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
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
25 @c readline appendices use @vindex, @findex and @ftable,
26 @c annotate.texi and gdbmi use @findex.
30 @c !!set GDB manual's edition---not the same as GDB version!
31 @c This is updated by GNU Press.
34 @c !!set GDB edit command default editor
37 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
39 @c This is a dir.info fragment to support semi-automated addition of
40 @c manuals to an info tree.
41 @dircategory Software development
43 * Gdb: (gdb). The GNU debugger.
47 This file documents the @sc{gnu} debugger @value{GDBN}.
50 This is the @value{EDITION} Edition, of @cite{Debugging with
51 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
52 Version @value{GDBVN}.
54 Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,@*
55 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006@*
56 Free Software Foundation, Inc.
58 Permission is granted to copy, distribute and/or modify this document
59 under the terms of the GNU Free Documentation License, Version 1.1 or
60 any later version published by the Free Software Foundation; with the
61 Invariant Sections being ``Free Software'' and ``Free Software Needs
62 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
63 and with the Back-Cover Texts as in (a) below.
65 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
66 this GNU Manual. Buying copies from GNU Press supports the FSF in
67 developing GNU and promoting software freedom.''
71 @title Debugging with @value{GDBN}
72 @subtitle The @sc{gnu} Source-Level Debugger
74 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
75 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
79 \hfill (Send bugs and comments on @value{GDBN} to bug-gdb\@gnu.org.)\par
80 \hfill {\it Debugging with @value{GDBN}}\par
81 \hfill \TeX{}info \texinfoversion\par
85 @vskip 0pt plus 1filll
86 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995,
87 1996, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2006
88 Free Software Foundation, Inc.
90 Published by the Free Software Foundation @*
91 51 Franklin Street, Fifth Floor,
92 Boston, MA 02110-1301, USA@*
95 Permission is granted to copy, distribute and/or modify this document
96 under the terms of the GNU Free Documentation License, Version 1.1 or
97 any later version published by the Free Software Foundation; with the
98 Invariant Sections being ``Free Software'' and ``Free Software Needs
99 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
100 and with the Back-Cover Texts as in (a) below.
102 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
103 this GNU Manual. Buying copies from GNU Press supports the FSF in
104 developing GNU and promoting software freedom.''
106 This edition of the GDB manual is dedicated to the memory of Fred
107 Fish. Fred was a long-standing contributor to GDB and to Free
108 software in general. We will miss him.
113 @node Top, Summary, (dir), (dir)
115 @top Debugging with @value{GDBN}
117 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
119 This is the @value{EDITION} Edition, for @value{GDBN} Version
122 Copyright (C) 1988-2006 Free Software Foundation, Inc.
124 This edition of the GDB manual is dedicated to the memory of Fred
125 Fish. Fred was a long-standing contributor to GDB and to Free
126 software in general. We will miss him.
129 * Summary:: Summary of @value{GDBN}
130 * Sample Session:: A sample @value{GDBN} session
132 * Invocation:: Getting in and out of @value{GDBN}
133 * Commands:: @value{GDBN} commands
134 * Running:: Running programs under @value{GDBN}
135 * Stopping:: Stopping and continuing
136 * Stack:: Examining the stack
137 * Source:: Examining source files
138 * Data:: Examining data
139 * Macros:: Preprocessor Macros
140 * Tracepoints:: Debugging remote targets non-intrusively
141 * Overlays:: Debugging programs that use overlays
143 * Languages:: Using @value{GDBN} with different languages
145 * Symbols:: Examining the symbol table
146 * Altering:: Altering execution
147 * GDB Files:: @value{GDBN} files
148 * Targets:: Specifying a debugging target
149 * Remote Debugging:: Debugging remote programs
150 * Configurations:: Configuration-specific information
151 * Controlling GDB:: Controlling @value{GDBN}
152 * Sequences:: Canned sequences of commands
153 * Interpreters:: Command Interpreters
154 * TUI:: @value{GDBN} Text User Interface
155 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
156 * GDB/MI:: @value{GDBN}'s Machine Interface.
157 * Annotations:: @value{GDBN}'s annotation interface.
159 * GDB Bugs:: Reporting bugs in @value{GDBN}
161 * Command Line Editing:: Command Line Editing
162 * Using History Interactively:: Using History Interactively
163 * Formatting Documentation:: How to format and print @value{GDBN} documentation
164 * Installing GDB:: Installing GDB
165 * Maintenance Commands:: Maintenance Commands
166 * Remote Protocol:: GDB Remote Serial Protocol
167 * Agent Expressions:: The GDB Agent Expression Mechanism
168 * Target Descriptions:: How targets can describe themselves to
170 * Copying:: GNU General Public License says
171 how you can copy and share GDB
172 * GNU Free Documentation License:: The license for this documentation
181 @unnumbered Summary of @value{GDBN}
183 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
184 going on ``inside'' another program while it executes---or what another
185 program was doing at the moment it crashed.
187 @value{GDBN} can do four main kinds of things (plus other things in support of
188 these) to help you catch bugs in the act:
192 Start your program, specifying anything that might affect its behavior.
195 Make your program stop on specified conditions.
198 Examine what has happened, when your program has stopped.
201 Change things in your program, so you can experiment with correcting the
202 effects of one bug and go on to learn about another.
205 You can use @value{GDBN} to debug programs written in C and C@t{++}.
206 For more information, see @ref{Supported Languages,,Supported Languages}.
207 For more information, see @ref{C,,C and C++}.
210 Support for Modula-2 is partial. For information on Modula-2, see
211 @ref{Modula-2,,Modula-2}.
214 Debugging Pascal programs which use sets, subranges, file variables, or
215 nested functions does not currently work. @value{GDBN} does not support
216 entering expressions, printing values, or similar features using Pascal
220 @value{GDBN} can be used to debug programs written in Fortran, although
221 it may be necessary to refer to some variables with a trailing
224 @value{GDBN} can be used to debug programs written in Objective-C,
225 using either the Apple/NeXT or the GNU Objective-C runtime.
228 * Free Software:: Freely redistributable software
229 * Contributors:: Contributors to GDB
233 @unnumberedsec Free Software
235 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
236 General Public License
237 (GPL). The GPL gives you the freedom to copy or adapt a licensed
238 program---but every person getting a copy also gets with it the
239 freedom to modify that copy (which means that they must get access to
240 the source code), and the freedom to distribute further copies.
241 Typical software companies use copyrights to limit your freedoms; the
242 Free Software Foundation uses the GPL to preserve these freedoms.
244 Fundamentally, the General Public License is a license which says that
245 you have these freedoms and that you cannot take these freedoms away
248 @unnumberedsec Free Software Needs Free Documentation
250 The biggest deficiency in the free software community today is not in
251 the software---it is the lack of good free documentation that we can
252 include with the free software. Many of our most important
253 programs do not come with free reference manuals and free introductory
254 texts. Documentation is an essential part of any software package;
255 when an important free software package does not come with a free
256 manual and a free tutorial, that is a major gap. We have many such
259 Consider Perl, for instance. The tutorial manuals that people
260 normally use are non-free. How did this come about? Because the
261 authors of those manuals published them with restrictive terms---no
262 copying, no modification, source files not available---which exclude
263 them from the free software world.
265 That wasn't the first time this sort of thing happened, and it was far
266 from the last. Many times we have heard a GNU user eagerly describe a
267 manual that he is writing, his intended contribution to the community,
268 only to learn that he had ruined everything by signing a publication
269 contract to make it non-free.
271 Free documentation, like free software, is a matter of freedom, not
272 price. The problem with the non-free manual is not that publishers
273 charge a price for printed copies---that in itself is fine. (The Free
274 Software Foundation sells printed copies of manuals, too.) The
275 problem is the restrictions on the use of the manual. Free manuals
276 are available in source code form, and give you permission to copy and
277 modify. Non-free manuals do not allow this.
279 The criteria of freedom for a free manual are roughly the same as for
280 free software. Redistribution (including the normal kinds of
281 commercial redistribution) must be permitted, so that the manual can
282 accompany every copy of the program, both on-line and on paper.
284 Permission for modification of the technical content is crucial too.
285 When people modify the software, adding or changing features, if they
286 are conscientious they will change the manual too---so they can
287 provide accurate and clear documentation for the modified program. A
288 manual that leaves you no choice but to write a new manual to document
289 a changed version of the program is not really available to our
292 Some kinds of limits on the way modification is handled are
293 acceptable. For example, requirements to preserve the original
294 author's copyright notice, the distribution terms, or the list of
295 authors, are ok. It is also no problem to require modified versions
296 to include notice that they were modified. Even entire sections that
297 may not be deleted or changed are acceptable, as long as they deal
298 with nontechnical topics (like this one). These kinds of restrictions
299 are acceptable because they don't obstruct the community's normal use
302 However, it must be possible to modify all the @emph{technical}
303 content of the manual, and then distribute the result in all the usual
304 media, through all the usual channels. Otherwise, the restrictions
305 obstruct the use of the manual, it is not free, and we need another
306 manual to replace it.
308 Please spread the word about this issue. Our community continues to
309 lose manuals to proprietary publishing. If we spread the word that
310 free software needs free reference manuals and free tutorials, perhaps
311 the next person who wants to contribute by writing documentation will
312 realize, before it is too late, that only free manuals contribute to
313 the free software community.
315 If you are writing documentation, please insist on publishing it under
316 the GNU Free Documentation License or another free documentation
317 license. Remember that this decision requires your approval---you
318 don't have to let the publisher decide. Some commercial publishers
319 will use a free license if you insist, but they will not propose the
320 option; it is up to you to raise the issue and say firmly that this is
321 what you want. If the publisher you are dealing with refuses, please
322 try other publishers. If you're not sure whether a proposed license
323 is free, write to @email{licensing@@gnu.org}.
325 You can encourage commercial publishers to sell more free, copylefted
326 manuals and tutorials by buying them, and particularly by buying
327 copies from the publishers that paid for their writing or for major
328 improvements. Meanwhile, try to avoid buying non-free documentation
329 at all. Check the distribution terms of a manual before you buy it,
330 and insist that whoever seeks your business must respect your freedom.
331 Check the history of the book, and try to reward the publishers that
332 have paid or pay the authors to work on it.
334 The Free Software Foundation maintains a list of free documentation
335 published by other publishers, at
336 @url{http://www.fsf.org/doc/other-free-books.html}.
339 @unnumberedsec Contributors to @value{GDBN}
341 Richard Stallman was the original author of @value{GDBN}, and of many
342 other @sc{gnu} programs. Many others have contributed to its
343 development. This section attempts to credit major contributors. One
344 of the virtues of free software is that everyone is free to contribute
345 to it; with regret, we cannot actually acknowledge everyone here. The
346 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
347 blow-by-blow account.
349 Changes much prior to version 2.0 are lost in the mists of time.
352 @emph{Plea:} Additions to this section are particularly welcome. If you
353 or your friends (or enemies, to be evenhanded) have been unfairly
354 omitted from this list, we would like to add your names!
357 So that they may not regard their many labors as thankless, we
358 particularly thank those who shepherded @value{GDBN} through major
360 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
361 Jim Blandy (release 4.18);
362 Jason Molenda (release 4.17);
363 Stan Shebs (release 4.14);
364 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
365 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
366 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
367 Jim Kingdon (releases 3.5, 3.4, and 3.3);
368 and Randy Smith (releases 3.2, 3.1, and 3.0).
370 Richard Stallman, assisted at various times by Peter TerMaat, Chris
371 Hanson, and Richard Mlynarik, handled releases through 2.8.
373 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
374 in @value{GDBN}, with significant additional contributions from Per
375 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
376 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
377 much general update work leading to release 3.0).
379 @value{GDBN} uses the BFD subroutine library to examine multiple
380 object-file formats; BFD was a joint project of David V.
381 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
383 David Johnson wrote the original COFF support; Pace Willison did
384 the original support for encapsulated COFF.
386 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
388 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
389 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
391 Jean-Daniel Fekete contributed Sun 386i support.
392 Chris Hanson improved the HP9000 support.
393 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
394 David Johnson contributed Encore Umax support.
395 Jyrki Kuoppala contributed Altos 3068 support.
396 Jeff Law contributed HP PA and SOM support.
397 Keith Packard contributed NS32K support.
398 Doug Rabson contributed Acorn Risc Machine support.
399 Bob Rusk contributed Harris Nighthawk CX-UX support.
400 Chris Smith contributed Convex support (and Fortran debugging).
401 Jonathan Stone contributed Pyramid support.
402 Michael Tiemann contributed SPARC support.
403 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
404 Pace Willison contributed Intel 386 support.
405 Jay Vosburgh contributed Symmetry support.
406 Marko Mlinar contributed OpenRISC 1000 support.
408 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
410 Rich Schaefer and Peter Schauer helped with support of SunOS shared
413 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
414 about several machine instruction sets.
416 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
417 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
418 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
419 and RDI targets, respectively.
421 Brian Fox is the author of the readline libraries providing
422 command-line editing and command history.
424 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
425 Modula-2 support, and contributed the Languages chapter of this manual.
427 Fred Fish wrote most of the support for Unix System Vr4.
428 He also enhanced the command-completion support to cover C@t{++} overloaded
431 Hitachi America (now Renesas America), Ltd. sponsored the support for
432 H8/300, H8/500, and Super-H processors.
434 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
436 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
439 Toshiba sponsored the support for the TX39 Mips processor.
441 Matsushita sponsored the support for the MN10200 and MN10300 processors.
443 Fujitsu sponsored the support for SPARClite and FR30 processors.
445 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
448 Michael Snyder added support for tracepoints.
450 Stu Grossman wrote gdbserver.
452 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
453 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
455 The following people at the Hewlett-Packard Company contributed
456 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
457 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
458 compiler, and the Text User Interface (nee Terminal User Interface):
459 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
460 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
461 provided HP-specific information in this manual.
463 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
464 Robert Hoehne made significant contributions to the DJGPP port.
466 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
467 development since 1991. Cygnus engineers who have worked on @value{GDBN}
468 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
469 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
470 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
471 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
472 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
473 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
474 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
475 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
476 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
477 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
478 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
479 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
480 Zuhn have made contributions both large and small.
482 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
483 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
485 Jim Blandy added support for preprocessor macros, while working for Red
488 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
489 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
490 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
491 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
492 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
493 with the migration of old architectures to this new framework.
495 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
496 unwinder framework, this consisting of a fresh new design featuring
497 frame IDs, independent frame sniffers, and the sentinel frame. Mark
498 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
499 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
500 trad unwinders. The architecture-specific changes, each involving a
501 complete rewrite of the architecture's frame code, were carried out by
502 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
503 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
504 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
505 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
508 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
509 Tensilica, Inc.@: contributed support for Xtensa processors. Others
510 who have worked on the Xtensa port of @value{GDBN} in the past include
511 Steve Tjiang, John Newlin, and Scott Foehner.
514 @chapter A Sample @value{GDBN} Session
516 You can use this manual at your leisure to read all about @value{GDBN}.
517 However, a handful of commands are enough to get started using the
518 debugger. This chapter illustrates those commands.
521 In this sample session, we emphasize user input like this: @b{input},
522 to make it easier to pick out from the surrounding output.
525 @c FIXME: this example may not be appropriate for some configs, where
526 @c FIXME...primary interest is in remote use.
528 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
529 processor) exhibits the following bug: sometimes, when we change its
530 quote strings from the default, the commands used to capture one macro
531 definition within another stop working. In the following short @code{m4}
532 session, we define a macro @code{foo} which expands to @code{0000}; we
533 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
534 same thing. However, when we change the open quote string to
535 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
536 procedure fails to define a new synonym @code{baz}:
545 @b{define(bar,defn(`foo'))}
549 @b{changequote(<QUOTE>,<UNQUOTE>)}
551 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
554 m4: End of input: 0: fatal error: EOF in string
558 Let us use @value{GDBN} to try to see what is going on.
561 $ @b{@value{GDBP} m4}
562 @c FIXME: this falsifies the exact text played out, to permit smallbook
563 @c FIXME... format to come out better.
564 @value{GDBN} is free software and you are welcome to distribute copies
565 of it under certain conditions; type "show copying" to see
567 There is absolutely no warranty for @value{GDBN}; type "show warranty"
570 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
575 @value{GDBN} reads only enough symbol data to know where to find the
576 rest when needed; as a result, the first prompt comes up very quickly.
577 We now tell @value{GDBN} to use a narrower display width than usual, so
578 that examples fit in this manual.
581 (@value{GDBP}) @b{set width 70}
585 We need to see how the @code{m4} built-in @code{changequote} works.
586 Having looked at the source, we know the relevant subroutine is
587 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
588 @code{break} command.
591 (@value{GDBP}) @b{break m4_changequote}
592 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
596 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
597 control; as long as control does not reach the @code{m4_changequote}
598 subroutine, the program runs as usual:
601 (@value{GDBP}) @b{run}
602 Starting program: /work/Editorial/gdb/gnu/m4/m4
610 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
611 suspends execution of @code{m4}, displaying information about the
612 context where it stops.
615 @b{changequote(<QUOTE>,<UNQUOTE>)}
617 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
619 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
623 Now we use the command @code{n} (@code{next}) to advance execution to
624 the next line of the current function.
628 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
633 @code{set_quotes} looks like a promising subroutine. We can go into it
634 by using the command @code{s} (@code{step}) instead of @code{next}.
635 @code{step} goes to the next line to be executed in @emph{any}
636 subroutine, so it steps into @code{set_quotes}.
640 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
642 530 if (lquote != def_lquote)
646 The display that shows the subroutine where @code{m4} is now
647 suspended (and its arguments) is called a stack frame display. It
648 shows a summary of the stack. We can use the @code{backtrace}
649 command (which can also be spelled @code{bt}), to see where we are
650 in the stack as a whole: the @code{backtrace} command displays a
651 stack frame for each active subroutine.
654 (@value{GDBP}) @b{bt}
655 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
657 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
659 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
660 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
662 #4 0x79dc in expand_input () at macro.c:40
663 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
667 We step through a few more lines to see what happens. The first two
668 times, we can use @samp{s}; the next two times we use @code{n} to avoid
669 falling into the @code{xstrdup} subroutine.
673 0x3b5c 532 if (rquote != def_rquote)
675 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
676 def_lquote : xstrdup(lq);
678 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
681 538 len_lquote = strlen(rquote);
685 The last line displayed looks a little odd; we can examine the variables
686 @code{lquote} and @code{rquote} to see if they are in fact the new left
687 and right quotes we specified. We use the command @code{p}
688 (@code{print}) to see their values.
691 (@value{GDBP}) @b{p lquote}
692 $1 = 0x35d40 "<QUOTE>"
693 (@value{GDBP}) @b{p rquote}
694 $2 = 0x35d50 "<UNQUOTE>"
698 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
699 To look at some context, we can display ten lines of source
700 surrounding the current line with the @code{l} (@code{list}) command.
706 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
708 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
711 538 len_lquote = strlen(rquote);
712 539 len_rquote = strlen(lquote);
719 Let us step past the two lines that set @code{len_lquote} and
720 @code{len_rquote}, and then examine the values of those variables.
724 539 len_rquote = strlen(lquote);
727 (@value{GDBP}) @b{p len_lquote}
729 (@value{GDBP}) @b{p len_rquote}
734 That certainly looks wrong, assuming @code{len_lquote} and
735 @code{len_rquote} are meant to be the lengths of @code{lquote} and
736 @code{rquote} respectively. We can set them to better values using
737 the @code{p} command, since it can print the value of
738 any expression---and that expression can include subroutine calls and
742 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
744 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
749 Is that enough to fix the problem of using the new quotes with the
750 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
751 executing with the @code{c} (@code{continue}) command, and then try the
752 example that caused trouble initially:
758 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
765 Success! The new quotes now work just as well as the default ones. The
766 problem seems to have been just the two typos defining the wrong
767 lengths. We allow @code{m4} exit by giving it an EOF as input:
771 Program exited normally.
775 The message @samp{Program exited normally.} is from @value{GDBN}; it
776 indicates @code{m4} has finished executing. We can end our @value{GDBN}
777 session with the @value{GDBN} @code{quit} command.
780 (@value{GDBP}) @b{quit}
784 @chapter Getting In and Out of @value{GDBN}
786 This chapter discusses how to start @value{GDBN}, and how to get out of it.
790 type @samp{@value{GDBP}} to start @value{GDBN}.
792 type @kbd{quit} or @kbd{Ctrl-d} to exit.
796 * Invoking GDB:: How to start @value{GDBN}
797 * Quitting GDB:: How to quit @value{GDBN}
798 * Shell Commands:: How to use shell commands inside @value{GDBN}
799 * Logging Output:: How to log @value{GDBN}'s output to a file
803 @section Invoking @value{GDBN}
805 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
806 @value{GDBN} reads commands from the terminal until you tell it to exit.
808 You can also run @code{@value{GDBP}} with a variety of arguments and options,
809 to specify more of your debugging environment at the outset.
811 The command-line options described here are designed
812 to cover a variety of situations; in some environments, some of these
813 options may effectively be unavailable.
815 The most usual way to start @value{GDBN} is with one argument,
816 specifying an executable program:
819 @value{GDBP} @var{program}
823 You can also start with both an executable program and a core file
827 @value{GDBP} @var{program} @var{core}
830 You can, instead, specify a process ID as a second argument, if you want
831 to debug a running process:
834 @value{GDBP} @var{program} 1234
838 would attach @value{GDBN} to process @code{1234} (unless you also have a file
839 named @file{1234}; @value{GDBN} does check for a core file first).
841 Taking advantage of the second command-line argument requires a fairly
842 complete operating system; when you use @value{GDBN} as a remote
843 debugger attached to a bare board, there may not be any notion of
844 ``process'', and there is often no way to get a core dump. @value{GDBN}
845 will warn you if it is unable to attach or to read core dumps.
847 You can optionally have @code{@value{GDBP}} pass any arguments after the
848 executable file to the inferior using @code{--args}. This option stops
851 @value{GDBP} --args gcc -O2 -c foo.c
853 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
854 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
856 You can run @code{@value{GDBP}} without printing the front material, which describes
857 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
864 You can further control how @value{GDBN} starts up by using command-line
865 options. @value{GDBN} itself can remind you of the options available.
875 to display all available options and briefly describe their use
876 (@samp{@value{GDBP} -h} is a shorter equivalent).
878 All options and command line arguments you give are processed
879 in sequential order. The order makes a difference when the
880 @samp{-x} option is used.
884 * File Options:: Choosing files
885 * Mode Options:: Choosing modes
886 * Startup:: What @value{GDBN} does during startup
890 @subsection Choosing Files
892 When @value{GDBN} starts, it reads any arguments other than options as
893 specifying an executable file and core file (or process ID). This is
894 the same as if the arguments were specified by the @samp{-se} and
895 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
896 first argument that does not have an associated option flag as
897 equivalent to the @samp{-se} option followed by that argument; and the
898 second argument that does not have an associated option flag, if any, as
899 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
900 If the second argument begins with a decimal digit, @value{GDBN} will
901 first attempt to attach to it as a process, and if that fails, attempt
902 to open it as a corefile. If you have a corefile whose name begins with
903 a digit, you can prevent @value{GDBN} from treating it as a pid by
904 prefixing it with @file{./}, e.g.@: @file{./12345}.
906 If @value{GDBN} has not been configured to included core file support,
907 such as for most embedded targets, then it will complain about a second
908 argument and ignore it.
910 Many options have both long and short forms; both are shown in the
911 following list. @value{GDBN} also recognizes the long forms if you truncate
912 them, so long as enough of the option is present to be unambiguous.
913 (If you prefer, you can flag option arguments with @samp{--} rather
914 than @samp{-}, though we illustrate the more usual convention.)
916 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
917 @c way, both those who look for -foo and --foo in the index, will find
921 @item -symbols @var{file}
923 @cindex @code{--symbols}
925 Read symbol table from file @var{file}.
927 @item -exec @var{file}
929 @cindex @code{--exec}
931 Use file @var{file} as the executable file to execute when appropriate,
932 and for examining pure data in conjunction with a core dump.
936 Read symbol table from file @var{file} and use it as the executable
939 @item -core @var{file}
941 @cindex @code{--core}
943 Use file @var{file} as a core dump to examine.
945 @item -c @var{number}
946 @item -pid @var{number}
947 @itemx -p @var{number}
950 Connect to process ID @var{number}, as with the @code{attach} command.
951 If there is no such process, @value{GDBN} will attempt to open a core
952 file named @var{number}.
954 @item -command @var{file}
956 @cindex @code{--command}
958 Execute @value{GDBN} commands from file @var{file}. @xref{Command
959 Files,, Command files}.
961 @item -eval-command @var{command}
962 @itemx -ex @var{command}
963 @cindex @code{--eval-command}
965 Execute a single @value{GDBN} command.
967 This option may be used multiple times to call multiple commands. It may
968 also be interleaved with @samp{-command} as required.
971 @value{GDBP} -ex 'target sim' -ex 'load' \
972 -x setbreakpoints -ex 'run' a.out
975 @item -directory @var{directory}
976 @itemx -d @var{directory}
977 @cindex @code{--directory}
979 Add @var{directory} to the path to search for source and script files.
983 @cindex @code{--readnow}
985 Read each symbol file's entire symbol table immediately, rather than
986 the default, which is to read it incrementally as it is needed.
987 This makes startup slower, but makes future operations faster.
992 @subsection Choosing Modes
994 You can run @value{GDBN} in various alternative modes---for example, in
995 batch mode or quiet mode.
1002 Do not execute commands found in any initialization files. Normally,
1003 @value{GDBN} executes the commands in these files after all the command
1004 options and arguments have been processed. @xref{Command Files,,Command
1010 @cindex @code{--quiet}
1011 @cindex @code{--silent}
1013 ``Quiet''. Do not print the introductory and copyright messages. These
1014 messages are also suppressed in batch mode.
1017 @cindex @code{--batch}
1018 Run in batch mode. Exit with status @code{0} after processing all the
1019 command files specified with @samp{-x} (and all commands from
1020 initialization files, if not inhibited with @samp{-n}). Exit with
1021 nonzero status if an error occurs in executing the @value{GDBN} commands
1022 in the command files.
1024 Batch mode may be useful for running @value{GDBN} as a filter, for
1025 example to download and run a program on another computer; in order to
1026 make this more useful, the message
1029 Program exited normally.
1033 (which is ordinarily issued whenever a program running under
1034 @value{GDBN} control terminates) is not issued when running in batch
1038 @cindex @code{--batch-silent}
1039 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1040 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1041 unaffected). This is much quieter than @samp{-silent} and would be useless
1042 for an interactive session.
1044 This is particularly useful when using targets that give @samp{Loading section}
1045 messages, for example.
1047 Note that targets that give their output via @value{GDBN}, as opposed to
1048 writing directly to @code{stdout}, will also be made silent.
1050 @item -return-child-result
1051 @cindex @code{--return-child-result}
1052 The return code from @value{GDBN} will be the return code from the child
1053 process (the process being debugged), with the following exceptions:
1057 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1058 internal error. In this case the exit code is the same as it would have been
1059 without @samp{-return-child-result}.
1061 The user quits with an explicit value. E.g., @samp{quit 1}.
1063 The child process never runs, or is not allowed to terminate, in which case
1064 the exit code will be -1.
1067 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1068 when @value{GDBN} is being used as a remote program loader or simulator
1073 @cindex @code{--nowindows}
1075 ``No windows''. If @value{GDBN} comes with a graphical user interface
1076 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1077 interface. If no GUI is available, this option has no effect.
1081 @cindex @code{--windows}
1083 If @value{GDBN} includes a GUI, then this option requires it to be
1086 @item -cd @var{directory}
1088 Run @value{GDBN} using @var{directory} as its working directory,
1089 instead of the current directory.
1093 @cindex @code{--fullname}
1095 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1096 subprocess. It tells @value{GDBN} to output the full file name and line
1097 number in a standard, recognizable fashion each time a stack frame is
1098 displayed (which includes each time your program stops). This
1099 recognizable format looks like two @samp{\032} characters, followed by
1100 the file name, line number and character position separated by colons,
1101 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1102 @samp{\032} characters as a signal to display the source code for the
1106 @cindex @code{--epoch}
1107 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1108 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1109 routines so as to allow Epoch to display values of expressions in a
1112 @item -annotate @var{level}
1113 @cindex @code{--annotate}
1114 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1115 effect is identical to using @samp{set annotate @var{level}}
1116 (@pxref{Annotations}). The annotation @var{level} controls how much
1117 information @value{GDBN} prints together with its prompt, values of
1118 expressions, source lines, and other types of output. Level 0 is the
1119 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1120 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1121 that control @value{GDBN}, and level 2 has been deprecated.
1123 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1127 @cindex @code{--args}
1128 Change interpretation of command line so that arguments following the
1129 executable file are passed as command line arguments to the inferior.
1130 This option stops option processing.
1132 @item -baud @var{bps}
1134 @cindex @code{--baud}
1136 Set the line speed (baud rate or bits per second) of any serial
1137 interface used by @value{GDBN} for remote debugging.
1139 @item -l @var{timeout}
1141 Set the timeout (in seconds) of any communication used by @value{GDBN}
1142 for remote debugging.
1144 @item -tty @var{device}
1145 @itemx -t @var{device}
1146 @cindex @code{--tty}
1148 Run using @var{device} for your program's standard input and output.
1149 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1151 @c resolve the situation of these eventually
1153 @cindex @code{--tui}
1154 Activate the @dfn{Text User Interface} when starting. The Text User
1155 Interface manages several text windows on the terminal, showing
1156 source, assembly, registers and @value{GDBN} command outputs
1157 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1158 Text User Interface can be enabled by invoking the program
1159 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1160 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1163 @c @cindex @code{--xdb}
1164 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1165 @c For information, see the file @file{xdb_trans.html}, which is usually
1166 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1169 @item -interpreter @var{interp}
1170 @cindex @code{--interpreter}
1171 Use the interpreter @var{interp} for interface with the controlling
1172 program or device. This option is meant to be set by programs which
1173 communicate with @value{GDBN} using it as a back end.
1174 @xref{Interpreters, , Command Interpreters}.
1176 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1177 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1178 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1179 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1180 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1181 @sc{gdb/mi} interfaces are no longer supported.
1184 @cindex @code{--write}
1185 Open the executable and core files for both reading and writing. This
1186 is equivalent to the @samp{set write on} command inside @value{GDBN}
1190 @cindex @code{--statistics}
1191 This option causes @value{GDBN} to print statistics about time and
1192 memory usage after it completes each command and returns to the prompt.
1195 @cindex @code{--version}
1196 This option causes @value{GDBN} to print its version number and
1197 no-warranty blurb, and exit.
1202 @subsection What @value{GDBN} Does During Startup
1203 @cindex @value{GDBN} startup
1205 Here's the description of what @value{GDBN} does during session startup:
1209 Sets up the command interpreter as specified by the command line
1210 (@pxref{Mode Options, interpreter}).
1214 Reads the @dfn{init file} (if any) in your home directory@footnote{On
1215 DOS/Windows systems, the home directory is the one pointed to by the
1216 @code{HOME} environment variable.} and executes all the commands in
1220 Processes command line options and operands.
1223 Reads and executes the commands from init file (if any) in the current
1224 working directory. This is only done if the current directory is
1225 different from your home directory. Thus, you can have more than one
1226 init file, one generic in your home directory, and another, specific
1227 to the program you are debugging, in the directory where you invoke
1231 Reads command files specified by the @samp{-x} option. @xref{Command
1232 Files}, for more details about @value{GDBN} command files.
1235 Reads the command history recorded in the @dfn{history file}.
1236 @xref{Command History}, for more details about the command history and the
1237 files where @value{GDBN} records it.
1240 Init files use the same syntax as @dfn{command files} (@pxref{Command
1241 Files}) and are processed by @value{GDBN} in the same way. The init
1242 file in your home directory can set options (such as @samp{set
1243 complaints}) that affect subsequent processing of command line options
1244 and operands. Init files are not executed if you use the @samp{-nx}
1245 option (@pxref{Mode Options, ,Choosing Modes}).
1247 @cindex init file name
1248 @cindex @file{.gdbinit}
1249 @cindex @file{gdb.ini}
1250 The @value{GDBN} init files are normally called @file{.gdbinit}.
1251 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1252 the limitations of file names imposed by DOS filesystems. The Windows
1253 ports of @value{GDBN} use the standard name, but if they find a
1254 @file{gdb.ini} file, they warn you about that and suggest to rename
1255 the file to the standard name.
1259 @section Quitting @value{GDBN}
1260 @cindex exiting @value{GDBN}
1261 @cindex leaving @value{GDBN}
1264 @kindex quit @r{[}@var{expression}@r{]}
1265 @kindex q @r{(@code{quit})}
1266 @item quit @r{[}@var{expression}@r{]}
1268 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1269 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1270 do not supply @var{expression}, @value{GDBN} will terminate normally;
1271 otherwise it will terminate using the result of @var{expression} as the
1276 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1277 terminates the action of any @value{GDBN} command that is in progress and
1278 returns to @value{GDBN} command level. It is safe to type the interrupt
1279 character at any time because @value{GDBN} does not allow it to take effect
1280 until a time when it is safe.
1282 If you have been using @value{GDBN} to control an attached process or
1283 device, you can release it with the @code{detach} command
1284 (@pxref{Attach, ,Debugging an Already-running Process}).
1286 @node Shell Commands
1287 @section Shell Commands
1289 If you need to execute occasional shell commands during your
1290 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1291 just use the @code{shell} command.
1295 @cindex shell escape
1296 @item shell @var{command string}
1297 Invoke a standard shell to execute @var{command string}.
1298 If it exists, the environment variable @code{SHELL} determines which
1299 shell to run. Otherwise @value{GDBN} uses the default shell
1300 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1303 The utility @code{make} is often needed in development environments.
1304 You do not have to use the @code{shell} command for this purpose in
1309 @cindex calling make
1310 @item make @var{make-args}
1311 Execute the @code{make} program with the specified
1312 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1315 @node Logging Output
1316 @section Logging Output
1317 @cindex logging @value{GDBN} output
1318 @cindex save @value{GDBN} output to a file
1320 You may want to save the output of @value{GDBN} commands to a file.
1321 There are several commands to control @value{GDBN}'s logging.
1325 @item set logging on
1327 @item set logging off
1329 @cindex logging file name
1330 @item set logging file @var{file}
1331 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1332 @item set logging overwrite [on|off]
1333 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1334 you want @code{set logging on} to overwrite the logfile instead.
1335 @item set logging redirect [on|off]
1336 By default, @value{GDBN} output will go to both the terminal and the logfile.
1337 Set @code{redirect} if you want output to go only to the log file.
1338 @kindex show logging
1340 Show the current values of the logging settings.
1344 @chapter @value{GDBN} Commands
1346 You can abbreviate a @value{GDBN} command to the first few letters of the command
1347 name, if that abbreviation is unambiguous; and you can repeat certain
1348 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1349 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1350 show you the alternatives available, if there is more than one possibility).
1353 * Command Syntax:: How to give commands to @value{GDBN}
1354 * Completion:: Command completion
1355 * Help:: How to ask @value{GDBN} for help
1358 @node Command Syntax
1359 @section Command Syntax
1361 A @value{GDBN} command is a single line of input. There is no limit on
1362 how long it can be. It starts with a command name, which is followed by
1363 arguments whose meaning depends on the command name. For example, the
1364 command @code{step} accepts an argument which is the number of times to
1365 step, as in @samp{step 5}. You can also use the @code{step} command
1366 with no arguments. Some commands do not allow any arguments.
1368 @cindex abbreviation
1369 @value{GDBN} command names may always be truncated if that abbreviation is
1370 unambiguous. Other possible command abbreviations are listed in the
1371 documentation for individual commands. In some cases, even ambiguous
1372 abbreviations are allowed; for example, @code{s} is specially defined as
1373 equivalent to @code{step} even though there are other commands whose
1374 names start with @code{s}. You can test abbreviations by using them as
1375 arguments to the @code{help} command.
1377 @cindex repeating commands
1378 @kindex RET @r{(repeat last command)}
1379 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1380 repeat the previous command. Certain commands (for example, @code{run})
1381 will not repeat this way; these are commands whose unintentional
1382 repetition might cause trouble and which you are unlikely to want to
1383 repeat. User-defined commands can disable this feature; see
1384 @ref{Define, dont-repeat}.
1386 The @code{list} and @code{x} commands, when you repeat them with
1387 @key{RET}, construct new arguments rather than repeating
1388 exactly as typed. This permits easy scanning of source or memory.
1390 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1391 output, in a way similar to the common utility @code{more}
1392 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1393 @key{RET} too many in this situation, @value{GDBN} disables command
1394 repetition after any command that generates this sort of display.
1396 @kindex # @r{(a comment)}
1398 Any text from a @kbd{#} to the end of the line is a comment; it does
1399 nothing. This is useful mainly in command files (@pxref{Command
1400 Files,,Command Files}).
1402 @cindex repeating command sequences
1403 @kindex Ctrl-o @r{(operate-and-get-next)}
1404 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1405 commands. This command accepts the current line, like @key{RET}, and
1406 then fetches the next line relative to the current line from the history
1410 @section Command Completion
1413 @cindex word completion
1414 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1415 only one possibility; it can also show you what the valid possibilities
1416 are for the next word in a command, at any time. This works for @value{GDBN}
1417 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1419 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1420 of a word. If there is only one possibility, @value{GDBN} fills in the
1421 word, and waits for you to finish the command (or press @key{RET} to
1422 enter it). For example, if you type
1424 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1425 @c complete accuracy in these examples; space introduced for clarity.
1426 @c If texinfo enhancements make it unnecessary, it would be nice to
1427 @c replace " @key" by "@key" in the following...
1429 (@value{GDBP}) info bre @key{TAB}
1433 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1434 the only @code{info} subcommand beginning with @samp{bre}:
1437 (@value{GDBP}) info breakpoints
1441 You can either press @key{RET} at this point, to run the @code{info
1442 breakpoints} command, or backspace and enter something else, if
1443 @samp{breakpoints} does not look like the command you expected. (If you
1444 were sure you wanted @code{info breakpoints} in the first place, you
1445 might as well just type @key{RET} immediately after @samp{info bre},
1446 to exploit command abbreviations rather than command completion).
1448 If there is more than one possibility for the next word when you press
1449 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1450 characters and try again, or just press @key{TAB} a second time;
1451 @value{GDBN} displays all the possible completions for that word. For
1452 example, you might want to set a breakpoint on a subroutine whose name
1453 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1454 just sounds the bell. Typing @key{TAB} again displays all the
1455 function names in your program that begin with those characters, for
1459 (@value{GDBP}) b make_ @key{TAB}
1460 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1461 make_a_section_from_file make_environ
1462 make_abs_section make_function_type
1463 make_blockvector make_pointer_type
1464 make_cleanup make_reference_type
1465 make_command make_symbol_completion_list
1466 (@value{GDBP}) b make_
1470 After displaying the available possibilities, @value{GDBN} copies your
1471 partial input (@samp{b make_} in the example) so you can finish the
1474 If you just want to see the list of alternatives in the first place, you
1475 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1476 means @kbd{@key{META} ?}. You can type this either by holding down a
1477 key designated as the @key{META} shift on your keyboard (if there is
1478 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1480 @cindex quotes in commands
1481 @cindex completion of quoted strings
1482 Sometimes the string you need, while logically a ``word'', may contain
1483 parentheses or other characters that @value{GDBN} normally excludes from
1484 its notion of a word. To permit word completion to work in this
1485 situation, you may enclose words in @code{'} (single quote marks) in
1486 @value{GDBN} commands.
1488 The most likely situation where you might need this is in typing the
1489 name of a C@t{++} function. This is because C@t{++} allows function
1490 overloading (multiple definitions of the same function, distinguished
1491 by argument type). For example, when you want to set a breakpoint you
1492 may need to distinguish whether you mean the version of @code{name}
1493 that takes an @code{int} parameter, @code{name(int)}, or the version
1494 that takes a @code{float} parameter, @code{name(float)}. To use the
1495 word-completion facilities in this situation, type a single quote
1496 @code{'} at the beginning of the function name. This alerts
1497 @value{GDBN} that it may need to consider more information than usual
1498 when you press @key{TAB} or @kbd{M-?} to request word completion:
1501 (@value{GDBP}) b 'bubble( @kbd{M-?}
1502 bubble(double,double) bubble(int,int)
1503 (@value{GDBP}) b 'bubble(
1506 In some cases, @value{GDBN} can tell that completing a name requires using
1507 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1508 completing as much as it can) if you do not type the quote in the first
1512 (@value{GDBP}) b bub @key{TAB}
1513 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1514 (@value{GDBP}) b 'bubble(
1518 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1519 you have not yet started typing the argument list when you ask for
1520 completion on an overloaded symbol.
1522 For more information about overloaded functions, see @ref{C Plus Plus
1523 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1524 overload-resolution off} to disable overload resolution;
1525 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1529 @section Getting Help
1530 @cindex online documentation
1533 You can always ask @value{GDBN} itself for information on its commands,
1534 using the command @code{help}.
1537 @kindex h @r{(@code{help})}
1540 You can use @code{help} (abbreviated @code{h}) with no arguments to
1541 display a short list of named classes of commands:
1545 List of classes of commands:
1547 aliases -- Aliases of other commands
1548 breakpoints -- Making program stop at certain points
1549 data -- Examining data
1550 files -- Specifying and examining files
1551 internals -- Maintenance commands
1552 obscure -- Obscure features
1553 running -- Running the program
1554 stack -- Examining the stack
1555 status -- Status inquiries
1556 support -- Support facilities
1557 tracepoints -- Tracing of program execution without
1558 stopping the program
1559 user-defined -- User-defined commands
1561 Type "help" followed by a class name for a list of
1562 commands in that class.
1563 Type "help" followed by command name for full
1565 Command name abbreviations are allowed if unambiguous.
1568 @c the above line break eliminates huge line overfull...
1570 @item help @var{class}
1571 Using one of the general help classes as an argument, you can get a
1572 list of the individual commands in that class. For example, here is the
1573 help display for the class @code{status}:
1576 (@value{GDBP}) help status
1581 @c Line break in "show" line falsifies real output, but needed
1582 @c to fit in smallbook page size.
1583 info -- Generic command for showing things
1584 about the program being debugged
1585 show -- Generic command for showing things
1588 Type "help" followed by command name for full
1590 Command name abbreviations are allowed if unambiguous.
1594 @item help @var{command}
1595 With a command name as @code{help} argument, @value{GDBN} displays a
1596 short paragraph on how to use that command.
1599 @item apropos @var{args}
1600 The @code{apropos} command searches through all of the @value{GDBN}
1601 commands, and their documentation, for the regular expression specified in
1602 @var{args}. It prints out all matches found. For example:
1613 set symbol-reloading -- Set dynamic symbol table reloading
1614 multiple times in one run
1615 show symbol-reloading -- Show dynamic symbol table reloading
1616 multiple times in one run
1621 @item complete @var{args}
1622 The @code{complete @var{args}} command lists all the possible completions
1623 for the beginning of a command. Use @var{args} to specify the beginning of the
1624 command you want completed. For example:
1630 @noindent results in:
1641 @noindent This is intended for use by @sc{gnu} Emacs.
1644 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1645 and @code{show} to inquire about the state of your program, or the state
1646 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1647 manual introduces each of them in the appropriate context. The listings
1648 under @code{info} and under @code{show} in the Index point to
1649 all the sub-commands. @xref{Index}.
1654 @kindex i @r{(@code{info})}
1656 This command (abbreviated @code{i}) is for describing the state of your
1657 program. For example, you can list the arguments given to your program
1658 with @code{info args}, list the registers currently in use with @code{info
1659 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1660 You can get a complete list of the @code{info} sub-commands with
1661 @w{@code{help info}}.
1665 You can assign the result of an expression to an environment variable with
1666 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1667 @code{set prompt $}.
1671 In contrast to @code{info}, @code{show} is for describing the state of
1672 @value{GDBN} itself.
1673 You can change most of the things you can @code{show}, by using the
1674 related command @code{set}; for example, you can control what number
1675 system is used for displays with @code{set radix}, or simply inquire
1676 which is currently in use with @code{show radix}.
1679 To display all the settable parameters and their current
1680 values, you can use @code{show} with no arguments; you may also use
1681 @code{info set}. Both commands produce the same display.
1682 @c FIXME: "info set" violates the rule that "info" is for state of
1683 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1684 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1688 Here are three miscellaneous @code{show} subcommands, all of which are
1689 exceptional in lacking corresponding @code{set} commands:
1692 @kindex show version
1693 @cindex @value{GDBN} version number
1695 Show what version of @value{GDBN} is running. You should include this
1696 information in @value{GDBN} bug-reports. If multiple versions of
1697 @value{GDBN} are in use at your site, you may need to determine which
1698 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1699 commands are introduced, and old ones may wither away. Also, many
1700 system vendors ship variant versions of @value{GDBN}, and there are
1701 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1702 The version number is the same as the one announced when you start
1705 @kindex show copying
1706 @kindex info copying
1707 @cindex display @value{GDBN} copyright
1710 Display information about permission for copying @value{GDBN}.
1712 @kindex show warranty
1713 @kindex info warranty
1715 @itemx info warranty
1716 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1717 if your version of @value{GDBN} comes with one.
1722 @chapter Running Programs Under @value{GDBN}
1724 When you run a program under @value{GDBN}, you must first generate
1725 debugging information when you compile it.
1727 You may start @value{GDBN} with its arguments, if any, in an environment
1728 of your choice. If you are doing native debugging, you may redirect
1729 your program's input and output, debug an already running process, or
1730 kill a child process.
1733 * Compilation:: Compiling for debugging
1734 * Starting:: Starting your program
1735 * Arguments:: Your program's arguments
1736 * Environment:: Your program's environment
1738 * Working Directory:: Your program's working directory
1739 * Input/Output:: Your program's input and output
1740 * Attach:: Debugging an already-running process
1741 * Kill Process:: Killing the child process
1743 * Threads:: Debugging programs with multiple threads
1744 * Processes:: Debugging programs with multiple processes
1745 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1749 @section Compiling for Debugging
1751 In order to debug a program effectively, you need to generate
1752 debugging information when you compile it. This debugging information
1753 is stored in the object file; it describes the data type of each
1754 variable or function and the correspondence between source line numbers
1755 and addresses in the executable code.
1757 To request debugging information, specify the @samp{-g} option when you run
1760 Programs that are to be shipped to your customers are compiled with
1761 optimizations, using the @samp{-O} compiler option. However, many
1762 compilers are unable to handle the @samp{-g} and @samp{-O} options
1763 together. Using those compilers, you cannot generate optimized
1764 executables containing debugging information.
1766 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1767 without @samp{-O}, making it possible to debug optimized code. We
1768 recommend that you @emph{always} use @samp{-g} whenever you compile a
1769 program. You may think your program is correct, but there is no sense
1770 in pushing your luck.
1772 @cindex optimized code, debugging
1773 @cindex debugging optimized code
1774 When you debug a program compiled with @samp{-g -O}, remember that the
1775 optimizer is rearranging your code; the debugger shows you what is
1776 really there. Do not be too surprised when the execution path does not
1777 exactly match your source file! An extreme example: if you define a
1778 variable, but never use it, @value{GDBN} never sees that
1779 variable---because the compiler optimizes it out of existence.
1781 Some things do not work as well with @samp{-g -O} as with just
1782 @samp{-g}, particularly on machines with instruction scheduling. If in
1783 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1784 please report it to us as a bug (including a test case!).
1785 @xref{Variables}, for more information about debugging optimized code.
1787 Older versions of the @sc{gnu} C compiler permitted a variant option
1788 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1789 format; if your @sc{gnu} C compiler has this option, do not use it.
1791 @value{GDBN} knows about preprocessor macros and can show you their
1792 expansion (@pxref{Macros}). Most compilers do not include information
1793 about preprocessor macros in the debugging information if you specify
1794 the @option{-g} flag alone, because this information is rather large.
1795 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1796 provides macro information if you specify the options
1797 @option{-gdwarf-2} and @option{-g3}; the former option requests
1798 debugging information in the Dwarf 2 format, and the latter requests
1799 ``extra information''. In the future, we hope to find more compact
1800 ways to represent macro information, so that it can be included with
1805 @section Starting your Program
1811 @kindex r @r{(@code{run})}
1814 Use the @code{run} command to start your program under @value{GDBN}.
1815 You must first specify the program name (except on VxWorks) with an
1816 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1817 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1818 (@pxref{Files, ,Commands to Specify Files}).
1822 If you are running your program in an execution environment that
1823 supports processes, @code{run} creates an inferior process and makes
1824 that process run your program. (In environments without processes,
1825 @code{run} jumps to the start of your program.)
1827 The execution of a program is affected by certain information it
1828 receives from its superior. @value{GDBN} provides ways to specify this
1829 information, which you must do @emph{before} starting your program. (You
1830 can change it after starting your program, but such changes only affect
1831 your program the next time you start it.) This information may be
1832 divided into four categories:
1835 @item The @emph{arguments.}
1836 Specify the arguments to give your program as the arguments of the
1837 @code{run} command. If a shell is available on your target, the shell
1838 is used to pass the arguments, so that you may use normal conventions
1839 (such as wildcard expansion or variable substitution) in describing
1841 In Unix systems, you can control which shell is used with the
1842 @code{SHELL} environment variable.
1843 @xref{Arguments, ,Your Program's Arguments}.
1845 @item The @emph{environment.}
1846 Your program normally inherits its environment from @value{GDBN}, but you can
1847 use the @value{GDBN} commands @code{set environment} and @code{unset
1848 environment} to change parts of the environment that affect
1849 your program. @xref{Environment, ,Your Program's Environment}.
1851 @item The @emph{working directory.}
1852 Your program inherits its working directory from @value{GDBN}. You can set
1853 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1854 @xref{Working Directory, ,Your Program's Working Directory}.
1856 @item The @emph{standard input and output.}
1857 Your program normally uses the same device for standard input and
1858 standard output as @value{GDBN} is using. You can redirect input and output
1859 in the @code{run} command line, or you can use the @code{tty} command to
1860 set a different device for your program.
1861 @xref{Input/Output, ,Your Program's Input and Output}.
1864 @emph{Warning:} While input and output redirection work, you cannot use
1865 pipes to pass the output of the program you are debugging to another
1866 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1870 When you issue the @code{run} command, your program begins to execute
1871 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1872 of how to arrange for your program to stop. Once your program has
1873 stopped, you may call functions in your program, using the @code{print}
1874 or @code{call} commands. @xref{Data, ,Examining Data}.
1876 If the modification time of your symbol file has changed since the last
1877 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1878 table, and reads it again. When it does this, @value{GDBN} tries to retain
1879 your current breakpoints.
1884 @cindex run to main procedure
1885 The name of the main procedure can vary from language to language.
1886 With C or C@t{++}, the main procedure name is always @code{main}, but
1887 other languages such as Ada do not require a specific name for their
1888 main procedure. The debugger provides a convenient way to start the
1889 execution of the program and to stop at the beginning of the main
1890 procedure, depending on the language used.
1892 The @samp{start} command does the equivalent of setting a temporary
1893 breakpoint at the beginning of the main procedure and then invoking
1894 the @samp{run} command.
1896 @cindex elaboration phase
1897 Some programs contain an @dfn{elaboration} phase where some startup code is
1898 executed before the main procedure is called. This depends on the
1899 languages used to write your program. In C@t{++}, for instance,
1900 constructors for static and global objects are executed before
1901 @code{main} is called. It is therefore possible that the debugger stops
1902 before reaching the main procedure. However, the temporary breakpoint
1903 will remain to halt execution.
1905 Specify the arguments to give to your program as arguments to the
1906 @samp{start} command. These arguments will be given verbatim to the
1907 underlying @samp{run} command. Note that the same arguments will be
1908 reused if no argument is provided during subsequent calls to
1909 @samp{start} or @samp{run}.
1911 It is sometimes necessary to debug the program during elaboration. In
1912 these cases, using the @code{start} command would stop the execution of
1913 your program too late, as the program would have already completed the
1914 elaboration phase. Under these circumstances, insert breakpoints in your
1915 elaboration code before running your program.
1919 @section Your Program's Arguments
1921 @cindex arguments (to your program)
1922 The arguments to your program can be specified by the arguments of the
1924 They are passed to a shell, which expands wildcard characters and
1925 performs redirection of I/O, and thence to your program. Your
1926 @code{SHELL} environment variable (if it exists) specifies what shell
1927 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1928 the default shell (@file{/bin/sh} on Unix).
1930 On non-Unix systems, the program is usually invoked directly by
1931 @value{GDBN}, which emulates I/O redirection via the appropriate system
1932 calls, and the wildcard characters are expanded by the startup code of
1933 the program, not by the shell.
1935 @code{run} with no arguments uses the same arguments used by the previous
1936 @code{run}, or those set by the @code{set args} command.
1941 Specify the arguments to be used the next time your program is run. If
1942 @code{set args} has no arguments, @code{run} executes your program
1943 with no arguments. Once you have run your program with arguments,
1944 using @code{set args} before the next @code{run} is the only way to run
1945 it again without arguments.
1949 Show the arguments to give your program when it is started.
1953 @section Your Program's Environment
1955 @cindex environment (of your program)
1956 The @dfn{environment} consists of a set of environment variables and
1957 their values. Environment variables conventionally record such things as
1958 your user name, your home directory, your terminal type, and your search
1959 path for programs to run. Usually you set up environment variables with
1960 the shell and they are inherited by all the other programs you run. When
1961 debugging, it can be useful to try running your program with a modified
1962 environment without having to start @value{GDBN} over again.
1966 @item path @var{directory}
1967 Add @var{directory} to the front of the @code{PATH} environment variable
1968 (the search path for executables) that will be passed to your program.
1969 The value of @code{PATH} used by @value{GDBN} does not change.
1970 You may specify several directory names, separated by whitespace or by a
1971 system-dependent separator character (@samp{:} on Unix, @samp{;} on
1972 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1973 is moved to the front, so it is searched sooner.
1975 You can use the string @samp{$cwd} to refer to whatever is the current
1976 working directory at the time @value{GDBN} searches the path. If you
1977 use @samp{.} instead, it refers to the directory where you executed the
1978 @code{path} command. @value{GDBN} replaces @samp{.} in the
1979 @var{directory} argument (with the current path) before adding
1980 @var{directory} to the search path.
1981 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1982 @c document that, since repeating it would be a no-op.
1986 Display the list of search paths for executables (the @code{PATH}
1987 environment variable).
1989 @kindex show environment
1990 @item show environment @r{[}@var{varname}@r{]}
1991 Print the value of environment variable @var{varname} to be given to
1992 your program when it starts. If you do not supply @var{varname},
1993 print the names and values of all environment variables to be given to
1994 your program. You can abbreviate @code{environment} as @code{env}.
1996 @kindex set environment
1997 @item set environment @var{varname} @r{[}=@var{value}@r{]}
1998 Set environment variable @var{varname} to @var{value}. The value
1999 changes for your program only, not for @value{GDBN} itself. @var{value} may
2000 be any string; the values of environment variables are just strings, and
2001 any interpretation is supplied by your program itself. The @var{value}
2002 parameter is optional; if it is eliminated, the variable is set to a
2004 @c "any string" here does not include leading, trailing
2005 @c blanks. Gnu asks: does anyone care?
2007 For example, this command:
2014 tells the debugged program, when subsequently run, that its user is named
2015 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2016 are not actually required.)
2018 @kindex unset environment
2019 @item unset environment @var{varname}
2020 Remove variable @var{varname} from the environment to be passed to your
2021 program. This is different from @samp{set env @var{varname} =};
2022 @code{unset environment} removes the variable from the environment,
2023 rather than assigning it an empty value.
2026 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2028 by your @code{SHELL} environment variable if it exists (or
2029 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2030 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2031 @file{.bashrc} for BASH---any variables you set in that file affect
2032 your program. You may wish to move setting of environment variables to
2033 files that are only run when you sign on, such as @file{.login} or
2036 @node Working Directory
2037 @section Your Program's Working Directory
2039 @cindex working directory (of your program)
2040 Each time you start your program with @code{run}, it inherits its
2041 working directory from the current working directory of @value{GDBN}.
2042 The @value{GDBN} working directory is initially whatever it inherited
2043 from its parent process (typically the shell), but you can specify a new
2044 working directory in @value{GDBN} with the @code{cd} command.
2046 The @value{GDBN} working directory also serves as a default for the commands
2047 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2052 @cindex change working directory
2053 @item cd @var{directory}
2054 Set the @value{GDBN} working directory to @var{directory}.
2058 Print the @value{GDBN} working directory.
2061 It is generally impossible to find the current working directory of
2062 the process being debugged (since a program can change its directory
2063 during its run). If you work on a system where @value{GDBN} is
2064 configured with the @file{/proc} support, you can use the @code{info
2065 proc} command (@pxref{SVR4 Process Information}) to find out the
2066 current working directory of the debuggee.
2069 @section Your Program's Input and Output
2074 By default, the program you run under @value{GDBN} does input and output to
2075 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2076 to its own terminal modes to interact with you, but it records the terminal
2077 modes your program was using and switches back to them when you continue
2078 running your program.
2081 @kindex info terminal
2083 Displays information recorded by @value{GDBN} about the terminal modes your
2087 You can redirect your program's input and/or output using shell
2088 redirection with the @code{run} command. For example,
2095 starts your program, diverting its output to the file @file{outfile}.
2098 @cindex controlling terminal
2099 Another way to specify where your program should do input and output is
2100 with the @code{tty} command. This command accepts a file name as
2101 argument, and causes this file to be the default for future @code{run}
2102 commands. It also resets the controlling terminal for the child
2103 process, for future @code{run} commands. For example,
2110 directs that processes started with subsequent @code{run} commands
2111 default to do input and output on the terminal @file{/dev/ttyb} and have
2112 that as their controlling terminal.
2114 An explicit redirection in @code{run} overrides the @code{tty} command's
2115 effect on the input/output device, but not its effect on the controlling
2118 When you use the @code{tty} command or redirect input in the @code{run}
2119 command, only the input @emph{for your program} is affected. The input
2120 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2121 for @code{set inferior-tty}.
2123 @cindex inferior tty
2124 @cindex set inferior controlling terminal
2125 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2126 display the name of the terminal that will be used for future runs of your
2130 @item set inferior-tty /dev/ttyb
2131 @kindex set inferior-tty
2132 Set the tty for the program being debugged to /dev/ttyb.
2134 @item show inferior-tty
2135 @kindex show inferior-tty
2136 Show the current tty for the program being debugged.
2140 @section Debugging an Already-running Process
2145 @item attach @var{process-id}
2146 This command attaches to a running process---one that was started
2147 outside @value{GDBN}. (@code{info files} shows your active
2148 targets.) The command takes as argument a process ID. The usual way to
2149 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2150 or with the @samp{jobs -l} shell command.
2152 @code{attach} does not repeat if you press @key{RET} a second time after
2153 executing the command.
2156 To use @code{attach}, your program must be running in an environment
2157 which supports processes; for example, @code{attach} does not work for
2158 programs on bare-board targets that lack an operating system. You must
2159 also have permission to send the process a signal.
2161 When you use @code{attach}, the debugger finds the program running in
2162 the process first by looking in the current working directory, then (if
2163 the program is not found) by using the source file search path
2164 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2165 the @code{file} command to load the program. @xref{Files, ,Commands to
2168 The first thing @value{GDBN} does after arranging to debug the specified
2169 process is to stop it. You can examine and modify an attached process
2170 with all the @value{GDBN} commands that are ordinarily available when
2171 you start processes with @code{run}. You can insert breakpoints; you
2172 can step and continue; you can modify storage. If you would rather the
2173 process continue running, you may use the @code{continue} command after
2174 attaching @value{GDBN} to the process.
2179 When you have finished debugging the attached process, you can use the
2180 @code{detach} command to release it from @value{GDBN} control. Detaching
2181 the process continues its execution. After the @code{detach} command,
2182 that process and @value{GDBN} become completely independent once more, and you
2183 are ready to @code{attach} another process or start one with @code{run}.
2184 @code{detach} does not repeat if you press @key{RET} again after
2185 executing the command.
2188 If you exit @value{GDBN} while you have an attached process, you detach
2189 that process. If you use the @code{run} command, you kill that process.
2190 By default, @value{GDBN} asks for confirmation if you try to do either of these
2191 things; you can control whether or not you need to confirm by using the
2192 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2196 @section Killing the Child Process
2201 Kill the child process in which your program is running under @value{GDBN}.
2204 This command is useful if you wish to debug a core dump instead of a
2205 running process. @value{GDBN} ignores any core dump file while your program
2208 On some operating systems, a program cannot be executed outside @value{GDBN}
2209 while you have breakpoints set on it inside @value{GDBN}. You can use the
2210 @code{kill} command in this situation to permit running your program
2211 outside the debugger.
2213 The @code{kill} command is also useful if you wish to recompile and
2214 relink your program, since on many systems it is impossible to modify an
2215 executable file while it is running in a process. In this case, when you
2216 next type @code{run}, @value{GDBN} notices that the file has changed, and
2217 reads the symbol table again (while trying to preserve your current
2218 breakpoint settings).
2221 @section Debugging Programs with Multiple Threads
2223 @cindex threads of execution
2224 @cindex multiple threads
2225 @cindex switching threads
2226 In some operating systems, such as HP-UX and Solaris, a single program
2227 may have more than one @dfn{thread} of execution. The precise semantics
2228 of threads differ from one operating system to another, but in general
2229 the threads of a single program are akin to multiple processes---except
2230 that they share one address space (that is, they can all examine and
2231 modify the same variables). On the other hand, each thread has its own
2232 registers and execution stack, and perhaps private memory.
2234 @value{GDBN} provides these facilities for debugging multi-thread
2238 @item automatic notification of new threads
2239 @item @samp{thread @var{threadno}}, a command to switch among threads
2240 @item @samp{info threads}, a command to inquire about existing threads
2241 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2242 a command to apply a command to a list of threads
2243 @item thread-specific breakpoints
2247 @emph{Warning:} These facilities are not yet available on every
2248 @value{GDBN} configuration where the operating system supports threads.
2249 If your @value{GDBN} does not support threads, these commands have no
2250 effect. For example, a system without thread support shows no output
2251 from @samp{info threads}, and always rejects the @code{thread} command,
2255 (@value{GDBP}) info threads
2256 (@value{GDBP}) thread 1
2257 Thread ID 1 not known. Use the "info threads" command to
2258 see the IDs of currently known threads.
2260 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2261 @c doesn't support threads"?
2264 @cindex focus of debugging
2265 @cindex current thread
2266 The @value{GDBN} thread debugging facility allows you to observe all
2267 threads while your program runs---but whenever @value{GDBN} takes
2268 control, one thread in particular is always the focus of debugging.
2269 This thread is called the @dfn{current thread}. Debugging commands show
2270 program information from the perspective of the current thread.
2272 @cindex @code{New} @var{systag} message
2273 @cindex thread identifier (system)
2274 @c FIXME-implementors!! It would be more helpful if the [New...] message
2275 @c included GDB's numeric thread handle, so you could just go to that
2276 @c thread without first checking `info threads'.
2277 Whenever @value{GDBN} detects a new thread in your program, it displays
2278 the target system's identification for the thread with a message in the
2279 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2280 whose form varies depending on the particular system. For example, on
2281 @sc{gnu}/Linux, you might see
2284 [New Thread 46912507313328 (LWP 25582)]
2288 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2289 the @var{systag} is simply something like @samp{process 368}, with no
2292 @c FIXME!! (1) Does the [New...] message appear even for the very first
2293 @c thread of a program, or does it only appear for the
2294 @c second---i.e.@: when it becomes obvious we have a multithread
2296 @c (2) *Is* there necessarily a first thread always? Or do some
2297 @c multithread systems permit starting a program with multiple
2298 @c threads ab initio?
2300 @cindex thread number
2301 @cindex thread identifier (GDB)
2302 For debugging purposes, @value{GDBN} associates its own thread
2303 number---always a single integer---with each thread in your program.
2306 @kindex info threads
2308 Display a summary of all threads currently in your
2309 program. @value{GDBN} displays for each thread (in this order):
2313 the thread number assigned by @value{GDBN}
2316 the target system's thread identifier (@var{systag})
2319 the current stack frame summary for that thread
2323 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2324 indicates the current thread.
2328 @c end table here to get a little more width for example
2331 (@value{GDBP}) info threads
2332 3 process 35 thread 27 0x34e5 in sigpause ()
2333 2 process 35 thread 23 0x34e5 in sigpause ()
2334 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2340 @cindex debugging multithreaded programs (on HP-UX)
2341 @cindex thread identifier (GDB), on HP-UX
2342 For debugging purposes, @value{GDBN} associates its own thread
2343 number---a small integer assigned in thread-creation order---with each
2344 thread in your program.
2346 @cindex @code{New} @var{systag} message, on HP-UX
2347 @cindex thread identifier (system), on HP-UX
2348 @c FIXME-implementors!! It would be more helpful if the [New...] message
2349 @c included GDB's numeric thread handle, so you could just go to that
2350 @c thread without first checking `info threads'.
2351 Whenever @value{GDBN} detects a new thread in your program, it displays
2352 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2353 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2354 whose form varies depending on the particular system. For example, on
2358 [New thread 2 (system thread 26594)]
2362 when @value{GDBN} notices a new thread.
2365 @kindex info threads (HP-UX)
2367 Display a summary of all threads currently in your
2368 program. @value{GDBN} displays for each thread (in this order):
2371 @item the thread number assigned by @value{GDBN}
2373 @item the target system's thread identifier (@var{systag})
2375 @item the current stack frame summary for that thread
2379 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2380 indicates the current thread.
2384 @c end table here to get a little more width for example
2387 (@value{GDBP}) info threads
2388 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2390 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2391 from /usr/lib/libc.2
2392 1 system thread 27905 0x7b003498 in _brk () \@*
2393 from /usr/lib/libc.2
2396 On Solaris, you can display more information about user threads with a
2397 Solaris-specific command:
2400 @item maint info sol-threads
2401 @kindex maint info sol-threads
2402 @cindex thread info (Solaris)
2403 Display info on Solaris user threads.
2407 @kindex thread @var{threadno}
2408 @item thread @var{threadno}
2409 Make thread number @var{threadno} the current thread. The command
2410 argument @var{threadno} is the internal @value{GDBN} thread number, as
2411 shown in the first field of the @samp{info threads} display.
2412 @value{GDBN} responds by displaying the system identifier of the thread
2413 you selected, and its current stack frame summary:
2416 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2417 (@value{GDBP}) thread 2
2418 [Switching to process 35 thread 23]
2419 0x34e5 in sigpause ()
2423 As with the @samp{[New @dots{}]} message, the form of the text after
2424 @samp{Switching to} depends on your system's conventions for identifying
2427 @kindex thread apply
2428 @cindex apply command to several threads
2429 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2430 The @code{thread apply} command allows you to apply the named
2431 @var{command} to one or more threads. Specify the numbers of the
2432 threads that you want affected with the command argument
2433 @var{threadno}. It can be a single thread number, one of the numbers
2434 shown in the first field of the @samp{info threads} display; or it
2435 could be a range of thread numbers, as in @code{2-4}. To apply a
2436 command to all threads, type @kbd{thread apply all @var{command}}.
2439 @cindex automatic thread selection
2440 @cindex switching threads automatically
2441 @cindex threads, automatic switching
2442 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2443 signal, it automatically selects the thread where that breakpoint or
2444 signal happened. @value{GDBN} alerts you to the context switch with a
2445 message of the form @samp{[Switching to @var{systag}]} to identify the
2448 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2449 more information about how @value{GDBN} behaves when you stop and start
2450 programs with multiple threads.
2452 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2453 watchpoints in programs with multiple threads.
2456 @section Debugging Programs with Multiple Processes
2458 @cindex fork, debugging programs which call
2459 @cindex multiple processes
2460 @cindex processes, multiple
2461 On most systems, @value{GDBN} has no special support for debugging
2462 programs which create additional processes using the @code{fork}
2463 function. When a program forks, @value{GDBN} will continue to debug the
2464 parent process and the child process will run unimpeded. If you have
2465 set a breakpoint in any code which the child then executes, the child
2466 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2467 will cause it to terminate.
2469 However, if you want to debug the child process there is a workaround
2470 which isn't too painful. Put a call to @code{sleep} in the code which
2471 the child process executes after the fork. It may be useful to sleep
2472 only if a certain environment variable is set, or a certain file exists,
2473 so that the delay need not occur when you don't want to run @value{GDBN}
2474 on the child. While the child is sleeping, use the @code{ps} program to
2475 get its process ID. Then tell @value{GDBN} (a new invocation of
2476 @value{GDBN} if you are also debugging the parent process) to attach to
2477 the child process (@pxref{Attach}). From that point on you can debug
2478 the child process just like any other process which you attached to.
2480 On some systems, @value{GDBN} provides support for debugging programs that
2481 create additional processes using the @code{fork} or @code{vfork} functions.
2482 Currently, the only platforms with this feature are HP-UX (11.x and later
2483 only?) and GNU/Linux (kernel version 2.5.60 and later).
2485 By default, when a program forks, @value{GDBN} will continue to debug
2486 the parent process and the child process will run unimpeded.
2488 If you want to follow the child process instead of the parent process,
2489 use the command @w{@code{set follow-fork-mode}}.
2492 @kindex set follow-fork-mode
2493 @item set follow-fork-mode @var{mode}
2494 Set the debugger response to a program call of @code{fork} or
2495 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2496 process. The @var{mode} argument can be:
2500 The original process is debugged after a fork. The child process runs
2501 unimpeded. This is the default.
2504 The new process is debugged after a fork. The parent process runs
2509 @kindex show follow-fork-mode
2510 @item show follow-fork-mode
2511 Display the current debugger response to a @code{fork} or @code{vfork} call.
2514 @cindex debugging multiple processes
2515 On Linux, if you want to debug both the parent and child processes, use the
2516 command @w{@code{set detach-on-fork}}.
2519 @kindex set detach-on-fork
2520 @item set detach-on-fork @var{mode}
2521 Tells gdb whether to detach one of the processes after a fork, or
2522 retain debugger control over them both.
2526 The child process (or parent process, depending on the value of
2527 @code{follow-fork-mode}) will be detached and allowed to run
2528 independently. This is the default.
2531 Both processes will be held under the control of @value{GDBN}.
2532 One process (child or parent, depending on the value of
2533 @code{follow-fork-mode}) is debugged as usual, while the other
2538 @kindex show detach-on-follow
2539 @item show detach-on-follow
2540 Show whether detach-on-follow mode is on/off.
2543 If you choose to set @var{detach-on-follow} mode off, then
2544 @value{GDBN} will retain control of all forked processes (including
2545 nested forks). You can list the forked processes under the control of
2546 @value{GDBN} by using the @w{@code{info forks}} command, and switch
2547 from one fork to another by using the @w{@code{fork}} command.
2552 Print a list of all forked processes under the control of @value{GDBN}.
2553 The listing will include a fork id, a process id, and the current
2554 position (program counter) of the process.
2557 @kindex fork @var{fork-id}
2558 @item fork @var{fork-id}
2559 Make fork number @var{fork-id} the current process. The argument
2560 @var{fork-id} is the internal fork number assigned by @value{GDBN},
2561 as shown in the first field of the @samp{info forks} display.
2565 To quit debugging one of the forked processes, you can either detach
2566 from it by using the @w{@code{detach fork}} command (allowing it to
2567 run independently), or delete (and kill) it using the
2568 @w{@code{delete fork}} command.
2571 @kindex detach fork @var{fork-id}
2572 @item detach fork @var{fork-id}
2573 Detach from the process identified by @value{GDBN} fork number
2574 @var{fork-id}, and remove it from the fork list. The process will be
2575 allowed to run independently.
2577 @kindex delete fork @var{fork-id}
2578 @item delete fork @var{fork-id}
2579 Kill the process identified by @value{GDBN} fork number @var{fork-id},
2580 and remove it from the fork list.
2584 If you ask to debug a child process and a @code{vfork} is followed by an
2585 @code{exec}, @value{GDBN} executes the new target up to the first
2586 breakpoint in the new target. If you have a breakpoint set on
2587 @code{main} in your original program, the breakpoint will also be set on
2588 the child process's @code{main}.
2590 When a child process is spawned by @code{vfork}, you cannot debug the
2591 child or parent until an @code{exec} call completes.
2593 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2594 call executes, the new target restarts. To restart the parent process,
2595 use the @code{file} command with the parent executable name as its
2598 You can use the @code{catch} command to make @value{GDBN} stop whenever
2599 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2600 Catchpoints, ,Setting Catchpoints}.
2602 @node Checkpoint/Restart
2603 @section Setting a @emph{Bookmark} to Return to Later
2608 @cindex snapshot of a process
2609 @cindex rewind program state
2611 On certain operating systems@footnote{Currently, only
2612 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
2613 program's state, called a @dfn{checkpoint}, and come back to it
2616 Returning to a checkpoint effectively undoes everything that has
2617 happened in the program since the @code{checkpoint} was saved. This
2618 includes changes in memory, registers, and even (within some limits)
2619 system state. Effectively, it is like going back in time to the
2620 moment when the checkpoint was saved.
2622 Thus, if you're stepping thru a program and you think you're
2623 getting close to the point where things go wrong, you can save
2624 a checkpoint. Then, if you accidentally go too far and miss
2625 the critical statement, instead of having to restart your program
2626 from the beginning, you can just go back to the checkpoint and
2627 start again from there.
2629 This can be especially useful if it takes a lot of time or
2630 steps to reach the point where you think the bug occurs.
2632 To use the @code{checkpoint}/@code{restart} method of debugging:
2637 Save a snapshot of the debugged program's current execution state.
2638 The @code{checkpoint} command takes no arguments, but each checkpoint
2639 is assigned a small integer id, similar to a breakpoint id.
2641 @kindex info checkpoints
2642 @item info checkpoints
2643 List the checkpoints that have been saved in the current debugging
2644 session. For each checkpoint, the following information will be
2651 @item Source line, or label
2654 @kindex restart @var{checkpoint-id}
2655 @item restart @var{checkpoint-id}
2656 Restore the program state that was saved as checkpoint number
2657 @var{checkpoint-id}. All program variables, registers, stack frames
2658 etc.@: will be returned to the values that they had when the checkpoint
2659 was saved. In essence, gdb will ``wind back the clock'' to the point
2660 in time when the checkpoint was saved.
2662 Note that breakpoints, @value{GDBN} variables, command history etc.
2663 are not affected by restoring a checkpoint. In general, a checkpoint
2664 only restores things that reside in the program being debugged, not in
2667 @kindex delete checkpoint @var{checkpoint-id}
2668 @item delete checkpoint @var{checkpoint-id}
2669 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
2673 Returning to a previously saved checkpoint will restore the user state
2674 of the program being debugged, plus a significant subset of the system
2675 (OS) state, including file pointers. It won't ``un-write'' data from
2676 a file, but it will rewind the file pointer to the previous location,
2677 so that the previously written data can be overwritten. For files
2678 opened in read mode, the pointer will also be restored so that the
2679 previously read data can be read again.
2681 Of course, characters that have been sent to a printer (or other
2682 external device) cannot be ``snatched back'', and characters received
2683 from eg.@: a serial device can be removed from internal program buffers,
2684 but they cannot be ``pushed back'' into the serial pipeline, ready to
2685 be received again. Similarly, the actual contents of files that have
2686 been changed cannot be restored (at this time).
2688 However, within those constraints, you actually can ``rewind'' your
2689 program to a previously saved point in time, and begin debugging it
2690 again --- and you can change the course of events so as to debug a
2691 different execution path this time.
2693 @cindex checkpoints and process id
2694 Finally, there is one bit of internal program state that will be
2695 different when you return to a checkpoint --- the program's process
2696 id. Each checkpoint will have a unique process id (or @var{pid}),
2697 and each will be different from the program's original @var{pid}.
2698 If your program has saved a local copy of its process id, this could
2699 potentially pose a problem.
2701 @subsection A Non-obvious Benefit of Using Checkpoints
2703 On some systems such as @sc{gnu}/Linux, address space randomization
2704 is performed on new processes for security reasons. This makes it
2705 difficult or impossible to set a breakpoint, or watchpoint, on an
2706 absolute address if you have to restart the program, since the
2707 absolute location of a symbol will change from one execution to the
2710 A checkpoint, however, is an @emph{identical} copy of a process.
2711 Therefore if you create a checkpoint at (eg.@:) the start of main,
2712 and simply return to that checkpoint instead of restarting the
2713 process, you can avoid the effects of address randomization and
2714 your symbols will all stay in the same place.
2717 @chapter Stopping and Continuing
2719 The principal purposes of using a debugger are so that you can stop your
2720 program before it terminates; or so that, if your program runs into
2721 trouble, you can investigate and find out why.
2723 Inside @value{GDBN}, your program may stop for any of several reasons,
2724 such as a signal, a breakpoint, or reaching a new line after a
2725 @value{GDBN} command such as @code{step}. You may then examine and
2726 change variables, set new breakpoints or remove old ones, and then
2727 continue execution. Usually, the messages shown by @value{GDBN} provide
2728 ample explanation of the status of your program---but you can also
2729 explicitly request this information at any time.
2732 @kindex info program
2734 Display information about the status of your program: whether it is
2735 running or not, what process it is, and why it stopped.
2739 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2740 * Continuing and Stepping:: Resuming execution
2742 * Thread Stops:: Stopping and starting multi-thread programs
2746 @section Breakpoints, Watchpoints, and Catchpoints
2749 A @dfn{breakpoint} makes your program stop whenever a certain point in
2750 the program is reached. For each breakpoint, you can add conditions to
2751 control in finer detail whether your program stops. You can set
2752 breakpoints with the @code{break} command and its variants (@pxref{Set
2753 Breaks, ,Setting Breakpoints}), to specify the place where your program
2754 should stop by line number, function name or exact address in the
2757 On some systems, you can set breakpoints in shared libraries before
2758 the executable is run. There is a minor limitation on HP-UX systems:
2759 you must wait until the executable is run in order to set breakpoints
2760 in shared library routines that are not called directly by the program
2761 (for example, routines that are arguments in a @code{pthread_create}
2765 @cindex data breakpoints
2766 @cindex memory tracing
2767 @cindex breakpoint on memory address
2768 @cindex breakpoint on variable modification
2769 A @dfn{watchpoint} is a special breakpoint that stops your program
2770 when the value of an expression changes. The expression may be a value
2771 of a variable, or it could involve values of one or more variables
2772 combined by operators, such as @samp{a + b}. This is sometimes called
2773 @dfn{data breakpoints}. You must use a different command to set
2774 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
2775 from that, you can manage a watchpoint like any other breakpoint: you
2776 enable, disable, and delete both breakpoints and watchpoints using the
2779 You can arrange to have values from your program displayed automatically
2780 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2784 @cindex breakpoint on events
2785 A @dfn{catchpoint} is another special breakpoint that stops your program
2786 when a certain kind of event occurs, such as the throwing of a C@t{++}
2787 exception or the loading of a library. As with watchpoints, you use a
2788 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2789 Catchpoints}), but aside from that, you can manage a catchpoint like any
2790 other breakpoint. (To stop when your program receives a signal, use the
2791 @code{handle} command; see @ref{Signals, ,Signals}.)
2793 @cindex breakpoint numbers
2794 @cindex numbers for breakpoints
2795 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2796 catchpoint when you create it; these numbers are successive integers
2797 starting with one. In many of the commands for controlling various
2798 features of breakpoints you use the breakpoint number to say which
2799 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2800 @dfn{disabled}; if disabled, it has no effect on your program until you
2803 @cindex breakpoint ranges
2804 @cindex ranges of breakpoints
2805 Some @value{GDBN} commands accept a range of breakpoints on which to
2806 operate. A breakpoint range is either a single breakpoint number, like
2807 @samp{5}, or two such numbers, in increasing order, separated by a
2808 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2809 all breakpoints in that range are operated on.
2812 * Set Breaks:: Setting breakpoints
2813 * Set Watchpoints:: Setting watchpoints
2814 * Set Catchpoints:: Setting catchpoints
2815 * Delete Breaks:: Deleting breakpoints
2816 * Disabling:: Disabling breakpoints
2817 * Conditions:: Break conditions
2818 * Break Commands:: Breakpoint command lists
2819 * Breakpoint Menus:: Breakpoint menus
2820 * Error in Breakpoints:: ``Cannot insert breakpoints''
2821 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
2825 @subsection Setting Breakpoints
2827 @c FIXME LMB what does GDB do if no code on line of breakpt?
2828 @c consider in particular declaration with/without initialization.
2830 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2833 @kindex b @r{(@code{break})}
2834 @vindex $bpnum@r{, convenience variable}
2835 @cindex latest breakpoint
2836 Breakpoints are set with the @code{break} command (abbreviated
2837 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2838 number of the breakpoint you've set most recently; see @ref{Convenience
2839 Vars,, Convenience Variables}, for a discussion of what you can do with
2840 convenience variables.
2842 You have several ways to say where the breakpoint should go.
2845 @item break @var{function}
2846 Set a breakpoint at entry to function @var{function}.
2847 When using source languages that permit overloading of symbols, such as
2848 C@t{++}, @var{function} may refer to more than one possible place to break.
2849 @xref{Breakpoint Menus,,Breakpoint Menus}, for a discussion of that situation.
2851 @item break +@var{offset}
2852 @itemx break -@var{offset}
2853 Set a breakpoint some number of lines forward or back from the position
2854 at which execution stopped in the currently selected @dfn{stack frame}.
2855 (@xref{Frames, ,Frames}, for a description of stack frames.)
2857 @item break @var{linenum}
2858 Set a breakpoint at line @var{linenum} in the current source file.
2859 The current source file is the last file whose source text was printed.
2860 The breakpoint will stop your program just before it executes any of the
2863 @item break @var{filename}:@var{linenum}
2864 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2866 @item break @var{filename}:@var{function}
2867 Set a breakpoint at entry to function @var{function} found in file
2868 @var{filename}. Specifying a file name as well as a function name is
2869 superfluous except when multiple files contain similarly named
2872 @item break *@var{address}
2873 Set a breakpoint at address @var{address}. You can use this to set
2874 breakpoints in parts of your program which do not have debugging
2875 information or source files.
2878 When called without any arguments, @code{break} sets a breakpoint at
2879 the next instruction to be executed in the selected stack frame
2880 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2881 innermost, this makes your program stop as soon as control
2882 returns to that frame. This is similar to the effect of a
2883 @code{finish} command in the frame inside the selected frame---except
2884 that @code{finish} does not leave an active breakpoint. If you use
2885 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2886 the next time it reaches the current location; this may be useful
2889 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2890 least one instruction has been executed. If it did not do this, you
2891 would be unable to proceed past a breakpoint without first disabling the
2892 breakpoint. This rule applies whether or not the breakpoint already
2893 existed when your program stopped.
2895 @item break @dots{} if @var{cond}
2896 Set a breakpoint with condition @var{cond}; evaluate the expression
2897 @var{cond} each time the breakpoint is reached, and stop only if the
2898 value is nonzero---that is, if @var{cond} evaluates as true.
2899 @samp{@dots{}} stands for one of the possible arguments described
2900 above (or no argument) specifying where to break. @xref{Conditions,
2901 ,Break Conditions}, for more information on breakpoint conditions.
2904 @item tbreak @var{args}
2905 Set a breakpoint enabled only for one stop. @var{args} are the
2906 same as for the @code{break} command, and the breakpoint is set in the same
2907 way, but the breakpoint is automatically deleted after the first time your
2908 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
2911 @cindex hardware breakpoints
2912 @item hbreak @var{args}
2913 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2914 @code{break} command and the breakpoint is set in the same way, but the
2915 breakpoint requires hardware support and some target hardware may not
2916 have this support. The main purpose of this is EPROM/ROM code
2917 debugging, so you can set a breakpoint at an instruction without
2918 changing the instruction. This can be used with the new trap-generation
2919 provided by SPARClite DSU and most x86-based targets. These targets
2920 will generate traps when a program accesses some data or instruction
2921 address that is assigned to the debug registers. However the hardware
2922 breakpoint registers can take a limited number of breakpoints. For
2923 example, on the DSU, only two data breakpoints can be set at a time, and
2924 @value{GDBN} will reject this command if more than two are used. Delete
2925 or disable unused hardware breakpoints before setting new ones
2926 (@pxref{Disabling, ,Disabling Breakpoints}).
2927 @xref{Conditions, ,Break Conditions}.
2928 For remote targets, you can restrict the number of hardware
2929 breakpoints @value{GDBN} will use, see @ref{set remote
2930 hardware-breakpoint-limit}.
2934 @item thbreak @var{args}
2935 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2936 are the same as for the @code{hbreak} command and the breakpoint is set in
2937 the same way. However, like the @code{tbreak} command,
2938 the breakpoint is automatically deleted after the
2939 first time your program stops there. Also, like the @code{hbreak}
2940 command, the breakpoint requires hardware support and some target hardware
2941 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
2942 See also @ref{Conditions, ,Break Conditions}.
2945 @cindex regular expression
2946 @cindex breakpoints in functions matching a regexp
2947 @cindex set breakpoints in many functions
2948 @item rbreak @var{regex}
2949 Set breakpoints on all functions matching the regular expression
2950 @var{regex}. This command sets an unconditional breakpoint on all
2951 matches, printing a list of all breakpoints it set. Once these
2952 breakpoints are set, they are treated just like the breakpoints set with
2953 the @code{break} command. You can delete them, disable them, or make
2954 them conditional the same way as any other breakpoint.
2956 The syntax of the regular expression is the standard one used with tools
2957 like @file{grep}. Note that this is different from the syntax used by
2958 shells, so for instance @code{foo*} matches all functions that include
2959 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2960 @code{.*} leading and trailing the regular expression you supply, so to
2961 match only functions that begin with @code{foo}, use @code{^foo}.
2963 @cindex non-member C@t{++} functions, set breakpoint in
2964 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2965 breakpoints on overloaded functions that are not members of any special
2968 @cindex set breakpoints on all functions
2969 The @code{rbreak} command can be used to set breakpoints in
2970 @strong{all} the functions in a program, like this:
2973 (@value{GDBP}) rbreak .
2976 @kindex info breakpoints
2977 @cindex @code{$_} and @code{info breakpoints}
2978 @item info breakpoints @r{[}@var{n}@r{]}
2979 @itemx info break @r{[}@var{n}@r{]}
2980 @itemx info watchpoints @r{[}@var{n}@r{]}
2981 Print a table of all breakpoints, watchpoints, and catchpoints set and
2982 not deleted. Optional argument @var{n} means print information only
2983 about the specified breakpoint (or watchpoint or catchpoint). For
2984 each breakpoint, following columns are printed:
2987 @item Breakpoint Numbers
2989 Breakpoint, watchpoint, or catchpoint.
2991 Whether the breakpoint is marked to be disabled or deleted when hit.
2992 @item Enabled or Disabled
2993 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2994 that are not enabled. An optional @samp{(p)} suffix marks pending
2995 breakpoints --- breakpoints for which address is either not yet
2996 resolved, pending load of a shared library, or for which address was
2997 in a shared library that was since unloaded. Such breakpoint won't
2998 fire until a shared library that has the symbol or line referred by
2999 breakpoint is loaded. See below for details.
3001 Where the breakpoint is in your program, as a memory address. For a
3002 pending breakpoint whose address is not yet known, this field will
3003 contain @samp{<PENDING>}. A breakpoint with several locations will
3004 have @samp{<MULTIPLE>} in this field --- see below for details.
3006 Where the breakpoint is in the source for your program, as a file and
3007 line number. For a pending breakpoint, the original string passed to
3008 the breakpoint command will be listed as it cannot be resolved until
3009 the appropriate shared library is loaded in the future.
3013 If a breakpoint is conditional, @code{info break} shows the condition on
3014 the line following the affected breakpoint; breakpoint commands, if any,
3015 are listed after that. A pending breakpoint is allowed to have a condition
3016 specified for it. The condition is not parsed for validity until a shared
3017 library is loaded that allows the pending breakpoint to resolve to a
3021 @code{info break} with a breakpoint
3022 number @var{n} as argument lists only that breakpoint. The
3023 convenience variable @code{$_} and the default examining-address for
3024 the @code{x} command are set to the address of the last breakpoint
3025 listed (@pxref{Memory, ,Examining Memory}).
3028 @code{info break} displays a count of the number of times the breakpoint
3029 has been hit. This is especially useful in conjunction with the
3030 @code{ignore} command. You can ignore a large number of breakpoint
3031 hits, look at the breakpoint info to see how many times the breakpoint
3032 was hit, and then run again, ignoring one less than that number. This
3033 will get you quickly to the last hit of that breakpoint.
3036 @value{GDBN} allows you to set any number of breakpoints at the same place in
3037 your program. There is nothing silly or meaningless about this. When
3038 the breakpoints are conditional, this is even useful
3039 (@pxref{Conditions, ,Break Conditions}).
3041 It is possible that a breakpoint corresponds to several locations
3042 in your program. Examples of this situation are:
3047 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3048 instances of the function body, used in different cases.
3051 For a C@t{++} template function, a given line in the function can
3052 correspond to any number of instantiations.
3055 For an inlined function, a given source line can correspond to
3056 several places where that function is inlined.
3060 In all those cases, @value{GDBN} will insert a breakpoint at all
3061 the relevant locations.
3063 A breakpoint with multiple locations is displayed in the
3064 breakpoint table using several rows --- one header row, followed
3065 by one row for each breakpoint location. The header row
3066 has @samp{<MULTIPLE>} in the address column. The rows for
3067 individual locations contain the actual addresses for locations,
3068 and say what functions those locations are in. The number
3069 column for a location has number in the format
3070 @var{breakpoint-number}.@var{location-number}.
3074 Num Type Disp Enb Address What
3075 1 breakpoint keep y <MULTIPLE>
3077 breakpoint already hit 1 time
3078 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3079 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3082 Each location can be individually enabled or disabled by passing
3083 @var{breakpoint-number}.@var{location-number} as argument to the
3084 @code{enable} and @code{disable} commands.
3086 @cindex pending breakpoints
3087 It's quite common to have a breakpoint inside a shared library.
3088 The shared library may be loaded and unloaded explicitly,
3089 and possibly repeatedly, as the program is executed. To support
3090 this use case, @value{GDBN} updates breakpoint locations whenever
3091 any shared library is loaded or unloaded. Typically, you would
3092 set a breakpoint in a shared library at the beginning of your
3093 debugging session, when the library is not loaded, and when the
3094 symbols from the library are not available. When you try to set
3095 breakpoint, @value{GDBN} will ask you if you want to set
3096 a so called @dfn{pending breakpoint} --- breakpoint whose address
3097 is not yet resolved.
3099 After the program is run, whenever a new shared library is loaded,
3100 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3101 shared library contains the symbol or line referred to by some
3102 pending breakpoint, that breakpoint is resolved and becomes an
3103 ordinary breakpoint. When a library is unloaded, all breakpoints
3104 that refer to its symbols or source lines become pending again.
3106 This logic works for breakpoints with multiple locations, too. For
3107 example, if you have a breakpoint in a C@t{++} template function, and
3108 a newly loaded shared library has an instantiation of that template,
3109 a new location is added to the list of locations for the breakpoint.
3111 Except for having unresolved address, pending breakpoints do not
3112 differ from regular breakpoints. You can set conditions or commands,
3113 enable and disable them and perform other breakpoint operations.
3115 @value{GDBN} provides some additional commands for controlling what
3116 happens when the @samp{break} command cannot resolve breakpoint
3117 address specification to an address:
3119 @kindex set breakpoint pending
3120 @kindex show breakpoint pending
3122 @item set breakpoint pending auto
3123 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3124 location, it queries you whether a pending breakpoint should be created.
3126 @item set breakpoint pending on
3127 This indicates that an unrecognized breakpoint location should automatically
3128 result in a pending breakpoint being created.
3130 @item set breakpoint pending off
3131 This indicates that pending breakpoints are not to be created. Any
3132 unrecognized breakpoint location results in an error. This setting does
3133 not affect any pending breakpoints previously created.
3135 @item show breakpoint pending
3136 Show the current behavior setting for creating pending breakpoints.
3139 The settings above only affect the @code{break} command and its
3140 variants. Once breakpoint is set, it will be automatically updated
3141 as shared libraries are loaded and unloaded.
3143 @cindex automatic hardware breakpoints
3144 For some targets, @value{GDBN} can automatically decide if hardware or
3145 software breakpoints should be used, depending on whether the
3146 breakpoint address is read-only or read-write. This applies to
3147 breakpoints set with the @code{break} command as well as to internal
3148 breakpoints set by commands like @code{next} and @code{finish}. For
3149 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3152 You can control this automatic behaviour with the following commands::
3154 @kindex set breakpoint auto-hw
3155 @kindex show breakpoint auto-hw
3157 @item set breakpoint auto-hw on
3158 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3159 will try to use the target memory map to decide if software or hardware
3160 breakpoint must be used.
3162 @item set breakpoint auto-hw off
3163 This indicates @value{GDBN} should not automatically select breakpoint
3164 type. If the target provides a memory map, @value{GDBN} will warn when
3165 trying to set software breakpoint at a read-only address.
3169 @cindex negative breakpoint numbers
3170 @cindex internal @value{GDBN} breakpoints
3171 @value{GDBN} itself sometimes sets breakpoints in your program for
3172 special purposes, such as proper handling of @code{longjmp} (in C
3173 programs). These internal breakpoints are assigned negative numbers,
3174 starting with @code{-1}; @samp{info breakpoints} does not display them.
3175 You can see these breakpoints with the @value{GDBN} maintenance command
3176 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3179 @node Set Watchpoints
3180 @subsection Setting Watchpoints
3182 @cindex setting watchpoints
3183 You can use a watchpoint to stop execution whenever the value of an
3184 expression changes, without having to predict a particular place where
3185 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3186 The expression may be as simple as the value of a single variable, or
3187 as complex as many variables combined by operators. Examples include:
3191 A reference to the value of a single variable.
3194 An address cast to an appropriate data type. For example,
3195 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3196 address (assuming an @code{int} occupies 4 bytes).
3199 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3200 expression can use any operators valid in the program's native
3201 language (@pxref{Languages}).
3204 @cindex software watchpoints
3205 @cindex hardware watchpoints
3206 Depending on your system, watchpoints may be implemented in software or
3207 hardware. @value{GDBN} does software watchpointing by single-stepping your
3208 program and testing the variable's value each time, which is hundreds of
3209 times slower than normal execution. (But this may still be worth it, to
3210 catch errors where you have no clue what part of your program is the
3213 On some systems, such as HP-UX, @sc{gnu}/Linux and most other
3214 x86-based targets, @value{GDBN} includes support for hardware
3215 watchpoints, which do not slow down the running of your program.
3219 @item watch @var{expr}
3220 Set a watchpoint for an expression. @value{GDBN} will break when the
3221 expression @var{expr} is written into by the program and its value
3222 changes. The simplest (and the most popular) use of this command is
3223 to watch the value of a single variable:
3226 (@value{GDBP}) watch foo
3230 @item rwatch @var{expr}
3231 Set a watchpoint that will break when the value of @var{expr} is read
3235 @item awatch @var{expr}
3236 Set a watchpoint that will break when @var{expr} is either read from
3237 or written into by the program.
3239 @kindex info watchpoints @r{[}@var{n}@r{]}
3240 @item info watchpoints
3241 This command prints a list of watchpoints, breakpoints, and catchpoints;
3242 it is the same as @code{info break} (@pxref{Set Breaks}).
3245 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3246 watchpoints execute very quickly, and the debugger reports a change in
3247 value at the exact instruction where the change occurs. If @value{GDBN}
3248 cannot set a hardware watchpoint, it sets a software watchpoint, which
3249 executes more slowly and reports the change in value at the next
3250 @emph{statement}, not the instruction, after the change occurs.
3252 @cindex use only software watchpoints
3253 You can force @value{GDBN} to use only software watchpoints with the
3254 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3255 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3256 the underlying system supports them. (Note that hardware-assisted
3257 watchpoints that were set @emph{before} setting
3258 @code{can-use-hw-watchpoints} to zero will still use the hardware
3259 mechanism of watching expression values.)
3262 @item set can-use-hw-watchpoints
3263 @kindex set can-use-hw-watchpoints
3264 Set whether or not to use hardware watchpoints.
3266 @item show can-use-hw-watchpoints
3267 @kindex show can-use-hw-watchpoints
3268 Show the current mode of using hardware watchpoints.
3271 For remote targets, you can restrict the number of hardware
3272 watchpoints @value{GDBN} will use, see @ref{set remote
3273 hardware-breakpoint-limit}.
3275 When you issue the @code{watch} command, @value{GDBN} reports
3278 Hardware watchpoint @var{num}: @var{expr}
3282 if it was able to set a hardware watchpoint.
3284 Currently, the @code{awatch} and @code{rwatch} commands can only set
3285 hardware watchpoints, because accesses to data that don't change the
3286 value of the watched expression cannot be detected without examining
3287 every instruction as it is being executed, and @value{GDBN} does not do
3288 that currently. If @value{GDBN} finds that it is unable to set a
3289 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3290 will print a message like this:
3293 Expression cannot be implemented with read/access watchpoint.
3296 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3297 data type of the watched expression is wider than what a hardware
3298 watchpoint on the target machine can handle. For example, some systems
3299 can only watch regions that are up to 4 bytes wide; on such systems you
3300 cannot set hardware watchpoints for an expression that yields a
3301 double-precision floating-point number (which is typically 8 bytes
3302 wide). As a work-around, it might be possible to break the large region
3303 into a series of smaller ones and watch them with separate watchpoints.
3305 If you set too many hardware watchpoints, @value{GDBN} might be unable
3306 to insert all of them when you resume the execution of your program.
3307 Since the precise number of active watchpoints is unknown until such
3308 time as the program is about to be resumed, @value{GDBN} might not be
3309 able to warn you about this when you set the watchpoints, and the
3310 warning will be printed only when the program is resumed:
3313 Hardware watchpoint @var{num}: Could not insert watchpoint
3317 If this happens, delete or disable some of the watchpoints.
3319 Watching complex expressions that reference many variables can also
3320 exhaust the resources available for hardware-assisted watchpoints.
3321 That's because @value{GDBN} needs to watch every variable in the
3322 expression with separately allocated resources.
3324 The SPARClite DSU will generate traps when a program accesses some data
3325 or instruction address that is assigned to the debug registers. For the
3326 data addresses, DSU facilitates the @code{watch} command. However the
3327 hardware breakpoint registers can only take two data watchpoints, and
3328 both watchpoints must be the same kind. For example, you can set two
3329 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
3330 @strong{or} two with @code{awatch} commands, but you cannot set one
3331 watchpoint with one command and the other with a different command.
3332 @value{GDBN} will reject the command if you try to mix watchpoints.
3333 Delete or disable unused watchpoint commands before setting new ones.
3335 If you call a function interactively using @code{print} or @code{call},
3336 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3337 kind of breakpoint or the call completes.
3339 @value{GDBN} automatically deletes watchpoints that watch local
3340 (automatic) variables, or expressions that involve such variables, when
3341 they go out of scope, that is, when the execution leaves the block in
3342 which these variables were defined. In particular, when the program
3343 being debugged terminates, @emph{all} local variables go out of scope,
3344 and so only watchpoints that watch global variables remain set. If you
3345 rerun the program, you will need to set all such watchpoints again. One
3346 way of doing that would be to set a code breakpoint at the entry to the
3347 @code{main} function and when it breaks, set all the watchpoints.
3349 @cindex watchpoints and threads
3350 @cindex threads and watchpoints
3351 In multi-threaded programs, watchpoints will detect changes to the
3352 watched expression from every thread.
3355 @emph{Warning:} In multi-threaded programs, software watchpoints
3356 have only limited usefulness. If @value{GDBN} creates a software
3357 watchpoint, it can only watch the value of an expression @emph{in a
3358 single thread}. If you are confident that the expression can only
3359 change due to the current thread's activity (and if you are also
3360 confident that no other thread can become current), then you can use
3361 software watchpoints as usual. However, @value{GDBN} may not notice
3362 when a non-current thread's activity changes the expression. (Hardware
3363 watchpoints, in contrast, watch an expression in all threads.)
3366 @xref{set remote hardware-watchpoint-limit}.
3368 @node Set Catchpoints
3369 @subsection Setting Catchpoints
3370 @cindex catchpoints, setting
3371 @cindex exception handlers
3372 @cindex event handling
3374 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3375 kinds of program events, such as C@t{++} exceptions or the loading of a
3376 shared library. Use the @code{catch} command to set a catchpoint.
3380 @item catch @var{event}
3381 Stop when @var{event} occurs. @var{event} can be any of the following:
3384 @cindex stop on C@t{++} exceptions
3385 The throwing of a C@t{++} exception.
3388 The catching of a C@t{++} exception.
3391 @cindex Ada exception catching
3392 @cindex catch Ada exceptions
3393 An Ada exception being raised. If an exception name is specified
3394 at the end of the command (eg @code{catch exception Program_Error}),
3395 the debugger will stop only when this specific exception is raised.
3396 Otherwise, the debugger stops execution when any Ada exception is raised.
3398 @item exception unhandled
3399 An exception that was raised but is not handled by the program.
3402 A failed Ada assertion.
3405 @cindex break on fork/exec
3406 A call to @code{exec}. This is currently only available for HP-UX.
3409 A call to @code{fork}. This is currently only available for HP-UX.
3412 A call to @code{vfork}. This is currently only available for HP-UX.
3415 @itemx load @var{libname}
3416 @cindex break on load/unload of shared library
3417 The dynamic loading of any shared library, or the loading of the library
3418 @var{libname}. This is currently only available for HP-UX.
3421 @itemx unload @var{libname}
3422 The unloading of any dynamically loaded shared library, or the unloading
3423 of the library @var{libname}. This is currently only available for HP-UX.
3426 @item tcatch @var{event}
3427 Set a catchpoint that is enabled only for one stop. The catchpoint is
3428 automatically deleted after the first time the event is caught.
3432 Use the @code{info break} command to list the current catchpoints.
3434 There are currently some limitations to C@t{++} exception handling
3435 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3439 If you call a function interactively, @value{GDBN} normally returns
3440 control to you when the function has finished executing. If the call
3441 raises an exception, however, the call may bypass the mechanism that
3442 returns control to you and cause your program either to abort or to
3443 simply continue running until it hits a breakpoint, catches a signal
3444 that @value{GDBN} is listening for, or exits. This is the case even if
3445 you set a catchpoint for the exception; catchpoints on exceptions are
3446 disabled within interactive calls.
3449 You cannot raise an exception interactively.
3452 You cannot install an exception handler interactively.
3455 @cindex raise exceptions
3456 Sometimes @code{catch} is not the best way to debug exception handling:
3457 if you need to know exactly where an exception is raised, it is better to
3458 stop @emph{before} the exception handler is called, since that way you
3459 can see the stack before any unwinding takes place. If you set a
3460 breakpoint in an exception handler instead, it may not be easy to find
3461 out where the exception was raised.
3463 To stop just before an exception handler is called, you need some
3464 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3465 raised by calling a library function named @code{__raise_exception}
3466 which has the following ANSI C interface:
3469 /* @var{addr} is where the exception identifier is stored.
3470 @var{id} is the exception identifier. */
3471 void __raise_exception (void **addr, void *id);
3475 To make the debugger catch all exceptions before any stack
3476 unwinding takes place, set a breakpoint on @code{__raise_exception}
3477 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
3479 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
3480 that depends on the value of @var{id}, you can stop your program when
3481 a specific exception is raised. You can use multiple conditional
3482 breakpoints to stop your program when any of a number of exceptions are
3487 @subsection Deleting Breakpoints
3489 @cindex clearing breakpoints, watchpoints, catchpoints
3490 @cindex deleting breakpoints, watchpoints, catchpoints
3491 It is often necessary to eliminate a breakpoint, watchpoint, or
3492 catchpoint once it has done its job and you no longer want your program
3493 to stop there. This is called @dfn{deleting} the breakpoint. A
3494 breakpoint that has been deleted no longer exists; it is forgotten.
3496 With the @code{clear} command you can delete breakpoints according to
3497 where they are in your program. With the @code{delete} command you can
3498 delete individual breakpoints, watchpoints, or catchpoints by specifying
3499 their breakpoint numbers.
3501 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3502 automatically ignores breakpoints on the first instruction to be executed
3503 when you continue execution without changing the execution address.
3508 Delete any breakpoints at the next instruction to be executed in the
3509 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
3510 the innermost frame is selected, this is a good way to delete a
3511 breakpoint where your program just stopped.
3513 @item clear @var{function}
3514 @itemx clear @var{filename}:@var{function}
3515 Delete any breakpoints set at entry to the named @var{function}.
3517 @item clear @var{linenum}
3518 @itemx clear @var{filename}:@var{linenum}
3519 Delete any breakpoints set at or within the code of the specified
3520 @var{linenum} of the specified @var{filename}.
3522 @cindex delete breakpoints
3524 @kindex d @r{(@code{delete})}
3525 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3526 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3527 ranges specified as arguments. If no argument is specified, delete all
3528 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3529 confirm off}). You can abbreviate this command as @code{d}.
3533 @subsection Disabling Breakpoints
3535 @cindex enable/disable a breakpoint
3536 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3537 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3538 it had been deleted, but remembers the information on the breakpoint so
3539 that you can @dfn{enable} it again later.
3541 You disable and enable breakpoints, watchpoints, and catchpoints with
3542 the @code{enable} and @code{disable} commands, optionally specifying one
3543 or more breakpoint numbers as arguments. Use @code{info break} or
3544 @code{info watch} to print a list of breakpoints, watchpoints, and
3545 catchpoints if you do not know which numbers to use.
3547 A breakpoint, watchpoint, or catchpoint can have any of four different
3548 states of enablement:
3552 Enabled. The breakpoint stops your program. A breakpoint set
3553 with the @code{break} command starts out in this state.
3555 Disabled. The breakpoint has no effect on your program.
3557 Enabled once. The breakpoint stops your program, but then becomes
3560 Enabled for deletion. The breakpoint stops your program, but
3561 immediately after it does so it is deleted permanently. A breakpoint
3562 set with the @code{tbreak} command starts out in this state.
3565 You can use the following commands to enable or disable breakpoints,
3566 watchpoints, and catchpoints:
3570 @kindex dis @r{(@code{disable})}
3571 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3572 Disable the specified breakpoints---or all breakpoints, if none are
3573 listed. A disabled breakpoint has no effect but is not forgotten. All
3574 options such as ignore-counts, conditions and commands are remembered in
3575 case the breakpoint is enabled again later. You may abbreviate
3576 @code{disable} as @code{dis}.
3579 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3580 Enable the specified breakpoints (or all defined breakpoints). They
3581 become effective once again in stopping your program.
3583 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3584 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3585 of these breakpoints immediately after stopping your program.
3587 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3588 Enable the specified breakpoints to work once, then die. @value{GDBN}
3589 deletes any of these breakpoints as soon as your program stops there.
3590 Breakpoints set by the @code{tbreak} command start out in this state.
3593 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3594 @c confusing: tbreak is also initially enabled.
3595 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3596 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
3597 subsequently, they become disabled or enabled only when you use one of
3598 the commands above. (The command @code{until} can set and delete a
3599 breakpoint of its own, but it does not change the state of your other
3600 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3604 @subsection Break Conditions
3605 @cindex conditional breakpoints
3606 @cindex breakpoint conditions
3608 @c FIXME what is scope of break condition expr? Context where wanted?
3609 @c in particular for a watchpoint?
3610 The simplest sort of breakpoint breaks every time your program reaches a
3611 specified place. You can also specify a @dfn{condition} for a
3612 breakpoint. A condition is just a Boolean expression in your
3613 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3614 a condition evaluates the expression each time your program reaches it,
3615 and your program stops only if the condition is @emph{true}.
3617 This is the converse of using assertions for program validation; in that
3618 situation, you want to stop when the assertion is violated---that is,
3619 when the condition is false. In C, if you want to test an assertion expressed
3620 by the condition @var{assert}, you should set the condition
3621 @samp{! @var{assert}} on the appropriate breakpoint.
3623 Conditions are also accepted for watchpoints; you may not need them,
3624 since a watchpoint is inspecting the value of an expression anyhow---but
3625 it might be simpler, say, to just set a watchpoint on a variable name,
3626 and specify a condition that tests whether the new value is an interesting
3629 Break conditions can have side effects, and may even call functions in
3630 your program. This can be useful, for example, to activate functions
3631 that log program progress, or to use your own print functions to
3632 format special data structures. The effects are completely predictable
3633 unless there is another enabled breakpoint at the same address. (In
3634 that case, @value{GDBN} might see the other breakpoint first and stop your
3635 program without checking the condition of this one.) Note that
3636 breakpoint commands are usually more convenient and flexible than break
3638 purpose of performing side effects when a breakpoint is reached
3639 (@pxref{Break Commands, ,Breakpoint Command Lists}).
3641 Break conditions can be specified when a breakpoint is set, by using
3642 @samp{if} in the arguments to the @code{break} command. @xref{Set
3643 Breaks, ,Setting Breakpoints}. They can also be changed at any time
3644 with the @code{condition} command.
3646 You can also use the @code{if} keyword with the @code{watch} command.
3647 The @code{catch} command does not recognize the @code{if} keyword;
3648 @code{condition} is the only way to impose a further condition on a
3653 @item condition @var{bnum} @var{expression}
3654 Specify @var{expression} as the break condition for breakpoint,
3655 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3656 breakpoint @var{bnum} stops your program only if the value of
3657 @var{expression} is true (nonzero, in C). When you use
3658 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3659 syntactic correctness, and to determine whether symbols in it have
3660 referents in the context of your breakpoint. If @var{expression} uses
3661 symbols not referenced in the context of the breakpoint, @value{GDBN}
3662 prints an error message:
3665 No symbol "foo" in current context.
3670 not actually evaluate @var{expression} at the time the @code{condition}
3671 command (or a command that sets a breakpoint with a condition, like
3672 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3674 @item condition @var{bnum}
3675 Remove the condition from breakpoint number @var{bnum}. It becomes
3676 an ordinary unconditional breakpoint.
3679 @cindex ignore count (of breakpoint)
3680 A special case of a breakpoint condition is to stop only when the
3681 breakpoint has been reached a certain number of times. This is so
3682 useful that there is a special way to do it, using the @dfn{ignore
3683 count} of the breakpoint. Every breakpoint has an ignore count, which
3684 is an integer. Most of the time, the ignore count is zero, and
3685 therefore has no effect. But if your program reaches a breakpoint whose
3686 ignore count is positive, then instead of stopping, it just decrements
3687 the ignore count by one and continues. As a result, if the ignore count
3688 value is @var{n}, the breakpoint does not stop the next @var{n} times
3689 your program reaches it.
3693 @item ignore @var{bnum} @var{count}
3694 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3695 The next @var{count} times the breakpoint is reached, your program's
3696 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3699 To make the breakpoint stop the next time it is reached, specify
3702 When you use @code{continue} to resume execution of your program from a
3703 breakpoint, you can specify an ignore count directly as an argument to
3704 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3705 Stepping,,Continuing and Stepping}.
3707 If a breakpoint has a positive ignore count and a condition, the
3708 condition is not checked. Once the ignore count reaches zero,
3709 @value{GDBN} resumes checking the condition.
3711 You could achieve the effect of the ignore count with a condition such
3712 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3713 is decremented each time. @xref{Convenience Vars, ,Convenience
3717 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3720 @node Break Commands
3721 @subsection Breakpoint Command Lists
3723 @cindex breakpoint commands
3724 You can give any breakpoint (or watchpoint or catchpoint) a series of
3725 commands to execute when your program stops due to that breakpoint. For
3726 example, you might want to print the values of certain expressions, or
3727 enable other breakpoints.
3731 @kindex end@r{ (breakpoint commands)}
3732 @item commands @r{[}@var{bnum}@r{]}
3733 @itemx @dots{} @var{command-list} @dots{}
3735 Specify a list of commands for breakpoint number @var{bnum}. The commands
3736 themselves appear on the following lines. Type a line containing just
3737 @code{end} to terminate the commands.
3739 To remove all commands from a breakpoint, type @code{commands} and
3740 follow it immediately with @code{end}; that is, give no commands.
3742 With no @var{bnum} argument, @code{commands} refers to the last
3743 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3744 recently encountered).
3747 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3748 disabled within a @var{command-list}.
3750 You can use breakpoint commands to start your program up again. Simply
3751 use the @code{continue} command, or @code{step}, or any other command
3752 that resumes execution.
3754 Any other commands in the command list, after a command that resumes
3755 execution, are ignored. This is because any time you resume execution
3756 (even with a simple @code{next} or @code{step}), you may encounter
3757 another breakpoint---which could have its own command list, leading to
3758 ambiguities about which list to execute.
3761 If the first command you specify in a command list is @code{silent}, the
3762 usual message about stopping at a breakpoint is not printed. This may
3763 be desirable for breakpoints that are to print a specific message and
3764 then continue. If none of the remaining commands print anything, you
3765 see no sign that the breakpoint was reached. @code{silent} is
3766 meaningful only at the beginning of a breakpoint command list.
3768 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3769 print precisely controlled output, and are often useful in silent
3770 breakpoints. @xref{Output, ,Commands for Controlled Output}.
3772 For example, here is how you could use breakpoint commands to print the
3773 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3779 printf "x is %d\n",x
3784 One application for breakpoint commands is to compensate for one bug so
3785 you can test for another. Put a breakpoint just after the erroneous line
3786 of code, give it a condition to detect the case in which something
3787 erroneous has been done, and give it commands to assign correct values
3788 to any variables that need them. End with the @code{continue} command
3789 so that your program does not stop, and start with the @code{silent}
3790 command so that no output is produced. Here is an example:
3801 @node Breakpoint Menus
3802 @subsection Breakpoint Menus
3804 @cindex symbol overloading
3806 Some programming languages (notably C@t{++} and Objective-C) permit a
3807 single function name
3808 to be defined several times, for application in different contexts.
3809 This is called @dfn{overloading}. When a function name is overloaded,
3810 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3811 a breakpoint. If you realize this is a problem, you can use
3812 something like @samp{break @var{function}(@var{types})} to specify which
3813 particular version of the function you want. Otherwise, @value{GDBN} offers
3814 you a menu of numbered choices for different possible breakpoints, and
3815 waits for your selection with the prompt @samp{>}. The first two
3816 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3817 sets a breakpoint at each definition of @var{function}, and typing
3818 @kbd{0} aborts the @code{break} command without setting any new
3821 For example, the following session excerpt shows an attempt to set a
3822 breakpoint at the overloaded symbol @code{String::after}.
3823 We choose three particular definitions of that function name:
3825 @c FIXME! This is likely to change to show arg type lists, at least
3828 (@value{GDBP}) b String::after
3831 [2] file:String.cc; line number:867
3832 [3] file:String.cc; line number:860
3833 [4] file:String.cc; line number:875
3834 [5] file:String.cc; line number:853
3835 [6] file:String.cc; line number:846
3836 [7] file:String.cc; line number:735
3838 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3839 Breakpoint 2 at 0xb344: file String.cc, line 875.
3840 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3841 Multiple breakpoints were set.
3842 Use the "delete" command to delete unwanted
3848 @c @ifclear BARETARGET
3849 @node Error in Breakpoints
3850 @subsection ``Cannot insert breakpoints''
3852 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3854 Under some operating systems, breakpoints cannot be used in a program if
3855 any other process is running that program. In this situation,
3856 attempting to run or continue a program with a breakpoint causes
3857 @value{GDBN} to print an error message:
3860 Cannot insert breakpoints.
3861 The same program may be running in another process.
3864 When this happens, you have three ways to proceed:
3868 Remove or disable the breakpoints, then continue.
3871 Suspend @value{GDBN}, and copy the file containing your program to a new
3872 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3873 that @value{GDBN} should run your program under that name.
3874 Then start your program again.
3877 Relink your program so that the text segment is nonsharable, using the
3878 linker option @samp{-N}. The operating system limitation may not apply
3879 to nonsharable executables.
3883 A similar message can be printed if you request too many active
3884 hardware-assisted breakpoints and watchpoints:
3886 @c FIXME: the precise wording of this message may change; the relevant
3887 @c source change is not committed yet (Sep 3, 1999).
3889 Stopped; cannot insert breakpoints.
3890 You may have requested too many hardware breakpoints and watchpoints.
3894 This message is printed when you attempt to resume the program, since
3895 only then @value{GDBN} knows exactly how many hardware breakpoints and
3896 watchpoints it needs to insert.
3898 When this message is printed, you need to disable or remove some of the
3899 hardware-assisted breakpoints and watchpoints, and then continue.
3901 @node Breakpoint-related Warnings
3902 @subsection ``Breakpoint address adjusted...''
3903 @cindex breakpoint address adjusted
3905 Some processor architectures place constraints on the addresses at
3906 which breakpoints may be placed. For architectures thus constrained,
3907 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3908 with the constraints dictated by the architecture.
3910 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3911 a VLIW architecture in which a number of RISC-like instructions may be
3912 bundled together for parallel execution. The FR-V architecture
3913 constrains the location of a breakpoint instruction within such a
3914 bundle to the instruction with the lowest address. @value{GDBN}
3915 honors this constraint by adjusting a breakpoint's address to the
3916 first in the bundle.
3918 It is not uncommon for optimized code to have bundles which contain
3919 instructions from different source statements, thus it may happen that
3920 a breakpoint's address will be adjusted from one source statement to
3921 another. Since this adjustment may significantly alter @value{GDBN}'s
3922 breakpoint related behavior from what the user expects, a warning is
3923 printed when the breakpoint is first set and also when the breakpoint
3926 A warning like the one below is printed when setting a breakpoint
3927 that's been subject to address adjustment:
3930 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3933 Such warnings are printed both for user settable and @value{GDBN}'s
3934 internal breakpoints. If you see one of these warnings, you should
3935 verify that a breakpoint set at the adjusted address will have the
3936 desired affect. If not, the breakpoint in question may be removed and
3937 other breakpoints may be set which will have the desired behavior.
3938 E.g., it may be sufficient to place the breakpoint at a later
3939 instruction. A conditional breakpoint may also be useful in some
3940 cases to prevent the breakpoint from triggering too often.
3942 @value{GDBN} will also issue a warning when stopping at one of these
3943 adjusted breakpoints:
3946 warning: Breakpoint 1 address previously adjusted from 0x00010414
3950 When this warning is encountered, it may be too late to take remedial
3951 action except in cases where the breakpoint is hit earlier or more
3952 frequently than expected.
3954 @node Continuing and Stepping
3955 @section Continuing and Stepping
3959 @cindex resuming execution
3960 @dfn{Continuing} means resuming program execution until your program
3961 completes normally. In contrast, @dfn{stepping} means executing just
3962 one more ``step'' of your program, where ``step'' may mean either one
3963 line of source code, or one machine instruction (depending on what
3964 particular command you use). Either when continuing or when stepping,
3965 your program may stop even sooner, due to a breakpoint or a signal. (If
3966 it stops due to a signal, you may want to use @code{handle}, or use
3967 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3971 @kindex c @r{(@code{continue})}
3972 @kindex fg @r{(resume foreground execution)}
3973 @item continue @r{[}@var{ignore-count}@r{]}
3974 @itemx c @r{[}@var{ignore-count}@r{]}
3975 @itemx fg @r{[}@var{ignore-count}@r{]}
3976 Resume program execution, at the address where your program last stopped;
3977 any breakpoints set at that address are bypassed. The optional argument
3978 @var{ignore-count} allows you to specify a further number of times to
3979 ignore a breakpoint at this location; its effect is like that of
3980 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
3982 The argument @var{ignore-count} is meaningful only when your program
3983 stopped due to a breakpoint. At other times, the argument to
3984 @code{continue} is ignored.
3986 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3987 debugged program is deemed to be the foreground program) are provided
3988 purely for convenience, and have exactly the same behavior as
3992 To resume execution at a different place, you can use @code{return}
3993 (@pxref{Returning, ,Returning from a Function}) to go back to the
3994 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3995 Different Address}) to go to an arbitrary location in your program.
3997 A typical technique for using stepping is to set a breakpoint
3998 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
3999 beginning of the function or the section of your program where a problem
4000 is believed to lie, run your program until it stops at that breakpoint,
4001 and then step through the suspect area, examining the variables that are
4002 interesting, until you see the problem happen.
4006 @kindex s @r{(@code{step})}
4008 Continue running your program until control reaches a different source
4009 line, then stop it and return control to @value{GDBN}. This command is
4010 abbreviated @code{s}.
4013 @c "without debugging information" is imprecise; actually "without line
4014 @c numbers in the debugging information". (gcc -g1 has debugging info but
4015 @c not line numbers). But it seems complex to try to make that
4016 @c distinction here.
4017 @emph{Warning:} If you use the @code{step} command while control is
4018 within a function that was compiled without debugging information,
4019 execution proceeds until control reaches a function that does have
4020 debugging information. Likewise, it will not step into a function which
4021 is compiled without debugging information. To step through functions
4022 without debugging information, use the @code{stepi} command, described
4026 The @code{step} command only stops at the first instruction of a source
4027 line. This prevents the multiple stops that could otherwise occur in
4028 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4029 to stop if a function that has debugging information is called within
4030 the line. In other words, @code{step} @emph{steps inside} any functions
4031 called within the line.
4033 Also, the @code{step} command only enters a function if there is line
4034 number information for the function. Otherwise it acts like the
4035 @code{next} command. This avoids problems when using @code{cc -gl}
4036 on MIPS machines. Previously, @code{step} entered subroutines if there
4037 was any debugging information about the routine.
4039 @item step @var{count}
4040 Continue running as in @code{step}, but do so @var{count} times. If a
4041 breakpoint is reached, or a signal not related to stepping occurs before
4042 @var{count} steps, stepping stops right away.
4045 @kindex n @r{(@code{next})}
4046 @item next @r{[}@var{count}@r{]}
4047 Continue to the next source line in the current (innermost) stack frame.
4048 This is similar to @code{step}, but function calls that appear within
4049 the line of code are executed without stopping. Execution stops when
4050 control reaches a different line of code at the original stack level
4051 that was executing when you gave the @code{next} command. This command
4052 is abbreviated @code{n}.
4054 An argument @var{count} is a repeat count, as for @code{step}.
4057 @c FIX ME!! Do we delete this, or is there a way it fits in with
4058 @c the following paragraph? --- Vctoria
4060 @c @code{next} within a function that lacks debugging information acts like
4061 @c @code{step}, but any function calls appearing within the code of the
4062 @c function are executed without stopping.
4064 The @code{next} command only stops at the first instruction of a
4065 source line. This prevents multiple stops that could otherwise occur in
4066 @code{switch} statements, @code{for} loops, etc.
4068 @kindex set step-mode
4070 @cindex functions without line info, and stepping
4071 @cindex stepping into functions with no line info
4072 @itemx set step-mode on
4073 The @code{set step-mode on} command causes the @code{step} command to
4074 stop at the first instruction of a function which contains no debug line
4075 information rather than stepping over it.
4077 This is useful in cases where you may be interested in inspecting the
4078 machine instructions of a function which has no symbolic info and do not
4079 want @value{GDBN} to automatically skip over this function.
4081 @item set step-mode off
4082 Causes the @code{step} command to step over any functions which contains no
4083 debug information. This is the default.
4085 @item show step-mode
4086 Show whether @value{GDBN} will stop in or step over functions without
4087 source line debug information.
4091 Continue running until just after function in the selected stack frame
4092 returns. Print the returned value (if any).
4094 Contrast this with the @code{return} command (@pxref{Returning,
4095 ,Returning from a Function}).
4098 @kindex u @r{(@code{until})}
4099 @cindex run until specified location
4102 Continue running until a source line past the current line, in the
4103 current stack frame, is reached. This command is used to avoid single
4104 stepping through a loop more than once. It is like the @code{next}
4105 command, except that when @code{until} encounters a jump, it
4106 automatically continues execution until the program counter is greater
4107 than the address of the jump.
4109 This means that when you reach the end of a loop after single stepping
4110 though it, @code{until} makes your program continue execution until it
4111 exits the loop. In contrast, a @code{next} command at the end of a loop
4112 simply steps back to the beginning of the loop, which forces you to step
4113 through the next iteration.
4115 @code{until} always stops your program if it attempts to exit the current
4118 @code{until} may produce somewhat counterintuitive results if the order
4119 of machine code does not match the order of the source lines. For
4120 example, in the following excerpt from a debugging session, the @code{f}
4121 (@code{frame}) command shows that execution is stopped at line
4122 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4126 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4128 (@value{GDBP}) until
4129 195 for ( ; argc > 0; NEXTARG) @{
4132 This happened because, for execution efficiency, the compiler had
4133 generated code for the loop closure test at the end, rather than the
4134 start, of the loop---even though the test in a C @code{for}-loop is
4135 written before the body of the loop. The @code{until} command appeared
4136 to step back to the beginning of the loop when it advanced to this
4137 expression; however, it has not really gone to an earlier
4138 statement---not in terms of the actual machine code.
4140 @code{until} with no argument works by means of single
4141 instruction stepping, and hence is slower than @code{until} with an
4144 @item until @var{location}
4145 @itemx u @var{location}
4146 Continue running your program until either the specified location is
4147 reached, or the current stack frame returns. @var{location} is any of
4148 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
4149 ,Setting Breakpoints}). This form of the command uses breakpoints, and
4150 hence is quicker than @code{until} without an argument. The specified
4151 location is actually reached only if it is in the current frame. This
4152 implies that @code{until} can be used to skip over recursive function
4153 invocations. For instance in the code below, if the current location is
4154 line @code{96}, issuing @code{until 99} will execute the program up to
4155 line @code{99} in the same invocation of factorial, i.e., after the inner
4156 invocations have returned.
4159 94 int factorial (int value)
4161 96 if (value > 1) @{
4162 97 value *= factorial (value - 1);
4169 @kindex advance @var{location}
4170 @itemx advance @var{location}
4171 Continue running the program up to the given @var{location}. An argument is
4172 required, which should be of the same form as arguments for the @code{break}
4173 command. Execution will also stop upon exit from the current stack
4174 frame. This command is similar to @code{until}, but @code{advance} will
4175 not skip over recursive function calls, and the target location doesn't
4176 have to be in the same frame as the current one.
4180 @kindex si @r{(@code{stepi})}
4182 @itemx stepi @var{arg}
4184 Execute one machine instruction, then stop and return to the debugger.
4186 It is often useful to do @samp{display/i $pc} when stepping by machine
4187 instructions. This makes @value{GDBN} automatically display the next
4188 instruction to be executed, each time your program stops. @xref{Auto
4189 Display,, Automatic Display}.
4191 An argument is a repeat count, as in @code{step}.
4195 @kindex ni @r{(@code{nexti})}
4197 @itemx nexti @var{arg}
4199 Execute one machine instruction, but if it is a function call,
4200 proceed until the function returns.
4202 An argument is a repeat count, as in @code{next}.
4209 A signal is an asynchronous event that can happen in a program. The
4210 operating system defines the possible kinds of signals, and gives each
4211 kind a name and a number. For example, in Unix @code{SIGINT} is the
4212 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4213 @code{SIGSEGV} is the signal a program gets from referencing a place in
4214 memory far away from all the areas in use; @code{SIGALRM} occurs when
4215 the alarm clock timer goes off (which happens only if your program has
4216 requested an alarm).
4218 @cindex fatal signals
4219 Some signals, including @code{SIGALRM}, are a normal part of the
4220 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4221 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4222 program has not specified in advance some other way to handle the signal.
4223 @code{SIGINT} does not indicate an error in your program, but it is normally
4224 fatal so it can carry out the purpose of the interrupt: to kill the program.
4226 @value{GDBN} has the ability to detect any occurrence of a signal in your
4227 program. You can tell @value{GDBN} in advance what to do for each kind of
4230 @cindex handling signals
4231 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4232 @code{SIGALRM} be silently passed to your program
4233 (so as not to interfere with their role in the program's functioning)
4234 but to stop your program immediately whenever an error signal happens.
4235 You can change these settings with the @code{handle} command.
4238 @kindex info signals
4242 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4243 handle each one. You can use this to see the signal numbers of all
4244 the defined types of signals.
4246 @item info signals @var{sig}
4247 Similar, but print information only about the specified signal number.
4249 @code{info handle} is an alias for @code{info signals}.
4252 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4253 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4254 can be the number of a signal or its name (with or without the
4255 @samp{SIG} at the beginning); a list of signal numbers of the form
4256 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4257 known signals. Optional arguments @var{keywords}, described below,
4258 say what change to make.
4262 The keywords allowed by the @code{handle} command can be abbreviated.
4263 Their full names are:
4267 @value{GDBN} should not stop your program when this signal happens. It may
4268 still print a message telling you that the signal has come in.
4271 @value{GDBN} should stop your program when this signal happens. This implies
4272 the @code{print} keyword as well.
4275 @value{GDBN} should print a message when this signal happens.
4278 @value{GDBN} should not mention the occurrence of the signal at all. This
4279 implies the @code{nostop} keyword as well.
4283 @value{GDBN} should allow your program to see this signal; your program
4284 can handle the signal, or else it may terminate if the signal is fatal
4285 and not handled. @code{pass} and @code{noignore} are synonyms.
4289 @value{GDBN} should not allow your program to see this signal.
4290 @code{nopass} and @code{ignore} are synonyms.
4294 When a signal stops your program, the signal is not visible to the
4296 continue. Your program sees the signal then, if @code{pass} is in
4297 effect for the signal in question @emph{at that time}. In other words,
4298 after @value{GDBN} reports a signal, you can use the @code{handle}
4299 command with @code{pass} or @code{nopass} to control whether your
4300 program sees that signal when you continue.
4302 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4303 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4304 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4307 You can also use the @code{signal} command to prevent your program from
4308 seeing a signal, or cause it to see a signal it normally would not see,
4309 or to give it any signal at any time. For example, if your program stopped
4310 due to some sort of memory reference error, you might store correct
4311 values into the erroneous variables and continue, hoping to see more
4312 execution; but your program would probably terminate immediately as
4313 a result of the fatal signal once it saw the signal. To prevent this,
4314 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4318 @section Stopping and Starting Multi-thread Programs
4320 When your program has multiple threads (@pxref{Threads,, Debugging
4321 Programs with Multiple Threads}), you can choose whether to set
4322 breakpoints on all threads, or on a particular thread.
4325 @cindex breakpoints and threads
4326 @cindex thread breakpoints
4327 @kindex break @dots{} thread @var{threadno}
4328 @item break @var{linespec} thread @var{threadno}
4329 @itemx break @var{linespec} thread @var{threadno} if @dots{}
4330 @var{linespec} specifies source lines; there are several ways of
4331 writing them, but the effect is always to specify some source line.
4333 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
4334 to specify that you only want @value{GDBN} to stop the program when a
4335 particular thread reaches this breakpoint. @var{threadno} is one of the
4336 numeric thread identifiers assigned by @value{GDBN}, shown in the first
4337 column of the @samp{info threads} display.
4339 If you do not specify @samp{thread @var{threadno}} when you set a
4340 breakpoint, the breakpoint applies to @emph{all} threads of your
4343 You can use the @code{thread} qualifier on conditional breakpoints as
4344 well; in this case, place @samp{thread @var{threadno}} before the
4345 breakpoint condition, like this:
4348 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
4353 @cindex stopped threads
4354 @cindex threads, stopped
4355 Whenever your program stops under @value{GDBN} for any reason,
4356 @emph{all} threads of execution stop, not just the current thread. This
4357 allows you to examine the overall state of the program, including
4358 switching between threads, without worrying that things may change
4361 @cindex thread breakpoints and system calls
4362 @cindex system calls and thread breakpoints
4363 @cindex premature return from system calls
4364 There is an unfortunate side effect. If one thread stops for a
4365 breakpoint, or for some other reason, and another thread is blocked in a
4366 system call, then the system call may return prematurely. This is a
4367 consequence of the interaction between multiple threads and the signals
4368 that @value{GDBN} uses to implement breakpoints and other events that
4371 To handle this problem, your program should check the return value of
4372 each system call and react appropriately. This is good programming
4375 For example, do not write code like this:
4381 The call to @code{sleep} will return early if a different thread stops
4382 at a breakpoint or for some other reason.
4384 Instead, write this:
4389 unslept = sleep (unslept);
4392 A system call is allowed to return early, so the system is still
4393 conforming to its specification. But @value{GDBN} does cause your
4394 multi-threaded program to behave differently than it would without
4397 Also, @value{GDBN} uses internal breakpoints in the thread library to
4398 monitor certain events such as thread creation and thread destruction.
4399 When such an event happens, a system call in another thread may return
4400 prematurely, even though your program does not appear to stop.
4402 @cindex continuing threads
4403 @cindex threads, continuing
4404 Conversely, whenever you restart the program, @emph{all} threads start
4405 executing. @emph{This is true even when single-stepping} with commands
4406 like @code{step} or @code{next}.
4408 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4409 Since thread scheduling is up to your debugging target's operating
4410 system (not controlled by @value{GDBN}), other threads may
4411 execute more than one statement while the current thread completes a
4412 single step. Moreover, in general other threads stop in the middle of a
4413 statement, rather than at a clean statement boundary, when the program
4416 You might even find your program stopped in another thread after
4417 continuing or even single-stepping. This happens whenever some other
4418 thread runs into a breakpoint, a signal, or an exception before the
4419 first thread completes whatever you requested.
4421 On some OSes, you can lock the OS scheduler and thus allow only a single
4425 @item set scheduler-locking @var{mode}
4426 @cindex scheduler locking mode
4427 @cindex lock scheduler
4428 Set the scheduler locking mode. If it is @code{off}, then there is no
4429 locking and any thread may run at any time. If @code{on}, then only the
4430 current thread may run when the inferior is resumed. The @code{step}
4431 mode optimizes for single-stepping. It stops other threads from
4432 ``seizing the prompt'' by preempting the current thread while you are
4433 stepping. Other threads will only rarely (or never) get a chance to run
4434 when you step. They are more likely to run when you @samp{next} over a
4435 function call, and they are completely free to run when you use commands
4436 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4437 thread hits a breakpoint during its timeslice, they will never steal the
4438 @value{GDBN} prompt away from the thread that you are debugging.
4440 @item show scheduler-locking
4441 Display the current scheduler locking mode.
4446 @chapter Examining the Stack
4448 When your program has stopped, the first thing you need to know is where it
4449 stopped and how it got there.
4452 Each time your program performs a function call, information about the call
4454 That information includes the location of the call in your program,
4455 the arguments of the call,
4456 and the local variables of the function being called.
4457 The information is saved in a block of data called a @dfn{stack frame}.
4458 The stack frames are allocated in a region of memory called the @dfn{call
4461 When your program stops, the @value{GDBN} commands for examining the
4462 stack allow you to see all of this information.
4464 @cindex selected frame
4465 One of the stack frames is @dfn{selected} by @value{GDBN} and many
4466 @value{GDBN} commands refer implicitly to the selected frame. In
4467 particular, whenever you ask @value{GDBN} for the value of a variable in
4468 your program, the value is found in the selected frame. There are
4469 special @value{GDBN} commands to select whichever frame you are
4470 interested in. @xref{Selection, ,Selecting a Frame}.
4472 When your program stops, @value{GDBN} automatically selects the
4473 currently executing frame and describes it briefly, similar to the
4474 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
4477 * Frames:: Stack frames
4478 * Backtrace:: Backtraces
4479 * Selection:: Selecting a frame
4480 * Frame Info:: Information on a frame
4485 @section Stack Frames
4487 @cindex frame, definition
4489 The call stack is divided up into contiguous pieces called @dfn{stack
4490 frames}, or @dfn{frames} for short; each frame is the data associated
4491 with one call to one function. The frame contains the arguments given
4492 to the function, the function's local variables, and the address at
4493 which the function is executing.
4495 @cindex initial frame
4496 @cindex outermost frame
4497 @cindex innermost frame
4498 When your program is started, the stack has only one frame, that of the
4499 function @code{main}. This is called the @dfn{initial} frame or the
4500 @dfn{outermost} frame. Each time a function is called, a new frame is
4501 made. Each time a function returns, the frame for that function invocation
4502 is eliminated. If a function is recursive, there can be many frames for
4503 the same function. The frame for the function in which execution is
4504 actually occurring is called the @dfn{innermost} frame. This is the most
4505 recently created of all the stack frames that still exist.
4507 @cindex frame pointer
4508 Inside your program, stack frames are identified by their addresses. A
4509 stack frame consists of many bytes, each of which has its own address; each
4510 kind of computer has a convention for choosing one byte whose
4511 address serves as the address of the frame. Usually this address is kept
4512 in a register called the @dfn{frame pointer register}
4513 (@pxref{Registers, $fp}) while execution is going on in that frame.
4515 @cindex frame number
4516 @value{GDBN} assigns numbers to all existing stack frames, starting with
4517 zero for the innermost frame, one for the frame that called it,
4518 and so on upward. These numbers do not really exist in your program;
4519 they are assigned by @value{GDBN} to give you a way of designating stack
4520 frames in @value{GDBN} commands.
4522 @c The -fomit-frame-pointer below perennially causes hbox overflow
4523 @c underflow problems.
4524 @cindex frameless execution
4525 Some compilers provide a way to compile functions so that they operate
4526 without stack frames. (For example, the @value{NGCC} option
4528 @samp{-fomit-frame-pointer}
4530 generates functions without a frame.)
4531 This is occasionally done with heavily used library functions to save
4532 the frame setup time. @value{GDBN} has limited facilities for dealing
4533 with these function invocations. If the innermost function invocation
4534 has no stack frame, @value{GDBN} nevertheless regards it as though
4535 it had a separate frame, which is numbered zero as usual, allowing
4536 correct tracing of the function call chain. However, @value{GDBN} has
4537 no provision for frameless functions elsewhere in the stack.
4540 @kindex frame@r{, command}
4541 @cindex current stack frame
4542 @item frame @var{args}
4543 The @code{frame} command allows you to move from one stack frame to another,
4544 and to print the stack frame you select. @var{args} may be either the
4545 address of the frame or the stack frame number. Without an argument,
4546 @code{frame} prints the current stack frame.
4548 @kindex select-frame
4549 @cindex selecting frame silently
4551 The @code{select-frame} command allows you to move from one stack frame
4552 to another without printing the frame. This is the silent version of
4560 @cindex call stack traces
4561 A backtrace is a summary of how your program got where it is. It shows one
4562 line per frame, for many frames, starting with the currently executing
4563 frame (frame zero), followed by its caller (frame one), and on up the
4568 @kindex bt @r{(@code{backtrace})}
4571 Print a backtrace of the entire stack: one line per frame for all
4572 frames in the stack.
4574 You can stop the backtrace at any time by typing the system interrupt
4575 character, normally @kbd{Ctrl-c}.
4577 @item backtrace @var{n}
4579 Similar, but print only the innermost @var{n} frames.
4581 @item backtrace -@var{n}
4583 Similar, but print only the outermost @var{n} frames.
4585 @item backtrace full
4587 @itemx bt full @var{n}
4588 @itemx bt full -@var{n}
4589 Print the values of the local variables also. @var{n} specifies the
4590 number of frames to print, as described above.
4595 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4596 are additional aliases for @code{backtrace}.
4598 @cindex multiple threads, backtrace
4599 In a multi-threaded program, @value{GDBN} by default shows the
4600 backtrace only for the current thread. To display the backtrace for
4601 several or all of the threads, use the command @code{thread apply}
4602 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
4603 apply all backtrace}, @value{GDBN} will display the backtrace for all
4604 the threads; this is handy when you debug a core dump of a
4605 multi-threaded program.
4607 Each line in the backtrace shows the frame number and the function name.
4608 The program counter value is also shown---unless you use @code{set
4609 print address off}. The backtrace also shows the source file name and
4610 line number, as well as the arguments to the function. The program
4611 counter value is omitted if it is at the beginning of the code for that
4614 Here is an example of a backtrace. It was made with the command
4615 @samp{bt 3}, so it shows the innermost three frames.
4619 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4621 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4622 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4624 (More stack frames follow...)
4629 The display for frame zero does not begin with a program counter
4630 value, indicating that your program has stopped at the beginning of the
4631 code for line @code{993} of @code{builtin.c}.
4633 @cindex value optimized out, in backtrace
4634 @cindex function call arguments, optimized out
4635 If your program was compiled with optimizations, some compilers will
4636 optimize away arguments passed to functions if those arguments are
4637 never used after the call. Such optimizations generate code that
4638 passes arguments through registers, but doesn't store those arguments
4639 in the stack frame. @value{GDBN} has no way of displaying such
4640 arguments in stack frames other than the innermost one. Here's what
4641 such a backtrace might look like:
4645 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4647 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
4648 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
4650 (More stack frames follow...)
4655 The values of arguments that were not saved in their stack frames are
4656 shown as @samp{<value optimized out>}.
4658 If you need to display the values of such optimized-out arguments,
4659 either deduce that from other variables whose values depend on the one
4660 you are interested in, or recompile without optimizations.
4662 @cindex backtrace beyond @code{main} function
4663 @cindex program entry point
4664 @cindex startup code, and backtrace
4665 Most programs have a standard user entry point---a place where system
4666 libraries and startup code transition into user code. For C this is
4667 @code{main}@footnote{
4668 Note that embedded programs (the so-called ``free-standing''
4669 environment) are not required to have a @code{main} function as the
4670 entry point. They could even have multiple entry points.}.
4671 When @value{GDBN} finds the entry function in a backtrace
4672 it will terminate the backtrace, to avoid tracing into highly
4673 system-specific (and generally uninteresting) code.
4675 If you need to examine the startup code, or limit the number of levels
4676 in a backtrace, you can change this behavior:
4679 @item set backtrace past-main
4680 @itemx set backtrace past-main on
4681 @kindex set backtrace
4682 Backtraces will continue past the user entry point.
4684 @item set backtrace past-main off
4685 Backtraces will stop when they encounter the user entry point. This is the
4688 @item show backtrace past-main
4689 @kindex show backtrace
4690 Display the current user entry point backtrace policy.
4692 @item set backtrace past-entry
4693 @itemx set backtrace past-entry on
4694 Backtraces will continue past the internal entry point of an application.
4695 This entry point is encoded by the linker when the application is built,
4696 and is likely before the user entry point @code{main} (or equivalent) is called.
4698 @item set backtrace past-entry off
4699 Backtraces will stop when they encounter the internal entry point of an
4700 application. This is the default.
4702 @item show backtrace past-entry
4703 Display the current internal entry point backtrace policy.
4705 @item set backtrace limit @var{n}
4706 @itemx set backtrace limit 0
4707 @cindex backtrace limit
4708 Limit the backtrace to @var{n} levels. A value of zero means
4711 @item show backtrace limit
4712 Display the current limit on backtrace levels.
4716 @section Selecting a Frame
4718 Most commands for examining the stack and other data in your program work on
4719 whichever stack frame is selected at the moment. Here are the commands for
4720 selecting a stack frame; all of them finish by printing a brief description
4721 of the stack frame just selected.
4724 @kindex frame@r{, selecting}
4725 @kindex f @r{(@code{frame})}
4728 Select frame number @var{n}. Recall that frame zero is the innermost
4729 (currently executing) frame, frame one is the frame that called the
4730 innermost one, and so on. The highest-numbered frame is the one for
4733 @item frame @var{addr}
4735 Select the frame at address @var{addr}. This is useful mainly if the
4736 chaining of stack frames has been damaged by a bug, making it
4737 impossible for @value{GDBN} to assign numbers properly to all frames. In
4738 addition, this can be useful when your program has multiple stacks and
4739 switches between them.
4741 On the SPARC architecture, @code{frame} needs two addresses to
4742 select an arbitrary frame: a frame pointer and a stack pointer.
4744 On the MIPS and Alpha architecture, it needs two addresses: a stack
4745 pointer and a program counter.
4747 On the 29k architecture, it needs three addresses: a register stack
4748 pointer, a program counter, and a memory stack pointer.
4752 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4753 advances toward the outermost frame, to higher frame numbers, to frames
4754 that have existed longer. @var{n} defaults to one.
4757 @kindex do @r{(@code{down})}
4759 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4760 advances toward the innermost frame, to lower frame numbers, to frames
4761 that were created more recently. @var{n} defaults to one. You may
4762 abbreviate @code{down} as @code{do}.
4765 All of these commands end by printing two lines of output describing the
4766 frame. The first line shows the frame number, the function name, the
4767 arguments, and the source file and line number of execution in that
4768 frame. The second line shows the text of that source line.
4776 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4778 10 read_input_file (argv[i]);
4782 After such a printout, the @code{list} command with no arguments
4783 prints ten lines centered on the point of execution in the frame.
4784 You can also edit the program at the point of execution with your favorite
4785 editing program by typing @code{edit}.
4786 @xref{List, ,Printing Source Lines},
4790 @kindex down-silently
4792 @item up-silently @var{n}
4793 @itemx down-silently @var{n}
4794 These two commands are variants of @code{up} and @code{down},
4795 respectively; they differ in that they do their work silently, without
4796 causing display of the new frame. They are intended primarily for use
4797 in @value{GDBN} command scripts, where the output might be unnecessary and
4802 @section Information About a Frame
4804 There are several other commands to print information about the selected
4810 When used without any argument, this command does not change which
4811 frame is selected, but prints a brief description of the currently
4812 selected stack frame. It can be abbreviated @code{f}. With an
4813 argument, this command is used to select a stack frame.
4814 @xref{Selection, ,Selecting a Frame}.
4817 @kindex info f @r{(@code{info frame})}
4820 This command prints a verbose description of the selected stack frame,
4825 the address of the frame
4827 the address of the next frame down (called by this frame)
4829 the address of the next frame up (caller of this frame)
4831 the language in which the source code corresponding to this frame is written
4833 the address of the frame's arguments
4835 the address of the frame's local variables
4837 the program counter saved in it (the address of execution in the caller frame)
4839 which registers were saved in the frame
4842 @noindent The verbose description is useful when
4843 something has gone wrong that has made the stack format fail to fit
4844 the usual conventions.
4846 @item info frame @var{addr}
4847 @itemx info f @var{addr}
4848 Print a verbose description of the frame at address @var{addr}, without
4849 selecting that frame. The selected frame remains unchanged by this
4850 command. This requires the same kind of address (more than one for some
4851 architectures) that you specify in the @code{frame} command.
4852 @xref{Selection, ,Selecting a Frame}.
4856 Print the arguments of the selected frame, each on a separate line.
4860 Print the local variables of the selected frame, each on a separate
4861 line. These are all variables (declared either static or automatic)
4862 accessible at the point of execution of the selected frame.
4865 @cindex catch exceptions, list active handlers
4866 @cindex exception handlers, how to list
4868 Print a list of all the exception handlers that are active in the
4869 current stack frame at the current point of execution. To see other
4870 exception handlers, visit the associated frame (using the @code{up},
4871 @code{down}, or @code{frame} commands); then type @code{info catch}.
4872 @xref{Set Catchpoints, , Setting Catchpoints}.
4878 @chapter Examining Source Files
4880 @value{GDBN} can print parts of your program's source, since the debugging
4881 information recorded in the program tells @value{GDBN} what source files were
4882 used to build it. When your program stops, @value{GDBN} spontaneously prints
4883 the line where it stopped. Likewise, when you select a stack frame
4884 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
4885 execution in that frame has stopped. You can print other portions of
4886 source files by explicit command.
4888 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4889 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4890 @value{GDBN} under @sc{gnu} Emacs}.
4893 * List:: Printing source lines
4894 * Edit:: Editing source files
4895 * Search:: Searching source files
4896 * Source Path:: Specifying source directories
4897 * Machine Code:: Source and machine code
4901 @section Printing Source Lines
4904 @kindex l @r{(@code{list})}
4905 To print lines from a source file, use the @code{list} command
4906 (abbreviated @code{l}). By default, ten lines are printed.
4907 There are several ways to specify what part of the file you want to print.
4909 Here are the forms of the @code{list} command most commonly used:
4912 @item list @var{linenum}
4913 Print lines centered around line number @var{linenum} in the
4914 current source file.
4916 @item list @var{function}
4917 Print lines centered around the beginning of function
4921 Print more lines. If the last lines printed were printed with a
4922 @code{list} command, this prints lines following the last lines
4923 printed; however, if the last line printed was a solitary line printed
4924 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4925 Stack}), this prints lines centered around that line.
4928 Print lines just before the lines last printed.
4931 @cindex @code{list}, how many lines to display
4932 By default, @value{GDBN} prints ten source lines with any of these forms of
4933 the @code{list} command. You can change this using @code{set listsize}:
4936 @kindex set listsize
4937 @item set listsize @var{count}
4938 Make the @code{list} command display @var{count} source lines (unless
4939 the @code{list} argument explicitly specifies some other number).
4941 @kindex show listsize
4943 Display the number of lines that @code{list} prints.
4946 Repeating a @code{list} command with @key{RET} discards the argument,
4947 so it is equivalent to typing just @code{list}. This is more useful
4948 than listing the same lines again. An exception is made for an
4949 argument of @samp{-}; that argument is preserved in repetition so that
4950 each repetition moves up in the source file.
4953 In general, the @code{list} command expects you to supply zero, one or two
4954 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4955 of writing them, but the effect is always to specify some source line.
4956 Here is a complete description of the possible arguments for @code{list}:
4959 @item list @var{linespec}
4960 Print lines centered around the line specified by @var{linespec}.
4962 @item list @var{first},@var{last}
4963 Print lines from @var{first} to @var{last}. Both arguments are
4966 @item list ,@var{last}
4967 Print lines ending with @var{last}.
4969 @item list @var{first},
4970 Print lines starting with @var{first}.
4973 Print lines just after the lines last printed.
4976 Print lines just before the lines last printed.
4979 As described in the preceding table.
4982 Here are the ways of specifying a single source line---all the
4987 Specifies line @var{number} of the current source file.
4988 When a @code{list} command has two linespecs, this refers to
4989 the same source file as the first linespec.
4992 Specifies the line @var{offset} lines after the last line printed.
4993 When used as the second linespec in a @code{list} command that has
4994 two, this specifies the line @var{offset} lines down from the
4998 Specifies the line @var{offset} lines before the last line printed.
5000 @item @var{filename}:@var{number}
5001 Specifies line @var{number} in the source file @var{filename}.
5003 @item @var{function}
5004 Specifies the line that begins the body of the function @var{function}.
5005 For example: in C, this is the line with the open brace.
5007 @item @var{filename}:@var{function}
5008 Specifies the line of the open-brace that begins the body of the
5009 function @var{function} in the file @var{filename}. You only need the
5010 file name with a function name to avoid ambiguity when there are
5011 identically named functions in different source files.
5013 @item *@var{address}
5014 Specifies the line containing the program address @var{address}.
5015 @var{address} may be any expression.
5019 @section Editing Source Files
5020 @cindex editing source files
5023 @kindex e @r{(@code{edit})}
5024 To edit the lines in a source file, use the @code{edit} command.
5025 The editing program of your choice
5026 is invoked with the current line set to
5027 the active line in the program.
5028 Alternatively, there are several ways to specify what part of the file you
5029 want to print if you want to see other parts of the program.
5031 Here are the forms of the @code{edit} command most commonly used:
5035 Edit the current source file at the active line number in the program.
5037 @item edit @var{number}
5038 Edit the current source file with @var{number} as the active line number.
5040 @item edit @var{function}
5041 Edit the file containing @var{function} at the beginning of its definition.
5043 @item edit @var{filename}:@var{number}
5044 Specifies line @var{number} in the source file @var{filename}.
5046 @item edit @var{filename}:@var{function}
5047 Specifies the line that begins the body of the
5048 function @var{function} in the file @var{filename}. You only need the
5049 file name with a function name to avoid ambiguity when there are
5050 identically named functions in different source files.
5052 @item edit *@var{address}
5053 Specifies the line containing the program address @var{address}.
5054 @var{address} may be any expression.
5057 @subsection Choosing your Editor
5058 You can customize @value{GDBN} to use any editor you want
5060 The only restriction is that your editor (say @code{ex}), recognizes the
5061 following command-line syntax:
5063 ex +@var{number} file
5065 The optional numeric value +@var{number} specifies the number of the line in
5066 the file where to start editing.}.
5067 By default, it is @file{@value{EDITOR}}, but you can change this
5068 by setting the environment variable @code{EDITOR} before using
5069 @value{GDBN}. For example, to configure @value{GDBN} to use the
5070 @code{vi} editor, you could use these commands with the @code{sh} shell:
5076 or in the @code{csh} shell,
5078 setenv EDITOR /usr/bin/vi
5083 @section Searching Source Files
5084 @cindex searching source files
5086 There are two commands for searching through the current source file for a
5091 @kindex forward-search
5092 @item forward-search @var{regexp}
5093 @itemx search @var{regexp}
5094 The command @samp{forward-search @var{regexp}} checks each line,
5095 starting with the one following the last line listed, for a match for
5096 @var{regexp}. It lists the line that is found. You can use the
5097 synonym @samp{search @var{regexp}} or abbreviate the command name as
5100 @kindex reverse-search
5101 @item reverse-search @var{regexp}
5102 The command @samp{reverse-search @var{regexp}} checks each line, starting
5103 with the one before the last line listed and going backward, for a match
5104 for @var{regexp}. It lists the line that is found. You can abbreviate
5105 this command as @code{rev}.
5109 @section Specifying Source Directories
5112 @cindex directories for source files
5113 Executable programs sometimes do not record the directories of the source
5114 files from which they were compiled, just the names. Even when they do,
5115 the directories could be moved between the compilation and your debugging
5116 session. @value{GDBN} has a list of directories to search for source files;
5117 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
5118 it tries all the directories in the list, in the order they are present
5119 in the list, until it finds a file with the desired name.
5121 For example, suppose an executable references the file
5122 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
5123 @file{/mnt/cross}. The file is first looked up literally; if this
5124 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
5125 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
5126 message is printed. @value{GDBN} does not look up the parts of the
5127 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
5128 Likewise, the subdirectories of the source path are not searched: if
5129 the source path is @file{/mnt/cross}, and the binary refers to
5130 @file{foo.c}, @value{GDBN} would not find it under
5131 @file{/mnt/cross/usr/src/foo-1.0/lib}.
5133 Plain file names, relative file names with leading directories, file
5134 names containing dots, etc.@: are all treated as described above; for
5135 instance, if the source path is @file{/mnt/cross}, and the source file
5136 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
5137 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
5138 that---@file{/mnt/cross/foo.c}.
5140 Note that the executable search path is @emph{not} used to locate the
5143 Whenever you reset or rearrange the source path, @value{GDBN} clears out
5144 any information it has cached about where source files are found and where
5145 each line is in the file.
5149 When you start @value{GDBN}, its source path includes only @samp{cdir}
5150 and @samp{cwd}, in that order.
5151 To add other directories, use the @code{directory} command.
5153 The search path is used to find both program source files and @value{GDBN}
5154 script files (read using the @samp{-command} option and @samp{source} command).
5156 In addition to the source path, @value{GDBN} provides a set of commands
5157 that manage a list of source path substitution rules. A @dfn{substitution
5158 rule} specifies how to rewrite source directories stored in the program's
5159 debug information in case the sources were moved to a different
5160 directory between compilation and debugging. A rule is made of
5161 two strings, the first specifying what needs to be rewritten in
5162 the path, and the second specifying how it should be rewritten.
5163 In @ref{set substitute-path}, we name these two parts @var{from} and
5164 @var{to} respectively. @value{GDBN} does a simple string replacement
5165 of @var{from} with @var{to} at the start of the directory part of the
5166 source file name, and uses that result instead of the original file
5167 name to look up the sources.
5169 Using the previous example, suppose the @file{foo-1.0} tree has been
5170 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
5171 @value{GDBN} to replace @file{/usr/src} in all source path names with
5172 @file{/mnt/cross}. The first lookup will then be
5173 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
5174 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
5175 substitution rule, use the @code{set substitute-path} command
5176 (@pxref{set substitute-path}).
5178 To avoid unexpected substitution results, a rule is applied only if the
5179 @var{from} part of the directory name ends at a directory separator.
5180 For instance, a rule substituting @file{/usr/source} into
5181 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
5182 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
5183 is applied only at the beginning of the directory name, this rule will
5184 not be applied to @file{/root/usr/source/baz.c} either.
5186 In many cases, you can achieve the same result using the @code{directory}
5187 command. However, @code{set substitute-path} can be more efficient in
5188 the case where the sources are organized in a complex tree with multiple
5189 subdirectories. With the @code{directory} command, you need to add each
5190 subdirectory of your project. If you moved the entire tree while
5191 preserving its internal organization, then @code{set substitute-path}
5192 allows you to direct the debugger to all the sources with one single
5195 @code{set substitute-path} is also more than just a shortcut command.
5196 The source path is only used if the file at the original location no
5197 longer exists. On the other hand, @code{set substitute-path} modifies
5198 the debugger behavior to look at the rewritten location instead. So, if
5199 for any reason a source file that is not relevant to your executable is
5200 located at the original location, a substitution rule is the only
5201 method available to point @value{GDBN} at the new location.
5204 @item directory @var{dirname} @dots{}
5205 @item dir @var{dirname} @dots{}
5206 Add directory @var{dirname} to the front of the source path. Several
5207 directory names may be given to this command, separated by @samp{:}
5208 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
5209 part of absolute file names) or
5210 whitespace. You may specify a directory that is already in the source
5211 path; this moves it forward, so @value{GDBN} searches it sooner.
5215 @vindex $cdir@r{, convenience variable}
5216 @vindex $cwd@r{, convenience variable}
5217 @cindex compilation directory
5218 @cindex current directory
5219 @cindex working directory
5220 @cindex directory, current
5221 @cindex directory, compilation
5222 You can use the string @samp{$cdir} to refer to the compilation
5223 directory (if one is recorded), and @samp{$cwd} to refer to the current
5224 working directory. @samp{$cwd} is not the same as @samp{.}---the former
5225 tracks the current working directory as it changes during your @value{GDBN}
5226 session, while the latter is immediately expanded to the current
5227 directory at the time you add an entry to the source path.
5230 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
5232 @c RET-repeat for @code{directory} is explicitly disabled, but since
5233 @c repeating it would be a no-op we do not say that. (thanks to RMS)
5235 @item show directories
5236 @kindex show directories
5237 Print the source path: show which directories it contains.
5239 @anchor{set substitute-path}
5240 @item set substitute-path @var{from} @var{to}
5241 @kindex set substitute-path
5242 Define a source path substitution rule, and add it at the end of the
5243 current list of existing substitution rules. If a rule with the same
5244 @var{from} was already defined, then the old rule is also deleted.
5246 For example, if the file @file{/foo/bar/baz.c} was moved to
5247 @file{/mnt/cross/baz.c}, then the command
5250 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
5254 will tell @value{GDBN} to replace @samp{/usr/src} with
5255 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
5256 @file{baz.c} even though it was moved.
5258 In the case when more than one substitution rule have been defined,
5259 the rules are evaluated one by one in the order where they have been
5260 defined. The first one matching, if any, is selected to perform
5263 For instance, if we had entered the following commands:
5266 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
5267 (@value{GDBP}) set substitute-path /usr/src /mnt/src
5271 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
5272 @file{/mnt/include/defs.h} by using the first rule. However, it would
5273 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
5274 @file{/mnt/src/lib/foo.c}.
5277 @item unset substitute-path [path]
5278 @kindex unset substitute-path
5279 If a path is specified, search the current list of substitution rules
5280 for a rule that would rewrite that path. Delete that rule if found.
5281 A warning is emitted by the debugger if no rule could be found.
5283 If no path is specified, then all substitution rules are deleted.
5285 @item show substitute-path [path]
5286 @kindex show substitute-path
5287 If a path is specified, then print the source path substitution rule
5288 which would rewrite that path, if any.
5290 If no path is specified, then print all existing source path substitution
5295 If your source path is cluttered with directories that are no longer of
5296 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
5297 versions of source. You can correct the situation as follows:
5301 Use @code{directory} with no argument to reset the source path to its default value.
5304 Use @code{directory} with suitable arguments to reinstall the
5305 directories you want in the source path. You can add all the
5306 directories in one command.
5310 @section Source and Machine Code
5311 @cindex source line and its code address
5313 You can use the command @code{info line} to map source lines to program
5314 addresses (and vice versa), and the command @code{disassemble} to display
5315 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
5316 mode, the @code{info line} command causes the arrow to point to the
5317 line specified. Also, @code{info line} prints addresses in symbolic form as
5322 @item info line @var{linespec}
5323 Print the starting and ending addresses of the compiled code for
5324 source line @var{linespec}. You can specify source lines in any of
5325 the ways understood by the @code{list} command (@pxref{List, ,Printing
5329 For example, we can use @code{info line} to discover the location of
5330 the object code for the first line of function
5331 @code{m4_changequote}:
5333 @c FIXME: I think this example should also show the addresses in
5334 @c symbolic form, as they usually would be displayed.
5336 (@value{GDBP}) info line m4_changequote
5337 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
5341 @cindex code address and its source line
5342 We can also inquire (using @code{*@var{addr}} as the form for
5343 @var{linespec}) what source line covers a particular address:
5345 (@value{GDBP}) info line *0x63ff
5346 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
5349 @cindex @code{$_} and @code{info line}
5350 @cindex @code{x} command, default address
5351 @kindex x@r{(examine), and} info line
5352 After @code{info line}, the default address for the @code{x} command
5353 is changed to the starting address of the line, so that @samp{x/i} is
5354 sufficient to begin examining the machine code (@pxref{Memory,
5355 ,Examining Memory}). Also, this address is saved as the value of the
5356 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
5361 @cindex assembly instructions
5362 @cindex instructions, assembly
5363 @cindex machine instructions
5364 @cindex listing machine instructions
5366 This specialized command dumps a range of memory as machine
5367 instructions. The default memory range is the function surrounding the
5368 program counter of the selected frame. A single argument to this
5369 command is a program counter value; @value{GDBN} dumps the function
5370 surrounding this value. Two arguments specify a range of addresses
5371 (first inclusive, second exclusive) to dump.
5374 The following example shows the disassembly of a range of addresses of
5375 HP PA-RISC 2.0 code:
5378 (@value{GDBP}) disas 0x32c4 0x32e4
5379 Dump of assembler code from 0x32c4 to 0x32e4:
5380 0x32c4 <main+204>: addil 0,dp
5381 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
5382 0x32cc <main+212>: ldil 0x3000,r31
5383 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
5384 0x32d4 <main+220>: ldo 0(r31),rp
5385 0x32d8 <main+224>: addil -0x800,dp
5386 0x32dc <main+228>: ldo 0x588(r1),r26
5387 0x32e0 <main+232>: ldil 0x3000,r31
5388 End of assembler dump.
5391 Some architectures have more than one commonly-used set of instruction
5392 mnemonics or other syntax.
5394 For programs that were dynamically linked and use shared libraries,
5395 instructions that call functions or branch to locations in the shared
5396 libraries might show a seemingly bogus location---it's actually a
5397 location of the relocation table. On some architectures, @value{GDBN}
5398 might be able to resolve these to actual function names.
5401 @kindex set disassembly-flavor
5402 @cindex Intel disassembly flavor
5403 @cindex AT&T disassembly flavor
5404 @item set disassembly-flavor @var{instruction-set}
5405 Select the instruction set to use when disassembling the
5406 program via the @code{disassemble} or @code{x/i} commands.
5408 Currently this command is only defined for the Intel x86 family. You
5409 can set @var{instruction-set} to either @code{intel} or @code{att}.
5410 The default is @code{att}, the AT&T flavor used by default by Unix
5411 assemblers for x86-based targets.
5413 @kindex show disassembly-flavor
5414 @item show disassembly-flavor
5415 Show the current setting of the disassembly flavor.
5420 @chapter Examining Data
5422 @cindex printing data
5423 @cindex examining data
5426 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
5427 @c document because it is nonstandard... Under Epoch it displays in a
5428 @c different window or something like that.
5429 The usual way to examine data in your program is with the @code{print}
5430 command (abbreviated @code{p}), or its synonym @code{inspect}. It
5431 evaluates and prints the value of an expression of the language your
5432 program is written in (@pxref{Languages, ,Using @value{GDBN} with
5433 Different Languages}).
5436 @item print @var{expr}
5437 @itemx print /@var{f} @var{expr}
5438 @var{expr} is an expression (in the source language). By default the
5439 value of @var{expr} is printed in a format appropriate to its data type;
5440 you can choose a different format by specifying @samp{/@var{f}}, where
5441 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
5445 @itemx print /@var{f}
5446 @cindex reprint the last value
5447 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
5448 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
5449 conveniently inspect the same value in an alternative format.
5452 A more low-level way of examining data is with the @code{x} command.
5453 It examines data in memory at a specified address and prints it in a
5454 specified format. @xref{Memory, ,Examining Memory}.
5456 If you are interested in information about types, or about how the
5457 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
5458 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
5462 * Expressions:: Expressions
5463 * Variables:: Program variables
5464 * Arrays:: Artificial arrays
5465 * Output Formats:: Output formats
5466 * Memory:: Examining memory
5467 * Auto Display:: Automatic display
5468 * Print Settings:: Print settings
5469 * Value History:: Value history
5470 * Convenience Vars:: Convenience variables
5471 * Registers:: Registers
5472 * Floating Point Hardware:: Floating point hardware
5473 * Vector Unit:: Vector Unit
5474 * OS Information:: Auxiliary data provided by operating system
5475 * Memory Region Attributes:: Memory region attributes
5476 * Dump/Restore Files:: Copy between memory and a file
5477 * Core File Generation:: Cause a program dump its core
5478 * Character Sets:: Debugging programs that use a different
5479 character set than GDB does
5480 * Caching Remote Data:: Data caching for remote targets
5484 @section Expressions
5487 @code{print} and many other @value{GDBN} commands accept an expression and
5488 compute its value. Any kind of constant, variable or operator defined
5489 by the programming language you are using is valid in an expression in
5490 @value{GDBN}. This includes conditional expressions, function calls,
5491 casts, and string constants. It also includes preprocessor macros, if
5492 you compiled your program to include this information; see
5495 @cindex arrays in expressions
5496 @value{GDBN} supports array constants in expressions input by
5497 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
5498 you can use the command @code{print @{1, 2, 3@}} to build up an array in
5499 memory that is @code{malloc}ed in the target program.
5501 Because C is so widespread, most of the expressions shown in examples in
5502 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
5503 Languages}, for information on how to use expressions in other
5506 In this section, we discuss operators that you can use in @value{GDBN}
5507 expressions regardless of your programming language.
5509 @cindex casts, in expressions
5510 Casts are supported in all languages, not just in C, because it is so
5511 useful to cast a number into a pointer in order to examine a structure
5512 at that address in memory.
5513 @c FIXME: casts supported---Mod2 true?
5515 @value{GDBN} supports these operators, in addition to those common
5516 to programming languages:
5520 @samp{@@} is a binary operator for treating parts of memory as arrays.
5521 @xref{Arrays, ,Artificial Arrays}, for more information.
5524 @samp{::} allows you to specify a variable in terms of the file or
5525 function where it is defined. @xref{Variables, ,Program Variables}.
5527 @cindex @{@var{type}@}
5528 @cindex type casting memory
5529 @cindex memory, viewing as typed object
5530 @cindex casts, to view memory
5531 @item @{@var{type}@} @var{addr}
5532 Refers to an object of type @var{type} stored at address @var{addr} in
5533 memory. @var{addr} may be any expression whose value is an integer or
5534 pointer (but parentheses are required around binary operators, just as in
5535 a cast). This construct is allowed regardless of what kind of data is
5536 normally supposed to reside at @var{addr}.
5540 @section Program Variables
5542 The most common kind of expression to use is the name of a variable
5545 Variables in expressions are understood in the selected stack frame
5546 (@pxref{Selection, ,Selecting a Frame}); they must be either:
5550 global (or file-static)
5557 visible according to the scope rules of the
5558 programming language from the point of execution in that frame
5561 @noindent This means that in the function
5576 you can examine and use the variable @code{a} whenever your program is
5577 executing within the function @code{foo}, but you can only use or
5578 examine the variable @code{b} while your program is executing inside
5579 the block where @code{b} is declared.
5581 @cindex variable name conflict
5582 There is an exception: you can refer to a variable or function whose
5583 scope is a single source file even if the current execution point is not
5584 in this file. But it is possible to have more than one such variable or
5585 function with the same name (in different source files). If that
5586 happens, referring to that name has unpredictable effects. If you wish,
5587 you can specify a static variable in a particular function or file,
5588 using the colon-colon (@code{::}) notation:
5590 @cindex colon-colon, context for variables/functions
5592 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
5593 @cindex @code{::}, context for variables/functions
5596 @var{file}::@var{variable}
5597 @var{function}::@var{variable}
5601 Here @var{file} or @var{function} is the name of the context for the
5602 static @var{variable}. In the case of file names, you can use quotes to
5603 make sure @value{GDBN} parses the file name as a single word---for example,
5604 to print a global value of @code{x} defined in @file{f2.c}:
5607 (@value{GDBP}) p 'f2.c'::x
5610 @cindex C@t{++} scope resolution
5611 This use of @samp{::} is very rarely in conflict with the very similar
5612 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
5613 scope resolution operator in @value{GDBN} expressions.
5614 @c FIXME: Um, so what happens in one of those rare cases where it's in
5617 @cindex wrong values
5618 @cindex variable values, wrong
5619 @cindex function entry/exit, wrong values of variables
5620 @cindex optimized code, wrong values of variables
5622 @emph{Warning:} Occasionally, a local variable may appear to have the
5623 wrong value at certain points in a function---just after entry to a new
5624 scope, and just before exit.
5626 You may see this problem when you are stepping by machine instructions.
5627 This is because, on most machines, it takes more than one instruction to
5628 set up a stack frame (including local variable definitions); if you are
5629 stepping by machine instructions, variables may appear to have the wrong
5630 values until the stack frame is completely built. On exit, it usually
5631 also takes more than one machine instruction to destroy a stack frame;
5632 after you begin stepping through that group of instructions, local
5633 variable definitions may be gone.
5635 This may also happen when the compiler does significant optimizations.
5636 To be sure of always seeing accurate values, turn off all optimization
5639 @cindex ``No symbol "foo" in current context''
5640 Another possible effect of compiler optimizations is to optimize
5641 unused variables out of existence, or assign variables to registers (as
5642 opposed to memory addresses). Depending on the support for such cases
5643 offered by the debug info format used by the compiler, @value{GDBN}
5644 might not be able to display values for such local variables. If that
5645 happens, @value{GDBN} will print a message like this:
5648 No symbol "foo" in current context.
5651 To solve such problems, either recompile without optimizations, or use a
5652 different debug info format, if the compiler supports several such
5653 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
5654 usually supports the @option{-gstabs+} option. @option{-gstabs+}
5655 produces debug info in a format that is superior to formats such as
5656 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
5657 an effective form for debug info. @xref{Debugging Options,,Options
5658 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
5659 Compiler Collection (GCC)}.
5660 @xref{C, ,C and C@t{++}}, for more information about debug info formats
5661 that are best suited to C@t{++} programs.
5663 If you ask to print an object whose contents are unknown to
5664 @value{GDBN}, e.g., because its data type is not completely specified
5665 by the debug information, @value{GDBN} will say @samp{<incomplete
5666 type>}. @xref{Symbols, incomplete type}, for more about this.
5668 Strings are identified as arrays of @code{char} values without specified
5669 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
5670 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
5671 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
5672 defines literal string type @code{"char"} as @code{char} without a sign.
5677 signed char var1[] = "A";
5680 You get during debugging
5685 $2 = @{65 'A', 0 '\0'@}
5689 @section Artificial Arrays
5691 @cindex artificial array
5693 @kindex @@@r{, referencing memory as an array}
5694 It is often useful to print out several successive objects of the
5695 same type in memory; a section of an array, or an array of
5696 dynamically determined size for which only a pointer exists in the
5699 You can do this by referring to a contiguous span of memory as an
5700 @dfn{artificial array}, using the binary operator @samp{@@}. The left
5701 operand of @samp{@@} should be the first element of the desired array
5702 and be an individual object. The right operand should be the desired length
5703 of the array. The result is an array value whose elements are all of
5704 the type of the left argument. The first element is actually the left
5705 argument; the second element comes from bytes of memory immediately
5706 following those that hold the first element, and so on. Here is an
5707 example. If a program says
5710 int *array = (int *) malloc (len * sizeof (int));
5714 you can print the contents of @code{array} with
5720 The left operand of @samp{@@} must reside in memory. Array values made
5721 with @samp{@@} in this way behave just like other arrays in terms of
5722 subscripting, and are coerced to pointers when used in expressions.
5723 Artificial arrays most often appear in expressions via the value history
5724 (@pxref{Value History, ,Value History}), after printing one out.
5726 Another way to create an artificial array is to use a cast.
5727 This re-interprets a value as if it were an array.
5728 The value need not be in memory:
5730 (@value{GDBP}) p/x (short[2])0x12345678
5731 $1 = @{0x1234, 0x5678@}
5734 As a convenience, if you leave the array length out (as in
5735 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
5736 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
5738 (@value{GDBP}) p/x (short[])0x12345678
5739 $2 = @{0x1234, 0x5678@}
5742 Sometimes the artificial array mechanism is not quite enough; in
5743 moderately complex data structures, the elements of interest may not
5744 actually be adjacent---for example, if you are interested in the values
5745 of pointers in an array. One useful work-around in this situation is
5746 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
5747 Variables}) as a counter in an expression that prints the first
5748 interesting value, and then repeat that expression via @key{RET}. For
5749 instance, suppose you have an array @code{dtab} of pointers to
5750 structures, and you are interested in the values of a field @code{fv}
5751 in each structure. Here is an example of what you might type:
5761 @node Output Formats
5762 @section Output Formats
5764 @cindex formatted output
5765 @cindex output formats
5766 By default, @value{GDBN} prints a value according to its data type. Sometimes
5767 this is not what you want. For example, you might want to print a number
5768 in hex, or a pointer in decimal. Or you might want to view data in memory
5769 at a certain address as a character string or as an instruction. To do
5770 these things, specify an @dfn{output format} when you print a value.
5772 The simplest use of output formats is to say how to print a value
5773 already computed. This is done by starting the arguments of the
5774 @code{print} command with a slash and a format letter. The format
5775 letters supported are:
5779 Regard the bits of the value as an integer, and print the integer in
5783 Print as integer in signed decimal.
5786 Print as integer in unsigned decimal.
5789 Print as integer in octal.
5792 Print as integer in binary. The letter @samp{t} stands for ``two''.
5793 @footnote{@samp{b} cannot be used because these format letters are also
5794 used with the @code{x} command, where @samp{b} stands for ``byte'';
5795 see @ref{Memory,,Examining Memory}.}
5798 @cindex unknown address, locating
5799 @cindex locate address
5800 Print as an address, both absolute in hexadecimal and as an offset from
5801 the nearest preceding symbol. You can use this format used to discover
5802 where (in what function) an unknown address is located:
5805 (@value{GDBP}) p/a 0x54320
5806 $3 = 0x54320 <_initialize_vx+396>
5810 The command @code{info symbol 0x54320} yields similar results.
5811 @xref{Symbols, info symbol}.
5814 Regard as an integer and print it as a character constant. This
5815 prints both the numerical value and its character representation. The
5816 character representation is replaced with the octal escape @samp{\nnn}
5817 for characters outside the 7-bit @sc{ascii} range.
5819 Without this format, @value{GDBN} displays @code{char},
5820 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
5821 constants. Single-byte members of vectors are displayed as integer
5825 Regard the bits of the value as a floating point number and print
5826 using typical floating point syntax.
5829 @cindex printing strings
5830 @cindex printing byte arrays
5831 Regard as a string, if possible. With this format, pointers to single-byte
5832 data are displayed as null-terminated strings and arrays of single-byte data
5833 are displayed as fixed-length strings. Other values are displayed in their
5836 Without this format, @value{GDBN} displays pointers to and arrays of
5837 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
5838 strings. Single-byte members of a vector are displayed as an integer
5842 For example, to print the program counter in hex (@pxref{Registers}), type
5849 Note that no space is required before the slash; this is because command
5850 names in @value{GDBN} cannot contain a slash.
5852 To reprint the last value in the value history with a different format,
5853 you can use the @code{print} command with just a format and no
5854 expression. For example, @samp{p/x} reprints the last value in hex.
5857 @section Examining Memory
5859 You can use the command @code{x} (for ``examine'') to examine memory in
5860 any of several formats, independently of your program's data types.
5862 @cindex examining memory
5864 @kindex x @r{(examine memory)}
5865 @item x/@var{nfu} @var{addr}
5868 Use the @code{x} command to examine memory.
5871 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
5872 much memory to display and how to format it; @var{addr} is an
5873 expression giving the address where you want to start displaying memory.
5874 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
5875 Several commands set convenient defaults for @var{addr}.
5878 @item @var{n}, the repeat count
5879 The repeat count is a decimal integer; the default is 1. It specifies
5880 how much memory (counting by units @var{u}) to display.
5881 @c This really is **decimal**; unaffected by 'set radix' as of GDB
5884 @item @var{f}, the display format
5885 The display format is one of the formats used by @code{print}
5886 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
5887 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
5888 The default is @samp{x} (hexadecimal) initially. The default changes
5889 each time you use either @code{x} or @code{print}.
5891 @item @var{u}, the unit size
5892 The unit size is any of
5898 Halfwords (two bytes).
5900 Words (four bytes). This is the initial default.
5902 Giant words (eight bytes).
5905 Each time you specify a unit size with @code{x}, that size becomes the
5906 default unit the next time you use @code{x}. (For the @samp{s} and
5907 @samp{i} formats, the unit size is ignored and is normally not written.)
5909 @item @var{addr}, starting display address
5910 @var{addr} is the address where you want @value{GDBN} to begin displaying
5911 memory. The expression need not have a pointer value (though it may);
5912 it is always interpreted as an integer address of a byte of memory.
5913 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
5914 @var{addr} is usually just after the last address examined---but several
5915 other commands also set the default address: @code{info breakpoints} (to
5916 the address of the last breakpoint listed), @code{info line} (to the
5917 starting address of a line), and @code{print} (if you use it to display
5918 a value from memory).
5921 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
5922 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
5923 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
5924 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
5925 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
5927 Since the letters indicating unit sizes are all distinct from the
5928 letters specifying output formats, you do not have to remember whether
5929 unit size or format comes first; either order works. The output
5930 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
5931 (However, the count @var{n} must come first; @samp{wx4} does not work.)
5933 Even though the unit size @var{u} is ignored for the formats @samp{s}
5934 and @samp{i}, you might still want to use a count @var{n}; for example,
5935 @samp{3i} specifies that you want to see three machine instructions,
5936 including any operands. For convenience, especially when used with
5937 the @code{display} command, the @samp{i} format also prints branch delay
5938 slot instructions, if any, beyond the count specified, which immediately
5939 follow the last instruction that is within the count. The command
5940 @code{disassemble} gives an alternative way of inspecting machine
5941 instructions; see @ref{Machine Code,,Source and Machine Code}.
5943 All the defaults for the arguments to @code{x} are designed to make it
5944 easy to continue scanning memory with minimal specifications each time
5945 you use @code{x}. For example, after you have inspected three machine
5946 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
5947 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
5948 the repeat count @var{n} is used again; the other arguments default as
5949 for successive uses of @code{x}.
5951 @cindex @code{$_}, @code{$__}, and value history
5952 The addresses and contents printed by the @code{x} command are not saved
5953 in the value history because there is often too much of them and they
5954 would get in the way. Instead, @value{GDBN} makes these values available for
5955 subsequent use in expressions as values of the convenience variables
5956 @code{$_} and @code{$__}. After an @code{x} command, the last address
5957 examined is available for use in expressions in the convenience variable
5958 @code{$_}. The contents of that address, as examined, are available in
5959 the convenience variable @code{$__}.
5961 If the @code{x} command has a repeat count, the address and contents saved
5962 are from the last memory unit printed; this is not the same as the last
5963 address printed if several units were printed on the last line of output.
5965 @cindex remote memory comparison
5966 @cindex verify remote memory image
5967 When you are debugging a program running on a remote target machine
5968 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
5969 remote machine's memory against the executable file you downloaded to
5970 the target. The @code{compare-sections} command is provided for such
5974 @kindex compare-sections
5975 @item compare-sections @r{[}@var{section-name}@r{]}
5976 Compare the data of a loadable section @var{section-name} in the
5977 executable file of the program being debugged with the same section in
5978 the remote machine's memory, and report any mismatches. With no
5979 arguments, compares all loadable sections. This command's
5980 availability depends on the target's support for the @code{"qCRC"}
5985 @section Automatic Display
5986 @cindex automatic display
5987 @cindex display of expressions
5989 If you find that you want to print the value of an expression frequently
5990 (to see how it changes), you might want to add it to the @dfn{automatic
5991 display list} so that @value{GDBN} prints its value each time your program stops.
5992 Each expression added to the list is given a number to identify it;
5993 to remove an expression from the list, you specify that number.
5994 The automatic display looks like this:
5998 3: bar[5] = (struct hack *) 0x3804
6002 This display shows item numbers, expressions and their current values. As with
6003 displays you request manually using @code{x} or @code{print}, you can
6004 specify the output format you prefer; in fact, @code{display} decides
6005 whether to use @code{print} or @code{x} depending your format
6006 specification---it uses @code{x} if you specify either the @samp{i}
6007 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
6011 @item display @var{expr}
6012 Add the expression @var{expr} to the list of expressions to display
6013 each time your program stops. @xref{Expressions, ,Expressions}.
6015 @code{display} does not repeat if you press @key{RET} again after using it.
6017 @item display/@var{fmt} @var{expr}
6018 For @var{fmt} specifying only a display format and not a size or
6019 count, add the expression @var{expr} to the auto-display list but
6020 arrange to display it each time in the specified format @var{fmt}.
6021 @xref{Output Formats,,Output Formats}.
6023 @item display/@var{fmt} @var{addr}
6024 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
6025 number of units, add the expression @var{addr} as a memory address to
6026 be examined each time your program stops. Examining means in effect
6027 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
6030 For example, @samp{display/i $pc} can be helpful, to see the machine
6031 instruction about to be executed each time execution stops (@samp{$pc}
6032 is a common name for the program counter; @pxref{Registers, ,Registers}).
6035 @kindex delete display
6037 @item undisplay @var{dnums}@dots{}
6038 @itemx delete display @var{dnums}@dots{}
6039 Remove item numbers @var{dnums} from the list of expressions to display.
6041 @code{undisplay} does not repeat if you press @key{RET} after using it.
6042 (Otherwise you would just get the error @samp{No display number @dots{}}.)
6044 @kindex disable display
6045 @item disable display @var{dnums}@dots{}
6046 Disable the display of item numbers @var{dnums}. A disabled display
6047 item is not printed automatically, but is not forgotten. It may be
6048 enabled again later.
6050 @kindex enable display
6051 @item enable display @var{dnums}@dots{}
6052 Enable display of item numbers @var{dnums}. It becomes effective once
6053 again in auto display of its expression, until you specify otherwise.
6056 Display the current values of the expressions on the list, just as is
6057 done when your program stops.
6059 @kindex info display
6061 Print the list of expressions previously set up to display
6062 automatically, each one with its item number, but without showing the
6063 values. This includes disabled expressions, which are marked as such.
6064 It also includes expressions which would not be displayed right now
6065 because they refer to automatic variables not currently available.
6068 @cindex display disabled out of scope
6069 If a display expression refers to local variables, then it does not make
6070 sense outside the lexical context for which it was set up. Such an
6071 expression is disabled when execution enters a context where one of its
6072 variables is not defined. For example, if you give the command
6073 @code{display last_char} while inside a function with an argument
6074 @code{last_char}, @value{GDBN} displays this argument while your program
6075 continues to stop inside that function. When it stops elsewhere---where
6076 there is no variable @code{last_char}---the display is disabled
6077 automatically. The next time your program stops where @code{last_char}
6078 is meaningful, you can enable the display expression once again.
6080 @node Print Settings
6081 @section Print Settings
6083 @cindex format options
6084 @cindex print settings
6085 @value{GDBN} provides the following ways to control how arrays, structures,
6086 and symbols are printed.
6089 These settings are useful for debugging programs in any language:
6093 @item set print address
6094 @itemx set print address on
6095 @cindex print/don't print memory addresses
6096 @value{GDBN} prints memory addresses showing the location of stack
6097 traces, structure values, pointer values, breakpoints, and so forth,
6098 even when it also displays the contents of those addresses. The default
6099 is @code{on}. For example, this is what a stack frame display looks like with
6100 @code{set print address on}:
6105 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
6107 530 if (lquote != def_lquote)
6111 @item set print address off
6112 Do not print addresses when displaying their contents. For example,
6113 this is the same stack frame displayed with @code{set print address off}:
6117 (@value{GDBP}) set print addr off
6119 #0 set_quotes (lq="<<", rq=">>") at input.c:530
6120 530 if (lquote != def_lquote)
6124 You can use @samp{set print address off} to eliminate all machine
6125 dependent displays from the @value{GDBN} interface. For example, with
6126 @code{print address off}, you should get the same text for backtraces on
6127 all machines---whether or not they involve pointer arguments.
6130 @item show print address
6131 Show whether or not addresses are to be printed.
6134 When @value{GDBN} prints a symbolic address, it normally prints the
6135 closest earlier symbol plus an offset. If that symbol does not uniquely
6136 identify the address (for example, it is a name whose scope is a single
6137 source file), you may need to clarify. One way to do this is with
6138 @code{info line}, for example @samp{info line *0x4537}. Alternately,
6139 you can set @value{GDBN} to print the source file and line number when
6140 it prints a symbolic address:
6143 @item set print symbol-filename on
6144 @cindex source file and line of a symbol
6145 @cindex symbol, source file and line
6146 Tell @value{GDBN} to print the source file name and line number of a
6147 symbol in the symbolic form of an address.
6149 @item set print symbol-filename off
6150 Do not print source file name and line number of a symbol. This is the
6153 @item show print symbol-filename
6154 Show whether or not @value{GDBN} will print the source file name and
6155 line number of a symbol in the symbolic form of an address.
6158 Another situation where it is helpful to show symbol filenames and line
6159 numbers is when disassembling code; @value{GDBN} shows you the line
6160 number and source file that corresponds to each instruction.
6162 Also, you may wish to see the symbolic form only if the address being
6163 printed is reasonably close to the closest earlier symbol:
6166 @item set print max-symbolic-offset @var{max-offset}
6167 @cindex maximum value for offset of closest symbol
6168 Tell @value{GDBN} to only display the symbolic form of an address if the
6169 offset between the closest earlier symbol and the address is less than
6170 @var{max-offset}. The default is 0, which tells @value{GDBN}
6171 to always print the symbolic form of an address if any symbol precedes it.
6173 @item show print max-symbolic-offset
6174 Ask how large the maximum offset is that @value{GDBN} prints in a
6178 @cindex wild pointer, interpreting
6179 @cindex pointer, finding referent
6180 If you have a pointer and you are not sure where it points, try
6181 @samp{set print symbol-filename on}. Then you can determine the name
6182 and source file location of the variable where it points, using
6183 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
6184 For example, here @value{GDBN} shows that a variable @code{ptt} points
6185 at another variable @code{t}, defined in @file{hi2.c}:
6188 (@value{GDBP}) set print symbol-filename on
6189 (@value{GDBP}) p/a ptt
6190 $4 = 0xe008 <t in hi2.c>
6194 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
6195 does not show the symbol name and filename of the referent, even with
6196 the appropriate @code{set print} options turned on.
6199 Other settings control how different kinds of objects are printed:
6202 @item set print array
6203 @itemx set print array on
6204 @cindex pretty print arrays
6205 Pretty print arrays. This format is more convenient to read,
6206 but uses more space. The default is off.
6208 @item set print array off
6209 Return to compressed format for arrays.
6211 @item show print array
6212 Show whether compressed or pretty format is selected for displaying
6215 @cindex print array indexes
6216 @item set print array-indexes
6217 @itemx set print array-indexes on
6218 Print the index of each element when displaying arrays. May be more
6219 convenient to locate a given element in the array or quickly find the
6220 index of a given element in that printed array. The default is off.
6222 @item set print array-indexes off
6223 Stop printing element indexes when displaying arrays.
6225 @item show print array-indexes
6226 Show whether the index of each element is printed when displaying
6229 @item set print elements @var{number-of-elements}
6230 @cindex number of array elements to print
6231 @cindex limit on number of printed array elements
6232 Set a limit on how many elements of an array @value{GDBN} will print.
6233 If @value{GDBN} is printing a large array, it stops printing after it has
6234 printed the number of elements set by the @code{set print elements} command.
6235 This limit also applies to the display of strings.
6236 When @value{GDBN} starts, this limit is set to 200.
6237 Setting @var{number-of-elements} to zero means that the printing is unlimited.
6239 @item show print elements
6240 Display the number of elements of a large array that @value{GDBN} will print.
6241 If the number is 0, then the printing is unlimited.
6243 @item set print repeats
6244 @cindex repeated array elements
6245 Set the threshold for suppressing display of repeated array
6246 elements. When the number of consecutive identical elements of an
6247 array exceeds the threshold, @value{GDBN} prints the string
6248 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
6249 identical repetitions, instead of displaying the identical elements
6250 themselves. Setting the threshold to zero will cause all elements to
6251 be individually printed. The default threshold is 10.
6253 @item show print repeats
6254 Display the current threshold for printing repeated identical
6257 @item set print null-stop
6258 @cindex @sc{null} elements in arrays
6259 Cause @value{GDBN} to stop printing the characters of an array when the first
6260 @sc{null} is encountered. This is useful when large arrays actually
6261 contain only short strings.
6264 @item show print null-stop
6265 Show whether @value{GDBN} stops printing an array on the first
6266 @sc{null} character.
6268 @item set print pretty on
6269 @cindex print structures in indented form
6270 @cindex indentation in structure display
6271 Cause @value{GDBN} to print structures in an indented format with one member
6272 per line, like this:
6287 @item set print pretty off
6288 Cause @value{GDBN} to print structures in a compact format, like this:
6292 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
6293 meat = 0x54 "Pork"@}
6298 This is the default format.
6300 @item show print pretty
6301 Show which format @value{GDBN} is using to print structures.
6303 @item set print sevenbit-strings on
6304 @cindex eight-bit characters in strings
6305 @cindex octal escapes in strings
6306 Print using only seven-bit characters; if this option is set,
6307 @value{GDBN} displays any eight-bit characters (in strings or
6308 character values) using the notation @code{\}@var{nnn}. This setting is
6309 best if you are working in English (@sc{ascii}) and you use the
6310 high-order bit of characters as a marker or ``meta'' bit.
6312 @item set print sevenbit-strings off
6313 Print full eight-bit characters. This allows the use of more
6314 international character sets, and is the default.
6316 @item show print sevenbit-strings
6317 Show whether or not @value{GDBN} is printing only seven-bit characters.
6319 @item set print union on
6320 @cindex unions in structures, printing
6321 Tell @value{GDBN} to print unions which are contained in structures
6322 and other unions. This is the default setting.
6324 @item set print union off
6325 Tell @value{GDBN} not to print unions which are contained in
6326 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
6329 @item show print union
6330 Ask @value{GDBN} whether or not it will print unions which are contained in
6331 structures and other unions.
6333 For example, given the declarations
6336 typedef enum @{Tree, Bug@} Species;
6337 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
6338 typedef enum @{Caterpillar, Cocoon, Butterfly@}
6349 struct thing foo = @{Tree, @{Acorn@}@};
6353 with @code{set print union on} in effect @samp{p foo} would print
6356 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
6360 and with @code{set print union off} in effect it would print
6363 $1 = @{it = Tree, form = @{...@}@}
6367 @code{set print union} affects programs written in C-like languages
6373 These settings are of interest when debugging C@t{++} programs:
6376 @cindex demangling C@t{++} names
6377 @item set print demangle
6378 @itemx set print demangle on
6379 Print C@t{++} names in their source form rather than in the encoded
6380 (``mangled'') form passed to the assembler and linker for type-safe
6381 linkage. The default is on.
6383 @item show print demangle
6384 Show whether C@t{++} names are printed in mangled or demangled form.
6386 @item set print asm-demangle
6387 @itemx set print asm-demangle on
6388 Print C@t{++} names in their source form rather than their mangled form, even
6389 in assembler code printouts such as instruction disassemblies.
6392 @item show print asm-demangle
6393 Show whether C@t{++} names in assembly listings are printed in mangled
6396 @cindex C@t{++} symbol decoding style
6397 @cindex symbol decoding style, C@t{++}
6398 @kindex set demangle-style
6399 @item set demangle-style @var{style}
6400 Choose among several encoding schemes used by different compilers to
6401 represent C@t{++} names. The choices for @var{style} are currently:
6405 Allow @value{GDBN} to choose a decoding style by inspecting your program.
6408 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
6409 This is the default.
6412 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
6415 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
6418 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
6419 @strong{Warning:} this setting alone is not sufficient to allow
6420 debugging @code{cfront}-generated executables. @value{GDBN} would
6421 require further enhancement to permit that.
6424 If you omit @var{style}, you will see a list of possible formats.
6426 @item show demangle-style
6427 Display the encoding style currently in use for decoding C@t{++} symbols.
6429 @item set print object
6430 @itemx set print object on
6431 @cindex derived type of an object, printing
6432 @cindex display derived types
6433 When displaying a pointer to an object, identify the @emph{actual}
6434 (derived) type of the object rather than the @emph{declared} type, using
6435 the virtual function table.
6437 @item set print object off
6438 Display only the declared type of objects, without reference to the
6439 virtual function table. This is the default setting.
6441 @item show print object
6442 Show whether actual, or declared, object types are displayed.
6444 @item set print static-members
6445 @itemx set print static-members on
6446 @cindex static members of C@t{++} objects
6447 Print static members when displaying a C@t{++} object. The default is on.
6449 @item set print static-members off
6450 Do not print static members when displaying a C@t{++} object.
6452 @item show print static-members
6453 Show whether C@t{++} static members are printed or not.
6455 @item set print pascal_static-members
6456 @itemx set print pascal_static-members on
6457 @cindex static members of Pascal objects
6458 @cindex Pascal objects, static members display
6459 Print static members when displaying a Pascal object. The default is on.
6461 @item set print pascal_static-members off
6462 Do not print static members when displaying a Pascal object.
6464 @item show print pascal_static-members
6465 Show whether Pascal static members are printed or not.
6467 @c These don't work with HP ANSI C++ yet.
6468 @item set print vtbl
6469 @itemx set print vtbl on
6470 @cindex pretty print C@t{++} virtual function tables
6471 @cindex virtual functions (C@t{++}) display
6472 @cindex VTBL display
6473 Pretty print C@t{++} virtual function tables. The default is off.
6474 (The @code{vtbl} commands do not work on programs compiled with the HP
6475 ANSI C@t{++} compiler (@code{aCC}).)
6477 @item set print vtbl off
6478 Do not pretty print C@t{++} virtual function tables.
6480 @item show print vtbl
6481 Show whether C@t{++} virtual function tables are pretty printed, or not.
6485 @section Value History
6487 @cindex value history
6488 @cindex history of values printed by @value{GDBN}
6489 Values printed by the @code{print} command are saved in the @value{GDBN}
6490 @dfn{value history}. This allows you to refer to them in other expressions.
6491 Values are kept until the symbol table is re-read or discarded
6492 (for example with the @code{file} or @code{symbol-file} commands).
6493 When the symbol table changes, the value history is discarded,
6494 since the values may contain pointers back to the types defined in the
6499 @cindex history number
6500 The values printed are given @dfn{history numbers} by which you can
6501 refer to them. These are successive integers starting with one.
6502 @code{print} shows you the history number assigned to a value by
6503 printing @samp{$@var{num} = } before the value; here @var{num} is the
6506 To refer to any previous value, use @samp{$} followed by the value's
6507 history number. The way @code{print} labels its output is designed to
6508 remind you of this. Just @code{$} refers to the most recent value in
6509 the history, and @code{$$} refers to the value before that.
6510 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
6511 is the value just prior to @code{$$}, @code{$$1} is equivalent to
6512 @code{$$}, and @code{$$0} is equivalent to @code{$}.
6514 For example, suppose you have just printed a pointer to a structure and
6515 want to see the contents of the structure. It suffices to type
6521 If you have a chain of structures where the component @code{next} points
6522 to the next one, you can print the contents of the next one with this:
6529 You can print successive links in the chain by repeating this
6530 command---which you can do by just typing @key{RET}.
6532 Note that the history records values, not expressions. If the value of
6533 @code{x} is 4 and you type these commands:
6541 then the value recorded in the value history by the @code{print} command
6542 remains 4 even though the value of @code{x} has changed.
6547 Print the last ten values in the value history, with their item numbers.
6548 This is like @samp{p@ $$9} repeated ten times, except that @code{show
6549 values} does not change the history.
6551 @item show values @var{n}
6552 Print ten history values centered on history item number @var{n}.
6555 Print ten history values just after the values last printed. If no more
6556 values are available, @code{show values +} produces no display.
6559 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
6560 same effect as @samp{show values +}.
6562 @node Convenience Vars
6563 @section Convenience Variables
6565 @cindex convenience variables
6566 @cindex user-defined variables
6567 @value{GDBN} provides @dfn{convenience variables} that you can use within
6568 @value{GDBN} to hold on to a value and refer to it later. These variables
6569 exist entirely within @value{GDBN}; they are not part of your program, and
6570 setting a convenience variable has no direct effect on further execution
6571 of your program. That is why you can use them freely.
6573 Convenience variables are prefixed with @samp{$}. Any name preceded by
6574 @samp{$} can be used for a convenience variable, unless it is one of
6575 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
6576 (Value history references, in contrast, are @emph{numbers} preceded
6577 by @samp{$}. @xref{Value History, ,Value History}.)
6579 You can save a value in a convenience variable with an assignment
6580 expression, just as you would set a variable in your program.
6584 set $foo = *object_ptr
6588 would save in @code{$foo} the value contained in the object pointed to by
6591 Using a convenience variable for the first time creates it, but its
6592 value is @code{void} until you assign a new value. You can alter the
6593 value with another assignment at any time.
6595 Convenience variables have no fixed types. You can assign a convenience
6596 variable any type of value, including structures and arrays, even if
6597 that variable already has a value of a different type. The convenience
6598 variable, when used as an expression, has the type of its current value.
6601 @kindex show convenience
6602 @cindex show all user variables
6603 @item show convenience
6604 Print a list of convenience variables used so far, and their values.
6605 Abbreviated @code{show conv}.
6607 @kindex init-if-undefined
6608 @cindex convenience variables, initializing
6609 @item init-if-undefined $@var{variable} = @var{expression}
6610 Set a convenience variable if it has not already been set. This is useful
6611 for user-defined commands that keep some state. It is similar, in concept,
6612 to using local static variables with initializers in C (except that
6613 convenience variables are global). It can also be used to allow users to
6614 override default values used in a command script.
6616 If the variable is already defined then the expression is not evaluated so
6617 any side-effects do not occur.
6620 One of the ways to use a convenience variable is as a counter to be
6621 incremented or a pointer to be advanced. For example, to print
6622 a field from successive elements of an array of structures:
6626 print bar[$i++]->contents
6630 Repeat that command by typing @key{RET}.
6632 Some convenience variables are created automatically by @value{GDBN} and given
6633 values likely to be useful.
6636 @vindex $_@r{, convenience variable}
6638 The variable @code{$_} is automatically set by the @code{x} command to
6639 the last address examined (@pxref{Memory, ,Examining Memory}). Other
6640 commands which provide a default address for @code{x} to examine also
6641 set @code{$_} to that address; these commands include @code{info line}
6642 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
6643 except when set by the @code{x} command, in which case it is a pointer
6644 to the type of @code{$__}.
6646 @vindex $__@r{, convenience variable}
6648 The variable @code{$__} is automatically set by the @code{x} command
6649 to the value found in the last address examined. Its type is chosen
6650 to match the format in which the data was printed.
6653 @vindex $_exitcode@r{, convenience variable}
6654 The variable @code{$_exitcode} is automatically set to the exit code when
6655 the program being debugged terminates.
6658 On HP-UX systems, if you refer to a function or variable name that
6659 begins with a dollar sign, @value{GDBN} searches for a user or system
6660 name first, before it searches for a convenience variable.
6666 You can refer to machine register contents, in expressions, as variables
6667 with names starting with @samp{$}. The names of registers are different
6668 for each machine; use @code{info registers} to see the names used on
6672 @kindex info registers
6673 @item info registers
6674 Print the names and values of all registers except floating-point
6675 and vector registers (in the selected stack frame).
6677 @kindex info all-registers
6678 @cindex floating point registers
6679 @item info all-registers
6680 Print the names and values of all registers, including floating-point
6681 and vector registers (in the selected stack frame).
6683 @item info registers @var{regname} @dots{}
6684 Print the @dfn{relativized} value of each specified register @var{regname}.
6685 As discussed in detail below, register values are normally relative to
6686 the selected stack frame. @var{regname} may be any register name valid on
6687 the machine you are using, with or without the initial @samp{$}.
6690 @cindex stack pointer register
6691 @cindex program counter register
6692 @cindex process status register
6693 @cindex frame pointer register
6694 @cindex standard registers
6695 @value{GDBN} has four ``standard'' register names that are available (in
6696 expressions) on most machines---whenever they do not conflict with an
6697 architecture's canonical mnemonics for registers. The register names
6698 @code{$pc} and @code{$sp} are used for the program counter register and
6699 the stack pointer. @code{$fp} is used for a register that contains a
6700 pointer to the current stack frame, and @code{$ps} is used for a
6701 register that contains the processor status. For example,
6702 you could print the program counter in hex with
6709 or print the instruction to be executed next with
6716 or add four to the stack pointer@footnote{This is a way of removing
6717 one word from the stack, on machines where stacks grow downward in
6718 memory (most machines, nowadays). This assumes that the innermost
6719 stack frame is selected; setting @code{$sp} is not allowed when other
6720 stack frames are selected. To pop entire frames off the stack,
6721 regardless of machine architecture, use @code{return};
6722 see @ref{Returning, ,Returning from a Function}.} with
6728 Whenever possible, these four standard register names are available on
6729 your machine even though the machine has different canonical mnemonics,
6730 so long as there is no conflict. The @code{info registers} command
6731 shows the canonical names. For example, on the SPARC, @code{info
6732 registers} displays the processor status register as @code{$psr} but you
6733 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
6734 is an alias for the @sc{eflags} register.
6736 @value{GDBN} always considers the contents of an ordinary register as an
6737 integer when the register is examined in this way. Some machines have
6738 special registers which can hold nothing but floating point; these
6739 registers are considered to have floating point values. There is no way
6740 to refer to the contents of an ordinary register as floating point value
6741 (although you can @emph{print} it as a floating point value with
6742 @samp{print/f $@var{regname}}).
6744 Some registers have distinct ``raw'' and ``virtual'' data formats. This
6745 means that the data format in which the register contents are saved by
6746 the operating system is not the same one that your program normally
6747 sees. For example, the registers of the 68881 floating point
6748 coprocessor are always saved in ``extended'' (raw) format, but all C
6749 programs expect to work with ``double'' (virtual) format. In such
6750 cases, @value{GDBN} normally works with the virtual format only (the format
6751 that makes sense for your program), but the @code{info registers} command
6752 prints the data in both formats.
6754 @cindex SSE registers (x86)
6755 @cindex MMX registers (x86)
6756 Some machines have special registers whose contents can be interpreted
6757 in several different ways. For example, modern x86-based machines
6758 have SSE and MMX registers that can hold several values packed
6759 together in several different formats. @value{GDBN} refers to such
6760 registers in @code{struct} notation:
6763 (@value{GDBP}) print $xmm1
6765 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
6766 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
6767 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
6768 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
6769 v4_int32 = @{0, 20657912, 11, 13@},
6770 v2_int64 = @{88725056443645952, 55834574859@},
6771 uint128 = 0x0000000d0000000b013b36f800000000
6776 To set values of such registers, you need to tell @value{GDBN} which
6777 view of the register you wish to change, as if you were assigning
6778 value to a @code{struct} member:
6781 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
6784 Normally, register values are relative to the selected stack frame
6785 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
6786 value that the register would contain if all stack frames farther in
6787 were exited and their saved registers restored. In order to see the
6788 true contents of hardware registers, you must select the innermost
6789 frame (with @samp{frame 0}).
6791 However, @value{GDBN} must deduce where registers are saved, from the machine
6792 code generated by your compiler. If some registers are not saved, or if
6793 @value{GDBN} is unable to locate the saved registers, the selected stack
6794 frame makes no difference.
6796 @node Floating Point Hardware
6797 @section Floating Point Hardware
6798 @cindex floating point
6800 Depending on the configuration, @value{GDBN} may be able to give
6801 you more information about the status of the floating point hardware.
6806 Display hardware-dependent information about the floating
6807 point unit. The exact contents and layout vary depending on the
6808 floating point chip. Currently, @samp{info float} is supported on
6809 the ARM and x86 machines.
6813 @section Vector Unit
6816 Depending on the configuration, @value{GDBN} may be able to give you
6817 more information about the status of the vector unit.
6822 Display information about the vector unit. The exact contents and
6823 layout vary depending on the hardware.
6826 @node OS Information
6827 @section Operating System Auxiliary Information
6828 @cindex OS information
6830 @value{GDBN} provides interfaces to useful OS facilities that can help
6831 you debug your program.
6833 @cindex @code{ptrace} system call
6834 @cindex @code{struct user} contents
6835 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
6836 machines), it interfaces with the inferior via the @code{ptrace}
6837 system call. The operating system creates a special sata structure,
6838 called @code{struct user}, for this interface. You can use the
6839 command @code{info udot} to display the contents of this data
6845 Display the contents of the @code{struct user} maintained by the OS
6846 kernel for the program being debugged. @value{GDBN} displays the
6847 contents of @code{struct user} as a list of hex numbers, similar to
6848 the @code{examine} command.
6851 @cindex auxiliary vector
6852 @cindex vector, auxiliary
6853 Some operating systems supply an @dfn{auxiliary vector} to programs at
6854 startup. This is akin to the arguments and environment that you
6855 specify for a program, but contains a system-dependent variety of
6856 binary values that tell system libraries important details about the
6857 hardware, operating system, and process. Each value's purpose is
6858 identified by an integer tag; the meanings are well-known but system-specific.
6859 Depending on the configuration and operating system facilities,
6860 @value{GDBN} may be able to show you this information. For remote
6861 targets, this functionality may further depend on the remote stub's
6862 support of the @samp{qXfer:auxv:read} packet, see
6863 @ref{qXfer auxiliary vector read}.
6868 Display the auxiliary vector of the inferior, which can be either a
6869 live process or a core dump file. @value{GDBN} prints each tag value
6870 numerically, and also shows names and text descriptions for recognized
6871 tags. Some values in the vector are numbers, some bit masks, and some
6872 pointers to strings or other data. @value{GDBN} displays each value in the
6873 most appropriate form for a recognized tag, and in hexadecimal for
6874 an unrecognized tag.
6878 @node Memory Region Attributes
6879 @section Memory Region Attributes
6880 @cindex memory region attributes
6882 @dfn{Memory region attributes} allow you to describe special handling
6883 required by regions of your target's memory. @value{GDBN} uses
6884 attributes to determine whether to allow certain types of memory
6885 accesses; whether to use specific width accesses; and whether to cache
6886 target memory. By default the description of memory regions is
6887 fetched from the target (if the current target supports this), but the
6888 user can override the fetched regions.
6890 Defined memory regions can be individually enabled and disabled. When a
6891 memory region is disabled, @value{GDBN} uses the default attributes when
6892 accessing memory in that region. Similarly, if no memory regions have
6893 been defined, @value{GDBN} uses the default attributes when accessing
6896 When a memory region is defined, it is given a number to identify it;
6897 to enable, disable, or remove a memory region, you specify that number.
6901 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
6902 Define a memory region bounded by @var{lower} and @var{upper} with
6903 attributes @var{attributes}@dots{}, and add it to the list of regions
6904 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
6905 case: it is treated as the target's maximum memory address.
6906 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
6909 Discard any user changes to the memory regions and use target-supplied
6910 regions, if available, or no regions if the target does not support.
6913 @item delete mem @var{nums}@dots{}
6914 Remove memory regions @var{nums}@dots{} from the list of regions
6915 monitored by @value{GDBN}.
6918 @item disable mem @var{nums}@dots{}
6919 Disable monitoring of memory regions @var{nums}@dots{}.
6920 A disabled memory region is not forgotten.
6921 It may be enabled again later.
6924 @item enable mem @var{nums}@dots{}
6925 Enable monitoring of memory regions @var{nums}@dots{}.
6929 Print a table of all defined memory regions, with the following columns
6933 @item Memory Region Number
6934 @item Enabled or Disabled.
6935 Enabled memory regions are marked with @samp{y}.
6936 Disabled memory regions are marked with @samp{n}.
6939 The address defining the inclusive lower bound of the memory region.
6942 The address defining the exclusive upper bound of the memory region.
6945 The list of attributes set for this memory region.
6950 @subsection Attributes
6952 @subsubsection Memory Access Mode
6953 The access mode attributes set whether @value{GDBN} may make read or
6954 write accesses to a memory region.
6956 While these attributes prevent @value{GDBN} from performing invalid
6957 memory accesses, they do nothing to prevent the target system, I/O DMA,
6958 etc.@: from accessing memory.
6962 Memory is read only.
6964 Memory is write only.
6966 Memory is read/write. This is the default.
6969 @subsubsection Memory Access Size
6970 The access size attribute tells @value{GDBN} to use specific sized
6971 accesses in the memory region. Often memory mapped device registers
6972 require specific sized accesses. If no access size attribute is
6973 specified, @value{GDBN} may use accesses of any size.
6977 Use 8 bit memory accesses.
6979 Use 16 bit memory accesses.
6981 Use 32 bit memory accesses.
6983 Use 64 bit memory accesses.
6986 @c @subsubsection Hardware/Software Breakpoints
6987 @c The hardware/software breakpoint attributes set whether @value{GDBN}
6988 @c will use hardware or software breakpoints for the internal breakpoints
6989 @c used by the step, next, finish, until, etc. commands.
6993 @c Always use hardware breakpoints
6994 @c @item swbreak (default)
6997 @subsubsection Data Cache
6998 The data cache attributes set whether @value{GDBN} will cache target
6999 memory. While this generally improves performance by reducing debug
7000 protocol overhead, it can lead to incorrect results because @value{GDBN}
7001 does not know about volatile variables or memory mapped device
7006 Enable @value{GDBN} to cache target memory.
7008 Disable @value{GDBN} from caching target memory. This is the default.
7011 @subsection Memory Access Checking
7012 @value{GDBN} can be instructed to refuse accesses to memory that is
7013 not explicitly described. This can be useful if accessing such
7014 regions has undesired effects for a specific target, or to provide
7015 better error checking. The following commands control this behaviour.
7018 @kindex set mem inaccessible-by-default
7019 @item set mem inaccessible-by-default [on|off]
7020 If @code{on} is specified, make @value{GDBN} treat memory not
7021 explicitly described by the memory ranges as non-existent and refuse accesses
7022 to such memory. The checks are only performed if there's at least one
7023 memory range defined. If @code{off} is specified, make @value{GDBN}
7024 treat the memory not explicitly described by the memory ranges as RAM.
7025 The default value is @code{on}.
7026 @kindex show mem inaccessible-by-default
7027 @item show mem inaccessible-by-default
7028 Show the current handling of accesses to unknown memory.
7032 @c @subsubsection Memory Write Verification
7033 @c The memory write verification attributes set whether @value{GDBN}
7034 @c will re-reads data after each write to verify the write was successful.
7038 @c @item noverify (default)
7041 @node Dump/Restore Files
7042 @section Copy Between Memory and a File
7043 @cindex dump/restore files
7044 @cindex append data to a file
7045 @cindex dump data to a file
7046 @cindex restore data from a file
7048 You can use the commands @code{dump}, @code{append}, and
7049 @code{restore} to copy data between target memory and a file. The
7050 @code{dump} and @code{append} commands write data to a file, and the
7051 @code{restore} command reads data from a file back into the inferior's
7052 memory. Files may be in binary, Motorola S-record, Intel hex, or
7053 Tektronix Hex format; however, @value{GDBN} can only append to binary
7059 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7060 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
7061 Dump the contents of memory from @var{start_addr} to @var{end_addr},
7062 or the value of @var{expr}, to @var{filename} in the given format.
7064 The @var{format} parameter may be any one of:
7071 Motorola S-record format.
7073 Tektronix Hex format.
7076 @value{GDBN} uses the same definitions of these formats as the
7077 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
7078 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
7082 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
7083 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
7084 Append the contents of memory from @var{start_addr} to @var{end_addr},
7085 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
7086 (@value{GDBN} can only append data to files in raw binary form.)
7089 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
7090 Restore the contents of file @var{filename} into memory. The
7091 @code{restore} command can automatically recognize any known @sc{bfd}
7092 file format, except for raw binary. To restore a raw binary file you
7093 must specify the optional keyword @code{binary} after the filename.
7095 If @var{bias} is non-zero, its value will be added to the addresses
7096 contained in the file. Binary files always start at address zero, so
7097 they will be restored at address @var{bias}. Other bfd files have
7098 a built-in location; they will be restored at offset @var{bias}
7101 If @var{start} and/or @var{end} are non-zero, then only data between
7102 file offset @var{start} and file offset @var{end} will be restored.
7103 These offsets are relative to the addresses in the file, before
7104 the @var{bias} argument is applied.
7108 @node Core File Generation
7109 @section How to Produce a Core File from Your Program
7110 @cindex dump core from inferior
7112 A @dfn{core file} or @dfn{core dump} is a file that records the memory
7113 image of a running process and its process status (register values
7114 etc.). Its primary use is post-mortem debugging of a program that
7115 crashed while it ran outside a debugger. A program that crashes
7116 automatically produces a core file, unless this feature is disabled by
7117 the user. @xref{Files}, for information on invoking @value{GDBN} in
7118 the post-mortem debugging mode.
7120 Occasionally, you may wish to produce a core file of the program you
7121 are debugging in order to preserve a snapshot of its state.
7122 @value{GDBN} has a special command for that.
7126 @kindex generate-core-file
7127 @item generate-core-file [@var{file}]
7128 @itemx gcore [@var{file}]
7129 Produce a core dump of the inferior process. The optional argument
7130 @var{file} specifies the file name where to put the core dump. If not
7131 specified, the file name defaults to @file{core.@var{pid}}, where
7132 @var{pid} is the inferior process ID.
7134 Note that this command is implemented only for some systems (as of
7135 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
7138 @node Character Sets
7139 @section Character Sets
7140 @cindex character sets
7142 @cindex translating between character sets
7143 @cindex host character set
7144 @cindex target character set
7146 If the program you are debugging uses a different character set to
7147 represent characters and strings than the one @value{GDBN} uses itself,
7148 @value{GDBN} can automatically translate between the character sets for
7149 you. The character set @value{GDBN} uses we call the @dfn{host
7150 character set}; the one the inferior program uses we call the
7151 @dfn{target character set}.
7153 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
7154 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
7155 remote protocol (@pxref{Remote Debugging}) to debug a program
7156 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
7157 then the host character set is Latin-1, and the target character set is
7158 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
7159 target-charset EBCDIC-US}, then @value{GDBN} translates between
7160 @sc{ebcdic} and Latin 1 as you print character or string values, or use
7161 character and string literals in expressions.
7163 @value{GDBN} has no way to automatically recognize which character set
7164 the inferior program uses; you must tell it, using the @code{set
7165 target-charset} command, described below.
7167 Here are the commands for controlling @value{GDBN}'s character set
7171 @item set target-charset @var{charset}
7172 @kindex set target-charset
7173 Set the current target character set to @var{charset}. We list the
7174 character set names @value{GDBN} recognizes below, but if you type
7175 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7176 list the target character sets it supports.
7180 @item set host-charset @var{charset}
7181 @kindex set host-charset
7182 Set the current host character set to @var{charset}.
7184 By default, @value{GDBN} uses a host character set appropriate to the
7185 system it is running on; you can override that default using the
7186 @code{set host-charset} command.
7188 @value{GDBN} can only use certain character sets as its host character
7189 set. We list the character set names @value{GDBN} recognizes below, and
7190 indicate which can be host character sets, but if you type
7191 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
7192 list the host character sets it supports.
7194 @item set charset @var{charset}
7196 Set the current host and target character sets to @var{charset}. As
7197 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
7198 @value{GDBN} will list the name of the character sets that can be used
7199 for both host and target.
7203 @kindex show charset
7204 Show the names of the current host and target charsets.
7206 @itemx show host-charset
7207 @kindex show host-charset
7208 Show the name of the current host charset.
7210 @itemx show target-charset
7211 @kindex show target-charset
7212 Show the name of the current target charset.
7216 @value{GDBN} currently includes support for the following character
7222 @cindex ASCII character set
7223 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
7227 @cindex ISO 8859-1 character set
7228 @cindex ISO Latin 1 character set
7229 The ISO Latin 1 character set. This extends @sc{ascii} with accented
7230 characters needed for French, German, and Spanish. @value{GDBN} can use
7231 this as its host character set.
7235 @cindex EBCDIC character set
7236 @cindex IBM1047 character set
7237 Variants of the @sc{ebcdic} character set, used on some of IBM's
7238 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
7239 @value{GDBN} cannot use these as its host character set.
7243 Note that these are all single-byte character sets. More work inside
7244 @value{GDBN} is needed to support multi-byte or variable-width character
7245 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
7247 Here is an example of @value{GDBN}'s character set support in action.
7248 Assume that the following source code has been placed in the file
7249 @file{charset-test.c}:
7255 = @{72, 101, 108, 108, 111, 44, 32, 119,
7256 111, 114, 108, 100, 33, 10, 0@};
7257 char ibm1047_hello[]
7258 = @{200, 133, 147, 147, 150, 107, 64, 166,
7259 150, 153, 147, 132, 90, 37, 0@};
7263 printf ("Hello, world!\n");
7267 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
7268 containing the string @samp{Hello, world!} followed by a newline,
7269 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
7271 We compile the program, and invoke the debugger on it:
7274 $ gcc -g charset-test.c -o charset-test
7275 $ gdb -nw charset-test
7276 GNU gdb 2001-12-19-cvs
7277 Copyright 2001 Free Software Foundation, Inc.
7282 We can use the @code{show charset} command to see what character sets
7283 @value{GDBN} is currently using to interpret and display characters and
7287 (@value{GDBP}) show charset
7288 The current host and target character set is `ISO-8859-1'.
7292 For the sake of printing this manual, let's use @sc{ascii} as our
7293 initial character set:
7295 (@value{GDBP}) set charset ASCII
7296 (@value{GDBP}) show charset
7297 The current host and target character set is `ASCII'.
7301 Let's assume that @sc{ascii} is indeed the correct character set for our
7302 host system --- in other words, let's assume that if @value{GDBN} prints
7303 characters using the @sc{ascii} character set, our terminal will display
7304 them properly. Since our current target character set is also
7305 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
7308 (@value{GDBP}) print ascii_hello
7309 $1 = 0x401698 "Hello, world!\n"
7310 (@value{GDBP}) print ascii_hello[0]
7315 @value{GDBN} uses the target character set for character and string
7316 literals you use in expressions:
7319 (@value{GDBP}) print '+'
7324 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
7327 @value{GDBN} relies on the user to tell it which character set the
7328 target program uses. If we print @code{ibm1047_hello} while our target
7329 character set is still @sc{ascii}, we get jibberish:
7332 (@value{GDBP}) print ibm1047_hello
7333 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
7334 (@value{GDBP}) print ibm1047_hello[0]
7339 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
7340 @value{GDBN} tells us the character sets it supports:
7343 (@value{GDBP}) set target-charset
7344 ASCII EBCDIC-US IBM1047 ISO-8859-1
7345 (@value{GDBP}) set target-charset
7348 We can select @sc{ibm1047} as our target character set, and examine the
7349 program's strings again. Now the @sc{ascii} string is wrong, but
7350 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
7351 target character set, @sc{ibm1047}, to the host character set,
7352 @sc{ascii}, and they display correctly:
7355 (@value{GDBP}) set target-charset IBM1047
7356 (@value{GDBP}) show charset
7357 The current host character set is `ASCII'.
7358 The current target character set is `IBM1047'.
7359 (@value{GDBP}) print ascii_hello
7360 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
7361 (@value{GDBP}) print ascii_hello[0]
7363 (@value{GDBP}) print ibm1047_hello
7364 $8 = 0x4016a8 "Hello, world!\n"
7365 (@value{GDBP}) print ibm1047_hello[0]
7370 As above, @value{GDBN} uses the target character set for character and
7371 string literals you use in expressions:
7374 (@value{GDBP}) print '+'
7379 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
7382 @node Caching Remote Data
7383 @section Caching Data of Remote Targets
7384 @cindex caching data of remote targets
7386 @value{GDBN} can cache data exchanged between the debugger and a
7387 remote target (@pxref{Remote Debugging}). Such caching generally improves
7388 performance, because it reduces the overhead of the remote protocol by
7389 bundling memory reads and writes into large chunks. Unfortunately,
7390 @value{GDBN} does not currently know anything about volatile
7391 registers, and thus data caching will produce incorrect results when
7392 volatile registers are in use.
7395 @kindex set remotecache
7396 @item set remotecache on
7397 @itemx set remotecache off
7398 Set caching state for remote targets. When @code{ON}, use data
7399 caching. By default, this option is @code{OFF}.
7401 @kindex show remotecache
7402 @item show remotecache
7403 Show the current state of data caching for remote targets.
7407 Print the information about the data cache performance. The
7408 information displayed includes: the dcache width and depth; and for
7409 each cache line, how many times it was referenced, and its data and
7410 state (dirty, bad, ok, etc.). This command is useful for debugging
7411 the data cache operation.
7416 @chapter C Preprocessor Macros
7418 Some languages, such as C and C@t{++}, provide a way to define and invoke
7419 ``preprocessor macros'' which expand into strings of tokens.
7420 @value{GDBN} can evaluate expressions containing macro invocations, show
7421 the result of macro expansion, and show a macro's definition, including
7422 where it was defined.
7424 You may need to compile your program specially to provide @value{GDBN}
7425 with information about preprocessor macros. Most compilers do not
7426 include macros in their debugging information, even when you compile
7427 with the @option{-g} flag. @xref{Compilation}.
7429 A program may define a macro at one point, remove that definition later,
7430 and then provide a different definition after that. Thus, at different
7431 points in the program, a macro may have different definitions, or have
7432 no definition at all. If there is a current stack frame, @value{GDBN}
7433 uses the macros in scope at that frame's source code line. Otherwise,
7434 @value{GDBN} uses the macros in scope at the current listing location;
7437 At the moment, @value{GDBN} does not support the @code{##}
7438 token-splicing operator, the @code{#} stringification operator, or
7439 variable-arity macros.
7441 Whenever @value{GDBN} evaluates an expression, it always expands any
7442 macro invocations present in the expression. @value{GDBN} also provides
7443 the following commands for working with macros explicitly.
7447 @kindex macro expand
7448 @cindex macro expansion, showing the results of preprocessor
7449 @cindex preprocessor macro expansion, showing the results of
7450 @cindex expanding preprocessor macros
7451 @item macro expand @var{expression}
7452 @itemx macro exp @var{expression}
7453 Show the results of expanding all preprocessor macro invocations in
7454 @var{expression}. Since @value{GDBN} simply expands macros, but does
7455 not parse the result, @var{expression} need not be a valid expression;
7456 it can be any string of tokens.
7459 @item macro expand-once @var{expression}
7460 @itemx macro exp1 @var{expression}
7461 @cindex expand macro once
7462 @i{(This command is not yet implemented.)} Show the results of
7463 expanding those preprocessor macro invocations that appear explicitly in
7464 @var{expression}. Macro invocations appearing in that expansion are
7465 left unchanged. This command allows you to see the effect of a
7466 particular macro more clearly, without being confused by further
7467 expansions. Since @value{GDBN} simply expands macros, but does not
7468 parse the result, @var{expression} need not be a valid expression; it
7469 can be any string of tokens.
7472 @cindex macro definition, showing
7473 @cindex definition, showing a macro's
7474 @item info macro @var{macro}
7475 Show the definition of the macro named @var{macro}, and describe the
7476 source location where that definition was established.
7478 @kindex macro define
7479 @cindex user-defined macros
7480 @cindex defining macros interactively
7481 @cindex macros, user-defined
7482 @item macro define @var{macro} @var{replacement-list}
7483 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
7484 @i{(This command is not yet implemented.)} Introduce a definition for a
7485 preprocessor macro named @var{macro}, invocations of which are replaced
7486 by the tokens given in @var{replacement-list}. The first form of this
7487 command defines an ``object-like'' macro, which takes no arguments; the
7488 second form defines a ``function-like'' macro, which takes the arguments
7489 given in @var{arglist}.
7491 A definition introduced by this command is in scope in every expression
7492 evaluated in @value{GDBN}, until it is removed with the @command{macro
7493 undef} command, described below. The definition overrides all
7494 definitions for @var{macro} present in the program being debugged, as
7495 well as any previous user-supplied definition.
7498 @item macro undef @var{macro}
7499 @i{(This command is not yet implemented.)} Remove any user-supplied
7500 definition for the macro named @var{macro}. This command only affects
7501 definitions provided with the @command{macro define} command, described
7502 above; it cannot remove definitions present in the program being
7507 @i{(This command is not yet implemented.)} List all the macros
7508 defined using the @code{macro define} command.
7511 @cindex macros, example of debugging with
7512 Here is a transcript showing the above commands in action. First, we
7513 show our source files:
7521 #define ADD(x) (M + x)
7526 printf ("Hello, world!\n");
7528 printf ("We're so creative.\n");
7530 printf ("Goodbye, world!\n");
7537 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
7538 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
7539 compiler includes information about preprocessor macros in the debugging
7543 $ gcc -gdwarf-2 -g3 sample.c -o sample
7547 Now, we start @value{GDBN} on our sample program:
7551 GNU gdb 2002-05-06-cvs
7552 Copyright 2002 Free Software Foundation, Inc.
7553 GDB is free software, @dots{}
7557 We can expand macros and examine their definitions, even when the
7558 program is not running. @value{GDBN} uses the current listing position
7559 to decide which macro definitions are in scope:
7562 (@value{GDBP}) list main
7565 5 #define ADD(x) (M + x)
7570 10 printf ("Hello, world!\n");
7572 12 printf ("We're so creative.\n");
7573 (@value{GDBP}) info macro ADD
7574 Defined at /home/jimb/gdb/macros/play/sample.c:5
7575 #define ADD(x) (M + x)
7576 (@value{GDBP}) info macro Q
7577 Defined at /home/jimb/gdb/macros/play/sample.h:1
7578 included at /home/jimb/gdb/macros/play/sample.c:2
7580 (@value{GDBP}) macro expand ADD(1)
7581 expands to: (42 + 1)
7582 (@value{GDBP}) macro expand-once ADD(1)
7583 expands to: once (M + 1)
7587 In the example above, note that @command{macro expand-once} expands only
7588 the macro invocation explicit in the original text --- the invocation of
7589 @code{ADD} --- but does not expand the invocation of the macro @code{M},
7590 which was introduced by @code{ADD}.
7592 Once the program is running, @value{GDBN} uses the macro definitions in
7593 force at the source line of the current stack frame:
7596 (@value{GDBP}) break main
7597 Breakpoint 1 at 0x8048370: file sample.c, line 10.
7599 Starting program: /home/jimb/gdb/macros/play/sample
7601 Breakpoint 1, main () at sample.c:10
7602 10 printf ("Hello, world!\n");
7606 At line 10, the definition of the macro @code{N} at line 9 is in force:
7609 (@value{GDBP}) info macro N
7610 Defined at /home/jimb/gdb/macros/play/sample.c:9
7612 (@value{GDBP}) macro expand N Q M
7614 (@value{GDBP}) print N Q M
7619 As we step over directives that remove @code{N}'s definition, and then
7620 give it a new definition, @value{GDBN} finds the definition (or lack
7621 thereof) in force at each point:
7626 12 printf ("We're so creative.\n");
7627 (@value{GDBP}) info macro N
7628 The symbol `N' has no definition as a C/C++ preprocessor macro
7629 at /home/jimb/gdb/macros/play/sample.c:12
7632 14 printf ("Goodbye, world!\n");
7633 (@value{GDBP}) info macro N
7634 Defined at /home/jimb/gdb/macros/play/sample.c:13
7636 (@value{GDBP}) macro expand N Q M
7637 expands to: 1729 < 42
7638 (@value{GDBP}) print N Q M
7645 @chapter Tracepoints
7646 @c This chapter is based on the documentation written by Michael
7647 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
7650 In some applications, it is not feasible for the debugger to interrupt
7651 the program's execution long enough for the developer to learn
7652 anything helpful about its behavior. If the program's correctness
7653 depends on its real-time behavior, delays introduced by a debugger
7654 might cause the program to change its behavior drastically, or perhaps
7655 fail, even when the code itself is correct. It is useful to be able
7656 to observe the program's behavior without interrupting it.
7658 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
7659 specify locations in the program, called @dfn{tracepoints}, and
7660 arbitrary expressions to evaluate when those tracepoints are reached.
7661 Later, using the @code{tfind} command, you can examine the values
7662 those expressions had when the program hit the tracepoints. The
7663 expressions may also denote objects in memory---structures or arrays,
7664 for example---whose values @value{GDBN} should record; while visiting
7665 a particular tracepoint, you may inspect those objects as if they were
7666 in memory at that moment. However, because @value{GDBN} records these
7667 values without interacting with you, it can do so quickly and
7668 unobtrusively, hopefully not disturbing the program's behavior.
7670 The tracepoint facility is currently available only for remote
7671 targets. @xref{Targets}. In addition, your remote target must know
7672 how to collect trace data. This functionality is implemented in the
7673 remote stub; however, none of the stubs distributed with @value{GDBN}
7674 support tracepoints as of this writing. The format of the remote
7675 packets used to implement tracepoints are described in @ref{Tracepoint
7678 This chapter describes the tracepoint commands and features.
7682 * Analyze Collected Data::
7683 * Tracepoint Variables::
7686 @node Set Tracepoints
7687 @section Commands to Set Tracepoints
7689 Before running such a @dfn{trace experiment}, an arbitrary number of
7690 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
7691 tracepoint has a number assigned to it by @value{GDBN}. Like with
7692 breakpoints, tracepoint numbers are successive integers starting from
7693 one. Many of the commands associated with tracepoints take the
7694 tracepoint number as their argument, to identify which tracepoint to
7697 For each tracepoint, you can specify, in advance, some arbitrary set
7698 of data that you want the target to collect in the trace buffer when
7699 it hits that tracepoint. The collected data can include registers,
7700 local variables, or global data. Later, you can use @value{GDBN}
7701 commands to examine the values these data had at the time the
7704 This section describes commands to set tracepoints and associated
7705 conditions and actions.
7708 * Create and Delete Tracepoints::
7709 * Enable and Disable Tracepoints::
7710 * Tracepoint Passcounts::
7711 * Tracepoint Actions::
7712 * Listing Tracepoints::
7713 * Starting and Stopping Trace Experiments::
7716 @node Create and Delete Tracepoints
7717 @subsection Create and Delete Tracepoints
7720 @cindex set tracepoint
7723 The @code{trace} command is very similar to the @code{break} command.
7724 Its argument can be a source line, a function name, or an address in
7725 the target program. @xref{Set Breaks}. The @code{trace} command
7726 defines a tracepoint, which is a point in the target program where the
7727 debugger will briefly stop, collect some data, and then allow the
7728 program to continue. Setting a tracepoint or changing its commands
7729 doesn't take effect until the next @code{tstart} command; thus, you
7730 cannot change the tracepoint attributes once a trace experiment is
7733 Here are some examples of using the @code{trace} command:
7736 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
7738 (@value{GDBP}) @b{trace +2} // 2 lines forward
7740 (@value{GDBP}) @b{trace my_function} // first source line of function
7742 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
7744 (@value{GDBP}) @b{trace *0x2117c4} // an address
7748 You can abbreviate @code{trace} as @code{tr}.
7751 @cindex last tracepoint number
7752 @cindex recent tracepoint number
7753 @cindex tracepoint number
7754 The convenience variable @code{$tpnum} records the tracepoint number
7755 of the most recently set tracepoint.
7757 @kindex delete tracepoint
7758 @cindex tracepoint deletion
7759 @item delete tracepoint @r{[}@var{num}@r{]}
7760 Permanently delete one or more tracepoints. With no argument, the
7761 default is to delete all tracepoints.
7766 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
7768 (@value{GDBP}) @b{delete trace} // remove all tracepoints
7772 You can abbreviate this command as @code{del tr}.
7775 @node Enable and Disable Tracepoints
7776 @subsection Enable and Disable Tracepoints
7779 @kindex disable tracepoint
7780 @item disable tracepoint @r{[}@var{num}@r{]}
7781 Disable tracepoint @var{num}, or all tracepoints if no argument
7782 @var{num} is given. A disabled tracepoint will have no effect during
7783 the next trace experiment, but it is not forgotten. You can re-enable
7784 a disabled tracepoint using the @code{enable tracepoint} command.
7786 @kindex enable tracepoint
7787 @item enable tracepoint @r{[}@var{num}@r{]}
7788 Enable tracepoint @var{num}, or all tracepoints. The enabled
7789 tracepoints will become effective the next time a trace experiment is
7793 @node Tracepoint Passcounts
7794 @subsection Tracepoint Passcounts
7798 @cindex tracepoint pass count
7799 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
7800 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
7801 automatically stop a trace experiment. If a tracepoint's passcount is
7802 @var{n}, then the trace experiment will be automatically stopped on
7803 the @var{n}'th time that tracepoint is hit. If the tracepoint number
7804 @var{num} is not specified, the @code{passcount} command sets the
7805 passcount of the most recently defined tracepoint. If no passcount is
7806 given, the trace experiment will run until stopped explicitly by the
7812 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
7813 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
7815 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
7816 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
7817 (@value{GDBP}) @b{trace foo}
7818 (@value{GDBP}) @b{pass 3}
7819 (@value{GDBP}) @b{trace bar}
7820 (@value{GDBP}) @b{pass 2}
7821 (@value{GDBP}) @b{trace baz}
7822 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
7823 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
7824 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
7825 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
7829 @node Tracepoint Actions
7830 @subsection Tracepoint Action Lists
7834 @cindex tracepoint actions
7835 @item actions @r{[}@var{num}@r{]}
7836 This command will prompt for a list of actions to be taken when the
7837 tracepoint is hit. If the tracepoint number @var{num} is not
7838 specified, this command sets the actions for the one that was most
7839 recently defined (so that you can define a tracepoint and then say
7840 @code{actions} without bothering about its number). You specify the
7841 actions themselves on the following lines, one action at a time, and
7842 terminate the actions list with a line containing just @code{end}. So
7843 far, the only defined actions are @code{collect} and
7844 @code{while-stepping}.
7846 @cindex remove actions from a tracepoint
7847 To remove all actions from a tracepoint, type @samp{actions @var{num}}
7848 and follow it immediately with @samp{end}.
7851 (@value{GDBP}) @b{collect @var{data}} // collect some data
7853 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
7855 (@value{GDBP}) @b{end} // signals the end of actions.
7858 In the following example, the action list begins with @code{collect}
7859 commands indicating the things to be collected when the tracepoint is
7860 hit. Then, in order to single-step and collect additional data
7861 following the tracepoint, a @code{while-stepping} command is used,
7862 followed by the list of things to be collected while stepping. The
7863 @code{while-stepping} command is terminated by its own separate
7864 @code{end} command. Lastly, the action list is terminated by an
7868 (@value{GDBP}) @b{trace foo}
7869 (@value{GDBP}) @b{actions}
7870 Enter actions for tracepoint 1, one per line:
7879 @kindex collect @r{(tracepoints)}
7880 @item collect @var{expr1}, @var{expr2}, @dots{}
7881 Collect values of the given expressions when the tracepoint is hit.
7882 This command accepts a comma-separated list of any valid expressions.
7883 In addition to global, static, or local variables, the following
7884 special arguments are supported:
7888 collect all registers
7891 collect all function arguments
7894 collect all local variables.
7897 You can give several consecutive @code{collect} commands, each one
7898 with a single argument, or one @code{collect} command with several
7899 arguments separated by commas: the effect is the same.
7901 The command @code{info scope} (@pxref{Symbols, info scope}) is
7902 particularly useful for figuring out what data to collect.
7904 @kindex while-stepping @r{(tracepoints)}
7905 @item while-stepping @var{n}
7906 Perform @var{n} single-step traces after the tracepoint, collecting
7907 new data at each step. The @code{while-stepping} command is
7908 followed by the list of what to collect while stepping (followed by
7909 its own @code{end} command):
7913 > collect $regs, myglobal
7919 You may abbreviate @code{while-stepping} as @code{ws} or
7923 @node Listing Tracepoints
7924 @subsection Listing Tracepoints
7927 @kindex info tracepoints
7929 @cindex information about tracepoints
7930 @item info tracepoints @r{[}@var{num}@r{]}
7931 Display information about the tracepoint @var{num}. If you don't specify
7932 a tracepoint number, displays information about all the tracepoints
7933 defined so far. For each tracepoint, the following information is
7940 whether it is enabled or disabled
7944 its passcount as given by the @code{passcount @var{n}} command
7946 its step count as given by the @code{while-stepping @var{n}} command
7948 where in the source files is the tracepoint set
7950 its action list as given by the @code{actions} command
7954 (@value{GDBP}) @b{info trace}
7955 Num Enb Address PassC StepC What
7956 1 y 0x002117c4 0 0 <gdb_asm>
7957 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
7958 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
7963 This command can be abbreviated @code{info tp}.
7966 @node Starting and Stopping Trace Experiments
7967 @subsection Starting and Stopping Trace Experiments
7971 @cindex start a new trace experiment
7972 @cindex collected data discarded
7974 This command takes no arguments. It starts the trace experiment, and
7975 begins collecting data. This has the side effect of discarding all
7976 the data collected in the trace buffer during the previous trace
7980 @cindex stop a running trace experiment
7982 This command takes no arguments. It ends the trace experiment, and
7983 stops collecting data.
7985 @strong{Note}: a trace experiment and data collection may stop
7986 automatically if any tracepoint's passcount is reached
7987 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
7990 @cindex status of trace data collection
7991 @cindex trace experiment, status of
7993 This command displays the status of the current trace data
7997 Here is an example of the commands we described so far:
8000 (@value{GDBP}) @b{trace gdb_c_test}
8001 (@value{GDBP}) @b{actions}
8002 Enter actions for tracepoint #1, one per line.
8003 > collect $regs,$locals,$args
8008 (@value{GDBP}) @b{tstart}
8009 [time passes @dots{}]
8010 (@value{GDBP}) @b{tstop}
8014 @node Analyze Collected Data
8015 @section Using the Collected Data
8017 After the tracepoint experiment ends, you use @value{GDBN} commands
8018 for examining the trace data. The basic idea is that each tracepoint
8019 collects a trace @dfn{snapshot} every time it is hit and another
8020 snapshot every time it single-steps. All these snapshots are
8021 consecutively numbered from zero and go into a buffer, and you can
8022 examine them later. The way you examine them is to @dfn{focus} on a
8023 specific trace snapshot. When the remote stub is focused on a trace
8024 snapshot, it will respond to all @value{GDBN} requests for memory and
8025 registers by reading from the buffer which belongs to that snapshot,
8026 rather than from @emph{real} memory or registers of the program being
8027 debugged. This means that @strong{all} @value{GDBN} commands
8028 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
8029 behave as if we were currently debugging the program state as it was
8030 when the tracepoint occurred. Any requests for data that are not in
8031 the buffer will fail.
8034 * tfind:: How to select a trace snapshot
8035 * tdump:: How to display all data for a snapshot
8036 * save-tracepoints:: How to save tracepoints for a future run
8040 @subsection @code{tfind @var{n}}
8043 @cindex select trace snapshot
8044 @cindex find trace snapshot
8045 The basic command for selecting a trace snapshot from the buffer is
8046 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
8047 counting from zero. If no argument @var{n} is given, the next
8048 snapshot is selected.
8050 Here are the various forms of using the @code{tfind} command.
8054 Find the first snapshot in the buffer. This is a synonym for
8055 @code{tfind 0} (since 0 is the number of the first snapshot).
8058 Stop debugging trace snapshots, resume @emph{live} debugging.
8061 Same as @samp{tfind none}.
8064 No argument means find the next trace snapshot.
8067 Find the previous trace snapshot before the current one. This permits
8068 retracing earlier steps.
8070 @item tfind tracepoint @var{num}
8071 Find the next snapshot associated with tracepoint @var{num}. Search
8072 proceeds forward from the last examined trace snapshot. If no
8073 argument @var{num} is given, it means find the next snapshot collected
8074 for the same tracepoint as the current snapshot.
8076 @item tfind pc @var{addr}
8077 Find the next snapshot associated with the value @var{addr} of the
8078 program counter. Search proceeds forward from the last examined trace
8079 snapshot. If no argument @var{addr} is given, it means find the next
8080 snapshot with the same value of PC as the current snapshot.
8082 @item tfind outside @var{addr1}, @var{addr2}
8083 Find the next snapshot whose PC is outside the given range of
8086 @item tfind range @var{addr1}, @var{addr2}
8087 Find the next snapshot whose PC is between @var{addr1} and
8088 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
8090 @item tfind line @r{[}@var{file}:@r{]}@var{n}
8091 Find the next snapshot associated with the source line @var{n}. If
8092 the optional argument @var{file} is given, refer to line @var{n} in
8093 that source file. Search proceeds forward from the last examined
8094 trace snapshot. If no argument @var{n} is given, it means find the
8095 next line other than the one currently being examined; thus saying
8096 @code{tfind line} repeatedly can appear to have the same effect as
8097 stepping from line to line in a @emph{live} debugging session.
8100 The default arguments for the @code{tfind} commands are specifically
8101 designed to make it easy to scan through the trace buffer. For
8102 instance, @code{tfind} with no argument selects the next trace
8103 snapshot, and @code{tfind -} with no argument selects the previous
8104 trace snapshot. So, by giving one @code{tfind} command, and then
8105 simply hitting @key{RET} repeatedly you can examine all the trace
8106 snapshots in order. Or, by saying @code{tfind -} and then hitting
8107 @key{RET} repeatedly you can examine the snapshots in reverse order.
8108 The @code{tfind line} command with no argument selects the snapshot
8109 for the next source line executed. The @code{tfind pc} command with
8110 no argument selects the next snapshot with the same program counter
8111 (PC) as the current frame. The @code{tfind tracepoint} command with
8112 no argument selects the next trace snapshot collected by the same
8113 tracepoint as the current one.
8115 In addition to letting you scan through the trace buffer manually,
8116 these commands make it easy to construct @value{GDBN} scripts that
8117 scan through the trace buffer and print out whatever collected data
8118 you are interested in. Thus, if we want to examine the PC, FP, and SP
8119 registers from each trace frame in the buffer, we can say this:
8122 (@value{GDBP}) @b{tfind start}
8123 (@value{GDBP}) @b{while ($trace_frame != -1)}
8124 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
8125 $trace_frame, $pc, $sp, $fp
8129 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
8130 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
8131 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
8132 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
8133 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
8134 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
8135 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
8136 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
8137 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
8138 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
8139 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
8142 Or, if we want to examine the variable @code{X} at each source line in
8146 (@value{GDBP}) @b{tfind start}
8147 (@value{GDBP}) @b{while ($trace_frame != -1)}
8148 > printf "Frame %d, X == %d\n", $trace_frame, X
8158 @subsection @code{tdump}
8160 @cindex dump all data collected at tracepoint
8161 @cindex tracepoint data, display
8163 This command takes no arguments. It prints all the data collected at
8164 the current trace snapshot.
8167 (@value{GDBP}) @b{trace 444}
8168 (@value{GDBP}) @b{actions}
8169 Enter actions for tracepoint #2, one per line:
8170 > collect $regs, $locals, $args, gdb_long_test
8173 (@value{GDBP}) @b{tstart}
8175 (@value{GDBP}) @b{tfind line 444}
8176 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
8178 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
8180 (@value{GDBP}) @b{tdump}
8181 Data collected at tracepoint 2, trace frame 1:
8182 d0 0xc4aa0085 -995491707
8186 d4 0x71aea3d 119204413
8191 a1 0x3000668 50333288
8194 a4 0x3000698 50333336
8196 fp 0x30bf3c 0x30bf3c
8197 sp 0x30bf34 0x30bf34
8199 pc 0x20b2c8 0x20b2c8
8203 p = 0x20e5b4 "gdb-test"
8210 gdb_long_test = 17 '\021'
8215 @node save-tracepoints
8216 @subsection @code{save-tracepoints @var{filename}}
8217 @kindex save-tracepoints
8218 @cindex save tracepoints for future sessions
8220 This command saves all current tracepoint definitions together with
8221 their actions and passcounts, into a file @file{@var{filename}}
8222 suitable for use in a later debugging session. To read the saved
8223 tracepoint definitions, use the @code{source} command (@pxref{Command
8226 @node Tracepoint Variables
8227 @section Convenience Variables for Tracepoints
8228 @cindex tracepoint variables
8229 @cindex convenience variables for tracepoints
8232 @vindex $trace_frame
8233 @item (int) $trace_frame
8234 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
8235 snapshot is selected.
8238 @item (int) $tracepoint
8239 The tracepoint for the current trace snapshot.
8242 @item (int) $trace_line
8243 The line number for the current trace snapshot.
8246 @item (char []) $trace_file
8247 The source file for the current trace snapshot.
8250 @item (char []) $trace_func
8251 The name of the function containing @code{$tracepoint}.
8254 Note: @code{$trace_file} is not suitable for use in @code{printf},
8255 use @code{output} instead.
8257 Here's a simple example of using these convenience variables for
8258 stepping through all the trace snapshots and printing some of their
8262 (@value{GDBP}) @b{tfind start}
8264 (@value{GDBP}) @b{while $trace_frame != -1}
8265 > output $trace_file
8266 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
8272 @chapter Debugging Programs That Use Overlays
8275 If your program is too large to fit completely in your target system's
8276 memory, you can sometimes use @dfn{overlays} to work around this
8277 problem. @value{GDBN} provides some support for debugging programs that
8281 * How Overlays Work:: A general explanation of overlays.
8282 * Overlay Commands:: Managing overlays in @value{GDBN}.
8283 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
8284 mapped by asking the inferior.
8285 * Overlay Sample Program:: A sample program using overlays.
8288 @node How Overlays Work
8289 @section How Overlays Work
8290 @cindex mapped overlays
8291 @cindex unmapped overlays
8292 @cindex load address, overlay's
8293 @cindex mapped address
8294 @cindex overlay area
8296 Suppose you have a computer whose instruction address space is only 64
8297 kilobytes long, but which has much more memory which can be accessed by
8298 other means: special instructions, segment registers, or memory
8299 management hardware, for example. Suppose further that you want to
8300 adapt a program which is larger than 64 kilobytes to run on this system.
8302 One solution is to identify modules of your program which are relatively
8303 independent, and need not call each other directly; call these modules
8304 @dfn{overlays}. Separate the overlays from the main program, and place
8305 their machine code in the larger memory. Place your main program in
8306 instruction memory, but leave at least enough space there to hold the
8307 largest overlay as well.
8309 Now, to call a function located in an overlay, you must first copy that
8310 overlay's machine code from the large memory into the space set aside
8311 for it in the instruction memory, and then jump to its entry point
8314 @c NB: In the below the mapped area's size is greater or equal to the
8315 @c size of all overlays. This is intentional to remind the developer
8316 @c that overlays don't necessarily need to be the same size.
8320 Data Instruction Larger
8321 Address Space Address Space Address Space
8322 +-----------+ +-----------+ +-----------+
8324 +-----------+ +-----------+ +-----------+<-- overlay 1
8325 | program | | main | .----| overlay 1 | load address
8326 | variables | | program | | +-----------+
8327 | and heap | | | | | |
8328 +-----------+ | | | +-----------+<-- overlay 2
8329 | | +-----------+ | | | load address
8330 +-----------+ | | | .-| overlay 2 |
8332 mapped --->+-----------+ | | +-----------+
8334 | overlay | <-' | | |
8335 | area | <---' +-----------+<-- overlay 3
8336 | | <---. | | load address
8337 +-----------+ `--| overlay 3 |
8344 @anchor{A code overlay}A code overlay
8348 The diagram (@pxref{A code overlay}) shows a system with separate data
8349 and instruction address spaces. To map an overlay, the program copies
8350 its code from the larger address space to the instruction address space.
8351 Since the overlays shown here all use the same mapped address, only one
8352 may be mapped at a time. For a system with a single address space for
8353 data and instructions, the diagram would be similar, except that the
8354 program variables and heap would share an address space with the main
8355 program and the overlay area.
8357 An overlay loaded into instruction memory and ready for use is called a
8358 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
8359 instruction memory. An overlay not present (or only partially present)
8360 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
8361 is its address in the larger memory. The mapped address is also called
8362 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
8363 called the @dfn{load memory address}, or @dfn{LMA}.
8365 Unfortunately, overlays are not a completely transparent way to adapt a
8366 program to limited instruction memory. They introduce a new set of
8367 global constraints you must keep in mind as you design your program:
8372 Before calling or returning to a function in an overlay, your program
8373 must make sure that overlay is actually mapped. Otherwise, the call or
8374 return will transfer control to the right address, but in the wrong
8375 overlay, and your program will probably crash.
8378 If the process of mapping an overlay is expensive on your system, you
8379 will need to choose your overlays carefully to minimize their effect on
8380 your program's performance.
8383 The executable file you load onto your system must contain each
8384 overlay's instructions, appearing at the overlay's load address, not its
8385 mapped address. However, each overlay's instructions must be relocated
8386 and its symbols defined as if the overlay were at its mapped address.
8387 You can use GNU linker scripts to specify different load and relocation
8388 addresses for pieces of your program; see @ref{Overlay Description,,,
8389 ld.info, Using ld: the GNU linker}.
8392 The procedure for loading executable files onto your system must be able
8393 to load their contents into the larger address space as well as the
8394 instruction and data spaces.
8398 The overlay system described above is rather simple, and could be
8399 improved in many ways:
8404 If your system has suitable bank switch registers or memory management
8405 hardware, you could use those facilities to make an overlay's load area
8406 contents simply appear at their mapped address in instruction space.
8407 This would probably be faster than copying the overlay to its mapped
8408 area in the usual way.
8411 If your overlays are small enough, you could set aside more than one
8412 overlay area, and have more than one overlay mapped at a time.
8415 You can use overlays to manage data, as well as instructions. In
8416 general, data overlays are even less transparent to your design than
8417 code overlays: whereas code overlays only require care when you call or
8418 return to functions, data overlays require care every time you access
8419 the data. Also, if you change the contents of a data overlay, you
8420 must copy its contents back out to its load address before you can copy a
8421 different data overlay into the same mapped area.
8426 @node Overlay Commands
8427 @section Overlay Commands
8429 To use @value{GDBN}'s overlay support, each overlay in your program must
8430 correspond to a separate section of the executable file. The section's
8431 virtual memory address and load memory address must be the overlay's
8432 mapped and load addresses. Identifying overlays with sections allows
8433 @value{GDBN} to determine the appropriate address of a function or
8434 variable, depending on whether the overlay is mapped or not.
8436 @value{GDBN}'s overlay commands all start with the word @code{overlay};
8437 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
8442 Disable @value{GDBN}'s overlay support. When overlay support is
8443 disabled, @value{GDBN} assumes that all functions and variables are
8444 always present at their mapped addresses. By default, @value{GDBN}'s
8445 overlay support is disabled.
8447 @item overlay manual
8448 @cindex manual overlay debugging
8449 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
8450 relies on you to tell it which overlays are mapped, and which are not,
8451 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
8452 commands described below.
8454 @item overlay map-overlay @var{overlay}
8455 @itemx overlay map @var{overlay}
8456 @cindex map an overlay
8457 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
8458 be the name of the object file section containing the overlay. When an
8459 overlay is mapped, @value{GDBN} assumes it can find the overlay's
8460 functions and variables at their mapped addresses. @value{GDBN} assumes
8461 that any other overlays whose mapped ranges overlap that of
8462 @var{overlay} are now unmapped.
8464 @item overlay unmap-overlay @var{overlay}
8465 @itemx overlay unmap @var{overlay}
8466 @cindex unmap an overlay
8467 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
8468 must be the name of the object file section containing the overlay.
8469 When an overlay is unmapped, @value{GDBN} assumes it can find the
8470 overlay's functions and variables at their load addresses.
8473 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
8474 consults a data structure the overlay manager maintains in the inferior
8475 to see which overlays are mapped. For details, see @ref{Automatic
8478 @item overlay load-target
8480 @cindex reloading the overlay table
8481 Re-read the overlay table from the inferior. Normally, @value{GDBN}
8482 re-reads the table @value{GDBN} automatically each time the inferior
8483 stops, so this command should only be necessary if you have changed the
8484 overlay mapping yourself using @value{GDBN}. This command is only
8485 useful when using automatic overlay debugging.
8487 @item overlay list-overlays
8489 @cindex listing mapped overlays
8490 Display a list of the overlays currently mapped, along with their mapped
8491 addresses, load addresses, and sizes.
8495 Normally, when @value{GDBN} prints a code address, it includes the name
8496 of the function the address falls in:
8499 (@value{GDBP}) print main
8500 $3 = @{int ()@} 0x11a0 <main>
8503 When overlay debugging is enabled, @value{GDBN} recognizes code in
8504 unmapped overlays, and prints the names of unmapped functions with
8505 asterisks around them. For example, if @code{foo} is a function in an
8506 unmapped overlay, @value{GDBN} prints it this way:
8509 (@value{GDBP}) overlay list
8510 No sections are mapped.
8511 (@value{GDBP}) print foo
8512 $5 = @{int (int)@} 0x100000 <*foo*>
8515 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
8519 (@value{GDBP}) overlay list
8520 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
8521 mapped at 0x1016 - 0x104a
8522 (@value{GDBP}) print foo
8523 $6 = @{int (int)@} 0x1016 <foo>
8526 When overlay debugging is enabled, @value{GDBN} can find the correct
8527 address for functions and variables in an overlay, whether or not the
8528 overlay is mapped. This allows most @value{GDBN} commands, like
8529 @code{break} and @code{disassemble}, to work normally, even on unmapped
8530 code. However, @value{GDBN}'s breakpoint support has some limitations:
8534 @cindex breakpoints in overlays
8535 @cindex overlays, setting breakpoints in
8536 You can set breakpoints in functions in unmapped overlays, as long as
8537 @value{GDBN} can write to the overlay at its load address.
8539 @value{GDBN} can not set hardware or simulator-based breakpoints in
8540 unmapped overlays. However, if you set a breakpoint at the end of your
8541 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
8542 you are using manual overlay management), @value{GDBN} will re-set its
8543 breakpoints properly.
8547 @node Automatic Overlay Debugging
8548 @section Automatic Overlay Debugging
8549 @cindex automatic overlay debugging
8551 @value{GDBN} can automatically track which overlays are mapped and which
8552 are not, given some simple co-operation from the overlay manager in the
8553 inferior. If you enable automatic overlay debugging with the
8554 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
8555 looks in the inferior's memory for certain variables describing the
8556 current state of the overlays.
8558 Here are the variables your overlay manager must define to support
8559 @value{GDBN}'s automatic overlay debugging:
8563 @item @code{_ovly_table}:
8564 This variable must be an array of the following structures:
8569 /* The overlay's mapped address. */
8572 /* The size of the overlay, in bytes. */
8575 /* The overlay's load address. */
8578 /* Non-zero if the overlay is currently mapped;
8580 unsigned long mapped;
8584 @item @code{_novlys}:
8585 This variable must be a four-byte signed integer, holding the total
8586 number of elements in @code{_ovly_table}.
8590 To decide whether a particular overlay is mapped or not, @value{GDBN}
8591 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
8592 @code{lma} members equal the VMA and LMA of the overlay's section in the
8593 executable file. When @value{GDBN} finds a matching entry, it consults
8594 the entry's @code{mapped} member to determine whether the overlay is
8597 In addition, your overlay manager may define a function called
8598 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
8599 will silently set a breakpoint there. If the overlay manager then
8600 calls this function whenever it has changed the overlay table, this
8601 will enable @value{GDBN} to accurately keep track of which overlays
8602 are in program memory, and update any breakpoints that may be set
8603 in overlays. This will allow breakpoints to work even if the
8604 overlays are kept in ROM or other non-writable memory while they
8605 are not being executed.
8607 @node Overlay Sample Program
8608 @section Overlay Sample Program
8609 @cindex overlay example program
8611 When linking a program which uses overlays, you must place the overlays
8612 at their load addresses, while relocating them to run at their mapped
8613 addresses. To do this, you must write a linker script (@pxref{Overlay
8614 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
8615 since linker scripts are specific to a particular host system, target
8616 architecture, and target memory layout, this manual cannot provide
8617 portable sample code demonstrating @value{GDBN}'s overlay support.
8619 However, the @value{GDBN} source distribution does contain an overlaid
8620 program, with linker scripts for a few systems, as part of its test
8621 suite. The program consists of the following files from
8622 @file{gdb/testsuite/gdb.base}:
8626 The main program file.
8628 A simple overlay manager, used by @file{overlays.c}.
8633 Overlay modules, loaded and used by @file{overlays.c}.
8636 Linker scripts for linking the test program on the @code{d10v-elf}
8637 and @code{m32r-elf} targets.
8640 You can build the test program using the @code{d10v-elf} GCC
8641 cross-compiler like this:
8644 $ d10v-elf-gcc -g -c overlays.c
8645 $ d10v-elf-gcc -g -c ovlymgr.c
8646 $ d10v-elf-gcc -g -c foo.c
8647 $ d10v-elf-gcc -g -c bar.c
8648 $ d10v-elf-gcc -g -c baz.c
8649 $ d10v-elf-gcc -g -c grbx.c
8650 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
8651 baz.o grbx.o -Wl,-Td10v.ld -o overlays
8654 The build process is identical for any other architecture, except that
8655 you must substitute the appropriate compiler and linker script for the
8656 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
8660 @chapter Using @value{GDBN} with Different Languages
8663 Although programming languages generally have common aspects, they are
8664 rarely expressed in the same manner. For instance, in ANSI C,
8665 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
8666 Modula-2, it is accomplished by @code{p^}. Values can also be
8667 represented (and displayed) differently. Hex numbers in C appear as
8668 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
8670 @cindex working language
8671 Language-specific information is built into @value{GDBN} for some languages,
8672 allowing you to express operations like the above in your program's
8673 native language, and allowing @value{GDBN} to output values in a manner
8674 consistent with the syntax of your program's native language. The
8675 language you use to build expressions is called the @dfn{working
8679 * Setting:: Switching between source languages
8680 * Show:: Displaying the language
8681 * Checks:: Type and range checks
8682 * Supported Languages:: Supported languages
8683 * Unsupported Languages:: Unsupported languages
8687 @section Switching Between Source Languages
8689 There are two ways to control the working language---either have @value{GDBN}
8690 set it automatically, or select it manually yourself. You can use the
8691 @code{set language} command for either purpose. On startup, @value{GDBN}
8692 defaults to setting the language automatically. The working language is
8693 used to determine how expressions you type are interpreted, how values
8696 In addition to the working language, every source file that
8697 @value{GDBN} knows about has its own working language. For some object
8698 file formats, the compiler might indicate which language a particular
8699 source file is in. However, most of the time @value{GDBN} infers the
8700 language from the name of the file. The language of a source file
8701 controls whether C@t{++} names are demangled---this way @code{backtrace} can
8702 show each frame appropriately for its own language. There is no way to
8703 set the language of a source file from within @value{GDBN}, but you can
8704 set the language associated with a filename extension. @xref{Show, ,
8705 Displaying the Language}.
8707 This is most commonly a problem when you use a program, such
8708 as @code{cfront} or @code{f2c}, that generates C but is written in
8709 another language. In that case, make the
8710 program use @code{#line} directives in its C output; that way
8711 @value{GDBN} will know the correct language of the source code of the original
8712 program, and will display that source code, not the generated C code.
8715 * Filenames:: Filename extensions and languages.
8716 * Manually:: Setting the working language manually
8717 * Automatically:: Having @value{GDBN} infer the source language
8721 @subsection List of Filename Extensions and Languages
8723 If a source file name ends in one of the following extensions, then
8724 @value{GDBN} infers that its language is the one indicated.
8745 Objective-C source file
8752 Modula-2 source file
8756 Assembler source file. This actually behaves almost like C, but
8757 @value{GDBN} does not skip over function prologues when stepping.
8760 In addition, you may set the language associated with a filename
8761 extension. @xref{Show, , Displaying the Language}.
8764 @subsection Setting the Working Language
8766 If you allow @value{GDBN} to set the language automatically,
8767 expressions are interpreted the same way in your debugging session and
8770 @kindex set language
8771 If you wish, you may set the language manually. To do this, issue the
8772 command @samp{set language @var{lang}}, where @var{lang} is the name of
8774 @code{c} or @code{modula-2}.
8775 For a list of the supported languages, type @samp{set language}.
8777 Setting the language manually prevents @value{GDBN} from updating the working
8778 language automatically. This can lead to confusion if you try
8779 to debug a program when the working language is not the same as the
8780 source language, when an expression is acceptable to both
8781 languages---but means different things. For instance, if the current
8782 source file were written in C, and @value{GDBN} was parsing Modula-2, a
8790 might not have the effect you intended. In C, this means to add
8791 @code{b} and @code{c} and place the result in @code{a}. The result
8792 printed would be the value of @code{a}. In Modula-2, this means to compare
8793 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
8796 @subsection Having @value{GDBN} Infer the Source Language
8798 To have @value{GDBN} set the working language automatically, use
8799 @samp{set language local} or @samp{set language auto}. @value{GDBN}
8800 then infers the working language. That is, when your program stops in a
8801 frame (usually by encountering a breakpoint), @value{GDBN} sets the
8802 working language to the language recorded for the function in that
8803 frame. If the language for a frame is unknown (that is, if the function
8804 or block corresponding to the frame was defined in a source file that
8805 does not have a recognized extension), the current working language is
8806 not changed, and @value{GDBN} issues a warning.
8808 This may not seem necessary for most programs, which are written
8809 entirely in one source language. However, program modules and libraries
8810 written in one source language can be used by a main program written in
8811 a different source language. Using @samp{set language auto} in this
8812 case frees you from having to set the working language manually.
8815 @section Displaying the Language
8817 The following commands help you find out which language is the
8818 working language, and also what language source files were written in.
8822 @kindex show language
8823 Display the current working language. This is the
8824 language you can use with commands such as @code{print} to
8825 build and compute expressions that may involve variables in your program.
8828 @kindex info frame@r{, show the source language}
8829 Display the source language for this frame. This language becomes the
8830 working language if you use an identifier from this frame.
8831 @xref{Frame Info, ,Information about a Frame}, to identify the other
8832 information listed here.
8835 @kindex info source@r{, show the source language}
8836 Display the source language of this source file.
8837 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
8838 information listed here.
8841 In unusual circumstances, you may have source files with extensions
8842 not in the standard list. You can then set the extension associated
8843 with a language explicitly:
8846 @item set extension-language @var{ext} @var{language}
8847 @kindex set extension-language
8848 Tell @value{GDBN} that source files with extension @var{ext} are to be
8849 assumed as written in the source language @var{language}.
8851 @item info extensions
8852 @kindex info extensions
8853 List all the filename extensions and the associated languages.
8857 @section Type and Range Checking
8860 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
8861 checking are included, but they do not yet have any effect. This
8862 section documents the intended facilities.
8864 @c FIXME remove warning when type/range code added
8866 Some languages are designed to guard you against making seemingly common
8867 errors through a series of compile- and run-time checks. These include
8868 checking the type of arguments to functions and operators, and making
8869 sure mathematical overflows are caught at run time. Checks such as
8870 these help to ensure a program's correctness once it has been compiled
8871 by eliminating type mismatches, and providing active checks for range
8872 errors when your program is running.
8874 @value{GDBN} can check for conditions like the above if you wish.
8875 Although @value{GDBN} does not check the statements in your program,
8876 it can check expressions entered directly into @value{GDBN} for
8877 evaluation via the @code{print} command, for example. As with the
8878 working language, @value{GDBN} can also decide whether or not to check
8879 automatically based on your program's source language.
8880 @xref{Supported Languages, ,Supported Languages}, for the default
8881 settings of supported languages.
8884 * Type Checking:: An overview of type checking
8885 * Range Checking:: An overview of range checking
8888 @cindex type checking
8889 @cindex checks, type
8891 @subsection An Overview of Type Checking
8893 Some languages, such as Modula-2, are strongly typed, meaning that the
8894 arguments to operators and functions have to be of the correct type,
8895 otherwise an error occurs. These checks prevent type mismatch
8896 errors from ever causing any run-time problems. For example,
8904 The second example fails because the @code{CARDINAL} 1 is not
8905 type-compatible with the @code{REAL} 2.3.
8907 For the expressions you use in @value{GDBN} commands, you can tell the
8908 @value{GDBN} type checker to skip checking;
8909 to treat any mismatches as errors and abandon the expression;
8910 or to only issue warnings when type mismatches occur,
8911 but evaluate the expression anyway. When you choose the last of
8912 these, @value{GDBN} evaluates expressions like the second example above, but
8913 also issues a warning.
8915 Even if you turn type checking off, there may be other reasons
8916 related to type that prevent @value{GDBN} from evaluating an expression.
8917 For instance, @value{GDBN} does not know how to add an @code{int} and
8918 a @code{struct foo}. These particular type errors have nothing to do
8919 with the language in use, and usually arise from expressions, such as
8920 the one described above, which make little sense to evaluate anyway.
8922 Each language defines to what degree it is strict about type. For
8923 instance, both Modula-2 and C require the arguments to arithmetical
8924 operators to be numbers. In C, enumerated types and pointers can be
8925 represented as numbers, so that they are valid arguments to mathematical
8926 operators. @xref{Supported Languages, ,Supported Languages}, for further
8927 details on specific languages.
8929 @value{GDBN} provides some additional commands for controlling the type checker:
8931 @kindex set check type
8932 @kindex show check type
8934 @item set check type auto
8935 Set type checking on or off based on the current working language.
8936 @xref{Supported Languages, ,Supported Languages}, for the default settings for
8939 @item set check type on
8940 @itemx set check type off
8941 Set type checking on or off, overriding the default setting for the
8942 current working language. Issue a warning if the setting does not
8943 match the language default. If any type mismatches occur in
8944 evaluating an expression while type checking is on, @value{GDBN} prints a
8945 message and aborts evaluation of the expression.
8947 @item set check type warn
8948 Cause the type checker to issue warnings, but to always attempt to
8949 evaluate the expression. Evaluating the expression may still
8950 be impossible for other reasons. For example, @value{GDBN} cannot add
8951 numbers and structures.
8954 Show the current setting of the type checker, and whether or not @value{GDBN}
8955 is setting it automatically.
8958 @cindex range checking
8959 @cindex checks, range
8960 @node Range Checking
8961 @subsection An Overview of Range Checking
8963 In some languages (such as Modula-2), it is an error to exceed the
8964 bounds of a type; this is enforced with run-time checks. Such range
8965 checking is meant to ensure program correctness by making sure
8966 computations do not overflow, or indices on an array element access do
8967 not exceed the bounds of the array.
8969 For expressions you use in @value{GDBN} commands, you can tell
8970 @value{GDBN} to treat range errors in one of three ways: ignore them,
8971 always treat them as errors and abandon the expression, or issue
8972 warnings but evaluate the expression anyway.
8974 A range error can result from numerical overflow, from exceeding an
8975 array index bound, or when you type a constant that is not a member
8976 of any type. Some languages, however, do not treat overflows as an
8977 error. In many implementations of C, mathematical overflow causes the
8978 result to ``wrap around'' to lower values---for example, if @var{m} is
8979 the largest integer value, and @var{s} is the smallest, then
8982 @var{m} + 1 @result{} @var{s}
8985 This, too, is specific to individual languages, and in some cases
8986 specific to individual compilers or machines. @xref{Supported Languages, ,
8987 Supported Languages}, for further details on specific languages.
8989 @value{GDBN} provides some additional commands for controlling the range checker:
8991 @kindex set check range
8992 @kindex show check range
8994 @item set check range auto
8995 Set range checking on or off based on the current working language.
8996 @xref{Supported Languages, ,Supported Languages}, for the default settings for
8999 @item set check range on
9000 @itemx set check range off
9001 Set range checking on or off, overriding the default setting for the
9002 current working language. A warning is issued if the setting does not
9003 match the language default. If a range error occurs and range checking is on,
9004 then a message is printed and evaluation of the expression is aborted.
9006 @item set check range warn
9007 Output messages when the @value{GDBN} range checker detects a range error,
9008 but attempt to evaluate the expression anyway. Evaluating the
9009 expression may still be impossible for other reasons, such as accessing
9010 memory that the process does not own (a typical example from many Unix
9014 Show the current setting of the range checker, and whether or not it is
9015 being set automatically by @value{GDBN}.
9018 @node Supported Languages
9019 @section Supported Languages
9021 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
9022 assembly, Modula-2, and Ada.
9023 @c This is false ...
9024 Some @value{GDBN} features may be used in expressions regardless of the
9025 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
9026 and the @samp{@{type@}addr} construct (@pxref{Expressions,
9027 ,Expressions}) can be used with the constructs of any supported
9030 The following sections detail to what degree each source language is
9031 supported by @value{GDBN}. These sections are not meant to be language
9032 tutorials or references, but serve only as a reference guide to what the
9033 @value{GDBN} expression parser accepts, and what input and output
9034 formats should look like for different languages. There are many good
9035 books written on each of these languages; please look to these for a
9036 language reference or tutorial.
9040 * Objective-C:: Objective-C
9043 * Modula-2:: Modula-2
9048 @subsection C and C@t{++}
9050 @cindex C and C@t{++}
9051 @cindex expressions in C or C@t{++}
9053 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
9054 to both languages. Whenever this is the case, we discuss those languages
9058 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
9059 @cindex @sc{gnu} C@t{++}
9060 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
9061 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
9062 effectively, you must compile your C@t{++} programs with a supported
9063 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
9064 compiler (@code{aCC}).
9066 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
9067 format; if it doesn't work on your system, try the stabs+ debugging
9068 format. You can select those formats explicitly with the @code{g++}
9069 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
9070 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
9071 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
9074 * C Operators:: C and C@t{++} operators
9075 * C Constants:: C and C@t{++} constants
9076 * C Plus Plus Expressions:: C@t{++} expressions
9077 * C Defaults:: Default settings for C and C@t{++}
9078 * C Checks:: C and C@t{++} type and range checks
9079 * Debugging C:: @value{GDBN} and C
9080 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
9084 @subsubsection C and C@t{++} Operators
9086 @cindex C and C@t{++} operators
9088 Operators must be defined on values of specific types. For instance,
9089 @code{+} is defined on numbers, but not on structures. Operators are
9090 often defined on groups of types.
9092 For the purposes of C and C@t{++}, the following definitions hold:
9097 @emph{Integral types} include @code{int} with any of its storage-class
9098 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
9101 @emph{Floating-point types} include @code{float}, @code{double}, and
9102 @code{long double} (if supported by the target platform).
9105 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
9108 @emph{Scalar types} include all of the above.
9113 The following operators are supported. They are listed here
9114 in order of increasing precedence:
9118 The comma or sequencing operator. Expressions in a comma-separated list
9119 are evaluated from left to right, with the result of the entire
9120 expression being the last expression evaluated.
9123 Assignment. The value of an assignment expression is the value
9124 assigned. Defined on scalar types.
9127 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
9128 and translated to @w{@code{@var{a} = @var{a op b}}}.
9129 @w{@code{@var{op}=}} and @code{=} have the same precedence.
9130 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
9131 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
9134 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
9135 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
9139 Logical @sc{or}. Defined on integral types.
9142 Logical @sc{and}. Defined on integral types.
9145 Bitwise @sc{or}. Defined on integral types.
9148 Bitwise exclusive-@sc{or}. Defined on integral types.
9151 Bitwise @sc{and}. Defined on integral types.
9154 Equality and inequality. Defined on scalar types. The value of these
9155 expressions is 0 for false and non-zero for true.
9157 @item <@r{, }>@r{, }<=@r{, }>=
9158 Less than, greater than, less than or equal, greater than or equal.
9159 Defined on scalar types. The value of these expressions is 0 for false
9160 and non-zero for true.
9163 left shift, and right shift. Defined on integral types.
9166 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9169 Addition and subtraction. Defined on integral types, floating-point types and
9172 @item *@r{, }/@r{, }%
9173 Multiplication, division, and modulus. Multiplication and division are
9174 defined on integral and floating-point types. Modulus is defined on
9178 Increment and decrement. When appearing before a variable, the
9179 operation is performed before the variable is used in an expression;
9180 when appearing after it, the variable's value is used before the
9181 operation takes place.
9184 Pointer dereferencing. Defined on pointer types. Same precedence as
9188 Address operator. Defined on variables. Same precedence as @code{++}.
9190 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
9191 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
9192 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
9193 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
9197 Negative. Defined on integral and floating-point types. Same
9198 precedence as @code{++}.
9201 Logical negation. Defined on integral types. Same precedence as
9205 Bitwise complement operator. Defined on integral types. Same precedence as
9210 Structure member, and pointer-to-structure member. For convenience,
9211 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
9212 pointer based on the stored type information.
9213 Defined on @code{struct} and @code{union} data.
9216 Dereferences of pointers to members.
9219 Array indexing. @code{@var{a}[@var{i}]} is defined as
9220 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
9223 Function parameter list. Same precedence as @code{->}.
9226 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
9227 and @code{class} types.
9230 Doubled colons also represent the @value{GDBN} scope operator
9231 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
9235 If an operator is redefined in the user code, @value{GDBN} usually
9236 attempts to invoke the redefined version instead of using the operator's
9240 @subsubsection C and C@t{++} Constants
9242 @cindex C and C@t{++} constants
9244 @value{GDBN} allows you to express the constants of C and C@t{++} in the
9249 Integer constants are a sequence of digits. Octal constants are
9250 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
9251 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
9252 @samp{l}, specifying that the constant should be treated as a
9256 Floating point constants are a sequence of digits, followed by a decimal
9257 point, followed by a sequence of digits, and optionally followed by an
9258 exponent. An exponent is of the form:
9259 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
9260 sequence of digits. The @samp{+} is optional for positive exponents.
9261 A floating-point constant may also end with a letter @samp{f} or
9262 @samp{F}, specifying that the constant should be treated as being of
9263 the @code{float} (as opposed to the default @code{double}) type; or with
9264 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
9268 Enumerated constants consist of enumerated identifiers, or their
9269 integral equivalents.
9272 Character constants are a single character surrounded by single quotes
9273 (@code{'}), or a number---the ordinal value of the corresponding character
9274 (usually its @sc{ascii} value). Within quotes, the single character may
9275 be represented by a letter or by @dfn{escape sequences}, which are of
9276 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
9277 of the character's ordinal value; or of the form @samp{\@var{x}}, where
9278 @samp{@var{x}} is a predefined special character---for example,
9279 @samp{\n} for newline.
9282 String constants are a sequence of character constants surrounded by
9283 double quotes (@code{"}). Any valid character constant (as described
9284 above) may appear. Double quotes within the string must be preceded by
9285 a backslash, so for instance @samp{"a\"b'c"} is a string of five
9289 Pointer constants are an integral value. You can also write pointers
9290 to constants using the C operator @samp{&}.
9293 Array constants are comma-separated lists surrounded by braces @samp{@{}
9294 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
9295 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
9296 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
9299 @node C Plus Plus Expressions
9300 @subsubsection C@t{++} Expressions
9302 @cindex expressions in C@t{++}
9303 @value{GDBN} expression handling can interpret most C@t{++} expressions.
9305 @cindex debugging C@t{++} programs
9306 @cindex C@t{++} compilers
9307 @cindex debug formats and C@t{++}
9308 @cindex @value{NGCC} and C@t{++}
9310 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
9311 proper compiler and the proper debug format. Currently, @value{GDBN}
9312 works best when debugging C@t{++} code that is compiled with
9313 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
9314 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
9315 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
9316 stabs+ as their default debug format, so you usually don't need to
9317 specify a debug format explicitly. Other compilers and/or debug formats
9318 are likely to work badly or not at all when using @value{GDBN} to debug
9324 @cindex member functions
9326 Member function calls are allowed; you can use expressions like
9329 count = aml->GetOriginal(x, y)
9332 @vindex this@r{, inside C@t{++} member functions}
9333 @cindex namespace in C@t{++}
9335 While a member function is active (in the selected stack frame), your
9336 expressions have the same namespace available as the member function;
9337 that is, @value{GDBN} allows implicit references to the class instance
9338 pointer @code{this} following the same rules as C@t{++}.
9340 @cindex call overloaded functions
9341 @cindex overloaded functions, calling
9342 @cindex type conversions in C@t{++}
9344 You can call overloaded functions; @value{GDBN} resolves the function
9345 call to the right definition, with some restrictions. @value{GDBN} does not
9346 perform overload resolution involving user-defined type conversions,
9347 calls to constructors, or instantiations of templates that do not exist
9348 in the program. It also cannot handle ellipsis argument lists or
9351 It does perform integral conversions and promotions, floating-point
9352 promotions, arithmetic conversions, pointer conversions, conversions of
9353 class objects to base classes, and standard conversions such as those of
9354 functions or arrays to pointers; it requires an exact match on the
9355 number of function arguments.
9357 Overload resolution is always performed, unless you have specified
9358 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
9359 ,@value{GDBN} Features for C@t{++}}.
9361 You must specify @code{set overload-resolution off} in order to use an
9362 explicit function signature to call an overloaded function, as in
9364 p 'foo(char,int)'('x', 13)
9367 The @value{GDBN} command-completion facility can simplify this;
9368 see @ref{Completion, ,Command Completion}.
9370 @cindex reference declarations
9372 @value{GDBN} understands variables declared as C@t{++} references; you can use
9373 them in expressions just as you do in C@t{++} source---they are automatically
9376 In the parameter list shown when @value{GDBN} displays a frame, the values of
9377 reference variables are not displayed (unlike other variables); this
9378 avoids clutter, since references are often used for large structures.
9379 The @emph{address} of a reference variable is always shown, unless
9380 you have specified @samp{set print address off}.
9383 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
9384 expressions can use it just as expressions in your program do. Since
9385 one scope may be defined in another, you can use @code{::} repeatedly if
9386 necessary, for example in an expression like
9387 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
9388 resolving name scope by reference to source files, in both C and C@t{++}
9389 debugging (@pxref{Variables, ,Program Variables}).
9392 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
9393 calling virtual functions correctly, printing out virtual bases of
9394 objects, calling functions in a base subobject, casting objects, and
9395 invoking user-defined operators.
9398 @subsubsection C and C@t{++} Defaults
9400 @cindex C and C@t{++} defaults
9402 If you allow @value{GDBN} to set type and range checking automatically, they
9403 both default to @code{off} whenever the working language changes to
9404 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
9405 selects the working language.
9407 If you allow @value{GDBN} to set the language automatically, it
9408 recognizes source files whose names end with @file{.c}, @file{.C}, or
9409 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
9410 these files, it sets the working language to C or C@t{++}.
9411 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
9412 for further details.
9414 @c Type checking is (a) primarily motivated by Modula-2, and (b)
9415 @c unimplemented. If (b) changes, it might make sense to let this node
9416 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
9419 @subsubsection C and C@t{++} Type and Range Checks
9421 @cindex C and C@t{++} checks
9423 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
9424 is not used. However, if you turn type checking on, @value{GDBN}
9425 considers two variables type equivalent if:
9429 The two variables are structured and have the same structure, union, or
9433 The two variables have the same type name, or types that have been
9434 declared equivalent through @code{typedef}.
9437 @c leaving this out because neither J Gilmore nor R Pesch understand it.
9440 The two @code{struct}, @code{union}, or @code{enum} variables are
9441 declared in the same declaration. (Note: this may not be true for all C
9446 Range checking, if turned on, is done on mathematical operations. Array
9447 indices are not checked, since they are often used to index a pointer
9448 that is not itself an array.
9451 @subsubsection @value{GDBN} and C
9453 The @code{set print union} and @code{show print union} commands apply to
9454 the @code{union} type. When set to @samp{on}, any @code{union} that is
9455 inside a @code{struct} or @code{class} is also printed. Otherwise, it
9456 appears as @samp{@{...@}}.
9458 The @code{@@} operator aids in the debugging of dynamic arrays, formed
9459 with pointers and a memory allocation function. @xref{Expressions,
9462 @node Debugging C Plus Plus
9463 @subsubsection @value{GDBN} Features for C@t{++}
9465 @cindex commands for C@t{++}
9467 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
9468 designed specifically for use with C@t{++}. Here is a summary:
9471 @cindex break in overloaded functions
9472 @item @r{breakpoint menus}
9473 When you want a breakpoint in a function whose name is overloaded,
9474 @value{GDBN} breakpoint menus help you specify which function definition
9475 you want. @xref{Breakpoint Menus,,Breakpoint Menus}.
9477 @cindex overloading in C@t{++}
9478 @item rbreak @var{regex}
9479 Setting breakpoints using regular expressions is helpful for setting
9480 breakpoints on overloaded functions that are not members of any special
9482 @xref{Set Breaks, ,Setting Breakpoints}.
9484 @cindex C@t{++} exception handling
9487 Debug C@t{++} exception handling using these commands. @xref{Set
9488 Catchpoints, , Setting Catchpoints}.
9491 @item ptype @var{typename}
9492 Print inheritance relationships as well as other information for type
9494 @xref{Symbols, ,Examining the Symbol Table}.
9496 @cindex C@t{++} symbol display
9497 @item set print demangle
9498 @itemx show print demangle
9499 @itemx set print asm-demangle
9500 @itemx show print asm-demangle
9501 Control whether C@t{++} symbols display in their source form, both when
9502 displaying code as C@t{++} source and when displaying disassemblies.
9503 @xref{Print Settings, ,Print Settings}.
9505 @item set print object
9506 @itemx show print object
9507 Choose whether to print derived (actual) or declared types of objects.
9508 @xref{Print Settings, ,Print Settings}.
9510 @item set print vtbl
9511 @itemx show print vtbl
9512 Control the format for printing virtual function tables.
9513 @xref{Print Settings, ,Print Settings}.
9514 (The @code{vtbl} commands do not work on programs compiled with the HP
9515 ANSI C@t{++} compiler (@code{aCC}).)
9517 @kindex set overload-resolution
9518 @cindex overloaded functions, overload resolution
9519 @item set overload-resolution on
9520 Enable overload resolution for C@t{++} expression evaluation. The default
9521 is on. For overloaded functions, @value{GDBN} evaluates the arguments
9522 and searches for a function whose signature matches the argument types,
9523 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
9524 Expressions, ,C@t{++} Expressions}, for details).
9525 If it cannot find a match, it emits a message.
9527 @item set overload-resolution off
9528 Disable overload resolution for C@t{++} expression evaluation. For
9529 overloaded functions that are not class member functions, @value{GDBN}
9530 chooses the first function of the specified name that it finds in the
9531 symbol table, whether or not its arguments are of the correct type. For
9532 overloaded functions that are class member functions, @value{GDBN}
9533 searches for a function whose signature @emph{exactly} matches the
9536 @kindex show overload-resolution
9537 @item show overload-resolution
9538 Show the current setting of overload resolution.
9540 @item @r{Overloaded symbol names}
9541 You can specify a particular definition of an overloaded symbol, using
9542 the same notation that is used to declare such symbols in C@t{++}: type
9543 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
9544 also use the @value{GDBN} command-line word completion facilities to list the
9545 available choices, or to finish the type list for you.
9546 @xref{Completion,, Command Completion}, for details on how to do this.
9550 @subsection Objective-C
9553 This section provides information about some commands and command
9554 options that are useful for debugging Objective-C code. See also
9555 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
9556 few more commands specific to Objective-C support.
9559 * Method Names in Commands::
9560 * The Print Command with Objective-C::
9563 @node Method Names in Commands
9564 @subsubsection Method Names in Commands
9566 The following commands have been extended to accept Objective-C method
9567 names as line specifications:
9569 @kindex clear@r{, and Objective-C}
9570 @kindex break@r{, and Objective-C}
9571 @kindex info line@r{, and Objective-C}
9572 @kindex jump@r{, and Objective-C}
9573 @kindex list@r{, and Objective-C}
9577 @item @code{info line}
9582 A fully qualified Objective-C method name is specified as
9585 -[@var{Class} @var{methodName}]
9588 where the minus sign is used to indicate an instance method and a
9589 plus sign (not shown) is used to indicate a class method. The class
9590 name @var{Class} and method name @var{methodName} are enclosed in
9591 brackets, similar to the way messages are specified in Objective-C
9592 source code. For example, to set a breakpoint at the @code{create}
9593 instance method of class @code{Fruit} in the program currently being
9597 break -[Fruit create]
9600 To list ten program lines around the @code{initialize} class method,
9604 list +[NSText initialize]
9607 In the current version of @value{GDBN}, the plus or minus sign is
9608 required. In future versions of @value{GDBN}, the plus or minus
9609 sign will be optional, but you can use it to narrow the search. It
9610 is also possible to specify just a method name:
9616 You must specify the complete method name, including any colons. If
9617 your program's source files contain more than one @code{create} method,
9618 you'll be presented with a numbered list of classes that implement that
9619 method. Indicate your choice by number, or type @samp{0} to exit if
9622 As another example, to clear a breakpoint established at the
9623 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
9626 clear -[NSWindow makeKeyAndOrderFront:]
9629 @node The Print Command with Objective-C
9630 @subsubsection The Print Command With Objective-C
9631 @cindex Objective-C, print objects
9632 @kindex print-object
9633 @kindex po @r{(@code{print-object})}
9635 The print command has also been extended to accept methods. For example:
9638 print -[@var{object} hash]
9641 @cindex print an Objective-C object description
9642 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
9644 will tell @value{GDBN} to send the @code{hash} message to @var{object}
9645 and print the result. Also, an additional command has been added,
9646 @code{print-object} or @code{po} for short, which is meant to print
9647 the description of an object. However, this command may only work
9648 with certain Objective-C libraries that have a particular hook
9649 function, @code{_NSPrintForDebugger}, defined.
9653 @cindex Fortran-specific support in @value{GDBN}
9655 @value{GDBN} can be used to debug programs written in Fortran, but it
9656 currently supports only the features of Fortran 77 language.
9658 @cindex trailing underscore, in Fortran symbols
9659 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
9660 among them) append an underscore to the names of variables and
9661 functions. When you debug programs compiled by those compilers, you
9662 will need to refer to variables and functions with a trailing
9666 * Fortran Operators:: Fortran operators and expressions
9667 * Fortran Defaults:: Default settings for Fortran
9668 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
9671 @node Fortran Operators
9672 @subsubsection Fortran Operators and Expressions
9674 @cindex Fortran operators and expressions
9676 Operators must be defined on values of specific types. For instance,
9677 @code{+} is defined on numbers, but not on characters or other non-
9678 arithmetic types. Operators are often defined on groups of types.
9682 The exponentiation operator. It raises the first operand to the power
9686 The range operator. Normally used in the form of array(low:high) to
9687 represent a section of array.
9690 @node Fortran Defaults
9691 @subsubsection Fortran Defaults
9693 @cindex Fortran Defaults
9695 Fortran symbols are usually case-insensitive, so @value{GDBN} by
9696 default uses case-insensitive matches for Fortran symbols. You can
9697 change that with the @samp{set case-insensitive} command, see
9698 @ref{Symbols}, for the details.
9700 @node Special Fortran Commands
9701 @subsubsection Special Fortran Commands
9703 @cindex Special Fortran commands
9705 @value{GDBN} has some commands to support Fortran-specific features,
9706 such as displaying common blocks.
9709 @cindex @code{COMMON} blocks, Fortran
9711 @item info common @r{[}@var{common-name}@r{]}
9712 This command prints the values contained in the Fortran @code{COMMON}
9713 block whose name is @var{common-name}. With no argument, the names of
9714 all @code{COMMON} blocks visible at the current program location are
9721 @cindex Pascal support in @value{GDBN}, limitations
9722 Debugging Pascal programs which use sets, subranges, file variables, or
9723 nested functions does not currently work. @value{GDBN} does not support
9724 entering expressions, printing values, or similar features using Pascal
9727 The Pascal-specific command @code{set print pascal_static-members}
9728 controls whether static members of Pascal objects are displayed.
9729 @xref{Print Settings, pascal_static-members}.
9732 @subsection Modula-2
9734 @cindex Modula-2, @value{GDBN} support
9736 The extensions made to @value{GDBN} to support Modula-2 only support
9737 output from the @sc{gnu} Modula-2 compiler (which is currently being
9738 developed). Other Modula-2 compilers are not currently supported, and
9739 attempting to debug executables produced by them is most likely
9740 to give an error as @value{GDBN} reads in the executable's symbol
9743 @cindex expressions in Modula-2
9745 * M2 Operators:: Built-in operators
9746 * Built-In Func/Proc:: Built-in functions and procedures
9747 * M2 Constants:: Modula-2 constants
9748 * M2 Types:: Modula-2 types
9749 * M2 Defaults:: Default settings for Modula-2
9750 * Deviations:: Deviations from standard Modula-2
9751 * M2 Checks:: Modula-2 type and range checks
9752 * M2 Scope:: The scope operators @code{::} and @code{.}
9753 * GDB/M2:: @value{GDBN} and Modula-2
9757 @subsubsection Operators
9758 @cindex Modula-2 operators
9760 Operators must be defined on values of specific types. For instance,
9761 @code{+} is defined on numbers, but not on structures. Operators are
9762 often defined on groups of types. For the purposes of Modula-2, the
9763 following definitions hold:
9768 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
9772 @emph{Character types} consist of @code{CHAR} and its subranges.
9775 @emph{Floating-point types} consist of @code{REAL}.
9778 @emph{Pointer types} consist of anything declared as @code{POINTER TO
9782 @emph{Scalar types} consist of all of the above.
9785 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
9788 @emph{Boolean types} consist of @code{BOOLEAN}.
9792 The following operators are supported, and appear in order of
9793 increasing precedence:
9797 Function argument or array index separator.
9800 Assignment. The value of @var{var} @code{:=} @var{value} is
9804 Less than, greater than on integral, floating-point, or enumerated
9808 Less than or equal to, greater than or equal to
9809 on integral, floating-point and enumerated types, or set inclusion on
9810 set types. Same precedence as @code{<}.
9812 @item =@r{, }<>@r{, }#
9813 Equality and two ways of expressing inequality, valid on scalar types.
9814 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
9815 available for inequality, since @code{#} conflicts with the script
9819 Set membership. Defined on set types and the types of their members.
9820 Same precedence as @code{<}.
9823 Boolean disjunction. Defined on boolean types.
9826 Boolean conjunction. Defined on boolean types.
9829 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9832 Addition and subtraction on integral and floating-point types, or union
9833 and difference on set types.
9836 Multiplication on integral and floating-point types, or set intersection
9840 Division on floating-point types, or symmetric set difference on set
9841 types. Same precedence as @code{*}.
9844 Integer division and remainder. Defined on integral types. Same
9845 precedence as @code{*}.
9848 Negative. Defined on @code{INTEGER} and @code{REAL} data.
9851 Pointer dereferencing. Defined on pointer types.
9854 Boolean negation. Defined on boolean types. Same precedence as
9858 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
9859 precedence as @code{^}.
9862 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
9865 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
9869 @value{GDBN} and Modula-2 scope operators.
9873 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
9874 treats the use of the operator @code{IN}, or the use of operators
9875 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
9876 @code{<=}, and @code{>=} on sets as an error.
9880 @node Built-In Func/Proc
9881 @subsubsection Built-in Functions and Procedures
9882 @cindex Modula-2 built-ins
9884 Modula-2 also makes available several built-in procedures and functions.
9885 In describing these, the following metavariables are used:
9890 represents an @code{ARRAY} variable.
9893 represents a @code{CHAR} constant or variable.
9896 represents a variable or constant of integral type.
9899 represents an identifier that belongs to a set. Generally used in the
9900 same function with the metavariable @var{s}. The type of @var{s} should
9901 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
9904 represents a variable or constant of integral or floating-point type.
9907 represents a variable or constant of floating-point type.
9913 represents a variable.
9916 represents a variable or constant of one of many types. See the
9917 explanation of the function for details.
9920 All Modula-2 built-in procedures also return a result, described below.
9924 Returns the absolute value of @var{n}.
9927 If @var{c} is a lower case letter, it returns its upper case
9928 equivalent, otherwise it returns its argument.
9931 Returns the character whose ordinal value is @var{i}.
9934 Decrements the value in the variable @var{v} by one. Returns the new value.
9936 @item DEC(@var{v},@var{i})
9937 Decrements the value in the variable @var{v} by @var{i}. Returns the
9940 @item EXCL(@var{m},@var{s})
9941 Removes the element @var{m} from the set @var{s}. Returns the new
9944 @item FLOAT(@var{i})
9945 Returns the floating point equivalent of the integer @var{i}.
9948 Returns the index of the last member of @var{a}.
9951 Increments the value in the variable @var{v} by one. Returns the new value.
9953 @item INC(@var{v},@var{i})
9954 Increments the value in the variable @var{v} by @var{i}. Returns the
9957 @item INCL(@var{m},@var{s})
9958 Adds the element @var{m} to the set @var{s} if it is not already
9959 there. Returns the new set.
9962 Returns the maximum value of the type @var{t}.
9965 Returns the minimum value of the type @var{t}.
9968 Returns boolean TRUE if @var{i} is an odd number.
9971 Returns the ordinal value of its argument. For example, the ordinal
9972 value of a character is its @sc{ascii} value (on machines supporting the
9973 @sc{ascii} character set). @var{x} must be of an ordered type, which include
9974 integral, character and enumerated types.
9977 Returns the size of its argument. @var{x} can be a variable or a type.
9979 @item TRUNC(@var{r})
9980 Returns the integral part of @var{r}.
9982 @item TSIZE(@var{x})
9983 Returns the size of its argument. @var{x} can be a variable or a type.
9985 @item VAL(@var{t},@var{i})
9986 Returns the member of the type @var{t} whose ordinal value is @var{i}.
9990 @emph{Warning:} Sets and their operations are not yet supported, so
9991 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
9995 @cindex Modula-2 constants
9997 @subsubsection Constants
9999 @value{GDBN} allows you to express the constants of Modula-2 in the following
10005 Integer constants are simply a sequence of digits. When used in an
10006 expression, a constant is interpreted to be type-compatible with the
10007 rest of the expression. Hexadecimal integers are specified by a
10008 trailing @samp{H}, and octal integers by a trailing @samp{B}.
10011 Floating point constants appear as a sequence of digits, followed by a
10012 decimal point and another sequence of digits. An optional exponent can
10013 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
10014 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
10015 digits of the floating point constant must be valid decimal (base 10)
10019 Character constants consist of a single character enclosed by a pair of
10020 like quotes, either single (@code{'}) or double (@code{"}). They may
10021 also be expressed by their ordinal value (their @sc{ascii} value, usually)
10022 followed by a @samp{C}.
10025 String constants consist of a sequence of characters enclosed by a
10026 pair of like quotes, either single (@code{'}) or double (@code{"}).
10027 Escape sequences in the style of C are also allowed. @xref{C
10028 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
10032 Enumerated constants consist of an enumerated identifier.
10035 Boolean constants consist of the identifiers @code{TRUE} and
10039 Pointer constants consist of integral values only.
10042 Set constants are not yet supported.
10046 @subsubsection Modula-2 Types
10047 @cindex Modula-2 types
10049 Currently @value{GDBN} can print the following data types in Modula-2
10050 syntax: array types, record types, set types, pointer types, procedure
10051 types, enumerated types, subrange types and base types. You can also
10052 print the contents of variables declared using these type.
10053 This section gives a number of simple source code examples together with
10054 sample @value{GDBN} sessions.
10056 The first example contains the following section of code:
10065 and you can request @value{GDBN} to interrogate the type and value of
10066 @code{r} and @code{s}.
10069 (@value{GDBP}) print s
10071 (@value{GDBP}) ptype s
10073 (@value{GDBP}) print r
10075 (@value{GDBP}) ptype r
10080 Likewise if your source code declares @code{s} as:
10084 s: SET ['A'..'Z'] ;
10088 then you may query the type of @code{s} by:
10091 (@value{GDBP}) ptype s
10092 type = SET ['A'..'Z']
10096 Note that at present you cannot interactively manipulate set
10097 expressions using the debugger.
10099 The following example shows how you might declare an array in Modula-2
10100 and how you can interact with @value{GDBN} to print its type and contents:
10104 s: ARRAY [-10..10] OF CHAR ;
10108 (@value{GDBP}) ptype s
10109 ARRAY [-10..10] OF CHAR
10112 Note that the array handling is not yet complete and although the type
10113 is printed correctly, expression handling still assumes that all
10114 arrays have a lower bound of zero and not @code{-10} as in the example
10117 Here are some more type related Modula-2 examples:
10121 colour = (blue, red, yellow, green) ;
10122 t = [blue..yellow] ;
10130 The @value{GDBN} interaction shows how you can query the data type
10131 and value of a variable.
10134 (@value{GDBP}) print s
10136 (@value{GDBP}) ptype t
10137 type = [blue..yellow]
10141 In this example a Modula-2 array is declared and its contents
10142 displayed. Observe that the contents are written in the same way as
10143 their @code{C} counterparts.
10147 s: ARRAY [1..5] OF CARDINAL ;
10153 (@value{GDBP}) print s
10154 $1 = @{1, 0, 0, 0, 0@}
10155 (@value{GDBP}) ptype s
10156 type = ARRAY [1..5] OF CARDINAL
10159 The Modula-2 language interface to @value{GDBN} also understands
10160 pointer types as shown in this example:
10164 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
10171 and you can request that @value{GDBN} describes the type of @code{s}.
10174 (@value{GDBP}) ptype s
10175 type = POINTER TO ARRAY [1..5] OF CARDINAL
10178 @value{GDBN} handles compound types as we can see in this example.
10179 Here we combine array types, record types, pointer types and subrange
10190 myarray = ARRAY myrange OF CARDINAL ;
10191 myrange = [-2..2] ;
10193 s: POINTER TO ARRAY myrange OF foo ;
10197 and you can ask @value{GDBN} to describe the type of @code{s} as shown
10201 (@value{GDBP}) ptype s
10202 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
10205 f3 : ARRAY [-2..2] OF CARDINAL;
10210 @subsubsection Modula-2 Defaults
10211 @cindex Modula-2 defaults
10213 If type and range checking are set automatically by @value{GDBN}, they
10214 both default to @code{on} whenever the working language changes to
10215 Modula-2. This happens regardless of whether you or @value{GDBN}
10216 selected the working language.
10218 If you allow @value{GDBN} to set the language automatically, then entering
10219 code compiled from a file whose name ends with @file{.mod} sets the
10220 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
10221 Infer the Source Language}, for further details.
10224 @subsubsection Deviations from Standard Modula-2
10225 @cindex Modula-2, deviations from
10227 A few changes have been made to make Modula-2 programs easier to debug.
10228 This is done primarily via loosening its type strictness:
10232 Unlike in standard Modula-2, pointer constants can be formed by
10233 integers. This allows you to modify pointer variables during
10234 debugging. (In standard Modula-2, the actual address contained in a
10235 pointer variable is hidden from you; it can only be modified
10236 through direct assignment to another pointer variable or expression that
10237 returned a pointer.)
10240 C escape sequences can be used in strings and characters to represent
10241 non-printable characters. @value{GDBN} prints out strings with these
10242 escape sequences embedded. Single non-printable characters are
10243 printed using the @samp{CHR(@var{nnn})} format.
10246 The assignment operator (@code{:=}) returns the value of its right-hand
10250 All built-in procedures both modify @emph{and} return their argument.
10254 @subsubsection Modula-2 Type and Range Checks
10255 @cindex Modula-2 checks
10258 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
10261 @c FIXME remove warning when type/range checks added
10263 @value{GDBN} considers two Modula-2 variables type equivalent if:
10267 They are of types that have been declared equivalent via a @code{TYPE
10268 @var{t1} = @var{t2}} statement
10271 They have been declared on the same line. (Note: This is true of the
10272 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
10275 As long as type checking is enabled, any attempt to combine variables
10276 whose types are not equivalent is an error.
10278 Range checking is done on all mathematical operations, assignment, array
10279 index bounds, and all built-in functions and procedures.
10282 @subsubsection The Scope Operators @code{::} and @code{.}
10284 @cindex @code{.}, Modula-2 scope operator
10285 @cindex colon, doubled as scope operator
10287 @vindex colon-colon@r{, in Modula-2}
10288 @c Info cannot handle :: but TeX can.
10291 @vindex ::@r{, in Modula-2}
10294 There are a few subtle differences between the Modula-2 scope operator
10295 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
10300 @var{module} . @var{id}
10301 @var{scope} :: @var{id}
10305 where @var{scope} is the name of a module or a procedure,
10306 @var{module} the name of a module, and @var{id} is any declared
10307 identifier within your program, except another module.
10309 Using the @code{::} operator makes @value{GDBN} search the scope
10310 specified by @var{scope} for the identifier @var{id}. If it is not
10311 found in the specified scope, then @value{GDBN} searches all scopes
10312 enclosing the one specified by @var{scope}.
10314 Using the @code{.} operator makes @value{GDBN} search the current scope for
10315 the identifier specified by @var{id} that was imported from the
10316 definition module specified by @var{module}. With this operator, it is
10317 an error if the identifier @var{id} was not imported from definition
10318 module @var{module}, or if @var{id} is not an identifier in
10322 @subsubsection @value{GDBN} and Modula-2
10324 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
10325 Five subcommands of @code{set print} and @code{show print} apply
10326 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
10327 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
10328 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
10329 analogue in Modula-2.
10331 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
10332 with any language, is not useful with Modula-2. Its
10333 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
10334 created in Modula-2 as they can in C or C@t{++}. However, because an
10335 address can be specified by an integral constant, the construct
10336 @samp{@{@var{type}@}@var{adrexp}} is still useful.
10338 @cindex @code{#} in Modula-2
10339 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
10340 interpreted as the beginning of a comment. Use @code{<>} instead.
10346 The extensions made to @value{GDBN} for Ada only support
10347 output from the @sc{gnu} Ada (GNAT) compiler.
10348 Other Ada compilers are not currently supported, and
10349 attempting to debug executables produced by them is most likely
10353 @cindex expressions in Ada
10355 * Ada Mode Intro:: General remarks on the Ada syntax
10356 and semantics supported by Ada mode
10358 * Omissions from Ada:: Restrictions on the Ada expression syntax.
10359 * Additions to Ada:: Extensions of the Ada expression syntax.
10360 * Stopping Before Main Program:: Debugging the program during elaboration.
10361 * Ada Glitches:: Known peculiarities of Ada mode.
10364 @node Ada Mode Intro
10365 @subsubsection Introduction
10366 @cindex Ada mode, general
10368 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
10369 syntax, with some extensions.
10370 The philosophy behind the design of this subset is
10374 That @value{GDBN} should provide basic literals and access to operations for
10375 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
10376 leaving more sophisticated computations to subprograms written into the
10377 program (which therefore may be called from @value{GDBN}).
10380 That type safety and strict adherence to Ada language restrictions
10381 are not particularly important to the @value{GDBN} user.
10384 That brevity is important to the @value{GDBN} user.
10387 Thus, for brevity, the debugger acts as if there were
10388 implicit @code{with} and @code{use} clauses in effect for all user-written
10389 packages, making it unnecessary to fully qualify most names with
10390 their packages, regardless of context. Where this causes ambiguity,
10391 @value{GDBN} asks the user's intent.
10393 The debugger will start in Ada mode if it detects an Ada main program.
10394 As for other languages, it will enter Ada mode when stopped in a program that
10395 was translated from an Ada source file.
10397 While in Ada mode, you may use `@t{--}' for comments. This is useful
10398 mostly for documenting command files. The standard @value{GDBN} comment
10399 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
10400 middle (to allow based literals).
10402 The debugger supports limited overloading. Given a subprogram call in which
10403 the function symbol has multiple definitions, it will use the number of
10404 actual parameters and some information about their types to attempt to narrow
10405 the set of definitions. It also makes very limited use of context, preferring
10406 procedures to functions in the context of the @code{call} command, and
10407 functions to procedures elsewhere.
10409 @node Omissions from Ada
10410 @subsubsection Omissions from Ada
10411 @cindex Ada, omissions from
10413 Here are the notable omissions from the subset:
10417 Only a subset of the attributes are supported:
10421 @t{'First}, @t{'Last}, and @t{'Length}
10422 on array objects (not on types and subtypes).
10425 @t{'Min} and @t{'Max}.
10428 @t{'Pos} and @t{'Val}.
10434 @t{'Range} on array objects (not subtypes), but only as the right
10435 operand of the membership (@code{in}) operator.
10438 @t{'Access}, @t{'Unchecked_Access}, and
10439 @t{'Unrestricted_Access} (a GNAT extension).
10447 @code{Characters.Latin_1} are not available and
10448 concatenation is not implemented. Thus, escape characters in strings are
10449 not currently available.
10452 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
10453 equality of representations. They will generally work correctly
10454 for strings and arrays whose elements have integer or enumeration types.
10455 They may not work correctly for arrays whose element
10456 types have user-defined equality, for arrays of real values
10457 (in particular, IEEE-conformant floating point, because of negative
10458 zeroes and NaNs), and for arrays whose elements contain unused bits with
10459 indeterminate values.
10462 The other component-by-component array operations (@code{and}, @code{or},
10463 @code{xor}, @code{not}, and relational tests other than equality)
10464 are not implemented.
10467 @cindex array aggregates (Ada)
10468 @cindex record aggregates (Ada)
10469 @cindex aggregates (Ada)
10470 There is limited support for array and record aggregates. They are
10471 permitted only on the right sides of assignments, as in these examples:
10474 set An_Array := (1, 2, 3, 4, 5, 6)
10475 set An_Array := (1, others => 0)
10476 set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
10477 set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
10478 set A_Record := (1, "Peter", True);
10479 set A_Record := (Name => "Peter", Id => 1, Alive => True)
10483 discriminant's value by assigning an aggregate has an
10484 undefined effect if that discriminant is used within the record.
10485 However, you can first modify discriminants by directly assigning to
10486 them (which normally would not be allowed in Ada), and then performing an
10487 aggregate assignment. For example, given a variable @code{A_Rec}
10488 declared to have a type such as:
10491 type Rec (Len : Small_Integer := 0) is record
10493 Vals : IntArray (1 .. Len);
10497 you can assign a value with a different size of @code{Vals} with two
10502 set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
10505 As this example also illustrates, @value{GDBN} is very loose about the usual
10506 rules concerning aggregates. You may leave out some of the
10507 components of an array or record aggregate (such as the @code{Len}
10508 component in the assignment to @code{A_Rec} above); they will retain their
10509 original values upon assignment. You may freely use dynamic values as
10510 indices in component associations. You may even use overlapping or
10511 redundant component associations, although which component values are
10512 assigned in such cases is not defined.
10515 Calls to dispatching subprograms are not implemented.
10518 The overloading algorithm is much more limited (i.e., less selective)
10519 than that of real Ada. It makes only limited use of the context in
10520 which a subexpression appears to resolve its meaning, and it is much
10521 looser in its rules for allowing type matches. As a result, some
10522 function calls will be ambiguous, and the user will be asked to choose
10523 the proper resolution.
10526 The @code{new} operator is not implemented.
10529 Entry calls are not implemented.
10532 Aside from printing, arithmetic operations on the native VAX floating-point
10533 formats are not supported.
10536 It is not possible to slice a packed array.
10539 @node Additions to Ada
10540 @subsubsection Additions to Ada
10541 @cindex Ada, deviations from
10543 As it does for other languages, @value{GDBN} makes certain generic
10544 extensions to Ada (@pxref{Expressions}):
10548 If the expression @var{E} is a variable residing in memory (typically
10549 a local variable or array element) and @var{N} is a positive integer,
10550 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
10551 @var{N}-1 adjacent variables following it in memory as an array. In
10552 Ada, this operator is generally not necessary, since its prime use is
10553 in displaying parts of an array, and slicing will usually do this in
10554 Ada. However, there are occasional uses when debugging programs in
10555 which certain debugging information has been optimized away.
10558 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
10559 appears in function or file @var{B}.'' When @var{B} is a file name,
10560 you must typically surround it in single quotes.
10563 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
10564 @var{type} that appears at address @var{addr}.''
10567 A name starting with @samp{$} is a convenience variable
10568 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
10571 In addition, @value{GDBN} provides a few other shortcuts and outright
10572 additions specific to Ada:
10576 The assignment statement is allowed as an expression, returning
10577 its right-hand operand as its value. Thus, you may enter
10581 print A(tmp := y + 1)
10585 The semicolon is allowed as an ``operator,'' returning as its value
10586 the value of its right-hand operand.
10587 This allows, for example,
10588 complex conditional breaks:
10592 condition 1 (report(i); k += 1; A(k) > 100)
10596 Rather than use catenation and symbolic character names to introduce special
10597 characters into strings, one may instead use a special bracket notation,
10598 which is also used to print strings. A sequence of characters of the form
10599 @samp{["@var{XX}"]} within a string or character literal denotes the
10600 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
10601 sequence of characters @samp{["""]} also denotes a single quotation mark
10602 in strings. For example,
10604 "One line.["0a"]Next line.["0a"]"
10607 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
10611 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
10612 @t{'Max} is optional (and is ignored in any case). For example, it is valid
10620 When printing arrays, @value{GDBN} uses positional notation when the
10621 array has a lower bound of 1, and uses a modified named notation otherwise.
10622 For example, a one-dimensional array of three integers with a lower bound
10623 of 3 might print as
10630 That is, in contrast to valid Ada, only the first component has a @code{=>}
10634 You may abbreviate attributes in expressions with any unique,
10635 multi-character subsequence of
10636 their names (an exact match gets preference).
10637 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
10638 in place of @t{a'length}.
10641 @cindex quoting Ada internal identifiers
10642 Since Ada is case-insensitive, the debugger normally maps identifiers you type
10643 to lower case. The GNAT compiler uses upper-case characters for
10644 some of its internal identifiers, which are normally of no interest to users.
10645 For the rare occasions when you actually have to look at them,
10646 enclose them in angle brackets to avoid the lower-case mapping.
10649 @value{GDBP} print <JMPBUF_SAVE>[0]
10653 Printing an object of class-wide type or dereferencing an
10654 access-to-class-wide value will display all the components of the object's
10655 specific type (as indicated by its run-time tag). Likewise, component
10656 selection on such a value will operate on the specific type of the
10661 @node Stopping Before Main Program
10662 @subsubsection Stopping at the Very Beginning
10664 @cindex breakpointing Ada elaboration code
10665 It is sometimes necessary to debug the program during elaboration, and
10666 before reaching the main procedure.
10667 As defined in the Ada Reference
10668 Manual, the elaboration code is invoked from a procedure called
10669 @code{adainit}. To run your program up to the beginning of
10670 elaboration, simply use the following two commands:
10671 @code{tbreak adainit} and @code{run}.
10674 @subsubsection Known Peculiarities of Ada Mode
10675 @cindex Ada, problems
10677 Besides the omissions listed previously (@pxref{Omissions from Ada}),
10678 we know of several problems with and limitations of Ada mode in
10680 some of which will be fixed with planned future releases of the debugger
10681 and the GNU Ada compiler.
10685 Currently, the debugger
10686 has insufficient information to determine whether certain pointers represent
10687 pointers to objects or the objects themselves.
10688 Thus, the user may have to tack an extra @code{.all} after an expression
10689 to get it printed properly.
10692 Static constants that the compiler chooses not to materialize as objects in
10693 storage are invisible to the debugger.
10696 Named parameter associations in function argument lists are ignored (the
10697 argument lists are treated as positional).
10700 Many useful library packages are currently invisible to the debugger.
10703 Fixed-point arithmetic, conversions, input, and output is carried out using
10704 floating-point arithmetic, and may give results that only approximate those on
10708 The type of the @t{'Address} attribute may not be @code{System.Address}.
10711 The GNAT compiler never generates the prefix @code{Standard} for any of
10712 the standard symbols defined by the Ada language. @value{GDBN} knows about
10713 this: it will strip the prefix from names when you use it, and will never
10714 look for a name you have so qualified among local symbols, nor match against
10715 symbols in other packages or subprograms. If you have
10716 defined entities anywhere in your program other than parameters and
10717 local variables whose simple names match names in @code{Standard},
10718 GNAT's lack of qualification here can cause confusion. When this happens,
10719 you can usually resolve the confusion
10720 by qualifying the problematic names with package
10721 @code{Standard} explicitly.
10724 @node Unsupported Languages
10725 @section Unsupported Languages
10727 @cindex unsupported languages
10728 @cindex minimal language
10729 In addition to the other fully-supported programming languages,
10730 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
10731 It does not represent a real programming language, but provides a set
10732 of capabilities close to what the C or assembly languages provide.
10733 This should allow most simple operations to be performed while debugging
10734 an application that uses a language currently not supported by @value{GDBN}.
10736 If the language is set to @code{auto}, @value{GDBN} will automatically
10737 select this language if the current frame corresponds to an unsupported
10741 @chapter Examining the Symbol Table
10743 The commands described in this chapter allow you to inquire about the
10744 symbols (names of variables, functions and types) defined in your
10745 program. This information is inherent in the text of your program and
10746 does not change as your program executes. @value{GDBN} finds it in your
10747 program's symbol table, in the file indicated when you started @value{GDBN}
10748 (@pxref{File Options, ,Choosing Files}), or by one of the
10749 file-management commands (@pxref{Files, ,Commands to Specify Files}).
10751 @cindex symbol names
10752 @cindex names of symbols
10753 @cindex quoting names
10754 Occasionally, you may need to refer to symbols that contain unusual
10755 characters, which @value{GDBN} ordinarily treats as word delimiters. The
10756 most frequent case is in referring to static variables in other
10757 source files (@pxref{Variables,,Program Variables}). File names
10758 are recorded in object files as debugging symbols, but @value{GDBN} would
10759 ordinarily parse a typical file name, like @file{foo.c}, as the three words
10760 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
10761 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
10768 looks up the value of @code{x} in the scope of the file @file{foo.c}.
10771 @cindex case-insensitive symbol names
10772 @cindex case sensitivity in symbol names
10773 @kindex set case-sensitive
10774 @item set case-sensitive on
10775 @itemx set case-sensitive off
10776 @itemx set case-sensitive auto
10777 Normally, when @value{GDBN} looks up symbols, it matches their names
10778 with case sensitivity determined by the current source language.
10779 Occasionally, you may wish to control that. The command @code{set
10780 case-sensitive} lets you do that by specifying @code{on} for
10781 case-sensitive matches or @code{off} for case-insensitive ones. If
10782 you specify @code{auto}, case sensitivity is reset to the default
10783 suitable for the source language. The default is case-sensitive
10784 matches for all languages except for Fortran, for which the default is
10785 case-insensitive matches.
10787 @kindex show case-sensitive
10788 @item show case-sensitive
10789 This command shows the current setting of case sensitivity for symbols
10792 @kindex info address
10793 @cindex address of a symbol
10794 @item info address @var{symbol}
10795 Describe where the data for @var{symbol} is stored. For a register
10796 variable, this says which register it is kept in. For a non-register
10797 local variable, this prints the stack-frame offset at which the variable
10800 Note the contrast with @samp{print &@var{symbol}}, which does not work
10801 at all for a register variable, and for a stack local variable prints
10802 the exact address of the current instantiation of the variable.
10804 @kindex info symbol
10805 @cindex symbol from address
10806 @cindex closest symbol and offset for an address
10807 @item info symbol @var{addr}
10808 Print the name of a symbol which is stored at the address @var{addr}.
10809 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
10810 nearest symbol and an offset from it:
10813 (@value{GDBP}) info symbol 0x54320
10814 _initialize_vx + 396 in section .text
10818 This is the opposite of the @code{info address} command. You can use
10819 it to find out the name of a variable or a function given its address.
10822 @item whatis [@var{arg}]
10823 Print the data type of @var{arg}, which can be either an expression or
10824 a data type. With no argument, print the data type of @code{$}, the
10825 last value in the value history. If @var{arg} is an expression, it is
10826 not actually evaluated, and any side-effecting operations (such as
10827 assignments or function calls) inside it do not take place. If
10828 @var{arg} is a type name, it may be the name of a type or typedef, or
10829 for C code it may have the form @samp{class @var{class-name}},
10830 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
10831 @samp{enum @var{enum-tag}}.
10832 @xref{Expressions, ,Expressions}.
10835 @item ptype [@var{arg}]
10836 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
10837 detailed description of the type, instead of just the name of the type.
10838 @xref{Expressions, ,Expressions}.
10840 For example, for this variable declaration:
10843 struct complex @{double real; double imag;@} v;
10847 the two commands give this output:
10851 (@value{GDBP}) whatis v
10852 type = struct complex
10853 (@value{GDBP}) ptype v
10854 type = struct complex @{
10862 As with @code{whatis}, using @code{ptype} without an argument refers to
10863 the type of @code{$}, the last value in the value history.
10865 @cindex incomplete type
10866 Sometimes, programs use opaque data types or incomplete specifications
10867 of complex data structure. If the debug information included in the
10868 program does not allow @value{GDBN} to display a full declaration of
10869 the data type, it will say @samp{<incomplete type>}. For example,
10870 given these declarations:
10874 struct foo *fooptr;
10878 but no definition for @code{struct foo} itself, @value{GDBN} will say:
10881 (@value{GDBP}) ptype foo
10882 $1 = <incomplete type>
10886 ``Incomplete type'' is C terminology for data types that are not
10887 completely specified.
10890 @item info types @var{regexp}
10892 Print a brief description of all types whose names match the regular
10893 expression @var{regexp} (or all types in your program, if you supply
10894 no argument). Each complete typename is matched as though it were a
10895 complete line; thus, @samp{i type value} gives information on all
10896 types in your program whose names include the string @code{value}, but
10897 @samp{i type ^value$} gives information only on types whose complete
10898 name is @code{value}.
10900 This command differs from @code{ptype} in two ways: first, like
10901 @code{whatis}, it does not print a detailed description; second, it
10902 lists all source files where a type is defined.
10905 @cindex local variables
10906 @item info scope @var{location}
10907 List all the variables local to a particular scope. This command
10908 accepts a @var{location} argument---a function name, a source line, or
10909 an address preceded by a @samp{*}, and prints all the variables local
10910 to the scope defined by that location. For example:
10913 (@value{GDBP}) @b{info scope command_line_handler}
10914 Scope for command_line_handler:
10915 Symbol rl is an argument at stack/frame offset 8, length 4.
10916 Symbol linebuffer is in static storage at address 0x150a18, length 4.
10917 Symbol linelength is in static storage at address 0x150a1c, length 4.
10918 Symbol p is a local variable in register $esi, length 4.
10919 Symbol p1 is a local variable in register $ebx, length 4.
10920 Symbol nline is a local variable in register $edx, length 4.
10921 Symbol repeat is a local variable at frame offset -8, length 4.
10925 This command is especially useful for determining what data to collect
10926 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
10929 @kindex info source
10931 Show information about the current source file---that is, the source file for
10932 the function containing the current point of execution:
10935 the name of the source file, and the directory containing it,
10937 the directory it was compiled in,
10939 its length, in lines,
10941 which programming language it is written in,
10943 whether the executable includes debugging information for that file, and
10944 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
10946 whether the debugging information includes information about
10947 preprocessor macros.
10951 @kindex info sources
10953 Print the names of all source files in your program for which there is
10954 debugging information, organized into two lists: files whose symbols
10955 have already been read, and files whose symbols will be read when needed.
10957 @kindex info functions
10958 @item info functions
10959 Print the names and data types of all defined functions.
10961 @item info functions @var{regexp}
10962 Print the names and data types of all defined functions
10963 whose names contain a match for regular expression @var{regexp}.
10964 Thus, @samp{info fun step} finds all functions whose names
10965 include @code{step}; @samp{info fun ^step} finds those whose names
10966 start with @code{step}. If a function name contains characters
10967 that conflict with the regular expression language (e.g.@:
10968 @samp{operator*()}), they may be quoted with a backslash.
10970 @kindex info variables
10971 @item info variables
10972 Print the names and data types of all variables that are declared
10973 outside of functions (i.e.@: excluding local variables).
10975 @item info variables @var{regexp}
10976 Print the names and data types of all variables (except for local
10977 variables) whose names contain a match for regular expression
10980 @kindex info classes
10981 @cindex Objective-C, classes and selectors
10983 @itemx info classes @var{regexp}
10984 Display all Objective-C classes in your program, or
10985 (with the @var{regexp} argument) all those matching a particular regular
10988 @kindex info selectors
10989 @item info selectors
10990 @itemx info selectors @var{regexp}
10991 Display all Objective-C selectors in your program, or
10992 (with the @var{regexp} argument) all those matching a particular regular
10996 This was never implemented.
10997 @kindex info methods
10999 @itemx info methods @var{regexp}
11000 The @code{info methods} command permits the user to examine all defined
11001 methods within C@t{++} program, or (with the @var{regexp} argument) a
11002 specific set of methods found in the various C@t{++} classes. Many
11003 C@t{++} classes provide a large number of methods. Thus, the output
11004 from the @code{ptype} command can be overwhelming and hard to use. The
11005 @code{info-methods} command filters the methods, printing only those
11006 which match the regular-expression @var{regexp}.
11009 @cindex reloading symbols
11010 Some systems allow individual object files that make up your program to
11011 be replaced without stopping and restarting your program. For example,
11012 in VxWorks you can simply recompile a defective object file and keep on
11013 running. If you are running on one of these systems, you can allow
11014 @value{GDBN} to reload the symbols for automatically relinked modules:
11017 @kindex set symbol-reloading
11018 @item set symbol-reloading on
11019 Replace symbol definitions for the corresponding source file when an
11020 object file with a particular name is seen again.
11022 @item set symbol-reloading off
11023 Do not replace symbol definitions when encountering object files of the
11024 same name more than once. This is the default state; if you are not
11025 running on a system that permits automatic relinking of modules, you
11026 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
11027 may discard symbols when linking large programs, that may contain
11028 several modules (from different directories or libraries) with the same
11031 @kindex show symbol-reloading
11032 @item show symbol-reloading
11033 Show the current @code{on} or @code{off} setting.
11036 @cindex opaque data types
11037 @kindex set opaque-type-resolution
11038 @item set opaque-type-resolution on
11039 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
11040 declared as a pointer to a @code{struct}, @code{class}, or
11041 @code{union}---for example, @code{struct MyType *}---that is used in one
11042 source file although the full declaration of @code{struct MyType} is in
11043 another source file. The default is on.
11045 A change in the setting of this subcommand will not take effect until
11046 the next time symbols for a file are loaded.
11048 @item set opaque-type-resolution off
11049 Tell @value{GDBN} not to resolve opaque types. In this case, the type
11050 is printed as follows:
11052 @{<no data fields>@}
11055 @kindex show opaque-type-resolution
11056 @item show opaque-type-resolution
11057 Show whether opaque types are resolved or not.
11059 @kindex maint print symbols
11060 @cindex symbol dump
11061 @kindex maint print psymbols
11062 @cindex partial symbol dump
11063 @item maint print symbols @var{filename}
11064 @itemx maint print psymbols @var{filename}
11065 @itemx maint print msymbols @var{filename}
11066 Write a dump of debugging symbol data into the file @var{filename}.
11067 These commands are used to debug the @value{GDBN} symbol-reading code. Only
11068 symbols with debugging data are included. If you use @samp{maint print
11069 symbols}, @value{GDBN} includes all the symbols for which it has already
11070 collected full details: that is, @var{filename} reflects symbols for
11071 only those files whose symbols @value{GDBN} has read. You can use the
11072 command @code{info sources} to find out which files these are. If you
11073 use @samp{maint print psymbols} instead, the dump shows information about
11074 symbols that @value{GDBN} only knows partially---that is, symbols defined in
11075 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
11076 @samp{maint print msymbols} dumps just the minimal symbol information
11077 required for each object file from which @value{GDBN} has read some symbols.
11078 @xref{Files, ,Commands to Specify Files}, for a discussion of how
11079 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
11081 @kindex maint info symtabs
11082 @kindex maint info psymtabs
11083 @cindex listing @value{GDBN}'s internal symbol tables
11084 @cindex symbol tables, listing @value{GDBN}'s internal
11085 @cindex full symbol tables, listing @value{GDBN}'s internal
11086 @cindex partial symbol tables, listing @value{GDBN}'s internal
11087 @item maint info symtabs @r{[} @var{regexp} @r{]}
11088 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
11090 List the @code{struct symtab} or @code{struct partial_symtab}
11091 structures whose names match @var{regexp}. If @var{regexp} is not
11092 given, list them all. The output includes expressions which you can
11093 copy into a @value{GDBN} debugging this one to examine a particular
11094 structure in more detail. For example:
11097 (@value{GDBP}) maint info psymtabs dwarf2read
11098 @{ objfile /home/gnu/build/gdb/gdb
11099 ((struct objfile *) 0x82e69d0)
11100 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
11101 ((struct partial_symtab *) 0x8474b10)
11104 text addresses 0x814d3c8 -- 0x8158074
11105 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
11106 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
11107 dependencies (none)
11110 (@value{GDBP}) maint info symtabs
11114 We see that there is one partial symbol table whose filename contains
11115 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
11116 and we see that @value{GDBN} has not read in any symtabs yet at all.
11117 If we set a breakpoint on a function, that will cause @value{GDBN} to
11118 read the symtab for the compilation unit containing that function:
11121 (@value{GDBP}) break dwarf2_psymtab_to_symtab
11122 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
11124 (@value{GDBP}) maint info symtabs
11125 @{ objfile /home/gnu/build/gdb/gdb
11126 ((struct objfile *) 0x82e69d0)
11127 @{ symtab /home/gnu/src/gdb/dwarf2read.c
11128 ((struct symtab *) 0x86c1f38)
11131 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
11132 debugformat DWARF 2
11141 @chapter Altering Execution
11143 Once you think you have found an error in your program, you might want to
11144 find out for certain whether correcting the apparent error would lead to
11145 correct results in the rest of the run. You can find the answer by
11146 experiment, using the @value{GDBN} features for altering execution of the
11149 For example, you can store new values into variables or memory
11150 locations, give your program a signal, restart it at a different
11151 address, or even return prematurely from a function.
11154 * Assignment:: Assignment to variables
11155 * Jumping:: Continuing at a different address
11156 * Signaling:: Giving your program a signal
11157 * Returning:: Returning from a function
11158 * Calling:: Calling your program's functions
11159 * Patching:: Patching your program
11163 @section Assignment to Variables
11166 @cindex setting variables
11167 To alter the value of a variable, evaluate an assignment expression.
11168 @xref{Expressions, ,Expressions}. For example,
11175 stores the value 4 into the variable @code{x}, and then prints the
11176 value of the assignment expression (which is 4).
11177 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
11178 information on operators in supported languages.
11180 @kindex set variable
11181 @cindex variables, setting
11182 If you are not interested in seeing the value of the assignment, use the
11183 @code{set} command instead of the @code{print} command. @code{set} is
11184 really the same as @code{print} except that the expression's value is
11185 not printed and is not put in the value history (@pxref{Value History,
11186 ,Value History}). The expression is evaluated only for its effects.
11188 If the beginning of the argument string of the @code{set} command
11189 appears identical to a @code{set} subcommand, use the @code{set
11190 variable} command instead of just @code{set}. This command is identical
11191 to @code{set} except for its lack of subcommands. For example, if your
11192 program has a variable @code{width}, you get an error if you try to set
11193 a new value with just @samp{set width=13}, because @value{GDBN} has the
11194 command @code{set width}:
11197 (@value{GDBP}) whatis width
11199 (@value{GDBP}) p width
11201 (@value{GDBP}) set width=47
11202 Invalid syntax in expression.
11206 The invalid expression, of course, is @samp{=47}. In
11207 order to actually set the program's variable @code{width}, use
11210 (@value{GDBP}) set var width=47
11213 Because the @code{set} command has many subcommands that can conflict
11214 with the names of program variables, it is a good idea to use the
11215 @code{set variable} command instead of just @code{set}. For example, if
11216 your program has a variable @code{g}, you run into problems if you try
11217 to set a new value with just @samp{set g=4}, because @value{GDBN} has
11218 the command @code{set gnutarget}, abbreviated @code{set g}:
11222 (@value{GDBP}) whatis g
11226 (@value{GDBP}) set g=4
11230 The program being debugged has been started already.
11231 Start it from the beginning? (y or n) y
11232 Starting program: /home/smith/cc_progs/a.out
11233 "/home/smith/cc_progs/a.out": can't open to read symbols:
11234 Invalid bfd target.
11235 (@value{GDBP}) show g
11236 The current BFD target is "=4".
11241 The program variable @code{g} did not change, and you silently set the
11242 @code{gnutarget} to an invalid value. In order to set the variable
11246 (@value{GDBP}) set var g=4
11249 @value{GDBN} allows more implicit conversions in assignments than C; you can
11250 freely store an integer value into a pointer variable or vice versa,
11251 and you can convert any structure to any other structure that is the
11252 same length or shorter.
11253 @comment FIXME: how do structs align/pad in these conversions?
11254 @comment /doc@cygnus.com 18dec1990
11256 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
11257 construct to generate a value of specified type at a specified address
11258 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
11259 to memory location @code{0x83040} as an integer (which implies a certain size
11260 and representation in memory), and
11263 set @{int@}0x83040 = 4
11267 stores the value 4 into that memory location.
11270 @section Continuing at a Different Address
11272 Ordinarily, when you continue your program, you do so at the place where
11273 it stopped, with the @code{continue} command. You can instead continue at
11274 an address of your own choosing, with the following commands:
11278 @item jump @var{linespec}
11279 Resume execution at line @var{linespec}. Execution stops again
11280 immediately if there is a breakpoint there. @xref{List, ,Printing
11281 Source Lines}, for a description of the different forms of
11282 @var{linespec}. It is common practice to use the @code{tbreak} command
11283 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
11286 The @code{jump} command does not change the current stack frame, or
11287 the stack pointer, or the contents of any memory location or any
11288 register other than the program counter. If line @var{linespec} is in
11289 a different function from the one currently executing, the results may
11290 be bizarre if the two functions expect different patterns of arguments or
11291 of local variables. For this reason, the @code{jump} command requests
11292 confirmation if the specified line is not in the function currently
11293 executing. However, even bizarre results are predictable if you are
11294 well acquainted with the machine-language code of your program.
11296 @item jump *@var{address}
11297 Resume execution at the instruction at address @var{address}.
11300 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
11301 On many systems, you can get much the same effect as the @code{jump}
11302 command by storing a new value into the register @code{$pc}. The
11303 difference is that this does not start your program running; it only
11304 changes the address of where it @emph{will} run when you continue. For
11312 makes the next @code{continue} command or stepping command execute at
11313 address @code{0x485}, rather than at the address where your program stopped.
11314 @xref{Continuing and Stepping, ,Continuing and Stepping}.
11316 The most common occasion to use the @code{jump} command is to back
11317 up---perhaps with more breakpoints set---over a portion of a program
11318 that has already executed, in order to examine its execution in more
11323 @section Giving your Program a Signal
11324 @cindex deliver a signal to a program
11328 @item signal @var{signal}
11329 Resume execution where your program stopped, but immediately give it the
11330 signal @var{signal}. @var{signal} can be the name or the number of a
11331 signal. For example, on many systems @code{signal 2} and @code{signal
11332 SIGINT} are both ways of sending an interrupt signal.
11334 Alternatively, if @var{signal} is zero, continue execution without
11335 giving a signal. This is useful when your program stopped on account of
11336 a signal and would ordinary see the signal when resumed with the
11337 @code{continue} command; @samp{signal 0} causes it to resume without a
11340 @code{signal} does not repeat when you press @key{RET} a second time
11341 after executing the command.
11345 Invoking the @code{signal} command is not the same as invoking the
11346 @code{kill} utility from the shell. Sending a signal with @code{kill}
11347 causes @value{GDBN} to decide what to do with the signal depending on
11348 the signal handling tables (@pxref{Signals}). The @code{signal} command
11349 passes the signal directly to your program.
11353 @section Returning from a Function
11356 @cindex returning from a function
11359 @itemx return @var{expression}
11360 You can cancel execution of a function call with the @code{return}
11361 command. If you give an
11362 @var{expression} argument, its value is used as the function's return
11366 When you use @code{return}, @value{GDBN} discards the selected stack frame
11367 (and all frames within it). You can think of this as making the
11368 discarded frame return prematurely. If you wish to specify a value to
11369 be returned, give that value as the argument to @code{return}.
11371 This pops the selected stack frame (@pxref{Selection, ,Selecting a
11372 Frame}), and any other frames inside of it, leaving its caller as the
11373 innermost remaining frame. That frame becomes selected. The
11374 specified value is stored in the registers used for returning values
11377 The @code{return} command does not resume execution; it leaves the
11378 program stopped in the state that would exist if the function had just
11379 returned. In contrast, the @code{finish} command (@pxref{Continuing
11380 and Stepping, ,Continuing and Stepping}) resumes execution until the
11381 selected stack frame returns naturally.
11384 @section Calling Program Functions
11387 @cindex calling functions
11388 @cindex inferior functions, calling
11389 @item print @var{expr}
11390 Evaluate the expression @var{expr} and display the resulting value.
11391 @var{expr} may include calls to functions in the program being
11395 @item call @var{expr}
11396 Evaluate the expression @var{expr} without displaying @code{void}
11399 You can use this variant of the @code{print} command if you want to
11400 execute a function from your program that does not return anything
11401 (a.k.a.@: @dfn{a void function}), but without cluttering the output
11402 with @code{void} returned values that @value{GDBN} will otherwise
11403 print. If the result is not void, it is printed and saved in the
11407 It is possible for the function you call via the @code{print} or
11408 @code{call} command to generate a signal (e.g., if there's a bug in
11409 the function, or if you passed it incorrect arguments). What happens
11410 in that case is controlled by the @code{set unwindonsignal} command.
11413 @item set unwindonsignal
11414 @kindex set unwindonsignal
11415 @cindex unwind stack in called functions
11416 @cindex call dummy stack unwinding
11417 Set unwinding of the stack if a signal is received while in a function
11418 that @value{GDBN} called in the program being debugged. If set to on,
11419 @value{GDBN} unwinds the stack it created for the call and restores
11420 the context to what it was before the call. If set to off (the
11421 default), @value{GDBN} stops in the frame where the signal was
11424 @item show unwindonsignal
11425 @kindex show unwindonsignal
11426 Show the current setting of stack unwinding in the functions called by
11430 @cindex weak alias functions
11431 Sometimes, a function you wish to call is actually a @dfn{weak alias}
11432 for another function. In such case, @value{GDBN} might not pick up
11433 the type information, including the types of the function arguments,
11434 which causes @value{GDBN} to call the inferior function incorrectly.
11435 As a result, the called function will function erroneously and may
11436 even crash. A solution to that is to use the name of the aliased
11440 @section Patching Programs
11442 @cindex patching binaries
11443 @cindex writing into executables
11444 @cindex writing into corefiles
11446 By default, @value{GDBN} opens the file containing your program's
11447 executable code (or the corefile) read-only. This prevents accidental
11448 alterations to machine code; but it also prevents you from intentionally
11449 patching your program's binary.
11451 If you'd like to be able to patch the binary, you can specify that
11452 explicitly with the @code{set write} command. For example, you might
11453 want to turn on internal debugging flags, or even to make emergency
11459 @itemx set write off
11460 If you specify @samp{set write on}, @value{GDBN} opens executable and
11461 core files for both reading and writing; if you specify @samp{set write
11462 off} (the default), @value{GDBN} opens them read-only.
11464 If you have already loaded a file, you must load it again (using the
11465 @code{exec-file} or @code{core-file} command) after changing @code{set
11466 write}, for your new setting to take effect.
11470 Display whether executable files and core files are opened for writing
11471 as well as reading.
11475 @chapter @value{GDBN} Files
11477 @value{GDBN} needs to know the file name of the program to be debugged,
11478 both in order to read its symbol table and in order to start your
11479 program. To debug a core dump of a previous run, you must also tell
11480 @value{GDBN} the name of the core dump file.
11483 * Files:: Commands to specify files
11484 * Separate Debug Files:: Debugging information in separate files
11485 * Symbol Errors:: Errors reading symbol files
11489 @section Commands to Specify Files
11491 @cindex symbol table
11492 @cindex core dump file
11494 You may want to specify executable and core dump file names. The usual
11495 way to do this is at start-up time, using the arguments to
11496 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
11497 Out of @value{GDBN}}).
11499 Occasionally it is necessary to change to a different file during a
11500 @value{GDBN} session. Or you may run @value{GDBN} and forget to
11501 specify a file you want to use. Or you are debugging a remote target
11502 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
11503 Program}). In these situations the @value{GDBN} commands to specify
11504 new files are useful.
11507 @cindex executable file
11509 @item file @var{filename}
11510 Use @var{filename} as the program to be debugged. It is read for its
11511 symbols and for the contents of pure memory. It is also the program
11512 executed when you use the @code{run} command. If you do not specify a
11513 directory and the file is not found in the @value{GDBN} working directory,
11514 @value{GDBN} uses the environment variable @code{PATH} as a list of
11515 directories to search, just as the shell does when looking for a program
11516 to run. You can change the value of this variable, for both @value{GDBN}
11517 and your program, using the @code{path} command.
11519 @cindex unlinked object files
11520 @cindex patching object files
11521 You can load unlinked object @file{.o} files into @value{GDBN} using
11522 the @code{file} command. You will not be able to ``run'' an object
11523 file, but you can disassemble functions and inspect variables. Also,
11524 if the underlying BFD functionality supports it, you could use
11525 @kbd{gdb -write} to patch object files using this technique. Note
11526 that @value{GDBN} can neither interpret nor modify relocations in this
11527 case, so branches and some initialized variables will appear to go to
11528 the wrong place. But this feature is still handy from time to time.
11531 @code{file} with no argument makes @value{GDBN} discard any information it
11532 has on both executable file and the symbol table.
11535 @item exec-file @r{[} @var{filename} @r{]}
11536 Specify that the program to be run (but not the symbol table) is found
11537 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
11538 if necessary to locate your program. Omitting @var{filename} means to
11539 discard information on the executable file.
11541 @kindex symbol-file
11542 @item symbol-file @r{[} @var{filename} @r{]}
11543 Read symbol table information from file @var{filename}. @code{PATH} is
11544 searched when necessary. Use the @code{file} command to get both symbol
11545 table and program to run from the same file.
11547 @code{symbol-file} with no argument clears out @value{GDBN} information on your
11548 program's symbol table.
11550 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
11551 some breakpoints and auto-display expressions. This is because they may
11552 contain pointers to the internal data recording symbols and data types,
11553 which are part of the old symbol table data being discarded inside
11556 @code{symbol-file} does not repeat if you press @key{RET} again after
11559 When @value{GDBN} is configured for a particular environment, it
11560 understands debugging information in whatever format is the standard
11561 generated for that environment; you may use either a @sc{gnu} compiler, or
11562 other compilers that adhere to the local conventions.
11563 Best results are usually obtained from @sc{gnu} compilers; for example,
11564 using @code{@value{NGCC}} you can generate debugging information for
11567 For most kinds of object files, with the exception of old SVR3 systems
11568 using COFF, the @code{symbol-file} command does not normally read the
11569 symbol table in full right away. Instead, it scans the symbol table
11570 quickly to find which source files and which symbols are present. The
11571 details are read later, one source file at a time, as they are needed.
11573 The purpose of this two-stage reading strategy is to make @value{GDBN}
11574 start up faster. For the most part, it is invisible except for
11575 occasional pauses while the symbol table details for a particular source
11576 file are being read. (The @code{set verbose} command can turn these
11577 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
11578 Warnings and Messages}.)
11580 We have not implemented the two-stage strategy for COFF yet. When the
11581 symbol table is stored in COFF format, @code{symbol-file} reads the
11582 symbol table data in full right away. Note that ``stabs-in-COFF''
11583 still does the two-stage strategy, since the debug info is actually
11587 @cindex reading symbols immediately
11588 @cindex symbols, reading immediately
11589 @item symbol-file @var{filename} @r{[} -readnow @r{]}
11590 @itemx file @var{filename} @r{[} -readnow @r{]}
11591 You can override the @value{GDBN} two-stage strategy for reading symbol
11592 tables by using the @samp{-readnow} option with any of the commands that
11593 load symbol table information, if you want to be sure @value{GDBN} has the
11594 entire symbol table available.
11596 @c FIXME: for now no mention of directories, since this seems to be in
11597 @c flux. 13mar1992 status is that in theory GDB would look either in
11598 @c current dir or in same dir as myprog; but issues like competing
11599 @c GDB's, or clutter in system dirs, mean that in practice right now
11600 @c only current dir is used. FFish says maybe a special GDB hierarchy
11601 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
11605 @item core-file @r{[}@var{filename}@r{]}
11607 Specify the whereabouts of a core dump file to be used as the ``contents
11608 of memory''. Traditionally, core files contain only some parts of the
11609 address space of the process that generated them; @value{GDBN} can access the
11610 executable file itself for other parts.
11612 @code{core-file} with no argument specifies that no core file is
11615 Note that the core file is ignored when your program is actually running
11616 under @value{GDBN}. So, if you have been running your program and you
11617 wish to debug a core file instead, you must kill the subprocess in which
11618 the program is running. To do this, use the @code{kill} command
11619 (@pxref{Kill Process, ,Killing the Child Process}).
11621 @kindex add-symbol-file
11622 @cindex dynamic linking
11623 @item add-symbol-file @var{filename} @var{address}
11624 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
11625 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
11626 The @code{add-symbol-file} command reads additional symbol table
11627 information from the file @var{filename}. You would use this command
11628 when @var{filename} has been dynamically loaded (by some other means)
11629 into the program that is running. @var{address} should be the memory
11630 address at which the file has been loaded; @value{GDBN} cannot figure
11631 this out for itself. You can additionally specify an arbitrary number
11632 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
11633 section name and base address for that section. You can specify any
11634 @var{address} as an expression.
11636 The symbol table of the file @var{filename} is added to the symbol table
11637 originally read with the @code{symbol-file} command. You can use the
11638 @code{add-symbol-file} command any number of times; the new symbol data
11639 thus read keeps adding to the old. To discard all old symbol data
11640 instead, use the @code{symbol-file} command without any arguments.
11642 @cindex relocatable object files, reading symbols from
11643 @cindex object files, relocatable, reading symbols from
11644 @cindex reading symbols from relocatable object files
11645 @cindex symbols, reading from relocatable object files
11646 @cindex @file{.o} files, reading symbols from
11647 Although @var{filename} is typically a shared library file, an
11648 executable file, or some other object file which has been fully
11649 relocated for loading into a process, you can also load symbolic
11650 information from relocatable @file{.o} files, as long as:
11654 the file's symbolic information refers only to linker symbols defined in
11655 that file, not to symbols defined by other object files,
11657 every section the file's symbolic information refers to has actually
11658 been loaded into the inferior, as it appears in the file, and
11660 you can determine the address at which every section was loaded, and
11661 provide these to the @code{add-symbol-file} command.
11665 Some embedded operating systems, like Sun Chorus and VxWorks, can load
11666 relocatable files into an already running program; such systems
11667 typically make the requirements above easy to meet. However, it's
11668 important to recognize that many native systems use complex link
11669 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
11670 assembly, for example) that make the requirements difficult to meet. In
11671 general, one cannot assume that using @code{add-symbol-file} to read a
11672 relocatable object file's symbolic information will have the same effect
11673 as linking the relocatable object file into the program in the normal
11676 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
11678 @kindex add-symbol-file-from-memory
11679 @cindex @code{syscall DSO}
11680 @cindex load symbols from memory
11681 @item add-symbol-file-from-memory @var{address}
11682 Load symbols from the given @var{address} in a dynamically loaded
11683 object file whose image is mapped directly into the inferior's memory.
11684 For example, the Linux kernel maps a @code{syscall DSO} into each
11685 process's address space; this DSO provides kernel-specific code for
11686 some system calls. The argument can be any expression whose
11687 evaluation yields the address of the file's shared object file header.
11688 For this command to work, you must have used @code{symbol-file} or
11689 @code{exec-file} commands in advance.
11691 @kindex add-shared-symbol-files
11693 @item add-shared-symbol-files @var{library-file}
11694 @itemx assf @var{library-file}
11695 The @code{add-shared-symbol-files} command can currently be used only
11696 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
11697 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
11698 @value{GDBN} automatically looks for shared libraries, however if
11699 @value{GDBN} does not find yours, you can invoke
11700 @code{add-shared-symbol-files}. It takes one argument: the shared
11701 library's file name. @code{assf} is a shorthand alias for
11702 @code{add-shared-symbol-files}.
11705 @item section @var{section} @var{addr}
11706 The @code{section} command changes the base address of the named
11707 @var{section} of the exec file to @var{addr}. This can be used if the
11708 exec file does not contain section addresses, (such as in the
11709 @code{a.out} format), or when the addresses specified in the file
11710 itself are wrong. Each section must be changed separately. The
11711 @code{info files} command, described below, lists all the sections and
11715 @kindex info target
11718 @code{info files} and @code{info target} are synonymous; both print the
11719 current target (@pxref{Targets, ,Specifying a Debugging Target}),
11720 including the names of the executable and core dump files currently in
11721 use by @value{GDBN}, and the files from which symbols were loaded. The
11722 command @code{help target} lists all possible targets rather than
11725 @kindex maint info sections
11726 @item maint info sections
11727 Another command that can give you extra information about program sections
11728 is @code{maint info sections}. In addition to the section information
11729 displayed by @code{info files}, this command displays the flags and file
11730 offset of each section in the executable and core dump files. In addition,
11731 @code{maint info sections} provides the following command options (which
11732 may be arbitrarily combined):
11736 Display sections for all loaded object files, including shared libraries.
11737 @item @var{sections}
11738 Display info only for named @var{sections}.
11739 @item @var{section-flags}
11740 Display info only for sections for which @var{section-flags} are true.
11741 The section flags that @value{GDBN} currently knows about are:
11744 Section will have space allocated in the process when loaded.
11745 Set for all sections except those containing debug information.
11747 Section will be loaded from the file into the child process memory.
11748 Set for pre-initialized code and data, clear for @code{.bss} sections.
11750 Section needs to be relocated before loading.
11752 Section cannot be modified by the child process.
11754 Section contains executable code only.
11756 Section contains data only (no executable code).
11758 Section will reside in ROM.
11760 Section contains data for constructor/destructor lists.
11762 Section is not empty.
11764 An instruction to the linker to not output the section.
11765 @item COFF_SHARED_LIBRARY
11766 A notification to the linker that the section contains
11767 COFF shared library information.
11769 Section contains common symbols.
11772 @kindex set trust-readonly-sections
11773 @cindex read-only sections
11774 @item set trust-readonly-sections on
11775 Tell @value{GDBN} that readonly sections in your object file
11776 really are read-only (i.e.@: that their contents will not change).
11777 In that case, @value{GDBN} can fetch values from these sections
11778 out of the object file, rather than from the target program.
11779 For some targets (notably embedded ones), this can be a significant
11780 enhancement to debugging performance.
11782 The default is off.
11784 @item set trust-readonly-sections off
11785 Tell @value{GDBN} not to trust readonly sections. This means that
11786 the contents of the section might change while the program is running,
11787 and must therefore be fetched from the target when needed.
11789 @item show trust-readonly-sections
11790 Show the current setting of trusting readonly sections.
11793 All file-specifying commands allow both absolute and relative file names
11794 as arguments. @value{GDBN} always converts the file name to an absolute file
11795 name and remembers it that way.
11797 @cindex shared libraries
11798 @anchor{Shared Libraries}
11799 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
11800 and IBM RS/6000 AIX shared libraries.
11802 On MS-Windows @value{GDBN} must be linked with the Expat library to support
11803 shared libraries. @xref{Expat}.
11805 @value{GDBN} automatically loads symbol definitions from shared libraries
11806 when you use the @code{run} command, or when you examine a core file.
11807 (Before you issue the @code{run} command, @value{GDBN} does not understand
11808 references to a function in a shared library, however---unless you are
11809 debugging a core file).
11811 On HP-UX, if the program loads a library explicitly, @value{GDBN}
11812 automatically loads the symbols at the time of the @code{shl_load} call.
11814 @c FIXME: some @value{GDBN} release may permit some refs to undef
11815 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
11816 @c FIXME...lib; check this from time to time when updating manual
11818 There are times, however, when you may wish to not automatically load
11819 symbol definitions from shared libraries, such as when they are
11820 particularly large or there are many of them.
11822 To control the automatic loading of shared library symbols, use the
11826 @kindex set auto-solib-add
11827 @item set auto-solib-add @var{mode}
11828 If @var{mode} is @code{on}, symbols from all shared object libraries
11829 will be loaded automatically when the inferior begins execution, you
11830 attach to an independently started inferior, or when the dynamic linker
11831 informs @value{GDBN} that a new library has been loaded. If @var{mode}
11832 is @code{off}, symbols must be loaded manually, using the
11833 @code{sharedlibrary} command. The default value is @code{on}.
11835 @cindex memory used for symbol tables
11836 If your program uses lots of shared libraries with debug info that
11837 takes large amounts of memory, you can decrease the @value{GDBN}
11838 memory footprint by preventing it from automatically loading the
11839 symbols from shared libraries. To that end, type @kbd{set
11840 auto-solib-add off} before running the inferior, then load each
11841 library whose debug symbols you do need with @kbd{sharedlibrary
11842 @var{regexp}}, where @var{regexp} is a regular expression that matches
11843 the libraries whose symbols you want to be loaded.
11845 @kindex show auto-solib-add
11846 @item show auto-solib-add
11847 Display the current autoloading mode.
11850 @cindex load shared library
11851 To explicitly load shared library symbols, use the @code{sharedlibrary}
11855 @kindex info sharedlibrary
11858 @itemx info sharedlibrary
11859 Print the names of the shared libraries which are currently loaded.
11861 @kindex sharedlibrary
11863 @item sharedlibrary @var{regex}
11864 @itemx share @var{regex}
11865 Load shared object library symbols for files matching a
11866 Unix regular expression.
11867 As with files loaded automatically, it only loads shared libraries
11868 required by your program for a core file or after typing @code{run}. If
11869 @var{regex} is omitted all shared libraries required by your program are
11872 @item nosharedlibrary
11873 @kindex nosharedlibrary
11874 @cindex unload symbols from shared libraries
11875 Unload all shared object library symbols. This discards all symbols
11876 that have been loaded from all shared libraries. Symbols from shared
11877 libraries that were loaded by explicit user requests are not
11881 Sometimes you may wish that @value{GDBN} stops and gives you control
11882 when any of shared library events happen. Use the @code{set
11883 stop-on-solib-events} command for this:
11886 @item set stop-on-solib-events
11887 @kindex set stop-on-solib-events
11888 This command controls whether @value{GDBN} should give you control
11889 when the dynamic linker notifies it about some shared library event.
11890 The most common event of interest is loading or unloading of a new
11893 @item show stop-on-solib-events
11894 @kindex show stop-on-solib-events
11895 Show whether @value{GDBN} stops and gives you control when shared
11896 library events happen.
11899 Shared libraries are also supported in many cross or remote debugging
11900 configurations. A copy of the target's libraries need to be present on the
11901 host system; they need to be the same as the target libraries, although the
11902 copies on the target can be stripped as long as the copies on the host are
11905 @cindex where to look for shared libraries
11906 For remote debugging, you need to tell @value{GDBN} where the target
11907 libraries are, so that it can load the correct copies---otherwise, it
11908 may try to load the host's libraries. @value{GDBN} has two variables
11909 to specify the search directories for target libraries.
11912 @cindex prefix for shared library file names
11913 @cindex system root, alternate
11914 @kindex set solib-absolute-prefix
11915 @kindex set sysroot
11916 @item set sysroot @var{path}
11917 Use @var{path} as the system root for the program being debugged. Any
11918 absolute shared library paths will be prefixed with @var{path}; many
11919 runtime loaders store the absolute paths to the shared library in the
11920 target program's memory. If you use @code{set sysroot} to find shared
11921 libraries, they need to be laid out in the same way that they are on
11922 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
11925 The @code{set solib-absolute-prefix} command is an alias for @code{set
11928 @cindex default system root
11929 @cindex @samp{--with-sysroot}
11930 You can set the default system root by using the configure-time
11931 @samp{--with-sysroot} option. If the system root is inside
11932 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
11933 @samp{--exec-prefix}), then the default system root will be updated
11934 automatically if the installed @value{GDBN} is moved to a new
11937 @kindex show sysroot
11939 Display the current shared library prefix.
11941 @kindex set solib-search-path
11942 @item set solib-search-path @var{path}
11943 If this variable is set, @var{path} is a colon-separated list of
11944 directories to search for shared libraries. @samp{solib-search-path}
11945 is used after @samp{sysroot} fails to locate the library, or if the
11946 path to the library is relative instead of absolute. If you want to
11947 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
11948 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
11949 finding your host's libraries. @samp{sysroot} is preferred; setting
11950 it to a nonexistent directory may interfere with automatic loading
11951 of shared library symbols.
11953 @kindex show solib-search-path
11954 @item show solib-search-path
11955 Display the current shared library search path.
11959 @node Separate Debug Files
11960 @section Debugging Information in Separate Files
11961 @cindex separate debugging information files
11962 @cindex debugging information in separate files
11963 @cindex @file{.debug} subdirectories
11964 @cindex debugging information directory, global
11965 @cindex global debugging information directory
11966 @cindex build ID, and separate debugging files
11967 @cindex @file{.build-id} directory
11969 @value{GDBN} allows you to put a program's debugging information in a
11970 file separate from the executable itself, in a way that allows
11971 @value{GDBN} to find and load the debugging information automatically.
11972 Since debugging information can be very large---sometimes larger
11973 than the executable code itself---some systems distribute debugging
11974 information for their executables in separate files, which users can
11975 install only when they need to debug a problem.
11977 @value{GDBN} supports two ways of specifying the separate debug info
11982 The executable contains a @dfn{debug link} that specifies the name of
11983 the separate debug info file. The separate debug file's name is
11984 usually @file{@var{executable}.debug}, where @var{executable} is the
11985 name of the corresponding executable file without leading directories
11986 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
11987 debug link specifies a CRC32 checksum for the debug file, which
11988 @value{GDBN} uses to validate that the executable and the debug file
11989 came from the same build.
11992 The executable contains a @dfn{build ID}, a unique bit string that is
11993 also present in the corresponding debug info file. (This is supported
11994 only on some operating systems, notably those which use the ELF format
11995 for binary files and the @sc{gnu} Binutils.) For more details about
11996 this feature, see the description of the @option{--build-id}
11997 command-line option in @ref{Options, , Command Line Options, ld.info,
11998 The GNU Linker}. The debug info file's name is not specified
11999 explicitly by the build ID, but can be computed from the build ID, see
12003 Depending on the way the debug info file is specified, @value{GDBN}
12004 uses two different methods of looking for the debug file:
12008 For the ``debug link'' method, @value{GDBN} looks up the named file in
12009 the directory of the executable file, then in a subdirectory of that
12010 directory named @file{.debug}, and finally under the global debug
12011 directory, in a subdirectory whose name is identical to the leading
12012 directories of the executable's absolute file name.
12015 For the ``build ID'' method, @value{GDBN} looks in the
12016 @file{.build-id} subdirectory of the global debug directory for a file
12017 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
12018 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
12019 are the rest of the bit string. (Real build ID strings are 32 or more
12020 hex characters, not 10.)
12023 So, for example, suppose you ask @value{GDBN} to debug
12024 @file{/usr/bin/ls}, which has a debug link that specifies the
12025 file @file{ls.debug}, and a build ID whose value in hex is
12026 @code{abcdef1234}. If the global debug directory is
12027 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
12028 debug information files, in the indicated order:
12032 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
12034 @file{/usr/bin/ls.debug}
12036 @file{/usr/bin/.debug/ls.debug}
12038 @file{/usr/lib/debug/usr/bin/ls.debug}.
12041 You can set the global debugging info directory's name, and view the
12042 name @value{GDBN} is currently using.
12046 @kindex set debug-file-directory
12047 @item set debug-file-directory @var{directory}
12048 Set the directory which @value{GDBN} searches for separate debugging
12049 information files to @var{directory}.
12051 @kindex show debug-file-directory
12052 @item show debug-file-directory
12053 Show the directory @value{GDBN} searches for separate debugging
12058 @cindex @code{.gnu_debuglink} sections
12059 @cindex debug link sections
12060 A debug link is a special section of the executable file named
12061 @code{.gnu_debuglink}. The section must contain:
12065 A filename, with any leading directory components removed, followed by
12068 zero to three bytes of padding, as needed to reach the next four-byte
12069 boundary within the section, and
12071 a four-byte CRC checksum, stored in the same endianness used for the
12072 executable file itself. The checksum is computed on the debugging
12073 information file's full contents by the function given below, passing
12074 zero as the @var{crc} argument.
12077 Any executable file format can carry a debug link, as long as it can
12078 contain a section named @code{.gnu_debuglink} with the contents
12081 @cindex @code{.note.gnu.build-id} sections
12082 @cindex build ID sections
12083 The build ID is a special section in the executable file (and in other
12084 ELF binary files that @value{GDBN} may consider). This section is
12085 often named @code{.note.gnu.build-id}, but that name is not mandatory.
12086 It contains unique identification for the built files---the ID remains
12087 the same across multiple builds of the same build tree. The default
12088 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
12089 content for the build ID string. The same section with an identical
12090 value is present in the original built binary with symbols, in its
12091 stripped variant, and in the separate debugging information file.
12093 The debugging information file itself should be an ordinary
12094 executable, containing a full set of linker symbols, sections, and
12095 debugging information. The sections of the debugging information file
12096 should have the same names, addresses, and sizes as the original file,
12097 but they need not contain any data---much like a @code{.bss} section
12098 in an ordinary executable.
12100 The @sc{gnu} binary utilities (Binutils) package includes the
12101 @samp{objcopy} utility that can produce
12102 the separated executable / debugging information file pairs using the
12103 following commands:
12106 @kbd{objcopy --only-keep-debug foo foo.debug}
12111 These commands remove the debugging
12112 information from the executable file @file{foo} and place it in the file
12113 @file{foo.debug}. You can use the first, second or both methods to link the
12118 The debug link method needs the following additional command to also leave
12119 behind a debug link in @file{foo}:
12122 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
12125 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
12126 a version of the @code{strip} command such that the command @kbd{strip foo -f
12127 foo.debug} has the same functionality as the two @code{objcopy} commands and
12128 the @code{ln -s} command above, together.
12131 Build ID gets embedded into the main executable using @code{ld --build-id} or
12132 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
12133 compatibility fixes for debug files separation are present in @sc{gnu} binary
12134 utilities (Binutils) package since version 2.18.
12139 Since there are many different ways to compute CRC's for the debug
12140 link (different polynomials, reversals, byte ordering, etc.), the
12141 simplest way to describe the CRC used in @code{.gnu_debuglink}
12142 sections is to give the complete code for a function that computes it:
12144 @kindex gnu_debuglink_crc32
12147 gnu_debuglink_crc32 (unsigned long crc,
12148 unsigned char *buf, size_t len)
12150 static const unsigned long crc32_table[256] =
12152 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
12153 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
12154 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
12155 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
12156 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
12157 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
12158 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
12159 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
12160 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
12161 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
12162 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
12163 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
12164 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
12165 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
12166 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
12167 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
12168 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
12169 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
12170 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
12171 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
12172 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
12173 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
12174 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
12175 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
12176 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
12177 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
12178 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
12179 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
12180 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
12181 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
12182 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
12183 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
12184 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
12185 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
12186 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
12187 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
12188 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
12189 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
12190 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
12191 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
12192 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
12193 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
12194 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
12195 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
12196 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
12197 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
12198 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
12199 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
12200 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
12201 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
12202 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
12205 unsigned char *end;
12207 crc = ~crc & 0xffffffff;
12208 for (end = buf + len; buf < end; ++buf)
12209 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
12210 return ~crc & 0xffffffff;
12215 This computation does not apply to the ``build ID'' method.
12218 @node Symbol Errors
12219 @section Errors Reading Symbol Files
12221 While reading a symbol file, @value{GDBN} occasionally encounters problems,
12222 such as symbol types it does not recognize, or known bugs in compiler
12223 output. By default, @value{GDBN} does not notify you of such problems, since
12224 they are relatively common and primarily of interest to people
12225 debugging compilers. If you are interested in seeing information
12226 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
12227 only one message about each such type of problem, no matter how many
12228 times the problem occurs; or you can ask @value{GDBN} to print more messages,
12229 to see how many times the problems occur, with the @code{set
12230 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
12233 The messages currently printed, and their meanings, include:
12236 @item inner block not inside outer block in @var{symbol}
12238 The symbol information shows where symbol scopes begin and end
12239 (such as at the start of a function or a block of statements). This
12240 error indicates that an inner scope block is not fully contained
12241 in its outer scope blocks.
12243 @value{GDBN} circumvents the problem by treating the inner block as if it had
12244 the same scope as the outer block. In the error message, @var{symbol}
12245 may be shown as ``@code{(don't know)}'' if the outer block is not a
12248 @item block at @var{address} out of order
12250 The symbol information for symbol scope blocks should occur in
12251 order of increasing addresses. This error indicates that it does not
12254 @value{GDBN} does not circumvent this problem, and has trouble
12255 locating symbols in the source file whose symbols it is reading. (You
12256 can often determine what source file is affected by specifying
12257 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
12260 @item bad block start address patched
12262 The symbol information for a symbol scope block has a start address
12263 smaller than the address of the preceding source line. This is known
12264 to occur in the SunOS 4.1.1 (and earlier) C compiler.
12266 @value{GDBN} circumvents the problem by treating the symbol scope block as
12267 starting on the previous source line.
12269 @item bad string table offset in symbol @var{n}
12272 Symbol number @var{n} contains a pointer into the string table which is
12273 larger than the size of the string table.
12275 @value{GDBN} circumvents the problem by considering the symbol to have the
12276 name @code{foo}, which may cause other problems if many symbols end up
12279 @item unknown symbol type @code{0x@var{nn}}
12281 The symbol information contains new data types that @value{GDBN} does
12282 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
12283 uncomprehended information, in hexadecimal.
12285 @value{GDBN} circumvents the error by ignoring this symbol information.
12286 This usually allows you to debug your program, though certain symbols
12287 are not accessible. If you encounter such a problem and feel like
12288 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
12289 on @code{complain}, then go up to the function @code{read_dbx_symtab}
12290 and examine @code{*bufp} to see the symbol.
12292 @item stub type has NULL name
12294 @value{GDBN} could not find the full definition for a struct or class.
12296 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
12297 The symbol information for a C@t{++} member function is missing some
12298 information that recent versions of the compiler should have output for
12301 @item info mismatch between compiler and debugger
12303 @value{GDBN} could not parse a type specification output by the compiler.
12308 @chapter Specifying a Debugging Target
12310 @cindex debugging target
12311 A @dfn{target} is the execution environment occupied by your program.
12313 Often, @value{GDBN} runs in the same host environment as your program;
12314 in that case, the debugging target is specified as a side effect when
12315 you use the @code{file} or @code{core} commands. When you need more
12316 flexibility---for example, running @value{GDBN} on a physically separate
12317 host, or controlling a standalone system over a serial port or a
12318 realtime system over a TCP/IP connection---you can use the @code{target}
12319 command to specify one of the target types configured for @value{GDBN}
12320 (@pxref{Target Commands, ,Commands for Managing Targets}).
12322 @cindex target architecture
12323 It is possible to build @value{GDBN} for several different @dfn{target
12324 architectures}. When @value{GDBN} is built like that, you can choose
12325 one of the available architectures with the @kbd{set architecture}
12329 @kindex set architecture
12330 @kindex show architecture
12331 @item set architecture @var{arch}
12332 This command sets the current target architecture to @var{arch}. The
12333 value of @var{arch} can be @code{"auto"}, in addition to one of the
12334 supported architectures.
12336 @item show architecture
12337 Show the current target architecture.
12339 @item set processor
12341 @kindex set processor
12342 @kindex show processor
12343 These are alias commands for, respectively, @code{set architecture}
12344 and @code{show architecture}.
12348 * Active Targets:: Active targets
12349 * Target Commands:: Commands for managing targets
12350 * Byte Order:: Choosing target byte order
12353 @node Active Targets
12354 @section Active Targets
12356 @cindex stacking targets
12357 @cindex active targets
12358 @cindex multiple targets
12360 There are three classes of targets: processes, core files, and
12361 executable files. @value{GDBN} can work concurrently on up to three
12362 active targets, one in each class. This allows you to (for example)
12363 start a process and inspect its activity without abandoning your work on
12366 For example, if you execute @samp{gdb a.out}, then the executable file
12367 @code{a.out} is the only active target. If you designate a core file as
12368 well---presumably from a prior run that crashed and coredumped---then
12369 @value{GDBN} has two active targets and uses them in tandem, looking
12370 first in the corefile target, then in the executable file, to satisfy
12371 requests for memory addresses. (Typically, these two classes of target
12372 are complementary, since core files contain only a program's
12373 read-write memory---variables and so on---plus machine status, while
12374 executable files contain only the program text and initialized data.)
12376 When you type @code{run}, your executable file becomes an active process
12377 target as well. When a process target is active, all @value{GDBN}
12378 commands requesting memory addresses refer to that target; addresses in
12379 an active core file or executable file target are obscured while the
12380 process target is active.
12382 Use the @code{core-file} and @code{exec-file} commands to select a new
12383 core file or executable target (@pxref{Files, ,Commands to Specify
12384 Files}). To specify as a target a process that is already running, use
12385 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
12388 @node Target Commands
12389 @section Commands for Managing Targets
12392 @item target @var{type} @var{parameters}
12393 Connects the @value{GDBN} host environment to a target machine or
12394 process. A target is typically a protocol for talking to debugging
12395 facilities. You use the argument @var{type} to specify the type or
12396 protocol of the target machine.
12398 Further @var{parameters} are interpreted by the target protocol, but
12399 typically include things like device names or host names to connect
12400 with, process numbers, and baud rates.
12402 The @code{target} command does not repeat if you press @key{RET} again
12403 after executing the command.
12405 @kindex help target
12407 Displays the names of all targets available. To display targets
12408 currently selected, use either @code{info target} or @code{info files}
12409 (@pxref{Files, ,Commands to Specify Files}).
12411 @item help target @var{name}
12412 Describe a particular target, including any parameters necessary to
12415 @kindex set gnutarget
12416 @item set gnutarget @var{args}
12417 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
12418 knows whether it is reading an @dfn{executable},
12419 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
12420 with the @code{set gnutarget} command. Unlike most @code{target} commands,
12421 with @code{gnutarget} the @code{target} refers to a program, not a machine.
12424 @emph{Warning:} To specify a file format with @code{set gnutarget},
12425 you must know the actual BFD name.
12429 @xref{Files, , Commands to Specify Files}.
12431 @kindex show gnutarget
12432 @item show gnutarget
12433 Use the @code{show gnutarget} command to display what file format
12434 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
12435 @value{GDBN} will determine the file format for each file automatically,
12436 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
12439 @cindex common targets
12440 Here are some common targets (available, or not, depending on the GDB
12445 @item target exec @var{program}
12446 @cindex executable file target
12447 An executable file. @samp{target exec @var{program}} is the same as
12448 @samp{exec-file @var{program}}.
12450 @item target core @var{filename}
12451 @cindex core dump file target
12452 A core dump file. @samp{target core @var{filename}} is the same as
12453 @samp{core-file @var{filename}}.
12455 @item target remote @var{medium}
12456 @cindex remote target
12457 A remote system connected to @value{GDBN} via a serial line or network
12458 connection. This command tells @value{GDBN} to use its own remote
12459 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
12461 For example, if you have a board connected to @file{/dev/ttya} on the
12462 machine running @value{GDBN}, you could say:
12465 target remote /dev/ttya
12468 @code{target remote} supports the @code{load} command. This is only
12469 useful if you have some other way of getting the stub to the target
12470 system, and you can put it somewhere in memory where it won't get
12471 clobbered by the download.
12474 @cindex built-in simulator target
12475 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
12483 works; however, you cannot assume that a specific memory map, device
12484 drivers, or even basic I/O is available, although some simulators do
12485 provide these. For info about any processor-specific simulator details,
12486 see the appropriate section in @ref{Embedded Processors, ,Embedded
12491 Some configurations may include these targets as well:
12495 @item target nrom @var{dev}
12496 @cindex NetROM ROM emulator target
12497 NetROM ROM emulator. This target only supports downloading.
12501 Different targets are available on different configurations of @value{GDBN};
12502 your configuration may have more or fewer targets.
12504 Many remote targets require you to download the executable's code once
12505 you've successfully established a connection. You may wish to control
12506 various aspects of this process.
12511 @kindex set hash@r{, for remote monitors}
12512 @cindex hash mark while downloading
12513 This command controls whether a hash mark @samp{#} is displayed while
12514 downloading a file to the remote monitor. If on, a hash mark is
12515 displayed after each S-record is successfully downloaded to the
12519 @kindex show hash@r{, for remote monitors}
12520 Show the current status of displaying the hash mark.
12522 @item set debug monitor
12523 @kindex set debug monitor
12524 @cindex display remote monitor communications
12525 Enable or disable display of communications messages between
12526 @value{GDBN} and the remote monitor.
12528 @item show debug monitor
12529 @kindex show debug monitor
12530 Show the current status of displaying communications between
12531 @value{GDBN} and the remote monitor.
12536 @kindex load @var{filename}
12537 @item load @var{filename}
12538 Depending on what remote debugging facilities are configured into
12539 @value{GDBN}, the @code{load} command may be available. Where it exists, it
12540 is meant to make @var{filename} (an executable) available for debugging
12541 on the remote system---by downloading, or dynamic linking, for example.
12542 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
12543 the @code{add-symbol-file} command.
12545 If your @value{GDBN} does not have a @code{load} command, attempting to
12546 execute it gets the error message ``@code{You can't do that when your
12547 target is @dots{}}''
12549 The file is loaded at whatever address is specified in the executable.
12550 For some object file formats, you can specify the load address when you
12551 link the program; for other formats, like a.out, the object file format
12552 specifies a fixed address.
12553 @c FIXME! This would be a good place for an xref to the GNU linker doc.
12555 Depending on the remote side capabilities, @value{GDBN} may be able to
12556 load programs into flash memory.
12558 @code{load} does not repeat if you press @key{RET} again after using it.
12562 @section Choosing Target Byte Order
12564 @cindex choosing target byte order
12565 @cindex target byte order
12567 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
12568 offer the ability to run either big-endian or little-endian byte
12569 orders. Usually the executable or symbol will include a bit to
12570 designate the endian-ness, and you will not need to worry about
12571 which to use. However, you may still find it useful to adjust
12572 @value{GDBN}'s idea of processor endian-ness manually.
12576 @item set endian big
12577 Instruct @value{GDBN} to assume the target is big-endian.
12579 @item set endian little
12580 Instruct @value{GDBN} to assume the target is little-endian.
12582 @item set endian auto
12583 Instruct @value{GDBN} to use the byte order associated with the
12587 Display @value{GDBN}'s current idea of the target byte order.
12591 Note that these commands merely adjust interpretation of symbolic
12592 data on the host, and that they have absolutely no effect on the
12596 @node Remote Debugging
12597 @chapter Debugging Remote Programs
12598 @cindex remote debugging
12600 If you are trying to debug a program running on a machine that cannot run
12601 @value{GDBN} in the usual way, it is often useful to use remote debugging.
12602 For example, you might use remote debugging on an operating system kernel,
12603 or on a small system which does not have a general purpose operating system
12604 powerful enough to run a full-featured debugger.
12606 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
12607 to make this work with particular debugging targets. In addition,
12608 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
12609 but not specific to any particular target system) which you can use if you
12610 write the remote stubs---the code that runs on the remote system to
12611 communicate with @value{GDBN}.
12613 Other remote targets may be available in your
12614 configuration of @value{GDBN}; use @code{help target} to list them.
12617 * Connecting:: Connecting to a remote target
12618 * Server:: Using the gdbserver program
12619 * Remote Configuration:: Remote configuration
12620 * Remote Stub:: Implementing a remote stub
12624 @section Connecting to a Remote Target
12626 On the @value{GDBN} host machine, you will need an unstripped copy of
12627 your program, since @value{GDBN} needs symbol and debugging information.
12628 Start up @value{GDBN} as usual, using the name of the local copy of your
12629 program as the first argument.
12631 @cindex @code{target remote}
12632 @value{GDBN} can communicate with the target over a serial line, or
12633 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
12634 each case, @value{GDBN} uses the same protocol for debugging your
12635 program; only the medium carrying the debugging packets varies. The
12636 @code{target remote} command establishes a connection to the target.
12637 Its arguments indicate which medium to use:
12641 @item target remote @var{serial-device}
12642 @cindex serial line, @code{target remote}
12643 Use @var{serial-device} to communicate with the target. For example,
12644 to use a serial line connected to the device named @file{/dev/ttyb}:
12647 target remote /dev/ttyb
12650 If you're using a serial line, you may want to give @value{GDBN} the
12651 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
12652 (@pxref{Remote Configuration, set remotebaud}) before the
12653 @code{target} command.
12655 @item target remote @code{@var{host}:@var{port}}
12656 @itemx target remote @code{tcp:@var{host}:@var{port}}
12657 @cindex @acronym{TCP} port, @code{target remote}
12658 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
12659 The @var{host} may be either a host name or a numeric @acronym{IP}
12660 address; @var{port} must be a decimal number. The @var{host} could be
12661 the target machine itself, if it is directly connected to the net, or
12662 it might be a terminal server which in turn has a serial line to the
12665 For example, to connect to port 2828 on a terminal server named
12669 target remote manyfarms:2828
12672 If your remote target is actually running on the same machine as your
12673 debugger session (e.g.@: a simulator for your target running on the
12674 same host), you can omit the hostname. For example, to connect to
12675 port 1234 on your local machine:
12678 target remote :1234
12682 Note that the colon is still required here.
12684 @item target remote @code{udp:@var{host}:@var{port}}
12685 @cindex @acronym{UDP} port, @code{target remote}
12686 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
12687 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
12690 target remote udp:manyfarms:2828
12693 When using a @acronym{UDP} connection for remote debugging, you should
12694 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
12695 can silently drop packets on busy or unreliable networks, which will
12696 cause havoc with your debugging session.
12698 @item target remote | @var{command}
12699 @cindex pipe, @code{target remote} to
12700 Run @var{command} in the background and communicate with it using a
12701 pipe. The @var{command} is a shell command, to be parsed and expanded
12702 by the system's command shell, @code{/bin/sh}; it should expect remote
12703 protocol packets on its standard input, and send replies on its
12704 standard output. You could use this to run a stand-alone simulator
12705 that speaks the remote debugging protocol, to make net connections
12706 using programs like @code{ssh}, or for other similar tricks.
12708 If @var{command} closes its standard output (perhaps by exiting),
12709 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
12710 program has already exited, this will have no effect.)
12714 Once the connection has been established, you can use all the usual
12715 commands to examine and change data and to step and continue the
12718 @cindex interrupting remote programs
12719 @cindex remote programs, interrupting
12720 Whenever @value{GDBN} is waiting for the remote program, if you type the
12721 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
12722 program. This may or may not succeed, depending in part on the hardware
12723 and the serial drivers the remote system uses. If you type the
12724 interrupt character once again, @value{GDBN} displays this prompt:
12727 Interrupted while waiting for the program.
12728 Give up (and stop debugging it)? (y or n)
12731 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
12732 (If you decide you want to try again later, you can use @samp{target
12733 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
12734 goes back to waiting.
12737 @kindex detach (remote)
12739 When you have finished debugging the remote program, you can use the
12740 @code{detach} command to release it from @value{GDBN} control.
12741 Detaching from the target normally resumes its execution, but the results
12742 will depend on your particular remote stub. After the @code{detach}
12743 command, @value{GDBN} is free to connect to another target.
12747 The @code{disconnect} command behaves like @code{detach}, except that
12748 the target is generally not resumed. It will wait for @value{GDBN}
12749 (this instance or another one) to connect and continue debugging. After
12750 the @code{disconnect} command, @value{GDBN} is again free to connect to
12753 @cindex send command to remote monitor
12754 @cindex extend @value{GDBN} for remote targets
12755 @cindex add new commands for external monitor
12757 @item monitor @var{cmd}
12758 This command allows you to send arbitrary commands directly to the
12759 remote monitor. Since @value{GDBN} doesn't care about the commands it
12760 sends like this, this command is the way to extend @value{GDBN}---you
12761 can add new commands that only the external monitor will understand
12766 @section Using the @code{gdbserver} Program
12769 @cindex remote connection without stubs
12770 @code{gdbserver} is a control program for Unix-like systems, which
12771 allows you to connect your program with a remote @value{GDBN} via
12772 @code{target remote}---but without linking in the usual debugging stub.
12774 @code{gdbserver} is not a complete replacement for the debugging stubs,
12775 because it requires essentially the same operating-system facilities
12776 that @value{GDBN} itself does. In fact, a system that can run
12777 @code{gdbserver} to connect to a remote @value{GDBN} could also run
12778 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
12779 because it is a much smaller program than @value{GDBN} itself. It is
12780 also easier to port than all of @value{GDBN}, so you may be able to get
12781 started more quickly on a new system by using @code{gdbserver}.
12782 Finally, if you develop code for real-time systems, you may find that
12783 the tradeoffs involved in real-time operation make it more convenient to
12784 do as much development work as possible on another system, for example
12785 by cross-compiling. You can use @code{gdbserver} to make a similar
12786 choice for debugging.
12788 @value{GDBN} and @code{gdbserver} communicate via either a serial line
12789 or a TCP connection, using the standard @value{GDBN} remote serial
12793 @item On the target machine,
12794 you need to have a copy of the program you want to debug.
12795 @code{gdbserver} does not need your program's symbol table, so you can
12796 strip the program if necessary to save space. @value{GDBN} on the host
12797 system does all the symbol handling.
12799 To use the server, you must tell it how to communicate with @value{GDBN};
12800 the name of your program; and the arguments for your program. The usual
12804 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
12807 @var{comm} is either a device name (to use a serial line) or a TCP
12808 hostname and portnumber. For example, to debug Emacs with the argument
12809 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
12813 target> gdbserver /dev/com1 emacs foo.txt
12816 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
12819 To use a TCP connection instead of a serial line:
12822 target> gdbserver host:2345 emacs foo.txt
12825 The only difference from the previous example is the first argument,
12826 specifying that you are communicating with the host @value{GDBN} via
12827 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
12828 expect a TCP connection from machine @samp{host} to local TCP port 2345.
12829 (Currently, the @samp{host} part is ignored.) You can choose any number
12830 you want for the port number as long as it does not conflict with any
12831 TCP ports already in use on the target system (for example, @code{23} is
12832 reserved for @code{telnet}).@footnote{If you choose a port number that
12833 conflicts with another service, @code{gdbserver} prints an error message
12834 and exits.} You must use the same port number with the host @value{GDBN}
12835 @code{target remote} command.
12837 On some targets, @code{gdbserver} can also attach to running programs.
12838 This is accomplished via the @code{--attach} argument. The syntax is:
12841 target> gdbserver @var{comm} --attach @var{pid}
12844 @var{pid} is the process ID of a currently running process. It isn't necessary
12845 to point @code{gdbserver} at a binary for the running process.
12848 @cindex attach to a program by name
12849 You can debug processes by name instead of process ID if your target has the
12850 @code{pidof} utility:
12853 target> gdbserver @var{comm} --attach `pidof @var{program}`
12856 In case more than one copy of @var{program} is running, or @var{program}
12857 has multiple threads, most versions of @code{pidof} support the
12858 @code{-s} option to only return the first process ID.
12860 @item On the host machine,
12861 first make sure you have the necessary symbol files. Load symbols for
12862 your application using the @code{file} command before you connect. Use
12863 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
12864 was compiled with the correct sysroot using @code{--with-system-root}).
12866 The symbol file and target libraries must exactly match the executable
12867 and libraries on the target, with one exception: the files on the host
12868 system should not be stripped, even if the files on the target system
12869 are. Mismatched or missing files will lead to confusing results
12870 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
12871 files may also prevent @code{gdbserver} from debugging multi-threaded
12874 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
12875 For TCP connections, you must start up @code{gdbserver} prior to using
12876 the @code{target remote} command. Otherwise you may get an error whose
12877 text depends on the host system, but which usually looks something like
12878 @samp{Connection refused}. You don't need to use the @code{load}
12879 command in @value{GDBN} when using @code{gdbserver}, since the program is
12880 already on the target.
12884 @subsection Monitor Commands for @code{gdbserver}
12885 @cindex monitor commands, for @code{gdbserver}
12887 During a @value{GDBN} session using @code{gdbserver}, you can use the
12888 @code{monitor} command to send special requests to @code{gdbserver}.
12889 Here are the available commands; they are only of interest when
12890 debugging @value{GDBN} or @code{gdbserver}.
12894 List the available monitor commands.
12896 @item monitor set debug 0
12897 @itemx monitor set debug 1
12898 Disable or enable general debugging messages.
12900 @item monitor set remote-debug 0
12901 @itemx monitor set remote-debug 1
12902 Disable or enable specific debugging messages associated with the remote
12903 protocol (@pxref{Remote Protocol}).
12907 @node Remote Configuration
12908 @section Remote Configuration
12911 @kindex show remote
12912 This section documents the configuration options available when
12913 debugging remote programs. For the options related to the File I/O
12914 extensions of the remote protocol, see @ref{system,
12915 system-call-allowed}.
12918 @item set remoteaddresssize @var{bits}
12919 @cindex address size for remote targets
12920 @cindex bits in remote address
12921 Set the maximum size of address in a memory packet to the specified
12922 number of bits. @value{GDBN} will mask off the address bits above
12923 that number, when it passes addresses to the remote target. The
12924 default value is the number of bits in the target's address.
12926 @item show remoteaddresssize
12927 Show the current value of remote address size in bits.
12929 @item set remotebaud @var{n}
12930 @cindex baud rate for remote targets
12931 Set the baud rate for the remote serial I/O to @var{n} baud. The
12932 value is used to set the speed of the serial port used for debugging
12935 @item show remotebaud
12936 Show the current speed of the remote connection.
12938 @item set remotebreak
12939 @cindex interrupt remote programs
12940 @cindex BREAK signal instead of Ctrl-C
12941 @anchor{set remotebreak}
12942 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
12943 when you type @kbd{Ctrl-c} to interrupt the program running
12944 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
12945 character instead. The default is off, since most remote systems
12946 expect to see @samp{Ctrl-C} as the interrupt signal.
12948 @item show remotebreak
12949 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
12950 interrupt the remote program.
12952 @item set remoteflow on
12953 @itemx set remoteflow off
12954 @kindex set remoteflow
12955 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
12956 on the serial port used to communicate to the remote target.
12958 @item show remoteflow
12959 @kindex show remoteflow
12960 Show the current setting of hardware flow control.
12962 @item set remotelogbase @var{base}
12963 Set the base (a.k.a.@: radix) of logging serial protocol
12964 communications to @var{base}. Supported values of @var{base} are:
12965 @code{ascii}, @code{octal}, and @code{hex}. The default is
12968 @item show remotelogbase
12969 Show the current setting of the radix for logging remote serial
12972 @item set remotelogfile @var{file}
12973 @cindex record serial communications on file
12974 Record remote serial communications on the named @var{file}. The
12975 default is not to record at all.
12977 @item show remotelogfile.
12978 Show the current setting of the file name on which to record the
12979 serial communications.
12981 @item set remotetimeout @var{num}
12982 @cindex timeout for serial communications
12983 @cindex remote timeout
12984 Set the timeout limit to wait for the remote target to respond to
12985 @var{num} seconds. The default is 2 seconds.
12987 @item show remotetimeout
12988 Show the current number of seconds to wait for the remote target
12991 @cindex limit hardware breakpoints and watchpoints
12992 @cindex remote target, limit break- and watchpoints
12993 @anchor{set remote hardware-watchpoint-limit}
12994 @anchor{set remote hardware-breakpoint-limit}
12995 @item set remote hardware-watchpoint-limit @var{limit}
12996 @itemx set remote hardware-breakpoint-limit @var{limit}
12997 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
12998 watchpoints. A limit of -1, the default, is treated as unlimited.
13001 @cindex remote packets, enabling and disabling
13002 The @value{GDBN} remote protocol autodetects the packets supported by
13003 your debugging stub. If you need to override the autodetection, you
13004 can use these commands to enable or disable individual packets. Each
13005 packet can be set to @samp{on} (the remote target supports this
13006 packet), @samp{off} (the remote target does not support this packet),
13007 or @samp{auto} (detect remote target support for this packet). They
13008 all default to @samp{auto}. For more information about each packet,
13009 see @ref{Remote Protocol}.
13011 During normal use, you should not have to use any of these commands.
13012 If you do, that may be a bug in your remote debugging stub, or a bug
13013 in @value{GDBN}. You may want to report the problem to the
13014 @value{GDBN} developers.
13016 For each packet @var{name}, the command to enable or disable the
13017 packet is @code{set remote @var{name}-packet}. The available settings
13020 @multitable @columnfractions 0.28 0.32 0.25
13023 @tab Related Features
13025 @item @code{fetch-register}
13027 @tab @code{info registers}
13029 @item @code{set-register}
13033 @item @code{binary-download}
13035 @tab @code{load}, @code{set}
13037 @item @code{read-aux-vector}
13038 @tab @code{qXfer:auxv:read}
13039 @tab @code{info auxv}
13041 @item @code{symbol-lookup}
13042 @tab @code{qSymbol}
13043 @tab Detecting multiple threads
13045 @item @code{verbose-resume}
13047 @tab Stepping or resuming multiple threads
13049 @item @code{software-breakpoint}
13053 @item @code{hardware-breakpoint}
13057 @item @code{write-watchpoint}
13061 @item @code{read-watchpoint}
13065 @item @code{access-watchpoint}
13069 @item @code{target-features}
13070 @tab @code{qXfer:features:read}
13071 @tab @code{set architecture}
13073 @item @code{library-info}
13074 @tab @code{qXfer:libraries:read}
13075 @tab @code{info sharedlibrary}
13077 @item @code{memory-map}
13078 @tab @code{qXfer:memory-map:read}
13079 @tab @code{info mem}
13081 @item @code{read-spu-object}
13082 @tab @code{qXfer:spu:read}
13083 @tab @code{info spu}
13085 @item @code{write-spu-object}
13086 @tab @code{qXfer:spu:write}
13087 @tab @code{info spu}
13089 @item @code{get-thread-local-@*storage-address}
13090 @tab @code{qGetTLSAddr}
13091 @tab Displaying @code{__thread} variables
13093 @item @code{supported-packets}
13094 @tab @code{qSupported}
13095 @tab Remote communications parameters
13097 @item @code{pass-signals}
13098 @tab @code{QPassSignals}
13099 @tab @code{handle @var{signal}}
13104 @section Implementing a Remote Stub
13106 @cindex debugging stub, example
13107 @cindex remote stub, example
13108 @cindex stub example, remote debugging
13109 The stub files provided with @value{GDBN} implement the target side of the
13110 communication protocol, and the @value{GDBN} side is implemented in the
13111 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
13112 these subroutines to communicate, and ignore the details. (If you're
13113 implementing your own stub file, you can still ignore the details: start
13114 with one of the existing stub files. @file{sparc-stub.c} is the best
13115 organized, and therefore the easiest to read.)
13117 @cindex remote serial debugging, overview
13118 To debug a program running on another machine (the debugging
13119 @dfn{target} machine), you must first arrange for all the usual
13120 prerequisites for the program to run by itself. For example, for a C
13125 A startup routine to set up the C runtime environment; these usually
13126 have a name like @file{crt0}. The startup routine may be supplied by
13127 your hardware supplier, or you may have to write your own.
13130 A C subroutine library to support your program's
13131 subroutine calls, notably managing input and output.
13134 A way of getting your program to the other machine---for example, a
13135 download program. These are often supplied by the hardware
13136 manufacturer, but you may have to write your own from hardware
13140 The next step is to arrange for your program to use a serial port to
13141 communicate with the machine where @value{GDBN} is running (the @dfn{host}
13142 machine). In general terms, the scheme looks like this:
13146 @value{GDBN} already understands how to use this protocol; when everything
13147 else is set up, you can simply use the @samp{target remote} command
13148 (@pxref{Targets,,Specifying a Debugging Target}).
13150 @item On the target,
13151 you must link with your program a few special-purpose subroutines that
13152 implement the @value{GDBN} remote serial protocol. The file containing these
13153 subroutines is called a @dfn{debugging stub}.
13155 On certain remote targets, you can use an auxiliary program
13156 @code{gdbserver} instead of linking a stub into your program.
13157 @xref{Server,,Using the @code{gdbserver} Program}, for details.
13160 The debugging stub is specific to the architecture of the remote
13161 machine; for example, use @file{sparc-stub.c} to debug programs on
13164 @cindex remote serial stub list
13165 These working remote stubs are distributed with @value{GDBN}:
13170 @cindex @file{i386-stub.c}
13173 For Intel 386 and compatible architectures.
13176 @cindex @file{m68k-stub.c}
13177 @cindex Motorola 680x0
13179 For Motorola 680x0 architectures.
13182 @cindex @file{sh-stub.c}
13185 For Renesas SH architectures.
13188 @cindex @file{sparc-stub.c}
13190 For @sc{sparc} architectures.
13192 @item sparcl-stub.c
13193 @cindex @file{sparcl-stub.c}
13196 For Fujitsu @sc{sparclite} architectures.
13200 The @file{README} file in the @value{GDBN} distribution may list other
13201 recently added stubs.
13204 * Stub Contents:: What the stub can do for you
13205 * Bootstrapping:: What you must do for the stub
13206 * Debug Session:: Putting it all together
13209 @node Stub Contents
13210 @subsection What the Stub Can Do for You
13212 @cindex remote serial stub
13213 The debugging stub for your architecture supplies these three
13217 @item set_debug_traps
13218 @findex set_debug_traps
13219 @cindex remote serial stub, initialization
13220 This routine arranges for @code{handle_exception} to run when your
13221 program stops. You must call this subroutine explicitly near the
13222 beginning of your program.
13224 @item handle_exception
13225 @findex handle_exception
13226 @cindex remote serial stub, main routine
13227 This is the central workhorse, but your program never calls it
13228 explicitly---the setup code arranges for @code{handle_exception} to
13229 run when a trap is triggered.
13231 @code{handle_exception} takes control when your program stops during
13232 execution (for example, on a breakpoint), and mediates communications
13233 with @value{GDBN} on the host machine. This is where the communications
13234 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
13235 representative on the target machine. It begins by sending summary
13236 information on the state of your program, then continues to execute,
13237 retrieving and transmitting any information @value{GDBN} needs, until you
13238 execute a @value{GDBN} command that makes your program resume; at that point,
13239 @code{handle_exception} returns control to your own code on the target
13243 @cindex @code{breakpoint} subroutine, remote
13244 Use this auxiliary subroutine to make your program contain a
13245 breakpoint. Depending on the particular situation, this may be the only
13246 way for @value{GDBN} to get control. For instance, if your target
13247 machine has some sort of interrupt button, you won't need to call this;
13248 pressing the interrupt button transfers control to
13249 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
13250 simply receiving characters on the serial port may also trigger a trap;
13251 again, in that situation, you don't need to call @code{breakpoint} from
13252 your own program---simply running @samp{target remote} from the host
13253 @value{GDBN} session gets control.
13255 Call @code{breakpoint} if none of these is true, or if you simply want
13256 to make certain your program stops at a predetermined point for the
13257 start of your debugging session.
13260 @node Bootstrapping
13261 @subsection What You Must Do for the Stub
13263 @cindex remote stub, support routines
13264 The debugging stubs that come with @value{GDBN} are set up for a particular
13265 chip architecture, but they have no information about the rest of your
13266 debugging target machine.
13268 First of all you need to tell the stub how to communicate with the
13272 @item int getDebugChar()
13273 @findex getDebugChar
13274 Write this subroutine to read a single character from the serial port.
13275 It may be identical to @code{getchar} for your target system; a
13276 different name is used to allow you to distinguish the two if you wish.
13278 @item void putDebugChar(int)
13279 @findex putDebugChar
13280 Write this subroutine to write a single character to the serial port.
13281 It may be identical to @code{putchar} for your target system; a
13282 different name is used to allow you to distinguish the two if you wish.
13285 @cindex control C, and remote debugging
13286 @cindex interrupting remote targets
13287 If you want @value{GDBN} to be able to stop your program while it is
13288 running, you need to use an interrupt-driven serial driver, and arrange
13289 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
13290 character). That is the character which @value{GDBN} uses to tell the
13291 remote system to stop.
13293 Getting the debugging target to return the proper status to @value{GDBN}
13294 probably requires changes to the standard stub; one quick and dirty way
13295 is to just execute a breakpoint instruction (the ``dirty'' part is that
13296 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
13298 Other routines you need to supply are:
13301 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
13302 @findex exceptionHandler
13303 Write this function to install @var{exception_address} in the exception
13304 handling tables. You need to do this because the stub does not have any
13305 way of knowing what the exception handling tables on your target system
13306 are like (for example, the processor's table might be in @sc{rom},
13307 containing entries which point to a table in @sc{ram}).
13308 @var{exception_number} is the exception number which should be changed;
13309 its meaning is architecture-dependent (for example, different numbers
13310 might represent divide by zero, misaligned access, etc). When this
13311 exception occurs, control should be transferred directly to
13312 @var{exception_address}, and the processor state (stack, registers,
13313 and so on) should be just as it is when a processor exception occurs. So if
13314 you want to use a jump instruction to reach @var{exception_address}, it
13315 should be a simple jump, not a jump to subroutine.
13317 For the 386, @var{exception_address} should be installed as an interrupt
13318 gate so that interrupts are masked while the handler runs. The gate
13319 should be at privilege level 0 (the most privileged level). The
13320 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
13321 help from @code{exceptionHandler}.
13323 @item void flush_i_cache()
13324 @findex flush_i_cache
13325 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
13326 instruction cache, if any, on your target machine. If there is no
13327 instruction cache, this subroutine may be a no-op.
13329 On target machines that have instruction caches, @value{GDBN} requires this
13330 function to make certain that the state of your program is stable.
13334 You must also make sure this library routine is available:
13337 @item void *memset(void *, int, int)
13339 This is the standard library function @code{memset} that sets an area of
13340 memory to a known value. If you have one of the free versions of
13341 @code{libc.a}, @code{memset} can be found there; otherwise, you must
13342 either obtain it from your hardware manufacturer, or write your own.
13345 If you do not use the GNU C compiler, you may need other standard
13346 library subroutines as well; this varies from one stub to another,
13347 but in general the stubs are likely to use any of the common library
13348 subroutines which @code{@value{NGCC}} generates as inline code.
13351 @node Debug Session
13352 @subsection Putting it All Together
13354 @cindex remote serial debugging summary
13355 In summary, when your program is ready to debug, you must follow these
13360 Make sure you have defined the supporting low-level routines
13361 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
13363 @code{getDebugChar}, @code{putDebugChar},
13364 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
13368 Insert these lines near the top of your program:
13376 For the 680x0 stub only, you need to provide a variable called
13377 @code{exceptionHook}. Normally you just use:
13380 void (*exceptionHook)() = 0;
13384 but if before calling @code{set_debug_traps}, you set it to point to a
13385 function in your program, that function is called when
13386 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
13387 error). The function indicated by @code{exceptionHook} is called with
13388 one parameter: an @code{int} which is the exception number.
13391 Compile and link together: your program, the @value{GDBN} debugging stub for
13392 your target architecture, and the supporting subroutines.
13395 Make sure you have a serial connection between your target machine and
13396 the @value{GDBN} host, and identify the serial port on the host.
13399 @c The "remote" target now provides a `load' command, so we should
13400 @c document that. FIXME.
13401 Download your program to your target machine (or get it there by
13402 whatever means the manufacturer provides), and start it.
13405 Start @value{GDBN} on the host, and connect to the target
13406 (@pxref{Connecting,,Connecting to a Remote Target}).
13410 @node Configurations
13411 @chapter Configuration-Specific Information
13413 While nearly all @value{GDBN} commands are available for all native and
13414 cross versions of the debugger, there are some exceptions. This chapter
13415 describes things that are only available in certain configurations.
13417 There are three major categories of configurations: native
13418 configurations, where the host and target are the same, embedded
13419 operating system configurations, which are usually the same for several
13420 different processor architectures, and bare embedded processors, which
13421 are quite different from each other.
13426 * Embedded Processors::
13433 This section describes details specific to particular native
13438 * BSD libkvm Interface:: Debugging BSD kernel memory images
13439 * SVR4 Process Information:: SVR4 process information
13440 * DJGPP Native:: Features specific to the DJGPP port
13441 * Cygwin Native:: Features specific to the Cygwin port
13442 * Hurd Native:: Features specific to @sc{gnu} Hurd
13443 * Neutrino:: Features specific to QNX Neutrino
13449 On HP-UX systems, if you refer to a function or variable name that
13450 begins with a dollar sign, @value{GDBN} searches for a user or system
13451 name first, before it searches for a convenience variable.
13454 @node BSD libkvm Interface
13455 @subsection BSD libkvm Interface
13458 @cindex kernel memory image
13459 @cindex kernel crash dump
13461 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
13462 interface that provides a uniform interface for accessing kernel virtual
13463 memory images, including live systems and crash dumps. @value{GDBN}
13464 uses this interface to allow you to debug live kernels and kernel crash
13465 dumps on many native BSD configurations. This is implemented as a
13466 special @code{kvm} debugging target. For debugging a live system, load
13467 the currently running kernel into @value{GDBN} and connect to the
13471 (@value{GDBP}) @b{target kvm}
13474 For debugging crash dumps, provide the file name of the crash dump as an
13478 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
13481 Once connected to the @code{kvm} target, the following commands are
13487 Set current context from the @dfn{Process Control Block} (PCB) address.
13490 Set current context from proc address. This command isn't available on
13491 modern FreeBSD systems.
13494 @node SVR4 Process Information
13495 @subsection SVR4 Process Information
13497 @cindex examine process image
13498 @cindex process info via @file{/proc}
13500 Many versions of SVR4 and compatible systems provide a facility called
13501 @samp{/proc} that can be used to examine the image of a running
13502 process using file-system subroutines. If @value{GDBN} is configured
13503 for an operating system with this facility, the command @code{info
13504 proc} is available to report information about the process running
13505 your program, or about any process running on your system. @code{info
13506 proc} works only on SVR4 systems that include the @code{procfs} code.
13507 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
13508 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
13514 @itemx info proc @var{process-id}
13515 Summarize available information about any running process. If a
13516 process ID is specified by @var{process-id}, display information about
13517 that process; otherwise display information about the program being
13518 debugged. The summary includes the debugged process ID, the command
13519 line used to invoke it, its current working directory, and its
13520 executable file's absolute file name.
13522 On some systems, @var{process-id} can be of the form
13523 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
13524 within a process. If the optional @var{pid} part is missing, it means
13525 a thread from the process being debugged (the leading @samp{/} still
13526 needs to be present, or else @value{GDBN} will interpret the number as
13527 a process ID rather than a thread ID).
13529 @item info proc mappings
13530 @cindex memory address space mappings
13531 Report the memory address space ranges accessible in the program, with
13532 information on whether the process has read, write, or execute access
13533 rights to each range. On @sc{gnu}/Linux systems, each memory range
13534 includes the object file which is mapped to that range, instead of the
13535 memory access rights to that range.
13537 @item info proc stat
13538 @itemx info proc status
13539 @cindex process detailed status information
13540 These subcommands are specific to @sc{gnu}/Linux systems. They show
13541 the process-related information, including the user ID and group ID;
13542 how many threads are there in the process; its virtual memory usage;
13543 the signals that are pending, blocked, and ignored; its TTY; its
13544 consumption of system and user time; its stack size; its @samp{nice}
13545 value; etc. For more information, see the @samp{proc} man page
13546 (type @kbd{man 5 proc} from your shell prompt).
13548 @item info proc all
13549 Show all the information about the process described under all of the
13550 above @code{info proc} subcommands.
13553 @comment These sub-options of 'info proc' were not included when
13554 @comment procfs.c was re-written. Keep their descriptions around
13555 @comment against the day when someone finds the time to put them back in.
13556 @kindex info proc times
13557 @item info proc times
13558 Starting time, user CPU time, and system CPU time for your program and
13561 @kindex info proc id
13563 Report on the process IDs related to your program: its own process ID,
13564 the ID of its parent, the process group ID, and the session ID.
13567 @item set procfs-trace
13568 @kindex set procfs-trace
13569 @cindex @code{procfs} API calls
13570 This command enables and disables tracing of @code{procfs} API calls.
13572 @item show procfs-trace
13573 @kindex show procfs-trace
13574 Show the current state of @code{procfs} API call tracing.
13576 @item set procfs-file @var{file}
13577 @kindex set procfs-file
13578 Tell @value{GDBN} to write @code{procfs} API trace to the named
13579 @var{file}. @value{GDBN} appends the trace info to the previous
13580 contents of the file. The default is to display the trace on the
13583 @item show procfs-file
13584 @kindex show procfs-file
13585 Show the file to which @code{procfs} API trace is written.
13587 @item proc-trace-entry
13588 @itemx proc-trace-exit
13589 @itemx proc-untrace-entry
13590 @itemx proc-untrace-exit
13591 @kindex proc-trace-entry
13592 @kindex proc-trace-exit
13593 @kindex proc-untrace-entry
13594 @kindex proc-untrace-exit
13595 These commands enable and disable tracing of entries into and exits
13596 from the @code{syscall} interface.
13599 @kindex info pidlist
13600 @cindex process list, QNX Neutrino
13601 For QNX Neutrino only, this command displays the list of all the
13602 processes and all the threads within each process.
13605 @kindex info meminfo
13606 @cindex mapinfo list, QNX Neutrino
13607 For QNX Neutrino only, this command displays the list of all mapinfos.
13611 @subsection Features for Debugging @sc{djgpp} Programs
13612 @cindex @sc{djgpp} debugging
13613 @cindex native @sc{djgpp} debugging
13614 @cindex MS-DOS-specific commands
13617 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
13618 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
13619 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
13620 top of real-mode DOS systems and their emulations.
13622 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
13623 defines a few commands specific to the @sc{djgpp} port. This
13624 subsection describes those commands.
13629 This is a prefix of @sc{djgpp}-specific commands which print
13630 information about the target system and important OS structures.
13633 @cindex MS-DOS system info
13634 @cindex free memory information (MS-DOS)
13635 @item info dos sysinfo
13636 This command displays assorted information about the underlying
13637 platform: the CPU type and features, the OS version and flavor, the
13638 DPMI version, and the available conventional and DPMI memory.
13643 @cindex segment descriptor tables
13644 @cindex descriptor tables display
13646 @itemx info dos ldt
13647 @itemx info dos idt
13648 These 3 commands display entries from, respectively, Global, Local,
13649 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
13650 tables are data structures which store a descriptor for each segment
13651 that is currently in use. The segment's selector is an index into a
13652 descriptor table; the table entry for that index holds the
13653 descriptor's base address and limit, and its attributes and access
13656 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
13657 segment (used for both data and the stack), and a DOS segment (which
13658 allows access to DOS/BIOS data structures and absolute addresses in
13659 conventional memory). However, the DPMI host will usually define
13660 additional segments in order to support the DPMI environment.
13662 @cindex garbled pointers
13663 These commands allow to display entries from the descriptor tables.
13664 Without an argument, all entries from the specified table are
13665 displayed. An argument, which should be an integer expression, means
13666 display a single entry whose index is given by the argument. For
13667 example, here's a convenient way to display information about the
13668 debugged program's data segment:
13671 @exdent @code{(@value{GDBP}) info dos ldt $ds}
13672 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
13676 This comes in handy when you want to see whether a pointer is outside
13677 the data segment's limit (i.e.@: @dfn{garbled}).
13679 @cindex page tables display (MS-DOS)
13681 @itemx info dos pte
13682 These two commands display entries from, respectively, the Page
13683 Directory and the Page Tables. Page Directories and Page Tables are
13684 data structures which control how virtual memory addresses are mapped
13685 into physical addresses. A Page Table includes an entry for every
13686 page of memory that is mapped into the program's address space; there
13687 may be several Page Tables, each one holding up to 4096 entries. A
13688 Page Directory has up to 4096 entries, one each for every Page Table
13689 that is currently in use.
13691 Without an argument, @kbd{info dos pde} displays the entire Page
13692 Directory, and @kbd{info dos pte} displays all the entries in all of
13693 the Page Tables. An argument, an integer expression, given to the
13694 @kbd{info dos pde} command means display only that entry from the Page
13695 Directory table. An argument given to the @kbd{info dos pte} command
13696 means display entries from a single Page Table, the one pointed to by
13697 the specified entry in the Page Directory.
13699 @cindex direct memory access (DMA) on MS-DOS
13700 These commands are useful when your program uses @dfn{DMA} (Direct
13701 Memory Access), which needs physical addresses to program the DMA
13704 These commands are supported only with some DPMI servers.
13706 @cindex physical address from linear address
13707 @item info dos address-pte @var{addr}
13708 This command displays the Page Table entry for a specified linear
13709 address. The argument @var{addr} is a linear address which should
13710 already have the appropriate segment's base address added to it,
13711 because this command accepts addresses which may belong to @emph{any}
13712 segment. For example, here's how to display the Page Table entry for
13713 the page where a variable @code{i} is stored:
13716 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
13717 @exdent @code{Page Table entry for address 0x11a00d30:}
13718 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
13722 This says that @code{i} is stored at offset @code{0xd30} from the page
13723 whose physical base address is @code{0x02698000}, and shows all the
13724 attributes of that page.
13726 Note that you must cast the addresses of variables to a @code{char *},
13727 since otherwise the value of @code{__djgpp_base_address}, the base
13728 address of all variables and functions in a @sc{djgpp} program, will
13729 be added using the rules of C pointer arithmetics: if @code{i} is
13730 declared an @code{int}, @value{GDBN} will add 4 times the value of
13731 @code{__djgpp_base_address} to the address of @code{i}.
13733 Here's another example, it displays the Page Table entry for the
13737 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
13738 @exdent @code{Page Table entry for address 0x29110:}
13739 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
13743 (The @code{+ 3} offset is because the transfer buffer's address is the
13744 3rd member of the @code{_go32_info_block} structure.) The output
13745 clearly shows that this DPMI server maps the addresses in conventional
13746 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
13747 linear (@code{0x29110}) addresses are identical.
13749 This command is supported only with some DPMI servers.
13752 @cindex DOS serial data link, remote debugging
13753 In addition to native debugging, the DJGPP port supports remote
13754 debugging via a serial data link. The following commands are specific
13755 to remote serial debugging in the DJGPP port of @value{GDBN}.
13758 @kindex set com1base
13759 @kindex set com1irq
13760 @kindex set com2base
13761 @kindex set com2irq
13762 @kindex set com3base
13763 @kindex set com3irq
13764 @kindex set com4base
13765 @kindex set com4irq
13766 @item set com1base @var{addr}
13767 This command sets the base I/O port address of the @file{COM1} serial
13770 @item set com1irq @var{irq}
13771 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
13772 for the @file{COM1} serial port.
13774 There are similar commands @samp{set com2base}, @samp{set com3irq},
13775 etc.@: for setting the port address and the @code{IRQ} lines for the
13778 @kindex show com1base
13779 @kindex show com1irq
13780 @kindex show com2base
13781 @kindex show com2irq
13782 @kindex show com3base
13783 @kindex show com3irq
13784 @kindex show com4base
13785 @kindex show com4irq
13786 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
13787 display the current settings of the base address and the @code{IRQ}
13788 lines used by the COM ports.
13791 @kindex info serial
13792 @cindex DOS serial port status
13793 This command prints the status of the 4 DOS serial ports. For each
13794 port, it prints whether it's active or not, its I/O base address and
13795 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
13796 counts of various errors encountered so far.
13800 @node Cygwin Native
13801 @subsection Features for Debugging MS Windows PE Executables
13802 @cindex MS Windows debugging
13803 @cindex native Cygwin debugging
13804 @cindex Cygwin-specific commands
13806 @value{GDBN} supports native debugging of MS Windows programs, including
13807 DLLs with and without symbolic debugging information. There are various
13808 additional Cygwin-specific commands, described in this section.
13809 Working with DLLs that have no debugging symbols is described in
13810 @ref{Non-debug DLL Symbols}.
13815 This is a prefix of MS Windows-specific commands which print
13816 information about the target system and important OS structures.
13818 @item info w32 selector
13819 This command displays information returned by
13820 the Win32 API @code{GetThreadSelectorEntry} function.
13821 It takes an optional argument that is evaluated to
13822 a long value to give the information about this given selector.
13823 Without argument, this command displays information
13824 about the six segment registers.
13828 This is a Cygwin-specific alias of @code{info shared}.
13830 @kindex dll-symbols
13832 This command loads symbols from a dll similarly to
13833 add-sym command but without the need to specify a base address.
13835 @kindex set cygwin-exceptions
13836 @cindex debugging the Cygwin DLL
13837 @cindex Cygwin DLL, debugging
13838 @item set cygwin-exceptions @var{mode}
13839 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
13840 happen inside the Cygwin DLL. If @var{mode} is @code{off},
13841 @value{GDBN} will delay recognition of exceptions, and may ignore some
13842 exceptions which seem to be caused by internal Cygwin DLL
13843 ``bookkeeping''. This option is meant primarily for debugging the
13844 Cygwin DLL itself; the default value is @code{off} to avoid annoying
13845 @value{GDBN} users with false @code{SIGSEGV} signals.
13847 @kindex show cygwin-exceptions
13848 @item show cygwin-exceptions
13849 Displays whether @value{GDBN} will break on exceptions that happen
13850 inside the Cygwin DLL itself.
13852 @kindex set new-console
13853 @item set new-console @var{mode}
13854 If @var{mode} is @code{on} the debuggee will
13855 be started in a new console on next start.
13856 If @var{mode} is @code{off}i, the debuggee will
13857 be started in the same console as the debugger.
13859 @kindex show new-console
13860 @item show new-console
13861 Displays whether a new console is used
13862 when the debuggee is started.
13864 @kindex set new-group
13865 @item set new-group @var{mode}
13866 This boolean value controls whether the debuggee should
13867 start a new group or stay in the same group as the debugger.
13868 This affects the way the Windows OS handles
13871 @kindex show new-group
13872 @item show new-group
13873 Displays current value of new-group boolean.
13875 @kindex set debugevents
13876 @item set debugevents
13877 This boolean value adds debug output concerning kernel events related
13878 to the debuggee seen by the debugger. This includes events that
13879 signal thread and process creation and exit, DLL loading and
13880 unloading, console interrupts, and debugging messages produced by the
13881 Windows @code{OutputDebugString} API call.
13883 @kindex set debugexec
13884 @item set debugexec
13885 This boolean value adds debug output concerning execute events
13886 (such as resume thread) seen by the debugger.
13888 @kindex set debugexceptions
13889 @item set debugexceptions
13890 This boolean value adds debug output concerning exceptions in the
13891 debuggee seen by the debugger.
13893 @kindex set debugmemory
13894 @item set debugmemory
13895 This boolean value adds debug output concerning debuggee memory reads
13896 and writes by the debugger.
13900 This boolean values specifies whether the debuggee is called
13901 via a shell or directly (default value is on).
13905 Displays if the debuggee will be started with a shell.
13910 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
13913 @node Non-debug DLL Symbols
13914 @subsubsection Support for DLLs without Debugging Symbols
13915 @cindex DLLs with no debugging symbols
13916 @cindex Minimal symbols and DLLs
13918 Very often on windows, some of the DLLs that your program relies on do
13919 not include symbolic debugging information (for example,
13920 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
13921 symbols in a DLL, it relies on the minimal amount of symbolic
13922 information contained in the DLL's export table. This section
13923 describes working with such symbols, known internally to @value{GDBN} as
13924 ``minimal symbols''.
13926 Note that before the debugged program has started execution, no DLLs
13927 will have been loaded. The easiest way around this problem is simply to
13928 start the program --- either by setting a breakpoint or letting the
13929 program run once to completion. It is also possible to force
13930 @value{GDBN} to load a particular DLL before starting the executable ---
13931 see the shared library information in @ref{Files}, or the
13932 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
13933 explicitly loading symbols from a DLL with no debugging information will
13934 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
13935 which may adversely affect symbol lookup performance.
13937 @subsubsection DLL Name Prefixes
13939 In keeping with the naming conventions used by the Microsoft debugging
13940 tools, DLL export symbols are made available with a prefix based on the
13941 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
13942 also entered into the symbol table, so @code{CreateFileA} is often
13943 sufficient. In some cases there will be name clashes within a program
13944 (particularly if the executable itself includes full debugging symbols)
13945 necessitating the use of the fully qualified name when referring to the
13946 contents of the DLL. Use single-quotes around the name to avoid the
13947 exclamation mark (``!'') being interpreted as a language operator.
13949 Note that the internal name of the DLL may be all upper-case, even
13950 though the file name of the DLL is lower-case, or vice-versa. Since
13951 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
13952 some confusion. If in doubt, try the @code{info functions} and
13953 @code{info variables} commands or even @code{maint print msymbols}
13954 (@pxref{Symbols}). Here's an example:
13957 (@value{GDBP}) info function CreateFileA
13958 All functions matching regular expression "CreateFileA":
13960 Non-debugging symbols:
13961 0x77e885f4 CreateFileA
13962 0x77e885f4 KERNEL32!CreateFileA
13966 (@value{GDBP}) info function !
13967 All functions matching regular expression "!":
13969 Non-debugging symbols:
13970 0x6100114c cygwin1!__assert
13971 0x61004034 cygwin1!_dll_crt0@@0
13972 0x61004240 cygwin1!dll_crt0(per_process *)
13976 @subsubsection Working with Minimal Symbols
13978 Symbols extracted from a DLL's export table do not contain very much
13979 type information. All that @value{GDBN} can do is guess whether a symbol
13980 refers to a function or variable depending on the linker section that
13981 contains the symbol. Also note that the actual contents of the memory
13982 contained in a DLL are not available unless the program is running. This
13983 means that you cannot examine the contents of a variable or disassemble
13984 a function within a DLL without a running program.
13986 Variables are generally treated as pointers and dereferenced
13987 automatically. For this reason, it is often necessary to prefix a
13988 variable name with the address-of operator (``&'') and provide explicit
13989 type information in the command. Here's an example of the type of
13993 (@value{GDBP}) print 'cygwin1!__argv'
13998 (@value{GDBP}) x 'cygwin1!__argv'
13999 0x10021610: "\230y\""
14002 And two possible solutions:
14005 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
14006 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
14010 (@value{GDBP}) x/2x &'cygwin1!__argv'
14011 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
14012 (@value{GDBP}) x/x 0x10021608
14013 0x10021608: 0x0022fd98
14014 (@value{GDBP}) x/s 0x0022fd98
14015 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
14018 Setting a break point within a DLL is possible even before the program
14019 starts execution. However, under these circumstances, @value{GDBN} can't
14020 examine the initial instructions of the function in order to skip the
14021 function's frame set-up code. You can work around this by using ``*&''
14022 to set the breakpoint at a raw memory address:
14025 (@value{GDBP}) break *&'python22!PyOS_Readline'
14026 Breakpoint 1 at 0x1e04eff0
14029 The author of these extensions is not entirely convinced that setting a
14030 break point within a shared DLL like @file{kernel32.dll} is completely
14034 @subsection Commands Specific to @sc{gnu} Hurd Systems
14035 @cindex @sc{gnu} Hurd debugging
14037 This subsection describes @value{GDBN} commands specific to the
14038 @sc{gnu} Hurd native debugging.
14043 @kindex set signals@r{, Hurd command}
14044 @kindex set sigs@r{, Hurd command}
14045 This command toggles the state of inferior signal interception by
14046 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
14047 affected by this command. @code{sigs} is a shorthand alias for
14052 @kindex show signals@r{, Hurd command}
14053 @kindex show sigs@r{, Hurd command}
14054 Show the current state of intercepting inferior's signals.
14056 @item set signal-thread
14057 @itemx set sigthread
14058 @kindex set signal-thread
14059 @kindex set sigthread
14060 This command tells @value{GDBN} which thread is the @code{libc} signal
14061 thread. That thread is run when a signal is delivered to a running
14062 process. @code{set sigthread} is the shorthand alias of @code{set
14065 @item show signal-thread
14066 @itemx show sigthread
14067 @kindex show signal-thread
14068 @kindex show sigthread
14069 These two commands show which thread will run when the inferior is
14070 delivered a signal.
14073 @kindex set stopped@r{, Hurd command}
14074 This commands tells @value{GDBN} that the inferior process is stopped,
14075 as with the @code{SIGSTOP} signal. The stopped process can be
14076 continued by delivering a signal to it.
14079 @kindex show stopped@r{, Hurd command}
14080 This command shows whether @value{GDBN} thinks the debuggee is
14083 @item set exceptions
14084 @kindex set exceptions@r{, Hurd command}
14085 Use this command to turn off trapping of exceptions in the inferior.
14086 When exception trapping is off, neither breakpoints nor
14087 single-stepping will work. To restore the default, set exception
14090 @item show exceptions
14091 @kindex show exceptions@r{, Hurd command}
14092 Show the current state of trapping exceptions in the inferior.
14094 @item set task pause
14095 @kindex set task@r{, Hurd commands}
14096 @cindex task attributes (@sc{gnu} Hurd)
14097 @cindex pause current task (@sc{gnu} Hurd)
14098 This command toggles task suspension when @value{GDBN} has control.
14099 Setting it to on takes effect immediately, and the task is suspended
14100 whenever @value{GDBN} gets control. Setting it to off will take
14101 effect the next time the inferior is continued. If this option is set
14102 to off, you can use @code{set thread default pause on} or @code{set
14103 thread pause on} (see below) to pause individual threads.
14105 @item show task pause
14106 @kindex show task@r{, Hurd commands}
14107 Show the current state of task suspension.
14109 @item set task detach-suspend-count
14110 @cindex task suspend count
14111 @cindex detach from task, @sc{gnu} Hurd
14112 This command sets the suspend count the task will be left with when
14113 @value{GDBN} detaches from it.
14115 @item show task detach-suspend-count
14116 Show the suspend count the task will be left with when detaching.
14118 @item set task exception-port
14119 @itemx set task excp
14120 @cindex task exception port, @sc{gnu} Hurd
14121 This command sets the task exception port to which @value{GDBN} will
14122 forward exceptions. The argument should be the value of the @dfn{send
14123 rights} of the task. @code{set task excp} is a shorthand alias.
14125 @item set noninvasive
14126 @cindex noninvasive task options
14127 This command switches @value{GDBN} to a mode that is the least
14128 invasive as far as interfering with the inferior is concerned. This
14129 is the same as using @code{set task pause}, @code{set exceptions}, and
14130 @code{set signals} to values opposite to the defaults.
14132 @item info send-rights
14133 @itemx info receive-rights
14134 @itemx info port-rights
14135 @itemx info port-sets
14136 @itemx info dead-names
14139 @cindex send rights, @sc{gnu} Hurd
14140 @cindex receive rights, @sc{gnu} Hurd
14141 @cindex port rights, @sc{gnu} Hurd
14142 @cindex port sets, @sc{gnu} Hurd
14143 @cindex dead names, @sc{gnu} Hurd
14144 These commands display information about, respectively, send rights,
14145 receive rights, port rights, port sets, and dead names of a task.
14146 There are also shorthand aliases: @code{info ports} for @code{info
14147 port-rights} and @code{info psets} for @code{info port-sets}.
14149 @item set thread pause
14150 @kindex set thread@r{, Hurd command}
14151 @cindex thread properties, @sc{gnu} Hurd
14152 @cindex pause current thread (@sc{gnu} Hurd)
14153 This command toggles current thread suspension when @value{GDBN} has
14154 control. Setting it to on takes effect immediately, and the current
14155 thread is suspended whenever @value{GDBN} gets control. Setting it to
14156 off will take effect the next time the inferior is continued.
14157 Normally, this command has no effect, since when @value{GDBN} has
14158 control, the whole task is suspended. However, if you used @code{set
14159 task pause off} (see above), this command comes in handy to suspend
14160 only the current thread.
14162 @item show thread pause
14163 @kindex show thread@r{, Hurd command}
14164 This command shows the state of current thread suspension.
14166 @item set thread run
14167 This command sets whether the current thread is allowed to run.
14169 @item show thread run
14170 Show whether the current thread is allowed to run.
14172 @item set thread detach-suspend-count
14173 @cindex thread suspend count, @sc{gnu} Hurd
14174 @cindex detach from thread, @sc{gnu} Hurd
14175 This command sets the suspend count @value{GDBN} will leave on a
14176 thread when detaching. This number is relative to the suspend count
14177 found by @value{GDBN} when it notices the thread; use @code{set thread
14178 takeover-suspend-count} to force it to an absolute value.
14180 @item show thread detach-suspend-count
14181 Show the suspend count @value{GDBN} will leave on the thread when
14184 @item set thread exception-port
14185 @itemx set thread excp
14186 Set the thread exception port to which to forward exceptions. This
14187 overrides the port set by @code{set task exception-port} (see above).
14188 @code{set thread excp} is the shorthand alias.
14190 @item set thread takeover-suspend-count
14191 Normally, @value{GDBN}'s thread suspend counts are relative to the
14192 value @value{GDBN} finds when it notices each thread. This command
14193 changes the suspend counts to be absolute instead.
14195 @item set thread default
14196 @itemx show thread default
14197 @cindex thread default settings, @sc{gnu} Hurd
14198 Each of the above @code{set thread} commands has a @code{set thread
14199 default} counterpart (e.g., @code{set thread default pause}, @code{set
14200 thread default exception-port}, etc.). The @code{thread default}
14201 variety of commands sets the default thread properties for all
14202 threads; you can then change the properties of individual threads with
14203 the non-default commands.
14208 @subsection QNX Neutrino
14209 @cindex QNX Neutrino
14211 @value{GDBN} provides the following commands specific to the QNX
14215 @item set debug nto-debug
14216 @kindex set debug nto-debug
14217 When set to on, enables debugging messages specific to the QNX
14220 @item show debug nto-debug
14221 @kindex show debug nto-debug
14222 Show the current state of QNX Neutrino messages.
14227 @section Embedded Operating Systems
14229 This section describes configurations involving the debugging of
14230 embedded operating systems that are available for several different
14234 * VxWorks:: Using @value{GDBN} with VxWorks
14237 @value{GDBN} includes the ability to debug programs running on
14238 various real-time operating systems.
14241 @subsection Using @value{GDBN} with VxWorks
14247 @kindex target vxworks
14248 @item target vxworks @var{machinename}
14249 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
14250 is the target system's machine name or IP address.
14254 On VxWorks, @code{load} links @var{filename} dynamically on the
14255 current target system as well as adding its symbols in @value{GDBN}.
14257 @value{GDBN} enables developers to spawn and debug tasks running on networked
14258 VxWorks targets from a Unix host. Already-running tasks spawned from
14259 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
14260 both the Unix host and on the VxWorks target. The program
14261 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
14262 installed with the name @code{vxgdb}, to distinguish it from a
14263 @value{GDBN} for debugging programs on the host itself.)
14266 @item VxWorks-timeout @var{args}
14267 @kindex vxworks-timeout
14268 All VxWorks-based targets now support the option @code{vxworks-timeout}.
14269 This option is set by the user, and @var{args} represents the number of
14270 seconds @value{GDBN} waits for responses to rpc's. You might use this if
14271 your VxWorks target is a slow software simulator or is on the far side
14272 of a thin network line.
14275 The following information on connecting to VxWorks was current when
14276 this manual was produced; newer releases of VxWorks may use revised
14279 @findex INCLUDE_RDB
14280 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
14281 to include the remote debugging interface routines in the VxWorks
14282 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
14283 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
14284 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
14285 source debugging task @code{tRdbTask} when VxWorks is booted. For more
14286 information on configuring and remaking VxWorks, see the manufacturer's
14288 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
14290 Once you have included @file{rdb.a} in your VxWorks system image and set
14291 your Unix execution search path to find @value{GDBN}, you are ready to
14292 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
14293 @code{vxgdb}, depending on your installation).
14295 @value{GDBN} comes up showing the prompt:
14302 * VxWorks Connection:: Connecting to VxWorks
14303 * VxWorks Download:: VxWorks download
14304 * VxWorks Attach:: Running tasks
14307 @node VxWorks Connection
14308 @subsubsection Connecting to VxWorks
14310 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
14311 network. To connect to a target whose host name is ``@code{tt}'', type:
14314 (vxgdb) target vxworks tt
14318 @value{GDBN} displays messages like these:
14321 Attaching remote machine across net...
14326 @value{GDBN} then attempts to read the symbol tables of any object modules
14327 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
14328 these files by searching the directories listed in the command search
14329 path (@pxref{Environment, ,Your Program's Environment}); if it fails
14330 to find an object file, it displays a message such as:
14333 prog.o: No such file or directory.
14336 When this happens, add the appropriate directory to the search path with
14337 the @value{GDBN} command @code{path}, and execute the @code{target}
14340 @node VxWorks Download
14341 @subsubsection VxWorks Download
14343 @cindex download to VxWorks
14344 If you have connected to the VxWorks target and you want to debug an
14345 object that has not yet been loaded, you can use the @value{GDBN}
14346 @code{load} command to download a file from Unix to VxWorks
14347 incrementally. The object file given as an argument to the @code{load}
14348 command is actually opened twice: first by the VxWorks target in order
14349 to download the code, then by @value{GDBN} in order to read the symbol
14350 table. This can lead to problems if the current working directories on
14351 the two systems differ. If both systems have NFS mounted the same
14352 filesystems, you can avoid these problems by using absolute paths.
14353 Otherwise, it is simplest to set the working directory on both systems
14354 to the directory in which the object file resides, and then to reference
14355 the file by its name, without any path. For instance, a program
14356 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
14357 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
14358 program, type this on VxWorks:
14361 -> cd "@var{vxpath}/vw/demo/rdb"
14365 Then, in @value{GDBN}, type:
14368 (vxgdb) cd @var{hostpath}/vw/demo/rdb
14369 (vxgdb) load prog.o
14372 @value{GDBN} displays a response similar to this:
14375 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
14378 You can also use the @code{load} command to reload an object module
14379 after editing and recompiling the corresponding source file. Note that
14380 this makes @value{GDBN} delete all currently-defined breakpoints,
14381 auto-displays, and convenience variables, and to clear the value
14382 history. (This is necessary in order to preserve the integrity of
14383 debugger's data structures that reference the target system's symbol
14386 @node VxWorks Attach
14387 @subsubsection Running Tasks
14389 @cindex running VxWorks tasks
14390 You can also attach to an existing task using the @code{attach} command as
14394 (vxgdb) attach @var{task}
14398 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
14399 or suspended when you attach to it. Running tasks are suspended at
14400 the time of attachment.
14402 @node Embedded Processors
14403 @section Embedded Processors
14405 This section goes into details specific to particular embedded
14408 @cindex send command to simulator
14409 Whenever a specific embedded processor has a simulator, @value{GDBN}
14410 allows to send an arbitrary command to the simulator.
14413 @item sim @var{command}
14414 @kindex sim@r{, a command}
14415 Send an arbitrary @var{command} string to the simulator. Consult the
14416 documentation for the specific simulator in use for information about
14417 acceptable commands.
14423 * M32R/D:: Renesas M32R/D
14424 * M68K:: Motorola M68K
14425 * MIPS Embedded:: MIPS Embedded
14426 * OpenRISC 1000:: OpenRisc 1000
14427 * PA:: HP PA Embedded
14428 * PowerPC:: PowerPC
14429 * Sparclet:: Tsqware Sparclet
14430 * Sparclite:: Fujitsu Sparclite
14431 * Z8000:: Zilog Z8000
14434 * Super-H:: Renesas Super-H
14443 @item target rdi @var{dev}
14444 ARM Angel monitor, via RDI library interface to ADP protocol. You may
14445 use this target to communicate with both boards running the Angel
14446 monitor, or with the EmbeddedICE JTAG debug device.
14449 @item target rdp @var{dev}
14454 @value{GDBN} provides the following ARM-specific commands:
14457 @item set arm disassembler
14459 This commands selects from a list of disassembly styles. The
14460 @code{"std"} style is the standard style.
14462 @item show arm disassembler
14464 Show the current disassembly style.
14466 @item set arm apcs32
14467 @cindex ARM 32-bit mode
14468 This command toggles ARM operation mode between 32-bit and 26-bit.
14470 @item show arm apcs32
14471 Display the current usage of the ARM 32-bit mode.
14473 @item set arm fpu @var{fputype}
14474 This command sets the ARM floating-point unit (FPU) type. The
14475 argument @var{fputype} can be one of these:
14479 Determine the FPU type by querying the OS ABI.
14481 Software FPU, with mixed-endian doubles on little-endian ARM
14484 GCC-compiled FPA co-processor.
14486 Software FPU with pure-endian doubles.
14492 Show the current type of the FPU.
14495 This command forces @value{GDBN} to use the specified ABI.
14498 Show the currently used ABI.
14500 @item set debug arm
14501 Toggle whether to display ARM-specific debugging messages from the ARM
14502 target support subsystem.
14504 @item show debug arm
14505 Show whether ARM-specific debugging messages are enabled.
14508 The following commands are available when an ARM target is debugged
14509 using the RDI interface:
14512 @item rdilogfile @r{[}@var{file}@r{]}
14514 @cindex ADP (Angel Debugger Protocol) logging
14515 Set the filename for the ADP (Angel Debugger Protocol) packet log.
14516 With an argument, sets the log file to the specified @var{file}. With
14517 no argument, show the current log file name. The default log file is
14520 @item rdilogenable @r{[}@var{arg}@r{]}
14521 @kindex rdilogenable
14522 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
14523 enables logging, with an argument 0 or @code{"no"} disables it. With
14524 no arguments displays the current setting. When logging is enabled,
14525 ADP packets exchanged between @value{GDBN} and the RDI target device
14526 are logged to a file.
14528 @item set rdiromatzero
14529 @kindex set rdiromatzero
14530 @cindex ROM at zero address, RDI
14531 Tell @value{GDBN} whether the target has ROM at address 0. If on,
14532 vector catching is disabled, so that zero address can be used. If off
14533 (the default), vector catching is enabled. For this command to take
14534 effect, it needs to be invoked prior to the @code{target rdi} command.
14536 @item show rdiromatzero
14537 @kindex show rdiromatzero
14538 Show the current setting of ROM at zero address.
14540 @item set rdiheartbeat
14541 @kindex set rdiheartbeat
14542 @cindex RDI heartbeat
14543 Enable or disable RDI heartbeat packets. It is not recommended to
14544 turn on this option, since it confuses ARM and EPI JTAG interface, as
14545 well as the Angel monitor.
14547 @item show rdiheartbeat
14548 @kindex show rdiheartbeat
14549 Show the setting of RDI heartbeat packets.
14554 @subsection Renesas M32R/D and M32R/SDI
14557 @kindex target m32r
14558 @item target m32r @var{dev}
14559 Renesas M32R/D ROM monitor.
14561 @kindex target m32rsdi
14562 @item target m32rsdi @var{dev}
14563 Renesas M32R SDI server, connected via parallel port to the board.
14566 The following @value{GDBN} commands are specific to the M32R monitor:
14569 @item set download-path @var{path}
14570 @kindex set download-path
14571 @cindex find downloadable @sc{srec} files (M32R)
14572 Set the default path for finding downloadable @sc{srec} files.
14574 @item show download-path
14575 @kindex show download-path
14576 Show the default path for downloadable @sc{srec} files.
14578 @item set board-address @var{addr}
14579 @kindex set board-address
14580 @cindex M32-EVA target board address
14581 Set the IP address for the M32R-EVA target board.
14583 @item show board-address
14584 @kindex show board-address
14585 Show the current IP address of the target board.
14587 @item set server-address @var{addr}
14588 @kindex set server-address
14589 @cindex download server address (M32R)
14590 Set the IP address for the download server, which is the @value{GDBN}'s
14593 @item show server-address
14594 @kindex show server-address
14595 Display the IP address of the download server.
14597 @item upload @r{[}@var{file}@r{]}
14598 @kindex upload@r{, M32R}
14599 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
14600 upload capability. If no @var{file} argument is given, the current
14601 executable file is uploaded.
14603 @item tload @r{[}@var{file}@r{]}
14604 @kindex tload@r{, M32R}
14605 Test the @code{upload} command.
14608 The following commands are available for M32R/SDI:
14613 @cindex reset SDI connection, M32R
14614 This command resets the SDI connection.
14618 This command shows the SDI connection status.
14621 @kindex debug_chaos
14622 @cindex M32R/Chaos debugging
14623 Instructs the remote that M32R/Chaos debugging is to be used.
14625 @item use_debug_dma
14626 @kindex use_debug_dma
14627 Instructs the remote to use the DEBUG_DMA method of accessing memory.
14630 @kindex use_mon_code
14631 Instructs the remote to use the MON_CODE method of accessing memory.
14634 @kindex use_ib_break
14635 Instructs the remote to set breakpoints by IB break.
14637 @item use_dbt_break
14638 @kindex use_dbt_break
14639 Instructs the remote to set breakpoints by DBT.
14645 The Motorola m68k configuration includes ColdFire support, and a
14646 target command for the following ROM monitor.
14650 @kindex target dbug
14651 @item target dbug @var{dev}
14652 dBUG ROM monitor for Motorola ColdFire.
14656 @node MIPS Embedded
14657 @subsection MIPS Embedded
14659 @cindex MIPS boards
14660 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
14661 MIPS board attached to a serial line. This is available when
14662 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
14665 Use these @value{GDBN} commands to specify the connection to your target board:
14668 @item target mips @var{port}
14669 @kindex target mips @var{port}
14670 To run a program on the board, start up @code{@value{GDBP}} with the
14671 name of your program as the argument. To connect to the board, use the
14672 command @samp{target mips @var{port}}, where @var{port} is the name of
14673 the serial port connected to the board. If the program has not already
14674 been downloaded to the board, you may use the @code{load} command to
14675 download it. You can then use all the usual @value{GDBN} commands.
14677 For example, this sequence connects to the target board through a serial
14678 port, and loads and runs a program called @var{prog} through the
14682 host$ @value{GDBP} @var{prog}
14683 @value{GDBN} is free software and @dots{}
14684 (@value{GDBP}) target mips /dev/ttyb
14685 (@value{GDBP}) load @var{prog}
14689 @item target mips @var{hostname}:@var{portnumber}
14690 On some @value{GDBN} host configurations, you can specify a TCP
14691 connection (for instance, to a serial line managed by a terminal
14692 concentrator) instead of a serial port, using the syntax
14693 @samp{@var{hostname}:@var{portnumber}}.
14695 @item target pmon @var{port}
14696 @kindex target pmon @var{port}
14699 @item target ddb @var{port}
14700 @kindex target ddb @var{port}
14701 NEC's DDB variant of PMON for Vr4300.
14703 @item target lsi @var{port}
14704 @kindex target lsi @var{port}
14705 LSI variant of PMON.
14707 @kindex target r3900
14708 @item target r3900 @var{dev}
14709 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
14711 @kindex target array
14712 @item target array @var{dev}
14713 Array Tech LSI33K RAID controller board.
14719 @value{GDBN} also supports these special commands for MIPS targets:
14722 @item set mipsfpu double
14723 @itemx set mipsfpu single
14724 @itemx set mipsfpu none
14725 @itemx set mipsfpu auto
14726 @itemx show mipsfpu
14727 @kindex set mipsfpu
14728 @kindex show mipsfpu
14729 @cindex MIPS remote floating point
14730 @cindex floating point, MIPS remote
14731 If your target board does not support the MIPS floating point
14732 coprocessor, you should use the command @samp{set mipsfpu none} (if you
14733 need this, you may wish to put the command in your @value{GDBN} init
14734 file). This tells @value{GDBN} how to find the return value of
14735 functions which return floating point values. It also allows
14736 @value{GDBN} to avoid saving the floating point registers when calling
14737 functions on the board. If you are using a floating point coprocessor
14738 with only single precision floating point support, as on the @sc{r4650}
14739 processor, use the command @samp{set mipsfpu single}. The default
14740 double precision floating point coprocessor may be selected using
14741 @samp{set mipsfpu double}.
14743 In previous versions the only choices were double precision or no
14744 floating point, so @samp{set mipsfpu on} will select double precision
14745 and @samp{set mipsfpu off} will select no floating point.
14747 As usual, you can inquire about the @code{mipsfpu} variable with
14748 @samp{show mipsfpu}.
14750 @item set timeout @var{seconds}
14751 @itemx set retransmit-timeout @var{seconds}
14752 @itemx show timeout
14753 @itemx show retransmit-timeout
14754 @cindex @code{timeout}, MIPS protocol
14755 @cindex @code{retransmit-timeout}, MIPS protocol
14756 @kindex set timeout
14757 @kindex show timeout
14758 @kindex set retransmit-timeout
14759 @kindex show retransmit-timeout
14760 You can control the timeout used while waiting for a packet, in the MIPS
14761 remote protocol, with the @code{set timeout @var{seconds}} command. The
14762 default is 5 seconds. Similarly, you can control the timeout used while
14763 waiting for an acknowledgement of a packet with the @code{set
14764 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
14765 You can inspect both values with @code{show timeout} and @code{show
14766 retransmit-timeout}. (These commands are @emph{only} available when
14767 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
14769 The timeout set by @code{set timeout} does not apply when @value{GDBN}
14770 is waiting for your program to stop. In that case, @value{GDBN} waits
14771 forever because it has no way of knowing how long the program is going
14772 to run before stopping.
14774 @item set syn-garbage-limit @var{num}
14775 @kindex set syn-garbage-limit@r{, MIPS remote}
14776 @cindex synchronize with remote MIPS target
14777 Limit the maximum number of characters @value{GDBN} should ignore when
14778 it tries to synchronize with the remote target. The default is 10
14779 characters. Setting the limit to -1 means there's no limit.
14781 @item show syn-garbage-limit
14782 @kindex show syn-garbage-limit@r{, MIPS remote}
14783 Show the current limit on the number of characters to ignore when
14784 trying to synchronize with the remote system.
14786 @item set monitor-prompt @var{prompt}
14787 @kindex set monitor-prompt@r{, MIPS remote}
14788 @cindex remote monitor prompt
14789 Tell @value{GDBN} to expect the specified @var{prompt} string from the
14790 remote monitor. The default depends on the target:
14800 @item show monitor-prompt
14801 @kindex show monitor-prompt@r{, MIPS remote}
14802 Show the current strings @value{GDBN} expects as the prompt from the
14805 @item set monitor-warnings
14806 @kindex set monitor-warnings@r{, MIPS remote}
14807 Enable or disable monitor warnings about hardware breakpoints. This
14808 has effect only for the @code{lsi} target. When on, @value{GDBN} will
14809 display warning messages whose codes are returned by the @code{lsi}
14810 PMON monitor for breakpoint commands.
14812 @item show monitor-warnings
14813 @kindex show monitor-warnings@r{, MIPS remote}
14814 Show the current setting of printing monitor warnings.
14816 @item pmon @var{command}
14817 @kindex pmon@r{, MIPS remote}
14818 @cindex send PMON command
14819 This command allows sending an arbitrary @var{command} string to the
14820 monitor. The monitor must be in debug mode for this to work.
14823 @node OpenRISC 1000
14824 @subsection OpenRISC 1000
14825 @cindex OpenRISC 1000
14827 @cindex or1k boards
14828 See OR1k Architecture document (@uref{www.opencores.org}) for more information
14829 about platform and commands.
14833 @kindex target jtag
14834 @item target jtag jtag://@var{host}:@var{port}
14836 Connects to remote JTAG server.
14837 JTAG remote server can be either an or1ksim or JTAG server,
14838 connected via parallel port to the board.
14840 Example: @code{target jtag jtag://localhost:9999}
14843 @item or1ksim @var{command}
14844 If connected to @code{or1ksim} OpenRISC 1000 Architectural
14845 Simulator, proprietary commands can be executed.
14847 @kindex info or1k spr
14848 @item info or1k spr
14849 Displays spr groups.
14851 @item info or1k spr @var{group}
14852 @itemx info or1k spr @var{groupno}
14853 Displays register names in selected group.
14855 @item info or1k spr @var{group} @var{register}
14856 @itemx info or1k spr @var{register}
14857 @itemx info or1k spr @var{groupno} @var{registerno}
14858 @itemx info or1k spr @var{registerno}
14859 Shows information about specified spr register.
14862 @item spr @var{group} @var{register} @var{value}
14863 @itemx spr @var{register @var{value}}
14864 @itemx spr @var{groupno} @var{registerno @var{value}}
14865 @itemx spr @var{registerno @var{value}}
14866 Writes @var{value} to specified spr register.
14869 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
14870 It is very similar to @value{GDBN} trace, except it does not interfere with normal
14871 program execution and is thus much faster. Hardware breakpoints/watchpoint
14872 triggers can be set using:
14875 Load effective address/data
14877 Store effective address/data
14879 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
14884 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
14885 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
14887 @code{htrace} commands:
14888 @cindex OpenRISC 1000 htrace
14891 @item hwatch @var{conditional}
14892 Set hardware watchpoint on combination of Load/Store Effective Address(es)
14893 or Data. For example:
14895 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
14897 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
14901 Display information about current HW trace configuration.
14903 @item htrace trigger @var{conditional}
14904 Set starting criteria for HW trace.
14906 @item htrace qualifier @var{conditional}
14907 Set acquisition qualifier for HW trace.
14909 @item htrace stop @var{conditional}
14910 Set HW trace stopping criteria.
14912 @item htrace record [@var{data}]*
14913 Selects the data to be recorded, when qualifier is met and HW trace was
14916 @item htrace enable
14917 @itemx htrace disable
14918 Enables/disables the HW trace.
14920 @item htrace rewind [@var{filename}]
14921 Clears currently recorded trace data.
14923 If filename is specified, new trace file is made and any newly collected data
14924 will be written there.
14926 @item htrace print [@var{start} [@var{len}]]
14927 Prints trace buffer, using current record configuration.
14929 @item htrace mode continuous
14930 Set continuous trace mode.
14932 @item htrace mode suspend
14933 Set suspend trace mode.
14938 @subsection PowerPC
14941 @kindex target dink32
14942 @item target dink32 @var{dev}
14943 DINK32 ROM monitor.
14945 @kindex target ppcbug
14946 @item target ppcbug @var{dev}
14947 @kindex target ppcbug1
14948 @item target ppcbug1 @var{dev}
14949 PPCBUG ROM monitor for PowerPC.
14952 @item target sds @var{dev}
14953 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
14956 @cindex SDS protocol
14957 The following commands specific to the SDS protocol are supported
14961 @item set sdstimeout @var{nsec}
14962 @kindex set sdstimeout
14963 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
14964 default is 2 seconds.
14966 @item show sdstimeout
14967 @kindex show sdstimeout
14968 Show the current value of the SDS timeout.
14970 @item sds @var{command}
14971 @kindex sds@r{, a command}
14972 Send the specified @var{command} string to the SDS monitor.
14977 @subsection HP PA Embedded
14981 @kindex target op50n
14982 @item target op50n @var{dev}
14983 OP50N monitor, running on an OKI HPPA board.
14985 @kindex target w89k
14986 @item target w89k @var{dev}
14987 W89K monitor, running on a Winbond HPPA board.
14992 @subsection Tsqware Sparclet
14996 @value{GDBN} enables developers to debug tasks running on
14997 Sparclet targets from a Unix host.
14998 @value{GDBN} uses code that runs on
14999 both the Unix host and on the Sparclet target. The program
15000 @code{@value{GDBP}} is installed and executed on the Unix host.
15003 @item remotetimeout @var{args}
15004 @kindex remotetimeout
15005 @value{GDBN} supports the option @code{remotetimeout}.
15006 This option is set by the user, and @var{args} represents the number of
15007 seconds @value{GDBN} waits for responses.
15010 @cindex compiling, on Sparclet
15011 When compiling for debugging, include the options @samp{-g} to get debug
15012 information and @samp{-Ttext} to relocate the program to where you wish to
15013 load it on the target. You may also want to add the options @samp{-n} or
15014 @samp{-N} in order to reduce the size of the sections. Example:
15017 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
15020 You can use @code{objdump} to verify that the addresses are what you intended:
15023 sparclet-aout-objdump --headers --syms prog
15026 @cindex running, on Sparclet
15028 your Unix execution search path to find @value{GDBN}, you are ready to
15029 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
15030 (or @code{sparclet-aout-gdb}, depending on your installation).
15032 @value{GDBN} comes up showing the prompt:
15039 * Sparclet File:: Setting the file to debug
15040 * Sparclet Connection:: Connecting to Sparclet
15041 * Sparclet Download:: Sparclet download
15042 * Sparclet Execution:: Running and debugging
15045 @node Sparclet File
15046 @subsubsection Setting File to Debug
15048 The @value{GDBN} command @code{file} lets you choose with program to debug.
15051 (gdbslet) file prog
15055 @value{GDBN} then attempts to read the symbol table of @file{prog}.
15056 @value{GDBN} locates
15057 the file by searching the directories listed in the command search
15059 If the file was compiled with debug information (option @samp{-g}), source
15060 files will be searched as well.
15061 @value{GDBN} locates
15062 the source files by searching the directories listed in the directory search
15063 path (@pxref{Environment, ,Your Program's Environment}).
15065 to find a file, it displays a message such as:
15068 prog: No such file or directory.
15071 When this happens, add the appropriate directories to the search paths with
15072 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
15073 @code{target} command again.
15075 @node Sparclet Connection
15076 @subsubsection Connecting to Sparclet
15078 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
15079 To connect to a target on serial port ``@code{ttya}'', type:
15082 (gdbslet) target sparclet /dev/ttya
15083 Remote target sparclet connected to /dev/ttya
15084 main () at ../prog.c:3
15088 @value{GDBN} displays messages like these:
15094 @node Sparclet Download
15095 @subsubsection Sparclet Download
15097 @cindex download to Sparclet
15098 Once connected to the Sparclet target,
15099 you can use the @value{GDBN}
15100 @code{load} command to download the file from the host to the target.
15101 The file name and load offset should be given as arguments to the @code{load}
15103 Since the file format is aout, the program must be loaded to the starting
15104 address. You can use @code{objdump} to find out what this value is. The load
15105 offset is an offset which is added to the VMA (virtual memory address)
15106 of each of the file's sections.
15107 For instance, if the program
15108 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
15109 and bss at 0x12010170, in @value{GDBN}, type:
15112 (gdbslet) load prog 0x12010000
15113 Loading section .text, size 0xdb0 vma 0x12010000
15116 If the code is loaded at a different address then what the program was linked
15117 to, you may need to use the @code{section} and @code{add-symbol-file} commands
15118 to tell @value{GDBN} where to map the symbol table.
15120 @node Sparclet Execution
15121 @subsubsection Running and Debugging
15123 @cindex running and debugging Sparclet programs
15124 You can now begin debugging the task using @value{GDBN}'s execution control
15125 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
15126 manual for the list of commands.
15130 Breakpoint 1 at 0x12010000: file prog.c, line 3.
15132 Starting program: prog
15133 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
15134 3 char *symarg = 0;
15136 4 char *execarg = "hello!";
15141 @subsection Fujitsu Sparclite
15145 @kindex target sparclite
15146 @item target sparclite @var{dev}
15147 Fujitsu sparclite boards, used only for the purpose of loading.
15148 You must use an additional command to debug the program.
15149 For example: target remote @var{dev} using @value{GDBN} standard
15155 @subsection Zilog Z8000
15158 @cindex simulator, Z8000
15159 @cindex Zilog Z8000 simulator
15161 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
15164 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
15165 unsegmented variant of the Z8000 architecture) or the Z8001 (the
15166 segmented variant). The simulator recognizes which architecture is
15167 appropriate by inspecting the object code.
15170 @item target sim @var{args}
15172 @kindex target sim@r{, with Z8000}
15173 Debug programs on a simulated CPU. If the simulator supports setup
15174 options, specify them via @var{args}.
15178 After specifying this target, you can debug programs for the simulated
15179 CPU in the same style as programs for your host computer; use the
15180 @code{file} command to load a new program image, the @code{run} command
15181 to run your program, and so on.
15183 As well as making available all the usual machine registers
15184 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
15185 additional items of information as specially named registers:
15190 Counts clock-ticks in the simulator.
15193 Counts instructions run in the simulator.
15196 Execution time in 60ths of a second.
15200 You can refer to these values in @value{GDBN} expressions with the usual
15201 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
15202 conditional breakpoint that suspends only after at least 5000
15203 simulated clock ticks.
15206 @subsection Atmel AVR
15209 When configured for debugging the Atmel AVR, @value{GDBN} supports the
15210 following AVR-specific commands:
15213 @item info io_registers
15214 @kindex info io_registers@r{, AVR}
15215 @cindex I/O registers (Atmel AVR)
15216 This command displays information about the AVR I/O registers. For
15217 each register, @value{GDBN} prints its number and value.
15224 When configured for debugging CRIS, @value{GDBN} provides the
15225 following CRIS-specific commands:
15228 @item set cris-version @var{ver}
15229 @cindex CRIS version
15230 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
15231 The CRIS version affects register names and sizes. This command is useful in
15232 case autodetection of the CRIS version fails.
15234 @item show cris-version
15235 Show the current CRIS version.
15237 @item set cris-dwarf2-cfi
15238 @cindex DWARF-2 CFI and CRIS
15239 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
15240 Change to @samp{off} when using @code{gcc-cris} whose version is below
15243 @item show cris-dwarf2-cfi
15244 Show the current state of using DWARF-2 CFI.
15246 @item set cris-mode @var{mode}
15248 Set the current CRIS mode to @var{mode}. It should only be changed when
15249 debugging in guru mode, in which case it should be set to
15250 @samp{guru} (the default is @samp{normal}).
15252 @item show cris-mode
15253 Show the current CRIS mode.
15257 @subsection Renesas Super-H
15260 For the Renesas Super-H processor, @value{GDBN} provides these
15265 @kindex regs@r{, Super-H}
15266 Show the values of all Super-H registers.
15270 @node Architectures
15271 @section Architectures
15273 This section describes characteristics of architectures that affect
15274 all uses of @value{GDBN} with the architecture, both native and cross.
15281 * HPPA:: HP PA architecture
15282 * SPU:: Cell Broadband Engine SPU architecture
15286 @subsection x86 Architecture-specific Issues
15289 @item set struct-convention @var{mode}
15290 @kindex set struct-convention
15291 @cindex struct return convention
15292 @cindex struct/union returned in registers
15293 Set the convention used by the inferior to return @code{struct}s and
15294 @code{union}s from functions to @var{mode}. Possible values of
15295 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
15296 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
15297 are returned on the stack, while @code{"reg"} means that a
15298 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
15299 be returned in a register.
15301 @item show struct-convention
15302 @kindex show struct-convention
15303 Show the current setting of the convention to return @code{struct}s
15312 @kindex set rstack_high_address
15313 @cindex AMD 29K register stack
15314 @cindex register stack, AMD29K
15315 @item set rstack_high_address @var{address}
15316 On AMD 29000 family processors, registers are saved in a separate
15317 @dfn{register stack}. There is no way for @value{GDBN} to determine the
15318 extent of this stack. Normally, @value{GDBN} just assumes that the
15319 stack is ``large enough''. This may result in @value{GDBN} referencing
15320 memory locations that do not exist. If necessary, you can get around
15321 this problem by specifying the ending address of the register stack with
15322 the @code{set rstack_high_address} command. The argument should be an
15323 address, which you probably want to precede with @samp{0x} to specify in
15326 @kindex show rstack_high_address
15327 @item show rstack_high_address
15328 Display the current limit of the register stack, on AMD 29000 family
15336 See the following section.
15341 @cindex stack on Alpha
15342 @cindex stack on MIPS
15343 @cindex Alpha stack
15345 Alpha- and MIPS-based computers use an unusual stack frame, which
15346 sometimes requires @value{GDBN} to search backward in the object code to
15347 find the beginning of a function.
15349 @cindex response time, MIPS debugging
15350 To improve response time (especially for embedded applications, where
15351 @value{GDBN} may be restricted to a slow serial line for this search)
15352 you may want to limit the size of this search, using one of these
15356 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
15357 @item set heuristic-fence-post @var{limit}
15358 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
15359 search for the beginning of a function. A value of @var{0} (the
15360 default) means there is no limit. However, except for @var{0}, the
15361 larger the limit the more bytes @code{heuristic-fence-post} must search
15362 and therefore the longer it takes to run. You should only need to use
15363 this command when debugging a stripped executable.
15365 @item show heuristic-fence-post
15366 Display the current limit.
15370 These commands are available @emph{only} when @value{GDBN} is configured
15371 for debugging programs on Alpha or MIPS processors.
15373 Several MIPS-specific commands are available when debugging MIPS
15377 @item set mips abi @var{arg}
15378 @kindex set mips abi
15379 @cindex set ABI for MIPS
15380 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
15381 values of @var{arg} are:
15385 The default ABI associated with the current binary (this is the
15396 @item show mips abi
15397 @kindex show mips abi
15398 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
15401 @itemx show mipsfpu
15402 @xref{MIPS Embedded, set mipsfpu}.
15404 @item set mips mask-address @var{arg}
15405 @kindex set mips mask-address
15406 @cindex MIPS addresses, masking
15407 This command determines whether the most-significant 32 bits of 64-bit
15408 MIPS addresses are masked off. The argument @var{arg} can be
15409 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
15410 setting, which lets @value{GDBN} determine the correct value.
15412 @item show mips mask-address
15413 @kindex show mips mask-address
15414 Show whether the upper 32 bits of MIPS addresses are masked off or
15417 @item set remote-mips64-transfers-32bit-regs
15418 @kindex set remote-mips64-transfers-32bit-regs
15419 This command controls compatibility with 64-bit MIPS targets that
15420 transfer data in 32-bit quantities. If you have an old MIPS 64 target
15421 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
15422 and 64 bits for other registers, set this option to @samp{on}.
15424 @item show remote-mips64-transfers-32bit-regs
15425 @kindex show remote-mips64-transfers-32bit-regs
15426 Show the current setting of compatibility with older MIPS 64 targets.
15428 @item set debug mips
15429 @kindex set debug mips
15430 This command turns on and off debugging messages for the MIPS-specific
15431 target code in @value{GDBN}.
15433 @item show debug mips
15434 @kindex show debug mips
15435 Show the current setting of MIPS debugging messages.
15441 @cindex HPPA support
15443 When @value{GDBN} is debugging the HP PA architecture, it provides the
15444 following special commands:
15447 @item set debug hppa
15448 @kindex set debug hppa
15449 This command determines whether HPPA architecture-specific debugging
15450 messages are to be displayed.
15452 @item show debug hppa
15453 Show whether HPPA debugging messages are displayed.
15455 @item maint print unwind @var{address}
15456 @kindex maint print unwind@r{, HPPA}
15457 This command displays the contents of the unwind table entry at the
15458 given @var{address}.
15464 @subsection Cell Broadband Engine SPU architecture
15465 @cindex Cell Broadband Engine
15468 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
15469 it provides the following special commands:
15472 @item info spu event
15474 Display SPU event facility status. Shows current event mask
15475 and pending event status.
15477 @item info spu signal
15478 Display SPU signal notification facility status. Shows pending
15479 signal-control word and signal notification mode of both signal
15480 notification channels.
15482 @item info spu mailbox
15483 Display SPU mailbox facility status. Shows all pending entries,
15484 in order of processing, in each of the SPU Write Outbound,
15485 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
15488 Display MFC DMA status. Shows all pending commands in the MFC
15489 DMA queue. For each entry, opcode, tag, class IDs, effective
15490 and local store addresses and transfer size are shown.
15492 @item info spu proxydma
15493 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
15494 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
15495 and local store addresses and transfer size are shown.
15500 @node Controlling GDB
15501 @chapter Controlling @value{GDBN}
15503 You can alter the way @value{GDBN} interacts with you by using the
15504 @code{set} command. For commands controlling how @value{GDBN} displays
15505 data, see @ref{Print Settings, ,Print Settings}. Other settings are
15510 * Editing:: Command editing
15511 * Command History:: Command history
15512 * Screen Size:: Screen size
15513 * Numbers:: Numbers
15514 * ABI:: Configuring the current ABI
15515 * Messages/Warnings:: Optional warnings and messages
15516 * Debugging Output:: Optional messages about internal happenings
15524 @value{GDBN} indicates its readiness to read a command by printing a string
15525 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
15526 can change the prompt string with the @code{set prompt} command. For
15527 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
15528 the prompt in one of the @value{GDBN} sessions so that you can always tell
15529 which one you are talking to.
15531 @emph{Note:} @code{set prompt} does not add a space for you after the
15532 prompt you set. This allows you to set a prompt which ends in a space
15533 or a prompt that does not.
15537 @item set prompt @var{newprompt}
15538 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
15540 @kindex show prompt
15542 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
15546 @section Command Editing
15548 @cindex command line editing
15550 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
15551 @sc{gnu} library provides consistent behavior for programs which provide a
15552 command line interface to the user. Advantages are @sc{gnu} Emacs-style
15553 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
15554 substitution, and a storage and recall of command history across
15555 debugging sessions.
15557 You may control the behavior of command line editing in @value{GDBN} with the
15558 command @code{set}.
15561 @kindex set editing
15564 @itemx set editing on
15565 Enable command line editing (enabled by default).
15567 @item set editing off
15568 Disable command line editing.
15570 @kindex show editing
15572 Show whether command line editing is enabled.
15575 @xref{Command Line Editing}, for more details about the Readline
15576 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
15577 encouraged to read that chapter.
15579 @node Command History
15580 @section Command History
15581 @cindex command history
15583 @value{GDBN} can keep track of the commands you type during your
15584 debugging sessions, so that you can be certain of precisely what
15585 happened. Use these commands to manage the @value{GDBN} command
15588 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
15589 package, to provide the history facility. @xref{Using History
15590 Interactively}, for the detailed description of the History library.
15592 To issue a command to @value{GDBN} without affecting certain aspects of
15593 the state which is seen by users, prefix it with @samp{server }
15594 (@pxref{Server Prefix}). This
15595 means that this command will not affect the command history, nor will it
15596 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
15597 pressed on a line by itself.
15599 @cindex @code{server}, command prefix
15600 The server prefix does not affect the recording of values into the value
15601 history; to print a value without recording it into the value history,
15602 use the @code{output} command instead of the @code{print} command.
15604 Here is the description of @value{GDBN} commands related to command
15608 @cindex history substitution
15609 @cindex history file
15610 @kindex set history filename
15611 @cindex @env{GDBHISTFILE}, environment variable
15612 @item set history filename @var{fname}
15613 Set the name of the @value{GDBN} command history file to @var{fname}.
15614 This is the file where @value{GDBN} reads an initial command history
15615 list, and where it writes the command history from this session when it
15616 exits. You can access this list through history expansion or through
15617 the history command editing characters listed below. This file defaults
15618 to the value of the environment variable @code{GDBHISTFILE}, or to
15619 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
15622 @cindex save command history
15623 @kindex set history save
15624 @item set history save
15625 @itemx set history save on
15626 Record command history in a file, whose name may be specified with the
15627 @code{set history filename} command. By default, this option is disabled.
15629 @item set history save off
15630 Stop recording command history in a file.
15632 @cindex history size
15633 @kindex set history size
15634 @cindex @env{HISTSIZE}, environment variable
15635 @item set history size @var{size}
15636 Set the number of commands which @value{GDBN} keeps in its history list.
15637 This defaults to the value of the environment variable
15638 @code{HISTSIZE}, or to 256 if this variable is not set.
15641 History expansion assigns special meaning to the character @kbd{!}.
15642 @xref{Event Designators}, for more details.
15644 @cindex history expansion, turn on/off
15645 Since @kbd{!} is also the logical not operator in C, history expansion
15646 is off by default. If you decide to enable history expansion with the
15647 @code{set history expansion on} command, you may sometimes need to
15648 follow @kbd{!} (when it is used as logical not, in an expression) with
15649 a space or a tab to prevent it from being expanded. The readline
15650 history facilities do not attempt substitution on the strings
15651 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
15653 The commands to control history expansion are:
15656 @item set history expansion on
15657 @itemx set history expansion
15658 @kindex set history expansion
15659 Enable history expansion. History expansion is off by default.
15661 @item set history expansion off
15662 Disable history expansion.
15665 @kindex show history
15667 @itemx show history filename
15668 @itemx show history save
15669 @itemx show history size
15670 @itemx show history expansion
15671 These commands display the state of the @value{GDBN} history parameters.
15672 @code{show history} by itself displays all four states.
15677 @kindex show commands
15678 @cindex show last commands
15679 @cindex display command history
15680 @item show commands
15681 Display the last ten commands in the command history.
15683 @item show commands @var{n}
15684 Print ten commands centered on command number @var{n}.
15686 @item show commands +
15687 Print ten commands just after the commands last printed.
15691 @section Screen Size
15692 @cindex size of screen
15693 @cindex pauses in output
15695 Certain commands to @value{GDBN} may produce large amounts of
15696 information output to the screen. To help you read all of it,
15697 @value{GDBN} pauses and asks you for input at the end of each page of
15698 output. Type @key{RET} when you want to continue the output, or @kbd{q}
15699 to discard the remaining output. Also, the screen width setting
15700 determines when to wrap lines of output. Depending on what is being
15701 printed, @value{GDBN} tries to break the line at a readable place,
15702 rather than simply letting it overflow onto the following line.
15704 Normally @value{GDBN} knows the size of the screen from the terminal
15705 driver software. For example, on Unix @value{GDBN} uses the termcap data base
15706 together with the value of the @code{TERM} environment variable and the
15707 @code{stty rows} and @code{stty cols} settings. If this is not correct,
15708 you can override it with the @code{set height} and @code{set
15715 @kindex show height
15716 @item set height @var{lpp}
15718 @itemx set width @var{cpl}
15720 These @code{set} commands specify a screen height of @var{lpp} lines and
15721 a screen width of @var{cpl} characters. The associated @code{show}
15722 commands display the current settings.
15724 If you specify a height of zero lines, @value{GDBN} does not pause during
15725 output no matter how long the output is. This is useful if output is to a
15726 file or to an editor buffer.
15728 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
15729 from wrapping its output.
15731 @item set pagination on
15732 @itemx set pagination off
15733 @kindex set pagination
15734 Turn the output pagination on or off; the default is on. Turning
15735 pagination off is the alternative to @code{set height 0}.
15737 @item show pagination
15738 @kindex show pagination
15739 Show the current pagination mode.
15744 @cindex number representation
15745 @cindex entering numbers
15747 You can always enter numbers in octal, decimal, or hexadecimal in
15748 @value{GDBN} by the usual conventions: octal numbers begin with
15749 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
15750 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
15751 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
15752 10; likewise, the default display for numbers---when no particular
15753 format is specified---is base 10. You can change the default base for
15754 both input and output with the commands described below.
15757 @kindex set input-radix
15758 @item set input-radix @var{base}
15759 Set the default base for numeric input. Supported choices
15760 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15761 specified either unambiguously or using the current input radix; for
15765 set input-radix 012
15766 set input-radix 10.
15767 set input-radix 0xa
15771 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
15772 leaves the input radix unchanged, no matter what it was, since
15773 @samp{10}, being without any leading or trailing signs of its base, is
15774 interpreted in the current radix. Thus, if the current radix is 16,
15775 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
15778 @kindex set output-radix
15779 @item set output-radix @var{base}
15780 Set the default base for numeric display. Supported choices
15781 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15782 specified either unambiguously or using the current input radix.
15784 @kindex show input-radix
15785 @item show input-radix
15786 Display the current default base for numeric input.
15788 @kindex show output-radix
15789 @item show output-radix
15790 Display the current default base for numeric display.
15792 @item set radix @r{[}@var{base}@r{]}
15796 These commands set and show the default base for both input and output
15797 of numbers. @code{set radix} sets the radix of input and output to
15798 the same base; without an argument, it resets the radix back to its
15799 default value of 10.
15804 @section Configuring the Current ABI
15806 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
15807 application automatically. However, sometimes you need to override its
15808 conclusions. Use these commands to manage @value{GDBN}'s view of the
15815 One @value{GDBN} configuration can debug binaries for multiple operating
15816 system targets, either via remote debugging or native emulation.
15817 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
15818 but you can override its conclusion using the @code{set osabi} command.
15819 One example where this is useful is in debugging of binaries which use
15820 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
15821 not have the same identifying marks that the standard C library for your
15826 Show the OS ABI currently in use.
15829 With no argument, show the list of registered available OS ABI's.
15831 @item set osabi @var{abi}
15832 Set the current OS ABI to @var{abi}.
15835 @cindex float promotion
15837 Generally, the way that an argument of type @code{float} is passed to a
15838 function depends on whether the function is prototyped. For a prototyped
15839 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
15840 according to the architecture's convention for @code{float}. For unprototyped
15841 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
15842 @code{double} and then passed.
15844 Unfortunately, some forms of debug information do not reliably indicate whether
15845 a function is prototyped. If @value{GDBN} calls a function that is not marked
15846 as prototyped, it consults @kbd{set coerce-float-to-double}.
15849 @kindex set coerce-float-to-double
15850 @item set coerce-float-to-double
15851 @itemx set coerce-float-to-double on
15852 Arguments of type @code{float} will be promoted to @code{double} when passed
15853 to an unprototyped function. This is the default setting.
15855 @item set coerce-float-to-double off
15856 Arguments of type @code{float} will be passed directly to unprototyped
15859 @kindex show coerce-float-to-double
15860 @item show coerce-float-to-double
15861 Show the current setting of promoting @code{float} to @code{double}.
15865 @kindex show cp-abi
15866 @value{GDBN} needs to know the ABI used for your program's C@t{++}
15867 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
15868 used to build your application. @value{GDBN} only fully supports
15869 programs with a single C@t{++} ABI; if your program contains code using
15870 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
15871 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
15872 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
15873 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
15874 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
15875 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
15880 Show the C@t{++} ABI currently in use.
15883 With no argument, show the list of supported C@t{++} ABI's.
15885 @item set cp-abi @var{abi}
15886 @itemx set cp-abi auto
15887 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
15890 @node Messages/Warnings
15891 @section Optional Warnings and Messages
15893 @cindex verbose operation
15894 @cindex optional warnings
15895 By default, @value{GDBN} is silent about its inner workings. If you are
15896 running on a slow machine, you may want to use the @code{set verbose}
15897 command. This makes @value{GDBN} tell you when it does a lengthy
15898 internal operation, so you will not think it has crashed.
15900 Currently, the messages controlled by @code{set verbose} are those
15901 which announce that the symbol table for a source file is being read;
15902 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
15905 @kindex set verbose
15906 @item set verbose on
15907 Enables @value{GDBN} output of certain informational messages.
15909 @item set verbose off
15910 Disables @value{GDBN} output of certain informational messages.
15912 @kindex show verbose
15914 Displays whether @code{set verbose} is on or off.
15917 By default, if @value{GDBN} encounters bugs in the symbol table of an
15918 object file, it is silent; but if you are debugging a compiler, you may
15919 find this information useful (@pxref{Symbol Errors, ,Errors Reading
15924 @kindex set complaints
15925 @item set complaints @var{limit}
15926 Permits @value{GDBN} to output @var{limit} complaints about each type of
15927 unusual symbols before becoming silent about the problem. Set
15928 @var{limit} to zero to suppress all complaints; set it to a large number
15929 to prevent complaints from being suppressed.
15931 @kindex show complaints
15932 @item show complaints
15933 Displays how many symbol complaints @value{GDBN} is permitted to produce.
15937 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
15938 lot of stupid questions to confirm certain commands. For example, if
15939 you try to run a program which is already running:
15943 The program being debugged has been started already.
15944 Start it from the beginning? (y or n)
15947 If you are willing to unflinchingly face the consequences of your own
15948 commands, you can disable this ``feature'':
15952 @kindex set confirm
15954 @cindex confirmation
15955 @cindex stupid questions
15956 @item set confirm off
15957 Disables confirmation requests.
15959 @item set confirm on
15960 Enables confirmation requests (the default).
15962 @kindex show confirm
15964 Displays state of confirmation requests.
15968 @cindex command tracing
15969 If you need to debug user-defined commands or sourced files you may find it
15970 useful to enable @dfn{command tracing}. In this mode each command will be
15971 printed as it is executed, prefixed with one or more @samp{+} symbols, the
15972 quantity denoting the call depth of each command.
15975 @kindex set trace-commands
15976 @cindex command scripts, debugging
15977 @item set trace-commands on
15978 Enable command tracing.
15979 @item set trace-commands off
15980 Disable command tracing.
15981 @item show trace-commands
15982 Display the current state of command tracing.
15985 @node Debugging Output
15986 @section Optional Messages about Internal Happenings
15987 @cindex optional debugging messages
15989 @value{GDBN} has commands that enable optional debugging messages from
15990 various @value{GDBN} subsystems; normally these commands are of
15991 interest to @value{GDBN} maintainers, or when reporting a bug. This
15992 section documents those commands.
15995 @kindex set exec-done-display
15996 @item set exec-done-display
15997 Turns on or off the notification of asynchronous commands'
15998 completion. When on, @value{GDBN} will print a message when an
15999 asynchronous command finishes its execution. The default is off.
16000 @kindex show exec-done-display
16001 @item show exec-done-display
16002 Displays the current setting of asynchronous command completion
16005 @cindex gdbarch debugging info
16006 @cindex architecture debugging info
16007 @item set debug arch
16008 Turns on or off display of gdbarch debugging info. The default is off
16010 @item show debug arch
16011 Displays the current state of displaying gdbarch debugging info.
16012 @item set debug aix-thread
16013 @cindex AIX threads
16014 Display debugging messages about inner workings of the AIX thread
16016 @item show debug aix-thread
16017 Show the current state of AIX thread debugging info display.
16018 @item set debug event
16019 @cindex event debugging info
16020 Turns on or off display of @value{GDBN} event debugging info. The
16022 @item show debug event
16023 Displays the current state of displaying @value{GDBN} event debugging
16025 @item set debug expression
16026 @cindex expression debugging info
16027 Turns on or off display of debugging info about @value{GDBN}
16028 expression parsing. The default is off.
16029 @item show debug expression
16030 Displays the current state of displaying debugging info about
16031 @value{GDBN} expression parsing.
16032 @item set debug frame
16033 @cindex frame debugging info
16034 Turns on or off display of @value{GDBN} frame debugging info. The
16036 @item show debug frame
16037 Displays the current state of displaying @value{GDBN} frame debugging
16039 @item set debug infrun
16040 @cindex inferior debugging info
16041 Turns on or off display of @value{GDBN} debugging info for running the inferior.
16042 The default is off. @file{infrun.c} contains GDB's runtime state machine used
16043 for implementing operations such as single-stepping the inferior.
16044 @item show debug infrun
16045 Displays the current state of @value{GDBN} inferior debugging.
16046 @item set debug lin-lwp
16047 @cindex @sc{gnu}/Linux LWP debug messages
16048 @cindex Linux lightweight processes
16049 Turns on or off debugging messages from the Linux LWP debug support.
16050 @item show debug lin-lwp
16051 Show the current state of Linux LWP debugging messages.
16052 @item set debug observer
16053 @cindex observer debugging info
16054 Turns on or off display of @value{GDBN} observer debugging. This
16055 includes info such as the notification of observable events.
16056 @item show debug observer
16057 Displays the current state of observer debugging.
16058 @item set debug overload
16059 @cindex C@t{++} overload debugging info
16060 Turns on or off display of @value{GDBN} C@t{++} overload debugging
16061 info. This includes info such as ranking of functions, etc. The default
16063 @item show debug overload
16064 Displays the current state of displaying @value{GDBN} C@t{++} overload
16066 @cindex packets, reporting on stdout
16067 @cindex serial connections, debugging
16068 @cindex debug remote protocol
16069 @cindex remote protocol debugging
16070 @cindex display remote packets
16071 @item set debug remote
16072 Turns on or off display of reports on all packets sent back and forth across
16073 the serial line to the remote machine. The info is printed on the
16074 @value{GDBN} standard output stream. The default is off.
16075 @item show debug remote
16076 Displays the state of display of remote packets.
16077 @item set debug serial
16078 Turns on or off display of @value{GDBN} serial debugging info. The
16080 @item show debug serial
16081 Displays the current state of displaying @value{GDBN} serial debugging
16083 @item set debug solib-frv
16084 @cindex FR-V shared-library debugging
16085 Turns on or off debugging messages for FR-V shared-library code.
16086 @item show debug solib-frv
16087 Display the current state of FR-V shared-library code debugging
16089 @item set debug target
16090 @cindex target debugging info
16091 Turns on or off display of @value{GDBN} target debugging info. This info
16092 includes what is going on at the target level of GDB, as it happens. The
16093 default is 0. Set it to 1 to track events, and to 2 to also track the
16094 value of large memory transfers. Changes to this flag do not take effect
16095 until the next time you connect to a target or use the @code{run} command.
16096 @item show debug target
16097 Displays the current state of displaying @value{GDBN} target debugging
16099 @item set debugvarobj
16100 @cindex variable object debugging info
16101 Turns on or off display of @value{GDBN} variable object debugging
16102 info. The default is off.
16103 @item show debugvarobj
16104 Displays the current state of displaying @value{GDBN} variable object
16106 @item set debug xml
16107 @cindex XML parser debugging
16108 Turns on or off debugging messages for built-in XML parsers.
16109 @item show debug xml
16110 Displays the current state of XML debugging messages.
16114 @chapter Canned Sequences of Commands
16116 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
16117 Command Lists}), @value{GDBN} provides two ways to store sequences of
16118 commands for execution as a unit: user-defined commands and command
16122 * Define:: How to define your own commands
16123 * Hooks:: Hooks for user-defined commands
16124 * Command Files:: How to write scripts of commands to be stored in a file
16125 * Output:: Commands for controlled output
16129 @section User-defined Commands
16131 @cindex user-defined command
16132 @cindex arguments, to user-defined commands
16133 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
16134 which you assign a new name as a command. This is done with the
16135 @code{define} command. User commands may accept up to 10 arguments
16136 separated by whitespace. Arguments are accessed within the user command
16137 via @code{$arg0@dots{}$arg9}. A trivial example:
16141 print $arg0 + $arg1 + $arg2
16146 To execute the command use:
16153 This defines the command @code{adder}, which prints the sum of
16154 its three arguments. Note the arguments are text substitutions, so they may
16155 reference variables, use complex expressions, or even perform inferior
16158 @cindex argument count in user-defined commands
16159 @cindex how many arguments (user-defined commands)
16160 In addition, @code{$argc} may be used to find out how many arguments have
16161 been passed. This expands to a number in the range 0@dots{}10.
16166 print $arg0 + $arg1
16169 print $arg0 + $arg1 + $arg2
16177 @item define @var{commandname}
16178 Define a command named @var{commandname}. If there is already a command
16179 by that name, you are asked to confirm that you want to redefine it.
16181 The definition of the command is made up of other @value{GDBN} command lines,
16182 which are given following the @code{define} command. The end of these
16183 commands is marked by a line containing @code{end}.
16186 @kindex end@r{ (user-defined commands)}
16187 @item document @var{commandname}
16188 Document the user-defined command @var{commandname}, so that it can be
16189 accessed by @code{help}. The command @var{commandname} must already be
16190 defined. This command reads lines of documentation just as @code{define}
16191 reads the lines of the command definition, ending with @code{end}.
16192 After the @code{document} command is finished, @code{help} on command
16193 @var{commandname} displays the documentation you have written.
16195 You may use the @code{document} command again to change the
16196 documentation of a command. Redefining the command with @code{define}
16197 does not change the documentation.
16199 @kindex dont-repeat
16200 @cindex don't repeat command
16202 Used inside a user-defined command, this tells @value{GDBN} that this
16203 command should not be repeated when the user hits @key{RET}
16204 (@pxref{Command Syntax, repeat last command}).
16206 @kindex help user-defined
16207 @item help user-defined
16208 List all user-defined commands, with the first line of the documentation
16213 @itemx show user @var{commandname}
16214 Display the @value{GDBN} commands used to define @var{commandname} (but
16215 not its documentation). If no @var{commandname} is given, display the
16216 definitions for all user-defined commands.
16218 @cindex infinite recursion in user-defined commands
16219 @kindex show max-user-call-depth
16220 @kindex set max-user-call-depth
16221 @item show max-user-call-depth
16222 @itemx set max-user-call-depth
16223 The value of @code{max-user-call-depth} controls how many recursion
16224 levels are allowed in user-defined commands before @value{GDBN} suspects an
16225 infinite recursion and aborts the command.
16228 In addition to the above commands, user-defined commands frequently
16229 use control flow commands, described in @ref{Command Files}.
16231 When user-defined commands are executed, the
16232 commands of the definition are not printed. An error in any command
16233 stops execution of the user-defined command.
16235 If used interactively, commands that would ask for confirmation proceed
16236 without asking when used inside a user-defined command. Many @value{GDBN}
16237 commands that normally print messages to say what they are doing omit the
16238 messages when used in a user-defined command.
16241 @section User-defined Command Hooks
16242 @cindex command hooks
16243 @cindex hooks, for commands
16244 @cindex hooks, pre-command
16247 You may define @dfn{hooks}, which are a special kind of user-defined
16248 command. Whenever you run the command @samp{foo}, if the user-defined
16249 command @samp{hook-foo} exists, it is executed (with no arguments)
16250 before that command.
16252 @cindex hooks, post-command
16254 A hook may also be defined which is run after the command you executed.
16255 Whenever you run the command @samp{foo}, if the user-defined command
16256 @samp{hookpost-foo} exists, it is executed (with no arguments) after
16257 that command. Post-execution hooks may exist simultaneously with
16258 pre-execution hooks, for the same command.
16260 It is valid for a hook to call the command which it hooks. If this
16261 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
16263 @c It would be nice if hookpost could be passed a parameter indicating
16264 @c if the command it hooks executed properly or not. FIXME!
16266 @kindex stop@r{, a pseudo-command}
16267 In addition, a pseudo-command, @samp{stop} exists. Defining
16268 (@samp{hook-stop}) makes the associated commands execute every time
16269 execution stops in your program: before breakpoint commands are run,
16270 displays are printed, or the stack frame is printed.
16272 For example, to ignore @code{SIGALRM} signals while
16273 single-stepping, but treat them normally during normal execution,
16278 handle SIGALRM nopass
16282 handle SIGALRM pass
16285 define hook-continue
16286 handle SIGALRM pass
16290 As a further example, to hook at the beginning and end of the @code{echo}
16291 command, and to add extra text to the beginning and end of the message,
16299 define hookpost-echo
16303 (@value{GDBP}) echo Hello World
16304 <<<---Hello World--->>>
16309 You can define a hook for any single-word command in @value{GDBN}, but
16310 not for command aliases; you should define a hook for the basic command
16311 name, e.g.@: @code{backtrace} rather than @code{bt}.
16312 @c FIXME! So how does Joe User discover whether a command is an alias
16314 If an error occurs during the execution of your hook, execution of
16315 @value{GDBN} commands stops and @value{GDBN} issues a prompt
16316 (before the command that you actually typed had a chance to run).
16318 If you try to define a hook which does not match any known command, you
16319 get a warning from the @code{define} command.
16321 @node Command Files
16322 @section Command Files
16324 @cindex command files
16325 @cindex scripting commands
16326 A command file for @value{GDBN} is a text file made of lines that are
16327 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
16328 also be included. An empty line in a command file does nothing; it
16329 does not mean to repeat the last command, as it would from the
16332 You can request the execution of a command file with the @code{source}
16337 @cindex execute commands from a file
16338 @item source [@code{-v}] @var{filename}
16339 Execute the command file @var{filename}.
16342 The lines in a command file are generally executed sequentially,
16343 unless the order of execution is changed by one of the
16344 @emph{flow-control commands} described below. The commands are not
16345 printed as they are executed. An error in any command terminates
16346 execution of the command file and control is returned to the console.
16348 @value{GDBN} searches for @var{filename} in the current directory and then
16349 on the search path (specified with the @samp{directory} command).
16351 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
16352 each command as it is executed. The option must be given before
16353 @var{filename}, and is interpreted as part of the filename anywhere else.
16355 Commands that would ask for confirmation if used interactively proceed
16356 without asking when used in a command file. Many @value{GDBN} commands that
16357 normally print messages to say what they are doing omit the messages
16358 when called from command files.
16360 @value{GDBN} also accepts command input from standard input. In this
16361 mode, normal output goes to standard output and error output goes to
16362 standard error. Errors in a command file supplied on standard input do
16363 not terminate execution of the command file---execution continues with
16367 gdb < cmds > log 2>&1
16370 (The syntax above will vary depending on the shell used.) This example
16371 will execute commands from the file @file{cmds}. All output and errors
16372 would be directed to @file{log}.
16374 Since commands stored on command files tend to be more general than
16375 commands typed interactively, they frequently need to deal with
16376 complicated situations, such as different or unexpected values of
16377 variables and symbols, changes in how the program being debugged is
16378 built, etc. @value{GDBN} provides a set of flow-control commands to
16379 deal with these complexities. Using these commands, you can write
16380 complex scripts that loop over data structures, execute commands
16381 conditionally, etc.
16388 This command allows to include in your script conditionally executed
16389 commands. The @code{if} command takes a single argument, which is an
16390 expression to evaluate. It is followed by a series of commands that
16391 are executed only if the expression is true (its value is nonzero).
16392 There can then optionally be an @code{else} line, followed by a series
16393 of commands that are only executed if the expression was false. The
16394 end of the list is marked by a line containing @code{end}.
16398 This command allows to write loops. Its syntax is similar to
16399 @code{if}: the command takes a single argument, which is an expression
16400 to evaluate, and must be followed by the commands to execute, one per
16401 line, terminated by an @code{end}. These commands are called the
16402 @dfn{body} of the loop. The commands in the body of @code{while} are
16403 executed repeatedly as long as the expression evaluates to true.
16407 This command exits the @code{while} loop in whose body it is included.
16408 Execution of the script continues after that @code{while}s @code{end}
16411 @kindex loop_continue
16412 @item loop_continue
16413 This command skips the execution of the rest of the body of commands
16414 in the @code{while} loop in whose body it is included. Execution
16415 branches to the beginning of the @code{while} loop, where it evaluates
16416 the controlling expression.
16418 @kindex end@r{ (if/else/while commands)}
16420 Terminate the block of commands that are the body of @code{if},
16421 @code{else}, or @code{while} flow-control commands.
16426 @section Commands for Controlled Output
16428 During the execution of a command file or a user-defined command, normal
16429 @value{GDBN} output is suppressed; the only output that appears is what is
16430 explicitly printed by the commands in the definition. This section
16431 describes three commands useful for generating exactly the output you
16436 @item echo @var{text}
16437 @c I do not consider backslash-space a standard C escape sequence
16438 @c because it is not in ANSI.
16439 Print @var{text}. Nonprinting characters can be included in
16440 @var{text} using C escape sequences, such as @samp{\n} to print a
16441 newline. @strong{No newline is printed unless you specify one.}
16442 In addition to the standard C escape sequences, a backslash followed
16443 by a space stands for a space. This is useful for displaying a
16444 string with spaces at the beginning or the end, since leading and
16445 trailing spaces are otherwise trimmed from all arguments.
16446 To print @samp{@w{ }and foo =@w{ }}, use the command
16447 @samp{echo \@w{ }and foo = \@w{ }}.
16449 A backslash at the end of @var{text} can be used, as in C, to continue
16450 the command onto subsequent lines. For example,
16453 echo This is some text\n\
16454 which is continued\n\
16455 onto several lines.\n
16458 produces the same output as
16461 echo This is some text\n
16462 echo which is continued\n
16463 echo onto several lines.\n
16467 @item output @var{expression}
16468 Print the value of @var{expression} and nothing but that value: no
16469 newlines, no @samp{$@var{nn} = }. The value is not entered in the
16470 value history either. @xref{Expressions, ,Expressions}, for more information
16473 @item output/@var{fmt} @var{expression}
16474 Print the value of @var{expression} in format @var{fmt}. You can use
16475 the same formats as for @code{print}. @xref{Output Formats,,Output
16476 Formats}, for more information.
16479 @item printf @var{template}, @var{expressions}@dots{}
16480 Print the values of one or more @var{expressions} under the control of
16481 the string @var{template}. To print several values, make
16482 @var{expressions} be a comma-separated list of individual expressions,
16483 which may be either numbers or pointers. Their values are printed as
16484 specified by @var{template}, exactly as a C program would do by
16485 executing the code below:
16488 printf (@var{template}, @var{expressions}@dots{});
16491 As in @code{C} @code{printf}, ordinary characters in @var{template}
16492 are printed verbatim, while @dfn{conversion specification} introduced
16493 by the @samp{%} character cause subsequent @var{expressions} to be
16494 evaluated, their values converted and formatted according to type and
16495 style information encoded in the conversion specifications, and then
16498 For example, you can print two values in hex like this:
16501 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
16504 @code{printf} supports all the standard @code{C} conversion
16505 specifications, including the flags and modifiers between the @samp{%}
16506 character and the conversion letter, with the following exceptions:
16510 The argument-ordering modifiers, such as @samp{2$}, are not supported.
16513 The modifier @samp{*} is not supported for specifying precision or
16517 The @samp{'} flag (for separation of digits into groups according to
16518 @code{LC_NUMERIC'}) is not supported.
16521 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
16525 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
16528 The conversion letters @samp{a} and @samp{A} are not supported.
16532 Note that the @samp{ll} type modifier is supported only if the
16533 underlying @code{C} implementation used to build @value{GDBN} supports
16534 the @code{long long int} type, and the @samp{L} type modifier is
16535 supported only if @code{long double} type is available.
16537 As in @code{C}, @code{printf} supports simple backslash-escape
16538 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
16539 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
16540 single character. Octal and hexadecimal escape sequences are not
16545 @chapter Command Interpreters
16546 @cindex command interpreters
16548 @value{GDBN} supports multiple command interpreters, and some command
16549 infrastructure to allow users or user interface writers to switch
16550 between interpreters or run commands in other interpreters.
16552 @value{GDBN} currently supports two command interpreters, the console
16553 interpreter (sometimes called the command-line interpreter or @sc{cli})
16554 and the machine interface interpreter (or @sc{gdb/mi}). This manual
16555 describes both of these interfaces in great detail.
16557 By default, @value{GDBN} will start with the console interpreter.
16558 However, the user may choose to start @value{GDBN} with another
16559 interpreter by specifying the @option{-i} or @option{--interpreter}
16560 startup options. Defined interpreters include:
16564 @cindex console interpreter
16565 The traditional console or command-line interpreter. This is the most often
16566 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
16567 @value{GDBN} will use this interpreter.
16570 @cindex mi interpreter
16571 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
16572 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
16573 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
16577 @cindex mi2 interpreter
16578 The current @sc{gdb/mi} interface.
16581 @cindex mi1 interpreter
16582 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
16586 @cindex invoke another interpreter
16587 The interpreter being used by @value{GDBN} may not be dynamically
16588 switched at runtime. Although possible, this could lead to a very
16589 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
16590 enters the command "interpreter-set console" in a console view,
16591 @value{GDBN} would switch to using the console interpreter, rendering
16592 the IDE inoperable!
16594 @kindex interpreter-exec
16595 Although you may only choose a single interpreter at startup, you may execute
16596 commands in any interpreter from the current interpreter using the appropriate
16597 command. If you are running the console interpreter, simply use the
16598 @code{interpreter-exec} command:
16601 interpreter-exec mi "-data-list-register-names"
16604 @sc{gdb/mi} has a similar command, although it is only available in versions of
16605 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
16608 @chapter @value{GDBN} Text User Interface
16610 @cindex Text User Interface
16613 * TUI Overview:: TUI overview
16614 * TUI Keys:: TUI key bindings
16615 * TUI Single Key Mode:: TUI single key mode
16616 * TUI Commands:: TUI-specific commands
16617 * TUI Configuration:: TUI configuration variables
16620 The @value{GDBN} Text User Interface (TUI) is a terminal
16621 interface which uses the @code{curses} library to show the source
16622 file, the assembly output, the program registers and @value{GDBN}
16623 commands in separate text windows. The TUI mode is supported only
16624 on platforms where a suitable version of the @code{curses} library
16627 @pindex @value{GDBTUI}
16628 The TUI mode is enabled by default when you invoke @value{GDBN} as
16629 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
16630 You can also switch in and out of TUI mode while @value{GDBN} runs by
16631 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
16632 @xref{TUI Keys, ,TUI Key Bindings}.
16635 @section TUI Overview
16637 In TUI mode, @value{GDBN} can display several text windows:
16641 This window is the @value{GDBN} command window with the @value{GDBN}
16642 prompt and the @value{GDBN} output. The @value{GDBN} input is still
16643 managed using readline.
16646 The source window shows the source file of the program. The current
16647 line and active breakpoints are displayed in this window.
16650 The assembly window shows the disassembly output of the program.
16653 This window shows the processor registers. Registers are highlighted
16654 when their values change.
16657 The source and assembly windows show the current program position
16658 by highlighting the current line and marking it with a @samp{>} marker.
16659 Breakpoints are indicated with two markers. The first marker
16660 indicates the breakpoint type:
16664 Breakpoint which was hit at least once.
16667 Breakpoint which was never hit.
16670 Hardware breakpoint which was hit at least once.
16673 Hardware breakpoint which was never hit.
16676 The second marker indicates whether the breakpoint is enabled or not:
16680 Breakpoint is enabled.
16683 Breakpoint is disabled.
16686 The source, assembly and register windows are updated when the current
16687 thread changes, when the frame changes, or when the program counter
16690 These windows are not all visible at the same time. The command
16691 window is always visible. The others can be arranged in several
16702 source and assembly,
16705 source and registers, or
16708 assembly and registers.
16711 A status line above the command window shows the following information:
16715 Indicates the current @value{GDBN} target.
16716 (@pxref{Targets, ,Specifying a Debugging Target}).
16719 Gives the current process or thread number.
16720 When no process is being debugged, this field is set to @code{No process}.
16723 Gives the current function name for the selected frame.
16724 The name is demangled if demangling is turned on (@pxref{Print Settings}).
16725 When there is no symbol corresponding to the current program counter,
16726 the string @code{??} is displayed.
16729 Indicates the current line number for the selected frame.
16730 When the current line number is not known, the string @code{??} is displayed.
16733 Indicates the current program counter address.
16737 @section TUI Key Bindings
16738 @cindex TUI key bindings
16740 The TUI installs several key bindings in the readline keymaps
16741 (@pxref{Command Line Editing}). The following key bindings
16742 are installed for both TUI mode and the @value{GDBN} standard mode.
16751 Enter or leave the TUI mode. When leaving the TUI mode,
16752 the curses window management stops and @value{GDBN} operates using
16753 its standard mode, writing on the terminal directly. When reentering
16754 the TUI mode, control is given back to the curses windows.
16755 The screen is then refreshed.
16759 Use a TUI layout with only one window. The layout will
16760 either be @samp{source} or @samp{assembly}. When the TUI mode
16761 is not active, it will switch to the TUI mode.
16763 Think of this key binding as the Emacs @kbd{C-x 1} binding.
16767 Use a TUI layout with at least two windows. When the current
16768 layout already has two windows, the next layout with two windows is used.
16769 When a new layout is chosen, one window will always be common to the
16770 previous layout and the new one.
16772 Think of it as the Emacs @kbd{C-x 2} binding.
16776 Change the active window. The TUI associates several key bindings
16777 (like scrolling and arrow keys) with the active window. This command
16778 gives the focus to the next TUI window.
16780 Think of it as the Emacs @kbd{C-x o} binding.
16784 Switch in and out of the TUI SingleKey mode that binds single
16785 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
16788 The following key bindings only work in the TUI mode:
16793 Scroll the active window one page up.
16797 Scroll the active window one page down.
16801 Scroll the active window one line up.
16805 Scroll the active window one line down.
16809 Scroll the active window one column left.
16813 Scroll the active window one column right.
16817 Refresh the screen.
16820 Because the arrow keys scroll the active window in the TUI mode, they
16821 are not available for their normal use by readline unless the command
16822 window has the focus. When another window is active, you must use
16823 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
16824 and @kbd{C-f} to control the command window.
16826 @node TUI Single Key Mode
16827 @section TUI Single Key Mode
16828 @cindex TUI single key mode
16830 The TUI also provides a @dfn{SingleKey} mode, which binds several
16831 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
16832 switch into this mode, where the following key bindings are used:
16835 @kindex c @r{(SingleKey TUI key)}
16839 @kindex d @r{(SingleKey TUI key)}
16843 @kindex f @r{(SingleKey TUI key)}
16847 @kindex n @r{(SingleKey TUI key)}
16851 @kindex q @r{(SingleKey TUI key)}
16853 exit the SingleKey mode.
16855 @kindex r @r{(SingleKey TUI key)}
16859 @kindex s @r{(SingleKey TUI key)}
16863 @kindex u @r{(SingleKey TUI key)}
16867 @kindex v @r{(SingleKey TUI key)}
16871 @kindex w @r{(SingleKey TUI key)}
16876 Other keys temporarily switch to the @value{GDBN} command prompt.
16877 The key that was pressed is inserted in the editing buffer so that
16878 it is possible to type most @value{GDBN} commands without interaction
16879 with the TUI SingleKey mode. Once the command is entered the TUI
16880 SingleKey mode is restored. The only way to permanently leave
16881 this mode is by typing @kbd{q} or @kbd{C-x s}.
16885 @section TUI-specific Commands
16886 @cindex TUI commands
16888 The TUI has specific commands to control the text windows.
16889 These commands are always available, even when @value{GDBN} is not in
16890 the TUI mode. When @value{GDBN} is in the standard mode, most
16891 of these commands will automatically switch to the TUI mode.
16896 List and give the size of all displayed windows.
16900 Display the next layout.
16903 Display the previous layout.
16906 Display the source window only.
16909 Display the assembly window only.
16912 Display the source and assembly window.
16915 Display the register window together with the source or assembly window.
16919 Make the next window active for scrolling.
16922 Make the previous window active for scrolling.
16925 Make the source window active for scrolling.
16928 Make the assembly window active for scrolling.
16931 Make the register window active for scrolling.
16934 Make the command window active for scrolling.
16938 Refresh the screen. This is similar to typing @kbd{C-L}.
16940 @item tui reg float
16942 Show the floating point registers in the register window.
16944 @item tui reg general
16945 Show the general registers in the register window.
16948 Show the next register group. The list of register groups as well as
16949 their order is target specific. The predefined register groups are the
16950 following: @code{general}, @code{float}, @code{system}, @code{vector},
16951 @code{all}, @code{save}, @code{restore}.
16953 @item tui reg system
16954 Show the system registers in the register window.
16958 Update the source window and the current execution point.
16960 @item winheight @var{name} +@var{count}
16961 @itemx winheight @var{name} -@var{count}
16963 Change the height of the window @var{name} by @var{count}
16964 lines. Positive counts increase the height, while negative counts
16967 @item tabset @var{nchars}
16969 Set the width of tab stops to be @var{nchars} characters.
16972 @node TUI Configuration
16973 @section TUI Configuration Variables
16974 @cindex TUI configuration variables
16976 Several configuration variables control the appearance of TUI windows.
16979 @item set tui border-kind @var{kind}
16980 @kindex set tui border-kind
16981 Select the border appearance for the source, assembly and register windows.
16982 The possible values are the following:
16985 Use a space character to draw the border.
16988 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
16991 Use the Alternate Character Set to draw the border. The border is
16992 drawn using character line graphics if the terminal supports them.
16995 @item set tui border-mode @var{mode}
16996 @kindex set tui border-mode
16997 @itemx set tui active-border-mode @var{mode}
16998 @kindex set tui active-border-mode
16999 Select the display attributes for the borders of the inactive windows
17000 or the active window. The @var{mode} can be one of the following:
17003 Use normal attributes to display the border.
17009 Use reverse video mode.
17012 Use half bright mode.
17014 @item half-standout
17015 Use half bright and standout mode.
17018 Use extra bright or bold mode.
17020 @item bold-standout
17021 Use extra bright or bold and standout mode.
17026 @chapter Using @value{GDBN} under @sc{gnu} Emacs
17029 @cindex @sc{gnu} Emacs
17030 A special interface allows you to use @sc{gnu} Emacs to view (and
17031 edit) the source files for the program you are debugging with
17034 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
17035 executable file you want to debug as an argument. This command starts
17036 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
17037 created Emacs buffer.
17038 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
17040 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
17045 All ``terminal'' input and output goes through an Emacs buffer, called
17048 This applies both to @value{GDBN} commands and their output, and to the input
17049 and output done by the program you are debugging.
17051 This is useful because it means that you can copy the text of previous
17052 commands and input them again; you can even use parts of the output
17055 All the facilities of Emacs' Shell mode are available for interacting
17056 with your program. In particular, you can send signals the usual
17057 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
17061 @value{GDBN} displays source code through Emacs.
17063 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
17064 source file for that frame and puts an arrow (@samp{=>}) at the
17065 left margin of the current line. Emacs uses a separate buffer for
17066 source display, and splits the screen to show both your @value{GDBN} session
17069 Explicit @value{GDBN} @code{list} or search commands still produce output as
17070 usual, but you probably have no reason to use them from Emacs.
17073 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
17074 a graphical mode, enabled by default, which provides further buffers
17075 that can control the execution and describe the state of your program.
17076 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
17078 If you specify an absolute file name when prompted for the @kbd{M-x
17079 gdb} argument, then Emacs sets your current working directory to where
17080 your program resides. If you only specify the file name, then Emacs
17081 sets your current working directory to to the directory associated
17082 with the previous buffer. In this case, @value{GDBN} may find your
17083 program by searching your environment's @code{PATH} variable, but on
17084 some operating systems it might not find the source. So, although the
17085 @value{GDBN} input and output session proceeds normally, the auxiliary
17086 buffer does not display the current source and line of execution.
17088 The initial working directory of @value{GDBN} is printed on the top
17089 line of the GUD buffer and this serves as a default for the commands
17090 that specify files for @value{GDBN} to operate on. @xref{Files,
17091 ,Commands to Specify Files}.
17093 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
17094 need to call @value{GDBN} by a different name (for example, if you
17095 keep several configurations around, with different names) you can
17096 customize the Emacs variable @code{gud-gdb-command-name} to run the
17099 In the GUD buffer, you can use these special Emacs commands in
17100 addition to the standard Shell mode commands:
17104 Describe the features of Emacs' GUD Mode.
17107 Execute to another source line, like the @value{GDBN} @code{step} command; also
17108 update the display window to show the current file and location.
17111 Execute to next source line in this function, skipping all function
17112 calls, like the @value{GDBN} @code{next} command. Then update the display window
17113 to show the current file and location.
17116 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
17117 display window accordingly.
17120 Execute until exit from the selected stack frame, like the @value{GDBN}
17121 @code{finish} command.
17124 Continue execution of your program, like the @value{GDBN} @code{continue}
17128 Go up the number of frames indicated by the numeric argument
17129 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
17130 like the @value{GDBN} @code{up} command.
17133 Go down the number of frames indicated by the numeric argument, like the
17134 @value{GDBN} @code{down} command.
17137 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
17138 tells @value{GDBN} to set a breakpoint on the source line point is on.
17140 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
17141 separate frame which shows a backtrace when the GUD buffer is current.
17142 Move point to any frame in the stack and type @key{RET} to make it
17143 become the current frame and display the associated source in the
17144 source buffer. Alternatively, click @kbd{Mouse-2} to make the
17145 selected frame become the current one. In graphical mode, the
17146 speedbar displays watch expressions.
17148 If you accidentally delete the source-display buffer, an easy way to get
17149 it back is to type the command @code{f} in the @value{GDBN} buffer, to
17150 request a frame display; when you run under Emacs, this recreates
17151 the source buffer if necessary to show you the context of the current
17154 The source files displayed in Emacs are in ordinary Emacs buffers
17155 which are visiting the source files in the usual way. You can edit
17156 the files with these buffers if you wish; but keep in mind that @value{GDBN}
17157 communicates with Emacs in terms of line numbers. If you add or
17158 delete lines from the text, the line numbers that @value{GDBN} knows cease
17159 to correspond properly with the code.
17161 A more detailed description of Emacs' interaction with @value{GDBN} is
17162 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
17165 @c The following dropped because Epoch is nonstandard. Reactivate
17166 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
17168 @kindex Emacs Epoch environment
17172 Version 18 of @sc{gnu} Emacs has a built-in window system
17173 called the @code{epoch}
17174 environment. Users of this environment can use a new command,
17175 @code{inspect} which performs identically to @code{print} except that
17176 each value is printed in its own window.
17181 @chapter The @sc{gdb/mi} Interface
17183 @unnumberedsec Function and Purpose
17185 @cindex @sc{gdb/mi}, its purpose
17186 @sc{gdb/mi} is a line based machine oriented text interface to
17187 @value{GDBN} and is activated by specifying using the
17188 @option{--interpreter} command line option (@pxref{Mode Options}). It
17189 is specifically intended to support the development of systems which
17190 use the debugger as just one small component of a larger system.
17192 This chapter is a specification of the @sc{gdb/mi} interface. It is written
17193 in the form of a reference manual.
17195 Note that @sc{gdb/mi} is still under construction, so some of the
17196 features described below are incomplete and subject to change
17197 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
17199 @unnumberedsec Notation and Terminology
17201 @cindex notational conventions, for @sc{gdb/mi}
17202 This chapter uses the following notation:
17206 @code{|} separates two alternatives.
17209 @code{[ @var{something} ]} indicates that @var{something} is optional:
17210 it may or may not be given.
17213 @code{( @var{group} )*} means that @var{group} inside the parentheses
17214 may repeat zero or more times.
17217 @code{( @var{group} )+} means that @var{group} inside the parentheses
17218 may repeat one or more times.
17221 @code{"@var{string}"} means a literal @var{string}.
17225 @heading Dependencies
17229 * GDB/MI Command Syntax::
17230 * GDB/MI Compatibility with CLI::
17231 * GDB/MI Development and Front Ends::
17232 * GDB/MI Output Records::
17233 * GDB/MI Simple Examples::
17234 * GDB/MI Command Description Format::
17235 * GDB/MI Breakpoint Commands::
17236 * GDB/MI Program Context::
17237 * GDB/MI Thread Commands::
17238 * GDB/MI Program Execution::
17239 * GDB/MI Stack Manipulation::
17240 * GDB/MI Variable Objects::
17241 * GDB/MI Data Manipulation::
17242 * GDB/MI Tracepoint Commands::
17243 * GDB/MI Symbol Query::
17244 * GDB/MI File Commands::
17246 * GDB/MI Kod Commands::
17247 * GDB/MI Memory Overlay Commands::
17248 * GDB/MI Signal Handling Commands::
17250 * GDB/MI Target Manipulation::
17251 * GDB/MI Miscellaneous Commands::
17254 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17255 @node GDB/MI Command Syntax
17256 @section @sc{gdb/mi} Command Syntax
17259 * GDB/MI Input Syntax::
17260 * GDB/MI Output Syntax::
17263 @node GDB/MI Input Syntax
17264 @subsection @sc{gdb/mi} Input Syntax
17266 @cindex input syntax for @sc{gdb/mi}
17267 @cindex @sc{gdb/mi}, input syntax
17269 @item @var{command} @expansion{}
17270 @code{@var{cli-command} | @var{mi-command}}
17272 @item @var{cli-command} @expansion{}
17273 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
17274 @var{cli-command} is any existing @value{GDBN} CLI command.
17276 @item @var{mi-command} @expansion{}
17277 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
17278 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
17280 @item @var{token} @expansion{}
17281 "any sequence of digits"
17283 @item @var{option} @expansion{}
17284 @code{"-" @var{parameter} [ " " @var{parameter} ]}
17286 @item @var{parameter} @expansion{}
17287 @code{@var{non-blank-sequence} | @var{c-string}}
17289 @item @var{operation} @expansion{}
17290 @emph{any of the operations described in this chapter}
17292 @item @var{non-blank-sequence} @expansion{}
17293 @emph{anything, provided it doesn't contain special characters such as
17294 "-", @var{nl}, """ and of course " "}
17296 @item @var{c-string} @expansion{}
17297 @code{""" @var{seven-bit-iso-c-string-content} """}
17299 @item @var{nl} @expansion{}
17308 The CLI commands are still handled by the @sc{mi} interpreter; their
17309 output is described below.
17312 The @code{@var{token}}, when present, is passed back when the command
17316 Some @sc{mi} commands accept optional arguments as part of the parameter
17317 list. Each option is identified by a leading @samp{-} (dash) and may be
17318 followed by an optional argument parameter. Options occur first in the
17319 parameter list and can be delimited from normal parameters using
17320 @samp{--} (this is useful when some parameters begin with a dash).
17327 We want easy access to the existing CLI syntax (for debugging).
17330 We want it to be easy to spot a @sc{mi} operation.
17333 @node GDB/MI Output Syntax
17334 @subsection @sc{gdb/mi} Output Syntax
17336 @cindex output syntax of @sc{gdb/mi}
17337 @cindex @sc{gdb/mi}, output syntax
17338 The output from @sc{gdb/mi} consists of zero or more out-of-band records
17339 followed, optionally, by a single result record. This result record
17340 is for the most recent command. The sequence of output records is
17341 terminated by @samp{(gdb)}.
17343 If an input command was prefixed with a @code{@var{token}} then the
17344 corresponding output for that command will also be prefixed by that same
17348 @item @var{output} @expansion{}
17349 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
17351 @item @var{result-record} @expansion{}
17352 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
17354 @item @var{out-of-band-record} @expansion{}
17355 @code{@var{async-record} | @var{stream-record}}
17357 @item @var{async-record} @expansion{}
17358 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
17360 @item @var{exec-async-output} @expansion{}
17361 @code{[ @var{token} ] "*" @var{async-output}}
17363 @item @var{status-async-output} @expansion{}
17364 @code{[ @var{token} ] "+" @var{async-output}}
17366 @item @var{notify-async-output} @expansion{}
17367 @code{[ @var{token} ] "=" @var{async-output}}
17369 @item @var{async-output} @expansion{}
17370 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
17372 @item @var{result-class} @expansion{}
17373 @code{"done" | "running" | "connected" | "error" | "exit"}
17375 @item @var{async-class} @expansion{}
17376 @code{"stopped" | @var{others}} (where @var{others} will be added
17377 depending on the needs---this is still in development).
17379 @item @var{result} @expansion{}
17380 @code{ @var{variable} "=" @var{value}}
17382 @item @var{variable} @expansion{}
17383 @code{ @var{string} }
17385 @item @var{value} @expansion{}
17386 @code{ @var{const} | @var{tuple} | @var{list} }
17388 @item @var{const} @expansion{}
17389 @code{@var{c-string}}
17391 @item @var{tuple} @expansion{}
17392 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
17394 @item @var{list} @expansion{}
17395 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
17396 @var{result} ( "," @var{result} )* "]" }
17398 @item @var{stream-record} @expansion{}
17399 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
17401 @item @var{console-stream-output} @expansion{}
17402 @code{"~" @var{c-string}}
17404 @item @var{target-stream-output} @expansion{}
17405 @code{"@@" @var{c-string}}
17407 @item @var{log-stream-output} @expansion{}
17408 @code{"&" @var{c-string}}
17410 @item @var{nl} @expansion{}
17413 @item @var{token} @expansion{}
17414 @emph{any sequence of digits}.
17422 All output sequences end in a single line containing a period.
17425 The @code{@var{token}} is from the corresponding request. If an execution
17426 command is interrupted by the @samp{-exec-interrupt} command, the
17427 @var{token} associated with the @samp{*stopped} message is the one of the
17428 original execution command, not the one of the interrupt command.
17431 @cindex status output in @sc{gdb/mi}
17432 @var{status-async-output} contains on-going status information about the
17433 progress of a slow operation. It can be discarded. All status output is
17434 prefixed by @samp{+}.
17437 @cindex async output in @sc{gdb/mi}
17438 @var{exec-async-output} contains asynchronous state change on the target
17439 (stopped, started, disappeared). All async output is prefixed by
17443 @cindex notify output in @sc{gdb/mi}
17444 @var{notify-async-output} contains supplementary information that the
17445 client should handle (e.g., a new breakpoint information). All notify
17446 output is prefixed by @samp{=}.
17449 @cindex console output in @sc{gdb/mi}
17450 @var{console-stream-output} is output that should be displayed as is in the
17451 console. It is the textual response to a CLI command. All the console
17452 output is prefixed by @samp{~}.
17455 @cindex target output in @sc{gdb/mi}
17456 @var{target-stream-output} is the output produced by the target program.
17457 All the target output is prefixed by @samp{@@}.
17460 @cindex log output in @sc{gdb/mi}
17461 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
17462 instance messages that should be displayed as part of an error log. All
17463 the log output is prefixed by @samp{&}.
17466 @cindex list output in @sc{gdb/mi}
17467 New @sc{gdb/mi} commands should only output @var{lists} containing
17473 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
17474 details about the various output records.
17476 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17477 @node GDB/MI Compatibility with CLI
17478 @section @sc{gdb/mi} Compatibility with CLI
17480 @cindex compatibility, @sc{gdb/mi} and CLI
17481 @cindex @sc{gdb/mi}, compatibility with CLI
17483 For the developers convenience CLI commands can be entered directly,
17484 but there may be some unexpected behaviour. For example, commands
17485 that query the user will behave as if the user replied yes, breakpoint
17486 command lists are not executed and some CLI commands, such as
17487 @code{if}, @code{when} and @code{define}, prompt for further input with
17488 @samp{>}, which is not valid MI output.
17490 This feature may be removed at some stage in the future and it is
17491 recommended that front ends use the @code{-interpreter-exec} command
17492 (@pxref{-interpreter-exec}).
17494 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17495 @node GDB/MI Development and Front Ends
17496 @section @sc{gdb/mi} Development and Front Ends
17497 @cindex @sc{gdb/mi} development
17499 The application which takes the MI output and presents the state of the
17500 program being debugged to the user is called a @dfn{front end}.
17502 Although @sc{gdb/mi} is still incomplete, it is currently being used
17503 by a variety of front ends to @value{GDBN}. This makes it difficult
17504 to introduce new functionality without breaking existing usage. This
17505 section tries to minimize the problems by describing how the protocol
17508 Some changes in MI need not break a carefully designed front end, and
17509 for these the MI version will remain unchanged. The following is a
17510 list of changes that may occur within one level, so front ends should
17511 parse MI output in a way that can handle them:
17515 New MI commands may be added.
17518 New fields may be added to the output of any MI command.
17521 The range of values for fields with specified values, e.g.,
17522 @code{in_scope} (@pxref{-var-update}) may be extended.
17524 @c The format of field's content e.g type prefix, may change so parse it
17525 @c at your own risk. Yes, in general?
17527 @c The order of fields may change? Shouldn't really matter but it might
17528 @c resolve inconsistencies.
17531 If the changes are likely to break front ends, the MI version level
17532 will be increased by one. This will allow the front end to parse the
17533 output according to the MI version. Apart from mi0, new versions of
17534 @value{GDBN} will not support old versions of MI and it will be the
17535 responsibility of the front end to work with the new one.
17537 @c Starting with mi3, add a new command -mi-version that prints the MI
17540 The best way to avoid unexpected changes in MI that might break your front
17541 end is to make your project known to @value{GDBN} developers and
17542 follow development on @email{gdb@@sourceware.org} and
17543 @email{gdb-patches@@sourceware.org}. There is also the mailing list
17544 @email{dmi-discuss@@lists.freestandards.org}, hosted by the Free Standards
17545 Group, which has the aim of creating a more general MI protocol
17546 called Debugger Machine Interface (DMI) that will become a standard
17547 for all debuggers, not just @value{GDBN}.
17548 @cindex mailing lists
17550 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17551 @node GDB/MI Output Records
17552 @section @sc{gdb/mi} Output Records
17555 * GDB/MI Result Records::
17556 * GDB/MI Stream Records::
17557 * GDB/MI Out-of-band Records::
17560 @node GDB/MI Result Records
17561 @subsection @sc{gdb/mi} Result Records
17563 @cindex result records in @sc{gdb/mi}
17564 @cindex @sc{gdb/mi}, result records
17565 In addition to a number of out-of-band notifications, the response to a
17566 @sc{gdb/mi} command includes one of the following result indications:
17570 @item "^done" [ "," @var{results} ]
17571 The synchronous operation was successful, @code{@var{results}} are the return
17576 @c Is this one correct? Should it be an out-of-band notification?
17577 The asynchronous operation was successfully started. The target is
17582 @value{GDBN} has connected to a remote target.
17584 @item "^error" "," @var{c-string}
17586 The operation failed. The @code{@var{c-string}} contains the corresponding
17591 @value{GDBN} has terminated.
17595 @node GDB/MI Stream Records
17596 @subsection @sc{gdb/mi} Stream Records
17598 @cindex @sc{gdb/mi}, stream records
17599 @cindex stream records in @sc{gdb/mi}
17600 @value{GDBN} internally maintains a number of output streams: the console, the
17601 target, and the log. The output intended for each of these streams is
17602 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
17604 Each stream record begins with a unique @dfn{prefix character} which
17605 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
17606 Syntax}). In addition to the prefix, each stream record contains a
17607 @code{@var{string-output}}. This is either raw text (with an implicit new
17608 line) or a quoted C string (which does not contain an implicit newline).
17611 @item "~" @var{string-output}
17612 The console output stream contains text that should be displayed in the
17613 CLI console window. It contains the textual responses to CLI commands.
17615 @item "@@" @var{string-output}
17616 The target output stream contains any textual output from the running
17617 target. This is only present when GDB's event loop is truly
17618 asynchronous, which is currently only the case for remote targets.
17620 @item "&" @var{string-output}
17621 The log stream contains debugging messages being produced by @value{GDBN}'s
17625 @node GDB/MI Out-of-band Records
17626 @subsection @sc{gdb/mi} Out-of-band Records
17628 @cindex out-of-band records in @sc{gdb/mi}
17629 @cindex @sc{gdb/mi}, out-of-band records
17630 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
17631 additional changes that have occurred. Those changes can either be a
17632 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
17633 target activity (e.g., target stopped).
17635 The following is a preliminary list of possible out-of-band records.
17636 In particular, the @var{exec-async-output} records.
17639 @item *stopped,reason="@var{reason}"
17642 @var{reason} can be one of the following:
17645 @item breakpoint-hit
17646 A breakpoint was reached.
17647 @item watchpoint-trigger
17648 A watchpoint was triggered.
17649 @item read-watchpoint-trigger
17650 A read watchpoint was triggered.
17651 @item access-watchpoint-trigger
17652 An access watchpoint was triggered.
17653 @item function-finished
17654 An -exec-finish or similar CLI command was accomplished.
17655 @item location-reached
17656 An -exec-until or similar CLI command was accomplished.
17657 @item watchpoint-scope
17658 A watchpoint has gone out of scope.
17659 @item end-stepping-range
17660 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
17661 similar CLI command was accomplished.
17662 @item exited-signalled
17663 The inferior exited because of a signal.
17665 The inferior exited.
17666 @item exited-normally
17667 The inferior exited normally.
17668 @item signal-received
17669 A signal was received by the inferior.
17673 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17674 @node GDB/MI Simple Examples
17675 @section Simple Examples of @sc{gdb/mi} Interaction
17676 @cindex @sc{gdb/mi}, simple examples
17678 This subsection presents several simple examples of interaction using
17679 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
17680 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
17681 the output received from @sc{gdb/mi}.
17683 Note the line breaks shown in the examples are here only for
17684 readability, they don't appear in the real output.
17686 @subheading Setting a Breakpoint
17688 Setting a breakpoint generates synchronous output which contains detailed
17689 information of the breakpoint.
17692 -> -break-insert main
17693 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
17694 enabled="y",addr="0x08048564",func="main",file="myprog.c",
17695 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
17699 @subheading Program Execution
17701 Program execution generates asynchronous records and MI gives the
17702 reason that execution stopped.
17708 <- *stopped,reason="breakpoint-hit",bkptno="1",thread-id="0",
17709 frame=@{addr="0x08048564",func="main",
17710 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
17711 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
17716 <- *stopped,reason="exited-normally"
17720 @subheading Quitting @value{GDBN}
17722 Quitting @value{GDBN} just prints the result class @samp{^exit}.
17730 @subheading A Bad Command
17732 Here's what happens if you pass a non-existent command:
17736 <- ^error,msg="Undefined MI command: rubbish"
17741 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17742 @node GDB/MI Command Description Format
17743 @section @sc{gdb/mi} Command Description Format
17745 The remaining sections describe blocks of commands. Each block of
17746 commands is laid out in a fashion similar to this section.
17748 @subheading Motivation
17750 The motivation for this collection of commands.
17752 @subheading Introduction
17754 A brief introduction to this collection of commands as a whole.
17756 @subheading Commands
17758 For each command in the block, the following is described:
17760 @subsubheading Synopsis
17763 -command @var{args}@dots{}
17766 @subsubheading Result
17768 @subsubheading @value{GDBN} Command
17770 The corresponding @value{GDBN} CLI command(s), if any.
17772 @subsubheading Example
17774 Example(s) formatted for readability. Some of the described commands have
17775 not been implemented yet and these are labeled N.A.@: (not available).
17778 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17779 @node GDB/MI Breakpoint Commands
17780 @section @sc{gdb/mi} Breakpoint Commands
17782 @cindex breakpoint commands for @sc{gdb/mi}
17783 @cindex @sc{gdb/mi}, breakpoint commands
17784 This section documents @sc{gdb/mi} commands for manipulating
17787 @subheading The @code{-break-after} Command
17788 @findex -break-after
17790 @subsubheading Synopsis
17793 -break-after @var{number} @var{count}
17796 The breakpoint number @var{number} is not in effect until it has been
17797 hit @var{count} times. To see how this is reflected in the output of
17798 the @samp{-break-list} command, see the description of the
17799 @samp{-break-list} command below.
17801 @subsubheading @value{GDBN} Command
17803 The corresponding @value{GDBN} command is @samp{ignore}.
17805 @subsubheading Example
17810 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",
17811 fullname="/home/foo/hello.c",line="5",times="0"@}
17818 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17819 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17820 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17821 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17822 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17823 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17824 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17825 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17826 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
17827 line="5",times="0",ignore="3"@}]@}
17832 @subheading The @code{-break-catch} Command
17833 @findex -break-catch
17835 @subheading The @code{-break-commands} Command
17836 @findex -break-commands
17840 @subheading The @code{-break-condition} Command
17841 @findex -break-condition
17843 @subsubheading Synopsis
17846 -break-condition @var{number} @var{expr}
17849 Breakpoint @var{number} will stop the program only if the condition in
17850 @var{expr} is true. The condition becomes part of the
17851 @samp{-break-list} output (see the description of the @samp{-break-list}
17854 @subsubheading @value{GDBN} Command
17856 The corresponding @value{GDBN} command is @samp{condition}.
17858 @subsubheading Example
17862 -break-condition 1 1
17866 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17867 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17868 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17869 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17870 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17871 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17872 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17873 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17874 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
17875 line="5",cond="1",times="0",ignore="3"@}]@}
17879 @subheading The @code{-break-delete} Command
17880 @findex -break-delete
17882 @subsubheading Synopsis
17885 -break-delete ( @var{breakpoint} )+
17888 Delete the breakpoint(s) whose number(s) are specified in the argument
17889 list. This is obviously reflected in the breakpoint list.
17891 @subsubheading @value{GDBN} Command
17893 The corresponding @value{GDBN} command is @samp{delete}.
17895 @subsubheading Example
17903 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
17904 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17905 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17906 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17907 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17908 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17909 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17914 @subheading The @code{-break-disable} Command
17915 @findex -break-disable
17917 @subsubheading Synopsis
17920 -break-disable ( @var{breakpoint} )+
17923 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
17924 break list is now set to @samp{n} for the named @var{breakpoint}(s).
17926 @subsubheading @value{GDBN} Command
17928 The corresponding @value{GDBN} command is @samp{disable}.
17930 @subsubheading Example
17938 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17939 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17940 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17941 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17942 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17943 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17944 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17945 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
17946 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
17947 line="5",times="0"@}]@}
17951 @subheading The @code{-break-enable} Command
17952 @findex -break-enable
17954 @subsubheading Synopsis
17957 -break-enable ( @var{breakpoint} )+
17960 Enable (previously disabled) @var{breakpoint}(s).
17962 @subsubheading @value{GDBN} Command
17964 The corresponding @value{GDBN} command is @samp{enable}.
17966 @subsubheading Example
17974 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17975 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17976 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17977 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17978 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17979 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17980 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17981 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
17982 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
17983 line="5",times="0"@}]@}
17987 @subheading The @code{-break-info} Command
17988 @findex -break-info
17990 @subsubheading Synopsis
17993 -break-info @var{breakpoint}
17997 Get information about a single breakpoint.
17999 @subsubheading @value{GDBN} Command
18001 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
18003 @subsubheading Example
18006 @subheading The @code{-break-insert} Command
18007 @findex -break-insert
18009 @subsubheading Synopsis
18012 -break-insert [ -t ] [ -h ] [ -r ]
18013 [ -c @var{condition} ] [ -i @var{ignore-count} ]
18014 [ -p @var{thread} ] [ @var{line} | @var{addr} ]
18018 If specified, @var{line}, can be one of:
18025 @item filename:linenum
18026 @item filename:function
18030 The possible optional parameters of this command are:
18034 Insert a temporary breakpoint.
18036 Insert a hardware breakpoint.
18037 @item -c @var{condition}
18038 Make the breakpoint conditional on @var{condition}.
18039 @item -i @var{ignore-count}
18040 Initialize the @var{ignore-count}.
18042 Insert a regular breakpoint in all the functions whose names match the
18043 given regular expression. Other flags are not applicable to regular
18047 @subsubheading Result
18049 The result is in the form:
18052 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
18053 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
18054 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
18055 times="@var{times}"@}
18059 where @var{number} is the @value{GDBN} number for this breakpoint,
18060 @var{funcname} is the name of the function where the breakpoint was
18061 inserted, @var{filename} is the name of the source file which contains
18062 this function, @var{lineno} is the source line number within that file
18063 and @var{times} the number of times that the breakpoint has been hit
18064 (always 0 for -break-insert but may be greater for -break-info or -break-list
18065 which use the same output).
18067 Note: this format is open to change.
18068 @c An out-of-band breakpoint instead of part of the result?
18070 @subsubheading @value{GDBN} Command
18072 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
18073 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
18075 @subsubheading Example
18080 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
18081 fullname="/home/foo/recursive2.c,line="4",times="0"@}
18083 -break-insert -t foo
18084 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
18085 fullname="/home/foo/recursive2.c,line="11",times="0"@}
18088 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18089 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18090 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18091 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18092 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18093 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18094 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18095 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18096 addr="0x0001072c", func="main",file="recursive2.c",
18097 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
18098 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
18099 addr="0x00010774",func="foo",file="recursive2.c",
18100 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
18102 -break-insert -r foo.*
18103 ~int foo(int, int);
18104 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
18105 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
18109 @subheading The @code{-break-list} Command
18110 @findex -break-list
18112 @subsubheading Synopsis
18118 Displays the list of inserted breakpoints, showing the following fields:
18122 number of the breakpoint
18124 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
18126 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
18129 is the breakpoint enabled or no: @samp{y} or @samp{n}
18131 memory location at which the breakpoint is set
18133 logical location of the breakpoint, expressed by function name, file
18136 number of times the breakpoint has been hit
18139 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
18140 @code{body} field is an empty list.
18142 @subsubheading @value{GDBN} Command
18144 The corresponding @value{GDBN} command is @samp{info break}.
18146 @subsubheading Example
18151 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18152 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18153 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18154 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18155 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18156 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18157 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18158 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18159 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
18160 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
18161 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
18162 line="13",times="0"@}]@}
18166 Here's an example of the result when there are no breakpoints:
18171 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
18172 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18173 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18174 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18175 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18176 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18177 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18182 @subheading The @code{-break-watch} Command
18183 @findex -break-watch
18185 @subsubheading Synopsis
18188 -break-watch [ -a | -r ]
18191 Create a watchpoint. With the @samp{-a} option it will create an
18192 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
18193 read from or on a write to the memory location. With the @samp{-r}
18194 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
18195 trigger only when the memory location is accessed for reading. Without
18196 either of the options, the watchpoint created is a regular watchpoint,
18197 i.e., it will trigger when the memory location is accessed for writing.
18198 @xref{Set Watchpoints, , Setting Watchpoints}.
18200 Note that @samp{-break-list} will report a single list of watchpoints and
18201 breakpoints inserted.
18203 @subsubheading @value{GDBN} Command
18205 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
18208 @subsubheading Example
18210 Setting a watchpoint on a variable in the @code{main} function:
18215 ^done,wpt=@{number="2",exp="x"@}
18220 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
18221 value=@{old="-268439212",new="55"@},
18222 frame=@{func="main",args=[],file="recursive2.c",
18223 fullname="/home/foo/bar/recursive2.c",line="5"@}
18227 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
18228 the program execution twice: first for the variable changing value, then
18229 for the watchpoint going out of scope.
18234 ^done,wpt=@{number="5",exp="C"@}
18239 *stopped,reason="watchpoint-trigger",
18240 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
18241 frame=@{func="callee4",args=[],
18242 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18243 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
18248 *stopped,reason="watchpoint-scope",wpnum="5",
18249 frame=@{func="callee3",args=[@{name="strarg",
18250 value="0x11940 \"A string argument.\""@}],
18251 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18252 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18256 Listing breakpoints and watchpoints, at different points in the program
18257 execution. Note that once the watchpoint goes out of scope, it is
18263 ^done,wpt=@{number="2",exp="C"@}
18266 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18267 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18268 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18269 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18270 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18271 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18272 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18273 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18274 addr="0x00010734",func="callee4",
18275 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18276 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
18277 bkpt=@{number="2",type="watchpoint",disp="keep",
18278 enabled="y",addr="",what="C",times="0"@}]@}
18283 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
18284 value=@{old="-276895068",new="3"@},
18285 frame=@{func="callee4",args=[],
18286 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18287 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
18290 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18291 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18292 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18293 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18294 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18295 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18296 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18297 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18298 addr="0x00010734",func="callee4",
18299 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18300 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
18301 bkpt=@{number="2",type="watchpoint",disp="keep",
18302 enabled="y",addr="",what="C",times="-5"@}]@}
18306 ^done,reason="watchpoint-scope",wpnum="2",
18307 frame=@{func="callee3",args=[@{name="strarg",
18308 value="0x11940 \"A string argument.\""@}],
18309 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18310 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18313 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18314 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18315 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18316 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18317 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18318 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18319 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18320 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18321 addr="0x00010734",func="callee4",
18322 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18323 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
18328 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18329 @node GDB/MI Program Context
18330 @section @sc{gdb/mi} Program Context
18332 @subheading The @code{-exec-arguments} Command
18333 @findex -exec-arguments
18336 @subsubheading Synopsis
18339 -exec-arguments @var{args}
18342 Set the inferior program arguments, to be used in the next
18345 @subsubheading @value{GDBN} Command
18347 The corresponding @value{GDBN} command is @samp{set args}.
18349 @subsubheading Example
18352 Don't have one around.
18355 @subheading The @code{-exec-show-arguments} Command
18356 @findex -exec-show-arguments
18358 @subsubheading Synopsis
18361 -exec-show-arguments
18364 Print the arguments of the program.
18366 @subsubheading @value{GDBN} Command
18368 The corresponding @value{GDBN} command is @samp{show args}.
18370 @subsubheading Example
18374 @subheading The @code{-environment-cd} Command
18375 @findex -environment-cd
18377 @subsubheading Synopsis
18380 -environment-cd @var{pathdir}
18383 Set @value{GDBN}'s working directory.
18385 @subsubheading @value{GDBN} Command
18387 The corresponding @value{GDBN} command is @samp{cd}.
18389 @subsubheading Example
18393 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18399 @subheading The @code{-environment-directory} Command
18400 @findex -environment-directory
18402 @subsubheading Synopsis
18405 -environment-directory [ -r ] [ @var{pathdir} ]+
18408 Add directories @var{pathdir} to beginning of search path for source files.
18409 If the @samp{-r} option is used, the search path is reset to the default
18410 search path. If directories @var{pathdir} are supplied in addition to the
18411 @samp{-r} option, the search path is first reset and then addition
18413 Multiple directories may be specified, separated by blanks. Specifying
18414 multiple directories in a single command
18415 results in the directories added to the beginning of the
18416 search path in the same order they were presented in the command.
18417 If blanks are needed as
18418 part of a directory name, double-quotes should be used around
18419 the name. In the command output, the path will show up separated
18420 by the system directory-separator character. The directory-separator
18421 character must not be used
18422 in any directory name.
18423 If no directories are specified, the current search path is displayed.
18425 @subsubheading @value{GDBN} Command
18427 The corresponding @value{GDBN} command is @samp{dir}.
18429 @subsubheading Example
18433 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18434 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18436 -environment-directory ""
18437 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18439 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
18440 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
18442 -environment-directory -r
18443 ^done,source-path="$cdir:$cwd"
18448 @subheading The @code{-environment-path} Command
18449 @findex -environment-path
18451 @subsubheading Synopsis
18454 -environment-path [ -r ] [ @var{pathdir} ]+
18457 Add directories @var{pathdir} to beginning of search path for object files.
18458 If the @samp{-r} option is used, the search path is reset to the original
18459 search path that existed at gdb start-up. If directories @var{pathdir} are
18460 supplied in addition to the
18461 @samp{-r} option, the search path is first reset and then addition
18463 Multiple directories may be specified, separated by blanks. Specifying
18464 multiple directories in a single command
18465 results in the directories added to the beginning of the
18466 search path in the same order they were presented in the command.
18467 If blanks are needed as
18468 part of a directory name, double-quotes should be used around
18469 the name. In the command output, the path will show up separated
18470 by the system directory-separator character. The directory-separator
18471 character must not be used
18472 in any directory name.
18473 If no directories are specified, the current path is displayed.
18476 @subsubheading @value{GDBN} Command
18478 The corresponding @value{GDBN} command is @samp{path}.
18480 @subsubheading Example
18485 ^done,path="/usr/bin"
18487 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
18488 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
18490 -environment-path -r /usr/local/bin
18491 ^done,path="/usr/local/bin:/usr/bin"
18496 @subheading The @code{-environment-pwd} Command
18497 @findex -environment-pwd
18499 @subsubheading Synopsis
18505 Show the current working directory.
18507 @subsubheading @value{GDBN} Command
18509 The corresponding @value{GDBN} command is @samp{pwd}.
18511 @subsubheading Example
18516 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
18520 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18521 @node GDB/MI Thread Commands
18522 @section @sc{gdb/mi} Thread Commands
18525 @subheading The @code{-thread-info} Command
18526 @findex -thread-info
18528 @subsubheading Synopsis
18534 @subsubheading @value{GDBN} Command
18538 @subsubheading Example
18542 @subheading The @code{-thread-list-all-threads} Command
18543 @findex -thread-list-all-threads
18545 @subsubheading Synopsis
18548 -thread-list-all-threads
18551 @subsubheading @value{GDBN} Command
18553 The equivalent @value{GDBN} command is @samp{info threads}.
18555 @subsubheading Example
18559 @subheading The @code{-thread-list-ids} Command
18560 @findex -thread-list-ids
18562 @subsubheading Synopsis
18568 Produces a list of the currently known @value{GDBN} thread ids. At the
18569 end of the list it also prints the total number of such threads.
18571 @subsubheading @value{GDBN} Command
18573 Part of @samp{info threads} supplies the same information.
18575 @subsubheading Example
18577 No threads present, besides the main process:
18582 ^done,thread-ids=@{@},number-of-threads="0"
18592 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18593 number-of-threads="3"
18598 @subheading The @code{-thread-select} Command
18599 @findex -thread-select
18601 @subsubheading Synopsis
18604 -thread-select @var{threadnum}
18607 Make @var{threadnum} the current thread. It prints the number of the new
18608 current thread, and the topmost frame for that thread.
18610 @subsubheading @value{GDBN} Command
18612 The corresponding @value{GDBN} command is @samp{thread}.
18614 @subsubheading Example
18621 *stopped,reason="end-stepping-range",thread-id="2",line="187",
18622 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
18626 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
18627 number-of-threads="3"
18630 ^done,new-thread-id="3",
18631 frame=@{level="0",func="vprintf",
18632 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
18633 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
18637 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18638 @node GDB/MI Program Execution
18639 @section @sc{gdb/mi} Program Execution
18641 These are the asynchronous commands which generate the out-of-band
18642 record @samp{*stopped}. Currently @value{GDBN} only really executes
18643 asynchronously with remote targets and this interaction is mimicked in
18646 @subheading The @code{-exec-continue} Command
18647 @findex -exec-continue
18649 @subsubheading Synopsis
18655 Resumes the execution of the inferior program until a breakpoint is
18656 encountered, or until the inferior exits.
18658 @subsubheading @value{GDBN} Command
18660 The corresponding @value{GDBN} corresponding is @samp{continue}.
18662 @subsubheading Example
18669 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
18670 file="hello.c",fullname="/home/foo/bar/hello.c",line="13"@}
18675 @subheading The @code{-exec-finish} Command
18676 @findex -exec-finish
18678 @subsubheading Synopsis
18684 Resumes the execution of the inferior program until the current
18685 function is exited. Displays the results returned by the function.
18687 @subsubheading @value{GDBN} Command
18689 The corresponding @value{GDBN} command is @samp{finish}.
18691 @subsubheading Example
18693 Function returning @code{void}.
18700 *stopped,reason="function-finished",frame=@{func="main",args=[],
18701 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
18705 Function returning other than @code{void}. The name of the internal
18706 @value{GDBN} variable storing the result is printed, together with the
18713 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
18714 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
18715 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
18716 gdb-result-var="$1",return-value="0"
18721 @subheading The @code{-exec-interrupt} Command
18722 @findex -exec-interrupt
18724 @subsubheading Synopsis
18730 Interrupts the background execution of the target. Note how the token
18731 associated with the stop message is the one for the execution command
18732 that has been interrupted. The token for the interrupt itself only
18733 appears in the @samp{^done} output. If the user is trying to
18734 interrupt a non-running program, an error message will be printed.
18736 @subsubheading @value{GDBN} Command
18738 The corresponding @value{GDBN} command is @samp{interrupt}.
18740 @subsubheading Example
18751 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
18752 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
18753 fullname="/home/foo/bar/try.c",line="13"@}
18758 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
18763 @subheading The @code{-exec-next} Command
18766 @subsubheading Synopsis
18772 Resumes execution of the inferior program, stopping when the beginning
18773 of the next source line is reached.
18775 @subsubheading @value{GDBN} Command
18777 The corresponding @value{GDBN} command is @samp{next}.
18779 @subsubheading Example
18785 *stopped,reason="end-stepping-range",line="8",file="hello.c"
18790 @subheading The @code{-exec-next-instruction} Command
18791 @findex -exec-next-instruction
18793 @subsubheading Synopsis
18796 -exec-next-instruction
18799 Executes one machine instruction. If the instruction is a function
18800 call, continues until the function returns. If the program stops at an
18801 instruction in the middle of a source line, the address will be
18804 @subsubheading @value{GDBN} Command
18806 The corresponding @value{GDBN} command is @samp{nexti}.
18808 @subsubheading Example
18812 -exec-next-instruction
18816 *stopped,reason="end-stepping-range",
18817 addr="0x000100d4",line="5",file="hello.c"
18822 @subheading The @code{-exec-return} Command
18823 @findex -exec-return
18825 @subsubheading Synopsis
18831 Makes current function return immediately. Doesn't execute the inferior.
18832 Displays the new current frame.
18834 @subsubheading @value{GDBN} Command
18836 The corresponding @value{GDBN} command is @samp{return}.
18838 @subsubheading Example
18842 200-break-insert callee4
18843 200^done,bkpt=@{number="1",addr="0x00010734",
18844 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
18849 000*stopped,reason="breakpoint-hit",bkptno="1",
18850 frame=@{func="callee4",args=[],
18851 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18852 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
18858 111^done,frame=@{level="0",func="callee3",
18859 args=[@{name="strarg",
18860 value="0x11940 \"A string argument.\""@}],
18861 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18862 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18867 @subheading The @code{-exec-run} Command
18870 @subsubheading Synopsis
18876 Starts execution of the inferior from the beginning. The inferior
18877 executes until either a breakpoint is encountered or the program
18878 exits. In the latter case the output will include an exit code, if
18879 the program has exited exceptionally.
18881 @subsubheading @value{GDBN} Command
18883 The corresponding @value{GDBN} command is @samp{run}.
18885 @subsubheading Examples
18890 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
18895 *stopped,reason="breakpoint-hit",bkptno="1",
18896 frame=@{func="main",args=[],file="recursive2.c",
18897 fullname="/home/foo/bar/recursive2.c",line="4"@}
18902 Program exited normally:
18910 *stopped,reason="exited-normally"
18915 Program exited exceptionally:
18923 *stopped,reason="exited",exit-code="01"
18927 Another way the program can terminate is if it receives a signal such as
18928 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
18932 *stopped,reason="exited-signalled",signal-name="SIGINT",
18933 signal-meaning="Interrupt"
18937 @c @subheading -exec-signal
18940 @subheading The @code{-exec-step} Command
18943 @subsubheading Synopsis
18949 Resumes execution of the inferior program, stopping when the beginning
18950 of the next source line is reached, if the next source line is not a
18951 function call. If it is, stop at the first instruction of the called
18954 @subsubheading @value{GDBN} Command
18956 The corresponding @value{GDBN} command is @samp{step}.
18958 @subsubheading Example
18960 Stepping into a function:
18966 *stopped,reason="end-stepping-range",
18967 frame=@{func="foo",args=[@{name="a",value="10"@},
18968 @{name="b",value="0"@}],file="recursive2.c",
18969 fullname="/home/foo/bar/recursive2.c",line="11"@}
18979 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
18984 @subheading The @code{-exec-step-instruction} Command
18985 @findex -exec-step-instruction
18987 @subsubheading Synopsis
18990 -exec-step-instruction
18993 Resumes the inferior which executes one machine instruction. The
18994 output, once @value{GDBN} has stopped, will vary depending on whether
18995 we have stopped in the middle of a source line or not. In the former
18996 case, the address at which the program stopped will be printed as
18999 @subsubheading @value{GDBN} Command
19001 The corresponding @value{GDBN} command is @samp{stepi}.
19003 @subsubheading Example
19007 -exec-step-instruction
19011 *stopped,reason="end-stepping-range",
19012 frame=@{func="foo",args=[],file="try.c",
19013 fullname="/home/foo/bar/try.c",line="10"@}
19015 -exec-step-instruction
19019 *stopped,reason="end-stepping-range",
19020 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
19021 fullname="/home/foo/bar/try.c",line="10"@}
19026 @subheading The @code{-exec-until} Command
19027 @findex -exec-until
19029 @subsubheading Synopsis
19032 -exec-until [ @var{location} ]
19035 Executes the inferior until the @var{location} specified in the
19036 argument is reached. If there is no argument, the inferior executes
19037 until a source line greater than the current one is reached. The
19038 reason for stopping in this case will be @samp{location-reached}.
19040 @subsubheading @value{GDBN} Command
19042 The corresponding @value{GDBN} command is @samp{until}.
19044 @subsubheading Example
19048 -exec-until recursive2.c:6
19052 *stopped,reason="location-reached",frame=@{func="main",args=[],
19053 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
19058 @subheading -file-clear
19059 Is this going away????
19062 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19063 @node GDB/MI Stack Manipulation
19064 @section @sc{gdb/mi} Stack Manipulation Commands
19067 @subheading The @code{-stack-info-frame} Command
19068 @findex -stack-info-frame
19070 @subsubheading Synopsis
19076 Get info on the selected frame.
19078 @subsubheading @value{GDBN} Command
19080 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
19081 (without arguments).
19083 @subsubheading Example
19088 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
19089 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19090 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
19094 @subheading The @code{-stack-info-depth} Command
19095 @findex -stack-info-depth
19097 @subsubheading Synopsis
19100 -stack-info-depth [ @var{max-depth} ]
19103 Return the depth of the stack. If the integer argument @var{max-depth}
19104 is specified, do not count beyond @var{max-depth} frames.
19106 @subsubheading @value{GDBN} Command
19108 There's no equivalent @value{GDBN} command.
19110 @subsubheading Example
19112 For a stack with frame levels 0 through 11:
19119 -stack-info-depth 4
19122 -stack-info-depth 12
19125 -stack-info-depth 11
19128 -stack-info-depth 13
19133 @subheading The @code{-stack-list-arguments} Command
19134 @findex -stack-list-arguments
19136 @subsubheading Synopsis
19139 -stack-list-arguments @var{show-values}
19140 [ @var{low-frame} @var{high-frame} ]
19143 Display a list of the arguments for the frames between @var{low-frame}
19144 and @var{high-frame} (inclusive). If @var{low-frame} and
19145 @var{high-frame} are not provided, list the arguments for the whole
19146 call stack. If the two arguments are equal, show the single frame
19147 at the corresponding level. It is an error if @var{low-frame} is
19148 larger than the actual number of frames. On the other hand,
19149 @var{high-frame} may be larger than the actual number of frames, in
19150 which case only existing frames will be returned.
19152 The @var{show-values} argument must have a value of 0 or 1. A value of
19153 0 means that only the names of the arguments are listed, a value of 1
19154 means that both names and values of the arguments are printed.
19156 @subsubheading @value{GDBN} Command
19158 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
19159 @samp{gdb_get_args} command which partially overlaps with the
19160 functionality of @samp{-stack-list-arguments}.
19162 @subsubheading Example
19169 frame=@{level="0",addr="0x00010734",func="callee4",
19170 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19171 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
19172 frame=@{level="1",addr="0x0001076c",func="callee3",
19173 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19174 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
19175 frame=@{level="2",addr="0x0001078c",func="callee2",
19176 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19177 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
19178 frame=@{level="3",addr="0x000107b4",func="callee1",
19179 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19180 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
19181 frame=@{level="4",addr="0x000107e0",func="main",
19182 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19183 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
19185 -stack-list-arguments 0
19188 frame=@{level="0",args=[]@},
19189 frame=@{level="1",args=[name="strarg"]@},
19190 frame=@{level="2",args=[name="intarg",name="strarg"]@},
19191 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
19192 frame=@{level="4",args=[]@}]
19194 -stack-list-arguments 1
19197 frame=@{level="0",args=[]@},
19199 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19200 frame=@{level="2",args=[
19201 @{name="intarg",value="2"@},
19202 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19203 @{frame=@{level="3",args=[
19204 @{name="intarg",value="2"@},
19205 @{name="strarg",value="0x11940 \"A string argument.\""@},
19206 @{name="fltarg",value="3.5"@}]@},
19207 frame=@{level="4",args=[]@}]
19209 -stack-list-arguments 0 2 2
19210 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
19212 -stack-list-arguments 1 2 2
19213 ^done,stack-args=[frame=@{level="2",
19214 args=[@{name="intarg",value="2"@},
19215 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
19219 @c @subheading -stack-list-exception-handlers
19222 @subheading The @code{-stack-list-frames} Command
19223 @findex -stack-list-frames
19225 @subsubheading Synopsis
19228 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
19231 List the frames currently on the stack. For each frame it displays the
19236 The frame number, 0 being the topmost frame, i.e., the innermost function.
19238 The @code{$pc} value for that frame.
19242 File name of the source file where the function lives.
19244 Line number corresponding to the @code{$pc}.
19247 If invoked without arguments, this command prints a backtrace for the
19248 whole stack. If given two integer arguments, it shows the frames whose
19249 levels are between the two arguments (inclusive). If the two arguments
19250 are equal, it shows the single frame at the corresponding level. It is
19251 an error if @var{low-frame} is larger than the actual number of
19252 frames. On the other hand, @var{high-frame} may be larger than the
19253 actual number of frames, in which case only existing frames will be returned.
19255 @subsubheading @value{GDBN} Command
19257 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
19259 @subsubheading Example
19261 Full stack backtrace:
19267 [frame=@{level="0",addr="0x0001076c",func="foo",
19268 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
19269 frame=@{level="1",addr="0x000107a4",func="foo",
19270 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19271 frame=@{level="2",addr="0x000107a4",func="foo",
19272 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19273 frame=@{level="3",addr="0x000107a4",func="foo",
19274 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19275 frame=@{level="4",addr="0x000107a4",func="foo",
19276 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19277 frame=@{level="5",addr="0x000107a4",func="foo",
19278 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19279 frame=@{level="6",addr="0x000107a4",func="foo",
19280 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19281 frame=@{level="7",addr="0x000107a4",func="foo",
19282 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19283 frame=@{level="8",addr="0x000107a4",func="foo",
19284 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19285 frame=@{level="9",addr="0x000107a4",func="foo",
19286 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19287 frame=@{level="10",addr="0x000107a4",func="foo",
19288 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19289 frame=@{level="11",addr="0x00010738",func="main",
19290 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
19294 Show frames between @var{low_frame} and @var{high_frame}:
19298 -stack-list-frames 3 5
19300 [frame=@{level="3",addr="0x000107a4",func="foo",
19301 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19302 frame=@{level="4",addr="0x000107a4",func="foo",
19303 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19304 frame=@{level="5",addr="0x000107a4",func="foo",
19305 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
19309 Show a single frame:
19313 -stack-list-frames 3 3
19315 [frame=@{level="3",addr="0x000107a4",func="foo",
19316 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
19321 @subheading The @code{-stack-list-locals} Command
19322 @findex -stack-list-locals
19324 @subsubheading Synopsis
19327 -stack-list-locals @var{print-values}
19330 Display the local variable names for the selected frame. If
19331 @var{print-values} is 0 or @code{--no-values}, print only the names of
19332 the variables; if it is 1 or @code{--all-values}, print also their
19333 values; and if it is 2 or @code{--simple-values}, print the name,
19334 type and value for simple data types and the name and type for arrays,
19335 structures and unions. In this last case, a frontend can immediately
19336 display the value of simple data types and create variable objects for
19337 other data types when the user wishes to explore their values in
19340 @subsubheading @value{GDBN} Command
19342 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
19344 @subsubheading Example
19348 -stack-list-locals 0
19349 ^done,locals=[name="A",name="B",name="C"]
19351 -stack-list-locals --all-values
19352 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
19353 @{name="C",value="@{1, 2, 3@}"@}]
19354 -stack-list-locals --simple-values
19355 ^done,locals=[@{name="A",type="int",value="1"@},
19356 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
19361 @subheading The @code{-stack-select-frame} Command
19362 @findex -stack-select-frame
19364 @subsubheading Synopsis
19367 -stack-select-frame @var{framenum}
19370 Change the selected frame. Select a different frame @var{framenum} on
19373 @subsubheading @value{GDBN} Command
19375 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
19376 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
19378 @subsubheading Example
19382 -stack-select-frame 2
19387 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19388 @node GDB/MI Variable Objects
19389 @section @sc{gdb/mi} Variable Objects
19393 @subheading Motivation for Variable Objects in @sc{gdb/mi}
19395 For the implementation of a variable debugger window (locals, watched
19396 expressions, etc.), we are proposing the adaptation of the existing code
19397 used by @code{Insight}.
19399 The two main reasons for that are:
19403 It has been proven in practice (it is already on its second generation).
19406 It will shorten development time (needless to say how important it is
19410 The original interface was designed to be used by Tcl code, so it was
19411 slightly changed so it could be used through @sc{gdb/mi}. This section
19412 describes the @sc{gdb/mi} operations that will be available and gives some
19413 hints about their use.
19415 @emph{Note}: In addition to the set of operations described here, we
19416 expect the @sc{gui} implementation of a variable window to require, at
19417 least, the following operations:
19420 @item @code{-gdb-show} @code{output-radix}
19421 @item @code{-stack-list-arguments}
19422 @item @code{-stack-list-locals}
19423 @item @code{-stack-select-frame}
19428 @subheading Introduction to Variable Objects
19430 @cindex variable objects in @sc{gdb/mi}
19432 Variable objects are "object-oriented" MI interface for examining and
19433 changing values of expressions. Unlike some other MI interfaces that
19434 work with expressions, variable objects are specifically designed for
19435 simple and efficient presentation in the frontend. A variable object
19436 is identified by string name. When a variable object is created, the
19437 frontend specifies the expression for that variable object. The
19438 expression can be a simple variable, or it can be an arbitrary complex
19439 expression, and can even involve CPU registers. After creating a
19440 variable object, the frontend can invoke other variable object
19441 operations---for example to obtain or change the value of a variable
19442 object, or to change display format.
19444 Variable objects have hierarchical tree structure. Any variable object
19445 that corresponds to a composite type, such as structure in C, has
19446 a number of child variable objects, for example corresponding to each
19447 element of a structure. A child variable object can itself have
19448 children, recursively. Recursion ends when we reach
19449 leaf variable objects, which always have built-in types. Child variable
19450 objects are created only by explicit request, so if a frontend
19451 is not interested in the children of a particular variable object, no
19452 child will be created.
19454 For a leaf variable object it is possible to obtain its value as a
19455 string, or set the value from a string. String value can be also
19456 obtained for a non-leaf variable object, but it's generally a string
19457 that only indicates the type of the object, and does not list its
19458 contents. Assignment to a non-leaf variable object is not allowed.
19460 A frontend does not need to read the values of all variable objects each time
19461 the program stops. Instead, MI provides an update command that lists all
19462 variable objects whose values has changed since the last update
19463 operation. This considerably reduces the amount of data that must
19464 be transferred to the frontend. As noted above, children variable
19465 objects are created on demand, and only leaf variable objects have a
19466 real value. As result, gdb will read target memory only for leaf
19467 variables that frontend has created.
19469 The automatic update is not always desirable. For example, a frontend
19470 might want to keep a value of some expression for future reference,
19471 and never update it. For another example, fetching memory is
19472 relatively slow for embedded targets, so a frontend might want
19473 to disable automatic update for the variables that are either not
19474 visible on the screen, or ``closed''. This is possible using so
19475 called ``frozen variable objects''. Such variable objects are never
19476 implicitly updated.
19478 The following is the complete set of @sc{gdb/mi} operations defined to
19479 access this functionality:
19481 @multitable @columnfractions .4 .6
19482 @item @strong{Operation}
19483 @tab @strong{Description}
19485 @item @code{-var-create}
19486 @tab create a variable object
19487 @item @code{-var-delete}
19488 @tab delete the variable object and/or its children
19489 @item @code{-var-set-format}
19490 @tab set the display format of this variable
19491 @item @code{-var-show-format}
19492 @tab show the display format of this variable
19493 @item @code{-var-info-num-children}
19494 @tab tells how many children this object has
19495 @item @code{-var-list-children}
19496 @tab return a list of the object's children
19497 @item @code{-var-info-type}
19498 @tab show the type of this variable object
19499 @item @code{-var-info-expression}
19500 @tab print parent-relative expression that this variable object represents
19501 @item @code{-var-info-path-expression}
19502 @tab print full expression that this variable object represents
19503 @item @code{-var-show-attributes}
19504 @tab is this variable editable? does it exist here?
19505 @item @code{-var-evaluate-expression}
19506 @tab get the value of this variable
19507 @item @code{-var-assign}
19508 @tab set the value of this variable
19509 @item @code{-var-update}
19510 @tab update the variable and its children
19511 @item @code{-var-set-frozen}
19512 @tab set frozeness attribute
19515 In the next subsection we describe each operation in detail and suggest
19516 how it can be used.
19518 @subheading Description And Use of Operations on Variable Objects
19520 @subheading The @code{-var-create} Command
19521 @findex -var-create
19523 @subsubheading Synopsis
19526 -var-create @{@var{name} | "-"@}
19527 @{@var{frame-addr} | "*"@} @var{expression}
19530 This operation creates a variable object, which allows the monitoring of
19531 a variable, the result of an expression, a memory cell or a CPU
19534 The @var{name} parameter is the string by which the object can be
19535 referenced. It must be unique. If @samp{-} is specified, the varobj
19536 system will generate a string ``varNNNNNN'' automatically. It will be
19537 unique provided that one does not specify @var{name} on that format.
19538 The command fails if a duplicate name is found.
19540 The frame under which the expression should be evaluated can be
19541 specified by @var{frame-addr}. A @samp{*} indicates that the current
19542 frame should be used.
19544 @var{expression} is any expression valid on the current language set (must not
19545 begin with a @samp{*}), or one of the following:
19549 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
19552 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
19555 @samp{$@var{regname}} --- a CPU register name
19558 @subsubheading Result
19560 This operation returns the name, number of children and the type of the
19561 object created. Type is returned as a string as the ones generated by
19562 the @value{GDBN} CLI:
19565 name="@var{name}",numchild="N",type="@var{type}"
19569 @subheading The @code{-var-delete} Command
19570 @findex -var-delete
19572 @subsubheading Synopsis
19575 -var-delete [ -c ] @var{name}
19578 Deletes a previously created variable object and all of its children.
19579 With the @samp{-c} option, just deletes the children.
19581 Returns an error if the object @var{name} is not found.
19584 @subheading The @code{-var-set-format} Command
19585 @findex -var-set-format
19587 @subsubheading Synopsis
19590 -var-set-format @var{name} @var{format-spec}
19593 Sets the output format for the value of the object @var{name} to be
19596 The syntax for the @var{format-spec} is as follows:
19599 @var{format-spec} @expansion{}
19600 @{binary | decimal | hexadecimal | octal | natural@}
19603 The natural format is the default format choosen automatically
19604 based on the variable type (like decimal for an @code{int}, hex
19605 for pointers, etc.).
19607 For a variable with children, the format is set only on the
19608 variable itself, and the children are not affected.
19610 @subheading The @code{-var-show-format} Command
19611 @findex -var-show-format
19613 @subsubheading Synopsis
19616 -var-show-format @var{name}
19619 Returns the format used to display the value of the object @var{name}.
19622 @var{format} @expansion{}
19627 @subheading The @code{-var-info-num-children} Command
19628 @findex -var-info-num-children
19630 @subsubheading Synopsis
19633 -var-info-num-children @var{name}
19636 Returns the number of children of a variable object @var{name}:
19643 @subheading The @code{-var-list-children} Command
19644 @findex -var-list-children
19646 @subsubheading Synopsis
19649 -var-list-children [@var{print-values}] @var{name}
19651 @anchor{-var-list-children}
19653 Return a list of the children of the specified variable object and
19654 create variable objects for them, if they do not already exist. With
19655 a single argument or if @var{print-values} has a value for of 0 or
19656 @code{--no-values}, print only the names of the variables; if
19657 @var{print-values} is 1 or @code{--all-values}, also print their
19658 values; and if it is 2 or @code{--simple-values} print the name and
19659 value for simple data types and just the name for arrays, structures
19662 @subsubheading Example
19666 -var-list-children n
19667 ^done,numchild=@var{n},children=[@{name=@var{name},
19668 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
19670 -var-list-children --all-values n
19671 ^done,numchild=@var{n},children=[@{name=@var{name},
19672 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
19676 @subheading The @code{-var-info-type} Command
19677 @findex -var-info-type
19679 @subsubheading Synopsis
19682 -var-info-type @var{name}
19685 Returns the type of the specified variable @var{name}. The type is
19686 returned as a string in the same format as it is output by the
19690 type=@var{typename}
19694 @subheading The @code{-var-info-expression} Command
19695 @findex -var-info-expression
19697 @subsubheading Synopsis
19700 -var-info-expression @var{name}
19703 Returns a string that is suitable for presenting this
19704 variable object in user interface. The string is generally
19705 not valid expression in the current language, and cannot be evaluated.
19707 For example, if @code{a} is an array, and variable object
19708 @code{A} was created for @code{a}, then we'll get this output:
19711 (gdb) -var-info-expression A.1
19712 ^done,lang="C",exp="1"
19716 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
19718 Note that the output of the @code{-var-list-children} command also
19719 includes those expressions, so the @code{-var-info-expression} command
19722 @subheading The @code{-var-info-path-expression} Command
19723 @findex -var-info-path-expression
19725 @subsubheading Synopsis
19728 -var-info-path-expression @var{name}
19731 Returns an expression that can be evaluated in the current
19732 context and will yield the same value that a variable object has.
19733 Compare this with the @code{-var-info-expression} command, which
19734 result can be used only for UI presentation. Typical use of
19735 the @code{-var-info-path-expression} command is creating a
19736 watchpoint from a variable object.
19738 For example, suppose @code{C} is a C@t{++} class, derived from class
19739 @code{Base}, and that the @code{Base} class has a member called
19740 @code{m_size}. Assume a variable @code{c} is has the type of
19741 @code{C} and a variable object @code{C} was created for variable
19742 @code{c}. Then, we'll get this output:
19744 (gdb) -var-info-path-expression C.Base.public.m_size
19745 ^done,path_expr=((Base)c).m_size)
19748 @subheading The @code{-var-show-attributes} Command
19749 @findex -var-show-attributes
19751 @subsubheading Synopsis
19754 -var-show-attributes @var{name}
19757 List attributes of the specified variable object @var{name}:
19760 status=@var{attr} [ ( ,@var{attr} )* ]
19764 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
19766 @subheading The @code{-var-evaluate-expression} Command
19767 @findex -var-evaluate-expression
19769 @subsubheading Synopsis
19772 -var-evaluate-expression @var{name}
19775 Evaluates the expression that is represented by the specified variable
19776 object and returns its value as a string. The format of the
19777 string can be changed using the @code{-var-set-format} command.
19783 Note that one must invoke @code{-var-list-children} for a variable
19784 before the value of a child variable can be evaluated.
19786 @subheading The @code{-var-assign} Command
19787 @findex -var-assign
19789 @subsubheading Synopsis
19792 -var-assign @var{name} @var{expression}
19795 Assigns the value of @var{expression} to the variable object specified
19796 by @var{name}. The object must be @samp{editable}. If the variable's
19797 value is altered by the assign, the variable will show up in any
19798 subsequent @code{-var-update} list.
19800 @subsubheading Example
19808 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
19812 @subheading The @code{-var-update} Command
19813 @findex -var-update
19815 @subsubheading Synopsis
19818 -var-update [@var{print-values}] @{@var{name} | "*"@}
19821 Reevaluate the expressions corresponding to the variable object
19822 @var{name} and all its direct and indirect children, and return the
19823 list of variable objects whose values have changed; @var{name} must
19824 be a root variable object. Here, ``changed'' means that the result of
19825 @code{-var-evaluate-expression} before and after the
19826 @code{-var-update} is different. If @samp{*} is used as the variable
19827 object names, all existing variable objects are updated, except
19828 for frozen ones (@pxref{-var-set-frozen}). The option
19829 @var{print-values} determines whether both names and values, or just
19830 names are printed. The possible values of this options are the same
19831 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
19832 recommended to use the @samp{--all-values} option, to reduce the
19833 number of MI commands needed on each program stop.
19836 @subsubheading Example
19843 -var-update --all-values var1
19844 ^done,changelist=[@{name="var1",value="3",in_scope="true",
19845 type_changed="false"@}]
19849 @anchor{-var-update}
19850 The field in_scope may take three values:
19854 The variable object's current value is valid.
19857 The variable object does not currently hold a valid value but it may
19858 hold one in the future if its associated expression comes back into
19862 The variable object no longer holds a valid value.
19863 This can occur when the executable file being debugged has changed,
19864 either through recompilation or by using the @value{GDBN} @code{file}
19865 command. The front end should normally choose to delete these variable
19869 In the future new values may be added to this list so the front should
19870 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
19872 @subheading The @code{-var-set-frozen} Command
19873 @findex -var-set-frozen
19874 @anchor{-var-set-frozen}
19876 @subsubheading Synopsis
19879 -var-set-frozen @var{name} @var{flag}
19882 Set the frozenness flag on the variable object @var{name}. The
19883 @var{flag} parameter should be either @samp{1} to make the variable
19884 frozen or @samp{0} to make it unfrozen. If a variable object is
19885 frozen, then neither itself, nor any of its children, are
19886 implicitly updated by @code{-var-update} of
19887 a parent variable or by @code{-var-update *}. Only
19888 @code{-var-update} of the variable itself will update its value and
19889 values of its children. After a variable object is unfrozen, it is
19890 implicitly updated by all subsequent @code{-var-update} operations.
19891 Unfreezing a variable does not update it, only subsequent
19892 @code{-var-update} does.
19894 @subsubheading Example
19898 -var-set-frozen V 1
19904 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19905 @node GDB/MI Data Manipulation
19906 @section @sc{gdb/mi} Data Manipulation
19908 @cindex data manipulation, in @sc{gdb/mi}
19909 @cindex @sc{gdb/mi}, data manipulation
19910 This section describes the @sc{gdb/mi} commands that manipulate data:
19911 examine memory and registers, evaluate expressions, etc.
19913 @c REMOVED FROM THE INTERFACE.
19914 @c @subheading -data-assign
19915 @c Change the value of a program variable. Plenty of side effects.
19916 @c @subsubheading GDB Command
19918 @c @subsubheading Example
19921 @subheading The @code{-data-disassemble} Command
19922 @findex -data-disassemble
19924 @subsubheading Synopsis
19928 [ -s @var{start-addr} -e @var{end-addr} ]
19929 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
19937 @item @var{start-addr}
19938 is the beginning address (or @code{$pc})
19939 @item @var{end-addr}
19941 @item @var{filename}
19942 is the name of the file to disassemble
19943 @item @var{linenum}
19944 is the line number to disassemble around
19946 is the number of disassembly lines to be produced. If it is -1,
19947 the whole function will be disassembled, in case no @var{end-addr} is
19948 specified. If @var{end-addr} is specified as a non-zero value, and
19949 @var{lines} is lower than the number of disassembly lines between
19950 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
19951 displayed; if @var{lines} is higher than the number of lines between
19952 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
19955 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
19959 @subsubheading Result
19961 The output for each instruction is composed of four fields:
19970 Note that whatever included in the instruction field, is not manipulated
19971 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
19973 @subsubheading @value{GDBN} Command
19975 There's no direct mapping from this command to the CLI.
19977 @subsubheading Example
19979 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
19983 -data-disassemble -s $pc -e "$pc + 20" -- 0
19986 @{address="0x000107c0",func-name="main",offset="4",
19987 inst="mov 2, %o0"@},
19988 @{address="0x000107c4",func-name="main",offset="8",
19989 inst="sethi %hi(0x11800), %o2"@},
19990 @{address="0x000107c8",func-name="main",offset="12",
19991 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
19992 @{address="0x000107cc",func-name="main",offset="16",
19993 inst="sethi %hi(0x11800), %o2"@},
19994 @{address="0x000107d0",func-name="main",offset="20",
19995 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
19999 Disassemble the whole @code{main} function. Line 32 is part of
20003 -data-disassemble -f basics.c -l 32 -- 0
20005 @{address="0x000107bc",func-name="main",offset="0",
20006 inst="save %sp, -112, %sp"@},
20007 @{address="0x000107c0",func-name="main",offset="4",
20008 inst="mov 2, %o0"@},
20009 @{address="0x000107c4",func-name="main",offset="8",
20010 inst="sethi %hi(0x11800), %o2"@},
20012 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
20013 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
20017 Disassemble 3 instructions from the start of @code{main}:
20021 -data-disassemble -f basics.c -l 32 -n 3 -- 0
20023 @{address="0x000107bc",func-name="main",offset="0",
20024 inst="save %sp, -112, %sp"@},
20025 @{address="0x000107c0",func-name="main",offset="4",
20026 inst="mov 2, %o0"@},
20027 @{address="0x000107c4",func-name="main",offset="8",
20028 inst="sethi %hi(0x11800), %o2"@}]
20032 Disassemble 3 instructions from the start of @code{main} in mixed mode:
20036 -data-disassemble -f basics.c -l 32 -n 3 -- 1
20038 src_and_asm_line=@{line="31",
20039 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
20040 testsuite/gdb.mi/basics.c",line_asm_insn=[
20041 @{address="0x000107bc",func-name="main",offset="0",
20042 inst="save %sp, -112, %sp"@}]@},
20043 src_and_asm_line=@{line="32",
20044 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
20045 testsuite/gdb.mi/basics.c",line_asm_insn=[
20046 @{address="0x000107c0",func-name="main",offset="4",
20047 inst="mov 2, %o0"@},
20048 @{address="0x000107c4",func-name="main",offset="8",
20049 inst="sethi %hi(0x11800), %o2"@}]@}]
20054 @subheading The @code{-data-evaluate-expression} Command
20055 @findex -data-evaluate-expression
20057 @subsubheading Synopsis
20060 -data-evaluate-expression @var{expr}
20063 Evaluate @var{expr} as an expression. The expression could contain an
20064 inferior function call. The function call will execute synchronously.
20065 If the expression contains spaces, it must be enclosed in double quotes.
20067 @subsubheading @value{GDBN} Command
20069 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
20070 @samp{call}. In @code{gdbtk} only, there's a corresponding
20071 @samp{gdb_eval} command.
20073 @subsubheading Example
20075 In the following example, the numbers that precede the commands are the
20076 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
20077 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
20081 211-data-evaluate-expression A
20084 311-data-evaluate-expression &A
20085 311^done,value="0xefffeb7c"
20087 411-data-evaluate-expression A+3
20090 511-data-evaluate-expression "A + 3"
20096 @subheading The @code{-data-list-changed-registers} Command
20097 @findex -data-list-changed-registers
20099 @subsubheading Synopsis
20102 -data-list-changed-registers
20105 Display a list of the registers that have changed.
20107 @subsubheading @value{GDBN} Command
20109 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
20110 has the corresponding command @samp{gdb_changed_register_list}.
20112 @subsubheading Example
20114 On a PPC MBX board:
20122 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
20123 args=[],file="try.c",fullname="/home/foo/bar/try.c",line="5"@}
20125 -data-list-changed-registers
20126 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
20127 "10","11","13","14","15","16","17","18","19","20","21","22","23",
20128 "24","25","26","27","28","30","31","64","65","66","67","69"]
20133 @subheading The @code{-data-list-register-names} Command
20134 @findex -data-list-register-names
20136 @subsubheading Synopsis
20139 -data-list-register-names [ ( @var{regno} )+ ]
20142 Show a list of register names for the current target. If no arguments
20143 are given, it shows a list of the names of all the registers. If
20144 integer numbers are given as arguments, it will print a list of the
20145 names of the registers corresponding to the arguments. To ensure
20146 consistency between a register name and its number, the output list may
20147 include empty register names.
20149 @subsubheading @value{GDBN} Command
20151 @value{GDBN} does not have a command which corresponds to
20152 @samp{-data-list-register-names}. In @code{gdbtk} there is a
20153 corresponding command @samp{gdb_regnames}.
20155 @subsubheading Example
20157 For the PPC MBX board:
20160 -data-list-register-names
20161 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
20162 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
20163 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
20164 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
20165 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
20166 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
20167 "", "pc","ps","cr","lr","ctr","xer"]
20169 -data-list-register-names 1 2 3
20170 ^done,register-names=["r1","r2","r3"]
20174 @subheading The @code{-data-list-register-values} Command
20175 @findex -data-list-register-values
20177 @subsubheading Synopsis
20180 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
20183 Display the registers' contents. @var{fmt} is the format according to
20184 which the registers' contents are to be returned, followed by an optional
20185 list of numbers specifying the registers to display. A missing list of
20186 numbers indicates that the contents of all the registers must be returned.
20188 Allowed formats for @var{fmt} are:
20205 @subsubheading @value{GDBN} Command
20207 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
20208 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
20210 @subsubheading Example
20212 For a PPC MBX board (note: line breaks are for readability only, they
20213 don't appear in the actual output):
20217 -data-list-register-values r 64 65
20218 ^done,register-values=[@{number="64",value="0xfe00a300"@},
20219 @{number="65",value="0x00029002"@}]
20221 -data-list-register-values x
20222 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
20223 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
20224 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
20225 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
20226 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
20227 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
20228 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
20229 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
20230 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
20231 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
20232 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
20233 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
20234 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
20235 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
20236 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
20237 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
20238 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
20239 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
20240 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
20241 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
20242 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
20243 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
20244 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
20245 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
20246 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
20247 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
20248 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
20249 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
20250 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
20251 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
20252 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
20253 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
20254 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
20255 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
20256 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
20257 @{number="69",value="0x20002b03"@}]
20262 @subheading The @code{-data-read-memory} Command
20263 @findex -data-read-memory
20265 @subsubheading Synopsis
20268 -data-read-memory [ -o @var{byte-offset} ]
20269 @var{address} @var{word-format} @var{word-size}
20270 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
20277 @item @var{address}
20278 An expression specifying the address of the first memory word to be
20279 read. Complex expressions containing embedded white space should be
20280 quoted using the C convention.
20282 @item @var{word-format}
20283 The format to be used to print the memory words. The notation is the
20284 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
20287 @item @var{word-size}
20288 The size of each memory word in bytes.
20290 @item @var{nr-rows}
20291 The number of rows in the output table.
20293 @item @var{nr-cols}
20294 The number of columns in the output table.
20297 If present, indicates that each row should include an @sc{ascii} dump. The
20298 value of @var{aschar} is used as a padding character when a byte is not a
20299 member of the printable @sc{ascii} character set (printable @sc{ascii}
20300 characters are those whose code is between 32 and 126, inclusively).
20302 @item @var{byte-offset}
20303 An offset to add to the @var{address} before fetching memory.
20306 This command displays memory contents as a table of @var{nr-rows} by
20307 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
20308 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
20309 (returned as @samp{total-bytes}). Should less than the requested number
20310 of bytes be returned by the target, the missing words are identified
20311 using @samp{N/A}. The number of bytes read from the target is returned
20312 in @samp{nr-bytes} and the starting address used to read memory in
20315 The address of the next/previous row or page is available in
20316 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
20319 @subsubheading @value{GDBN} Command
20321 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
20322 @samp{gdb_get_mem} memory read command.
20324 @subsubheading Example
20326 Read six bytes of memory starting at @code{bytes+6} but then offset by
20327 @code{-6} bytes. Format as three rows of two columns. One byte per
20328 word. Display each word in hex.
20332 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
20333 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
20334 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
20335 prev-page="0x0000138a",memory=[
20336 @{addr="0x00001390",data=["0x00","0x01"]@},
20337 @{addr="0x00001392",data=["0x02","0x03"]@},
20338 @{addr="0x00001394",data=["0x04","0x05"]@}]
20342 Read two bytes of memory starting at address @code{shorts + 64} and
20343 display as a single word formatted in decimal.
20347 5-data-read-memory shorts+64 d 2 1 1
20348 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
20349 next-row="0x00001512",prev-row="0x0000150e",
20350 next-page="0x00001512",prev-page="0x0000150e",memory=[
20351 @{addr="0x00001510",data=["128"]@}]
20355 Read thirty two bytes of memory starting at @code{bytes+16} and format
20356 as eight rows of four columns. Include a string encoding with @samp{x}
20357 used as the non-printable character.
20361 4-data-read-memory bytes+16 x 1 8 4 x
20362 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
20363 next-row="0x000013c0",prev-row="0x0000139c",
20364 next-page="0x000013c0",prev-page="0x00001380",memory=[
20365 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
20366 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
20367 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
20368 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
20369 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
20370 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
20371 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
20372 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
20376 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20377 @node GDB/MI Tracepoint Commands
20378 @section @sc{gdb/mi} Tracepoint Commands
20380 The tracepoint commands are not yet implemented.
20382 @c @subheading -trace-actions
20384 @c @subheading -trace-delete
20386 @c @subheading -trace-disable
20388 @c @subheading -trace-dump
20390 @c @subheading -trace-enable
20392 @c @subheading -trace-exists
20394 @c @subheading -trace-find
20396 @c @subheading -trace-frame-number
20398 @c @subheading -trace-info
20400 @c @subheading -trace-insert
20402 @c @subheading -trace-list
20404 @c @subheading -trace-pass-count
20406 @c @subheading -trace-save
20408 @c @subheading -trace-start
20410 @c @subheading -trace-stop
20413 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20414 @node GDB/MI Symbol Query
20415 @section @sc{gdb/mi} Symbol Query Commands
20418 @subheading The @code{-symbol-info-address} Command
20419 @findex -symbol-info-address
20421 @subsubheading Synopsis
20424 -symbol-info-address @var{symbol}
20427 Describe where @var{symbol} is stored.
20429 @subsubheading @value{GDBN} Command
20431 The corresponding @value{GDBN} command is @samp{info address}.
20433 @subsubheading Example
20437 @subheading The @code{-symbol-info-file} Command
20438 @findex -symbol-info-file
20440 @subsubheading Synopsis
20446 Show the file for the symbol.
20448 @subsubheading @value{GDBN} Command
20450 There's no equivalent @value{GDBN} command. @code{gdbtk} has
20451 @samp{gdb_find_file}.
20453 @subsubheading Example
20457 @subheading The @code{-symbol-info-function} Command
20458 @findex -symbol-info-function
20460 @subsubheading Synopsis
20463 -symbol-info-function
20466 Show which function the symbol lives in.
20468 @subsubheading @value{GDBN} Command
20470 @samp{gdb_get_function} in @code{gdbtk}.
20472 @subsubheading Example
20476 @subheading The @code{-symbol-info-line} Command
20477 @findex -symbol-info-line
20479 @subsubheading Synopsis
20485 Show the core addresses of the code for a source line.
20487 @subsubheading @value{GDBN} Command
20489 The corresponding @value{GDBN} command is @samp{info line}.
20490 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
20492 @subsubheading Example
20496 @subheading The @code{-symbol-info-symbol} Command
20497 @findex -symbol-info-symbol
20499 @subsubheading Synopsis
20502 -symbol-info-symbol @var{addr}
20505 Describe what symbol is at location @var{addr}.
20507 @subsubheading @value{GDBN} Command
20509 The corresponding @value{GDBN} command is @samp{info symbol}.
20511 @subsubheading Example
20515 @subheading The @code{-symbol-list-functions} Command
20516 @findex -symbol-list-functions
20518 @subsubheading Synopsis
20521 -symbol-list-functions
20524 List the functions in the executable.
20526 @subsubheading @value{GDBN} Command
20528 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
20529 @samp{gdb_search} in @code{gdbtk}.
20531 @subsubheading Example
20535 @subheading The @code{-symbol-list-lines} Command
20536 @findex -symbol-list-lines
20538 @subsubheading Synopsis
20541 -symbol-list-lines @var{filename}
20544 Print the list of lines that contain code and their associated program
20545 addresses for the given source filename. The entries are sorted in
20546 ascending PC order.
20548 @subsubheading @value{GDBN} Command
20550 There is no corresponding @value{GDBN} command.
20552 @subsubheading Example
20555 -symbol-list-lines basics.c
20556 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
20561 @subheading The @code{-symbol-list-types} Command
20562 @findex -symbol-list-types
20564 @subsubheading Synopsis
20570 List all the type names.
20572 @subsubheading @value{GDBN} Command
20574 The corresponding commands are @samp{info types} in @value{GDBN},
20575 @samp{gdb_search} in @code{gdbtk}.
20577 @subsubheading Example
20581 @subheading The @code{-symbol-list-variables} Command
20582 @findex -symbol-list-variables
20584 @subsubheading Synopsis
20587 -symbol-list-variables
20590 List all the global and static variable names.
20592 @subsubheading @value{GDBN} Command
20594 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
20596 @subsubheading Example
20600 @subheading The @code{-symbol-locate} Command
20601 @findex -symbol-locate
20603 @subsubheading Synopsis
20609 @subsubheading @value{GDBN} Command
20611 @samp{gdb_loc} in @code{gdbtk}.
20613 @subsubheading Example
20617 @subheading The @code{-symbol-type} Command
20618 @findex -symbol-type
20620 @subsubheading Synopsis
20623 -symbol-type @var{variable}
20626 Show type of @var{variable}.
20628 @subsubheading @value{GDBN} Command
20630 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
20631 @samp{gdb_obj_variable}.
20633 @subsubheading Example
20637 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20638 @node GDB/MI File Commands
20639 @section @sc{gdb/mi} File Commands
20641 This section describes the GDB/MI commands to specify executable file names
20642 and to read in and obtain symbol table information.
20644 @subheading The @code{-file-exec-and-symbols} Command
20645 @findex -file-exec-and-symbols
20647 @subsubheading Synopsis
20650 -file-exec-and-symbols @var{file}
20653 Specify the executable file to be debugged. This file is the one from
20654 which the symbol table is also read. If no file is specified, the
20655 command clears the executable and symbol information. If breakpoints
20656 are set when using this command with no arguments, @value{GDBN} will produce
20657 error messages. Otherwise, no output is produced, except a completion
20660 @subsubheading @value{GDBN} Command
20662 The corresponding @value{GDBN} command is @samp{file}.
20664 @subsubheading Example
20668 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
20674 @subheading The @code{-file-exec-file} Command
20675 @findex -file-exec-file
20677 @subsubheading Synopsis
20680 -file-exec-file @var{file}
20683 Specify the executable file to be debugged. Unlike
20684 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
20685 from this file. If used without argument, @value{GDBN} clears the information
20686 about the executable file. No output is produced, except a completion
20689 @subsubheading @value{GDBN} Command
20691 The corresponding @value{GDBN} command is @samp{exec-file}.
20693 @subsubheading Example
20697 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
20703 @subheading The @code{-file-list-exec-sections} Command
20704 @findex -file-list-exec-sections
20706 @subsubheading Synopsis
20709 -file-list-exec-sections
20712 List the sections of the current executable file.
20714 @subsubheading @value{GDBN} Command
20716 The @value{GDBN} command @samp{info file} shows, among the rest, the same
20717 information as this command. @code{gdbtk} has a corresponding command
20718 @samp{gdb_load_info}.
20720 @subsubheading Example
20724 @subheading The @code{-file-list-exec-source-file} Command
20725 @findex -file-list-exec-source-file
20727 @subsubheading Synopsis
20730 -file-list-exec-source-file
20733 List the line number, the current source file, and the absolute path
20734 to the current source file for the current executable.
20736 @subsubheading @value{GDBN} Command
20738 The @value{GDBN} equivalent is @samp{info source}
20740 @subsubheading Example
20744 123-file-list-exec-source-file
20745 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
20750 @subheading The @code{-file-list-exec-source-files} Command
20751 @findex -file-list-exec-source-files
20753 @subsubheading Synopsis
20756 -file-list-exec-source-files
20759 List the source files for the current executable.
20761 It will always output the filename, but only when @value{GDBN} can find
20762 the absolute file name of a source file, will it output the fullname.
20764 @subsubheading @value{GDBN} Command
20766 The @value{GDBN} equivalent is @samp{info sources}.
20767 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
20769 @subsubheading Example
20772 -file-list-exec-source-files
20774 @{file=foo.c,fullname=/home/foo.c@},
20775 @{file=/home/bar.c,fullname=/home/bar.c@},
20776 @{file=gdb_could_not_find_fullpath.c@}]
20780 @subheading The @code{-file-list-shared-libraries} Command
20781 @findex -file-list-shared-libraries
20783 @subsubheading Synopsis
20786 -file-list-shared-libraries
20789 List the shared libraries in the program.
20791 @subsubheading @value{GDBN} Command
20793 The corresponding @value{GDBN} command is @samp{info shared}.
20795 @subsubheading Example
20799 @subheading The @code{-file-list-symbol-files} Command
20800 @findex -file-list-symbol-files
20802 @subsubheading Synopsis
20805 -file-list-symbol-files
20810 @subsubheading @value{GDBN} Command
20812 The corresponding @value{GDBN} command is @samp{info file} (part of it).
20814 @subsubheading Example
20818 @subheading The @code{-file-symbol-file} Command
20819 @findex -file-symbol-file
20821 @subsubheading Synopsis
20824 -file-symbol-file @var{file}
20827 Read symbol table info from the specified @var{file} argument. When
20828 used without arguments, clears @value{GDBN}'s symbol table info. No output is
20829 produced, except for a completion notification.
20831 @subsubheading @value{GDBN} Command
20833 The corresponding @value{GDBN} command is @samp{symbol-file}.
20835 @subsubheading Example
20839 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
20845 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20846 @node GDB/MI Memory Overlay Commands
20847 @section @sc{gdb/mi} Memory Overlay Commands
20849 The memory overlay commands are not implemented.
20851 @c @subheading -overlay-auto
20853 @c @subheading -overlay-list-mapping-state
20855 @c @subheading -overlay-list-overlays
20857 @c @subheading -overlay-map
20859 @c @subheading -overlay-off
20861 @c @subheading -overlay-on
20863 @c @subheading -overlay-unmap
20865 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20866 @node GDB/MI Signal Handling Commands
20867 @section @sc{gdb/mi} Signal Handling Commands
20869 Signal handling commands are not implemented.
20871 @c @subheading -signal-handle
20873 @c @subheading -signal-list-handle-actions
20875 @c @subheading -signal-list-signal-types
20879 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20880 @node GDB/MI Target Manipulation
20881 @section @sc{gdb/mi} Target Manipulation Commands
20884 @subheading The @code{-target-attach} Command
20885 @findex -target-attach
20887 @subsubheading Synopsis
20890 -target-attach @var{pid} | @var{file}
20893 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
20895 @subsubheading @value{GDBN} Command
20897 The corresponding @value{GDBN} command is @samp{attach}.
20899 @subsubheading Example
20903 @subheading The @code{-target-compare-sections} Command
20904 @findex -target-compare-sections
20906 @subsubheading Synopsis
20909 -target-compare-sections [ @var{section} ]
20912 Compare data of section @var{section} on target to the exec file.
20913 Without the argument, all sections are compared.
20915 @subsubheading @value{GDBN} Command
20917 The @value{GDBN} equivalent is @samp{compare-sections}.
20919 @subsubheading Example
20923 @subheading The @code{-target-detach} Command
20924 @findex -target-detach
20926 @subsubheading Synopsis
20932 Detach from the remote target which normally resumes its execution.
20935 @subsubheading @value{GDBN} Command
20937 The corresponding @value{GDBN} command is @samp{detach}.
20939 @subsubheading Example
20949 @subheading The @code{-target-disconnect} Command
20950 @findex -target-disconnect
20952 @subsubheading Synopsis
20958 Disconnect from the remote target. There's no output and the target is
20959 generally not resumed.
20961 @subsubheading @value{GDBN} Command
20963 The corresponding @value{GDBN} command is @samp{disconnect}.
20965 @subsubheading Example
20975 @subheading The @code{-target-download} Command
20976 @findex -target-download
20978 @subsubheading Synopsis
20984 Loads the executable onto the remote target.
20985 It prints out an update message every half second, which includes the fields:
20989 The name of the section.
20991 The size of what has been sent so far for that section.
20993 The size of the section.
20995 The total size of what was sent so far (the current and the previous sections).
20997 The size of the overall executable to download.
21001 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
21002 @sc{gdb/mi} Output Syntax}).
21004 In addition, it prints the name and size of the sections, as they are
21005 downloaded. These messages include the following fields:
21009 The name of the section.
21011 The size of the section.
21013 The size of the overall executable to download.
21017 At the end, a summary is printed.
21019 @subsubheading @value{GDBN} Command
21021 The corresponding @value{GDBN} command is @samp{load}.
21023 @subsubheading Example
21025 Note: each status message appears on a single line. Here the messages
21026 have been broken down so that they can fit onto a page.
21031 +download,@{section=".text",section-size="6668",total-size="9880"@}
21032 +download,@{section=".text",section-sent="512",section-size="6668",
21033 total-sent="512",total-size="9880"@}
21034 +download,@{section=".text",section-sent="1024",section-size="6668",
21035 total-sent="1024",total-size="9880"@}
21036 +download,@{section=".text",section-sent="1536",section-size="6668",
21037 total-sent="1536",total-size="9880"@}
21038 +download,@{section=".text",section-sent="2048",section-size="6668",
21039 total-sent="2048",total-size="9880"@}
21040 +download,@{section=".text",section-sent="2560",section-size="6668",
21041 total-sent="2560",total-size="9880"@}
21042 +download,@{section=".text",section-sent="3072",section-size="6668",
21043 total-sent="3072",total-size="9880"@}
21044 +download,@{section=".text",section-sent="3584",section-size="6668",
21045 total-sent="3584",total-size="9880"@}
21046 +download,@{section=".text",section-sent="4096",section-size="6668",
21047 total-sent="4096",total-size="9880"@}
21048 +download,@{section=".text",section-sent="4608",section-size="6668",
21049 total-sent="4608",total-size="9880"@}
21050 +download,@{section=".text",section-sent="5120",section-size="6668",
21051 total-sent="5120",total-size="9880"@}
21052 +download,@{section=".text",section-sent="5632",section-size="6668",
21053 total-sent="5632",total-size="9880"@}
21054 +download,@{section=".text",section-sent="6144",section-size="6668",
21055 total-sent="6144",total-size="9880"@}
21056 +download,@{section=".text",section-sent="6656",section-size="6668",
21057 total-sent="6656",total-size="9880"@}
21058 +download,@{section=".init",section-size="28",total-size="9880"@}
21059 +download,@{section=".fini",section-size="28",total-size="9880"@}
21060 +download,@{section=".data",section-size="3156",total-size="9880"@}
21061 +download,@{section=".data",section-sent="512",section-size="3156",
21062 total-sent="7236",total-size="9880"@}
21063 +download,@{section=".data",section-sent="1024",section-size="3156",
21064 total-sent="7748",total-size="9880"@}
21065 +download,@{section=".data",section-sent="1536",section-size="3156",
21066 total-sent="8260",total-size="9880"@}
21067 +download,@{section=".data",section-sent="2048",section-size="3156",
21068 total-sent="8772",total-size="9880"@}
21069 +download,@{section=".data",section-sent="2560",section-size="3156",
21070 total-sent="9284",total-size="9880"@}
21071 +download,@{section=".data",section-sent="3072",section-size="3156",
21072 total-sent="9796",total-size="9880"@}
21073 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
21079 @subheading The @code{-target-exec-status} Command
21080 @findex -target-exec-status
21082 @subsubheading Synopsis
21085 -target-exec-status
21088 Provide information on the state of the target (whether it is running or
21089 not, for instance).
21091 @subsubheading @value{GDBN} Command
21093 There's no equivalent @value{GDBN} command.
21095 @subsubheading Example
21099 @subheading The @code{-target-list-available-targets} Command
21100 @findex -target-list-available-targets
21102 @subsubheading Synopsis
21105 -target-list-available-targets
21108 List the possible targets to connect to.
21110 @subsubheading @value{GDBN} Command
21112 The corresponding @value{GDBN} command is @samp{help target}.
21114 @subsubheading Example
21118 @subheading The @code{-target-list-current-targets} Command
21119 @findex -target-list-current-targets
21121 @subsubheading Synopsis
21124 -target-list-current-targets
21127 Describe the current target.
21129 @subsubheading @value{GDBN} Command
21131 The corresponding information is printed by @samp{info file} (among
21134 @subsubheading Example
21138 @subheading The @code{-target-list-parameters} Command
21139 @findex -target-list-parameters
21141 @subsubheading Synopsis
21144 -target-list-parameters
21149 @subsubheading @value{GDBN} Command
21153 @subsubheading Example
21157 @subheading The @code{-target-select} Command
21158 @findex -target-select
21160 @subsubheading Synopsis
21163 -target-select @var{type} @var{parameters @dots{}}
21166 Connect @value{GDBN} to the remote target. This command takes two args:
21170 The type of target, for instance @samp{async}, @samp{remote}, etc.
21171 @item @var{parameters}
21172 Device names, host names and the like. @xref{Target Commands, ,
21173 Commands for Managing Targets}, for more details.
21176 The output is a connection notification, followed by the address at
21177 which the target program is, in the following form:
21180 ^connected,addr="@var{address}",func="@var{function name}",
21181 args=[@var{arg list}]
21184 @subsubheading @value{GDBN} Command
21186 The corresponding @value{GDBN} command is @samp{target}.
21188 @subsubheading Example
21192 -target-select async /dev/ttya
21193 ^connected,addr="0xfe00a300",func="??",args=[]
21197 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
21198 @node GDB/MI Miscellaneous Commands
21199 @section Miscellaneous @sc{gdb/mi} Commands
21201 @c @subheading -gdb-complete
21203 @subheading The @code{-gdb-exit} Command
21206 @subsubheading Synopsis
21212 Exit @value{GDBN} immediately.
21214 @subsubheading @value{GDBN} Command
21216 Approximately corresponds to @samp{quit}.
21218 @subsubheading Example
21227 @subheading The @code{-exec-abort} Command
21228 @findex -exec-abort
21230 @subsubheading Synopsis
21236 Kill the inferior running program.
21238 @subsubheading @value{GDBN} Command
21240 The corresponding @value{GDBN} command is @samp{kill}.
21242 @subsubheading Example
21246 @subheading The @code{-gdb-set} Command
21249 @subsubheading Synopsis
21255 Set an internal @value{GDBN} variable.
21256 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
21258 @subsubheading @value{GDBN} Command
21260 The corresponding @value{GDBN} command is @samp{set}.
21262 @subsubheading Example
21272 @subheading The @code{-gdb-show} Command
21275 @subsubheading Synopsis
21281 Show the current value of a @value{GDBN} variable.
21283 @subsubheading @value{GDBN} Command
21285 The corresponding @value{GDBN} command is @samp{show}.
21287 @subsubheading Example
21296 @c @subheading -gdb-source
21299 @subheading The @code{-gdb-version} Command
21300 @findex -gdb-version
21302 @subsubheading Synopsis
21308 Show version information for @value{GDBN}. Used mostly in testing.
21310 @subsubheading @value{GDBN} Command
21312 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
21313 default shows this information when you start an interactive session.
21315 @subsubheading Example
21317 @c This example modifies the actual output from GDB to avoid overfull
21323 ~Copyright 2000 Free Software Foundation, Inc.
21324 ~GDB is free software, covered by the GNU General Public License, and
21325 ~you are welcome to change it and/or distribute copies of it under
21326 ~ certain conditions.
21327 ~Type "show copying" to see the conditions.
21328 ~There is absolutely no warranty for GDB. Type "show warranty" for
21330 ~This GDB was configured as
21331 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
21336 @subheading The @code{-list-features} Command
21337 @findex -list-features
21339 Returns a list of particular features of the MI protocol that
21340 this version of gdb implements. A feature can be a command,
21341 or a new field in an output of some command, or even an
21342 important bugfix. While a frontend can sometimes detect presence
21343 of a feature at runtime, it is easier to perform detection at debugger
21346 The command returns a list of strings, with each string naming an
21347 available feature. Each returned string is just a name, it does not
21348 have any internal structure. The list of possible feature names
21354 (gdb) -list-features
21355 ^done,result=["feature1","feature2"]
21358 The current list of features is:
21362 @samp{frozen-varobjs}---indicates presence of the
21363 @code{-var-set-frozen} command, as well as possible presense of the
21364 @code{frozen} field in the output of @code{-varobj-create}.
21367 @subheading The @code{-interpreter-exec} Command
21368 @findex -interpreter-exec
21370 @subheading Synopsis
21373 -interpreter-exec @var{interpreter} @var{command}
21375 @anchor{-interpreter-exec}
21377 Execute the specified @var{command} in the given @var{interpreter}.
21379 @subheading @value{GDBN} Command
21381 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
21383 @subheading Example
21387 -interpreter-exec console "break main"
21388 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
21389 &"During symbol reading, bad structure-type format.\n"
21390 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
21395 @subheading The @code{-inferior-tty-set} Command
21396 @findex -inferior-tty-set
21398 @subheading Synopsis
21401 -inferior-tty-set /dev/pts/1
21404 Set terminal for future runs of the program being debugged.
21406 @subheading @value{GDBN} Command
21408 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
21410 @subheading Example
21414 -inferior-tty-set /dev/pts/1
21419 @subheading The @code{-inferior-tty-show} Command
21420 @findex -inferior-tty-show
21422 @subheading Synopsis
21428 Show terminal for future runs of program being debugged.
21430 @subheading @value{GDBN} Command
21432 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
21434 @subheading Example
21438 -inferior-tty-set /dev/pts/1
21442 ^done,inferior_tty_terminal="/dev/pts/1"
21446 @subheading The @code{-enable-timings} Command
21447 @findex -enable-timings
21449 @subheading Synopsis
21452 -enable-timings [yes | no]
21455 Toggle the printing of the wallclock, user and system times for an MI
21456 command as a field in its output. This command is to help frontend
21457 developers optimize the performance of their code. No argument is
21458 equivalent to @samp{yes}.
21460 @subheading @value{GDBN} Command
21464 @subheading Example
21472 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
21473 addr="0x080484ed",func="main",file="myprog.c",
21474 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
21475 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
21483 *stopped,reason="breakpoint-hit",bkptno="1",thread-id="0",
21484 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
21485 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
21486 fullname="/home/nickrob/myprog.c",line="73"@}
21491 @chapter @value{GDBN} Annotations
21493 This chapter describes annotations in @value{GDBN}. Annotations were
21494 designed to interface @value{GDBN} to graphical user interfaces or other
21495 similar programs which want to interact with @value{GDBN} at a
21496 relatively high level.
21498 The annotation mechanism has largely been superseded by @sc{gdb/mi}
21502 This is Edition @value{EDITION}, @value{DATE}.
21506 * Annotations Overview:: What annotations are; the general syntax.
21507 * Server Prefix:: Issuing a command without affecting user state.
21508 * Prompting:: Annotations marking @value{GDBN}'s need for input.
21509 * Errors:: Annotations for error messages.
21510 * Invalidation:: Some annotations describe things now invalid.
21511 * Annotations for Running::
21512 Whether the program is running, how it stopped, etc.
21513 * Source Annotations:: Annotations describing source code.
21516 @node Annotations Overview
21517 @section What is an Annotation?
21518 @cindex annotations
21520 Annotations start with a newline character, two @samp{control-z}
21521 characters, and the name of the annotation. If there is no additional
21522 information associated with this annotation, the name of the annotation
21523 is followed immediately by a newline. If there is additional
21524 information, the name of the annotation is followed by a space, the
21525 additional information, and a newline. The additional information
21526 cannot contain newline characters.
21528 Any output not beginning with a newline and two @samp{control-z}
21529 characters denotes literal output from @value{GDBN}. Currently there is
21530 no need for @value{GDBN} to output a newline followed by two
21531 @samp{control-z} characters, but if there was such a need, the
21532 annotations could be extended with an @samp{escape} annotation which
21533 means those three characters as output.
21535 The annotation @var{level}, which is specified using the
21536 @option{--annotate} command line option (@pxref{Mode Options}), controls
21537 how much information @value{GDBN} prints together with its prompt,
21538 values of expressions, source lines, and other types of output. Level 0
21539 is for no annotations, level 1 is for use when @value{GDBN} is run as a
21540 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
21541 for programs that control @value{GDBN}, and level 2 annotations have
21542 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
21543 Interface, annotate, GDB's Obsolete Annotations}).
21546 @kindex set annotate
21547 @item set annotate @var{level}
21548 The @value{GDBN} command @code{set annotate} sets the level of
21549 annotations to the specified @var{level}.
21551 @item show annotate
21552 @kindex show annotate
21553 Show the current annotation level.
21556 This chapter describes level 3 annotations.
21558 A simple example of starting up @value{GDBN} with annotations is:
21561 $ @kbd{gdb --annotate=3}
21563 Copyright 2003 Free Software Foundation, Inc.
21564 GDB is free software, covered by the GNU General Public License,
21565 and you are welcome to change it and/or distribute copies of it
21566 under certain conditions.
21567 Type "show copying" to see the conditions.
21568 There is absolutely no warranty for GDB. Type "show warranty"
21570 This GDB was configured as "i386-pc-linux-gnu"
21581 Here @samp{quit} is input to @value{GDBN}; the rest is output from
21582 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
21583 denotes a @samp{control-z} character) are annotations; the rest is
21584 output from @value{GDBN}.
21586 @node Server Prefix
21587 @section The Server Prefix
21588 @cindex server prefix
21590 If you prefix a command with @samp{server } then it will not affect
21591 the command history, nor will it affect @value{GDBN}'s notion of which
21592 command to repeat if @key{RET} is pressed on a line by itself. This
21593 means that commands can be run behind a user's back by a front-end in
21594 a transparent manner.
21596 The server prefix does not affect the recording of values into the value
21597 history; to print a value without recording it into the value history,
21598 use the @code{output} command instead of the @code{print} command.
21601 @section Annotation for @value{GDBN} Input
21603 @cindex annotations for prompts
21604 When @value{GDBN} prompts for input, it annotates this fact so it is possible
21605 to know when to send output, when the output from a given command is
21608 Different kinds of input each have a different @dfn{input type}. Each
21609 input type has three annotations: a @code{pre-} annotation, which
21610 denotes the beginning of any prompt which is being output, a plain
21611 annotation, which denotes the end of the prompt, and then a @code{post-}
21612 annotation which denotes the end of any echo which may (or may not) be
21613 associated with the input. For example, the @code{prompt} input type
21614 features the following annotations:
21622 The input types are
21625 @findex pre-prompt annotation
21626 @findex prompt annotation
21627 @findex post-prompt annotation
21629 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
21631 @findex pre-commands annotation
21632 @findex commands annotation
21633 @findex post-commands annotation
21635 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
21636 command. The annotations are repeated for each command which is input.
21638 @findex pre-overload-choice annotation
21639 @findex overload-choice annotation
21640 @findex post-overload-choice annotation
21641 @item overload-choice
21642 When @value{GDBN} wants the user to select between various overloaded functions.
21644 @findex pre-query annotation
21645 @findex query annotation
21646 @findex post-query annotation
21648 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
21650 @findex pre-prompt-for-continue annotation
21651 @findex prompt-for-continue annotation
21652 @findex post-prompt-for-continue annotation
21653 @item prompt-for-continue
21654 When @value{GDBN} is asking the user to press return to continue. Note: Don't
21655 expect this to work well; instead use @code{set height 0} to disable
21656 prompting. This is because the counting of lines is buggy in the
21657 presence of annotations.
21662 @cindex annotations for errors, warnings and interrupts
21664 @findex quit annotation
21669 This annotation occurs right before @value{GDBN} responds to an interrupt.
21671 @findex error annotation
21676 This annotation occurs right before @value{GDBN} responds to an error.
21678 Quit and error annotations indicate that any annotations which @value{GDBN} was
21679 in the middle of may end abruptly. For example, if a
21680 @code{value-history-begin} annotation is followed by a @code{error}, one
21681 cannot expect to receive the matching @code{value-history-end}. One
21682 cannot expect not to receive it either, however; an error annotation
21683 does not necessarily mean that @value{GDBN} is immediately returning all the way
21686 @findex error-begin annotation
21687 A quit or error annotation may be preceded by
21693 Any output between that and the quit or error annotation is the error
21696 Warning messages are not yet annotated.
21697 @c If we want to change that, need to fix warning(), type_error(),
21698 @c range_error(), and possibly other places.
21701 @section Invalidation Notices
21703 @cindex annotations for invalidation messages
21704 The following annotations say that certain pieces of state may have
21708 @findex frames-invalid annotation
21709 @item ^Z^Zframes-invalid
21711 The frames (for example, output from the @code{backtrace} command) may
21714 @findex breakpoints-invalid annotation
21715 @item ^Z^Zbreakpoints-invalid
21717 The breakpoints may have changed. For example, the user just added or
21718 deleted a breakpoint.
21721 @node Annotations for Running
21722 @section Running the Program
21723 @cindex annotations for running programs
21725 @findex starting annotation
21726 @findex stopping annotation
21727 When the program starts executing due to a @value{GDBN} command such as
21728 @code{step} or @code{continue},
21734 is output. When the program stops,
21740 is output. Before the @code{stopped} annotation, a variety of
21741 annotations describe how the program stopped.
21744 @findex exited annotation
21745 @item ^Z^Zexited @var{exit-status}
21746 The program exited, and @var{exit-status} is the exit status (zero for
21747 successful exit, otherwise nonzero).
21749 @findex signalled annotation
21750 @findex signal-name annotation
21751 @findex signal-name-end annotation
21752 @findex signal-string annotation
21753 @findex signal-string-end annotation
21754 @item ^Z^Zsignalled
21755 The program exited with a signal. After the @code{^Z^Zsignalled}, the
21756 annotation continues:
21762 ^Z^Zsignal-name-end
21766 ^Z^Zsignal-string-end
21771 where @var{name} is the name of the signal, such as @code{SIGILL} or
21772 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
21773 as @code{Illegal Instruction} or @code{Segmentation fault}.
21774 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
21775 user's benefit and have no particular format.
21777 @findex signal annotation
21779 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
21780 just saying that the program received the signal, not that it was
21781 terminated with it.
21783 @findex breakpoint annotation
21784 @item ^Z^Zbreakpoint @var{number}
21785 The program hit breakpoint number @var{number}.
21787 @findex watchpoint annotation
21788 @item ^Z^Zwatchpoint @var{number}
21789 The program hit watchpoint number @var{number}.
21792 @node Source Annotations
21793 @section Displaying Source
21794 @cindex annotations for source display
21796 @findex source annotation
21797 The following annotation is used instead of displaying source code:
21800 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
21803 where @var{filename} is an absolute file name indicating which source
21804 file, @var{line} is the line number within that file (where 1 is the
21805 first line in the file), @var{character} is the character position
21806 within the file (where 0 is the first character in the file) (for most
21807 debug formats this will necessarily point to the beginning of a line),
21808 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
21809 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
21810 @var{addr} is the address in the target program associated with the
21811 source which is being displayed. @var{addr} is in the form @samp{0x}
21812 followed by one or more lowercase hex digits (note that this does not
21813 depend on the language).
21816 @chapter Reporting Bugs in @value{GDBN}
21817 @cindex bugs in @value{GDBN}
21818 @cindex reporting bugs in @value{GDBN}
21820 Your bug reports play an essential role in making @value{GDBN} reliable.
21822 Reporting a bug may help you by bringing a solution to your problem, or it
21823 may not. But in any case the principal function of a bug report is to help
21824 the entire community by making the next version of @value{GDBN} work better. Bug
21825 reports are your contribution to the maintenance of @value{GDBN}.
21827 In order for a bug report to serve its purpose, you must include the
21828 information that enables us to fix the bug.
21831 * Bug Criteria:: Have you found a bug?
21832 * Bug Reporting:: How to report bugs
21836 @section Have You Found a Bug?
21837 @cindex bug criteria
21839 If you are not sure whether you have found a bug, here are some guidelines:
21842 @cindex fatal signal
21843 @cindex debugger crash
21844 @cindex crash of debugger
21846 If the debugger gets a fatal signal, for any input whatever, that is a
21847 @value{GDBN} bug. Reliable debuggers never crash.
21849 @cindex error on valid input
21851 If @value{GDBN} produces an error message for valid input, that is a
21852 bug. (Note that if you're cross debugging, the problem may also be
21853 somewhere in the connection to the target.)
21855 @cindex invalid input
21857 If @value{GDBN} does not produce an error message for invalid input,
21858 that is a bug. However, you should note that your idea of
21859 ``invalid input'' might be our idea of ``an extension'' or ``support
21860 for traditional practice''.
21863 If you are an experienced user of debugging tools, your suggestions
21864 for improvement of @value{GDBN} are welcome in any case.
21867 @node Bug Reporting
21868 @section How to Report Bugs
21869 @cindex bug reports
21870 @cindex @value{GDBN} bugs, reporting
21872 A number of companies and individuals offer support for @sc{gnu} products.
21873 If you obtained @value{GDBN} from a support organization, we recommend you
21874 contact that organization first.
21876 You can find contact information for many support companies and
21877 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
21879 @c should add a web page ref...
21881 In any event, we also recommend that you submit bug reports for
21882 @value{GDBN}. The preferred method is to submit them directly using
21883 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
21884 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
21887 @strong{Do not send bug reports to @samp{info-gdb}, or to
21888 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
21889 not want to receive bug reports. Those that do have arranged to receive
21892 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
21893 serves as a repeater. The mailing list and the newsgroup carry exactly
21894 the same messages. Often people think of posting bug reports to the
21895 newsgroup instead of mailing them. This appears to work, but it has one
21896 problem which can be crucial: a newsgroup posting often lacks a mail
21897 path back to the sender. Thus, if we need to ask for more information,
21898 we may be unable to reach you. For this reason, it is better to send
21899 bug reports to the mailing list.
21901 The fundamental principle of reporting bugs usefully is this:
21902 @strong{report all the facts}. If you are not sure whether to state a
21903 fact or leave it out, state it!
21905 Often people omit facts because they think they know what causes the
21906 problem and assume that some details do not matter. Thus, you might
21907 assume that the name of the variable you use in an example does not matter.
21908 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
21909 stray memory reference which happens to fetch from the location where that
21910 name is stored in memory; perhaps, if the name were different, the contents
21911 of that location would fool the debugger into doing the right thing despite
21912 the bug. Play it safe and give a specific, complete example. That is the
21913 easiest thing for you to do, and the most helpful.
21915 Keep in mind that the purpose of a bug report is to enable us to fix the
21916 bug. It may be that the bug has been reported previously, but neither
21917 you nor we can know that unless your bug report is complete and
21920 Sometimes people give a few sketchy facts and ask, ``Does this ring a
21921 bell?'' Those bug reports are useless, and we urge everyone to
21922 @emph{refuse to respond to them} except to chide the sender to report
21925 To enable us to fix the bug, you should include all these things:
21929 The version of @value{GDBN}. @value{GDBN} announces it if you start
21930 with no arguments; you can also print it at any time using @code{show
21933 Without this, we will not know whether there is any point in looking for
21934 the bug in the current version of @value{GDBN}.
21937 The type of machine you are using, and the operating system name and
21941 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
21942 ``@value{GCC}--2.8.1''.
21945 What compiler (and its version) was used to compile the program you are
21946 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
21947 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
21948 to get this information; for other compilers, see the documentation for
21952 The command arguments you gave the compiler to compile your example and
21953 observe the bug. For example, did you use @samp{-O}? To guarantee
21954 you will not omit something important, list them all. A copy of the
21955 Makefile (or the output from make) is sufficient.
21957 If we were to try to guess the arguments, we would probably guess wrong
21958 and then we might not encounter the bug.
21961 A complete input script, and all necessary source files, that will
21965 A description of what behavior you observe that you believe is
21966 incorrect. For example, ``It gets a fatal signal.''
21968 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
21969 will certainly notice it. But if the bug is incorrect output, we might
21970 not notice unless it is glaringly wrong. You might as well not give us
21971 a chance to make a mistake.
21973 Even if the problem you experience is a fatal signal, you should still
21974 say so explicitly. Suppose something strange is going on, such as, your
21975 copy of @value{GDBN} is out of synch, or you have encountered a bug in
21976 the C library on your system. (This has happened!) Your copy might
21977 crash and ours would not. If you told us to expect a crash, then when
21978 ours fails to crash, we would know that the bug was not happening for
21979 us. If you had not told us to expect a crash, then we would not be able
21980 to draw any conclusion from our observations.
21983 @cindex recording a session script
21984 To collect all this information, you can use a session recording program
21985 such as @command{script}, which is available on many Unix systems.
21986 Just run your @value{GDBN} session inside @command{script} and then
21987 include the @file{typescript} file with your bug report.
21989 Another way to record a @value{GDBN} session is to run @value{GDBN}
21990 inside Emacs and then save the entire buffer to a file.
21993 If you wish to suggest changes to the @value{GDBN} source, send us context
21994 diffs. If you even discuss something in the @value{GDBN} source, refer to
21995 it by context, not by line number.
21997 The line numbers in our development sources will not match those in your
21998 sources. Your line numbers would convey no useful information to us.
22002 Here are some things that are not necessary:
22006 A description of the envelope of the bug.
22008 Often people who encounter a bug spend a lot of time investigating
22009 which changes to the input file will make the bug go away and which
22010 changes will not affect it.
22012 This is often time consuming and not very useful, because the way we
22013 will find the bug is by running a single example under the debugger
22014 with breakpoints, not by pure deduction from a series of examples.
22015 We recommend that you save your time for something else.
22017 Of course, if you can find a simpler example to report @emph{instead}
22018 of the original one, that is a convenience for us. Errors in the
22019 output will be easier to spot, running under the debugger will take
22020 less time, and so on.
22022 However, simplification is not vital; if you do not want to do this,
22023 report the bug anyway and send us the entire test case you used.
22026 A patch for the bug.
22028 A patch for the bug does help us if it is a good one. But do not omit
22029 the necessary information, such as the test case, on the assumption that
22030 a patch is all we need. We might see problems with your patch and decide
22031 to fix the problem another way, or we might not understand it at all.
22033 Sometimes with a program as complicated as @value{GDBN} it is very hard to
22034 construct an example that will make the program follow a certain path
22035 through the code. If you do not send us the example, we will not be able
22036 to construct one, so we will not be able to verify that the bug is fixed.
22038 And if we cannot understand what bug you are trying to fix, or why your
22039 patch should be an improvement, we will not install it. A test case will
22040 help us to understand.
22043 A guess about what the bug is or what it depends on.
22045 Such guesses are usually wrong. Even we cannot guess right about such
22046 things without first using the debugger to find the facts.
22049 @c The readline documentation is distributed with the readline code
22050 @c and consists of the two following files:
22052 @c inc-hist.texinfo
22053 @c Use -I with makeinfo to point to the appropriate directory,
22054 @c environment var TEXINPUTS with TeX.
22055 @include rluser.texi
22056 @include inc-hist.texinfo
22059 @node Formatting Documentation
22060 @appendix Formatting Documentation
22062 @cindex @value{GDBN} reference card
22063 @cindex reference card
22064 The @value{GDBN} 4 release includes an already-formatted reference card, ready
22065 for printing with PostScript or Ghostscript, in the @file{gdb}
22066 subdirectory of the main source directory@footnote{In
22067 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
22068 release.}. If you can use PostScript or Ghostscript with your printer,
22069 you can print the reference card immediately with @file{refcard.ps}.
22071 The release also includes the source for the reference card. You
22072 can format it, using @TeX{}, by typing:
22078 The @value{GDBN} reference card is designed to print in @dfn{landscape}
22079 mode on US ``letter'' size paper;
22080 that is, on a sheet 11 inches wide by 8.5 inches
22081 high. You will need to specify this form of printing as an option to
22082 your @sc{dvi} output program.
22084 @cindex documentation
22086 All the documentation for @value{GDBN} comes as part of the machine-readable
22087 distribution. The documentation is written in Texinfo format, which is
22088 a documentation system that uses a single source file to produce both
22089 on-line information and a printed manual. You can use one of the Info
22090 formatting commands to create the on-line version of the documentation
22091 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
22093 @value{GDBN} includes an already formatted copy of the on-line Info
22094 version of this manual in the @file{gdb} subdirectory. The main Info
22095 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
22096 subordinate files matching @samp{gdb.info*} in the same directory. If
22097 necessary, you can print out these files, or read them with any editor;
22098 but they are easier to read using the @code{info} subsystem in @sc{gnu}
22099 Emacs or the standalone @code{info} program, available as part of the
22100 @sc{gnu} Texinfo distribution.
22102 If you want to format these Info files yourself, you need one of the
22103 Info formatting programs, such as @code{texinfo-format-buffer} or
22106 If you have @code{makeinfo} installed, and are in the top level
22107 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
22108 version @value{GDBVN}), you can make the Info file by typing:
22115 If you want to typeset and print copies of this manual, you need @TeX{},
22116 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
22117 Texinfo definitions file.
22119 @TeX{} is a typesetting program; it does not print files directly, but
22120 produces output files called @sc{dvi} files. To print a typeset
22121 document, you need a program to print @sc{dvi} files. If your system
22122 has @TeX{} installed, chances are it has such a program. The precise
22123 command to use depends on your system; @kbd{lpr -d} is common; another
22124 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
22125 require a file name without any extension or a @samp{.dvi} extension.
22127 @TeX{} also requires a macro definitions file called
22128 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
22129 written in Texinfo format. On its own, @TeX{} cannot either read or
22130 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
22131 and is located in the @file{gdb-@var{version-number}/texinfo}
22134 If you have @TeX{} and a @sc{dvi} printer program installed, you can
22135 typeset and print this manual. First switch to the @file{gdb}
22136 subdirectory of the main source directory (for example, to
22137 @file{gdb-@value{GDBVN}/gdb}) and type:
22143 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
22145 @node Installing GDB
22146 @appendix Installing @value{GDBN}
22147 @cindex installation
22150 * Requirements:: Requirements for building @value{GDBN}
22151 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
22152 * Separate Objdir:: Compiling @value{GDBN} in another directory
22153 * Config Names:: Specifying names for hosts and targets
22154 * Configure Options:: Summary of options for configure
22158 @section Requirements for Building @value{GDBN}
22159 @cindex building @value{GDBN}, requirements for
22161 Building @value{GDBN} requires various tools and packages to be available.
22162 Other packages will be used only if they are found.
22164 @heading Tools/Packages Necessary for Building @value{GDBN}
22166 @item ISO C90 compiler
22167 @value{GDBN} is written in ISO C90. It should be buildable with any
22168 working C90 compiler, e.g.@: GCC.
22172 @heading Tools/Packages Optional for Building @value{GDBN}
22176 @value{GDBN} can use the Expat XML parsing library. This library may be
22177 included with your operating system distribution; if it is not, you
22178 can get the latest version from @url{http://expat.sourceforge.net}.
22179 The @file{configure} script will search for this library in several
22180 standard locations; if it is installed in an unusual path, you can
22181 use the @option{--with-libexpat-prefix} option to specify its location.
22187 Remote protocol memory maps (@pxref{Memory Map Format})
22189 Target descriptions (@pxref{Target Descriptions})
22191 Remote shared library lists (@pxref{Library List Format})
22193 MS-Windows shared libraries (@pxref{Shared Libraries})
22198 @node Running Configure
22199 @section Invoking the @value{GDBN} @file{configure} Script
22200 @cindex configuring @value{GDBN}
22201 @value{GDBN} comes with a @file{configure} script that automates the process
22202 of preparing @value{GDBN} for installation; you can then use @code{make} to
22203 build the @code{gdb} program.
22205 @c irrelevant in info file; it's as current as the code it lives with.
22206 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
22207 look at the @file{README} file in the sources; we may have improved the
22208 installation procedures since publishing this manual.}
22211 The @value{GDBN} distribution includes all the source code you need for
22212 @value{GDBN} in a single directory, whose name is usually composed by
22213 appending the version number to @samp{gdb}.
22215 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
22216 @file{gdb-@value{GDBVN}} directory. That directory contains:
22219 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
22220 script for configuring @value{GDBN} and all its supporting libraries
22222 @item gdb-@value{GDBVN}/gdb
22223 the source specific to @value{GDBN} itself
22225 @item gdb-@value{GDBVN}/bfd
22226 source for the Binary File Descriptor library
22228 @item gdb-@value{GDBVN}/include
22229 @sc{gnu} include files
22231 @item gdb-@value{GDBVN}/libiberty
22232 source for the @samp{-liberty} free software library
22234 @item gdb-@value{GDBVN}/opcodes
22235 source for the library of opcode tables and disassemblers
22237 @item gdb-@value{GDBVN}/readline
22238 source for the @sc{gnu} command-line interface
22240 @item gdb-@value{GDBVN}/glob
22241 source for the @sc{gnu} filename pattern-matching subroutine
22243 @item gdb-@value{GDBVN}/mmalloc
22244 source for the @sc{gnu} memory-mapped malloc package
22247 The simplest way to configure and build @value{GDBN} is to run @file{configure}
22248 from the @file{gdb-@var{version-number}} source directory, which in
22249 this example is the @file{gdb-@value{GDBVN}} directory.
22251 First switch to the @file{gdb-@var{version-number}} source directory
22252 if you are not already in it; then run @file{configure}. Pass the
22253 identifier for the platform on which @value{GDBN} will run as an
22259 cd gdb-@value{GDBVN}
22260 ./configure @var{host}
22265 where @var{host} is an identifier such as @samp{sun4} or
22266 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
22267 (You can often leave off @var{host}; @file{configure} tries to guess the
22268 correct value by examining your system.)
22270 Running @samp{configure @var{host}} and then running @code{make} builds the
22271 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
22272 libraries, then @code{gdb} itself. The configured source files, and the
22273 binaries, are left in the corresponding source directories.
22276 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
22277 system does not recognize this automatically when you run a different
22278 shell, you may need to run @code{sh} on it explicitly:
22281 sh configure @var{host}
22284 If you run @file{configure} from a directory that contains source
22285 directories for multiple libraries or programs, such as the
22286 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
22288 creates configuration files for every directory level underneath (unless
22289 you tell it not to, with the @samp{--norecursion} option).
22291 You should run the @file{configure} script from the top directory in the
22292 source tree, the @file{gdb-@var{version-number}} directory. If you run
22293 @file{configure} from one of the subdirectories, you will configure only
22294 that subdirectory. That is usually not what you want. In particular,
22295 if you run the first @file{configure} from the @file{gdb} subdirectory
22296 of the @file{gdb-@var{version-number}} directory, you will omit the
22297 configuration of @file{bfd}, @file{readline}, and other sibling
22298 directories of the @file{gdb} subdirectory. This leads to build errors
22299 about missing include files such as @file{bfd/bfd.h}.
22301 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
22302 However, you should make sure that the shell on your path (named by
22303 the @samp{SHELL} environment variable) is publicly readable. Remember
22304 that @value{GDBN} uses the shell to start your program---some systems refuse to
22305 let @value{GDBN} debug child processes whose programs are not readable.
22307 @node Separate Objdir
22308 @section Compiling @value{GDBN} in Another Directory
22310 If you want to run @value{GDBN} versions for several host or target machines,
22311 you need a different @code{gdb} compiled for each combination of
22312 host and target. @file{configure} is designed to make this easy by
22313 allowing you to generate each configuration in a separate subdirectory,
22314 rather than in the source directory. If your @code{make} program
22315 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
22316 @code{make} in each of these directories builds the @code{gdb}
22317 program specified there.
22319 To build @code{gdb} in a separate directory, run @file{configure}
22320 with the @samp{--srcdir} option to specify where to find the source.
22321 (You also need to specify a path to find @file{configure}
22322 itself from your working directory. If the path to @file{configure}
22323 would be the same as the argument to @samp{--srcdir}, you can leave out
22324 the @samp{--srcdir} option; it is assumed.)
22326 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
22327 separate directory for a Sun 4 like this:
22331 cd gdb-@value{GDBVN}
22334 ../gdb-@value{GDBVN}/configure sun4
22339 When @file{configure} builds a configuration using a remote source
22340 directory, it creates a tree for the binaries with the same structure
22341 (and using the same names) as the tree under the source directory. In
22342 the example, you'd find the Sun 4 library @file{libiberty.a} in the
22343 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
22344 @file{gdb-sun4/gdb}.
22346 Make sure that your path to the @file{configure} script has just one
22347 instance of @file{gdb} in it. If your path to @file{configure} looks
22348 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
22349 one subdirectory of @value{GDBN}, not the whole package. This leads to
22350 build errors about missing include files such as @file{bfd/bfd.h}.
22352 One popular reason to build several @value{GDBN} configurations in separate
22353 directories is to configure @value{GDBN} for cross-compiling (where
22354 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
22355 programs that run on another machine---the @dfn{target}).
22356 You specify a cross-debugging target by
22357 giving the @samp{--target=@var{target}} option to @file{configure}.
22359 When you run @code{make} to build a program or library, you must run
22360 it in a configured directory---whatever directory you were in when you
22361 called @file{configure} (or one of its subdirectories).
22363 The @code{Makefile} that @file{configure} generates in each source
22364 directory also runs recursively. If you type @code{make} in a source
22365 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
22366 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
22367 will build all the required libraries, and then build GDB.
22369 When you have multiple hosts or targets configured in separate
22370 directories, you can run @code{make} on them in parallel (for example,
22371 if they are NFS-mounted on each of the hosts); they will not interfere
22375 @section Specifying Names for Hosts and Targets
22377 The specifications used for hosts and targets in the @file{configure}
22378 script are based on a three-part naming scheme, but some short predefined
22379 aliases are also supported. The full naming scheme encodes three pieces
22380 of information in the following pattern:
22383 @var{architecture}-@var{vendor}-@var{os}
22386 For example, you can use the alias @code{sun4} as a @var{host} argument,
22387 or as the value for @var{target} in a @code{--target=@var{target}}
22388 option. The equivalent full name is @samp{sparc-sun-sunos4}.
22390 The @file{configure} script accompanying @value{GDBN} does not provide
22391 any query facility to list all supported host and target names or
22392 aliases. @file{configure} calls the Bourne shell script
22393 @code{config.sub} to map abbreviations to full names; you can read the
22394 script, if you wish, or you can use it to test your guesses on
22395 abbreviations---for example:
22398 % sh config.sub i386-linux
22400 % sh config.sub alpha-linux
22401 alpha-unknown-linux-gnu
22402 % sh config.sub hp9k700
22404 % sh config.sub sun4
22405 sparc-sun-sunos4.1.1
22406 % sh config.sub sun3
22407 m68k-sun-sunos4.1.1
22408 % sh config.sub i986v
22409 Invalid configuration `i986v': machine `i986v' not recognized
22413 @code{config.sub} is also distributed in the @value{GDBN} source
22414 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
22416 @node Configure Options
22417 @section @file{configure} Options
22419 Here is a summary of the @file{configure} options and arguments that
22420 are most often useful for building @value{GDBN}. @file{configure} also has
22421 several other options not listed here. @inforef{What Configure
22422 Does,,configure.info}, for a full explanation of @file{configure}.
22425 configure @r{[}--help@r{]}
22426 @r{[}--prefix=@var{dir}@r{]}
22427 @r{[}--exec-prefix=@var{dir}@r{]}
22428 @r{[}--srcdir=@var{dirname}@r{]}
22429 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
22430 @r{[}--target=@var{target}@r{]}
22435 You may introduce options with a single @samp{-} rather than
22436 @samp{--} if you prefer; but you may abbreviate option names if you use
22441 Display a quick summary of how to invoke @file{configure}.
22443 @item --prefix=@var{dir}
22444 Configure the source to install programs and files under directory
22447 @item --exec-prefix=@var{dir}
22448 Configure the source to install programs under directory
22451 @c avoid splitting the warning from the explanation:
22453 @item --srcdir=@var{dirname}
22454 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
22455 @code{make} that implements the @code{VPATH} feature.}@*
22456 Use this option to make configurations in directories separate from the
22457 @value{GDBN} source directories. Among other things, you can use this to
22458 build (or maintain) several configurations simultaneously, in separate
22459 directories. @file{configure} writes configuration-specific files in
22460 the current directory, but arranges for them to use the source in the
22461 directory @var{dirname}. @file{configure} creates directories under
22462 the working directory in parallel to the source directories below
22465 @item --norecursion
22466 Configure only the directory level where @file{configure} is executed; do not
22467 propagate configuration to subdirectories.
22469 @item --target=@var{target}
22470 Configure @value{GDBN} for cross-debugging programs running on the specified
22471 @var{target}. Without this option, @value{GDBN} is configured to debug
22472 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
22474 There is no convenient way to generate a list of all available targets.
22476 @item @var{host} @dots{}
22477 Configure @value{GDBN} to run on the specified @var{host}.
22479 There is no convenient way to generate a list of all available hosts.
22482 There are many other options available as well, but they are generally
22483 needed for special purposes only.
22485 @node Maintenance Commands
22486 @appendix Maintenance Commands
22487 @cindex maintenance commands
22488 @cindex internal commands
22490 In addition to commands intended for @value{GDBN} users, @value{GDBN}
22491 includes a number of commands intended for @value{GDBN} developers,
22492 that are not documented elsewhere in this manual. These commands are
22493 provided here for reference. (For commands that turn on debugging
22494 messages, see @ref{Debugging Output}.)
22497 @kindex maint agent
22498 @item maint agent @var{expression}
22499 Translate the given @var{expression} into remote agent bytecodes.
22500 This command is useful for debugging the Agent Expression mechanism
22501 (@pxref{Agent Expressions}).
22503 @kindex maint info breakpoints
22504 @item @anchor{maint info breakpoints}maint info breakpoints
22505 Using the same format as @samp{info breakpoints}, display both the
22506 breakpoints you've set explicitly, and those @value{GDBN} is using for
22507 internal purposes. Internal breakpoints are shown with negative
22508 breakpoint numbers. The type column identifies what kind of breakpoint
22513 Normal, explicitly set breakpoint.
22516 Normal, explicitly set watchpoint.
22519 Internal breakpoint, used to handle correctly stepping through
22520 @code{longjmp} calls.
22522 @item longjmp resume
22523 Internal breakpoint at the target of a @code{longjmp}.
22526 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
22529 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
22532 Shared library events.
22536 @kindex maint check-symtabs
22537 @item maint check-symtabs
22538 Check the consistency of psymtabs and symtabs.
22540 @kindex maint cplus first_component
22541 @item maint cplus first_component @var{name}
22542 Print the first C@t{++} class/namespace component of @var{name}.
22544 @kindex maint cplus namespace
22545 @item maint cplus namespace
22546 Print the list of possible C@t{++} namespaces.
22548 @kindex maint demangle
22549 @item maint demangle @var{name}
22550 Demangle a C@t{++} or Objective-C mangled @var{name}.
22552 @kindex maint deprecate
22553 @kindex maint undeprecate
22554 @cindex deprecated commands
22555 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
22556 @itemx maint undeprecate @var{command}
22557 Deprecate or undeprecate the named @var{command}. Deprecated commands
22558 cause @value{GDBN} to issue a warning when you use them. The optional
22559 argument @var{replacement} says which newer command should be used in
22560 favor of the deprecated one; if it is given, @value{GDBN} will mention
22561 the replacement as part of the warning.
22563 @kindex maint dump-me
22564 @item maint dump-me
22565 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
22566 Cause a fatal signal in the debugger and force it to dump its core.
22567 This is supported only on systems which support aborting a program
22568 with the @code{SIGQUIT} signal.
22570 @kindex maint internal-error
22571 @kindex maint internal-warning
22572 @item maint internal-error @r{[}@var{message-text}@r{]}
22573 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
22574 Cause @value{GDBN} to call the internal function @code{internal_error}
22575 or @code{internal_warning} and hence behave as though an internal error
22576 or internal warning has been detected. In addition to reporting the
22577 internal problem, these functions give the user the opportunity to
22578 either quit @value{GDBN} or create a core file of the current
22579 @value{GDBN} session.
22581 These commands take an optional parameter @var{message-text} that is
22582 used as the text of the error or warning message.
22584 Here's an example of using @code{internal-error}:
22587 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
22588 @dots{}/maint.c:121: internal-error: testing, 1, 2
22589 A problem internal to GDB has been detected. Further
22590 debugging may prove unreliable.
22591 Quit this debugging session? (y or n) @kbd{n}
22592 Create a core file? (y or n) @kbd{n}
22596 @kindex maint packet
22597 @item maint packet @var{text}
22598 If @value{GDBN} is talking to an inferior via the serial protocol,
22599 then this command sends the string @var{text} to the inferior, and
22600 displays the response packet. @value{GDBN} supplies the initial
22601 @samp{$} character, the terminating @samp{#} character, and the
22604 @kindex maint print architecture
22605 @item maint print architecture @r{[}@var{file}@r{]}
22606 Print the entire architecture configuration. The optional argument
22607 @var{file} names the file where the output goes.
22609 @kindex maint print c-tdesc
22610 @item maint print c-tdesc
22611 Print the current target description (@pxref{Target Descriptions}) as
22612 a C source file. The created source file can be used in @value{GDBN}
22613 when an XML parser is not available to parse the description.
22615 @kindex maint print dummy-frames
22616 @item maint print dummy-frames
22617 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
22620 (@value{GDBP}) @kbd{b add}
22622 (@value{GDBP}) @kbd{print add(2,3)}
22623 Breakpoint 2, add (a=2, b=3) at @dots{}
22625 The program being debugged stopped while in a function called from GDB.
22627 (@value{GDBP}) @kbd{maint print dummy-frames}
22628 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
22629 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
22630 call_lo=0x01014000 call_hi=0x01014001
22634 Takes an optional file parameter.
22636 @kindex maint print registers
22637 @kindex maint print raw-registers
22638 @kindex maint print cooked-registers
22639 @kindex maint print register-groups
22640 @item maint print registers @r{[}@var{file}@r{]}
22641 @itemx maint print raw-registers @r{[}@var{file}@r{]}
22642 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
22643 @itemx maint print register-groups @r{[}@var{file}@r{]}
22644 Print @value{GDBN}'s internal register data structures.
22646 The command @code{maint print raw-registers} includes the contents of
22647 the raw register cache; the command @code{maint print cooked-registers}
22648 includes the (cooked) value of all registers; and the command
22649 @code{maint print register-groups} includes the groups that each
22650 register is a member of. @xref{Registers,, Registers, gdbint,
22651 @value{GDBN} Internals}.
22653 These commands take an optional parameter, a file name to which to
22654 write the information.
22656 @kindex maint print reggroups
22657 @item maint print reggroups @r{[}@var{file}@r{]}
22658 Print @value{GDBN}'s internal register group data structures. The
22659 optional argument @var{file} tells to what file to write the
22662 The register groups info looks like this:
22665 (@value{GDBP}) @kbd{maint print reggroups}
22678 This command forces @value{GDBN} to flush its internal register cache.
22680 @kindex maint print objfiles
22681 @cindex info for known object files
22682 @item maint print objfiles
22683 Print a dump of all known object files. For each object file, this
22684 command prints its name, address in memory, and all of its psymtabs
22687 @kindex maint print statistics
22688 @cindex bcache statistics
22689 @item maint print statistics
22690 This command prints, for each object file in the program, various data
22691 about that object file followed by the byte cache (@dfn{bcache})
22692 statistics for the object file. The objfile data includes the number
22693 of minimal, partial, full, and stabs symbols, the number of types
22694 defined by the objfile, the number of as yet unexpanded psym tables,
22695 the number of line tables and string tables, and the amount of memory
22696 used by the various tables. The bcache statistics include the counts,
22697 sizes, and counts of duplicates of all and unique objects, max,
22698 average, and median entry size, total memory used and its overhead and
22699 savings, and various measures of the hash table size and chain
22702 @kindex maint print target-stack
22703 @cindex target stack description
22704 @item maint print target-stack
22705 A @dfn{target} is an interface between the debugger and a particular
22706 kind of file or process. Targets can be stacked in @dfn{strata},
22707 so that more than one target can potentially respond to a request.
22708 In particular, memory accesses will walk down the stack of targets
22709 until they find a target that is interested in handling that particular
22712 This command prints a short description of each layer that was pushed on
22713 the @dfn{target stack}, starting from the top layer down to the bottom one.
22715 @kindex maint print type
22716 @cindex type chain of a data type
22717 @item maint print type @var{expr}
22718 Print the type chain for a type specified by @var{expr}. The argument
22719 can be either a type name or a symbol. If it is a symbol, the type of
22720 that symbol is described. The type chain produced by this command is
22721 a recursive definition of the data type as stored in @value{GDBN}'s
22722 data structures, including its flags and contained types.
22724 @kindex maint set dwarf2 max-cache-age
22725 @kindex maint show dwarf2 max-cache-age
22726 @item maint set dwarf2 max-cache-age
22727 @itemx maint show dwarf2 max-cache-age
22728 Control the DWARF 2 compilation unit cache.
22730 @cindex DWARF 2 compilation units cache
22731 In object files with inter-compilation-unit references, such as those
22732 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
22733 reader needs to frequently refer to previously read compilation units.
22734 This setting controls how long a compilation unit will remain in the
22735 cache if it is not referenced. A higher limit means that cached
22736 compilation units will be stored in memory longer, and more total
22737 memory will be used. Setting it to zero disables caching, which will
22738 slow down @value{GDBN} startup, but reduce memory consumption.
22740 @kindex maint set profile
22741 @kindex maint show profile
22742 @cindex profiling GDB
22743 @item maint set profile
22744 @itemx maint show profile
22745 Control profiling of @value{GDBN}.
22747 Profiling will be disabled until you use the @samp{maint set profile}
22748 command to enable it. When you enable profiling, the system will begin
22749 collecting timing and execution count data; when you disable profiling or
22750 exit @value{GDBN}, the results will be written to a log file. Remember that
22751 if you use profiling, @value{GDBN} will overwrite the profiling log file
22752 (often called @file{gmon.out}). If you have a record of important profiling
22753 data in a @file{gmon.out} file, be sure to move it to a safe location.
22755 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
22756 compiled with the @samp{-pg} compiler option.
22758 @kindex maint show-debug-regs
22759 @cindex x86 hardware debug registers
22760 @item maint show-debug-regs
22761 Control whether to show variables that mirror the x86 hardware debug
22762 registers. Use @code{ON} to enable, @code{OFF} to disable. If
22763 enabled, the debug registers values are shown when @value{GDBN} inserts or
22764 removes a hardware breakpoint or watchpoint, and when the inferior
22765 triggers a hardware-assisted breakpoint or watchpoint.
22767 @kindex maint space
22768 @cindex memory used by commands
22770 Control whether to display memory usage for each command. If set to a
22771 nonzero value, @value{GDBN} will display how much memory each command
22772 took, following the command's own output. This can also be requested
22773 by invoking @value{GDBN} with the @option{--statistics} command-line
22774 switch (@pxref{Mode Options}).
22777 @cindex time of command execution
22779 Control whether to display the execution time for each command. If
22780 set to a nonzero value, @value{GDBN} will display how much time it
22781 took to execute each command, following the command's own output.
22782 This can also be requested by invoking @value{GDBN} with the
22783 @option{--statistics} command-line switch (@pxref{Mode Options}).
22785 @kindex maint translate-address
22786 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
22787 Find the symbol stored at the location specified by the address
22788 @var{addr} and an optional section name @var{section}. If found,
22789 @value{GDBN} prints the name of the closest symbol and an offset from
22790 the symbol's location to the specified address. This is similar to
22791 the @code{info address} command (@pxref{Symbols}), except that this
22792 command also allows to find symbols in other sections.
22796 The following command is useful for non-interactive invocations of
22797 @value{GDBN}, such as in the test suite.
22800 @item set watchdog @var{nsec}
22801 @kindex set watchdog
22802 @cindex watchdog timer
22803 @cindex timeout for commands
22804 Set the maximum number of seconds @value{GDBN} will wait for the
22805 target operation to finish. If this time expires, @value{GDBN}
22806 reports and error and the command is aborted.
22808 @item show watchdog
22809 Show the current setting of the target wait timeout.
22812 @node Remote Protocol
22813 @appendix @value{GDBN} Remote Serial Protocol
22818 * Stop Reply Packets::
22819 * General Query Packets::
22820 * Register Packet Format::
22821 * Tracepoint Packets::
22824 * File-I/O Remote Protocol Extension::
22825 * Library List Format::
22826 * Memory Map Format::
22832 There may be occasions when you need to know something about the
22833 protocol---for example, if there is only one serial port to your target
22834 machine, you might want your program to do something special if it
22835 recognizes a packet meant for @value{GDBN}.
22837 In the examples below, @samp{->} and @samp{<-} are used to indicate
22838 transmitted and received data, respectively.
22840 @cindex protocol, @value{GDBN} remote serial
22841 @cindex serial protocol, @value{GDBN} remote
22842 @cindex remote serial protocol
22843 All @value{GDBN} commands and responses (other than acknowledgments) are
22844 sent as a @var{packet}. A @var{packet} is introduced with the character
22845 @samp{$}, the actual @var{packet-data}, and the terminating character
22846 @samp{#} followed by a two-digit @var{checksum}:
22849 @code{$}@var{packet-data}@code{#}@var{checksum}
22853 @cindex checksum, for @value{GDBN} remote
22855 The two-digit @var{checksum} is computed as the modulo 256 sum of all
22856 characters between the leading @samp{$} and the trailing @samp{#} (an
22857 eight bit unsigned checksum).
22859 Implementors should note that prior to @value{GDBN} 5.0 the protocol
22860 specification also included an optional two-digit @var{sequence-id}:
22863 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
22866 @cindex sequence-id, for @value{GDBN} remote
22868 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
22869 has never output @var{sequence-id}s. Stubs that handle packets added
22870 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
22872 @cindex acknowledgment, for @value{GDBN} remote
22873 When either the host or the target machine receives a packet, the first
22874 response expected is an acknowledgment: either @samp{+} (to indicate
22875 the package was received correctly) or @samp{-} (to request
22879 -> @code{$}@var{packet-data}@code{#}@var{checksum}
22884 The host (@value{GDBN}) sends @var{command}s, and the target (the
22885 debugging stub incorporated in your program) sends a @var{response}. In
22886 the case of step and continue @var{command}s, the response is only sent
22887 when the operation has completed (the target has again stopped).
22889 @var{packet-data} consists of a sequence of characters with the
22890 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
22893 @cindex remote protocol, field separator
22894 Fields within the packet should be separated using @samp{,} @samp{;} or
22895 @samp{:}. Except where otherwise noted all numbers are represented in
22896 @sc{hex} with leading zeros suppressed.
22898 Implementors should note that prior to @value{GDBN} 5.0, the character
22899 @samp{:} could not appear as the third character in a packet (as it
22900 would potentially conflict with the @var{sequence-id}).
22902 @cindex remote protocol, binary data
22903 @anchor{Binary Data}
22904 Binary data in most packets is encoded either as two hexadecimal
22905 digits per byte of binary data. This allowed the traditional remote
22906 protocol to work over connections which were only seven-bit clean.
22907 Some packets designed more recently assume an eight-bit clean
22908 connection, and use a more efficient encoding to send and receive
22911 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
22912 as an escape character. Any escaped byte is transmitted as the escape
22913 character followed by the original character XORed with @code{0x20}.
22914 For example, the byte @code{0x7d} would be transmitted as the two
22915 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
22916 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
22917 @samp{@}}) must always be escaped. Responses sent by the stub
22918 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
22919 is not interpreted as the start of a run-length encoded sequence
22922 Response @var{data} can be run-length encoded to save space. A @samp{*}
22923 means that the next character is an @sc{ascii} encoding giving a repeat count
22924 which stands for that many repetitions of the character preceding the
22925 @samp{*}. The encoding is @code{n+29}, yielding a printable character
22926 where @code{n >=3} (which is where rle starts to win). The printable
22927 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
22928 value greater than 126 should not be used.
22935 means the same as "0000".
22937 The error response returned for some packets includes a two character
22938 error number. That number is not well defined.
22940 @cindex empty response, for unsupported packets
22941 For any @var{command} not supported by the stub, an empty response
22942 (@samp{$#00}) should be returned. That way it is possible to extend the
22943 protocol. A newer @value{GDBN} can tell if a packet is supported based
22946 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
22947 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
22953 The following table provides a complete list of all currently defined
22954 @var{command}s and their corresponding response @var{data}.
22955 @xref{File-I/O Remote Protocol Extension}, for details about the File
22956 I/O extension of the remote protocol.
22958 Each packet's description has a template showing the packet's overall
22959 syntax, followed by an explanation of the packet's meaning. We
22960 include spaces in some of the templates for clarity; these are not
22961 part of the packet's syntax. No @value{GDBN} packet uses spaces to
22962 separate its components. For example, a template like @samp{foo
22963 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
22964 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
22965 @var{baz}. @value{GDBN} does not transmit a space character between the
22966 @samp{foo} and the @var{bar}, or between the @var{bar} and the
22969 Note that all packet forms beginning with an upper- or lower-case
22970 letter, other than those described here, are reserved for future use.
22972 Here are the packet descriptions.
22977 @cindex @samp{!} packet
22978 Enable extended mode. In extended mode, the remote server is made
22979 persistent. The @samp{R} packet is used to restart the program being
22985 The remote target both supports and has enabled extended mode.
22989 @cindex @samp{?} packet
22990 Indicate the reason the target halted. The reply is the same as for
22994 @xref{Stop Reply Packets}, for the reply specifications.
22996 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
22997 @cindex @samp{A} packet
22998 Initialized @code{argv[]} array passed into program. @var{arglen}
22999 specifies the number of bytes in the hex encoded byte stream
23000 @var{arg}. See @code{gdbserver} for more details.
23005 The arguments were set.
23011 @cindex @samp{b} packet
23012 (Don't use this packet; its behavior is not well-defined.)
23013 Change the serial line speed to @var{baud}.
23015 JTC: @emph{When does the transport layer state change? When it's
23016 received, or after the ACK is transmitted. In either case, there are
23017 problems if the command or the acknowledgment packet is dropped.}
23019 Stan: @emph{If people really wanted to add something like this, and get
23020 it working for the first time, they ought to modify ser-unix.c to send
23021 some kind of out-of-band message to a specially-setup stub and have the
23022 switch happen "in between" packets, so that from remote protocol's point
23023 of view, nothing actually happened.}
23025 @item B @var{addr},@var{mode}
23026 @cindex @samp{B} packet
23027 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
23028 breakpoint at @var{addr}.
23030 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
23031 (@pxref{insert breakpoint or watchpoint packet}).
23033 @item c @r{[}@var{addr}@r{]}
23034 @cindex @samp{c} packet
23035 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
23036 resume at current address.
23039 @xref{Stop Reply Packets}, for the reply specifications.
23041 @item C @var{sig}@r{[};@var{addr}@r{]}
23042 @cindex @samp{C} packet
23043 Continue with signal @var{sig} (hex signal number). If
23044 @samp{;@var{addr}} is omitted, resume at same address.
23047 @xref{Stop Reply Packets}, for the reply specifications.
23050 @cindex @samp{d} packet
23053 Don't use this packet; instead, define a general set packet
23054 (@pxref{General Query Packets}).
23057 @cindex @samp{D} packet
23058 Detach @value{GDBN} from the remote system. Sent to the remote target
23059 before @value{GDBN} disconnects via the @code{detach} command.
23069 @item F @var{RC},@var{EE},@var{CF};@var{XX}
23070 @cindex @samp{F} packet
23071 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
23072 This is part of the File-I/O protocol extension. @xref{File-I/O
23073 Remote Protocol Extension}, for the specification.
23076 @anchor{read registers packet}
23077 @cindex @samp{g} packet
23078 Read general registers.
23082 @item @var{XX@dots{}}
23083 Each byte of register data is described by two hex digits. The bytes
23084 with the register are transmitted in target byte order. The size of
23085 each register and their position within the @samp{g} packet are
23086 determined by the @value{GDBN} internal gdbarch functions
23087 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
23088 specification of several standard @samp{g} packets is specified below.
23093 @item G @var{XX@dots{}}
23094 @cindex @samp{G} packet
23095 Write general registers. @xref{read registers packet}, for a
23096 description of the @var{XX@dots{}} data.
23106 @item H @var{c} @var{t}
23107 @cindex @samp{H} packet
23108 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
23109 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
23110 should be @samp{c} for step and continue operations, @samp{g} for other
23111 operations. The thread designator @var{t} may be @samp{-1}, meaning all
23112 the threads, a thread number, or @samp{0} which means pick any thread.
23123 @c 'H': How restrictive (or permissive) is the thread model. If a
23124 @c thread is selected and stopped, are other threads allowed
23125 @c to continue to execute? As I mentioned above, I think the
23126 @c semantics of each command when a thread is selected must be
23127 @c described. For example:
23129 @c 'g': If the stub supports threads and a specific thread is
23130 @c selected, returns the register block from that thread;
23131 @c otherwise returns current registers.
23133 @c 'G' If the stub supports threads and a specific thread is
23134 @c selected, sets the registers of the register block of
23135 @c that thread; otherwise sets current registers.
23137 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
23138 @anchor{cycle step packet}
23139 @cindex @samp{i} packet
23140 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
23141 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
23142 step starting at that address.
23145 @cindex @samp{I} packet
23146 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
23150 @cindex @samp{k} packet
23153 FIXME: @emph{There is no description of how to operate when a specific
23154 thread context has been selected (i.e.@: does 'k' kill only that
23157 @item m @var{addr},@var{length}
23158 @cindex @samp{m} packet
23159 Read @var{length} bytes of memory starting at address @var{addr}.
23160 Note that @var{addr} may not be aligned to any particular boundary.
23162 The stub need not use any particular size or alignment when gathering
23163 data from memory for the response; even if @var{addr} is word-aligned
23164 and @var{length} is a multiple of the word size, the stub is free to
23165 use byte accesses, or not. For this reason, this packet may not be
23166 suitable for accessing memory-mapped I/O devices.
23167 @cindex alignment of remote memory accesses
23168 @cindex size of remote memory accesses
23169 @cindex memory, alignment and size of remote accesses
23173 @item @var{XX@dots{}}
23174 Memory contents; each byte is transmitted as a two-digit hexadecimal
23175 number. The reply may contain fewer bytes than requested if the
23176 server was able to read only part of the region of memory.
23181 @item M @var{addr},@var{length}:@var{XX@dots{}}
23182 @cindex @samp{M} packet
23183 Write @var{length} bytes of memory starting at address @var{addr}.
23184 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
23185 hexadecimal number.
23192 for an error (this includes the case where only part of the data was
23197 @cindex @samp{p} packet
23198 Read the value of register @var{n}; @var{n} is in hex.
23199 @xref{read registers packet}, for a description of how the returned
23200 register value is encoded.
23204 @item @var{XX@dots{}}
23205 the register's value
23209 Indicating an unrecognized @var{query}.
23212 @item P @var{n@dots{}}=@var{r@dots{}}
23213 @anchor{write register packet}
23214 @cindex @samp{P} packet
23215 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
23216 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
23217 digits for each byte in the register (target byte order).
23227 @item q @var{name} @var{params}@dots{}
23228 @itemx Q @var{name} @var{params}@dots{}
23229 @cindex @samp{q} packet
23230 @cindex @samp{Q} packet
23231 General query (@samp{q}) and set (@samp{Q}). These packets are
23232 described fully in @ref{General Query Packets}.
23235 @cindex @samp{r} packet
23236 Reset the entire system.
23238 Don't use this packet; use the @samp{R} packet instead.
23241 @cindex @samp{R} packet
23242 Restart the program being debugged. @var{XX}, while needed, is ignored.
23243 This packet is only available in extended mode.
23245 The @samp{R} packet has no reply.
23247 @item s @r{[}@var{addr}@r{]}
23248 @cindex @samp{s} packet
23249 Single step. @var{addr} is the address at which to resume. If
23250 @var{addr} is omitted, resume at same address.
23253 @xref{Stop Reply Packets}, for the reply specifications.
23255 @item S @var{sig}@r{[};@var{addr}@r{]}
23256 @anchor{step with signal packet}
23257 @cindex @samp{S} packet
23258 Step with signal. This is analogous to the @samp{C} packet, but
23259 requests a single-step, rather than a normal resumption of execution.
23262 @xref{Stop Reply Packets}, for the reply specifications.
23264 @item t @var{addr}:@var{PP},@var{MM}
23265 @cindex @samp{t} packet
23266 Search backwards starting at address @var{addr} for a match with pattern
23267 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
23268 @var{addr} must be at least 3 digits.
23271 @cindex @samp{T} packet
23272 Find out if the thread XX is alive.
23277 thread is still alive
23283 Packets starting with @samp{v} are identified by a multi-letter name,
23284 up to the first @samp{;} or @samp{?} (or the end of the packet).
23286 @item vCont@r{[};@var{action}@r{[}:@var{tid}@r{]]}@dots{}
23287 @cindex @samp{vCont} packet
23288 Resume the inferior, specifying different actions for each thread.
23289 If an action is specified with no @var{tid}, then it is applied to any
23290 threads that don't have a specific action specified; if no default action is
23291 specified then other threads should remain stopped. Specifying multiple
23292 default actions is an error; specifying no actions is also an error.
23293 Thread IDs are specified in hexadecimal. Currently supported actions are:
23299 Continue with signal @var{sig}. @var{sig} should be two hex digits.
23303 Step with signal @var{sig}. @var{sig} should be two hex digits.
23306 The optional @var{addr} argument normally associated with these packets is
23307 not supported in @samp{vCont}.
23310 @xref{Stop Reply Packets}, for the reply specifications.
23313 @cindex @samp{vCont?} packet
23314 Request a list of actions supported by the @samp{vCont} packet.
23318 @item vCont@r{[};@var{action}@dots{}@r{]}
23319 The @samp{vCont} packet is supported. Each @var{action} is a supported
23320 command in the @samp{vCont} packet.
23322 The @samp{vCont} packet is not supported.
23325 @item vFlashErase:@var{addr},@var{length}
23326 @cindex @samp{vFlashErase} packet
23327 Direct the stub to erase @var{length} bytes of flash starting at
23328 @var{addr}. The region may enclose any number of flash blocks, but
23329 its start and end must fall on block boundaries, as indicated by the
23330 flash block size appearing in the memory map (@pxref{Memory Map
23331 Format}). @value{GDBN} groups flash memory programming operations
23332 together, and sends a @samp{vFlashDone} request after each group; the
23333 stub is allowed to delay erase operation until the @samp{vFlashDone}
23334 packet is received.
23344 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
23345 @cindex @samp{vFlashWrite} packet
23346 Direct the stub to write data to flash address @var{addr}. The data
23347 is passed in binary form using the same encoding as for the @samp{X}
23348 packet (@pxref{Binary Data}). The memory ranges specified by
23349 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
23350 not overlap, and must appear in order of increasing addresses
23351 (although @samp{vFlashErase} packets for higher addresses may already
23352 have been received; the ordering is guaranteed only between
23353 @samp{vFlashWrite} packets). If a packet writes to an address that was
23354 neither erased by a preceding @samp{vFlashErase} packet nor by some other
23355 target-specific method, the results are unpredictable.
23363 for vFlashWrite addressing non-flash memory
23369 @cindex @samp{vFlashDone} packet
23370 Indicate to the stub that flash programming operation is finished.
23371 The stub is permitted to delay or batch the effects of a group of
23372 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
23373 @samp{vFlashDone} packet is received. The contents of the affected
23374 regions of flash memory are unpredictable until the @samp{vFlashDone}
23375 request is completed.
23377 @item X @var{addr},@var{length}:@var{XX@dots{}}
23379 @cindex @samp{X} packet
23380 Write data to memory, where the data is transmitted in binary.
23381 @var{addr} is address, @var{length} is number of bytes,
23382 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
23392 @item z @var{type},@var{addr},@var{length}
23393 @itemx Z @var{type},@var{addr},@var{length}
23394 @anchor{insert breakpoint or watchpoint packet}
23395 @cindex @samp{z} packet
23396 @cindex @samp{Z} packets
23397 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
23398 watchpoint starting at address @var{address} and covering the next
23399 @var{length} bytes.
23401 Each breakpoint and watchpoint packet @var{type} is documented
23404 @emph{Implementation notes: A remote target shall return an empty string
23405 for an unrecognized breakpoint or watchpoint packet @var{type}. A
23406 remote target shall support either both or neither of a given
23407 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
23408 avoid potential problems with duplicate packets, the operations should
23409 be implemented in an idempotent way.}
23411 @item z0,@var{addr},@var{length}
23412 @itemx Z0,@var{addr},@var{length}
23413 @cindex @samp{z0} packet
23414 @cindex @samp{Z0} packet
23415 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
23416 @var{addr} of size @var{length}.
23418 A memory breakpoint is implemented by replacing the instruction at
23419 @var{addr} with a software breakpoint or trap instruction. The
23420 @var{length} is used by targets that indicates the size of the
23421 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
23422 @sc{mips} can insert either a 2 or 4 byte breakpoint).
23424 @emph{Implementation note: It is possible for a target to copy or move
23425 code that contains memory breakpoints (e.g., when implementing
23426 overlays). The behavior of this packet, in the presence of such a
23427 target, is not defined.}
23439 @item z1,@var{addr},@var{length}
23440 @itemx Z1,@var{addr},@var{length}
23441 @cindex @samp{z1} packet
23442 @cindex @samp{Z1} packet
23443 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
23444 address @var{addr} of size @var{length}.
23446 A hardware breakpoint is implemented using a mechanism that is not
23447 dependant on being able to modify the target's memory.
23449 @emph{Implementation note: A hardware breakpoint is not affected by code
23462 @item z2,@var{addr},@var{length}
23463 @itemx Z2,@var{addr},@var{length}
23464 @cindex @samp{z2} packet
23465 @cindex @samp{Z2} packet
23466 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
23478 @item z3,@var{addr},@var{length}
23479 @itemx Z3,@var{addr},@var{length}
23480 @cindex @samp{z3} packet
23481 @cindex @samp{Z3} packet
23482 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
23494 @item z4,@var{addr},@var{length}
23495 @itemx Z4,@var{addr},@var{length}
23496 @cindex @samp{z4} packet
23497 @cindex @samp{Z4} packet
23498 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
23512 @node Stop Reply Packets
23513 @section Stop Reply Packets
23514 @cindex stop reply packets
23516 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
23517 receive any of the below as a reply. In the case of the @samp{C},
23518 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
23519 when the target halts. In the below the exact meaning of @dfn{signal
23520 number} is defined by the header @file{include/gdb/signals.h} in the
23521 @value{GDBN} source code.
23523 As in the description of request packets, we include spaces in the
23524 reply templates for clarity; these are not part of the reply packet's
23525 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
23531 The program received signal number @var{AA} (a two-digit hexadecimal
23532 number). This is equivalent to a @samp{T} response with no
23533 @var{n}:@var{r} pairs.
23535 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
23536 @cindex @samp{T} packet reply
23537 The program received signal number @var{AA} (a two-digit hexadecimal
23538 number). This is equivalent to an @samp{S} response, except that the
23539 @samp{@var{n}:@var{r}} pairs can carry values of important registers
23540 and other information directly in the stop reply packet, reducing
23541 round-trip latency. Single-step and breakpoint traps are reported
23542 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
23546 If @var{n} is a hexadecimal number, it is a register number, and the
23547 corresponding @var{r} gives that register's value. @var{r} is a
23548 series of bytes in target byte order, with each byte given by a
23549 two-digit hex number.
23552 If @var{n} is @samp{thread}, then @var{r} is the thread process ID, in
23556 If @var{n} is a recognized @dfn{stop reason}, it describes a more
23557 specific event that stopped the target. The currently defined stop
23558 reasons are listed below. @var{aa} should be @samp{05}, the trap
23559 signal. At most one stop reason should be present.
23562 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
23563 and go on to the next; this allows us to extend the protocol in the
23567 The currently defined stop reasons are:
23573 The packet indicates a watchpoint hit, and @var{r} is the data address, in
23576 @cindex shared library events, remote reply
23578 The packet indicates that the loaded libraries have changed.
23579 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
23580 list of loaded libraries. @var{r} is ignored.
23584 The process exited, and @var{AA} is the exit status. This is only
23585 applicable to certain targets.
23588 The process terminated with signal @var{AA}.
23590 @item O @var{XX}@dots{}
23591 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
23592 written as the program's console output. This can happen at any time
23593 while the program is running and the debugger should continue to wait
23594 for @samp{W}, @samp{T}, etc.
23596 @item F @var{call-id},@var{parameter}@dots{}
23597 @var{call-id} is the identifier which says which host system call should
23598 be called. This is just the name of the function. Translation into the
23599 correct system call is only applicable as it's defined in @value{GDBN}.
23600 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
23603 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
23604 this very system call.
23606 The target replies with this packet when it expects @value{GDBN} to
23607 call a host system call on behalf of the target. @value{GDBN} replies
23608 with an appropriate @samp{F} packet and keeps up waiting for the next
23609 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
23610 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
23611 Protocol Extension}, for more details.
23615 @node General Query Packets
23616 @section General Query Packets
23617 @cindex remote query requests
23619 Packets starting with @samp{q} are @dfn{general query packets};
23620 packets starting with @samp{Q} are @dfn{general set packets}. General
23621 query and set packets are a semi-unified form for retrieving and
23622 sending information to and from the stub.
23624 The initial letter of a query or set packet is followed by a name
23625 indicating what sort of thing the packet applies to. For example,
23626 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
23627 definitions with the stub. These packet names follow some
23632 The name must not contain commas, colons or semicolons.
23634 Most @value{GDBN} query and set packets have a leading upper case
23637 The names of custom vendor packets should use a company prefix, in
23638 lower case, followed by a period. For example, packets designed at
23639 the Acme Corporation might begin with @samp{qacme.foo} (for querying
23640 foos) or @samp{Qacme.bar} (for setting bars).
23643 The name of a query or set packet should be separated from any
23644 parameters by a @samp{:}; the parameters themselves should be
23645 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
23646 full packet name, and check for a separator or the end of the packet,
23647 in case two packet names share a common prefix. New packets should not begin
23648 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
23649 packets predate these conventions, and have arguments without any terminator
23650 for the packet name; we suspect they are in widespread use in places that
23651 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
23652 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
23655 Like the descriptions of the other packets, each description here
23656 has a template showing the packet's overall syntax, followed by an
23657 explanation of the packet's meaning. We include spaces in some of the
23658 templates for clarity; these are not part of the packet's syntax. No
23659 @value{GDBN} packet uses spaces to separate its components.
23661 Here are the currently defined query and set packets:
23666 @cindex current thread, remote request
23667 @cindex @samp{qC} packet
23668 Return the current thread id.
23673 Where @var{pid} is an unsigned hexadecimal process id.
23674 @item @r{(anything else)}
23675 Any other reply implies the old pid.
23678 @item qCRC:@var{addr},@var{length}
23679 @cindex CRC of memory block, remote request
23680 @cindex @samp{qCRC} packet
23681 Compute the CRC checksum of a block of memory.
23685 An error (such as memory fault)
23686 @item C @var{crc32}
23687 The specified memory region's checksum is @var{crc32}.
23691 @itemx qsThreadInfo
23692 @cindex list active threads, remote request
23693 @cindex @samp{qfThreadInfo} packet
23694 @cindex @samp{qsThreadInfo} packet
23695 Obtain a list of all active thread ids from the target (OS). Since there
23696 may be too many active threads to fit into one reply packet, this query
23697 works iteratively: it may require more than one query/reply sequence to
23698 obtain the entire list of threads. The first query of the sequence will
23699 be the @samp{qfThreadInfo} query; subsequent queries in the
23700 sequence will be the @samp{qsThreadInfo} query.
23702 NOTE: This packet replaces the @samp{qL} query (see below).
23708 @item m @var{id},@var{id}@dots{}
23709 a comma-separated list of thread ids
23711 (lower case letter @samp{L}) denotes end of list.
23714 In response to each query, the target will reply with a list of one or
23715 more thread ids, in big-endian unsigned hex, separated by commas.
23716 @value{GDBN} will respond to each reply with a request for more thread
23717 ids (using the @samp{qs} form of the query), until the target responds
23718 with @samp{l} (lower-case el, for @dfn{last}).
23720 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
23721 @cindex get thread-local storage address, remote request
23722 @cindex @samp{qGetTLSAddr} packet
23723 Fetch the address associated with thread local storage specified
23724 by @var{thread-id}, @var{offset}, and @var{lm}.
23726 @var{thread-id} is the (big endian, hex encoded) thread id associated with the
23727 thread for which to fetch the TLS address.
23729 @var{offset} is the (big endian, hex encoded) offset associated with the
23730 thread local variable. (This offset is obtained from the debug
23731 information associated with the variable.)
23733 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
23734 the load module associated with the thread local storage. For example,
23735 a @sc{gnu}/Linux system will pass the link map address of the shared
23736 object associated with the thread local storage under consideration.
23737 Other operating environments may choose to represent the load module
23738 differently, so the precise meaning of this parameter will vary.
23742 @item @var{XX}@dots{}
23743 Hex encoded (big endian) bytes representing the address of the thread
23744 local storage requested.
23747 An error occurred. @var{nn} are hex digits.
23750 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
23753 @item qL @var{startflag} @var{threadcount} @var{nextthread}
23754 Obtain thread information from RTOS. Where: @var{startflag} (one hex
23755 digit) is one to indicate the first query and zero to indicate a
23756 subsequent query; @var{threadcount} (two hex digits) is the maximum
23757 number of threads the response packet can contain; and @var{nextthread}
23758 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
23759 returned in the response as @var{argthread}.
23761 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
23765 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
23766 Where: @var{count} (two hex digits) is the number of threads being
23767 returned; @var{done} (one hex digit) is zero to indicate more threads
23768 and one indicates no further threads; @var{argthreadid} (eight hex
23769 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
23770 is a sequence of thread IDs from the target. @var{threadid} (eight hex
23771 digits). See @code{remote.c:parse_threadlist_response()}.
23775 @cindex section offsets, remote request
23776 @cindex @samp{qOffsets} packet
23777 Get section offsets that the target used when relocating the downloaded
23782 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
23783 Relocate the @code{Text} section by @var{xxx} from its original address.
23784 Relocate the @code{Data} section by @var{yyy} from its original address.
23785 If the object file format provides segment information (e.g.@: @sc{elf}
23786 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
23787 segments by the supplied offsets.
23789 @emph{Note: while a @code{Bss} offset may be included in the response,
23790 @value{GDBN} ignores this and instead applies the @code{Data} offset
23791 to the @code{Bss} section.}
23793 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
23794 Relocate the first segment of the object file, which conventionally
23795 contains program code, to a starting address of @var{xxx}. If
23796 @samp{DataSeg} is specified, relocate the second segment, which
23797 conventionally contains modifiable data, to a starting address of
23798 @var{yyy}. @value{GDBN} will report an error if the object file
23799 does not contain segment information, or does not contain at least
23800 as many segments as mentioned in the reply. Extra segments are
23801 kept at fixed offsets relative to the last relocated segment.
23804 @item qP @var{mode} @var{threadid}
23805 @cindex thread information, remote request
23806 @cindex @samp{qP} packet
23807 Returns information on @var{threadid}. Where: @var{mode} is a hex
23808 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
23810 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
23813 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
23815 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
23816 @cindex pass signals to inferior, remote request
23817 @cindex @samp{QPassSignals} packet
23818 @anchor{QPassSignals}
23819 Each listed @var{signal} should be passed directly to the inferior process.
23820 Signals are numbered identically to continue packets and stop replies
23821 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
23822 strictly greater than the previous item. These signals do not need to stop
23823 the inferior, or be reported to @value{GDBN}. All other signals should be
23824 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
23825 combine; any earlier @samp{QPassSignals} list is completely replaced by the
23826 new list. This packet improves performance when using @samp{handle
23827 @var{signal} nostop noprint pass}.
23832 The request succeeded.
23835 An error occurred. @var{nn} are hex digits.
23838 An empty reply indicates that @samp{QPassSignals} is not supported by
23842 Use of this packet is controlled by the @code{set remote pass-signals}
23843 command (@pxref{Remote Configuration, set remote pass-signals}).
23844 This packet is not probed by default; the remote stub must request it,
23845 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
23847 @item qRcmd,@var{command}
23848 @cindex execute remote command, remote request
23849 @cindex @samp{qRcmd} packet
23850 @var{command} (hex encoded) is passed to the local interpreter for
23851 execution. Invalid commands should be reported using the output
23852 string. Before the final result packet, the target may also respond
23853 with a number of intermediate @samp{O@var{output}} console output
23854 packets. @emph{Implementors should note that providing access to a
23855 stubs's interpreter may have security implications}.
23860 A command response with no output.
23862 A command response with the hex encoded output string @var{OUTPUT}.
23864 Indicate a badly formed request.
23866 An empty reply indicates that @samp{qRcmd} is not recognized.
23869 (Note that the @code{qRcmd} packet's name is separated from the
23870 command by a @samp{,}, not a @samp{:}, contrary to the naming
23871 conventions above. Please don't use this packet as a model for new
23874 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
23875 @cindex supported packets, remote query
23876 @cindex features of the remote protocol
23877 @cindex @samp{qSupported} packet
23878 @anchor{qSupported}
23879 Tell the remote stub about features supported by @value{GDBN}, and
23880 query the stub for features it supports. This packet allows
23881 @value{GDBN} and the remote stub to take advantage of each others'
23882 features. @samp{qSupported} also consolidates multiple feature probes
23883 at startup, to improve @value{GDBN} performance---a single larger
23884 packet performs better than multiple smaller probe packets on
23885 high-latency links. Some features may enable behavior which must not
23886 be on by default, e.g.@: because it would confuse older clients or
23887 stubs. Other features may describe packets which could be
23888 automatically probed for, but are not. These features must be
23889 reported before @value{GDBN} will use them. This ``default
23890 unsupported'' behavior is not appropriate for all packets, but it
23891 helps to keep the initial connection time under control with new
23892 versions of @value{GDBN} which support increasing numbers of packets.
23896 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
23897 The stub supports or does not support each returned @var{stubfeature},
23898 depending on the form of each @var{stubfeature} (see below for the
23901 An empty reply indicates that @samp{qSupported} is not recognized,
23902 or that no features needed to be reported to @value{GDBN}.
23905 The allowed forms for each feature (either a @var{gdbfeature} in the
23906 @samp{qSupported} packet, or a @var{stubfeature} in the response)
23910 @item @var{name}=@var{value}
23911 The remote protocol feature @var{name} is supported, and associated
23912 with the specified @var{value}. The format of @var{value} depends
23913 on the feature, but it must not include a semicolon.
23915 The remote protocol feature @var{name} is supported, and does not
23916 need an associated value.
23918 The remote protocol feature @var{name} is not supported.
23920 The remote protocol feature @var{name} may be supported, and
23921 @value{GDBN} should auto-detect support in some other way when it is
23922 needed. This form will not be used for @var{gdbfeature} notifications,
23923 but may be used for @var{stubfeature} responses.
23926 Whenever the stub receives a @samp{qSupported} request, the
23927 supplied set of @value{GDBN} features should override any previous
23928 request. This allows @value{GDBN} to put the stub in a known
23929 state, even if the stub had previously been communicating with
23930 a different version of @value{GDBN}.
23932 No values of @var{gdbfeature} (for the packet sent by @value{GDBN})
23933 are defined yet. Stubs should ignore any unknown values for
23934 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
23935 packet supports receiving packets of unlimited length (earlier
23936 versions of @value{GDBN} may reject overly long responses). Values
23937 for @var{gdbfeature} may be defined in the future to let the stub take
23938 advantage of new features in @value{GDBN}, e.g.@: incompatible
23939 improvements in the remote protocol---support for unlimited length
23940 responses would be a @var{gdbfeature} example, if it were not implied by
23941 the @samp{qSupported} query. The stub's reply should be independent
23942 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
23943 describes all the features it supports, and then the stub replies with
23944 all the features it supports.
23946 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
23947 responses, as long as each response uses one of the standard forms.
23949 Some features are flags. A stub which supports a flag feature
23950 should respond with a @samp{+} form response. Other features
23951 require values, and the stub should respond with an @samp{=}
23954 Each feature has a default value, which @value{GDBN} will use if
23955 @samp{qSupported} is not available or if the feature is not mentioned
23956 in the @samp{qSupported} response. The default values are fixed; a
23957 stub is free to omit any feature responses that match the defaults.
23959 Not all features can be probed, but for those which can, the probing
23960 mechanism is useful: in some cases, a stub's internal
23961 architecture may not allow the protocol layer to know some information
23962 about the underlying target in advance. This is especially common in
23963 stubs which may be configured for multiple targets.
23965 These are the currently defined stub features and their properties:
23967 @multitable @columnfractions 0.35 0.2 0.12 0.2
23968 @c NOTE: The first row should be @headitem, but we do not yet require
23969 @c a new enough version of Texinfo (4.7) to use @headitem.
23971 @tab Value Required
23975 @item @samp{PacketSize}
23980 @item @samp{qXfer:auxv:read}
23985 @item @samp{qXfer:features:read}
23990 @item @samp{qXfer:libraries:read}
23995 @item @samp{qXfer:memory-map:read}
24000 @item @samp{qXfer:spu:read}
24005 @item @samp{qXfer:spu:write}
24010 @item @samp{QPassSignals}
24017 These are the currently defined stub features, in more detail:
24020 @cindex packet size, remote protocol
24021 @item PacketSize=@var{bytes}
24022 The remote stub can accept packets up to at least @var{bytes} in
24023 length. @value{GDBN} will send packets up to this size for bulk
24024 transfers, and will never send larger packets. This is a limit on the
24025 data characters in the packet, including the frame and checksum.
24026 There is no trailing NUL byte in a remote protocol packet; if the stub
24027 stores packets in a NUL-terminated format, it should allow an extra
24028 byte in its buffer for the NUL. If this stub feature is not supported,
24029 @value{GDBN} guesses based on the size of the @samp{g} packet response.
24031 @item qXfer:auxv:read
24032 The remote stub understands the @samp{qXfer:auxv:read} packet
24033 (@pxref{qXfer auxiliary vector read}).
24035 @item qXfer:features:read
24036 The remote stub understands the @samp{qXfer:features:read} packet
24037 (@pxref{qXfer target description read}).
24039 @item qXfer:libraries:read
24040 The remote stub understands the @samp{qXfer:libraries:read} packet
24041 (@pxref{qXfer library list read}).
24043 @item qXfer:memory-map:read
24044 The remote stub understands the @samp{qXfer:memory-map:read} packet
24045 (@pxref{qXfer memory map read}).
24047 @item qXfer:spu:read
24048 The remote stub understands the @samp{qXfer:spu:read} packet
24049 (@pxref{qXfer spu read}).
24051 @item qXfer:spu:write
24052 The remote stub understands the @samp{qXfer:spu:write} packet
24053 (@pxref{qXfer spu write}).
24056 The remote stub understands the @samp{QPassSignals} packet
24057 (@pxref{QPassSignals}).
24062 @cindex symbol lookup, remote request
24063 @cindex @samp{qSymbol} packet
24064 Notify the target that @value{GDBN} is prepared to serve symbol lookup
24065 requests. Accept requests from the target for the values of symbols.
24070 The target does not need to look up any (more) symbols.
24071 @item qSymbol:@var{sym_name}
24072 The target requests the value of symbol @var{sym_name} (hex encoded).
24073 @value{GDBN} may provide the value by using the
24074 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
24078 @item qSymbol:@var{sym_value}:@var{sym_name}
24079 Set the value of @var{sym_name} to @var{sym_value}.
24081 @var{sym_name} (hex encoded) is the name of a symbol whose value the
24082 target has previously requested.
24084 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
24085 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
24091 The target does not need to look up any (more) symbols.
24092 @item qSymbol:@var{sym_name}
24093 The target requests the value of a new symbol @var{sym_name} (hex
24094 encoded). @value{GDBN} will continue to supply the values of symbols
24095 (if available), until the target ceases to request them.
24100 @xref{Tracepoint Packets}.
24102 @item qThreadExtraInfo,@var{id}
24103 @cindex thread attributes info, remote request
24104 @cindex @samp{qThreadExtraInfo} packet
24105 Obtain a printable string description of a thread's attributes from
24106 the target OS. @var{id} is a thread-id in big-endian hex. This
24107 string may contain anything that the target OS thinks is interesting
24108 for @value{GDBN} to tell the user about the thread. The string is
24109 displayed in @value{GDBN}'s @code{info threads} display. Some
24110 examples of possible thread extra info strings are @samp{Runnable}, or
24111 @samp{Blocked on Mutex}.
24115 @item @var{XX}@dots{}
24116 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
24117 comprising the printable string containing the extra information about
24118 the thread's attributes.
24121 (Note that the @code{qThreadExtraInfo} packet's name is separated from
24122 the command by a @samp{,}, not a @samp{:}, contrary to the naming
24123 conventions above. Please don't use this packet as a model for new
24131 @xref{Tracepoint Packets}.
24133 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
24134 @cindex read special object, remote request
24135 @cindex @samp{qXfer} packet
24136 @anchor{qXfer read}
24137 Read uninterpreted bytes from the target's special data area
24138 identified by the keyword @var{object}. Request @var{length} bytes
24139 starting at @var{offset} bytes into the data. The content and
24140 encoding of @var{annex} is specific to @var{object}; it can supply
24141 additional details about what data to access.
24143 Here are the specific requests of this form defined so far. All
24144 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
24145 formats, listed below.
24148 @item qXfer:auxv:read::@var{offset},@var{length}
24149 @anchor{qXfer auxiliary vector read}
24150 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
24151 auxiliary vector}. Note @var{annex} must be empty.
24153 This packet is not probed by default; the remote stub must request it,
24154 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24156 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
24157 @anchor{qXfer target description read}
24158 Access the @dfn{target description}. @xref{Target Descriptions}. The
24159 annex specifies which XML document to access. The main description is
24160 always loaded from the @samp{target.xml} annex.
24162 This packet is not probed by default; the remote stub must request it,
24163 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24165 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
24166 @anchor{qXfer library list read}
24167 Access the target's list of loaded libraries. @xref{Library List Format}.
24168 The annex part of the generic @samp{qXfer} packet must be empty
24169 (@pxref{qXfer read}).
24171 Targets which maintain a list of libraries in the program's memory do
24172 not need to implement this packet; it is designed for platforms where
24173 the operating system manages the list of loaded libraries.
24175 This packet is not probed by default; the remote stub must request it,
24176 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24178 @item qXfer:memory-map:read::@var{offset},@var{length}
24179 @anchor{qXfer memory map read}
24180 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
24181 annex part of the generic @samp{qXfer} packet must be empty
24182 (@pxref{qXfer read}).
24184 This packet is not probed by default; the remote stub must request it,
24185 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24187 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
24188 @anchor{qXfer spu read}
24189 Read contents of an @code{spufs} file on the target system. The
24190 annex specifies which file to read; it must be of the form
24191 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
24192 in the target process, and @var{name} identifes the @code{spufs} file
24193 in that context to be accessed.
24195 This packet is not probed by default; the remote stub must request it,
24196 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24202 Data @var{data} (@pxref{Binary Data}) has been read from the
24203 target. There may be more data at a higher address (although
24204 it is permitted to return @samp{m} even for the last valid
24205 block of data, as long as at least one byte of data was read).
24206 @var{data} may have fewer bytes than the @var{length} in the
24210 Data @var{data} (@pxref{Binary Data}) has been read from the target.
24211 There is no more data to be read. @var{data} may have fewer bytes
24212 than the @var{length} in the request.
24215 The @var{offset} in the request is at the end of the data.
24216 There is no more data to be read.
24219 The request was malformed, or @var{annex} was invalid.
24222 The offset was invalid, or there was an error encountered reading the data.
24223 @var{nn} is a hex-encoded @code{errno} value.
24226 An empty reply indicates the @var{object} string was not recognized by
24227 the stub, or that the object does not support reading.
24230 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
24231 @cindex write data into object, remote request
24232 Write uninterpreted bytes into the target's special data area
24233 identified by the keyword @var{object}, starting at @var{offset} bytes
24234 into the data. @var{data}@dots{} is the binary-encoded data
24235 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
24236 is specific to @var{object}; it can supply additional details about what data
24239 Here are the specific requests of this form defined so far. All
24240 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
24241 formats, listed below.
24244 @item qXfer:@var{spu}:write:@var{annex}:@var{offset}:@var{data}@dots{}
24245 @anchor{qXfer spu write}
24246 Write @var{data} to an @code{spufs} file on the target system. The
24247 annex specifies which file to write; it must be of the form
24248 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
24249 in the target process, and @var{name} identifes the @code{spufs} file
24250 in that context to be accessed.
24252 This packet is not probed by default; the remote stub must request it,
24253 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
24259 @var{nn} (hex encoded) is the number of bytes written.
24260 This may be fewer bytes than supplied in the request.
24263 The request was malformed, or @var{annex} was invalid.
24266 The offset was invalid, or there was an error encountered writing the data.
24267 @var{nn} is a hex-encoded @code{errno} value.
24270 An empty reply indicates the @var{object} string was not
24271 recognized by the stub, or that the object does not support writing.
24274 @item qXfer:@var{object}:@var{operation}:@dots{}
24275 Requests of this form may be added in the future. When a stub does
24276 not recognize the @var{object} keyword, or its support for
24277 @var{object} does not recognize the @var{operation} keyword, the stub
24278 must respond with an empty packet.
24282 @node Register Packet Format
24283 @section Register Packet Format
24285 The following @code{g}/@code{G} packets have previously been defined.
24286 In the below, some thirty-two bit registers are transferred as
24287 sixty-four bits. Those registers should be zero/sign extended (which?)
24288 to fill the space allocated. Register bytes are transferred in target
24289 byte order. The two nibbles within a register byte are transferred
24290 most-significant - least-significant.
24296 All registers are transferred as thirty-two bit quantities in the order:
24297 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
24298 registers; fsr; fir; fp.
24302 All registers are transferred as sixty-four bit quantities (including
24303 thirty-two bit registers such as @code{sr}). The ordering is the same
24308 @node Tracepoint Packets
24309 @section Tracepoint Packets
24310 @cindex tracepoint packets
24311 @cindex packets, tracepoint
24313 Here we describe the packets @value{GDBN} uses to implement
24314 tracepoints (@pxref{Tracepoints}).
24318 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}@r{[}-@r{]}
24319 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
24320 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
24321 the tracepoint is disabled. @var{step} is the tracepoint's step
24322 count, and @var{pass} is its pass count. If the trailing @samp{-} is
24323 present, further @samp{QTDP} packets will follow to specify this
24324 tracepoint's actions.
24329 The packet was understood and carried out.
24331 The packet was not recognized.
24334 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
24335 Define actions to be taken when a tracepoint is hit. @var{n} and
24336 @var{addr} must be the same as in the initial @samp{QTDP} packet for
24337 this tracepoint. This packet may only be sent immediately after
24338 another @samp{QTDP} packet that ended with a @samp{-}. If the
24339 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
24340 specifying more actions for this tracepoint.
24342 In the series of action packets for a given tracepoint, at most one
24343 can have an @samp{S} before its first @var{action}. If such a packet
24344 is sent, it and the following packets define ``while-stepping''
24345 actions. Any prior packets define ordinary actions --- that is, those
24346 taken when the tracepoint is first hit. If no action packet has an
24347 @samp{S}, then all the packets in the series specify ordinary
24348 tracepoint actions.
24350 The @samp{@var{action}@dots{}} portion of the packet is a series of
24351 actions, concatenated without separators. Each action has one of the
24357 Collect the registers whose bits are set in @var{mask}. @var{mask} is
24358 a hexadecimal number whose @var{i}'th bit is set if register number
24359 @var{i} should be collected. (The least significant bit is numbered
24360 zero.) Note that @var{mask} may be any number of digits long; it may
24361 not fit in a 32-bit word.
24363 @item M @var{basereg},@var{offset},@var{len}
24364 Collect @var{len} bytes of memory starting at the address in register
24365 number @var{basereg}, plus @var{offset}. If @var{basereg} is
24366 @samp{-1}, then the range has a fixed address: @var{offset} is the
24367 address of the lowest byte to collect. The @var{basereg},
24368 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
24369 values (the @samp{-1} value for @var{basereg} is a special case).
24371 @item X @var{len},@var{expr}
24372 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
24373 it directs. @var{expr} is an agent expression, as described in
24374 @ref{Agent Expressions}. Each byte of the expression is encoded as a
24375 two-digit hex number in the packet; @var{len} is the number of bytes
24376 in the expression (and thus one-half the number of hex digits in the
24381 Any number of actions may be packed together in a single @samp{QTDP}
24382 packet, as long as the packet does not exceed the maximum packet
24383 length (400 bytes, for many stubs). There may be only one @samp{R}
24384 action per tracepoint, and it must precede any @samp{M} or @samp{X}
24385 actions. Any registers referred to by @samp{M} and @samp{X} actions
24386 must be collected by a preceding @samp{R} action. (The
24387 ``while-stepping'' actions are treated as if they were attached to a
24388 separate tracepoint, as far as these restrictions are concerned.)
24393 The packet was understood and carried out.
24395 The packet was not recognized.
24398 @item QTFrame:@var{n}
24399 Select the @var{n}'th tracepoint frame from the buffer, and use the
24400 register and memory contents recorded there to answer subsequent
24401 request packets from @value{GDBN}.
24403 A successful reply from the stub indicates that the stub has found the
24404 requested frame. The response is a series of parts, concatenated
24405 without separators, describing the frame we selected. Each part has
24406 one of the following forms:
24410 The selected frame is number @var{n} in the trace frame buffer;
24411 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
24412 was no frame matching the criteria in the request packet.
24415 The selected trace frame records a hit of tracepoint number @var{t};
24416 @var{t} is a hexadecimal number.
24420 @item QTFrame:pc:@var{addr}
24421 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
24422 currently selected frame whose PC is @var{addr};
24423 @var{addr} is a hexadecimal number.
24425 @item QTFrame:tdp:@var{t}
24426 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
24427 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
24428 is a hexadecimal number.
24430 @item QTFrame:range:@var{start}:@var{end}
24431 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
24432 currently selected frame whose PC is between @var{start} (inclusive)
24433 and @var{end} (exclusive); @var{start} and @var{end} are hexadecimal
24436 @item QTFrame:outside:@var{start}:@var{end}
24437 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
24438 frame @emph{outside} the given range of addresses.
24441 Begin the tracepoint experiment. Begin collecting data from tracepoint
24442 hits in the trace frame buffer.
24445 End the tracepoint experiment. Stop collecting trace frames.
24448 Clear the table of tracepoints, and empty the trace frame buffer.
24450 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
24451 Establish the given ranges of memory as ``transparent''. The stub
24452 will answer requests for these ranges from memory's current contents,
24453 if they were not collected as part of the tracepoint hit.
24455 @value{GDBN} uses this to mark read-only regions of memory, like those
24456 containing program code. Since these areas never change, they should
24457 still have the same contents they did when the tracepoint was hit, so
24458 there's no reason for the stub to refuse to provide their contents.
24461 Ask the stub if there is a trace experiment running right now.
24466 There is no trace experiment running.
24468 There is a trace experiment running.
24475 @section Interrupts
24476 @cindex interrupts (remote protocol)
24478 When a program on the remote target is running, @value{GDBN} may
24479 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
24480 control of which is specified via @value{GDBN}'s @samp{remotebreak}
24481 setting (@pxref{set remotebreak}).
24483 The precise meaning of @code{BREAK} is defined by the transport
24484 mechanism and may, in fact, be undefined. @value{GDBN} does
24485 not currently define a @code{BREAK} mechanism for any of the network
24488 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
24489 transport mechanisms. It is represented by sending the single byte
24490 @code{0x03} without any of the usual packet overhead described in
24491 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
24492 transmitted as part of a packet, it is considered to be packet data
24493 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
24494 (@pxref{X packet}), used for binary downloads, may include an unescaped
24495 @code{0x03} as part of its packet.
24497 Stubs are not required to recognize these interrupt mechanisms and the
24498 precise meaning associated with receipt of the interrupt is
24499 implementation defined. If the stub is successful at interrupting the
24500 running program, it is expected that it will send one of the Stop
24501 Reply Packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
24502 of successfully stopping the program. Interrupts received while the
24503 program is stopped will be discarded.
24508 Example sequence of a target being re-started. Notice how the restart
24509 does not get any direct output:
24514 @emph{target restarts}
24517 <- @code{T001:1234123412341234}
24521 Example sequence of a target being stepped by a single instruction:
24524 -> @code{G1445@dots{}}
24529 <- @code{T001:1234123412341234}
24533 <- @code{1455@dots{}}
24537 @node File-I/O Remote Protocol Extension
24538 @section File-I/O Remote Protocol Extension
24539 @cindex File-I/O remote protocol extension
24542 * File-I/O Overview::
24543 * Protocol Basics::
24544 * The F Request Packet::
24545 * The F Reply Packet::
24546 * The Ctrl-C Message::
24548 * List of Supported Calls::
24549 * Protocol-specific Representation of Datatypes::
24551 * File-I/O Examples::
24554 @node File-I/O Overview
24555 @subsection File-I/O Overview
24556 @cindex file-i/o overview
24558 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
24559 target to use the host's file system and console I/O to perform various
24560 system calls. System calls on the target system are translated into a
24561 remote protocol packet to the host system, which then performs the needed
24562 actions and returns a response packet to the target system.
24563 This simulates file system operations even on targets that lack file systems.
24565 The protocol is defined to be independent of both the host and target systems.
24566 It uses its own internal representation of datatypes and values. Both
24567 @value{GDBN} and the target's @value{GDBN} stub are responsible for
24568 translating the system-dependent value representations into the internal
24569 protocol representations when data is transmitted.
24571 The communication is synchronous. A system call is possible only when
24572 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
24573 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
24574 the target is stopped to allow deterministic access to the target's
24575 memory. Therefore File-I/O is not interruptible by target signals. On
24576 the other hand, it is possible to interrupt File-I/O by a user interrupt
24577 (@samp{Ctrl-C}) within @value{GDBN}.
24579 The target's request to perform a host system call does not finish
24580 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
24581 after finishing the system call, the target returns to continuing the
24582 previous activity (continue, step). No additional continue or step
24583 request from @value{GDBN} is required.
24586 (@value{GDBP}) continue
24587 <- target requests 'system call X'
24588 target is stopped, @value{GDBN} executes system call
24589 -> @value{GDBN} returns result
24590 ... target continues, @value{GDBN} returns to wait for the target
24591 <- target hits breakpoint and sends a Txx packet
24594 The protocol only supports I/O on the console and to regular files on
24595 the host file system. Character or block special devices, pipes,
24596 named pipes, sockets or any other communication method on the host
24597 system are not supported by this protocol.
24599 @node Protocol Basics
24600 @subsection Protocol Basics
24601 @cindex protocol basics, file-i/o
24603 The File-I/O protocol uses the @code{F} packet as the request as well
24604 as reply packet. Since a File-I/O system call can only occur when
24605 @value{GDBN} is waiting for a response from the continuing or stepping target,
24606 the File-I/O request is a reply that @value{GDBN} has to expect as a result
24607 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
24608 This @code{F} packet contains all information needed to allow @value{GDBN}
24609 to call the appropriate host system call:
24613 A unique identifier for the requested system call.
24616 All parameters to the system call. Pointers are given as addresses
24617 in the target memory address space. Pointers to strings are given as
24618 pointer/length pair. Numerical values are given as they are.
24619 Numerical control flags are given in a protocol-specific representation.
24623 At this point, @value{GDBN} has to perform the following actions.
24627 If the parameters include pointer values to data needed as input to a
24628 system call, @value{GDBN} requests this data from the target with a
24629 standard @code{m} packet request. This additional communication has to be
24630 expected by the target implementation and is handled as any other @code{m}
24634 @value{GDBN} translates all value from protocol representation to host
24635 representation as needed. Datatypes are coerced into the host types.
24638 @value{GDBN} calls the system call.
24641 It then coerces datatypes back to protocol representation.
24644 If the system call is expected to return data in buffer space specified
24645 by pointer parameters to the call, the data is transmitted to the
24646 target using a @code{M} or @code{X} packet. This packet has to be expected
24647 by the target implementation and is handled as any other @code{M} or @code{X}
24652 Eventually @value{GDBN} replies with another @code{F} packet which contains all
24653 necessary information for the target to continue. This at least contains
24660 @code{errno}, if has been changed by the system call.
24667 After having done the needed type and value coercion, the target continues
24668 the latest continue or step action.
24670 @node The F Request Packet
24671 @subsection The @code{F} Request Packet
24672 @cindex file-i/o request packet
24673 @cindex @code{F} request packet
24675 The @code{F} request packet has the following format:
24678 @item F@var{call-id},@var{parameter@dots{}}
24680 @var{call-id} is the identifier to indicate the host system call to be called.
24681 This is just the name of the function.
24683 @var{parameter@dots{}} are the parameters to the system call.
24684 Parameters are hexadecimal integer values, either the actual values in case
24685 of scalar datatypes, pointers to target buffer space in case of compound
24686 datatypes and unspecified memory areas, or pointer/length pairs in case
24687 of string parameters. These are appended to the @var{call-id} as a
24688 comma-delimited list. All values are transmitted in ASCII
24689 string representation, pointer/length pairs separated by a slash.
24695 @node The F Reply Packet
24696 @subsection The @code{F} Reply Packet
24697 @cindex file-i/o reply packet
24698 @cindex @code{F} reply packet
24700 The @code{F} reply packet has the following format:
24704 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
24706 @var{retcode} is the return code of the system call as hexadecimal value.
24708 @var{errno} is the @code{errno} set by the call, in protocol-specific
24710 This parameter can be omitted if the call was successful.
24712 @var{Ctrl-C flag} is only sent if the user requested a break. In this
24713 case, @var{errno} must be sent as well, even if the call was successful.
24714 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
24721 or, if the call was interrupted before the host call has been performed:
24728 assuming 4 is the protocol-specific representation of @code{EINTR}.
24733 @node The Ctrl-C Message
24734 @subsection The @samp{Ctrl-C} Message
24735 @cindex ctrl-c message, in file-i/o protocol
24737 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
24738 reply packet (@pxref{The F Reply Packet}),
24739 the target should behave as if it had
24740 gotten a break message. The meaning for the target is ``system call
24741 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
24742 (as with a break message) and return to @value{GDBN} with a @code{T02}
24745 It's important for the target to know in which
24746 state the system call was interrupted. There are two possible cases:
24750 The system call hasn't been performed on the host yet.
24753 The system call on the host has been finished.
24757 These two states can be distinguished by the target by the value of the
24758 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
24759 call hasn't been performed. This is equivalent to the @code{EINTR} handling
24760 on POSIX systems. In any other case, the target may presume that the
24761 system call has been finished --- successfully or not --- and should behave
24762 as if the break message arrived right after the system call.
24764 @value{GDBN} must behave reliably. If the system call has not been called
24765 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
24766 @code{errno} in the packet. If the system call on the host has been finished
24767 before the user requests a break, the full action must be finished by
24768 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
24769 The @code{F} packet may only be sent when either nothing has happened
24770 or the full action has been completed.
24773 @subsection Console I/O
24774 @cindex console i/o as part of file-i/o
24776 By default and if not explicitly closed by the target system, the file
24777 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
24778 on the @value{GDBN} console is handled as any other file output operation
24779 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
24780 by @value{GDBN} so that after the target read request from file descriptor
24781 0 all following typing is buffered until either one of the following
24786 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
24788 system call is treated as finished.
24791 The user presses @key{RET}. This is treated as end of input with a trailing
24795 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
24796 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
24800 If the user has typed more characters than fit in the buffer given to
24801 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
24802 either another @code{read(0, @dots{})} is requested by the target, or debugging
24803 is stopped at the user's request.
24806 @node List of Supported Calls
24807 @subsection List of Supported Calls
24808 @cindex list of supported file-i/o calls
24825 @unnumberedsubsubsec open
24826 @cindex open, file-i/o system call
24831 int open(const char *pathname, int flags);
24832 int open(const char *pathname, int flags, mode_t mode);
24836 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
24839 @var{flags} is the bitwise @code{OR} of the following values:
24843 If the file does not exist it will be created. The host
24844 rules apply as far as file ownership and time stamps
24848 When used with @code{O_CREAT}, if the file already exists it is
24849 an error and open() fails.
24852 If the file already exists and the open mode allows
24853 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
24854 truncated to zero length.
24857 The file is opened in append mode.
24860 The file is opened for reading only.
24863 The file is opened for writing only.
24866 The file is opened for reading and writing.
24870 Other bits are silently ignored.
24874 @var{mode} is the bitwise @code{OR} of the following values:
24878 User has read permission.
24881 User has write permission.
24884 Group has read permission.
24887 Group has write permission.
24890 Others have read permission.
24893 Others have write permission.
24897 Other bits are silently ignored.
24900 @item Return value:
24901 @code{open} returns the new file descriptor or -1 if an error
24908 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
24911 @var{pathname} refers to a directory.
24914 The requested access is not allowed.
24917 @var{pathname} was too long.
24920 A directory component in @var{pathname} does not exist.
24923 @var{pathname} refers to a device, pipe, named pipe or socket.
24926 @var{pathname} refers to a file on a read-only filesystem and
24927 write access was requested.
24930 @var{pathname} is an invalid pointer value.
24933 No space on device to create the file.
24936 The process already has the maximum number of files open.
24939 The limit on the total number of files open on the system
24943 The call was interrupted by the user.
24949 @unnumberedsubsubsec close
24950 @cindex close, file-i/o system call
24959 @samp{Fclose,@var{fd}}
24961 @item Return value:
24962 @code{close} returns zero on success, or -1 if an error occurred.
24968 @var{fd} isn't a valid open file descriptor.
24971 The call was interrupted by the user.
24977 @unnumberedsubsubsec read
24978 @cindex read, file-i/o system call
24983 int read(int fd, void *buf, unsigned int count);
24987 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
24989 @item Return value:
24990 On success, the number of bytes read is returned.
24991 Zero indicates end of file. If count is zero, read
24992 returns zero as well. On error, -1 is returned.
24998 @var{fd} is not a valid file descriptor or is not open for
25002 @var{bufptr} is an invalid pointer value.
25005 The call was interrupted by the user.
25011 @unnumberedsubsubsec write
25012 @cindex write, file-i/o system call
25017 int write(int fd, const void *buf, unsigned int count);
25021 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
25023 @item Return value:
25024 On success, the number of bytes written are returned.
25025 Zero indicates nothing was written. On error, -1
25032 @var{fd} is not a valid file descriptor or is not open for
25036 @var{bufptr} is an invalid pointer value.
25039 An attempt was made to write a file that exceeds the
25040 host-specific maximum file size allowed.
25043 No space on device to write the data.
25046 The call was interrupted by the user.
25052 @unnumberedsubsubsec lseek
25053 @cindex lseek, file-i/o system call
25058 long lseek (int fd, long offset, int flag);
25062 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
25064 @var{flag} is one of:
25068 The offset is set to @var{offset} bytes.
25071 The offset is set to its current location plus @var{offset}
25075 The offset is set to the size of the file plus @var{offset}
25079 @item Return value:
25080 On success, the resulting unsigned offset in bytes from
25081 the beginning of the file is returned. Otherwise, a
25082 value of -1 is returned.
25088 @var{fd} is not a valid open file descriptor.
25091 @var{fd} is associated with the @value{GDBN} console.
25094 @var{flag} is not a proper value.
25097 The call was interrupted by the user.
25103 @unnumberedsubsubsec rename
25104 @cindex rename, file-i/o system call
25109 int rename(const char *oldpath, const char *newpath);
25113 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
25115 @item Return value:
25116 On success, zero is returned. On error, -1 is returned.
25122 @var{newpath} is an existing directory, but @var{oldpath} is not a
25126 @var{newpath} is a non-empty directory.
25129 @var{oldpath} or @var{newpath} is a directory that is in use by some
25133 An attempt was made to make a directory a subdirectory
25137 A component used as a directory in @var{oldpath} or new
25138 path is not a directory. Or @var{oldpath} is a directory
25139 and @var{newpath} exists but is not a directory.
25142 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
25145 No access to the file or the path of the file.
25149 @var{oldpath} or @var{newpath} was too long.
25152 A directory component in @var{oldpath} or @var{newpath} does not exist.
25155 The file is on a read-only filesystem.
25158 The device containing the file has no room for the new
25162 The call was interrupted by the user.
25168 @unnumberedsubsubsec unlink
25169 @cindex unlink, file-i/o system call
25174 int unlink(const char *pathname);
25178 @samp{Funlink,@var{pathnameptr}/@var{len}}
25180 @item Return value:
25181 On success, zero is returned. On error, -1 is returned.
25187 No access to the file or the path of the file.
25190 The system does not allow unlinking of directories.
25193 The file @var{pathname} cannot be unlinked because it's
25194 being used by another process.
25197 @var{pathnameptr} is an invalid pointer value.
25200 @var{pathname} was too long.
25203 A directory component in @var{pathname} does not exist.
25206 A component of the path is not a directory.
25209 The file is on a read-only filesystem.
25212 The call was interrupted by the user.
25218 @unnumberedsubsubsec stat/fstat
25219 @cindex fstat, file-i/o system call
25220 @cindex stat, file-i/o system call
25225 int stat(const char *pathname, struct stat *buf);
25226 int fstat(int fd, struct stat *buf);
25230 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
25231 @samp{Ffstat,@var{fd},@var{bufptr}}
25233 @item Return value:
25234 On success, zero is returned. On error, -1 is returned.
25240 @var{fd} is not a valid open file.
25243 A directory component in @var{pathname} does not exist or the
25244 path is an empty string.
25247 A component of the path is not a directory.
25250 @var{pathnameptr} is an invalid pointer value.
25253 No access to the file or the path of the file.
25256 @var{pathname} was too long.
25259 The call was interrupted by the user.
25265 @unnumberedsubsubsec gettimeofday
25266 @cindex gettimeofday, file-i/o system call
25271 int gettimeofday(struct timeval *tv, void *tz);
25275 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
25277 @item Return value:
25278 On success, 0 is returned, -1 otherwise.
25284 @var{tz} is a non-NULL pointer.
25287 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
25293 @unnumberedsubsubsec isatty
25294 @cindex isatty, file-i/o system call
25299 int isatty(int fd);
25303 @samp{Fisatty,@var{fd}}
25305 @item Return value:
25306 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
25312 The call was interrupted by the user.
25317 Note that the @code{isatty} call is treated as a special case: it returns
25318 1 to the target if the file descriptor is attached
25319 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
25320 would require implementing @code{ioctl} and would be more complex than
25325 @unnumberedsubsubsec system
25326 @cindex system, file-i/o system call
25331 int system(const char *command);
25335 @samp{Fsystem,@var{commandptr}/@var{len}}
25337 @item Return value:
25338 If @var{len} is zero, the return value indicates whether a shell is
25339 available. A zero return value indicates a shell is not available.
25340 For non-zero @var{len}, the value returned is -1 on error and the
25341 return status of the command otherwise. Only the exit status of the
25342 command is returned, which is extracted from the host's @code{system}
25343 return value by calling @code{WEXITSTATUS(retval)}. In case
25344 @file{/bin/sh} could not be executed, 127 is returned.
25350 The call was interrupted by the user.
25355 @value{GDBN} takes over the full task of calling the necessary host calls
25356 to perform the @code{system} call. The return value of @code{system} on
25357 the host is simplified before it's returned
25358 to the target. Any termination signal information from the child process
25359 is discarded, and the return value consists
25360 entirely of the exit status of the called command.
25362 Due to security concerns, the @code{system} call is by default refused
25363 by @value{GDBN}. The user has to allow this call explicitly with the
25364 @code{set remote system-call-allowed 1} command.
25367 @item set remote system-call-allowed
25368 @kindex set remote system-call-allowed
25369 Control whether to allow the @code{system} calls in the File I/O
25370 protocol for the remote target. The default is zero (disabled).
25372 @item show remote system-call-allowed
25373 @kindex show remote system-call-allowed
25374 Show whether the @code{system} calls are allowed in the File I/O
25378 @node Protocol-specific Representation of Datatypes
25379 @subsection Protocol-specific Representation of Datatypes
25380 @cindex protocol-specific representation of datatypes, in file-i/o protocol
25383 * Integral Datatypes::
25385 * Memory Transfer::
25390 @node Integral Datatypes
25391 @unnumberedsubsubsec Integral Datatypes
25392 @cindex integral datatypes, in file-i/o protocol
25394 The integral datatypes used in the system calls are @code{int},
25395 @code{unsigned int}, @code{long}, @code{unsigned long},
25396 @code{mode_t}, and @code{time_t}.
25398 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
25399 implemented as 32 bit values in this protocol.
25401 @code{long} and @code{unsigned long} are implemented as 64 bit types.
25403 @xref{Limits}, for corresponding MIN and MAX values (similar to those
25404 in @file{limits.h}) to allow range checking on host and target.
25406 @code{time_t} datatypes are defined as seconds since the Epoch.
25408 All integral datatypes transferred as part of a memory read or write of a
25409 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
25412 @node Pointer Values
25413 @unnumberedsubsubsec Pointer Values
25414 @cindex pointer values, in file-i/o protocol
25416 Pointers to target data are transmitted as they are. An exception
25417 is made for pointers to buffers for which the length isn't
25418 transmitted as part of the function call, namely strings. Strings
25419 are transmitted as a pointer/length pair, both as hex values, e.g.@:
25426 which is a pointer to data of length 18 bytes at position 0x1aaf.
25427 The length is defined as the full string length in bytes, including
25428 the trailing null byte. For example, the string @code{"hello world"}
25429 at address 0x123456 is transmitted as
25435 @node Memory Transfer
25436 @unnumberedsubsubsec Memory Transfer
25437 @cindex memory transfer, in file-i/o protocol
25439 Structured data which is transferred using a memory read or write (for
25440 example, a @code{struct stat}) is expected to be in a protocol-specific format
25441 with all scalar multibyte datatypes being big endian. Translation to
25442 this representation needs to be done both by the target before the @code{F}
25443 packet is sent, and by @value{GDBN} before
25444 it transfers memory to the target. Transferred pointers to structured
25445 data should point to the already-coerced data at any time.
25449 @unnumberedsubsubsec struct stat
25450 @cindex struct stat, in file-i/o protocol
25452 The buffer of type @code{struct stat} used by the target and @value{GDBN}
25453 is defined as follows:
25457 unsigned int st_dev; /* device */
25458 unsigned int st_ino; /* inode */
25459 mode_t st_mode; /* protection */
25460 unsigned int st_nlink; /* number of hard links */
25461 unsigned int st_uid; /* user ID of owner */
25462 unsigned int st_gid; /* group ID of owner */
25463 unsigned int st_rdev; /* device type (if inode device) */
25464 unsigned long st_size; /* total size, in bytes */
25465 unsigned long st_blksize; /* blocksize for filesystem I/O */
25466 unsigned long st_blocks; /* number of blocks allocated */
25467 time_t st_atime; /* time of last access */
25468 time_t st_mtime; /* time of last modification */
25469 time_t st_ctime; /* time of last change */
25473 The integral datatypes conform to the definitions given in the
25474 appropriate section (see @ref{Integral Datatypes}, for details) so this
25475 structure is of size 64 bytes.
25477 The values of several fields have a restricted meaning and/or
25483 A value of 0 represents a file, 1 the console.
25486 No valid meaning for the target. Transmitted unchanged.
25489 Valid mode bits are described in @ref{Constants}. Any other
25490 bits have currently no meaning for the target.
25495 No valid meaning for the target. Transmitted unchanged.
25500 These values have a host and file system dependent
25501 accuracy. Especially on Windows hosts, the file system may not
25502 support exact timing values.
25505 The target gets a @code{struct stat} of the above representation and is
25506 responsible for coercing it to the target representation before
25509 Note that due to size differences between the host, target, and protocol
25510 representations of @code{struct stat} members, these members could eventually
25511 get truncated on the target.
25513 @node struct timeval
25514 @unnumberedsubsubsec struct timeval
25515 @cindex struct timeval, in file-i/o protocol
25517 The buffer of type @code{struct timeval} used by the File-I/O protocol
25518 is defined as follows:
25522 time_t tv_sec; /* second */
25523 long tv_usec; /* microsecond */
25527 The integral datatypes conform to the definitions given in the
25528 appropriate section (see @ref{Integral Datatypes}, for details) so this
25529 structure is of size 8 bytes.
25532 @subsection Constants
25533 @cindex constants, in file-i/o protocol
25535 The following values are used for the constants inside of the
25536 protocol. @value{GDBN} and target are responsible for translating these
25537 values before and after the call as needed.
25548 @unnumberedsubsubsec Open Flags
25549 @cindex open flags, in file-i/o protocol
25551 All values are given in hexadecimal representation.
25563 @node mode_t Values
25564 @unnumberedsubsubsec mode_t Values
25565 @cindex mode_t values, in file-i/o protocol
25567 All values are given in octal representation.
25584 @unnumberedsubsubsec Errno Values
25585 @cindex errno values, in file-i/o protocol
25587 All values are given in decimal representation.
25612 @code{EUNKNOWN} is used as a fallback error value if a host system returns
25613 any error value not in the list of supported error numbers.
25616 @unnumberedsubsubsec Lseek Flags
25617 @cindex lseek flags, in file-i/o protocol
25626 @unnumberedsubsubsec Limits
25627 @cindex limits, in file-i/o protocol
25629 All values are given in decimal representation.
25632 INT_MIN -2147483648
25634 UINT_MAX 4294967295
25635 LONG_MIN -9223372036854775808
25636 LONG_MAX 9223372036854775807
25637 ULONG_MAX 18446744073709551615
25640 @node File-I/O Examples
25641 @subsection File-I/O Examples
25642 @cindex file-i/o examples
25644 Example sequence of a write call, file descriptor 3, buffer is at target
25645 address 0x1234, 6 bytes should be written:
25648 <- @code{Fwrite,3,1234,6}
25649 @emph{request memory read from target}
25652 @emph{return "6 bytes written"}
25656 Example sequence of a read call, file descriptor 3, buffer is at target
25657 address 0x1234, 6 bytes should be read:
25660 <- @code{Fread,3,1234,6}
25661 @emph{request memory write to target}
25662 -> @code{X1234,6:XXXXXX}
25663 @emph{return "6 bytes read"}
25667 Example sequence of a read call, call fails on the host due to invalid
25668 file descriptor (@code{EBADF}):
25671 <- @code{Fread,3,1234,6}
25675 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
25679 <- @code{Fread,3,1234,6}
25684 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
25688 <- @code{Fread,3,1234,6}
25689 -> @code{X1234,6:XXXXXX}
25693 @node Library List Format
25694 @section Library List Format
25695 @cindex library list format, remote protocol
25697 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
25698 same process as your application to manage libraries. In this case,
25699 @value{GDBN} can use the loader's symbol table and normal memory
25700 operations to maintain a list of shared libraries. On other
25701 platforms, the operating system manages loaded libraries.
25702 @value{GDBN} can not retrieve the list of currently loaded libraries
25703 through memory operations, so it uses the @samp{qXfer:libraries:read}
25704 packet (@pxref{qXfer library list read}) instead. The remote stub
25705 queries the target's operating system and reports which libraries
25708 The @samp{qXfer:libraries:read} packet returns an XML document which
25709 lists loaded libraries and their offsets. Each library has an
25710 associated name and one or more segment base addresses, which report
25711 where the library was loaded in memory. The segment bases are start
25712 addresses, not relocation offsets; they do not depend on the library's
25713 link-time base addresses.
25715 @value{GDBN} must be linked with the Expat library to support XML
25716 library lists. @xref{Expat}.
25718 A simple memory map, with one loaded library relocated by a single
25719 offset, looks like this:
25723 <library name="/lib/libc.so.6">
25724 <segment address="0x10000000"/>
25729 The format of a library list is described by this DTD:
25732 <!-- library-list: Root element with versioning -->
25733 <!ELEMENT library-list (library)*>
25734 <!ATTLIST library-list version CDATA #FIXED "1.0">
25735 <!ELEMENT library (segment)*>
25736 <!ATTLIST library name CDATA #REQUIRED>
25737 <!ELEMENT segment EMPTY>
25738 <!ATTLIST segment address CDATA #REQUIRED>
25741 @node Memory Map Format
25742 @section Memory Map Format
25743 @cindex memory map format
25745 To be able to write into flash memory, @value{GDBN} needs to obtain a
25746 memory map from the target. This section describes the format of the
25749 The memory map is obtained using the @samp{qXfer:memory-map:read}
25750 (@pxref{qXfer memory map read}) packet and is an XML document that
25751 lists memory regions.
25753 @value{GDBN} must be linked with the Expat library to support XML
25754 memory maps. @xref{Expat}.
25756 The top-level structure of the document is shown below:
25759 <?xml version="1.0"?>
25760 <!DOCTYPE memory-map
25761 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
25762 "http://sourceware.org/gdb/gdb-memory-map.dtd">
25768 Each region can be either:
25773 A region of RAM starting at @var{addr} and extending for @var{length}
25777 <memory type="ram" start="@var{addr}" length="@var{length}"/>
25782 A region of read-only memory:
25785 <memory type="rom" start="@var{addr}" length="@var{length}"/>
25790 A region of flash memory, with erasure blocks @var{blocksize}
25794 <memory type="flash" start="@var{addr}" length="@var{length}">
25795 <property name="blocksize">@var{blocksize}</property>
25801 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
25802 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
25803 packets to write to addresses in such ranges.
25805 The formal DTD for memory map format is given below:
25808 <!-- ................................................... -->
25809 <!-- Memory Map XML DTD ................................ -->
25810 <!-- File: memory-map.dtd .............................. -->
25811 <!-- .................................... .............. -->
25812 <!-- memory-map.dtd -->
25813 <!-- memory-map: Root element with versioning -->
25814 <!ELEMENT memory-map (memory | property)>
25815 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
25816 <!ELEMENT memory (property)>
25817 <!-- memory: Specifies a memory region,
25818 and its type, or device. -->
25819 <!ATTLIST memory type CDATA #REQUIRED
25820 start CDATA #REQUIRED
25821 length CDATA #REQUIRED
25822 device CDATA #IMPLIED>
25823 <!-- property: Generic attribute tag -->
25824 <!ELEMENT property (#PCDATA | property)*>
25825 <!ATTLIST property name CDATA #REQUIRED>
25828 @include agentexpr.texi
25830 @node Target Descriptions
25831 @appendix Target Descriptions
25832 @cindex target descriptions
25834 @strong{Warning:} target descriptions are still under active development,
25835 and the contents and format may change between @value{GDBN} releases.
25836 The format is expected to stabilize in the future.
25838 One of the challenges of using @value{GDBN} to debug embedded systems
25839 is that there are so many minor variants of each processor
25840 architecture in use. It is common practice for vendors to start with
25841 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
25842 and then make changes to adapt it to a particular market niche. Some
25843 architectures have hundreds of variants, available from dozens of
25844 vendors. This leads to a number of problems:
25848 With so many different customized processors, it is difficult for
25849 the @value{GDBN} maintainers to keep up with the changes.
25851 Since individual variants may have short lifetimes or limited
25852 audiences, it may not be worthwhile to carry information about every
25853 variant in the @value{GDBN} source tree.
25855 When @value{GDBN} does support the architecture of the embedded system
25856 at hand, the task of finding the correct architecture name to give the
25857 @command{set architecture} command can be error-prone.
25860 To address these problems, the @value{GDBN} remote protocol allows a
25861 target system to not only identify itself to @value{GDBN}, but to
25862 actually describe its own features. This lets @value{GDBN} support
25863 processor variants it has never seen before --- to the extent that the
25864 descriptions are accurate, and that @value{GDBN} understands them.
25866 @value{GDBN} must be linked with the Expat library to support XML
25867 target descriptions. @xref{Expat}.
25870 * Retrieving Descriptions:: How descriptions are fetched from a target.
25871 * Target Description Format:: The contents of a target description.
25872 * Predefined Target Types:: Standard types available for target
25874 * Standard Target Features:: Features @value{GDBN} knows about.
25877 @node Retrieving Descriptions
25878 @section Retrieving Descriptions
25880 Target descriptions can be read from the target automatically, or
25881 specified by the user manually. The default behavior is to read the
25882 description from the target. @value{GDBN} retrieves it via the remote
25883 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
25884 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
25885 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
25886 XML document, of the form described in @ref{Target Description
25889 Alternatively, you can specify a file to read for the target description.
25890 If a file is set, the target will not be queried. The commands to
25891 specify a file are:
25894 @cindex set tdesc filename
25895 @item set tdesc filename @var{path}
25896 Read the target description from @var{path}.
25898 @cindex unset tdesc filename
25899 @item unset tdesc filename
25900 Do not read the XML target description from a file. @value{GDBN}
25901 will use the description supplied by the current target.
25903 @cindex show tdesc filename
25904 @item show tdesc filename
25905 Show the filename to read for a target description, if any.
25909 @node Target Description Format
25910 @section Target Description Format
25911 @cindex target descriptions, XML format
25913 A target description annex is an @uref{http://www.w3.org/XML/, XML}
25914 document which complies with the Document Type Definition provided in
25915 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
25916 means you can use generally available tools like @command{xmllint} to
25917 check that your feature descriptions are well-formed and valid.
25918 However, to help people unfamiliar with XML write descriptions for
25919 their targets, we also describe the grammar here.
25921 Target descriptions can identify the architecture of the remote target
25922 and (for some architectures) provide information about custom register
25923 sets. @value{GDBN} can use this information to autoconfigure for your
25924 target, or to warn you if you connect to an unsupported target.
25926 Here is a simple target description:
25929 <target version="1.0">
25930 <architecture>i386:x86-64</architecture>
25935 This minimal description only says that the target uses
25936 the x86-64 architecture.
25938 A target description has the following overall form, with [ ] marking
25939 optional elements and @dots{} marking repeatable elements. The elements
25940 are explained further below.
25943 <?xml version="1.0"?>
25944 <!DOCTYPE target SYSTEM "gdb-target.dtd">
25945 <target version="1.0">
25946 @r{[}@var{architecture}@r{]}
25947 @r{[}@var{feature}@dots{}@r{]}
25952 The description is generally insensitive to whitespace and line
25953 breaks, under the usual common-sense rules. The XML version
25954 declaration and document type declaration can generally be omitted
25955 (@value{GDBN} does not require them), but specifying them may be
25956 useful for XML validation tools. The @samp{version} attribute for
25957 @samp{<target>} may also be omitted, but we recommend
25958 including it; if future versions of @value{GDBN} use an incompatible
25959 revision of @file{gdb-target.dtd}, they will detect and report
25960 the version mismatch.
25962 @subsection Inclusion
25963 @cindex target descriptions, inclusion
25966 @cindex <xi:include>
25969 It can sometimes be valuable to split a target description up into
25970 several different annexes, either for organizational purposes, or to
25971 share files between different possible target descriptions. You can
25972 divide a description into multiple files by replacing any element of
25973 the target description with an inclusion directive of the form:
25976 <xi:include href="@var{document}"/>
25980 When @value{GDBN} encounters an element of this form, it will retrieve
25981 the named XML @var{document}, and replace the inclusion directive with
25982 the contents of that document. If the current description was read
25983 using @samp{qXfer}, then so will be the included document;
25984 @var{document} will be interpreted as the name of an annex. If the
25985 current description was read from a file, @value{GDBN} will look for
25986 @var{document} as a file in the same directory where it found the
25987 original description.
25989 @subsection Architecture
25990 @cindex <architecture>
25992 An @samp{<architecture>} element has this form:
25995 <architecture>@var{arch}</architecture>
25998 @var{arch} is an architecture name from the same selection
25999 accepted by @code{set architecture} (@pxref{Targets, ,Specifying a
26000 Debugging Target}).
26002 @subsection Features
26005 Each @samp{<feature>} describes some logical portion of the target
26006 system. Features are currently used to describe available CPU
26007 registers and the types of their contents. A @samp{<feature>} element
26011 <feature name="@var{name}">
26012 @r{[}@var{type}@dots{}@r{]}
26018 Each feature's name should be unique within the description. The name
26019 of a feature does not matter unless @value{GDBN} has some special
26020 knowledge of the contents of that feature; if it does, the feature
26021 should have its standard name. @xref{Standard Target Features}.
26025 Any register's value is a collection of bits which @value{GDBN} must
26026 interpret. The default interpretation is a two's complement integer,
26027 but other types can be requested by name in the register description.
26028 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
26029 Target Types}), and the description can define additional composite types.
26031 Each type element must have an @samp{id} attribute, which gives
26032 a unique (within the containing @samp{<feature>}) name to the type.
26033 Types must be defined before they are used.
26036 Some targets offer vector registers, which can be treated as arrays
26037 of scalar elements. These types are written as @samp{<vector>} elements,
26038 specifying the array element type, @var{type}, and the number of elements,
26042 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
26046 If a register's value is usefully viewed in multiple ways, define it
26047 with a union type containing the useful representations. The
26048 @samp{<union>} element contains one or more @samp{<field>} elements,
26049 each of which has a @var{name} and a @var{type}:
26052 <union id="@var{id}">
26053 <field name="@var{name}" type="@var{type}"/>
26058 @subsection Registers
26061 Each register is represented as an element with this form:
26064 <reg name="@var{name}"
26065 bitsize="@var{size}"
26066 @r{[}regnum="@var{num}"@r{]}
26067 @r{[}save-restore="@var{save-restore}"@r{]}
26068 @r{[}type="@var{type}"@r{]}
26069 @r{[}group="@var{group}"@r{]}/>
26073 The components are as follows:
26078 The register's name; it must be unique within the target description.
26081 The register's size, in bits.
26084 The register's number. If omitted, a register's number is one greater
26085 than that of the previous register (either in the current feature or in
26086 a preceeding feature); the first register in the target description
26087 defaults to zero. This register number is used to read or write
26088 the register; e.g.@: it is used in the remote @code{p} and @code{P}
26089 packets, and registers appear in the @code{g} and @code{G} packets
26090 in order of increasing register number.
26093 Whether the register should be preserved across inferior function
26094 calls; this must be either @code{yes} or @code{no}. The default is
26095 @code{yes}, which is appropriate for most registers except for
26096 some system control registers; this is not related to the target's
26100 The type of the register. @var{type} may be a predefined type, a type
26101 defined in the current feature, or one of the special types @code{int}
26102 and @code{float}. @code{int} is an integer type of the correct size
26103 for @var{bitsize}, and @code{float} is a floating point type (in the
26104 architecture's normal floating point format) of the correct size for
26105 @var{bitsize}. The default is @code{int}.
26108 The register group to which this register belongs. @var{group} must
26109 be either @code{general}, @code{float}, or @code{vector}. If no
26110 @var{group} is specified, @value{GDBN} will not display the register
26111 in @code{info registers}.
26115 @node Predefined Target Types
26116 @section Predefined Target Types
26117 @cindex target descriptions, predefined types
26119 Type definitions in the self-description can build up composite types
26120 from basic building blocks, but can not define fundamental types. Instead,
26121 standard identifiers are provided by @value{GDBN} for the fundamental
26122 types. The currently supported types are:
26131 Signed integer types holding the specified number of bits.
26138 Unsigned integer types holding the specified number of bits.
26142 Pointers to unspecified code and data. The program counter and
26143 any dedicated return address register may be marked as code
26144 pointers; printing a code pointer converts it into a symbolic
26145 address. The stack pointer and any dedicated address registers
26146 may be marked as data pointers.
26149 Single precision IEEE floating point.
26152 Double precision IEEE floating point.
26155 The 12-byte extended precision format used by ARM FPA registers.
26159 @node Standard Target Features
26160 @section Standard Target Features
26161 @cindex target descriptions, standard features
26163 A target description must contain either no registers or all the
26164 target's registers. If the description contains no registers, then
26165 @value{GDBN} will assume a default register layout, selected based on
26166 the architecture. If the description contains any registers, the
26167 default layout will not be used; the standard registers must be
26168 described in the target description, in such a way that @value{GDBN}
26169 can recognize them.
26171 This is accomplished by giving specific names to feature elements
26172 which contain standard registers. @value{GDBN} will look for features
26173 with those names and verify that they contain the expected registers;
26174 if any known feature is missing required registers, or if any required
26175 feature is missing, @value{GDBN} will reject the target
26176 description. You can add additional registers to any of the
26177 standard features --- @value{GDBN} will display them just as if
26178 they were added to an unrecognized feature.
26180 This section lists the known features and their expected contents.
26181 Sample XML documents for these features are included in the
26182 @value{GDBN} source tree, in the directory @file{gdb/features}.
26184 Names recognized by @value{GDBN} should include the name of the
26185 company or organization which selected the name, and the overall
26186 architecture to which the feature applies; so e.g.@: the feature
26187 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
26189 The names of registers are not case sensitive for the purpose
26190 of recognizing standard features, but @value{GDBN} will only display
26191 registers using the capitalization used in the description.
26200 @subsection ARM Features
26201 @cindex target descriptions, ARM features
26203 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
26204 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
26205 @samp{lr}, @samp{pc}, and @samp{cpsr}.
26207 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
26208 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
26210 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
26211 it should contain at least registers @samp{wR0} through @samp{wR15} and
26212 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
26213 @samp{wCSSF}, and @samp{wCASF} registers are optional.
26215 @subsection MIPS Features
26216 @cindex target descriptions, MIPS features
26218 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
26219 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
26220 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
26223 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
26224 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
26225 registers. They may be 32-bit or 64-bit depending on the target.
26227 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
26228 it may be optional in a future version of @value{GDBN}. It should
26229 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
26230 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
26232 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
26233 contain a single register, @samp{restart}, which is used by the
26234 Linux kernel to control restartable syscalls.
26236 @node M68K Features
26237 @subsection M68K Features
26238 @cindex target descriptions, M68K features
26241 @item @samp{org.gnu.gdb.m68k.core}
26242 @itemx @samp{org.gnu.gdb.coldfire.core}
26243 @itemx @samp{org.gnu.gdb.fido.core}
26244 One of those features must be always present.
26245 The feature that is present determines which flavor of m86k is
26246 used. The feature that is present should contain registers
26247 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
26248 @samp{sp}, @samp{ps} and @samp{pc}.
26250 @item @samp{org.gnu.gdb.coldfire.fp}
26251 This feature is optional. If present, it should contain registers
26252 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
26256 @subsection PowerPC Features
26257 @cindex target descriptions, PowerPC features
26259 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
26260 targets. It should contain registers @samp{r0} through @samp{r31},
26261 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
26262 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
26264 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
26265 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
26267 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
26268 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
26271 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
26272 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
26273 @samp{spefscr}. SPE targets should provide 32-bit registers in
26274 @samp{org.gnu.gdb.power.core} and provide the upper halves in
26275 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
26276 these to present registers @samp{ev0} through @samp{ev31} to the
26291 % I think something like @colophon should be in texinfo. In the
26293 \long\def\colophon{\hbox to0pt{}\vfill
26294 \centerline{The body of this manual is set in}
26295 \centerline{\fontname\tenrm,}
26296 \centerline{with headings in {\bf\fontname\tenbf}}
26297 \centerline{and examples in {\tt\fontname\tentt}.}
26298 \centerline{{\it\fontname\tenit\/},}
26299 \centerline{{\bf\fontname\tenbf}, and}
26300 \centerline{{\sl\fontname\tensl\/}}
26301 \centerline{are used for emphasis.}\vfill}
26303 % Blame: doc@cygnus.com, 1991.