, as the program would have already completed the
1961 elaboration phase. Under these circumstances, insert breakpoints in your
1962 elaboration code before running your program.
1964 @kindex set exec-wrapper
1965 @item set exec-wrapper @var{wrapper}
1966 @itemx show exec-wrapper
1967 @itemx unset exec-wrapper
1968 When @samp{exec-wrapper} is set, the specified wrapper is used to
1969 launch programs for debugging. @value{GDBN} starts your program
1970 with a shell command of the form @kbd{exec @var{wrapper}
1971 @var{program}}. Quoting is added to @var{program} and its
1972 arguments, but not to @var{wrapper}, so you should add quotes if
1973 appropriate for your shell. The wrapper runs until it executes
1974 your program, and then @value{GDBN} takes control.
1976 You can use any program that eventually calls @code{execve} with
1977 its arguments as a wrapper. Several standard Unix utilities do
1978 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
1979 with @code{exec "$@@"} will also work.
1981 For example, you can use @code{env} to pass an environment variable to
1982 the debugged program, without setting the variable in your shell's
1986 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
1990 This command is available when debugging locally on most targets, excluding
1991 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
1993 @kindex set disable-randomization
1994 @item set disable-randomization
1995 @itemx set disable-randomization on
1996 This option (enabled by default in @value{GDBN}) will turn off the native
1997 randomization of the virtual address space of the started program. This option
1998 is useful for multiple debugging sessions to make the execution better
1999 reproducible and memory addresses reusable across debugging sessions.
2001 This feature is implemented only on @sc{gnu}/Linux. You can get the same
2005 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2008 @item set disable-randomization off
2009 Leave the behavior of the started executable unchanged. Some bugs rear their
2010 ugly heads only when the program is loaded at certain addresses. If your bug
2011 disappears when you run the program under @value{GDBN}, that might be because
2012 @value{GDBN} by default disables the address randomization on platforms, such
2013 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2014 disable-randomization off} to try to reproduce such elusive bugs.
2016 The virtual address space randomization is implemented only on @sc{gnu}/Linux.
2017 It protects the programs against some kinds of security attacks. In these
2018 cases the attacker needs to know the exact location of a concrete executable
2019 code. Randomizing its location makes it impossible to inject jumps misusing
2020 a code at its expected addresses.
2022 Prelinking shared libraries provides a startup performance advantage but it
2023 makes addresses in these libraries predictable for privileged processes by
2024 having just unprivileged access at the target system. Reading the shared
2025 library binary gives enough information for assembling the malicious code
2026 misusing it. Still even a prelinked shared library can get loaded at a new
2027 random address just requiring the regular relocation process during the
2028 startup. Shared libraries not already prelinked are always loaded at
2029 a randomly chosen address.
2031 Position independent executables (PIE) contain position independent code
2032 similar to the shared libraries and therefore such executables get loaded at
2033 a randomly chosen address upon startup. PIE executables always load even
2034 already prelinked shared libraries at a random address. You can build such
2035 executable using @command{gcc -fPIE -pie}.
2037 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2038 (as long as the randomization is enabled).
2040 @item show disable-randomization
2041 Show the current setting of the explicit disable of the native randomization of
2042 the virtual address space of the started program.
2047 @section Your Program's Arguments
2049 @cindex arguments (to your program)
2050 The arguments to your program can be specified by the arguments of the
2052 They are passed to a shell, which expands wildcard characters and
2053 performs redirection of I/O, and thence to your program. Your
2054 @code{SHELL} environment variable (if it exists) specifies what shell
2055 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2056 the default shell (@file{/bin/sh} on Unix).
2058 On non-Unix systems, the program is usually invoked directly by
2059 @value{GDBN}, which emulates I/O redirection via the appropriate system
2060 calls, and the wildcard characters are expanded by the startup code of
2061 the program, not by the shell.
2063 @code{run} with no arguments uses the same arguments used by the previous
2064 @code{run}, or those set by the @code{set args} command.
2069 Specify the arguments to be used the next time your program is run. If
2070 @code{set args} has no arguments, @code{run} executes your program
2071 with no arguments. Once you have run your program with arguments,
2072 using @code{set args} before the next @code{run} is the only way to run
2073 it again without arguments.
2077 Show the arguments to give your program when it is started.
2081 @section Your Program's Environment
2083 @cindex environment (of your program)
2084 The @dfn{environment} consists of a set of environment variables and
2085 their values. Environment variables conventionally record such things as
2086 your user name, your home directory, your terminal type, and your search
2087 path for programs to run. Usually you set up environment variables with
2088 the shell and they are inherited by all the other programs you run. When
2089 debugging, it can be useful to try running your program with a modified
2090 environment without having to start @value{GDBN} over again.
2094 @item path @var{directory}
2095 Add @var{directory} to the front of the @code{PATH} environment variable
2096 (the search path for executables) that will be passed to your program.
2097 The value of @code{PATH} used by @value{GDBN} does not change.
2098 You may specify several directory names, separated by whitespace or by a
2099 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2100 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2101 is moved to the front, so it is searched sooner.
2103 You can use the string @samp{$cwd} to refer to whatever is the current
2104 working directory at the time @value{GDBN} searches the path. If you
2105 use @samp{.} instead, it refers to the directory where you executed the
2106 @code{path} command. @value{GDBN} replaces @samp{.} in the
2107 @var{directory} argument (with the current path) before adding
2108 @var{directory} to the search path.
2109 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2110 @c document that, since repeating it would be a no-op.
2114 Display the list of search paths for executables (the @code{PATH}
2115 environment variable).
2117 @kindex show environment
2118 @item show environment @r{[}@var{varname}@r{]}
2119 Print the value of environment variable @var{varname} to be given to
2120 your program when it starts. If you do not supply @var{varname},
2121 print the names and values of all environment variables to be given to
2122 your program. You can abbreviate @code{environment} as @code{env}.
2124 @kindex set environment
2125 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2126 Set environment variable @var{varname} to @var{value}. The value
2127 changes for your program only, not for @value{GDBN} itself. @var{value} may
2128 be any string; the values of environment variables are just strings, and
2129 any interpretation is supplied by your program itself. The @var{value}
2130 parameter is optional; if it is eliminated, the variable is set to a
2132 @c "any string" here does not include leading, trailing
2133 @c blanks. Gnu asks: does anyone care?
2135 For example, this command:
2142 tells the debugged program, when subsequently run, that its user is named
2143 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2144 are not actually required.)
2146 @kindex unset environment
2147 @item unset environment @var{varname}
2148 Remove variable @var{varname} from the environment to be passed to your
2149 program. This is different from @samp{set env @var{varname} =};
2150 @code{unset environment} removes the variable from the environment,
2151 rather than assigning it an empty value.
2154 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2156 by your @code{SHELL} environment variable if it exists (or
2157 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2158 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2159 @file{.bashrc} for BASH---any variables you set in that file affect
2160 your program. You may wish to move setting of environment variables to
2161 files that are only run when you sign on, such as @file{.login} or
2164 @node Working Directory
2165 @section Your Program's Working Directory
2167 @cindex working directory (of your program)
2168 Each time you start your program with @code{run}, it inherits its
2169 working directory from the current working directory of @value{GDBN}.
2170 The @value{GDBN} working directory is initially whatever it inherited
2171 from its parent process (typically the shell), but you can specify a new
2172 working directory in @value{GDBN} with the @code{cd} command.
2174 The @value{GDBN} working directory also serves as a default for the commands
2175 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2180 @cindex change working directory
2181 @item cd @var{directory}
2182 Set the @value{GDBN} working directory to @var{directory}.
2186 Print the @value{GDBN} working directory.
2189 It is generally impossible to find the current working directory of
2190 the process being debugged (since a program can change its directory
2191 during its run). If you work on a system where @value{GDBN} is
2192 configured with the @file{/proc} support, you can use the @code{info
2193 proc} command (@pxref{SVR4 Process Information}) to find out the
2194 current working directory of the debuggee.
2197 @section Your Program's Input and Output
2202 By default, the program you run under @value{GDBN} does input and output to
2203 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2204 to its own terminal modes to interact with you, but it records the terminal
2205 modes your program was using and switches back to them when you continue
2206 running your program.
2209 @kindex info terminal
2211 Displays information recorded by @value{GDBN} about the terminal modes your
2215 You can redirect your program's input and/or output using shell
2216 redirection with the @code{run} command. For example,
2223 starts your program, diverting its output to the file @file{outfile}.
2226 @cindex controlling terminal
2227 Another way to specify where your program should do input and output is
2228 with the @code{tty} command. This command accepts a file name as
2229 argument, and causes this file to be the default for future @code{run}
2230 commands. It also resets the controlling terminal for the child
2231 process, for future @code{run} commands. For example,
2238 directs that processes started with subsequent @code{run} commands
2239 default to do input and output on the terminal @file{/dev/ttyb} and have
2240 that as their controlling terminal.
2242 An explicit redirection in @code{run} overrides the @code{tty} command's
2243 effect on the input/output device, but not its effect on the controlling
2246 When you use the @code{tty} command or redirect input in the @code{run}
2247 command, only the input @emph{for your program} is affected. The input
2248 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2249 for @code{set inferior-tty}.
2251 @cindex inferior tty
2252 @cindex set inferior controlling terminal
2253 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2254 display the name of the terminal that will be used for future runs of your
2258 @item set inferior-tty /dev/ttyb
2259 @kindex set inferior-tty
2260 Set the tty for the program being debugged to /dev/ttyb.
2262 @item show inferior-tty
2263 @kindex show inferior-tty
2264 Show the current tty for the program being debugged.
2268 @section Debugging an Already-running Process
2273 @item attach @var{process-id}
2274 This command attaches to a running process---one that was started
2275 outside @value{GDBN}. (@code{info files} shows your active
2276 targets.) The command takes as argument a process ID. The usual way to
2277 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2278 or with the @samp{jobs -l} shell command.
2280 @code{attach} does not repeat if you press @key{RET} a second time after
2281 executing the command.
2284 To use @code{attach}, your program must be running in an environment
2285 which supports processes; for example, @code{attach} does not work for
2286 programs on bare-board targets that lack an operating system. You must
2287 also have permission to send the process a signal.
2289 When you use @code{attach}, the debugger finds the program running in
2290 the process first by looking in the current working directory, then (if
2291 the program is not found) by using the source file search path
2292 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2293 the @code{file} command to load the program. @xref{Files, ,Commands to
2296 The first thing @value{GDBN} does after arranging to debug the specified
2297 process is to stop it. You can examine and modify an attached process
2298 with all the @value{GDBN} commands that are ordinarily available when
2299 you start processes with @code{run}. You can insert breakpoints; you
2300 can step and continue; you can modify storage. If you would rather the
2301 process continue running, you may use the @code{continue} command after
2302 attaching @value{GDBN} to the process.
2307 When you have finished debugging the attached process, you can use the
2308 @code{detach} command to release it from @value{GDBN} control. Detaching
2309 the process continues its execution. After the @code{detach} command,
2310 that process and @value{GDBN} become completely independent once more, and you
2311 are ready to @code{attach} another process or start one with @code{run}.
2312 @code{detach} does not repeat if you press @key{RET} again after
2313 executing the command.
2316 If you exit @value{GDBN} while you have an attached process, you detach
2317 that process. If you use the @code{run} command, you kill that process.
2318 By default, @value{GDBN} asks for confirmation if you try to do either of these
2319 things; you can control whether or not you need to confirm by using the
2320 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2324 @section Killing the Child Process
2329 Kill the child process in which your program is running under @value{GDBN}.
2332 This command is useful if you wish to debug a core dump instead of a
2333 running process. @value{GDBN} ignores any core dump file while your program
2336 On some operating systems, a program cannot be executed outside @value{GDBN}
2337 while you have breakpoints set on it inside @value{GDBN}. You can use the
2338 @code{kill} command in this situation to permit running your program
2339 outside the debugger.
2341 The @code{kill} command is also useful if you wish to recompile and
2342 relink your program, since on many systems it is impossible to modify an
2343 executable file while it is running in a process. In this case, when you
2344 next type @code{run}, @value{GDBN} notices that the file has changed, and
2345 reads the symbol table again (while trying to preserve your current
2346 breakpoint settings).
2349 @section Debugging Multiple Inferiors
2351 Some @value{GDBN} targets are able to run multiple processes created
2352 from a single executable. This can happen, for instance, with an
2353 embedded system reporting back several processes via the remote
2357 @value{GDBN} represents the state of each program execution with an
2358 object called an @dfn{inferior}. An inferior typically corresponds to
2359 a process, but is more general and applies also to targets that do not
2360 have processes. Inferiors may be created before a process runs, and
2361 may (in future) be retained after a process exits. Each run of an
2362 executable creates a new inferior, as does each attachment to an
2363 existing process. Inferiors have unique identifiers that are
2364 different from process ids, and may optionally be named as well.
2365 Usually each inferior will also have its own distinct address space,
2366 although some embedded targets may have several inferiors running in
2367 different parts of a single space.
2369 Each inferior may in turn have multiple threads running in it.
2371 To find out what inferiors exist at any moment, use @code{info inferiors}:
2374 @kindex info inferiors
2375 @item info inferiors
2376 Print a list of all inferiors currently being managed by @value{GDBN}.
2379 To switch focus between inferiors, use the @code{inferior} command:
2382 @kindex inferior @var{inferior-id}
2383 @item inferior @var{inferior-id}
2384 Make inferior number @var{inferior-id} the current inferior. The
2385 argument @var{inferior-id} is the internal inferior number assigned by
2386 @value{GDBN}, as shown in the first field of the @samp{info inferiors}
2390 To quit debugging one of the inferiors, you can either detach from it
2391 by using the @w{@code{detach inferior}} command (allowing it to run
2392 independently), or kill it using the @w{@code{kill inferior}} command:
2395 @kindex detach inferior @var{inferior-id}
2396 @item detach inferior @var{inferior-id}
2397 Detach from the inferior identified by @value{GDBN} inferior number
2398 @var{inferior-id}, and remove it from the inferior list.
2400 @kindex kill inferior @var{inferior-id}
2401 @item kill inferior @var{inferior-id}
2402 Kill the inferior identified by @value{GDBN} inferior number
2403 @var{inferior-id}, and remove it from the inferior list.
2406 To be notified when inferiors are started or exit under @value{GDBN}'s
2407 control use @w{@code{set print inferior-events}}:
2410 @kindex set print inferior-events
2411 @cindex print messages on inferior start and exit
2412 @item set print inferior-events
2413 @itemx set print inferior-events on
2414 @itemx set print inferior-events off
2415 The @code{set print inferior-events} command allows you to enable or
2416 disable printing of messages when @value{GDBN} notices that new
2417 inferiors have started or that inferiors have exited or have been
2418 detached. By default, these messages will not be printed.
2420 @kindex show print inferior-events
2421 @item show print inferior-events
2422 Show whether messages will be printed when @value{GDBN} detects that
2423 inferiors have started, exited or have been detached.
2427 @section Debugging Programs with Multiple Threads
2429 @cindex threads of execution
2430 @cindex multiple threads
2431 @cindex switching threads
2432 In some operating systems, such as HP-UX and Solaris, a single program
2433 may have more than one @dfn{thread} of execution. The precise semantics
2434 of threads differ from one operating system to another, but in general
2435 the threads of a single program are akin to multiple processes---except
2436 that they share one address space (that is, they can all examine and
2437 modify the same variables). On the other hand, each thread has its own
2438 registers and execution stack, and perhaps private memory.
2440 @value{GDBN} provides these facilities for debugging multi-thread
2444 @item automatic notification of new threads
2445 @item @samp{thread @var{threadno}}, a command to switch among threads
2446 @item @samp{info threads}, a command to inquire about existing threads
2447 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2448 a command to apply a command to a list of threads
2449 @item thread-specific breakpoints
2450 @item @samp{set print thread-events}, which controls printing of
2451 messages on thread start and exit.
2452 @item @samp{set libthread-db-search-path @var{path}}, which lets
2453 the user specify which @code{libthread_db} to use if the default choice
2454 isn't compatible with the program.
2458 @emph{Warning:} These facilities are not yet available on every
2459 @value{GDBN} configuration where the operating system supports threads.
2460 If your @value{GDBN} does not support threads, these commands have no
2461 effect. For example, a system without thread support shows no output
2462 from @samp{info threads}, and always rejects the @code{thread} command,
2466 (@value{GDBP}) info threads
2467 (@value{GDBP}) thread 1
2468 Thread ID 1 not known. Use the "info threads" command to
2469 see the IDs of currently known threads.
2471 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2472 @c doesn't support threads"?
2475 @cindex focus of debugging
2476 @cindex current thread
2477 The @value{GDBN} thread debugging facility allows you to observe all
2478 threads while your program runs---but whenever @value{GDBN} takes
2479 control, one thread in particular is always the focus of debugging.
2480 This thread is called the @dfn{current thread}. Debugging commands show
2481 program information from the perspective of the current thread.
2483 @cindex @code{New} @var{systag} message
2484 @cindex thread identifier (system)
2485 @c FIXME-implementors!! It would be more helpful if the [New...] message
2486 @c included GDB's numeric thread handle, so you could just go to that
2487 @c thread without first checking `info threads'.
2488 Whenever @value{GDBN} detects a new thread in your program, it displays
2489 the target system's identification for the thread with a message in the
2490 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2491 whose form varies depending on the particular system. For example, on
2492 @sc{gnu}/Linux, you might see
2495 [New Thread 46912507313328 (LWP 25582)]
2499 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2500 the @var{systag} is simply something like @samp{process 368}, with no
2503 @c FIXME!! (1) Does the [New...] message appear even for the very first
2504 @c thread of a program, or does it only appear for the
2505 @c second---i.e.@: when it becomes obvious we have a multithread
2507 @c (2) *Is* there necessarily a first thread always? Or do some
2508 @c multithread systems permit starting a program with multiple
2509 @c threads ab initio?
2511 @cindex thread number
2512 @cindex thread identifier (GDB)
2513 For debugging purposes, @value{GDBN} associates its own thread
2514 number---always a single integer---with each thread in your program.
2517 @kindex info threads
2519 Display a summary of all threads currently in your
2520 program. @value{GDBN} displays for each thread (in this order):
2524 the thread number assigned by @value{GDBN}
2527 the target system's thread identifier (@var{systag})
2530 the current stack frame summary for that thread
2534 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2535 indicates the current thread.
2539 @c end table here to get a little more width for example
2542 (@value{GDBP}) info threads
2543 3 process 35 thread 27 0x34e5 in sigpause ()
2544 2 process 35 thread 23 0x34e5 in sigpause ()
2545 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2551 @cindex debugging multithreaded programs (on HP-UX)
2552 @cindex thread identifier (GDB), on HP-UX
2553 For debugging purposes, @value{GDBN} associates its own thread
2554 number---a small integer assigned in thread-creation order---with each
2555 thread in your program.
2557 @cindex @code{New} @var{systag} message, on HP-UX
2558 @cindex thread identifier (system), on HP-UX
2559 @c FIXME-implementors!! It would be more helpful if the [New...] message
2560 @c included GDB's numeric thread handle, so you could just go to that
2561 @c thread without first checking `info threads'.
2562 Whenever @value{GDBN} detects a new thread in your program, it displays
2563 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2564 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2565 whose form varies depending on the particular system. For example, on
2569 [New thread 2 (system thread 26594)]
2573 when @value{GDBN} notices a new thread.
2576 @kindex info threads (HP-UX)
2578 Display a summary of all threads currently in your
2579 program. @value{GDBN} displays for each thread (in this order):
2582 @item the thread number assigned by @value{GDBN}
2584 @item the target system's thread identifier (@var{systag})
2586 @item the current stack frame summary for that thread
2590 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2591 indicates the current thread.
2595 @c end table here to get a little more width for example
2598 (@value{GDBP}) info threads
2599 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2601 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2602 from /usr/lib/libc.2
2603 1 system thread 27905 0x7b003498 in _brk () \@*
2604 from /usr/lib/libc.2
2607 On Solaris, you can display more information about user threads with a
2608 Solaris-specific command:
2611 @item maint info sol-threads
2612 @kindex maint info sol-threads
2613 @cindex thread info (Solaris)
2614 Display info on Solaris user threads.
2618 @kindex thread @var{threadno}
2619 @item thread @var{threadno}
2620 Make thread number @var{threadno} the current thread. The command
2621 argument @var{threadno} is the internal @value{GDBN} thread number, as
2622 shown in the first field of the @samp{info threads} display.
2623 @value{GDBN} responds by displaying the system identifier of the thread
2624 you selected, and its current stack frame summary:
2627 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2628 (@value{GDBP}) thread 2
2629 [Switching to process 35 thread 23]
2630 0x34e5 in sigpause ()
2634 As with the @samp{[New @dots{}]} message, the form of the text after
2635 @samp{Switching to} depends on your system's conventions for identifying
2638 @kindex thread apply
2639 @cindex apply command to several threads
2640 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2641 The @code{thread apply} command allows you to apply the named
2642 @var{command} to one or more threads. Specify the numbers of the
2643 threads that you want affected with the command argument
2644 @var{threadno}. It can be a single thread number, one of the numbers
2645 shown in the first field of the @samp{info threads} display; or it
2646 could be a range of thread numbers, as in @code{2-4}. To apply a
2647 command to all threads, type @kbd{thread apply all @var{command}}.
2649 @kindex set print thread-events
2650 @cindex print messages on thread start and exit
2651 @item set print thread-events
2652 @itemx set print thread-events on
2653 @itemx set print thread-events off
2654 The @code{set print thread-events} command allows you to enable or
2655 disable printing of messages when @value{GDBN} notices that new threads have
2656 started or that threads have exited. By default, these messages will
2657 be printed if detection of these events is supported by the target.
2658 Note that these messages cannot be disabled on all targets.
2660 @kindex show print thread-events
2661 @item show print thread-events
2662 Show whether messages will be printed when @value{GDBN} detects that threads
2663 have started and exited.
2666 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2667 more information about how @value{GDBN} behaves when you stop and start
2668 programs with multiple threads.
2670 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2671 watchpoints in programs with multiple threads.
2674 @kindex set libthread-db-search-path
2675 @cindex search path for @code{libthread_db}
2676 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2677 If this variable is set, @var{path} is a colon-separated list of
2678 directories @value{GDBN} will use to search for @code{libthread_db}.
2679 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2682 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2683 @code{libthread_db} library to obtain information about threads in the
2684 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2685 to find @code{libthread_db}. If that fails, @value{GDBN} will continue
2686 with default system shared library directories, and finally the directory
2687 from which @code{libpthread} was loaded in the inferior process.
2689 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2690 @value{GDBN} attempts to initialize it with the current inferior process.
2691 If this initialization fails (which could happen because of a version
2692 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2693 will unload @code{libthread_db}, and continue with the next directory.
2694 If none of @code{libthread_db} libraries initialize successfully,
2695 @value{GDBN} will issue a warning and thread debugging will be disabled.
2697 Setting @code{libthread-db-search-path} is currently implemented
2698 only on some platforms.
2700 @kindex show libthread-db-search-path
2701 @item show libthread-db-search-path
2702 Display current libthread_db search path.
2706 @section Debugging Programs with Multiple Processes
2708 @cindex fork, debugging programs which call
2709 @cindex multiple processes
2710 @cindex processes, multiple
2711 On most systems, @value{GDBN} has no special support for debugging
2712 programs which create additional processes using the @code{fork}
2713 function. When a program forks, @value{GDBN} will continue to debug the
2714 parent process and the child process will run unimpeded. If you have
2715 set a breakpoint in any code which the child then executes, the child
2716 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2717 will cause it to terminate.
2719 However, if you want to debug the child process there is a workaround
2720 which isn't too painful. Put a call to @code{sleep} in the code which
2721 the child process executes after the fork. It may be useful to sleep
2722 only if a certain environment variable is set, or a certain file exists,
2723 so that the delay need not occur when you don't want to run @value{GDBN}
2724 on the child. While the child is sleeping, use the @code{ps} program to
2725 get its process ID. Then tell @value{GDBN} (a new invocation of
2726 @value{GDBN} if you are also debugging the parent process) to attach to
2727 the child process (@pxref{Attach}). From that point on you can debug
2728 the child process just like any other process which you attached to.
2730 On some systems, @value{GDBN} provides support for debugging programs that
2731 create additional processes using the @code{fork} or @code{vfork} functions.
2732 Currently, the only platforms with this feature are HP-UX (11.x and later
2733 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2735 By default, when a program forks, @value{GDBN} will continue to debug
2736 the parent process and the child process will run unimpeded.
2738 If you want to follow the child process instead of the parent process,
2739 use the command @w{@code{set follow-fork-mode}}.
2742 @kindex set follow-fork-mode
2743 @item set follow-fork-mode @var{mode}
2744 Set the debugger response to a program call of @code{fork} or
2745 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2746 process. The @var{mode} argument can be:
2750 The original process is debugged after a fork. The child process runs
2751 unimpeded. This is the default.
2754 The new process is debugged after a fork. The parent process runs
2759 @kindex show follow-fork-mode
2760 @item show follow-fork-mode
2761 Display the current debugger response to a @code{fork} or @code{vfork} call.
2764 @cindex debugging multiple processes
2765 On Linux, if you want to debug both the parent and child processes, use the
2766 command @w{@code{set detach-on-fork}}.
2769 @kindex set detach-on-fork
2770 @item set detach-on-fork @var{mode}
2771 Tells gdb whether to detach one of the processes after a fork, or
2772 retain debugger control over them both.
2776 The child process (or parent process, depending on the value of
2777 @code{follow-fork-mode}) will be detached and allowed to run
2778 independently. This is the default.
2781 Both processes will be held under the control of @value{GDBN}.
2782 One process (child or parent, depending on the value of
2783 @code{follow-fork-mode}) is debugged as usual, while the other
2788 @kindex show detach-on-fork
2789 @item show detach-on-fork
2790 Show whether detach-on-fork mode is on/off.
2793 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
2794 will retain control of all forked processes (including nested forks).
2795 You can list the forked processes under the control of @value{GDBN} by
2796 using the @w{@code{info inferiors}} command, and switch from one fork
2797 to another by using the @code{inferior} command (@pxref{Inferiors,
2798 ,Debugging Multiple Inferiors}).
2800 To quit debugging one of the forked processes, you can either detach
2801 from it by using the @w{@code{detach inferior}} command (allowing it
2802 to run independently), or kill it using the @w{@code{kill inferior}}
2803 command. @xref{Inferiors, ,Debugging Multiple Inferiors}.
2805 If you ask to debug a child process and a @code{vfork} is followed by an
2806 @code{exec}, @value{GDBN} executes the new target up to the first
2807 breakpoint in the new target. If you have a breakpoint set on
2808 @code{main} in your original program, the breakpoint will also be set on
2809 the child process's @code{main}.
2811 On some systems, when a child process is spawned by @code{vfork}, you
2812 cannot debug the child or parent until an @code{exec} call completes.
2814 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2815 call executes, the new target restarts. To restart the parent process,
2816 use the @code{file} command with the parent executable name as its
2819 You can use the @code{catch} command to make @value{GDBN} stop whenever
2820 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2821 Catchpoints, ,Setting Catchpoints}.
2823 @node Checkpoint/Restart
2824 @section Setting a @emph{Bookmark} to Return to Later
2829 @cindex snapshot of a process
2830 @cindex rewind program state
2832 On certain operating systems@footnote{Currently, only
2833 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
2834 program's state, called a @dfn{checkpoint}, and come back to it
2837 Returning to a checkpoint effectively undoes everything that has
2838 happened in the program since the @code{checkpoint} was saved. This
2839 includes changes in memory, registers, and even (within some limits)
2840 system state. Effectively, it is like going back in time to the
2841 moment when the checkpoint was saved.
2843 Thus, if you're stepping thru a program and you think you're
2844 getting close to the point where things go wrong, you can save
2845 a checkpoint. Then, if you accidentally go too far and miss
2846 the critical statement, instead of having to restart your program
2847 from the beginning, you can just go back to the checkpoint and
2848 start again from there.
2850 This can be especially useful if it takes a lot of time or
2851 steps to reach the point where you think the bug occurs.
2853 To use the @code{checkpoint}/@code{restart} method of debugging:
2858 Save a snapshot of the debugged program's current execution state.
2859 The @code{checkpoint} command takes no arguments, but each checkpoint
2860 is assigned a small integer id, similar to a breakpoint id.
2862 @kindex info checkpoints
2863 @item info checkpoints
2864 List the checkpoints that have been saved in the current debugging
2865 session. For each checkpoint, the following information will be
2872 @item Source line, or label
2875 @kindex restart @var{checkpoint-id}
2876 @item restart @var{checkpoint-id}
2877 Restore the program state that was saved as checkpoint number
2878 @var{checkpoint-id}. All program variables, registers, stack frames
2879 etc.@: will be returned to the values that they had when the checkpoint
2880 was saved. In essence, gdb will ``wind back the clock'' to the point
2881 in time when the checkpoint was saved.
2883 Note that breakpoints, @value{GDBN} variables, command history etc.
2884 are not affected by restoring a checkpoint. In general, a checkpoint
2885 only restores things that reside in the program being debugged, not in
2888 @kindex delete checkpoint @var{checkpoint-id}
2889 @item delete checkpoint @var{checkpoint-id}
2890 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
2894 Returning to a previously saved checkpoint will restore the user state
2895 of the program being debugged, plus a significant subset of the system
2896 (OS) state, including file pointers. It won't ``un-write'' data from
2897 a file, but it will rewind the file pointer to the previous location,
2898 so that the previously written data can be overwritten. For files
2899 opened in read mode, the pointer will also be restored so that the
2900 previously read data can be read again.
2902 Of course, characters that have been sent to a printer (or other
2903 external device) cannot be ``snatched back'', and characters received
2904 from eg.@: a serial device can be removed from internal program buffers,
2905 but they cannot be ``pushed back'' into the serial pipeline, ready to
2906 be received again. Similarly, the actual contents of files that have
2907 been changed cannot be restored (at this time).
2909 However, within those constraints, you actually can ``rewind'' your
2910 program to a previously saved point in time, and begin debugging it
2911 again --- and you can change the course of events so as to debug a
2912 different execution path this time.
2914 @cindex checkpoints and process id
2915 Finally, there is one bit of internal program state that will be
2916 different when you return to a checkpoint --- the program's process
2917 id. Each checkpoint will have a unique process id (or @var{pid}),
2918 and each will be different from the program's original @var{pid}.
2919 If your program has saved a local copy of its process id, this could
2920 potentially pose a problem.
2922 @subsection A Non-obvious Benefit of Using Checkpoints
2924 On some systems such as @sc{gnu}/Linux, address space randomization
2925 is performed on new processes for security reasons. This makes it
2926 difficult or impossible to set a breakpoint, or watchpoint, on an
2927 absolute address if you have to restart the program, since the
2928 absolute location of a symbol will change from one execution to the
2931 A checkpoint, however, is an @emph{identical} copy of a process.
2932 Therefore if you create a checkpoint at (eg.@:) the start of main,
2933 and simply return to that checkpoint instead of restarting the
2934 process, you can avoid the effects of address randomization and
2935 your symbols will all stay in the same place.
2938 @chapter Stopping and Continuing
2940 The principal purposes of using a debugger are so that you can stop your
2941 program before it terminates; or so that, if your program runs into
2942 trouble, you can investigate and find out why.
2944 Inside @value{GDBN}, your program may stop for any of several reasons,
2945 such as a signal, a breakpoint, or reaching a new line after a
2946 @value{GDBN} command such as @code{step}. You may then examine and
2947 change variables, set new breakpoints or remove old ones, and then
2948 continue execution. Usually, the messages shown by @value{GDBN} provide
2949 ample explanation of the status of your program---but you can also
2950 explicitly request this information at any time.
2953 @kindex info program
2955 Display information about the status of your program: whether it is
2956 running or not, what process it is, and why it stopped.
2960 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2961 * Continuing and Stepping:: Resuming execution
2963 * Thread Stops:: Stopping and starting multi-thread programs
2967 @section Breakpoints, Watchpoints, and Catchpoints
2970 A @dfn{breakpoint} makes your program stop whenever a certain point in
2971 the program is reached. For each breakpoint, you can add conditions to
2972 control in finer detail whether your program stops. You can set
2973 breakpoints with the @code{break} command and its variants (@pxref{Set
2974 Breaks, ,Setting Breakpoints}), to specify the place where your program
2975 should stop by line number, function name or exact address in the
2978 On some systems, you can set breakpoints in shared libraries before
2979 the executable is run. There is a minor limitation on HP-UX systems:
2980 you must wait until the executable is run in order to set breakpoints
2981 in shared library routines that are not called directly by the program
2982 (for example, routines that are arguments in a @code{pthread_create}
2986 @cindex data breakpoints
2987 @cindex memory tracing
2988 @cindex breakpoint on memory address
2989 @cindex breakpoint on variable modification
2990 A @dfn{watchpoint} is a special breakpoint that stops your program
2991 when the value of an expression changes. The expression may be a value
2992 of a variable, or it could involve values of one or more variables
2993 combined by operators, such as @samp{a + b}. This is sometimes called
2994 @dfn{data breakpoints}. You must use a different command to set
2995 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
2996 from that, you can manage a watchpoint like any other breakpoint: you
2997 enable, disable, and delete both breakpoints and watchpoints using the
3000 You can arrange to have values from your program displayed automatically
3001 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3005 @cindex breakpoint on events
3006 A @dfn{catchpoint} is another special breakpoint that stops your program
3007 when a certain kind of event occurs, such as the throwing of a C@t{++}
3008 exception or the loading of a library. As with watchpoints, you use a
3009 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3010 Catchpoints}), but aside from that, you can manage a catchpoint like any
3011 other breakpoint. (To stop when your program receives a signal, use the
3012 @code{handle} command; see @ref{Signals, ,Signals}.)
3014 @cindex breakpoint numbers
3015 @cindex numbers for breakpoints
3016 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3017 catchpoint when you create it; these numbers are successive integers
3018 starting with one. In many of the commands for controlling various
3019 features of breakpoints you use the breakpoint number to say which
3020 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3021 @dfn{disabled}; if disabled, it has no effect on your program until you
3024 @cindex breakpoint ranges
3025 @cindex ranges of breakpoints
3026 Some @value{GDBN} commands accept a range of breakpoints on which to
3027 operate. A breakpoint range is either a single breakpoint number, like
3028 @samp{5}, or two such numbers, in increasing order, separated by a
3029 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3030 all breakpoints in that range are operated on.
3033 * Set Breaks:: Setting breakpoints
3034 * Set Watchpoints:: Setting watchpoints
3035 * Set Catchpoints:: Setting catchpoints
3036 * Delete Breaks:: Deleting breakpoints
3037 * Disabling:: Disabling breakpoints
3038 * Conditions:: Break conditions
3039 * Break Commands:: Breakpoint command lists
3040 * Error in Breakpoints:: ``Cannot insert breakpoints''
3041 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3045 @subsection Setting Breakpoints
3047 @c FIXME LMB what does GDB do if no code on line of breakpt?
3048 @c consider in particular declaration with/without initialization.
3050 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3053 @kindex b @r{(@code{break})}
3054 @vindex $bpnum@r{, convenience variable}
3055 @cindex latest breakpoint
3056 Breakpoints are set with the @code{break} command (abbreviated
3057 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3058 number of the breakpoint you've set most recently; see @ref{Convenience
3059 Vars,, Convenience Variables}, for a discussion of what you can do with
3060 convenience variables.
3063 @item break @var{location}
3064 Set a breakpoint at the given @var{location}, which can specify a
3065 function name, a line number, or an address of an instruction.
3066 (@xref{Specify Location}, for a list of all the possible ways to
3067 specify a @var{location}.) The breakpoint will stop your program just
3068 before it executes any of the code in the specified @var{location}.
3070 When using source languages that permit overloading of symbols, such as
3071 C@t{++}, a function name may refer to more than one possible place to break.
3072 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3075 It is also possible to insert a breakpoint that will stop the program
3076 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3077 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3080 When called without any arguments, @code{break} sets a breakpoint at
3081 the next instruction to be executed in the selected stack frame
3082 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3083 innermost, this makes your program stop as soon as control
3084 returns to that frame. This is similar to the effect of a
3085 @code{finish} command in the frame inside the selected frame---except
3086 that @code{finish} does not leave an active breakpoint. If you use
3087 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3088 the next time it reaches the current location; this may be useful
3091 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3092 least one instruction has been executed. If it did not do this, you
3093 would be unable to proceed past a breakpoint without first disabling the
3094 breakpoint. This rule applies whether or not the breakpoint already
3095 existed when your program stopped.
3097 @item break @dots{} if @var{cond}
3098 Set a breakpoint with condition @var{cond}; evaluate the expression
3099 @var{cond} each time the breakpoint is reached, and stop only if the
3100 value is nonzero---that is, if @var{cond} evaluates as true.
3101 @samp{@dots{}} stands for one of the possible arguments described
3102 above (or no argument) specifying where to break. @xref{Conditions,
3103 ,Break Conditions}, for more information on breakpoint conditions.
3106 @item tbreak @var{args}
3107 Set a breakpoint enabled only for one stop. @var{args} are the
3108 same as for the @code{break} command, and the breakpoint is set in the same
3109 way, but the breakpoint is automatically deleted after the first time your
3110 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3113 @cindex hardware breakpoints
3114 @item hbreak @var{args}
3115 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3116 @code{break} command and the breakpoint is set in the same way, but the
3117 breakpoint requires hardware support and some target hardware may not
3118 have this support. The main purpose of this is EPROM/ROM code
3119 debugging, so you can set a breakpoint at an instruction without
3120 changing the instruction. This can be used with the new trap-generation
3121 provided by SPARClite DSU and most x86-based targets. These targets
3122 will generate traps when a program accesses some data or instruction
3123 address that is assigned to the debug registers. However the hardware
3124 breakpoint registers can take a limited number of breakpoints. For
3125 example, on the DSU, only two data breakpoints can be set at a time, and
3126 @value{GDBN} will reject this command if more than two are used. Delete
3127 or disable unused hardware breakpoints before setting new ones
3128 (@pxref{Disabling, ,Disabling Breakpoints}).
3129 @xref{Conditions, ,Break Conditions}.
3130 For remote targets, you can restrict the number of hardware
3131 breakpoints @value{GDBN} will use, see @ref{set remote
3132 hardware-breakpoint-limit}.
3135 @item thbreak @var{args}
3136 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3137 are the same as for the @code{hbreak} command and the breakpoint is set in
3138 the same way. However, like the @code{tbreak} command,
3139 the breakpoint is automatically deleted after the
3140 first time your program stops there. Also, like the @code{hbreak}
3141 command, the breakpoint requires hardware support and some target hardware
3142 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3143 See also @ref{Conditions, ,Break Conditions}.
3146 @cindex regular expression
3147 @cindex breakpoints in functions matching a regexp
3148 @cindex set breakpoints in many functions
3149 @item rbreak @var{regex}
3150 Set breakpoints on all functions matching the regular expression
3151 @var{regex}. This command sets an unconditional breakpoint on all
3152 matches, printing a list of all breakpoints it set. Once these
3153 breakpoints are set, they are treated just like the breakpoints set with
3154 the @code{break} command. You can delete them, disable them, or make
3155 them conditional the same way as any other breakpoint.
3157 The syntax of the regular expression is the standard one used with tools
3158 like @file{grep}. Note that this is different from the syntax used by
3159 shells, so for instance @code{foo*} matches all functions that include
3160 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3161 @code{.*} leading and trailing the regular expression you supply, so to
3162 match only functions that begin with @code{foo}, use @code{^foo}.
3164 @cindex non-member C@t{++} functions, set breakpoint in
3165 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3166 breakpoints on overloaded functions that are not members of any special
3169 @cindex set breakpoints on all functions
3170 The @code{rbreak} command can be used to set breakpoints in
3171 @strong{all} the functions in a program, like this:
3174 (@value{GDBP}) rbreak .
3177 @kindex info breakpoints
3178 @cindex @code{$_} and @code{info breakpoints}
3179 @item info breakpoints @r{[}@var{n}@r{]}
3180 @itemx info break @r{[}@var{n}@r{]}
3181 @itemx info watchpoints @r{[}@var{n}@r{]}
3182 Print a table of all breakpoints, watchpoints, and catchpoints set and
3183 not deleted. Optional argument @var{n} means print information only
3184 about the specified breakpoint (or watchpoint or catchpoint). For
3185 each breakpoint, following columns are printed:
3188 @item Breakpoint Numbers
3190 Breakpoint, watchpoint, or catchpoint.
3192 Whether the breakpoint is marked to be disabled or deleted when hit.
3193 @item Enabled or Disabled
3194 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3195 that are not enabled.
3197 Where the breakpoint is in your program, as a memory address. For a
3198 pending breakpoint whose address is not yet known, this field will
3199 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3200 library that has the symbol or line referred by breakpoint is loaded.
3201 See below for details. A breakpoint with several locations will
3202 have @samp{<MULTIPLE>} in this field---see below for details.
3204 Where the breakpoint is in the source for your program, as a file and
3205 line number. For a pending breakpoint, the original string passed to
3206 the breakpoint command will be listed as it cannot be resolved until
3207 the appropriate shared library is loaded in the future.
3211 If a breakpoint is conditional, @code{info break} shows the condition on
3212 the line following the affected breakpoint; breakpoint commands, if any,
3213 are listed after that. A pending breakpoint is allowed to have a condition
3214 specified for it. The condition is not parsed for validity until a shared
3215 library is loaded that allows the pending breakpoint to resolve to a
3219 @code{info break} with a breakpoint
3220 number @var{n} as argument lists only that breakpoint. The
3221 convenience variable @code{$_} and the default examining-address for
3222 the @code{x} command are set to the address of the last breakpoint
3223 listed (@pxref{Memory, ,Examining Memory}).
3226 @code{info break} displays a count of the number of times the breakpoint
3227 has been hit. This is especially useful in conjunction with the
3228 @code{ignore} command. You can ignore a large number of breakpoint
3229 hits, look at the breakpoint info to see how many times the breakpoint
3230 was hit, and then run again, ignoring one less than that number. This
3231 will get you quickly to the last hit of that breakpoint.
3234 @value{GDBN} allows you to set any number of breakpoints at the same place in
3235 your program. There is nothing silly or meaningless about this. When
3236 the breakpoints are conditional, this is even useful
3237 (@pxref{Conditions, ,Break Conditions}).
3239 @cindex multiple locations, breakpoints
3240 @cindex breakpoints, multiple locations
3241 It is possible that a breakpoint corresponds to several locations
3242 in your program. Examples of this situation are:
3246 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3247 instances of the function body, used in different cases.
3250 For a C@t{++} template function, a given line in the function can
3251 correspond to any number of instantiations.
3254 For an inlined function, a given source line can correspond to
3255 several places where that function is inlined.
3258 In all those cases, @value{GDBN} will insert a breakpoint at all
3259 the relevant locations@footnote{
3260 As of this writing, multiple-location breakpoints work only if there's
3261 line number information for all the locations. This means that they
3262 will generally not work in system libraries, unless you have debug
3263 info with line numbers for them.}.
3265 A breakpoint with multiple locations is displayed in the breakpoint
3266 table using several rows---one header row, followed by one row for
3267 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3268 address column. The rows for individual locations contain the actual
3269 addresses for locations, and show the functions to which those
3270 locations belong. The number column for a location is of the form
3271 @var{breakpoint-number}.@var{location-number}.
3276 Num Type Disp Enb Address What
3277 1 breakpoint keep y <MULTIPLE>
3279 breakpoint already hit 1 time
3280 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3281 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3284 Each location can be individually enabled or disabled by passing
3285 @var{breakpoint-number}.@var{location-number} as argument to the
3286 @code{enable} and @code{disable} commands. Note that you cannot
3287 delete the individual locations from the list, you can only delete the
3288 entire list of locations that belong to their parent breakpoint (with
3289 the @kbd{delete @var{num}} command, where @var{num} is the number of
3290 the parent breakpoint, 1 in the above example). Disabling or enabling
3291 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3292 that belong to that breakpoint.
3294 @cindex pending breakpoints
3295 It's quite common to have a breakpoint inside a shared library.
3296 Shared libraries can be loaded and unloaded explicitly,
3297 and possibly repeatedly, as the program is executed. To support
3298 this use case, @value{GDBN} updates breakpoint locations whenever
3299 any shared library is loaded or unloaded. Typically, you would
3300 set a breakpoint in a shared library at the beginning of your
3301 debugging session, when the library is not loaded, and when the
3302 symbols from the library are not available. When you try to set
3303 breakpoint, @value{GDBN} will ask you if you want to set
3304 a so called @dfn{pending breakpoint}---breakpoint whose address
3305 is not yet resolved.
3307 After the program is run, whenever a new shared library is loaded,
3308 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3309 shared library contains the symbol or line referred to by some
3310 pending breakpoint, that breakpoint is resolved and becomes an
3311 ordinary breakpoint. When a library is unloaded, all breakpoints
3312 that refer to its symbols or source lines become pending again.
3314 This logic works for breakpoints with multiple locations, too. For
3315 example, if you have a breakpoint in a C@t{++} template function, and
3316 a newly loaded shared library has an instantiation of that template,
3317 a new location is added to the list of locations for the breakpoint.
3319 Except for having unresolved address, pending breakpoints do not
3320 differ from regular breakpoints. You can set conditions or commands,
3321 enable and disable them and perform other breakpoint operations.
3323 @value{GDBN} provides some additional commands for controlling what
3324 happens when the @samp{break} command cannot resolve breakpoint
3325 address specification to an address:
3327 @kindex set breakpoint pending
3328 @kindex show breakpoint pending
3330 @item set breakpoint pending auto
3331 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3332 location, it queries you whether a pending breakpoint should be created.
3334 @item set breakpoint pending on
3335 This indicates that an unrecognized breakpoint location should automatically
3336 result in a pending breakpoint being created.
3338 @item set breakpoint pending off
3339 This indicates that pending breakpoints are not to be created. Any
3340 unrecognized breakpoint location results in an error. This setting does
3341 not affect any pending breakpoints previously created.
3343 @item show breakpoint pending
3344 Show the current behavior setting for creating pending breakpoints.
3347 The settings above only affect the @code{break} command and its
3348 variants. Once breakpoint is set, it will be automatically updated
3349 as shared libraries are loaded and unloaded.
3351 @cindex automatic hardware breakpoints
3352 For some targets, @value{GDBN} can automatically decide if hardware or
3353 software breakpoints should be used, depending on whether the
3354 breakpoint address is read-only or read-write. This applies to
3355 breakpoints set with the @code{break} command as well as to internal
3356 breakpoints set by commands like @code{next} and @code{finish}. For
3357 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3360 You can control this automatic behaviour with the following commands::
3362 @kindex set breakpoint auto-hw
3363 @kindex show breakpoint auto-hw
3365 @item set breakpoint auto-hw on
3366 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3367 will try to use the target memory map to decide if software or hardware
3368 breakpoint must be used.
3370 @item set breakpoint auto-hw off
3371 This indicates @value{GDBN} should not automatically select breakpoint
3372 type. If the target provides a memory map, @value{GDBN} will warn when
3373 trying to set software breakpoint at a read-only address.
3376 @value{GDBN} normally implements breakpoints by replacing the program code
3377 at the breakpoint address with a special instruction, which, when
3378 executed, given control to the debugger. By default, the program
3379 code is so modified only when the program is resumed. As soon as
3380 the program stops, @value{GDBN} restores the original instructions. This
3381 behaviour guards against leaving breakpoints inserted in the
3382 target should gdb abrubptly disconnect. However, with slow remote
3383 targets, inserting and removing breakpoint can reduce the performance.
3384 This behavior can be controlled with the following commands::
3386 @kindex set breakpoint always-inserted
3387 @kindex show breakpoint always-inserted
3389 @item set breakpoint always-inserted off
3390 All breakpoints, including newly added by the user, are inserted in
3391 the target only when the target is resumed. All breakpoints are
3392 removed from the target when it stops.
3394 @item set breakpoint always-inserted on
3395 Causes all breakpoints to be inserted in the target at all times. If
3396 the user adds a new breakpoint, or changes an existing breakpoint, the
3397 breakpoints in the target are updated immediately. A breakpoint is
3398 removed from the target only when breakpoint itself is removed.
3400 @cindex non-stop mode, and @code{breakpoint always-inserted}
3401 @item set breakpoint always-inserted auto
3402 This is the default mode. If @value{GDBN} is controlling the inferior
3403 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3404 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3405 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3406 @code{breakpoint always-inserted} mode is off.
3409 @cindex negative breakpoint numbers
3410 @cindex internal @value{GDBN} breakpoints
3411 @value{GDBN} itself sometimes sets breakpoints in your program for
3412 special purposes, such as proper handling of @code{longjmp} (in C
3413 programs). These internal breakpoints are assigned negative numbers,
3414 starting with @code{-1}; @samp{info breakpoints} does not display them.
3415 You can see these breakpoints with the @value{GDBN} maintenance command
3416 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3419 @node Set Watchpoints
3420 @subsection Setting Watchpoints
3422 @cindex setting watchpoints
3423 You can use a watchpoint to stop execution whenever the value of an
3424 expression changes, without having to predict a particular place where
3425 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3426 The expression may be as simple as the value of a single variable, or
3427 as complex as many variables combined by operators. Examples include:
3431 A reference to the value of a single variable.
3434 An address cast to an appropriate data type. For example,
3435 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3436 address (assuming an @code{int} occupies 4 bytes).
3439 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3440 expression can use any operators valid in the program's native
3441 language (@pxref{Languages}).
3444 You can set a watchpoint on an expression even if the expression can
3445 not be evaluated yet. For instance, you can set a watchpoint on
3446 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3447 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3448 the expression produces a valid value. If the expression becomes
3449 valid in some other way than changing a variable (e.g.@: if the memory
3450 pointed to by @samp{*global_ptr} becomes readable as the result of a
3451 @code{malloc} call), @value{GDBN} may not stop until the next time
3452 the expression changes.
3454 @cindex software watchpoints
3455 @cindex hardware watchpoints
3456 Depending on your system, watchpoints may be implemented in software or
3457 hardware. @value{GDBN} does software watchpointing by single-stepping your
3458 program and testing the variable's value each time, which is hundreds of
3459 times slower than normal execution. (But this may still be worth it, to
3460 catch errors where you have no clue what part of your program is the
3463 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3464 x86-based targets, @value{GDBN} includes support for hardware
3465 watchpoints, which do not slow down the running of your program.
3469 @item watch @var{expr} @r{[}thread @var{threadnum}@r{]}
3470 Set a watchpoint for an expression. @value{GDBN} will break when the
3471 expression @var{expr} is written into by the program and its value
3472 changes. The simplest (and the most popular) use of this command is
3473 to watch the value of a single variable:
3476 (@value{GDBP}) watch foo
3479 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3480 clause, @value{GDBN} breaks only when the thread identified by
3481 @var{threadnum} changes the value of @var{expr}. If any other threads
3482 change the value of @var{expr}, @value{GDBN} will not break. Note
3483 that watchpoints restricted to a single thread in this way only work
3484 with Hardware Watchpoints.
3487 @item rwatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3488 Set a watchpoint that will break when the value of @var{expr} is read
3492 @item awatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3493 Set a watchpoint that will break when @var{expr} is either read from
3494 or written into by the program.
3496 @kindex info watchpoints @r{[}@var{n}@r{]}
3497 @item info watchpoints
3498 This command prints a list of watchpoints, breakpoints, and catchpoints;
3499 it is the same as @code{info break} (@pxref{Set Breaks}).
3502 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3503 watchpoints execute very quickly, and the debugger reports a change in
3504 value at the exact instruction where the change occurs. If @value{GDBN}
3505 cannot set a hardware watchpoint, it sets a software watchpoint, which
3506 executes more slowly and reports the change in value at the next
3507 @emph{statement}, not the instruction, after the change occurs.
3509 @cindex use only software watchpoints
3510 You can force @value{GDBN} to use only software watchpoints with the
3511 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3512 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3513 the underlying system supports them. (Note that hardware-assisted
3514 watchpoints that were set @emph{before} setting
3515 @code{can-use-hw-watchpoints} to zero will still use the hardware
3516 mechanism of watching expression values.)
3519 @item set can-use-hw-watchpoints
3520 @kindex set can-use-hw-watchpoints
3521 Set whether or not to use hardware watchpoints.
3523 @item show can-use-hw-watchpoints
3524 @kindex show can-use-hw-watchpoints
3525 Show the current mode of using hardware watchpoints.
3528 For remote targets, you can restrict the number of hardware
3529 watchpoints @value{GDBN} will use, see @ref{set remote
3530 hardware-breakpoint-limit}.
3532 When you issue the @code{watch} command, @value{GDBN} reports
3535 Hardware watchpoint @var{num}: @var{expr}
3539 if it was able to set a hardware watchpoint.
3541 Currently, the @code{awatch} and @code{rwatch} commands can only set
3542 hardware watchpoints, because accesses to data that don't change the
3543 value of the watched expression cannot be detected without examining
3544 every instruction as it is being executed, and @value{GDBN} does not do
3545 that currently. If @value{GDBN} finds that it is unable to set a
3546 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3547 will print a message like this:
3550 Expression cannot be implemented with read/access watchpoint.
3553 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3554 data type of the watched expression is wider than what a hardware
3555 watchpoint on the target machine can handle. For example, some systems
3556 can only watch regions that are up to 4 bytes wide; on such systems you
3557 cannot set hardware watchpoints for an expression that yields a
3558 double-precision floating-point number (which is typically 8 bytes
3559 wide). As a work-around, it might be possible to break the large region
3560 into a series of smaller ones and watch them with separate watchpoints.
3562 If you set too many hardware watchpoints, @value{GDBN} might be unable
3563 to insert all of them when you resume the execution of your program.
3564 Since the precise number of active watchpoints is unknown until such
3565 time as the program is about to be resumed, @value{GDBN} might not be
3566 able to warn you about this when you set the watchpoints, and the
3567 warning will be printed only when the program is resumed:
3570 Hardware watchpoint @var{num}: Could not insert watchpoint
3574 If this happens, delete or disable some of the watchpoints.
3576 Watching complex expressions that reference many variables can also
3577 exhaust the resources available for hardware-assisted watchpoints.
3578 That's because @value{GDBN} needs to watch every variable in the
3579 expression with separately allocated resources.
3581 If you call a function interactively using @code{print} or @code{call},
3582 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3583 kind of breakpoint or the call completes.
3585 @value{GDBN} automatically deletes watchpoints that watch local
3586 (automatic) variables, or expressions that involve such variables, when
3587 they go out of scope, that is, when the execution leaves the block in
3588 which these variables were defined. In particular, when the program
3589 being debugged terminates, @emph{all} local variables go out of scope,
3590 and so only watchpoints that watch global variables remain set. If you
3591 rerun the program, you will need to set all such watchpoints again. One
3592 way of doing that would be to set a code breakpoint at the entry to the
3593 @code{main} function and when it breaks, set all the watchpoints.
3595 @cindex watchpoints and threads
3596 @cindex threads and watchpoints
3597 In multi-threaded programs, watchpoints will detect changes to the
3598 watched expression from every thread.
3601 @emph{Warning:} In multi-threaded programs, software watchpoints
3602 have only limited usefulness. If @value{GDBN} creates a software
3603 watchpoint, it can only watch the value of an expression @emph{in a
3604 single thread}. If you are confident that the expression can only
3605 change due to the current thread's activity (and if you are also
3606 confident that no other thread can become current), then you can use
3607 software watchpoints as usual. However, @value{GDBN} may not notice
3608 when a non-current thread's activity changes the expression. (Hardware
3609 watchpoints, in contrast, watch an expression in all threads.)
3612 @xref{set remote hardware-watchpoint-limit}.
3614 @node Set Catchpoints
3615 @subsection Setting Catchpoints
3616 @cindex catchpoints, setting
3617 @cindex exception handlers
3618 @cindex event handling
3620 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3621 kinds of program events, such as C@t{++} exceptions or the loading of a
3622 shared library. Use the @code{catch} command to set a catchpoint.
3626 @item catch @var{event}
3627 Stop when @var{event} occurs. @var{event} can be any of the following:
3630 @cindex stop on C@t{++} exceptions
3631 The throwing of a C@t{++} exception.
3634 The catching of a C@t{++} exception.
3637 @cindex Ada exception catching
3638 @cindex catch Ada exceptions
3639 An Ada exception being raised. If an exception name is specified
3640 at the end of the command (eg @code{catch exception Program_Error}),
3641 the debugger will stop only when this specific exception is raised.
3642 Otherwise, the debugger stops execution when any Ada exception is raised.
3644 When inserting an exception catchpoint on a user-defined exception whose
3645 name is identical to one of the exceptions defined by the language, the
3646 fully qualified name must be used as the exception name. Otherwise,
3647 @value{GDBN} will assume that it should stop on the pre-defined exception
3648 rather than the user-defined one. For instance, assuming an exception
3649 called @code{Constraint_Error} is defined in package @code{Pck}, then
3650 the command to use to catch such exceptions is @kbd{catch exception
3651 Pck.Constraint_Error}.
3653 @item exception unhandled
3654 An exception that was raised but is not handled by the program.
3657 A failed Ada assertion.
3660 @cindex break on fork/exec
3661 A call to @code{exec}. This is currently only available for HP-UX
3665 A call to @code{fork}. This is currently only available for HP-UX
3669 A call to @code{vfork}. This is currently only available for HP-UX
3674 @item tcatch @var{event}
3675 Set a catchpoint that is enabled only for one stop. The catchpoint is
3676 automatically deleted after the first time the event is caught.
3680 Use the @code{info break} command to list the current catchpoints.
3682 There are currently some limitations to C@t{++} exception handling
3683 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3687 If you call a function interactively, @value{GDBN} normally returns
3688 control to you when the function has finished executing. If the call
3689 raises an exception, however, the call may bypass the mechanism that
3690 returns control to you and cause your program either to abort or to
3691 simply continue running until it hits a breakpoint, catches a signal
3692 that @value{GDBN} is listening for, or exits. This is the case even if
3693 you set a catchpoint for the exception; catchpoints on exceptions are
3694 disabled within interactive calls.
3697 You cannot raise an exception interactively.
3700 You cannot install an exception handler interactively.
3703 @cindex raise exceptions
3704 Sometimes @code{catch} is not the best way to debug exception handling:
3705 if you need to know exactly where an exception is raised, it is better to
3706 stop @emph{before} the exception handler is called, since that way you
3707 can see the stack before any unwinding takes place. If you set a
3708 breakpoint in an exception handler instead, it may not be easy to find
3709 out where the exception was raised.
3711 To stop just before an exception handler is called, you need some
3712 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3713 raised by calling a library function named @code{__raise_exception}
3714 which has the following ANSI C interface:
3717 /* @var{addr} is where the exception identifier is stored.
3718 @var{id} is the exception identifier. */
3719 void __raise_exception (void **addr, void *id);
3723 To make the debugger catch all exceptions before any stack
3724 unwinding takes place, set a breakpoint on @code{__raise_exception}
3725 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
3727 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
3728 that depends on the value of @var{id}, you can stop your program when
3729 a specific exception is raised. You can use multiple conditional
3730 breakpoints to stop your program when any of a number of exceptions are
3735 @subsection Deleting Breakpoints
3737 @cindex clearing breakpoints, watchpoints, catchpoints
3738 @cindex deleting breakpoints, watchpoints, catchpoints
3739 It is often necessary to eliminate a breakpoint, watchpoint, or
3740 catchpoint once it has done its job and you no longer want your program
3741 to stop there. This is called @dfn{deleting} the breakpoint. A
3742 breakpoint that has been deleted no longer exists; it is forgotten.
3744 With the @code{clear} command you can delete breakpoints according to
3745 where they are in your program. With the @code{delete} command you can
3746 delete individual breakpoints, watchpoints, or catchpoints by specifying
3747 their breakpoint numbers.
3749 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3750 automatically ignores breakpoints on the first instruction to be executed
3751 when you continue execution without changing the execution address.
3756 Delete any breakpoints at the next instruction to be executed in the
3757 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
3758 the innermost frame is selected, this is a good way to delete a
3759 breakpoint where your program just stopped.
3761 @item clear @var{location}
3762 Delete any breakpoints set at the specified @var{location}.
3763 @xref{Specify Location}, for the various forms of @var{location}; the
3764 most useful ones are listed below:
3767 @item clear @var{function}
3768 @itemx clear @var{filename}:@var{function}
3769 Delete any breakpoints set at entry to the named @var{function}.
3771 @item clear @var{linenum}
3772 @itemx clear @var{filename}:@var{linenum}
3773 Delete any breakpoints set at or within the code of the specified
3774 @var{linenum} of the specified @var{filename}.
3777 @cindex delete breakpoints
3779 @kindex d @r{(@code{delete})}
3780 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3781 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3782 ranges specified as arguments. If no argument is specified, delete all
3783 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3784 confirm off}). You can abbreviate this command as @code{d}.
3788 @subsection Disabling Breakpoints
3790 @cindex enable/disable a breakpoint
3791 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3792 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3793 it had been deleted, but remembers the information on the breakpoint so
3794 that you can @dfn{enable} it again later.
3796 You disable and enable breakpoints, watchpoints, and catchpoints with
3797 the @code{enable} and @code{disable} commands, optionally specifying one
3798 or more breakpoint numbers as arguments. Use @code{info break} or
3799 @code{info watch} to print a list of breakpoints, watchpoints, and
3800 catchpoints if you do not know which numbers to use.
3802 Disabling and enabling a breakpoint that has multiple locations
3803 affects all of its locations.
3805 A breakpoint, watchpoint, or catchpoint can have any of four different
3806 states of enablement:
3810 Enabled. The breakpoint stops your program. A breakpoint set
3811 with the @code{break} command starts out in this state.
3813 Disabled. The breakpoint has no effect on your program.
3815 Enabled once. The breakpoint stops your program, but then becomes
3818 Enabled for deletion. The breakpoint stops your program, but
3819 immediately after it does so it is deleted permanently. A breakpoint
3820 set with the @code{tbreak} command starts out in this state.
3823 You can use the following commands to enable or disable breakpoints,
3824 watchpoints, and catchpoints:
3828 @kindex dis @r{(@code{disable})}
3829 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3830 Disable the specified breakpoints---or all breakpoints, if none are
3831 listed. A disabled breakpoint has no effect but is not forgotten. All
3832 options such as ignore-counts, conditions and commands are remembered in
3833 case the breakpoint is enabled again later. You may abbreviate
3834 @code{disable} as @code{dis}.
3837 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3838 Enable the specified breakpoints (or all defined breakpoints). They
3839 become effective once again in stopping your program.
3841 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3842 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3843 of these breakpoints immediately after stopping your program.
3845 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3846 Enable the specified breakpoints to work once, then die. @value{GDBN}
3847 deletes any of these breakpoints as soon as your program stops there.
3848 Breakpoints set by the @code{tbreak} command start out in this state.
3851 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3852 @c confusing: tbreak is also initially enabled.
3853 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3854 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
3855 subsequently, they become disabled or enabled only when you use one of
3856 the commands above. (The command @code{until} can set and delete a
3857 breakpoint of its own, but it does not change the state of your other
3858 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3862 @subsection Break Conditions
3863 @cindex conditional breakpoints
3864 @cindex breakpoint conditions
3866 @c FIXME what is scope of break condition expr? Context where wanted?
3867 @c in particular for a watchpoint?
3868 The simplest sort of breakpoint breaks every time your program reaches a
3869 specified place. You can also specify a @dfn{condition} for a
3870 breakpoint. A condition is just a Boolean expression in your
3871 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3872 a condition evaluates the expression each time your program reaches it,
3873 and your program stops only if the condition is @emph{true}.
3875 This is the converse of using assertions for program validation; in that
3876 situation, you want to stop when the assertion is violated---that is,
3877 when the condition is false. In C, if you want to test an assertion expressed
3878 by the condition @var{assert}, you should set the condition
3879 @samp{! @var{assert}} on the appropriate breakpoint.
3881 Conditions are also accepted for watchpoints; you may not need them,
3882 since a watchpoint is inspecting the value of an expression anyhow---but
3883 it might be simpler, say, to just set a watchpoint on a variable name,
3884 and specify a condition that tests whether the new value is an interesting
3887 Break conditions can have side effects, and may even call functions in
3888 your program. This can be useful, for example, to activate functions
3889 that log program progress, or to use your own print functions to
3890 format special data structures. The effects are completely predictable
3891 unless there is another enabled breakpoint at the same address. (In
3892 that case, @value{GDBN} might see the other breakpoint first and stop your
3893 program without checking the condition of this one.) Note that
3894 breakpoint commands are usually more convenient and flexible than break
3896 purpose of performing side effects when a breakpoint is reached
3897 (@pxref{Break Commands, ,Breakpoint Command Lists}).
3899 Break conditions can be specified when a breakpoint is set, by using
3900 @samp{if} in the arguments to the @code{break} command. @xref{Set
3901 Breaks, ,Setting Breakpoints}. They can also be changed at any time
3902 with the @code{condition} command.
3904 You can also use the @code{if} keyword with the @code{watch} command.
3905 The @code{catch} command does not recognize the @code{if} keyword;
3906 @code{condition} is the only way to impose a further condition on a
3911 @item condition @var{bnum} @var{expression}
3912 Specify @var{expression} as the break condition for breakpoint,
3913 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3914 breakpoint @var{bnum} stops your program only if the value of
3915 @var{expression} is true (nonzero, in C). When you use
3916 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3917 syntactic correctness, and to determine whether symbols in it have
3918 referents in the context of your breakpoint. If @var{expression} uses
3919 symbols not referenced in the context of the breakpoint, @value{GDBN}
3920 prints an error message:
3923 No symbol "foo" in current context.
3928 not actually evaluate @var{expression} at the time the @code{condition}
3929 command (or a command that sets a breakpoint with a condition, like
3930 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3932 @item condition @var{bnum}
3933 Remove the condition from breakpoint number @var{bnum}. It becomes
3934 an ordinary unconditional breakpoint.
3937 @cindex ignore count (of breakpoint)
3938 A special case of a breakpoint condition is to stop only when the
3939 breakpoint has been reached a certain number of times. This is so
3940 useful that there is a special way to do it, using the @dfn{ignore
3941 count} of the breakpoint. Every breakpoint has an ignore count, which
3942 is an integer. Most of the time, the ignore count is zero, and
3943 therefore has no effect. But if your program reaches a breakpoint whose
3944 ignore count is positive, then instead of stopping, it just decrements
3945 the ignore count by one and continues. As a result, if the ignore count
3946 value is @var{n}, the breakpoint does not stop the next @var{n} times
3947 your program reaches it.
3951 @item ignore @var{bnum} @var{count}
3952 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3953 The next @var{count} times the breakpoint is reached, your program's
3954 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3957 To make the breakpoint stop the next time it is reached, specify
3960 When you use @code{continue} to resume execution of your program from a
3961 breakpoint, you can specify an ignore count directly as an argument to
3962 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3963 Stepping,,Continuing and Stepping}.
3965 If a breakpoint has a positive ignore count and a condition, the
3966 condition is not checked. Once the ignore count reaches zero,
3967 @value{GDBN} resumes checking the condition.
3969 You could achieve the effect of the ignore count with a condition such
3970 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3971 is decremented each time. @xref{Convenience Vars, ,Convenience
3975 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3978 @node Break Commands
3979 @subsection Breakpoint Command Lists
3981 @cindex breakpoint commands
3982 You can give any breakpoint (or watchpoint or catchpoint) a series of
3983 commands to execute when your program stops due to that breakpoint. For
3984 example, you might want to print the values of certain expressions, or
3985 enable other breakpoints.
3989 @kindex end@r{ (breakpoint commands)}
3990 @item commands @r{[}@var{bnum}@r{]}
3991 @itemx @dots{} @var{command-list} @dots{}
3993 Specify a list of commands for breakpoint number @var{bnum}. The commands
3994 themselves appear on the following lines. Type a line containing just
3995 @code{end} to terminate the commands.
3997 To remove all commands from a breakpoint, type @code{commands} and
3998 follow it immediately with @code{end}; that is, give no commands.
4000 With no @var{bnum} argument, @code{commands} refers to the last
4001 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
4002 recently encountered).
4005 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4006 disabled within a @var{command-list}.
4008 You can use breakpoint commands to start your program up again. Simply
4009 use the @code{continue} command, or @code{step}, or any other command
4010 that resumes execution.
4012 Any other commands in the command list, after a command that resumes
4013 execution, are ignored. This is because any time you resume execution
4014 (even with a simple @code{next} or @code{step}), you may encounter
4015 another breakpoint---which could have its own command list, leading to
4016 ambiguities about which list to execute.
4019 If the first command you specify in a command list is @code{silent}, the
4020 usual message about stopping at a breakpoint is not printed. This may
4021 be desirable for breakpoints that are to print a specific message and
4022 then continue. If none of the remaining commands print anything, you
4023 see no sign that the breakpoint was reached. @code{silent} is
4024 meaningful only at the beginning of a breakpoint command list.
4026 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4027 print precisely controlled output, and are often useful in silent
4028 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4030 For example, here is how you could use breakpoint commands to print the
4031 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4037 printf "x is %d\n",x
4042 One application for breakpoint commands is to compensate for one bug so
4043 you can test for another. Put a breakpoint just after the erroneous line
4044 of code, give it a condition to detect the case in which something
4045 erroneous has been done, and give it commands to assign correct values
4046 to any variables that need them. End with the @code{continue} command
4047 so that your program does not stop, and start with the @code{silent}
4048 command so that no output is produced. Here is an example:
4059 @c @ifclear BARETARGET
4060 @node Error in Breakpoints
4061 @subsection ``Cannot insert breakpoints''
4063 If you request too many active hardware-assisted breakpoints and
4064 watchpoints, you will see this error message:
4066 @c FIXME: the precise wording of this message may change; the relevant
4067 @c source change is not committed yet (Sep 3, 1999).
4069 Stopped; cannot insert breakpoints.
4070 You may have requested too many hardware breakpoints and watchpoints.
4074 This message is printed when you attempt to resume the program, since
4075 only then @value{GDBN} knows exactly how many hardware breakpoints and
4076 watchpoints it needs to insert.
4078 When this message is printed, you need to disable or remove some of the
4079 hardware-assisted breakpoints and watchpoints, and then continue.
4081 @node Breakpoint-related Warnings
4082 @subsection ``Breakpoint address adjusted...''
4083 @cindex breakpoint address adjusted
4085 Some processor architectures place constraints on the addresses at
4086 which breakpoints may be placed. For architectures thus constrained,
4087 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4088 with the constraints dictated by the architecture.
4090 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4091 a VLIW architecture in which a number of RISC-like instructions may be
4092 bundled together for parallel execution. The FR-V architecture
4093 constrains the location of a breakpoint instruction within such a
4094 bundle to the instruction with the lowest address. @value{GDBN}
4095 honors this constraint by adjusting a breakpoint's address to the
4096 first in the bundle.
4098 It is not uncommon for optimized code to have bundles which contain
4099 instructions from different source statements, thus it may happen that
4100 a breakpoint's address will be adjusted from one source statement to
4101 another. Since this adjustment may significantly alter @value{GDBN}'s
4102 breakpoint related behavior from what the user expects, a warning is
4103 printed when the breakpoint is first set and also when the breakpoint
4106 A warning like the one below is printed when setting a breakpoint
4107 that's been subject to address adjustment:
4110 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4113 Such warnings are printed both for user settable and @value{GDBN}'s
4114 internal breakpoints. If you see one of these warnings, you should
4115 verify that a breakpoint set at the adjusted address will have the
4116 desired affect. If not, the breakpoint in question may be removed and
4117 other breakpoints may be set which will have the desired behavior.
4118 E.g., it may be sufficient to place the breakpoint at a later
4119 instruction. A conditional breakpoint may also be useful in some
4120 cases to prevent the breakpoint from triggering too often.
4122 @value{GDBN} will also issue a warning when stopping at one of these
4123 adjusted breakpoints:
4126 warning: Breakpoint 1 address previously adjusted from 0x00010414
4130 When this warning is encountered, it may be too late to take remedial
4131 action except in cases where the breakpoint is hit earlier or more
4132 frequently than expected.
4134 @node Continuing and Stepping
4135 @section Continuing and Stepping
4139 @cindex resuming execution
4140 @dfn{Continuing} means resuming program execution until your program
4141 completes normally. In contrast, @dfn{stepping} means executing just
4142 one more ``step'' of your program, where ``step'' may mean either one
4143 line of source code, or one machine instruction (depending on what
4144 particular command you use). Either when continuing or when stepping,
4145 your program may stop even sooner, due to a breakpoint or a signal. (If
4146 it stops due to a signal, you may want to use @code{handle}, or use
4147 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4151 @kindex c @r{(@code{continue})}
4152 @kindex fg @r{(resume foreground execution)}
4153 @item continue @r{[}@var{ignore-count}@r{]}
4154 @itemx c @r{[}@var{ignore-count}@r{]}
4155 @itemx fg @r{[}@var{ignore-count}@r{]}
4156 Resume program execution, at the address where your program last stopped;
4157 any breakpoints set at that address are bypassed. The optional argument
4158 @var{ignore-count} allows you to specify a further number of times to
4159 ignore a breakpoint at this location; its effect is like that of
4160 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4162 The argument @var{ignore-count} is meaningful only when your program
4163 stopped due to a breakpoint. At other times, the argument to
4164 @code{continue} is ignored.
4166 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4167 debugged program is deemed to be the foreground program) are provided
4168 purely for convenience, and have exactly the same behavior as
4172 To resume execution at a different place, you can use @code{return}
4173 (@pxref{Returning, ,Returning from a Function}) to go back to the
4174 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4175 Different Address}) to go to an arbitrary location in your program.
4177 A typical technique for using stepping is to set a breakpoint
4178 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4179 beginning of the function or the section of your program where a problem
4180 is believed to lie, run your program until it stops at that breakpoint,
4181 and then step through the suspect area, examining the variables that are
4182 interesting, until you see the problem happen.
4186 @kindex s @r{(@code{step})}
4188 Continue running your program until control reaches a different source
4189 line, then stop it and return control to @value{GDBN}. This command is
4190 abbreviated @code{s}.
4193 @c "without debugging information" is imprecise; actually "without line
4194 @c numbers in the debugging information". (gcc -g1 has debugging info but
4195 @c not line numbers). But it seems complex to try to make that
4196 @c distinction here.
4197 @emph{Warning:} If you use the @code{step} command while control is
4198 within a function that was compiled without debugging information,
4199 execution proceeds until control reaches a function that does have
4200 debugging information. Likewise, it will not step into a function which
4201 is compiled without debugging information. To step through functions
4202 without debugging information, use the @code{stepi} command, described
4206 The @code{step} command only stops at the first instruction of a source
4207 line. This prevents the multiple stops that could otherwise occur in
4208 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4209 to stop if a function that has debugging information is called within
4210 the line. In other words, @code{step} @emph{steps inside} any functions
4211 called within the line.
4213 Also, the @code{step} command only enters a function if there is line
4214 number information for the function. Otherwise it acts like the
4215 @code{next} command. This avoids problems when using @code{cc -gl}
4216 on MIPS machines. Previously, @code{step} entered subroutines if there
4217 was any debugging information about the routine.
4219 @item step @var{count}
4220 Continue running as in @code{step}, but do so @var{count} times. If a
4221 breakpoint is reached, or a signal not related to stepping occurs before
4222 @var{count} steps, stepping stops right away.
4225 @kindex n @r{(@code{next})}
4226 @item next @r{[}@var{count}@r{]}
4227 Continue to the next source line in the current (innermost) stack frame.
4228 This is similar to @code{step}, but function calls that appear within
4229 the line of code are executed without stopping. Execution stops when
4230 control reaches a different line of code at the original stack level
4231 that was executing when you gave the @code{next} command. This command
4232 is abbreviated @code{n}.
4234 An argument @var{count} is a repeat count, as for @code{step}.
4237 @c FIX ME!! Do we delete this, or is there a way it fits in with
4238 @c the following paragraph? --- Vctoria
4240 @c @code{next} within a function that lacks debugging information acts like
4241 @c @code{step}, but any function calls appearing within the code of the
4242 @c function are executed without stopping.
4244 The @code{next} command only stops at the first instruction of a
4245 source line. This prevents multiple stops that could otherwise occur in
4246 @code{switch} statements, @code{for} loops, etc.
4248 @kindex set step-mode
4250 @cindex functions without line info, and stepping
4251 @cindex stepping into functions with no line info
4252 @itemx set step-mode on
4253 The @code{set step-mode on} command causes the @code{step} command to
4254 stop at the first instruction of a function which contains no debug line
4255 information rather than stepping over it.
4257 This is useful in cases where you may be interested in inspecting the
4258 machine instructions of a function which has no symbolic info and do not
4259 want @value{GDBN} to automatically skip over this function.
4261 @item set step-mode off
4262 Causes the @code{step} command to step over any functions which contains no
4263 debug information. This is the default.
4265 @item show step-mode
4266 Show whether @value{GDBN} will stop in or step over functions without
4267 source line debug information.
4270 @kindex fin @r{(@code{finish})}
4272 Continue running until just after function in the selected stack frame
4273 returns. Print the returned value (if any). This command can be
4274 abbreviated as @code{fin}.
4276 Contrast this with the @code{return} command (@pxref{Returning,
4277 ,Returning from a Function}).
4280 @kindex u @r{(@code{until})}
4281 @cindex run until specified location
4284 Continue running until a source line past the current line, in the
4285 current stack frame, is reached. This command is used to avoid single
4286 stepping through a loop more than once. It is like the @code{next}
4287 command, except that when @code{until} encounters a jump, it
4288 automatically continues execution until the program counter is greater
4289 than the address of the jump.
4291 This means that when you reach the end of a loop after single stepping
4292 though it, @code{until} makes your program continue execution until it
4293 exits the loop. In contrast, a @code{next} command at the end of a loop
4294 simply steps back to the beginning of the loop, which forces you to step
4295 through the next iteration.
4297 @code{until} always stops your program if it attempts to exit the current
4300 @code{until} may produce somewhat counterintuitive results if the order
4301 of machine code does not match the order of the source lines. For
4302 example, in the following excerpt from a debugging session, the @code{f}
4303 (@code{frame}) command shows that execution is stopped at line
4304 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4308 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4310 (@value{GDBP}) until
4311 195 for ( ; argc > 0; NEXTARG) @{
4314 This happened because, for execution efficiency, the compiler had
4315 generated code for the loop closure test at the end, rather than the
4316 start, of the loop---even though the test in a C @code{for}-loop is
4317 written before the body of the loop. The @code{until} command appeared
4318 to step back to the beginning of the loop when it advanced to this
4319 expression; however, it has not really gone to an earlier
4320 statement---not in terms of the actual machine code.
4322 @code{until} with no argument works by means of single
4323 instruction stepping, and hence is slower than @code{until} with an
4326 @item until @var{location}
4327 @itemx u @var{location}
4328 Continue running your program until either the specified location is
4329 reached, or the current stack frame returns. @var{location} is any of
4330 the forms described in @ref{Specify Location}.
4331 This form of the command uses temporary breakpoints, and
4332 hence is quicker than @code{until} without an argument. The specified
4333 location is actually reached only if it is in the current frame. This
4334 implies that @code{until} can be used to skip over recursive function
4335 invocations. For instance in the code below, if the current location is
4336 line @code{96}, issuing @code{until 99} will execute the program up to
4337 line @code{99} in the same invocation of factorial, i.e., after the inner
4338 invocations have returned.
4341 94 int factorial (int value)
4343 96 if (value > 1) @{
4344 97 value *= factorial (value - 1);
4351 @kindex advance @var{location}
4352 @itemx advance @var{location}
4353 Continue running the program up to the given @var{location}. An argument is
4354 required, which should be of one of the forms described in
4355 @ref{Specify Location}.
4356 Execution will also stop upon exit from the current stack
4357 frame. This command is similar to @code{until}, but @code{advance} will
4358 not skip over recursive function calls, and the target location doesn't
4359 have to be in the same frame as the current one.
4363 @kindex si @r{(@code{stepi})}
4365 @itemx stepi @var{arg}
4367 Execute one machine instruction, then stop and return to the debugger.
4369 It is often useful to do @samp{display/i $pc} when stepping by machine
4370 instructions. This makes @value{GDBN} automatically display the next
4371 instruction to be executed, each time your program stops. @xref{Auto
4372 Display,, Automatic Display}.
4374 An argument is a repeat count, as in @code{step}.
4378 @kindex ni @r{(@code{nexti})}
4380 @itemx nexti @var{arg}
4382 Execute one machine instruction, but if it is a function call,
4383 proceed until the function returns.
4385 An argument is a repeat count, as in @code{next}.
4392 A signal is an asynchronous event that can happen in a program. The
4393 operating system defines the possible kinds of signals, and gives each
4394 kind a name and a number. For example, in Unix @code{SIGINT} is the
4395 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4396 @code{SIGSEGV} is the signal a program gets from referencing a place in
4397 memory far away from all the areas in use; @code{SIGALRM} occurs when
4398 the alarm clock timer goes off (which happens only if your program has
4399 requested an alarm).
4401 @cindex fatal signals
4402 Some signals, including @code{SIGALRM}, are a normal part of the
4403 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4404 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4405 program has not specified in advance some other way to handle the signal.
4406 @code{SIGINT} does not indicate an error in your program, but it is normally
4407 fatal so it can carry out the purpose of the interrupt: to kill the program.
4409 @value{GDBN} has the ability to detect any occurrence of a signal in your
4410 program. You can tell @value{GDBN} in advance what to do for each kind of
4413 @cindex handling signals
4414 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4415 @code{SIGALRM} be silently passed to your program
4416 (so as not to interfere with their role in the program's functioning)
4417 but to stop your program immediately whenever an error signal happens.
4418 You can change these settings with the @code{handle} command.
4421 @kindex info signals
4425 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4426 handle each one. You can use this to see the signal numbers of all
4427 the defined types of signals.
4429 @item info signals @var{sig}
4430 Similar, but print information only about the specified signal number.
4432 @code{info handle} is an alias for @code{info signals}.
4435 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4436 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4437 can be the number of a signal or its name (with or without the
4438 @samp{SIG} at the beginning); a list of signal numbers of the form
4439 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4440 known signals. Optional arguments @var{keywords}, described below,
4441 say what change to make.
4445 The keywords allowed by the @code{handle} command can be abbreviated.
4446 Their full names are:
4450 @value{GDBN} should not stop your program when this signal happens. It may
4451 still print a message telling you that the signal has come in.
4454 @value{GDBN} should stop your program when this signal happens. This implies
4455 the @code{print} keyword as well.
4458 @value{GDBN} should print a message when this signal happens.
4461 @value{GDBN} should not mention the occurrence of the signal at all. This
4462 implies the @code{nostop} keyword as well.
4466 @value{GDBN} should allow your program to see this signal; your program
4467 can handle the signal, or else it may terminate if the signal is fatal
4468 and not handled. @code{pass} and @code{noignore} are synonyms.
4472 @value{GDBN} should not allow your program to see this signal.
4473 @code{nopass} and @code{ignore} are synonyms.
4477 When a signal stops your program, the signal is not visible to the
4479 continue. Your program sees the signal then, if @code{pass} is in
4480 effect for the signal in question @emph{at that time}. In other words,
4481 after @value{GDBN} reports a signal, you can use the @code{handle}
4482 command with @code{pass} or @code{nopass} to control whether your
4483 program sees that signal when you continue.
4485 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4486 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4487 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4490 You can also use the @code{signal} command to prevent your program from
4491 seeing a signal, or cause it to see a signal it normally would not see,
4492 or to give it any signal at any time. For example, if your program stopped
4493 due to some sort of memory reference error, you might store correct
4494 values into the erroneous variables and continue, hoping to see more
4495 execution; but your program would probably terminate immediately as
4496 a result of the fatal signal once it saw the signal. To prevent this,
4497 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4500 @cindex extra signal information
4501 @anchor{extra signal information}
4503 On some targets, @value{GDBN} can inspect extra signal information
4504 associated with the intercepted signal, before it is actually
4505 delivered to the program being debugged. This information is exported
4506 by the convenience variable @code{$_siginfo}, and consists of data
4507 that is passed by the kernel to the signal handler at the time of the
4508 receipt of a signal. The data type of the information itself is
4509 target dependent. You can see the data type using the @code{ptype
4510 $_siginfo} command. On Unix systems, it typically corresponds to the
4511 standard @code{siginfo_t} type, as defined in the @file{signal.h}
4514 Here's an example, on a @sc{gnu}/Linux system, printing the stray
4515 referenced address that raised a segmentation fault.
4519 (@value{GDBP}) continue
4520 Program received signal SIGSEGV, Segmentation fault.
4521 0x0000000000400766 in main ()
4523 (@value{GDBP}) ptype $_siginfo
4530 struct @{...@} _kill;
4531 struct @{...@} _timer;
4533 struct @{...@} _sigchld;
4534 struct @{...@} _sigfault;
4535 struct @{...@} _sigpoll;
4538 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
4542 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
4543 $1 = (void *) 0x7ffff7ff7000
4547 Depending on target support, @code{$_siginfo} may also be writable.
4550 @section Stopping and Starting Multi-thread Programs
4552 @cindex stopped threads
4553 @cindex threads, stopped
4555 @cindex continuing threads
4556 @cindex threads, continuing
4558 @value{GDBN} supports debugging programs with multiple threads
4559 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
4560 are two modes of controlling execution of your program within the
4561 debugger. In the default mode, referred to as @dfn{all-stop mode},
4562 when any thread in your program stops (for example, at a breakpoint
4563 or while being stepped), all other threads in the program are also stopped by
4564 @value{GDBN}. On some targets, @value{GDBN} also supports
4565 @dfn{non-stop mode}, in which other threads can continue to run freely while
4566 you examine the stopped thread in the debugger.
4569 * All-Stop Mode:: All threads stop when GDB takes control
4570 * Non-Stop Mode:: Other threads continue to execute
4571 * Background Execution:: Running your program asynchronously
4572 * Thread-Specific Breakpoints:: Controlling breakpoints
4573 * Interrupted System Calls:: GDB may interfere with system calls
4577 @subsection All-Stop Mode
4579 @cindex all-stop mode
4581 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
4582 @emph{all} threads of execution stop, not just the current thread. This
4583 allows you to examine the overall state of the program, including
4584 switching between threads, without worrying that things may change
4587 Conversely, whenever you restart the program, @emph{all} threads start
4588 executing. @emph{This is true even when single-stepping} with commands
4589 like @code{step} or @code{next}.
4591 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4592 Since thread scheduling is up to your debugging target's operating
4593 system (not controlled by @value{GDBN}), other threads may
4594 execute more than one statement while the current thread completes a
4595 single step. Moreover, in general other threads stop in the middle of a
4596 statement, rather than at a clean statement boundary, when the program
4599 You might even find your program stopped in another thread after
4600 continuing or even single-stepping. This happens whenever some other
4601 thread runs into a breakpoint, a signal, or an exception before the
4602 first thread completes whatever you requested.
4604 @cindex automatic thread selection
4605 @cindex switching threads automatically
4606 @cindex threads, automatic switching
4607 Whenever @value{GDBN} stops your program, due to a breakpoint or a
4608 signal, it automatically selects the thread where that breakpoint or
4609 signal happened. @value{GDBN} alerts you to the context switch with a
4610 message such as @samp{[Switching to Thread @var{n}]} to identify the
4613 On some OSes, you can modify @value{GDBN}'s default behavior by
4614 locking the OS scheduler to allow only a single thread to run.
4617 @item set scheduler-locking @var{mode}
4618 @cindex scheduler locking mode
4619 @cindex lock scheduler
4620 Set the scheduler locking mode. If it is @code{off}, then there is no
4621 locking and any thread may run at any time. If @code{on}, then only the
4622 current thread may run when the inferior is resumed. The @code{step}
4623 mode optimizes for single-stepping; it prevents other threads
4624 from preempting the current thread while you are stepping, so that
4625 the focus of debugging does not change unexpectedly.
4626 Other threads only rarely (or never) get a chance to run
4627 when you step. They are more likely to run when you @samp{next} over a
4628 function call, and they are completely free to run when you use commands
4629 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4630 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
4631 the current thread away from the thread that you are debugging.
4633 @item show scheduler-locking
4634 Display the current scheduler locking mode.
4637 @cindex resume threads of multiple processes simultaneously
4638 By default, when you issue one of the execution commands such as
4639 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
4640 threads of the current inferior to run. For example, if @value{GDBN}
4641 is attached to two inferiors, each with two threads, the
4642 @code{continue} command resumes only the two threads of the current
4643 inferior. This is useful, for example, when you debug a program that
4644 forks and you want to hold the parent stopped (so that, for instance,
4645 it doesn't run to exit), while you debug the child. In other
4646 situations, you may not be interested in inspecting the current state
4647 of any of the processes @value{GDBN} is attached to, and you may want
4648 to resume them all until some breakpoint is hit. In the latter case,
4649 you can instruct @value{GDBN} to allow all threads of all the
4650 inferiors to run with the @w{@code{set schedule-multiple}} command.
4653 @kindex set schedule-multiple
4654 @item set schedule-multiple
4655 Set the mode for allowing threads of multiple processes to be resumed
4656 when an execution command is issued. When @code{on}, all threads of
4657 all processes are allowed to run. When @code{off}, only the threads
4658 of the current process are resumed. The default is @code{off}. The
4659 @code{scheduler-locking} mode takes precedence when set to @code{on},
4660 or while you are stepping and set to @code{step}.
4662 @item show schedule-multiple
4663 Display the current mode for resuming the execution of threads of
4668 @subsection Non-Stop Mode
4670 @cindex non-stop mode
4672 @c This section is really only a place-holder, and needs to be expanded
4673 @c with more details.
4675 For some multi-threaded targets, @value{GDBN} supports an optional
4676 mode of operation in which you can examine stopped program threads in
4677 the debugger while other threads continue to execute freely. This
4678 minimizes intrusion when debugging live systems, such as programs
4679 where some threads have real-time constraints or must continue to
4680 respond to external events. This is referred to as @dfn{non-stop} mode.
4682 In non-stop mode, when a thread stops to report a debugging event,
4683 @emph{only} that thread is stopped; @value{GDBN} does not stop other
4684 threads as well, in contrast to the all-stop mode behavior. Additionally,
4685 execution commands such as @code{continue} and @code{step} apply by default
4686 only to the current thread in non-stop mode, rather than all threads as
4687 in all-stop mode. This allows you to control threads explicitly in
4688 ways that are not possible in all-stop mode --- for example, stepping
4689 one thread while allowing others to run freely, stepping
4690 one thread while holding all others stopped, or stepping several threads
4691 independently and simultaneously.
4693 To enter non-stop mode, use this sequence of commands before you run
4694 or attach to your program:
4697 # Enable the async interface.
4700 # If using the CLI, pagination breaks non-stop.
4703 # Finally, turn it on!
4707 You can use these commands to manipulate the non-stop mode setting:
4710 @kindex set non-stop
4711 @item set non-stop on
4712 Enable selection of non-stop mode.
4713 @item set non-stop off
4714 Disable selection of non-stop mode.
4715 @kindex show non-stop
4717 Show the current non-stop enablement setting.
4720 Note these commands only reflect whether non-stop mode is enabled,
4721 not whether the currently-executing program is being run in non-stop mode.
4722 In particular, the @code{set non-stop} preference is only consulted when
4723 @value{GDBN} starts or connects to the target program, and it is generally
4724 not possible to switch modes once debugging has started. Furthermore,
4725 since not all targets support non-stop mode, even when you have enabled
4726 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
4729 In non-stop mode, all execution commands apply only to the current thread
4730 by default. That is, @code{continue} only continues one thread.
4731 To continue all threads, issue @code{continue -a} or @code{c -a}.
4733 You can use @value{GDBN}'s background execution commands
4734 (@pxref{Background Execution}) to run some threads in the background
4735 while you continue to examine or step others from @value{GDBN}.
4736 The MI execution commands (@pxref{GDB/MI Program Execution}) are
4737 always executed asynchronously in non-stop mode.
4739 Suspending execution is done with the @code{interrupt} command when
4740 running in the background, or @kbd{Ctrl-c} during foreground execution.
4741 In all-stop mode, this stops the whole process;
4742 but in non-stop mode the interrupt applies only to the current thread.
4743 To stop the whole program, use @code{interrupt -a}.
4745 Other execution commands do not currently support the @code{-a} option.
4747 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
4748 that thread current, as it does in all-stop mode. This is because the
4749 thread stop notifications are asynchronous with respect to @value{GDBN}'s
4750 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
4751 changed to a different thread just as you entered a command to operate on the
4752 previously current thread.
4754 @node Background Execution
4755 @subsection Background Execution
4757 @cindex foreground execution
4758 @cindex background execution
4759 @cindex asynchronous execution
4760 @cindex execution, foreground, background and asynchronous
4762 @value{GDBN}'s execution commands have two variants: the normal
4763 foreground (synchronous) behavior, and a background
4764 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
4765 the program to report that some thread has stopped before prompting for
4766 another command. In background execution, @value{GDBN} immediately gives
4767 a command prompt so that you can issue other commands while your program runs.
4769 You need to explicitly enable asynchronous mode before you can use
4770 background execution commands. You can use these commands to
4771 manipulate the asynchronous mode setting:
4774 @kindex set target-async
4775 @item set target-async on
4776 Enable asynchronous mode.
4777 @item set target-async off
4778 Disable asynchronous mode.
4779 @kindex show target-async
4780 @item show target-async
4781 Show the current target-async setting.
4784 If the target doesn't support async mode, @value{GDBN} issues an error
4785 message if you attempt to use the background execution commands.
4787 To specify background execution, add a @code{&} to the command. For example,
4788 the background form of the @code{continue} command is @code{continue&}, or
4789 just @code{c&}. The execution commands that accept background execution
4795 @xref{Starting, , Starting your Program}.
4799 @xref{Attach, , Debugging an Already-running Process}.
4803 @xref{Continuing and Stepping, step}.
4807 @xref{Continuing and Stepping, stepi}.
4811 @xref{Continuing and Stepping, next}.
4815 @xref{Continuing and Stepping, nexti}.
4819 @xref{Continuing and Stepping, continue}.
4823 @xref{Continuing and Stepping, finish}.
4827 @xref{Continuing and Stepping, until}.
4831 Background execution is especially useful in conjunction with non-stop
4832 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
4833 However, you can also use these commands in the normal all-stop mode with
4834 the restriction that you cannot issue another execution command until the
4835 previous one finishes. Examples of commands that are valid in all-stop
4836 mode while the program is running include @code{help} and @code{info break}.
4838 You can interrupt your program while it is running in the background by
4839 using the @code{interrupt} command.
4846 Suspend execution of the running program. In all-stop mode,
4847 @code{interrupt} stops the whole process, but in non-stop mode, it stops
4848 only the current thread. To stop the whole program in non-stop mode,
4849 use @code{interrupt -a}.
4852 @node Thread-Specific Breakpoints
4853 @subsection Thread-Specific Breakpoints
4855 When your program has multiple threads (@pxref{Threads,, Debugging
4856 Programs with Multiple Threads}), you can choose whether to set
4857 breakpoints on all threads, or on a particular thread.
4860 @cindex breakpoints and threads
4861 @cindex thread breakpoints
4862 @kindex break @dots{} thread @var{threadno}
4863 @item break @var{linespec} thread @var{threadno}
4864 @itemx break @var{linespec} thread @var{threadno} if @dots{}
4865 @var{linespec} specifies source lines; there are several ways of
4866 writing them (@pxref{Specify Location}), but the effect is always to
4867 specify some source line.
4869 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
4870 to specify that you only want @value{GDBN} to stop the program when a
4871 particular thread reaches this breakpoint. @var{threadno} is one of the
4872 numeric thread identifiers assigned by @value{GDBN}, shown in the first
4873 column of the @samp{info threads} display.
4875 If you do not specify @samp{thread @var{threadno}} when you set a
4876 breakpoint, the breakpoint applies to @emph{all} threads of your
4879 You can use the @code{thread} qualifier on conditional breakpoints as
4880 well; in this case, place @samp{thread @var{threadno}} before the
4881 breakpoint condition, like this:
4884 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
4889 @node Interrupted System Calls
4890 @subsection Interrupted System Calls
4892 @cindex thread breakpoints and system calls
4893 @cindex system calls and thread breakpoints
4894 @cindex premature return from system calls
4895 There is an unfortunate side effect when using @value{GDBN} to debug
4896 multi-threaded programs. If one thread stops for a
4897 breakpoint, or for some other reason, and another thread is blocked in a
4898 system call, then the system call may return prematurely. This is a
4899 consequence of the interaction between multiple threads and the signals
4900 that @value{GDBN} uses to implement breakpoints and other events that
4903 To handle this problem, your program should check the return value of
4904 each system call and react appropriately. This is good programming
4907 For example, do not write code like this:
4913 The call to @code{sleep} will return early if a different thread stops
4914 at a breakpoint or for some other reason.
4916 Instead, write this:
4921 unslept = sleep (unslept);
4924 A system call is allowed to return early, so the system is still
4925 conforming to its specification. But @value{GDBN} does cause your
4926 multi-threaded program to behave differently than it would without
4929 Also, @value{GDBN} uses internal breakpoints in the thread library to
4930 monitor certain events such as thread creation and thread destruction.
4931 When such an event happens, a system call in another thread may return
4932 prematurely, even though your program does not appear to stop.
4935 @node Reverse Execution
4936 @chapter Running programs backward
4937 @cindex reverse execution
4938 @cindex running programs backward
4940 When you are debugging a program, it is not unusual to realize that
4941 you have gone too far, and some event of interest has already happened.
4942 If the target environment supports it, @value{GDBN} can allow you to
4943 ``rewind'' the program by running it backward.
4945 A target environment that supports reverse execution should be able
4946 to ``undo'' the changes in machine state that have taken place as the
4947 program was executing normally. Variables, registers etc.@: should
4948 revert to their previous values. Obviously this requires a great
4949 deal of sophistication on the part of the target environment; not
4950 all target environments can support reverse execution.
4952 When a program is executed in reverse, the instructions that
4953 have most recently been executed are ``un-executed'', in reverse
4954 order. The program counter runs backward, following the previous
4955 thread of execution in reverse. As each instruction is ``un-executed'',
4956 the values of memory and/or registers that were changed by that
4957 instruction are reverted to their previous states. After executing
4958 a piece of source code in reverse, all side effects of that code
4959 should be ``undone'', and all variables should be returned to their
4960 prior values@footnote{
4961 Note that some side effects are easier to undo than others. For instance,
4962 memory and registers are relatively easy, but device I/O is hard. Some
4963 targets may be able undo things like device I/O, and some may not.
4965 The contract between @value{GDBN} and the reverse executing target
4966 requires only that the target do something reasonable when
4967 @value{GDBN} tells it to execute backwards, and then report the
4968 results back to @value{GDBN}. Whatever the target reports back to
4969 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
4970 assumes that the memory and registers that the target reports are in a
4971 consistant state, but @value{GDBN} accepts whatever it is given.
4974 If you are debugging in a target environment that supports
4975 reverse execution, @value{GDBN} provides the following commands.
4978 @kindex reverse-continue
4979 @kindex rc @r{(@code{reverse-continue})}
4980 @item reverse-continue @r{[}@var{ignore-count}@r{]}
4981 @itemx rc @r{[}@var{ignore-count}@r{]}
4982 Beginning at the point where your program last stopped, start executing
4983 in reverse. Reverse execution will stop for breakpoints and synchronous
4984 exceptions (signals), just like normal execution. Behavior of
4985 asynchronous signals depends on the target environment.
4987 @kindex reverse-step
4988 @kindex rs @r{(@code{step})}
4989 @item reverse-step @r{[}@var{count}@r{]}
4990 Run the program backward until control reaches the start of a
4991 different source line; then stop it, and return control to @value{GDBN}.
4993 Like the @code{step} command, @code{reverse-step} will only stop
4994 at the beginning of a source line. It ``un-executes'' the previously
4995 executed source line. If the previous source line included calls to
4996 debuggable functions, @code{reverse-step} will step (backward) into
4997 the called function, stopping at the beginning of the @emph{last}
4998 statement in the called function (typically a return statement).
5000 Also, as with the @code{step} command, if non-debuggable functions are
5001 called, @code{reverse-step} will run thru them backward without stopping.
5003 @kindex reverse-stepi
5004 @kindex rsi @r{(@code{reverse-stepi})}
5005 @item reverse-stepi @r{[}@var{count}@r{]}
5006 Reverse-execute one machine instruction. Note that the instruction
5007 to be reverse-executed is @emph{not} the one pointed to by the program
5008 counter, but the instruction executed prior to that one. For instance,
5009 if the last instruction was a jump, @code{reverse-stepi} will take you
5010 back from the destination of the jump to the jump instruction itself.
5012 @kindex reverse-next
5013 @kindex rn @r{(@code{reverse-next})}
5014 @item reverse-next @r{[}@var{count}@r{]}
5015 Run backward to the beginning of the previous line executed in
5016 the current (innermost) stack frame. If the line contains function
5017 calls, they will be ``un-executed'' without stopping. Starting from
5018 the first line of a function, @code{reverse-next} will take you back
5019 to the caller of that function, @emph{before} the function was called,
5020 just as the normal @code{next} command would take you from the last
5021 line of a function back to its return to its caller
5022 @footnote{Unles the code is too heavily optimized.}.
5024 @kindex reverse-nexti
5025 @kindex rni @r{(@code{reverse-nexti})}
5026 @item reverse-nexti @r{[}@var{count}@r{]}
5027 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5028 in reverse, except that called functions are ``un-executed'' atomically.
5029 That is, if the previously executed instruction was a return from
5030 another instruction, @code{reverse-nexti} will continue to execute
5031 in reverse until the call to that function (from the current stack
5034 @kindex reverse-finish
5035 @item reverse-finish
5036 Just as the @code{finish} command takes you to the point where the
5037 current function returns, @code{reverse-finish} takes you to the point
5038 where it was called. Instead of ending up at the end of the current
5039 function invocation, you end up at the beginning.
5041 @kindex set exec-direction
5042 @item set exec-direction
5043 Set the direction of target execution.
5044 @itemx set exec-direction reverse
5045 @cindex execute forward or backward in time
5046 @value{GDBN} will perform all execution commands in reverse, until the
5047 exec-direction mode is changed to ``forward''. Affected commands include
5048 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5049 command cannot be used in reverse mode.
5050 @item set exec-direction forward
5051 @value{GDBN} will perform all execution commands in the normal fashion.
5052 This is the default.
5056 @node Process Record and Replay
5057 @chapter Recording Inferior's Execution and Replaying It
5058 @cindex process record and replay
5059 @cindex recording inferior's execution and replaying it
5061 On some platforms, @value{GDBN} provides a special @dfn{process record
5062 and replay} target that can record a log of the process execution, and
5063 replay it later with both forward and reverse execution commands.
5066 When this target is in use, if the execution log includes the record
5067 for the next instruction, @value{GDBN} will debug in @dfn{replay
5068 mode}. In the replay mode, the inferior does not really execute code
5069 instructions. Instead, all the events that normally happen during
5070 code execution are taken from the execution log. While code is not
5071 really executed in replay mode, the values of registers (including the
5072 program counter register) and the memory of the inferior are still
5073 changed as they normally would. Their contents are taken from the
5077 If the record for the next instruction is not in the execution log,
5078 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5079 inferior executes normally, and @value{GDBN} records the execution log
5082 The process record and replay target supports reverse execution
5083 (@pxref{Reverse Execution}), even if the platform on which the
5084 inferior runs does not. However, the reverse execution is limited in
5085 this case by the range of the instructions recorded in the execution
5086 log. In other words, reverse execution on platforms that don't
5087 support it directly can only be done in the replay mode.
5089 When debugging in the reverse direction, @value{GDBN} will work in
5090 replay mode as long as the execution log includes the record for the
5091 previous instruction; otherwise, it will work in record mode, if the
5092 platform supports reverse execution, or stop if not.
5094 For architecture environments that support process record and replay,
5095 @value{GDBN} provides the following commands:
5098 @kindex target record
5102 This command starts the process record and replay target. The process
5103 record and replay target can only debug a process that is already
5104 running. Therefore, you need first to start the process with the
5105 @kbd{run} or @kbd{start} commands, and then start the recording with
5106 the @kbd{target record} command.
5108 Both @code{record} and @code{rec} are aliases of @code{target record}.
5110 @cindex displaced stepping, and process record and replay
5111 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5112 will be automatically disabled when process record and replay target
5113 is started. That's because the process record and replay target
5114 doesn't support displaced stepping.
5116 @cindex non-stop mode, and process record and replay
5117 @cindex asynchronous execution, and process record and replay
5118 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5119 the asynchronous execution mode (@pxref{Background Execution}), the
5120 process record and replay target cannot be started because it doesn't
5121 support these two modes.
5126 Stop the process record and replay target. When process record and
5127 replay target stops, the entire execution log will be deleted and the
5128 inferior will either be terminated, or will remain in its final state.
5130 When you stop the process record and replay target in record mode (at
5131 the end of the execution log), the inferior will be stopped at the
5132 next instruction that would have been recorded. In other words, if
5133 you record for a while and then stop recording, the inferior process
5134 will be left in the same state as if the recording never happened.
5136 On the other hand, if the process record and replay target is stopped
5137 while in replay mode (that is, not at the end of the execution log,
5138 but at some earlier point), the inferior process will become ``live''
5139 at that earlier state, and it will then be possible to continue the
5140 usual ``live'' debugging of the process from that state.
5142 When the inferior process exits, or @value{GDBN} detaches from it,
5143 process record and replay target will automatically stop itself.
5145 @kindex set record insn-number-max
5146 @item set record insn-number-max @var{limit}
5147 Set the limit of instructions to be recorded. Default value is 200000.
5149 If @var{limit} is a positive number, then @value{GDBN} will start
5150 deleting instructions from the log once the number of the record
5151 instructions becomes greater than @var{limit}. For every new recorded
5152 instruction, @value{GDBN} will delete the earliest recorded
5153 instruction to keep the number of recorded instructions at the limit.
5154 (Since deleting recorded instructions loses information, @value{GDBN}
5155 lets you control what happens when the limit is reached, by means of
5156 the @code{stop-at-limit} option, described below.)
5158 If @var{limit} is zero, @value{GDBN} will never delete recorded
5159 instructions from the execution log. The number of recorded
5160 instructions is unlimited in this case.
5162 @kindex show record insn-number-max
5163 @item show record insn-number-max
5164 Show the limit of instructions to be recorded.
5166 @kindex set record stop-at-limit
5167 @item set record stop-at-limit
5168 Control the behavior when the number of recorded instructions reaches
5169 the limit. If ON (the default), @value{GDBN} will stop when the limit
5170 is reached for the first time and ask you whether you want to stop the
5171 inferior or continue running it and recording the execution log. If
5172 you decide to continue recording, each new recorded instruction will
5173 cause the oldest one to be deleted.
5175 If this option is OFF, @value{GDBN} will automatically delete the
5176 oldest record to make room for each new one, without asking.
5178 @kindex show record stop-at-limit
5179 @item show record stop-at-limit
5180 Show the current setting of @code{stop-at-limit}.
5182 @kindex info record insn-number
5183 @item info record insn-number
5184 Show the current number of recorded instructions.
5186 @kindex record delete
5189 When record target runs in replay mode (``in the past''), delete the
5190 subsequent execution log and begin to record a new execution log starting
5191 from the current address. This means you will abandon the previously
5192 recorded ``future'' and begin recording a new ``future''.
5197 @chapter Examining the Stack
5199 When your program has stopped, the first thing you need to know is where it
5200 stopped and how it got there.
5203 Each time your program performs a function call, information about the call
5205 That information includes the location of the call in your program,
5206 the arguments of the call,
5207 and the local variables of the function being called.
5208 The information is saved in a block of data called a @dfn{stack frame}.
5209 The stack frames are allocated in a region of memory called the @dfn{call
5212 When your program stops, the @value{GDBN} commands for examining the
5213 stack allow you to see all of this information.
5215 @cindex selected frame
5216 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5217 @value{GDBN} commands refer implicitly to the selected frame. In
5218 particular, whenever you ask @value{GDBN} for the value of a variable in
5219 your program, the value is found in the selected frame. There are
5220 special @value{GDBN} commands to select whichever frame you are
5221 interested in. @xref{Selection, ,Selecting a Frame}.
5223 When your program stops, @value{GDBN} automatically selects the
5224 currently executing frame and describes it briefly, similar to the
5225 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5228 * Frames:: Stack frames
5229 * Backtrace:: Backtraces
5230 * Selection:: Selecting a frame
5231 * Frame Info:: Information on a frame
5236 @section Stack Frames
5238 @cindex frame, definition
5240 The call stack is divided up into contiguous pieces called @dfn{stack
5241 frames}, or @dfn{frames} for short; each frame is the data associated
5242 with one call to one function. The frame contains the arguments given
5243 to the function, the function's local variables, and the address at
5244 which the function is executing.
5246 @cindex initial frame
5247 @cindex outermost frame
5248 @cindex innermost frame
5249 When your program is started, the stack has only one frame, that of the
5250 function @code{main}. This is called the @dfn{initial} frame or the
5251 @dfn{outermost} frame. Each time a function is called, a new frame is
5252 made. Each time a function returns, the frame for that function invocation
5253 is eliminated. If a function is recursive, there can be many frames for
5254 the same function. The frame for the function in which execution is
5255 actually occurring is called the @dfn{innermost} frame. This is the most
5256 recently created of all the stack frames that still exist.
5258 @cindex frame pointer
5259 Inside your program, stack frames are identified by their addresses. A
5260 stack frame consists of many bytes, each of which has its own address; each
5261 kind of computer has a convention for choosing one byte whose
5262 address serves as the address of the frame. Usually this address is kept
5263 in a register called the @dfn{frame pointer register}
5264 (@pxref{Registers, $fp}) while execution is going on in that frame.
5266 @cindex frame number
5267 @value{GDBN} assigns numbers to all existing stack frames, starting with
5268 zero for the innermost frame, one for the frame that called it,
5269 and so on upward. These numbers do not really exist in your program;
5270 they are assigned by @value{GDBN} to give you a way of designating stack
5271 frames in @value{GDBN} commands.
5273 @c The -fomit-frame-pointer below perennially causes hbox overflow
5274 @c underflow problems.
5275 @cindex frameless execution
5276 Some compilers provide a way to compile functions so that they operate
5277 without stack frames. (For example, the @value{NGCC} option
5279 @samp{-fomit-frame-pointer}
5281 generates functions without a frame.)
5282 This is occasionally done with heavily used library functions to save
5283 the frame setup time. @value{GDBN} has limited facilities for dealing
5284 with these function invocations. If the innermost function invocation
5285 has no stack frame, @value{GDBN} nevertheless regards it as though
5286 it had a separate frame, which is numbered zero as usual, allowing
5287 correct tracing of the function call chain. However, @value{GDBN} has
5288 no provision for frameless functions elsewhere in the stack.
5291 @kindex frame@r{, command}
5292 @cindex current stack frame
5293 @item frame @var{args}
5294 The @code{frame} command allows you to move from one stack frame to another,
5295 and to print the stack frame you select. @var{args} may be either the
5296 address of the frame or the stack frame number. Without an argument,
5297 @code{frame} prints the current stack frame.
5299 @kindex select-frame
5300 @cindex selecting frame silently
5302 The @code{select-frame} command allows you to move from one stack frame
5303 to another without printing the frame. This is the silent version of
5311 @cindex call stack traces
5312 A backtrace is a summary of how your program got where it is. It shows one
5313 line per frame, for many frames, starting with the currently executing
5314 frame (frame zero), followed by its caller (frame one), and on up the
5319 @kindex bt @r{(@code{backtrace})}
5322 Print a backtrace of the entire stack: one line per frame for all
5323 frames in the stack.
5325 You can stop the backtrace at any time by typing the system interrupt
5326 character, normally @kbd{Ctrl-c}.
5328 @item backtrace @var{n}
5330 Similar, but print only the innermost @var{n} frames.
5332 @item backtrace -@var{n}
5334 Similar, but print only the outermost @var{n} frames.
5336 @item backtrace full
5338 @itemx bt full @var{n}
5339 @itemx bt full -@var{n}
5340 Print the values of the local variables also. @var{n} specifies the
5341 number of frames to print, as described above.
5346 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5347 are additional aliases for @code{backtrace}.
5349 @cindex multiple threads, backtrace
5350 In a multi-threaded program, @value{GDBN} by default shows the
5351 backtrace only for the current thread. To display the backtrace for
5352 several or all of the threads, use the command @code{thread apply}
5353 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5354 apply all backtrace}, @value{GDBN} will display the backtrace for all
5355 the threads; this is handy when you debug a core dump of a
5356 multi-threaded program.
5358 Each line in the backtrace shows the frame number and the function name.
5359 The program counter value is also shown---unless you use @code{set
5360 print address off}. The backtrace also shows the source file name and
5361 line number, as well as the arguments to the function. The program
5362 counter value is omitted if it is at the beginning of the code for that
5365 Here is an example of a backtrace. It was made with the command
5366 @samp{bt 3}, so it shows the innermost three frames.
5370 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5372 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
5373 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5375 (More stack frames follow...)
5380 The display for frame zero does not begin with a program counter
5381 value, indicating that your program has stopped at the beginning of the
5382 code for line @code{993} of @code{builtin.c}.
5385 The value of parameter @code{data} in frame 1 has been replaced by
5386 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
5387 only if it is a scalar (integer, pointer, enumeration, etc). See command
5388 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
5389 on how to configure the way function parameter values are printed.
5391 @cindex value optimized out, in backtrace
5392 @cindex function call arguments, optimized out
5393 If your program was compiled with optimizations, some compilers will
5394 optimize away arguments passed to functions if those arguments are
5395 never used after the call. Such optimizations generate code that
5396 passes arguments through registers, but doesn't store those arguments
5397 in the stack frame. @value{GDBN} has no way of displaying such
5398 arguments in stack frames other than the innermost one. Here's what
5399 such a backtrace might look like:
5403 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5405 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
5406 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
5408 (More stack frames follow...)
5413 The values of arguments that were not saved in their stack frames are
5414 shown as @samp{<value optimized out>}.
5416 If you need to display the values of such optimized-out arguments,
5417 either deduce that from other variables whose values depend on the one
5418 you are interested in, or recompile without optimizations.
5420 @cindex backtrace beyond @code{main} function
5421 @cindex program entry point
5422 @cindex startup code, and backtrace
5423 Most programs have a standard user entry point---a place where system
5424 libraries and startup code transition into user code. For C this is
5425 @code{main}@footnote{
5426 Note that embedded programs (the so-called ``free-standing''
5427 environment) are not required to have a @code{main} function as the
5428 entry point. They could even have multiple entry points.}.
5429 When @value{GDBN} finds the entry function in a backtrace
5430 it will terminate the backtrace, to avoid tracing into highly
5431 system-specific (and generally uninteresting) code.
5433 If you need to examine the startup code, or limit the number of levels
5434 in a backtrace, you can change this behavior:
5437 @item set backtrace past-main
5438 @itemx set backtrace past-main on
5439 @kindex set backtrace
5440 Backtraces will continue past the user entry point.
5442 @item set backtrace past-main off
5443 Backtraces will stop when they encounter the user entry point. This is the
5446 @item show backtrace past-main
5447 @kindex show backtrace
5448 Display the current user entry point backtrace policy.
5450 @item set backtrace past-entry
5451 @itemx set backtrace past-entry on
5452 Backtraces will continue past the internal entry point of an application.
5453 This entry point is encoded by the linker when the application is built,
5454 and is likely before the user entry point @code{main} (or equivalent) is called.
5456 @item set backtrace past-entry off
5457 Backtraces will stop when they encounter the internal entry point of an
5458 application. This is the default.
5460 @item show backtrace past-entry
5461 Display the current internal entry point backtrace policy.
5463 @item set backtrace limit @var{n}
5464 @itemx set backtrace limit 0
5465 @cindex backtrace limit
5466 Limit the backtrace to @var{n} levels. A value of zero means
5469 @item show backtrace limit
5470 Display the current limit on backtrace levels.
5474 @section Selecting a Frame
5476 Most commands for examining the stack and other data in your program work on
5477 whichever stack frame is selected at the moment. Here are the commands for
5478 selecting a stack frame; all of them finish by printing a brief description
5479 of the stack frame just selected.
5482 @kindex frame@r{, selecting}
5483 @kindex f @r{(@code{frame})}
5486 Select frame number @var{n}. Recall that frame zero is the innermost
5487 (currently executing) frame, frame one is the frame that called the
5488 innermost one, and so on. The highest-numbered frame is the one for
5491 @item frame @var{addr}
5493 Select the frame at address @var{addr}. This is useful mainly if the
5494 chaining of stack frames has been damaged by a bug, making it
5495 impossible for @value{GDBN} to assign numbers properly to all frames. In
5496 addition, this can be useful when your program has multiple stacks and
5497 switches between them.
5499 On the SPARC architecture, @code{frame} needs two addresses to
5500 select an arbitrary frame: a frame pointer and a stack pointer.
5502 On the MIPS and Alpha architecture, it needs two addresses: a stack
5503 pointer and a program counter.
5505 On the 29k architecture, it needs three addresses: a register stack
5506 pointer, a program counter, and a memory stack pointer.
5510 Move @var{n} frames up the stack. For positive numbers @var{n}, this
5511 advances toward the outermost frame, to higher frame numbers, to frames
5512 that have existed longer. @var{n} defaults to one.
5515 @kindex do @r{(@code{down})}
5517 Move @var{n} frames down the stack. For positive numbers @var{n}, this
5518 advances toward the innermost frame, to lower frame numbers, to frames
5519 that were created more recently. @var{n} defaults to one. You may
5520 abbreviate @code{down} as @code{do}.
5523 All of these commands end by printing two lines of output describing the
5524 frame. The first line shows the frame number, the function name, the
5525 arguments, and the source file and line number of execution in that
5526 frame. The second line shows the text of that source line.
5534 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
5536 10 read_input_file (argv[i]);
5540 After such a printout, the @code{list} command with no arguments
5541 prints ten lines centered on the point of execution in the frame.
5542 You can also edit the program at the point of execution with your favorite
5543 editing program by typing @code{edit}.
5544 @xref{List, ,Printing Source Lines},
5548 @kindex down-silently
5550 @item up-silently @var{n}
5551 @itemx down-silently @var{n}
5552 These two commands are variants of @code{up} and @code{down},
5553 respectively; they differ in that they do their work silently, without
5554 causing display of the new frame. They are intended primarily for use
5555 in @value{GDBN} command scripts, where the output might be unnecessary and
5560 @section Information About a Frame
5562 There are several other commands to print information about the selected
5568 When used without any argument, this command does not change which
5569 frame is selected, but prints a brief description of the currently
5570 selected stack frame. It can be abbreviated @code{f}. With an
5571 argument, this command is used to select a stack frame.
5572 @xref{Selection, ,Selecting a Frame}.
5575 @kindex info f @r{(@code{info frame})}
5578 This command prints a verbose description of the selected stack frame,
5583 the address of the frame
5585 the address of the next frame down (called by this frame)
5587 the address of the next frame up (caller of this frame)
5589 the language in which the source code corresponding to this frame is written
5591 the address of the frame's arguments
5593 the address of the frame's local variables
5595 the program counter saved in it (the address of execution in the caller frame)
5597 which registers were saved in the frame
5600 @noindent The verbose description is useful when
5601 something has gone wrong that has made the stack format fail to fit
5602 the usual conventions.
5604 @item info frame @var{addr}
5605 @itemx info f @var{addr}
5606 Print a verbose description of the frame at address @var{addr}, without
5607 selecting that frame. The selected frame remains unchanged by this
5608 command. This requires the same kind of address (more than one for some
5609 architectures) that you specify in the @code{frame} command.
5610 @xref{Selection, ,Selecting a Frame}.
5614 Print the arguments of the selected frame, each on a separate line.
5618 Print the local variables of the selected frame, each on a separate
5619 line. These are all variables (declared either static or automatic)
5620 accessible at the point of execution of the selected frame.
5623 @cindex catch exceptions, list active handlers
5624 @cindex exception handlers, how to list
5626 Print a list of all the exception handlers that are active in the
5627 current stack frame at the current point of execution. To see other
5628 exception handlers, visit the associated frame (using the @code{up},
5629 @code{down}, or @code{frame} commands); then type @code{info catch}.
5630 @xref{Set Catchpoints, , Setting Catchpoints}.
5636 @chapter Examining Source Files
5638 @value{GDBN} can print parts of your program's source, since the debugging
5639 information recorded in the program tells @value{GDBN} what source files were
5640 used to build it. When your program stops, @value{GDBN} spontaneously prints
5641 the line where it stopped. Likewise, when you select a stack frame
5642 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
5643 execution in that frame has stopped. You can print other portions of
5644 source files by explicit command.
5646 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
5647 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
5648 @value{GDBN} under @sc{gnu} Emacs}.
5651 * List:: Printing source lines
5652 * Specify Location:: How to specify code locations
5653 * Edit:: Editing source files
5654 * Search:: Searching source files
5655 * Source Path:: Specifying source directories
5656 * Machine Code:: Source and machine code
5660 @section Printing Source Lines
5663 @kindex l @r{(@code{list})}
5664 To print lines from a source file, use the @code{list} command
5665 (abbreviated @code{l}). By default, ten lines are printed.
5666 There are several ways to specify what part of the file you want to
5667 print; see @ref{Specify Location}, for the full list.
5669 Here are the forms of the @code{list} command most commonly used:
5672 @item list @var{linenum}
5673 Print lines centered around line number @var{linenum} in the
5674 current source file.
5676 @item list @var{function}
5677 Print lines centered around the beginning of function
5681 Print more lines. If the last lines printed were printed with a
5682 @code{list} command, this prints lines following the last lines
5683 printed; however, if the last line printed was a solitary line printed
5684 as part of displaying a stack frame (@pxref{Stack, ,Examining the
5685 Stack}), this prints lines centered around that line.
5688 Print lines just before the lines last printed.
5691 @cindex @code{list}, how many lines to display
5692 By default, @value{GDBN} prints ten source lines with any of these forms of
5693 the @code{list} command. You can change this using @code{set listsize}:
5696 @kindex set listsize
5697 @item set listsize @var{count}
5698 Make the @code{list} command display @var{count} source lines (unless
5699 the @code{list} argument explicitly specifies some other number).
5701 @kindex show listsize
5703 Display the number of lines that @code{list} prints.
5706 Repeating a @code{list} command with @key{RET} discards the argument,
5707 so it is equivalent to typing just @code{list}. This is more useful
5708 than listing the same lines again. An exception is made for an
5709 argument of @samp{-}; that argument is preserved in repetition so that
5710 each repetition moves up in the source file.
5712 In general, the @code{list} command expects you to supply zero, one or two
5713 @dfn{linespecs}. Linespecs specify source lines; there are several ways
5714 of writing them (@pxref{Specify Location}), but the effect is always
5715 to specify some source line.
5717 Here is a complete description of the possible arguments for @code{list}:
5720 @item list @var{linespec}
5721 Print lines centered around the line specified by @var{linespec}.
5723 @item list @var{first},@var{last}
5724 Print lines from @var{first} to @var{last}. Both arguments are
5725 linespecs. When a @code{list} command has two linespecs, and the
5726 source file of the second linespec is omitted, this refers to
5727 the same source file as the first linespec.
5729 @item list ,@var{last}
5730 Print lines ending with @var{last}.
5732 @item list @var{first},
5733 Print lines starting with @var{first}.
5736 Print lines just after the lines last printed.
5739 Print lines just before the lines last printed.
5742 As described in the preceding table.
5745 @node Specify Location
5746 @section Specifying a Location
5747 @cindex specifying location
5750 Several @value{GDBN} commands accept arguments that specify a location
5751 of your program's code. Since @value{GDBN} is a source-level
5752 debugger, a location usually specifies some line in the source code;
5753 for that reason, locations are also known as @dfn{linespecs}.
5755 Here are all the different ways of specifying a code location that
5756 @value{GDBN} understands:
5760 Specifies the line number @var{linenum} of the current source file.
5763 @itemx +@var{offset}
5764 Specifies the line @var{offset} lines before or after the @dfn{current
5765 line}. For the @code{list} command, the current line is the last one
5766 printed; for the breakpoint commands, this is the line at which
5767 execution stopped in the currently selected @dfn{stack frame}
5768 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
5769 used as the second of the two linespecs in a @code{list} command,
5770 this specifies the line @var{offset} lines up or down from the first
5773 @item @var{filename}:@var{linenum}
5774 Specifies the line @var{linenum} in the source file @var{filename}.
5776 @item @var{function}
5777 Specifies the line that begins the body of the function @var{function}.
5778 For example, in C, this is the line with the open brace.
5780 @item @var{filename}:@var{function}
5781 Specifies the line that begins the body of the function @var{function}
5782 in the file @var{filename}. You only need the file name with a
5783 function name to avoid ambiguity when there are identically named
5784 functions in different source files.
5786 @item *@var{address}
5787 Specifies the program address @var{address}. For line-oriented
5788 commands, such as @code{list} and @code{edit}, this specifies a source
5789 line that contains @var{address}. For @code{break} and other
5790 breakpoint oriented commands, this can be used to set breakpoints in
5791 parts of your program which do not have debugging information or
5794 Here @var{address} may be any expression valid in the current working
5795 language (@pxref{Languages, working language}) that specifies a code
5796 address. In addition, as a convenience, @value{GDBN} extends the
5797 semantics of expressions used in locations to cover the situations
5798 that frequently happen during debugging. Here are the various forms
5802 @item @var{expression}
5803 Any expression valid in the current working language.
5805 @item @var{funcaddr}
5806 An address of a function or procedure derived from its name. In C,
5807 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
5808 simply the function's name @var{function} (and actually a special case
5809 of a valid expression). In Pascal and Modula-2, this is
5810 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
5811 (although the Pascal form also works).
5813 This form specifies the address of the function's first instruction,
5814 before the stack frame and arguments have been set up.
5816 @item '@var{filename}'::@var{funcaddr}
5817 Like @var{funcaddr} above, but also specifies the name of the source
5818 file explicitly. This is useful if the name of the function does not
5819 specify the function unambiguously, e.g., if there are several
5820 functions with identical names in different source files.
5827 @section Editing Source Files
5828 @cindex editing source files
5831 @kindex e @r{(@code{edit})}
5832 To edit the lines in a source file, use the @code{edit} command.
5833 The editing program of your choice
5834 is invoked with the current line set to
5835 the active line in the program.
5836 Alternatively, there are several ways to specify what part of the file you
5837 want to print if you want to see other parts of the program:
5840 @item edit @var{location}
5841 Edit the source file specified by @code{location}. Editing starts at
5842 that @var{location}, e.g., at the specified source line of the
5843 specified file. @xref{Specify Location}, for all the possible forms
5844 of the @var{location} argument; here are the forms of the @code{edit}
5845 command most commonly used:
5848 @item edit @var{number}
5849 Edit the current source file with @var{number} as the active line number.
5851 @item edit @var{function}
5852 Edit the file containing @var{function} at the beginning of its definition.
5857 @subsection Choosing your Editor
5858 You can customize @value{GDBN} to use any editor you want
5860 The only restriction is that your editor (say @code{ex}), recognizes the
5861 following command-line syntax:
5863 ex +@var{number} file
5865 The optional numeric value +@var{number} specifies the number of the line in
5866 the file where to start editing.}.
5867 By default, it is @file{@value{EDITOR}}, but you can change this
5868 by setting the environment variable @code{EDITOR} before using
5869 @value{GDBN}. For example, to configure @value{GDBN} to use the
5870 @code{vi} editor, you could use these commands with the @code{sh} shell:
5876 or in the @code{csh} shell,
5878 setenv EDITOR /usr/bin/vi
5883 @section Searching Source Files
5884 @cindex searching source files
5886 There are two commands for searching through the current source file for a
5891 @kindex forward-search
5892 @item forward-search @var{regexp}
5893 @itemx search @var{regexp}
5894 The command @samp{forward-search @var{regexp}} checks each line,
5895 starting with the one following the last line listed, for a match for
5896 @var{regexp}. It lists the line that is found. You can use the
5897 synonym @samp{search @var{regexp}} or abbreviate the command name as
5900 @kindex reverse-search
5901 @item reverse-search @var{regexp}
5902 The command @samp{reverse-search @var{regexp}} checks each line, starting
5903 with the one before the last line listed and going backward, for a match
5904 for @var{regexp}. It lists the line that is found. You can abbreviate
5905 this command as @code{rev}.
5909 @section Specifying Source Directories
5912 @cindex directories for source files
5913 Executable programs sometimes do not record the directories of the source
5914 files from which they were compiled, just the names. Even when they do,
5915 the directories could be moved between the compilation and your debugging
5916 session. @value{GDBN} has a list of directories to search for source files;
5917 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
5918 it tries all the directories in the list, in the order they are present
5919 in the list, until it finds a file with the desired name.
5921 For example, suppose an executable references the file
5922 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
5923 @file{/mnt/cross}. The file is first looked up literally; if this
5924 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
5925 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
5926 message is printed. @value{GDBN} does not look up the parts of the
5927 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
5928 Likewise, the subdirectories of the source path are not searched: if
5929 the source path is @file{/mnt/cross}, and the binary refers to
5930 @file{foo.c}, @value{GDBN} would not find it under
5931 @file{/mnt/cross/usr/src/foo-1.0/lib}.
5933 Plain file names, relative file names with leading directories, file
5934 names containing dots, etc.@: are all treated as described above; for
5935 instance, if the source path is @file{/mnt/cross}, and the source file
5936 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
5937 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
5938 that---@file{/mnt/cross/foo.c}.
5940 Note that the executable search path is @emph{not} used to locate the
5943 Whenever you reset or rearrange the source path, @value{GDBN} clears out
5944 any information it has cached about where source files are found and where
5945 each line is in the file.
5949 When you start @value{GDBN}, its source path includes only @samp{cdir}
5950 and @samp{cwd}, in that order.
5951 To add other directories, use the @code{directory} command.
5953 The search path is used to find both program source files and @value{GDBN}
5954 script files (read using the @samp{-command} option and @samp{source} command).
5956 In addition to the source path, @value{GDBN} provides a set of commands
5957 that manage a list of source path substitution rules. A @dfn{substitution
5958 rule} specifies how to rewrite source directories stored in the program's
5959 debug information in case the sources were moved to a different
5960 directory between compilation and debugging. A rule is made of
5961 two strings, the first specifying what needs to be rewritten in
5962 the path, and the second specifying how it should be rewritten.
5963 In @ref{set substitute-path}, we name these two parts @var{from} and
5964 @var{to} respectively. @value{GDBN} does a simple string replacement
5965 of @var{from} with @var{to} at the start of the directory part of the
5966 source file name, and uses that result instead of the original file
5967 name to look up the sources.
5969 Using the previous example, suppose the @file{foo-1.0} tree has been
5970 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
5971 @value{GDBN} to replace @file{/usr/src} in all source path names with
5972 @file{/mnt/cross}. The first lookup will then be
5973 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
5974 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
5975 substitution rule, use the @code{set substitute-path} command
5976 (@pxref{set substitute-path}).
5978 To avoid unexpected substitution results, a rule is applied only if the
5979 @var{from} part of the directory name ends at a directory separator.
5980 For instance, a rule substituting @file{/usr/source} into
5981 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
5982 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
5983 is applied only at the beginning of the directory name, this rule will
5984 not be applied to @file{/root/usr/source/baz.c} either.
5986 In many cases, you can achieve the same result using the @code{directory}
5987 command. However, @code{set substitute-path} can be more efficient in
5988 the case where the sources are organized in a complex tree with multiple
5989 subdirectories. With the @code{directory} command, you need to add each
5990 subdirectory of your project. If you moved the entire tree while
5991 preserving its internal organization, then @code{set substitute-path}
5992 allows you to direct the debugger to all the sources with one single
5995 @code{set substitute-path} is also more than just a shortcut command.
5996 The source path is only used if the file at the original location no
5997 longer exists. On the other hand, @code{set substitute-path} modifies
5998 the debugger behavior to look at the rewritten location instead. So, if
5999 for any reason a source file that is not relevant to your executable is
6000 located at the original location, a substitution rule is the only
6001 method available to point @value{GDBN} at the new location.
6003 @cindex @samp{--with-relocated-sources}
6004 @cindex default source path substitution
6005 You can configure a default source path substitution rule by
6006 configuring @value{GDBN} with the
6007 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6008 should be the name of a directory under @value{GDBN}'s configured
6009 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6010 directory names in debug information under @var{dir} will be adjusted
6011 automatically if the installed @value{GDBN} is moved to a new
6012 location. This is useful if @value{GDBN}, libraries or executables
6013 with debug information and corresponding source code are being moved
6017 @item directory @var{dirname} @dots{}
6018 @item dir @var{dirname} @dots{}
6019 Add directory @var{dirname} to the front of the source path. Several
6020 directory names may be given to this command, separated by @samp{:}
6021 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6022 part of absolute file names) or
6023 whitespace. You may specify a directory that is already in the source
6024 path; this moves it forward, so @value{GDBN} searches it sooner.
6028 @vindex $cdir@r{, convenience variable}
6029 @vindex $cwd@r{, convenience variable}
6030 @cindex compilation directory
6031 @cindex current directory
6032 @cindex working directory
6033 @cindex directory, current
6034 @cindex directory, compilation
6035 You can use the string @samp{$cdir} to refer to the compilation
6036 directory (if one is recorded), and @samp{$cwd} to refer to the current
6037 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6038 tracks the current working directory as it changes during your @value{GDBN}
6039 session, while the latter is immediately expanded to the current
6040 directory at the time you add an entry to the source path.
6043 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6045 @c RET-repeat for @code{directory} is explicitly disabled, but since
6046 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6048 @item show directories
6049 @kindex show directories
6050 Print the source path: show which directories it contains.
6052 @anchor{set substitute-path}
6053 @item set substitute-path @var{from} @var{to}
6054 @kindex set substitute-path
6055 Define a source path substitution rule, and add it at the end of the
6056 current list of existing substitution rules. If a rule with the same
6057 @var{from} was already defined, then the old rule is also deleted.
6059 For example, if the file @file{/foo/bar/baz.c} was moved to
6060 @file{/mnt/cross/baz.c}, then the command
6063 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6067 will tell @value{GDBN} to replace @samp{/usr/src} with
6068 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6069 @file{baz.c} even though it was moved.
6071 In the case when more than one substitution rule have been defined,
6072 the rules are evaluated one by one in the order where they have been
6073 defined. The first one matching, if any, is selected to perform
6076 For instance, if we had entered the following commands:
6079 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6080 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6084 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6085 @file{/mnt/include/defs.h} by using the first rule. However, it would
6086 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6087 @file{/mnt/src/lib/foo.c}.
6090 @item unset substitute-path [path]
6091 @kindex unset substitute-path
6092 If a path is specified, search the current list of substitution rules
6093 for a rule that would rewrite that path. Delete that rule if found.
6094 A warning is emitted by the debugger if no rule could be found.
6096 If no path is specified, then all substitution rules are deleted.
6098 @item show substitute-path [path]
6099 @kindex show substitute-path
6100 If a path is specified, then print the source path substitution rule
6101 which would rewrite that path, if any.
6103 If no path is specified, then print all existing source path substitution
6108 If your source path is cluttered with directories that are no longer of
6109 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6110 versions of source. You can correct the situation as follows:
6114 Use @code{directory} with no argument to reset the source path to its default value.
6117 Use @code{directory} with suitable arguments to reinstall the
6118 directories you want in the source path. You can add all the
6119 directories in one command.
6123 @section Source and Machine Code
6124 @cindex source line and its code address
6126 You can use the command @code{info line} to map source lines to program
6127 addresses (and vice versa), and the command @code{disassemble} to display
6128 a range of addresses as machine instructions. You can use the command
6129 @code{set disassemble-next-line} to set whether to disassemble next
6130 source line when execution stops. When run under @sc{gnu} Emacs
6131 mode, the @code{info line} command causes the arrow to point to the
6132 line specified. Also, @code{info line} prints addresses in symbolic form as
6137 @item info line @var{linespec}
6138 Print the starting and ending addresses of the compiled code for
6139 source line @var{linespec}. You can specify source lines in any of
6140 the ways documented in @ref{Specify Location}.
6143 For example, we can use @code{info line} to discover the location of
6144 the object code for the first line of function
6145 @code{m4_changequote}:
6147 @c FIXME: I think this example should also show the addresses in
6148 @c symbolic form, as they usually would be displayed.
6150 (@value{GDBP}) info line m4_changequote
6151 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6155 @cindex code address and its source line
6156 We can also inquire (using @code{*@var{addr}} as the form for
6157 @var{linespec}) what source line covers a particular address:
6159 (@value{GDBP}) info line *0x63ff
6160 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6163 @cindex @code{$_} and @code{info line}
6164 @cindex @code{x} command, default address
6165 @kindex x@r{(examine), and} info line
6166 After @code{info line}, the default address for the @code{x} command
6167 is changed to the starting address of the line, so that @samp{x/i} is
6168 sufficient to begin examining the machine code (@pxref{Memory,
6169 ,Examining Memory}). Also, this address is saved as the value of the
6170 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6175 @cindex assembly instructions
6176 @cindex instructions, assembly
6177 @cindex machine instructions
6178 @cindex listing machine instructions
6180 @itemx disassemble /m
6181 @itemx disassemble /r
6182 This specialized command dumps a range of memory as machine
6183 instructions. It can also print mixed source+disassembly by specifying
6184 the @code{/m} modifier and print the raw instructions in hex as well as
6185 in symbolic form by specifying the @code{/r}.
6186 The default memory range is the function surrounding the
6187 program counter of the selected frame. A single argument to this
6188 command is a program counter value; @value{GDBN} dumps the function
6189 surrounding this value. Two arguments specify a range of addresses
6190 (first inclusive, second exclusive) to dump.
6193 The following example shows the disassembly of a range of addresses of
6194 HP PA-RISC 2.0 code:
6197 (@value{GDBP}) disas 0x32c4 0x32e4
6198 Dump of assembler code from 0x32c4 to 0x32e4:
6199 0x32c4 <main+204>: addil 0,dp
6200 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6201 0x32cc <main+212>: ldil 0x3000,r31
6202 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6203 0x32d4 <main+220>: ldo 0(r31),rp
6204 0x32d8 <main+224>: addil -0x800,dp
6205 0x32dc <main+228>: ldo 0x588(r1),r26
6206 0x32e0 <main+232>: ldil 0x3000,r31
6207 End of assembler dump.
6210 Here is an example showing mixed source+assembly for Intel x86:
6213 (@value{GDBP}) disas /m main
6214 Dump of assembler code for function main:
6216 0x08048330 <main+0>: push %ebp
6217 0x08048331 <main+1>: mov %esp,%ebp
6218 0x08048333 <main+3>: sub $0x8,%esp
6219 0x08048336 <main+6>: and $0xfffffff0,%esp
6220 0x08048339 <main+9>: sub $0x10,%esp
6222 6 printf ("Hello.\n");
6223 0x0804833c <main+12>: movl $0x8048440,(%esp)
6224 0x08048343 <main+19>: call 0x8048284 <puts@@plt>
6228 0x08048348 <main+24>: mov $0x0,%eax
6229 0x0804834d <main+29>: leave
6230 0x0804834e <main+30>: ret
6232 End of assembler dump.
6235 Some architectures have more than one commonly-used set of instruction
6236 mnemonics or other syntax.
6238 For programs that were dynamically linked and use shared libraries,
6239 instructions that call functions or branch to locations in the shared
6240 libraries might show a seemingly bogus location---it's actually a
6241 location of the relocation table. On some architectures, @value{GDBN}
6242 might be able to resolve these to actual function names.
6245 @kindex set disassembly-flavor
6246 @cindex Intel disassembly flavor
6247 @cindex AT&T disassembly flavor
6248 @item set disassembly-flavor @var{instruction-set}
6249 Select the instruction set to use when disassembling the
6250 program via the @code{disassemble} or @code{x/i} commands.
6252 Currently this command is only defined for the Intel x86 family. You
6253 can set @var{instruction-set} to either @code{intel} or @code{att}.
6254 The default is @code{att}, the AT&T flavor used by default by Unix
6255 assemblers for x86-based targets.
6257 @kindex show disassembly-flavor
6258 @item show disassembly-flavor
6259 Show the current setting of the disassembly flavor.
6263 @kindex set disassemble-next-line
6264 @kindex show disassemble-next-line
6265 @item set disassemble-next-line
6266 @itemx show disassemble-next-line
6267 Control whether or not @value{GDBN} will disassemble the next source
6268 line or instruction when execution stops. If ON, @value{GDBN} will
6269 display disassembly of the next source line when execution of the
6270 program being debugged stops. This is @emph{in addition} to
6271 displaying the source line itself, which @value{GDBN} always does if
6272 possible. If the next source line cannot be displayed for some reason
6273 (e.g., if @value{GDBN} cannot find the source file, or there's no line
6274 info in the debug info), @value{GDBN} will display disassembly of the
6275 next @emph{instruction} instead of showing the next source line. If
6276 AUTO, @value{GDBN} will display disassembly of next instruction only
6277 if the source line cannot be displayed. This setting causes
6278 @value{GDBN} to display some feedback when you step through a function
6279 with no line info or whose source file is unavailable. The default is
6280 OFF, which means never display the disassembly of the next line or
6286 @chapter Examining Data
6288 @cindex printing data
6289 @cindex examining data
6292 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6293 @c document because it is nonstandard... Under Epoch it displays in a
6294 @c different window or something like that.
6295 The usual way to examine data in your program is with the @code{print}
6296 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6297 evaluates and prints the value of an expression of the language your
6298 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6299 Different Languages}).
6302 @item print @var{expr}
6303 @itemx print /@var{f} @var{expr}
6304 @var{expr} is an expression (in the source language). By default the
6305 value of @var{expr} is printed in a format appropriate to its data type;
6306 you can choose a different format by specifying @samp{/@var{f}}, where
6307 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6311 @itemx print /@var{f}
6312 @cindex reprint the last value
6313 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6314 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6315 conveniently inspect the same value in an alternative format.
6318 A more low-level way of examining data is with the @code{x} command.
6319 It examines data in memory at a specified address and prints it in a
6320 specified format. @xref{Memory, ,Examining Memory}.
6322 If you are interested in information about types, or about how the
6323 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6324 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6328 * Expressions:: Expressions
6329 * Ambiguous Expressions:: Ambiguous Expressions
6330 * Variables:: Program variables
6331 * Arrays:: Artificial arrays
6332 * Output Formats:: Output formats
6333 * Memory:: Examining memory
6334 * Auto Display:: Automatic display
6335 * Print Settings:: Print settings
6336 * Value History:: Value history
6337 * Convenience Vars:: Convenience variables
6338 * Registers:: Registers
6339 * Floating Point Hardware:: Floating point hardware
6340 * Vector Unit:: Vector Unit
6341 * OS Information:: Auxiliary data provided by operating system
6342 * Memory Region Attributes:: Memory region attributes
6343 * Dump/Restore Files:: Copy between memory and a file
6344 * Core File Generation:: Cause a program dump its core
6345 * Character Sets:: Debugging programs that use a different
6346 character set than GDB does
6347 * Caching Remote Data:: Data caching for remote targets
6348 * Searching Memory:: Searching memory for a sequence of bytes
6352 @section Expressions
6355 @code{print} and many other @value{GDBN} commands accept an expression and
6356 compute its value. Any kind of constant, variable or operator defined
6357 by the programming language you are using is valid in an expression in
6358 @value{GDBN}. This includes conditional expressions, function calls,
6359 casts, and string constants. It also includes preprocessor macros, if
6360 you compiled your program to include this information; see
6363 @cindex arrays in expressions
6364 @value{GDBN} supports array constants in expressions input by
6365 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
6366 you can use the command @code{print @{1, 2, 3@}} to create an array
6367 of three integers. If you pass an array to a function or assign it
6368 to a program variable, @value{GDBN} copies the array to memory that
6369 is @code{malloc}ed in the target program.
6371 Because C is so widespread, most of the expressions shown in examples in
6372 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
6373 Languages}, for information on how to use expressions in other
6376 In this section, we discuss operators that you can use in @value{GDBN}
6377 expressions regardless of your programming language.
6379 @cindex casts, in expressions
6380 Casts are supported in all languages, not just in C, because it is so
6381 useful to cast a number into a pointer in order to examine a structure
6382 at that address in memory.
6383 @c FIXME: casts supported---Mod2 true?
6385 @value{GDBN} supports these operators, in addition to those common
6386 to programming languages:
6390 @samp{@@} is a binary operator for treating parts of memory as arrays.
6391 @xref{Arrays, ,Artificial Arrays}, for more information.
6394 @samp{::} allows you to specify a variable in terms of the file or
6395 function where it is defined. @xref{Variables, ,Program Variables}.
6397 @cindex @{@var{type}@}
6398 @cindex type casting memory
6399 @cindex memory, viewing as typed object
6400 @cindex casts, to view memory
6401 @item @{@var{type}@} @var{addr}
6402 Refers to an object of type @var{type} stored at address @var{addr} in
6403 memory. @var{addr} may be any expression whose value is an integer or
6404 pointer (but parentheses are required around binary operators, just as in
6405 a cast). This construct is allowed regardless of what kind of data is
6406 normally supposed to reside at @var{addr}.
6409 @node Ambiguous Expressions
6410 @section Ambiguous Expressions
6411 @cindex ambiguous expressions
6413 Expressions can sometimes contain some ambiguous elements. For instance,
6414 some programming languages (notably Ada, C@t{++} and Objective-C) permit
6415 a single function name to be defined several times, for application in
6416 different contexts. This is called @dfn{overloading}. Another example
6417 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
6418 templates and is typically instantiated several times, resulting in
6419 the same function name being defined in different contexts.
6421 In some cases and depending on the language, it is possible to adjust
6422 the expression to remove the ambiguity. For instance in C@t{++}, you
6423 can specify the signature of the function you want to break on, as in
6424 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
6425 qualified name of your function often makes the expression unambiguous
6428 When an ambiguity that needs to be resolved is detected, the debugger
6429 has the capability to display a menu of numbered choices for each
6430 possibility, and then waits for the selection with the prompt @samp{>}.
6431 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
6432 aborts the current command. If the command in which the expression was
6433 used allows more than one choice to be selected, the next option in the
6434 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
6437 For example, the following session excerpt shows an attempt to set a
6438 breakpoint at the overloaded symbol @code{String::after}.
6439 We choose three particular definitions of that function name:
6441 @c FIXME! This is likely to change to show arg type lists, at least
6444 (@value{GDBP}) b String::after
6447 [2] file:String.cc; line number:867
6448 [3] file:String.cc; line number:860
6449 [4] file:String.cc; line number:875
6450 [5] file:String.cc; line number:853
6451 [6] file:String.cc; line number:846
6452 [7] file:String.cc; line number:735
6454 Breakpoint 1 at 0xb26c: file String.cc, line 867.
6455 Breakpoint 2 at 0xb344: file String.cc, line 875.
6456 Breakpoint 3 at 0xafcc: file String.cc, line 846.
6457 Multiple breakpoints were set.
6458 Use the "delete" command to delete unwanted
6465 @kindex set multiple-symbols
6466 @item set multiple-symbols @var{mode}
6467 @cindex multiple-symbols menu
6469 This option allows you to adjust the debugger behavior when an expression
6472 By default, @var{mode} is set to @code{all}. If the command with which
6473 the expression is used allows more than one choice, then @value{GDBN}
6474 automatically selects all possible choices. For instance, inserting
6475 a breakpoint on a function using an ambiguous name results in a breakpoint
6476 inserted on each possible match. However, if a unique choice must be made,
6477 then @value{GDBN} uses the menu to help you disambiguate the expression.
6478 For instance, printing the address of an overloaded function will result
6479 in the use of the menu.
6481 When @var{mode} is set to @code{ask}, the debugger always uses the menu
6482 when an ambiguity is detected.
6484 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
6485 an error due to the ambiguity and the command is aborted.
6487 @kindex show multiple-symbols
6488 @item show multiple-symbols
6489 Show the current value of the @code{multiple-symbols} setting.
6493 @section Program Variables
6495 The most common kind of expression to use is the name of a variable
6498 Variables in expressions are understood in the selected stack frame
6499 (@pxref{Selection, ,Selecting a Frame}); they must be either:
6503 global (or file-static)
6510 visible according to the scope rules of the
6511 programming language from the point of execution in that frame
6514 @noindent This means that in the function
6529 you can examine and use the variable @code{a} whenever your program is
6530 executing within the function @code{foo}, but you can only use or
6531 examine the variable @code{b} while your program is executing inside
6532 the block where @code{b} is declared.
6534 @cindex variable name conflict
6535 There is an exception: you can refer to a variable or function whose
6536 scope is a single source file even if the current execution point is not
6537 in this file. But it is possible to have more than one such variable or
6538 function with the same name (in different source files). If that
6539 happens, referring to that name has unpredictable effects. If you wish,
6540 you can specify a static variable in a particular function or file,
6541 using the colon-colon (@code{::}) notation:
6543 @cindex colon-colon, context for variables/functions
6545 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
6546 @cindex @code{::}, context for variables/functions
6549 @var{file}::@var{variable}
6550 @var{function}::@var{variable}
6554 Here @var{file} or @var{function} is the name of the context for the
6555 static @var{variable}. In the case of file names, you can use quotes to
6556 make sure @value{GDBN} parses the file name as a single word---for example,
6557 to print a global value of @code{x} defined in @file{f2.c}:
6560 (@value{GDBP}) p 'f2.c'::x
6563 @cindex C@t{++} scope resolution
6564 This use of @samp{::} is very rarely in conflict with the very similar
6565 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
6566 scope resolution operator in @value{GDBN} expressions.
6567 @c FIXME: Um, so what happens in one of those rare cases where it's in
6570 @cindex wrong values
6571 @cindex variable values, wrong
6572 @cindex function entry/exit, wrong values of variables
6573 @cindex optimized code, wrong values of variables
6575 @emph{Warning:} Occasionally, a local variable may appear to have the
6576 wrong value at certain points in a function---just after entry to a new
6577 scope, and just before exit.
6579 You may see this problem when you are stepping by machine instructions.
6580 This is because, on most machines, it takes more than one instruction to
6581 set up a stack frame (including local variable definitions); if you are
6582 stepping by machine instructions, variables may appear to have the wrong
6583 values until the stack frame is completely built. On exit, it usually
6584 also takes more than one machine instruction to destroy a stack frame;
6585 after you begin stepping through that group of instructions, local
6586 variable definitions may be gone.
6588 This may also happen when the compiler does significant optimizations.
6589 To be sure of always seeing accurate values, turn off all optimization
6592 @cindex ``No symbol "foo" in current context''
6593 Another possible effect of compiler optimizations is to optimize
6594 unused variables out of existence, or assign variables to registers (as
6595 opposed to memory addresses). Depending on the support for such cases
6596 offered by the debug info format used by the compiler, @value{GDBN}
6597 might not be able to display values for such local variables. If that
6598 happens, @value{GDBN} will print a message like this:
6601 No symbol "foo" in current context.
6604 To solve such problems, either recompile without optimizations, or use a
6605 different debug info format, if the compiler supports several such
6606 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
6607 usually supports the @option{-gstabs+} option. @option{-gstabs+}
6608 produces debug info in a format that is superior to formats such as
6609 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
6610 an effective form for debug info. @xref{Debugging Options,,Options
6611 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
6612 Compiler Collection (GCC)}.
6613 @xref{C, ,C and C@t{++}}, for more information about debug info formats
6614 that are best suited to C@t{++} programs.
6616 If you ask to print an object whose contents are unknown to
6617 @value{GDBN}, e.g., because its data type is not completely specified
6618 by the debug information, @value{GDBN} will say @samp{<incomplete
6619 type>}. @xref{Symbols, incomplete type}, for more about this.
6621 Strings are identified as arrays of @code{char} values without specified
6622 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
6623 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
6624 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
6625 defines literal string type @code{"char"} as @code{char} without a sign.
6630 signed char var1[] = "A";
6633 You get during debugging
6638 $2 = @{65 'A', 0 '\0'@}
6642 @section Artificial Arrays
6644 @cindex artificial array
6646 @kindex @@@r{, referencing memory as an array}
6647 It is often useful to print out several successive objects of the
6648 same type in memory; a section of an array, or an array of
6649 dynamically determined size for which only a pointer exists in the
6652 You can do this by referring to a contiguous span of memory as an
6653 @dfn{artificial array}, using the binary operator @samp{@@}. The left
6654 operand of @samp{@@} should be the first element of the desired array
6655 and be an individual object. The right operand should be the desired length
6656 of the array. The result is an array value whose elements are all of
6657 the type of the left argument. The first element is actually the left
6658 argument; the second element comes from bytes of memory immediately
6659 following those that hold the first element, and so on. Here is an
6660 example. If a program says
6663 int *array = (int *) malloc (len * sizeof (int));
6667 you can print the contents of @code{array} with
6673 The left operand of @samp{@@} must reside in memory. Array values made
6674 with @samp{@@} in this way behave just like other arrays in terms of
6675 subscripting, and are coerced to pointers when used in expressions.
6676 Artificial arrays most often appear in expressions via the value history
6677 (@pxref{Value History, ,Value History}), after printing one out.
6679 Another way to create an artificial array is to use a cast.
6680 This re-interprets a value as if it were an array.
6681 The value need not be in memory:
6683 (@value{GDBP}) p/x (short[2])0x12345678
6684 $1 = @{0x1234, 0x5678@}
6687 As a convenience, if you leave the array length out (as in
6688 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
6689 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
6691 (@value{GDBP}) p/x (short[])0x12345678
6692 $2 = @{0x1234, 0x5678@}
6695 Sometimes the artificial array mechanism is not quite enough; in
6696 moderately complex data structures, the elements of interest may not
6697 actually be adjacent---for example, if you are interested in the values
6698 of pointers in an array. One useful work-around in this situation is
6699 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
6700 Variables}) as a counter in an expression that prints the first
6701 interesting value, and then repeat that expression via @key{RET}. For
6702 instance, suppose you have an array @code{dtab} of pointers to
6703 structures, and you are interested in the values of a field @code{fv}
6704 in each structure. Here is an example of what you might type:
6714 @node Output Formats
6715 @section Output Formats
6717 @cindex formatted output
6718 @cindex output formats
6719 By default, @value{GDBN} prints a value according to its data type. Sometimes
6720 this is not what you want. For example, you might want to print a number
6721 in hex, or a pointer in decimal. Or you might want to view data in memory
6722 at a certain address as a character string or as an instruction. To do
6723 these things, specify an @dfn{output format} when you print a value.
6725 The simplest use of output formats is to say how to print a value
6726 already computed. This is done by starting the arguments of the
6727 @code{print} command with a slash and a format letter. The format
6728 letters supported are:
6732 Regard the bits of the value as an integer, and print the integer in
6736 Print as integer in signed decimal.
6739 Print as integer in unsigned decimal.
6742 Print as integer in octal.
6745 Print as integer in binary. The letter @samp{t} stands for ``two''.
6746 @footnote{@samp{b} cannot be used because these format letters are also
6747 used with the @code{x} command, where @samp{b} stands for ``byte'';
6748 see @ref{Memory,,Examining Memory}.}
6751 @cindex unknown address, locating
6752 @cindex locate address
6753 Print as an address, both absolute in hexadecimal and as an offset from
6754 the nearest preceding symbol. You can use this format used to discover
6755 where (in what function) an unknown address is located:
6758 (@value{GDBP}) p/a 0x54320
6759 $3 = 0x54320 <_initialize_vx+396>
6763 The command @code{info symbol 0x54320} yields similar results.
6764 @xref{Symbols, info symbol}.
6767 Regard as an integer and print it as a character constant. This
6768 prints both the numerical value and its character representation. The
6769 character representation is replaced with the octal escape @samp{\nnn}
6770 for characters outside the 7-bit @sc{ascii} range.
6772 Without this format, @value{GDBN} displays @code{char},
6773 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
6774 constants. Single-byte members of vectors are displayed as integer
6778 Regard the bits of the value as a floating point number and print
6779 using typical floating point syntax.
6782 @cindex printing strings
6783 @cindex printing byte arrays
6784 Regard as a string, if possible. With this format, pointers to single-byte
6785 data are displayed as null-terminated strings and arrays of single-byte data
6786 are displayed as fixed-length strings. Other values are displayed in their
6789 Without this format, @value{GDBN} displays pointers to and arrays of
6790 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
6791 strings. Single-byte members of a vector are displayed as an integer
6795 @cindex raw printing
6796 Print using the @samp{raw} formatting. By default, @value{GDBN} will
6797 use a type-specific pretty-printer. The @samp{r} format bypasses any
6798 pretty-printer which might exist for the value's type.
6801 For example, to print the program counter in hex (@pxref{Registers}), type
6808 Note that no space is required before the slash; this is because command
6809 names in @value{GDBN} cannot contain a slash.
6811 To reprint the last value in the value history with a different format,
6812 you can use the @code{print} command with just a format and no
6813 expression. For example, @samp{p/x} reprints the last value in hex.
6816 @section Examining Memory
6818 You can use the command @code{x} (for ``examine'') to examine memory in
6819 any of several formats, independently of your program's data types.
6821 @cindex examining memory
6823 @kindex x @r{(examine memory)}
6824 @item x/@var{nfu} @var{addr}
6827 Use the @code{x} command to examine memory.
6830 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
6831 much memory to display and how to format it; @var{addr} is an
6832 expression giving the address where you want to start displaying memory.
6833 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
6834 Several commands set convenient defaults for @var{addr}.
6837 @item @var{n}, the repeat count
6838 The repeat count is a decimal integer; the default is 1. It specifies
6839 how much memory (counting by units @var{u}) to display.
6840 @c This really is **decimal**; unaffected by 'set radix' as of GDB
6843 @item @var{f}, the display format
6844 The display format is one of the formats used by @code{print}
6845 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
6846 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
6847 The default is @samp{x} (hexadecimal) initially. The default changes
6848 each time you use either @code{x} or @code{print}.
6850 @item @var{u}, the unit size
6851 The unit size is any of
6857 Halfwords (two bytes).
6859 Words (four bytes). This is the initial default.
6861 Giant words (eight bytes).
6864 Each time you specify a unit size with @code{x}, that size becomes the
6865 default unit the next time you use @code{x}. (For the @samp{s} and
6866 @samp{i} formats, the unit size is ignored and is normally not written.)
6868 @item @var{addr}, starting display address
6869 @var{addr} is the address where you want @value{GDBN} to begin displaying
6870 memory. The expression need not have a pointer value (though it may);
6871 it is always interpreted as an integer address of a byte of memory.
6872 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
6873 @var{addr} is usually just after the last address examined---but several
6874 other commands also set the default address: @code{info breakpoints} (to
6875 the address of the last breakpoint listed), @code{info line} (to the
6876 starting address of a line), and @code{print} (if you use it to display
6877 a value from memory).
6880 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
6881 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
6882 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
6883 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
6884 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
6886 Since the letters indicating unit sizes are all distinct from the
6887 letters specifying output formats, you do not have to remember whether
6888 unit size or format comes first; either order works. The output
6889 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
6890 (However, the count @var{n} must come first; @samp{wx4} does not work.)
6892 Even though the unit size @var{u} is ignored for the formats @samp{s}
6893 and @samp{i}, you might still want to use a count @var{n}; for example,
6894 @samp{3i} specifies that you want to see three machine instructions,
6895 including any operands. For convenience, especially when used with
6896 the @code{display} command, the @samp{i} format also prints branch delay
6897 slot instructions, if any, beyond the count specified, which immediately
6898 follow the last instruction that is within the count. The command
6899 @code{disassemble} gives an alternative way of inspecting machine
6900 instructions; see @ref{Machine Code,,Source and Machine Code}.
6902 All the defaults for the arguments to @code{x} are designed to make it
6903 easy to continue scanning memory with minimal specifications each time
6904 you use @code{x}. For example, after you have inspected three machine
6905 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
6906 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
6907 the repeat count @var{n} is used again; the other arguments default as
6908 for successive uses of @code{x}.
6910 @cindex @code{$_}, @code{$__}, and value history
6911 The addresses and contents printed by the @code{x} command are not saved
6912 in the value history because there is often too much of them and they
6913 would get in the way. Instead, @value{GDBN} makes these values available for
6914 subsequent use in expressions as values of the convenience variables
6915 @code{$_} and @code{$__}. After an @code{x} command, the last address
6916 examined is available for use in expressions in the convenience variable
6917 @code{$_}. The contents of that address, as examined, are available in
6918 the convenience variable @code{$__}.
6920 If the @code{x} command has a repeat count, the address and contents saved
6921 are from the last memory unit printed; this is not the same as the last
6922 address printed if several units were printed on the last line of output.
6924 @cindex remote memory comparison
6925 @cindex verify remote memory image
6926 When you are debugging a program running on a remote target machine
6927 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
6928 remote machine's memory against the executable file you downloaded to
6929 the target. The @code{compare-sections} command is provided for such
6933 @kindex compare-sections
6934 @item compare-sections @r{[}@var{section-name}@r{]}
6935 Compare the data of a loadable section @var{section-name} in the
6936 executable file of the program being debugged with the same section in
6937 the remote machine's memory, and report any mismatches. With no
6938 arguments, compares all loadable sections. This command's
6939 availability depends on the target's support for the @code{"qCRC"}
6944 @section Automatic Display
6945 @cindex automatic display
6946 @cindex display of expressions
6948 If you find that you want to print the value of an expression frequently
6949 (to see how it changes), you might want to add it to the @dfn{automatic
6950 display list} so that @value{GDBN} prints its value each time your program stops.
6951 Each expression added to the list is given a number to identify it;
6952 to remove an expression from the list, you specify that number.
6953 The automatic display looks like this:
6957 3: bar[5] = (struct hack *) 0x3804
6961 This display shows item numbers, expressions and their current values. As with
6962 displays you request manually using @code{x} or @code{print}, you can
6963 specify the output format you prefer; in fact, @code{display} decides
6964 whether to use @code{print} or @code{x} depending your format
6965 specification---it uses @code{x} if you specify either the @samp{i}
6966 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
6970 @item display @var{expr}
6971 Add the expression @var{expr} to the list of expressions to display
6972 each time your program stops. @xref{Expressions, ,Expressions}.
6974 @code{display} does not repeat if you press @key{RET} again after using it.
6976 @item display/@var{fmt} @var{expr}
6977 For @var{fmt} specifying only a display format and not a size or
6978 count, add the expression @var{expr} to the auto-display list but
6979 arrange to display it each time in the specified format @var{fmt}.
6980 @xref{Output Formats,,Output Formats}.
6982 @item display/@var{fmt} @var{addr}
6983 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
6984 number of units, add the expression @var{addr} as a memory address to
6985 be examined each time your program stops. Examining means in effect
6986 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
6989 For example, @samp{display/i $pc} can be helpful, to see the machine
6990 instruction about to be executed each time execution stops (@samp{$pc}
6991 is a common name for the program counter; @pxref{Registers, ,Registers}).
6994 @kindex delete display
6996 @item undisplay @var{dnums}@dots{}
6997 @itemx delete display @var{dnums}@dots{}
6998 Remove item numbers @var{dnums} from the list of expressions to display.
7000 @code{undisplay} does not repeat if you press @key{RET} after using it.
7001 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7003 @kindex disable display
7004 @item disable display @var{dnums}@dots{}
7005 Disable the display of item numbers @var{dnums}. A disabled display
7006 item is not printed automatically, but is not forgotten. It may be
7007 enabled again later.
7009 @kindex enable display
7010 @item enable display @var{dnums}@dots{}
7011 Enable display of item numbers @var{dnums}. It becomes effective once
7012 again in auto display of its expression, until you specify otherwise.
7015 Display the current values of the expressions on the list, just as is
7016 done when your program stops.
7018 @kindex info display
7020 Print the list of expressions previously set up to display
7021 automatically, each one with its item number, but without showing the
7022 values. This includes disabled expressions, which are marked as such.
7023 It also includes expressions which would not be displayed right now
7024 because they refer to automatic variables not currently available.
7027 @cindex display disabled out of scope
7028 If a display expression refers to local variables, then it does not make
7029 sense outside the lexical context for which it was set up. Such an
7030 expression is disabled when execution enters a context where one of its
7031 variables is not defined. For example, if you give the command
7032 @code{display last_char} while inside a function with an argument
7033 @code{last_char}, @value{GDBN} displays this argument while your program
7034 continues to stop inside that function. When it stops elsewhere---where
7035 there is no variable @code{last_char}---the display is disabled
7036 automatically. The next time your program stops where @code{last_char}
7037 is meaningful, you can enable the display expression once again.
7039 @node Print Settings
7040 @section Print Settings
7042 @cindex format options
7043 @cindex print settings
7044 @value{GDBN} provides the following ways to control how arrays, structures,
7045 and symbols are printed.
7048 These settings are useful for debugging programs in any language:
7052 @item set print address
7053 @itemx set print address on
7054 @cindex print/don't print memory addresses
7055 @value{GDBN} prints memory addresses showing the location of stack
7056 traces, structure values, pointer values, breakpoints, and so forth,
7057 even when it also displays the contents of those addresses. The default
7058 is @code{on}. For example, this is what a stack frame display looks like with
7059 @code{set print address on}:
7064 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7066 530 if (lquote != def_lquote)
7070 @item set print address off
7071 Do not print addresses when displaying their contents. For example,
7072 this is the same stack frame displayed with @code{set print address off}:
7076 (@value{GDBP}) set print addr off
7078 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7079 530 if (lquote != def_lquote)
7083 You can use @samp{set print address off} to eliminate all machine
7084 dependent displays from the @value{GDBN} interface. For example, with
7085 @code{print address off}, you should get the same text for backtraces on
7086 all machines---whether or not they involve pointer arguments.
7089 @item show print address
7090 Show whether or not addresses are to be printed.
7093 When @value{GDBN} prints a symbolic address, it normally prints the
7094 closest earlier symbol plus an offset. If that symbol does not uniquely
7095 identify the address (for example, it is a name whose scope is a single
7096 source file), you may need to clarify. One way to do this is with
7097 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7098 you can set @value{GDBN} to print the source file and line number when
7099 it prints a symbolic address:
7102 @item set print symbol-filename on
7103 @cindex source file and line of a symbol
7104 @cindex symbol, source file and line
7105 Tell @value{GDBN} to print the source file name and line number of a
7106 symbol in the symbolic form of an address.
7108 @item set print symbol-filename off
7109 Do not print source file name and line number of a symbol. This is the
7112 @item show print symbol-filename
7113 Show whether or not @value{GDBN} will print the source file name and
7114 line number of a symbol in the symbolic form of an address.
7117 Another situation where it is helpful to show symbol filenames and line
7118 numbers is when disassembling code; @value{GDBN} shows you the line
7119 number and source file that corresponds to each instruction.
7121 Also, you may wish to see the symbolic form only if the address being
7122 printed is reasonably close to the closest earlier symbol:
7125 @item set print max-symbolic-offset @var{max-offset}
7126 @cindex maximum value for offset of closest symbol
7127 Tell @value{GDBN} to only display the symbolic form of an address if the
7128 offset between the closest earlier symbol and the address is less than
7129 @var{max-offset}. The default is 0, which tells @value{GDBN}
7130 to always print the symbolic form of an address if any symbol precedes it.
7132 @item show print max-symbolic-offset
7133 Ask how large the maximum offset is that @value{GDBN} prints in a
7137 @cindex wild pointer, interpreting
7138 @cindex pointer, finding referent
7139 If you have a pointer and you are not sure where it points, try
7140 @samp{set print symbol-filename on}. Then you can determine the name
7141 and source file location of the variable where it points, using
7142 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7143 For example, here @value{GDBN} shows that a variable @code{ptt} points
7144 at another variable @code{t}, defined in @file{hi2.c}:
7147 (@value{GDBP}) set print symbol-filename on
7148 (@value{GDBP}) p/a ptt
7149 $4 = 0xe008 <t in hi2.c>
7153 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
7154 does not show the symbol name and filename of the referent, even with
7155 the appropriate @code{set print} options turned on.
7158 Other settings control how different kinds of objects are printed:
7161 @item set print array
7162 @itemx set print array on
7163 @cindex pretty print arrays
7164 Pretty print arrays. This format is more convenient to read,
7165 but uses more space. The default is off.
7167 @item set print array off
7168 Return to compressed format for arrays.
7170 @item show print array
7171 Show whether compressed or pretty format is selected for displaying
7174 @cindex print array indexes
7175 @item set print array-indexes
7176 @itemx set print array-indexes on
7177 Print the index of each element when displaying arrays. May be more
7178 convenient to locate a given element in the array or quickly find the
7179 index of a given element in that printed array. The default is off.
7181 @item set print array-indexes off
7182 Stop printing element indexes when displaying arrays.
7184 @item show print array-indexes
7185 Show whether the index of each element is printed when displaying
7188 @item set print elements @var{number-of-elements}
7189 @cindex number of array elements to print
7190 @cindex limit on number of printed array elements
7191 Set a limit on how many elements of an array @value{GDBN} will print.
7192 If @value{GDBN} is printing a large array, it stops printing after it has
7193 printed the number of elements set by the @code{set print elements} command.
7194 This limit also applies to the display of strings.
7195 When @value{GDBN} starts, this limit is set to 200.
7196 Setting @var{number-of-elements} to zero means that the printing is unlimited.
7198 @item show print elements
7199 Display the number of elements of a large array that @value{GDBN} will print.
7200 If the number is 0, then the printing is unlimited.
7202 @item set print frame-arguments @var{value}
7203 @kindex set print frame-arguments
7204 @cindex printing frame argument values
7205 @cindex print all frame argument values
7206 @cindex print frame argument values for scalars only
7207 @cindex do not print frame argument values
7208 This command allows to control how the values of arguments are printed
7209 when the debugger prints a frame (@pxref{Frames}). The possible
7214 The values of all arguments are printed.
7217 Print the value of an argument only if it is a scalar. The value of more
7218 complex arguments such as arrays, structures, unions, etc, is replaced
7219 by @code{@dots{}}. This is the default. Here is an example where
7220 only scalar arguments are shown:
7223 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
7228 None of the argument values are printed. Instead, the value of each argument
7229 is replaced by @code{@dots{}}. In this case, the example above now becomes:
7232 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
7237 By default, only scalar arguments are printed. This command can be used
7238 to configure the debugger to print the value of all arguments, regardless
7239 of their type. However, it is often advantageous to not print the value
7240 of more complex parameters. For instance, it reduces the amount of
7241 information printed in each frame, making the backtrace more readable.
7242 Also, it improves performance when displaying Ada frames, because
7243 the computation of large arguments can sometimes be CPU-intensive,
7244 especially in large applications. Setting @code{print frame-arguments}
7245 to @code{scalars} (the default) or @code{none} avoids this computation,
7246 thus speeding up the display of each Ada frame.
7248 @item show print frame-arguments
7249 Show how the value of arguments should be displayed when printing a frame.
7251 @item set print repeats
7252 @cindex repeated array elements
7253 Set the threshold for suppressing display of repeated array
7254 elements. When the number of consecutive identical elements of an
7255 array exceeds the threshold, @value{GDBN} prints the string
7256 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
7257 identical repetitions, instead of displaying the identical elements
7258 themselves. Setting the threshold to zero will cause all elements to
7259 be individually printed. The default threshold is 10.
7261 @item show print repeats
7262 Display the current threshold for printing repeated identical
7265 @item set print null-stop
7266 @cindex @sc{null} elements in arrays
7267 Cause @value{GDBN} to stop printing the characters of an array when the first
7268 @sc{null} is encountered. This is useful when large arrays actually
7269 contain only short strings.
7272 @item show print null-stop
7273 Show whether @value{GDBN} stops printing an array on the first
7274 @sc{null} character.
7276 @item set print pretty on
7277 @cindex print structures in indented form
7278 @cindex indentation in structure display
7279 Cause @value{GDBN} to print structures in an indented format with one member
7280 per line, like this:
7295 @item set print pretty off
7296 Cause @value{GDBN} to print structures in a compact format, like this:
7300 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
7301 meat = 0x54 "Pork"@}
7306 This is the default format.
7308 @item show print pretty
7309 Show which format @value{GDBN} is using to print structures.
7311 @item set print sevenbit-strings on
7312 @cindex eight-bit characters in strings
7313 @cindex octal escapes in strings
7314 Print using only seven-bit characters; if this option is set,
7315 @value{GDBN} displays any eight-bit characters (in strings or
7316 character values) using the notation @code{\}@var{nnn}. This setting is
7317 best if you are working in English (@sc{ascii}) and you use the
7318 high-order bit of characters as a marker or ``meta'' bit.
7320 @item set print sevenbit-strings off
7321 Print full eight-bit characters. This allows the use of more
7322 international character sets, and is the default.
7324 @item show print sevenbit-strings
7325 Show whether or not @value{GDBN} is printing only seven-bit characters.
7327 @item set print union on
7328 @cindex unions in structures, printing
7329 Tell @value{GDBN} to print unions which are contained in structures
7330 and other unions. This is the default setting.
7332 @item set print union off
7333 Tell @value{GDBN} not to print unions which are contained in
7334 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
7337 @item show print union
7338 Ask @value{GDBN} whether or not it will print unions which are contained in
7339 structures and other unions.
7341 For example, given the declarations
7344 typedef enum @{Tree, Bug@} Species;
7345 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
7346 typedef enum @{Caterpillar, Cocoon, Butterfly@}
7357 struct thing foo = @{Tree, @{Acorn@}@};
7361 with @code{set print union on} in effect @samp{p foo} would print
7364 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
7368 and with @code{set print union off} in effect it would print
7371 $1 = @{it = Tree, form = @{...@}@}
7375 @code{set print union} affects programs written in C-like languages
7381 These settings are of interest when debugging C@t{++} programs:
7384 @cindex demangling C@t{++} names
7385 @item set print demangle
7386 @itemx set print demangle on
7387 Print C@t{++} names in their source form rather than in the encoded
7388 (``mangled'') form passed to the assembler and linker for type-safe
7389 linkage. The default is on.
7391 @item show print demangle
7392 Show whether C@t{++} names are printed in mangled or demangled form.
7394 @item set print asm-demangle
7395 @itemx set print asm-demangle on
7396 Print C@t{++} names in their source form rather than their mangled form, even
7397 in assembler code printouts such as instruction disassemblies.
7400 @item show print asm-demangle
7401 Show whether C@t{++} names in assembly listings are printed in mangled
7404 @cindex C@t{++} symbol decoding style
7405 @cindex symbol decoding style, C@t{++}
7406 @kindex set demangle-style
7407 @item set demangle-style @var{style}
7408 Choose among several encoding schemes used by different compilers to
7409 represent C@t{++} names. The choices for @var{style} are currently:
7413 Allow @value{GDBN} to choose a decoding style by inspecting your program.
7416 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
7417 This is the default.
7420 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
7423 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
7426 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
7427 @strong{Warning:} this setting alone is not sufficient to allow
7428 debugging @code{cfront}-generated executables. @value{GDBN} would
7429 require further enhancement to permit that.
7432 If you omit @var{style}, you will see a list of possible formats.
7434 @item show demangle-style
7435 Display the encoding style currently in use for decoding C@t{++} symbols.
7437 @item set print object
7438 @itemx set print object on
7439 @cindex derived type of an object, printing
7440 @cindex display derived types
7441 When displaying a pointer to an object, identify the @emph{actual}
7442 (derived) type of the object rather than the @emph{declared} type, using
7443 the virtual function table.
7445 @item set print object off
7446 Display only the declared type of objects, without reference to the
7447 virtual function table. This is the default setting.
7449 @item show print object
7450 Show whether actual, or declared, object types are displayed.
7452 @item set print static-members
7453 @itemx set print static-members on
7454 @cindex static members of C@t{++} objects
7455 Print static members when displaying a C@t{++} object. The default is on.
7457 @item set print static-members off
7458 Do not print static members when displaying a C@t{++} object.
7460 @item show print static-members
7461 Show whether C@t{++} static members are printed or not.
7463 @item set print pascal_static-members
7464 @itemx set print pascal_static-members on
7465 @cindex static members of Pascal objects
7466 @cindex Pascal objects, static members display
7467 Print static members when displaying a Pascal object. The default is on.
7469 @item set print pascal_static-members off
7470 Do not print static members when displaying a Pascal object.
7472 @item show print pascal_static-members
7473 Show whether Pascal static members are printed or not.
7475 @c These don't work with HP ANSI C++ yet.
7476 @item set print vtbl
7477 @itemx set print vtbl on
7478 @cindex pretty print C@t{++} virtual function tables
7479 @cindex virtual functions (C@t{++}) display
7480 @cindex VTBL display
7481 Pretty print C@t{++} virtual function tables. The default is off.
7482 (The @code{vtbl} commands do not work on programs compiled with the HP
7483 ANSI C@t{++} compiler (@code{aCC}).)
7485 @item set print vtbl off
7486 Do not pretty print C@t{++} virtual function tables.
7488 @item show print vtbl
7489 Show whether C@t{++} virtual function tables are pretty printed, or not.
7493 @section Value History
7495 @cindex value history
7496 @cindex history of values printed by @value{GDBN}
7497 Values printed by the @code{print} command are saved in the @value{GDBN}
7498 @dfn{value history}. This allows you to refer to them in other expressions.
7499 Values are kept until the symbol table is re-read or discarded
7500 (for example with the @code{file} or @code{symbol-file} commands).
7501 When the symbol table changes, the value history is discarded,
7502 since the values may contain pointers back to the types defined in the
7507 @cindex history number
7508 The values printed are given @dfn{history numbers} by which you can
7509 refer to them. These are successive integers starting with one.
7510 @code{print} shows you the history number assigned to a value by
7511 printing @samp{$@var{num} = } before the value; here @var{num} is the
7514 To refer to any previous value, use @samp{$} followed by the value's
7515 history number. The way @code{print} labels its output is designed to
7516 remind you of this. Just @code{$} refers to the most recent value in
7517 the history, and @code{$$} refers to the value before that.
7518 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
7519 is the value just prior to @code{$$}, @code{$$1} is equivalent to
7520 @code{$$}, and @code{$$0} is equivalent to @code{$}.
7522 For example, suppose you have just printed a pointer to a structure and
7523 want to see the contents of the structure. It suffices to type
7529 If you have a chain of structures where the component @code{next} points
7530 to the next one, you can print the contents of the next one with this:
7537 You can print successive links in the chain by repeating this
7538 command---which you can do by just typing @key{RET}.
7540 Note that the history records values, not expressions. If the value of
7541 @code{x} is 4 and you type these commands:
7549 then the value recorded in the value history by the @code{print} command
7550 remains 4 even though the value of @code{x} has changed.
7555 Print the last ten values in the value history, with their item numbers.
7556 This is like @samp{p@ $$9} repeated ten times, except that @code{show
7557 values} does not change the history.
7559 @item show values @var{n}
7560 Print ten history values centered on history item number @var{n}.
7563 Print ten history values just after the values last printed. If no more
7564 values are available, @code{show values +} produces no display.
7567 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
7568 same effect as @samp{show values +}.
7570 @node Convenience Vars
7571 @section Convenience Variables
7573 @cindex convenience variables
7574 @cindex user-defined variables
7575 @value{GDBN} provides @dfn{convenience variables} that you can use within
7576 @value{GDBN} to hold on to a value and refer to it later. These variables
7577 exist entirely within @value{GDBN}; they are not part of your program, and
7578 setting a convenience variable has no direct effect on further execution
7579 of your program. That is why you can use them freely.
7581 Convenience variables are prefixed with @samp{$}. Any name preceded by
7582 @samp{$} can be used for a convenience variable, unless it is one of
7583 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
7584 (Value history references, in contrast, are @emph{numbers} preceded
7585 by @samp{$}. @xref{Value History, ,Value History}.)
7587 You can save a value in a convenience variable with an assignment
7588 expression, just as you would set a variable in your program.
7592 set $foo = *object_ptr
7596 would save in @code{$foo} the value contained in the object pointed to by
7599 Using a convenience variable for the first time creates it, but its
7600 value is @code{void} until you assign a new value. You can alter the
7601 value with another assignment at any time.
7603 Convenience variables have no fixed types. You can assign a convenience
7604 variable any type of value, including structures and arrays, even if
7605 that variable already has a value of a different type. The convenience
7606 variable, when used as an expression, has the type of its current value.
7609 @kindex show convenience
7610 @cindex show all user variables
7611 @item show convenience
7612 Print a list of convenience variables used so far, and their values.
7613 Abbreviated @code{show conv}.
7615 @kindex init-if-undefined
7616 @cindex convenience variables, initializing
7617 @item init-if-undefined $@var{variable} = @var{expression}
7618 Set a convenience variable if it has not already been set. This is useful
7619 for user-defined commands that keep some state. It is similar, in concept,
7620 to using local static variables with initializers in C (except that
7621 convenience variables are global). It can also be used to allow users to
7622 override default values used in a command script.
7624 If the variable is already defined then the expression is not evaluated so
7625 any side-effects do not occur.
7628 One of the ways to use a convenience variable is as a counter to be
7629 incremented or a pointer to be advanced. For example, to print
7630 a field from successive elements of an array of structures:
7634 print bar[$i++]->contents
7638 Repeat that command by typing @key{RET}.
7640 Some convenience variables are created automatically by @value{GDBN} and given
7641 values likely to be useful.
7644 @vindex $_@r{, convenience variable}
7646 The variable @code{$_} is automatically set by the @code{x} command to
7647 the last address examined (@pxref{Memory, ,Examining Memory}). Other
7648 commands which provide a default address for @code{x} to examine also
7649 set @code{$_} to that address; these commands include @code{info line}
7650 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
7651 except when set by the @code{x} command, in which case it is a pointer
7652 to the type of @code{$__}.
7654 @vindex $__@r{, convenience variable}
7656 The variable @code{$__} is automatically set by the @code{x} command
7657 to the value found in the last address examined. Its type is chosen
7658 to match the format in which the data was printed.
7661 @vindex $_exitcode@r{, convenience variable}
7662 The variable @code{$_exitcode} is automatically set to the exit code when
7663 the program being debugged terminates.
7666 @vindex $_siginfo@r{, convenience variable}
7667 The variable @code{$_siginfo} is bound to extra signal information
7668 inspection (@pxref{extra signal information}).
7671 On HP-UX systems, if you refer to a function or variable name that
7672 begins with a dollar sign, @value{GDBN} searches for a user or system
7673 name first, before it searches for a convenience variable.
7675 @cindex convenience functions
7676 @value{GDBN} also supplies some @dfn{convenience functions}. These
7677 have a syntax similar to convenience variables. A convenience
7678 function can be used in an expression just like an ordinary function;
7679 however, a convenience function is implemented internally to
7684 @kindex help function
7685 @cindex show all convenience functions
7686 Print a list of all convenience functions.
7693 You can refer to machine register contents, in expressions, as variables
7694 with names starting with @samp{$}. The names of registers are different
7695 for each machine; use @code{info registers} to see the names used on
7699 @kindex info registers
7700 @item info registers
7701 Print the names and values of all registers except floating-point
7702 and vector registers (in the selected stack frame).
7704 @kindex info all-registers
7705 @cindex floating point registers
7706 @item info all-registers
7707 Print the names and values of all registers, including floating-point
7708 and vector registers (in the selected stack frame).
7710 @item info registers @var{regname} @dots{}
7711 Print the @dfn{relativized} value of each specified register @var{regname}.
7712 As discussed in detail below, register values are normally relative to
7713 the selected stack frame. @var{regname} may be any register name valid on
7714 the machine you are using, with or without the initial @samp{$}.
7717 @cindex stack pointer register
7718 @cindex program counter register
7719 @cindex process status register
7720 @cindex frame pointer register
7721 @cindex standard registers
7722 @value{GDBN} has four ``standard'' register names that are available (in
7723 expressions) on most machines---whenever they do not conflict with an
7724 architecture's canonical mnemonics for registers. The register names
7725 @code{$pc} and @code{$sp} are used for the program counter register and
7726 the stack pointer. @code{$fp} is used for a register that contains a
7727 pointer to the current stack frame, and @code{$ps} is used for a
7728 register that contains the processor status. For example,
7729 you could print the program counter in hex with
7736 or print the instruction to be executed next with
7743 or add four to the stack pointer@footnote{This is a way of removing
7744 one word from the stack, on machines where stacks grow downward in
7745 memory (most machines, nowadays). This assumes that the innermost
7746 stack frame is selected; setting @code{$sp} is not allowed when other
7747 stack frames are selected. To pop entire frames off the stack,
7748 regardless of machine architecture, use @code{return};
7749 see @ref{Returning, ,Returning from a Function}.} with
7755 Whenever possible, these four standard register names are available on
7756 your machine even though the machine has different canonical mnemonics,
7757 so long as there is no conflict. The @code{info registers} command
7758 shows the canonical names. For example, on the SPARC, @code{info
7759 registers} displays the processor status register as @code{$psr} but you
7760 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
7761 is an alias for the @sc{eflags} register.
7763 @value{GDBN} always considers the contents of an ordinary register as an
7764 integer when the register is examined in this way. Some machines have
7765 special registers which can hold nothing but floating point; these
7766 registers are considered to have floating point values. There is no way
7767 to refer to the contents of an ordinary register as floating point value
7768 (although you can @emph{print} it as a floating point value with
7769 @samp{print/f $@var{regname}}).
7771 Some registers have distinct ``raw'' and ``virtual'' data formats. This
7772 means that the data format in which the register contents are saved by
7773 the operating system is not the same one that your program normally
7774 sees. For example, the registers of the 68881 floating point
7775 coprocessor are always saved in ``extended'' (raw) format, but all C
7776 programs expect to work with ``double'' (virtual) format. In such
7777 cases, @value{GDBN} normally works with the virtual format only (the format
7778 that makes sense for your program), but the @code{info registers} command
7779 prints the data in both formats.
7781 @cindex SSE registers (x86)
7782 @cindex MMX registers (x86)
7783 Some machines have special registers whose contents can be interpreted
7784 in several different ways. For example, modern x86-based machines
7785 have SSE and MMX registers that can hold several values packed
7786 together in several different formats. @value{GDBN} refers to such
7787 registers in @code{struct} notation:
7790 (@value{GDBP}) print $xmm1
7792 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
7793 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
7794 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
7795 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
7796 v4_int32 = @{0, 20657912, 11, 13@},
7797 v2_int64 = @{88725056443645952, 55834574859@},
7798 uint128 = 0x0000000d0000000b013b36f800000000
7803 To set values of such registers, you need to tell @value{GDBN} which
7804 view of the register you wish to change, as if you were assigning
7805 value to a @code{struct} member:
7808 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
7811 Normally, register values are relative to the selected stack frame
7812 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
7813 value that the register would contain if all stack frames farther in
7814 were exited and their saved registers restored. In order to see the
7815 true contents of hardware registers, you must select the innermost
7816 frame (with @samp{frame 0}).
7818 However, @value{GDBN} must deduce where registers are saved, from the machine
7819 code generated by your compiler. If some registers are not saved, or if
7820 @value{GDBN} is unable to locate the saved registers, the selected stack
7821 frame makes no difference.
7823 @node Floating Point Hardware
7824 @section Floating Point Hardware
7825 @cindex floating point
7827 Depending on the configuration, @value{GDBN} may be able to give
7828 you more information about the status of the floating point hardware.
7833 Display hardware-dependent information about the floating
7834 point unit. The exact contents and layout vary depending on the
7835 floating point chip. Currently, @samp{info float} is supported on
7836 the ARM and x86 machines.
7840 @section Vector Unit
7843 Depending on the configuration, @value{GDBN} may be able to give you
7844 more information about the status of the vector unit.
7849 Display information about the vector unit. The exact contents and
7850 layout vary depending on the hardware.
7853 @node OS Information
7854 @section Operating System Auxiliary Information
7855 @cindex OS information
7857 @value{GDBN} provides interfaces to useful OS facilities that can help
7858 you debug your program.
7860 @cindex @code{ptrace} system call
7861 @cindex @code{struct user} contents
7862 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
7863 machines), it interfaces with the inferior via the @code{ptrace}
7864 system call. The operating system creates a special sata structure,
7865 called @code{struct user}, for this interface. You can use the
7866 command @code{info udot} to display the contents of this data
7872 Display the contents of the @code{struct user} maintained by the OS
7873 kernel for the program being debugged. @value{GDBN} displays the
7874 contents of @code{struct user} as a list of hex numbers, similar to
7875 the @code{examine} command.
7878 @cindex auxiliary vector
7879 @cindex vector, auxiliary
7880 Some operating systems supply an @dfn{auxiliary vector} to programs at
7881 startup. This is akin to the arguments and environment that you
7882 specify for a program, but contains a system-dependent variety of
7883 binary values that tell system libraries important details about the
7884 hardware, operating system, and process. Each value's purpose is
7885 identified by an integer tag; the meanings are well-known but system-specific.
7886 Depending on the configuration and operating system facilities,
7887 @value{GDBN} may be able to show you this information. For remote
7888 targets, this functionality may further depend on the remote stub's
7889 support of the @samp{qXfer:auxv:read} packet, see
7890 @ref{qXfer auxiliary vector read}.
7895 Display the auxiliary vector of the inferior, which can be either a
7896 live process or a core dump file. @value{GDBN} prints each tag value
7897 numerically, and also shows names and text descriptions for recognized
7898 tags. Some values in the vector are numbers, some bit masks, and some
7899 pointers to strings or other data. @value{GDBN} displays each value in the
7900 most appropriate form for a recognized tag, and in hexadecimal for
7901 an unrecognized tag.
7904 On some targets, @value{GDBN} can access operating-system-specific information
7905 and display it to user, without interpretation. For remote targets,
7906 this functionality depends on the remote stub's support of the
7907 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
7910 @kindex info os processes
7911 @item info os processes
7912 Display the list of processes on the target. For each process,
7913 @value{GDBN} prints the process identifier, the name of the user, and
7914 the command corresponding to the process.
7917 @node Memory Region Attributes
7918 @section Memory Region Attributes
7919 @cindex memory region attributes
7921 @dfn{Memory region attributes} allow you to describe special handling
7922 required by regions of your target's memory. @value{GDBN} uses
7923 attributes to determine whether to allow certain types of memory
7924 accesses; whether to use specific width accesses; and whether to cache
7925 target memory. By default the description of memory regions is
7926 fetched from the target (if the current target supports this), but the
7927 user can override the fetched regions.
7929 Defined memory regions can be individually enabled and disabled. When a
7930 memory region is disabled, @value{GDBN} uses the default attributes when
7931 accessing memory in that region. Similarly, if no memory regions have
7932 been defined, @value{GDBN} uses the default attributes when accessing
7935 When a memory region is defined, it is given a number to identify it;
7936 to enable, disable, or remove a memory region, you specify that number.
7940 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
7941 Define a memory region bounded by @var{lower} and @var{upper} with
7942 attributes @var{attributes}@dots{}, and add it to the list of regions
7943 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
7944 case: it is treated as the target's maximum memory address.
7945 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
7948 Discard any user changes to the memory regions and use target-supplied
7949 regions, if available, or no regions if the target does not support.
7952 @item delete mem @var{nums}@dots{}
7953 Remove memory regions @var{nums}@dots{} from the list of regions
7954 monitored by @value{GDBN}.
7957 @item disable mem @var{nums}@dots{}
7958 Disable monitoring of memory regions @var{nums}@dots{}.
7959 A disabled memory region is not forgotten.
7960 It may be enabled again later.
7963 @item enable mem @var{nums}@dots{}
7964 Enable monitoring of memory regions @var{nums}@dots{}.
7968 Print a table of all defined memory regions, with the following columns
7972 @item Memory Region Number
7973 @item Enabled or Disabled.
7974 Enabled memory regions are marked with @samp{y}.
7975 Disabled memory regions are marked with @samp{n}.
7978 The address defining the inclusive lower bound of the memory region.
7981 The address defining the exclusive upper bound of the memory region.
7984 The list of attributes set for this memory region.
7989 @subsection Attributes
7991 @subsubsection Memory Access Mode
7992 The access mode attributes set whether @value{GDBN} may make read or
7993 write accesses to a memory region.
7995 While these attributes prevent @value{GDBN} from performing invalid
7996 memory accesses, they do nothing to prevent the target system, I/O DMA,
7997 etc.@: from accessing memory.
8001 Memory is read only.
8003 Memory is write only.
8005 Memory is read/write. This is the default.
8008 @subsubsection Memory Access Size
8009 The access size attribute tells @value{GDBN} to use specific sized
8010 accesses in the memory region. Often memory mapped device registers
8011 require specific sized accesses. If no access size attribute is
8012 specified, @value{GDBN} may use accesses of any size.
8016 Use 8 bit memory accesses.
8018 Use 16 bit memory accesses.
8020 Use 32 bit memory accesses.
8022 Use 64 bit memory accesses.
8025 @c @subsubsection Hardware/Software Breakpoints
8026 @c The hardware/software breakpoint attributes set whether @value{GDBN}
8027 @c will use hardware or software breakpoints for the internal breakpoints
8028 @c used by the step, next, finish, until, etc. commands.
8032 @c Always use hardware breakpoints
8033 @c @item swbreak (default)
8036 @subsubsection Data Cache
8037 The data cache attributes set whether @value{GDBN} will cache target
8038 memory. While this generally improves performance by reducing debug
8039 protocol overhead, it can lead to incorrect results because @value{GDBN}
8040 does not know about volatile variables or memory mapped device
8045 Enable @value{GDBN} to cache target memory.
8047 Disable @value{GDBN} from caching target memory. This is the default.
8050 @subsection Memory Access Checking
8051 @value{GDBN} can be instructed to refuse accesses to memory that is
8052 not explicitly described. This can be useful if accessing such
8053 regions has undesired effects for a specific target, or to provide
8054 better error checking. The following commands control this behaviour.
8057 @kindex set mem inaccessible-by-default
8058 @item set mem inaccessible-by-default [on|off]
8059 If @code{on} is specified, make @value{GDBN} treat memory not
8060 explicitly described by the memory ranges as non-existent and refuse accesses
8061 to such memory. The checks are only performed if there's at least one
8062 memory range defined. If @code{off} is specified, make @value{GDBN}
8063 treat the memory not explicitly described by the memory ranges as RAM.
8064 The default value is @code{on}.
8065 @kindex show mem inaccessible-by-default
8066 @item show mem inaccessible-by-default
8067 Show the current handling of accesses to unknown memory.
8071 @c @subsubsection Memory Write Verification
8072 @c The memory write verification attributes set whether @value{GDBN}
8073 @c will re-reads data after each write to verify the write was successful.
8077 @c @item noverify (default)
8080 @node Dump/Restore Files
8081 @section Copy Between Memory and a File
8082 @cindex dump/restore files
8083 @cindex append data to a file
8084 @cindex dump data to a file
8085 @cindex restore data from a file
8087 You can use the commands @code{dump}, @code{append}, and
8088 @code{restore} to copy data between target memory and a file. The
8089 @code{dump} and @code{append} commands write data to a file, and the
8090 @code{restore} command reads data from a file back into the inferior's
8091 memory. Files may be in binary, Motorola S-record, Intel hex, or
8092 Tektronix Hex format; however, @value{GDBN} can only append to binary
8098 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8099 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
8100 Dump the contents of memory from @var{start_addr} to @var{end_addr},
8101 or the value of @var{expr}, to @var{filename} in the given format.
8103 The @var{format} parameter may be any one of:
8110 Motorola S-record format.
8112 Tektronix Hex format.
8115 @value{GDBN} uses the same definitions of these formats as the
8116 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
8117 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
8121 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8122 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
8123 Append the contents of memory from @var{start_addr} to @var{end_addr},
8124 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
8125 (@value{GDBN} can only append data to files in raw binary form.)
8128 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
8129 Restore the contents of file @var{filename} into memory. The
8130 @code{restore} command can automatically recognize any known @sc{bfd}
8131 file format, except for raw binary. To restore a raw binary file you
8132 must specify the optional keyword @code{binary} after the filename.
8134 If @var{bias} is non-zero, its value will be added to the addresses
8135 contained in the file. Binary files always start at address zero, so
8136 they will be restored at address @var{bias}. Other bfd files have
8137 a built-in location; they will be restored at offset @var{bias}
8140 If @var{start} and/or @var{end} are non-zero, then only data between
8141 file offset @var{start} and file offset @var{end} will be restored.
8142 These offsets are relative to the addresses in the file, before
8143 the @var{bias} argument is applied.
8147 @node Core File Generation
8148 @section How to Produce a Core File from Your Program
8149 @cindex dump core from inferior
8151 A @dfn{core file} or @dfn{core dump} is a file that records the memory
8152 image of a running process and its process status (register values
8153 etc.). Its primary use is post-mortem debugging of a program that
8154 crashed while it ran outside a debugger. A program that crashes
8155 automatically produces a core file, unless this feature is disabled by
8156 the user. @xref{Files}, for information on invoking @value{GDBN} in
8157 the post-mortem debugging mode.
8159 Occasionally, you may wish to produce a core file of the program you
8160 are debugging in order to preserve a snapshot of its state.
8161 @value{GDBN} has a special command for that.
8165 @kindex generate-core-file
8166 @item generate-core-file [@var{file}]
8167 @itemx gcore [@var{file}]
8168 Produce a core dump of the inferior process. The optional argument
8169 @var{file} specifies the file name where to put the core dump. If not
8170 specified, the file name defaults to @file{core.@var{pid}}, where
8171 @var{pid} is the inferior process ID.
8173 Note that this command is implemented only for some systems (as of
8174 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
8177 @node Character Sets
8178 @section Character Sets
8179 @cindex character sets
8181 @cindex translating between character sets
8182 @cindex host character set
8183 @cindex target character set
8185 If the program you are debugging uses a different character set to
8186 represent characters and strings than the one @value{GDBN} uses itself,
8187 @value{GDBN} can automatically translate between the character sets for
8188 you. The character set @value{GDBN} uses we call the @dfn{host
8189 character set}; the one the inferior program uses we call the
8190 @dfn{target character set}.
8192 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
8193 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
8194 remote protocol (@pxref{Remote Debugging}) to debug a program
8195 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
8196 then the host character set is Latin-1, and the target character set is
8197 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
8198 target-charset EBCDIC-US}, then @value{GDBN} translates between
8199 @sc{ebcdic} and Latin 1 as you print character or string values, or use
8200 character and string literals in expressions.
8202 @value{GDBN} has no way to automatically recognize which character set
8203 the inferior program uses; you must tell it, using the @code{set
8204 target-charset} command, described below.
8206 Here are the commands for controlling @value{GDBN}'s character set
8210 @item set target-charset @var{charset}
8211 @kindex set target-charset
8212 Set the current target character set to @var{charset}. To display the
8213 list of supported target character sets, type
8214 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
8216 @item set host-charset @var{charset}
8217 @kindex set host-charset
8218 Set the current host character set to @var{charset}.
8220 By default, @value{GDBN} uses a host character set appropriate to the
8221 system it is running on; you can override that default using the
8222 @code{set host-charset} command. On some systems, @value{GDBN} cannot
8223 automatically determine the appropriate host character set. In this
8224 case, @value{GDBN} uses @samp{UTF-8}.
8226 @value{GDBN} can only use certain character sets as its host character
8227 set. If you type @kbd{@w{set target-charset @key{TAB}@key{TAB}}},
8228 @value{GDBN} will list the host character sets it supports.
8230 @item set charset @var{charset}
8232 Set the current host and target character sets to @var{charset}. As
8233 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
8234 @value{GDBN} will list the names of the character sets that can be used
8235 for both host and target.
8238 @kindex show charset
8239 Show the names of the current host and target character sets.
8241 @item show host-charset
8242 @kindex show host-charset
8243 Show the name of the current host character set.
8245 @item show target-charset
8246 @kindex show target-charset
8247 Show the name of the current target character set.
8249 @item set target-wide-charset @var{charset}
8250 @kindex set target-wide-charset
8251 Set the current target's wide character set to @var{charset}. This is
8252 the character set used by the target's @code{wchar_t} type. To
8253 display the list of supported wide character sets, type
8254 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
8256 @item show target-wide-charset
8257 @kindex show target-wide-charset
8258 Show the name of the current target's wide character set.
8261 Here is an example of @value{GDBN}'s character set support in action.
8262 Assume that the following source code has been placed in the file
8263 @file{charset-test.c}:
8269 = @{72, 101, 108, 108, 111, 44, 32, 119,
8270 111, 114, 108, 100, 33, 10, 0@};
8271 char ibm1047_hello[]
8272 = @{200, 133, 147, 147, 150, 107, 64, 166,
8273 150, 153, 147, 132, 90, 37, 0@};
8277 printf ("Hello, world!\n");
8281 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
8282 containing the string @samp{Hello, world!} followed by a newline,
8283 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
8285 We compile the program, and invoke the debugger on it:
8288 $ gcc -g charset-test.c -o charset-test
8289 $ gdb -nw charset-test
8290 GNU gdb 2001-12-19-cvs
8291 Copyright 2001 Free Software Foundation, Inc.
8296 We can use the @code{show charset} command to see what character sets
8297 @value{GDBN} is currently using to interpret and display characters and
8301 (@value{GDBP}) show charset
8302 The current host and target character set is `ISO-8859-1'.
8306 For the sake of printing this manual, let's use @sc{ascii} as our
8307 initial character set:
8309 (@value{GDBP}) set charset ASCII
8310 (@value{GDBP}) show charset
8311 The current host and target character set is `ASCII'.
8315 Let's assume that @sc{ascii} is indeed the correct character set for our
8316 host system --- in other words, let's assume that if @value{GDBN} prints
8317 characters using the @sc{ascii} character set, our terminal will display
8318 them properly. Since our current target character set is also
8319 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
8322 (@value{GDBP}) print ascii_hello
8323 $1 = 0x401698 "Hello, world!\n"
8324 (@value{GDBP}) print ascii_hello[0]
8329 @value{GDBN} uses the target character set for character and string
8330 literals you use in expressions:
8333 (@value{GDBP}) print '+'
8338 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
8341 @value{GDBN} relies on the user to tell it which character set the
8342 target program uses. If we print @code{ibm1047_hello} while our target
8343 character set is still @sc{ascii}, we get jibberish:
8346 (@value{GDBP}) print ibm1047_hello
8347 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
8348 (@value{GDBP}) print ibm1047_hello[0]
8353 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
8354 @value{GDBN} tells us the character sets it supports:
8357 (@value{GDBP}) set target-charset
8358 ASCII EBCDIC-US IBM1047 ISO-8859-1
8359 (@value{GDBP}) set target-charset
8362 We can select @sc{ibm1047} as our target character set, and examine the
8363 program's strings again. Now the @sc{ascii} string is wrong, but
8364 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
8365 target character set, @sc{ibm1047}, to the host character set,
8366 @sc{ascii}, and they display correctly:
8369 (@value{GDBP}) set target-charset IBM1047
8370 (@value{GDBP}) show charset
8371 The current host character set is `ASCII'.
8372 The current target character set is `IBM1047'.
8373 (@value{GDBP}) print ascii_hello
8374 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
8375 (@value{GDBP}) print ascii_hello[0]
8377 (@value{GDBP}) print ibm1047_hello
8378 $8 = 0x4016a8 "Hello, world!\n"
8379 (@value{GDBP}) print ibm1047_hello[0]
8384 As above, @value{GDBN} uses the target character set for character and
8385 string literals you use in expressions:
8388 (@value{GDBP}) print '+'
8393 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
8396 @node Caching Remote Data
8397 @section Caching Data of Remote Targets
8398 @cindex caching data of remote targets
8400 @value{GDBN} can cache data exchanged between the debugger and a
8401 remote target (@pxref{Remote Debugging}). Such caching generally improves
8402 performance, because it reduces the overhead of the remote protocol by
8403 bundling memory reads and writes into large chunks. Unfortunately,
8404 @value{GDBN} does not currently know anything about volatile
8405 registers, and thus data caching will produce incorrect results when
8406 volatile registers are in use.
8409 @kindex set remotecache
8410 @item set remotecache on
8411 @itemx set remotecache off
8412 Set caching state for remote targets. When @code{ON}, use data
8413 caching. By default, this option is @code{OFF}.
8415 @kindex show remotecache
8416 @item show remotecache
8417 Show the current state of data caching for remote targets.
8421 Print the information about the data cache performance. The
8422 information displayed includes: the dcache width and depth; and for
8423 each cache line, how many times it was referenced, and its data and
8424 state (invalid, dirty, valid). This command is useful for debugging
8425 the data cache operation.
8428 @node Searching Memory
8429 @section Search Memory
8430 @cindex searching memory
8432 Memory can be searched for a particular sequence of bytes with the
8433 @code{find} command.
8437 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8438 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8439 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
8440 etc. The search begins at address @var{start_addr} and continues for either
8441 @var{len} bytes or through to @var{end_addr} inclusive.
8444 @var{s} and @var{n} are optional parameters.
8445 They may be specified in either order, apart or together.
8448 @item @var{s}, search query size
8449 The size of each search query value.
8455 halfwords (two bytes)
8459 giant words (eight bytes)
8462 All values are interpreted in the current language.
8463 This means, for example, that if the current source language is C/C@t{++}
8464 then searching for the string ``hello'' includes the trailing '\0'.
8466 If the value size is not specified, it is taken from the
8467 value's type in the current language.
8468 This is useful when one wants to specify the search
8469 pattern as a mixture of types.
8470 Note that this means, for example, that in the case of C-like languages
8471 a search for an untyped 0x42 will search for @samp{(int) 0x42}
8472 which is typically four bytes.
8474 @item @var{n}, maximum number of finds
8475 The maximum number of matches to print. The default is to print all finds.
8478 You can use strings as search values. Quote them with double-quotes
8480 The string value is copied into the search pattern byte by byte,
8481 regardless of the endianness of the target and the size specification.
8483 The address of each match found is printed as well as a count of the
8484 number of matches found.
8486 The address of the last value found is stored in convenience variable
8488 A count of the number of matches is stored in @samp{$numfound}.
8490 For example, if stopped at the @code{printf} in this function:
8496 static char hello[] = "hello-hello";
8497 static struct @{ char c; short s; int i; @}
8498 __attribute__ ((packed)) mixed
8499 = @{ 'c', 0x1234, 0x87654321 @};
8500 printf ("%s\n", hello);
8505 you get during debugging:
8508 (gdb) find &hello[0], +sizeof(hello), "hello"
8509 0x804956d <hello.1620+6>
8511 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
8512 0x8049567 <hello.1620>
8513 0x804956d <hello.1620+6>
8515 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
8516 0x8049567 <hello.1620>
8518 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
8519 0x8049560 <mixed.1625>
8521 (gdb) print $numfound
8524 $2 = (void *) 0x8049560
8527 @node Optimized Code
8528 @chapter Debugging Optimized Code
8529 @cindex optimized code, debugging
8530 @cindex debugging optimized code
8532 Almost all compilers support optimization. With optimization
8533 disabled, the compiler generates assembly code that corresponds
8534 directly to your source code, in a simplistic way. As the compiler
8535 applies more powerful optimizations, the generated assembly code
8536 diverges from your original source code. With help from debugging
8537 information generated by the compiler, @value{GDBN} can map from
8538 the running program back to constructs from your original source.
8540 @value{GDBN} is more accurate with optimization disabled. If you
8541 can recompile without optimization, it is easier to follow the
8542 progress of your program during debugging. But, there are many cases
8543 where you may need to debug an optimized version.
8545 When you debug a program compiled with @samp{-g -O}, remember that the
8546 optimizer has rearranged your code; the debugger shows you what is
8547 really there. Do not be too surprised when the execution path does not
8548 exactly match your source file! An extreme example: if you define a
8549 variable, but never use it, @value{GDBN} never sees that
8550 variable---because the compiler optimizes it out of existence.
8552 Some things do not work as well with @samp{-g -O} as with just
8553 @samp{-g}, particularly on machines with instruction scheduling. If in
8554 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
8555 please report it to us as a bug (including a test case!).
8556 @xref{Variables}, for more information about debugging optimized code.
8559 * Inline Functions:: How @value{GDBN} presents inlining
8562 @node Inline Functions
8563 @section Inline Functions
8564 @cindex inline functions, debugging
8566 @dfn{Inlining} is an optimization that inserts a copy of the function
8567 body directly at each call site, instead of jumping to a shared
8568 routine. @value{GDBN} displays inlined functions just like
8569 non-inlined functions. They appear in backtraces. You can view their
8570 arguments and local variables, step into them with @code{step}, skip
8571 them with @code{next}, and escape from them with @code{finish}.
8572 You can check whether a function was inlined by using the
8573 @code{info frame} command.
8575 For @value{GDBN} to support inlined functions, the compiler must
8576 record information about inlining in the debug information ---
8577 @value{NGCC} using the @sc{dwarf 2} format does this, and several
8578 other compilers do also. @value{GDBN} only supports inlined functions
8579 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
8580 do not emit two required attributes (@samp{DW_AT_call_file} and
8581 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
8582 function calls with earlier versions of @value{NGCC}. It instead
8583 displays the arguments and local variables of inlined functions as
8584 local variables in the caller.
8586 The body of an inlined function is directly included at its call site;
8587 unlike a non-inlined function, there are no instructions devoted to
8588 the call. @value{GDBN} still pretends that the call site and the
8589 start of the inlined function are different instructions. Stepping to
8590 the call site shows the call site, and then stepping again shows
8591 the first line of the inlined function, even though no additional
8592 instructions are executed.
8594 This makes source-level debugging much clearer; you can see both the
8595 context of the call and then the effect of the call. Only stepping by
8596 a single instruction using @code{stepi} or @code{nexti} does not do
8597 this; single instruction steps always show the inlined body.
8599 There are some ways that @value{GDBN} does not pretend that inlined
8600 function calls are the same as normal calls:
8604 You cannot set breakpoints on inlined functions. @value{GDBN}
8605 either reports that there is no symbol with that name, or else sets the
8606 breakpoint only on non-inlined copies of the function. This limitation
8607 will be removed in a future version of @value{GDBN}; until then,
8608 set a breakpoint by line number on the first line of the inlined
8612 Setting breakpoints at the call site of an inlined function may not
8613 work, because the call site does not contain any code. @value{GDBN}
8614 may incorrectly move the breakpoint to the next line of the enclosing
8615 function, after the call. This limitation will be removed in a future
8616 version of @value{GDBN}; until then, set a breakpoint on an earlier line
8617 or inside the inlined function instead.
8620 @value{GDBN} cannot locate the return value of inlined calls after
8621 using the @code{finish} command. This is a limitation of compiler-generated
8622 debugging information; after @code{finish}, you can step to the next line
8623 and print a variable where your program stored the return value.
8629 @chapter C Preprocessor Macros
8631 Some languages, such as C and C@t{++}, provide a way to define and invoke
8632 ``preprocessor macros'' which expand into strings of tokens.
8633 @value{GDBN} can evaluate expressions containing macro invocations, show
8634 the result of macro expansion, and show a macro's definition, including
8635 where it was defined.
8637 You may need to compile your program specially to provide @value{GDBN}
8638 with information about preprocessor macros. Most compilers do not
8639 include macros in their debugging information, even when you compile
8640 with the @option{-g} flag. @xref{Compilation}.
8642 A program may define a macro at one point, remove that definition later,
8643 and then provide a different definition after that. Thus, at different
8644 points in the program, a macro may have different definitions, or have
8645 no definition at all. If there is a current stack frame, @value{GDBN}
8646 uses the macros in scope at that frame's source code line. Otherwise,
8647 @value{GDBN} uses the macros in scope at the current listing location;
8650 Whenever @value{GDBN} evaluates an expression, it always expands any
8651 macro invocations present in the expression. @value{GDBN} also provides
8652 the following commands for working with macros explicitly.
8656 @kindex macro expand
8657 @cindex macro expansion, showing the results of preprocessor
8658 @cindex preprocessor macro expansion, showing the results of
8659 @cindex expanding preprocessor macros
8660 @item macro expand @var{expression}
8661 @itemx macro exp @var{expression}
8662 Show the results of expanding all preprocessor macro invocations in
8663 @var{expression}. Since @value{GDBN} simply expands macros, but does
8664 not parse the result, @var{expression} need not be a valid expression;
8665 it can be any string of tokens.
8668 @item macro expand-once @var{expression}
8669 @itemx macro exp1 @var{expression}
8670 @cindex expand macro once
8671 @i{(This command is not yet implemented.)} Show the results of
8672 expanding those preprocessor macro invocations that appear explicitly in
8673 @var{expression}. Macro invocations appearing in that expansion are
8674 left unchanged. This command allows you to see the effect of a
8675 particular macro more clearly, without being confused by further
8676 expansions. Since @value{GDBN} simply expands macros, but does not
8677 parse the result, @var{expression} need not be a valid expression; it
8678 can be any string of tokens.
8681 @cindex macro definition, showing
8682 @cindex definition, showing a macro's
8683 @item info macro @var{macro}
8684 Show the definition of the macro named @var{macro}, and describe the
8685 source location or compiler command-line where that definition was established.
8687 @kindex macro define
8688 @cindex user-defined macros
8689 @cindex defining macros interactively
8690 @cindex macros, user-defined
8691 @item macro define @var{macro} @var{replacement-list}
8692 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
8693 Introduce a definition for a preprocessor macro named @var{macro},
8694 invocations of which are replaced by the tokens given in
8695 @var{replacement-list}. The first form of this command defines an
8696 ``object-like'' macro, which takes no arguments; the second form
8697 defines a ``function-like'' macro, which takes the arguments given in
8700 A definition introduced by this command is in scope in every
8701 expression evaluated in @value{GDBN}, until it is removed with the
8702 @code{macro undef} command, described below. The definition overrides
8703 all definitions for @var{macro} present in the program being debugged,
8704 as well as any previous user-supplied definition.
8707 @item macro undef @var{macro}
8708 Remove any user-supplied definition for the macro named @var{macro}.
8709 This command only affects definitions provided with the @code{macro
8710 define} command, described above; it cannot remove definitions present
8711 in the program being debugged.
8715 List all the macros defined using the @code{macro define} command.
8718 @cindex macros, example of debugging with
8719 Here is a transcript showing the above commands in action. First, we
8720 show our source files:
8728 #define ADD(x) (M + x)
8733 printf ("Hello, world!\n");
8735 printf ("We're so creative.\n");
8737 printf ("Goodbye, world!\n");
8744 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
8745 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
8746 compiler includes information about preprocessor macros in the debugging
8750 $ gcc -gdwarf-2 -g3 sample.c -o sample
8754 Now, we start @value{GDBN} on our sample program:
8758 GNU gdb 2002-05-06-cvs
8759 Copyright 2002 Free Software Foundation, Inc.
8760 GDB is free software, @dots{}
8764 We can expand macros and examine their definitions, even when the
8765 program is not running. @value{GDBN} uses the current listing position
8766 to decide which macro definitions are in scope:
8769 (@value{GDBP}) list main
8772 5 #define ADD(x) (M + x)
8777 10 printf ("Hello, world!\n");
8779 12 printf ("We're so creative.\n");
8780 (@value{GDBP}) info macro ADD
8781 Defined at /home/jimb/gdb/macros/play/sample.c:5
8782 #define ADD(x) (M + x)
8783 (@value{GDBP}) info macro Q
8784 Defined at /home/jimb/gdb/macros/play/sample.h:1
8785 included at /home/jimb/gdb/macros/play/sample.c:2
8787 (@value{GDBP}) macro expand ADD(1)
8788 expands to: (42 + 1)
8789 (@value{GDBP}) macro expand-once ADD(1)
8790 expands to: once (M + 1)
8794 In the example above, note that @code{macro expand-once} expands only
8795 the macro invocation explicit in the original text --- the invocation of
8796 @code{ADD} --- but does not expand the invocation of the macro @code{M},
8797 which was introduced by @code{ADD}.
8799 Once the program is running, @value{GDBN} uses the macro definitions in
8800 force at the source line of the current stack frame:
8803 (@value{GDBP}) break main
8804 Breakpoint 1 at 0x8048370: file sample.c, line 10.
8806 Starting program: /home/jimb/gdb/macros/play/sample
8808 Breakpoint 1, main () at sample.c:10
8809 10 printf ("Hello, world!\n");
8813 At line 10, the definition of the macro @code{N} at line 9 is in force:
8816 (@value{GDBP}) info macro N
8817 Defined at /home/jimb/gdb/macros/play/sample.c:9
8819 (@value{GDBP}) macro expand N Q M
8821 (@value{GDBP}) print N Q M
8826 As we step over directives that remove @code{N}'s definition, and then
8827 give it a new definition, @value{GDBN} finds the definition (or lack
8828 thereof) in force at each point:
8833 12 printf ("We're so creative.\n");
8834 (@value{GDBP}) info macro N
8835 The symbol `N' has no definition as a C/C++ preprocessor macro
8836 at /home/jimb/gdb/macros/play/sample.c:12
8839 14 printf ("Goodbye, world!\n");
8840 (@value{GDBP}) info macro N
8841 Defined at /home/jimb/gdb/macros/play/sample.c:13
8843 (@value{GDBP}) macro expand N Q M
8844 expands to: 1729 < 42
8845 (@value{GDBP}) print N Q M
8850 In addition to source files, macros can be defined on the compilation command
8851 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
8852 such a way, @value{GDBN} displays the location of their definition as line zero
8853 of the source file submitted to the compiler.
8856 (@value{GDBP}) info macro __STDC__
8857 Defined at /home/jimb/gdb/macros/play/sample.c:0
8864 @chapter Tracepoints
8865 @c This chapter is based on the documentation written by Michael
8866 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
8869 In some applications, it is not feasible for the debugger to interrupt
8870 the program's execution long enough for the developer to learn
8871 anything helpful about its behavior. If the program's correctness
8872 depends on its real-time behavior, delays introduced by a debugger
8873 might cause the program to change its behavior drastically, or perhaps
8874 fail, even when the code itself is correct. It is useful to be able
8875 to observe the program's behavior without interrupting it.
8877 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
8878 specify locations in the program, called @dfn{tracepoints}, and
8879 arbitrary expressions to evaluate when those tracepoints are reached.
8880 Later, using the @code{tfind} command, you can examine the values
8881 those expressions had when the program hit the tracepoints. The
8882 expressions may also denote objects in memory---structures or arrays,
8883 for example---whose values @value{GDBN} should record; while visiting
8884 a particular tracepoint, you may inspect those objects as if they were
8885 in memory at that moment. However, because @value{GDBN} records these
8886 values without interacting with you, it can do so quickly and
8887 unobtrusively, hopefully not disturbing the program's behavior.
8889 The tracepoint facility is currently available only for remote
8890 targets. @xref{Targets}. In addition, your remote target must know
8891 how to collect trace data. This functionality is implemented in the
8892 remote stub; however, none of the stubs distributed with @value{GDBN}
8893 support tracepoints as of this writing. The format of the remote
8894 packets used to implement tracepoints are described in @ref{Tracepoint
8897 This chapter describes the tracepoint commands and features.
8901 * Analyze Collected Data::
8902 * Tracepoint Variables::
8905 @node Set Tracepoints
8906 @section Commands to Set Tracepoints
8908 Before running such a @dfn{trace experiment}, an arbitrary number of
8909 tracepoints can be set. A tracepoint is actually a special type of
8910 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
8911 standard breakpoint commands. For instance, as with breakpoints,
8912 tracepoint numbers are successive integers starting from one, and many
8913 of the commands associated with tracepoints take the tracepoint number
8914 as their argument, to identify which tracepoint to work on.
8916 For each tracepoint, you can specify, in advance, some arbitrary set
8917 of data that you want the target to collect in the trace buffer when
8918 it hits that tracepoint. The collected data can include registers,
8919 local variables, or global data. Later, you can use @value{GDBN}
8920 commands to examine the values these data had at the time the
8923 Tracepoints do not support every breakpoint feature. Conditional
8924 expressions and ignore counts on tracepoints have no effect, and
8925 tracepoints cannot run @value{GDBN} commands when they are
8926 hit. Tracepoints may not be thread-specific either.
8928 This section describes commands to set tracepoints and associated
8929 conditions and actions.
8932 * Create and Delete Tracepoints::
8933 * Enable and Disable Tracepoints::
8934 * Tracepoint Passcounts::
8935 * Tracepoint Conditions::
8936 * Tracepoint Actions::
8937 * Listing Tracepoints::
8938 * Starting and Stopping Trace Experiments::
8941 @node Create and Delete Tracepoints
8942 @subsection Create and Delete Tracepoints
8945 @cindex set tracepoint
8947 @item trace @var{location}
8948 The @code{trace} command is very similar to the @code{break} command.
8949 Its argument @var{location} can be a source line, a function name, or
8950 an address in the target program. @xref{Specify Location}. The
8951 @code{trace} command defines a tracepoint, which is a point in the
8952 target program where the debugger will briefly stop, collect some
8953 data, and then allow the program to continue. Setting a tracepoint or
8954 changing its actions doesn't take effect until the next @code{tstart}
8955 command, and once a trace experiment is running, further changes will
8956 not have any effect until the next trace experiment starts.
8958 Here are some examples of using the @code{trace} command:
8961 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
8963 (@value{GDBP}) @b{trace +2} // 2 lines forward
8965 (@value{GDBP}) @b{trace my_function} // first source line of function
8967 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
8969 (@value{GDBP}) @b{trace *0x2117c4} // an address
8973 You can abbreviate @code{trace} as @code{tr}.
8975 @item trace @var{location} if @var{cond}
8976 Set a tracepoint with condition @var{cond}; evaluate the expression
8977 @var{cond} each time the tracepoint is reached, and collect data only
8978 if the value is nonzero---that is, if @var{cond} evaluates as true.
8979 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
8980 information on tracepoint conditions.
8983 @cindex last tracepoint number
8984 @cindex recent tracepoint number
8985 @cindex tracepoint number
8986 The convenience variable @code{$tpnum} records the tracepoint number
8987 of the most recently set tracepoint.
8989 @kindex delete tracepoint
8990 @cindex tracepoint deletion
8991 @item delete tracepoint @r{[}@var{num}@r{]}
8992 Permanently delete one or more tracepoints. With no argument, the
8993 default is to delete all tracepoints. Note that the regular
8994 @code{delete} command can remove tracepoints also.
8999 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
9001 (@value{GDBP}) @b{delete trace} // remove all tracepoints
9005 You can abbreviate this command as @code{del tr}.
9008 @node Enable and Disable Tracepoints
9009 @subsection Enable and Disable Tracepoints
9011 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
9014 @kindex disable tracepoint
9015 @item disable tracepoint @r{[}@var{num}@r{]}
9016 Disable tracepoint @var{num}, or all tracepoints if no argument
9017 @var{num} is given. A disabled tracepoint will have no effect during
9018 the next trace experiment, but it is not forgotten. You can re-enable
9019 a disabled tracepoint using the @code{enable tracepoint} command.
9021 @kindex enable tracepoint
9022 @item enable tracepoint @r{[}@var{num}@r{]}
9023 Enable tracepoint @var{num}, or all tracepoints. The enabled
9024 tracepoints will become effective the next time a trace experiment is
9028 @node Tracepoint Passcounts
9029 @subsection Tracepoint Passcounts
9033 @cindex tracepoint pass count
9034 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
9035 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
9036 automatically stop a trace experiment. If a tracepoint's passcount is
9037 @var{n}, then the trace experiment will be automatically stopped on
9038 the @var{n}'th time that tracepoint is hit. If the tracepoint number
9039 @var{num} is not specified, the @code{passcount} command sets the
9040 passcount of the most recently defined tracepoint. If no passcount is
9041 given, the trace experiment will run until stopped explicitly by the
9047 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
9048 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
9050 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
9051 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
9052 (@value{GDBP}) @b{trace foo}
9053 (@value{GDBP}) @b{pass 3}
9054 (@value{GDBP}) @b{trace bar}
9055 (@value{GDBP}) @b{pass 2}
9056 (@value{GDBP}) @b{trace baz}
9057 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
9058 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
9059 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
9060 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
9064 @node Tracepoint Conditions
9065 @subsection Tracepoint Conditions
9066 @cindex conditional tracepoints
9067 @cindex tracepoint conditions
9069 The simplest sort of tracepoint collects data every time your program
9070 reaches a specified place. You can also specify a @dfn{condition} for
9071 a tracepoint. A condition is just a Boolean expression in your
9072 programming language (@pxref{Expressions, ,Expressions}). A
9073 tracepoint with a condition evaluates the expression each time your
9074 program reaches it, and data collection happens only if the condition
9077 Tracepoint conditions can be specified when a tracepoint is set, by
9078 using @samp{if} in the arguments to the @code{trace} command.
9079 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
9080 also be set or changed at any time with the @code{condition} command,
9081 just as with breakpoints.
9083 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
9084 the conditional expression itself. Instead, @value{GDBN} encodes the
9085 expression into an agent expression (@pxref{Agent Expressions}
9086 suitable for execution on the target, independently of @value{GDBN}.
9087 Global variables become raw memory locations, locals become stack
9088 accesses, and so forth.
9090 For instance, suppose you have a function that is usually called
9091 frequently, but should not be called after an error has occurred. You
9092 could use the following tracepoint command to collect data about calls
9093 of that function that happen while the error code is propagating
9094 through the program; an unconditional tracepoint could end up
9095 collecting thousands of useless trace frames that you would have to
9099 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
9102 @node Tracepoint Actions
9103 @subsection Tracepoint Action Lists
9107 @cindex tracepoint actions
9108 @item actions @r{[}@var{num}@r{]}
9109 This command will prompt for a list of actions to be taken when the
9110 tracepoint is hit. If the tracepoint number @var{num} is not
9111 specified, this command sets the actions for the one that was most
9112 recently defined (so that you can define a tracepoint and then say
9113 @code{actions} without bothering about its number). You specify the
9114 actions themselves on the following lines, one action at a time, and
9115 terminate the actions list with a line containing just @code{end}. So
9116 far, the only defined actions are @code{collect} and
9117 @code{while-stepping}.
9119 @cindex remove actions from a tracepoint
9120 To remove all actions from a tracepoint, type @samp{actions @var{num}}
9121 and follow it immediately with @samp{end}.
9124 (@value{GDBP}) @b{collect @var{data}} // collect some data
9126 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
9128 (@value{GDBP}) @b{end} // signals the end of actions.
9131 In the following example, the action list begins with @code{collect}
9132 commands indicating the things to be collected when the tracepoint is
9133 hit. Then, in order to single-step and collect additional data
9134 following the tracepoint, a @code{while-stepping} command is used,
9135 followed by the list of things to be collected while stepping. The
9136 @code{while-stepping} command is terminated by its own separate
9137 @code{end} command. Lastly, the action list is terminated by an
9141 (@value{GDBP}) @b{trace foo}
9142 (@value{GDBP}) @b{actions}
9143 Enter actions for tracepoint 1, one per line:
9152 @kindex collect @r{(tracepoints)}
9153 @item collect @var{expr1}, @var{expr2}, @dots{}
9154 Collect values of the given expressions when the tracepoint is hit.
9155 This command accepts a comma-separated list of any valid expressions.
9156 In addition to global, static, or local variables, the following
9157 special arguments are supported:
9161 collect all registers
9164 collect all function arguments
9167 collect all local variables.
9170 You can give several consecutive @code{collect} commands, each one
9171 with a single argument, or one @code{collect} command with several
9172 arguments separated by commas: the effect is the same.
9174 The command @code{info scope} (@pxref{Symbols, info scope}) is
9175 particularly useful for figuring out what data to collect.
9177 @kindex while-stepping @r{(tracepoints)}
9178 @item while-stepping @var{n}
9179 Perform @var{n} single-step traces after the tracepoint, collecting
9180 new data at each step. The @code{while-stepping} command is
9181 followed by the list of what to collect while stepping (followed by
9182 its own @code{end} command):
9186 > collect $regs, myglobal
9192 You may abbreviate @code{while-stepping} as @code{ws} or
9196 @node Listing Tracepoints
9197 @subsection Listing Tracepoints
9200 @kindex info tracepoints
9202 @cindex information about tracepoints
9203 @item info tracepoints @r{[}@var{num}@r{]}
9204 Display information about the tracepoint @var{num}. If you don't
9205 specify a tracepoint number, displays information about all the
9206 tracepoints defined so far. The format is similar to that used for
9207 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
9208 command, simply restricting itself to tracepoints.
9210 A tracepoint's listing may include additional information specific to
9215 its passcount as given by the @code{passcount @var{n}} command
9217 its step count as given by the @code{while-stepping @var{n}} command
9219 its action list as given by the @code{actions} command. The actions
9220 are prefixed with an @samp{A} so as to distinguish them from commands.
9224 (@value{GDBP}) @b{info trace}
9225 Num Type Disp Enb Address What
9226 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
9230 A collect globfoo, $regs
9238 This command can be abbreviated @code{info tp}.
9241 @node Starting and Stopping Trace Experiments
9242 @subsection Starting and Stopping Trace Experiments
9246 @cindex start a new trace experiment
9247 @cindex collected data discarded
9249 This command takes no arguments. It starts the trace experiment, and
9250 begins collecting data. This has the side effect of discarding all
9251 the data collected in the trace buffer during the previous trace
9255 @cindex stop a running trace experiment
9257 This command takes no arguments. It ends the trace experiment, and
9258 stops collecting data.
9260 @strong{Note}: a trace experiment and data collection may stop
9261 automatically if any tracepoint's passcount is reached
9262 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
9265 @cindex status of trace data collection
9266 @cindex trace experiment, status of
9268 This command displays the status of the current trace data
9272 Here is an example of the commands we described so far:
9275 (@value{GDBP}) @b{trace gdb_c_test}
9276 (@value{GDBP}) @b{actions}
9277 Enter actions for tracepoint #1, one per line.
9278 > collect $regs,$locals,$args
9283 (@value{GDBP}) @b{tstart}
9284 [time passes @dots{}]
9285 (@value{GDBP}) @b{tstop}
9289 @node Analyze Collected Data
9290 @section Using the Collected Data
9292 After the tracepoint experiment ends, you use @value{GDBN} commands
9293 for examining the trace data. The basic idea is that each tracepoint
9294 collects a trace @dfn{snapshot} every time it is hit and another
9295 snapshot every time it single-steps. All these snapshots are
9296 consecutively numbered from zero and go into a buffer, and you can
9297 examine them later. The way you examine them is to @dfn{focus} on a
9298 specific trace snapshot. When the remote stub is focused on a trace
9299 snapshot, it will respond to all @value{GDBN} requests for memory and
9300 registers by reading from the buffer which belongs to that snapshot,
9301 rather than from @emph{real} memory or registers of the program being
9302 debugged. This means that @strong{all} @value{GDBN} commands
9303 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
9304 behave as if we were currently debugging the program state as it was
9305 when the tracepoint occurred. Any requests for data that are not in
9306 the buffer will fail.
9309 * tfind:: How to select a trace snapshot
9310 * tdump:: How to display all data for a snapshot
9311 * save-tracepoints:: How to save tracepoints for a future run
9315 @subsection @code{tfind @var{n}}
9318 @cindex select trace snapshot
9319 @cindex find trace snapshot
9320 The basic command for selecting a trace snapshot from the buffer is
9321 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
9322 counting from zero. If no argument @var{n} is given, the next
9323 snapshot is selected.
9325 Here are the various forms of using the @code{tfind} command.
9329 Find the first snapshot in the buffer. This is a synonym for
9330 @code{tfind 0} (since 0 is the number of the first snapshot).
9333 Stop debugging trace snapshots, resume @emph{live} debugging.
9336 Same as @samp{tfind none}.
9339 No argument means find the next trace snapshot.
9342 Find the previous trace snapshot before the current one. This permits
9343 retracing earlier steps.
9345 @item tfind tracepoint @var{num}
9346 Find the next snapshot associated with tracepoint @var{num}. Search
9347 proceeds forward from the last examined trace snapshot. If no
9348 argument @var{num} is given, it means find the next snapshot collected
9349 for the same tracepoint as the current snapshot.
9351 @item tfind pc @var{addr}
9352 Find the next snapshot associated with the value @var{addr} of the
9353 program counter. Search proceeds forward from the last examined trace
9354 snapshot. If no argument @var{addr} is given, it means find the next
9355 snapshot with the same value of PC as the current snapshot.
9357 @item tfind outside @var{addr1}, @var{addr2}
9358 Find the next snapshot whose PC is outside the given range of
9361 @item tfind range @var{addr1}, @var{addr2}
9362 Find the next snapshot whose PC is between @var{addr1} and
9363 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
9365 @item tfind line @r{[}@var{file}:@r{]}@var{n}
9366 Find the next snapshot associated with the source line @var{n}. If
9367 the optional argument @var{file} is given, refer to line @var{n} in
9368 that source file. Search proceeds forward from the last examined
9369 trace snapshot. If no argument @var{n} is given, it means find the
9370 next line other than the one currently being examined; thus saying
9371 @code{tfind line} repeatedly can appear to have the same effect as
9372 stepping from line to line in a @emph{live} debugging session.
9375 The default arguments for the @code{tfind} commands are specifically
9376 designed to make it easy to scan through the trace buffer. For
9377 instance, @code{tfind} with no argument selects the next trace
9378 snapshot, and @code{tfind -} with no argument selects the previous
9379 trace snapshot. So, by giving one @code{tfind} command, and then
9380 simply hitting @key{RET} repeatedly you can examine all the trace
9381 snapshots in order. Or, by saying @code{tfind -} and then hitting
9382 @key{RET} repeatedly you can examine the snapshots in reverse order.
9383 The @code{tfind line} command with no argument selects the snapshot
9384 for the next source line executed. The @code{tfind pc} command with
9385 no argument selects the next snapshot with the same program counter
9386 (PC) as the current frame. The @code{tfind tracepoint} command with
9387 no argument selects the next trace snapshot collected by the same
9388 tracepoint as the current one.
9390 In addition to letting you scan through the trace buffer manually,
9391 these commands make it easy to construct @value{GDBN} scripts that
9392 scan through the trace buffer and print out whatever collected data
9393 you are interested in. Thus, if we want to examine the PC, FP, and SP
9394 registers from each trace frame in the buffer, we can say this:
9397 (@value{GDBP}) @b{tfind start}
9398 (@value{GDBP}) @b{while ($trace_frame != -1)}
9399 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
9400 $trace_frame, $pc, $sp, $fp
9404 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
9405 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
9406 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
9407 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
9408 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
9409 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
9410 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
9411 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
9412 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
9413 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
9414 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
9417 Or, if we want to examine the variable @code{X} at each source line in
9421 (@value{GDBP}) @b{tfind start}
9422 (@value{GDBP}) @b{while ($trace_frame != -1)}
9423 > printf "Frame %d, X == %d\n", $trace_frame, X
9433 @subsection @code{tdump}
9435 @cindex dump all data collected at tracepoint
9436 @cindex tracepoint data, display
9438 This command takes no arguments. It prints all the data collected at
9439 the current trace snapshot.
9442 (@value{GDBP}) @b{trace 444}
9443 (@value{GDBP}) @b{actions}
9444 Enter actions for tracepoint #2, one per line:
9445 > collect $regs, $locals, $args, gdb_long_test
9448 (@value{GDBP}) @b{tstart}
9450 (@value{GDBP}) @b{tfind line 444}
9451 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
9453 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
9455 (@value{GDBP}) @b{tdump}
9456 Data collected at tracepoint 2, trace frame 1:
9457 d0 0xc4aa0085 -995491707
9461 d4 0x71aea3d 119204413
9466 a1 0x3000668 50333288
9469 a4 0x3000698 50333336
9471 fp 0x30bf3c 0x30bf3c
9472 sp 0x30bf34 0x30bf34
9474 pc 0x20b2c8 0x20b2c8
9478 p = 0x20e5b4 "gdb-test"
9485 gdb_long_test = 17 '\021'
9490 @node save-tracepoints
9491 @subsection @code{save-tracepoints @var{filename}}
9492 @kindex save-tracepoints
9493 @cindex save tracepoints for future sessions
9495 This command saves all current tracepoint definitions together with
9496 their actions and passcounts, into a file @file{@var{filename}}
9497 suitable for use in a later debugging session. To read the saved
9498 tracepoint definitions, use the @code{source} command (@pxref{Command
9501 @node Tracepoint Variables
9502 @section Convenience Variables for Tracepoints
9503 @cindex tracepoint variables
9504 @cindex convenience variables for tracepoints
9507 @vindex $trace_frame
9508 @item (int) $trace_frame
9509 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
9510 snapshot is selected.
9513 @item (int) $tracepoint
9514 The tracepoint for the current trace snapshot.
9517 @item (int) $trace_line
9518 The line number for the current trace snapshot.
9521 @item (char []) $trace_file
9522 The source file for the current trace snapshot.
9525 @item (char []) $trace_func
9526 The name of the function containing @code{$tracepoint}.
9529 Note: @code{$trace_file} is not suitable for use in @code{printf},
9530 use @code{output} instead.
9532 Here's a simple example of using these convenience variables for
9533 stepping through all the trace snapshots and printing some of their
9537 (@value{GDBP}) @b{tfind start}
9539 (@value{GDBP}) @b{while $trace_frame != -1}
9540 > output $trace_file
9541 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
9547 @chapter Debugging Programs That Use Overlays
9550 If your program is too large to fit completely in your target system's
9551 memory, you can sometimes use @dfn{overlays} to work around this
9552 problem. @value{GDBN} provides some support for debugging programs that
9556 * How Overlays Work:: A general explanation of overlays.
9557 * Overlay Commands:: Managing overlays in @value{GDBN}.
9558 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
9559 mapped by asking the inferior.
9560 * Overlay Sample Program:: A sample program using overlays.
9563 @node How Overlays Work
9564 @section How Overlays Work
9565 @cindex mapped overlays
9566 @cindex unmapped overlays
9567 @cindex load address, overlay's
9568 @cindex mapped address
9569 @cindex overlay area
9571 Suppose you have a computer whose instruction address space is only 64
9572 kilobytes long, but which has much more memory which can be accessed by
9573 other means: special instructions, segment registers, or memory
9574 management hardware, for example. Suppose further that you want to
9575 adapt a program which is larger than 64 kilobytes to run on this system.
9577 One solution is to identify modules of your program which are relatively
9578 independent, and need not call each other directly; call these modules
9579 @dfn{overlays}. Separate the overlays from the main program, and place
9580 their machine code in the larger memory. Place your main program in
9581 instruction memory, but leave at least enough space there to hold the
9582 largest overlay as well.
9584 Now, to call a function located in an overlay, you must first copy that
9585 overlay's machine code from the large memory into the space set aside
9586 for it in the instruction memory, and then jump to its entry point
9589 @c NB: In the below the mapped area's size is greater or equal to the
9590 @c size of all overlays. This is intentional to remind the developer
9591 @c that overlays don't necessarily need to be the same size.
9595 Data Instruction Larger
9596 Address Space Address Space Address Space
9597 +-----------+ +-----------+ +-----------+
9599 +-----------+ +-----------+ +-----------+<-- overlay 1
9600 | program | | main | .----| overlay 1 | load address
9601 | variables | | program | | +-----------+
9602 | and heap | | | | | |
9603 +-----------+ | | | +-----------+<-- overlay 2
9604 | | +-----------+ | | | load address
9605 +-----------+ | | | .-| overlay 2 |
9607 mapped --->+-----------+ | | +-----------+
9609 | overlay | <-' | | |
9610 | area | <---' +-----------+<-- overlay 3
9611 | | <---. | | load address
9612 +-----------+ `--| overlay 3 |
9619 @anchor{A code overlay}A code overlay
9623 The diagram (@pxref{A code overlay}) shows a system with separate data
9624 and instruction address spaces. To map an overlay, the program copies
9625 its code from the larger address space to the instruction address space.
9626 Since the overlays shown here all use the same mapped address, only one
9627 may be mapped at a time. For a system with a single address space for
9628 data and instructions, the diagram would be similar, except that the
9629 program variables and heap would share an address space with the main
9630 program and the overlay area.
9632 An overlay loaded into instruction memory and ready for use is called a
9633 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
9634 instruction memory. An overlay not present (or only partially present)
9635 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
9636 is its address in the larger memory. The mapped address is also called
9637 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
9638 called the @dfn{load memory address}, or @dfn{LMA}.
9640 Unfortunately, overlays are not a completely transparent way to adapt a
9641 program to limited instruction memory. They introduce a new set of
9642 global constraints you must keep in mind as you design your program:
9647 Before calling or returning to a function in an overlay, your program
9648 must make sure that overlay is actually mapped. Otherwise, the call or
9649 return will transfer control to the right address, but in the wrong
9650 overlay, and your program will probably crash.
9653 If the process of mapping an overlay is expensive on your system, you
9654 will need to choose your overlays carefully to minimize their effect on
9655 your program's performance.
9658 The executable file you load onto your system must contain each
9659 overlay's instructions, appearing at the overlay's load address, not its
9660 mapped address. However, each overlay's instructions must be relocated
9661 and its symbols defined as if the overlay were at its mapped address.
9662 You can use GNU linker scripts to specify different load and relocation
9663 addresses for pieces of your program; see @ref{Overlay Description,,,
9664 ld.info, Using ld: the GNU linker}.
9667 The procedure for loading executable files onto your system must be able
9668 to load their contents into the larger address space as well as the
9669 instruction and data spaces.
9673 The overlay system described above is rather simple, and could be
9674 improved in many ways:
9679 If your system has suitable bank switch registers or memory management
9680 hardware, you could use those facilities to make an overlay's load area
9681 contents simply appear at their mapped address in instruction space.
9682 This would probably be faster than copying the overlay to its mapped
9683 area in the usual way.
9686 If your overlays are small enough, you could set aside more than one
9687 overlay area, and have more than one overlay mapped at a time.
9690 You can use overlays to manage data, as well as instructions. In
9691 general, data overlays are even less transparent to your design than
9692 code overlays: whereas code overlays only require care when you call or
9693 return to functions, data overlays require care every time you access
9694 the data. Also, if you change the contents of a data overlay, you
9695 must copy its contents back out to its load address before you can copy a
9696 different data overlay into the same mapped area.
9701 @node Overlay Commands
9702 @section Overlay Commands
9704 To use @value{GDBN}'s overlay support, each overlay in your program must
9705 correspond to a separate section of the executable file. The section's
9706 virtual memory address and load memory address must be the overlay's
9707 mapped and load addresses. Identifying overlays with sections allows
9708 @value{GDBN} to determine the appropriate address of a function or
9709 variable, depending on whether the overlay is mapped or not.
9711 @value{GDBN}'s overlay commands all start with the word @code{overlay};
9712 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
9717 Disable @value{GDBN}'s overlay support. When overlay support is
9718 disabled, @value{GDBN} assumes that all functions and variables are
9719 always present at their mapped addresses. By default, @value{GDBN}'s
9720 overlay support is disabled.
9722 @item overlay manual
9723 @cindex manual overlay debugging
9724 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
9725 relies on you to tell it which overlays are mapped, and which are not,
9726 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
9727 commands described below.
9729 @item overlay map-overlay @var{overlay}
9730 @itemx overlay map @var{overlay}
9731 @cindex map an overlay
9732 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
9733 be the name of the object file section containing the overlay. When an
9734 overlay is mapped, @value{GDBN} assumes it can find the overlay's
9735 functions and variables at their mapped addresses. @value{GDBN} assumes
9736 that any other overlays whose mapped ranges overlap that of
9737 @var{overlay} are now unmapped.
9739 @item overlay unmap-overlay @var{overlay}
9740 @itemx overlay unmap @var{overlay}
9741 @cindex unmap an overlay
9742 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
9743 must be the name of the object file section containing the overlay.
9744 When an overlay is unmapped, @value{GDBN} assumes it can find the
9745 overlay's functions and variables at their load addresses.
9748 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
9749 consults a data structure the overlay manager maintains in the inferior
9750 to see which overlays are mapped. For details, see @ref{Automatic
9753 @item overlay load-target
9755 @cindex reloading the overlay table
9756 Re-read the overlay table from the inferior. Normally, @value{GDBN}
9757 re-reads the table @value{GDBN} automatically each time the inferior
9758 stops, so this command should only be necessary if you have changed the
9759 overlay mapping yourself using @value{GDBN}. This command is only
9760 useful when using automatic overlay debugging.
9762 @item overlay list-overlays
9764 @cindex listing mapped overlays
9765 Display a list of the overlays currently mapped, along with their mapped
9766 addresses, load addresses, and sizes.
9770 Normally, when @value{GDBN} prints a code address, it includes the name
9771 of the function the address falls in:
9774 (@value{GDBP}) print main
9775 $3 = @{int ()@} 0x11a0 <main>
9778 When overlay debugging is enabled, @value{GDBN} recognizes code in
9779 unmapped overlays, and prints the names of unmapped functions with
9780 asterisks around them. For example, if @code{foo} is a function in an
9781 unmapped overlay, @value{GDBN} prints it this way:
9784 (@value{GDBP}) overlay list
9785 No sections are mapped.
9786 (@value{GDBP}) print foo
9787 $5 = @{int (int)@} 0x100000 <*foo*>
9790 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
9794 (@value{GDBP}) overlay list
9795 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
9796 mapped at 0x1016 - 0x104a
9797 (@value{GDBP}) print foo
9798 $6 = @{int (int)@} 0x1016 <foo>
9801 When overlay debugging is enabled, @value{GDBN} can find the correct
9802 address for functions and variables in an overlay, whether or not the
9803 overlay is mapped. This allows most @value{GDBN} commands, like
9804 @code{break} and @code{disassemble}, to work normally, even on unmapped
9805 code. However, @value{GDBN}'s breakpoint support has some limitations:
9809 @cindex breakpoints in overlays
9810 @cindex overlays, setting breakpoints in
9811 You can set breakpoints in functions in unmapped overlays, as long as
9812 @value{GDBN} can write to the overlay at its load address.
9814 @value{GDBN} can not set hardware or simulator-based breakpoints in
9815 unmapped overlays. However, if you set a breakpoint at the end of your
9816 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
9817 you are using manual overlay management), @value{GDBN} will re-set its
9818 breakpoints properly.
9822 @node Automatic Overlay Debugging
9823 @section Automatic Overlay Debugging
9824 @cindex automatic overlay debugging
9826 @value{GDBN} can automatically track which overlays are mapped and which
9827 are not, given some simple co-operation from the overlay manager in the
9828 inferior. If you enable automatic overlay debugging with the
9829 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
9830 looks in the inferior's memory for certain variables describing the
9831 current state of the overlays.
9833 Here are the variables your overlay manager must define to support
9834 @value{GDBN}'s automatic overlay debugging:
9838 @item @code{_ovly_table}:
9839 This variable must be an array of the following structures:
9844 /* The overlay's mapped address. */
9847 /* The size of the overlay, in bytes. */
9850 /* The overlay's load address. */
9853 /* Non-zero if the overlay is currently mapped;
9855 unsigned long mapped;
9859 @item @code{_novlys}:
9860 This variable must be a four-byte signed integer, holding the total
9861 number of elements in @code{_ovly_table}.
9865 To decide whether a particular overlay is mapped or not, @value{GDBN}
9866 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
9867 @code{lma} members equal the VMA and LMA of the overlay's section in the
9868 executable file. When @value{GDBN} finds a matching entry, it consults
9869 the entry's @code{mapped} member to determine whether the overlay is
9872 In addition, your overlay manager may define a function called
9873 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
9874 will silently set a breakpoint there. If the overlay manager then
9875 calls this function whenever it has changed the overlay table, this
9876 will enable @value{GDBN} to accurately keep track of which overlays
9877 are in program memory, and update any breakpoints that may be set
9878 in overlays. This will allow breakpoints to work even if the
9879 overlays are kept in ROM or other non-writable memory while they
9880 are not being executed.
9882 @node Overlay Sample Program
9883 @section Overlay Sample Program
9884 @cindex overlay example program
9886 When linking a program which uses overlays, you must place the overlays
9887 at their load addresses, while relocating them to run at their mapped
9888 addresses. To do this, you must write a linker script (@pxref{Overlay
9889 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
9890 since linker scripts are specific to a particular host system, target
9891 architecture, and target memory layout, this manual cannot provide
9892 portable sample code demonstrating @value{GDBN}'s overlay support.
9894 However, the @value{GDBN} source distribution does contain an overlaid
9895 program, with linker scripts for a few systems, as part of its test
9896 suite. The program consists of the following files from
9897 @file{gdb/testsuite/gdb.base}:
9901 The main program file.
9903 A simple overlay manager, used by @file{overlays.c}.
9908 Overlay modules, loaded and used by @file{overlays.c}.
9911 Linker scripts for linking the test program on the @code{d10v-elf}
9912 and @code{m32r-elf} targets.
9915 You can build the test program using the @code{d10v-elf} GCC
9916 cross-compiler like this:
9919 $ d10v-elf-gcc -g -c overlays.c
9920 $ d10v-elf-gcc -g -c ovlymgr.c
9921 $ d10v-elf-gcc -g -c foo.c
9922 $ d10v-elf-gcc -g -c bar.c
9923 $ d10v-elf-gcc -g -c baz.c
9924 $ d10v-elf-gcc -g -c grbx.c
9925 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
9926 baz.o grbx.o -Wl,-Td10v.ld -o overlays
9929 The build process is identical for any other architecture, except that
9930 you must substitute the appropriate compiler and linker script for the
9931 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
9935 @chapter Using @value{GDBN} with Different Languages
9938 Although programming languages generally have common aspects, they are
9939 rarely expressed in the same manner. For instance, in ANSI C,
9940 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
9941 Modula-2, it is accomplished by @code{p^}. Values can also be
9942 represented (and displayed) differently. Hex numbers in C appear as
9943 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
9945 @cindex working language
9946 Language-specific information is built into @value{GDBN} for some languages,
9947 allowing you to express operations like the above in your program's
9948 native language, and allowing @value{GDBN} to output values in a manner
9949 consistent with the syntax of your program's native language. The
9950 language you use to build expressions is called the @dfn{working
9954 * Setting:: Switching between source languages
9955 * Show:: Displaying the language
9956 * Checks:: Type and range checks
9957 * Supported Languages:: Supported languages
9958 * Unsupported Languages:: Unsupported languages
9962 @section Switching Between Source Languages
9964 There are two ways to control the working language---either have @value{GDBN}
9965 set it automatically, or select it manually yourself. You can use the
9966 @code{set language} command for either purpose. On startup, @value{GDBN}
9967 defaults to setting the language automatically. The working language is
9968 used to determine how expressions you type are interpreted, how values
9971 In addition to the working language, every source file that
9972 @value{GDBN} knows about has its own working language. For some object
9973 file formats, the compiler might indicate which language a particular
9974 source file is in. However, most of the time @value{GDBN} infers the
9975 language from the name of the file. The language of a source file
9976 controls whether C@t{++} names are demangled---this way @code{backtrace} can
9977 show each frame appropriately for its own language. There is no way to
9978 set the language of a source file from within @value{GDBN}, but you can
9979 set the language associated with a filename extension. @xref{Show, ,
9980 Displaying the Language}.
9982 This is most commonly a problem when you use a program, such
9983 as @code{cfront} or @code{f2c}, that generates C but is written in
9984 another language. In that case, make the
9985 program use @code{#line} directives in its C output; that way
9986 @value{GDBN} will know the correct language of the source code of the original
9987 program, and will display that source code, not the generated C code.
9990 * Filenames:: Filename extensions and languages.
9991 * Manually:: Setting the working language manually
9992 * Automatically:: Having @value{GDBN} infer the source language
9996 @subsection List of Filename Extensions and Languages
9998 If a source file name ends in one of the following extensions, then
9999 @value{GDBN} infers that its language is the one indicated.
10017 C@t{++} source file
10020 Objective-C source file
10024 Fortran source file
10027 Modula-2 source file
10031 Assembler source file. This actually behaves almost like C, but
10032 @value{GDBN} does not skip over function prologues when stepping.
10035 In addition, you may set the language associated with a filename
10036 extension. @xref{Show, , Displaying the Language}.
10039 @subsection Setting the Working Language
10041 If you allow @value{GDBN} to set the language automatically,
10042 expressions are interpreted the same way in your debugging session and
10045 @kindex set language
10046 If you wish, you may set the language manually. To do this, issue the
10047 command @samp{set language @var{lang}}, where @var{lang} is the name of
10048 a language, such as
10049 @code{c} or @code{modula-2}.
10050 For a list of the supported languages, type @samp{set language}.
10052 Setting the language manually prevents @value{GDBN} from updating the working
10053 language automatically. This can lead to confusion if you try
10054 to debug a program when the working language is not the same as the
10055 source language, when an expression is acceptable to both
10056 languages---but means different things. For instance, if the current
10057 source file were written in C, and @value{GDBN} was parsing Modula-2, a
10065 might not have the effect you intended. In C, this means to add
10066 @code{b} and @code{c} and place the result in @code{a}. The result
10067 printed would be the value of @code{a}. In Modula-2, this means to compare
10068 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
10070 @node Automatically
10071 @subsection Having @value{GDBN} Infer the Source Language
10073 To have @value{GDBN} set the working language automatically, use
10074 @samp{set language local} or @samp{set language auto}. @value{GDBN}
10075 then infers the working language. That is, when your program stops in a
10076 frame (usually by encountering a breakpoint), @value{GDBN} sets the
10077 working language to the language recorded for the function in that
10078 frame. If the language for a frame is unknown (that is, if the function
10079 or block corresponding to the frame was defined in a source file that
10080 does not have a recognized extension), the current working language is
10081 not changed, and @value{GDBN} issues a warning.
10083 This may not seem necessary for most programs, which are written
10084 entirely in one source language. However, program modules and libraries
10085 written in one source language can be used by a main program written in
10086 a different source language. Using @samp{set language auto} in this
10087 case frees you from having to set the working language manually.
10090 @section Displaying the Language
10092 The following commands help you find out which language is the
10093 working language, and also what language source files were written in.
10096 @item show language
10097 @kindex show language
10098 Display the current working language. This is the
10099 language you can use with commands such as @code{print} to
10100 build and compute expressions that may involve variables in your program.
10103 @kindex info frame@r{, show the source language}
10104 Display the source language for this frame. This language becomes the
10105 working language if you use an identifier from this frame.
10106 @xref{Frame Info, ,Information about a Frame}, to identify the other
10107 information listed here.
10110 @kindex info source@r{, show the source language}
10111 Display the source language of this source file.
10112 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
10113 information listed here.
10116 In unusual circumstances, you may have source files with extensions
10117 not in the standard list. You can then set the extension associated
10118 with a language explicitly:
10121 @item set extension-language @var{ext} @var{language}
10122 @kindex set extension-language
10123 Tell @value{GDBN} that source files with extension @var{ext} are to be
10124 assumed as written in the source language @var{language}.
10126 @item info extensions
10127 @kindex info extensions
10128 List all the filename extensions and the associated languages.
10132 @section Type and Range Checking
10135 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
10136 checking are included, but they do not yet have any effect. This
10137 section documents the intended facilities.
10139 @c FIXME remove warning when type/range code added
10141 Some languages are designed to guard you against making seemingly common
10142 errors through a series of compile- and run-time checks. These include
10143 checking the type of arguments to functions and operators, and making
10144 sure mathematical overflows are caught at run time. Checks such as
10145 these help to ensure a program's correctness once it has been compiled
10146 by eliminating type mismatches, and providing active checks for range
10147 errors when your program is running.
10149 @value{GDBN} can check for conditions like the above if you wish.
10150 Although @value{GDBN} does not check the statements in your program,
10151 it can check expressions entered directly into @value{GDBN} for
10152 evaluation via the @code{print} command, for example. As with the
10153 working language, @value{GDBN} can also decide whether or not to check
10154 automatically based on your program's source language.
10155 @xref{Supported Languages, ,Supported Languages}, for the default
10156 settings of supported languages.
10159 * Type Checking:: An overview of type checking
10160 * Range Checking:: An overview of range checking
10163 @cindex type checking
10164 @cindex checks, type
10165 @node Type Checking
10166 @subsection An Overview of Type Checking
10168 Some languages, such as Modula-2, are strongly typed, meaning that the
10169 arguments to operators and functions have to be of the correct type,
10170 otherwise an error occurs. These checks prevent type mismatch
10171 errors from ever causing any run-time problems. For example,
10179 The second example fails because the @code{CARDINAL} 1 is not
10180 type-compatible with the @code{REAL} 2.3.
10182 For the expressions you use in @value{GDBN} commands, you can tell the
10183 @value{GDBN} type checker to skip checking;
10184 to treat any mismatches as errors and abandon the expression;
10185 or to only issue warnings when type mismatches occur,
10186 but evaluate the expression anyway. When you choose the last of
10187 these, @value{GDBN} evaluates expressions like the second example above, but
10188 also issues a warning.
10190 Even if you turn type checking off, there may be other reasons
10191 related to type that prevent @value{GDBN} from evaluating an expression.
10192 For instance, @value{GDBN} does not know how to add an @code{int} and
10193 a @code{struct foo}. These particular type errors have nothing to do
10194 with the language in use, and usually arise from expressions, such as
10195 the one described above, which make little sense to evaluate anyway.
10197 Each language defines to what degree it is strict about type. For
10198 instance, both Modula-2 and C require the arguments to arithmetical
10199 operators to be numbers. In C, enumerated types and pointers can be
10200 represented as numbers, so that they are valid arguments to mathematical
10201 operators. @xref{Supported Languages, ,Supported Languages}, for further
10202 details on specific languages.
10204 @value{GDBN} provides some additional commands for controlling the type checker:
10206 @kindex set check type
10207 @kindex show check type
10209 @item set check type auto
10210 Set type checking on or off based on the current working language.
10211 @xref{Supported Languages, ,Supported Languages}, for the default settings for
10214 @item set check type on
10215 @itemx set check type off
10216 Set type checking on or off, overriding the default setting for the
10217 current working language. Issue a warning if the setting does not
10218 match the language default. If any type mismatches occur in
10219 evaluating an expression while type checking is on, @value{GDBN} prints a
10220 message and aborts evaluation of the expression.
10222 @item set check type warn
10223 Cause the type checker to issue warnings, but to always attempt to
10224 evaluate the expression. Evaluating the expression may still
10225 be impossible for other reasons. For example, @value{GDBN} cannot add
10226 numbers and structures.
10229 Show the current setting of the type checker, and whether or not @value{GDBN}
10230 is setting it automatically.
10233 @cindex range checking
10234 @cindex checks, range
10235 @node Range Checking
10236 @subsection An Overview of Range Checking
10238 In some languages (such as Modula-2), it is an error to exceed the
10239 bounds of a type; this is enforced with run-time checks. Such range
10240 checking is meant to ensure program correctness by making sure
10241 computations do not overflow, or indices on an array element access do
10242 not exceed the bounds of the array.
10244 For expressions you use in @value{GDBN} commands, you can tell
10245 @value{GDBN} to treat range errors in one of three ways: ignore them,
10246 always treat them as errors and abandon the expression, or issue
10247 warnings but evaluate the expression anyway.
10249 A range error can result from numerical overflow, from exceeding an
10250 array index bound, or when you type a constant that is not a member
10251 of any type. Some languages, however, do not treat overflows as an
10252 error. In many implementations of C, mathematical overflow causes the
10253 result to ``wrap around'' to lower values---for example, if @var{m} is
10254 the largest integer value, and @var{s} is the smallest, then
10257 @var{m} + 1 @result{} @var{s}
10260 This, too, is specific to individual languages, and in some cases
10261 specific to individual compilers or machines. @xref{Supported Languages, ,
10262 Supported Languages}, for further details on specific languages.
10264 @value{GDBN} provides some additional commands for controlling the range checker:
10266 @kindex set check range
10267 @kindex show check range
10269 @item set check range auto
10270 Set range checking on or off based on the current working language.
10271 @xref{Supported Languages, ,Supported Languages}, for the default settings for
10274 @item set check range on
10275 @itemx set check range off
10276 Set range checking on or off, overriding the default setting for the
10277 current working language. A warning is issued if the setting does not
10278 match the language default. If a range error occurs and range checking is on,
10279 then a message is printed and evaluation of the expression is aborted.
10281 @item set check range warn
10282 Output messages when the @value{GDBN} range checker detects a range error,
10283 but attempt to evaluate the expression anyway. Evaluating the
10284 expression may still be impossible for other reasons, such as accessing
10285 memory that the process does not own (a typical example from many Unix
10289 Show the current setting of the range checker, and whether or not it is
10290 being set automatically by @value{GDBN}.
10293 @node Supported Languages
10294 @section Supported Languages
10296 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
10297 assembly, Modula-2, and Ada.
10298 @c This is false ...
10299 Some @value{GDBN} features may be used in expressions regardless of the
10300 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
10301 and the @samp{@{type@}addr} construct (@pxref{Expressions,
10302 ,Expressions}) can be used with the constructs of any supported
10305 The following sections detail to what degree each source language is
10306 supported by @value{GDBN}. These sections are not meant to be language
10307 tutorials or references, but serve only as a reference guide to what the
10308 @value{GDBN} expression parser accepts, and what input and output
10309 formats should look like for different languages. There are many good
10310 books written on each of these languages; please look to these for a
10311 language reference or tutorial.
10314 * C:: C and C@t{++}
10315 * Objective-C:: Objective-C
10316 * Fortran:: Fortran
10318 * Modula-2:: Modula-2
10323 @subsection C and C@t{++}
10325 @cindex C and C@t{++}
10326 @cindex expressions in C or C@t{++}
10328 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
10329 to both languages. Whenever this is the case, we discuss those languages
10333 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
10334 @cindex @sc{gnu} C@t{++}
10335 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
10336 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
10337 effectively, you must compile your C@t{++} programs with a supported
10338 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
10339 compiler (@code{aCC}).
10341 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
10342 format; if it doesn't work on your system, try the stabs+ debugging
10343 format. You can select those formats explicitly with the @code{g++}
10344 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
10345 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
10346 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
10349 * C Operators:: C and C@t{++} operators
10350 * C Constants:: C and C@t{++} constants
10351 * C Plus Plus Expressions:: C@t{++} expressions
10352 * C Defaults:: Default settings for C and C@t{++}
10353 * C Checks:: C and C@t{++} type and range checks
10354 * Debugging C:: @value{GDBN} and C
10355 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
10356 * Decimal Floating Point:: Numbers in Decimal Floating Point format
10360 @subsubsection C and C@t{++} Operators
10362 @cindex C and C@t{++} operators
10364 Operators must be defined on values of specific types. For instance,
10365 @code{+} is defined on numbers, but not on structures. Operators are
10366 often defined on groups of types.
10368 For the purposes of C and C@t{++}, the following definitions hold:
10373 @emph{Integral types} include @code{int} with any of its storage-class
10374 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
10377 @emph{Floating-point types} include @code{float}, @code{double}, and
10378 @code{long double} (if supported by the target platform).
10381 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
10384 @emph{Scalar types} include all of the above.
10389 The following operators are supported. They are listed here
10390 in order of increasing precedence:
10394 The comma or sequencing operator. Expressions in a comma-separated list
10395 are evaluated from left to right, with the result of the entire
10396 expression being the last expression evaluated.
10399 Assignment. The value of an assignment expression is the value
10400 assigned. Defined on scalar types.
10403 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
10404 and translated to @w{@code{@var{a} = @var{a op b}}}.
10405 @w{@code{@var{op}=}} and @code{=} have the same precedence.
10406 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
10407 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
10410 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
10411 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
10415 Logical @sc{or}. Defined on integral types.
10418 Logical @sc{and}. Defined on integral types.
10421 Bitwise @sc{or}. Defined on integral types.
10424 Bitwise exclusive-@sc{or}. Defined on integral types.
10427 Bitwise @sc{and}. Defined on integral types.
10430 Equality and inequality. Defined on scalar types. The value of these
10431 expressions is 0 for false and non-zero for true.
10433 @item <@r{, }>@r{, }<=@r{, }>=
10434 Less than, greater than, less than or equal, greater than or equal.
10435 Defined on scalar types. The value of these expressions is 0 for false
10436 and non-zero for true.
10439 left shift, and right shift. Defined on integral types.
10442 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
10445 Addition and subtraction. Defined on integral types, floating-point types and
10448 @item *@r{, }/@r{, }%
10449 Multiplication, division, and modulus. Multiplication and division are
10450 defined on integral and floating-point types. Modulus is defined on
10454 Increment and decrement. When appearing before a variable, the
10455 operation is performed before the variable is used in an expression;
10456 when appearing after it, the variable's value is used before the
10457 operation takes place.
10460 Pointer dereferencing. Defined on pointer types. Same precedence as
10464 Address operator. Defined on variables. Same precedence as @code{++}.
10466 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
10467 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
10468 to examine the address
10469 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
10473 Negative. Defined on integral and floating-point types. Same
10474 precedence as @code{++}.
10477 Logical negation. Defined on integral types. Same precedence as
10481 Bitwise complement operator. Defined on integral types. Same precedence as
10486 Structure member, and pointer-to-structure member. For convenience,
10487 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
10488 pointer based on the stored type information.
10489 Defined on @code{struct} and @code{union} data.
10492 Dereferences of pointers to members.
10495 Array indexing. @code{@var{a}[@var{i}]} is defined as
10496 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
10499 Function parameter list. Same precedence as @code{->}.
10502 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
10503 and @code{class} types.
10506 Doubled colons also represent the @value{GDBN} scope operator
10507 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
10511 If an operator is redefined in the user code, @value{GDBN} usually
10512 attempts to invoke the redefined version instead of using the operator's
10513 predefined meaning.
10516 @subsubsection C and C@t{++} Constants
10518 @cindex C and C@t{++} constants
10520 @value{GDBN} allows you to express the constants of C and C@t{++} in the
10525 Integer constants are a sequence of digits. Octal constants are
10526 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
10527 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
10528 @samp{l}, specifying that the constant should be treated as a
10532 Floating point constants are a sequence of digits, followed by a decimal
10533 point, followed by a sequence of digits, and optionally followed by an
10534 exponent. An exponent is of the form:
10535 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
10536 sequence of digits. The @samp{+} is optional for positive exponents.
10537 A floating-point constant may also end with a letter @samp{f} or
10538 @samp{F}, specifying that the constant should be treated as being of
10539 the @code{float} (as opposed to the default @code{double}) type; or with
10540 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
10544 Enumerated constants consist of enumerated identifiers, or their
10545 integral equivalents.
10548 Character constants are a single character surrounded by single quotes
10549 (@code{'}), or a number---the ordinal value of the corresponding character
10550 (usually its @sc{ascii} value). Within quotes, the single character may
10551 be represented by a letter or by @dfn{escape sequences}, which are of
10552 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
10553 of the character's ordinal value; or of the form @samp{\@var{x}}, where
10554 @samp{@var{x}} is a predefined special character---for example,
10555 @samp{\n} for newline.
10558 String constants are a sequence of character constants surrounded by
10559 double quotes (@code{"}). Any valid character constant (as described
10560 above) may appear. Double quotes within the string must be preceded by
10561 a backslash, so for instance @samp{"a\"b'c"} is a string of five
10565 Pointer constants are an integral value. You can also write pointers
10566 to constants using the C operator @samp{&}.
10569 Array constants are comma-separated lists surrounded by braces @samp{@{}
10570 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
10571 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
10572 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
10575 @node C Plus Plus Expressions
10576 @subsubsection C@t{++} Expressions
10578 @cindex expressions in C@t{++}
10579 @value{GDBN} expression handling can interpret most C@t{++} expressions.
10581 @cindex debugging C@t{++} programs
10582 @cindex C@t{++} compilers
10583 @cindex debug formats and C@t{++}
10584 @cindex @value{NGCC} and C@t{++}
10586 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
10587 proper compiler and the proper debug format. Currently, @value{GDBN}
10588 works best when debugging C@t{++} code that is compiled with
10589 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
10590 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
10591 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
10592 stabs+ as their default debug format, so you usually don't need to
10593 specify a debug format explicitly. Other compilers and/or debug formats
10594 are likely to work badly or not at all when using @value{GDBN} to debug
10600 @cindex member functions
10602 Member function calls are allowed; you can use expressions like
10605 count = aml->GetOriginal(x, y)
10608 @vindex this@r{, inside C@t{++} member functions}
10609 @cindex namespace in C@t{++}
10611 While a member function is active (in the selected stack frame), your
10612 expressions have the same namespace available as the member function;
10613 that is, @value{GDBN} allows implicit references to the class instance
10614 pointer @code{this} following the same rules as C@t{++}.
10616 @cindex call overloaded functions
10617 @cindex overloaded functions, calling
10618 @cindex type conversions in C@t{++}
10620 You can call overloaded functions; @value{GDBN} resolves the function
10621 call to the right definition, with some restrictions. @value{GDBN} does not
10622 perform overload resolution involving user-defined type conversions,
10623 calls to constructors, or instantiations of templates that do not exist
10624 in the program. It also cannot handle ellipsis argument lists or
10627 It does perform integral conversions and promotions, floating-point
10628 promotions, arithmetic conversions, pointer conversions, conversions of
10629 class objects to base classes, and standard conversions such as those of
10630 functions or arrays to pointers; it requires an exact match on the
10631 number of function arguments.
10633 Overload resolution is always performed, unless you have specified
10634 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
10635 ,@value{GDBN} Features for C@t{++}}.
10637 You must specify @code{set overload-resolution off} in order to use an
10638 explicit function signature to call an overloaded function, as in
10640 p 'foo(char,int)'('x', 13)
10643 The @value{GDBN} command-completion facility can simplify this;
10644 see @ref{Completion, ,Command Completion}.
10646 @cindex reference declarations
10648 @value{GDBN} understands variables declared as C@t{++} references; you can use
10649 them in expressions just as you do in C@t{++} source---they are automatically
10652 In the parameter list shown when @value{GDBN} displays a frame, the values of
10653 reference variables are not displayed (unlike other variables); this
10654 avoids clutter, since references are often used for large structures.
10655 The @emph{address} of a reference variable is always shown, unless
10656 you have specified @samp{set print address off}.
10659 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
10660 expressions can use it just as expressions in your program do. Since
10661 one scope may be defined in another, you can use @code{::} repeatedly if
10662 necessary, for example in an expression like
10663 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
10664 resolving name scope by reference to source files, in both C and C@t{++}
10665 debugging (@pxref{Variables, ,Program Variables}).
10668 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
10669 calling virtual functions correctly, printing out virtual bases of
10670 objects, calling functions in a base subobject, casting objects, and
10671 invoking user-defined operators.
10674 @subsubsection C and C@t{++} Defaults
10676 @cindex C and C@t{++} defaults
10678 If you allow @value{GDBN} to set type and range checking automatically, they
10679 both default to @code{off} whenever the working language changes to
10680 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
10681 selects the working language.
10683 If you allow @value{GDBN} to set the language automatically, it
10684 recognizes source files whose names end with @file{.c}, @file{.C}, or
10685 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
10686 these files, it sets the working language to C or C@t{++}.
10687 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
10688 for further details.
10690 @c Type checking is (a) primarily motivated by Modula-2, and (b)
10691 @c unimplemented. If (b) changes, it might make sense to let this node
10692 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
10695 @subsubsection C and C@t{++} Type and Range Checks
10697 @cindex C and C@t{++} checks
10699 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
10700 is not used. However, if you turn type checking on, @value{GDBN}
10701 considers two variables type equivalent if:
10705 The two variables are structured and have the same structure, union, or
10709 The two variables have the same type name, or types that have been
10710 declared equivalent through @code{typedef}.
10713 @c leaving this out because neither J Gilmore nor R Pesch understand it.
10716 The two @code{struct}, @code{union}, or @code{enum} variables are
10717 declared in the same declaration. (Note: this may not be true for all C
10722 Range checking, if turned on, is done on mathematical operations. Array
10723 indices are not checked, since they are often used to index a pointer
10724 that is not itself an array.
10727 @subsubsection @value{GDBN} and C
10729 The @code{set print union} and @code{show print union} commands apply to
10730 the @code{union} type. When set to @samp{on}, any @code{union} that is
10731 inside a @code{struct} or @code{class} is also printed. Otherwise, it
10732 appears as @samp{@{...@}}.
10734 The @code{@@} operator aids in the debugging of dynamic arrays, formed
10735 with pointers and a memory allocation function. @xref{Expressions,
10738 @node Debugging C Plus Plus
10739 @subsubsection @value{GDBN} Features for C@t{++}
10741 @cindex commands for C@t{++}
10743 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
10744 designed specifically for use with C@t{++}. Here is a summary:
10747 @cindex break in overloaded functions
10748 @item @r{breakpoint menus}
10749 When you want a breakpoint in a function whose name is overloaded,
10750 @value{GDBN} has the capability to display a menu of possible breakpoint
10751 locations to help you specify which function definition you want.
10752 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
10754 @cindex overloading in C@t{++}
10755 @item rbreak @var{regex}
10756 Setting breakpoints using regular expressions is helpful for setting
10757 breakpoints on overloaded functions that are not members of any special
10759 @xref{Set Breaks, ,Setting Breakpoints}.
10761 @cindex C@t{++} exception handling
10764 Debug C@t{++} exception handling using these commands. @xref{Set
10765 Catchpoints, , Setting Catchpoints}.
10767 @cindex inheritance
10768 @item ptype @var{typename}
10769 Print inheritance relationships as well as other information for type
10771 @xref{Symbols, ,Examining the Symbol Table}.
10773 @cindex C@t{++} symbol display
10774 @item set print demangle
10775 @itemx show print demangle
10776 @itemx set print asm-demangle
10777 @itemx show print asm-demangle
10778 Control whether C@t{++} symbols display in their source form, both when
10779 displaying code as C@t{++} source and when displaying disassemblies.
10780 @xref{Print Settings, ,Print Settings}.
10782 @item set print object
10783 @itemx show print object
10784 Choose whether to print derived (actual) or declared types of objects.
10785 @xref{Print Settings, ,Print Settings}.
10787 @item set print vtbl
10788 @itemx show print vtbl
10789 Control the format for printing virtual function tables.
10790 @xref{Print Settings, ,Print Settings}.
10791 (The @code{vtbl} commands do not work on programs compiled with the HP
10792 ANSI C@t{++} compiler (@code{aCC}).)
10794 @kindex set overload-resolution
10795 @cindex overloaded functions, overload resolution
10796 @item set overload-resolution on
10797 Enable overload resolution for C@t{++} expression evaluation. The default
10798 is on. For overloaded functions, @value{GDBN} evaluates the arguments
10799 and searches for a function whose signature matches the argument types,
10800 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
10801 Expressions, ,C@t{++} Expressions}, for details).
10802 If it cannot find a match, it emits a message.
10804 @item set overload-resolution off
10805 Disable overload resolution for C@t{++} expression evaluation. For
10806 overloaded functions that are not class member functions, @value{GDBN}
10807 chooses the first function of the specified name that it finds in the
10808 symbol table, whether or not its arguments are of the correct type. For
10809 overloaded functions that are class member functions, @value{GDBN}
10810 searches for a function whose signature @emph{exactly} matches the
10813 @kindex show overload-resolution
10814 @item show overload-resolution
10815 Show the current setting of overload resolution.
10817 @item @r{Overloaded symbol names}
10818 You can specify a particular definition of an overloaded symbol, using
10819 the same notation that is used to declare such symbols in C@t{++}: type
10820 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
10821 also use the @value{GDBN} command-line word completion facilities to list the
10822 available choices, or to finish the type list for you.
10823 @xref{Completion,, Command Completion}, for details on how to do this.
10826 @node Decimal Floating Point
10827 @subsubsection Decimal Floating Point format
10828 @cindex decimal floating point format
10830 @value{GDBN} can examine, set and perform computations with numbers in
10831 decimal floating point format, which in the C language correspond to the
10832 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
10833 specified by the extension to support decimal floating-point arithmetic.
10835 There are two encodings in use, depending on the architecture: BID (Binary
10836 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
10837 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
10840 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
10841 to manipulate decimal floating point numbers, it is not possible to convert
10842 (using a cast, for example) integers wider than 32-bit to decimal float.
10844 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
10845 point computations, error checking in decimal float operations ignores
10846 underflow, overflow and divide by zero exceptions.
10848 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
10849 to inspect @code{_Decimal128} values stored in floating point registers. See
10850 @ref{PowerPC,,PowerPC} for more details.
10853 @subsection Objective-C
10855 @cindex Objective-C
10856 This section provides information about some commands and command
10857 options that are useful for debugging Objective-C code. See also
10858 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
10859 few more commands specific to Objective-C support.
10862 * Method Names in Commands::
10863 * The Print Command with Objective-C::
10866 @node Method Names in Commands
10867 @subsubsection Method Names in Commands
10869 The following commands have been extended to accept Objective-C method
10870 names as line specifications:
10872 @kindex clear@r{, and Objective-C}
10873 @kindex break@r{, and Objective-C}
10874 @kindex info line@r{, and Objective-C}
10875 @kindex jump@r{, and Objective-C}
10876 @kindex list@r{, and Objective-C}
10880 @item @code{info line}
10885 A fully qualified Objective-C method name is specified as
10888 -[@var{Class} @var{methodName}]
10891 where the minus sign is used to indicate an instance method and a
10892 plus sign (not shown) is used to indicate a class method. The class
10893 name @var{Class} and method name @var{methodName} are enclosed in
10894 brackets, similar to the way messages are specified in Objective-C
10895 source code. For example, to set a breakpoint at the @code{create}
10896 instance method of class @code{Fruit} in the program currently being
10900 break -[Fruit create]
10903 To list ten program lines around the @code{initialize} class method,
10907 list +[NSText initialize]
10910 In the current version of @value{GDBN}, the plus or minus sign is
10911 required. In future versions of @value{GDBN}, the plus or minus
10912 sign will be optional, but you can use it to narrow the search. It
10913 is also possible to specify just a method name:
10919 You must specify the complete method name, including any colons. If
10920 your program's source files contain more than one @code{create} method,
10921 you'll be presented with a numbered list of classes that implement that
10922 method. Indicate your choice by number, or type @samp{0} to exit if
10925 As another example, to clear a breakpoint established at the
10926 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
10929 clear -[NSWindow makeKeyAndOrderFront:]
10932 @node The Print Command with Objective-C
10933 @subsubsection The Print Command With Objective-C
10934 @cindex Objective-C, print objects
10935 @kindex print-object
10936 @kindex po @r{(@code{print-object})}
10938 The print command has also been extended to accept methods. For example:
10941 print -[@var{object} hash]
10944 @cindex print an Objective-C object description
10945 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
10947 will tell @value{GDBN} to send the @code{hash} message to @var{object}
10948 and print the result. Also, an additional command has been added,
10949 @code{print-object} or @code{po} for short, which is meant to print
10950 the description of an object. However, this command may only work
10951 with certain Objective-C libraries that have a particular hook
10952 function, @code{_NSPrintForDebugger}, defined.
10955 @subsection Fortran
10956 @cindex Fortran-specific support in @value{GDBN}
10958 @value{GDBN} can be used to debug programs written in Fortran, but it
10959 currently supports only the features of Fortran 77 language.
10961 @cindex trailing underscore, in Fortran symbols
10962 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
10963 among them) append an underscore to the names of variables and
10964 functions. When you debug programs compiled by those compilers, you
10965 will need to refer to variables and functions with a trailing
10969 * Fortran Operators:: Fortran operators and expressions
10970 * Fortran Defaults:: Default settings for Fortran
10971 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
10974 @node Fortran Operators
10975 @subsubsection Fortran Operators and Expressions
10977 @cindex Fortran operators and expressions
10979 Operators must be defined on values of specific types. For instance,
10980 @code{+} is defined on numbers, but not on characters or other non-
10981 arithmetic types. Operators are often defined on groups of types.
10985 The exponentiation operator. It raises the first operand to the power
10989 The range operator. Normally used in the form of array(low:high) to
10990 represent a section of array.
10993 The access component operator. Normally used to access elements in derived
10994 types. Also suitable for unions. As unions aren't part of regular Fortran,
10995 this can only happen when accessing a register that uses a gdbarch-defined
10999 @node Fortran Defaults
11000 @subsubsection Fortran Defaults
11002 @cindex Fortran Defaults
11004 Fortran symbols are usually case-insensitive, so @value{GDBN} by
11005 default uses case-insensitive matches for Fortran symbols. You can
11006 change that with the @samp{set case-insensitive} command, see
11007 @ref{Symbols}, for the details.
11009 @node Special Fortran Commands
11010 @subsubsection Special Fortran Commands
11012 @cindex Special Fortran commands
11014 @value{GDBN} has some commands to support Fortran-specific features,
11015 such as displaying common blocks.
11018 @cindex @code{COMMON} blocks, Fortran
11019 @kindex info common
11020 @item info common @r{[}@var{common-name}@r{]}
11021 This command prints the values contained in the Fortran @code{COMMON}
11022 block whose name is @var{common-name}. With no argument, the names of
11023 all @code{COMMON} blocks visible at the current program location are
11030 @cindex Pascal support in @value{GDBN}, limitations
11031 Debugging Pascal programs which use sets, subranges, file variables, or
11032 nested functions does not currently work. @value{GDBN} does not support
11033 entering expressions, printing values, or similar features using Pascal
11036 The Pascal-specific command @code{set print pascal_static-members}
11037 controls whether static members of Pascal objects are displayed.
11038 @xref{Print Settings, pascal_static-members}.
11041 @subsection Modula-2
11043 @cindex Modula-2, @value{GDBN} support
11045 The extensions made to @value{GDBN} to support Modula-2 only support
11046 output from the @sc{gnu} Modula-2 compiler (which is currently being
11047 developed). Other Modula-2 compilers are not currently supported, and
11048 attempting to debug executables produced by them is most likely
11049 to give an error as @value{GDBN} reads in the executable's symbol
11052 @cindex expressions in Modula-2
11054 * M2 Operators:: Built-in operators
11055 * Built-In Func/Proc:: Built-in functions and procedures
11056 * M2 Constants:: Modula-2 constants
11057 * M2 Types:: Modula-2 types
11058 * M2 Defaults:: Default settings for Modula-2
11059 * Deviations:: Deviations from standard Modula-2
11060 * M2 Checks:: Modula-2 type and range checks
11061 * M2 Scope:: The scope operators @code{::} and @code{.}
11062 * GDB/M2:: @value{GDBN} and Modula-2
11066 @subsubsection Operators
11067 @cindex Modula-2 operators
11069 Operators must be defined on values of specific types. For instance,
11070 @code{+} is defined on numbers, but not on structures. Operators are
11071 often defined on groups of types. For the purposes of Modula-2, the
11072 following definitions hold:
11077 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
11081 @emph{Character types} consist of @code{CHAR} and its subranges.
11084 @emph{Floating-point types} consist of @code{REAL}.
11087 @emph{Pointer types} consist of anything declared as @code{POINTER TO
11091 @emph{Scalar types} consist of all of the above.
11094 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
11097 @emph{Boolean types} consist of @code{BOOLEAN}.
11101 The following operators are supported, and appear in order of
11102 increasing precedence:
11106 Function argument or array index separator.
11109 Assignment. The value of @var{var} @code{:=} @var{value} is
11113 Less than, greater than on integral, floating-point, or enumerated
11117 Less than or equal to, greater than or equal to
11118 on integral, floating-point and enumerated types, or set inclusion on
11119 set types. Same precedence as @code{<}.
11121 @item =@r{, }<>@r{, }#
11122 Equality and two ways of expressing inequality, valid on scalar types.
11123 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
11124 available for inequality, since @code{#} conflicts with the script
11128 Set membership. Defined on set types and the types of their members.
11129 Same precedence as @code{<}.
11132 Boolean disjunction. Defined on boolean types.
11135 Boolean conjunction. Defined on boolean types.
11138 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
11141 Addition and subtraction on integral and floating-point types, or union
11142 and difference on set types.
11145 Multiplication on integral and floating-point types, or set intersection
11149 Division on floating-point types, or symmetric set difference on set
11150 types. Same precedence as @code{*}.
11153 Integer division and remainder. Defined on integral types. Same
11154 precedence as @code{*}.
11157 Negative. Defined on @code{INTEGER} and @code{REAL} data.
11160 Pointer dereferencing. Defined on pointer types.
11163 Boolean negation. Defined on boolean types. Same precedence as
11167 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
11168 precedence as @code{^}.
11171 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
11174 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
11178 @value{GDBN} and Modula-2 scope operators.
11182 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
11183 treats the use of the operator @code{IN}, or the use of operators
11184 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
11185 @code{<=}, and @code{>=} on sets as an error.
11189 @node Built-In Func/Proc
11190 @subsubsection Built-in Functions and Procedures
11191 @cindex Modula-2 built-ins
11193 Modula-2 also makes available several built-in procedures and functions.
11194 In describing these, the following metavariables are used:
11199 represents an @code{ARRAY} variable.
11202 represents a @code{CHAR} constant or variable.
11205 represents a variable or constant of integral type.
11208 represents an identifier that belongs to a set. Generally used in the
11209 same function with the metavariable @var{s}. The type of @var{s} should
11210 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
11213 represents a variable or constant of integral or floating-point type.
11216 represents a variable or constant of floating-point type.
11222 represents a variable.
11225 represents a variable or constant of one of many types. See the
11226 explanation of the function for details.
11229 All Modula-2 built-in procedures also return a result, described below.
11233 Returns the absolute value of @var{n}.
11236 If @var{c} is a lower case letter, it returns its upper case
11237 equivalent, otherwise it returns its argument.
11240 Returns the character whose ordinal value is @var{i}.
11243 Decrements the value in the variable @var{v} by one. Returns the new value.
11245 @item DEC(@var{v},@var{i})
11246 Decrements the value in the variable @var{v} by @var{i}. Returns the
11249 @item EXCL(@var{m},@var{s})
11250 Removes the element @var{m} from the set @var{s}. Returns the new
11253 @item FLOAT(@var{i})
11254 Returns the floating point equivalent of the integer @var{i}.
11256 @item HIGH(@var{a})
11257 Returns the index of the last member of @var{a}.
11260 Increments the value in the variable @var{v} by one. Returns the new value.
11262 @item INC(@var{v},@var{i})
11263 Increments the value in the variable @var{v} by @var{i}. Returns the
11266 @item INCL(@var{m},@var{s})
11267 Adds the element @var{m} to the set @var{s} if it is not already
11268 there. Returns the new set.
11271 Returns the maximum value of the type @var{t}.
11274 Returns the minimum value of the type @var{t}.
11277 Returns boolean TRUE if @var{i} is an odd number.
11280 Returns the ordinal value of its argument. For example, the ordinal
11281 value of a character is its @sc{ascii} value (on machines supporting the
11282 @sc{ascii} character set). @var{x} must be of an ordered type, which include
11283 integral, character and enumerated types.
11285 @item SIZE(@var{x})
11286 Returns the size of its argument. @var{x} can be a variable or a type.
11288 @item TRUNC(@var{r})
11289 Returns the integral part of @var{r}.
11291 @item TSIZE(@var{x})
11292 Returns the size of its argument. @var{x} can be a variable or a type.
11294 @item VAL(@var{t},@var{i})
11295 Returns the member of the type @var{t} whose ordinal value is @var{i}.
11299 @emph{Warning:} Sets and their operations are not yet supported, so
11300 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
11304 @cindex Modula-2 constants
11306 @subsubsection Constants
11308 @value{GDBN} allows you to express the constants of Modula-2 in the following
11314 Integer constants are simply a sequence of digits. When used in an
11315 expression, a constant is interpreted to be type-compatible with the
11316 rest of the expression. Hexadecimal integers are specified by a
11317 trailing @samp{H}, and octal integers by a trailing @samp{B}.
11320 Floating point constants appear as a sequence of digits, followed by a
11321 decimal point and another sequence of digits. An optional exponent can
11322 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
11323 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
11324 digits of the floating point constant must be valid decimal (base 10)
11328 Character constants consist of a single character enclosed by a pair of
11329 like quotes, either single (@code{'}) or double (@code{"}). They may
11330 also be expressed by their ordinal value (their @sc{ascii} value, usually)
11331 followed by a @samp{C}.
11334 String constants consist of a sequence of characters enclosed by a
11335 pair of like quotes, either single (@code{'}) or double (@code{"}).
11336 Escape sequences in the style of C are also allowed. @xref{C
11337 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
11341 Enumerated constants consist of an enumerated identifier.
11344 Boolean constants consist of the identifiers @code{TRUE} and
11348 Pointer constants consist of integral values only.
11351 Set constants are not yet supported.
11355 @subsubsection Modula-2 Types
11356 @cindex Modula-2 types
11358 Currently @value{GDBN} can print the following data types in Modula-2
11359 syntax: array types, record types, set types, pointer types, procedure
11360 types, enumerated types, subrange types and base types. You can also
11361 print the contents of variables declared using these type.
11362 This section gives a number of simple source code examples together with
11363 sample @value{GDBN} sessions.
11365 The first example contains the following section of code:
11374 and you can request @value{GDBN} to interrogate the type and value of
11375 @code{r} and @code{s}.
11378 (@value{GDBP}) print s
11380 (@value{GDBP}) ptype s
11382 (@value{GDBP}) print r
11384 (@value{GDBP}) ptype r
11389 Likewise if your source code declares @code{s} as:
11393 s: SET ['A'..'Z'] ;
11397 then you may query the type of @code{s} by:
11400 (@value{GDBP}) ptype s
11401 type = SET ['A'..'Z']
11405 Note that at present you cannot interactively manipulate set
11406 expressions using the debugger.
11408 The following example shows how you might declare an array in Modula-2
11409 and how you can interact with @value{GDBN} to print its type and contents:
11413 s: ARRAY [-10..10] OF CHAR ;
11417 (@value{GDBP}) ptype s
11418 ARRAY [-10..10] OF CHAR
11421 Note that the array handling is not yet complete and although the type
11422 is printed correctly, expression handling still assumes that all
11423 arrays have a lower bound of zero and not @code{-10} as in the example
11426 Here are some more type related Modula-2 examples:
11430 colour = (blue, red, yellow, green) ;
11431 t = [blue..yellow] ;
11439 The @value{GDBN} interaction shows how you can query the data type
11440 and value of a variable.
11443 (@value{GDBP}) print s
11445 (@value{GDBP}) ptype t
11446 type = [blue..yellow]
11450 In this example a Modula-2 array is declared and its contents
11451 displayed. Observe that the contents are written in the same way as
11452 their @code{C} counterparts.
11456 s: ARRAY [1..5] OF CARDINAL ;
11462 (@value{GDBP}) print s
11463 $1 = @{1, 0, 0, 0, 0@}
11464 (@value{GDBP}) ptype s
11465 type = ARRAY [1..5] OF CARDINAL
11468 The Modula-2 language interface to @value{GDBN} also understands
11469 pointer types as shown in this example:
11473 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
11480 and you can request that @value{GDBN} describes the type of @code{s}.
11483 (@value{GDBP}) ptype s
11484 type = POINTER TO ARRAY [1..5] OF CARDINAL
11487 @value{GDBN} handles compound types as we can see in this example.
11488 Here we combine array types, record types, pointer types and subrange
11499 myarray = ARRAY myrange OF CARDINAL ;
11500 myrange = [-2..2] ;
11502 s: POINTER TO ARRAY myrange OF foo ;
11506 and you can ask @value{GDBN} to describe the type of @code{s} as shown
11510 (@value{GDBP}) ptype s
11511 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
11514 f3 : ARRAY [-2..2] OF CARDINAL;
11519 @subsubsection Modula-2 Defaults
11520 @cindex Modula-2 defaults
11522 If type and range checking are set automatically by @value{GDBN}, they
11523 both default to @code{on} whenever the working language changes to
11524 Modula-2. This happens regardless of whether you or @value{GDBN}
11525 selected the working language.
11527 If you allow @value{GDBN} to set the language automatically, then entering
11528 code compiled from a file whose name ends with @file{.mod} sets the
11529 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
11530 Infer the Source Language}, for further details.
11533 @subsubsection Deviations from Standard Modula-2
11534 @cindex Modula-2, deviations from
11536 A few changes have been made to make Modula-2 programs easier to debug.
11537 This is done primarily via loosening its type strictness:
11541 Unlike in standard Modula-2, pointer constants can be formed by
11542 integers. This allows you to modify pointer variables during
11543 debugging. (In standard Modula-2, the actual address contained in a
11544 pointer variable is hidden from you; it can only be modified
11545 through direct assignment to another pointer variable or expression that
11546 returned a pointer.)
11549 C escape sequences can be used in strings and characters to represent
11550 non-printable characters. @value{GDBN} prints out strings with these
11551 escape sequences embedded. Single non-printable characters are
11552 printed using the @samp{CHR(@var{nnn})} format.
11555 The assignment operator (@code{:=}) returns the value of its right-hand
11559 All built-in procedures both modify @emph{and} return their argument.
11563 @subsubsection Modula-2 Type and Range Checks
11564 @cindex Modula-2 checks
11567 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
11570 @c FIXME remove warning when type/range checks added
11572 @value{GDBN} considers two Modula-2 variables type equivalent if:
11576 They are of types that have been declared equivalent via a @code{TYPE
11577 @var{t1} = @var{t2}} statement
11580 They have been declared on the same line. (Note: This is true of the
11581 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
11584 As long as type checking is enabled, any attempt to combine variables
11585 whose types are not equivalent is an error.
11587 Range checking is done on all mathematical operations, assignment, array
11588 index bounds, and all built-in functions and procedures.
11591 @subsubsection The Scope Operators @code{::} and @code{.}
11593 @cindex @code{.}, Modula-2 scope operator
11594 @cindex colon, doubled as scope operator
11596 @vindex colon-colon@r{, in Modula-2}
11597 @c Info cannot handle :: but TeX can.
11600 @vindex ::@r{, in Modula-2}
11603 There are a few subtle differences between the Modula-2 scope operator
11604 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
11609 @var{module} . @var{id}
11610 @var{scope} :: @var{id}
11614 where @var{scope} is the name of a module or a procedure,
11615 @var{module} the name of a module, and @var{id} is any declared
11616 identifier within your program, except another module.
11618 Using the @code{::} operator makes @value{GDBN} search the scope
11619 specified by @var{scope} for the identifier @var{id}. If it is not
11620 found in the specified scope, then @value{GDBN} searches all scopes
11621 enclosing the one specified by @var{scope}.
11623 Using the @code{.} operator makes @value{GDBN} search the current scope for
11624 the identifier specified by @var{id} that was imported from the
11625 definition module specified by @var{module}. With this operator, it is
11626 an error if the identifier @var{id} was not imported from definition
11627 module @var{module}, or if @var{id} is not an identifier in
11631 @subsubsection @value{GDBN} and Modula-2
11633 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
11634 Five subcommands of @code{set print} and @code{show print} apply
11635 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
11636 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
11637 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
11638 analogue in Modula-2.
11640 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
11641 with any language, is not useful with Modula-2. Its
11642 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
11643 created in Modula-2 as they can in C or C@t{++}. However, because an
11644 address can be specified by an integral constant, the construct
11645 @samp{@{@var{type}@}@var{adrexp}} is still useful.
11647 @cindex @code{#} in Modula-2
11648 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
11649 interpreted as the beginning of a comment. Use @code{<>} instead.
11655 The extensions made to @value{GDBN} for Ada only support
11656 output from the @sc{gnu} Ada (GNAT) compiler.
11657 Other Ada compilers are not currently supported, and
11658 attempting to debug executables produced by them is most likely
11662 @cindex expressions in Ada
11664 * Ada Mode Intro:: General remarks on the Ada syntax
11665 and semantics supported by Ada mode
11667 * Omissions from Ada:: Restrictions on the Ada expression syntax.
11668 * Additions to Ada:: Extensions of the Ada expression syntax.
11669 * Stopping Before Main Program:: Debugging the program during elaboration.
11670 * Ada Tasks:: Listing and setting breakpoints in tasks.
11671 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
11672 * Ada Glitches:: Known peculiarities of Ada mode.
11675 @node Ada Mode Intro
11676 @subsubsection Introduction
11677 @cindex Ada mode, general
11679 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
11680 syntax, with some extensions.
11681 The philosophy behind the design of this subset is
11685 That @value{GDBN} should provide basic literals and access to operations for
11686 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
11687 leaving more sophisticated computations to subprograms written into the
11688 program (which therefore may be called from @value{GDBN}).
11691 That type safety and strict adherence to Ada language restrictions
11692 are not particularly important to the @value{GDBN} user.
11695 That brevity is important to the @value{GDBN} user.
11698 Thus, for brevity, the debugger acts as if all names declared in
11699 user-written packages are directly visible, even if they are not visible
11700 according to Ada rules, thus making it unnecessary to fully qualify most
11701 names with their packages, regardless of context. Where this causes
11702 ambiguity, @value{GDBN} asks the user's intent.
11704 The debugger will start in Ada mode if it detects an Ada main program.
11705 As for other languages, it will enter Ada mode when stopped in a program that
11706 was translated from an Ada source file.
11708 While in Ada mode, you may use `@t{--}' for comments. This is useful
11709 mostly for documenting command files. The standard @value{GDBN} comment
11710 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
11711 middle (to allow based literals).
11713 The debugger supports limited overloading. Given a subprogram call in which
11714 the function symbol has multiple definitions, it will use the number of
11715 actual parameters and some information about their types to attempt to narrow
11716 the set of definitions. It also makes very limited use of context, preferring
11717 procedures to functions in the context of the @code{call} command, and
11718 functions to procedures elsewhere.
11720 @node Omissions from Ada
11721 @subsubsection Omissions from Ada
11722 @cindex Ada, omissions from
11724 Here are the notable omissions from the subset:
11728 Only a subset of the attributes are supported:
11732 @t{'First}, @t{'Last}, and @t{'Length}
11733 on array objects (not on types and subtypes).
11736 @t{'Min} and @t{'Max}.
11739 @t{'Pos} and @t{'Val}.
11745 @t{'Range} on array objects (not subtypes), but only as the right
11746 operand of the membership (@code{in}) operator.
11749 @t{'Access}, @t{'Unchecked_Access}, and
11750 @t{'Unrestricted_Access} (a GNAT extension).
11758 @code{Characters.Latin_1} are not available and
11759 concatenation is not implemented. Thus, escape characters in strings are
11760 not currently available.
11763 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
11764 equality of representations. They will generally work correctly
11765 for strings and arrays whose elements have integer or enumeration types.
11766 They may not work correctly for arrays whose element
11767 types have user-defined equality, for arrays of real values
11768 (in particular, IEEE-conformant floating point, because of negative
11769 zeroes and NaNs), and for arrays whose elements contain unused bits with
11770 indeterminate values.
11773 The other component-by-component array operations (@code{and}, @code{or},
11774 @code{xor}, @code{not}, and relational tests other than equality)
11775 are not implemented.
11778 @cindex array aggregates (Ada)
11779 @cindex record aggregates (Ada)
11780 @cindex aggregates (Ada)
11781 There is limited support for array and record aggregates. They are
11782 permitted only on the right sides of assignments, as in these examples:
11785 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
11786 (@value{GDBP}) set An_Array := (1, others => 0)
11787 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
11788 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
11789 (@value{GDBP}) set A_Record := (1, "Peter", True);
11790 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
11794 discriminant's value by assigning an aggregate has an
11795 undefined effect if that discriminant is used within the record.
11796 However, you can first modify discriminants by directly assigning to
11797 them (which normally would not be allowed in Ada), and then performing an
11798 aggregate assignment. For example, given a variable @code{A_Rec}
11799 declared to have a type such as:
11802 type Rec (Len : Small_Integer := 0) is record
11804 Vals : IntArray (1 .. Len);
11808 you can assign a value with a different size of @code{Vals} with two
11812 (@value{GDBP}) set A_Rec.Len := 4
11813 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
11816 As this example also illustrates, @value{GDBN} is very loose about the usual
11817 rules concerning aggregates. You may leave out some of the
11818 components of an array or record aggregate (such as the @code{Len}
11819 component in the assignment to @code{A_Rec} above); they will retain their
11820 original values upon assignment. You may freely use dynamic values as
11821 indices in component associations. You may even use overlapping or
11822 redundant component associations, although which component values are
11823 assigned in such cases is not defined.
11826 Calls to dispatching subprograms are not implemented.
11829 The overloading algorithm is much more limited (i.e., less selective)
11830 than that of real Ada. It makes only limited use of the context in
11831 which a subexpression appears to resolve its meaning, and it is much
11832 looser in its rules for allowing type matches. As a result, some
11833 function calls will be ambiguous, and the user will be asked to choose
11834 the proper resolution.
11837 The @code{new} operator is not implemented.
11840 Entry calls are not implemented.
11843 Aside from printing, arithmetic operations on the native VAX floating-point
11844 formats are not supported.
11847 It is not possible to slice a packed array.
11850 The names @code{True} and @code{False}, when not part of a qualified name,
11851 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
11853 Should your program
11854 redefine these names in a package or procedure (at best a dubious practice),
11855 you will have to use fully qualified names to access their new definitions.
11858 @node Additions to Ada
11859 @subsubsection Additions to Ada
11860 @cindex Ada, deviations from
11862 As it does for other languages, @value{GDBN} makes certain generic
11863 extensions to Ada (@pxref{Expressions}):
11867 If the expression @var{E} is a variable residing in memory (typically
11868 a local variable or array element) and @var{N} is a positive integer,
11869 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
11870 @var{N}-1 adjacent variables following it in memory as an array. In
11871 Ada, this operator is generally not necessary, since its prime use is
11872 in displaying parts of an array, and slicing will usually do this in
11873 Ada. However, there are occasional uses when debugging programs in
11874 which certain debugging information has been optimized away.
11877 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
11878 appears in function or file @var{B}.'' When @var{B} is a file name,
11879 you must typically surround it in single quotes.
11882 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
11883 @var{type} that appears at address @var{addr}.''
11886 A name starting with @samp{$} is a convenience variable
11887 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
11890 In addition, @value{GDBN} provides a few other shortcuts and outright
11891 additions specific to Ada:
11895 The assignment statement is allowed as an expression, returning
11896 its right-hand operand as its value. Thus, you may enter
11899 (@value{GDBP}) set x := y + 3
11900 (@value{GDBP}) print A(tmp := y + 1)
11904 The semicolon is allowed as an ``operator,'' returning as its value
11905 the value of its right-hand operand.
11906 This allows, for example,
11907 complex conditional breaks:
11910 (@value{GDBP}) break f
11911 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
11915 Rather than use catenation and symbolic character names to introduce special
11916 characters into strings, one may instead use a special bracket notation,
11917 which is also used to print strings. A sequence of characters of the form
11918 @samp{["@var{XX}"]} within a string or character literal denotes the
11919 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
11920 sequence of characters @samp{["""]} also denotes a single quotation mark
11921 in strings. For example,
11923 "One line.["0a"]Next line.["0a"]"
11926 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
11930 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
11931 @t{'Max} is optional (and is ignored in any case). For example, it is valid
11935 (@value{GDBP}) print 'max(x, y)
11939 When printing arrays, @value{GDBN} uses positional notation when the
11940 array has a lower bound of 1, and uses a modified named notation otherwise.
11941 For example, a one-dimensional array of three integers with a lower bound
11942 of 3 might print as
11949 That is, in contrast to valid Ada, only the first component has a @code{=>}
11953 You may abbreviate attributes in expressions with any unique,
11954 multi-character subsequence of
11955 their names (an exact match gets preference).
11956 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
11957 in place of @t{a'length}.
11960 @cindex quoting Ada internal identifiers
11961 Since Ada is case-insensitive, the debugger normally maps identifiers you type
11962 to lower case. The GNAT compiler uses upper-case characters for
11963 some of its internal identifiers, which are normally of no interest to users.
11964 For the rare occasions when you actually have to look at them,
11965 enclose them in angle brackets to avoid the lower-case mapping.
11968 (@value{GDBP}) print <JMPBUF_SAVE>[0]
11972 Printing an object of class-wide type or dereferencing an
11973 access-to-class-wide value will display all the components of the object's
11974 specific type (as indicated by its run-time tag). Likewise, component
11975 selection on such a value will operate on the specific type of the
11980 @node Stopping Before Main Program
11981 @subsubsection Stopping at the Very Beginning
11983 @cindex breakpointing Ada elaboration code
11984 It is sometimes necessary to debug the program during elaboration, and
11985 before reaching the main procedure.
11986 As defined in the Ada Reference
11987 Manual, the elaboration code is invoked from a procedure called
11988 @code{adainit}. To run your program up to the beginning of
11989 elaboration, simply use the following two commands:
11990 @code{tbreak adainit} and @code{run}.
11993 @subsubsection Extensions for Ada Tasks
11994 @cindex Ada, tasking
11996 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
11997 @value{GDBN} provides the following task-related commands:
12002 This command shows a list of current Ada tasks, as in the following example:
12009 (@value{GDBP}) info tasks
12010 ID TID P-ID Pri State Name
12011 1 8088000 0 15 Child Activation Wait main_task
12012 2 80a4000 1 15 Accept Statement b
12013 3 809a800 1 15 Child Activation Wait a
12014 * 4 80ae800 3 15 Runnable c
12019 In this listing, the asterisk before the last task indicates it to be the
12020 task currently being inspected.
12024 Represents @value{GDBN}'s internal task number.
12030 The parent's task ID (@value{GDBN}'s internal task number).
12033 The base priority of the task.
12036 Current state of the task.
12040 The task has been created but has not been activated. It cannot be
12044 The task is not blocked for any reason known to Ada. (It may be waiting
12045 for a mutex, though.) It is conceptually "executing" in normal mode.
12048 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
12049 that were waiting on terminate alternatives have been awakened and have
12050 terminated themselves.
12052 @item Child Activation Wait
12053 The task is waiting for created tasks to complete activation.
12055 @item Accept Statement
12056 The task is waiting on an accept or selective wait statement.
12058 @item Waiting on entry call
12059 The task is waiting on an entry call.
12061 @item Async Select Wait
12062 The task is waiting to start the abortable part of an asynchronous
12066 The task is waiting on a select statement with only a delay
12069 @item Child Termination Wait
12070 The task is sleeping having completed a master within itself, and is
12071 waiting for the tasks dependent on that master to become terminated or
12072 waiting on a terminate Phase.
12074 @item Wait Child in Term Alt
12075 The task is sleeping waiting for tasks on terminate alternatives to
12076 finish terminating.
12078 @item Accepting RV with @var{taskno}
12079 The task is accepting a rendez-vous with the task @var{taskno}.
12083 Name of the task in the program.
12087 @kindex info task @var{taskno}
12088 @item info task @var{taskno}
12089 This command shows detailled informations on the specified task, as in
12090 the following example:
12095 (@value{GDBP}) info tasks
12096 ID TID P-ID Pri State Name
12097 1 8077880 0 15 Child Activation Wait main_task
12098 * 2 807c468 1 15 Runnable task_1
12099 (@value{GDBP}) info task 2
12100 Ada Task: 0x807c468
12103 Parent: 1 (main_task)
12109 @kindex task@r{ (Ada)}
12110 @cindex current Ada task ID
12111 This command prints the ID of the current task.
12117 (@value{GDBP}) info tasks
12118 ID TID P-ID Pri State Name
12119 1 8077870 0 15 Child Activation Wait main_task
12120 * 2 807c458 1 15 Runnable t
12121 (@value{GDBP}) task
12122 [Current task is 2]
12125 @item task @var{taskno}
12126 @cindex Ada task switching
12127 This command is like the @code{thread @var{threadno}}
12128 command (@pxref{Threads}). It switches the context of debugging
12129 from the current task to the given task.
12135 (@value{GDBP}) info tasks
12136 ID TID P-ID Pri State Name
12137 1 8077870 0 15 Child Activation Wait main_task
12138 * 2 807c458 1 15 Runnable t
12139 (@value{GDBP}) task 1
12140 [Switching to task 1]
12141 #0 0x8067726 in pthread_cond_wait ()
12143 #0 0x8067726 in pthread_cond_wait ()
12144 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
12145 #2 0x805cb63 in system.task_primitives.operations.sleep ()
12146 #3 0x806153e in system.tasking.stages.activate_tasks ()
12147 #4 0x804aacc in un () at un.adb:5
12150 @item break @var{linespec} task @var{taskno}
12151 @itemx break @var{linespec} task @var{taskno} if @dots{}
12152 @cindex breakpoints and tasks, in Ada
12153 @cindex task breakpoints, in Ada
12154 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
12155 These commands are like the @code{break @dots{} thread @dots{}}
12156 command (@pxref{Thread Stops}).
12157 @var{linespec} specifies source lines, as described
12158 in @ref{Specify Location}.
12160 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
12161 to specify that you only want @value{GDBN} to stop the program when a
12162 particular Ada task reaches this breakpoint. @var{taskno} is one of the
12163 numeric task identifiers assigned by @value{GDBN}, shown in the first
12164 column of the @samp{info tasks} display.
12166 If you do not specify @samp{task @var{taskno}} when you set a
12167 breakpoint, the breakpoint applies to @emph{all} tasks of your
12170 You can use the @code{task} qualifier on conditional breakpoints as
12171 well; in this case, place @samp{task @var{taskno}} before the
12172 breakpoint condition (before the @code{if}).
12180 (@value{GDBP}) info tasks
12181 ID TID P-ID Pri State Name
12182 1 140022020 0 15 Child Activation Wait main_task
12183 2 140045060 1 15 Accept/Select Wait t2
12184 3 140044840 1 15 Runnable t1
12185 * 4 140056040 1 15 Runnable t3
12186 (@value{GDBP}) b 15 task 2
12187 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
12188 (@value{GDBP}) cont
12193 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
12195 (@value{GDBP}) info tasks
12196 ID TID P-ID Pri State Name
12197 1 140022020 0 15 Child Activation Wait main_task
12198 * 2 140045060 1 15 Runnable t2
12199 3 140044840 1 15 Runnable t1
12200 4 140056040 1 15 Delay Sleep t3
12204 @node Ada Tasks and Core Files
12205 @subsubsection Tasking Support when Debugging Core Files
12206 @cindex Ada tasking and core file debugging
12208 When inspecting a core file, as opposed to debugging a live program,
12209 tasking support may be limited or even unavailable, depending on
12210 the platform being used.
12211 For instance, on x86-linux, the list of tasks is available, but task
12212 switching is not supported. On Tru64, however, task switching will work
12215 On certain platforms, including Tru64, the debugger needs to perform some
12216 memory writes in order to provide Ada tasking support. When inspecting
12217 a core file, this means that the core file must be opened with read-write
12218 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
12219 Under these circumstances, you should make a backup copy of the core
12220 file before inspecting it with @value{GDBN}.
12223 @subsubsection Known Peculiarities of Ada Mode
12224 @cindex Ada, problems
12226 Besides the omissions listed previously (@pxref{Omissions from Ada}),
12227 we know of several problems with and limitations of Ada mode in
12229 some of which will be fixed with planned future releases of the debugger
12230 and the GNU Ada compiler.
12234 Currently, the debugger
12235 has insufficient information to determine whether certain pointers represent
12236 pointers to objects or the objects themselves.
12237 Thus, the user may have to tack an extra @code{.all} after an expression
12238 to get it printed properly.
12241 Static constants that the compiler chooses not to materialize as objects in
12242 storage are invisible to the debugger.
12245 Named parameter associations in function argument lists are ignored (the
12246 argument lists are treated as positional).
12249 Many useful library packages are currently invisible to the debugger.
12252 Fixed-point arithmetic, conversions, input, and output is carried out using
12253 floating-point arithmetic, and may give results that only approximate those on
12257 The GNAT compiler never generates the prefix @code{Standard} for any of
12258 the standard symbols defined by the Ada language. @value{GDBN} knows about
12259 this: it will strip the prefix from names when you use it, and will never
12260 look for a name you have so qualified among local symbols, nor match against
12261 symbols in other packages or subprograms. If you have
12262 defined entities anywhere in your program other than parameters and
12263 local variables whose simple names match names in @code{Standard},
12264 GNAT's lack of qualification here can cause confusion. When this happens,
12265 you can usually resolve the confusion
12266 by qualifying the problematic names with package
12267 @code{Standard} explicitly.
12270 @node Unsupported Languages
12271 @section Unsupported Languages
12273 @cindex unsupported languages
12274 @cindex minimal language
12275 In addition to the other fully-supported programming languages,
12276 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
12277 It does not represent a real programming language, but provides a set
12278 of capabilities close to what the C or assembly languages provide.
12279 This should allow most simple operations to be performed while debugging
12280 an application that uses a language currently not supported by @value{GDBN}.
12282 If the language is set to @code{auto}, @value{GDBN} will automatically
12283 select this language if the current frame corresponds to an unsupported
12287 @chapter Examining the Symbol Table
12289 The commands described in this chapter allow you to inquire about the
12290 symbols (names of variables, functions and types) defined in your
12291 program. This information is inherent in the text of your program and
12292 does not change as your program executes. @value{GDBN} finds it in your
12293 program's symbol table, in the file indicated when you started @value{GDBN}
12294 (@pxref{File Options, ,Choosing Files}), or by one of the
12295 file-management commands (@pxref{Files, ,Commands to Specify Files}).
12297 @cindex symbol names
12298 @cindex names of symbols
12299 @cindex quoting names
12300 Occasionally, you may need to refer to symbols that contain unusual
12301 characters, which @value{GDBN} ordinarily treats as word delimiters. The
12302 most frequent case is in referring to static variables in other
12303 source files (@pxref{Variables,,Program Variables}). File names
12304 are recorded in object files as debugging symbols, but @value{GDBN} would
12305 ordinarily parse a typical file name, like @file{foo.c}, as the three words
12306 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
12307 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
12314 looks up the value of @code{x} in the scope of the file @file{foo.c}.
12317 @cindex case-insensitive symbol names
12318 @cindex case sensitivity in symbol names
12319 @kindex set case-sensitive
12320 @item set case-sensitive on
12321 @itemx set case-sensitive off
12322 @itemx set case-sensitive auto
12323 Normally, when @value{GDBN} looks up symbols, it matches their names
12324 with case sensitivity determined by the current source language.
12325 Occasionally, you may wish to control that. The command @code{set
12326 case-sensitive} lets you do that by specifying @code{on} for
12327 case-sensitive matches or @code{off} for case-insensitive ones. If
12328 you specify @code{auto}, case sensitivity is reset to the default
12329 suitable for the source language. The default is case-sensitive
12330 matches for all languages except for Fortran, for which the default is
12331 case-insensitive matches.
12333 @kindex show case-sensitive
12334 @item show case-sensitive
12335 This command shows the current setting of case sensitivity for symbols
12338 @kindex info address
12339 @cindex address of a symbol
12340 @item info address @var{symbol}
12341 Describe where the data for @var{symbol} is stored. For a register
12342 variable, this says which register it is kept in. For a non-register
12343 local variable, this prints the stack-frame offset at which the variable
12346 Note the contrast with @samp{print &@var{symbol}}, which does not work
12347 at all for a register variable, and for a stack local variable prints
12348 the exact address of the current instantiation of the variable.
12350 @kindex info symbol
12351 @cindex symbol from address
12352 @cindex closest symbol and offset for an address
12353 @item info symbol @var{addr}
12354 Print the name of a symbol which is stored at the address @var{addr}.
12355 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
12356 nearest symbol and an offset from it:
12359 (@value{GDBP}) info symbol 0x54320
12360 _initialize_vx + 396 in section .text
12364 This is the opposite of the @code{info address} command. You can use
12365 it to find out the name of a variable or a function given its address.
12367 For dynamically linked executables, the name of executable or shared
12368 library containing the symbol is also printed:
12371 (@value{GDBP}) info symbol 0x400225
12372 _start + 5 in section .text of /tmp/a.out
12373 (@value{GDBP}) info symbol 0x2aaaac2811cf
12374 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
12378 @item whatis [@var{arg}]
12379 Print the data type of @var{arg}, which can be either an expression or
12380 a data type. With no argument, print the data type of @code{$}, the
12381 last value in the value history. If @var{arg} is an expression, it is
12382 not actually evaluated, and any side-effecting operations (such as
12383 assignments or function calls) inside it do not take place. If
12384 @var{arg} is a type name, it may be the name of a type or typedef, or
12385 for C code it may have the form @samp{class @var{class-name}},
12386 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
12387 @samp{enum @var{enum-tag}}.
12388 @xref{Expressions, ,Expressions}.
12391 @item ptype [@var{arg}]
12392 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
12393 detailed description of the type, instead of just the name of the type.
12394 @xref{Expressions, ,Expressions}.
12396 For example, for this variable declaration:
12399 struct complex @{double real; double imag;@} v;
12403 the two commands give this output:
12407 (@value{GDBP}) whatis v
12408 type = struct complex
12409 (@value{GDBP}) ptype v
12410 type = struct complex @{
12418 As with @code{whatis}, using @code{ptype} without an argument refers to
12419 the type of @code{$}, the last value in the value history.
12421 @cindex incomplete type
12422 Sometimes, programs use opaque data types or incomplete specifications
12423 of complex data structure. If the debug information included in the
12424 program does not allow @value{GDBN} to display a full declaration of
12425 the data type, it will say @samp{<incomplete type>}. For example,
12426 given these declarations:
12430 struct foo *fooptr;
12434 but no definition for @code{struct foo} itself, @value{GDBN} will say:
12437 (@value{GDBP}) ptype foo
12438 $1 = <incomplete type>
12442 ``Incomplete type'' is C terminology for data types that are not
12443 completely specified.
12446 @item info types @var{regexp}
12448 Print a brief description of all types whose names match the regular
12449 expression @var{regexp} (or all types in your program, if you supply
12450 no argument). Each complete typename is matched as though it were a
12451 complete line; thus, @samp{i type value} gives information on all
12452 types in your program whose names include the string @code{value}, but
12453 @samp{i type ^value$} gives information only on types whose complete
12454 name is @code{value}.
12456 This command differs from @code{ptype} in two ways: first, like
12457 @code{whatis}, it does not print a detailed description; second, it
12458 lists all source files where a type is defined.
12461 @cindex local variables
12462 @item info scope @var{location}
12463 List all the variables local to a particular scope. This command
12464 accepts a @var{location} argument---a function name, a source line, or
12465 an address preceded by a @samp{*}, and prints all the variables local
12466 to the scope defined by that location. (@xref{Specify Location}, for
12467 details about supported forms of @var{location}.) For example:
12470 (@value{GDBP}) @b{info scope command_line_handler}
12471 Scope for command_line_handler:
12472 Symbol rl is an argument at stack/frame offset 8, length 4.
12473 Symbol linebuffer is in static storage at address 0x150a18, length 4.
12474 Symbol linelength is in static storage at address 0x150a1c, length 4.
12475 Symbol p is a local variable in register $esi, length 4.
12476 Symbol p1 is a local variable in register $ebx, length 4.
12477 Symbol nline is a local variable in register $edx, length 4.
12478 Symbol repeat is a local variable at frame offset -8, length 4.
12482 This command is especially useful for determining what data to collect
12483 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
12486 @kindex info source
12488 Show information about the current source file---that is, the source file for
12489 the function containing the current point of execution:
12492 the name of the source file, and the directory containing it,
12494 the directory it was compiled in,
12496 its length, in lines,
12498 which programming language it is written in,
12500 whether the executable includes debugging information for that file, and
12501 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
12503 whether the debugging information includes information about
12504 preprocessor macros.
12508 @kindex info sources
12510 Print the names of all source files in your program for which there is
12511 debugging information, organized into two lists: files whose symbols
12512 have already been read, and files whose symbols will be read when needed.
12514 @kindex info functions
12515 @item info functions
12516 Print the names and data types of all defined functions.
12518 @item info functions @var{regexp}
12519 Print the names and data types of all defined functions
12520 whose names contain a match for regular expression @var{regexp}.
12521 Thus, @samp{info fun step} finds all functions whose names
12522 include @code{step}; @samp{info fun ^step} finds those whose names
12523 start with @code{step}. If a function name contains characters
12524 that conflict with the regular expression language (e.g.@:
12525 @samp{operator*()}), they may be quoted with a backslash.
12527 @kindex info variables
12528 @item info variables
12529 Print the names and data types of all variables that are declared
12530 outside of functions (i.e.@: excluding local variables).
12532 @item info variables @var{regexp}
12533 Print the names and data types of all variables (except for local
12534 variables) whose names contain a match for regular expression
12537 @kindex info classes
12538 @cindex Objective-C, classes and selectors
12540 @itemx info classes @var{regexp}
12541 Display all Objective-C classes in your program, or
12542 (with the @var{regexp} argument) all those matching a particular regular
12545 @kindex info selectors
12546 @item info selectors
12547 @itemx info selectors @var{regexp}
12548 Display all Objective-C selectors in your program, or
12549 (with the @var{regexp} argument) all those matching a particular regular
12553 This was never implemented.
12554 @kindex info methods
12556 @itemx info methods @var{regexp}
12557 The @code{info methods} command permits the user to examine all defined
12558 methods within C@t{++} program, or (with the @var{regexp} argument) a
12559 specific set of methods found in the various C@t{++} classes. Many
12560 C@t{++} classes provide a large number of methods. Thus, the output
12561 from the @code{ptype} command can be overwhelming and hard to use. The
12562 @code{info-methods} command filters the methods, printing only those
12563 which match the regular-expression @var{regexp}.
12566 @cindex reloading symbols
12567 Some systems allow individual object files that make up your program to
12568 be replaced without stopping and restarting your program. For example,
12569 in VxWorks you can simply recompile a defective object file and keep on
12570 running. If you are running on one of these systems, you can allow
12571 @value{GDBN} to reload the symbols for automatically relinked modules:
12574 @kindex set symbol-reloading
12575 @item set symbol-reloading on
12576 Replace symbol definitions for the corresponding source file when an
12577 object file with a particular name is seen again.
12579 @item set symbol-reloading off
12580 Do not replace symbol definitions when encountering object files of the
12581 same name more than once. This is the default state; if you are not
12582 running on a system that permits automatic relinking of modules, you
12583 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
12584 may discard symbols when linking large programs, that may contain
12585 several modules (from different directories or libraries) with the same
12588 @kindex show symbol-reloading
12589 @item show symbol-reloading
12590 Show the current @code{on} or @code{off} setting.
12593 @cindex opaque data types
12594 @kindex set opaque-type-resolution
12595 @item set opaque-type-resolution on
12596 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
12597 declared as a pointer to a @code{struct}, @code{class}, or
12598 @code{union}---for example, @code{struct MyType *}---that is used in one
12599 source file although the full declaration of @code{struct MyType} is in
12600 another source file. The default is on.
12602 A change in the setting of this subcommand will not take effect until
12603 the next time symbols for a file are loaded.
12605 @item set opaque-type-resolution off
12606 Tell @value{GDBN} not to resolve opaque types. In this case, the type
12607 is printed as follows:
12609 @{<no data fields>@}
12612 @kindex show opaque-type-resolution
12613 @item show opaque-type-resolution
12614 Show whether opaque types are resolved or not.
12616 @kindex set print symbol-loading
12617 @cindex print messages when symbols are loaded
12618 @item set print symbol-loading
12619 @itemx set print symbol-loading on
12620 @itemx set print symbol-loading off
12621 The @code{set print symbol-loading} command allows you to enable or
12622 disable printing of messages when @value{GDBN} loads symbols.
12623 By default, these messages will be printed, and normally this is what
12624 you want. Disabling these messages is useful when debugging applications
12625 with lots of shared libraries where the quantity of output can be more
12626 annoying than useful.
12628 @kindex show print symbol-loading
12629 @item show print symbol-loading
12630 Show whether messages will be printed when @value{GDBN} loads symbols.
12632 @kindex maint print symbols
12633 @cindex symbol dump
12634 @kindex maint print psymbols
12635 @cindex partial symbol dump
12636 @item maint print symbols @var{filename}
12637 @itemx maint print psymbols @var{filename}
12638 @itemx maint print msymbols @var{filename}
12639 Write a dump of debugging symbol data into the file @var{filename}.
12640 These commands are used to debug the @value{GDBN} symbol-reading code. Only
12641 symbols with debugging data are included. If you use @samp{maint print
12642 symbols}, @value{GDBN} includes all the symbols for which it has already
12643 collected full details: that is, @var{filename} reflects symbols for
12644 only those files whose symbols @value{GDBN} has read. You can use the
12645 command @code{info sources} to find out which files these are. If you
12646 use @samp{maint print psymbols} instead, the dump shows information about
12647 symbols that @value{GDBN} only knows partially---that is, symbols defined in
12648 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
12649 @samp{maint print msymbols} dumps just the minimal symbol information
12650 required for each object file from which @value{GDBN} has read some symbols.
12651 @xref{Files, ,Commands to Specify Files}, for a discussion of how
12652 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
12654 @kindex maint info symtabs
12655 @kindex maint info psymtabs
12656 @cindex listing @value{GDBN}'s internal symbol tables
12657 @cindex symbol tables, listing @value{GDBN}'s internal
12658 @cindex full symbol tables, listing @value{GDBN}'s internal
12659 @cindex partial symbol tables, listing @value{GDBN}'s internal
12660 @item maint info symtabs @r{[} @var{regexp} @r{]}
12661 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
12663 List the @code{struct symtab} or @code{struct partial_symtab}
12664 structures whose names match @var{regexp}. If @var{regexp} is not
12665 given, list them all. The output includes expressions which you can
12666 copy into a @value{GDBN} debugging this one to examine a particular
12667 structure in more detail. For example:
12670 (@value{GDBP}) maint info psymtabs dwarf2read
12671 @{ objfile /home/gnu/build/gdb/gdb
12672 ((struct objfile *) 0x82e69d0)
12673 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
12674 ((struct partial_symtab *) 0x8474b10)
12677 text addresses 0x814d3c8 -- 0x8158074
12678 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
12679 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
12680 dependencies (none)
12683 (@value{GDBP}) maint info symtabs
12687 We see that there is one partial symbol table whose filename contains
12688 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
12689 and we see that @value{GDBN} has not read in any symtabs yet at all.
12690 If we set a breakpoint on a function, that will cause @value{GDBN} to
12691 read the symtab for the compilation unit containing that function:
12694 (@value{GDBP}) break dwarf2_psymtab_to_symtab
12695 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
12697 (@value{GDBP}) maint info symtabs
12698 @{ objfile /home/gnu/build/gdb/gdb
12699 ((struct objfile *) 0x82e69d0)
12700 @{ symtab /home/gnu/src/gdb/dwarf2read.c
12701 ((struct symtab *) 0x86c1f38)
12704 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
12705 linetable ((struct linetable *) 0x8370fa0)
12706 debugformat DWARF 2
12715 @chapter Altering Execution
12717 Once you think you have found an error in your program, you might want to
12718 find out for certain whether correcting the apparent error would lead to
12719 correct results in the rest of the run. You can find the answer by
12720 experiment, using the @value{GDBN} features for altering execution of the
12723 For example, you can store new values into variables or memory
12724 locations, give your program a signal, restart it at a different
12725 address, or even return prematurely from a function.
12728 * Assignment:: Assignment to variables
12729 * Jumping:: Continuing at a different address
12730 * Signaling:: Giving your program a signal
12731 * Returning:: Returning from a function
12732 * Calling:: Calling your program's functions
12733 * Patching:: Patching your program
12737 @section Assignment to Variables
12740 @cindex setting variables
12741 To alter the value of a variable, evaluate an assignment expression.
12742 @xref{Expressions, ,Expressions}. For example,
12749 stores the value 4 into the variable @code{x}, and then prints the
12750 value of the assignment expression (which is 4).
12751 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
12752 information on operators in supported languages.
12754 @kindex set variable
12755 @cindex variables, setting
12756 If you are not interested in seeing the value of the assignment, use the
12757 @code{set} command instead of the @code{print} command. @code{set} is
12758 really the same as @code{print} except that the expression's value is
12759 not printed and is not put in the value history (@pxref{Value History,
12760 ,Value History}). The expression is evaluated only for its effects.
12762 If the beginning of the argument string of the @code{set} command
12763 appears identical to a @code{set} subcommand, use the @code{set
12764 variable} command instead of just @code{set}. This command is identical
12765 to @code{set} except for its lack of subcommands. For example, if your
12766 program has a variable @code{width}, you get an error if you try to set
12767 a new value with just @samp{set width=13}, because @value{GDBN} has the
12768 command @code{set width}:
12771 (@value{GDBP}) whatis width
12773 (@value{GDBP}) p width
12775 (@value{GDBP}) set width=47
12776 Invalid syntax in expression.
12780 The invalid expression, of course, is @samp{=47}. In
12781 order to actually set the program's variable @code{width}, use
12784 (@value{GDBP}) set var width=47
12787 Because the @code{set} command has many subcommands that can conflict
12788 with the names of program variables, it is a good idea to use the
12789 @code{set variable} command instead of just @code{set}. For example, if
12790 your program has a variable @code{g}, you run into problems if you try
12791 to set a new value with just @samp{set g=4}, because @value{GDBN} has
12792 the command @code{set gnutarget}, abbreviated @code{set g}:
12796 (@value{GDBP}) whatis g
12800 (@value{GDBP}) set g=4
12804 The program being debugged has been started already.
12805 Start it from the beginning? (y or n) y
12806 Starting program: /home/smith/cc_progs/a.out
12807 "/home/smith/cc_progs/a.out": can't open to read symbols:
12808 Invalid bfd target.
12809 (@value{GDBP}) show g
12810 The current BFD target is "=4".
12815 The program variable @code{g} did not change, and you silently set the
12816 @code{gnutarget} to an invalid value. In order to set the variable
12820 (@value{GDBP}) set var g=4
12823 @value{GDBN} allows more implicit conversions in assignments than C; you can
12824 freely store an integer value into a pointer variable or vice versa,
12825 and you can convert any structure to any other structure that is the
12826 same length or shorter.
12827 @comment FIXME: how do structs align/pad in these conversions?
12828 @comment /doc@cygnus.com 18dec1990
12830 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
12831 construct to generate a value of specified type at a specified address
12832 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
12833 to memory location @code{0x83040} as an integer (which implies a certain size
12834 and representation in memory), and
12837 set @{int@}0x83040 = 4
12841 stores the value 4 into that memory location.
12844 @section Continuing at a Different Address
12846 Ordinarily, when you continue your program, you do so at the place where
12847 it stopped, with the @code{continue} command. You can instead continue at
12848 an address of your own choosing, with the following commands:
12852 @item jump @var{linespec}
12853 @itemx jump @var{location}
12854 Resume execution at line @var{linespec} or at address given by
12855 @var{location}. Execution stops again immediately if there is a
12856 breakpoint there. @xref{Specify Location}, for a description of the
12857 different forms of @var{linespec} and @var{location}. It is common
12858 practice to use the @code{tbreak} command in conjunction with
12859 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
12861 The @code{jump} command does not change the current stack frame, or
12862 the stack pointer, or the contents of any memory location or any
12863 register other than the program counter. If line @var{linespec} is in
12864 a different function from the one currently executing, the results may
12865 be bizarre if the two functions expect different patterns of arguments or
12866 of local variables. For this reason, the @code{jump} command requests
12867 confirmation if the specified line is not in the function currently
12868 executing. However, even bizarre results are predictable if you are
12869 well acquainted with the machine-language code of your program.
12872 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
12873 On many systems, you can get much the same effect as the @code{jump}
12874 command by storing a new value into the register @code{$pc}. The
12875 difference is that this does not start your program running; it only
12876 changes the address of where it @emph{will} run when you continue. For
12884 makes the next @code{continue} command or stepping command execute at
12885 address @code{0x485}, rather than at the address where your program stopped.
12886 @xref{Continuing and Stepping, ,Continuing and Stepping}.
12888 The most common occasion to use the @code{jump} command is to back
12889 up---perhaps with more breakpoints set---over a portion of a program
12890 that has already executed, in order to examine its execution in more
12895 @section Giving your Program a Signal
12896 @cindex deliver a signal to a program
12900 @item signal @var{signal}
12901 Resume execution where your program stopped, but immediately give it the
12902 signal @var{signal}. @var{signal} can be the name or the number of a
12903 signal. For example, on many systems @code{signal 2} and @code{signal
12904 SIGINT} are both ways of sending an interrupt signal.
12906 Alternatively, if @var{signal} is zero, continue execution without
12907 giving a signal. This is useful when your program stopped on account of
12908 a signal and would ordinary see the signal when resumed with the
12909 @code{continue} command; @samp{signal 0} causes it to resume without a
12912 @code{signal} does not repeat when you press @key{RET} a second time
12913 after executing the command.
12917 Invoking the @code{signal} command is not the same as invoking the
12918 @code{kill} utility from the shell. Sending a signal with @code{kill}
12919 causes @value{GDBN} to decide what to do with the signal depending on
12920 the signal handling tables (@pxref{Signals}). The @code{signal} command
12921 passes the signal directly to your program.
12925 @section Returning from a Function
12928 @cindex returning from a function
12931 @itemx return @var{expression}
12932 You can cancel execution of a function call with the @code{return}
12933 command. If you give an
12934 @var{expression} argument, its value is used as the function's return
12938 When you use @code{return}, @value{GDBN} discards the selected stack frame
12939 (and all frames within it). You can think of this as making the
12940 discarded frame return prematurely. If you wish to specify a value to
12941 be returned, give that value as the argument to @code{return}.
12943 This pops the selected stack frame (@pxref{Selection, ,Selecting a
12944 Frame}), and any other frames inside of it, leaving its caller as the
12945 innermost remaining frame. That frame becomes selected. The
12946 specified value is stored in the registers used for returning values
12949 The @code{return} command does not resume execution; it leaves the
12950 program stopped in the state that would exist if the function had just
12951 returned. In contrast, the @code{finish} command (@pxref{Continuing
12952 and Stepping, ,Continuing and Stepping}) resumes execution until the
12953 selected stack frame returns naturally.
12955 @value{GDBN} needs to know how the @var{expression} argument should be set for
12956 the inferior. The concrete registers assignment depends on the OS ABI and the
12957 type being returned by the selected stack frame. For example it is common for
12958 OS ABI to return floating point values in FPU registers while integer values in
12959 CPU registers. Still some ABIs return even floating point values in CPU
12960 registers. Larger integer widths (such as @code{long long int}) also have
12961 specific placement rules. @value{GDBN} already knows the OS ABI from its
12962 current target so it needs to find out also the type being returned to make the
12963 assignment into the right register(s).
12965 Normally, the selected stack frame has debug info. @value{GDBN} will always
12966 use the debug info instead of the implicit type of @var{expression} when the
12967 debug info is available. For example, if you type @kbd{return -1}, and the
12968 function in the current stack frame is declared to return a @code{long long
12969 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
12970 into a @code{long long int}:
12973 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
12975 (@value{GDBP}) return -1
12976 Make func return now? (y or n) y
12977 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
12978 43 printf ("result=%lld\n", func ());
12982 However, if the selected stack frame does not have a debug info, e.g., if the
12983 function was compiled without debug info, @value{GDBN} has to find out the type
12984 to return from user. Specifying a different type by mistake may set the value
12985 in different inferior registers than the caller code expects. For example,
12986 typing @kbd{return -1} with its implicit type @code{int} would set only a part
12987 of a @code{long long int} result for a debug info less function (on 32-bit
12988 architectures). Therefore the user is required to specify the return type by
12989 an appropriate cast explicitly:
12992 Breakpoint 2, 0x0040050b in func ()
12993 (@value{GDBP}) return -1
12994 Return value type not available for selected stack frame.
12995 Please use an explicit cast of the value to return.
12996 (@value{GDBP}) return (long long int) -1
12997 Make selected stack frame return now? (y or n) y
12998 #0 0x00400526 in main ()
13003 @section Calling Program Functions
13006 @cindex calling functions
13007 @cindex inferior functions, calling
13008 @item print @var{expr}
13009 Evaluate the expression @var{expr} and display the resulting value.
13010 @var{expr} may include calls to functions in the program being
13014 @item call @var{expr}
13015 Evaluate the expression @var{expr} without displaying @code{void}
13018 You can use this variant of the @code{print} command if you want to
13019 execute a function from your program that does not return anything
13020 (a.k.a.@: @dfn{a void function}), but without cluttering the output
13021 with @code{void} returned values that @value{GDBN} will otherwise
13022 print. If the result is not void, it is printed and saved in the
13026 It is possible for the function you call via the @code{print} or
13027 @code{call} command to generate a signal (e.g., if there's a bug in
13028 the function, or if you passed it incorrect arguments). What happens
13029 in that case is controlled by the @code{set unwindonsignal} command.
13031 Similarly, with a C@t{++} program it is possible for the function you
13032 call via the @code{print} or @code{call} command to generate an
13033 exception that is not handled due to the constraints of the dummy
13034 frame. In this case, any exception that is raised in the frame, but has
13035 an out-of-frame exception handler will not be found. GDB builds a
13036 dummy-frame for the inferior function call, and the unwinder cannot
13037 seek for exception handlers outside of this dummy-frame. What happens
13038 in that case is controlled by the
13039 @code{set unwind-on-terminating-exception} command.
13042 @item set unwindonsignal
13043 @kindex set unwindonsignal
13044 @cindex unwind stack in called functions
13045 @cindex call dummy stack unwinding
13046 Set unwinding of the stack if a signal is received while in a function
13047 that @value{GDBN} called in the program being debugged. If set to on,
13048 @value{GDBN} unwinds the stack it created for the call and restores
13049 the context to what it was before the call. If set to off (the
13050 default), @value{GDBN} stops in the frame where the signal was
13053 @item show unwindonsignal
13054 @kindex show unwindonsignal
13055 Show the current setting of stack unwinding in the functions called by
13058 @item set unwind-on-terminating-exception
13059 @kindex set unwind-on-terminating-exception
13060 @cindex unwind stack in called functions with unhandled exceptions
13061 @cindex call dummy stack unwinding on unhandled exception.
13062 Set unwinding of the stack if a C@t{++} exception is raised, but left
13063 unhandled while in a function that @value{GDBN} called in the program being
13064 debugged. If set to on (the default), @value{GDBN} unwinds the stack
13065 it created for the call and restores the context to what it was before
13066 the call. If set to off, @value{GDBN} the exception is delivered to
13067 the default C@t{++} exception handler and the inferior terminated.
13069 @item show unwind-on-terminating-exception
13070 @kindex show unwind-on-terminating-exception
13071 Show the current setting of stack unwinding in the functions called by
13076 @cindex weak alias functions
13077 Sometimes, a function you wish to call is actually a @dfn{weak alias}
13078 for another function. In such case, @value{GDBN} might not pick up
13079 the type information, including the types of the function arguments,
13080 which causes @value{GDBN} to call the inferior function incorrectly.
13081 As a result, the called function will function erroneously and may
13082 even crash. A solution to that is to use the name of the aliased
13086 @section Patching Programs
13088 @cindex patching binaries
13089 @cindex writing into executables
13090 @cindex writing into corefiles
13092 By default, @value{GDBN} opens the file containing your program's
13093 executable code (or the corefile) read-only. This prevents accidental
13094 alterations to machine code; but it also prevents you from intentionally
13095 patching your program's binary.
13097 If you'd like to be able to patch the binary, you can specify that
13098 explicitly with the @code{set write} command. For example, you might
13099 want to turn on internal debugging flags, or even to make emergency
13105 @itemx set write off
13106 If you specify @samp{set write on}, @value{GDBN} opens executable and
13107 core files for both reading and writing; if you specify @kbd{set write
13108 off} (the default), @value{GDBN} opens them read-only.
13110 If you have already loaded a file, you must load it again (using the
13111 @code{exec-file} or @code{core-file} command) after changing @code{set
13112 write}, for your new setting to take effect.
13116 Display whether executable files and core files are opened for writing
13117 as well as reading.
13121 @chapter @value{GDBN} Files
13123 @value{GDBN} needs to know the file name of the program to be debugged,
13124 both in order to read its symbol table and in order to start your
13125 program. To debug a core dump of a previous run, you must also tell
13126 @value{GDBN} the name of the core dump file.
13129 * Files:: Commands to specify files
13130 * Separate Debug Files:: Debugging information in separate files
13131 * Symbol Errors:: Errors reading symbol files
13132 * Data Files:: GDB data files
13136 @section Commands to Specify Files
13138 @cindex symbol table
13139 @cindex core dump file
13141 You may want to specify executable and core dump file names. The usual
13142 way to do this is at start-up time, using the arguments to
13143 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
13144 Out of @value{GDBN}}).
13146 Occasionally it is necessary to change to a different file during a
13147 @value{GDBN} session. Or you may run @value{GDBN} and forget to
13148 specify a file you want to use. Or you are debugging a remote target
13149 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
13150 Program}). In these situations the @value{GDBN} commands to specify
13151 new files are useful.
13154 @cindex executable file
13156 @item file @var{filename}
13157 Use @var{filename} as the program to be debugged. It is read for its
13158 symbols and for the contents of pure memory. It is also the program
13159 executed when you use the @code{run} command. If you do not specify a
13160 directory and the file is not found in the @value{GDBN} working directory,
13161 @value{GDBN} uses the environment variable @code{PATH} as a list of
13162 directories to search, just as the shell does when looking for a program
13163 to run. You can change the value of this variable, for both @value{GDBN}
13164 and your program, using the @code{path} command.
13166 @cindex unlinked object files
13167 @cindex patching object files
13168 You can load unlinked object @file{.o} files into @value{GDBN} using
13169 the @code{file} command. You will not be able to ``run'' an object
13170 file, but you can disassemble functions and inspect variables. Also,
13171 if the underlying BFD functionality supports it, you could use
13172 @kbd{gdb -write} to patch object files using this technique. Note
13173 that @value{GDBN} can neither interpret nor modify relocations in this
13174 case, so branches and some initialized variables will appear to go to
13175 the wrong place. But this feature is still handy from time to time.
13178 @code{file} with no argument makes @value{GDBN} discard any information it
13179 has on both executable file and the symbol table.
13182 @item exec-file @r{[} @var{filename} @r{]}
13183 Specify that the program to be run (but not the symbol table) is found
13184 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
13185 if necessary to locate your program. Omitting @var{filename} means to
13186 discard information on the executable file.
13188 @kindex symbol-file
13189 @item symbol-file @r{[} @var{filename} @r{]}
13190 Read symbol table information from file @var{filename}. @code{PATH} is
13191 searched when necessary. Use the @code{file} command to get both symbol
13192 table and program to run from the same file.
13194 @code{symbol-file} with no argument clears out @value{GDBN} information on your
13195 program's symbol table.
13197 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
13198 some breakpoints and auto-display expressions. This is because they may
13199 contain pointers to the internal data recording symbols and data types,
13200 which are part of the old symbol table data being discarded inside
13203 @code{symbol-file} does not repeat if you press @key{RET} again after
13206 When @value{GDBN} is configured for a particular environment, it
13207 understands debugging information in whatever format is the standard
13208 generated for that environment; you may use either a @sc{gnu} compiler, or
13209 other compilers that adhere to the local conventions.
13210 Best results are usually obtained from @sc{gnu} compilers; for example,
13211 using @code{@value{NGCC}} you can generate debugging information for
13214 For most kinds of object files, with the exception of old SVR3 systems
13215 using COFF, the @code{symbol-file} command does not normally read the
13216 symbol table in full right away. Instead, it scans the symbol table
13217 quickly to find which source files and which symbols are present. The
13218 details are read later, one source file at a time, as they are needed.
13220 The purpose of this two-stage reading strategy is to make @value{GDBN}
13221 start up faster. For the most part, it is invisible except for
13222 occasional pauses while the symbol table details for a particular source
13223 file are being read. (The @code{set verbose} command can turn these
13224 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
13225 Warnings and Messages}.)
13227 We have not implemented the two-stage strategy for COFF yet. When the
13228 symbol table is stored in COFF format, @code{symbol-file} reads the
13229 symbol table data in full right away. Note that ``stabs-in-COFF''
13230 still does the two-stage strategy, since the debug info is actually
13234 @cindex reading symbols immediately
13235 @cindex symbols, reading immediately
13236 @item symbol-file @var{filename} @r{[} -readnow @r{]}
13237 @itemx file @var{filename} @r{[} -readnow @r{]}
13238 You can override the @value{GDBN} two-stage strategy for reading symbol
13239 tables by using the @samp{-readnow} option with any of the commands that
13240 load symbol table information, if you want to be sure @value{GDBN} has the
13241 entire symbol table available.
13243 @c FIXME: for now no mention of directories, since this seems to be in
13244 @c flux. 13mar1992 status is that in theory GDB would look either in
13245 @c current dir or in same dir as myprog; but issues like competing
13246 @c GDB's, or clutter in system dirs, mean that in practice right now
13247 @c only current dir is used. FFish says maybe a special GDB hierarchy
13248 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
13252 @item core-file @r{[}@var{filename}@r{]}
13254 Specify the whereabouts of a core dump file to be used as the ``contents
13255 of memory''. Traditionally, core files contain only some parts of the
13256 address space of the process that generated them; @value{GDBN} can access the
13257 executable file itself for other parts.
13259 @code{core-file} with no argument specifies that no core file is
13262 Note that the core file is ignored when your program is actually running
13263 under @value{GDBN}. So, if you have been running your program and you
13264 wish to debug a core file instead, you must kill the subprocess in which
13265 the program is running. To do this, use the @code{kill} command
13266 (@pxref{Kill Process, ,Killing the Child Process}).
13268 @kindex add-symbol-file
13269 @cindex dynamic linking
13270 @item add-symbol-file @var{filename} @var{address}
13271 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
13272 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
13273 The @code{add-symbol-file} command reads additional symbol table
13274 information from the file @var{filename}. You would use this command
13275 when @var{filename} has been dynamically loaded (by some other means)
13276 into the program that is running. @var{address} should be the memory
13277 address at which the file has been loaded; @value{GDBN} cannot figure
13278 this out for itself. You can additionally specify an arbitrary number
13279 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
13280 section name and base address for that section. You can specify any
13281 @var{address} as an expression.
13283 The symbol table of the file @var{filename} is added to the symbol table
13284 originally read with the @code{symbol-file} command. You can use the
13285 @code{add-symbol-file} command any number of times; the new symbol data
13286 thus read keeps adding to the old. To discard all old symbol data
13287 instead, use the @code{symbol-file} command without any arguments.
13289 @cindex relocatable object files, reading symbols from
13290 @cindex object files, relocatable, reading symbols from
13291 @cindex reading symbols from relocatable object files
13292 @cindex symbols, reading from relocatable object files
13293 @cindex @file{.o} files, reading symbols from
13294 Although @var{filename} is typically a shared library file, an
13295 executable file, or some other object file which has been fully
13296 relocated for loading into a process, you can also load symbolic
13297 information from relocatable @file{.o} files, as long as:
13301 the file's symbolic information refers only to linker symbols defined in
13302 that file, not to symbols defined by other object files,
13304 every section the file's symbolic information refers to has actually
13305 been loaded into the inferior, as it appears in the file, and
13307 you can determine the address at which every section was loaded, and
13308 provide these to the @code{add-symbol-file} command.
13312 Some embedded operating systems, like Sun Chorus and VxWorks, can load
13313 relocatable files into an already running program; such systems
13314 typically make the requirements above easy to meet. However, it's
13315 important to recognize that many native systems use complex link
13316 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
13317 assembly, for example) that make the requirements difficult to meet. In
13318 general, one cannot assume that using @code{add-symbol-file} to read a
13319 relocatable object file's symbolic information will have the same effect
13320 as linking the relocatable object file into the program in the normal
13323 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
13325 @kindex add-symbol-file-from-memory
13326 @cindex @code{syscall DSO}
13327 @cindex load symbols from memory
13328 @item add-symbol-file-from-memory @var{address}
13329 Load symbols from the given @var{address} in a dynamically loaded
13330 object file whose image is mapped directly into the inferior's memory.
13331 For example, the Linux kernel maps a @code{syscall DSO} into each
13332 process's address space; this DSO provides kernel-specific code for
13333 some system calls. The argument can be any expression whose
13334 evaluation yields the address of the file's shared object file header.
13335 For this command to work, you must have used @code{symbol-file} or
13336 @code{exec-file} commands in advance.
13338 @kindex add-shared-symbol-files
13340 @item add-shared-symbol-files @var{library-file}
13341 @itemx assf @var{library-file}
13342 The @code{add-shared-symbol-files} command can currently be used only
13343 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
13344 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
13345 @value{GDBN} automatically looks for shared libraries, however if
13346 @value{GDBN} does not find yours, you can invoke
13347 @code{add-shared-symbol-files}. It takes one argument: the shared
13348 library's file name. @code{assf} is a shorthand alias for
13349 @code{add-shared-symbol-files}.
13352 @item section @var{section} @var{addr}
13353 The @code{section} command changes the base address of the named
13354 @var{section} of the exec file to @var{addr}. This can be used if the
13355 exec file does not contain section addresses, (such as in the
13356 @code{a.out} format), or when the addresses specified in the file
13357 itself are wrong. Each section must be changed separately. The
13358 @code{info files} command, described below, lists all the sections and
13362 @kindex info target
13365 @code{info files} and @code{info target} are synonymous; both print the
13366 current target (@pxref{Targets, ,Specifying a Debugging Target}),
13367 including the names of the executable and core dump files currently in
13368 use by @value{GDBN}, and the files from which symbols were loaded. The
13369 command @code{help target} lists all possible targets rather than
13372 @kindex maint info sections
13373 @item maint info sections
13374 Another command that can give you extra information about program sections
13375 is @code{maint info sections}. In addition to the section information
13376 displayed by @code{info files}, this command displays the flags and file
13377 offset of each section in the executable and core dump files. In addition,
13378 @code{maint info sections} provides the following command options (which
13379 may be arbitrarily combined):
13383 Display sections for all loaded object files, including shared libraries.
13384 @item @var{sections}
13385 Display info only for named @var{sections}.
13386 @item @var{section-flags}
13387 Display info only for sections for which @var{section-flags} are true.
13388 The section flags that @value{GDBN} currently knows about are:
13391 Section will have space allocated in the process when loaded.
13392 Set for all sections except those containing debug information.
13394 Section will be loaded from the file into the child process memory.
13395 Set for pre-initialized code and data, clear for @code{.bss} sections.
13397 Section needs to be relocated before loading.
13399 Section cannot be modified by the child process.
13401 Section contains executable code only.
13403 Section contains data only (no executable code).
13405 Section will reside in ROM.
13407 Section contains data for constructor/destructor lists.
13409 Section is not empty.
13411 An instruction to the linker to not output the section.
13412 @item COFF_SHARED_LIBRARY
13413 A notification to the linker that the section contains
13414 COFF shared library information.
13416 Section contains common symbols.
13419 @kindex set trust-readonly-sections
13420 @cindex read-only sections
13421 @item set trust-readonly-sections on
13422 Tell @value{GDBN} that readonly sections in your object file
13423 really are read-only (i.e.@: that their contents will not change).
13424 In that case, @value{GDBN} can fetch values from these sections
13425 out of the object file, rather than from the target program.
13426 For some targets (notably embedded ones), this can be a significant
13427 enhancement to debugging performance.
13429 The default is off.
13431 @item set trust-readonly-sections off
13432 Tell @value{GDBN} not to trust readonly sections. This means that
13433 the contents of the section might change while the program is running,
13434 and must therefore be fetched from the target when needed.
13436 @item show trust-readonly-sections
13437 Show the current setting of trusting readonly sections.
13440 All file-specifying commands allow both absolute and relative file names
13441 as arguments. @value{GDBN} always converts the file name to an absolute file
13442 name and remembers it that way.
13444 @cindex shared libraries
13445 @anchor{Shared Libraries}
13446 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
13447 and IBM RS/6000 AIX shared libraries.
13449 On MS-Windows @value{GDBN} must be linked with the Expat library to support
13450 shared libraries. @xref{Expat}.
13452 @value{GDBN} automatically loads symbol definitions from shared libraries
13453 when you use the @code{run} command, or when you examine a core file.
13454 (Before you issue the @code{run} command, @value{GDBN} does not understand
13455 references to a function in a shared library, however---unless you are
13456 debugging a core file).
13458 On HP-UX, if the program loads a library explicitly, @value{GDBN}
13459 automatically loads the symbols at the time of the @code{shl_load} call.
13461 @c FIXME: some @value{GDBN} release may permit some refs to undef
13462 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
13463 @c FIXME...lib; check this from time to time when updating manual
13465 There are times, however, when you may wish to not automatically load
13466 symbol definitions from shared libraries, such as when they are
13467 particularly large or there are many of them.
13469 To control the automatic loading of shared library symbols, use the
13473 @kindex set auto-solib-add
13474 @item set auto-solib-add @var{mode}
13475 If @var{mode} is @code{on}, symbols from all shared object libraries
13476 will be loaded automatically when the inferior begins execution, you
13477 attach to an independently started inferior, or when the dynamic linker
13478 informs @value{GDBN} that a new library has been loaded. If @var{mode}
13479 is @code{off}, symbols must be loaded manually, using the
13480 @code{sharedlibrary} command. The default value is @code{on}.
13482 @cindex memory used for symbol tables
13483 If your program uses lots of shared libraries with debug info that
13484 takes large amounts of memory, you can decrease the @value{GDBN}
13485 memory footprint by preventing it from automatically loading the
13486 symbols from shared libraries. To that end, type @kbd{set
13487 auto-solib-add off} before running the inferior, then load each
13488 library whose debug symbols you do need with @kbd{sharedlibrary
13489 @var{regexp}}, where @var{regexp} is a regular expression that matches
13490 the libraries whose symbols you want to be loaded.
13492 @kindex show auto-solib-add
13493 @item show auto-solib-add
13494 Display the current autoloading mode.
13497 @cindex load shared library
13498 To explicitly load shared library symbols, use the @code{sharedlibrary}
13502 @kindex info sharedlibrary
13505 @itemx info sharedlibrary
13506 Print the names of the shared libraries which are currently loaded.
13508 @kindex sharedlibrary
13510 @item sharedlibrary @var{regex}
13511 @itemx share @var{regex}
13512 Load shared object library symbols for files matching a
13513 Unix regular expression.
13514 As with files loaded automatically, it only loads shared libraries
13515 required by your program for a core file or after typing @code{run}. If
13516 @var{regex} is omitted all shared libraries required by your program are
13519 @item nosharedlibrary
13520 @kindex nosharedlibrary
13521 @cindex unload symbols from shared libraries
13522 Unload all shared object library symbols. This discards all symbols
13523 that have been loaded from all shared libraries. Symbols from shared
13524 libraries that were loaded by explicit user requests are not
13528 Sometimes you may wish that @value{GDBN} stops and gives you control
13529 when any of shared library events happen. Use the @code{set
13530 stop-on-solib-events} command for this:
13533 @item set stop-on-solib-events
13534 @kindex set stop-on-solib-events
13535 This command controls whether @value{GDBN} should give you control
13536 when the dynamic linker notifies it about some shared library event.
13537 The most common event of interest is loading or unloading of a new
13540 @item show stop-on-solib-events
13541 @kindex show stop-on-solib-events
13542 Show whether @value{GDBN} stops and gives you control when shared
13543 library events happen.
13546 Shared libraries are also supported in many cross or remote debugging
13547 configurations. @value{GDBN} needs to have access to the target's libraries;
13548 this can be accomplished either by providing copies of the libraries
13549 on the host system, or by asking @value{GDBN} to automatically retrieve the
13550 libraries from the target. If copies of the target libraries are
13551 provided, they need to be the same as the target libraries, although the
13552 copies on the target can be stripped as long as the copies on the host are
13555 @cindex where to look for shared libraries
13556 For remote debugging, you need to tell @value{GDBN} where the target
13557 libraries are, so that it can load the correct copies---otherwise, it
13558 may try to load the host's libraries. @value{GDBN} has two variables
13559 to specify the search directories for target libraries.
13562 @cindex prefix for shared library file names
13563 @cindex system root, alternate
13564 @kindex set solib-absolute-prefix
13565 @kindex set sysroot
13566 @item set sysroot @var{path}
13567 Use @var{path} as the system root for the program being debugged. Any
13568 absolute shared library paths will be prefixed with @var{path}; many
13569 runtime loaders store the absolute paths to the shared library in the
13570 target program's memory. If you use @code{set sysroot} to find shared
13571 libraries, they need to be laid out in the same way that they are on
13572 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
13575 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
13576 retrieve the target libraries from the remote system. This is only
13577 supported when using a remote target that supports the @code{remote get}
13578 command (@pxref{File Transfer,,Sending files to a remote system}).
13579 The part of @var{path} following the initial @file{remote:}
13580 (if present) is used as system root prefix on the remote file system.
13581 @footnote{If you want to specify a local system root using a directory
13582 that happens to be named @file{remote:}, you need to use some equivalent
13583 variant of the name like @file{./remote:}.}
13585 The @code{set solib-absolute-prefix} command is an alias for @code{set
13588 @cindex default system root
13589 @cindex @samp{--with-sysroot}
13590 You can set the default system root by using the configure-time
13591 @samp{--with-sysroot} option. If the system root is inside
13592 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
13593 @samp{--exec-prefix}), then the default system root will be updated
13594 automatically if the installed @value{GDBN} is moved to a new
13597 @kindex show sysroot
13599 Display the current shared library prefix.
13601 @kindex set solib-search-path
13602 @item set solib-search-path @var{path}
13603 If this variable is set, @var{path} is a colon-separated list of
13604 directories to search for shared libraries. @samp{solib-search-path}
13605 is used after @samp{sysroot} fails to locate the library, or if the
13606 path to the library is relative instead of absolute. If you want to
13607 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
13608 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
13609 finding your host's libraries. @samp{sysroot} is preferred; setting
13610 it to a nonexistent directory may interfere with automatic loading
13611 of shared library symbols.
13613 @kindex show solib-search-path
13614 @item show solib-search-path
13615 Display the current shared library search path.
13619 @node Separate Debug Files
13620 @section Debugging Information in Separate Files
13621 @cindex separate debugging information files
13622 @cindex debugging information in separate files
13623 @cindex @file{.debug} subdirectories
13624 @cindex debugging information directory, global
13625 @cindex global debugging information directory
13626 @cindex build ID, and separate debugging files
13627 @cindex @file{.build-id} directory
13629 @value{GDBN} allows you to put a program's debugging information in a
13630 file separate from the executable itself, in a way that allows
13631 @value{GDBN} to find and load the debugging information automatically.
13632 Since debugging information can be very large---sometimes larger
13633 than the executable code itself---some systems distribute debugging
13634 information for their executables in separate files, which users can
13635 install only when they need to debug a problem.
13637 @value{GDBN} supports two ways of specifying the separate debug info
13642 The executable contains a @dfn{debug link} that specifies the name of
13643 the separate debug info file. The separate debug file's name is
13644 usually @file{@var{executable}.debug}, where @var{executable} is the
13645 name of the corresponding executable file without leading directories
13646 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
13647 debug link specifies a CRC32 checksum for the debug file, which
13648 @value{GDBN} uses to validate that the executable and the debug file
13649 came from the same build.
13652 The executable contains a @dfn{build ID}, a unique bit string that is
13653 also present in the corresponding debug info file. (This is supported
13654 only on some operating systems, notably those which use the ELF format
13655 for binary files and the @sc{gnu} Binutils.) For more details about
13656 this feature, see the description of the @option{--build-id}
13657 command-line option in @ref{Options, , Command Line Options, ld.info,
13658 The GNU Linker}. The debug info file's name is not specified
13659 explicitly by the build ID, but can be computed from the build ID, see
13663 Depending on the way the debug info file is specified, @value{GDBN}
13664 uses two different methods of looking for the debug file:
13668 For the ``debug link'' method, @value{GDBN} looks up the named file in
13669 the directory of the executable file, then in a subdirectory of that
13670 directory named @file{.debug}, and finally under the global debug
13671 directory, in a subdirectory whose name is identical to the leading
13672 directories of the executable's absolute file name.
13675 For the ``build ID'' method, @value{GDBN} looks in the
13676 @file{.build-id} subdirectory of the global debug directory for a file
13677 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
13678 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
13679 are the rest of the bit string. (Real build ID strings are 32 or more
13680 hex characters, not 10.)
13683 So, for example, suppose you ask @value{GDBN} to debug
13684 @file{/usr/bin/ls}, which has a debug link that specifies the
13685 file @file{ls.debug}, and a build ID whose value in hex is
13686 @code{abcdef1234}. If the global debug directory is
13687 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
13688 debug information files, in the indicated order:
13692 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
13694 @file{/usr/bin/ls.debug}
13696 @file{/usr/bin/.debug/ls.debug}
13698 @file{/usr/lib/debug/usr/bin/ls.debug}.
13701 You can set the global debugging info directory's name, and view the
13702 name @value{GDBN} is currently using.
13706 @kindex set debug-file-directory
13707 @item set debug-file-directory @var{directory}
13708 Set the directory which @value{GDBN} searches for separate debugging
13709 information files to @var{directory}.
13711 @kindex show debug-file-directory
13712 @item show debug-file-directory
13713 Show the directory @value{GDBN} searches for separate debugging
13718 @cindex @code{.gnu_debuglink} sections
13719 @cindex debug link sections
13720 A debug link is a special section of the executable file named
13721 @code{.gnu_debuglink}. The section must contain:
13725 A filename, with any leading directory components removed, followed by
13728 zero to three bytes of padding, as needed to reach the next four-byte
13729 boundary within the section, and
13731 a four-byte CRC checksum, stored in the same endianness used for the
13732 executable file itself. The checksum is computed on the debugging
13733 information file's full contents by the function given below, passing
13734 zero as the @var{crc} argument.
13737 Any executable file format can carry a debug link, as long as it can
13738 contain a section named @code{.gnu_debuglink} with the contents
13741 @cindex @code{.note.gnu.build-id} sections
13742 @cindex build ID sections
13743 The build ID is a special section in the executable file (and in other
13744 ELF binary files that @value{GDBN} may consider). This section is
13745 often named @code{.note.gnu.build-id}, but that name is not mandatory.
13746 It contains unique identification for the built files---the ID remains
13747 the same across multiple builds of the same build tree. The default
13748 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
13749 content for the build ID string. The same section with an identical
13750 value is present in the original built binary with symbols, in its
13751 stripped variant, and in the separate debugging information file.
13753 The debugging information file itself should be an ordinary
13754 executable, containing a full set of linker symbols, sections, and
13755 debugging information. The sections of the debugging information file
13756 should have the same names, addresses, and sizes as the original file,
13757 but they need not contain any data---much like a @code{.bss} section
13758 in an ordinary executable.
13760 The @sc{gnu} binary utilities (Binutils) package includes the
13761 @samp{objcopy} utility that can produce
13762 the separated executable / debugging information file pairs using the
13763 following commands:
13766 @kbd{objcopy --only-keep-debug foo foo.debug}
13771 These commands remove the debugging
13772 information from the executable file @file{foo} and place it in the file
13773 @file{foo.debug}. You can use the first, second or both methods to link the
13778 The debug link method needs the following additional command to also leave
13779 behind a debug link in @file{foo}:
13782 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
13785 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
13786 a version of the @code{strip} command such that the command @kbd{strip foo -f
13787 foo.debug} has the same functionality as the two @code{objcopy} commands and
13788 the @code{ln -s} command above, together.
13791 Build ID gets embedded into the main executable using @code{ld --build-id} or
13792 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
13793 compatibility fixes for debug files separation are present in @sc{gnu} binary
13794 utilities (Binutils) package since version 2.18.
13799 Since there are many different ways to compute CRC's for the debug
13800 link (different polynomials, reversals, byte ordering, etc.), the
13801 simplest way to describe the CRC used in @code{.gnu_debuglink}
13802 sections is to give the complete code for a function that computes it:
13804 @kindex gnu_debuglink_crc32
13807 gnu_debuglink_crc32 (unsigned long crc,
13808 unsigned char *buf, size_t len)
13810 static const unsigned long crc32_table[256] =
13812 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
13813 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
13814 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
13815 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
13816 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
13817 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
13818 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
13819 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
13820 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
13821 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
13822 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
13823 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
13824 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
13825 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
13826 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
13827 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
13828 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
13829 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
13830 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
13831 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
13832 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
13833 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
13834 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
13835 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
13836 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
13837 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
13838 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
13839 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
13840 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
13841 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
13842 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
13843 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
13844 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
13845 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
13846 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
13847 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
13848 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
13849 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
13850 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
13851 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
13852 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
13853 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
13854 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
13855 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
13856 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
13857 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
13858 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
13859 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
13860 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
13861 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
13862 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
13865 unsigned char *end;
13867 crc = ~crc & 0xffffffff;
13868 for (end = buf + len; buf < end; ++buf)
13869 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
13870 return ~crc & 0xffffffff;
13875 This computation does not apply to the ``build ID'' method.
13878 @node Symbol Errors
13879 @section Errors Reading Symbol Files
13881 While reading a symbol file, @value{GDBN} occasionally encounters problems,
13882 such as symbol types it does not recognize, or known bugs in compiler
13883 output. By default, @value{GDBN} does not notify you of such problems, since
13884 they are relatively common and primarily of interest to people
13885 debugging compilers. If you are interested in seeing information
13886 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
13887 only one message about each such type of problem, no matter how many
13888 times the problem occurs; or you can ask @value{GDBN} to print more messages,
13889 to see how many times the problems occur, with the @code{set
13890 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
13893 The messages currently printed, and their meanings, include:
13896 @item inner block not inside outer block in @var{symbol}
13898 The symbol information shows where symbol scopes begin and end
13899 (such as at the start of a function or a block of statements). This
13900 error indicates that an inner scope block is not fully contained
13901 in its outer scope blocks.
13903 @value{GDBN} circumvents the problem by treating the inner block as if it had
13904 the same scope as the outer block. In the error message, @var{symbol}
13905 may be shown as ``@code{(don't know)}'' if the outer block is not a
13908 @item block at @var{address} out of order
13910 The symbol information for symbol scope blocks should occur in
13911 order of increasing addresses. This error indicates that it does not
13914 @value{GDBN} does not circumvent this problem, and has trouble
13915 locating symbols in the source file whose symbols it is reading. (You
13916 can often determine what source file is affected by specifying
13917 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
13920 @item bad block start address patched
13922 The symbol information for a symbol scope block has a start address
13923 smaller than the address of the preceding source line. This is known
13924 to occur in the SunOS 4.1.1 (and earlier) C compiler.
13926 @value{GDBN} circumvents the problem by treating the symbol scope block as
13927 starting on the previous source line.
13929 @item bad string table offset in symbol @var{n}
13932 Symbol number @var{n} contains a pointer into the string table which is
13933 larger than the size of the string table.
13935 @value{GDBN} circumvents the problem by considering the symbol to have the
13936 name @code{foo}, which may cause other problems if many symbols end up
13939 @item unknown symbol type @code{0x@var{nn}}
13941 The symbol information contains new data types that @value{GDBN} does
13942 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
13943 uncomprehended information, in hexadecimal.
13945 @value{GDBN} circumvents the error by ignoring this symbol information.
13946 This usually allows you to debug your program, though certain symbols
13947 are not accessible. If you encounter such a problem and feel like
13948 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
13949 on @code{complain}, then go up to the function @code{read_dbx_symtab}
13950 and examine @code{*bufp} to see the symbol.
13952 @item stub type has NULL name
13954 @value{GDBN} could not find the full definition for a struct or class.
13956 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
13957 The symbol information for a C@t{++} member function is missing some
13958 information that recent versions of the compiler should have output for
13961 @item info mismatch between compiler and debugger
13963 @value{GDBN} could not parse a type specification output by the compiler.
13968 @section GDB Data Files
13970 @cindex prefix for data files
13971 @value{GDBN} will sometimes read an auxiliary data file. These files
13972 are kept in a directory known as the @dfn{data directory}.
13974 You can set the data directory's name, and view the name @value{GDBN}
13975 is currently using.
13978 @kindex set data-directory
13979 @item set data-directory @var{directory}
13980 Set the directory which @value{GDBN} searches for auxiliary data files
13981 to @var{directory}.
13983 @kindex show data-directory
13984 @item show data-directory
13985 Show the directory @value{GDBN} searches for auxiliary data files.
13988 @cindex default data directory
13989 @cindex @samp{--with-gdb-datadir}
13990 You can set the default data directory by using the configure-time
13991 @samp{--with-gdb-datadir} option. If the data directory is inside
13992 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
13993 @samp{--exec-prefix}), then the default data directory will be updated
13994 automatically if the installed @value{GDBN} is moved to a new
13998 @chapter Specifying a Debugging Target
14000 @cindex debugging target
14001 A @dfn{target} is the execution environment occupied by your program.
14003 Often, @value{GDBN} runs in the same host environment as your program;
14004 in that case, the debugging target is specified as a side effect when
14005 you use the @code{file} or @code{core} commands. When you need more
14006 flexibility---for example, running @value{GDBN} on a physically separate
14007 host, or controlling a standalone system over a serial port or a
14008 realtime system over a TCP/IP connection---you can use the @code{target}
14009 command to specify one of the target types configured for @value{GDBN}
14010 (@pxref{Target Commands, ,Commands for Managing Targets}).
14012 @cindex target architecture
14013 It is possible to build @value{GDBN} for several different @dfn{target
14014 architectures}. When @value{GDBN} is built like that, you can choose
14015 one of the available architectures with the @kbd{set architecture}
14019 @kindex set architecture
14020 @kindex show architecture
14021 @item set architecture @var{arch}
14022 This command sets the current target architecture to @var{arch}. The
14023 value of @var{arch} can be @code{"auto"}, in addition to one of the
14024 supported architectures.
14026 @item show architecture
14027 Show the current target architecture.
14029 @item set processor
14031 @kindex set processor
14032 @kindex show processor
14033 These are alias commands for, respectively, @code{set architecture}
14034 and @code{show architecture}.
14038 * Active Targets:: Active targets
14039 * Target Commands:: Commands for managing targets
14040 * Byte Order:: Choosing target byte order
14043 @node Active Targets
14044 @section Active Targets
14046 @cindex stacking targets
14047 @cindex active targets
14048 @cindex multiple targets
14050 There are three classes of targets: processes, core files, and
14051 executable files. @value{GDBN} can work concurrently on up to three
14052 active targets, one in each class. This allows you to (for example)
14053 start a process and inspect its activity without abandoning your work on
14056 For example, if you execute @samp{gdb a.out}, then the executable file
14057 @code{a.out} is the only active target. If you designate a core file as
14058 well---presumably from a prior run that crashed and coredumped---then
14059 @value{GDBN} has two active targets and uses them in tandem, looking
14060 first in the corefile target, then in the executable file, to satisfy
14061 requests for memory addresses. (Typically, these two classes of target
14062 are complementary, since core files contain only a program's
14063 read-write memory---variables and so on---plus machine status, while
14064 executable files contain only the program text and initialized data.)
14066 When you type @code{run}, your executable file becomes an active process
14067 target as well. When a process target is active, all @value{GDBN}
14068 commands requesting memory addresses refer to that target; addresses in
14069 an active core file or executable file target are obscured while the
14070 process target is active.
14072 Use the @code{core-file} and @code{exec-file} commands to select a new
14073 core file or executable target (@pxref{Files, ,Commands to Specify
14074 Files}). To specify as a target a process that is already running, use
14075 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
14078 @node Target Commands
14079 @section Commands for Managing Targets
14082 @item target @var{type} @var{parameters}
14083 Connects the @value{GDBN} host environment to a target machine or
14084 process. A target is typically a protocol for talking to debugging
14085 facilities. You use the argument @var{type} to specify the type or
14086 protocol of the target machine.
14088 Further @var{parameters} are interpreted by the target protocol, but
14089 typically include things like device names or host names to connect
14090 with, process numbers, and baud rates.
14092 The @code{target} command does not repeat if you press @key{RET} again
14093 after executing the command.
14095 @kindex help target
14097 Displays the names of all targets available. To display targets
14098 currently selected, use either @code{info target} or @code{info files}
14099 (@pxref{Files, ,Commands to Specify Files}).
14101 @item help target @var{name}
14102 Describe a particular target, including any parameters necessary to
14105 @kindex set gnutarget
14106 @item set gnutarget @var{args}
14107 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
14108 knows whether it is reading an @dfn{executable},
14109 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
14110 with the @code{set gnutarget} command. Unlike most @code{target} commands,
14111 with @code{gnutarget} the @code{target} refers to a program, not a machine.
14114 @emph{Warning:} To specify a file format with @code{set gnutarget},
14115 you must know the actual BFD name.
14119 @xref{Files, , Commands to Specify Files}.
14121 @kindex show gnutarget
14122 @item show gnutarget
14123 Use the @code{show gnutarget} command to display what file format
14124 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
14125 @value{GDBN} will determine the file format for each file automatically,
14126 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
14129 @cindex common targets
14130 Here are some common targets (available, or not, depending on the GDB
14135 @item target exec @var{program}
14136 @cindex executable file target
14137 An executable file. @samp{target exec @var{program}} is the same as
14138 @samp{exec-file @var{program}}.
14140 @item target core @var{filename}
14141 @cindex core dump file target
14142 A core dump file. @samp{target core @var{filename}} is the same as
14143 @samp{core-file @var{filename}}.
14145 @item target remote @var{medium}
14146 @cindex remote target
14147 A remote system connected to @value{GDBN} via a serial line or network
14148 connection. This command tells @value{GDBN} to use its own remote
14149 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
14151 For example, if you have a board connected to @file{/dev/ttya} on the
14152 machine running @value{GDBN}, you could say:
14155 target remote /dev/ttya
14158 @code{target remote} supports the @code{load} command. This is only
14159 useful if you have some other way of getting the stub to the target
14160 system, and you can put it somewhere in memory where it won't get
14161 clobbered by the download.
14164 @cindex built-in simulator target
14165 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
14173 works; however, you cannot assume that a specific memory map, device
14174 drivers, or even basic I/O is available, although some simulators do
14175 provide these. For info about any processor-specific simulator details,
14176 see the appropriate section in @ref{Embedded Processors, ,Embedded
14181 Some configurations may include these targets as well:
14185 @item target nrom @var{dev}
14186 @cindex NetROM ROM emulator target
14187 NetROM ROM emulator. This target only supports downloading.
14191 Different targets are available on different configurations of @value{GDBN};
14192 your configuration may have more or fewer targets.
14194 Many remote targets require you to download the executable's code once
14195 you've successfully established a connection. You may wish to control
14196 various aspects of this process.
14201 @kindex set hash@r{, for remote monitors}
14202 @cindex hash mark while downloading
14203 This command controls whether a hash mark @samp{#} is displayed while
14204 downloading a file to the remote monitor. If on, a hash mark is
14205 displayed after each S-record is successfully downloaded to the
14209 @kindex show hash@r{, for remote monitors}
14210 Show the current status of displaying the hash mark.
14212 @item set debug monitor
14213 @kindex set debug monitor
14214 @cindex display remote monitor communications
14215 Enable or disable display of communications messages between
14216 @value{GDBN} and the remote monitor.
14218 @item show debug monitor
14219 @kindex show debug monitor
14220 Show the current status of displaying communications between
14221 @value{GDBN} and the remote monitor.
14226 @kindex load @var{filename}
14227 @item load @var{filename}
14229 Depending on what remote debugging facilities are configured into
14230 @value{GDBN}, the @code{load} command may be available. Where it exists, it
14231 is meant to make @var{filename} (an executable) available for debugging
14232 on the remote system---by downloading, or dynamic linking, for example.
14233 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
14234 the @code{add-symbol-file} command.
14236 If your @value{GDBN} does not have a @code{load} command, attempting to
14237 execute it gets the error message ``@code{You can't do that when your
14238 target is @dots{}}''
14240 The file is loaded at whatever address is specified in the executable.
14241 For some object file formats, you can specify the load address when you
14242 link the program; for other formats, like a.out, the object file format
14243 specifies a fixed address.
14244 @c FIXME! This would be a good place for an xref to the GNU linker doc.
14246 Depending on the remote side capabilities, @value{GDBN} may be able to
14247 load programs into flash memory.
14249 @code{load} does not repeat if you press @key{RET} again after using it.
14253 @section Choosing Target Byte Order
14255 @cindex choosing target byte order
14256 @cindex target byte order
14258 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
14259 offer the ability to run either big-endian or little-endian byte
14260 orders. Usually the executable or symbol will include a bit to
14261 designate the endian-ness, and you will not need to worry about
14262 which to use. However, you may still find it useful to adjust
14263 @value{GDBN}'s idea of processor endian-ness manually.
14267 @item set endian big
14268 Instruct @value{GDBN} to assume the target is big-endian.
14270 @item set endian little
14271 Instruct @value{GDBN} to assume the target is little-endian.
14273 @item set endian auto
14274 Instruct @value{GDBN} to use the byte order associated with the
14278 Display @value{GDBN}'s current idea of the target byte order.
14282 Note that these commands merely adjust interpretation of symbolic
14283 data on the host, and that they have absolutely no effect on the
14287 @node Remote Debugging
14288 @chapter Debugging Remote Programs
14289 @cindex remote debugging
14291 If you are trying to debug a program running on a machine that cannot run
14292 @value{GDBN} in the usual way, it is often useful to use remote debugging.
14293 For example, you might use remote debugging on an operating system kernel,
14294 or on a small system which does not have a general purpose operating system
14295 powerful enough to run a full-featured debugger.
14297 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
14298 to make this work with particular debugging targets. In addition,
14299 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
14300 but not specific to any particular target system) which you can use if you
14301 write the remote stubs---the code that runs on the remote system to
14302 communicate with @value{GDBN}.
14304 Other remote targets may be available in your
14305 configuration of @value{GDBN}; use @code{help target} to list them.
14308 * Connecting:: Connecting to a remote target
14309 * File Transfer:: Sending files to a remote system
14310 * Server:: Using the gdbserver program
14311 * Remote Configuration:: Remote configuration
14312 * Remote Stub:: Implementing a remote stub
14316 @section Connecting to a Remote Target
14318 On the @value{GDBN} host machine, you will need an unstripped copy of
14319 your program, since @value{GDBN} needs symbol and debugging information.
14320 Start up @value{GDBN} as usual, using the name of the local copy of your
14321 program as the first argument.
14323 @cindex @code{target remote}
14324 @value{GDBN} can communicate with the target over a serial line, or
14325 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
14326 each case, @value{GDBN} uses the same protocol for debugging your
14327 program; only the medium carrying the debugging packets varies. The
14328 @code{target remote} command establishes a connection to the target.
14329 Its arguments indicate which medium to use:
14333 @item target remote @var{serial-device}
14334 @cindex serial line, @code{target remote}
14335 Use @var{serial-device} to communicate with the target. For example,
14336 to use a serial line connected to the device named @file{/dev/ttyb}:
14339 target remote /dev/ttyb
14342 If you're using a serial line, you may want to give @value{GDBN} the
14343 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
14344 (@pxref{Remote Configuration, set remotebaud}) before the
14345 @code{target} command.
14347 @item target remote @code{@var{host}:@var{port}}
14348 @itemx target remote @code{tcp:@var{host}:@var{port}}
14349 @cindex @acronym{TCP} port, @code{target remote}
14350 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
14351 The @var{host} may be either a host name or a numeric @acronym{IP}
14352 address; @var{port} must be a decimal number. The @var{host} could be
14353 the target machine itself, if it is directly connected to the net, or
14354 it might be a terminal server which in turn has a serial line to the
14357 For example, to connect to port 2828 on a terminal server named
14361 target remote manyfarms:2828
14364 If your remote target is actually running on the same machine as your
14365 debugger session (e.g.@: a simulator for your target running on the
14366 same host), you can omit the hostname. For example, to connect to
14367 port 1234 on your local machine:
14370 target remote :1234
14374 Note that the colon is still required here.
14376 @item target remote @code{udp:@var{host}:@var{port}}
14377 @cindex @acronym{UDP} port, @code{target remote}
14378 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
14379 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
14382 target remote udp:manyfarms:2828
14385 When using a @acronym{UDP} connection for remote debugging, you should
14386 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
14387 can silently drop packets on busy or unreliable networks, which will
14388 cause havoc with your debugging session.
14390 @item target remote | @var{command}
14391 @cindex pipe, @code{target remote} to
14392 Run @var{command} in the background and communicate with it using a
14393 pipe. The @var{command} is a shell command, to be parsed and expanded
14394 by the system's command shell, @code{/bin/sh}; it should expect remote
14395 protocol packets on its standard input, and send replies on its
14396 standard output. You could use this to run a stand-alone simulator
14397 that speaks the remote debugging protocol, to make net connections
14398 using programs like @code{ssh}, or for other similar tricks.
14400 If @var{command} closes its standard output (perhaps by exiting),
14401 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
14402 program has already exited, this will have no effect.)
14406 Once the connection has been established, you can use all the usual
14407 commands to examine and change data. The remote program is already
14408 running; you can use @kbd{step} and @kbd{continue}, and you do not
14409 need to use @kbd{run}.
14411 @cindex interrupting remote programs
14412 @cindex remote programs, interrupting
14413 Whenever @value{GDBN} is waiting for the remote program, if you type the
14414 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
14415 program. This may or may not succeed, depending in part on the hardware
14416 and the serial drivers the remote system uses. If you type the
14417 interrupt character once again, @value{GDBN} displays this prompt:
14420 Interrupted while waiting for the program.
14421 Give up (and stop debugging it)? (y or n)
14424 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
14425 (If you decide you want to try again later, you can use @samp{target
14426 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
14427 goes back to waiting.
14430 @kindex detach (remote)
14432 When you have finished debugging the remote program, you can use the
14433 @code{detach} command to release it from @value{GDBN} control.
14434 Detaching from the target normally resumes its execution, but the results
14435 will depend on your particular remote stub. After the @code{detach}
14436 command, @value{GDBN} is free to connect to another target.
14440 The @code{disconnect} command behaves like @code{detach}, except that
14441 the target is generally not resumed. It will wait for @value{GDBN}
14442 (this instance or another one) to connect and continue debugging. After
14443 the @code{disconnect} command, @value{GDBN} is again free to connect to
14446 @cindex send command to remote monitor
14447 @cindex extend @value{GDBN} for remote targets
14448 @cindex add new commands for external monitor
14450 @item monitor @var{cmd}
14451 This command allows you to send arbitrary commands directly to the
14452 remote monitor. Since @value{GDBN} doesn't care about the commands it
14453 sends like this, this command is the way to extend @value{GDBN}---you
14454 can add new commands that only the external monitor will understand
14458 @node File Transfer
14459 @section Sending files to a remote system
14460 @cindex remote target, file transfer
14461 @cindex file transfer
14462 @cindex sending files to remote systems
14464 Some remote targets offer the ability to transfer files over the same
14465 connection used to communicate with @value{GDBN}. This is convenient
14466 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
14467 running @code{gdbserver} over a network interface. For other targets,
14468 e.g.@: embedded devices with only a single serial port, this may be
14469 the only way to upload or download files.
14471 Not all remote targets support these commands.
14475 @item remote put @var{hostfile} @var{targetfile}
14476 Copy file @var{hostfile} from the host system (the machine running
14477 @value{GDBN}) to @var{targetfile} on the target system.
14480 @item remote get @var{targetfile} @var{hostfile}
14481 Copy file @var{targetfile} from the target system to @var{hostfile}
14482 on the host system.
14484 @kindex remote delete
14485 @item remote delete @var{targetfile}
14486 Delete @var{targetfile} from the target system.
14491 @section Using the @code{gdbserver} Program
14494 @cindex remote connection without stubs
14495 @code{gdbserver} is a control program for Unix-like systems, which
14496 allows you to connect your program with a remote @value{GDBN} via
14497 @code{target remote}---but without linking in the usual debugging stub.
14499 @code{gdbserver} is not a complete replacement for the debugging stubs,
14500 because it requires essentially the same operating-system facilities
14501 that @value{GDBN} itself does. In fact, a system that can run
14502 @code{gdbserver} to connect to a remote @value{GDBN} could also run
14503 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
14504 because it is a much smaller program than @value{GDBN} itself. It is
14505 also easier to port than all of @value{GDBN}, so you may be able to get
14506 started more quickly on a new system by using @code{gdbserver}.
14507 Finally, if you develop code for real-time systems, you may find that
14508 the tradeoffs involved in real-time operation make it more convenient to
14509 do as much development work as possible on another system, for example
14510 by cross-compiling. You can use @code{gdbserver} to make a similar
14511 choice for debugging.
14513 @value{GDBN} and @code{gdbserver} communicate via either a serial line
14514 or a TCP connection, using the standard @value{GDBN} remote serial
14518 @emph{Warning:} @code{gdbserver} does not have any built-in security.
14519 Do not run @code{gdbserver} connected to any public network; a
14520 @value{GDBN} connection to @code{gdbserver} provides access to the
14521 target system with the same privileges as the user running
14525 @subsection Running @code{gdbserver}
14526 @cindex arguments, to @code{gdbserver}
14528 Run @code{gdbserver} on the target system. You need a copy of the
14529 program you want to debug, including any libraries it requires.
14530 @code{gdbserver} does not need your program's symbol table, so you can
14531 strip the program if necessary to save space. @value{GDBN} on the host
14532 system does all the symbol handling.
14534 To use the server, you must tell it how to communicate with @value{GDBN};
14535 the name of your program; and the arguments for your program. The usual
14539 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
14542 @var{comm} is either a device name (to use a serial line) or a TCP
14543 hostname and portnumber. For example, to debug Emacs with the argument
14544 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
14548 target> gdbserver /dev/com1 emacs foo.txt
14551 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
14554 To use a TCP connection instead of a serial line:
14557 target> gdbserver host:2345 emacs foo.txt
14560 The only difference from the previous example is the first argument,
14561 specifying that you are communicating with the host @value{GDBN} via
14562 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
14563 expect a TCP connection from machine @samp{host} to local TCP port 2345.
14564 (Currently, the @samp{host} part is ignored.) You can choose any number
14565 you want for the port number as long as it does not conflict with any
14566 TCP ports already in use on the target system (for example, @code{23} is
14567 reserved for @code{telnet}).@footnote{If you choose a port number that
14568 conflicts with another service, @code{gdbserver} prints an error message
14569 and exits.} You must use the same port number with the host @value{GDBN}
14570 @code{target remote} command.
14572 @subsubsection Attaching to a Running Program
14574 On some targets, @code{gdbserver} can also attach to running programs.
14575 This is accomplished via the @code{--attach} argument. The syntax is:
14578 target> gdbserver --attach @var{comm} @var{pid}
14581 @var{pid} is the process ID of a currently running process. It isn't necessary
14582 to point @code{gdbserver} at a binary for the running process.
14585 @cindex attach to a program by name
14586 You can debug processes by name instead of process ID if your target has the
14587 @code{pidof} utility:
14590 target> gdbserver --attach @var{comm} `pidof @var{program}`
14593 In case more than one copy of @var{program} is running, or @var{program}
14594 has multiple threads, most versions of @code{pidof} support the
14595 @code{-s} option to only return the first process ID.
14597 @subsubsection Multi-Process Mode for @code{gdbserver}
14598 @cindex gdbserver, multiple processes
14599 @cindex multiple processes with gdbserver
14601 When you connect to @code{gdbserver} using @code{target remote},
14602 @code{gdbserver} debugs the specified program only once. When the
14603 program exits, or you detach from it, @value{GDBN} closes the connection
14604 and @code{gdbserver} exits.
14606 If you connect using @kbd{target extended-remote}, @code{gdbserver}
14607 enters multi-process mode. When the debugged program exits, or you
14608 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
14609 though no program is running. The @code{run} and @code{attach}
14610 commands instruct @code{gdbserver} to run or attach to a new program.
14611 The @code{run} command uses @code{set remote exec-file} (@pxref{set
14612 remote exec-file}) to select the program to run. Command line
14613 arguments are supported, except for wildcard expansion and I/O
14614 redirection (@pxref{Arguments}).
14616 To start @code{gdbserver} without supplying an initial command to run
14617 or process ID to attach, use the @option{--multi} command line option.
14618 Then you can connect using @kbd{target extended-remote} and start
14619 the program you want to debug.
14621 @code{gdbserver} does not automatically exit in multi-process mode.
14622 You can terminate it by using @code{monitor exit}
14623 (@pxref{Monitor Commands for gdbserver}).
14625 @subsubsection Other Command-Line Arguments for @code{gdbserver}
14627 The @option{--debug} option tells @code{gdbserver} to display extra
14628 status information about the debugging process. The
14629 @option{--remote-debug} option tells @code{gdbserver} to display
14630 remote protocol debug output. These options are intended for
14631 @code{gdbserver} development and for bug reports to the developers.
14633 The @option{--wrapper} option specifies a wrapper to launch programs
14634 for debugging. The option should be followed by the name of the
14635 wrapper, then any command-line arguments to pass to the wrapper, then
14636 @kbd{--} indicating the end of the wrapper arguments.
14638 @code{gdbserver} runs the specified wrapper program with a combined
14639 command line including the wrapper arguments, then the name of the
14640 program to debug, then any arguments to the program. The wrapper
14641 runs until it executes your program, and then @value{GDBN} gains control.
14643 You can use any program that eventually calls @code{execve} with
14644 its arguments as a wrapper. Several standard Unix utilities do
14645 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
14646 with @code{exec "$@@"} will also work.
14648 For example, you can use @code{env} to pass an environment variable to
14649 the debugged program, without setting the variable in @code{gdbserver}'s
14653 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
14656 @subsection Connecting to @code{gdbserver}
14658 Run @value{GDBN} on the host system.
14660 First make sure you have the necessary symbol files. Load symbols for
14661 your application using the @code{file} command before you connect. Use
14662 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
14663 was compiled with the correct sysroot using @code{--with-sysroot}).
14665 The symbol file and target libraries must exactly match the executable
14666 and libraries on the target, with one exception: the files on the host
14667 system should not be stripped, even if the files on the target system
14668 are. Mismatched or missing files will lead to confusing results
14669 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
14670 files may also prevent @code{gdbserver} from debugging multi-threaded
14673 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
14674 For TCP connections, you must start up @code{gdbserver} prior to using
14675 the @code{target remote} command. Otherwise you may get an error whose
14676 text depends on the host system, but which usually looks something like
14677 @samp{Connection refused}. Don't use the @code{load}
14678 command in @value{GDBN} when using @code{gdbserver}, since the program is
14679 already on the target.
14681 @subsection Monitor Commands for @code{gdbserver}
14682 @cindex monitor commands, for @code{gdbserver}
14683 @anchor{Monitor Commands for gdbserver}
14685 During a @value{GDBN} session using @code{gdbserver}, you can use the
14686 @code{monitor} command to send special requests to @code{gdbserver}.
14687 Here are the available commands.
14691 List the available monitor commands.
14693 @item monitor set debug 0
14694 @itemx monitor set debug 1
14695 Disable or enable general debugging messages.
14697 @item monitor set remote-debug 0
14698 @itemx monitor set remote-debug 1
14699 Disable or enable specific debugging messages associated with the remote
14700 protocol (@pxref{Remote Protocol}).
14703 Tell gdbserver to exit immediately. This command should be followed by
14704 @code{disconnect} to close the debugging session. @code{gdbserver} will
14705 detach from any attached processes and kill any processes it created.
14706 Use @code{monitor exit} to terminate @code{gdbserver} at the end
14707 of a multi-process mode debug session.
14711 @node Remote Configuration
14712 @section Remote Configuration
14715 @kindex show remote
14716 This section documents the configuration options available when
14717 debugging remote programs. For the options related to the File I/O
14718 extensions of the remote protocol, see @ref{system,
14719 system-call-allowed}.
14722 @item set remoteaddresssize @var{bits}
14723 @cindex address size for remote targets
14724 @cindex bits in remote address
14725 Set the maximum size of address in a memory packet to the specified
14726 number of bits. @value{GDBN} will mask off the address bits above
14727 that number, when it passes addresses to the remote target. The
14728 default value is the number of bits in the target's address.
14730 @item show remoteaddresssize
14731 Show the current value of remote address size in bits.
14733 @item set remotebaud @var{n}
14734 @cindex baud rate for remote targets
14735 Set the baud rate for the remote serial I/O to @var{n} baud. The
14736 value is used to set the speed of the serial port used for debugging
14739 @item show remotebaud
14740 Show the current speed of the remote connection.
14742 @item set remotebreak
14743 @cindex interrupt remote programs
14744 @cindex BREAK signal instead of Ctrl-C
14745 @anchor{set remotebreak}
14746 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
14747 when you type @kbd{Ctrl-c} to interrupt the program running
14748 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
14749 character instead. The default is off, since most remote systems
14750 expect to see @samp{Ctrl-C} as the interrupt signal.
14752 @item show remotebreak
14753 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
14754 interrupt the remote program.
14756 @item set remoteflow on
14757 @itemx set remoteflow off
14758 @kindex set remoteflow
14759 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
14760 on the serial port used to communicate to the remote target.
14762 @item show remoteflow
14763 @kindex show remoteflow
14764 Show the current setting of hardware flow control.
14766 @item set remotelogbase @var{base}
14767 Set the base (a.k.a.@: radix) of logging serial protocol
14768 communications to @var{base}. Supported values of @var{base} are:
14769 @code{ascii}, @code{octal}, and @code{hex}. The default is
14772 @item show remotelogbase
14773 Show the current setting of the radix for logging remote serial
14776 @item set remotelogfile @var{file}
14777 @cindex record serial communications on file
14778 Record remote serial communications on the named @var{file}. The
14779 default is not to record at all.
14781 @item show remotelogfile.
14782 Show the current setting of the file name on which to record the
14783 serial communications.
14785 @item set remotetimeout @var{num}
14786 @cindex timeout for serial communications
14787 @cindex remote timeout
14788 Set the timeout limit to wait for the remote target to respond to
14789 @var{num} seconds. The default is 2 seconds.
14791 @item show remotetimeout
14792 Show the current number of seconds to wait for the remote target
14795 @cindex limit hardware breakpoints and watchpoints
14796 @cindex remote target, limit break- and watchpoints
14797 @anchor{set remote hardware-watchpoint-limit}
14798 @anchor{set remote hardware-breakpoint-limit}
14799 @item set remote hardware-watchpoint-limit @var{limit}
14800 @itemx set remote hardware-breakpoint-limit @var{limit}
14801 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
14802 watchpoints. A limit of -1, the default, is treated as unlimited.
14804 @item set remote exec-file @var{filename}
14805 @itemx show remote exec-file
14806 @anchor{set remote exec-file}
14807 @cindex executable file, for remote target
14808 Select the file used for @code{run} with @code{target
14809 extended-remote}. This should be set to a filename valid on the
14810 target system. If it is not set, the target will use a default
14811 filename (e.g.@: the last program run).
14815 @item set tcp auto-retry on
14816 @cindex auto-retry, for remote TCP target
14817 Enable auto-retry for remote TCP connections. This is useful if the remote
14818 debugging agent is launched in parallel with @value{GDBN}; there is a race
14819 condition because the agent may not become ready to accept the connection
14820 before @value{GDBN} attempts to connect. When auto-retry is
14821 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
14822 to establish the connection using the timeout specified by
14823 @code{set tcp connect-timeout}.
14825 @item set tcp auto-retry off
14826 Do not auto-retry failed TCP connections.
14828 @item show tcp auto-retry
14829 Show the current auto-retry setting.
14831 @item set tcp connect-timeout @var{seconds}
14832 @cindex connection timeout, for remote TCP target
14833 @cindex timeout, for remote target connection
14834 Set the timeout for establishing a TCP connection to the remote target to
14835 @var{seconds}. The timeout affects both polling to retry failed connections
14836 (enabled by @code{set tcp auto-retry on}) and waiting for connections
14837 that are merely slow to complete, and represents an approximate cumulative
14840 @item show tcp connect-timeout
14841 Show the current connection timeout setting.
14844 @cindex remote packets, enabling and disabling
14845 The @value{GDBN} remote protocol autodetects the packets supported by
14846 your debugging stub. If you need to override the autodetection, you
14847 can use these commands to enable or disable individual packets. Each
14848 packet can be set to @samp{on} (the remote target supports this
14849 packet), @samp{off} (the remote target does not support this packet),
14850 or @samp{auto} (detect remote target support for this packet). They
14851 all default to @samp{auto}. For more information about each packet,
14852 see @ref{Remote Protocol}.
14854 During normal use, you should not have to use any of these commands.
14855 If you do, that may be a bug in your remote debugging stub, or a bug
14856 in @value{GDBN}. You may want to report the problem to the
14857 @value{GDBN} developers.
14859 For each packet @var{name}, the command to enable or disable the
14860 packet is @code{set remote @var{name}-packet}. The available settings
14863 @multitable @columnfractions 0.28 0.32 0.25
14866 @tab Related Features
14868 @item @code{fetch-register}
14870 @tab @code{info registers}
14872 @item @code{set-register}
14876 @item @code{binary-download}
14878 @tab @code{load}, @code{set}
14880 @item @code{read-aux-vector}
14881 @tab @code{qXfer:auxv:read}
14882 @tab @code{info auxv}
14884 @item @code{symbol-lookup}
14885 @tab @code{qSymbol}
14886 @tab Detecting multiple threads
14888 @item @code{attach}
14889 @tab @code{vAttach}
14892 @item @code{verbose-resume}
14894 @tab Stepping or resuming multiple threads
14900 @item @code{software-breakpoint}
14904 @item @code{hardware-breakpoint}
14908 @item @code{write-watchpoint}
14912 @item @code{read-watchpoint}
14916 @item @code{access-watchpoint}
14920 @item @code{target-features}
14921 @tab @code{qXfer:features:read}
14922 @tab @code{set architecture}
14924 @item @code{library-info}
14925 @tab @code{qXfer:libraries:read}
14926 @tab @code{info sharedlibrary}
14928 @item @code{memory-map}
14929 @tab @code{qXfer:memory-map:read}
14930 @tab @code{info mem}
14932 @item @code{read-spu-object}
14933 @tab @code{qXfer:spu:read}
14934 @tab @code{info spu}
14936 @item @code{write-spu-object}
14937 @tab @code{qXfer:spu:write}
14938 @tab @code{info spu}
14940 @item @code{read-siginfo-object}
14941 @tab @code{qXfer:siginfo:read}
14942 @tab @code{print $_siginfo}
14944 @item @code{write-siginfo-object}
14945 @tab @code{qXfer:siginfo:write}
14946 @tab @code{set $_siginfo}
14948 @item @code{get-thread-local-@*storage-address}
14949 @tab @code{qGetTLSAddr}
14950 @tab Displaying @code{__thread} variables
14952 @item @code{search-memory}
14953 @tab @code{qSearch:memory}
14956 @item @code{supported-packets}
14957 @tab @code{qSupported}
14958 @tab Remote communications parameters
14960 @item @code{pass-signals}
14961 @tab @code{QPassSignals}
14962 @tab @code{handle @var{signal}}
14964 @item @code{hostio-close-packet}
14965 @tab @code{vFile:close}
14966 @tab @code{remote get}, @code{remote put}
14968 @item @code{hostio-open-packet}
14969 @tab @code{vFile:open}
14970 @tab @code{remote get}, @code{remote put}
14972 @item @code{hostio-pread-packet}
14973 @tab @code{vFile:pread}
14974 @tab @code{remote get}, @code{remote put}
14976 @item @code{hostio-pwrite-packet}
14977 @tab @code{vFile:pwrite}
14978 @tab @code{remote get}, @code{remote put}
14980 @item @code{hostio-unlink-packet}
14981 @tab @code{vFile:unlink}
14982 @tab @code{remote delete}
14984 @item @code{noack-packet}
14985 @tab @code{QStartNoAckMode}
14986 @tab Packet acknowledgment
14988 @item @code{osdata}
14989 @tab @code{qXfer:osdata:read}
14990 @tab @code{info os}
14992 @item @code{query-attached}
14993 @tab @code{qAttached}
14994 @tab Querying remote process attach state.
14998 @section Implementing a Remote Stub
15000 @cindex debugging stub, example
15001 @cindex remote stub, example
15002 @cindex stub example, remote debugging
15003 The stub files provided with @value{GDBN} implement the target side of the
15004 communication protocol, and the @value{GDBN} side is implemented in the
15005 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
15006 these subroutines to communicate, and ignore the details. (If you're
15007 implementing your own stub file, you can still ignore the details: start
15008 with one of the existing stub files. @file{sparc-stub.c} is the best
15009 organized, and therefore the easiest to read.)
15011 @cindex remote serial debugging, overview
15012 To debug a program running on another machine (the debugging
15013 @dfn{target} machine), you must first arrange for all the usual
15014 prerequisites for the program to run by itself. For example, for a C
15019 A startup routine to set up the C runtime environment; these usually
15020 have a name like @file{crt0}. The startup routine may be supplied by
15021 your hardware supplier, or you may have to write your own.
15024 A C subroutine library to support your program's
15025 subroutine calls, notably managing input and output.
15028 A way of getting your program to the other machine---for example, a
15029 download program. These are often supplied by the hardware
15030 manufacturer, but you may have to write your own from hardware
15034 The next step is to arrange for your program to use a serial port to
15035 communicate with the machine where @value{GDBN} is running (the @dfn{host}
15036 machine). In general terms, the scheme looks like this:
15040 @value{GDBN} already understands how to use this protocol; when everything
15041 else is set up, you can simply use the @samp{target remote} command
15042 (@pxref{Targets,,Specifying a Debugging Target}).
15044 @item On the target,
15045 you must link with your program a few special-purpose subroutines that
15046 implement the @value{GDBN} remote serial protocol. The file containing these
15047 subroutines is called a @dfn{debugging stub}.
15049 On certain remote targets, you can use an auxiliary program
15050 @code{gdbserver} instead of linking a stub into your program.
15051 @xref{Server,,Using the @code{gdbserver} Program}, for details.
15054 The debugging stub is specific to the architecture of the remote
15055 machine; for example, use @file{sparc-stub.c} to debug programs on
15058 @cindex remote serial stub list
15059 These working remote stubs are distributed with @value{GDBN}:
15064 @cindex @file{i386-stub.c}
15067 For Intel 386 and compatible architectures.
15070 @cindex @file{m68k-stub.c}
15071 @cindex Motorola 680x0
15073 For Motorola 680x0 architectures.
15076 @cindex @file{sh-stub.c}
15079 For Renesas SH architectures.
15082 @cindex @file{sparc-stub.c}
15084 For @sc{sparc} architectures.
15086 @item sparcl-stub.c
15087 @cindex @file{sparcl-stub.c}
15090 For Fujitsu @sc{sparclite} architectures.
15094 The @file{README} file in the @value{GDBN} distribution may list other
15095 recently added stubs.
15098 * Stub Contents:: What the stub can do for you
15099 * Bootstrapping:: What you must do for the stub
15100 * Debug Session:: Putting it all together
15103 @node Stub Contents
15104 @subsection What the Stub Can Do for You
15106 @cindex remote serial stub
15107 The debugging stub for your architecture supplies these three
15111 @item set_debug_traps
15112 @findex set_debug_traps
15113 @cindex remote serial stub, initialization
15114 This routine arranges for @code{handle_exception} to run when your
15115 program stops. You must call this subroutine explicitly near the
15116 beginning of your program.
15118 @item handle_exception
15119 @findex handle_exception
15120 @cindex remote serial stub, main routine
15121 This is the central workhorse, but your program never calls it
15122 explicitly---the setup code arranges for @code{handle_exception} to
15123 run when a trap is triggered.
15125 @code{handle_exception} takes control when your program stops during
15126 execution (for example, on a breakpoint), and mediates communications
15127 with @value{GDBN} on the host machine. This is where the communications
15128 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
15129 representative on the target machine. It begins by sending summary
15130 information on the state of your program, then continues to execute,
15131 retrieving and transmitting any information @value{GDBN} needs, until you
15132 execute a @value{GDBN} command that makes your program resume; at that point,
15133 @code{handle_exception} returns control to your own code on the target
15137 @cindex @code{breakpoint} subroutine, remote
15138 Use this auxiliary subroutine to make your program contain a
15139 breakpoint. Depending on the particular situation, this may be the only
15140 way for @value{GDBN} to get control. For instance, if your target
15141 machine has some sort of interrupt button, you won't need to call this;
15142 pressing the interrupt button transfers control to
15143 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
15144 simply receiving characters on the serial port may also trigger a trap;
15145 again, in that situation, you don't need to call @code{breakpoint} from
15146 your own program---simply running @samp{target remote} from the host
15147 @value{GDBN} session gets control.
15149 Call @code{breakpoint} if none of these is true, or if you simply want
15150 to make certain your program stops at a predetermined point for the
15151 start of your debugging session.
15154 @node Bootstrapping
15155 @subsection What You Must Do for the Stub
15157 @cindex remote stub, support routines
15158 The debugging stubs that come with @value{GDBN} are set up for a particular
15159 chip architecture, but they have no information about the rest of your
15160 debugging target machine.
15162 First of all you need to tell the stub how to communicate with the
15166 @item int getDebugChar()
15167 @findex getDebugChar
15168 Write this subroutine to read a single character from the serial port.
15169 It may be identical to @code{getchar} for your target system; a
15170 different name is used to allow you to distinguish the two if you wish.
15172 @item void putDebugChar(int)
15173 @findex putDebugChar
15174 Write this subroutine to write a single character to the serial port.
15175 It may be identical to @code{putchar} for your target system; a
15176 different name is used to allow you to distinguish the two if you wish.
15179 @cindex control C, and remote debugging
15180 @cindex interrupting remote targets
15181 If you want @value{GDBN} to be able to stop your program while it is
15182 running, you need to use an interrupt-driven serial driver, and arrange
15183 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
15184 character). That is the character which @value{GDBN} uses to tell the
15185 remote system to stop.
15187 Getting the debugging target to return the proper status to @value{GDBN}
15188 probably requires changes to the standard stub; one quick and dirty way
15189 is to just execute a breakpoint instruction (the ``dirty'' part is that
15190 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
15192 Other routines you need to supply are:
15195 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
15196 @findex exceptionHandler
15197 Write this function to install @var{exception_address} in the exception
15198 handling tables. You need to do this because the stub does not have any
15199 way of knowing what the exception handling tables on your target system
15200 are like (for example, the processor's table might be in @sc{rom},
15201 containing entries which point to a table in @sc{ram}).
15202 @var{exception_number} is the exception number which should be changed;
15203 its meaning is architecture-dependent (for example, different numbers
15204 might represent divide by zero, misaligned access, etc). When this
15205 exception occurs, control should be transferred directly to
15206 @var{exception_address}, and the processor state (stack, registers,
15207 and so on) should be just as it is when a processor exception occurs. So if
15208 you want to use a jump instruction to reach @var{exception_address}, it
15209 should be a simple jump, not a jump to subroutine.
15211 For the 386, @var{exception_address} should be installed as an interrupt
15212 gate so that interrupts are masked while the handler runs. The gate
15213 should be at privilege level 0 (the most privileged level). The
15214 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
15215 help from @code{exceptionHandler}.
15217 @item void flush_i_cache()
15218 @findex flush_i_cache
15219 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
15220 instruction cache, if any, on your target machine. If there is no
15221 instruction cache, this subroutine may be a no-op.
15223 On target machines that have instruction caches, @value{GDBN} requires this
15224 function to make certain that the state of your program is stable.
15228 You must also make sure this library routine is available:
15231 @item void *memset(void *, int, int)
15233 This is the standard library function @code{memset} that sets an area of
15234 memory to a known value. If you have one of the free versions of
15235 @code{libc.a}, @code{memset} can be found there; otherwise, you must
15236 either obtain it from your hardware manufacturer, or write your own.
15239 If you do not use the GNU C compiler, you may need other standard
15240 library subroutines as well; this varies from one stub to another,
15241 but in general the stubs are likely to use any of the common library
15242 subroutines which @code{@value{NGCC}} generates as inline code.
15245 @node Debug Session
15246 @subsection Putting it All Together
15248 @cindex remote serial debugging summary
15249 In summary, when your program is ready to debug, you must follow these
15254 Make sure you have defined the supporting low-level routines
15255 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
15257 @code{getDebugChar}, @code{putDebugChar},
15258 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
15262 Insert these lines near the top of your program:
15270 For the 680x0 stub only, you need to provide a variable called
15271 @code{exceptionHook}. Normally you just use:
15274 void (*exceptionHook)() = 0;
15278 but if before calling @code{set_debug_traps}, you set it to point to a
15279 function in your program, that function is called when
15280 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
15281 error). The function indicated by @code{exceptionHook} is called with
15282 one parameter: an @code{int} which is the exception number.
15285 Compile and link together: your program, the @value{GDBN} debugging stub for
15286 your target architecture, and the supporting subroutines.
15289 Make sure you have a serial connection between your target machine and
15290 the @value{GDBN} host, and identify the serial port on the host.
15293 @c The "remote" target now provides a `load' command, so we should
15294 @c document that. FIXME.
15295 Download your program to your target machine (or get it there by
15296 whatever means the manufacturer provides), and start it.
15299 Start @value{GDBN} on the host, and connect to the target
15300 (@pxref{Connecting,,Connecting to a Remote Target}).
15304 @node Configurations
15305 @chapter Configuration-Specific Information
15307 While nearly all @value{GDBN} commands are available for all native and
15308 cross versions of the debugger, there are some exceptions. This chapter
15309 describes things that are only available in certain configurations.
15311 There are three major categories of configurations: native
15312 configurations, where the host and target are the same, embedded
15313 operating system configurations, which are usually the same for several
15314 different processor architectures, and bare embedded processors, which
15315 are quite different from each other.
15320 * Embedded Processors::
15327 This section describes details specific to particular native
15332 * BSD libkvm Interface:: Debugging BSD kernel memory images
15333 * SVR4 Process Information:: SVR4 process information
15334 * DJGPP Native:: Features specific to the DJGPP port
15335 * Cygwin Native:: Features specific to the Cygwin port
15336 * Hurd Native:: Features specific to @sc{gnu} Hurd
15337 * Neutrino:: Features specific to QNX Neutrino
15338 * Darwin:: Features specific to Darwin
15344 On HP-UX systems, if you refer to a function or variable name that
15345 begins with a dollar sign, @value{GDBN} searches for a user or system
15346 name first, before it searches for a convenience variable.
15349 @node BSD libkvm Interface
15350 @subsection BSD libkvm Interface
15353 @cindex kernel memory image
15354 @cindex kernel crash dump
15356 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
15357 interface that provides a uniform interface for accessing kernel virtual
15358 memory images, including live systems and crash dumps. @value{GDBN}
15359 uses this interface to allow you to debug live kernels and kernel crash
15360 dumps on many native BSD configurations. This is implemented as a
15361 special @code{kvm} debugging target. For debugging a live system, load
15362 the currently running kernel into @value{GDBN} and connect to the
15366 (@value{GDBP}) @b{target kvm}
15369 For debugging crash dumps, provide the file name of the crash dump as an
15373 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
15376 Once connected to the @code{kvm} target, the following commands are
15382 Set current context from the @dfn{Process Control Block} (PCB) address.
15385 Set current context from proc address. This command isn't available on
15386 modern FreeBSD systems.
15389 @node SVR4 Process Information
15390 @subsection SVR4 Process Information
15392 @cindex examine process image
15393 @cindex process info via @file{/proc}
15395 Many versions of SVR4 and compatible systems provide a facility called
15396 @samp{/proc} that can be used to examine the image of a running
15397 process using file-system subroutines. If @value{GDBN} is configured
15398 for an operating system with this facility, the command @code{info
15399 proc} is available to report information about the process running
15400 your program, or about any process running on your system. @code{info
15401 proc} works only on SVR4 systems that include the @code{procfs} code.
15402 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
15403 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
15409 @itemx info proc @var{process-id}
15410 Summarize available information about any running process. If a
15411 process ID is specified by @var{process-id}, display information about
15412 that process; otherwise display information about the program being
15413 debugged. The summary includes the debugged process ID, the command
15414 line used to invoke it, its current working directory, and its
15415 executable file's absolute file name.
15417 On some systems, @var{process-id} can be of the form
15418 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
15419 within a process. If the optional @var{pid} part is missing, it means
15420 a thread from the process being debugged (the leading @samp{/} still
15421 needs to be present, or else @value{GDBN} will interpret the number as
15422 a process ID rather than a thread ID).
15424 @item info proc mappings
15425 @cindex memory address space mappings
15426 Report the memory address space ranges accessible in the program, with
15427 information on whether the process has read, write, or execute access
15428 rights to each range. On @sc{gnu}/Linux systems, each memory range
15429 includes the object file which is mapped to that range, instead of the
15430 memory access rights to that range.
15432 @item info proc stat
15433 @itemx info proc status
15434 @cindex process detailed status information
15435 These subcommands are specific to @sc{gnu}/Linux systems. They show
15436 the process-related information, including the user ID and group ID;
15437 how many threads are there in the process; its virtual memory usage;
15438 the signals that are pending, blocked, and ignored; its TTY; its
15439 consumption of system and user time; its stack size; its @samp{nice}
15440 value; etc. For more information, see the @samp{proc} man page
15441 (type @kbd{man 5 proc} from your shell prompt).
15443 @item info proc all
15444 Show all the information about the process described under all of the
15445 above @code{info proc} subcommands.
15448 @comment These sub-options of 'info proc' were not included when
15449 @comment procfs.c was re-written. Keep their descriptions around
15450 @comment against the day when someone finds the time to put them back in.
15451 @kindex info proc times
15452 @item info proc times
15453 Starting time, user CPU time, and system CPU time for your program and
15456 @kindex info proc id
15458 Report on the process IDs related to your program: its own process ID,
15459 the ID of its parent, the process group ID, and the session ID.
15462 @item set procfs-trace
15463 @kindex set procfs-trace
15464 @cindex @code{procfs} API calls
15465 This command enables and disables tracing of @code{procfs} API calls.
15467 @item show procfs-trace
15468 @kindex show procfs-trace
15469 Show the current state of @code{procfs} API call tracing.
15471 @item set procfs-file @var{file}
15472 @kindex set procfs-file
15473 Tell @value{GDBN} to write @code{procfs} API trace to the named
15474 @var{file}. @value{GDBN} appends the trace info to the previous
15475 contents of the file. The default is to display the trace on the
15478 @item show procfs-file
15479 @kindex show procfs-file
15480 Show the file to which @code{procfs} API trace is written.
15482 @item proc-trace-entry
15483 @itemx proc-trace-exit
15484 @itemx proc-untrace-entry
15485 @itemx proc-untrace-exit
15486 @kindex proc-trace-entry
15487 @kindex proc-trace-exit
15488 @kindex proc-untrace-entry
15489 @kindex proc-untrace-exit
15490 These commands enable and disable tracing of entries into and exits
15491 from the @code{syscall} interface.
15494 @kindex info pidlist
15495 @cindex process list, QNX Neutrino
15496 For QNX Neutrino only, this command displays the list of all the
15497 processes and all the threads within each process.
15500 @kindex info meminfo
15501 @cindex mapinfo list, QNX Neutrino
15502 For QNX Neutrino only, this command displays the list of all mapinfos.
15506 @subsection Features for Debugging @sc{djgpp} Programs
15507 @cindex @sc{djgpp} debugging
15508 @cindex native @sc{djgpp} debugging
15509 @cindex MS-DOS-specific commands
15512 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
15513 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
15514 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
15515 top of real-mode DOS systems and their emulations.
15517 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
15518 defines a few commands specific to the @sc{djgpp} port. This
15519 subsection describes those commands.
15524 This is a prefix of @sc{djgpp}-specific commands which print
15525 information about the target system and important OS structures.
15528 @cindex MS-DOS system info
15529 @cindex free memory information (MS-DOS)
15530 @item info dos sysinfo
15531 This command displays assorted information about the underlying
15532 platform: the CPU type and features, the OS version and flavor, the
15533 DPMI version, and the available conventional and DPMI memory.
15538 @cindex segment descriptor tables
15539 @cindex descriptor tables display
15541 @itemx info dos ldt
15542 @itemx info dos idt
15543 These 3 commands display entries from, respectively, Global, Local,
15544 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
15545 tables are data structures which store a descriptor for each segment
15546 that is currently in use. The segment's selector is an index into a
15547 descriptor table; the table entry for that index holds the
15548 descriptor's base address and limit, and its attributes and access
15551 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
15552 segment (used for both data and the stack), and a DOS segment (which
15553 allows access to DOS/BIOS data structures and absolute addresses in
15554 conventional memory). However, the DPMI host will usually define
15555 additional segments in order to support the DPMI environment.
15557 @cindex garbled pointers
15558 These commands allow to display entries from the descriptor tables.
15559 Without an argument, all entries from the specified table are
15560 displayed. An argument, which should be an integer expression, means
15561 display a single entry whose index is given by the argument. For
15562 example, here's a convenient way to display information about the
15563 debugged program's data segment:
15566 @exdent @code{(@value{GDBP}) info dos ldt $ds}
15567 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
15571 This comes in handy when you want to see whether a pointer is outside
15572 the data segment's limit (i.e.@: @dfn{garbled}).
15574 @cindex page tables display (MS-DOS)
15576 @itemx info dos pte
15577 These two commands display entries from, respectively, the Page
15578 Directory and the Page Tables. Page Directories and Page Tables are
15579 data structures which control how virtual memory addresses are mapped
15580 into physical addresses. A Page Table includes an entry for every
15581 page of memory that is mapped into the program's address space; there
15582 may be several Page Tables, each one holding up to 4096 entries. A
15583 Page Directory has up to 4096 entries, one each for every Page Table
15584 that is currently in use.
15586 Without an argument, @kbd{info dos pde} displays the entire Page
15587 Directory, and @kbd{info dos pte} displays all the entries in all of
15588 the Page Tables. An argument, an integer expression, given to the
15589 @kbd{info dos pde} command means display only that entry from the Page
15590 Directory table. An argument given to the @kbd{info dos pte} command
15591 means display entries from a single Page Table, the one pointed to by
15592 the specified entry in the Page Directory.
15594 @cindex direct memory access (DMA) on MS-DOS
15595 These commands are useful when your program uses @dfn{DMA} (Direct
15596 Memory Access), which needs physical addresses to program the DMA
15599 These commands are supported only with some DPMI servers.
15601 @cindex physical address from linear address
15602 @item info dos address-pte @var{addr}
15603 This command displays the Page Table entry for a specified linear
15604 address. The argument @var{addr} is a linear address which should
15605 already have the appropriate segment's base address added to it,
15606 because this command accepts addresses which may belong to @emph{any}
15607 segment. For example, here's how to display the Page Table entry for
15608 the page where a variable @code{i} is stored:
15611 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
15612 @exdent @code{Page Table entry for address 0x11a00d30:}
15613 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
15617 This says that @code{i} is stored at offset @code{0xd30} from the page
15618 whose physical base address is @code{0x02698000}, and shows all the
15619 attributes of that page.
15621 Note that you must cast the addresses of variables to a @code{char *},
15622 since otherwise the value of @code{__djgpp_base_address}, the base
15623 address of all variables and functions in a @sc{djgpp} program, will
15624 be added using the rules of C pointer arithmetics: if @code{i} is
15625 declared an @code{int}, @value{GDBN} will add 4 times the value of
15626 @code{__djgpp_base_address} to the address of @code{i}.
15628 Here's another example, it displays the Page Table entry for the
15632 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
15633 @exdent @code{Page Table entry for address 0x29110:}
15634 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
15638 (The @code{+ 3} offset is because the transfer buffer's address is the
15639 3rd member of the @code{_go32_info_block} structure.) The output
15640 clearly shows that this DPMI server maps the addresses in conventional
15641 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
15642 linear (@code{0x29110}) addresses are identical.
15644 This command is supported only with some DPMI servers.
15647 @cindex DOS serial data link, remote debugging
15648 In addition to native debugging, the DJGPP port supports remote
15649 debugging via a serial data link. The following commands are specific
15650 to remote serial debugging in the DJGPP port of @value{GDBN}.
15653 @kindex set com1base
15654 @kindex set com1irq
15655 @kindex set com2base
15656 @kindex set com2irq
15657 @kindex set com3base
15658 @kindex set com3irq
15659 @kindex set com4base
15660 @kindex set com4irq
15661 @item set com1base @var{addr}
15662 This command sets the base I/O port address of the @file{COM1} serial
15665 @item set com1irq @var{irq}
15666 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
15667 for the @file{COM1} serial port.
15669 There are similar commands @samp{set com2base}, @samp{set com3irq},
15670 etc.@: for setting the port address and the @code{IRQ} lines for the
15673 @kindex show com1base
15674 @kindex show com1irq
15675 @kindex show com2base
15676 @kindex show com2irq
15677 @kindex show com3base
15678 @kindex show com3irq
15679 @kindex show com4base
15680 @kindex show com4irq
15681 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
15682 display the current settings of the base address and the @code{IRQ}
15683 lines used by the COM ports.
15686 @kindex info serial
15687 @cindex DOS serial port status
15688 This command prints the status of the 4 DOS serial ports. For each
15689 port, it prints whether it's active or not, its I/O base address and
15690 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
15691 counts of various errors encountered so far.
15695 @node Cygwin Native
15696 @subsection Features for Debugging MS Windows PE Executables
15697 @cindex MS Windows debugging
15698 @cindex native Cygwin debugging
15699 @cindex Cygwin-specific commands
15701 @value{GDBN} supports native debugging of MS Windows programs, including
15702 DLLs with and without symbolic debugging information. There are various
15703 additional Cygwin-specific commands, described in this section.
15704 Working with DLLs that have no debugging symbols is described in
15705 @ref{Non-debug DLL Symbols}.
15710 This is a prefix of MS Windows-specific commands which print
15711 information about the target system and important OS structures.
15713 @item info w32 selector
15714 This command displays information returned by
15715 the Win32 API @code{GetThreadSelectorEntry} function.
15716 It takes an optional argument that is evaluated to
15717 a long value to give the information about this given selector.
15718 Without argument, this command displays information
15719 about the six segment registers.
15723 This is a Cygwin-specific alias of @code{info shared}.
15725 @kindex dll-symbols
15727 This command loads symbols from a dll similarly to
15728 add-sym command but without the need to specify a base address.
15730 @kindex set cygwin-exceptions
15731 @cindex debugging the Cygwin DLL
15732 @cindex Cygwin DLL, debugging
15733 @item set cygwin-exceptions @var{mode}
15734 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
15735 happen inside the Cygwin DLL. If @var{mode} is @code{off},
15736 @value{GDBN} will delay recognition of exceptions, and may ignore some
15737 exceptions which seem to be caused by internal Cygwin DLL
15738 ``bookkeeping''. This option is meant primarily for debugging the
15739 Cygwin DLL itself; the default value is @code{off} to avoid annoying
15740 @value{GDBN} users with false @code{SIGSEGV} signals.
15742 @kindex show cygwin-exceptions
15743 @item show cygwin-exceptions
15744 Displays whether @value{GDBN} will break on exceptions that happen
15745 inside the Cygwin DLL itself.
15747 @kindex set new-console
15748 @item set new-console @var{mode}
15749 If @var{mode} is @code{on} the debuggee will
15750 be started in a new console on next start.
15751 If @var{mode} is @code{off}i, the debuggee will
15752 be started in the same console as the debugger.
15754 @kindex show new-console
15755 @item show new-console
15756 Displays whether a new console is used
15757 when the debuggee is started.
15759 @kindex set new-group
15760 @item set new-group @var{mode}
15761 This boolean value controls whether the debuggee should
15762 start a new group or stay in the same group as the debugger.
15763 This affects the way the Windows OS handles
15766 @kindex show new-group
15767 @item show new-group
15768 Displays current value of new-group boolean.
15770 @kindex set debugevents
15771 @item set debugevents
15772 This boolean value adds debug output concerning kernel events related
15773 to the debuggee seen by the debugger. This includes events that
15774 signal thread and process creation and exit, DLL loading and
15775 unloading, console interrupts, and debugging messages produced by the
15776 Windows @code{OutputDebugString} API call.
15778 @kindex set debugexec
15779 @item set debugexec
15780 This boolean value adds debug output concerning execute events
15781 (such as resume thread) seen by the debugger.
15783 @kindex set debugexceptions
15784 @item set debugexceptions
15785 This boolean value adds debug output concerning exceptions in the
15786 debuggee seen by the debugger.
15788 @kindex set debugmemory
15789 @item set debugmemory
15790 This boolean value adds debug output concerning debuggee memory reads
15791 and writes by the debugger.
15795 This boolean values specifies whether the debuggee is called
15796 via a shell or directly (default value is on).
15800 Displays if the debuggee will be started with a shell.
15805 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
15808 @node Non-debug DLL Symbols
15809 @subsubsection Support for DLLs without Debugging Symbols
15810 @cindex DLLs with no debugging symbols
15811 @cindex Minimal symbols and DLLs
15813 Very often on windows, some of the DLLs that your program relies on do
15814 not include symbolic debugging information (for example,
15815 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
15816 symbols in a DLL, it relies on the minimal amount of symbolic
15817 information contained in the DLL's export table. This section
15818 describes working with such symbols, known internally to @value{GDBN} as
15819 ``minimal symbols''.
15821 Note that before the debugged program has started execution, no DLLs
15822 will have been loaded. The easiest way around this problem is simply to
15823 start the program --- either by setting a breakpoint or letting the
15824 program run once to completion. It is also possible to force
15825 @value{GDBN} to load a particular DLL before starting the executable ---
15826 see the shared library information in @ref{Files}, or the
15827 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
15828 explicitly loading symbols from a DLL with no debugging information will
15829 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
15830 which may adversely affect symbol lookup performance.
15832 @subsubsection DLL Name Prefixes
15834 In keeping with the naming conventions used by the Microsoft debugging
15835 tools, DLL export symbols are made available with a prefix based on the
15836 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
15837 also entered into the symbol table, so @code{CreateFileA} is often
15838 sufficient. In some cases there will be name clashes within a program
15839 (particularly if the executable itself includes full debugging symbols)
15840 necessitating the use of the fully qualified name when referring to the
15841 contents of the DLL. Use single-quotes around the name to avoid the
15842 exclamation mark (``!'') being interpreted as a language operator.
15844 Note that the internal name of the DLL may be all upper-case, even
15845 though the file name of the DLL is lower-case, or vice-versa. Since
15846 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
15847 some confusion. If in doubt, try the @code{info functions} and
15848 @code{info variables} commands or even @code{maint print msymbols}
15849 (@pxref{Symbols}). Here's an example:
15852 (@value{GDBP}) info function CreateFileA
15853 All functions matching regular expression "CreateFileA":
15855 Non-debugging symbols:
15856 0x77e885f4 CreateFileA
15857 0x77e885f4 KERNEL32!CreateFileA
15861 (@value{GDBP}) info function !
15862 All functions matching regular expression "!":
15864 Non-debugging symbols:
15865 0x6100114c cygwin1!__assert
15866 0x61004034 cygwin1!_dll_crt0@@0
15867 0x61004240 cygwin1!dll_crt0(per_process *)
15871 @subsubsection Working with Minimal Symbols
15873 Symbols extracted from a DLL's export table do not contain very much
15874 type information. All that @value{GDBN} can do is guess whether a symbol
15875 refers to a function or variable depending on the linker section that
15876 contains the symbol. Also note that the actual contents of the memory
15877 contained in a DLL are not available unless the program is running. This
15878 means that you cannot examine the contents of a variable or disassemble
15879 a function within a DLL without a running program.
15881 Variables are generally treated as pointers and dereferenced
15882 automatically. For this reason, it is often necessary to prefix a
15883 variable name with the address-of operator (``&'') and provide explicit
15884 type information in the command. Here's an example of the type of
15888 (@value{GDBP}) print 'cygwin1!__argv'
15893 (@value{GDBP}) x 'cygwin1!__argv'
15894 0x10021610: "\230y\""
15897 And two possible solutions:
15900 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
15901 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
15905 (@value{GDBP}) x/2x &'cygwin1!__argv'
15906 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
15907 (@value{GDBP}) x/x 0x10021608
15908 0x10021608: 0x0022fd98
15909 (@value{GDBP}) x/s 0x0022fd98
15910 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
15913 Setting a break point within a DLL is possible even before the program
15914 starts execution. However, under these circumstances, @value{GDBN} can't
15915 examine the initial instructions of the function in order to skip the
15916 function's frame set-up code. You can work around this by using ``*&''
15917 to set the breakpoint at a raw memory address:
15920 (@value{GDBP}) break *&'python22!PyOS_Readline'
15921 Breakpoint 1 at 0x1e04eff0
15924 The author of these extensions is not entirely convinced that setting a
15925 break point within a shared DLL like @file{kernel32.dll} is completely
15929 @subsection Commands Specific to @sc{gnu} Hurd Systems
15930 @cindex @sc{gnu} Hurd debugging
15932 This subsection describes @value{GDBN} commands specific to the
15933 @sc{gnu} Hurd native debugging.
15938 @kindex set signals@r{, Hurd command}
15939 @kindex set sigs@r{, Hurd command}
15940 This command toggles the state of inferior signal interception by
15941 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
15942 affected by this command. @code{sigs} is a shorthand alias for
15947 @kindex show signals@r{, Hurd command}
15948 @kindex show sigs@r{, Hurd command}
15949 Show the current state of intercepting inferior's signals.
15951 @item set signal-thread
15952 @itemx set sigthread
15953 @kindex set signal-thread
15954 @kindex set sigthread
15955 This command tells @value{GDBN} which thread is the @code{libc} signal
15956 thread. That thread is run when a signal is delivered to a running
15957 process. @code{set sigthread} is the shorthand alias of @code{set
15960 @item show signal-thread
15961 @itemx show sigthread
15962 @kindex show signal-thread
15963 @kindex show sigthread
15964 These two commands show which thread will run when the inferior is
15965 delivered a signal.
15968 @kindex set stopped@r{, Hurd command}
15969 This commands tells @value{GDBN} that the inferior process is stopped,
15970 as with the @code{SIGSTOP} signal. The stopped process can be
15971 continued by delivering a signal to it.
15974 @kindex show stopped@r{, Hurd command}
15975 This command shows whether @value{GDBN} thinks the debuggee is
15978 @item set exceptions
15979 @kindex set exceptions@r{, Hurd command}
15980 Use this command to turn off trapping of exceptions in the inferior.
15981 When exception trapping is off, neither breakpoints nor
15982 single-stepping will work. To restore the default, set exception
15985 @item show exceptions
15986 @kindex show exceptions@r{, Hurd command}
15987 Show the current state of trapping exceptions in the inferior.
15989 @item set task pause
15990 @kindex set task@r{, Hurd commands}
15991 @cindex task attributes (@sc{gnu} Hurd)
15992 @cindex pause current task (@sc{gnu} Hurd)
15993 This command toggles task suspension when @value{GDBN} has control.
15994 Setting it to on takes effect immediately, and the task is suspended
15995 whenever @value{GDBN} gets control. Setting it to off will take
15996 effect the next time the inferior is continued. If this option is set
15997 to off, you can use @code{set thread default pause on} or @code{set
15998 thread pause on} (see below) to pause individual threads.
16000 @item show task pause
16001 @kindex show task@r{, Hurd commands}
16002 Show the current state of task suspension.
16004 @item set task detach-suspend-count
16005 @cindex task suspend count
16006 @cindex detach from task, @sc{gnu} Hurd
16007 This command sets the suspend count the task will be left with when
16008 @value{GDBN} detaches from it.
16010 @item show task detach-suspend-count
16011 Show the suspend count the task will be left with when detaching.
16013 @item set task exception-port
16014 @itemx set task excp
16015 @cindex task exception port, @sc{gnu} Hurd
16016 This command sets the task exception port to which @value{GDBN} will
16017 forward exceptions. The argument should be the value of the @dfn{send
16018 rights} of the task. @code{set task excp} is a shorthand alias.
16020 @item set noninvasive
16021 @cindex noninvasive task options
16022 This command switches @value{GDBN} to a mode that is the least
16023 invasive as far as interfering with the inferior is concerned. This
16024 is the same as using @code{set task pause}, @code{set exceptions}, and
16025 @code{set signals} to values opposite to the defaults.
16027 @item info send-rights
16028 @itemx info receive-rights
16029 @itemx info port-rights
16030 @itemx info port-sets
16031 @itemx info dead-names
16034 @cindex send rights, @sc{gnu} Hurd
16035 @cindex receive rights, @sc{gnu} Hurd
16036 @cindex port rights, @sc{gnu} Hurd
16037 @cindex port sets, @sc{gnu} Hurd
16038 @cindex dead names, @sc{gnu} Hurd
16039 These commands display information about, respectively, send rights,
16040 receive rights, port rights, port sets, and dead names of a task.
16041 There are also shorthand aliases: @code{info ports} for @code{info
16042 port-rights} and @code{info psets} for @code{info port-sets}.
16044 @item set thread pause
16045 @kindex set thread@r{, Hurd command}
16046 @cindex thread properties, @sc{gnu} Hurd
16047 @cindex pause current thread (@sc{gnu} Hurd)
16048 This command toggles current thread suspension when @value{GDBN} has
16049 control. Setting it to on takes effect immediately, and the current
16050 thread is suspended whenever @value{GDBN} gets control. Setting it to
16051 off will take effect the next time the inferior is continued.
16052 Normally, this command has no effect, since when @value{GDBN} has
16053 control, the whole task is suspended. However, if you used @code{set
16054 task pause off} (see above), this command comes in handy to suspend
16055 only the current thread.
16057 @item show thread pause
16058 @kindex show thread@r{, Hurd command}
16059 This command shows the state of current thread suspension.
16061 @item set thread run
16062 This command sets whether the current thread is allowed to run.
16064 @item show thread run
16065 Show whether the current thread is allowed to run.
16067 @item set thread detach-suspend-count
16068 @cindex thread suspend count, @sc{gnu} Hurd
16069 @cindex detach from thread, @sc{gnu} Hurd
16070 This command sets the suspend count @value{GDBN} will leave on a
16071 thread when detaching. This number is relative to the suspend count
16072 found by @value{GDBN} when it notices the thread; use @code{set thread
16073 takeover-suspend-count} to force it to an absolute value.
16075 @item show thread detach-suspend-count
16076 Show the suspend count @value{GDBN} will leave on the thread when
16079 @item set thread exception-port
16080 @itemx set thread excp
16081 Set the thread exception port to which to forward exceptions. This
16082 overrides the port set by @code{set task exception-port} (see above).
16083 @code{set thread excp} is the shorthand alias.
16085 @item set thread takeover-suspend-count
16086 Normally, @value{GDBN}'s thread suspend counts are relative to the
16087 value @value{GDBN} finds when it notices each thread. This command
16088 changes the suspend counts to be absolute instead.
16090 @item set thread default
16091 @itemx show thread default
16092 @cindex thread default settings, @sc{gnu} Hurd
16093 Each of the above @code{set thread} commands has a @code{set thread
16094 default} counterpart (e.g., @code{set thread default pause}, @code{set
16095 thread default exception-port}, etc.). The @code{thread default}
16096 variety of commands sets the default thread properties for all
16097 threads; you can then change the properties of individual threads with
16098 the non-default commands.
16103 @subsection QNX Neutrino
16104 @cindex QNX Neutrino
16106 @value{GDBN} provides the following commands specific to the QNX
16110 @item set debug nto-debug
16111 @kindex set debug nto-debug
16112 When set to on, enables debugging messages specific to the QNX
16115 @item show debug nto-debug
16116 @kindex show debug nto-debug
16117 Show the current state of QNX Neutrino messages.
16124 @value{GDBN} provides the following commands specific to the Darwin target:
16127 @item set debug darwin @var{num}
16128 @kindex set debug darwin
16129 When set to a non zero value, enables debugging messages specific to
16130 the Darwin support. Higher values produce more verbose output.
16132 @item show debug darwin
16133 @kindex show debug darwin
16134 Show the current state of Darwin messages.
16136 @item set debug mach-o @var{num}
16137 @kindex set debug mach-o
16138 When set to a non zero value, enables debugging messages while
16139 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
16140 file format used on Darwin for object and executable files.) Higher
16141 values produce more verbose output. This is a command to diagnose
16142 problems internal to @value{GDBN} and should not be needed in normal
16145 @item show debug mach-o
16146 @kindex show debug mach-o
16147 Show the current state of Mach-O file messages.
16149 @item set mach-exceptions on
16150 @itemx set mach-exceptions off
16151 @kindex set mach-exceptions
16152 On Darwin, faults are first reported as a Mach exception and are then
16153 mapped to a Posix signal. Use this command to turn on trapping of
16154 Mach exceptions in the inferior. This might be sometimes useful to
16155 better understand the cause of a fault. The default is off.
16157 @item show mach-exceptions
16158 @kindex show mach-exceptions
16159 Show the current state of exceptions trapping.
16164 @section Embedded Operating Systems
16166 This section describes configurations involving the debugging of
16167 embedded operating systems that are available for several different
16171 * VxWorks:: Using @value{GDBN} with VxWorks
16174 @value{GDBN} includes the ability to debug programs running on
16175 various real-time operating systems.
16178 @subsection Using @value{GDBN} with VxWorks
16184 @kindex target vxworks
16185 @item target vxworks @var{machinename}
16186 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
16187 is the target system's machine name or IP address.
16191 On VxWorks, @code{load} links @var{filename} dynamically on the
16192 current target system as well as adding its symbols in @value{GDBN}.
16194 @value{GDBN} enables developers to spawn and debug tasks running on networked
16195 VxWorks targets from a Unix host. Already-running tasks spawned from
16196 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
16197 both the Unix host and on the VxWorks target. The program
16198 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
16199 installed with the name @code{vxgdb}, to distinguish it from a
16200 @value{GDBN} for debugging programs on the host itself.)
16203 @item VxWorks-timeout @var{args}
16204 @kindex vxworks-timeout
16205 All VxWorks-based targets now support the option @code{vxworks-timeout}.
16206 This option is set by the user, and @var{args} represents the number of
16207 seconds @value{GDBN} waits for responses to rpc's. You might use this if
16208 your VxWorks target is a slow software simulator or is on the far side
16209 of a thin network line.
16212 The following information on connecting to VxWorks was current when
16213 this manual was produced; newer releases of VxWorks may use revised
16216 @findex INCLUDE_RDB
16217 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
16218 to include the remote debugging interface routines in the VxWorks
16219 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
16220 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
16221 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
16222 source debugging task @code{tRdbTask} when VxWorks is booted. For more
16223 information on configuring and remaking VxWorks, see the manufacturer's
16225 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
16227 Once you have included @file{rdb.a} in your VxWorks system image and set
16228 your Unix execution search path to find @value{GDBN}, you are ready to
16229 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
16230 @code{vxgdb}, depending on your installation).
16232 @value{GDBN} comes up showing the prompt:
16239 * VxWorks Connection:: Connecting to VxWorks
16240 * VxWorks Download:: VxWorks download
16241 * VxWorks Attach:: Running tasks
16244 @node VxWorks Connection
16245 @subsubsection Connecting to VxWorks
16247 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
16248 network. To connect to a target whose host name is ``@code{tt}'', type:
16251 (vxgdb) target vxworks tt
16255 @value{GDBN} displays messages like these:
16258 Attaching remote machine across net...
16263 @value{GDBN} then attempts to read the symbol tables of any object modules
16264 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
16265 these files by searching the directories listed in the command search
16266 path (@pxref{Environment, ,Your Program's Environment}); if it fails
16267 to find an object file, it displays a message such as:
16270 prog.o: No such file or directory.
16273 When this happens, add the appropriate directory to the search path with
16274 the @value{GDBN} command @code{path}, and execute the @code{target}
16277 @node VxWorks Download
16278 @subsubsection VxWorks Download
16280 @cindex download to VxWorks
16281 If you have connected to the VxWorks target and you want to debug an
16282 object that has not yet been loaded, you can use the @value{GDBN}
16283 @code{load} command to download a file from Unix to VxWorks
16284 incrementally. The object file given as an argument to the @code{load}
16285 command is actually opened twice: first by the VxWorks target in order
16286 to download the code, then by @value{GDBN} in order to read the symbol
16287 table. This can lead to problems if the current working directories on
16288 the two systems differ. If both systems have NFS mounted the same
16289 filesystems, you can avoid these problems by using absolute paths.
16290 Otherwise, it is simplest to set the working directory on both systems
16291 to the directory in which the object file resides, and then to reference
16292 the file by its name, without any path. For instance, a program
16293 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
16294 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
16295 program, type this on VxWorks:
16298 -> cd "@var{vxpath}/vw/demo/rdb"
16302 Then, in @value{GDBN}, type:
16305 (vxgdb) cd @var{hostpath}/vw/demo/rdb
16306 (vxgdb) load prog.o
16309 @value{GDBN} displays a response similar to this:
16312 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
16315 You can also use the @code{load} command to reload an object module
16316 after editing and recompiling the corresponding source file. Note that
16317 this makes @value{GDBN} delete all currently-defined breakpoints,
16318 auto-displays, and convenience variables, and to clear the value
16319 history. (This is necessary in order to preserve the integrity of
16320 debugger's data structures that reference the target system's symbol
16323 @node VxWorks Attach
16324 @subsubsection Running Tasks
16326 @cindex running VxWorks tasks
16327 You can also attach to an existing task using the @code{attach} command as
16331 (vxgdb) attach @var{task}
16335 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
16336 or suspended when you attach to it. Running tasks are suspended at
16337 the time of attachment.
16339 @node Embedded Processors
16340 @section Embedded Processors
16342 This section goes into details specific to particular embedded
16345 @cindex send command to simulator
16346 Whenever a specific embedded processor has a simulator, @value{GDBN}
16347 allows to send an arbitrary command to the simulator.
16350 @item sim @var{command}
16351 @kindex sim@r{, a command}
16352 Send an arbitrary @var{command} string to the simulator. Consult the
16353 documentation for the specific simulator in use for information about
16354 acceptable commands.
16360 * M32R/D:: Renesas M32R/D
16361 * M68K:: Motorola M68K
16362 * MIPS Embedded:: MIPS Embedded
16363 * OpenRISC 1000:: OpenRisc 1000
16364 * PA:: HP PA Embedded
16365 * PowerPC Embedded:: PowerPC Embedded
16366 * Sparclet:: Tsqware Sparclet
16367 * Sparclite:: Fujitsu Sparclite
16368 * Z8000:: Zilog Z8000
16371 * Super-H:: Renesas Super-H
16380 @item target rdi @var{dev}
16381 ARM Angel monitor, via RDI library interface to ADP protocol. You may
16382 use this target to communicate with both boards running the Angel
16383 monitor, or with the EmbeddedICE JTAG debug device.
16386 @item target rdp @var{dev}
16391 @value{GDBN} provides the following ARM-specific commands:
16394 @item set arm disassembler
16396 This commands selects from a list of disassembly styles. The
16397 @code{"std"} style is the standard style.
16399 @item show arm disassembler
16401 Show the current disassembly style.
16403 @item set arm apcs32
16404 @cindex ARM 32-bit mode
16405 This command toggles ARM operation mode between 32-bit and 26-bit.
16407 @item show arm apcs32
16408 Display the current usage of the ARM 32-bit mode.
16410 @item set arm fpu @var{fputype}
16411 This command sets the ARM floating-point unit (FPU) type. The
16412 argument @var{fputype} can be one of these:
16416 Determine the FPU type by querying the OS ABI.
16418 Software FPU, with mixed-endian doubles on little-endian ARM
16421 GCC-compiled FPA co-processor.
16423 Software FPU with pure-endian doubles.
16429 Show the current type of the FPU.
16432 This command forces @value{GDBN} to use the specified ABI.
16435 Show the currently used ABI.
16437 @item set arm fallback-mode (arm|thumb|auto)
16438 @value{GDBN} uses the symbol table, when available, to determine
16439 whether instructions are ARM or Thumb. This command controls
16440 @value{GDBN}'s default behavior when the symbol table is not
16441 available. The default is @samp{auto}, which causes @value{GDBN} to
16442 use the current execution mode (from the @code{T} bit in the @code{CPSR}
16445 @item show arm fallback-mode
16446 Show the current fallback instruction mode.
16448 @item set arm force-mode (arm|thumb|auto)
16449 This command overrides use of the symbol table to determine whether
16450 instructions are ARM or Thumb. The default is @samp{auto}, which
16451 causes @value{GDBN} to use the symbol table and then the setting
16452 of @samp{set arm fallback-mode}.
16454 @item show arm force-mode
16455 Show the current forced instruction mode.
16457 @item set debug arm
16458 Toggle whether to display ARM-specific debugging messages from the ARM
16459 target support subsystem.
16461 @item show debug arm
16462 Show whether ARM-specific debugging messages are enabled.
16465 The following commands are available when an ARM target is debugged
16466 using the RDI interface:
16469 @item rdilogfile @r{[}@var{file}@r{]}
16471 @cindex ADP (Angel Debugger Protocol) logging
16472 Set the filename for the ADP (Angel Debugger Protocol) packet log.
16473 With an argument, sets the log file to the specified @var{file}. With
16474 no argument, show the current log file name. The default log file is
16477 @item rdilogenable @r{[}@var{arg}@r{]}
16478 @kindex rdilogenable
16479 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
16480 enables logging, with an argument 0 or @code{"no"} disables it. With
16481 no arguments displays the current setting. When logging is enabled,
16482 ADP packets exchanged between @value{GDBN} and the RDI target device
16483 are logged to a file.
16485 @item set rdiromatzero
16486 @kindex set rdiromatzero
16487 @cindex ROM at zero address, RDI
16488 Tell @value{GDBN} whether the target has ROM at address 0. If on,
16489 vector catching is disabled, so that zero address can be used. If off
16490 (the default), vector catching is enabled. For this command to take
16491 effect, it needs to be invoked prior to the @code{target rdi} command.
16493 @item show rdiromatzero
16494 @kindex show rdiromatzero
16495 Show the current setting of ROM at zero address.
16497 @item set rdiheartbeat
16498 @kindex set rdiheartbeat
16499 @cindex RDI heartbeat
16500 Enable or disable RDI heartbeat packets. It is not recommended to
16501 turn on this option, since it confuses ARM and EPI JTAG interface, as
16502 well as the Angel monitor.
16504 @item show rdiheartbeat
16505 @kindex show rdiheartbeat
16506 Show the setting of RDI heartbeat packets.
16511 @subsection Renesas M32R/D and M32R/SDI
16514 @kindex target m32r
16515 @item target m32r @var{dev}
16516 Renesas M32R/D ROM monitor.
16518 @kindex target m32rsdi
16519 @item target m32rsdi @var{dev}
16520 Renesas M32R SDI server, connected via parallel port to the board.
16523 The following @value{GDBN} commands are specific to the M32R monitor:
16526 @item set download-path @var{path}
16527 @kindex set download-path
16528 @cindex find downloadable @sc{srec} files (M32R)
16529 Set the default path for finding downloadable @sc{srec} files.
16531 @item show download-path
16532 @kindex show download-path
16533 Show the default path for downloadable @sc{srec} files.
16535 @item set board-address @var{addr}
16536 @kindex set board-address
16537 @cindex M32-EVA target board address
16538 Set the IP address for the M32R-EVA target board.
16540 @item show board-address
16541 @kindex show board-address
16542 Show the current IP address of the target board.
16544 @item set server-address @var{addr}
16545 @kindex set server-address
16546 @cindex download server address (M32R)
16547 Set the IP address for the download server, which is the @value{GDBN}'s
16550 @item show server-address
16551 @kindex show server-address
16552 Display the IP address of the download server.
16554 @item upload @r{[}@var{file}@r{]}
16555 @kindex upload@r{, M32R}
16556 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
16557 upload capability. If no @var{file} argument is given, the current
16558 executable file is uploaded.
16560 @item tload @r{[}@var{file}@r{]}
16561 @kindex tload@r{, M32R}
16562 Test the @code{upload} command.
16565 The following commands are available for M32R/SDI:
16570 @cindex reset SDI connection, M32R
16571 This command resets the SDI connection.
16575 This command shows the SDI connection status.
16578 @kindex debug_chaos
16579 @cindex M32R/Chaos debugging
16580 Instructs the remote that M32R/Chaos debugging is to be used.
16582 @item use_debug_dma
16583 @kindex use_debug_dma
16584 Instructs the remote to use the DEBUG_DMA method of accessing memory.
16587 @kindex use_mon_code
16588 Instructs the remote to use the MON_CODE method of accessing memory.
16591 @kindex use_ib_break
16592 Instructs the remote to set breakpoints by IB break.
16594 @item use_dbt_break
16595 @kindex use_dbt_break
16596 Instructs the remote to set breakpoints by DBT.
16602 The Motorola m68k configuration includes ColdFire support, and a
16603 target command for the following ROM monitor.
16607 @kindex target dbug
16608 @item target dbug @var{dev}
16609 dBUG ROM monitor for Motorola ColdFire.
16613 @node MIPS Embedded
16614 @subsection MIPS Embedded
16616 @cindex MIPS boards
16617 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
16618 MIPS board attached to a serial line. This is available when
16619 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
16622 Use these @value{GDBN} commands to specify the connection to your target board:
16625 @item target mips @var{port}
16626 @kindex target mips @var{port}
16627 To run a program on the board, start up @code{@value{GDBP}} with the
16628 name of your program as the argument. To connect to the board, use the
16629 command @samp{target mips @var{port}}, where @var{port} is the name of
16630 the serial port connected to the board. If the program has not already
16631 been downloaded to the board, you may use the @code{load} command to
16632 download it. You can then use all the usual @value{GDBN} commands.
16634 For example, this sequence connects to the target board through a serial
16635 port, and loads and runs a program called @var{prog} through the
16639 host$ @value{GDBP} @var{prog}
16640 @value{GDBN} is free software and @dots{}
16641 (@value{GDBP}) target mips /dev/ttyb
16642 (@value{GDBP}) load @var{prog}
16646 @item target mips @var{hostname}:@var{portnumber}
16647 On some @value{GDBN} host configurations, you can specify a TCP
16648 connection (for instance, to a serial line managed by a terminal
16649 concentrator) instead of a serial port, using the syntax
16650 @samp{@var{hostname}:@var{portnumber}}.
16652 @item target pmon @var{port}
16653 @kindex target pmon @var{port}
16656 @item target ddb @var{port}
16657 @kindex target ddb @var{port}
16658 NEC's DDB variant of PMON for Vr4300.
16660 @item target lsi @var{port}
16661 @kindex target lsi @var{port}
16662 LSI variant of PMON.
16664 @kindex target r3900
16665 @item target r3900 @var{dev}
16666 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
16668 @kindex target array
16669 @item target array @var{dev}
16670 Array Tech LSI33K RAID controller board.
16676 @value{GDBN} also supports these special commands for MIPS targets:
16679 @item set mipsfpu double
16680 @itemx set mipsfpu single
16681 @itemx set mipsfpu none
16682 @itemx set mipsfpu auto
16683 @itemx show mipsfpu
16684 @kindex set mipsfpu
16685 @kindex show mipsfpu
16686 @cindex MIPS remote floating point
16687 @cindex floating point, MIPS remote
16688 If your target board does not support the MIPS floating point
16689 coprocessor, you should use the command @samp{set mipsfpu none} (if you
16690 need this, you may wish to put the command in your @value{GDBN} init
16691 file). This tells @value{GDBN} how to find the return value of
16692 functions which return floating point values. It also allows
16693 @value{GDBN} to avoid saving the floating point registers when calling
16694 functions on the board. If you are using a floating point coprocessor
16695 with only single precision floating point support, as on the @sc{r4650}
16696 processor, use the command @samp{set mipsfpu single}. The default
16697 double precision floating point coprocessor may be selected using
16698 @samp{set mipsfpu double}.
16700 In previous versions the only choices were double precision or no
16701 floating point, so @samp{set mipsfpu on} will select double precision
16702 and @samp{set mipsfpu off} will select no floating point.
16704 As usual, you can inquire about the @code{mipsfpu} variable with
16705 @samp{show mipsfpu}.
16707 @item set timeout @var{seconds}
16708 @itemx set retransmit-timeout @var{seconds}
16709 @itemx show timeout
16710 @itemx show retransmit-timeout
16711 @cindex @code{timeout}, MIPS protocol
16712 @cindex @code{retransmit-timeout}, MIPS protocol
16713 @kindex set timeout
16714 @kindex show timeout
16715 @kindex set retransmit-timeout
16716 @kindex show retransmit-timeout
16717 You can control the timeout used while waiting for a packet, in the MIPS
16718 remote protocol, with the @code{set timeout @var{seconds}} command. The
16719 default is 5 seconds. Similarly, you can control the timeout used while
16720 waiting for an acknowledgment of a packet with the @code{set
16721 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
16722 You can inspect both values with @code{show timeout} and @code{show
16723 retransmit-timeout}. (These commands are @emph{only} available when
16724 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
16726 The timeout set by @code{set timeout} does not apply when @value{GDBN}
16727 is waiting for your program to stop. In that case, @value{GDBN} waits
16728 forever because it has no way of knowing how long the program is going
16729 to run before stopping.
16731 @item set syn-garbage-limit @var{num}
16732 @kindex set syn-garbage-limit@r{, MIPS remote}
16733 @cindex synchronize with remote MIPS target
16734 Limit the maximum number of characters @value{GDBN} should ignore when
16735 it tries to synchronize with the remote target. The default is 10
16736 characters. Setting the limit to -1 means there's no limit.
16738 @item show syn-garbage-limit
16739 @kindex show syn-garbage-limit@r{, MIPS remote}
16740 Show the current limit on the number of characters to ignore when
16741 trying to synchronize with the remote system.
16743 @item set monitor-prompt @var{prompt}
16744 @kindex set monitor-prompt@r{, MIPS remote}
16745 @cindex remote monitor prompt
16746 Tell @value{GDBN} to expect the specified @var{prompt} string from the
16747 remote monitor. The default depends on the target:
16757 @item show monitor-prompt
16758 @kindex show monitor-prompt@r{, MIPS remote}
16759 Show the current strings @value{GDBN} expects as the prompt from the
16762 @item set monitor-warnings
16763 @kindex set monitor-warnings@r{, MIPS remote}
16764 Enable or disable monitor warnings about hardware breakpoints. This
16765 has effect only for the @code{lsi} target. When on, @value{GDBN} will
16766 display warning messages whose codes are returned by the @code{lsi}
16767 PMON monitor for breakpoint commands.
16769 @item show monitor-warnings
16770 @kindex show monitor-warnings@r{, MIPS remote}
16771 Show the current setting of printing monitor warnings.
16773 @item pmon @var{command}
16774 @kindex pmon@r{, MIPS remote}
16775 @cindex send PMON command
16776 This command allows sending an arbitrary @var{command} string to the
16777 monitor. The monitor must be in debug mode for this to work.
16780 @node OpenRISC 1000
16781 @subsection OpenRISC 1000
16782 @cindex OpenRISC 1000
16784 @cindex or1k boards
16785 See OR1k Architecture document (@uref{www.opencores.org}) for more information
16786 about platform and commands.
16790 @kindex target jtag
16791 @item target jtag jtag://@var{host}:@var{port}
16793 Connects to remote JTAG server.
16794 JTAG remote server can be either an or1ksim or JTAG server,
16795 connected via parallel port to the board.
16797 Example: @code{target jtag jtag://localhost:9999}
16800 @item or1ksim @var{command}
16801 If connected to @code{or1ksim} OpenRISC 1000 Architectural
16802 Simulator, proprietary commands can be executed.
16804 @kindex info or1k spr
16805 @item info or1k spr
16806 Displays spr groups.
16808 @item info or1k spr @var{group}
16809 @itemx info or1k spr @var{groupno}
16810 Displays register names in selected group.
16812 @item info or1k spr @var{group} @var{register}
16813 @itemx info or1k spr @var{register}
16814 @itemx info or1k spr @var{groupno} @var{registerno}
16815 @itemx info or1k spr @var{registerno}
16816 Shows information about specified spr register.
16819 @item spr @var{group} @var{register} @var{value}
16820 @itemx spr @var{register @var{value}}
16821 @itemx spr @var{groupno} @var{registerno @var{value}}
16822 @itemx spr @var{registerno @var{value}}
16823 Writes @var{value} to specified spr register.
16826 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
16827 It is very similar to @value{GDBN} trace, except it does not interfere with normal
16828 program execution and is thus much faster. Hardware breakpoints/watchpoint
16829 triggers can be set using:
16832 Load effective address/data
16834 Store effective address/data
16836 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
16841 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
16842 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
16844 @code{htrace} commands:
16845 @cindex OpenRISC 1000 htrace
16848 @item hwatch @var{conditional}
16849 Set hardware watchpoint on combination of Load/Store Effective Address(es)
16850 or Data. For example:
16852 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
16854 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
16858 Display information about current HW trace configuration.
16860 @item htrace trigger @var{conditional}
16861 Set starting criteria for HW trace.
16863 @item htrace qualifier @var{conditional}
16864 Set acquisition qualifier for HW trace.
16866 @item htrace stop @var{conditional}
16867 Set HW trace stopping criteria.
16869 @item htrace record [@var{data}]*
16870 Selects the data to be recorded, when qualifier is met and HW trace was
16873 @item htrace enable
16874 @itemx htrace disable
16875 Enables/disables the HW trace.
16877 @item htrace rewind [@var{filename}]
16878 Clears currently recorded trace data.
16880 If filename is specified, new trace file is made and any newly collected data
16881 will be written there.
16883 @item htrace print [@var{start} [@var{len}]]
16884 Prints trace buffer, using current record configuration.
16886 @item htrace mode continuous
16887 Set continuous trace mode.
16889 @item htrace mode suspend
16890 Set suspend trace mode.
16894 @node PowerPC Embedded
16895 @subsection PowerPC Embedded
16897 @value{GDBN} provides the following PowerPC-specific commands:
16900 @kindex set powerpc
16901 @item set powerpc soft-float
16902 @itemx show powerpc soft-float
16903 Force @value{GDBN} to use (or not use) a software floating point calling
16904 convention. By default, @value{GDBN} selects the calling convention based
16905 on the selected architecture and the provided executable file.
16907 @item set powerpc vector-abi
16908 @itemx show powerpc vector-abi
16909 Force @value{GDBN} to use the specified calling convention for vector
16910 arguments and return values. The valid options are @samp{auto};
16911 @samp{generic}, to avoid vector registers even if they are present;
16912 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
16913 registers. By default, @value{GDBN} selects the calling convention
16914 based on the selected architecture and the provided executable file.
16916 @kindex target dink32
16917 @item target dink32 @var{dev}
16918 DINK32 ROM monitor.
16920 @kindex target ppcbug
16921 @item target ppcbug @var{dev}
16922 @kindex target ppcbug1
16923 @item target ppcbug1 @var{dev}
16924 PPCBUG ROM monitor for PowerPC.
16927 @item target sds @var{dev}
16928 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
16931 @cindex SDS protocol
16932 The following commands specific to the SDS protocol are supported
16936 @item set sdstimeout @var{nsec}
16937 @kindex set sdstimeout
16938 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
16939 default is 2 seconds.
16941 @item show sdstimeout
16942 @kindex show sdstimeout
16943 Show the current value of the SDS timeout.
16945 @item sds @var{command}
16946 @kindex sds@r{, a command}
16947 Send the specified @var{command} string to the SDS monitor.
16952 @subsection HP PA Embedded
16956 @kindex target op50n
16957 @item target op50n @var{dev}
16958 OP50N monitor, running on an OKI HPPA board.
16960 @kindex target w89k
16961 @item target w89k @var{dev}
16962 W89K monitor, running on a Winbond HPPA board.
16967 @subsection Tsqware Sparclet
16971 @value{GDBN} enables developers to debug tasks running on
16972 Sparclet targets from a Unix host.
16973 @value{GDBN} uses code that runs on
16974 both the Unix host and on the Sparclet target. The program
16975 @code{@value{GDBP}} is installed and executed on the Unix host.
16978 @item remotetimeout @var{args}
16979 @kindex remotetimeout
16980 @value{GDBN} supports the option @code{remotetimeout}.
16981 This option is set by the user, and @var{args} represents the number of
16982 seconds @value{GDBN} waits for responses.
16985 @cindex compiling, on Sparclet
16986 When compiling for debugging, include the options @samp{-g} to get debug
16987 information and @samp{-Ttext} to relocate the program to where you wish to
16988 load it on the target. You may also want to add the options @samp{-n} or
16989 @samp{-N} in order to reduce the size of the sections. Example:
16992 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
16995 You can use @code{objdump} to verify that the addresses are what you intended:
16998 sparclet-aout-objdump --headers --syms prog
17001 @cindex running, on Sparclet
17003 your Unix execution search path to find @value{GDBN}, you are ready to
17004 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
17005 (or @code{sparclet-aout-gdb}, depending on your installation).
17007 @value{GDBN} comes up showing the prompt:
17014 * Sparclet File:: Setting the file to debug
17015 * Sparclet Connection:: Connecting to Sparclet
17016 * Sparclet Download:: Sparclet download
17017 * Sparclet Execution:: Running and debugging
17020 @node Sparclet File
17021 @subsubsection Setting File to Debug
17023 The @value{GDBN} command @code{file} lets you choose with program to debug.
17026 (gdbslet) file prog
17030 @value{GDBN} then attempts to read the symbol table of @file{prog}.
17031 @value{GDBN} locates
17032 the file by searching the directories listed in the command search
17034 If the file was compiled with debug information (option @samp{-g}), source
17035 files will be searched as well.
17036 @value{GDBN} locates
17037 the source files by searching the directories listed in the directory search
17038 path (@pxref{Environment, ,Your Program's Environment}).
17040 to find a file, it displays a message such as:
17043 prog: No such file or directory.
17046 When this happens, add the appropriate directories to the search paths with
17047 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
17048 @code{target} command again.
17050 @node Sparclet Connection
17051 @subsubsection Connecting to Sparclet
17053 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
17054 To connect to a target on serial port ``@code{ttya}'', type:
17057 (gdbslet) target sparclet /dev/ttya
17058 Remote target sparclet connected to /dev/ttya
17059 main () at ../prog.c:3
17063 @value{GDBN} displays messages like these:
17069 @node Sparclet Download
17070 @subsubsection Sparclet Download
17072 @cindex download to Sparclet
17073 Once connected to the Sparclet target,
17074 you can use the @value{GDBN}
17075 @code{load} command to download the file from the host to the target.
17076 The file name and load offset should be given as arguments to the @code{load}
17078 Since the file format is aout, the program must be loaded to the starting
17079 address. You can use @code{objdump} to find out what this value is. The load
17080 offset is an offset which is added to the VMA (virtual memory address)
17081 of each of the file's sections.
17082 For instance, if the program
17083 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
17084 and bss at 0x12010170, in @value{GDBN}, type:
17087 (gdbslet) load prog 0x12010000
17088 Loading section .text, size 0xdb0 vma 0x12010000
17091 If the code is loaded at a different address then what the program was linked
17092 to, you may need to use the @code{section} and @code{add-symbol-file} commands
17093 to tell @value{GDBN} where to map the symbol table.
17095 @node Sparclet Execution
17096 @subsubsection Running and Debugging
17098 @cindex running and debugging Sparclet programs
17099 You can now begin debugging the task using @value{GDBN}'s execution control
17100 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
17101 manual for the list of commands.
17105 Breakpoint 1 at 0x12010000: file prog.c, line 3.
17107 Starting program: prog
17108 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
17109 3 char *symarg = 0;
17111 4 char *execarg = "hello!";
17116 @subsection Fujitsu Sparclite
17120 @kindex target sparclite
17121 @item target sparclite @var{dev}
17122 Fujitsu sparclite boards, used only for the purpose of loading.
17123 You must use an additional command to debug the program.
17124 For example: target remote @var{dev} using @value{GDBN} standard
17130 @subsection Zilog Z8000
17133 @cindex simulator, Z8000
17134 @cindex Zilog Z8000 simulator
17136 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
17139 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
17140 unsegmented variant of the Z8000 architecture) or the Z8001 (the
17141 segmented variant). The simulator recognizes which architecture is
17142 appropriate by inspecting the object code.
17145 @item target sim @var{args}
17147 @kindex target sim@r{, with Z8000}
17148 Debug programs on a simulated CPU. If the simulator supports setup
17149 options, specify them via @var{args}.
17153 After specifying this target, you can debug programs for the simulated
17154 CPU in the same style as programs for your host computer; use the
17155 @code{file} command to load a new program image, the @code{run} command
17156 to run your program, and so on.
17158 As well as making available all the usual machine registers
17159 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
17160 additional items of information as specially named registers:
17165 Counts clock-ticks in the simulator.
17168 Counts instructions run in the simulator.
17171 Execution time in 60ths of a second.
17175 You can refer to these values in @value{GDBN} expressions with the usual
17176 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
17177 conditional breakpoint that suspends only after at least 5000
17178 simulated clock ticks.
17181 @subsection Atmel AVR
17184 When configured for debugging the Atmel AVR, @value{GDBN} supports the
17185 following AVR-specific commands:
17188 @item info io_registers
17189 @kindex info io_registers@r{, AVR}
17190 @cindex I/O registers (Atmel AVR)
17191 This command displays information about the AVR I/O registers. For
17192 each register, @value{GDBN} prints its number and value.
17199 When configured for debugging CRIS, @value{GDBN} provides the
17200 following CRIS-specific commands:
17203 @item set cris-version @var{ver}
17204 @cindex CRIS version
17205 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
17206 The CRIS version affects register names and sizes. This command is useful in
17207 case autodetection of the CRIS version fails.
17209 @item show cris-version
17210 Show the current CRIS version.
17212 @item set cris-dwarf2-cfi
17213 @cindex DWARF-2 CFI and CRIS
17214 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
17215 Change to @samp{off} when using @code{gcc-cris} whose version is below
17218 @item show cris-dwarf2-cfi
17219 Show the current state of using DWARF-2 CFI.
17221 @item set cris-mode @var{mode}
17223 Set the current CRIS mode to @var{mode}. It should only be changed when
17224 debugging in guru mode, in which case it should be set to
17225 @samp{guru} (the default is @samp{normal}).
17227 @item show cris-mode
17228 Show the current CRIS mode.
17232 @subsection Renesas Super-H
17235 For the Renesas Super-H processor, @value{GDBN} provides these
17240 @kindex regs@r{, Super-H}
17241 Show the values of all Super-H registers.
17243 @item set sh calling-convention @var{convention}
17244 @kindex set sh calling-convention
17245 Set the calling-convention used when calling functions from @value{GDBN}.
17246 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
17247 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
17248 convention. If the DWARF-2 information of the called function specifies
17249 that the function follows the Renesas calling convention, the function
17250 is called using the Renesas calling convention. If the calling convention
17251 is set to @samp{renesas}, the Renesas calling convention is always used,
17252 regardless of the DWARF-2 information. This can be used to override the
17253 default of @samp{gcc} if debug information is missing, or the compiler
17254 does not emit the DWARF-2 calling convention entry for a function.
17256 @item show sh calling-convention
17257 @kindex show sh calling-convention
17258 Show the current calling convention setting.
17263 @node Architectures
17264 @section Architectures
17266 This section describes characteristics of architectures that affect
17267 all uses of @value{GDBN} with the architecture, both native and cross.
17274 * HPPA:: HP PA architecture
17275 * SPU:: Cell Broadband Engine SPU architecture
17280 @subsection x86 Architecture-specific Issues
17283 @item set struct-convention @var{mode}
17284 @kindex set struct-convention
17285 @cindex struct return convention
17286 @cindex struct/union returned in registers
17287 Set the convention used by the inferior to return @code{struct}s and
17288 @code{union}s from functions to @var{mode}. Possible values of
17289 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
17290 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
17291 are returned on the stack, while @code{"reg"} means that a
17292 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
17293 be returned in a register.
17295 @item show struct-convention
17296 @kindex show struct-convention
17297 Show the current setting of the convention to return @code{struct}s
17306 @kindex set rstack_high_address
17307 @cindex AMD 29K register stack
17308 @cindex register stack, AMD29K
17309 @item set rstack_high_address @var{address}
17310 On AMD 29000 family processors, registers are saved in a separate
17311 @dfn{register stack}. There is no way for @value{GDBN} to determine the
17312 extent of this stack. Normally, @value{GDBN} just assumes that the
17313 stack is ``large enough''. This may result in @value{GDBN} referencing
17314 memory locations that do not exist. If necessary, you can get around
17315 this problem by specifying the ending address of the register stack with
17316 the @code{set rstack_high_address} command. The argument should be an
17317 address, which you probably want to precede with @samp{0x} to specify in
17320 @kindex show rstack_high_address
17321 @item show rstack_high_address
17322 Display the current limit of the register stack, on AMD 29000 family
17330 See the following section.
17335 @cindex stack on Alpha
17336 @cindex stack on MIPS
17337 @cindex Alpha stack
17339 Alpha- and MIPS-based computers use an unusual stack frame, which
17340 sometimes requires @value{GDBN} to search backward in the object code to
17341 find the beginning of a function.
17343 @cindex response time, MIPS debugging
17344 To improve response time (especially for embedded applications, where
17345 @value{GDBN} may be restricted to a slow serial line for this search)
17346 you may want to limit the size of this search, using one of these
17350 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
17351 @item set heuristic-fence-post @var{limit}
17352 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
17353 search for the beginning of a function. A value of @var{0} (the
17354 default) means there is no limit. However, except for @var{0}, the
17355 larger the limit the more bytes @code{heuristic-fence-post} must search
17356 and therefore the longer it takes to run. You should only need to use
17357 this command when debugging a stripped executable.
17359 @item show heuristic-fence-post
17360 Display the current limit.
17364 These commands are available @emph{only} when @value{GDBN} is configured
17365 for debugging programs on Alpha or MIPS processors.
17367 Several MIPS-specific commands are available when debugging MIPS
17371 @item set mips abi @var{arg}
17372 @kindex set mips abi
17373 @cindex set ABI for MIPS
17374 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
17375 values of @var{arg} are:
17379 The default ABI associated with the current binary (this is the
17390 @item show mips abi
17391 @kindex show mips abi
17392 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
17395 @itemx show mipsfpu
17396 @xref{MIPS Embedded, set mipsfpu}.
17398 @item set mips mask-address @var{arg}
17399 @kindex set mips mask-address
17400 @cindex MIPS addresses, masking
17401 This command determines whether the most-significant 32 bits of 64-bit
17402 MIPS addresses are masked off. The argument @var{arg} can be
17403 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
17404 setting, which lets @value{GDBN} determine the correct value.
17406 @item show mips mask-address
17407 @kindex show mips mask-address
17408 Show whether the upper 32 bits of MIPS addresses are masked off or
17411 @item set remote-mips64-transfers-32bit-regs
17412 @kindex set remote-mips64-transfers-32bit-regs
17413 This command controls compatibility with 64-bit MIPS targets that
17414 transfer data in 32-bit quantities. If you have an old MIPS 64 target
17415 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
17416 and 64 bits for other registers, set this option to @samp{on}.
17418 @item show remote-mips64-transfers-32bit-regs
17419 @kindex show remote-mips64-transfers-32bit-regs
17420 Show the current setting of compatibility with older MIPS 64 targets.
17422 @item set debug mips
17423 @kindex set debug mips
17424 This command turns on and off debugging messages for the MIPS-specific
17425 target code in @value{GDBN}.
17427 @item show debug mips
17428 @kindex show debug mips
17429 Show the current setting of MIPS debugging messages.
17435 @cindex HPPA support
17437 When @value{GDBN} is debugging the HP PA architecture, it provides the
17438 following special commands:
17441 @item set debug hppa
17442 @kindex set debug hppa
17443 This command determines whether HPPA architecture-specific debugging
17444 messages are to be displayed.
17446 @item show debug hppa
17447 Show whether HPPA debugging messages are displayed.
17449 @item maint print unwind @var{address}
17450 @kindex maint print unwind@r{, HPPA}
17451 This command displays the contents of the unwind table entry at the
17452 given @var{address}.
17458 @subsection Cell Broadband Engine SPU architecture
17459 @cindex Cell Broadband Engine
17462 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
17463 it provides the following special commands:
17466 @item info spu event
17468 Display SPU event facility status. Shows current event mask
17469 and pending event status.
17471 @item info spu signal
17472 Display SPU signal notification facility status. Shows pending
17473 signal-control word and signal notification mode of both signal
17474 notification channels.
17476 @item info spu mailbox
17477 Display SPU mailbox facility status. Shows all pending entries,
17478 in order of processing, in each of the SPU Write Outbound,
17479 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
17482 Display MFC DMA status. Shows all pending commands in the MFC
17483 DMA queue. For each entry, opcode, tag, class IDs, effective
17484 and local store addresses and transfer size are shown.
17486 @item info spu proxydma
17487 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
17488 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
17489 and local store addresses and transfer size are shown.
17493 When @value{GDBN} is debugging a combined PowerPC/SPU application
17494 on the Cell Broadband Engine, it provides in addition the following
17498 @item set spu stop-on-load @var{arg}
17500 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
17501 will give control to the user when a new SPE thread enters its @code{main}
17502 function. The default is @code{off}.
17504 @item show spu stop-on-load
17506 Show whether to stop for new SPE threads.
17511 @subsection PowerPC
17512 @cindex PowerPC architecture
17514 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
17515 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
17516 numbers stored in the floating point registers. These values must be stored
17517 in two consecutive registers, always starting at an even register like
17518 @code{f0} or @code{f2}.
17520 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
17521 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
17522 @code{f2} and @code{f3} for @code{$dl1} and so on.
17524 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
17525 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
17528 @node Controlling GDB
17529 @chapter Controlling @value{GDBN}
17531 You can alter the way @value{GDBN} interacts with you by using the
17532 @code{set} command. For commands controlling how @value{GDBN} displays
17533 data, see @ref{Print Settings, ,Print Settings}. Other settings are
17538 * Editing:: Command editing
17539 * Command History:: Command history
17540 * Screen Size:: Screen size
17541 * Numbers:: Numbers
17542 * ABI:: Configuring the current ABI
17543 * Messages/Warnings:: Optional warnings and messages
17544 * Debugging Output:: Optional messages about internal happenings
17552 @value{GDBN} indicates its readiness to read a command by printing a string
17553 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
17554 can change the prompt string with the @code{set prompt} command. For
17555 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
17556 the prompt in one of the @value{GDBN} sessions so that you can always tell
17557 which one you are talking to.
17559 @emph{Note:} @code{set prompt} does not add a space for you after the
17560 prompt you set. This allows you to set a prompt which ends in a space
17561 or a prompt that does not.
17565 @item set prompt @var{newprompt}
17566 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
17568 @kindex show prompt
17570 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
17574 @section Command Editing
17576 @cindex command line editing
17578 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
17579 @sc{gnu} library provides consistent behavior for programs which provide a
17580 command line interface to the user. Advantages are @sc{gnu} Emacs-style
17581 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
17582 substitution, and a storage and recall of command history across
17583 debugging sessions.
17585 You may control the behavior of command line editing in @value{GDBN} with the
17586 command @code{set}.
17589 @kindex set editing
17592 @itemx set editing on
17593 Enable command line editing (enabled by default).
17595 @item set editing off
17596 Disable command line editing.
17598 @kindex show editing
17600 Show whether command line editing is enabled.
17603 @xref{Command Line Editing}, for more details about the Readline
17604 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
17605 encouraged to read that chapter.
17607 @node Command History
17608 @section Command History
17609 @cindex command history
17611 @value{GDBN} can keep track of the commands you type during your
17612 debugging sessions, so that you can be certain of precisely what
17613 happened. Use these commands to manage the @value{GDBN} command
17616 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
17617 package, to provide the history facility. @xref{Using History
17618 Interactively}, for the detailed description of the History library.
17620 To issue a command to @value{GDBN} without affecting certain aspects of
17621 the state which is seen by users, prefix it with @samp{server }
17622 (@pxref{Server Prefix}). This
17623 means that this command will not affect the command history, nor will it
17624 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
17625 pressed on a line by itself.
17627 @cindex @code{server}, command prefix
17628 The server prefix does not affect the recording of values into the value
17629 history; to print a value without recording it into the value history,
17630 use the @code{output} command instead of the @code{print} command.
17632 Here is the description of @value{GDBN} commands related to command
17636 @cindex history substitution
17637 @cindex history file
17638 @kindex set history filename
17639 @cindex @env{GDBHISTFILE}, environment variable
17640 @item set history filename @var{fname}
17641 Set the name of the @value{GDBN} command history file to @var{fname}.
17642 This is the file where @value{GDBN} reads an initial command history
17643 list, and where it writes the command history from this session when it
17644 exits. You can access this list through history expansion or through
17645 the history command editing characters listed below. This file defaults
17646 to the value of the environment variable @code{GDBHISTFILE}, or to
17647 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
17650 @cindex save command history
17651 @kindex set history save
17652 @item set history save
17653 @itemx set history save on
17654 Record command history in a file, whose name may be specified with the
17655 @code{set history filename} command. By default, this option is disabled.
17657 @item set history save off
17658 Stop recording command history in a file.
17660 @cindex history size
17661 @kindex set history size
17662 @cindex @env{HISTSIZE}, environment variable
17663 @item set history size @var{size}
17664 Set the number of commands which @value{GDBN} keeps in its history list.
17665 This defaults to the value of the environment variable
17666 @code{HISTSIZE}, or to 256 if this variable is not set.
17669 History expansion assigns special meaning to the character @kbd{!}.
17670 @xref{Event Designators}, for more details.
17672 @cindex history expansion, turn on/off
17673 Since @kbd{!} is also the logical not operator in C, history expansion
17674 is off by default. If you decide to enable history expansion with the
17675 @code{set history expansion on} command, you may sometimes need to
17676 follow @kbd{!} (when it is used as logical not, in an expression) with
17677 a space or a tab to prevent it from being expanded. The readline
17678 history facilities do not attempt substitution on the strings
17679 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
17681 The commands to control history expansion are:
17684 @item set history expansion on
17685 @itemx set history expansion
17686 @kindex set history expansion
17687 Enable history expansion. History expansion is off by default.
17689 @item set history expansion off
17690 Disable history expansion.
17693 @kindex show history
17695 @itemx show history filename
17696 @itemx show history save
17697 @itemx show history size
17698 @itemx show history expansion
17699 These commands display the state of the @value{GDBN} history parameters.
17700 @code{show history} by itself displays all four states.
17705 @kindex show commands
17706 @cindex show last commands
17707 @cindex display command history
17708 @item show commands
17709 Display the last ten commands in the command history.
17711 @item show commands @var{n}
17712 Print ten commands centered on command number @var{n}.
17714 @item show commands +
17715 Print ten commands just after the commands last printed.
17719 @section Screen Size
17720 @cindex size of screen
17721 @cindex pauses in output
17723 Certain commands to @value{GDBN} may produce large amounts of
17724 information output to the screen. To help you read all of it,
17725 @value{GDBN} pauses and asks you for input at the end of each page of
17726 output. Type @key{RET} when you want to continue the output, or @kbd{q}
17727 to discard the remaining output. Also, the screen width setting
17728 determines when to wrap lines of output. Depending on what is being
17729 printed, @value{GDBN} tries to break the line at a readable place,
17730 rather than simply letting it overflow onto the following line.
17732 Normally @value{GDBN} knows the size of the screen from the terminal
17733 driver software. For example, on Unix @value{GDBN} uses the termcap data base
17734 together with the value of the @code{TERM} environment variable and the
17735 @code{stty rows} and @code{stty cols} settings. If this is not correct,
17736 you can override it with the @code{set height} and @code{set
17743 @kindex show height
17744 @item set height @var{lpp}
17746 @itemx set width @var{cpl}
17748 These @code{set} commands specify a screen height of @var{lpp} lines and
17749 a screen width of @var{cpl} characters. The associated @code{show}
17750 commands display the current settings.
17752 If you specify a height of zero lines, @value{GDBN} does not pause during
17753 output no matter how long the output is. This is useful if output is to a
17754 file or to an editor buffer.
17756 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
17757 from wrapping its output.
17759 @item set pagination on
17760 @itemx set pagination off
17761 @kindex set pagination
17762 Turn the output pagination on or off; the default is on. Turning
17763 pagination off is the alternative to @code{set height 0}.
17765 @item show pagination
17766 @kindex show pagination
17767 Show the current pagination mode.
17772 @cindex number representation
17773 @cindex entering numbers
17775 You can always enter numbers in octal, decimal, or hexadecimal in
17776 @value{GDBN} by the usual conventions: octal numbers begin with
17777 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
17778 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
17779 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
17780 10; likewise, the default display for numbers---when no particular
17781 format is specified---is base 10. You can change the default base for
17782 both input and output with the commands described below.
17785 @kindex set input-radix
17786 @item set input-radix @var{base}
17787 Set the default base for numeric input. Supported choices
17788 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
17789 specified either unambiguously or using the current input radix; for
17793 set input-radix 012
17794 set input-radix 10.
17795 set input-radix 0xa
17799 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
17800 leaves the input radix unchanged, no matter what it was, since
17801 @samp{10}, being without any leading or trailing signs of its base, is
17802 interpreted in the current radix. Thus, if the current radix is 16,
17803 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
17806 @kindex set output-radix
17807 @item set output-radix @var{base}
17808 Set the default base for numeric display. Supported choices
17809 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
17810 specified either unambiguously or using the current input radix.
17812 @kindex show input-radix
17813 @item show input-radix
17814 Display the current default base for numeric input.
17816 @kindex show output-radix
17817 @item show output-radix
17818 Display the current default base for numeric display.
17820 @item set radix @r{[}@var{base}@r{]}
17824 These commands set and show the default base for both input and output
17825 of numbers. @code{set radix} sets the radix of input and output to
17826 the same base; without an argument, it resets the radix back to its
17827 default value of 10.
17832 @section Configuring the Current ABI
17834 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
17835 application automatically. However, sometimes you need to override its
17836 conclusions. Use these commands to manage @value{GDBN}'s view of the
17843 One @value{GDBN} configuration can debug binaries for multiple operating
17844 system targets, either via remote debugging or native emulation.
17845 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
17846 but you can override its conclusion using the @code{set osabi} command.
17847 One example where this is useful is in debugging of binaries which use
17848 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
17849 not have the same identifying marks that the standard C library for your
17854 Show the OS ABI currently in use.
17857 With no argument, show the list of registered available OS ABI's.
17859 @item set osabi @var{abi}
17860 Set the current OS ABI to @var{abi}.
17863 @cindex float promotion
17865 Generally, the way that an argument of type @code{float} is passed to a
17866 function depends on whether the function is prototyped. For a prototyped
17867 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
17868 according to the architecture's convention for @code{float}. For unprototyped
17869 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
17870 @code{double} and then passed.
17872 Unfortunately, some forms of debug information do not reliably indicate whether
17873 a function is prototyped. If @value{GDBN} calls a function that is not marked
17874 as prototyped, it consults @kbd{set coerce-float-to-double}.
17877 @kindex set coerce-float-to-double
17878 @item set coerce-float-to-double
17879 @itemx set coerce-float-to-double on
17880 Arguments of type @code{float} will be promoted to @code{double} when passed
17881 to an unprototyped function. This is the default setting.
17883 @item set coerce-float-to-double off
17884 Arguments of type @code{float} will be passed directly to unprototyped
17887 @kindex show coerce-float-to-double
17888 @item show coerce-float-to-double
17889 Show the current setting of promoting @code{float} to @code{double}.
17893 @kindex show cp-abi
17894 @value{GDBN} needs to know the ABI used for your program's C@t{++}
17895 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
17896 used to build your application. @value{GDBN} only fully supports
17897 programs with a single C@t{++} ABI; if your program contains code using
17898 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
17899 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
17900 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
17901 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
17902 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
17903 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
17908 Show the C@t{++} ABI currently in use.
17911 With no argument, show the list of supported C@t{++} ABI's.
17913 @item set cp-abi @var{abi}
17914 @itemx set cp-abi auto
17915 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
17918 @node Messages/Warnings
17919 @section Optional Warnings and Messages
17921 @cindex verbose operation
17922 @cindex optional warnings
17923 By default, @value{GDBN} is silent about its inner workings. If you are
17924 running on a slow machine, you may want to use the @code{set verbose}
17925 command. This makes @value{GDBN} tell you when it does a lengthy
17926 internal operation, so you will not think it has crashed.
17928 Currently, the messages controlled by @code{set verbose} are those
17929 which announce that the symbol table for a source file is being read;
17930 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
17933 @kindex set verbose
17934 @item set verbose on
17935 Enables @value{GDBN} output of certain informational messages.
17937 @item set verbose off
17938 Disables @value{GDBN} output of certain informational messages.
17940 @kindex show verbose
17942 Displays whether @code{set verbose} is on or off.
17945 By default, if @value{GDBN} encounters bugs in the symbol table of an
17946 object file, it is silent; but if you are debugging a compiler, you may
17947 find this information useful (@pxref{Symbol Errors, ,Errors Reading
17952 @kindex set complaints
17953 @item set complaints @var{limit}
17954 Permits @value{GDBN} to output @var{limit} complaints about each type of
17955 unusual symbols before becoming silent about the problem. Set
17956 @var{limit} to zero to suppress all complaints; set it to a large number
17957 to prevent complaints from being suppressed.
17959 @kindex show complaints
17960 @item show complaints
17961 Displays how many symbol complaints @value{GDBN} is permitted to produce.
17965 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
17966 lot of stupid questions to confirm certain commands. For example, if
17967 you try to run a program which is already running:
17971 The program being debugged has been started already.
17972 Start it from the beginning? (y or n)
17975 If you are willing to unflinchingly face the consequences of your own
17976 commands, you can disable this ``feature'':
17980 @kindex set confirm
17982 @cindex confirmation
17983 @cindex stupid questions
17984 @item set confirm off
17985 Disables confirmation requests.
17987 @item set confirm on
17988 Enables confirmation requests (the default).
17990 @kindex show confirm
17992 Displays state of confirmation requests.
17996 @cindex command tracing
17997 If you need to debug user-defined commands or sourced files you may find it
17998 useful to enable @dfn{command tracing}. In this mode each command will be
17999 printed as it is executed, prefixed with one or more @samp{+} symbols, the
18000 quantity denoting the call depth of each command.
18003 @kindex set trace-commands
18004 @cindex command scripts, debugging
18005 @item set trace-commands on
18006 Enable command tracing.
18007 @item set trace-commands off
18008 Disable command tracing.
18009 @item show trace-commands
18010 Display the current state of command tracing.
18013 @node Debugging Output
18014 @section Optional Messages about Internal Happenings
18015 @cindex optional debugging messages
18017 @value{GDBN} has commands that enable optional debugging messages from
18018 various @value{GDBN} subsystems; normally these commands are of
18019 interest to @value{GDBN} maintainers, or when reporting a bug. This
18020 section documents those commands.
18023 @kindex set exec-done-display
18024 @item set exec-done-display
18025 Turns on or off the notification of asynchronous commands'
18026 completion. When on, @value{GDBN} will print a message when an
18027 asynchronous command finishes its execution. The default is off.
18028 @kindex show exec-done-display
18029 @item show exec-done-display
18030 Displays the current setting of asynchronous command completion
18033 @cindex gdbarch debugging info
18034 @cindex architecture debugging info
18035 @item set debug arch
18036 Turns on or off display of gdbarch debugging info. The default is off
18038 @item show debug arch
18039 Displays the current state of displaying gdbarch debugging info.
18040 @item set debug aix-thread
18041 @cindex AIX threads
18042 Display debugging messages about inner workings of the AIX thread
18044 @item show debug aix-thread
18045 Show the current state of AIX thread debugging info display.
18046 @item set debug dwarf2-die
18047 @cindex DWARF2 DIEs
18048 Dump DWARF2 DIEs after they are read in.
18049 The value is the number of nesting levels to print.
18050 A value of zero turns off the display.
18051 @item show debug dwarf2-die
18052 Show the current state of DWARF2 DIE debugging.
18053 @item set debug displaced
18054 @cindex displaced stepping debugging info
18055 Turns on or off display of @value{GDBN} debugging info for the
18056 displaced stepping support. The default is off.
18057 @item show debug displaced
18058 Displays the current state of displaying @value{GDBN} debugging info
18059 related to displaced stepping.
18060 @item set debug event
18061 @cindex event debugging info
18062 Turns on or off display of @value{GDBN} event debugging info. The
18064 @item show debug event
18065 Displays the current state of displaying @value{GDBN} event debugging
18067 @item set debug expression
18068 @cindex expression debugging info
18069 Turns on or off display of debugging info about @value{GDBN}
18070 expression parsing. The default is off.
18071 @item show debug expression
18072 Displays the current state of displaying debugging info about
18073 @value{GDBN} expression parsing.
18074 @item set debug frame
18075 @cindex frame debugging info
18076 Turns on or off display of @value{GDBN} frame debugging info. The
18078 @item show debug frame
18079 Displays the current state of displaying @value{GDBN} frame debugging
18081 @item set debug gnu-nat
18082 @cindex @sc{gnu}/Hurd debug messages
18083 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
18084 @item show debug gnu-nat
18085 Show the current state of @sc{gnu}/Hurd debugging messages.
18086 @item set debug infrun
18087 @cindex inferior debugging info
18088 Turns on or off display of @value{GDBN} debugging info for running the inferior.
18089 The default is off. @file{infrun.c} contains GDB's runtime state machine used
18090 for implementing operations such as single-stepping the inferior.
18091 @item show debug infrun
18092 Displays the current state of @value{GDBN} inferior debugging.
18093 @item set debug lin-lwp
18094 @cindex @sc{gnu}/Linux LWP debug messages
18095 @cindex Linux lightweight processes
18096 Turns on or off debugging messages from the Linux LWP debug support.
18097 @item show debug lin-lwp
18098 Show the current state of Linux LWP debugging messages.
18099 @item set debug lin-lwp-async
18100 @cindex @sc{gnu}/Linux LWP async debug messages
18101 @cindex Linux lightweight processes
18102 Turns on or off debugging messages from the Linux LWP async debug support.
18103 @item show debug lin-lwp-async
18104 Show the current state of Linux LWP async debugging messages.
18105 @item set debug observer
18106 @cindex observer debugging info
18107 Turns on or off display of @value{GDBN} observer debugging. This
18108 includes info such as the notification of observable events.
18109 @item show debug observer
18110 Displays the current state of observer debugging.
18111 @item set debug overload
18112 @cindex C@t{++} overload debugging info
18113 Turns on or off display of @value{GDBN} C@t{++} overload debugging
18114 info. This includes info such as ranking of functions, etc. The default
18116 @item show debug overload
18117 Displays the current state of displaying @value{GDBN} C@t{++} overload
18119 @cindex packets, reporting on stdout
18120 @cindex serial connections, debugging
18121 @cindex debug remote protocol
18122 @cindex remote protocol debugging
18123 @cindex display remote packets
18124 @item set debug remote
18125 Turns on or off display of reports on all packets sent back and forth across
18126 the serial line to the remote machine. The info is printed on the
18127 @value{GDBN} standard output stream. The default is off.
18128 @item show debug remote
18129 Displays the state of display of remote packets.
18130 @item set debug serial
18131 Turns on or off display of @value{GDBN} serial debugging info. The
18133 @item show debug serial
18134 Displays the current state of displaying @value{GDBN} serial debugging
18136 @item set debug solib-frv
18137 @cindex FR-V shared-library debugging
18138 Turns on or off debugging messages for FR-V shared-library code.
18139 @item show debug solib-frv
18140 Display the current state of FR-V shared-library code debugging
18142 @item set debug target
18143 @cindex target debugging info
18144 Turns on or off display of @value{GDBN} target debugging info. This info
18145 includes what is going on at the target level of GDB, as it happens. The
18146 default is 0. Set it to 1 to track events, and to 2 to also track the
18147 value of large memory transfers. Changes to this flag do not take effect
18148 until the next time you connect to a target or use the @code{run} command.
18149 @item show debug target
18150 Displays the current state of displaying @value{GDBN} target debugging
18152 @item set debug timestamp
18153 @cindex timestampping debugging info
18154 Turns on or off display of timestamps with @value{GDBN} debugging info.
18155 When enabled, seconds and microseconds are displayed before each debugging
18157 @item show debug timestamp
18158 Displays the current state of displaying timestamps with @value{GDBN}
18160 @item set debugvarobj
18161 @cindex variable object debugging info
18162 Turns on or off display of @value{GDBN} variable object debugging
18163 info. The default is off.
18164 @item show debugvarobj
18165 Displays the current state of displaying @value{GDBN} variable object
18167 @item set debug xml
18168 @cindex XML parser debugging
18169 Turns on or off debugging messages for built-in XML parsers.
18170 @item show debug xml
18171 Displays the current state of XML debugging messages.
18174 @node Extending GDB
18175 @chapter Extending @value{GDBN}
18176 @cindex extending GDB
18178 @value{GDBN} provides two mechanisms for extension. The first is based
18179 on composition of @value{GDBN} commands, and the second is based on the
18180 Python scripting language.
18183 * Sequences:: Canned Sequences of Commands
18184 * Python:: Scripting @value{GDBN} using Python
18188 @section Canned Sequences of Commands
18190 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
18191 Command Lists}), @value{GDBN} provides two ways to store sequences of
18192 commands for execution as a unit: user-defined commands and command
18196 * Define:: How to define your own commands
18197 * Hooks:: Hooks for user-defined commands
18198 * Command Files:: How to write scripts of commands to be stored in a file
18199 * Output:: Commands for controlled output
18203 @subsection User-defined Commands
18205 @cindex user-defined command
18206 @cindex arguments, to user-defined commands
18207 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
18208 which you assign a new name as a command. This is done with the
18209 @code{define} command. User commands may accept up to 10 arguments
18210 separated by whitespace. Arguments are accessed within the user command
18211 via @code{$arg0@dots{}$arg9}. A trivial example:
18215 print $arg0 + $arg1 + $arg2
18220 To execute the command use:
18227 This defines the command @code{adder}, which prints the sum of
18228 its three arguments. Note the arguments are text substitutions, so they may
18229 reference variables, use complex expressions, or even perform inferior
18232 @cindex argument count in user-defined commands
18233 @cindex how many arguments (user-defined commands)
18234 In addition, @code{$argc} may be used to find out how many arguments have
18235 been passed. This expands to a number in the range 0@dots{}10.
18240 print $arg0 + $arg1
18243 print $arg0 + $arg1 + $arg2
18251 @item define @var{commandname}
18252 Define a command named @var{commandname}. If there is already a command
18253 by that name, you are asked to confirm that you want to redefine it.
18254 @var{commandname} may be a bare command name consisting of letters,
18255 numbers, dashes, and underscores. It may also start with any predefined
18256 prefix command. For example, @samp{define target my-target} creates
18257 a user-defined @samp{target my-target} command.
18259 The definition of the command is made up of other @value{GDBN} command lines,
18260 which are given following the @code{define} command. The end of these
18261 commands is marked by a line containing @code{end}.
18264 @kindex end@r{ (user-defined commands)}
18265 @item document @var{commandname}
18266 Document the user-defined command @var{commandname}, so that it can be
18267 accessed by @code{help}. The command @var{commandname} must already be
18268 defined. This command reads lines of documentation just as @code{define}
18269 reads the lines of the command definition, ending with @code{end}.
18270 After the @code{document} command is finished, @code{help} on command
18271 @var{commandname} displays the documentation you have written.
18273 You may use the @code{document} command again to change the
18274 documentation of a command. Redefining the command with @code{define}
18275 does not change the documentation.
18277 @kindex dont-repeat
18278 @cindex don't repeat command
18280 Used inside a user-defined command, this tells @value{GDBN} that this
18281 command should not be repeated when the user hits @key{RET}
18282 (@pxref{Command Syntax, repeat last command}).
18284 @kindex help user-defined
18285 @item help user-defined
18286 List all user-defined commands, with the first line of the documentation
18291 @itemx show user @var{commandname}
18292 Display the @value{GDBN} commands used to define @var{commandname} (but
18293 not its documentation). If no @var{commandname} is given, display the
18294 definitions for all user-defined commands.
18296 @cindex infinite recursion in user-defined commands
18297 @kindex show max-user-call-depth
18298 @kindex set max-user-call-depth
18299 @item show max-user-call-depth
18300 @itemx set max-user-call-depth
18301 The value of @code{max-user-call-depth} controls how many recursion
18302 levels are allowed in user-defined commands before @value{GDBN} suspects an
18303 infinite recursion and aborts the command.
18306 In addition to the above commands, user-defined commands frequently
18307 use control flow commands, described in @ref{Command Files}.
18309 When user-defined commands are executed, the
18310 commands of the definition are not printed. An error in any command
18311 stops execution of the user-defined command.
18313 If used interactively, commands that would ask for confirmation proceed
18314 without asking when used inside a user-defined command. Many @value{GDBN}
18315 commands that normally print messages to say what they are doing omit the
18316 messages when used in a user-defined command.
18319 @subsection User-defined Command Hooks
18320 @cindex command hooks
18321 @cindex hooks, for commands
18322 @cindex hooks, pre-command
18325 You may define @dfn{hooks}, which are a special kind of user-defined
18326 command. Whenever you run the command @samp{foo}, if the user-defined
18327 command @samp{hook-foo} exists, it is executed (with no arguments)
18328 before that command.
18330 @cindex hooks, post-command
18332 A hook may also be defined which is run after the command you executed.
18333 Whenever you run the command @samp{foo}, if the user-defined command
18334 @samp{hookpost-foo} exists, it is executed (with no arguments) after
18335 that command. Post-execution hooks may exist simultaneously with
18336 pre-execution hooks, for the same command.
18338 It is valid for a hook to call the command which it hooks. If this
18339 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
18341 @c It would be nice if hookpost could be passed a parameter indicating
18342 @c if the command it hooks executed properly or not. FIXME!
18344 @kindex stop@r{, a pseudo-command}
18345 In addition, a pseudo-command, @samp{stop} exists. Defining
18346 (@samp{hook-stop}) makes the associated commands execute every time
18347 execution stops in your program: before breakpoint commands are run,
18348 displays are printed, or the stack frame is printed.
18350 For example, to ignore @code{SIGALRM} signals while
18351 single-stepping, but treat them normally during normal execution,
18356 handle SIGALRM nopass
18360 handle SIGALRM pass
18363 define hook-continue
18364 handle SIGALRM pass
18368 As a further example, to hook at the beginning and end of the @code{echo}
18369 command, and to add extra text to the beginning and end of the message,
18377 define hookpost-echo
18381 (@value{GDBP}) echo Hello World
18382 <<<---Hello World--->>>
18387 You can define a hook for any single-word command in @value{GDBN}, but
18388 not for command aliases; you should define a hook for the basic command
18389 name, e.g.@: @code{backtrace} rather than @code{bt}.
18390 @c FIXME! So how does Joe User discover whether a command is an alias
18392 You can hook a multi-word command by adding @code{hook-} or
18393 @code{hookpost-} to the last word of the command, e.g.@:
18394 @samp{define target hook-remote} to add a hook to @samp{target remote}.
18396 If an error occurs during the execution of your hook, execution of
18397 @value{GDBN} commands stops and @value{GDBN} issues a prompt
18398 (before the command that you actually typed had a chance to run).
18400 If you try to define a hook which does not match any known command, you
18401 get a warning from the @code{define} command.
18403 @node Command Files
18404 @subsection Command Files
18406 @cindex command files
18407 @cindex scripting commands
18408 A command file for @value{GDBN} is a text file made of lines that are
18409 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
18410 also be included. An empty line in a command file does nothing; it
18411 does not mean to repeat the last command, as it would from the
18414 You can request the execution of a command file with the @code{source}
18419 @cindex execute commands from a file
18420 @item source [@code{-v}] @var{filename}
18421 Execute the command file @var{filename}.
18424 The lines in a command file are generally executed sequentially,
18425 unless the order of execution is changed by one of the
18426 @emph{flow-control commands} described below. The commands are not
18427 printed as they are executed. An error in any command terminates
18428 execution of the command file and control is returned to the console.
18430 @value{GDBN} searches for @var{filename} in the current directory and then
18431 on the search path (specified with the @samp{directory} command).
18433 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
18434 each command as it is executed. The option must be given before
18435 @var{filename}, and is interpreted as part of the filename anywhere else.
18437 Commands that would ask for confirmation if used interactively proceed
18438 without asking when used in a command file. Many @value{GDBN} commands that
18439 normally print messages to say what they are doing omit the messages
18440 when called from command files.
18442 @value{GDBN} also accepts command input from standard input. In this
18443 mode, normal output goes to standard output and error output goes to
18444 standard error. Errors in a command file supplied on standard input do
18445 not terminate execution of the command file---execution continues with
18449 gdb < cmds > log 2>&1
18452 (The syntax above will vary depending on the shell used.) This example
18453 will execute commands from the file @file{cmds}. All output and errors
18454 would be directed to @file{log}.
18456 Since commands stored on command files tend to be more general than
18457 commands typed interactively, they frequently need to deal with
18458 complicated situations, such as different or unexpected values of
18459 variables and symbols, changes in how the program being debugged is
18460 built, etc. @value{GDBN} provides a set of flow-control commands to
18461 deal with these complexities. Using these commands, you can write
18462 complex scripts that loop over data structures, execute commands
18463 conditionally, etc.
18470 This command allows to include in your script conditionally executed
18471 commands. The @code{if} command takes a single argument, which is an
18472 expression to evaluate. It is followed by a series of commands that
18473 are executed only if the expression is true (its value is nonzero).
18474 There can then optionally be an @code{else} line, followed by a series
18475 of commands that are only executed if the expression was false. The
18476 end of the list is marked by a line containing @code{end}.
18480 This command allows to write loops. Its syntax is similar to
18481 @code{if}: the command takes a single argument, which is an expression
18482 to evaluate, and must be followed by the commands to execute, one per
18483 line, terminated by an @code{end}. These commands are called the
18484 @dfn{body} of the loop. The commands in the body of @code{while} are
18485 executed repeatedly as long as the expression evaluates to true.
18489 This command exits the @code{while} loop in whose body it is included.
18490 Execution of the script continues after that @code{while}s @code{end}
18493 @kindex loop_continue
18494 @item loop_continue
18495 This command skips the execution of the rest of the body of commands
18496 in the @code{while} loop in whose body it is included. Execution
18497 branches to the beginning of the @code{while} loop, where it evaluates
18498 the controlling expression.
18500 @kindex end@r{ (if/else/while commands)}
18502 Terminate the block of commands that are the body of @code{if},
18503 @code{else}, or @code{while} flow-control commands.
18508 @subsection Commands for Controlled Output
18510 During the execution of a command file or a user-defined command, normal
18511 @value{GDBN} output is suppressed; the only output that appears is what is
18512 explicitly printed by the commands in the definition. This section
18513 describes three commands useful for generating exactly the output you
18518 @item echo @var{text}
18519 @c I do not consider backslash-space a standard C escape sequence
18520 @c because it is not in ANSI.
18521 Print @var{text}. Nonprinting characters can be included in
18522 @var{text} using C escape sequences, such as @samp{\n} to print a
18523 newline. @strong{No newline is printed unless you specify one.}
18524 In addition to the standard C escape sequences, a backslash followed
18525 by a space stands for a space. This is useful for displaying a
18526 string with spaces at the beginning or the end, since leading and
18527 trailing spaces are otherwise trimmed from all arguments.
18528 To print @samp{@w{ }and foo =@w{ }}, use the command
18529 @samp{echo \@w{ }and foo = \@w{ }}.
18531 A backslash at the end of @var{text} can be used, as in C, to continue
18532 the command onto subsequent lines. For example,
18535 echo This is some text\n\
18536 which is continued\n\
18537 onto several lines.\n
18540 produces the same output as
18543 echo This is some text\n
18544 echo which is continued\n
18545 echo onto several lines.\n
18549 @item output @var{expression}
18550 Print the value of @var{expression} and nothing but that value: no
18551 newlines, no @samp{$@var{nn} = }. The value is not entered in the
18552 value history either. @xref{Expressions, ,Expressions}, for more information
18555 @item output/@var{fmt} @var{expression}
18556 Print the value of @var{expression} in format @var{fmt}. You can use
18557 the same formats as for @code{print}. @xref{Output Formats,,Output
18558 Formats}, for more information.
18561 @item printf @var{template}, @var{expressions}@dots{}
18562 Print the values of one or more @var{expressions} under the control of
18563 the string @var{template}. To print several values, make
18564 @var{expressions} be a comma-separated list of individual expressions,
18565 which may be either numbers or pointers. Their values are printed as
18566 specified by @var{template}, exactly as a C program would do by
18567 executing the code below:
18570 printf (@var{template}, @var{expressions}@dots{});
18573 As in @code{C} @code{printf}, ordinary characters in @var{template}
18574 are printed verbatim, while @dfn{conversion specification} introduced
18575 by the @samp{%} character cause subsequent @var{expressions} to be
18576 evaluated, their values converted and formatted according to type and
18577 style information encoded in the conversion specifications, and then
18580 For example, you can print two values in hex like this:
18583 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
18586 @code{printf} supports all the standard @code{C} conversion
18587 specifications, including the flags and modifiers between the @samp{%}
18588 character and the conversion letter, with the following exceptions:
18592 The argument-ordering modifiers, such as @samp{2$}, are not supported.
18595 The modifier @samp{*} is not supported for specifying precision or
18599 The @samp{'} flag (for separation of digits into groups according to
18600 @code{LC_NUMERIC'}) is not supported.
18603 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
18607 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
18610 The conversion letters @samp{a} and @samp{A} are not supported.
18614 Note that the @samp{ll} type modifier is supported only if the
18615 underlying @code{C} implementation used to build @value{GDBN} supports
18616 the @code{long long int} type, and the @samp{L} type modifier is
18617 supported only if @code{long double} type is available.
18619 As in @code{C}, @code{printf} supports simple backslash-escape
18620 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
18621 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
18622 single character. Octal and hexadecimal escape sequences are not
18625 Additionally, @code{printf} supports conversion specifications for DFP
18626 (@dfn{Decimal Floating Point}) types using the following length modifiers
18627 together with a floating point specifier.
18632 @samp{H} for printing @code{Decimal32} types.
18635 @samp{D} for printing @code{Decimal64} types.
18638 @samp{DD} for printing @code{Decimal128} types.
18641 If the underlying @code{C} implementation used to build @value{GDBN} has
18642 support for the three length modifiers for DFP types, other modifiers
18643 such as width and precision will also be available for @value{GDBN} to use.
18645 In case there is no such @code{C} support, no additional modifiers will be
18646 available and the value will be printed in the standard way.
18648 Here's an example of printing DFP types using the above conversion letters:
18650 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
18656 @section Scripting @value{GDBN} using Python
18657 @cindex python scripting
18658 @cindex scripting with python
18660 You can script @value{GDBN} using the @uref{http://www.python.org/,
18661 Python programming language}. This feature is available only if
18662 @value{GDBN} was configured using @option{--with-python}.
18665 * Python Commands:: Accessing Python from @value{GDBN}.
18666 * Python API:: Accessing @value{GDBN} from Python.
18669 @node Python Commands
18670 @subsection Python Commands
18671 @cindex python commands
18672 @cindex commands to access python
18674 @value{GDBN} provides one command for accessing the Python interpreter,
18675 and one related setting:
18679 @item python @r{[}@var{code}@r{]}
18680 The @code{python} command can be used to evaluate Python code.
18682 If given an argument, the @code{python} command will evaluate the
18683 argument as a Python command. For example:
18686 (@value{GDBP}) python print 23
18690 If you do not provide an argument to @code{python}, it will act as a
18691 multi-line command, like @code{define}. In this case, the Python
18692 script is made up of subsequent command lines, given after the
18693 @code{python} command. This command list is terminated using a line
18694 containing @code{end}. For example:
18697 (@value{GDBP}) python
18699 End with a line saying just "end".
18705 @kindex maint set python print-stack
18706 @item maint set python print-stack
18707 By default, @value{GDBN} will print a stack trace when an error occurs
18708 in a Python script. This can be controlled using @code{maint set
18709 python print-stack}: if @code{on}, the default, then Python stack
18710 printing is enabled; if @code{off}, then Python stack printing is
18715 @subsection Python API
18717 @cindex programming in python
18719 @cindex python stdout
18720 @cindex python pagination
18721 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
18722 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
18723 A Python program which outputs to one of these streams may have its
18724 output interrupted by the user (@pxref{Screen Size}). In this
18725 situation, a Python @code{KeyboardInterrupt} exception is thrown.
18728 * Basic Python:: Basic Python Functions.
18729 * Exception Handling::
18730 * Auto-loading:: Automatically loading Python code.
18731 * Values From Inferior::
18732 * Types In Python:: Python representation of types.
18733 * Pretty Printing:: Pretty-printing values.
18734 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
18735 * Commands In Python:: Implementing new commands in Python.
18736 * Functions In Python:: Writing new convenience functions.
18737 * Objfiles In Python:: Object files.
18738 * Frames In Python:: Acessing inferior stack frames from Python.
18742 @subsubsection Basic Python
18744 @cindex python functions
18745 @cindex python module
18747 @value{GDBN} introduces a new Python module, named @code{gdb}. All
18748 methods and classes added by @value{GDBN} are placed in this module.
18749 @value{GDBN} automatically @code{import}s the @code{gdb} module for
18750 use in all scripts evaluated by the @code{python} command.
18752 @findex gdb.execute
18753 @defun execute command [from_tty]
18754 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
18755 If a GDB exception happens while @var{command} runs, it is
18756 translated as described in @ref{Exception Handling,,Exception Handling}.
18757 If no exceptions occur, this function returns @code{None}.
18759 @var{from_tty} specifies whether @value{GDBN} ought to consider this
18760 command as having originated from the user invoking it interactively.
18761 It must be a boolean value. If omitted, it defaults to @code{False}.
18764 @findex gdb.parameter
18765 @defun parameter parameter
18766 Return the value of a @value{GDBN} parameter. @var{parameter} is a
18767 string naming the parameter to look up; @var{parameter} may contain
18768 spaces if the parameter has a multi-part name. For example,
18769 @samp{print object} is a valid parameter name.
18771 If the named parameter does not exist, this function throws a
18772 @code{RuntimeError}. Otherwise, the parameter's value is converted to
18773 a Python value of the appropriate type, and returned.
18776 @findex gdb.history
18777 @defun history number
18778 Return a value from @value{GDBN}'s value history (@pxref{Value
18779 History}). @var{number} indicates which history element to return.
18780 If @var{number} is negative, then @value{GDBN} will take its absolute value
18781 and count backward from the last element (i.e., the most recent element) to
18782 find the value to return. If @var{number} is zero, then @value{GDBN} will
18783 return the most recent element. If the element specified by @var{number}
18784 doesn't exist in the value history, a @code{RuntimeError} exception will be
18787 If no exception is raised, the return value is always an instance of
18788 @code{gdb.Value} (@pxref{Values From Inferior}).
18792 @defun write string
18793 Print a string to @value{GDBN}'s paginated standard output stream.
18794 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
18795 call this function.
18800 Flush @value{GDBN}'s paginated standard output stream. Flushing
18801 @code{sys.stdout} or @code{sys.stderr} will automatically call this
18805 @node Exception Handling
18806 @subsubsection Exception Handling
18807 @cindex python exceptions
18808 @cindex exceptions, python
18810 When executing the @code{python} command, Python exceptions
18811 uncaught within the Python code are translated to calls to
18812 @value{GDBN} error-reporting mechanism. If the command that called
18813 @code{python} does not handle the error, @value{GDBN} will
18814 terminate it and print an error message containing the Python
18815 exception name, the associated value, and the Python call stack
18816 backtrace at the point where the exception was raised. Example:
18819 (@value{GDBP}) python print foo
18820 Traceback (most recent call last):
18821 File "<string>", line 1, in <module>
18822 NameError: name 'foo' is not defined
18825 @value{GDBN} errors that happen in @value{GDBN} commands invoked by Python
18826 code are converted to Python @code{RuntimeError} exceptions. User
18827 interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
18828 prompt) is translated to a Python @code{KeyboardInterrupt}
18829 exception. If you catch these exceptions in your Python code, your
18830 exception handler will see @code{RuntimeError} or
18831 @code{KeyboardInterrupt} as the exception type, the @value{GDBN} error
18832 message as its value, and the Python call stack backtrace at the
18833 Python statement closest to where the @value{GDBN} error occured as the
18837 @subsubsection Auto-loading
18838 @cindex auto-loading, Python
18840 When a new object file is read (for example, due to the @code{file}
18841 command, or because the inferior has loaded a shared library),
18842 @value{GDBN} will look for a file named @file{@var{objfile}-gdb.py},
18843 where @var{objfile} is the object file's real name, formed by ensuring
18844 that the file name is absolute, following all symlinks, and resolving
18845 @code{.} and @code{..} components. If this file exists and is
18846 readable, @value{GDBN} will evaluate it as a Python script.
18848 If this file does not exist, and if the parameter
18849 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
18850 then @value{GDBN} will use the file named
18851 @file{@var{debug-file-directory}/@var{real-name}}, where
18852 @var{real-name} is the object file's real name, as described above.
18854 Finally, if this file does not exist, then @value{GDBN} will look for
18855 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
18856 @var{data-directory} is @value{GDBN}'s data directory (available via
18857 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
18858 is the object file's real name, as described above.
18860 When reading an auto-loaded file, @value{GDBN} sets the ``current
18861 objfile''. This is available via the @code{gdb.current_objfile}
18862 function (@pxref{Objfiles In Python}). This can be useful for
18863 registering objfile-specific pretty-printers.
18865 The auto-loading feature is useful for supplying application-specific
18866 debugging commands and scripts. You can enable or disable this
18867 feature, and view its current state.
18870 @kindex maint set python auto-load
18871 @item maint set python auto-load [yes|no]
18872 Enable or disable the Python auto-loading feature.
18874 @kindex show python auto-load
18875 @item show python auto-load
18876 Show whether Python auto-loading is enabled or disabled.
18879 @value{GDBN} does not track which files it has already auto-loaded.
18880 So, your @samp{-gdb.py} file should take care to ensure that it may be
18881 evaluated multiple times without error.
18883 @node Values From Inferior
18884 @subsubsection Values From Inferior
18885 @cindex values from inferior, with Python
18886 @cindex python, working with values from inferior
18888 @cindex @code{gdb.Value}
18889 @value{GDBN} provides values it obtains from the inferior program in
18890 an object of type @code{gdb.Value}. @value{GDBN} uses this object
18891 for its internal bookkeeping of the inferior's values, and for
18892 fetching values when necessary.
18894 Inferior values that are simple scalars can be used directly in
18895 Python expressions that are valid for the value's data type. Here's
18896 an example for an integer or floating-point value @code{some_val}:
18903 As result of this, @code{bar} will also be a @code{gdb.Value} object
18904 whose values are of the same type as those of @code{some_val}.
18906 Inferior values that are structures or instances of some class can
18907 be accessed using the Python @dfn{dictionary syntax}. For example, if
18908 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
18909 can access its @code{foo} element with:
18912 bar = some_val['foo']
18915 Again, @code{bar} will also be a @code{gdb.Value} object.
18917 The following attributes are provided:
18920 @defivar Value address
18921 If this object is addressable, this read-only attribute holds a
18922 @code{gdb.Value} object representing the address. Otherwise,
18923 this attribute holds @code{None}.
18926 @cindex optimized out value in Python
18927 @defivar Value is_optimized_out
18928 This read-only boolean attribute is true if the compiler optimized out
18929 this value, thus it is not available for fetching from the inferior.
18932 @defivar Value type
18933 The type of this @code{gdb.Value}. The value of this attribute is a
18934 @code{gdb.Type} object.
18938 The following methods are provided:
18941 @defmethod Value dereference
18942 For pointer data types, this method returns a new @code{gdb.Value} object
18943 whose contents is the object pointed to by the pointer. For example, if
18944 @code{foo} is a C pointer to an @code{int}, declared in your C program as
18951 then you can use the corresponding @code{gdb.Value} to access what
18952 @code{foo} points to like this:
18955 bar = foo.dereference ()
18958 The result @code{bar} will be a @code{gdb.Value} object holding the
18959 value pointed to by @code{foo}.
18962 @defmethod Value string @r{[}encoding@r{]} @r{[}errors@r{]} @r{[}length@r{]}
18963 If this @code{gdb.Value} represents a string, then this method
18964 converts the contents to a Python string. Otherwise, this method will
18965 throw an exception.
18967 Strings are recognized in a language-specific way; whether a given
18968 @code{gdb.Value} represents a string is determined by the current
18971 For C-like languages, a value is a string if it is a pointer to or an
18972 array of characters or ints. The string is assumed to be terminated
18973 by a zero of the appropriate width. However if the optional length
18974 argument is given, the string will be converted to that given length,
18975 ignoring any embedded zeros that the string may contain.
18977 If the optional @var{encoding} argument is given, it must be a string
18978 naming the encoding of the string in the @code{gdb.Value}, such as
18979 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
18980 the same encodings as the corresponding argument to Python's
18981 @code{string.decode} method, and the Python codec machinery will be used
18982 to convert the string. If @var{encoding} is not given, or if
18983 @var{encoding} is the empty string, then either the @code{target-charset}
18984 (@pxref{Character Sets}) will be used, or a language-specific encoding
18985 will be used, if the current language is able to supply one.
18987 The optional @var{errors} argument is the same as the corresponding
18988 argument to Python's @code{string.decode} method.
18990 If the optional @var{length} argument is given, the string will be
18991 fetched and converted to the given length.
18995 @node Types In Python
18996 @subsubsection Types In Python
18997 @cindex types in Python
18998 @cindex Python, working with types
19001 @value{GDBN} represents types from the inferior using the class
19004 The following type-related functions are available in the @code{gdb}
19007 @findex gdb.lookup_type
19008 @defun lookup_type name [block]
19009 This function looks up a type by name. @var{name} is the name of the
19010 type to look up. It must be a string.
19012 Ordinarily, this function will return an instance of @code{gdb.Type}.
19013 If the named type cannot be found, it will throw an exception.
19016 An instance of @code{Type} has the following attributes:
19020 The type code for this type. The type code will be one of the
19021 @code{TYPE_CODE_} constants defined below.
19024 @defivar Type sizeof
19025 The size of this type, in target @code{char} units. Usually, a
19026 target's @code{char} type will be an 8-bit byte. However, on some
19027 unusual platforms, this type may have a different size.
19031 The tag name for this type. The tag name is the name after
19032 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
19033 languages have this concept. If this type has no tag name, then
19034 @code{None} is returned.
19038 The following methods are provided:
19041 @defmethod Type fields
19042 For structure and union types, this method returns the fields. Range
19043 types have two fields, the minimum and maximum values. Enum types
19044 have one field per enum constant. Function and method types have one
19045 field per parameter. The base types of C@t{++} classes are also
19046 represented as fields. If the type has no fields, or does not fit
19047 into one of these categories, an empty sequence will be returned.
19049 Each field is an object, with some pre-defined attributes:
19052 This attribute is not available for @code{static} fields (as in
19053 C@t{++} or Java). For non-@code{static} fields, the value is the bit
19054 position of the field.
19057 The name of the field, or @code{None} for anonymous fields.
19060 This is @code{True} if the field is artificial, usually meaning that
19061 it was provided by the compiler and not the user. This attribute is
19062 always provided, and is @code{False} if the field is not artificial.
19065 If the field is packed, or is a bitfield, then this will have a
19066 non-zero value, which is the size of the field in bits. Otherwise,
19067 this will be zero; in this case the field's size is given by its type.
19070 The type of the field. This is usually an instance of @code{Type},
19071 but it can be @code{None} in some situations.
19075 @defmethod Type const
19076 Return a new @code{gdb.Type} object which represents a
19077 @code{const}-qualified variant of this type.
19080 @defmethod Type volatile
19081 Return a new @code{gdb.Type} object which represents a
19082 @code{volatile}-qualified variant of this type.
19085 @defmethod Type unqualified
19086 Return a new @code{gdb.Type} object which represents an unqualified
19087 variant of this type. That is, the result is neither @code{const} nor
19091 @defmethod Type reference
19092 Return a new @code{gdb.Type} object which represents a reference to this
19096 @defmethod Type strip_typedefs
19097 Return a new @code{gdb.Type} that represents the real type,
19098 after removing all layers of typedefs.
19101 @defmethod Type target
19102 Return a new @code{gdb.Type} object which represents the target type
19105 For a pointer type, the target type is the type of the pointed-to
19106 object. For an array type (meaning C-like arrays), the target type is
19107 the type of the elements of the array. For a function or method type,
19108 the target type is the type of the return value. For a complex type,
19109 the target type is the type of the elements. For a typedef, the
19110 target type is the aliased type.
19112 If the type does not have a target, this method will throw an
19116 @defmethod Type template_argument n
19117 If this @code{gdb.Type} is an instantiation of a template, this will
19118 return a new @code{gdb.Type} which represents the type of the
19119 @var{n}th template argument.
19121 If this @code{gdb.Type} is not a template type, this will throw an
19122 exception. Ordinarily, only C@t{++} code will have template types.
19124 @var{name} is searched for globally.
19129 Each type has a code, which indicates what category this type falls
19130 into. The available type categories are represented by constants
19131 defined in the @code{gdb} module:
19134 @findex TYPE_CODE_PTR
19135 @findex gdb.TYPE_CODE_PTR
19136 @item TYPE_CODE_PTR
19137 The type is a pointer.
19139 @findex TYPE_CODE_ARRAY
19140 @findex gdb.TYPE_CODE_ARRAY
19141 @item TYPE_CODE_ARRAY
19142 The type is an array.
19144 @findex TYPE_CODE_STRUCT
19145 @findex gdb.TYPE_CODE_STRUCT
19146 @item TYPE_CODE_STRUCT
19147 The type is a structure.
19149 @findex TYPE_CODE_UNION
19150 @findex gdb.TYPE_CODE_UNION
19151 @item TYPE_CODE_UNION
19152 The type is a union.
19154 @findex TYPE_CODE_ENUM
19155 @findex gdb.TYPE_CODE_ENUM
19156 @item TYPE_CODE_ENUM
19157 The type is an enum.
19159 @findex TYPE_CODE_FLAGS
19160 @findex gdb.TYPE_CODE_FLAGS
19161 @item TYPE_CODE_FLAGS
19162 A bit flags type, used for things such as status registers.
19164 @findex TYPE_CODE_FUNC
19165 @findex gdb.TYPE_CODE_FUNC
19166 @item TYPE_CODE_FUNC
19167 The type is a function.
19169 @findex TYPE_CODE_INT
19170 @findex gdb.TYPE_CODE_INT
19171 @item TYPE_CODE_INT
19172 The type is an integer type.
19174 @findex TYPE_CODE_FLT
19175 @findex gdb.TYPE_CODE_FLT
19176 @item TYPE_CODE_FLT
19177 A floating point type.
19179 @findex TYPE_CODE_VOID
19180 @findex gdb.TYPE_CODE_VOID
19181 @item TYPE_CODE_VOID
19182 The special type @code{void}.
19184 @findex TYPE_CODE_SET
19185 @findex gdb.TYPE_CODE_SET
19186 @item TYPE_CODE_SET
19189 @findex TYPE_CODE_RANGE
19190 @findex gdb.TYPE_CODE_RANGE
19191 @item TYPE_CODE_RANGE
19192 A range type, that is, an integer type with bounds.
19194 @findex TYPE_CODE_STRING
19195 @findex gdb.TYPE_CODE_STRING
19196 @item TYPE_CODE_STRING
19197 A string type. Note that this is only used for certain languages with
19198 language-defined string types; C strings are not represented this way.
19200 @findex TYPE_CODE_BITSTRING
19201 @findex gdb.TYPE_CODE_BITSTRING
19202 @item TYPE_CODE_BITSTRING
19205 @findex TYPE_CODE_ERROR
19206 @findex gdb.TYPE_CODE_ERROR
19207 @item TYPE_CODE_ERROR
19208 An unknown or erroneous type.
19210 @findex TYPE_CODE_METHOD
19211 @findex gdb.TYPE_CODE_METHOD
19212 @item TYPE_CODE_METHOD
19213 A method type, as found in C@t{++} or Java.
19215 @findex TYPE_CODE_METHODPTR
19216 @findex gdb.TYPE_CODE_METHODPTR
19217 @item TYPE_CODE_METHODPTR
19218 A pointer-to-member-function.
19220 @findex TYPE_CODE_MEMBERPTR
19221 @findex gdb.TYPE_CODE_MEMBERPTR
19222 @item TYPE_CODE_MEMBERPTR
19223 A pointer-to-member.
19225 @findex TYPE_CODE_REF
19226 @findex gdb.TYPE_CODE_REF
19227 @item TYPE_CODE_REF
19230 @findex TYPE_CODE_CHAR
19231 @findex gdb.TYPE_CODE_CHAR
19232 @item TYPE_CODE_CHAR
19235 @findex TYPE_CODE_BOOL
19236 @findex gdb.TYPE_CODE_BOOL
19237 @item TYPE_CODE_BOOL
19240 @findex TYPE_CODE_COMPLEX
19241 @findex gdb.TYPE_CODE_COMPLEX
19242 @item TYPE_CODE_COMPLEX
19243 A complex float type.
19245 @findex TYPE_CODE_TYPEDEF
19246 @findex gdb.TYPE_CODE_TYPEDEF
19247 @item TYPE_CODE_TYPEDEF
19248 A typedef to some other type.
19250 @findex TYPE_CODE_NAMESPACE
19251 @findex gdb.TYPE_CODE_NAMESPACE
19252 @item TYPE_CODE_NAMESPACE
19253 A C@t{++} namespace.
19255 @findex TYPE_CODE_DECFLOAT
19256 @findex gdb.TYPE_CODE_DECFLOAT
19257 @item TYPE_CODE_DECFLOAT
19258 A decimal floating point type.
19260 @findex TYPE_CODE_INTERNAL_FUNCTION
19261 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
19262 @item TYPE_CODE_INTERNAL_FUNCTION
19263 A function internal to @value{GDBN}. This is the type used to represent
19264 convenience functions.
19267 @node Pretty Printing
19268 @subsubsection Pretty Printing
19270 @value{GDBN} provides a mechanism to allow pretty-printing of values
19271 using Python code. The pretty-printer API allows application-specific
19272 code to greatly simplify the display of complex objects. This
19273 mechanism works for both MI and the CLI.
19275 For example, here is how a C@t{++} @code{std::string} looks without a
19279 (@value{GDBP}) print s
19281 static npos = 4294967295,
19283 <std::allocator<char>> = @{
19284 <__gnu_cxx::new_allocator<char>> = @{<No data fields>@}, <No data fields>@},
19285 members of std::basic_string<char, std::char_traits<char>, std::allocator<char> >::_Alloc_hider:
19286 _M_p = 0x804a014 "abcd"
19291 After a pretty-printer for @code{std::string} has been installed, only
19292 the contents are printed:
19295 (@value{GDBP}) print s
19299 A pretty-printer is just an object that holds a value and implements a
19300 specific interface, defined here.
19302 @defop Operation {pretty printer} children (self)
19303 @value{GDBN} will call this method on a pretty-printer to compute the
19304 children of the pretty-printer's value.
19306 This method must return an object conforming to the Python iterator
19307 protocol. Each item returned by the iterator must be a tuple holding
19308 two elements. The first element is the ``name'' of the child; the
19309 second element is the child's value. The value can be any Python
19310 object which is convertible to a @value{GDBN} value.
19312 This method is optional. If it does not exist, @value{GDBN} will act
19313 as though the value has no children.
19316 @defop Operation {pretty printer} display_hint (self)
19317 The CLI may call this method and use its result to change the
19318 formatting of a value. The result will also be supplied to an MI
19319 consumer as a @samp{displayhint} attribute of the variable being
19322 This method is optional. If it does exist, this method must return a
19325 Some display hints are predefined by @value{GDBN}:
19329 Indicate that the object being printed is ``array-like''. The CLI
19330 uses this to respect parameters such as @code{set print elements} and
19331 @code{set print array}.
19334 Indicate that the object being printed is ``map-like'', and that the
19335 children of this value can be assumed to alternate between keys and
19339 Indicate that the object being printed is ``string-like''. If the
19340 printer's @code{to_string} method returns a Python string of some
19341 kind, then @value{GDBN} will call its internal language-specific
19342 string-printing function to format the string. For the CLI this means
19343 adding quotation marks, possibly escaping some characters, respecting
19344 @code{set print elements}, and the like.
19348 @defop Operation {pretty printer} to_string (self)
19349 @value{GDBN} will call this method to display the string
19350 representation of the value passed to the object's constructor.
19352 When printing from the CLI, if the @code{to_string} method exists,
19353 then @value{GDBN} will prepend its result to the values returned by
19354 @code{children}. Exactly how this formatting is done is dependent on
19355 the display hint, and may change as more hints are added. Also,
19356 depending on the print settings (@pxref{Print Settings}), the CLI may
19357 print just the result of @code{to_string} in a stack trace, omitting
19358 the result of @code{children}.
19360 If this method returns a string, it is printed verbatim.
19362 Otherwise, if this method returns an instance of @code{gdb.Value},
19363 then @value{GDBN} prints this value. This may result in a call to
19364 another pretty-printer.
19366 If instead the method returns a Python value which is convertible to a
19367 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
19368 the resulting value. Again, this may result in a call to another
19369 pretty-printer. Python scalars (integers, floats, and booleans) and
19370 strings are convertible to @code{gdb.Value}; other types are not.
19372 If the result is not one of these types, an exception is raised.
19375 @node Selecting Pretty-Printers
19376 @subsubsection Selecting Pretty-Printers
19378 The Python list @code{gdb.pretty_printers} contains an array of
19379 functions that have been registered via addition as a pretty-printer.
19380 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
19383 A function on one of these lists is passed a single @code{gdb.Value}
19384 argument and should return a pretty-printer object conforming to the
19385 interface definition above (@pxref{Pretty Printing}). If a function
19386 cannot create a pretty-printer for the value, it should return
19389 @value{GDBN} first checks the @code{pretty_printers} attribute of each
19390 @code{gdb.Objfile} and iteratively calls each function in the list for
19391 that @code{gdb.Objfile} until it receives a pretty-printer object.
19392 After these lists have been exhausted, it tries the global
19393 @code{gdb.pretty-printers} list, again calling each function until an
19394 object is returned.
19396 The order in which the objfiles are searched is not specified. For a
19397 given list, functions are always invoked from the head of the list,
19398 and iterated over sequentially until the end of the list, or a printer
19399 object is returned.
19401 Here is an example showing how a @code{std::string} printer might be
19405 class StdStringPrinter:
19406 "Print a std::string"
19408 def __init__ (self, val):
19411 def to_string (self):
19412 return self.val['_M_dataplus']['_M_p']
19414 def display_hint (self):
19418 And here is an example showing how a lookup function for the printer
19419 example above might be written.
19422 def str_lookup_function (val):
19424 lookup_tag = val.type.tag
19425 regex = re.compile ("^std::basic_string<char,.*>$")
19426 if lookup_tag == None:
19428 if regex.match (lookup_tag):
19429 return StdStringPrinter (val)
19434 The example lookup function extracts the value's type, and attempts to
19435 match it to a type that it can pretty-print. If it is a type the
19436 printer can pretty-print, it will return a printer object. If not, it
19437 returns @code{None}.
19439 We recommend that you put your core pretty-printers into a Python
19440 package. If your pretty-printers are for use with a library, we
19441 further recommend embedding a version number into the package name.
19442 This practice will enable @value{GDBN} to load multiple versions of
19443 your pretty-printers at the same time, because they will have
19446 You should write auto-loaded code (@pxref{Auto-loading}) such that it
19447 can be evaluated multiple times without changing its meaning. An
19448 ideal auto-load file will consist solely of @code{import}s of your
19449 printer modules, followed by a call to a register pretty-printers with
19450 the current objfile.
19452 Taken as a whole, this approach will scale nicely to multiple
19453 inferiors, each potentially using a different library version.
19454 Embedding a version number in the Python package name will ensure that
19455 @value{GDBN} is able to load both sets of printers simultaneously.
19456 Then, because the search for pretty-printers is done by objfile, and
19457 because your auto-loaded code took care to register your library's
19458 printers with a specific objfile, @value{GDBN} will find the correct
19459 printers for the specific version of the library used by each
19462 To continue the @code{std::string} example (@pxref{Pretty Printing}),
19463 this code might appear in @code{gdb.libstdcxx.v6}:
19466 def register_printers (objfile):
19467 objfile.pretty_printers.add (str_lookup_function)
19471 And then the corresponding contents of the auto-load file would be:
19474 import gdb.libstdcxx.v6
19475 gdb.libstdcxx.v6.register_printers (gdb.current_objfile ())
19478 @node Commands In Python
19479 @subsubsection Commands In Python
19481 @cindex commands in python
19482 @cindex python commands
19483 You can implement new @value{GDBN} CLI commands in Python. A CLI
19484 command is implemented using an instance of the @code{gdb.Command}
19485 class, most commonly using a subclass.
19487 @defmethod Command __init__ name @var{command_class} @r{[}@var{completer_class}@r{]} @r{[}@var{prefix}@r{]}
19488 The object initializer for @code{Command} registers the new command
19489 with @value{GDBN}. This initializer is normally invoked from the
19490 subclass' own @code{__init__} method.
19492 @var{name} is the name of the command. If @var{name} consists of
19493 multiple words, then the initial words are looked for as prefix
19494 commands. In this case, if one of the prefix commands does not exist,
19495 an exception is raised.
19497 There is no support for multi-line commands.
19499 @var{command_class} should be one of the @samp{COMMAND_} constants
19500 defined below. This argument tells @value{GDBN} how to categorize the
19501 new command in the help system.
19503 @var{completer_class} is an optional argument. If given, it should be
19504 one of the @samp{COMPLETE_} constants defined below. This argument
19505 tells @value{GDBN} how to perform completion for this command. If not
19506 given, @value{GDBN} will attempt to complete using the object's
19507 @code{complete} method (see below); if no such method is found, an
19508 error will occur when completion is attempted.
19510 @var{prefix} is an optional argument. If @code{True}, then the new
19511 command is a prefix command; sub-commands of this command may be
19514 The help text for the new command is taken from the Python
19515 documentation string for the command's class, if there is one. If no
19516 documentation string is provided, the default value ``This command is
19517 not documented.'' is used.
19520 @cindex don't repeat Python command
19521 @defmethod Command dont_repeat
19522 By default, a @value{GDBN} command is repeated when the user enters a
19523 blank line at the command prompt. A command can suppress this
19524 behavior by invoking the @code{dont_repeat} method. This is similar
19525 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
19528 @defmethod Command invoke argument from_tty
19529 This method is called by @value{GDBN} when this command is invoked.
19531 @var{argument} is a string. It is the argument to the command, after
19532 leading and trailing whitespace has been stripped.
19534 @var{from_tty} is a boolean argument. When true, this means that the
19535 command was entered by the user at the terminal; when false it means
19536 that the command came from elsewhere.
19538 If this method throws an exception, it is turned into a @value{GDBN}
19539 @code{error} call. Otherwise, the return value is ignored.
19542 @cindex completion of Python commands
19543 @defmethod Command complete text word
19544 This method is called by @value{GDBN} when the user attempts
19545 completion on this command. All forms of completion are handled by
19546 this method, that is, the @key{TAB} and @key{M-?} key bindings
19547 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
19550 The arguments @var{text} and @var{word} are both strings. @var{text}
19551 holds the complete command line up to the cursor's location.
19552 @var{word} holds the last word of the command line; this is computed
19553 using a word-breaking heuristic.
19555 The @code{complete} method can return several values:
19558 If the return value is a sequence, the contents of the sequence are
19559 used as the completions. It is up to @code{complete} to ensure that the
19560 contents actually do complete the word. A zero-length sequence is
19561 allowed, it means that there were no completions available. Only
19562 string elements of the sequence are used; other elements in the
19563 sequence are ignored.
19566 If the return value is one of the @samp{COMPLETE_} constants defined
19567 below, then the corresponding @value{GDBN}-internal completion
19568 function is invoked, and its result is used.
19571 All other results are treated as though there were no available
19576 When a new command is registered, it must be declared as a member of
19577 some general class of commands. This is used to classify top-level
19578 commands in the on-line help system; note that prefix commands are not
19579 listed under their own category but rather that of their top-level
19580 command. The available classifications are represented by constants
19581 defined in the @code{gdb} module:
19584 @findex COMMAND_NONE
19585 @findex gdb.COMMAND_NONE
19587 The command does not belong to any particular class. A command in
19588 this category will not be displayed in any of the help categories.
19590 @findex COMMAND_RUNNING
19591 @findex gdb.COMMAND_RUNNING
19592 @item COMMAND_RUNNING
19593 The command is related to running the inferior. For example,
19594 @code{start}, @code{step}, and @code{continue} are in this category.
19595 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
19596 commands in this category.
19598 @findex COMMAND_DATA
19599 @findex gdb.COMMAND_DATA
19601 The command is related to data or variables. For example,
19602 @code{call}, @code{find}, and @code{print} are in this category. Type
19603 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
19606 @findex COMMAND_STACK
19607 @findex gdb.COMMAND_STACK
19608 @item COMMAND_STACK
19609 The command has to do with manipulation of the stack. For example,
19610 @code{backtrace}, @code{frame}, and @code{return} are in this
19611 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
19612 list of commands in this category.
19614 @findex COMMAND_FILES
19615 @findex gdb.COMMAND_FILES
19616 @item COMMAND_FILES
19617 This class is used for file-related commands. For example,
19618 @code{file}, @code{list} and @code{section} are in this category.
19619 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
19620 commands in this category.
19622 @findex COMMAND_SUPPORT
19623 @findex gdb.COMMAND_SUPPORT
19624 @item COMMAND_SUPPORT
19625 This should be used for ``support facilities'', generally meaning
19626 things that are useful to the user when interacting with @value{GDBN},
19627 but not related to the state of the inferior. For example,
19628 @code{help}, @code{make}, and @code{shell} are in this category. Type
19629 @kbd{help support} at the @value{GDBN} prompt to see a list of
19630 commands in this category.
19632 @findex COMMAND_STATUS
19633 @findex gdb.COMMAND_STATUS
19634 @item COMMAND_STATUS
19635 The command is an @samp{info}-related command, that is, related to the
19636 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
19637 and @code{show} are in this category. Type @kbd{help status} at the
19638 @value{GDBN} prompt to see a list of commands in this category.
19640 @findex COMMAND_BREAKPOINTS
19641 @findex gdb.COMMAND_BREAKPOINTS
19642 @item COMMAND_BREAKPOINTS
19643 The command has to do with breakpoints. For example, @code{break},
19644 @code{clear}, and @code{delete} are in this category. Type @kbd{help
19645 breakpoints} at the @value{GDBN} prompt to see a list of commands in
19648 @findex COMMAND_TRACEPOINTS
19649 @findex gdb.COMMAND_TRACEPOINTS
19650 @item COMMAND_TRACEPOINTS
19651 The command has to do with tracepoints. For example, @code{trace},
19652 @code{actions}, and @code{tfind} are in this category. Type
19653 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
19654 commands in this category.
19656 @findex COMMAND_OBSCURE
19657 @findex gdb.COMMAND_OBSCURE
19658 @item COMMAND_OBSCURE
19659 The command is only used in unusual circumstances, or is not of
19660 general interest to users. For example, @code{checkpoint},
19661 @code{fork}, and @code{stop} are in this category. Type @kbd{help
19662 obscure} at the @value{GDBN} prompt to see a list of commands in this
19665 @findex COMMAND_MAINTENANCE
19666 @findex gdb.COMMAND_MAINTENANCE
19667 @item COMMAND_MAINTENANCE
19668 The command is only useful to @value{GDBN} maintainers. The
19669 @code{maintenance} and @code{flushregs} commands are in this category.
19670 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
19671 commands in this category.
19674 A new command can use a predefined completion function, either by
19675 specifying it via an argument at initialization, or by returning it
19676 from the @code{complete} method. These predefined completion
19677 constants are all defined in the @code{gdb} module:
19680 @findex COMPLETE_NONE
19681 @findex gdb.COMPLETE_NONE
19682 @item COMPLETE_NONE
19683 This constant means that no completion should be done.
19685 @findex COMPLETE_FILENAME
19686 @findex gdb.COMPLETE_FILENAME
19687 @item COMPLETE_FILENAME
19688 This constant means that filename completion should be performed.
19690 @findex COMPLETE_LOCATION
19691 @findex gdb.COMPLETE_LOCATION
19692 @item COMPLETE_LOCATION
19693 This constant means that location completion should be done.
19694 @xref{Specify Location}.
19696 @findex COMPLETE_COMMAND
19697 @findex gdb.COMPLETE_COMMAND
19698 @item COMPLETE_COMMAND
19699 This constant means that completion should examine @value{GDBN}
19702 @findex COMPLETE_SYMBOL
19703 @findex gdb.COMPLETE_SYMBOL
19704 @item COMPLETE_SYMBOL
19705 This constant means that completion should be done using symbol names
19709 The following code snippet shows how a trivial CLI command can be
19710 implemented in Python:
19713 class HelloWorld (gdb.Command):
19714 """Greet the whole world."""
19716 def __init__ (self):
19717 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
19719 def invoke (self, arg, from_tty):
19720 print "Hello, World!"
19725 The last line instantiates the class, and is necessary to trigger the
19726 registration of the command with @value{GDBN}. Depending on how the
19727 Python code is read into @value{GDBN}, you may need to import the
19728 @code{gdb} module explicitly.
19730 @node Functions In Python
19731 @subsubsection Writing new convenience functions
19733 @cindex writing convenience functions
19734 @cindex convenience functions in python
19735 @cindex python convenience functions
19736 @tindex gdb.Function
19738 You can implement new convenience functions (@pxref{Convenience Vars})
19739 in Python. A convenience function is an instance of a subclass of the
19740 class @code{gdb.Function}.
19742 @defmethod Function __init__ name
19743 The initializer for @code{Function} registers the new function with
19744 @value{GDBN}. The argument @var{name} is the name of the function,
19745 a string. The function will be visible to the user as a convenience
19746 variable of type @code{internal function}, whose name is the same as
19747 the given @var{name}.
19749 The documentation for the new function is taken from the documentation
19750 string for the new class.
19753 @defmethod Function invoke @var{*args}
19754 When a convenience function is evaluated, its arguments are converted
19755 to instances of @code{gdb.Value}, and then the function's
19756 @code{invoke} method is called. Note that @value{GDBN} does not
19757 predetermine the arity of convenience functions. Instead, all
19758 available arguments are passed to @code{invoke}, following the
19759 standard Python calling convention. In particular, a convenience
19760 function can have default values for parameters without ill effect.
19762 The return value of this method is used as its value in the enclosing
19763 expression. If an ordinary Python value is returned, it is converted
19764 to a @code{gdb.Value} following the usual rules.
19767 The following code snippet shows how a trivial convenience function can
19768 be implemented in Python:
19771 class Greet (gdb.Function):
19772 """Return string to greet someone.
19773 Takes a name as argument."""
19775 def __init__ (self):
19776 super (Greet, self).__init__ ("greet")
19778 def invoke (self, name):
19779 return "Hello, %s!" % name.string ()
19784 The last line instantiates the class, and is necessary to trigger the
19785 registration of the function with @value{GDBN}. Depending on how the
19786 Python code is read into @value{GDBN}, you may need to import the
19787 @code{gdb} module explicitly.
19789 @node Objfiles In Python
19790 @subsubsection Objfiles In Python
19792 @cindex objfiles in python
19793 @tindex gdb.Objfile
19795 @value{GDBN} loads symbols for an inferior from various
19796 symbol-containing files (@pxref{Files}). These include the primary
19797 executable file, any shared libraries used by the inferior, and any
19798 separate debug info files (@pxref{Separate Debug Files}).
19799 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
19801 The following objfile-related functions are available in the
19804 @findex gdb.current_objfile
19805 @defun current_objfile
19806 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
19807 sets the ``current objfile'' to the corresponding objfile. This
19808 function returns the current objfile. If there is no current objfile,
19809 this function returns @code{None}.
19812 @findex gdb.objfiles
19814 Return a sequence of all the objfiles current known to @value{GDBN}.
19815 @xref{Objfiles In Python}.
19818 Each objfile is represented by an instance of the @code{gdb.Objfile}
19821 @defivar Objfile filename
19822 The file name of the objfile as a string.
19825 @defivar Objfile pretty_printers
19826 The @code{pretty_printers} attribute is a list of functions. It is
19827 used to look up pretty-printers. A @code{Value} is passed to each
19828 function in order; if the function returns @code{None}, then the
19829 search continues. Otherwise, the return value should be an object
19830 which is used to format the value. @xref{Pretty Printing}, for more
19834 @node Frames In Python
19835 @subsubsection Acessing inferior stack frames from Python.
19837 @cindex frames in python
19838 When the debugged program stops, @value{GDBN} is able to analyze its call
19839 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
19840 represents a frame in the stack. A @code{gdb.Frame} object is only valid
19841 while its corresponding frame exists in the inferior's stack. If you try
19842 to use an invalid frame object, @value{GDBN} will throw a @code{RuntimeError}
19845 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
19849 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
19853 The following frame-related functions are available in the @code{gdb} module:
19855 @findex gdb.selected_frame
19856 @defun selected_frame
19857 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
19860 @defun frame_stop_reason_string reason
19861 Return a string explaining the reason why @value{GDBN} stopped unwinding
19862 frames, as expressed by the given @var{reason} code (an integer, see the
19863 @code{unwind_stop_reason} method further down in this section).
19866 A @code{gdb.Frame} object has the following methods:
19869 @defmethod Frame is_valid
19870 Returns true if the @code{gdb.Frame} object is valid, false if not.
19871 A frame object can become invalid if the frame it refers to doesn't
19872 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
19873 an exception if it is invalid at the time the method is called.
19876 @defmethod Frame name
19877 Returns the function name of the frame, or @code{None} if it can't be
19881 @defmethod Frame type
19882 Returns the type of the frame. The value can be one of
19883 @code{gdb.NORMAL_FRAME}, @code{gdb.DUMMY_FRAME}, @code{gdb.SIGTRAMP_FRAME}
19884 or @code{gdb.SENTINEL_FRAME}.
19887 @defmethod Frame unwind_stop_reason
19888 Return an integer representing the reason why it's not possible to find
19889 more frames toward the outermost frame. Use
19890 @code{gdb.frame_stop_reason_string} to convert the value returned by this
19891 function to a string.
19894 @defmethod Frame pc
19895 Returns the frame's resume address.
19898 @defmethod Frame older
19899 Return the frame that called this frame.
19902 @defmethod Frame newer
19903 Return the frame called by this frame.
19906 @defmethod Frame read_var variable
19907 Return the value of the given variable in this frame. @var{variable} must
19913 @chapter Command Interpreters
19914 @cindex command interpreters
19916 @value{GDBN} supports multiple command interpreters, and some command
19917 infrastructure to allow users or user interface writers to switch
19918 between interpreters or run commands in other interpreters.
19920 @value{GDBN} currently supports two command interpreters, the console
19921 interpreter (sometimes called the command-line interpreter or @sc{cli})
19922 and the machine interface interpreter (or @sc{gdb/mi}). This manual
19923 describes both of these interfaces in great detail.
19925 By default, @value{GDBN} will start with the console interpreter.
19926 However, the user may choose to start @value{GDBN} with another
19927 interpreter by specifying the @option{-i} or @option{--interpreter}
19928 startup options. Defined interpreters include:
19932 @cindex console interpreter
19933 The traditional console or command-line interpreter. This is the most often
19934 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
19935 @value{GDBN} will use this interpreter.
19938 @cindex mi interpreter
19939 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
19940 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
19941 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
19945 @cindex mi2 interpreter
19946 The current @sc{gdb/mi} interface.
19949 @cindex mi1 interpreter
19950 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
19954 @cindex invoke another interpreter
19955 The interpreter being used by @value{GDBN} may not be dynamically
19956 switched at runtime. Although possible, this could lead to a very
19957 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
19958 enters the command "interpreter-set console" in a console view,
19959 @value{GDBN} would switch to using the console interpreter, rendering
19960 the IDE inoperable!
19962 @kindex interpreter-exec
19963 Although you may only choose a single interpreter at startup, you may execute
19964 commands in any interpreter from the current interpreter using the appropriate
19965 command. If you are running the console interpreter, simply use the
19966 @code{interpreter-exec} command:
19969 interpreter-exec mi "-data-list-register-names"
19972 @sc{gdb/mi} has a similar command, although it is only available in versions of
19973 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
19976 @chapter @value{GDBN} Text User Interface
19978 @cindex Text User Interface
19981 * TUI Overview:: TUI overview
19982 * TUI Keys:: TUI key bindings
19983 * TUI Single Key Mode:: TUI single key mode
19984 * TUI Commands:: TUI-specific commands
19985 * TUI Configuration:: TUI configuration variables
19988 The @value{GDBN} Text User Interface (TUI) is a terminal
19989 interface which uses the @code{curses} library to show the source
19990 file, the assembly output, the program registers and @value{GDBN}
19991 commands in separate text windows. The TUI mode is supported only
19992 on platforms where a suitable version of the @code{curses} library
19995 @pindex @value{GDBTUI}
19996 The TUI mode is enabled by default when you invoke @value{GDBN} as
19997 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
19998 You can also switch in and out of TUI mode while @value{GDBN} runs by
19999 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
20000 @xref{TUI Keys, ,TUI Key Bindings}.
20003 @section TUI Overview
20005 In TUI mode, @value{GDBN} can display several text windows:
20009 This window is the @value{GDBN} command window with the @value{GDBN}
20010 prompt and the @value{GDBN} output. The @value{GDBN} input is still
20011 managed using readline.
20014 The source window shows the source file of the program. The current
20015 line and active breakpoints are displayed in this window.
20018 The assembly window shows the disassembly output of the program.
20021 This window shows the processor registers. Registers are highlighted
20022 when their values change.
20025 The source and assembly windows show the current program position
20026 by highlighting the current line and marking it with a @samp{>} marker.
20027 Breakpoints are indicated with two markers. The first marker
20028 indicates the breakpoint type:
20032 Breakpoint which was hit at least once.
20035 Breakpoint which was never hit.
20038 Hardware breakpoint which was hit at least once.
20041 Hardware breakpoint which was never hit.
20044 The second marker indicates whether the breakpoint is enabled or not:
20048 Breakpoint is enabled.
20051 Breakpoint is disabled.
20054 The source, assembly and register windows are updated when the current
20055 thread changes, when the frame changes, or when the program counter
20058 These windows are not all visible at the same time. The command
20059 window is always visible. The others can be arranged in several
20070 source and assembly,
20073 source and registers, or
20076 assembly and registers.
20079 A status line above the command window shows the following information:
20083 Indicates the current @value{GDBN} target.
20084 (@pxref{Targets, ,Specifying a Debugging Target}).
20087 Gives the current process or thread number.
20088 When no process is being debugged, this field is set to @code{No process}.
20091 Gives the current function name for the selected frame.
20092 The name is demangled if demangling is turned on (@pxref{Print Settings}).
20093 When there is no symbol corresponding to the current program counter,
20094 the string @code{??} is displayed.
20097 Indicates the current line number for the selected frame.
20098 When the current line number is not known, the string @code{??} is displayed.
20101 Indicates the current program counter address.
20105 @section TUI Key Bindings
20106 @cindex TUI key bindings
20108 The TUI installs several key bindings in the readline keymaps
20109 (@pxref{Command Line Editing}). The following key bindings
20110 are installed for both TUI mode and the @value{GDBN} standard mode.
20119 Enter or leave the TUI mode. When leaving the TUI mode,
20120 the curses window management stops and @value{GDBN} operates using
20121 its standard mode, writing on the terminal directly. When reentering
20122 the TUI mode, control is given back to the curses windows.
20123 The screen is then refreshed.
20127 Use a TUI layout with only one window. The layout will
20128 either be @samp{source} or @samp{assembly}. When the TUI mode
20129 is not active, it will switch to the TUI mode.
20131 Think of this key binding as the Emacs @kbd{C-x 1} binding.
20135 Use a TUI layout with at least two windows. When the current
20136 layout already has two windows, the next layout with two windows is used.
20137 When a new layout is chosen, one window will always be common to the
20138 previous layout and the new one.
20140 Think of it as the Emacs @kbd{C-x 2} binding.
20144 Change the active window. The TUI associates several key bindings
20145 (like scrolling and arrow keys) with the active window. This command
20146 gives the focus to the next TUI window.
20148 Think of it as the Emacs @kbd{C-x o} binding.
20152 Switch in and out of the TUI SingleKey mode that binds single
20153 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
20156 The following key bindings only work in the TUI mode:
20161 Scroll the active window one page up.
20165 Scroll the active window one page down.
20169 Scroll the active window one line up.
20173 Scroll the active window one line down.
20177 Scroll the active window one column left.
20181 Scroll the active window one column right.
20185 Refresh the screen.
20188 Because the arrow keys scroll the active window in the TUI mode, they
20189 are not available for their normal use by readline unless the command
20190 window has the focus. When another window is active, you must use
20191 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
20192 and @kbd{C-f} to control the command window.
20194 @node TUI Single Key Mode
20195 @section TUI Single Key Mode
20196 @cindex TUI single key mode
20198 The TUI also provides a @dfn{SingleKey} mode, which binds several
20199 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
20200 switch into this mode, where the following key bindings are used:
20203 @kindex c @r{(SingleKey TUI key)}
20207 @kindex d @r{(SingleKey TUI key)}
20211 @kindex f @r{(SingleKey TUI key)}
20215 @kindex n @r{(SingleKey TUI key)}
20219 @kindex q @r{(SingleKey TUI key)}
20221 exit the SingleKey mode.
20223 @kindex r @r{(SingleKey TUI key)}
20227 @kindex s @r{(SingleKey TUI key)}
20231 @kindex u @r{(SingleKey TUI key)}
20235 @kindex v @r{(SingleKey TUI key)}
20239 @kindex w @r{(SingleKey TUI key)}
20244 Other keys temporarily switch to the @value{GDBN} command prompt.
20245 The key that was pressed is inserted in the editing buffer so that
20246 it is possible to type most @value{GDBN} commands without interaction
20247 with the TUI SingleKey mode. Once the command is entered the TUI
20248 SingleKey mode is restored. The only way to permanently leave
20249 this mode is by typing @kbd{q} or @kbd{C-x s}.
20253 @section TUI-specific Commands
20254 @cindex TUI commands
20256 The TUI has specific commands to control the text windows.
20257 These commands are always available, even when @value{GDBN} is not in
20258 the TUI mode. When @value{GDBN} is in the standard mode, most
20259 of these commands will automatically switch to the TUI mode.
20264 List and give the size of all displayed windows.
20268 Display the next layout.
20271 Display the previous layout.
20274 Display the source window only.
20277 Display the assembly window only.
20280 Display the source and assembly window.
20283 Display the register window together with the source or assembly window.
20287 Make the next window active for scrolling.
20290 Make the previous window active for scrolling.
20293 Make the source window active for scrolling.
20296 Make the assembly window active for scrolling.
20299 Make the register window active for scrolling.
20302 Make the command window active for scrolling.
20306 Refresh the screen. This is similar to typing @kbd{C-L}.
20308 @item tui reg float
20310 Show the floating point registers in the register window.
20312 @item tui reg general
20313 Show the general registers in the register window.
20316 Show the next register group. The list of register groups as well as
20317 their order is target specific. The predefined register groups are the
20318 following: @code{general}, @code{float}, @code{system}, @code{vector},
20319 @code{all}, @code{save}, @code{restore}.
20321 @item tui reg system
20322 Show the system registers in the register window.
20326 Update the source window and the current execution point.
20328 @item winheight @var{name} +@var{count}
20329 @itemx winheight @var{name} -@var{count}
20331 Change the height of the window @var{name} by @var{count}
20332 lines. Positive counts increase the height, while negative counts
20335 @item tabset @var{nchars}
20337 Set the width of tab stops to be @var{nchars} characters.
20340 @node TUI Configuration
20341 @section TUI Configuration Variables
20342 @cindex TUI configuration variables
20344 Several configuration variables control the appearance of TUI windows.
20347 @item set tui border-kind @var{kind}
20348 @kindex set tui border-kind
20349 Select the border appearance for the source, assembly and register windows.
20350 The possible values are the following:
20353 Use a space character to draw the border.
20356 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
20359 Use the Alternate Character Set to draw the border. The border is
20360 drawn using character line graphics if the terminal supports them.
20363 @item set tui border-mode @var{mode}
20364 @kindex set tui border-mode
20365 @itemx set tui active-border-mode @var{mode}
20366 @kindex set tui active-border-mode
20367 Select the display attributes for the borders of the inactive windows
20368 or the active window. The @var{mode} can be one of the following:
20371 Use normal attributes to display the border.
20377 Use reverse video mode.
20380 Use half bright mode.
20382 @item half-standout
20383 Use half bright and standout mode.
20386 Use extra bright or bold mode.
20388 @item bold-standout
20389 Use extra bright or bold and standout mode.
20394 @chapter Using @value{GDBN} under @sc{gnu} Emacs
20397 @cindex @sc{gnu} Emacs
20398 A special interface allows you to use @sc{gnu} Emacs to view (and
20399 edit) the source files for the program you are debugging with
20402 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
20403 executable file you want to debug as an argument. This command starts
20404 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
20405 created Emacs buffer.
20406 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
20408 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
20413 All ``terminal'' input and output goes through an Emacs buffer, called
20416 This applies both to @value{GDBN} commands and their output, and to the input
20417 and output done by the program you are debugging.
20419 This is useful because it means that you can copy the text of previous
20420 commands and input them again; you can even use parts of the output
20423 All the facilities of Emacs' Shell mode are available for interacting
20424 with your program. In particular, you can send signals the usual
20425 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
20429 @value{GDBN} displays source code through Emacs.
20431 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
20432 source file for that frame and puts an arrow (@samp{=>}) at the
20433 left margin of the current line. Emacs uses a separate buffer for
20434 source display, and splits the screen to show both your @value{GDBN} session
20437 Explicit @value{GDBN} @code{list} or search commands still produce output as
20438 usual, but you probably have no reason to use them from Emacs.
20441 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
20442 a graphical mode, enabled by default, which provides further buffers
20443 that can control the execution and describe the state of your program.
20444 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
20446 If you specify an absolute file name when prompted for the @kbd{M-x
20447 gdb} argument, then Emacs sets your current working directory to where
20448 your program resides. If you only specify the file name, then Emacs
20449 sets your current working directory to to the directory associated
20450 with the previous buffer. In this case, @value{GDBN} may find your
20451 program by searching your environment's @code{PATH} variable, but on
20452 some operating systems it might not find the source. So, although the
20453 @value{GDBN} input and output session proceeds normally, the auxiliary
20454 buffer does not display the current source and line of execution.
20456 The initial working directory of @value{GDBN} is printed on the top
20457 line of the GUD buffer and this serves as a default for the commands
20458 that specify files for @value{GDBN} to operate on. @xref{Files,
20459 ,Commands to Specify Files}.
20461 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
20462 need to call @value{GDBN} by a different name (for example, if you
20463 keep several configurations around, with different names) you can
20464 customize the Emacs variable @code{gud-gdb-command-name} to run the
20467 In the GUD buffer, you can use these special Emacs commands in
20468 addition to the standard Shell mode commands:
20472 Describe the features of Emacs' GUD Mode.
20475 Execute to another source line, like the @value{GDBN} @code{step} command; also
20476 update the display window to show the current file and location.
20479 Execute to next source line in this function, skipping all function
20480 calls, like the @value{GDBN} @code{next} command. Then update the display window
20481 to show the current file and location.
20484 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
20485 display window accordingly.
20488 Execute until exit from the selected stack frame, like the @value{GDBN}
20489 @code{finish} command.
20492 Continue execution of your program, like the @value{GDBN} @code{continue}
20496 Go up the number of frames indicated by the numeric argument
20497 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
20498 like the @value{GDBN} @code{up} command.
20501 Go down the number of frames indicated by the numeric argument, like the
20502 @value{GDBN} @code{down} command.
20505 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
20506 tells @value{GDBN} to set a breakpoint on the source line point is on.
20508 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
20509 separate frame which shows a backtrace when the GUD buffer is current.
20510 Move point to any frame in the stack and type @key{RET} to make it
20511 become the current frame and display the associated source in the
20512 source buffer. Alternatively, click @kbd{Mouse-2} to make the
20513 selected frame become the current one. In graphical mode, the
20514 speedbar displays watch expressions.
20516 If you accidentally delete the source-display buffer, an easy way to get
20517 it back is to type the command @code{f} in the @value{GDBN} buffer, to
20518 request a frame display; when you run under Emacs, this recreates
20519 the source buffer if necessary to show you the context of the current
20522 The source files displayed in Emacs are in ordinary Emacs buffers
20523 which are visiting the source files in the usual way. You can edit
20524 the files with these buffers if you wish; but keep in mind that @value{GDBN}
20525 communicates with Emacs in terms of line numbers. If you add or
20526 delete lines from the text, the line numbers that @value{GDBN} knows cease
20527 to correspond properly with the code.
20529 A more detailed description of Emacs' interaction with @value{GDBN} is
20530 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
20533 @c The following dropped because Epoch is nonstandard. Reactivate
20534 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
20536 @kindex Emacs Epoch environment
20540 Version 18 of @sc{gnu} Emacs has a built-in window system
20541 called the @code{epoch}
20542 environment. Users of this environment can use a new command,
20543 @code{inspect} which performs identically to @code{print} except that
20544 each value is printed in its own window.
20549 @chapter The @sc{gdb/mi} Interface
20551 @unnumberedsec Function and Purpose
20553 @cindex @sc{gdb/mi}, its purpose
20554 @sc{gdb/mi} is a line based machine oriented text interface to
20555 @value{GDBN} and is activated by specifying using the
20556 @option{--interpreter} command line option (@pxref{Mode Options}). It
20557 is specifically intended to support the development of systems which
20558 use the debugger as just one small component of a larger system.
20560 This chapter is a specification of the @sc{gdb/mi} interface. It is written
20561 in the form of a reference manual.
20563 Note that @sc{gdb/mi} is still under construction, so some of the
20564 features described below are incomplete and subject to change
20565 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
20567 @unnumberedsec Notation and Terminology
20569 @cindex notational conventions, for @sc{gdb/mi}
20570 This chapter uses the following notation:
20574 @code{|} separates two alternatives.
20577 @code{[ @var{something} ]} indicates that @var{something} is optional:
20578 it may or may not be given.
20581 @code{( @var{group} )*} means that @var{group} inside the parentheses
20582 may repeat zero or more times.
20585 @code{( @var{group} )+} means that @var{group} inside the parentheses
20586 may repeat one or more times.
20589 @code{"@var{string}"} means a literal @var{string}.
20593 @heading Dependencies
20597 * GDB/MI General Design::
20598 * GDB/MI Command Syntax::
20599 * GDB/MI Compatibility with CLI::
20600 * GDB/MI Development and Front Ends::
20601 * GDB/MI Output Records::
20602 * GDB/MI Simple Examples::
20603 * GDB/MI Command Description Format::
20604 * GDB/MI Breakpoint Commands::
20605 * GDB/MI Program Context::
20606 * GDB/MI Thread Commands::
20607 * GDB/MI Program Execution::
20608 * GDB/MI Stack Manipulation::
20609 * GDB/MI Variable Objects::
20610 * GDB/MI Data Manipulation::
20611 * GDB/MI Tracepoint Commands::
20612 * GDB/MI Symbol Query::
20613 * GDB/MI File Commands::
20615 * GDB/MI Kod Commands::
20616 * GDB/MI Memory Overlay Commands::
20617 * GDB/MI Signal Handling Commands::
20619 * GDB/MI Target Manipulation::
20620 * GDB/MI File Transfer Commands::
20621 * GDB/MI Miscellaneous Commands::
20624 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20625 @node GDB/MI General Design
20626 @section @sc{gdb/mi} General Design
20627 @cindex GDB/MI General Design
20629 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
20630 parts---commands sent to @value{GDBN}, responses to those commands
20631 and notifications. Each command results in exactly one response,
20632 indicating either successful completion of the command, or an error.
20633 For the commands that do not resume the target, the response contains the
20634 requested information. For the commands that resume the target, the
20635 response only indicates whether the target was successfully resumed.
20636 Notifications is the mechanism for reporting changes in the state of the
20637 target, or in @value{GDBN} state, that cannot conveniently be associated with
20638 a command and reported as part of that command response.
20640 The important examples of notifications are:
20644 Exec notifications. These are used to report changes in
20645 target state---when a target is resumed, or stopped. It would not
20646 be feasible to include this information in response of resuming
20647 commands, because one resume commands can result in multiple events in
20648 different threads. Also, quite some time may pass before any event
20649 happens in the target, while a frontend needs to know whether the resuming
20650 command itself was successfully executed.
20653 Console output, and status notifications. Console output
20654 notifications are used to report output of CLI commands, as well as
20655 diagnostics for other commands. Status notifications are used to
20656 report the progress of a long-running operation. Naturally, including
20657 this information in command response would mean no output is produced
20658 until the command is finished, which is undesirable.
20661 General notifications. Commands may have various side effects on
20662 the @value{GDBN} or target state beyond their official purpose. For example,
20663 a command may change the selected thread. Although such changes can
20664 be included in command response, using notification allows for more
20665 orthogonal frontend design.
20669 There's no guarantee that whenever an MI command reports an error,
20670 @value{GDBN} or the target are in any specific state, and especially,
20671 the state is not reverted to the state before the MI command was
20672 processed. Therefore, whenever an MI command results in an error,
20673 we recommend that the frontend refreshes all the information shown in
20674 the user interface.
20678 * Context management::
20679 * Asynchronous and non-stop modes::
20683 @node Context management
20684 @subsection Context management
20686 In most cases when @value{GDBN} accesses the target, this access is
20687 done in context of a specific thread and frame (@pxref{Frames}).
20688 Often, even when accessing global data, the target requires that a thread
20689 be specified. The CLI interface maintains the selected thread and frame,
20690 and supplies them to target on each command. This is convenient,
20691 because a command line user would not want to specify that information
20692 explicitly on each command, and because user interacts with
20693 @value{GDBN} via a single terminal, so no confusion is possible as
20694 to what thread and frame are the current ones.
20696 In the case of MI, the concept of selected thread and frame is less
20697 useful. First, a frontend can easily remember this information
20698 itself. Second, a graphical frontend can have more than one window,
20699 each one used for debugging a different thread, and the frontend might
20700 want to access additional threads for internal purposes. This
20701 increases the risk that by relying on implicitly selected thread, the
20702 frontend may be operating on a wrong one. Therefore, each MI command
20703 should explicitly specify which thread and frame to operate on. To
20704 make it possible, each MI command accepts the @samp{--thread} and
20705 @samp{--frame} options, the value to each is @value{GDBN} identifier
20706 for thread and frame to operate on.
20708 Usually, each top-level window in a frontend allows the user to select
20709 a thread and a frame, and remembers the user selection for further
20710 operations. However, in some cases @value{GDBN} may suggest that the
20711 current thread be changed. For example, when stopping on a breakpoint
20712 it is reasonable to switch to the thread where breakpoint is hit. For
20713 another example, if the user issues the CLI @samp{thread} command via
20714 the frontend, it is desirable to change the frontend's selected thread to the
20715 one specified by user. @value{GDBN} communicates the suggestion to
20716 change current thread using the @samp{=thread-selected} notification.
20717 No such notification is available for the selected frame at the moment.
20719 Note that historically, MI shares the selected thread with CLI, so
20720 frontends used the @code{-thread-select} to execute commands in the
20721 right context. However, getting this to work right is cumbersome. The
20722 simplest way is for frontend to emit @code{-thread-select} command
20723 before every command. This doubles the number of commands that need
20724 to be sent. The alternative approach is to suppress @code{-thread-select}
20725 if the selected thread in @value{GDBN} is supposed to be identical to the
20726 thread the frontend wants to operate on. However, getting this
20727 optimization right can be tricky. In particular, if the frontend
20728 sends several commands to @value{GDBN}, and one of the commands changes the
20729 selected thread, then the behaviour of subsequent commands will
20730 change. So, a frontend should either wait for response from such
20731 problematic commands, or explicitly add @code{-thread-select} for
20732 all subsequent commands. No frontend is known to do this exactly
20733 right, so it is suggested to just always pass the @samp{--thread} and
20734 @samp{--frame} options.
20736 @node Asynchronous and non-stop modes
20737 @subsection Asynchronous command execution and non-stop mode
20739 On some targets, @value{GDBN} is capable of processing MI commands
20740 even while the target is running. This is called @dfn{asynchronous
20741 command execution} (@pxref{Background Execution}). The frontend may
20742 specify a preferrence for asynchronous execution using the
20743 @code{-gdb-set target-async 1} command, which should be emitted before
20744 either running the executable or attaching to the target. After the
20745 frontend has started the executable or attached to the target, it can
20746 find if asynchronous execution is enabled using the
20747 @code{-list-target-features} command.
20749 Even if @value{GDBN} can accept a command while target is running,
20750 many commands that access the target do not work when the target is
20751 running. Therefore, asynchronous command execution is most useful
20752 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
20753 it is possible to examine the state of one thread, while other threads
20756 When a given thread is running, MI commands that try to access the
20757 target in the context of that thread may not work, or may work only on
20758 some targets. In particular, commands that try to operate on thread's
20759 stack will not work, on any target. Commands that read memory, or
20760 modify breakpoints, may work or not work, depending on the target. Note
20761 that even commands that operate on global state, such as @code{print},
20762 @code{set}, and breakpoint commands, still access the target in the
20763 context of a specific thread, so frontend should try to find a
20764 stopped thread and perform the operation on that thread (using the
20765 @samp{--thread} option).
20767 Which commands will work in the context of a running thread is
20768 highly target dependent. However, the two commands
20769 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
20770 to find the state of a thread, will always work.
20772 @node Thread groups
20773 @subsection Thread groups
20774 @value{GDBN} may be used to debug several processes at the same time.
20775 On some platfroms, @value{GDBN} may support debugging of several
20776 hardware systems, each one having several cores with several different
20777 processes running on each core. This section describes the MI
20778 mechanism to support such debugging scenarios.
20780 The key observation is that regardless of the structure of the
20781 target, MI can have a global list of threads, because most commands that
20782 accept the @samp{--thread} option do not need to know what process that
20783 thread belongs to. Therefore, it is not necessary to introduce
20784 neither additional @samp{--process} option, nor an notion of the
20785 current process in the MI interface. The only strictly new feature
20786 that is required is the ability to find how the threads are grouped
20789 To allow the user to discover such grouping, and to support arbitrary
20790 hierarchy of machines/cores/processes, MI introduces the concept of a
20791 @dfn{thread group}. Thread group is a collection of threads and other
20792 thread groups. A thread group always has a string identifier, a type,
20793 and may have additional attributes specific to the type. A new
20794 command, @code{-list-thread-groups}, returns the list of top-level
20795 thread groups, which correspond to processes that @value{GDBN} is
20796 debugging at the moment. By passing an identifier of a thread group
20797 to the @code{-list-thread-groups} command, it is possible to obtain
20798 the members of specific thread group.
20800 To allow the user to easily discover processes, and other objects, he
20801 wishes to debug, a concept of @dfn{available thread group} is
20802 introduced. Available thread group is an thread group that
20803 @value{GDBN} is not debugging, but that can be attached to, using the
20804 @code{-target-attach} command. The list of available top-level thread
20805 groups can be obtained using @samp{-list-thread-groups --available}.
20806 In general, the content of a thread group may be only retrieved only
20807 after attaching to that thread group.
20809 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20810 @node GDB/MI Command Syntax
20811 @section @sc{gdb/mi} Command Syntax
20814 * GDB/MI Input Syntax::
20815 * GDB/MI Output Syntax::
20818 @node GDB/MI Input Syntax
20819 @subsection @sc{gdb/mi} Input Syntax
20821 @cindex input syntax for @sc{gdb/mi}
20822 @cindex @sc{gdb/mi}, input syntax
20824 @item @var{command} @expansion{}
20825 @code{@var{cli-command} | @var{mi-command}}
20827 @item @var{cli-command} @expansion{}
20828 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
20829 @var{cli-command} is any existing @value{GDBN} CLI command.
20831 @item @var{mi-command} @expansion{}
20832 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
20833 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
20835 @item @var{token} @expansion{}
20836 "any sequence of digits"
20838 @item @var{option} @expansion{}
20839 @code{"-" @var{parameter} [ " " @var{parameter} ]}
20841 @item @var{parameter} @expansion{}
20842 @code{@var{non-blank-sequence} | @var{c-string}}
20844 @item @var{operation} @expansion{}
20845 @emph{any of the operations described in this chapter}
20847 @item @var{non-blank-sequence} @expansion{}
20848 @emph{anything, provided it doesn't contain special characters such as
20849 "-", @var{nl}, """ and of course " "}
20851 @item @var{c-string} @expansion{}
20852 @code{""" @var{seven-bit-iso-c-string-content} """}
20854 @item @var{nl} @expansion{}
20863 The CLI commands are still handled by the @sc{mi} interpreter; their
20864 output is described below.
20867 The @code{@var{token}}, when present, is passed back when the command
20871 Some @sc{mi} commands accept optional arguments as part of the parameter
20872 list. Each option is identified by a leading @samp{-} (dash) and may be
20873 followed by an optional argument parameter. Options occur first in the
20874 parameter list and can be delimited from normal parameters using
20875 @samp{--} (this is useful when some parameters begin with a dash).
20882 We want easy access to the existing CLI syntax (for debugging).
20885 We want it to be easy to spot a @sc{mi} operation.
20888 @node GDB/MI Output Syntax
20889 @subsection @sc{gdb/mi} Output Syntax
20891 @cindex output syntax of @sc{gdb/mi}
20892 @cindex @sc{gdb/mi}, output syntax
20893 The output from @sc{gdb/mi} consists of zero or more out-of-band records
20894 followed, optionally, by a single result record. This result record
20895 is for the most recent command. The sequence of output records is
20896 terminated by @samp{(gdb)}.
20898 If an input command was prefixed with a @code{@var{token}} then the
20899 corresponding output for that command will also be prefixed by that same
20903 @item @var{output} @expansion{}
20904 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
20906 @item @var{result-record} @expansion{}
20907 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
20909 @item @var{out-of-band-record} @expansion{}
20910 @code{@var{async-record} | @var{stream-record}}
20912 @item @var{async-record} @expansion{}
20913 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
20915 @item @var{exec-async-output} @expansion{}
20916 @code{[ @var{token} ] "*" @var{async-output}}
20918 @item @var{status-async-output} @expansion{}
20919 @code{[ @var{token} ] "+" @var{async-output}}
20921 @item @var{notify-async-output} @expansion{}
20922 @code{[ @var{token} ] "=" @var{async-output}}
20924 @item @var{async-output} @expansion{}
20925 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
20927 @item @var{result-class} @expansion{}
20928 @code{"done" | "running" | "connected" | "error" | "exit"}
20930 @item @var{async-class} @expansion{}
20931 @code{"stopped" | @var{others}} (where @var{others} will be added
20932 depending on the needs---this is still in development).
20934 @item @var{result} @expansion{}
20935 @code{ @var{variable} "=" @var{value}}
20937 @item @var{variable} @expansion{}
20938 @code{ @var{string} }
20940 @item @var{value} @expansion{}
20941 @code{ @var{const} | @var{tuple} | @var{list} }
20943 @item @var{const} @expansion{}
20944 @code{@var{c-string}}
20946 @item @var{tuple} @expansion{}
20947 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
20949 @item @var{list} @expansion{}
20950 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
20951 @var{result} ( "," @var{result} )* "]" }
20953 @item @var{stream-record} @expansion{}
20954 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
20956 @item @var{console-stream-output} @expansion{}
20957 @code{"~" @var{c-string}}
20959 @item @var{target-stream-output} @expansion{}
20960 @code{"@@" @var{c-string}}
20962 @item @var{log-stream-output} @expansion{}
20963 @code{"&" @var{c-string}}
20965 @item @var{nl} @expansion{}
20968 @item @var{token} @expansion{}
20969 @emph{any sequence of digits}.
20977 All output sequences end in a single line containing a period.
20980 The @code{@var{token}} is from the corresponding request. Note that
20981 for all async output, while the token is allowed by the grammar and
20982 may be output by future versions of @value{GDBN} for select async
20983 output messages, it is generally omitted. Frontends should treat
20984 all async output as reporting general changes in the state of the
20985 target and there should be no need to associate async output to any
20989 @cindex status output in @sc{gdb/mi}
20990 @var{status-async-output} contains on-going status information about the
20991 progress of a slow operation. It can be discarded. All status output is
20992 prefixed by @samp{+}.
20995 @cindex async output in @sc{gdb/mi}
20996 @var{exec-async-output} contains asynchronous state change on the target
20997 (stopped, started, disappeared). All async output is prefixed by
21001 @cindex notify output in @sc{gdb/mi}
21002 @var{notify-async-output} contains supplementary information that the
21003 client should handle (e.g., a new breakpoint information). All notify
21004 output is prefixed by @samp{=}.
21007 @cindex console output in @sc{gdb/mi}
21008 @var{console-stream-output} is output that should be displayed as is in the
21009 console. It is the textual response to a CLI command. All the console
21010 output is prefixed by @samp{~}.
21013 @cindex target output in @sc{gdb/mi}
21014 @var{target-stream-output} is the output produced by the target program.
21015 All the target output is prefixed by @samp{@@}.
21018 @cindex log output in @sc{gdb/mi}
21019 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
21020 instance messages that should be displayed as part of an error log. All
21021 the log output is prefixed by @samp{&}.
21024 @cindex list output in @sc{gdb/mi}
21025 New @sc{gdb/mi} commands should only output @var{lists} containing
21031 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
21032 details about the various output records.
21034 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21035 @node GDB/MI Compatibility with CLI
21036 @section @sc{gdb/mi} Compatibility with CLI
21038 @cindex compatibility, @sc{gdb/mi} and CLI
21039 @cindex @sc{gdb/mi}, compatibility with CLI
21041 For the developers convenience CLI commands can be entered directly,
21042 but there may be some unexpected behaviour. For example, commands
21043 that query the user will behave as if the user replied yes, breakpoint
21044 command lists are not executed and some CLI commands, such as
21045 @code{if}, @code{when} and @code{define}, prompt for further input with
21046 @samp{>}, which is not valid MI output.
21048 This feature may be removed at some stage in the future and it is
21049 recommended that front ends use the @code{-interpreter-exec} command
21050 (@pxref{-interpreter-exec}).
21052 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21053 @node GDB/MI Development and Front Ends
21054 @section @sc{gdb/mi} Development and Front Ends
21055 @cindex @sc{gdb/mi} development
21057 The application which takes the MI output and presents the state of the
21058 program being debugged to the user is called a @dfn{front end}.
21060 Although @sc{gdb/mi} is still incomplete, it is currently being used
21061 by a variety of front ends to @value{GDBN}. This makes it difficult
21062 to introduce new functionality without breaking existing usage. This
21063 section tries to minimize the problems by describing how the protocol
21066 Some changes in MI need not break a carefully designed front end, and
21067 for these the MI version will remain unchanged. The following is a
21068 list of changes that may occur within one level, so front ends should
21069 parse MI output in a way that can handle them:
21073 New MI commands may be added.
21076 New fields may be added to the output of any MI command.
21079 The range of values for fields with specified values, e.g.,
21080 @code{in_scope} (@pxref{-var-update}) may be extended.
21082 @c The format of field's content e.g type prefix, may change so parse it
21083 @c at your own risk. Yes, in general?
21085 @c The order of fields may change? Shouldn't really matter but it might
21086 @c resolve inconsistencies.
21089 If the changes are likely to break front ends, the MI version level
21090 will be increased by one. This will allow the front end to parse the
21091 output according to the MI version. Apart from mi0, new versions of
21092 @value{GDBN} will not support old versions of MI and it will be the
21093 responsibility of the front end to work with the new one.
21095 @c Starting with mi3, add a new command -mi-version that prints the MI
21098 The best way to avoid unexpected changes in MI that might break your front
21099 end is to make your project known to @value{GDBN} developers and
21100 follow development on @email{gdb@@sourceware.org} and
21101 @email{gdb-patches@@sourceware.org}.
21102 @cindex mailing lists
21104 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21105 @node GDB/MI Output Records
21106 @section @sc{gdb/mi} Output Records
21109 * GDB/MI Result Records::
21110 * GDB/MI Stream Records::
21111 * GDB/MI Async Records::
21112 * GDB/MI Frame Information::
21115 @node GDB/MI Result Records
21116 @subsection @sc{gdb/mi} Result Records
21118 @cindex result records in @sc{gdb/mi}
21119 @cindex @sc{gdb/mi}, result records
21120 In addition to a number of out-of-band notifications, the response to a
21121 @sc{gdb/mi} command includes one of the following result indications:
21125 @item "^done" [ "," @var{results} ]
21126 The synchronous operation was successful, @code{@var{results}} are the return
21131 @c Is this one correct? Should it be an out-of-band notification?
21132 The asynchronous operation was successfully started. The target is
21137 @value{GDBN} has connected to a remote target.
21139 @item "^error" "," @var{c-string}
21141 The operation failed. The @code{@var{c-string}} contains the corresponding
21146 @value{GDBN} has terminated.
21150 @node GDB/MI Stream Records
21151 @subsection @sc{gdb/mi} Stream Records
21153 @cindex @sc{gdb/mi}, stream records
21154 @cindex stream records in @sc{gdb/mi}
21155 @value{GDBN} internally maintains a number of output streams: the console, the
21156 target, and the log. The output intended for each of these streams is
21157 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
21159 Each stream record begins with a unique @dfn{prefix character} which
21160 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
21161 Syntax}). In addition to the prefix, each stream record contains a
21162 @code{@var{string-output}}. This is either raw text (with an implicit new
21163 line) or a quoted C string (which does not contain an implicit newline).
21166 @item "~" @var{string-output}
21167 The console output stream contains text that should be displayed in the
21168 CLI console window. It contains the textual responses to CLI commands.
21170 @item "@@" @var{string-output}
21171 The target output stream contains any textual output from the running
21172 target. This is only present when GDB's event loop is truly
21173 asynchronous, which is currently only the case for remote targets.
21175 @item "&" @var{string-output}
21176 The log stream contains debugging messages being produced by @value{GDBN}'s
21180 @node GDB/MI Async Records
21181 @subsection @sc{gdb/mi} Async Records
21183 @cindex async records in @sc{gdb/mi}
21184 @cindex @sc{gdb/mi}, async records
21185 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
21186 additional changes that have occurred. Those changes can either be a
21187 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
21188 target activity (e.g., target stopped).
21190 The following is the list of possible async records:
21194 @item *running,thread-id="@var{thread}"
21195 The target is now running. The @var{thread} field tells which
21196 specific thread is now running, and can be @samp{all} if all threads
21197 are running. The frontend should assume that no interaction with a
21198 running thread is possible after this notification is produced.
21199 The frontend should not assume that this notification is output
21200 only once for any command. @value{GDBN} may emit this notification
21201 several times, either for different threads, because it cannot resume
21202 all threads together, or even for a single thread, if the thread must
21203 be stepped though some code before letting it run freely.
21205 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}"
21206 The target has stopped. The @var{reason} field can have one of the
21210 @item breakpoint-hit
21211 A breakpoint was reached.
21212 @item watchpoint-trigger
21213 A watchpoint was triggered.
21214 @item read-watchpoint-trigger
21215 A read watchpoint was triggered.
21216 @item access-watchpoint-trigger
21217 An access watchpoint was triggered.
21218 @item function-finished
21219 An -exec-finish or similar CLI command was accomplished.
21220 @item location-reached
21221 An -exec-until or similar CLI command was accomplished.
21222 @item watchpoint-scope
21223 A watchpoint has gone out of scope.
21224 @item end-stepping-range
21225 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
21226 similar CLI command was accomplished.
21227 @item exited-signalled
21228 The inferior exited because of a signal.
21230 The inferior exited.
21231 @item exited-normally
21232 The inferior exited normally.
21233 @item signal-received
21234 A signal was received by the inferior.
21237 The @var{id} field identifies the thread that directly caused the stop
21238 -- for example by hitting a breakpoint. Depending on whether all-stop
21239 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
21240 stop all threads, or only the thread that directly triggered the stop.
21241 If all threads are stopped, the @var{stopped} field will have the
21242 value of @code{"all"}. Otherwise, the value of the @var{stopped}
21243 field will be a list of thread identifiers. Presently, this list will
21244 always include a single thread, but frontend should be prepared to see
21245 several threads in the list.
21247 @item =thread-group-created,id="@var{id}"
21248 @itemx =thread-group-exited,id="@var{id}"
21249 A thread thread group either was attached to, or has exited/detached
21250 from. The @var{id} field contains the @value{GDBN} identifier of the
21253 @item =thread-created,id="@var{id}",group-id="@var{gid}"
21254 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
21255 A thread either was created, or has exited. The @var{id} field
21256 contains the @value{GDBN} identifier of the thread. The @var{gid}
21257 field identifies the thread group this thread belongs to.
21259 @item =thread-selected,id="@var{id}"
21260 Informs that the selected thread was changed as result of the last
21261 command. This notification is not emitted as result of @code{-thread-select}
21262 command but is emitted whenever an MI command that is not documented
21263 to change the selected thread actually changes it. In particular,
21264 invoking, directly or indirectly (via user-defined command), the CLI
21265 @code{thread} command, will generate this notification.
21267 We suggest that in response to this notification, front ends
21268 highlight the selected thread and cause subsequent commands to apply to
21271 @item =library-loaded,...
21272 Reports that a new library file was loaded by the program. This
21273 notification has 4 fields---@var{id}, @var{target-name},
21274 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
21275 opaque identifier of the library. For remote debugging case,
21276 @var{target-name} and @var{host-name} fields give the name of the
21277 library file on the target, and on the host respectively. For native
21278 debugging, both those fields have the same value. The
21279 @var{symbols-loaded} field reports if the debug symbols for this
21280 library are loaded.
21282 @item =library-unloaded,...
21283 Reports that a library was unloaded by the program. This notification
21284 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
21285 the same meaning as for the @code{=library-loaded} notification
21289 @node GDB/MI Frame Information
21290 @subsection @sc{gdb/mi} Frame Information
21292 Response from many MI commands includes an information about stack
21293 frame. This information is a tuple that may have the following
21298 The level of the stack frame. The innermost frame has the level of
21299 zero. This field is always present.
21302 The name of the function corresponding to the frame. This field may
21303 be absent if @value{GDBN} is unable to determine the function name.
21306 The code address for the frame. This field is always present.
21309 The name of the source files that correspond to the frame's code
21310 address. This field may be absent.
21313 The source line corresponding to the frames' code address. This field
21317 The name of the binary file (either executable or shared library) the
21318 corresponds to the frame's code address. This field may be absent.
21323 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21324 @node GDB/MI Simple Examples
21325 @section Simple Examples of @sc{gdb/mi} Interaction
21326 @cindex @sc{gdb/mi}, simple examples
21328 This subsection presents several simple examples of interaction using
21329 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
21330 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
21331 the output received from @sc{gdb/mi}.
21333 Note the line breaks shown in the examples are here only for
21334 readability, they don't appear in the real output.
21336 @subheading Setting a Breakpoint
21338 Setting a breakpoint generates synchronous output which contains detailed
21339 information of the breakpoint.
21342 -> -break-insert main
21343 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
21344 enabled="y",addr="0x08048564",func="main",file="myprog.c",
21345 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
21349 @subheading Program Execution
21351 Program execution generates asynchronous records and MI gives the
21352 reason that execution stopped.
21358 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
21359 frame=@{addr="0x08048564",func="main",
21360 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
21361 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
21366 <- *stopped,reason="exited-normally"
21370 @subheading Quitting @value{GDBN}
21372 Quitting @value{GDBN} just prints the result class @samp{^exit}.
21380 @subheading A Bad Command
21382 Here's what happens if you pass a non-existent command:
21386 <- ^error,msg="Undefined MI command: rubbish"
21391 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21392 @node GDB/MI Command Description Format
21393 @section @sc{gdb/mi} Command Description Format
21395 The remaining sections describe blocks of commands. Each block of
21396 commands is laid out in a fashion similar to this section.
21398 @subheading Motivation
21400 The motivation for this collection of commands.
21402 @subheading Introduction
21404 A brief introduction to this collection of commands as a whole.
21406 @subheading Commands
21408 For each command in the block, the following is described:
21410 @subsubheading Synopsis
21413 -command @var{args}@dots{}
21416 @subsubheading Result
21418 @subsubheading @value{GDBN} Command
21420 The corresponding @value{GDBN} CLI command(s), if any.
21422 @subsubheading Example
21424 Example(s) formatted for readability. Some of the described commands have
21425 not been implemented yet and these are labeled N.A.@: (not available).
21428 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21429 @node GDB/MI Breakpoint Commands
21430 @section @sc{gdb/mi} Breakpoint Commands
21432 @cindex breakpoint commands for @sc{gdb/mi}
21433 @cindex @sc{gdb/mi}, breakpoint commands
21434 This section documents @sc{gdb/mi} commands for manipulating
21437 @subheading The @code{-break-after} Command
21438 @findex -break-after
21440 @subsubheading Synopsis
21443 -break-after @var{number} @var{count}
21446 The breakpoint number @var{number} is not in effect until it has been
21447 hit @var{count} times. To see how this is reflected in the output of
21448 the @samp{-break-list} command, see the description of the
21449 @samp{-break-list} command below.
21451 @subsubheading @value{GDBN} Command
21453 The corresponding @value{GDBN} command is @samp{ignore}.
21455 @subsubheading Example
21460 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
21461 enabled="y",addr="0x000100d0",func="main",file="hello.c",
21462 fullname="/home/foo/hello.c",line="5",times="0"@}
21469 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
21470 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
21471 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
21472 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
21473 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
21474 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
21475 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
21476 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
21477 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
21478 line="5",times="0",ignore="3"@}]@}
21483 @subheading The @code{-break-catch} Command
21484 @findex -break-catch
21486 @subheading The @code{-break-commands} Command
21487 @findex -break-commands
21491 @subheading The @code{-break-condition} Command
21492 @findex -break-condition
21494 @subsubheading Synopsis
21497 -break-condition @var{number} @var{expr}
21500 Breakpoint @var{number} will stop the program only if the condition in
21501 @var{expr} is true. The condition becomes part of the
21502 @samp{-break-list} output (see the description of the @samp{-break-list}
21505 @subsubheading @value{GDBN} Command
21507 The corresponding @value{GDBN} command is @samp{condition}.
21509 @subsubheading Example
21513 -break-condition 1 1
21517 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
21518 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
21519 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
21520 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
21521 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
21522 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
21523 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
21524 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
21525 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
21526 line="5",cond="1",times="0",ignore="3"@}]@}
21530 @subheading The @code{-break-delete} Command
21531 @findex -break-delete
21533 @subsubheading Synopsis
21536 -break-delete ( @var{breakpoint} )+
21539 Delete the breakpoint(s) whose number(s) are specified in the argument
21540 list. This is obviously reflected in the breakpoint list.
21542 @subsubheading @value{GDBN} Command
21544 The corresponding @value{GDBN} command is @samp{delete}.
21546 @subsubheading Example
21554 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
21555 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
21556 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
21557 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
21558 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
21559 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
21560 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
21565 @subheading The @code{-break-disable} Command
21566 @findex -break-disable
21568 @subsubheading Synopsis
21571 -break-disable ( @var{breakpoint} )+
21574 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
21575 break list is now set to @samp{n} for the named @var{breakpoint}(s).
21577 @subsubheading @value{GDBN} Command
21579 The corresponding @value{GDBN} command is @samp{disable}.
21581 @subsubheading Example
21589 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
21590 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
21591 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
21592 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
21593 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
21594 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
21595 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
21596 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
21597 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
21598 line="5",times="0"@}]@}
21602 @subheading The @code{-break-enable} Command
21603 @findex -break-enable
21605 @subsubheading Synopsis
21608 -break-enable ( @var{breakpoint} )+
21611 Enable (previously disabled) @var{breakpoint}(s).
21613 @subsubheading @value{GDBN} Command
21615 The corresponding @value{GDBN} command is @samp{enable}.
21617 @subsubheading Example
21625 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
21626 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
21627 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
21628 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
21629 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
21630 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
21631 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
21632 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
21633 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
21634 line="5",times="0"@}]@}
21638 @subheading The @code{-break-info} Command
21639 @findex -break-info
21641 @subsubheading Synopsis
21644 -break-info @var{breakpoint}
21648 Get information about a single breakpoint.
21650 @subsubheading @value{GDBN} Command
21652 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
21654 @subsubheading Example
21657 @subheading The @code{-break-insert} Command
21658 @findex -break-insert
21660 @subsubheading Synopsis
21663 -break-insert [ -t ] [ -h ] [ -f ] [ -d ]
21664 [ -c @var{condition} ] [ -i @var{ignore-count} ]
21665 [ -p @var{thread} ] [ @var{location} ]
21669 If specified, @var{location}, can be one of:
21676 @item filename:linenum
21677 @item filename:function
21681 The possible optional parameters of this command are:
21685 Insert a temporary breakpoint.
21687 Insert a hardware breakpoint.
21688 @item -c @var{condition}
21689 Make the breakpoint conditional on @var{condition}.
21690 @item -i @var{ignore-count}
21691 Initialize the @var{ignore-count}.
21693 If @var{location} cannot be parsed (for example if it
21694 refers to unknown files or functions), create a pending
21695 breakpoint. Without this flag, @value{GDBN} will report
21696 an error, and won't create a breakpoint, if @var{location}
21699 Create a disabled breakpoint.
21702 @subsubheading Result
21704 The result is in the form:
21707 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
21708 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
21709 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
21710 times="@var{times}"@}
21714 where @var{number} is the @value{GDBN} number for this breakpoint,
21715 @var{funcname} is the name of the function where the breakpoint was
21716 inserted, @var{filename} is the name of the source file which contains
21717 this function, @var{lineno} is the source line number within that file
21718 and @var{times} the number of times that the breakpoint has been hit
21719 (always 0 for -break-insert but may be greater for -break-info or -break-list
21720 which use the same output).
21722 Note: this format is open to change.
21723 @c An out-of-band breakpoint instead of part of the result?
21725 @subsubheading @value{GDBN} Command
21727 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
21728 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
21730 @subsubheading Example
21735 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
21736 fullname="/home/foo/recursive2.c,line="4",times="0"@}
21738 -break-insert -t foo
21739 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
21740 fullname="/home/foo/recursive2.c,line="11",times="0"@}
21743 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
21744 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
21745 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
21746 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
21747 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
21748 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
21749 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
21750 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
21751 addr="0x0001072c", func="main",file="recursive2.c",
21752 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
21753 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
21754 addr="0x00010774",func="foo",file="recursive2.c",
21755 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
21757 -break-insert -r foo.*
21758 ~int foo(int, int);
21759 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
21760 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
21764 @subheading The @code{-break-list} Command
21765 @findex -break-list
21767 @subsubheading Synopsis
21773 Displays the list of inserted breakpoints, showing the following fields:
21777 number of the breakpoint
21779 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
21781 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
21784 is the breakpoint enabled or no: @samp{y} or @samp{n}
21786 memory location at which the breakpoint is set
21788 logical location of the breakpoint, expressed by function name, file
21791 number of times the breakpoint has been hit
21794 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
21795 @code{body} field is an empty list.
21797 @subsubheading @value{GDBN} Command
21799 The corresponding @value{GDBN} command is @samp{info break}.
21801 @subsubheading Example
21806 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
21807 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
21808 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
21809 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
21810 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
21811 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
21812 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
21813 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
21814 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
21815 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
21816 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
21817 line="13",times="0"@}]@}
21821 Here's an example of the result when there are no breakpoints:
21826 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
21827 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
21828 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
21829 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
21830 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
21831 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
21832 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
21837 @subheading The @code{-break-watch} Command
21838 @findex -break-watch
21840 @subsubheading Synopsis
21843 -break-watch [ -a | -r ]
21846 Create a watchpoint. With the @samp{-a} option it will create an
21847 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
21848 read from or on a write to the memory location. With the @samp{-r}
21849 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
21850 trigger only when the memory location is accessed for reading. Without
21851 either of the options, the watchpoint created is a regular watchpoint,
21852 i.e., it will trigger when the memory location is accessed for writing.
21853 @xref{Set Watchpoints, , Setting Watchpoints}.
21855 Note that @samp{-break-list} will report a single list of watchpoints and
21856 breakpoints inserted.
21858 @subsubheading @value{GDBN} Command
21860 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
21863 @subsubheading Example
21865 Setting a watchpoint on a variable in the @code{main} function:
21870 ^done,wpt=@{number="2",exp="x"@}
21875 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
21876 value=@{old="-268439212",new="55"@},
21877 frame=@{func="main",args=[],file="recursive2.c",
21878 fullname="/home/foo/bar/recursive2.c",line="5"@}
21882 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
21883 the program execution twice: first for the variable changing value, then
21884 for the watchpoint going out of scope.
21889 ^done,wpt=@{number="5",exp="C"@}
21894 *stopped,reason="watchpoint-trigger",
21895 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
21896 frame=@{func="callee4",args=[],
21897 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21898 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
21903 *stopped,reason="watchpoint-scope",wpnum="5",
21904 frame=@{func="callee3",args=[@{name="strarg",
21905 value="0x11940 \"A string argument.\""@}],
21906 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21907 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
21911 Listing breakpoints and watchpoints, at different points in the program
21912 execution. Note that once the watchpoint goes out of scope, it is
21918 ^done,wpt=@{number="2",exp="C"@}
21921 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
21922 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
21923 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
21924 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
21925 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
21926 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
21927 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
21928 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
21929 addr="0x00010734",func="callee4",
21930 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21931 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
21932 bkpt=@{number="2",type="watchpoint",disp="keep",
21933 enabled="y",addr="",what="C",times="0"@}]@}
21938 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
21939 value=@{old="-276895068",new="3"@},
21940 frame=@{func="callee4",args=[],
21941 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21942 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
21945 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
21946 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
21947 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
21948 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
21949 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
21950 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
21951 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
21952 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
21953 addr="0x00010734",func="callee4",
21954 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21955 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
21956 bkpt=@{number="2",type="watchpoint",disp="keep",
21957 enabled="y",addr="",what="C",times="-5"@}]@}
21961 ^done,reason="watchpoint-scope",wpnum="2",
21962 frame=@{func="callee3",args=[@{name="strarg",
21963 value="0x11940 \"A string argument.\""@}],
21964 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21965 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
21968 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
21969 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
21970 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
21971 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
21972 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
21973 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
21974 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
21975 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
21976 addr="0x00010734",func="callee4",
21977 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
21978 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
21983 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21984 @node GDB/MI Program Context
21985 @section @sc{gdb/mi} Program Context
21987 @subheading The @code{-exec-arguments} Command
21988 @findex -exec-arguments
21991 @subsubheading Synopsis
21994 -exec-arguments @var{args}
21997 Set the inferior program arguments, to be used in the next
22000 @subsubheading @value{GDBN} Command
22002 The corresponding @value{GDBN} command is @samp{set args}.
22004 @subsubheading Example
22008 -exec-arguments -v word
22015 @subheading The @code{-exec-show-arguments} Command
22016 @findex -exec-show-arguments
22018 @subsubheading Synopsis
22021 -exec-show-arguments
22024 Print the arguments of the program.
22026 @subsubheading @value{GDBN} Command
22028 The corresponding @value{GDBN} command is @samp{show args}.
22030 @subsubheading Example
22035 @subheading The @code{-environment-cd} Command
22036 @findex -environment-cd
22038 @subsubheading Synopsis
22041 -environment-cd @var{pathdir}
22044 Set @value{GDBN}'s working directory.
22046 @subsubheading @value{GDBN} Command
22048 The corresponding @value{GDBN} command is @samp{cd}.
22050 @subsubheading Example
22054 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
22060 @subheading The @code{-environment-directory} Command
22061 @findex -environment-directory
22063 @subsubheading Synopsis
22066 -environment-directory [ -r ] [ @var{pathdir} ]+
22069 Add directories @var{pathdir} to beginning of search path for source files.
22070 If the @samp{-r} option is used, the search path is reset to the default
22071 search path. If directories @var{pathdir} are supplied in addition to the
22072 @samp{-r} option, the search path is first reset and then addition
22074 Multiple directories may be specified, separated by blanks. Specifying
22075 multiple directories in a single command
22076 results in the directories added to the beginning of the
22077 search path in the same order they were presented in the command.
22078 If blanks are needed as
22079 part of a directory name, double-quotes should be used around
22080 the name. In the command output, the path will show up separated
22081 by the system directory-separator character. The directory-separator
22082 character must not be used
22083 in any directory name.
22084 If no directories are specified, the current search path is displayed.
22086 @subsubheading @value{GDBN} Command
22088 The corresponding @value{GDBN} command is @samp{dir}.
22090 @subsubheading Example
22094 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
22095 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
22097 -environment-directory ""
22098 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
22100 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
22101 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
22103 -environment-directory -r
22104 ^done,source-path="$cdir:$cwd"
22109 @subheading The @code{-environment-path} Command
22110 @findex -environment-path
22112 @subsubheading Synopsis
22115 -environment-path [ -r ] [ @var{pathdir} ]+
22118 Add directories @var{pathdir} to beginning of search path for object files.
22119 If the @samp{-r} option is used, the search path is reset to the original
22120 search path that existed at gdb start-up. If directories @var{pathdir} are
22121 supplied in addition to the
22122 @samp{-r} option, the search path is first reset and then addition
22124 Multiple directories may be specified, separated by blanks. Specifying
22125 multiple directories in a single command
22126 results in the directories added to the beginning of the
22127 search path in the same order they were presented in the command.
22128 If blanks are needed as
22129 part of a directory name, double-quotes should be used around
22130 the name. In the command output, the path will show up separated
22131 by the system directory-separator character. The directory-separator
22132 character must not be used
22133 in any directory name.
22134 If no directories are specified, the current path is displayed.
22137 @subsubheading @value{GDBN} Command
22139 The corresponding @value{GDBN} command is @samp{path}.
22141 @subsubheading Example
22146 ^done,path="/usr/bin"
22148 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
22149 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
22151 -environment-path -r /usr/local/bin
22152 ^done,path="/usr/local/bin:/usr/bin"
22157 @subheading The @code{-environment-pwd} Command
22158 @findex -environment-pwd
22160 @subsubheading Synopsis
22166 Show the current working directory.
22168 @subsubheading @value{GDBN} Command
22170 The corresponding @value{GDBN} command is @samp{pwd}.
22172 @subsubheading Example
22177 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
22181 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22182 @node GDB/MI Thread Commands
22183 @section @sc{gdb/mi} Thread Commands
22186 @subheading The @code{-thread-info} Command
22187 @findex -thread-info
22189 @subsubheading Synopsis
22192 -thread-info [ @var{thread-id} ]
22195 Reports information about either a specific thread, if
22196 the @var{thread-id} parameter is present, or about all
22197 threads. When printing information about all threads,
22198 also reports the current thread.
22200 @subsubheading @value{GDBN} Command
22202 The @samp{info thread} command prints the same information
22205 @subsubheading Example
22210 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
22211 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
22212 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
22213 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
22214 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}],
22215 current-thread-id="1"
22219 The @samp{state} field may have the following values:
22223 The thread is stopped. Frame information is available for stopped
22227 The thread is running. There's no frame information for running
22232 @subheading The @code{-thread-list-ids} Command
22233 @findex -thread-list-ids
22235 @subsubheading Synopsis
22241 Produces a list of the currently known @value{GDBN} thread ids. At the
22242 end of the list it also prints the total number of such threads.
22244 This command is retained for historical reasons, the
22245 @code{-thread-info} command should be used instead.
22247 @subsubheading @value{GDBN} Command
22249 Part of @samp{info threads} supplies the same information.
22251 @subsubheading Example
22256 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
22257 current-thread-id="1",number-of-threads="3"
22262 @subheading The @code{-thread-select} Command
22263 @findex -thread-select
22265 @subsubheading Synopsis
22268 -thread-select @var{threadnum}
22271 Make @var{threadnum} the current thread. It prints the number of the new
22272 current thread, and the topmost frame for that thread.
22274 This command is deprecated in favor of explicitly using the
22275 @samp{--thread} option to each command.
22277 @subsubheading @value{GDBN} Command
22279 The corresponding @value{GDBN} command is @samp{thread}.
22281 @subsubheading Example
22288 *stopped,reason="end-stepping-range",thread-id="2",line="187",
22289 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
22293 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
22294 number-of-threads="3"
22297 ^done,new-thread-id="3",
22298 frame=@{level="0",func="vprintf",
22299 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
22300 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
22304 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22305 @node GDB/MI Program Execution
22306 @section @sc{gdb/mi} Program Execution
22308 These are the asynchronous commands which generate the out-of-band
22309 record @samp{*stopped}. Currently @value{GDBN} only really executes
22310 asynchronously with remote targets and this interaction is mimicked in
22313 @subheading The @code{-exec-continue} Command
22314 @findex -exec-continue
22316 @subsubheading Synopsis
22319 -exec-continue [--all|--thread-group N]
22322 Resumes the execution of the inferior program until a breakpoint is
22323 encountered, or until the inferior exits. In all-stop mode
22324 (@pxref{All-Stop Mode}), may resume only one thread, or all threads,
22325 depending on the value of the @samp{scheduler-locking} variable. In
22326 non-stop mode (@pxref{Non-Stop Mode}), if the @samp{--all} is not
22327 specified, only the thread specified with the @samp{--thread} option
22328 (or current thread, if no @samp{--thread} is provided) is resumed. If
22329 @samp{--all} is specified, all threads will be resumed. The
22330 @samp{--all} option is ignored in all-stop mode. If the
22331 @samp{--thread-group} options is specified, then all threads in that
22332 thread group are resumed.
22334 @subsubheading @value{GDBN} Command
22336 The corresponding @value{GDBN} corresponding is @samp{continue}.
22338 @subsubheading Example
22345 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
22346 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
22352 @subheading The @code{-exec-finish} Command
22353 @findex -exec-finish
22355 @subsubheading Synopsis
22361 Resumes the execution of the inferior program until the current
22362 function is exited. Displays the results returned by the function.
22364 @subsubheading @value{GDBN} Command
22366 The corresponding @value{GDBN} command is @samp{finish}.
22368 @subsubheading Example
22370 Function returning @code{void}.
22377 *stopped,reason="function-finished",frame=@{func="main",args=[],
22378 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
22382 Function returning other than @code{void}. The name of the internal
22383 @value{GDBN} variable storing the result is printed, together with the
22390 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
22391 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
22392 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
22393 gdb-result-var="$1",return-value="0"
22398 @subheading The @code{-exec-interrupt} Command
22399 @findex -exec-interrupt
22401 @subsubheading Synopsis
22404 -exec-interrupt [--all|--thread-group N]
22407 Interrupts the background execution of the target. Note how the token
22408 associated with the stop message is the one for the execution command
22409 that has been interrupted. The token for the interrupt itself only
22410 appears in the @samp{^done} output. If the user is trying to
22411 interrupt a non-running program, an error message will be printed.
22413 Note that when asynchronous execution is enabled, this command is
22414 asynchronous just like other execution commands. That is, first the
22415 @samp{^done} response will be printed, and the target stop will be
22416 reported after that using the @samp{*stopped} notification.
22418 In non-stop mode, only the context thread is interrupted by default.
22419 All threads will be interrupted if the @samp{--all} option is
22420 specified. If the @samp{--thread-group} option is specified, all
22421 threads in that group will be interrupted.
22423 @subsubheading @value{GDBN} Command
22425 The corresponding @value{GDBN} command is @samp{interrupt}.
22427 @subsubheading Example
22438 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
22439 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
22440 fullname="/home/foo/bar/try.c",line="13"@}
22445 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
22449 @subheading The @code{-exec-jump} Command
22452 @subsubheading Synopsis
22455 -exec-jump @var{location}
22458 Resumes execution of the inferior program at the location specified by
22459 parameter. @xref{Specify Location}, for a description of the
22460 different forms of @var{location}.
22462 @subsubheading @value{GDBN} Command
22464 The corresponding @value{GDBN} command is @samp{jump}.
22466 @subsubheading Example
22469 -exec-jump foo.c:10
22470 *running,thread-id="all"
22475 @subheading The @code{-exec-next} Command
22478 @subsubheading Synopsis
22484 Resumes execution of the inferior program, stopping when the beginning
22485 of the next source line is reached.
22487 @subsubheading @value{GDBN} Command
22489 The corresponding @value{GDBN} command is @samp{next}.
22491 @subsubheading Example
22497 *stopped,reason="end-stepping-range",line="8",file="hello.c"
22502 @subheading The @code{-exec-next-instruction} Command
22503 @findex -exec-next-instruction
22505 @subsubheading Synopsis
22508 -exec-next-instruction
22511 Executes one machine instruction. If the instruction is a function
22512 call, continues until the function returns. If the program stops at an
22513 instruction in the middle of a source line, the address will be
22516 @subsubheading @value{GDBN} Command
22518 The corresponding @value{GDBN} command is @samp{nexti}.
22520 @subsubheading Example
22524 -exec-next-instruction
22528 *stopped,reason="end-stepping-range",
22529 addr="0x000100d4",line="5",file="hello.c"
22534 @subheading The @code{-exec-return} Command
22535 @findex -exec-return
22537 @subsubheading Synopsis
22543 Makes current function return immediately. Doesn't execute the inferior.
22544 Displays the new current frame.
22546 @subsubheading @value{GDBN} Command
22548 The corresponding @value{GDBN} command is @samp{return}.
22550 @subsubheading Example
22554 200-break-insert callee4
22555 200^done,bkpt=@{number="1",addr="0x00010734",
22556 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
22561 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
22562 frame=@{func="callee4",args=[],
22563 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22564 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
22570 111^done,frame=@{level="0",func="callee3",
22571 args=[@{name="strarg",
22572 value="0x11940 \"A string argument.\""@}],
22573 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22574 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
22579 @subheading The @code{-exec-run} Command
22582 @subsubheading Synopsis
22588 Starts execution of the inferior from the beginning. The inferior
22589 executes until either a breakpoint is encountered or the program
22590 exits. In the latter case the output will include an exit code, if
22591 the program has exited exceptionally.
22593 @subsubheading @value{GDBN} Command
22595 The corresponding @value{GDBN} command is @samp{run}.
22597 @subsubheading Examples
22602 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
22607 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
22608 frame=@{func="main",args=[],file="recursive2.c",
22609 fullname="/home/foo/bar/recursive2.c",line="4"@}
22614 Program exited normally:
22622 *stopped,reason="exited-normally"
22627 Program exited exceptionally:
22635 *stopped,reason="exited",exit-code="01"
22639 Another way the program can terminate is if it receives a signal such as
22640 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
22644 *stopped,reason="exited-signalled",signal-name="SIGINT",
22645 signal-meaning="Interrupt"
22649 @c @subheading -exec-signal
22652 @subheading The @code{-exec-step} Command
22655 @subsubheading Synopsis
22661 Resumes execution of the inferior program, stopping when the beginning
22662 of the next source line is reached, if the next source line is not a
22663 function call. If it is, stop at the first instruction of the called
22666 @subsubheading @value{GDBN} Command
22668 The corresponding @value{GDBN} command is @samp{step}.
22670 @subsubheading Example
22672 Stepping into a function:
22678 *stopped,reason="end-stepping-range",
22679 frame=@{func="foo",args=[@{name="a",value="10"@},
22680 @{name="b",value="0"@}],file="recursive2.c",
22681 fullname="/home/foo/bar/recursive2.c",line="11"@}
22691 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
22696 @subheading The @code{-exec-step-instruction} Command
22697 @findex -exec-step-instruction
22699 @subsubheading Synopsis
22702 -exec-step-instruction
22705 Resumes the inferior which executes one machine instruction. The
22706 output, once @value{GDBN} has stopped, will vary depending on whether
22707 we have stopped in the middle of a source line or not. In the former
22708 case, the address at which the program stopped will be printed as
22711 @subsubheading @value{GDBN} Command
22713 The corresponding @value{GDBN} command is @samp{stepi}.
22715 @subsubheading Example
22719 -exec-step-instruction
22723 *stopped,reason="end-stepping-range",
22724 frame=@{func="foo",args=[],file="try.c",
22725 fullname="/home/foo/bar/try.c",line="10"@}
22727 -exec-step-instruction
22731 *stopped,reason="end-stepping-range",
22732 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
22733 fullname="/home/foo/bar/try.c",line="10"@}
22738 @subheading The @code{-exec-until} Command
22739 @findex -exec-until
22741 @subsubheading Synopsis
22744 -exec-until [ @var{location} ]
22747 Executes the inferior until the @var{location} specified in the
22748 argument is reached. If there is no argument, the inferior executes
22749 until a source line greater than the current one is reached. The
22750 reason for stopping in this case will be @samp{location-reached}.
22752 @subsubheading @value{GDBN} Command
22754 The corresponding @value{GDBN} command is @samp{until}.
22756 @subsubheading Example
22760 -exec-until recursive2.c:6
22764 *stopped,reason="location-reached",frame=@{func="main",args=[],
22765 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
22770 @subheading -file-clear
22771 Is this going away????
22774 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22775 @node GDB/MI Stack Manipulation
22776 @section @sc{gdb/mi} Stack Manipulation Commands
22779 @subheading The @code{-stack-info-frame} Command
22780 @findex -stack-info-frame
22782 @subsubheading Synopsis
22788 Get info on the selected frame.
22790 @subsubheading @value{GDBN} Command
22792 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
22793 (without arguments).
22795 @subsubheading Example
22800 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
22801 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22802 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
22806 @subheading The @code{-stack-info-depth} Command
22807 @findex -stack-info-depth
22809 @subsubheading Synopsis
22812 -stack-info-depth [ @var{max-depth} ]
22815 Return the depth of the stack. If the integer argument @var{max-depth}
22816 is specified, do not count beyond @var{max-depth} frames.
22818 @subsubheading @value{GDBN} Command
22820 There's no equivalent @value{GDBN} command.
22822 @subsubheading Example
22824 For a stack with frame levels 0 through 11:
22831 -stack-info-depth 4
22834 -stack-info-depth 12
22837 -stack-info-depth 11
22840 -stack-info-depth 13
22845 @subheading The @code{-stack-list-arguments} Command
22846 @findex -stack-list-arguments
22848 @subsubheading Synopsis
22851 -stack-list-arguments @var{show-values}
22852 [ @var{low-frame} @var{high-frame} ]
22855 Display a list of the arguments for the frames between @var{low-frame}
22856 and @var{high-frame} (inclusive). If @var{low-frame} and
22857 @var{high-frame} are not provided, list the arguments for the whole
22858 call stack. If the two arguments are equal, show the single frame
22859 at the corresponding level. It is an error if @var{low-frame} is
22860 larger than the actual number of frames. On the other hand,
22861 @var{high-frame} may be larger than the actual number of frames, in
22862 which case only existing frames will be returned.
22864 The @var{show-values} argument must have a value of 0 or 1. A value of
22865 0 means that only the names of the arguments are listed, a value of 1
22866 means that both names and values of the arguments are printed.
22868 @subsubheading @value{GDBN} Command
22870 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
22871 @samp{gdb_get_args} command which partially overlaps with the
22872 functionality of @samp{-stack-list-arguments}.
22874 @subsubheading Example
22881 frame=@{level="0",addr="0x00010734",func="callee4",
22882 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22883 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
22884 frame=@{level="1",addr="0x0001076c",func="callee3",
22885 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22886 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
22887 frame=@{level="2",addr="0x0001078c",func="callee2",
22888 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22889 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
22890 frame=@{level="3",addr="0x000107b4",func="callee1",
22891 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22892 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
22893 frame=@{level="4",addr="0x000107e0",func="main",
22894 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
22895 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
22897 -stack-list-arguments 0
22900 frame=@{level="0",args=[]@},
22901 frame=@{level="1",args=[name="strarg"]@},
22902 frame=@{level="2",args=[name="intarg",name="strarg"]@},
22903 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
22904 frame=@{level="4",args=[]@}]
22906 -stack-list-arguments 1
22909 frame=@{level="0",args=[]@},
22911 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
22912 frame=@{level="2",args=[
22913 @{name="intarg",value="2"@},
22914 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
22915 @{frame=@{level="3",args=[
22916 @{name="intarg",value="2"@},
22917 @{name="strarg",value="0x11940 \"A string argument.\""@},
22918 @{name="fltarg",value="3.5"@}]@},
22919 frame=@{level="4",args=[]@}]
22921 -stack-list-arguments 0 2 2
22922 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
22924 -stack-list-arguments 1 2 2
22925 ^done,stack-args=[frame=@{level="2",
22926 args=[@{name="intarg",value="2"@},
22927 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
22931 @c @subheading -stack-list-exception-handlers
22934 @subheading The @code{-stack-list-frames} Command
22935 @findex -stack-list-frames
22937 @subsubheading Synopsis
22940 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
22943 List the frames currently on the stack. For each frame it displays the
22948 The frame number, 0 being the topmost frame, i.e., the innermost function.
22950 The @code{$pc} value for that frame.
22954 File name of the source file where the function lives.
22956 Line number corresponding to the @code{$pc}.
22959 If invoked without arguments, this command prints a backtrace for the
22960 whole stack. If given two integer arguments, it shows the frames whose
22961 levels are between the two arguments (inclusive). If the two arguments
22962 are equal, it shows the single frame at the corresponding level. It is
22963 an error if @var{low-frame} is larger than the actual number of
22964 frames. On the other hand, @var{high-frame} may be larger than the
22965 actual number of frames, in which case only existing frames will be returned.
22967 @subsubheading @value{GDBN} Command
22969 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
22971 @subsubheading Example
22973 Full stack backtrace:
22979 [frame=@{level="0",addr="0x0001076c",func="foo",
22980 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
22981 frame=@{level="1",addr="0x000107a4",func="foo",
22982 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
22983 frame=@{level="2",addr="0x000107a4",func="foo",
22984 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
22985 frame=@{level="3",addr="0x000107a4",func="foo",
22986 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
22987 frame=@{level="4",addr="0x000107a4",func="foo",
22988 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
22989 frame=@{level="5",addr="0x000107a4",func="foo",
22990 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
22991 frame=@{level="6",addr="0x000107a4",func="foo",
22992 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
22993 frame=@{level="7",addr="0x000107a4",func="foo",
22994 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
22995 frame=@{level="8",addr="0x000107a4",func="foo",
22996 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
22997 frame=@{level="9",addr="0x000107a4",func="foo",
22998 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
22999 frame=@{level="10",addr="0x000107a4",func="foo",
23000 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23001 frame=@{level="11",addr="0x00010738",func="main",
23002 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
23006 Show frames between @var{low_frame} and @var{high_frame}:
23010 -stack-list-frames 3 5
23012 [frame=@{level="3",addr="0x000107a4",func="foo",
23013 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23014 frame=@{level="4",addr="0x000107a4",func="foo",
23015 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23016 frame=@{level="5",addr="0x000107a4",func="foo",
23017 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
23021 Show a single frame:
23025 -stack-list-frames 3 3
23027 [frame=@{level="3",addr="0x000107a4",func="foo",
23028 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
23033 @subheading The @code{-stack-list-locals} Command
23034 @findex -stack-list-locals
23036 @subsubheading Synopsis
23039 -stack-list-locals @var{print-values}
23042 Display the local variable names for the selected frame. If
23043 @var{print-values} is 0 or @code{--no-values}, print only the names of
23044 the variables; if it is 1 or @code{--all-values}, print also their
23045 values; and if it is 2 or @code{--simple-values}, print the name,
23046 type and value for simple data types and the name and type for arrays,
23047 structures and unions. In this last case, a frontend can immediately
23048 display the value of simple data types and create variable objects for
23049 other data types when the user wishes to explore their values in
23052 @subsubheading @value{GDBN} Command
23054 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
23056 @subsubheading Example
23060 -stack-list-locals 0
23061 ^done,locals=[name="A",name="B",name="C"]
23063 -stack-list-locals --all-values
23064 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
23065 @{name="C",value="@{1, 2, 3@}"@}]
23066 -stack-list-locals --simple-values
23067 ^done,locals=[@{name="A",type="int",value="1"@},
23068 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
23073 @subheading The @code{-stack-select-frame} Command
23074 @findex -stack-select-frame
23076 @subsubheading Synopsis
23079 -stack-select-frame @var{framenum}
23082 Change the selected frame. Select a different frame @var{framenum} on
23085 This command in deprecated in favor of passing the @samp{--frame}
23086 option to every command.
23088 @subsubheading @value{GDBN} Command
23090 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
23091 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
23093 @subsubheading Example
23097 -stack-select-frame 2
23102 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23103 @node GDB/MI Variable Objects
23104 @section @sc{gdb/mi} Variable Objects
23108 @subheading Motivation for Variable Objects in @sc{gdb/mi}
23110 For the implementation of a variable debugger window (locals, watched
23111 expressions, etc.), we are proposing the adaptation of the existing code
23112 used by @code{Insight}.
23114 The two main reasons for that are:
23118 It has been proven in practice (it is already on its second generation).
23121 It will shorten development time (needless to say how important it is
23125 The original interface was designed to be used by Tcl code, so it was
23126 slightly changed so it could be used through @sc{gdb/mi}. This section
23127 describes the @sc{gdb/mi} operations that will be available and gives some
23128 hints about their use.
23130 @emph{Note}: In addition to the set of operations described here, we
23131 expect the @sc{gui} implementation of a variable window to require, at
23132 least, the following operations:
23135 @item @code{-gdb-show} @code{output-radix}
23136 @item @code{-stack-list-arguments}
23137 @item @code{-stack-list-locals}
23138 @item @code{-stack-select-frame}
23143 @subheading Introduction to Variable Objects
23145 @cindex variable objects in @sc{gdb/mi}
23147 Variable objects are "object-oriented" MI interface for examining and
23148 changing values of expressions. Unlike some other MI interfaces that
23149 work with expressions, variable objects are specifically designed for
23150 simple and efficient presentation in the frontend. A variable object
23151 is identified by string name. When a variable object is created, the
23152 frontend specifies the expression for that variable object. The
23153 expression can be a simple variable, or it can be an arbitrary complex
23154 expression, and can even involve CPU registers. After creating a
23155 variable object, the frontend can invoke other variable object
23156 operations---for example to obtain or change the value of a variable
23157 object, or to change display format.
23159 Variable objects have hierarchical tree structure. Any variable object
23160 that corresponds to a composite type, such as structure in C, has
23161 a number of child variable objects, for example corresponding to each
23162 element of a structure. A child variable object can itself have
23163 children, recursively. Recursion ends when we reach
23164 leaf variable objects, which always have built-in types. Child variable
23165 objects are created only by explicit request, so if a frontend
23166 is not interested in the children of a particular variable object, no
23167 child will be created.
23169 For a leaf variable object it is possible to obtain its value as a
23170 string, or set the value from a string. String value can be also
23171 obtained for a non-leaf variable object, but it's generally a string
23172 that only indicates the type of the object, and does not list its
23173 contents. Assignment to a non-leaf variable object is not allowed.
23175 A frontend does not need to read the values of all variable objects each time
23176 the program stops. Instead, MI provides an update command that lists all
23177 variable objects whose values has changed since the last update
23178 operation. This considerably reduces the amount of data that must
23179 be transferred to the frontend. As noted above, children variable
23180 objects are created on demand, and only leaf variable objects have a
23181 real value. As result, gdb will read target memory only for leaf
23182 variables that frontend has created.
23184 The automatic update is not always desirable. For example, a frontend
23185 might want to keep a value of some expression for future reference,
23186 and never update it. For another example, fetching memory is
23187 relatively slow for embedded targets, so a frontend might want
23188 to disable automatic update for the variables that are either not
23189 visible on the screen, or ``closed''. This is possible using so
23190 called ``frozen variable objects''. Such variable objects are never
23191 implicitly updated.
23193 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
23194 fixed variable object, the expression is parsed when the variable
23195 object is created, including associating identifiers to specific
23196 variables. The meaning of expression never changes. For a floating
23197 variable object the values of variables whose names appear in the
23198 expressions are re-evaluated every time in the context of the current
23199 frame. Consider this example:
23204 struct work_state state;
23211 If a fixed variable object for the @code{state} variable is created in
23212 this function, and we enter the recursive call, the the variable
23213 object will report the value of @code{state} in the top-level
23214 @code{do_work} invocation. On the other hand, a floating variable
23215 object will report the value of @code{state} in the current frame.
23217 If an expression specified when creating a fixed variable object
23218 refers to a local variable, the variable object becomes bound to the
23219 thread and frame in which the variable object is created. When such
23220 variable object is updated, @value{GDBN} makes sure that the
23221 thread/frame combination the variable object is bound to still exists,
23222 and re-evaluates the variable object in context of that thread/frame.
23224 The following is the complete set of @sc{gdb/mi} operations defined to
23225 access this functionality:
23227 @multitable @columnfractions .4 .6
23228 @item @strong{Operation}
23229 @tab @strong{Description}
23231 @item @code{-var-create}
23232 @tab create a variable object
23233 @item @code{-var-delete}
23234 @tab delete the variable object and/or its children
23235 @item @code{-var-set-format}
23236 @tab set the display format of this variable
23237 @item @code{-var-show-format}
23238 @tab show the display format of this variable
23239 @item @code{-var-info-num-children}
23240 @tab tells how many children this object has
23241 @item @code{-var-list-children}
23242 @tab return a list of the object's children
23243 @item @code{-var-info-type}
23244 @tab show the type of this variable object
23245 @item @code{-var-info-expression}
23246 @tab print parent-relative expression that this variable object represents
23247 @item @code{-var-info-path-expression}
23248 @tab print full expression that this variable object represents
23249 @item @code{-var-show-attributes}
23250 @tab is this variable editable? does it exist here?
23251 @item @code{-var-evaluate-expression}
23252 @tab get the value of this variable
23253 @item @code{-var-assign}
23254 @tab set the value of this variable
23255 @item @code{-var-update}
23256 @tab update the variable and its children
23257 @item @code{-var-set-frozen}
23258 @tab set frozeness attribute
23261 In the next subsection we describe each operation in detail and suggest
23262 how it can be used.
23264 @subheading Description And Use of Operations on Variable Objects
23266 @subheading The @code{-var-create} Command
23267 @findex -var-create
23269 @subsubheading Synopsis
23272 -var-create @{@var{name} | "-"@}
23273 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
23276 This operation creates a variable object, which allows the monitoring of
23277 a variable, the result of an expression, a memory cell or a CPU
23280 The @var{name} parameter is the string by which the object can be
23281 referenced. It must be unique. If @samp{-} is specified, the varobj
23282 system will generate a string ``varNNNNNN'' automatically. It will be
23283 unique provided that one does not specify @var{name} of that format.
23284 The command fails if a duplicate name is found.
23286 The frame under which the expression should be evaluated can be
23287 specified by @var{frame-addr}. A @samp{*} indicates that the current
23288 frame should be used. A @samp{@@} indicates that a floating variable
23289 object must be created.
23291 @var{expression} is any expression valid on the current language set (must not
23292 begin with a @samp{*}), or one of the following:
23296 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
23299 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
23302 @samp{$@var{regname}} --- a CPU register name
23305 @subsubheading Result
23307 This operation returns the name, number of children and the type of the
23308 object created. Type is returned as a string as the ones generated by
23309 the @value{GDBN} CLI. If a fixed variable object is bound to a
23310 specific thread, the thread is is also printed:
23313 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}"
23317 @subheading The @code{-var-delete} Command
23318 @findex -var-delete
23320 @subsubheading Synopsis
23323 -var-delete [ -c ] @var{name}
23326 Deletes a previously created variable object and all of its children.
23327 With the @samp{-c} option, just deletes the children.
23329 Returns an error if the object @var{name} is not found.
23332 @subheading The @code{-var-set-format} Command
23333 @findex -var-set-format
23335 @subsubheading Synopsis
23338 -var-set-format @var{name} @var{format-spec}
23341 Sets the output format for the value of the object @var{name} to be
23344 @anchor{-var-set-format}
23345 The syntax for the @var{format-spec} is as follows:
23348 @var{format-spec} @expansion{}
23349 @{binary | decimal | hexadecimal | octal | natural@}
23352 The natural format is the default format choosen automatically
23353 based on the variable type (like decimal for an @code{int}, hex
23354 for pointers, etc.).
23356 For a variable with children, the format is set only on the
23357 variable itself, and the children are not affected.
23359 @subheading The @code{-var-show-format} Command
23360 @findex -var-show-format
23362 @subsubheading Synopsis
23365 -var-show-format @var{name}
23368 Returns the format used to display the value of the object @var{name}.
23371 @var{format} @expansion{}
23376 @subheading The @code{-var-info-num-children} Command
23377 @findex -var-info-num-children
23379 @subsubheading Synopsis
23382 -var-info-num-children @var{name}
23385 Returns the number of children of a variable object @var{name}:
23392 @subheading The @code{-var-list-children} Command
23393 @findex -var-list-children
23395 @subsubheading Synopsis
23398 -var-list-children [@var{print-values}] @var{name}
23400 @anchor{-var-list-children}
23402 Return a list of the children of the specified variable object and
23403 create variable objects for them, if they do not already exist. With
23404 a single argument or if @var{print-values} has a value for of 0 or
23405 @code{--no-values}, print only the names of the variables; if
23406 @var{print-values} is 1 or @code{--all-values}, also print their
23407 values; and if it is 2 or @code{--simple-values} print the name and
23408 value for simple data types and just the name for arrays, structures
23411 For each child the following results are returned:
23416 Name of the variable object created for this child.
23419 The expression to be shown to the user by the front end to designate this child.
23420 For example this may be the name of a structure member.
23422 For C/C@t{++} structures there are several pseudo children returned to
23423 designate access qualifiers. For these pseudo children @var{exp} is
23424 @samp{public}, @samp{private}, or @samp{protected}. In this case the
23425 type and value are not present.
23428 Number of children this child has.
23431 The type of the child.
23434 If values were requested, this is the value.
23437 If this variable object is associated with a thread, this is the thread id.
23438 Otherwise this result is not present.
23441 If the variable object is frozen, this variable will be present with a value of 1.
23444 @subsubheading Example
23448 -var-list-children n
23449 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
23450 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
23452 -var-list-children --all-values n
23453 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
23454 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
23458 @subheading The @code{-var-info-type} Command
23459 @findex -var-info-type
23461 @subsubheading Synopsis
23464 -var-info-type @var{name}
23467 Returns the type of the specified variable @var{name}. The type is
23468 returned as a string in the same format as it is output by the
23472 type=@var{typename}
23476 @subheading The @code{-var-info-expression} Command
23477 @findex -var-info-expression
23479 @subsubheading Synopsis
23482 -var-info-expression @var{name}
23485 Returns a string that is suitable for presenting this
23486 variable object in user interface. The string is generally
23487 not valid expression in the current language, and cannot be evaluated.
23489 For example, if @code{a} is an array, and variable object
23490 @code{A} was created for @code{a}, then we'll get this output:
23493 (gdb) -var-info-expression A.1
23494 ^done,lang="C",exp="1"
23498 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
23500 Note that the output of the @code{-var-list-children} command also
23501 includes those expressions, so the @code{-var-info-expression} command
23504 @subheading The @code{-var-info-path-expression} Command
23505 @findex -var-info-path-expression
23507 @subsubheading Synopsis
23510 -var-info-path-expression @var{name}
23513 Returns an expression that can be evaluated in the current
23514 context and will yield the same value that a variable object has.
23515 Compare this with the @code{-var-info-expression} command, which
23516 result can be used only for UI presentation. Typical use of
23517 the @code{-var-info-path-expression} command is creating a
23518 watchpoint from a variable object.
23520 For example, suppose @code{C} is a C@t{++} class, derived from class
23521 @code{Base}, and that the @code{Base} class has a member called
23522 @code{m_size}. Assume a variable @code{c} is has the type of
23523 @code{C} and a variable object @code{C} was created for variable
23524 @code{c}. Then, we'll get this output:
23526 (gdb) -var-info-path-expression C.Base.public.m_size
23527 ^done,path_expr=((Base)c).m_size)
23530 @subheading The @code{-var-show-attributes} Command
23531 @findex -var-show-attributes
23533 @subsubheading Synopsis
23536 -var-show-attributes @var{name}
23539 List attributes of the specified variable object @var{name}:
23542 status=@var{attr} [ ( ,@var{attr} )* ]
23546 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
23548 @subheading The @code{-var-evaluate-expression} Command
23549 @findex -var-evaluate-expression
23551 @subsubheading Synopsis
23554 -var-evaluate-expression [-f @var{format-spec}] @var{name}
23557 Evaluates the expression that is represented by the specified variable
23558 object and returns its value as a string. The format of the string
23559 can be specified with the @samp{-f} option. The possible values of
23560 this option are the same as for @code{-var-set-format}
23561 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
23562 the current display format will be used. The current display format
23563 can be changed using the @code{-var-set-format} command.
23569 Note that one must invoke @code{-var-list-children} for a variable
23570 before the value of a child variable can be evaluated.
23572 @subheading The @code{-var-assign} Command
23573 @findex -var-assign
23575 @subsubheading Synopsis
23578 -var-assign @var{name} @var{expression}
23581 Assigns the value of @var{expression} to the variable object specified
23582 by @var{name}. The object must be @samp{editable}. If the variable's
23583 value is altered by the assign, the variable will show up in any
23584 subsequent @code{-var-update} list.
23586 @subsubheading Example
23594 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
23598 @subheading The @code{-var-update} Command
23599 @findex -var-update
23601 @subsubheading Synopsis
23604 -var-update [@var{print-values}] @{@var{name} | "*"@}
23607 Reevaluate the expressions corresponding to the variable object
23608 @var{name} and all its direct and indirect children, and return the
23609 list of variable objects whose values have changed; @var{name} must
23610 be a root variable object. Here, ``changed'' means that the result of
23611 @code{-var-evaluate-expression} before and after the
23612 @code{-var-update} is different. If @samp{*} is used as the variable
23613 object names, all existing variable objects are updated, except
23614 for frozen ones (@pxref{-var-set-frozen}). The option
23615 @var{print-values} determines whether both names and values, or just
23616 names are printed. The possible values of this option are the same
23617 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
23618 recommended to use the @samp{--all-values} option, to reduce the
23619 number of MI commands needed on each program stop.
23621 With the @samp{*} parameter, if a variable object is bound to a
23622 currently running thread, it will not be updated, without any
23625 @subsubheading Example
23632 -var-update --all-values var1
23633 ^done,changelist=[@{name="var1",value="3",in_scope="true",
23634 type_changed="false"@}]
23638 @anchor{-var-update}
23639 The field in_scope may take three values:
23643 The variable object's current value is valid.
23646 The variable object does not currently hold a valid value but it may
23647 hold one in the future if its associated expression comes back into
23651 The variable object no longer holds a valid value.
23652 This can occur when the executable file being debugged has changed,
23653 either through recompilation or by using the @value{GDBN} @code{file}
23654 command. The front end should normally choose to delete these variable
23658 In the future new values may be added to this list so the front should
23659 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
23661 @subheading The @code{-var-set-frozen} Command
23662 @findex -var-set-frozen
23663 @anchor{-var-set-frozen}
23665 @subsubheading Synopsis
23668 -var-set-frozen @var{name} @var{flag}
23671 Set the frozenness flag on the variable object @var{name}. The
23672 @var{flag} parameter should be either @samp{1} to make the variable
23673 frozen or @samp{0} to make it unfrozen. If a variable object is
23674 frozen, then neither itself, nor any of its children, are
23675 implicitly updated by @code{-var-update} of
23676 a parent variable or by @code{-var-update *}. Only
23677 @code{-var-update} of the variable itself will update its value and
23678 values of its children. After a variable object is unfrozen, it is
23679 implicitly updated by all subsequent @code{-var-update} operations.
23680 Unfreezing a variable does not update it, only subsequent
23681 @code{-var-update} does.
23683 @subsubheading Example
23687 -var-set-frozen V 1
23692 @subheading The @code{-var-set-visualizer} command
23693 @findex -var-set-visualizer
23694 @anchor{-var-set-visualizer}
23696 @subsubheading Synopsis
23699 -var-set-visualizer @var{name} @var{visualizer}
23702 Set a visualizer for the variable object @var{name}.
23704 @var{visualizer} is the visualizer to use. The special value
23705 @samp{None} means to disable any visualizer in use.
23707 If not @samp{None}, @var{visualizer} must be a Python expression.
23708 This expression must evaluate to a callable object which accepts a
23709 single argument. @value{GDBN} will call this object with the value of
23710 the varobj @var{name} as an argument (this is done so that the same
23711 Python pretty-printing code can be used for both the CLI and MI).
23712 When called, this object must return an object which conforms to the
23713 pretty-printing interface (@pxref{Pretty Printing}).
23715 The pre-defined function @code{gdb.default_visualizer} may be used to
23716 select a visualizer by following the built-in process
23717 (@pxref{Selecting Pretty-Printers}). This is done automatically when
23718 a varobj is created, and so ordinarily is not needed.
23720 This feature is only available if Python support is enabled. The MI
23721 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
23722 can be used to check this.
23724 @subsubheading Example
23726 Resetting the visualizer:
23730 -var-set-visualizer V None
23734 Reselecting the default (type-based) visualizer:
23738 -var-set-visualizer V gdb.default_visualizer
23742 Suppose @code{SomeClass} is a visualizer class. A lambda expression
23743 can be used to instantiate this class for a varobj:
23747 -var-set-visualizer V "lambda val: SomeClass()"
23751 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23752 @node GDB/MI Data Manipulation
23753 @section @sc{gdb/mi} Data Manipulation
23755 @cindex data manipulation, in @sc{gdb/mi}
23756 @cindex @sc{gdb/mi}, data manipulation
23757 This section describes the @sc{gdb/mi} commands that manipulate data:
23758 examine memory and registers, evaluate expressions, etc.
23760 @c REMOVED FROM THE INTERFACE.
23761 @c @subheading -data-assign
23762 @c Change the value of a program variable. Plenty of side effects.
23763 @c @subsubheading GDB Command
23765 @c @subsubheading Example
23768 @subheading The @code{-data-disassemble} Command
23769 @findex -data-disassemble
23771 @subsubheading Synopsis
23775 [ -s @var{start-addr} -e @var{end-addr} ]
23776 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
23784 @item @var{start-addr}
23785 is the beginning address (or @code{$pc})
23786 @item @var{end-addr}
23788 @item @var{filename}
23789 is the name of the file to disassemble
23790 @item @var{linenum}
23791 is the line number to disassemble around
23793 is the number of disassembly lines to be produced. If it is -1,
23794 the whole function will be disassembled, in case no @var{end-addr} is
23795 specified. If @var{end-addr} is specified as a non-zero value, and
23796 @var{lines} is lower than the number of disassembly lines between
23797 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
23798 displayed; if @var{lines} is higher than the number of lines between
23799 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
23802 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
23806 @subsubheading Result
23808 The output for each instruction is composed of four fields:
23817 Note that whatever included in the instruction field, is not manipulated
23818 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
23820 @subsubheading @value{GDBN} Command
23822 There's no direct mapping from this command to the CLI.
23824 @subsubheading Example
23826 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
23830 -data-disassemble -s $pc -e "$pc + 20" -- 0
23833 @{address="0x000107c0",func-name="main",offset="4",
23834 inst="mov 2, %o0"@},
23835 @{address="0x000107c4",func-name="main",offset="8",
23836 inst="sethi %hi(0x11800), %o2"@},
23837 @{address="0x000107c8",func-name="main",offset="12",
23838 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
23839 @{address="0x000107cc",func-name="main",offset="16",
23840 inst="sethi %hi(0x11800), %o2"@},
23841 @{address="0x000107d0",func-name="main",offset="20",
23842 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
23846 Disassemble the whole @code{main} function. Line 32 is part of
23850 -data-disassemble -f basics.c -l 32 -- 0
23852 @{address="0x000107bc",func-name="main",offset="0",
23853 inst="save %sp, -112, %sp"@},
23854 @{address="0x000107c0",func-name="main",offset="4",
23855 inst="mov 2, %o0"@},
23856 @{address="0x000107c4",func-name="main",offset="8",
23857 inst="sethi %hi(0x11800), %o2"@},
23859 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
23860 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
23864 Disassemble 3 instructions from the start of @code{main}:
23868 -data-disassemble -f basics.c -l 32 -n 3 -- 0
23870 @{address="0x000107bc",func-name="main",offset="0",
23871 inst="save %sp, -112, %sp"@},
23872 @{address="0x000107c0",func-name="main",offset="4",
23873 inst="mov 2, %o0"@},
23874 @{address="0x000107c4",func-name="main",offset="8",
23875 inst="sethi %hi(0x11800), %o2"@}]
23879 Disassemble 3 instructions from the start of @code{main} in mixed mode:
23883 -data-disassemble -f basics.c -l 32 -n 3 -- 1
23885 src_and_asm_line=@{line="31",
23886 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
23887 testsuite/gdb.mi/basics.c",line_asm_insn=[
23888 @{address="0x000107bc",func-name="main",offset="0",
23889 inst="save %sp, -112, %sp"@}]@},
23890 src_and_asm_line=@{line="32",
23891 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
23892 testsuite/gdb.mi/basics.c",line_asm_insn=[
23893 @{address="0x000107c0",func-name="main",offset="4",
23894 inst="mov 2, %o0"@},
23895 @{address="0x000107c4",func-name="main",offset="8",
23896 inst="sethi %hi(0x11800), %o2"@}]@}]
23901 @subheading The @code{-data-evaluate-expression} Command
23902 @findex -data-evaluate-expression
23904 @subsubheading Synopsis
23907 -data-evaluate-expression @var{expr}
23910 Evaluate @var{expr} as an expression. The expression could contain an
23911 inferior function call. The function call will execute synchronously.
23912 If the expression contains spaces, it must be enclosed in double quotes.
23914 @subsubheading @value{GDBN} Command
23916 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
23917 @samp{call}. In @code{gdbtk} only, there's a corresponding
23918 @samp{gdb_eval} command.
23920 @subsubheading Example
23922 In the following example, the numbers that precede the commands are the
23923 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
23924 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
23928 211-data-evaluate-expression A
23931 311-data-evaluate-expression &A
23932 311^done,value="0xefffeb7c"
23934 411-data-evaluate-expression A+3
23937 511-data-evaluate-expression "A + 3"
23943 @subheading The @code{-data-list-changed-registers} Command
23944 @findex -data-list-changed-registers
23946 @subsubheading Synopsis
23949 -data-list-changed-registers
23952 Display a list of the registers that have changed.
23954 @subsubheading @value{GDBN} Command
23956 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
23957 has the corresponding command @samp{gdb_changed_register_list}.
23959 @subsubheading Example
23961 On a PPC MBX board:
23969 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
23970 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
23973 -data-list-changed-registers
23974 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
23975 "10","11","13","14","15","16","17","18","19","20","21","22","23",
23976 "24","25","26","27","28","30","31","64","65","66","67","69"]
23981 @subheading The @code{-data-list-register-names} Command
23982 @findex -data-list-register-names
23984 @subsubheading Synopsis
23987 -data-list-register-names [ ( @var{regno} )+ ]
23990 Show a list of register names for the current target. If no arguments
23991 are given, it shows a list of the names of all the registers. If
23992 integer numbers are given as arguments, it will print a list of the
23993 names of the registers corresponding to the arguments. To ensure
23994 consistency between a register name and its number, the output list may
23995 include empty register names.
23997 @subsubheading @value{GDBN} Command
23999 @value{GDBN} does not have a command which corresponds to
24000 @samp{-data-list-register-names}. In @code{gdbtk} there is a
24001 corresponding command @samp{gdb_regnames}.
24003 @subsubheading Example
24005 For the PPC MBX board:
24008 -data-list-register-names
24009 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
24010 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
24011 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
24012 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
24013 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
24014 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
24015 "", "pc","ps","cr","lr","ctr","xer"]
24017 -data-list-register-names 1 2 3
24018 ^done,register-names=["r1","r2","r3"]
24022 @subheading The @code{-data-list-register-values} Command
24023 @findex -data-list-register-values
24025 @subsubheading Synopsis
24028 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
24031 Display the registers' contents. @var{fmt} is the format according to
24032 which the registers' contents are to be returned, followed by an optional
24033 list of numbers specifying the registers to display. A missing list of
24034 numbers indicates that the contents of all the registers must be returned.
24036 Allowed formats for @var{fmt} are:
24053 @subsubheading @value{GDBN} Command
24055 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
24056 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
24058 @subsubheading Example
24060 For a PPC MBX board (note: line breaks are for readability only, they
24061 don't appear in the actual output):
24065 -data-list-register-values r 64 65
24066 ^done,register-values=[@{number="64",value="0xfe00a300"@},
24067 @{number="65",value="0x00029002"@}]
24069 -data-list-register-values x
24070 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
24071 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
24072 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
24073 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
24074 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
24075 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
24076 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
24077 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
24078 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
24079 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
24080 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
24081 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
24082 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
24083 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
24084 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
24085 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
24086 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
24087 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
24088 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
24089 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
24090 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
24091 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
24092 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
24093 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
24094 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
24095 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
24096 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
24097 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
24098 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
24099 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
24100 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
24101 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
24102 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
24103 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
24104 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
24105 @{number="69",value="0x20002b03"@}]
24110 @subheading The @code{-data-read-memory} Command
24111 @findex -data-read-memory
24113 @subsubheading Synopsis
24116 -data-read-memory [ -o @var{byte-offset} ]
24117 @var{address} @var{word-format} @var{word-size}
24118 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
24125 @item @var{address}
24126 An expression specifying the address of the first memory word to be
24127 read. Complex expressions containing embedded white space should be
24128 quoted using the C convention.
24130 @item @var{word-format}
24131 The format to be used to print the memory words. The notation is the
24132 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
24135 @item @var{word-size}
24136 The size of each memory word in bytes.
24138 @item @var{nr-rows}
24139 The number of rows in the output table.
24141 @item @var{nr-cols}
24142 The number of columns in the output table.
24145 If present, indicates that each row should include an @sc{ascii} dump. The
24146 value of @var{aschar} is used as a padding character when a byte is not a
24147 member of the printable @sc{ascii} character set (printable @sc{ascii}
24148 characters are those whose code is between 32 and 126, inclusively).
24150 @item @var{byte-offset}
24151 An offset to add to the @var{address} before fetching memory.
24154 This command displays memory contents as a table of @var{nr-rows} by
24155 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
24156 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
24157 (returned as @samp{total-bytes}). Should less than the requested number
24158 of bytes be returned by the target, the missing words are identified
24159 using @samp{N/A}. The number of bytes read from the target is returned
24160 in @samp{nr-bytes} and the starting address used to read memory in
24163 The address of the next/previous row or page is available in
24164 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
24167 @subsubheading @value{GDBN} Command
24169 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
24170 @samp{gdb_get_mem} memory read command.
24172 @subsubheading Example
24174 Read six bytes of memory starting at @code{bytes+6} but then offset by
24175 @code{-6} bytes. Format as three rows of two columns. One byte per
24176 word. Display each word in hex.
24180 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
24181 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
24182 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
24183 prev-page="0x0000138a",memory=[
24184 @{addr="0x00001390",data=["0x00","0x01"]@},
24185 @{addr="0x00001392",data=["0x02","0x03"]@},
24186 @{addr="0x00001394",data=["0x04","0x05"]@}]
24190 Read two bytes of memory starting at address @code{shorts + 64} and
24191 display as a single word formatted in decimal.
24195 5-data-read-memory shorts+64 d 2 1 1
24196 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
24197 next-row="0x00001512",prev-row="0x0000150e",
24198 next-page="0x00001512",prev-page="0x0000150e",memory=[
24199 @{addr="0x00001510",data=["128"]@}]
24203 Read thirty two bytes of memory starting at @code{bytes+16} and format
24204 as eight rows of four columns. Include a string encoding with @samp{x}
24205 used as the non-printable character.
24209 4-data-read-memory bytes+16 x 1 8 4 x
24210 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
24211 next-row="0x000013c0",prev-row="0x0000139c",
24212 next-page="0x000013c0",prev-page="0x00001380",memory=[
24213 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
24214 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
24215 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
24216 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
24217 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
24218 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
24219 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
24220 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
24224 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24225 @node GDB/MI Tracepoint Commands
24226 @section @sc{gdb/mi} Tracepoint Commands
24228 The tracepoint commands are not yet implemented.
24230 @c @subheading -trace-actions
24232 @c @subheading -trace-delete
24234 @c @subheading -trace-disable
24236 @c @subheading -trace-dump
24238 @c @subheading -trace-enable
24240 @c @subheading -trace-exists
24242 @c @subheading -trace-find
24244 @c @subheading -trace-frame-number
24246 @c @subheading -trace-info
24248 @c @subheading -trace-insert
24250 @c @subheading -trace-list
24252 @c @subheading -trace-pass-count
24254 @c @subheading -trace-save
24256 @c @subheading -trace-start
24258 @c @subheading -trace-stop
24261 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24262 @node GDB/MI Symbol Query
24263 @section @sc{gdb/mi} Symbol Query Commands
24267 @subheading The @code{-symbol-info-address} Command
24268 @findex -symbol-info-address
24270 @subsubheading Synopsis
24273 -symbol-info-address @var{symbol}
24276 Describe where @var{symbol} is stored.
24278 @subsubheading @value{GDBN} Command
24280 The corresponding @value{GDBN} command is @samp{info address}.
24282 @subsubheading Example
24286 @subheading The @code{-symbol-info-file} Command
24287 @findex -symbol-info-file
24289 @subsubheading Synopsis
24295 Show the file for the symbol.
24297 @subsubheading @value{GDBN} Command
24299 There's no equivalent @value{GDBN} command. @code{gdbtk} has
24300 @samp{gdb_find_file}.
24302 @subsubheading Example
24306 @subheading The @code{-symbol-info-function} Command
24307 @findex -symbol-info-function
24309 @subsubheading Synopsis
24312 -symbol-info-function
24315 Show which function the symbol lives in.
24317 @subsubheading @value{GDBN} Command
24319 @samp{gdb_get_function} in @code{gdbtk}.
24321 @subsubheading Example
24325 @subheading The @code{-symbol-info-line} Command
24326 @findex -symbol-info-line
24328 @subsubheading Synopsis
24334 Show the core addresses of the code for a source line.
24336 @subsubheading @value{GDBN} Command
24338 The corresponding @value{GDBN} command is @samp{info line}.
24339 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
24341 @subsubheading Example
24345 @subheading The @code{-symbol-info-symbol} Command
24346 @findex -symbol-info-symbol
24348 @subsubheading Synopsis
24351 -symbol-info-symbol @var{addr}
24354 Describe what symbol is at location @var{addr}.
24356 @subsubheading @value{GDBN} Command
24358 The corresponding @value{GDBN} command is @samp{info symbol}.
24360 @subsubheading Example
24364 @subheading The @code{-symbol-list-functions} Command
24365 @findex -symbol-list-functions
24367 @subsubheading Synopsis
24370 -symbol-list-functions
24373 List the functions in the executable.
24375 @subsubheading @value{GDBN} Command
24377 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
24378 @samp{gdb_search} in @code{gdbtk}.
24380 @subsubheading Example
24385 @subheading The @code{-symbol-list-lines} Command
24386 @findex -symbol-list-lines
24388 @subsubheading Synopsis
24391 -symbol-list-lines @var{filename}
24394 Print the list of lines that contain code and their associated program
24395 addresses for the given source filename. The entries are sorted in
24396 ascending PC order.
24398 @subsubheading @value{GDBN} Command
24400 There is no corresponding @value{GDBN} command.
24402 @subsubheading Example
24405 -symbol-list-lines basics.c
24406 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
24412 @subheading The @code{-symbol-list-types} Command
24413 @findex -symbol-list-types
24415 @subsubheading Synopsis
24421 List all the type names.
24423 @subsubheading @value{GDBN} Command
24425 The corresponding commands are @samp{info types} in @value{GDBN},
24426 @samp{gdb_search} in @code{gdbtk}.
24428 @subsubheading Example
24432 @subheading The @code{-symbol-list-variables} Command
24433 @findex -symbol-list-variables
24435 @subsubheading Synopsis
24438 -symbol-list-variables
24441 List all the global and static variable names.
24443 @subsubheading @value{GDBN} Command
24445 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
24447 @subsubheading Example
24451 @subheading The @code{-symbol-locate} Command
24452 @findex -symbol-locate
24454 @subsubheading Synopsis
24460 @subsubheading @value{GDBN} Command
24462 @samp{gdb_loc} in @code{gdbtk}.
24464 @subsubheading Example
24468 @subheading The @code{-symbol-type} Command
24469 @findex -symbol-type
24471 @subsubheading Synopsis
24474 -symbol-type @var{variable}
24477 Show type of @var{variable}.
24479 @subsubheading @value{GDBN} Command
24481 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
24482 @samp{gdb_obj_variable}.
24484 @subsubheading Example
24489 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24490 @node GDB/MI File Commands
24491 @section @sc{gdb/mi} File Commands
24493 This section describes the GDB/MI commands to specify executable file names
24494 and to read in and obtain symbol table information.
24496 @subheading The @code{-file-exec-and-symbols} Command
24497 @findex -file-exec-and-symbols
24499 @subsubheading Synopsis
24502 -file-exec-and-symbols @var{file}
24505 Specify the executable file to be debugged. This file is the one from
24506 which the symbol table is also read. If no file is specified, the
24507 command clears the executable and symbol information. If breakpoints
24508 are set when using this command with no arguments, @value{GDBN} will produce
24509 error messages. Otherwise, no output is produced, except a completion
24512 @subsubheading @value{GDBN} Command
24514 The corresponding @value{GDBN} command is @samp{file}.
24516 @subsubheading Example
24520 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
24526 @subheading The @code{-file-exec-file} Command
24527 @findex -file-exec-file
24529 @subsubheading Synopsis
24532 -file-exec-file @var{file}
24535 Specify the executable file to be debugged. Unlike
24536 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
24537 from this file. If used without argument, @value{GDBN} clears the information
24538 about the executable file. No output is produced, except a completion
24541 @subsubheading @value{GDBN} Command
24543 The corresponding @value{GDBN} command is @samp{exec-file}.
24545 @subsubheading Example
24549 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
24556 @subheading The @code{-file-list-exec-sections} Command
24557 @findex -file-list-exec-sections
24559 @subsubheading Synopsis
24562 -file-list-exec-sections
24565 List the sections of the current executable file.
24567 @subsubheading @value{GDBN} Command
24569 The @value{GDBN} command @samp{info file} shows, among the rest, the same
24570 information as this command. @code{gdbtk} has a corresponding command
24571 @samp{gdb_load_info}.
24573 @subsubheading Example
24578 @subheading The @code{-file-list-exec-source-file} Command
24579 @findex -file-list-exec-source-file
24581 @subsubheading Synopsis
24584 -file-list-exec-source-file
24587 List the line number, the current source file, and the absolute path
24588 to the current source file for the current executable. The macro
24589 information field has a value of @samp{1} or @samp{0} depending on
24590 whether or not the file includes preprocessor macro information.
24592 @subsubheading @value{GDBN} Command
24594 The @value{GDBN} equivalent is @samp{info source}
24596 @subsubheading Example
24600 123-file-list-exec-source-file
24601 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
24606 @subheading The @code{-file-list-exec-source-files} Command
24607 @findex -file-list-exec-source-files
24609 @subsubheading Synopsis
24612 -file-list-exec-source-files
24615 List the source files for the current executable.
24617 It will always output the filename, but only when @value{GDBN} can find
24618 the absolute file name of a source file, will it output the fullname.
24620 @subsubheading @value{GDBN} Command
24622 The @value{GDBN} equivalent is @samp{info sources}.
24623 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
24625 @subsubheading Example
24628 -file-list-exec-source-files
24630 @{file=foo.c,fullname=/home/foo.c@},
24631 @{file=/home/bar.c,fullname=/home/bar.c@},
24632 @{file=gdb_could_not_find_fullpath.c@}]
24637 @subheading The @code{-file-list-shared-libraries} Command
24638 @findex -file-list-shared-libraries
24640 @subsubheading Synopsis
24643 -file-list-shared-libraries
24646 List the shared libraries in the program.
24648 @subsubheading @value{GDBN} Command
24650 The corresponding @value{GDBN} command is @samp{info shared}.
24652 @subsubheading Example
24656 @subheading The @code{-file-list-symbol-files} Command
24657 @findex -file-list-symbol-files
24659 @subsubheading Synopsis
24662 -file-list-symbol-files
24667 @subsubheading @value{GDBN} Command
24669 The corresponding @value{GDBN} command is @samp{info file} (part of it).
24671 @subsubheading Example
24676 @subheading The @code{-file-symbol-file} Command
24677 @findex -file-symbol-file
24679 @subsubheading Synopsis
24682 -file-symbol-file @var{file}
24685 Read symbol table info from the specified @var{file} argument. When
24686 used without arguments, clears @value{GDBN}'s symbol table info. No output is
24687 produced, except for a completion notification.
24689 @subsubheading @value{GDBN} Command
24691 The corresponding @value{GDBN} command is @samp{symbol-file}.
24693 @subsubheading Example
24697 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
24703 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24704 @node GDB/MI Memory Overlay Commands
24705 @section @sc{gdb/mi} Memory Overlay Commands
24707 The memory overlay commands are not implemented.
24709 @c @subheading -overlay-auto
24711 @c @subheading -overlay-list-mapping-state
24713 @c @subheading -overlay-list-overlays
24715 @c @subheading -overlay-map
24717 @c @subheading -overlay-off
24719 @c @subheading -overlay-on
24721 @c @subheading -overlay-unmap
24723 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24724 @node GDB/MI Signal Handling Commands
24725 @section @sc{gdb/mi} Signal Handling Commands
24727 Signal handling commands are not implemented.
24729 @c @subheading -signal-handle
24731 @c @subheading -signal-list-handle-actions
24733 @c @subheading -signal-list-signal-types
24737 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24738 @node GDB/MI Target Manipulation
24739 @section @sc{gdb/mi} Target Manipulation Commands
24742 @subheading The @code{-target-attach} Command
24743 @findex -target-attach
24745 @subsubheading Synopsis
24748 -target-attach @var{pid} | @var{gid} | @var{file}
24751 Attach to a process @var{pid} or a file @var{file} outside of
24752 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
24753 group, the id previously returned by
24754 @samp{-list-thread-groups --available} must be used.
24756 @subsubheading @value{GDBN} Command
24758 The corresponding @value{GDBN} command is @samp{attach}.
24760 @subsubheading Example
24764 =thread-created,id="1"
24765 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
24771 @subheading The @code{-target-compare-sections} Command
24772 @findex -target-compare-sections
24774 @subsubheading Synopsis
24777 -target-compare-sections [ @var{section} ]
24780 Compare data of section @var{section} on target to the exec file.
24781 Without the argument, all sections are compared.
24783 @subsubheading @value{GDBN} Command
24785 The @value{GDBN} equivalent is @samp{compare-sections}.
24787 @subsubheading Example
24792 @subheading The @code{-target-detach} Command
24793 @findex -target-detach
24795 @subsubheading Synopsis
24798 -target-detach [ @var{pid} | @var{gid} ]
24801 Detach from the remote target which normally resumes its execution.
24802 If either @var{pid} or @var{gid} is specified, detaches from either
24803 the specified process, or specified thread group. There's no output.
24805 @subsubheading @value{GDBN} Command
24807 The corresponding @value{GDBN} command is @samp{detach}.
24809 @subsubheading Example
24819 @subheading The @code{-target-disconnect} Command
24820 @findex -target-disconnect
24822 @subsubheading Synopsis
24828 Disconnect from the remote target. There's no output and the target is
24829 generally not resumed.
24831 @subsubheading @value{GDBN} Command
24833 The corresponding @value{GDBN} command is @samp{disconnect}.
24835 @subsubheading Example
24845 @subheading The @code{-target-download} Command
24846 @findex -target-download
24848 @subsubheading Synopsis
24854 Loads the executable onto the remote target.
24855 It prints out an update message every half second, which includes the fields:
24859 The name of the section.
24861 The size of what has been sent so far for that section.
24863 The size of the section.
24865 The total size of what was sent so far (the current and the previous sections).
24867 The size of the overall executable to download.
24871 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
24872 @sc{gdb/mi} Output Syntax}).
24874 In addition, it prints the name and size of the sections, as they are
24875 downloaded. These messages include the following fields:
24879 The name of the section.
24881 The size of the section.
24883 The size of the overall executable to download.
24887 At the end, a summary is printed.
24889 @subsubheading @value{GDBN} Command
24891 The corresponding @value{GDBN} command is @samp{load}.
24893 @subsubheading Example
24895 Note: each status message appears on a single line. Here the messages
24896 have been broken down so that they can fit onto a page.
24901 +download,@{section=".text",section-size="6668",total-size="9880"@}
24902 +download,@{section=".text",section-sent="512",section-size="6668",
24903 total-sent="512",total-size="9880"@}
24904 +download,@{section=".text",section-sent="1024",section-size="6668",
24905 total-sent="1024",total-size="9880"@}
24906 +download,@{section=".text",section-sent="1536",section-size="6668",
24907 total-sent="1536",total-size="9880"@}
24908 +download,@{section=".text",section-sent="2048",section-size="6668",
24909 total-sent="2048",total-size="9880"@}
24910 +download,@{section=".text",section-sent="2560",section-size="6668",
24911 total-sent="2560",total-size="9880"@}
24912 +download,@{section=".text",section-sent="3072",section-size="6668",
24913 total-sent="3072",total-size="9880"@}
24914 +download,@{section=".text",section-sent="3584",section-size="6668",
24915 total-sent="3584",total-size="9880"@}
24916 +download,@{section=".text",section-sent="4096",section-size="6668",
24917 total-sent="4096",total-size="9880"@}
24918 +download,@{section=".text",section-sent="4608",section-size="6668",
24919 total-sent="4608",total-size="9880"@}
24920 +download,@{section=".text",section-sent="5120",section-size="6668",
24921 total-sent="5120",total-size="9880"@}
24922 +download,@{section=".text",section-sent="5632",section-size="6668",
24923 total-sent="5632",total-size="9880"@}
24924 +download,@{section=".text",section-sent="6144",section-size="6668",
24925 total-sent="6144",total-size="9880"@}
24926 +download,@{section=".text",section-sent="6656",section-size="6668",
24927 total-sent="6656",total-size="9880"@}
24928 +download,@{section=".init",section-size="28",total-size="9880"@}
24929 +download,@{section=".fini",section-size="28",total-size="9880"@}
24930 +download,@{section=".data",section-size="3156",total-size="9880"@}
24931 +download,@{section=".data",section-sent="512",section-size="3156",
24932 total-sent="7236",total-size="9880"@}
24933 +download,@{section=".data",section-sent="1024",section-size="3156",
24934 total-sent="7748",total-size="9880"@}
24935 +download,@{section=".data",section-sent="1536",section-size="3156",
24936 total-sent="8260",total-size="9880"@}
24937 +download,@{section=".data",section-sent="2048",section-size="3156",
24938 total-sent="8772",total-size="9880"@}
24939 +download,@{section=".data",section-sent="2560",section-size="3156",
24940 total-sent="9284",total-size="9880"@}
24941 +download,@{section=".data",section-sent="3072",section-size="3156",
24942 total-sent="9796",total-size="9880"@}
24943 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
24950 @subheading The @code{-target-exec-status} Command
24951 @findex -target-exec-status
24953 @subsubheading Synopsis
24956 -target-exec-status
24959 Provide information on the state of the target (whether it is running or
24960 not, for instance).
24962 @subsubheading @value{GDBN} Command
24964 There's no equivalent @value{GDBN} command.
24966 @subsubheading Example
24970 @subheading The @code{-target-list-available-targets} Command
24971 @findex -target-list-available-targets
24973 @subsubheading Synopsis
24976 -target-list-available-targets
24979 List the possible targets to connect to.
24981 @subsubheading @value{GDBN} Command
24983 The corresponding @value{GDBN} command is @samp{help target}.
24985 @subsubheading Example
24989 @subheading The @code{-target-list-current-targets} Command
24990 @findex -target-list-current-targets
24992 @subsubheading Synopsis
24995 -target-list-current-targets
24998 Describe the current target.
25000 @subsubheading @value{GDBN} Command
25002 The corresponding information is printed by @samp{info file} (among
25005 @subsubheading Example
25009 @subheading The @code{-target-list-parameters} Command
25010 @findex -target-list-parameters
25012 @subsubheading Synopsis
25015 -target-list-parameters
25021 @subsubheading @value{GDBN} Command
25025 @subsubheading Example
25029 @subheading The @code{-target-select} Command
25030 @findex -target-select
25032 @subsubheading Synopsis
25035 -target-select @var{type} @var{parameters @dots{}}
25038 Connect @value{GDBN} to the remote target. This command takes two args:
25042 The type of target, for instance @samp{remote}, etc.
25043 @item @var{parameters}
25044 Device names, host names and the like. @xref{Target Commands, ,
25045 Commands for Managing Targets}, for more details.
25048 The output is a connection notification, followed by the address at
25049 which the target program is, in the following form:
25052 ^connected,addr="@var{address}",func="@var{function name}",
25053 args=[@var{arg list}]
25056 @subsubheading @value{GDBN} Command
25058 The corresponding @value{GDBN} command is @samp{target}.
25060 @subsubheading Example
25064 -target-select remote /dev/ttya
25065 ^connected,addr="0xfe00a300",func="??",args=[]
25069 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25070 @node GDB/MI File Transfer Commands
25071 @section @sc{gdb/mi} File Transfer Commands
25074 @subheading The @code{-target-file-put} Command
25075 @findex -target-file-put
25077 @subsubheading Synopsis
25080 -target-file-put @var{hostfile} @var{targetfile}
25083 Copy file @var{hostfile} from the host system (the machine running
25084 @value{GDBN}) to @var{targetfile} on the target system.
25086 @subsubheading @value{GDBN} Command
25088 The corresponding @value{GDBN} command is @samp{remote put}.
25090 @subsubheading Example
25094 -target-file-put localfile remotefile
25100 @subheading The @code{-target-file-get} Command
25101 @findex -target-file-get
25103 @subsubheading Synopsis
25106 -target-file-get @var{targetfile} @var{hostfile}
25109 Copy file @var{targetfile} from the target system to @var{hostfile}
25110 on the host system.
25112 @subsubheading @value{GDBN} Command
25114 The corresponding @value{GDBN} command is @samp{remote get}.
25116 @subsubheading Example
25120 -target-file-get remotefile localfile
25126 @subheading The @code{-target-file-delete} Command
25127 @findex -target-file-delete
25129 @subsubheading Synopsis
25132 -target-file-delete @var{targetfile}
25135 Delete @var{targetfile} from the target system.
25137 @subsubheading @value{GDBN} Command
25139 The corresponding @value{GDBN} command is @samp{remote delete}.
25141 @subsubheading Example
25145 -target-file-delete remotefile
25151 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25152 @node GDB/MI Miscellaneous Commands
25153 @section Miscellaneous @sc{gdb/mi} Commands
25155 @c @subheading -gdb-complete
25157 @subheading The @code{-gdb-exit} Command
25160 @subsubheading Synopsis
25166 Exit @value{GDBN} immediately.
25168 @subsubheading @value{GDBN} Command
25170 Approximately corresponds to @samp{quit}.
25172 @subsubheading Example
25182 @subheading The @code{-exec-abort} Command
25183 @findex -exec-abort
25185 @subsubheading Synopsis
25191 Kill the inferior running program.
25193 @subsubheading @value{GDBN} Command
25195 The corresponding @value{GDBN} command is @samp{kill}.
25197 @subsubheading Example
25202 @subheading The @code{-gdb-set} Command
25205 @subsubheading Synopsis
25211 Set an internal @value{GDBN} variable.
25212 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
25214 @subsubheading @value{GDBN} Command
25216 The corresponding @value{GDBN} command is @samp{set}.
25218 @subsubheading Example
25228 @subheading The @code{-gdb-show} Command
25231 @subsubheading Synopsis
25237 Show the current value of a @value{GDBN} variable.
25239 @subsubheading @value{GDBN} Command
25241 The corresponding @value{GDBN} command is @samp{show}.
25243 @subsubheading Example
25252 @c @subheading -gdb-source
25255 @subheading The @code{-gdb-version} Command
25256 @findex -gdb-version
25258 @subsubheading Synopsis
25264 Show version information for @value{GDBN}. Used mostly in testing.
25266 @subsubheading @value{GDBN} Command
25268 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
25269 default shows this information when you start an interactive session.
25271 @subsubheading Example
25273 @c This example modifies the actual output from GDB to avoid overfull
25279 ~Copyright 2000 Free Software Foundation, Inc.
25280 ~GDB is free software, covered by the GNU General Public License, and
25281 ~you are welcome to change it and/or distribute copies of it under
25282 ~ certain conditions.
25283 ~Type "show copying" to see the conditions.
25284 ~There is absolutely no warranty for GDB. Type "show warranty" for
25286 ~This GDB was configured as
25287 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
25292 @subheading The @code{-list-features} Command
25293 @findex -list-features
25295 Returns a list of particular features of the MI protocol that
25296 this version of gdb implements. A feature can be a command,
25297 or a new field in an output of some command, or even an
25298 important bugfix. While a frontend can sometimes detect presence
25299 of a feature at runtime, it is easier to perform detection at debugger
25302 The command returns a list of strings, with each string naming an
25303 available feature. Each returned string is just a name, it does not
25304 have any internal structure. The list of possible feature names
25310 (gdb) -list-features
25311 ^done,result=["feature1","feature2"]
25314 The current list of features is:
25317 @item frozen-varobjs
25318 Indicates presence of the @code{-var-set-frozen} command, as well
25319 as possible presense of the @code{frozen} field in the output
25320 of @code{-varobj-create}.
25321 @item pending-breakpoints
25322 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
25324 Indicates presence of Python scripting support, Python-based
25325 pretty-printing commands, and possible presence of the
25326 @samp{display_hint} field in the output of @code{-var-list-children}
25328 Indicates presence of the @code{-thread-info} command.
25332 @subheading The @code{-list-target-features} Command
25333 @findex -list-target-features
25335 Returns a list of particular features that are supported by the
25336 target. Those features affect the permitted MI commands, but
25337 unlike the features reported by the @code{-list-features} command, the
25338 features depend on which target GDB is using at the moment. Whenever
25339 a target can change, due to commands such as @code{-target-select},
25340 @code{-target-attach} or @code{-exec-run}, the list of target features
25341 may change, and the frontend should obtain it again.
25345 (gdb) -list-features
25346 ^done,result=["async"]
25349 The current list of features is:
25353 Indicates that the target is capable of asynchronous command
25354 execution, which means that @value{GDBN} will accept further commands
25355 while the target is running.
25359 @subheading The @code{-list-thread-groups} Command
25360 @findex -list-thread-groups
25362 @subheading Synopsis
25365 -list-thread-groups [ --available ] [ @var{group} ]
25368 When used without the @var{group} parameter, lists top-level thread
25369 groups that are being debugged. When used with the @var{group}
25370 parameter, the children of the specified group are listed. The
25371 children can be either threads, or other groups. At present,
25372 @value{GDBN} will not report both threads and groups as children at
25373 the same time, but it may change in future.
25375 With the @samp{--available} option, instead of reporting groups that
25376 are been debugged, GDB will report all thread groups available on the
25377 target. Using the @samp{--available} option together with @var{group}
25380 @subheading Example
25384 -list-thread-groups
25385 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
25386 -list-thread-groups 17
25387 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
25388 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
25389 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
25390 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
25391 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
25394 @subheading The @code{-interpreter-exec} Command
25395 @findex -interpreter-exec
25397 @subheading Synopsis
25400 -interpreter-exec @var{interpreter} @var{command}
25402 @anchor{-interpreter-exec}
25404 Execute the specified @var{command} in the given @var{interpreter}.
25406 @subheading @value{GDBN} Command
25408 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
25410 @subheading Example
25414 -interpreter-exec console "break main"
25415 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
25416 &"During symbol reading, bad structure-type format.\n"
25417 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
25422 @subheading The @code{-inferior-tty-set} Command
25423 @findex -inferior-tty-set
25425 @subheading Synopsis
25428 -inferior-tty-set /dev/pts/1
25431 Set terminal for future runs of the program being debugged.
25433 @subheading @value{GDBN} Command
25435 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
25437 @subheading Example
25441 -inferior-tty-set /dev/pts/1
25446 @subheading The @code{-inferior-tty-show} Command
25447 @findex -inferior-tty-show
25449 @subheading Synopsis
25455 Show terminal for future runs of program being debugged.
25457 @subheading @value{GDBN} Command
25459 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
25461 @subheading Example
25465 -inferior-tty-set /dev/pts/1
25469 ^done,inferior_tty_terminal="/dev/pts/1"
25473 @subheading The @code{-enable-timings} Command
25474 @findex -enable-timings
25476 @subheading Synopsis
25479 -enable-timings [yes | no]
25482 Toggle the printing of the wallclock, user and system times for an MI
25483 command as a field in its output. This command is to help frontend
25484 developers optimize the performance of their code. No argument is
25485 equivalent to @samp{yes}.
25487 @subheading @value{GDBN} Command
25491 @subheading Example
25499 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25500 addr="0x080484ed",func="main",file="myprog.c",
25501 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
25502 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
25510 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
25511 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
25512 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
25513 fullname="/home/nickrob/myprog.c",line="73"@}
25518 @chapter @value{GDBN} Annotations
25520 This chapter describes annotations in @value{GDBN}. Annotations were
25521 designed to interface @value{GDBN} to graphical user interfaces or other
25522 similar programs which want to interact with @value{GDBN} at a
25523 relatively high level.
25525 The annotation mechanism has largely been superseded by @sc{gdb/mi}
25529 This is Edition @value{EDITION}, @value{DATE}.
25533 * Annotations Overview:: What annotations are; the general syntax.
25534 * Server Prefix:: Issuing a command without affecting user state.
25535 * Prompting:: Annotations marking @value{GDBN}'s need for input.
25536 * Errors:: Annotations for error messages.
25537 * Invalidation:: Some annotations describe things now invalid.
25538 * Annotations for Running::
25539 Whether the program is running, how it stopped, etc.
25540 * Source Annotations:: Annotations describing source code.
25543 @node Annotations Overview
25544 @section What is an Annotation?
25545 @cindex annotations
25547 Annotations start with a newline character, two @samp{control-z}
25548 characters, and the name of the annotation. If there is no additional
25549 information associated with this annotation, the name of the annotation
25550 is followed immediately by a newline. If there is additional
25551 information, the name of the annotation is followed by a space, the
25552 additional information, and a newline. The additional information
25553 cannot contain newline characters.
25555 Any output not beginning with a newline and two @samp{control-z}
25556 characters denotes literal output from @value{GDBN}. Currently there is
25557 no need for @value{GDBN} to output a newline followed by two
25558 @samp{control-z} characters, but if there was such a need, the
25559 annotations could be extended with an @samp{escape} annotation which
25560 means those three characters as output.
25562 The annotation @var{level}, which is specified using the
25563 @option{--annotate} command line option (@pxref{Mode Options}), controls
25564 how much information @value{GDBN} prints together with its prompt,
25565 values of expressions, source lines, and other types of output. Level 0
25566 is for no annotations, level 1 is for use when @value{GDBN} is run as a
25567 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
25568 for programs that control @value{GDBN}, and level 2 annotations have
25569 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
25570 Interface, annotate, GDB's Obsolete Annotations}).
25573 @kindex set annotate
25574 @item set annotate @var{level}
25575 The @value{GDBN} command @code{set annotate} sets the level of
25576 annotations to the specified @var{level}.
25578 @item show annotate
25579 @kindex show annotate
25580 Show the current annotation level.
25583 This chapter describes level 3 annotations.
25585 A simple example of starting up @value{GDBN} with annotations is:
25588 $ @kbd{gdb --annotate=3}
25590 Copyright 2003 Free Software Foundation, Inc.
25591 GDB is free software, covered by the GNU General Public License,
25592 and you are welcome to change it and/or distribute copies of it
25593 under certain conditions.
25594 Type "show copying" to see the conditions.
25595 There is absolutely no warranty for GDB. Type "show warranty"
25597 This GDB was configured as "i386-pc-linux-gnu"
25608 Here @samp{quit} is input to @value{GDBN}; the rest is output from
25609 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
25610 denotes a @samp{control-z} character) are annotations; the rest is
25611 output from @value{GDBN}.
25613 @node Server Prefix
25614 @section The Server Prefix
25615 @cindex server prefix
25617 If you prefix a command with @samp{server } then it will not affect
25618 the command history, nor will it affect @value{GDBN}'s notion of which
25619 command to repeat if @key{RET} is pressed on a line by itself. This
25620 means that commands can be run behind a user's back by a front-end in
25621 a transparent manner.
25623 The server prefix does not affect the recording of values into the value
25624 history; to print a value without recording it into the value history,
25625 use the @code{output} command instead of the @code{print} command.
25628 @section Annotation for @value{GDBN} Input
25630 @cindex annotations for prompts
25631 When @value{GDBN} prompts for input, it annotates this fact so it is possible
25632 to know when to send output, when the output from a given command is
25635 Different kinds of input each have a different @dfn{input type}. Each
25636 input type has three annotations: a @code{pre-} annotation, which
25637 denotes the beginning of any prompt which is being output, a plain
25638 annotation, which denotes the end of the prompt, and then a @code{post-}
25639 annotation which denotes the end of any echo which may (or may not) be
25640 associated with the input. For example, the @code{prompt} input type
25641 features the following annotations:
25649 The input types are
25652 @findex pre-prompt annotation
25653 @findex prompt annotation
25654 @findex post-prompt annotation
25656 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
25658 @findex pre-commands annotation
25659 @findex commands annotation
25660 @findex post-commands annotation
25662 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
25663 command. The annotations are repeated for each command which is input.
25665 @findex pre-overload-choice annotation
25666 @findex overload-choice annotation
25667 @findex post-overload-choice annotation
25668 @item overload-choice
25669 When @value{GDBN} wants the user to select between various overloaded functions.
25671 @findex pre-query annotation
25672 @findex query annotation
25673 @findex post-query annotation
25675 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
25677 @findex pre-prompt-for-continue annotation
25678 @findex prompt-for-continue annotation
25679 @findex post-prompt-for-continue annotation
25680 @item prompt-for-continue
25681 When @value{GDBN} is asking the user to press return to continue. Note: Don't
25682 expect this to work well; instead use @code{set height 0} to disable
25683 prompting. This is because the counting of lines is buggy in the
25684 presence of annotations.
25689 @cindex annotations for errors, warnings and interrupts
25691 @findex quit annotation
25696 This annotation occurs right before @value{GDBN} responds to an interrupt.
25698 @findex error annotation
25703 This annotation occurs right before @value{GDBN} responds to an error.
25705 Quit and error annotations indicate that any annotations which @value{GDBN} was
25706 in the middle of may end abruptly. For example, if a
25707 @code{value-history-begin} annotation is followed by a @code{error}, one
25708 cannot expect to receive the matching @code{value-history-end}. One
25709 cannot expect not to receive it either, however; an error annotation
25710 does not necessarily mean that @value{GDBN} is immediately returning all the way
25713 @findex error-begin annotation
25714 A quit or error annotation may be preceded by
25720 Any output between that and the quit or error annotation is the error
25723 Warning messages are not yet annotated.
25724 @c If we want to change that, need to fix warning(), type_error(),
25725 @c range_error(), and possibly other places.
25728 @section Invalidation Notices
25730 @cindex annotations for invalidation messages
25731 The following annotations say that certain pieces of state may have
25735 @findex frames-invalid annotation
25736 @item ^Z^Zframes-invalid
25738 The frames (for example, output from the @code{backtrace} command) may
25741 @findex breakpoints-invalid annotation
25742 @item ^Z^Zbreakpoints-invalid
25744 The breakpoints may have changed. For example, the user just added or
25745 deleted a breakpoint.
25748 @node Annotations for Running
25749 @section Running the Program
25750 @cindex annotations for running programs
25752 @findex starting annotation
25753 @findex stopping annotation
25754 When the program starts executing due to a @value{GDBN} command such as
25755 @code{step} or @code{continue},
25761 is output. When the program stops,
25767 is output. Before the @code{stopped} annotation, a variety of
25768 annotations describe how the program stopped.
25771 @findex exited annotation
25772 @item ^Z^Zexited @var{exit-status}
25773 The program exited, and @var{exit-status} is the exit status (zero for
25774 successful exit, otherwise nonzero).
25776 @findex signalled annotation
25777 @findex signal-name annotation
25778 @findex signal-name-end annotation
25779 @findex signal-string annotation
25780 @findex signal-string-end annotation
25781 @item ^Z^Zsignalled
25782 The program exited with a signal. After the @code{^Z^Zsignalled}, the
25783 annotation continues:
25789 ^Z^Zsignal-name-end
25793 ^Z^Zsignal-string-end
25798 where @var{name} is the name of the signal, such as @code{SIGILL} or
25799 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
25800 as @code{Illegal Instruction} or @code{Segmentation fault}.
25801 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
25802 user's benefit and have no particular format.
25804 @findex signal annotation
25806 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
25807 just saying that the program received the signal, not that it was
25808 terminated with it.
25810 @findex breakpoint annotation
25811 @item ^Z^Zbreakpoint @var{number}
25812 The program hit breakpoint number @var{number}.
25814 @findex watchpoint annotation
25815 @item ^Z^Zwatchpoint @var{number}
25816 The program hit watchpoint number @var{number}.
25819 @node Source Annotations
25820 @section Displaying Source
25821 @cindex annotations for source display
25823 @findex source annotation
25824 The following annotation is used instead of displaying source code:
25827 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
25830 where @var{filename} is an absolute file name indicating which source
25831 file, @var{line} is the line number within that file (where 1 is the
25832 first line in the file), @var{character} is the character position
25833 within the file (where 0 is the first character in the file) (for most
25834 debug formats this will necessarily point to the beginning of a line),
25835 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
25836 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
25837 @var{addr} is the address in the target program associated with the
25838 source which is being displayed. @var{addr} is in the form @samp{0x}
25839 followed by one or more lowercase hex digits (note that this does not
25840 depend on the language).
25843 @chapter Reporting Bugs in @value{GDBN}
25844 @cindex bugs in @value{GDBN}
25845 @cindex reporting bugs in @value{GDBN}
25847 Your bug reports play an essential role in making @value{GDBN} reliable.
25849 Reporting a bug may help you by bringing a solution to your problem, or it
25850 may not. But in any case the principal function of a bug report is to help
25851 the entire community by making the next version of @value{GDBN} work better. Bug
25852 reports are your contribution to the maintenance of @value{GDBN}.
25854 In order for a bug report to serve its purpose, you must include the
25855 information that enables us to fix the bug.
25858 * Bug Criteria:: Have you found a bug?
25859 * Bug Reporting:: How to report bugs
25863 @section Have You Found a Bug?
25864 @cindex bug criteria
25866 If you are not sure whether you have found a bug, here are some guidelines:
25869 @cindex fatal signal
25870 @cindex debugger crash
25871 @cindex crash of debugger
25873 If the debugger gets a fatal signal, for any input whatever, that is a
25874 @value{GDBN} bug. Reliable debuggers never crash.
25876 @cindex error on valid input
25878 If @value{GDBN} produces an error message for valid input, that is a
25879 bug. (Note that if you're cross debugging, the problem may also be
25880 somewhere in the connection to the target.)
25882 @cindex invalid input
25884 If @value{GDBN} does not produce an error message for invalid input,
25885 that is a bug. However, you should note that your idea of
25886 ``invalid input'' might be our idea of ``an extension'' or ``support
25887 for traditional practice''.
25890 If you are an experienced user of debugging tools, your suggestions
25891 for improvement of @value{GDBN} are welcome in any case.
25894 @node Bug Reporting
25895 @section How to Report Bugs
25896 @cindex bug reports
25897 @cindex @value{GDBN} bugs, reporting
25899 A number of companies and individuals offer support for @sc{gnu} products.
25900 If you obtained @value{GDBN} from a support organization, we recommend you
25901 contact that organization first.
25903 You can find contact information for many support companies and
25904 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
25906 @c should add a web page ref...
25909 @ifset BUGURL_DEFAULT
25910 In any event, we also recommend that you submit bug reports for
25911 @value{GDBN}. The preferred method is to submit them directly using
25912 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
25913 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
25916 @strong{Do not send bug reports to @samp{info-gdb}, or to
25917 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
25918 not want to receive bug reports. Those that do have arranged to receive
25921 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
25922 serves as a repeater. The mailing list and the newsgroup carry exactly
25923 the same messages. Often people think of posting bug reports to the
25924 newsgroup instead of mailing them. This appears to work, but it has one
25925 problem which can be crucial: a newsgroup posting often lacks a mail
25926 path back to the sender. Thus, if we need to ask for more information,
25927 we may be unable to reach you. For this reason, it is better to send
25928 bug reports to the mailing list.
25930 @ifclear BUGURL_DEFAULT
25931 In any event, we also recommend that you submit bug reports for
25932 @value{GDBN} to @value{BUGURL}.
25936 The fundamental principle of reporting bugs usefully is this:
25937 @strong{report all the facts}. If you are not sure whether to state a
25938 fact or leave it out, state it!
25940 Often people omit facts because they think they know what causes the
25941 problem and assume that some details do not matter. Thus, you might
25942 assume that the name of the variable you use in an example does not matter.
25943 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
25944 stray memory reference which happens to fetch from the location where that
25945 name is stored in memory; perhaps, if the name were different, the contents
25946 of that location would fool the debugger into doing the right thing despite
25947 the bug. Play it safe and give a specific, complete example. That is the
25948 easiest thing for you to do, and the most helpful.
25950 Keep in mind that the purpose of a bug report is to enable us to fix the
25951 bug. It may be that the bug has been reported previously, but neither
25952 you nor we can know that unless your bug report is complete and
25955 Sometimes people give a few sketchy facts and ask, ``Does this ring a
25956 bell?'' Those bug reports are useless, and we urge everyone to
25957 @emph{refuse to respond to them} except to chide the sender to report
25960 To enable us to fix the bug, you should include all these things:
25964 The version of @value{GDBN}. @value{GDBN} announces it if you start
25965 with no arguments; you can also print it at any time using @code{show
25968 Without this, we will not know whether there is any point in looking for
25969 the bug in the current version of @value{GDBN}.
25972 The type of machine you are using, and the operating system name and
25976 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
25977 ``@value{GCC}--2.8.1''.
25980 What compiler (and its version) was used to compile the program you are
25981 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
25982 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
25983 to get this information; for other compilers, see the documentation for
25987 The command arguments you gave the compiler to compile your example and
25988 observe the bug. For example, did you use @samp{-O}? To guarantee
25989 you will not omit something important, list them all. A copy of the
25990 Makefile (or the output from make) is sufficient.
25992 If we were to try to guess the arguments, we would probably guess wrong
25993 and then we might not encounter the bug.
25996 A complete input script, and all necessary source files, that will
26000 A description of what behavior you observe that you believe is
26001 incorrect. For example, ``It gets a fatal signal.''
26003 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
26004 will certainly notice it. But if the bug is incorrect output, we might
26005 not notice unless it is glaringly wrong. You might as well not give us
26006 a chance to make a mistake.
26008 Even if the problem you experience is a fatal signal, you should still
26009 say so explicitly. Suppose something strange is going on, such as, your
26010 copy of @value{GDBN} is out of synch, or you have encountered a bug in
26011 the C library on your system. (This has happened!) Your copy might
26012 crash and ours would not. If you told us to expect a crash, then when
26013 ours fails to crash, we would know that the bug was not happening for
26014 us. If you had not told us to expect a crash, then we would not be able
26015 to draw any conclusion from our observations.
26018 @cindex recording a session script
26019 To collect all this information, you can use a session recording program
26020 such as @command{script}, which is available on many Unix systems.
26021 Just run your @value{GDBN} session inside @command{script} and then
26022 include the @file{typescript} file with your bug report.
26024 Another way to record a @value{GDBN} session is to run @value{GDBN}
26025 inside Emacs and then save the entire buffer to a file.
26028 If you wish to suggest changes to the @value{GDBN} source, send us context
26029 diffs. If you even discuss something in the @value{GDBN} source, refer to
26030 it by context, not by line number.
26032 The line numbers in our development sources will not match those in your
26033 sources. Your line numbers would convey no useful information to us.
26037 Here are some things that are not necessary:
26041 A description of the envelope of the bug.
26043 Often people who encounter a bug spend a lot of time investigating
26044 which changes to the input file will make the bug go away and which
26045 changes will not affect it.
26047 This is often time consuming and not very useful, because the way we
26048 will find the bug is by running a single example under the debugger
26049 with breakpoints, not by pure deduction from a series of examples.
26050 We recommend that you save your time for something else.
26052 Of course, if you can find a simpler example to report @emph{instead}
26053 of the original one, that is a convenience for us. Errors in the
26054 output will be easier to spot, running under the debugger will take
26055 less time, and so on.
26057 However, simplification is not vital; if you do not want to do this,
26058 report the bug anyway and send us the entire test case you used.
26061 A patch for the bug.
26063 A patch for the bug does help us if it is a good one. But do not omit
26064 the necessary information, such as the test case, on the assumption that
26065 a patch is all we need. We might see problems with your patch and decide
26066 to fix the problem another way, or we might not understand it at all.
26068 Sometimes with a program as complicated as @value{GDBN} it is very hard to
26069 construct an example that will make the program follow a certain path
26070 through the code. If you do not send us the example, we will not be able
26071 to construct one, so we will not be able to verify that the bug is fixed.
26073 And if we cannot understand what bug you are trying to fix, or why your
26074 patch should be an improvement, we will not install it. A test case will
26075 help us to understand.
26078 A guess about what the bug is or what it depends on.
26080 Such guesses are usually wrong. Even we cannot guess right about such
26081 things without first using the debugger to find the facts.
26084 @c The readline documentation is distributed with the readline code
26085 @c and consists of the two following files:
26087 @c inc-hist.texinfo
26088 @c Use -I with makeinfo to point to the appropriate directory,
26089 @c environment var TEXINPUTS with TeX.
26090 @include rluser.texi
26091 @include inc-hist.texinfo
26094 @node Formatting Documentation
26095 @appendix Formatting Documentation
26097 @cindex @value{GDBN} reference card
26098 @cindex reference card
26099 The @value{GDBN} 4 release includes an already-formatted reference card, ready
26100 for printing with PostScript or Ghostscript, in the @file{gdb}
26101 subdirectory of the main source directory@footnote{In
26102 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
26103 release.}. If you can use PostScript or Ghostscript with your printer,
26104 you can print the reference card immediately with @file{refcard.ps}.
26106 The release also includes the source for the reference card. You
26107 can format it, using @TeX{}, by typing:
26113 The @value{GDBN} reference card is designed to print in @dfn{landscape}
26114 mode on US ``letter'' size paper;
26115 that is, on a sheet 11 inches wide by 8.5 inches
26116 high. You will need to specify this form of printing as an option to
26117 your @sc{dvi} output program.
26119 @cindex documentation
26121 All the documentation for @value{GDBN} comes as part of the machine-readable
26122 distribution. The documentation is written in Texinfo format, which is
26123 a documentation system that uses a single source file to produce both
26124 on-line information and a printed manual. You can use one of the Info
26125 formatting commands to create the on-line version of the documentation
26126 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
26128 @value{GDBN} includes an already formatted copy of the on-line Info
26129 version of this manual in the @file{gdb} subdirectory. The main Info
26130 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
26131 subordinate files matching @samp{gdb.info*} in the same directory. If
26132 necessary, you can print out these files, or read them with any editor;
26133 but they are easier to read using the @code{info} subsystem in @sc{gnu}
26134 Emacs or the standalone @code{info} program, available as part of the
26135 @sc{gnu} Texinfo distribution.
26137 If you want to format these Info files yourself, you need one of the
26138 Info formatting programs, such as @code{texinfo-format-buffer} or
26141 If you have @code{makeinfo} installed, and are in the top level
26142 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
26143 version @value{GDBVN}), you can make the Info file by typing:
26150 If you want to typeset and print copies of this manual, you need @TeX{},
26151 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
26152 Texinfo definitions file.
26154 @TeX{} is a typesetting program; it does not print files directly, but
26155 produces output files called @sc{dvi} files. To print a typeset
26156 document, you need a program to print @sc{dvi} files. If your system
26157 has @TeX{} installed, chances are it has such a program. The precise
26158 command to use depends on your system; @kbd{lpr -d} is common; another
26159 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
26160 require a file name without any extension or a @samp{.dvi} extension.
26162 @TeX{} also requires a macro definitions file called
26163 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
26164 written in Texinfo format. On its own, @TeX{} cannot either read or
26165 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
26166 and is located in the @file{gdb-@var{version-number}/texinfo}
26169 If you have @TeX{} and a @sc{dvi} printer program installed, you can
26170 typeset and print this manual. First switch to the @file{gdb}
26171 subdirectory of the main source directory (for example, to
26172 @file{gdb-@value{GDBVN}/gdb}) and type:
26178 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
26180 @node Installing GDB
26181 @appendix Installing @value{GDBN}
26182 @cindex installation
26185 * Requirements:: Requirements for building @value{GDBN}
26186 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
26187 * Separate Objdir:: Compiling @value{GDBN} in another directory
26188 * Config Names:: Specifying names for hosts and targets
26189 * Configure Options:: Summary of options for configure
26190 * System-wide configuration:: Having a system-wide init file
26194 @section Requirements for Building @value{GDBN}
26195 @cindex building @value{GDBN}, requirements for
26197 Building @value{GDBN} requires various tools and packages to be available.
26198 Other packages will be used only if they are found.
26200 @heading Tools/Packages Necessary for Building @value{GDBN}
26202 @item ISO C90 compiler
26203 @value{GDBN} is written in ISO C90. It should be buildable with any
26204 working C90 compiler, e.g.@: GCC.
26208 @heading Tools/Packages Optional for Building @value{GDBN}
26212 @value{GDBN} can use the Expat XML parsing library. This library may be
26213 included with your operating system distribution; if it is not, you
26214 can get the latest version from @url{http://expat.sourceforge.net}.
26215 The @file{configure} script will search for this library in several
26216 standard locations; if it is installed in an unusual path, you can
26217 use the @option{--with-libexpat-prefix} option to specify its location.
26223 Remote protocol memory maps (@pxref{Memory Map Format})
26225 Target descriptions (@pxref{Target Descriptions})
26227 Remote shared library lists (@pxref{Library List Format})
26229 MS-Windows shared libraries (@pxref{Shared Libraries})
26233 @cindex compressed debug sections
26234 @value{GDBN} will use the @samp{zlib} library, if available, to read
26235 compressed debug sections. Some linkers, such as GNU gold, are capable
26236 of producing binaries with compressed debug sections. If @value{GDBN}
26237 is compiled with @samp{zlib}, it will be able to read the debug
26238 information in such binaries.
26240 The @samp{zlib} library is likely included with your operating system
26241 distribution; if it is not, you can get the latest version from
26242 @url{http://zlib.net}.
26245 @value{GDBN}'s features related to character sets (@pxref{Character
26246 Sets}) require a functioning @code{iconv} implementation. If you are
26247 on a GNU system, then this is provided by the GNU C Library. Some
26248 other systems also provide a working @code{iconv}.
26250 On systems with @code{iconv}, you can install GNU Libiconv. If you
26251 have previously installed Libiconv, you can use the
26252 @option{--with-libiconv-prefix} option to configure.
26254 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
26255 arrange to build Libiconv if a directory named @file{libiconv} appears
26256 in the top-most source directory. If Libiconv is built this way, and
26257 if the operating system does not provide a suitable @code{iconv}
26258 implementation, then the just-built library will automatically be used
26259 by @value{GDBN}. One easy way to set this up is to download GNU
26260 Libiconv, unpack it, and then rename the directory holding the
26261 Libiconv source code to @samp{libiconv}.
26264 @node Running Configure
26265 @section Invoking the @value{GDBN} @file{configure} Script
26266 @cindex configuring @value{GDBN}
26267 @value{GDBN} comes with a @file{configure} script that automates the process
26268 of preparing @value{GDBN} for installation; you can then use @code{make} to
26269 build the @code{gdb} program.
26271 @c irrelevant in info file; it's as current as the code it lives with.
26272 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
26273 look at the @file{README} file in the sources; we may have improved the
26274 installation procedures since publishing this manual.}
26277 The @value{GDBN} distribution includes all the source code you need for
26278 @value{GDBN} in a single directory, whose name is usually composed by
26279 appending the version number to @samp{gdb}.
26281 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
26282 @file{gdb-@value{GDBVN}} directory. That directory contains:
26285 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
26286 script for configuring @value{GDBN} and all its supporting libraries
26288 @item gdb-@value{GDBVN}/gdb
26289 the source specific to @value{GDBN} itself
26291 @item gdb-@value{GDBVN}/bfd
26292 source for the Binary File Descriptor library
26294 @item gdb-@value{GDBVN}/include
26295 @sc{gnu} include files
26297 @item gdb-@value{GDBVN}/libiberty
26298 source for the @samp{-liberty} free software library
26300 @item gdb-@value{GDBVN}/opcodes
26301 source for the library of opcode tables and disassemblers
26303 @item gdb-@value{GDBVN}/readline
26304 source for the @sc{gnu} command-line interface
26306 @item gdb-@value{GDBVN}/glob
26307 source for the @sc{gnu} filename pattern-matching subroutine
26309 @item gdb-@value{GDBVN}/mmalloc
26310 source for the @sc{gnu} memory-mapped malloc package
26313 The simplest way to configure and build @value{GDBN} is to run @file{configure}
26314 from the @file{gdb-@var{version-number}} source directory, which in
26315 this example is the @file{gdb-@value{GDBVN}} directory.
26317 First switch to the @file{gdb-@var{version-number}} source directory
26318 if you are not already in it; then run @file{configure}. Pass the
26319 identifier for the platform on which @value{GDBN} will run as an
26325 cd gdb-@value{GDBVN}
26326 ./configure @var{host}
26331 where @var{host} is an identifier such as @samp{sun4} or
26332 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
26333 (You can often leave off @var{host}; @file{configure} tries to guess the
26334 correct value by examining your system.)
26336 Running @samp{configure @var{host}} and then running @code{make} builds the
26337 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
26338 libraries, then @code{gdb} itself. The configured source files, and the
26339 binaries, are left in the corresponding source directories.
26342 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
26343 system does not recognize this automatically when you run a different
26344 shell, you may need to run @code{sh} on it explicitly:
26347 sh configure @var{host}
26350 If you run @file{configure} from a directory that contains source
26351 directories for multiple libraries or programs, such as the
26352 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
26354 creates configuration files for every directory level underneath (unless
26355 you tell it not to, with the @samp{--norecursion} option).
26357 You should run the @file{configure} script from the top directory in the
26358 source tree, the @file{gdb-@var{version-number}} directory. If you run
26359 @file{configure} from one of the subdirectories, you will configure only
26360 that subdirectory. That is usually not what you want. In particular,
26361 if you run the first @file{configure} from the @file{gdb} subdirectory
26362 of the @file{gdb-@var{version-number}} directory, you will omit the
26363 configuration of @file{bfd}, @file{readline}, and other sibling
26364 directories of the @file{gdb} subdirectory. This leads to build errors
26365 about missing include files such as @file{bfd/bfd.h}.
26367 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
26368 However, you should make sure that the shell on your path (named by
26369 the @samp{SHELL} environment variable) is publicly readable. Remember
26370 that @value{GDBN} uses the shell to start your program---some systems refuse to
26371 let @value{GDBN} debug child processes whose programs are not readable.
26373 @node Separate Objdir
26374 @section Compiling @value{GDBN} in Another Directory
26376 If you want to run @value{GDBN} versions for several host or target machines,
26377 you need a different @code{gdb} compiled for each combination of
26378 host and target. @file{configure} is designed to make this easy by
26379 allowing you to generate each configuration in a separate subdirectory,
26380 rather than in the source directory. If your @code{make} program
26381 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
26382 @code{make} in each of these directories builds the @code{gdb}
26383 program specified there.
26385 To build @code{gdb} in a separate directory, run @file{configure}
26386 with the @samp{--srcdir} option to specify where to find the source.
26387 (You also need to specify a path to find @file{configure}
26388 itself from your working directory. If the path to @file{configure}
26389 would be the same as the argument to @samp{--srcdir}, you can leave out
26390 the @samp{--srcdir} option; it is assumed.)
26392 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
26393 separate directory for a Sun 4 like this:
26397 cd gdb-@value{GDBVN}
26400 ../gdb-@value{GDBVN}/configure sun4
26405 When @file{configure} builds a configuration using a remote source
26406 directory, it creates a tree for the binaries with the same structure
26407 (and using the same names) as the tree under the source directory. In
26408 the example, you'd find the Sun 4 library @file{libiberty.a} in the
26409 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
26410 @file{gdb-sun4/gdb}.
26412 Make sure that your path to the @file{configure} script has just one
26413 instance of @file{gdb} in it. If your path to @file{configure} looks
26414 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
26415 one subdirectory of @value{GDBN}, not the whole package. This leads to
26416 build errors about missing include files such as @file{bfd/bfd.h}.
26418 One popular reason to build several @value{GDBN} configurations in separate
26419 directories is to configure @value{GDBN} for cross-compiling (where
26420 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
26421 programs that run on another machine---the @dfn{target}).
26422 You specify a cross-debugging target by
26423 giving the @samp{--target=@var{target}} option to @file{configure}.
26425 When you run @code{make} to build a program or library, you must run
26426 it in a configured directory---whatever directory you were in when you
26427 called @file{configure} (or one of its subdirectories).
26429 The @code{Makefile} that @file{configure} generates in each source
26430 directory also runs recursively. If you type @code{make} in a source
26431 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
26432 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
26433 will build all the required libraries, and then build GDB.
26435 When you have multiple hosts or targets configured in separate
26436 directories, you can run @code{make} on them in parallel (for example,
26437 if they are NFS-mounted on each of the hosts); they will not interfere
26441 @section Specifying Names for Hosts and Targets
26443 The specifications used for hosts and targets in the @file{configure}
26444 script are based on a three-part naming scheme, but some short predefined
26445 aliases are also supported. The full naming scheme encodes three pieces
26446 of information in the following pattern:
26449 @var{architecture}-@var{vendor}-@var{os}
26452 For example, you can use the alias @code{sun4} as a @var{host} argument,
26453 or as the value for @var{target} in a @code{--target=@var{target}}
26454 option. The equivalent full name is @samp{sparc-sun-sunos4}.
26456 The @file{configure} script accompanying @value{GDBN} does not provide
26457 any query facility to list all supported host and target names or
26458 aliases. @file{configure} calls the Bourne shell script
26459 @code{config.sub} to map abbreviations to full names; you can read the
26460 script, if you wish, or you can use it to test your guesses on
26461 abbreviations---for example:
26464 % sh config.sub i386-linux
26466 % sh config.sub alpha-linux
26467 alpha-unknown-linux-gnu
26468 % sh config.sub hp9k700
26470 % sh config.sub sun4
26471 sparc-sun-sunos4.1.1
26472 % sh config.sub sun3
26473 m68k-sun-sunos4.1.1
26474 % sh config.sub i986v
26475 Invalid configuration `i986v': machine `i986v' not recognized
26479 @code{config.sub} is also distributed in the @value{GDBN} source
26480 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
26482 @node Configure Options
26483 @section @file{configure} Options
26485 Here is a summary of the @file{configure} options and arguments that
26486 are most often useful for building @value{GDBN}. @file{configure} also has
26487 several other options not listed here. @inforef{What Configure
26488 Does,,configure.info}, for a full explanation of @file{configure}.
26491 configure @r{[}--help@r{]}
26492 @r{[}--prefix=@var{dir}@r{]}
26493 @r{[}--exec-prefix=@var{dir}@r{]}
26494 @r{[}--srcdir=@var{dirname}@r{]}
26495 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
26496 @r{[}--target=@var{target}@r{]}
26501 You may introduce options with a single @samp{-} rather than
26502 @samp{--} if you prefer; but you may abbreviate option names if you use
26507 Display a quick summary of how to invoke @file{configure}.
26509 @item --prefix=@var{dir}
26510 Configure the source to install programs and files under directory
26513 @item --exec-prefix=@var{dir}
26514 Configure the source to install programs under directory
26517 @c avoid splitting the warning from the explanation:
26519 @item --srcdir=@var{dirname}
26520 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
26521 @code{make} that implements the @code{VPATH} feature.}@*
26522 Use this option to make configurations in directories separate from the
26523 @value{GDBN} source directories. Among other things, you can use this to
26524 build (or maintain) several configurations simultaneously, in separate
26525 directories. @file{configure} writes configuration-specific files in
26526 the current directory, but arranges for them to use the source in the
26527 directory @var{dirname}. @file{configure} creates directories under
26528 the working directory in parallel to the source directories below
26531 @item --norecursion
26532 Configure only the directory level where @file{configure} is executed; do not
26533 propagate configuration to subdirectories.
26535 @item --target=@var{target}
26536 Configure @value{GDBN} for cross-debugging programs running on the specified
26537 @var{target}. Without this option, @value{GDBN} is configured to debug
26538 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
26540 There is no convenient way to generate a list of all available targets.
26542 @item @var{host} @dots{}
26543 Configure @value{GDBN} to run on the specified @var{host}.
26545 There is no convenient way to generate a list of all available hosts.
26548 There are many other options available as well, but they are generally
26549 needed for special purposes only.
26551 @node System-wide configuration
26552 @section System-wide configuration and settings
26553 @cindex system-wide init file
26555 @value{GDBN} can be configured to have a system-wide init file;
26556 this file will be read and executed at startup (@pxref{Startup, , What
26557 @value{GDBN} does during startup}).
26559 Here is the corresponding configure option:
26562 @item --with-system-gdbinit=@var{file}
26563 Specify that the default location of the system-wide init file is
26567 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
26568 it may be subject to relocation. Two possible cases:
26572 If the default location of this init file contains @file{$prefix},
26573 it will be subject to relocation. Suppose that the configure options
26574 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
26575 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
26576 init file is looked for as @file{$install/etc/gdbinit} instead of
26577 @file{$prefix/etc/gdbinit}.
26580 By contrast, if the default location does not contain the prefix,
26581 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
26582 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
26583 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
26584 wherever @value{GDBN} is installed.
26587 @node Maintenance Commands
26588 @appendix Maintenance Commands
26589 @cindex maintenance commands
26590 @cindex internal commands
26592 In addition to commands intended for @value{GDBN} users, @value{GDBN}
26593 includes a number of commands intended for @value{GDBN} developers,
26594 that are not documented elsewhere in this manual. These commands are
26595 provided here for reference. (For commands that turn on debugging
26596 messages, see @ref{Debugging Output}.)
26599 @kindex maint agent
26600 @kindex maint agent-eval
26601 @item maint agent @var{expression}
26602 @itemx maint agent-eval @var{expression}
26603 Translate the given @var{expression} into remote agent bytecodes.
26604 This command is useful for debugging the Agent Expression mechanism
26605 (@pxref{Agent Expressions}). The @samp{agent} version produces an
26606 expression useful for data collection, such as by tracepoints, while
26607 @samp{maint agent-eval} produces an expression that evaluates directly
26608 to a result. For instance, a collection expression for @code{globa +
26609 globb} will include bytecodes to record four bytes of memory at each
26610 of the addresses of @code{globa} and @code{globb}, while discarding
26611 the result of the addition, while an evaluation expression will do the
26612 addition and return the sum.
26614 @kindex maint info breakpoints
26615 @item @anchor{maint info breakpoints}maint info breakpoints
26616 Using the same format as @samp{info breakpoints}, display both the
26617 breakpoints you've set explicitly, and those @value{GDBN} is using for
26618 internal purposes. Internal breakpoints are shown with negative
26619 breakpoint numbers. The type column identifies what kind of breakpoint
26624 Normal, explicitly set breakpoint.
26627 Normal, explicitly set watchpoint.
26630 Internal breakpoint, used to handle correctly stepping through
26631 @code{longjmp} calls.
26633 @item longjmp resume
26634 Internal breakpoint at the target of a @code{longjmp}.
26637 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
26640 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
26643 Shared library events.
26647 @kindex set displaced-stepping
26648 @kindex show displaced-stepping
26649 @cindex displaced stepping support
26650 @cindex out-of-line single-stepping
26651 @item set displaced-stepping
26652 @itemx show displaced-stepping
26653 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
26654 if the target supports it. Displaced stepping is a way to single-step
26655 over breakpoints without removing them from the inferior, by executing
26656 an out-of-line copy of the instruction that was originally at the
26657 breakpoint location. It is also known as out-of-line single-stepping.
26660 @item set displaced-stepping on
26661 If the target architecture supports it, @value{GDBN} will use
26662 displaced stepping to step over breakpoints.
26664 @item set displaced-stepping off
26665 @value{GDBN} will not use displaced stepping to step over breakpoints,
26666 even if such is supported by the target architecture.
26668 @cindex non-stop mode, and @samp{set displaced-stepping}
26669 @item set displaced-stepping auto
26670 This is the default mode. @value{GDBN} will use displaced stepping
26671 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
26672 architecture supports displaced stepping.
26675 @kindex maint check-symtabs
26676 @item maint check-symtabs
26677 Check the consistency of psymtabs and symtabs.
26679 @kindex maint cplus first_component
26680 @item maint cplus first_component @var{name}
26681 Print the first C@t{++} class/namespace component of @var{name}.
26683 @kindex maint cplus namespace
26684 @item maint cplus namespace
26685 Print the list of possible C@t{++} namespaces.
26687 @kindex maint demangle
26688 @item maint demangle @var{name}
26689 Demangle a C@t{++} or Objective-C mangled @var{name}.
26691 @kindex maint deprecate
26692 @kindex maint undeprecate
26693 @cindex deprecated commands
26694 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
26695 @itemx maint undeprecate @var{command}
26696 Deprecate or undeprecate the named @var{command}. Deprecated commands
26697 cause @value{GDBN} to issue a warning when you use them. The optional
26698 argument @var{replacement} says which newer command should be used in
26699 favor of the deprecated one; if it is given, @value{GDBN} will mention
26700 the replacement as part of the warning.
26702 @kindex maint dump-me
26703 @item maint dump-me
26704 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
26705 Cause a fatal signal in the debugger and force it to dump its core.
26706 This is supported only on systems which support aborting a program
26707 with the @code{SIGQUIT} signal.
26709 @kindex maint internal-error
26710 @kindex maint internal-warning
26711 @item maint internal-error @r{[}@var{message-text}@r{]}
26712 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
26713 Cause @value{GDBN} to call the internal function @code{internal_error}
26714 or @code{internal_warning} and hence behave as though an internal error
26715 or internal warning has been detected. In addition to reporting the
26716 internal problem, these functions give the user the opportunity to
26717 either quit @value{GDBN} or create a core file of the current
26718 @value{GDBN} session.
26720 These commands take an optional parameter @var{message-text} that is
26721 used as the text of the error or warning message.
26723 Here's an example of using @code{internal-error}:
26726 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
26727 @dots{}/maint.c:121: internal-error: testing, 1, 2
26728 A problem internal to GDB has been detected. Further
26729 debugging may prove unreliable.
26730 Quit this debugging session? (y or n) @kbd{n}
26731 Create a core file? (y or n) @kbd{n}
26735 @cindex @value{GDBN} internal error
26736 @cindex internal errors, control of @value{GDBN} behavior
26738 @kindex maint set internal-error
26739 @kindex maint show internal-error
26740 @kindex maint set internal-warning
26741 @kindex maint show internal-warning
26742 @item maint set internal-error @var{action} [ask|yes|no]
26743 @itemx maint show internal-error @var{action}
26744 @itemx maint set internal-warning @var{action} [ask|yes|no]
26745 @itemx maint show internal-warning @var{action}
26746 When @value{GDBN} reports an internal problem (error or warning) it
26747 gives the user the opportunity to both quit @value{GDBN} and create a
26748 core file of the current @value{GDBN} session. These commands let you
26749 override the default behaviour for each particular @var{action},
26750 described in the table below.
26754 You can specify that @value{GDBN} should always (yes) or never (no)
26755 quit. The default is to ask the user what to do.
26758 You can specify that @value{GDBN} should always (yes) or never (no)
26759 create a core file. The default is to ask the user what to do.
26762 @kindex maint packet
26763 @item maint packet @var{text}
26764 If @value{GDBN} is talking to an inferior via the serial protocol,
26765 then this command sends the string @var{text} to the inferior, and
26766 displays the response packet. @value{GDBN} supplies the initial
26767 @samp{$} character, the terminating @samp{#} character, and the
26770 @kindex maint print architecture
26771 @item maint print architecture @r{[}@var{file}@r{]}
26772 Print the entire architecture configuration. The optional argument
26773 @var{file} names the file where the output goes.
26775 @kindex maint print c-tdesc
26776 @item maint print c-tdesc
26777 Print the current target description (@pxref{Target Descriptions}) as
26778 a C source file. The created source file can be used in @value{GDBN}
26779 when an XML parser is not available to parse the description.
26781 @kindex maint print dummy-frames
26782 @item maint print dummy-frames
26783 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
26786 (@value{GDBP}) @kbd{b add}
26788 (@value{GDBP}) @kbd{print add(2,3)}
26789 Breakpoint 2, add (a=2, b=3) at @dots{}
26791 The program being debugged stopped while in a function called from GDB.
26793 (@value{GDBP}) @kbd{maint print dummy-frames}
26794 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
26795 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
26796 call_lo=0x01014000 call_hi=0x01014001
26800 Takes an optional file parameter.
26802 @kindex maint print registers
26803 @kindex maint print raw-registers
26804 @kindex maint print cooked-registers
26805 @kindex maint print register-groups
26806 @item maint print registers @r{[}@var{file}@r{]}
26807 @itemx maint print raw-registers @r{[}@var{file}@r{]}
26808 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
26809 @itemx maint print register-groups @r{[}@var{file}@r{]}
26810 Print @value{GDBN}'s internal register data structures.
26812 The command @code{maint print raw-registers} includes the contents of
26813 the raw register cache; the command @code{maint print cooked-registers}
26814 includes the (cooked) value of all registers; and the command
26815 @code{maint print register-groups} includes the groups that each
26816 register is a member of. @xref{Registers,, Registers, gdbint,
26817 @value{GDBN} Internals}.
26819 These commands take an optional parameter, a file name to which to
26820 write the information.
26822 @kindex maint print reggroups
26823 @item maint print reggroups @r{[}@var{file}@r{]}
26824 Print @value{GDBN}'s internal register group data structures. The
26825 optional argument @var{file} tells to what file to write the
26828 The register groups info looks like this:
26831 (@value{GDBP}) @kbd{maint print reggroups}
26844 This command forces @value{GDBN} to flush its internal register cache.
26846 @kindex maint print objfiles
26847 @cindex info for known object files
26848 @item maint print objfiles
26849 Print a dump of all known object files. For each object file, this
26850 command prints its name, address in memory, and all of its psymtabs
26853 @kindex maint print statistics
26854 @cindex bcache statistics
26855 @item maint print statistics
26856 This command prints, for each object file in the program, various data
26857 about that object file followed by the byte cache (@dfn{bcache})
26858 statistics for the object file. The objfile data includes the number
26859 of minimal, partial, full, and stabs symbols, the number of types
26860 defined by the objfile, the number of as yet unexpanded psym tables,
26861 the number of line tables and string tables, and the amount of memory
26862 used by the various tables. The bcache statistics include the counts,
26863 sizes, and counts of duplicates of all and unique objects, max,
26864 average, and median entry size, total memory used and its overhead and
26865 savings, and various measures of the hash table size and chain
26868 @kindex maint print target-stack
26869 @cindex target stack description
26870 @item maint print target-stack
26871 A @dfn{target} is an interface between the debugger and a particular
26872 kind of file or process. Targets can be stacked in @dfn{strata},
26873 so that more than one target can potentially respond to a request.
26874 In particular, memory accesses will walk down the stack of targets
26875 until they find a target that is interested in handling that particular
26878 This command prints a short description of each layer that was pushed on
26879 the @dfn{target stack}, starting from the top layer down to the bottom one.
26881 @kindex maint print type
26882 @cindex type chain of a data type
26883 @item maint print type @var{expr}
26884 Print the type chain for a type specified by @var{expr}. The argument
26885 can be either a type name or a symbol. If it is a symbol, the type of
26886 that symbol is described. The type chain produced by this command is
26887 a recursive definition of the data type as stored in @value{GDBN}'s
26888 data structures, including its flags and contained types.
26890 @kindex maint set dwarf2 max-cache-age
26891 @kindex maint show dwarf2 max-cache-age
26892 @item maint set dwarf2 max-cache-age
26893 @itemx maint show dwarf2 max-cache-age
26894 Control the DWARF 2 compilation unit cache.
26896 @cindex DWARF 2 compilation units cache
26897 In object files with inter-compilation-unit references, such as those
26898 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
26899 reader needs to frequently refer to previously read compilation units.
26900 This setting controls how long a compilation unit will remain in the
26901 cache if it is not referenced. A higher limit means that cached
26902 compilation units will be stored in memory longer, and more total
26903 memory will be used. Setting it to zero disables caching, which will
26904 slow down @value{GDBN} startup, but reduce memory consumption.
26906 @kindex maint set profile
26907 @kindex maint show profile
26908 @cindex profiling GDB
26909 @item maint set profile
26910 @itemx maint show profile
26911 Control profiling of @value{GDBN}.
26913 Profiling will be disabled until you use the @samp{maint set profile}
26914 command to enable it. When you enable profiling, the system will begin
26915 collecting timing and execution count data; when you disable profiling or
26916 exit @value{GDBN}, the results will be written to a log file. Remember that
26917 if you use profiling, @value{GDBN} will overwrite the profiling log file
26918 (often called @file{gmon.out}). If you have a record of important profiling
26919 data in a @file{gmon.out} file, be sure to move it to a safe location.
26921 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
26922 compiled with the @samp{-pg} compiler option.
26924 @kindex maint set show-debug-regs
26925 @kindex maint show show-debug-regs
26926 @cindex hardware debug registers
26927 @item maint set show-debug-regs
26928 @itemx maint show show-debug-regs
26929 Control whether to show variables that mirror the hardware debug
26930 registers. Use @code{ON} to enable, @code{OFF} to disable. If
26931 enabled, the debug registers values are shown when @value{GDBN} inserts or
26932 removes a hardware breakpoint or watchpoint, and when the inferior
26933 triggers a hardware-assisted breakpoint or watchpoint.
26935 @kindex maint space
26936 @cindex memory used by commands
26938 Control whether to display memory usage for each command. If set to a
26939 nonzero value, @value{GDBN} will display how much memory each command
26940 took, following the command's own output. This can also be requested
26941 by invoking @value{GDBN} with the @option{--statistics} command-line
26942 switch (@pxref{Mode Options}).
26945 @cindex time of command execution
26947 Control whether to display the execution time for each command. If
26948 set to a nonzero value, @value{GDBN} will display how much time it
26949 took to execute each command, following the command's own output.
26950 The time is not printed for the commands that run the target, since
26951 there's no mechanism currently to compute how much time was spend
26952 by @value{GDBN} and how much time was spend by the program been debugged.
26953 it's not possibly currently
26954 This can also be requested by invoking @value{GDBN} with the
26955 @option{--statistics} command-line switch (@pxref{Mode Options}).
26957 @kindex maint translate-address
26958 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
26959 Find the symbol stored at the location specified by the address
26960 @var{addr} and an optional section name @var{section}. If found,
26961 @value{GDBN} prints the name of the closest symbol and an offset from
26962 the symbol's location to the specified address. This is similar to
26963 the @code{info address} command (@pxref{Symbols}), except that this
26964 command also allows to find symbols in other sections.
26966 If section was not specified, the section in which the symbol was found
26967 is also printed. For dynamically linked executables, the name of
26968 executable or shared library containing the symbol is printed as well.
26972 The following command is useful for non-interactive invocations of
26973 @value{GDBN}, such as in the test suite.
26976 @item set watchdog @var{nsec}
26977 @kindex set watchdog
26978 @cindex watchdog timer
26979 @cindex timeout for commands
26980 Set the maximum number of seconds @value{GDBN} will wait for the
26981 target operation to finish. If this time expires, @value{GDBN}
26982 reports and error and the command is aborted.
26984 @item show watchdog
26985 Show the current setting of the target wait timeout.
26988 @node Remote Protocol
26989 @appendix @value{GDBN} Remote Serial Protocol
26994 * Stop Reply Packets::
26995 * General Query Packets::
26996 * Register Packet Format::
26997 * Tracepoint Packets::
26998 * Host I/O Packets::
27000 * Notification Packets::
27001 * Remote Non-Stop::
27002 * Packet Acknowledgment::
27004 * File-I/O Remote Protocol Extension::
27005 * Library List Format::
27006 * Memory Map Format::
27012 There may be occasions when you need to know something about the
27013 protocol---for example, if there is only one serial port to your target
27014 machine, you might want your program to do something special if it
27015 recognizes a packet meant for @value{GDBN}.
27017 In the examples below, @samp{->} and @samp{<-} are used to indicate
27018 transmitted and received data, respectively.
27020 @cindex protocol, @value{GDBN} remote serial
27021 @cindex serial protocol, @value{GDBN} remote
27022 @cindex remote serial protocol
27023 All @value{GDBN} commands and responses (other than acknowledgments
27024 and notifications, see @ref{Notification Packets}) are sent as a
27025 @var{packet}. A @var{packet} is introduced with the character
27026 @samp{$}, the actual @var{packet-data}, and the terminating character
27027 @samp{#} followed by a two-digit @var{checksum}:
27030 @code{$}@var{packet-data}@code{#}@var{checksum}
27034 @cindex checksum, for @value{GDBN} remote
27036 The two-digit @var{checksum} is computed as the modulo 256 sum of all
27037 characters between the leading @samp{$} and the trailing @samp{#} (an
27038 eight bit unsigned checksum).
27040 Implementors should note that prior to @value{GDBN} 5.0 the protocol
27041 specification also included an optional two-digit @var{sequence-id}:
27044 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
27047 @cindex sequence-id, for @value{GDBN} remote
27049 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
27050 has never output @var{sequence-id}s. Stubs that handle packets added
27051 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
27053 When either the host or the target machine receives a packet, the first
27054 response expected is an acknowledgment: either @samp{+} (to indicate
27055 the package was received correctly) or @samp{-} (to request
27059 -> @code{$}@var{packet-data}@code{#}@var{checksum}
27064 The @samp{+}/@samp{-} acknowledgments can be disabled
27065 once a connection is established.
27066 @xref{Packet Acknowledgment}, for details.
27068 The host (@value{GDBN}) sends @var{command}s, and the target (the
27069 debugging stub incorporated in your program) sends a @var{response}. In
27070 the case of step and continue @var{command}s, the response is only sent
27071 when the operation has completed, and the target has again stopped all
27072 threads in all attached processes. This is the default all-stop mode
27073 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
27074 execution mode; see @ref{Remote Non-Stop}, for details.
27076 @var{packet-data} consists of a sequence of characters with the
27077 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
27080 @cindex remote protocol, field separator
27081 Fields within the packet should be separated using @samp{,} @samp{;} or
27082 @samp{:}. Except where otherwise noted all numbers are represented in
27083 @sc{hex} with leading zeros suppressed.
27085 Implementors should note that prior to @value{GDBN} 5.0, the character
27086 @samp{:} could not appear as the third character in a packet (as it
27087 would potentially conflict with the @var{sequence-id}).
27089 @cindex remote protocol, binary data
27090 @anchor{Binary Data}
27091 Binary data in most packets is encoded either as two hexadecimal
27092 digits per byte of binary data. This allowed the traditional remote
27093 protocol to work over connections which were only seven-bit clean.
27094 Some packets designed more recently assume an eight-bit clean
27095 connection, and use a more efficient encoding to send and receive
27098 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
27099 as an escape character. Any escaped byte is transmitted as the escape
27100 character followed by the original character XORed with @code{0x20}.
27101 For example, the byte @code{0x7d} would be transmitted as the two
27102 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
27103 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
27104 @samp{@}}) must always be escaped. Responses sent by the stub
27105 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
27106 is not interpreted as the start of a run-length encoded sequence
27109 Response @var{data} can be run-length encoded to save space.
27110 Run-length encoding replaces runs of identical characters with one
27111 instance of the repeated character, followed by a @samp{*} and a
27112 repeat count. The repeat count is itself sent encoded, to avoid
27113 binary characters in @var{data}: a value of @var{n} is sent as
27114 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
27115 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
27116 code 32) for a repeat count of 3. (This is because run-length
27117 encoding starts to win for counts 3 or more.) Thus, for example,
27118 @samp{0* } is a run-length encoding of ``0000'': the space character
27119 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
27122 The printable characters @samp{#} and @samp{$} or with a numeric value
27123 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
27124 seven repeats (@samp{$}) can be expanded using a repeat count of only
27125 five (@samp{"}). For example, @samp{00000000} can be encoded as
27128 The error response returned for some packets includes a two character
27129 error number. That number is not well defined.
27131 @cindex empty response, for unsupported packets
27132 For any @var{command} not supported by the stub, an empty response
27133 (@samp{$#00}) should be returned. That way it is possible to extend the
27134 protocol. A newer @value{GDBN} can tell if a packet is supported based
27137 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
27138 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
27144 The following table provides a complete list of all currently defined
27145 @var{command}s and their corresponding response @var{data}.
27146 @xref{File-I/O Remote Protocol Extension}, for details about the File
27147 I/O extension of the remote protocol.
27149 Each packet's description has a template showing the packet's overall
27150 syntax, followed by an explanation of the packet's meaning. We
27151 include spaces in some of the templates for clarity; these are not
27152 part of the packet's syntax. No @value{GDBN} packet uses spaces to
27153 separate its components. For example, a template like @samp{foo
27154 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
27155 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
27156 @var{baz}. @value{GDBN} does not transmit a space character between the
27157 @samp{foo} and the @var{bar}, or between the @var{bar} and the
27160 @cindex @var{thread-id}, in remote protocol
27161 @anchor{thread-id syntax}
27162 Several packets and replies include a @var{thread-id} field to identify
27163 a thread. Normally these are positive numbers with a target-specific
27164 interpretation, formatted as big-endian hex strings. A @var{thread-id}
27165 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
27168 In addition, the remote protocol supports a multiprocess feature in
27169 which the @var{thread-id} syntax is extended to optionally include both
27170 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
27171 The @var{pid} (process) and @var{tid} (thread) components each have the
27172 format described above: a positive number with target-specific
27173 interpretation formatted as a big-endian hex string, literal @samp{-1}
27174 to indicate all processes or threads (respectively), or @samp{0} to
27175 indicate an arbitrary process or thread. Specifying just a process, as
27176 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
27177 error to specify all processes but a specific thread, such as
27178 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
27179 for those packets and replies explicitly documented to include a process
27180 ID, rather than a @var{thread-id}.
27182 The multiprocess @var{thread-id} syntax extensions are only used if both
27183 @value{GDBN} and the stub report support for the @samp{multiprocess}
27184 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
27187 Note that all packet forms beginning with an upper- or lower-case
27188 letter, other than those described here, are reserved for future use.
27190 Here are the packet descriptions.
27195 @cindex @samp{!} packet
27196 @anchor{extended mode}
27197 Enable extended mode. In extended mode, the remote server is made
27198 persistent. The @samp{R} packet is used to restart the program being
27204 The remote target both supports and has enabled extended mode.
27208 @cindex @samp{?} packet
27209 Indicate the reason the target halted. The reply is the same as for
27210 step and continue. This packet has a special interpretation when the
27211 target is in non-stop mode; see @ref{Remote Non-Stop}.
27214 @xref{Stop Reply Packets}, for the reply specifications.
27216 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
27217 @cindex @samp{A} packet
27218 Initialized @code{argv[]} array passed into program. @var{arglen}
27219 specifies the number of bytes in the hex encoded byte stream
27220 @var{arg}. See @code{gdbserver} for more details.
27225 The arguments were set.
27231 @cindex @samp{b} packet
27232 (Don't use this packet; its behavior is not well-defined.)
27233 Change the serial line speed to @var{baud}.
27235 JTC: @emph{When does the transport layer state change? When it's
27236 received, or after the ACK is transmitted. In either case, there are
27237 problems if the command or the acknowledgment packet is dropped.}
27239 Stan: @emph{If people really wanted to add something like this, and get
27240 it working for the first time, they ought to modify ser-unix.c to send
27241 some kind of out-of-band message to a specially-setup stub and have the
27242 switch happen "in between" packets, so that from remote protocol's point
27243 of view, nothing actually happened.}
27245 @item B @var{addr},@var{mode}
27246 @cindex @samp{B} packet
27247 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
27248 breakpoint at @var{addr}.
27250 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
27251 (@pxref{insert breakpoint or watchpoint packet}).
27254 @cindex @samp{bc} packet
27255 Backward continue. Execute the target system in reverse. No parameter.
27256 @xref{Reverse Execution}, for more information.
27259 @xref{Stop Reply Packets}, for the reply specifications.
27262 @cindex @samp{bs} packet
27263 Backward single step. Execute one instruction in reverse. No parameter.
27264 @xref{Reverse Execution}, for more information.
27267 @xref{Stop Reply Packets}, for the reply specifications.
27269 @item c @r{[}@var{addr}@r{]}
27270 @cindex @samp{c} packet
27271 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
27272 resume at current address.
27275 @xref{Stop Reply Packets}, for the reply specifications.
27277 @item C @var{sig}@r{[};@var{addr}@r{]}
27278 @cindex @samp{C} packet
27279 Continue with signal @var{sig} (hex signal number). If
27280 @samp{;@var{addr}} is omitted, resume at same address.
27283 @xref{Stop Reply Packets}, for the reply specifications.
27286 @cindex @samp{d} packet
27289 Don't use this packet; instead, define a general set packet
27290 (@pxref{General Query Packets}).
27294 @cindex @samp{D} packet
27295 The first form of the packet is used to detach @value{GDBN} from the
27296 remote system. It is sent to the remote target
27297 before @value{GDBN} disconnects via the @code{detach} command.
27299 The second form, including a process ID, is used when multiprocess
27300 protocol extensions are enabled (@pxref{multiprocess extensions}), to
27301 detach only a specific process. The @var{pid} is specified as a
27302 big-endian hex string.
27312 @item F @var{RC},@var{EE},@var{CF};@var{XX}
27313 @cindex @samp{F} packet
27314 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
27315 This is part of the File-I/O protocol extension. @xref{File-I/O
27316 Remote Protocol Extension}, for the specification.
27319 @anchor{read registers packet}
27320 @cindex @samp{g} packet
27321 Read general registers.
27325 @item @var{XX@dots{}}
27326 Each byte of register data is described by two hex digits. The bytes
27327 with the register are transmitted in target byte order. The size of
27328 each register and their position within the @samp{g} packet are
27329 determined by the @value{GDBN} internal gdbarch functions
27330 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
27331 specification of several standard @samp{g} packets is specified below.
27336 @item G @var{XX@dots{}}
27337 @cindex @samp{G} packet
27338 Write general registers. @xref{read registers packet}, for a
27339 description of the @var{XX@dots{}} data.
27349 @item H @var{c} @var{thread-id}
27350 @cindex @samp{H} packet
27351 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
27352 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
27353 should be @samp{c} for step and continue operations, @samp{g} for other
27354 operations. The thread designator @var{thread-id} has the format and
27355 interpretation described in @ref{thread-id syntax}.
27366 @c 'H': How restrictive (or permissive) is the thread model. If a
27367 @c thread is selected and stopped, are other threads allowed
27368 @c to continue to execute? As I mentioned above, I think the
27369 @c semantics of each command when a thread is selected must be
27370 @c described. For example:
27372 @c 'g': If the stub supports threads and a specific thread is
27373 @c selected, returns the register block from that thread;
27374 @c otherwise returns current registers.
27376 @c 'G' If the stub supports threads and a specific thread is
27377 @c selected, sets the registers of the register block of
27378 @c that thread; otherwise sets current registers.
27380 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
27381 @anchor{cycle step packet}
27382 @cindex @samp{i} packet
27383 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
27384 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
27385 step starting at that address.
27388 @cindex @samp{I} packet
27389 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
27393 @cindex @samp{k} packet
27396 FIXME: @emph{There is no description of how to operate when a specific
27397 thread context has been selected (i.e.@: does 'k' kill only that
27400 @item m @var{addr},@var{length}
27401 @cindex @samp{m} packet
27402 Read @var{length} bytes of memory starting at address @var{addr}.
27403 Note that @var{addr} may not be aligned to any particular boundary.
27405 The stub need not use any particular size or alignment when gathering
27406 data from memory for the response; even if @var{addr} is word-aligned
27407 and @var{length} is a multiple of the word size, the stub is free to
27408 use byte accesses, or not. For this reason, this packet may not be
27409 suitable for accessing memory-mapped I/O devices.
27410 @cindex alignment of remote memory accesses
27411 @cindex size of remote memory accesses
27412 @cindex memory, alignment and size of remote accesses
27416 @item @var{XX@dots{}}
27417 Memory contents; each byte is transmitted as a two-digit hexadecimal
27418 number. The reply may contain fewer bytes than requested if the
27419 server was able to read only part of the region of memory.
27424 @item M @var{addr},@var{length}:@var{XX@dots{}}
27425 @cindex @samp{M} packet
27426 Write @var{length} bytes of memory starting at address @var{addr}.
27427 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
27428 hexadecimal number.
27435 for an error (this includes the case where only part of the data was
27440 @cindex @samp{p} packet
27441 Read the value of register @var{n}; @var{n} is in hex.
27442 @xref{read registers packet}, for a description of how the returned
27443 register value is encoded.
27447 @item @var{XX@dots{}}
27448 the register's value
27452 Indicating an unrecognized @var{query}.
27455 @item P @var{n@dots{}}=@var{r@dots{}}
27456 @anchor{write register packet}
27457 @cindex @samp{P} packet
27458 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
27459 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
27460 digits for each byte in the register (target byte order).
27470 @item q @var{name} @var{params}@dots{}
27471 @itemx Q @var{name} @var{params}@dots{}
27472 @cindex @samp{q} packet
27473 @cindex @samp{Q} packet
27474 General query (@samp{q}) and set (@samp{Q}). These packets are
27475 described fully in @ref{General Query Packets}.
27478 @cindex @samp{r} packet
27479 Reset the entire system.
27481 Don't use this packet; use the @samp{R} packet instead.
27484 @cindex @samp{R} packet
27485 Restart the program being debugged. @var{XX}, while needed, is ignored.
27486 This packet is only available in extended mode (@pxref{extended mode}).
27488 The @samp{R} packet has no reply.
27490 @item s @r{[}@var{addr}@r{]}
27491 @cindex @samp{s} packet
27492 Single step. @var{addr} is the address at which to resume. If
27493 @var{addr} is omitted, resume at same address.
27496 @xref{Stop Reply Packets}, for the reply specifications.
27498 @item S @var{sig}@r{[};@var{addr}@r{]}
27499 @anchor{step with signal packet}
27500 @cindex @samp{S} packet
27501 Step with signal. This is analogous to the @samp{C} packet, but
27502 requests a single-step, rather than a normal resumption of execution.
27505 @xref{Stop Reply Packets}, for the reply specifications.
27507 @item t @var{addr}:@var{PP},@var{MM}
27508 @cindex @samp{t} packet
27509 Search backwards starting at address @var{addr} for a match with pattern
27510 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
27511 @var{addr} must be at least 3 digits.
27513 @item T @var{thread-id}
27514 @cindex @samp{T} packet
27515 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
27520 thread is still alive
27526 Packets starting with @samp{v} are identified by a multi-letter name,
27527 up to the first @samp{;} or @samp{?} (or the end of the packet).
27529 @item vAttach;@var{pid}
27530 @cindex @samp{vAttach} packet
27531 Attach to a new process with the specified process ID @var{pid}.
27532 The process ID is a
27533 hexadecimal integer identifying the process. In all-stop mode, all
27534 threads in the attached process are stopped; in non-stop mode, it may be
27535 attached without being stopped if that is supported by the target.
27537 @c In non-stop mode, on a successful vAttach, the stub should set the
27538 @c current thread to a thread of the newly-attached process. After
27539 @c attaching, GDB queries for the attached process's thread ID with qC.
27540 @c Also note that, from a user perspective, whether or not the
27541 @c target is stopped on attach in non-stop mode depends on whether you
27542 @c use the foreground or background version of the attach command, not
27543 @c on what vAttach does; GDB does the right thing with respect to either
27544 @c stopping or restarting threads.
27546 This packet is only available in extended mode (@pxref{extended mode}).
27552 @item @r{Any stop packet}
27553 for success in all-stop mode (@pxref{Stop Reply Packets})
27555 for success in non-stop mode (@pxref{Remote Non-Stop})
27558 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
27559 @cindex @samp{vCont} packet
27560 Resume the inferior, specifying different actions for each thread.
27561 If an action is specified with no @var{thread-id}, then it is applied to any
27562 threads that don't have a specific action specified; if no default action is
27563 specified then other threads should remain stopped in all-stop mode and
27564 in their current state in non-stop mode.
27565 Specifying multiple
27566 default actions is an error; specifying no actions is also an error.
27567 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
27569 Currently supported actions are:
27575 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
27579 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
27583 Stop with signal @var{sig}. The signal @var{sig} should be two hex digits.
27586 The optional argument @var{addr} normally associated with the
27587 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
27588 not supported in @samp{vCont}.
27590 The @samp{t} and @samp{T} actions are only relevant in non-stop mode
27591 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
27592 A stop reply should be generated for any affected thread not already stopped.
27593 When a thread is stopped by means of a @samp{t} action,
27594 the corresponding stop reply should indicate that the thread has stopped with
27595 signal @samp{0}, regardless of whether the target uses some other signal
27596 as an implementation detail.
27599 @xref{Stop Reply Packets}, for the reply specifications.
27602 @cindex @samp{vCont?} packet
27603 Request a list of actions supported by the @samp{vCont} packet.
27607 @item vCont@r{[};@var{action}@dots{}@r{]}
27608 The @samp{vCont} packet is supported. Each @var{action} is a supported
27609 command in the @samp{vCont} packet.
27611 The @samp{vCont} packet is not supported.
27614 @item vFile:@var{operation}:@var{parameter}@dots{}
27615 @cindex @samp{vFile} packet
27616 Perform a file operation on the target system. For details,
27617 see @ref{Host I/O Packets}.
27619 @item vFlashErase:@var{addr},@var{length}
27620 @cindex @samp{vFlashErase} packet
27621 Direct the stub to erase @var{length} bytes of flash starting at
27622 @var{addr}. The region may enclose any number of flash blocks, but
27623 its start and end must fall on block boundaries, as indicated by the
27624 flash block size appearing in the memory map (@pxref{Memory Map
27625 Format}). @value{GDBN} groups flash memory programming operations
27626 together, and sends a @samp{vFlashDone} request after each group; the
27627 stub is allowed to delay erase operation until the @samp{vFlashDone}
27628 packet is received.
27630 The stub must support @samp{vCont} if it reports support for
27631 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
27632 this case @samp{vCont} actions can be specified to apply to all threads
27633 in a process by using the @samp{p@var{pid}.-1} form of the
27644 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
27645 @cindex @samp{vFlashWrite} packet
27646 Direct the stub to write data to flash address @var{addr}. The data
27647 is passed in binary form using the same encoding as for the @samp{X}
27648 packet (@pxref{Binary Data}). The memory ranges specified by
27649 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
27650 not overlap, and must appear in order of increasing addresses
27651 (although @samp{vFlashErase} packets for higher addresses may already
27652 have been received; the ordering is guaranteed only between
27653 @samp{vFlashWrite} packets). If a packet writes to an address that was
27654 neither erased by a preceding @samp{vFlashErase} packet nor by some other
27655 target-specific method, the results are unpredictable.
27663 for vFlashWrite addressing non-flash memory
27669 @cindex @samp{vFlashDone} packet
27670 Indicate to the stub that flash programming operation is finished.
27671 The stub is permitted to delay or batch the effects of a group of
27672 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
27673 @samp{vFlashDone} packet is received. The contents of the affected
27674 regions of flash memory are unpredictable until the @samp{vFlashDone}
27675 request is completed.
27677 @item vKill;@var{pid}
27678 @cindex @samp{vKill} packet
27679 Kill the process with the specified process ID. @var{pid} is a
27680 hexadecimal integer identifying the process. This packet is used in
27681 preference to @samp{k} when multiprocess protocol extensions are
27682 supported; see @ref{multiprocess extensions}.
27692 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
27693 @cindex @samp{vRun} packet
27694 Run the program @var{filename}, passing it each @var{argument} on its
27695 command line. The file and arguments are hex-encoded strings. If
27696 @var{filename} is an empty string, the stub may use a default program
27697 (e.g.@: the last program run). The program is created in the stopped
27700 @c FIXME: What about non-stop mode?
27702 This packet is only available in extended mode (@pxref{extended mode}).
27708 @item @r{Any stop packet}
27709 for success (@pxref{Stop Reply Packets})
27713 @anchor{vStopped packet}
27714 @cindex @samp{vStopped} packet
27716 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
27717 reply and prompt for the stub to report another one.
27721 @item @r{Any stop packet}
27722 if there is another unreported stop event (@pxref{Stop Reply Packets})
27724 if there are no unreported stop events
27727 @item X @var{addr},@var{length}:@var{XX@dots{}}
27729 @cindex @samp{X} packet
27730 Write data to memory, where the data is transmitted in binary.
27731 @var{addr} is address, @var{length} is number of bytes,
27732 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
27742 @item z @var{type},@var{addr},@var{length}
27743 @itemx Z @var{type},@var{addr},@var{length}
27744 @anchor{insert breakpoint or watchpoint packet}
27745 @cindex @samp{z} packet
27746 @cindex @samp{Z} packets
27747 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
27748 watchpoint starting at address @var{address} and covering the next
27749 @var{length} bytes.
27751 Each breakpoint and watchpoint packet @var{type} is documented
27754 @emph{Implementation notes: A remote target shall return an empty string
27755 for an unrecognized breakpoint or watchpoint packet @var{type}. A
27756 remote target shall support either both or neither of a given
27757 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
27758 avoid potential problems with duplicate packets, the operations should
27759 be implemented in an idempotent way.}
27761 @item z0,@var{addr},@var{length}
27762 @itemx Z0,@var{addr},@var{length}
27763 @cindex @samp{z0} packet
27764 @cindex @samp{Z0} packet
27765 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
27766 @var{addr} of size @var{length}.
27768 A memory breakpoint is implemented by replacing the instruction at
27769 @var{addr} with a software breakpoint or trap instruction. The
27770 @var{length} is used by targets that indicates the size of the
27771 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
27772 @sc{mips} can insert either a 2 or 4 byte breakpoint).
27774 @emph{Implementation note: It is possible for a target to copy or move
27775 code that contains memory breakpoints (e.g., when implementing
27776 overlays). The behavior of this packet, in the presence of such a
27777 target, is not defined.}
27789 @item z1,@var{addr},@var{length}
27790 @itemx Z1,@var{addr},@var{length}
27791 @cindex @samp{z1} packet
27792 @cindex @samp{Z1} packet
27793 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
27794 address @var{addr} of size @var{length}.
27796 A hardware breakpoint is implemented using a mechanism that is not
27797 dependant on being able to modify the target's memory.
27799 @emph{Implementation note: A hardware breakpoint is not affected by code
27812 @item z2,@var{addr},@var{length}
27813 @itemx Z2,@var{addr},@var{length}
27814 @cindex @samp{z2} packet
27815 @cindex @samp{Z2} packet
27816 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
27828 @item z3,@var{addr},@var{length}
27829 @itemx Z3,@var{addr},@var{length}
27830 @cindex @samp{z3} packet
27831 @cindex @samp{Z3} packet
27832 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
27844 @item z4,@var{addr},@var{length}
27845 @itemx Z4,@var{addr},@var{length}
27846 @cindex @samp{z4} packet
27847 @cindex @samp{Z4} packet
27848 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
27862 @node Stop Reply Packets
27863 @section Stop Reply Packets
27864 @cindex stop reply packets
27866 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
27867 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
27868 receive any of the below as a reply. Except for @samp{?}
27869 and @samp{vStopped}, that reply is only returned
27870 when the target halts. In the below the exact meaning of @dfn{signal
27871 number} is defined by the header @file{include/gdb/signals.h} in the
27872 @value{GDBN} source code.
27874 As in the description of request packets, we include spaces in the
27875 reply templates for clarity; these are not part of the reply packet's
27876 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
27882 The program received signal number @var{AA} (a two-digit hexadecimal
27883 number). This is equivalent to a @samp{T} response with no
27884 @var{n}:@var{r} pairs.
27886 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
27887 @cindex @samp{T} packet reply
27888 The program received signal number @var{AA} (a two-digit hexadecimal
27889 number). This is equivalent to an @samp{S} response, except that the
27890 @samp{@var{n}:@var{r}} pairs can carry values of important registers
27891 and other information directly in the stop reply packet, reducing
27892 round-trip latency. Single-step and breakpoint traps are reported
27893 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
27897 If @var{n} is a hexadecimal number, it is a register number, and the
27898 corresponding @var{r} gives that register's value. @var{r} is a
27899 series of bytes in target byte order, with each byte given by a
27900 two-digit hex number.
27903 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
27904 the stopped thread, as specified in @ref{thread-id syntax}.
27907 If @var{n} is a recognized @dfn{stop reason}, it describes a more
27908 specific event that stopped the target. The currently defined stop
27909 reasons are listed below. @var{aa} should be @samp{05}, the trap
27910 signal. At most one stop reason should be present.
27913 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
27914 and go on to the next; this allows us to extend the protocol in the
27918 The currently defined stop reasons are:
27924 The packet indicates a watchpoint hit, and @var{r} is the data address, in
27927 @cindex shared library events, remote reply
27929 The packet indicates that the loaded libraries have changed.
27930 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
27931 list of loaded libraries. @var{r} is ignored.
27933 @cindex replay log events, remote reply
27935 The packet indicates that the target cannot continue replaying
27936 logged execution events, because it has reached the end (or the
27937 beginning when executing backward) of the log. The value of @var{r}
27938 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
27939 for more information.
27945 @itemx W @var{AA} ; process:@var{pid}
27946 The process exited, and @var{AA} is the exit status. This is only
27947 applicable to certain targets.
27949 The second form of the response, including the process ID of the exited
27950 process, can be used only when @value{GDBN} has reported support for
27951 multiprocess protocol extensions; see @ref{multiprocess extensions}.
27952 The @var{pid} is formatted as a big-endian hex string.
27955 @itemx X @var{AA} ; process:@var{pid}
27956 The process terminated with signal @var{AA}.
27958 The second form of the response, including the process ID of the
27959 terminated process, can be used only when @value{GDBN} has reported
27960 support for multiprocess protocol extensions; see @ref{multiprocess
27961 extensions}. The @var{pid} is formatted as a big-endian hex string.
27963 @item O @var{XX}@dots{}
27964 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
27965 written as the program's console output. This can happen at any time
27966 while the program is running and the debugger should continue to wait
27967 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
27969 @item F @var{call-id},@var{parameter}@dots{}
27970 @var{call-id} is the identifier which says which host system call should
27971 be called. This is just the name of the function. Translation into the
27972 correct system call is only applicable as it's defined in @value{GDBN}.
27973 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
27976 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
27977 this very system call.
27979 The target replies with this packet when it expects @value{GDBN} to
27980 call a host system call on behalf of the target. @value{GDBN} replies
27981 with an appropriate @samp{F} packet and keeps up waiting for the next
27982 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
27983 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
27984 Protocol Extension}, for more details.
27988 @node General Query Packets
27989 @section General Query Packets
27990 @cindex remote query requests
27992 Packets starting with @samp{q} are @dfn{general query packets};
27993 packets starting with @samp{Q} are @dfn{general set packets}. General
27994 query and set packets are a semi-unified form for retrieving and
27995 sending information to and from the stub.
27997 The initial letter of a query or set packet is followed by a name
27998 indicating what sort of thing the packet applies to. For example,
27999 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
28000 definitions with the stub. These packet names follow some
28005 The name must not contain commas, colons or semicolons.
28007 Most @value{GDBN} query and set packets have a leading upper case
28010 The names of custom vendor packets should use a company prefix, in
28011 lower case, followed by a period. For example, packets designed at
28012 the Acme Corporation might begin with @samp{qacme.foo} (for querying
28013 foos) or @samp{Qacme.bar} (for setting bars).
28016 The name of a query or set packet should be separated from any
28017 parameters by a @samp{:}; the parameters themselves should be
28018 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
28019 full packet name, and check for a separator or the end of the packet,
28020 in case two packet names share a common prefix. New packets should not begin
28021 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
28022 packets predate these conventions, and have arguments without any terminator
28023 for the packet name; we suspect they are in widespread use in places that
28024 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
28025 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
28028 Like the descriptions of the other packets, each description here
28029 has a template showing the packet's overall syntax, followed by an
28030 explanation of the packet's meaning. We include spaces in some of the
28031 templates for clarity; these are not part of the packet's syntax. No
28032 @value{GDBN} packet uses spaces to separate its components.
28034 Here are the currently defined query and set packets:
28039 @cindex current thread, remote request
28040 @cindex @samp{qC} packet
28041 Return the current thread ID.
28045 @item QC @var{thread-id}
28046 Where @var{thread-id} is a thread ID as documented in
28047 @ref{thread-id syntax}.
28048 @item @r{(anything else)}
28049 Any other reply implies the old thread ID.
28052 @item qCRC:@var{addr},@var{length}
28053 @cindex CRC of memory block, remote request
28054 @cindex @samp{qCRC} packet
28055 Compute the CRC checksum of a block of memory.
28059 An error (such as memory fault)
28060 @item C @var{crc32}
28061 The specified memory region's checksum is @var{crc32}.
28065 @itemx qsThreadInfo
28066 @cindex list active threads, remote request
28067 @cindex @samp{qfThreadInfo} packet
28068 @cindex @samp{qsThreadInfo} packet
28069 Obtain a list of all active thread IDs from the target (OS). Since there
28070 may be too many active threads to fit into one reply packet, this query
28071 works iteratively: it may require more than one query/reply sequence to
28072 obtain the entire list of threads. The first query of the sequence will
28073 be the @samp{qfThreadInfo} query; subsequent queries in the
28074 sequence will be the @samp{qsThreadInfo} query.
28076 NOTE: This packet replaces the @samp{qL} query (see below).
28080 @item m @var{thread-id}
28082 @item m @var{thread-id},@var{thread-id}@dots{}
28083 a comma-separated list of thread IDs
28085 (lower case letter @samp{L}) denotes end of list.
28088 In response to each query, the target will reply with a list of one or
28089 more thread IDs, separated by commas.
28090 @value{GDBN} will respond to each reply with a request for more thread
28091 ids (using the @samp{qs} form of the query), until the target responds
28092 with @samp{l} (lower-case el, for @dfn{last}).
28093 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
28096 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
28097 @cindex get thread-local storage address, remote request
28098 @cindex @samp{qGetTLSAddr} packet
28099 Fetch the address associated with thread local storage specified
28100 by @var{thread-id}, @var{offset}, and @var{lm}.
28102 @var{thread-id} is the thread ID associated with the
28103 thread for which to fetch the TLS address. @xref{thread-id syntax}.
28105 @var{offset} is the (big endian, hex encoded) offset associated with the
28106 thread local variable. (This offset is obtained from the debug
28107 information associated with the variable.)
28109 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
28110 the load module associated with the thread local storage. For example,
28111 a @sc{gnu}/Linux system will pass the link map address of the shared
28112 object associated with the thread local storage under consideration.
28113 Other operating environments may choose to represent the load module
28114 differently, so the precise meaning of this parameter will vary.
28118 @item @var{XX}@dots{}
28119 Hex encoded (big endian) bytes representing the address of the thread
28120 local storage requested.
28123 An error occurred. @var{nn} are hex digits.
28126 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
28129 @item qL @var{startflag} @var{threadcount} @var{nextthread}
28130 Obtain thread information from RTOS. Where: @var{startflag} (one hex
28131 digit) is one to indicate the first query and zero to indicate a
28132 subsequent query; @var{threadcount} (two hex digits) is the maximum
28133 number of threads the response packet can contain; and @var{nextthread}
28134 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
28135 returned in the response as @var{argthread}.
28137 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
28141 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
28142 Where: @var{count} (two hex digits) is the number of threads being
28143 returned; @var{done} (one hex digit) is zero to indicate more threads
28144 and one indicates no further threads; @var{argthreadid} (eight hex
28145 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
28146 is a sequence of thread IDs from the target. @var{threadid} (eight hex
28147 digits). See @code{remote.c:parse_threadlist_response()}.
28151 @cindex section offsets, remote request
28152 @cindex @samp{qOffsets} packet
28153 Get section offsets that the target used when relocating the downloaded
28158 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
28159 Relocate the @code{Text} section by @var{xxx} from its original address.
28160 Relocate the @code{Data} section by @var{yyy} from its original address.
28161 If the object file format provides segment information (e.g.@: @sc{elf}
28162 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
28163 segments by the supplied offsets.
28165 @emph{Note: while a @code{Bss} offset may be included in the response,
28166 @value{GDBN} ignores this and instead applies the @code{Data} offset
28167 to the @code{Bss} section.}
28169 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
28170 Relocate the first segment of the object file, which conventionally
28171 contains program code, to a starting address of @var{xxx}. If
28172 @samp{DataSeg} is specified, relocate the second segment, which
28173 conventionally contains modifiable data, to a starting address of
28174 @var{yyy}. @value{GDBN} will report an error if the object file
28175 does not contain segment information, or does not contain at least
28176 as many segments as mentioned in the reply. Extra segments are
28177 kept at fixed offsets relative to the last relocated segment.
28180 @item qP @var{mode} @var{thread-id}
28181 @cindex thread information, remote request
28182 @cindex @samp{qP} packet
28183 Returns information on @var{thread-id}. Where: @var{mode} is a hex
28184 encoded 32 bit mode; @var{thread-id} is a thread ID
28185 (@pxref{thread-id syntax}).
28187 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
28190 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
28194 @cindex non-stop mode, remote request
28195 @cindex @samp{QNonStop} packet
28197 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
28198 @xref{Remote Non-Stop}, for more information.
28203 The request succeeded.
28206 An error occurred. @var{nn} are hex digits.
28209 An empty reply indicates that @samp{QNonStop} is not supported by
28213 This packet is not probed by default; the remote stub must request it,
28214 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
28215 Use of this packet is controlled by the @code{set non-stop} command;
28216 @pxref{Non-Stop Mode}.
28218 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
28219 @cindex pass signals to inferior, remote request
28220 @cindex @samp{QPassSignals} packet
28221 @anchor{QPassSignals}
28222 Each listed @var{signal} should be passed directly to the inferior process.
28223 Signals are numbered identically to continue packets and stop replies
28224 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
28225 strictly greater than the previous item. These signals do not need to stop
28226 the inferior, or be reported to @value{GDBN}. All other signals should be
28227 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
28228 combine; any earlier @samp{QPassSignals} list is completely replaced by the
28229 new list. This packet improves performance when using @samp{handle
28230 @var{signal} nostop noprint pass}.
28235 The request succeeded.
28238 An error occurred. @var{nn} are hex digits.
28241 An empty reply indicates that @samp{QPassSignals} is not supported by
28245 Use of this packet is controlled by the @code{set remote pass-signals}
28246 command (@pxref{Remote Configuration, set remote pass-signals}).
28247 This packet is not probed by default; the remote stub must request it,
28248 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
28250 @item qRcmd,@var{command}
28251 @cindex execute remote command, remote request
28252 @cindex @samp{qRcmd} packet
28253 @var{command} (hex encoded) is passed to the local interpreter for
28254 execution. Invalid commands should be reported using the output
28255 string. Before the final result packet, the target may also respond
28256 with a number of intermediate @samp{O@var{output}} console output
28257 packets. @emph{Implementors should note that providing access to a
28258 stubs's interpreter may have security implications}.
28263 A command response with no output.
28265 A command response with the hex encoded output string @var{OUTPUT}.
28267 Indicate a badly formed request.
28269 An empty reply indicates that @samp{qRcmd} is not recognized.
28272 (Note that the @code{qRcmd} packet's name is separated from the
28273 command by a @samp{,}, not a @samp{:}, contrary to the naming
28274 conventions above. Please don't use this packet as a model for new
28277 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
28278 @cindex searching memory, in remote debugging
28279 @cindex @samp{qSearch:memory} packet
28280 @anchor{qSearch memory}
28281 Search @var{length} bytes at @var{address} for @var{search-pattern}.
28282 @var{address} and @var{length} are encoded in hex.
28283 @var{search-pattern} is a sequence of bytes, hex encoded.
28288 The pattern was not found.
28290 The pattern was found at @var{address}.
28292 A badly formed request or an error was encountered while searching memory.
28294 An empty reply indicates that @samp{qSearch:memory} is not recognized.
28297 @item QStartNoAckMode
28298 @cindex @samp{QStartNoAckMode} packet
28299 @anchor{QStartNoAckMode}
28300 Request that the remote stub disable the normal @samp{+}/@samp{-}
28301 protocol acknowledgments (@pxref{Packet Acknowledgment}).
28306 The stub has switched to no-acknowledgment mode.
28307 @value{GDBN} acknowledges this reponse,
28308 but neither the stub nor @value{GDBN} shall send or expect further
28309 @samp{+}/@samp{-} acknowledgments in the current connection.
28311 An empty reply indicates that the stub does not support no-acknowledgment mode.
28314 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
28315 @cindex supported packets, remote query
28316 @cindex features of the remote protocol
28317 @cindex @samp{qSupported} packet
28318 @anchor{qSupported}
28319 Tell the remote stub about features supported by @value{GDBN}, and
28320 query the stub for features it supports. This packet allows
28321 @value{GDBN} and the remote stub to take advantage of each others'
28322 features. @samp{qSupported} also consolidates multiple feature probes
28323 at startup, to improve @value{GDBN} performance---a single larger
28324 packet performs better than multiple smaller probe packets on
28325 high-latency links. Some features may enable behavior which must not
28326 be on by default, e.g.@: because it would confuse older clients or
28327 stubs. Other features may describe packets which could be
28328 automatically probed for, but are not. These features must be
28329 reported before @value{GDBN} will use them. This ``default
28330 unsupported'' behavior is not appropriate for all packets, but it
28331 helps to keep the initial connection time under control with new
28332 versions of @value{GDBN} which support increasing numbers of packets.
28336 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
28337 The stub supports or does not support each returned @var{stubfeature},
28338 depending on the form of each @var{stubfeature} (see below for the
28341 An empty reply indicates that @samp{qSupported} is not recognized,
28342 or that no features needed to be reported to @value{GDBN}.
28345 The allowed forms for each feature (either a @var{gdbfeature} in the
28346 @samp{qSupported} packet, or a @var{stubfeature} in the response)
28350 @item @var{name}=@var{value}
28351 The remote protocol feature @var{name} is supported, and associated
28352 with the specified @var{value}. The format of @var{value} depends
28353 on the feature, but it must not include a semicolon.
28355 The remote protocol feature @var{name} is supported, and does not
28356 need an associated value.
28358 The remote protocol feature @var{name} is not supported.
28360 The remote protocol feature @var{name} may be supported, and
28361 @value{GDBN} should auto-detect support in some other way when it is
28362 needed. This form will not be used for @var{gdbfeature} notifications,
28363 but may be used for @var{stubfeature} responses.
28366 Whenever the stub receives a @samp{qSupported} request, the
28367 supplied set of @value{GDBN} features should override any previous
28368 request. This allows @value{GDBN} to put the stub in a known
28369 state, even if the stub had previously been communicating with
28370 a different version of @value{GDBN}.
28372 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
28377 This feature indicates whether @value{GDBN} supports multiprocess
28378 extensions to the remote protocol. @value{GDBN} does not use such
28379 extensions unless the stub also reports that it supports them by
28380 including @samp{multiprocess+} in its @samp{qSupported} reply.
28381 @xref{multiprocess extensions}, for details.
28384 Stubs should ignore any unknown values for
28385 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
28386 packet supports receiving packets of unlimited length (earlier
28387 versions of @value{GDBN} may reject overly long responses). Additional values
28388 for @var{gdbfeature} may be defined in the future to let the stub take
28389 advantage of new features in @value{GDBN}, e.g.@: incompatible
28390 improvements in the remote protocol---the @samp{multiprocess} feature is
28391 an example of such a feature. The stub's reply should be independent
28392 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
28393 describes all the features it supports, and then the stub replies with
28394 all the features it supports.
28396 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
28397 responses, as long as each response uses one of the standard forms.
28399 Some features are flags. A stub which supports a flag feature
28400 should respond with a @samp{+} form response. Other features
28401 require values, and the stub should respond with an @samp{=}
28404 Each feature has a default value, which @value{GDBN} will use if
28405 @samp{qSupported} is not available or if the feature is not mentioned
28406 in the @samp{qSupported} response. The default values are fixed; a
28407 stub is free to omit any feature responses that match the defaults.
28409 Not all features can be probed, but for those which can, the probing
28410 mechanism is useful: in some cases, a stub's internal
28411 architecture may not allow the protocol layer to know some information
28412 about the underlying target in advance. This is especially common in
28413 stubs which may be configured for multiple targets.
28415 These are the currently defined stub features and their properties:
28417 @multitable @columnfractions 0.35 0.2 0.12 0.2
28418 @c NOTE: The first row should be @headitem, but we do not yet require
28419 @c a new enough version of Texinfo (4.7) to use @headitem.
28421 @tab Value Required
28425 @item @samp{PacketSize}
28430 @item @samp{qXfer:auxv:read}
28435 @item @samp{qXfer:features:read}
28440 @item @samp{qXfer:libraries:read}
28445 @item @samp{qXfer:memory-map:read}
28450 @item @samp{qXfer:spu:read}
28455 @item @samp{qXfer:spu:write}
28460 @item @samp{qXfer:siginfo:read}
28465 @item @samp{qXfer:siginfo:write}
28470 @item @samp{QNonStop}
28475 @item @samp{QPassSignals}
28480 @item @samp{QStartNoAckMode}
28485 @item @samp{multiprocess}
28490 @item @samp{ConditionalTracepoints}
28497 These are the currently defined stub features, in more detail:
28500 @cindex packet size, remote protocol
28501 @item PacketSize=@var{bytes}
28502 The remote stub can accept packets up to at least @var{bytes} in
28503 length. @value{GDBN} will send packets up to this size for bulk
28504 transfers, and will never send larger packets. This is a limit on the
28505 data characters in the packet, including the frame and checksum.
28506 There is no trailing NUL byte in a remote protocol packet; if the stub
28507 stores packets in a NUL-terminated format, it should allow an extra
28508 byte in its buffer for the NUL. If this stub feature is not supported,
28509 @value{GDBN} guesses based on the size of the @samp{g} packet response.
28511 @item qXfer:auxv:read
28512 The remote stub understands the @samp{qXfer:auxv:read} packet
28513 (@pxref{qXfer auxiliary vector read}).
28515 @item qXfer:features:read
28516 The remote stub understands the @samp{qXfer:features:read} packet
28517 (@pxref{qXfer target description read}).
28519 @item qXfer:libraries:read
28520 The remote stub understands the @samp{qXfer:libraries:read} packet
28521 (@pxref{qXfer library list read}).
28523 @item qXfer:memory-map:read
28524 The remote stub understands the @samp{qXfer:memory-map:read} packet
28525 (@pxref{qXfer memory map read}).
28527 @item qXfer:spu:read
28528 The remote stub understands the @samp{qXfer:spu:read} packet
28529 (@pxref{qXfer spu read}).
28531 @item qXfer:spu:write
28532 The remote stub understands the @samp{qXfer:spu:write} packet
28533 (@pxref{qXfer spu write}).
28535 @item qXfer:siginfo:read
28536 The remote stub understands the @samp{qXfer:siginfo:read} packet
28537 (@pxref{qXfer siginfo read}).
28539 @item qXfer:siginfo:write
28540 The remote stub understands the @samp{qXfer:siginfo:write} packet
28541 (@pxref{qXfer siginfo write}).
28544 The remote stub understands the @samp{QNonStop} packet
28545 (@pxref{QNonStop}).
28548 The remote stub understands the @samp{QPassSignals} packet
28549 (@pxref{QPassSignals}).
28551 @item QStartNoAckMode
28552 The remote stub understands the @samp{QStartNoAckMode} packet and
28553 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
28556 @anchor{multiprocess extensions}
28557 @cindex multiprocess extensions, in remote protocol
28558 The remote stub understands the multiprocess extensions to the remote
28559 protocol syntax. The multiprocess extensions affect the syntax of
28560 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
28561 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
28562 replies. Note that reporting this feature indicates support for the
28563 syntactic extensions only, not that the stub necessarily supports
28564 debugging of more than one process at a time. The stub must not use
28565 multiprocess extensions in packet replies unless @value{GDBN} has also
28566 indicated it supports them in its @samp{qSupported} request.
28568 @item qXfer:osdata:read
28569 The remote stub understands the @samp{qXfer:osdata:read} packet
28570 ((@pxref{qXfer osdata read}).
28572 @item ConditionalTracepoints
28573 The remote stub accepts and implements conditional expressions defined
28574 for tracepoints (@pxref{Tracepoint Conditions}).
28579 @cindex symbol lookup, remote request
28580 @cindex @samp{qSymbol} packet
28581 Notify the target that @value{GDBN} is prepared to serve symbol lookup
28582 requests. Accept requests from the target for the values of symbols.
28587 The target does not need to look up any (more) symbols.
28588 @item qSymbol:@var{sym_name}
28589 The target requests the value of symbol @var{sym_name} (hex encoded).
28590 @value{GDBN} may provide the value by using the
28591 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
28595 @item qSymbol:@var{sym_value}:@var{sym_name}
28596 Set the value of @var{sym_name} to @var{sym_value}.
28598 @var{sym_name} (hex encoded) is the name of a symbol whose value the
28599 target has previously requested.
28601 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
28602 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
28608 The target does not need to look up any (more) symbols.
28609 @item qSymbol:@var{sym_name}
28610 The target requests the value of a new symbol @var{sym_name} (hex
28611 encoded). @value{GDBN} will continue to supply the values of symbols
28612 (if available), until the target ceases to request them.
28617 @xref{Tracepoint Packets}.
28619 @item qThreadExtraInfo,@var{thread-id}
28620 @cindex thread attributes info, remote request
28621 @cindex @samp{qThreadExtraInfo} packet
28622 Obtain a printable string description of a thread's attributes from
28623 the target OS. @var{thread-id} is a thread ID;
28624 see @ref{thread-id syntax}. This
28625 string may contain anything that the target OS thinks is interesting
28626 for @value{GDBN} to tell the user about the thread. The string is
28627 displayed in @value{GDBN}'s @code{info threads} display. Some
28628 examples of possible thread extra info strings are @samp{Runnable}, or
28629 @samp{Blocked on Mutex}.
28633 @item @var{XX}@dots{}
28634 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
28635 comprising the printable string containing the extra information about
28636 the thread's attributes.
28639 (Note that the @code{qThreadExtraInfo} packet's name is separated from
28640 the command by a @samp{,}, not a @samp{:}, contrary to the naming
28641 conventions above. Please don't use this packet as a model for new
28649 @xref{Tracepoint Packets}.
28651 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
28652 @cindex read special object, remote request
28653 @cindex @samp{qXfer} packet
28654 @anchor{qXfer read}
28655 Read uninterpreted bytes from the target's special data area
28656 identified by the keyword @var{object}. Request @var{length} bytes
28657 starting at @var{offset} bytes into the data. The content and
28658 encoding of @var{annex} is specific to @var{object}; it can supply
28659 additional details about what data to access.
28661 Here are the specific requests of this form defined so far. All
28662 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
28663 formats, listed below.
28666 @item qXfer:auxv:read::@var{offset},@var{length}
28667 @anchor{qXfer auxiliary vector read}
28668 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
28669 auxiliary vector}. Note @var{annex} must be empty.
28671 This packet is not probed by default; the remote stub must request it,
28672 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
28674 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
28675 @anchor{qXfer target description read}
28676 Access the @dfn{target description}. @xref{Target Descriptions}. The
28677 annex specifies which XML document to access. The main description is
28678 always loaded from the @samp{target.xml} annex.
28680 This packet is not probed by default; the remote stub must request it,
28681 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
28683 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
28684 @anchor{qXfer library list read}
28685 Access the target's list of loaded libraries. @xref{Library List Format}.
28686 The annex part of the generic @samp{qXfer} packet must be empty
28687 (@pxref{qXfer read}).
28689 Targets which maintain a list of libraries in the program's memory do
28690 not need to implement this packet; it is designed for platforms where
28691 the operating system manages the list of loaded libraries.
28693 This packet is not probed by default; the remote stub must request it,
28694 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
28696 @item qXfer:memory-map:read::@var{offset},@var{length}
28697 @anchor{qXfer memory map read}
28698 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
28699 annex part of the generic @samp{qXfer} packet must be empty
28700 (@pxref{qXfer read}).
28702 This packet is not probed by default; the remote stub must request it,
28703 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
28705 @item qXfer:siginfo:read::@var{offset},@var{length}
28706 @anchor{qXfer siginfo read}
28707 Read contents of the extra signal information on the target
28708 system. The annex part of the generic @samp{qXfer} packet must be
28709 empty (@pxref{qXfer read}).
28711 This packet is not probed by default; the remote stub must request it,
28712 by supplying an appropriate @samp{qSupported} response
28713 (@pxref{qSupported}).
28715 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
28716 @anchor{qXfer spu read}
28717 Read contents of an @code{spufs} file on the target system. The
28718 annex specifies which file to read; it must be of the form
28719 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
28720 in the target process, and @var{name} identifes the @code{spufs} file
28721 in that context to be accessed.
28723 This packet is not probed by default; the remote stub must request it,
28724 by supplying an appropriate @samp{qSupported} response
28725 (@pxref{qSupported}).
28727 @item qXfer:osdata:read::@var{offset},@var{length}
28728 @anchor{qXfer osdata read}
28729 Access the target's @dfn{operating system information}.
28730 @xref{Operating System Information}.
28737 Data @var{data} (@pxref{Binary Data}) has been read from the
28738 target. There may be more data at a higher address (although
28739 it is permitted to return @samp{m} even for the last valid
28740 block of data, as long as at least one byte of data was read).
28741 @var{data} may have fewer bytes than the @var{length} in the
28745 Data @var{data} (@pxref{Binary Data}) has been read from the target.
28746 There is no more data to be read. @var{data} may have fewer bytes
28747 than the @var{length} in the request.
28750 The @var{offset} in the request is at the end of the data.
28751 There is no more data to be read.
28754 The request was malformed, or @var{annex} was invalid.
28757 The offset was invalid, or there was an error encountered reading the data.
28758 @var{nn} is a hex-encoded @code{errno} value.
28761 An empty reply indicates the @var{object} string was not recognized by
28762 the stub, or that the object does not support reading.
28765 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
28766 @cindex write data into object, remote request
28767 @anchor{qXfer write}
28768 Write uninterpreted bytes into the target's special data area
28769 identified by the keyword @var{object}, starting at @var{offset} bytes
28770 into the data. @var{data}@dots{} is the binary-encoded data
28771 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
28772 is specific to @var{object}; it can supply additional details about what data
28775 Here are the specific requests of this form defined so far. All
28776 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
28777 formats, listed below.
28780 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
28781 @anchor{qXfer siginfo write}
28782 Write @var{data} to the extra signal information on the target system.
28783 The annex part of the generic @samp{qXfer} packet must be
28784 empty (@pxref{qXfer write}).
28786 This packet is not probed by default; the remote stub must request it,
28787 by supplying an appropriate @samp{qSupported} response
28788 (@pxref{qSupported}).
28790 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
28791 @anchor{qXfer spu write}
28792 Write @var{data} to an @code{spufs} file on the target system. The
28793 annex specifies which file to write; it must be of the form
28794 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
28795 in the target process, and @var{name} identifes the @code{spufs} file
28796 in that context to be accessed.
28798 This packet is not probed by default; the remote stub must request it,
28799 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
28805 @var{nn} (hex encoded) is the number of bytes written.
28806 This may be fewer bytes than supplied in the request.
28809 The request was malformed, or @var{annex} was invalid.
28812 The offset was invalid, or there was an error encountered writing the data.
28813 @var{nn} is a hex-encoded @code{errno} value.
28816 An empty reply indicates the @var{object} string was not
28817 recognized by the stub, or that the object does not support writing.
28820 @item qXfer:@var{object}:@var{operation}:@dots{}
28821 Requests of this form may be added in the future. When a stub does
28822 not recognize the @var{object} keyword, or its support for
28823 @var{object} does not recognize the @var{operation} keyword, the stub
28824 must respond with an empty packet.
28826 @item qAttached:@var{pid}
28827 @cindex query attached, remote request
28828 @cindex @samp{qAttached} packet
28829 Return an indication of whether the remote server attached to an
28830 existing process or created a new process. When the multiprocess
28831 protocol extensions are supported (@pxref{multiprocess extensions}),
28832 @var{pid} is an integer in hexadecimal format identifying the target
28833 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
28834 the query packet will be simplified as @samp{qAttached}.
28836 This query is used, for example, to know whether the remote process
28837 should be detached or killed when a @value{GDBN} session is ended with
28838 the @code{quit} command.
28843 The remote server attached to an existing process.
28845 The remote server created a new process.
28847 A badly formed request or an error was encountered.
28852 @node Register Packet Format
28853 @section Register Packet Format
28855 The following @code{g}/@code{G} packets have previously been defined.
28856 In the below, some thirty-two bit registers are transferred as
28857 sixty-four bits. Those registers should be zero/sign extended (which?)
28858 to fill the space allocated. Register bytes are transferred in target
28859 byte order. The two nibbles within a register byte are transferred
28860 most-significant - least-significant.
28866 All registers are transferred as thirty-two bit quantities in the order:
28867 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
28868 registers; fsr; fir; fp.
28872 All registers are transferred as sixty-four bit quantities (including
28873 thirty-two bit registers such as @code{sr}). The ordering is the same
28878 @node Tracepoint Packets
28879 @section Tracepoint Packets
28880 @cindex tracepoint packets
28881 @cindex packets, tracepoint
28883 Here we describe the packets @value{GDBN} uses to implement
28884 tracepoints (@pxref{Tracepoints}).
28888 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:X@var{len},@var{bytes}]@r{[}-@r{]}
28889 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
28890 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
28891 the tracepoint is disabled. @var{step} is the tracepoint's step
28892 count, and @var{pass} is its pass count. If an @samp{X} is present,
28893 it introduces a tracepoint condition, which consists of a hexadecimal
28894 length, followed by a comma and hex-encoded bytes, in a manner similar
28895 to action encodings as described below. If the trailing @samp{-} is
28896 present, further @samp{QTDP} packets will follow to specify this
28897 tracepoint's actions.
28902 The packet was understood and carried out.
28904 The packet was not recognized.
28907 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
28908 Define actions to be taken when a tracepoint is hit. @var{n} and
28909 @var{addr} must be the same as in the initial @samp{QTDP} packet for
28910 this tracepoint. This packet may only be sent immediately after
28911 another @samp{QTDP} packet that ended with a @samp{-}. If the
28912 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
28913 specifying more actions for this tracepoint.
28915 In the series of action packets for a given tracepoint, at most one
28916 can have an @samp{S} before its first @var{action}. If such a packet
28917 is sent, it and the following packets define ``while-stepping''
28918 actions. Any prior packets define ordinary actions --- that is, those
28919 taken when the tracepoint is first hit. If no action packet has an
28920 @samp{S}, then all the packets in the series specify ordinary
28921 tracepoint actions.
28923 The @samp{@var{action}@dots{}} portion of the packet is a series of
28924 actions, concatenated without separators. Each action has one of the
28930 Collect the registers whose bits are set in @var{mask}. @var{mask} is
28931 a hexadecimal number whose @var{i}'th bit is set if register number
28932 @var{i} should be collected. (The least significant bit is numbered
28933 zero.) Note that @var{mask} may be any number of digits long; it may
28934 not fit in a 32-bit word.
28936 @item M @var{basereg},@var{offset},@var{len}
28937 Collect @var{len} bytes of memory starting at the address in register
28938 number @var{basereg}, plus @var{offset}. If @var{basereg} is
28939 @samp{-1}, then the range has a fixed address: @var{offset} is the
28940 address of the lowest byte to collect. The @var{basereg},
28941 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
28942 values (the @samp{-1} value for @var{basereg} is a special case).
28944 @item X @var{len},@var{expr}
28945 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
28946 it directs. @var{expr} is an agent expression, as described in
28947 @ref{Agent Expressions}. Each byte of the expression is encoded as a
28948 two-digit hex number in the packet; @var{len} is the number of bytes
28949 in the expression (and thus one-half the number of hex digits in the
28954 Any number of actions may be packed together in a single @samp{QTDP}
28955 packet, as long as the packet does not exceed the maximum packet
28956 length (400 bytes, for many stubs). There may be only one @samp{R}
28957 action per tracepoint, and it must precede any @samp{M} or @samp{X}
28958 actions. Any registers referred to by @samp{M} and @samp{X} actions
28959 must be collected by a preceding @samp{R} action. (The
28960 ``while-stepping'' actions are treated as if they were attached to a
28961 separate tracepoint, as far as these restrictions are concerned.)
28966 The packet was understood and carried out.
28968 The packet was not recognized.
28971 @item QTFrame:@var{n}
28972 Select the @var{n}'th tracepoint frame from the buffer, and use the
28973 register and memory contents recorded there to answer subsequent
28974 request packets from @value{GDBN}.
28976 A successful reply from the stub indicates that the stub has found the
28977 requested frame. The response is a series of parts, concatenated
28978 without separators, describing the frame we selected. Each part has
28979 one of the following forms:
28983 The selected frame is number @var{n} in the trace frame buffer;
28984 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
28985 was no frame matching the criteria in the request packet.
28988 The selected trace frame records a hit of tracepoint number @var{t};
28989 @var{t} is a hexadecimal number.
28993 @item QTFrame:pc:@var{addr}
28994 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
28995 currently selected frame whose PC is @var{addr};
28996 @var{addr} is a hexadecimal number.
28998 @item QTFrame:tdp:@var{t}
28999 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
29000 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
29001 is a hexadecimal number.
29003 @item QTFrame:range:@var{start}:@var{end}
29004 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
29005 currently selected frame whose PC is between @var{start} (inclusive)
29006 and @var{end} (exclusive); @var{start} and @var{end} are hexadecimal
29009 @item QTFrame:outside:@var{start}:@var{end}
29010 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
29011 frame @emph{outside} the given range of addresses.
29014 Begin the tracepoint experiment. Begin collecting data from tracepoint
29015 hits in the trace frame buffer.
29018 End the tracepoint experiment. Stop collecting trace frames.
29021 Clear the table of tracepoints, and empty the trace frame buffer.
29023 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
29024 Establish the given ranges of memory as ``transparent''. The stub
29025 will answer requests for these ranges from memory's current contents,
29026 if they were not collected as part of the tracepoint hit.
29028 @value{GDBN} uses this to mark read-only regions of memory, like those
29029 containing program code. Since these areas never change, they should
29030 still have the same contents they did when the tracepoint was hit, so
29031 there's no reason for the stub to refuse to provide their contents.
29034 Ask the stub if there is a trace experiment running right now.
29039 There is no trace experiment running.
29041 There is a trace experiment running.
29047 @node Host I/O Packets
29048 @section Host I/O Packets
29049 @cindex Host I/O, remote protocol
29050 @cindex file transfer, remote protocol
29052 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
29053 operations on the far side of a remote link. For example, Host I/O is
29054 used to upload and download files to a remote target with its own
29055 filesystem. Host I/O uses the same constant values and data structure
29056 layout as the target-initiated File-I/O protocol. However, the
29057 Host I/O packets are structured differently. The target-initiated
29058 protocol relies on target memory to store parameters and buffers.
29059 Host I/O requests are initiated by @value{GDBN}, and the
29060 target's memory is not involved. @xref{File-I/O Remote Protocol
29061 Extension}, for more details on the target-initiated protocol.
29063 The Host I/O request packets all encode a single operation along with
29064 its arguments. They have this format:
29068 @item vFile:@var{operation}: @var{parameter}@dots{}
29069 @var{operation} is the name of the particular request; the target
29070 should compare the entire packet name up to the second colon when checking
29071 for a supported operation. The format of @var{parameter} depends on
29072 the operation. Numbers are always passed in hexadecimal. Negative
29073 numbers have an explicit minus sign (i.e.@: two's complement is not
29074 used). Strings (e.g.@: filenames) are encoded as a series of
29075 hexadecimal bytes. The last argument to a system call may be a
29076 buffer of escaped binary data (@pxref{Binary Data}).
29080 The valid responses to Host I/O packets are:
29084 @item F @var{result} [, @var{errno}] [; @var{attachment}]
29085 @var{result} is the integer value returned by this operation, usually
29086 non-negative for success and -1 for errors. If an error has occured,
29087 @var{errno} will be included in the result. @var{errno} will have a
29088 value defined by the File-I/O protocol (@pxref{Errno Values}). For
29089 operations which return data, @var{attachment} supplies the data as a
29090 binary buffer. Binary buffers in response packets are escaped in the
29091 normal way (@pxref{Binary Data}). See the individual packet
29092 documentation for the interpretation of @var{result} and
29096 An empty response indicates that this operation is not recognized.
29100 These are the supported Host I/O operations:
29103 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
29104 Open a file at @var{pathname} and return a file descriptor for it, or
29105 return -1 if an error occurs. @var{pathname} is a string,
29106 @var{flags} is an integer indicating a mask of open flags
29107 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
29108 of mode bits to use if the file is created (@pxref{mode_t Values}).
29109 @xref{open}, for details of the open flags and mode values.
29111 @item vFile:close: @var{fd}
29112 Close the open file corresponding to @var{fd} and return 0, or
29113 -1 if an error occurs.
29115 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
29116 Read data from the open file corresponding to @var{fd}. Up to
29117 @var{count} bytes will be read from the file, starting at @var{offset}
29118 relative to the start of the file. The target may read fewer bytes;
29119 common reasons include packet size limits and an end-of-file
29120 condition. The number of bytes read is returned. Zero should only be
29121 returned for a successful read at the end of the file, or if
29122 @var{count} was zero.
29124 The data read should be returned as a binary attachment on success.
29125 If zero bytes were read, the response should include an empty binary
29126 attachment (i.e.@: a trailing semicolon). The return value is the
29127 number of target bytes read; the binary attachment may be longer if
29128 some characters were escaped.
29130 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
29131 Write @var{data} (a binary buffer) to the open file corresponding
29132 to @var{fd}. Start the write at @var{offset} from the start of the
29133 file. Unlike many @code{write} system calls, there is no
29134 separate @var{count} argument; the length of @var{data} in the
29135 packet is used. @samp{vFile:write} returns the number of bytes written,
29136 which may be shorter than the length of @var{data}, or -1 if an
29139 @item vFile:unlink: @var{pathname}
29140 Delete the file at @var{pathname} on the target. Return 0,
29141 or -1 if an error occurs. @var{pathname} is a string.
29146 @section Interrupts
29147 @cindex interrupts (remote protocol)
29149 When a program on the remote target is running, @value{GDBN} may
29150 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
29151 control of which is specified via @value{GDBN}'s @samp{remotebreak}
29152 setting (@pxref{set remotebreak}).
29154 The precise meaning of @code{BREAK} is defined by the transport
29155 mechanism and may, in fact, be undefined. @value{GDBN} does not
29156 currently define a @code{BREAK} mechanism for any of the network
29157 interfaces except for TCP, in which case @value{GDBN} sends the
29158 @code{telnet} BREAK sequence.
29160 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
29161 transport mechanisms. It is represented by sending the single byte
29162 @code{0x03} without any of the usual packet overhead described in
29163 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
29164 transmitted as part of a packet, it is considered to be packet data
29165 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
29166 (@pxref{X packet}), used for binary downloads, may include an unescaped
29167 @code{0x03} as part of its packet.
29169 Stubs are not required to recognize these interrupt mechanisms and the
29170 precise meaning associated with receipt of the interrupt is
29171 implementation defined. If the target supports debugging of multiple
29172 threads and/or processes, it should attempt to interrupt all
29173 currently-executing threads and processes.
29174 If the stub is successful at interrupting the
29175 running program, it should send one of the stop
29176 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
29177 of successfully stopping the program in all-stop mode, and a stop reply
29178 for each stopped thread in non-stop mode.
29179 Interrupts received while the
29180 program is stopped are discarded.
29182 @node Notification Packets
29183 @section Notification Packets
29184 @cindex notification packets
29185 @cindex packets, notification
29187 The @value{GDBN} remote serial protocol includes @dfn{notifications},
29188 packets that require no acknowledgment. Both the GDB and the stub
29189 may send notifications (although the only notifications defined at
29190 present are sent by the stub). Notifications carry information
29191 without incurring the round-trip latency of an acknowledgment, and so
29192 are useful for low-impact communications where occasional packet loss
29195 A notification packet has the form @samp{% @var{data} #
29196 @var{checksum}}, where @var{data} is the content of the notification,
29197 and @var{checksum} is a checksum of @var{data}, computed and formatted
29198 as for ordinary @value{GDBN} packets. A notification's @var{data}
29199 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
29200 receiving a notification, the recipient sends no @samp{+} or @samp{-}
29201 to acknowledge the notification's receipt or to report its corruption.
29203 Every notification's @var{data} begins with a name, which contains no
29204 colon characters, followed by a colon character.
29206 Recipients should silently ignore corrupted notifications and
29207 notifications they do not understand. Recipients should restart
29208 timeout periods on receipt of a well-formed notification, whether or
29209 not they understand it.
29211 Senders should only send the notifications described here when this
29212 protocol description specifies that they are permitted. In the
29213 future, we may extend the protocol to permit existing notifications in
29214 new contexts; this rule helps older senders avoid confusing newer
29217 (Older versions of @value{GDBN} ignore bytes received until they see
29218 the @samp{$} byte that begins an ordinary packet, so new stubs may
29219 transmit notifications without fear of confusing older clients. There
29220 are no notifications defined for @value{GDBN} to send at the moment, but we
29221 assume that most older stubs would ignore them, as well.)
29223 The following notification packets from the stub to @value{GDBN} are
29227 @item Stop: @var{reply}
29228 Report an asynchronous stop event in non-stop mode.
29229 The @var{reply} has the form of a stop reply, as
29230 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
29231 for information on how these notifications are acknowledged by
29235 @node Remote Non-Stop
29236 @section Remote Protocol Support for Non-Stop Mode
29238 @value{GDBN}'s remote protocol supports non-stop debugging of
29239 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
29240 supports non-stop mode, it should report that to @value{GDBN} by including
29241 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
29243 @value{GDBN} typically sends a @samp{QNonStop} packet only when
29244 establishing a new connection with the stub. Entering non-stop mode
29245 does not alter the state of any currently-running threads, but targets
29246 must stop all threads in any already-attached processes when entering
29247 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
29248 probe the target state after a mode change.
29250 In non-stop mode, when an attached process encounters an event that
29251 would otherwise be reported with a stop reply, it uses the
29252 asynchronous notification mechanism (@pxref{Notification Packets}) to
29253 inform @value{GDBN}. In contrast to all-stop mode, where all threads
29254 in all processes are stopped when a stop reply is sent, in non-stop
29255 mode only the thread reporting the stop event is stopped. That is,
29256 when reporting a @samp{S} or @samp{T} response to indicate completion
29257 of a step operation, hitting a breakpoint, or a fault, only the
29258 affected thread is stopped; any other still-running threads continue
29259 to run. When reporting a @samp{W} or @samp{X} response, all running
29260 threads belonging to other attached processes continue to run.
29262 Only one stop reply notification at a time may be pending; if
29263 additional stop events occur before @value{GDBN} has acknowledged the
29264 previous notification, they must be queued by the stub for later
29265 synchronous transmission in response to @samp{vStopped} packets from
29266 @value{GDBN}. Because the notification mechanism is unreliable,
29267 the stub is permitted to resend a stop reply notification
29268 if it believes @value{GDBN} may not have received it. @value{GDBN}
29269 ignores additional stop reply notifications received before it has
29270 finished processing a previous notification and the stub has completed
29271 sending any queued stop events.
29273 Otherwise, @value{GDBN} must be prepared to receive a stop reply
29274 notification at any time. Specifically, they may appear when
29275 @value{GDBN} is not otherwise reading input from the stub, or when
29276 @value{GDBN} is expecting to read a normal synchronous response or a
29277 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
29278 Notification packets are distinct from any other communication from
29279 the stub so there is no ambiguity.
29281 After receiving a stop reply notification, @value{GDBN} shall
29282 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
29283 as a regular, synchronous request to the stub. Such acknowledgment
29284 is not required to happen immediately, as @value{GDBN} is permitted to
29285 send other, unrelated packets to the stub first, which the stub should
29288 Upon receiving a @samp{vStopped} packet, if the stub has other queued
29289 stop events to report to @value{GDBN}, it shall respond by sending a
29290 normal stop reply response. @value{GDBN} shall then send another
29291 @samp{vStopped} packet to solicit further responses; again, it is
29292 permitted to send other, unrelated packets as well which the stub
29293 should process normally.
29295 If the stub receives a @samp{vStopped} packet and there are no
29296 additional stop events to report, the stub shall return an @samp{OK}
29297 response. At this point, if further stop events occur, the stub shall
29298 send a new stop reply notification, @value{GDBN} shall accept the
29299 notification, and the process shall be repeated.
29301 In non-stop mode, the target shall respond to the @samp{?} packet as
29302 follows. First, any incomplete stop reply notification/@samp{vStopped}
29303 sequence in progress is abandoned. The target must begin a new
29304 sequence reporting stop events for all stopped threads, whether or not
29305 it has previously reported those events to @value{GDBN}. The first
29306 stop reply is sent as a synchronous reply to the @samp{?} packet, and
29307 subsequent stop replies are sent as responses to @samp{vStopped} packets
29308 using the mechanism described above. The target must not send
29309 asynchronous stop reply notifications until the sequence is complete.
29310 If all threads are running when the target receives the @samp{?} packet,
29311 or if the target is not attached to any process, it shall respond
29314 @node Packet Acknowledgment
29315 @section Packet Acknowledgment
29317 @cindex acknowledgment, for @value{GDBN} remote
29318 @cindex packet acknowledgment, for @value{GDBN} remote
29319 By default, when either the host or the target machine receives a packet,
29320 the first response expected is an acknowledgment: either @samp{+} (to indicate
29321 the package was received correctly) or @samp{-} (to request retransmission).
29322 This mechanism allows the @value{GDBN} remote protocol to operate over
29323 unreliable transport mechanisms, such as a serial line.
29325 In cases where the transport mechanism is itself reliable (such as a pipe or
29326 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
29327 It may be desirable to disable them in that case to reduce communication
29328 overhead, or for other reasons. This can be accomplished by means of the
29329 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
29331 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
29332 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
29333 and response format still includes the normal checksum, as described in
29334 @ref{Overview}, but the checksum may be ignored by the receiver.
29336 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
29337 no-acknowledgment mode, it should report that to @value{GDBN}
29338 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
29339 @pxref{qSupported}.
29340 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
29341 disabled via the @code{set remote noack-packet off} command
29342 (@pxref{Remote Configuration}),
29343 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
29344 Only then may the stub actually turn off packet acknowledgments.
29345 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
29346 response, which can be safely ignored by the stub.
29348 Note that @code{set remote noack-packet} command only affects negotiation
29349 between @value{GDBN} and the stub when subsequent connections are made;
29350 it does not affect the protocol acknowledgment state for any current
29352 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
29353 new connection is established,
29354 there is also no protocol request to re-enable the acknowledgments
29355 for the current connection, once disabled.
29360 Example sequence of a target being re-started. Notice how the restart
29361 does not get any direct output:
29366 @emph{target restarts}
29369 <- @code{T001:1234123412341234}
29373 Example sequence of a target being stepped by a single instruction:
29376 -> @code{G1445@dots{}}
29381 <- @code{T001:1234123412341234}
29385 <- @code{1455@dots{}}
29389 @node File-I/O Remote Protocol Extension
29390 @section File-I/O Remote Protocol Extension
29391 @cindex File-I/O remote protocol extension
29394 * File-I/O Overview::
29395 * Protocol Basics::
29396 * The F Request Packet::
29397 * The F Reply Packet::
29398 * The Ctrl-C Message::
29400 * List of Supported Calls::
29401 * Protocol-specific Representation of Datatypes::
29403 * File-I/O Examples::
29406 @node File-I/O Overview
29407 @subsection File-I/O Overview
29408 @cindex file-i/o overview
29410 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
29411 target to use the host's file system and console I/O to perform various
29412 system calls. System calls on the target system are translated into a
29413 remote protocol packet to the host system, which then performs the needed
29414 actions and returns a response packet to the target system.
29415 This simulates file system operations even on targets that lack file systems.
29417 The protocol is defined to be independent of both the host and target systems.
29418 It uses its own internal representation of datatypes and values. Both
29419 @value{GDBN} and the target's @value{GDBN} stub are responsible for
29420 translating the system-dependent value representations into the internal
29421 protocol representations when data is transmitted.
29423 The communication is synchronous. A system call is possible only when
29424 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
29425 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
29426 the target is stopped to allow deterministic access to the target's
29427 memory. Therefore File-I/O is not interruptible by target signals. On
29428 the other hand, it is possible to interrupt File-I/O by a user interrupt
29429 (@samp{Ctrl-C}) within @value{GDBN}.
29431 The target's request to perform a host system call does not finish
29432 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
29433 after finishing the system call, the target returns to continuing the
29434 previous activity (continue, step). No additional continue or step
29435 request from @value{GDBN} is required.
29438 (@value{GDBP}) continue
29439 <- target requests 'system call X'
29440 target is stopped, @value{GDBN} executes system call
29441 -> @value{GDBN} returns result
29442 ... target continues, @value{GDBN} returns to wait for the target
29443 <- target hits breakpoint and sends a Txx packet
29446 The protocol only supports I/O on the console and to regular files on
29447 the host file system. Character or block special devices, pipes,
29448 named pipes, sockets or any other communication method on the host
29449 system are not supported by this protocol.
29451 File I/O is not supported in non-stop mode.
29453 @node Protocol Basics
29454 @subsection Protocol Basics
29455 @cindex protocol basics, file-i/o
29457 The File-I/O protocol uses the @code{F} packet as the request as well
29458 as reply packet. Since a File-I/O system call can only occur when
29459 @value{GDBN} is waiting for a response from the continuing or stepping target,
29460 the File-I/O request is a reply that @value{GDBN} has to expect as a result
29461 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
29462 This @code{F} packet contains all information needed to allow @value{GDBN}
29463 to call the appropriate host system call:
29467 A unique identifier for the requested system call.
29470 All parameters to the system call. Pointers are given as addresses
29471 in the target memory address space. Pointers to strings are given as
29472 pointer/length pair. Numerical values are given as they are.
29473 Numerical control flags are given in a protocol-specific representation.
29477 At this point, @value{GDBN} has to perform the following actions.
29481 If the parameters include pointer values to data needed as input to a
29482 system call, @value{GDBN} requests this data from the target with a
29483 standard @code{m} packet request. This additional communication has to be
29484 expected by the target implementation and is handled as any other @code{m}
29488 @value{GDBN} translates all value from protocol representation to host
29489 representation as needed. Datatypes are coerced into the host types.
29492 @value{GDBN} calls the system call.
29495 It then coerces datatypes back to protocol representation.
29498 If the system call is expected to return data in buffer space specified
29499 by pointer parameters to the call, the data is transmitted to the
29500 target using a @code{M} or @code{X} packet. This packet has to be expected
29501 by the target implementation and is handled as any other @code{M} or @code{X}
29506 Eventually @value{GDBN} replies with another @code{F} packet which contains all
29507 necessary information for the target to continue. This at least contains
29514 @code{errno}, if has been changed by the system call.
29521 After having done the needed type and value coercion, the target continues
29522 the latest continue or step action.
29524 @node The F Request Packet
29525 @subsection The @code{F} Request Packet
29526 @cindex file-i/o request packet
29527 @cindex @code{F} request packet
29529 The @code{F} request packet has the following format:
29532 @item F@var{call-id},@var{parameter@dots{}}
29534 @var{call-id} is the identifier to indicate the host system call to be called.
29535 This is just the name of the function.
29537 @var{parameter@dots{}} are the parameters to the system call.
29538 Parameters are hexadecimal integer values, either the actual values in case
29539 of scalar datatypes, pointers to target buffer space in case of compound
29540 datatypes and unspecified memory areas, or pointer/length pairs in case
29541 of string parameters. These are appended to the @var{call-id} as a
29542 comma-delimited list. All values are transmitted in ASCII
29543 string representation, pointer/length pairs separated by a slash.
29549 @node The F Reply Packet
29550 @subsection The @code{F} Reply Packet
29551 @cindex file-i/o reply packet
29552 @cindex @code{F} reply packet
29554 The @code{F} reply packet has the following format:
29558 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
29560 @var{retcode} is the return code of the system call as hexadecimal value.
29562 @var{errno} is the @code{errno} set by the call, in protocol-specific
29564 This parameter can be omitted if the call was successful.
29566 @var{Ctrl-C flag} is only sent if the user requested a break. In this
29567 case, @var{errno} must be sent as well, even if the call was successful.
29568 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
29575 or, if the call was interrupted before the host call has been performed:
29582 assuming 4 is the protocol-specific representation of @code{EINTR}.
29587 @node The Ctrl-C Message
29588 @subsection The @samp{Ctrl-C} Message
29589 @cindex ctrl-c message, in file-i/o protocol
29591 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
29592 reply packet (@pxref{The F Reply Packet}),
29593 the target should behave as if it had
29594 gotten a break message. The meaning for the target is ``system call
29595 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
29596 (as with a break message) and return to @value{GDBN} with a @code{T02}
29599 It's important for the target to know in which
29600 state the system call was interrupted. There are two possible cases:
29604 The system call hasn't been performed on the host yet.
29607 The system call on the host has been finished.
29611 These two states can be distinguished by the target by the value of the
29612 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
29613 call hasn't been performed. This is equivalent to the @code{EINTR} handling
29614 on POSIX systems. In any other case, the target may presume that the
29615 system call has been finished --- successfully or not --- and should behave
29616 as if the break message arrived right after the system call.
29618 @value{GDBN} must behave reliably. If the system call has not been called
29619 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
29620 @code{errno} in the packet. If the system call on the host has been finished
29621 before the user requests a break, the full action must be finished by
29622 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
29623 The @code{F} packet may only be sent when either nothing has happened
29624 or the full action has been completed.
29627 @subsection Console I/O
29628 @cindex console i/o as part of file-i/o
29630 By default and if not explicitly closed by the target system, the file
29631 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
29632 on the @value{GDBN} console is handled as any other file output operation
29633 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
29634 by @value{GDBN} so that after the target read request from file descriptor
29635 0 all following typing is buffered until either one of the following
29640 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
29642 system call is treated as finished.
29645 The user presses @key{RET}. This is treated as end of input with a trailing
29649 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
29650 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
29654 If the user has typed more characters than fit in the buffer given to
29655 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
29656 either another @code{read(0, @dots{})} is requested by the target, or debugging
29657 is stopped at the user's request.
29660 @node List of Supported Calls
29661 @subsection List of Supported Calls
29662 @cindex list of supported file-i/o calls
29679 @unnumberedsubsubsec open
29680 @cindex open, file-i/o system call
29685 int open(const char *pathname, int flags);
29686 int open(const char *pathname, int flags, mode_t mode);
29690 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
29693 @var{flags} is the bitwise @code{OR} of the following values:
29697 If the file does not exist it will be created. The host
29698 rules apply as far as file ownership and time stamps
29702 When used with @code{O_CREAT}, if the file already exists it is
29703 an error and open() fails.
29706 If the file already exists and the open mode allows
29707 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
29708 truncated to zero length.
29711 The file is opened in append mode.
29714 The file is opened for reading only.
29717 The file is opened for writing only.
29720 The file is opened for reading and writing.
29724 Other bits are silently ignored.
29728 @var{mode} is the bitwise @code{OR} of the following values:
29732 User has read permission.
29735 User has write permission.
29738 Group has read permission.
29741 Group has write permission.
29744 Others have read permission.
29747 Others have write permission.
29751 Other bits are silently ignored.
29754 @item Return value:
29755 @code{open} returns the new file descriptor or -1 if an error
29762 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
29765 @var{pathname} refers to a directory.
29768 The requested access is not allowed.
29771 @var{pathname} was too long.
29774 A directory component in @var{pathname} does not exist.
29777 @var{pathname} refers to a device, pipe, named pipe or socket.
29780 @var{pathname} refers to a file on a read-only filesystem and
29781 write access was requested.
29784 @var{pathname} is an invalid pointer value.
29787 No space on device to create the file.
29790 The process already has the maximum number of files open.
29793 The limit on the total number of files open on the system
29797 The call was interrupted by the user.
29803 @unnumberedsubsubsec close
29804 @cindex close, file-i/o system call
29813 @samp{Fclose,@var{fd}}
29815 @item Return value:
29816 @code{close} returns zero on success, or -1 if an error occurred.
29822 @var{fd} isn't a valid open file descriptor.
29825 The call was interrupted by the user.
29831 @unnumberedsubsubsec read
29832 @cindex read, file-i/o system call
29837 int read(int fd, void *buf, unsigned int count);
29841 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
29843 @item Return value:
29844 On success, the number of bytes read is returned.
29845 Zero indicates end of file. If count is zero, read
29846 returns zero as well. On error, -1 is returned.
29852 @var{fd} is not a valid file descriptor or is not open for
29856 @var{bufptr} is an invalid pointer value.
29859 The call was interrupted by the user.
29865 @unnumberedsubsubsec write
29866 @cindex write, file-i/o system call
29871 int write(int fd, const void *buf, unsigned int count);
29875 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
29877 @item Return value:
29878 On success, the number of bytes written are returned.
29879 Zero indicates nothing was written. On error, -1
29886 @var{fd} is not a valid file descriptor or is not open for
29890 @var{bufptr} is an invalid pointer value.
29893 An attempt was made to write a file that exceeds the
29894 host-specific maximum file size allowed.
29897 No space on device to write the data.
29900 The call was interrupted by the user.
29906 @unnumberedsubsubsec lseek
29907 @cindex lseek, file-i/o system call
29912 long lseek (int fd, long offset, int flag);
29916 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
29918 @var{flag} is one of:
29922 The offset is set to @var{offset} bytes.
29925 The offset is set to its current location plus @var{offset}
29929 The offset is set to the size of the file plus @var{offset}
29933 @item Return value:
29934 On success, the resulting unsigned offset in bytes from
29935 the beginning of the file is returned. Otherwise, a
29936 value of -1 is returned.
29942 @var{fd} is not a valid open file descriptor.
29945 @var{fd} is associated with the @value{GDBN} console.
29948 @var{flag} is not a proper value.
29951 The call was interrupted by the user.
29957 @unnumberedsubsubsec rename
29958 @cindex rename, file-i/o system call
29963 int rename(const char *oldpath, const char *newpath);
29967 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
29969 @item Return value:
29970 On success, zero is returned. On error, -1 is returned.
29976 @var{newpath} is an existing directory, but @var{oldpath} is not a
29980 @var{newpath} is a non-empty directory.
29983 @var{oldpath} or @var{newpath} is a directory that is in use by some
29987 An attempt was made to make a directory a subdirectory
29991 A component used as a directory in @var{oldpath} or new
29992 path is not a directory. Or @var{oldpath} is a directory
29993 and @var{newpath} exists but is not a directory.
29996 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
29999 No access to the file or the path of the file.
30003 @var{oldpath} or @var{newpath} was too long.
30006 A directory component in @var{oldpath} or @var{newpath} does not exist.
30009 The file is on a read-only filesystem.
30012 The device containing the file has no room for the new
30016 The call was interrupted by the user.
30022 @unnumberedsubsubsec unlink
30023 @cindex unlink, file-i/o system call
30028 int unlink(const char *pathname);
30032 @samp{Funlink,@var{pathnameptr}/@var{len}}
30034 @item Return value:
30035 On success, zero is returned. On error, -1 is returned.
30041 No access to the file or the path of the file.
30044 The system does not allow unlinking of directories.
30047 The file @var{pathname} cannot be unlinked because it's
30048 being used by another process.
30051 @var{pathnameptr} is an invalid pointer value.
30054 @var{pathname} was too long.
30057 A directory component in @var{pathname} does not exist.
30060 A component of the path is not a directory.
30063 The file is on a read-only filesystem.
30066 The call was interrupted by the user.
30072 @unnumberedsubsubsec stat/fstat
30073 @cindex fstat, file-i/o system call
30074 @cindex stat, file-i/o system call
30079 int stat(const char *pathname, struct stat *buf);
30080 int fstat(int fd, struct stat *buf);
30084 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
30085 @samp{Ffstat,@var{fd},@var{bufptr}}
30087 @item Return value:
30088 On success, zero is returned. On error, -1 is returned.
30094 @var{fd} is not a valid open file.
30097 A directory component in @var{pathname} does not exist or the
30098 path is an empty string.
30101 A component of the path is not a directory.
30104 @var{pathnameptr} is an invalid pointer value.
30107 No access to the file or the path of the file.
30110 @var{pathname} was too long.
30113 The call was interrupted by the user.
30119 @unnumberedsubsubsec gettimeofday
30120 @cindex gettimeofday, file-i/o system call
30125 int gettimeofday(struct timeval *tv, void *tz);
30129 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
30131 @item Return value:
30132 On success, 0 is returned, -1 otherwise.
30138 @var{tz} is a non-NULL pointer.
30141 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
30147 @unnumberedsubsubsec isatty
30148 @cindex isatty, file-i/o system call
30153 int isatty(int fd);
30157 @samp{Fisatty,@var{fd}}
30159 @item Return value:
30160 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
30166 The call was interrupted by the user.
30171 Note that the @code{isatty} call is treated as a special case: it returns
30172 1 to the target if the file descriptor is attached
30173 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
30174 would require implementing @code{ioctl} and would be more complex than
30179 @unnumberedsubsubsec system
30180 @cindex system, file-i/o system call
30185 int system(const char *command);
30189 @samp{Fsystem,@var{commandptr}/@var{len}}
30191 @item Return value:
30192 If @var{len} is zero, the return value indicates whether a shell is
30193 available. A zero return value indicates a shell is not available.
30194 For non-zero @var{len}, the value returned is -1 on error and the
30195 return status of the command otherwise. Only the exit status of the
30196 command is returned, which is extracted from the host's @code{system}
30197 return value by calling @code{WEXITSTATUS(retval)}. In case
30198 @file{/bin/sh} could not be executed, 127 is returned.
30204 The call was interrupted by the user.
30209 @value{GDBN} takes over the full task of calling the necessary host calls
30210 to perform the @code{system} call. The return value of @code{system} on
30211 the host is simplified before it's returned
30212 to the target. Any termination signal information from the child process
30213 is discarded, and the return value consists
30214 entirely of the exit status of the called command.
30216 Due to security concerns, the @code{system} call is by default refused
30217 by @value{GDBN}. The user has to allow this call explicitly with the
30218 @code{set remote system-call-allowed 1} command.
30221 @item set remote system-call-allowed
30222 @kindex set remote system-call-allowed
30223 Control whether to allow the @code{system} calls in the File I/O
30224 protocol for the remote target. The default is zero (disabled).
30226 @item show remote system-call-allowed
30227 @kindex show remote system-call-allowed
30228 Show whether the @code{system} calls are allowed in the File I/O
30232 @node Protocol-specific Representation of Datatypes
30233 @subsection Protocol-specific Representation of Datatypes
30234 @cindex protocol-specific representation of datatypes, in file-i/o protocol
30237 * Integral Datatypes::
30239 * Memory Transfer::
30244 @node Integral Datatypes
30245 @unnumberedsubsubsec Integral Datatypes
30246 @cindex integral datatypes, in file-i/o protocol
30248 The integral datatypes used in the system calls are @code{int},
30249 @code{unsigned int}, @code{long}, @code{unsigned long},
30250 @code{mode_t}, and @code{time_t}.
30252 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
30253 implemented as 32 bit values in this protocol.
30255 @code{long} and @code{unsigned long} are implemented as 64 bit types.
30257 @xref{Limits}, for corresponding MIN and MAX values (similar to those
30258 in @file{limits.h}) to allow range checking on host and target.
30260 @code{time_t} datatypes are defined as seconds since the Epoch.
30262 All integral datatypes transferred as part of a memory read or write of a
30263 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
30266 @node Pointer Values
30267 @unnumberedsubsubsec Pointer Values
30268 @cindex pointer values, in file-i/o protocol
30270 Pointers to target data are transmitted as they are. An exception
30271 is made for pointers to buffers for which the length isn't
30272 transmitted as part of the function call, namely strings. Strings
30273 are transmitted as a pointer/length pair, both as hex values, e.g.@:
30280 which is a pointer to data of length 18 bytes at position 0x1aaf.
30281 The length is defined as the full string length in bytes, including
30282 the trailing null byte. For example, the string @code{"hello world"}
30283 at address 0x123456 is transmitted as
30289 @node Memory Transfer
30290 @unnumberedsubsubsec Memory Transfer
30291 @cindex memory transfer, in file-i/o protocol
30293 Structured data which is transferred using a memory read or write (for
30294 example, a @code{struct stat}) is expected to be in a protocol-specific format
30295 with all scalar multibyte datatypes being big endian. Translation to
30296 this representation needs to be done both by the target before the @code{F}
30297 packet is sent, and by @value{GDBN} before
30298 it transfers memory to the target. Transferred pointers to structured
30299 data should point to the already-coerced data at any time.
30303 @unnumberedsubsubsec struct stat
30304 @cindex struct stat, in file-i/o protocol
30306 The buffer of type @code{struct stat} used by the target and @value{GDBN}
30307 is defined as follows:
30311 unsigned int st_dev; /* device */
30312 unsigned int st_ino; /* inode */
30313 mode_t st_mode; /* protection */
30314 unsigned int st_nlink; /* number of hard links */
30315 unsigned int st_uid; /* user ID of owner */
30316 unsigned int st_gid; /* group ID of owner */
30317 unsigned int st_rdev; /* device type (if inode device) */
30318 unsigned long st_size; /* total size, in bytes */
30319 unsigned long st_blksize; /* blocksize for filesystem I/O */
30320 unsigned long st_blocks; /* number of blocks allocated */
30321 time_t st_atime; /* time of last access */
30322 time_t st_mtime; /* time of last modification */
30323 time_t st_ctime; /* time of last change */
30327 The integral datatypes conform to the definitions given in the
30328 appropriate section (see @ref{Integral Datatypes}, for details) so this
30329 structure is of size 64 bytes.
30331 The values of several fields have a restricted meaning and/or
30337 A value of 0 represents a file, 1 the console.
30340 No valid meaning for the target. Transmitted unchanged.
30343 Valid mode bits are described in @ref{Constants}. Any other
30344 bits have currently no meaning for the target.
30349 No valid meaning for the target. Transmitted unchanged.
30354 These values have a host and file system dependent
30355 accuracy. Especially on Windows hosts, the file system may not
30356 support exact timing values.
30359 The target gets a @code{struct stat} of the above representation and is
30360 responsible for coercing it to the target representation before
30363 Note that due to size differences between the host, target, and protocol
30364 representations of @code{struct stat} members, these members could eventually
30365 get truncated on the target.
30367 @node struct timeval
30368 @unnumberedsubsubsec struct timeval
30369 @cindex struct timeval, in file-i/o protocol
30371 The buffer of type @code{struct timeval} used by the File-I/O protocol
30372 is defined as follows:
30376 time_t tv_sec; /* second */
30377 long tv_usec; /* microsecond */
30381 The integral datatypes conform to the definitions given in the
30382 appropriate section (see @ref{Integral Datatypes}, for details) so this
30383 structure is of size 8 bytes.
30386 @subsection Constants
30387 @cindex constants, in file-i/o protocol
30389 The following values are used for the constants inside of the
30390 protocol. @value{GDBN} and target are responsible for translating these
30391 values before and after the call as needed.
30402 @unnumberedsubsubsec Open Flags
30403 @cindex open flags, in file-i/o protocol
30405 All values are given in hexadecimal representation.
30417 @node mode_t Values
30418 @unnumberedsubsubsec mode_t Values
30419 @cindex mode_t values, in file-i/o protocol
30421 All values are given in octal representation.
30438 @unnumberedsubsubsec Errno Values
30439 @cindex errno values, in file-i/o protocol
30441 All values are given in decimal representation.
30466 @code{EUNKNOWN} is used as a fallback error value if a host system returns
30467 any error value not in the list of supported error numbers.
30470 @unnumberedsubsubsec Lseek Flags
30471 @cindex lseek flags, in file-i/o protocol
30480 @unnumberedsubsubsec Limits
30481 @cindex limits, in file-i/o protocol
30483 All values are given in decimal representation.
30486 INT_MIN -2147483648
30488 UINT_MAX 4294967295
30489 LONG_MIN -9223372036854775808
30490 LONG_MAX 9223372036854775807
30491 ULONG_MAX 18446744073709551615
30494 @node File-I/O Examples
30495 @subsection File-I/O Examples
30496 @cindex file-i/o examples
30498 Example sequence of a write call, file descriptor 3, buffer is at target
30499 address 0x1234, 6 bytes should be written:
30502 <- @code{Fwrite,3,1234,6}
30503 @emph{request memory read from target}
30506 @emph{return "6 bytes written"}
30510 Example sequence of a read call, file descriptor 3, buffer is at target
30511 address 0x1234, 6 bytes should be read:
30514 <- @code{Fread,3,1234,6}
30515 @emph{request memory write to target}
30516 -> @code{X1234,6:XXXXXX}
30517 @emph{return "6 bytes read"}
30521 Example sequence of a read call, call fails on the host due to invalid
30522 file descriptor (@code{EBADF}):
30525 <- @code{Fread,3,1234,6}
30529 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
30533 <- @code{Fread,3,1234,6}
30538 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
30542 <- @code{Fread,3,1234,6}
30543 -> @code{X1234,6:XXXXXX}
30547 @node Library List Format
30548 @section Library List Format
30549 @cindex library list format, remote protocol
30551 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
30552 same process as your application to manage libraries. In this case,
30553 @value{GDBN} can use the loader's symbol table and normal memory
30554 operations to maintain a list of shared libraries. On other
30555 platforms, the operating system manages loaded libraries.
30556 @value{GDBN} can not retrieve the list of currently loaded libraries
30557 through memory operations, so it uses the @samp{qXfer:libraries:read}
30558 packet (@pxref{qXfer library list read}) instead. The remote stub
30559 queries the target's operating system and reports which libraries
30562 The @samp{qXfer:libraries:read} packet returns an XML document which
30563 lists loaded libraries and their offsets. Each library has an
30564 associated name and one or more segment or section base addresses,
30565 which report where the library was loaded in memory.
30567 For the common case of libraries that are fully linked binaries, the
30568 library should have a list of segments. If the target supports
30569 dynamic linking of a relocatable object file, its library XML element
30570 should instead include a list of allocated sections. The segment or
30571 section bases are start addresses, not relocation offsets; they do not
30572 depend on the library's link-time base addresses.
30574 @value{GDBN} must be linked with the Expat library to support XML
30575 library lists. @xref{Expat}.
30577 A simple memory map, with one loaded library relocated by a single
30578 offset, looks like this:
30582 <library name="/lib/libc.so.6">
30583 <segment address="0x10000000"/>
30588 Another simple memory map, with one loaded library with three
30589 allocated sections (.text, .data, .bss), looks like this:
30593 <library name="sharedlib.o">
30594 <section address="0x10000000"/>
30595 <section address="0x20000000"/>
30596 <section address="0x30000000"/>
30601 The format of a library list is described by this DTD:
30604 <!-- library-list: Root element with versioning -->
30605 <!ELEMENT library-list (library)*>
30606 <!ATTLIST library-list version CDATA #FIXED "1.0">
30607 <!ELEMENT library (segment*, section*)>
30608 <!ATTLIST library name CDATA #REQUIRED>
30609 <!ELEMENT segment EMPTY>
30610 <!ATTLIST segment address CDATA #REQUIRED>
30611 <!ELEMENT section EMPTY>
30612 <!ATTLIST section address CDATA #REQUIRED>
30615 In addition, segments and section descriptors cannot be mixed within a
30616 single library element, and you must supply at least one segment or
30617 section for each library.
30619 @node Memory Map Format
30620 @section Memory Map Format
30621 @cindex memory map format
30623 To be able to write into flash memory, @value{GDBN} needs to obtain a
30624 memory map from the target. This section describes the format of the
30627 The memory map is obtained using the @samp{qXfer:memory-map:read}
30628 (@pxref{qXfer memory map read}) packet and is an XML document that
30629 lists memory regions.
30631 @value{GDBN} must be linked with the Expat library to support XML
30632 memory maps. @xref{Expat}.
30634 The top-level structure of the document is shown below:
30637 <?xml version="1.0"?>
30638 <!DOCTYPE memory-map
30639 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
30640 "http://sourceware.org/gdb/gdb-memory-map.dtd">
30646 Each region can be either:
30651 A region of RAM starting at @var{addr} and extending for @var{length}
30655 <memory type="ram" start="@var{addr}" length="@var{length}"/>
30660 A region of read-only memory:
30663 <memory type="rom" start="@var{addr}" length="@var{length}"/>
30668 A region of flash memory, with erasure blocks @var{blocksize}
30672 <memory type="flash" start="@var{addr}" length="@var{length}">
30673 <property name="blocksize">@var{blocksize}</property>
30679 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
30680 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
30681 packets to write to addresses in such ranges.
30683 The formal DTD for memory map format is given below:
30686 <!-- ................................................... -->
30687 <!-- Memory Map XML DTD ................................ -->
30688 <!-- File: memory-map.dtd .............................. -->
30689 <!-- .................................... .............. -->
30690 <!-- memory-map.dtd -->
30691 <!-- memory-map: Root element with versioning -->
30692 <!ELEMENT memory-map (memory | property)>
30693 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
30694 <!ELEMENT memory (property)>
30695 <!-- memory: Specifies a memory region,
30696 and its type, or device. -->
30697 <!ATTLIST memory type CDATA #REQUIRED
30698 start CDATA #REQUIRED
30699 length CDATA #REQUIRED
30700 device CDATA #IMPLIED>
30701 <!-- property: Generic attribute tag -->
30702 <!ELEMENT property (#PCDATA | property)*>
30703 <!ATTLIST property name CDATA #REQUIRED>
30706 @include agentexpr.texi
30708 @node Target Descriptions
30709 @appendix Target Descriptions
30710 @cindex target descriptions
30712 @strong{Warning:} target descriptions are still under active development,
30713 and the contents and format may change between @value{GDBN} releases.
30714 The format is expected to stabilize in the future.
30716 One of the challenges of using @value{GDBN} to debug embedded systems
30717 is that there are so many minor variants of each processor
30718 architecture in use. It is common practice for vendors to start with
30719 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
30720 and then make changes to adapt it to a particular market niche. Some
30721 architectures have hundreds of variants, available from dozens of
30722 vendors. This leads to a number of problems:
30726 With so many different customized processors, it is difficult for
30727 the @value{GDBN} maintainers to keep up with the changes.
30729 Since individual variants may have short lifetimes or limited
30730 audiences, it may not be worthwhile to carry information about every
30731 variant in the @value{GDBN} source tree.
30733 When @value{GDBN} does support the architecture of the embedded system
30734 at hand, the task of finding the correct architecture name to give the
30735 @command{set architecture} command can be error-prone.
30738 To address these problems, the @value{GDBN} remote protocol allows a
30739 target system to not only identify itself to @value{GDBN}, but to
30740 actually describe its own features. This lets @value{GDBN} support
30741 processor variants it has never seen before --- to the extent that the
30742 descriptions are accurate, and that @value{GDBN} understands them.
30744 @value{GDBN} must be linked with the Expat library to support XML
30745 target descriptions. @xref{Expat}.
30748 * Retrieving Descriptions:: How descriptions are fetched from a target.
30749 * Target Description Format:: The contents of a target description.
30750 * Predefined Target Types:: Standard types available for target
30752 * Standard Target Features:: Features @value{GDBN} knows about.
30755 @node Retrieving Descriptions
30756 @section Retrieving Descriptions
30758 Target descriptions can be read from the target automatically, or
30759 specified by the user manually. The default behavior is to read the
30760 description from the target. @value{GDBN} retrieves it via the remote
30761 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
30762 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
30763 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
30764 XML document, of the form described in @ref{Target Description
30767 Alternatively, you can specify a file to read for the target description.
30768 If a file is set, the target will not be queried. The commands to
30769 specify a file are:
30772 @cindex set tdesc filename
30773 @item set tdesc filename @var{path}
30774 Read the target description from @var{path}.
30776 @cindex unset tdesc filename
30777 @item unset tdesc filename
30778 Do not read the XML target description from a file. @value{GDBN}
30779 will use the description supplied by the current target.
30781 @cindex show tdesc filename
30782 @item show tdesc filename
30783 Show the filename to read for a target description, if any.
30787 @node Target Description Format
30788 @section Target Description Format
30789 @cindex target descriptions, XML format
30791 A target description annex is an @uref{http://www.w3.org/XML/, XML}
30792 document which complies with the Document Type Definition provided in
30793 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
30794 means you can use generally available tools like @command{xmllint} to
30795 check that your feature descriptions are well-formed and valid.
30796 However, to help people unfamiliar with XML write descriptions for
30797 their targets, we also describe the grammar here.
30799 Target descriptions can identify the architecture of the remote target
30800 and (for some architectures) provide information about custom register
30801 sets. They can also identify the OS ABI of the remote target.
30802 @value{GDBN} can use this information to autoconfigure for your
30803 target, or to warn you if you connect to an unsupported target.
30805 Here is a simple target description:
30808 <target version="1.0">
30809 <architecture>i386:x86-64</architecture>
30814 This minimal description only says that the target uses
30815 the x86-64 architecture.
30817 A target description has the following overall form, with [ ] marking
30818 optional elements and @dots{} marking repeatable elements. The elements
30819 are explained further below.
30822 <?xml version="1.0"?>
30823 <!DOCTYPE target SYSTEM "gdb-target.dtd">
30824 <target version="1.0">
30825 @r{[}@var{architecture}@r{]}
30826 @r{[}@var{osabi}@r{]}
30827 @r{[}@var{compatible}@r{]}
30828 @r{[}@var{feature}@dots{}@r{]}
30833 The description is generally insensitive to whitespace and line
30834 breaks, under the usual common-sense rules. The XML version
30835 declaration and document type declaration can generally be omitted
30836 (@value{GDBN} does not require them), but specifying them may be
30837 useful for XML validation tools. The @samp{version} attribute for
30838 @samp{<target>} may also be omitted, but we recommend
30839 including it; if future versions of @value{GDBN} use an incompatible
30840 revision of @file{gdb-target.dtd}, they will detect and report
30841 the version mismatch.
30843 @subsection Inclusion
30844 @cindex target descriptions, inclusion
30847 @cindex <xi:include>
30850 It can sometimes be valuable to split a target description up into
30851 several different annexes, either for organizational purposes, or to
30852 share files between different possible target descriptions. You can
30853 divide a description into multiple files by replacing any element of
30854 the target description with an inclusion directive of the form:
30857 <xi:include href="@var{document}"/>
30861 When @value{GDBN} encounters an element of this form, it will retrieve
30862 the named XML @var{document}, and replace the inclusion directive with
30863 the contents of that document. If the current description was read
30864 using @samp{qXfer}, then so will be the included document;
30865 @var{document} will be interpreted as the name of an annex. If the
30866 current description was read from a file, @value{GDBN} will look for
30867 @var{document} as a file in the same directory where it found the
30868 original description.
30870 @subsection Architecture
30871 @cindex <architecture>
30873 An @samp{<architecture>} element has this form:
30876 <architecture>@var{arch}</architecture>
30879 @var{arch} is one of the architectures from the set accepted by
30880 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
30883 @cindex @code{<osabi>}
30885 This optional field was introduced in @value{GDBN} version 7.0.
30886 Previous versions of @value{GDBN} ignore it.
30888 An @samp{<osabi>} element has this form:
30891 <osabi>@var{abi-name}</osabi>
30894 @var{abi-name} is an OS ABI name from the same selection accepted by
30895 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
30897 @subsection Compatible Architecture
30898 @cindex @code{<compatible>}
30900 This optional field was introduced in @value{GDBN} version 7.0.
30901 Previous versions of @value{GDBN} ignore it.
30903 A @samp{<compatible>} element has this form:
30906 <compatible>@var{arch}</compatible>
30909 @var{arch} is one of the architectures from the set accepted by
30910 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
30912 A @samp{<compatible>} element is used to specify that the target
30913 is able to run binaries in some other than the main target architecture
30914 given by the @samp{<architecture>} element. For example, on the
30915 Cell Broadband Engine, the main architecture is @code{powerpc:common}
30916 or @code{powerpc:common64}, but the system is able to run binaries
30917 in the @code{spu} architecture as well. The way to describe this
30918 capability with @samp{<compatible>} is as follows:
30921 <architecture>powerpc:common</architecture>
30922 <compatible>spu</compatible>
30925 @subsection Features
30928 Each @samp{<feature>} describes some logical portion of the target
30929 system. Features are currently used to describe available CPU
30930 registers and the types of their contents. A @samp{<feature>} element
30934 <feature name="@var{name}">
30935 @r{[}@var{type}@dots{}@r{]}
30941 Each feature's name should be unique within the description. The name
30942 of a feature does not matter unless @value{GDBN} has some special
30943 knowledge of the contents of that feature; if it does, the feature
30944 should have its standard name. @xref{Standard Target Features}.
30948 Any register's value is a collection of bits which @value{GDBN} must
30949 interpret. The default interpretation is a two's complement integer,
30950 but other types can be requested by name in the register description.
30951 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
30952 Target Types}), and the description can define additional composite types.
30954 Each type element must have an @samp{id} attribute, which gives
30955 a unique (within the containing @samp{<feature>}) name to the type.
30956 Types must be defined before they are used.
30959 Some targets offer vector registers, which can be treated as arrays
30960 of scalar elements. These types are written as @samp{<vector>} elements,
30961 specifying the array element type, @var{type}, and the number of elements,
30965 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
30969 If a register's value is usefully viewed in multiple ways, define it
30970 with a union type containing the useful representations. The
30971 @samp{<union>} element contains one or more @samp{<field>} elements,
30972 each of which has a @var{name} and a @var{type}:
30975 <union id="@var{id}">
30976 <field name="@var{name}" type="@var{type}"/>
30981 @subsection Registers
30984 Each register is represented as an element with this form:
30987 <reg name="@var{name}"
30988 bitsize="@var{size}"
30989 @r{[}regnum="@var{num}"@r{]}
30990 @r{[}save-restore="@var{save-restore}"@r{]}
30991 @r{[}type="@var{type}"@r{]}
30992 @r{[}group="@var{group}"@r{]}/>
30996 The components are as follows:
31001 The register's name; it must be unique within the target description.
31004 The register's size, in bits.
31007 The register's number. If omitted, a register's number is one greater
31008 than that of the previous register (either in the current feature or in
31009 a preceeding feature); the first register in the target description
31010 defaults to zero. This register number is used to read or write
31011 the register; e.g.@: it is used in the remote @code{p} and @code{P}
31012 packets, and registers appear in the @code{g} and @code{G} packets
31013 in order of increasing register number.
31016 Whether the register should be preserved across inferior function
31017 calls; this must be either @code{yes} or @code{no}. The default is
31018 @code{yes}, which is appropriate for most registers except for
31019 some system control registers; this is not related to the target's
31023 The type of the register. @var{type} may be a predefined type, a type
31024 defined in the current feature, or one of the special types @code{int}
31025 and @code{float}. @code{int} is an integer type of the correct size
31026 for @var{bitsize}, and @code{float} is a floating point type (in the
31027 architecture's normal floating point format) of the correct size for
31028 @var{bitsize}. The default is @code{int}.
31031 The register group to which this register belongs. @var{group} must
31032 be either @code{general}, @code{float}, or @code{vector}. If no
31033 @var{group} is specified, @value{GDBN} will not display the register
31034 in @code{info registers}.
31038 @node Predefined Target Types
31039 @section Predefined Target Types
31040 @cindex target descriptions, predefined types
31042 Type definitions in the self-description can build up composite types
31043 from basic building blocks, but can not define fundamental types. Instead,
31044 standard identifiers are provided by @value{GDBN} for the fundamental
31045 types. The currently supported types are:
31054 Signed integer types holding the specified number of bits.
31061 Unsigned integer types holding the specified number of bits.
31065 Pointers to unspecified code and data. The program counter and
31066 any dedicated return address register may be marked as code
31067 pointers; printing a code pointer converts it into a symbolic
31068 address. The stack pointer and any dedicated address registers
31069 may be marked as data pointers.
31072 Single precision IEEE floating point.
31075 Double precision IEEE floating point.
31078 The 12-byte extended precision format used by ARM FPA registers.
31082 @node Standard Target Features
31083 @section Standard Target Features
31084 @cindex target descriptions, standard features
31086 A target description must contain either no registers or all the
31087 target's registers. If the description contains no registers, then
31088 @value{GDBN} will assume a default register layout, selected based on
31089 the architecture. If the description contains any registers, the
31090 default layout will not be used; the standard registers must be
31091 described in the target description, in such a way that @value{GDBN}
31092 can recognize them.
31094 This is accomplished by giving specific names to feature elements
31095 which contain standard registers. @value{GDBN} will look for features
31096 with those names and verify that they contain the expected registers;
31097 if any known feature is missing required registers, or if any required
31098 feature is missing, @value{GDBN} will reject the target
31099 description. You can add additional registers to any of the
31100 standard features --- @value{GDBN} will display them just as if
31101 they were added to an unrecognized feature.
31103 This section lists the known features and their expected contents.
31104 Sample XML documents for these features are included in the
31105 @value{GDBN} source tree, in the directory @file{gdb/features}.
31107 Names recognized by @value{GDBN} should include the name of the
31108 company or organization which selected the name, and the overall
31109 architecture to which the feature applies; so e.g.@: the feature
31110 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
31112 The names of registers are not case sensitive for the purpose
31113 of recognizing standard features, but @value{GDBN} will only display
31114 registers using the capitalization used in the description.
31120 * PowerPC Features::
31125 @subsection ARM Features
31126 @cindex target descriptions, ARM features
31128 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
31129 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
31130 @samp{lr}, @samp{pc}, and @samp{cpsr}.
31132 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
31133 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
31135 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
31136 it should contain at least registers @samp{wR0} through @samp{wR15} and
31137 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
31138 @samp{wCSSF}, and @samp{wCASF} registers are optional.
31140 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
31141 should contain at least registers @samp{d0} through @samp{d15}. If
31142 they are present, @samp{d16} through @samp{d31} should also be included.
31143 @value{GDBN} will synthesize the single-precision registers from
31144 halves of the double-precision registers.
31146 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
31147 need to contain registers; it instructs @value{GDBN} to display the
31148 VFP double-precision registers as vectors and to synthesize the
31149 quad-precision registers from pairs of double-precision registers.
31150 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
31151 be present and include 32 double-precision registers.
31153 @node MIPS Features
31154 @subsection MIPS Features
31155 @cindex target descriptions, MIPS features
31157 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
31158 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
31159 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
31162 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
31163 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
31164 registers. They may be 32-bit or 64-bit depending on the target.
31166 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
31167 it may be optional in a future version of @value{GDBN}. It should
31168 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
31169 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
31171 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
31172 contain a single register, @samp{restart}, which is used by the
31173 Linux kernel to control restartable syscalls.
31175 @node M68K Features
31176 @subsection M68K Features
31177 @cindex target descriptions, M68K features
31180 @item @samp{org.gnu.gdb.m68k.core}
31181 @itemx @samp{org.gnu.gdb.coldfire.core}
31182 @itemx @samp{org.gnu.gdb.fido.core}
31183 One of those features must be always present.
31184 The feature that is present determines which flavor of m68k is
31185 used. The feature that is present should contain registers
31186 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
31187 @samp{sp}, @samp{ps} and @samp{pc}.
31189 @item @samp{org.gnu.gdb.coldfire.fp}
31190 This feature is optional. If present, it should contain registers
31191 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
31195 @node PowerPC Features
31196 @subsection PowerPC Features
31197 @cindex target descriptions, PowerPC features
31199 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
31200 targets. It should contain registers @samp{r0} through @samp{r31},
31201 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
31202 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
31204 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
31205 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
31207 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
31208 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
31211 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
31212 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
31213 will combine these registers with the floating point registers
31214 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
31215 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
31216 through @samp{vs63}, the set of vector registers for POWER7.
31218 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
31219 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
31220 @samp{spefscr}. SPE targets should provide 32-bit registers in
31221 @samp{org.gnu.gdb.power.core} and provide the upper halves in
31222 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
31223 these to present registers @samp{ev0} through @samp{ev31} to the
31226 @node Operating System Information
31227 @appendix Operating System Information
31228 @cindex operating system information
31234 Users of @value{GDBN} often wish to obtain information about the state of
31235 the operating system running on the target---for example the list of
31236 processes, or the list of open files. This section describes the
31237 mechanism that makes it possible. This mechanism is similar to the
31238 target features mechanism (@pxref{Target Descriptions}), but focuses
31239 on a different aspect of target.
31241 Operating system information is retrived from the target via the
31242 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
31243 read}). The object name in the request should be @samp{osdata}, and
31244 the @var{annex} identifies the data to be fetched.
31247 @appendixsection Process list
31248 @cindex operating system information, process list
31250 When requesting the process list, the @var{annex} field in the
31251 @samp{qXfer} request should be @samp{processes}. The returned data is
31252 an XML document. The formal syntax of this document is defined in
31253 @file{gdb/features/osdata.dtd}.
31255 An example document is:
31258 <?xml version="1.0"?>
31259 <!DOCTYPE target SYSTEM "osdata.dtd">
31260 <osdata type="processes">
31262 <column name="pid">1</column>
31263 <column name="user">root</column>
31264 <column name="command">/sbin/init</column>
31269 Each item should include a column whose name is @samp{pid}. The value
31270 of that column should identify the process on the target. The
31271 @samp{user} and @samp{command} columns are optional, and will be
31272 displayed by @value{GDBN}. Target may provide additional columns,
31273 which @value{GDBN} currently ignores.
31287 % I think something like @colophon should be in texinfo. In the
31289 \long\def\colophon{\hbox to0pt{}\vfill
31290 \centerline{The body of this manual is set in}
31291 \centerline{\fontname\tenrm,}
31292 \centerline{with headings in {\bf\fontname\tenbf}}
31293 \centerline{and examples in {\tt\fontname\tentt}.}
31294 \centerline{{\it\fontname\tenit\/},}
31295 \centerline{{\bf\fontname\tenbf}, and}
31296 \centerline{{\sl\fontname\tensl\/}}
31297 \centerline{are used for emphasis.}\vfill}
31299 % Blame: doc@cygnus.com, 1991.