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 Free Software Foundation's Back-Cover Text is: ``You have
66 freedom to copy and modify this GNU Manual, like GNU software. Copies
67 published by the Free Software Foundation raise funds for GNU
72 @title Debugging with @value{GDBN}
73 @subtitle The @sc{gnu} Source-Level Debugger
75 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
76 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
80 \hfill (Send bugs and comments on @value{GDBN} to bug-gdb\@gnu.org.)\par
81 \hfill {\it Debugging with @value{GDBN}}\par
82 \hfill \TeX{}info \texinfoversion\par
86 @vskip 0pt plus 1filll
87 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995,
88 1996, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2006
89 Free Software Foundation, Inc.
91 Published by the Free Software Foundation @*
92 51 Franklin Street, Fifth Floor,
93 Boston, MA 02110-1301, USA@*
96 Permission is granted to copy, distribute and/or modify this document
97 under the terms of the GNU Free Documentation License, Version 1.1 or
98 any later version published by the Free Software Foundation; with the
99 Invariant Sections being ``Free Software'' and ``Free Software Needs
100 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
101 and with the Back-Cover Texts as in (a) below.
103 (a) The Free Software Foundation's Back-Cover Text is: ``You have
104 freedom to copy and modify this GNU Manual, like GNU software. Copies
105 published by the Free Software Foundation raise funds for GNU
111 @node Top, Summary, (dir), (dir)
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN} Version
120 Copyright (C) 1988-2006 Free Software Foundation, Inc.
123 * Summary:: Summary of @value{GDBN}
124 * Sample Session:: A sample @value{GDBN} session
126 * Invocation:: Getting in and out of @value{GDBN}
127 * Commands:: @value{GDBN} commands
128 * Running:: Running programs under @value{GDBN}
129 * Stopping:: Stopping and continuing
130 * Stack:: Examining the stack
131 * Source:: Examining source files
132 * Data:: Examining data
133 * Macros:: Preprocessor Macros
134 * Tracepoints:: Debugging remote targets non-intrusively
135 * Overlays:: Debugging programs that use overlays
137 * Languages:: Using @value{GDBN} with different languages
139 * Symbols:: Examining the symbol table
140 * Altering:: Altering execution
141 * GDB Files:: @value{GDBN} files
142 * Targets:: Specifying a debugging target
143 * Remote Debugging:: Debugging remote programs
144 * Configurations:: Configuration-specific information
145 * Controlling GDB:: Controlling @value{GDBN}
146 * Sequences:: Canned sequences of commands
147 * TUI:: @value{GDBN} Text User Interface
148 * Interpreters:: Command Interpreters
149 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
150 * Annotations:: @value{GDBN}'s annotation interface.
151 * GDB/MI:: @value{GDBN}'s Machine Interface.
153 * GDB Bugs:: Reporting bugs in @value{GDBN}
154 * Formatting Documentation:: How to format and print @value{GDBN} documentation
156 * Command Line Editing:: Command Line Editing
157 * Using History Interactively:: Using History Interactively
158 * Installing GDB:: Installing GDB
159 * Maintenance Commands:: Maintenance Commands
160 * Remote Protocol:: GDB Remote Serial Protocol
161 * Agent Expressions:: The GDB Agent Expression Mechanism
162 * Copying:: GNU General Public License says
163 how you can copy and share GDB
164 * GNU Free Documentation License:: The license for this documentation
173 @unnumbered Summary of @value{GDBN}
175 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
176 going on ``inside'' another program while it executes---or what another
177 program was doing at the moment it crashed.
179 @value{GDBN} can do four main kinds of things (plus other things in support of
180 these) to help you catch bugs in the act:
184 Start your program, specifying anything that might affect its behavior.
187 Make your program stop on specified conditions.
190 Examine what has happened, when your program has stopped.
193 Change things in your program, so you can experiment with correcting the
194 effects of one bug and go on to learn about another.
197 You can use @value{GDBN} to debug programs written in C and C@t{++}.
198 For more information, see @ref{Supported languages,,Supported languages}.
199 For more information, see @ref{C,,C and C++}.
202 Support for Modula-2 is partial. For information on Modula-2, see
203 @ref{Modula-2,,Modula-2}.
206 Debugging Pascal programs which use sets, subranges, file variables, or
207 nested functions does not currently work. @value{GDBN} does not support
208 entering expressions, printing values, or similar features using Pascal
212 @value{GDBN} can be used to debug programs written in Fortran, although
213 it may be necessary to refer to some variables with a trailing
216 @value{GDBN} can be used to debug programs written in Objective-C,
217 using either the Apple/NeXT or the GNU Objective-C runtime.
220 * Free Software:: Freely redistributable software
221 * Contributors:: Contributors to GDB
225 @unnumberedsec Free software
227 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
228 General Public License
229 (GPL). The GPL gives you the freedom to copy or adapt a licensed
230 program---but every person getting a copy also gets with it the
231 freedom to modify that copy (which means that they must get access to
232 the source code), and the freedom to distribute further copies.
233 Typical software companies use copyrights to limit your freedoms; the
234 Free Software Foundation uses the GPL to preserve these freedoms.
236 Fundamentally, the General Public License is a license which says that
237 you have these freedoms and that you cannot take these freedoms away
240 @unnumberedsec Free Software Needs Free Documentation
242 The biggest deficiency in the free software community today is not in
243 the software---it is the lack of good free documentation that we can
244 include with the free software. Many of our most important
245 programs do not come with free reference manuals and free introductory
246 texts. Documentation is an essential part of any software package;
247 when an important free software package does not come with a free
248 manual and a free tutorial, that is a major gap. We have many such
251 Consider Perl, for instance. The tutorial manuals that people
252 normally use are non-free. How did this come about? Because the
253 authors of those manuals published them with restrictive terms---no
254 copying, no modification, source files not available---which exclude
255 them from the free software world.
257 That wasn't the first time this sort of thing happened, and it was far
258 from the last. Many times we have heard a GNU user eagerly describe a
259 manual that he is writing, his intended contribution to the community,
260 only to learn that he had ruined everything by signing a publication
261 contract to make it non-free.
263 Free documentation, like free software, is a matter of freedom, not
264 price. The problem with the non-free manual is not that publishers
265 charge a price for printed copies---that in itself is fine. (The Free
266 Software Foundation sells printed copies of manuals, too.) The
267 problem is the restrictions on the use of the manual. Free manuals
268 are available in source code form, and give you permission to copy and
269 modify. Non-free manuals do not allow this.
271 The criteria of freedom for a free manual are roughly the same as for
272 free software. Redistribution (including the normal kinds of
273 commercial redistribution) must be permitted, so that the manual can
274 accompany every copy of the program, both on-line and on paper.
276 Permission for modification of the technical content is crucial too.
277 When people modify the software, adding or changing features, if they
278 are conscientious they will change the manual too---so they can
279 provide accurate and clear documentation for the modified program. A
280 manual that leaves you no choice but to write a new manual to document
281 a changed version of the program is not really available to our
284 Some kinds of limits on the way modification is handled are
285 acceptable. For example, requirements to preserve the original
286 author's copyright notice, the distribution terms, or the list of
287 authors, are ok. It is also no problem to require modified versions
288 to include notice that they were modified. Even entire sections that
289 may not be deleted or changed are acceptable, as long as they deal
290 with nontechnical topics (like this one). These kinds of restrictions
291 are acceptable because they don't obstruct the community's normal use
294 However, it must be possible to modify all the @emph{technical}
295 content of the manual, and then distribute the result in all the usual
296 media, through all the usual channels. Otherwise, the restrictions
297 obstruct the use of the manual, it is not free, and we need another
298 manual to replace it.
300 Please spread the word about this issue. Our community continues to
301 lose manuals to proprietary publishing. If we spread the word that
302 free software needs free reference manuals and free tutorials, perhaps
303 the next person who wants to contribute by writing documentation will
304 realize, before it is too late, that only free manuals contribute to
305 the free software community.
307 If you are writing documentation, please insist on publishing it under
308 the GNU Free Documentation License or another free documentation
309 license. Remember that this decision requires your approval---you
310 don't have to let the publisher decide. Some commercial publishers
311 will use a free license if you insist, but they will not propose the
312 option; it is up to you to raise the issue and say firmly that this is
313 what you want. If the publisher you are dealing with refuses, please
314 try other publishers. If you're not sure whether a proposed license
315 is free, write to @email{licensing@@gnu.org}.
317 You can encourage commercial publishers to sell more free, copylefted
318 manuals and tutorials by buying them, and particularly by buying
319 copies from the publishers that paid for their writing or for major
320 improvements. Meanwhile, try to avoid buying non-free documentation
321 at all. Check the distribution terms of a manual before you buy it,
322 and insist that whoever seeks your business must respect your freedom.
323 Check the history of the book, and try to reward the publishers that
324 have paid or pay the authors to work on it.
326 The Free Software Foundation maintains a list of free documentation
327 published by other publishers, at
328 @url{http://www.fsf.org/doc/other-free-books.html}.
331 @unnumberedsec Contributors to @value{GDBN}
333 Richard Stallman was the original author of @value{GDBN}, and of many
334 other @sc{gnu} programs. Many others have contributed to its
335 development. This section attempts to credit major contributors. One
336 of the virtues of free software is that everyone is free to contribute
337 to it; with regret, we cannot actually acknowledge everyone here. The
338 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
339 blow-by-blow account.
341 Changes much prior to version 2.0 are lost in the mists of time.
344 @emph{Plea:} Additions to this section are particularly welcome. If you
345 or your friends (or enemies, to be evenhanded) have been unfairly
346 omitted from this list, we would like to add your names!
349 So that they may not regard their many labors as thankless, we
350 particularly thank those who shepherded @value{GDBN} through major
352 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
353 Jim Blandy (release 4.18);
354 Jason Molenda (release 4.17);
355 Stan Shebs (release 4.14);
356 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
357 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
358 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
359 Jim Kingdon (releases 3.5, 3.4, and 3.3);
360 and Randy Smith (releases 3.2, 3.1, and 3.0).
362 Richard Stallman, assisted at various times by Peter TerMaat, Chris
363 Hanson, and Richard Mlynarik, handled releases through 2.8.
365 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
366 in @value{GDBN}, with significant additional contributions from Per
367 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
368 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
369 much general update work leading to release 3.0).
371 @value{GDBN} uses the BFD subroutine library to examine multiple
372 object-file formats; BFD was a joint project of David V.
373 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
375 David Johnson wrote the original COFF support; Pace Willison did
376 the original support for encapsulated COFF.
378 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
380 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
381 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
383 Jean-Daniel Fekete contributed Sun 386i support.
384 Chris Hanson improved the HP9000 support.
385 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
386 David Johnson contributed Encore Umax support.
387 Jyrki Kuoppala contributed Altos 3068 support.
388 Jeff Law contributed HP PA and SOM support.
389 Keith Packard contributed NS32K support.
390 Doug Rabson contributed Acorn Risc Machine support.
391 Bob Rusk contributed Harris Nighthawk CX-UX support.
392 Chris Smith contributed Convex support (and Fortran debugging).
393 Jonathan Stone contributed Pyramid support.
394 Michael Tiemann contributed SPARC support.
395 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
396 Pace Willison contributed Intel 386 support.
397 Jay Vosburgh contributed Symmetry support.
398 Marko Mlinar contributed OpenRISC 1000 support.
400 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
402 Rich Schaefer and Peter Schauer helped with support of SunOS shared
405 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
406 about several machine instruction sets.
408 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
409 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
410 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
411 and RDI targets, respectively.
413 Brian Fox is the author of the readline libraries providing
414 command-line editing and command history.
416 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
417 Modula-2 support, and contributed the Languages chapter of this manual.
419 Fred Fish wrote most of the support for Unix System Vr4.
420 He also enhanced the command-completion support to cover C@t{++} overloaded
423 Hitachi America (now Renesas America), Ltd. sponsored the support for
424 H8/300, H8/500, and Super-H processors.
426 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
428 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
431 Toshiba sponsored the support for the TX39 Mips processor.
433 Matsushita sponsored the support for the MN10200 and MN10300 processors.
435 Fujitsu sponsored the support for SPARClite and FR30 processors.
437 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
440 Michael Snyder added support for tracepoints.
442 Stu Grossman wrote gdbserver.
444 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
445 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
447 The following people at the Hewlett-Packard Company contributed
448 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
449 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
450 compiler, and the Text User Interface (nee Terminal User Interface):
451 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
452 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
453 provided HP-specific information in this manual.
455 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
456 Robert Hoehne made significant contributions to the DJGPP port.
458 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
459 development since 1991. Cygnus engineers who have worked on @value{GDBN}
460 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
461 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
462 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
463 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
464 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
465 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
466 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
467 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
468 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
469 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
470 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
471 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
472 Zuhn have made contributions both large and small.
474 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
475 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
477 Jim Blandy added support for preprocessor macros, while working for Red
480 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
481 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
482 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
483 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
484 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
485 with the migration of old architectures to this new framework.
487 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
488 unwinder framework, this consisting of a fresh new design featuring
489 frame IDs, independent frame sniffers, and the sentinel frame. Mark
490 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
491 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
492 trad unwinders. The architecture specific changes, each involving a
493 complete rewrite of the architecture's frame code, were carried out by
494 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
495 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
496 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
497 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
501 @chapter A Sample @value{GDBN} Session
503 You can use this manual at your leisure to read all about @value{GDBN}.
504 However, a handful of commands are enough to get started using the
505 debugger. This chapter illustrates those commands.
508 In this sample session, we emphasize user input like this: @b{input},
509 to make it easier to pick out from the surrounding output.
512 @c FIXME: this example may not be appropriate for some configs, where
513 @c FIXME...primary interest is in remote use.
515 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
516 processor) exhibits the following bug: sometimes, when we change its
517 quote strings from the default, the commands used to capture one macro
518 definition within another stop working. In the following short @code{m4}
519 session, we define a macro @code{foo} which expands to @code{0000}; we
520 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
521 same thing. However, when we change the open quote string to
522 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
523 procedure fails to define a new synonym @code{baz}:
532 @b{define(bar,defn(`foo'))}
536 @b{changequote(<QUOTE>,<UNQUOTE>)}
538 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
541 m4: End of input: 0: fatal error: EOF in string
545 Let us use @value{GDBN} to try to see what is going on.
548 $ @b{@value{GDBP} m4}
549 @c FIXME: this falsifies the exact text played out, to permit smallbook
550 @c FIXME... format to come out better.
551 @value{GDBN} is free software and you are welcome to distribute copies
552 of it under certain conditions; type "show copying" to see
554 There is absolutely no warranty for @value{GDBN}; type "show warranty"
557 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
562 @value{GDBN} reads only enough symbol data to know where to find the
563 rest when needed; as a result, the first prompt comes up very quickly.
564 We now tell @value{GDBN} to use a narrower display width than usual, so
565 that examples fit in this manual.
568 (@value{GDBP}) @b{set width 70}
572 We need to see how the @code{m4} built-in @code{changequote} works.
573 Having looked at the source, we know the relevant subroutine is
574 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
575 @code{break} command.
578 (@value{GDBP}) @b{break m4_changequote}
579 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
583 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
584 control; as long as control does not reach the @code{m4_changequote}
585 subroutine, the program runs as usual:
588 (@value{GDBP}) @b{run}
589 Starting program: /work/Editorial/gdb/gnu/m4/m4
597 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
598 suspends execution of @code{m4}, displaying information about the
599 context where it stops.
602 @b{changequote(<QUOTE>,<UNQUOTE>)}
604 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
606 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
610 Now we use the command @code{n} (@code{next}) to advance execution to
611 the next line of the current function.
615 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
620 @code{set_quotes} looks like a promising subroutine. We can go into it
621 by using the command @code{s} (@code{step}) instead of @code{next}.
622 @code{step} goes to the next line to be executed in @emph{any}
623 subroutine, so it steps into @code{set_quotes}.
627 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
629 530 if (lquote != def_lquote)
633 The display that shows the subroutine where @code{m4} is now
634 suspended (and its arguments) is called a stack frame display. It
635 shows a summary of the stack. We can use the @code{backtrace}
636 command (which can also be spelled @code{bt}), to see where we are
637 in the stack as a whole: the @code{backtrace} command displays a
638 stack frame for each active subroutine.
641 (@value{GDBP}) @b{bt}
642 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
644 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
646 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
647 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
649 #4 0x79dc in expand_input () at macro.c:40
650 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
654 We step through a few more lines to see what happens. The first two
655 times, we can use @samp{s}; the next two times we use @code{n} to avoid
656 falling into the @code{xstrdup} subroutine.
660 0x3b5c 532 if (rquote != def_rquote)
662 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
663 def_lquote : xstrdup(lq);
665 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
668 538 len_lquote = strlen(rquote);
672 The last line displayed looks a little odd; we can examine the variables
673 @code{lquote} and @code{rquote} to see if they are in fact the new left
674 and right quotes we specified. We use the command @code{p}
675 (@code{print}) to see their values.
678 (@value{GDBP}) @b{p lquote}
679 $1 = 0x35d40 "<QUOTE>"
680 (@value{GDBP}) @b{p rquote}
681 $2 = 0x35d50 "<UNQUOTE>"
685 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
686 To look at some context, we can display ten lines of source
687 surrounding the current line with the @code{l} (@code{list}) command.
693 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
695 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
698 538 len_lquote = strlen(rquote);
699 539 len_rquote = strlen(lquote);
706 Let us step past the two lines that set @code{len_lquote} and
707 @code{len_rquote}, and then examine the values of those variables.
711 539 len_rquote = strlen(lquote);
714 (@value{GDBP}) @b{p len_lquote}
716 (@value{GDBP}) @b{p len_rquote}
721 That certainly looks wrong, assuming @code{len_lquote} and
722 @code{len_rquote} are meant to be the lengths of @code{lquote} and
723 @code{rquote} respectively. We can set them to better values using
724 the @code{p} command, since it can print the value of
725 any expression---and that expression can include subroutine calls and
729 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
731 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
736 Is that enough to fix the problem of using the new quotes with the
737 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
738 executing with the @code{c} (@code{continue}) command, and then try the
739 example that caused trouble initially:
745 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
752 Success! The new quotes now work just as well as the default ones. The
753 problem seems to have been just the two typos defining the wrong
754 lengths. We allow @code{m4} exit by giving it an EOF as input:
758 Program exited normally.
762 The message @samp{Program exited normally.} is from @value{GDBN}; it
763 indicates @code{m4} has finished executing. We can end our @value{GDBN}
764 session with the @value{GDBN} @code{quit} command.
767 (@value{GDBP}) @b{quit}
771 @chapter Getting In and Out of @value{GDBN}
773 This chapter discusses how to start @value{GDBN}, and how to get out of it.
777 type @samp{@value{GDBP}} to start @value{GDBN}.
779 type @kbd{quit} or @kbd{C-d} to exit.
783 * Invoking GDB:: How to start @value{GDBN}
784 * Quitting GDB:: How to quit @value{GDBN}
785 * Shell Commands:: How to use shell commands inside @value{GDBN}
786 * Logging output:: How to log @value{GDBN}'s output to a file
790 @section Invoking @value{GDBN}
792 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
793 @value{GDBN} reads commands from the terminal until you tell it to exit.
795 You can also run @code{@value{GDBP}} with a variety of arguments and options,
796 to specify more of your debugging environment at the outset.
798 The command-line options described here are designed
799 to cover a variety of situations; in some environments, some of these
800 options may effectively be unavailable.
802 The most usual way to start @value{GDBN} is with one argument,
803 specifying an executable program:
806 @value{GDBP} @var{program}
810 You can also start with both an executable program and a core file
814 @value{GDBP} @var{program} @var{core}
817 You can, instead, specify a process ID as a second argument, if you want
818 to debug a running process:
821 @value{GDBP} @var{program} 1234
825 would attach @value{GDBN} to process @code{1234} (unless you also have a file
826 named @file{1234}; @value{GDBN} does check for a core file first).
828 Taking advantage of the second command-line argument requires a fairly
829 complete operating system; when you use @value{GDBN} as a remote
830 debugger attached to a bare board, there may not be any notion of
831 ``process'', and there is often no way to get a core dump. @value{GDBN}
832 will warn you if it is unable to attach or to read core dumps.
834 You can optionally have @code{@value{GDBP}} pass any arguments after the
835 executable file to the inferior using @code{--args}. This option stops
838 gdb --args gcc -O2 -c foo.c
840 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
841 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
843 You can run @code{@value{GDBP}} without printing the front material, which describes
844 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
851 You can further control how @value{GDBN} starts up by using command-line
852 options. @value{GDBN} itself can remind you of the options available.
862 to display all available options and briefly describe their use
863 (@samp{@value{GDBP} -h} is a shorter equivalent).
865 All options and command line arguments you give are processed
866 in sequential order. The order makes a difference when the
867 @samp{-x} option is used.
871 * File Options:: Choosing files
872 * Mode Options:: Choosing modes
873 * Startup:: What @value{GDBN} does during startup
877 @subsection Choosing files
879 When @value{GDBN} starts, it reads any arguments other than options as
880 specifying an executable file and core file (or process ID). This is
881 the same as if the arguments were specified by the @samp{-se} and
882 @samp{-c} (or @samp{-p} options respectively. (@value{GDBN} reads the
883 first argument that does not have an associated option flag as
884 equivalent to the @samp{-se} option followed by that argument; and the
885 second argument that does not have an associated option flag, if any, as
886 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
887 If the second argument begins with a decimal digit, @value{GDBN} will
888 first attempt to attach to it as a process, and if that fails, attempt
889 to open it as a corefile. If you have a corefile whose name begins with
890 a digit, you can prevent @value{GDBN} from treating it as a pid by
891 prefixing it with @file{./}, e.g.@: @file{./12345}.
893 If @value{GDBN} has not been configured to included core file support,
894 such as for most embedded targets, then it will complain about a second
895 argument and ignore it.
897 Many options have both long and short forms; both are shown in the
898 following list. @value{GDBN} also recognizes the long forms if you truncate
899 them, so long as enough of the option is present to be unambiguous.
900 (If you prefer, you can flag option arguments with @samp{--} rather
901 than @samp{-}, though we illustrate the more usual convention.)
903 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
904 @c way, both those who look for -foo and --foo in the index, will find
908 @item -symbols @var{file}
910 @cindex @code{--symbols}
912 Read symbol table from file @var{file}.
914 @item -exec @var{file}
916 @cindex @code{--exec}
918 Use file @var{file} as the executable file to execute when appropriate,
919 and for examining pure data in conjunction with a core dump.
923 Read symbol table from file @var{file} and use it as the executable
926 @item -core @var{file}
928 @cindex @code{--core}
930 Use file @var{file} as a core dump to examine.
932 @item -c @var{number}
933 @item -pid @var{number}
934 @itemx -p @var{number}
937 Connect to process ID @var{number}, as with the @code{attach} command.
938 If there is no such process, @value{GDBN} will attempt to open a core
939 file named @var{number}.
941 @item -command @var{file}
943 @cindex @code{--command}
945 Execute @value{GDBN} commands from file @var{file}. @xref{Command
946 Files,, Command files}.
948 @item -eval-command @var{command}
949 @itemx -ex @var{command}
950 @cindex @code{--eval-command}
952 Execute a single @value{GDBN} command.
954 This option may be used multiple times to call multiple commands. It may
955 also be interleaved with @samp{-command} as required.
958 @value{GDBP} -ex 'target sim' -ex 'load' \
959 -x setbreakpoints -ex 'run' a.out
962 @item -directory @var{directory}
963 @itemx -d @var{directory}
964 @cindex @code{--directory}
966 Add @var{directory} to the path to search for source and script files.
970 @cindex @code{--readnow}
972 Read each symbol file's entire symbol table immediately, rather than
973 the default, which is to read it incrementally as it is needed.
974 This makes startup slower, but makes future operations faster.
979 @subsection Choosing modes
981 You can run @value{GDBN} in various alternative modes---for example, in
982 batch mode or quiet mode.
989 Do not execute commands found in any initialization files. Normally,
990 @value{GDBN} executes the commands in these files after all the command
991 options and arguments have been processed. @xref{Command Files,,Command
997 @cindex @code{--quiet}
998 @cindex @code{--silent}
1000 ``Quiet''. Do not print the introductory and copyright messages. These
1001 messages are also suppressed in batch mode.
1004 @cindex @code{--batch}
1005 Run in batch mode. Exit with status @code{0} after processing all the
1006 command files specified with @samp{-x} (and all commands from
1007 initialization files, if not inhibited with @samp{-n}). Exit with
1008 nonzero status if an error occurs in executing the @value{GDBN} commands
1009 in the command files.
1011 Batch mode may be useful for running @value{GDBN} as a filter, for
1012 example to download and run a program on another computer; in order to
1013 make this more useful, the message
1016 Program exited normally.
1020 (which is ordinarily issued whenever a program running under
1021 @value{GDBN} control terminates) is not issued when running in batch
1025 @cindex @code{--batch-silent}
1026 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1027 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1028 unaffected). This is much quieter than @samp{-silent} and would be useless
1029 for an interactive session.
1031 This is particularly useful when using targets that give @samp{Loading section}
1032 messages, for example.
1034 Note that targets that give their output via @value{GDBN}, as opposed to
1035 writing directly to @code{stdout}, will also be made silent.
1037 @item -return-child-result
1038 @cindex @code{--return-child-result}
1039 The return code from @value{GDBN} will be the return code from the child
1040 process (the process being debugged), with the following exceptions:
1044 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1045 internal error. In this case the exit code is the same as it would have been
1046 without @samp{-return-child-result}.
1048 The user quits with an explicit value. E.g., @samp{quit 1}.
1050 The child process never runs, or is not allowed to terminate, in which case
1051 the exit code will be -1.
1054 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1055 when @value{GDBN} is being used as a remote program loader or simulator
1060 @cindex @code{--nowindows}
1062 ``No windows''. If @value{GDBN} comes with a graphical user interface
1063 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1064 interface. If no GUI is available, this option has no effect.
1068 @cindex @code{--windows}
1070 If @value{GDBN} includes a GUI, then this option requires it to be
1073 @item -cd @var{directory}
1075 Run @value{GDBN} using @var{directory} as its working directory,
1076 instead of the current directory.
1080 @cindex @code{--fullname}
1082 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1083 subprocess. It tells @value{GDBN} to output the full file name and line
1084 number in a standard, recognizable fashion each time a stack frame is
1085 displayed (which includes each time your program stops). This
1086 recognizable format looks like two @samp{\032} characters, followed by
1087 the file name, line number and character position separated by colons,
1088 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1089 @samp{\032} characters as a signal to display the source code for the
1093 @cindex @code{--epoch}
1094 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1095 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1096 routines so as to allow Epoch to display values of expressions in a
1099 @item -annotate @var{level}
1100 @cindex @code{--annotate}
1101 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1102 effect is identical to using @samp{set annotate @var{level}}
1103 (@pxref{Annotations}). The annotation @var{level} controls how much
1104 information @value{GDBN} prints together with its prompt, values of
1105 expressions, source lines, and other types of output. Level 0 is the
1106 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1107 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1108 that control @value{GDBN}, and level 2 has been deprecated.
1110 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1114 @cindex @code{--args}
1115 Change interpretation of command line so that arguments following the
1116 executable file are passed as command line arguments to the inferior.
1117 This option stops option processing.
1119 @item -baud @var{bps}
1121 @cindex @code{--baud}
1123 Set the line speed (baud rate or bits per second) of any serial
1124 interface used by @value{GDBN} for remote debugging.
1126 @item -l @var{timeout}
1128 Set the timeout (in seconds) of any communication used by @value{GDBN}
1129 for remote debugging.
1131 @item -tty @var{device}
1132 @itemx -t @var{device}
1133 @cindex @code{--tty}
1135 Run using @var{device} for your program's standard input and output.
1136 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1138 @c resolve the situation of these eventually
1140 @cindex @code{--tui}
1141 Activate the @dfn{Text User Interface} when starting. The Text User
1142 Interface manages several text windows on the terminal, showing
1143 source, assembly, registers and @value{GDBN} command outputs
1144 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1145 Text User Interface can be enabled by invoking the program
1146 @samp{gdbtui}. Do not use this option if you run @value{GDBN} from
1147 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1150 @c @cindex @code{--xdb}
1151 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1152 @c For information, see the file @file{xdb_trans.html}, which is usually
1153 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1156 @item -interpreter @var{interp}
1157 @cindex @code{--interpreter}
1158 Use the interpreter @var{interp} for interface with the controlling
1159 program or device. This option is meant to be set by programs which
1160 communicate with @value{GDBN} using it as a back end.
1161 @xref{Interpreters, , Command Interpreters}.
1163 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1164 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1165 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1166 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1167 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1168 @sc{gdb/mi} interfaces are no longer supported.
1171 @cindex @code{--write}
1172 Open the executable and core files for both reading and writing. This
1173 is equivalent to the @samp{set write on} command inside @value{GDBN}
1177 @cindex @code{--statistics}
1178 This option causes @value{GDBN} to print statistics about time and
1179 memory usage after it completes each command and returns to the prompt.
1182 @cindex @code{--version}
1183 This option causes @value{GDBN} to print its version number and
1184 no-warranty blurb, and exit.
1189 @subsection What @value{GDBN} does during startup
1190 @cindex @value{GDBN} startup
1192 Here's the description of what @value{GDBN} does during session startup:
1196 Sets up the command interpreter as specified by the command line
1197 (@pxref{Mode Options, interpreter}).
1201 Reads the @dfn{init file} (if any) in your home directory@footnote{On
1202 DOS/Windows systems, the home directory is the one pointed to by the
1203 @code{HOME} environment variable.} and executes all the commands in
1207 Processes command line options and operands.
1210 Reads and executes the commands from init file (if any) in the current
1211 working directory. This is only done if the current directory is
1212 different from your home directory. Thus, you can have more than one
1213 init file, one generic in your home directory, and another, specific
1214 to the program you are debugging, in the directory where you invoke
1218 Reads command files specified by the @samp{-x} option. @xref{Command
1219 Files}, for more details about @value{GDBN} command files.
1222 Reads the command history recorded in the @dfn{history file}.
1223 @xref{Command History}, for more details about the command history and the
1224 files where @value{GDBN} records it.
1227 Init files use the same syntax as @dfn{command files} (@pxref{Command
1228 Files}) and are processed by @value{GDBN} in the same way. The init
1229 file in your home directory can set options (such as @samp{set
1230 complaints}) that affect subsequent processing of command line options
1231 and operands. Init files are not executed if you use the @samp{-nx}
1232 option (@pxref{Mode Options, ,Choosing modes}).
1234 @cindex init file name
1235 @cindex @file{.gdbinit}
1236 The @value{GDBN} init files are normally called @file{.gdbinit}.
1237 On some configurations of @value{GDBN}, the init file is known by a
1238 different name (these are typically environments where a specialized
1239 form of @value{GDBN} may need to coexist with other forms, hence a
1240 different name for the specialized version's init file). These are the
1241 environments with special init file names:
1244 @cindex @file{gdb.ini}
1246 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1247 the limitations of file names imposed by DOS filesystems. The Windows
1248 ports of @value{GDBN} use the standard name, but if they find a
1249 @file{gdb.ini} file, they warn you about that and suggest to rename
1250 the file to the standard name.
1252 @cindex @file{.vxgdbinit}
1254 VxWorks (Wind River Systems real-time OS): @file{.vxgdbinit}
1256 @cindex @file{.os68gdbinit}
1258 OS68K (Enea Data Systems real-time OS): @file{.os68gdbinit}
1260 @cindex @file{.esgdbinit}
1262 ES-1800 (Ericsson Telecom AB M68000 emulator): @file{.esgdbinit}
1265 CISCO 68k: @file{.cisco-gdbinit}
1270 @section Quitting @value{GDBN}
1271 @cindex exiting @value{GDBN}
1272 @cindex leaving @value{GDBN}
1275 @kindex quit @r{[}@var{expression}@r{]}
1276 @kindex q @r{(@code{quit})}
1277 @item quit @r{[}@var{expression}@r{]}
1279 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1280 @code{q}), or type an end-of-file character (usually @kbd{C-d}). If you
1281 do not supply @var{expression}, @value{GDBN} will terminate normally;
1282 otherwise it will terminate using the result of @var{expression} as the
1287 An interrupt (often @kbd{C-c}) does not exit from @value{GDBN}, but rather
1288 terminates the action of any @value{GDBN} command that is in progress and
1289 returns to @value{GDBN} command level. It is safe to type the interrupt
1290 character at any time because @value{GDBN} does not allow it to take effect
1291 until a time when it is safe.
1293 If you have been using @value{GDBN} to control an attached process or
1294 device, you can release it with the @code{detach} command
1295 (@pxref{Attach, ,Debugging an already-running process}).
1297 @node Shell Commands
1298 @section Shell commands
1300 If you need to execute occasional shell commands during your
1301 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1302 just use the @code{shell} command.
1306 @cindex shell escape
1307 @item shell @var{command string}
1308 Invoke a standard shell to execute @var{command string}.
1309 If it exists, the environment variable @code{SHELL} determines which
1310 shell to run. Otherwise @value{GDBN} uses the default shell
1311 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1314 The utility @code{make} is often needed in development environments.
1315 You do not have to use the @code{shell} command for this purpose in
1320 @cindex calling make
1321 @item make @var{make-args}
1322 Execute the @code{make} program with the specified
1323 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1326 @node Logging output
1327 @section Logging output
1328 @cindex logging @value{GDBN} output
1329 @cindex save @value{GDBN} output to a file
1331 You may want to save the output of @value{GDBN} commands to a file.
1332 There are several commands to control @value{GDBN}'s logging.
1336 @item set logging on
1338 @item set logging off
1340 @cindex logging file name
1341 @item set logging file @var{file}
1342 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1343 @item set logging overwrite [on|off]
1344 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1345 you want @code{set logging on} to overwrite the logfile instead.
1346 @item set logging redirect [on|off]
1347 By default, @value{GDBN} output will go to both the terminal and the logfile.
1348 Set @code{redirect} if you want output to go only to the log file.
1349 @kindex show logging
1351 Show the current values of the logging settings.
1355 @chapter @value{GDBN} Commands
1357 You can abbreviate a @value{GDBN} command to the first few letters of the command
1358 name, if that abbreviation is unambiguous; and you can repeat certain
1359 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1360 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1361 show you the alternatives available, if there is more than one possibility).
1364 * Command Syntax:: How to give commands to @value{GDBN}
1365 * Completion:: Command completion
1366 * Help:: How to ask @value{GDBN} for help
1369 @node Command Syntax
1370 @section Command syntax
1372 A @value{GDBN} command is a single line of input. There is no limit on
1373 how long it can be. It starts with a command name, which is followed by
1374 arguments whose meaning depends on the command name. For example, the
1375 command @code{step} accepts an argument which is the number of times to
1376 step, as in @samp{step 5}. You can also use the @code{step} command
1377 with no arguments. Some commands do not allow any arguments.
1379 @cindex abbreviation
1380 @value{GDBN} command names may always be truncated if that abbreviation is
1381 unambiguous. Other possible command abbreviations are listed in the
1382 documentation for individual commands. In some cases, even ambiguous
1383 abbreviations are allowed; for example, @code{s} is specially defined as
1384 equivalent to @code{step} even though there are other commands whose
1385 names start with @code{s}. You can test abbreviations by using them as
1386 arguments to the @code{help} command.
1388 @cindex repeating commands
1389 @kindex RET @r{(repeat last command)}
1390 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1391 repeat the previous command. Certain commands (for example, @code{run})
1392 will not repeat this way; these are commands whose unintentional
1393 repetition might cause trouble and which you are unlikely to want to
1394 repeat. User-defined commands can disable this feature; see
1395 @ref{Define, dont-repeat}.
1397 The @code{list} and @code{x} commands, when you repeat them with
1398 @key{RET}, construct new arguments rather than repeating
1399 exactly as typed. This permits easy scanning of source or memory.
1401 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1402 output, in a way similar to the common utility @code{more}
1403 (@pxref{Screen Size,,Screen size}). Since it is easy to press one
1404 @key{RET} too many in this situation, @value{GDBN} disables command
1405 repetition after any command that generates this sort of display.
1407 @kindex # @r{(a comment)}
1409 Any text from a @kbd{#} to the end of the line is a comment; it does
1410 nothing. This is useful mainly in command files (@pxref{Command
1411 Files,,Command files}).
1413 @cindex repeating command sequences
1414 @kindex C-o @r{(operate-and-get-next)}
1415 The @kbd{C-o} binding is useful for repeating a complex sequence of
1416 commands. This command accepts the current line, like @kbd{RET}, and
1417 then fetches the next line relative to the current line from the history
1421 @section Command completion
1424 @cindex word completion
1425 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1426 only one possibility; it can also show you what the valid possibilities
1427 are for the next word in a command, at any time. This works for @value{GDBN}
1428 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1430 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1431 of a word. If there is only one possibility, @value{GDBN} fills in the
1432 word, and waits for you to finish the command (or press @key{RET} to
1433 enter it). For example, if you type
1435 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1436 @c complete accuracy in these examples; space introduced for clarity.
1437 @c If texinfo enhancements make it unnecessary, it would be nice to
1438 @c replace " @key" by "@key" in the following...
1440 (@value{GDBP}) info bre @key{TAB}
1444 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1445 the only @code{info} subcommand beginning with @samp{bre}:
1448 (@value{GDBP}) info breakpoints
1452 You can either press @key{RET} at this point, to run the @code{info
1453 breakpoints} command, or backspace and enter something else, if
1454 @samp{breakpoints} does not look like the command you expected. (If you
1455 were sure you wanted @code{info breakpoints} in the first place, you
1456 might as well just type @key{RET} immediately after @samp{info bre},
1457 to exploit command abbreviations rather than command completion).
1459 If there is more than one possibility for the next word when you press
1460 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1461 characters and try again, or just press @key{TAB} a second time;
1462 @value{GDBN} displays all the possible completions for that word. For
1463 example, you might want to set a breakpoint on a subroutine whose name
1464 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1465 just sounds the bell. Typing @key{TAB} again displays all the
1466 function names in your program that begin with those characters, for
1470 (@value{GDBP}) b make_ @key{TAB}
1471 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1472 make_a_section_from_file make_environ
1473 make_abs_section make_function_type
1474 make_blockvector make_pointer_type
1475 make_cleanup make_reference_type
1476 make_command make_symbol_completion_list
1477 (@value{GDBP}) b make_
1481 After displaying the available possibilities, @value{GDBN} copies your
1482 partial input (@samp{b make_} in the example) so you can finish the
1485 If you just want to see the list of alternatives in the first place, you
1486 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1487 means @kbd{@key{META} ?}. You can type this either by holding down a
1488 key designated as the @key{META} shift on your keyboard (if there is
1489 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1491 @cindex quotes in commands
1492 @cindex completion of quoted strings
1493 Sometimes the string you need, while logically a ``word'', may contain
1494 parentheses or other characters that @value{GDBN} normally excludes from
1495 its notion of a word. To permit word completion to work in this
1496 situation, you may enclose words in @code{'} (single quote marks) in
1497 @value{GDBN} commands.
1499 The most likely situation where you might need this is in typing the
1500 name of a C@t{++} function. This is because C@t{++} allows function
1501 overloading (multiple definitions of the same function, distinguished
1502 by argument type). For example, when you want to set a breakpoint you
1503 may need to distinguish whether you mean the version of @code{name}
1504 that takes an @code{int} parameter, @code{name(int)}, or the version
1505 that takes a @code{float} parameter, @code{name(float)}. To use the
1506 word-completion facilities in this situation, type a single quote
1507 @code{'} at the beginning of the function name. This alerts
1508 @value{GDBN} that it may need to consider more information than usual
1509 when you press @key{TAB} or @kbd{M-?} to request word completion:
1512 (@value{GDBP}) b 'bubble( @kbd{M-?}
1513 bubble(double,double) bubble(int,int)
1514 (@value{GDBP}) b 'bubble(
1517 In some cases, @value{GDBN} can tell that completing a name requires using
1518 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1519 completing as much as it can) if you do not type the quote in the first
1523 (@value{GDBP}) b bub @key{TAB}
1524 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1525 (@value{GDBP}) b 'bubble(
1529 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1530 you have not yet started typing the argument list when you ask for
1531 completion on an overloaded symbol.
1533 For more information about overloaded functions, see @ref{C plus plus
1534 expressions, ,C@t{++} expressions}. You can use the command @code{set
1535 overload-resolution off} to disable overload resolution;
1536 see @ref{Debugging C plus plus, ,@value{GDBN} features for C@t{++}}.
1540 @section Getting help
1541 @cindex online documentation
1544 You can always ask @value{GDBN} itself for information on its commands,
1545 using the command @code{help}.
1548 @kindex h @r{(@code{help})}
1551 You can use @code{help} (abbreviated @code{h}) with no arguments to
1552 display a short list of named classes of commands:
1556 List of classes of commands:
1558 aliases -- Aliases of other commands
1559 breakpoints -- Making program stop at certain points
1560 data -- Examining data
1561 files -- Specifying and examining files
1562 internals -- Maintenance commands
1563 obscure -- Obscure features
1564 running -- Running the program
1565 stack -- Examining the stack
1566 status -- Status inquiries
1567 support -- Support facilities
1568 tracepoints -- Tracing of program execution without@*
1569 stopping the program
1570 user-defined -- User-defined commands
1572 Type "help" followed by a class name for a list of
1573 commands in that class.
1574 Type "help" followed by command name for full
1576 Command name abbreviations are allowed if unambiguous.
1579 @c the above line break eliminates huge line overfull...
1581 @item help @var{class}
1582 Using one of the general help classes as an argument, you can get a
1583 list of the individual commands in that class. For example, here is the
1584 help display for the class @code{status}:
1587 (@value{GDBP}) help status
1592 @c Line break in "show" line falsifies real output, but needed
1593 @c to fit in smallbook page size.
1594 info -- Generic command for showing things
1595 about the program being debugged
1596 show -- Generic command for showing things
1599 Type "help" followed by command name for full
1601 Command name abbreviations are allowed if unambiguous.
1605 @item help @var{command}
1606 With a command name as @code{help} argument, @value{GDBN} displays a
1607 short paragraph on how to use that command.
1610 @item apropos @var{args}
1611 The @code{apropos} command searches through all of the @value{GDBN}
1612 commands, and their documentation, for the regular expression specified in
1613 @var{args}. It prints out all matches found. For example:
1624 set symbol-reloading -- Set dynamic symbol table reloading
1625 multiple times in one run
1626 show symbol-reloading -- Show dynamic symbol table reloading
1627 multiple times in one run
1632 @item complete @var{args}
1633 The @code{complete @var{args}} command lists all the possible completions
1634 for the beginning of a command. Use @var{args} to specify the beginning of the
1635 command you want completed. For example:
1641 @noindent results in:
1652 @noindent This is intended for use by @sc{gnu} Emacs.
1655 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1656 and @code{show} to inquire about the state of your program, or the state
1657 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1658 manual introduces each of them in the appropriate context. The listings
1659 under @code{info} and under @code{show} in the Index point to
1660 all the sub-commands. @xref{Index}.
1665 @kindex i @r{(@code{info})}
1667 This command (abbreviated @code{i}) is for describing the state of your
1668 program. For example, you can list the arguments given to your program
1669 with @code{info args}, list the registers currently in use with @code{info
1670 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1671 You can get a complete list of the @code{info} sub-commands with
1672 @w{@code{help info}}.
1676 You can assign the result of an expression to an environment variable with
1677 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1678 @code{set prompt $}.
1682 In contrast to @code{info}, @code{show} is for describing the state of
1683 @value{GDBN} itself.
1684 You can change most of the things you can @code{show}, by using the
1685 related command @code{set}; for example, you can control what number
1686 system is used for displays with @code{set radix}, or simply inquire
1687 which is currently in use with @code{show radix}.
1690 To display all the settable parameters and their current
1691 values, you can use @code{show} with no arguments; you may also use
1692 @code{info set}. Both commands produce the same display.
1693 @c FIXME: "info set" violates the rule that "info" is for state of
1694 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1695 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1699 Here are three miscellaneous @code{show} subcommands, all of which are
1700 exceptional in lacking corresponding @code{set} commands:
1703 @kindex show version
1704 @cindex @value{GDBN} version number
1706 Show what version of @value{GDBN} is running. You should include this
1707 information in @value{GDBN} bug-reports. If multiple versions of
1708 @value{GDBN} are in use at your site, you may need to determine which
1709 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1710 commands are introduced, and old ones may wither away. Also, many
1711 system vendors ship variant versions of @value{GDBN}, and there are
1712 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1713 The version number is the same as the one announced when you start
1716 @kindex show copying
1717 @kindex info copying
1718 @cindex display @value{GDBN} copyright
1721 Display information about permission for copying @value{GDBN}.
1723 @kindex show warranty
1724 @kindex info warranty
1726 @itemx info warranty
1727 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1728 if your version of @value{GDBN} comes with one.
1733 @chapter Running Programs Under @value{GDBN}
1735 When you run a program under @value{GDBN}, you must first generate
1736 debugging information when you compile it.
1738 You may start @value{GDBN} with its arguments, if any, in an environment
1739 of your choice. If you are doing native debugging, you may redirect
1740 your program's input and output, debug an already running process, or
1741 kill a child process.
1744 * Compilation:: Compiling for debugging
1745 * Starting:: Starting your program
1746 * Arguments:: Your program's arguments
1747 * Environment:: Your program's environment
1749 * Working Directory:: Your program's working directory
1750 * Input/Output:: Your program's input and output
1751 * Attach:: Debugging an already-running process
1752 * Kill Process:: Killing the child process
1754 * Threads:: Debugging programs with multiple threads
1755 * Processes:: Debugging programs with multiple processes
1756 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1760 @section Compiling for debugging
1762 In order to debug a program effectively, you need to generate
1763 debugging information when you compile it. This debugging information
1764 is stored in the object file; it describes the data type of each
1765 variable or function and the correspondence between source line numbers
1766 and addresses in the executable code.
1768 To request debugging information, specify the @samp{-g} option when you run
1771 Programs that are to be shipped to your customers are compiled with
1772 optimizations, using the @samp{-O} compiler option. However, many
1773 compilers are unable to handle the @samp{-g} and @samp{-O} options
1774 together. Using those compilers, you cannot generate optimized
1775 executables containing debugging information.
1777 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1778 without @samp{-O}, making it possible to debug optimized code. We
1779 recommend that you @emph{always} use @samp{-g} whenever you compile a
1780 program. You may think your program is correct, but there is no sense
1781 in pushing your luck.
1783 @cindex optimized code, debugging
1784 @cindex debugging optimized code
1785 When you debug a program compiled with @samp{-g -O}, remember that the
1786 optimizer is rearranging your code; the debugger shows you what is
1787 really there. Do not be too surprised when the execution path does not
1788 exactly match your source file! An extreme example: if you define a
1789 variable, but never use it, @value{GDBN} never sees that
1790 variable---because the compiler optimizes it out of existence.
1792 Some things do not work as well with @samp{-g -O} as with just
1793 @samp{-g}, particularly on machines with instruction scheduling. If in
1794 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1795 please report it to us as a bug (including a test case!).
1796 @xref{Variables}, for more information about debugging optimized code.
1798 Older versions of the @sc{gnu} C compiler permitted a variant option
1799 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1800 format; if your @sc{gnu} C compiler has this option, do not use it.
1802 @value{GDBN} knows about preprocessor macros and can show you their
1803 expansion (@pxref{Macros}). Most compilers do not include information
1804 about preprocessor macros in the debugging information if you specify
1805 the @option{-g} flag alone, because this information is rather large.
1806 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1807 provides macro information if you specify the options
1808 @option{-gdwarf-2} and @option{-g3}; the former option requests
1809 debugging information in the Dwarf 2 format, and the latter requests
1810 ``extra information''. In the future, we hope to find more compact
1811 ways to represent macro information, so that it can be included with
1816 @section Starting your program
1822 @kindex r @r{(@code{run})}
1825 Use the @code{run} command to start your program under @value{GDBN}.
1826 You must first specify the program name (except on VxWorks) with an
1827 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1828 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1829 (@pxref{Files, ,Commands to specify files}).
1833 If you are running your program in an execution environment that
1834 supports processes, @code{run} creates an inferior process and makes
1835 that process run your program. (In environments without processes,
1836 @code{run} jumps to the start of your program.)
1838 The execution of a program is affected by certain information it
1839 receives from its superior. @value{GDBN} provides ways to specify this
1840 information, which you must do @emph{before} starting your program. (You
1841 can change it after starting your program, but such changes only affect
1842 your program the next time you start it.) This information may be
1843 divided into four categories:
1846 @item The @emph{arguments.}
1847 Specify the arguments to give your program as the arguments of the
1848 @code{run} command. If a shell is available on your target, the shell
1849 is used to pass the arguments, so that you may use normal conventions
1850 (such as wildcard expansion or variable substitution) in describing
1852 In Unix systems, you can control which shell is used with the
1853 @code{SHELL} environment variable.
1854 @xref{Arguments, ,Your program's arguments}.
1856 @item The @emph{environment.}
1857 Your program normally inherits its environment from @value{GDBN}, but you can
1858 use the @value{GDBN} commands @code{set environment} and @code{unset
1859 environment} to change parts of the environment that affect
1860 your program. @xref{Environment, ,Your program's environment}.
1862 @item The @emph{working directory.}
1863 Your program inherits its working directory from @value{GDBN}. You can set
1864 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1865 @xref{Working Directory, ,Your program's working directory}.
1867 @item The @emph{standard input and output.}
1868 Your program normally uses the same device for standard input and
1869 standard output as @value{GDBN} is using. You can redirect input and output
1870 in the @code{run} command line, or you can use the @code{tty} command to
1871 set a different device for your program.
1872 @xref{Input/Output, ,Your program's input and output}.
1875 @emph{Warning:} While input and output redirection work, you cannot use
1876 pipes to pass the output of the program you are debugging to another
1877 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1881 When you issue the @code{run} command, your program begins to execute
1882 immediately. @xref{Stopping, ,Stopping and continuing}, for discussion
1883 of how to arrange for your program to stop. Once your program has
1884 stopped, you may call functions in your program, using the @code{print}
1885 or @code{call} commands. @xref{Data, ,Examining Data}.
1887 If the modification time of your symbol file has changed since the last
1888 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1889 table, and reads it again. When it does this, @value{GDBN} tries to retain
1890 your current breakpoints.
1895 @cindex run to main procedure
1896 The name of the main procedure can vary from language to language.
1897 With C or C@t{++}, the main procedure name is always @code{main}, but
1898 other languages such as Ada do not require a specific name for their
1899 main procedure. The debugger provides a convenient way to start the
1900 execution of the program and to stop at the beginning of the main
1901 procedure, depending on the language used.
1903 The @samp{start} command does the equivalent of setting a temporary
1904 breakpoint at the beginning of the main procedure and then invoking
1905 the @samp{run} command.
1907 @cindex elaboration phase
1908 Some programs contain an @dfn{elaboration} phase where some startup code is
1909 executed before the main procedure is called. This depends on the
1910 languages used to write your program. In C@t{++}, for instance,
1911 constructors for static and global objects are executed before
1912 @code{main} is called. It is therefore possible that the debugger stops
1913 before reaching the main procedure. However, the temporary breakpoint
1914 will remain to halt execution.
1916 Specify the arguments to give to your program as arguments to the
1917 @samp{start} command. These arguments will be given verbatim to the
1918 underlying @samp{run} command. Note that the same arguments will be
1919 reused if no argument is provided during subsequent calls to
1920 @samp{start} or @samp{run}.
1922 It is sometimes necessary to debug the program during elaboration. In
1923 these cases, using the @code{start} command would stop the execution of
1924 your program too late, as the program would have already completed the
1925 elaboration phase. Under these circumstances, insert breakpoints in your
1926 elaboration code before running your program.
1930 @section Your program's arguments
1932 @cindex arguments (to your program)
1933 The arguments to your program can be specified by the arguments of the
1935 They are passed to a shell, which expands wildcard characters and
1936 performs redirection of I/O, and thence to your program. Your
1937 @code{SHELL} environment variable (if it exists) specifies what shell
1938 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1939 the default shell (@file{/bin/sh} on Unix).
1941 On non-Unix systems, the program is usually invoked directly by
1942 @value{GDBN}, which emulates I/O redirection via the appropriate system
1943 calls, and the wildcard characters are expanded by the startup code of
1944 the program, not by the shell.
1946 @code{run} with no arguments uses the same arguments used by the previous
1947 @code{run}, or those set by the @code{set args} command.
1952 Specify the arguments to be used the next time your program is run. If
1953 @code{set args} has no arguments, @code{run} executes your program
1954 with no arguments. Once you have run your program with arguments,
1955 using @code{set args} before the next @code{run} is the only way to run
1956 it again without arguments.
1960 Show the arguments to give your program when it is started.
1964 @section Your program's environment
1966 @cindex environment (of your program)
1967 The @dfn{environment} consists of a set of environment variables and
1968 their values. Environment variables conventionally record such things as
1969 your user name, your home directory, your terminal type, and your search
1970 path for programs to run. Usually you set up environment variables with
1971 the shell and they are inherited by all the other programs you run. When
1972 debugging, it can be useful to try running your program with a modified
1973 environment without having to start @value{GDBN} over again.
1977 @item path @var{directory}
1978 Add @var{directory} to the front of the @code{PATH} environment variable
1979 (the search path for executables) that will be passed to your program.
1980 The value of @code{PATH} used by @value{GDBN} does not change.
1981 You may specify several directory names, separated by whitespace or by a
1982 system-dependent separator character (@samp{:} on Unix, @samp{;} on
1983 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1984 is moved to the front, so it is searched sooner.
1986 You can use the string @samp{$cwd} to refer to whatever is the current
1987 working directory at the time @value{GDBN} searches the path. If you
1988 use @samp{.} instead, it refers to the directory where you executed the
1989 @code{path} command. @value{GDBN} replaces @samp{.} in the
1990 @var{directory} argument (with the current path) before adding
1991 @var{directory} to the search path.
1992 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1993 @c document that, since repeating it would be a no-op.
1997 Display the list of search paths for executables (the @code{PATH}
1998 environment variable).
2000 @kindex show environment
2001 @item show environment @r{[}@var{varname}@r{]}
2002 Print the value of environment variable @var{varname} to be given to
2003 your program when it starts. If you do not supply @var{varname},
2004 print the names and values of all environment variables to be given to
2005 your program. You can abbreviate @code{environment} as @code{env}.
2007 @kindex set environment
2008 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2009 Set environment variable @var{varname} to @var{value}. The value
2010 changes for your program only, not for @value{GDBN} itself. @var{value} may
2011 be any string; the values of environment variables are just strings, and
2012 any interpretation is supplied by your program itself. The @var{value}
2013 parameter is optional; if it is eliminated, the variable is set to a
2015 @c "any string" here does not include leading, trailing
2016 @c blanks. Gnu asks: does anyone care?
2018 For example, this command:
2025 tells the debugged program, when subsequently run, that its user is named
2026 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2027 are not actually required.)
2029 @kindex unset environment
2030 @item unset environment @var{varname}
2031 Remove variable @var{varname} from the environment to be passed to your
2032 program. This is different from @samp{set env @var{varname} =};
2033 @code{unset environment} removes the variable from the environment,
2034 rather than assigning it an empty value.
2037 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2039 by your @code{SHELL} environment variable if it exists (or
2040 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2041 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2042 @file{.bashrc} for BASH---any variables you set in that file affect
2043 your program. You may wish to move setting of environment variables to
2044 files that are only run when you sign on, such as @file{.login} or
2047 @node Working Directory
2048 @section Your program's working directory
2050 @cindex working directory (of your program)
2051 Each time you start your program with @code{run}, it inherits its
2052 working directory from the current working directory of @value{GDBN}.
2053 The @value{GDBN} working directory is initially whatever it inherited
2054 from its parent process (typically the shell), but you can specify a new
2055 working directory in @value{GDBN} with the @code{cd} command.
2057 The @value{GDBN} working directory also serves as a default for the commands
2058 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2063 @cindex change working directory
2064 @item cd @var{directory}
2065 Set the @value{GDBN} working directory to @var{directory}.
2069 Print the @value{GDBN} working directory.
2072 It is generally impossible to find the current working directory of
2073 the process being debugged (since a program can change its directory
2074 during its run). If you work on a system where @value{GDBN} is
2075 configured with the @file{/proc} support, you can use the @code{info
2076 proc} command (@pxref{SVR4 Process Information}) to find out the
2077 current working directory of the debuggee.
2080 @section Your program's input and output
2085 By default, the program you run under @value{GDBN} does input and output to
2086 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2087 to its own terminal modes to interact with you, but it records the terminal
2088 modes your program was using and switches back to them when you continue
2089 running your program.
2092 @kindex info terminal
2094 Displays information recorded by @value{GDBN} about the terminal modes your
2098 You can redirect your program's input and/or output using shell
2099 redirection with the @code{run} command. For example,
2106 starts your program, diverting its output to the file @file{outfile}.
2109 @cindex controlling terminal
2110 Another way to specify where your program should do input and output is
2111 with the @code{tty} command. This command accepts a file name as
2112 argument, and causes this file to be the default for future @code{run}
2113 commands. It also resets the controlling terminal for the child
2114 process, for future @code{run} commands. For example,
2121 directs that processes started with subsequent @code{run} commands
2122 default to do input and output on the terminal @file{/dev/ttyb} and have
2123 that as their controlling terminal.
2125 An explicit redirection in @code{run} overrides the @code{tty} command's
2126 effect on the input/output device, but not its effect on the controlling
2129 When you use the @code{tty} command or redirect input in the @code{run}
2130 command, only the input @emph{for your program} is affected. The input
2131 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2132 for @code{set inferior-tty}.
2134 @cindex inferior tty
2135 @cindex set inferior controlling terminal
2136 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2137 display the name of the terminal that will be used for future runs of your
2141 @item set inferior-tty /dev/ttyb
2142 @kindex set inferior-tty
2143 Set the tty for the program being debugged to /dev/ttyb.
2145 @item show inferior-tty
2146 @kindex show inferior-tty
2147 Show the current tty for the program being debugged.
2151 @section Debugging an already-running process
2156 @item attach @var{process-id}
2157 This command attaches to a running process---one that was started
2158 outside @value{GDBN}. (@code{info files} shows your active
2159 targets.) The command takes as argument a process ID. The usual way to
2160 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2161 or with the @samp{jobs -l} shell command.
2163 @code{attach} does not repeat if you press @key{RET} a second time after
2164 executing the command.
2167 To use @code{attach}, your program must be running in an environment
2168 which supports processes; for example, @code{attach} does not work for
2169 programs on bare-board targets that lack an operating system. You must
2170 also have permission to send the process a signal.
2172 When you use @code{attach}, the debugger finds the program running in
2173 the process first by looking in the current working directory, then (if
2174 the program is not found) by using the source file search path
2175 (@pxref{Source Path, ,Specifying source directories}). You can also use
2176 the @code{file} command to load the program. @xref{Files, ,Commands to
2179 The first thing @value{GDBN} does after arranging to debug the specified
2180 process is to stop it. You can examine and modify an attached process
2181 with all the @value{GDBN} commands that are ordinarily available when
2182 you start processes with @code{run}. You can insert breakpoints; you
2183 can step and continue; you can modify storage. If you would rather the
2184 process continue running, you may use the @code{continue} command after
2185 attaching @value{GDBN} to the process.
2190 When you have finished debugging the attached process, you can use the
2191 @code{detach} command to release it from @value{GDBN} control. Detaching
2192 the process continues its execution. After the @code{detach} command,
2193 that process and @value{GDBN} become completely independent once more, and you
2194 are ready to @code{attach} another process or start one with @code{run}.
2195 @code{detach} does not repeat if you press @key{RET} again after
2196 executing the command.
2199 If you exit @value{GDBN} or use the @code{run} command while you have an
2200 attached process, you kill that process. By default, @value{GDBN} asks
2201 for confirmation if you try to do either of these things; you can
2202 control whether or not you need to confirm by using the @code{set
2203 confirm} command (@pxref{Messages/Warnings, ,Optional warnings and
2207 @section Killing the child process
2212 Kill the child process in which your program is running under @value{GDBN}.
2215 This command is useful if you wish to debug a core dump instead of a
2216 running process. @value{GDBN} ignores any core dump file while your program
2219 On some operating systems, a program cannot be executed outside @value{GDBN}
2220 while you have breakpoints set on it inside @value{GDBN}. You can use the
2221 @code{kill} command in this situation to permit running your program
2222 outside the debugger.
2224 The @code{kill} command is also useful if you wish to recompile and
2225 relink your program, since on many systems it is impossible to modify an
2226 executable file while it is running in a process. In this case, when you
2227 next type @code{run}, @value{GDBN} notices that the file has changed, and
2228 reads the symbol table again (while trying to preserve your current
2229 breakpoint settings).
2232 @section Debugging programs with multiple threads
2234 @cindex threads of execution
2235 @cindex multiple threads
2236 @cindex switching threads
2237 In some operating systems, such as HP-UX and Solaris, a single program
2238 may have more than one @dfn{thread} of execution. The precise semantics
2239 of threads differ from one operating system to another, but in general
2240 the threads of a single program are akin to multiple processes---except
2241 that they share one address space (that is, they can all examine and
2242 modify the same variables). On the other hand, each thread has its own
2243 registers and execution stack, and perhaps private memory.
2245 @value{GDBN} provides these facilities for debugging multi-thread
2249 @item automatic notification of new threads
2250 @item @samp{thread @var{threadno}}, a command to switch among threads
2251 @item @samp{info threads}, a command to inquire about existing threads
2252 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2253 a command to apply a command to a list of threads
2254 @item thread-specific breakpoints
2258 @emph{Warning:} These facilities are not yet available on every
2259 @value{GDBN} configuration where the operating system supports threads.
2260 If your @value{GDBN} does not support threads, these commands have no
2261 effect. For example, a system without thread support shows no output
2262 from @samp{info threads}, and always rejects the @code{thread} command,
2266 (@value{GDBP}) info threads
2267 (@value{GDBP}) thread 1
2268 Thread ID 1 not known. Use the "info threads" command to
2269 see the IDs of currently known threads.
2271 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2272 @c doesn't support threads"?
2275 @cindex focus of debugging
2276 @cindex current thread
2277 The @value{GDBN} thread debugging facility allows you to observe all
2278 threads while your program runs---but whenever @value{GDBN} takes
2279 control, one thread in particular is always the focus of debugging.
2280 This thread is called the @dfn{current thread}. Debugging commands show
2281 program information from the perspective of the current thread.
2283 @cindex @code{New} @var{systag} message
2284 @cindex thread identifier (system)
2285 @c FIXME-implementors!! It would be more helpful if the [New...] message
2286 @c included GDB's numeric thread handle, so you could just go to that
2287 @c thread without first checking `info threads'.
2288 Whenever @value{GDBN} detects a new thread in your program, it displays
2289 the target system's identification for the thread with a message in the
2290 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2291 whose form varies depending on the particular system. For example, on
2292 LynxOS, you might see
2295 [New process 35 thread 27]
2299 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2300 the @var{systag} is simply something like @samp{process 368}, with no
2303 @c FIXME!! (1) Does the [New...] message appear even for the very first
2304 @c thread of a program, or does it only appear for the
2305 @c second---i.e.@: when it becomes obvious we have a multithread
2307 @c (2) *Is* there necessarily a first thread always? Or do some
2308 @c multithread systems permit starting a program with multiple
2309 @c threads ab initio?
2311 @cindex thread number
2312 @cindex thread identifier (GDB)
2313 For debugging purposes, @value{GDBN} associates its own thread
2314 number---always a single integer---with each thread in your program.
2317 @kindex info threads
2319 Display a summary of all threads currently in your
2320 program. @value{GDBN} displays for each thread (in this order):
2324 the thread number assigned by @value{GDBN}
2327 the target system's thread identifier (@var{systag})
2330 the current stack frame summary for that thread
2334 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2335 indicates the current thread.
2339 @c end table here to get a little more width for example
2342 (@value{GDBP}) info threads
2343 3 process 35 thread 27 0x34e5 in sigpause ()
2344 2 process 35 thread 23 0x34e5 in sigpause ()
2345 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2351 @cindex debugging multithreaded programs (on HP-UX)
2352 @cindex thread identifier (GDB), on HP-UX
2353 For debugging purposes, @value{GDBN} associates its own thread
2354 number---a small integer assigned in thread-creation order---with each
2355 thread in your program.
2357 @cindex @code{New} @var{systag} message, on HP-UX
2358 @cindex thread identifier (system), on HP-UX
2359 @c FIXME-implementors!! It would be more helpful if the [New...] message
2360 @c included GDB's numeric thread handle, so you could just go to that
2361 @c thread without first checking `info threads'.
2362 Whenever @value{GDBN} detects a new thread in your program, it displays
2363 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2364 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2365 whose form varies depending on the particular system. For example, on
2369 [New thread 2 (system thread 26594)]
2373 when @value{GDBN} notices a new thread.
2376 @kindex info threads (HP-UX)
2378 Display a summary of all threads currently in your
2379 program. @value{GDBN} displays for each thread (in this order):
2382 @item the thread number assigned by @value{GDBN}
2384 @item the target system's thread identifier (@var{systag})
2386 @item the current stack frame summary for that thread
2390 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2391 indicates the current thread.
2395 @c end table here to get a little more width for example
2398 (@value{GDBP}) info threads
2399 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2401 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2402 from /usr/lib/libc.2
2403 1 system thread 27905 0x7b003498 in _brk () \@*
2404 from /usr/lib/libc.2
2407 On Solaris, you can display more information about user threads with a
2408 Solaris-specific command:
2411 @item maint info sol-threads
2412 @kindex maint info sol-threads
2413 @cindex thread info (Solaris)
2414 Display info on Solaris user threads.
2418 @kindex thread @var{threadno}
2419 @item thread @var{threadno}
2420 Make thread number @var{threadno} the current thread. The command
2421 argument @var{threadno} is the internal @value{GDBN} thread number, as
2422 shown in the first field of the @samp{info threads} display.
2423 @value{GDBN} responds by displaying the system identifier of the thread
2424 you selected, and its current stack frame summary:
2427 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2428 (@value{GDBP}) thread 2
2429 [Switching to process 35 thread 23]
2430 0x34e5 in sigpause ()
2434 As with the @samp{[New @dots{}]} message, the form of the text after
2435 @samp{Switching to} depends on your system's conventions for identifying
2438 @kindex thread apply
2439 @cindex apply command to several threads
2440 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2441 The @code{thread apply} command allows you to apply the named
2442 @var{command} to one or more threads. Specify the numbers of the
2443 threads that you want affected with the command argument
2444 @var{threadno}. It can be a single thread number, one of the numbers
2445 shown in the first field of the @samp{info threads} display; or it
2446 could be a range of thread numbers, as in @code{2-4}. To apply a
2447 command to all threads, type @kbd{thread apply all @var{command}}.
2450 @cindex automatic thread selection
2451 @cindex switching threads automatically
2452 @cindex threads, automatic switching
2453 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2454 signal, it automatically selects the thread where that breakpoint or
2455 signal happened. @value{GDBN} alerts you to the context switch with a
2456 message of the form @samp{[Switching to @var{systag}]} to identify the
2459 @xref{Thread Stops,,Stopping and starting multi-thread programs}, for
2460 more information about how @value{GDBN} behaves when you stop and start
2461 programs with multiple threads.
2463 @xref{Set Watchpoints,,Setting watchpoints}, for information about
2464 watchpoints in programs with multiple threads.
2467 @section Debugging programs with multiple processes
2469 @cindex fork, debugging programs which call
2470 @cindex multiple processes
2471 @cindex processes, multiple
2472 On most systems, @value{GDBN} has no special support for debugging
2473 programs which create additional processes using the @code{fork}
2474 function. When a program forks, @value{GDBN} will continue to debug the
2475 parent process and the child process will run unimpeded. If you have
2476 set a breakpoint in any code which the child then executes, the child
2477 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2478 will cause it to terminate.
2480 However, if you want to debug the child process there is a workaround
2481 which isn't too painful. Put a call to @code{sleep} in the code which
2482 the child process executes after the fork. It may be useful to sleep
2483 only if a certain environment variable is set, or a certain file exists,
2484 so that the delay need not occur when you don't want to run @value{GDBN}
2485 on the child. While the child is sleeping, use the @code{ps} program to
2486 get its process ID. Then tell @value{GDBN} (a new invocation of
2487 @value{GDBN} if you are also debugging the parent process) to attach to
2488 the child process (@pxref{Attach}). From that point on you can debug
2489 the child process just like any other process which you attached to.
2491 On some systems, @value{GDBN} provides support for debugging programs that
2492 create additional processes using the @code{fork} or @code{vfork} functions.
2493 Currently, the only platforms with this feature are HP-UX (11.x and later
2494 only?) and GNU/Linux (kernel version 2.5.60 and later).
2496 By default, when a program forks, @value{GDBN} will continue to debug
2497 the parent process and the child process will run unimpeded.
2499 If you want to follow the child process instead of the parent process,
2500 use the command @w{@code{set follow-fork-mode}}.
2503 @kindex set follow-fork-mode
2504 @item set follow-fork-mode @var{mode}
2505 Set the debugger response to a program call of @code{fork} or
2506 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2507 process. The @var{mode} argument can be:
2511 The original process is debugged after a fork. The child process runs
2512 unimpeded. This is the default.
2515 The new process is debugged after a fork. The parent process runs
2520 @kindex show follow-fork-mode
2521 @item show follow-fork-mode
2522 Display the current debugger response to a @code{fork} or @code{vfork} call.
2525 @cindex debugging multiple processes
2526 On Linux, if you want to debug both the parent and child processes, use the
2527 command @w{@code{set detach-on-fork}}.
2530 @kindex set detach-on-fork
2531 @item set detach-on-fork @var{mode}
2532 Tells gdb whether to detach one of the processes after a fork, or
2533 retain debugger control over them both.
2537 The child process (or parent process, depending on the value of
2538 @code{follow-fork-mode}) will be detached and allowed to run
2539 independently. This is the default.
2542 Both processes will be held under the control of @value{GDBN}.
2543 One process (child or parent, depending on the value of
2544 @code{follow-fork-mode}) is debugged as usual, while the other
2549 @kindex show detach-on-follow
2550 @item show detach-on-follow
2551 Show whether detach-on-follow mode is on/off.
2554 If you choose to set @var{detach-on-follow} mode off, then
2555 @value{GDBN} will retain control of all forked processes (including
2556 nested forks). You can list the forked processes under the control of
2557 @value{GDBN} by using the @w{@code{info forks}} command, and switch
2558 from one fork to another by using the @w{@code{fork}} command.
2563 Print a list of all forked processes under the control of @value{GDBN}.
2564 The listing will include a fork id, a process id, and the current
2565 position (program counter) of the process.
2568 @kindex fork @var{fork-id}
2569 @item fork @var{fork-id}
2570 Make fork number @var{fork-id} the current process. The argument
2571 @var{fork-id} is the internal fork number assigned by @value{GDBN},
2572 as shown in the first field of the @samp{info forks} display.
2576 To quit debugging one of the forked processes, you can either detach
2577 from it by using the @w{@code{detach-fork}} command (allowing it to
2578 run independently), or delete (and kill) it using the
2579 @w{@code{delete fork}} command.
2582 @kindex detach-fork @var{fork-id}
2583 @item detach-fork @var{fork-id}
2584 Detach from the process identified by @value{GDBN} fork number
2585 @var{fork-id}, and remove it from the fork list. The process will be
2586 allowed to run independently.
2588 @kindex delete fork @var{fork-id}
2589 @item delete fork @var{fork-id}
2590 Kill the process identified by @value{GDBN} fork number @var{fork-id},
2591 and remove it from the fork list.
2595 If you ask to debug a child process and a @code{vfork} is followed by an
2596 @code{exec}, @value{GDBN} executes the new target up to the first
2597 breakpoint in the new target. If you have a breakpoint set on
2598 @code{main} in your original program, the breakpoint will also be set on
2599 the child process's @code{main}.
2601 When a child process is spawned by @code{vfork}, you cannot debug the
2602 child or parent until an @code{exec} call completes.
2604 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2605 call executes, the new target restarts. To restart the parent process,
2606 use the @code{file} command with the parent executable name as its
2609 You can use the @code{catch} command to make @value{GDBN} stop whenever
2610 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2611 Catchpoints, ,Setting catchpoints}.
2613 @node Checkpoint/Restart
2614 @section Setting a @emph{bookmark} to return to later
2619 @cindex snapshot of a process
2620 @cindex rewind program state
2622 On certain operating systems@footnote{Currently, only
2623 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
2624 program's state, called a @dfn{checkpoint}, and come back to it
2627 Returning to a checkpoint effectively undoes everything that has
2628 happened in the program since the @code{checkpoint} was saved. This
2629 includes changes in memory, registers, and even (within some limits)
2630 system state. Effectively, it is like going back in time to the
2631 moment when the checkpoint was saved.
2633 Thus, if you're stepping thru a program and you think you're
2634 getting close to the point where things go wrong, you can save
2635 a checkpoint. Then, if you accidentally go too far and miss
2636 the critical statement, instead of having to restart your program
2637 from the beginning, you can just go back to the checkpoint and
2638 start again from there.
2640 This can be especially useful if it takes a lot of time or
2641 steps to reach the point where you think the bug occurs.
2643 To use the @code{checkpoint}/@code{restart} method of debugging:
2648 Save a snapshot of the debugged program's current execution state.
2649 The @code{checkpoint} command takes no arguments, but each checkpoint
2650 is assigned a small integer id, similar to a breakpoint id.
2652 @kindex info checkpoints
2653 @item info checkpoints
2654 List the checkpoints that have been saved in the current debugging
2655 session. For each checkpoint, the following information will be
2662 @item Source line, or label
2665 @kindex restart @var{checkpoint-id}
2666 @item restart @var{checkpoint-id}
2667 Restore the program state that was saved as checkpoint number
2668 @var{checkpoint-id}. All program variables, registers, stack frames
2669 etc.@: will be returned to the values that they had when the checkpoint
2670 was saved. In essence, gdb will ``wind back the clock'' to the point
2671 in time when the checkpoint was saved.
2673 Note that breakpoints, @value{GDBN} variables, command history etc.
2674 are not affected by restoring a checkpoint. In general, a checkpoint
2675 only restores things that reside in the program being debugged, not in
2678 @kindex delete checkpoint @var{checkpoint-id}
2679 @item delete checkpoint @var{checkpoint-id}
2680 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
2684 Returning to a previously saved checkpoint will restore the user state
2685 of the program being debugged, plus a significant subset of the system
2686 (OS) state, including file pointers. It won't ``un-write'' data from
2687 a file, but it will rewind the file pointer to the previous location,
2688 so that the previously written data can be overwritten. For files
2689 opened in read mode, the pointer will also be restored so that the
2690 previously read data can be read again.
2692 Of course, characters that have been sent to a printer (or other
2693 external device) cannot be ``snatched back'', and characters received
2694 from eg.@: a serial device can be removed from internal program buffers,
2695 but they cannot be ``pushed back'' into the serial pipeline, ready to
2696 be received again. Similarly, the actual contents of files that have
2697 been changed cannot be restored (at this time).
2699 However, within those constraints, you actually can ``rewind'' your
2700 program to a previously saved point in time, and begin debugging it
2701 again --- and you can change the course of events so as to debug a
2702 different execution path this time.
2704 @cindex checkpoints and process id
2705 Finally, there is one bit of internal program state that will be
2706 different when you return to a checkpoint --- the program's process
2707 id. Each checkpoint will have a unique process id (or @var{pid}),
2708 and each will be different from the program's original @var{pid}.
2709 If your program has saved a local copy of its process id, this could
2710 potentially pose a problem.
2712 @subsection A non-obvious benefit of using checkpoints
2714 On some systems such as @sc{gnu}/Linux, address space randomization
2715 is performed on new processes for security reasons. This makes it
2716 difficult or impossible to set a breakpoint, or watchpoint, on an
2717 absolute address if you have to restart the program, since the
2718 absolute location of a symbol will change from one execution to the
2721 A checkpoint, however, is an @emph{identical} copy of a process.
2722 Therefore if you create a checkpoint at (eg.@:) the start of main,
2723 and simply return to that checkpoint instead of restarting the
2724 process, you can avoid the effects of address randomization and
2725 your symbols will all stay in the same place.
2728 @chapter Stopping and Continuing
2730 The principal purposes of using a debugger are so that you can stop your
2731 program before it terminates; or so that, if your program runs into
2732 trouble, you can investigate and find out why.
2734 Inside @value{GDBN}, your program may stop for any of several reasons,
2735 such as a signal, a breakpoint, or reaching a new line after a
2736 @value{GDBN} command such as @code{step}. You may then examine and
2737 change variables, set new breakpoints or remove old ones, and then
2738 continue execution. Usually, the messages shown by @value{GDBN} provide
2739 ample explanation of the status of your program---but you can also
2740 explicitly request this information at any time.
2743 @kindex info program
2745 Display information about the status of your program: whether it is
2746 running or not, what process it is, and why it stopped.
2750 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2751 * Continuing and Stepping:: Resuming execution
2753 * Thread Stops:: Stopping and starting multi-thread programs
2757 @section Breakpoints, watchpoints, and catchpoints
2760 A @dfn{breakpoint} makes your program stop whenever a certain point in
2761 the program is reached. For each breakpoint, you can add conditions to
2762 control in finer detail whether your program stops. You can set
2763 breakpoints with the @code{break} command and its variants (@pxref{Set
2764 Breaks, ,Setting breakpoints}), to specify the place where your program
2765 should stop by line number, function name or exact address in the
2768 On some systems, you can set breakpoints in shared libraries before
2769 the executable is run. There is a minor limitation on HP-UX systems:
2770 you must wait until the executable is run in order to set breakpoints
2771 in shared library routines that are not called directly by the program
2772 (for example, routines that are arguments in a @code{pthread_create}
2776 @cindex memory tracing
2777 @cindex breakpoint on memory address
2778 @cindex breakpoint on variable modification
2779 A @dfn{watchpoint} is a special breakpoint that stops your program
2780 when the value of an expression changes. You must use a different
2781 command to set watchpoints (@pxref{Set Watchpoints, ,Setting
2782 watchpoints}), but aside from that, you can manage a watchpoint like
2783 any other breakpoint: you enable, disable, and delete both breakpoints
2784 and watchpoints using the same commands.
2786 You can arrange to have values from your program displayed automatically
2787 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2791 @cindex breakpoint on events
2792 A @dfn{catchpoint} is another special breakpoint that stops your program
2793 when a certain kind of event occurs, such as the throwing of a C@t{++}
2794 exception or the loading of a library. As with watchpoints, you use a
2795 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2796 catchpoints}), but aside from that, you can manage a catchpoint like any
2797 other breakpoint. (To stop when your program receives a signal, use the
2798 @code{handle} command; see @ref{Signals, ,Signals}.)
2800 @cindex breakpoint numbers
2801 @cindex numbers for breakpoints
2802 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2803 catchpoint when you create it; these numbers are successive integers
2804 starting with one. In many of the commands for controlling various
2805 features of breakpoints you use the breakpoint number to say which
2806 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2807 @dfn{disabled}; if disabled, it has no effect on your program until you
2810 @cindex breakpoint ranges
2811 @cindex ranges of breakpoints
2812 Some @value{GDBN} commands accept a range of breakpoints on which to
2813 operate. A breakpoint range is either a single breakpoint number, like
2814 @samp{5}, or two such numbers, in increasing order, separated by a
2815 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2816 all breakpoint in that range are operated on.
2819 * Set Breaks:: Setting breakpoints
2820 * Set Watchpoints:: Setting watchpoints
2821 * Set Catchpoints:: Setting catchpoints
2822 * Delete Breaks:: Deleting breakpoints
2823 * Disabling:: Disabling breakpoints
2824 * Conditions:: Break conditions
2825 * Break Commands:: Breakpoint command lists
2826 * Breakpoint Menus:: Breakpoint menus
2827 * Error in Breakpoints:: ``Cannot insert breakpoints''
2828 * Breakpoint related warnings:: ``Breakpoint address adjusted...''
2832 @subsection Setting breakpoints
2834 @c FIXME LMB what does GDB do if no code on line of breakpt?
2835 @c consider in particular declaration with/without initialization.
2837 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2840 @kindex b @r{(@code{break})}
2841 @vindex $bpnum@r{, convenience variable}
2842 @cindex latest breakpoint
2843 Breakpoints are set with the @code{break} command (abbreviated
2844 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2845 number of the breakpoint you've set most recently; see @ref{Convenience
2846 Vars,, Convenience variables}, for a discussion of what you can do with
2847 convenience variables.
2849 You have several ways to say where the breakpoint should go.
2852 @item break @var{function}
2853 Set a breakpoint at entry to function @var{function}.
2854 When using source languages that permit overloading of symbols, such as
2855 C@t{++}, @var{function} may refer to more than one possible place to break.
2856 @xref{Breakpoint Menus,,Breakpoint menus}, for a discussion of that situation.
2858 @item break +@var{offset}
2859 @itemx break -@var{offset}
2860 Set a breakpoint some number of lines forward or back from the position
2861 at which execution stopped in the currently selected @dfn{stack frame}.
2862 (@xref{Frames, ,Frames}, for a description of stack frames.)
2864 @item break @var{linenum}
2865 Set a breakpoint at line @var{linenum} in the current source file.
2866 The current source file is the last file whose source text was printed.
2867 The breakpoint will stop your program just before it executes any of the
2870 @item break @var{filename}:@var{linenum}
2871 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2873 @item break @var{filename}:@var{function}
2874 Set a breakpoint at entry to function @var{function} found in file
2875 @var{filename}. Specifying a file name as well as a function name is
2876 superfluous except when multiple files contain similarly named
2879 @item break *@var{address}
2880 Set a breakpoint at address @var{address}. You can use this to set
2881 breakpoints in parts of your program which do not have debugging
2882 information or source files.
2885 When called without any arguments, @code{break} sets a breakpoint at
2886 the next instruction to be executed in the selected stack frame
2887 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2888 innermost, this makes your program stop as soon as control
2889 returns to that frame. This is similar to the effect of a
2890 @code{finish} command in the frame inside the selected frame---except
2891 that @code{finish} does not leave an active breakpoint. If you use
2892 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2893 the next time it reaches the current location; this may be useful
2896 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2897 least one instruction has been executed. If it did not do this, you
2898 would be unable to proceed past a breakpoint without first disabling the
2899 breakpoint. This rule applies whether or not the breakpoint already
2900 existed when your program stopped.
2902 @item break @dots{} if @var{cond}
2903 Set a breakpoint with condition @var{cond}; evaluate the expression
2904 @var{cond} each time the breakpoint is reached, and stop only if the
2905 value is nonzero---that is, if @var{cond} evaluates as true.
2906 @samp{@dots{}} stands for one of the possible arguments described
2907 above (or no argument) specifying where to break. @xref{Conditions,
2908 ,Break conditions}, for more information on breakpoint conditions.
2911 @item tbreak @var{args}
2912 Set a breakpoint enabled only for one stop. @var{args} are the
2913 same as for the @code{break} command, and the breakpoint is set in the same
2914 way, but the breakpoint is automatically deleted after the first time your
2915 program stops there. @xref{Disabling, ,Disabling breakpoints}.
2918 @cindex hardware breakpoints
2919 @item hbreak @var{args}
2920 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2921 @code{break} command and the breakpoint is set in the same way, but the
2922 breakpoint requires hardware support and some target hardware may not
2923 have this support. The main purpose of this is EPROM/ROM code
2924 debugging, so you can set a breakpoint at an instruction without
2925 changing the instruction. This can be used with the new trap-generation
2926 provided by SPARClite DSU and most x86-based targets. These targets
2927 will generate traps when a program accesses some data or instruction
2928 address that is assigned to the debug registers. However the hardware
2929 breakpoint registers can take a limited number of breakpoints. For
2930 example, on the DSU, only two data breakpoints can be set at a time, and
2931 @value{GDBN} will reject this command if more than two are used. Delete
2932 or disable unused hardware breakpoints before setting new ones
2933 (@pxref{Disabling, ,Disabling}). @xref{Conditions, ,Break conditions}.
2934 For remote targets, you can restrict the number of hardware
2935 breakpoints @value{GDBN} will use, see @ref{set remote
2936 hardware-breakpoint-limit}.
2940 @item thbreak @var{args}
2941 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2942 are the same as for the @code{hbreak} command and the breakpoint is set in
2943 the same way. However, like the @code{tbreak} command,
2944 the breakpoint is automatically deleted after the
2945 first time your program stops there. Also, like the @code{hbreak}
2946 command, the breakpoint requires hardware support and some target hardware
2947 may not have this support. @xref{Disabling, ,Disabling breakpoints}.
2948 See also @ref{Conditions, ,Break conditions}.
2951 @cindex regular expression
2952 @cindex breakpoints in functions matching a regexp
2953 @cindex set breakpoints in many functions
2954 @item rbreak @var{regex}
2955 Set breakpoints on all functions matching the regular expression
2956 @var{regex}. This command sets an unconditional breakpoint on all
2957 matches, printing a list of all breakpoints it set. Once these
2958 breakpoints are set, they are treated just like the breakpoints set with
2959 the @code{break} command. You can delete them, disable them, or make
2960 them conditional the same way as any other breakpoint.
2962 The syntax of the regular expression is the standard one used with tools
2963 like @file{grep}. Note that this is different from the syntax used by
2964 shells, so for instance @code{foo*} matches all functions that include
2965 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2966 @code{.*} leading and trailing the regular expression you supply, so to
2967 match only functions that begin with @code{foo}, use @code{^foo}.
2969 @cindex non-member C@t{++} functions, set breakpoint in
2970 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2971 breakpoints on overloaded functions that are not members of any special
2974 @cindex set breakpoints on all functions
2975 The @code{rbreak} command can be used to set breakpoints in
2976 @strong{all} the functions in a program, like this:
2979 (@value{GDBP}) rbreak .
2982 @kindex info breakpoints
2983 @cindex @code{$_} and @code{info breakpoints}
2984 @item info breakpoints @r{[}@var{n}@r{]}
2985 @itemx info break @r{[}@var{n}@r{]}
2986 @itemx info watchpoints @r{[}@var{n}@r{]}
2987 Print a table of all breakpoints, watchpoints, and catchpoints set and
2988 not deleted, with the following columns for each breakpoint:
2991 @item Breakpoint Numbers
2993 Breakpoint, watchpoint, or catchpoint.
2995 Whether the breakpoint is marked to be disabled or deleted when hit.
2996 @item Enabled or Disabled
2997 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2998 that are not enabled.
3000 Where the breakpoint is in your program, as a memory address. If the
3001 breakpoint is pending (see below for details) on a future load of a shared library, the address
3002 will be listed as @samp{<PENDING>}.
3004 Where the breakpoint is in the source for your program, as a file and
3005 line number. For a pending breakpoint, the original string passed to
3006 the breakpoint command will be listed as it cannot be resolved until
3007 the appropriate shared library is loaded in the future.
3011 If a breakpoint is conditional, @code{info break} shows the condition on
3012 the line following the affected breakpoint; breakpoint commands, if any,
3013 are listed after that. A pending breakpoint is allowed to have a condition
3014 specified for it. The condition is not parsed for validity until a shared
3015 library is loaded that allows the pending breakpoint to resolve to a
3019 @code{info break} with a breakpoint
3020 number @var{n} as argument lists only that breakpoint. The
3021 convenience variable @code{$_} and the default examining-address for
3022 the @code{x} command are set to the address of the last breakpoint
3023 listed (@pxref{Memory, ,Examining memory}).
3026 @code{info break} displays a count of the number of times the breakpoint
3027 has been hit. This is especially useful in conjunction with the
3028 @code{ignore} command. You can ignore a large number of breakpoint
3029 hits, look at the breakpoint info to see how many times the breakpoint
3030 was hit, and then run again, ignoring one less than that number. This
3031 will get you quickly to the last hit of that breakpoint.
3034 @value{GDBN} allows you to set any number of breakpoints at the same place in
3035 your program. There is nothing silly or meaningless about this. When
3036 the breakpoints are conditional, this is even useful
3037 (@pxref{Conditions, ,Break conditions}).
3039 @cindex pending breakpoints
3040 If a specified breakpoint location cannot be found, it may be due to the fact
3041 that the location is in a shared library that is yet to be loaded. In such
3042 a case, you may want @value{GDBN} to create a special breakpoint (known as
3043 a @dfn{pending breakpoint}) that
3044 attempts to resolve itself in the future when an appropriate shared library
3047 Pending breakpoints are useful to set at the start of your
3048 @value{GDBN} session for locations that you know will be dynamically loaded
3049 later by the program being debugged. When shared libraries are loaded,
3050 a check is made to see if the load resolves any pending breakpoint locations.
3051 If a pending breakpoint location gets resolved,
3052 a regular breakpoint is created and the original pending breakpoint is removed.
3054 @value{GDBN} provides some additional commands for controlling pending
3057 @kindex set breakpoint pending
3058 @kindex show breakpoint pending
3060 @item set breakpoint pending auto
3061 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3062 location, it queries you whether a pending breakpoint should be created.
3064 @item set breakpoint pending on
3065 This indicates that an unrecognized breakpoint location should automatically
3066 result in a pending breakpoint being created.
3068 @item set breakpoint pending off
3069 This indicates that pending breakpoints are not to be created. Any
3070 unrecognized breakpoint location results in an error. This setting does
3071 not affect any pending breakpoints previously created.
3073 @item show breakpoint pending
3074 Show the current behavior setting for creating pending breakpoints.
3077 @cindex operations allowed on pending breakpoints
3078 Normal breakpoint operations apply to pending breakpoints as well. You may
3079 specify a condition for a pending breakpoint and/or commands to run when the
3080 breakpoint is reached. You can also enable or disable
3081 the pending breakpoint. When you specify a condition for a pending breakpoint,
3082 the parsing of the condition will be deferred until the point where the
3083 pending breakpoint location is resolved. Disabling a pending breakpoint
3084 tells @value{GDBN} to not attempt to resolve the breakpoint on any subsequent
3085 shared library load. When a pending breakpoint is re-enabled,
3086 @value{GDBN} checks to see if the location is already resolved.
3087 This is done because any number of shared library loads could have
3088 occurred since the time the breakpoint was disabled and one or more
3089 of these loads could resolve the location.
3091 @cindex negative breakpoint numbers
3092 @cindex internal @value{GDBN} breakpoints
3093 @value{GDBN} itself sometimes sets breakpoints in your program for
3094 special purposes, such as proper handling of @code{longjmp} (in C
3095 programs). These internal breakpoints are assigned negative numbers,
3096 starting with @code{-1}; @samp{info breakpoints} does not display them.
3097 You can see these breakpoints with the @value{GDBN} maintenance command
3098 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3101 @node Set Watchpoints
3102 @subsection Setting watchpoints
3104 @cindex setting watchpoints
3105 You can use a watchpoint to stop execution whenever the value of an
3106 expression changes, without having to predict a particular place where
3109 @cindex software watchpoints
3110 @cindex hardware watchpoints
3111 Depending on your system, watchpoints may be implemented in software or
3112 hardware. @value{GDBN} does software watchpointing by single-stepping your
3113 program and testing the variable's value each time, which is hundreds of
3114 times slower than normal execution. (But this may still be worth it, to
3115 catch errors where you have no clue what part of your program is the
3118 On some systems, such as HP-UX, @sc{gnu}/Linux and most other
3119 x86-based targets, @value{GDBN} includes support for hardware
3120 watchpoints, which do not slow down the running of your program.
3124 @item watch @var{expr}
3125 Set a watchpoint for an expression. @value{GDBN} will break when @var{expr}
3126 is written into by the program and its value changes.
3129 @item rwatch @var{expr}
3130 Set a watchpoint that will break when the value of @var{expr} is read
3134 @item awatch @var{expr}
3135 Set a watchpoint that will break when @var{expr} is either read from
3136 or written into by the program.
3138 @kindex info watchpoints
3139 @item info watchpoints
3140 This command prints a list of watchpoints, breakpoints, and catchpoints;
3141 it is the same as @code{info break} (@pxref{Set Breaks}).
3144 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3145 watchpoints execute very quickly, and the debugger reports a change in
3146 value at the exact instruction where the change occurs. If @value{GDBN}
3147 cannot set a hardware watchpoint, it sets a software watchpoint, which
3148 executes more slowly and reports the change in value at the next
3149 @emph{statement}, not the instruction, after the change occurs.
3151 @cindex use only software watchpoints
3152 You can force @value{GDBN} to use only software watchpoints with the
3153 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3154 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3155 the underlying system supports them. (Note that hardware-assisted
3156 watchpoints that were set @emph{before} setting
3157 @code{can-use-hw-watchpoints} to zero will still use the hardware
3158 mechanism of watching expressiion values.)
3161 @item set can-use-hw-watchpoints
3162 @kindex set can-use-hw-watchpoints
3163 Set whether or not to use hardware watchpoints.
3165 @item show can-use-hw-watchpoints
3166 @kindex show can-use-hw-watchpoints
3167 Show the current mode of using hardware watchpoints.
3170 For remote targets, you can restrict the number of hardware
3171 watchpoints @value{GDBN} will use, see @ref{set remote
3172 hardware-breakpoint-limit}.
3174 When you issue the @code{watch} command, @value{GDBN} reports
3177 Hardware watchpoint @var{num}: @var{expr}
3181 if it was able to set a hardware watchpoint.
3183 Currently, the @code{awatch} and @code{rwatch} commands can only set
3184 hardware watchpoints, because accesses to data that don't change the
3185 value of the watched expression cannot be detected without examining
3186 every instruction as it is being executed, and @value{GDBN} does not do
3187 that currently. If @value{GDBN} finds that it is unable to set a
3188 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3189 will print a message like this:
3192 Expression cannot be implemented with read/access watchpoint.
3195 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3196 data type of the watched expression is wider than what a hardware
3197 watchpoint on the target machine can handle. For example, some systems
3198 can only watch regions that are up to 4 bytes wide; on such systems you
3199 cannot set hardware watchpoints for an expression that yields a
3200 double-precision floating-point number (which is typically 8 bytes
3201 wide). As a work-around, it might be possible to break the large region
3202 into a series of smaller ones and watch them with separate watchpoints.
3204 If you set too many hardware watchpoints, @value{GDBN} might be unable
3205 to insert all of them when you resume the execution of your program.
3206 Since the precise number of active watchpoints is unknown until such
3207 time as the program is about to be resumed, @value{GDBN} might not be
3208 able to warn you about this when you set the watchpoints, and the
3209 warning will be printed only when the program is resumed:
3212 Hardware watchpoint @var{num}: Could not insert watchpoint
3216 If this happens, delete or disable some of the watchpoints.
3218 The SPARClite DSU will generate traps when a program accesses some data
3219 or instruction address that is assigned to the debug registers. For the
3220 data addresses, DSU facilitates the @code{watch} command. However the
3221 hardware breakpoint registers can only take two data watchpoints, and
3222 both watchpoints must be the same kind. For example, you can set two
3223 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
3224 @strong{or} two with @code{awatch} commands, but you cannot set one
3225 watchpoint with one command and the other with a different command.
3226 @value{GDBN} will reject the command if you try to mix watchpoints.
3227 Delete or disable unused watchpoint commands before setting new ones.
3229 If you call a function interactively using @code{print} or @code{call},
3230 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3231 kind of breakpoint or the call completes.
3233 @value{GDBN} automatically deletes watchpoints that watch local
3234 (automatic) variables, or expressions that involve such variables, when
3235 they go out of scope, that is, when the execution leaves the block in
3236 which these variables were defined. In particular, when the program
3237 being debugged terminates, @emph{all} local variables go out of scope,
3238 and so only watchpoints that watch global variables remain set. If you
3239 rerun the program, you will need to set all such watchpoints again. One
3240 way of doing that would be to set a code breakpoint at the entry to the
3241 @code{main} function and when it breaks, set all the watchpoints.
3244 @cindex watchpoints and threads
3245 @cindex threads and watchpoints
3246 @emph{Warning:} In multi-thread programs, watchpoints have only limited
3247 usefulness. With the current watchpoint implementation, @value{GDBN}
3248 can only watch the value of an expression @emph{in a single thread}. If
3249 you are confident that the expression can only change due to the current
3250 thread's activity (and if you are also confident that no other thread
3251 can become current), then you can use watchpoints as usual. However,
3252 @value{GDBN} may not notice when a non-current thread's activity changes
3255 @c FIXME: this is almost identical to the previous paragraph.
3256 @emph{HP-UX Warning:} In multi-thread programs, software watchpoints
3257 have only limited usefulness. If @value{GDBN} creates a software
3258 watchpoint, it can only watch the value of an expression @emph{in a
3259 single thread}. If you are confident that the expression can only
3260 change due to the current thread's activity (and if you are also
3261 confident that no other thread can become current), then you can use
3262 software watchpoints as usual. However, @value{GDBN} may not notice
3263 when a non-current thread's activity changes the expression. (Hardware
3264 watchpoints, in contrast, watch an expression in all threads.)
3267 @xref{set remote hardware-watchpoint-limit}.
3269 @node Set Catchpoints
3270 @subsection Setting catchpoints
3271 @cindex catchpoints, setting
3272 @cindex exception handlers
3273 @cindex event handling
3275 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3276 kinds of program events, such as C@t{++} exceptions or the loading of a
3277 shared library. Use the @code{catch} command to set a catchpoint.
3281 @item catch @var{event}
3282 Stop when @var{event} occurs. @var{event} can be any of the following:
3285 @cindex stop on C@t{++} exceptions
3286 The throwing of a C@t{++} exception.
3289 The catching of a C@t{++} exception.
3292 @cindex break on fork/exec
3293 A call to @code{exec}. This is currently only available for HP-UX.
3296 A call to @code{fork}. This is currently only available for HP-UX.
3299 A call to @code{vfork}. This is currently only available for HP-UX.
3302 @itemx load @var{libname}
3303 @cindex break on load/unload of shared library
3304 The dynamic loading of any shared library, or the loading of the library
3305 @var{libname}. This is currently only available for HP-UX.
3308 @itemx unload @var{libname}
3309 The unloading of any dynamically loaded shared library, or the unloading
3310 of the library @var{libname}. This is currently only available for HP-UX.
3313 @item tcatch @var{event}
3314 Set a catchpoint that is enabled only for one stop. The catchpoint is
3315 automatically deleted after the first time the event is caught.
3319 Use the @code{info break} command to list the current catchpoints.
3321 There are currently some limitations to C@t{++} exception handling
3322 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3326 If you call a function interactively, @value{GDBN} normally returns
3327 control to you when the function has finished executing. If the call
3328 raises an exception, however, the call may bypass the mechanism that
3329 returns control to you and cause your program either to abort or to
3330 simply continue running until it hits a breakpoint, catches a signal
3331 that @value{GDBN} is listening for, or exits. This is the case even if
3332 you set a catchpoint for the exception; catchpoints on exceptions are
3333 disabled within interactive calls.
3336 You cannot raise an exception interactively.
3339 You cannot install an exception handler interactively.
3342 @cindex raise exceptions
3343 Sometimes @code{catch} is not the best way to debug exception handling:
3344 if you need to know exactly where an exception is raised, it is better to
3345 stop @emph{before} the exception handler is called, since that way you
3346 can see the stack before any unwinding takes place. If you set a
3347 breakpoint in an exception handler instead, it may not be easy to find
3348 out where the exception was raised.
3350 To stop just before an exception handler is called, you need some
3351 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3352 raised by calling a library function named @code{__raise_exception}
3353 which has the following ANSI C interface:
3356 /* @var{addr} is where the exception identifier is stored.
3357 @var{id} is the exception identifier. */
3358 void __raise_exception (void **addr, void *id);
3362 To make the debugger catch all exceptions before any stack
3363 unwinding takes place, set a breakpoint on @code{__raise_exception}
3364 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}).
3366 With a conditional breakpoint (@pxref{Conditions, ,Break conditions})
3367 that depends on the value of @var{id}, you can stop your program when
3368 a specific exception is raised. You can use multiple conditional
3369 breakpoints to stop your program when any of a number of exceptions are
3374 @subsection Deleting breakpoints
3376 @cindex clearing breakpoints, watchpoints, catchpoints
3377 @cindex deleting breakpoints, watchpoints, catchpoints
3378 It is often necessary to eliminate a breakpoint, watchpoint, or
3379 catchpoint once it has done its job and you no longer want your program
3380 to stop there. This is called @dfn{deleting} the breakpoint. A
3381 breakpoint that has been deleted no longer exists; it is forgotten.
3383 With the @code{clear} command you can delete breakpoints according to
3384 where they are in your program. With the @code{delete} command you can
3385 delete individual breakpoints, watchpoints, or catchpoints by specifying
3386 their breakpoint numbers.
3388 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3389 automatically ignores breakpoints on the first instruction to be executed
3390 when you continue execution without changing the execution address.
3395 Delete any breakpoints at the next instruction to be executed in the
3396 selected stack frame (@pxref{Selection, ,Selecting a frame}). When
3397 the innermost frame is selected, this is a good way to delete a
3398 breakpoint where your program just stopped.
3400 @item clear @var{function}
3401 @itemx clear @var{filename}:@var{function}
3402 Delete any breakpoints set at entry to the named @var{function}.
3404 @item clear @var{linenum}
3405 @itemx clear @var{filename}:@var{linenum}
3406 Delete any breakpoints set at or within the code of the specified
3407 @var{linenum} of the specified @var{filename}.
3409 @cindex delete breakpoints
3411 @kindex d @r{(@code{delete})}
3412 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3413 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3414 ranges specified as arguments. If no argument is specified, delete all
3415 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3416 confirm off}). You can abbreviate this command as @code{d}.
3420 @subsection Disabling breakpoints
3422 @cindex enable/disable a breakpoint
3423 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3424 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3425 it had been deleted, but remembers the information on the breakpoint so
3426 that you can @dfn{enable} it again later.
3428 You disable and enable breakpoints, watchpoints, and catchpoints with
3429 the @code{enable} and @code{disable} commands, optionally specifying one
3430 or more breakpoint numbers as arguments. Use @code{info break} or
3431 @code{info watch} to print a list of breakpoints, watchpoints, and
3432 catchpoints if you do not know which numbers to use.
3434 A breakpoint, watchpoint, or catchpoint can have any of four different
3435 states of enablement:
3439 Enabled. The breakpoint stops your program. A breakpoint set
3440 with the @code{break} command starts out in this state.
3442 Disabled. The breakpoint has no effect on your program.
3444 Enabled once. The breakpoint stops your program, but then becomes
3447 Enabled for deletion. The breakpoint stops your program, but
3448 immediately after it does so it is deleted permanently. A breakpoint
3449 set with the @code{tbreak} command starts out in this state.
3452 You can use the following commands to enable or disable breakpoints,
3453 watchpoints, and catchpoints:
3457 @kindex dis @r{(@code{disable})}
3458 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3459 Disable the specified breakpoints---or all breakpoints, if none are
3460 listed. A disabled breakpoint has no effect but is not forgotten. All
3461 options such as ignore-counts, conditions and commands are remembered in
3462 case the breakpoint is enabled again later. You may abbreviate
3463 @code{disable} as @code{dis}.
3466 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3467 Enable the specified breakpoints (or all defined breakpoints). They
3468 become effective once again in stopping your program.
3470 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3471 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3472 of these breakpoints immediately after stopping your program.
3474 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3475 Enable the specified breakpoints to work once, then die. @value{GDBN}
3476 deletes any of these breakpoints as soon as your program stops there.
3477 Breakpoints set by the @code{tbreak} command start out in this state.
3480 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3481 @c confusing: tbreak is also initially enabled.
3482 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3483 ,Setting breakpoints}), breakpoints that you set are initially enabled;
3484 subsequently, they become disabled or enabled only when you use one of
3485 the commands above. (The command @code{until} can set and delete a
3486 breakpoint of its own, but it does not change the state of your other
3487 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3491 @subsection Break conditions
3492 @cindex conditional breakpoints
3493 @cindex breakpoint conditions
3495 @c FIXME what is scope of break condition expr? Context where wanted?
3496 @c in particular for a watchpoint?
3497 The simplest sort of breakpoint breaks every time your program reaches a
3498 specified place. You can also specify a @dfn{condition} for a
3499 breakpoint. A condition is just a Boolean expression in your
3500 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3501 a condition evaluates the expression each time your program reaches it,
3502 and your program stops only if the condition is @emph{true}.
3504 This is the converse of using assertions for program validation; in that
3505 situation, you want to stop when the assertion is violated---that is,
3506 when the condition is false. In C, if you want to test an assertion expressed
3507 by the condition @var{assert}, you should set the condition
3508 @samp{! @var{assert}} on the appropriate breakpoint.
3510 Conditions are also accepted for watchpoints; you may not need them,
3511 since a watchpoint is inspecting the value of an expression anyhow---but
3512 it might be simpler, say, to just set a watchpoint on a variable name,
3513 and specify a condition that tests whether the new value is an interesting
3516 Break conditions can have side effects, and may even call functions in
3517 your program. This can be useful, for example, to activate functions
3518 that log program progress, or to use your own print functions to
3519 format special data structures. The effects are completely predictable
3520 unless there is another enabled breakpoint at the same address. (In
3521 that case, @value{GDBN} might see the other breakpoint first and stop your
3522 program without checking the condition of this one.) Note that
3523 breakpoint commands are usually more convenient and flexible than break
3525 purpose of performing side effects when a breakpoint is reached
3526 (@pxref{Break Commands, ,Breakpoint command lists}).
3528 Break conditions can be specified when a breakpoint is set, by using
3529 @samp{if} in the arguments to the @code{break} command. @xref{Set
3530 Breaks, ,Setting breakpoints}. They can also be changed at any time
3531 with the @code{condition} command.
3533 You can also use the @code{if} keyword with the @code{watch} command.
3534 The @code{catch} command does not recognize the @code{if} keyword;
3535 @code{condition} is the only way to impose a further condition on a
3540 @item condition @var{bnum} @var{expression}
3541 Specify @var{expression} as the break condition for breakpoint,
3542 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3543 breakpoint @var{bnum} stops your program only if the value of
3544 @var{expression} is true (nonzero, in C). When you use
3545 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3546 syntactic correctness, and to determine whether symbols in it have
3547 referents in the context of your breakpoint. If @var{expression} uses
3548 symbols not referenced in the context of the breakpoint, @value{GDBN}
3549 prints an error message:
3552 No symbol "foo" in current context.
3557 not actually evaluate @var{expression} at the time the @code{condition}
3558 command (or a command that sets a breakpoint with a condition, like
3559 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3561 @item condition @var{bnum}
3562 Remove the condition from breakpoint number @var{bnum}. It becomes
3563 an ordinary unconditional breakpoint.
3566 @cindex ignore count (of breakpoint)
3567 A special case of a breakpoint condition is to stop only when the
3568 breakpoint has been reached a certain number of times. This is so
3569 useful that there is a special way to do it, using the @dfn{ignore
3570 count} of the breakpoint. Every breakpoint has an ignore count, which
3571 is an integer. Most of the time, the ignore count is zero, and
3572 therefore has no effect. But if your program reaches a breakpoint whose
3573 ignore count is positive, then instead of stopping, it just decrements
3574 the ignore count by one and continues. As a result, if the ignore count
3575 value is @var{n}, the breakpoint does not stop the next @var{n} times
3576 your program reaches it.
3580 @item ignore @var{bnum} @var{count}
3581 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3582 The next @var{count} times the breakpoint is reached, your program's
3583 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3586 To make the breakpoint stop the next time it is reached, specify
3589 When you use @code{continue} to resume execution of your program from a
3590 breakpoint, you can specify an ignore count directly as an argument to
3591 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3592 Stepping,,Continuing and stepping}.
3594 If a breakpoint has a positive ignore count and a condition, the
3595 condition is not checked. Once the ignore count reaches zero,
3596 @value{GDBN} resumes checking the condition.
3598 You could achieve the effect of the ignore count with a condition such
3599 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3600 is decremented each time. @xref{Convenience Vars, ,Convenience
3604 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3607 @node Break Commands
3608 @subsection Breakpoint command lists
3610 @cindex breakpoint commands
3611 You can give any breakpoint (or watchpoint or catchpoint) a series of
3612 commands to execute when your program stops due to that breakpoint. For
3613 example, you might want to print the values of certain expressions, or
3614 enable other breakpoints.
3618 @kindex end@r{ (breakpoint commands)}
3619 @item commands @r{[}@var{bnum}@r{]}
3620 @itemx @dots{} @var{command-list} @dots{}
3622 Specify a list of commands for breakpoint number @var{bnum}. The commands
3623 themselves appear on the following lines. Type a line containing just
3624 @code{end} to terminate the commands.
3626 To remove all commands from a breakpoint, type @code{commands} and
3627 follow it immediately with @code{end}; that is, give no commands.
3629 With no @var{bnum} argument, @code{commands} refers to the last
3630 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3631 recently encountered).
3634 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3635 disabled within a @var{command-list}.
3637 You can use breakpoint commands to start your program up again. Simply
3638 use the @code{continue} command, or @code{step}, or any other command
3639 that resumes execution.
3641 Any other commands in the command list, after a command that resumes
3642 execution, are ignored. This is because any time you resume execution
3643 (even with a simple @code{next} or @code{step}), you may encounter
3644 another breakpoint---which could have its own command list, leading to
3645 ambiguities about which list to execute.
3648 If the first command you specify in a command list is @code{silent}, the
3649 usual message about stopping at a breakpoint is not printed. This may
3650 be desirable for breakpoints that are to print a specific message and
3651 then continue. If none of the remaining commands print anything, you
3652 see no sign that the breakpoint was reached. @code{silent} is
3653 meaningful only at the beginning of a breakpoint command list.
3655 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3656 print precisely controlled output, and are often useful in silent
3657 breakpoints. @xref{Output, ,Commands for controlled output}.
3659 For example, here is how you could use breakpoint commands to print the
3660 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3666 printf "x is %d\n",x
3671 One application for breakpoint commands is to compensate for one bug so
3672 you can test for another. Put a breakpoint just after the erroneous line
3673 of code, give it a condition to detect the case in which something
3674 erroneous has been done, and give it commands to assign correct values
3675 to any variables that need them. End with the @code{continue} command
3676 so that your program does not stop, and start with the @code{silent}
3677 command so that no output is produced. Here is an example:
3688 @node Breakpoint Menus
3689 @subsection Breakpoint menus
3691 @cindex symbol overloading
3693 Some programming languages (notably C@t{++} and Objective-C) permit a
3694 single function name
3695 to be defined several times, for application in different contexts.
3696 This is called @dfn{overloading}. When a function name is overloaded,
3697 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3698 a breakpoint. If you realize this is a problem, you can use
3699 something like @samp{break @var{function}(@var{types})} to specify which
3700 particular version of the function you want. Otherwise, @value{GDBN} offers
3701 you a menu of numbered choices for different possible breakpoints, and
3702 waits for your selection with the prompt @samp{>}. The first two
3703 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3704 sets a breakpoint at each definition of @var{function}, and typing
3705 @kbd{0} aborts the @code{break} command without setting any new
3708 For example, the following session excerpt shows an attempt to set a
3709 breakpoint at the overloaded symbol @code{String::after}.
3710 We choose three particular definitions of that function name:
3712 @c FIXME! This is likely to change to show arg type lists, at least
3715 (@value{GDBP}) b String::after
3718 [2] file:String.cc; line number:867
3719 [3] file:String.cc; line number:860
3720 [4] file:String.cc; line number:875
3721 [5] file:String.cc; line number:853
3722 [6] file:String.cc; line number:846
3723 [7] file:String.cc; line number:735
3725 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3726 Breakpoint 2 at 0xb344: file String.cc, line 875.
3727 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3728 Multiple breakpoints were set.
3729 Use the "delete" command to delete unwanted
3735 @c @ifclear BARETARGET
3736 @node Error in Breakpoints
3737 @subsection ``Cannot insert breakpoints''
3739 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3741 Under some operating systems, breakpoints cannot be used in a program if
3742 any other process is running that program. In this situation,
3743 attempting to run or continue a program with a breakpoint causes
3744 @value{GDBN} to print an error message:
3747 Cannot insert breakpoints.
3748 The same program may be running in another process.
3751 When this happens, you have three ways to proceed:
3755 Remove or disable the breakpoints, then continue.
3758 Suspend @value{GDBN}, and copy the file containing your program to a new
3759 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3760 that @value{GDBN} should run your program under that name.
3761 Then start your program again.
3764 Relink your program so that the text segment is nonsharable, using the
3765 linker option @samp{-N}. The operating system limitation may not apply
3766 to nonsharable executables.
3770 A similar message can be printed if you request too many active
3771 hardware-assisted breakpoints and watchpoints:
3773 @c FIXME: the precise wording of this message may change; the relevant
3774 @c source change is not committed yet (Sep 3, 1999).
3776 Stopped; cannot insert breakpoints.
3777 You may have requested too many hardware breakpoints and watchpoints.
3781 This message is printed when you attempt to resume the program, since
3782 only then @value{GDBN} knows exactly how many hardware breakpoints and
3783 watchpoints it needs to insert.
3785 When this message is printed, you need to disable or remove some of the
3786 hardware-assisted breakpoints and watchpoints, and then continue.
3788 @node Breakpoint related warnings
3789 @subsection ``Breakpoint address adjusted...''
3790 @cindex breakpoint address adjusted
3792 Some processor architectures place constraints on the addresses at
3793 which breakpoints may be placed. For architectures thus constrained,
3794 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3795 with the constraints dictated by the architecture.
3797 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3798 a VLIW architecture in which a number of RISC-like instructions may be
3799 bundled together for parallel execution. The FR-V architecture
3800 constrains the location of a breakpoint instruction within such a
3801 bundle to the instruction with the lowest address. @value{GDBN}
3802 honors this constraint by adjusting a breakpoint's address to the
3803 first in the bundle.
3805 It is not uncommon for optimized code to have bundles which contain
3806 instructions from different source statements, thus it may happen that
3807 a breakpoint's address will be adjusted from one source statement to
3808 another. Since this adjustment may significantly alter @value{GDBN}'s
3809 breakpoint related behavior from what the user expects, a warning is
3810 printed when the breakpoint is first set and also when the breakpoint
3813 A warning like the one below is printed when setting a breakpoint
3814 that's been subject to address adjustment:
3817 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3820 Such warnings are printed both for user settable and @value{GDBN}'s
3821 internal breakpoints. If you see one of these warnings, you should
3822 verify that a breakpoint set at the adjusted address will have the
3823 desired affect. If not, the breakpoint in question may be removed and
3824 other breakpoints may be set which will have the desired behavior.
3825 E.g., it may be sufficient to place the breakpoint at a later
3826 instruction. A conditional breakpoint may also be useful in some
3827 cases to prevent the breakpoint from triggering too often.
3829 @value{GDBN} will also issue a warning when stopping at one of these
3830 adjusted breakpoints:
3833 warning: Breakpoint 1 address previously adjusted from 0x00010414
3837 When this warning is encountered, it may be too late to take remedial
3838 action except in cases where the breakpoint is hit earlier or more
3839 frequently than expected.
3841 @node Continuing and Stepping
3842 @section Continuing and stepping
3846 @cindex resuming execution
3847 @dfn{Continuing} means resuming program execution until your program
3848 completes normally. In contrast, @dfn{stepping} means executing just
3849 one more ``step'' of your program, where ``step'' may mean either one
3850 line of source code, or one machine instruction (depending on what
3851 particular command you use). Either when continuing or when stepping,
3852 your program may stop even sooner, due to a breakpoint or a signal. (If
3853 it stops due to a signal, you may want to use @code{handle}, or use
3854 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3858 @kindex c @r{(@code{continue})}
3859 @kindex fg @r{(resume foreground execution)}
3860 @item continue @r{[}@var{ignore-count}@r{]}
3861 @itemx c @r{[}@var{ignore-count}@r{]}
3862 @itemx fg @r{[}@var{ignore-count}@r{]}
3863 Resume program execution, at the address where your program last stopped;
3864 any breakpoints set at that address are bypassed. The optional argument
3865 @var{ignore-count} allows you to specify a further number of times to
3866 ignore a breakpoint at this location; its effect is like that of
3867 @code{ignore} (@pxref{Conditions, ,Break conditions}).
3869 The argument @var{ignore-count} is meaningful only when your program
3870 stopped due to a breakpoint. At other times, the argument to
3871 @code{continue} is ignored.
3873 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3874 debugged program is deemed to be the foreground program) are provided
3875 purely for convenience, and have exactly the same behavior as
3879 To resume execution at a different place, you can use @code{return}
3880 (@pxref{Returning, ,Returning from a function}) to go back to the
3881 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3882 different address}) to go to an arbitrary location in your program.
3884 A typical technique for using stepping is to set a breakpoint
3885 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and catchpoints}) at the
3886 beginning of the function or the section of your program where a problem
3887 is believed to lie, run your program until it stops at that breakpoint,
3888 and then step through the suspect area, examining the variables that are
3889 interesting, until you see the problem happen.
3893 @kindex s @r{(@code{step})}
3895 Continue running your program until control reaches a different source
3896 line, then stop it and return control to @value{GDBN}. This command is
3897 abbreviated @code{s}.
3900 @c "without debugging information" is imprecise; actually "without line
3901 @c numbers in the debugging information". (gcc -g1 has debugging info but
3902 @c not line numbers). But it seems complex to try to make that
3903 @c distinction here.
3904 @emph{Warning:} If you use the @code{step} command while control is
3905 within a function that was compiled without debugging information,
3906 execution proceeds until control reaches a function that does have
3907 debugging information. Likewise, it will not step into a function which
3908 is compiled without debugging information. To step through functions
3909 without debugging information, use the @code{stepi} command, described
3913 The @code{step} command only stops at the first instruction of a source
3914 line. This prevents the multiple stops that could otherwise occur in
3915 @code{switch} statements, @code{for} loops, etc. @code{step} continues
3916 to stop if a function that has debugging information is called within
3917 the line. In other words, @code{step} @emph{steps inside} any functions
3918 called within the line.
3920 Also, the @code{step} command only enters a function if there is line
3921 number information for the function. Otherwise it acts like the
3922 @code{next} command. This avoids problems when using @code{cc -gl}
3923 on MIPS machines. Previously, @code{step} entered subroutines if there
3924 was any debugging information about the routine.
3926 @item step @var{count}
3927 Continue running as in @code{step}, but do so @var{count} times. If a
3928 breakpoint is reached, or a signal not related to stepping occurs before
3929 @var{count} steps, stepping stops right away.
3932 @kindex n @r{(@code{next})}
3933 @item next @r{[}@var{count}@r{]}
3934 Continue to the next source line in the current (innermost) stack frame.
3935 This is similar to @code{step}, but function calls that appear within
3936 the line of code are executed without stopping. Execution stops when
3937 control reaches a different line of code at the original stack level
3938 that was executing when you gave the @code{next} command. This command
3939 is abbreviated @code{n}.
3941 An argument @var{count} is a repeat count, as for @code{step}.
3944 @c FIX ME!! Do we delete this, or is there a way it fits in with
3945 @c the following paragraph? --- Vctoria
3947 @c @code{next} within a function that lacks debugging information acts like
3948 @c @code{step}, but any function calls appearing within the code of the
3949 @c function are executed without stopping.
3951 The @code{next} command only stops at the first instruction of a
3952 source line. This prevents multiple stops that could otherwise occur in
3953 @code{switch} statements, @code{for} loops, etc.
3955 @kindex set step-mode
3957 @cindex functions without line info, and stepping
3958 @cindex stepping into functions with no line info
3959 @itemx set step-mode on
3960 The @code{set step-mode on} command causes the @code{step} command to
3961 stop at the first instruction of a function which contains no debug line
3962 information rather than stepping over it.
3964 This is useful in cases where you may be interested in inspecting the
3965 machine instructions of a function which has no symbolic info and do not
3966 want @value{GDBN} to automatically skip over this function.
3968 @item set step-mode off
3969 Causes the @code{step} command to step over any functions which contains no
3970 debug information. This is the default.
3972 @item show step-mode
3973 Show whether @value{GDBN} will stop in or step over functions without
3974 source line debug information.
3978 Continue running until just after function in the selected stack frame
3979 returns. Print the returned value (if any).
3981 Contrast this with the @code{return} command (@pxref{Returning,
3982 ,Returning from a function}).
3985 @kindex u @r{(@code{until})}
3986 @cindex run until specified location
3989 Continue running until a source line past the current line, in the
3990 current stack frame, is reached. This command is used to avoid single
3991 stepping through a loop more than once. It is like the @code{next}
3992 command, except that when @code{until} encounters a jump, it
3993 automatically continues execution until the program counter is greater
3994 than the address of the jump.
3996 This means that when you reach the end of a loop after single stepping
3997 though it, @code{until} makes your program continue execution until it
3998 exits the loop. In contrast, a @code{next} command at the end of a loop
3999 simply steps back to the beginning of the loop, which forces you to step
4000 through the next iteration.
4002 @code{until} always stops your program if it attempts to exit the current
4005 @code{until} may produce somewhat counterintuitive results if the order
4006 of machine code does not match the order of the source lines. For
4007 example, in the following excerpt from a debugging session, the @code{f}
4008 (@code{frame}) command shows that execution is stopped at line
4009 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4013 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4015 (@value{GDBP}) until
4016 195 for ( ; argc > 0; NEXTARG) @{
4019 This happened because, for execution efficiency, the compiler had
4020 generated code for the loop closure test at the end, rather than the
4021 start, of the loop---even though the test in a C @code{for}-loop is
4022 written before the body of the loop. The @code{until} command appeared
4023 to step back to the beginning of the loop when it advanced to this
4024 expression; however, it has not really gone to an earlier
4025 statement---not in terms of the actual machine code.
4027 @code{until} with no argument works by means of single
4028 instruction stepping, and hence is slower than @code{until} with an
4031 @item until @var{location}
4032 @itemx u @var{location}
4033 Continue running your program until either the specified location is
4034 reached, or the current stack frame returns. @var{location} is any of
4035 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
4036 ,Setting breakpoints}). This form of the command uses breakpoints, and
4037 hence is quicker than @code{until} without an argument. The specified
4038 location is actually reached only if it is in the current frame. This
4039 implies that @code{until} can be used to skip over recursive function
4040 invocations. For instance in the code below, if the current location is
4041 line @code{96}, issuing @code{until 99} will execute the program up to
4042 line @code{99} in the same invocation of factorial, i.e. after the inner
4043 invocations have returned.
4046 94 int factorial (int value)
4048 96 if (value > 1) @{
4049 97 value *= factorial (value - 1);
4056 @kindex advance @var{location}
4057 @itemx advance @var{location}
4058 Continue running the program up to the given @var{location}. An argument is
4059 required, which should be of the same form as arguments for the @code{break}
4060 command. Execution will also stop upon exit from the current stack
4061 frame. This command is similar to @code{until}, but @code{advance} will
4062 not skip over recursive function calls, and the target location doesn't
4063 have to be in the same frame as the current one.
4067 @kindex si @r{(@code{stepi})}
4069 @itemx stepi @var{arg}
4071 Execute one machine instruction, then stop and return to the debugger.
4073 It is often useful to do @samp{display/i $pc} when stepping by machine
4074 instructions. This makes @value{GDBN} automatically display the next
4075 instruction to be executed, each time your program stops. @xref{Auto
4076 Display,, Automatic display}.
4078 An argument is a repeat count, as in @code{step}.
4082 @kindex ni @r{(@code{nexti})}
4084 @itemx nexti @var{arg}
4086 Execute one machine instruction, but if it is a function call,
4087 proceed until the function returns.
4089 An argument is a repeat count, as in @code{next}.
4096 A signal is an asynchronous event that can happen in a program. The
4097 operating system defines the possible kinds of signals, and gives each
4098 kind a name and a number. For example, in Unix @code{SIGINT} is the
4099 signal a program gets when you type an interrupt character (often @kbd{C-c});
4100 @code{SIGSEGV} is the signal a program gets from referencing a place in
4101 memory far away from all the areas in use; @code{SIGALRM} occurs when
4102 the alarm clock timer goes off (which happens only if your program has
4103 requested an alarm).
4105 @cindex fatal signals
4106 Some signals, including @code{SIGALRM}, are a normal part of the
4107 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4108 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4109 program has not specified in advance some other way to handle the signal.
4110 @code{SIGINT} does not indicate an error in your program, but it is normally
4111 fatal so it can carry out the purpose of the interrupt: to kill the program.
4113 @value{GDBN} has the ability to detect any occurrence of a signal in your
4114 program. You can tell @value{GDBN} in advance what to do for each kind of
4117 @cindex handling signals
4118 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4119 @code{SIGALRM} be silently passed to your program
4120 (so as not to interfere with their role in the program's functioning)
4121 but to stop your program immediately whenever an error signal happens.
4122 You can change these settings with the @code{handle} command.
4125 @kindex info signals
4129 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4130 handle each one. You can use this to see the signal numbers of all
4131 the defined types of signals.
4133 @code{info handle} is an alias for @code{info signals}.
4136 @item handle @var{signal} @var{keywords}@dots{}
4137 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4138 can be the number of a signal or its name (with or without the
4139 @samp{SIG} at the beginning); a list of signal numbers of the form
4140 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4141 known signals. The @var{keywords} say what change to make.
4145 The keywords allowed by the @code{handle} command can be abbreviated.
4146 Their full names are:
4150 @value{GDBN} should not stop your program when this signal happens. It may
4151 still print a message telling you that the signal has come in.
4154 @value{GDBN} should stop your program when this signal happens. This implies
4155 the @code{print} keyword as well.
4158 @value{GDBN} should print a message when this signal happens.
4161 @value{GDBN} should not mention the occurrence of the signal at all. This
4162 implies the @code{nostop} keyword as well.
4166 @value{GDBN} should allow your program to see this signal; your program
4167 can handle the signal, or else it may terminate if the signal is fatal
4168 and not handled. @code{pass} and @code{noignore} are synonyms.
4172 @value{GDBN} should not allow your program to see this signal.
4173 @code{nopass} and @code{ignore} are synonyms.
4177 When a signal stops your program, the signal is not visible to the
4179 continue. Your program sees the signal then, if @code{pass} is in
4180 effect for the signal in question @emph{at that time}. In other words,
4181 after @value{GDBN} reports a signal, you can use the @code{handle}
4182 command with @code{pass} or @code{nopass} to control whether your
4183 program sees that signal when you continue.
4185 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4186 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4187 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4190 You can also use the @code{signal} command to prevent your program from
4191 seeing a signal, or cause it to see a signal it normally would not see,
4192 or to give it any signal at any time. For example, if your program stopped
4193 due to some sort of memory reference error, you might store correct
4194 values into the erroneous variables and continue, hoping to see more
4195 execution; but your program would probably terminate immediately as
4196 a result of the fatal signal once it saw the signal. To prevent this,
4197 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4201 @section Stopping and starting multi-thread programs
4203 When your program has multiple threads (@pxref{Threads,, Debugging
4204 programs with multiple threads}), you can choose whether to set
4205 breakpoints on all threads, or on a particular thread.
4208 @cindex breakpoints and threads
4209 @cindex thread breakpoints
4210 @kindex break @dots{} thread @var{threadno}
4211 @item break @var{linespec} thread @var{threadno}
4212 @itemx break @var{linespec} thread @var{threadno} if @dots{}
4213 @var{linespec} specifies source lines; there are several ways of
4214 writing them, but the effect is always to specify some source line.
4216 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
4217 to specify that you only want @value{GDBN} to stop the program when a
4218 particular thread reaches this breakpoint. @var{threadno} is one of the
4219 numeric thread identifiers assigned by @value{GDBN}, shown in the first
4220 column of the @samp{info threads} display.
4222 If you do not specify @samp{thread @var{threadno}} when you set a
4223 breakpoint, the breakpoint applies to @emph{all} threads of your
4226 You can use the @code{thread} qualifier on conditional breakpoints as
4227 well; in this case, place @samp{thread @var{threadno}} before the
4228 breakpoint condition, like this:
4231 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
4236 @cindex stopped threads
4237 @cindex threads, stopped
4238 Whenever your program stops under @value{GDBN} for any reason,
4239 @emph{all} threads of execution stop, not just the current thread. This
4240 allows you to examine the overall state of the program, including
4241 switching between threads, without worrying that things may change
4244 @cindex thread breakpoints and system calls
4245 @cindex system calls and thread breakpoints
4246 @cindex premature return from system calls
4247 There is an unfortunate side effect. If one thread stops for a
4248 breakpoint, or for some other reason, and another thread is blocked in a
4249 system call, then the system call may return prematurely. This is a
4250 consequence of the interaction between multiple threads and the signals
4251 that @value{GDBN} uses to implement breakpoints and other events that
4254 To handle this problem, your program should check the return value of
4255 each system call and react appropriately. This is good programming
4258 For example, do not write code like this:
4264 The call to @code{sleep} will return early if a different thread stops
4265 at a breakpoint or for some other reason.
4267 Instead, write this:
4272 unslept = sleep (unslept);
4275 A system call is allowed to return early, so the system is still
4276 conforming to its specification. But @value{GDBN} does cause your
4277 multi-threaded program to behave differently than it would without
4280 Also, @value{GDBN} uses internal breakpoints in the thread library to
4281 monitor certain events such as thread creation and thread destruction.
4282 When such an event happens, a system call in another thread may return
4283 prematurely, even though your program does not appear to stop.
4285 @cindex continuing threads
4286 @cindex threads, continuing
4287 Conversely, whenever you restart the program, @emph{all} threads start
4288 executing. @emph{This is true even when single-stepping} with commands
4289 like @code{step} or @code{next}.
4291 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4292 Since thread scheduling is up to your debugging target's operating
4293 system (not controlled by @value{GDBN}), other threads may
4294 execute more than one statement while the current thread completes a
4295 single step. Moreover, in general other threads stop in the middle of a
4296 statement, rather than at a clean statement boundary, when the program
4299 You might even find your program stopped in another thread after
4300 continuing or even single-stepping. This happens whenever some other
4301 thread runs into a breakpoint, a signal, or an exception before the
4302 first thread completes whatever you requested.
4304 On some OSes, you can lock the OS scheduler and thus allow only a single
4308 @item set scheduler-locking @var{mode}
4309 @cindex scheduler locking mode
4310 @cindex lock scheduler
4311 Set the scheduler locking mode. If it is @code{off}, then there is no
4312 locking and any thread may run at any time. If @code{on}, then only the
4313 current thread may run when the inferior is resumed. The @code{step}
4314 mode optimizes for single-stepping. It stops other threads from
4315 ``seizing the prompt'' by preempting the current thread while you are
4316 stepping. Other threads will only rarely (or never) get a chance to run
4317 when you step. They are more likely to run when you @samp{next} over a
4318 function call, and they are completely free to run when you use commands
4319 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4320 thread hits a breakpoint during its timeslice, they will never steal the
4321 @value{GDBN} prompt away from the thread that you are debugging.
4323 @item show scheduler-locking
4324 Display the current scheduler locking mode.
4329 @chapter Examining the Stack
4331 When your program has stopped, the first thing you need to know is where it
4332 stopped and how it got there.
4335 Each time your program performs a function call, information about the call
4337 That information includes the location of the call in your program,
4338 the arguments of the call,
4339 and the local variables of the function being called.
4340 The information is saved in a block of data called a @dfn{stack frame}.
4341 The stack frames are allocated in a region of memory called the @dfn{call
4344 When your program stops, the @value{GDBN} commands for examining the
4345 stack allow you to see all of this information.
4347 @cindex selected frame
4348 One of the stack frames is @dfn{selected} by @value{GDBN} and many
4349 @value{GDBN} commands refer implicitly to the selected frame. In
4350 particular, whenever you ask @value{GDBN} for the value of a variable in
4351 your program, the value is found in the selected frame. There are
4352 special @value{GDBN} commands to select whichever frame you are
4353 interested in. @xref{Selection, ,Selecting a frame}.
4355 When your program stops, @value{GDBN} automatically selects the
4356 currently executing frame and describes it briefly, similar to the
4357 @code{frame} command (@pxref{Frame Info, ,Information about a frame}).
4360 * Frames:: Stack frames
4361 * Backtrace:: Backtraces
4362 * Selection:: Selecting a frame
4363 * Frame Info:: Information on a frame
4368 @section Stack frames
4370 @cindex frame, definition
4372 The call stack is divided up into contiguous pieces called @dfn{stack
4373 frames}, or @dfn{frames} for short; each frame is the data associated
4374 with one call to one function. The frame contains the arguments given
4375 to the function, the function's local variables, and the address at
4376 which the function is executing.
4378 @cindex initial frame
4379 @cindex outermost frame
4380 @cindex innermost frame
4381 When your program is started, the stack has only one frame, that of the
4382 function @code{main}. This is called the @dfn{initial} frame or the
4383 @dfn{outermost} frame. Each time a function is called, a new frame is
4384 made. Each time a function returns, the frame for that function invocation
4385 is eliminated. If a function is recursive, there can be many frames for
4386 the same function. The frame for the function in which execution is
4387 actually occurring is called the @dfn{innermost} frame. This is the most
4388 recently created of all the stack frames that still exist.
4390 @cindex frame pointer
4391 Inside your program, stack frames are identified by their addresses. A
4392 stack frame consists of many bytes, each of which has its own address; each
4393 kind of computer has a convention for choosing one byte whose
4394 address serves as the address of the frame. Usually this address is kept
4395 in a register called the @dfn{frame pointer register}
4396 (@pxref{Registers, $fp}) while execution is going on in that frame.
4398 @cindex frame number
4399 @value{GDBN} assigns numbers to all existing stack frames, starting with
4400 zero for the innermost frame, one for the frame that called it,
4401 and so on upward. These numbers do not really exist in your program;
4402 they are assigned by @value{GDBN} to give you a way of designating stack
4403 frames in @value{GDBN} commands.
4405 @c The -fomit-frame-pointer below perennially causes hbox overflow
4406 @c underflow problems.
4407 @cindex frameless execution
4408 Some compilers provide a way to compile functions so that they operate
4409 without stack frames. (For example, the @value{GCC} option
4411 @samp{-fomit-frame-pointer}
4413 generates functions without a frame.)
4414 This is occasionally done with heavily used library functions to save
4415 the frame setup time. @value{GDBN} has limited facilities for dealing
4416 with these function invocations. If the innermost function invocation
4417 has no stack frame, @value{GDBN} nevertheless regards it as though
4418 it had a separate frame, which is numbered zero as usual, allowing
4419 correct tracing of the function call chain. However, @value{GDBN} has
4420 no provision for frameless functions elsewhere in the stack.
4423 @kindex frame@r{, command}
4424 @cindex current stack frame
4425 @item frame @var{args}
4426 The @code{frame} command allows you to move from one stack frame to another,
4427 and to print the stack frame you select. @var{args} may be either the
4428 address of the frame or the stack frame number. Without an argument,
4429 @code{frame} prints the current stack frame.
4431 @kindex select-frame
4432 @cindex selecting frame silently
4434 The @code{select-frame} command allows you to move from one stack frame
4435 to another without printing the frame. This is the silent version of
4443 @cindex call stack traces
4444 A backtrace is a summary of how your program got where it is. It shows one
4445 line per frame, for many frames, starting with the currently executing
4446 frame (frame zero), followed by its caller (frame one), and on up the
4451 @kindex bt @r{(@code{backtrace})}
4454 Print a backtrace of the entire stack: one line per frame for all
4455 frames in the stack.
4457 You can stop the backtrace at any time by typing the system interrupt
4458 character, normally @kbd{C-c}.
4460 @item backtrace @var{n}
4462 Similar, but print only the innermost @var{n} frames.
4464 @item backtrace -@var{n}
4466 Similar, but print only the outermost @var{n} frames.
4468 @item backtrace full
4469 Print the values of the local variables also.
4475 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4476 are additional aliases for @code{backtrace}.
4478 @cindex multiple threads, backtrace
4479 In a multi-threaded program, @value{GDBN} by default shows the
4480 backtrace only for the current thread. To display the backtrace for
4481 several or all of the threads, use the command @code{thread apply}
4482 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
4483 apply all backtrace}, @value{GDBN} will display the backtrace for all
4484 the threads; this is handy when you debug a core dump of a
4485 multi-threaded program.
4487 Each line in the backtrace shows the frame number and the function name.
4488 The program counter value is also shown---unless you use @code{set
4489 print address off}. The backtrace also shows the source file name and
4490 line number, as well as the arguments to the function. The program
4491 counter value is omitted if it is at the beginning of the code for that
4494 Here is an example of a backtrace. It was made with the command
4495 @samp{bt 3}, so it shows the innermost three frames.
4499 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4501 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4502 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4504 (More stack frames follow...)
4509 The display for frame zero does not begin with a program counter
4510 value, indicating that your program has stopped at the beginning of the
4511 code for line @code{993} of @code{builtin.c}.
4513 @cindex value optimized out, in backtrace
4514 @cindex function call arguments, optimized out
4515 If your program was compiled with optimizations, some compilers will
4516 optimize away arguments passed to functions if those arguments are
4517 never used after the call. Such optimizations generate code that
4518 passes arguments through registers, but doesn't store those arguments
4519 in the stack frame. @value{GDBN} has no way of displaying such
4520 arguments in stack frames other than the innermost one. Here's what
4521 such a backtrace might look like:
4525 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4527 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
4528 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
4530 (More stack frames follow...)
4535 The values of arguments that were not saved in their stack frames are
4536 shown as @samp{<value optimized out>}.
4538 If you need to display the values of such optimized-out arguments,
4539 either deduce that from other variables whose values depend on the one
4540 you are interested in, or recompile without optimizations.
4542 @cindex backtrace beyond @code{main} function
4543 @cindex program entry point
4544 @cindex startup code, and backtrace
4545 Most programs have a standard user entry point---a place where system
4546 libraries and startup code transition into user code. For C this is
4547 @code{main}@footnote{
4548 Note that embedded programs (the so-called ``free-standing''
4549 environment) are not required to have a @code{main} function as the
4550 entry point. They could even have multiple entry points.}.
4551 When @value{GDBN} finds the entry function in a backtrace
4552 it will terminate the backtrace, to avoid tracing into highly
4553 system-specific (and generally uninteresting) code.
4555 If you need to examine the startup code, or limit the number of levels
4556 in a backtrace, you can change this behavior:
4559 @item set backtrace past-main
4560 @itemx set backtrace past-main on
4561 @kindex set backtrace
4562 Backtraces will continue past the user entry point.
4564 @item set backtrace past-main off
4565 Backtraces will stop when they encounter the user entry point. This is the
4568 @item show backtrace past-main
4569 @kindex show backtrace
4570 Display the current user entry point backtrace policy.
4572 @item set backtrace past-entry
4573 @itemx set backtrace past-entry on
4574 Backtraces will continue past the internal entry point of an application.
4575 This entry point is encoded by the linker when the application is built,
4576 and is likely before the user entry point @code{main} (or equivalent) is called.
4578 @item set backtrace past-entry off
4579 Backtraces will stop when they encouter the internal entry point of an
4580 application. This is the default.
4582 @item show backtrace past-entry
4583 Display the current internal entry point backtrace policy.
4585 @item set backtrace limit @var{n}
4586 @itemx set backtrace limit 0
4587 @cindex backtrace limit
4588 Limit the backtrace to @var{n} levels. A value of zero means
4591 @item show backtrace limit
4592 Display the current limit on backtrace levels.
4596 @section Selecting a frame
4598 Most commands for examining the stack and other data in your program work on
4599 whichever stack frame is selected at the moment. Here are the commands for
4600 selecting a stack frame; all of them finish by printing a brief description
4601 of the stack frame just selected.
4604 @kindex frame@r{, selecting}
4605 @kindex f @r{(@code{frame})}
4608 Select frame number @var{n}. Recall that frame zero is the innermost
4609 (currently executing) frame, frame one is the frame that called the
4610 innermost one, and so on. The highest-numbered frame is the one for
4613 @item frame @var{addr}
4615 Select the frame at address @var{addr}. This is useful mainly if the
4616 chaining of stack frames has been damaged by a bug, making it
4617 impossible for @value{GDBN} to assign numbers properly to all frames. In
4618 addition, this can be useful when your program has multiple stacks and
4619 switches between them.
4621 On the SPARC architecture, @code{frame} needs two addresses to
4622 select an arbitrary frame: a frame pointer and a stack pointer.
4624 On the MIPS and Alpha architecture, it needs two addresses: a stack
4625 pointer and a program counter.
4627 On the 29k architecture, it needs three addresses: a register stack
4628 pointer, a program counter, and a memory stack pointer.
4632 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4633 advances toward the outermost frame, to higher frame numbers, to frames
4634 that have existed longer. @var{n} defaults to one.
4637 @kindex do @r{(@code{down})}
4639 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4640 advances toward the innermost frame, to lower frame numbers, to frames
4641 that were created more recently. @var{n} defaults to one. You may
4642 abbreviate @code{down} as @code{do}.
4645 All of these commands end by printing two lines of output describing the
4646 frame. The first line shows the frame number, the function name, the
4647 arguments, and the source file and line number of execution in that
4648 frame. The second line shows the text of that source line.
4656 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4658 10 read_input_file (argv[i]);
4662 After such a printout, the @code{list} command with no arguments
4663 prints ten lines centered on the point of execution in the frame.
4664 You can also edit the program at the point of execution with your favorite
4665 editing program by typing @code{edit}.
4666 @xref{List, ,Printing source lines},
4670 @kindex down-silently
4672 @item up-silently @var{n}
4673 @itemx down-silently @var{n}
4674 These two commands are variants of @code{up} and @code{down},
4675 respectively; they differ in that they do their work silently, without
4676 causing display of the new frame. They are intended primarily for use
4677 in @value{GDBN} command scripts, where the output might be unnecessary and
4682 @section Information about a frame
4684 There are several other commands to print information about the selected
4690 When used without any argument, this command does not change which
4691 frame is selected, but prints a brief description of the currently
4692 selected stack frame. It can be abbreviated @code{f}. With an
4693 argument, this command is used to select a stack frame.
4694 @xref{Selection, ,Selecting a frame}.
4697 @kindex info f @r{(@code{info frame})}
4700 This command prints a verbose description of the selected stack frame,
4705 the address of the frame
4707 the address of the next frame down (called by this frame)
4709 the address of the next frame up (caller of this frame)
4711 the language in which the source code corresponding to this frame is written
4713 the address of the frame's arguments
4715 the address of the frame's local variables
4717 the program counter saved in it (the address of execution in the caller frame)
4719 which registers were saved in the frame
4722 @noindent The verbose description is useful when
4723 something has gone wrong that has made the stack format fail to fit
4724 the usual conventions.
4726 @item info frame @var{addr}
4727 @itemx info f @var{addr}
4728 Print a verbose description of the frame at address @var{addr}, without
4729 selecting that frame. The selected frame remains unchanged by this
4730 command. This requires the same kind of address (more than one for some
4731 architectures) that you specify in the @code{frame} command.
4732 @xref{Selection, ,Selecting a frame}.
4736 Print the arguments of the selected frame, each on a separate line.
4740 Print the local variables of the selected frame, each on a separate
4741 line. These are all variables (declared either static or automatic)
4742 accessible at the point of execution of the selected frame.
4745 @cindex catch exceptions, list active handlers
4746 @cindex exception handlers, how to list
4748 Print a list of all the exception handlers that are active in the
4749 current stack frame at the current point of execution. To see other
4750 exception handlers, visit the associated frame (using the @code{up},
4751 @code{down}, or @code{frame} commands); then type @code{info catch}.
4752 @xref{Set Catchpoints, , Setting catchpoints}.
4758 @chapter Examining Source Files
4760 @value{GDBN} can print parts of your program's source, since the debugging
4761 information recorded in the program tells @value{GDBN} what source files were
4762 used to build it. When your program stops, @value{GDBN} spontaneously prints
4763 the line where it stopped. Likewise, when you select a stack frame
4764 (@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where
4765 execution in that frame has stopped. You can print other portions of
4766 source files by explicit command.
4768 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4769 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4770 @value{GDBN} under @sc{gnu} Emacs}.
4773 * List:: Printing source lines
4774 * Edit:: Editing source files
4775 * Search:: Searching source files
4776 * Source Path:: Specifying source directories
4777 * Machine Code:: Source and machine code
4781 @section Printing source lines
4784 @kindex l @r{(@code{list})}
4785 To print lines from a source file, use the @code{list} command
4786 (abbreviated @code{l}). By default, ten lines are printed.
4787 There are several ways to specify what part of the file you want to print.
4789 Here are the forms of the @code{list} command most commonly used:
4792 @item list @var{linenum}
4793 Print lines centered around line number @var{linenum} in the
4794 current source file.
4796 @item list @var{function}
4797 Print lines centered around the beginning of function
4801 Print more lines. If the last lines printed were printed with a
4802 @code{list} command, this prints lines following the last lines
4803 printed; however, if the last line printed was a solitary line printed
4804 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4805 Stack}), this prints lines centered around that line.
4808 Print lines just before the lines last printed.
4811 @cindex @code{list}, how many lines to display
4812 By default, @value{GDBN} prints ten source lines with any of these forms of
4813 the @code{list} command. You can change this using @code{set listsize}:
4816 @kindex set listsize
4817 @item set listsize @var{count}
4818 Make the @code{list} command display @var{count} source lines (unless
4819 the @code{list} argument explicitly specifies some other number).
4821 @kindex show listsize
4823 Display the number of lines that @code{list} prints.
4826 Repeating a @code{list} command with @key{RET} discards the argument,
4827 so it is equivalent to typing just @code{list}. This is more useful
4828 than listing the same lines again. An exception is made for an
4829 argument of @samp{-}; that argument is preserved in repetition so that
4830 each repetition moves up in the source file.
4833 In general, the @code{list} command expects you to supply zero, one or two
4834 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4835 of writing them, but the effect is always to specify some source line.
4836 Here is a complete description of the possible arguments for @code{list}:
4839 @item list @var{linespec}
4840 Print lines centered around the line specified by @var{linespec}.
4842 @item list @var{first},@var{last}
4843 Print lines from @var{first} to @var{last}. Both arguments are
4846 @item list ,@var{last}
4847 Print lines ending with @var{last}.
4849 @item list @var{first},
4850 Print lines starting with @var{first}.
4853 Print lines just after the lines last printed.
4856 Print lines just before the lines last printed.
4859 As described in the preceding table.
4862 Here are the ways of specifying a single source line---all the
4867 Specifies line @var{number} of the current source file.
4868 When a @code{list} command has two linespecs, this refers to
4869 the same source file as the first linespec.
4872 Specifies the line @var{offset} lines after the last line printed.
4873 When used as the second linespec in a @code{list} command that has
4874 two, this specifies the line @var{offset} lines down from the
4878 Specifies the line @var{offset} lines before the last line printed.
4880 @item @var{filename}:@var{number}
4881 Specifies line @var{number} in the source file @var{filename}.
4883 @item @var{function}
4884 Specifies the line that begins the body of the function @var{function}.
4885 For example: in C, this is the line with the open brace.
4887 @item @var{filename}:@var{function}
4888 Specifies the line of the open-brace that begins the body of the
4889 function @var{function} in the file @var{filename}. You only need the
4890 file name with a function name to avoid ambiguity when there are
4891 identically named functions in different source files.
4893 @item *@var{address}
4894 Specifies the line containing the program address @var{address}.
4895 @var{address} may be any expression.
4899 @section Editing source files
4900 @cindex editing source files
4903 @kindex e @r{(@code{edit})}
4904 To edit the lines in a source file, use the @code{edit} command.
4905 The editing program of your choice
4906 is invoked with the current line set to
4907 the active line in the program.
4908 Alternatively, there are several ways to specify what part of the file you
4909 want to print if you want to see other parts of the program.
4911 Here are the forms of the @code{edit} command most commonly used:
4915 Edit the current source file at the active line number in the program.
4917 @item edit @var{number}
4918 Edit the current source file with @var{number} as the active line number.
4920 @item edit @var{function}
4921 Edit the file containing @var{function} at the beginning of its definition.
4923 @item edit @var{filename}:@var{number}
4924 Specifies line @var{number} in the source file @var{filename}.
4926 @item edit @var{filename}:@var{function}
4927 Specifies the line that begins the body of the
4928 function @var{function} in the file @var{filename}. You only need the
4929 file name with a function name to avoid ambiguity when there are
4930 identically named functions in different source files.
4932 @item edit *@var{address}
4933 Specifies the line containing the program address @var{address}.
4934 @var{address} may be any expression.
4937 @subsection Choosing your editor
4938 You can customize @value{GDBN} to use any editor you want
4940 The only restriction is that your editor (say @code{ex}), recognizes the
4941 following command-line syntax:
4943 ex +@var{number} file
4945 The optional numeric value +@var{number} specifies the number of the line in
4946 the file where to start editing.}.
4947 By default, it is @file{@value{EDITOR}}, but you can change this
4948 by setting the environment variable @code{EDITOR} before using
4949 @value{GDBN}. For example, to configure @value{GDBN} to use the
4950 @code{vi} editor, you could use these commands with the @code{sh} shell:
4956 or in the @code{csh} shell,
4958 setenv EDITOR /usr/bin/vi
4963 @section Searching source files
4964 @cindex searching source files
4966 There are two commands for searching through the current source file for a
4971 @kindex forward-search
4972 @item forward-search @var{regexp}
4973 @itemx search @var{regexp}
4974 The command @samp{forward-search @var{regexp}} checks each line,
4975 starting with the one following the last line listed, for a match for
4976 @var{regexp}. It lists the line that is found. You can use the
4977 synonym @samp{search @var{regexp}} or abbreviate the command name as
4980 @kindex reverse-search
4981 @item reverse-search @var{regexp}
4982 The command @samp{reverse-search @var{regexp}} checks each line, starting
4983 with the one before the last line listed and going backward, for a match
4984 for @var{regexp}. It lists the line that is found. You can abbreviate
4985 this command as @code{rev}.
4989 @section Specifying source directories
4992 @cindex directories for source files
4993 Executable programs sometimes do not record the directories of the source
4994 files from which they were compiled, just the names. Even when they do,
4995 the directories could be moved between the compilation and your debugging
4996 session. @value{GDBN} has a list of directories to search for source files;
4997 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
4998 it tries all the directories in the list, in the order they are present
4999 in the list, until it finds a file with the desired name.
5001 For example, suppose an executable references the file
5002 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
5003 @file{/mnt/cross}. The file is first looked up literally; if this
5004 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
5005 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
5006 message is printed. @value{GDBN} does not look up the parts of the
5007 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
5008 Likewise, the subdirectories of the source path are not searched: if
5009 the source path is @file{/mnt/cross}, and the binary refers to
5010 @file{foo.c}, @value{GDBN} would not find it under
5011 @file{/mnt/cross/usr/src/foo-1.0/lib}.
5013 Plain file names, relative file names with leading directories, file
5014 names containing dots, etc.@: are all treated as described above; for
5015 instance, if the source path is @file{/mnt/cross}, and the source file
5016 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
5017 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
5018 that---@file{/mnt/cross/foo.c}.
5020 Note that the executable search path is @emph{not} used to locate the
5023 Whenever you reset or rearrange the source path, @value{GDBN} clears out
5024 any information it has cached about where source files are found and where
5025 each line is in the file.
5029 When you start @value{GDBN}, its source path includes only @samp{cdir}
5030 and @samp{cwd}, in that order.
5031 To add other directories, use the @code{directory} command.
5033 The search path is used to find both program source files and @value{GDBN}
5034 script files (read using the @samp{-command} option and @samp{source} command).
5037 @item directory @var{dirname} @dots{}
5038 @item dir @var{dirname} @dots{}
5039 Add directory @var{dirname} to the front of the source path. Several
5040 directory names may be given to this command, separated by @samp{:}
5041 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
5042 part of absolute file names) or
5043 whitespace. You may specify a directory that is already in the source
5044 path; this moves it forward, so @value{GDBN} searches it sooner.
5048 @vindex $cdir@r{, convenience variable}
5049 @vindex $cwdr@r{, convenience variable}
5050 @cindex compilation directory
5051 @cindex current directory
5052 @cindex working directory
5053 @cindex directory, current
5054 @cindex directory, compilation
5055 You can use the string @samp{$cdir} to refer to the compilation
5056 directory (if one is recorded), and @samp{$cwd} to refer to the current
5057 working directory. @samp{$cwd} is not the same as @samp{.}---the former
5058 tracks the current working directory as it changes during your @value{GDBN}
5059 session, while the latter is immediately expanded to the current
5060 directory at the time you add an entry to the source path.
5063 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
5065 @c RET-repeat for @code{directory} is explicitly disabled, but since
5066 @c repeating it would be a no-op we do not say that. (thanks to RMS)
5068 @item show directories
5069 @kindex show directories
5070 Print the source path: show which directories it contains.
5073 If your source path is cluttered with directories that are no longer of
5074 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
5075 versions of source. You can correct the situation as follows:
5079 Use @code{directory} with no argument to reset the source path to its default value.
5082 Use @code{directory} with suitable arguments to reinstall the
5083 directories you want in the source path. You can add all the
5084 directories in one command.
5088 @section Source and machine code
5089 @cindex source line and its code address
5091 You can use the command @code{info line} to map source lines to program
5092 addresses (and vice versa), and the command @code{disassemble} to display
5093 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
5094 mode, the @code{info line} command causes the arrow to point to the
5095 line specified. Also, @code{info line} prints addresses in symbolic form as
5100 @item info line @var{linespec}
5101 Print the starting and ending addresses of the compiled code for
5102 source line @var{linespec}. You can specify source lines in any of
5103 the ways understood by the @code{list} command (@pxref{List, ,Printing
5107 For example, we can use @code{info line} to discover the location of
5108 the object code for the first line of function
5109 @code{m4_changequote}:
5111 @c FIXME: I think this example should also show the addresses in
5112 @c symbolic form, as they usually would be displayed.
5114 (@value{GDBP}) info line m4_changequote
5115 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
5119 @cindex code address and its source line
5120 We can also inquire (using @code{*@var{addr}} as the form for
5121 @var{linespec}) what source line covers a particular address:
5123 (@value{GDBP}) info line *0x63ff
5124 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
5127 @cindex @code{$_} and @code{info line}
5128 @cindex @code{x} command, default address
5129 @kindex x@r{(examine), and} info line
5130 After @code{info line}, the default address for the @code{x} command
5131 is changed to the starting address of the line, so that @samp{x/i} is
5132 sufficient to begin examining the machine code (@pxref{Memory,
5133 ,Examining memory}). Also, this address is saved as the value of the
5134 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
5139 @cindex assembly instructions
5140 @cindex instructions, assembly
5141 @cindex machine instructions
5142 @cindex listing machine instructions
5144 This specialized command dumps a range of memory as machine
5145 instructions. The default memory range is the function surrounding the
5146 program counter of the selected frame. A single argument to this
5147 command is a program counter value; @value{GDBN} dumps the function
5148 surrounding this value. Two arguments specify a range of addresses
5149 (first inclusive, second exclusive) to dump.
5152 The following example shows the disassembly of a range of addresses of
5153 HP PA-RISC 2.0 code:
5156 (@value{GDBP}) disas 0x32c4 0x32e4
5157 Dump of assembler code from 0x32c4 to 0x32e4:
5158 0x32c4 <main+204>: addil 0,dp
5159 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
5160 0x32cc <main+212>: ldil 0x3000,r31
5161 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
5162 0x32d4 <main+220>: ldo 0(r31),rp
5163 0x32d8 <main+224>: addil -0x800,dp
5164 0x32dc <main+228>: ldo 0x588(r1),r26
5165 0x32e0 <main+232>: ldil 0x3000,r31
5166 End of assembler dump.
5169 Some architectures have more than one commonly-used set of instruction
5170 mnemonics or other syntax.
5172 For programs that were dynamically linked and use shared libraries,
5173 instructions that call functions or branch to locations in the shared
5174 libraries might show a seemingly bogus location---it's actually a
5175 location of the relocation table. On some architectures, @value{GDBN}
5176 might be able to resolve these to actual function names.
5179 @kindex set disassembly-flavor
5180 @cindex Intel disassembly flavor
5181 @cindex AT&T disassembly flavor
5182 @item set disassembly-flavor @var{instruction-set}
5183 Select the instruction set to use when disassembling the
5184 program via the @code{disassemble} or @code{x/i} commands.
5186 Currently this command is only defined for the Intel x86 family. You
5187 can set @var{instruction-set} to either @code{intel} or @code{att}.
5188 The default is @code{att}, the AT&T flavor used by default by Unix
5189 assemblers for x86-based targets.
5191 @kindex show disassembly-flavor
5192 @item show disassembly-flavor
5193 Show the current setting of the disassembly flavor.
5198 @chapter Examining Data
5200 @cindex printing data
5201 @cindex examining data
5204 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
5205 @c document because it is nonstandard... Under Epoch it displays in a
5206 @c different window or something like that.
5207 The usual way to examine data in your program is with the @code{print}
5208 command (abbreviated @code{p}), or its synonym @code{inspect}. It
5209 evaluates and prints the value of an expression of the language your
5210 program is written in (@pxref{Languages, ,Using @value{GDBN} with
5211 Different Languages}).
5214 @item print @var{expr}
5215 @itemx print /@var{f} @var{expr}
5216 @var{expr} is an expression (in the source language). By default the
5217 value of @var{expr} is printed in a format appropriate to its data type;
5218 you can choose a different format by specifying @samp{/@var{f}}, where
5219 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
5223 @itemx print /@var{f}
5224 @cindex reprint the last value
5225 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
5226 @dfn{value history}; @pxref{Value History, ,Value history}). This allows you to
5227 conveniently inspect the same value in an alternative format.
5230 A more low-level way of examining data is with the @code{x} command.
5231 It examines data in memory at a specified address and prints it in a
5232 specified format. @xref{Memory, ,Examining memory}.
5234 If you are interested in information about types, or about how the
5235 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
5236 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
5240 * Expressions:: Expressions
5241 * Variables:: Program variables
5242 * Arrays:: Artificial arrays
5243 * Output Formats:: Output formats
5244 * Memory:: Examining memory
5245 * Auto Display:: Automatic display
5246 * Print Settings:: Print settings
5247 * Value History:: Value history
5248 * Convenience Vars:: Convenience variables
5249 * Registers:: Registers
5250 * Floating Point Hardware:: Floating point hardware
5251 * Vector Unit:: Vector Unit
5252 * OS Information:: Auxiliary data provided by operating system
5253 * Memory Region Attributes:: Memory region attributes
5254 * Dump/Restore Files:: Copy between memory and a file
5255 * Core File Generation:: Cause a program dump its core
5256 * Character Sets:: Debugging programs that use a different
5257 character set than GDB does
5258 * Caching Remote Data:: Data caching for remote targets
5262 @section Expressions
5265 @code{print} and many other @value{GDBN} commands accept an expression and
5266 compute its value. Any kind of constant, variable or operator defined
5267 by the programming language you are using is valid in an expression in
5268 @value{GDBN}. This includes conditional expressions, function calls,
5269 casts, and string constants. It also includes preprocessor macros, if
5270 you compiled your program to include this information; see
5273 @cindex arrays in expressions
5274 @value{GDBN} supports array constants in expressions input by
5275 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
5276 you can use the command @code{print @{1, 2, 3@}} to build up an array in
5277 memory that is @code{malloc}ed in the target program.
5279 Because C is so widespread, most of the expressions shown in examples in
5280 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
5281 Languages}, for information on how to use expressions in other
5284 In this section, we discuss operators that you can use in @value{GDBN}
5285 expressions regardless of your programming language.
5287 @cindex casts, in expressions
5288 Casts are supported in all languages, not just in C, because it is so
5289 useful to cast a number into a pointer in order to examine a structure
5290 at that address in memory.
5291 @c FIXME: casts supported---Mod2 true?
5293 @value{GDBN} supports these operators, in addition to those common
5294 to programming languages:
5298 @samp{@@} is a binary operator for treating parts of memory as arrays.
5299 @xref{Arrays, ,Artificial arrays}, for more information.
5302 @samp{::} allows you to specify a variable in terms of the file or
5303 function where it is defined. @xref{Variables, ,Program variables}.
5305 @cindex @{@var{type}@}
5306 @cindex type casting memory
5307 @cindex memory, viewing as typed object
5308 @cindex casts, to view memory
5309 @item @{@var{type}@} @var{addr}
5310 Refers to an object of type @var{type} stored at address @var{addr} in
5311 memory. @var{addr} may be any expression whose value is an integer or
5312 pointer (but parentheses are required around binary operators, just as in
5313 a cast). This construct is allowed regardless of what kind of data is
5314 normally supposed to reside at @var{addr}.
5318 @section Program variables
5320 The most common kind of expression to use is the name of a variable
5323 Variables in expressions are understood in the selected stack frame
5324 (@pxref{Selection, ,Selecting a frame}); they must be either:
5328 global (or file-static)
5335 visible according to the scope rules of the
5336 programming language from the point of execution in that frame
5339 @noindent This means that in the function
5354 you can examine and use the variable @code{a} whenever your program is
5355 executing within the function @code{foo}, but you can only use or
5356 examine the variable @code{b} while your program is executing inside
5357 the block where @code{b} is declared.
5359 @cindex variable name conflict
5360 There is an exception: you can refer to a variable or function whose
5361 scope is a single source file even if the current execution point is not
5362 in this file. But it is possible to have more than one such variable or
5363 function with the same name (in different source files). If that
5364 happens, referring to that name has unpredictable effects. If you wish,
5365 you can specify a static variable in a particular function or file,
5366 using the colon-colon (@code{::}) notation:
5368 @cindex colon-colon, context for variables/functions
5370 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
5371 @cindex @code{::}, context for variables/functions
5374 @var{file}::@var{variable}
5375 @var{function}::@var{variable}
5379 Here @var{file} or @var{function} is the name of the context for the
5380 static @var{variable}. In the case of file names, you can use quotes to
5381 make sure @value{GDBN} parses the file name as a single word---for example,
5382 to print a global value of @code{x} defined in @file{f2.c}:
5385 (@value{GDBP}) p 'f2.c'::x
5388 @cindex C@t{++} scope resolution
5389 This use of @samp{::} is very rarely in conflict with the very similar
5390 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
5391 scope resolution operator in @value{GDBN} expressions.
5392 @c FIXME: Um, so what happens in one of those rare cases where it's in
5395 @cindex wrong values
5396 @cindex variable values, wrong
5397 @cindex function entry/exit, wrong values of variables
5398 @cindex optimized code, wrong values of variables
5400 @emph{Warning:} Occasionally, a local variable may appear to have the
5401 wrong value at certain points in a function---just after entry to a new
5402 scope, and just before exit.
5404 You may see this problem when you are stepping by machine instructions.
5405 This is because, on most machines, it takes more than one instruction to
5406 set up a stack frame (including local variable definitions); if you are
5407 stepping by machine instructions, variables may appear to have the wrong
5408 values until the stack frame is completely built. On exit, it usually
5409 also takes more than one machine instruction to destroy a stack frame;
5410 after you begin stepping through that group of instructions, local
5411 variable definitions may be gone.
5413 This may also happen when the compiler does significant optimizations.
5414 To be sure of always seeing accurate values, turn off all optimization
5417 @cindex ``No symbol "foo" in current context''
5418 Another possible effect of compiler optimizations is to optimize
5419 unused variables out of existence, or assign variables to registers (as
5420 opposed to memory addresses). Depending on the support for such cases
5421 offered by the debug info format used by the compiler, @value{GDBN}
5422 might not be able to display values for such local variables. If that
5423 happens, @value{GDBN} will print a message like this:
5426 No symbol "foo" in current context.
5429 To solve such problems, either recompile without optimizations, or use a
5430 different debug info format, if the compiler supports several such
5431 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
5432 usually supports the @option{-gstabs+} option. @option{-gstabs+}
5433 produces debug info in a format that is superior to formats such as
5434 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
5435 an effective form for debug info. @xref{Debugging Options,,Options
5436 for Debugging Your Program or @sc{gnu} CC, gcc.info, Using @sc{gnu} CC}.
5437 @xref{C, , Debugging C++}, for more info about debug info formats
5438 that are best suited to C@t{++} programs.
5440 If you ask to print an object whose contents are unknown to
5441 @value{GDBN}, e.g., because its data type is not completely specified
5442 by the debug information, @value{GDBN} will say @samp{<incomplete
5443 type>}. @xref{Symbols, incomplete type}, for more about this.
5446 @section Artificial arrays
5448 @cindex artificial array
5450 @kindex @@@r{, referencing memory as an array}
5451 It is often useful to print out several successive objects of the
5452 same type in memory; a section of an array, or an array of
5453 dynamically determined size for which only a pointer exists in the
5456 You can do this by referring to a contiguous span of memory as an
5457 @dfn{artificial array}, using the binary operator @samp{@@}. The left
5458 operand of @samp{@@} should be the first element of the desired array
5459 and be an individual object. The right operand should be the desired length
5460 of the array. The result is an array value whose elements are all of
5461 the type of the left argument. The first element is actually the left
5462 argument; the second element comes from bytes of memory immediately
5463 following those that hold the first element, and so on. Here is an
5464 example. If a program says
5467 int *array = (int *) malloc (len * sizeof (int));
5471 you can print the contents of @code{array} with
5477 The left operand of @samp{@@} must reside in memory. Array values made
5478 with @samp{@@} in this way behave just like other arrays in terms of
5479 subscripting, and are coerced to pointers when used in expressions.
5480 Artificial arrays most often appear in expressions via the value history
5481 (@pxref{Value History, ,Value history}), after printing one out.
5483 Another way to create an artificial array is to use a cast.
5484 This re-interprets a value as if it were an array.
5485 The value need not be in memory:
5487 (@value{GDBP}) p/x (short[2])0x12345678
5488 $1 = @{0x1234, 0x5678@}
5491 As a convenience, if you leave the array length out (as in
5492 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
5493 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
5495 (@value{GDBP}) p/x (short[])0x12345678
5496 $2 = @{0x1234, 0x5678@}
5499 Sometimes the artificial array mechanism is not quite enough; in
5500 moderately complex data structures, the elements of interest may not
5501 actually be adjacent---for example, if you are interested in the values
5502 of pointers in an array. One useful work-around in this situation is
5503 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
5504 variables}) as a counter in an expression that prints the first
5505 interesting value, and then repeat that expression via @key{RET}. For
5506 instance, suppose you have an array @code{dtab} of pointers to
5507 structures, and you are interested in the values of a field @code{fv}
5508 in each structure. Here is an example of what you might type:
5518 @node Output Formats
5519 @section Output formats
5521 @cindex formatted output
5522 @cindex output formats
5523 By default, @value{GDBN} prints a value according to its data type. Sometimes
5524 this is not what you want. For example, you might want to print a number
5525 in hex, or a pointer in decimal. Or you might want to view data in memory
5526 at a certain address as a character string or as an instruction. To do
5527 these things, specify an @dfn{output format} when you print a value.
5529 The simplest use of output formats is to say how to print a value
5530 already computed. This is done by starting the arguments of the
5531 @code{print} command with a slash and a format letter. The format
5532 letters supported are:
5536 Regard the bits of the value as an integer, and print the integer in
5540 Print as integer in signed decimal.
5543 Print as integer in unsigned decimal.
5546 Print as integer in octal.
5549 Print as integer in binary. The letter @samp{t} stands for ``two''.
5550 @footnote{@samp{b} cannot be used because these format letters are also
5551 used with the @code{x} command, where @samp{b} stands for ``byte'';
5552 see @ref{Memory,,Examining memory}.}
5555 @cindex unknown address, locating
5556 @cindex locate address
5557 Print as an address, both absolute in hexadecimal and as an offset from
5558 the nearest preceding symbol. You can use this format used to discover
5559 where (in what function) an unknown address is located:
5562 (@value{GDBP}) p/a 0x54320
5563 $3 = 0x54320 <_initialize_vx+396>
5567 The command @code{info symbol 0x54320} yields similar results.
5568 @xref{Symbols, info symbol}.
5571 Regard as an integer and print it as a character constant. This
5572 prints both the numerical value and its character representation. The
5573 character representation is replaced with the octal escape @samp{\nnn}
5574 for characters outside the 7-bit @sc{ascii} range.
5577 Regard the bits of the value as a floating point number and print
5578 using typical floating point syntax.
5581 For example, to print the program counter in hex (@pxref{Registers}), type
5588 Note that no space is required before the slash; this is because command
5589 names in @value{GDBN} cannot contain a slash.
5591 To reprint the last value in the value history with a different format,
5592 you can use the @code{print} command with just a format and no
5593 expression. For example, @samp{p/x} reprints the last value in hex.
5596 @section Examining memory
5598 You can use the command @code{x} (for ``examine'') to examine memory in
5599 any of several formats, independently of your program's data types.
5601 @cindex examining memory
5603 @kindex x @r{(examine memory)}
5604 @item x/@var{nfu} @var{addr}
5607 Use the @code{x} command to examine memory.
5610 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
5611 much memory to display and how to format it; @var{addr} is an
5612 expression giving the address where you want to start displaying memory.
5613 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
5614 Several commands set convenient defaults for @var{addr}.
5617 @item @var{n}, the repeat count
5618 The repeat count is a decimal integer; the default is 1. It specifies
5619 how much memory (counting by units @var{u}) to display.
5620 @c This really is **decimal**; unaffected by 'set radix' as of GDB
5623 @item @var{f}, the display format
5624 The display format is one of the formats used by @code{print}
5625 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
5626 @samp{f}), and in addition @samp{s} (for null-terminated strings) and
5627 @samp{i} (for machine instructions). The default is @samp{x}
5628 (hexadecimal) initially. The default changes each time you use either
5629 @code{x} or @code{print}.
5631 @item @var{u}, the unit size
5632 The unit size is any of
5638 Halfwords (two bytes).
5640 Words (four bytes). This is the initial default.
5642 Giant words (eight bytes).
5645 Each time you specify a unit size with @code{x}, that size becomes the
5646 default unit the next time you use @code{x}. (For the @samp{s} and
5647 @samp{i} formats, the unit size is ignored and is normally not written.)
5649 @item @var{addr}, starting display address
5650 @var{addr} is the address where you want @value{GDBN} to begin displaying
5651 memory. The expression need not have a pointer value (though it may);
5652 it is always interpreted as an integer address of a byte of memory.
5653 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
5654 @var{addr} is usually just after the last address examined---but several
5655 other commands also set the default address: @code{info breakpoints} (to
5656 the address of the last breakpoint listed), @code{info line} (to the
5657 starting address of a line), and @code{print} (if you use it to display
5658 a value from memory).
5661 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
5662 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
5663 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
5664 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
5665 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
5667 Since the letters indicating unit sizes are all distinct from the
5668 letters specifying output formats, you do not have to remember whether
5669 unit size or format comes first; either order works. The output
5670 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
5671 (However, the count @var{n} must come first; @samp{wx4} does not work.)
5673 Even though the unit size @var{u} is ignored for the formats @samp{s}
5674 and @samp{i}, you might still want to use a count @var{n}; for example,
5675 @samp{3i} specifies that you want to see three machine instructions,
5676 including any operands. The command @code{disassemble} gives an
5677 alternative way of inspecting machine instructions; see @ref{Machine
5678 Code,,Source and machine code}.
5680 All the defaults for the arguments to @code{x} are designed to make it
5681 easy to continue scanning memory with minimal specifications each time
5682 you use @code{x}. For example, after you have inspected three machine
5683 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
5684 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
5685 the repeat count @var{n} is used again; the other arguments default as
5686 for successive uses of @code{x}.
5688 @cindex @code{$_}, @code{$__}, and value history
5689 The addresses and contents printed by the @code{x} command are not saved
5690 in the value history because there is often too much of them and they
5691 would get in the way. Instead, @value{GDBN} makes these values available for
5692 subsequent use in expressions as values of the convenience variables
5693 @code{$_} and @code{$__}. After an @code{x} command, the last address
5694 examined is available for use in expressions in the convenience variable
5695 @code{$_}. The contents of that address, as examined, are available in
5696 the convenience variable @code{$__}.
5698 If the @code{x} command has a repeat count, the address and contents saved
5699 are from the last memory unit printed; this is not the same as the last
5700 address printed if several units were printed on the last line of output.
5702 @cindex remote memory comparison
5703 @cindex verify remote memory image
5704 When you are debugging a program running on a remote target machine
5705 (@pxref{Remote}), you may wish to verify the program's image in the
5706 remote machine's memory against the executable file you downloaded to
5707 the target. The @code{compare-sections} command is provided for such
5711 @kindex compare-sections
5712 @item compare-sections @r{[}@var{section-name}@r{]}
5713 Compare the data of a loadable section @var{section-name} in the
5714 executable file of the program being debugged with the same section in
5715 the remote machine's memory, and report any mismatches. With no
5716 arguments, compares all loadable sections. This command's
5717 availability depends on the target's support for the @code{"qCRC"}
5722 @section Automatic display
5723 @cindex automatic display
5724 @cindex display of expressions
5726 If you find that you want to print the value of an expression frequently
5727 (to see how it changes), you might want to add it to the @dfn{automatic
5728 display list} so that @value{GDBN} prints its value each time your program stops.
5729 Each expression added to the list is given a number to identify it;
5730 to remove an expression from the list, you specify that number.
5731 The automatic display looks like this:
5735 3: bar[5] = (struct hack *) 0x3804
5739 This display shows item numbers, expressions and their current values. As with
5740 displays you request manually using @code{x} or @code{print}, you can
5741 specify the output format you prefer; in fact, @code{display} decides
5742 whether to use @code{print} or @code{x} depending on how elaborate your
5743 format specification is---it uses @code{x} if you specify a unit size,
5744 or one of the two formats (@samp{i} and @samp{s}) that are only
5745 supported by @code{x}; otherwise it uses @code{print}.
5749 @item display @var{expr}
5750 Add the expression @var{expr} to the list of expressions to display
5751 each time your program stops. @xref{Expressions, ,Expressions}.
5753 @code{display} does not repeat if you press @key{RET} again after using it.
5755 @item display/@var{fmt} @var{expr}
5756 For @var{fmt} specifying only a display format and not a size or
5757 count, add the expression @var{expr} to the auto-display list but
5758 arrange to display it each time in the specified format @var{fmt}.
5759 @xref{Output Formats,,Output formats}.
5761 @item display/@var{fmt} @var{addr}
5762 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
5763 number of units, add the expression @var{addr} as a memory address to
5764 be examined each time your program stops. Examining means in effect
5765 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}.
5768 For example, @samp{display/i $pc} can be helpful, to see the machine
5769 instruction about to be executed each time execution stops (@samp{$pc}
5770 is a common name for the program counter; @pxref{Registers, ,Registers}).
5773 @kindex delete display
5775 @item undisplay @var{dnums}@dots{}
5776 @itemx delete display @var{dnums}@dots{}
5777 Remove item numbers @var{dnums} from the list of expressions to display.
5779 @code{undisplay} does not repeat if you press @key{RET} after using it.
5780 (Otherwise you would just get the error @samp{No display number @dots{}}.)
5782 @kindex disable display
5783 @item disable display @var{dnums}@dots{}
5784 Disable the display of item numbers @var{dnums}. A disabled display
5785 item is not printed automatically, but is not forgotten. It may be
5786 enabled again later.
5788 @kindex enable display
5789 @item enable display @var{dnums}@dots{}
5790 Enable display of item numbers @var{dnums}. It becomes effective once
5791 again in auto display of its expression, until you specify otherwise.
5794 Display the current values of the expressions on the list, just as is
5795 done when your program stops.
5797 @kindex info display
5799 Print the list of expressions previously set up to display
5800 automatically, each one with its item number, but without showing the
5801 values. This includes disabled expressions, which are marked as such.
5802 It also includes expressions which would not be displayed right now
5803 because they refer to automatic variables not currently available.
5806 @cindex display disabled out of scope
5807 If a display expression refers to local variables, then it does not make
5808 sense outside the lexical context for which it was set up. Such an
5809 expression is disabled when execution enters a context where one of its
5810 variables is not defined. For example, if you give the command
5811 @code{display last_char} while inside a function with an argument
5812 @code{last_char}, @value{GDBN} displays this argument while your program
5813 continues to stop inside that function. When it stops elsewhere---where
5814 there is no variable @code{last_char}---the display is disabled
5815 automatically. The next time your program stops where @code{last_char}
5816 is meaningful, you can enable the display expression once again.
5818 @node Print Settings
5819 @section Print settings
5821 @cindex format options
5822 @cindex print settings
5823 @value{GDBN} provides the following ways to control how arrays, structures,
5824 and symbols are printed.
5827 These settings are useful for debugging programs in any language:
5831 @item set print address
5832 @itemx set print address on
5833 @cindex print/don't print memory addresses
5834 @value{GDBN} prints memory addresses showing the location of stack
5835 traces, structure values, pointer values, breakpoints, and so forth,
5836 even when it also displays the contents of those addresses. The default
5837 is @code{on}. For example, this is what a stack frame display looks like with
5838 @code{set print address on}:
5843 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
5845 530 if (lquote != def_lquote)
5849 @item set print address off
5850 Do not print addresses when displaying their contents. For example,
5851 this is the same stack frame displayed with @code{set print address off}:
5855 (@value{GDBP}) set print addr off
5857 #0 set_quotes (lq="<<", rq=">>") at input.c:530
5858 530 if (lquote != def_lquote)
5862 You can use @samp{set print address off} to eliminate all machine
5863 dependent displays from the @value{GDBN} interface. For example, with
5864 @code{print address off}, you should get the same text for backtraces on
5865 all machines---whether or not they involve pointer arguments.
5868 @item show print address
5869 Show whether or not addresses are to be printed.
5872 When @value{GDBN} prints a symbolic address, it normally prints the
5873 closest earlier symbol plus an offset. If that symbol does not uniquely
5874 identify the address (for example, it is a name whose scope is a single
5875 source file), you may need to clarify. One way to do this is with
5876 @code{info line}, for example @samp{info line *0x4537}. Alternately,
5877 you can set @value{GDBN} to print the source file and line number when
5878 it prints a symbolic address:
5881 @item set print symbol-filename on
5882 @cindex source file and line of a symbol
5883 @cindex symbol, source file and line
5884 Tell @value{GDBN} to print the source file name and line number of a
5885 symbol in the symbolic form of an address.
5887 @item set print symbol-filename off
5888 Do not print source file name and line number of a symbol. This is the
5891 @item show print symbol-filename
5892 Show whether or not @value{GDBN} will print the source file name and
5893 line number of a symbol in the symbolic form of an address.
5896 Another situation where it is helpful to show symbol filenames and line
5897 numbers is when disassembling code; @value{GDBN} shows you the line
5898 number and source file that corresponds to each instruction.
5900 Also, you may wish to see the symbolic form only if the address being
5901 printed is reasonably close to the closest earlier symbol:
5904 @item set print max-symbolic-offset @var{max-offset}
5905 @cindex maximum value for offset of closest symbol
5906 Tell @value{GDBN} to only display the symbolic form of an address if the
5907 offset between the closest earlier symbol and the address is less than
5908 @var{max-offset}. The default is 0, which tells @value{GDBN}
5909 to always print the symbolic form of an address if any symbol precedes it.
5911 @item show print max-symbolic-offset
5912 Ask how large the maximum offset is that @value{GDBN} prints in a
5916 @cindex wild pointer, interpreting
5917 @cindex pointer, finding referent
5918 If you have a pointer and you are not sure where it points, try
5919 @samp{set print symbol-filename on}. Then you can determine the name
5920 and source file location of the variable where it points, using
5921 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
5922 For example, here @value{GDBN} shows that a variable @code{ptt} points
5923 at another variable @code{t}, defined in @file{hi2.c}:
5926 (@value{GDBP}) set print symbol-filename on
5927 (@value{GDBP}) p/a ptt
5928 $4 = 0xe008 <t in hi2.c>
5932 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
5933 does not show the symbol name and filename of the referent, even with
5934 the appropriate @code{set print} options turned on.
5937 Other settings control how different kinds of objects are printed:
5940 @item set print array
5941 @itemx set print array on
5942 @cindex pretty print arrays
5943 Pretty print arrays. This format is more convenient to read,
5944 but uses more space. The default is off.
5946 @item set print array off
5947 Return to compressed format for arrays.
5949 @item show print array
5950 Show whether compressed or pretty format is selected for displaying
5953 @cindex print array indexes
5954 @item set print array-indexes
5955 @itemx set print array-indexes on
5956 Print the index of each element when displaying arrays. May be more
5957 convenient to locate a given element in the array or quickly find the
5958 index of a given element in that printed array. The default is off.
5960 @item set print array-indexes off
5961 Stop printing element indexes when displaying arrays.
5963 @item show print array-indexes
5964 Show whether the index of each element is printed when displaying
5967 @item set print elements @var{number-of-elements}
5968 @cindex number of array elements to print
5969 @cindex limit on number of printed array elements
5970 Set a limit on how many elements of an array @value{GDBN} will print.
5971 If @value{GDBN} is printing a large array, it stops printing after it has
5972 printed the number of elements set by the @code{set print elements} command.
5973 This limit also applies to the display of strings.
5974 When @value{GDBN} starts, this limit is set to 200.
5975 Setting @var{number-of-elements} to zero means that the printing is unlimited.
5977 @item show print elements
5978 Display the number of elements of a large array that @value{GDBN} will print.
5979 If the number is 0, then the printing is unlimited.
5981 @item set print repeats
5982 @cindex repeated array elements
5983 Set the threshold for suppressing display of repeated array
5984 elelments. When the number of consecutive identical elements of an
5985 array exceeds the threshold, @value{GDBN} prints the string
5986 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
5987 identical repetitions, instead of displaying the identical elements
5988 themselves. Setting the threshold to zero will cause all elements to
5989 be individually printed. The default threshold is 10.
5991 @item show print repeats
5992 Display the current threshold for printing repeated identical
5995 @item set print null-stop
5996 @cindex @sc{null} elements in arrays
5997 Cause @value{GDBN} to stop printing the characters of an array when the first
5998 @sc{null} is encountered. This is useful when large arrays actually
5999 contain only short strings.
6002 @item show print null-stop
6003 Show whether @value{GDBN} stops printing an array on the first
6004 @sc{null} character.
6006 @item set print pretty on
6007 @cindex print structures in indented form
6008 @cindex indentation in structure display
6009 Cause @value{GDBN} to print structures in an indented format with one member
6010 per line, like this:
6025 @item set print pretty off
6026 Cause @value{GDBN} to print structures in a compact format, like this:
6030 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
6031 meat = 0x54 "Pork"@}
6036 This is the default format.
6038 @item show print pretty
6039 Show which format @value{GDBN} is using to print structures.
6041 @item set print sevenbit-strings on
6042 @cindex eight-bit characters in strings
6043 @cindex octal escapes in strings
6044 Print using only seven-bit characters; if this option is set,
6045 @value{GDBN} displays any eight-bit characters (in strings or
6046 character values) using the notation @code{\}@var{nnn}. This setting is
6047 best if you are working in English (@sc{ascii}) and you use the
6048 high-order bit of characters as a marker or ``meta'' bit.
6050 @item set print sevenbit-strings off
6051 Print full eight-bit characters. This allows the use of more
6052 international character sets, and is the default.
6054 @item show print sevenbit-strings
6055 Show whether or not @value{GDBN} is printing only seven-bit characters.
6057 @item set print union on
6058 @cindex unions in structures, printing
6059 Tell @value{GDBN} to print unions which are contained in structures
6060 and other unions. This is the default setting.
6062 @item set print union off
6063 Tell @value{GDBN} not to print unions which are contained in
6064 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
6067 @item show print union
6068 Ask @value{GDBN} whether or not it will print unions which are contained in
6069 structures and other unions.
6071 For example, given the declarations
6074 typedef enum @{Tree, Bug@} Species;
6075 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
6076 typedef enum @{Caterpillar, Cocoon, Butterfly@}
6087 struct thing foo = @{Tree, @{Acorn@}@};
6091 with @code{set print union on} in effect @samp{p foo} would print
6094 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
6098 and with @code{set print union off} in effect it would print
6101 $1 = @{it = Tree, form = @{...@}@}
6105 @code{set print union} affects programs written in C-like languages
6111 These settings are of interest when debugging C@t{++} programs:
6114 @cindex demangling C@t{++} names
6115 @item set print demangle
6116 @itemx set print demangle on
6117 Print C@t{++} names in their source form rather than in the encoded
6118 (``mangled'') form passed to the assembler and linker for type-safe
6119 linkage. The default is on.
6121 @item show print demangle
6122 Show whether C@t{++} names are printed in mangled or demangled form.
6124 @item set print asm-demangle
6125 @itemx set print asm-demangle on
6126 Print C@t{++} names in their source form rather than their mangled form, even
6127 in assembler code printouts such as instruction disassemblies.
6130 @item show print asm-demangle
6131 Show whether C@t{++} names in assembly listings are printed in mangled
6134 @cindex C@t{++} symbol decoding style
6135 @cindex symbol decoding style, C@t{++}
6136 @kindex set demangle-style
6137 @item set demangle-style @var{style}
6138 Choose among several encoding schemes used by different compilers to
6139 represent C@t{++} names. The choices for @var{style} are currently:
6143 Allow @value{GDBN} to choose a decoding style by inspecting your program.
6146 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
6147 This is the default.
6150 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
6153 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
6156 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
6157 @strong{Warning:} this setting alone is not sufficient to allow
6158 debugging @code{cfront}-generated executables. @value{GDBN} would
6159 require further enhancement to permit that.
6162 If you omit @var{style}, you will see a list of possible formats.
6164 @item show demangle-style
6165 Display the encoding style currently in use for decoding C@t{++} symbols.
6167 @item set print object
6168 @itemx set print object on
6169 @cindex derived type of an object, printing
6170 @cindex display derived types
6171 When displaying a pointer to an object, identify the @emph{actual}
6172 (derived) type of the object rather than the @emph{declared} type, using
6173 the virtual function table.
6175 @item set print object off
6176 Display only the declared type of objects, without reference to the
6177 virtual function table. This is the default setting.
6179 @item show print object
6180 Show whether actual, or declared, object types are displayed.
6182 @item set print static-members
6183 @itemx set print static-members on
6184 @cindex static members of C@t{++} objects
6185 Print static members when displaying a C@t{++} object. The default is on.
6187 @item set print static-members off
6188 Do not print static members when displaying a C@t{++} object.
6190 @item show print static-members
6191 Show whether C@t{++} static members are printed or not.
6193 @item set print pascal_static-members
6194 @itemx set print pascal_static-members on
6195 @cindex static members of Pacal objects
6196 @cindex Pacal objects, static members display
6197 Print static members when displaying a Pascal object. The default is on.
6199 @item set print pascal_static-members off
6200 Do not print static members when displaying a Pascal object.
6202 @item show print pascal_static-members
6203 Show whether Pascal static members are printed or not.
6205 @c These don't work with HP ANSI C++ yet.
6206 @item set print vtbl
6207 @itemx set print vtbl on
6208 @cindex pretty print C@t{++} virtual function tables
6209 @cindex virtual functions (C@t{++}) display
6210 @cindex VTBL display
6211 Pretty print C@t{++} virtual function tables. The default is off.
6212 (The @code{vtbl} commands do not work on programs compiled with the HP
6213 ANSI C@t{++} compiler (@code{aCC}).)
6215 @item set print vtbl off
6216 Do not pretty print C@t{++} virtual function tables.
6218 @item show print vtbl
6219 Show whether C@t{++} virtual function tables are pretty printed, or not.
6223 @section Value history
6225 @cindex value history
6226 @cindex history of values printed by @value{GDBN}
6227 Values printed by the @code{print} command are saved in the @value{GDBN}
6228 @dfn{value history}. This allows you to refer to them in other expressions.
6229 Values are kept until the symbol table is re-read or discarded
6230 (for example with the @code{file} or @code{symbol-file} commands).
6231 When the symbol table changes, the value history is discarded,
6232 since the values may contain pointers back to the types defined in the
6237 @cindex history number
6238 The values printed are given @dfn{history numbers} by which you can
6239 refer to them. These are successive integers starting with one.
6240 @code{print} shows you the history number assigned to a value by
6241 printing @samp{$@var{num} = } before the value; here @var{num} is the
6244 To refer to any previous value, use @samp{$} followed by the value's
6245 history number. The way @code{print} labels its output is designed to
6246 remind you of this. Just @code{$} refers to the most recent value in
6247 the history, and @code{$$} refers to the value before that.
6248 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
6249 is the value just prior to @code{$$}, @code{$$1} is equivalent to
6250 @code{$$}, and @code{$$0} is equivalent to @code{$}.
6252 For example, suppose you have just printed a pointer to a structure and
6253 want to see the contents of the structure. It suffices to type
6259 If you have a chain of structures where the component @code{next} points
6260 to the next one, you can print the contents of the next one with this:
6267 You can print successive links in the chain by repeating this
6268 command---which you can do by just typing @key{RET}.
6270 Note that the history records values, not expressions. If the value of
6271 @code{x} is 4 and you type these commands:
6279 then the value recorded in the value history by the @code{print} command
6280 remains 4 even though the value of @code{x} has changed.
6285 Print the last ten values in the value history, with their item numbers.
6286 This is like @samp{p@ $$9} repeated ten times, except that @code{show
6287 values} does not change the history.
6289 @item show values @var{n}
6290 Print ten history values centered on history item number @var{n}.
6293 Print ten history values just after the values last printed. If no more
6294 values are available, @code{show values +} produces no display.
6297 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
6298 same effect as @samp{show values +}.
6300 @node Convenience Vars
6301 @section Convenience variables
6303 @cindex convenience variables
6304 @cindex user-defined variables
6305 @value{GDBN} provides @dfn{convenience variables} that you can use within
6306 @value{GDBN} to hold on to a value and refer to it later. These variables
6307 exist entirely within @value{GDBN}; they are not part of your program, and
6308 setting a convenience variable has no direct effect on further execution
6309 of your program. That is why you can use them freely.
6311 Convenience variables are prefixed with @samp{$}. Any name preceded by
6312 @samp{$} can be used for a convenience variable, unless it is one of
6313 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
6314 (Value history references, in contrast, are @emph{numbers} preceded
6315 by @samp{$}. @xref{Value History, ,Value history}.)
6317 You can save a value in a convenience variable with an assignment
6318 expression, just as you would set a variable in your program.
6322 set $foo = *object_ptr
6326 would save in @code{$foo} the value contained in the object pointed to by
6329 Using a convenience variable for the first time creates it, but its
6330 value is @code{void} until you assign a new value. You can alter the
6331 value with another assignment at any time.
6333 Convenience variables have no fixed types. You can assign a convenience
6334 variable any type of value, including structures and arrays, even if
6335 that variable already has a value of a different type. The convenience
6336 variable, when used as an expression, has the type of its current value.
6339 @kindex show convenience
6340 @cindex show all user variables
6341 @item show convenience
6342 Print a list of convenience variables used so far, and their values.
6343 Abbreviated @code{show conv}.
6345 @kindex init-if-undefined
6346 @cindex convenience variables, initializing
6347 @item init-if-undefined $@var{variable} = @var{expression}
6348 Set a convenience variable if it has not already been set. This is useful
6349 for user-defined commands that keep some state. It is similar, in concept,
6350 to using local static variables with initializers in C (except that
6351 convenience variables are global). It can also be used to allow users to
6352 override default values used in a command script.
6354 If the variable is already defined then the expression is not evaluated so
6355 any side-effects do not occur.
6358 One of the ways to use a convenience variable is as a counter to be
6359 incremented or a pointer to be advanced. For example, to print
6360 a field from successive elements of an array of structures:
6364 print bar[$i++]->contents
6368 Repeat that command by typing @key{RET}.
6370 Some convenience variables are created automatically by @value{GDBN} and given
6371 values likely to be useful.
6374 @vindex $_@r{, convenience variable}
6376 The variable @code{$_} is automatically set by the @code{x} command to
6377 the last address examined (@pxref{Memory, ,Examining memory}). Other
6378 commands which provide a default address for @code{x} to examine also
6379 set @code{$_} to that address; these commands include @code{info line}
6380 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
6381 except when set by the @code{x} command, in which case it is a pointer
6382 to the type of @code{$__}.
6384 @vindex $__@r{, convenience variable}
6386 The variable @code{$__} is automatically set by the @code{x} command
6387 to the value found in the last address examined. Its type is chosen
6388 to match the format in which the data was printed.
6391 @vindex $_exitcode@r{, convenience variable}
6392 The variable @code{$_exitcode} is automatically set to the exit code when
6393 the program being debugged terminates.
6396 On HP-UX systems, if you refer to a function or variable name that
6397 begins with a dollar sign, @value{GDBN} searches for a user or system
6398 name first, before it searches for a convenience variable.
6404 You can refer to machine register contents, in expressions, as variables
6405 with names starting with @samp{$}. The names of registers are different
6406 for each machine; use @code{info registers} to see the names used on
6410 @kindex info registers
6411 @item info registers
6412 Print the names and values of all registers except floating-point
6413 and vector registers (in the selected stack frame).
6415 @kindex info all-registers
6416 @cindex floating point registers
6417 @item info all-registers
6418 Print the names and values of all registers, including floating-point
6419 and vector registers (in the selected stack frame).
6421 @item info registers @var{regname} @dots{}
6422 Print the @dfn{relativized} value of each specified register @var{regname}.
6423 As discussed in detail below, register values are normally relative to
6424 the selected stack frame. @var{regname} may be any register name valid on
6425 the machine you are using, with or without the initial @samp{$}.
6428 @cindex stack pointer register
6429 @cindex program counter register
6430 @cindex process status register
6431 @cindex frame pointer register
6432 @cindex standard registers
6433 @value{GDBN} has four ``standard'' register names that are available (in
6434 expressions) on most machines---whenever they do not conflict with an
6435 architecture's canonical mnemonics for registers. The register names
6436 @code{$pc} and @code{$sp} are used for the program counter register and
6437 the stack pointer. @code{$fp} is used for a register that contains a
6438 pointer to the current stack frame, and @code{$ps} is used for a
6439 register that contains the processor status. For example,
6440 you could print the program counter in hex with
6447 or print the instruction to be executed next with
6454 or add four to the stack pointer@footnote{This is a way of removing
6455 one word from the stack, on machines where stacks grow downward in
6456 memory (most machines, nowadays). This assumes that the innermost
6457 stack frame is selected; setting @code{$sp} is not allowed when other
6458 stack frames are selected. To pop entire frames off the stack,
6459 regardless of machine architecture, use @code{return};
6460 see @ref{Returning, ,Returning from a function}.} with
6466 Whenever possible, these four standard register names are available on
6467 your machine even though the machine has different canonical mnemonics,
6468 so long as there is no conflict. The @code{info registers} command
6469 shows the canonical names. For example, on the SPARC, @code{info
6470 registers} displays the processor status register as @code{$psr} but you
6471 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
6472 is an alias for the @sc{eflags} register.
6474 @value{GDBN} always considers the contents of an ordinary register as an
6475 integer when the register is examined in this way. Some machines have
6476 special registers which can hold nothing but floating point; these
6477 registers are considered to have floating point values. There is no way
6478 to refer to the contents of an ordinary register as floating point value
6479 (although you can @emph{print} it as a floating point value with
6480 @samp{print/f $@var{regname}}).
6482 Some registers have distinct ``raw'' and ``virtual'' data formats. This
6483 means that the data format in which the register contents are saved by
6484 the operating system is not the same one that your program normally
6485 sees. For example, the registers of the 68881 floating point
6486 coprocessor are always saved in ``extended'' (raw) format, but all C
6487 programs expect to work with ``double'' (virtual) format. In such
6488 cases, @value{GDBN} normally works with the virtual format only (the format
6489 that makes sense for your program), but the @code{info registers} command
6490 prints the data in both formats.
6492 @cindex SSE registers (x86)
6493 @cindex MMX registers (x86)
6494 Some machines have special registers whose contents can be interpreted
6495 in several different ways. For example, modern x86-based machines
6496 have SSE and MMX registers that can hold several values packed
6497 together in several different formats. @value{GDBN} refers to such
6498 registers in @code{struct} notation:
6501 (@value{GDBP}) print $xmm1
6503 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
6504 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
6505 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
6506 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
6507 v4_int32 = @{0, 20657912, 11, 13@},
6508 v2_int64 = @{88725056443645952, 55834574859@},
6509 uint128 = 0x0000000d0000000b013b36f800000000
6514 To set values of such registers, you need to tell @value{GDBN} which
6515 view of the register you wish to change, as if you were assigning
6516 value to a @code{struct} member:
6519 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
6522 Normally, register values are relative to the selected stack frame
6523 (@pxref{Selection, ,Selecting a frame}). This means that you get the
6524 value that the register would contain if all stack frames farther in
6525 were exited and their saved registers restored. In order to see the
6526 true contents of hardware registers, you must select the innermost
6527 frame (with @samp{frame 0}).
6529 However, @value{GDBN} must deduce where registers are saved, from the machine
6530 code generated by your compiler. If some registers are not saved, or if
6531 @value{GDBN} is unable to locate the saved registers, the selected stack
6532 frame makes no difference.
6534 @node Floating Point Hardware
6535 @section Floating point hardware
6536 @cindex floating point
6538 Depending on the configuration, @value{GDBN} may be able to give
6539 you more information about the status of the floating point hardware.
6544 Display hardware-dependent information about the floating
6545 point unit. The exact contents and layout vary depending on the
6546 floating point chip. Currently, @samp{info float} is supported on
6547 the ARM and x86 machines.
6551 @section Vector Unit
6554 Depending on the configuration, @value{GDBN} may be able to give you
6555 more information about the status of the vector unit.
6560 Display information about the vector unit. The exact contents and
6561 layout vary depending on the hardware.
6564 @node OS Information
6565 @section Operating system auxiliary information
6566 @cindex OS information
6568 @value{GDBN} provides interfaces to useful OS facilities that can help
6569 you debug your program.
6571 @cindex @code{ptrace} system call
6572 @cindex @code{struct user} contents
6573 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
6574 machines), it interfaces with the inferior via the @code{ptrace}
6575 system call. The operating system creates a special sata structure,
6576 called @code{struct user}, for this interface. You can use the
6577 command @code{info udot} to display the contents of this data
6583 Display the contents of the @code{struct user} maintained by the OS
6584 kernel for the program being debugged. @value{GDBN} displays the
6585 contents of @code{struct user} as a list of hex numbers, similar to
6586 the @code{examine} command.
6589 @cindex auxiliary vector
6590 @cindex vector, auxiliary
6591 Some operating systems supply an @dfn{auxiliary vector} to programs at
6592 startup. This is akin to the arguments and environment that you
6593 specify for a program, but contains a system-dependent variety of
6594 binary values that tell system libraries important details about the
6595 hardware, operating system, and process. Each value's purpose is
6596 identified by an integer tag; the meanings are well-known but system-specific.
6597 Depending on the configuration and operating system facilities,
6598 @value{GDBN} may be able to show you this information. For remote
6599 targets, this functionality may further depend on the remote stub's
6600 support of the @samp{qPart:auxv:read} packet, see @ref{Remote
6601 configuration, auxiliary vector}.
6606 Display the auxiliary vector of the inferior, which can be either a
6607 live process or a core dump file. @value{GDBN} prints each tag value
6608 numerically, and also shows names and text descriptions for recognized
6609 tags. Some values in the vector are numbers, some bit masks, and some
6610 pointers to strings or other data. @value{GDBN} displays each value in the
6611 most appropriate form for a recognized tag, and in hexadecimal for
6612 an unrecognized tag.
6616 @node Memory Region Attributes
6617 @section Memory region attributes
6618 @cindex memory region attributes
6620 @dfn{Memory region attributes} allow you to describe special handling
6621 required by regions of your target's memory. @value{GDBN} uses attributes
6622 to determine whether to allow certain types of memory accesses; whether to
6623 use specific width accesses; and whether to cache target memory.
6625 Defined memory regions can be individually enabled and disabled. When a
6626 memory region is disabled, @value{GDBN} uses the default attributes when
6627 accessing memory in that region. Similarly, if no memory regions have
6628 been defined, @value{GDBN} uses the default attributes when accessing
6631 When a memory region is defined, it is given a number to identify it;
6632 to enable, disable, or remove a memory region, you specify that number.
6636 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
6637 Define a memory region bounded by @var{lower} and @var{upper} with
6638 attributes @var{attributes}@dots{}, and add it to the list of regions
6639 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
6640 case: it is treated as the the target's maximum memory address.
6641 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
6644 @item delete mem @var{nums}@dots{}
6645 Remove memory regions @var{nums}@dots{} from the list of regions
6646 monitored by @value{GDBN}.
6649 @item disable mem @var{nums}@dots{}
6650 Disable monitoring of memory regions @var{nums}@dots{}.
6651 A disabled memory region is not forgotten.
6652 It may be enabled again later.
6655 @item enable mem @var{nums}@dots{}
6656 Enable monitoring of memory regions @var{nums}@dots{}.
6660 Print a table of all defined memory regions, with the following columns
6664 @item Memory Region Number
6665 @item Enabled or Disabled.
6666 Enabled memory regions are marked with @samp{y}.
6667 Disabled memory regions are marked with @samp{n}.
6670 The address defining the inclusive lower bound of the memory region.
6673 The address defining the exclusive upper bound of the memory region.
6676 The list of attributes set for this memory region.
6681 @subsection Attributes
6683 @subsubsection Memory Access Mode
6684 The access mode attributes set whether @value{GDBN} may make read or
6685 write accesses to a memory region.
6687 While these attributes prevent @value{GDBN} from performing invalid
6688 memory accesses, they do nothing to prevent the target system, I/O DMA,
6689 etc.@: from accessing memory.
6693 Memory is read only.
6695 Memory is write only.
6697 Memory is read/write. This is the default.
6700 @subsubsection Memory Access Size
6701 The acccess size attributes tells @value{GDBN} to use specific sized
6702 accesses in the memory region. Often memory mapped device registers
6703 require specific sized accesses. If no access size attribute is
6704 specified, @value{GDBN} may use accesses of any size.
6708 Use 8 bit memory accesses.
6710 Use 16 bit memory accesses.
6712 Use 32 bit memory accesses.
6714 Use 64 bit memory accesses.
6717 @c @subsubsection Hardware/Software Breakpoints
6718 @c The hardware/software breakpoint attributes set whether @value{GDBN}
6719 @c will use hardware or software breakpoints for the internal breakpoints
6720 @c used by the step, next, finish, until, etc. commands.
6724 @c Always use hardware breakpoints
6725 @c @item swbreak (default)
6728 @subsubsection Data Cache
6729 The data cache attributes set whether @value{GDBN} will cache target
6730 memory. While this generally improves performance by reducing debug
6731 protocol overhead, it can lead to incorrect results because @value{GDBN}
6732 does not know about volatile variables or memory mapped device
6737 Enable @value{GDBN} to cache target memory.
6739 Disable @value{GDBN} from caching target memory. This is the default.
6742 @c @subsubsection Memory Write Verification
6743 @c The memory write verification attributes set whether @value{GDBN}
6744 @c will re-reads data after each write to verify the write was successful.
6748 @c @item noverify (default)
6751 @node Dump/Restore Files
6752 @section Copy between memory and a file
6753 @cindex dump/restore files
6754 @cindex append data to a file
6755 @cindex dump data to a file
6756 @cindex restore data from a file
6758 You can use the commands @code{dump}, @code{append}, and
6759 @code{restore} to copy data between target memory and a file. The
6760 @code{dump} and @code{append} commands write data to a file, and the
6761 @code{restore} command reads data from a file back into the inferior's
6762 memory. Files may be in binary, Motorola S-record, Intel hex, or
6763 Tektronix Hex format; however, @value{GDBN} can only append to binary
6769 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6770 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
6771 Dump the contents of memory from @var{start_addr} to @var{end_addr},
6772 or the value of @var{expr}, to @var{filename} in the given format.
6774 The @var{format} parameter may be any one of:
6781 Motorola S-record format.
6783 Tektronix Hex format.
6786 @value{GDBN} uses the same definitions of these formats as the
6787 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
6788 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
6792 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6793 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
6794 Append the contents of memory from @var{start_addr} to @var{end_addr},
6795 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
6796 (@value{GDBN} can only append data to files in raw binary form.)
6799 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
6800 Restore the contents of file @var{filename} into memory. The
6801 @code{restore} command can automatically recognize any known @sc{bfd}
6802 file format, except for raw binary. To restore a raw binary file you
6803 must specify the optional keyword @code{binary} after the filename.
6805 If @var{bias} is non-zero, its value will be added to the addresses
6806 contained in the file. Binary files always start at address zero, so
6807 they will be restored at address @var{bias}. Other bfd files have
6808 a built-in location; they will be restored at offset @var{bias}
6811 If @var{start} and/or @var{end} are non-zero, then only data between
6812 file offset @var{start} and file offset @var{end} will be restored.
6813 These offsets are relative to the addresses in the file, before
6814 the @var{bias} argument is applied.
6818 @node Core File Generation
6819 @section How to Produce a Core File from Your Program
6820 @cindex dump core from inferior
6822 A @dfn{core file} or @dfn{core dump} is a file that records the memory
6823 image of a running process and its process status (register values
6824 etc.). Its primary use is post-mortem debugging of a program that
6825 crashed while it ran outside a debugger. A program that crashes
6826 automatically produces a core file, unless this feature is disabled by
6827 the user. @xref{Files}, for information on invoking @value{GDBN} in
6828 the post-mortem debugging mode.
6830 Occasionally, you may wish to produce a core file of the program you
6831 are debugging in order to preserve a snapshot of its state.
6832 @value{GDBN} has a special command for that.
6836 @kindex generate-core-file
6837 @item generate-core-file [@var{file}]
6838 @itemx gcore [@var{file}]
6839 Produce a core dump of the inferior process. The optional argument
6840 @var{file} specifies the file name where to put the core dump. If not
6841 specified, the file name defaults to @file{core.@var{pid}}, where
6842 @var{pid} is the inferior process ID.
6844 Note that this command is implemented only for some systems (as of
6845 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
6848 @node Character Sets
6849 @section Character Sets
6850 @cindex character sets
6852 @cindex translating between character sets
6853 @cindex host character set
6854 @cindex target character set
6856 If the program you are debugging uses a different character set to
6857 represent characters and strings than the one @value{GDBN} uses itself,
6858 @value{GDBN} can automatically translate between the character sets for
6859 you. The character set @value{GDBN} uses we call the @dfn{host
6860 character set}; the one the inferior program uses we call the
6861 @dfn{target character set}.
6863 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
6864 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
6865 remote protocol (@pxref{Remote,Remote Debugging}) to debug a program
6866 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
6867 then the host character set is Latin-1, and the target character set is
6868 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
6869 target-charset EBCDIC-US}, then @value{GDBN} translates between
6870 @sc{ebcdic} and Latin 1 as you print character or string values, or use
6871 character and string literals in expressions.
6873 @value{GDBN} has no way to automatically recognize which character set
6874 the inferior program uses; you must tell it, using the @code{set
6875 target-charset} command, described below.
6877 Here are the commands for controlling @value{GDBN}'s character set
6881 @item set target-charset @var{charset}
6882 @kindex set target-charset
6883 Set the current target character set to @var{charset}. We list the
6884 character set names @value{GDBN} recognizes below, but if you type
6885 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6886 list the target character sets it supports.
6890 @item set host-charset @var{charset}
6891 @kindex set host-charset
6892 Set the current host character set to @var{charset}.
6894 By default, @value{GDBN} uses a host character set appropriate to the
6895 system it is running on; you can override that default using the
6896 @code{set host-charset} command.
6898 @value{GDBN} can only use certain character sets as its host character
6899 set. We list the character set names @value{GDBN} recognizes below, and
6900 indicate which can be host character sets, but if you type
6901 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6902 list the host character sets it supports.
6904 @item set charset @var{charset}
6906 Set the current host and target character sets to @var{charset}. As
6907 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
6908 @value{GDBN} will list the name of the character sets that can be used
6909 for both host and target.
6913 @kindex show charset
6914 Show the names of the current host and target charsets.
6916 @itemx show host-charset
6917 @kindex show host-charset
6918 Show the name of the current host charset.
6920 @itemx show target-charset
6921 @kindex show target-charset
6922 Show the name of the current target charset.
6926 @value{GDBN} currently includes support for the following character
6932 @cindex ASCII character set
6933 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
6937 @cindex ISO 8859-1 character set
6938 @cindex ISO Latin 1 character set
6939 The ISO Latin 1 character set. This extends @sc{ascii} with accented
6940 characters needed for French, German, and Spanish. @value{GDBN} can use
6941 this as its host character set.
6945 @cindex EBCDIC character set
6946 @cindex IBM1047 character set
6947 Variants of the @sc{ebcdic} character set, used on some of IBM's
6948 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
6949 @value{GDBN} cannot use these as its host character set.
6953 Note that these are all single-byte character sets. More work inside
6954 GDB is needed to support multi-byte or variable-width character
6955 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
6957 Here is an example of @value{GDBN}'s character set support in action.
6958 Assume that the following source code has been placed in the file
6959 @file{charset-test.c}:
6965 = @{72, 101, 108, 108, 111, 44, 32, 119,
6966 111, 114, 108, 100, 33, 10, 0@};
6967 char ibm1047_hello[]
6968 = @{200, 133, 147, 147, 150, 107, 64, 166,
6969 150, 153, 147, 132, 90, 37, 0@};
6973 printf ("Hello, world!\n");
6977 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
6978 containing the string @samp{Hello, world!} followed by a newline,
6979 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
6981 We compile the program, and invoke the debugger on it:
6984 $ gcc -g charset-test.c -o charset-test
6985 $ gdb -nw charset-test
6986 GNU gdb 2001-12-19-cvs
6987 Copyright 2001 Free Software Foundation, Inc.
6992 We can use the @code{show charset} command to see what character sets
6993 @value{GDBN} is currently using to interpret and display characters and
6997 (@value{GDBP}) show charset
6998 The current host and target character set is `ISO-8859-1'.
7002 For the sake of printing this manual, let's use @sc{ascii} as our
7003 initial character set:
7005 (@value{GDBP}) set charset ASCII
7006 (@value{GDBP}) show charset
7007 The current host and target character set is `ASCII'.
7011 Let's assume that @sc{ascii} is indeed the correct character set for our
7012 host system --- in other words, let's assume that if @value{GDBN} prints
7013 characters using the @sc{ascii} character set, our terminal will display
7014 them properly. Since our current target character set is also
7015 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
7018 (@value{GDBP}) print ascii_hello
7019 $1 = 0x401698 "Hello, world!\n"
7020 (@value{GDBP}) print ascii_hello[0]
7025 @value{GDBN} uses the target character set for character and string
7026 literals you use in expressions:
7029 (@value{GDBP}) print '+'
7034 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
7037 @value{GDBN} relies on the user to tell it which character set the
7038 target program uses. If we print @code{ibm1047_hello} while our target
7039 character set is still @sc{ascii}, we get jibberish:
7042 (@value{GDBP}) print ibm1047_hello
7043 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
7044 (@value{GDBP}) print ibm1047_hello[0]
7049 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
7050 @value{GDBN} tells us the character sets it supports:
7053 (@value{GDBP}) set target-charset
7054 ASCII EBCDIC-US IBM1047 ISO-8859-1
7055 (@value{GDBP}) set target-charset
7058 We can select @sc{ibm1047} as our target character set, and examine the
7059 program's strings again. Now the @sc{ascii} string is wrong, but
7060 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
7061 target character set, @sc{ibm1047}, to the host character set,
7062 @sc{ascii}, and they display correctly:
7065 (@value{GDBP}) set target-charset IBM1047
7066 (@value{GDBP}) show charset
7067 The current host character set is `ASCII'.
7068 The current target character set is `IBM1047'.
7069 (@value{GDBP}) print ascii_hello
7070 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
7071 (@value{GDBP}) print ascii_hello[0]
7073 (@value{GDBP}) print ibm1047_hello
7074 $8 = 0x4016a8 "Hello, world!\n"
7075 (@value{GDBP}) print ibm1047_hello[0]
7080 As above, @value{GDBN} uses the target character set for character and
7081 string literals you use in expressions:
7084 (@value{GDBP}) print '+'
7089 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
7092 @node Caching Remote Data
7093 @section Caching Data of Remote Targets
7094 @cindex caching data of remote targets
7096 @value{GDBN} can cache data exchanged between the debugger and a
7097 remote target (@pxref{Remote}). Such caching generally improves
7098 performance, because it reduces the overhead of the remote protocol by
7099 bundling memory reads and writes into large chunks. Unfortunately,
7100 @value{GDBN} does not currently know anything about volatile
7101 registers, and thus data caching will produce incorrect results when
7102 volatile registers are in use.
7105 @kindex set remotecache
7106 @item set remotecache on
7107 @itemx set remotecache off
7108 Set caching state for remote targets. When @code{ON}, use data
7109 caching. By default, this option is @code{OFF}.
7111 @kindex show remotecache
7112 @item show remotecache
7113 Show the current state of data caching for remote targets.
7117 Print the information about the data cache performance. The
7118 information displayed includes: the dcache width and depth; and for
7119 each cache line, how many times it was referenced, and its data and
7120 state (dirty, bad, ok, etc.). This command is useful for debugging
7121 the data cache operation.
7126 @chapter C Preprocessor Macros
7128 Some languages, such as C and C@t{++}, provide a way to define and invoke
7129 ``preprocessor macros'' which expand into strings of tokens.
7130 @value{GDBN} can evaluate expressions containing macro invocations, show
7131 the result of macro expansion, and show a macro's definition, including
7132 where it was defined.
7134 You may need to compile your program specially to provide @value{GDBN}
7135 with information about preprocessor macros. Most compilers do not
7136 include macros in their debugging information, even when you compile
7137 with the @option{-g} flag. @xref{Compilation}.
7139 A program may define a macro at one point, remove that definition later,
7140 and then provide a different definition after that. Thus, at different
7141 points in the program, a macro may have different definitions, or have
7142 no definition at all. If there is a current stack frame, @value{GDBN}
7143 uses the macros in scope at that frame's source code line. Otherwise,
7144 @value{GDBN} uses the macros in scope at the current listing location;
7147 At the moment, @value{GDBN} does not support the @code{##}
7148 token-splicing operator, the @code{#} stringification operator, or
7149 variable-arity macros.
7151 Whenever @value{GDBN} evaluates an expression, it always expands any
7152 macro invocations present in the expression. @value{GDBN} also provides
7153 the following commands for working with macros explicitly.
7157 @kindex macro expand
7158 @cindex macro expansion, showing the results of preprocessor
7159 @cindex preprocessor macro expansion, showing the results of
7160 @cindex expanding preprocessor macros
7161 @item macro expand @var{expression}
7162 @itemx macro exp @var{expression}
7163 Show the results of expanding all preprocessor macro invocations in
7164 @var{expression}. Since @value{GDBN} simply expands macros, but does
7165 not parse the result, @var{expression} need not be a valid expression;
7166 it can be any string of tokens.
7169 @item macro expand-once @var{expression}
7170 @itemx macro exp1 @var{expression}
7171 @cindex expand macro once
7172 @i{(This command is not yet implemented.)} Show the results of
7173 expanding those preprocessor macro invocations that appear explicitly in
7174 @var{expression}. Macro invocations appearing in that expansion are
7175 left unchanged. This command allows you to see the effect of a
7176 particular macro more clearly, without being confused by further
7177 expansions. Since @value{GDBN} simply expands macros, but does not
7178 parse the result, @var{expression} need not be a valid expression; it
7179 can be any string of tokens.
7182 @cindex macro definition, showing
7183 @cindex definition, showing a macro's
7184 @item info macro @var{macro}
7185 Show the definition of the macro named @var{macro}, and describe the
7186 source location where that definition was established.
7188 @kindex macro define
7189 @cindex user-defined macros
7190 @cindex defining macros interactively
7191 @cindex macros, user-defined
7192 @item macro define @var{macro} @var{replacement-list}
7193 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
7194 @i{(This command is not yet implemented.)} Introduce a definition for a
7195 preprocessor macro named @var{macro}, invocations of which are replaced
7196 by the tokens given in @var{replacement-list}. The first form of this
7197 command defines an ``object-like'' macro, which takes no arguments; the
7198 second form defines a ``function-like'' macro, which takes the arguments
7199 given in @var{arglist}.
7201 A definition introduced by this command is in scope in every expression
7202 evaluated in @value{GDBN}, until it is removed with the @command{macro
7203 undef} command, described below. The definition overrides all
7204 definitions for @var{macro} present in the program being debugged, as
7205 well as any previous user-supplied definition.
7208 @item macro undef @var{macro}
7209 @i{(This command is not yet implemented.)} Remove any user-supplied
7210 definition for the macro named @var{macro}. This command only affects
7211 definitions provided with the @command{macro define} command, described
7212 above; it cannot remove definitions present in the program being
7217 @i{(This command is not yet implemented.)} List all the macros
7218 defined using the @code{macro define} command.
7221 @cindex macros, example of debugging with
7222 Here is a transcript showing the above commands in action. First, we
7223 show our source files:
7231 #define ADD(x) (M + x)
7236 printf ("Hello, world!\n");
7238 printf ("We're so creative.\n");
7240 printf ("Goodbye, world!\n");
7247 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
7248 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
7249 compiler includes information about preprocessor macros in the debugging
7253 $ gcc -gdwarf-2 -g3 sample.c -o sample
7257 Now, we start @value{GDBN} on our sample program:
7261 GNU gdb 2002-05-06-cvs
7262 Copyright 2002 Free Software Foundation, Inc.
7263 GDB is free software, @dots{}
7267 We can expand macros and examine their definitions, even when the
7268 program is not running. @value{GDBN} uses the current listing position
7269 to decide which macro definitions are in scope:
7272 (@value{GDBP}) list main
7275 5 #define ADD(x) (M + x)
7280 10 printf ("Hello, world!\n");
7282 12 printf ("We're so creative.\n");
7283 (@value{GDBP}) info macro ADD
7284 Defined at /home/jimb/gdb/macros/play/sample.c:5
7285 #define ADD(x) (M + x)
7286 (@value{GDBP}) info macro Q
7287 Defined at /home/jimb/gdb/macros/play/sample.h:1
7288 included at /home/jimb/gdb/macros/play/sample.c:2
7290 (@value{GDBP}) macro expand ADD(1)
7291 expands to: (42 + 1)
7292 (@value{GDBP}) macro expand-once ADD(1)
7293 expands to: once (M + 1)
7297 In the example above, note that @command{macro expand-once} expands only
7298 the macro invocation explicit in the original text --- the invocation of
7299 @code{ADD} --- but does not expand the invocation of the macro @code{M},
7300 which was introduced by @code{ADD}.
7302 Once the program is running, GDB uses the macro definitions in force at
7303 the source line of the current stack frame:
7306 (@value{GDBP}) break main
7307 Breakpoint 1 at 0x8048370: file sample.c, line 10.
7309 Starting program: /home/jimb/gdb/macros/play/sample
7311 Breakpoint 1, main () at sample.c:10
7312 10 printf ("Hello, world!\n");
7316 At line 10, the definition of the macro @code{N} at line 9 is in force:
7319 (@value{GDBP}) info macro N
7320 Defined at /home/jimb/gdb/macros/play/sample.c:9
7322 (@value{GDBP}) macro expand N Q M
7324 (@value{GDBP}) print N Q M
7329 As we step over directives that remove @code{N}'s definition, and then
7330 give it a new definition, @value{GDBN} finds the definition (or lack
7331 thereof) in force at each point:
7336 12 printf ("We're so creative.\n");
7337 (@value{GDBP}) info macro N
7338 The symbol `N' has no definition as a C/C++ preprocessor macro
7339 at /home/jimb/gdb/macros/play/sample.c:12
7342 14 printf ("Goodbye, world!\n");
7343 (@value{GDBP}) info macro N
7344 Defined at /home/jimb/gdb/macros/play/sample.c:13
7346 (@value{GDBP}) macro expand N Q M
7347 expands to: 1729 < 42
7348 (@value{GDBP}) print N Q M
7355 @chapter Tracepoints
7356 @c This chapter is based on the documentation written by Michael
7357 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
7360 In some applications, it is not feasible for the debugger to interrupt
7361 the program's execution long enough for the developer to learn
7362 anything helpful about its behavior. If the program's correctness
7363 depends on its real-time behavior, delays introduced by a debugger
7364 might cause the program to change its behavior drastically, or perhaps
7365 fail, even when the code itself is correct. It is useful to be able
7366 to observe the program's behavior without interrupting it.
7368 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
7369 specify locations in the program, called @dfn{tracepoints}, and
7370 arbitrary expressions to evaluate when those tracepoints are reached.
7371 Later, using the @code{tfind} command, you can examine the values
7372 those expressions had when the program hit the tracepoints. The
7373 expressions may also denote objects in memory---structures or arrays,
7374 for example---whose values @value{GDBN} should record; while visiting
7375 a particular tracepoint, you may inspect those objects as if they were
7376 in memory at that moment. However, because @value{GDBN} records these
7377 values without interacting with you, it can do so quickly and
7378 unobtrusively, hopefully not disturbing the program's behavior.
7380 The tracepoint facility is currently available only for remote
7381 targets. @xref{Targets}. In addition, your remote target must know
7382 how to collect trace data. This functionality is implemented in the
7383 remote stub; however, none of the stubs distributed with @value{GDBN}
7384 support tracepoints as of this writing. The format of the remote
7385 packets used to implement tracepoints are described in @ref{Tracepoint
7388 This chapter describes the tracepoint commands and features.
7392 * Analyze Collected Data::
7393 * Tracepoint Variables::
7396 @node Set Tracepoints
7397 @section Commands to Set Tracepoints
7399 Before running such a @dfn{trace experiment}, an arbitrary number of
7400 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
7401 tracepoint has a number assigned to it by @value{GDBN}. Like with
7402 breakpoints, tracepoint numbers are successive integers starting from
7403 one. Many of the commands associated with tracepoints take the
7404 tracepoint number as their argument, to identify which tracepoint to
7407 For each tracepoint, you can specify, in advance, some arbitrary set
7408 of data that you want the target to collect in the trace buffer when
7409 it hits that tracepoint. The collected data can include registers,
7410 local variables, or global data. Later, you can use @value{GDBN}
7411 commands to examine the values these data had at the time the
7414 This section describes commands to set tracepoints and associated
7415 conditions and actions.
7418 * Create and Delete Tracepoints::
7419 * Enable and Disable Tracepoints::
7420 * Tracepoint Passcounts::
7421 * Tracepoint Actions::
7422 * Listing Tracepoints::
7423 * Starting and Stopping Trace Experiment::
7426 @node Create and Delete Tracepoints
7427 @subsection Create and Delete Tracepoints
7430 @cindex set tracepoint
7433 The @code{trace} command is very similar to the @code{break} command.
7434 Its argument can be a source line, a function name, or an address in
7435 the target program. @xref{Set Breaks}. The @code{trace} command
7436 defines a tracepoint, which is a point in the target program where the
7437 debugger will briefly stop, collect some data, and then allow the
7438 program to continue. Setting a tracepoint or changing its commands
7439 doesn't take effect until the next @code{tstart} command; thus, you
7440 cannot change the tracepoint attributes once a trace experiment is
7443 Here are some examples of using the @code{trace} command:
7446 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
7448 (@value{GDBP}) @b{trace +2} // 2 lines forward
7450 (@value{GDBP}) @b{trace my_function} // first source line of function
7452 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
7454 (@value{GDBP}) @b{trace *0x2117c4} // an address
7458 You can abbreviate @code{trace} as @code{tr}.
7461 @cindex last tracepoint number
7462 @cindex recent tracepoint number
7463 @cindex tracepoint number
7464 The convenience variable @code{$tpnum} records the tracepoint number
7465 of the most recently set tracepoint.
7467 @kindex delete tracepoint
7468 @cindex tracepoint deletion
7469 @item delete tracepoint @r{[}@var{num}@r{]}
7470 Permanently delete one or more tracepoints. With no argument, the
7471 default is to delete all tracepoints.
7476 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
7478 (@value{GDBP}) @b{delete trace} // remove all tracepoints
7482 You can abbreviate this command as @code{del tr}.
7485 @node Enable and Disable Tracepoints
7486 @subsection Enable and Disable Tracepoints
7489 @kindex disable tracepoint
7490 @item disable tracepoint @r{[}@var{num}@r{]}
7491 Disable tracepoint @var{num}, or all tracepoints if no argument
7492 @var{num} is given. A disabled tracepoint will have no effect during
7493 the next trace experiment, but it is not forgotten. You can re-enable
7494 a disabled tracepoint using the @code{enable tracepoint} command.
7496 @kindex enable tracepoint
7497 @item enable tracepoint @r{[}@var{num}@r{]}
7498 Enable tracepoint @var{num}, or all tracepoints. The enabled
7499 tracepoints will become effective the next time a trace experiment is
7503 @node Tracepoint Passcounts
7504 @subsection Tracepoint Passcounts
7508 @cindex tracepoint pass count
7509 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
7510 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
7511 automatically stop a trace experiment. If a tracepoint's passcount is
7512 @var{n}, then the trace experiment will be automatically stopped on
7513 the @var{n}'th time that tracepoint is hit. If the tracepoint number
7514 @var{num} is not specified, the @code{passcount} command sets the
7515 passcount of the most recently defined tracepoint. If no passcount is
7516 given, the trace experiment will run until stopped explicitly by the
7522 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
7523 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
7525 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
7526 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
7527 (@value{GDBP}) @b{trace foo}
7528 (@value{GDBP}) @b{pass 3}
7529 (@value{GDBP}) @b{trace bar}
7530 (@value{GDBP}) @b{pass 2}
7531 (@value{GDBP}) @b{trace baz}
7532 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
7533 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
7534 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
7535 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
7539 @node Tracepoint Actions
7540 @subsection Tracepoint Action Lists
7544 @cindex tracepoint actions
7545 @item actions @r{[}@var{num}@r{]}
7546 This command will prompt for a list of actions to be taken when the
7547 tracepoint is hit. If the tracepoint number @var{num} is not
7548 specified, this command sets the actions for the one that was most
7549 recently defined (so that you can define a tracepoint and then say
7550 @code{actions} without bothering about its number). You specify the
7551 actions themselves on the following lines, one action at a time, and
7552 terminate the actions list with a line containing just @code{end}. So
7553 far, the only defined actions are @code{collect} and
7554 @code{while-stepping}.
7556 @cindex remove actions from a tracepoint
7557 To remove all actions from a tracepoint, type @samp{actions @var{num}}
7558 and follow it immediately with @samp{end}.
7561 (@value{GDBP}) @b{collect @var{data}} // collect some data
7563 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
7565 (@value{GDBP}) @b{end} // signals the end of actions.
7568 In the following example, the action list begins with @code{collect}
7569 commands indicating the things to be collected when the tracepoint is
7570 hit. Then, in order to single-step and collect additional data
7571 following the tracepoint, a @code{while-stepping} command is used,
7572 followed by the list of things to be collected while stepping. The
7573 @code{while-stepping} command is terminated by its own separate
7574 @code{end} command. Lastly, the action list is terminated by an
7578 (@value{GDBP}) @b{trace foo}
7579 (@value{GDBP}) @b{actions}
7580 Enter actions for tracepoint 1, one per line:
7589 @kindex collect @r{(tracepoints)}
7590 @item collect @var{expr1}, @var{expr2}, @dots{}
7591 Collect values of the given expressions when the tracepoint is hit.
7592 This command accepts a comma-separated list of any valid expressions.
7593 In addition to global, static, or local variables, the following
7594 special arguments are supported:
7598 collect all registers
7601 collect all function arguments
7604 collect all local variables.
7607 You can give several consecutive @code{collect} commands, each one
7608 with a single argument, or one @code{collect} command with several
7609 arguments separated by commas: the effect is the same.
7611 The command @code{info scope} (@pxref{Symbols, info scope}) is
7612 particularly useful for figuring out what data to collect.
7614 @kindex while-stepping @r{(tracepoints)}
7615 @item while-stepping @var{n}
7616 Perform @var{n} single-step traces after the tracepoint, collecting
7617 new data at each step. The @code{while-stepping} command is
7618 followed by the list of what to collect while stepping (followed by
7619 its own @code{end} command):
7623 > collect $regs, myglobal
7629 You may abbreviate @code{while-stepping} as @code{ws} or
7633 @node Listing Tracepoints
7634 @subsection Listing Tracepoints
7637 @kindex info tracepoints
7639 @cindex information about tracepoints
7640 @item info tracepoints @r{[}@var{num}@r{]}
7641 Display information about the tracepoint @var{num}. If you don't specify
7642 a tracepoint number, displays information about all the tracepoints
7643 defined so far. For each tracepoint, the following information is
7650 whether it is enabled or disabled
7654 its passcount as given by the @code{passcount @var{n}} command
7656 its step count as given by the @code{while-stepping @var{n}} command
7658 where in the source files is the tracepoint set
7660 its action list as given by the @code{actions} command
7664 (@value{GDBP}) @b{info trace}
7665 Num Enb Address PassC StepC What
7666 1 y 0x002117c4 0 0 <gdb_asm>
7667 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
7668 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
7673 This command can be abbreviated @code{info tp}.
7676 @node Starting and Stopping Trace Experiment
7677 @subsection Starting and Stopping Trace Experiment
7681 @cindex start a new trace experiment
7682 @cindex collected data discarded
7684 This command takes no arguments. It starts the trace experiment, and
7685 begins collecting data. This has the side effect of discarding all
7686 the data collected in the trace buffer during the previous trace
7690 @cindex stop a running trace experiment
7692 This command takes no arguments. It ends the trace experiment, and
7693 stops collecting data.
7695 @strong{Note}: a trace experiment and data collection may stop
7696 automatically if any tracepoint's passcount is reached
7697 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
7700 @cindex status of trace data collection
7701 @cindex trace experiment, status of
7703 This command displays the status of the current trace data
7707 Here is an example of the commands we described so far:
7710 (@value{GDBP}) @b{trace gdb_c_test}
7711 (@value{GDBP}) @b{actions}
7712 Enter actions for tracepoint #1, one per line.
7713 > collect $regs,$locals,$args
7718 (@value{GDBP}) @b{tstart}
7719 [time passes @dots{}]
7720 (@value{GDBP}) @b{tstop}
7724 @node Analyze Collected Data
7725 @section Using the collected data
7727 After the tracepoint experiment ends, you use @value{GDBN} commands
7728 for examining the trace data. The basic idea is that each tracepoint
7729 collects a trace @dfn{snapshot} every time it is hit and another
7730 snapshot every time it single-steps. All these snapshots are
7731 consecutively numbered from zero and go into a buffer, and you can
7732 examine them later. The way you examine them is to @dfn{focus} on a
7733 specific trace snapshot. When the remote stub is focused on a trace
7734 snapshot, it will respond to all @value{GDBN} requests for memory and
7735 registers by reading from the buffer which belongs to that snapshot,
7736 rather than from @emph{real} memory or registers of the program being
7737 debugged. This means that @strong{all} @value{GDBN} commands
7738 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
7739 behave as if we were currently debugging the program state as it was
7740 when the tracepoint occurred. Any requests for data that are not in
7741 the buffer will fail.
7744 * tfind:: How to select a trace snapshot
7745 * tdump:: How to display all data for a snapshot
7746 * save-tracepoints:: How to save tracepoints for a future run
7750 @subsection @code{tfind @var{n}}
7753 @cindex select trace snapshot
7754 @cindex find trace snapshot
7755 The basic command for selecting a trace snapshot from the buffer is
7756 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
7757 counting from zero. If no argument @var{n} is given, the next
7758 snapshot is selected.
7760 Here are the various forms of using the @code{tfind} command.
7764 Find the first snapshot in the buffer. This is a synonym for
7765 @code{tfind 0} (since 0 is the number of the first snapshot).
7768 Stop debugging trace snapshots, resume @emph{live} debugging.
7771 Same as @samp{tfind none}.
7774 No argument means find the next trace snapshot.
7777 Find the previous trace snapshot before the current one. This permits
7778 retracing earlier steps.
7780 @item tfind tracepoint @var{num}
7781 Find the next snapshot associated with tracepoint @var{num}. Search
7782 proceeds forward from the last examined trace snapshot. If no
7783 argument @var{num} is given, it means find the next snapshot collected
7784 for the same tracepoint as the current snapshot.
7786 @item tfind pc @var{addr}
7787 Find the next snapshot associated with the value @var{addr} of the
7788 program counter. Search proceeds forward from the last examined trace
7789 snapshot. If no argument @var{addr} is given, it means find the next
7790 snapshot with the same value of PC as the current snapshot.
7792 @item tfind outside @var{addr1}, @var{addr2}
7793 Find the next snapshot whose PC is outside the given range of
7796 @item tfind range @var{addr1}, @var{addr2}
7797 Find the next snapshot whose PC is between @var{addr1} and
7798 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
7800 @item tfind line @r{[}@var{file}:@r{]}@var{n}
7801 Find the next snapshot associated with the source line @var{n}. If
7802 the optional argument @var{file} is given, refer to line @var{n} in
7803 that source file. Search proceeds forward from the last examined
7804 trace snapshot. If no argument @var{n} is given, it means find the
7805 next line other than the one currently being examined; thus saying
7806 @code{tfind line} repeatedly can appear to have the same effect as
7807 stepping from line to line in a @emph{live} debugging session.
7810 The default arguments for the @code{tfind} commands are specifically
7811 designed to make it easy to scan through the trace buffer. For
7812 instance, @code{tfind} with no argument selects the next trace
7813 snapshot, and @code{tfind -} with no argument selects the previous
7814 trace snapshot. So, by giving one @code{tfind} command, and then
7815 simply hitting @key{RET} repeatedly you can examine all the trace
7816 snapshots in order. Or, by saying @code{tfind -} and then hitting
7817 @key{RET} repeatedly you can examine the snapshots in reverse order.
7818 The @code{tfind line} command with no argument selects the snapshot
7819 for the next source line executed. The @code{tfind pc} command with
7820 no argument selects the next snapshot with the same program counter
7821 (PC) as the current frame. The @code{tfind tracepoint} command with
7822 no argument selects the next trace snapshot collected by the same
7823 tracepoint as the current one.
7825 In addition to letting you scan through the trace buffer manually,
7826 these commands make it easy to construct @value{GDBN} scripts that
7827 scan through the trace buffer and print out whatever collected data
7828 you are interested in. Thus, if we want to examine the PC, FP, and SP
7829 registers from each trace frame in the buffer, we can say this:
7832 (@value{GDBP}) @b{tfind start}
7833 (@value{GDBP}) @b{while ($trace_frame != -1)}
7834 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
7835 $trace_frame, $pc, $sp, $fp
7839 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
7840 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
7841 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
7842 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
7843 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
7844 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
7845 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
7846 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
7847 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
7848 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
7849 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
7852 Or, if we want to examine the variable @code{X} at each source line in
7856 (@value{GDBP}) @b{tfind start}
7857 (@value{GDBP}) @b{while ($trace_frame != -1)}
7858 > printf "Frame %d, X == %d\n", $trace_frame, X
7868 @subsection @code{tdump}
7870 @cindex dump all data collected at tracepoint
7871 @cindex tracepoint data, display
7873 This command takes no arguments. It prints all the data collected at
7874 the current trace snapshot.
7877 (@value{GDBP}) @b{trace 444}
7878 (@value{GDBP}) @b{actions}
7879 Enter actions for tracepoint #2, one per line:
7880 > collect $regs, $locals, $args, gdb_long_test
7883 (@value{GDBP}) @b{tstart}
7885 (@value{GDBP}) @b{tfind line 444}
7886 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
7888 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
7890 (@value{GDBP}) @b{tdump}
7891 Data collected at tracepoint 2, trace frame 1:
7892 d0 0xc4aa0085 -995491707
7896 d4 0x71aea3d 119204413
7901 a1 0x3000668 50333288
7904 a4 0x3000698 50333336
7906 fp 0x30bf3c 0x30bf3c
7907 sp 0x30bf34 0x30bf34
7909 pc 0x20b2c8 0x20b2c8
7913 p = 0x20e5b4 "gdb-test"
7920 gdb_long_test = 17 '\021'
7925 @node save-tracepoints
7926 @subsection @code{save-tracepoints @var{filename}}
7927 @kindex save-tracepoints
7928 @cindex save tracepoints for future sessions
7930 This command saves all current tracepoint definitions together with
7931 their actions and passcounts, into a file @file{@var{filename}}
7932 suitable for use in a later debugging session. To read the saved
7933 tracepoint definitions, use the @code{source} command (@pxref{Command
7936 @node Tracepoint Variables
7937 @section Convenience Variables for Tracepoints
7938 @cindex tracepoint variables
7939 @cindex convenience variables for tracepoints
7942 @vindex $trace_frame
7943 @item (int) $trace_frame
7944 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
7945 snapshot is selected.
7948 @item (int) $tracepoint
7949 The tracepoint for the current trace snapshot.
7952 @item (int) $trace_line
7953 The line number for the current trace snapshot.
7956 @item (char []) $trace_file
7957 The source file for the current trace snapshot.
7960 @item (char []) $trace_func
7961 The name of the function containing @code{$tracepoint}.
7964 Note: @code{$trace_file} is not suitable for use in @code{printf},
7965 use @code{output} instead.
7967 Here's a simple example of using these convenience variables for
7968 stepping through all the trace snapshots and printing some of their
7972 (@value{GDBP}) @b{tfind start}
7974 (@value{GDBP}) @b{while $trace_frame != -1}
7975 > output $trace_file
7976 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
7982 @chapter Debugging Programs That Use Overlays
7985 If your program is too large to fit completely in your target system's
7986 memory, you can sometimes use @dfn{overlays} to work around this
7987 problem. @value{GDBN} provides some support for debugging programs that
7991 * How Overlays Work:: A general explanation of overlays.
7992 * Overlay Commands:: Managing overlays in @value{GDBN}.
7993 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
7994 mapped by asking the inferior.
7995 * Overlay Sample Program:: A sample program using overlays.
7998 @node How Overlays Work
7999 @section How Overlays Work
8000 @cindex mapped overlays
8001 @cindex unmapped overlays
8002 @cindex load address, overlay's
8003 @cindex mapped address
8004 @cindex overlay area
8006 Suppose you have a computer whose instruction address space is only 64
8007 kilobytes long, but which has much more memory which can be accessed by
8008 other means: special instructions, segment registers, or memory
8009 management hardware, for example. Suppose further that you want to
8010 adapt a program which is larger than 64 kilobytes to run on this system.
8012 One solution is to identify modules of your program which are relatively
8013 independent, and need not call each other directly; call these modules
8014 @dfn{overlays}. Separate the overlays from the main program, and place
8015 their machine code in the larger memory. Place your main program in
8016 instruction memory, but leave at least enough space there to hold the
8017 largest overlay as well.
8019 Now, to call a function located in an overlay, you must first copy that
8020 overlay's machine code from the large memory into the space set aside
8021 for it in the instruction memory, and then jump to its entry point
8024 @c NB: In the below the mapped area's size is greater or equal to the
8025 @c size of all overlays. This is intentional to remind the developer
8026 @c that overlays don't necessarily need to be the same size.
8030 Data Instruction Larger
8031 Address Space Address Space Address Space
8032 +-----------+ +-----------+ +-----------+
8034 +-----------+ +-----------+ +-----------+<-- overlay 1
8035 | program | | main | .----| overlay 1 | load address
8036 | variables | | program | | +-----------+
8037 | and heap | | | | | |
8038 +-----------+ | | | +-----------+<-- overlay 2
8039 | | +-----------+ | | | load address
8040 +-----------+ | | | .-| overlay 2 |
8042 mapped --->+-----------+ | | +-----------+
8044 | overlay | <-' | | |
8045 | area | <---' +-----------+<-- overlay 3
8046 | | <---. | | load address
8047 +-----------+ `--| overlay 3 |
8054 @anchor{A code overlay}A code overlay
8058 The diagram (@pxref{A code overlay}) shows a system with separate data
8059 and instruction address spaces. To map an overlay, the program copies
8060 its code from the larger address space to the instruction address space.
8061 Since the overlays shown here all use the same mapped address, only one
8062 may be mapped at a time. For a system with a single address space for
8063 data and instructions, the diagram would be similar, except that the
8064 program variables and heap would share an address space with the main
8065 program and the overlay area.
8067 An overlay loaded into instruction memory and ready for use is called a
8068 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
8069 instruction memory. An overlay not present (or only partially present)
8070 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
8071 is its address in the larger memory. The mapped address is also called
8072 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
8073 called the @dfn{load memory address}, or @dfn{LMA}.
8075 Unfortunately, overlays are not a completely transparent way to adapt a
8076 program to limited instruction memory. They introduce a new set of
8077 global constraints you must keep in mind as you design your program:
8082 Before calling or returning to a function in an overlay, your program
8083 must make sure that overlay is actually mapped. Otherwise, the call or
8084 return will transfer control to the right address, but in the wrong
8085 overlay, and your program will probably crash.
8088 If the process of mapping an overlay is expensive on your system, you
8089 will need to choose your overlays carefully to minimize their effect on
8090 your program's performance.
8093 The executable file you load onto your system must contain each
8094 overlay's instructions, appearing at the overlay's load address, not its
8095 mapped address. However, each overlay's instructions must be relocated
8096 and its symbols defined as if the overlay were at its mapped address.
8097 You can use GNU linker scripts to specify different load and relocation
8098 addresses for pieces of your program; see @ref{Overlay Description,,,
8099 ld.info, Using ld: the GNU linker}.
8102 The procedure for loading executable files onto your system must be able
8103 to load their contents into the larger address space as well as the
8104 instruction and data spaces.
8108 The overlay system described above is rather simple, and could be
8109 improved in many ways:
8114 If your system has suitable bank switch registers or memory management
8115 hardware, you could use those facilities to make an overlay's load area
8116 contents simply appear at their mapped address in instruction space.
8117 This would probably be faster than copying the overlay to its mapped
8118 area in the usual way.
8121 If your overlays are small enough, you could set aside more than one
8122 overlay area, and have more than one overlay mapped at a time.
8125 You can use overlays to manage data, as well as instructions. In
8126 general, data overlays are even less transparent to your design than
8127 code overlays: whereas code overlays only require care when you call or
8128 return to functions, data overlays require care every time you access
8129 the data. Also, if you change the contents of a data overlay, you
8130 must copy its contents back out to its load address before you can copy a
8131 different data overlay into the same mapped area.
8136 @node Overlay Commands
8137 @section Overlay Commands
8139 To use @value{GDBN}'s overlay support, each overlay in your program must
8140 correspond to a separate section of the executable file. The section's
8141 virtual memory address and load memory address must be the overlay's
8142 mapped and load addresses. Identifying overlays with sections allows
8143 @value{GDBN} to determine the appropriate address of a function or
8144 variable, depending on whether the overlay is mapped or not.
8146 @value{GDBN}'s overlay commands all start with the word @code{overlay};
8147 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
8152 Disable @value{GDBN}'s overlay support. When overlay support is
8153 disabled, @value{GDBN} assumes that all functions and variables are
8154 always present at their mapped addresses. By default, @value{GDBN}'s
8155 overlay support is disabled.
8157 @item overlay manual
8158 @cindex manual overlay debugging
8159 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
8160 relies on you to tell it which overlays are mapped, and which are not,
8161 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
8162 commands described below.
8164 @item overlay map-overlay @var{overlay}
8165 @itemx overlay map @var{overlay}
8166 @cindex map an overlay
8167 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
8168 be the name of the object file section containing the overlay. When an
8169 overlay is mapped, @value{GDBN} assumes it can find the overlay's
8170 functions and variables at their mapped addresses. @value{GDBN} assumes
8171 that any other overlays whose mapped ranges overlap that of
8172 @var{overlay} are now unmapped.
8174 @item overlay unmap-overlay @var{overlay}
8175 @itemx overlay unmap @var{overlay}
8176 @cindex unmap an overlay
8177 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
8178 must be the name of the object file section containing the overlay.
8179 When an overlay is unmapped, @value{GDBN} assumes it can find the
8180 overlay's functions and variables at their load addresses.
8183 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
8184 consults a data structure the overlay manager maintains in the inferior
8185 to see which overlays are mapped. For details, see @ref{Automatic
8188 @item overlay load-target
8190 @cindex reloading the overlay table
8191 Re-read the overlay table from the inferior. Normally, @value{GDBN}
8192 re-reads the table @value{GDBN} automatically each time the inferior
8193 stops, so this command should only be necessary if you have changed the
8194 overlay mapping yourself using @value{GDBN}. This command is only
8195 useful when using automatic overlay debugging.
8197 @item overlay list-overlays
8199 @cindex listing mapped overlays
8200 Display a list of the overlays currently mapped, along with their mapped
8201 addresses, load addresses, and sizes.
8205 Normally, when @value{GDBN} prints a code address, it includes the name
8206 of the function the address falls in:
8209 (@value{GDBP}) print main
8210 $3 = @{int ()@} 0x11a0 <main>
8213 When overlay debugging is enabled, @value{GDBN} recognizes code in
8214 unmapped overlays, and prints the names of unmapped functions with
8215 asterisks around them. For example, if @code{foo} is a function in an
8216 unmapped overlay, @value{GDBN} prints it this way:
8219 (@value{GDBP}) overlay list
8220 No sections are mapped.
8221 (@value{GDBP}) print foo
8222 $5 = @{int (int)@} 0x100000 <*foo*>
8225 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
8229 (@value{GDBP}) overlay list
8230 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
8231 mapped at 0x1016 - 0x104a
8232 (@value{GDBP}) print foo
8233 $6 = @{int (int)@} 0x1016 <foo>
8236 When overlay debugging is enabled, @value{GDBN} can find the correct
8237 address for functions and variables in an overlay, whether or not the
8238 overlay is mapped. This allows most @value{GDBN} commands, like
8239 @code{break} and @code{disassemble}, to work normally, even on unmapped
8240 code. However, @value{GDBN}'s breakpoint support has some limitations:
8244 @cindex breakpoints in overlays
8245 @cindex overlays, setting breakpoints in
8246 You can set breakpoints in functions in unmapped overlays, as long as
8247 @value{GDBN} can write to the overlay at its load address.
8249 @value{GDBN} can not set hardware or simulator-based breakpoints in
8250 unmapped overlays. However, if you set a breakpoint at the end of your
8251 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
8252 you are using manual overlay management), @value{GDBN} will re-set its
8253 breakpoints properly.
8257 @node Automatic Overlay Debugging
8258 @section Automatic Overlay Debugging
8259 @cindex automatic overlay debugging
8261 @value{GDBN} can automatically track which overlays are mapped and which
8262 are not, given some simple co-operation from the overlay manager in the
8263 inferior. If you enable automatic overlay debugging with the
8264 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
8265 looks in the inferior's memory for certain variables describing the
8266 current state of the overlays.
8268 Here are the variables your overlay manager must define to support
8269 @value{GDBN}'s automatic overlay debugging:
8273 @item @code{_ovly_table}:
8274 This variable must be an array of the following structures:
8279 /* The overlay's mapped address. */
8282 /* The size of the overlay, in bytes. */
8285 /* The overlay's load address. */
8288 /* Non-zero if the overlay is currently mapped;
8290 unsigned long mapped;
8294 @item @code{_novlys}:
8295 This variable must be a four-byte signed integer, holding the total
8296 number of elements in @code{_ovly_table}.
8300 To decide whether a particular overlay is mapped or not, @value{GDBN}
8301 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
8302 @code{lma} members equal the VMA and LMA of the overlay's section in the
8303 executable file. When @value{GDBN} finds a matching entry, it consults
8304 the entry's @code{mapped} member to determine whether the overlay is
8307 In addition, your overlay manager may define a function called
8308 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
8309 will silently set a breakpoint there. If the overlay manager then
8310 calls this function whenever it has changed the overlay table, this
8311 will enable @value{GDBN} to accurately keep track of which overlays
8312 are in program memory, and update any breakpoints that may be set
8313 in overlays. This will allow breakpoints to work even if the
8314 overlays are kept in ROM or other non-writable memory while they
8315 are not being executed.
8317 @node Overlay Sample Program
8318 @section Overlay Sample Program
8319 @cindex overlay example program
8321 When linking a program which uses overlays, you must place the overlays
8322 at their load addresses, while relocating them to run at their mapped
8323 addresses. To do this, you must write a linker script (@pxref{Overlay
8324 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
8325 since linker scripts are specific to a particular host system, target
8326 architecture, and target memory layout, this manual cannot provide
8327 portable sample code demonstrating @value{GDBN}'s overlay support.
8329 However, the @value{GDBN} source distribution does contain an overlaid
8330 program, with linker scripts for a few systems, as part of its test
8331 suite. The program consists of the following files from
8332 @file{gdb/testsuite/gdb.base}:
8336 The main program file.
8338 A simple overlay manager, used by @file{overlays.c}.
8343 Overlay modules, loaded and used by @file{overlays.c}.
8346 Linker scripts for linking the test program on the @code{d10v-elf}
8347 and @code{m32r-elf} targets.
8350 You can build the test program using the @code{d10v-elf} GCC
8351 cross-compiler like this:
8354 $ d10v-elf-gcc -g -c overlays.c
8355 $ d10v-elf-gcc -g -c ovlymgr.c
8356 $ d10v-elf-gcc -g -c foo.c
8357 $ d10v-elf-gcc -g -c bar.c
8358 $ d10v-elf-gcc -g -c baz.c
8359 $ d10v-elf-gcc -g -c grbx.c
8360 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
8361 baz.o grbx.o -Wl,-Td10v.ld -o overlays
8364 The build process is identical for any other architecture, except that
8365 you must substitute the appropriate compiler and linker script for the
8366 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
8370 @chapter Using @value{GDBN} with Different Languages
8373 Although programming languages generally have common aspects, they are
8374 rarely expressed in the same manner. For instance, in ANSI C,
8375 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
8376 Modula-2, it is accomplished by @code{p^}. Values can also be
8377 represented (and displayed) differently. Hex numbers in C appear as
8378 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
8380 @cindex working language
8381 Language-specific information is built into @value{GDBN} for some languages,
8382 allowing you to express operations like the above in your program's
8383 native language, and allowing @value{GDBN} to output values in a manner
8384 consistent with the syntax of your program's native language. The
8385 language you use to build expressions is called the @dfn{working
8389 * Setting:: Switching between source languages
8390 * Show:: Displaying the language
8391 * Checks:: Type and range checks
8392 * Supported languages:: Supported languages
8393 * Unsupported languages:: Unsupported languages
8397 @section Switching between source languages
8399 There are two ways to control the working language---either have @value{GDBN}
8400 set it automatically, or select it manually yourself. You can use the
8401 @code{set language} command for either purpose. On startup, @value{GDBN}
8402 defaults to setting the language automatically. The working language is
8403 used to determine how expressions you type are interpreted, how values
8406 In addition to the working language, every source file that
8407 @value{GDBN} knows about has its own working language. For some object
8408 file formats, the compiler might indicate which language a particular
8409 source file is in. However, most of the time @value{GDBN} infers the
8410 language from the name of the file. The language of a source file
8411 controls whether C@t{++} names are demangled---this way @code{backtrace} can
8412 show each frame appropriately for its own language. There is no way to
8413 set the language of a source file from within @value{GDBN}, but you can
8414 set the language associated with a filename extension. @xref{Show, ,
8415 Displaying the language}.
8417 This is most commonly a problem when you use a program, such
8418 as @code{cfront} or @code{f2c}, that generates C but is written in
8419 another language. In that case, make the
8420 program use @code{#line} directives in its C output; that way
8421 @value{GDBN} will know the correct language of the source code of the original
8422 program, and will display that source code, not the generated C code.
8425 * Filenames:: Filename extensions and languages.
8426 * Manually:: Setting the working language manually
8427 * Automatically:: Having @value{GDBN} infer the source language
8431 @subsection List of filename extensions and languages
8433 If a source file name ends in one of the following extensions, then
8434 @value{GDBN} infers that its language is the one indicated.
8455 Objective-C source file
8462 Modula-2 source file
8466 Assembler source file. This actually behaves almost like C, but
8467 @value{GDBN} does not skip over function prologues when stepping.
8470 In addition, you may set the language associated with a filename
8471 extension. @xref{Show, , Displaying the language}.
8474 @subsection Setting the working language
8476 If you allow @value{GDBN} to set the language automatically,
8477 expressions are interpreted the same way in your debugging session and
8480 @kindex set language
8481 If you wish, you may set the language manually. To do this, issue the
8482 command @samp{set language @var{lang}}, where @var{lang} is the name of
8484 @code{c} or @code{modula-2}.
8485 For a list of the supported languages, type @samp{set language}.
8487 Setting the language manually prevents @value{GDBN} from updating the working
8488 language automatically. This can lead to confusion if you try
8489 to debug a program when the working language is not the same as the
8490 source language, when an expression is acceptable to both
8491 languages---but means different things. For instance, if the current
8492 source file were written in C, and @value{GDBN} was parsing Modula-2, a
8500 might not have the effect you intended. In C, this means to add
8501 @code{b} and @code{c} and place the result in @code{a}. The result
8502 printed would be the value of @code{a}. In Modula-2, this means to compare
8503 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
8506 @subsection Having @value{GDBN} infer the source language
8508 To have @value{GDBN} set the working language automatically, use
8509 @samp{set language local} or @samp{set language auto}. @value{GDBN}
8510 then infers the working language. That is, when your program stops in a
8511 frame (usually by encountering a breakpoint), @value{GDBN} sets the
8512 working language to the language recorded for the function in that
8513 frame. If the language for a frame is unknown (that is, if the function
8514 or block corresponding to the frame was defined in a source file that
8515 does not have a recognized extension), the current working language is
8516 not changed, and @value{GDBN} issues a warning.
8518 This may not seem necessary for most programs, which are written
8519 entirely in one source language. However, program modules and libraries
8520 written in one source language can be used by a main program written in
8521 a different source language. Using @samp{set language auto} in this
8522 case frees you from having to set the working language manually.
8525 @section Displaying the language
8527 The following commands help you find out which language is the
8528 working language, and also what language source files were written in.
8532 @kindex show language
8533 Display the current working language. This is the
8534 language you can use with commands such as @code{print} to
8535 build and compute expressions that may involve variables in your program.
8538 @kindex info frame@r{, show the source language}
8539 Display the source language for this frame. This language becomes the
8540 working language if you use an identifier from this frame.
8541 @xref{Frame Info, ,Information about a frame}, to identify the other
8542 information listed here.
8545 @kindex info source@r{, show the source language}
8546 Display the source language of this source file.
8547 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
8548 information listed here.
8551 In unusual circumstances, you may have source files with extensions
8552 not in the standard list. You can then set the extension associated
8553 with a language explicitly:
8556 @item set extension-language @var{ext} @var{language}
8557 @kindex set extension-language
8558 Tell @value{GDBN} that source files with extension @var{ext} are to be
8559 assumed as written in the source language @var{language}.
8561 @item info extensions
8562 @kindex info extensions
8563 List all the filename extensions and the associated languages.
8567 @section Type and range checking
8570 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
8571 checking are included, but they do not yet have any effect. This
8572 section documents the intended facilities.
8574 @c FIXME remove warning when type/range code added
8576 Some languages are designed to guard you against making seemingly common
8577 errors through a series of compile- and run-time checks. These include
8578 checking the type of arguments to functions and operators, and making
8579 sure mathematical overflows are caught at run time. Checks such as
8580 these help to ensure a program's correctness once it has been compiled
8581 by eliminating type mismatches, and providing active checks for range
8582 errors when your program is running.
8584 @value{GDBN} can check for conditions like the above if you wish.
8585 Although @value{GDBN} does not check the statements in your program,
8586 it can check expressions entered directly into @value{GDBN} for
8587 evaluation via the @code{print} command, for example. As with the
8588 working language, @value{GDBN} can also decide whether or not to check
8589 automatically based on your program's source language.
8590 @xref{Supported languages, ,Supported languages}, for the default
8591 settings of supported languages.
8594 * Type Checking:: An overview of type checking
8595 * Range Checking:: An overview of range checking
8598 @cindex type checking
8599 @cindex checks, type
8601 @subsection An overview of type checking
8603 Some languages, such as Modula-2, are strongly typed, meaning that the
8604 arguments to operators and functions have to be of the correct type,
8605 otherwise an error occurs. These checks prevent type mismatch
8606 errors from ever causing any run-time problems. For example,
8614 The second example fails because the @code{CARDINAL} 1 is not
8615 type-compatible with the @code{REAL} 2.3.
8617 For the expressions you use in @value{GDBN} commands, you can tell the
8618 @value{GDBN} type checker to skip checking;
8619 to treat any mismatches as errors and abandon the expression;
8620 or to only issue warnings when type mismatches occur,
8621 but evaluate the expression anyway. When you choose the last of
8622 these, @value{GDBN} evaluates expressions like the second example above, but
8623 also issues a warning.
8625 Even if you turn type checking off, there may be other reasons
8626 related to type that prevent @value{GDBN} from evaluating an expression.
8627 For instance, @value{GDBN} does not know how to add an @code{int} and
8628 a @code{struct foo}. These particular type errors have nothing to do
8629 with the language in use, and usually arise from expressions, such as
8630 the one described above, which make little sense to evaluate anyway.
8632 Each language defines to what degree it is strict about type. For
8633 instance, both Modula-2 and C require the arguments to arithmetical
8634 operators to be numbers. In C, enumerated types and pointers can be
8635 represented as numbers, so that they are valid arguments to mathematical
8636 operators. @xref{Supported languages, ,Supported languages}, for further
8637 details on specific languages.
8639 @value{GDBN} provides some additional commands for controlling the type checker:
8641 @kindex set check type
8642 @kindex show check type
8644 @item set check type auto
8645 Set type checking on or off based on the current working language.
8646 @xref{Supported languages, ,Supported languages}, for the default settings for
8649 @item set check type on
8650 @itemx set check type off
8651 Set type checking on or off, overriding the default setting for the
8652 current working language. Issue a warning if the setting does not
8653 match the language default. If any type mismatches occur in
8654 evaluating an expression while type checking is on, @value{GDBN} prints a
8655 message and aborts evaluation of the expression.
8657 @item set check type warn
8658 Cause the type checker to issue warnings, but to always attempt to
8659 evaluate the expression. Evaluating the expression may still
8660 be impossible for other reasons. For example, @value{GDBN} cannot add
8661 numbers and structures.
8664 Show the current setting of the type checker, and whether or not @value{GDBN}
8665 is setting it automatically.
8668 @cindex range checking
8669 @cindex checks, range
8670 @node Range Checking
8671 @subsection An overview of range checking
8673 In some languages (such as Modula-2), it is an error to exceed the
8674 bounds of a type; this is enforced with run-time checks. Such range
8675 checking is meant to ensure program correctness by making sure
8676 computations do not overflow, or indices on an array element access do
8677 not exceed the bounds of the array.
8679 For expressions you use in @value{GDBN} commands, you can tell
8680 @value{GDBN} to treat range errors in one of three ways: ignore them,
8681 always treat them as errors and abandon the expression, or issue
8682 warnings but evaluate the expression anyway.
8684 A range error can result from numerical overflow, from exceeding an
8685 array index bound, or when you type a constant that is not a member
8686 of any type. Some languages, however, do not treat overflows as an
8687 error. In many implementations of C, mathematical overflow causes the
8688 result to ``wrap around'' to lower values---for example, if @var{m} is
8689 the largest integer value, and @var{s} is the smallest, then
8692 @var{m} + 1 @result{} @var{s}
8695 This, too, is specific to individual languages, and in some cases
8696 specific to individual compilers or machines. @xref{Supported languages, ,
8697 Supported languages}, for further details on specific languages.
8699 @value{GDBN} provides some additional commands for controlling the range checker:
8701 @kindex set check range
8702 @kindex show check range
8704 @item set check range auto
8705 Set range checking on or off based on the current working language.
8706 @xref{Supported languages, ,Supported languages}, for the default settings for
8709 @item set check range on
8710 @itemx set check range off
8711 Set range checking on or off, overriding the default setting for the
8712 current working language. A warning is issued if the setting does not
8713 match the language default. If a range error occurs and range checking is on,
8714 then a message is printed and evaluation of the expression is aborted.
8716 @item set check range warn
8717 Output messages when the @value{GDBN} range checker detects a range error,
8718 but attempt to evaluate the expression anyway. Evaluating the
8719 expression may still be impossible for other reasons, such as accessing
8720 memory that the process does not own (a typical example from many Unix
8724 Show the current setting of the range checker, and whether or not it is
8725 being set automatically by @value{GDBN}.
8728 @node Supported languages
8729 @section Supported languages
8731 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
8732 assembly, Modula-2, and Ada.
8733 @c This is false ...
8734 Some @value{GDBN} features may be used in expressions regardless of the
8735 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
8736 and the @samp{@{type@}addr} construct (@pxref{Expressions,
8737 ,Expressions}) can be used with the constructs of any supported
8740 The following sections detail to what degree each source language is
8741 supported by @value{GDBN}. These sections are not meant to be language
8742 tutorials or references, but serve only as a reference guide to what the
8743 @value{GDBN} expression parser accepts, and what input and output
8744 formats should look like for different languages. There are many good
8745 books written on each of these languages; please look to these for a
8746 language reference or tutorial.
8750 * Objective-C:: Objective-C
8753 * Modula-2:: Modula-2
8758 @subsection C and C@t{++}
8760 @cindex C and C@t{++}
8761 @cindex expressions in C or C@t{++}
8763 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
8764 to both languages. Whenever this is the case, we discuss those languages
8768 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
8769 @cindex @sc{gnu} C@t{++}
8770 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
8771 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
8772 effectively, you must compile your C@t{++} programs with a supported
8773 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
8774 compiler (@code{aCC}).
8776 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
8777 format; if it doesn't work on your system, try the stabs+ debugging
8778 format. You can select those formats explicitly with the @code{g++}
8779 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
8780 @xref{Debugging Options,,Options for Debugging Your Program or @sc{gnu}
8781 CC, gcc.info, Using @sc{gnu} CC}.
8784 * C Operators:: C and C@t{++} operators
8785 * C Constants:: C and C@t{++} constants
8786 * C plus plus expressions:: C@t{++} expressions
8787 * C Defaults:: Default settings for C and C@t{++}
8788 * C Checks:: C and C@t{++} type and range checks
8789 * Debugging C:: @value{GDBN} and C
8790 * Debugging C plus plus:: @value{GDBN} features for C@t{++}
8794 @subsubsection C and C@t{++} operators
8796 @cindex C and C@t{++} operators
8798 Operators must be defined on values of specific types. For instance,
8799 @code{+} is defined on numbers, but not on structures. Operators are
8800 often defined on groups of types.
8802 For the purposes of C and C@t{++}, the following definitions hold:
8807 @emph{Integral types} include @code{int} with any of its storage-class
8808 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
8811 @emph{Floating-point types} include @code{float}, @code{double}, and
8812 @code{long double} (if supported by the target platform).
8815 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
8818 @emph{Scalar types} include all of the above.
8823 The following operators are supported. They are listed here
8824 in order of increasing precedence:
8828 The comma or sequencing operator. Expressions in a comma-separated list
8829 are evaluated from left to right, with the result of the entire
8830 expression being the last expression evaluated.
8833 Assignment. The value of an assignment expression is the value
8834 assigned. Defined on scalar types.
8837 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
8838 and translated to @w{@code{@var{a} = @var{a op b}}}.
8839 @w{@code{@var{op}=}} and @code{=} have the same precedence.
8840 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
8841 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
8844 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
8845 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
8849 Logical @sc{or}. Defined on integral types.
8852 Logical @sc{and}. Defined on integral types.
8855 Bitwise @sc{or}. Defined on integral types.
8858 Bitwise exclusive-@sc{or}. Defined on integral types.
8861 Bitwise @sc{and}. Defined on integral types.
8864 Equality and inequality. Defined on scalar types. The value of these
8865 expressions is 0 for false and non-zero for true.
8867 @item <@r{, }>@r{, }<=@r{, }>=
8868 Less than, greater than, less than or equal, greater than or equal.
8869 Defined on scalar types. The value of these expressions is 0 for false
8870 and non-zero for true.
8873 left shift, and right shift. Defined on integral types.
8876 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8879 Addition and subtraction. Defined on integral types, floating-point types and
8882 @item *@r{, }/@r{, }%
8883 Multiplication, division, and modulus. Multiplication and division are
8884 defined on integral and floating-point types. Modulus is defined on
8888 Increment and decrement. When appearing before a variable, the
8889 operation is performed before the variable is used in an expression;
8890 when appearing after it, the variable's value is used before the
8891 operation takes place.
8894 Pointer dereferencing. Defined on pointer types. Same precedence as
8898 Address operator. Defined on variables. Same precedence as @code{++}.
8900 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
8901 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
8902 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
8903 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
8907 Negative. Defined on integral and floating-point types. Same
8908 precedence as @code{++}.
8911 Logical negation. Defined on integral types. Same precedence as
8915 Bitwise complement operator. Defined on integral types. Same precedence as
8920 Structure member, and pointer-to-structure member. For convenience,
8921 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
8922 pointer based on the stored type information.
8923 Defined on @code{struct} and @code{union} data.
8926 Dereferences of pointers to members.
8929 Array indexing. @code{@var{a}[@var{i}]} is defined as
8930 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
8933 Function parameter list. Same precedence as @code{->}.
8936 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
8937 and @code{class} types.
8940 Doubled colons also represent the @value{GDBN} scope operator
8941 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
8945 If an operator is redefined in the user code, @value{GDBN} usually
8946 attempts to invoke the redefined version instead of using the operator's
8954 @subsubsection C and C@t{++} constants
8956 @cindex C and C@t{++} constants
8958 @value{GDBN} allows you to express the constants of C and C@t{++} in the
8963 Integer constants are a sequence of digits. Octal constants are
8964 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
8965 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
8966 @samp{l}, specifying that the constant should be treated as a
8970 Floating point constants are a sequence of digits, followed by a decimal
8971 point, followed by a sequence of digits, and optionally followed by an
8972 exponent. An exponent is of the form:
8973 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
8974 sequence of digits. The @samp{+} is optional for positive exponents.
8975 A floating-point constant may also end with a letter @samp{f} or
8976 @samp{F}, specifying that the constant should be treated as being of
8977 the @code{float} (as opposed to the default @code{double}) type; or with
8978 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
8982 Enumerated constants consist of enumerated identifiers, or their
8983 integral equivalents.
8986 Character constants are a single character surrounded by single quotes
8987 (@code{'}), or a number---the ordinal value of the corresponding character
8988 (usually its @sc{ascii} value). Within quotes, the single character may
8989 be represented by a letter or by @dfn{escape sequences}, which are of
8990 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
8991 of the character's ordinal value; or of the form @samp{\@var{x}}, where
8992 @samp{@var{x}} is a predefined special character---for example,
8993 @samp{\n} for newline.
8996 String constants are a sequence of character constants surrounded by
8997 double quotes (@code{"}). Any valid character constant (as described
8998 above) may appear. Double quotes within the string must be preceded by
8999 a backslash, so for instance @samp{"a\"b'c"} is a string of five
9003 Pointer constants are an integral value. You can also write pointers
9004 to constants using the C operator @samp{&}.
9007 Array constants are comma-separated lists surrounded by braces @samp{@{}
9008 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
9009 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
9010 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
9014 * C plus plus expressions::
9021 @node C plus plus expressions
9022 @subsubsection C@t{++} expressions
9024 @cindex expressions in C@t{++}
9025 @value{GDBN} expression handling can interpret most C@t{++} expressions.
9027 @cindex debugging C@t{++} programs
9028 @cindex C@t{++} compilers
9029 @cindex debug formats and C@t{++}
9030 @cindex @value{NGCC} and C@t{++}
9032 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
9033 proper compiler and the proper debug format. Currently, @value{GDBN}
9034 works best when debugging C@t{++} code that is compiled with
9035 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
9036 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
9037 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
9038 stabs+ as their default debug format, so you usually don't need to
9039 specify a debug format explicitly. Other compilers and/or debug formats
9040 are likely to work badly or not at all when using @value{GDBN} to debug
9046 @cindex member functions
9048 Member function calls are allowed; you can use expressions like
9051 count = aml->GetOriginal(x, y)
9054 @vindex this@r{, inside C@t{++} member functions}
9055 @cindex namespace in C@t{++}
9057 While a member function is active (in the selected stack frame), your
9058 expressions have the same namespace available as the member function;
9059 that is, @value{GDBN} allows implicit references to the class instance
9060 pointer @code{this} following the same rules as C@t{++}.
9062 @cindex call overloaded functions
9063 @cindex overloaded functions, calling
9064 @cindex type conversions in C@t{++}
9066 You can call overloaded functions; @value{GDBN} resolves the function
9067 call to the right definition, with some restrictions. @value{GDBN} does not
9068 perform overload resolution involving user-defined type conversions,
9069 calls to constructors, or instantiations of templates that do not exist
9070 in the program. It also cannot handle ellipsis argument lists or
9073 It does perform integral conversions and promotions, floating-point
9074 promotions, arithmetic conversions, pointer conversions, conversions of
9075 class objects to base classes, and standard conversions such as those of
9076 functions or arrays to pointers; it requires an exact match on the
9077 number of function arguments.
9079 Overload resolution is always performed, unless you have specified
9080 @code{set overload-resolution off}. @xref{Debugging C plus plus,
9081 ,@value{GDBN} features for C@t{++}}.
9083 You must specify @code{set overload-resolution off} in order to use an
9084 explicit function signature to call an overloaded function, as in
9086 p 'foo(char,int)'('x', 13)
9089 The @value{GDBN} command-completion facility can simplify this;
9090 see @ref{Completion, ,Command completion}.
9092 @cindex reference declarations
9094 @value{GDBN} understands variables declared as C@t{++} references; you can use
9095 them in expressions just as you do in C@t{++} source---they are automatically
9098 In the parameter list shown when @value{GDBN} displays a frame, the values of
9099 reference variables are not displayed (unlike other variables); this
9100 avoids clutter, since references are often used for large structures.
9101 The @emph{address} of a reference variable is always shown, unless
9102 you have specified @samp{set print address off}.
9105 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
9106 expressions can use it just as expressions in your program do. Since
9107 one scope may be defined in another, you can use @code{::} repeatedly if
9108 necessary, for example in an expression like
9109 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
9110 resolving name scope by reference to source files, in both C and C@t{++}
9111 debugging (@pxref{Variables, ,Program variables}).
9114 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
9115 calling virtual functions correctly, printing out virtual bases of
9116 objects, calling functions in a base subobject, casting objects, and
9117 invoking user-defined operators.
9120 @subsubsection C and C@t{++} defaults
9122 @cindex C and C@t{++} defaults
9124 If you allow @value{GDBN} to set type and range checking automatically, they
9125 both default to @code{off} whenever the working language changes to
9126 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
9127 selects the working language.
9129 If you allow @value{GDBN} to set the language automatically, it
9130 recognizes source files whose names end with @file{.c}, @file{.C}, or
9131 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
9132 these files, it sets the working language to C or C@t{++}.
9133 @xref{Automatically, ,Having @value{GDBN} infer the source language},
9134 for further details.
9136 @c Type checking is (a) primarily motivated by Modula-2, and (b)
9137 @c unimplemented. If (b) changes, it might make sense to let this node
9138 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
9141 @subsubsection C and C@t{++} type and range checks
9143 @cindex C and C@t{++} checks
9145 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
9146 is not used. However, if you turn type checking on, @value{GDBN}
9147 considers two variables type equivalent if:
9151 The two variables are structured and have the same structure, union, or
9155 The two variables have the same type name, or types that have been
9156 declared equivalent through @code{typedef}.
9159 @c leaving this out because neither J Gilmore nor R Pesch understand it.
9162 The two @code{struct}, @code{union}, or @code{enum} variables are
9163 declared in the same declaration. (Note: this may not be true for all C
9168 Range checking, if turned on, is done on mathematical operations. Array
9169 indices are not checked, since they are often used to index a pointer
9170 that is not itself an array.
9173 @subsubsection @value{GDBN} and C
9175 The @code{set print union} and @code{show print union} commands apply to
9176 the @code{union} type. When set to @samp{on}, any @code{union} that is
9177 inside a @code{struct} or @code{class} is also printed. Otherwise, it
9178 appears as @samp{@{...@}}.
9180 The @code{@@} operator aids in the debugging of dynamic arrays, formed
9181 with pointers and a memory allocation function. @xref{Expressions,
9185 * Debugging C plus plus::
9188 @node Debugging C plus plus
9189 @subsubsection @value{GDBN} features for C@t{++}
9191 @cindex commands for C@t{++}
9193 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
9194 designed specifically for use with C@t{++}. Here is a summary:
9197 @cindex break in overloaded functions
9198 @item @r{breakpoint menus}
9199 When you want a breakpoint in a function whose name is overloaded,
9200 @value{GDBN} breakpoint menus help you specify which function definition
9201 you want. @xref{Breakpoint Menus,,Breakpoint menus}.
9203 @cindex overloading in C@t{++}
9204 @item rbreak @var{regex}
9205 Setting breakpoints using regular expressions is helpful for setting
9206 breakpoints on overloaded functions that are not members of any special
9208 @xref{Set Breaks, ,Setting breakpoints}.
9210 @cindex C@t{++} exception handling
9213 Debug C@t{++} exception handling using these commands. @xref{Set
9214 Catchpoints, , Setting catchpoints}.
9217 @item ptype @var{typename}
9218 Print inheritance relationships as well as other information for type
9220 @xref{Symbols, ,Examining the Symbol Table}.
9222 @cindex C@t{++} symbol display
9223 @item set print demangle
9224 @itemx show print demangle
9225 @itemx set print asm-demangle
9226 @itemx show print asm-demangle
9227 Control whether C@t{++} symbols display in their source form, both when
9228 displaying code as C@t{++} source and when displaying disassemblies.
9229 @xref{Print Settings, ,Print settings}.
9231 @item set print object
9232 @itemx show print object
9233 Choose whether to print derived (actual) or declared types of objects.
9234 @xref{Print Settings, ,Print settings}.
9236 @item set print vtbl
9237 @itemx show print vtbl
9238 Control the format for printing virtual function tables.
9239 @xref{Print Settings, ,Print settings}.
9240 (The @code{vtbl} commands do not work on programs compiled with the HP
9241 ANSI C@t{++} compiler (@code{aCC}).)
9243 @kindex set overload-resolution
9244 @cindex overloaded functions, overload resolution
9245 @item set overload-resolution on
9246 Enable overload resolution for C@t{++} expression evaluation. The default
9247 is on. For overloaded functions, @value{GDBN} evaluates the arguments
9248 and searches for a function whose signature matches the argument types,
9249 using the standard C@t{++} conversion rules (see @ref{C plus plus expressions, ,C@t{++}
9250 expressions}, for details). If it cannot find a match, it emits a
9253 @item set overload-resolution off
9254 Disable overload resolution for C@t{++} expression evaluation. For
9255 overloaded functions that are not class member functions, @value{GDBN}
9256 chooses the first function of the specified name that it finds in the
9257 symbol table, whether or not its arguments are of the correct type. For
9258 overloaded functions that are class member functions, @value{GDBN}
9259 searches for a function whose signature @emph{exactly} matches the
9262 @kindex show overload-resolution
9263 @item show overload-resolution
9264 Show the current setting of overload resolution.
9266 @item @r{Overloaded symbol names}
9267 You can specify a particular definition of an overloaded symbol, using
9268 the same notation that is used to declare such symbols in C@t{++}: type
9269 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
9270 also use the @value{GDBN} command-line word completion facilities to list the
9271 available choices, or to finish the type list for you.
9272 @xref{Completion,, Command completion}, for details on how to do this.
9276 @subsection Objective-C
9279 This section provides information about some commands and command
9280 options that are useful for debugging Objective-C code. See also
9281 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
9282 few more commands specific to Objective-C support.
9285 * Method Names in Commands::
9286 * The Print Command with Objective-C::
9289 @node Method Names in Commands, The Print Command with Objective-C, Objective-C, Objective-C
9290 @subsubsection Method Names in Commands
9292 The following commands have been extended to accept Objective-C method
9293 names as line specifications:
9295 @kindex clear@r{, and Objective-C}
9296 @kindex break@r{, and Objective-C}
9297 @kindex info line@r{, and Objective-C}
9298 @kindex jump@r{, and Objective-C}
9299 @kindex list@r{, and Objective-C}
9303 @item @code{info line}
9308 A fully qualified Objective-C method name is specified as
9311 -[@var{Class} @var{methodName}]
9314 where the minus sign is used to indicate an instance method and a
9315 plus sign (not shown) is used to indicate a class method. The class
9316 name @var{Class} and method name @var{methodName} are enclosed in
9317 brackets, similar to the way messages are specified in Objective-C
9318 source code. For example, to set a breakpoint at the @code{create}
9319 instance method of class @code{Fruit} in the program currently being
9323 break -[Fruit create]
9326 To list ten program lines around the @code{initialize} class method,
9330 list +[NSText initialize]
9333 In the current version of @value{GDBN}, the plus or minus sign is
9334 required. In future versions of @value{GDBN}, the plus or minus
9335 sign will be optional, but you can use it to narrow the search. It
9336 is also possible to specify just a method name:
9342 You must specify the complete method name, including any colons. If
9343 your program's source files contain more than one @code{create} method,
9344 you'll be presented with a numbered list of classes that implement that
9345 method. Indicate your choice by number, or type @samp{0} to exit if
9348 As another example, to clear a breakpoint established at the
9349 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
9352 clear -[NSWindow makeKeyAndOrderFront:]
9355 @node The Print Command with Objective-C
9356 @subsubsection The Print Command With Objective-C
9357 @cindex Objective-C, print objects
9358 @kindex print-object
9359 @kindex po @r{(@code{print-object})}
9361 The print command has also been extended to accept methods. For example:
9364 print -[@var{object} hash]
9367 @cindex print an Objective-C object description
9368 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
9370 will tell @value{GDBN} to send the @code{hash} message to @var{object}
9371 and print the result. Also, an additional command has been added,
9372 @code{print-object} or @code{po} for short, which is meant to print
9373 the description of an object. However, this command may only work
9374 with certain Objective-C libraries that have a particular hook
9375 function, @code{_NSPrintForDebugger}, defined.
9379 @cindex Fortran-specific support in @value{GDBN}
9381 @value{GDBN} can be used to debug programs written in Fortran, but it
9382 currently supports only the features of Fortran 77 language.
9384 @cindex trailing underscore, in Fortran symbols
9385 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
9386 among them) append an underscore to the names of variables and
9387 functions. When you debug programs compiled by those compilers, you
9388 will need to refer to variables and functions with a trailing
9392 * Fortran Operators:: Fortran operators and expressions
9393 * Fortran Defaults:: Default settings for Fortran
9394 * Special Fortran commands:: Special @value{GDBN} commands for Fortran
9397 @node Fortran Operators
9398 @subsubsection Fortran operators and expressions
9400 @cindex Fortran operators and expressions
9402 Operators must be defined on values of specific types. For instance,
9403 @code{+} is defined on numbers, but not on characters or other non-
9404 arithmetic types. Operators are often defined on groups of types.
9408 The exponentiation operator. It raises the first operand to the power
9412 The range operator. Normally used in the form of array(low:high) to
9413 represent a section of array.
9416 @node Fortran Defaults
9417 @subsubsection Fortran Defaults
9419 @cindex Fortran Defaults
9421 Fortran symbols are usually case-insensitive, so @value{GDBN} by
9422 default uses case-insensitive matches for Fortran symbols. You can
9423 change that with the @samp{set case-insensitive} command, see
9424 @ref{Symbols}, for the details.
9426 @node Special Fortran commands
9427 @subsubsection Special Fortran commands
9429 @cindex Special Fortran commands
9431 @value{GDBN} had some commands to support Fortran specific feature,
9432 such as common block displaying.
9435 @cindex @code{COMMON} blocks, Fortran
9437 @item info common @r{[}@var{common-name}@r{]}
9438 This command prints the values contained in the Fortran @code{COMMON}
9439 block whose name is @var{common-name}. With no argument, the names of
9440 all @code{COMMON} blocks visible at current program location are
9447 @cindex Pascal support in @value{GDBN}, limitations
9448 Debugging Pascal programs which use sets, subranges, file variables, or
9449 nested functions does not currently work. @value{GDBN} does not support
9450 entering expressions, printing values, or similar features using Pascal
9453 The Pascal-specific command @code{set print pascal_static-members}
9454 controls whether static members of Pascal objects are displayed.
9455 @xref{Print Settings, pascal_static-members}.
9458 @subsection Modula-2
9460 @cindex Modula-2, @value{GDBN} support
9462 The extensions made to @value{GDBN} to support Modula-2 only support
9463 output from the @sc{gnu} Modula-2 compiler (which is currently being
9464 developed). Other Modula-2 compilers are not currently supported, and
9465 attempting to debug executables produced by them is most likely
9466 to give an error as @value{GDBN} reads in the executable's symbol
9469 @cindex expressions in Modula-2
9471 * M2 Operators:: Built-in operators
9472 * Built-In Func/Proc:: Built-in functions and procedures
9473 * M2 Constants:: Modula-2 constants
9474 * M2 Defaults:: Default settings for Modula-2
9475 * Deviations:: Deviations from standard Modula-2
9476 * M2 Checks:: Modula-2 type and range checks
9477 * M2 Scope:: The scope operators @code{::} and @code{.}
9478 * GDB/M2:: @value{GDBN} and Modula-2
9482 @subsubsection Operators
9483 @cindex Modula-2 operators
9485 Operators must be defined on values of specific types. For instance,
9486 @code{+} is defined on numbers, but not on structures. Operators are
9487 often defined on groups of types. For the purposes of Modula-2, the
9488 following definitions hold:
9493 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
9497 @emph{Character types} consist of @code{CHAR} and its subranges.
9500 @emph{Floating-point types} consist of @code{REAL}.
9503 @emph{Pointer types} consist of anything declared as @code{POINTER TO
9507 @emph{Scalar types} consist of all of the above.
9510 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
9513 @emph{Boolean types} consist of @code{BOOLEAN}.
9517 The following operators are supported, and appear in order of
9518 increasing precedence:
9522 Function argument or array index separator.
9525 Assignment. The value of @var{var} @code{:=} @var{value} is
9529 Less than, greater than on integral, floating-point, or enumerated
9533 Less than or equal to, greater than or equal to
9534 on integral, floating-point and enumerated types, or set inclusion on
9535 set types. Same precedence as @code{<}.
9537 @item =@r{, }<>@r{, }#
9538 Equality and two ways of expressing inequality, valid on scalar types.
9539 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
9540 available for inequality, since @code{#} conflicts with the script
9544 Set membership. Defined on set types and the types of their members.
9545 Same precedence as @code{<}.
9548 Boolean disjunction. Defined on boolean types.
9551 Boolean conjunction. Defined on boolean types.
9554 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9557 Addition and subtraction on integral and floating-point types, or union
9558 and difference on set types.
9561 Multiplication on integral and floating-point types, or set intersection
9565 Division on floating-point types, or symmetric set difference on set
9566 types. Same precedence as @code{*}.
9569 Integer division and remainder. Defined on integral types. Same
9570 precedence as @code{*}.
9573 Negative. Defined on @code{INTEGER} and @code{REAL} data.
9576 Pointer dereferencing. Defined on pointer types.
9579 Boolean negation. Defined on boolean types. Same precedence as
9583 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
9584 precedence as @code{^}.
9587 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
9590 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
9594 @value{GDBN} and Modula-2 scope operators.
9598 @emph{Warning:} Sets and their operations are not yet supported, so @value{GDBN}
9599 treats the use of the operator @code{IN}, or the use of operators
9600 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
9601 @code{<=}, and @code{>=} on sets as an error.
9605 @node Built-In Func/Proc
9606 @subsubsection Built-in functions and procedures
9607 @cindex Modula-2 built-ins
9609 Modula-2 also makes available several built-in procedures and functions.
9610 In describing these, the following metavariables are used:
9615 represents an @code{ARRAY} variable.
9618 represents a @code{CHAR} constant or variable.
9621 represents a variable or constant of integral type.
9624 represents an identifier that belongs to a set. Generally used in the
9625 same function with the metavariable @var{s}. The type of @var{s} should
9626 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
9629 represents a variable or constant of integral or floating-point type.
9632 represents a variable or constant of floating-point type.
9638 represents a variable.
9641 represents a variable or constant of one of many types. See the
9642 explanation of the function for details.
9645 All Modula-2 built-in procedures also return a result, described below.
9649 Returns the absolute value of @var{n}.
9652 If @var{c} is a lower case letter, it returns its upper case
9653 equivalent, otherwise it returns its argument.
9656 Returns the character whose ordinal value is @var{i}.
9659 Decrements the value in the variable @var{v} by one. Returns the new value.
9661 @item DEC(@var{v},@var{i})
9662 Decrements the value in the variable @var{v} by @var{i}. Returns the
9665 @item EXCL(@var{m},@var{s})
9666 Removes the element @var{m} from the set @var{s}. Returns the new
9669 @item FLOAT(@var{i})
9670 Returns the floating point equivalent of the integer @var{i}.
9673 Returns the index of the last member of @var{a}.
9676 Increments the value in the variable @var{v} by one. Returns the new value.
9678 @item INC(@var{v},@var{i})
9679 Increments the value in the variable @var{v} by @var{i}. Returns the
9682 @item INCL(@var{m},@var{s})
9683 Adds the element @var{m} to the set @var{s} if it is not already
9684 there. Returns the new set.
9687 Returns the maximum value of the type @var{t}.
9690 Returns the minimum value of the type @var{t}.
9693 Returns boolean TRUE if @var{i} is an odd number.
9696 Returns the ordinal value of its argument. For example, the ordinal
9697 value of a character is its @sc{ascii} value (on machines supporting the
9698 @sc{ascii} character set). @var{x} must be of an ordered type, which include
9699 integral, character and enumerated types.
9702 Returns the size of its argument. @var{x} can be a variable or a type.
9704 @item TRUNC(@var{r})
9705 Returns the integral part of @var{r}.
9707 @item VAL(@var{t},@var{i})
9708 Returns the member of the type @var{t} whose ordinal value is @var{i}.
9712 @emph{Warning:} Sets and their operations are not yet supported, so
9713 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
9717 @cindex Modula-2 constants
9719 @subsubsection Constants
9721 @value{GDBN} allows you to express the constants of Modula-2 in the following
9727 Integer constants are simply a sequence of digits. When used in an
9728 expression, a constant is interpreted to be type-compatible with the
9729 rest of the expression. Hexadecimal integers are specified by a
9730 trailing @samp{H}, and octal integers by a trailing @samp{B}.
9733 Floating point constants appear as a sequence of digits, followed by a
9734 decimal point and another sequence of digits. An optional exponent can
9735 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
9736 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
9737 digits of the floating point constant must be valid decimal (base 10)
9741 Character constants consist of a single character enclosed by a pair of
9742 like quotes, either single (@code{'}) or double (@code{"}). They may
9743 also be expressed by their ordinal value (their @sc{ascii} value, usually)
9744 followed by a @samp{C}.
9747 String constants consist of a sequence of characters enclosed by a
9748 pair of like quotes, either single (@code{'}) or double (@code{"}).
9749 Escape sequences in the style of C are also allowed. @xref{C
9750 Constants, ,C and C@t{++} constants}, for a brief explanation of escape
9754 Enumerated constants consist of an enumerated identifier.
9757 Boolean constants consist of the identifiers @code{TRUE} and
9761 Pointer constants consist of integral values only.
9764 Set constants are not yet supported.
9768 @subsubsection Modula-2 defaults
9769 @cindex Modula-2 defaults
9771 If type and range checking are set automatically by @value{GDBN}, they
9772 both default to @code{on} whenever the working language changes to
9773 Modula-2. This happens regardless of whether you or @value{GDBN}
9774 selected the working language.
9776 If you allow @value{GDBN} to set the language automatically, then entering
9777 code compiled from a file whose name ends with @file{.mod} sets the
9778 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set
9779 the language automatically}, for further details.
9782 @subsubsection Deviations from standard Modula-2
9783 @cindex Modula-2, deviations from
9785 A few changes have been made to make Modula-2 programs easier to debug.
9786 This is done primarily via loosening its type strictness:
9790 Unlike in standard Modula-2, pointer constants can be formed by
9791 integers. This allows you to modify pointer variables during
9792 debugging. (In standard Modula-2, the actual address contained in a
9793 pointer variable is hidden from you; it can only be modified
9794 through direct assignment to another pointer variable or expression that
9795 returned a pointer.)
9798 C escape sequences can be used in strings and characters to represent
9799 non-printable characters. @value{GDBN} prints out strings with these
9800 escape sequences embedded. Single non-printable characters are
9801 printed using the @samp{CHR(@var{nnn})} format.
9804 The assignment operator (@code{:=}) returns the value of its right-hand
9808 All built-in procedures both modify @emph{and} return their argument.
9812 @subsubsection Modula-2 type and range checks
9813 @cindex Modula-2 checks
9816 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
9819 @c FIXME remove warning when type/range checks added
9821 @value{GDBN} considers two Modula-2 variables type equivalent if:
9825 They are of types that have been declared equivalent via a @code{TYPE
9826 @var{t1} = @var{t2}} statement
9829 They have been declared on the same line. (Note: This is true of the
9830 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
9833 As long as type checking is enabled, any attempt to combine variables
9834 whose types are not equivalent is an error.
9836 Range checking is done on all mathematical operations, assignment, array
9837 index bounds, and all built-in functions and procedures.
9840 @subsubsection The scope operators @code{::} and @code{.}
9842 @cindex @code{.}, Modula-2 scope operator
9843 @cindex colon, doubled as scope operator
9845 @vindex colon-colon@r{, in Modula-2}
9846 @c Info cannot handle :: but TeX can.
9849 @vindex ::@r{, in Modula-2}
9852 There are a few subtle differences between the Modula-2 scope operator
9853 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
9858 @var{module} . @var{id}
9859 @var{scope} :: @var{id}
9863 where @var{scope} is the name of a module or a procedure,
9864 @var{module} the name of a module, and @var{id} is any declared
9865 identifier within your program, except another module.
9867 Using the @code{::} operator makes @value{GDBN} search the scope
9868 specified by @var{scope} for the identifier @var{id}. If it is not
9869 found in the specified scope, then @value{GDBN} searches all scopes
9870 enclosing the one specified by @var{scope}.
9872 Using the @code{.} operator makes @value{GDBN} search the current scope for
9873 the identifier specified by @var{id} that was imported from the
9874 definition module specified by @var{module}. With this operator, it is
9875 an error if the identifier @var{id} was not imported from definition
9876 module @var{module}, or if @var{id} is not an identifier in
9880 @subsubsection @value{GDBN} and Modula-2
9882 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
9883 Five subcommands of @code{set print} and @code{show print} apply
9884 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
9885 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
9886 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
9887 analogue in Modula-2.
9889 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
9890 with any language, is not useful with Modula-2. Its
9891 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
9892 created in Modula-2 as they can in C or C@t{++}. However, because an
9893 address can be specified by an integral constant, the construct
9894 @samp{@{@var{type}@}@var{adrexp}} is still useful.
9896 @cindex @code{#} in Modula-2
9897 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
9898 interpreted as the beginning of a comment. Use @code{<>} instead.
9904 The extensions made to @value{GDBN} for Ada only support
9905 output from the @sc{gnu} Ada (GNAT) compiler.
9906 Other Ada compilers are not currently supported, and
9907 attempting to debug executables produced by them is most likely
9911 @cindex expressions in Ada
9913 * Ada Mode Intro:: General remarks on the Ada syntax
9914 and semantics supported by Ada mode
9916 * Omissions from Ada:: Restrictions on the Ada expression syntax.
9917 * Additions to Ada:: Extensions of the Ada expression syntax.
9918 * Stopping Before Main Program:: Debugging the program during elaboration.
9919 * Ada Glitches:: Known peculiarities of Ada mode.
9922 @node Ada Mode Intro
9923 @subsubsection Introduction
9924 @cindex Ada mode, general
9926 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
9927 syntax, with some extensions.
9928 The philosophy behind the design of this subset is
9932 That @value{GDBN} should provide basic literals and access to operations for
9933 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
9934 leaving more sophisticated computations to subprograms written into the
9935 program (which therefore may be called from @value{GDBN}).
9938 That type safety and strict adherence to Ada language restrictions
9939 are not particularly important to the @value{GDBN} user.
9942 That brevity is important to the @value{GDBN} user.
9945 Thus, for brevity, the debugger acts as if there were
9946 implicit @code{with} and @code{use} clauses in effect for all user-written
9947 packages, making it unnecessary to fully qualify most names with
9948 their packages, regardless of context. Where this causes ambiguity,
9949 @value{GDBN} asks the user's intent.
9951 The debugger will start in Ada mode if it detects an Ada main program.
9952 As for other languages, it will enter Ada mode when stopped in a program that
9953 was translated from an Ada source file.
9955 While in Ada mode, you may use `@t{--}' for comments. This is useful
9956 mostly for documenting command files. The standard @value{GDBN} comment
9957 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
9958 middle (to allow based literals).
9960 The debugger supports limited overloading. Given a subprogram call in which
9961 the function symbol has multiple definitions, it will use the number of
9962 actual parameters and some information about their types to attempt to narrow
9963 the set of definitions. It also makes very limited use of context, preferring
9964 procedures to functions in the context of the @code{call} command, and
9965 functions to procedures elsewhere.
9967 @node Omissions from Ada
9968 @subsubsection Omissions from Ada
9969 @cindex Ada, omissions from
9971 Here are the notable omissions from the subset:
9975 Only a subset of the attributes are supported:
9979 @t{'First}, @t{'Last}, and @t{'Length}
9980 on array objects (not on types and subtypes).
9983 @t{'Min} and @t{'Max}.
9986 @t{'Pos} and @t{'Val}.
9992 @t{'Range} on array objects (not subtypes), but only as the right
9993 operand of the membership (@code{in}) operator.
9996 @t{'Access}, @t{'Unchecked_Access}, and
9997 @t{'Unrestricted_Access} (a GNAT extension).
10005 @code{Characters.Latin_1} are not available and
10006 concatenation is not implemented. Thus, escape characters in strings are
10007 not currently available.
10010 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
10011 equality of representations. They will generally work correctly
10012 for strings and arrays whose elements have integer or enumeration types.
10013 They may not work correctly for arrays whose element
10014 types have user-defined equality, for arrays of real values
10015 (in particular, IEEE-conformant floating point, because of negative
10016 zeroes and NaNs), and for arrays whose elements contain unused bits with
10017 indeterminate values.
10020 The other component-by-component array operations (@code{and}, @code{or},
10021 @code{xor}, @code{not}, and relational tests other than equality)
10022 are not implemented.
10025 @cindex array aggregates (Ada)
10026 @cindex record aggregates (Ada)
10027 @cindex aggregates (Ada)
10028 There is limited support for array and record aggregates. They are
10029 permitted only on the right sides of assignments, as in these examples:
10032 set An_Array := (1, 2, 3, 4, 5, 6)
10033 set An_Array := (1, others => 0)
10034 set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
10035 set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
10036 set A_Record := (1, "Peter", True);
10037 set A_Record := (Name => "Peter", Id => 1, Alive => True)
10041 discriminant's value by assigning an aggregate has an
10042 undefined effect if that discriminant is used within the record.
10043 However, you can first modify discriminants by directly assigning to
10044 them (which normally would not be allowed in Ada), and then performing an
10045 aggregate assignment. For example, given a variable @code{A_Rec}
10046 declared to have a type such as:
10049 type Rec (Len : Small_Integer := 0) is record
10051 Vals : IntArray (1 .. Len);
10055 you can assign a value with a different size of @code{Vals} with two
10060 set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
10063 As this example also illustrates, @value{GDBN} is very loose about the usual
10064 rules concerning aggregates. You may leave out some of the
10065 components of an array or record aggregate (such as the @code{Len}
10066 component in the assignment to @code{A_Rec} above); they will retain their
10067 original values upon assignment. You may freely use dynamic values as
10068 indices in component associations. You may even use overlapping or
10069 redundant component associations, although which component values are
10070 assigned in such cases is not defined.
10073 Calls to dispatching subprograms are not implemented.
10076 The overloading algorithm is much more limited (i.e., less selective)
10077 than that of real Ada. It makes only limited use of the context in which a subexpression
10078 appears to resolve its meaning, and it is much looser in its rules for allowing
10079 type matches. As a result, some function calls will be ambiguous, and the user
10080 will be asked to choose the proper resolution.
10083 The @code{new} operator is not implemented.
10086 Entry calls are not implemented.
10089 Aside from printing, arithmetic operations on the native VAX floating-point
10090 formats are not supported.
10093 It is not possible to slice a packed array.
10096 @node Additions to Ada
10097 @subsubsection Additions to Ada
10098 @cindex Ada, deviations from
10100 As it does for other languages, @value{GDBN} makes certain generic
10101 extensions to Ada (@pxref{Expressions}):
10105 If the expression @var{E} is a variable residing in memory
10106 (typically a local variable or array element) and @var{N} is
10107 a positive integer, then @code{@var{E}@@@var{N}} displays the values of
10108 @var{E} and the @var{N}-1 adjacent variables following it in memory as an array.
10109 In Ada, this operator is generally not necessary, since its prime use
10110 is in displaying parts of an array, and slicing will usually do this in Ada.
10111 However, there are occasional uses when debugging programs
10112 in which certain debugging information has been optimized away.
10115 @code{@var{B}::@var{var}} means ``the variable named @var{var} that appears
10116 in function or file @var{B}.'' When @var{B} is a file name, you must typically
10117 surround it in single quotes.
10120 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
10121 @var{type} that appears at address @var{addr}.''
10124 A name starting with @samp{$} is a convenience variable
10125 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
10128 In addition, @value{GDBN} provides a few other shortcuts and outright additions specific
10133 The assignment statement is allowed as an expression, returning
10134 its right-hand operand as its value. Thus, you may enter
10138 print A(tmp := y + 1)
10142 The semicolon is allowed as an ``operator,'' returning as its value
10143 the value of its right-hand operand.
10144 This allows, for example,
10145 complex conditional breaks:
10149 condition 1 (report(i); k += 1; A(k) > 100)
10153 Rather than use catenation and symbolic character names to introduce special
10154 characters into strings, one may instead use a special bracket notation,
10155 which is also used to print strings. A sequence of characters of the form
10156 @samp{["@var{XX}"]} within a string or character literal denotes the
10157 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
10158 sequence of characters @samp{["""]} also denotes a single quotation mark
10159 in strings. For example,
10161 "One line.["0a"]Next line.["0a"]"
10164 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF}) after each
10168 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
10169 @t{'Max} is optional (and is ignored in any case). For example, it is valid
10177 When printing arrays, @value{GDBN} uses positional notation when the
10178 array has a lower bound of 1, and uses a modified named notation otherwise.
10179 For example, a one-dimensional array of three integers with a lower bound of 3 might print as
10186 That is, in contrast to valid Ada, only the first component has a @code{=>}
10190 You may abbreviate attributes in expressions with any unique,
10191 multi-character subsequence of
10192 their names (an exact match gets preference).
10193 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
10194 in place of @t{a'length}.
10197 @cindex quoting Ada internal identifiers
10198 Since Ada is case-insensitive, the debugger normally maps identifiers you type
10199 to lower case. The GNAT compiler uses upper-case characters for
10200 some of its internal identifiers, which are normally of no interest to users.
10201 For the rare occasions when you actually have to look at them,
10202 enclose them in angle brackets to avoid the lower-case mapping.
10205 @value{GDBP} print <JMPBUF_SAVE>[0]
10209 Printing an object of class-wide type or dereferencing an
10210 access-to-class-wide value will display all the components of the object's
10211 specific type (as indicated by its run-time tag). Likewise, component
10212 selection on such a value will operate on the specific type of the
10217 @node Stopping Before Main Program
10218 @subsubsection Stopping at the Very Beginning
10220 @cindex breakpointing Ada elaboration code
10221 It is sometimes necessary to debug the program during elaboration, and
10222 before reaching the main procedure.
10223 As defined in the Ada Reference
10224 Manual, the elaboration code is invoked from a procedure called
10225 @code{adainit}. To run your program up to the beginning of
10226 elaboration, simply use the following two commands:
10227 @code{tbreak adainit} and @code{run}.
10230 @subsubsection Known Peculiarities of Ada Mode
10231 @cindex Ada, problems
10233 Besides the omissions listed previously (@pxref{Omissions from Ada}),
10234 we know of several problems with and limitations of Ada mode in
10236 some of which will be fixed with planned future releases of the debugger
10237 and the GNU Ada compiler.
10241 Currently, the debugger
10242 has insufficient information to determine whether certain pointers represent
10243 pointers to objects or the objects themselves.
10244 Thus, the user may have to tack an extra @code{.all} after an expression
10245 to get it printed properly.
10248 Static constants that the compiler chooses not to materialize as objects in
10249 storage are invisible to the debugger.
10252 Named parameter associations in function argument lists are ignored (the
10253 argument lists are treated as positional).
10256 Many useful library packages are currently invisible to the debugger.
10259 Fixed-point arithmetic, conversions, input, and output is carried out using
10260 floating-point arithmetic, and may give results that only approximate those on
10264 The type of the @t{'Address} attribute may not be @code{System.Address}.
10267 The GNAT compiler never generates the prefix @code{Standard} for any of
10268 the standard symbols defined by the Ada language. @value{GDBN} knows about
10269 this: it will strip the prefix from names when you use it, and will never
10270 look for a name you have so qualified among local symbols, nor match against
10271 symbols in other packages or subprograms. If you have
10272 defined entities anywhere in your program other than parameters and
10273 local variables whose simple names match names in @code{Standard},
10274 GNAT's lack of qualification here can cause confusion. When this happens,
10275 you can usually resolve the confusion
10276 by qualifying the problematic names with package
10277 @code{Standard} explicitly.
10280 @node Unsupported languages
10281 @section Unsupported languages
10283 @cindex unsupported languages
10284 @cindex minimal language
10285 In addition to the other fully-supported programming languages,
10286 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
10287 It does not represent a real programming language, but provides a set
10288 of capabilities close to what the C or assembly languages provide.
10289 This should allow most simple operations to be performed while debugging
10290 an application that uses a language currently not supported by @value{GDBN}.
10292 If the language is set to @code{auto}, @value{GDBN} will automatically
10293 select this language if the current frame corresponds to an unsupported
10297 @chapter Examining the Symbol Table
10299 The commands described in this chapter allow you to inquire about the
10300 symbols (names of variables, functions and types) defined in your
10301 program. This information is inherent in the text of your program and
10302 does not change as your program executes. @value{GDBN} finds it in your
10303 program's symbol table, in the file indicated when you started @value{GDBN}
10304 (@pxref{File Options, ,Choosing files}), or by one of the
10305 file-management commands (@pxref{Files, ,Commands to specify files}).
10307 @cindex symbol names
10308 @cindex names of symbols
10309 @cindex quoting names
10310 Occasionally, you may need to refer to symbols that contain unusual
10311 characters, which @value{GDBN} ordinarily treats as word delimiters. The
10312 most frequent case is in referring to static variables in other
10313 source files (@pxref{Variables,,Program variables}). File names
10314 are recorded in object files as debugging symbols, but @value{GDBN} would
10315 ordinarily parse a typical file name, like @file{foo.c}, as the three words
10316 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
10317 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
10324 looks up the value of @code{x} in the scope of the file @file{foo.c}.
10327 @cindex case-insensitive symbol names
10328 @cindex case sensitivity in symbol names
10329 @kindex set case-sensitive
10330 @item set case-sensitive on
10331 @itemx set case-sensitive off
10332 @itemx set case-sensitive auto
10333 Normally, when @value{GDBN} looks up symbols, it matches their names
10334 with case sensitivity determined by the current source language.
10335 Occasionally, you may wish to control that. The command @code{set
10336 case-sensitive} lets you do that by specifying @code{on} for
10337 case-sensitive matches or @code{off} for case-insensitive ones. If
10338 you specify @code{auto}, case sensitivity is reset to the default
10339 suitable for the source language. The default is case-sensitive
10340 matches for all languages except for Fortran, for which the default is
10341 case-insensitive matches.
10343 @kindex show case-sensitive
10344 @item show case-sensitive
10345 This command shows the current setting of case sensitivity for symbols
10348 @kindex info address
10349 @cindex address of a symbol
10350 @item info address @var{symbol}
10351 Describe where the data for @var{symbol} is stored. For a register
10352 variable, this says which register it is kept in. For a non-register
10353 local variable, this prints the stack-frame offset at which the variable
10356 Note the contrast with @samp{print &@var{symbol}}, which does not work
10357 at all for a register variable, and for a stack local variable prints
10358 the exact address of the current instantiation of the variable.
10360 @kindex info symbol
10361 @cindex symbol from address
10362 @cindex closest symbol and offset for an address
10363 @item info symbol @var{addr}
10364 Print the name of a symbol which is stored at the address @var{addr}.
10365 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
10366 nearest symbol and an offset from it:
10369 (@value{GDBP}) info symbol 0x54320
10370 _initialize_vx + 396 in section .text
10374 This is the opposite of the @code{info address} command. You can use
10375 it to find out the name of a variable or a function given its address.
10378 @item whatis [@var{arg}]
10379 Print the data type of @var{arg}, which can be either an expression or
10380 a data type. With no argument, print the data type of @code{$}, the
10381 last value in the value history. If @var{arg} is an expression, it is
10382 not actually evaluated, and any side-effecting operations (such as
10383 assignments or function calls) inside it do not take place. If
10384 @var{arg} is a type name, it may be the name of a type or typedef, or
10385 for C code it may have the form @samp{class @var{class-name}},
10386 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
10387 @samp{enum @var{enum-tag}}.
10388 @xref{Expressions, ,Expressions}.
10391 @item ptype [@var{arg}]
10392 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
10393 detailed description of the type, instead of just the name of the type.
10394 @xref{Expressions, ,Expressions}.
10396 For example, for this variable declaration:
10399 struct complex @{double real; double imag;@} v;
10403 the two commands give this output:
10407 (@value{GDBP}) whatis v
10408 type = struct complex
10409 (@value{GDBP}) ptype v
10410 type = struct complex @{
10418 As with @code{whatis}, using @code{ptype} without an argument refers to
10419 the type of @code{$}, the last value in the value history.
10421 @cindex incomplete type
10422 Sometimes, programs use opaque data types or incomplete specifications
10423 of complex data structure. If the debug information included in the
10424 program does not allow @value{GDBN} to display a full declaration of
10425 the data type, it will say @samp{<incomplete type>}. For example,
10426 given these declarations:
10430 struct foo *fooptr;
10434 but no definition for @code{struct foo} itself, @value{GDBN} will say:
10438 $1 = <incomplete type>
10442 ``Incomplete type'' is C terminology for data types that are not
10443 completely specified.
10446 @item info types @var{regexp}
10448 Print a brief description of all types whose names match the regular
10449 expression @var{regexp} (or all types in your program, if you supply
10450 no argument). Each complete typename is matched as though it were a
10451 complete line; thus, @samp{i type value} gives information on all
10452 types in your program whose names include the string @code{value}, but
10453 @samp{i type ^value$} gives information only on types whose complete
10454 name is @code{value}.
10456 This command differs from @code{ptype} in two ways: first, like
10457 @code{whatis}, it does not print a detailed description; second, it
10458 lists all source files where a type is defined.
10461 @cindex local variables
10462 @item info scope @var{location}
10463 List all the variables local to a particular scope. This command
10464 accepts a @var{location} argument---a function name, a source line, or
10465 an address preceded by a @samp{*}, and prints all the variables local
10466 to the scope defined by that location. For example:
10469 (@value{GDBP}) @b{info scope command_line_handler}
10470 Scope for command_line_handler:
10471 Symbol rl is an argument at stack/frame offset 8, length 4.
10472 Symbol linebuffer is in static storage at address 0x150a18, length 4.
10473 Symbol linelength is in static storage at address 0x150a1c, length 4.
10474 Symbol p is a local variable in register $esi, length 4.
10475 Symbol p1 is a local variable in register $ebx, length 4.
10476 Symbol nline is a local variable in register $edx, length 4.
10477 Symbol repeat is a local variable at frame offset -8, length 4.
10481 This command is especially useful for determining what data to collect
10482 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
10485 @kindex info source
10487 Show information about the current source file---that is, the source file for
10488 the function containing the current point of execution:
10491 the name of the source file, and the directory containing it,
10493 the directory it was compiled in,
10495 its length, in lines,
10497 which programming language it is written in,
10499 whether the executable includes debugging information for that file, and
10500 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
10502 whether the debugging information includes information about
10503 preprocessor macros.
10507 @kindex info sources
10509 Print the names of all source files in your program for which there is
10510 debugging information, organized into two lists: files whose symbols
10511 have already been read, and files whose symbols will be read when needed.
10513 @kindex info functions
10514 @item info functions
10515 Print the names and data types of all defined functions.
10517 @item info functions @var{regexp}
10518 Print the names and data types of all defined functions
10519 whose names contain a match for regular expression @var{regexp}.
10520 Thus, @samp{info fun step} finds all functions whose names
10521 include @code{step}; @samp{info fun ^step} finds those whose names
10522 start with @code{step}. If a function name contains characters
10523 that conflict with the regular expression language (e.g.@:
10524 @samp{operator*()}), they may be quoted with a backslash.
10526 @kindex info variables
10527 @item info variables
10528 Print the names and data types of all variables that are declared
10529 outside of functions (i.e.@: excluding local variables).
10531 @item info variables @var{regexp}
10532 Print the names and data types of all variables (except for local
10533 variables) whose names contain a match for regular expression
10536 @kindex info classes
10537 @cindex Objective-C, classes and selectors
10539 @itemx info classes @var{regexp}
10540 Display all Objective-C classes in your program, or
10541 (with the @var{regexp} argument) all those matching a particular regular
10544 @kindex info selectors
10545 @item info selectors
10546 @itemx info selectors @var{regexp}
10547 Display all Objective-C selectors in your program, or
10548 (with the @var{regexp} argument) all those matching a particular regular
10552 This was never implemented.
10553 @kindex info methods
10555 @itemx info methods @var{regexp}
10556 The @code{info methods} command permits the user to examine all defined
10557 methods within C@t{++} program, or (with the @var{regexp} argument) a
10558 specific set of methods found in the various C@t{++} classes. Many
10559 C@t{++} classes provide a large number of methods. Thus, the output
10560 from the @code{ptype} command can be overwhelming and hard to use. The
10561 @code{info-methods} command filters the methods, printing only those
10562 which match the regular-expression @var{regexp}.
10565 @cindex reloading symbols
10566 Some systems allow individual object files that make up your program to
10567 be replaced without stopping and restarting your program. For example,
10568 in VxWorks you can simply recompile a defective object file and keep on
10569 running. If you are running on one of these systems, you can allow
10570 @value{GDBN} to reload the symbols for automatically relinked modules:
10573 @kindex set symbol-reloading
10574 @item set symbol-reloading on
10575 Replace symbol definitions for the corresponding source file when an
10576 object file with a particular name is seen again.
10578 @item set symbol-reloading off
10579 Do not replace symbol definitions when encountering object files of the
10580 same name more than once. This is the default state; if you are not
10581 running on a system that permits automatic relinking of modules, you
10582 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
10583 may discard symbols when linking large programs, that may contain
10584 several modules (from different directories or libraries) with the same
10587 @kindex show symbol-reloading
10588 @item show symbol-reloading
10589 Show the current @code{on} or @code{off} setting.
10592 @cindex opaque data types
10593 @kindex set opaque-type-resolution
10594 @item set opaque-type-resolution on
10595 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
10596 declared as a pointer to a @code{struct}, @code{class}, or
10597 @code{union}---for example, @code{struct MyType *}---that is used in one
10598 source file although the full declaration of @code{struct MyType} is in
10599 another source file. The default is on.
10601 A change in the setting of this subcommand will not take effect until
10602 the next time symbols for a file are loaded.
10604 @item set opaque-type-resolution off
10605 Tell @value{GDBN} not to resolve opaque types. In this case, the type
10606 is printed as follows:
10608 @{<no data fields>@}
10611 @kindex show opaque-type-resolution
10612 @item show opaque-type-resolution
10613 Show whether opaque types are resolved or not.
10615 @kindex maint print symbols
10616 @cindex symbol dump
10617 @kindex maint print psymbols
10618 @cindex partial symbol dump
10619 @item maint print symbols @var{filename}
10620 @itemx maint print psymbols @var{filename}
10621 @itemx maint print msymbols @var{filename}
10622 Write a dump of debugging symbol data into the file @var{filename}.
10623 These commands are used to debug the @value{GDBN} symbol-reading code. Only
10624 symbols with debugging data are included. If you use @samp{maint print
10625 symbols}, @value{GDBN} includes all the symbols for which it has already
10626 collected full details: that is, @var{filename} reflects symbols for
10627 only those files whose symbols @value{GDBN} has read. You can use the
10628 command @code{info sources} to find out which files these are. If you
10629 use @samp{maint print psymbols} instead, the dump shows information about
10630 symbols that @value{GDBN} only knows partially---that is, symbols defined in
10631 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
10632 @samp{maint print msymbols} dumps just the minimal symbol information
10633 required for each object file from which @value{GDBN} has read some symbols.
10634 @xref{Files, ,Commands to specify files}, for a discussion of how
10635 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
10637 @kindex maint info symtabs
10638 @kindex maint info psymtabs
10639 @cindex listing @value{GDBN}'s internal symbol tables
10640 @cindex symbol tables, listing @value{GDBN}'s internal
10641 @cindex full symbol tables, listing @value{GDBN}'s internal
10642 @cindex partial symbol tables, listing @value{GDBN}'s internal
10643 @item maint info symtabs @r{[} @var{regexp} @r{]}
10644 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
10646 List the @code{struct symtab} or @code{struct partial_symtab}
10647 structures whose names match @var{regexp}. If @var{regexp} is not
10648 given, list them all. The output includes expressions which you can
10649 copy into a @value{GDBN} debugging this one to examine a particular
10650 structure in more detail. For example:
10653 (@value{GDBP}) maint info psymtabs dwarf2read
10654 @{ objfile /home/gnu/build/gdb/gdb
10655 ((struct objfile *) 0x82e69d0)
10656 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
10657 ((struct partial_symtab *) 0x8474b10)
10660 text addresses 0x814d3c8 -- 0x8158074
10661 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
10662 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
10663 dependencies (none)
10666 (@value{GDBP}) maint info symtabs
10670 We see that there is one partial symbol table whose filename contains
10671 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
10672 and we see that @value{GDBN} has not read in any symtabs yet at all.
10673 If we set a breakpoint on a function, that will cause @value{GDBN} to
10674 read the symtab for the compilation unit containing that function:
10677 (@value{GDBP}) break dwarf2_psymtab_to_symtab
10678 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
10680 (@value{GDBP}) maint info symtabs
10681 @{ objfile /home/gnu/build/gdb/gdb
10682 ((struct objfile *) 0x82e69d0)
10683 @{ symtab /home/gnu/src/gdb/dwarf2read.c
10684 ((struct symtab *) 0x86c1f38)
10687 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
10688 debugformat DWARF 2
10697 @chapter Altering Execution
10699 Once you think you have found an error in your program, you might want to
10700 find out for certain whether correcting the apparent error would lead to
10701 correct results in the rest of the run. You can find the answer by
10702 experiment, using the @value{GDBN} features for altering execution of the
10705 For example, you can store new values into variables or memory
10706 locations, give your program a signal, restart it at a different
10707 address, or even return prematurely from a function.
10710 * Assignment:: Assignment to variables
10711 * Jumping:: Continuing at a different address
10712 * Signaling:: Giving your program a signal
10713 * Returning:: Returning from a function
10714 * Calling:: Calling your program's functions
10715 * Patching:: Patching your program
10719 @section Assignment to variables
10722 @cindex setting variables
10723 To alter the value of a variable, evaluate an assignment expression.
10724 @xref{Expressions, ,Expressions}. For example,
10731 stores the value 4 into the variable @code{x}, and then prints the
10732 value of the assignment expression (which is 4).
10733 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
10734 information on operators in supported languages.
10736 @kindex set variable
10737 @cindex variables, setting
10738 If you are not interested in seeing the value of the assignment, use the
10739 @code{set} command instead of the @code{print} command. @code{set} is
10740 really the same as @code{print} except that the expression's value is
10741 not printed and is not put in the value history (@pxref{Value History,
10742 ,Value history}). The expression is evaluated only for its effects.
10744 If the beginning of the argument string of the @code{set} command
10745 appears identical to a @code{set} subcommand, use the @code{set
10746 variable} command instead of just @code{set}. This command is identical
10747 to @code{set} except for its lack of subcommands. For example, if your
10748 program has a variable @code{width}, you get an error if you try to set
10749 a new value with just @samp{set width=13}, because @value{GDBN} has the
10750 command @code{set width}:
10753 (@value{GDBP}) whatis width
10755 (@value{GDBP}) p width
10757 (@value{GDBP}) set width=47
10758 Invalid syntax in expression.
10762 The invalid expression, of course, is @samp{=47}. In
10763 order to actually set the program's variable @code{width}, use
10766 (@value{GDBP}) set var width=47
10769 Because the @code{set} command has many subcommands that can conflict
10770 with the names of program variables, it is a good idea to use the
10771 @code{set variable} command instead of just @code{set}. For example, if
10772 your program has a variable @code{g}, you run into problems if you try
10773 to set a new value with just @samp{set g=4}, because @value{GDBN} has
10774 the command @code{set gnutarget}, abbreviated @code{set g}:
10778 (@value{GDBP}) whatis g
10782 (@value{GDBP}) set g=4
10786 The program being debugged has been started already.
10787 Start it from the beginning? (y or n) y
10788 Starting program: /home/smith/cc_progs/a.out
10789 "/home/smith/cc_progs/a.out": can't open to read symbols:
10790 Invalid bfd target.
10791 (@value{GDBP}) show g
10792 The current BFD target is "=4".
10797 The program variable @code{g} did not change, and you silently set the
10798 @code{gnutarget} to an invalid value. In order to set the variable
10802 (@value{GDBP}) set var g=4
10805 @value{GDBN} allows more implicit conversions in assignments than C; you can
10806 freely store an integer value into a pointer variable or vice versa,
10807 and you can convert any structure to any other structure that is the
10808 same length or shorter.
10809 @comment FIXME: how do structs align/pad in these conversions?
10810 @comment /doc@cygnus.com 18dec1990
10812 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
10813 construct to generate a value of specified type at a specified address
10814 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
10815 to memory location @code{0x83040} as an integer (which implies a certain size
10816 and representation in memory), and
10819 set @{int@}0x83040 = 4
10823 stores the value 4 into that memory location.
10826 @section Continuing at a different address
10828 Ordinarily, when you continue your program, you do so at the place where
10829 it stopped, with the @code{continue} command. You can instead continue at
10830 an address of your own choosing, with the following commands:
10834 @item jump @var{linespec}
10835 Resume execution at line @var{linespec}. Execution stops again
10836 immediately if there is a breakpoint there. @xref{List, ,Printing
10837 source lines}, for a description of the different forms of
10838 @var{linespec}. It is common practice to use the @code{tbreak} command
10839 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
10842 The @code{jump} command does not change the current stack frame, or
10843 the stack pointer, or the contents of any memory location or any
10844 register other than the program counter. If line @var{linespec} is in
10845 a different function from the one currently executing, the results may
10846 be bizarre if the two functions expect different patterns of arguments or
10847 of local variables. For this reason, the @code{jump} command requests
10848 confirmation if the specified line is not in the function currently
10849 executing. However, even bizarre results are predictable if you are
10850 well acquainted with the machine-language code of your program.
10852 @item jump *@var{address}
10853 Resume execution at the instruction at address @var{address}.
10856 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
10857 On many systems, you can get much the same effect as the @code{jump}
10858 command by storing a new value into the register @code{$pc}. The
10859 difference is that this does not start your program running; it only
10860 changes the address of where it @emph{will} run when you continue. For
10868 makes the next @code{continue} command or stepping command execute at
10869 address @code{0x485}, rather than at the address where your program stopped.
10870 @xref{Continuing and Stepping, ,Continuing and stepping}.
10872 The most common occasion to use the @code{jump} command is to back
10873 up---perhaps with more breakpoints set---over a portion of a program
10874 that has already executed, in order to examine its execution in more
10879 @section Giving your program a signal
10880 @cindex deliver a signal to a program
10884 @item signal @var{signal}
10885 Resume execution where your program stopped, but immediately give it the
10886 signal @var{signal}. @var{signal} can be the name or the number of a
10887 signal. For example, on many systems @code{signal 2} and @code{signal
10888 SIGINT} are both ways of sending an interrupt signal.
10890 Alternatively, if @var{signal} is zero, continue execution without
10891 giving a signal. This is useful when your program stopped on account of
10892 a signal and would ordinary see the signal when resumed with the
10893 @code{continue} command; @samp{signal 0} causes it to resume without a
10896 @code{signal} does not repeat when you press @key{RET} a second time
10897 after executing the command.
10901 Invoking the @code{signal} command is not the same as invoking the
10902 @code{kill} utility from the shell. Sending a signal with @code{kill}
10903 causes @value{GDBN} to decide what to do with the signal depending on
10904 the signal handling tables (@pxref{Signals}). The @code{signal} command
10905 passes the signal directly to your program.
10909 @section Returning from a function
10912 @cindex returning from a function
10915 @itemx return @var{expression}
10916 You can cancel execution of a function call with the @code{return}
10917 command. If you give an
10918 @var{expression} argument, its value is used as the function's return
10922 When you use @code{return}, @value{GDBN} discards the selected stack frame
10923 (and all frames within it). You can think of this as making the
10924 discarded frame return prematurely. If you wish to specify a value to
10925 be returned, give that value as the argument to @code{return}.
10927 This pops the selected stack frame (@pxref{Selection, ,Selecting a
10928 frame}), and any other frames inside of it, leaving its caller as the
10929 innermost remaining frame. That frame becomes selected. The
10930 specified value is stored in the registers used for returning values
10933 The @code{return} command does not resume execution; it leaves the
10934 program stopped in the state that would exist if the function had just
10935 returned. In contrast, the @code{finish} command (@pxref{Continuing
10936 and Stepping, ,Continuing and stepping}) resumes execution until the
10937 selected stack frame returns naturally.
10940 @section Calling program functions
10943 @cindex calling functions
10944 @cindex inferior functions, calling
10945 @item print @var{expr}
10946 Evaluate the expression @var{expr} and display the resuling value.
10947 @var{expr} may include calls to functions in the program being
10951 @item call @var{expr}
10952 Evaluate the expression @var{expr} without displaying @code{void}
10955 You can use this variant of the @code{print} command if you want to
10956 execute a function from your program that does not return anything
10957 (a.k.a.@: @dfn{a void function}), but without cluttering the output
10958 with @code{void} returned values that @value{GDBN} will otherwise
10959 print. If the result is not void, it is printed and saved in the
10963 It is possible for the function you call via the @code{print} or
10964 @code{call} command to generate a signal (e.g., if there's a bug in
10965 the function, or if you passed it incorrect arguments). What happens
10966 in that case is controlled by the @code{set unwindonsignal} command.
10969 @item set unwindonsignal
10970 @kindex set unwindonsignal
10971 @cindex unwind stack in called functions
10972 @cindex call dummy stack unwinding
10973 Set unwinding of the stack if a signal is received while in a function
10974 that @value{GDBN} called in the program being debugged. If set to on,
10975 @value{GDBN} unwinds the stack it created for the call and restores
10976 the context to what it was before the call. If set to off (the
10977 default), @value{GDBN} stops in the frame where the signal was
10980 @item show unwindonsignal
10981 @kindex show unwindonsignal
10982 Show the current setting of stack unwinding in the functions called by
10986 @cindex weak alias functions
10987 Sometimes, a function you wish to call is actually a @dfn{weak alias}
10988 for another function. In such case, @value{GDBN} might not pick up
10989 the type information, including the types of the function arguments,
10990 which causes @value{GDBN} to call the inferior function incorrectly.
10991 As a result, the called function will function erroneously and may
10992 even crash. A solution to that is to use the name of the aliased
10996 @section Patching programs
10998 @cindex patching binaries
10999 @cindex writing into executables
11000 @cindex writing into corefiles
11002 By default, @value{GDBN} opens the file containing your program's
11003 executable code (or the corefile) read-only. This prevents accidental
11004 alterations to machine code; but it also prevents you from intentionally
11005 patching your program's binary.
11007 If you'd like to be able to patch the binary, you can specify that
11008 explicitly with the @code{set write} command. For example, you might
11009 want to turn on internal debugging flags, or even to make emergency
11015 @itemx set write off
11016 If you specify @samp{set write on}, @value{GDBN} opens executable and
11017 core files for both reading and writing; if you specify @samp{set write
11018 off} (the default), @value{GDBN} opens them read-only.
11020 If you have already loaded a file, you must load it again (using the
11021 @code{exec-file} or @code{core-file} command) after changing @code{set
11022 write}, for your new setting to take effect.
11026 Display whether executable files and core files are opened for writing
11027 as well as reading.
11031 @chapter @value{GDBN} Files
11033 @value{GDBN} needs to know the file name of the program to be debugged,
11034 both in order to read its symbol table and in order to start your
11035 program. To debug a core dump of a previous run, you must also tell
11036 @value{GDBN} the name of the core dump file.
11039 * Files:: Commands to specify files
11040 * Separate Debug Files:: Debugging information in separate files
11041 * Symbol Errors:: Errors reading symbol files
11045 @section Commands to specify files
11047 @cindex symbol table
11048 @cindex core dump file
11050 You may want to specify executable and core dump file names. The usual
11051 way to do this is at start-up time, using the arguments to
11052 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
11053 Out of @value{GDBN}}).
11055 Occasionally it is necessary to change to a different file during a
11056 @value{GDBN} session. Or you may run @value{GDBN} and forget to
11057 specify a file you want to use. Or you are debugging a remote target
11058 via @code{gdbserver} (@pxref{Server, file}). In these situations the
11059 @value{GDBN} commands to specify new files are useful.
11062 @cindex executable file
11064 @item file @var{filename}
11065 Use @var{filename} as the program to be debugged. It is read for its
11066 symbols and for the contents of pure memory. It is also the program
11067 executed when you use the @code{run} command. If you do not specify a
11068 directory and the file is not found in the @value{GDBN} working directory,
11069 @value{GDBN} uses the environment variable @code{PATH} as a list of
11070 directories to search, just as the shell does when looking for a program
11071 to run. You can change the value of this variable, for both @value{GDBN}
11072 and your program, using the @code{path} command.
11074 @cindex unlinked object files
11075 @cindex patching object files
11076 You can load unlinked object @file{.o} files into @value{GDBN} using
11077 the @code{file} command. You will not be able to ``run'' an object
11078 file, but you can disassemble functions and inspect variables. Also,
11079 if the underlying BFD functionality supports it, you could use
11080 @kbd{gdb -write} to patch object files using this technique. Note
11081 that @value{GDBN} can neither interpret nor modify relocations in this
11082 case, so branches and some initialized variables will appear to go to
11083 the wrong place. But this feature is still handy from time to time.
11086 @code{file} with no argument makes @value{GDBN} discard any information it
11087 has on both executable file and the symbol table.
11090 @item exec-file @r{[} @var{filename} @r{]}
11091 Specify that the program to be run (but not the symbol table) is found
11092 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
11093 if necessary to locate your program. Omitting @var{filename} means to
11094 discard information on the executable file.
11096 @kindex symbol-file
11097 @item symbol-file @r{[} @var{filename} @r{]}
11098 Read symbol table information from file @var{filename}. @code{PATH} is
11099 searched when necessary. Use the @code{file} command to get both symbol
11100 table and program to run from the same file.
11102 @code{symbol-file} with no argument clears out @value{GDBN} information on your
11103 program's symbol table.
11105 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
11106 some breakpoints and auto-display expressions. This is because they may
11107 contain pointers to the internal data recording symbols and data types,
11108 which are part of the old symbol table data being discarded inside
11111 @code{symbol-file} does not repeat if you press @key{RET} again after
11114 When @value{GDBN} is configured for a particular environment, it
11115 understands debugging information in whatever format is the standard
11116 generated for that environment; you may use either a @sc{gnu} compiler, or
11117 other compilers that adhere to the local conventions.
11118 Best results are usually obtained from @sc{gnu} compilers; for example,
11119 using @code{@value{GCC}} you can generate debugging information for
11122 For most kinds of object files, with the exception of old SVR3 systems
11123 using COFF, the @code{symbol-file} command does not normally read the
11124 symbol table in full right away. Instead, it scans the symbol table
11125 quickly to find which source files and which symbols are present. The
11126 details are read later, one source file at a time, as they are needed.
11128 The purpose of this two-stage reading strategy is to make @value{GDBN}
11129 start up faster. For the most part, it is invisible except for
11130 occasional pauses while the symbol table details for a particular source
11131 file are being read. (The @code{set verbose} command can turn these
11132 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
11133 warnings and messages}.)
11135 We have not implemented the two-stage strategy for COFF yet. When the
11136 symbol table is stored in COFF format, @code{symbol-file} reads the
11137 symbol table data in full right away. Note that ``stabs-in-COFF''
11138 still does the two-stage strategy, since the debug info is actually
11142 @cindex reading symbols immediately
11143 @cindex symbols, reading immediately
11144 @item symbol-file @var{filename} @r{[} -readnow @r{]}
11145 @itemx file @var{filename} @r{[} -readnow @r{]}
11146 You can override the @value{GDBN} two-stage strategy for reading symbol
11147 tables by using the @samp{-readnow} option with any of the commands that
11148 load symbol table information, if you want to be sure @value{GDBN} has the
11149 entire symbol table available.
11151 @c FIXME: for now no mention of directories, since this seems to be in
11152 @c flux. 13mar1992 status is that in theory GDB would look either in
11153 @c current dir or in same dir as myprog; but issues like competing
11154 @c GDB's, or clutter in system dirs, mean that in practice right now
11155 @c only current dir is used. FFish says maybe a special GDB hierarchy
11156 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
11160 @item core-file @r{[}@var{filename}@r{]}
11162 Specify the whereabouts of a core dump file to be used as the ``contents
11163 of memory''. Traditionally, core files contain only some parts of the
11164 address space of the process that generated them; @value{GDBN} can access the
11165 executable file itself for other parts.
11167 @code{core-file} with no argument specifies that no core file is
11170 Note that the core file is ignored when your program is actually running
11171 under @value{GDBN}. So, if you have been running your program and you
11172 wish to debug a core file instead, you must kill the subprocess in which
11173 the program is running. To do this, use the @code{kill} command
11174 (@pxref{Kill Process, ,Killing the child process}).
11176 @kindex add-symbol-file
11177 @cindex dynamic linking
11178 @item add-symbol-file @var{filename} @var{address}
11179 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
11180 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
11181 The @code{add-symbol-file} command reads additional symbol table
11182 information from the file @var{filename}. You would use this command
11183 when @var{filename} has been dynamically loaded (by some other means)
11184 into the program that is running. @var{address} should be the memory
11185 address at which the file has been loaded; @value{GDBN} cannot figure
11186 this out for itself. You can additionally specify an arbitrary number
11187 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
11188 section name and base address for that section. You can specify any
11189 @var{address} as an expression.
11191 The symbol table of the file @var{filename} is added to the symbol table
11192 originally read with the @code{symbol-file} command. You can use the
11193 @code{add-symbol-file} command any number of times; the new symbol data
11194 thus read keeps adding to the old. To discard all old symbol data
11195 instead, use the @code{symbol-file} command without any arguments.
11197 @cindex relocatable object files, reading symbols from
11198 @cindex object files, relocatable, reading symbols from
11199 @cindex reading symbols from relocatable object files
11200 @cindex symbols, reading from relocatable object files
11201 @cindex @file{.o} files, reading symbols from
11202 Although @var{filename} is typically a shared library file, an
11203 executable file, or some other object file which has been fully
11204 relocated for loading into a process, you can also load symbolic
11205 information from relocatable @file{.o} files, as long as:
11209 the file's symbolic information refers only to linker symbols defined in
11210 that file, not to symbols defined by other object files,
11212 every section the file's symbolic information refers to has actually
11213 been loaded into the inferior, as it appears in the file, and
11215 you can determine the address at which every section was loaded, and
11216 provide these to the @code{add-symbol-file} command.
11220 Some embedded operating systems, like Sun Chorus and VxWorks, can load
11221 relocatable files into an already running program; such systems
11222 typically make the requirements above easy to meet. However, it's
11223 important to recognize that many native systems use complex link
11224 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
11225 assembly, for example) that make the requirements difficult to meet. In
11226 general, one cannot assume that using @code{add-symbol-file} to read a
11227 relocatable object file's symbolic information will have the same effect
11228 as linking the relocatable object file into the program in the normal
11231 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
11233 @kindex add-symbol-file-from-memory
11234 @cindex @code{syscall DSO}
11235 @cindex load symbols from memory
11236 @item add-symbol-file-from-memory @var{address}
11237 Load symbols from the given @var{address} in a dynamically loaded
11238 object file whose image is mapped directly into the inferior's memory.
11239 For example, the Linux kernel maps a @code{syscall DSO} into each
11240 process's address space; this DSO provides kernel-specific code for
11241 some system calls. The argument can be any expression whose
11242 evaluation yields the address of the file's shared object file header.
11243 For this command to work, you must have used @code{symbol-file} or
11244 @code{exec-file} commands in advance.
11246 @kindex add-shared-symbol-files
11248 @item add-shared-symbol-files @var{library-file}
11249 @itemx assf @var{library-file}
11250 The @code{add-shared-symbol-files} command can currently be used only
11251 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
11252 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
11253 @value{GDBN} automatically looks for shared libraries, however if
11254 @value{GDBN} does not find yours, you can invoke
11255 @code{add-shared-symbol-files}. It takes one argument: the shared
11256 library's file name. @code{assf} is a shorthand alias for
11257 @code{add-shared-symbol-files}.
11260 @item section @var{section} @var{addr}
11261 The @code{section} command changes the base address of the named
11262 @var{section} of the exec file to @var{addr}. This can be used if the
11263 exec file does not contain section addresses, (such as in the
11264 @code{a.out} format), or when the addresses specified in the file
11265 itself are wrong. Each section must be changed separately. The
11266 @code{info files} command, described below, lists all the sections and
11270 @kindex info target
11273 @code{info files} and @code{info target} are synonymous; both print the
11274 current target (@pxref{Targets, ,Specifying a Debugging Target}),
11275 including the names of the executable and core dump files currently in
11276 use by @value{GDBN}, and the files from which symbols were loaded. The
11277 command @code{help target} lists all possible targets rather than
11280 @kindex maint info sections
11281 @item maint info sections
11282 Another command that can give you extra information about program sections
11283 is @code{maint info sections}. In addition to the section information
11284 displayed by @code{info files}, this command displays the flags and file
11285 offset of each section in the executable and core dump files. In addition,
11286 @code{maint info sections} provides the following command options (which
11287 may be arbitrarily combined):
11291 Display sections for all loaded object files, including shared libraries.
11292 @item @var{sections}
11293 Display info only for named @var{sections}.
11294 @item @var{section-flags}
11295 Display info only for sections for which @var{section-flags} are true.
11296 The section flags that @value{GDBN} currently knows about are:
11299 Section will have space allocated in the process when loaded.
11300 Set for all sections except those containing debug information.
11302 Section will be loaded from the file into the child process memory.
11303 Set for pre-initialized code and data, clear for @code{.bss} sections.
11305 Section needs to be relocated before loading.
11307 Section cannot be modified by the child process.
11309 Section contains executable code only.
11311 Section contains data only (no executable code).
11313 Section will reside in ROM.
11315 Section contains data for constructor/destructor lists.
11317 Section is not empty.
11319 An instruction to the linker to not output the section.
11320 @item COFF_SHARED_LIBRARY
11321 A notification to the linker that the section contains
11322 COFF shared library information.
11324 Section contains common symbols.
11327 @kindex set trust-readonly-sections
11328 @cindex read-only sections
11329 @item set trust-readonly-sections on
11330 Tell @value{GDBN} that readonly sections in your object file
11331 really are read-only (i.e.@: that their contents will not change).
11332 In that case, @value{GDBN} can fetch values from these sections
11333 out of the object file, rather than from the target program.
11334 For some targets (notably embedded ones), this can be a significant
11335 enhancement to debugging performance.
11337 The default is off.
11339 @item set trust-readonly-sections off
11340 Tell @value{GDBN} not to trust readonly sections. This means that
11341 the contents of the section might change while the program is running,
11342 and must therefore be fetched from the target when needed.
11344 @item show trust-readonly-sections
11345 Show the current setting of trusting readonly sections.
11348 All file-specifying commands allow both absolute and relative file names
11349 as arguments. @value{GDBN} always converts the file name to an absolute file
11350 name and remembers it that way.
11352 @cindex shared libraries
11353 @value{GDBN} supports GNU/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
11354 and IBM RS/6000 AIX shared libraries.
11356 @value{GDBN} automatically loads symbol definitions from shared libraries
11357 when you use the @code{run} command, or when you examine a core file.
11358 (Before you issue the @code{run} command, @value{GDBN} does not understand
11359 references to a function in a shared library, however---unless you are
11360 debugging a core file).
11362 On HP-UX, if the program loads a library explicitly, @value{GDBN}
11363 automatically loads the symbols at the time of the @code{shl_load} call.
11365 @c FIXME: some @value{GDBN} release may permit some refs to undef
11366 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
11367 @c FIXME...lib; check this from time to time when updating manual
11369 There are times, however, when you may wish to not automatically load
11370 symbol definitions from shared libraries, such as when they are
11371 particularly large or there are many of them.
11373 To control the automatic loading of shared library symbols, use the
11377 @kindex set auto-solib-add
11378 @item set auto-solib-add @var{mode}
11379 If @var{mode} is @code{on}, symbols from all shared object libraries
11380 will be loaded automatically when the inferior begins execution, you
11381 attach to an independently started inferior, or when the dynamic linker
11382 informs @value{GDBN} that a new library has been loaded. If @var{mode}
11383 is @code{off}, symbols must be loaded manually, using the
11384 @code{sharedlibrary} command. The default value is @code{on}.
11386 @cindex memory used for symbol tables
11387 If your program uses lots of shared libraries with debug info that
11388 takes large amounts of memory, you can decrease the @value{GDBN}
11389 memory footprint by preventing it from automatically loading the
11390 symbols from shared libraries. To that end, type @kbd{set
11391 auto-solib-add off} before running the inferior, then load each
11392 library whose debug symbols you do need with @kbd{sharedlibrary
11393 @var{regexp}}, where @var{regexp} is a regular expresion that matches
11394 the libraries whose symbols you want to be loaded.
11396 @kindex show auto-solib-add
11397 @item show auto-solib-add
11398 Display the current autoloading mode.
11401 @cindex load shared library
11402 To explicitly load shared library symbols, use the @code{sharedlibrary}
11406 @kindex info sharedlibrary
11409 @itemx info sharedlibrary
11410 Print the names of the shared libraries which are currently loaded.
11412 @kindex sharedlibrary
11414 @item sharedlibrary @var{regex}
11415 @itemx share @var{regex}
11416 Load shared object library symbols for files matching a
11417 Unix regular expression.
11418 As with files loaded automatically, it only loads shared libraries
11419 required by your program for a core file or after typing @code{run}. If
11420 @var{regex} is omitted all shared libraries required by your program are
11423 @item nosharedlibrary
11424 @kindex nosharedlibrary
11425 @cindex unload symbols from shared libraries
11426 Unload all shared object library symbols. This discards all symbols
11427 that have been loaded from all shared libraries. Symbols from shared
11428 libraries that were loaded by explicit user requests are not
11432 Sometimes you may wish that @value{GDBN} stops and gives you control
11433 when any of shared library events happen. Use the @code{set
11434 stop-on-solib-events} command for this:
11437 @item set stop-on-solib-events
11438 @kindex set stop-on-solib-events
11439 This command controls whether @value{GDBN} should give you control
11440 when the dynamic linker notifies it about some shared library event.
11441 The most common event of interest is loading or unloading of a new
11444 @item show stop-on-solib-events
11445 @kindex show stop-on-solib-events
11446 Show whether @value{GDBN} stops and gives you control when shared
11447 library events happen.
11450 Shared libraries are also supported in many cross or remote debugging
11451 configurations. A copy of the target's libraries need to be present on the
11452 host system; they need to be the same as the target libraries, although the
11453 copies on the target can be stripped as long as the copies on the host are
11456 @cindex where to look for shared libraries
11457 For remote debugging, you need to tell @value{GDBN} where the target
11458 libraries are, so that it can load the correct copies---otherwise, it
11459 may try to load the host's libraries. @value{GDBN} has two variables
11460 to specify the search directories for target libraries.
11463 @cindex prefix for shared library file names
11464 @kindex set solib-absolute-prefix
11465 @item set solib-absolute-prefix @var{path}
11466 If this variable is set, @var{path} will be used as a prefix for any
11467 absolute shared library paths; many runtime loaders store the absolute
11468 paths to the shared library in the target program's memory. If you use
11469 @samp{solib-absolute-prefix} to find shared libraries, they need to be laid
11470 out in the same way that they are on the target, with e.g.@: a
11471 @file{/usr/lib} hierarchy under @var{path}.
11473 @cindex default value of @samp{solib-absolute-prefix}
11474 @cindex @samp{--with-sysroot}
11475 You can set the default value of @samp{solib-absolute-prefix} by using the
11476 configure-time @samp{--with-sysroot} option.
11478 @kindex show solib-absolute-prefix
11479 @item show solib-absolute-prefix
11480 Display the current shared library prefix.
11482 @kindex set solib-search-path
11483 @item set solib-search-path @var{path}
11484 If this variable is set, @var{path} is a colon-separated list of directories
11485 to search for shared libraries. @samp{solib-search-path} is used after
11486 @samp{solib-absolute-prefix} fails to locate the library, or if the path to
11487 the library is relative instead of absolute. If you want to use
11488 @samp{solib-search-path} instead of @samp{solib-absolute-prefix}, be sure to
11489 set @samp{solib-absolute-prefix} to a nonexistant directory to prevent
11490 @value{GDBN} from finding your host's libraries.
11492 @kindex show solib-search-path
11493 @item show solib-search-path
11494 Display the current shared library search path.
11498 @node Separate Debug Files
11499 @section Debugging Information in Separate Files
11500 @cindex separate debugging information files
11501 @cindex debugging information in separate files
11502 @cindex @file{.debug} subdirectories
11503 @cindex debugging information directory, global
11504 @cindex global debugging information directory
11506 @value{GDBN} allows you to put a program's debugging information in a
11507 file separate from the executable itself, in a way that allows
11508 @value{GDBN} to find and load the debugging information automatically.
11509 Since debugging information can be very large --- sometimes larger
11510 than the executable code itself --- some systems distribute debugging
11511 information for their executables in separate files, which users can
11512 install only when they need to debug a problem.
11514 If an executable's debugging information has been extracted to a
11515 separate file, the executable should contain a @dfn{debug link} giving
11516 the name of the debugging information file (with no directory
11517 components), and a checksum of its contents. (The exact form of a
11518 debug link is described below.) If the full name of the directory
11519 containing the executable is @var{execdir}, and the executable has a
11520 debug link that specifies the name @var{debugfile}, then @value{GDBN}
11521 will automatically search for the debugging information file in three
11526 the directory containing the executable file (that is, it will look
11527 for a file named @file{@var{execdir}/@var{debugfile}},
11529 a subdirectory of that directory named @file{.debug} (that is, the
11530 file @file{@var{execdir}/.debug/@var{debugfile}}, and
11532 a subdirectory of the global debug file directory that includes the
11533 executable's full path, and the name from the link (that is, the file
11534 @file{@var{globaldebugdir}/@var{execdir}/@var{debugfile}}, where
11535 @var{globaldebugdir} is the global debug file directory, and
11536 @var{execdir} has been turned into a relative path).
11539 @value{GDBN} checks under each of these names for a debugging
11540 information file whose checksum matches that given in the link, and
11541 reads the debugging information from the first one it finds.
11543 So, for example, if you ask @value{GDBN} to debug @file{/usr/bin/ls},
11544 which has a link containing the name @file{ls.debug}, and the global
11545 debug directory is @file{/usr/lib/debug}, then @value{GDBN} will look
11546 for debug information in @file{/usr/bin/ls.debug},
11547 @file{/usr/bin/.debug/ls.debug}, and
11548 @file{/usr/lib/debug/usr/bin/ls.debug}.
11550 You can set the global debugging info directory's name, and view the
11551 name @value{GDBN} is currently using.
11555 @kindex set debug-file-directory
11556 @item set debug-file-directory @var{directory}
11557 Set the directory which @value{GDBN} searches for separate debugging
11558 information files to @var{directory}.
11560 @kindex show debug-file-directory
11561 @item show debug-file-directory
11562 Show the directory @value{GDBN} searches for separate debugging
11567 @cindex @code{.gnu_debuglink} sections
11568 @cindex debug links
11569 A debug link is a special section of the executable file named
11570 @code{.gnu_debuglink}. The section must contain:
11574 A filename, with any leading directory components removed, followed by
11577 zero to three bytes of padding, as needed to reach the next four-byte
11578 boundary within the section, and
11580 a four-byte CRC checksum, stored in the same endianness used for the
11581 executable file itself. The checksum is computed on the debugging
11582 information file's full contents by the function given below, passing
11583 zero as the @var{crc} argument.
11586 Any executable file format can carry a debug link, as long as it can
11587 contain a section named @code{.gnu_debuglink} with the contents
11590 The debugging information file itself should be an ordinary
11591 executable, containing a full set of linker symbols, sections, and
11592 debugging information. The sections of the debugging information file
11593 should have the same names, addresses and sizes as the original file,
11594 but they need not contain any data --- much like a @code{.bss} section
11595 in an ordinary executable.
11597 As of December 2002, there is no standard GNU utility to produce
11598 separated executable / debugging information file pairs. Ulrich
11599 Drepper's @file{elfutils} package, starting with version 0.53,
11600 contains a version of the @code{strip} command such that the command
11601 @kbd{strip foo -f foo.debug} removes the debugging information from
11602 the executable file @file{foo}, places it in the file
11603 @file{foo.debug}, and leaves behind a debug link in @file{foo}.
11605 Since there are many different ways to compute CRC's (different
11606 polynomials, reversals, byte ordering, etc.), the simplest way to
11607 describe the CRC used in @code{.gnu_debuglink} sections is to give the
11608 complete code for a function that computes it:
11610 @kindex gnu_debuglink_crc32
11613 gnu_debuglink_crc32 (unsigned long crc,
11614 unsigned char *buf, size_t len)
11616 static const unsigned long crc32_table[256] =
11618 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
11619 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
11620 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
11621 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
11622 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
11623 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
11624 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
11625 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
11626 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
11627 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
11628 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
11629 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
11630 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
11631 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
11632 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
11633 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
11634 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
11635 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
11636 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
11637 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
11638 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
11639 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
11640 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
11641 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
11642 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
11643 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
11644 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
11645 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
11646 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
11647 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
11648 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
11649 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
11650 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
11651 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
11652 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
11653 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
11654 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
11655 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
11656 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
11657 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
11658 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
11659 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
11660 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
11661 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
11662 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
11663 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
11664 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
11665 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
11666 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
11667 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
11668 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
11671 unsigned char *end;
11673 crc = ~crc & 0xffffffff;
11674 for (end = buf + len; buf < end; ++buf)
11675 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
11676 return ~crc & 0xffffffff;
11681 @node Symbol Errors
11682 @section Errors reading symbol files
11684 While reading a symbol file, @value{GDBN} occasionally encounters problems,
11685 such as symbol types it does not recognize, or known bugs in compiler
11686 output. By default, @value{GDBN} does not notify you of such problems, since
11687 they are relatively common and primarily of interest to people
11688 debugging compilers. If you are interested in seeing information
11689 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
11690 only one message about each such type of problem, no matter how many
11691 times the problem occurs; or you can ask @value{GDBN} to print more messages,
11692 to see how many times the problems occur, with the @code{set
11693 complaints} command (@pxref{Messages/Warnings, ,Optional warnings and
11696 The messages currently printed, and their meanings, include:
11699 @item inner block not inside outer block in @var{symbol}
11701 The symbol information shows where symbol scopes begin and end
11702 (such as at the start of a function or a block of statements). This
11703 error indicates that an inner scope block is not fully contained
11704 in its outer scope blocks.
11706 @value{GDBN} circumvents the problem by treating the inner block as if it had
11707 the same scope as the outer block. In the error message, @var{symbol}
11708 may be shown as ``@code{(don't know)}'' if the outer block is not a
11711 @item block at @var{address} out of order
11713 The symbol information for symbol scope blocks should occur in
11714 order of increasing addresses. This error indicates that it does not
11717 @value{GDBN} does not circumvent this problem, and has trouble
11718 locating symbols in the source file whose symbols it is reading. (You
11719 can often determine what source file is affected by specifying
11720 @code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and
11723 @item bad block start address patched
11725 The symbol information for a symbol scope block has a start address
11726 smaller than the address of the preceding source line. This is known
11727 to occur in the SunOS 4.1.1 (and earlier) C compiler.
11729 @value{GDBN} circumvents the problem by treating the symbol scope block as
11730 starting on the previous source line.
11732 @item bad string table offset in symbol @var{n}
11735 Symbol number @var{n} contains a pointer into the string table which is
11736 larger than the size of the string table.
11738 @value{GDBN} circumvents the problem by considering the symbol to have the
11739 name @code{foo}, which may cause other problems if many symbols end up
11742 @item unknown symbol type @code{0x@var{nn}}
11744 The symbol information contains new data types that @value{GDBN} does
11745 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
11746 uncomprehended information, in hexadecimal.
11748 @value{GDBN} circumvents the error by ignoring this symbol information.
11749 This usually allows you to debug your program, though certain symbols
11750 are not accessible. If you encounter such a problem and feel like
11751 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
11752 on @code{complain}, then go up to the function @code{read_dbx_symtab}
11753 and examine @code{*bufp} to see the symbol.
11755 @item stub type has NULL name
11757 @value{GDBN} could not find the full definition for a struct or class.
11759 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
11760 The symbol information for a C@t{++} member function is missing some
11761 information that recent versions of the compiler should have output for
11764 @item info mismatch between compiler and debugger
11766 @value{GDBN} could not parse a type specification output by the compiler.
11771 @chapter Specifying a Debugging Target
11773 @cindex debugging target
11774 A @dfn{target} is the execution environment occupied by your program.
11776 Often, @value{GDBN} runs in the same host environment as your program;
11777 in that case, the debugging target is specified as a side effect when
11778 you use the @code{file} or @code{core} commands. When you need more
11779 flexibility---for example, running @value{GDBN} on a physically separate
11780 host, or controlling a standalone system over a serial port or a
11781 realtime system over a TCP/IP connection---you can use the @code{target}
11782 command to specify one of the target types configured for @value{GDBN}
11783 (@pxref{Target Commands, ,Commands for managing targets}).
11785 @cindex target architecture
11786 It is possible to build @value{GDBN} for several different @dfn{target
11787 architectures}. When @value{GDBN} is built like that, you can choose
11788 one of the available architectures with the @kbd{set architecture}
11792 @kindex set architecture
11793 @kindex show architecture
11794 @item set architecture @var{arch}
11795 This command sets the current target architecture to @var{arch}. The
11796 value of @var{arch} can be @code{"auto"}, in addition to one of the
11797 supported architectures.
11799 @item show architecture
11800 Show the current target architecture.
11802 @item set processor
11804 @kindex set processor
11805 @kindex show processor
11806 These are alias commands for, respectively, @code{set architecture}
11807 and @code{show architecture}.
11811 * Active Targets:: Active targets
11812 * Target Commands:: Commands for managing targets
11813 * Byte Order:: Choosing target byte order
11814 * Remote:: Remote debugging
11815 * KOD:: Kernel Object Display
11819 @node Active Targets
11820 @section Active targets
11822 @cindex stacking targets
11823 @cindex active targets
11824 @cindex multiple targets
11826 There are three classes of targets: processes, core files, and
11827 executable files. @value{GDBN} can work concurrently on up to three
11828 active targets, one in each class. This allows you to (for example)
11829 start a process and inspect its activity without abandoning your work on
11832 For example, if you execute @samp{gdb a.out}, then the executable file
11833 @code{a.out} is the only active target. If you designate a core file as
11834 well---presumably from a prior run that crashed and coredumped---then
11835 @value{GDBN} has two active targets and uses them in tandem, looking
11836 first in the corefile target, then in the executable file, to satisfy
11837 requests for memory addresses. (Typically, these two classes of target
11838 are complementary, since core files contain only a program's
11839 read-write memory---variables and so on---plus machine status, while
11840 executable files contain only the program text and initialized data.)
11842 When you type @code{run}, your executable file becomes an active process
11843 target as well. When a process target is active, all @value{GDBN}
11844 commands requesting memory addresses refer to that target; addresses in
11845 an active core file or executable file target are obscured while the
11846 process target is active.
11848 Use the @code{core-file} and @code{exec-file} commands to select a new
11849 core file or executable target (@pxref{Files, ,Commands to specify
11850 files}). To specify as a target a process that is already running, use
11851 the @code{attach} command (@pxref{Attach, ,Debugging an already-running
11854 @node Target Commands
11855 @section Commands for managing targets
11858 @item target @var{type} @var{parameters}
11859 Connects the @value{GDBN} host environment to a target machine or
11860 process. A target is typically a protocol for talking to debugging
11861 facilities. You use the argument @var{type} to specify the type or
11862 protocol of the target machine.
11864 Further @var{parameters} are interpreted by the target protocol, but
11865 typically include things like device names or host names to connect
11866 with, process numbers, and baud rates.
11868 The @code{target} command does not repeat if you press @key{RET} again
11869 after executing the command.
11871 @kindex help target
11873 Displays the names of all targets available. To display targets
11874 currently selected, use either @code{info target} or @code{info files}
11875 (@pxref{Files, ,Commands to specify files}).
11877 @item help target @var{name}
11878 Describe a particular target, including any parameters necessary to
11881 @kindex set gnutarget
11882 @item set gnutarget @var{args}
11883 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
11884 knows whether it is reading an @dfn{executable},
11885 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
11886 with the @code{set gnutarget} command. Unlike most @code{target} commands,
11887 with @code{gnutarget} the @code{target} refers to a program, not a machine.
11890 @emph{Warning:} To specify a file format with @code{set gnutarget},
11891 you must know the actual BFD name.
11895 @xref{Files, , Commands to specify files}.
11897 @kindex show gnutarget
11898 @item show gnutarget
11899 Use the @code{show gnutarget} command to display what file format
11900 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
11901 @value{GDBN} will determine the file format for each file automatically,
11902 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
11905 @cindex common targets
11906 Here are some common targets (available, or not, depending on the GDB
11911 @item target exec @var{program}
11912 @cindex executable file target
11913 An executable file. @samp{target exec @var{program}} is the same as
11914 @samp{exec-file @var{program}}.
11916 @item target core @var{filename}
11917 @cindex core dump file target
11918 A core dump file. @samp{target core @var{filename}} is the same as
11919 @samp{core-file @var{filename}}.
11921 @item target remote @var{medium}
11922 @cindex remote target
11923 A remote system connected to @value{GDBN} via a serial line or network
11924 connection. This command tells @value{GDBN} to use its own remote
11925 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
11927 For example, if you have a board connected to @file{/dev/ttya} on the
11928 machine running @value{GDBN}, you could say:
11931 target remote /dev/ttya
11934 @code{target remote} supports the @code{load} command. This is only
11935 useful if you have some other way of getting the stub to the target
11936 system, and you can put it somewhere in memory where it won't get
11937 clobbered by the download.
11940 @cindex built-in simulator target
11941 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
11949 works; however, you cannot assume that a specific memory map, device
11950 drivers, or even basic I/O is available, although some simulators do
11951 provide these. For info about any processor-specific simulator details,
11952 see the appropriate section in @ref{Embedded Processors, ,Embedded
11957 Some configurations may include these targets as well:
11961 @item target nrom @var{dev}
11962 @cindex NetROM ROM emulator target
11963 NetROM ROM emulator. This target only supports downloading.
11967 Different targets are available on different configurations of @value{GDBN};
11968 your configuration may have more or fewer targets.
11970 Many remote targets require you to download the executable's code once
11971 you've successfully established a connection. You may wish to control
11972 various aspects of this process, such as the size of the data chunks
11973 used by @value{GDBN} to download program parts to the remote target.
11976 @kindex set download-write-size
11977 @item set download-write-size @var{size}
11978 Set the write size used when downloading a program. Only used when
11979 downloading a program onto a remote target. Specify zero or a
11980 negative value to disable blocked writes. The actual size of each
11981 transfer is also limited by the size of the target packet and the
11984 @kindex show download-write-size
11985 @item show download-write-size
11986 @kindex show download-write-size
11987 Show the current value of the write size.
11990 @kindex set hash@r{, for remote monitors}
11991 @cindex hash mark while downloading
11992 This command controls whether a hash mark @samp{#} is displayed while
11993 downloading a file to the remote monitor. If on, a hash mark is
11994 displayed after each S-record is successfully downloaded to the
11998 @kindex show hash@r{, for remote monitors}
11999 Show the current status of displaying the hash mark.
12001 @item set debug monitor
12002 @kindex set debug monitor
12003 @cindex display remote monitor communications
12004 Enable or disable display of communications messages between
12005 @value{GDBN} and the remote monitor.
12007 @item show debug monitor
12008 @kindex show debug monitor
12009 Show the current status of displaying communications between
12010 @value{GDBN} and the remote monitor.
12015 @kindex load @var{filename}
12016 @item load @var{filename}
12017 Depending on what remote debugging facilities are configured into
12018 @value{GDBN}, the @code{load} command may be available. Where it exists, it
12019 is meant to make @var{filename} (an executable) available for debugging
12020 on the remote system---by downloading, or dynamic linking, for example.
12021 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
12022 the @code{add-symbol-file} command.
12024 If your @value{GDBN} does not have a @code{load} command, attempting to
12025 execute it gets the error message ``@code{You can't do that when your
12026 target is @dots{}}''
12028 The file is loaded at whatever address is specified in the executable.
12029 For some object file formats, you can specify the load address when you
12030 link the program; for other formats, like a.out, the object file format
12031 specifies a fixed address.
12032 @c FIXME! This would be a good place for an xref to the GNU linker doc.
12034 @code{load} does not repeat if you press @key{RET} again after using it.
12038 @section Choosing target byte order
12040 @cindex choosing target byte order
12041 @cindex target byte order
12043 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
12044 offer the ability to run either big-endian or little-endian byte
12045 orders. Usually the executable or symbol will include a bit to
12046 designate the endian-ness, and you will not need to worry about
12047 which to use. However, you may still find it useful to adjust
12048 @value{GDBN}'s idea of processor endian-ness manually.
12052 @item set endian big
12053 Instruct @value{GDBN} to assume the target is big-endian.
12055 @item set endian little
12056 Instruct @value{GDBN} to assume the target is little-endian.
12058 @item set endian auto
12059 Instruct @value{GDBN} to use the byte order associated with the
12063 Display @value{GDBN}'s current idea of the target byte order.
12067 Note that these commands merely adjust interpretation of symbolic
12068 data on the host, and that they have absolutely no effect on the
12072 @section Remote debugging
12073 @cindex remote debugging
12075 If you are trying to debug a program running on a machine that cannot run
12076 @value{GDBN} in the usual way, it is often useful to use remote debugging.
12077 For example, you might use remote debugging on an operating system kernel,
12078 or on a small system which does not have a general purpose operating system
12079 powerful enough to run a full-featured debugger.
12081 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
12082 to make this work with particular debugging targets. In addition,
12083 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
12084 but not specific to any particular target system) which you can use if you
12085 write the remote stubs---the code that runs on the remote system to
12086 communicate with @value{GDBN}.
12088 Other remote targets may be available in your
12089 configuration of @value{GDBN}; use @code{help target} to list them.
12091 Once you've connected to the remote target, @value{GDBN} allows you to
12092 send arbitrary commands to the remote monitor:
12095 @item remote @var{command}
12096 @kindex remote@r{, a command}
12097 @cindex send command to remote monitor
12098 Send an arbitrary @var{command} string to the remote monitor.
12103 @section Kernel Object Display
12104 @cindex kernel object display
12107 Some targets support kernel object display. Using this facility,
12108 @value{GDBN} communicates specially with the underlying operating system
12109 and can display information about operating system-level objects such as
12110 mutexes and other synchronization objects. Exactly which objects can be
12111 displayed is determined on a per-OS basis.
12114 Use the @code{set os} command to set the operating system. This tells
12115 @value{GDBN} which kernel object display module to initialize:
12118 (@value{GDBP}) set os cisco
12122 The associated command @code{show os} displays the operating system
12123 set with the @code{set os} command; if no operating system has been
12124 set, @code{show os} will display an empty string @samp{""}.
12126 If @code{set os} succeeds, @value{GDBN} will display some information
12127 about the operating system, and will create a new @code{info} command
12128 which can be used to query the target. The @code{info} command is named
12129 after the operating system:
12133 (@value{GDBP}) info cisco
12134 List of Cisco Kernel Objects
12136 any Any and all objects
12139 Further subcommands can be used to query about particular objects known
12142 There is currently no way to determine whether a given operating
12143 system is supported other than to try setting it with @kbd{set os
12144 @var{name}}, where @var{name} is the name of the operating system you
12148 @node Remote Debugging
12149 @chapter Debugging remote programs
12152 * Connecting:: Connecting to a remote target
12153 * Server:: Using the gdbserver program
12154 * Remote configuration:: Remote configuration
12155 * remote stub:: Implementing a remote stub
12159 @section Connecting to a remote target
12161 On the @value{GDBN} host machine, you will need an unstripped copy of
12162 your program, since @value{GDBN} needs symobl and debugging information.
12163 Start up @value{GDBN} as usual, using the name of the local copy of your
12164 program as the first argument.
12166 @cindex @code{target remote}
12167 @value{GDBN} can communicate with the target over a serial line, or
12168 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
12169 each case, @value{GDBN} uses the same protocol for debugging your
12170 program; only the medium carrying the debugging packets varies. The
12171 @code{target remote} command establishes a connection to the target.
12172 Its arguments indicate which medium to use:
12176 @item target remote @var{serial-device}
12177 @cindex serial line, @code{target remote}
12178 Use @var{serial-device} to communicate with the target. For example,
12179 to use a serial line connected to the device named @file{/dev/ttyb}:
12182 target remote /dev/ttyb
12185 If you're using a serial line, you may want to give @value{GDBN} the
12186 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
12187 (@pxref{Remote configuration, set remotebaud}) before the
12188 @code{target} command.
12190 @item target remote @code{@var{host}:@var{port}}
12191 @itemx target remote @code{tcp:@var{host}:@var{port}}
12192 @cindex @acronym{TCP} port, @code{target remote}
12193 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
12194 The @var{host} may be either a host name or a numeric @acronym{IP}
12195 address; @var{port} must be a decimal number. The @var{host} could be
12196 the target machine itself, if it is directly connected to the net, or
12197 it might be a terminal server which in turn has a serial line to the
12200 For example, to connect to port 2828 on a terminal server named
12204 target remote manyfarms:2828
12207 If your remote target is actually running on the same machine as your
12208 debugger session (e.g.@: a simulator for your target running on the
12209 same host), you can omit the hostname. For example, to connect to
12210 port 1234 on your local machine:
12213 target remote :1234
12217 Note that the colon is still required here.
12219 @item target remote @code{udp:@var{host}:@var{port}}
12220 @cindex @acronym{UDP} port, @code{target remote}
12221 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
12222 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
12225 target remote udp:manyfarms:2828
12228 When using a @acronym{UDP} connection for remote debugging, you should
12229 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
12230 can silently drop packets on busy or unreliable networks, which will
12231 cause havoc with your debugging session.
12233 @item target remote | @var{command}
12234 @cindex pipe, @code{target remote} to
12235 Run @var{command} in the background and communicate with it using a
12236 pipe. The @var{command} is a shell command, to be parsed and expanded
12237 by the system's command shell, @code{/bin/sh}; it should expect remote
12238 protocol packets on its standard input, and send replies on its
12239 standard output. You could use this to run a stand-alone simulator
12240 that speaks the remote debugging protocol, to make net connections
12241 using programs like @code{ssh}, or for other similar tricks.
12243 If @var{command} closes its standard output (perhaps by exiting),
12244 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
12245 program has already exited, this will have no effect.)
12249 Once the connection has been established, you can use all the usual
12250 commands to examine and change data and to step and continue the
12253 @cindex interrupting remote programs
12254 @cindex remote programs, interrupting
12255 Whenever @value{GDBN} is waiting for the remote program, if you type the
12256 interrupt character (often @key{C-C}), @value{GDBN} attempts to stop the
12257 program. This may or may not succeed, depending in part on the hardware
12258 and the serial drivers the remote system uses. If you type the
12259 interrupt character once again, @value{GDBN} displays this prompt:
12262 Interrupted while waiting for the program.
12263 Give up (and stop debugging it)? (y or n)
12266 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
12267 (If you decide you want to try again later, you can use @samp{target
12268 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
12269 goes back to waiting.
12272 @kindex detach (remote)
12274 When you have finished debugging the remote program, you can use the
12275 @code{detach} command to release it from @value{GDBN} control.
12276 Detaching from the target normally resumes its execution, but the results
12277 will depend on your particular remote stub. After the @code{detach}
12278 command, @value{GDBN} is free to connect to another target.
12282 The @code{disconnect} command behaves like @code{detach}, except that
12283 the target is generally not resumed. It will wait for @value{GDBN}
12284 (this instance or another one) to connect and continue debugging. After
12285 the @code{disconnect} command, @value{GDBN} is again free to connect to
12288 @cindex send command to remote monitor
12289 @cindex extend @value{GDBN} for remote targets
12290 @cindex add new commands for external monitor
12292 @item monitor @var{cmd}
12293 This command allows you to send arbitrary commands directly to the
12294 remote monitor. Since @value{GDBN} doesn't care about the commands it
12295 sends like this, this command is the way to extend @value{GDBN}---you
12296 can add new commands that only the external monitor will understand
12301 @section Using the @code{gdbserver} program
12304 @cindex remote connection without stubs
12305 @code{gdbserver} is a control program for Unix-like systems, which
12306 allows you to connect your program with a remote @value{GDBN} via
12307 @code{target remote}---but without linking in the usual debugging stub.
12309 @code{gdbserver} is not a complete replacement for the debugging stubs,
12310 because it requires essentially the same operating-system facilities
12311 that @value{GDBN} itself does. In fact, a system that can run
12312 @code{gdbserver} to connect to a remote @value{GDBN} could also run
12313 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
12314 because it is a much smaller program than @value{GDBN} itself. It is
12315 also easier to port than all of @value{GDBN}, so you may be able to get
12316 started more quickly on a new system by using @code{gdbserver}.
12317 Finally, if you develop code for real-time systems, you may find that
12318 the tradeoffs involved in real-time operation make it more convenient to
12319 do as much development work as possible on another system, for example
12320 by cross-compiling. You can use @code{gdbserver} to make a similar
12321 choice for debugging.
12323 @value{GDBN} and @code{gdbserver} communicate via either a serial line
12324 or a TCP connection, using the standard @value{GDBN} remote serial
12328 @item On the target machine,
12329 you need to have a copy of the program you want to debug.
12330 @code{gdbserver} does not need your program's symbol table, so you can
12331 strip the program if necessary to save space. @value{GDBN} on the host
12332 system does all the symbol handling.
12334 To use the server, you must tell it how to communicate with @value{GDBN};
12335 the name of your program; and the arguments for your program. The usual
12339 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
12342 @var{comm} is either a device name (to use a serial line) or a TCP
12343 hostname and portnumber. For example, to debug Emacs with the argument
12344 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
12348 target> gdbserver /dev/com1 emacs foo.txt
12351 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
12354 To use a TCP connection instead of a serial line:
12357 target> gdbserver host:2345 emacs foo.txt
12360 The only difference from the previous example is the first argument,
12361 specifying that you are communicating with the host @value{GDBN} via
12362 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
12363 expect a TCP connection from machine @samp{host} to local TCP port 2345.
12364 (Currently, the @samp{host} part is ignored.) You can choose any number
12365 you want for the port number as long as it does not conflict with any
12366 TCP ports already in use on the target system (for example, @code{23} is
12367 reserved for @code{telnet}).@footnote{If you choose a port number that
12368 conflicts with another service, @code{gdbserver} prints an error message
12369 and exits.} You must use the same port number with the host @value{GDBN}
12370 @code{target remote} command.
12372 On some targets, @code{gdbserver} can also attach to running programs.
12373 This is accomplished via the @code{--attach} argument. The syntax is:
12376 target> gdbserver @var{comm} --attach @var{pid}
12379 @var{pid} is the process ID of a currently running process. It isn't necessary
12380 to point @code{gdbserver} at a binary for the running process.
12383 @cindex attach to a program by name
12384 You can debug processes by name instead of process ID if your target has the
12385 @code{pidof} utility:
12388 target> gdbserver @var{comm} --attach `pidof @var{PROGRAM}`
12391 In case more than one copy of @var{PROGRAM} is running, or @var{PROGRAM}
12392 has multiple threads, most versions of @code{pidof} support the
12393 @code{-s} option to only return the first process ID.
12395 @item On the host machine,
12396 connect to your target (@pxref{Connecting,,Connecting to a remote target}).
12397 For TCP connections, you must start up @code{gdbserver} prior to using
12398 the @code{target remote} command. Otherwise you may get an error whose
12399 text depends on the host system, but which usually looks something like
12400 @samp{Connection refused}. You don't need to use the @code{load}
12401 command in @value{GDBN} when using @code{gdbserver}, since the program is
12402 already on the target. However, if you want to load the symbols (as
12403 you normally would), do that with the @code{file} command, and issue
12404 it @emph{before} connecting to the server; otherwise, you will get an
12405 error message saying @code{"Program is already running"}, since the
12406 program is considered running after the connection.
12410 @node Remote configuration
12411 @section Remote configuration
12414 @kindex show remote
12415 This section documents the configuration options available when
12416 debugging remote programs. For the options related to the File I/O
12417 extensions of the remote protocol, see @ref{The system call,
12418 system-call-allowed}.
12421 @item set remoteaddresssize @var{bits}
12422 @cindex adress size for remote targets
12423 @cindex bits in remote address
12424 Set the maximum size of address in a memory packet to the specified
12425 number of bits. @value{GDBN} will mask off the address bits above
12426 that number, when it passes addresses to the remote target. The
12427 default value is the number of bits in the target's address.
12429 @item show remoteaddresssize
12430 Show the current value of remote address size in bits.
12432 @item set remotebaud @var{n}
12433 @cindex baud rate for remote targets
12434 Set the baud rate for the remote serial I/O to @var{n} baud. The
12435 value is used to set the speed of the serial port used for debugging
12438 @item show remotebaud
12439 Show the current speed of the remote connection.
12441 @item set remotebreak
12442 @cindex interrupt remote programs
12443 @cindex BREAK signal instead of Ctrl-C
12444 @anchor{set remotebreak}
12445 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
12446 when you press the @key{Ctrl-C} key to interrupt the program running
12447 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
12448 character instead. The default is off, since most remote systems
12449 expect to see @samp{Ctrl-C} as the interrupt signal.
12451 @item show remotebreak
12452 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
12453 interrupt the remote program.
12455 @item set remotedevice @var{device}
12456 @cindex serial port name
12457 Set the name of the serial port through which to communicate to the
12458 remote target to @var{device}. This is the device used by
12459 @value{GDBN} to open the serial communications line to the remote
12460 target. There's no default, so you must set a valid port name for the
12461 remote serial communications to work. (Some varieties of the
12462 @code{target} command accept the port name as part of their
12465 @item show remotedevice
12466 Show the current name of the serial port.
12468 @item set remotelogbase @var{base}
12469 Set the base (a.k.a.@: radix) of logging serial protocol
12470 communications to @var{base}. Supported values of @var{base} are:
12471 @code{ascii}, @code{octal}, and @code{hex}. The default is
12474 @item show remotelogbase
12475 Show the current setting of the radix for logging remote serial
12478 @item set remotelogfile @var{file}
12479 @cindex record serial communications on file
12480 Record remote serial communications on the named @var{file}. The
12481 default is not to record at all.
12483 @item show remotelogfile.
12484 Show the current setting of the file name on which to record the
12485 serial communications.
12487 @item set remotetimeout @var{num}
12488 @cindex timeout for serial communications
12489 @cindex remote timeout
12490 Set the timeout limit to wait for the remote target to respond to
12491 @var{num} seconds. The default is 2 seconds.
12493 @item show remotetimeout
12494 Show the current number of seconds to wait for the remote target
12497 @cindex limit hardware breakpoints and watchpoints
12498 @cindex remote target, limit break- and watchpoints
12499 @anchor{set remote hardware-watchpoint-limit}
12500 @anchor{set remote hardware-breakpoint-limit}
12501 @item set remote hardware-watchpoint-limit @var{limit}
12502 @itemx set remote hardware-breakpoint-limit @var{limit}
12503 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
12504 watchpoints. A limit of -1, the default, is treated as unlimited.
12506 @item set remote fetch-register-packet
12507 @itemx set remote set-register-packet
12508 @itemx set remote P-packet
12509 @itemx set remote p-packet
12511 @cindex fetch registers from remote targets
12512 @cindex set registers in remote targets
12513 Determine whether @value{GDBN} can set and fetch registers from the
12514 remote target using the @samp{P} packets. The default depends on the
12515 remote stub's support of the @samp{P} packets (@value{GDBN} queries
12516 the stub when this packet is first required).
12518 @item show remote fetch-register-packet
12519 @itemx show remote set-register-packet
12520 @itemx show remote P-packet
12521 @itemx show remote p-packet
12522 Show the current setting of using the @samp{P} packets for setting and
12523 fetching registers from the remote target.
12525 @cindex binary downloads
12527 @item set remote binary-download-packet
12528 @itemx set remote X-packet
12529 Determine whether @value{GDBN} sends downloads in binary mode using
12530 the @samp{X} packets. The default is on.
12532 @item show remote binary-download-packet
12533 @itemx show remote X-packet
12534 Show the current setting of using the @samp{X} packets for binary
12537 @item set remote read-aux-vector-packet
12538 @cindex auxiliary vector of remote target
12539 @cindex @code{auxv}, and remote targets
12540 Set the use of the remote protocol's @samp{qPart:auxv:read} (target
12541 auxiliary vector read) request. This request is used to fetch the
12542 remote target's @dfn{auxiliary vector}, see @ref{OS Information,
12543 Auxiliary Vector}. The default setting depends on the remote stub's
12544 support of this request (@value{GDBN} queries the stub when this
12545 request is first required). @xref{General Query Packets, qPart}, for
12546 more information about this request.
12548 @item show remote read-aux-vector-packet
12549 Show the current setting of use of the @samp{qPart:auxv:read} request.
12551 @item set remote symbol-lookup-packet
12552 @cindex remote symbol lookup request
12553 Set the use of the remote protocol's @samp{qSymbol} (target symbol
12554 lookup) request. This request is used to communicate symbol
12555 information to the remote target, e.g., whenever a new shared library
12556 is loaded by the remote (@pxref{Files, shared libraries}). The
12557 default setting depends on the remote stub's support of this request
12558 (@value{GDBN} queries the stub when this request is first required).
12559 @xref{General Query Packets, qSymbol}, for more information about this
12562 @item show remote symbol-lookup-packet
12563 Show the current setting of use of the @samp{qSymbol} request.
12565 @item set remote verbose-resume-packet
12566 @cindex resume remote target
12567 @cindex signal thread, and remote targets
12568 @cindex single-step thread, and remote targets
12569 @cindex thread-specific operations on remote targets
12570 Set the use of the remote protocol's @samp{vCont} (descriptive resume)
12571 request. This request is used to resume specific threads in the
12572 remote target, and to single-step or signal them. The default setting
12573 depends on the remote stub's support of this request (@value{GDBN}
12574 queries the stub when this request is first required). This setting
12575 affects debugging of multithreaded programs: if @samp{vCont} cannot be
12576 used, @value{GDBN} might be unable to single-step a specific thread,
12577 especially under @code{set scheduler-locking off}; it is also
12578 impossible to pause a specific thread. @xref{Packets, vCont}, for
12581 @item show remote verbose-resume-packet
12582 Show the current setting of use of the @samp{vCont} request
12584 @item set remote software-breakpoint-packet
12585 @itemx set remote hardware-breakpoint-packet
12586 @itemx set remote write-watchpoint-packet
12587 @itemx set remote read-watchpoint-packet
12588 @itemx set remote access-watchpoint-packet
12589 @itemx set remote Z-packet
12591 @cindex remote hardware breakpoints and watchpoints
12592 These commands enable or disable the use of @samp{Z} packets for
12593 setting breakpoints and watchpoints in the remote target. The default
12594 depends on the remote stub's support of the @samp{Z} packets
12595 (@value{GDBN} queries the stub when each packet is first required).
12596 The command @code{set remote Z-packet}, kept for back-compatibility,
12597 turns on or off all the features that require the use of @samp{Z}
12600 @item show remote software-breakpoint-packet
12601 @itemx show remote hardware-breakpoint-packet
12602 @itemx show remote write-watchpoint-packet
12603 @itemx show remote read-watchpoint-packet
12604 @itemx show remote access-watchpoint-packet
12605 @itemx show remote Z-packet
12606 Show the current setting of @samp{Z} packets usage.
12608 @item set remote get-thread-local-storage-address
12609 @kindex set remote get-thread-local-storage-address
12610 @cindex thread local storage of remote targets
12611 This command enables or disables the use of the @samp{qGetTLSAddr}
12612 (Get Thread Local Storage Address) request packet. The default
12613 depends on whether the remote stub supports this request.
12614 @xref{General Query Packets, qGetTLSAddr}, for more details about this
12617 @item show remote get-thread-local-storage-address
12618 @kindex show remote get-thread-local-storage-address
12619 Show the current setting of @samp{qGetTLSAddr} packet usage.
12623 @section Implementing a remote stub
12625 @cindex debugging stub, example
12626 @cindex remote stub, example
12627 @cindex stub example, remote debugging
12628 The stub files provided with @value{GDBN} implement the target side of the
12629 communication protocol, and the @value{GDBN} side is implemented in the
12630 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
12631 these subroutines to communicate, and ignore the details. (If you're
12632 implementing your own stub file, you can still ignore the details: start
12633 with one of the existing stub files. @file{sparc-stub.c} is the best
12634 organized, and therefore the easiest to read.)
12636 @cindex remote serial debugging, overview
12637 To debug a program running on another machine (the debugging
12638 @dfn{target} machine), you must first arrange for all the usual
12639 prerequisites for the program to run by itself. For example, for a C
12644 A startup routine to set up the C runtime environment; these usually
12645 have a name like @file{crt0}. The startup routine may be supplied by
12646 your hardware supplier, or you may have to write your own.
12649 A C subroutine library to support your program's
12650 subroutine calls, notably managing input and output.
12653 A way of getting your program to the other machine---for example, a
12654 download program. These are often supplied by the hardware
12655 manufacturer, but you may have to write your own from hardware
12659 The next step is to arrange for your program to use a serial port to
12660 communicate with the machine where @value{GDBN} is running (the @dfn{host}
12661 machine). In general terms, the scheme looks like this:
12665 @value{GDBN} already understands how to use this protocol; when everything
12666 else is set up, you can simply use the @samp{target remote} command
12667 (@pxref{Targets,,Specifying a Debugging Target}).
12669 @item On the target,
12670 you must link with your program a few special-purpose subroutines that
12671 implement the @value{GDBN} remote serial protocol. The file containing these
12672 subroutines is called a @dfn{debugging stub}.
12674 On certain remote targets, you can use an auxiliary program
12675 @code{gdbserver} instead of linking a stub into your program.
12676 @xref{Server,,Using the @code{gdbserver} program}, for details.
12679 The debugging stub is specific to the architecture of the remote
12680 machine; for example, use @file{sparc-stub.c} to debug programs on
12683 @cindex remote serial stub list
12684 These working remote stubs are distributed with @value{GDBN}:
12689 @cindex @file{i386-stub.c}
12692 For Intel 386 and compatible architectures.
12695 @cindex @file{m68k-stub.c}
12696 @cindex Motorola 680x0
12698 For Motorola 680x0 architectures.
12701 @cindex @file{sh-stub.c}
12704 For Renesas SH architectures.
12707 @cindex @file{sparc-stub.c}
12709 For @sc{sparc} architectures.
12711 @item sparcl-stub.c
12712 @cindex @file{sparcl-stub.c}
12715 For Fujitsu @sc{sparclite} architectures.
12719 The @file{README} file in the @value{GDBN} distribution may list other
12720 recently added stubs.
12723 * Stub Contents:: What the stub can do for you
12724 * Bootstrapping:: What you must do for the stub
12725 * Debug Session:: Putting it all together
12728 @node Stub Contents
12729 @subsection What the stub can do for you
12731 @cindex remote serial stub
12732 The debugging stub for your architecture supplies these three
12736 @item set_debug_traps
12737 @findex set_debug_traps
12738 @cindex remote serial stub, initialization
12739 This routine arranges for @code{handle_exception} to run when your
12740 program stops. You must call this subroutine explicitly near the
12741 beginning of your program.
12743 @item handle_exception
12744 @findex handle_exception
12745 @cindex remote serial stub, main routine
12746 This is the central workhorse, but your program never calls it
12747 explicitly---the setup code arranges for @code{handle_exception} to
12748 run when a trap is triggered.
12750 @code{handle_exception} takes control when your program stops during
12751 execution (for example, on a breakpoint), and mediates communications
12752 with @value{GDBN} on the host machine. This is where the communications
12753 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
12754 representative on the target machine. It begins by sending summary
12755 information on the state of your program, then continues to execute,
12756 retrieving and transmitting any information @value{GDBN} needs, until you
12757 execute a @value{GDBN} command that makes your program resume; at that point,
12758 @code{handle_exception} returns control to your own code on the target
12762 @cindex @code{breakpoint} subroutine, remote
12763 Use this auxiliary subroutine to make your program contain a
12764 breakpoint. Depending on the particular situation, this may be the only
12765 way for @value{GDBN} to get control. For instance, if your target
12766 machine has some sort of interrupt button, you won't need to call this;
12767 pressing the interrupt button transfers control to
12768 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
12769 simply receiving characters on the serial port may also trigger a trap;
12770 again, in that situation, you don't need to call @code{breakpoint} from
12771 your own program---simply running @samp{target remote} from the host
12772 @value{GDBN} session gets control.
12774 Call @code{breakpoint} if none of these is true, or if you simply want
12775 to make certain your program stops at a predetermined point for the
12776 start of your debugging session.
12779 @node Bootstrapping
12780 @subsection What you must do for the stub
12782 @cindex remote stub, support routines
12783 The debugging stubs that come with @value{GDBN} are set up for a particular
12784 chip architecture, but they have no information about the rest of your
12785 debugging target machine.
12787 First of all you need to tell the stub how to communicate with the
12791 @item int getDebugChar()
12792 @findex getDebugChar
12793 Write this subroutine to read a single character from the serial port.
12794 It may be identical to @code{getchar} for your target system; a
12795 different name is used to allow you to distinguish the two if you wish.
12797 @item void putDebugChar(int)
12798 @findex putDebugChar
12799 Write this subroutine to write a single character to the serial port.
12800 It may be identical to @code{putchar} for your target system; a
12801 different name is used to allow you to distinguish the two if you wish.
12804 @cindex control C, and remote debugging
12805 @cindex interrupting remote targets
12806 If you want @value{GDBN} to be able to stop your program while it is
12807 running, you need to use an interrupt-driven serial driver, and arrange
12808 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
12809 character). That is the character which @value{GDBN} uses to tell the
12810 remote system to stop.
12812 Getting the debugging target to return the proper status to @value{GDBN}
12813 probably requires changes to the standard stub; one quick and dirty way
12814 is to just execute a breakpoint instruction (the ``dirty'' part is that
12815 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
12817 Other routines you need to supply are:
12820 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
12821 @findex exceptionHandler
12822 Write this function to install @var{exception_address} in the exception
12823 handling tables. You need to do this because the stub does not have any
12824 way of knowing what the exception handling tables on your target system
12825 are like (for example, the processor's table might be in @sc{rom},
12826 containing entries which point to a table in @sc{ram}).
12827 @var{exception_number} is the exception number which should be changed;
12828 its meaning is architecture-dependent (for example, different numbers
12829 might represent divide by zero, misaligned access, etc). When this
12830 exception occurs, control should be transferred directly to
12831 @var{exception_address}, and the processor state (stack, registers,
12832 and so on) should be just as it is when a processor exception occurs. So if
12833 you want to use a jump instruction to reach @var{exception_address}, it
12834 should be a simple jump, not a jump to subroutine.
12836 For the 386, @var{exception_address} should be installed as an interrupt
12837 gate so that interrupts are masked while the handler runs. The gate
12838 should be at privilege level 0 (the most privileged level). The
12839 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
12840 help from @code{exceptionHandler}.
12842 @item void flush_i_cache()
12843 @findex flush_i_cache
12844 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
12845 instruction cache, if any, on your target machine. If there is no
12846 instruction cache, this subroutine may be a no-op.
12848 On target machines that have instruction caches, @value{GDBN} requires this
12849 function to make certain that the state of your program is stable.
12853 You must also make sure this library routine is available:
12856 @item void *memset(void *, int, int)
12858 This is the standard library function @code{memset} that sets an area of
12859 memory to a known value. If you have one of the free versions of
12860 @code{libc.a}, @code{memset} can be found there; otherwise, you must
12861 either obtain it from your hardware manufacturer, or write your own.
12864 If you do not use the GNU C compiler, you may need other standard
12865 library subroutines as well; this varies from one stub to another,
12866 but in general the stubs are likely to use any of the common library
12867 subroutines which @code{@value{GCC}} generates as inline code.
12870 @node Debug Session
12871 @subsection Putting it all together
12873 @cindex remote serial debugging summary
12874 In summary, when your program is ready to debug, you must follow these
12879 Make sure you have defined the supporting low-level routines
12880 (@pxref{Bootstrapping,,What you must do for the stub}):
12882 @code{getDebugChar}, @code{putDebugChar},
12883 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
12887 Insert these lines near the top of your program:
12895 For the 680x0 stub only, you need to provide a variable called
12896 @code{exceptionHook}. Normally you just use:
12899 void (*exceptionHook)() = 0;
12903 but if before calling @code{set_debug_traps}, you set it to point to a
12904 function in your program, that function is called when
12905 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
12906 error). The function indicated by @code{exceptionHook} is called with
12907 one parameter: an @code{int} which is the exception number.
12910 Compile and link together: your program, the @value{GDBN} debugging stub for
12911 your target architecture, and the supporting subroutines.
12914 Make sure you have a serial connection between your target machine and
12915 the @value{GDBN} host, and identify the serial port on the host.
12918 @c The "remote" target now provides a `load' command, so we should
12919 @c document that. FIXME.
12920 Download your program to your target machine (or get it there by
12921 whatever means the manufacturer provides), and start it.
12924 Start @value{GDBN} on the host, and connect to the target
12925 (@pxref{Connecting,,Connecting to a remote target}).
12929 @node Configurations
12930 @chapter Configuration-Specific Information
12932 While nearly all @value{GDBN} commands are available for all native and
12933 cross versions of the debugger, there are some exceptions. This chapter
12934 describes things that are only available in certain configurations.
12936 There are three major categories of configurations: native
12937 configurations, where the host and target are the same, embedded
12938 operating system configurations, which are usually the same for several
12939 different processor architectures, and bare embedded processors, which
12940 are quite different from each other.
12945 * Embedded Processors::
12952 This section describes details specific to particular native
12957 * BSD libkvm Interface:: Debugging BSD kernel memory images
12958 * SVR4 Process Information:: SVR4 process information
12959 * DJGPP Native:: Features specific to the DJGPP port
12960 * Cygwin Native:: Features specific to the Cygwin port
12961 * Hurd Native:: Features specific to @sc{gnu} Hurd
12962 * Neutrino:: Features specific to QNX Neutrino
12968 On HP-UX systems, if you refer to a function or variable name that
12969 begins with a dollar sign, @value{GDBN} searches for a user or system
12970 name first, before it searches for a convenience variable.
12973 @node BSD libkvm Interface
12974 @subsection BSD libkvm Interface
12977 @cindex kernel memory image
12978 @cindex kernel crash dump
12980 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
12981 interface that provides a uniform interface for accessing kernel virtual
12982 memory images, including live systems and crash dumps. @value{GDBN}
12983 uses this interface to allow you to debug live kernels and kernel crash
12984 dumps on many native BSD configurations. This is implemented as a
12985 special @code{kvm} debugging target. For debugging a live system, load
12986 the currently running kernel into @value{GDBN} and connect to the
12990 (@value{GDBP}) @b{target kvm}
12993 For debugging crash dumps, provide the file name of the crash dump as an
12997 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
13000 Once connected to the @code{kvm} target, the following commands are
13006 Set current context from the @dfn{Process Control Block} (PCB) address.
13009 Set current context from proc address. This command isn't available on
13010 modern FreeBSD systems.
13013 @node SVR4 Process Information
13014 @subsection SVR4 process information
13016 @cindex examine process image
13017 @cindex process info via @file{/proc}
13019 Many versions of SVR4 and compatible systems provide a facility called
13020 @samp{/proc} that can be used to examine the image of a running
13021 process using file-system subroutines. If @value{GDBN} is configured
13022 for an operating system with this facility, the command @code{info
13023 proc} is available to report information about the process running
13024 your program, or about any process running on your system. @code{info
13025 proc} works only on SVR4 systems that include the @code{procfs} code.
13026 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
13027 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
13033 @itemx info proc @var{process-id}
13034 Summarize available information about any running process. If a
13035 process ID is specified by @var{process-id}, display information about
13036 that process; otherwise display information about the program being
13037 debugged. The summary includes the debugged process ID, the command
13038 line used to invoke it, its current working directory, and its
13039 executable file's absolute file name.
13041 On some systems, @var{process-id} can be of the form
13042 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
13043 within a process. If the optional @var{pid} part is missing, it means
13044 a thread from the process being debugged (the leading @samp{/} still
13045 needs to be present, or else @value{GDBN} will interpret the number as
13046 a process ID rather than a thread ID).
13048 @item info proc mappings
13049 @cindex memory address space mappings
13050 Report the memory address space ranges accessible in the program, with
13051 information on whether the process has read, write, or execute access
13052 rights to each range. On @sc{gnu}/Linux systems, each memory range
13053 includes the object file which is mapped to that range, instead of the
13054 memory access rights to that range.
13056 @item info proc stat
13057 @itemx info proc status
13058 @cindex process detailed status information
13059 These subcommands are specific to @sc{gnu}/Linux systems. They show
13060 the process-related information, including the user ID and group ID;
13061 how many threads are there in the process; its virtual memory usage;
13062 the signals that are pending, blocked, and ignored; its TTY; its
13063 consumption of system and user time; its stack size; its @samp{nice}
13064 value; etc. For more information, see the @samp{proc} man page
13065 (type @kbd{man 5 proc} from your shell prompt).
13067 @item info proc all
13068 Show all the information about the process described under all of the
13069 above @code{info proc} subcommands.
13072 @comment These sub-options of 'info proc' were not included when
13073 @comment procfs.c was re-written. Keep their descriptions around
13074 @comment against the day when someone finds the time to put them back in.
13075 @kindex info proc times
13076 @item info proc times
13077 Starting time, user CPU time, and system CPU time for your program and
13080 @kindex info proc id
13082 Report on the process IDs related to your program: its own process ID,
13083 the ID of its parent, the process group ID, and the session ID.
13086 @item set procfs-trace
13087 @kindex set procfs-trace
13088 @cindex @code{procfs} API calls
13089 This command enables and disables tracing of @code{procfs} API calls.
13091 @item show procfs-trace
13092 @kindex show procfs-trace
13093 Show the current state of @code{procfs} API call tracing.
13095 @item set procfs-file @var{file}
13096 @kindex set procfs-file
13097 Tell @value{GDBN} to write @code{procfs} API trace to the named
13098 @var{file}. @value{GDBN} appends the trace info to the previous
13099 contents of the file. The default is to display the trace on the
13102 @item show procfs-file
13103 @kindex show procfs-file
13104 Show the file to which @code{procfs} API trace is written.
13106 @item proc-trace-entry
13107 @itemx proc-trace-exit
13108 @itemx proc-untrace-entry
13109 @itemx proc-untrace-exit
13110 @kindex proc-trace-entry
13111 @kindex proc-trace-exit
13112 @kindex proc-untrace-entry
13113 @kindex proc-untrace-exit
13114 These commands enable and disable tracing of entries into and exits
13115 from the @code{syscall} interface.
13118 @kindex info pidlist
13119 @cindex process list, QNX Neutrino
13120 For QNX Neutrino only, this command displays the list of all the
13121 processes and all the threads within each process.
13124 @kindex info meminfo
13125 @cindex mapinfo list, QNX Neutrino
13126 For QNX Neutrino only, this command displays the list of all mapinfos.
13130 @subsection Features for Debugging @sc{djgpp} Programs
13131 @cindex @sc{djgpp} debugging
13132 @cindex native @sc{djgpp} debugging
13133 @cindex MS-DOS-specific commands
13136 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
13137 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
13138 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
13139 top of real-mode DOS systems and their emulations.
13141 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
13142 defines a few commands specific to the @sc{djgpp} port. This
13143 subsection describes those commands.
13148 This is a prefix of @sc{djgpp}-specific commands which print
13149 information about the target system and important OS structures.
13152 @cindex MS-DOS system info
13153 @cindex free memory information (MS-DOS)
13154 @item info dos sysinfo
13155 This command displays assorted information about the underlying
13156 platform: the CPU type and features, the OS version and flavor, the
13157 DPMI version, and the available conventional and DPMI memory.
13162 @cindex segment descriptor tables
13163 @cindex descriptor tables display
13165 @itemx info dos ldt
13166 @itemx info dos idt
13167 These 3 commands display entries from, respectively, Global, Local,
13168 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
13169 tables are data structures which store a descriptor for each segment
13170 that is currently in use. The segment's selector is an index into a
13171 descriptor table; the table entry for that index holds the
13172 descriptor's base address and limit, and its attributes and access
13175 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
13176 segment (used for both data and the stack), and a DOS segment (which
13177 allows access to DOS/BIOS data structures and absolute addresses in
13178 conventional memory). However, the DPMI host will usually define
13179 additional segments in order to support the DPMI environment.
13181 @cindex garbled pointers
13182 These commands allow to display entries from the descriptor tables.
13183 Without an argument, all entries from the specified table are
13184 displayed. An argument, which should be an integer expression, means
13185 display a single entry whose index is given by the argument. For
13186 example, here's a convenient way to display information about the
13187 debugged program's data segment:
13190 @exdent @code{(@value{GDBP}) info dos ldt $ds}
13191 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
13195 This comes in handy when you want to see whether a pointer is outside
13196 the data segment's limit (i.e.@: @dfn{garbled}).
13198 @cindex page tables display (MS-DOS)
13200 @itemx info dos pte
13201 These two commands display entries from, respectively, the Page
13202 Directory and the Page Tables. Page Directories and Page Tables are
13203 data structures which control how virtual memory addresses are mapped
13204 into physical addresses. A Page Table includes an entry for every
13205 page of memory that is mapped into the program's address space; there
13206 may be several Page Tables, each one holding up to 4096 entries. A
13207 Page Directory has up to 4096 entries, one each for every Page Table
13208 that is currently in use.
13210 Without an argument, @kbd{info dos pde} displays the entire Page
13211 Directory, and @kbd{info dos pte} displays all the entries in all of
13212 the Page Tables. An argument, an integer expression, given to the
13213 @kbd{info dos pde} command means display only that entry from the Page
13214 Directory table. An argument given to the @kbd{info dos pte} command
13215 means display entries from a single Page Table, the one pointed to by
13216 the specified entry in the Page Directory.
13218 @cindex direct memory access (DMA) on MS-DOS
13219 These commands are useful when your program uses @dfn{DMA} (Direct
13220 Memory Access), which needs physical addresses to program the DMA
13223 These commands are supported only with some DPMI servers.
13225 @cindex physical address from linear address
13226 @item info dos address-pte @var{addr}
13227 This command displays the Page Table entry for a specified linear
13228 address. The argument @var{addr} is a linear address which should
13229 already have the appropriate segment's base address added to it,
13230 because this command accepts addresses which may belong to @emph{any}
13231 segment. For example, here's how to display the Page Table entry for
13232 the page where a variable @code{i} is stored:
13235 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
13236 @exdent @code{Page Table entry for address 0x11a00d30:}
13237 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
13241 This says that @code{i} is stored at offset @code{0xd30} from the page
13242 whose physical base address is @code{0x02698000}, and shows all the
13243 attributes of that page.
13245 Note that you must cast the addresses of variables to a @code{char *},
13246 since otherwise the value of @code{__djgpp_base_address}, the base
13247 address of all variables and functions in a @sc{djgpp} program, will
13248 be added using the rules of C pointer arithmetics: if @code{i} is
13249 declared an @code{int}, @value{GDBN} will add 4 times the value of
13250 @code{__djgpp_base_address} to the address of @code{i}.
13252 Here's another example, it displays the Page Table entry for the
13256 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
13257 @exdent @code{Page Table entry for address 0x29110:}
13258 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
13262 (The @code{+ 3} offset is because the transfer buffer's address is the
13263 3rd member of the @code{_go32_info_block} structure.) The output
13264 clearly shows that this DPMI server maps the addresses in conventional
13265 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
13266 linear (@code{0x29110}) addresses are identical.
13268 This command is supported only with some DPMI servers.
13271 @cindex DOS serial data link, remote debugging
13272 In addition to native debugging, the DJGPP port supports remote
13273 debugging via a serial data link. The following commands are specific
13274 to remote serial debugging in the DJGPP port of @value{GDBN}.
13277 @kindex set com1base
13278 @kindex set com1irq
13279 @kindex set com2base
13280 @kindex set com2irq
13281 @kindex set com3base
13282 @kindex set com3irq
13283 @kindex set com4base
13284 @kindex set com4irq
13285 @item set com1base @var{addr}
13286 This command sets the base I/O port address of the @file{COM1} serial
13289 @item set com1irq @var{irq}
13290 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
13291 for the @file{COM1} serial port.
13293 There are similar commands @samp{set com2base}, @samp{set com3irq},
13294 etc.@: for setting the port address and the @code{IRQ} lines for the
13297 @kindex show com1base
13298 @kindex show com1irq
13299 @kindex show com2base
13300 @kindex show com2irq
13301 @kindex show com3base
13302 @kindex show com3irq
13303 @kindex show com4base
13304 @kindex show com4irq
13305 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
13306 display the current settings of the base address and the @code{IRQ}
13307 lines used by the COM ports.
13310 @kindex info serial
13311 @cindex DOS serial port status
13312 This command prints the status of the 4 DOS serial ports. For each
13313 port, it prints whether it's active or not, its I/O base address and
13314 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
13315 counts of various errors encountered so far.
13319 @node Cygwin Native
13320 @subsection Features for Debugging MS Windows PE executables
13321 @cindex MS Windows debugging
13322 @cindex native Cygwin debugging
13323 @cindex Cygwin-specific commands
13325 @value{GDBN} supports native debugging of MS Windows programs, including
13326 DLLs with and without symbolic debugging information. There are various
13327 additional Cygwin-specific commands, described in this subsection. The
13328 subsubsection @pxref{Non-debug DLL symbols} describes working with DLLs
13329 that have no debugging symbols.
13335 This is a prefix of MS Windows specific commands which print
13336 information about the target system and important OS structures.
13338 @item info w32 selector
13339 This command displays information returned by
13340 the Win32 API @code{GetThreadSelectorEntry} function.
13341 It takes an optional argument that is evaluated to
13342 a long value to give the information about this given selector.
13343 Without argument, this command displays information
13344 about the the six segment registers.
13348 This is a Cygwin specific alias of info shared.
13350 @kindex dll-symbols
13352 This command loads symbols from a dll similarly to
13353 add-sym command but without the need to specify a base address.
13355 @kindex set new-console
13356 @item set new-console @var{mode}
13357 If @var{mode} is @code{on} the debuggee will
13358 be started in a new console on next start.
13359 If @var{mode} is @code{off}i, the debuggee will
13360 be started in the same console as the debugger.
13362 @kindex show new-console
13363 @item show new-console
13364 Displays whether a new console is used
13365 when the debuggee is started.
13367 @kindex set new-group
13368 @item set new-group @var{mode}
13369 This boolean value controls whether the debuggee should
13370 start a new group or stay in the same group as the debugger.
13371 This affects the way the Windows OS handles
13374 @kindex show new-group
13375 @item show new-group
13376 Displays current value of new-group boolean.
13378 @kindex set debugevents
13379 @item set debugevents
13380 This boolean value adds debug output concerning kernel events related
13381 to the debuggee seen by the debugger. This includes events that
13382 signal thread and process creation and exit, DLL loading and
13383 unloading, console interrupts, and debugging messages produced by the
13384 Windows @code{OutputDebugString} API call.
13386 @kindex set debugexec
13387 @item set debugexec
13388 This boolean value adds debug output concerning execute events
13389 (such as resume thread) seen by the debugger.
13391 @kindex set debugexceptions
13392 @item set debugexceptions
13393 This boolean value adds debug output concerning exceptions in the
13394 debuggee seen by the debugger.
13396 @kindex set debugmemory
13397 @item set debugmemory
13398 This boolean value adds debug output concerning debuggee memory reads
13399 and writes by the debugger.
13403 This boolean values specifies whether the debuggee is called
13404 via a shell or directly (default value is on).
13408 Displays if the debuggee will be started with a shell.
13413 * Non-debug DLL symbols:: Support for DLLs without debugging symbols
13416 @node Non-debug DLL symbols
13417 @subsubsection Support for DLLs without debugging symbols
13418 @cindex DLLs with no debugging symbols
13419 @cindex Minimal symbols and DLLs
13421 Very often on windows, some of the DLLs that your program relies on do
13422 not include symbolic debugging information (for example,
13423 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
13424 symbols in a DLL, it relies on the minimal amount of symbolic
13425 information contained in the DLL's export table. This subsubsection
13426 describes working with such symbols, known internally to @value{GDBN} as
13427 ``minimal symbols''.
13429 Note that before the debugged program has started execution, no DLLs
13430 will have been loaded. The easiest way around this problem is simply to
13431 start the program --- either by setting a breakpoint or letting the
13432 program run once to completion. It is also possible to force
13433 @value{GDBN} to load a particular DLL before starting the executable ---
13434 see the shared library information in @pxref{Files} or the
13435 @code{dll-symbols} command in @pxref{Cygwin Native}. Currently,
13436 explicitly loading symbols from a DLL with no debugging information will
13437 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
13438 which may adversely affect symbol lookup performance.
13440 @subsubsection DLL name prefixes
13442 In keeping with the naming conventions used by the Microsoft debugging
13443 tools, DLL export symbols are made available with a prefix based on the
13444 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
13445 also entered into the symbol table, so @code{CreateFileA} is often
13446 sufficient. In some cases there will be name clashes within a program
13447 (particularly if the executable itself includes full debugging symbols)
13448 necessitating the use of the fully qualified name when referring to the
13449 contents of the DLL. Use single-quotes around the name to avoid the
13450 exclamation mark (``!'') being interpreted as a language operator.
13452 Note that the internal name of the DLL may be all upper-case, even
13453 though the file name of the DLL is lower-case, or vice-versa. Since
13454 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
13455 some confusion. If in doubt, try the @code{info functions} and
13456 @code{info variables} commands or even @code{maint print msymbols} (see
13457 @pxref{Symbols}). Here's an example:
13460 (@value{GDBP}) info function CreateFileA
13461 All functions matching regular expression "CreateFileA":
13463 Non-debugging symbols:
13464 0x77e885f4 CreateFileA
13465 0x77e885f4 KERNEL32!CreateFileA
13469 (@value{GDBP}) info function !
13470 All functions matching regular expression "!":
13472 Non-debugging symbols:
13473 0x6100114c cygwin1!__assert
13474 0x61004034 cygwin1!_dll_crt0@@0
13475 0x61004240 cygwin1!dll_crt0(per_process *)
13479 @subsubsection Working with minimal symbols
13481 Symbols extracted from a DLL's export table do not contain very much
13482 type information. All that @value{GDBN} can do is guess whether a symbol
13483 refers to a function or variable depending on the linker section that
13484 contains the symbol. Also note that the actual contents of the memory
13485 contained in a DLL are not available unless the program is running. This
13486 means that you cannot examine the contents of a variable or disassemble
13487 a function within a DLL without a running program.
13489 Variables are generally treated as pointers and dereferenced
13490 automatically. For this reason, it is often necessary to prefix a
13491 variable name with the address-of operator (``&'') and provide explicit
13492 type information in the command. Here's an example of the type of
13496 (@value{GDBP}) print 'cygwin1!__argv'
13501 (@value{GDBP}) x 'cygwin1!__argv'
13502 0x10021610: "\230y\""
13505 And two possible solutions:
13508 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
13509 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
13513 (@value{GDBP}) x/2x &'cygwin1!__argv'
13514 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
13515 (@value{GDBP}) x/x 0x10021608
13516 0x10021608: 0x0022fd98
13517 (@value{GDBP}) x/s 0x0022fd98
13518 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
13521 Setting a break point within a DLL is possible even before the program
13522 starts execution. However, under these circumstances, @value{GDBN} can't
13523 examine the initial instructions of the function in order to skip the
13524 function's frame set-up code. You can work around this by using ``*&''
13525 to set the breakpoint at a raw memory address:
13528 (@value{GDBP}) break *&'python22!PyOS_Readline'
13529 Breakpoint 1 at 0x1e04eff0
13532 The author of these extensions is not entirely convinced that setting a
13533 break point within a shared DLL like @file{kernel32.dll} is completely
13537 @subsection Commands specific to @sc{gnu} Hurd systems
13538 @cindex @sc{gnu} Hurd debugging
13540 This subsection describes @value{GDBN} commands specific to the
13541 @sc{gnu} Hurd native debugging.
13546 @kindex set signals@r{, Hurd command}
13547 @kindex set sigs@r{, Hurd command}
13548 This command toggles the state of inferior signal interception by
13549 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
13550 affected by this command. @code{sigs} is a shorthand alias for
13555 @kindex show signals@r{, Hurd command}
13556 @kindex show sigs@r{, Hurd command}
13557 Show the current state of intercepting inferior's signals.
13559 @item set signal-thread
13560 @itemx set sigthread
13561 @kindex set signal-thread
13562 @kindex set sigthread
13563 This command tells @value{GDBN} which thread is the @code{libc} signal
13564 thread. That thread is run when a signal is delivered to a running
13565 process. @code{set sigthread} is the shorthand alias of @code{set
13568 @item show signal-thread
13569 @itemx show sigthread
13570 @kindex show signal-thread
13571 @kindex show sigthread
13572 These two commands show which thread will run when the inferior is
13573 delivered a signal.
13576 @kindex set stopped@r{, Hurd command}
13577 This commands tells @value{GDBN} that the inferior process is stopped,
13578 as with the @code{SIGSTOP} signal. The stopped process can be
13579 continued by delivering a signal to it.
13582 @kindex show stopped@r{, Hurd command}
13583 This command shows whether @value{GDBN} thinks the debuggee is
13586 @item set exceptions
13587 @kindex set exceptions@r{, Hurd command}
13588 Use this command to turn off trapping of exceptions in the inferior.
13589 When exception trapping is off, neither breakpoints nor
13590 single-stepping will work. To restore the default, set exception
13593 @item show exceptions
13594 @kindex show exceptions@r{, Hurd command}
13595 Show the current state of trapping exceptions in the inferior.
13597 @item set task pause
13598 @kindex set task@r{, Hurd commands}
13599 @cindex task attributes (@sc{gnu} Hurd)
13600 @cindex pause current task (@sc{gnu} Hurd)
13601 This command toggles task suspension when @value{GDBN} has control.
13602 Setting it to on takes effect immediately, and the task is suspended
13603 whenever @value{GDBN} gets control. Setting it to off will take
13604 effect the next time the inferior is continued. If this option is set
13605 to off, you can use @code{set thread default pause on} or @code{set
13606 thread pause on} (see below) to pause individual threads.
13608 @item show task pause
13609 @kindex show task@r{, Hurd commands}
13610 Show the current state of task suspension.
13612 @item set task detach-suspend-count
13613 @cindex task suspend count
13614 @cindex detach from task, @sc{gnu} Hurd
13615 This command sets the suspend count the task will be left with when
13616 @value{GDBN} detaches from it.
13618 @item show task detach-suspend-count
13619 Show the suspend count the task will be left with when detaching.
13621 @item set task exception-port
13622 @itemx set task excp
13623 @cindex task exception port, @sc{gnu} Hurd
13624 This command sets the task exception port to which @value{GDBN} will
13625 forward exceptions. The argument should be the value of the @dfn{send
13626 rights} of the task. @code{set task excp} is a shorthand alias.
13628 @item set noninvasive
13629 @cindex noninvasive task options
13630 This command switches @value{GDBN} to a mode that is the least
13631 invasive as far as interfering with the inferior is concerned. This
13632 is the same as using @code{set task pause}, @code{set exceptions}, and
13633 @code{set signals} to values opposite to the defaults.
13635 @item info send-rights
13636 @itemx info receive-rights
13637 @itemx info port-rights
13638 @itemx info port-sets
13639 @itemx info dead-names
13642 @cindex send rights, @sc{gnu} Hurd
13643 @cindex receive rights, @sc{gnu} Hurd
13644 @cindex port rights, @sc{gnu} Hurd
13645 @cindex port sets, @sc{gnu} Hurd
13646 @cindex dead names, @sc{gnu} Hurd
13647 These commands display information about, respectively, send rights,
13648 receive rights, port rights, port sets, and dead names of a task.
13649 There are also shorthand aliases: @code{info ports} for @code{info
13650 port-rights} and @code{info psets} for @code{info port-sets}.
13652 @item set thread pause
13653 @kindex set thread@r{, Hurd command}
13654 @cindex thread properties, @sc{gnu} Hurd
13655 @cindex pause current thread (@sc{gnu} Hurd)
13656 This command toggles current thread suspension when @value{GDBN} has
13657 control. Setting it to on takes effect immediately, and the current
13658 thread is suspended whenever @value{GDBN} gets control. Setting it to
13659 off will take effect the next time the inferior is continued.
13660 Normally, this command has no effect, since when @value{GDBN} has
13661 control, the whole task is suspended. However, if you used @code{set
13662 task pause off} (see above), this command comes in handy to suspend
13663 only the current thread.
13665 @item show thread pause
13666 @kindex show thread@r{, Hurd command}
13667 This command shows the state of current thread suspension.
13669 @item set thread run
13670 This comamnd sets whether the current thread is allowed to run.
13672 @item show thread run
13673 Show whether the current thread is allowed to run.
13675 @item set thread detach-suspend-count
13676 @cindex thread suspend count, @sc{gnu} Hurd
13677 @cindex detach from thread, @sc{gnu} Hurd
13678 This command sets the suspend count @value{GDBN} will leave on a
13679 thread when detaching. This number is relative to the suspend count
13680 found by @value{GDBN} when it notices the thread; use @code{set thread
13681 takeover-suspend-count} to force it to an absolute value.
13683 @item show thread detach-suspend-count
13684 Show the suspend count @value{GDBN} will leave on the thread when
13687 @item set thread exception-port
13688 @itemx set thread excp
13689 Set the thread exception port to which to forward exceptions. This
13690 overrides the port set by @code{set task exception-port} (see above).
13691 @code{set thread excp} is the shorthand alias.
13693 @item set thread takeover-suspend-count
13694 Normally, @value{GDBN}'s thread suspend counts are relative to the
13695 value @value{GDBN} finds when it notices each thread. This command
13696 changes the suspend counts to be absolute instead.
13698 @item set thread default
13699 @itemx show thread default
13700 @cindex thread default settings, @sc{gnu} Hurd
13701 Each of the above @code{set thread} commands has a @code{set thread
13702 default} counterpart (e.g., @code{set thread default pause}, @code{set
13703 thread default exception-port}, etc.). The @code{thread default}
13704 variety of commands sets the default thread properties for all
13705 threads; you can then change the properties of individual threads with
13706 the non-default commands.
13711 @subsection QNX Neutrino
13712 @cindex QNX Neutrino
13714 @value{GDBN} provides the following commands specific to the QNX
13718 @item set debug nto-debug
13719 @kindex set debug nto-debug
13720 When set to on, enables debugging messages specific to the QNX
13723 @item show debug nto-debug
13724 @kindex show debug nto-debug
13725 Show the current state of QNX Neutrino messages.
13730 @section Embedded Operating Systems
13732 This section describes configurations involving the debugging of
13733 embedded operating systems that are available for several different
13737 * VxWorks:: Using @value{GDBN} with VxWorks
13740 @value{GDBN} includes the ability to debug programs running on
13741 various real-time operating systems.
13744 @subsection Using @value{GDBN} with VxWorks
13750 @kindex target vxworks
13751 @item target vxworks @var{machinename}
13752 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
13753 is the target system's machine name or IP address.
13757 On VxWorks, @code{load} links @var{filename} dynamically on the
13758 current target system as well as adding its symbols in @value{GDBN}.
13760 @value{GDBN} enables developers to spawn and debug tasks running on networked
13761 VxWorks targets from a Unix host. Already-running tasks spawned from
13762 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
13763 both the Unix host and on the VxWorks target. The program
13764 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
13765 installed with the name @code{vxgdb}, to distinguish it from a
13766 @value{GDBN} for debugging programs on the host itself.)
13769 @item VxWorks-timeout @var{args}
13770 @kindex vxworks-timeout
13771 All VxWorks-based targets now support the option @code{vxworks-timeout}.
13772 This option is set by the user, and @var{args} represents the number of
13773 seconds @value{GDBN} waits for responses to rpc's. You might use this if
13774 your VxWorks target is a slow software simulator or is on the far side
13775 of a thin network line.
13778 The following information on connecting to VxWorks was current when
13779 this manual was produced; newer releases of VxWorks may use revised
13782 @findex INCLUDE_RDB
13783 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
13784 to include the remote debugging interface routines in the VxWorks
13785 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
13786 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
13787 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
13788 source debugging task @code{tRdbTask} when VxWorks is booted. For more
13789 information on configuring and remaking VxWorks, see the manufacturer's
13791 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
13793 Once you have included @file{rdb.a} in your VxWorks system image and set
13794 your Unix execution search path to find @value{GDBN}, you are ready to
13795 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
13796 @code{vxgdb}, depending on your installation).
13798 @value{GDBN} comes up showing the prompt:
13805 * VxWorks Connection:: Connecting to VxWorks
13806 * VxWorks Download:: VxWorks download
13807 * VxWorks Attach:: Running tasks
13810 @node VxWorks Connection
13811 @subsubsection Connecting to VxWorks
13813 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
13814 network. To connect to a target whose host name is ``@code{tt}'', type:
13817 (vxgdb) target vxworks tt
13821 @value{GDBN} displays messages like these:
13824 Attaching remote machine across net...
13829 @value{GDBN} then attempts to read the symbol tables of any object modules
13830 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
13831 these files by searching the directories listed in the command search
13832 path (@pxref{Environment, ,Your program's environment}); if it fails
13833 to find an object file, it displays a message such as:
13836 prog.o: No such file or directory.
13839 When this happens, add the appropriate directory to the search path with
13840 the @value{GDBN} command @code{path}, and execute the @code{target}
13843 @node VxWorks Download
13844 @subsubsection VxWorks download
13846 @cindex download to VxWorks
13847 If you have connected to the VxWorks target and you want to debug an
13848 object that has not yet been loaded, you can use the @value{GDBN}
13849 @code{load} command to download a file from Unix to VxWorks
13850 incrementally. The object file given as an argument to the @code{load}
13851 command is actually opened twice: first by the VxWorks target in order
13852 to download the code, then by @value{GDBN} in order to read the symbol
13853 table. This can lead to problems if the current working directories on
13854 the two systems differ. If both systems have NFS mounted the same
13855 filesystems, you can avoid these problems by using absolute paths.
13856 Otherwise, it is simplest to set the working directory on both systems
13857 to the directory in which the object file resides, and then to reference
13858 the file by its name, without any path. For instance, a program
13859 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
13860 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
13861 program, type this on VxWorks:
13864 -> cd "@var{vxpath}/vw/demo/rdb"
13868 Then, in @value{GDBN}, type:
13871 (vxgdb) cd @var{hostpath}/vw/demo/rdb
13872 (vxgdb) load prog.o
13875 @value{GDBN} displays a response similar to this:
13878 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
13881 You can also use the @code{load} command to reload an object module
13882 after editing and recompiling the corresponding source file. Note that
13883 this makes @value{GDBN} delete all currently-defined breakpoints,
13884 auto-displays, and convenience variables, and to clear the value
13885 history. (This is necessary in order to preserve the integrity of
13886 debugger's data structures that reference the target system's symbol
13889 @node VxWorks Attach
13890 @subsubsection Running tasks
13892 @cindex running VxWorks tasks
13893 You can also attach to an existing task using the @code{attach} command as
13897 (vxgdb) attach @var{task}
13901 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
13902 or suspended when you attach to it. Running tasks are suspended at
13903 the time of attachment.
13905 @node Embedded Processors
13906 @section Embedded Processors
13908 This section goes into details specific to particular embedded
13911 @cindex send command to simulator
13912 Whenever a specific embedded processor has a simulator, @value{GDBN}
13913 allows to send an arbitrary command to the simulator.
13916 @item sim @var{command}
13917 @kindex sim@r{, a command}
13918 Send an arbitrary @var{command} string to the simulator. Consult the
13919 documentation for the specific simulator in use for information about
13920 acceptable commands.
13926 * H8/300:: Renesas H8/300
13927 * H8/500:: Renesas H8/500
13928 * M32R/D:: Renesas M32R/D
13929 * M68K:: Motorola M68K
13930 * MIPS Embedded:: MIPS Embedded
13931 * OpenRISC 1000:: OpenRisc 1000
13932 * PA:: HP PA Embedded
13935 * Sparclet:: Tsqware Sparclet
13936 * Sparclite:: Fujitsu Sparclite
13937 * ST2000:: Tandem ST2000
13938 * Z8000:: Zilog Z8000
13941 * Super-H:: Renesas Super-H
13942 * WinCE:: Windows CE child processes
13951 @item target rdi @var{dev}
13952 ARM Angel monitor, via RDI library interface to ADP protocol. You may
13953 use this target to communicate with both boards running the Angel
13954 monitor, or with the EmbeddedICE JTAG debug device.
13957 @item target rdp @var{dev}
13962 @value{GDBN} provides the following ARM-specific commands:
13965 @item set arm disassembler
13967 This commands selects from a list of disassembly styles. The
13968 @code{"std"} style is the standard style.
13970 @item show arm disassembler
13972 Show the current disassembly style.
13974 @item set arm apcs32
13975 @cindex ARM 32-bit mode
13976 This command toggles ARM operation mode between 32-bit and 26-bit.
13978 @item show arm apcs32
13979 Display the current usage of the ARM 32-bit mode.
13981 @item set arm fpu @var{fputype}
13982 This command sets the ARM floating-point unit (FPU) type. The
13983 argument @var{fputype} can be one of these:
13987 Determine the FPU type by querying the OS ABI.
13989 Software FPU, with mixed-endian doubles on little-endian ARM
13992 GCC-compiled FPA co-processor.
13994 Software FPU with pure-endian doubles.
14000 Show the current type of the FPU.
14003 This command forces @value{GDBN} to use the specified ABI.
14006 Show the currently used ABI.
14008 @item set debug arm
14009 Toggle whether to display ARM-specific debugging messages from the ARM
14010 target support subsystem.
14012 @item show debug arm
14013 Show whether ARM-specific debugging messages are enabled.
14016 The following commands are available when an ARM target is debugged
14017 using the RDI interface:
14020 @item rdilogfile @r{[}@var{file}@r{]}
14022 @cindex ADP (Angel Debugger Protocol) logging
14023 Set the filename for the ADP (Angel Debugger Protocol) packet log.
14024 With an argument, sets the log file to the specified @var{file}. With
14025 no argument, show the current log file name. The default log file is
14028 @item rdilogenable @r{[}@var{arg}@r{]}
14029 @kindex rdilogenable
14030 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
14031 enables logging, with an argument 0 or @code{"no"} disables it. With
14032 no arguments displays the current setting. When logging is enabled,
14033 ADP packets exchanged between @value{GDBN} and the RDI target device
14034 are logged to a file.
14036 @item set rdiromatzero
14037 @kindex set rdiromatzero
14038 @cindex ROM at zero address, RDI
14039 Tell @value{GDBN} whether the target has ROM at address 0. If on,
14040 vector catching is disabled, so that zero address can be used. If off
14041 (the default), vector catching is enabled. For this command to take
14042 effect, it needs to be invoked prior to the @code{target rdi} command.
14044 @item show rdiromatzero
14045 @kindex show rdiromatzero
14046 Show the current setting of ROM at zero address.
14048 @item set rdiheartbeat
14049 @kindex set rdiheartbeat
14050 @cindex RDI heartbeat
14051 Enable or disable RDI heartbeat packets. It is not recommended to
14052 turn on this option, since it confuses ARM and EPI JTAG interface, as
14053 well as the Angel monitor.
14055 @item show rdiheartbeat
14056 @kindex show rdiheartbeat
14057 Show the setting of RDI heartbeat packets.
14062 @subsection Renesas H8/300
14066 @kindex target hms@r{, with H8/300}
14067 @item target hms @var{dev}
14068 A Renesas SH, H8/300, or H8/500 board, attached via serial line to your host.
14069 Use special commands @code{device} and @code{speed} to control the serial
14070 line and the communications speed used.
14072 @kindex target e7000@r{, with H8/300}
14073 @item target e7000 @var{dev}
14074 E7000 emulator for Renesas H8 and SH.
14076 @kindex target sh3@r{, with H8/300}
14077 @kindex target sh3e@r{, with H8/300}
14078 @item target sh3 @var{dev}
14079 @itemx target sh3e @var{dev}
14080 Renesas SH-3 and SH-3E target systems.
14084 @cindex download to H8/300 or H8/500
14085 @cindex H8/300 or H8/500 download
14086 @cindex download to Renesas SH
14087 @cindex Renesas SH download
14088 When you select remote debugging to a Renesas SH, H8/300, or H8/500
14089 board, the @code{load} command downloads your program to the Renesas
14090 board and also opens it as the current executable target for
14091 @value{GDBN} on your host (like the @code{file} command).
14093 @value{GDBN} needs to know these things to talk to your
14094 Renesas SH, H8/300, or H8/500:
14098 that you want to use @samp{target hms}, the remote debugging interface
14099 for Renesas microprocessors, or @samp{target e7000}, the in-circuit
14100 emulator for the Renesas SH and the Renesas 300H. (@samp{target hms} is
14101 the default when @value{GDBN} is configured specifically for the Renesas SH,
14102 H8/300, or H8/500.)
14105 what serial device connects your host to your Renesas board (the first
14106 serial device available on your host is the default).
14109 what speed to use over the serial device.
14113 * Renesas Boards:: Connecting to Renesas boards.
14114 * Renesas ICE:: Using the E7000 In-Circuit Emulator.
14115 * Renesas Special:: Special @value{GDBN} commands for Renesas micros.
14118 @node Renesas Boards
14119 @subsubsection Connecting to Renesas boards
14121 @c only for Unix hosts
14123 @cindex serial device, Renesas micros
14124 Use the special @code{@value{GDBN}} command @samp{device @var{port}} if you
14125 need to explicitly set the serial device. The default @var{port} is the
14126 first available port on your host. This is only necessary on Unix
14127 hosts, where it is typically something like @file{/dev/ttya}.
14130 @cindex serial line speed, Renesas micros
14131 @code{@value{GDBN}} has another special command to set the communications
14132 speed: @samp{speed @var{bps}}. This command also is only used from Unix
14133 hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with
14134 the DOS @code{mode} command (for instance,
14135 @w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection).
14137 The @samp{device} and @samp{speed} commands are available only when you
14138 use a Unix host to debug your Renesas microprocessor programs. If you
14140 @value{GDBN} depends on an auxiliary terminate-and-stay-resident program
14141 called @code{asynctsr} to communicate with the development board
14142 through a PC serial port. You must also use the DOS @code{mode} command
14143 to set up the serial port on the DOS side.
14145 The following sample session illustrates the steps needed to start a
14146 program under @value{GDBN} control on an H8/300. The example uses a
14147 sample H8/300 program called @file{t.x}. The procedure is the same for
14148 the Renesas SH and the H8/500.
14150 First hook up your development board. In this example, we use a
14151 board attached to serial port @code{COM2}; if you use a different serial
14152 port, substitute its name in the argument of the @code{mode} command.
14153 When you call @code{asynctsr}, the auxiliary comms program used by the
14154 debugger, you give it just the numeric part of the serial port's name;
14155 for example, @samp{asyncstr 2} below runs @code{asyncstr} on
14159 C:\H8300\TEST> asynctsr 2
14160 C:\H8300\TEST> mode com2:9600,n,8,1,p
14162 Resident portion of MODE loaded
14164 COM2: 9600, n, 8, 1, p
14169 @emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
14170 @code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
14171 disable it, or even boot without it, to use @code{asynctsr} to control
14172 your development board.
14175 @kindex target hms@r{, and serial protocol}
14176 Now that serial communications are set up, and the development board is
14177 connected, you can start up @value{GDBN}. Call @code{@value{GDBN}} with
14178 the name of your program as the argument. @code{@value{GDBN}} prompts
14179 you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
14180 commands to begin your debugging session: @samp{target hms} to specify
14181 cross-debugging to the Renesas board, and the @code{load} command to
14182 download your program to the board. @code{load} displays the names of
14183 the program's sections, and a @samp{*} for each 2K of data downloaded.
14184 (If you want to refresh @value{GDBN} data on symbols or on the
14185 executable file without downloading, use the @value{GDBN} commands
14186 @code{file} or @code{symbol-file}. These commands, and @code{load}
14187 itself, are described in @ref{Files,,Commands to specify files}.)
14190 (eg-C:\H8300\TEST) @value{GDBP} t.x
14191 @value{GDBN} is free software and you are welcome to distribute copies
14192 of it under certain conditions; type "show copying" to see
14194 There is absolutely no warranty for @value{GDBN}; type "show warranty"
14196 @value{GDBN} @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
14197 (@value{GDBP}) target hms
14198 Connected to remote H8/300 HMS system.
14199 (@value{GDBP}) load t.x
14200 .text : 0x8000 .. 0xabde ***********
14201 .data : 0xabde .. 0xad30 *
14202 .stack : 0xf000 .. 0xf014 *
14205 At this point, you're ready to run or debug your program. From here on,
14206 you can use all the usual @value{GDBN} commands. The @code{break} command
14207 sets breakpoints; the @code{run} command starts your program;
14208 @code{print} or @code{x} display data; the @code{continue} command
14209 resumes execution after stopping at a breakpoint. You can use the
14210 @code{help} command at any time to find out more about @value{GDBN} commands.
14212 Remember, however, that @emph{operating system} facilities aren't
14213 available on your development board; for example, if your program hangs,
14214 you can't send an interrupt---but you can press the @sc{reset} switch!
14216 Use the @sc{reset} button on the development board
14219 to interrupt your program (don't use @kbd{ctl-C} on the DOS host---it has
14220 no way to pass an interrupt signal to the development board); and
14223 to return to the @value{GDBN} command prompt after your program finishes
14224 normally. The communications protocol provides no other way for @value{GDBN}
14225 to detect program completion.
14228 In either case, @value{GDBN} sees the effect of a @sc{reset} on the
14229 development board as a ``normal exit'' of your program.
14232 @subsubsection Using the E7000 in-circuit emulator
14234 @kindex target e7000@r{, with Renesas ICE}
14235 You can use the E7000 in-circuit emulator to develop code for either the
14236 Renesas SH or the H8/300H. Use one of these forms of the @samp{target
14237 e7000} command to connect @value{GDBN} to your E7000:
14240 @item target e7000 @var{port} @var{speed}
14241 Use this form if your E7000 is connected to a serial port. The
14242 @var{port} argument identifies what serial port to use (for example,
14243 @samp{com2}). The third argument is the line speed in bits per second
14244 (for example, @samp{9600}).
14246 @item target e7000 @var{hostname}
14247 If your E7000 is installed as a host on a TCP/IP network, you can just
14248 specify its hostname; @value{GDBN} uses @code{telnet} to connect.
14251 The following special commands are available when debugging with the
14255 @item e7000 @var{command}
14257 @cindex send command to E7000 monitor
14258 This sends the specified @var{command} to the E7000 monitor.
14260 @item ftplogin @var{machine} @var{username} @var{password} @var{dir}
14261 @kindex ftplogin@r{, E7000}
14262 This command records information for subsequent interface with the
14263 E7000 monitor via the FTP protocol: @value{GDBN} will log into the
14264 named @var{machine} using specified @var{username} and @var{password},
14265 and then chdir to the named directory @var{dir}.
14267 @item ftpload @var{file}
14268 @kindex ftpload@r{, E7000}
14269 This command uses credentials recorded by @code{ftplogin} to fetch and
14270 load the named @var{file} from the E7000 monitor.
14273 @kindex drain@r{, E7000}
14274 This command drains any pending text buffers stored on the E7000.
14276 @item set usehardbreakpoints
14277 @itemx show usehardbreakpoints
14278 @kindex set usehardbreakpoints@r{, E7000}
14279 @kindex show usehardbreakpoints@r{, E7000}
14280 @cindex hardware breakpoints, and E7000
14281 These commands set and show the use of hardware breakpoints for all
14282 breakpoints. @xref{Set Breaks, hardware-assisted breakpoint}, for
14283 more information about using hardware breakpoints selectively.
14286 @node Renesas Special
14287 @subsubsection Special @value{GDBN} commands for Renesas micros
14289 Some @value{GDBN} commands are available only for the H8/300:
14293 @kindex set machine
14294 @kindex show machine
14295 @item set machine h8300
14296 @itemx set machine h8300h
14297 Condition @value{GDBN} for one of the two variants of the H8/300
14298 architecture with @samp{set machine}. You can use @samp{show machine}
14299 to check which variant is currently in effect.
14308 @kindex set memory @var{mod}
14309 @cindex memory models, H8/500
14310 @item set memory @var{mod}
14312 Specify which H8/500 memory model (@var{mod}) you are using with
14313 @samp{set memory}; check which memory model is in effect with @samp{show
14314 memory}. The accepted values for @var{mod} are @code{small},
14315 @code{big}, @code{medium}, and @code{compact}.
14320 @subsection Renesas M32R/D and M32R/SDI
14323 @kindex target m32r
14324 @item target m32r @var{dev}
14325 Renesas M32R/D ROM monitor.
14327 @kindex target m32rsdi
14328 @item target m32rsdi @var{dev}
14329 Renesas M32R SDI server, connected via parallel port to the board.
14332 The following @value{GDBN} commands are specific to the M32R monitor:
14335 @item set download-path @var{path}
14336 @kindex set download-path
14337 @cindex find downloadable @sc{srec} files (M32R)
14338 Set the default path for finding donwloadable @sc{srec} files.
14340 @item show download-path
14341 @kindex show download-path
14342 Show the default path for downloadable @sc{srec} files.
14344 @item set board-address @var{addr}
14345 @kindex set board-address
14346 @cindex M32-EVA target board address
14347 Set the IP address for the M32R-EVA target board.
14349 @item show board-address
14350 @kindex show board-address
14351 Show the current IP address of the target board.
14353 @item set server-address @var{addr}
14354 @kindex set server-address
14355 @cindex download server address (M32R)
14356 Set the IP address for the download server, which is the @value{GDBN}'s
14359 @item show server-address
14360 @kindex show server-address
14361 Display the IP address of the download server.
14363 @item upload @r{[}@var{file}@r{]}
14364 @kindex upload@r{, M32R}
14365 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
14366 upload capability. If no @var{file} argument is given, the current
14367 executable file is uploaded.
14369 @item tload @r{[}@var{file}@r{]}
14370 @kindex tload@r{, M32R}
14371 Test the @code{upload} command.
14374 The following commands are available for M32R/SDI:
14379 @cindex reset SDI connection, M32R
14380 This command resets the SDI connection.
14384 This command shows the SDI connection status.
14387 @kindex debug_chaos
14388 @cindex M32R/Chaos debugging
14389 Instructs the remote that M32R/Chaos debugging is to be used.
14391 @item use_debug_dma
14392 @kindex use_debug_dma
14393 Instructs the remote to use the DEBUG_DMA method of accessing memory.
14396 @kindex use_mon_code
14397 Instructs the remote to use the MON_CODE method of accessing memory.
14400 @kindex use_ib_break
14401 Instructs the remote to set breakpoints by IB break.
14403 @item use_dbt_break
14404 @kindex use_dbt_break
14405 Instructs the remote to set breakpoints by DBT.
14411 The Motorola m68k configuration includes ColdFire support, and
14412 target command for the following ROM monitors.
14416 @kindex target abug
14417 @item target abug @var{dev}
14418 ABug ROM monitor for M68K.
14420 @kindex target cpu32bug
14421 @item target cpu32bug @var{dev}
14422 CPU32BUG monitor, running on a CPU32 (M68K) board.
14424 @kindex target dbug
14425 @item target dbug @var{dev}
14426 dBUG ROM monitor for Motorola ColdFire.
14429 @item target est @var{dev}
14430 EST-300 ICE monitor, running on a CPU32 (M68K) board.
14432 @kindex target rom68k
14433 @item target rom68k @var{dev}
14434 ROM 68K monitor, running on an M68K IDP board.
14440 @kindex target rombug
14441 @item target rombug @var{dev}
14442 ROMBUG ROM monitor for OS/9000.
14446 @node MIPS Embedded
14447 @subsection MIPS Embedded
14449 @cindex MIPS boards
14450 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
14451 MIPS board attached to a serial line. This is available when
14452 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
14455 Use these @value{GDBN} commands to specify the connection to your target board:
14458 @item target mips @var{port}
14459 @kindex target mips @var{port}
14460 To run a program on the board, start up @code{@value{GDBP}} with the
14461 name of your program as the argument. To connect to the board, use the
14462 command @samp{target mips @var{port}}, where @var{port} is the name of
14463 the serial port connected to the board. If the program has not already
14464 been downloaded to the board, you may use the @code{load} command to
14465 download it. You can then use all the usual @value{GDBN} commands.
14467 For example, this sequence connects to the target board through a serial
14468 port, and loads and runs a program called @var{prog} through the
14472 host$ @value{GDBP} @var{prog}
14473 @value{GDBN} is free software and @dots{}
14474 (@value{GDBP}) target mips /dev/ttyb
14475 (@value{GDBP}) load @var{prog}
14479 @item target mips @var{hostname}:@var{portnumber}
14480 On some @value{GDBN} host configurations, you can specify a TCP
14481 connection (for instance, to a serial line managed by a terminal
14482 concentrator) instead of a serial port, using the syntax
14483 @samp{@var{hostname}:@var{portnumber}}.
14485 @item target pmon @var{port}
14486 @kindex target pmon @var{port}
14489 @item target ddb @var{port}
14490 @kindex target ddb @var{port}
14491 NEC's DDB variant of PMON for Vr4300.
14493 @item target lsi @var{port}
14494 @kindex target lsi @var{port}
14495 LSI variant of PMON.
14497 @kindex target r3900
14498 @item target r3900 @var{dev}
14499 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
14501 @kindex target array
14502 @item target array @var{dev}
14503 Array Tech LSI33K RAID controller board.
14509 @value{GDBN} also supports these special commands for MIPS targets:
14512 @item set mipsfpu double
14513 @itemx set mipsfpu single
14514 @itemx set mipsfpu none
14515 @itemx set mipsfpu auto
14516 @itemx show mipsfpu
14517 @kindex set mipsfpu
14518 @kindex show mipsfpu
14519 @cindex MIPS remote floating point
14520 @cindex floating point, MIPS remote
14521 If your target board does not support the MIPS floating point
14522 coprocessor, you should use the command @samp{set mipsfpu none} (if you
14523 need this, you may wish to put the command in your @value{GDBN} init
14524 file). This tells @value{GDBN} how to find the return value of
14525 functions which return floating point values. It also allows
14526 @value{GDBN} to avoid saving the floating point registers when calling
14527 functions on the board. If you are using a floating point coprocessor
14528 with only single precision floating point support, as on the @sc{r4650}
14529 processor, use the command @samp{set mipsfpu single}. The default
14530 double precision floating point coprocessor may be selected using
14531 @samp{set mipsfpu double}.
14533 In previous versions the only choices were double precision or no
14534 floating point, so @samp{set mipsfpu on} will select double precision
14535 and @samp{set mipsfpu off} will select no floating point.
14537 As usual, you can inquire about the @code{mipsfpu} variable with
14538 @samp{show mipsfpu}.
14540 @item set timeout @var{seconds}
14541 @itemx set retransmit-timeout @var{seconds}
14542 @itemx show timeout
14543 @itemx show retransmit-timeout
14544 @cindex @code{timeout}, MIPS protocol
14545 @cindex @code{retransmit-timeout}, MIPS protocol
14546 @kindex set timeout
14547 @kindex show timeout
14548 @kindex set retransmit-timeout
14549 @kindex show retransmit-timeout
14550 You can control the timeout used while waiting for a packet, in the MIPS
14551 remote protocol, with the @code{set timeout @var{seconds}} command. The
14552 default is 5 seconds. Similarly, you can control the timeout used while
14553 waiting for an acknowledgement of a packet with the @code{set
14554 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
14555 You can inspect both values with @code{show timeout} and @code{show
14556 retransmit-timeout}. (These commands are @emph{only} available when
14557 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
14559 The timeout set by @code{set timeout} does not apply when @value{GDBN}
14560 is waiting for your program to stop. In that case, @value{GDBN} waits
14561 forever because it has no way of knowing how long the program is going
14562 to run before stopping.
14564 @item set syn-garbage-limit @var{num}
14565 @kindex set syn-garbage-limit@r{, MIPS remote}
14566 @cindex synchronize with remote MIPS target
14567 Limit the maximum number of characters @value{GDBN} should ignore when
14568 it tries to synchronize with the remote target. The default is 10
14569 characters. Setting the limit to -1 means there's no limit.
14571 @item show syn-garbage-limit
14572 @kindex show syn-garbage-limit@r{, MIPS remote}
14573 Show the current limit on the number of characters to ignore when
14574 trying to synchronize with the remote system.
14576 @item set monitor-prompt @var{prompt}
14577 @kindex set monitor-prompt@r{, MIPS remote}
14578 @cindex remote monitor prompt
14579 Tell @value{GDBN} to expect the specified @var{prompt} string from the
14580 remote monitor. The default depends on the target:
14590 @item show monitor-prompt
14591 @kindex show monitor-prompt@r{, MIPS remote}
14592 Show the current strings @value{GDBN} expects as the prompt from the
14595 @item set monitor-warnings
14596 @kindex set monitor-warnings@r{, MIPS remote}
14597 Enable or disable monitor warnings about hardware breakpoints. This
14598 has effect only for the @code{lsi} target. When on, @value{GDBN} will
14599 display warning messages whose codes are returned by the @code{lsi}
14600 PMON monitor for breakpoint commands.
14602 @item show monitor-warnings
14603 @kindex show monitor-warnings@r{, MIPS remote}
14604 Show the current setting of printing monitor warnings.
14606 @item pmon @var{command}
14607 @kindex pmon@r{, MIPS remote}
14608 @cindex send PMON command
14609 This command allows sending an arbitrary @var{command} string to the
14610 monitor. The monitor must be in debug mode for this to work.
14613 @node OpenRISC 1000
14614 @subsection OpenRISC 1000
14615 @cindex OpenRISC 1000
14617 @cindex or1k boards
14618 See OR1k Architecture document (@uref{www.opencores.org}) for more information
14619 about platform and commands.
14623 @kindex target jtag
14624 @item target jtag jtag://@var{host}:@var{port}
14626 Connects to remote JTAG server.
14627 JTAG remote server can be either an or1ksim or JTAG server,
14628 connected via parallel port to the board.
14630 Example: @code{target jtag jtag://localhost:9999}
14633 @item or1ksim @var{command}
14634 If connected to @code{or1ksim} OpenRISC 1000 Architectural
14635 Simulator, proprietary commands can be executed.
14637 @kindex info or1k spr
14638 @item info or1k spr
14639 Displays spr groups.
14641 @item info or1k spr @var{group}
14642 @itemx info or1k spr @var{groupno}
14643 Displays register names in selected group.
14645 @item info or1k spr @var{group} @var{register}
14646 @itemx info or1k spr @var{register}
14647 @itemx info or1k spr @var{groupno} @var{registerno}
14648 @itemx info or1k spr @var{registerno}
14649 Shows information about specified spr register.
14652 @item spr @var{group} @var{register} @var{value}
14653 @itemx spr @var{register @var{value}}
14654 @itemx spr @var{groupno} @var{registerno @var{value}}
14655 @itemx spr @var{registerno @var{value}}
14656 Writes @var{value} to specified spr register.
14659 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
14660 It is very similar to @value{GDBN} trace, except it does not interfere with normal
14661 program execution and is thus much faster. Hardware breakpoints/watchpoint
14662 triggers can be set using:
14665 Load effective address/data
14667 Store effective address/data
14669 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
14674 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
14675 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
14677 @code{htrace} commands:
14678 @cindex OpenRISC 1000 htrace
14681 @item hwatch @var{conditional}
14682 Set hardware watchpoint on combination of Load/Store Effecive Address(es)
14683 or Data. For example:
14685 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
14687 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
14691 Display information about current HW trace configuration.
14693 @item htrace trigger @var{conditional}
14694 Set starting criteria for HW trace.
14696 @item htrace qualifier @var{conditional}
14697 Set acquisition qualifier for HW trace.
14699 @item htrace stop @var{conditional}
14700 Set HW trace stopping criteria.
14702 @item htrace record [@var{data}]*
14703 Selects the data to be recorded, when qualifier is met and HW trace was
14706 @item htrace enable
14707 @itemx htrace disable
14708 Enables/disables the HW trace.
14710 @item htrace rewind [@var{filename}]
14711 Clears currently recorded trace data.
14713 If filename is specified, new trace file is made and any newly collected data
14714 will be written there.
14716 @item htrace print [@var{start} [@var{len}]]
14717 Prints trace buffer, using current record configuration.
14719 @item htrace mode continuous
14720 Set continuous trace mode.
14722 @item htrace mode suspend
14723 Set suspend trace mode.
14728 @subsection PowerPC
14731 @kindex target dink32
14732 @item target dink32 @var{dev}
14733 DINK32 ROM monitor.
14735 @kindex target ppcbug
14736 @item target ppcbug @var{dev}
14737 @kindex target ppcbug1
14738 @item target ppcbug1 @var{dev}
14739 PPCBUG ROM monitor for PowerPC.
14742 @item target sds @var{dev}
14743 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
14746 @cindex SDS protocol
14747 The following commands specifi to the SDS protocol are supported
14751 @item set sdstimeout @var{nsec}
14752 @kindex set sdstimeout
14753 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
14754 default is 2 seconds.
14756 @item show sdstimeout
14757 @kindex show sdstimeout
14758 Show the current value of the SDS timeout.
14760 @item sds @var{command}
14761 @kindex sds@r{, a command}
14762 Send the specified @var{command} string to the SDS monitor.
14767 @subsection HP PA Embedded
14771 @kindex target op50n
14772 @item target op50n @var{dev}
14773 OP50N monitor, running on an OKI HPPA board.
14775 @kindex target w89k
14776 @item target w89k @var{dev}
14777 W89K monitor, running on a Winbond HPPA board.
14782 @subsection Renesas SH
14786 @kindex target hms@r{, with Renesas SH}
14787 @item target hms @var{dev}
14788 A Renesas SH board attached via serial line to your host. Use special
14789 commands @code{device} and @code{speed} to control the serial line and
14790 the communications speed used.
14792 @kindex target e7000@r{, with Renesas SH}
14793 @item target e7000 @var{dev}
14794 E7000 emulator for Renesas SH.
14796 @kindex target sh3@r{, with SH}
14797 @kindex target sh3e@r{, with SH}
14798 @item target sh3 @var{dev}
14799 @item target sh3e @var{dev}
14800 Renesas SH-3 and SH-3E target systems.
14805 @subsection Tsqware Sparclet
14809 @value{GDBN} enables developers to debug tasks running on
14810 Sparclet targets from a Unix host.
14811 @value{GDBN} uses code that runs on
14812 both the Unix host and on the Sparclet target. The program
14813 @code{@value{GDBP}} is installed and executed on the Unix host.
14816 @item remotetimeout @var{args}
14817 @kindex remotetimeout
14818 @value{GDBN} supports the option @code{remotetimeout}.
14819 This option is set by the user, and @var{args} represents the number of
14820 seconds @value{GDBN} waits for responses.
14823 @cindex compiling, on Sparclet
14824 When compiling for debugging, include the options @samp{-g} to get debug
14825 information and @samp{-Ttext} to relocate the program to where you wish to
14826 load it on the target. You may also want to add the options @samp{-n} or
14827 @samp{-N} in order to reduce the size of the sections. Example:
14830 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
14833 You can use @code{objdump} to verify that the addresses are what you intended:
14836 sparclet-aout-objdump --headers --syms prog
14839 @cindex running, on Sparclet
14841 your Unix execution search path to find @value{GDBN}, you are ready to
14842 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
14843 (or @code{sparclet-aout-gdb}, depending on your installation).
14845 @value{GDBN} comes up showing the prompt:
14852 * Sparclet File:: Setting the file to debug
14853 * Sparclet Connection:: Connecting to Sparclet
14854 * Sparclet Download:: Sparclet download
14855 * Sparclet Execution:: Running and debugging
14858 @node Sparclet File
14859 @subsubsection Setting file to debug
14861 The @value{GDBN} command @code{file} lets you choose with program to debug.
14864 (gdbslet) file prog
14868 @value{GDBN} then attempts to read the symbol table of @file{prog}.
14869 @value{GDBN} locates
14870 the file by searching the directories listed in the command search
14872 If the file was compiled with debug information (option "-g"), source
14873 files will be searched as well.
14874 @value{GDBN} locates
14875 the source files by searching the directories listed in the directory search
14876 path (@pxref{Environment, ,Your program's environment}).
14878 to find a file, it displays a message such as:
14881 prog: No such file or directory.
14884 When this happens, add the appropriate directories to the search paths with
14885 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
14886 @code{target} command again.
14888 @node Sparclet Connection
14889 @subsubsection Connecting to Sparclet
14891 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
14892 To connect to a target on serial port ``@code{ttya}'', type:
14895 (gdbslet) target sparclet /dev/ttya
14896 Remote target sparclet connected to /dev/ttya
14897 main () at ../prog.c:3
14901 @value{GDBN} displays messages like these:
14907 @node Sparclet Download
14908 @subsubsection Sparclet download
14910 @cindex download to Sparclet
14911 Once connected to the Sparclet target,
14912 you can use the @value{GDBN}
14913 @code{load} command to download the file from the host to the target.
14914 The file name and load offset should be given as arguments to the @code{load}
14916 Since the file format is aout, the program must be loaded to the starting
14917 address. You can use @code{objdump} to find out what this value is. The load
14918 offset is an offset which is added to the VMA (virtual memory address)
14919 of each of the file's sections.
14920 For instance, if the program
14921 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
14922 and bss at 0x12010170, in @value{GDBN}, type:
14925 (gdbslet) load prog 0x12010000
14926 Loading section .text, size 0xdb0 vma 0x12010000
14929 If the code is loaded at a different address then what the program was linked
14930 to, you may need to use the @code{section} and @code{add-symbol-file} commands
14931 to tell @value{GDBN} where to map the symbol table.
14933 @node Sparclet Execution
14934 @subsubsection Running and debugging
14936 @cindex running and debugging Sparclet programs
14937 You can now begin debugging the task using @value{GDBN}'s execution control
14938 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
14939 manual for the list of commands.
14943 Breakpoint 1 at 0x12010000: file prog.c, line 3.
14945 Starting program: prog
14946 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
14947 3 char *symarg = 0;
14949 4 char *execarg = "hello!";
14954 @subsection Fujitsu Sparclite
14958 @kindex target sparclite
14959 @item target sparclite @var{dev}
14960 Fujitsu sparclite boards, used only for the purpose of loading.
14961 You must use an additional command to debug the program.
14962 For example: target remote @var{dev} using @value{GDBN} standard
14968 @subsection Tandem ST2000
14970 @value{GDBN} may be used with a Tandem ST2000 phone switch, running Tandem's
14973 To connect your ST2000 to the host system, see the manufacturer's
14974 manual. Once the ST2000 is physically attached, you can run:
14977 target st2000 @var{dev} @var{speed}
14981 to establish it as your debugging environment. @var{dev} is normally
14982 the name of a serial device, such as @file{/dev/ttya}, connected to the
14983 ST2000 via a serial line. You can instead specify @var{dev} as a TCP
14984 connection (for example, to a serial line attached via a terminal
14985 concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}.
14987 The @code{load} and @code{attach} commands are @emph{not} defined for
14988 this target; you must load your program into the ST2000 as you normally
14989 would for standalone operation. @value{GDBN} reads debugging information
14990 (such as symbols) from a separate, debugging version of the program
14991 available on your host computer.
14992 @c FIXME!! This is terribly vague; what little content is here is
14993 @c basically hearsay.
14995 @cindex ST2000 auxiliary commands
14996 These auxiliary @value{GDBN} commands are available to help you with the ST2000
15000 @item st2000 @var{command}
15001 @kindex st2000 @var{cmd}
15002 @cindex STDBUG commands (ST2000)
15003 @cindex commands to STDBUG (ST2000)
15004 Send a @var{command} to the STDBUG monitor. See the manufacturer's
15005 manual for available commands.
15008 @cindex connect (to STDBUG)
15009 Connect the controlling terminal to the STDBUG command monitor. When
15010 you are done interacting with STDBUG, typing either of two character
15011 sequences gets you back to the @value{GDBN} command prompt:
15012 @kbd{@key{RET}~.} (Return, followed by tilde and period) or
15013 @kbd{@key{RET}~@key{C-d}} (Return, followed by tilde and control-D).
15017 @subsection Zilog Z8000
15020 @cindex simulator, Z8000
15021 @cindex Zilog Z8000 simulator
15023 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
15026 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
15027 unsegmented variant of the Z8000 architecture) or the Z8001 (the
15028 segmented variant). The simulator recognizes which architecture is
15029 appropriate by inspecting the object code.
15032 @item target sim @var{args}
15034 @kindex target sim@r{, with Z8000}
15035 Debug programs on a simulated CPU. If the simulator supports setup
15036 options, specify them via @var{args}.
15040 After specifying this target, you can debug programs for the simulated
15041 CPU in the same style as programs for your host computer; use the
15042 @code{file} command to load a new program image, the @code{run} command
15043 to run your program, and so on.
15045 As well as making available all the usual machine registers
15046 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
15047 additional items of information as specially named registers:
15052 Counts clock-ticks in the simulator.
15055 Counts instructions run in the simulator.
15058 Execution time in 60ths of a second.
15062 You can refer to these values in @value{GDBN} expressions with the usual
15063 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
15064 conditional breakpoint that suspends only after at least 5000
15065 simulated clock ticks.
15068 @subsection Atmel AVR
15071 When configured for debugging the Atmel AVR, @value{GDBN} supports the
15072 following AVR-specific commands:
15075 @item info io_registers
15076 @kindex info io_registers@r{, AVR}
15077 @cindex I/O registers (Atmel AVR)
15078 This command displays information about the AVR I/O registers. For
15079 each register, @value{GDBN} prints its number and value.
15086 When configured for debugging CRIS, @value{GDBN} provides the
15087 following CRIS-specific commands:
15090 @item set cris-version @var{ver}
15091 @cindex CRIS version
15092 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
15093 The CRIS version affects register names and sizes. This command is useful in
15094 case autodetection of the CRIS version fails.
15096 @item show cris-version
15097 Show the current CRIS version.
15099 @item set cris-dwarf2-cfi
15100 @cindex DWARF-2 CFI and CRIS
15101 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
15102 Change to @samp{off} when using @code{gcc-cris} whose version is below
15105 @item show cris-dwarf2-cfi
15106 Show the current state of using DWARF-2 CFI.
15108 @item set cris-mode @var{mode}
15110 Set the current CRIS mode to @var{mode}. It should only be changed when
15111 debugging in guru mode, in which case it should be set to
15112 @samp{guru} (the default is @samp{normal}).
15114 @item show cris-mode
15115 Show the current CRIS mode.
15119 @subsection Renesas Super-H
15122 For the Renesas Super-H processor, @value{GDBN} provides these
15127 @kindex regs@r{, Super-H}
15128 Show the values of all Super-H registers.
15132 @subsection Windows CE
15135 The following commands are available for Windows CE:
15138 @item set remotedirectory @var{dir}
15139 @kindex set remotedirectory
15140 Tell @value{GDBN} to upload files from the named directory @var{dir}.
15141 The default is @file{/gdb}, i.e.@: the root directory on the current
15144 @item show remotedirectory
15145 @kindex show remotedirectory
15146 Show the current value of the upload directory.
15148 @item set remoteupload @var{method}
15149 @kindex set remoteupload
15150 Set the method used to upload files to remote device. Valid values
15151 for @var{method} are @samp{always}, @samp{newer}, and @samp{never}.
15152 The default is @samp{newer}.
15154 @item show remoteupload
15155 @kindex show remoteupload
15156 Show the current setting of the upload method.
15158 @item set remoteaddhost
15159 @kindex set remoteaddhost
15160 Tell @value{GDBN} whether to add this host to the remote stub's
15161 arguments when you debug over a network.
15163 @item show remoteaddhost
15164 @kindex show remoteaddhost
15165 Show whether to add this host to remote stub's arguments when
15166 debugging over a network.
15170 @node Architectures
15171 @section Architectures
15173 This section describes characteristics of architectures that affect
15174 all uses of @value{GDBN} with the architecture, both native and cross.
15181 * HPPA:: HP PA architecture
15185 @subsection x86 Architecture-specific issues.
15188 @item set struct-convention @var{mode}
15189 @kindex set struct-convention
15190 @cindex struct return convention
15191 @cindex struct/union returned in registers
15192 Set the convention used by the inferior to return @code{struct}s and
15193 @code{union}s from functions to @var{mode}. Possible values of
15194 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
15195 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
15196 are returned on the stack, while @code{"reg"} means that a
15197 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
15198 be returned in a register.
15200 @item show struct-convention
15201 @kindex show struct-convention
15202 Show the current setting of the convention to return @code{struct}s
15211 @kindex set rstack_high_address
15212 @cindex AMD 29K register stack
15213 @cindex register stack, AMD29K
15214 @item set rstack_high_address @var{address}
15215 On AMD 29000 family processors, registers are saved in a separate
15216 @dfn{register stack}. There is no way for @value{GDBN} to determine the
15217 extent of this stack. Normally, @value{GDBN} just assumes that the
15218 stack is ``large enough''. This may result in @value{GDBN} referencing
15219 memory locations that do not exist. If necessary, you can get around
15220 this problem by specifying the ending address of the register stack with
15221 the @code{set rstack_high_address} command. The argument should be an
15222 address, which you probably want to precede with @samp{0x} to specify in
15225 @kindex show rstack_high_address
15226 @item show rstack_high_address
15227 Display the current limit of the register stack, on AMD 29000 family
15235 See the following section.
15240 @cindex stack on Alpha
15241 @cindex stack on MIPS
15242 @cindex Alpha stack
15244 Alpha- and MIPS-based computers use an unusual stack frame, which
15245 sometimes requires @value{GDBN} to search backward in the object code to
15246 find the beginning of a function.
15248 @cindex response time, MIPS debugging
15249 To improve response time (especially for embedded applications, where
15250 @value{GDBN} may be restricted to a slow serial line for this search)
15251 you may want to limit the size of this search, using one of these
15255 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
15256 @item set heuristic-fence-post @var{limit}
15257 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
15258 search for the beginning of a function. A value of @var{0} (the
15259 default) means there is no limit. However, except for @var{0}, the
15260 larger the limit the more bytes @code{heuristic-fence-post} must search
15261 and therefore the longer it takes to run. You should only need to use
15262 this command when debugging a stripped executable.
15264 @item show heuristic-fence-post
15265 Display the current limit.
15269 These commands are available @emph{only} when @value{GDBN} is configured
15270 for debugging programs on Alpha or MIPS processors.
15272 Several MIPS-specific commands are available when debugging MIPS
15276 @item set mips saved-gpreg-size @var{size}
15277 @kindex set mips saved-gpreg-size
15278 @cindex MIPS GP register size on stack
15279 Set the size of MIPS general-purpose registers saved on the stack.
15280 The argument @var{size} can be one of the following:
15284 32-bit GP registers
15286 64-bit GP registers
15288 Use the target's default setting or autodetect the saved size from the
15289 information contained in the executable. This is the default
15292 @item show mips saved-gpreg-size
15293 @kindex show mips saved-gpreg-size
15294 Show the current size of MIPS GP registers on the stack.
15296 @item set mips stack-arg-size @var{size}
15297 @kindex set mips stack-arg-size
15298 @cindex MIPS stack space for arguments
15299 Set the amount of stack space reserved for arguments to functions.
15300 The argument can be one of @code{"32"}, @code{"64"} or @code{"auto"}
15303 @item set mips abi @var{arg}
15304 @kindex set mips abi
15305 @cindex set ABI for MIPS
15306 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
15307 values of @var{arg} are:
15311 The default ABI associated with the current binary (this is the
15322 @item show mips abi
15323 @kindex show mips abi
15324 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
15327 @itemx show mipsfpu
15328 @xref{MIPS Embedded, set mipsfpu}.
15330 @item set mips mask-address @var{arg}
15331 @kindex set mips mask-address
15332 @cindex MIPS addresses, masking
15333 This command determines whether the most-significant 32 bits of 64-bit
15334 MIPS addresses are masked off. The argument @var{arg} can be
15335 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
15336 setting, which lets @value{GDBN} determine the correct value.
15338 @item show mips mask-address
15339 @kindex show mips mask-address
15340 Show whether the upper 32 bits of MIPS addresses are masked off or
15343 @item set remote-mips64-transfers-32bit-regs
15344 @kindex set remote-mips64-transfers-32bit-regs
15345 This command controls compatibility with 64-bit MIPS targets that
15346 transfer data in 32-bit quantities. If you have an old MIPS 64 target
15347 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
15348 and 64 bits for other registers, set this option to @samp{on}.
15350 @item show remote-mips64-transfers-32bit-regs
15351 @kindex show remote-mips64-transfers-32bit-regs
15352 Show the current setting of compatibility with older MIPS 64 targets.
15354 @item set debug mips
15355 @kindex set debug mips
15356 This command turns on and off debugging messages for the MIPS-specific
15357 target code in @value{GDBN}.
15359 @item show debug mips
15360 @kindex show debug mips
15361 Show the current setting of MIPS debugging messages.
15367 @cindex HPPA support
15369 When @value{GDBN} is debugging te HP PA architecture, it provides the
15370 following special commands:
15373 @item set debug hppa
15374 @kindex set debug hppa
15375 THis command determines whether HPPA architecture specific debugging
15376 messages are to be displayed.
15378 @item show debug hppa
15379 Show whether HPPA debugging messages are displayed.
15381 @item maint print unwind @var{address}
15382 @kindex maint print unwind@r{, HPPA}
15383 This command displays the contents of the unwind table entry at the
15384 given @var{address}.
15389 @node Controlling GDB
15390 @chapter Controlling @value{GDBN}
15392 You can alter the way @value{GDBN} interacts with you by using the
15393 @code{set} command. For commands controlling how @value{GDBN} displays
15394 data, see @ref{Print Settings, ,Print settings}. Other settings are
15399 * Editing:: Command editing
15400 * Command History:: Command history
15401 * Screen Size:: Screen size
15402 * Numbers:: Numbers
15403 * ABI:: Configuring the current ABI
15404 * Messages/Warnings:: Optional warnings and messages
15405 * Debugging Output:: Optional messages about internal happenings
15413 @value{GDBN} indicates its readiness to read a command by printing a string
15414 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
15415 can change the prompt string with the @code{set prompt} command. For
15416 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
15417 the prompt in one of the @value{GDBN} sessions so that you can always tell
15418 which one you are talking to.
15420 @emph{Note:} @code{set prompt} does not add a space for you after the
15421 prompt you set. This allows you to set a prompt which ends in a space
15422 or a prompt that does not.
15426 @item set prompt @var{newprompt}
15427 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
15429 @kindex show prompt
15431 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
15435 @section Command editing
15437 @cindex command line editing
15439 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
15440 @sc{gnu} library provides consistent behavior for programs which provide a
15441 command line interface to the user. Advantages are @sc{gnu} Emacs-style
15442 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
15443 substitution, and a storage and recall of command history across
15444 debugging sessions.
15446 You may control the behavior of command line editing in @value{GDBN} with the
15447 command @code{set}.
15450 @kindex set editing
15453 @itemx set editing on
15454 Enable command line editing (enabled by default).
15456 @item set editing off
15457 Disable command line editing.
15459 @kindex show editing
15461 Show whether command line editing is enabled.
15464 @xref{Command Line Editing}, for more details about the Readline
15465 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
15466 encouraged to read that chapter.
15468 @node Command History
15469 @section Command history
15470 @cindex command history
15472 @value{GDBN} can keep track of the commands you type during your
15473 debugging sessions, so that you can be certain of precisely what
15474 happened. Use these commands to manage the @value{GDBN} command
15477 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
15478 package, to provide the history facility. @xref{Using History
15479 Interactively}, for the detailed description of the History library.
15481 To issue a command to @value{GDBN} without affecting certain aspects of
15482 the state which is seen by users, prefix it with @samp{server }. This
15483 means that this command will not affect the command history, nor will it
15484 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
15485 pressed on a line by itself.
15487 @cindex @code{server}, command prefix
15488 The server prefix does not affect the recording of values into the value
15489 history; to print a value without recording it into the value history,
15490 use the @code{output} command instead of the @code{print} command.
15492 Here is the description of @value{GDBN} commands related to command
15496 @cindex history substitution
15497 @cindex history file
15498 @kindex set history filename
15499 @cindex @env{GDBHISTFILE}, environment variable
15500 @item set history filename @var{fname}
15501 Set the name of the @value{GDBN} command history file to @var{fname}.
15502 This is the file where @value{GDBN} reads an initial command history
15503 list, and where it writes the command history from this session when it
15504 exits. You can access this list through history expansion or through
15505 the history command editing characters listed below. This file defaults
15506 to the value of the environment variable @code{GDBHISTFILE}, or to
15507 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
15510 @cindex save command history
15511 @kindex set history save
15512 @item set history save
15513 @itemx set history save on
15514 Record command history in a file, whose name may be specified with the
15515 @code{set history filename} command. By default, this option is disabled.
15517 @item set history save off
15518 Stop recording command history in a file.
15520 @cindex history size
15521 @kindex set history size
15522 @cindex @env{HISTSIZE}, environment variable
15523 @item set history size @var{size}
15524 Set the number of commands which @value{GDBN} keeps in its history list.
15525 This defaults to the value of the environment variable
15526 @code{HISTSIZE}, or to 256 if this variable is not set.
15529 History expansion assigns special meaning to the character @kbd{!}.
15530 @xref{Event Designators}, for more details.
15532 @cindex history expansion, turn on/off
15533 Since @kbd{!} is also the logical not operator in C, history expansion
15534 is off by default. If you decide to enable history expansion with the
15535 @code{set history expansion on} command, you may sometimes need to
15536 follow @kbd{!} (when it is used as logical not, in an expression) with
15537 a space or a tab to prevent it from being expanded. The readline
15538 history facilities do not attempt substitution on the strings
15539 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
15541 The commands to control history expansion are:
15544 @item set history expansion on
15545 @itemx set history expansion
15546 @kindex set history expansion
15547 Enable history expansion. History expansion is off by default.
15549 @item set history expansion off
15550 Disable history expansion.
15553 @kindex show history
15555 @itemx show history filename
15556 @itemx show history save
15557 @itemx show history size
15558 @itemx show history expansion
15559 These commands display the state of the @value{GDBN} history parameters.
15560 @code{show history} by itself displays all four states.
15565 @kindex show commands
15566 @cindex show last commands
15567 @cindex display command history
15568 @item show commands
15569 Display the last ten commands in the command history.
15571 @item show commands @var{n}
15572 Print ten commands centered on command number @var{n}.
15574 @item show commands +
15575 Print ten commands just after the commands last printed.
15579 @section Screen size
15580 @cindex size of screen
15581 @cindex pauses in output
15583 Certain commands to @value{GDBN} may produce large amounts of
15584 information output to the screen. To help you read all of it,
15585 @value{GDBN} pauses and asks you for input at the end of each page of
15586 output. Type @key{RET} when you want to continue the output, or @kbd{q}
15587 to discard the remaining output. Also, the screen width setting
15588 determines when to wrap lines of output. Depending on what is being
15589 printed, @value{GDBN} tries to break the line at a readable place,
15590 rather than simply letting it overflow onto the following line.
15592 Normally @value{GDBN} knows the size of the screen from the terminal
15593 driver software. For example, on Unix @value{GDBN} uses the termcap data base
15594 together with the value of the @code{TERM} environment variable and the
15595 @code{stty rows} and @code{stty cols} settings. If this is not correct,
15596 you can override it with the @code{set height} and @code{set
15603 @kindex show height
15604 @item set height @var{lpp}
15606 @itemx set width @var{cpl}
15608 These @code{set} commands specify a screen height of @var{lpp} lines and
15609 a screen width of @var{cpl} characters. The associated @code{show}
15610 commands display the current settings.
15612 If you specify a height of zero lines, @value{GDBN} does not pause during
15613 output no matter how long the output is. This is useful if output is to a
15614 file or to an editor buffer.
15616 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
15617 from wrapping its output.
15619 @item set pagination on
15620 @itemx set pagination off
15621 @kindex set pagination
15622 Turn the output pagination on or off; the default is on. Turning
15623 pagination off is the alternative to @code{set height 0}.
15625 @item show pagination
15626 @kindex show pagination
15627 Show the current pagination mode.
15632 @cindex number representation
15633 @cindex entering numbers
15635 You can always enter numbers in octal, decimal, or hexadecimal in
15636 @value{GDBN} by the usual conventions: octal numbers begin with
15637 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
15638 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
15639 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
15640 10; likewise, the default display for numbers---when no particular
15641 format is specified---is base 10. You can change the default base for
15642 both input and output with the commands described below.
15645 @kindex set input-radix
15646 @item set input-radix @var{base}
15647 Set the default base for numeric input. Supported choices
15648 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15649 specified either unambiguously or using the current input radix; for
15653 set input-radix 012
15654 set input-radix 10.
15655 set input-radix 0xa
15659 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
15660 leaves the input radix unchanged, no matter what it was, since
15661 @samp{10}, being without any leading or trailing signs of its base, is
15662 interpreted in the current radix. Thus, if the current radix is 16,
15663 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
15666 @kindex set output-radix
15667 @item set output-radix @var{base}
15668 Set the default base for numeric display. Supported choices
15669 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15670 specified either unambiguously or using the current input radix.
15672 @kindex show input-radix
15673 @item show input-radix
15674 Display the current default base for numeric input.
15676 @kindex show output-radix
15677 @item show output-radix
15678 Display the current default base for numeric display.
15680 @item set radix @r{[}@var{base}@r{]}
15684 These commands set and show the default base for both input and output
15685 of numbers. @code{set radix} sets the radix of input and output to
15686 the same base; without an argument, it resets the radix back to its
15687 default value of 10.
15692 @section Configuring the current ABI
15694 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
15695 application automatically. However, sometimes you need to override its
15696 conclusions. Use these commands to manage @value{GDBN}'s view of the
15703 One @value{GDBN} configuration can debug binaries for multiple operating
15704 system targets, either via remote debugging or native emulation.
15705 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
15706 but you can override its conclusion using the @code{set osabi} command.
15707 One example where this is useful is in debugging of binaries which use
15708 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
15709 not have the same identifying marks that the standard C library for your
15714 Show the OS ABI currently in use.
15717 With no argument, show the list of registered available OS ABI's.
15719 @item set osabi @var{abi}
15720 Set the current OS ABI to @var{abi}.
15723 @cindex float promotion
15725 Generally, the way that an argument of type @code{float} is passed to a
15726 function depends on whether the function is prototyped. For a prototyped
15727 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
15728 according to the architecture's convention for @code{float}. For unprototyped
15729 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
15730 @code{double} and then passed.
15732 Unfortunately, some forms of debug information do not reliably indicate whether
15733 a function is prototyped. If @value{GDBN} calls a function that is not marked
15734 as prototyped, it consults @kbd{set coerce-float-to-double}.
15737 @kindex set coerce-float-to-double
15738 @item set coerce-float-to-double
15739 @itemx set coerce-float-to-double on
15740 Arguments of type @code{float} will be promoted to @code{double} when passed
15741 to an unprototyped function. This is the default setting.
15743 @item set coerce-float-to-double off
15744 Arguments of type @code{float} will be passed directly to unprototyped
15747 @kindex show coerce-float-to-double
15748 @item show coerce-float-to-double
15749 Show the current setting of promoting @code{float} to @code{double}.
15753 @kindex show cp-abi
15754 @value{GDBN} needs to know the ABI used for your program's C@t{++}
15755 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
15756 used to build your application. @value{GDBN} only fully supports
15757 programs with a single C@t{++} ABI; if your program contains code using
15758 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
15759 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
15760 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
15761 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
15762 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
15763 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
15768 Show the C@t{++} ABI currently in use.
15771 With no argument, show the list of supported C@t{++} ABI's.
15773 @item set cp-abi @var{abi}
15774 @itemx set cp-abi auto
15775 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
15778 @node Messages/Warnings
15779 @section Optional warnings and messages
15781 @cindex verbose operation
15782 @cindex optional warnings
15783 By default, @value{GDBN} is silent about its inner workings. If you are
15784 running on a slow machine, you may want to use the @code{set verbose}
15785 command. This makes @value{GDBN} tell you when it does a lengthy
15786 internal operation, so you will not think it has crashed.
15788 Currently, the messages controlled by @code{set verbose} are those
15789 which announce that the symbol table for a source file is being read;
15790 see @code{symbol-file} in @ref{Files, ,Commands to specify files}.
15793 @kindex set verbose
15794 @item set verbose on
15795 Enables @value{GDBN} output of certain informational messages.
15797 @item set verbose off
15798 Disables @value{GDBN} output of certain informational messages.
15800 @kindex show verbose
15802 Displays whether @code{set verbose} is on or off.
15805 By default, if @value{GDBN} encounters bugs in the symbol table of an
15806 object file, it is silent; but if you are debugging a compiler, you may
15807 find this information useful (@pxref{Symbol Errors, ,Errors reading
15812 @kindex set complaints
15813 @item set complaints @var{limit}
15814 Permits @value{GDBN} to output @var{limit} complaints about each type of
15815 unusual symbols before becoming silent about the problem. Set
15816 @var{limit} to zero to suppress all complaints; set it to a large number
15817 to prevent complaints from being suppressed.
15819 @kindex show complaints
15820 @item show complaints
15821 Displays how many symbol complaints @value{GDBN} is permitted to produce.
15825 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
15826 lot of stupid questions to confirm certain commands. For example, if
15827 you try to run a program which is already running:
15831 The program being debugged has been started already.
15832 Start it from the beginning? (y or n)
15835 If you are willing to unflinchingly face the consequences of your own
15836 commands, you can disable this ``feature'':
15840 @kindex set confirm
15842 @cindex confirmation
15843 @cindex stupid questions
15844 @item set confirm off
15845 Disables confirmation requests.
15847 @item set confirm on
15848 Enables confirmation requests (the default).
15850 @kindex show confirm
15852 Displays state of confirmation requests.
15856 @node Debugging Output
15857 @section Optional messages about internal happenings
15858 @cindex optional debugging messages
15860 @value{GDBN} has commands that enable optional debugging messages from
15861 various @value{GDBN} subsystems; normally these commands are of
15862 interest to @value{GDBN} maintainers, or when reporting a bug. This
15863 section documents those commands.
15866 @kindex set exec-done-display
15867 @item set exec-done-display
15868 Turns on or off the notification of asynchronous commands'
15869 completion. When on, @value{GDBN} will print a message when an
15870 asynchronous command finishes its execution. The default is off.
15871 @kindex show exec-done-display
15872 @item show exec-done-display
15873 Displays the current setting of asynchronous command completion
15876 @cindex gdbarch debugging info
15877 @cindex architecture debugging info
15878 @item set debug arch
15879 Turns on or off display of gdbarch debugging info. The default is off
15881 @item show debug arch
15882 Displays the current state of displaying gdbarch debugging info.
15883 @item set debug aix-thread
15884 @cindex AIX threads
15885 Display debugging messages about inner workings of the AIX thread
15887 @item show debug aix-thread
15888 Show the current state of AIX thread debugging info display.
15889 @item set debug event
15890 @cindex event debugging info
15891 Turns on or off display of @value{GDBN} event debugging info. The
15893 @item show debug event
15894 Displays the current state of displaying @value{GDBN} event debugging
15896 @item set debug expression
15897 @cindex expression debugging info
15898 Turns on or off display of debugging info about @value{GDBN}
15899 expression parsing. The default is off.
15900 @item show debug expression
15901 Displays the current state of displaying debugging info about
15902 @value{GDBN} expression parsing.
15903 @item set debug frame
15904 @cindex frame debugging info
15905 Turns on or off display of @value{GDBN} frame debugging info. The
15907 @item show debug frame
15908 Displays the current state of displaying @value{GDBN} frame debugging
15910 @item set debug infrun
15911 @cindex inferior debugging info
15912 Turns on or off display of @value{GDBN} debugging info for running the inferior.
15913 The default is off. @file{infrun.c} contains GDB's runtime state machine used
15914 for implementing operations such as single-stepping the inferior.
15915 @item show debug infrun
15916 Displays the current state of @value{GDBN} inferior debugging.
15917 @item set debug lin-lwp
15918 @cindex @sc{gnu}/Linux LWP debug messages
15919 @cindex Linux lightweight processes
15920 Turns on or off debugging messages from the Linux LWP debug support.
15921 @item show debug lin-lwp
15922 Show the current state of Linux LWP debugging messages.
15923 @item set debug observer
15924 @cindex observer debugging info
15925 Turns on or off display of @value{GDBN} observer debugging. This
15926 includes info such as the notification of observable events.
15927 @item show debug observer
15928 Displays the current state of observer debugging.
15929 @item set debug overload
15930 @cindex C@t{++} overload debugging info
15931 Turns on or off display of @value{GDBN} C@t{++} overload debugging
15932 info. This includes info such as ranking of functions, etc. The default
15934 @item show debug overload
15935 Displays the current state of displaying @value{GDBN} C@t{++} overload
15937 @cindex packets, reporting on stdout
15938 @cindex serial connections, debugging
15939 @cindex debug remote protocol
15940 @cindex remote protocol debugging
15941 @cindex display remote packets
15942 @item set debug remote
15943 Turns on or off display of reports on all packets sent back and forth across
15944 the serial line to the remote machine. The info is printed on the
15945 @value{GDBN} standard output stream. The default is off.
15946 @item show debug remote
15947 Displays the state of display of remote packets.
15948 @item set debug serial
15949 Turns on or off display of @value{GDBN} serial debugging info. The
15951 @item show debug serial
15952 Displays the current state of displaying @value{GDBN} serial debugging
15954 @item set debug solib-frv
15955 @cindex FR-V shared-library debugging
15956 Turns on or off debugging messages for FR-V shared-library code.
15957 @item show debug solib-frv
15958 Display the current state of FR-V shared-library code debugging
15960 @item set debug target
15961 @cindex target debugging info
15962 Turns on or off display of @value{GDBN} target debugging info. This info
15963 includes what is going on at the target level of GDB, as it happens. The
15964 default is 0. Set it to 1 to track events, and to 2 to also track the
15965 value of large memory transfers. Changes to this flag do not take effect
15966 until the next time you connect to a target or use the @code{run} command.
15967 @item show debug target
15968 Displays the current state of displaying @value{GDBN} target debugging
15970 @item set debugvarobj
15971 @cindex variable object debugging info
15972 Turns on or off display of @value{GDBN} variable object debugging
15973 info. The default is off.
15974 @item show debugvarobj
15975 Displays the current state of displaying @value{GDBN} variable object
15980 @chapter Canned Sequences of Commands
15982 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
15983 command lists}), @value{GDBN} provides two ways to store sequences of
15984 commands for execution as a unit: user-defined commands and command
15988 * Define:: How to define your own commands
15989 * Hooks:: Hooks for user-defined commands
15990 * Command Files:: How to write scripts of commands to be stored in a file
15991 * Output:: Commands for controlled output
15995 @section User-defined commands
15997 @cindex user-defined command
15998 @cindex arguments, to user-defined commands
15999 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
16000 which you assign a new name as a command. This is done with the
16001 @code{define} command. User commands may accept up to 10 arguments
16002 separated by whitespace. Arguments are accessed within the user command
16003 via @code{$arg0@dots{}$arg9}. A trivial example:
16007 print $arg0 + $arg1 + $arg2
16012 To execute the command use:
16019 This defines the command @code{adder}, which prints the sum of
16020 its three arguments. Note the arguments are text substitutions, so they may
16021 reference variables, use complex expressions, or even perform inferior
16024 @cindex argument count in user-defined commands
16025 @cindex how many arguments (user-defined commands)
16026 In addition, @code{$argc} may be used to find out how many arguments have
16027 been passed. This expands to a number in the range 0@dots{}10.
16032 print $arg0 + $arg1
16035 print $arg0 + $arg1 + $arg2
16043 @item define @var{commandname}
16044 Define a command named @var{commandname}. If there is already a command
16045 by that name, you are asked to confirm that you want to redefine it.
16047 The definition of the command is made up of other @value{GDBN} command lines,
16048 which are given following the @code{define} command. The end of these
16049 commands is marked by a line containing @code{end}.
16052 @kindex end@r{ (user-defined commands)}
16053 @item document @var{commandname}
16054 Document the user-defined command @var{commandname}, so that it can be
16055 accessed by @code{help}. The command @var{commandname} must already be
16056 defined. This command reads lines of documentation just as @code{define}
16057 reads the lines of the command definition, ending with @code{end}.
16058 After the @code{document} command is finished, @code{help} on command
16059 @var{commandname} displays the documentation you have written.
16061 You may use the @code{document} command again to change the
16062 documentation of a command. Redefining the command with @code{define}
16063 does not change the documentation.
16065 @kindex dont-repeat
16066 @cindex don't repeat command
16068 Used inside a user-defined command, this tells @value{GDBN} that this
16069 command should not be repeated when the user hits @key{RET}
16070 (@pxref{Command Syntax, repeat last command}).
16072 @kindex help user-defined
16073 @item help user-defined
16074 List all user-defined commands, with the first line of the documentation
16079 @itemx show user @var{commandname}
16080 Display the @value{GDBN} commands used to define @var{commandname} (but
16081 not its documentation). If no @var{commandname} is given, display the
16082 definitions for all user-defined commands.
16084 @cindex infinite recursion in user-defined commands
16085 @kindex show max-user-call-depth
16086 @kindex set max-user-call-depth
16087 @item show max-user-call-depth
16088 @itemx set max-user-call-depth
16089 The value of @code{max-user-call-depth} controls how many recursion
16090 levels are allowed in user-defined commands before GDB suspects an
16091 infinite recursion and aborts the command.
16094 In addition to the above commands, user-defined commands frequently
16095 use control flow commands, described in @ref{Command Files}.
16097 When user-defined commands are executed, the
16098 commands of the definition are not printed. An error in any command
16099 stops execution of the user-defined command.
16101 If used interactively, commands that would ask for confirmation proceed
16102 without asking when used inside a user-defined command. Many @value{GDBN}
16103 commands that normally print messages to say what they are doing omit the
16104 messages when used in a user-defined command.
16107 @section User-defined command hooks
16108 @cindex command hooks
16109 @cindex hooks, for commands
16110 @cindex hooks, pre-command
16113 You may define @dfn{hooks}, which are a special kind of user-defined
16114 command. Whenever you run the command @samp{foo}, if the user-defined
16115 command @samp{hook-foo} exists, it is executed (with no arguments)
16116 before that command.
16118 @cindex hooks, post-command
16120 A hook may also be defined which is run after the command you executed.
16121 Whenever you run the command @samp{foo}, if the user-defined command
16122 @samp{hookpost-foo} exists, it is executed (with no arguments) after
16123 that command. Post-execution hooks may exist simultaneously with
16124 pre-execution hooks, for the same command.
16126 It is valid for a hook to call the command which it hooks. If this
16127 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
16129 @c It would be nice if hookpost could be passed a parameter indicating
16130 @c if the command it hooks executed properly or not. FIXME!
16132 @kindex stop@r{, a pseudo-command}
16133 In addition, a pseudo-command, @samp{stop} exists. Defining
16134 (@samp{hook-stop}) makes the associated commands execute every time
16135 execution stops in your program: before breakpoint commands are run,
16136 displays are printed, or the stack frame is printed.
16138 For example, to ignore @code{SIGALRM} signals while
16139 single-stepping, but treat them normally during normal execution,
16144 handle SIGALRM nopass
16148 handle SIGALRM pass
16151 define hook-continue
16152 handle SIGLARM pass
16156 As a further example, to hook at the begining and end of the @code{echo}
16157 command, and to add extra text to the beginning and end of the message,
16165 define hookpost-echo
16169 (@value{GDBP}) echo Hello World
16170 <<<---Hello World--->>>
16175 You can define a hook for any single-word command in @value{GDBN}, but
16176 not for command aliases; you should define a hook for the basic command
16177 name, e.g.@: @code{backtrace} rather than @code{bt}.
16178 @c FIXME! So how does Joe User discover whether a command is an alias
16180 If an error occurs during the execution of your hook, execution of
16181 @value{GDBN} commands stops and @value{GDBN} issues a prompt
16182 (before the command that you actually typed had a chance to run).
16184 If you try to define a hook which does not match any known command, you
16185 get a warning from the @code{define} command.
16187 @node Command Files
16188 @section Command files
16190 @cindex command files
16191 @cindex scripting commands
16192 A command file for @value{GDBN} is a text file made of lines that are
16193 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
16194 also be included. An empty line in a command file does nothing; it
16195 does not mean to repeat the last command, as it would from the
16198 You can request the execution of a command file with the @code{source}
16203 @cindex execute commands from a file
16204 @item source @var{filename}
16205 Execute the command file @var{filename}.
16208 The lines in a command file are generally executed sequentially,
16209 unless the order of execution is changed by one of the
16210 @emph{flow-control commands} described below. The commands are not
16211 printed as they are executed. An error in any command terminates
16212 execution of the command file and control is returned to the console.
16214 @value{GDBN} searches for @var{filename} in the current directory and then
16215 on the search path (specified with the @samp{directory} command).
16217 Commands that would ask for confirmation if used interactively proceed
16218 without asking when used in a command file. Many @value{GDBN} commands that
16219 normally print messages to say what they are doing omit the messages
16220 when called from command files.
16222 @value{GDBN} also accepts command input from standard input. In this
16223 mode, normal output goes to standard output and error output goes to
16224 standard error. Errors in a command file supplied on standard input do
16225 not terminate execution of the command file---execution continues with
16229 gdb < cmds > log 2>&1
16232 (The syntax above will vary depending on the shell used.) This example
16233 will execute commands from the file @file{cmds}. All output and errors
16234 would be directed to @file{log}.
16236 Since commands stored on command files tend to be more general than
16237 commands typed interactively, they frequently need to deal with
16238 complicated situations, such as different or unexpected values of
16239 variables and symbols, changes in how the program being debugged is
16240 built, etc. @value{GDBN} provides a set of flow-control commands to
16241 deal with these complexities. Using these commands, you can write
16242 complex scripts that loop over data structures, execute commands
16243 conditionally, etc.
16250 This command allows to include in your script conditionally executed
16251 commands. The @code{if} command takes a single argument, which is an
16252 expression to evaluate. It is followed by a series of commands that
16253 are executed only if the expression is true (its value is nonzero).
16254 There can then optionally be an @code{else} line, followed by a series
16255 of commands that are only executed if the expression was false. The
16256 end of the list is marked by a line containing @code{end}.
16260 This command allows to write loops. Its syntax is similar to
16261 @code{if}: the command takes a single argument, which is an expression
16262 to evaluate, and must be followed by the commands to execute, one per
16263 line, terminated by an @code{end}. These commands are called the
16264 @dfn{body} of the loop. The commands in the body of @code{while} are
16265 executed repeatedly as long as the expression evaluates to true.
16269 This command exits the @code{while} loop in whose body it is included.
16270 Execution of the script continues after that @code{while}s @code{end}
16273 @kindex loop_continue
16274 @item loop_continue
16275 This command skips the execution of the rest of the body of commands
16276 in the @code{while} loop in whose body it is included. Execution
16277 branches to the beginning of the @code{while} loop, where it evaluates
16278 the controlling expression.
16280 @kindex end@r{ (if/else/while commands)}
16282 Terminate the block of commands that are the body of @code{if},
16283 @code{else}, or @code{while} flow-control commands.
16288 @section Commands for controlled output
16290 During the execution of a command file or a user-defined command, normal
16291 @value{GDBN} output is suppressed; the only output that appears is what is
16292 explicitly printed by the commands in the definition. This section
16293 describes three commands useful for generating exactly the output you
16298 @item echo @var{text}
16299 @c I do not consider backslash-space a standard C escape sequence
16300 @c because it is not in ANSI.
16301 Print @var{text}. Nonprinting characters can be included in
16302 @var{text} using C escape sequences, such as @samp{\n} to print a
16303 newline. @strong{No newline is printed unless you specify one.}
16304 In addition to the standard C escape sequences, a backslash followed
16305 by a space stands for a space. This is useful for displaying a
16306 string with spaces at the beginning or the end, since leading and
16307 trailing spaces are otherwise trimmed from all arguments.
16308 To print @samp{@w{ }and foo =@w{ }}, use the command
16309 @samp{echo \@w{ }and foo = \@w{ }}.
16311 A backslash at the end of @var{text} can be used, as in C, to continue
16312 the command onto subsequent lines. For example,
16315 echo This is some text\n\
16316 which is continued\n\
16317 onto several lines.\n
16320 produces the same output as
16323 echo This is some text\n
16324 echo which is continued\n
16325 echo onto several lines.\n
16329 @item output @var{expression}
16330 Print the value of @var{expression} and nothing but that value: no
16331 newlines, no @samp{$@var{nn} = }. The value is not entered in the
16332 value history either. @xref{Expressions, ,Expressions}, for more information
16335 @item output/@var{fmt} @var{expression}
16336 Print the value of @var{expression} in format @var{fmt}. You can use
16337 the same formats as for @code{print}. @xref{Output Formats,,Output
16338 formats}, for more information.
16341 @item printf @var{string}, @var{expressions}@dots{}
16342 Print the values of the @var{expressions} under the control of
16343 @var{string}. The @var{expressions} are separated by commas and may be
16344 either numbers or pointers. Their values are printed as specified by
16345 @var{string}, exactly as if your program were to execute the C
16347 @c FIXME: the above implies that at least all ANSI C formats are
16348 @c supported, but it isn't true: %E and %G don't work (or so it seems).
16349 @c Either this is a bug, or the manual should document what formats are
16353 printf (@var{string}, @var{expressions}@dots{});
16356 For example, you can print two values in hex like this:
16359 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
16362 The only backslash-escape sequences that you can use in the format
16363 string are the simple ones that consist of backslash followed by a
16368 @chapter Command Interpreters
16369 @cindex command interpreters
16371 @value{GDBN} supports multiple command interpreters, and some command
16372 infrastructure to allow users or user interface writers to switch
16373 between interpreters or run commands in other interpreters.
16375 @value{GDBN} currently supports two command interpreters, the console
16376 interpreter (sometimes called the command-line interpreter or @sc{cli})
16377 and the machine interface interpreter (or @sc{gdb/mi}). This manual
16378 describes both of these interfaces in great detail.
16380 By default, @value{GDBN} will start with the console interpreter.
16381 However, the user may choose to start @value{GDBN} with another
16382 interpreter by specifying the @option{-i} or @option{--interpreter}
16383 startup options. Defined interpreters include:
16387 @cindex console interpreter
16388 The traditional console or command-line interpreter. This is the most often
16389 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
16390 @value{GDBN} will use this interpreter.
16393 @cindex mi interpreter
16394 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
16395 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
16396 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
16400 @cindex mi2 interpreter
16401 The current @sc{gdb/mi} interface.
16404 @cindex mi1 interpreter
16405 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
16409 @cindex invoke another interpreter
16410 The interpreter being used by @value{GDBN} may not be dynamically
16411 switched at runtime. Although possible, this could lead to a very
16412 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
16413 enters the command "interpreter-set console" in a console view,
16414 @value{GDBN} would switch to using the console interpreter, rendering
16415 the IDE inoperable!
16417 @kindex interpreter-exec
16418 Although you may only choose a single interpreter at startup, you may execute
16419 commands in any interpreter from the current interpreter using the appropriate
16420 command. If you are running the console interpreter, simply use the
16421 @code{interpreter-exec} command:
16424 interpreter-exec mi "-data-list-register-names"
16427 @sc{gdb/mi} has a similar command, although it is only available in versions of
16428 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
16431 @chapter @value{GDBN} Text User Interface
16433 @cindex Text User Interface
16436 * TUI Overview:: TUI overview
16437 * TUI Keys:: TUI key bindings
16438 * TUI Single Key Mode:: TUI single key mode
16439 * TUI Commands:: TUI specific commands
16440 * TUI Configuration:: TUI configuration variables
16443 The @value{GDBN} Text User Interface, TUI in short, is a terminal
16444 interface which uses the @code{curses} library to show the source
16445 file, the assembly output, the program registers and @value{GDBN}
16446 commands in separate text windows.
16448 The TUI is enabled by invoking @value{GDBN} using either
16450 @samp{gdbtui} or @samp{gdb -tui}.
16453 @section TUI overview
16455 The TUI has two display modes that can be switched while
16460 A curses (or TUI) mode in which it displays several text
16461 windows on the terminal.
16464 A standard mode which corresponds to the @value{GDBN} configured without
16468 In the TUI mode, @value{GDBN} can display several text window
16473 This window is the @value{GDBN} command window with the @value{GDBN}
16474 prompt and the @value{GDBN} outputs. The @value{GDBN} input is still
16475 managed using readline but through the TUI. The @emph{command}
16476 window is always visible.
16479 The source window shows the source file of the program. The current
16480 line as well as active breakpoints are displayed in this window.
16483 The assembly window shows the disassembly output of the program.
16486 This window shows the processor registers. It detects when
16487 a register is changed and when this is the case, registers that have
16488 changed are highlighted.
16492 The source and assembly windows show the current program position
16493 by highlighting the current line and marking them with the @samp{>} marker.
16494 Breakpoints are also indicated with two markers. A first one
16495 indicates the breakpoint type:
16499 Breakpoint which was hit at least once.
16502 Breakpoint which was never hit.
16505 Hardware breakpoint which was hit at least once.
16508 Hardware breakpoint which was never hit.
16512 The second marker indicates whether the breakpoint is enabled or not:
16516 Breakpoint is enabled.
16519 Breakpoint is disabled.
16523 The source, assembly and register windows are attached to the thread
16524 and the frame position. They are updated when the current thread
16525 changes, when the frame changes or when the program counter changes.
16526 These three windows are arranged by the TUI according to several
16527 layouts. The layout defines which of these three windows are visible.
16528 The following layouts are available:
16538 source and assembly
16541 source and registers
16544 assembly and registers
16548 On top of the command window a status line gives various information
16549 concerning the current process begin debugged. The status line is
16550 updated when the information it shows changes. The following fields
16555 Indicates the current gdb target
16556 (@pxref{Targets, ,Specifying a Debugging Target}).
16559 Gives information about the current process or thread number.
16560 When no process is being debugged, this field is set to @code{No process}.
16563 Gives the current function name for the selected frame.
16564 The name is demangled if demangling is turned on (@pxref{Print Settings}).
16565 When there is no symbol corresponding to the current program counter
16566 the string @code{??} is displayed.
16569 Indicates the current line number for the selected frame.
16570 When the current line number is not known the string @code{??} is displayed.
16573 Indicates the current program counter address.
16578 @section TUI Key Bindings
16579 @cindex TUI key bindings
16581 The TUI installs several key bindings in the readline keymaps
16582 (@pxref{Command Line Editing}).
16583 They allow to leave or enter in the TUI mode or they operate
16584 directly on the TUI layout and windows. The TUI also provides
16585 a @emph{SingleKey} keymap which binds several keys directly to
16586 @value{GDBN} commands. The following key bindings
16587 are installed for both TUI mode and the @value{GDBN} standard mode.
16596 Enter or leave the TUI mode. When the TUI mode is left,
16597 the curses window management is left and @value{GDBN} operates using
16598 its standard mode writing on the terminal directly. When the TUI
16599 mode is entered, the control is given back to the curses windows.
16600 The screen is then refreshed.
16604 Use a TUI layout with only one window. The layout will
16605 either be @samp{source} or @samp{assembly}. When the TUI mode
16606 is not active, it will switch to the TUI mode.
16608 Think of this key binding as the Emacs @kbd{C-x 1} binding.
16612 Use a TUI layout with at least two windows. When the current
16613 layout shows already two windows, a next layout with two windows is used.
16614 When a new layout is chosen, one window will always be common to the
16615 previous layout and the new one.
16617 Think of it as the Emacs @kbd{C-x 2} binding.
16621 Change the active window. The TUI associates several key bindings
16622 (like scrolling and arrow keys) to the active window. This command
16623 gives the focus to the next TUI window.
16625 Think of it as the Emacs @kbd{C-x o} binding.
16629 Use the TUI @emph{SingleKey} keymap that binds single key to gdb commands
16630 (@pxref{TUI Single Key Mode}).
16634 The following key bindings are handled only by the TUI mode:
16639 Scroll the active window one page up.
16643 Scroll the active window one page down.
16647 Scroll the active window one line up.
16651 Scroll the active window one line down.
16655 Scroll the active window one column left.
16659 Scroll the active window one column right.
16663 Refresh the screen.
16667 In the TUI mode, the arrow keys are used by the active window
16668 for scrolling. This means they are available for readline when the
16669 active window is the command window. When the command window
16670 does not have the focus, it is necessary to use other readline
16671 key bindings such as @key{C-p}, @key{C-n}, @key{C-b} and @key{C-f}.
16673 @node TUI Single Key Mode
16674 @section TUI Single Key Mode
16675 @cindex TUI single key mode
16677 The TUI provides a @emph{SingleKey} mode in which it installs a particular
16678 key binding in the readline keymaps to connect single keys to
16682 @kindex c @r{(SingleKey TUI key)}
16686 @kindex d @r{(SingleKey TUI key)}
16690 @kindex f @r{(SingleKey TUI key)}
16694 @kindex n @r{(SingleKey TUI key)}
16698 @kindex q @r{(SingleKey TUI key)}
16700 exit the @emph{SingleKey} mode.
16702 @kindex r @r{(SingleKey TUI key)}
16706 @kindex s @r{(SingleKey TUI key)}
16710 @kindex u @r{(SingleKey TUI key)}
16714 @kindex v @r{(SingleKey TUI key)}
16718 @kindex w @r{(SingleKey TUI key)}
16724 Other keys temporarily switch to the @value{GDBN} command prompt.
16725 The key that was pressed is inserted in the editing buffer so that
16726 it is possible to type most @value{GDBN} commands without interaction
16727 with the TUI @emph{SingleKey} mode. Once the command is entered the TUI
16728 @emph{SingleKey} mode is restored. The only way to permanently leave
16729 this mode is by hitting @key{q} or @samp{@key{C-x} @key{s}}.
16733 @section TUI specific commands
16734 @cindex TUI commands
16736 The TUI has specific commands to control the text windows.
16737 These commands are always available, that is they do not depend on
16738 the current terminal mode in which @value{GDBN} runs. When @value{GDBN}
16739 is in the standard mode, using these commands will automatically switch
16745 List and give the size of all displayed windows.
16749 Display the next layout.
16752 Display the previous layout.
16755 Display the source window only.
16758 Display the assembly window only.
16761 Display the source and assembly window.
16764 Display the register window together with the source or assembly window.
16766 @item focus next | prev | src | asm | regs | split
16768 Set the focus to the named window.
16769 This command allows to change the active window so that scrolling keys
16770 can be affected to another window.
16774 Refresh the screen. This is similar to using @key{C-L} key.
16776 @item tui reg float
16778 Show the floating point registers in the register window.
16780 @item tui reg general
16781 Show the general registers in the register window.
16784 Show the next register group. The list of register groups as well as
16785 their order is target specific. The predefined register groups are the
16786 following: @code{general}, @code{float}, @code{system}, @code{vector},
16787 @code{all}, @code{save}, @code{restore}.
16789 @item tui reg system
16790 Show the system registers in the register window.
16794 Update the source window and the current execution point.
16796 @item winheight @var{name} +@var{count}
16797 @itemx winheight @var{name} -@var{count}
16799 Change the height of the window @var{name} by @var{count}
16800 lines. Positive counts increase the height, while negative counts
16804 @kindex tabset @var{nchars}
16805 Set the width of tab stops to be @var{nchars} characters.
16809 @node TUI Configuration
16810 @section TUI configuration variables
16811 @cindex TUI configuration variables
16813 The TUI has several configuration variables that control the
16814 appearance of windows on the terminal.
16817 @item set tui border-kind @var{kind}
16818 @kindex set tui border-kind
16819 Select the border appearance for the source, assembly and register windows.
16820 The possible values are the following:
16823 Use a space character to draw the border.
16826 Use ascii characters + - and | to draw the border.
16829 Use the Alternate Character Set to draw the border. The border is
16830 drawn using character line graphics if the terminal supports them.
16834 @item set tui active-border-mode @var{mode}
16835 @kindex set tui active-border-mode
16836 Select the attributes to display the border of the active window.
16837 The possible values are @code{normal}, @code{standout}, @code{reverse},
16838 @code{half}, @code{half-standout}, @code{bold} and @code{bold-standout}.
16840 @item set tui border-mode @var{mode}
16841 @kindex set tui border-mode
16842 Select the attributes to display the border of other windows.
16843 The @var{mode} can be one of the following:
16846 Use normal attributes to display the border.
16852 Use reverse video mode.
16855 Use half bright mode.
16857 @item half-standout
16858 Use half bright and standout mode.
16861 Use extra bright or bold mode.
16863 @item bold-standout
16864 Use extra bright or bold and standout mode.
16871 @chapter Using @value{GDBN} under @sc{gnu} Emacs
16874 @cindex @sc{gnu} Emacs
16875 A special interface allows you to use @sc{gnu} Emacs to view (and
16876 edit) the source files for the program you are debugging with
16879 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
16880 executable file you want to debug as an argument. This command starts
16881 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
16882 created Emacs buffer.
16883 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
16885 Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two
16890 All ``terminal'' input and output goes through the Emacs buffer.
16893 This applies both to @value{GDBN} commands and their output, and to the input
16894 and output done by the program you are debugging.
16896 This is useful because it means that you can copy the text of previous
16897 commands and input them again; you can even use parts of the output
16900 All the facilities of Emacs' Shell mode are available for interacting
16901 with your program. In particular, you can send signals the usual
16902 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
16907 @value{GDBN} displays source code through Emacs.
16910 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
16911 source file for that frame and puts an arrow (@samp{=>}) at the
16912 left margin of the current line. Emacs uses a separate buffer for
16913 source display, and splits the screen to show both your @value{GDBN} session
16916 Explicit @value{GDBN} @code{list} or search commands still produce output as
16917 usual, but you probably have no reason to use them from Emacs.
16919 If you specify an absolute file name when prompted for the @kbd{M-x
16920 gdb} argument, then Emacs sets your current working directory to where
16921 your program resides. If you only specify the file name, then Emacs
16922 sets your current working directory to to the directory associated
16923 with the previous buffer. In this case, @value{GDBN} may find your
16924 program by searching your environment's @code{PATH} variable, but on
16925 some operating systems it might not find the source. So, although the
16926 @value{GDBN} input and output session proceeds normally, the auxiliary
16927 buffer does not display the current source and line of execution.
16929 The initial working directory of @value{GDBN} is printed on the top
16930 line of the @value{GDBN} I/O buffer and this serves as a default for
16931 the commands that specify files for @value{GDBN} to operate
16932 on. @xref{Files, ,Commands to specify files}.
16934 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
16935 need to call @value{GDBN} by a different name (for example, if you
16936 keep several configurations around, with different names) you can
16937 customize the Emacs variable @code{gud-gdb-command-name} to run the
16940 In the @value{GDBN} I/O buffer, you can use these special Emacs commands in
16941 addition to the standard Shell mode commands:
16945 Describe the features of Emacs' @value{GDBN} Mode.
16948 Execute to another source line, like the @value{GDBN} @code{step} command; also
16949 update the display window to show the current file and location.
16952 Execute to next source line in this function, skipping all function
16953 calls, like the @value{GDBN} @code{next} command. Then update the display window
16954 to show the current file and location.
16957 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
16958 display window accordingly.
16961 Execute until exit from the selected stack frame, like the @value{GDBN}
16962 @code{finish} command.
16965 Continue execution of your program, like the @value{GDBN} @code{continue}
16969 Go up the number of frames indicated by the numeric argument
16970 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
16971 like the @value{GDBN} @code{up} command.
16974 Go down the number of frames indicated by the numeric argument, like the
16975 @value{GDBN} @code{down} command.
16978 In any source file, the Emacs command @kbd{C-x SPC} (@code{gud-break})
16979 tells @value{GDBN} to set a breakpoint on the source line point is on.
16981 If you type @kbd{M-x speedbar}, then Emacs displays a separate frame which
16982 shows a backtrace when the @value{GDBN} I/O buffer is current. Move
16983 point to any frame in the stack and type @key{RET} to make it become the
16984 current frame and display the associated source in the source buffer.
16985 Alternatively, click @kbd{Mouse-2} to make the selected frame become the
16988 If you accidentally delete the source-display buffer, an easy way to get
16989 it back is to type the command @code{f} in the @value{GDBN} buffer, to
16990 request a frame display; when you run under Emacs, this recreates
16991 the source buffer if necessary to show you the context of the current
16994 The source files displayed in Emacs are in ordinary Emacs buffers
16995 which are visiting the source files in the usual way. You can edit
16996 the files with these buffers if you wish; but keep in mind that @value{GDBN}
16997 communicates with Emacs in terms of line numbers. If you add or
16998 delete lines from the text, the line numbers that @value{GDBN} knows cease
16999 to correspond properly with the code.
17001 The description given here is for GNU Emacs version 21.3 and a more
17002 detailed description of its interaction with @value{GDBN} is given in
17003 the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu} Emacs Manual}).
17005 @c The following dropped because Epoch is nonstandard. Reactivate
17006 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
17008 @kindex Emacs Epoch environment
17012 Version 18 of @sc{gnu} Emacs has a built-in window system
17013 called the @code{epoch}
17014 environment. Users of this environment can use a new command,
17015 @code{inspect} which performs identically to @code{print} except that
17016 each value is printed in its own window.
17021 @chapter The @sc{gdb/mi} Interface
17023 @unnumberedsec Function and Purpose
17025 @cindex @sc{gdb/mi}, its purpose
17026 @sc{gdb/mi} is a line based machine oriented text interface to
17027 @value{GDBN} and is activated by specifying using the
17028 @option{--interpreter} command line option (@pxref{Mode Options}). It
17029 is specifically intended to support the development of systems which
17030 use the debugger as just one small component of a larger system.
17032 This chapter is a specification of the @sc{gdb/mi} interface. It is written
17033 in the form of a reference manual.
17035 Note that @sc{gdb/mi} is still under construction, so some of the
17036 features described below are incomplete and subject to change.
17038 @unnumberedsec Notation and Terminology
17040 @cindex notational conventions, for @sc{gdb/mi}
17041 This chapter uses the following notation:
17045 @code{|} separates two alternatives.
17048 @code{[ @var{something} ]} indicates that @var{something} is optional:
17049 it may or may not be given.
17052 @code{( @var{group} )*} means that @var{group} inside the parentheses
17053 may repeat zero or more times.
17056 @code{( @var{group} )+} means that @var{group} inside the parentheses
17057 may repeat one or more times.
17060 @code{"@var{string}"} means a literal @var{string}.
17064 @heading Dependencies
17067 @heading Acknowledgments
17069 In alphabetic order: Andrew Cagney, Fernando Nasser, Stan Shebs and
17073 * GDB/MI Command Syntax::
17074 * GDB/MI Compatibility with CLI::
17075 * GDB/MI Output Records::
17076 * GDB/MI Command Description Format::
17077 * GDB/MI Breakpoint Table Commands::
17078 * GDB/MI Data Manipulation::
17079 * GDB/MI Program Control::
17080 * GDB/MI Miscellaneous Commands::
17082 * GDB/MI Kod Commands::
17083 * GDB/MI Memory Overlay Commands::
17084 * GDB/MI Signal Handling Commands::
17086 * GDB/MI Stack Manipulation::
17087 * GDB/MI Symbol Query::
17088 * GDB/MI Target Manipulation::
17089 * GDB/MI Thread Commands::
17090 * GDB/MI Tracepoint Commands::
17091 * GDB/MI Variable Objects::
17094 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17095 @node GDB/MI Command Syntax
17096 @section @sc{gdb/mi} Command Syntax
17099 * GDB/MI Input Syntax::
17100 * GDB/MI Output Syntax::
17101 * GDB/MI Simple Examples::
17104 @node GDB/MI Input Syntax
17105 @subsection @sc{gdb/mi} Input Syntax
17107 @cindex input syntax for @sc{gdb/mi}
17108 @cindex @sc{gdb/mi}, input syntax
17110 @item @var{command} @expansion{}
17111 @code{@var{cli-command} | @var{mi-command}}
17113 @item @var{cli-command} @expansion{}
17114 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
17115 @var{cli-command} is any existing @value{GDBN} CLI command.
17117 @item @var{mi-command} @expansion{}
17118 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
17119 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
17121 @item @var{token} @expansion{}
17122 "any sequence of digits"
17124 @item @var{option} @expansion{}
17125 @code{"-" @var{parameter} [ " " @var{parameter} ]}
17127 @item @var{parameter} @expansion{}
17128 @code{@var{non-blank-sequence} | @var{c-string}}
17130 @item @var{operation} @expansion{}
17131 @emph{any of the operations described in this chapter}
17133 @item @var{non-blank-sequence} @expansion{}
17134 @emph{anything, provided it doesn't contain special characters such as
17135 "-", @var{nl}, """ and of course " "}
17137 @item @var{c-string} @expansion{}
17138 @code{""" @var{seven-bit-iso-c-string-content} """}
17140 @item @var{nl} @expansion{}
17149 The CLI commands are still handled by the @sc{mi} interpreter; their
17150 output is described below.
17153 The @code{@var{token}}, when present, is passed back when the command
17157 Some @sc{mi} commands accept optional arguments as part of the parameter
17158 list. Each option is identified by a leading @samp{-} (dash) and may be
17159 followed by an optional argument parameter. Options occur first in the
17160 parameter list and can be delimited from normal parameters using
17161 @samp{--} (this is useful when some parameters begin with a dash).
17168 We want easy access to the existing CLI syntax (for debugging).
17171 We want it to be easy to spot a @sc{mi} operation.
17174 @node GDB/MI Output Syntax
17175 @subsection @sc{gdb/mi} Output Syntax
17177 @cindex output syntax of @sc{gdb/mi}
17178 @cindex @sc{gdb/mi}, output syntax
17179 The output from @sc{gdb/mi} consists of zero or more out-of-band records
17180 followed, optionally, by a single result record. This result record
17181 is for the most recent command. The sequence of output records is
17182 terminated by @samp{(@value{GDBP})}.
17184 If an input command was prefixed with a @code{@var{token}} then the
17185 corresponding output for that command will also be prefixed by that same
17189 @item @var{output} @expansion{}
17190 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(@value{GDBP})" @var{nl}}
17192 @item @var{result-record} @expansion{}
17193 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
17195 @item @var{out-of-band-record} @expansion{}
17196 @code{@var{async-record} | @var{stream-record}}
17198 @item @var{async-record} @expansion{}
17199 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
17201 @item @var{exec-async-output} @expansion{}
17202 @code{[ @var{token} ] "*" @var{async-output}}
17204 @item @var{status-async-output} @expansion{}
17205 @code{[ @var{token} ] "+" @var{async-output}}
17207 @item @var{notify-async-output} @expansion{}
17208 @code{[ @var{token} ] "=" @var{async-output}}
17210 @item @var{async-output} @expansion{}
17211 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
17213 @item @var{result-class} @expansion{}
17214 @code{"done" | "running" | "connected" | "error" | "exit"}
17216 @item @var{async-class} @expansion{}
17217 @code{"stopped" | @var{others}} (where @var{others} will be added
17218 depending on the needs---this is still in development).
17220 @item @var{result} @expansion{}
17221 @code{ @var{variable} "=" @var{value}}
17223 @item @var{variable} @expansion{}
17224 @code{ @var{string} }
17226 @item @var{value} @expansion{}
17227 @code{ @var{const} | @var{tuple} | @var{list} }
17229 @item @var{const} @expansion{}
17230 @code{@var{c-string}}
17232 @item @var{tuple} @expansion{}
17233 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
17235 @item @var{list} @expansion{}
17236 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
17237 @var{result} ( "," @var{result} )* "]" }
17239 @item @var{stream-record} @expansion{}
17240 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
17242 @item @var{console-stream-output} @expansion{}
17243 @code{"~" @var{c-string}}
17245 @item @var{target-stream-output} @expansion{}
17246 @code{"@@" @var{c-string}}
17248 @item @var{log-stream-output} @expansion{}
17249 @code{"&" @var{c-string}}
17251 @item @var{nl} @expansion{}
17254 @item @var{token} @expansion{}
17255 @emph{any sequence of digits}.
17263 All output sequences end in a single line containing a period.
17266 The @code{@var{token}} is from the corresponding request. If an execution
17267 command is interrupted by the @samp{-exec-interrupt} command, the
17268 @var{token} associated with the @samp{*stopped} message is the one of the
17269 original execution command, not the one of the interrupt command.
17272 @cindex status output in @sc{gdb/mi}
17273 @var{status-async-output} contains on-going status information about the
17274 progress of a slow operation. It can be discarded. All status output is
17275 prefixed by @samp{+}.
17278 @cindex async output in @sc{gdb/mi}
17279 @var{exec-async-output} contains asynchronous state change on the target
17280 (stopped, started, disappeared). All async output is prefixed by
17284 @cindex notify output in @sc{gdb/mi}
17285 @var{notify-async-output} contains supplementary information that the
17286 client should handle (e.g., a new breakpoint information). All notify
17287 output is prefixed by @samp{=}.
17290 @cindex console output in @sc{gdb/mi}
17291 @var{console-stream-output} is output that should be displayed as is in the
17292 console. It is the textual response to a CLI command. All the console
17293 output is prefixed by @samp{~}.
17296 @cindex target output in @sc{gdb/mi}
17297 @var{target-stream-output} is the output produced by the target program.
17298 All the target output is prefixed by @samp{@@}.
17301 @cindex log output in @sc{gdb/mi}
17302 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
17303 instance messages that should be displayed as part of an error log. All
17304 the log output is prefixed by @samp{&}.
17307 @cindex list output in @sc{gdb/mi}
17308 New @sc{gdb/mi} commands should only output @var{lists} containing
17314 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
17315 details about the various output records.
17317 @node GDB/MI Simple Examples
17318 @subsection Simple Examples of @sc{gdb/mi} Interaction
17319 @cindex @sc{gdb/mi}, simple examples
17321 This subsection presents several simple examples of interaction using
17322 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
17323 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
17324 the output received from @sc{gdb/mi}.
17326 @subsubheading Target Stop
17327 @c Ummm... There is no "-stop" command. This assumes async, no?
17328 Here's an example of stopping the inferior process:
17339 <- *stop,reason="stop",address="0x123",source="a.c:123"
17343 @subsubheading Simple CLI Command
17345 Here's an example of a simple CLI command being passed through
17346 @sc{gdb/mi} and on to the CLI.
17356 @subsubheading Command With Side Effects
17359 -> -symbol-file xyz.exe
17360 <- *breakpoint,nr="3",address="0x123",source="a.c:123"
17364 @subsubheading A Bad Command
17366 Here's what happens if you pass a non-existent command:
17370 <- ^error,msg="Undefined MI command: rubbish"
17374 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17375 @node GDB/MI Compatibility with CLI
17376 @section @sc{gdb/mi} Compatibility with CLI
17378 @cindex compatibility, @sc{gdb/mi} and CLI
17379 @cindex @sc{gdb/mi}, compatibility with CLI
17380 To help users familiar with @value{GDBN}'s existing CLI interface, @sc{gdb/mi}
17381 accepts existing CLI commands. As specified by the syntax, such
17382 commands can be directly entered into the @sc{gdb/mi} interface and @value{GDBN} will
17385 This mechanism is provided as an aid to developers of @sc{gdb/mi}
17386 clients and not as a reliable interface into the CLI. Since the command
17387 is being interpreteted in an environment that assumes @sc{gdb/mi}
17388 behaviour, the exact output of such commands is likely to end up being
17389 an un-supported hybrid of @sc{gdb/mi} and CLI output.
17391 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17392 @node GDB/MI Output Records
17393 @section @sc{gdb/mi} Output Records
17396 * GDB/MI Result Records::
17397 * GDB/MI Stream Records::
17398 * GDB/MI Out-of-band Records::
17401 @node GDB/MI Result Records
17402 @subsection @sc{gdb/mi} Result Records
17404 @cindex result records in @sc{gdb/mi}
17405 @cindex @sc{gdb/mi}, result records
17406 In addition to a number of out-of-band notifications, the response to a
17407 @sc{gdb/mi} command includes one of the following result indications:
17411 @item "^done" [ "," @var{results} ]
17412 The synchronous operation was successful, @code{@var{results}} are the return
17417 @c Is this one correct? Should it be an out-of-band notification?
17418 The asynchronous operation was successfully started. The target is
17421 @item "^error" "," @var{c-string}
17423 The operation failed. The @code{@var{c-string}} contains the corresponding
17427 @node GDB/MI Stream Records
17428 @subsection @sc{gdb/mi} Stream Records
17430 @cindex @sc{gdb/mi}, stream records
17431 @cindex stream records in @sc{gdb/mi}
17432 @value{GDBN} internally maintains a number of output streams: the console, the
17433 target, and the log. The output intended for each of these streams is
17434 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
17436 Each stream record begins with a unique @dfn{prefix character} which
17437 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
17438 Syntax}). In addition to the prefix, each stream record contains a
17439 @code{@var{string-output}}. This is either raw text (with an implicit new
17440 line) or a quoted C string (which does not contain an implicit newline).
17443 @item "~" @var{string-output}
17444 The console output stream contains text that should be displayed in the
17445 CLI console window. It contains the textual responses to CLI commands.
17447 @item "@@" @var{string-output}
17448 The target output stream contains any textual output from the running
17451 @item "&" @var{string-output}
17452 The log stream contains debugging messages being produced by @value{GDBN}'s
17456 @node GDB/MI Out-of-band Records
17457 @subsection @sc{gdb/mi} Out-of-band Records
17459 @cindex out-of-band records in @sc{gdb/mi}
17460 @cindex @sc{gdb/mi}, out-of-band records
17461 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
17462 additional changes that have occurred. Those changes can either be a
17463 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
17464 target activity (e.g., target stopped).
17466 The following is a preliminary list of possible out-of-band records.
17467 In particular, the @var{exec-async-output} records.
17470 @item *stopped,reason="@var{reason}"
17473 @var{reason} can be one of the following:
17476 @item breakpoint-hit
17477 A breakpoint was reached.
17478 @item watchpoint-trigger
17479 A watchpoint was triggered.
17480 @item read-watchpoint-trigger
17481 A read watchpoint was triggered.
17482 @item access-watchpoint-trigger
17483 An access watchpoint was triggered.
17484 @item function-finished
17485 An -exec-finish or similar CLI command was accomplished.
17486 @item location-reached
17487 An -exec-until or similar CLI command was accomplished.
17488 @item watchpoint-scope
17489 A watchpoint has gone out of scope.
17490 @item end-stepping-range
17491 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
17492 similar CLI command was accomplished.
17493 @item exited-signalled
17494 The inferior exited because of a signal.
17496 The inferior exited.
17497 @item exited-normally
17498 The inferior exited normally.
17499 @item signal-received
17500 A signal was received by the inferior.
17504 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17505 @node GDB/MI Command Description Format
17506 @section @sc{gdb/mi} Command Description Format
17508 The remaining sections describe blocks of commands. Each block of
17509 commands is laid out in a fashion similar to this section.
17511 Note the the line breaks shown in the examples are here only for
17512 readability. They don't appear in the real output.
17513 Also note that the commands with a non-available example (N.A.@:) are
17514 not yet implemented.
17516 @subheading Motivation
17518 The motivation for this collection of commands.
17520 @subheading Introduction
17522 A brief introduction to this collection of commands as a whole.
17524 @subheading Commands
17526 For each command in the block, the following is described:
17528 @subsubheading Synopsis
17531 -command @var{args}@dots{}
17534 @subsubheading Result
17536 @subsubheading @value{GDBN} Command
17538 The corresponding @value{GDBN} CLI command(s), if any.
17540 @subsubheading Example
17542 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17543 @node GDB/MI Breakpoint Table Commands
17544 @section @sc{gdb/mi} Breakpoint table commands
17546 @cindex breakpoint commands for @sc{gdb/mi}
17547 @cindex @sc{gdb/mi}, breakpoint commands
17548 This section documents @sc{gdb/mi} commands for manipulating
17551 @subheading The @code{-break-after} Command
17552 @findex -break-after
17554 @subsubheading Synopsis
17557 -break-after @var{number} @var{count}
17560 The breakpoint number @var{number} is not in effect until it has been
17561 hit @var{count} times. To see how this is reflected in the output of
17562 the @samp{-break-list} command, see the description of the
17563 @samp{-break-list} command below.
17565 @subsubheading @value{GDBN} Command
17567 The corresponding @value{GDBN} command is @samp{ignore}.
17569 @subsubheading Example
17574 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",
17575 fullname="/home/foo/hello.c",line="5",times="0"@}
17582 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17583 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17584 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17585 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17586 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17587 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17588 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17589 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17590 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
17591 line="5",times="0",ignore="3"@}]@}
17596 @subheading The @code{-break-catch} Command
17597 @findex -break-catch
17599 @subheading The @code{-break-commands} Command
17600 @findex -break-commands
17604 @subheading The @code{-break-condition} Command
17605 @findex -break-condition
17607 @subsubheading Synopsis
17610 -break-condition @var{number} @var{expr}
17613 Breakpoint @var{number} will stop the program only if the condition in
17614 @var{expr} is true. The condition becomes part of the
17615 @samp{-break-list} output (see the description of the @samp{-break-list}
17618 @subsubheading @value{GDBN} Command
17620 The corresponding @value{GDBN} command is @samp{condition}.
17622 @subsubheading Example
17626 -break-condition 1 1
17630 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17631 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17632 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17633 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17634 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17635 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17636 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17637 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17638 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
17639 line="5",cond="1",times="0",ignore="3"@}]@}
17643 @subheading The @code{-break-delete} Command
17644 @findex -break-delete
17646 @subsubheading Synopsis
17649 -break-delete ( @var{breakpoint} )+
17652 Delete the breakpoint(s) whose number(s) are specified in the argument
17653 list. This is obviously reflected in the breakpoint list.
17655 @subsubheading @value{GDBN} command
17657 The corresponding @value{GDBN} command is @samp{delete}.
17659 @subsubheading Example
17667 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
17668 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17669 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17670 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17671 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17672 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17673 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17678 @subheading The @code{-break-disable} Command
17679 @findex -break-disable
17681 @subsubheading Synopsis
17684 -break-disable ( @var{breakpoint} )+
17687 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
17688 break list is now set to @samp{n} for the named @var{breakpoint}(s).
17690 @subsubheading @value{GDBN} Command
17692 The corresponding @value{GDBN} command is @samp{disable}.
17694 @subsubheading Example
17702 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17703 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17704 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17705 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17706 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17707 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17708 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17709 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
17710 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
17711 line="5",times="0"@}]@}
17715 @subheading The @code{-break-enable} Command
17716 @findex -break-enable
17718 @subsubheading Synopsis
17721 -break-enable ( @var{breakpoint} )+
17724 Enable (previously disabled) @var{breakpoint}(s).
17726 @subsubheading @value{GDBN} Command
17728 The corresponding @value{GDBN} command is @samp{enable}.
17730 @subsubheading Example
17738 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17739 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17740 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17741 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17742 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17743 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17744 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17745 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
17746 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
17747 line="5",times="0"@}]@}
17751 @subheading The @code{-break-info} Command
17752 @findex -break-info
17754 @subsubheading Synopsis
17757 -break-info @var{breakpoint}
17761 Get information about a single breakpoint.
17763 @subsubheading @value{GDBN} command
17765 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
17767 @subsubheading Example
17770 @subheading The @code{-break-insert} Command
17771 @findex -break-insert
17773 @subsubheading Synopsis
17776 -break-insert [ -t ] [ -h ] [ -r ]
17777 [ -c @var{condition} ] [ -i @var{ignore-count} ]
17778 [ -p @var{thread} ] [ @var{line} | @var{addr} ]
17782 If specified, @var{line}, can be one of:
17789 @item filename:linenum
17790 @item filename:function
17794 The possible optional parameters of this command are:
17798 Insert a temporary breakpoint.
17800 Insert a hardware breakpoint.
17801 @item -c @var{condition}
17802 Make the breakpoint conditional on @var{condition}.
17803 @item -i @var{ignore-count}
17804 Initialize the @var{ignore-count}.
17806 Insert a regular breakpoint in all the functions whose names match the
17807 given regular expression. Other flags are not applicable to regular
17811 @subsubheading Result
17813 The result is in the form:
17816 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
17817 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
17818 fullname="@var{full_filename}",line="@var{lineno}",times="@var{times}"@}
17822 where @var{number} is the @value{GDBN} number for this breakpoint,
17823 @var{funcname} is the name of the function where the breakpoint was
17824 inserted, @var{filename} is the name of the source file which contains
17825 this function, @var{lineno} is the source line number within that file
17826 and @var{times} the number of times that the breakpoint has been hit
17827 (always 0 for -break-insert but may be greater for -break-info or -break-list
17828 which use the same output).
17830 Note: this format is open to change.
17831 @c An out-of-band breakpoint instead of part of the result?
17833 @subsubheading @value{GDBN} Command
17835 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
17836 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
17838 @subsubheading Example
17843 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
17844 fullname="/home/foo/recursive2.c,line="4",times="0"@}
17846 -break-insert -t foo
17847 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
17848 fullname="/home/foo/recursive2.c,line="11",times="0"@}
17851 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17852 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17853 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17854 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17855 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17856 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17857 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17858 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17859 addr="0x0001072c", func="main",file="recursive2.c",
17860 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
17861 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
17862 addr="0x00010774",func="foo",file="recursive2.c",
17863 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
17865 -break-insert -r foo.*
17866 ~int foo(int, int);
17867 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
17868 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
17872 @subheading The @code{-break-list} Command
17873 @findex -break-list
17875 @subsubheading Synopsis
17881 Displays the list of inserted breakpoints, showing the following fields:
17885 number of the breakpoint
17887 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
17889 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
17892 is the breakpoint enabled or no: @samp{y} or @samp{n}
17894 memory location at which the breakpoint is set
17896 logical location of the breakpoint, expressed by function name, file
17899 number of times the breakpoint has been hit
17902 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
17903 @code{body} field is an empty list.
17905 @subsubheading @value{GDBN} Command
17907 The corresponding @value{GDBN} command is @samp{info break}.
17909 @subsubheading Example
17914 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17915 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17916 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17917 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17918 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17919 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17920 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17921 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17922 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
17923 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
17924 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
17925 line="13",times="0"@}]@}
17929 Here's an example of the result when there are no breakpoints:
17934 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
17935 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17936 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17937 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17938 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17939 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17940 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17945 @subheading The @code{-break-watch} Command
17946 @findex -break-watch
17948 @subsubheading Synopsis
17951 -break-watch [ -a | -r ]
17954 Create a watchpoint. With the @samp{-a} option it will create an
17955 @dfn{access} watchpoint, i.e. a watchpoint that triggers either on a
17956 read from or on a write to the memory location. With the @samp{-r}
17957 option, the watchpoint created is a @dfn{read} watchpoint, i.e. it will
17958 trigger only when the memory location is accessed for reading. Without
17959 either of the options, the watchpoint created is a regular watchpoint,
17960 i.e. it will trigger when the memory location is accessed for writing.
17961 @xref{Set Watchpoints, , Setting watchpoints}.
17963 Note that @samp{-break-list} will report a single list of watchpoints and
17964 breakpoints inserted.
17966 @subsubheading @value{GDBN} Command
17968 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
17971 @subsubheading Example
17973 Setting a watchpoint on a variable in the @code{main} function:
17978 ^done,wpt=@{number="2",exp="x"@}
17982 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
17983 value=@{old="-268439212",new="55"@},
17984 frame=@{func="main",args=[],file="recursive2.c",
17985 fullname="/home/foo/bar/recursive2.c",line="5"@}
17989 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
17990 the program execution twice: first for the variable changing value, then
17991 for the watchpoint going out of scope.
17996 ^done,wpt=@{number="5",exp="C"@}
18000 ^done,reason="watchpoint-trigger",
18001 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
18002 frame=@{func="callee4",args=[],
18003 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18004 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
18008 ^done,reason="watchpoint-scope",wpnum="5",
18009 frame=@{func="callee3",args=[@{name="strarg",
18010 value="0x11940 \"A string argument.\""@}],
18011 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18012 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18016 Listing breakpoints and watchpoints, at different points in the program
18017 execution. Note that once the watchpoint goes out of scope, it is
18023 ^done,wpt=@{number="2",exp="C"@}
18026 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18027 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18028 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18029 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18030 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18031 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18032 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18033 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18034 addr="0x00010734",func="callee4",
18035 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18036 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
18037 bkpt=@{number="2",type="watchpoint",disp="keep",
18038 enabled="y",addr="",what="C",times="0"@}]@}
18042 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
18043 value=@{old="-276895068",new="3"@},
18044 frame=@{func="callee4",args=[],
18045 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18046 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
18049 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
18050 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18051 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18052 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18053 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18054 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18055 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18056 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18057 addr="0x00010734",func="callee4",
18058 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18059 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
18060 bkpt=@{number="2",type="watchpoint",disp="keep",
18061 enabled="y",addr="",what="C",times="-5"@}]@}
18065 ^done,reason="watchpoint-scope",wpnum="2",
18066 frame=@{func="callee3",args=[@{name="strarg",
18067 value="0x11940 \"A string argument.\""@}],
18068 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18069 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18072 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
18073 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
18074 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
18075 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
18076 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
18077 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
18078 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
18079 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
18080 addr="0x00010734",func="callee4",
18081 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18082 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
18087 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18088 @node GDB/MI Data Manipulation
18089 @section @sc{gdb/mi} Data Manipulation
18091 @cindex data manipulation, in @sc{gdb/mi}
18092 @cindex @sc{gdb/mi}, data manipulation
18093 This section describes the @sc{gdb/mi} commands that manipulate data:
18094 examine memory and registers, evaluate expressions, etc.
18096 @c REMOVED FROM THE INTERFACE.
18097 @c @subheading -data-assign
18098 @c Change the value of a program variable. Plenty of side effects.
18099 @c @subsubheading GDB command
18101 @c @subsubheading Example
18104 @subheading The @code{-data-disassemble} Command
18105 @findex -data-disassemble
18107 @subsubheading Synopsis
18111 [ -s @var{start-addr} -e @var{end-addr} ]
18112 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
18120 @item @var{start-addr}
18121 is the beginning address (or @code{$pc})
18122 @item @var{end-addr}
18124 @item @var{filename}
18125 is the name of the file to disassemble
18126 @item @var{linenum}
18127 is the line number to disassemble around
18129 is the the number of disassembly lines to be produced. If it is -1,
18130 the whole function will be disassembled, in case no @var{end-addr} is
18131 specified. If @var{end-addr} is specified as a non-zero value, and
18132 @var{lines} is lower than the number of disassembly lines between
18133 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
18134 displayed; if @var{lines} is higher than the number of lines between
18135 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
18138 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
18142 @subsubheading Result
18144 The output for each instruction is composed of four fields:
18153 Note that whatever included in the instruction field, is not manipulated
18154 directely by @sc{gdb/mi}, i.e. it is not possible to adjust its format.
18156 @subsubheading @value{GDBN} Command
18158 There's no direct mapping from this command to the CLI.
18160 @subsubheading Example
18162 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
18166 -data-disassemble -s $pc -e "$pc + 20" -- 0
18169 @{address="0x000107c0",func-name="main",offset="4",
18170 inst="mov 2, %o0"@},
18171 @{address="0x000107c4",func-name="main",offset="8",
18172 inst="sethi %hi(0x11800), %o2"@},
18173 @{address="0x000107c8",func-name="main",offset="12",
18174 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
18175 @{address="0x000107cc",func-name="main",offset="16",
18176 inst="sethi %hi(0x11800), %o2"@},
18177 @{address="0x000107d0",func-name="main",offset="20",
18178 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
18182 Disassemble the whole @code{main} function. Line 32 is part of
18186 -data-disassemble -f basics.c -l 32 -- 0
18188 @{address="0x000107bc",func-name="main",offset="0",
18189 inst="save %sp, -112, %sp"@},
18190 @{address="0x000107c0",func-name="main",offset="4",
18191 inst="mov 2, %o0"@},
18192 @{address="0x000107c4",func-name="main",offset="8",
18193 inst="sethi %hi(0x11800), %o2"@},
18195 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
18196 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
18200 Disassemble 3 instructions from the start of @code{main}:
18204 -data-disassemble -f basics.c -l 32 -n 3 -- 0
18206 @{address="0x000107bc",func-name="main",offset="0",
18207 inst="save %sp, -112, %sp"@},
18208 @{address="0x000107c0",func-name="main",offset="4",
18209 inst="mov 2, %o0"@},
18210 @{address="0x000107c4",func-name="main",offset="8",
18211 inst="sethi %hi(0x11800), %o2"@}]
18215 Disassemble 3 instructions from the start of @code{main} in mixed mode:
18219 -data-disassemble -f basics.c -l 32 -n 3 -- 1
18221 src_and_asm_line=@{line="31",
18222 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
18223 testsuite/gdb.mi/basics.c",line_asm_insn=[
18224 @{address="0x000107bc",func-name="main",offset="0",
18225 inst="save %sp, -112, %sp"@}]@},
18226 src_and_asm_line=@{line="32",
18227 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
18228 testsuite/gdb.mi/basics.c",line_asm_insn=[
18229 @{address="0x000107c0",func-name="main",offset="4",
18230 inst="mov 2, %o0"@},
18231 @{address="0x000107c4",func-name="main",offset="8",
18232 inst="sethi %hi(0x11800), %o2"@}]@}]
18237 @subheading The @code{-data-evaluate-expression} Command
18238 @findex -data-evaluate-expression
18240 @subsubheading Synopsis
18243 -data-evaluate-expression @var{expr}
18246 Evaluate @var{expr} as an expression. The expression could contain an
18247 inferior function call. The function call will execute synchronously.
18248 If the expression contains spaces, it must be enclosed in double quotes.
18250 @subsubheading @value{GDBN} Command
18252 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
18253 @samp{call}. In @code{gdbtk} only, there's a corresponding
18254 @samp{gdb_eval} command.
18256 @subsubheading Example
18258 In the following example, the numbers that precede the commands are the
18259 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
18260 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
18264 211-data-evaluate-expression A
18267 311-data-evaluate-expression &A
18268 311^done,value="0xefffeb7c"
18270 411-data-evaluate-expression A+3
18273 511-data-evaluate-expression "A + 3"
18279 @subheading The @code{-data-list-changed-registers} Command
18280 @findex -data-list-changed-registers
18282 @subsubheading Synopsis
18285 -data-list-changed-registers
18288 Display a list of the registers that have changed.
18290 @subsubheading @value{GDBN} Command
18292 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
18293 has the corresponding command @samp{gdb_changed_register_list}.
18295 @subsubheading Example
18297 On a PPC MBX board:
18305 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
18306 args=[],file="try.c",fullname="/home/foo/bar/try.c",line="5"@}
18308 -data-list-changed-registers
18309 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
18310 "10","11","13","14","15","16","17","18","19","20","21","22","23",
18311 "24","25","26","27","28","30","31","64","65","66","67","69"]
18316 @subheading The @code{-data-list-register-names} Command
18317 @findex -data-list-register-names
18319 @subsubheading Synopsis
18322 -data-list-register-names [ ( @var{regno} )+ ]
18325 Show a list of register names for the current target. If no arguments
18326 are given, it shows a list of the names of all the registers. If
18327 integer numbers are given as arguments, it will print a list of the
18328 names of the registers corresponding to the arguments. To ensure
18329 consistency between a register name and its number, the output list may
18330 include empty register names.
18332 @subsubheading @value{GDBN} Command
18334 @value{GDBN} does not have a command which corresponds to
18335 @samp{-data-list-register-names}. In @code{gdbtk} there is a
18336 corresponding command @samp{gdb_regnames}.
18338 @subsubheading Example
18340 For the PPC MBX board:
18343 -data-list-register-names
18344 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
18345 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
18346 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
18347 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
18348 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
18349 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
18350 "", "pc","ps","cr","lr","ctr","xer"]
18352 -data-list-register-names 1 2 3
18353 ^done,register-names=["r1","r2","r3"]
18357 @subheading The @code{-data-list-register-values} Command
18358 @findex -data-list-register-values
18360 @subsubheading Synopsis
18363 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
18366 Display the registers' contents. @var{fmt} is the format according to
18367 which the registers' contents are to be returned, followed by an optional
18368 list of numbers specifying the registers to display. A missing list of
18369 numbers indicates that the contents of all the registers must be returned.
18371 Allowed formats for @var{fmt} are:
18388 @subsubheading @value{GDBN} Command
18390 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
18391 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
18393 @subsubheading Example
18395 For a PPC MBX board (note: line breaks are for readability only, they
18396 don't appear in the actual output):
18400 -data-list-register-values r 64 65
18401 ^done,register-values=[@{number="64",value="0xfe00a300"@},
18402 @{number="65",value="0x00029002"@}]
18404 -data-list-register-values x
18405 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
18406 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
18407 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
18408 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
18409 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
18410 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
18411 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
18412 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
18413 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
18414 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
18415 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
18416 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
18417 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
18418 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
18419 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
18420 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
18421 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
18422 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
18423 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
18424 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
18425 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
18426 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
18427 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
18428 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
18429 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
18430 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
18431 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
18432 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
18433 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
18434 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
18435 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
18436 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
18437 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
18438 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
18439 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
18440 @{number="69",value="0x20002b03"@}]
18445 @subheading The @code{-data-read-memory} Command
18446 @findex -data-read-memory
18448 @subsubheading Synopsis
18451 -data-read-memory [ -o @var{byte-offset} ]
18452 @var{address} @var{word-format} @var{word-size}
18453 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
18460 @item @var{address}
18461 An expression specifying the address of the first memory word to be
18462 read. Complex expressions containing embedded white space should be
18463 quoted using the C convention.
18465 @item @var{word-format}
18466 The format to be used to print the memory words. The notation is the
18467 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
18470 @item @var{word-size}
18471 The size of each memory word in bytes.
18473 @item @var{nr-rows}
18474 The number of rows in the output table.
18476 @item @var{nr-cols}
18477 The number of columns in the output table.
18480 If present, indicates that each row should include an @sc{ascii} dump. The
18481 value of @var{aschar} is used as a padding character when a byte is not a
18482 member of the printable @sc{ascii} character set (printable @sc{ascii}
18483 characters are those whose code is between 32 and 126, inclusively).
18485 @item @var{byte-offset}
18486 An offset to add to the @var{address} before fetching memory.
18489 This command displays memory contents as a table of @var{nr-rows} by
18490 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
18491 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
18492 (returned as @samp{total-bytes}). Should less than the requested number
18493 of bytes be returned by the target, the missing words are identified
18494 using @samp{N/A}. The number of bytes read from the target is returned
18495 in @samp{nr-bytes} and the starting address used to read memory in
18498 The address of the next/previous row or page is available in
18499 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
18502 @subsubheading @value{GDBN} Command
18504 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
18505 @samp{gdb_get_mem} memory read command.
18507 @subsubheading Example
18509 Read six bytes of memory starting at @code{bytes+6} but then offset by
18510 @code{-6} bytes. Format as three rows of two columns. One byte per
18511 word. Display each word in hex.
18515 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
18516 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
18517 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
18518 prev-page="0x0000138a",memory=[
18519 @{addr="0x00001390",data=["0x00","0x01"]@},
18520 @{addr="0x00001392",data=["0x02","0x03"]@},
18521 @{addr="0x00001394",data=["0x04","0x05"]@}]
18525 Read two bytes of memory starting at address @code{shorts + 64} and
18526 display as a single word formatted in decimal.
18530 5-data-read-memory shorts+64 d 2 1 1
18531 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
18532 next-row="0x00001512",prev-row="0x0000150e",
18533 next-page="0x00001512",prev-page="0x0000150e",memory=[
18534 @{addr="0x00001510",data=["128"]@}]
18538 Read thirty two bytes of memory starting at @code{bytes+16} and format
18539 as eight rows of four columns. Include a string encoding with @samp{x}
18540 used as the non-printable character.
18544 4-data-read-memory bytes+16 x 1 8 4 x
18545 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
18546 next-row="0x000013c0",prev-row="0x0000139c",
18547 next-page="0x000013c0",prev-page="0x00001380",memory=[
18548 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
18549 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
18550 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
18551 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
18552 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
18553 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
18554 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
18555 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
18559 @subheading The @code{-display-delete} Command
18560 @findex -display-delete
18562 @subsubheading Synopsis
18565 -display-delete @var{number}
18568 Delete the display @var{number}.
18570 @subsubheading @value{GDBN} Command
18572 The corresponding @value{GDBN} command is @samp{delete display}.
18574 @subsubheading Example
18578 @subheading The @code{-display-disable} Command
18579 @findex -display-disable
18581 @subsubheading Synopsis
18584 -display-disable @var{number}
18587 Disable display @var{number}.
18589 @subsubheading @value{GDBN} Command
18591 The corresponding @value{GDBN} command is @samp{disable display}.
18593 @subsubheading Example
18597 @subheading The @code{-display-enable} Command
18598 @findex -display-enable
18600 @subsubheading Synopsis
18603 -display-enable @var{number}
18606 Enable display @var{number}.
18608 @subsubheading @value{GDBN} Command
18610 The corresponding @value{GDBN} command is @samp{enable display}.
18612 @subsubheading Example
18616 @subheading The @code{-display-insert} Command
18617 @findex -display-insert
18619 @subsubheading Synopsis
18622 -display-insert @var{expression}
18625 Display @var{expression} every time the program stops.
18627 @subsubheading @value{GDBN} Command
18629 The corresponding @value{GDBN} command is @samp{display}.
18631 @subsubheading Example
18635 @subheading The @code{-display-list} Command
18636 @findex -display-list
18638 @subsubheading Synopsis
18644 List the displays. Do not show the current values.
18646 @subsubheading @value{GDBN} Command
18648 The corresponding @value{GDBN} command is @samp{info display}.
18650 @subsubheading Example
18654 @subheading The @code{-environment-cd} Command
18655 @findex -environment-cd
18657 @subsubheading Synopsis
18660 -environment-cd @var{pathdir}
18663 Set @value{GDBN}'s working directory.
18665 @subsubheading @value{GDBN} Command
18667 The corresponding @value{GDBN} command is @samp{cd}.
18669 @subsubheading Example
18673 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18679 @subheading The @code{-environment-directory} Command
18680 @findex -environment-directory
18682 @subsubheading Synopsis
18685 -environment-directory [ -r ] [ @var{pathdir} ]+
18688 Add directories @var{pathdir} to beginning of search path for source files.
18689 If the @samp{-r} option is used, the search path is reset to the default
18690 search path. If directories @var{pathdir} are supplied in addition to the
18691 @samp{-r} option, the search path is first reset and then addition
18693 Multiple directories may be specified, separated by blanks. Specifying
18694 multiple directories in a single command
18695 results in the directories added to the beginning of the
18696 search path in the same order they were presented in the command.
18697 If blanks are needed as
18698 part of a directory name, double-quotes should be used around
18699 the name. In the command output, the path will show up separated
18700 by the system directory-separator character. The directory-seperator
18701 character must not be used
18702 in any directory name.
18703 If no directories are specified, the current search path is displayed.
18705 @subsubheading @value{GDBN} Command
18707 The corresponding @value{GDBN} command is @samp{dir}.
18709 @subsubheading Example
18713 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18714 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18716 -environment-directory ""
18717 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18719 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
18720 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
18722 -environment-directory -r
18723 ^done,source-path="$cdir:$cwd"
18728 @subheading The @code{-environment-path} Command
18729 @findex -environment-path
18731 @subsubheading Synopsis
18734 -environment-path [ -r ] [ @var{pathdir} ]+
18737 Add directories @var{pathdir} to beginning of search path for object files.
18738 If the @samp{-r} option is used, the search path is reset to the original
18739 search path that existed at gdb start-up. If directories @var{pathdir} are
18740 supplied in addition to the
18741 @samp{-r} option, the search path is first reset and then addition
18743 Multiple directories may be specified, separated by blanks. Specifying
18744 multiple directories in a single command
18745 results in the directories added to the beginning of the
18746 search path in the same order they were presented in the command.
18747 If blanks are needed as
18748 part of a directory name, double-quotes should be used around
18749 the name. In the command output, the path will show up separated
18750 by the system directory-separator character. The directory-seperator
18751 character must not be used
18752 in any directory name.
18753 If no directories are specified, the current path is displayed.
18756 @subsubheading @value{GDBN} Command
18758 The corresponding @value{GDBN} command is @samp{path}.
18760 @subsubheading Example
18765 ^done,path="/usr/bin"
18767 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
18768 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
18770 -environment-path -r /usr/local/bin
18771 ^done,path="/usr/local/bin:/usr/bin"
18776 @subheading The @code{-environment-pwd} Command
18777 @findex -environment-pwd
18779 @subsubheading Synopsis
18785 Show the current working directory.
18787 @subsubheading @value{GDBN} command
18789 The corresponding @value{GDBN} command is @samp{pwd}.
18791 @subsubheading Example
18796 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
18800 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18801 @node GDB/MI Program Control
18802 @section @sc{gdb/mi} Program control
18804 @subsubheading Program termination
18806 As a result of execution, the inferior program can run to completion, if
18807 it doesn't encounter any breakpoints. In this case the output will
18808 include an exit code, if the program has exited exceptionally.
18810 @subsubheading Examples
18813 Program exited normally:
18821 *stopped,reason="exited-normally"
18826 Program exited exceptionally:
18834 *stopped,reason="exited",exit-code="01"
18838 Another way the program can terminate is if it receives a signal such as
18839 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
18843 *stopped,reason="exited-signalled",signal-name="SIGINT",
18844 signal-meaning="Interrupt"
18848 @subheading The @code{-exec-abort} Command
18849 @findex -exec-abort
18851 @subsubheading Synopsis
18857 Kill the inferior running program.
18859 @subsubheading @value{GDBN} Command
18861 The corresponding @value{GDBN} command is @samp{kill}.
18863 @subsubheading Example
18867 @subheading The @code{-exec-arguments} Command
18868 @findex -exec-arguments
18870 @subsubheading Synopsis
18873 -exec-arguments @var{args}
18876 Set the inferior program arguments, to be used in the next
18879 @subsubheading @value{GDBN} Command
18881 The corresponding @value{GDBN} command is @samp{set args}.
18883 @subsubheading Example
18886 Don't have one around.
18889 @subheading The @code{-exec-continue} Command
18890 @findex -exec-continue
18892 @subsubheading Synopsis
18898 Asynchronous command. Resumes the execution of the inferior program
18899 until a breakpoint is encountered, or until the inferior exits.
18901 @subsubheading @value{GDBN} Command
18903 The corresponding @value{GDBN} corresponding is @samp{continue}.
18905 @subsubheading Example
18912 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
18913 file="hello.c",fullname="/home/foo/bar/hello.c",line="13"@}
18918 @subheading The @code{-exec-finish} Command
18919 @findex -exec-finish
18921 @subsubheading Synopsis
18927 Asynchronous command. Resumes the execution of the inferior program
18928 until the current function is exited. Displays the results returned by
18931 @subsubheading @value{GDBN} Command
18933 The corresponding @value{GDBN} command is @samp{finish}.
18935 @subsubheading Example
18937 Function returning @code{void}.
18944 *stopped,reason="function-finished",frame=@{func="main",args=[],
18945 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
18949 Function returning other than @code{void}. The name of the internal
18950 @value{GDBN} variable storing the result is printed, together with the
18957 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
18958 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
18959 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
18960 gdb-result-var="$1",return-value="0"
18965 @subheading The @code{-exec-interrupt} Command
18966 @findex -exec-interrupt
18968 @subsubheading Synopsis
18974 Asynchronous command. Interrupts the background execution of the target.
18975 Note how the token associated with the stop message is the one for the
18976 execution command that has been interrupted. The token for the interrupt
18977 itself only appears in the @samp{^done} output. If the user is trying to
18978 interrupt a non-running program, an error message will be printed.
18980 @subsubheading @value{GDBN} Command
18982 The corresponding @value{GDBN} command is @samp{interrupt}.
18984 @subsubheading Example
18995 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
18996 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
18997 fullname="/home/foo/bar/try.c",line="13"@}
19002 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
19007 @subheading The @code{-exec-next} Command
19010 @subsubheading Synopsis
19016 Asynchronous command. Resumes execution of the inferior program, stopping
19017 when the beginning of the next source line is reached.
19019 @subsubheading @value{GDBN} Command
19021 The corresponding @value{GDBN} command is @samp{next}.
19023 @subsubheading Example
19029 *stopped,reason="end-stepping-range",line="8",file="hello.c"
19034 @subheading The @code{-exec-next-instruction} Command
19035 @findex -exec-next-instruction
19037 @subsubheading Synopsis
19040 -exec-next-instruction
19043 Asynchronous command. Executes one machine instruction. If the
19044 instruction is a function call continues until the function returns. If
19045 the program stops at an instruction in the middle of a source line, the
19046 address will be printed as well.
19048 @subsubheading @value{GDBN} Command
19050 The corresponding @value{GDBN} command is @samp{nexti}.
19052 @subsubheading Example
19056 -exec-next-instruction
19060 *stopped,reason="end-stepping-range",
19061 addr="0x000100d4",line="5",file="hello.c"
19066 @subheading The @code{-exec-return} Command
19067 @findex -exec-return
19069 @subsubheading Synopsis
19075 Makes current function return immediately. Doesn't execute the inferior.
19076 Displays the new current frame.
19078 @subsubheading @value{GDBN} Command
19080 The corresponding @value{GDBN} command is @samp{return}.
19082 @subsubheading Example
19086 200-break-insert callee4
19087 200^done,bkpt=@{number="1",addr="0x00010734",
19088 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
19093 000*stopped,reason="breakpoint-hit",bkptno="1",
19094 frame=@{func="callee4",args=[],
19095 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19096 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
19102 111^done,frame=@{level="0",func="callee3",
19103 args=[@{name="strarg",
19104 value="0x11940 \"A string argument.\""@}],
19105 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19106 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
19111 @subheading The @code{-exec-run} Command
19114 @subsubheading Synopsis
19120 Asynchronous command. Starts execution of the inferior from the
19121 beginning. The inferior executes until either a breakpoint is
19122 encountered or the program exits.
19124 @subsubheading @value{GDBN} Command
19126 The corresponding @value{GDBN} command is @samp{run}.
19128 @subsubheading Example
19133 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
19138 *stopped,reason="breakpoint-hit",bkptno="1",
19139 frame=@{func="main",args=[],file="recursive2.c",
19140 fullname="/home/foo/bar/recursive2.c",line="4"@}
19145 @subheading The @code{-exec-show-arguments} Command
19146 @findex -exec-show-arguments
19148 @subsubheading Synopsis
19151 -exec-show-arguments
19154 Print the arguments of the program.
19156 @subsubheading @value{GDBN} Command
19158 The corresponding @value{GDBN} command is @samp{show args}.
19160 @subsubheading Example
19163 @c @subheading -exec-signal
19165 @subheading The @code{-exec-step} Command
19168 @subsubheading Synopsis
19174 Asynchronous command. Resumes execution of the inferior program, stopping
19175 when the beginning of the next source line is reached, if the next
19176 source line is not a function call. If it is, stop at the first
19177 instruction of the called function.
19179 @subsubheading @value{GDBN} Command
19181 The corresponding @value{GDBN} command is @samp{step}.
19183 @subsubheading Example
19185 Stepping into a function:
19191 *stopped,reason="end-stepping-range",
19192 frame=@{func="foo",args=[@{name="a",value="10"@},
19193 @{name="b",value="0"@}],file="recursive2.c",
19194 fullname="/home/foo/bar/recursive2.c",line="11"@}
19204 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
19209 @subheading The @code{-exec-step-instruction} Command
19210 @findex -exec-step-instruction
19212 @subsubheading Synopsis
19215 -exec-step-instruction
19218 Asynchronous command. Resumes the inferior which executes one machine
19219 instruction. The output, once @value{GDBN} has stopped, will vary depending on
19220 whether we have stopped in the middle of a source line or not. In the
19221 former case, the address at which the program stopped will be printed as
19224 @subsubheading @value{GDBN} Command
19226 The corresponding @value{GDBN} command is @samp{stepi}.
19228 @subsubheading Example
19232 -exec-step-instruction
19236 *stopped,reason="end-stepping-range",
19237 frame=@{func="foo",args=[],file="try.c",
19238 fullname="/home/foo/bar/try.c",line="10"@}
19240 -exec-step-instruction
19244 *stopped,reason="end-stepping-range",
19245 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
19246 fullname="/home/foo/bar/try.c",line="10"@}
19251 @subheading The @code{-exec-until} Command
19252 @findex -exec-until
19254 @subsubheading Synopsis
19257 -exec-until [ @var{location} ]
19260 Asynchronous command. Executes the inferior until the @var{location}
19261 specified in the argument is reached. If there is no argument, the inferior
19262 executes until a source line greater than the current one is reached.
19263 The reason for stopping in this case will be @samp{location-reached}.
19265 @subsubheading @value{GDBN} Command
19267 The corresponding @value{GDBN} command is @samp{until}.
19269 @subsubheading Example
19273 -exec-until recursive2.c:6
19277 *stopped,reason="location-reached",frame=@{func="main",args=[],
19278 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
19283 @subheading -file-clear
19284 Is this going away????
19288 @subheading The @code{-file-exec-and-symbols} Command
19289 @findex -file-exec-and-symbols
19291 @subsubheading Synopsis
19294 -file-exec-and-symbols @var{file}
19297 Specify the executable file to be debugged. This file is the one from
19298 which the symbol table is also read. If no file is specified, the
19299 command clears the executable and symbol information. If breakpoints
19300 are set when using this command with no arguments, @value{GDBN} will produce
19301 error messages. Otherwise, no output is produced, except a completion
19304 @subsubheading @value{GDBN} Command
19306 The corresponding @value{GDBN} command is @samp{file}.
19308 @subsubheading Example
19312 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
19318 @subheading The @code{-file-exec-file} Command
19319 @findex -file-exec-file
19321 @subsubheading Synopsis
19324 -file-exec-file @var{file}
19327 Specify the executable file to be debugged. Unlike
19328 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
19329 from this file. If used without argument, @value{GDBN} clears the information
19330 about the executable file. No output is produced, except a completion
19333 @subsubheading @value{GDBN} Command
19335 The corresponding @value{GDBN} command is @samp{exec-file}.
19337 @subsubheading Example
19341 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
19347 @subheading The @code{-file-list-exec-sections} Command
19348 @findex -file-list-exec-sections
19350 @subsubheading Synopsis
19353 -file-list-exec-sections
19356 List the sections of the current executable file.
19358 @subsubheading @value{GDBN} Command
19360 The @value{GDBN} command @samp{info file} shows, among the rest, the same
19361 information as this command. @code{gdbtk} has a corresponding command
19362 @samp{gdb_load_info}.
19364 @subsubheading Example
19368 @subheading The @code{-file-list-exec-source-file} Command
19369 @findex -file-list-exec-source-file
19371 @subsubheading Synopsis
19374 -file-list-exec-source-file
19377 List the line number, the current source file, and the absolute path
19378 to the current source file for the current executable.
19380 @subsubheading @value{GDBN} Command
19382 There's no @value{GDBN} command which directly corresponds to this one.
19384 @subsubheading Example
19388 123-file-list-exec-source-file
19389 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
19394 @subheading The @code{-file-list-exec-source-files} Command
19395 @findex -file-list-exec-source-files
19397 @subsubheading Synopsis
19400 -file-list-exec-source-files
19403 List the source files for the current executable.
19405 It will always output the filename, but only when GDB can find the absolute
19406 file name of a source file, will it output the fullname.
19408 @subsubheading @value{GDBN} Command
19410 There's no @value{GDBN} command which directly corresponds to this one.
19411 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
19413 @subsubheading Example
19416 -file-list-exec-source-files
19418 @{file=foo.c,fullname=/home/foo.c@},
19419 @{file=/home/bar.c,fullname=/home/bar.c@},
19420 @{file=gdb_could_not_find_fullpath.c@}]
19424 @subheading The @code{-file-list-shared-libraries} Command
19425 @findex -file-list-shared-libraries
19427 @subsubheading Synopsis
19430 -file-list-shared-libraries
19433 List the shared libraries in the program.
19435 @subsubheading @value{GDBN} Command
19437 The corresponding @value{GDBN} command is @samp{info shared}.
19439 @subsubheading Example
19443 @subheading The @code{-file-list-symbol-files} Command
19444 @findex -file-list-symbol-files
19446 @subsubheading Synopsis
19449 -file-list-symbol-files
19454 @subsubheading @value{GDBN} Command
19456 The corresponding @value{GDBN} command is @samp{info file} (part of it).
19458 @subsubheading Example
19462 @subheading The @code{-file-symbol-file} Command
19463 @findex -file-symbol-file
19465 @subsubheading Synopsis
19468 -file-symbol-file @var{file}
19471 Read symbol table info from the specified @var{file} argument. When
19472 used without arguments, clears @value{GDBN}'s symbol table info. No output is
19473 produced, except for a completion notification.
19475 @subsubheading @value{GDBN} Command
19477 The corresponding @value{GDBN} command is @samp{symbol-file}.
19479 @subsubheading Example
19483 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
19488 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19489 @node GDB/MI Miscellaneous Commands
19490 @section Miscellaneous @value{GDBN} commands in @sc{gdb/mi}
19492 @c @subheading -gdb-complete
19494 @subheading The @code{-gdb-exit} Command
19497 @subsubheading Synopsis
19503 Exit @value{GDBN} immediately.
19505 @subsubheading @value{GDBN} Command
19507 Approximately corresponds to @samp{quit}.
19509 @subsubheading Example
19516 @subheading The @code{-gdb-set} Command
19519 @subsubheading Synopsis
19525 Set an internal @value{GDBN} variable.
19526 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
19528 @subsubheading @value{GDBN} Command
19530 The corresponding @value{GDBN} command is @samp{set}.
19532 @subsubheading Example
19542 @subheading The @code{-gdb-show} Command
19545 @subsubheading Synopsis
19551 Show the current value of a @value{GDBN} variable.
19553 @subsubheading @value{GDBN} command
19555 The corresponding @value{GDBN} command is @samp{show}.
19557 @subsubheading Example
19566 @c @subheading -gdb-source
19569 @subheading The @code{-gdb-version} Command
19570 @findex -gdb-version
19572 @subsubheading Synopsis
19578 Show version information for @value{GDBN}. Used mostly in testing.
19580 @subsubheading @value{GDBN} Command
19582 There's no equivalent @value{GDBN} command. @value{GDBN} by default shows this
19583 information when you start an interactive session.
19585 @subsubheading Example
19587 @c This example modifies the actual output from GDB to avoid overfull
19593 ~Copyright 2000 Free Software Foundation, Inc.
19594 ~GDB is free software, covered by the GNU General Public License, and
19595 ~you are welcome to change it and/or distribute copies of it under
19596 ~ certain conditions.
19597 ~Type "show copying" to see the conditions.
19598 ~There is absolutely no warranty for GDB. Type "show warranty" for
19600 ~This GDB was configured as
19601 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
19606 @subheading The @code{-interpreter-exec} Command
19607 @findex -interpreter-exec
19609 @subheading Synopsis
19612 -interpreter-exec @var{interpreter} @var{command}
19615 Execute the specified @var{command} in the given @var{interpreter}.
19617 @subheading @value{GDBN} Command
19619 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
19621 @subheading Example
19625 -interpreter-exec console "break main"
19626 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
19627 &"During symbol reading, bad structure-type format.\n"
19628 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
19633 @subheading The @code{-inferior-tty-set} Command
19634 @findex -inferior-tty-set
19636 @subheading Synopsis
19639 -inferior-tty-set /dev/pts/1
19642 Set terminal for future runs of the program being debugged.
19644 @subheading @value{GDBN} Command
19646 The corresponding @value{GDBN} command is @samp{set inferior-tty /dev/pts/1}.
19648 @subheading Example
19652 -inferior-tty-set /dev/pts/1
19657 @subheading The @code{-inferior-tty-show} Command
19658 @findex -inferior-tty-show
19660 @subheading Synopsis
19666 Show terminal for future runs of program being debugged.
19668 @subheading @value{GDBN} Command
19670 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
19672 @subheading Example
19676 -inferior-tty-set /dev/pts/1
19680 ^done,inferior_tty_terminal="/dev/pts/1"
19685 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19686 @node GDB/MI Kod Commands
19687 @section @sc{gdb/mi} Kod Commands
19689 The Kod commands are not implemented.
19691 @c @subheading -kod-info
19693 @c @subheading -kod-list
19695 @c @subheading -kod-list-object-types
19697 @c @subheading -kod-show
19699 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19700 @node GDB/MI Memory Overlay Commands
19701 @section @sc{gdb/mi} Memory Overlay Commands
19703 The memory overlay commands are not implemented.
19705 @c @subheading -overlay-auto
19707 @c @subheading -overlay-list-mapping-state
19709 @c @subheading -overlay-list-overlays
19711 @c @subheading -overlay-map
19713 @c @subheading -overlay-off
19715 @c @subheading -overlay-on
19717 @c @subheading -overlay-unmap
19719 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19720 @node GDB/MI Signal Handling Commands
19721 @section @sc{gdb/mi} Signal Handling Commands
19723 Signal handling commands are not implemented.
19725 @c @subheading -signal-handle
19727 @c @subheading -signal-list-handle-actions
19729 @c @subheading -signal-list-signal-types
19733 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19734 @node GDB/MI Stack Manipulation
19735 @section @sc{gdb/mi} Stack Manipulation Commands
19738 @subheading The @code{-stack-info-frame} Command
19739 @findex -stack-info-frame
19741 @subsubheading Synopsis
19747 Get info on the selected frame.
19749 @subsubheading @value{GDBN} Command
19751 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
19752 (without arguments).
19754 @subsubheading Example
19759 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
19760 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19761 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
19765 @subheading The @code{-stack-info-depth} Command
19766 @findex -stack-info-depth
19768 @subsubheading Synopsis
19771 -stack-info-depth [ @var{max-depth} ]
19774 Return the depth of the stack. If the integer argument @var{max-depth}
19775 is specified, do not count beyond @var{max-depth} frames.
19777 @subsubheading @value{GDBN} Command
19779 There's no equivalent @value{GDBN} command.
19781 @subsubheading Example
19783 For a stack with frame levels 0 through 11:
19790 -stack-info-depth 4
19793 -stack-info-depth 12
19796 -stack-info-depth 11
19799 -stack-info-depth 13
19804 @subheading The @code{-stack-list-arguments} Command
19805 @findex -stack-list-arguments
19807 @subsubheading Synopsis
19810 -stack-list-arguments @var{show-values}
19811 [ @var{low-frame} @var{high-frame} ]
19814 Display a list of the arguments for the frames between @var{low-frame}
19815 and @var{high-frame} (inclusive). If @var{low-frame} and
19816 @var{high-frame} are not provided, list the arguments for the whole call
19819 The @var{show-values} argument must have a value of 0 or 1. A value of
19820 0 means that only the names of the arguments are listed, a value of 1
19821 means that both names and values of the arguments are printed.
19823 @subsubheading @value{GDBN} Command
19825 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
19826 @samp{gdb_get_args} command which partially overlaps with the
19827 functionality of @samp{-stack-list-arguments}.
19829 @subsubheading Example
19836 frame=@{level="0",addr="0x00010734",func="callee4",
19837 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19838 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
19839 frame=@{level="1",addr="0x0001076c",func="callee3",
19840 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19841 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
19842 frame=@{level="2",addr="0x0001078c",func="callee2",
19843 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19844 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
19845 frame=@{level="3",addr="0x000107b4",func="callee1",
19846 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19847 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
19848 frame=@{level="4",addr="0x000107e0",func="main",
19849 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19850 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
19852 -stack-list-arguments 0
19855 frame=@{level="0",args=[]@},
19856 frame=@{level="1",args=[name="strarg"]@},
19857 frame=@{level="2",args=[name="intarg",name="strarg"]@},
19858 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
19859 frame=@{level="4",args=[]@}]
19861 -stack-list-arguments 1
19864 frame=@{level="0",args=[]@},
19866 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19867 frame=@{level="2",args=[
19868 @{name="intarg",value="2"@},
19869 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19870 @{frame=@{level="3",args=[
19871 @{name="intarg",value="2"@},
19872 @{name="strarg",value="0x11940 \"A string argument.\""@},
19873 @{name="fltarg",value="3.5"@}]@},
19874 frame=@{level="4",args=[]@}]
19876 -stack-list-arguments 0 2 2
19877 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
19879 -stack-list-arguments 1 2 2
19880 ^done,stack-args=[frame=@{level="2",
19881 args=[@{name="intarg",value="2"@},
19882 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
19886 @c @subheading -stack-list-exception-handlers
19889 @subheading The @code{-stack-list-frames} Command
19890 @findex -stack-list-frames
19892 @subsubheading Synopsis
19895 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
19898 List the frames currently on the stack. For each frame it displays the
19903 The frame number, 0 being the topmost frame, i.e. the innermost function.
19905 The @code{$pc} value for that frame.
19909 File name of the source file where the function lives.
19911 Line number corresponding to the @code{$pc}.
19914 If invoked without arguments, this command prints a backtrace for the
19915 whole stack. If given two integer arguments, it shows the frames whose
19916 levels are between the two arguments (inclusive). If the two arguments
19917 are equal, it shows the single frame at the corresponding level.
19919 @subsubheading @value{GDBN} Command
19921 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
19923 @subsubheading Example
19925 Full stack backtrace:
19931 [frame=@{level="0",addr="0x0001076c",func="foo",
19932 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
19933 frame=@{level="1",addr="0x000107a4",func="foo",
19934 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19935 frame=@{level="2",addr="0x000107a4",func="foo",
19936 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19937 frame=@{level="3",addr="0x000107a4",func="foo",
19938 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19939 frame=@{level="4",addr="0x000107a4",func="foo",
19940 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19941 frame=@{level="5",addr="0x000107a4",func="foo",
19942 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19943 frame=@{level="6",addr="0x000107a4",func="foo",
19944 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19945 frame=@{level="7",addr="0x000107a4",func="foo",
19946 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19947 frame=@{level="8",addr="0x000107a4",func="foo",
19948 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19949 frame=@{level="9",addr="0x000107a4",func="foo",
19950 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19951 frame=@{level="10",addr="0x000107a4",func="foo",
19952 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19953 frame=@{level="11",addr="0x00010738",func="main",
19954 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
19958 Show frames between @var{low_frame} and @var{high_frame}:
19962 -stack-list-frames 3 5
19964 [frame=@{level="3",addr="0x000107a4",func="foo",
19965 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19966 frame=@{level="4",addr="0x000107a4",func="foo",
19967 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
19968 frame=@{level="5",addr="0x000107a4",func="foo",
19969 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
19973 Show a single frame:
19977 -stack-list-frames 3 3
19979 [frame=@{level="3",addr="0x000107a4",func="foo",
19980 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
19985 @subheading The @code{-stack-list-locals} Command
19986 @findex -stack-list-locals
19988 @subsubheading Synopsis
19991 -stack-list-locals @var{print-values}
19994 Display the local variable names for the selected frame. If
19995 @var{print-values} is 0 or @code{--no-values}, print only the names of
19996 the variables; if it is 1 or @code{--all-values}, print also their
19997 values; and if it is 2 or @code{--simple-values}, print the name,
19998 type and value for simple data types and the name and type for arrays,
19999 structures and unions. In this last case, a frontend can immediately
20000 display the value of simple data types and create variable objects for
20001 other data types when the the user wishes to explore their values in
20004 @subsubheading @value{GDBN} Command
20006 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
20008 @subsubheading Example
20012 -stack-list-locals 0
20013 ^done,locals=[name="A",name="B",name="C"]
20015 -stack-list-locals --all-values
20016 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
20017 @{name="C",value="@{1, 2, 3@}"@}]
20018 -stack-list-locals --simple-values
20019 ^done,locals=[@{name="A",type="int",value="1"@},
20020 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
20025 @subheading The @code{-stack-select-frame} Command
20026 @findex -stack-select-frame
20028 @subsubheading Synopsis
20031 -stack-select-frame @var{framenum}
20034 Change the selected frame. Select a different frame @var{framenum} on
20037 @subsubheading @value{GDBN} Command
20039 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
20040 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
20042 @subsubheading Example
20046 -stack-select-frame 2
20051 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20052 @node GDB/MI Symbol Query
20053 @section @sc{gdb/mi} Symbol Query Commands
20056 @subheading The @code{-symbol-info-address} Command
20057 @findex -symbol-info-address
20059 @subsubheading Synopsis
20062 -symbol-info-address @var{symbol}
20065 Describe where @var{symbol} is stored.
20067 @subsubheading @value{GDBN} Command
20069 The corresponding @value{GDBN} command is @samp{info address}.
20071 @subsubheading Example
20075 @subheading The @code{-symbol-info-file} Command
20076 @findex -symbol-info-file
20078 @subsubheading Synopsis
20084 Show the file for the symbol.
20086 @subsubheading @value{GDBN} Command
20088 There's no equivalent @value{GDBN} command. @code{gdbtk} has
20089 @samp{gdb_find_file}.
20091 @subsubheading Example
20095 @subheading The @code{-symbol-info-function} Command
20096 @findex -symbol-info-function
20098 @subsubheading Synopsis
20101 -symbol-info-function
20104 Show which function the symbol lives in.
20106 @subsubheading @value{GDBN} Command
20108 @samp{gdb_get_function} in @code{gdbtk}.
20110 @subsubheading Example
20114 @subheading The @code{-symbol-info-line} Command
20115 @findex -symbol-info-line
20117 @subsubheading Synopsis
20123 Show the core addresses of the code for a source line.
20125 @subsubheading @value{GDBN} Command
20127 The corresponding @value{GDBN} command is @samp{info line}.
20128 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
20130 @subsubheading Example
20134 @subheading The @code{-symbol-info-symbol} Command
20135 @findex -symbol-info-symbol
20137 @subsubheading Synopsis
20140 -symbol-info-symbol @var{addr}
20143 Describe what symbol is at location @var{addr}.
20145 @subsubheading @value{GDBN} Command
20147 The corresponding @value{GDBN} command is @samp{info symbol}.
20149 @subsubheading Example
20153 @subheading The @code{-symbol-list-functions} Command
20154 @findex -symbol-list-functions
20156 @subsubheading Synopsis
20159 -symbol-list-functions
20162 List the functions in the executable.
20164 @subsubheading @value{GDBN} Command
20166 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
20167 @samp{gdb_search} in @code{gdbtk}.
20169 @subsubheading Example
20173 @subheading The @code{-symbol-list-lines} Command
20174 @findex -symbol-list-lines
20176 @subsubheading Synopsis
20179 -symbol-list-lines @var{filename}
20182 Print the list of lines that contain code and their associated program
20183 addresses for the given source filename. The entries are sorted in
20184 ascending PC order.
20186 @subsubheading @value{GDBN} Command
20188 There is no corresponding @value{GDBN} command.
20190 @subsubheading Example
20193 -symbol-list-lines basics.c
20194 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
20199 @subheading The @code{-symbol-list-types} Command
20200 @findex -symbol-list-types
20202 @subsubheading Synopsis
20208 List all the type names.
20210 @subsubheading @value{GDBN} Command
20212 The corresponding commands are @samp{info types} in @value{GDBN},
20213 @samp{gdb_search} in @code{gdbtk}.
20215 @subsubheading Example
20219 @subheading The @code{-symbol-list-variables} Command
20220 @findex -symbol-list-variables
20222 @subsubheading Synopsis
20225 -symbol-list-variables
20228 List all the global and static variable names.
20230 @subsubheading @value{GDBN} Command
20232 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
20234 @subsubheading Example
20238 @subheading The @code{-symbol-locate} Command
20239 @findex -symbol-locate
20241 @subsubheading Synopsis
20247 @subsubheading @value{GDBN} Command
20249 @samp{gdb_loc} in @code{gdbtk}.
20251 @subsubheading Example
20255 @subheading The @code{-symbol-type} Command
20256 @findex -symbol-type
20258 @subsubheading Synopsis
20261 -symbol-type @var{variable}
20264 Show type of @var{variable}.
20266 @subsubheading @value{GDBN} Command
20268 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
20269 @samp{gdb_obj_variable}.
20271 @subsubheading Example
20275 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20276 @node GDB/MI Target Manipulation
20277 @section @sc{gdb/mi} Target Manipulation Commands
20280 @subheading The @code{-target-attach} Command
20281 @findex -target-attach
20283 @subsubheading Synopsis
20286 -target-attach @var{pid} | @var{file}
20289 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
20291 @subsubheading @value{GDBN} command
20293 The corresponding @value{GDBN} command is @samp{attach}.
20295 @subsubheading Example
20299 @subheading The @code{-target-compare-sections} Command
20300 @findex -target-compare-sections
20302 @subsubheading Synopsis
20305 -target-compare-sections [ @var{section} ]
20308 Compare data of section @var{section} on target to the exec file.
20309 Without the argument, all sections are compared.
20311 @subsubheading @value{GDBN} Command
20313 The @value{GDBN} equivalent is @samp{compare-sections}.
20315 @subsubheading Example
20319 @subheading The @code{-target-detach} Command
20320 @findex -target-detach
20322 @subsubheading Synopsis
20328 Disconnect from the remote target. There's no output.
20330 @subsubheading @value{GDBN} command
20332 The corresponding @value{GDBN} command is @samp{detach}.
20334 @subsubheading Example
20344 @subheading The @code{-target-disconnect} Command
20345 @findex -target-disconnect
20347 @subsubheading Synopsis
20353 Disconnect from the remote target. There's no output.
20355 @subsubheading @value{GDBN} command
20357 The corresponding @value{GDBN} command is @samp{disconnect}.
20359 @subsubheading Example
20369 @subheading The @code{-target-download} Command
20370 @findex -target-download
20372 @subsubheading Synopsis
20378 Loads the executable onto the remote target.
20379 It prints out an update message every half second, which includes the fields:
20383 The name of the section.
20385 The size of what has been sent so far for that section.
20387 The size of the section.
20389 The total size of what was sent so far (the current and the previous sections).
20391 The size of the overall executable to download.
20395 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
20396 @sc{gdb/mi} Output Syntax}).
20398 In addition, it prints the name and size of the sections, as they are
20399 downloaded. These messages include the following fields:
20403 The name of the section.
20405 The size of the section.
20407 The size of the overall executable to download.
20411 At the end, a summary is printed.
20413 @subsubheading @value{GDBN} Command
20415 The corresponding @value{GDBN} command is @samp{load}.
20417 @subsubheading Example
20419 Note: each status message appears on a single line. Here the messages
20420 have been broken down so that they can fit onto a page.
20425 +download,@{section=".text",section-size="6668",total-size="9880"@}
20426 +download,@{section=".text",section-sent="512",section-size="6668",
20427 total-sent="512",total-size="9880"@}
20428 +download,@{section=".text",section-sent="1024",section-size="6668",
20429 total-sent="1024",total-size="9880"@}
20430 +download,@{section=".text",section-sent="1536",section-size="6668",
20431 total-sent="1536",total-size="9880"@}
20432 +download,@{section=".text",section-sent="2048",section-size="6668",
20433 total-sent="2048",total-size="9880"@}
20434 +download,@{section=".text",section-sent="2560",section-size="6668",
20435 total-sent="2560",total-size="9880"@}
20436 +download,@{section=".text",section-sent="3072",section-size="6668",
20437 total-sent="3072",total-size="9880"@}
20438 +download,@{section=".text",section-sent="3584",section-size="6668",
20439 total-sent="3584",total-size="9880"@}
20440 +download,@{section=".text",section-sent="4096",section-size="6668",
20441 total-sent="4096",total-size="9880"@}
20442 +download,@{section=".text",section-sent="4608",section-size="6668",
20443 total-sent="4608",total-size="9880"@}
20444 +download,@{section=".text",section-sent="5120",section-size="6668",
20445 total-sent="5120",total-size="9880"@}
20446 +download,@{section=".text",section-sent="5632",section-size="6668",
20447 total-sent="5632",total-size="9880"@}
20448 +download,@{section=".text",section-sent="6144",section-size="6668",
20449 total-sent="6144",total-size="9880"@}
20450 +download,@{section=".text",section-sent="6656",section-size="6668",
20451 total-sent="6656",total-size="9880"@}
20452 +download,@{section=".init",section-size="28",total-size="9880"@}
20453 +download,@{section=".fini",section-size="28",total-size="9880"@}
20454 +download,@{section=".data",section-size="3156",total-size="9880"@}
20455 +download,@{section=".data",section-sent="512",section-size="3156",
20456 total-sent="7236",total-size="9880"@}
20457 +download,@{section=".data",section-sent="1024",section-size="3156",
20458 total-sent="7748",total-size="9880"@}
20459 +download,@{section=".data",section-sent="1536",section-size="3156",
20460 total-sent="8260",total-size="9880"@}
20461 +download,@{section=".data",section-sent="2048",section-size="3156",
20462 total-sent="8772",total-size="9880"@}
20463 +download,@{section=".data",section-sent="2560",section-size="3156",
20464 total-sent="9284",total-size="9880"@}
20465 +download,@{section=".data",section-sent="3072",section-size="3156",
20466 total-sent="9796",total-size="9880"@}
20467 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
20473 @subheading The @code{-target-exec-status} Command
20474 @findex -target-exec-status
20476 @subsubheading Synopsis
20479 -target-exec-status
20482 Provide information on the state of the target (whether it is running or
20483 not, for instance).
20485 @subsubheading @value{GDBN} Command
20487 There's no equivalent @value{GDBN} command.
20489 @subsubheading Example
20493 @subheading The @code{-target-list-available-targets} Command
20494 @findex -target-list-available-targets
20496 @subsubheading Synopsis
20499 -target-list-available-targets
20502 List the possible targets to connect to.
20504 @subsubheading @value{GDBN} Command
20506 The corresponding @value{GDBN} command is @samp{help target}.
20508 @subsubheading Example
20512 @subheading The @code{-target-list-current-targets} Command
20513 @findex -target-list-current-targets
20515 @subsubheading Synopsis
20518 -target-list-current-targets
20521 Describe the current target.
20523 @subsubheading @value{GDBN} Command
20525 The corresponding information is printed by @samp{info file} (among
20528 @subsubheading Example
20532 @subheading The @code{-target-list-parameters} Command
20533 @findex -target-list-parameters
20535 @subsubheading Synopsis
20538 -target-list-parameters
20543 @subsubheading @value{GDBN} Command
20547 @subsubheading Example
20551 @subheading The @code{-target-select} Command
20552 @findex -target-select
20554 @subsubheading Synopsis
20557 -target-select @var{type} @var{parameters @dots{}}
20560 Connect @value{GDBN} to the remote target. This command takes two args:
20564 The type of target, for instance @samp{async}, @samp{remote}, etc.
20565 @item @var{parameters}
20566 Device names, host names and the like. @xref{Target Commands, ,
20567 Commands for managing targets}, for more details.
20570 The output is a connection notification, followed by the address at
20571 which the target program is, in the following form:
20574 ^connected,addr="@var{address}",func="@var{function name}",
20575 args=[@var{arg list}]
20578 @subsubheading @value{GDBN} Command
20580 The corresponding @value{GDBN} command is @samp{target}.
20582 @subsubheading Example
20586 -target-select async /dev/ttya
20587 ^connected,addr="0xfe00a300",func="??",args=[]
20591 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20592 @node GDB/MI Thread Commands
20593 @section @sc{gdb/mi} Thread Commands
20596 @subheading The @code{-thread-info} Command
20597 @findex -thread-info
20599 @subsubheading Synopsis
20605 @subsubheading @value{GDBN} command
20609 @subsubheading Example
20613 @subheading The @code{-thread-list-all-threads} Command
20614 @findex -thread-list-all-threads
20616 @subsubheading Synopsis
20619 -thread-list-all-threads
20622 @subsubheading @value{GDBN} Command
20624 The equivalent @value{GDBN} command is @samp{info threads}.
20626 @subsubheading Example
20630 @subheading The @code{-thread-list-ids} Command
20631 @findex -thread-list-ids
20633 @subsubheading Synopsis
20639 Produces a list of the currently known @value{GDBN} thread ids. At the
20640 end of the list it also prints the total number of such threads.
20642 @subsubheading @value{GDBN} Command
20644 Part of @samp{info threads} supplies the same information.
20646 @subsubheading Example
20648 No threads present, besides the main process:
20653 ^done,thread-ids=@{@},number-of-threads="0"
20663 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
20664 number-of-threads="3"
20669 @subheading The @code{-thread-select} Command
20670 @findex -thread-select
20672 @subsubheading Synopsis
20675 -thread-select @var{threadnum}
20678 Make @var{threadnum} the current thread. It prints the number of the new
20679 current thread, and the topmost frame for that thread.
20681 @subsubheading @value{GDBN} Command
20683 The corresponding @value{GDBN} command is @samp{thread}.
20685 @subsubheading Example
20692 *stopped,reason="end-stepping-range",thread-id="2",line="187",
20693 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
20697 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
20698 number-of-threads="3"
20701 ^done,new-thread-id="3",
20702 frame=@{level="0",func="vprintf",
20703 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
20704 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
20708 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20709 @node GDB/MI Tracepoint Commands
20710 @section @sc{gdb/mi} Tracepoint Commands
20712 The tracepoint commands are not yet implemented.
20714 @c @subheading -trace-actions
20716 @c @subheading -trace-delete
20718 @c @subheading -trace-disable
20720 @c @subheading -trace-dump
20722 @c @subheading -trace-enable
20724 @c @subheading -trace-exists
20726 @c @subheading -trace-find
20728 @c @subheading -trace-frame-number
20730 @c @subheading -trace-info
20732 @c @subheading -trace-insert
20734 @c @subheading -trace-list
20736 @c @subheading -trace-pass-count
20738 @c @subheading -trace-save
20740 @c @subheading -trace-start
20742 @c @subheading -trace-stop
20745 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20746 @node GDB/MI Variable Objects
20747 @section @sc{gdb/mi} Variable Objects
20750 @subheading Motivation for Variable Objects in @sc{gdb/mi}
20752 For the implementation of a variable debugger window (locals, watched
20753 expressions, etc.), we are proposing the adaptation of the existing code
20754 used by @code{Insight}.
20756 The two main reasons for that are:
20760 It has been proven in practice (it is already on its second generation).
20763 It will shorten development time (needless to say how important it is
20767 The original interface was designed to be used by Tcl code, so it was
20768 slightly changed so it could be used through @sc{gdb/mi}. This section
20769 describes the @sc{gdb/mi} operations that will be available and gives some
20770 hints about their use.
20772 @emph{Note}: In addition to the set of operations described here, we
20773 expect the @sc{gui} implementation of a variable window to require, at
20774 least, the following operations:
20777 @item @code{-gdb-show} @code{output-radix}
20778 @item @code{-stack-list-arguments}
20779 @item @code{-stack-list-locals}
20780 @item @code{-stack-select-frame}
20783 @subheading Introduction to Variable Objects in @sc{gdb/mi}
20785 @cindex variable objects in @sc{gdb/mi}
20786 The basic idea behind variable objects is the creation of a named object
20787 to represent a variable, an expression, a memory location or even a CPU
20788 register. For each object created, a set of operations is available for
20789 examining or changing its properties.
20791 Furthermore, complex data types, such as C structures, are represented
20792 in a tree format. For instance, the @code{struct} type variable is the
20793 root and the children will represent the struct members. If a child
20794 is itself of a complex type, it will also have children of its own.
20795 Appropriate language differences are handled for C, C@t{++} and Java.
20797 When returning the actual values of the objects, this facility allows
20798 for the individual selection of the display format used in the result
20799 creation. It can be chosen among: binary, decimal, hexadecimal, octal
20800 and natural. Natural refers to a default format automatically
20801 chosen based on the variable type (like decimal for an @code{int}, hex
20802 for pointers, etc.).
20804 The following is the complete set of @sc{gdb/mi} operations defined to
20805 access this functionality:
20807 @multitable @columnfractions .4 .6
20808 @item @strong{Operation}
20809 @tab @strong{Description}
20811 @item @code{-var-create}
20812 @tab create a variable object
20813 @item @code{-var-delete}
20814 @tab delete the variable object and its children
20815 @item @code{-var-set-format}
20816 @tab set the display format of this variable
20817 @item @code{-var-show-format}
20818 @tab show the display format of this variable
20819 @item @code{-var-info-num-children}
20820 @tab tells how many children this object has
20821 @item @code{-var-list-children}
20822 @tab return a list of the object's children
20823 @item @code{-var-info-type}
20824 @tab show the type of this variable object
20825 @item @code{-var-info-expression}
20826 @tab print what this variable object represents
20827 @item @code{-var-show-attributes}
20828 @tab is this variable editable? does it exist here?
20829 @item @code{-var-evaluate-expression}
20830 @tab get the value of this variable
20831 @item @code{-var-assign}
20832 @tab set the value of this variable
20833 @item @code{-var-update}
20834 @tab update the variable and its children
20837 In the next subsection we describe each operation in detail and suggest
20838 how it can be used.
20840 @subheading Description And Use of Operations on Variable Objects
20842 @subheading The @code{-var-create} Command
20843 @findex -var-create
20845 @subsubheading Synopsis
20848 -var-create @{@var{name} | "-"@}
20849 @{@var{frame-addr} | "*"@} @var{expression}
20852 This operation creates a variable object, which allows the monitoring of
20853 a variable, the result of an expression, a memory cell or a CPU
20856 The @var{name} parameter is the string by which the object can be
20857 referenced. It must be unique. If @samp{-} is specified, the varobj
20858 system will generate a string ``varNNNNNN'' automatically. It will be
20859 unique provided that one does not specify @var{name} on that format.
20860 The command fails if a duplicate name is found.
20862 The frame under which the expression should be evaluated can be
20863 specified by @var{frame-addr}. A @samp{*} indicates that the current
20864 frame should be used.
20866 @var{expression} is any expression valid on the current language set (must not
20867 begin with a @samp{*}), or one of the following:
20871 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
20874 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
20877 @samp{$@var{regname}} --- a CPU register name
20880 @subsubheading Result
20882 This operation returns the name, number of children and the type of the
20883 object created. Type is returned as a string as the ones generated by
20884 the @value{GDBN} CLI:
20887 name="@var{name}",numchild="N",type="@var{type}"
20891 @subheading The @code{-var-delete} Command
20892 @findex -var-delete
20894 @subsubheading Synopsis
20897 -var-delete @var{name}
20900 Deletes a previously created variable object and all of its children.
20902 Returns an error if the object @var{name} is not found.
20905 @subheading The @code{-var-set-format} Command
20906 @findex -var-set-format
20908 @subsubheading Synopsis
20911 -var-set-format @var{name} @var{format-spec}
20914 Sets the output format for the value of the object @var{name} to be
20917 The syntax for the @var{format-spec} is as follows:
20920 @var{format-spec} @expansion{}
20921 @{binary | decimal | hexadecimal | octal | natural@}
20925 @subheading The @code{-var-show-format} Command
20926 @findex -var-show-format
20928 @subsubheading Synopsis
20931 -var-show-format @var{name}
20934 Returns the format used to display the value of the object @var{name}.
20937 @var{format} @expansion{}
20942 @subheading The @code{-var-info-num-children} Command
20943 @findex -var-info-num-children
20945 @subsubheading Synopsis
20948 -var-info-num-children @var{name}
20951 Returns the number of children of a variable object @var{name}:
20958 @subheading The @code{-var-list-children} Command
20959 @findex -var-list-children
20961 @subsubheading Synopsis
20964 -var-list-children [@var{print-values}] @var{name}
20966 @anchor{-var-list-children}
20968 Return a list of the children of the specified variable object and
20969 create variable objects for them, if they do not already exist. With
20970 a single argument or if @var{print-values} has a value for of 0 or
20971 @code{--no-values}, print only the names of the variables; if
20972 @var{print-values} is 1 or @code{--all-values}, also print their
20973 values; and if it is 2 or @code{--simple-values} print the name and
20974 value for simple data types and just the name for arrays, structures
20977 @subsubheading Example
20981 -var-list-children n
20982 ^done,numchild=@var{n},children=[@{name=@var{name},
20983 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
20985 -var-list-children --all-values n
20986 ^done,numchild=@var{n},children=[@{name=@var{name},
20987 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
20991 @subheading The @code{-var-info-type} Command
20992 @findex -var-info-type
20994 @subsubheading Synopsis
20997 -var-info-type @var{name}
21000 Returns the type of the specified variable @var{name}. The type is
21001 returned as a string in the same format as it is output by the
21005 type=@var{typename}
21009 @subheading The @code{-var-info-expression} Command
21010 @findex -var-info-expression
21012 @subsubheading Synopsis
21015 -var-info-expression @var{name}
21018 Returns what is represented by the variable object @var{name}:
21021 lang=@var{lang-spec},exp=@var{expression}
21025 where @var{lang-spec} is @code{@{"C" | "C++" | "Java"@}}.
21027 @subheading The @code{-var-show-attributes} Command
21028 @findex -var-show-attributes
21030 @subsubheading Synopsis
21033 -var-show-attributes @var{name}
21036 List attributes of the specified variable object @var{name}:
21039 status=@var{attr} [ ( ,@var{attr} )* ]
21043 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
21045 @subheading The @code{-var-evaluate-expression} Command
21046 @findex -var-evaluate-expression
21048 @subsubheading Synopsis
21051 -var-evaluate-expression @var{name}
21054 Evaluates the expression that is represented by the specified variable
21055 object and returns its value as a string in the current format specified
21062 Note that one must invoke @code{-var-list-children} for a variable
21063 before the value of a child variable can be evaluated.
21065 @subheading The @code{-var-assign} Command
21066 @findex -var-assign
21068 @subsubheading Synopsis
21071 -var-assign @var{name} @var{expression}
21074 Assigns the value of @var{expression} to the variable object specified
21075 by @var{name}. The object must be @samp{editable}. If the variable's
21076 value is altered by the assign, the variable will show up in any
21077 subsequent @code{-var-update} list.
21079 @subsubheading Example
21087 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
21091 @subheading The @code{-var-update} Command
21092 @findex -var-update
21094 @subsubheading Synopsis
21097 -var-update [@var{print-values}] @{@var{name} | "*"@}
21100 Update the value of the variable object @var{name} by evaluating its
21101 expression after fetching all the new values from memory or registers.
21102 A @samp{*} causes all existing variable objects to be updated. The
21103 option @var{print-values} determines whether names both and values, or
21104 just names are printed in the manner described for
21105 @code{-var-list-children} (@pxref{-var-list-children}).
21107 @subsubheading Example
21114 -var-update --all-values var1
21115 ^done,changelist=[@{name="var1",value="3",in_scope="true",
21116 type_changed="false"@}]
21121 @chapter @value{GDBN} Annotations
21123 This chapter describes annotations in @value{GDBN}. Annotations were
21124 designed to interface @value{GDBN} to graphical user interfaces or other
21125 similar programs which want to interact with @value{GDBN} at a
21126 relatively high level.
21128 The annotation mechanism has largely been superseeded by @sc{gdb/mi}
21132 This is Edition @value{EDITION}, @value{DATE}.
21136 * Annotations Overview:: What annotations are; the general syntax.
21137 * Prompting:: Annotations marking @value{GDBN}'s need for input.
21138 * Errors:: Annotations for error messages.
21139 * Invalidation:: Some annotations describe things now invalid.
21140 * Annotations for Running::
21141 Whether the program is running, how it stopped, etc.
21142 * Source Annotations:: Annotations describing source code.
21145 @node Annotations Overview
21146 @section What is an Annotation?
21147 @cindex annotations
21149 Annotations start with a newline character, two @samp{control-z}
21150 characters, and the name of the annotation. If there is no additional
21151 information associated with this annotation, the name of the annotation
21152 is followed immediately by a newline. If there is additional
21153 information, the name of the annotation is followed by a space, the
21154 additional information, and a newline. The additional information
21155 cannot contain newline characters.
21157 Any output not beginning with a newline and two @samp{control-z}
21158 characters denotes literal output from @value{GDBN}. Currently there is
21159 no need for @value{GDBN} to output a newline followed by two
21160 @samp{control-z} characters, but if there was such a need, the
21161 annotations could be extended with an @samp{escape} annotation which
21162 means those three characters as output.
21164 The annotation @var{level}, which is specified using the
21165 @option{--annotate} command line option (@pxref{Mode Options}), controls
21166 how much information @value{GDBN} prints together with its prompt,
21167 values of expressions, source lines, and other types of output. Level 0
21168 is for no anntations, level 1 is for use when @value{GDBN} is run as a
21169 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
21170 for programs that control @value{GDBN}, and level 2 annotations have
21171 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
21172 Interface, annotate, GDB's Obsolete Annotations}).
21175 @kindex set annotate
21176 @item set annotate @var{level}
21177 The @value{GDBN} command @code{set annotate} sets the level of
21178 annotations to the specified @var{level}.
21180 @item show annotate
21181 @kindex show annotate
21182 Show the current annotation level.
21185 This chapter describes level 3 annotations.
21187 A simple example of starting up @value{GDBN} with annotations is:
21190 $ @kbd{gdb --annotate=3}
21192 Copyright 2003 Free Software Foundation, Inc.
21193 GDB is free software, covered by the GNU General Public License,
21194 and you are welcome to change it and/or distribute copies of it
21195 under certain conditions.
21196 Type "show copying" to see the conditions.
21197 There is absolutely no warranty for GDB. Type "show warranty"
21199 This GDB was configured as "i386-pc-linux-gnu"
21210 Here @samp{quit} is input to @value{GDBN}; the rest is output from
21211 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
21212 denotes a @samp{control-z} character) are annotations; the rest is
21213 output from @value{GDBN}.
21216 @section Annotation for @value{GDBN} Input
21218 @cindex annotations for prompts
21219 When @value{GDBN} prompts for input, it annotates this fact so it is possible
21220 to know when to send output, when the output from a given command is
21223 Different kinds of input each have a different @dfn{input type}. Each
21224 input type has three annotations: a @code{pre-} annotation, which
21225 denotes the beginning of any prompt which is being output, a plain
21226 annotation, which denotes the end of the prompt, and then a @code{post-}
21227 annotation which denotes the end of any echo which may (or may not) be
21228 associated with the input. For example, the @code{prompt} input type
21229 features the following annotations:
21237 The input types are
21242 @findex post-prompt
21244 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
21246 @findex pre-commands
21248 @findex post-commands
21250 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
21251 command. The annotations are repeated for each command which is input.
21253 @findex pre-overload-choice
21254 @findex overload-choice
21255 @findex post-overload-choice
21256 @item overload-choice
21257 When @value{GDBN} wants the user to select between various overloaded functions.
21263 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
21265 @findex pre-prompt-for-continue
21266 @findex prompt-for-continue
21267 @findex post-prompt-for-continue
21268 @item prompt-for-continue
21269 When @value{GDBN} is asking the user to press return to continue. Note: Don't
21270 expect this to work well; instead use @code{set height 0} to disable
21271 prompting. This is because the counting of lines is buggy in the
21272 presence of annotations.
21277 @cindex annotations for errors, warnings and interrupts
21284 This annotation occurs right before @value{GDBN} responds to an interrupt.
21291 This annotation occurs right before @value{GDBN} responds to an error.
21293 Quit and error annotations indicate that any annotations which @value{GDBN} was
21294 in the middle of may end abruptly. For example, if a
21295 @code{value-history-begin} annotation is followed by a @code{error}, one
21296 cannot expect to receive the matching @code{value-history-end}. One
21297 cannot expect not to receive it either, however; an error annotation
21298 does not necessarily mean that @value{GDBN} is immediately returning all the way
21301 @findex error-begin
21302 A quit or error annotation may be preceded by
21308 Any output between that and the quit or error annotation is the error
21311 Warning messages are not yet annotated.
21312 @c If we want to change that, need to fix warning(), type_error(),
21313 @c range_error(), and possibly other places.
21316 @section Invalidation Notices
21318 @cindex annotations for invalidation messages
21319 The following annotations say that certain pieces of state may have
21323 @findex frames-invalid
21324 @item ^Z^Zframes-invalid
21326 The frames (for example, output from the @code{backtrace} command) may
21329 @findex breakpoints-invalid
21330 @item ^Z^Zbreakpoints-invalid
21332 The breakpoints may have changed. For example, the user just added or
21333 deleted a breakpoint.
21336 @node Annotations for Running
21337 @section Running the Program
21338 @cindex annotations for running programs
21342 When the program starts executing due to a @value{GDBN} command such as
21343 @code{step} or @code{continue},
21349 is output. When the program stops,
21355 is output. Before the @code{stopped} annotation, a variety of
21356 annotations describe how the program stopped.
21360 @item ^Z^Zexited @var{exit-status}
21361 The program exited, and @var{exit-status} is the exit status (zero for
21362 successful exit, otherwise nonzero).
21365 @findex signal-name
21366 @findex signal-name-end
21367 @findex signal-string
21368 @findex signal-string-end
21369 @item ^Z^Zsignalled
21370 The program exited with a signal. After the @code{^Z^Zsignalled}, the
21371 annotation continues:
21377 ^Z^Zsignal-name-end
21381 ^Z^Zsignal-string-end
21386 where @var{name} is the name of the signal, such as @code{SIGILL} or
21387 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
21388 as @code{Illegal Instruction} or @code{Segmentation fault}.
21389 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
21390 user's benefit and have no particular format.
21394 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
21395 just saying that the program received the signal, not that it was
21396 terminated with it.
21399 @item ^Z^Zbreakpoint @var{number}
21400 The program hit breakpoint number @var{number}.
21403 @item ^Z^Zwatchpoint @var{number}
21404 The program hit watchpoint number @var{number}.
21407 @node Source Annotations
21408 @section Displaying Source
21409 @cindex annotations for source display
21412 The following annotation is used instead of displaying source code:
21415 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
21418 where @var{filename} is an absolute file name indicating which source
21419 file, @var{line} is the line number within that file (where 1 is the
21420 first line in the file), @var{character} is the character position
21421 within the file (where 0 is the first character in the file) (for most
21422 debug formats this will necessarily point to the beginning of a line),
21423 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
21424 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
21425 @var{addr} is the address in the target program associated with the
21426 source which is being displayed. @var{addr} is in the form @samp{0x}
21427 followed by one or more lowercase hex digits (note that this does not
21428 depend on the language).
21431 @chapter Reporting Bugs in @value{GDBN}
21432 @cindex bugs in @value{GDBN}
21433 @cindex reporting bugs in @value{GDBN}
21435 Your bug reports play an essential role in making @value{GDBN} reliable.
21437 Reporting a bug may help you by bringing a solution to your problem, or it
21438 may not. But in any case the principal function of a bug report is to help
21439 the entire community by making the next version of @value{GDBN} work better. Bug
21440 reports are your contribution to the maintenance of @value{GDBN}.
21442 In order for a bug report to serve its purpose, you must include the
21443 information that enables us to fix the bug.
21446 * Bug Criteria:: Have you found a bug?
21447 * Bug Reporting:: How to report bugs
21451 @section Have you found a bug?
21452 @cindex bug criteria
21454 If you are not sure whether you have found a bug, here are some guidelines:
21457 @cindex fatal signal
21458 @cindex debugger crash
21459 @cindex crash of debugger
21461 If the debugger gets a fatal signal, for any input whatever, that is a
21462 @value{GDBN} bug. Reliable debuggers never crash.
21464 @cindex error on valid input
21466 If @value{GDBN} produces an error message for valid input, that is a
21467 bug. (Note that if you're cross debugging, the problem may also be
21468 somewhere in the connection to the target.)
21470 @cindex invalid input
21472 If @value{GDBN} does not produce an error message for invalid input,
21473 that is a bug. However, you should note that your idea of
21474 ``invalid input'' might be our idea of ``an extension'' or ``support
21475 for traditional practice''.
21478 If you are an experienced user of debugging tools, your suggestions
21479 for improvement of @value{GDBN} are welcome in any case.
21482 @node Bug Reporting
21483 @section How to report bugs
21484 @cindex bug reports
21485 @cindex @value{GDBN} bugs, reporting
21487 A number of companies and individuals offer support for @sc{gnu} products.
21488 If you obtained @value{GDBN} from a support organization, we recommend you
21489 contact that organization first.
21491 You can find contact information for many support companies and
21492 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
21494 @c should add a web page ref...
21496 In any event, we also recommend that you submit bug reports for
21497 @value{GDBN}. The prefered method is to submit them directly using
21498 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
21499 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
21502 @strong{Do not send bug reports to @samp{info-gdb}, or to
21503 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
21504 not want to receive bug reports. Those that do have arranged to receive
21507 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
21508 serves as a repeater. The mailing list and the newsgroup carry exactly
21509 the same messages. Often people think of posting bug reports to the
21510 newsgroup instead of mailing them. This appears to work, but it has one
21511 problem which can be crucial: a newsgroup posting often lacks a mail
21512 path back to the sender. Thus, if we need to ask for more information,
21513 we may be unable to reach you. For this reason, it is better to send
21514 bug reports to the mailing list.
21516 The fundamental principle of reporting bugs usefully is this:
21517 @strong{report all the facts}. If you are not sure whether to state a
21518 fact or leave it out, state it!
21520 Often people omit facts because they think they know what causes the
21521 problem and assume that some details do not matter. Thus, you might
21522 assume that the name of the variable you use in an example does not matter.
21523 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
21524 stray memory reference which happens to fetch from the location where that
21525 name is stored in memory; perhaps, if the name were different, the contents
21526 of that location would fool the debugger into doing the right thing despite
21527 the bug. Play it safe and give a specific, complete example. That is the
21528 easiest thing for you to do, and the most helpful.
21530 Keep in mind that the purpose of a bug report is to enable us to fix the
21531 bug. It may be that the bug has been reported previously, but neither
21532 you nor we can know that unless your bug report is complete and
21535 Sometimes people give a few sketchy facts and ask, ``Does this ring a
21536 bell?'' Those bug reports are useless, and we urge everyone to
21537 @emph{refuse to respond to them} except to chide the sender to report
21540 To enable us to fix the bug, you should include all these things:
21544 The version of @value{GDBN}. @value{GDBN} announces it if you start
21545 with no arguments; you can also print it at any time using @code{show
21548 Without this, we will not know whether there is any point in looking for
21549 the bug in the current version of @value{GDBN}.
21552 The type of machine you are using, and the operating system name and
21556 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
21557 ``@value{GCC}--2.8.1''.
21560 What compiler (and its version) was used to compile the program you are
21561 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
21562 C Compiler''. For GCC, you can say @code{gcc --version} to get this
21563 information; for other compilers, see the documentation for those
21567 The command arguments you gave the compiler to compile your example and
21568 observe the bug. For example, did you use @samp{-O}? To guarantee
21569 you will not omit something important, list them all. A copy of the
21570 Makefile (or the output from make) is sufficient.
21572 If we were to try to guess the arguments, we would probably guess wrong
21573 and then we might not encounter the bug.
21576 A complete input script, and all necessary source files, that will
21580 A description of what behavior you observe that you believe is
21581 incorrect. For example, ``It gets a fatal signal.''
21583 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
21584 will certainly notice it. But if the bug is incorrect output, we might
21585 not notice unless it is glaringly wrong. You might as well not give us
21586 a chance to make a mistake.
21588 Even if the problem you experience is a fatal signal, you should still
21589 say so explicitly. Suppose something strange is going on, such as, your
21590 copy of @value{GDBN} is out of synch, or you have encountered a bug in
21591 the C library on your system. (This has happened!) Your copy might
21592 crash and ours would not. If you told us to expect a crash, then when
21593 ours fails to crash, we would know that the bug was not happening for
21594 us. If you had not told us to expect a crash, then we would not be able
21595 to draw any conclusion from our observations.
21598 @cindex recording a session script
21599 To collect all this information, you can use a session recording program
21600 such as @command{script}, which is available on many Unix systems.
21601 Just run your @value{GDBN} session inside @command{script} and then
21602 include the @file{typescript} file with your bug report.
21604 Another way to record a @value{GDBN} session is to run @value{GDBN}
21605 inside Emacs and then save the entire buffer to a file.
21608 If you wish to suggest changes to the @value{GDBN} source, send us context
21609 diffs. If you even discuss something in the @value{GDBN} source, refer to
21610 it by context, not by line number.
21612 The line numbers in our development sources will not match those in your
21613 sources. Your line numbers would convey no useful information to us.
21617 Here are some things that are not necessary:
21621 A description of the envelope of the bug.
21623 Often people who encounter a bug spend a lot of time investigating
21624 which changes to the input file will make the bug go away and which
21625 changes will not affect it.
21627 This is often time consuming and not very useful, because the way we
21628 will find the bug is by running a single example under the debugger
21629 with breakpoints, not by pure deduction from a series of examples.
21630 We recommend that you save your time for something else.
21632 Of course, if you can find a simpler example to report @emph{instead}
21633 of the original one, that is a convenience for us. Errors in the
21634 output will be easier to spot, running under the debugger will take
21635 less time, and so on.
21637 However, simplification is not vital; if you do not want to do this,
21638 report the bug anyway and send us the entire test case you used.
21641 A patch for the bug.
21643 A patch for the bug does help us if it is a good one. But do not omit
21644 the necessary information, such as the test case, on the assumption that
21645 a patch is all we need. We might see problems with your patch and decide
21646 to fix the problem another way, or we might not understand it at all.
21648 Sometimes with a program as complicated as @value{GDBN} it is very hard to
21649 construct an example that will make the program follow a certain path
21650 through the code. If you do not send us the example, we will not be able
21651 to construct one, so we will not be able to verify that the bug is fixed.
21653 And if we cannot understand what bug you are trying to fix, or why your
21654 patch should be an improvement, we will not install it. A test case will
21655 help us to understand.
21658 A guess about what the bug is or what it depends on.
21660 Such guesses are usually wrong. Even we cannot guess right about such
21661 things without first using the debugger to find the facts.
21664 @c The readline documentation is distributed with the readline code
21665 @c and consists of the two following files:
21667 @c inc-hist.texinfo
21668 @c Use -I with makeinfo to point to the appropriate directory,
21669 @c environment var TEXINPUTS with TeX.
21670 @include rluser.texi
21671 @include inc-hist.texinfo
21674 @node Formatting Documentation
21675 @appendix Formatting Documentation
21677 @cindex @value{GDBN} reference card
21678 @cindex reference card
21679 The @value{GDBN} 4 release includes an already-formatted reference card, ready
21680 for printing with PostScript or Ghostscript, in the @file{gdb}
21681 subdirectory of the main source directory@footnote{In
21682 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
21683 release.}. If you can use PostScript or Ghostscript with your printer,
21684 you can print the reference card immediately with @file{refcard.ps}.
21686 The release also includes the source for the reference card. You
21687 can format it, using @TeX{}, by typing:
21693 The @value{GDBN} reference card is designed to print in @dfn{landscape}
21694 mode on US ``letter'' size paper;
21695 that is, on a sheet 11 inches wide by 8.5 inches
21696 high. You will need to specify this form of printing as an option to
21697 your @sc{dvi} output program.
21699 @cindex documentation
21701 All the documentation for @value{GDBN} comes as part of the machine-readable
21702 distribution. The documentation is written in Texinfo format, which is
21703 a documentation system that uses a single source file to produce both
21704 on-line information and a printed manual. You can use one of the Info
21705 formatting commands to create the on-line version of the documentation
21706 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
21708 @value{GDBN} includes an already formatted copy of the on-line Info
21709 version of this manual in the @file{gdb} subdirectory. The main Info
21710 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
21711 subordinate files matching @samp{gdb.info*} in the same directory. If
21712 necessary, you can print out these files, or read them with any editor;
21713 but they are easier to read using the @code{info} subsystem in @sc{gnu}
21714 Emacs or the standalone @code{info} program, available as part of the
21715 @sc{gnu} Texinfo distribution.
21717 If you want to format these Info files yourself, you need one of the
21718 Info formatting programs, such as @code{texinfo-format-buffer} or
21721 If you have @code{makeinfo} installed, and are in the top level
21722 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
21723 version @value{GDBVN}), you can make the Info file by typing:
21730 If you want to typeset and print copies of this manual, you need @TeX{},
21731 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
21732 Texinfo definitions file.
21734 @TeX{} is a typesetting program; it does not print files directly, but
21735 produces output files called @sc{dvi} files. To print a typeset
21736 document, you need a program to print @sc{dvi} files. If your system
21737 has @TeX{} installed, chances are it has such a program. The precise
21738 command to use depends on your system; @kbd{lpr -d} is common; another
21739 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
21740 require a file name without any extension or a @samp{.dvi} extension.
21742 @TeX{} also requires a macro definitions file called
21743 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
21744 written in Texinfo format. On its own, @TeX{} cannot either read or
21745 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
21746 and is located in the @file{gdb-@var{version-number}/texinfo}
21749 If you have @TeX{} and a @sc{dvi} printer program installed, you can
21750 typeset and print this manual. First switch to the the @file{gdb}
21751 subdirectory of the main source directory (for example, to
21752 @file{gdb-@value{GDBVN}/gdb}) and type:
21758 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
21760 @node Installing GDB
21761 @appendix Installing @value{GDBN}
21762 @cindex configuring @value{GDBN}
21763 @cindex installation
21764 @cindex configuring @value{GDBN}, and source tree subdirectories
21766 @value{GDBN} comes with a @code{configure} script that automates the process
21767 of preparing @value{GDBN} for installation; you can then use @code{make} to
21768 build the @code{gdb} program.
21770 @c irrelevant in info file; it's as current as the code it lives with.
21771 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
21772 look at the @file{README} file in the sources; we may have improved the
21773 installation procedures since publishing this manual.}
21776 The @value{GDBN} distribution includes all the source code you need for
21777 @value{GDBN} in a single directory, whose name is usually composed by
21778 appending the version number to @samp{gdb}.
21780 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
21781 @file{gdb-@value{GDBVN}} directory. That directory contains:
21784 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
21785 script for configuring @value{GDBN} and all its supporting libraries
21787 @item gdb-@value{GDBVN}/gdb
21788 the source specific to @value{GDBN} itself
21790 @item gdb-@value{GDBVN}/bfd
21791 source for the Binary File Descriptor library
21793 @item gdb-@value{GDBVN}/include
21794 @sc{gnu} include files
21796 @item gdb-@value{GDBVN}/libiberty
21797 source for the @samp{-liberty} free software library
21799 @item gdb-@value{GDBVN}/opcodes
21800 source for the library of opcode tables and disassemblers
21802 @item gdb-@value{GDBVN}/readline
21803 source for the @sc{gnu} command-line interface
21805 @item gdb-@value{GDBVN}/glob
21806 source for the @sc{gnu} filename pattern-matching subroutine
21808 @item gdb-@value{GDBVN}/mmalloc
21809 source for the @sc{gnu} memory-mapped malloc package
21812 The simplest way to configure and build @value{GDBN} is to run @code{configure}
21813 from the @file{gdb-@var{version-number}} source directory, which in
21814 this example is the @file{gdb-@value{GDBVN}} directory.
21816 First switch to the @file{gdb-@var{version-number}} source directory
21817 if you are not already in it; then run @code{configure}. Pass the
21818 identifier for the platform on which @value{GDBN} will run as an
21824 cd gdb-@value{GDBVN}
21825 ./configure @var{host}
21830 where @var{host} is an identifier such as @samp{sun4} or
21831 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
21832 (You can often leave off @var{host}; @code{configure} tries to guess the
21833 correct value by examining your system.)
21835 Running @samp{configure @var{host}} and then running @code{make} builds the
21836 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
21837 libraries, then @code{gdb} itself. The configured source files, and the
21838 binaries, are left in the corresponding source directories.
21841 @code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
21842 system does not recognize this automatically when you run a different
21843 shell, you may need to run @code{sh} on it explicitly:
21846 sh configure @var{host}
21849 If you run @code{configure} from a directory that contains source
21850 directories for multiple libraries or programs, such as the
21851 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure}
21852 creates configuration files for every directory level underneath (unless
21853 you tell it not to, with the @samp{--norecursion} option).
21855 You should run the @code{configure} script from the top directory in the
21856 source tree, the @file{gdb-@var{version-number}} directory. If you run
21857 @code{configure} from one of the subdirectories, you will configure only
21858 that subdirectory. That is usually not what you want. In particular,
21859 if you run the first @code{configure} from the @file{gdb} subdirectory
21860 of the @file{gdb-@var{version-number}} directory, you will omit the
21861 configuration of @file{bfd}, @file{readline}, and other sibling
21862 directories of the @file{gdb} subdirectory. This leads to build errors
21863 about missing include files such as @file{bfd/bfd.h}.
21865 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
21866 However, you should make sure that the shell on your path (named by
21867 the @samp{SHELL} environment variable) is publicly readable. Remember
21868 that @value{GDBN} uses the shell to start your program---some systems refuse to
21869 let @value{GDBN} debug child processes whose programs are not readable.
21872 * Separate Objdir:: Compiling @value{GDBN} in another directory
21873 * Config Names:: Specifying names for hosts and targets
21874 * Configure Options:: Summary of options for configure
21877 @node Separate Objdir
21878 @section Compiling @value{GDBN} in another directory
21880 If you want to run @value{GDBN} versions for several host or target machines,
21881 you need a different @code{gdb} compiled for each combination of
21882 host and target. @code{configure} is designed to make this easy by
21883 allowing you to generate each configuration in a separate subdirectory,
21884 rather than in the source directory. If your @code{make} program
21885 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
21886 @code{make} in each of these directories builds the @code{gdb}
21887 program specified there.
21889 To build @code{gdb} in a separate directory, run @code{configure}
21890 with the @samp{--srcdir} option to specify where to find the source.
21891 (You also need to specify a path to find @code{configure}
21892 itself from your working directory. If the path to @code{configure}
21893 would be the same as the argument to @samp{--srcdir}, you can leave out
21894 the @samp{--srcdir} option; it is assumed.)
21896 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
21897 separate directory for a Sun 4 like this:
21901 cd gdb-@value{GDBVN}
21904 ../gdb-@value{GDBVN}/configure sun4
21909 When @code{configure} builds a configuration using a remote source
21910 directory, it creates a tree for the binaries with the same structure
21911 (and using the same names) as the tree under the source directory. In
21912 the example, you'd find the Sun 4 library @file{libiberty.a} in the
21913 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
21914 @file{gdb-sun4/gdb}.
21916 Make sure that your path to the @file{configure} script has just one
21917 instance of @file{gdb} in it. If your path to @file{configure} looks
21918 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
21919 one subdirectory of @value{GDBN}, not the whole package. This leads to
21920 build errors about missing include files such as @file{bfd/bfd.h}.
21922 One popular reason to build several @value{GDBN} configurations in separate
21923 directories is to configure @value{GDBN} for cross-compiling (where
21924 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
21925 programs that run on another machine---the @dfn{target}).
21926 You specify a cross-debugging target by
21927 giving the @samp{--target=@var{target}} option to @code{configure}.
21929 When you run @code{make} to build a program or library, you must run
21930 it in a configured directory---whatever directory you were in when you
21931 called @code{configure} (or one of its subdirectories).
21933 The @code{Makefile} that @code{configure} generates in each source
21934 directory also runs recursively. If you type @code{make} in a source
21935 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
21936 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
21937 will build all the required libraries, and then build GDB.
21939 When you have multiple hosts or targets configured in separate
21940 directories, you can run @code{make} on them in parallel (for example,
21941 if they are NFS-mounted on each of the hosts); they will not interfere
21945 @section Specifying names for hosts and targets
21947 The specifications used for hosts and targets in the @code{configure}
21948 script are based on a three-part naming scheme, but some short predefined
21949 aliases are also supported. The full naming scheme encodes three pieces
21950 of information in the following pattern:
21953 @var{architecture}-@var{vendor}-@var{os}
21956 For example, you can use the alias @code{sun4} as a @var{host} argument,
21957 or as the value for @var{target} in a @code{--target=@var{target}}
21958 option. The equivalent full name is @samp{sparc-sun-sunos4}.
21960 The @code{configure} script accompanying @value{GDBN} does not provide
21961 any query facility to list all supported host and target names or
21962 aliases. @code{configure} calls the Bourne shell script
21963 @code{config.sub} to map abbreviations to full names; you can read the
21964 script, if you wish, or you can use it to test your guesses on
21965 abbreviations---for example:
21968 % sh config.sub i386-linux
21970 % sh config.sub alpha-linux
21971 alpha-unknown-linux-gnu
21972 % sh config.sub hp9k700
21974 % sh config.sub sun4
21975 sparc-sun-sunos4.1.1
21976 % sh config.sub sun3
21977 m68k-sun-sunos4.1.1
21978 % sh config.sub i986v
21979 Invalid configuration `i986v': machine `i986v' not recognized
21983 @code{config.sub} is also distributed in the @value{GDBN} source
21984 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
21986 @node Configure Options
21987 @section @code{configure} options
21989 Here is a summary of the @code{configure} options and arguments that
21990 are most often useful for building @value{GDBN}. @code{configure} also has
21991 several other options not listed here. @inforef{What Configure
21992 Does,,configure.info}, for a full explanation of @code{configure}.
21995 configure @r{[}--help@r{]}
21996 @r{[}--prefix=@var{dir}@r{]}
21997 @r{[}--exec-prefix=@var{dir}@r{]}
21998 @r{[}--srcdir=@var{dirname}@r{]}
21999 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
22000 @r{[}--target=@var{target}@r{]}
22005 You may introduce options with a single @samp{-} rather than
22006 @samp{--} if you prefer; but you may abbreviate option names if you use
22011 Display a quick summary of how to invoke @code{configure}.
22013 @item --prefix=@var{dir}
22014 Configure the source to install programs and files under directory
22017 @item --exec-prefix=@var{dir}
22018 Configure the source to install programs under directory
22021 @c avoid splitting the warning from the explanation:
22023 @item --srcdir=@var{dirname}
22024 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
22025 @code{make} that implements the @code{VPATH} feature.}@*
22026 Use this option to make configurations in directories separate from the
22027 @value{GDBN} source directories. Among other things, you can use this to
22028 build (or maintain) several configurations simultaneously, in separate
22029 directories. @code{configure} writes configuration specific files in
22030 the current directory, but arranges for them to use the source in the
22031 directory @var{dirname}. @code{configure} creates directories under
22032 the working directory in parallel to the source directories below
22035 @item --norecursion
22036 Configure only the directory level where @code{configure} is executed; do not
22037 propagate configuration to subdirectories.
22039 @item --target=@var{target}
22040 Configure @value{GDBN} for cross-debugging programs running on the specified
22041 @var{target}. Without this option, @value{GDBN} is configured to debug
22042 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
22044 There is no convenient way to generate a list of all available targets.
22046 @item @var{host} @dots{}
22047 Configure @value{GDBN} to run on the specified @var{host}.
22049 There is no convenient way to generate a list of all available hosts.
22052 There are many other options available as well, but they are generally
22053 needed for special purposes only.
22055 @node Maintenance Commands
22056 @appendix Maintenance Commands
22057 @cindex maintenance commands
22058 @cindex internal commands
22060 In addition to commands intended for @value{GDBN} users, @value{GDBN}
22061 includes a number of commands intended for @value{GDBN} developers,
22062 that are not documented elsewhere in this manual. These commands are
22063 provided here for reference. (For commands that turn on debugging
22064 messages, see @ref{Debugging Output}.)
22067 @kindex maint agent
22068 @item maint agent @var{expression}
22069 Translate the given @var{expression} into remote agent bytecodes.
22070 This command is useful for debugging the Agent Expression mechanism
22071 (@pxref{Agent Expressions}).
22073 @kindex maint info breakpoints
22074 @item @anchor{maint info breakpoints}maint info breakpoints
22075 Using the same format as @samp{info breakpoints}, display both the
22076 breakpoints you've set explicitly, and those @value{GDBN} is using for
22077 internal purposes. Internal breakpoints are shown with negative
22078 breakpoint numbers. The type column identifies what kind of breakpoint
22083 Normal, explicitly set breakpoint.
22086 Normal, explicitly set watchpoint.
22089 Internal breakpoint, used to handle correctly stepping through
22090 @code{longjmp} calls.
22092 @item longjmp resume
22093 Internal breakpoint at the target of a @code{longjmp}.
22096 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
22099 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
22102 Shared library events.
22106 @kindex maint check-symtabs
22107 @item maint check-symtabs
22108 Check the consistency of psymtabs and symtabs.
22110 @kindex maint cplus first_component
22111 @item maint cplus first_component @var{name}
22112 Print the first C@t{++} class/namespace component of @var{name}.
22114 @kindex maint cplus namespace
22115 @item maint cplus namespace
22116 Print the list of possible C@t{++} namespaces.
22118 @kindex maint demangle
22119 @item maint demangle @var{name}
22120 Demangle a C@t{++} or Objective-C manled @var{name}.
22122 @kindex maint deprecate
22123 @kindex maint undeprecate
22124 @cindex deprecated commands
22125 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
22126 @itemx maint undeprecate @var{command}
22127 Deprecate or undeprecate the named @var{command}. Deprecated commands
22128 cause @value{GDBN} to issue a warning when you use them. The optional
22129 argument @var{replacement} says which newer command should be used in
22130 favor of the deprecated one; if it is given, @value{GDBN} will mention
22131 the replacement as part of the warning.
22133 @kindex maint dump-me
22134 @item maint dump-me
22135 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
22136 Cause a fatal signal in the debugger and force it to dump its core.
22137 This is supported only on systems which support aborting a program
22138 with the @code{SIGQUIT} signal.
22140 @kindex maint internal-error
22141 @kindex maint internal-warning
22142 @item maint internal-error @r{[}@var{message-text}@r{]}
22143 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
22144 Cause @value{GDBN} to call the internal function @code{internal_error}
22145 or @code{internal_warning} and hence behave as though an internal error
22146 or internal warning has been detected. In addition to reporting the
22147 internal problem, these functions give the user the opportunity to
22148 either quit @value{GDBN} or create a core file of the current
22149 @value{GDBN} session.
22151 These commands take an optional parameter @var{message-text} that is
22152 used as the text of the error or warning message.
22154 Here's an example of using @code{indernal-error}:
22157 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
22158 @dots{}/maint.c:121: internal-error: testing, 1, 2
22159 A problem internal to GDB has been detected. Further
22160 debugging may prove unreliable.
22161 Quit this debugging session? (y or n) @kbd{n}
22162 Create a core file? (y or n) @kbd{n}
22166 @kindex maint packet
22167 @item maint packet @var{text}
22168 If @value{GDBN} is talking to an inferior via the serial protocol,
22169 then this command sends the string @var{text} to the inferior, and
22170 displays the response packet. @value{GDBN} supplies the initial
22171 @samp{$} character, the terminating @samp{#} character, and the
22174 @kindex maint print architecture
22175 @item maint print architecture @r{[}@var{file}@r{]}
22176 Print the entire architecture configuration. The optional argument
22177 @var{file} names the file where the output goes.
22179 @kindex maint print dummy-frames
22180 @item maint print dummy-frames
22181 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
22184 (@value{GDBP}) @kbd{b add}
22186 (@value{GDBP}) @kbd{print add(2,3)}
22187 Breakpoint 2, add (a=2, b=3) at @dots{}
22189 The program being debugged stopped while in a function called from GDB.
22191 (@value{GDBP}) @kbd{maint print dummy-frames}
22192 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
22193 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
22194 call_lo=0x01014000 call_hi=0x01014001
22198 Takes an optional file parameter.
22200 @kindex maint print registers
22201 @kindex maint print raw-registers
22202 @kindex maint print cooked-registers
22203 @kindex maint print register-groups
22204 @item maint print registers @r{[}@var{file}@r{]}
22205 @itemx maint print raw-registers @r{[}@var{file}@r{]}
22206 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
22207 @itemx maint print register-groups @r{[}@var{file}@r{]}
22208 Print @value{GDBN}'s internal register data structures.
22210 The command @code{maint print raw-registers} includes the contents of
22211 the raw register cache; the command @code{maint print cooked-registers}
22212 includes the (cooked) value of all registers; and the command
22213 @code{maint print register-groups} includes the groups that each
22214 register is a member of. @xref{Registers,, Registers, gdbint,
22215 @value{GDBN} Internals}.
22217 These commands take an optional parameter, a file name to which to
22218 write the information.
22220 @kindex maint print reggroups
22221 @item maint print reggroups @r{[}@var{file}@r{]}
22222 Print @value{GDBN}'s internal register group data structures. The
22223 optional argument @var{file} tells to what file to write the
22226 The register groups info looks like this:
22229 (@value{GDBP}) @kbd{maint print reggroups}
22242 This command forces @value{GDBN} to flush its internal register cache.
22244 @kindex maint print objfiles
22245 @cindex info for known object files
22246 @item maint print objfiles
22247 Print a dump of all known object files. For each object file, this
22248 command prints its name, address in memory, and all of its psymtabs
22251 @kindex maint print statistics
22252 @cindex bcache statistics
22253 @item maint print statistics
22254 This command prints, for each object file in the program, various data
22255 about that object file followed by the byte cache (@dfn{bcache})
22256 statistics for the object file. The objfile data includes the number
22257 of minimal, partical, full, and stabs symbols, the number of types
22258 defined by the objfile, the number of as yet unexpanded psym tables,
22259 the number of line tables and string tables, and the amount of memory
22260 used by the various tables. The bcache statistics include the counts,
22261 sizes, and counts of duplicates of all and unique objects, max,
22262 average, and median entry size, total memory used and its overhead and
22263 savings, and various measures of the hash table size and chain
22266 @kindex maint print type
22267 @cindex type chain of a data type
22268 @item maint print type @var{expr}
22269 Print the type chain for a type specified by @var{expr}. The argument
22270 can be either a type name or a symbol. If it is a symbol, the type of
22271 that symbol is described. The type chain produced by this command is
22272 a recursive definition of the data type as stored in @value{GDBN}'s
22273 data structures, including its flags and contained types.
22275 @kindex maint set dwarf2 max-cache-age
22276 @kindex maint show dwarf2 max-cache-age
22277 @item maint set dwarf2 max-cache-age
22278 @itemx maint show dwarf2 max-cache-age
22279 Control the DWARF 2 compilation unit cache.
22281 @cindex DWARF 2 compilation units cache
22282 In object files with inter-compilation-unit references, such as those
22283 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
22284 reader needs to frequently refer to previously read compilation units.
22285 This setting controls how long a compilation unit will remain in the
22286 cache if it is not referenced. A higher limit means that cached
22287 compilation units will be stored in memory longer, and more total
22288 memory will be used. Setting it to zero disables caching, which will
22289 slow down @value{GDBN} startup, but reduce memory consumption.
22291 @kindex maint set profile
22292 @kindex maint show profile
22293 @cindex profiling GDB
22294 @item maint set profile
22295 @itemx maint show profile
22296 Control profiling of @value{GDBN}.
22298 Profiling will be disabled until you use the @samp{maint set profile}
22299 command to enable it. When you enable profiling, the system will begin
22300 collecting timing and execution count data; when you disable profiling or
22301 exit @value{GDBN}, the results will be written to a log file. Remember that
22302 if you use profiling, @value{GDBN} will overwrite the profiling log file
22303 (often called @file{gmon.out}). If you have a record of important profiling
22304 data in a @file{gmon.out} file, be sure to move it to a safe location.
22306 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
22307 compiled with the @samp{-pg} compiler option.
22309 @kindex maint show-debug-regs
22310 @cindex x86 hardware debug registers
22311 @item maint show-debug-regs
22312 Control whether to show variables that mirror the x86 hardware debug
22313 registers. Use @code{ON} to enable, @code{OFF} to disable. If
22314 enabled, the debug registers values are shown when GDB inserts or
22315 removes a hardware breakpoint or watchpoint, and when the inferior
22316 triggers a hardware-assisted breakpoint or watchpoint.
22318 @kindex maint space
22319 @cindex memory used by commands
22321 Control whether to display memory usage for each command. If set to a
22322 nonzero value, @value{GDBN} will display how much memory each command
22323 took, following the command's own output. This can also be requested
22324 by invoking @value{GDBN} with the @option{--statistics} command-line
22325 switch (@pxref{Mode Options}).
22328 @cindex time of command execution
22330 Control whether to display the execution time for each command. If
22331 set to a nonzero value, @value{GDBN} will display how much time it
22332 took to execute each command, following the command's own output.
22333 This can also be requested by invoking @value{GDBN} with the
22334 @option{--statistics} command-line switch (@pxref{Mode Options}).
22336 @kindex maint translate-address
22337 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
22338 Find the symbol stored at the location specified by the address
22339 @var{addr} and an optional section name @var{section}. If found,
22340 @value{GDBN} prints the name of the closest symbol and an offset from
22341 the symbol's location to the specified address. This is similar to
22342 the @code{info address} command (@pxref{Symbols}), except that this
22343 command also allows to find symbols in other sections.
22347 The following command is useful for non-interactive invocations of
22348 @value{GDBN}, such as in the test suite.
22351 @item set watchdog @var{nsec}
22352 @kindex set watchdog
22353 @cindex watchdog timer
22354 @cindex timeout for commands
22355 Set the maximum number of seconds @value{GDBN} will wait for the
22356 target operation to finish. If this time expires, @value{GDBN}
22357 reports and error and the command is aborted.
22359 @item show watchdog
22360 Show the current setting of the target wait timeout.
22363 @node Remote Protocol
22364 @appendix @value{GDBN} Remote Serial Protocol
22369 * Stop Reply Packets::
22370 * General Query Packets::
22371 * Register Packet Format::
22372 * Tracepoint Packets::
22375 * File-I/O remote protocol extension::
22381 There may be occasions when you need to know something about the
22382 protocol---for example, if there is only one serial port to your target
22383 machine, you might want your program to do something special if it
22384 recognizes a packet meant for @value{GDBN}.
22386 In the examples below, @samp{->} and @samp{<-} are used to indicate
22387 transmitted and received data respectfully.
22389 @cindex protocol, @value{GDBN} remote serial
22390 @cindex serial protocol, @value{GDBN} remote
22391 @cindex remote serial protocol
22392 All @value{GDBN} commands and responses (other than acknowledgments) are
22393 sent as a @var{packet}. A @var{packet} is introduced with the character
22394 @samp{$}, the actual @var{packet-data}, and the terminating character
22395 @samp{#} followed by a two-digit @var{checksum}:
22398 @code{$}@var{packet-data}@code{#}@var{checksum}
22402 @cindex checksum, for @value{GDBN} remote
22404 The two-digit @var{checksum} is computed as the modulo 256 sum of all
22405 characters between the leading @samp{$} and the trailing @samp{#} (an
22406 eight bit unsigned checksum).
22408 Implementors should note that prior to @value{GDBN} 5.0 the protocol
22409 specification also included an optional two-digit @var{sequence-id}:
22412 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
22415 @cindex sequence-id, for @value{GDBN} remote
22417 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
22418 has never output @var{sequence-id}s. Stubs that handle packets added
22419 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
22421 @cindex acknowledgment, for @value{GDBN} remote
22422 When either the host or the target machine receives a packet, the first
22423 response expected is an acknowledgment: either @samp{+} (to indicate
22424 the package was received correctly) or @samp{-} (to request
22428 -> @code{$}@var{packet-data}@code{#}@var{checksum}
22433 The host (@value{GDBN}) sends @var{command}s, and the target (the
22434 debugging stub incorporated in your program) sends a @var{response}. In
22435 the case of step and continue @var{command}s, the response is only sent
22436 when the operation has completed (the target has again stopped).
22438 @var{packet-data} consists of a sequence of characters with the
22439 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
22442 Fields within the packet should be separated using @samp{,} @samp{;} or
22443 @cindex remote protocol, field separator
22444 @samp{:}. Except where otherwise noted all numbers are represented in
22445 @sc{hex} with leading zeros suppressed.
22447 Implementors should note that prior to @value{GDBN} 5.0, the character
22448 @samp{:} could not appear as the third character in a packet (as it
22449 would potentially conflict with the @var{sequence-id}).
22451 Response @var{data} can be run-length encoded to save space. A @samp{*}
22452 means that the next character is an @sc{ascii} encoding giving a repeat count
22453 which stands for that many repetitions of the character preceding the
22454 @samp{*}. The encoding is @code{n+29}, yielding a printable character
22455 where @code{n >=3} (which is where rle starts to win). The printable
22456 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
22457 value greater than 126 should not be used.
22464 means the same as "0000".
22466 The error response returned for some packets includes a two character
22467 error number. That number is not well defined.
22469 @cindex empty response, for unsupported packets
22470 For any @var{command} not supported by the stub, an empty response
22471 (@samp{$#00}) should be returned. That way it is possible to extend the
22472 protocol. A newer @value{GDBN} can tell if a packet is supported based
22475 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
22476 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
22482 The following table provides a complete list of all currently defined
22483 @var{command}s and their corresponding response @var{data}.
22484 @xref{File-I/O remote protocol extension}, for details about the File
22485 I/O extension of the remote protocol.
22487 Each packet's description has a template showing the packet's overall
22488 syntax, followed by an explanation of the packet's meaning. We
22489 include spaces in some of the templates for clarity; these are not
22490 part of the packet's syntax. No @value{GDBN} packet uses spaces to
22491 separate its components. For example, a template like @samp{foo
22492 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
22493 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
22494 @var{baz}. GDB does not transmit a space character between the
22495 @samp{foo} and the @var{bar}, or between the @var{bar} and the
22498 Note that all packet forms beginning with an upper- or lower-case
22499 letter, other than those described here, are reserved for future use.
22501 Here are the packet descriptions.
22506 @cindex @samp{!} packet
22507 Enable extended mode. In extended mode, the remote server is made
22508 persistent. The @samp{R} packet is used to restart the program being
22514 The remote target both supports and has enabled extended mode.
22518 @cindex @samp{?} packet
22519 Indicate the reason the target halted. The reply is the same as for
22523 @xref{Stop Reply Packets}, for the reply specifications.
22525 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
22526 @cindex @samp{A} packet
22527 Initialized @code{argv[]} array passed into program. @var{arglen}
22528 specifies the number of bytes in the hex encoded byte stream
22529 @var{arg}. See @code{gdbserver} for more details.
22534 The arguments were set.
22540 @cindex @samp{b} packet
22541 (Don't use this packet; its behavior is not well-defined.)
22542 Change the serial line speed to @var{baud}.
22544 JTC: @emph{When does the transport layer state change? When it's
22545 received, or after the ACK is transmitted. In either case, there are
22546 problems if the command or the acknowledgment packet is dropped.}
22548 Stan: @emph{If people really wanted to add something like this, and get
22549 it working for the first time, they ought to modify ser-unix.c to send
22550 some kind of out-of-band message to a specially-setup stub and have the
22551 switch happen "in between" packets, so that from remote protocol's point
22552 of view, nothing actually happened.}
22554 @item B @var{addr},@var{mode}
22555 @cindex @samp{B} packet
22556 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
22557 breakpoint at @var{addr}.
22559 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
22560 (@pxref{insert breakpoint or watchpoint packet}).
22562 @item c @r{[}@var{addr}@r{]}
22563 @cindex @samp{c} packet
22564 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
22565 resume at current address.
22568 @xref{Stop Reply Packets}, for the reply specifications.
22570 @item C @var{sig}@r{[};@var{addr}@r{]}
22571 @cindex @samp{C} packet
22572 Continue with signal @var{sig} (hex signal number). If
22573 @samp{;@var{addr}} is omitted, resume at same address.
22576 @xref{Stop Reply Packets}, for the reply specifications.
22579 @cindex @samp{d} packet
22582 Don't use this packet; instead, define a general set packet
22583 (@pxref{General Query Packets}).
22586 @cindex @samp{D} packet
22587 Detach @value{GDBN} from the remote system. Sent to the remote target
22588 before @value{GDBN} disconnects via the @code{detach} command.
22598 @item F @var{RC},@var{EE},@var{CF};@var{XX}
22599 @cindex @samp{F} packet
22600 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
22601 This is part of the File-I/O protocol extension. @xref{File-I/O
22602 remote protocol extension}, for the specification.
22605 @anchor{read registers packet}
22606 @cindex @samp{g} packet
22607 Read general registers.
22611 @item @var{XX@dots{}}
22612 Each byte of register data is described by two hex digits. The bytes
22613 with the register are transmitted in target byte order. The size of
22614 each register and their position within the @samp{g} packet are
22615 determined by the @value{GDBN} internal macros
22616 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{REGISTER_NAME} macros. The
22617 specification of several standard @samp{g} packets is specified below.
22622 @item G @var{XX@dots{}}
22623 @cindex @samp{G} packet
22624 Write general registers. @xref{read registers packet}, for a
22625 description of the @var{XX@dots{}} data.
22635 @item H @var{c} @var{t}
22636 @cindex @samp{H} packet
22637 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
22638 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
22639 should be @samp{c} for step and continue operations, @samp{g} for other
22640 operations. The thread designator @var{t} may be @samp{-1}, meaning all
22641 the threads, a thread number, or @samp{0} which means pick any thread.
22652 @c 'H': How restrictive (or permissive) is the thread model. If a
22653 @c thread is selected and stopped, are other threads allowed
22654 @c to continue to execute? As I mentioned above, I think the
22655 @c semantics of each command when a thread is selected must be
22656 @c described. For example:
22658 @c 'g': If the stub supports threads and a specific thread is
22659 @c selected, returns the register block from that thread;
22660 @c otherwise returns current registers.
22662 @c 'G' If the stub supports threads and a specific thread is
22663 @c selected, sets the registers of the register block of
22664 @c that thread; otherwise sets current registers.
22666 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
22667 @anchor{cycle step packet}
22668 @cindex @samp{i} packet
22669 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
22670 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
22671 step starting at that address.
22674 @cindex @samp{I} packet
22675 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
22679 @cindex @samp{k} packet
22682 FIXME: @emph{There is no description of how to operate when a specific
22683 thread context has been selected (i.e.@: does 'k' kill only that
22686 @item m @var{addr},@var{length}
22687 @cindex @samp{m} packet
22688 Read @var{length} bytes of memory starting at address @var{addr}.
22689 Note that @var{addr} may not be aligned to any particular boundary.
22691 The stub need not use any particular size or alignment when gathering
22692 data from memory for the response; even if @var{addr} is word-aligned
22693 and @var{length} is a multiple of the word size, the stub is free to
22694 use byte accesses, or not. For this reason, this packet may not be
22695 suitable for accessing memory-mapped I/O devices.
22696 @cindex alignment of remote memory accesses
22697 @cindex size of remote memory accesses
22698 @cindex memory, alignment and size of remote accesses
22702 @item @var{XX@dots{}}
22703 Memory contents; each byte is transmitted as a two-digit hexidecimal
22704 number. The reply may contain fewer bytes than requested if the
22705 server was able to read only part of the region of memory.
22710 @item M @var{addr},@var{length}:@var{XX@dots{}}
22711 @cindex @samp{M} packet
22712 Write @var{length} bytes of memory starting at address @var{addr}.
22713 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
22714 hexidecimal number.
22721 for an error (this includes the case where only part of the data was
22726 @cindex @samp{p} packet
22727 Read the value of register @var{n}; @var{n} is in hex.
22728 @xref{read registers packet}, for a description of how the returned
22729 register value is encoded.
22733 @item @var{XX@dots{}}
22734 the register's value
22738 Indicating an unrecognized @var{query}.
22741 @item P @var{n@dots{}}=@var{r@dots{}}
22742 @anchor{write register packet}
22743 @cindex @samp{P} packet
22744 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
22745 number @var{n} is in hexidecimal, and @var{r@dots{}} contains two hex
22746 digits for each byte in the register (target byte order).
22756 @item q @var{name} @var{params}@dots{}
22757 @itemx Q @var{name} @var{params}@dots{}
22758 @cindex @samp{q} packet
22759 @cindex @samp{Q} packet
22760 General query (@samp{q}) and set (@samp{Q}). These packets are
22761 described fully in @ref{General Query Packets}.
22764 @cindex @samp{r} packet
22765 Reset the entire system.
22767 Don't use this packet; use the @samp{R} packet instead.
22770 @cindex @samp{R} packet
22771 Restart the program being debugged. @var{XX}, while needed, is ignored.
22772 This packet is only available in extended mode.
22774 The @samp{R} packet has no reply.
22776 @item s @r{[}@var{addr}@r{]}
22777 @cindex @samp{s} packet
22778 Single step. @var{addr} is the address at which to resume. If
22779 @var{addr} is omitted, resume at same address.
22782 @xref{Stop Reply Packets}, for the reply specifications.
22784 @item S @var{sig}@r{[};@var{addr}@r{]}
22785 @anchor{step with signal packet}
22786 @cindex @samp{S} packet
22787 Step with signal. This is analogous to the @samp{C} packet, but
22788 requests a single-step, rather than a normal resumption of execution.
22791 @xref{Stop Reply Packets}, for the reply specifications.
22793 @item t @var{addr}:@var{PP},@var{MM}
22794 @cindex @samp{t} packet
22795 Search backwards starting at address @var{addr} for a match with pattern
22796 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
22797 @var{addr} must be at least 3 digits.
22800 @cindex @samp{T} packet
22801 Find out if the thread XX is alive.
22806 thread is still alive
22812 Packets starting with @samp{v} are identified by a multi-letter name,
22813 up to the first @samp{;} or @samp{?} (or the end of the packet).
22815 @item vCont@r{[};@var{action}@r{[}:@var{tid}@r{]]}@dots{}
22816 @cindex @samp{vCont} packet
22817 Resume the inferior, specifying different actions for each thread.
22818 If an action is specified with no @var{tid}, then it is applied to any
22819 threads that don't have a specific action specified; if no default action is
22820 specified then other threads should remain stopped. Specifying multiple
22821 default actions is an error; specifying no actions is also an error.
22822 Thread IDs are specified in hexadecimal. Currently supported actions are:
22828 Continue with signal @var{sig}. @var{sig} should be two hex digits.
22832 Step with signal @var{sig}. @var{sig} should be two hex digits.
22835 The optional @var{addr} argument normally associated with these packets is
22836 not supported in @samp{vCont}.
22839 @xref{Stop Reply Packets}, for the reply specifications.
22842 @cindex @samp{vCont?} packet
22843 Request a list of actions supporetd by the @samp{vCont} packet.
22847 @item vCont@r{[};@var{action}@dots{}@r{]}
22848 The @samp{vCont} packet is supported. Each @var{action} is a supported
22849 command in the @samp{vCont} packet.
22851 The @samp{vCont} packet is not supported.
22854 @item X @var{addr},@var{length}:@var{XX@dots{}}
22856 @cindex @samp{X} packet
22857 Write data to memory, where the data is transmitted in binary.
22858 @var{addr} is address, @var{length} is number of bytes,
22859 @samp{@var{XX}@dots{}} is binary data. The bytes @code{0x23}
22860 (@sc{ascii} @samp{#}), @code{0x24} (@sc{ascii} @samp{$}), and
22861 @code{0x7d} (@sc{ascii} @samp{@}}) are escaped using @code{0x7d}
22862 (@sc{ascii} @samp{@}}), and then XORed with @code{0x20}. For example,
22863 the byte @code{0x7d} would be transmitted as the two bytes @code{0x7d
22874 @item z @var{type},@var{addr},@var{length}
22875 @itemx Z @var{type},@var{addr},@var{length}
22876 @anchor{insert breakpoint or watchpoint packet}
22877 @cindex @samp{z} packet
22878 @cindex @samp{Z} packets
22879 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
22880 watchpoint starting at address @var{address} and covering the next
22881 @var{length} bytes.
22883 Each breakpoint and watchpoint packet @var{type} is documented
22886 @emph{Implementation notes: A remote target shall return an empty string
22887 for an unrecognized breakpoint or watchpoint packet @var{type}. A
22888 remote target shall support either both or neither of a given
22889 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
22890 avoid potential problems with duplicate packets, the operations should
22891 be implemented in an idempotent way.}
22893 @item z0,@var{addr},@var{length}
22894 @itemx Z0,@var{addr},@var{length}
22895 @cindex @samp{z0} packet
22896 @cindex @samp{Z0} packet
22897 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
22898 @var{addr} of size @var{length}.
22900 A memory breakpoint is implemented by replacing the instruction at
22901 @var{addr} with a software breakpoint or trap instruction. The
22902 @var{length} is used by targets that indicates the size of the
22903 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
22904 @sc{mips} can insert either a 2 or 4 byte breakpoint).
22906 @emph{Implementation note: It is possible for a target to copy or move
22907 code that contains memory breakpoints (e.g., when implementing
22908 overlays). The behavior of this packet, in the presence of such a
22909 target, is not defined.}
22921 @item z1,@var{addr},@var{length}
22922 @itemx Z1,@var{addr},@var{length}
22923 @cindex @samp{z1} packet
22924 @cindex @samp{Z1} packet
22925 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
22926 address @var{addr} of size @var{length}.
22928 A hardware breakpoint is implemented using a mechanism that is not
22929 dependant on being able to modify the target's memory.
22931 @emph{Implementation note: A hardware breakpoint is not affected by code
22944 @item z2,@var{addr},@var{length}
22945 @itemx Z2,@var{addr},@var{length}
22946 @cindex @samp{z2} packet
22947 @cindex @samp{Z2} packet
22948 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint.
22960 @item z3,@var{addr},@var{length}
22961 @itemx Z3,@var{addr},@var{length}
22962 @cindex @samp{z3} packet
22963 @cindex @samp{Z3} packet
22964 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint.
22976 @item z4,@var{addr},@var{length}
22977 @itemx Z4,@var{addr},@var{length}
22978 @cindex @samp{z4} packet
22979 @cindex @samp{Z4} packet
22980 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint.
22994 @node Stop Reply Packets
22995 @section Stop Reply Packets
22996 @cindex stop reply packets
22998 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
22999 receive any of the below as a reply. In the case of the @samp{C},
23000 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
23001 when the target halts. In the below the exact meaning of @dfn{signal
23002 number} is poorly defined. In general one of the UNIX signal
23003 numbering conventions is used.
23005 As in the description of request packets, we include spaces in the
23006 reply templates for clarity; these are not part of the reply packet's
23007 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
23013 The program received signal number @var{AA} (a two-digit hexidecimal
23016 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
23017 @cindex @samp{T} packet reply
23018 The program received signal number @var{AA} (a two-digit hexidecimal
23019 number). Single-step and breakpoint traps are reported this way. The
23020 @samp{@var{n}:@var{r}} pairs give the values of important registers or
23024 If @var{n} is a hexidecimal number, it is a register number, and the
23025 corresponding @var{r} gives that register's value. @var{r} is a
23026 series of bytes in target byte order, with each byte given by a
23027 two-digit hex number.
23029 If @var{n} is @samp{thread}, then @var{r} is the thread process ID, in
23032 If @var{n} is @samp{watch}, @samp{rwatch}, or @samp{awatch}, then the
23033 packet indicates a watchpoint hit, and @var{r} is the data address, in
23036 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
23037 and go on to the next; this allows us to extend the protocol in the
23042 The process exited, and @var{AA} is the exit status. This is only
23043 applicable to certain targets.
23046 The process terminated with signal @var{AA}.
23048 @item O @var{XX}@dots{}
23049 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
23050 written as the program's console output. This can happen at any time
23051 while the program is running and the debugger should continue to wait
23052 for @samp{W}, @samp{T}, etc.
23054 @item F @var{call-id},@var{parameter}@dots{}
23055 @var{call-id} is the identifier which says which host system call should
23056 be called. This is just the name of the function. Translation into the
23057 correct system call is only applicable as it's defined in @value{GDBN}.
23058 @xref{File-I/O remote protocol extension}, for a list of implemented
23061 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
23062 this very system call.
23064 The target replies with this packet when it expects @value{GDBN} to
23065 call a host system call on behalf of the target. @value{GDBN} replies
23066 with an appropriate @samp{F} packet and keeps up waiting for the next
23067 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
23068 or @samp{s} action is expected to be continued. @xref{File-I/O remote
23069 protocol extension}, for more details.
23073 @node General Query Packets
23074 @section General Query Packets
23075 @cindex remote query requests
23077 Packets starting with @samp{q} are @dfn{general query packets};
23078 packets starting with @samp{Q} are @dfn{general set packets}. General
23079 query and set packets are a semi-unified form for retrieving and
23080 sending information to and from the stub.
23082 The initial letter of a query or set packet is followed by a name
23083 indicating what sort of thing the packet applies to. For example,
23084 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
23085 definitions with the stub. These packet names follow some
23090 The name must not contain commas, colons or semicolons.
23092 Most @value{GDBN} query and set packets have a leading upper case
23095 The names of custom vendor packets should use a company prefix, in
23096 lower case, followed by a period. For example, packets designed at
23097 the Acme Corporation might begin with @samp{qacme.foo} (for querying
23098 foos) or @samp{Qacme.bar} (for setting bars).
23101 A query or set packet may optionally be followed by a @samp{,} or
23102 @samp{;} separated list. Stubs must be careful to match the full
23103 packet name, in case packet names have common prefixes.
23105 Like the descriptions of the other packets, each description here
23106 has a template showing the packet's overall syntax, followed by an
23107 explanation of the packet's meaning. We include spaces in some of the
23108 templates for clarity; these are not part of the packet's syntax. No
23109 @value{GDBN} packet uses spaces to separate its components.
23111 Here are the currently defined query and set packets:
23116 @cindex current thread, remote request
23117 @cindex @samp{qC} packet
23118 Return the current thread id.
23123 Where @var{pid} is an unsigned hexidecimal process id.
23124 @item @r{(anything else)}
23125 Any other reply implies the old pid.
23128 @item qCRC:@var{addr},@var{length}
23129 @cindex CRC of memory block, remote request
23130 @cindex @samp{qCRC} packet
23131 Compute the CRC checksum of a block of memory.
23135 An error (such as memory fault)
23136 @item C @var{crc32}
23137 The specified memory region's checksum is @var{crc32}.
23141 @itemx qsThreadInfo
23142 @cindex list active threads, remote request
23143 @cindex @samp{qfThreadInfo} packet
23144 @cindex @samp{qsThreadInfo} packet
23145 Obtain a list of all active thread ids from the target (OS). Since there
23146 may be too many active threads to fit into one reply packet, this query
23147 works iteratively: it may require more than one query/reply sequence to
23148 obtain the entire list of threads. The first query of the sequence will
23149 be the @samp{qfThreadInfo} query; subsequent queries in the
23150 sequence will be the @samp{qsThreadInfo} query.
23152 NOTE: This packet replaces the @samp{qL} query (see below).
23158 @item m @var{id},@var{id}@dots{}
23159 a comma-separated list of thread ids
23161 (lower case letter @samp{L}) denotes end of list.
23164 In response to each query, the target will reply with a list of one or
23165 more thread ids, in big-endian unsigned hex, separated by commas.
23166 @value{GDBN} will respond to each reply with a request for more thread
23167 ids (using the @samp{qs} form of the query), until the target responds
23168 with @samp{l} (lower-case el, for @dfn{last}).
23170 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
23171 @cindex get thread-local storage address, remote request
23172 @cindex @samp{qGetTLSAddr} packet
23173 Fetch the address associated with thread local storage specified
23174 by @var{thread-id}, @var{offset}, and @var{lm}.
23176 @var{thread-id} is the (big endian, hex encoded) thread id associated with the
23177 thread for which to fetch the TLS address.
23179 @var{offset} is the (big endian, hex encoded) offset associated with the
23180 thread local variable. (This offset is obtained from the debug
23181 information associated with the variable.)
23183 @var{lm} is the (big endian, hex encoded) OS/ABI specific encoding of the
23184 the load module associated with the thread local storage. For example,
23185 a @sc{gnu}/Linux system will pass the link map address of the shared
23186 object associated with the thread local storage under consideration.
23187 Other operating environments may choose to represent the load module
23188 differently, so the precise meaning of this parameter will vary.
23192 @item @var{XX}@dots{}
23193 Hex encoded (big endian) bytes representing the address of the thread
23194 local storage requested.
23197 An error occurred. @var{nn} are hex digits.
23200 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
23203 Use of this request packet is controlled by the @code{set remote
23204 get-thread-local-storage-address} command (@pxref{Remote
23205 configuration, set remote get-thread-local-storage-address}).
23207 @item qL @var{startflag} @var{threadcount} @var{nextthread}
23208 Obtain thread information from RTOS. Where: @var{startflag} (one hex
23209 digit) is one to indicate the first query and zero to indicate a
23210 subsequent query; @var{threadcount} (two hex digits) is the maximum
23211 number of threads the response packet can contain; and @var{nextthread}
23212 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
23213 returned in the response as @var{argthread}.
23215 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
23219 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
23220 Where: @var{count} (two hex digits) is the number of threads being
23221 returned; @var{done} (one hex digit) is zero to indicate more threads
23222 and one indicates no further threads; @var{argthreadid} (eight hex
23223 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
23224 is a sequence of thread IDs from the target. @var{threadid} (eight hex
23225 digits). See @code{remote.c:parse_threadlist_response()}.
23229 @cindex section offsets, remote request
23230 @cindex @samp{qOffsets} packet
23231 Get section offsets that the target used when re-locating the downloaded
23232 image. @emph{Note: while a @code{Bss} offset is included in the
23233 response, @value{GDBN} ignores this and instead applies the @code{Data}
23234 offset to the @code{Bss} section.}
23238 @item Text=@var{xxx};Data=@var{yyy};Bss=@var{zzz}
23241 @item qP @var{mode} @var{threadid}
23242 @cindex thread information, remote request
23243 @cindex @samp{qP} packet
23244 Returns information on @var{threadid}. Where: @var{mode} is a hex
23245 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
23247 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
23249 @item qPart:@var{object}:read:@var{annex}:@var{offset},@var{length}
23250 @cindex read special object, remote request
23251 @cindex @samp{qPart} packet
23252 Read uninterpreted bytes from the target's special data area
23253 identified by the keyword @var{object}. Request @var{length} bytes
23254 starting at @var{offset} bytes into the data. The content and
23255 encoding of @var{annex} is specific to the object; it can supply
23256 additional details about what data to access.
23258 Here are the specific requests of this form defined so far. All
23259 @samp{qPart:@var{object}:read:@dots{}} requests use the same reply
23260 formats, listed below.
23263 @item qPart:auxv:read::@var{offset},@var{length}
23264 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
23265 auxiliary vector}, and see @ref{Remote configuration,
23266 read-aux-vector-packet}. Note @var{annex} must be empty.
23272 The @var{offset} in the request is at the end of the data.
23273 There is no more data to be read.
23275 @item @var{XX}@dots{}
23276 Hex encoded data bytes read.
23277 This may be fewer bytes than the @var{length} in the request.
23280 The request was malformed, or @var{annex} was invalid.
23283 The offset was invalid, or there was an error encountered reading the data.
23284 @var{nn} is a hex-encoded @code{errno} value.
23287 An empty reply indicates the @var{object} or @var{annex} string was not
23288 recognized by the stub.
23291 @item qPart:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
23292 @cindex write data into object, remote request
23293 Write uninterpreted bytes into the target's special data area
23294 identified by the keyword @var{object}, starting at @var{offset} bytes
23295 into the data. @samp{@var{data}@dots{}} is the hex-encoded data to be
23296 written. The content and encoding of @var{annex} is specific to the
23297 object; it can supply additional details about what data to access.
23299 No requests of this form are presently in use. This specification
23300 serves as a placeholder to document the common format that new
23301 specific request specifications ought to use.
23306 @var{nn} (hex encoded) is the number of bytes written.
23307 This may be fewer bytes than supplied in the request.
23310 The request was malformed, or @var{annex} was invalid.
23313 The offset was invalid, or there was an error encountered writing the data.
23314 @var{nn} is a hex-encoded @code{errno} value.
23317 An empty reply indicates the @var{object} or @var{annex} string was not
23318 recognized by the stub, or that the object does not support writing.
23321 @item qPart:@var{object}:@var{operation}:@dots{}
23322 Requests of this form may be added in the future. When a stub does
23323 not recognize the @var{object} keyword, or its support for
23324 @var{object} does not recognize the @var{operation} keyword, the stub
23325 must respond with an empty packet.
23327 @item qRcmd,@var{command}
23328 @cindex execute remote command, remote request
23329 @cindex @samp{qRcmd} packet
23330 @var{command} (hex encoded) is passed to the local interpreter for
23331 execution. Invalid commands should be reported using the output
23332 string. Before the final result packet, the target may also respond
23333 with a number of intermediate @samp{O@var{output}} console output
23334 packets. @emph{Implementors should note that providing access to a
23335 stubs's interpreter may have security implications}.
23340 A command response with no output.
23342 A command response with the hex encoded output string @var{OUTPUT}.
23344 Indicate a badly formed request.
23346 An empty reply indicates that @samp{qRcmd} is not recognized.
23350 @cindex symbol lookup, remote request
23351 @cindex @samp{qSymbol} packet
23352 Notify the target that @value{GDBN} is prepared to serve symbol lookup
23353 requests. Accept requests from the target for the values of symbols.
23358 The target does not need to look up any (more) symbols.
23359 @item qSymbol:@var{sym_name}
23360 The target requests the value of symbol @var{sym_name} (hex encoded).
23361 @value{GDBN} may provide the value by using the
23362 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
23366 @item qSymbol:@var{sym_value}:@var{sym_name}
23367 Set the value of @var{sym_name} to @var{sym_value}.
23369 @var{sym_name} (hex encoded) is the name of a symbol whose value the
23370 target has previously requested.
23372 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
23373 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
23379 The target does not need to look up any (more) symbols.
23380 @item qSymbol:@var{sym_name}
23381 The target requests the value of a new symbol @var{sym_name} (hex
23382 encoded). @value{GDBN} will continue to supply the values of symbols
23383 (if available), until the target ceases to request them.
23388 @xref{Tracepoint Packets}.
23390 @item qThreadExtraInfo,@var{id}
23391 @cindex thread attributes info, remote request
23392 @cindex @samp{qThreadExtraInfo} packet
23393 Obtain a printable string description of a thread's attributes from
23394 the target OS. @var{id} is a thread-id in big-endian hex. This
23395 string may contain anything that the target OS thinks is interesting
23396 for @value{GDBN} to tell the user about the thread. The string is
23397 displayed in @value{GDBN}'s @code{info threads} display. Some
23398 examples of possible thread extra info strings are @samp{Runnable}, or
23399 @samp{Blocked on Mutex}.
23403 @item @var{XX}@dots{}
23404 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
23405 comprising the printable string containing the extra information about
23406 the thread's attributes.
23414 @xref{Tracepoint Packets}.
23418 @node Register Packet Format
23419 @section Register Packet Format
23421 The following @code{g}/@code{G} packets have previously been defined.
23422 In the below, some thirty-two bit registers are transferred as
23423 sixty-four bits. Those registers should be zero/sign extended (which?)
23424 to fill the space allocated. Register bytes are transfered in target
23425 byte order. The two nibbles within a register byte are transfered
23426 most-significant - least-significant.
23432 All registers are transfered as thirty-two bit quantities in the order:
23433 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
23434 registers; fsr; fir; fp.
23438 All registers are transfered as sixty-four bit quantities (including
23439 thirty-two bit registers such as @code{sr}). The ordering is the same
23444 @node Tracepoint Packets
23445 @section Tracepoint Packets
23446 @cindex tracepoint packets
23447 @cindex packets, tracepoint
23449 Here we describe the packets @value{GDBN} uses to implement
23450 tracepoints (@pxref{Tracepoints}).
23454 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}@r{[}-@r{]}
23455 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
23456 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
23457 the tracepoint is disabled. @var{step} is the tracepoint's step
23458 count, and @var{pass} is its pass count. If the trailing @samp{-} is
23459 present, further @samp{QTDP} packets will follow to specify this
23460 tracepoint's actions.
23465 The packet was understood and carried out.
23467 The packet was not recognized.
23470 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
23471 Define actions to be taken when a tracepoint is hit. @var{n} and
23472 @var{addr} must be the same as in the initial @samp{QTDP} packet for
23473 this tracepoint. This packet may only be sent immediately after
23474 another @samp{QTDP} packet that ended with a @samp{-}. If the
23475 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
23476 specifying more actions for this tracepoint.
23478 In the series of action packets for a given tracepoint, at most one
23479 can have an @samp{S} before its first @var{action}. If such a packet
23480 is sent, it and the following packets define ``while-stepping''
23481 actions. Any prior packets define ordinary actions --- that is, those
23482 taken when the tracepoint is first hit. If no action packet has an
23483 @samp{S}, then all the packets in the series specify ordinary
23484 tracepoint actions.
23486 The @samp{@var{action}@dots{}} portion of the packet is a series of
23487 actions, concatenated without separators. Each action has one of the
23493 Collect the registers whose bits are set in @var{mask}. @var{mask} is
23494 a hexidecimal number whose @var{i}'th bit is set if register number
23495 @var{i} should be collected. (The least significant bit is numbered
23496 zero.) Note that @var{mask} may be any number of digits long; it may
23497 not fit in a 32-bit word.
23499 @item M @var{basereg},@var{offset},@var{len}
23500 Collect @var{len} bytes of memory starting at the address in register
23501 number @var{basereg}, plus @var{offset}. If @var{basereg} is
23502 @samp{-1}, then the range has a fixed address: @var{offset} is the
23503 address of the lowest byte to collect. The @var{basereg},
23504 @var{offset}, and @var{len} parameters are all unsigned hexidecimal
23505 values (the @samp{-1} value for @var{basereg} is a special case).
23507 @item X @var{len},@var{expr}
23508 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
23509 it directs. @var{expr} is an agent expression, as described in
23510 @ref{Agent Expressions}. Each byte of the expression is encoded as a
23511 two-digit hex number in the packet; @var{len} is the number of bytes
23512 in the expression (and thus one-half the number of hex digits in the
23517 Any number of actions may be packed together in a single @samp{QTDP}
23518 packet, as long as the packet does not exceed the maximum packet
23519 length (400 bytes, for many stubs). There may be only one @samp{R}
23520 action per tracepoint, and it must precede any @samp{M} or @samp{X}
23521 actions. Any registers referred to by @samp{M} and @samp{X} actions
23522 must be collected by a preceding @samp{R} action. (The
23523 ``while-stepping'' actions are treated as if they were attached to a
23524 separate tracepoint, as far as these restrictions are concerned.)
23529 The packet was understood and carried out.
23531 The packet was not recognized.
23534 @item QTFrame:@var{n}
23535 Select the @var{n}'th tracepoint frame from the buffer, and use the
23536 register and memory contents recorded there to answer subsequent
23537 request packets from @value{GDBN}.
23539 A successful reply from the stub indicates that the stub has found the
23540 requested frame. The response is a series of parts, concatenated
23541 without separators, describing the frame we selected. Each part has
23542 one of the following forms:
23546 The selected frame is number @var{n} in the trace frame buffer;
23547 @var{f} is a hexidecimal number. If @var{f} is @samp{-1}, then there
23548 was no frame matching the criteria in the request packet.
23551 The selected trace frame records a hit of tracepoint number @var{t};
23552 @var{t} is a hexidecimal number.
23556 @item QTFrame:pc:@var{addr}
23557 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
23558 currently selected frame whose PC is @var{addr};
23559 @var{addr} is a hexidecimal number.
23561 @item QTFrame:tdp:@var{t}
23562 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
23563 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
23564 is a hexidecimal number.
23566 @item QTFrame:range:@var{start}:@var{end}
23567 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
23568 currently selected frame whose PC is between @var{start} (inclusive)
23569 and @var{end} (exclusive); @var{start} and @var{end} are hexidecimal
23572 @item QTFrame:outside:@var{start}:@var{end}
23573 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
23574 frame @emph{outside} the given range of addresses.
23577 Begin the tracepoint experiment. Begin collecting data from tracepoint
23578 hits in the trace frame buffer.
23581 End the tracepoint experiment. Stop collecting trace frames.
23584 Clear the table of tracepoints, and empty the trace frame buffer.
23586 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
23587 Establish the given ranges of memory as ``transparent''. The stub
23588 will answer requests for these ranges from memory's current contents,
23589 if they were not collected as part of the tracepoint hit.
23591 @value{GDBN} uses this to mark read-only regions of memory, like those
23592 containing program code. Since these areas never change, they should
23593 still have the same contents they did when the tracepoint was hit, so
23594 there's no reason for the stub to refuse to provide their contents.
23597 Ask the stub if there is a trace experiment running right now.
23602 There is no trace experiment running.
23604 There is a trace experiment running.
23611 @section Interrupts
23612 @cindex interrupts (remote protocol)
23614 When a program on the remote target is running, @value{GDBN} may
23615 attempt to interrupt it by sending a @samp{Ctrl-C} or a @code{BREAK},
23616 control of which is specified via @value{GDBN}'s @samp{remotebreak}
23617 setting (@pxref{set remotebreak}).
23619 The precise meaning of @code{BREAK} is defined by the transport
23620 mechanism and may, in fact, be undefined. @value{GDBN} does
23621 not currently define a @code{BREAK} mechanism for any of the network
23624 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
23625 transport mechanisms. It is represented by sending the single byte
23626 @code{0x03} without any of the usual packet overhead described in
23627 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
23628 transmitted as part of a packet, it is considered to be packet data
23629 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
23630 (@pxref{X packet}, used for binary downloads, may include an unescaped
23631 @code{0x03} as part of its packet.
23633 Stubs are not required to recognize these interrupt mechanisms and the
23634 precise meaning associated with receipt of the interrupt is
23635 implementation defined. If the stub is successful at interrupting the
23636 running program, it is expected that it will send one of the Stop
23637 Reply Packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
23638 of successfully stopping the program. Interrupts received while the
23639 program is stopped will be discarded.
23644 Example sequence of a target being re-started. Notice how the restart
23645 does not get any direct output:
23650 @emph{target restarts}
23653 <- @code{T001:1234123412341234}
23657 Example sequence of a target being stepped by a single instruction:
23660 -> @code{G1445@dots{}}
23665 <- @code{T001:1234123412341234}
23669 <- @code{1455@dots{}}
23673 @node File-I/O remote protocol extension
23674 @section File-I/O remote protocol extension
23675 @cindex File-I/O remote protocol extension
23678 * File-I/O Overview::
23679 * Protocol basics::
23680 * The F request packet::
23681 * The F reply packet::
23682 * Memory transfer::
23683 * The Ctrl-C message::
23685 * The isatty call::
23686 * The system call::
23687 * List of supported calls::
23688 * Protocol specific representation of datatypes::
23690 * File-I/O Examples::
23693 @node File-I/O Overview
23694 @subsection File-I/O Overview
23695 @cindex file-i/o overview
23697 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
23698 target to use the host's file system and console I/O when calling various
23699 system calls. System calls on the target system are translated into a
23700 remote protocol packet to the host system which then performs the needed
23701 actions and returns with an adequate response packet to the target system.
23702 This simulates file system operations even on targets that lack file systems.
23704 The protocol is defined host- and target-system independent. It uses
23705 its own independent representation of datatypes and values. Both,
23706 @value{GDBN} and the target's @value{GDBN} stub are responsible for
23707 translating the system dependent values into the unified protocol values
23708 when data is transmitted.
23710 The communication is synchronous. A system call is possible only
23711 when GDB is waiting for the @samp{C}, @samp{c}, @samp{S} or @samp{s}
23712 packets. While @value{GDBN} handles the request for a system call,
23713 the target is stopped to allow deterministic access to the target's
23714 memory. Therefore File-I/O is not interuptible by target signals. It
23715 is possible to interrupt File-I/O by a user interrupt (Ctrl-C), though.
23717 The target's request to perform a host system call does not finish
23718 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
23719 after finishing the system call, the target returns to continuing the
23720 previous activity (continue, step). No additional continue or step
23721 request from @value{GDBN} is required.
23724 (@value{GDBP}) continue
23725 <- target requests 'system call X'
23726 target is stopped, @value{GDBN} executes system call
23727 -> GDB returns result
23728 ... target continues, GDB returns to wait for the target
23729 <- target hits breakpoint and sends a Txx packet
23732 The protocol is only used for files on the host file system and
23733 for I/O on the console. Character or block special devices, pipes,
23734 named pipes or sockets or any other communication method on the host
23735 system are not supported by this protocol.
23737 @node Protocol basics
23738 @subsection Protocol basics
23739 @cindex protocol basics, file-i/o
23741 The File-I/O protocol uses the @code{F} packet, as request as well
23742 as as reply packet. Since a File-I/O system call can only occur when
23743 @value{GDBN} is waiting for the continuing or stepping target, the
23744 File-I/O request is a reply that @value{GDBN} has to expect as a result
23745 of a former @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
23746 This @code{F} packet contains all information needed to allow @value{GDBN}
23747 to call the appropriate host system call:
23751 A unique identifier for the requested system call.
23754 All parameters to the system call. Pointers are given as addresses
23755 in the target memory address space. Pointers to strings are given as
23756 pointer/length pair. Numerical values are given as they are.
23757 Numerical control values are given in a protocol specific representation.
23761 At that point @value{GDBN} has to perform the following actions.
23765 If parameter pointer values are given, which point to data needed as input
23766 to a system call, @value{GDBN} requests this data from the target with a
23767 standard @code{m} packet request. This additional communication has to be
23768 expected by the target implementation and is handled as any other @code{m}
23772 @value{GDBN} translates all value from protocol representation to host
23773 representation as needed. Datatypes are coerced into the host types.
23776 @value{GDBN} calls the system call
23779 It then coerces datatypes back to protocol representation.
23782 If pointer parameters in the request packet point to buffer space in which
23783 a system call is expected to copy data to, the data is transmitted to the
23784 target using a @code{M} or @code{X} packet. This packet has to be expected
23785 by the target implementation and is handled as any other @code{M} or @code{X}
23790 Eventually @value{GDBN} replies with another @code{F} packet which contains all
23791 necessary information for the target to continue. This at least contains
23798 @code{errno}, if has been changed by the system call.
23805 After having done the needed type and value coercion, the target continues
23806 the latest continue or step action.
23808 @node The F request packet
23809 @subsection The @code{F} request packet
23810 @cindex file-i/o request packet
23811 @cindex @code{F} request packet
23813 The @code{F} request packet has the following format:
23818 @code{F}@var{call-id}@code{,}@var{parameter@dots{}}
23821 @var{call-id} is the identifier to indicate the host system call to be called.
23822 This is just the name of the function.
23824 @var{parameter@dots{}} are the parameters to the system call.
23828 Parameters are hexadecimal integer values, either the real values in case
23829 of scalar datatypes, as pointers to target buffer space in case of compound
23830 datatypes and unspecified memory areas or as pointer/length pairs in case
23831 of string parameters. These are appended to the call-id, each separated
23832 from its predecessor by a comma. All values are transmitted in ASCII
23833 string representation, pointer/length pairs separated by a slash.
23835 @node The F reply packet
23836 @subsection The @code{F} reply packet
23837 @cindex file-i/o reply packet
23838 @cindex @code{F} reply packet
23840 The @code{F} reply packet has the following format:
23845 @code{F}@var{retcode}@code{,}@var{errno}@code{,}@var{Ctrl-C flag}@code{;}@var{call specific attachment}
23848 @var{retcode} is the return code of the system call as hexadecimal value.
23850 @var{errno} is the errno set by the call, in protocol specific representation.
23851 This parameter can be omitted if the call was successful.
23853 @var{Ctrl-C flag} is only send if the user requested a break. In this
23854 case, @var{errno} must be send as well, even if the call was successful.
23855 The @var{Ctrl-C flag} itself consists of the character 'C':
23862 or, if the call was interupted before the host call has been performed:
23869 assuming 4 is the protocol specific representation of @code{EINTR}.
23873 @node Memory transfer
23874 @subsection Memory transfer
23875 @cindex memory transfer, in file-i/o protocol
23877 Structured data which is transferred using a memory read or write as e.g.@:
23878 a @code{struct stat} is expected to be in a protocol specific format with
23879 all scalar multibyte datatypes being big endian. This should be done by
23880 the target before the @code{F} packet is sent resp.@: by @value{GDBN} before
23881 it transfers memory to the target. Transferred pointers to structured
23882 data should point to the already coerced data at any time.
23884 @node The Ctrl-C message
23885 @subsection The Ctrl-C message
23886 @cindex ctrl-c message, in file-i/o protocol
23888 A special case is, if the @var{Ctrl-C flag} is set in the @value{GDBN}
23889 reply packet. In this case the target should behave, as if it had
23890 gotten a break message. The meaning for the target is ``system call
23891 interupted by @code{SIGINT}''. Consequentially, the target should actually stop
23892 (as with a break message) and return to @value{GDBN} with a @code{T02}
23893 packet. In this case, it's important for the target to know, in which
23894 state the system call was interrupted. Since this action is by design
23895 not an atomic operation, we have to differ between two cases:
23899 The system call hasn't been performed on the host yet.
23902 The system call on the host has been finished.
23906 These two states can be distinguished by the target by the value of the
23907 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
23908 call hasn't been performed. This is equivalent to the @code{EINTR} handling
23909 on POSIX systems. In any other case, the target may presume that the
23910 system call has been finished --- successful or not --- and should behave
23911 as if the break message arrived right after the system call.
23913 @value{GDBN} must behave reliable. If the system call has not been called
23914 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
23915 @code{errno} in the packet. If the system call on the host has been finished
23916 before the user requests a break, the full action must be finshed by
23917 @value{GDBN}. This requires sending @code{M} or @code{X} packets as they fit.
23918 The @code{F} packet may only be send when either nothing has happened
23919 or the full action has been completed.
23922 @subsection Console I/O
23923 @cindex console i/o as part of file-i/o
23925 By default and if not explicitely closed by the target system, the file
23926 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
23927 on the @value{GDBN} console is handled as any other file output operation
23928 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
23929 by @value{GDBN} so that after the target read request from file descriptor
23930 0 all following typing is buffered until either one of the following
23935 The user presses @kbd{Ctrl-C}. The behaviour is as explained above, the
23937 system call is treated as finished.
23940 The user presses @kbd{Enter}. This is treated as end of input with a trailing
23944 The user presses @kbd{Ctrl-D}. This is treated as end of input. No trailing
23945 character, especially no Ctrl-D is appended to the input.
23949 If the user has typed more characters as fit in the buffer given to
23950 the read call, the trailing characters are buffered in @value{GDBN} until
23951 either another @code{read(0, @dots{})} is requested by the target or debugging
23952 is stopped on users request.
23954 @node The isatty call
23955 @subsection The @samp{isatty} function call
23956 @cindex isatty call, file-i/o protocol
23958 A special case in this protocol is the library call @code{isatty} which
23959 is implemented as its own call inside of this protocol. It returns
23960 1 to the target if the file descriptor given as parameter is attached
23961 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
23962 would require implementing @code{ioctl} and would be more complex than
23965 @node The system call
23966 @subsection The @samp{system} function call
23967 @cindex system call, file-i/o protocol
23969 The other special case in this protocol is the @code{system} call which
23970 is implemented as its own call, too. @value{GDBN} is taking over the full
23971 task of calling the necessary host calls to perform the @code{system}
23972 call. The return value of @code{system} is simplified before it's returned
23973 to the target. Basically, the only signal transmitted back is @code{EINTR}
23974 in case the user pressed @kbd{Ctrl-C}. Otherwise the return value consists
23975 entirely of the exit status of the called command.
23977 Due to security concerns, the @code{system} call is by default refused
23978 by @value{GDBN}. The user has to allow this call explicitly with the
23979 @kbd{set remote system-call-allowed 1} command.
23982 @item set remote system-call-allowed
23983 @kindex set remote system-call-allowed
23984 Control whether to allow the @code{system} calls in the File I/O
23985 protocol for the remote target. The default is zero (disabled).
23987 @item show remote system-call-allowed
23988 @kindex show remote system-call-allowed
23989 Show the current setting of system calls for the remote File I/O
23993 @node List of supported calls
23994 @subsection List of supported calls
23995 @cindex list of supported file-i/o calls
24012 @unnumberedsubsubsec open
24013 @cindex open, file-i/o system call
24017 int open(const char *pathname, int flags);
24018 int open(const char *pathname, int flags, mode_t mode);
24021 Fopen,pathptr/len,flags,mode
24025 @code{flags} is the bitwise or of the following values:
24029 If the file does not exist it will be created. The host
24030 rules apply as far as file ownership and time stamps
24034 When used with O_CREAT, if the file already exists it is
24035 an error and open() fails.
24038 If the file already exists and the open mode allows
24039 writing (O_RDWR or O_WRONLY is given) it will be
24040 truncated to length 0.
24043 The file is opened in append mode.
24046 The file is opened for reading only.
24049 The file is opened for writing only.
24052 The file is opened for reading and writing.
24055 Each other bit is silently ignored.
24060 @code{mode} is the bitwise or of the following values:
24064 User has read permission.
24067 User has write permission.
24070 Group has read permission.
24073 Group has write permission.
24076 Others have read permission.
24079 Others have write permission.
24082 Each other bit is silently ignored.
24087 @exdent Return value:
24088 open returns the new file descriptor or -1 if an error
24096 pathname already exists and O_CREAT and O_EXCL were used.
24099 pathname refers to a directory.
24102 The requested access is not allowed.
24105 pathname was too long.
24108 A directory component in pathname does not exist.
24111 pathname refers to a device, pipe, named pipe or socket.
24114 pathname refers to a file on a read-only filesystem and
24115 write access was requested.
24118 pathname is an invalid pointer value.
24121 No space on device to create the file.
24124 The process already has the maximum number of files open.
24127 The limit on the total number of files open on the system
24131 The call was interrupted by the user.
24135 @unnumberedsubsubsec close
24136 @cindex close, file-i/o system call
24145 @exdent Return value:
24146 close returns zero on success, or -1 if an error occurred.
24153 fd isn't a valid open file descriptor.
24156 The call was interrupted by the user.
24160 @unnumberedsubsubsec read
24161 @cindex read, file-i/o system call
24165 int read(int fd, void *buf, unsigned int count);
24168 Fread,fd,bufptr,count
24170 @exdent Return value:
24171 On success, the number of bytes read is returned.
24172 Zero indicates end of file. If count is zero, read
24173 returns zero as well. On error, -1 is returned.
24180 fd is not a valid file descriptor or is not open for
24184 buf is an invalid pointer value.
24187 The call was interrupted by the user.
24191 @unnumberedsubsubsec write
24192 @cindex write, file-i/o system call
24196 int write(int fd, const void *buf, unsigned int count);
24199 Fwrite,fd,bufptr,count
24201 @exdent Return value:
24202 On success, the number of bytes written are returned.
24203 Zero indicates nothing was written. On error, -1
24211 fd is not a valid file descriptor or is not open for
24215 buf is an invalid pointer value.
24218 An attempt was made to write a file that exceeds the
24219 host specific maximum file size allowed.
24222 No space on device to write the data.
24225 The call was interrupted by the user.
24229 @unnumberedsubsubsec lseek
24230 @cindex lseek, file-i/o system call
24234 long lseek (int fd, long offset, int flag);
24237 Flseek,fd,offset,flag
24240 @code{flag} is one of:
24244 The offset is set to offset bytes.
24247 The offset is set to its current location plus offset
24251 The offset is set to the size of the file plus offset
24256 @exdent Return value:
24257 On success, the resulting unsigned offset in bytes from
24258 the beginning of the file is returned. Otherwise, a
24259 value of -1 is returned.
24266 fd is not a valid open file descriptor.
24269 fd is associated with the @value{GDBN} console.
24272 flag is not a proper value.
24275 The call was interrupted by the user.
24279 @unnumberedsubsubsec rename
24280 @cindex rename, file-i/o system call
24284 int rename(const char *oldpath, const char *newpath);
24287 Frename,oldpathptr/len,newpathptr/len
24289 @exdent Return value:
24290 On success, zero is returned. On error, -1 is returned.
24297 newpath is an existing directory, but oldpath is not a
24301 newpath is a non-empty directory.
24304 oldpath or newpath is a directory that is in use by some
24308 An attempt was made to make a directory a subdirectory
24312 A component used as a directory in oldpath or new
24313 path is not a directory. Or oldpath is a directory
24314 and newpath exists but is not a directory.
24317 oldpathptr or newpathptr are invalid pointer values.
24320 No access to the file or the path of the file.
24324 oldpath or newpath was too long.
24327 A directory component in oldpath or newpath does not exist.
24330 The file is on a read-only filesystem.
24333 The device containing the file has no room for the new
24337 The call was interrupted by the user.
24341 @unnumberedsubsubsec unlink
24342 @cindex unlink, file-i/o system call
24346 int unlink(const char *pathname);
24349 Funlink,pathnameptr/len
24351 @exdent Return value:
24352 On success, zero is returned. On error, -1 is returned.
24359 No access to the file or the path of the file.
24362 The system does not allow unlinking of directories.
24365 The file pathname cannot be unlinked because it's
24366 being used by another process.
24369 pathnameptr is an invalid pointer value.
24372 pathname was too long.
24375 A directory component in pathname does not exist.
24378 A component of the path is not a directory.
24381 The file is on a read-only filesystem.
24384 The call was interrupted by the user.
24388 @unnumberedsubsubsec stat/fstat
24389 @cindex fstat, file-i/o system call
24390 @cindex stat, file-i/o system call
24394 int stat(const char *pathname, struct stat *buf);
24395 int fstat(int fd, struct stat *buf);
24398 Fstat,pathnameptr/len,bufptr
24401 @exdent Return value:
24402 On success, zero is returned. On error, -1 is returned.
24409 fd is not a valid open file.
24412 A directory component in pathname does not exist or the
24413 path is an empty string.
24416 A component of the path is not a directory.
24419 pathnameptr is an invalid pointer value.
24422 No access to the file or the path of the file.
24425 pathname was too long.
24428 The call was interrupted by the user.
24432 @unnumberedsubsubsec gettimeofday
24433 @cindex gettimeofday, file-i/o system call
24437 int gettimeofday(struct timeval *tv, void *tz);
24440 Fgettimeofday,tvptr,tzptr
24442 @exdent Return value:
24443 On success, 0 is returned, -1 otherwise.
24450 tz is a non-NULL pointer.
24453 tvptr and/or tzptr is an invalid pointer value.
24457 @unnumberedsubsubsec isatty
24458 @cindex isatty, file-i/o system call
24462 int isatty(int fd);
24467 @exdent Return value:
24468 Returns 1 if fd refers to the @value{GDBN} console, 0 otherwise.
24475 The call was interrupted by the user.
24479 @unnumberedsubsubsec system
24480 @cindex system, file-i/o system call
24484 int system(const char *command);
24487 Fsystem,commandptr/len
24489 @exdent Return value:
24490 The value returned is -1 on error and the return status
24491 of the command otherwise. Only the exit status of the
24492 command is returned, which is extracted from the hosts
24493 system return value by calling WEXITSTATUS(retval).
24494 In case /bin/sh could not be executed, 127 is returned.
24501 The call was interrupted by the user.
24504 @node Protocol specific representation of datatypes
24505 @subsection Protocol specific representation of datatypes
24506 @cindex protocol specific representation of datatypes, in file-i/o protocol
24509 * Integral datatypes::
24515 @node Integral datatypes
24516 @unnumberedsubsubsec Integral datatypes
24517 @cindex integral datatypes, in file-i/o protocol
24519 The integral datatypes used in the system calls are
24522 int@r{,} unsigned int@r{,} long@r{,} unsigned long@r{,} mode_t @r{and} time_t
24525 @code{Int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
24526 implemented as 32 bit values in this protocol.
24528 @code{Long} and @code{unsigned long} are implemented as 64 bit types.
24530 @xref{Limits}, for corresponding MIN and MAX values (similar to those
24531 in @file{limits.h}) to allow range checking on host and target.
24533 @code{time_t} datatypes are defined as seconds since the Epoch.
24535 All integral datatypes transferred as part of a memory read or write of a
24536 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
24539 @node Pointer values
24540 @unnumberedsubsubsec Pointer values
24541 @cindex pointer values, in file-i/o protocol
24543 Pointers to target data are transmitted as they are. An exception
24544 is made for pointers to buffers for which the length isn't
24545 transmitted as part of the function call, namely strings. Strings
24546 are transmitted as a pointer/length pair, both as hex values, e.g.@:
24553 which is a pointer to data of length 18 bytes at position 0x1aaf.
24554 The length is defined as the full string length in bytes, including
24555 the trailing null byte. Example:
24558 ``hello, world'' at address 0x123456
24569 @unnumberedsubsubsec struct stat
24570 @cindex struct stat, in file-i/o protocol
24572 The buffer of type struct stat used by the target and @value{GDBN} is defined
24577 unsigned int st_dev; /* device */
24578 unsigned int st_ino; /* inode */
24579 mode_t st_mode; /* protection */
24580 unsigned int st_nlink; /* number of hard links */
24581 unsigned int st_uid; /* user ID of owner */
24582 unsigned int st_gid; /* group ID of owner */
24583 unsigned int st_rdev; /* device type (if inode device) */
24584 unsigned long st_size; /* total size, in bytes */
24585 unsigned long st_blksize; /* blocksize for filesystem I/O */
24586 unsigned long st_blocks; /* number of blocks allocated */
24587 time_t st_atime; /* time of last access */
24588 time_t st_mtime; /* time of last modification */
24589 time_t st_ctime; /* time of last change */
24593 The integral datatypes are conforming to the definitions given in the
24594 approriate section (see @ref{Integral datatypes}, for details) so this
24595 structure is of size 64 bytes.
24597 The values of several fields have a restricted meaning and/or
24604 st_ino: No valid meaning for the target. Transmitted unchanged.
24606 st_mode: Valid mode bits are described in Appendix C. Any other
24607 bits have currently no meaning for the target.
24609 st_uid: No valid meaning for the target. Transmitted unchanged.
24611 st_gid: No valid meaning for the target. Transmitted unchanged.
24613 st_rdev: No valid meaning for the target. Transmitted unchanged.
24615 st_atime, st_mtime, st_ctime:
24616 These values have a host and file system dependent
24617 accuracy. Especially on Windows hosts the file systems
24618 don't support exact timing values.
24621 The target gets a struct stat of the above representation and is
24622 responsible to coerce it to the target representation before
24625 Note that due to size differences between the host and target
24626 representation of stat members, these members could eventually
24627 get truncated on the target.
24629 @node struct timeval
24630 @unnumberedsubsubsec struct timeval
24631 @cindex struct timeval, in file-i/o protocol
24633 The buffer of type struct timeval used by the target and @value{GDBN}
24634 is defined as follows:
24638 time_t tv_sec; /* second */
24639 long tv_usec; /* microsecond */
24643 The integral datatypes are conforming to the definitions given in the
24644 approriate section (see @ref{Integral datatypes}, for details) so this
24645 structure is of size 8 bytes.
24648 @subsection Constants
24649 @cindex constants, in file-i/o protocol
24651 The following values are used for the constants inside of the
24652 protocol. @value{GDBN} and target are resposible to translate these
24653 values before and after the call as needed.
24664 @unnumberedsubsubsec Open flags
24665 @cindex open flags, in file-i/o protocol
24667 All values are given in hexadecimal representation.
24679 @node mode_t values
24680 @unnumberedsubsubsec mode_t values
24681 @cindex mode_t values, in file-i/o protocol
24683 All values are given in octal representation.
24700 @unnumberedsubsubsec Errno values
24701 @cindex errno values, in file-i/o protocol
24703 All values are given in decimal representation.
24728 EUNKNOWN is used as a fallback error value if a host system returns
24729 any error value not in the list of supported error numbers.
24732 @unnumberedsubsubsec Lseek flags
24733 @cindex lseek flags, in file-i/o protocol
24742 @unnumberedsubsubsec Limits
24743 @cindex limits, in file-i/o protocol
24745 All values are given in decimal representation.
24748 INT_MIN -2147483648
24750 UINT_MAX 4294967295
24751 LONG_MIN -9223372036854775808
24752 LONG_MAX 9223372036854775807
24753 ULONG_MAX 18446744073709551615
24756 @node File-I/O Examples
24757 @subsection File-I/O Examples
24758 @cindex file-i/o examples
24760 Example sequence of a write call, file descriptor 3, buffer is at target
24761 address 0x1234, 6 bytes should be written:
24764 <- @code{Fwrite,3,1234,6}
24765 @emph{request memory read from target}
24768 @emph{return "6 bytes written"}
24772 Example sequence of a read call, file descriptor 3, buffer is at target
24773 address 0x1234, 6 bytes should be read:
24776 <- @code{Fread,3,1234,6}
24777 @emph{request memory write to target}
24778 -> @code{X1234,6:XXXXXX}
24779 @emph{return "6 bytes read"}
24783 Example sequence of a read call, call fails on the host due to invalid
24784 file descriptor (EBADF):
24787 <- @code{Fread,3,1234,6}
24791 Example sequence of a read call, user presses Ctrl-C before syscall on
24795 <- @code{Fread,3,1234,6}
24800 Example sequence of a read call, user presses Ctrl-C after syscall on
24804 <- @code{Fread,3,1234,6}
24805 -> @code{X1234,6:XXXXXX}
24809 @include agentexpr.texi
24823 % I think something like @colophon should be in texinfo. In the
24825 \long\def\colophon{\hbox to0pt{}\vfill
24826 \centerline{The body of this manual is set in}
24827 \centerline{\fontname\tenrm,}
24828 \centerline{with headings in {\bf\fontname\tenbf}}
24829 \centerline{and examples in {\tt\fontname\tentt}.}
24830 \centerline{{\it\fontname\tenit\/},}
24831 \centerline{{\bf\fontname\tenbf}, and}
24832 \centerline{{\sl\fontname\tensl\/}}
24833 \centerline{are used for emphasis.}\vfill}
24835 % Blame: doc@cygnus.com, 1991.